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1
Bjerkås, Morten. "Ice Actions on Offshore Structures – With Applications of Continuous Wavelet Transforms on Ice Load Signals". Doctoral thesis, Norwegian University of Science and Technology, Department of Civil and Transport Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1576.
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Ice actions on offshore structures are one of the main concerns for engineering activities in cold areas with ice-infested waters. This thesis deals with three aspects of ice actions, namely design ice loads from level ice, dynamic ice actions of resonant character, and the actions caused by ridged ice.
Ice pressures on full-scale structures have been summarized in the present work. The scatter in reported values has been partly explained by categorization with respect to the applied measuring devices, structural characteristics and geographical locations. An existing design code was found to fit well for the widest structures and dramatically over-predict ice loads for structures of widths less than four metres. The present work was concerned with the analyses of full-scale data from the Norströmsgrund lighthouse conducted in the LOLEIF and STRICE projects (1999-2003). Analyses of time records from ice crushing indicate that the effective structural width should not be reduced from full width when predicting design ice loads.
New applications of continuous wavelet transforms have been presented using the Morlet wavelet for the detection of intervals with ice loads of resonant character. The typical length of intervals with ice-induced structural vibrations appeared to be from 1.9-8.6 seconds; however, one interval lasting for 80 seconds was also detected. Ice loads of resonant character were found to occur more frequently warmer the ice. A critical speed was also found. This critical speed seemed to be higher the thicker the ice. Studies of the initial phase of intervals with ice-induced vibrations also revealed two mechanisms that could cause steady-state vibrations, namely circumferential cracking and internal cracking.
Fourteen incidents of ice ridge actions on the Norströmsgrund lighthouse were selected to reveal more details about actions from ridged ice to a vertical structure. A keel-to-sail ratio of 8.2 was estimated with a keel depth evolution of -0.04 m/day during a period from 3 March to 4 April, 2002. Four different failure modes were detected together with an insignificant influence from the increasing keel depth on the highest measured loads.
In-situ and laboratory measurements were conducted on ridged and level ice from the Barents Sea and the Van Mijen fjord on Svalbard where the level ice generally was found to be stronger than consolidated ice in ridges. Vertical samples with ice columns in the loading direction were found to be stronger than horizontal samples. Consolidated ice from ridges had an equal hardness to level ice, but was harder than ice rubble.
Paper 1 reprinted with kind permission of Elsevier, sciencedirect.com
2
Grozdek, Marino. "Load Shifting and Storage of Cooling Energy through Ice Bank or Ice Slurry Systems modelling and experimental analysis /". Doctoral thesis, Stockholm : Skolan för industriell teknik och management, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11119.
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Nugroho, Widijanto Satyo. "Waves generated by a load moving on an ice sheet over water". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ32720.pdf.
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Karampour, Mazyar. "MEASUREMENT AND MODELLING OF ICE RINK HEAT LOADS". Thesis, KTH, Tillämpad termodynamik och kylteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-61330.
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Ice rinks are among the most energy intensive public buildings in developed and developing countries. According to a research on Swedish ice rinks; a typical ice rink consumes approximately 1185 MWh/year which leads to more than 300 GWh/year for the 342 Swedish indoor ice rinks. The refrigeration system is usually the largest consumer by 43% average share of the total energy consumption. To decrease the refrigeration system energy demand, there are a variety of energy efficiency techniques known and available but the key to select the best ones is finding the major heat loads on the ice sheet and refrigeration system, which is unique for each ice rink. To fulfil this objective and in addition to review literature, this study has two main approaches. The first approach is to measure and evaluate the performance of the refrigeration system in two ice rinks, called Norrtälje and Älta. The estimated cooling capacity is approximately equal to the total heat load on the ice plus the heat gains in the distribution system. This goal has been accomplished by using a performance analyser called “ClimaCheck” which is based on an “internal method” because it uses the compressor as an internal mass flow meter and consequently, there is no need for an external one. The refrigerant mass flow rate is calculated by an energy balance over the compressor. By knowing the mass flow, enthalpy of the refrigerant, etc. the cooling capacity and COP of the system can be calculated. While the total heat load is known by the first approach, the second approach tries to discover different heat loads shares by analytical modelling. The measured physical and thermodynamical parameters plus the ice rink geometrical characteristics are input to the heat transfer correlations to estimate the heat load magnitude. The results of the measurements show that the total energy consumption in Norrtälje is about two third of Älta. The main reasons for this less energy consumption are smarter control systems for compressors and pumps, better ventilation distribution design and 1°C-2°C higher ice temperature. Analytical modelling for a sample day has estimated that about 84% of the total heat loads is originated from the heat loads on ice sheet while the distribution system causes the remaining 16%. Moreover, calculations show that convection plus small portion of condensation (altogether 36%), radiation (23%), ice resurfacing (14%) and lighting (7%) are the largest heat loads in winter while in summer condensation is another significant heat load (10%). Comparing two six-hour periods, one without ice resurfacing and four resurfacings in the second one, 30% more cooling demand has been calculated for the second period. Furthermore, it has been shown that the evaporator to brine is the contributor for 66% of the heat transfer resistances from ice to evaporator while brine to bottom ice and bottom to top ice accounts for 27% and 7% respectively. To conclude, a parallel “performance analysis of the refrigeration system” and “heat loads estimation” proves to be a useful tool for adopting proper design and control for energy efficient operation.Stoppsladd financed by Swedish Energy Agency (Energimyndigheten) and Swedish Ice Hockey Association
5
Xiao, Jing. "Damage and fracture of brittle viscoelastic solids with application to ice load models". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0019/NQ47510.pdf.
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Moores, Corwyn E. W. "Shaft and blade load measurements on a highly skewed propeller model in ice". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ62405.pdf.
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7
Sundin, Eva. "Atmospheric icing : failure studies and ice load predictions on masts by weather station data". Licentiate thesis, Luleå tekniska universitet, 1995. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17222.
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Khalid, Waqas. "Energy Usage prediction model comparing Indoor Vs. Outdoor Ice Rinks". Thesis, KTH, Tillämpad termodynamik och kylteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-91164.
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Indoor ice rinks use 1091 MWh per annum for ice hockey based on statistics from over 100 Swedish ice rinks (Stoppsladd, 2011).The refrigeration system contributes 35 to75%( (Rogstam, 2010) of total energy usage in ice rinks with average value of 43% (Stoppsladd, 2010) for indoor to 75% for outdoor ice rinks. The basic aim of project is to reduce energy consumption in Swedish ice rinks and scope is for indoor and outdoor ice rinks in cold and mild summer climatic conditions like Sweden. To achieve target of energy reduction in ice rinks actual heat loads on outdoor bandy ice rink are being estimated along with performance analysis of refrigeration machine. The refrigeration system, heat loads on ice surface and their correlation is studied and analyzed in detail for Norrtälje Outdoor bandy ice rink for four warm days and whole season 2010-2011. The tricky and significant task of validation of input climate data for accurate heat loads calculations is completed with Swedish Metrological & Hydrological (SMHI) climate model data, correlations and related web based geographical data. The heat loads (conductive, convective and radiant) on outdoor bandy ice rink are calculated through thermodynamic relations with validated input climate data and measurements where as refrigeration system performance is monitored and analyzed with ClimaCheck(CC) instrumentation. The average cooling capacity is calculated for four warm days by CC internal method and actual cooling energy produced is obtained by practically assumed COP of system with aid of MYCOM compressor software. The cooling capacity and heat loads on ice surface are compared and analyzed considering energy usage affecting parameters and weather parameters like temperature, wind speed, relative humidity and solar load. The convection and condensation are contributing 75%, radiation 18%, ice resurfacing 4% and ground and header heat gain 3% to total heat loads on ice sheet for whole season. The deviation between total cooling energy produced by refrigeration machine and total heat load energy is found 19% and 27% for four warm days and whole season 2010-2011.The deviation is due to overestimation of heat losses from compressor’s body, compressor’s on and off operations, overestimated radiation heat load due to unmeasured negative radiation and lack of actual ice resurfacing heat load evaluation. The developed model in MS Excel allows comparison of field climate data with SMHI model data, indoor and outdoor ice rinks in terms of predicted energy usage by refrigeration system and in total and acts as decision tool to choose for building an indoor/outdoor ice rink.
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Mengistu, Meron Mulatu. "Study of Solar Cooling Alternatives for Residential Houses in Bahir dar city :". Thesis, KTH, Energiteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-63419.
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The energy consumption rate of non-OECD countries rises about 2.3 percent per year as compared to the energy consumption rate of OECD countries which is 0.6 percent. If developing countries use energy efficient technology and integrate renewable energy systems in the new building their carbon dioxide emission rate reduces by 25 to 44 percent. However, even now, renewable energy integrated buildings are hardly considered while constructing them. This thesis work focuses on the study of solar cooling system options for residential house in Bahir Dar city. To meet the demand of housing in the city, different type of apartments and villa houses are under construction. Case study was made focusing on two types of residential houses (condominium apartment and Impact Real-estate Villa house) to determine the cooling load and to select cooling system. Simulation results of IDA ICE software show that the average operative temperatures and cooling loads for condominium apartment and Real-estate Vila are 31.8oC and 30.7oC, 5.53 kW and 5.73 kW respectively. Most of the residences are not satisfied at this operating temperature. There are different types of solar cooling systems. Solar Sorption cooling systems are commonly used which can also be classified in to absorption, adsorption and desiccant cooling systems. Solar adsorption cooling systems are easy to manufacture locally as compared to solar absorption cooling systems. They do not have moving parts. Some of the working medium pairs used in adsorption cooling system are: Activated Carbon/Ammonia, Silica gel/ water, Zeolite/water. Adsorption chillier with Silica gel/ water as a working pair was selected since it can operate at regeneration/desorption temperature as low as 45oC coming from flat plate collectors. At 75oC regeneration temperature, the system delivers 9oC chilled water temperature. The selected solar adsorption chiller has been compared with kerosene based adsorption cooling system using HOMER software. In this project, the optimization was limited on cost comparison between the two energy sources. The solar based cooling system has lower working cost. From cooling load simulation result direct solar irradiation is the highest source of cooling load for both houses. This gives an opportunity for passive solar cooling technology.
10
Zuwak, Imal, e Wasseem Kordoghly. "Numerical study of the effect of thermal ice loads on concrete dams". Thesis, KTH, Betongbyggnad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-278545.
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It is essential to understand the mechanics of ice load and how it affects concrete dams located in a cold climate, such as Sweden, where the temperature becomes sufficiently cold to freeze the surface of the reservoir. The purpose of this thesis is to study ice load distribution along concrete dams, and its response during the application of an ice load. Two types of concrete dams were analysed, an arch dam and a buttress dam. For these dams, the influence from different parameters on the ice load distribution along the dams is studied. In addition to this, a study on how the ice load affects dam stability had also been performed. Stability analyses based on the finite element method were performed using both linear and nonlinear formulation of the interaction behaviour between the base of the dam and the underlying rock. A parametric study of ice sheet expansion on different dam types and geometries were performed. The expansion of the ice sheet was assumed to either be caused by a constant temperature 15 ˚C uniformly distributed over the ice thickness, or by a temperature gradient from 15 ˚C at the top surface of the ice sheet and 0 ˚C at the bottom. The parametric study also includes an investigation about influence of the shape of the reservoir beaches, where it either had a perpendicular shape towards the surface of the dam, or it had an angle of 30˚ with the dam surface. In the linear stability analysis, the structure continued to deform with increasing of the resultant pressure until it reached nonlinearity. The dam deflection had a linear relation with the applied ice load force until it reached the point when structure behaviour was nonlinear. The structure failed due to sliding, overturning or combination of both sliding and overturning. A material failure can also occur if the nonlinear material behaviour is considered, however this was not considered in this study. The parametric study showed that the ice load distribution was less near the beaches, and the distribution of the load on the concrete dam was higher near the top surface of the ice sheet. It was also shown in the study that the distribution of the ice load along the dam was as a cosine function where it had the maximum value at the buttress and the minimum at monolith connections. The result also showed that the load distribution over the thickness of the ice sheet was the same along the dam, regardless of the shape of the beaches or the length of the ice sheet.Det är viktigt att förstå hur islasten beter sig och hur den påverkar betongdammar som är belägna i kallt klimat, som t.ex. Sverige, där temperaturen blir tillräckligt låg för att frysa ytvattnet i en flod. Syftet med detta examensarbete är att studera isbelastningsfördelningen längs en betongdamm och dess respons under en belastningen. Två olika typer av betongdammar har analyserats, vilka är valvdamm samt lamelldamm. För dessa, studerades det hur olika parametrar påverkar lastfördelningen från istrycket längsmed dessa dammar. Slutligen har det studerats hur islasten påverkar dammsäkerheten och risken för dammbrott. Inverkan från interaktionen mellan dammen och det underliggande berget som linjär eller olinjärt har studerats i stabilitetsanalyser baserade på finita elementmetoden. En parameterstudie har också genomförts för olika dammtyper och geometrier där islasten orsakades av en expansion av isytan. Denna expansion antogs vara orsakad av antingen av en jämn fördelad temperatur över istjockleken på 15 ˚C, eller en temperaturgradient över istjockleken med +15 ˚C på den övre ytan och 0 °C vid isens bottenyta. Den parametriska studien beaktar även inverkan från utformningen av stränderna, där den har definierats som antingen vinkelrät mot dammen eller med en lutande vinkel på 30 grader. I fallet med linjära stabilitetsanalyser kommer konstruktionen att fortsätta att deformeras som ett resultat av ökande resulterande tryckkraft. Dammens deformation har ett linjärt förhållande med den applicerade islasten till dess att den når en punkt då strukturens beteende övergå till olinjärt. Strukturens brottmod kan uppstå på grund av glidning, stjälpning eller i en kombination av både glidning och stjälpning. materialbrott kan uppstå om icke-lineariteterna beaktas. Dammen gick till brott på grund av glidning, vältning eller i kombinationen av dessa då. Materialbrott kan uppstå om icke-linjära materialmodeller inkluderas, men detta beaktades dock ej i denna studie. Den parametriska studien visar att isbelastningen är mindre nära stränderna och att belastningen på betongdammen är högre vid isens ovanyta. Studien visar att islastfördelningen längsmed dammen liknar en cosinusfunktion som når sitt maximum vid stödskivan och sitt minimum vid monolitanslutningen. Resultatet visar även att islastfördelningen genom islastens tjocklek har samma form längsmed dammen oavsett utformningen av stränder eller istäckets längd.
11
Su, Chang. "Electricity Projection with Peak Load Shifting Strategy in Wuxi Sino-Swedish Eco-City". Thesis, KTH, Tillämpad termodynamik och kylteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-133920.
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Wuxi Sino-Swedish Eco-City, a pilot city region with an area of 2.4 km2, is a demonstration project for innovation in energy technology and integrated smart city solutions in China. After the 1st phase of the project, general outlines of the city’s energy system were drawn and applicable technologies are provided. However, no work has been performed on building electricity load projection and load analysis. This thesis will therefore firstly focus on establishing the building electricity load projection model, using simulation software STELLA. Then the model is scaled up for the whole city region. The simulation results show that there is foreseen to be electricity peak in summer and winter, due to the cooling and heating demand. Based on simulation results, an electricity DSM (demand side management) strategy should be implemented in order to balance the load. Peak load shifting strategy is thus chosen to be investigated. Two technology options (ice-storage system and thermal storage system), which could be implemented to balance the electricity peak, is analyzed by scenarios. Also, commercial feasibility of implementing such technologies is discussed.Wuxi Taihu Sino-Swedish Eco-City
12
Björkman, Helena. "Stabilitetsberäkningar och åtgärdsförslag vid islast på Skålandammen". Thesis, Uppsala University, Department of Earth Sciences, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9284.
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Hydropower is an important source of energy in Sweden and accounts for about 46 % of the total energy production. Sweden has about 1 200 hydropower plants and with the intention of raising the pressure head of the water and to store water, dams are built by the power plants. The storage reservoirs make it possible to adjust the energy production by demand and season. Dams in connection to the reservoirs are subjected to additional loading during periods of high floods or when an icecap in the winter is formed on the reservoirs. In order to maintain the dam safety, the power companies in Sweden are working with guidelines for dam safety from RIDAS. An important part of the work of dam safety is FDU that is carried out with purposes of improving the work of dam safety. A FDU made for the Skålan dam in the River of Ljungan showed that the levels of the safety factors for sliding and overturning of the dam was not fulfilled when subjected to loads from an icecap. The object of this thesis was to follow up the FDU and by carrying out extensive stability calculations on all parts of the Skålan dam, investigate what safety factors the different parts will get and also investigate some proposal measures in order to increase the dam stability.
The stability calculations for the dam have been performed according to directions in RIDAS at four loading cases. Loading case I and II means a water level to the retained water level and an ice load of 200 and 100 kN/m respectively. Loading case III and IV means a situation without ice load but with a water level to the retained water level respectively a water level to a meter above the retained water level. The stability of the dam was studied with regards to sliding and overturning. The results from the stability calculations showed for both loading case I and II that the majority of the parts of the Skålan dam did not fulfill the levels of the safety factors. The calculations also showed that some parts of the dam did not fulfill the stability criteria of sliding at loading case III, which implies that these parts of the dam actually have not enough weight.
The measure proposals studied were the ice preventive measures IR-elements and circulation of the deep warm water and the stability increasing measure with pre strained rock anchorages. The net present value (NVP) for the different measures were calculated with a life length of the dam estimated to 60 years. The results from the calculations of the NVP showed that the most economically feasible measure is circulation of the water but when considering the results from the stability calculations, the most suitable measure is the rock anchorages. Therefore, a combination of rock anchorages on parts which not fulfills the stability criteria in combination with circulation of the water is suggested to be the best measure.
Vattenkraften är en viktig energikälla i Sverige som utgör ca 46 % av den totala energiproduktionen. I Sverige finns det ca 1 200 kraftverk och i syfte att öka fallhöjden och lagra vatten bygger man dammar i anslutning till kraftverken. Dammarna skapar stora magasin med vatten och gör det möjligt att anpassa elproduktionen efter säsong och behov.
Dammar och kraftverk vid vattenmagasinen utsätts för extra belastning under perioder med höga flöden samt vid islaster och för att upprätthålla dammsäkerheten har man tagit fram RIDAS - kraftföretagens riktlinjer för dammsäkerhet. Inom ramen för dammsäkerhetsarbete utförs fördjupade dammsäkerhetsutvärderingar, FDU, för att arbeta förebyggande och hitta möjligheter till förbättring av dammsäkerhetsarbetet. I en FDU gjord för Skålandammen i Ljungan påvisades att de av RIDAS uppsatta säkerhetsfaktorerna för glidning och stjälpning inte uppfylldes vid islast. Syftet med detta arbete var att följa upp FDU:n och med utförliga stabilitetsberäkningar på Skålandammens alla delar (monoliter) undersöka hur dessa klarar säkerhetsfaktorerna vid olika lastfall, hur stort problemet med islast är samt ta fram åtgärdsförslag för att öka dammens stabilitet.
Beräkningarna har utförts enligt RIDAS anvisningar för stabilitetsberäkningar vid fyra olika lastfall där de två första innebär en vattennivå till magasinets dämningsgräns samt en islast på 200 respektive 100 kN/m och de två andra behandlar en situation utan islast men med en vattennivå till dämningsgränsen respektive en vattennivå till 1 meter över dämningsgränsen. Stabiliteten kontrollerades med avseende på stjälpning och glidning.
Resultatet av stabilitetsberäkningarna visade att för majoriteten av Skålandammens monoliter uppfylls inte stabilitetskraven vid en islast på vare sig 200 eller 100 kN/m. Det visades även att ett fåtal monoliter inte uppfyller säkerhetskraven för glidning vid lastfallet utan islast med en vattennivå till dämningsgränsen, vilket indikerar på att dessa monoliter är för lätta.
De isfrihållande åtgärdsförslagen som jämfördes var IR-element och cirkulering av vattnet med hjälp av luftbubblor och den stabilitetshöjande åtgärden med förspända bergförankringar. Nuvärdet för dessa åtgärder beräknades sedan med antagandet att dammen har en livslängd på 60 år. Resultatet från nuvärdesberäkningen visade att det billigaste alternativet är cirkulering av vattnet men utifrån stabilitetsberäkningarna är det mest fördelaktigt att använda den stabilitetshöjande åtgärden med bergförankringar. Med anledning av detta föreslås ett alternativ med bergförankringar på de monoliter som inte uppfyllde säkerhetskraven vid lastfall utan is i kombination med cirkulering av vattnet som den mest lämpliga åtgärden.
13
Al-Hadban, Yehya. "Demand-side management in office buildings in Kuwait through an ice-storage assisted HVAC system with model predictive control". Thesis, Cranfield University, 2005. http://hdl.handle.net/1826/3885.
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Examining methods for controlling the electricity demand in Kuwait was the main
objective and motivation of this researchp roject. The extensiveu se of air-conditioning
for indoor cooling in office and large commercial buildings in Kuwait and the Gulf
States represents a major part of the power and electricity consumption in such
countries. The rising electricity generation cost and growing rates of consumption
continuously demand the construction new power plants. Devising and enforcing
Demand-SideM anagemen(t DSM) in the form of energye fficient operations trategies
was the response of this research project to provide a means to rectify this situation
using the demand-side management technique known as demand levelling or load
shifting. State of the art demand-sidem anagementte chniquesh ave been examined
through the developmenot f a model basedp redictive control optimisations trategyf or
an integrateda ndm odulara pproachto the provisiono f ice thermals torage.
To evaluate the potential of ice-storage assisted air-conditioning systems in flattening
the demand curve at peak times during the summer months in Kuwait, a model of a
Heating, Ventilation, and Air-conditioning (HVAC) plant was developed in Matlab. The
model engaged the use of model based predictive control (MPQ as an optimisation tool
for the plant as a whole. The model with MPC was developed to chose and decide on
which control strategy to operate the integrated ice-storage HVAC plant. The model
succeeded in optimising the operation of the plant and introduced encouraging
improvement of the performance of the system as a whole.
The concept of the modular ice-storage system was introduced through a control zoning
strategy based on zonal orientation. It is believed that such strategy could lead to the
modularisation of ice-storage systems. Additionally, the model was examined and tested
in relation to load flattening and demonstrated promising enhancement in the shape of
the load curve and demonstrated flattened demand curves through the employed
strategy. When compared with measured data from existing buildings, the model
showed potential for the techniques utilised to improve the load factor for office
buildings.
14
Cheemakurthy, Harsha. "Efficient commuter craft for urban waterborne public transportation". Licentiate thesis, KTH, Marina system, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-287834.
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There has been a recent surge in interest in waterborne public transportation (WPT). Publictransport providers (PTP) are seeing its potential in complementing the existing transportnetwork and alleviating urban traffic congestion and pollution. But the adoption of WPTtoday is challenging due to a series of technical and implementation challenges. Thesechallenges include ferry procurement practices, local legislation and policies andenvironmental factors like winter ice. Several of these challenges can be alleviated if efficientferries can be made accessible off-the-shelf with a low manufacturing time and cost. Thethesis focuses on developing such a ferry concept based on modular design whose overalldimensions are standardized and internal arrangement is customizable towards operationalrequirements, with a focus towards sustainable and safe operations in ice.Starting with the characterization of WPT, ferry routes are broadly classified into three types.These routes are described with an operational requirements framework considering allrelevant stakeholder expectations. Then, overall dimensions of vessels representative ofWPT are deduced. Using these dimensions to standardize the overall dimensions, a modularferry concept is developed as an assembly of modules and submodules. The modules arepresented as standardized units having fixed dimensions and interfaces whose internalarrangements can be tailored to meet operational requirements. Design standardizationlowers costs and manufacturing time while internal customization favours tailoring the ferryconcept. One challenge associated with this for the PTP is the difficulty in choosingappropriate modules among multiple alternatives. This is overcome through thedevelopment of a ranking and selection method which benchmarks competing designs andhelps in decision making.In terms of technical challenges for the developed ferry concept, cities like Stockholmexperience freezing of water bodies during winter months. For reliable year-roundoperations that are safe and sustainable in terms of economy and environment, there is aneed for the development of lightweight and robust ice going hulls. This thesis lays thefoundation for the development of such hulls by studying the prevalent ice data and proposesa probabilistic method for estimating the design ice pressures.One must rely on probabilistic methods since most experimental studies are based on seaice whose mechanical properties are different from freshwater ice, which is typical for WPT.Traditionally, classification society rules like the Finnish Swedish Ice Class Rules are usedfor first year light ice conditions which were developed for the Baltic Sea consideringicebreaker vessels. They work well in ensuring a safe design, but their performance forfreshwater ice, applied to commuter ferries have not been tested. Therefore, a probabilisticapproach is adopted where the unknown parameters are incorporated as random variables.The probabilistic method reduces the hull-ice interaction to a pressure and contact-arearelationship. With arctic datasets that closely match WPT conditions as the parent dataset,the probabilistic method is calibrated with exposure conditions for WPT to give the designpressure-area curve. The different uncertainties arising from operations in ice are studied using a statistical tool and the leading source of uncertainty is attributed to ice-loadprediction methods. This establishes the need for more robust methods for prediction of iceloads so that a lightweight, yet robust hull may be designed which is efficient in terms of fueleconomy and emissions.WPT presents a tremendous opportunity in complementing the existing transport network.With careful design and development of the modular ferry concept and its technicalchallenges, it would be easier for PTPs to adopt WPT globally.De senaste decenniet har intresset ökat för kollektivtrafik på vatten (WPT).Kollektivtrafikleverantörer ser potential att minska trängsel och utsläpp och tillförakapacitet genom att utnyttja de urbana vattenvägarna. Men realiseringen har utmaningar,så väl tekniska som relaterade till regelverk och systempraxis. Dessa omfattar inköp av färjoroch upphandling av vattenburen trafik, lokal lagstiftning och policyer, miljöfaktorer ochdessutom isen vintertid. Flera av dessa utmaningar kan hanteras om effektiva färjor kangöras lättillgängliga med kort tillverkningstid till ett pris i paritet med övrig kollektivtrafik.Avhandlingen fokuserar på att utveckla ett färjekoncept baserat på modulär design medövergripande, standardiserade, dimensioner och med möjlighet att anpassa inredningenefter operativa krav.Efter karaktäriseringen av WPT klassificeras färjerutter i tre kategorier. Dessa rutterbeskrivs i ett operativt ramverk som beaktar relevanta intressenters förväntningar. Därefterbestäms de övergripande dimensionerna för WPT fartyg. Baserat på dessa utvecklas ettmodulärt färjekoncept som en sammansättning av moduler och delmoduler. Modulerna harstandarddimensioner och gränssnitt så att arrangemang kan skräddarsys för att uppfyllaaktuella operativa krav. En utmaning med det modulära färjekonceptet är svårigheten attbedöma vilken kombination av moduler som är bäst när det finns många möjligakombinationer som uppfyller en kravprofil. För att hantera detta utvecklas en rankningsochurvalsmetod för att kunna jämföra konkurrerande lösningar och därmed ge stöd i valetav design.En teknisk utmaning i städer som Stockholm är isen vintertid. För tillförlitlig trafik, åretrunt, som är både säker och hållbar, ekonomiskt och miljömässigt, finns det ett behov avutveckling av lätta och starka skrov som tål att operera i is. Avhandlingen närmar sigutvecklingen av sådana skrov genom att föreslå lämpliga isdata och en sannolikhetsbaseradmetod för att uppskatta dimensionerande isbelastningar.Is för nordiska WPT förhållanden är vanligtvis sötvattensis, vars mekaniska egenskaperskiljer sig från havsis. De flesta studier som beskriver isegenskaper är experimentella ochbaserade på havsis där man måste förlita sig på probabilistiska metoder för att ta hänsyn tillosäkerheter. Traditionellt används regler från klassificeringssällskap, som de finsk-svenskaisklassreglerna FSICR för första års isförhållanden vilket utvecklats för Östersjön ochisbrytande fartyg. Reglerna fungerar för att säkerställa en säker konstruktion men hur välde är anpassade för att dimensionera effektiva pendelfärjor i sötvattenis har inte utretts. Iavhandlingen antas ett probabilistiskt tillvägagångssätt där de okända parametrarna antassom slumpmässiga variabler. Den probabilistiska metoden förenklar interaktionen mellanskrov och is till ett förhållande mellan tryck och kontaktyta. Med publicerad data, som näramatchar WPT-förhållanden, som bas, kalibreras den probabilistiska metoden tillexponeringsförhållanden för WPT för att formulera den dimensionerande tryck-kurvan. Deolika osäkerhetsfaktorerna vid operation i is studeras med statistisk analys som visar att denfrämsta källan till osäkerhet är just förutsägelsen av isbelastningen. Detta fastställer behovet av mer robusta metoder för förutsägelse av isbelastningar så att ett lätt, men ändå starktskrov kan utformas som är effektivt med avseende på bränsleekonomi och utsläpp.WPT ger stora möjligheter att komplettera ett befintligt kollektivtrafik nätverk. Mednoggrann design och tillämpning av det modulära färjekonceptet kan det bli enklare att tatillvara möjligheterna runt om i världen.
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Sultan, Sahira. "Cost Evaluation of Building Space Heating; District Heating and Heat Pumps". Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-37137.
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Climate change and energy efficiency has become a matter of concern in recent times; therefore, energy efficiency of buildings has drawn major attention. According to the European Commission, EU countries must improve energy efficiency of existing buildings by retrofitting and renovating the buildings. A case study of a renovated commercial building is considered in this degree project. A model of the building is developed in the IDA Indoor Climate and Energy (IDA ICE) software. The model is then augmented to include renovations in the building. Further, the model is simulated in IDA ICE before and after renovations to investigate the impact of renovations on energy consumption of the building for one year. The simulation results indicate peak demands of district heating that occur in the coldest days of the year. The peak demands of energy are expected to increase the district heating cost because they serve as a basis for new pricing model introduced by the energy providers. Hence, it is important from the customer point of view to reduce the peak loads for cost shavings. The project work also provides an insight into the alternative source of energy such as heat pumps to reduce the peak load demands of district heating.
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Klasson, Svensson Emil, e Anton Persson. "En statistisk analys av islastens effekt på en dammkonstruktion". Thesis, Linköpings universitet, Statistik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-129963.
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En damm används i huvudsak för att magasinera vatten i energiutvinningssyfte. Dammen rör sig fram och tillbaka i ett säsongsmönster mestadels beroende på skillnader i utomhustemperatur och vattentemperaturen i magasinet. Det nordiska klimatet innebär risk för isläggning i magasinet, för vilken lasten är relativt outforskad. Denna rapport syftar till ett med multipla linjära regressionsmodeller samt dynamiska regressionsmodeller avgöra vilka variabler som förklarar en specifik svensk dammkonstruktions rörelse. Dammens rörelse mäts genom att mäta dammens förflyttning kontra berggrunden med data från dammens inverterade pendlar. Av särskilt intresse är att avgöra islastens påverkan på rörelsen. Resultaten visar att multipla linjära regressions-modeller inte fullständigt lyckas modellera dammens rörelse, då de har problem med autokorrelerade residualer. Detta hanteras med hjälp av autoregressiva regressionsmodeller där de initiala förklarande variablerna inkluderas, kallat dynamisk regression. Denna rapports resultat visar att de autoregressiva parametrarna fungerar mycket väl för att förklara pendlarna, men att även tid, temperatur, det hydrostatiska trycket samt istjocklek är användbara förklarande variabler. Istjockleken visar signifikant påverkan på 5 % signifikansnivå på två av de undersökta pendlarna, vilket är ett noterbart resultat. Författarna menar att rapportens resultat indikerar att det finns anledning att fortsätta forska kring islastens påverkan på dammkonstruktioner.A dam is a structure mainly used for storing water and generating electricity. The structure of a dam moves in a season-based pattern, mainly because of the difference in temperature between the air on outside of the dam and the water on the inside. Due to the Nordic climate, occurrences of icing on the water in the basin is fairly frequent. The effects of ice on the structural load of the dam are relatively unexplored and are the subject to this bachelor’s thesis. The goal of this project is to evaluate which predictors are significant to the movement of the dam with multiple linear regression models and dynamic regressions. The movement is measured by inverted pendulums that register the dam’s movement compared to the foundation. It is of particular interest to determine if the ice load influences the movement of the dam. The multiple regression models used to explain the dam’s movement were all discarded due to autocorrelation in the residuals. This falsifies the models, since autocorrelation means that they don’t meet the needed assumptions. To counteract the autocorrelation, dynamic models with autoregressive terms were fitted. These models showed no problem with autocorrelation. The result from the dynamic models were successful and managed to significantly explain the movement of the dam. The autoregressive terms proved to be efficient explanatory variables. The dynamic regression models also show that the time, temperature, hydrostatic pressure and ice thickness variables are also useful explanatory variables. The ice thickness shows a significant effect at the 5 % significance level on two of the investigated pendulums. The report's results indicate that there is reason to continue research on the ice load impact on dam constructions.
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Kárník, Miroslav. "Zimní stadion". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392216.
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The goal of the diploma thesis is to design and assess a steel structure of ice stadium in Česká Třebová. The ground plan dimensions of the load–bearing structure are 66 meters in width and 66 meters in length. The maximal height of the structure is 15 meters. The main frames are made of truss girders of elliptical shape. The girders are pin–supported on solid columns on both sides. The distance between the main frames is 6 meters, the distance between the solid purlins on the girder is 3 meters. There are two variants designed and compared in the thesis. In the first variant there are two-dimensional truss girders in the main hall, whereas in the second variant they are replaced with three dimensional ones.
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Belozaras, Evaldas. "Ledo apkrovų įtaka tvenkinių šlaitų gelžbetoninėms tvirtinimo plokštėms". Master's thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20090603_100405-96922.
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Tvenkinių šlaitų tvirtinimo plokščių būklę, ilgaamžiškumą lemia jas veikiantys poveikiai ir apkrovos, susidarantys veikiant klimato sąlygoms, agresyviai aplinkai bei kitiems įvairiems veiksniams. Darbo tikslas – įvertinti Lietuvos tvenkiniuose susidarančias ledo apkrovas ir jų įtaką šlaitų tvirtinimo gelžbetoninėms plokštėms. Šiam tikslui pasiekti buvo atlikta literatūros analizė, siekiant nustatyti ledo apkrovų tipus. 2008 – 2009 m. mokslinių ekspedicijų metu natūriniais tyrimais įvertinta 14 tvenkinių šlaitų tvirtinimo gelžbetoninių plokščių būklė pagal STR.1.12.03:2006. Remiantis literatūros ir natūrinių tyrimų rezultatų analize, nustatyta, kad tvenkinių šlaitų tvirtinimo gelžbetoninės plokštės labiausiai ardomos dėl ledo poveikio. Detalesniam tyrinėjimui parinktos 4 tvenkinių plokštės, kurių suardymo pobūdis leidžia teigti, kad šlaitų tvirtinimo plokštės buvo suardytos veikiant ledo apkrovoms. Darbe ledo poveikis analizuotas vertinant prie tvenkinių šlaitų tvirtinimo plokščių prišalusio ledo vertikaliąją apkrovą Fd ir susidarantį lenkimo momentą M dėl pažemėjusio vandens lygio. Atlikus ledo apkrovos kintant vandens lygiui analitinius skaičiavimus, sudaryta šlaitų tvirtinimo gelžbetonines plokštes veikiančios apkrovos dydžio priklausomybė nuo ledo storio. Nustatyta, kad tvenkinių ledo apkrovos labiausiai priklauso nuo ledo storio – didėjant ledo storiui bendruoju atveju ir ledo apkrovos didėja.The state and durability of the slabs strengthening slopes of the ponds are influenced by the impacts and loads occurring because of the climatic conditions, aggressive environment and other various factors. The aim of the work is to assess the ice loads that occur on the Lithuanian ponds and their influence on the concrete slabs strengthening slopes. To achieve this objective, analysis of the literature was performed to determine the types of ice loads. The state of 14 concrete slabs was evaluated by field investigations in accordance with STR. 1.12.03:2006 during the scientific expeditions in 2008-2009. In accordance with the literary and field investigation analysis, it was found out that the concrete slabs strengthening the slopes of the ponds are mostly damaged by the influence of the ice. 4 slabs of the ponds were chosen for the more detailed research. The character of the damage allows proposing that the strengthening slabs were influenced by the ice loads. In the research the effect of the ice was analyzed estimating the vertical load of the ice frozen on to the slabs strengthening slopes of the ponds Fd and bending moment M emerging because of the dropped level of the water. After analytical calculations of the ice load, when the water level is changing, were performed, the dependence of the load size on the thickness of ice was made. It was determined that ice loads of the ponds mostly depend on the thickness of the ice –in general case, when the ice is getting... [to full text]
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Andersson, Oskar, e Max Seppälä. "Verification of the response of a concrete arch dam subjected to seasonal temperature variations". Thesis, KTH, Betongbyggnad, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-169917.
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Many dams existing today were constructed around fifty years ago. Condition monitoring is essential for maintaining high safety and determining the current level of safety and stability for these dams. There is a need for new monitoring techniques and finite element coupled monitoring could be one of these techniques. A concrete arch dam located in Sweden is modelled and calibrated with respect to concrete temperature measurements. The temperature distribution is then defined as a prescribed strain in a structural mechanical model in which a parametric study is performed. The results from the parametric study are compared to measurements of the crest deformation and a combination of parameters is found giving the lowest difference between measurements and model results for the mid-section. The results show that the finite element model can be used to predict the behavior of the dam with acceptable deviation. The parametric study indicates that the reference temperature of the concrete has little effect on the amplitude of the deformation and that the governing factor is the coefficient of thermal expansion.Många av de dammar som finns idag byggdes för omkring femtio år sedan. Tillståndsövervakning är avgörande för att kunna bestämma nivån av säkerhet och stabilitet för dessa dammar. Det finns ett behov av ny övervakningsteknik och finita element-kopplad övervakning kan vara en av dessa tekniker. En betongvalvdamm modelleras och kalibreras med avseende på uppmätt betongtemperatur. Den beräknade temperaturfördelningen definieras sedan som en föreskriven töjning en strukturmekanisk modell i vilken en parametrisk studie utförs. Resultaten från parameterstudien jämförs med mätningar av kröndeformation och en kombination av parametrar identifieras som ger lägsta skillnad mellan mätningar och modellresultat för mittsektionen. Resultaten visar att modellen kan användas för att förutsäga dammens beteende med acceptabel avvikelse. Parameterstudien indikerar att referenstemperaturen för betongen har liten inverkan på amplituden för deformationen och att den styrande faktorn är längdutvidgningskoefficienten.
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El-Fashny, Kamal. "Modeling ice loads using passive ice meter obervations in Quebec". Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82865.
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Climatic loads (wind speed and ice accumulation) are the main factors that govern the planning and design of telecommunication towers and electric transmission lines. Whilst wind loads are covered comprehensively in the literature and in design standards, ice loads and rules for combination of wind speed on ice-covered-structures are still in development. The main difficulty in achieving a design that meets a target reliability level as specified in design codes is the uncertainty in the temporal and spatial variation of ice accretion. Due to the lack of sufficient direct field measurements, empirical models are usually utilized in combination with meteorological data to estimate the intensity of ice accumulation at specific locations.A unique database of direct measurements on ice accumulation is available in Quebec. More than 20 years of observations from a network of 180 Passive Ice Meters (PIM) are available throughout the province. The objective of this study is to analyze this data set in order to improve existing regional design criteria and for better understanding of the atmospheric icing phenomena in Quebec. The research is limited to the study of glaze ice, which occurs in conjunction with freezing precipitation.
Firstly, several extreme-value statistical models are investigated to determine the best one or ones for describing the intensity of glaze ice accumulation. In order to increase the sample size, an event-based model, in which every icing event is counted as an independent event, is adopted. Twelve probability distribution functions are examined. The distributions are compared on the basis of the overall fit to the data and the sampling characteristics of the right tail of the distributions. No single distribution fits the data perfectly at all stations. However, the three-parameter distributions, and in particular, the Pearson type III, Generalized Pareto, Generalized Normal, and Generalized Extreme-Value distributions are the best on average. The commonly used Gumbel distribution is consistently outperformed by the three-parameter distributions.
Secondly, a reliability-based procedure is proposed for the analysis of the combined wind and ice loads and in particular for associated pressure on overhead transmission lines. Finally, a procedure for the spatial interpolation of design criteria is investigated. Spatial interpolations of the design ice thickness for a 50-years return period is performed using Kriging.
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Holm, Herman. "Ice-Induced Loads on Ship Hulls". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18651.
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The calculation of ice-induced loads on ships is still mainly based on empirical models. In order to gain a better physical understanding of the loading on ice-going vessels, Det Norske Veritas launched an <i>ice load monitoring<i> project involving full scale trials with the coastguard vessel KV Svalbard during the winters 2006, 2007 and 2011. The results from the full scale measurements conducted with KV Svalbard has been topic of several earlier master's thesis at NTNU,The master thesis consists of four parts. The first part is a literature review of the mechanical and physical properties of sea ice.The second part is a review of the rule sets developed by DNV and the IACS regarding vessels operating in ice infested waters. Both design principles and numerical values have been evaluated. The main difference between the designs principles used, is that IACS base their rules on a plastic method of approach, while DNV uses an elastic method. Despite the difference in the design principles, when comparing their numerical values turned out to be quite similar. The DNV rules are in general most conservative for the smaller vessels and the IACS rules the most conservative for large vessels. The third part consists of a finite element study of a part of the bow on KV Svalbard. A systematic load scheme is used, consisting of 102 load cases. For each of the stress factors there where made graphs that showed the stress at the sensor location when moving the patch load. The sensor mounted on the frame were able to measure load that was within the frame loading area and sensor mounted on the stringer could measure stress for all of the load cases in the horizontal directions. One of the explanations for this is that the stringer transfers stress from the load patch area that could be measured by the sensors.The last part consists of a comparison between measurements from the full scale trials and the results from the 102 load cases. This comparison is done through a weighted summation method where 5 different load cases are combined to represent the measured result, and a load factor is calculated for each load case for its contribution of the measured results. The stress component used in this comparison is the shear stress tau xy The load cases were tested against the 11 measurements from the full scale trials. There were in total 11 load cases that gave positive factors for all of the 11 measurements at the same time. A figure was made to show which load cases were likely to contribute in the solution of the load cases. Load cases inside the frame loading area have the largest load factors for the solution of measurements.This load decision scheme is very sensitive to the selection of load cases and boundary conditions. A change of the boundary conditions for the model was tried out for 7 load cases, and with changed boundary conditions, only 5 gave positive load factors.The results of this thesis shows that is possible to find many solution to the measured result by combining many load case, but is it not possible to decide <i>the<i> solution.
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Varma, Gottumukkala Chandrasekhar. "Ice loads on propellers under extreme operating conditions". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0030/MQ62437.pdf.
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Fjellvang, Heidi. "Prediction of ice loads of an Arctic SPAR". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-15737.
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Asubstantial amount of the world’s hydrocarbon deposits is assumed to be found in the Arctic. The Arctic region differs from other regions mainly due to the climate and presence of sea ice features. In order to minimize the ice loads from the drifting ice, structures with sloping waterline geometry have been introduced to the marked. The breaking angle in the waterline allows the ice to fail in a flexural mode, and to further transport the broken ice pieces around the hull. A numerical model for estimation of the level ice loads acting on a sloping structure in the time-domain has been developed based on the existing methodology given in the new ISO 19906 standard on Arctic Offshore Structures. The numerical model has been corrected based on actually measured time series and videos recorded from an ice test campaign performed in the Aker Arctic Technologies ice model tank.
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Berggren, Axel, e Ebba Lindh. "ICE LOADS AND RESISTANCES ON A SMALL COMMUTER VESSEL : A comparative study of rule based design and analytical ice loads and resistances". Thesis, KTH, Marina system, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-162063.
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The aim of the thesis is to investigate what the results are when applying DNV ice class design rules on a vessel that falls outside the validity range and how it does compare to direct calculations. The vessel to be investigated is a smaller ice going commuter ferry intended for freshwater Lake Mälaren in Stockholm. Due to increased need of public transport in the area, political decisions have been made to incorporate ferry lines in the public transport system. The number of commuters’ peak during January and February and it is thus necessary to design a ferry that works all year around, in all possible weather conditions, including the ice conditions that occur winter time (Rindeskär, 2014). In order to make a comparative study of the DNV ice class and direct calculations with regards to resistances and structural loads on the hull, a general arrangement of the ferry is developed. Icebreaking resistance models based on DNV ice class (Det Norske Veritas, 2014), Riska (Riska, Willhelmson, Englund, & Leiviskä, 1997) and Lindqvist (Lindqvist, 1989) can be compared based on the ferry’s main data. The bow section of the hull is designed to handle the DNV design pressure according to DNV ice class 1C. The structural response is investigated using a finite element model, applying different load cases given from DNV as well as from the studied semi empirical ice load models mentioned above. The bow design is of great importance for the icebreaking performance and the speed. The greater the stem angles the higher the resistance. A large variation in the results was also noted as only Lindqvist’s model took the freshwater ice properties into account. Further measurements have to be made in freshwater for smaller vessels to validate the results. In the FE-analysis it was seen that the hull structure coped well with the DNV design pressure of 1 MPa. However, the empirical design pressure of 1.5 MPa resulted in too high stresses in the structure. The result indicates that the design rules work well for the intended design pressure, but the minimum empirical design pressure is still higher than the DNV design pressure for the commuter vessel. It can be that the DNV design rules can be used in the case of the ferry, but further investigations has to be made with regards to minimum design pressure. In general, the results can be used as a basis for further investigations in the field of vessels operating in freshwater ice conditions.
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Su, Biao. "Numerical Predictions of Global and Local Ice Loads on Ships". Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14506.
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Ice loads represent the dominant load for ice-going ships, and it is important to estimate both global and local ice loads on ship hulls. The global ice load governs the ship’s overall performance in ice, and it is an integrated effect of local ice loads over the hull area. Information on the distributions of local ice loads around the hull can be used for more effective design of ice-going ships both in terms of overall operation and from the structural point of view. The present thesis focuses on a numerical model for simulating ice–hull interaction and ship maneuvers in level ice. This model is partly based on the empirical data, by which the observed phenomena of continuous icebreaking can be reproduced. In the simulation of a full-scale icebreaking run, the interdependence between the ice load and the ship’s motion is considered, and the three degree-of-freedom (DOF) rigid body equations of surge, sway and yaw are solved by numerical integration. The thickness and strength properties of the ice encountered by the ship are assumed to be constant or predefined based on the statistical data. Accordingly the global and local ice loads on ship hulls can be obtained in a deterministic or probabilistic way. The convergence tests are carried out to make sure that this numerical method can give a convergent solution of both global and local ice loads. The computation time is also examined with the purpose of determining a balance between the computation time and the convergence. The influences of the assumptions and simplifications made in this numerical model are analyzed by changing different parameters and comparing with an empirical method and the measured data. The simulation results are discussed through three case studies, in which the global ice load effects on ship’s performance, the probabilistic and spatial variations of local ice loads around the hull and the short-term distribution of maximum ice loads on a frame are respectively analyzed and compared with field measurements conducted in the Baltic Sea. The ship’s performance in level ice is usually described by the speed that the ship can attain in the ice of a certain thickness. A case study with an icebreaker, Tor Viking II, is carried out by using the simulation program. In this study, the ice encountered by the ship is assumed to be uniform. The ship’s motion is obtained by solving the equations of motion in which the thrust and the global ice load both are identified. The speed that the ship can attain is then simulated in the ice of different thicknesses. The simulation results agree well with the full-scale measurements. The turning circle diameter which is a measure of the ship’s maneuverability in ice is also investigated by using the simulation program. Herein the ship is assumed to turn freely with a given rudder angle, and the simulated turning circles are comparable to the full-scale ice trials. It is also found that the ship’s performance can be considerably affected by the geometry of simulated icebreaking patterns. If the shoulder crushing takes place (i.e. the ice is continuously crushed by hull shoulder without bending failure) both the forward speed and the turning rate of the ship will be significantly slowed down. This phenomenon is also observed in full-scale trials, but it is difficult to learn about its effect on ship’s performance as the actual ice conditions in-service usually are uncontrollable. It is expected that numerical simulations can supplement full-scale tests in providing more details about the continuous icebreaking processes and the global ice load effects on ship’s performance. The local ice loading process has a clear stochastic nature due to variations in the ice conditions and in the icebreaking processes of ships. A case study with an icebreaking tanker, MT Uikku, is carried out by using the simulation program. In this study, the thickness and strength properties of the ice encountered by the ship are assumed to be constant or randomly generated using the Monte Carlo method. It is found that the variation of simulated ice loading process on a frame is noteworthy even if the ice properties are fixed. If the statistical variation of the ice conditions is considered, then the distributions of simulated load peaks are found to be comparable to the measured statistical distributions. In this case study, the spatial distribution of local ice loads around the hull is also investigated. The simulation results agree with previous experimental studies, that the turning operation may develop a high load level on the aft shoulder area. Ice conditions and ship operations in ice vary in the short term from voyage to voyage and in the long term from winter to winter. Long-term ice load measurements conducted in the Baltic Sea consist mainly of 12-hour load maxima which are gathered during the normal operation of the ship over several years. A case study with a chemical tanker, MS Kemira, is carried out by using the simulation program. In this study, the statistical data on the strength properties of Baltic Sea ice are applied and the thickness of the ice encountered by the ship are classified referring to the full-scale measurements onboard MS Kemira. The 12-hour maximum ice loads on a frame are evaluated by fitting a Gumbel I asymptotic extreme value distribution to the simulated 10-min load maxima in a certain ice condition. It can be expected that if a reasonable variance of the ice thickness is defined, the simulation results can be used for a preliminary estimation of the maximum ice loads within a 12 hours’ voyage in level ice. By applying the different ice thicknesses in simulations, the probable correlation between the simulated load maxima and the ice thickness is analyzed. A potential way to evaluate the long-term ice load statistics based on short-term simulations is then introduced. Up to now the main source of knowledge about ice load statistics has been field measurement. While field measurements will continue to be important, numerical methods can provide useful information, since they can be easily used to study the effect of different parameters. As far as we know the present numerical model is the first one to deal with multiple subjects including the ice–hull interaction, the overall performance of icebreaking ships and the statistics of local ice loads around the hull. It is hoped that further studies on this numerical model can supplement the field and laboratory measurements in establishing a design basis for the ice-going ships, especially for ships navigating in first-year ice conditions
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Šadzevičius, Raimondas. "Aplinkos poveikio žemių užtvankų šlaitų tvirtinimo gelžbetoninėms plokštėms modeliavimas ir analizė". Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2005. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2005~D_20051108_145159-47758.
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In the dissertation evaluated frost influence to the change of physical–mechanical properties of the reinforced concrete slabs for earth dam slope protection. Established ice thermal expansion linear load acting the slabs and proposed more exact calculation of this load. Evaluated deterioration indices and defects influence to slabs state and durability.
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Wells, Eric M. "An Assessment of Surface Ice Sheet Loads and Their Effects on an Offshore Wind Turbine Structure". University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1345214125.
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Kharik, Ekaterina. "Numerical simulations of thermal loads exerted on dams by laterally confined ice covers". Doctoral thesis, Université Laval, 2018. http://hdl.handle.net/20.500.11794/29824.
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Les barrages hydro-électriques construits dans les climats froids subissent des poussées des glaces importantes. Ces charges doivent être prises en compte pour l’évaluation de la sécurité de ces structures. Bien que les barrages aient été construits et exploités dans différents pays pendant de nombreuses années, il n’y a pas de consensus sur les critères de charge de glace. Les valeurs de conception varient considérablement – plus de 3 fois d’une autorité internationale à l’autre. La nature complexe des poussées des glaces implique de nombreux facteurs et incertitudes qui empêchent encore la pleine compréhension des processus en jeu, malgré les avancées récentes. Cette recherche doctorale vise à donner une nouvelle approche aux calculs des poussées des glaces sur les barrages et, ainsi, faire progresser l’objectif d’harmonisation des critères de conception pour les poussées des glaces. L’approche méthodologique de cette recherche consiste à compiler les modèles existants de comportement rhéologique de la glace et les inclure dans la simulation numérique des principaux événements historiques de poussées des glaces mesurés au Canada. La construction d’un modèle numérique commence par un choix de processus et d’hypothèses clés, ainsi que par des modèles rhéologiques à inclure. Par conséquent, une revue compréhensive de la littérature sur le comportement rhéologique de la glace a été réalisée. Cette thèse décrit un modèle de fluage 3D du comportement rhéologique pour deux types de glace (glace columnaire et glace de neige). Le modèle construit peut être implémenté dans un logiciel d’éléments finis pour simuler le comportement de la glace sous les charges statiques. Au cours du projet, le logiciel ANSYS a été utilisé pour construire un modèle d’éléments finis pour des simulations d’événements mesurés. Le modèle d’éléments finis a été validé et étalonné par rapport à des expériences en laboratoire provenant de la littérature. Par la suite, il a été utilisé dans la simulation d’événements de poussées des glaces sur des barrages au Canada. Seule expansion thermique de la glace a été simulée par le modèle d’éléments finis. Les fluctuations de niveau d’eau ont été indirectement incluses dans le modèle par la simulation de la glace confinée latéralement. L’influence de différents facteurs sur la poussée des glaces simulées a été étudiée. Les conseils et les lignes directrices pour le choix et l’implémentation du modèle rhéologique de fluage dans un logiciel d’éléments finis commercial sont également fournis. La thèse est basée sur des résultats d’études qui ont été publiés dans deux articles de colloques et dans un article de journal. La thèse inclut l’introduction des poussées des glaces sur les barrages, les objectifs du projet, les revues de littérature sur les processus influents des poussées des glaces, sur les propriétés rhéologiques des deux types de glace fréquents sur un réservoir et la modélisation du comportement de la glace, ainsi que la présentation des données de terrain, la description du modèle, les études non encore publiées, la conclusion et les recommandations. La thèse discute du lien entre les expériences en laboratoire sur la glace et les mesures in situ des poussées des glaces sur les barrages. L’étude documente le fait que le fluage élastique retardé de la glace a un effet limité sur les poussées des glaces résultantes pour les grandeurs de grains de 3 mm à 20 mm, et son calcul peut être omis dans des évaluations approximatives des poussées des glaces avec cettes grandeurs de grains moyennes. Il est également montré que la variabilité du coefficient de dilatation thermique de la glace avec la température n’est pas importante pour les températures étudiées. L’importance des conditions initiales et du comportement de la glace en tension pour les poussées des glaces résultantes est également montrée. La thèse met l’accent sur l’importance de la considération correcte du confinement latéral et du type de glace pour les calculs de poussées des glaces sur les barrages. Il a été montré que la hausse du niveau d’eau et le confinement latéral de la glace peuvent produire très grandes forces de poussées, si la glace est principalement columnaire. De ce fait, il devient important d’évaluer la possibilité d’avoir des hivers secs ayant peu d’accumulation de neige sur la glace (les conditions favorables à la formation de la glace columnaire) pour la sélection de la charge de conception.Hydroelectric dams are subjected to ice loads in cold climates. Withstanding such loads is an important safety requirement for the structures. Although dams have been built and operated by different countries for many years, there is no consensus on a design ice load criteria. Design values vary considerably – by more than 3 times from one international authority to another. The complex nature of ice loads involves many factors and uncertainties that still prevent the full understanding of ice field processes in spite of much progress done in this direction. This doctoral research aims to give new insights into reservoir ice loads, and, thus, to move forward the objective of harmonization of ice load design criteria. The main approach of this research is a compilation of existing models of ice material behaviour and their inclusion in the numerical simulation of key historical ice load events measured in Canada. A construction of a numerical model begins with a choice of key processes and key assumptions as well as material models to include. Therefore, a comprehensive literature review on the topic is required. During the project, diverse literature on ice material behaviour was reviewed. This thesis describes a 3D creep material model for rheological behaviour of two types of ice, namely columnar (S2) ice and snow (T1) ice. The constructed model can be implemented into software to simulate behaviour of ice under the static loads. In this project, the commercial software ANSYS was used for this purpose to build a finite element model (FEM) for simulations of field events. After the FEM was built, it was validated and calibrated against laboratory experiments taken from the literature. Subsequently, the resulting FEM was used for simulation of key Canadian field events. Only thermal expansion of ice was simulated by the FEM with indirect accounting of the impact of water level fluctuations through the modelling of ice cover under lateral confinement. The influence of different factors on the simulated ice load was studied, namely, the influence (i) of selected material constants, (ii) of lateral confinement, (iii) of grain size and of delayed elastic creep, (iv) of variable or constant coefficient of thermal dilatation, (v) of ice type, (vi) of initial stresses as well as (vii) the influence of ice behaviour in tension. The advice and guidelines for the choice and implementation of a creep material model into commercial finite element software are also given. The thesis is based on studies conducted for two conference papers and one journal paper. The thesis includes introduction to the ice loads on dams, objectives of the project, literature reviews on governing ice loading processes, on material properties of two types of ice of frequent occurrence on a reservoir and on modelling of ice behaviour as well as field data presentation, model description, yet unpublished studies, conclusion and recommendations. The thesis discusses the linkage between laboratory experiments on ice and in situ measurements of reservoir ice loads on dams through the numerical modelling of field events. It documents the fact that delayed elastic creep has a limited effect on the resulting ice load for grain sizes of 3 mm – 20 mm, and its calculation can be omitted in approximate assessments of field ice loads for ice cover with these average grain sizes. It is also shown that variability of coefficient of thermal dilatation of ice with temperature is not important for the temperature range studied. The importance of initial conditions and ice behaviour in tension for the resulting ice load is also shown. The thesis emphasizes the importance of correct accounting of lateral confinement and ice type for ice load calculations. It is shown that when water level rises and the ice is confined laterally, if the reservoir consists primarily of columnar ice, the loads can be very substantial. As such, it is recommended that engineers pay particular attention to the possibility of having cold dry winters with little snow accumulations on an ice cover (favorable conditions for columnar ice formation) when choosing their design criteria.
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Hao, Nguyen Anh. "Parallel lamella dome under wind and snow loads". Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/101117.
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A well structured computer program has been developed to perform geometrically nonlinear finite element analysis of space trusses and to study the sensitivity of parallel lamella dome under wind and snow loads. The modified Riks/Wempner method is used to perform the prebuckling and postbuckling analysis. The European Convention for Constructional Steelwork (ECCS code) is used as the code of practice for design wind pressures on domes.
Failures of domes have occurred during snow storms and have attributed to heavy local snow concentrations. Most codes of practice do not provide design wind and snow loads for domes, and a few international codes do show significant differences in the distributions of design wind pressure for domes. Moreover, current design practices for domes do not reflect the possibility of heavy local snow concentrations. Since wind load data is widely varied among the codes, and specific information on local snow concentrations is not available, the study of the behavior of a full-size lamella dome under different wind pressures and various snow distributions will be carried out with the finite element analysis, and critical load combinations will be obtained with the aid of stability boundary. The proposed study is expected to provide guidelines for the determination of critical wind and snow load conditions.M.S.
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Shakir, Anmar, e Romeo Eileia. "Informationshantering med VDC". Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Byggnadsteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-29629.
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Chalupa, Vojtěch. "Zastřešení zimního stadionu". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226898.
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The aim of this diploma thesis is the design of the roofing of an ice hockey stadium situated in Žďár nad Sázavou. Plan view dimensions are 55 m x 77 m. The structural height of the roof varies from 10 to 17 m. The roof itself consists of pipe truss girders with a span of 55 m, which are supported by columns on each side. The girders are suspended by a load-carrying arch with a span of 96 m and a camber of 29 m through a system of pre-stressed cables. To determine the internal forces, structural analysis software Scia Engineer was used. Individual elements were then manually designed.
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Olsen, Anna Ivanova. "Time-variant reliability of dynamic systems by importance sampling and probabilistic analysis of ice loads". Doctoral thesis, Norwegian University of Science and Technology, Department of Structural Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1913.
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The main objective of this thesis is to develop an efficient simulation technique to estimate the failure probability of time-dependent systems, whose state is expressed as a solution of Itô stochastic differential equations.
The work is divided in two topics due to requirements of the scholarship.
The first part addresses to the problem of assessing the reliability of dynamic systems, where the first-passage probability is chosen as a performance measure of structures subjected to the irregular, stochastic environmental loads. This problem has received considerable attention recently but it still remains a challenge for a wide class of systems.
The improved importance sampling method is developed which allows the solution of the first-passage problem and its applicability for single degree of freedom linear and nonlinear systems. Firstly, it is efficient for assessing small probabilities and it increases the convergence rate compared with the crude Monte Carlo method. Secondly, the procedure uses as much known analytical information about systems as possible.
The second part of the thesis features the probabilistic analysis of the ice loads on the Norstr¨omsgrund lighthouse situated in the Baltic Sea. The objective is to verify the spatial correlation model of the ice forces on the structure and estimate the design values from the appropriately chosen extreme value distribution.
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Petronis, Andrius. "Ledo apkrovų įtaka hidromazgų taurų gelžbetoninėms konstrukcijoms". Master's thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20100616_095335-65213.
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Hidromazgų taurų būklę, ilgaamžiškumą lemia juos veikiantys poveikiai ir apkrovos, susidarantys veikiant klimato sąlygoms, agresyviai aplinkai bei kitiems įvairiems veiksniams. Tyrimų tikslas – įvertinti Lietuvos tvenkiniuose susidarančias ledo apkrovas ir jų įtaką taurų gelžbetoninėms konstrukcijoms. Šiam tikslui pasiekti buvo atlikta literatūros analizė, siekiant nustatyti ledo apkrovų tipus. 2007 – 2010 m. mokslinių ekspedicijų metu natūriniais tyrimais įvertinta 10 hidromazgų taurų gelžbetoninių konstrukcijų būklė pagal STR.1.12.03:2006. Remiantis literatūros ir natūrinių tyrimų rezultatų analize, nustatyta, kad hidromazgų taurų gelžbetoninės konstrukcijos labiausiai ardomos dėl ledo poveikio. Detalesniam tyrinėjimui parinkti 6 hidromazgų taurai, kurių pažaidos leidžia teigti, kad taurų paviršinis betoninis sluoksnis buvo suardytas veikiant ledo apkrovoms. Darbe ledo poveikis analizuotas vertinant: 1) judančiųjų ledo laukų poveikio jėgą atskirai stovinčiai atramai; 2) sustojusiojo ledo lauko, atsirėmusio į statinį ir veikiamo tėkmės ir vėjo, poveikio jėgą; 3) jėgą, susidarančią atramai prarėžiant ledokamšą; 4) jėgą susidarančią dėl ledokamšos atsirėmimo į statinį statmenai jo frontui; 5) jėgą, kuria atrama pjauna ledogrūdą. Nustatyta, kad tvenkinių ledo apkrovos labiausiai priklauso nuo tauro pločio – didėjant tauro pločiui bendruoju atveju ir ledo apkrovos didėja.Technical state of hydroschemes, durability leads to them acting and the effects of load resulting from operation of weather conditions, aggressive environment, and other various factors. The aim of this work - to evaluate ice loads formed in the ponds of Lithuania and their impact on the reinforced concrete piers structures. The state of 10 reinforced concrete structures were evaluated by field investigations in accordance with STR.1.12.03: 2006 during the scientific expeditions in 2007 - 2010. On the basis of literature analysis and field investigations it was found that piers in hydroschemes suffer most from the ice impacts. More detailed investigation were selected 6 hydroschemes, in witcth were noticed the deterioration and it is posssibillity of concrete covering layer breaking due the impacts of ice loads. The ice loads were analyzed in this work: 1) the force of moving ice fields in contact with single pier; 2) the force of standing ice field, in the impact due wind and water drag forces; 3) the force from ice jam cutting by pier; 4) the force of ice jam in the perpendicular contact with stucture front, 5) the force, which is cutting support of the ice plug. It was found that the pond ice load is dependent on ice thickness - increases the overall thickness of the ice and the ice load increases. 5) the force from breakup jam cutting by pier.
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Mazur, David Christopher. "An Electrical Mine Monitoring System Utilizing the IEC 61850 Standard". Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/52239.
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Motor control assets are foundational elements in many industrial operations. In the mining industry, these assets primarily consist of motor control centers and drives, which are available with a comprehensive assortment of control and monitoring devices. Various intelligent electronic devices (IEDs) are now used to prevent machine damage and downtime. As motor control devices have advanced in technology, so too have the IEDs that protect them. These advances have resulted in new standards, such as IEC 61850, that have embedded intelligence and a standard set of communication schemes by which IEDs can share information in a peer-to-peer or one-to-many fashion.
This dissertation investigated the steps involved in interfacing IEDs to a mining process control network via the use of the IEC 61850 standard. As a result of this study, several key technological advancements were made including the development of (i) vendor independent system to communicate with IEDs in a mining environment over IEC 61850, (ii) command and control methods for communication based assisted automation of IEDs for mining firms, (iii) effective solutions to incorporate electrical distribution data in the process control system, (iv) enhanced safety platforms through remote operation of IEDs, (v) standard visualization faceplate graphics for HMI operators with enhanced security, and (vi) new methods for time stamped dataflow to be correctly inserted into a process historian for 'true' Sequence of Events Records.Ph. D.
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Farshidi, Azadeh. "A Secondary Task Test for Evaluating Cognitive Load of MRP Pilots". Thesis, Umeå universitet, Institutionen för informatik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-144143.
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Remotely-controlled technologies are no longer limited to military applications, such as unmanned military airborne weapons or explosive diffuser robots. Nowadays we can see more and more of remotely controlled devices used as medical equipment, toys, and so forth. One of the most recent areas of interest is robotic telepresence, also known as Mobile Robot Presence (MRP), which provides the ability to interact socially and professionally with other people and even objects in remote locations. One of the known issues with using remotely-controlled devices is the cognitive overload which their operators (pilots) experience and MRP pilots are no exception. However, despite vast research on different ways to address this in military or medical scenarios, little has been done regarding MRPs. This thesis study aims to make a contribution in closing that gap by suggesting a method, developing a prototype implementing it; then conducting an empirical assessment of the method and the prototype as a part of a broader study on MRP, supported by Swedish Research Council. I have suggested a method comprised of a Secondary-task (ST) method and Subjective Rating Scales (SRS), in which the latter act as an evaluation method for the former. Both of them were used in an overarching study in search for the best control device amongst four chosen devices. I collected and analyzed secondary task performance data (e.g. response time, error rates), subjective user ratings, explicit rankings, and observations recordings. My analysis of the collected data shows that using a monitoring and response face recognition secondary task is a plausible method for the assessment of MRP pilot’s cognitive load.
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Uherek, Jan. "Statická a dynamická analýzy ocelové konstrukce". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-409745.
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The thesis deals with a description and a static and dynamic analysis for an existing construction of lookout tower. The steel watchtower is located in Město Albrechtice and is made up of two lattice towers connected by a bridge. Main point was to create calculation models for the purpose of dynamic and static analysis, in the software SCIA Engineer 19.1, which is based on the principle of finite element method. Attention was paid to load created by winds according to Eurocode 1 and Eurocode 3, glaze and rime ice load and dynamic coefficient calculation. The thesis also includes an assesment of selected parts of the construction according to Eurocodes.
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Cook, Byron Lloyd. "An investigation of an existing aluminum lattice dome under snow loads". Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08042009-040245/.
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Haas, Karsten. "Evaluation of GC-ICP-MS method for the determination of volatile metal(loid) compounds in environmental gas samples". Thesis, University of Aberdeen, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430377.
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The aim of this study is to perform multielemental determinations of volatile organometal(loid) compounds (VOMs) in environmental gases such as landfill gas and sewage sludge fermentation gases. The analytical method focuses on the on-line coupling of capillary GC with ICP-TOF-MS and provide excellent separation as well as sensitive element selective detection. It involves a cryotrapping step for these (VOMs) such as hydrides, methylated and permethylated species of e.g. As, Sb, Sn, Bi, Hg, Pb etc. In-house standards were generated in Tedlar® bags and a classical external calibration (R2 >0.99) was applied. The precision of injections was good (RSD = 3-11%, N=10) and the standards were reproducibly generated (RSD = 3.20%, N=3). A total number of 4 landfill sites and 5 sewage sludge treatment sites were sampled. One landfill site contained 15 different Sn-compounds, 5 species of which had a concentration of more than 13 ng/l, with a maximum concentration of 1050 ng/l for Me4Sn. Overall, the concentration range of most of the Sn-compounds was 0,01-0,5 ng/l and some unknown species could also be identified. In addition, the permethylated species of As, Se, Sb and Bi could be detected in the range of 0,01 – 117 ng/l. Although their concentration was usually relatively low (at 0,01 – 0,09 ng/l), the variety of volatile Sn-compounds in the sludge fermentation gas samples was quite astonishing. Me3Bi and Me3Sb were the dominant species in the sludge fermentation gases at concentrations of up to 42 ng/l.
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Fahed, Jeff. "Etude numérique du potentiel de rafraichissement des techniques de réduction des ilots de chaleur urbain (ICU) sous climat méditerranéen". Thesis, Toulouse, INSA, 2018. http://www.theses.fr/2018ISAT0024/document.
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Le phénomène d’ilot de chaleur urbain « ICU » souvent observé dans les villes à forte densité urbaine, provoque des impacts négatifs surtout sur le confort thermique extérieur et sur la consommation énergétique des bâtiments. D’où l’importance d’intégrer des dispositifs d’atténuation de ce phénomène dans la conception des projets et des espaces urbains. Cette thèse vise à étudier les effets des différentes stratégies de limitation d’ICU sur les paramètres microclimatiques sous climat méditerranéen. Le cas étudié est un quartier compact de la ville libanaise Beyrouth qui est classifié comme un territoire artificialisé. Jusqu’à présent, peu de recherches microclimatiques ont été réalisées pour le cas Libanais et il y absence des codes et des mesures d’adaptation luttant contre l’ICU. Des simulations numériques sont réalisées à l’aide d’un outil microclimatique « ENVI-met », permettant d’identifier le potentiel rafraichissant de chaque stratégie proposée. Ces stratégies sont basées sur l’augmentation de l’albédo des revêtements du sol et de l’enveloppe des bâtiments, l’augmentation des espaces verts et des surfaces végétalisées, ainsi que sur la mise en place des sources d’eau comme les fontaines et les brumisateurs. Les charges de climatisation relatives à chaque mesure d’atténuation ont été évaluées à l’aide du couplage des données extraites avec ENVI-met avec le logiciel Hourly Analysis Program. Le travail de cette thèse a présenté la capacité des scenarios proposés à modifier les charges de climatisation sensibles ainsi que celles latentes. Le confort du piéton est aussi étudié en analysant l’indice de confort PETThe urban heat island "UHI" phenomenon, frequently detected in cities with high urban density, leads to negative impacts especially on outdoor thermal comfort and buildings energy consumption. Accordingly, it is important to integrate mitigation measures into the design of projects and urban spaces. This thesis aims to study the effects of different UHI limitation strategies on microclimatic parameters in Mediterranean climate. The case of study is a com pact district of the Lebanese city Beirut which is classified as an artificial territory. Little microclimatic researches have been done for the Lebanese case and there is a lack of codes and adaptation measures to mitigate the effect of UHI. Numerical simulations are realized using "ENVI-met" software, to identify the cooling potential of each proposed strategy. These strategies are based on increasing the albedo of urban surfaces and buildings facades and roofs, increasing green spaces and vegetation surfaces, as well as the implementation of water sources such as fountains and water sprays. The cooling loads for each mitigation strategy were evaluated by linking ENVI-met results to the “Hourly Analysis Program” software. This thesis presented the capacity of the proposed scenarios to modify the sensible and latent cooling loads. The pedestrian comfort is also studied by analyzing the index of comfort PET
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Ssenyonga, Lydia V. N. "Effects of decreasing maternal separation of under 6-month old infants directly before and after surgery on allostatic load and outcomes : a randomised control trail [i.e. trial]". Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/6058.
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Includes abstract.Includes bibliographical references.
The current understanding is that infants below six months old do not show separation anxiety (Bretherton, 1985). The objective of the study was to measure the evidence of stress using heart rate variability and impedance cardiograph as indicators of autonomic nervous system activation in order to determine whether decreasing maternal separation of under 6-month-old infants directly before and after surgery decreases their stress experience. The hypothesis was a mother’s presence makes a difference to the autonomic response to stress in infants under six months old undergoing elective hernia surgery.
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Vazquez-Pereira, Grace. "PRODUCIR--the effects of community participation in the establishment of two business [i.e. businesses] : a savings and loan cooperative and a bakery". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/71447.
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Hellgren, Rikard. "Condition assessment of concrete dams in cold climate". Licentiate thesis, KTH, Betongbyggnad, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-259719.
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Dams in many countries are approaching their expected service life. Proper assessment of the aging dams structural health increase the knowledge of the current safety, and allow for better planning of renovation and rebuilding investments. The behavior of concrete dams is, to a great extent, governed by the ambient variation in temperature and water level. In cold regions, the ice sheet formed in the reservoir may subject a pressure load on the dams. Theoretically, this load has a significant impact on the structural behavior of dams. Despite this, the maximum magnitude, as well as the seasonal variation of the ice load, constitute the most considerable uncertainty in the safety assessment of dams. This thesis presents research that examines how to model the expected behavior of dams in cold climate. The underlying problem is to predict the response of dams due to variation in the external conditions. Since the ice load is such a vital part of the external conditions in cold climate, the understanding and modeling of ice loads have been given extra attention. Models suitable to predict the long-term behavior of dams can be divided between theoretical, data-based, and hybrid. Prediction accuracy is essential to set alert thresholds, and in that regard, the data-based models are generally superior. The major contribution of this thesis is the design and installation of a prototype ice load panel with direct measurement of the ice pressure acting on a dam. The panel is attached on the upstream face of the dam and is large enough so that the whole thickness of the ice sheet is in contact with the panel. The predicted ice load from the best available model that includes loads from both thermal events and water level changes did not correspond to the measured ice loads. As there are no validated models or measurement methods for ice load on the dam, continued research is necessary, both through further measurements to increase knowledge and development of models.I många länder närmar sig vattenkraftsdammarna deras förväntade tekniska livslängd. Korrekt utvärdering av dammens strukturella status ökar kunskapen om det nuvarande säkerhetsläget och möjliggör för bättre planering av renoveringar och ombyggnadsinvesteringar. Betongdammarnas beteende styrs till stor del av variationen i omgivande temperaturer och vattennivå. I kalla regioner kan is som bildas i magasinet utsätta dammen för en tryckande last. Teoretiskt har denna belastning en betydande inverkan på dammarsstrukturella beteende. Trots detta är den maximala storleken såväl som säsongsvariationen för islasten en av de mest betydande osäkerheterna vidsäkerhetsbedömningen av dammar. Denna uppsats presenterar forskning som undersöker hur förväntat beteendehos dammar i kallt klimat kan modelleras. Den underliggande frågeställningen är att förutsäga en damms respons orsakad av variation i de yttre förhållandena. Extra fokus har lagts på förståelsen och modelleringen av islasten då den är en viktig del av de yttre förhållandena för dammar i kalla klimat. Modeller som är lämpliga för att förutsäga dammars beteende kan delas upp i teoretiska, databaserad, och hybridmodeller. Förutsägbarhetsnoggrannhet är avgörande för att ställa in varningsnivåer, och i det avseendet är de databaserade modellerna i allmänhet överlägsna. Det huvudsakliga bidraget från detta projekt är utvecklandet och installationen av en prototyp av en islast panel, fäst på en damms uppströmssida. Panelen mäter istrycket direkt mot dammen och är tillräckligt stor så att helaisens tjocklek förblir i kontakt med panelen. Panelen bidrar till ökad kunskap om säsongsvariationen i istryck och mekanismen för islaster orsakad av variation i vattennivån. Den predikterade islaten från den bästa tillgängliga islastmodellen som inkluderar termiska islaster och islaster från vattennivåförändringar överensstämmer inte med de uppmätta islastpanelen som uppmätts med panelen. Då det saknas validerade modeller eller mätmetoder för islast är det viktigt med fortsatt forskning, dels genom ytterligare mätningar för att öka kunskapen men även fortsatt modellutveckling.
QC 20190926
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Natishan, Georgia Kathryn. "Returning the King: the Medieval King in Modern Fantasy". Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/32346.
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In an interview with Hy Bender, Neil Gaiman states, â We have the right, and the obligation, to tell old stories in our own ways, because they are our stories.â While fantasy stands apart from other types of fiction, it still provides a particular kind of commentary on the culture/time it is being created in, often by toying with older themes and conventions. Stories of the quest for kingship tend to fall by the wayside in favor of the â unlikely heroâ tale. While the kingâ s story is not always vastly different from that of the hero, there are some key points that need to be taken into consideration. Unlike many heroes, especially in the modern sense, kings (whether recognized at first or not) are born for the duty they must eventually fulfill. A hero may be unaware of the problem at first or later reluctant to engage it; more often than not in tales of kingship there is a deep awareness of the problem and the knowledge of their potential in solving it. There is always a sense of inherent purpose and destiny: they must undertake quests in order to legitimize themselves and their power â their right to rule. These stories bear a similar structure and shared themes that can be found in medieval sources as well as earlier myths.
Tales of kingship in modern fiction, specifically in the work of Neil Gaiman (The Sandman) and George R. R. Martin (A Game of Thrones), are similar to the medieval models, as kingship and the requirements of kingship were popular themes in medieval texts, including Beowulf and King Horn. The role of the king in epic tales varies from hero to villain, at times even occupying both roles depending on the story. In the tales explored herein and in much of the medieval source material that inspired the fantasy tradition, the king also takes on the role of healer. The interwoven plots of George R. R. Martinâ s A Song of Fire and Ice series revolve around the struggle for the rightful rule over seven kingdoms, and while the protagonist in The Sandman is in many ways vastly different from Tolkienâ s Aragorn, the character still exists with a sense of purpose, responsibility, and duty; a regal bearing that does not necessarily occur in the majority of typical heroes. The influence of Tolkienâ s work both as a scholar and an author is apparent in Gaimanâ s use of mythology and Martinâ s style of world creation; both authors have admitted their creative debt to and continuing admiration of Tolkienâ s style of fantasy. It is impossible to discuss modern fantasy without acknowledging Tolkien as an influence to these two more recent authors. This paper will discuss The Lord of the Rings as a bridge between modern fantasy and medieval/mythological sources.
In each of these modern fantasy tales of kingship, healing and reunion become major themes, tied into the right/duty of a ruler. The patterns established by medieval tales are used by modern authors to create fantasy kings, giving their narratives legitimacy that may have been difficult to establish without these patterns and links back to the medieval tradition.Master of Arts
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Sandels, Claes. "Modeling and Simulation of Electricity Consumption Profiles in the Northern European Building Stock". Doctoral thesis, KTH, Elkraftteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-184093.
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The electric power systems are currently being transformed through the integration of intermittent renewable energy resources and new types of electric loads. These developments run the risk of increasing mismatches between electricity supply and demand, and may cause non-favorable utilization rates of some power system components. Using Demand Response (DR) from flexible loads in the building stock is a promising solution to overcome these challenges for electricity market actors. However, as DR is not used at a large scale today, there are validity concerns regarding its cost-benefit and reliability when compared to traditional investment options in the power sector, e.g. network refurbishment. To analyze the potential in DR solutions, bottom-up simulation models which capture consumption processes in buildings is an alternative. These models must be simple enough to allow aggregations of buildings to be instantiated and at the same time intricate enough to include variations in individual behaviors of end-users. This is done so the electricity market actor can analyze how large volumes of flexibility acts in various market and power system operation contexts, but also can appreciate how individual end-users are affected by DR actions in terms of cost and comfort. The contribution of this thesis is bottom-up simulation models for generating load profiles in detached houses and office buildings. The models connect end-user behavior with the usage of appliances and hot water loads through non-homogenous Markov chains, along with physical modeling of the indoor environment and consumption of heating and cooling loads through lumped capacitance models. The modeling is based on a simplified approach where openly available data and statistics are used, i.e. data that is subject to privacy limitations, such as smart meter measurements are excluded. The models have been validated using real load data from detached houses and office buildings, related models in literature, along with energy-use statistics from national databases. The validation shows that the modeling approach is sound and can provide reasonably accurate load profiles as the error results are in alignment with related models from other research groups. This thesis is a composite thesis of five papers. Paper 1 presents a bottom-up simulation model to generate load profiles from space heating, hot water and appliances in detached houses. Paper 2 presents a data analytic framework for analyzing electricity-use from heating ventilation and air conditioning (HVAC) loads and appliance loads in an office building. Paper 3 presents a non-homogeneous Markov chain model to simulate representative occupancy profiles in single office rooms. Paper 4 utilizes the results in paper 2 and 3 to describe a bottom-up simulation model that generates load profiles in office buildings including HVAC loads and appliances. Paper 5 uses the model in paper 1 to analyze the technical feasibility of using DR to solve congestion problems in a distribution grid.Integrering av förnybara energikällor och nya typer av laster i de elektriska energisystemen är möjliga svar till klimatförändringar och uttömning av ändliga naturresurser. Denna integration kan dock öka obalanserna mellan utbud och efterfrågan av elektricitet, och orsaka en ogynnsam utnyttjandegrad av vissa kraftsystemkomponenter. Att använda efterfrågeflexibilitet (Demand Response) i byggnadsbeståndet är en möjlig lösning till dessa problem för olika elmarknadsaktörer. Men eftersom efterfrågeflexibilitet inte används i stor skala idag finns det obesvarade frågor gällande lösningens kostnadsnytta och tillförlitlighet jämfört med traditionella investeringsalternativ i kraftsektorn. För att analysera efterfrågeflexibilitetslösningar är botten-upp-simuleringsmodeller som fångar elförbrukningsprocesser i byggnaderna ett alternativ. Dessa modeller måste vara enkla nog för att kunna representera aggregeringar av många byggnader men samtidigt tillräckligt komplicerade för att kunna inkludera unika slutanvändarbeteenden. Detta är nödvändigt när elmarknadsaktören vill analysera hur stora volymer efterfrågeflexibilitet påverkar elmarknaden och kraftsystemen, men samtidigt förstå hur styrningen inverkar på den enskilda slutanvändaren. Bidraget från denna avhandling är botten-upp-simuleringsmodeller för generering av elförbrukningsprofiler i småhus och kontorsbyggnader. Modellerna kopplar slutanvändarbeteende med elförbrukning från apparater och varmvattenanvändning tillsammans med fysikaliska modeller av värmedynamiken i byggnaderna. Modellerna är byggda på en förenklad approach som använder öppen data och statistisk, där data som har integritetsproblem har exkluderats. Simuleringsresultat har validerats mot elförbrukningsdata från småhus och kontorsbyggnader, relaterade modeller från andra forskargrupper samt energistatistik från nationella databaser. Valideringen visar att modellerna kan generera elförbrukningsprofiler med rimlig noggrannhet. Denna avhandling är en sammanläggningsavhandling bestående av fem artiklar. Artikel 1 presenterar botten-upp-simuleringsmodellen för genereringen av elförbrukningsprofiler från uppvärmning, varmvatten och apparater i småhus. Artikel 2 presenterar ett dataanalytiskt ramverk för analys av elanvändningen från uppvärmning, ventilation, och luftkonditioneringslaster (HVAC) och apparatlaster i en kontorsbyggnad. Artikel 3 presenterar en icke-homogen Markovkedjemodell för simulering av representativa närvaroprofiler i enskilda kontorsrum. Artikel 4 använder resultaten i artiklarna 2 och 3 för att beskriva en botten-upp-simuleringsmodell för generering av elförbrukningsprofiler från HVAC-laster och apparater i kontorsbyggnader. Artikel 5 använder modellen i artikel 1 för att analysera den tekniska möjligheten att använda efterfrågeflexibilitet för att lösa överbelastningsproblem i ett eldistributionsnät.
QC 20160329
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Teklemariam, Daniel Mekonnen, e Bennie Hamunzala. "Design of Thick Concrete Beams : Using Non-Linear FEM". Thesis, KTH, Bro- och stålbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-189141.
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The experimental studies performed on the behaviour of very thick concrete beams subjected to static loads have revealed that the shear mechanisms play an important role in the overall response and failure behaviour. The aim of this thesis is to recommend suitable design methods for thick concrete beams subjected to off-centre static concentrated load according Eurocode 2 by using non-linear finite element analysis (NLFEA). To achieve this task, Abaqus/Explicit has been used by employing constitutive material models to capture the material non-linearity and stiffness degradation of concrete. Concrete damaged plasticity model and perfect plasticity model has been used for concrete and steel respectively. Three dilation angles (30º, 38º and 45º) and fracture energy from FIB 1990 (76 N/m) and FIB 2010 (142 N/m) has been used to investigate their influence on the finite element model. The dilation angle of 38º and FIB 2010 fracture energy was adopted as the suitable choice that reasonably matched with the experimental results. In verifying and calibrating the finite element model, the experimental results of the thick reinforced concrete beam conducted by the American Concrete Institute have been used. Three design approaches in the ultimate and serviceability limit state according to Eurocode 2 recommendations have been used namely; the beam method, strut and tie method and shell element method. Using the reinforcement detailing of the hand calculations of beam method and strut and tie method and linear finite element analysis of shell element method, non-linear finite element models have been pre-processed and analysed in Abaqus/Explicit. During the post-processing, the results have been interpreted and compared between the three design methods. The results under consideration are hand-calculated load at 0.3 mm crack width, FE-load at 0.3 mm crack width, amount of reinforcement and FE-failure load. The comparison of the results between the three design approaches (beam method, strut and tie method and shell element method) indicates that strut and tie method is better design approach, because it is relatively economic with regards to the quantity of reinforcement bars, has the higher load capacity and has a higher load at crack width of 0.3 mm crack width.De experimentella studier som utförts på tjocka betongbalkar som utsätts för statisk last har visat att skjuvning spelar en viktig roll i brottmekanismen. Syftet med detta examensarbete är att rekommendera lämpliga dimensioneringsmetoder för tjock betongbalkar utsatt for statisk koncentrerad last enligt Eurokod 2 med hjälp av ickelinjära finita element metod. Abaqus/Explicit användes genom att utnyttja konstitutiva materialmodeller för att fånga materialens icke-linjäritet och minskad styvhet. Tre dilatationsvinklar (30°, 38° och 45°) och två brottenergi från FIB 1990 (76 N/m) och FIB 2010 (142 N/m) tillämpas för att kontrollera deras inverkan på FE-modellerna. Dilatationsvinkel med 38° och FIB 2010 med högre brottenergi valdes i de icke-linjära finita elementanalyserna. Kontroll av FE-modellerna är baserad på ”American Concret Institutes” experimentella resultat på de tjocka betongbalkarna. Handberäkningar av tjocka betongbalkar har utförts i brott- och bruksgränstillstånd med tre dimensioneringsmetoder i Eurokod 2 nämligen balk metoden, fackverksmetoden och linjära-FE skalelementmetoden. Jämförelse har gjorts för de olika dimensioneringsmetoderna, genom att använda de armeringsdetaljer av handberäkningar i de verifierade och kalibrerade icke linjära FE-modellerna i Abaqus/Explicit. Resultaten i fråga är last för 0.3 mm handberäknad sprikvidd, FE-last för 0.3 mm sprikvidd, armeringsmängd och FE-brottlast. Jämförelse av resultaten mellan de tre dimensioneringsmetoder (balkmetod, fackverksmetod och skalelementmetod) visar att fackverksmetod är bättre design metod, eftersom det är relativt ekonomiskt med avseende på armeringsmängd, har högre lastkapacitet och last på 0.3 mm sprickvidd.
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Hosseini, Rahimeh, e Anita Nolsjö. "The effect of reinforcement configuration on crack widths in concrete deep beams". Thesis, KTH, Betongbyggnad, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-208709.
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Reinforced concrete deep beams are known for applications in tall buildings, foundations and offshore structures. Deep beams are structural elements with length and height within the same magnitude and have significantly smaller thickness compared to a conventional concrete beam. Deep beams in bending have non-linear strain distribution compared to conventional beams where Bernoulli’s hypothesis is valid. Crack formation is a common problem in reinforced concrete structures, which reduce the durability of the structure. Once the concrete cracks the tension reinforcement carry the tensile forces instead of the concrete. Therefore, the design of tension reinforcement is important since the serviceability should be retained even after the structure cracks. The crack widths can be limited by using proper reinforcement and one alternative is to combine tensile reinforcement with crack reinforcement. The function of the reinforcement is to distribute the cracks over the cross section which leads to that many smaller cracks occur instead of fewer, wider cracks. Small cracks are seen as less of a problem compared to large cracks since larger cracks reduce the durability significantly. For deep beams, there is at the present no well-substantiated analysis model for how crack widths shall be calculated when having reinforcement in multiple layers with different diameters. The use of crack reinforcement in the outer bottom layer has by tradition been considered as a cost efficient way to achieve small crack widths. In this work the crack width in deep beams have been analysed using the finite element program Atena 2D. The numerical results have been verified by analytical calculations based on Eurocode 2. The aim is to achieve reduced crack widths by analysing the combination of crack- and tensile reinforcement compared to the case with tensile reinforcement only. Tensile reinforcement has a larger diameter, for example ø25 mm, and crack reinforcement has smaller diameters, often between ø10 and ø16 mm. The result from the calculations with Atena showed that there was an improvement regarding the reduction of crack widths when using crack reinforcement in combination with tensile reinforcement compared to using tensile reinforcement only. However, this improvement decreased by using reinforcement in multiple layers since a tensile reinforcement bar 1ø25 mm needed to be replaced by approximately six crack reinforcement bars 6ø10 mm in order to achieve the same total reinforcement area. The main disadvantage was that more space was required to place all reinforcement bars in the cross section, which reduced the lever arm. The reduction of the lever arm resulted in a reduced capacity for the reinforcement and the cracks might unintentionally become wider than expected. Furthermore, significant reduction of both crack widths and reinforcement stresses were obtained when the total area for a case with 7ø25 mm was increased to 9ø25 mm. The increased total area of only tensile reinforcement ø25 mm reduced the crack width more compared to using a combination of crack- and tensile reinforcement, which could simplify the construction work at building sites and minimize time consumption.Armerade höga betongbalkar är kända för tillämpningar i höga byggnader, grundsulor och offshore konstruktioner. Höga balkar är konstruktionselement med längd och höjd i samma storleksordning och har betydligt mindre tjocklek jämfört med en konventionell betongbalk. Höga balkar i böjning har en icke-linjär töjningsfördelning jämfört med konventionella balkar där Bernoullis hypotes gäller. Sprickbildning är ett vanligt problem i armerade betongkonstruktioner, vilket minskar beständigheten hos konstruktionen. När betongbalken spricker kommer armeringen att ta upp dragkraften istället för betongen därför är utformningen av böjarmering viktig eftersom bruksgränstillståndet bör behållas även efter att konstruktionen spricker. Sprickvidderna kan begränsas genom att använda korrekt armering och ett alternativ är att kombinera kraftarmering med sprickarmering. Armeringens funktion är att sprida ut sprickorna över tvärsnittet vilket leder till att många små sprickor uppkommer i stället för färre, bredare sprickor. Små sprickor ses som ett mindre problem jämfört med stora sprickor eftersom större sprickor minskar beständigheten avsevärt. För höga balkar finns det för närvarande ingen välunderbyggd analysmodell för hur sprickvidder ska beräknas när de har armering i flera lager och med olika diametrar. Användningen av sprickarmering har traditionellt ansetts vara ett kostnadseffektivt sätt att uppnå små sprickvidder. I detta arbete har sprickvidden i höga balkar analyserats med hjälp av finita elementprogrammet Atena 2D. De numeriska resultaten har verifierats med analytiska beräkningar baserade på Eurokod 2. Syftet är att uppnå reducerade sprickvidder genom att analysera kombinationen av sprick- och kraftarmering jämfört med fallet med endast kraftarmering. Kraftarmeringen har en större diameter, till exempel ø25 mm och sprickarmering har mindre diametrar, ofta mellan ø10 och ø16 mm. Resultaten från beräkningarna i Atena visade att sprickvidderna minskade vid användning av sprickarmering i kombination med kraftarmering jämfört med användning av endast kraftarmering. Denna förbättring minskade emellertid i och med användning av armering i flera lager. En kraftarmeringsstång 1ø25 mm behöver ersättas med ungefär sex sprickarmeringsstänger, 6ø10 mm, för att uppnå samma totala armeringsarea. Den största nackdelen var att det krävdes mer utrymme för att placera alla sprickarmeringsstänger i tvärsnittet, vilket minskade hävarmen. Minskningen av hävarmen medförde en reducerad kapacitet i armeringen och sprickorna blev bredare än förväntat. Vidare erhölls signifikant reduktion av både sprickvidder och armeringsspänningar när den totala arean för ett fall med 7ø25 mm ökades till 9ø25 mm. Den ökade totalarean av endast kraftarmeringsstänger ø25 mm minskade sprickvidden mer jämfört med att använda en kombination av sprick- och kraftarmering vilket skulle kunna förenkla byggarbetet på byggarbetsplatser och minimera tidsförbrukningen.
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Laubscher, Dorothy Joy. "Mathematics teacher–students attitude towards information and communication technology across three countries / D.J. Laubscher". Thesis, North-West University, 2010. http://hdl.handle.net/10394/4718.
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Low achievement in Mathematics is a problem that faces schools, colleges and universities, not only in South Africa, but worldwide. Many efforts have been made to explore different ways in which teaching and learning can be more effective. ICT provides endless possibili–ties to enhance the teaching and learning of Mathematics. The purpose of this study is to determine teacher–students’ attitude towards ICTs in order to plan for effective, efficient and appropriate methods of Mathematics education. It further aims to determine to what extent these students will be willing to use ICTs in their own studies as well as in the teaching pro–cess in their classrooms, and aims to compare the students’ attitudes across three countries i.e. South Africa, Tanzania and Finland. The population consisted of Mathematics education teacher–students enrolled at the following institutions: School for Continuing Teacher Educa–tion (SCTE) at the North–West University in South Africa (317 students), the Iringa University College, University of Tumaini in Tanzania (111 students), and the University of Joensuu in Finland (56 students). This study followed a quantitative cross–sectional survey design com–prising a single mode research questionnaire to three groups of students in three countries. The instrument that was used was based on the Loyd and Gressard Computer Attitude Sur–vey (1984) (CAS), with a few additional questions to add to the relevance of this study. Questionnaires were completed by each group of students. The questionnaires were posted to each Mathematics teacher–student at the SCTE with a return envelope included. The re–searcher visited Tanzania and administered the questionnaire to the students at their univer–sity and some students in Finland completed the survey online while others completed a pa–per–based copy, which was returned to the researcher. Descriptive statistical techniques, reliability and validity of the instrument scale, inferential statistics (ANOVA), and cross–tabulations were used, and where appropriate, effect sizes were calculated. Findings indi–cated that the teacher–students have a positive attitude to computers and that they are willing to use ICTs in their own studies and in their teaching at school. The comparison of their atti–tudes revealed that the South African and Tanzanian teacher–students have a more positive attitude towards ICTs than the Finnish students. The teacher–students in the two African countries were also more willing to use ICTs than the students in Finland, despite their in–creased exposure and access to technology. To create an environment of effective Mathe–matics education, a number of factors play an important role. Mathematics education sup–ported by good pedagogical content knowledge can be transformed into effective Mathemat–ics education with the aid of a positive computer attitude and willingness to use technology. Together these aspects are supported by the technological pedagogical content knowledge (TPCK) framework.Thesis (M.Ed.)--North-West University, Potchefstroom Campus, 2011.
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Zhang, Meng. "Ice load prediction for design of ice-going ships for inland waterways". Licentiate thesis, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-266251.
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With increasing interest in utilizing the inland waterways (IWW) in European countries, the design of IWW vessels gains attention both from a transport efficiency and an emission control point of view. However, unlike in western and central European countries, in Nordic countries, e.g. Sweden, IWW ships must deal with ice on the fairway during every winter. Usually, IWW ships are designed without ice concerns and are structurally weaker compared to ships designed according to ice class notification from the classification societies. Developing such ships requires particular concerns since there is no strict requirements regarding ice class notifications for IWW ships. A primary challenge is to estimate both the global and local ice loads acting on the ship hull structure. To consolidate the design problems for IWW ice-going ships, Lake Mälaren is selected. Ice conditions, i.e. ice type and concentration, and ice data, e.g. ice thickness and ice flexural strength, are extracted and analysed for the ice load estimation. The ice mechanical properties have great influence on the ice load. Ice characteristics are studied based on empirical formulae and properties are calibrated by reference data. The deterministic approach is widely used to predict the ice loads. It is suitable when all variables, i.e. ship geometry and ice properties, are known and refers to rule-based design hereby. For first year light ice conditions in Lake Mälaren, the Finnish Swedish Ice Class Rule (FSICR) is widely used. The thesis uses guidelines from the Finnish Swedish Ice Class Rules as a reference and compare the results with other methods. The probabilistic approach, on contrary, is useful when certain variables are unknow, which are interpreted as random variables, for instance ice breaking pattern. Here the probabilistic method and ice-hull interaction mechanism are studied. The probabilistic method simplifies the ice pressure in relation to the contact area between the ice and the ship hull. It predicts maximum ice pressure acting on the ship hull based on field ice test data and ice exposure conditions. Such semi-empirical method can be used regardless of ship type and size. For this, a numerical model is introduced based on ice-hull collision mechanisms and the essential ice breaking characteristics. The physical mechanism is studied for idealizing ship-ice impact model. The idealization model includes the ice failure process, ice conditions and ship geometry. The ice failure is assumed to be initiated by crushing ice and followed by breaking due to bending failure. Ice properties are set as constant values without any variations. The stochasticity in interact process is represented by randomness in collision location and number of pieces of ice floe formed after breaking. An energy method is used to calculate the ice crushing force, indentation displacement and contact area. The ice bending scenario is simplified as an infinite plate resting on an elastic foundation under a concentrated load. Ice impact load and critical load can be obtained for global and local structural assessment respectively. The structural responses and structural strength of a representative panel at linear and nonlinear contexts are investigated as well. Ship structure is commonly designed with material yield strength as limit. However, the study shows a lighter structure can be achieved if plastic deformation is allowed without causing failure. Therefore, the design can be optimized with regards to ice loading capacity and weight control.
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"Implementing Load Shifting Using Thermal Energy Ice Storage". Master's thesis, 2016. http://hdl.handle.net/2286/R.I.40351.
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abstract: For decades, load shifting control, one of the most effective peak demand management methods, has attracted attention from both researchers and engineers. Various load shifting controls have been developed and introduced in mainly commercial buildings. Utility companies typically penalize consumers with “demand rates”. This along with increased population and increased customer energy demand will only increase the need for load shifting. There have been many white papers, thesis papers and case studies written on the different types of Thermal Energy Storage and their uses. Previous papers have been written by Engineers, Manufacturers and Researchers. This thesis paper is unique because it will be presented from the application and applied perspective of the Facilities Manager. There is a need in the field of Facilities Management for relevant applications. This paper will present and discuss the methodology, process applications and challenges of load shifting using (TES) Thermal Energy Storage, mainly ice storage.Dissertation/Thesis
Masters Thesis Construction 2016
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Bruneau, Stephen Earl. "Development of a first-year ridge keel load model /". 1996.
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