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Erlebach, Christopher B. "Bubble heterogeneities in bread, caused by sheeting." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246474.
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Lai, Kwok-leung. "Mortgage securitization : prepayment analysis of mortgage-backed securities /." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B25939993.
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Korula, Febin. "The Credit Risk in Stock-Based Loans." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29380.
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Stock-based loans are an increasingly popular form of loan that are collateralised using stocks. Since these loans are often non-recourse loans, the lenders are subject to the risk that the collateral is worth less than the loan, and the borrower defaults. This dissertation will consider the credit risk faced by lenders when issuing these loans. To achieve this, this dissertation will propose different models to quantify this risk using various credit measures. A sensitivity analysis to key model parameters is then conducted. Some brief comments about capital requirements will also be made.
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Zabri, Siti Normi. "Study of thin resistively loaded FSS based microwave absorbers." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.676498.
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The purpose of this study was to develop new FSS based microwave absorber designs to minimise the physical thickness, increase the bandwidth and provide radar backscatter suppression that is independent of the wave polarization at large incident angles. A new low cost, accurate and rapid printing technique is employed to pattern the periodic arrays with the precise surface resistance required for each of the FSS elements to optimize the performance of this class of absorber. The electromagnetic behaviour of five new FSS based structures, two standalone arrays, and three absorber arrangements, have been studied using CST Microwave Studio software. The FSS structures consist of two closely spaced arrays of rings with the conductor split at one or two locations to provide independent control of the resonances. By careful design these are shown to exhibit coincident spectral transmission responses in the TE and TM plane. Based on this design methodology, a very thin 4-layer metal backed resistively loaded rectangular loop FSS absorber which works from 0° - 22.5° is shown to give a wide band performance that is independent of the orientation of the impinging signals. To reduce the manufacturing complexity, a single layer FSS absorber which operates at 45° incidence has been designed to give a polarisation independent performance by employing an array of rectangular split loops with discrete pairs of resistive elements of unequal value inserted at the midpoint of the four sides. A major increase in bandwidth is obtained from a single layer FSS absorber which is composed of an array of nested hexagonal loops. Moreover the use of the same surface resistance for all four elements in the unit cell is shown to significantly simplify the construction of the structure which was designed to provide radar cloaking from 0° to 45° incidence. A new manufacturing strategy is presented, where the required surface resistances are obtained by employing an ink-jet printer to simultaneously pattern the FSS elements on the substrate and digitally control the dot density of the nano silver ink and aqueous vehicle mixture.
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黎國樑 and Kwok-leung Lai. "Mortgage securitization: prepayment analysis of mortgage-backed securities." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31256879.
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Ghosh, Sudip. "Risk based capital requirements and the U.S. loan market." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=853.
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Thesis (Ph. D.)--West Virginia University, 1999.<br>Title from document title page. Document formatted into pages; contains vi, 175 p. : ill. Includes abstract. Includes bibliographical references (p. 173-175).
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Samuelsson, Ted. "Load Unit Geometry Optimization for Heavy Duty Machinery." Thesis, Umeå universitet, Institutionen för fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-108618.
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The construction equipment industry is developing at a fast pace, increasing the expectation on the next-generation machines. Wheel loaders and backhoe loaders are part of this evolution and all subsystems in those machines need to be developed to meet the high demands in energy eciency and productivity. One of the most important parts of the wheel loader is the loading unit. This is traditionally designed using highly experienced engineers and CAD software. To simplify the early stages of this process was an optimization tool developed to generate a design outlay. The optimization will minimize the mass of the linkage since unnecessary weight will lower the eciency. The minimum can be found by moving the joints and adjusting the shape of the device. The optimization will also include constraints to assure the correct performance of the linkage. Since there are a high number of design variables, a gradient-based optimization method was used. A finite element solver was also implemented to calculate the forces and stresses in the linkage. The linkages studied in this report are one from a typical wheel loader and one from a backhoe loader. Since these machines are extremely versatile, and used formany diferent tasks, two sets of constraints are compiled. One of the constraint sets yields a linkage suitable for machines only equipped with bucket, while the other results in an all-round linkage suitable for most tools and applications. The optimized linkages are compared to existing devices. The results show that there are some improvements possible and that the software could be used to help designers. However, the optimization problem is hard to solve due to non-smooth constraints functions and numerical instabilities. This issue could be overcome by diferent means, like using automatic diferentiation, a non-gradient based optimization method, decreasing the number of constraints or decreasing the number of design variables.<br>Utvecklingen av anlaggningsmaskiner sker i snabb takt och detta ökar förväntningarna på framtidens maskiner. En stor andel av alla anläggningsmaskiner är hjullastare och traktorgrävare och alla delsystem på dessa maskiner måste följa med i utvecklingen. En av de viktigaste delarna pa en hjullastare ar lastaggregatet. Det designas traditionellt med hjälp av CAD mjukvara och mycket erfarna konstruktörer. För att underlätta denna process har en optimeringsrutin utvecklats, som generarar ett designförslag. Optimeringen minskar länkagets massa genom att fytta lagringspositioner och ändra delarnas dimensioner. Detta ökar efektiviteten hos maskinen eftersom den slipper köra runt på onödig vikt. Optimeringen innehåller även villkor för att säkerställa god prestanda hos det optimerade aggregatet. Eftersom det ingår väldigt många designvariabler i optimeringen används en gradientbaserad metod. En finita element approximation används for att beräkna krafter och spänningar i länkaget. De länkage som undersöks i detta projekt är ett typsikt hjullastaraggregat och ett typiskt traktorgrävaraggregat. Eftersom dessa maskiner ar väldigt mångsidiga sammanställdes två olika uppsättningar av villkor. Den ena uppsättningen används för att optimera ett aggregat som endast ska användas med skopa, medan den andra uppsättningen används för att ta fram ett mer mångsidigt aggregat avsätt for att kunna klara av de flesta situationer och verktyg. De optimerade lastaggregaten är jämförda med produktionsaggregat och det visar sig att vissa förbättringar är möjliga. Slutsattsen är att optimeringsrutinen kan bli ett bra hjälpmedel for konstruktörer men att den behöver lite mer veriering. Villkorsfunktionen som optimeringen måste lösa är inte helt slät vilket är ett problem för en gradientbaserade metod och dessutom finns vissa numeriska instabiliteter. Dessa svårigheter kan undkommas pa olika sätt, t.ex. genom att använda automatisk derivering,byta optimeringsalgoritm, minska antalet villkor eller minska antalet variabler.
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Jaoui, Abdelhak. "Can the Baker plan work?" Virtual Press, 1987. http://liblink.bsu.edu/uhtbin/catkey/490119.
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The purpose of this study was to analyze, using a medium term scenario of three years, the impact 9f the Baker Plan on the economies of fifteen debt laden countries. A central argument of this scenario was to assess whether growth and creditworthiness would be restored in these countries. A model using projections of debt service, imports, exports and capital requirements was developed to test these variables. Baker's package of $29 billion over three years (1985-1988) was contrasted with the model projections. The findings showed that, in the short-term, Baker's proposal will fall short of restoring growth and creditworthiness. However, the supply side policies suggested by Baker Initiative are the right way to go if the indebted countries are to resume growth and creditworthiness in the long run.
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Hong, Won-Jong. "Direct Decomposition of NO over Ba-loaded Ce-based Mixed Oxide Catalysts." 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142237.
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Gentles, Jeremy A. "Monitoring Training Loads with a Web Based Athlete Monitoring System." Digital Commons @ East Tennessee State University, 2011. https://dc.etsu.edu/etsu-works/3988.
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Jastram, John Dietrich. "Improving Turbidity-Based Estimates of Suspended Sediment Concentrations and Loads." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/32514.
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As the impacts of human activities increase sediment transport by aquatic systems the need to accurately quantify this transport becomes paramount. Turbidity is recognized as an effective tool for monitoring suspended sediments in aquatic systems, and with recent technological advances turbidity can be measured in-situ remotely, continuously, and at much finer temporal scales than was previously possible. Although turbidity provides an improved method for estimation of suspended-sediment concentration (SSC), compared to traditional discharge-based methods, there is still significant variability in turbidity-based SSC estimates and in sediment loadings calculated from those estimates. The purpose of this study was to improve the turbidity-based estimation of SSC. Working at two monitoring sites on the Roanoke River in southwestern Virginia, stage, turbidity, and other water-quality parameters and were monitored with in-situ instrumentation, suspended sediments were sampled manually during elevated turbidity events; those samples were analyzed for SSC and for physical properties; rainfall was quantified by geologic source area. The study identified physical properties of the suspended-sediment samples that contribute to SSC-estimation variance and hydrologic variables that contribute to variance in those physical properties. Results indicated that the inclusion of any of the measured physical properties, which included grain-size distributions, specific surface-area, and organic carbon, in turbidity-based SSC estimation models reduces unexplained variance. Further, the use of hydrologic variables, which were measured remotely and on the same temporal scale as turbidity, to represent these physical properties, resulted in a model which was equally as capable of predicting SSC. A square-root transformed turbidity-based SSC estimation model developed for the Roanoke River at Route 117 monitoring station, which included a water level variable, provided 63% less unexplained variance in SSC estimations and 50% narrower 95% prediction intervals for an annual loading estimate, when compared to a simple linear regression using a logarithmic transformation of the response and regressor (turbidity). Unexplained variance and prediction interval width were also reduced using this approach at a second monitoring site, Roanoke River at Thirteenth Street Bridge; the log-based transformation of SSC and regressors was found to be most appropriate at this monitoring station. Furthermore, this study demonstrated the potential for a single model, generated from a pooled set of data from the two monitoring sites, to estimate SSC with less variance than a model generated only from data collected at this single site. When applied at suitable locations, the use of this pooled model approach could provide many benefits to monitoring programs, such as developing SSC-estimation models for multiple sites which individually do not have enough data to generate a robust model or extending the model to monitoring sites between those for which the model was developed and significantly reducing sampling costs for intensive monitoring programs.<br>Master of Science
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Reichenwallner, Christopher, and Daniel Wasborg. "Control of a Hydraulic Hybrid System for Wheel Loaders." Thesis, Linköpings universitet, Fluida och mekatroniska system, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-158902.
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In recent years many companies have investigated the use of hybrid technology due to the potential of increasing the driveline’s efficiency and thus reducing fuel consumption. Previous studies show that hydraulic hybrid technology can be favourable to use in construction machinery such as wheel loaders, which often operate in repetitive drive cycles and have high transient power demands. Parallel as well as Series hybrid configurations are both found suitable for wheel loader applications as the hybrid configurations can decrease the dependency on the torque converter. This project has investigated a novel hydraulic hybrid concept which utilizes the wheel loaders auxiliary pump as a supplement to enable both Series and Parallel hybrid operation. Impact of accumulator sizes has also been investigated, for which smaller accumulator sizes resembles a hydrostatic transmission. The hybrid concept has been evaluated by developing a wheel loader simulation model and a control system based on a rule-based energy management strategy. Simulation results indicate improved energy efficiency of up to 18.80 % for the Combined hybrid. Moreover, the accumulator sizes prove to have less impact on the energy efficiency. A hybrid system with decreased accumulator sizes shows improved energy efficiency of up to 16.40 %.
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Raychowdhury, Prishati. "Nonlinear Winkler-based shallow foundation model for performance assessment of seismically loaded structures." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3307689.
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Thesis (Ph. D.)--University of California, San Diego, 2008.<br>Title from first page of PDF file (viewed August 13, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 282-294).
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Marpu, Ritu Priyanka. "Physics based prediction of aeromechanical loads for the UH-60A rotor." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47661.
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Helicopters in forward flight experience complex aerodynamic phenomena to various degrees. In low speed level flight, the vortex wake remains close to the rotor disk and interacts with the rotor blades to give rise to blade vortex interaction phenomena. In high speed flight, compressibility effects dominate leading to the formation of shocks. If the required thrust is high, the combination of high collective pitch and cyclic pitch variations give rise to three-dimensional dynamic stall phenomena.
Maneuvers further exacerbate the unsteady airloads and affect rotor and hub design. The strength and durability of the rotor blades and hub components is dependent on accurate estimates of peak-to-peak structural loads. Accurate knowledge of control loads is important for sizing the expensive swash-plate components and assuring long fatigue life.
Over the last two decades, computational tools have been developed for modeling rotorcraft aeromechanics. In spite of this progress, loads prediction in unsteady maneuvers which is critical for peak design loads continues to be a challenging task.
The primary goal of this research effort is to investigate important physical phenomena that cause severe loads on the rotor in steady flight and in extreme maneuvers. The present work utilizes a hybrid Navier-Stokes/free-wake CFD methodology coupled to a finite element based multi-body dynamics analysis to systematically study steady level and maneuvering flight conditions.
Computational results are presented for the UH-60A rotor for a parametric sweep of speed and thrust conditions and correlated with test data at the NFAC Wind Tunnel. Good agreement with test data has been achieved using the current methodology for trim settings and integrated hub loads, torque, and power.
Two severe diving turn maneuvers for the UH-60A recorded in the NASA/Army Airloads Flight Tests Database have also been investigated. These maneuvers are characterized by high load factors and high speed flight. The helicopter experiences significant vibration during these maneuvers. Mean and peak-to-peak structural loads and extensive stall phenomena including an advancing side stall phenomena have been captured by the present analyses.
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Kim, Hongjin. "WAVELET-BASED ADAPTIVE CONTROL OF STRUCTURES UNDER SEISMIC AND WIND LOADS." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1039128747.
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Yung, I. "Automation of front-end loaders : electronic self leveling and payload estimation." Doctoral thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-134338.
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A growing population is driving automatization in agricultural industry to strive for more productive arable land. Being part of this process, this work is aimed to investigate the possibility to implement sensor-based automation in a particular system called Front End Loader, which is a lifting arms that is commonly mounted on the front of a tractor. Two main tasks are considered here, namely Electronic Self Leveling (ESL) and payload estimation. To propose commercially implementable solutions for these tasks, specific objectives are set, which are: 1) to propose a controller to perform ESL under typical disturbances 2) to propose a methodology for payload estimation considering realistic estimation conditions. Lastly, aligned with these goals, 3) to propose models for the Front End Loader under consideration for derivation of solutions of the specified tasks. The self-leveling task assists farmers in maintaining the angular position of the mounted implements, e.g. a bale handler or a bucket, with respect to the ground when the loader is manually lifted or lowered. Experimental results show that different controllers are required in lifting and lowering motions to maintain the implement's angular position with a required accuracy due to principle differences in gravity impact. The gravity helps the necessary correction in lifting motion, but works against the correction in lowering motions. This led us to propose a controller with a proportional term, a discontinuous term and an on-line disturbance estimation and compensation as well as the tuning procedure to achieve a 2 degrees tracking error for lowering motions in steady state. The proposed controller shows less sensitive performance to lowering velocity, as the main disturbance, in comparison to a linear controller. The second task, payload estimation, assists farmers to work within safety range as well as to work with a weight measurement tool. A mechanical model derived based on equations of motion is improved by a pressure based friction to sufficiently accurately represent the motion of the front end loader under consideration. The proposed model satisfies the desired estimation accuracy of 2\% full scale error in a certain estimation condition domain in constant velocity regions, with off-line calibration step and off-line payload estimation step. An on-line version of the estimation based on Recursive Least Squares also fulfills the desired accuracy, while keeping the calibration step off-line.
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Bouchard, Keith M. (Keith Michael). "A performance-based approach to retrofitting unreinforced masonry structures for seismic loads." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38944.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2007.<br>Includes bibliographical references (leaves 58-59).<br>The structural inadequacy of existing unreinforced masonry (URM) buildings to resist possible seismic loading is a serious problem in many parts of the United States, including the Northeast and Midwest. The fact that many of these buildings are deemed historic structures or house critical facilities, like firehouses, emphasizes the need for an effective retrofitting program. The Federal Emergency Management Agency published a performance-based design code - FEMA 356 - in 2000 to use for analyzing and retrofitting existing structures. This code includes procedures for URM buildings. This paper applies these performance-based analysis procedures to a URM shear wall and compares the results to a modified analysis proposed by researchers. The wall is then rehabilitated using two common retrofit methods and again analyzed using the code. Recommendations are made for practicing engineers when evaluating URM structures for seismic loads.<br>by Keith M. Bouchard.<br>M.Eng.
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Perez, Tellez Adriel. "Modelling aggregate loads in power systems." Thesis, KTH, Elkraftteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-204600.
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The load response to voltage and frequency changeshas a considerable impact on the behaviour of the powersystem. Thus, the selection of a load model structure andits corresponding parameters is an important task in orderto study and predict the system behaviour. Currently,the Nordic Transmission System Operators (TSO) use theZIP load model, as it provides an easy and flexible way ofrepresenting the load. The main goal of the thesis has beento test two approaches for deriving ZIP model parameters,namely the component-based and measurement-basedapproaches. The former approach uses predefined parametervalues, and information on the loads electricityconsumption, whereas the latter uses measurement dataand curve-fitting techniques. In order to evaluate themethodology, a case study has been performed, wherethe two aggregation approaches were applied on anevaluation point. It was found that the aggregation bymeans of the component-based approach may result in ZIPparameters lacking physical significance. ZIP parameterswithout physical significance pose a challenge for systemplanners, who may have difficulties in accepting thesevalues as they are less intuitive than physically significantones. Furthermore, the results of the measurement-basedapproach indicate that the ZIP model has some limitationwhen it comes to the sudden load changes that it canaccommodate. This has been the case with the measuredreactive power in the case study. Based on the resultsof applying the methodology, it can be concluded thatthe component-based and measurement-based approachesprovide useful information when understanding powersystem loads.<br>Lastens svar på spänning och frekvensförändringarhar en betydande inverkan på elkraftsystemet. Sålundaär valet av en lastmodell och dess parametrar viktigt föratt kunna studera och förutsäga systemets beteende. Förnärvarande använder de nordiska stamnätsägarna (TSO)ZIP lastmodellen, eftersom det ger ett enkelt och flexibeltsätt att representera lasten. Huvudsyftet med den häravhandlingen har varit att testa två metoder för att ta framZIP modellparametrar, nämligen en komponent-baseradoch en mätnings-baserade metod. Den tidigare metodenanvänder fördefinierade parametervärden, och informationom lasternas elförbrukning, medan den senare användermätdata och kurvanpassningstekniker. För att utvärderametoden har en fallstudie genomförts där de två metodernaapplicerades på en utvärderingspunkt. Det konstateradesatt den komponent-baserade metoden kan resultera i ZIPparametrar som saknar fysisk betydelse. ZIP parametrarutan fysisk betydelse utgör en utmaning för systemplanerare,som kan ha svårt att acceptera dessa värden eftersom deär mindre intuitiva än fysiskt betydande sådana. Dessutomindikeras det, att ZIP modellen har begränsningar när detgäller att representera stora steg i den uppmätta effektenssvar, då den mätnings-baserade metoden används. Dettaär fallet för den reaktiva effekten i fallstudien. Baserat påresultaten av tillämpningen av metoden, kan man dra slutsatsenatt den komponent-baserade och mätnings-baserademetoden ge användbar information när man vill förståkraftsystems laster.
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Berggren, Axel, and 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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Seagraves, Philip. "A Multi-Factor Probit Analysis of Non-Performing Commercial Mortgage-Backed Security Loans." Digital Archive @ GSU, 2012. http://digitalarchive.gsu.edu/real_estate_diss/13.
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Commercial mortgage underwriters have traditionally relied upon a standard set of criteria for approving and pricing loans. The increased level of commercial mortgage loan defaults from 1% at the start of 2009 to 9.32% by the end of 2011 provides motivation for questioning underwriting standards which previously served the lending industry well. This dissertation investigates factors that affect the probability of Non-performance among commercial mortgage-backed security (CMBS) loans, proposes conditions under which the standard ratios may not apply, and tests additional criteria which may prove useful during economic periods previously not experienced by commercial mortgage underwriters. In this dissertation, Cap Rate Spread, the difference between the cap rate of a property and the Coupon Rate of the associated loan, is introduced to test whether the probability of Non-performance can be better predicted than by relying on traditional commercial mortgage underwriting criteria such as Loan to Value (LTV) and Debt Service Coverage Ratio (DSCR). Testing the research hypotheses with a probit model using a database of 47,883 U.S. CMBS loans from 1993 to 2011, Cap Rate Spread is found to have a significantly negative relationship with loan Non-performance. That is, as the Cap Rate Spread falls, the probability of Non-performance rises appreciably.
A numerical model suggests that among loans which would have passed the standard ratio tests requiring loans to have values of LTV less than .8 and DSCR greater than 1.25, a Cap Rate Spread criteria requiring loans to have a value greater than 1% would have prevented the origination of an additional 1,798 CMBS loans reducing the rate of Non-performance from 14.9% with only the LTV and DSCR criteria to just 11.6% by adding the Cap Rate Spread criteria. Of course, adding additional criteria will also lead to errors of rejecting loans which would have performed well. Back testing with the same sample of CMBS loans, this Type I error rate rises from 19% with only the LTV and DSCR criteria to 34% with the addition of the Cap Rate Spread.
Ultimately, CMBS loan underwriters must individually determine an acceptable level of Non-performance appropriate to their business model and tolerance for risk. Using intuition, experience, tools, and rules, each underwriter must choose a balance between the competing risks of rejecting potentially profitable loans and accepting loans which will fail. This research result is important because it helps deepen our understanding of the relationships between property income and loan performance and provides an additional tool that underwriters may employ in assessing CMBS loan risk.
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姜瑞娟 and Ruijuan Jiang. "Identification of dynamic load and vehicle parameters based on bridge dynamic responses." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31244270.
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Bulusu, Prashant. "Rolling contact fatigue predictions based on elastic-plastic finite element stress analysis and multiaxial fatigue /." abstract and full text PDF (free order & download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1437664.
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Thesis (M.S.)--University of Nevada, Reno, 2006.<br>"August, 2006." Includes bibliographical references (leaves 38-45). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2006]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.
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Rantis, Theofanis D. "Probability-based stability analysis of a laminated composite plate under combined in-plane loads." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-07292009-090358/.
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SILVA, VICTOR HUGO MARTINS MATOS. "THERMODYNAMIC AND ENVIRONMENTAL ANALYSIS OF TRIGENERATION SYSTEMS BASED ON SYSTEM STRUCTURE AND ENERGY LOADS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=31637@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>PROGRAMA DE EXCELENCIA ACADEMICA<br>O presente trabalho tem por objetivo analisar e comparar sistemas de trigeração (produção simultânea de eletricidade, aquecimento e refrigeração) de diferentes arquiteturas com base nas eficiências energética e exergética e nas emissões de CO2. Sistemas de trigeração são considerados mais eficientes na conversão de energia, se comparados a sistemas convencionais, devido ao reaproveitamento do calor de rejeito do motor térmico para outros fins (aquecimento, acionamento de chiller, ou geração de eletricidade). Quatro configurações (com chiller de compressão de vapor, com chiller de absorção, com a combinação dos ciclos anteriores, e combinado com um ciclo Rankine orgânico) foram estudadas a partir de modelos matemáticos resultantes dos balanços de energia e de exergia, e do cálculo de emissão de CO2 considerando as demandas energéticas (eletricidade, aquecimento e refrigeração) como independentes do desempenho do sistema. Todas as arquiteturas de trigeração aqui analisadas apresentaram um ponto ótimo de operação, onde o calor de rejeito recuperado para aquecimento se iguala à respectiva demanda. Neste ponto, o fator de utilização de energia (indicador de desempenho pela primeira Lei) e a eficiência exergética são máximos, e a emissão de CO2, mínima. A solução das equações resultantes mostrou também que a melhor arquitetura, do ponto de vista energético, exergético ou ambiental, dependerá da combinação das demandas energéticas.<br>The present work aims at analyzing and comparing trigeneration systems (for the simultaneous production of electricity, heating and refrigeration) of different architectures based on energetic and exergetic efficiencies and on CO2 emissions. Trigeneration systems are regarded as more efficient in energy conversion, if compared to conventional systems, due to the recovery of waste heat from the heat engine. The waste heat is used for different purposes, including heating, chiller driving or electricity generation. Four trigeneration configurations (with vapor compression chiller, absorption chiller, with a combination of the two previous cycles, or combined with an organic Rankine cycle) were studied. Mathematical models resulting from the energy and exergy balances and from the calculation of CO2 emissions were developed taking into account that the three energy demands (electricity, heating and refrigeration) are independent from the trigeneration system performance. Solution of the resulting equations indicated an optimal point of operation, for all trigeneration architectures under study, where the waste heat recovered for heating equals the heating demand. At this point, the energy utilization factor (first Law indicator) and the exergy efficiency reach their maximum value, and the CO2 emissions, its lowest. Another important finding is that the configuration with best performance, from the energetic, exergetic, or environmental point of view, will depend on how the energy demands relate to each other.
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Mazaheri, Said. "Response based analysis of an FPSO due to arbitrary wave, wind and current loads." Thesis, University of Newcastle upon Tyne, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289168.
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Kabani, Matongo. "Reliability based live loads for structural assessment of bridges on heavy-haul railway lines." Doctoral thesis, Faculty of Engineering and the Built Environment, 2018. http://hdl.handle.net/11427/30126.
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The highest live loads on railway lines are on dedicated freight corridors operated as heavy-haul lines. These lines carry high axle loads above 25 tonnes and total tonnage above 20 million tonnes per annum over distances greater than 150km. The South African iron ore line currently operates long trains of length 4.1km with 30 tonne per axle wagons on a narrow gage (1065mm) line over a distance of 861km. The operation of heavy haul lines require close monitoring and structural performance evaluation of existing bridges. This study covered both analytical studies and field measurements of bridge dynamic response and static vertical loads required to compute moments shear for beam-type bridges. The field study of dynamic amplification factors was based on strain measurements on the Olifants bridge located on the heavy-haul iron line in South Africa. The Olifants bridge is a 23 span box girder consisting of 2 continuous span segments of 11 spans at either end and a drop span in the middle. The collected strain data consisted 1174 loaded and 1372 empty train crossing events from June 2016 to March 2017. The probabilistic study was based on weigh-in-motion data of heavy-haul freight collected from January 2016 to August 2016. The study was limited to single span, 2 span and 4 span bridges with equal spans and did not consider fatigue. The dynamic response parameters of interest were frequency time evolution of bridge under heavy loads and dynamic amplification factors. An approximate formula derived using 2 dimensional beam model with moving masses is presented. The approximate formulae predicts the reduced frequency within 12% of the estimate from field vibration measurements of an 11 span continuous bridge with train to bridge linear mass ratio of 88%. The approximate formula underestimates the frequency as the stiffening contribution from train suspension system is ignored in a moving mass approximation. Dynamic amplification factors from strain measurements of a continuous 11 span bridge where considerably higher with maximum of 12% compared to 5% from a moving force analytical model for train speed below 60km/h. The amplification from measurements were considerably higher due to the additional local amplification of strains in upper flange of the box girder. A comparison of amplification factors for loaded and empty trains shows that increase in gross weight increases amplification factors. Furthermore, dynamic amplification factors are not dependent on changes in speed during train crossing. Different extrapolation techniques were used to obtain load effects from the same block maxima data. It was shown that the normal, GEV and Bayesian extrapolation methods give load effects within 1% of each other with the normal extrapolation being marginally on the lower end. This observation holds across beam types and span lengths from 5m to 50m. Although the GEV allows for all the three extreme type distributions, an analysis based on available weigh-in-motion data of axle weights show that the fitted distributions using Bayesian and Maximum Likelihood Estimate for all load effects for the span ranges are all Weibull type. On the other hand it is known that the domain of attraction for the normal distribution is Gumbel type. The study also found that extrapolated loads effects are less sensitive to increase in return period beyond 50 years. This aspect is significant as return period is a measure of safety target when determining design values for loads. The study investigated the impact of traffic volume increase and wagon axle load dependencies. The load effects on heavy-haul were shown to be more sensitive to the weak dependence than to traffic growth over the remaining service life of 50 years. The increase in return levels of load effects is less than 1% for traffic volume growth of 4% over a period of 50 years in contrast to the much higher values between 6% and 9% reported on highway bridges for 3% traffic volume growth over 40 year period. Assessment loads that account for some wagon axle dependence have lower return values of load effects than the assume that axle loads are independent which is consistent with theory.
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Bingham, Garett. "The Impact of Training Loads on In-Match Soccer Performance Variables: A Position-Based Case Report." Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/etd/2561.
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It is critical to maintain multiple fitness characteristics during the soccer season through the use of training, but also to ensure that the training loads do not hinder subsequent match performance. The purpose of this thesis is to investigate the impact of the training load on key physical performance variables in the subsequent match. Five Division I female soccer players were analyzed across six weeks of training and matches. Training loads in the forms of odometer, high intensity odometer, estimated odometer and sRPE were accumulated at time points from one to five days prior to a match. The accumulated training loads were then correlated with the same performance measures from match play. The greatest significant correlations were seen in sRPE training loads when compared to match odometer and estimated distance. There does not appear to be negative effect on match performance when looking at any of the accumulated training load values.
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Tošić, Marko. "Model of Thermal EHL Based on Navier-Stokes Equations : Effects of Asperities and Extreme Loads." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-75694.
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A common approach in numerical studies of elastohydrodynamic lubrication (EHL) is based on solving the Reynolds equation that governs pressure distribution in thin lubricant films. The Reynolds equation is derived from the Navier-Stokes equations by taking assumptions that are considered valid when the thickness of the lubricant film is much smaller than its length. A massive increase in the computing power over the last decades has enabled the use of CFD (computational fluid dynamics) approach, based on the Navier-Stokes equations, in solving the EHL problem. Comparisons between the CFD and Reynolds approach have generally shown very good agreement. Differences can occur when the thin film assumptions of the Reynolds equation are not applicable. In this study, a CFD approach has been chosen with the aim of investigating effects of asperities and rheology at high loads on the behavior of the thin EHL films. A high quality mesh was generated in ANSYS ICEM CFD, while ANSYS Fluent has been employed in solving the Navier-Stokes equation by finite volume method (FVM). For EHL modeling, a set of user-defined functions (UDFs) were used for computing density, viscosity, wall temperature, heat source and elastic deformation of one of the contacting surfaces. Two lubricants were used, a commonly used oil in CFD analyses of EHL and Squalane. Non-Newtonian fluid behavior and thermal effects were considered. For Squalane, the two rheology models, Ree-Eyring and Carreau were compared. Squalane has been chosen in this study since it is one of the rare fluids with known parameters for both rheology models. Finally, the influence of surface roughness was explored for the cases of a single asperity and a completely rough wall. A surface roughness profile is generated in MATLAB by using the Pearson distribution function. In the cases where the surfaces are assumed to be completely smooth, the obtained results at the pressure of about 0.5 GPa closely correspond to literature, both in the case of Newtonian and non-Newtonian fluid behavior. At the pressure of about 1 GPa, severe shearing of the lubricant film has been noticed, characterized by a pronounced shear-band and plug flow. It was found that the choice of viscosity and rheology models has a large influence on the obtained results, especially at the high pressure levels. Finally, it was discovered that the developed CFD model of EHL has a great potential in studying the effects of surface roughness on the lubricant film behavior.
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Chang, Joon Keun. "Analysis of distressed Commercial Mortgage backed Securities (CMBS) loans and special servicing : a case study." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/129103.
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Thesis: S.M. in Real Estate Development, Massachusetts Institute of Technology, Program in Real Estate Development in conjunction with the Center for Real Estate, September, 2020<br>Cataloged from student-submitted PDF of thesis.<br>Includes bibliographical references (pages 49-53).<br>The outbreak of the COVID-19 pandemic in late 2019 has largely impacted the global economy by changing every aspect of our living environment with limited social and economic activities throughout 2020. This unprecedented economic downfall exposed real estate properties to high risk of default, pushing the CMBS loans delinquency rate to 10.32% in June 2020. As such an economic halt is likely to prevail, it is expected that the Commercial Real Estate (CRE) market would experience more distress in terms of debt service. Thus, it is imperative to overview the CMBS securitization process, the servicing structure, and the workout scenarios in case of loan default in order to understand the complexity of the CMBS structure and better prepare appropriate measures or strategies in response to current market landscape. By having a case study on 666 Fifth Avenue in New York, this paper will analyze one of the most high-profile properties that was transferred to special servicing to review strategies to resolve financial distress.<br>by Joon Keun Chang.<br>S.M. in Real Estate Development<br>S.M.inRealEstateDevelopment Massachusetts Institute of Technology, Program in Real Estate Development in conjunction with the Center for Real Estate
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Alfred, Mohammed Emmanuel. "Reliability based methodology for the assessment of cumulative life-time hydrodynamic loads and structural capacity." Thesis, University of Newcastle upon Tyne, 2015. http://hdl.handle.net/10443/2854.
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A methodology for the assessment of global wave load combinations on a container ship is developed taking into account load modelling uncertainties such as the sea state, the speed with and direction in which the ship travels etc. Data from wave statistics are used to determine the sea state which is required for specifying the sea spectrum associated with a given sea state. The sea spectrum together with the response amplitude operators (RAOs) of the ship are used to determine the stochastic responses of the ship in waves. This load combination methodology employs stochastic analysis in conjunction with cross-spectral analysis to determine a given wave-induced load that is associated with a principal wave-induced load which have been determined a priori via common spectral methods. All the global wave-induced loads are assumed to be random variables that are Gaussian distributions with zero means and variances obtained from their respective zeroth spectral moments. The peaks of the responses are modelled as Rayleigh distributions and the combination of any two responses modelled by a copula function which is a bivariate Rayleigh distribution with parameters such as the zeroth spectral moments of the responses concerned and their interactions in form of a correlation parameter obtained via a cross-spectral analysis of the given responses. Load combinations are obtained with respect to any given design extreme global wave-induced load as the principal load whose effects may be a source for concern at the design stage of the ship. The results were compared to results obtained from existing methods of load combinations. A Spearman’s rank correlation test shows a very good covariation between the compared methods. Nonlinear finite element modelling and analyses on the midship section of a 10,000 TEU container ship are used to assess its ultimate strength under combined loads such as the vertical bending moment, horizontal bending moment and torsional moment. The primary loads that act on an actual ship hull girder are of different modes corresponding to the six degrees of freedom hence it is more realistic to consider the ii E. Alfred Mohammed effects of loads in other modes other than the dominant vertical bending moment in the determination of the longitudinal strength of the hull girder. Torsional moment is particularly important because it can be a serious problem for container ships which have wide open hatches and hence low torsional rigidity. A three-compartment finite element model for the container ship OL185 is developed from the transverse section detail of the ship. A progressive collapse analyses are performed on it using the Abaqus finite element code to determine the ultimate strength of the container ship under combined vertical bending, horizontal bending and torsional moments. These provide a basis for load interaction and combination studies via interaction relationships featuring the relevant load combinations. Finally, the interaction relationships are used to show the hull girder safety margin via a comparison with a predetermined global wave-induced load combination for the midship section of OL185 container ship obtained using the cross-spectral probabilistic methodology.
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Péan, Thibault Q. "Heat pump controls to exploit the energy flexibility of building thermal loads." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/669805.
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Smart controls for heat pumps are required to harness the full energy flexibility potential of building thermal loads. A literature review revealed that most strategies used for this purpose can be classified in two categories: simpler rule-based control (RBC), and model predictive control (MPC), a more complex strategy based on optimization and requiring a prior model of the systems. Both RBC and MPC can use external penalty signals to prompt their actions. The price of electricity is most often used for this purpose, leading to strategies of cost reduction. As an alternative penalty signal, a novel marginal CO2 emissions signals was also conceived.
In this thesis, both an RBC and an MPC controllers were developed as supervisory controls for an air-to-water heat pump supplying the heating and cooling needs of a residential building type from the Mediterranean area of Spain. The RBC strategy modulates the temperature set-points, while the MPC strategy minimizes the overall summed penalties (costs or emissions) due to the heat pump use, while balancing with comfort constraints and a proper operation of the systems. The MPC controller in particular required the development of a simplified model of the building envelope and of the heat pump performance, both adjusted differently for heating or cooling. The MPC included several novelties, such as the mixed-integer formulation, the heat pump simplified model based on experimental data and the consideration of its computational delay.
The developed controllers were then tested, firstly in an experimental “hardware-in-the-loop” setup, with a real heat pump installed in the laboratory facilities, and connected to thermal benches that emulated the loads from a building model. Implementing the control strategies on a real heat pump enabled to highlight some practical challenges such as model mismatch in the MPC, communication issues, interfacing and control conflicts with the heat pump local controller. Secondly, a simulation-only framework was developed to test other configurations of the controllers, with TRNSYS as the main dynamic building simulation tool, coupled with MATLAB for the MPC controller. In that case, the real heat pump was replaced by a detailed model which was specially developed for this purpose. It is based on static tests performed in the laboratory, and therefore reproduces the dynamic behavior of the heat pump with high fidelity.
The results from experimental and simulation studies revealed the ability of both types of controllers to shift the building loads towards periods of cheaper or less CO2-emitting electricity, these two objectives being in fact contradictory. In the cases where the reference control presented a large margin for improvements, the RBC and MPC controllers performed equally and provided important savings: around 15% emissions savings in heating mode, and 30% cost savings in cooling mode. In the cases where the reference control already performed close to optimally, the RBC controller failed to provide improvements, while the MPC benefitted from its stronger optimization and prediction features, reaching 5% cost savings in heating mode and 10% emissions savings in cooling mode.
The research carried out in this thesis covered many aspects of energy flexibility in buildings: creation of input penalty signals, graphical representation of flexibility, development of controllers, performance in realistic experimental setup, fitting of appropriate models and compared performance in heating and cooling. The development efforts and barriers hindering the deployment of MPC controllers at large scale for building climate control have additionally been discussed. The performance of the developed controllers was evidenced in the thesis, proving their potential for load-shifting incentivized by different penalty signals: they could become a strong asset to unlock demand-side flexibility and in fine, help integrating a larger share of RES in the grid.<br>Para aprovechar todo el potencial de flexibilidad energética de las cargas térmicas en los edificios equipados con bombas de calor se requiere de sistemas de control inteligente. Una revisión bibliográfica ha revelado que la mayoría de las estrategias de gestión utilizadas para esta finalidad pueden ser clasificadas en dos categorías: control en base a reglas (RBC en inglés) o predictivo (MPC en inglés), basado en optimización y en el uso de modelos. Tanto RBC como MPC pueden utilizar señales externas de penalización para fundamentar sus decisiones. El precio de la electricidad es utilizado a este fin de forma habitual en estrategias de reducción de coste. Una nueva señal de emisiones marginales de CO2 fue también creada como alternativa. Se han desarrollado un controlador RBC y un MPC para sistemas de bombas de calor aire-agua que cubren las demandas de climatización y agua caliente en el ámbito residencial. El RBC modula las consignas de temperatura, y el MPC minimiza las penalizaciones totales del sistema, al mismo tiempo que se consideran restricciones operativas y de confort. En particular, el MPC ha requerido el desarrollo de nuevos modelos simplificados, para predecir la demanda del edificio y el rendimiento de la bomba de calor, tanto en modo calefacción como en modo refrigeración. Otras novedades añadidas en la configuración del MPC son la formulación entera mixta, y la consideración del retraso debido al tiempo de cómputo. Los controladores fueron testeados, primeramente, en un entorno experimental -hardware-in-the-loop-, con una bomba de calor real instalada en el laboratorio y conectada a unos bancos térmicos que emulan las cargas térmicas del edificio. El entorno experimental ha permitido poner de manifiesto algunos retos prácticos tales como la discrepancia en el modelo del MPC y conflictos de conexión con el controlador local de la bomba de calor. En segundo lugar, un entorno de simulación ha sido creado para testear diversas configuraciones, usando TRNSYS acoplado con MATLAB. Para ello, se ha desarrollado un modelo detallado de la bomba de calor, basado en ensayos realizados en laboratorio, que reproduce el comportamiento dinámico de la bomba de calor con alta fidelidad. Tanto los resultados experimentales como los simulados han revelado la capacidad de los dos tipos de control de desplazar las cargas del edificio hacia periodos donde la electricidad era más barata o había menos emisiones de CO2, estos dos objetivos presentando de hecho impactos contradictorios. En los casos donde el control de referencia presentaba un amplio margen de mejora, los controladores RBC y MPC han demostrado la capacidad de actuar eficientemente y proveer ahorros importantes: alrededor de un 15% de emisiones en modo calefacción, y de un 30% de coste en modo frío. En aquellos casos en el que el control de referencia actuaba de forma cercana a la óptima, los controladores RBC no han sido capaces de aportar mejoras significativas, mientras que el MPC ha demostrado la capacidad de conseguir ahorros de un 5% de coste en modo calefacción y de un 10% de emisiones en modo frío. La investigación realizada en esta tesis ha abarcado amplios aspectos de la flexibilidad energética en los edificios: la generación de señales de penalización, la representación gráfica del potencial de flexibilidad, el ajuste de modelos simplificados, el desarrollo de controladores, el ensayo en entorno experimental y de simulación, con la consecuente evaluación de su rendimiento comparado en periodos de invierno y de verano, así como una discusión de las barreras que dificultan la implementación de controladores MPC y RBC a gran escala.
Finalmente, la tesis ha evidenciado el rendimiento de los controladores desarrollados si se formulan de forma adecuada, demostrando su potencial para el desplazamiento del consumo eléctrico en la edificación residencial con sistemas de bomba de calor respondiendo a diferentes señales de penalización. En conclusión, los sistemas
propuestos pueden ser elementos muy valiosos para favorecer la necesaria flexibilidad de la demanda térmica en la edificación y posibilitar la integración de sistemas de generación renovables en la red
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Sällqvist, Jessica. "Real-time 3D Semantic Segmentation of Timber Loads with Convolutional Neural Networks." Thesis, Linköpings universitet, Datorseende, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-148862.
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Volume measurements of timber loads is done in conjunction with timber trade. When dealing with goods of major economic values such as these, it is important to achieve an impartial and fair assessment when determining price-based volumes. With the help of Saab’s missile targeting technology, CIND AB develops products for digital volume measurement of timber loads. Currently there is a system in operation that automatically reconstructs timber trucks in motion to create measurable images of them. Future iterations of the system is expected to fully automate the scaling by generating a volumetric representation of the timber and calculate its external gross volume. The first challenge towards this development is to separate the timber load from the truck. This thesis aims to evaluate and implement appropriate method for semantic pixel-wise segmentation of timber loads in real time. Image segmentation is a classic but difficult problem in computer vision. To achieve greater robustness, it is therefore important to carefully study and make use of the conditions given by the existing system. Variations in timber type, truck type and packing together create unique combinations that the system must be able to handle. The system must work around the clock in different weather conditions while maintaining high precision and performance.
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Yavuz, Ercan Aykan. "Reliability Based Safety Assessment Of Buried Continuous Pipelines Subjected To Earthquake Effects." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615423/index.pdf.
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Lifelines provide the vital utilities for human being in the modern life. They convey a great
variety of products in order to meet the general needs. Also, buried continuous pipelines are
generally used to transmit energy sources, such as natural gas and crude oil, from production
sources to target places. To be able to sustain this energy corridor efficiently and safely,
interruption of the flow should be prevented as much as possible. This can be achieved providing
target reliability index standing for the desired level of performance and reliability. For natural
gas transmission, assessment of earthquake threats to buried continuous pipelines is the primary
concern of this thesis in terms of reliability. Operating loads due to internal pressure and
temperature changes are also discussed. Seismic wave propagation effects, liquefaction induced
lateral spreading, including longitudinal and transverse permanent ground deformation effects,
liquefaction induced buoyancy effects and fault crossing effects that the buried continuous
pipelines subjected to are explained in detail. Limit state functions are presented for each one of
the above mentioned earthquake effects combined with operating loads. Advanced First Order
Second Moment method is used in reliability calculations. Two case studies are presented. In the
first study, considering only the load effect due to internal pressure, reliability of an existing
natural gas pipeline is evaluated. Additionally, safety factors are recommended for achieving the
specified target reliability indexes. In the second case study, reliability of another existing natural
gas pipeline subjected to above mentioned earthquake effects is evaluated in detail.
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Gil, Raga Jordi. "Full-wave analysis and design of passive microwave and millimetre-wave devices based on dielectric-loaded cavity resonators." Doctoral thesis, Universitat Politècnica de València, 2010. http://hdl.handle.net/10251/7442.
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Desde los primeros estudios desarrollados por S.B. Cohn a finales de los años 60, los resonadores dieléctricos, con factor de calidad elevado, han sido utilizados para el diseño de filtros paso-banda de microondas. A partir de la aparición en los años 70 de materiales dieléctricos con las propiedades eléctricas y estabilidad térmica idónes, los resonadores dieléctricos se convirtieron en elementos clave en numerosos diseños de filtros. De hecho, esta tecnología se encuentra frecuentemente en sistemas de comunicaciones míviles y por satélite debido a sus ventajas en términos de reducción de masa y volumen, bajas pérdidas, y estabilidad térmica. Por todo ello, el análisis y diseño riguroso de este tipo de filtros ha suscitado un gran interés en la literatura técnica.
El objetivo principal de esta tesis doctoral es el desarrollo de una técnica modal eficiente para caracterizar el comportamiento electromagnético de cavidades resonantes cargadas con dieléctricos. Para ello, se presenta una nueva formulación de ecuación integral en el espacio de estados basada en el método BI-RME (del inglés, boundary integral-resonant mode expansion). En dicha formulación, para resolver la ecuación integral de volumen planteada, el resonador dieléctrico se caracteriza de manera rigurosa por medio de las densidades de carga y corriente de polarización equivalentes definidas en el volumen del objeto dieléctrico. Siguiendo este método, los modos resonantes de las cavidades se obtienen a través de la solución de un problema lineal de autovalres. Así mismo, se obtiene la matriz generalizada de admitancias de la cavidad resonante cargada con dieléctrico como una expansión en serie de polos en el dominio de la varable de Laplace. De esta manera, la respuesta electromagnética de las cavidades resonantes puede resolverse en un rango amplio de puntos de frecuencia haciendo uso de un reducido esfuerzo computacional, y evitando así, cálculos intensos en cada punto de frecuencia.<br>Gil Raga, J. (2010). Full-wave analysis and design of passive microwave and millimetre-wave devices based on dielectric-loaded cavity resonators [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/7442<br>Palancia
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Bornkessel, Thomas [Verfasser]. "Numerical Analysis of the Mechanical Performance and the Thermal Loads of Ground-Based Telescopes / Thomas Bornkessel." Aachen : Shaker, 2007. http://d-nb.info/1166508897/34.
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Imran, Kashif. "Agent based modelling and simulation of operating strategies of generators and loads in wholesale electricity markets." Thesis, University of Strathclyde, 2015. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25991.
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Mohammadi, M. Sajad, and Rishiraj Mukherjee. "Wind Loads on Bridges : Analysis of a three span bridge based on theoretical methods and Eurocode 1." Thesis, KTH, Bro- och stålbyggnad, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-125349.
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The limitations lying behind the applications of EN-1991-1-4, Eurocode1, actions on structures-general actions-wind load-part 1-4, lead the structural designers to a great confusion. This may be due to the fact that EC1 only provides the guidance for bridges whose fundamental modes of vibration have a constant sign (e.g. simply supported structures) or a simple linear sign (e.g. cantilever structures) and these modes are the governing modes of vibration of the structure. EC1 analyzes only the along-wind response of the structure and does not deal with the cross wind response. The simplified methods that are recommended in this code can be used to analyze structures with simple geometrical configurations. In this report, the analytical methods which are used to describe the fluctuating wind behavior and predict the relative static and dynamic response of the structure are studied and presented. The criteria used to judge the acceptability of the wind load and the corresponding structural responses along with the serviceability considerations are also presented. Then based on the given methods the wind forces acting on a continuous bridge whose main span is larger than the 50 meters (i.e. > 50 meter requires dynamic assessment) is studied and compared with the results which could be obtained from the simplified methods recommended in the EC1.
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Hasan, Mehedi. "Aggregator-Assisted Residential Participation in Demand Response Program." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/32546.
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The demand for electricity of a particular location can vary significantly based on season, ambient temperature, time of the day etc. High demand can result in very high wholesale price of electricity. The reason for this is very short operating duration of peaking power plants which require large capital investments to establish. Those power plants remain idle for most of the time of a year except for some peak demand periods during hot summer days. This process is inherently inefficient but it is necessary to meet the uninterrupted power supply criterion. With the advantage of new technologies, demand response can be a preferable alternative, where peak reduction can be obtained during the short durations of peak demand by controlling loads. Some controllable loads are with thermal inertia and some loads are deferrable for a short duration without making any significant impact on usersâ lifestyle and comfort. Demand response can help to attain supply - demand balance without completely depending on expensive peaking power plants.
In this research work, an incentive-based model is considered to determine the potential of peak demand reduction due to the participation of residential customers in a demand response program. Electric water heating and air-conditioning are two largest residential loads. In this work, hot water preheating and air-conditioning pre-cooling techniques are investigated with the help of developed mathematical models to find out demand response potentials of those loads. The developed water heater model is validated by comparing results of two test-case simulations with the expected outcomes. Additional energy loss possibility associated with water preheating is also investigated using the developed energy loss model. The preheating temperature set-point is mathematically determined to obtain maximum demand reduction by keeping thermal loss to a minimal level. Case studies are performed for 15 summer days to investigate the demand response potential of water preheating. Similarly, demand response potential associated with pre-cooling operation of air-conditioning is also investigated with the help of the developed mathematical model. The required temperature set-point modification is determined mathematically and validated with the help of known outdoor temperature profiles. Case studies are performed for 15 summer days to demonstrate effectiveness of this procedure. On the other hand, total load and demand response potential of a single house is usually too small to participate in an incentive-based demand response program. Thus, the scope of combining several houses together under a single platform is also investigated in this work. Monte Carlo procedure-based simulations are performed to get an insight about the best and the worst case demand response outcomes of a cluster of houses. In case of electrical water heater control, aggregate demand response potential of 25 houses is determined. Similarly, in case of air-conditioning control (pre-cooling), approximate values of maximum, minimum and mean demand reduction amounts are determined for a cluster of 25 houses. Expected increase in indoor temperature of a house is calculated. Afterwards, the air-conditioning demand scheduling algorithm is developed to keep aggregate air-conditioning power demand to a minimal level during a demand response event. Simulation results are provided to demonstrate the effectiveness of the proposed algorithm.<br>Master of Science
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Ritz, Guillaume Henri [Verfasser]. "Performance of tungsten-based materials and components under ITER and DEMO relevant steady-state thermal loads / Guillaume Henri Ritz." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2011. http://d-nb.info/1018203524/34.
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Karlsrud, Kjell. "Prediction of load-displacement behaviour and capacity ofaxially loaded piles in clay based on analyses and interpretation of pile load test results." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bygg, anlegg og transport, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-17071.
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The main objective of the work presented herein was to develop new semi-empirical design procedures for determination of bearing capacity and load-displacement response of axially loaded piles in clay. Hereunder also prediction of how the capacity will build up with time following the pile installation, primarily as a result of consolidation. A main basis for developing new procedures was the collection, detailed review and assessment of results from a series test programs carried out over the past 30 years on well instrumented piles. The data collected and reviewed include the pile installation, re-consolidation, and loading phases. The pile instrumentation includes measurement of the distribution of loads or shaft friction, pore pressure and earth pressure along the pile shafts. The soil conditions range from soft NC clays with undrained shear strength down to about 15 kPa, to very stiff and high OCR clays with undrained shear strength up to about 500 kPa. The plasticity index of the clays mostly lies in range 10 to 60 %. The test piles range from small scale model piles with diameter down to 36 mm and length down to 1- 2 m, to large scale piles with diameter up to 800 mm and length up 71 m. In addition to these fully instrumented pile tests, some recent large scale tests on non-instrumented piles are also reviewed and included as basis for developing the new proposed design procedures. Two new procedures for predicting ultimate shaft friction are proposed, respectively a so-called α- and β approach. They tie the local ultimate shaft friction along a pile to the “true” undisturbed in-situ undrained strength of the clay as determined from Direct Simple Shear Tests, the in-situ vertical effective stress, the overconsolidation ratio, and the plasticity index of the clay. No clear evidence is found of effects of pile diameter, length or stiffness on the local ultimate shaft friction, or whether the pile is open-or closed- ended. A moderate effect of pile length or flexibility on the total ultimate pile capacity will still come out of the proposed t-z curves, which include some postpeak reduction. A brief review and summary is also given of measured effects of cyclic loads on the axial capacity and pile head displacements of piles. It is concluded that this issue can be well accounted for by analytical or numerical procedures already in existence. A semi – empirical analytical procedure, based on linear radial consolidation theory, is proposed for predicting the time required for re-consolidation and “set-up” of the ultimate shaft friction. The main input parameters are the in-situ permeability and virgin modulus number (or virgin compression index) of the undisturbed clay. The same basic formula and correlations were found applicable to both open- and closed- ended or partially plugging piles. For design purposes it is very important to recognise that the time for full set-up can easily be a factor of 10 longer for a closed– ended pile than for an ideal nonplugging open- ended pile. It was also an objective to study how well the measured pile response during installation, re-consolidation and pile loading could be predicted from analytical and numerical models. Although such procedures can give very valuable insight, there is still a way to go before they can correctly capture all relevant elements of the pile response. The greatest need for improvement is to establish a better understanding of how the severe disturbance and strains induced by the pile installation affects the basic stress-strain, strength-, and volumetric compressibility- characteristics of the clay, depending on the level of induced shear strains as function of radial distance from the pile wall.
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Rahman, Md Moshiur. "Design and Implementation of a Web-based Home Energy Management System for Demand Response Applications." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23689.
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The objective of this work is to design and implement an architectural framework for a web-based demand management system that allows an electric utility to reduce system peak load by automatically managing end-use appliances based on homeowners\' preferences. The proposed framework comprises the following components: human user interface, home energy management (HEM) algorithms, web services for demand response communications, selected ZigBee and smart energy profile features for appliance interface, and security aspects for a web-based HEM system. <br />The proposed web-based HEM system allows homeowners to be more aware about their electricity consumption by allowing visualization of their real-time and historical electricity consumption data. The HEM system enables customers to monitor and control their household appliances from anywhere with an Internet connection. It offers a user-friendly and attractive display panel for a homeowner to easily set his/her preferences and comfort settings. <br />An algorithm to autonomously control appliance operation is incorporated in the proposed web-based HEM system, which makes it possible for residential customers to participate in demand response programs. In this work, the algorithm is demonstrated to manage power-intensive appliances in a single home, keeping the total household load within a certain limit while satisfying preset comfort settings and user preferences. Furthermore, an extended version of the algorithm is demonstrated to manage power-intensive appliances for multiple homes within a neighborhood.<br />As one of the demand response (DR)-enabling technologies, the web services-based DR communication has been developed to enable households without smart meters or advanced metering infrastructure (AMI) to participate in a DR event via the HEM system. This implies that an electric utility can send a DR signal via a web services-enabled HEM system, and appropriate appliances can be controlled within each home based on homeowner preferences. The interoperability with other systems, such as utility systems, third-party Home Area Network (HAN) systems, etc., is also taken into account in the design of the proposed web services-based HEM system. That is, it is designed to allow interaction with authorized third-party systems by means of web services, which are collectively an interface for machine-to-machine interaction. <br />This work also designs and implements device organization and interface for end-use appliances utilizing ZigBee Device Profile and Smart Energy Profile. Development of the Home Area Network (HAN) of appliances and the HAN Coordinator has been performed using a ZigBee network. Analyses of security risks for a web-based HEM system and their mitigation strategies have been discussed as well.<br /><br>Master of Science
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Reeb, Alexander Brenton. "Response of Pile-Supported T-Walls to Fill Loading and Flood Loading Based on Physical Model Studies and Numerical Analyses." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/64498.
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Pile-supported T-walls, which are concrete floodwalls that are shaped like an inverted "T" and supported by batter piles, are commonly used by the United States Army Corps of Engineers (USACE) to protect low-lying portions of New Orleans and other areas. The design of a T-wall in southern Louisiana is complex, as the structure needs to resist both 1) large settlements caused by fill placed beneath and beside the T-wall before T-wall construction or by fill placed beside the T-wall after T-wall construction, and 2) large lateral flood loads that are imposed during a hurricane. As a result of these loading conditions, large bending moments can develop in the batter piles and these moments need to be accounted for as part of the T wall design.
The goal of this research is to develop a more complete understanding of the pile bending moments in T wall systems, specifically for cross sections where large settlements may occur. As a first step towards this goal, Rensselaer Polytechnic Institute (RPI) performed a series of eight centrifuge tests to investigate and physically model the effects of settlement-induced bending moments on pile-supported T-walls. The centrifuge tests were evaluated and interpreted, and in order to better capture uncertainty, upper and lower bounds were estimated for the interpreted data. The centrifuge results offered some valuable insights on their own, but were ultimately used as the basis for validating and calibrating corresponding numerical models.
The numerical models were developed following a rigorous modeling approach and using rational and reasonable assumptions based on widely-accepted and well-justified procedures. The numerical model results were in good agreement with the centrifuge results without the need for significant calibration or modifications. This good agreement indicates that similar numerical models can be developed to reliably analyze actual T-wall cross sections.
Detailed recommendations were developed for using numerical models to analyze pile-supported T walls, and an example problem is presented herein that illustrates the application of this approach. These same techniques were then used to perform a parametric study to analyze the combined and separate effects of flood loading for a wide range of different T-wall cross sections. The range was selected in collaboration with the USACE in order to reasonably cover cross sections and conditions that 1) are typically encountered in practice, and 2) were expected to generate both upper and lower bound pile bending moments. In total, 3,648 cross sections were analyzed, and 29,184 sets of analysis results were generated since each cross section was analyzed for eight different loading conditions. Summary results are provided to show the influence of the loading conditions and parameters on T-wall response, including the influence of flood loading, new fill symmetry, pile fixity, number of piles, subsurface profile, pile batter, pile type, levee slope, T-wall elevation, and the presence of existing levee fill. In addition, the key results for all of the analyses are provided in the appendices and in an electronic database.
Based on the parametric study results, a simplified analysis procedure was developed that can be used to calculated maximum pile bending moments for T walls installed directly on foundation soils due to settlements. In this procedure, the loads from new fill placed during or after T-wall construction are distributed onto the pile, and the pile response is analyzed using traditional p-y curves and a beam on elastic foundation formulation. This procedure shows good agreement with the numerical model results for a range of conditions. To demonstrate the application of the procedure, the same example problem that is analyzed numerically is reanalyzed using the simplified analysis procedure. Due to the complexity of the problem, it was not possible to modify this procedure or develop a similar procedure for T-walls installed on top of new or existing levees.
Overall, this research demonstrates that numerical models can be used to calculate the bending moments that can develop in pile-supported T-walls due to settlements and flood loading, provides valuable insights into the behavior of T-walls and the influence of various parameters on T-wall response, presents a large database of T-wall analysis results, and recommends a simplified analysis procedure that can be used in some cases to calculate pile bending moments due to settlements.<br>Ph. D.
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Ironside, James G. "An in vitro analysis of the behaviour of an alumina based dental all-ceramic restorative system subjected to occlusal loads." University of Sydney, 2001. http://hdl.handle.net/2123/4254.
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Doctor of Philosophy<br>The commercial introduction of glass infiltrated slip cast ceramic technology as a core dental ceramic for crowns and bridges began in 1990. The system known as Inceram® provided a metal free ceramic core with a flexural strength that was reported to be between 400 and 600 MPa. The first aim of this study was to investigate in vitro fractures for this type of crown that occurred from high localized occlusal loading. The second aim was to propose suitable guidelines for the construction of crowns that are more crack resistant when loaded by a spherical object such as an opposinc cusp. The review of the literature identified Young’s modulus (E) as an important aspect for the behaviour of a brittle solid when it is exposed to load. Young’s modulus is involved in the total energy of the solid, its free surface energy, its toughness, parameters involved in contact areas, stresses from indenters on those contact areas and at the interface between two materials with different moduli. This mismatch was to become more important when Finite Element Analysis was applied to the test results. A second physical property that has importance in bilaminar minerals is Poisson’s ratio. Less important than Young’s modulus, Poisson’s ratio still provides some of the answers to crack propagation at an interface, highlighted by the description of Dundurs parameters (Mencik 1996). The use of Weibull statistics provided information concerning reliability for different core to veneer thickness ratios in the experimental models and crown designs. The first experimental part was to establish a crown model suitable for investigation. The porcelain jacked crown restoration for an upper incisor was chosen because it provided the best opportunity to vary the construction parameters of the crown without sacrificing the aesthetics. The results from this initial in vitro study established thickness ranges for the standard design of these crowns, the loads that could be expected and the two types of fracture patterns that might occur when the bilaminar system is loaded via a hard steel ball indenter in the middle of the palatal surface. The data from chapter three were then compared with two basic bilaminar and monolithic disc designs to establish the relevance of the dimensions of the ISO standard test specimen design for flexural strength. The results of this chapter confirmed that the loads were in the same range for the bilaminate discs, and that the flexural strengths for the two component parts were in agreement with other known results. The use of Finite Element Analysis (FEA) was employed to provide an additional method for testing the model to establish areas when principal stresses might lie and how they were distributed. It was found that the ISO flexural strength test was not ideal for testing bilaminates because it did not account for the large mismatch in Young’s modulus between the two component materials. The FEA revealed an unexpected increase in tensile stress on the bottom surface of the In-Ceram when it was the bottom layer in the bilaminate. The FEA did confirm the difference between a flat punch and a ball indenter for stress intensities around the contact area with the ball indenter producing higher stresses for a given load…
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Fathi, Navid. "Study of an axially loaded sandwich panel : Study based on finite element analysis and experimentation of a 1 mm flat profiled steel plate." Thesis, Luleå tekniska universitet, Byggkonstruktion och brand, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-66975.
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Sandwich panels produced by Isolamin AB are comprised of a core, such as polyurethane or mineral wool that is attached between two steel plates. The problem that the thesis attempts to solve is whether a flat profiled sandwich panel of 1mm can withstand loads from 3-storey modular house. To solve this problem investigation in other forms of buckling behaviour will be done. This investigation will be carried out through experimentation, finite element modelling and calculations to find resistance values. Ultimately, these results will be analysed and examined and prove if the sandwich panel with 1mm steel plate is able to withstand a 3-storey modular house.
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Ievdokymov, Mykola [Verfasser], Holm [Akademischer Betreuer] Altenbach, and Manja [Akademischer Betreuer] Krüger. "Identification technique of mechanism-based constitutive model for cast iron under thermo-mechanical loads / Mykola Ievdokymov. Betreuer: Holm Altenbach ; Manja Krüger." Magdeburg : Universitätsbibliothek, 2015. http://d-nb.info/1072146681/34.
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Wang, Naiyu. "Reliability-based condition assessment of existing highway bridges." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34835.
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Condition assessment and safety verification of existing bridges and decisions as to whether bridge posting is required are addressed through analysis, load testing, or a combination of methods. Bridge rating through structural analysis is by far the most common procedure for rating existing bridges. The American Association of State Highway and Transportation Officials (AASHTO) Manual for Bridge Evaluation (MBE), First Edition permits bridge capacity ratings to be determined through allowable stress rating (ASR), load factor rating (LFR) or load and resistance factor rating (LRFR); the latter method is keyed to the AASHTO LRFD Bridge Design Specifications, which is reliability-based and has been required for the design of new bridges built with federal findings since October, 2007. A survey of current bridge rating practices in the United States has revealed that these three methods may lead to different ratings and posting limits for the same bridge, a situation that carries serious implications with regard to the safety of the public and the economic well-being of communities that may be affected by bridge postings or closures.
To address this issue, a research program has been conducted with the overall objective of providing recommendations for improving the process by which the condition of existing bridge structures is assessed. This research required a coordinated program of load testing and finite element analysis of selected bridges in the State of Georgia to gain perspectives on the behavior of older bridges under various load conditions. Structural system reliability assessments of these bridges were conducted and bridge fragilities were developed for purposes of comparison with component reliability benchmarks for new bridges. A reliability-based bridge rating framework was developed, along with a series of recommended improvements to the current bridge rating methods, which facilitate the incorporation of various in situ conditions of existing bridges into the bridge rating process at both component and system levels. This framework permits bridge ratings to be conducted at three levels of increasing complexity to achieve the performance objectives, expressed in the terms of reliability, that are embedded in the LRFR option of the AASHTO Manual of Bridge Evaluation. This research was sponsored by the Georgia Department of Transportation, and has led to a set of Recommended Guidelines for Condition Assessment and Evaluation of Existing Bridges in Georgia.
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Petrovic, Marko. "Approaching Complex Credit-Driven Economies From The Bottom Up: An Agent-Based Model for Open Economies And An Empirical Study on Loans’ Distribution." Doctoral thesis, Universitat Jaume I, 2017. http://hdl.handle.net/10803/457537.
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In this thesis we use methodologies that are grounded on a ``bottom-up'' approach, denoting the importance of considering the emergence of the aggregate economic behavior from the interaction of heterogeneous economic agents. We apply this ``bottom-up' methodology both for designing a macroeconomic multi-country model and for studying the bank credit allocation in Spain from micro data about the balance sheet of Spanish companies. The work on the multi-country model allows us to examine the macroeconomic implications of joining a union for two countries in different economic scenarios. Our main conclusions are that the performance of the union is in general superior to the performance of isolated countries, but in some cases the union can exacerbate inequalities between the countries. In empirical work we discovered that large companies obtained most of the loans in Spain.<br>En esta tesis utilizamos metodologías basadas en un enfoque "bottom-up", que denotan la importancia de considerar la formación del comportamiento económico agregado a partir de la interacción de los agentes económicos heterogéneos. Aplicamos esta metodología "bottom-up" tanto para el diseño de un modelo macroeconómico multinacional como para el estudio de la asignación de crédito bancario en España a partir de datos microeconómicos sobre el balance de las empresas españolas. El trabajo sobre el modelo multinacional nos permite examinar las implicaciones macroeconómicas de unirse en una unión para dos países en diferentes escenarios económicos. Nuestras principales conclusiones son que la performance de la unión es en general superior a la performance de los países aislados, pero en algunos casos la unión puede exacerbar las desigualdades entre los países. En el trabajo empírico descubrimos que las grandes empresas obtuvieron la mayor parte de los préstamos en España.
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Huang, De-Xing, and 黃得興. "Loaded front vehicle detection based on neural networks." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/c8chfd.
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碩士<br>國立中正大學<br>電機工程研究所<br>106<br>In recent years, Taiwan has continuously report cases of injuries caused by traffic accidents, so people pay more attention to driving safety. With the progress of science and technology, the Advanced Driver Assistance System (ADAS) has the purpose of improving the safety of driving and alerting the drivers whether there is danger around the vehicle ahead. On the highway, some vehicle will load the cargo, but not tie securely and strongly. This may cause these objects fall on the road, makes the rear vehicle to bump the objects and lead to the occurrence of traffic accident casualties. Therefore, this study uses a neural network to detect whether in front of the vehicle has potential falling objects. This experiment first detects the lane and find the vehicle image in region of interest (ROI). We can calculate shadow characters and edge features by ROI, and through these functions and find the vehicle detection. Using the front of vehicle to detect objects by a neural network and compared with applying image segmentation based on the color of the vehicle, the correct rates of unloaded and loaded vehicles are 75.9% and 82.5% respectively. The result shows recognition effect is relatively improved than. Through the analysis and discussion of this study, it further contribute to the traffic safety field.
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Liu, Pei-Ling, and 劉佩鈴. "Nanocapsules loaded HEMA-based Hydrogel Composites for Drug Delivery." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/74379955590890371682.
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碩士<br>國立交通大學<br>材料科學與工程學系<br>99<br>Only about 5% of the dose delivered from an eye drop penetrates through the cornea to reach the intraocular tissue, while the rest is lost due to tear drainage. Besides, the dose has a short residence time in the film due to ocular barriers, and the presence of certain drugs in the bloodstream leads to undesirable side effects. In this study, incorporation of amphiphilic chitosan-crystalline silica hybrid macromolecule in a p(HEMA-MAA) hydrogel matrix prepared the particle-laden gels. The chemical structure of this hybrid molecule was characterized by FT-IR and 13C-, 29Si-nuclear magnetic resonance. Amphiphilic nature of the hybrid molecule rendered subsequent self-assembly forming nanocapsules in aqueous solutions. Structural morphology of the hybrid nanoparticles was investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM). And the mean size of the hybrid macromolecules was characterized by SEM and dynamic light scatter (DLS) measurements which demonstrated a concentration-dependent assembly size. On the other hand, structural morphology of the particle-laden gels was investigated using SEM. And the optical characterization of the particle-laden gels was measured by UV-Vis spectrometer which demonstrated the hybrid nanoparticles have great polydispersion in the polymerizing medium. In term of the drug loading method, according to photosensitivity or water solubility, developed two types of loading method: encapsulation, for non-photosensitive or hydrophobic drugs and impregnation, for photosensitive or hydrophilic drugs. A subsequent application to carry drugs of various degree toward water affinity (from water insoluble, azithromycin (AZM), to water soluble, Vitamin B12, following a controlled drug release in vitro has been systematically investigated. The experimental results indicated a long-term, sustained release profile for both types of drugs were monitored and release kinetics suggested a two-stage profile, suggesting a bimodal release pattern, and has been confirmed to be a result of drug distribution, i.e, within the nanocapsules and inter-capsule regions. Furthermore, the experimental results indicated the drug release behavior influences on hybrid/drug concentration, ambient temperature, pH-value medium, and drug loading method. And, the particle-laden gels showed an outstanding biocompatibility towards the BCE cell line, as well as the commercially lens, ACUVUE, suggest a promising vehicle for ocular drug delivery application.
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Fu, Li-Tse, and 符立澤. "Development and Evaluation of Estradiol-Loaded Microemulsion-Based Gel." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/34658918430509229022.
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碩士<br>高雄醫學大學<br>藥學研究所<br>100<br>The purpose of this study was to develop and evaluate microemulsion-based gel for topical delivery of Estradiol (E2). Estradiol is effective in treatment of postmenopause hormonal deficiency, which may lead to vasomotor flushes, atherosclerosis, and osteoporosis. However, oral administration of estradiol would be inactivated by gastrointestinal and liver first-pass metabolism effect; hence, the transdermal administration route was the most suitable for estadiol.
Microemulsions are the mixtures of oil, aqueous phase, surfactant, and co-surfactant. Because of several advantages such as thermodynamic stability, optical isotropy, high solubilization capacity and easy formation, it has been widely used in recent years. In many studies, microemulsions have demonstrated a great potential for improving the systemic and local bioavailability of hydrophobic and hydrophilic therapeutic agents. However, the characteristic of low viscosity would be restricted its application.
In this study, Response surface methodology was used to evaluate the effect of ingredient of the E2-loaded microemulsions on the physicochemical property and permeability, to obtain an optimal formulation with desirable goals. Then, the various gelling agents were evaluated for their potential to gel the optimal formulation of E2-loaded microemulsion. Carbopol and poloxamer series can successfully gel the E2-loaded microemulsion without affecting its structure. Compared to control group and commodity, the E2-loaded microemulsion-based gel with higher permeation rate, 20.0~21.3 fold and 2.33~2.42 fold respectively, was expected to provide effective therapeutic concentration in a workable administration.