To see the other types of publications on this topic, follow the link: Welds assessment.
Dissertations / Theses on the topic 'Welds assessment'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 45 dissertations / theses for your research on the topic 'Welds assessment.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Kocak, Okan Okay. "Defect Assessment Of Spot Welds By Ndi." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/4/1027382/index.pdf.
Full textAbstract:
Resistance spot welding is used frequently as a successful joining method for
a variety of work commonly in automotive and other manufacturing
processes. Spot weld nugget is generally hidden between two sheets,
causing its inspection difficult and expensive. Undersized nuggets, brittle or
cracked nuggets, and excessive indentation of electrodes reveals the lack of
fusion between the parts that can make the weld sub-standard.
Visual inspection, pry testing and physical teardown with chisel and hammer
method or a combination of them are being used traditionally. However, this
study presents a more effective nondestructive inspection method based
upon an ultrasonic pulse-echo technique. The theory of the technique together with the experimental verification are presented and its advantages over the other destructive and nondestructive
techniques are considered.
2
Lefebvre, Fabien. "Micromechanical assessment of fatigue in airframe fusion welds." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416080.
Full text
3
Bäckström, Mika. "Multiaxial fatigue life assessment of welds based on nominal and hot spot stresses /." Espoo : Technical Research Centre of Finland, 2003. http://www.vtt.fi/inf/pdf/publications/2003/P502.pdf.
Full text
4
BUENO, SERGIO IBAJE OLIVEIRA. "STRUCTURAL ASSESSMENT OF PIPELINES WITH BLUNT CORROSION DEFECTS COINCIDENT WITH LONG-SEAM WELDS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=10728@1.
Full textAbstract:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROA redução de espessura de parede causada por corrosão é um dos defeitos que mais afetam a integridade dos dutos. Estes defeitos podem ocorrer no metal base, nas soldas longitudinais ou circunferenciais, bem como nas zonas afetadas pelo calor. Os métodos de avaliação da resistência remanescente introduzem ressalvas ou proíbem o tratamento de defeitos de corrosão coincidentes com as juntas soldadas. No presente trabalho foram avaliados os níveis de segurança dos métodos usuais de avaliação da resistência de dutos com defeitos introduzidos na região da solda longitudinal de tubos soldados por arco submerso. Os tubos testados eram de aço C-Mn fabricados na década de 60 e foram retirados de operação após uma campanha superior a 30 anos. Com estes tubos foram fabricados 5 espécimes, cada qual com 1 defeito externo produzido por eletro-erosão, sendo posteriormente submetidos a testes de pressão monitorados. Foram realizados ensaios de tração, ensaios de impacto Charpy e ensaios de dobramento, para determinação das propriedades mecânicas do metal de base, do metal de solda e da zona termicamente afetada (ZTA). Foram realizados também ensaios metalográficos do metal de base e do metal de solda, análise química do metal de base e do metal de solda e medição das tensões residuais no metal de solda. A aplicação dos métodos de nível 1 (ASME B31G, 085dL, RPA, DNV isolado e PCORRC) resultou em pressões previstas inferiores às pressões reais de ruptura para defeitos de formato esférico. Para defeitos de seção retangular a aplicação dos métodos de nível 1 resultou em pressões superiores às pressões reais. A aplicação dos métodos de nível 2 (Effective Area e DNV geometria complexa) resultou em pressões previstas superiores às pressões reais de ruptura para defeitos de formato esférico e de seção retangular. As análises das fraturas indicaram que não ocorreu falha por deficiência de tenacidade em nenhum espécime. A corrosão alveolar leve pré-existente na superfície interna dos espécimes foi apontada como causa mais provável das pressões previstas superiores às pressões reais de ruptura.
One of the most important issues that affects pipeline integrity is corrosion-caused metal loss. This type of defect can occur over the pipe body, seam or girth welds or even on heat affected zones. Pipeline remaining strength criterions are restricted or even prohibited for assessing corrosion defects coincident with weld regions. This present work investigated the reliability of the most common assessment criteria for corroded pipes when defects were coincident with seam weld region in submerged arc welded pipes. The tested specimens were C-Mn steel pipe, from a pipeline manufactured in the 60´s and had operated for over 30 years. Five external defects were created on five pipe specimens and pressure tested until rupture. Stress, charpy V-notch and bending tests were carried out to find the mechanical properties of the welded joints. Microstructure and chemical composition from base metal and weld metal were also analyzed. Residual stresses on welds were measured. The level 1 criterion (ASME B31G, 085dL, RPA, DNV single and PCORRC) applications have underestimated failure pressure for spherical shaped defects. On the other hand, the same criterions have overestimated failure pressure for rectangular shaped defects. The level 2 criterions (Effective Area e DNV complex geometry) application overestimated failure pressure for all 5 specimens with both spherical and rectangular shaped defects. Fracture analyses have indicated that no specimen had a toughness controlled failure. Internal pit corrosion that was found after pressure testing is recognized as the most probable cause of underestimated pressure forecasts.
5
Ceyhan, Ümit [Verfasser]. "High temperature deformation and fracture assessment of similar steel welds / vorgelegt von Ümit Ceyhan." [Clausthal-Zellerfeld] : [Univ.-Bibliothek], 2007. http://d-nb.info/985769653/34.
Full text
6
Ren, Yao. "Investigation of residual stresses in X65 narrow-gap pipe girth welds." Thesis, Brunel University, 2018. http://bura.brunel.ac.uk/handle/2438/16658.
Full textAbstract:
This research investigated the residual stresses in narrow-gap API 5L X65 pipe girth welds in as-welded and after post weld heat treatment (PWHT) conditions. The PWHT included global furnace and local practices. Non-destructive neutron diffraction (ND) strain scanning was carried out on selected pipe spools and strainfree reference samples for the determination of the lattice spacing before and after PWHT. The as-welded and post-heat treatment residual stresses measured in the pipe spools were examined and compared. Experimental work also included full residual stress mapping in the weldment and through-thickness measurement at weld centre and close to the external and internal pipe surfaces. The measured profiles were compared with the recommendations given in British flaw assessment procedure BS 7910 "Guide to methods for assessing the acceptability of flaws in metallic structures" and the UK nuclear industry's R6 procedure. The design, preparation and experimental neutron diffraction measurement procedures for the determination of the strain-free lattice parameter in various configurations of reference samples and in the required directions were discussed. The variability of the lattice spacing in the reference samples was found depended on the specimen manufacture methods and thermal process. Welding residual stresses were also simulated using finite element analysis (FEA) modelling approach. The simulated thermal cycles and transient strains at specific locations were compared with the experimental readings. The residual stress profiles derived from finite element model were compared with the measurements from neutron diffraction. It was found, the measured and simulated, as-welded - residual stress profiles showed good consistency in terms of stress distribution and magnitude to reasonable extent. Measurement results also indicated that local PWHT was effective in reducing the residual stresses in the pipes to a level similar to that achieved by a global approach.
7
Zia, Tabari M. "Design, development and assessment of an automated ultrasonic inspection system in production and experimental analysis if tubular butt welds for identification and characterisation of weld defect." Thesis, University of Newcastle Upon Tyne, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376231.
Full text
8
Peč, Michal. "Rozbor únosnosti vybraných svařovaných konstrukčních uzlů zatěžovaných staticky a cyklicky." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231975.
Full textAbstract:
Welding is a widely used method of connecting components because of its efficiency, great value and almost endless possibilities of join types. A great variability of geometrical configurations of welds is problematic due to the assessment of the weld joint. Depending on this topic this thesis was focused on the assessment of weld joints statically and cyclically. Work in the first part deals with the search of methods for evaluation of welds and depending on identified options is subsequently selected American standard AISC assessment of welded joints. The method is applied into FEA analysis and simple welded joints are evaluated. Using FEM are computed three examples on which a comparative analysis was performed. Comparisons were made with the analytical solution based on changes in the parameters of the computational model. The change is primarily related to material properties, mesh size and division of the weld on segments. On the basis of knowledge from analysis of simple joints, method was extended to more general welded joints with the possibility of determining the maximum loading force.
9
Smith, Carey. "Studies on weed risk assessment." Title page, contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09AFM/09afms644.pdf.
Full textAbstract:
Bibliography: leaves 124-136. This thesis gives an overview of factors used in weed risk assessments and explores the disparity between the measured high accuracy rate of the weed risk assessment system (WRA) as implemented in Australia and the pessimistic assessments of some workers about the possibility of predicting the weed potential of plant species imported in the future. The accuracy of the WRA may not be as high as previously thought, and it varies with weed definition and taxonomic groups. Cluster analysis and comparative analysis by independent contrasts were employed to determine the value of individual biological and ecological questions on the WRA questionnaire. Results showed that some WRA questions could be deleted from the questionnaire and the scores for others weighted differently. The WRA is not a reliable predictor of weeds when it is considered in the context of the base-rate probability of an introduced plant becoming weedy in Australia. As a result a far greater number on non-weeds will be placed on the prohibited imported list than was initially expected.
10
Prus, J. L. "New methods of risk assessment for the release of transgenic plants." Thesis, Cranfield University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360068.
Full text
11
Storesund, Jan. "Life assessment from weld microstructures at high temperatures /." Stockholm, 1998. http://www.lib.kth.se/abs98/stor0615.pdf.
Full text
12
Kountouris, Ioannis Savvas. "The assessment of weld defects in offshore structures." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47520.
Full text
13
Hultgren, Gustav. "Assessment of fatigue for laser-scanned weld surfaces : Correlation between weld geometry and fatigue initiation." Thesis, KTH, Hållfasthetslära (Avd.), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-259518.
Full textAbstract:
The work conducted in this project proposes a method to determine the location of fracture initiation for non-load carrying fillet welds based on continuous geometry measurements. Measurements were carried out on welded specimens using a laser line triangluator together with the weld quality evaluation software qWeld from Winteria®. The 119 specimens produced were after scanning fatigue tested until failure. The fracture surfaces have been investigated in order to find the most probable location(s) of fracture initiation. This data was then used to fit the proposed model parameters used to analytically predict the point(s) of fracture initiation. Local weld geometry measurements were extracted from the predicted fracture initiation location(s) in an effort to analyse the correlation between local weld geometry and fatigue life. This showed that fatigue life and leg length were positively correlated and that strong correlations exists between the individual geometrical parameters. New specimens were produced to test the fitted data of the proposed model, this data was however inconclusive as the new specimens had a high ratio of weld defects.Arbetet i detta projekt föreslår en metod för att bestämma punkten/punkterna för sprickinitiering för icke-lastbärande kälsvetsar baserat på kontinuerliga mätmetoder. Mätningar utfördes på svetsade prover med hjälp av en laserlinjetriangluator tillsammans med utvärderingsprogrammet qWeld från Winteria®. De 119 provstavar som producerades testades efter mätningarna med en cyklisk belastning till de gick till brott. Brottytorna undersöktes sedan för att hitta platsen/platserna för de mest sannolika startpunkterna. Dessa punkter användes sedan för att passa de föreslagna modellparametrarna som användes för att förutsäga startpunkten. Lokal svetsgeometri extraherades från de förutsagda sprickinitieringsplatserna i ett försök att analysera korrelationen mellan lokal svetsgeometri och antalet cykler till brott. Detta visade att antalet cykler och katetlängden var positivt korrelerade och att det finns starka korrelationer mellan de enskilda geometriska parametrarna. Nya provbitar framställdes för att testa de anpassade parametrarna i den framtagna metoden, dessa gav dock inga tydliga resultat då en hög andel svetsdefekter upptäcktes efter att de provats.
14
Zhang, Xutuan. "Quantitative risk assessment in drill casing design for oil and gas wells." Thesis, University of Wolverhampton, 2004. http://hdl.handle.net/2436/89102.
Full text
15
Brourman, Hanna Rose. "Hydrogeological Assessment of Fracking Fluid Injection in Wells of Athens County, Ohio." Ohio University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1526032506663764.
Full text
16
Mrdjanov, Nikola. "Fatigue life assessment of potential weld improvement techniques using 3D fracture analysis." Thesis, KTH, Lättkonstruktioner, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-159272.
Full textAbstract:
This thesis work was done in conjunction with the VINNOVA-funded research and development project LIGHTSTRUCT. It was performed in the department of lightweight structures at KTH. The thesis investigated two potential weld improvement techniques called toe weaving and extended leg. These methods use double pass welding in order to create favorable weld geometries in order to improve the fatigue life. The toe weaving technique produces a wavy weld toe line that should induce a specific crack growth behavior, while the extended leg technique has a straight toe line and will provide a smoother transition between weld and baseplate. The investigation was done by performing 3D fracture analyses of the weld geometries as well as fatigue tests on manually welded cruciform joints. Both simulations and fatigue tests showed a slight fatigue life improvement for both techniques. A high variation in fatigue lives was observed in testing, mostly due to the prevalence of undercut defects. The specific crack growth for the toe weaved specimens could not be observed as in previous studies. The fatigue life enhancement was therefore most likely due to a smoother weld transition between weld and baseplate, reducing the stress concentration factor at the weld toe. The weaving technique is not suitable for welded joints loaded in the longitudinal direction, making its use more limited compared to the extended leg technique. From a production point of view, the toe weaving technique is more time and knowledge demanding than the extended leg technique. It is therefore recommended to further investigate the extended leg technique.
17
Kveselys, Donatas. "Weld Producibility Assessment System : Evaluation of Producibility Assessment tools using Set-based approach in Multi-disciplinary Aerospace Design." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Produktutveckling, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-36010.
Full textAbstract:
This thesis is a continuation of design automation studies within research projects financed by VINNOVA (the Swedish Governmental Agency for Innovation Systems) and Knowledge foundation that contributed to the development of producibility assessment system at a global aerospace products supplier, GKN Aerospace Sweden. A case study was carried at the company on Turbine Rear Structure (TRS) component design of a jet engine with the main objective to evaluate weld producibility assessment tools and to demonstrate system’s performance in multi-disciplinary design environment. The context of this thesis is a set-based product design development where several studies, i.e. thermal, structural, aerodynamic etc. are carried concurrently to gather knowledge between their parameter relations. The thesis contributes to the goal of fully integrated producibility assessment in multi-disciplinary studies to support product development process. The problems encountered during the thesis execution involved systematic analysis setup to extract and verify CAD geometry data, assessment of meaningfulness of producibility indicators, development of semi-automated data post-processing module and relating product design to its manufacturing aspects. Commercial and in-house developed software were used extensively to demonstrate the results of the system with the help of continuous company support to mitigate indispensable bottlenecks along the way. The work has led to systematic improvements, determined assessment limitations and most relevant weld producibility aspects. Collected feedback to evaluate prepared demonstrator showed promising results to support product design decisions considering both performance and producibility.
18
Bowness, D. "Fracture mechanics based fatigue assessment of weld toe cracks in offshore tubular structures." Thesis, Swansea University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636138.
Full textAbstract:
Fatigue cracking is currently regarded as the principal cause of damage to ageing offshore jacket structures in the North Sea. The significance of such cracking is usually assessed using fracture mechanics analysis based on in-service inspection data, allowing the operator of the offshore installation to formulate an effective inspection strategy and to effect repair when necessary. A fundamental requirement for a fracture mechanics based fatigue assessment of a tubular joint are suitable stress intensity factor solutions. At present, there are many different sets of solutions in existence which may be applied to tubular joints. Some of these solutions are of limited applicability, and others are based on unsubstantiated assumptions, making the accuracy of any assessment difficult to judge. In this thesis, a thorough review and evaluation of the existing stress intensity factor solutions are reported. To investigate the reliability of the solutions, an accurate three-dimensional numerical modelling procedure for cracked tubular T-joints was developed and used to produce benchmark stress intensity factors. The numerical procedure, which can model doubly curved semi-elliptical weld toe cracks, was also used to conduct a detailed investigation into fatigue crack curvature under the weld toe. The review and evaluation of the existing stress intensity factor solutions highlighted a number of deficiencies in the existing solutions. A parametric study of 3-D T-butts was therefore carried out and new improved solutions proposed. The proposed solutions make physical sense and provide a clear understanding of the effects of the attachment a T-butt. Used in conjunction with the hot spot SCF and DOB, the proposed solutions were also shown to approximate the tubular joint benchmark stress intensity factors well. Fatigue crack growth calculations, performed using the proposed and existing solutions, further illustrate the superiority of the new solutions, which accurately predicted the crack shape development and provided good remaining life estimates.
19
Li, Ben. "A Preliminary Assessment of Leakage Possibility of CO2 Sequestration Wells in Two Gulf Coast Fields." Thesis, University of Louisiana at Lafayette, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1557563.
Full textAbstract:
Analytical models were derived in this work to predict the Maximum Permissible Pressure (MaxPP) and Minimum Permissible Pressure (MinPP) in CO2 sequestration and other fluid injection wells. The outer radius of the cement sheath should be estimated on the basis of cement placement efficiency measured by the CBL.
The West Hastings Oil Field and Oyster Bayou Oil Field in Gulf of Mexico region were analyzed to identify the potential leakage of the current CO 2 injection wells using the analytical models. Potential problems for the current wells were identified. There are potential risks for the CO 2 injection wells with relatively smaller wellbore diameter and casing diameter.
36 CO2 injection wells of the West Hastings and Oyster Bayou fields were taken as learning wells to train the neural network model, which was tested by 21 wells in the fields. The results show that the neural network model could be used for predicting the potential likelihood of leakage for CO2 injection wells, which could be an alternative and convenient way to assess the risk of leakage CO2 .
Sensitivity analysis was also performed considering cement mechanical properties, well structure and reservoir pressure. Results show that improving cement sheath mechanical properties (cement tensile strength, cement cohesive strength, internal friction angle) is not a very effective means of decreasing potential leakage of CO2 during CO2 EOR and carbon sequestration processes. The potential risk of leakage for CO2 injection wells should be decreased by maximizing the outer radius of the cement sheath and improving the cement placement efficiency. For the current CO2 EOR activities and carbon sequestration processes, the well head maximum water injection pressure could be increased as the reservoir pressure increases.
20
Delagrange, Susan L. "An assessment of the anthropometric status and self-reported nutritional intake and physical activity level of students in fourth, sixth, and eighth grades in Wells County, Indiana." Virtual Press, 2006. http://liblink.bsu.edu/uhtbin/catkey/1339143.
Full textAbstract:
The purpose of this study was to assess the nutritional practices, physical activity level, and anthropometric measurements of students in grades 4, 6, and 8 in Wells County, IN. The sample included all students enrolled in these grades in the fall of 2002. Parental consent to complete the School Physical Activity and Nutrition (SPAN) survey used to collect food and activity practices and to measure heights and weights was obtained for 670 of the 1,248 students. Individuals were classified into weight groups using the CDC growth charts. Thirty-eight percent of all students were "at risk for overweight" or were "overweight." Students reported spending 3.3 hours of screen time per day. Males consumed more grains and legumes, and participated in more physical activities, than females. Normal weight students consumed more grains and dairy products than overweight students. There were few statistically significant differences by weight classification. Programs that encourage increasing physical activity, decreasing screen time, and making healthier food choices should be emphasized in this community.Department of Family and Consumer Sciences
21
Jimenez, Acosta Carlos Efren. "Assessment of weld residual stress effects on fatigue crack propagation in ferritic pressure vessel steels." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/assessment-of-weld-residual-stress-effects-on-fatigue-crack-propagation-in-ferritic-pressure-vessel-steels(ef8f4e14-3b9c-4f45-876b-dca5d5e9c121).html.
Full textAbstract:
This project aims to characterise the fatigue behaviour of a crack propagating in a residual stress field changing from tension to compression in the welded zone of a ferritic pressure vessel steel. The fatigue tests were carried out keeping the applied stress intensity factor range constant to determine the role of residual stresses on fatigue crack growth. The residual stresses prior to crack growth were evaluated by X-ray diffraction. The weight function method was used to infer the expected influence of the residual stress on the crack tip in terms of the residual stress intensity factor. Two metrics were used to quantify the crack driving force local to the fatigue crack. Firstly the stress intensity amplitude expressed in terms of the change in the J-integral between maximum and minimum load and secondly the change in the crack opening displacement COD to estimate closure stress intensity factor. The displacement fields local to a fatigue crack were obtained by Digital Image Correlation (DIC) and then analysed by JMAN, an in-house developed algorithm to extract the J-integral based on finite element method and implemented using MATLAB. The difference between the applied stress intensity factor range and the effective crack driving force at the crack tip was determined in order to understand the interaction between the prior residual stresses and crack closure phenomena. Three different R-ratios were evaluated during the experiment (R=0.1, R=0.3 and R=0.5) in order to quantify the effect of residual stress on crack tip stress intensity and crack opening displacement. R-ratio plays a very important role on the fatigue crack growth rate (FCGR): as R increases, FCGR also increases. The COD was assessed by means of the displacements obtained by DIC local to the crack faces. The COD method turned out to be more insightful than the JMAN method for characterising the crack propagation, this is due to the presence of plasticity in the ligament which breaks the non-linear elastic conditions, causing the path-dependence on the J-integral. The FCGR is influenced to a greater degree by the R-ratio and to a lesser degree by the residual stress effect. There is a direct relationship between R and FCGR: as R increases, FCGR also increases, irrespective of the presence of tensile or compressive residual stresses, with the crack closure showing more tendency to occur at low R (i.e. R=0.1) than at high R (i.e. R=0.5). The relationship between R and the residual stress effects on FCGR is inversely proportional: as R increases, the effect of RS decreases.
22
Godfrey, Sam. "Microbiological risk assessment and management of shallow groundwater sources in Lichinga, Mozambique." Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/7814.
Full textAbstract:
The principal Water target of the Millennium Development Goals (MDG) is to Ensure environmental sustainability by halving the proportion of people without access to safe water by 2015. Although great strides have been made in meeting this challenge in terms of provision of services since the year 2000, the safety of many these water supplies remains unknown. One of the biggest challenges therefore facing water development professionals is how to ensure sufficient levels of both quantity and guality of safe water. One of the principal mechanisms for monitoring the progress towards attaining the MDG goals for access to safe water is the UNICEF/WHO Joint Monitoring Programme (JMP). However, the JMP acknowledges that one of its current weaknesses is in assessing safety related to different technology types. In acknowledgement of these weaknesses and of the weakness of reliance on "end product testing" as a means of assuring microbiological safety, the thesis proposes improved methods of assessment and management of microbiological water safety based on a "risk" paradigm. Coinciding with proposed new risk based methods of assessing water safety outlined in the 3d edition of the World Health Organization Guidelines for Drinking Water Quality (2004), the thesis researches the risk to three well technology types in Mozambique. Principal pathways to microbiological contamination of shallow groundwater were assessed which included both the conventional aquifer pathways and preferential or localised pathways. The research adopted an experimental design that uses a mix of qualitative and quantitative data collection techniques. Data were collected over 12 months in 25 well sites in Lichinga, Mozambique. Findings from the research demonstrated that risk assessment and management are effective tools in understanding the level of safety associated with the well technologies under study. The research indicated firstly that risk assessment aids the identification of specific risk variables (of which animal faeces is a predominant risk), secondly that the use of alternative indicator organisms (e.g. enterococci) may improve risk understanding, thirdly that there is a strong statistical correlation between use of surrogates (e. g. turbidity) and microbes and fourthly that Water Safety Plans are an appropriate method of risk management. Furthermore, the research supports the JMP definitions of improved water sources, which suggest that upgraded wells are not an improved source due to their high vulnerability to contamination through localised pathways. The recommendations from the thesis include; non-inclusion of upgraded wells in the JMP in Mozambique, greater use of enterococci and turbidity as surrogate indicators of faecal pollution, the need for the development of rapid risk assessment and management techniques for rural areas in developing countries and the inclusion of localised pathways as a principal route of assessment. Potential areas of further research include field-based studies of assessment of faecal sources of Enterococci bacteria, and rapid methods for the development of model Water Safety Plans.
23
Thurlbeck, Simon David. "A fracture mechanics based methodology for the assessment of weld toe cracks in tubular offshore joints." Thesis, University of Manchester, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306520.
Full text
24
Pearson, Karen Aileen. "Characterisation of Fusarium isolates infecting roots of ragwort (Jacobaea vulgaris syn. Senecio jacobaea) and an assessment of their potential as a biological control agents." Thesis, University of Aberdeen, 2011. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=166174.
Full textAbstract:
Ragwort (Jacobaea vulgaris syn. Senecio jacobaea), a common weed of pasture and poorly managed land worldwide, is toxic to livestock and horses. There is no fully satisfactory control option available. The aim of the work described in this thesis was to assess the potential of root infecting pathogens to cause disease in ragwort, and to examine the possibility of using them as biological control agents against this weed. Thirty-six root infecting isolates were obtained from ragwort roots, collected from a nationwide postal survey where Pony Club adult leaders were asked to provide samples. Twenty-one of these were identified as Fusarium spp. by morphological identification and tested for the ability to cause disease on aseptically raised ragwort seedlings. Twelve isolates demonstrated virulence towards ragwort when measured by disease score over a 14 day period. These isolates were identified by molecular means using the internal transcribed spacer and translation elongation factor genes, as either Fusarium avenaceum or F. acuminatum while isolates of F. solani, F. redolens, F. cerealis or F. culmorum did not exhibit virulence except one isolate of F. culmorum which was weakly virulent. To investigate the biological control potential of virulent isolates, a representative of F. avenaceum and F. acuminatum plus the one weakly virulent F. culmorum isolate, were tested against plants of agricultural importance in grasslands. Six grasses (crested dogs tail, Cynosurus cristatus; Timothy, Phleum pratense; red fescue Festuca rubra; Italian ryegrass, Lolium multiflorum; and two varieties of perennial ryegrass, L. perenne) were unaffected by inoculation with any of the isolates. There was no significant difference between the symptoms caused by F. avenaceum and F. acuminatum on ragwort, red clover (Trifolium pratense) and white clover (T. repens). F. culmorum was more virulent towards white clover than either red clover or ragwort. This suggests that although high concentrations of pure PA may inhibit fungal growth, the range of other nutrients in the plants can counteract this negative effect.
25
Stenberg, Thomas. "Fatigue properties of cut and welded high strength steels : Quality aspects in design and production." Doctoral thesis, KTH, Lättkonstruktioner, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-188225.
Full textAbstract:
This doctoral thesis concerns fatigue of welded structures. Welding is one of the world’s most common joining methods and it is frequently used in several structural applications in many fields. Some examples are construction vehicles, loader cranes, trucks, busses, forestry and agricultural machines, bridges and ships. Since these structures are subjected to repeated loading, fatigue is the most common cause of failure. A novel numerical algorithm has been developed which assesses the welded surface and calculates and quantifies weld quality parameters and the presence of defects which are critical in fatigue applications. The algorithm is designed for implementation in serial production. It will provide robust and reliable feedback on the quality being produced, which is essential if high strength steels are utilized. Two welding procedures which can increase the weld quality in as welded conditions have been assessed. These procedures utilize welding in different positions and pendling techniques, which can be accomplished using the existing welding equipment. It was found that by using these methods, the fatigue strength can be increased compared to normal weld quality. Furthermore, two fatigue assessment methods ability to account for increased weld quality in low cycle and high cycle fatigue applications has been studied. One of these methods showed sufficient accuracy in predicting the fatigue strength with small scatter and also account for increased weld quality. When implementing thinner high strength steels, the overall stress level in the structure increase. Therefore, other locations such as the steel cut edges may become critical for fatigue failure unless they are not designed and manufactured with the same quality as the welded joint. The influence of surface quality on cut edges was studied and the fatigue strength was estimated using international standards and a fatigue strength model for cut edges.QC 20160613
WIQ
LIGHTSTRUCT
ONWELD
26
Schalkwyk, Hugh Je-Marco. "Assessment controls on reservoir performance and the affects of granulation seam mechanics in the Bredasdorp Basin, South Africa." Thesis, University of the Western Cape, 2006. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_3459_1183461991.
Full textAbstract:
The Bredasdorp Basin is one of the largest hydrocarbon producing blocks within Southern Africa. The E-M field is situated approximate 50 km west from the FA platform and was brought into commission due to the potential hydrocarbons it may hold. If this field is brought up to full producing capability it will extend the lifespan of the refining station in Mosselbay, situated on the south coast of South Africa, by approximately 8 to 10 years. An unexpected pressure drop within the E-M field caused the suite not to perform optimally and thus further analysis was imminent to assess and alleviate the predicament. The first step within the project was to determine what might have cause the pressure drop and thus we had to go back to cores drilled by Soekor now known as Petroleum South Africa, in the early 1980&rsquo
s.
Analyses of the cores exposed a high presence of granulation seams. The granulation seams were mainly subjected within sand units within the cores. This was caused by rolling of sand grains over one another rearranging themselves due to pressure exerted through compaction and faulting, creating seal like fractures within the sand. These fractures caused these sand units to compartmentalize and prohibit flow from one on block to the next. With advance inquiry it was discovered that there was a shale unit situated within the reservoir dividing the reservoir into two main compartments. At this point it was determined to use Petrel which is windows based software for 3D visualization with a user interface based on the Windows Microsoft standards. This is easy as well as user friendly software thus the choice to go with it. The software uses shared earth modeling tool bringing about reservoir disciplines trough common data modelling. This is one of the best modelling applications in the available and it was for this reason that it was chosen to apply within the given aspects of the project A lack of data was available to model the granulation seams but with the data acquired during the core analyses it was possible to model the shale unit and factor in the influences of the granulation seams to asses the extent of compartmentalization. The core revealed a thick shale layer dividing the reservoir within two sections which was not previously noted. This shale layer act as a buffer/barrier restricting flow from the bottom to the top halve of the reservoir. This layer is thickest at the crest of the 10km²
domal closure and thins toward the confines of the E-M suite. Small incisions, visible within the 3 dimensional models could serve as a guide for possible re-entry points for future drilling. These incisions which were formed through Lowstand and Highstand systems tracts with the rise and fall of the sea level. The Bredasdorp Basin consists mainly of tilting half graben structures that formed through rifting with the break-up of Gondwanaland. The model also revealed that these faults segregate the reservoir further creating bigger compartments. The reservoir is highly compartmentalized which will explain the pressure loss within the E-M suite. The production well was drilled within one of these compartments and when the confining pressure was relieved the pressure dropped and the production decrease. As recommendation, additional wells are required to appraise the E-M structure and determine to what extent the granulation seems has affected fluid flow as well as the degree of sedimentation that could impede fluid flow. There are areas still containing untapped resources thus the recommendation for extra wells.
27
Magdic, Matthew James. "Assessment of Soil Properties in Proximity to Abandoned Oil Wells usingRemote Sensing and Clay X-ray Analysis, Wood County, Ohio." Bowling Green State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1462537679.
Full text
28
Annaduzzaman, Md. "Effectiveness of Tubewell platform color as screening tool for arsenic and manganese in drinking water wells: An assessment from Matlab region Southeastern Bangladesh." Thesis, KTH, Mark- och vattenteknik (flyttat 20130630), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-124582.
Full textAbstract:
Arsenic (As) contamination in groundwater is a severe and adverse water quality issue for drinking purposes, particularly in Southeast Asia, where groundwater is the main drinking water source. Bangladesh is one of the countries where arsenic poisoning in groundwater is massive and it is essential to find out a reliable alternative safe drinking water source. In this process, it is very much needed to identify As-rich wells to avoid drinking water from them and to assess the extent of contamination as well. This study attempts to evaluate the potentiality of tube-well (TW) platform color as low-cost quick screening tool for As and Mn as well in drinking water wells (n=272). The result shows strong association of red color platform with As-rich water in the corresponding wells compared to WHO guideline value of 10 μg/L (98.7% certainty) and regional (Bangladesh/India) standard of 50 μg/L (98.3% certainty). The sensitivity and efficiency of red color platforms to screen high As water in TW for 10 μg/L are 98% and 97%. Similarly, for 50 μg/L, it is 98% for both sensitivity and efficiency. However, because of a very low number (n=4) of TW platform stained with black color, it is not possible to make any conclusion on the potentiality of black color as a screening tool for Mn. This study suggests that red colored platform can be potentially used for primary identification of TWs with elevated As concentration and to prioritise sustainable As mitigation management. However, this study does not discard the concept of black colored platform as a screening tool for Mn-rich water. Further study is recommended to evaluate the efficiency of black color as a screening tool for Mn.
29
Barsoum, Zuheir. "Residual Stress Analysis and Fatigue Assessment of Welded Steel Structures." Doctoral thesis, Stockholm : Farkost och flyg, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4687.
Full text
30
Bickel, Ken (Kenneth E. ). "Assessment of Changes in Aquatic Macrophyte Occurrence Following Introduction of Triploid Grass Carp in a North Texas Reservoir." Thesis, University of North Texas, 1997. https://digital.library.unt.edu/ark:/67531/metadc332827/.
Full textAbstract:
The objectives of this project were to measure changes in frequency of occurrence of submerged macrophytes over the first two growing seasons following stocking with triploid grass carp at two fish per acre and to measure differences in macrophyte biomass between areas excluded from herbivory and adjacent control sites after 16 months following establishment of exclosures. The project also seeks to measure concentrations of fluridone following the herbicide treatment, and to compare two methods of aquatic vegetation sampling.
31
Eriksson, Marcus. "A Risk Assessment Analysis : The risk of saltwater intrusion into freshwater wells and the effects of a futuresea level rise on the Baltic Sea island of Öland." Thesis, Stockholms universitet, Institutionen för naturgeografi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-145319.
Full textAbstract:
Freshwater is essential for a functional society and the human well-being. However, it should not be taken for granted. Freshwater aquifers in coastal are subject to current and future risk of becoming saltwater contaminated – reaching a tipping point. Freshwater security on islands is vulnerable. The aim of this empirical study is to identify the effects of a 2-meter sea level rise and the current risk of well salinization at the Baltic Sea island of Öland, Sweden. A Geographical Information System (GIS) was used to conduct a quantitative risk assessment analysis. Natural and physical parameters affect the risk of intrusion into wells including hydrology, geomorphology, and climatology. Anthropogenic causes and climate change also add to the risk of salinization. However, they are not included in the quantitative study. The spatial distribution of the current risk is mapped in this study and can be used as a tool to identify wells at risk. Moreover, a future sea level rise has been visualized and show that 3% of all wells on the island will get directly inundated along with 5% of the total land area. Important land such as urban areas, nature reserves, and animal protection areas will get inundated including the loss of environmental and socio-economic values. A precautionary approach needs to be implemented in future planning since many wells are already at risk of salinization. The complexity of the problem is vast, and this study aims to fill the gaps in literature and previous research in a more multi-criterion way. Nevertheless, the political discussion urgently needs to address the topic and a mitigation and adaptation strategy must be on the agenda.
32
Midgley, John Claude. "Invasive perennial species in an agricultural area of the Western Cape Province : distribution and relationship with various land-use types." Thesis, Stellenbosch : Stellenbosch University, 2005. http://hdl.handle.net/10019.1/20899.
Full textAbstract:
Thesis (MSc)--University of Stellenbosch, 2005.ENGLISH ABSTRACT: This project consists of two botanical investigations in an agricultural area of the Western Cape Province. A farm known as De Rust, in the Elgin Valley, was used to sample the geographic location, density, height and life stage of six prominent invasive plant species in various land-use categories. In the first investigation, the density, height and age structures of the six invasive species populations were analyzed. The density distribution of the six species was also displayed cartographically. Species were then ranked according to the potential threat that they pose to the conservation of the remaining natural areas on the farm. Results indicated that Acacia mearnsii and Acacia saligna are the major invaders at De Rust and that Hakea sericea can be considered as an emerging invader. The second investigation explores the statistical relationship between the various land-use categories and density, height and age of the six prominent invaders identified in the first investigation. The loglikelihood ratio analysis of observed frequencies resulted in statistically significant (P<0.01; P-values range between 1.35 x 10-3 and 2.7 x 10-224) relationships between certain land-use types and certain invasive species. A conclusion was reached that it could be useful to include land-use categories in simulation models of invasive plant species distribution and spread.
AFRIKAANSE OPSOMMING: Hierdie projek behels twee botaniese ondersoeke in ‘n landbou gebied van die Weskaap. Die plaas bekend as De Rust, in die Elgin Vallei, was gebruik vir die versameling van data te doen met die geografiese ligging, plant digtheid, lengte en lewens stadium van ses prominente indringer plant spesies in verskeie landgebruik kategorieë. Die digtheid, lengte en ouderdomstruktuur van ses indringerspesies was in die eerste ondersoek geanaliseer. Die verspreiding van digtheid was ook in kaarte uitgelê. Spesies was daarna volgens hulle potentiële dreiging teen die bewaring van oorblywende natuurlike dele van die plaas in ‘n rangorde geplaas. Resiltate dui aan dat Acacia mearnsii en Acacia saligna die belangrikste indringer plante op De Rust is en dat Hakea sericea as ‘n opkomende indringer beskou kan word. Die tweede ondersoek kyk na die verhouding tussen verskeie grondgebruik kategorië en die digtheid, lengte en ouderdom van die ses prominente indringer spesies wat in die eerste ondersoek identifiseër is. ‘n Log tipe ratios ontleding van bewaarde frekwensies het ‘n statisties belangrike uitkoms gehad (P<0.01; P-waardes tussen 1.35 x 10-3 en 2.7 x 10-224) vir die verhoudings tussen sekere grondgebruik tipes en sekere indringer spesies. Die gevolgtrekking was dat dit handig mag wees om grondgebruik kategorieë in simulasies van indringer plant verspreiding te gebruik.
33
Larson, Daniel. "Non-indigenous freshwater plants : patterns, processes and risk evaluation /." Uppsala : Dept. of Environmental Assessment, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200715.pdf.
Full text
34
Whelan, Helen G. "The effect of crop yield potential on disease yield loss relationships in barley (Hordeum vulgare L.)." Lincoln University, 1992. http://hdl.handle.net/10182/1980.
Full textAbstract:
Proportional loss models commonly used in disease surveys are based on the assumption that per cent yield loss is the same in all crops, regardless of their yield potential. Estimates of regional crop loss may be inaccurate if the relationship between disease and yield loss is affected by crop yield potential. The importance of crop yield potential in disease: yield loss modelling was investigated and models for more accurate regional crop loss estimates were developed, taking crop yield potential into account. Two spring sown barley (cv. Triumph) experiments were conducted in 1987/88 and 1988/89 in Canterbury, New Zealand, to study the effect of crop yield potential on the relationship between disease and yield loss. Crop yield potentials of 323 to 806gDM/m² were generated in seven crops by varying nitrogen and water inputs, sowing date (mid-spring and early-summer) and season. Leaf rust (Puccinia hordei Otth) epidemics of different severity were generated by applying fungicides at different times, frequencies and rates to control the natural epidemics. Disease was measured as per cent disease severity (%DS), green leaf area, radiation interception and near-infrared radiation (NIR) reflectance from crop canopies. Yield was measured as total and grain dry weight. Epidemics were severe in the fully diseased plots from GS 34 and 46 to maturity in the late and early sown crops respectively. Disease reduced grain yield by 50 to 63% in 1987/88 and 24 to 38% in 1988/89 in the fully diseased plots. Disease: yield loss models were derived by regression analysis for each crop in 1987/88. Single point, multiple point and area under curve models were derived from %DS and GLAI variables, and proportional (%) and actual (gDM/m²) grain yield. The effect of yield potential was determined by comparing regression equation coefficients for each crop with crop yield potential. An area under green leaf area index curve (AUGLAIC): actual yield model was best suited to determining the effect of yield potential on yield loss. This model was selected because AUGLAIC summarised the effect of disease on plant growth over the season and actual yield represented the crop yield potential in the absence of disease and the response of actual yield to disease. Crop yield potential did not affect actual yield loss caused by leaf rust. Disease measured as AUGLAIC explained most of the variation in yield (R²adj=0.93) for all crops in both years. Assessment of GLAI is not suitable for estimation of regional crop loss because of the requirement for a rapid and low cost method. Reflectance of NIR from the crop canopy was investigated as an alternative to GLAI measurements. Reflectance was correlated significantly (P<0.001) with GLAI (r=0.66 to 0.89) and green area index (r=0.76 to 0.92). Reflectance measured at grain-filling (GS 85-87) explained most (R²adj=0.94) of the variation in yield for all crops in both years. The relationship between AUGLAIC and yield was validated with data from independent diseased and healthy barley crops. The AUGLAIC: yield model described the effects of disease on yield accurately but overestimated yield by 49 to 108% in the healthy crops. Models based on accumulated PAR (photosynthetically active radiation) intercepted by green leaves explained the observed deviations in yield of these crops from the AUGLAIC: yield model. Accumulated PAR models accounted for differences in incident radiation, canopy structure, radiation interception by green leaves, radiation use efficiency and harvest index which are important in determining dry matter production and grain yield. Accumulated PAR models described the effects of disease on crop growth which were not represented by GLAI alone. Variation in crop yield potential at the regional scale is important in disease: yield loss modelling and can be accounted for by using either separate equations for each yield potential crop or crop category, robust models, inclusion of a form function for yield potential or choice of disease and yield variables which integrate yield potential.
35
Fordham, Colin Justin. "A spatial and temporal analysis of the changes in alien macrophyte communities and a baseline assessment of the macroinvertebrates associated with Eurasian watermilfoil, Myriophyllum spicatum L. (Haloragaceae) in the Vaal River." Thesis, Rhodes University, 2012. http://hdl.handle.net/10962/d1005455.
Full textAbstract:
The majority of South Africa’s fresh water (lotic and lentic), is eutrophic and this has resulted in water hyacinth, Eichhornia crassipes (C.Mart.) Solms. (Pontederiaceae) becoming South Africa’s most damaging aquatic macrophyte. Recently however, concerns have also been voiced over the presence of highly invasive submerged macrophyte species, such as Eurasian water-milfoil, Myriophyllum spicatum L. (Haloragaceae) in the Vaal River. Interaction studies between floating and submerged macrophytes have shown that floating macrophyte dominance restricts light penetration into the water column shading out submerged macrophytes while submerged macrophyte dominance reduces nutrient availability in the water column limiting floating macrophyte growth. This cycle ensures that these species cannot coexist in the same habitat for extended periods of time. The aims of this thesis were to: 1. Investigate changes in the historical and current macrophyte dominance in the Vaal River 2. Determine whether these changes could be attributed to stochastic events, such as floods and herbicide control measures. 3. The physio-chemical conditions of the water column, and whether pressure from herbivory by macroinvertebrates had possibly influenced Eurasian water-milfoil’s ability to dominate. Spatial and temporal analysis of satellite imagery revealed that water hyacinth and submerged macrophyte species dominated different regions of the study area over different periods of time from 2006 to 2010. This was significantly correlated with nitrate concentrations of the water column. One of the lower Vaal River Water Management Areas (WMA) had changed from a water hyacinth dominated state in 2006 to an alternative submerged macrophyte dominated stable state in 2008. It was concluded that this change could be attributed to: a stochastic flooding event in 2006; perturbation from integrated control measures implemented against water hyacinth; and low nitrate concentrations of the WMA. The lack of any substantial macroinvertebrate herbivory pressure or control measures implemented against Eurasian water-milfoil, compared to similar surveys conducted in the U.S.A. and its native range in Eurasia was shown to contribute to its dominance. Future successful integrated control programmes, including biological control against Eurasian water-milfoil, could provide the perturbation required to restore the ecosystem. However, without the reduction in nitrate concentration levels, water hyacinth will remain the dominant stable state of the rest of the Vaal River.
36
Pimenta, Raquel Ribeiro Gomes 1978. "Seleção da estratégia de produção de um reservatório fraturado sob incerteza." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265734.
Full textAbstract:
Orientador: Denis José SchiozerDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências
Made available in DSpace on 2018-08-28T14:19:52Z (GMT). No. of bitstreams: 1 Pimenta_RaquelRibeiroGomes_M.pdf: 41409019 bytes, checksum: 19305e480d226d75f53cde7de5f86b95 (MD5) Previous issue date: 2014
Resumo: O sucesso econômico de projetos e o desenvolvimento de campos de petróleo dependem não só de atributos de reservatório como também de estratégias de produção. Em reservatórios naturalmente fraturados uma combinação de atributos como: conectividade de fraturas alta, influxo de aquífero forte e molhabilidade variável com parâmetros de projetos como injeção de água, podem resultar na chegada antecipada de água e até mesmo no fracasso do projeto. Os atributos de reservatórios geralmente não são conhecidos no momento da elaboração dos projetos quando a maior parte do investimento é efetuada; para campos marítimos, há ainda pouca flexibilidade para mudanças ao longo do tempo. A avaliação do risco envolvido então se torna muito importante. O resultado de projetos com reservatórios naturalmente fraturados depende muito da estratégia de produção, principalmente do número e da localização de poços. A otimização destes parâmetros aumenta a produção de óleo e a rentabilidade dos projetos. Esta dissertação apresenta uma metodologia de seleção de estratégia de produção que incorpora a análise de risco. As incertezas de reservatório são quantificadas e são selecionados três modelos para representar a variabilidade técnica e financeira. Estes modelos são usados como apoio para a seleção de estratégias de produção sob incertezas. Para este fim, primeiro se faz uma análise de risco onde se escolhem os denominados modelos de reservatórios variados, depois se escolhe uma estratégia de produção através de um estudo comparativo com diferentes métodos de explotação e, por fim, faz-se um estudo da robustez da estratégia escolhida para cada caso através da realização de uma análise de incerteza. No estudo comparativo de estratégias de produção são avaliados os métodos de depleção, injeção de água, gás, água e gás e alternada de água e gás e cada estratégia citada acima é otimizada de maneira assistida. Conclui-se que o estudo atinge o objetivo principal, já que a estratégia de injeção de água e gás é escolhida como a melhor estratégia de produção através da aplicação da metodologia de análise de risco. Esta estratégia é escolhida porque tem o maior valor presente líquido, o menor risco financeiro e ainda apresenta flexibilidade de projeto
Abstract: Economical results of an oilfield development depend on both reservoir attributes and strategy selection. For instance, water injection implementation in naturally fractured reservoir can result in early water production and poor economical results if this reservoir has high fracture connectivity, aquifer influx and mixed wettability. Reservoir attributes are generally unknown at the beginning of the project, when most of the investment is made. Since there is no much flexibility for changes during a life cycle of an offshore field, risk analysis is very important at this moment. Optimization of project parameters such as production strategy, well number and well location usually increase oil production and project profitability. This study presents a methodology to select the best production strategy incorporating risk analysis. Reservoir uncertainties are evaluated and all technical and financial variability are resumed in three models. This task is performed using the following steps: risk analysis where three models are selected among five hundred; production strategies comparison and finally a robust test using a complete risk analysis for all three models. The evaluations of the following production strategies are performed: depletion, water injection, gas injection, water and gas injection and water alternating gas injection. Each strategy is optimized using assisted technics and the best economical result is selected for development. This study results are successful and concludes that water and gas injection is the best strategy for this reservoir since it has the highest net present value, the lowest financial risk and adds project flexibility because it injects two different fluids
Mestrado
Reservatórios e Gestão
Mestra em Ciências e Engenharia de Petróleo
37
Peacock, Lora. "Eco-climatic assessment of the potential establishment of exotic insects in New Zealand." Lincoln University, 2005. http://hdl.handle.net/10182/1530.
Full textAbstract:
To refine our knowledge and to adequately test hypotheses concerning theoretical and applied aspects of invasion biology, successful and unsuccessful invaders should be compared. This study investigated insect establishment patterns by comparing the climatic preferences and biological attributes of two groups of polyphagous insect species that are constantly intercepted at New Zealand's border. One group of species is established in New Zealand (n = 15), the other group comprised species that are not established (n = 21). In the present study the two groups were considered to represent successful and unsuccessful invaders. To provide background for interpretation of results of the comparative analysis, global areas that are climatically analogous to sites in New Zealand were identified by an eco-climatic assessment model, CLIMEX, to determine possible sources of insect pest invasion. It was found that south east Australia is one of the regions that are climatically very similar to New Zealand. Furthermore, New Zealand shares 90% of its insect pest species with that region. South east Australia has close trade and tourism links with New Zealand and because of its proximity a new incursion in that analogous climate should alert biosecurity authorities in New Zealand. Other regions in western Europe and the east coast of the United States are also climatically similar and share a high proportion of pest species with New Zealand. Principal component analysis was used to investigate patterns in insect global distributions of the two groups of species in relation to climate. Climate variables were reduced to temperature and moisture based principal components defining four climate regions, that were identified in the present study as, warm/dry, warm/wet, cool/dry and cool/moist. Most of the insect species established in New Zealand had a wide distribution in all four climate regions defined by the principal components and their global distributions overlapped into the cool/moist, temperate climate where all the New Zealand sites belong. The insect species that have not established in New Zealand had narrow distributions within the warm/wet, tropical climates. Discriminant analysis was then used to identify which climate variables best discriminate between species presence/absence at a site in relation to climate. The discriminant analysis classified the presence and absence of most insect species significantly better than chance. Late spring and early summer temperatures correctly classified a high proportion of sites where many insect species were present. Soil moisture and winter rainfall were less effective discriminating the presence of the insect species studied here. Biological attributes were compared between the two groups of species. It was found that the species established in New Zealand had a significantly wider host plant range than species that have not established. The lower developmental threshold temperature was on average, 4°C lower for established species compared with non-established species. These data suggest that species that establish well in New Zealand have a wide host range and can tolerate lower temperatures compared with those that have not established. No firm conclusions could be drawn about the importance of propagule pressure, body size, fecundity or phylogeny for successful establishment because data availability constrained sample sizes and the data were highly variable. The predictive capacity of a new tool that has potential for eco-climatic assessment, the artificial neural network (ANN), was compared with other well used models. Using climate variables as predictors, artificial neural network predictions were compared with binary logistic regression and CLIMEX. Using bootstrapping, artificial neural networks predicted insect presence and absence significantly better than the binary logistic regression model. When model prediction success was assessed by the kappa statistic there were also significant differences in prediction performance between the two groups of study insects. For established species, the models were able to provide predictions that were in moderate agreement with the observed data. For non-established species, model predictions were on average only slightly better than chance. The predictions of CLIMEX and artificial neural networks when given novel data, were difficult to compare because both models have different theoretical bases and different climate databases. However, it is clear that both models have potential to give insights into invasive species distributions. Finally the results of the studies in this thesis were drawn together to provide a framework for a prototype pest risk assessment decision support system. Future research is needed to refine the analyses and models that are the components of this system.
38
Baars, Jan-Robert. "Biological control initiatives against Lantana camara L. (Verbenaceae) in South Africa : an assessment of the present status of the programme, and an evaluation of Coelocephalapion camarae Kissinger (Coleoptera: Brentidae) and Falconia intermedia (Distant) (Heteroptera: Miridae), two new candidate natural enemies for release on the weed." Thesis, Rhodes University, 2003. http://hdl.handle.net/10962/d1005329.
Full textAbstract:
Lantana camara (lantana), a thicket-forming shrub, a number of different varieties of which were introduced into South Africa as ornamental plants but which has become a serious invasive weed. Conventional control measures for lantana are expensive and ineffective and it has therefore been targeted for biological control since 1961. To date, eleven biological control agent species have become established on lantana in South Africa. However, most agents persist at low densities and only occasionally impact plant populations. Three species regularly cause significant damage, but only reach sufficiently high numbers by midsummer after populations crash during the winter. Overall, the impact of the biological control programme on the weed is negligible and this has been ascribed to the poor selection of agents for release, the accumulation of native parasitoids, differences in insect preference for different varieties of the weed and variable climatic conditions over the weed’s range. This study suggests that the importance of varietal preferences has been over-estimated. A predictive bioclimatic modelling technique showed that most of the agents established in South Africa have a wide climatic tolerance and that the redistribution and importation of new climatypes of these agents will not improve the level of control. Additional agents are required to improve the biocontrol in the temperate conditions, and also to increase damage in the sub-tropical areas where most of the agents are established and where the weed retains its leaves year round. New candidate agents that possess biological attributes that favour a high intrinsic rate of increase, a high impact per individual and that improve the synchrony between the weed and the agent in climatic conditions that promote the seasonal leaflessness of plants should receive prior consideration. A survey in Jamaica indicated that additional biological control agents are available in the region of origin but that care should be taken to prioritise the most effective agents. The various selection systems currently available in weed biocontrol produce contradictory results in the priority assigned to candidate agents and a new selection system is proposed. The biology and host range of two new candidate natural enemies, the leaf-galling weevil, Coelocephalapion camarae and the leaf-sucking mirid, Falconia intermedia were investigated for the biocontrol of lantana. The studies indicated that these have considerable biocontrol potential, in that the weevil has a wide climatic tolerance and has the potential to survive the host leaflessness typical of temperate conditions, while the mirid has a high intrinsic rate of increase, and the potential for several generations a year. Both agents caused a high level of damage to the leaves, with the weevil galling the vascular tissue in the leaf-petiole and the mirid causing chlorotic speckling of the leaves. During laboratory trials both agents accepted indigenous species in the genus Lippia. However, under multiple choice conditions these agents showed a significant and strong oviposition preference for lantana. A risk assessment and post release field trials indicated that F. intermedia is likely to attack some Lippia species in the presence of lantana, but the levels of damage are predicted to be relatively low. A possible low incidence of damage to indigenous species was considered a justifiable ‘trade-off’ for the potentially marked impact on L. camara. Preference and performance studies on the two candidate agents suggested that most of the South African lantana varieties are suitable host plants. The mirid preferred certain varieties in multiple choice experiments, but this is unlikely to affect its impact under field conditions. Permission for release was accordingly sought for both species. Finally, the challenges facing the biological control programme and the potential for improving the control of L. camara in South Africa are considered.
39
Gatehouse, Hazel A. W. "Ecology of the naturalisation and geographic distribution of the non-indigenous seed plant species of New Zealand." Diss., Lincoln University, 2008. http://hdl.handle.net/10182/1009.
Full textAbstract:
The naturalisation and subsequent spread of non-indigenous plant species (NIPS) is a major problem for most regions of the world. Managing plant invasions requires greater understanding of factors that determine initial naturalisation and distribution of wild NIPS. By the year 2000, 2252 NIPS were recorded as wild (1773 fully naturalised and 479 casual) in New Zealand. From published literature and electronic herbaria records, I recorded year of discovery of wild populations, and regional distribution of these wild NIPS. I also recorded species related attributes hypothesised to affect naturalisation and/or distribution, including global trade, human activities, native range and biological data; and regional attributes hypothesised to affect distribution, including human population densities, land use/cover, and environmental data. I used interval-censored time-to-event analyses to estimate year of naturalisation from discovery records, then analysed the importance of historical, human activity, biogeographical and biological attributes in determining patterns of naturalisation. Typically, NIPS that naturalised earlier were herbaceous, utilitarian species that were also accidentally introduced and/or distributed, with a wide native range that included Eurasia, naturalised elsewhere, with a native congener in New Zealand. In the year 2000, 28% of wild NIPS occupied only one region, 18% occupied two regions, decreasing incrementally to 2.5 % for nine regions, but with 13.5% occupying all ten regions. I used generalised linear models (GLMs) with binomial distribution to determine predictors of whether a wild NIPS occupied ten regions or not, and GLMs with Poisson distribution for wild NIPS occupying 0 – 9 regions. As expected, the dominant effect was that species discovered earlier occupied more regions. Utilitarian wild NIPS that were also accidentally introduced and/or distributed, and wild NIPS with a native congener tended to be more widely distributed, but results for other attributes varied between datasets. Although numbers of wild NIPS recorded in regions of New Zealand were sometimes similar, composition of wild NIPS was often very different. I used nonmetric multidimensional scaling (NMDS) to determine dissimilarity in composition between regions. Then, after reducing correlation between predictor variables using principal components analyses (PCAs), I tested the importance of regional variables in determining the regional composition of wild NIPS using metaMDS. The density of human populations best explained the dissimilarity in composition, but temperature gradients and water availability gradients were also important. In the year 2000 more than 1100 (60%) of the 1773 fully naturalised NIPS in mainland New Zealand had each been recorded in Northland/Auckland and Canterbury, and at the other end of the scale, Southland and Westland each had fewer than 500 (30%). I used GLMs to analyse the importance of people and environment in determining the numbers of wild NIPS in each region. Because I conducted multiple tests on the same dataset I used sequential Bonferroni procedures to adjust the critical P-value. Only human population density was important in explaining the numbers of NIPS in the regions. Overall, humans were the dominant drivers in determining the patterns of naturalisation and spread, although environment helps determine the composition of NIPS in regions. Incorporating human associated factors into studies of wild NIPS helps improve the understanding of the stages in the naturalisation and spread process.
40
Houška, Daniel. "Sportovní hala v Prostějově." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227186.
Full textAbstract:
The goal of the submitted thesis is a design and assessment of a steel load-bearing structure of a multipurpose sports hall situated in Prostějov. The floor plan measurements of the object are 38x54 m with the maximum ceiling height of 9,5 m. Final design variant was chosen on the basis of two preliminary drafts, both processed according to standard ČSN EN. The structure is designed with respect to ultimate and serviceability limit states. The construction consists of 10 cross-links spaced by 6,0 m. The spatial rigidity of the structure’s main load-bearing system is provided by spatial elliptic trussed girders, longitudinal and sway bracings. Roof cladding is carried by purlins placed on trusses. Steel columns are designed as a part of gable walls. The project was carried out in Scia Engineer 2014 software. Some particular elements were subsequently assessed by means of manual calculation. The thesis also includes assessment of joints, construction details and drawing documentation.
41
Michálek, Vojtěch. "Zastřešení víceúčelového sportovního objektu." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227533.
Full textAbstract:
The topic of the thesis is a project of roof of a multifunctional sport object with a ground-plan covering area 35x48m, and maximum height of 16m. This construction is projected for Brno and its surroundings. The project of roofing is evolved in two different variants. First one is formed by double-jointed arched latticed truss. Supporting components such as purlins, lateral and longitudal bracings, frontal column and anchorage are designed and assessed in static calculation. At the end of the thesis, comparison of both variants is elaborated. Design documentation, which consists of dispositional drawing, drawing of truss for manufacturing, drawing of indicative details and plan of anchorage, is a part of the thesis.
42
Balasubramaniam, Rengasamy. "The effects of foliar diseases and irrigation on root development, yield and yield components of wheat (Triticum aestivum L.)." Lincoln College, University of Canterbury, 1985. http://hdl.handle.net/10182/1514.
Full textAbstract:
Studies were conducted on three field trials of wheat cv. Kopara to investigate the lack of compensation by later determined components of yield because of early disease constraints. The investigation was based on the hypothesis that early disease reduces root development and thus causes the plants to be water constrained at later growth stages when soil water deficits usually occur. The reduced root development and soil water deficits may reduce the ability of the plant to compensate for reductions in early determined components. The hypothesis was tested by the application of irrigation to alleviate water stress. In a disease free crop, the possible phytotonic effects of the fungicides benomyl and triadimefon on wheat were investigated. These fungicides had no phytotonic effects on shoot, root growth, or yield under the prevailing conditions. The effect of disease on root development was analysed by root length measurements. Disease present in the crop at any stage of growth affected root development. Root development in the upper zones of the soil profile was reduced more by disease compared to those zones below 35 cm. A full disease epidemic reduced root development more than an early or late disease epidemic. The early and late disease epidemics had similar effects on root length. Alleviation of early disease constraints enabled greater development of roots to offset any earlier reductions. Soil water deficits increased root development in the lower zones of the nil disease plants. The presence of adequate soil water from irrigation reduced the requirement for further root growth in all treatments. In the 1981-1982 field trial a full disease epidemic reduced yield by 14% whereas an early disease epidemic reduced yield by 7%. The reduction in yield was attributed to a lower grain number. With irrigation the yield reduction in the full disease plants was 12% whereas in the early disease plants the reduction was only 2.4%. This indicated that plants affected by the early disease epidemic were water constrained. In this study, the results suggested that, for conditions prevailing in Canterbury, the supply of water at later growth stages increased grain weight in plants which were subject to early disease epidemics. This suggests that reduced root development caused by early disease and soil water deficits may prevent compensation by grain weight. Water use was similar in all disease treatments. After irrigation the irrigated plants of all treatments used more water. Disease affected water use in relation to yield production however, and was better expressed by water use efficiency. Water use efficiency was reduced in the full disease plants. A stepwise regression analysis suggested that water use efficiency was affected directly by disease at later growth stages, and indirectly via an effect on total green leaf area at early growth stages. This study partially proves the hypothesis that reductions in root development caused by an early disease epidemic may constrain the plants at later growth stages when water deficits usually occur. It was shown that the reduction in root development caused by disease could be counteracted by irrigation. In this respect, water served as a tool to study the effect of disease constraints on the yield of wheat. A knowledge of cereal crop physiology, root growth and function is used to explain and discuss the observations made in this research programme. The results are discussed in relation to the way in which disease affects yield through its effect on root development. The possible reasons for the continued effects of disease even after the control of disease at later growth stages are discussed. The economic use of fungicides and water in diseased crops are also outlined. Suggestions for future studies on disease-yield loss relationships are provided. The repetition of these experiments in different sites and climatic regions could provide information which may be incorporated in disease-yield loss simulation models. This could then be used to predict root development and water requirements of diseased plants, and provide a basis for economic use of fungicides and water, and for better disease management programmes.
43
Chiou, Rong-Chieh, and 邱榮杰. "Performance Assessment of Steel Coupler and Investigation of the Strength of Welds Used to Connect Coupler and Steel Plate." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/92892738859988497708.
Full textAbstract:
碩士國立台灣工業技術學院
營建工程技術研究所
85
In this study, the strength of welds connecting steel plate and steelcoupler is investigated. A total of 88 specimens, including partial penetration groove welds with single-J bevel and fillet welds, using #10 steel coupler are tested. Test results show that：(1) AWS prequalified partial penetration groove welds with single-J bevel is suitable for assemblage of couplers and steel. (2) The formula suggested in chapter 4 gives a good estimation of the weld strength of partial penetration groove welds with single-J bevel couplers, (3) In the practical range, the thickness combination of box column plate and diaphragm does not influence the strength of welds. (4) Eccentricity, between coupler and diaphragm, smaller than 7 mm, does not decrease the strength of welds.
44
Maphalala, Kwanele Zakhele. "Field assessment of agronomic traits and in vitro acetolactate synthase characterisation of imazapyr herbicide tolerant sugarcane." Thesis, 2013. http://hdl.handle.net/10413/10980.
Full textAbstract:
Weed control is a major cost for growers in the sugarcane industry, especially for monocotyledonous species such as Cynodon and Rottboellia spp. The introduction of imazapyr-tolerant sugarcane would be advantageous as this herbicide has shown to be effective against the above-mentioned weeds but it also kills sugarcane. In a previous study in our laboratory, several sugarcane putative-mutant lines of variety N12 were generated by in vitro exposure of embryogenic callus to 16 mM ethyl methanesulfonate (EMS), followed by selection on imazapyr-containing medium. Tolerance to a low dose of imazapyr was confirmed in seven of those lines when the herbicide was applied (182 g a.i. ha-1) to 3 month-old plants in pots. The aim of the present study was to identify which of the seven herbicide mutant lines had agronomic characteristics at least equivalent to un-mutated N12. The objectives were to: 1) confirm tolerance to increased rate (312 and 625 g a.i. ha-1) of imazapyr in field plants; 2) measure the agronomic characteristics of these lines; 3) determine the effect of residual soil herbicide activity on germination of sugarcane setts.
The seven mutant lines (Mut1-Mut7) and un-mutated N12 were clonally propagated in vitro by shoot multiplication followed by rooting and planted in three plots (untreated, sprayed with 312 or 625 g a.i. ha-1 imazapyr), in the field, in a randomized complete block design. In the untreated control plot there were no significant differences between the control and the mutant plants for agronomic traits (tiller number/plot, stalk height and stalk diameter) or estimated yield (kg/plot) after 10 months, indicating that the mutation process had no effect on general plant phenotype. In the sprayed (312 and 625 g a.i. ha-1) plots, Mut1, Mut4, Mut5, Mut6 and Mut7 plants showed tolerance to imazapyr as the leaves remained green compared with Mut2, Mut3 and N12 control plants, which displayed chlorotic leaves and eventually died in the plot sprayed with 625 g a.i. ha-1. Post-herbicide application, the yields of Mut5, Mut6 and Mut7 (52.33, 43.43 and 41.43 kg/plot, respectively) from the 312 g a.i. ha-1 plot were not significantly different from that of N12 control (53. 61 kg/plot) in the untreated plot. However, in the 312 g a.i. ha-1 plot, the yield and agronomic trait measurements of the untreated N12 control were significantly higher than those of the herbicide-susceptible plants Mut2 and Mut3. Similarly, in the 625 g a.i. ha-1 plot, the recorded yields for Mut4, Mut6 and Mut7 were 41.60, 43.44 and 36.30 kg/plot, respectively, indicating that their imazapyr tolerance and yield characteristics were comparable to the untreated N12 control.
Imazapyr is conventionally applied to a fallow field 3-4 months prior to planting sugarcane as there is residual herbicide activity in the soil that suppresses sugarcane germination and growth. Therefore, in order to establish if the herbicide-tolerant mutants could germinate in
iii
an imazapyr-treated field, 3-budded setts of the mutant lines (Mut1-Mut7) and N12 control were planted in two plots, one unsprayed and one sprayed with 1254 g a.i. ha-1 imazapyr, 2 weeks previously. Germination was calculated after 3 weeks as the number of germinated setts in each plot/no. germinated setts in unsprayed plot x100. In the sprayed plot, the setts from Mut1, Mut4 and Mut6 displayed the highest germination percentages (60, 71 and 74%, respectively) compared with Mut2 (24%), Mut3 (46%), Mut5 (34%), Mut7 (40%) and the N12 control (12%).
The in vitro acetolactate synthase (ALS) enzyme activity of 10 month-old plants from the untreated plot was assessed in the presence of 0-30 μM imazapyr to determine the herbicide concentration that inhibited ALS activity by 50% (IC50). The IC50 values for the mutated lines were between 3 and 30 μM, i.e. 1.5-8.8 times more tolerant to imazapyr than the N12 control plants, with Mut6 displaying the highest IC50 value (30 μM). On the basis of the results, it was concluded that Mut1, Mut6 and Mut7 lines were more tolerant to imazapyr than N12 and the other tested lines. Future work includes phenotypically assessing these lines for traits including sucrose content, fibre content, actual yield (tons cane ha-1) and altered pest and disease resistance. Once isolated and sequenced, the ALS gene conferring imazapyr tolerance can be used in genetic bombardment in the genetic modification approach as the gene of interest or as a selectable marker. In addition, the imazapyr-tolerant line can be used for commercial purposes in the field and as the parent plant in the breeding programme.Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Durban, 2013.
45
Sebola, Azwinndini Patricia. "An assessment of the impact of alien plant invasions along the Riparian Zones: a case study at Luvuvhu, Lutanandwa and Mutshindudi Rivers, Limpopo Province, South Africa." Diss., 2015. http://hdl.handle.net/11602/280.
Full text