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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
781

Reliability Analysis of Low-Silver BGA Solder Joints Using Four Failure Criteria

Kimura, Erin A. 01 November 2012 (has links) (PDF)
The appropriate selection of failure criterion for solder joint studies is necessary to correctly estimate reliability life. The objective of this study is to compare the effect of different failure criteria on the reliability life estimation. The four failure criteria in this study are a 20% resistance increase defined in the IPC-9701A standard, a resistance beyond 500 Ω, an infinite resistance (hard open), and a failure criterion based on X-bar and R control charts. Accelerated thermal cycling conditions of a low-silver BGA study included 0°C to 100 °C with ten minute dwell times and -40°C to 125°C with ten minute dwell times. The results show that the life estimation based on X-bar and R failure criterion is very similar to the life estimation when a 20% resistance increase defined in the IPC-9701A failure criterion is used. The results also show that the reliability life would be overestimated if the failure criterion of a resistance threshold of 500 Ω or an infinite resistance (hard open) is used.
782

Surface Modifications of Reverse Osmosis Membranes for Removal of Bromide and Reduction of Fouling

Seo, Joseph 01 June 2020 (has links) (PDF)
Reverse osmosis (RO) is widely used for water reuse and desalination. Although RO membranes are known for their high salt rejection and practical permeate flux, their performance can be impaired by fouling, and their removal of some disinfection byproducts and their precursors (e.g., bromide, N-Nitrosodimethylamine [NDMA]) does not meet drinking water standards. RO membrane modifications have been widely studied to overcome these limitations. In this research, RO membranes were grafted with cationic polymers to induce a positive charge on the RO membrane surface. This modification aimed at enhancing the rejection of negatively charged bromide ions by removing them from solution by binding them to the membrane surface. The results showed that the modified (positively charged) RO membranes achieved lower rejection (82% rejection) for bromide ions compared to the unmodified ones (94.5% rejection). This behavior was likely a result of increased concentration polarization of the bromide ions at the membrane surface and/or increase in porosity of the modified membranes. Calculations based on the film theory indicate that the concentration of bromide ions at the surface of the modified membrane was 1371 ppm compared to 1307 ppm at the surface of the unmodified membrane. Evidently, the polymer attraction energy was not sufficient to keep the bromide ions attached to the membrane surface and prevent their diffusion across the membrane. Although the goal of the modification in the current study (i.e., enhancing removal of bromide ions) was not met, the permeate flux of the modified membrane was improved compared to the unmodified one. The literature suggests that increasing flux after modification is likely a result of increase in membrane pore size and hydrophilicity. In addition to the experimental work conducted in this study, a multi-criteria decision analysis was performed to prioritize research on surface modifications of reverse osmosis membranes. It was found that surface modifications have been mainly focused on reducing membrane fouling and to a much lower extent on removal of disinfection byproducts and their precursors. The RO membrane modification alternatives for fouling reduction and N-Nitrosodimethylamine (NDMA) removal were ranked based on multiple criteria using the Analytical Hierarchy Process (AHP) and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). This multi-criteria decision analysis process resulted in the identification of the top five promising modifications to reduce fouling and improve NDMA rejection. Grafting and coating the RO membranes with complex polymeric salts were the highest ranked modification approaches to reduce fouling. Heat-treatment of RO membranes achieved the highest NDMA rejection (98%); however, this technique was the second highest ranked modification approach for NDMA removal because it scored lower for other evaluation criteria.
783

Evaluating native warm-season grass and wildflower mixtures for beef cattle production in the Mid-Atlantic

Kubesch, Jonathan Omar Cole 20 December 2023 (has links)
Tall fescue grasslands are the dominant form of grasslands in the North American transition zone, however, warm-season forages provide necessary forage for livestock in the summer. Pollinators require steady forage availability in the same fashion as cattle. Native warm-season grasses (NWSG) and wildflowers (WF) could be incorporated into tall fescue (TF) grasslands to improve pollinator resources within agricultural landscapes without sacrificing livestock production. This balance of ecosystem services can be considered bee-friendly beef. Previous establishment experiments suggests that bee-friendly beef is a possibility, although establishment and persistence of NWSG-WF stands warrants additional research. Three small plot experiments were conducted to evaluate different planting methods designed to optimize establishment of NWSG-WF stands. Additionally, a grazing study examined whether NWSG-WF pasture enhancement could improve animal performance in TF grazing systems. The small plot experiments experienced extreme weed competition in the establishment year, although plots with higher NWSG content had fewer weeds over time. Floral production was comparable across treatment, which suggests lower WF seeding rates can generate comparable pollinator resources. Major findings from these experiments suggested that spatial or temporal separation of NWSGWF was unnecessary to generate successful establishment, varying the ratio of NWSG-WF in seed mixtures produced similar establishment outcomes, and that adding companion crops to NWSG-WF mixtures did not improve establishment success appreciably. In the grazing experiment, animal performance was improved in the biodiverse grazing systems when heifers 3 had access to the NWSG. Biodiverse and shaded grazing systems modified animal behavior and reduced body temperature relative to control grazing systems, although only biodiverse grazing systems improved animal performance. Native WF species failed to establish within the biodiverse grazing system, but white clover provided all subsequent floral production. Establishing WF in pastures is challenging and warrants additional study on more effective weed control strategies and systems to ensure establishment success. Selecting WF for agronomic performance or breeding such plant material will be necessary to improve emergence and establishment dynamics. Ideally trait data can identify the optimal WF species for specific grazing systems. Biodiverse NWSG-WF can be highly effective at improving summer weight gain in beef cattle. Future studies should focus on finding a more optimal balance of NWSG, WF, and TF that can benefit beef cattle production, pollinator services, and ecosystem services regarding soil and water quality, as well as pasture resiliency to dynamic conditions. / Doctor of Philosophy / Tall fescue grasslands are the dominant form of grasslands in the North American transition zone, however, warm-season forages provide necessary forage for livestock in the summer. Pollinators require steady forage availability in the same fashion as cattle. Native warm-season grasses (NWSG) and wildflowers (WF) could be incorporated into tall fescue (TF) grasslands to improve pollinator resources within agricultural landscapes without sacrificing livestock production. This balance of ecosystem services can be considered bee-friendly beef. Previous establishment experiments suggests that bee-friendly beef is a possibility, although establishment and persistence of NWSG-WF stands warrants additional research. Three small plot experiments were conducted to evaluate different planting methods designed to optimize establishment of NWSG-WF stands. Additionally, a grazing study examined whether NWSG-WF pasture enhancement could improve animal performance in TF grazing systems. The small plot experiments experienced extreme weed competition in the establishment year, although plots with higher NWSG content had fewer weeds over time. Floral production was comparable across treatment, which suggests lower WF seeding rates can generate comparable pollinator resources. Major findings from these experiments suggested that spatial or temporal separation of NWSGWF was unnecessary to generate successful establishment, varying the ratio of NWSG-WF in seed mixtures produced similar establishment outcomes, and that adding companion crops to NWSG-WF mixtures did not improve establishment success appreciably. In the grazing experiment, animal performance was improved in the biodiverse grazing systems when heifers 3 had access to the NWSG. Biodiverse and shaded grazing systems modified animal behavior and reduced body temperature relative to control grazing systems, although only biodiverse grazing systems improved animal performance. Native WF species failed to establish within the biodiverse grazing system, but white clover provided all subsequent floral production. Establishing WF in pastures is challenging and warrants additional study on more effective weed control strategies and systems to ensure establishment success. Selecting WF for agronomic performance or breeding such plant material will be necessary to improve emergence and establishment dynamics. Ideally trait data can identify the optimal WF species for specific grazing systems. Biodiverse NWSG-WF can be highly effective at improving summer weight gain in beef cattle. Future studies should focus on finding a more optimal balance of NWSG, WF, and TF that can benefit beef cattle production, pollinator services, and ecosystem services regarding soil and water quality, as well as pasture resiliency to dynamic conditions.
784

Clinical diagnosis and risk factors for chronic traumatic encephalopathy

Montenigro, Philip Homes 03 November 2016 (has links)
Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease characterized by a pathognomonic distribution of hyperphosphorylated tau accumulations in neurons, astrocytes, and cell processes, situated around vessels at the depths of cortical sulci. Case reports of CTE pathology exhibit a common exposure to repetitive head impacts (RHI), suggesting that RHI are a necessary factor in the disease’s etiology. Currently, it is only possible to definitively diagnose CTE after death using histopathological techniques and consensus-based neuropathological diagnostic criteria recently established by the National Institute of Health and National Institute of Neurological Disorders and Stroke. Though considerable progress has been made in characterizing the neuropathology of CTE, less is known about the clinical aspects of the disease. Specifically, additional research is needed to identify disease-specific clinical manifestations, clinicopathological correlations, and a means of diagnosis during life, all of which are critical to developing future epidemiological studies, preventative measures, and treatment trials. Moreover, it is not yet known which specific aspects of RHI exposure (type, frequency, duration) are causally linked to developing clinically meaningful neurological impairments or CTE neuropathology, nor have studies identified risk-modifying factors, such as genotype (e.g. APOE). The objective of this dissertation’s published works was to systematically address these gaps in knowledge. First, to define a common clinical presentation of CTE, we conducted a retrospective analysis of medical records and semi-structured next-of-kin reports of 36 former athletes with autopsy-confirmed CTE without comorbid neurodegenerative disease. We then published clinical diagnostic criteria for CTE based on a systematic review of clinical features exhibited in 202 former athlete cases and a pooled analysis of 83 neuropathologically confirmed CTE cases. In subsequent analyses, we operationalized clinical criteria to investigate specific clinicopathological associations between tau, amyloid beta, age, APOE genotype, and clinical outcomes and utilized the clinical criteria to explore potential risk-factors related to RHI from boxing and football. Lastly, we developed a metric to quantify cumulative RHI exposure in retired, living, football players. Using this metric, our study was the first to indicate a causal relationship between cumulative RHI exposure and risk of later life cognitive, mood, and behavioral impairment. These studies are preliminary, and our results require replication and validation in larger, longitudinal prospective studies.
785

Intelligent phishing website detection system using fuzzy techniques

Aburrous, Maher R., Hossain, M. Alamgir, Thabatah, F., Dahal, Keshav P. January 2008 (has links)
Phishing websites are forged web pages that are created by malicious people to mimic web pages of real websites and it attempts to defraud people of their personal information. Detecting and identifying Phishing websites is really a complex and dynamic problem involving many factors and criteria, and because of the subjective considerations and the ambiguities involved in the detection, Fuzzy Logic model can be an effective tool in assessing and identifying phishing websites than any other traditional tool since it offers a more natural way of dealing with quality factors rather than exact values. In this paper, we present novel approach to overcome the `fuzziness¿ in traditional website phishing risk assessment and propose an intelligent resilient and effective model for detecting phishing websites. The proposed model is based on FL operators which is used to characterize the website phishing factors and indicators as fuzzy variables and produces six measures and criteria¿s of website phishing attack dimensions with a layer structure. Our experimental results showed the significance and importance of the phishing website criteria (URL & Domain Identity) represented by layer one, and the variety influence of the phishing characteristic layers on the final phishing website rate.
786

Betyg i musik, syfte och funktion

Svedjebrant, Carl-Olov January 2013 (has links)
The object of this thesis was to find out the opinion about grades among teachers in music, taking into consideration the underlying purposes, which are normally highlighted to motivate grades and to elucidate the music teachers view on the their possibilities to evaluate the pupils achievements and to give fair grades. Four music teachers were interviewed and transcriptions were made from the interviews. Relevant substance of the interviews was described and in the discussion part of the study a comparison was made with the research that was reviewed in the background. The main conclusion in the study is the teachers in music are not basically against grades and that they have a good understanding of the purposes with grades. They are also of the opinion that there are good opportunities to tool and individualise the pedagogy even though lack of resources is an obstacle. Guidance is needed on a national level but there is a hesitation about national tests. Teachers have a clear opinion about the certain difficulties, which are related to evaluation and grades in the subject music. / <p>Validerat; 20130520 (global_studentproject_submitter)</p>
787

Spatial vulnerability analysis and thematic mapping of urban floods: A case study of 100-year floodplain areas of Birmingham, Alabama

Hossain, Mohammad Khalid 25 November 2020 (has links)
The social and economic impact of urban flooding is becoming more severe in the United States over time. Urban areas are mostly vulnerable to flash floods because of the impervious surface, which increases the surface runoff. More than 80 percent of people live in urban areas in the United States, and they are at higher risk of urban flooding. Although many urban areas have a higher risk of urban flooding, there is still a significant knowledge gap of understanding between the minority's and nonminority's vulnerability to urban floods. Therefore, using Birmingham, Alabama, as a study area, this research designs a quantitative thematic mapping method to assess the flood risks of urban population and buildings. In this research, census data was used to assess urban residents' vulnerability to flooding using thematic mapping method – location quotient (LQ) and compare it with the widely used social vulnerability index. The findings suggest that the aggregation of White populations is much higher compared to minorities. This research also developed a flood risk model using integrated GIS and cartographic approach considering different environmental factors that influence the urban floods. This study found that the Valley Creek area is the highest flood risk zone in Birmingham, and has the highest percentage of residential (i.e., 56.14 %) and commercial (i.e., 75.34 %) buildings located in very high flood risk areas. The decennial census data from 1990 to 2015 was used to examine whether vulnerable population groups aggregated more in the flooding areas or moved away from Birmingham's flooding areas in the past thirty years. The findings of this research indicate that most minorities are aggregating more in the floodplain areas, whereas the non-minorities are moving away from the flooding regions.
788

The Figures that Matter: People-related criteria used by Swedish venture capitals in assessing new technology-based firms

Osataphan, Nachomkorn (Maew) January 2014 (has links)
Venture Capitals (VCs) are important providers of funds and competence to new technology-based firms (NTBFs) and VC-backed NTBFs are more likely to succeed than those that are not. Past researches into VC selection criteria suggested people-related criteria as being the most important out of all the criteria but as they were focused on ranking certain criteria against each other, they did not describe what they mean and how they are used and could have overlooked other criteria used that were not ranked. This research is addressing such gap by exploring people-related criteria used by VCs through collecting qualitative data from semi-structured interviews with Swedish VC investment managers. The results present 25 people-related criteria; what they mean, when they are used, and how they are assessed. Twelve of these criteria are new and have not been featured in past studies. In the screening stage, only a few people-related criteria are used while all but one people-related criteria identified are used in the assessment stage. The criteria most commonly used in the evaluation stage are new to this study. Themes arising from results are also discussed, such as coachable entrepreneurs as positive criterion and technical-driven NTBF teams as negative criterion. This research extends the knowledge in the area of entrepreneurship studies and provides practical implications for NTBFs seeking to raise funds.
789

Методика оценки сборно-монолитных зданий на примере китайского гражданского строительства : магистерская диссертация / Methodology for the evaluation of prefabricated monolithic buildings on the example of Chinese civil construction

Чжао, П., Zhao, P. January 2023 (has links)
В настоящее время Китай еще не достиг наивысшего уровня развития сборно-монолитных зданий, обладающих высоким уровнем сборности. Поэтому исследования сборно-монолитного строительства актуальны. В работе представлен вариант совершенствования оценки сборно-монолитных зданий на примере китайского гражданского строительства. Кратко рассмотрена история развития сборно-монолитных зданий в Китае и других странах. Разработан алгоритм оценки сборно-монолитного здания, представлен пример практического применения методики и алгоритма. / At present, China has not yet reached the highest level of development of prefabricated monolithic buildings with a high level of prefabrication. Therefore, research into prefabricated monolithic construction is relevant. The paper presents an option for improving the assessment of prefabricated monolithic buildings using the example of Chinese civil engineering. The history of the development of prefabricated monolithic buildings in China and other countries is briefly reviewed. An algorithm for assessing a prefabricated monolithic building has been developed, and an example of the practical application of the methodology and algorithm is presented.
790

Exploring the Nature of Benefits and Costs of Open Innovation for Universities by Using a Stochastic Multi-Criteria Clustering Approach: The Case of University-Industry Research Collaboration

Zare, Javid January 2022 (has links)
Open innovation that Henry Chesbrough introduced in 2003 promotes the usage of the input of outsiders to strengthen internal innovation processes and the search for outside commercialization opportunities for what is developed internally. Open innovation has enabled both academics and practitioners to design innovation strategies based on the reality of our connected world. Although the literature has identified and explored a variety of benefits and costs, to the best of our knowledge, no study has reviewed the benefits and costs of open innovation in terms of their importance for strategic performance. To conduct such a study, we need to take into account two main issues. First, the number of benefits and costs of open innovation are multifold; so, to have a comprehensive comparison, a large number of benefits and costs must be compared. Second, to have a fair comparison, benefits and costs must be compared in terms of different performance criteria, including financial and non-financial. Concerning the issues above, we will face a complex process of exploring benefits and costs. In this regard, we use multiple criterion decision-making (MCDM) methods that have shown promising solutions to complex exploratory problems. In particular, we present how using a stochastic multi-criteria clustering algorithm that is one of the recently introduced MCDM methods can bring promising results when it comes to exploring the strategic importance of benefits and costs of open innovation. Since there is no comprehensive understanding of the nature of the benefits and costs of open innovation, the proposed model aims to cluster them into hierarchical groups to help researchers identify the most crucial benefits and costs concerning different dimensions of performance. In addition, the model is able to deal with uncertainties related to technical parameters such as criteria weights and preference thresholds. We apply the model in the context of open innovation for universities concerning their research collaboration with industries. An online survey was conducted to collect experts' opinions on the open-innovation benefits and costs of university-industry research collaboration, given different performance dimensions. The results obtained through the cluster analysis specify that university researchers collaborate with industry mainly because of knowledge-related and research-related reasons rather than economic reasons. This research also indicates that the most important benefits of university-industry research collaboration for universities are implementing the learnings, increased know-how, accessing specialized infrastructures, accessing a greater idea and knowledge base, sensing and seizing new technological trends, and keeping the employees engaged. In addition, the results show that the most important costs are the lack of necessary resources to monitor activities between university and industry, an increased resistance to change among employees, conflict of interest (different missions), an increased employees' tendency to avoid using the knowledge that they do not create themselves, paying time costs associated with bureaucracy rules, and loss of focus. The research's findings enable researchers to analyze open innovation's related issues for universities more effectively and define their research projects on these issues in line with the priorities of universities.

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