• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 91
  • 33
  • 11
  • 7
  • 5
  • 5
  • 3
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 200
  • 29
  • 25
  • 21
  • 20
  • 17
  • 16
  • 16
  • 15
  • 15
  • 14
  • 14
  • 13
  • 13
  • 13
  • 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.
1

ADVANTAGES OF GPS OVER RADAR IN WIND WEIGHTING OF UNGUIDED SOUNDING ROCKETS

May, Linda R. 10 1900 (has links)
ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California / “Wind Weighting” is the process of assessing the effect of wind on a launch vehicle and determining launcher settings which would counteract that effect. This paper discusses the advantages of using GPS radiosondes to determine wind profiles over the historical method of tracking balloon positions with radar for the purposes of Wind Weighting. The primary advantages are lower costs and greater portability. Also presented is evidence of improved accuracy and reliability. Engineering testing is described and test results are reported.
2

The statistical analysis of complex sampling data

Paulse, Bradley January 2018 (has links)
>Magister Scientiae - MSc / Most standard statistical techniques illustrated in text books assume that the data are collected from a simple random sample (SRS) and hence are independently and identically distributed (i.i.d.). In reality, data are often sourced through complex sampling (CS) designs, with a combination of stratification and clustering at different levels of the design. Consequently, the CS data are not i.i.d. and sampling weights that are developed over different stages, are calculated and included in the analysis of this data to account for the sampling design. Logistic regression is often employed in the modelling of survey data since the response under investigation typically has a dichotomous outcome. Furthermore, since the logistic regression model has no homogeneity or normality assumptions, it is appealing when modelling a dichotomous response from survey data. This research considers the comparison of the estimates of the logistic regression model parameters when the CS design is accounted for, i.e. weighting is present, to when the data are modelled using an SRS design, i.e. no weighting. In addition, the standard errors of the estimators will be obtained using three different variance techniques, viz. Taylor series linearization, the jackknife and the bootstrap. The different estimated standard errors will be used in the calculation of the standard (asymptotic) interval which will be compared to the bootstrap percentile interval in terms of the interval coverage probability. A further level of comparison is obtained when using only design weights to those obtained using calibrated and integrated sampling weights. This simulation study is based on the Income and Expenditure Survey (IES) of 2005/2006. The results showed that generally when weighting was used the estimators performed better as opposed to when the design was ignored, i.e. under the assumption of SRS, with the results for the Taylor series linearization being more stable.
3

Strategies and Adaptations Seen with Unilateral Lower Limb Weighting during Level Ground Walking and Obstacle Clearance Tasks

DeRochie, Marc 14 January 2010 (has links)
Abstract: Previous lower limb weighting studies have placed a load on the legs bilaterally and tested different placement locations. It was previously determined that kinematic changes occur with greater masses and at joints proximal to weight placement [1]. Other studies have determined that these changes exist for a short adaptation period before parameters revert to a steady state [2]. Tasks that require voluntary gait modifications such as obstacle clearance have also been performed with lower leg bilateral weight addition [4]. In cases of normal obstacle clearance increased flexion at all three joints in the lower limb is needed to safely traverse the obstacle [3]. The goal of this study was to investigate joint kinematics and kinetics of unilaterally weighted participants using level ground force platform collection techniques, rather than a treadmill. It was hoped that this would allow for new insight into the adaptation periods and strategic motor pattern changes seen at the ankle, knee and hip. Kinematic and force platform data were collected on two groups of 10 healthy male subjects. Group 1 (mean age = 23years, mean weight = 82.181kg, mean height = 1.798m) was a normal walking group and group 2 (mean age = 24.8years, mean weight = 79.901kg, mean height = 1.773m) was an obstacle clearance group. Both groups participated in 20 trials each of three different conditions; normal, weighted and weight off using a 2.27kg limb mass attached just proximal to the right maleoli markers. A repeated-measures two-way ANOVA was carried out on relevant variables in order to determine statistical significance. Weight addition and removal affected the kinematics and kinetics of the normal walking and obstacle clearance groups. This effect was more prominent in the normal walking group. If changes were seen, trials 1 through 3 were the locations showing a quick adaptation followed by a leveling off back to a new steady state in later trials. Participants in the normal walking group chose to utilize the hip joint in order to control for weight addition and removal. Kinematically, changes in the hip joint angle occurred at all instances analyzed throughout the gait cycle with this effect being more prominent in the weight off condition. In conjunction with this, the hip joint energy generation increased during all phases of the gait cycle while the ankle and knee joints either decreased energy generation or increased energy absorption. In the obstacle group, participants also chose to increase flexion at the hip joint. However, the ankle joint also had either decreased plantarflexion or increased dorsiflexion at all the instances analyzed during the gait cycle. However, joint energy generation increases at these joints were only found during stance and at heel contact. The toe obstacle clearance values also showed a marked increase in trial 1 for the weighted condition which demonstrates a voluntary gait modification made by participants to safely traverse the obstacle that was quickly adapted for. Overall, the results found by previous studies using treadmill collection techniques were still seen in overground force platform data but they were not as robust. References: 1.Martin PE et al. J Biomech. 1990; 23(6):529-536. 2.Noble et al. Exp Brain Res. 2006; 169: 482-495. 3.Patla AE et al. Exp Brain Res. 1995; 196: 499-504. 4.Reid MJ et al. Neurosci Res Comm. 2001; 29(2): 79-87.
4

Strategies and Adaptations Seen with Unilateral Lower Limb Weighting during Level Ground Walking and Obstacle Clearance Tasks

DeRochie, Marc 14 January 2010 (has links)
Abstract: Previous lower limb weighting studies have placed a load on the legs bilaterally and tested different placement locations. It was previously determined that kinematic changes occur with greater masses and at joints proximal to weight placement [1]. Other studies have determined that these changes exist for a short adaptation period before parameters revert to a steady state [2]. Tasks that require voluntary gait modifications such as obstacle clearance have also been performed with lower leg bilateral weight addition [4]. In cases of normal obstacle clearance increased flexion at all three joints in the lower limb is needed to safely traverse the obstacle [3]. The goal of this study was to investigate joint kinematics and kinetics of unilaterally weighted participants using level ground force platform collection techniques, rather than a treadmill. It was hoped that this would allow for new insight into the adaptation periods and strategic motor pattern changes seen at the ankle, knee and hip. Kinematic and force platform data were collected on two groups of 10 healthy male subjects. Group 1 (mean age = 23years, mean weight = 82.181kg, mean height = 1.798m) was a normal walking group and group 2 (mean age = 24.8years, mean weight = 79.901kg, mean height = 1.773m) was an obstacle clearance group. Both groups participated in 20 trials each of three different conditions; normal, weighted and weight off using a 2.27kg limb mass attached just proximal to the right maleoli markers. A repeated-measures two-way ANOVA was carried out on relevant variables in order to determine statistical significance. Weight addition and removal affected the kinematics and kinetics of the normal walking and obstacle clearance groups. This effect was more prominent in the normal walking group. If changes were seen, trials 1 through 3 were the locations showing a quick adaptation followed by a leveling off back to a new steady state in later trials. Participants in the normal walking group chose to utilize the hip joint in order to control for weight addition and removal. Kinematically, changes in the hip joint angle occurred at all instances analyzed throughout the gait cycle with this effect being more prominent in the weight off condition. In conjunction with this, the hip joint energy generation increased during all phases of the gait cycle while the ankle and knee joints either decreased energy generation or increased energy absorption. In the obstacle group, participants also chose to increase flexion at the hip joint. However, the ankle joint also had either decreased plantarflexion or increased dorsiflexion at all the instances analyzed during the gait cycle. However, joint energy generation increases at these joints were only found during stance and at heel contact. The toe obstacle clearance values also showed a marked increase in trial 1 for the weighted condition which demonstrates a voluntary gait modification made by participants to safely traverse the obstacle that was quickly adapted for. Overall, the results found by previous studies using treadmill collection techniques were still seen in overground force platform data but they were not as robust. References: 1.Martin PE et al. J Biomech. 1990; 23(6):529-536. 2.Noble et al. Exp Brain Res. 2006; 169: 482-495. 3.Patla AE et al. Exp Brain Res. 1995; 196: 499-504. 4.Reid MJ et al. Neurosci Res Comm. 2001; 29(2): 79-87.
5

EFFICIENT CONSTRUCTION OF ACCURATE MULTIPLE ALIGNMENTS AND LARGE-SCALE PHYLOGENIES

Wheeler, Travis John January 2009 (has links)
A central focus of computational biology is to organize and make use of vast stores of molecular sequence data. Two of the most studied and fundamental problems in the field are sequence alignment and phylogeny inference. The problem of multiple sequence alignment is to take a set of DNA, RNA, or protein sequences and identify related segments of these sequences. Perhaps the most common use of alignments of multiple sequences is as input for methods designed to infer a phylogeny, or tree describing the evolutionary history of the sequences. The two problems are circularly related: standard phylogeny inference methods take a multiple sequence alignment as input, while computation of a rudimentary phylogeny is a step in the standard multiple sequence alignment method.Efficient computation of high-quality alignments, and of high-quality phylogenies based on those alignments, are both open problems in the field of computational biology. The first part of the dissertation gives details of my efforts to identify a best-of-breed method for each stage of the standard form-and-polish heuristic for aligning multiple sequences; the result of these efforts is a tool, called Opal, that achieves state-of-the-art 84.7% accuracy on the BAliBASE alignment benchmark. The second part of the dissertation describes a new algorithm that dramatically increases the speed and scalability of a common method for phylogeny inference called neighbor-joining; this algorithm is implemented in a new tool, called NINJA, which is more than an order of magnitude faster than a very fast implementation of the canonical algorithm, for example building a tree on 218,000 sequences in under 6 days using a single processor computer.
6

The Economic Implications of Proposed Changes in the Retail Meat Pricing Series

Lensing, Christine 06 December 2002 (has links)
The Bureau of Labor Statistics (BLS) has historically collected retail meat prices from various supermarkets to use in its calculation of the Consumer Price Index. The Economic Research Service (ERS) of the U.S. Department of Agriculture is responsible for reporting retail meat prices, which it acquires from the BLS. The Mandatory Price Reporting legislation of 1999 mandated that the ERS develop and report a more extensive set of retail meat prices. The legislative initiative of 1999 came about due to the absence of prices for some species and classes of meat as well as the growing and pervasive belief that BLS price series were incorrect, inaccurate, or were at the very least not accounting for the large volume of meat sales at special and/or discounted prices. The main purpose of this thesis project was to identify some of the major data shortcomings of the current retail meat price series that should be addressed in the restructuring of a new price reporting system. A survey was administered to retail meat price users to establish which shortcomings in the historical retail meat price series they consider to be the most significant. The other aspect of this study was concerned with analyzing weekly retail scanner meat price data for five beef cuts to establish the impact of quantity-weighting on the mean and variance of the retail meat price series, as well as the own-price elasticity parameter. / Master of Science
7

Development of a Knowledge Assessment System Based on Concept Maps and Differential Weighting Approaches

Tao, Congwu 27 October 2015 (has links)
This study explored the feasibility and practicability of designing and developing a Knowledge Assessment System (KAS) for assessing different types of knowledge as defined in the revision of Bloom's Taxonomy (Anderson et al., 2001). The KAS created as a result of this study is based on concept maps and employs two differential weighting approaches. It is a developmental study, which includes the design phase, development phase and evaluation phase. The general software system design model (Sommerville, 2009) was adopted to guide the design of the Knowledge Assessment System based on its procedures, including system requirements analysis, architecture design, component design, interface design, and database design. The assessment criteria in this system are designed to be proposition-based and consist of either a non-weighting approach or a weighting approach, which can help provide instructors with flexible assessing methods as well as help them obtain a whole picture of what kinds of knowledge their students have grasped and to what extent the students have mastered that knowledge, based on the student-created concept maps. The two differential weighting approaches initially compare student-created concept maps with expert maps stored in the system. Because some correct propositions in student concept maps may be not included in the initial expert concept maps, the system is designed to continually refine the assessment criterion by inspecting and evaluating the correctness of the propositions in the student-created concept maps and adding the results to the system's database. The current system is able to assess three types of knowledge: factual, conceptual, and procedural, all of which are defined in the revision of Bloom's Taxonomy (Anderson et al., 2001). The assessment process begins with the assignment of different types of concept map tasks entered and stored in the Knowledge Assessment System. Following by student completion of the tasks and submission of a concept map, the submitted concept map is compared to the criteria stored in the system and a performance report is generated. The research results show that the Knowledge Assessment System based on concept maps and two differential weighting approaches can act as a useful tool for assessing students' factual, conceptual and procedural knowledge based on their concept maps. / Ph. D.
8

Utvärderingsmodeller vid offentlig upphandling : En granskning av förekommande modeller och möjlighet till ett enhetligt val av en modell

Adjoudani, Soheil January 2013 (has links)
Syftet med studien var att behandla utvärderingsfasen inom offentliga upphandlingar och mer specifikt från ett leverantörsperspektiv. Offentliga upphandlingar utförs för att få bra kvalitet till ett lågt pris. De kan utföras genom lägsta pris eller ekonomiskt mest fördelaktiga anbud. Genom begärda avslutade upphandlingar kunde modeller som använts identifieras ända ner till dess korresponderande matematiska modell. Poängvägningsmodeller anses inte konsistenta på grund av att de påverkas av irrelevanta variabler likaså den relativa kvalitetsvärderingsmodellen i teorin. Detta betyder att icke intressanta anbud påverkar utfallet för de andra anbuden. Studien visade att det med fördel går att välja den relativa kvalitetsvärderingsmodellen över poängvägningsmodellerna då den inte lider av problemet med irrelevanta variabler. Genom analys likställs den relativa kvalitetsvägningsmetoden med den mer resurskrävande kvalitetsvägningsmetoden som använder sig av absolut påslag/avdrag. Analys visade att rangordningen av anbuden inte förändrades. Genom en känslighetsanalys visades att viktningen för kvalitet och pris från poängvägningsmetoden inte spelade någon roll i den relativa kvalitetsvärderingsmodellen, även detta till fördel då den många gånger godtyckligt sätts av upphandlaren. / The purpose of this study was to address the evaluation phase within the area of public procurement and more specifically, from a supplier perspective. Public procurement is carried out in order to get good quality at a low price. The procurement can be performed by the lowest price or by the most economically advantageous tender. Previously concluded contracts were requested and the evaluation model that they used was identified and also it’s corresponding mathematical model. The score-weighted models were not consistent because they depended on irrelevant variables, as did the relative quality-weighted model in theory. This means that non-competitive tender affects the outcome of the other tenders. The study showed that it is more beneficial to choose the relative quality-weighted model over the score-weighting model, as it does not suffer from the irrelevant variable situation. The relative quality-weighted model is equivalent to the more superior quality-weighted model with discrete premium/discounts. This is the case as the ranking of the tenderers bids were the same in the two models. Furthermore, it was shown through a sensitivity analysis, that the weighting for the quality and the price from the score-weighted model played no role in the relative quality-weighted model; this is also an advantage as the purchaser often arbitrarily sets it.
9

Proposed automobile steering wheel test method for vibration

Jeon, Byung Ho January 2010 (has links)
This thesis proposes a test method for evaluating the perceived vibration which occurs at the driver's hand in automotive steering wheel interface. The objective of the research was to develop frequency weightings for quantifying the human perception of steering wheel hand-arm vibration. Family of frequency weightings were developed from equal sensation curves obtained from the psychophysical laboratory experimental tests. The previous literature suggests that the only internationally standardised frequency weighting Wh is not accurate to predict human perception of steering wheel hand-arm vibration (Amman et. al, 2005) because Wh was developed originally for health effects, not for the human perception. In addition, most of the data in hand-arm vibration are based upon responses from male subjects (Neely and Burström, 2006) and previous studies based only on sinusoidal stimuli. Further, it has been continuously suggested by researchers (Gnanasekarna et al., 2006; Morioka and Griffin, 2006; Ajovalasit and Giacomin, 2009) that only one weighting is not optimal to estimate the human perception at all vibrational magnitudes. In order to address these problems, the investigation of the effect of gender, body mass and the signal type on the equal sensation curves has been performed by means of psychophysical laboratory experimental tests. The test participants were seated on a steering wheel simulator which consists of a rigid frame, a rigid steering wheel, an automobile seat, an electrodynamic shaker unit, a power amplifier and a signal generator. The category-ratio Borg CR10 scale procedure was used to quantify the perceived vibration intensity. A same test protocol was used for each test and for each test subject. The first experiment was conducted to investigate the effect of gender using sinusoidal vibration with 40 test participants (20 males and 20 females). The results suggested that the male participants provided generally lower subjective ratings than the female participants. The second experiment was conducted using band-limited random vibration to investigate the effect of signal type between sinusoidal and band-limited random vibration with 30 test participants (15 males and 15 females). The results suggested that the equal sensation curves obtained using random vibration were generally steeper and deeper in the shape of the curves than those obtained using sinusoidal vibration. These differences may be due to the characteristics of random vibration which produce generally higher crest factors than sinusoidal vibration. The third experiment was conducted to investigate the effect of physical body mass with 40 test participants (20 light and 20 heavy participants) using sinusoidal vibration. The results suggested that the light participants produced generally higher subjective ratings than the heavy participants. From the results it can be suggested that the equal sensation curves for steering wheel rotational vibration differ mainly due to differences of body size rather than differences of gender. The final experiments was conducted using real road signals to quantify the human subjective response to representative driving condition and to use the results to define the selection method for choosing the adequate frequency weightings for the road signals by means of correlation analysis. The final experiment was performed with 40 test participants (20 light and 20 heavy participants) using 21 real road signals obtained from the road tests. From the results the hypothesis was established that different amplitude groups may require different frequency weightings. Three amplitude groups were defined and the frequency weightings were selected for each amplitude group. The following findings can be drawn from the research: • the equal sensation curves suggest a nonlinear dependency on both the frequency and the amplitude. • the subjective responses obtained from band-limited random stimuli were steeper and the deeper in the shape of the equal sensation curves than those obtained using sinusoidal vibration stimuli. • females provided higher perceived intensity values than the males for the same physical stimulus at most frequencies. • light test participants provided higher perceived intensity than the heavy test participants for the same physical stimulus at most frequencies. • the equal sensation curves for steering wheel rotational vibration differ mainly due to differences in body size, rather than differences of gender. • at least three frequency weightings may be necessary to estimate the subjective intensity for road surface stimuli.
10

Avaliação da dinâmica de áreas de conservação por meio de ferramentas de suporte à decisão na Bacia Hidrográfica da Represa do Lobo (Itirapina, SP) / Dynamics evaluation of environmental conservation areas through decision support tools, in Lobo Reservoir Basin (Itirapina, SP)

Santos, Allita Rezende dos 08 February 2019 (has links)
As atividades humanas geram um conjunto de impactos negativos que afetam os ecossistemas aquáticos das bacias hidrográficas em geral. Essa deterioração dos corpos dágua está relacionada também ao crescimento e à diversificação das atividades agrícolas, assim como ao aumento da urbanização. Diante do exposto, o objetivo desta pesquisa foi avaliar a integração das ferramentas de suporte à decisão, predição da cobertura do solo e análise multicritérios, na dinâmica de áreas de conservação ambiental da Bacia Hidrográfica da Represa do Lobo (Itirapina, SP). Para isso, foi realizada a classificação supervisionada de imagens de satélites para a obtenção da cobertura do solo para os anos 2008, 2013 e 2018. Por meio de modelagem obteve-se a cobertura do solo para o ano 2028. Por fim, aplicou-se a avaliação multicritérios (padronização; hierarquização e geração de pesos; e ponderação) para a elaboração de cenários contendo os níveis de conservação para os anos 2008, 2018 e 2028. Os níveis de conservação para a data atual também foram obtidos em campo por meio de aplicação de um protocolo da diversidade de habitats nas estações seca e chuvosa. Os resultados demonstraram que houveram mudanças significativas durante o período analisado, mas principalmente nas classes relacionadas às perturbações antrópicas. O padrão espacial da bacia demonstrou que a área antropizada, a pastagem e o reflorestamento são as classes dominantes. A vegetação natural foi identificada em fragmentos nas áreas de nascentes do rio Itaqueri e ribeirão do Lobo, o que pode afetar de forma drástica esses corpos hídricos. Os maiores valores de conservação ambiental foram obtidos nas áreas de proteção ambiental e proteção permanente. No entanto, as áreas onde estão localizadas as nascentes do rio Itaqueri e ribeirão do Lobo resultaram principalmente em valores baixos e médios de conservação ambiental. Foram obtidos valores baixos em áreas no entorno da represa, devido as atividades de turismo e lazer. Diante do exposto, a integração das metodologias se mostrou satisfatória para a avaliação da dinâmica de áreas de conservação ambiental e os respectivos resultados podem auxiliar em um planejamento estratégico para a gestão adequada voltada à sustentabilidade dos recursos naturais da região. / In addition to the permanent protection areas, it is necessary that the entire watershed ecosystem is balanced, however, human activities generate a set of negative impacts that affect aquatic ecosystems. This deterioration of the water bodies is also related to the growth and diversification of agricultural activities, as well as to the increase of urbanization. In view of the above, the objective of this research was to evaluate the integration of decision support tools, soil cover prediction and multicriteria analysis, in the dynamics of environmental conservation areas in Lobo Reservoir Basin Basin (Itirapina, SP). For this, the supervised classification of satellite images allowed to obtain the soil cover for the years 2008, 2013 and 2018. The soil cover for the year 2028 was obtained by modeling. Finally, the multicriteria evaluation was apllied (standardization, hierarchy and weight generation and weighting) for the elaboration of conservation levels scenarios for the years 2008, 2018 and 2028. Conservation levels for the current date were also obtained in the field by means of application of a habitat diversity protocol in dry and rainy seasons. The results showed that there were significant changes during the analyzed period, but mainly in the classes related to anthropic disturbances. The spatial pattern of the basin has shown that the anthropic area, pasture and reforestation are the dominant classes. The natural vegetation was identified in fragments in the springs of the Itaqueri and Lobo rivers, which can drastically affect these water bodies. The highest environmental conservation values were found where the environmental protection areas and riparian forest are located. However, the areas where the springs of the Itaqueri and Lobo rivers are located have mainly resulted in low and medium values. Low values were obtained in areas around the reservoir, due to tourism and recreation activities. Thus, the integration of the methodologies was satisfactory for the dynamics evaluation of environmental conservation areas and the respective results can help in a strategic planning for the proper management directed to the sustainability of the natural resources of the region.

Page generated in 0.0575 seconds