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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.
11

Proposta de redução da dose de radiação na mamografia digital utilizando novos algoritmos de filtragem de ruído Poisson / Proposal of radiation dose reduction in digital mammography using new algorithms for Poisson noise filtering

Helder Cesar Rodrigues de Oliveira 19 February 2016 (has links)
O objetivo deste trabalho é apresentar um novo método para a remoção do ruído Poisson em imagens de mamografia digital adquiridas com baixa dosagem de radiação. Sabe-se que a mamografia por raios X é o exame mais eficiente para a detecção precoce do câncer de mama, aumentando consideravelmente as chances de cura da doença. No entanto, a radiação absorvida pela paciente durante o exame ainda é um problema a ser tratado. Estudos indicam que a exposição à radiação pode induzir a formação do câncer em algumas mulheres radiografadas. Apesar desse número ser significativamente baixo em relação ao número de mulheres que são salvas pelo exame, existe a necessidade do desenvolvimento de meios que viabilizem a diminuição da dose de radiação empregada. No entanto, uma redução na dose de radiação piora a qualidade da imagem pela diminuição da relação sinal-ruído, prejudicando o diagnóstico médico e a detecção precoce da doença. Nesse sentido, a proposta deste trabalho é apresentar um método para a filtragem do ruído Poisson que é adicionado às das imagens mamográficas quando adquiridas com baixa dosagem de radiação, fazendo com que ela apresente qualidade equivalente àquela adquirida com a dose padrão de radiação. O algoritmo proposto foi desenvolvido baseado em adaptações de algoritmos bem estabelecidos na literatura, como a filtragem no domínio Wavelet, aqui usando o Shrink-thresholding (WTST), e o Block-matching and 3D Filtering (BM3D). Os resultados obtidos com imagens mamográficas adquiridas com phantom e também imagens clínicas, mostraram que o método proposto é capaz de filtrar o ruído adicional incorporado nas imagens sem perda aparente de informação. / The aim of this work is to present a novel method for removing the Poisson noise in digital mammography images acquired with reduced radiation dose. It is known that the X-ray mammography is the most effective exam for early detection of breast cancer, greatly increasing the chances of healing the disease. However, the radiation absorbed by the patient during the exam is still a problem to be treated. Some studies showed that mammography can induce breast cancer in a few women. Although this number is significantly low compared to the number of women who are saved by the exam, it is important to develop methods to enable the reduction of the radiation dose used in the exam. However, dose reduction led to a decrease in image quality by means of the signal to noise ratio, impairing medical diagnosis and the early detection of the disease. In this sense, the purpose of this study is to propose a new method to reduce Poisson noise in mammographic images acquired with low radiation dose, in order to achive the same quality as those acquired with the standard dose. The method is based on well established algorithms in the literature as the filtering in Wavelet domain, here using Shrink-thresholding (WTST) and the Block-matching and 3D Filtering (BM3D). Results using phantom and clinical images showed that the proposed algorithm is capable of filtering the additional noise in images without apparent loss of information.
12

Die Stress And Friction Behaviour Analysis In Bolt Forming

Aygen, Mert 01 December 2006 (has links) (PDF)
In cold forming operations, tool geometry has a direct influence on the product quality, forming force, load acting on dies and tool life. Finite element method provides a means to analyse these parameters to predict forming defects and die failures. In this study, shrink fitting the components of a bolt forming die is modelled and the finite element results are compared with the analytical solutions and experiments. In order to perform die stress analyses, deformable die models are implemented in the forging simulations. Furthermore, effect of using rigid and deformable dies on the stress distributions in the tools, forming force and product dimensions are examined. Some applications of tool geometry improvements and optimization of prestressing are presented in the case studies. In the second part of the study, the appropriate friction model for the cold forming operation of bolts is investigated. For this purpose, ring compression and forward rod extrusion tests are conducted. Dimensional variations and deformation forces are compared with the finite element simulations performed for different friction models and constants. The results of shrink fit analyses of die prestressing are in good agreement with the elasticity formulations and real applications. In the studied bolt production cases, after improving the die stress distributions by using FE simulations, longer tool lives are achieved. Finally, for more accurate results, Coulomb friction model is determined as an appropiate model for bolt forming analyses.
13

A western Canadian study of the effect of winter transport conditions including acceleration on animal outcomes in cattle

Kehler, Carollyne 10 September 2015 (has links)
The intent of this study was to monitor the effect of Canadian winter commercial transport conditions on animal outcomes. A methodology was developed to measure acceleration on trailers transporting cull cows and a preliminary comparison of acceleration and carcass bruising revealed that further study of the relationship was warranted. The accelerometer methodology was used as one tool to examine factors influencing internal trailer microclimate and trailer acceleration on shrink, and severe bruising in finished cattle. This research has improved our understanding of Canadian winter transport conditions affecting finished cattle and demonstrated that there is a relationship between vertical rms of acceleration (P=0.0025), beta agonist use (P=0.0323), total wait time (P=0.0052) and the two way interaction of carcass position and yield score (P=0.0025) with cattle bruising. It also demonstrated that there is a relationship between journey duration (P<0.001), allometric coefficient (P<0.001), temperature humidity index (P<0.001) and prod use during loading (P=0.0012) with cattle shrink. / October 2015
14

Shrink-Swell Dynamics of Vertisol Catenae under Different Land Uses

Dinka, Takele Mitiku 2011 December 1900 (has links)
Because of the dynamic nature of shrinking and swelling of soils that are classified as Vertisols, partitioning of rainfall into infiltration and runoff in a Vertic watershed is more temporally and spatially unique than in most other watersheds. Hydrology models that account for realistic representation of crack dynamics are rarely used because the spatial and temporal patterns of cracking across a catena and under different land uses are poorly understood. The objectives of the study were to 1) determine if variability in soil cracking on a Vertisol catena, having the same soil and land cover, could be explained by shrink-swell potential of the soil and changes in soil water content; 2) characterize the temporal and spatial variability of the shrinkage of a Vertisol under different land uses; and 3) determine the relationship between specific volume and water content of soils, particularly between saturation and field capacity. The research was conducted in Vertisol catenae of the Houston Black and Heiden soil series. The catenae were located within the USDA-ARS Grassland, Soil and Water Research Laboratory, Riesel Texas. Soil samples were taken to characterize the general properties of the soils. In situ bi-weekly measurements of vertical soil movements and soil water contents were made over a two-year span. Because shrink-swell potential was high at most landscape positions, soil water content was the primary factor driving the spatial and temporal variability of soil shrinking and swelling. The measured relationship between the amount of soil subsidence and water loss generally agreed with what would be theoretically expected. Maximum soil subsidence was 120 mm in the grazed pasture, 75 mm in the native prairie, and 76 mm in the row cropped field. Shrinkage of the whole soil was not equidimensional, and the study generally indicates more horizontal shrinkage than vertical shrinkage. Laboratory analysis showed an appreciable change in volume of soils between saturation and field capacity, suggests a layer of soil layer can subside up to 4% while drying from saturation to field capacity, which indicates the common laboratory measure of shrink swell potential does not capture the complete shrink-swell behavior of soils.
15

TRAILER MICRO-CLIMATE DURING LONG-DISTANCE TRANSPORT OF FINISHED BEEF CATTLE FOR THE SUMMER MONTHS IN NORTH AMERICA

2013 December 1900 (has links)
Transporting cattle from southern Alberta into the United States (US) plays a substantial economic role in the western Canadian beef industry. Thermal environments within cattle transport trailers are dependent on ambient conditions, and if inadequately managed, can be a welfare concern. To effectively manage cattle transport, the environmental conditions throughout the livestock trailer must be understood. The objective of the present study was to investigate the trailer micro-climate and welfare during 5-paired commercial long-haul transports of slaughter cattle from Alberta, Canada to Washington State, US during summer months. In addition, the effect of compartment location and trailer porosity (8.7% vs 9.6%) on trailer micro-climate, shrink and core body temperature were also investigated during the warmest in-transit hour and stationary events. The compartment location had an effect on micro-climate variables where the upper compartment had greater (P < 0.05) temperature than the bottom deck compartments and relative humidity variables had the opposite effect for both the warmest in-transit hour and stationary events. There was also an effect of trailer porosity on micro-climate variables where it was generally warmer in the trailer with the higher porosity in the stationary event. Differences between trailers included 2 additional roof hatches on the trailer with lower side-wall porosity and lower internal temperatures, which could suggest the location of the trailer porosity, could be important for heat and moisture exchange during transit. The nose of the trailer with higher porosity had generally warmer internal conditions (larger T(trailer)°C and THI(trailer)) than the trailer with lower porosity. This study also found that the temperatures inside the trailer can be 10.5°C greater than ambient temperatures during stationary events and 9°C greater than ambient levels during the warmest in-transit hour. The average amount of per-animal weight loss was 4.3 0.3 % and was affected by trailer porosity and compartment, which followed the trends in thermal environment variables. The transit status (stationary or in-transit) and trailer porosity affected the vaginal core body temperature of the heifers in transit. The core body temperature was greater during stationary events for animals transported in the trailer with lower porosity. It is suggested that the lower side-wall porosity and/or the shape of perforation pattern could impair the movement of fresh air to the respiratory tract of heifers, thus impacting the main mechanism for dissipating heat. The difference in temperature from the trailer ceiling to the animal level was 3.38°C in the trailer with lower porosity (cooler at the ceiling) and 2.23°C in the trailer with the higher porosity. This relationship also had a compartment location effect that followed the micro-climate compartmental differences. This could suggest that excess heat in the trailer with the lower porosity, that also had lower overall temperatures, exited through roof hatches, while in the trailer with the higher porosity, the heat escaped through the side-wall perforations. This theory also supports the idea that the location of where the porosity is located on the trailer may be important to alleviating heat stress in summer months during transport. The results of this study also indicated that there was no difference in the location of the data logger plane (driver, middle passenger) and within the compartments (front, middle, back), suggesting that compartment location effect is substantial when considering micro-climate but temperatures within a compartment are mostly homogenous. The trip that had average ambient temperatures of 25.9 ± 6.06°C for the entire journey, had a temperature Humidity Index that was considered in the danger or emergency category according to the Livestock Weather Heat Index during 95% of the warmest in-transit hour. This suggests that during ambient temperatures of 25.9°C, both trailers used in this study did not have sufficient heat exchange to mitigate the risk of heat stress for cattle.
16

Etude d'un emmanchement fretté compte tenu de l'effet combiné des défauts de forme et d'état de surface / Study of shrink fitting considering the combined effect of phase defects and surface roughness

Boutoutaou, Hamid 24 January 2012 (has links)
Le but principal de cette thèse est de présenter deux contributions dans le domaine desassemblages frettés en prenant en considération les défauts de forme et d’état de surface. Lapremière contribution concerne l’étude de l’influence du défaut de forme sur les caractéristiquesdes assemblages frettés en utilisant une approche basée sur la modélisation par éléments finis.Nous avons constaté que ce défaut a une influence notable sur la résistance de l’assemblage. Destravaux déjà réalisés dans le laboratoire de mécanique de l’université de Bourgogne ont étéconfirmés. Dans la deuxième contribution, nous avons proposé d’intégrer les défauts d’état desurface (rugosité) en créant un élément fini homogénéisé d’interface. Cette technique nous afacilité le maillage de l’interface formés par de macro-éléments traduisant le comportement desaspérités. Ce comportement particulier, dépend de plusieurs paramètres mécaniques etgéométriques qui ont été pris en compte pour définir et identifier numériquement une loid’élasticité isotrope transverse. Cette nouvelle loi a permis de simuler correctement lesassemblages frettés en prenant en compte le défaut d’état de surface. Les résultats obtenus ont étéconfrontés aux expérimentations. En fin, une méthodologie de conception des spécifications dufrettage en considérant le processus d’élaboration des surfaces a été proposée. / The main purpose of this thesis is to present two contributions in the field of shrink fitassembly taking into account the defects of form and roughness surfaces. The first contributionconcerns the study of the influence of the defect forme on the characteristics of shrinked assemblyusing an approach based on finite element modeling. We found that this defect has a significantinfluence on the resistance of the assembly. The work already done in the laboratory of mechanicsat the University of Bourgogne have been confirmed. In the second contribution, we proposed tointegrate the surface defects (roughness) by creating a homogenized finite element interface. Thistechnique has facilitated the mesh of the interface formed by the macro-elements reflecting thebehavior of the asperities. This particular behavior, depends on several mechanical andgeometrical parameters that have been taken into account in defining and identifying a digitallytransverse isotropic elastic law. The new law was used to simulate properly shrinked assembliestaking into account the defect of roughness surface. The results were compared withexperiments. In the end, a design methodology specification by considering the shrinking processof surfaces has been proposed
17

SEDIMENTARY RESPONSES TO GROWTH FAULT SLIP AND CLAY SHRINK AND SWELL INDUCED ELEVATION VARIATIONS: EAST MATAGORDA PENINSULA, TEXAS

Ji, Wei 01 January 2017 (has links)
East Matagorda Peninsula in southwestern Texas is characterized geologically by active, regional-scale and near-surface growth faulting. Decimeter scale (up to 0.42 m) vertical displacement was recorded at the study site over a period of four years, not believed to be associated with growth faulting. This research tested the hypotheses that fault slip rates were correlated with sediment accumulation rates, and that the observed vertical displacement was produced by shrink-and-swell clays in near surface sediments. To quantify sediment accumulation rates, a suite of radionuclides (7Be, 137Cs, and 210Pb) were used. To understand the effects of shrink-and-swell clays, analyses including particle size distribution, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) were completed. Additionally, the free swell index test (FSI) was used to record the swelling potential of the sediment. Strong correlation (R2 = 0.99) indicates coupling between mean fault slip rates and mean sediment accumulation rates. Near surface sediment clay size fraction percentages ranged from 0.96 - 6.26% containing more than 90% smectite. Based on FSI results, maximum volume change in the top six cm was determined to be 208%. The presence and behavior of shrink-and-swell clay minerals in the region is an important contributor to the vertical displacement observed.
18

Control and Automation of a Heat Shrink Tubing Process

Yousefi Darani, Shahrokh 08 1900 (has links)
Heat shrink tubing is used to insulate wire conductors, protect wires, and to create cable entry seals in wire harnessing industries. Performing this sensitive process manually is time consuming, the results are strongly dependent on the operator’s expertise, and the process presents safety concerns. Alternatively, automating the process minimizes the operators’ direct interaction, decreases the production cost over the long term, and improves quantitative and qualitative production indicators dramatically. This thesis introduces the automation of a heat shrink tubing prototype machine that benefits the wire harnessing industry. The prototype consists of an instrumented heat chamber on a linear positioning system, and is fitted with two heat guns. The chamber design allows for the directing of hot air from the heat guns onto the wire harness uniformly through radially-distributed channels. The linear positioning system is designed to move the heat chamber along the wire harness as the proper shrinkage temperature level is reached. Heat exposure time as a major factor in the heat shrink tubing process can be governed by controlling the linear speed of the heat chamber. A control unit manages the actuator position continuously by measuring the chamber’s speed and temperature. A model-based design approach is followed to design and test the controller, and MATLAB/Simulink is used as the simulation environment. A programmable logic controller is selected as the controller implementation platform. The control unit performance is examined and its responses follow the simulation results with adequate accuracy.
19

Avtal i riggade system / Contracts in fixed systems

Gramenius, Tore January 2020 (has links)
Avtalslagen trädde i kraft för över hundra år sedan, och har sedan dess varit hörnstenen i den svenska avtalsrätten. Trots att avtalslagen endast var tänkt att behandla avtal som sluts genom korrespendens används den av dagens jurister för att beskriva avtalsslut för nästan alla typer av avtal, med blandade resultat. En typ av avtal för vilken avtalslagen passar särskilt dåligt är avtal slutna i riggade system, d.v.s. avtal där bara den ena parten aktivt handlar med ett på förhand uppriggat system. Ett nytt sätt att tänka kring avtal måste därför ställas upp för avtalstypen. Uppsatsens syfte är att klargöra vilken avtalsmekanism som används för avtal i riggade system samt hur avtalsinnehållet fastsälls i dessa. Syftet uppnås genom att analysera fyra typfall (Shrink och Click wrap-villkor, onlineauktioner, butikshandel och parkering) och sedan med grund i dessa ställa upp allmänna riktlinjer för hur avtal i riggade system bör behandlas.
20

Avfallshantering i kommersiellafastigheter : En utredning av utvecklingsmöjligheterna för avfallshanteringen i köpcentrum / Waste management in commercial real estate : An investigation of the development opportunities for waste management in shopping malls

Smedberg Svensk, William, Zinn, Karl-Johan January 2017 (has links)
AMF Fastigheter is shortly for the procurement of a waste contractor for all of its commercial properties. The investigation will identify the problem of how the waste is handled in shopping centers and inform AMF Fastigheter about how this can be improved. Through study visits and interviews, necessary information is gathered to make concrete proposals. A comprehensive analysis of the waste generated in the properties describes in the report that large waste volumes consist of combustible. The authors provide suggestions on how this can be avoided, as well as highlighting fractions that should be recycled to a greater extent. According to the authors, there may be problems about the waste contractors' intentions in the properties visited, as recycling is not a priority. The human factor is considered to be a major problem where it is difficult to achieve long-term changes in tenants' behavior regarding waste sorting. Initial explanation of these issues is presented in the report and details that the property owner should consider in the procurement of waste contractor. / AMF Fastigheter står inom kort inför upphandling av en avfallsentreprenör för samtliga av sina kommersiella fastigheter. Utredningen ska identifiera problematiken i hur avfallet hanteras i köpcentrum och upplysa AMF Fastigheter om hur detta kan förbättras. Genom studiebesök och intervjuer samlas nödvändig information för att komma med konkreta förslag. En övergripande analys av det avfall som uppstår i fastigheterna beskriver i rapporten att stora avfallsvolymer består av brännbart. Författarna ger i rapporten förslag på hur detta kan undvikas, samt lyfter fram fraktioner som bör återvinnas i större utsträckning. Enligt författarna kan det finnas problem kring avfallsentreprenörernas intentioner i de besökta fastigheterna då återvinning prioriteras för lite. Den mänskliga faktorn upplevs vara en stor problematik där det är svårt att nå långsiktiga förändringar kring hyresgästernas beteende och avfallssortering. Ingående förklaring om dessa problem presenteras i rapporten samt detaljer fastighetsägaren ska tänka på vid upphandling av avfallsentreprenör.

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