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Manufacturihng of heavy rings and large copper canisters by plastic deformationSsemakula, Hamzah January 2003 (has links)
Plastic deformation processes transform material fromas-received state to products meeting certain requirements inproperties, microstructure and shape. To achieve thistransformation, the relationship between material response andprocess conditions should be understood. This is usuallycomplicated by the complex conditions describing the actualprocess. Numerous techniques including empirical, physical,analytical and numerical can be employed. In this thesis, numerical technique supported by lab- andfull-scale experiments has been employed to analyse the formingparameters. The first part of the thesis is focused on the useof such parameters to predict occurrence of material poresduring manufacturing of bearing rings. The second part dealswith the influence of forming parameters on the grain sizeduring fabrication of large copper canisters for encapsulationof nuclear waste. The primary task has been to study with thehelp of commercial FE-codes the magnitude and distribution offorming parameters such as accumulated effective strain,temperature, instantaneous hydrostatic pressure and materialflow at different stages of the forming process. In the firstpart, two types of ring manufacturing routes, which result inpore free and pore loaded rings are studied and compared.Material elements located in different areas of the workpiecehave been traced throughout the process. Results of theaccumulated strain and instant hydrostatic pressure have beenanalysed and presented in pressure-strain space. Itsassumed that high hydrostatic pressures together with higheffective strains are favourable for pore closure. Area of theworkpiece with unfavourable parameters have been identified andcompared with ultrasonic test results. Good agreement has beenobtained. Based on the results of this analysis, a new conceptfor avoiding pores in manufacturing of yet heavier rings hasbeen presented. The concept proposes a lighter upsetting in theinitial stage of the process and a more efficient piercingwhich results in higher hydrostatic pressure and bigger andbetter distributed effective strain. In the second part of the thesis, the influence of formingparameters such as effective strain and temperature on thefinal grain size of the product has been studied in laboratoryscale. As-cast billets of cylindrical shape were extruded atdifferent temperatures and reductions. It has been shown thatthe grain size in the final product should be small in order toenable ultrasonic tests and to guarantee resistance towardscreep and corrosion. Simulations for different materialelements located at different distances from the axis ofsymmetry of the initial cylindrical workpiece have been carriedout. In this way, the parameters describing the deformationhistory of the elements have been determined as functions oftime. Experimentally obtained pre- and post deformation grainsize in the corresponding locations of the material weredetermined. Its concluded that low temperature coupledwith high effective strain are conducive for obtaining a smallgrain size. Based on the beneficial conditions for extrusion ofcopper, a more detailed FE-analysis of a full-scale industrialprocess is carried out. A coarse-grained cast ingot of purecopper is heated and by upset forging formed into a cylinder,which is then punched into a hollow blank for subsequentextrusion. The blank is extruded over a mandrel through a45-degree semi-angle die. Accumulated effective strain andtemperatureas functions of the tubular wall thickness havebeen studied at five different locations along the tubularaxis. Forming load requirement as function of tool displacementfor each stage of the process has been determined. Strain andtemperature levels obtained have been related to the grain sizeinterval obtained in the earlier work. It has been concludedthat the levels reached are within the interval that ensures asmall grain size. A similar analysis has been carried out forforging of large copper lids and bottoms. Die designmodifications to improve the grain size in the lid and tooptimise the forging process with respect to forging load andmaterial yield have been proposed. A method requiring a smallforging load for fabrication of the lids has been analysed <b>Keywords:</b>Pores; grain size; low forging load; effective strain;temperature; hydrostatic pressure; extrusion; forging;canister; lid; rings
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CEO Compensation : Relationship with Performance and Influence of Board of DirectorsTariq, Usman January 2010 (has links)
This paper tries to find the relationship between the compensation given to the chief executive officer and the performance of the company. Further, it tries to determine the influence of the size of the Board members on the pay scale of the executive. The data consisted of the largest thirty companies in Sweden for the period of 2004-2008. After controlling for firm size and growth opportunities, I find a negative and insignificant relationship between pay and performance. Contradictory to previous studies no correlation between large board size and chief executive officers compensation was found. This paper adds more empirical evidence to the idea of chief executives pay being independent of his performance.
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Sedimentation av lera och fosfor i en anlagd våtmarkPeters, Jessica January 2010 (has links)
The amount of various phosphorus (P) fractions in the sediment and the relationship between the amount of P and sediment particle size were investigated in a constructed wetland southwest of Linköping. Furthermore, the possible correlation between clay content in the sediment and distance from the inlet was investigated. Sediment samples were collected along three transects from the inlet to the outlet, with six samples in each transect. In order to measure the soluble P, an NH4Cl extraction was done. This was also analysed for total soluble P after oxidation with peroxodisulphate. The sediment was also analysed for total-P and organic P by drying, dispersion in a mortar and sieving followed by boiling in HCl. Analysis of phosphate-P in all extracts was done with an acid molybdate solution and ascorbic acid, forming a blue complex that was measured spectrophotometrically. There was no significant relationship between soluble P or soluble total-P and the proportion of clay in the sediment samples. This was also the case for total-P and organic-P. Generally, the levels of phosphorus in the sediment were low, which may result from too deep sediment samples, causing the settled P-rich sediment to be diluted by the terrestrial soil underneath the wetland. There was a low proportion of clay in the sediment (4 – 18 %), which made it difficult to detect any correlation with soluble-P content. When omitting the samples at the inlet (which were more influenced by vegetation than the others), a significant positive correlation between percentage of clay and distance from the inlet was detected, suggesting that clay particles were settling in the wetland.
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Experience in Shopping Centers : An Accessibility Analysis of Swedish Shopping CentersÖner, Özge January 2010 (has links)
This study aims to investigate how market size impacts the level of economic success, diversity, entertainment, arts, and experience of shopping centers in Sweden. More specifically the paper uses regression analyses to test the relation between different forms of shopping center performance and market size. The results show that the municipality market size plays an important role in all analyzed cases. The results also showed that local labor market size does not have a significant impact on the dependent variables.
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Human echolocation : The effect of object size, distance and auditory angleRådsten-Ekman, Maria January 2008 (has links)
Both blind and sighted persons may use echoes for detecting objects. The effect of object size on echolocation was tested in a listening experiment with 15 sighted participants. Noise burst of 500-ms were generated and recorded in an ordinary room, with and without a reflecting object. The diameter of the reflecting object was 0.25 or 0.50 m, and it was located at a distance of 0.5, 1, 2, 3 m from the microphones. Pairs of sounds, one with and one without the object, were presented to the listeners. Their task was to decide which of the two sounds that were recorded with the reflecting object. The results showed that it was harder to detect the 0.25 than the 0.5 m object, and that performance generally decreased with distance. The auditory angle, which is a function of the size to distance ratio, was found to predict detection performance fairly well. Sighted
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Monte Carlo Simulations of Grid Walled Proportional Counters with Different Site Sizes for HZE RadiationLiu, Haifeng 2012 May 1900 (has links)
Tissue-equivalent proportional counters are frequently used to measure dose and dose equivalent in cosmic radiation fields that include high-Z, high-energy (HZE) particles. The fact that particles with different stopping powers can produce the same energy deposition in the same detector means that the measure of lineal energy cannot provide enough information to evaluate the equivalent dose due to HZE particles. To characterize incident particles by mass and velocity, a multiple-detector system composed of three tissue-equivalent proportional counters simulating different size tissue volumes was proposed to be built. This system took advantage of the well-known fact that lineal energy (y) of a HZE particle depends on the site size, as well as the particle mass and energy.
Monte Carlo calculations were used to evaluate lineal energy, using GEANT4, in grid-walled (wall-less) proportional counters with simulated unit density site diameter of 0.1, 0.5 and 2.5 micrometers in a uniform HZE particle field. Uniform beams of 1000 MeV/n and 100 MeV/n 56Fe26+, 28Si14+, 16O8+, 12C6+, 4He2+ ions and proton particles bombarding the detectors were simulated. The results of the calculations were used to determine how much additional information about particle charge and velocity could be obtained from such a detector system. Comparison of simulation results with those of walled detectors was included in the study to illustrate the wall effect.
The results shows that the detector system is capable of characterizing HZE particles in a mixed unknown field based on the lineal energy spectra as well as the calculated mean lineal energy. This suggests that it may be practical to use such a system to measure the average particle velocity of HZE particles in space. The parameters used in the simulation are also good references for detector construction. There is only limited experimental data for lineal energy resulting from a large uniform field of HZE particles incident on a wall-less detector. However, the Monte Carlo results are consistent with the experimental data available.
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Is the Yes/No method reliable for measuring vocabulary size?Andersson, Lisa January 2008 (has links)
The main purpose of this paper was to construct and try out a test that could measure the size of both the receptive and productive vocabulary. This was a joint project, done by three students at the C-level in English in 1997. Before the test was constructed the students looked into previous investigations and different test methods used. The project group chose the Yes/No method as their test format. 23 students in their second year of their education at a theorectical programme in upper secondary school and 16 adult students at Komvux took the test in this paper. The results of the test taken by the students showed that it is impossible for a language teacher to construct a reliable and valid test for measuring vocabulary size using the Yes/No method.
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The Impact of Capital Structure Determinants on Small and Medium size Enterprise LeverageHashemi, Roshanak January 2013 (has links)
Finding the suitable capital structure for small and medium size enterprises, SMEs, is vital. A suitable capital structure helps SMEs to stay alive in the competitive market and has a positive effect on the national economy. Wealth maximization is the first objective of the firms, and capital structure proposition shows how a firm plans to finance its projects to meet its first objective. The purpose of this thesis is to investigate the impact of the capital structure determinants on the SMEs borrowing behavior. SMEs in this research are defined as the small independent privately held firm with less than 250 employees. In order to reach the purpose of this thesis, I have consulted the relevant theories of capital structure. By the support of the earlier studies, as well as the related theories, I have developed the testable hypotheses to examine the impact of capital structure determinants on the decomposed leverage level. To conduct this thesis, I have used the deductive approach, which is a similar approach suggested by the key reference of this study, Michaels et al (1999). Size, age, profitability, growth, operating risk, and asset structure are selected as the determinant of capital structure. With the unique set of data gathered from 201 SMEs in Iran over the period of 2006 to 2010, the statistic panel data regression is used to analyze the empirical data. To investigate the borrowing behavior of the SMEs comprehensively, the observed SMEs were picked up from different manufacturing industries in Iran. The result of this research reveals that the impacts of capital structure determinants on SMEs leverage levels are different in terms of both magnitude and direction. The result indicates that profitability has a strong impact on SMEs borrowing decisions. Besides profitability, size and asset structure appear to have an impact on leverage level in compare with other determinants. This thesis finding shed lights on the necessity of using the maturity structure of debt (short-term debt and long-term debt) as dependent variables. Firms are more willing to finance their projects with short term debt, rather than long term debt. Long term debt is costly, and the probability of bankruptcy is higher with long term debt. Although long term debt is riskier for SMEs, but it shows the management confident in the firm’s future since it obliges the firm’s management to make legally binding future payments of interest. However, the empirical result of this study shows that all the determinants have an effect on the level of leverage in SMEs.
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Upper slope sedimentation environments in the Gaoping river-sea system of SW TaiwanHansson, Lina January 2013 (has links)
The Gaoping Slope, off the south west coast of Taiwan, is a tectonically active sedimentation environment attaining most of its sediment from the Gaoping River. This study examines sediment cores from two localities at 375 m and 495 m water depth by using X-radiography, Grain size- and 210Pb analysis, with the purpose of comparing the sedimentation environment at the two sites and examine how they were both affected by high sediment delivery during typhoon Morakot.The shallow site has coarse bioturbated sediment, whereas the deeper site had laminated fine sediment containing high amounts of organic material. Both localities display a 13-20 cm thick recently deposited layer in the cores taken after typhoon Morakot. The layers are characterized by coarsening-fining sequences. All cores show cyclicity in the grain size data.We suggest that the shallow station has a more energetic environment, affected by wave reworking, tides, and alongshore currents supplying riverine material from the Gaoping river. The deep site has a calmer sedimentation environment dominated by hemipelagic settling of suspended material. The recent accumulated deposits are most likely hyperpycnites from density driven hyperpycnal flows, originally caused by canyon overflows in the Gaoping- and the Kaohsiung canyon during the typhoon. The strata found at the Gaoping slope is a result of submarine mass transport of sediment, and reflect the interaction between annual seasons and extreme events triggered by typhoons and earthquakes - eroding, transporting, and depositing sediment in the area.
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Phytoplankton Communities in Temperate RiversContant, Jacinthe 23 January 2012 (has links)
The structure of phytoplankton communities was examined seasonally across five rivers with a focus on small cells and their relative importance. Picophytoplankton (0.2-2 μm), previously considered insignificant in rivers, reached densities as high as those observed in lakes and oceans (~ 10e4-10e5 cells/mL). Their relative importance was not a function of trophic state with the highest contribution to algal biomass found in the most eutrophic river. Body size distributions were analyzed from both chlorophyll-a size fractions and taxonomic enumerations; no significant effect of river or season was detected, suggesting that phytoplankton size distribution is not a useful metric of change in rivers. Unlike lake ecosystems, the rivers were uniformly dominated by small cells (< 20 μm). Taxonomic analyses of the seasonal succession did not reveal a common periodicity of particular divisions (e.g. diatoms). However, strong dominance was more typical of eutrophic rivers even though taxa richness was similar.
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