4,951 research outputs found
Salience, Risky Choices and Gender
No full textRisk theories typically assume individuals make risky choices using probability weights that differ from objective probabilities. Recent theories suggest that probability weights vary depending on which portion of a risky environment is made salient. Using experimental data we show that salience affects young men and women differently, even after controlling for cognitive and non-cognitive skills. Men are significantly more likely than women to switch from a certain to a risky choice once the upside of winning is made salient, even though the expected value of the choice remains the same.gender, salience, risk-aversion, probability weights, cognitive ability
Past veterinarians in South Africa
No full textAn alphabetical list containing short biographies of all deceased South African veterinarians up to 1990.[compiled by] P.J. (Bill) PosthumusVolume 1: AL -- Volume 2: M-ZAlso available in print http://137.215.9.20/record=b1893606ab2013ab201
Fatigue of friction stir welded 2024-T351 aluminium alloy
No full textFatigue failure characteristics of friction stir welds in 13mm gauge 2024-T351 plate have been assessed. Failure occurred from either the weld region (nugget/flow arm) or from the material immediately surrounding the weld. Fatigue failure from the surrounding material was essentially conventional, initiating from large S-phase intermetallic particles and growing in a macroscopic mode I manner. Corresponding fatigue lives were seen to be comparable to parent plate and results previously reported for similar welds in thinner plate. Failure over the weld region was identified with discontinuities in the macroscopic flow pattern of the weld flow arm. Subsequent crack growth showed pronounced macroscopic crack deflection around the ‘onion ring’ structure of the weld nugget. The bands making up the onion rings were identified with variations in local hardness levels, consistent with a mechanical contribution to the crack deflection process
Open brief aan den WelEdel. Gestr. Heer P.J. Joubert
No full textleyds-70-7201.pdf created from original pamphlet in the WJ Leyds Collection held in the Africana Section of the Stellenbosch University Library and Information Service.Dutch open letter to P.J. Joubert concerning a railroad concession granted to the author and two of his friends in 1885
Design considerations and performance of a PM linear actuator in a radiation environment
No full textThis paper discusses design considerations for a water cooled high acceleration 3-phase air-cored brushless DC PM linear actuator used in a vacuum radiation environment. Radiation can cause damage to magnets, and the requirement for a vacuum chamber around the moving parts imposes additional constraints that further complicate the electromagnetic and mechanical design of the actuator. This paper discusses the selection of suitable materials and bearings that are compatible with operation in vacuum and can cope with the required millions of actuation cycles. The selection of suitable bearings with low friction and wear is discussed and the design of a low inertia shaft is described. The factors that have an influence on the susceptibility of the magnets to radiation damage are discussed. These factors include magnet dimensions, magnet material, external magnetic field, temperature and the directions of both the magnetic flux and radiation. FLUKA simulations are presented showing the fluences of protons, neutrons, electrons and gamma radiation to which the magnets are exposed. Based on these simulations, loss of magnetisation for different magnet materials can be predicted, and used to estimate the effect of magnet radiation ageing on actuator current, and increased temperature rise. The paper also presents transient electromagnet FEA computation of the force produced by the actuator when magnets are housed in a stainless steel vacuum chamber
Design, Modeling and Simulation of a 52MHz MEMS Gyroscope Device in 1.5um SOI
No full textIn this thesis , a simulation model of a MEMS gyroscope is presented. The model enables mode matching and analysis of the dynamic behavior of a gyroscope. Furthermore, the model allows the optimization the design parameters of the gyroscope. The simulated gyroscope operates at a frequency of 52MHz with amplitudes of 10nm and quality factor of 50,000. Finally, the drive mode measurements are presented at different bias voltages.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Het gemeentelijk Investeringsraadsel: Het verband tussen gemeentelijke investeringen en lokale welvaartsontwikkeling
No full textDit proefschrift gaat over de vraag in hoeverre in Nederland de lokale welvaartsontwikkeling wordt bepaald door de gemeentelijke investeringsinspanning. Op project niveau is meestal wel het een en ander bekend over de maatschappelijke effecten, maar over de impact van de totale investeringsinspanning ontbreekt zowel fundamentele als toepasbare kennis. Het is een raadsel dat nog opgelost dient te worden. De doelstelling van dit proefschrift is daaraan een bijdrage te leveren.Housing System
Coupled thermo–hydro–mechanical processes for the Dutch radioactive waste repository
No full textDisposal of spent nuclear fuel and long lived radioactive waste in deep clay geological formations is one of the promising options worldwide. In this concept of the geological disposal system, the Boom Clay is considered as a potential host rock when designing a generic waste repository in the Netherlands. For design and evaluation of a repository for geologic disposal of nuclear wastes one of its principal concern is the thermal loading. High-level radioactive waste and spent fuel generate considerable amounts of heat. When those waste types are disposed in a geological repository the elevated thermal effect on the behaviour of soils surrounding nuclear waste disposal give rise to change in hydraulic and mechanical properties is a significant factor for repository design. Understanding these time-dependent phenomena processes in relation to both the effects of pore water dissipation and of the thermal expansion is essential for reliably assessing repository performance and evaluating the safety case. This paper presents some of the investigation on the thermal processes with emphasis on the coupled Thermo-Hydro- Mechanical (THM) processes for the disposal concept of a radioactive waste disposal facility, in Boom Clay at a depth of about 500m.Geo-engineerin
Probabilistic performance assessment of a deep tunnel for a radioactive waste repository in French COx claystone
No full textA preliminary probabilistic study of the stability of a circular drift excavated for a radioactive waste repository in the French Callovo-Oxfordian claystone is presented and discussed. An analytical mechanical model assuming isotropic elastic behaviour and linear plastic softening was used. Particular emphasis here is placed on the uncertainty of mechanical property values. The test results from several laboratories showed considerably variable property values and they have been interpreted statistically in this investigation. The obtained statistical results were used in a Monte Carlo framework. The performance of the drift was evaluated in terms of the probability of threshold exceedance in the extent of the plastic zone.Geo-engineerin
Point and interval forecasts of mortality rates and life expectancy: A comparison of ten principal component methods
No full textUsing the age- and sex-specific data of 14 developed countries, we compare the point and interval forecast accuracy and bias of ten principal component methods for forecasting mortality rates and life expectancy. The ten methods are variants and extensions of the Lee-Carter method. Based on one-step forecast errors, the weighted Hyndman-Ullah method provides the most accurate point forecasts of mortality rates and the Lee-Miller method is the least biased. For the accuracy and bias of life expectancy, the weighted Hyndman-Ullah method performs the best for female mortality and the Lee-Miller method for male mortality. While all methods underestimate variability in mortality rates, the more complex Hyndman-Ullah methods are more accurate than the simpler methods. The weighted Hyndman-Ullah method provides the most accurate interval forecasts for mortality rates, while the robust Hyndman-Ullah method provides the best interval forecast accuracy for life expectancy.forecasting, forecasting time series, interval forecasts, Lee-Carter method, life expectancy, mortality forecasting, principal components analysis
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