22,102 research outputs found

    The detection of large amounts of cool, x ray absorbing gas in distant clusters of galaxies. What does this mean?

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    We present an x-ray spectral study of 12 distant (z = 0.17-0.54) rich clusters of galaxies observed with the Einstein Observatory Imaging Proportional Counter. These x-ray spectral data show evidence for substantial excess absorptions beyond those expected in the galaxy, indicating the presence of large amounts of x-ray absorbing cool gas in these distant clusters. The mean value of the excess absorptions corresponds to an absorbing gas column density approximately greater than 10(exp 21)/sq cm. We calculate the x-ray luminosities of the clusters with observed fluxes only in the 0.8-3.5 keV band where the fluxes are less effected by the absorptions, and use the temperature-to-luminosity correlation (known only for nearby clusters) to estimate the temperatures of the hot intracluster medium (ICM) in the distant clusters. These temperature estimates, together with the spectral fits, provide further constraints on the column densities in the individual clusters. For the cluster CL 0016+16, the lower limit on the column density is found to be 8 x 10(exp 20)/sq cm at the 99 percent confidence limit. We also show that the ratio of the temperature obtained from the spectral fit to the temperature expected from the correlation tends to decrease with increasing look-back time, indicating possible temperature evolution of the hot ICM in the recent past. The inclusion of this evolutionary effect further increases the absorptions required in fitting the spectra

    The Labor Supply and Retirement Behavior of China's Older Workers and Elderly in Comparative Perspective

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    This paper highlights the employment patterns of China’s over-45 population and, for perspective, places them in the context of work and retirement patterns in Indonesia, Korea, the United States, and the United Kingdom. As is common in many developing countries, China can be characterized as having two retirement systems: a formal system, under which urban employees receive generous pensions and face mandatory retirement by age 60, and an informal system, under which rural residents and individuals in the informal sector rely on family support in old age and have much longer working lives. Gender differences in age of exit from work are shown to be much greater in urban China than in rural areas, and also greater than observed in Korea and Indonesia. Descriptive evidence is presented suggesting that pension eligible workers are far more likely to cease productive activity at a relatively young age. A strong relationship between health status and labor supply in rural areas is observed, indicating the potential role that improvements in access to health care may play in extending working lives and also providing some basis for a common perception that older rural residents tend to work as long as they are physically capable. The paper concludes with a discussion of measures that may facilitate longer working lives as China’s population ages.retirement, population aging, labor supply, pensions, China, Indonesia, Korea

    Investigating Some Technical Issues on Cohesive Zone Modeling of Fracture

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    This study investigates some technical issues related to the use of cohesive zone models (CZMs) in modeling fracture processes. These issues include: why cohesive laws of different shapes can produce similar fracture predictions; under what conditions CZM predictions have a high degree of agreement with linear elastic fracture mechanics (LEFM) analysis results; when the shape of cohesive laws becomes important in the fracture predictions; and why the opening profile along the cohesive zone length needs to be accurately predicted. Two cohesive models were used in this study to address these technical issues. They are the linear softening cohesive model and the Dugdale perfectly plastic cohesive model. Each cohesive model constitutes five cohesive laws of different maximum tractions. All cohesive laws have the same cohesive work rate (CWR) which is defined by the area under the traction-separation curve. The effects of the maximum traction on the cohesive zone length and the critical remote applied stress are investigated for both models. For a CZM to predict a fracture load similar to that obtained by an LEFM analysis, the cohesive zone length needs to be much smaller than the crack length, which reflects the small scale yielding condition requirement for LEFM analysis to be valid. For large-scale cohesive zone cases, the predicted critical remote applied stresses depend on the shape of cohesive models used and can significantly deviate from LEFM results. Furthermore, this study also reveals the importance of accurately predicting the cohesive zone profile in determining the critical remote applied load

    How Do Consumers Use Nutrition Labels on Food Products in the United States?

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    This study examined how consumers use food labels in the United States. Based on the results from the cluster analysis, eight nutrition label questions from the Health and Diet Survey fell into 2 categories of label usage: for shopping or for dietary decisions. Survey respondents reported equal or more consideration of nutrition-label information for dietary choices than for shopping decisions in 2008 compared with prior survey years. Female consumers, frequent label users, well-educated, consumers aged 50 to 59, or consumers with any health issues were significantly more likely to use food labels for all kinds of purposes than their corresponding counterparts

    Dynamic Deployment Simulations of Inflatable Space Structures

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    The feasibility of using Control Volume (CV) method and the Arbitrary Lagrangian Eulerian (ALE) method in LSDYNA to simulate the dynamic deployment of inflatable space structures is investigated. The CV and ALE methods were used to predict the inflation deployments of three folded tube configurations. The CV method was found to be a simple and computationally efficient method that may be adequate for modeling slow inflation deployment sine the inertia of the inflation gas can be neglected. The ALE method was found to be very computationally intensive since it involves the solving of three conservative equations of fluid as well as dealing with complex fluid structure interactions

    Global and Local Stress Analyses of McDonnell Douglas Stitched/RFI Composite Wing Stub Box

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    This report contains results of structural analyses performed in support of the NASA structural testing of an all-composite stitched/RFI (resin film infusion) wing stub box. McDonnell Douglas Aerospace Company designed and fabricated the wing stub box. The analyses used a global/local approach. The global model contains the entire test article. It includes the all-composite stub box, a metallic load-transition box and a metallic wing-tip extension box. The two metallic boxes are connected to the inboard and outboard ends of the composite wing stub box, respectively. The load-transition box was attached to a steel and concrete vertical reaction structure and a load was applied at the tip of the extension box to bend the wing stub box upward. The local model contains an upper cover region surrounding three stringer runouts. In that region, a large nonlinear deformation was identified by the global analyses. A more detailed mesh was used for the local model to obtain more accurate analysis results near stringer runouts. Numerous analysis results such as deformed shapes, displacements at selected locations, and strains at critical locations are included in this report

    THE CYCLIC WHOLENESS OF BING, TAO AND LAW IN SUN TZU’S THE ART OF WAR

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    The Art of War by Sun Tzu (Pingyin: Sunzi Bing Fa)is well-known as one of the oldest writings in Chinesehistory attributed to an individual author. It is the mostfamous treatise of the Military School (Bingjia), of TheHundred Schools of Thought of the Pre-Qin and Han period.However, the text is often misunderstood in the based uponthe misunderstanding of its terms. Readers and scholarsoften interpret the text in a pragmatic or utilitarian way,ignoring its philosophical Taoist subtexts. In the text, theterm translated as war – Bing – is related to two complicatedphilosophical terms and concepts: Tao (Dao) and Law (Fa).Therefore, for fully understanding Sun Tzu’s philosophicaltreatise on Bing, this paper will investigate, how changesof Tao (Dao) and Law (Fa) in relation to Bing occur in aholistic cycle. Bing, Tao and Law must be coordinated,otherwise any operation whether military or political willnot be in conformity with the Grand Tao, and will not beable to achieve its aims

    Electron Detachment for H-(D-) in Collisions with Ne

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    Total cross sections for electron detachment in collisions of H− and D− with Ne are calculated, using a model based on a first‐order solution to close‐coupled equations. Quantities needed for the calculation are the energy gap and the coupling between bound and free states. The energy gap is taken from previous calculations and the coupling is assumed to be of exponential form, with parameters adjusted to fit experimental data. Special examination is made of isotope effects in the cross sections

    Electron Detachment in Negative-Ion Collisions. III. Model Calculations.

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    With the use of a previously developed close-coupling theory, and simple models for the energy gap and propagator that arise in that theory, calculations are made of the properties of the survival probability for the negative ions and of the energy spectrum of detached electrons. Special attention is given to interference effects that might be seen under favorable circumstances
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