56,641 research outputs found
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Extracting Boer-Mulders functions from p+D Drell-Yan processes
No full textWe extract the Boer- Mulders functions of valence and sea quarks in the proton from unpolarized p + D Drell- Yan data measured by the FNAL E866 Collaboration. Using these Boer- Mulders functions, we calculate the cos2 phi asymmetries in unpolarized pp Drell- Yan processes, both for the FNAL E866/ NuSea and the BNL Relativistic Heavy Ion Collider experiments. We also estimate the cos2 phi asymmetries in the unpolarized p (P) over bar Drell- Yan processes at GSI.Astronomy & AstrophysicsPhysics, Particles & FieldsSCI(E)37ARTICLE5null7
Nearly optimal asset allocations in retirement
No full textAn important and frequently studied question for retirees is: what is the optimal asset allocation during retirement? This article provides a brief but simple message that conservative asset allocations in retirement are quite acceptable after all. A wide range of asset allocations tend to provide very similar results in terms of sustainable withdrawal rates for given probabilities of failure. For example, with Monte Carlo simulations based on historical data parameters, a 4.4 percent withdrawal rate for a 30-year horizon could be supported with a 10 percent chance of failure using a 50/50 asset allocation of stocks and bonds. But the range of stock allocations supporting a withdrawal rate within 0.1 percentage points of this maximum extend from 27 to 87 percent. Though asset allocation will also impact the amount which can be left as bequests, it is the case that relatively low stock allocations can support retirees just as well for a given failure rate and retirement duration.retirement planning; safe withdrawal rates; asset allocation
Can We Predict the Sustainable Withdrawal Rate for New Retirees?
No full textI investigate how well market valuation and yield measures predict the maximum sustainable withdrawal rate (MWR) that a person can use with their retirement savings to obtain inflation-adjusted income over a 30-year period. The regression framework includes variables to predict long-term stock returns, bond returns, and inflation (the components driving a retiree's remaining portfolio balance). It produces estimates that fit the historical data well. This study suggests that a 4 percent withdrawal rate cannot be considered as safe for U.S. retirees in recent years when the cyclically-adjusted price-earnings ratio has experienced historical highs and the dividend yield has experienced historical lows. Nevertheless, there are important qualifications for these predictions. Most importantly, they depend on out-of-sample estimates as the circumstances of the past 15 years have not been witnessed before. Readers persuaded by this analysis may wish to include TIPS and other assets as a part of their portfolios, and recent retirees should closely monitor their spending and portfolio balance. Maintaining flexibility with retirement spending is important. More generally, this framework can guide new retirees toward a reasonable range for their expected MWR so that the 4 percent rule need not be blindly followed.safe withdrawal rates, retirement planning, market valuation, price-earnings ratio, dividend yield, stock returns, bond returns
Catastrophe and control : how technological disasters enhance democracy
No full textThesis (Ph. D.)--Massachusetts Institute of Technology, Program in Science, Technology, and Society, 1994.Includes bibliographical references (p. 401-422).by Wade Edmund Roush.Ph.D
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Pedagogical Evaluation of a Domain-Driven Design Framework
No full textThis paper presents a pedagogical evaluation of the framework SDDD as a “soft systems” approach to Domain-Driven Design of computer-based information systems development. The framework combined techniques from Soft Systems Methodology (SSM), the Unified Modelling Language (UML), and an implementation pattern. Systems development and teaching evaluations are done to find better framework which can be used for teaching and developing information systems. More Feedback and reflections from the lecturers and Msc students of the module Methods and Modeling are presented. The results are supported our previous work of proposing the framework to enhance the understanding of the business process modeling and implementation into an integrated framework. This is an enhancement of Domain Driven Design approach because new “soft layer” is added and the framework used for teaching further than development as DDD. Comments received from all participants are used to enhance the framework development and for further evaluation in the future
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
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