Primary propulsion of electrothermal, ion and chemical systems for space-based radar orbit transfer

An orbit transfer mission concept has been studied for a Space-Based Radar (SBR) where 40 kW required for radar operation is assumed available for orbit transfer propulsion. Arcjet, pulsed electrothermal (PET), ion, and storable chemical systems are considered for the primary propulsion. Transferring two SBR per shuttle flight to 1112 km/60 deg using electrical propulsion systems offers an increased payload at the expense of increased trip time, up to 2000 kg each, which may be critical for survivability. Trade offs between payload mass, transfer time, launch site, inclination, and height of parking orbits are presented

Randomness Relative to Cantor Expansions

Imagine a sequence in which the first letter comes from a binary alphabet, the second letter can be chosen on an alphabet with 10 elements, the third letter can be chosen on an alphabet with 3 elements and so on. When such a sequence can be called random? In this paper we offer a solution to the above question using the approach to randomness proposed by Algorithmic Information Theory.Comment: several small change

A MHD channel study for the ETF conceptual design

The procedures and computations used to identify an MHD channel for a 540 mW(I) EFT-scale plant are presented. Under the assumed constraints of maximum E(x), E(y), J(y) and Beta; results show the best plant performance is obtained for active length, L is approximately 12 M, whereas in the initial ETF studies, L is approximately 16 M. As MHD channel length is reduced from 16 M, the channel enthalpy extraction falls off, slowly. This tends to reduce the MHD power output; however, the shorter channels result in lower heat losses to the MHD channel cooling water which allows for the incorporation of more low pressure boiler feedwater heaters into the system and an increase in steam plant efficiency. The net result of these changes is a net increase in the over all MHD/steam plant efficiency. In addition to the sensitivity of various channel parameters, the trade-offs between the level of oxygen enrichment and the electrical stress on the channel are also discussed

Preferences and Heterogeneous Treatment Effects in a Public School Choice Lottery

This paper combines a model of parental school choice with randomized school lotteries in order to understand the effects of being assigned to a first-choice school on academic outcomes. We outline a simple framework in which those who place the highest weight on academics when choosing a school benefit the most academically when admitted. Although the average student does not improve academically when winning a school lottery, this average impact conceals a range of impacts for identifiable subgroups of students. Children of parents whose choices revealed a strong preference for academic quality experienced significant gains in test scores as a result of attending their chosen school, while children whose parents weighted academic characteristics less heavily experienced academic losses. This differential effect is largest for children of parents who forfeit the most in terms of utility gains from proximity and racial match to choose a school with stronger academics. Depending on one's own race and neighborhood, a preference for academic quality can either conflict with or be reinforced by other objectives, such as a desire for proximity and same-race peers.

Parental Preferences and School Competition: Evidence from a Public School Choice Program

This paper uses data from the implementation of a district-wide public school choice plan in Mecklenburg County, North Carolina to estimate preferences for school characteristics and examine their implications for the local educational market. We use parental rankings of their top three choices of schools matched with student demographic and test score data to estimate a mixed-logit discrete choice demand model for schools. We find that parents value proximity highly and the preference attached to a school's mean test score increases with student's income and own academic ability. We also find considerable heterogeneity in preferences even after controlling for income, academic achievement and race, with strong negative correlations between preferences for academics and school proximity. Simulations of parental responses to test score improvements at a school suggest that the demand response at high-performing schools would be larger than the response at low-performing schools, leading to disparate demand-side pressure to improve performance under school choice.

The Effect of Randomized School Admissions on Voter Participation

There is little causal evidence on the effect of economic and policy outcomes on voting behavior. This paper uses randomized outcomes from a school choice lottery to examine if lottery outcomes affect voting behavior in a school board election. We show that losing the lottery has no significant impact on overall voting behavior; however, among white families, those with above median income and prior voting history, lottery losers were significantly more likely to vote than lottery winners. Using propensity score methods, we compare the voting of lottery participants to similar families who did not participate in the lottery. We find that losing the school choice lottery caused an increase in voter turnout among whites, while winning the lottery had no effect relative to non-participants. Overall, our empirical results lend support to models of expressive and retrospective voting, where likely voters are motivated to vote by past negative policy outcomes.

Improving the retention rate for residential treatment of substance abuse by sequential intervention for social anxiety

BACKGROUND Residential drug rehabilitation is often seen as a treatment of last resort for people with severe substance abuse issues. These clients present with more severe symptoms, and frequent psychiatric comorbidities relative to outpatients. Given the complex nature of this client group, a high proportion of clients seeking treatment often do not enter treatment, and of those who do, many exit prematurely. Given the highly social nature of residential drug rehabilitation services, it has been argued that social anxieties might decrease the likelihood of an individual entering treatment, or increase the likelihood of them prematurely exiting treatment. The current paper reports on the protocol of a Randomised Control Trial which examined whether treatment of social anxiety prior to entry to treatment improves entry rates and retention in residential drug rehabilitation. METHOD/DESIGN A Randomised Control Trial comparing a social skills treatment with a treatment as usual control group was employed. The social skills training program was based on the principles of Cognitive Behaviour Therapy, and was adapted from Ron Rapee's social skills training program. A permutated block randomisation procedure was utilised. Participants are followed up at the completion of the program (or baseline plus six weeks for controls) and at three months following entry into residential rehabilitation (or six months post-baseline for participants who do not enter treatment). DISCUSSION The current study could potentially have implications for addressing social anxiety within residential drug treatment services in order to improve entry and retention in treatment. The results might suggest that the use of additional screening tools in intake assessments, a focus on coping with social anxieties in support groups for clients waiting to enter treatment, and greater awareness of social anxiety issues is warranted. AUSTRALIAN NEW ZEALAND CLINICAL TRIALS REGISTRY Australian New Zealand Clinical Trials Registry (ACTRN) registration number: ACTRN12611000579998.This research was supported under Australian Research Council's Linkage Projects funding scheme (project number: LP0990162)

Integración de la gestión y el intercambio del conocimiento para apoyar el aprendizaje organizacional y el impacto de la investigación agrícola para el desarrollo

Para potenciar la competitividad, la resiliencia y la sostenibilidad de la agricultura en los países en desarrollo, es necesario un intercambio continuo de procesos y resultados de investigación entre agricultores, expertos en desarrollo, científicos y formuladores de políticas, entre otros. En los últimos años, han surgido nuevas oportunidades que permiten que las organizaciones de investigación adopten prácticas innovadoras que fomentan la gestión y el intercambio del conocimiento, tanto a nivel interno como entre sus respectivas redes. Este documento sintetiza 10 años de experiencia del CIAT y CGIAR en este campo, con énfasis especial en las opciones para integrar la gestión y el intercambio del conocimiento en la investigación para el desarrollo, y está dirigido a profesionales y grupos directivos que buscan adoptar un enfoque integral de este proceso en sus organizaciones y redes

Mainstreaming knowledge management and sharing to support organizational learning and increase the impact of agricultural research for development

Making agriculture more competitive, resilient, and sustainable in developing countries requires continuous sharing of research processes and outcomes between farmers, development experts, scientists, and policymakers, among others. In recent years, new opportunities have emerged for research organizations to adopt innovative practices that foster knowledge management and sharing (referred to subsequently as KM) both internally and within their networks. This policy brief summarizes 10 years of experience with KM in CIAT and CGIAR, with particular emphasis on options for mainstreaming KM in research for development. The document is intended for professionals and management teams interested in a comprehensive KM approach for their organizations and networks

Is There Monopsony in the Labor Market? Evidence from a Natural Experiment

Recent theoretical and empirical advances have renewed interest in monopsonistic models of the labor market. However, there is little direct empirical support for these models. We use an exogenous change in wages at Department of Veterans Affairs (VA) hospitals as a natural experiment to investigate the extent of monopsony in the nurse labor market. We estimate that labor supply to individual hospitals is quite inelastic, with short-run elasticity around 0.1. We also find that non-VA hospitals responded to the VA wage change by changing their own wages