Central Asia Wars and Ethnic Conflicts – Rebuilding Failed States

human development, culture

Satellite applications to electric-utility communications needs

Significant changes in the Nation's electric power systems are expected to result from the integration of new technology, possible during the next decade. Digital communications for monitor and control, exclusive of protective relaying, are expected to double or triple current traffic. A nationwide estimate of 13 Mb/s traffic is projected. Of this total, 8 Mb/s is attributed to the bulk-power system as it is now being operated (4 Mb/s). This traffic could be accommodated by current communications satellites using 3- to 4.5-m-diameter ground terminals costing $35,000 to$70,000 each. The remaining 5-Mb/s traffic is attributed to new technology concepts integrated into the distribution system. Such traffic is not compatible with current satellite technology because it requires small, low-cost ground terminals. Therefore, a high effective isotropic radiated power satellite, such as the one being planned by NASA for the Land Mobile Satellite Service, is required

Analysis of changes in leg volume parameters, and orthostatic tolerance in response to lower body negative pressure during 59 days exposure to zero gravity Skylab 3

The cardiovascular responses of the Apollo crewmen associated with postflight evaluations indicate varying decrements of orthostatic tolerance. The postflight changes indicate a slightly diminished ability to the cardiovascular system to function effectively against gravity following exposure to weightlessness. The objective of the Skylab LBNP experiments (M092) was to provide information about the magnitude and time course of the cardiovascular changes associated with prolonged periods of exposure to weightlessness. This report details the equipment, signal processing and analysis of the leg volume data obtained from the M092 experiment of the Skylab 3 Mission

Incorporation of the statistical uncertainty in the background estimate into the upper limit on the signal

We present a procedure for calculating an upper limit on the number of signal events which incorporates the Poisson uncertainty in the background, estimated from control regions of one or two dimensions. For small number of signal events, the upper limit obtained is more stringent than that extracted without including the Poisson uncertainty. This trend continues until the number of background events is comparable with the signal. When the number of background events is comparable or larger than the signal, the upper limit obtained is less stringent than that extracted without including the Poisson uncertainty. It is therefore important to incorporate the Poisson uncertainty into the upper limit; otherwise the upper limit obtained could be too stringent.Comment: 14 pages, 4 figure

Early childhood development and social mobility

Steven Barnett and Clive Belfield examine the effects of preschool education on social mobility in the United States. They note that under current policy three- and four-year-old children from economically and educationally disadvantaged families have higher preschool attendance rates than other children. But current programs fail to enroll even half of poor three-and four-year olds. Hispanics and children of mothers who drop out of school also participate at relatively low rates. The programs also do little to improve learning and development. Barnett and Belfield point out that preschool programs raise academic skills on average, but do not appear to have notably different effects for different groups of children, and so do not strongly enhance social mobility. In such areas as crime, welfare, and teen parenting, however, preschool seems more able to break links between parental behaviors and child outcomes. Increased investment in preschool, conclude Barnett and Belfield, could raise social mombility. Program expansions targeted to disadvantaged children would help them move up the ladder, as would a more universal set of policies from which disadvantaged children gained disproportionately. Increasing the educational effectiveness of early childhood programs would provide for greater gains in social mobility than increasing participation rates alone. The authors observe that if future expansions of preschool programs end up serving all children, not just the poorest, society as a whole would gain. Benefits would exceed costs and there would be more economic growth, but relative gains for disadvantaged children would be smaller than absolute gains because there would be some (smaller) benefits to other children.early childhood education; social mobility; benefit/cost analyses; income disparity; disadvantaged children

High performance structures

Materials selection, structural geometry, proof testing and statistical screening, prestressing, and system energy as tools for designing optimum trusses and other high performance structure

Studies in prestressed and segmented brittle structures

Application of nonlinear bending theory to prestressed and segmented brittle structure

Flexible Invariants Through Semantic Collaboration

Modular reasoning about class invariants is challenging in the presence of dependencies among collaborating objects that need to maintain global consistency. This paper presents semantic collaboration: a novel methodology to specify and reason about class invariants of sequential object-oriented programs, which models dependencies between collaborating objects by semantic means. Combined with a simple ownership mechanism and useful default schemes, semantic collaboration achieves the flexibility necessary to reason about complicated inter-object dependencies but requires limited annotation burden when applied to standard specification patterns. The methodology is implemented in AutoProof, our program verifier for the Eiffel programming language (but it is applicable to any language supporting some form of representation invariants). An evaluation on several challenge problems proposed in the literature demonstrates that it can handle a variety of idiomatic collaboration patterns, and is more widely applicable than the existing invariant methodologies.Comment: 22 page