5,974 research outputs found
The Excess Sensitivity of Layoffs and Quits to Demand
Excessive layoffs in bad times and excessive quits in good times both stem from the same weakness in practical employment arrangements: the specific nature of worker-firm relations creates a situation of bilateral monopoly. Institutions which have arisen to avert the associated inefficiency cannot mimic the separation decisions of a perfect-information, first-best allocation rule. Simple employment rules based on predetermined or indexed wages are in many cases the most desirable among the class of feasible employment arrangements. More complicated contracts which seem to deal more effectively with turnover issues are either infeasible because of informational requirements or create adverse incentives on some other dimension.
Investigation of advanced counterrotation blade configuration concepts for high speed turboprop systems. Task 5: Unsteady counterrotation ducted propfan analysis
The primary objective of this study was the development of a time-marching three-dimensional Euler/Navier-Stokes aerodynamic analysis to predict steady and unsteady compressible transonic flows about ducted and unducted propfan propulsion systems employing multiple blade rows. The computer codes resulting from this study are referred to as ADPAC-AOAR\CR (Advanced Ducted Propfan Analysis Codes-Angle of Attack Coupled Row). This document is the final report describing the theoretical basis and analytical results from the ADPAC-AOACR codes developed under task 5 of NASA Contract NAS3-25270, Unsteady Counterrotating Ducted Propfan Analysis. The ADPAC-AOACR Program is based on a flexible multiple blocked grid discretization scheme permitting coupled 2-D/3-D mesh block solutions with application to a wide variety of geometries. For convenience, several standard mesh block structures are described for turbomachinery applications. Aerodynamic calculations are based on a four-stage Runge-Kutta time-marching finite volume solution technique with added numerical dissipation. Steady flow predictions are accelerated by a multigrid procedure. Numerical calculations are compared with experimental data for several test cases to demonstrate the utility of this approach for predicting the aerodynamics of modern turbomachinery configurations employing multiple blade rows
Understanding How Students Use Physical Ideas in Introductory Biology Courses
The University of Maryland (UMD) Biology Education and Physics Education
Research Groups are investigating students' views on the role of physics in
introductory biology courses. This paper presents data from an introductory
course that addresses the fundamental principles of organismal biology and that
incorporates several topics directly related to physics, including
thermodynamics, diffusion, and fluid flow. We examine how the instructors use
mathematics and physics in this introductory biology course and look at two
students' responses to this use. Our preliminary observations are intended to
start a discussion about the epistemological issues resulting from the
integration of the science disciplines and to motivate the need for further
research.Comment: Physics Education Research Conference 2010, Portland OR, 4 page
A linearized Euler analysis of unsteady flows in turbomachinery
A method for calculating unsteady flows in cascades is presented. The model, which is based on the linearized unsteady Euler equations, accounts for blade loading shock motion, wake motion, and blade geometry. The mean flow through the cascade is determined by solving the full nonlinear Euler equations. Assuming the unsteadiness in the flow is small, then the Euler equations are linearized about the mean flow to obtain a set of linear variable coefficient equations which describe the small amplitude, harmonic motion of the flow. These equations are discretized on a computational grid via a finite volume operator and solved directly subject to an appropriate set of linearized boundary conditions. The steady flow, which is calculated prior to the unsteady flow, is found via a Newton iteration procedure. An important feature of the analysis is the use of shock fitting to model steady and unsteady shocks. Use of the Euler equations with the unsteady Rankine-Hugoniot shock jump conditions correctly models the generation of steady and unsteady entropy and vorticity at shocks. In particular, the low frequency shock displacement is correctly predicted. Results of this method are presented for a variety of test cases. Predicted unsteady transonic flows in channels are compared to full nonlinear Euler solutions obtained using time-accurate, time-marching methods. The agreement between the two methods is excellent for small to moderate levels of flow unsteadiness. The method is also used to predict unsteady flows in cascades due to blade motion (flutter problem) and incoming disturbances (gust response problem)
There is ample scope for questioning Nick Clegg’s political integrity
Questions about the moral character of Nick Clegg have hardly gone away since he broke his promise not to raise tuition fees. Some have defended the deputy prime minister, noting that breaking promises is an inevitable feature of politics and joining coalition government meant not all the Lib Dem manifesto pledges were realistic. But by making such an unbending statement in the first place and by seeking to benefit from it electorally, Clegg violated the reasonable expectations of a significant proportion of his voters, a decision which displays a blatant disregard for some of the most basic principles of representative politics that we expect politicians to take seriously in a democracy, writes Edward Hall
From flood science to flood policy: The Foresight Future Flooding Project, seven years on.
Purpose: The Foresight Future Flooding (FFF) project researched flood risk in the UK to the year 2100 for central government, using scenarios and a national risk assessment model backed by qualitative analysis from panels of some 45 senior scientists. The purpose of this paper is to assess the impact of the project, both nationally and internationally. Design/methodology/approach: This paper assesses the impact of the FFF project, both nationally and internationally, using web searches, document analysis, and a questionnaire survey of key actors in the flood risk management policy field. Findings: It was found that the penetration of the project into professionals' consciousness was high in relation to other comparable projects and publications, and its impact on policy - both immediately and continuing - was profound. The FFF initiative did not create policy change, however, but facilitated its legitimation, adding impetus to what was already there, as one element of a part-catalytic and part-incremental process of policy evolution. Research limitations/implications: Special circumstances, internal and external to the project, mean that this cannot be a simple model for matching research to policymakers' needs in the future. Practical implications: Important lessons may be learnt from this project about both the methods of forward-looking foresight-type research, and the way that its results are disseminated to its target audiences. Originality/value: This is an innovative attempt to assess the impact of a new type of foresight project. © Emerald Group Publishing Limited
The evolution of Permo-Triassic fluvial and alluvial systems in the central Iberian basin, central Spain
EThOS - Electronic Theses Online ServiceGBUnited Kingdo
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