206 research outputs found

    LES of an Inclined Jet into a Supersonic Turbulent Crossflow

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    This short article describes flow parameters, numerical method, and animations of the fluid dynamics video "LES of an Inclined Jet into a Supersonic Turbulent Crossflow" (http://ecommons.library.cornell.edu/bitstream/1813/14073/3/GFM-2009.mpg [high-resolution] and http://ecommons.library.cornell.edu/bitstream/1813/14073/2/GFM-2009-web.m1v [low-resolution] video). We performed large-eddy simulation with the sub-grid scale (LES-SGS) stretched-vortex model of momentum and scalar transport to study the gas-dynamics interactions of a helium inclined round jet into a supersonic (M=3.6M=3.6) turbulent (\Reth=13Ă—103 =13\times10^3) air flow over a flat surface. The video shows the temporal development of Mach-number and magnitude of density-gradient in the mid-span plane, and isosurface of helium mass-fraction and \lam_2 (vortical structures). The identified vortical structures are sheets, tilted tubes, and discontinuous rings. The vortical structures are shown to be well correlated in space and time with helium mass-fraction isosurface (YHe=0.25Y_{\rm He}=0.25).Comment: 7 pages, 1 figure, 1 table, article describing fluid dynamics video submitted to Gallery of Fluid Motion, APS-DFD 200

    Public perceptions of the police: effects of police investigation and police resources

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    Since the 1980s, successive UK governments have sought to increase efficiency in, and effectiveness of, policing through what has been described as “cycles of reform” (Reiner, 2000, p. 204). The reforms typically involved exerting greater central control over regional police forces. Many of the early initiatives met with resistance from within the police and, as a result, were not fully implemented (McLaughlin and Murji, 1995). By the late 1990s and early 2000s, however, more effective and direct control over police performance was finally established. This took the form of a centralisation of police management, which resulted in the introduction of more uniform measures of monitoring police performance, including the regular recording of crime and crime detection rates among police forces. Performance targets were set and the public’s satisfaction with the work of the police in their local area became one of several performance indicators. Performance targets and measures to generate greater cost efficiency in service provision, however, can have unexpected, sometimes perverse side effects. Two of these are focus of this paper. First, it explores how shifts in the police’s focus on specific types of crime in response to the introduction of performance targets affected the public’s reporting of crime. Second, it asks whether, in the light of efforts to achieve efficiency savings in the police, public spending on police forces has had any bearing on the public’s perception of the quality of local policing

    Police authorities, accountability, and citizenship

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    Policing has recently attracted a great deal of controversy set against the recent wave of student disturbances and the use of paramilitary tactics to disperse, contain, and kettle protestors. Moreover, the controversial application of stop and search powers under the Terrorism Act 2000 has raised further questions about the accountability of the police. The responsibility of holding the police to account currently falls to the 43 police authorities operating across England and Wales. This article draws on ground-breaking research on police authorities using questionnaire and in-depth interview data to outline just how it is that police authority members approach their duties and responsibilities. It outlines the role and potential of police authorities to influence police policy and operations and discusses how the work of police authorities has impacted on participation by local citizens. Our starting position is that citizen participation is a prerequisite for the effective delivery of accountable policing. This has serious consequences for the proposed Police and Crime Commissioners, which are intended to replace police authorities in November 2012

    Policing and accountability: the working of Police Authorities

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    In recent times policing has attracted a good deal of controversy, such as the paramilitary tactics employed at demonstrations, the use of stop and search powers under the Terrorism Act 2000, and the manner in which police officers are deployed on day-to-day duties. This paper outlines the role and potential of police authorities to influence police policy and operations and also highlights the need to seek greater citizen participation in holding the police to account. The major part of the paper draws on ground-breaking research on police authorities using questionnaire and in-depth interview data to outline just how it is that police authority members approach their duties

    The Drought Monitor

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    There is a need for improved drought monitoring and assessment methods in the United States. Drought is the most costly natural disaster [Federal Emergency Management Agancy (FEMA 1995; Wilhite 2000)], but it is often neglected by developers of assessment and forecast products. Drought is more nebulous than other disasters and does not lend itself to traditional assessments or forecast methods. Its relatively slow onset and the complexity of its impacts are reasons for the new assessment methodology. Improvements in drought monitoring and forecasting techniques will allow for better preparation, lead to better management practices, and reduce the vulnerability of society to drought and its subsequent impacts. The Drought Monitor (additional information available online at http://drought.unl/edu/dm) was created with the goal of tracking and displaying the magnitude and spatial extent of drought and its impacts across the United States. The Drought Monitor is produced weekly and classifies drought severity into four major categories, with a fifth category threshold assigned to locations on a map are determined from a number of indicators, or tools, blended with subjective interpretation

    The 'sluice-gate' public sphere and the national DNA database in the UK

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    Habermas’s amendments to his original public sphere thesis have been recognized by a number of media scholars in recent years. His original thesis of a decline or refeudalization of the public sphere where politics is played out in front of the public has been modified, under the influence of Bernhard Peters’ work, to incorporate the possibility of action from the periphery of the public sphere influencing, if not exclusively determining, decisions made at the administrative core via sluice-gates. There has been limited work, however, on exploring the operation of the sluices in greater detail, and particularly on the role of the mass media in acting as a communication channel between peripheral publics and core elites. The purpose of this article is to do so via a case study of the mass media public debate in the UK about the existence and extent of the national DNA database as it is a prima facie candidate for observing the operation of the sluice-gates

    Numerical simulation of transom-stern waves

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    The flow field generated by a transom-stern hullform is a complex, broad-banded, three-dimensional phenomenon marked by a large breaking wave. This unsteady multiphase turbulent flow feature is difficult to study experimentally and simulate numerically. The results of a set of numerical simulations, which use the Numerical Flow Analysis (NFA) code, of the flow around the Model 5673 transom stern at speeds covering both wet- and dry-transom operating conditions are shown in the accompanying fluid dynamics video. The numerical predictions for wet-transom and dry-transom conditions are presented to demonstrate the current state of the art in the simulation of ship generated breaking waves. The interested reader is referred to Drazen et al. (2010) for a detailed and comprehensive comparison with experiments conducted at the Naval Surface Warfare Center Carderock Division (NSWCCD).Comment: Fluid Dynamics Video for 2010 APS Division of Fluid Dynamics Gallery of Fluid Motion include
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