10,807 research outputs found
Criminal law as a security project
This paper asks how criminal might be understood as a security project. Following Valverde’s lead, it does this not by trying to define the concept of security, but by looking at the operation of the temporal and spatial logics of the criminal law. It looks first at the basic logics of time and space in conceptions of criminal liability and jurisdiction, before reviewing some recent developments which challenge these practices and what these might mean for criminal law as a security project
Particle phase function measurements by a new Fiber Array Nephelometer: FAN 1
A fiber array polar nephelometer of advanced design, the FAN I is capable of in-situ phase function measurements of scattered light from man-made or natural atmospheric particles. The scattered light is measured at 100 different angles throughout 360 degrees, thus providing a potential measurement of the asymmetry of irregularly shaped particles. Phase functions can be measured at 10 to 100 Hz rates and the range of measurable single particle sizes is from 5 micron m to as large as 8mm. For particles smaller than 5 micro m the ensemble average can be measured. The FAN I is microprocessor controlled and the data may be stored on floppy disk or printed out in tabular and/or graphical form. The optical head may be separated from the computer system for operation in field or adverse conditions. Examples of laboratory measured scattering phase functions obtained with the FAN I for spherical particles is given to illustrate its measurement capabilities
Within-socket Myoelectric Prediction of Continuous Ankle Kinematics for Control of a Powered Transtibial Prosthesis
Objective. Powered robotic prostheses create a need for natural-feeling user interfaces and robust control schemes. Here, we examined the ability of a nonlinear autoregressive model to continuously map the kinematics of a transtibial prosthesis and electromyographic (EMG) activity recorded within socket to the future estimates of the prosthetic ankle angle in three transtibial amputees. Approach. Model performance was examined across subjects during level treadmill ambulation as a function of the size of the EMG sampling window and the temporal \u27prediction\u27 interval between the EMG/kinematic input and the model\u27s estimate of future ankle angle to characterize the trade-off between model error, sampling window and prediction interval. Main results. Across subjects, deviations in the estimated ankle angle from the actual movement were robust to variations in the EMG sampling window and increased systematically with prediction interval. For prediction intervals up to 150 ms, the average error in the model estimate of ankle angle across the gait cycle was less than 6°. EMG contributions to the model prediction varied across subjects but were consistently localized to the transitions to/from single to double limb support and captured variations from the typical ankle kinematics during level walking. Significance. The use of an autoregressive modeling approach to continuously predict joint kinematics using natural residual muscle activity provides opportunities for direct (transparent) control of a prosthetic joint by the user. The model\u27s predictive capability could prove particularly useful for overcoming delays in signal processing and actuation of the prosthesis, providing a more biomimetic ankle response
Crystallization of random trigonometric polynomials
We give a precise measure of the rate at which repeated differentiation of a
random trigonometric polynomial causes the roots of the function to approach
equal spacing. This can be viewed as a toy model of crystallization in one
dimension. In particular we determine the asymptotics of the distribution of
the roots around the crystalline configuration and find that the distribution
is not Gaussian.Comment: 10 pages, 3 figure
Adding value and meaning to coheating tests
Purpose: The coheating test is the standard method of measuring the heat loss coefficient of a building, but to be useful the test requires careful and thoughtful execution. Testing should take place in the context of additional investigations in order to achieve a good understanding of the building and a qualitative and (if possible) quantitative understanding of the reasons for any performance shortfall. The paper aims to discuss these issues. Design/methodology/approach: Leeds Metropolitan University has more than 20 years of experience in coheating testing. This experience is drawn upon to discuss practical factors which can affect the outcome, together with supporting tests and investigations which are often necessary in order to fully understand the results. Findings: If testing is approached using coheating as part of a suite of investigations, a much deeper understanding of the test building results. In some cases it is possible to identify and quantify the contributions of different factors which result in an overall performance shortfall. Practical implications: Although it is not practicable to use a fully investigative approach for large scale routine quality assurance, it is extremely useful for purposes such as validating other testing procedures, in-depth study of prototypes or detailed investigations where problems are known to exist. Social implications: Successful building performance testing is a vital tool to achieve energy saving targets. Originality/value: The approach discussed clarifies some of the technical pitfalls which may be encountered in the execution of coheating tests and points to ways in which the maximum value can be extracted from the test period, leading to a meaningful analysis of the building's overall thermal performance
Conceptual design of a synchronous Mars telecommunications satellite
Future missions to Mars will require a communications system to link activities on the Martian surface with each other and with mission controllers on Earth. A conceptual design is presented for an aerosynchronous communications satellite to provide these links. The satellite provides the capability for voice, data/command, and video transmissions. The mission scenario assumed for the design is described, and a description of a single aerosynchronous satellite is explained. A viable spacecraft design is then presented. Communication band selection and channel allocation are discussed. The communications system conceptual design is presented along with the trades used in sizing each of the required antennas. Also, the analyses used to develop the supporting subsystem designs are described as is the communications impact on each subsystem design
Random polynomials, random matrices, and -functions
We show that the Circular Orthogonal Ensemble of random matrices arises
naturally from a family of random polynomials. This sheds light on the
appearance of random matrix statistics in the zeros of the Riemann
zeta-function.Comment: Added background material. Final version. To appear in Nonlinearit
A Bit-String Model for Biological Aging
We present a simple model for biological aging. We studied it through
computer simulations and we have found this model to reflect some features of
real populations.Comment: LaTeX file, 4 PS figures include
Identification of Gravity-Related Effects on Crystal Growth From Melts With an Immiscibility Gap
This work involves an experimental-numerical approach to study the effects of natural and Marangoni convections on solidification of single crystals from a silicate melt with a liquid-liquid immiscibility gap. Industrial use of crystals grown from silicate melts is becoming increasingly important in electronic, optical, and high temperature structural applications. Even the simplest silicate systems like Al203-SiO2 have had, and will continue to have, a significant role in the development of traditional and advanced ceramics. A unique feature of crystals grown from the silicate systems is their outstanding linear electro-optic properties. They also exhibit exceptionally high optical rotativity. As a result, these crystals are attractive materials for dielectric, optical, and microwave applications. Experimental work in our laboratory has indicated that directional solidification of a single crystal mullite appears to be preceded by liquid-liquid phase separation in the melt. Disruption of the immiscible state results in crystallization of a two phase structure. There is also evidence that mixing in the melt caused by density-driven convection can significantly affect the stability of the immiscible liquid layers and result in poly-crystalline growth. On earth, the immiscible state has only been observed for small diameter crystals grown in float zone systems where natural convection is almost negligible. Therefore, it is anticipated that growth of large single crystals from silicate melts would benefit from microgravity conditions because of the reduction of the natural convective mixing. The main objective of this research is to determine the effects of transport processes on the phase separation in the melt during growth of a single crystal while addressing the following issues: (1) When do the immiscible layers form and are they real?; (2) What are the main physical characteristics of the immiscible liquids?; and (3) How mixing by natural or Marangoni convection affects the stability of the phase separated melt
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