Suprathermal plasma observed on STS-3 Mission by plasma diagnostics package

Artificially produced electron beams were used extensively during the past decade as a means of probing the magnetosphere, and more recently as a means of actively controlling spacecraft potential. Experimentation in these areas has proven valuable, yet at times confusing, due to the interaction of the electron beam with the ambient plasma. The OSS-1/STS-3 Mission in March 1982 provided a unique opportunity to study beam-plasma interactions at an altitude of 240 km. On board for this mission was a Fast Pulse Electron Generator (FPEG). Measurements made by the Plasma Diagnostics Package (PDP) while extended on the Orbiter RMS show modifications of the ion and electron energy distributions during electron beam injection. Observations made by charged particle detectors are discussed and related to measurements of Orbiter potential. Several of the PDP instruments, the joint PDP/FPEG experiment, and observations made during electron beam injection are described

Registration of retinal images from Public Health by minimising an error between vessels using an affine model with radial distortions

In order to estimate a registration model of eye fundus images made of an affinity and two radial distortions, we introduce an estimation criterion based on an error between the vessels. In [1], we estimated this model by minimising the error between characteristics points. In this paper, the detected vessels are selected using the circle and ellipse equations of the overlap area boundaries deduced from our model. Our method successfully registers 96 % of the 271 pairs in a Public Health dataset acquired mostly with different cameras. This is better than our previous method [1] and better than three other state-of-the-art methods. On a publicly available dataset, ours still better register the images than the reference method

OpenCL Actors - Adding Data Parallelism to Actor-based Programming with CAF

The actor model of computation has been designed for a seamless support of concurrency and distribution. However, it remains unspecific about data parallel program flows, while available processing power of modern many core hardware such as graphics processing units (GPUs) or coprocessors increases the relevance of data parallelism for general-purpose computation. In this work, we introduce OpenCL-enabled actors to the C++ Actor Framework (CAF). This offers a high level interface for accessing any OpenCL device without leaving the actor paradigm. The new type of actor is integrated into the runtime environment of CAF and gives rise to transparent message passing in distributed systems on heterogeneous hardware. Following the actor logic in CAF, OpenCL kernels can be composed while encapsulated in C++ actors, hence operate in a multi-stage fashion on data resident at the GPU. Developers are thus enabled to build complex data parallel programs from primitives without leaving the actor paradigm, nor sacrificing performance. Our evaluations on commodity GPUs, an Nvidia TESLA, and an Intel PHI reveal the expected linear scaling behavior when offloading larger workloads. For sub-second duties, the efficiency of offloading was found to largely differ between devices. Moreover, our findings indicate a negligible overhead over programming with the native OpenCL API.Comment: 28 page

Environment and Energy Injection Effects in GRB Afterglows

In a recent paper (Dai & Lu 1999), we have proposed a simple model in which the steepening in the light curve of the R-band afterglow of the gamma-ray burst (GRB) 990123 is caused by the adiabatic shock which has evolved from an ultrarelativistic phase to a nonrelativistic phase in a dense medium. We find that such a model is quite consistent with observations if the medium density is about $3\times 10^6 {\rm cm}^{-3}$. Here we discuss this model in more details. In particular, we investigate the effects of synchrotron self absorption and energy injection. A shock in a dense medium becomes nonrelativistic rapidly after a short relativistic phase. The afterglow from the shock at the nonrelativistic stage decays more rapidly than at the relativistic stage. Since some models for GRB energy sources predict that a strongly magnetic millisecond pulsar may be born during the formation of GRB, we discuss the effect of such a pulsar on the evolution of the nonrelativistic shock through magnetic dipole radiation. We find that after the energy which the shock obtains from the pulsar is much more than the initial energy of the shock, the afterglow decay will flatten significantly. When the pulsar energy input effect disappears, the decay will steepen again. These features are in excellent agreement with the afterglows of GRB 980519, GRB 990510 and GRB 980326. Furthermore, our model fits very well all the observational data of GRB 980519 including the last two detections.Comment: 21 pages, LaTeX, accepted for publication in ApJ, one paragraph adde

Norm Optimal Iterative Learning Control with Application to Problems in Accelerator based Free Electron Lasers and Rehabilitation Robotics

This paper gives an overview of the theoretical basis of the norm optimal approach to iterative learning control followed by results that describe more recent work which has experimentally benchmarking the performance that can be achieved. The remainder of then paper then describes its actual application to a physical process and a very novel application in stroke rehabilitation

The Assessment of Commercial Fishing Effort in Virginia Annual Report 1989

This report summarizes an assessment of commercial fishing effort in the Chesapeake Bay and its Virginia tributaries during the period 1 October 1988 through 30 June 1989. Objectives of the study were: 1) to assess pound net fishing effort in Chesapeake Bay, in the James, York, Rappahannock, and Potomac rivers, and the Virginia tributaries to the Potomac River; and 2) to assess stake, anchor and drift gill net fishing effort in the James, York and Rappahannock rivers. The study period began on 1 October 1988 and ended on 30 June 1989. Data for fyke net, haul seine and mullet net fisheries, when available, have also been included

The Assessment of Commercial Fishing Effort in Virginia Annual Report 1990

The Virginia Institute of Marine Science (VIMS), through funding by the Virginia Marine Resources Commission (VMRC), has conducted an assessment of commercial fishing effort in Virginia\u27s major rivers and Chesapeake Bay beginning in late 1985 to the present, except for brief intervals when funding was unavailable. This report primarily summarizes the final year of assessment, from 1 October 1989 through 30 September 1990. Objectives of the study were: -1) to assess pound net fishing effort in Chesapeake Bay, in the James, York, Rappahannock, and Potomac rivers, and the Virginia tributaries to the Potomac River; and, 2) to assess stake, anchor and drift gill net fishing effort in the three major Virginia river systems. In the course of our data collection for the James, York and Rappahannock rivers, we have also obtained incidental effort data for these rivers and other areas in the Bay. Fyke net, haul seine and gill net fisheries data are included in this report

Evidence for a Molecular Cloud Origin for Gamma-Ray Bursts: Implications for the Nature of Star Formation in the Universe

It appears that the majority of rapidly-, well-localized gamma-ray bursts with undetected, or dark, optical afterglows, or `dark bursts' for short, occur in clouds of size R > 10L_{49}^{1/2} pc and mass M > 3x10^5L_{49} M_{sun}, where L is the isotropic-equivalent peak luminosity of the optical flash. We show that clouds of this size and mass cannot be modeled as a gas that is bound by pressure equilibrium with a warm or hot phase of the interstellar medium (i.e., a diffuse cloud): Such a cloud would be unstable to gravitational collapse, resulting in the collapse and fragmentation of the cloud until a burst of star formation re-establishes pressure equilibrium within the fragments, and the fragments are bound by self-gravity (i.e., a molecular cloud). Consequently, dark bursts probably occur in molecular clouds, in which case dark bursts are probably a byproduct of this burst of star formation if the molecular cloud formed recently, and/or the result of lingering or latter generation star formation if the molecular cloud formed some time ago. We then show that if bursts occur in Galactic-like molecular clouds, the column densities of which might be universal, the number of dark bursts can be comparable to the number of bursts with detected optical afterglows: This is what is observed, which suggests that the bursts with detected optical afterglows might also occur in molecular clouds. We confirm this by modeling and constraining the distribution of column densities, measured from absorption of the X-ray afterglow, of the bursts with detected optical afterglows: We find that this distribution is consistent with the expectation for bursts that occur in molecular clouds, and is not consistent with the expectation for bursts that occur in diffuse clouds. More...Comment: Accepted to The Astrophysical Journal, 22 pages, 6 figures, LaTe

The floor in the interplanetary magnetic field: Estimation on the basis of relative duration of ICME observations in solar wind during 1976-2000

To measure the floor in interplanetary magnetic field and estimate the time- invariant open magnetic flux of Sun, it is necessary to know a part of magnetic field of Sun carried away by CMEs. In contrast with previous papers, we did not use global solar parameters: we identified different large-scale types of solar wind for 1976-2000 interval, obtained a fraction of interplanetary CMEs (ICMEs) and calculated magnitude of interplanetary magnetic field B averaged over 2 Carrington rotations. The floor of magnetic field is estimated as B value at solar cycle minimum when the ICMEs were not observed and it was calculated to be 4,65 \pm 6,0 nT. Obtained value is in a good agreement with previous results.Comment: 10 pages, 2 figures, submitted in GR

Exclusive W^+ + photon production in proton-antiproton collisions II: results

We present results for total cross sections, single and double differential distributions and correlations between pairs of outgoing particles in the reactions p + antip --> W^+ + photon and p + antip --> W^+ + photon + jet at sqrt(S)=1.8 TeV. Order alpha-strong QCD corrections and leading logarithm photon bremsstrahlung contributions are included in the MS-bar mass factorization scheme for three experimental scenarios: 1) 2-body inclusive production of W^+ and photon, 2) exclusive production of W^+, photon and 1 jet and 3) exclusive production of W^+ and photon with 0 jet. The latest CTEQ parton distribution functions, which fit the newly released HERA data, are used in our analysis. The dependence of our results on the mass factorization scale is used to place error bars on our predictions for the single differential distributions and correlations.Comment: 15 pages (LateX). 50 pages of postscript figures available via ftp anonymous from max.physics.sunysb.edu in the directory preprints/mendoza/EXCLUSIVE_W_GAMMA_II.dir (files named fig_*.ps) ITP-SB-93-80. ([email protected])([email protected]