The Computational Grid is a promising platform for the efficient execution of parameter sweep applications over large parameter spaces. To achieve performance on the Grid, such applications must be scheduled so that shared data files are strategically placed to maximize reuse, and so that the application execution can adapt to the deliverable performance potential of target heterogeneous, distributed and shared resources. Parameter sweep applications are an important class of applications and would greatly benefit from the development of Grid middleware that embeds a scheduler for performance and targets Grid resources transparently. In this paper we describe a user-level Grid middleware project, the AppLeS Parameter Sweep Template (APST), that uses application-level scheduling techniques [1] and various Grid technologies to allow the efficient deployment of parameter sweep applications over the Grid. We discuss...

The Computational Grid is a promising platform for the deployment of various high-performance computing applications. A number of projects have addressed the idea of software as a service on the network. These systems usually implement client-server architectures with many servers running on distributed Grid resources and have commonly been referred to as Network-enabled servers (NES). An important question is that of scheduling in this multi-client multi-server scenario. Note that in this context most requests are computationally intensive as they are generated by high-performance computing applications. The Bricks simulation framework has been developed and extensively used to evaluate scheduling strategies for NES systems. In this paper we first present recent developments and extensions to the Bricks simulation models. We discuss a deadline scheduling strategy that is appropriate for the multi-client multi-server case, and augment it with “Load Correction” and “Fallback ” mechanisms which could improve the performance of the algorithm. We then give Bricks simulation results. The results show that future NES systems should use deadline-scheduling with multiple fallbacks and it is possible to allow users to make a trade-off between failure-rate and cost by adjusting the level of conservatism of deadlinescheduling algorithms.

The Computational Grid [1] is a promising platform for running large scale scientic applications. It provides a base software infrastructure that allows for the development of \middleware" aimed at deploying applications on Grid resources. The NetworkEnabled Server (NES) paradigm is a good candidate as a viable Grid middleware that oers a simple yet powerful programming model (RPC-style programming for the Grid). This paradigm is amenable to many large-scale applications and especially to scienti c simulations. This paper builds on the experience acquired while building two well-known NES systems (Ninf [2] and NetSolve [3]). Our goal is to clarify major NES design issues as well as to dene a common set of services and concepts that are necessary for implementing and deploying NES systems on the Computational Grid. This paper also describes current work with scientic and engineering simulations that are enabled by NES systems in the Grid context.

A Monte Carlo radiation transport simulation program, EGS Nova, and a Computer Aided Design software, BRL-CAD, have been coupled within the framework of Sindbad, a Nondestructive Evaluation (NDE) simulation system. In its current status, the program is very valuable in a NDE laboratory context, as it helps simulate the images due to the uncollided and scattered photon fluxes in a single NDE software environment, without having to switch to a Monte Carlo code parameters set. Numerical validations show a good agreement with EGS4 computed and published data. As the program's major drawback is the execution time, computational efficiency improvements are foreseen.

High-energy 7-ray astronomy was revolutionized in 1991 with the launch of the Ener- getic Gamma-Ray Experiment Telescope (EGRET) on board the Compton Gamma- Ray Observatory. In addition to unprecedented instrument effective area and a narrow point-spread function, EGRET provided photon time-tagging to an absolute accu- racy of 100/s. Such instrument capabilities offer the opportunity to analyze sources whose flux modulates in a coherent periodic way. Part I describes the analysis of periodic signals in EGRET data. Statistical methods using maximum likelihood and Bayesian inference are developed and implemented to extract periodic signals from if-ray sources in the presence of significant astrophysical background radiation. The methods allow searches for periodic modulation without a priori knowledge of the period or period derivative. The analysis was performed on six pulsars and three pul- sar candidates. The three brightest pulsars, Crab, Vela, and Geminga, were readily identified, and would have been detected independently in the EGRET data without knowledge of the pulse period. No significant pulsation was detected in the three pulsar candidates. Furthermore, the method allows the analysis of sources with peri- ods on the same order as the time scales associated with changes in the instrumental sensitivity, such as the orbital time scale of CGRO around the Earth. Eighteen X- ray binaries were examined. None showed any evidence of periodicity. In addition, methods for calculating the detection threshold of periodic flux modulation were de- veloped.

This paper presents a software simulation package of the entire X-ray projection radiography process including beam generation, absorber structure and composition, irradiation set up, radiation transport through the absorbing medium, image formation and dose calculation. Phantoms are created as composite objects from geometrical or voxelized primitives and can be subjected to simulated irradiation process. The acquired projection images represent the two-dimensional spatial distribution of the energy absorbed in the detector and are formed at any geometry, taking into account energy spectrum, beam geometry and detector response. This software tool is the evolution of a previously presented system, with new functionalities, user interface and an expanded range of applications. This has been achieved mainly by the use of combinatorial geometry for phantom design and the implementation of a Monte Carlo code for the simulation of the radiation interaction at the absorber and the detector. © 2002 Published by

Abstract-The photoneutron yields produced indifferent components of the medical accelerator heads evaluated in these studies (24-MV Clinac 2500 and a Clinac 2100C/2300C runfing in the 1O-MV, 15-MV, 18-MV and 20-MV modes) were calculated by the EGS4 Monte Carlo code using a modified version of the Combinatorial Geometry of MORSE-CG. Actual component dimensions and materials (i.e., targets, collimators, flattening filters, jaws and shielding for specific accelerator heads) were used in the geometric simulations. Calculated relative neutron yields in different components of a 24-MV Clinac 2500 were compared with the published measured data, and were found to agree to within HOYO. Total neutron yields produced in the Clinac 2100/2300, as a function of primary electron energy and field size, are presented. A simplified Clinac 2100/2300C geometry is presented to calculate neutron yields, which were compared with those calculated by using the fully-described geometry. (Submitted to the Health Physics Society)

To reduce the size of this section's PostScript file, we have divided it into three PostScript files. We present the following index:

this report has been plagiarised unashamedly from the original EGS3 (Electron Gamma Shower Code Version 3) document authored by Richard Ford and Ralph Nelson [1]. There are several reasons for this aside from laziness. This history predates one of the author's (AFB) involvement with EGS and he found it very difficult to improve upon the words penned by Ford and Nelson in that original document. Moreover, the EGS3 manual is now out-of-print and this history might have eventually been lost to the ever-burgeoning EGS-community now estimated to be at least 6000 strong. There had been one previous attempt to give a historical perspective of EGS [2]. However, this article was very brief and did not convey the large effort that went into the development of EGS. In this report the historical section on EGS4 as well as the summary of EGS3 to EGS4 conversion and the overview of EGS4 was taken directly from the EGS4 manual [3]. This is done for completeness only. The EGS4 manual gives much more detail and ought to be referred to for technical details. Finally, recent improvements to EGS4 are listed herein and represent the first time that this information is available in one place. The reader should consult the references cited in this report for more details regarding motivation and implementation.

this paper we present a baseline design that is reasonably conservative and uses only existing technologies. We use the SLC positron source [3] as the basis for our design, as its design principles have been well tested in many years of SLC operation, and make necessary changes to accommodate the significantly higher beam intensity requirement for the NLC. Table 1 lists the important parameters for the NLC positron source, along with the SLC positron source parameters for comparison.