Scattering center parameterization of wide-angle backscattered datausing adaptive Gaussian representation

We present a scattering center extraction algorithm to parameterize the backscattered data from complex targets collected over large angular apertures. This parameterization is based on a scattering center model of the target, but includes an aspect-dependent amplitude function for each scattering center. A two-dimensional (2-D) adaptive Gaussian representation (AGR) algorithm is used to extract the position and the amplitude function associated with each scattering center. The algorithm is tested with data generated by the Xpatch radar simulation code as well as chamber measurement data. The results show that a very good compression ratio can be achieved, resulting in a compact scattering center model of the target. Once such model is available, we can easily reconstruct range profiles and ISAR images at any aspect on the same plane with good accuracy     

Performance and buffering requirements of Internet protocols overATM ABR and UBR services

ATM networks are quickly being adopted as backbones over various parts of the Internet. This article studies the dynamics and performance of the TCP/IP protocol over the ABR and UBR services of ATM networks. Specifically the buffering requirements in the ATM switches as well as the ATM edge devices. It is shown that with a good switch algorithm, ABR pushes congestion to the edges of the ATM network while UBR leaves it inside the ATM portion. As a result, the switch ABR buffer requirement for zero-packet-loss high-throughput TCP transmission is a sublinear function of the number of TCP connections     

Metabolic activation and inactivation of metanil yellow and orange II in the Salmonella typhimurium his-reversion assay.

Among a variety of experimental protocols used, the combined use of 0.5% dextrose in bottom agar and 1 micromol of flavin mononucleotide (FMN) in preincubation mixtures without fraction S9 mix resulted in the highest level of induced Salmonella typhimurium his reversions with both dyes metanil yellow and orange 11 with strain TA100. Strain TA98 yielded notably lower levels of reversions under the same conditions. The presence of uninduced hamster liver S9 fraction resulted in a weak mutagenic response while Aroclor 1254-induced rat liver S9 fraction resulted in the complete absence of mutagenicity with both strains and with both dyes.     

Random discrete PWM method for DC-DC power converters

A random discrete pulse-width modulation (RDPWM) scheme is examined and compared with the randomised pulse-position modulation (RPPM) method for DC-DC power conversion. The RDPWM method has no switching harmonics while the RPPM method has significant switching harmonics. Power spectral characteristics of the two methods are presented and discussed     

Producing content producers [computer animation]

Several off-the-shelf animation software packages provide extensive capabilities, obviating the need for studios to develop their own software, except for highly specialized effects and interfaces. These capabilities make it feasible for a university to educate students in animation production without years of software development. The author discusses The UTS School of Cinema-Television and The USC Computer Animation Laboratory in particular     

Thermal stratification and reactor piping integrity

Thermal stratification, cycling, and striping phenomena have drawn much attention recently because of the incidents at several nuclear plants that raised significant safety concerns. The concerns due to these phenomena relate to thermal fatigue in branch pipes connected to the main coolant piping. Nuclear utility industry is addressing the issue with the aim to understand the mechanisms that lead to fatigue in nominally stagnant piping systems near the reactor coolant piping. Two key results from this effort are described in this paper. First, tests to investigate the interaction between the main coolant piping and the stagnant attached lines by turbulence penetration are described and a working correlation is obtained. Turbulence penetration into unisolable lines, or the transport of turbulence into stagnant piping from the reactor coolant system (RCS) line, represents a mechanism for carrying hot RCS water into regions filled with cold water. The possibility of stratification of the two fluids (and the resultant thermal stresses) is the reason for developing an understanding of the turbulence penetration process. Secondly, results of an evaluation to develop a loading definition for thermal striping are included. Based on this testing several important conclusions relating to fatigue in nominally static reactor coolant systems are reached.     

Reactive energy measurement using frequency controlled analog-to-pulse-rate converter

Contents This paper analyzes a problem of phase shifting and deseribes a novel method for electronic reactive energy measurement. The proposed measurement structure, composed of an integrator as a phase shifting circuit and a frequency controlled analog-to-pulse-rate converter, provides for the measurement completely in accordance with IEC definition of reactive energy, which is performed with simple but high performance metering device.

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Die Blindverbrauchsmessung anhand eines netzsynchronisierten Analog-Frequenz-Wandlers

Übersicht In diesem Artikel wird das Problem der Phasenverschiebung analysiert und eine neue Meßmethode für elektronische Blindverbrauschsmessung aufgezeigt. Die vorgeschlagene Strucktur, bestehend aus einem Integrator als Phasenschieber und netzkontrolliertem Analog-Frequenz-Wandler, ermöglicht die Verwirklichung eines einfachen aber präzisen Elektrizitätszählers zur Messung der Blindenergie, dessen Arbeitsprinzip mit den IEC Empfehlungen vollkommen übereinstimmt.

     

A critique of the methods for measuring the impact of CASE software

There is a common belief that CASE software enhances developer productivity and the quality of applications software. However, though the few empirical studies of the impact of CASE have produced inconclusive findings, they do indicate an absence of appreciable productivity gains. There is a need to determine the extent to which CASE products are worth their cost, and this paper focuses on the key methodological issues involved in assessing the cost-effectiveness of CASE products. Existing studies of the impact of CASE software have considered developers' perceptions, but have not considered system users' perceptions nor used software metrics to assess applications software. It is also rare for the characteristics of the development environments and other factors that have an important bearing on the productivity and quality of software to be investigated. In this paper, perceptual and objective measurement, and the different ways of designing the research and of accessing the population of CASE users, are outlined and evaluated. While the aim is to establish the most appropriate research design and measurement approaches for determining the value of CASE tools, the conclusions are also relevant to the assessment of the impact of other new software technologies.