A parallel Beowulf-based system for the detection of gravitational waves in interferometric detectors

The detection, in a modern interferometric detector like Virgo, of a gravitational wave signal from a coalescing binary stellar system is an intensive computational task both for the on-line and off-line computer systems. A parallel computing scheme using the Message Passing Interface (MPI) is described. Performance results on a small scale cluster are reported.     

A new strategy for improved spectral performance in solar power plants

One method of achieving improved electrical conversion efficiencies in solar power plants is to employ a spectrally selective filter that splits the collected beam into optimised components for two or more spectral receivers. The added cost of supplementary optics and receivers can only be justified if the filter has high performance in operation. The design and manufacture of broadband, low-loss filters however, face several challenges. One of these is the wide range of incidence angles at which the collected beam hits the beam splitter, as the performance of common filters degrades when the incidence angle deviates from the design angle. Dish receivers and micro-tracking Fresnel concentrators, such as the heliostat field in a central receiver design, may provide a fixed distribution of incidence angles across the receiver surface so that the filter can be spatially optimised for a defined angular and energy flux distribution pattern. This paper will discuss the theory and application of such a strategy based on flux mappings produced by raytracing methods for a Multi Tower Solar Array central receiver system planned for construction in Newcastle, Australia.     

Innovative extraction procedure for obtaining high pure lycopene from tomato

Many researchers have studied the biological effects of carotenoids and the more appropriate procedure for extracting them from vegetable sources. In this work we propose a rapid and low-cost procedure to extract lycopene from tomato in order to by-pass the problems related to the high cost of this molecule. Following this procedure we have obtained over 95% pure all-trans-lycopene checked by DAD-HPLC coupled with mass-spectrometer equipped with APCI source and by UV–Vis spectroscopy. Moreover, in order to evaluate the effectiveness of this procedure, we have assayed the capacity of the extracted lycopene to inhibit proliferation in T-lymphocyte jurkat J32 cells in comparison with authentic standard all-trans-lycopene. On this cellular line both standard lycopene and extracted lycopene tended to be dose-dependent but this latter seems to be more active even at lowest concentration.     

Enhancing CLP branch and bound techniques for scheduling problems

In this paper, we propose a constraint logic programming (CLP) approach to the solution of a job shop scheduling problem in the field of production planning in orthopaedic hospital departments. A pure CLP on finite domain (CLP(FD)) approach to the problem has been developed, leading to disappointing results. In fact, although CLP(FD) has been recognized as a suitable tool for solving combinatorial problems, it presents some drawbacks for optimization problems. The main reason concerns the fact that CLP(FD) solvers do not effectively handle the objective function and cost‐based reasoning through the simple branch and bound scheme they embed. Therefore, we have proposed an improvement of the standard CLP branch and bound algorithm by exploiting some well‐known operations research results. The branch and bound we integrate in a CLP environment is based on the optimal solution of a relaxation of the original problem. In particular, the relaxation used for the job shop scheduling problem considered is the well‐known shifted bottleneck procedure considering single machine problems. The idea is to decompose the original problem into subproblems and solve each of them independently. Clearly, the solutions of each subproblem may violate constraints among different subproblems which are not taken into account. However, these solutions can be exploited in order to improve the pruning of the search space and to guide the search by defining cost‐based heuristics. The resulting algorithm achieves a significant improvement with respect to the pure CLP(FD) approach that enables the solution of problems which are one order of magnitude greater than those solved by a pure CLP(FD) algorithm. In addition, the resulting code is less dependent on the input data configuration. Copyright © 2001 John Wiley & Sons, Ltd.     

Habitat suitability curves for brown trout (Salmo trutta fario L.) in the River Adda,Northern Italy: comparing univariate and multivariate approaches

Habitat suitability of brown trout (Salmo trutta fario) was studied in the upper portion of the Adda River, Northern Italy. Measurements were made for 528 individuals distributed in two life‐stage classes, adult and juvenile, based on body length. In order to provide basic biological information for the physical habitat simulation (PHABSIM) system of the instream flow incremental methodology (IFIM) in the Italian regulated rivers, habitat suitability curves (HSCs) have been developed with respect to several microhabitat riverine parameters. Initially, current velocity, water depth, substrate class size and cover were analysed with an univariate approach, then bivariate habitat suitability models were developed from depth and velocity data. The comparison of experimental univariate HSCs with those from the literature outlined some differences that can essentially be explained by characteristics of the investigated river, confirming the necessity of using site‐specific curves in relation to each experimental study area. To compare the univariate and bivariate approaches, the weighted usable area (WUA)–discharge relationships were calculated using both types of HSCs. Response curves obtained from the two approaches turned out to be quite different. In PHABSIM habitat modelling, HSCs univariate functions need to be aggregated to produce the WUA–discharge relationship. A multiplicative criterion is generally used for the combined suitability factor; by means of this aggregation criterion all variables have equal weight. According to bivariate models, depth is much more important than velocity in defining habitat suitability requirements. Copyright © 2001 John Wiley & Sons, Ltd.     

Reconfigurable pipelined 2-D convolvers for fast digital signalprocessing

In order to make software applications simpler to write and easier to maintain, a software digital signal-processing library that performs essential signal- and image-processing functions is an important part of every digital signal processor (DSP) developer's toolset. In general, such a library provides high-level interface and mechanisms, therefore, developers only need to know how to use algorithms, not the details of how they work. Complex signal transformations then become function calls, e.g., C-callable functions. Considering the two-dimensional (2-D) convolver function as an example of great significance for DSP's, this paper proposes to replace this software function by an emulation on a field-programmable gate array (FPGA) initially configured by software programming. Therefore, the exploration of the 2-D convolver's design space will provide guidelines for the development of a library of DSP-oriented hardware configurations intended to significantly speed up the performance of general DSP processors. Based on the specific convolver, and considering operators supported in the library as hardware accelerators, a series of tradeoffs for efficiently exploiting the bandwidth between the general-purpose DSP and accelerators are proposed. In terms of implementation, this paper explores the performance and architectural tradeoffs involved in the design of an FPGA-based 2-D convolution coprocessor for the TMS320C40 DSP microprocessor available from Texas Instruments Incorporated. However, the proposed concept is not limited to a particular processor     

A new growth method for the synthesis of 3C-SiC nanowires

A new method has been developed to grow nickel-catalysed SiC nanowires on silicon, by a chemical reaction involving carbon tetrachloride as a single precursor. This produces long crystalline 3C-SiC nanowires with <111> axis, as verified by transmission electron microscopy. A broad optical emission centred at about 2 eV is detected by cathodoluminescence spectroscopy. The Gaussian component at about 2.2 eV corresponds to the indirect 3C-SiC band gap emission, while the dominant red emission is related to oxygen incorporation.     

A sequence of critical temperatures in YBCO between 20 and 70 K

Evidence has been found for a number of discrete and sharp transitions in the magnetic susceptibility transition of many single crystals of YBCO. These appear to favour certain temperatures and at least eight transitions are observed between 20 K and 70 K. One of these transitions dominates the behaviour of one of the individual crystals and X-ray studies indicate that the oxygenation value corresponds to O_6·7. We suggest that these transitions are associated with different ordered states in the oxygen deficient lattice.     

PCH法铜管接头成形技术

采用以PCH为代号的有机混合填料作传压介质,在自制的设备上用PCH法一次冷成形制成各种类型的铜管接头。该方法在很多方面优于国际上先进的液压胀形法及常用的橡胶凸形法。其主要特点是设备及控制系统简单,填料价廉且可反复回用,成本低,产品质量有确切保证。