A multiple objective grouping genetic algorithm for assembly line design

The purpose of this paper is to describe some of the main problems concerning assembly line design. The focus will be on the following steps: (1) the input data preparation, (2) the elaboration of the logical layout of the line, which consists in the distribution of operations among stations along the line and an assignment of resources to the different stations, (3) finally the mapping phase using a simulation package to check the obtained results. This work presents a new method to tackle the hybrid assembly line design, dealing with multiple objectives. The goal is to minimize the total cost of the line by integrating design (station space, cost, etc.) and operation issues (cycle time, precedence constraints, availability, etc.). This paper also presents in detail a very promising approach to solve multiple objective problems. It is a multiple objective grouping genetic algorithm hybridized with the multicriteria decision-aid method PROMETHEE II. An approach to deal with users preferences in design problems is also introduced. The essential concepts adopted by the method are described and its application to an industrial case study is presented.     

Current Harmonics Measurement by Means of Current Transformers

This paper analyzes the accuracy of current transformers (CT) when excited with nonsinusoidal currents. It uses a nonlinear model that accounts for the minor hysteresis loop of the core. It was concluded that instrument transformers with accuracy class 0.6 or better provide reasonably accurate measurements of current harmonics magnitudes, however the phase angle error may lead to unacceptable errors when the current transformers are used to measure active powers. If such measurements are used to determine the power flow direction, i.e., if a load or consumer pollutes or is polluted, even high accuracy class CTs may yield unsatisfactory results.     

Calculations and hypotheses relating to the input conductivity function of an infinite grid of similar nonlinear resistors

A formula for the input conductivity characteristic of an infinite grid of similar, weakly nonlinear resistors (conductors) measured between two nodes is obtained using a specific approximate representation of the grid. This formula is more precise than the corresponding formula given earlier by Gluskin. Some hypotheses concerning the analytical features of the input resistive (conductive) function, not necessarily associated with weak nonlinearity, and also related to circuits of other topologies, are considered. One of the hypotheses leads to a simplified method of calculation of the input conductivity, which has a reasonable engineering precision and may replace incomparably more difficult calculations. The derivations are given in detail.     

Operational Considerations for Teaming Manned and Unmanned Helicopter

“Manned-Unmanned Teaming” among others refers to the use of an unmanned, flying sensor. One use for this is as an integral part of air units’ flying systems. Secondly, it can be used as an independent, recessed robotic component during missions, even from far away and ahead of time. As part of the German R&T project “Manned- Unmanned Teaming” (MUM-T), Elektroniksystem- und Logistik-GmbH (ESG) was assigned the task of investigating these concepts and the options for their realization. The focus of the investigation was initial operation capability within a narrow time frame concentrating on German Army Aviation helicopters. The paper focuses on the results achieved by ESG and begins with a short project overview. In the main part a representative MUM-T mission based on a personnel recovery mission is presented. The mission was demonstrated by ESG in close cooperation with German Army Aviation Combat Development Division (Ger AAV CDD). Beside operational aspects, technical aspects will be discussed. The lecture will close with a short outlook on the next steps, bringing MUM-T missions into service.     

Integral transform solution for hyperbolic heat conduction in a finite slab

An analytical integral transformation of the thermal wave propagation problem in a finite slab is obtained through the generalized integral transform technique (GITT). The use of the GITT approach in the analysis of the hyperbolic heat conduction equation leads to a coupled system of second order ordinary differential equations in the time variable. The resulting transformed ODE system is then numerically solved by Gear's method for stiff initial value problems. Numerical results are presented for the local and average temperatures with different Biot numbers and dimensionless thermal relaxation times, permitting a critical evaluation of the technique performance. A comparison is also performed with previously reported results in the literature for special cases and with those produced through the application of the Laplace transform method (LTM), and the finite volume-Gear method (FVGM).     

Superresolution algorithms for spatial extended scattering centers

Scattering centers model (SCM) is usually considered for modeling target backscattered signal in high-resolution radar. In this case the impulse response of each scattering center is represented by a time-delayed Dirac pulse. Some of most popular superresolution imagery techniques, such as MUSIC or ESPRIT, are well-matched to this model. Under this hypothesis, they outperform Fourier-based techniques in terms of both spatial and dynamic resolutions. However, the behavior of real-world targets is often very different from that of the SCM. Indeed, their reflectivity function is not confined just to several perfectly localized scattering centers, but it can be rather approximated by a set of scattering regions having different spatial extent. SCM becomes then inappropriate and the superresolution methods may provide unexpected results. Furthermore, the amplitude information is difficult to interpret in this case. In this paper we propose an extension of two superresolution methods, MUSIC and ESPRIT, to cope with extended scattering centers (ESC). According to this model, the impulse response of an ESC is not a Dirac pulse, but a window of finite support. Besides the position, the size (spatial extent) of this window is also recovered. This additional information about the target structure can be used for increasing ATR (automatic target recognition) accuracy and robustness.     

Predictive closed-loop power control for frequency-division duplexwireless systems

A novel method for performing uplink closed-loop power control is proposed, namely with uplink prediction and downlink-derived predictor coefficients. The lack of correlation between the fading processes on uplink and downlink (due to frequency division duplex and frequency selective fading) is circumvented by using the uplink fading history, together with a set of link-independent, autoregressive coefficients     

High impedance fault arcing on sandy soil in 15 kV distributionfeeders: contributions to the evaluation of the low frequency spectrum

The measured values of current harmonics at a staged high-impedance ground fault on sandy soil are presented. The measured low-frequency spectrum is compared with current harmonics recorded continuously for one week at the substation. This comparison was carried out to determine to what extent 120 Hz and 180 Hz components can be used to help detect a high-impedance fault. The field measurements are supported by a simple theoretical model and laboratory measurements. It is concluded that, for the studied feeder, detection of high-impedance arcing faults may be possible by monitoring of the second-harmonic current     

Secondary data — the Poor Relative of Business Continuity

Cable & Wireless Plc acquired Exodus on the 1st February 2002.You think you’ve got BCP covered because you take regular backups and store them safely off site and perhaps even encrypt them … Think again. There is a whole plethora of devices and programs that facilitate your users accessing that data after you have dutifully restored it from your backup medium of choice. These facilitators contain secondary data and this data needs backing up and security measures as well, otherwise your primary data will resemble a newly restored vintage car: great looks, but no leaded gasoline available to run on.     

Polymer-Derived SiOC/ZrO2 Ceramic Nanocomposites with Excellent High-Temperature Stability

Polymer-derived SiOC/ZrO₂ ceramic nanocomposites have been prepared using two synthetic approaches. A commercially available polymethylsilsesquioxane (MK Belsil PMS) was filled with nanocrystalline zirconia particles in the first approach. The second method involved the addition of zirconium tetra( n -propoxide), Zr(OⁿPr)₄, as zirconia precursor to polysilsesquioxane. The prepared materials have been subsequently cross-linked and pyrolyzed at 1100°C in argon atmosphere to provide SiOC/ZrO₂ ceramics. The obtained SiOC/ZrO₂ materials were characterized by means of X-ray diffraction, elemental analysis, Raman spectroscopy as well as transmission electron microscopy. Furthermore, annealing experiments at temperatures from 1300° to 1600°C have been performed. The annealing experiments revealed that the incorporation of ZrO₂ into the SiOC matrix remarkably increases the thermal stability of the composites with respect to crystallization and decomposition at temperatures exceeding 1300°C. The results obtained within this study emphasize the enormous potential of polymer-derived SiOC/ZrO₂ composites for high-temperature applications.