ALBERT

Notizen: Purpose - Optimisation in electromagnetics, based on finite element models, is often very time-consuming. In this paper, we present the space-mapping (SM) technique which aims at speeding up such procedures by exploiting auxiliary models that are less accurate but much cheaper to compute. Design/methodology/approach - The key element in this technique is the SM function. Its purpose is to relate the two models. The SM function, combined with the low accuracy model, makes a surrogate model that can be optimised more efficiently. Findings - By two examples we show that the SM technique is effective. Further we show how the choice of the low accuracy model can influence the acceleration process. On one hand, taking into account more essential features of the problem helps speeding up the whole procedure. On the other hand, extremely simple auxiliary models can already yield a significant acceleration. Research limitations/implications - Obtaining the low accuracy model is not always straightforward. Some research could be done in this direction. The SM technique can also be applied iteratively, i.e. the auxiliary model is optimised aided by a coarser one. Thus, the generation of hierarchies of models seems to be a promising venue for the SM technique. Originality/value - Optimisation in electromagnetics, based on finite element models, is often very time-consuming. The results given show that the SM technique is effective for speeding up such procedures.

Notizen: Purpose - To compare the profitability and technical efficiency of firms in a monopoly industry, airports, operating with different degrees of market power and under differing regulatory regimes, minimalist in New Zealand and interventionist in Australia. Design/methodology/approach - Unlike previous privatisation studies, this study measures efficiency and profitability separately. Using data envelopment analysis (DEA), the technical efficiency of privatised airports is assessed, and this independent measure is used in regression analyses to determine whether efficiency, regulation or privatisation is related to airport profitability. Findings - For firms with monopolistic characteristics operating under minimalist regulation, profitability is related to market power, not efficiency improvements. For firms operating in a regulated environment, profitability is related to regulation, which constrains market power but does not impede efficiency. Research limitations/implications - This study is limited by its small sample size and its generalisability due to its single industry and regional focus. However, the findings support assertions that the impact of privatisation cannot be assessed independently of industry structure and regulation. Practical implications - Policy makers considering SOE privatisation in non-competitive markets should introduce either competition or regulation if firm efficiency is a desired outcome. Originality/value - Academics and policy makers should be aware that privatisation and competition are not only complementary, as per the extant literature, but they are essential bedfellows. In the absence of competition, regulation is required to control for market power.

Notizen: Purpose - To produce a controlled stirring in a low conducting liquid thanks to a new kind of multiphase inductor. Design/methodology/approach - An experimental pilot consisting of a cylindrical salt water pool surrounded by an innovative multiphase inductor configuration, based on the single phase asynchronous motor principle, is setup. The maximum bulk stirring velocities are measured and compared with the estimate by numerical modelling. Findings - Shows the possibility of controlling the stirring of a low conducting liquid thanks to a multiphase inductive system. The corresponding measurement results give a significant bulk velocity of a few centimetres per second. Practical implications - This new kind of multiphase inductor, working with a single phase induction generator, seems a promising way to produce a controlled stirring in low conducting media which cover a large range of induction applications. Originality/value - Such an innovative inductor configuration has already been tested successfully for metal alloys stirring in the middle frequency area. In this paper, an extension of this kind of multiphase inductive system for electromagnetic stirring of low conducting liquids like electrolytes in the high frequency area is presented.

Notizen: Purpose - To investigate the general necessary condition for synthesis of square, real rational matrices of complex frequency as admittance matrices of active multiports with resistors, inductors, capacitors and possibly multiport transformers and to prove that this condition is also sufficient for synthesis of stable, square, real rational matrices of complex frequency as admittance matrices of balanced active multiports having only resistors, capacitors and voltage-amplifiers with sufficiently large amplifications. The main aim of the paper is to provide a new and general method for stable admittance matrices synthesis and to develop strict realization algorithm by active balanced transformerless multiport networks. Design/methodology/approach - The objectives of the paper are achieved by using factorization of regular polynomial matrices in complex frequency with certain degree as products of other regular polynomial matrices with specified degrees. A set of sufficient conditions for such a factorization is presented and derived a pertinent algorithm as the starting point for investigation and solving network synthesis problem and generation of class of equivalent realizations. Findings - Theorem 1 states that sufficient condition for factorization of Pth order, generally regular polynomial matrix P(s) in complex frequency s with degree L, whose determinant has K distinct zeros, in form P(s)=P1(s)·P2(s), where 1=p2=P20=L-1 is degree of polynomial matrix P2(s), reads: K〉(P-1)·L+p2-1. The coefficient-matrices of s, s2,... in P1(s) and P2(s) are real or complex depending on whether distinct zeros of det?P(s) are real or complex, respectively. Theorem 2 states that: (a) for realization of Pth order matrix of real rational functions in complex frequency s (i.e. RRF matrix) as admittance matrix of active balanced RLC P-port network with multiport transformers, or without them, P generalized controlled-sources and P controlling-ports are necessary, in general; and (b) P balanced voltage-controlled voltage-sources (VCVSs) with real and by module greater than unity controlling coefficients ("voltage amplifications") are sufficient for realization of stable admittance RRF matrix by active, balanced, transformerless, RC P-port network. Originality/value - This is a research paper with the following two main contributions (original results). First, a theorem on sufficient conditions for factorization of regular polynomial matrices in complex frequency; and second, a theorem relating to sufficient conditions for synthesis of matrices of real rational functions in complex frequency by active, balanced, transformerless networks. The results may be interesting for network theorists and researchers in the field of electric circuits and systems.

Notizen: Purpose - The aim of this paper is to obtain an extensive experimental characterization of a DC magnetron sputtering device used for plasma processing of materials. Design/methodology/approach - Models and measurements are combined for an interdisciplinary characterization of a DC magnetron sputtering device. Langmuir probes are used for the plasma characterization; the magnetic field is measured by using Hall probes and the data are used to validate a magnetostatic three-dimensional numerical analysis of the device; precision mechanical measurements are done for the target erosion profile and the results are related to a simple estimation formula; a simple model is proposed for the target heating. Findings - Data on magnetic and electric fields, electron temperature and density, plasma potential and target erosion are provided. An estimation of the target heating is proposed. Finally, an application concerning thin film deposition is reported. Research limitations/implications - Measurement of the target surface temperature for the validation of the proposed target heating estimation has not been done. Originality/value - In the field of the electromagnetic processing of materials, the reported extensive device characterization is a valuable set of information for an optimized utilization of DC magnetron sputtering devices.

Notizen: Purpose - In this paper, a new method for estimating iron loss under a distorted elliptical rotating flux is proposed. Design/methodology/approach - In order to precisely analyze the iron loss of rotating machines, the iron loss under distorted rotating flux should be taken into account. However, reports of precise analysis considering measured iron loss data under rotating flux are few. Findings - The iron loss of surface permanent magnet (SPM) motor model proposed by the investigation committee of IEE of Japan is estimated using the proposed method. The experimental examination is carried out by measuring the iron loss of the motor using a torque meter. Originality/value - Examines an estimation method of iron loss of motors.