Effect of various dither forms on quantization errors of ideal A/Dconverters

The quantization error of a quantizer (ideal A/D converter) is investigated. Correlation between quantization error and quantizer input is considered. The input signal is taken as a sinusoid due to its importance in instrumentation systems. The cases of no dither, uniform dither, and discrete (digital) dither are considered. Effects of the dither probability density function (PDF) are discussed. The relationship between uniform dithered and discrete dithered quantizer inputs is derived. Spectra of the average quantization error, corresponding to an arbitrary input signal, are investigated. Different dither forms (Gaussian, uniform, and discrete) are compared, and the effects of the dither PDF are discussed. A quantitative basis for comparing dither forms, and hence, selecting the one most appropriate for a particular application, is provided     

Comments, with reply, on ;Characterization of piezoceramics' by M. Brissaud

The commenters note that when M. Brissaud, in the above-titled paper (see ibid., vol.38, no.6, p.603-617, 1991), attempted to solve several piezoceramic bar, plate, and disk problems by superposition of bulk longitudinal waves, he neglected the shear wave contributions. Therefore, the commenters suggest that his solutions do not satisfy the appropriate stress-free boundary conditions. Brissaud, responding to the comments, discusses the validity of the models used.     

Comments, with reply, on `A digital frequency independentphasemeter' by A. Nemat

The commenters point out that the phase-measurement scheme presented in the above-titled paper by A. Nemat (see ibid., vol.39, p.665-7, Aug. 1990) is essentially the same as that previously presented by the commenters (Proc. IEEE, vol.72, p.397-8, Mar. 1984). In fact, it is suggested that the former scheme is a special case of the latter one when the counting time interval τ is equal to the time period T _s of the signals. In reply, Nemat agrees that his scheme can be regarded as another approach to achieving the same goal. He goes on to point out some differences between his approach and that of the commenters     

Comments with reply, on `A simple technique for analog tuning offrequency synthesizers' by J.P. Hauser

The commenter points out that an analog implementation of the fractional N phase-locked loop variable frequency synthesis technique described by J.P. Hauser (ibid., vol.38, no.6, p.1141-4, 1989) results in a novel minimization of active hardware, but that there are significant performance compromises. The original author's reply is included     

Comments, with reply, on `Continuous and discrete Fouriertransforms of steplike waveforms' by W.L. Gans and N.S. Nahman

The commenters point out errors in several equations and figures in the above-titled paper (ibid., vol.IM-31, p.97-101, June 1982). N.S. Nahman takes issue with some of the corrections, rebutting them on the basis of the paper's objectives     

Comments, on `A novel digital phase meter' by K.M. Ibrahim andM.A.H. Abdul-Karim

It is pointed out that a circuit given in Fig.4 of the above-titled paper (ibid., vol.36, no.3, p.711-16, 1987) will not operate if the output of the divide by 2 counter is connected to the AND gate as it is shown     

Balancing Single Model Assembly Lines: Comments on A Paper by E. M. Dar-El (Mansoor)

In this brief note, we comment upon a statement made by E. M. Dar-El on the “computational impracticality” of a precedence matrix, enumeration method for balancing assembly lines,and show through an examination of several randomly generated, large problems, that the technique involved may indeed be quite effective in balancing assembly lines involving numerous individual work elements in a reasonable amount of computation time.     

A note on an assertion by E. Gutiérrez-Peña and A.F.M. Smith (Test, 1997, p.87)

In estimating the discrete parameter of a Binomial distribution, to choose a truncated Poisson model as the prior distribution of this parameter is shown to be unsuitable. This research has been partially supported by Proyect DGES-PB97-1403-C03     

Environment conscious manufacturing edited by S.M. Gupta and A.J.D. Lambert

The dynamic facility layout problem (DFLP) aims to minimise the sum of handling and re-layout costs by devising an individual layout for each distinctive production period. In this paper, a hybrid particle swarm optimisation (HPSO) algorithm is proposed to find near-optimal solutions of DFLP. We use a coding and decoding technique that permits a one to one mapping of a solution in discrete space of DFLP to a PSO particle position in continuous space. The proposed PSO will further use this coding technique to explore the continuous solution space. For further enhancement, the proposed PSO is hybridised with a simple and fast simulated annealing. The developed algorithm is capable of being extended to more general cases although equal area machines and standardised handling equipments with identical unit costs are assumed for the time being. Computational results show the efficiency of the proposed algorithm compared to other heuristics.