STABILITY OF THE FILM MODEL FOR MULTICOMPONENT MASS TRANSFER

The computational algorithm for calculating rates of mass transfer in multicomponent mixtures using the film model proposed by Krishna and Standart can be unstable for certain physical processes. Successful prediction of the molar fluxes can usually be achieved by evaluating the diffusive fluxes at the appropriate position on the diffusion path.     

Seasonal Unit Root Tests Based on Forward and Reverse Estimation

In this paper, we suggest a new set of regression-based statistics for testing the seasonal unit root null hypothesis. These tests are based on combining conventional Hylleberg et al . (1990 ) -type seasonal unit root test statistics calculated from both forward and reverse estimation of the auxiliary regression equation. We derive the asymptotic distributions of the new test statistics under the seasonal unit root null hypothesis. We provide finite sample critical values appropriate for the case of quarterly data together with asymptotic critical values, the latter appropriate for any seasonal aspect. Monte Carlo simulation of the finite-sample size and power properties of the new tests reveals that, overall, they perform rather better than extant tests of the seasonal unit root hypothesis.     

Locally Optimal Tests Against Unit Roots in Seasonal Time Series Processes

This paper builds on the existing literature on tests of the null hypothesis of deterministic seasonality in a univariate time-series process. Under the assumption of independent Gaussian errors, we derive the class of locally weighted mean most powerful invariant tests against unit roots at the zero and/or seasonal frequencies in a seasonally observed process. Representations for the limiting distributions of the proposed test statistics under sequences of local alternatives are derived, and the relationship with tests for corresponding moving average unit roots is explored. We also propose nonparametric modifications of these test statistics designed to have limit distributions which are free of nuisance parameters under weaker conditions on the errors. Our tests are shown to contain existing stationarity tests as special cases and to extend these tests in a number of useful directions.     

On the Fourier transform of sequency limited signals with applications to delta modulation and medicine†

It is the binary nature of the Walsh basis functions that make the Walsh transform a potentially useful signal processing tool. Unlike the FFT, which produces a database in the easily interpreted frequency domain, a Walsh data base resides in the obscure sequency domain. Using a fast Walsh algorithm, an N-point transform can, however, be computed more rapidly than a FFT using a similar computer architecture. Even though the sequency space has been shown to be useful in coding and picture processing applications, the aperiodic behaviour of its basis functions make it. unsuitable for many traditional signal-processing problems. It would be desirable, for example, to be able to relate the computationally efficient Walsh spectra to the intuitively pleasing Fourier spectra. This work will address that problem and present new results.     

Modelling of an hydraulic excavator using simplified refined instrumental variable (SRIV) algorithm

Instead of establishing mathematical hydraulic system models from physical laws usually done with the problems of complex modelling processes, low reliability and practicality caused by large uncertainties, a novel modelling method for a highly nonlinear system of a hydraulic excavator is presented. Based on the data collected in the excavator's arms driving experiments, a data-based excavator dynamic model using Simplified Refined Instrumental Variable (SRIV) identification and estimation algorithms is established. The validity of the proposed data-based model is indirectly demonstrated by the performance of computer simulation and the real machine motion control experiments.     

Modelling of an hydraulic excavator using simplified refined instrumental variable （SRIV） algorithm

Instead of establishing mathematical hydraulic system models from physical laws usually done with the problems of complex modelling processes, low reliability and practicality caused by large uncertainties, a novel modelling method for a highly nonlinear system of a hydraulic excavator is presented. Based on the data collected in the excavator＇s arms driving experiments, a data-based excavator dynamic model using Simplified Refined Instrumental Variable （SRIV） identification and estimation algorithms is established. The validity of the proposed data-based model is indirectly demonstrated by the performance of computer simulation and the.real machine motion control exoeriments.     

Proposed Structure for Calcium Silicate Hydrate Gel

Calcium silicate hydrate gel is a very poorly crystalline material that is the main product of reaction of portland cement with water. Evidence is presented for a disordered layer structure, in which most of the layers are structurally imperfect ones of jennite (Ca₉Si₆O₃₂H₂₂), and others are similarly related to 1.4-nm tobermorite (Ca₅Si₆O₂₆H₁₈), both structures being modified by omission of many of their silicate tetrahedra. The evidence comprises conditions of formation, silicate anion type, Ca/Si ratio, H₂O/Ca ratios and densities for various drying conditions, thermogravimetric curve, X-ray powder and selected-area electron diffraction patterns, and results of analytical electron microfcopy.     

A FINITE POINT METHOD IN COMPUTATIONAL MECHANICS. APPLICATIONS TO CONVECTIVE TRANSPORT AND FLUID FLOW

The paper presents a fully meshless procedure fo solving partial differential equations. The approach termed generically the ‘finite point method’ is based on a weighted least square interpolation of point data and point collocation for evaluating the approximation integrals. Some examples showing the accuracy of the method for solution of adjoint and non-self adjoint equations typical of convective-diffusive transport and also to the analysis of compressible fluid mechanics problem are presented.