Study on ASTM E399 and ASTM E1921 standards

Costs of ASTM E399 and ASTM E1921 tests, which were developed to determine the fracture toughness (K_Ic) and the ductile–brittle transition temperature of ferritic steels, respectively, are considered high and the procedures are also very complicated. In this study, a method, which is more cost‐effective and easier to carry out, is proposed.     

Discrete two-time-scale systems

In this paper reduced-order modelling and control analysis of linear, discrete-time systems having dominant and non-dominant modes are presented. Decoupling of modes is achieved using an explicitly invertible linear transformation. A matrix norm condition is derived, the satisfaction of which enables approximate expressions for the block-diagonalizing matrices, eigenvalue distribution and state trajectories to be obtained. Design of stabilizing feedback controllers is developed and it is shown that two gain matrices are needed for separate assignment of dominant and non-dominant eigenvalues. The theoretical analysis is illustrated by control system examples.     

Technical note: On a slight mis-registration of AVHRR channels 3 and 4

Abstract

When using multispectral techniques that exploit the channels of the Advanced Very-High Resolution Radiometer (AVHRR), it is assumed that the radiation measured in the different channels emanates from the same place. Evidence is presented to suggest that for one particular pass of NOAA-7, there was a mis-registration of about one-quarter of a pixel between AVHRR channels 3 and 4. A simple correction is shown to be effective in this case.     

The use of pseudo and oblique pseudo-inverse matrices in power system state estimation algorithms

The applications of generalized, pseudo and oblique pseudo-inverse matrices to both linear and non-linear state estimation algorithms are studied. Examples showing the solutions to power system network state estimation problems are given along with computational schemes for the matrices. The oblique pseudo-inverse matrix is shown to be particularly useful when parts of the system are effectively isolated because of lost data measurements.     

Linear optimal control of national econometric models

A control optimization approach is developed in this paper for the purpose of investigating the impact of alternative development strategies on the national economy of Egypt. Basic to this approach is the formulation of an aggregate econometric model and the manipulation of its performance as a linear quadratic tracking problem. The model comprises three major sectors ; namely agriculture, industry and services. Data processing and model parameter estimation and implementation are performed for the period 1961–1976 and further projected to the period 1976–1980. In light of the assumptions made, the obtained results are interpreted and found to be satisfactory.     

AN EXACT QUADRATIC STATE ESTIMATION ALGORITHM USING LINEAR PROGRAMING

ABSTRACT

This paper presents a linear programming approach to an iterative, exact, and fast state estimation algorithm. The exactness of the algorithm is enhanced via retaining the nonlinearity of the problem. The cartisian form of the quadratic system equations is adopted. Taylor&squo;s expansion of these equations contains terms up to second order only. The estimation algorithm is formulated as a constrined linear optimization problem with no approximation. During the iterative process both the objective function and coefficients of constraint matrix need not be updated. Rather, only a simple modification is to be introduced in the constraint inequalities. The performance of the proposed estimator is examined for different applications. Simulation results show that the proposed estimator combines the advantages of a better estimation accuracy provided by nonlinear approaches, and high computational speed of linear approaches.     

Application of multivariate statistical analyses in the differentiation between two phosphate ores from the Nuba Mountains,Sudan

In previously published research, uranium abundance and major and trace element content were determined in phosphate ore samples from the Kurun and Uro areas of the Nuba Mountains in Sudan. The current work aims to characterise and differentiate between the phosphate ores from these two areas by subjecting the obtained geochemical data to quantitative and qualitative statistical analyses. Multivariate statistical analyses and correlation studies show several geochemical differences in the occurrence of uranium in Kurun and Uro phosphate ores. Uranium in Uro phosphate ore shows a higher degree of mobility coefficient of variability (CV%?=?91) than that in Kurun phosphate ore (CV%?=?48). Kurun and Uro phosphate ores are found to be good sources of titanium and strontium. The average concentrations of Ti and Sr in Uro phosphate ore are 4880 and 2780?mg?kg^–1, respectively. The corresponding values in Kurun phosphate ore are 7300 and 2630?mg?kg^–1, respectively. A cluster analysis of trace elements demonstrates that both Ti and Sr, which are the most abundant trace elements, appear in individual groups or in sub-groups. Uranium behaves in the same manner in both phosphate ores in that it associates in groups containing all the transition metals except for the most abundant trace element, titanium.     

A MODIFIED DECOMPOSITION ALGORITHM FOR SCHEDULING PROBLEMS

A decomposition approach developed by the author is modified to reduce the computational effort involved. The modified algorithm is discussed. Computational experiments have been conducted for comparative evaluation of both original and modified decomposition algorithms. Significant results are reported.     

Hierarchical dynamic optimization for induction motors regulation

A hierarchical dynamic optimization technique is developed to tentatively regulate the performance of non-linear induction motor systems. The decomposition process of the non-linear model is achieved using a new method called the parameters-transformation method. Manipulation of the interaction patterns is performed via a predictive-type algorithmic procedure. The developed computation structure has the features of relatively simple calculations at the lower level, minimal storage requirements at the higher level, moderate information processing between hierarchical levels and guaranteed convergence properties.