Weak and strong stabilization of linear systems

We study the problem of stabilizing a distributed linear system on a subregion of its geometrical domain. We are concerned with two methods： the first approach enables us to characterize a stabilizing control via the steady state Riccati equation, and the second one is based on decomposing the state space into two suitable subspaces and studying the projections of the initial system onto such subspaces. The obtained results are performed through various examples.     

Technical Note Photointerpretation of Pleistocene Mediterranean ridges south-west of Alexandria

Abstract

The Pleistocene ridges south-west of Alexandria are of marine origin and represent the ancient shoreline of the former sea levels. Several authors have described the nature, origin and geomorphology of the Pleistocene ridges. The objective is to delineate these ridges using aerial photomosaics at 1:100000 scale and a Landsat image at 1:250000 scale.

The area is covered by beach sands in the northern part and consolidated limestone forming coastal ridges southwards. The lowlands between the ridges are occupied by marshes, lagoons or mixtures of clay and lime materials. Plant cover occurs in the central part. The different ridges recognized photogeologically are eight ridges and the foreshore ridges are more distinct than those of the backshore. Owing to the presence of plant cover, some ridges appear as faint lines. The ridges and lowlands appear on photomosaics with tonal contrast where successive light and dark toned areas can be easily identified. The interpreted ridges were correlated with those in the topographic map with the same scale and covering the same area. It was found that a number of these ridges follow the configuration of the relief where they are represented by high peaks. Ridges appear as elongated alignments nearly parallel with the Mediterranean Sea shore with a general trend NE-SW. The presence of some minerals such as augite and the size of their grains indicate that the sea currents and prevailing wind directions were coming mainly from the east or north-east whereas the reverse case occurs nowadays. Photointerpretation indicated the presence of a number of fractures trending NW-SE, dissecting the ridges in the northern part of the area.     

Application of Ellipsometry to Evaluate Surface Cleaning Effectiveness

Mechanisms associated with the cleaning of food contact surfaces are not completely understood, and attempts to evaluate or improve cleaning processes are consequently hindered. The usefulness of ellipsometry as a technique to rate efficiency of different cleaning methods with respect to ability to remove milk soils from various materials is described. Film properties obtainable with ellipsometry, including a measure of the apparent mass remaining on a given surface after cleaning, can be used to provide an indication of the relative effectiveness of a cleaning method. This information contributes to establishment of criteria by which the effectiveness of a cleaning operation can be judged.     

Parallel Structural Analysis Using Threads

Practical solution of the structural analysis problem in a parallel processing environment is investigated through the use of the notion of cheap concurrency and the concept of threads. A thread is a lightweight process or independent instructions executing agent capable of concurrent execution with other threads. Portions of a structural analysis code implemented in C have been parallelized employing the Encore Parallel Threads on an Encore Multimax multiprocessor computer. The issues of racing condition, synchronization, and mapping are considered and discussed. Two synchronization mechanisms, semaphores and monitors, have been employed and compared. Two different mapping strategies have been implemented and studied. Results are reported on the effect of amount and frequency of shared memory access on the speed-up, the overhead time required for creating threads, and comparison of overall computational time performance using two space truss examples. An overall efficiency of 90–95% was achieved for 11 processors.     

The Organization of Product Development

This paper develops a critical perspective on the theory underlyingcontemporary product development practice. It contrasts whatis today the dominant approach to design and product development,an approach that is analytical and problem-oriented, with analternative approach that is interpretative and process-oriented.The interpretative approach views product development as enteringinto an ongoing process in which people are already engaged.It sees the interactions between the different communities involvedin product development as a set of ongoing conversations. Itsuggests the need for a set of conceptual tools for managingthis process which are quite distinct from those associatedwith the analytical approach.     

On the evaluation of transition matrices in finite fields

A technique for evaluating the transition matrix A^k of a linear sequential machine has been given by Seherba and Roesser by transforming matrix A into a matrix A_R in the real field, finding the powers A_R ^k of.A_R In in the real field and then transforming A_R ^k back to finite field. A technique for the same problem is suggested by carrying out all the computations in the finite field only, thus avoiding the cumbersomeness of the earlier technique.     

SIMULATION AND STATIC BIFURCATION BEHAVIOR OF INDUSTRIAL FCC UNITS

A relatively simple model of optimum degree of sophistication for riser-reactor industrial fluid catalytic cracking (FCC) units is developed. An efficient iterative computer code is developed for the solution of the nonlinear two-point boundary value model equations. Sets of data for three industrial units are used to adjust the parameters of the model. Independent sets of data for each unit are used to verify the reliability of the model without any adjustable parameters. The model is used to investigate the static bifurcation behavior and its implications for design, operation, and control.     

Non-linearity detection of weakly non-linear dynamic systems using cumulants

Non-linearity detection in dynamic systems is a fundamental issue in non-linear system identification. This problem is treated with the aid of the perturbation technique. A criterion for the detection of even non-linearities is developed in terms of the third-order cumulants of vector stochastic processes.     

APPLICATION OF WLF AND ARRHENIUS KINETICS TO RHEOLOGY OF SELECTED DARK-COLORED HONEY

The rheological properties of Common Black Horehound, Globe Thistle, and Squill types of dark‐colored Jordanian honey were examined. The types of honey used were identified via assessing the source of nectar using pollen analysis (Melissopalynology). The apparent viscosity, η, was measured as a function of the shear rate, γ. In addition, the apparent viscosity was measured, at constant shear rate (6.12 s^?1), as a function of shearing time. Newton's law of viscosity (i.e., τ=ηγ) was found to adequately (R²～ 0.99) describe the flow behavior of honey samples. The apparent viscosity was found to decrease with temperature, and the temperature dependence of viscosity was contrasted versus both Arrhenius model (η=η_oe^Ea/RT) and WLF model (η/η_G= 10 (C₁(T–T)/C₂+(T–T_G))). Although Arrhenius kinetics may fit the viscosity versus temperature data for the examined types of honey, nevertheless, it gives a relatively high value of activation energy that is quite comparable with, if not even larger than, that of a typical chemical reaction. On the other hand, WLF‐model was found to adequately describe the data while at the same time it gives quite reasonable values of both T_G and η_G, which are in agreement with those cited in literature.