Required steps for successful design and implementation of simulation

Use of simulation modeling as a tool to address manufacturing issues enables the modeler to measure the performance of the existing or proposed systems under different operating schemes. It can help management make basic evaluations of the different options. Therefore, simulation of the system's operation has rapidly become one of the most useful and common applications of computers. But, along with the prevailing use of simulation has come a great deal of misuse. Underlying all misuses is lack of knowledge. In this article the process of simulation modeling, data collection, common pitfalls in simulation modeling and its implementations, data analysis, output interpretation design of simulation experiments, and training requirements are described.     

Rectifier-Inverter Frequency Changers with Suppressed DC Link Components

Rectifier-inverter types of static frequency changers (SFC's) typically employ bulky dc link reactive components to establish the required dc bus voltage. The negative effects of these components on overall system performance and evolution have been the subject of many past research publications. It is demonstrated that these unwanted components can be eliminated through the use of suitable SFC power circuit topologies. Two such topologies (i.e.,SFC Structures 1 and 2) are investigated here. These converter structures employ state-of-the-art power semiconductor components and optimized rectifier-inverter switching schemes. Finally, theoretical and experimental results show that proposed converter structures offer significant performance improvements at the cost of only moderate power and logic circuit complexity.     

Application of the CPA code of ethics: Towards integrating the science and practice of psychology.

Comments on S. Harvey's (see record 1994-43015-001) article on using the Canadian Psychological Association's Code of Ethics for psychologists in an organizational case. Harvey demonstrates that the Code of Ethics can be used as a metatheoretical framework that may lead to an integrated value system. The code must become part of the shared background of scientific activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Investigation of the Electronic Structure of Y2Cu2O5–xSx(x — 0.0, 0.25, 0.75) by X-ray Emission Spectroscopy and Xα Scattered Wave Calculation Methods

The investigation of the electronic properties of various copper oxides, containing structural fragments with specific Cu-O polyhedra, has been carried out. The electronic structure of Y₂Cu₂O_5–xS_x compounds (x = 0.0, 0.25, 0.75) has been studied by X-ray emission spectroscopy and the X_α scattered wave (SW) method of calculation. It is shown that substituting apical oxygen by sulfur in the squarepyramid fragments in high-temperature superconductors will result in a decrease of the density of hole carriers in "superconducting" grids of CuO₂ and in the suppression of superconductivity .     

Transmission Electron Microscopic Observations of α-Cristobalite in Fused Silica

Distinct crystalline phases in some commercial fused silicas were shown by transmission electron microscopy. They were identified to be α-cristobalite by selectedarea electron diffraction. Their origin and the effect on the glass matrix are discussed.     

Axisymmetric Vibrations of Reinforced Orthotropic Shallow Spherical Caps

Axisymmetric vibrations of reinforced shallow. spherical caps manufactured from orthotropic materials are considered. The closed form solution is obtained for the natural frequency of the cap with a clamped and immovable circular edge by assuming that the motion component parallel to the cap boundary plane (in plane) is negligible. Parametric studies are performed to assess the effect of various geometric and structural parameters on the natural frequency of the cap and, most importantly, to identify the most influencing parameters of the problem. From the generated data, it is concluded that the national frequency increases with increasing extensional stiffness and eccentricity of reinforcements and to a lesser extent with increasing bending stiffness of reinforcements. Other important parameters include the base circle radius and the initial rise of the cap.     

Analyzing Dynamic Behavior of Geosynthetic-Reinforced Soil Retaining Walls

An advanced generalized plasticity soil model and bounding surface geosynthetic model, in conjunction with a dynamic finite element procedure, are used to analyze the behavior of geosynthetic-reinforced soil retaining walls. The construction behavior of a full-scale wall is first analyzed followed by a series of five shaking table tests conducted in a centrifuge. The parameters for the sandy backfill soils are calibrated through the results of monotonic and cyclic triaxial tests. The wall facing deformations, strains in the geogrid reinforcement layers, lateral earth pressures acting at the facing blocks, and vertical stresses at the foundation are presented. In the centrifugal shaking table tests, the response of the walls subject to 20 cycles of sinusoidal wave having a frequency of 2 Hz and of acceleration amplitude of 0.2g are compared with the results of analysis. The acceleration in the backfill, strain in the geogrid layers, and facing deformation are computed and compared to the test results. The results of analysis for both static and dynamic tests compared reasonably well with the experimental results.