Non-linear bending analysis of laminated sector plates using Generalized Differential Quadrature

Non-linear static analysis of laminated sector plates with any combination of clamped, simply supported and free edges is presented using Generalized Differential Quadrature (GDQ) method. Particular interest of this study is large deformation of asymmetric sector plates with free edges. Based on the first-order shear deformation theory and von Kármán type non-linearity, the governing system of equations include a system of 13 partial differential equations (PDEs) in terms of unknown displacements, forces and moments. Successive application of the GDQ technique to the governing equations resulted in a system of non-linear algebraic equations. The Newton–Raphson iterative scheme is then employed to solve the system of non-linear equations. Illustrative examples are presented to demonstrate accuracy and rapid convergences of the method with small number of grid points. Predictions of the presented method show very good agreement with other numerical studies available in the literature. Further results for asymmetric laminated sector plates with free edges are also presented for future references.     

Coordinate Transformations with Multiple Computer-generated Optical Elements

Abstract

An afocal system for coherent optical coordinate transformation using computer-generated holograms is presented. The afocal geometry allows cascading of transformations and simple incorporation into optical systems. A two-element afocal transformation system from Cartesian to log-polar coordinates, and a three-element cascaded afocal transformation system from polar to Cartesian coordinates, are presented for simple objects.     

Digital imaging with a pressured xenon filled MWPC working at a high data rate

A MWPC based detection system for medical imaging is presented. The system consists of a pressurized Xenon filled MWPC and of a monochromatic, fluorescent, X-ray source using a conventional diagnostic tube with various target/filter combinations. The main performance of the system are: 10% efficiency, 30% energy resolution, 500 μm spatial resolution, ±5 uniformity. The preliminary results of the application of this system to bone densitometry are presented.     

Precise integration methods based on Lagrange piecewise interpolation polynomials

This paper introduces two new types of precise integration methods for dynamic response analysis of structures, namely, the integral formula method and the homogenized initial system method. The applied loading vectors in the two algorithms are simulated by the Lagrange piecewise interpolation polynomials based on the zeros of the first Chebyshev polynomial. Developed on the basis of the integral formula and the Lagrange piecewise interpolation polynomial and combined with the recurrence relationship of some key parameters in the integral computation suggested in this paper with the solving process of linear algebraic equations, the integral formula method has been set up. On the basis of the Lagrange piecewise interpolation polynomial, and transforming the non‐homogenous initial system into the homogeneous dynamic system, the homogenized initial system method without dimensional expanding is presented; this homogenized initial system method avoids the matrix inversion operation and is a general homogenized high‐precision direct integration scheme. The accuracy of the presented time integration schemes is studied and is compared with those of other commonly used schemes; the presented time integration schemes have arbitrary order of accuracy, wider application and are less time consuming. Two numerical examples are also presented to demonstrate the applicability of these new methods. Copyright © 2008 John Wiley & Sons, Ltd.     

A comparative study on the environmental impact of supermarket refrigeration systems using low GWP refrigerants

Supermarket refrigeration systems have high environmental impact due to their large refrigerant charge and high leak rates. Consequently, the interest in using low GWP refrigerants such as carbon dioxide (CO₂) and new refrigerant blends is increasing. In this paper, an open-source Life Cycle Climate Performance (LCCP) framework is presented and used to compare the environmental impact of four supermarket refrigeration systems: a transcritical CO₂ booster system, a cascade CO₂/N-40 system, a combined secondary circuit with central DX N-40/L-40 system, and a baseline multiplex direct expansion system utilizing R-404A and N-40. The study is performed for different climates within the USA using EnergyPlus to simulate the systems' hourly performance. Further analyses are presented such as parametric, sensitivity, and uncertainty analyses to study the impact of different system parameters on the LCCP.     

Electromagnetic system for determining the mutual angular position of two objects in space

A magnetometric method is proposed for determining the mutual angular position of two objects in space. A system of nonlinear equations that must be solved numerically is introduced. Results are presented from a computer analysis of solutions that are obtained for the system, and a structural diagram of an instrument that was developed is presented together with experimental data from the measurement of angles. It is shown that the proposed system makes it possible to determine the mutual angular position of two objects with a random error of 0.03°. Translated from Izmeritel'naya Tekhnika, No. 9, pp. 35–38, September, 1999.     

Time-redundant system reliability under randomly constrained time resources

The paper considers the time-redundant system where the system total task is a sequence of n phases and the total task must be executed during constrained time. For every phase, there is its own server, which executes the phase task during randomly distributed time. The server is not perfectly reliable and two types of failure (“open” and “closed”) are possible. Redundant servers may be used in any phase. The time–probability characteristics are introduced for any task, based on which the system reliability is treated as a probability that the system total task will be correctly completed during a corresponding time resource, which also may be randomly distributed. The adequate model is presented and a semi-Markov process is used as a mathematical technique. The closed-form solution was derived based on an acyclic Semi-Markov process. The numerical example of the elaborated approach is presented.     

Parallel algorithms for generating combinatorial objects on linear processor arrays with reconfigurable bus systems

A bus system whose configuration can be dynamically changed is called reconfigurable bus system. In this paper, parallel algorithms for generating combinations, subsets, and binary trees on linear processor array with reconfigurable bus systems (PARBS) are presented. Preliminary version of this paper has been presented at the 6th National Seminar on Theoretical Computer Science, held at Bhanasthali Vidyapith, Aug. 8–12, 1996     

A frequency‐locked position servo control system by microprocessor‐based slope‐varied technique

Abstract

A microprocessor‐based slope‐varied frequency‐pumped controller (μP‐SVFPC) for improving the locking performance of the frequency‐locked position servo control system (FLPS) is presented. The presented slope‐varied pump technique is to perform the position control process fast for a long distance servo, while nearly similar acquisition times for different distance servos are obtained during the servo range. The motion profiles for system locking are adaptively generated according to the coming frequency error. No motion profiles are required to be pre‐installed in the controller. A prototype of μP‐FLPS is realized, simulated, and tested. Computer simulation and experimental result confirm that the system acquisition times of μP‐FLPS for short, middle, and long distance servos are nearly similar to each other. In comparison with the basic FLPS system, the acquisition times of the presented μP‐FLPS for the middle and long distance servos are improved by about 58% and 85%, respectively.     

A logic flowgraph-based concept for decision support and management of nuclear plant operation

The architecture of au automated decision support system for nuclear plant operators is presented and discussed. The system is based on the use of ‘logic flowgraph’ process models and is designed in a hierarchical fashion. Its functionality spans from ‘function oriented’ plant status and alternative success path information displayed to the plant operators at its higher access levels to ‘process oriented’ diagnostic and recovery information deduced and displayed at its lowest. The design basis for this architecture is the ‘defense in depth’ plant safety concept. The decision support system goal is to provide plant operators, in the presence of an unforeseen transient, with the best and safest alternative between plant stabilization after shutdown and recovery of normal operation based on early diagnosis. Examples of the system capability to interpret and diagnose abnormal plant conditions and of the information that it can supply to the operators at its three access levels are presented and discussed.     

The embedded discontinuous Galerkin method: application to linear shell problems

A new discontinuous Galerkin method for elliptic problems which is capable of rendering the same set of unknowns in the final system of equations as for the continuous displacement‐based Galerkin method is presented. Those equations are obtained by the assembly of element matrices whose structure in particular cases is also identical to that of the continuous displacement approach. This makes the present formulation easily implementable within the existing commercial computer codes. The proposed approach is named the embedded discontinuous Galerkin method. It is applicable to any system of linear partial differential equations but it is presented here in the context of linear elasticity. An application of the method to linear shell problems is then outlined and numerical results are presented. Copyright © 2006 John Wiley & Sons, Ltd.     

DESIGN AND CONTROL SENSITIVITY ANALYSIS OF MULTIPLE HYPERELASTIC BODY SYSTEMS

A statement of Hamilton's principle for a multiple-body system in the finite theory of elasticity is presented. Surface interaction, among the bodies and with the ground, is materialized by kinematic boundary condition, holonomic constraints, a potential and a dissipation function. As additional data, there are body forces and tractions, and three kinds of time limit conditions. The design and control of the system is defined by a parametric representation of data. Material properties, time interval of analysis and control discontinuities are considered. An incremental form of Hamilton's principle is presented, in connection with a perturbation of the data. The virtual work of stress, global and incremental, is represented by differential operators and transformation laws for these operators, under rigid-body motions, are derived. Sensitivity analysis results by the adjoint method for a mechanical system with small strains overlying large rigid-body motions are presented.     

The vibration and pull-in mechanism of two coupled elastically restrained beams assembly subjected to electrostatic force

ABSTRACT

The novel model of the coupled beam-type electrodes with elastic roots, subjected to the AC and DC voltages is constructed. The exact critical pull-in voltage of the two coupled elastically restrained beams with size effect is presented. The analytical method of the general system subjected to the AC and DC voltages simultaneously is presented. The characteristic mechanism of coupled vibration is investigated.     

Accurate interferometric system to perform the substrate focusing and alignment in laser writing processes

Abstract

A simple, low cost system useful in laser writing processes to set the focal spot on the substrate surface with micrometre precision is described. Evaluation of its sensitivity is also presented. The lack of essential critical adjustments accounts for the utility of this system and its performance.     

Investigation into the use of solid nitrogen to create a “Thermal Battery” for cooling a portable high-temperature superconducting magnet

The design of a portable, “stand-alone” cooling system, for use with a high-temperature superconducting (HTS) magnet, is discussed. The HTS magnet is used to propel a magnetohydrodynamically powered model boat (approximately 120 cm × 60 cm). The aim of this investigation was to establish the suitability of solid nitrogen for use in the stand-alone cooling system, and determine the optimum method for exploiting its cooling power. It was found that obtaining good thermal contact between solid nitrogen and its container is very difficult if the nitrogen is frozen under vacuum, due to the formation of a thermal barrier between the nitrogen and its container. This problem is overcome if the nitrogen is frozen via conduction cooling from cold helium gas (at ∼4.2 K); and the design for a near isothermal “thermal battery” based on this principle is presented. This thermal battery has been constructed and integrated into the HTS magnet system onboard the model boat, and the results from the first trials of this system are presented here.     

Performance of real-time distributed arrival time control in heterarchical manufacturing systems

A highly distributed feedback control algorithm for autonomous part entities in heterarchical manufacturing systems is presented in this paper. A difference equation-based model is developed to analyze the discrete time dynamics of the resulting nonlinear control system. Control parameters are found analytically that guarantee that the system is bounded under disturbances. The dynamic response to: (i) changes in due dates; and (ii) the bulk arrival of parts is presented. The ability of the system to exponentially reduce the mean and variance of due-date deviation in the single machine case makes it an attractive option for real-time control of just-in-time production.     

人工神经网络-研究制冷系统的新方法

本文介绍了应用于工程研究中的MLP、RBF神经网络的结构及学习训练算法，结合实例详述了将人工神经网络技术应用于制冷系统研究的各种途径，分析了神经网络应用的难点及解决办法，并指出人工神经网络技术在制冷系统研究中的应用方向。     

Reliability of an Independent Component,s-Spare System with Exponential Life Times and General Repair Times

In this paper, the reliability of a system with N independent components supplied with a pool of s spares is investigated. The components have an exponential life time distribution and the failed components are repaired, one at a time, with a general repair time distribution. Numerical results are presented for the mean time to system failure (system is said to fail when a component fails with no spare available) and the reliability of the system in some special cases of interest.