scispace - formally typeset
Search or ask a question

Showing papers by "Northeastern University (China) published in 1998"


Journal ArticleDOI
TL;DR: In this article, the authors present a numerical approach for the simulation of damage initiation and propagation causing seismic energy release during unstable failure of brittle rock, which is assumed that the radiated energy is equal to the energy stored in the element before failure is triggered.

255 citations


Journal ArticleDOI
TL;DR: This paper presents a methodology for the design of reliable control systems by using multiple identical controllers to a given plant, which provides guaranteed internal stability and H/sub /spl infin// performance, not only when all controllers are operational but also when some controller outages occur.
Abstract: This paper presents a methodology for the design of reliable control systems by using multiple identical controllers to a given plant. The resulting closed-loop control system is reliable in the sense that it provides guaranteed internal stability and H/sub /spl infin// performance (in terms of disturbance attenuation), not only when all controllers are operational but also when some controller outages (sensor and/or actuator) occur. A numerical example is given to illustrate the proposed design procedures.

139 citations


Journal ArticleDOI
TL;DR: RFPA 2D as discussed by the authors is a linear and continuum mechanics method for numerically processing nonlinear and discontinuum mechanics problems in rock failure, which allows one to model the observed evolution of the progressive failure leading to collapse in brittle rocks.

125 citations


Journal ArticleDOI
TL;DR: In this article, a path independent parameter for multiaxial fatigue damage is proposed based on the critical plane approach, where both parameters of shear strain and normal strain excursion are considered in this parameter.

97 citations


Journal ArticleDOI
TL;DR: In this paper, a dual stage preconcentration system based on flow injection on-line ion exchange and solvent extraction has been developed for flame atomic absorption spectrometry, where lead is taken as a model trace element.
Abstract: A dual stage preconcentration system based on flow injection on-line ion-exchange and solvent-extraction has been developed for flame atomic absorption spectrometry. Lead is taken as a model trace element. A column packed with Amberlite IRC-718 cation exchanger is incorporated into the FI manifold. The analyte is retained on the column by time-based sample loading and eluted by 1 mol/L HNO3. The eluate is subsequently merged with potassium iodide and tetrabutylammonium bromide (TBABr), and isobutyl methyl ketone (IBMK). Lead is extracted on-line into IBMK as the ion-pair formed between the iodoplumbate anion and tetrabutylammonium cation. The organic phase is separated from the aqueous phase by a gravity phase separator. 50 μL of concentrate is introduced into the nebulizer-burner system of the spectrometer. An enhancement factor of 550 is achieved with a 30 mL sample consumption at a sampling frequency of 30/h. The precision (relative standard deviation) is 2.4% at 10 μg/L level and the detection limit is 0.3 μg/L (3 σ). The method was successfully applied to the determination of lead in water samples.

70 citations


Journal ArticleDOI
TL;DR: In this paper, the influence of material and loading system properties including stiffness and strength on pillar failure and associated seismic patterns is studied, and the results confirm that soft loading systems promote unstable failure or collapse of pillars.

65 citations


Journal ArticleDOI
TL;DR: In this paper, the first passage of uncertain single degree-of-freedom nonlinear oscillators subjected to random excitation is examined and statistical fourth moment method is developed to determine first four moments of system response and state function.

64 citations


Journal ArticleDOI
TL;DR: In this paper, the authors defined the definition of fatigue crack initiation size and determining method were presented on the basis of the non-propagating cracks behaviour, and explained the physical significance of the initiation size from the point of view of the fatigue damage.

62 citations


Journal ArticleDOI
TL;DR: A microchip-based capillary electrophoresis (CE) system with amperometric detection, combined with flow injection (FI) sample introduction, was constructed from components readily available in the analytical laboratory.

61 citations


Journal ArticleDOI
TL;DR: The vehicle routing problem with time window (VRPTW) of combinational optimization is used to analyze and model the rolling batch planning problem and the genetic algorithm is superior to other methods.

50 citations


Journal ArticleDOI
TL;DR: This paper outlines the fundamental issues of the manufacturing design in a genetic algorithm formulation and results indicate that this new scheduling scheme is an effective and efficient technique to tackle the problem of earliness and tardiness production scheduling and planning.

Journal ArticleDOI
TL;DR: A new fuzzy method for formulating and evaluating illegal points and three new kinds of evaluation functions are proposed and a special Hybrid Genetic Algorithm (HGA) with penalty function and gradient direction search for nonlinear programming problems is developed.
Abstract: Based on the introduction of some new concepts of semifeasible direction, Feasible Degree (FD1) of semifeasible direction, feasible degree (FD2) of illegal points ‘belonging to’ feasible domain, etc., this paper proposed a new fuzzy method for formulating and evaluating illegal points and three new kinds of evaluation functions and developed a special Hybrid Genetic Algorithm (HGA) with penalty function and gradient direction search for nonlinear programming problems. It uses mutation along the weighted gradient direction as its main operator and uses arithmetic combinatorial crossover only in the later generation process. Simulation of some examples show that this method is effective.

Journal ArticleDOI
TL;DR: A method to determine the card number of the CONWIP system for a production line with a bottleneck is introduced and simulation results show that theCONWIP production control system is very efficient for the production and inventory control of semi-continuous manufacturing.

Journal ArticleDOI
TL;DR: In this article, the authors analyzed the relationship between the steady-state creep rate and the applied stress of DZ17G, a modern DS cast nickel-base superalloy used for producing turbine blades and vanes for aeroengine applications.

Journal ArticleDOI
TL;DR: A new iterative method is given for solving large sparse least squares problems and computing the minimum norm solution to underdetermined consistent linear systems and is shown to be convergent if A is full column rank.
Abstract: In this paper a new iterative method is given for solving large sparse least squares problems and computing the minimum norm solution to underdetermined consistent linear systems. The new scheme is called the generalized successive overrelaxation (GSOR) method and is shown to be convergent ifA is full column rank. The GSOR method involves a parameter ρ and an auxiliary matrixP. One can choose matrix P so that the GSOR method only involves matrix and vector operations; therefore the GSOR method is suitable for parallel computations. Besides, the GSOR method can be combined with preconditioning techniques, and therefore can be expected to be more effective.

Journal ArticleDOI
TL;DR: In this paper, the steady-state optimal state estimation problem for discrete-time stochastic singular linear systems is considered via the innovation analysis method in the time domain, and the filter, predictor and smoother are derived by using the projection formula and are calculated based on the ARMA innovation model.

Journal ArticleDOI
TL;DR: XPS, XRD and other techniques were used to study the phase, composition and valence states of W and ions of electrochromic (EC) WOx films prepared by DC magnetron reactive sputtering.
Abstract: XPS, XRD and other techniques were used to study the phase, composition and valence states of W and ions of electrochromic (EC) WOx films prepared by DC magnetron reactive sputtering. The XRD results indicate that different EC WOx films consist of different phases and compositions. XPS results reveal that W+,, W+ a and W+ i ions coexist in colored WOx films, but only W+ i ions are detected in bleached WOx films. The binding energy and the relative content of the O 1s peaks of WOx films are very different for the bleached and colored states.

Journal ArticleDOI
TL;DR: In this article, a fast method for calculating the sensitivity distributions in capacitance tomography sensors, based on the finite element method, is proposed, by fast generation of the global system matrix and capacitance values, the calculation time is reduced by 98%.
Abstract: A fast method for calculating the sensitivity distributions in capacitance tomography sensors, based on the finite element method, is proposed. By fast generation of the global system matrix and capacitance values, the calculation time is reduced by ~98%.

Journal ArticleDOI
TL;DR: An automated system for drug-dissolution studies based on the sequential-injection (SI) technique is described and evaluated for monitoring of dissolution profiles of ibuprofen tablets, sustained-release capsules and controlled-release matrix tablets as mentioned in this paper.

Journal ArticleDOI
01 Aug 1998
TL;DR: A combined due-date assignment and production planning methodology for the make-to-order manufacturing systems is developed using manufacturing resource planning data from a furniture manufacturing company, and experimental results indicate its potential as a useful tool for real applications.
Abstract: For a make-to-order manufacturing system, the uncertainty and flexibility of the due dates required by customers and the production capacity owned by the manufacturer can be modeled in a fuzzy environment. A combined due-date assignment and production planning methodology for the make-to-order manufacturing systems is developed. The fuzzy approach determines the optimal due dates for the manufacturer based upon a "rough-cut" resource balance, while a customer can request earlier due dates by paying a higher price to cover the extra manufacturing cost incurred. The resulting fuzzy due-date bargainer is exercised using manufacturing resource planning (MRP-II) data from a furniture manufacturing company. Experimental results indicate its potential as a useful tool for real applications.

Journal ArticleDOI
TL;DR: In this article, a thermotropic side-chain liquid crystalline ionomer (LCI) containing sulfonic acid groups on the side chain was synthesized by graft copolymerization of mesogenic monomer 4-allyloxy-benzoxy-4'-methoxyphenyl (ABM) and nonemesogenic non-mesogenic mixtures of AABS upon polymethylhydrosiloxane (PMHS).
Abstract: A novel thermotropic side-chain liquid crystalline ionomer (LCI) containing sulfonic acid groups on the side-chain was synthesized by graft copolymerization of mesogenic monomer 4-allyloxy-benzoxy-4'-methoxyphenyl (ABM) and nonemesogenic monomer 4-allyloxy-azobenzene sulfonic acid (AABS) upon polymethylhydrosiloxane (PMHS). The chemical structures of the polymers were confirmed by IR spectroscopy. DSC and TGA were used to measure the thermal properties of those polymers and the mesogenic properties were characterized by polarized optical micrography (POM), DSC, and WAXD. The clearing point temperature (T c ) of these liquid crystalline ionomers was enhanced 50-60°C compared with the polymer without ionic groups. The LCIs exhibit a broad smectic mesogenic region of 80-90°C; the thermal stability below 200°C of the polymers decreases with increasing sulfonic acid concentration. The inherent viscosity of 0.5% solutions decreased with increasing sulfonic acid concentration in the polymer chains.

Journal ArticleDOI
TL;DR: A nonlinear feedback control law is constructed which ensures, under appropriate conditions, that the closed-loop system has a unique bounded differentiable solution and the tracking error in the closed -loop system approaches zero when time goes to infinity.

Journal ArticleDOI
TL;DR: In this article, the authors presented elastic contact models for plane lapping and polishing with or without guard ring, based on these models, the pressure distribution has been obtained and the effects of various parameters, such as the material properties of the workpiece, the plate and the pad, the ratio of load bearing on the guard ring to the total load, the width of the guard round, the gap between the work piece and the guard, and the thickness of the polishing pad, have been discussed.

Journal ArticleDOI
TL;DR: In this article, the existence of Gamma 1 phase is further confirmed by present EPMA and X-ray diffraction results as well as metallographic observations in 1000 and 1150 °C isothermal sections.

Journal ArticleDOI
TL;DR: In this article, an effective field theory with correlations is used to a mixed spin-1 and spin-3/2 Ising ferromagnetic (J > 0) system with two crystal-field interactions on a square lattice.

Journal ArticleDOI
TL;DR: In this paper, the response of uncertain nonlinear vibration systems to vector-valued and matrix-valued functions is extended using a second order expansion of the governing equations and matrix calculus, Kronecker algebra.
Abstract: This paper extends the response of uncertain nonlinear vibration systems to vector-valued and matrix-valued functions. Random variables and system derivatives are conveniently arranged into 2D matrices. The method is based on a second order expansion of the governing equations and matrix calculus, Kronecker algebra are used in the mathematical development. The results derived are easily amenable to computational procedures.

Proceedings ArticleDOI
21 Jun 1998
TL;DR: A direct adaptive tracking control architecture based on fuzzy logic is developed for a class of nonlinear dynamic systems, with global asymptotic stability established in the Lyapunov sense, with tracking errors convergence to a neighborhood of zero.
Abstract: A direct adaptive tracking control architecture based on fuzzy logic is developed for a class of nonlinear dynamic systems. In the procedure, the controller is composed of fuzzy approximate controller and fuzzy sliding mode compensating controller. Global asymptotic stability of the algorithm is established in the Lyapunov sense, with tracking errors convergence to a neighborhood of zero. Simulation results demonstrate the effectiveness of the proposed algorithm.

Proceedings ArticleDOI
04 May 1998
TL;DR: Simulation results verified that the approach is superior to the PID algorithm, and the effectiveness of the technique is demonstrated by its application to the HVAC of one building.
Abstract: A simple and practical fuzzy sliding mode adaptive control is presented in this paper and applied to HVAC (heating, ventilating and air-condition). The effects of parameters variance of the air-conditioner are considered, and performance to uncertainty is assessed. The proposed control methodology address the fundamental issues of stability and performance requirement. Simulation results verified that the approach is superior to the PID algorithm, and the effectiveness of the technique is demonstrated by its application to the HVAC of one building.


Journal ArticleDOI
TL;DR: In this article, the magnetic properties of diluted mixed-spin-1 2 and spin-1 Ising magnetic systems with crystal-field interactions on a honeycomb lattice were investigated by using the effective field theory with correlations.
Abstract: The magnetic properties of diluted mixed-spin- 1 2 and spin-1 Ising magnetic systems with crystal-field interactions on a honeycomb lattice (z = 3) are investigated by using the effective-field theory with correlations. The phase diagrams are given for both ferromagnet and ferrimagnet. The influence of crystal-field interaction, D, and the concentrations of magnetic atoms, Pα(α = A or B represent the two sublattice), on the properties of such a system is discussed. The results show that the reentrant phenomena and two-compensation point exist. Especially, the independent modulation of PA and PB may result in some interesting phenomena, such as three thresholds exist when PA = 1.0 and seven thresholds exist when PB = 1.0.