Showing papers by "South China University of Technology published in 1992"
TL;DR: In this paper, a sliding mode control algorithm is presented for trajectory tracking of an end-effector on a constrained surface with specified constraint forces by using the theory of variable structure systems.
Abstract: A sliding mode control algorithm is presented for trajectory tracking of an end-effector on a constrained surface with specified constraint forces by using the theory of variable structure systems. The development of the algorithm is based on a new formulation of the dynamic model and the expansion of sliding surfaces to include the constraint force error. The proposed sliding controller is explicit, which ensures the occurrence of the sliding mode on the intersection of the surfaces. A detailed numerical example is presented to illustrate the method. >
97 citations
TL;DR: In this article, a three direction observation method was developed to decide the magnitude and direction of principal stresses in silicon wafer, and the stress states in (100 and (111) silicon wafers after certain device processes were also measured and calculated.
Abstract: Two‐dimensional state of stress in (001) and (111) silicon wafer is studied with infrared photoelasticity. In two widely used groups of coordinate systems, the silicon piezo‐optical coefficient tensors due to photoelastic anisotropy of silicon crystal are derived. The relation between stress ellipsoid and refractive index ellipsoid is analyzed with infrared polarized light transmitting through the silicon crystal in certain directions. The applicability of the stress‐optical law in (001) and (111) silicon wafers is presented. A three direction observation method is developed to decide the magnitude and direction of principal stresses in silicon wafer. The stress states in (100) and (111) silicon wafers after certain device processes are also measured and calculated. Comparisons of experimental and calculated results are made.
29 citations
TL;DR: In this article, a new class of 1D quasiperiodic lattices, for which the substitution rules are B → BA, and A → BAB, has been studied in several aspects.
Abstract: A new class of 1D quasiperiodic lattices, for which the substitution rules are B → BA, and A → BAB, has been studied in several aspects The high-dimensional projection method for obtaining the quasilattice is presented A multifractral spectral behavior and gap labeling properties have been found, which display the perfect quasiperiodicity of the studied model
24 citations
TL;DR: In this paper, a composite microstructure consisting of upper bainite laths and lower Bainite plates, both carbide-free, plate (twinned) martensite, and carbon-enriched retained austenite, was produced by air-cooling a medium-carbon alloy steel (0.55 pct C, 1.35 pct Si, 0.78 pct Mn, 045 pct Mo) from 900 °C.
Abstract: A composite microstructure consisting of upper bainite laths and lower bainite plates, both carbide-free, plate (twinned) martensite, and carbon-enriched retained austenite, was produced by air-cooling a medium-carbon alloy steel (0.55 pct C, 1.35 pct Si, 0.78 pct Mn, 0.45 pct Mo) from 900 °C. Well-defined midribs and subunits were found to be associated with both the upper bainite laths and lower bainite plates, clearly showing that the two kinds of bainite growvia a sympathetic nucleation and growth process. The orientation relationship between the bainite and austenite, as determined by electron diffraction, showed that the close-packed planes in the two phases were separated by 0.5 deg and the close-packed directions were 1.9 apart. The habit plane determined from the midrib was (5 127)f, about 20 deg away from the nearly parallel close-packed planes (111)f/(011)b. The experimentally determined orientation relation-ship and habit plane (as defined by the midrib) were in good agreement with the predictions of the phenomenological theory of martensite crystallography.
16 citations
TL;DR: In this paper, a new concept, practical stability in the pth mean, is proposed for nonlinear stochastic systems, based on the Lyapunov-like functions and the basic comparison principle.
14 citations
TL;DR: In this paper, the gap-labeling properties of the energy spectrum for one-dimensional Fibonacci quasilattices were studied and the occupation probabilities on subbands of the hierarchical energy spectrum and step heights of the integrated density of states were analyzed.
Abstract: We study the gap-labeling properties of the energy spectrum for one-dimensional Fibonacci quasilattices. We have obtained the occupation probabilities on subbands of the hierarchical energy spectrum and the step heights of the integrated density of states. It is analytically proved that the step height is equal to {m\ensuremath{\tau}}, where the braces denote the fractional part, and m is an integer that can be used to label the corresponding energy gap. Numerical simulation confirms these results.
13 citations
01 Jun 1992
TL;DR: In this paper, a novel realization of five-mode filters using only the transverse magnetic or transverse electric mode degeneracies in a single spherical cavity is presented, and experimental results obtained with a prototype fivemode quasi-elliptic function filter by exciting and controlling a five degenerate modes in a one spherical cavity with a new technique using dielectric coupling are reported.
Abstract: Triple-mode degeneracy in cylindrical cavities has been successfully applied to the design of a satellite communications filter and multiplexer. A novel realization of five-mode filters using only the transverse magnetic mode or the transverse electric mode degeneracies in a single spherical cavity is presented. Experimental results obtained with a prototype five-mode quasi-elliptic function filter by exciting and controlling a five degenerate modes in a single spherical cavity with a new technique using dielectric coupling are reported. The curves measured agreed well with the theoretical values. >
11 citations
TL;DR: The magnetic-field-strength and quantum-well-width dependence of the ground-state energies of a magnetoexciton in a GaAs/Ga1-xAlxAs quantum- well structure are studied for arbitrary magnetic field strengths and it is found that the magneto Exciton in the l(e,h) = 1 state is more stable than in the e,h = 2 state.
Abstract: The magnetic-field-strength and quantum-well-width dependence of the ground-state energies of a magnetoexciton in a GaAs/${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Al}}_{\mathit{x}}$As quantum-well structure are studied for arbitrary magnetic field strengths. The results show that the energy of the magnetoexciton will increase with increasing quantum-well width and magnetic field strength. We also found that the magnetoexciton in the ${\mathit{l}}_{\mathit{e},}$h=1 state is more stable than in the ${\mathit{l}}_{\mathit{e},}$h=2 state.
11 citations
TL;DR: In this article, a porous hydrogen diffusion anode was used and the results compared with those using a lead anode for the electrochemical reduction of glucose to sorbitol at a lead cathode.
Abstract: For the electrochemical reduction of glucose to sorbitol at a lead cathode the effect of varying the secondary electrode is examined. A porous hydrogen diffusion anode was used and the results compared with those using a lead anode. Reaction conditions involved change of pH from 3.5 to 9.5, temperature from 30 to 45°C and concentration of glucose from 0.5 to 2.5m. Using the gas diffusion anode, efficient operation was possible without a diaphragm and the cell voltage decreased by about 50% with no change to the efficiency of the cathodic reduction compared with the conventional divided cell with lead electrodes. Thus the power usage can be reduced greatly, which may influence competition between electrochemical and pressure hydrogenation routes.
9 citations
TL;DR: In this article, the effect of grinding aids on the grinding of ultrafine particles was demonstrated by comparing particles such as Portland cement clinker, alumina, zircon and quartz produced by a vibration mill and a planet-vibration mill, respectively.
9 citations
TL;DR: In this paper, the multiplicative complexity of the two-dimensional discrete Hartley transform (2D DHT) over rational numbers has been shown to be 2 2n+1 -6(n-1)2 n -8.
Abstract: The multiplicative complexity or the two-dimensional discrete Hartley transform (2D DHT) or size 2 n ×2 n , where n is a positive integer, is determined. The method or deviation is based on linear congruences and a ring structure. The minimal number or real multiplications necessary to compute a length-2 n two-dimensional discrete Hartley transform over the field Q or rational numbers is 2 2n+1 -6(n-1)2 n -8. DHT (2 n ; 2) has the same multiplicative complexity as a corresponding real data 2D-DFT
04 Oct 1992
TL;DR: In this paper, the influence of the cross-term in the traditional Wigner-Ville distribution is reduced through the time-averaging technique, with the time interval adaptive to the fundamental frequency.
Abstract: A method for fundamental frequency estimation based on the Wigner-Ville distribution is presented. The influence of the cross-term in the traditional Wigner-Ville distribution is reduced through the time-averaging technique, with the time interval adaptive to the fundamental frequency. Experimental results using speech signals show that this method can achieve a fairly good estimation of the fundamental frequency. >
24 Jun 1992
TL;DR: Variable structure control method is introduced to robustify the neural network controller and can achieve fast and precise robot motion control under the circumstances of load changing and inaccuracy of inverse-dynamics learning.
Abstract: In this paper we propose a new strategy for nonlinear system control based on the true inverse-dynamics learning Variable structure control method is introduced to robustify the neural network controller This scheme is applied to control a two-link robotic manipulator The simulation results demonstrate that this scheme can achieve fast and precise robot motion control under the circumstances of load changing and inaccuracy of inverse-dynamics learning
TL;DR: In this article, the analysis of a shaft by the line-loaded integral equation method is presented, where the shaft is considered to be an elastic cylindrical shell, with constant or step-varied thickness, with or without hinged supports, embedded in a granular half space under the action of gravity.
TL;DR: In this article, an instability test of externally pressurized U-shaped bellows is performed and its instability mechanisms are studied and the results indicate that the instability of an externally pressurized bellows can be predicted by a similar method as before, which is not the same as the prediction method in EJMA standards.
TL;DR: In this article, a flow-injection analysis (FIA) system based on the enzymatic reactor with immobilized penicillinase on silica gel is developed for the measurement of Penicillin.
TL;DR: In this article, the binding energy of the ground-state exciton in type-II quantum well structures, staggered and misaligned configurations, is calculated with a variational method, and the resulting binding energy in the InAs/GaSb structure for the zero field case is much larger than that reported previously by other authors.
Abstract: The binding energy of the ground-state exciton in type-II quantum well structures, staggered and misaligned configurations, is calculated with a variational method. The resulting binding energy in the InAs/GaSb structure for the zero field case is much larger than that reported previously by other authors. The effect of the electric field on the exciton binding energy is investigated. It is found that the behavior of the exciton formed by the electron and the hole within the right neighbour well of the electron is obviously different from that formed by the electron and the hole within the left neighbour well of the electron, that is, with increasing electric field, the binding energy decreases for the right-well hole exciton, and increases for the left-well hole exciton. Also, the semiconductor-semimetal transition is effectively influenced by the electric field.
07 Jun 1992
TL;DR: A fast-converging Hamming net with two memory layers is proposed corresponding to two shiftable stages of feature extraction in the Chinese recognition system, and the attention shift process is realized automatically.
Abstract: The authors (1991) previously proposed a revised version of a holographic memory model based on adaptive feature detection with an attention shift switch. To implement it in a Chinese character recognition system, a fast-converging Hamming net with two memory layers is proposed corresponding to two shiftable stages of feature extraction in the Chinese recognition system. The attention shift process is realized automatically. The system was used to learn 50 Chinese characters. With a recognition test on a set of 30 samples for each character, a recognition rate of about 85% and a recognition speed of about 3.3 words per second were achieved. >
17 Sep 1992
TL;DR: In this article, the authors discuss the local asymptotical stability problem of continuous bidirectional associative memory and present some sufficient conditions which appear as a set of piecewise-linear inequality relations.
Abstract: The authors discuss the local asymptotical stability problem of continuous bidirectional associative memory (BAM) and present some sufficient conditions which appear as a set of piecewise-linear inequality relations. Some sufficient conditions for a desired equilibrium to be asymptotically stable are examined. For M library vector pairs to be memorized, the conditions appear as M(N+P) linear equations and M(N+P) piecewise-linear inequalities in N+P+2NP unknowns of entries of a, b, W and V. These results have practical significance in the hardware implementation of the BAM. >
24 Jun 1992
TL;DR: In this paper, the mean-square stability of multidelay linear stochastic systems described by differential difference equations is investigated, which is independent of multiple delays in the system.
Abstract: Multidelay linear stochastic systems described by stochastic differential difference equations are considered. Criteria are established for mean-square stability, which is independent of multiple delays in the stochastic systems. These criteria make it possible to check the mean-square stability of the multidelay stochastic systems by testing several simple and explicit algebraic conditions. A specific example is given to show the applicability of the results.
TL;DR: It is shown that the electric field affects effectively the difference between the binding energies calcuated from a spatially-dependent-screening theory and those from a constant- Screening theory.
Abstract: The binding energy of a shallow acceptor in GaAs/Al x Ga 1-x As quantum wells subjected to a longitudinal electric field is calculated with use of a variational method. The spatially dependent screening effect is taken into account with an r-dependent dielectric function to evaluate the acceptor binding energy. The effect of the electric field on the spatially dependent screening of the acceptor states is investigated. It is shown that the electric field affects effectively the difference between the binding energies calcuated from a spatially-dependent-screening theory and those from a constant-screening theory
TL;DR: In this paper, the Mobius inverse formula is extended to an operator form which is much more useful for studying some inverse physical problems, and several new results are given, the contents of which cover many previous works on the mobius inverse formulas.
01 Jan 1992
TL;DR: Gangling et al. as discussed by the authors showed that the biaxial yield strength of titanium sheet (commercially pure titanium) is about 40% greater than its uniaxual yield strength.
Abstract: This is a national problem. The experiments described show that the titanium sheet exhibits a remarkable anisotropy and biaxial strengthening effect. The biaxial yield strength of titanium sheet (commercially pure titanium) is about 40% greater than its uniaxial yield strength. It is worthy of special mention that the strengthening effect from the tests of the titanium pressure vessels is basically in good agreement with this experimental results (LI Gangling et al , 1989). The deviation brtween the theoretical and experimental values is only 4-7%.
07 Jun 1992
TL;DR: It is shown that the equations depicting the continuous Hopfield model and the continuous BAM are the same, suggesting that the two models share common features in their analysis and design, though the functions and the structures of the two seem different.
Abstract: Bidirectional associative memory (BAM) is generally considered as a generalization of the Hopfield model. In the present work, it is shown that the equations depicting the continuous Hopfield model and the continuous BAM are the same, suggesting that the two models share common features in their analysis and design, though the functions and the structures of the two seem different. Several results of the Hopfield model are extended to the BAM, including the equilibrium characterization and the asymptotical stability, which are of practical importance in BAM design. >
28 Oct 1992
TL;DR: In this article, an approach to the interaction of coherent light with the anharmonic lattice vibration of ionic crystal and give a mechanism for increasing absorption optical bistability.
Abstract: We present herein an approach to the interaction of coherent light with the anharmonic lattice vibration of ionic crystal and give a mechanism for increasing absorption optical bistability.
TL;DR: In this article, the authors considered a class of quasilinear elliptic eigenvalue problems with limiting nonlinearity and used the concentration-compactness principle to get the existence of a minimum solution.
Abstract: In this paper, we consider a class of quasilinear elliptic eigenvalue problems with limiting nonlinearity. First, we use the concentration-compactness principle to get the existence of a minimum ueH
0
1
(ω,R
N
) of the minimization problem
$$I_{\lambda _0 } = \inf \{ \smallint _\Omega (a_{\alpha \beta } (x)g_{ij} (u)D_\alpha u^i D_\beta u^j + h(x)|u|^2 )|u \in H_0^1 (\Omega ,R^N ),\smallint _\Omega |u|^{2n/(n - 2)} = \lambda _0 \} ;$$
then we apply the reverse Holder inequality to prove thatueL
∞
(ω, R
N
).
28 Oct 1992
TL;DR: In this article, the authors studied the increasing absorptive OB, the behaviors of responding to inject signal, also the self-pulsing and chaotic phenomena in the excitonic OB systems.
Abstract: Some results of probing to the common properties, including bistability, transient behavior, and instability of the excitonic optical nonlinear dynamic systems, such as interaction of light field with carrier in semiconductor, or anharmonic vibration of lattice in ionic crystal, are presented. Since the excitonic optical bistability (EOB) was found, it has garnered much attention for its advantage in properties and application prospects. Some models have been proposed for different kinds of OB. However, so far as we know, there has been relatively less concern given to the common dynamic characteristics of these systems, which are significant for applications. On the other hand, the instability of the EOB device certainly has the same importance, the study for which is not ample yet. In this paper we study the increasing absorptive OB, the behaviors of responding to inject signal, also the self-pulsing and chaotic phenomena in the excitonic OB systems.
TL;DR: In this paper, the authors used the concentration compactness principle to study the existence of a minimiser of the minimisation problem where u =( u 1, u 1, …, u N ), and proved the boundedness of l 1 by using the reverse Holder inequality.
Abstract: We use the concentration compactness principle to study the existence of a minimiser of the minimisation problem where u =( u 1 , …, u N ), . We also prove the boundedness of the minimiser of l 1 by using the reverse Holder inequality.
24 Jun 1992
TL;DR: In this paper, a general sliding mode controller is presented for trajectory tracking of nonlinear robot manipulator systems which guarantees occurrence of sliding mode on a specified general sliding surface The controller is, in a simple manner, related to the manipulator and load parameters, which greatly reduces the complexity of design.
Abstract: A general sliding mode controller is presented for trajectory tracking of nonlinear robot manipulator systems which guarantees occurrence of sliding mode on a specified general sliding surface The controller is, in a simple manner, related to the manipulator and load parameters, which greatly reduces the complexity of design In the sliding mode, desired performance can be obtained by selecting a suitable sliding surface The algorithm can also be applied to Cartesian space
TL;DR: In this article, a planetary vibration mill (PVM) was used for fine-grinding a number of materials, and its working principle, the influence of technical parameters on grinding and the motion of the grinding media within the mill were discussed.