Showing papers by "Nanjing University of Science and Technology published in 2000"
TL;DR: In this article, the authors proposed two different approaches for deriving heat transfer correlation of the nanofluid, and investigated the mechanism of heat transfer enhancement of the nano-fluid.
2,355 citations
TL;DR: In this article, the authors present a procedure for preparing a nanofluid which is a suspension consisting of nanophase powders and a base liquid, and their TEM photographs are given to illustrate the stability and evenness of suspension.
2,341 citations
TL;DR: A systematic design approach based on time-delay feedback is developed for anticontrol of chaos in a continuous-time system that can drive a finite-dimensional, continuous- time, autonomous system from nonchaotic to chaotic, and can also enhance the existing chaos of an originally chaotic system.
Abstract: In this paper, a systematic design approach based on time-delay feedback is developed for anticontrol of chaos in a continuous-time system. This anticontrol method can drive a finite-dimensional, continuous-time, autonomous system from nonchaotic to chaotic, and can also enhance the existing chaos of an originally chaotic system. Asymptotic analysis is used to establish an approximate relationship between a time-delay differential equation and a discrete map. Anticontrol of chaos is then accomplished based on this relationship and the differential-geometry control theory. Several examples are given to verify the effectiveness of the methodology and to illustrate the systematic design procedure.
167 citations
TL;DR: It is mathematically prove that the controlled system is indeed chaotic in the sense of Li and Yorke.
Abstract: In this paper, the problem of making a stable nonlinear autonomous system chaotic or enhancing the existing chaos of an originally chaotic system by using a small-amplitude feedback controller is studied. The designed controller is a linear feedback controller composed with a nonlinear modulo or sawtooth function, which can lead to uniformly bounded state vectors of the controlled system with positive Lyapunov exponents, thereby yielding chaotic dynamics. We mathematically prove that the controlled system is indeed chaotic in the sense of Li and Yorke. A few potential applications of the new chaotification algorithm are briefly discussed.
155 citations
TL;DR: The problem is the design of a state feedback controller, such that the resulting closed-loop system is not only regular, causal, and stable, but also satisfies a prescribed H/sub /spl infin//-norm-bound condition.
Abstract: Deals with the problem of state feedback H/sub /spl infin// control for discrete singular systems It is not assumed that the singular system under consideration is necessarily regular The problem we address is the design of a state feedback controller, such that the resulting closed-loop system is not only regular, causal, and stable, but also satisfies a prescribed H/sub /spl infin//-norm-bound condition In terms of certain matrix inequalities, a necessary and sufficient condition for the solution to this problem is obtained, and a suitable state feedback-control law is also given
153 citations
30 Sep 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, a sol-gel method with inorganotitanates and polyethylene glycol (PEG) was used to obtain ultra-fine (∼4 nm) and crystallized (anatase phase) TiO 2 particles.
Abstract: TiO 2 nanoparticles were prepared using a sol-gel method with inorganotitanates and polyethylene glycol (PEG). However, the way TiO 2 particles were obtained from the dry gel was not by calcining but by redissolving the dry gel which had been treated at 100°C, thereby releasing the particles. The TiO 2 powder prepared in this manner was ultra-fine (∼4 nm) and crystallized (anatase phase) merely by being exposed to 100°C while inside the gel. It was supposed that this low temperature crystallization of TiO 2 results from the special structure of the gel which formed through the linking of TiO(NO 3 ) 2 · H 2 O with PEG chains by a hydrogen bond. This preparation method also has an advantage in environmental protection.
107 citations
TL;DR: According to the requirements of concurrent engineering, three interdependency relationships (uncoupled relationship, coupled relationship and decoupling relationship) between design activities are presented in this paper and an algorithm of recognizing the coupled activities during the design process is presented.
93 citations
TL;DR: In this paper, the vibratory characteristics of a rectangular plate in contact with water on one side are studied, and an analytical-Ritz method is developed to analyse the interaction of the plate-water system.
Abstract: In this paper, the vibratory characteristics of a rectangular plate in contact with water on one side are studied. The elastic plate is considered to be a part of a vertical rectangular rigid wall in contact with water, the edges of which are elastically restrained and parallel to those of the rigid wall. The location and size of the plate on the rigid wall may vary arbitrarily. The water with a free surface is in a rectangular domain infinite in the length direction. The effects of free surface waves, compressibility of the water and the hydrostatic water pressure are neglected in the analysis. An analytical-Ritz method is developed to analyse the interaction of the plate–water system. First of all, by using the method of separation of variables and the method of Fourier series expansion, the exact expression of the motion of water is derived in the form of integral equations including the dynamic deformation of the plate. Then the Rayleigh–Ritz approach is used to derive the eigenfrequency equation of the system via the variational principle of energy. By selecting beam vibrating functions as the admissible functions of the plate, the added virtual mass incremental (AVMI) matrices for plate vibration are obtained. The convergency studies are carried out. The effects of some parameters such as the depth and width of water, the support stiffnesses, location and aspect ratio of the plate and the plate–water size and density ratios on the eigenfrequencies of the plate–water system are investigated. Several numerical examples are given. The validity of AVMI factor approach is also confirmed by comparing the AVMI factor solutions with the analytical-Ritz solutions. The results show that the approach presented here can also be used as excellent approximate solutions for rectangular plates in contact with water of infinite width and/or infinite depth. Copyright © 2000 John Wiley & Sons, Ltd.
91 citations
TL;DR: In this article, an analytical-Ritz method is developed to study the vibratory characteristics of the elastic thin plate placed into a rectangular hole and connected to the rigid bottom slab of a rectangular container filled with fluid having a free surface.
88 citations
TL;DR: In this article, the problem of making a stable linear time-invariant (LTI) system chaotic by using state-feedback control of arbitrarily small magnitude is studied, where the feedback controller used is a simple sawtooth or modulo function of the system states, which can lead to uniformly bounded state vectors of the controlled system with positive Lyapunov exponents, thereby yielding chaotic dynamics.
Abstract: The problem of making a stable linear time-invariant (LTI) system chaotic by using state-feedback control of arbitrarily small magnitude is studied. The feedback controller used is a simple sawtooth or modulo function of the system states, which can lead to uniformly bounded state vectors of the controlled system with positive Lyapunov exponents, thereby yielding chaotic dynamics. In fact, we mathematically prove that this controlled system is chaotic in the sense of Li and Yorke (1975).
88 citations
TL;DR: In this paper, a series of tetrazole derivatives and their metal salts were investigated to investigate the relationship between the relative order of impact sensitivity and activation energy of thermal decomposition.
Abstract: Calculations with both DFT-B3LYP and semiempirical quantum chemical PM3 methods are carried out on a series of tetrazole derivatives and their metal salts to investigate the relationship between the relative order of impact sensitivity and activation energy of thermal decomposition. The results show that the relative order of sensitivity for the titled compounds can be predicted by examining the activation energy for breaking down of tetrazole ring. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 79: 350–357, 2000
TL;DR: In this paper, the vibrational characteristics of tapered beams with continuously varying rectangular cross-section of depth and breadth proportional to xs and xt, where both s and t are arbitrary real numbers for a truncated beam and arbitrary positive number for a sharp ended beam and x is the axial co-ordinate measured from the sharp end of the beam.
TL;DR: In this paper, a set of static Timoshenko beam functions is developed as the admissible functions to study the free vibrations of moderately thick rectangular plates using the Rayleigh-Ritz method.
TL;DR: In this paper, the motion of dust suspensions accelerated by shock waves has been experimentally investigated in a vertical shock tube, in which a completely developed plane shock wave of moderate strength propagates into a homogeneously distributed dust suspension with a planar interface.
Abstract: The motion of dust suspensions accelerated by shock waves has been experimentally investigated in a vertical shock tube, in which a completely developed plane shock wave of moderate strength propagates into a homogeneously distributed dust suspension with a planar interface. Trajectories of the accelerated interfaces as well as transmitted and reflected shock waves are recorded by using a shadowgraph system with a Cranz-Schardin camera. Two kinds of particle samples, i.e. porous lycopodium particles 30 μm in diameter and corn starch particles with a mean diameter of 10 μm, are employed. The effects of shock wave strength and particle loading ratio are also examined. Experimental data are compared with theoretical results, and the agreement is good.
TL;DR: A systematic stability theory is developed for 2-D singular systems based on the observation that once a boundary condition or the input is inadmissible in the classical sense, a group of non-causal or backward jumpsof the system states will be incited.
Abstract: In this paper, we discuss the jump behavior and stability problems for 2-D linear shift-invariant singular systems under the standard boundary conditions. It is shown that once a boundary condition or the input is inadmissible in the classical sense, a group of non-causal or backward jumps of the system states will be incited. This interpretation releases the conventional admissibility constraints on the boundary conditions and inputs. Based on this observation, a systematic stability theory is developed for 2-D singular systems. The well-known basic stability theorem for the 1-D singular systems or 2-D regular systems is thus extended to the 2-D singular case.
TL;DR: In this paper, the hardness-duration correlation of gamma-ray bursts was investigated using data from the 4B catalog, and the existence of two classes of GRBs was confirmed.
Abstract: The well-known hardness-duration correlation of gamma-ray bursts (GRBs) is investigated using data from the 4B catalog. We find that, while the hardness ratio and the duration are obviously correlated for the entire set of the 4B catalog, they are not at all correlated for the two subsets divided at the duration of 2 seconds. However, for other subsets with comparable sizes, the two quantities are significantly correlated. The following conclusions are thus reached: (1) the existence of two classes of GRBs is confirmed; (2) the hardness ratio and the duration are not at all correlated for any of the two classes; (3) different classes of GRBs have different distributions of the hardness ratio and the duration, and it is this difference that causes the correlation between the two quantities for the entire set of bursts.
TL;DR: The magnetic properties of these samples are different from those of the bulk Z-type hexagonal ferrite with a lower specific saturation magnetization, which can be attributed to the existing of a nonmagnetic layer existing on the surface of the particles as mentioned in this paper.
Abstract: Ba3Co2Fe24O41 nanocrystals are synthesized through a stearic acid sol-gel method. The reaction temperatures are dramatically lower than that of the conventional ceramic method. The nanocrystalline powders obtained at 750°C were spherical in shape with grain sizes in the range 15–25 nm and become a plate-like form when the heat-treatment temperature increased. The magnetic properties of these samples are different from those of the bulk Z-type hexagonal ferrite with a lower specific saturation magnetization. This phenomenon can be attributed to the existing of a nonmagnetic layer existing on the surface of the particles. The higher value of the coercivity force is obtained when the particle sizes approximately are equal to 90 nm and assume a single-domain character. The surface composition of the nanocrystalline Co2-Z hexagonal ferrite is different from that of the bulk counterpart material with a higher content of the Ba element and Co element.
TL;DR: The ultrathin films of polyaniline (PAni)/poly (styrenesulfonic acid)(PSSA) were fabricated via a self-assembling process by alternately immersing the substrates into dilute PAni solution in N-methylpyrrolidinone (NMP) and the aqueous solution of PSSA as discussed by the authors.
TL;DR: In this article, a new set of two-dimensional basic functions, which satisfy the kinematic boundary conditions at the edges of the plate and the zero-displacement conditions at point supports, is developed to describe the variation of three-dimensional displacements in the plane of a thin finite layer.
TL;DR: In this article, a set of static beam functions, which are the solutions of an elastically point-supported beam under a Fourier series of static sinusoidal loads distributed along the length of the beam, are developed as the admissible functions to analyze the vibrations of orthotropic rectangular plates with elastic intermediate line-supports using the Rayleigh-Ritz method.
Abstract: A set of static beam functions, which are the solutions of an elastically point-supported beam under a Fourier series of static sinusoidal loads distributed along the length of the beam, are developed as the admissible functions to analyze the vibrations of orthotropic rectangular plates with elastic intermediate line-supports using the Rayleigh–Ritz method. Both the elastic rotational and the elastic translational constraints along the edges of the plate are also considered simultaneously. Unlike conventional admissible functions, this set of static beam functions not only can automatically adjust to the stiffnesses of the intermediate line-supports but also can properly describe the discontinuity of shear forces at the line-supports so that higher accuracy and faster convergence can be expected for the dynamic analysis of such plates. The suggested approach is effective even for various limiting cases by letting the corresponding stiffnesses approach their natural limits of zero or infinity. The present method is theoretically sound and mathematically simple, with each of the static beam functions being only a third-order polynomial plus a sine function. A common and efficient computational program can be compiled because of the fact that a change of the line-support parameters (locations, number and stiffnesses) and the boundary conditions of the plate only results in a corresponding change of the coefficients of the polynomial in the static beam functions. Several numerical examples are presented and the results obtained, where possible, are compared with the known solutions in literature. The present method has proved to be extremely effective for solving the aforementioned problems.
TL;DR: In this article, a truncated-ogive-nose projectile penetration into semi-infinite concrete targets is described, and a semi-analytical penetration equation is developed by introducing a resistance constant which takes into account the truncation effect of the ogive-noses projectile on penetration.
TL;DR: In this paper, an effective symmetric successive overrelaxation (SSOR) preconditioning scheme is applied to the conjugate-gradient method for solving a large system of linear equations resulting from the use of the edge-based finite-element method (FEM).
Abstract: In this letter, an effective symmetric successive overrelaxation (SSOR) preconditioning scheme is applied to the conjugate-gradient method for solving a large system of linear equations resulting from the use of the edge-based finite-element method (FEM). With SSOR as the preconditioner as well as its efficient implementation in the conjugate-gradient (CG) algorithm, the PCG method converges five times as fast as the CG method. This result demonstrates that SSOR is a good preconditioner for the CG iterative method when the FEM is applied to solve large-scale electromagnetic problems. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 235–238, 2000.
TL;DR: Simulations showed that the proposed method was better than the conventional matrix filter design techniques and greatly improved the estimation accuracy at low signal-to-noise ratios (SNRs).
Abstract: We propose using a semi-infinite programming technique to design a matrix filter. The idea is to formulate the design problem into a semi-infinite optimization model where the mean square error between the desired response and the designed filter in the passband and stopband is minimized subject to a set of nonlinear functional inequalities. These inequality constraints are used to ensure that the stopband attenuation and the passband deviation satisfy the prescribed specifications. Simulations showed that the proposed method was better than the conventional matrix filter design techniques. The matrix filters based on the proposed design method was also applied to the direction-of-arrival (DOA) estimation problem. It was shown that the filter greatly improved the estimation accuracy at low signal-to-noise ratios (SNRs).
TL;DR: A novel approach to update the interweights of integrated probability function by using the information of both relevant and irrelevant retrieved images, especially in the situation of no relevant retrieved images is presented.
Abstract: Relevance feedback is a powerful technique for content-based image retrieval. Many parameter estimation approaches have been proposed for relevance feedback. However, most of them have only utilized information of the relevant retrieved images, and have given up, or have not made great use of information of the irrelevant retrieved images. This paper presents a novel approach to update the interweights of integrated probability function by using the information of both relevant and irrelevant retrieved images. Experimental results have shown the effectiveness and robustness of our proposed approach, especially in the situation of no relevant retrieved images.
TL;DR: In this article, a dual-band patch antenna with two U-shaped slots was experimentally demonstrated and the frequency ratio was tunable in the range of ∼1.43-1.6.
Abstract: A dual-band patch antenna with two U-shaped slots is experimentally demonstrated. By varying the length of the two arms of each U-shaped slot, the frequency ratio tunable in the range of ∼1.43–1.6 and a considerable antenna size reduction for fixed dual-frequency operation are shown. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 73–75, 2000.
TL;DR: In this article, the problem of robust H∞ control for uncertain discrete-time systems with circular pole constraints was investigated and sufficient conditions for quadratic d stabilizability with an H ∞ norm-bound were derived.
TL;DR: In this paper, a prototype capacitor-type humidity sensor was designed and fabricated by a layer-by-layer self-assembling technique, which consists of a self-assembled electrically conductive polyaniline film and an insulating polyelectrolyte film which act as the top electrode and the dielectric layer, respectively.
TL;DR: In this article, the initial formation process of laser-induced plasma shock wave in air during laser damage process has been studied experimentally with a well-designed optical fiber sensor based on detecting beam deflection.