Showing papers by "Nanjing University of Science and Technology published in 2003"
TL;DR: In this article, an innovative new class of heat transfer fluids can be engineered by suspending metallic nanoparticles in conventional heat-transfer fluids, which are expected to exhibit high thermal conductivities compared to those of currently used heat transfer fluid, and they represent the best hope for enhancing heat transfer.
Abstract: Low thermal conductivity is a primary limitation in the development of energy-efficient heat transfer fluids that are required in many industrial applications. In this paper we propose that an innovative new class of heat transfer fluids can be engineered by suspending metallic nanoparticles in conventional heat transfer fluids. The resulting {open_quotes}nanofluids{close_quotes} are expected to exhibit high thermal conductivities compared to those of currently used heat transfer fluids, and they represent the best hope for enhancement of heat transfer. The results of a theoretical study of the thermal conductivity of nanofluids with copper nanophase materials are presented, the potential benefits of the fluids are estimated, and it is shown that one of the benefits of nanofluids will be dramatic reductions in heat exchanger pumping power.
4,634 citations
TL;DR: In this article, the theory of Brownian motion and diffusion-limited aggregation model are applied to simulate random motion and the aggregation process of the nanoparticles, and a theoretical model is developed to predict the thermal conductivity of nanofluids.
Abstract: Nanofluids are obtained by suspending metallic nanoparticles in conventional base liquids. Such a new class of heat-transfer fluid is superior to the base liquids in energy-transport performance, which depends on the distribution, volume fraction and thermal properties of the suspended nanoparticles. The theory of Brownian motion and the diffusion-limited aggregation model are applied to simulate random motion and the aggregation process of the nanoparticles. A theoretical model is developed to predict the thermal conductivity of nanofluids. Comparison between the theoretical and experimental results shows the validity and accuracy of the theoretical model.
746 citations
TL;DR: This paper points out the weakness of the previous LDA based methods, and suggests a complete PCA plus LDA algorithm, and experimental results indicate that the proposed method is more effective than the previous ones.
583 citations
TL;DR: The experimental results indicate that the classification accuracy is increased significantly under parallel feature fusion and also demonstrate that the developed parallel fusion is more effective than the classical serial feature fusion.
418 citations
TL;DR: A new active queue management (AQM) scheme based on the proportional derivative (PD) control principle, which demonstrates the improvement in performance of PD-RED over adaptive RED AQM by simulations.
Abstract: We propose a new active queue management (AQM) scheme to improve the performance of the well-known random early detection (RED) AQM. The new AQM is based on the proportional derivative (PD) control principle, and we call it PD-RED. In PD-RED we introduce minimal changes to RED. We demonstrate the improvement in performance of PD-RED over adaptive RED AQM by simulations.
128 citations
TL;DR: In this paper, a three-dimensional free vibration analysis of circular and annular plates via the Chebyshev-Ritz method is presented, which is based on the linear, small strain, 3D elasticity theory.
122 citations
TL;DR: In this paper, the problem of guaranteed cost control for uncertain neutral delay systems with a quadratic cost function is considered and a sufficient condition for the existence of a guaranteed cost controller is given in terms of a linear matrix inequality (LMI).
Abstract: This paper considers the problem of guaranteed cost control for uncertain neutral delay systems with a quadratic cost function. The system under consideration is subject to norm-bounded time-varying parametric uncertainty appearing in all the matrices of the state-space model. The problem we address is the design of a state feedback controller such that the closed-loop system is not only stable but also guarantees an adequate level of performance for all admissible uncertainties. A sufficient condition for the existence of guaranteed cost controllers is given in terms of a linear matrix inequality (LMI). When this condition is feasible, the desired state feedback controller gain matrices can be obtained via convex optimization. An illustrative example is provided to demonstrate the effectiveness of the proposed approach. Copyright © 2002 John Wiley & Sons, Ltd.
93 citations
TL;DR: In this paper, a general approach for solving the free vibration of solid and hollow circular cylinders is presented, which is based on the small-strain, linear and exact elasticity theory.
90 citations
TL;DR: In this paper, surface pretreatment of nano-TiO2 with special structure dispersing agent (TAS) and master batch manufacturing technology was used to increase the impact strength, tensile strength, and elastic modulus of high impact polystyrene (HIPS)/nano- TiO2 nanocomposites.
Abstract: High-impact polystyrene (HIPS)/nano-TiO2 nanocomposites were prepared by surface pretreatment of nano-TiO2 with special structure dispersing agent (TAS) and master batch manufacturing technology. The results show that when the nano-TiO2 content is 2%, the notched impact strength, tensile strength, and elastic modulus of HIPS/nano-TiO2 nanocomposites increased to a maximum. This result indicates that nano-TiO2 has both toughening and reinforcing effects on HIPS. The heat-deflection temperature and flame-retardance of HIPS/nano-TiO2 nanocomposites are also obviously improved as the nano-TiO2 content is increased. The nanocomposites manufactured by the two-step method have better mechanical properties than that made by a one-step method. HIPS/nano-TiO2 nanocomposites are also non-Newtonian and pseudoplastic fluids. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 381–385, 2003
88 citations
TL;DR: In this article, the problem of robust H∞ control for uncertain continuous singular systems with state delay and time-invariant norm-bounded uncertainty is addressed, and a memoryless state feedback controller law is designed based on the linear matrix inequality (LMI) approach, which guarantees that, for all admissible uncertainties, the resulting closed-loop system is not only regular, impulse free and stable, but also meets an H ∞-norm bound constraint on disturbance attenuation.
Abstract: This paper addresses the problem of robust H∞ control for uncertain continuous singular systems with state delay. The singular system under consideration involves state time delay and time-invariant norm-bounded uncertainty. Based on the linear matrix inequality (LMI) approach, we design a memoryless state feedback controller law, which guarantees that, for all admissible uncertainties, the resulting closed-loop system is not only regular, impulse free and stable, but also meets an H∞-norm bound constraint on disturbance attenuation. A numerical example is provided to demonstrate the applicability of the proposed method. Copyright © 2003 John Wiley & Sons, Ltd.
87 citations
01 Dec 2003
TL;DR: The results demonstrate that the PD-controller AQM is stable and robust against traffic load fluctuations, UDP and HTTP disturbances, and its superiority over other AQMs is also demonstrated.
Abstract: This paper describes a proportional-differential (PD) control algorithm as a new active queue management (AQM) scheme for TCP/IP congestion control. From the viewpoint of the control theory, TCP congestion control system can be regarded as a feedback regulating system. In this paper, a robust AQM called PD-controller is proposed. The design principles of PD-controller are presented in details. Its performance is extensively evaluated by simulations. The results demonstrate that the PD-controller AQM is stable and robust against traffic load fluctuations, UDP and HTTP disturbances. Its superiority over other AQMs is also demonstrated.
TL;DR: A Complex LDA based combined Fisherfaces framework, coined Complex Fisherfaces, is developed for face feature extraction and recognition and is demonstrated to be much more effective and robust than the super-vector based serial feature fusion strategy for face recognition.
TL;DR: In this article, an extended version of the controlling unstable equilibrium point (CUEP) method for network-preserving power systems has been proposed, where the target point of the fault-clearing point (i.e., the initial point in the post-fault system), instead of the faulty point as in classical case, plays a crucial role in direct stability analysis.
Abstract: The controlling unstable equilibrium point (CUEP) method developed for the traditional network-reduction power-system (transient-stability) model requires some modification for direct stability analysis of the network-preserving power system model. This is mainly due to the peculiar nonlinear jump behaviors occurring in network-preserving power system model. An extended CUEP method suitable for direct stability analysis of network-preserving models is developed. The extended CUEP method examines both external jump behaviors and stability regions of network-preserving models. It is shown that the target point of the fault-clearing point (i.e., the initial point of the post-fault system), instead of the fault-clearing point as in classical case, plays a crucial role in direct stability analysis of network-preserving power systems models. A theoretical foundation for the extended CUEP method is developed. A variation of the extended CUEP method is presented.
TL;DR: In this article, two high input-isolation dual-polarized dielectric resonator (DR) antennas are presented in this communication, where a slot-coupled feed technique with two narrow slots forming a "T" configuration is employed to design a dual polarized DR antenna.
Abstract: Two high input-isolation dual-polarized dielectric resonator (DR) antennas are presented in this communication. First, a slot-coupled feed technique with two narrow slots forming a "T" configuration is employed to design a dual-polarized DR antenna. Input isolation exceeding 35 dB has been obtained in the band for this design. Secondly, a hybrid feed mechanism with a coplanar waveguide (CPW) feed and a slot feed is used to achieve a dual-polarized DR antenna. A vertical strip is added at the center strip of the CPW feed to improve the coupling to the DR antenna. Also, input isolation exceeding 35 dB has been obtained in the band. Good cross-polarization levels less than -20 dB in the broadside direction are attained. The measured far-field radiation patterns are stable in the passband and the measured gains are around 5.5 dBi for the two feed ports of both cases.
TL;DR: The method for the derivatization of carbohydrates with 1-phenyl-3-methyl-5-pyrazolone (PMP) was simplified and one-third of the derivation time was saved, and good reproducibility could be obtained.
29 Sep 2003
TL;DR: Benders decomposition method is proposed to partition the ATC problem with state-steady security constraints into a base case master problem and a series of subproblems relevant to various contingencies to include their impacts on ATC.
Abstract: Available transfer capability (ATC) is an important indicator of the usable amount of transmission capacity accessible by assorted parties for commercial trading. ATC calculation is nontrivial when steady-state security constraints are included. In this paper, Benders decomposition method is proposed to partition the ATC problem with state-steady security constraints into a base case master problem and a series of subproblems relevant to various contingencies to include their impacts on ATC. The mathematical model is formulated and the two solution schemes are presented. Computer testing on the 4-bus system and IEEE 30-bus system shows the effectiveness of the proposed method and the solution schemes.
TL;DR: In this article, a study on active vibration suppression for a flexible structural beam via a system identification approach was experimentally performed, and an active control system, considering both the actuators and sensor, was configured using the ARMAX (auto-regressive moving average exogenous) model.
Abstract: A study on active vibration suppression for a flexible structural beam via a system identification approach was experimentally performed. The beam, incorporating a pair of piezoceramic transducers as actuators and a set of surface-bonded strain gauges as sensors, was evaluated. The relationship between the input control voltage applied on the actuators and the consequently induced strain, measured by the sensor, was then derived. An active control system, considering both the actuators and sensor, was configured using the ARMAX (auto-regressive moving average exogenous) model. A continuous signal with step waveform was selected as the input excitation. A digital-signal-processor-based real-time adaptive vibration control algorithm, supported by Agilent® E1415A, SCPs 1511 and SCPs 1532, was developed, and an algorithm was established using a pole placement control method, so as to achieve the desired closed-loop control. The effectiveness of the ARMAX model was examined by comparing it with the ARX (auto-regression with extra inputs) model. The results show good performance of the ARMAX model for system identification purposes and excellent effectiveness for active structural vibration control.
TL;DR: This paper briefly presents a model of collaborative design and the definition, classification and relationship of the features in this system; discusses key techniques related to realizing feature-based collaborative design in detail; and gives the architecture of the feature- based collaborative design system.
TL;DR: In this article, an elaborately simulated decomposition kinetic method for organic peroxide with the Semenov model of thermal explosion was proposed to predict the self-accelerating decomposition temperatures (SADTs) of organic peroxides.
Abstract: By combining a recent proposed elaborately simulated decomposition kinetic method for organic peroxide with the Semenov model of thermal explosion, the self-accelerating decomposition temperatures (SADTs) of organic peroxides were predicted. The heat generation equation is based on a reaction rate equation, which was expressed by differentiation of a fractional conversion equation with respect to time. The kinetic parameters involved in the calculation are the contribution fraction φ i , the end point temperature T di , and the reaction temperature range parameter K Ti , which are directly determined by observing the thermal behavior of peroxides under non-isothermal decomposition condition. The non-isothermal decomposition behaviors of eight organic peroxides were measured by the heat flux calorimeter C80D. By using the experimental results and the developed method, the no return temperature and the self-accelerating decomposition temperatures of these substances in UN 25 kg test and 0.5 liter Dewar test were predicted. The predicted SADTs were in agreement with the literature values.
TL;DR: The algorithms to obtain S t − orthogonal eigenvectors of the generalized eigenequation are equivalent to the ULDA algorithm, and it is possible to work out ULDA discriminant vectors more efficiently.
TL;DR: In this article, two isomorphous tetranuclear cubane-like heterothiometallic clusters with oxotrithiometalate anions have been synthesized and characterized crystallographically.
Abstract: Using low heating temperature solid-state reactions and self-assembly reactions, two new candidates [Et4N]3[MOS3(μ3-I)(AgI)3]
(M = Mo, 1; W, 2) for nonlinear optical (NLO) materials have been synthesized and characterized crystallographically as tetranuclear cubane-like heterothiometallic clusters. Their optical nonlinearities were measured by the Z-scan technique with an 8 ns pulsed laser at 532 nm. These two isomorphous clusters both exhibit strong NLO absorptive abilities [α2
= 1.0 × 10−9 m W−1 (1), 1.2 × 10−9 m W−1 (2)] and effective self-focusing performance [n2
= 8.8 × 10−17 m2 W−1 (1), 4.5 × 10−17 m2 W−1 (2)]. The optical limiting (OL) investigation demonstrates that these two clusters show large OL effects. The NLO properties of tetranuclear Ag-containing cubane-like clusters with oxotrithiometalate anions are reported here for the first time and the third-order NLO properties and OL effects suggest that clusters 1 and 2 are promising candidates for NLO applications. A comparison of the NLO effect among clusters with the same C3v symmetry has been made in order to further understand and explore the function–structure relationships of these heterothiometallic clusters.
TL;DR: UIPDA is superior to Liu's projection discriminant method and more efficient than Eigenfaces and Fisherfaces; EULDA outperforms the existing PCA plus LDA strategy and is a very effective two-stage strategy for image feature extraction.
Abstract: In this paper, a novel image projection analysis method (UIPDA) is first developed for image feature extraction. In contrast to Liu's projection discriminant method, UIPDA has the desirable property that the projected feature vectors are mutually uncorrelated. Also, a new LDA technique called EULDA is presented for further feature extraction. The proposed methods are tested on the ORL and the NUST603 face databases. The experimental results demonstrate that: (i) UIPDA is superior to Liu's projection discriminant method and more efficient than Eigenfaces and Fisherfaces; (ii) EULDA outperforms the existing PCA plus LDA strategy; (iii) UIPDA plus EULDA is a very effective two-stage strategy for image feature extraction.
TL;DR: In this article, the crystal and molecular structure of the N-(4-chloro)benzoyl-N′-(4tolyl)thiourea (C15H13N2OSCl, Mr=304.79) is determined by X-ray diffraction.
TL;DR: The K-L expansion method, which is able to extract the discriminatory information contained in class-mean vectors, is generalised to make it suitable for solving small sample size problems, and a simple and efficient GKLE algorithm is developed.
Abstract: The K-L expansion method, which is able to extract the discriminatory information contained in class-mean vectors, is generalised, in this paper, to make it suitable for solving small sample size problems. We further investigate, theoretically, how to reduce the method’s computational complexity in high-dimensional cases. As a result, a simple and efficient GKLE algorithm is developed. We test our method on the ORL face image database and the NUST603 handwritten Chinese character database, and our experimental results demonstrate that GKLE outperforms the existing techniques of PCA, PCA plus LDA, and Direct LDA.
TL;DR: In this paper, an LMI based re-formulation of the stability conditions can be used to enable the design of a family of control laws which have a well defined physical basis.
Abstract: Discrete linear repetitive processes are a distinct class of 2D linear systems with applications in areas ranging from long-wall coal cutting through to iterative learning control schemes. The main feature which makes them distinct from other classes of 2D linear systems is that information propagation in one of the two independent directions only occurs over a finite duration. This, in turn, means that a distinct systems theory must be developed for them. In this paper, the major new development is that an LMI based re-formulation of the stability conditions can used to enable the design of a family of control laws which have a well defined physical basis. It is also noted that this setting can be used to investigate robustness aspects.
TL;DR: In this paper, a reaction profile for the nitration of benzene with nitronium ion has been successfully calculated for the first time, and stationary points were located and characterized by the DFT procedures at the B3LYP/6-311G** level.
Abstract: A reaction profile for the nitration of benzene with nitronium ion has been successfully calculated for the first time. Stationary points were located and characterized by the DFT procedures at the B3LYP/ 6-311G** level. When NO2+ approaches the benzene molecule, a weakly bound π-complex was first produced, in which the distances between the nitrogen atom of nitronium ion to both carbon atoms C1 and C6 of benzene ring were equal. This bifurcation point was characterized as a transition state leading to a σ-complex reactant by shifting the positive ion to either single carbon C1 or C6. The σ-complex reactant (σ-R) finally reaches to the Wheland intermediate (σ-INT) via a σ-complex transition state (σ-TS). The formation of the σ-TS is the rate-determining step, and the barrier height is 8.37 kJ/mol with the correction for ZPVE. A comparison of the intensities and the shifts given by the computational infrared C−N and C−H stretching frequencies on going from σ-TS to σ-INT shows that the formation of bond C1−...
TL;DR: Results show that random signal radar has excellent LPI property and EMC performance simultaneously, which can satisfy both military and civilian requirements.
Abstract: Besides some general requirements, modern military radars should possess excellent LPI (low probability of intercept) properties. And civilian radars should satisfy the rigorous requirement of EMC (electro-magnetic compatibility) performance. The special features of random signal radar are analyzed here based on the different requirements for military and civilian use. Results show that random signal radar has excellent LPI property and EMC performance simultaneously, which can satisfy both military and civilian requirements.
TL;DR: In this article, the transient temperature fields generated by a pulsed laser in a film-substrate system were obtained by using the finite element method, where the temperature dependences of material properties were taken into account, which has a great influence on the temperature fields indicated by the numerical results.
TL;DR: In this paper, a solid-state reaction of Na2CO3 and TiO2 with different average particle sizes was studied and it was found that nanometer sized TiO 2 facilitates the solid state reaction and leads to the formation of ultrafine titanate.
Abstract: Layered titanate Na2Ti3O7 powders with varying sizes were prepared by solid-state reaction of Na2CO3 and TiO2 with different average particle sizes. The structures of the titanates and the products which had undergone H+ and Ag+ exchange were investigated by XRD, TEM and BET analysis. The influence of the particle size of starting material TiO2 on the reaction rate, the particle size and ion-exchange property of the resulting products was studied. It is found that nanometer sized TiO2 facilitates the solid-state reaction and leads to the formation of ultrafine titanate. The H+-exchange property is improved by decreasing the particle size of Na2Ti3O7 and the small sized layered titanate can be exfoliated easily by AgNO3 solution.
TL;DR: In this paper, the free vibrations of rectangular Mindlin plates with variable thickness in one or two directions are investigated, and the eigenfrequency equation is obtained by using the Rayleigh-Ritz method.