Showing papers by "Southeast University published in 2000"
TL;DR: In this article, the optimization of fiber size, fibre content, and fly ash content in hybrid polypropylene-steel fiber concrete with low fibre content based on general mechanical properties was investigated.
390 citations
TL;DR: In this article, the porosity and pore size distribution of the concrete were investigated by using mercury intrusion porosimetry, and a model was developed by optimizing the parameters in the Ryshkewitch model to predict the relationship between porosity, and the strength of HPC.
275 citations
TL;DR: An efficient algorithm is proposed to reduce the computation cost of block matching algorithms for motion estimation in video coding by using the sum norms of the blocks and the subblocks for eliminating the search positions.
Abstract: An efficient algorithm is proposed to reduce the computation cost of block matching algorithms for motion estimation in video coding. Based on a new insight in block matching algorithms, we extend the successive elimination algorithm to a multilevel case. By using the sum norms of the blocks and the subblocks, tighter and tighter decision boundaries can be obtained for eliminating the search positions. The efficiency of the proposed algorithm combined with the full search algorithm and several fast search algorithms is verified by simulation results.
271 citations
TL;DR: In this paper, the hydration processes of high-volume fly ash cement paste were investigated by examining the non-evaporable water content, the CH content, pH of pore solution and the fraction of reacted fly ash, curing at either 20°c or elevated temperatures after an initial curing at 20°C.
Abstract: The hydration processes of high-volume fly ash cement paste were investigated by examining the non-evaporable water content, the CH content, the pH of pore solution and the fraction of reacted fly ash, curing at either 20°C or elevated temperatures after an initial curing at 20°C. The replacement percentage levels of fly ash were 40%, 50% and 60% by weight, respectively. The results revealed that the non-evaporable water content in high-volume fly ash cement pastes does not develop as plain cement pastes does, so it may be improper to apply the non-evaporable water content to evaluate the hydration process in high-volume fly ash cement matrix. The reduction in CH content increases with the progressing of hydration process and varies linearly with the logarithm of curing age. The addition of 3.0% of Na2SO4 could accelerate the pozzolanic reaction of fly ash at early ages. At 20°C, the pH of pore solution of high-volume fly ash cement paste was reduced to a great extent at early ages and it continued to decline at later ages due to the inclusion of large amount of fly ashes. At elevated temperatures, however, this trend was not found. The fraction of reacted fly ash directly reflects the pozzolanic reactivity of fly ash both at normal and elevated temperatures. There is some inherent correlation between the reduction in CH content, the pH of pore solution and the fraction of reacted fly ash. For specified matrix, the consumption of CH and the pH of pore solutions change linearly with the increase of the fraction of reacted fly ash.
182 citations
TL;DR: These conditions are presented in terms of system parameters, and have an important leading significance in the design and applications of periodic oscillatory neural circuits for the BAM with delays.
Abstract: Periodic oscillatory phenomena of bidirectional associative memory (BAM) networks with axonal signal transmission delays are investigated by constructing suitable Lyapunov functionals and some analysis techniques. Some simple sufficient conditions are derived ensuring the existence and uniqueness of periodic oscillatory solutions of the BAM with delays, and all other solutions of the BAM converge exponentially to a periodic oscillatory solution. These conditions are presented in terms of system parameters, and have an important leading significance in the design and applications of periodic oscillatory neural circuits for the BAM with delays.
165 citations
TL;DR: In this article, the global exponential stability and the periodic oscillation of a class of delayed cellular neural networks (DCNNs) are investigated and sufficient conditions are given to design globally exponentially stable DCNNs and periodic oscillatory DNNs.
141 citations
TL;DR: In this paper, the residual compressive strength of high performance concrete (HPC) and normal strength concrete (NSC) was investigated after they were exposed to high temperatures, 800°C and 1100°C, and two cooling regimes.
129 citations
TL;DR: In this paper, the authors analyzed further problems of global exponential stability and the existence of periodic solutions of cellular neural networks with delays (DCNNs) by applying some new analysis techniques and constructing suitable Lyapunov functionals.
127 citations
TL;DR: In this paper, the behavior of high performance concrete (HPC), compared with normal strength concrete (NSC), after subject to different high temperatures (800 and 1100°C) and cooling regimes (gradual and rapid cooling).
122 citations
TL;DR: In this article, a four-point bending test is adopted on the notched prisms with the size of 100×100×500 mm 3 to investigate the effect of hybrid fibres on crack arresting.
Abstract: This research discusses polypropylene fibres and three sizes of steel fibres reinforced concrete The total fibre content ranges from 0% to 095% by volume of concrete A four-point bending test is adopted on the notched prisms with the size of 100×100×500 mm 3 to investigate the effect of hybrid fibres on crack arresting The research results show that there is a positive synergy effect between large steel fibres and polypropylene fibres on the load-bearing capacity and fracture toughness in the small displacement range But this synergy effect disappears in the large displacement range The large and strong steel fibre is better than soft polypropylene fibre and small steel fibre in the aspect of energy absorption capacity in the large displacement range The static service limitation for the hybrid fibres concrete, with “a wide peak” or “multi-peaks” load–CMOD patterns, should be carefully selected The ultimate load bearing capacity and the crack width or CMOD at this load level should be jointly considered in this case The K IC and fracture toughness of proper hybrid fibre system can be higher than that of mono-fibre system
112 citations
TL;DR: In this article, the relationship between the resistance of the targets against impact and the parameters concerned was analyzed, and it was possible to predict the penetration performance in a real situation by using the test results from a simulation test.
TL;DR: In this article, the controllability and control ranges of power flow on a transmission line installed with a single FACTS device are analyzed first, and then, the coordination of the power flow control with several FACTS devices is described as an optimization problem.
Abstract: In this paper, based on the steady state models of FACTS devices, the controllability and control ranges of power flow on a transmission line installed with a single FACTS device are analyzed first. Then, the coordination of power flow control with several FACTS devices is described as an optimization problem. To solve this problem, a new method based on the genetic algorithm (GA) has been proposed. With this proposed method, the maximum range of power flow control on any transmission line or any set of transmission lines can easily be obtained. Examples demonstrate the proposed method is both reliable and effective, and the power flow control range is dependent not only on the type of FACTS device, but also the initial power flow on transmission line.
TL;DR: In this paper, a set of criteria for the global exponential stability and the existence of periodic solutions of delayed cellular neural networks (DCNNs) by constructing suitable Lyapunov functionals, introducing many parameters and combining with the elementary inequality technique is presented.
TL;DR: By introducing an integral action into the Luenberger observer, a new kind of observer with integrators is presented and an illustrative example is included.
Abstract: The problem of observer design for linear systems with unknown input disturbances is considered. By introducing an integral action into the Luenberger observer, a new kind of observer with integrators is presented. The existence condition for such an observer is given and an illustrative example is included.
TL;DR: In this article, the global existence and finite time blow up of positive solution for the initial-boundary value problem of a reaction-diffusion system was studied, and it was shown that positive solutions can be found in finite time.
Abstract: In this paper, we study the global existence and finite time blow up of positive solution for the initial-boundary value problem of a reaction-diffusion system.
TL;DR: A new type controller, fuzzy neural networks sliding mode controller (FNNSMC), is developed for a class of large-scale systems with unknown bounds of high-order interconnections and disturbances, which can eliminate the chattering by using the continuous output of the FNN to replace the "discontinuous" sign term in the SMC.
Abstract: A new type controller, fuzzy neural networks sliding mode controller (FNNSMC), is developed for a class of large-scale systems with unknown bounds of high-order interconnections and disturbances. Although sliding mode control is simple and insensitive to uncertainties and disturbances, there are two main problems in the sliding mode controller (SMC): control input chattering and the assumption of known bounds of uncertainties and disturbances. The FNNSMC, which incorporates the fuzzy neural networks (FNNs) and the SMC, can eliminate the chattering by using the continuous output of the FNN to replace the "discontinuous" sign term in the SMC. The bounds of uncertainties and disturbances are also not required in the FNNSMC design. Two examples are presented to support the validity of the new controller. The simulation results show that the FNNSMC is more robust than the SMC.
30 Apr 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the microstructure and heterogeneous nucleation phenomena in cast SiC particles reinforced magnesium composite have been studied using optical and transmission electron microscopy (TEM) techniques.
Abstract: The microstructure and heterogeneous nucleation phenomena in cast SiC particles reinforced magnesium composite have been studied using optical and transmission electron microscopy (TEM). The microstructure of magnesium composites showed that most SiC particles were pushed and segregated at the grain boundaries while few SiC particles (3%) were entrapped in the magnesium grain. The SiC particles in the magnesium composite were identified as 6Hα-SiC structure. Stacking faults and pits defects were also observed within the SiC particles. The primary magnesium phase which heterogeneously nucleated on the SiC particle surface has been identified with a small lattice disregistry (2.3%) while their crystallographic orientation relationship was (10 1 0)Mg//(0001)SiC. Examination of the composite interface indicated that the eutectic and Cu5Zn8 phases were able to wet the SiC particles and heterogeneously nucleate on the SiC particles while the crystallographic orientation relationships between them were (01 1 1)SiC//(110)Mg17Al12 and (0001)SiC//(001)Cu5Zn8, respectively. Finally, the factors that influence the heterogeneous nucleation of primary magnesium phase, eutectic and Cu5Zn8 phases on the SiC particles are discussed.
01 Mar 2000
TL;DR: In this paper, a pattern recognition method for localisation of the partial discharge (PD) site in an oil-filled transformer by acoustic measurements is presented, where the transformer is divided into a number of 20/spl times/20/spltimes/20 mm/sup 3/ sub-modules, and the site is localised by comparing the spatial distance of each sub-module to the acoustic sensors.
Abstract: A pattern recognition method for localisation of the partial discharge (PD) site in an oil-filled transformer by acoustic measurements is presented. By dividing the transformer into a number of 20/spl times/20/spl times/20 mm/sup 3/ sub-modules, the PD site is localised by comparing the spatial distance of each sub-module to the acoustic sensors. The numerical cases indicate that the proposed method is general and practical, while avoiding some drawbacks in current algorithms. Moreover, the method improves the accuracy of localisation substantially when compared with the conventional localisation method.
TL;DR: In this article, the strength of roller-compacted concrete with high volume fly ash (HFRCC) is examined by using the notion of specific strength, the qualified contribution of fly ash effect to construction formation and strength development of HFRCC is also analyzed.
TL;DR: In this article, a comparison was performed among the capabilities of coal ashes in laboratory ashing procedure, pulverised coal-fired combustor and fluidised bed combustor (FBC), and it was shown that calcium plays a dominant role in sulphur retention of laboratory-prepared ash and the sulphur percentage increases with the increase of Ca/S molar ratio of the parent coal, while the contributions of other elements are limited.
TL;DR: In this article, the formulae of Laplace transform with respect to time for frost forces of the lining-frozen surrounding rock-unfrozen around rock system are derived from the elastic-viscoelastic corresponding principle.
01 Jun 2000
TL;DR: A user's Web surfing action is abstracted as a Markov model and a new rank algorithm is proposed, which synthesizes the relevance, authority, integrativity and novelty of each Web resource and can be computed efficiently through solving a group of linear equations.
Abstract: How to rank Web resources is critical to Web Resource Discovery (Search Engine). This paper not only points out the weakness of current approaches, but also presents in-depth analysis of the multidimensionality and subjectivity of rank algorithms. From a dynamics viewpoint, this paper abstracts a user's Web surfing action as a Markov model. Based on this model, we propose a new rank algorithm. The result of our rank algorithm, which synthesizes the relevance, authority, integrativity and novelty of each Web resource, can be computed efficiently not by iteration but through solving a group of linear equations.
TL;DR: In this paper, the effects of melt viscosity on the foaming process and the structures of foamed aluminum have been examined, and methods for measuring the melt visco-ness, pore structure, and process parameters are introduced.
Abstract: The effects of melt viscosity on the foaming process and the structures of foamed aluminum have been examined Methods for measuring the melt viscosity, pore structure, and foaming process are introduced To increase the stability of the foaming melt and get the sample with a uniform pore distribution, a proper viscosity is needed Further, the structure of foamed aluminum can be controlled by adjusting the Ca addition and other process parameters
TL;DR: This study confirmed the potential of preparing dense, homogeneous, highly specific, and highly stable antibody surfaces by immobilizing antibodies on polystyrene surfaces with controlled roughness and expected that such biofunctional surfaces could be of interest for the development of new solid-phase immunoassay techniques and biosensor techniques.
Abstract: Background: Functional antibody surfaces were prepared on ultraflat polystyrene surfaces by physical adsorption, and the uniform distribution of monoclonal antibodies against hepatitis B surface antigen (anti-HBs) on such surfaces and the presence of dense hepatitis B surface antigen (HBsAg) particles captured by immobilized antibodies were identified.
Methods: A model polystyrene film was spin-coated directly onto a silicon wafer surface. Atomic force microscopy was used to directly monitor the immobilization of anti-HBs antibodies and their specific molecular interaction with HBsAg. Enzyme immunoassay was also used to characterize functional antibody surfaces.
Results: A mean roughness of 2 A for areas of 25 μm2 was produced. We found a uniform distribution of anti-HBs antibodies on ultraflat polystyrene surfaces and the presence of dense HBsAg particles bound to such anti-HBs surfaces after incubation with HBsAg.
Conclusions: This study confirmed the potential of preparing dense, homogeneous, highly specific, and highly stable antibody surfaces by immobilizing antibodies on polystyrene surfaces with controlled roughness. It is expected that such biofunctional surfaces could be of interest for the development of new solid-phase immunoassay techniques and biosensor techniques.
TL;DR: In this paper, the tensile behavior, thermal expansion and dimensional stability of aluminum-silicon (Al-12 wt.%Si) alloy reinforced with potassium titanate whiskers were investigated.
TL;DR: In this paper, a novel spiral antenna backed on photonic bandgap (PBG) material is presented, which consists of a spiral radiator, a PBG substrate and a feed network, and exhibits a wider frequency bandwidth, larger ratio of front-to-back radiation level, and higher gain than a traditional spiral antenna with /spl lambda/4 spaced ground plate.
Abstract: A novel spiral antenna backed on photonic bandgap (PBG) material is presented It consists of a spiral radiator, a PBG substrate and a feed network; and exhibits a wider frequency bandwidth, larger ratio of front-to-back radiation level, and higher gain than a traditional spiral antenna with /spl lambda//4 spaced ground plate
TL;DR: A bilevel programming method is developed to determine the optimal fare structure for the transit operator while taking passengers' response into account, and a heuristic solution algorithm based on sensitivity analysis is proposed.
Abstract: A bilevel model is presented to optimize the fare structure for transit networks with elastic demand under the assumption of fixed transit service frequency. It is known that the transit fare structure has significant effects on passengers' demand and route choice behavior. The transit operator therefore should predict passengers' response to changing fare charges. A bilevel programming method is developed to determine the optimal fare structure for the transit operator while taking passengers' response into account. The upper-level problem seeks to maximize the operator's revenue, whereas the lower-level problem is a stochastic user equilibrium transit assignment model with capacity constraints. A heuristic solution algorithm based on sensitivity analysis is proposed. Finally, a numerical example is given together with some useful discussion.
TL;DR: In this paper, a variety of results are pointed out which assure global existence of solutions to fuzzy differential equations.
TL;DR: A novel time-delayed control method is proposed for stabilizing inherent unstable periodic orbits (UPOs) in chaotic systems and uses the inherent properties of chaotic systems in forming a performance index so that when the index is minimized, the resulting controller enables stabilization of the desired UPOs.
Abstract: A novel time-delayed control method is proposed for stabilizing inherent unstable periodic orbits (UPOs) in chaotic systems. Differing from the commonly used linear time-delayed feedback control form, we adopt an optimal control principle for the design of the time delayed feedback control. We explore the inherent properties of chaotic systems and use the system states and time-delayed system states in forming a performance index so that when the index is minimized, the resulting controller enables stabilization of the desired UPOs. The effectiveness of the method is confirmed by computer simulations.