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Search Results: 1 - 10 of 91021 matches for " Chen Xiang "
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Exponential Dichotomies and Homoclinic Orbits from Heteroclinic Cycles  [PDF]
Tiejun Chen, Yu Xiang, Yuxiao Chen
American Journal of Computational Mathematics (AJCM) , 2012, DOI: 10.4236/ajcm.2012.22014
Abstract: In this paper, we investigate the homoclinic bifurcations from a heteroclinic cycle by using exponential dichotomies. We give a Melnikov—type condition assuring the existence of homoclinic orbits form heteroclinic cycle. We improve some important results.
Assessment of modification level of hypoeutectic Al -Si alloys by pattern recognition of cooling curves
CHEN Xiang
China Foundry , 2005,
Abstract: Most evaluations of modification level are done according to a specific scale based on an merican Foundry Society (AFS) standard wall chart as qualitative analysis in Al-Si casting production currently. This method is quite dependent on human experience when making comparisons of the microstructure with the standard chart. And the structures depicted in the AFS chart do not always resemble those seen in actual Al-Si castings. Therefore, this ualitativeanalysis procedure is subjective and can introduce human-caused errors into comparative metallographic analyses. A quantization parameter of the modification level was introduced by setting up the relationship between mean area weighted shape factor of eutectic silicon phase and the modification level using image analysis technology. In order to evaluate the modification level, a new method called "intelligent evaluating of melt quality by pattern recognition of hermal analysis cooling curves" has also been introduced. The results show that silicon modification level can be precisely assessed by comparison of the cooling curve of the melt to be evaluated with the one most similar to it in a database.
Delay-Optimal Buffer-Aware Probabilistic Scheduling with Adaptive Transmission
Xiang Chen,Wei Chen
Mathematics , 2015,
Abstract: Cross-layer scheduling is a promising way to improve Quality of Service (QoS) given a power constraint. In this paper, we investigate the system with random data arrival and adaptive transmission. Probabilistic scheduling strategies aware of the buffer state are applied to generalize conventional deterministic scheduling. Based on this, the average delay and power consumption are analysed by Markov reward process. The optimal delay-power tradeoff curve is the Pareto frontier of the feasible delay-power region. It is proved that the optimal delay-power tradeoff is piecewise-linear, whose vertices are obtained by deterministic strategies. Moreover, the corresponding strategies of the optimal tradeoff curve are threshold-based, hence can be obtained by a proposed effective algorithm. On the other hand, we formulate a linear programming to minimize the average delay given a fixed power constraint. By varying the power constraint, the optimal delay-power tradeoff curve can also be obtained. It is demonstrated that the algorithm result and the optimization result match each other, and are further validated by Monte-Carlo simulation.
Thermal Conductivity of Carbon/Carbon Composites with the Fiber/Matrix Interface Modified by Silicon Carbide Nanofibers  [PDF]
Jie Chen, Xiang Xiong, Peng Xiao
Advances in Chemical Engineering and Science (ACES) , 2016, DOI: 10.4236/aces.2016.64045
Abstract: Silicon carbide nanofibers grew on the surface of carbon fibers of a unidirectional carbon preform by CCVD and then chemical vapor infiltration was used to densify the preform to get the SiCNF-C/C composite. The effects of silicon carbide nanofibers on the microstructure of the pyrolytic carbon and the thermal conductivity of the SiCNF-C/C composite were investigated. Results show that silicon carbide nanofibers on the surface of carbon fibers induce the deposition of high texture pyrolytic carbon around them. The interface bonding between carbon fibers and pyrolytic carbon is well adjusted. So the efficiency of heat transfer in the interface of the composite is well enhanced. The thermal conductivity of the SiCNF-C/C composite is greater than that of the C/C composite, especially the thermal conductivity perpendicular to the fiber axis.
Robust Reliable Stabilization of Switched Nonlinear Systems with Time-Varying Delays and Delayed Switching
Zhengrong Xiang,Qingwei Chen
Mathematical Problems in Engineering , 2010, DOI: 10.1155/2010/471680
Abstract: This paper is concerned with the problem of robust reliable stabilization of switched nonlinear systems with time-varying delays and delayed switching is investigated. The parameter uncertainties are allowed to be norm-bounded. The switching instants of the controller experience delays with respect to those of the system. The purpose of this problem is to design a reliable state feedback controller such that, for all admissible parameter uncertainties and actuator failure, the system state of the closed-loop system is exponentially stable. We show that the addressed problem can be solved by means of algebraic matrix inequalities. The explicit expression of the desired robust controllers is derived in terms of linear matrix inequalities (LMIs).
Stability Analysis and Robust Control of Switched Stochastic Systems with Time-Varying Delay
Zhengrong Xiang,Guoxin Chen
Journal of Applied Mathematics , 2012, DOI: 10.1155/2012/202916
Abstract: The problems of mean-square exponential stability and robust ∞ control of switched stochastic systems with time-varying delay are investigated in this paper. Based on the average dwell time method and Gronwall-Bellman inequality, a new mean-square exponential stability criterion of such system is derived in terms of linear matrix inequalities (LMIs). Then, ∞ performance is studied and robust ∞ controller is designed. Finally, a numerical example is given to illustrate the effectiveness of the proposed approach.
Studies on the excitation-dependent expression of nucleus respiration factors of rat visual cortical neurons
Xiang CHEN,Xiao ZHAO
Medical Journal of Chinese People's Liberation Army , 2013,
Abstract: Objective  To study the expression profile of nucleus respiration factors (NRFs) and related genes in a rat neuron model after KCl(25mmol/L)-mediated membrane depolarization. Methods  Primary cultured visual cortical neurons of newborn rats were stimulated with KCl (25mmol/L). The cells were collected at 1, 3, 5, 7 and 10h after stimulation, and the intracellular RNA was extracted and amplified by RT-PCR. The expressions of NRFs subtypes (NRF-1, NRF-2α and NRF-2β) in neuron, upstream gene PGC-1 and downstream gene mtTFA were then examined. Results  NRFs gene expressed differently after KCl stimulation: the expression of NRF-1 reached peak value two times at 3h and 7h, respectively, after simulation. NRF-2α reached the peak at 3h after simulation, and then it declined at 5h, followed by a rise again, and it then maintained at that level, while NRF-2β reached a peak value at 7h after stimulation. The expression of mtTFA expression reached peak value two times at 3h and 7h, respectively, after simulation, while the expression of PGC-1 was up-regulated progressively for two times, reaching the peak value at 10h after stimulation. The expressions of NRF-1, NRF-2α and NRF-2β were significantly different compared with that of controls (P<0.05). Conclusion  NRFs in visual cortex have different reaction mode, and they may play different roles in response to stimulation.
SAD-Based Stereo Vision Machine on a System-on-Programmable-Chip (SoPC)
Xiang Zhang,Zhangwei Chen
Sensors , 2013, DOI: 10.3390/s130303014
Abstract: This paper, proposes a novel solution for a stereo vision machine based on the System-on-Programmable-Chip (SoPC) architecture. The SOPC technology provides great convenience for accessing many hardware devices such as DDRII, SSRAM, Flash, etc., by IP reuse . The system hardware is implemented in a single FPGA chip involving a 32-bit Nios II microprocessor, which is a configurable soft IP core in charge of managing the image buffer and users’ configuration data. The Sum of Absolute Differences (SAD) algorithm is used for dense disparity map computation. The circuits of the algorithmic module are modeled by the Matlab-based DSP Builder. With a set of configuration interfaces, the machine can process many different sizes of stereo pair images. The maximum image size is up to 512 K pixels. This machine is designed to focus on real time stereo vision applications. The stereo vision machine offers good performance and high efficiency in real time. Considering a hardware FPGA clock of 90 MHz, 23 frames of 640 × 480 disparity maps can be obtained in one second with 5 × 5 matching window and maximum 64 disparity pixels.
The Effect of the Confidence Notion in the Chinese Culture Through the Dictums
Sui-xiang CHEN
Canadian Social Science , 2010,
Abstract: The Chinese dictum conveys his culture. The present paper aims to make a survey on the confidence notion in the Chinese culture. This notion is bound to the anthers virtues such as human sense, ritual spirit, just sense, wisdom. Theses notions constitute five guiding principles. The confidence notion is worth considering, because it can ensure the human contact. We attach attention to this notion in order to construct a harmonious society. Key words: dictum; confidence notion; interpersonal relation; the Chinese culture Résumé: Les dictons chinois charrient sa culture. Notre texte vise à souligner le r le de la notion de confiance dans la culture chinoise. Cette notion se rattache aux autres vertus comme le sens humain, l’esprit rituel, le sens du juste, la sagesse, ce qui constitue cinq constantes. Si la confiance est digne de considération, c’est qu’elle assure le contact du soi à l’autre. La prise en compte de cette notion est de mise dans le cadre de la construction d’une société harmonieuse. Mots–clés: dicton; la notion de confiance; les relations interpersonnelles, la culture chinoise
Effects of strontium and boron interactions in Al-7Si alloys
Chen Xiang,Li Yanxiang
China Foundry , 2010,
Abstract: Effects of boron and strontium combined treatment on the microstructure of hypoeutectic Al-7Si alloy have been studied. Experimental results show that strontium has no significant effect on the grain refinement efficiency of boron and the eutectic silicon modification efficiency is not only related to the strontium content but also related to the boron content in the Al-7Si alloy melt. There is a negative interaction between boron and strontium that results in the formation of a strontium-boron-aluminum containing compound, which reduces the effective strontium level and decreases the eutectic silicon modification efficiency substantially. The refinement and modification mechanisms remain unchanged after the combined addition of strontium and boron. Based on the experimental results, a model for assessing the modification level in the Al-Si alloy melts after combined addition of boron and strontium was presented.
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