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Fractional delay compensated discrete-time SMC for networked control system

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digital Communications and Networks 2017年第2期3卷 112-117页

作者： d.h. Shah A.J. Mehta Gujarat Technological University Gujarat India Institute of Infrastructure Technology Research and Management Gujarat India

Time-varying network induced delay in the communication channel severely affects the performance of closed loop network control systems. In this paper, a novel idea of compensating the fractional time varying communication delay in the sliding Surface is presented. The fractional time delay in the sensor to controller and controller to actuator channel is approximated using the Thiran approximation technique to design the sliding surface. A discrete-time sliding mode control law is derived using the proposed surface that compensates fractional time delay in sensor to controller and controller to actuator channels for uncertain network control systems. The sufficient condition for closed loop stability of the system is derived using the Lyapunov function. The efficacy of the proposed strategy is supported by the simulation results.

关键词： discrete-time sliding mode control Networked control Network delay

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恋爱中的女人

A strategy for rock/coal outburst prevention

作者： (英)d.h. 劳伦斯(d.h. Lawrence)

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Journal of Coal Science & Engineering(China) 2007年第3期13卷 225-229页

作者： d.h. Steve Zou 程久龙 Mineral Resource Engineering Dalhousie University Halifax B3J1Z1 Key Laboratory of Mine disaster Prevention and Control Shandong University of Science ＆ Technology Qingdao 266510 China

The current practice of rock/coal outburst monitoring, prevention and control was reviewed. The uncertainty of major factors contributing to the occurrence of such hazards and the complexicity of mining conditions surrounding the occurrence were analyzed. A strategic concept for rock/coal outburst prevention was introduced. The objective is to identify the bursting potential in an area, rather than predicting the bursting, by introducing a multi- dimension index model： potential-of-bursting （POB）, taking into consideration major contributing factors. In application, once the index has passed certain critical level indicating high risk, actions must be taken to reduce the bursting potential and to effectively prevent the hazard from occurring. A conceptual 2d model involving stress and methane pressure was described to demonstrate the methodology for determining the POB. however in practice, a POB model has to be established through experiments, field monitoring and calibration against case studies. To achieve this objective, coordinated research and international collaboration will be needed.

关键词： rock/coal outbursts mine hazards bursting potential

The h_∞ synchronization of nonlinear Bloch systems via dynamic feedback control approach

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Chinese Physics B 2011年第7期20卷 101-106页

作者： d.h. Ji J.h. Koo S.C. Won Ju h. Park Mobile Communication division Digital Media and Communications Samsung Electronics Co. Ltd 416-2 Maetan-Dong Suwon 443-803 Republic of Korea department of Electronic and Electrical Engineering Pohang University of Science and Technology San 31 Hyoja-Dong Pohang 790-784 Republic of Korea department of Electrical Engineering Yeungnam University 214-1 Dae-Dong Kyongsan 712-749 Republic of Korea

We consider an h∞ synchronization problem in nonlinear Bloch systems. Based on Lyapunov stability theory and linear matrix inequality formulation, a dynamic feedback controller is designed to guarantee asymptotic stability of the master-slave synchronization. Moreover, this controller reduces the effect of an external disturbance to the h∞ norm constraint. A numerical example is given to validate the proposed synchronization scheme.

关键词： h∞ synchronization Bloch system dynamic control linear matrix inequality

Chaos,Transport and Mesh Convergence for Fluid Mixing

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Acta Mathematicae Applicatae Sinica 2008年第3期24卷 355-368页

作者： h. Lim Y. Yu J. Glimm X.L. Li d.h. Sharp department of Applied Mathematics and Statistics Stony Brook University Stony Brook NY 11794-3600 USA Computational Science Center Brookhaven National Laboratory Upton N~ 11793-6000 USA Los Alamos National Laboratory Los Alamos NM USA

Chaotic mixing of distinct fluids produces a convoluted structure to the interface separating these fluids. For miscible fluids （as considered.h.re）, this interface is defined as a 50% mass concentration isosurface. For shock wave induced （Richtmyer-Meshkov） instabilities, we find the interface to be increasingly complex as the computational mesh is refined. This interfacial chaos is cut off by viscosity, or by the computational mesh if the Kolmogorov scale is small relative to the mesh. In a regime of converged interface statistics, we then examine mixing, i.e. concentration statistics, regularized by mass diffusion. For Schmidt numbers significantly larger than unity, typical of a liquid or dense plasma, additional mesh refinement is normally needed to overcome numerical mass diffusion and to achieve a converged solution of the mixing problem. however, with the benefit of front tracking and with an algorithm that allows limited interface diffusion, we can assure convergence uniformly in the Schmidt number. We show that different solutions result from variation of the Schmidt number. We propose subgrid viscosity and mass diffusion parameterizations which might allow converged solutions at realistic grid levels.

关键词： Schmidt number mass diffusion turbulence multiphase flow

Fabrication of ultrafine Nd-Fe-B powder by a modified reduction-diffusion process

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Rare Metals 2006年第z2期25卷 223-226页

作者： JANG T.S. LEE d.h. ChOI C.J. SEO W.S. LEE Y.h. department of Electronic Materials Engineering Sunmoon University Korea Powder Materials Research Center Korea Institute of Machinery and Materials Korea Advanced Materials Analysis & Evaluation Center Korea Institute of Ceramic Engineering and Technology Korea

In order to obtain ultrafine Nd-Fe-B powder, a spray-dried precursor was treated by reduction-diffusion (R/d) process. And, unlike the conventional R/d process, calcium reduction that is a crucial step for the formation of Nd2Fe14B was performed without conglomerating the precursor with Ca powder. By adopting this modified process, it is possible to synthesize the hard magnetic Nd2Fe14B at the reaction temperature as low as 850 ℃. The average size of Nd2Fe14B particles that are uniformly distributed in the optimally treated powder was d2Fe14B particles were enclosed with thin layers of Nd-rich phase. Typical magnetic properties of such powder without eliminating impurity CaO were ihc=～5.9 kOe, Br=～5.5 kG, and (Bh)max=～6 MGOe.

关键词： NdFeB powder spray drying reduction-diffusion process Nd2Fe14B magnetic powder

AB INITIO CALCULATION OF ThE ELASTIC ANd OPTICAL PROPERTIES OF Al3Sc COMPOUNd

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Acta Metallurgica Sinica(English Letters) 2007年第6期20卷 425-428页

作者： M. Song d.h. Xiao State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083 China

The ab initio method.h.s been performed to explore the elastic and optical properties of Al3Sc compound, based on a plane wave pseudopotential method. It can be seen that the calculated equilibrium lattice parameter and elastic constants are in reasonable agreement with the previous experimental data. The elastic constants satisfy the requirement for mechanical stability in the cubic structure of the Al3Sc compound. The optical property calculations show that a strong absorptive peak exists from O-15eV and a relative small absorptive peak exists around 30eV. The form is caused by the optical transitions between high s, p, and d bands, and the latter results from the optical transitions from high s, p, and d bands to the low 2p band.

关键词： intermetallic compound Al3Sc, elastic property optical property ab initio calculation

dynamic stress concentration in an infinitely long cylindrical cavity due to a point spherical source embedded within a fluid-saturated poroelastic formation of infinite extent

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Applied Mathematics and Mechanics(English Edition) 2025年第1期46卷 139-156页

作者： h.hOSSEINI O.BALILAShAKI department of Mechanical Engineering Faculty of EngineeringGolestan University

The effects of a harmonically exciting monopole source on an infinitely long cylindrical cavity embedded entirely within a fluid-saturated poroelastic formation of infinite extent are examined theoretically. It is assumed that the source is located outside the cavity at a specified distance from the borehole axis. The magnitudes of the hoop and radial stresses beside the pore pressures exerted on the interface and inside the porous medium surrounding the borehole are calculated and discussed. Biot's poroelastic modeling along with three types of boundary conditions for the cylindrical interface including the ideal fluid, empty borehole, and rigid inclusion with a hard boundary is employed for the analysis. Utilizing a proper translational addition theorem for expressing the incident spherical wave in terms of cylindrical wave expansions, the proposed boundary conditions at the interface are satisfied. Stresses are formulated by means of wave potential functions in a three-dimensional(3d) manner. The effects of the frequency and the radial distance between the source and borehole on the induced stresses are examined for the first cylindrical modes over frequency spectra. Two permeability conditions for the interface and three types of soils for the porous formation are considered throughout the analysis. To give an overall outline of the study, a numerical example is presented. The results clearly indicate that the distance is a key parameter and.h.s considerable effects on the induced stress values. In addition, the interface permeability condition and soil characteristics play an important role in determining the dynamic response of the borehole. Finally,the obtained results are compared with the relevant analyses existing in the literature for some limit cases, and good agreement is achieved.

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Neuroinflammation as a therapeutic target in huntington's disease

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Neural Regeneration Research 2025年第3期20卷 817-818页

作者： Andrea Kwakowsky Thulani h.Palpagama Center for Brain Research and department of Anatomy and Medical Imaging Faculty of Medical and Health SciencesUniversity of AucklandAucklandNew Zealand Pharmacology and Therapeutics School of MedicineGalway Neuroscience CentreUniversity of GalwayGalwayIreland

In 1872, George huntington presented.h.s essay “On Chorea” to the Meigs and Mason Academy of Medicine and, in doing so, detailed a disease that would later bear his name. huntington's disease(hd) is a genetic, neurodegenerative disease that manifests as the loss of motor control,cognitive impairment,and mood and psychiatric changes in paents.

关键词： huntington inflammation Medicine