检索结果-南通市图书馆

Influences of TiC Impurities on Dry-sliding Wear of Polycrystalline Ceramic

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2022年第4期37卷 570-575页

作者： BENDAOUDI Seif Eddine BOUNAZEF mokhtar DJEFFAL Ali Laboratory of Industrial Engineering and Sustainable Development Department of Mechanical EngineeringUniversity of RelizaneAlgeria Department of Mechanical Engineering University Djillali LIABES of Sidi Bel AbbesAlgeria

The wear behavior of titanium silicon carbide MAX phase was *** of highly pure TiSiCand containing 8% of TiC,sliding dryly against Corundum counterpart,were tested at various speeds increasing from 5 to 60 m/s and under applied pressure of 0.1-0.8 *** sliding-wear tests were performed on Tribometer,at room temperature of 15℃ with a relative humidity of 10%.The expermental results show that the presence of TiC particles can be beneficial to reducing the wear rate for certain ranges of sliding speed and applied *** sliding-wear performances were expressed as a mathematical model,obtained through a modelling by the method of design of *** influence of TiC impurities on the wear behaviors was also *** is concluded that the wear mechanisms of samples are more affected by the presence of TiC under the effect of applied pressure compared with that of the sliding speed.

关键词： sliding-wear pin-on-disc design of experiments mathematical model polycrystalline ceramic

A new impedance and robust adaptive inverse control approach for a teleoperation system with varying time delay

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2009年第9期52卷 2629-2643页

作者： mokhtar SHA SADEGHI Hamid Reza MOMENI Electrical and Electronic Engineering Department Shiraz University of TechnologyShiraz Iran Electrical Engineering Department Faculty of Engineering Tarbiat Modares UniversityTehran Iran

This paper presents a new robust adaptive inverse control approach for a force-reflecting teleoperation system with varying time delay. First,an impedance control is designed for the master robot. Second,an adaptive inverse control is proposed for the slave robot. Finally,the slave side controller is modified such that the robust stability and performance are achieved. In addition,robust stability analysis has been performed and optimal behavior is ensured by using standard characteristic polynomials. It is shown that despite of presence of randomly-varying time delay,the proposed control algorithm compensates the position drifts efficiently. Demonstrable simulation studies confirm the effectiveness of the proposed control system and its advantages over the existing sliding mode control strategies.

关键词： teleoperation bilateral force feedback adaptive inverse control time delay system

A comparative study on p-doping behavior of polythiophenes with CH_3SO_3H

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2007年第1期50卷 18-22页

作者： IMIT mokhtar YAMAMOTO Takakazu IMIN Patigul School of Chemistry and Chemical Engineering Xinjiang University Chemical Resources Laboratory Tokyo Institute of Technology4259 NagatsutaMidori-kuYokohama 226-8503Japan

Four kinds of polythiophenes have been doped with CH3SO3H in CHCl3 under air,oxygen,and nitrogen. In the doping of two types of poly(3-hexylthiophene)s,P3HexTh(Zn/Ni)and P3HexTh(Fe)with different contents of a head-to-tail unit,the p-doping occurs at a similar *** reaction between poly(3-dodecylthiophene),P3DodTh,and the acid takes place more rapidly.P3OBuTh with a butoxy substituent undergoes more facile p-doping and receives photochemical reaction with CHCl3,and this reaction obeys a pseudo-first-order rate law with a rate constant kobs of 1.42×10-5s-1at room tempera- ture.

关键词： polythiophenes p-doping methanesulfonic acid

Crystal structure and infrared spectrum of thallium holmium polyphosphate, TlHo(PO_3)_4

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2008年第6期26卷 765-769页

作者： Karima Horchani-Naifer Jaouher Amami mokhtar Férid Unité de Recherches de Matériaux de Terres Rares Centre National de Recherches en Sciences des Matériaux

Crystals of thallium-holmium polyphosphate T1Ho（PO3）4 were grown by flux method technique and characterized by single crystal X-ray diffraction. Structure of T1Ho（PO3）4 was solved for the first time, and it crystallized in the monoclinic P21/n space group with the following unit-cell dimensions： a=1.02225（3） nm, b=0.88536（2） nm, c=1.09541（4） nm, β=105.888（1）°, V=0.95354（5） nm^3 and Z=4. The crystal structure was solved from 2174 independent reflections with final R1（F^2）=0.0442 and Rw（F^2）=0.0861 refined with 164 parameters. The atomic arrangement could be described as a long chain polyphosphate organization. Holmium atoms had eightfold coordination. The structure of T1Ho（PO3）4 consisted of HoO8 polyhedra sharing oxygen atoms with phosphoric group PO4. Infrared spectrum was investigated at room temperature in the frequencies range, 350--4000 cm^-1, showing some characteristic vibration bands of infinite chain structure of PO4 tetrahedra linked by bridging oxygen.

关键词： polyphosphate holmium crystal structure infrared spectroscopy rare earths

Combustion synthesis and luminescence properties of LaPO4： Eu （5%）

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2009年第2期27卷 182-186页

作者： Mounir Ferhi Karima Horchani-Naifer mokhtar Férid Research Unit of Rare Earth Materials National Research Center in Sciences of Materials B.P. 95 Hammam-Lif 2050 Tunisia

Rare earth doped materials are an important type of phosphors due to their excellent performance such as stability at high temperature and light emission covering the entire visible domain. The combustion synthesis at acid pH of the monoclinic LaPO4： Eu（5%） powders was described. A mixture of La（NO3）3·6H2O, EuCly6H2O and （NH4）2HPO4 was used as anion precursor and glycin as fuel. The synthesis was followed by structure, morphology characterisation and luminescent properties of the obtained compound. The room temperature emission measurements under ultraviolet excitation at 254 nm were made for the emission transition ^5D0→^7FJ of this phosphor. The CIE （Commission Intemationale de L＇Eclairage） chromatic coordinates, dominant wavelength and colour purity were determined and compared to other luminescent materials obtained by other methods.

关键词： rare earth phosphates combustion optical materials luminescence chromaticity

A Mean-Field Necessary and Sufficient Conditions for Optimal Singular Stochastic Control

在线全文

学校读者我要写书评

暂无评论

Communications in Mathematics and Statistics 2013年第4期1卷 417-435页

作者： mokhtar Hafayed Laboratory of Applied Mathematics Biskra UniversityPO Box 14507000 BiskraAlgeria

This paper studies singular optimal control problems for systems described by nonlinear-controlled stochastic differential equations of mean-field type(MFSDEs in short),in which the coefficients depend on the state of the solution process as well as of its expected ***,the cost functional is also of mean-field *** control variable has two components,the first being absolutely continuous and the second *** establish necessary as well as sufficient conditions for optimal singular stochastic control where the system evolves according to *** conditions of optimality differs from the classical one in the sense that here the adjoint equation turns out to be a linear mean-field backward stochastic differential *** proof of our result is based on convex perturbation method of a given optimal *** control domain is assumed to be convex.A linear quadratic stochastic optimal control problem of mean-field type is discussed as an illustrated example.

关键词： Stochastic optimal singular control Mean-field stochastic maximum principle Mean-field necessary and sufficient conditions of optimality McKean-Vlasov SDEs Convex perturbation

Pointwise Second-Order Necessary Conditions for Stochastic Optimal Control with Jump Diffusions

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Communications in Mathematics and Statistics 2023年第4期11卷 741-766页

作者： Abdelhak Ghoul mokhtar Hafayed Imad Eddine Lakhdari Shahlar Meherrem Laboratory of Mathematical Analysis Probabilities and OptimizationsUniversity of BiskraPo Box 14507000 BiskraAlgeria Department of Mathematics Yasar UniversityUniversity avenAgaclıYol No.35-57IzmirTurkey

In this paper,we establish a second-order necessary conditions for stochastic optimal control for jump *** controlled system is described by a stochastic differential systems driven by Poisson random measure and an independent Brownian *** control domain is assumed to be *** second-order maximum principle for controlled jump diffusion in terms of the martingale with respect to the time variable is *** proof of the main result is based on variational approach using the stochastic calculus of jump diffusions and some estimates on the state processes.

关键词： Optimal control Stochastic systems with jumps Pointwise second-order necessary condition Maximum principle Variational equation

Impact of gamma radiation and salinity on growth and K+/Na+ balance in two populations of Medicago sativa （L.） cultivar Gabès

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2008年第9期18卷 1095-1105页

作者： mokhtar Rejili Dalel Telahigue Belgacem Lachiheb Abdessalem Mrabet Ali Ferchichi Arid & Oases Cropping Laboratory Arid Area Institute (IRA) Medenine 4119 Tunisia

The perennial Medicago sativa ***ès is widely grown on saline soils in Tunisian *** and physiological analyses of two populations (Mareth and Gannouch) were conducted in order to study the efiect of salinity and gamma radiation (350 Gy) inter-action on two populations of this *** has been shown that the two irradiated populations of Medicago sativa are fairly tolerant to salt at growth phase compared to the *** to gamma irradiation (350 Gy), alone or in combination with salt stress, increased significantly (p < 0.001) shoot number, stem height and chlorophyll b pigment especially for the Gannouch population, while no change occurred for the Mareth *** presence of salt to 9 g/l afiected significantly the root biomass and induced a reduc-tion of shoot development of both control and irradiated alfalfa *** all treatments, plants of two populations remained able to produce and to allocate dry matter to the difierent *** survey of Na+/K+ ratio showed that the growth of the aerial organs of two non-irradiated populations was at least determined by a selectivity in favour of the K+ ions (r2 = 0.97 and r2 = 0.59 for Mareth and Gannouch non-irradiated populations, respectively).However, the rather weak correlation detected for the irradiated populations, par-ticularly for the irradiated Gannouch, seems to be the consequence of the efiect of irradiation that improved potassium availability, essential element for growth and *** also showed that the two irradiated populations, especially the Mareth, accumu-lated Na+ ions in its photosynthetic *** accumulation was associated with an improvement of foliar water content at a level of salinity around 5 g/*** a mechanism refiects probably an inclusive behaviour of the plants and a good aptitude to use the dominant ions (Na+) for the osmotic ***, the non-irradiated populations are unable to adjust their internal osmot

关键词： Medicago sativa Gamma radiation Salinity Osmotic adjustment K+/Na+ balance Tolerance

Reflective Ladder Topology Network Based on White Light Fiber-Optic Mach-Zehnder Interferometer

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Harbin Institute of Technology(New Series) 2013年第3期20卷 63-66页

作者： Song Li Ferhati mokhtar Li-Bo Yuan Photonics Research Center School of ScienceHarbin Engineering University

In order to improve the multiplexing capability of the optical sensors based on the lower interferential optic fiber sensing technology and the white light fiber-optic Mach-Zehnder interferometer,reflective ladder topology network ( RLT) with tailored formula was proposed. The topology network consists of 6 rungs sensing elements linked by 5 couplers. Two cases with different choices of couplers were contrasted: one is equal coupling ratio,and the other is tailored coupling ratio. Through the simulation of these two cases,the detailed multiplexing capability was analyzed,and accordingly the experiments were also carried out. The simulation results showed that,the tailored formula enhances the multiplexing capability of the structure. In the first case, the maximum number of sensors which can be multiplexed is 8,and in the other case is 12 fiber optic sensors. The experimental results have a good agreement with numerical simulation results. Thus,it is considered expedient to incorporate RLT into large-scale building,grounds,bridges,dams,tunnels,highways and perimeter security.

关键词： fiber-optic sensor white light interferometer multiplexing technique reflective ladder topology network tailored formula