H∞ stochastic synchronization for master–slave semi‐Markovian switching system via sliding mode control

In this article, synchronization problem of master–slave system with phase‐type semi‐Markovian switching is investigated via sliding mode control scheme. By utilizing a supplementary variable technique and a plant transformation, the master–slave semi‐Markovian switching system can be equivalently expressed as its associated Markovian switching system. Then an integral sliding surface is constructed to guarantee stochastic synchronization of master–slave semi‐Markovian switching system, and the suitable controller is synthesized to ensure that the trajectory of the closed‐loop error system can be driven onto the prescribed sliding mode surface. Finally, numerical simulations are presented to show the effectiveness of the proposed sliding‐mode design scheme. © 2015 Wiley Periodicals, Inc. Complexity 21: 430–441, 2016     

氧分压对Ni/HfO_x/TiN阻变存储单元阻变特性的影响

采用射频磁控溅射的方法,基于不同氧分压制备的氧化铪构建了Ni/HfO_x/TiN结构阻变存储单元.研究发现,随着氧分压的增加,薄膜表面粗糙度略有降低;另一方面,阻变单元功耗降低,循环耐受性能可达10~3次,且转变电压分布的一致性得到改善.结合电流-电压曲线线性拟合结果及外加温度测试探究了器件的转变机理,得出在低阻态的传导机理为欧姆传导机理,在高阻态的传导机理为肖特基发射机理,并根据氧空位导电细丝理论,对高低阻态的阻变机理进行了详细的理论分析.     

Self-Assembled Monolayers of Molecular Conductors with Terpyridine-Metal Redox Switching Elements: A Combined AFM,STM and Electrochemical Study

Self-assembled monolayers (SAMs) of terpyridine-based transition metal (ruthenium and osmium) complexes, anchored to gold substrate via tripodal anchoring groups, have been investigated as possible redox switching elements for molecular electronics. An electrochemical study was complemented by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) methods. STM was used for determination of the SAM conductance values, and computation of the attenuation factor β from tunneling current–distance curves. We have shown that SAMs of Os-tripod molecules contain larger adlayer structures compared with SAMs of Ru-tripod molecules, which are characterized by a large number of almost evenly distributed small islands. Furthermore, upon cyclic voltammetric experimentation, Os-tripod films rearrange to form a smaller number of even larger islands, reminiscent of the Ostwald ripening process. Os-tripod SAMs displayed a higher surface concentration of molecules and lower conductance compared with Ru-tripod SAMs. The attenuation factor of Os-tripod films changed dramatically, upon electrochemical cycling, to a higher value. These observations are in accordance with previously reported electron transfer kinetics studies.     

Nanostructured thermoresponsive quantum dot/PNIPAM assemblies

Synthesis, characterization, and applications of novel thermoresponsive polymeric coatings for quantum dots (QDs) are presented. Comb-copolymers featuring hydrophobic alkyl groups, carboxylic groups and poly(N-isopropylacrylamide) (PNIPAM) side chains with molar masses ranging from 1000 g/mol to 25,400 g/mol were obtained. The amphiphilic comb-copolymers were shown to efficiently transfer the QDs to aqueous media. The PNIPAM-coated QD materials display a lower critical solution temperature (LCST). The absorbance, luminescence emission, size of the assemblies, and electrophoretic mobility were followed as a function of temperature and the reversibility of the temperature induced changes is demonstrated by cyclic heating and cooling.     

Silicon–oxygen‐bonded oligomers having thermoelectric switching properties

The electrical properties of siloxane oligomers prepared from the reaction of 1,4‐naphthalenediol or 1,4‐naphthoquinone with diphenylsilane using different palladium catalysts, such as PdCl₂, Pd(TMEDA)Cl₂, Pd(TEEDA)Cl₂ (where TMEDA = N,N′‐tetramethylethylenediamine, TEEDA = N,N′‐tetraethylethylenediamine), are dependent on the catalyst. Thermoelectric switching properties can be obtained from the siloxane prepared from the coupling reaction of diphenylsilane with 1,4‐naphthoquinone or 1,4‐naphthalenediol using Pd(TMEDA)Cl₂ as catalyst. Copyright © 2001 John Wiley & Sons, Ltd.     

A production system with two job classes,changeover times and revisitation

This paper, motivated by the need to predict performance of production systems with random arrivals, setup times and revisitation, presents an imbedded Markov chain analysis of the underlyingM/G/1 queue with two customer classes, changeover times and instantaneous Bernoulli feedback. It is assumed that jobs are scheduled according to the exhaustive alternative priority queue discipline. Expressions for the mean waiting time and the nonsaturation condition are derived under two different priority assignments to the repeat customers. Sojourn times under these priority assignments are shown to possess a convex ordering. Results of the study are also applicable to data communication networks that operate under cyclic switching mechanisms. Research supported in part by Natural Sciences and Engineering Research Council of Canada.     

Stochastic Optimization Algorithms for Pricing American Put Options Under Regime-Switching Models

This work provides a Markov-modulated stochastic approximation based approach for pricing American put options under a regime-switching geometric Brownian motion market model. The solutions of pricing American options may be characterized by certain threshold values. Here, a class of Markov-modulated stochastic approximation (SA) algorithms is developed to determine the optimal threshold levels. For option pricing in a finite horizon, a SA procedure is carried out for a fixed time T. As T varies, the optimal threshold values obtained via SA trace out a curve, called the threshold frontier. Numerical experiments are reported to demonstrate the effectiveness of the approach. Our approach provides us with a viable computational tool and has advantage in terms of the reduced computational complexity compared with the variational or quasivariational inequality methods for optimal stopping.Communicated by C. T. LeondesThis research was supported in part by the National Science Foundation under Grant DMS-0304928, and in part by the National Natural Science Foundation of China under Grant 60574069.     

ATMOS (ATM optical switching)—system perspective

The expected traffic growth from new broadband services will require network capacities that can be beneficially provided by optical WDM transport networks. Optical packet techniques are essential for large networks to provide flexibility and granularity. A layered network architecture with a transparent optical layer and optical packet layers has been elaborated. Four switching concept options for large optical ATM switch fabrics in the public network and small access nodes are presented. The technology for the related key functions of space and wavelength switching was developed in the RACE ATMOS project and the feasibility of concepts and technologies was verified in four system demonstrators.     

Solving a concrete sleepers production scheduling by genetic algorithms

PRECON S.A. is a manufacturing company devoted to produce prefabricated concrete parts for several industries as railway transportation and agricultural industries. Recently, PRECON S.A. signed a contract with RENFE, the Spanish National Railway Company, to manufacture pre-stressed concrete sleepers for the sidings of the new railways of the high speed train (AVE). The scheduling problem associated with the manufacturing process of the sleepers is very complex, since this involves several constraints and objectives. These constraints are related to production capacity, the quantity of available moulds, demand satisfaction and other operational constraints. The two main objectives are related to the way to maximize the utilization of manufacturing resources and minimize mould movements. We developed a deterministic crowding genetic algorithm for this multiobjective problem. The algorithm has proved to be a powerful and flexible tool to solve large-scale instances of this real and complex scheduling problem.