H

This paper addresses the problem of H∞ control for a class of uncertain stochastic systems with Markovian switching and time-varying delays. The system under consideration is subject to time-varying norm-bounded parameter uncertainties and an unknown nonlinear function in the state. An integral sliding surface corresponding to every mode is first constructed, and the given sliding mode controller concerning the transition rates of modes can deal with the effect of Markovian switching. The synthesized sliding mode control law ensures the reachability of the sliding surface for corresponding subsystems and the global stochastic stability of the sliding mode dynamics. A simulation example is presented to illustrate the proposed method

Modeling and adaptive tracking for stochastic nonholonomic constrained mechanical systems

This paper is devoted to the problem of modeling and trajectory tracking for stochastic nonholonomic dynamic systems in the presence of unknown parameters. Prior to tracking controller design, the rigorous derivation of stochastic nonholonomic dynamic model is given. By reasonably introducing so-called internal state vector, a reduced dynamic model, which is suitable for control design, is proposed. Based on the backstepping technique in vector form, an adaptive tracking controller is then derived, guaranteeing that the mean square of the tracking error converges to an arbitrarily small neighborhood of zero by tuning design parameters. The efficiency of the controller is demonstrated by a mechanics system: a vertical mobile wheel in random vibration environment

Minimax Weight Learning for Absorbing MDPs

Reinforcement learning policy evaluation problems are often modeled as finite or discounted/averaged infinite-horizon MDPs. In this paper, we study undiscounted off-policy policy evaluation for absorbing MDPs. Given the dataset consisting of the i.i.d episodes with a given truncation level, we propose a so-called MWLA algorithm to directly estimate the expected return via the importance ratio of the state-action occupancy measure. The Mean Square Error (MSE) bound for the MWLA method is investigated and the dependence of statistical errors on the data size and the truncation level are analyzed. With an episodic taxi environment, computational experiments illustrate the performance of the MWLA algorithm.Comment: 36 pages, 9 figure

Aqua­(benzamidato-κN)bis­[3,5-difluoro-2-(pyridin-2-yl)phenyl-κC 1]iridium(III) methanol monosolvate

In the title compound, [Ir(C11H6F2N)2(C7H6NO)(H2O)]·CH3OH, the IrIII ion adopts an octa­hedral geometry, and is coordinated by two 3,5-difluoro-2-(pyridin-2-yl)phenyl ligands, one mol­ecule of water and one benzamidate anion. The two 2-(4,6-difluoro­phen­yl)pyridyl ligands are arranged in a cis-C,C′ and trans-N,N′ fashion. Additionally, there is a bystanding methanol mol­ecule outside the coordination sphere of the IrIII ion. In the crystal, mol­ecules of the title compound are linked by O—H⋯O and O—H⋯N hydrogen bonds. One F atom of each ligand is equally disordered over two sites. The C atom of the solvent molecule is likewise disordered over two sites in a 0.589 (11):0.411 (11) ratio

Observation of thermal feedback on the optical coupling noise of a microsphere attached to a low-spring-constant cantilever

A silica microsphere on a low-spring-constant cantilever (pendulum) is fabricated and evanescently coupled to a tapered optical fiber. The motion of the pendulum is detected as variations in the transmitted laser power through the tapered fiber. The optical coupling noise created by the pendulum motion is recorded by taking a fast Fourier transform of the transmitted laser power and the fundamental mechanical mode of the pendulum at 1.16 kHz is observed. The thermal damping and amplification of the coupling noise is investigated and the effect of the thermal feedback on the noise spectrum is examined. The response of the thermo-optical feedback to small transient and driven variations in the taper-pendulum separation for different values of laser detuning is demonstrated. Preliminary results on the optical force between the pendulum and the tapered fiber are also presented. Microspherical pendulums, with low mechanical spring constant, could be used for studying nanoscopic optical and mechanical forces, or optical cooling

Ultralow threshold green lasing and optical bistability in ZBNA (ZrF4–BaF2–NaF–AlF3) microspheres

Upconversion lasing and fluorescence from active microspheres fabricated from a novel fluorozirconate, Er3+ doped glass, ZBNA (ZrF4-BaF2-NaF-AlF3), when pumped at 978 nm via a tapered optical fiber is demonstrated. An ultralow, green lasing threshold of similar to 3 mu W for 550 nm emissions is measured. This is one order of magnitude lower than that previously reported for ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) microspheres. Optical bistability effects in ZBNA microspheres are reported and the bistable mechanism is discussed and attributed to shifts of the whispering gallery modes due to thermal expansion of the sphere, where heating is achieved by optical pumping around 978 nm. The effect of the bistability on the upconversion lasing is examined and we report multiple bistability loops within the microspheres

Short vertical tube furnace for the fabrication of doped glass microsphere lasers

We report on the design of an electric tube furnace that can be used for the fabrication of doped glass microsphere lasers. The tube furnace has a short hot zone of length 133 mm and is based on a quartz tube design. Doped laser glass particles, specifically Er:Yb phosphate glass (IOG-2), of ∼ 1 μm diameter are blown into the furnace using a 60 ml syringe and microspheres ranging in size from 10 to 400 μm are collected at the output of the tube furnace in a Petri dish. The furnace operates at a wall temperature of ∼ 900 °C and is capable of making microspheres from glasses with glass transition temperatures of at least 375 °C. High quality (Q ∼ 10^5) whispering gallery modes have been excited within the microspheres by optically pumping at 978 nm via a tapered optical fiber

UNDERSTANDING THE EVOLUTION OF INFORMATION SYSTEMS RESEARCH FROM THE PERSPECTIVE OF CO-AUTHORSHIP NETWORK: A COMPREHENSIVE DATA ANALYSIS FROM 1993 TO 2012

Based on the articles published in three top journals in the field of information systems (MISQ, ISR and JMIS) from 1993 to 2012, we conduct a research of the structure, characteristics and development trend of co-authorship network through scientometrics and social network analysis approaches. We gain a number of insights after synthetical analysis. In the last two decades the whole co-authorship network density in information systems faces a tendency of decrease. The co-authorship network presents properties of “small world”. The number of articles published by scholars and institutions in the three elite journals all display a ‘long tail’ phenomenon. The field of information systems has a stable development in the biggest component, and has not yet went into a mature and steady stage. Quite a lot of outstanding scholars and educational resources came from USA, Canada and Hong Kong, and USA has held eight institutions of the top ten. The ranking of an entire institution can be influenced by even one or two authors, indicating that outcome from one level might propagate to the next level