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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ejor.2008.12.024 Byline: S.J. Li (a), X.B. Li (a), L.N. Wang (a), K.L. Teo (b) Keywords: Generalized vector equilibrium problems; Holder continuity; Hausdorff distance; Metric spaces Abstract: In this paper, by using a weaker assumption, we discuss the Holder continuity of solution maps for two cases of parametric generalized vector equilibrium problems under the case that the solution map is a general set-valued one, but not a single-valued one. These results extend the recent ones in the literature. Several examples are given for the illustration of our results. Author Affiliation: (a) College of Mathematics and Science, Chongqing University, Chongqing 400030, China (b) Department of Mathematics and Statistics, Curtin University of Technology, G.P.O. Box U1987, Perth, WA 6845, Australia Article History: Received 15 July 2008; Accepted 20 December 2008 Article Note: (footnote) [star] This research was partially supported by the National Natural Science Foundation of China (Grant Numbers: 10871216 and 60574073) and Natural Science Foundation Project of CQ CSTC (Grant Number: 2007BB6117).

This paper presents an application of the weighted least squares (WLS) method to the design of sharp linear phase finite-impulse response (FIR) digital filters synthesized using a modified frequency-response masking (FRM) structure. In our approach, the original minimax design problem is converted into a WLS problem. The WLS problem is highly nonlinear with respect to the coefficients of the filter. However, it can be decomposed into four linear least squares (LS) problems, each of which can be solved analytically. The design problem is then solved iteratively by using an alternating variable approach. The effectiveness of the method is demonstrated through solving a low-pass linear phase sharp FIR digital filter example. Index Terms--Frequency-response masking (FRM), minimax error, weighted least squares (WLS), alternating variable approach.

In this paper, we formulate a general design of transversal filter structures with maximum relative passband-to-stopband energy ratio subject to complex frequency response constraints in the passband and the stopband as well as additional constraints such as null constraints. These null constraints are important for applications where the suppression of noise at certain frequencies are important. Additional constraints are introduced allowing approximately linear phase and constant group delay in the passband. For a given set of basis functions, the design problem can be formulated as a semi-infinite quadratic optimization problem in the filter coefficients, which are the decision variables to be optimized. In this paper, we focus on the design of digital Laguerre filter and digital finite impulse response (FIR) filter structures. A modified bridging algorithm is developed for searching for the optimum pole of the Laguerre filters. Design examples are given to demonstrate the effectiveness of the proposed algorithm. Index Terms--Bridging method, digital Laguerre filter, group delay constraints, maximum passband-to-stopband energy ratio.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ejor.2004.05.028 Byline: X.M. Yang (a)(b), X.Q. Yang (c), K.L. Teo (c) Keywords: Converse duality; Nonlinear programming; Pseudo-invexity; Positive definiteness Abstract: The purpose of this paper is to establish various converse duality results for nonlinear programming with cone constraints and its four dual models introduced by Chandra and Abha [S. Chandra, Abha, A note on pseudo-invex and duality in nonlinear programming, European Journal of Operational Research 122 (2000) 161-165]. Author Affiliation: (a) Department of Mathematics, Chongqing Normal University, Chongqing 400047, China (b) Key Laboratory of Operational Research of Chongqing, Chongqing 400047, China (c) Department of Applied Mathematics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong Article History: Received 30 October 2003; Accepted 13 May 2004

Nonlinear programming with cone constraints is examined, to identify converse duality.

A ballistic, coherent transmission system that utilizes the magnetic and electric barriers as Boolen input variables to realize functions similar to the conventional logic gates, is proposed. A device is used to propose construct based on the high-electron-mobility transistor (HEMT) with ferromagnetic (FM) and nonmagnetic (NM) metal gates deposited on top of the HEMT heterostructure.

Solutions to F-convexity under second-order symmetric duality in multiobjective nonlinear programming are examined.

Empirical results of duality theorems, which are used to examine second order F-convexity problems in mathematical programming, are presented.

Algorithms for solving the envelope-constrained filtering problem have been presented. Unconstrained minimization problems are constructed to approximate the original problem. The findings indicate that the parameters of the unconstrained problem can be chosen to yield a filter whereby the noise gain deviation from that of the optimal EC filter is less than any prescribed tolerance. The efficiency of these algorithms is confirmed by numerical results.

This paper deals with the position and force control for mechanical systems with holonomic constraints. Our concern is the design of a feedback controller such that the closed-loop system has a satisfactory transient response and is less sensitive to various types of disturbances. Using an appropriate transformation, the constrained system is converted into an unconstrained system of lower order. Then, an [H.sub.[infinity]] control problem involving the reduced system is formulated. In the case of state feedback, a systematic design procedure for solving the problem is presented, where the key step is the solution of an algebraic Riccati equation. An example is given to illustrate the effectiveness of the proposed method.

In this paper, singular control systems are studied from the frequency domain point of view. The proper stable factorization of a singular system is derived. The stability of the closed-loop system consisting of a singular system and controller is addressed. Most significantly, all proper stabilizing controllers are parameterized for a given singular system. Index Terms - Factorization of system plant, singular systems, stabilizing controller, Youla parameterization.

In a recent paper, a set of necessary and sufficient conditions for the existence of solutions to the combined sensitivity and complementary sensitivity (CSCS) problem in control systems was given. However, a practical method for constructing solutions to this problem was not presented. The computation procedure that was proposed involves constructing a sequence of rational functions to approximate an irrational function and may result in complicated high-order controllers. In this paper, we consider the synthesis aspect of the CSCS problem and derive an algorithm for constructing controllers that solve our CSCS problem in a simple manner. Moreover, an error in the closed-form solution of the Nevanlinna-Pick interpolation problem is revealed.

This paper is concerned with instantaneous jumps in the state trajectory of a singular system. It is shown that such jumps generically exist at the initial time due to inconsistent initial states. The formula for the jumps is derived, which indicates that the jumps linearly depend on the initial state. Moreover, the set of all initial states which do not cause any state jumps for any output feedback is characterized and is revealed to be a linear subspace. In the meantime, the necessary and sufficient conditions are given for the existence of an output feedback to suppress completely the jumps for a given initial state. Finally, we formulate the problem of designing an output feedback not only to stabilize the plant but also to achieve minimum initial jumps as a minimization problem.

A novel method for optimizing envelope-constrained filters with uncertain input (ECUI) uses a standard quadratic programing problem to yield an efficient solution. The process enables a given signal to occur within a designated envelope or mask. The algorithm proposed has superior convergence characteristics compared to previous ECUI proposals.

Empirical pseudopotential (EPM) and virtual crystal approximation methods facilitate the evaluation of the band structure of Zn(1 - x)CdxSySe(1 - y) quaternary alloy. EPM is characterized by a pseudopotential substituting the atomic potential. Accuracy of evaluation of energy bands is ensured by manipulating a set of atomic factors. Band gap energy and composition of the alloy are correlated in a nonlinear manner. Effective mass, a device parameter of semiconductors, and its reciprocal are experimentally demonstrated to be monlinear functions of composition. The pseudopotential for cubic semiconductors of the zinc-blende kind can be expressed as the sum of antisymmetric and symmetric for factors.

In this paper, we present a new method for solving a class of optimization problems with nonsmooth constraints. In particular, we apply the method to the design of narrow-band minimum-power antenna array processors which are robust in the presence of errors such as array element placement, look direction misalignment and frequency offset. We first show that the constrained minimum power problem has a unique global minimum provided that the constraint set is nonempty. We then show how the design problem derived directly from considerations of the sensitivity of the antenna array processor to errors can be transformed into a quadratic programming problem with linear inequality constraints which can be solved efficiently by the standard active set strategy. We also present numerical results for two types of nonsmooth constraints developed to provided robustness. These results confirm the effectiveness of the method described in this paper.

We report the synthesis of zinc-blende CrTe (zb-CrTe) as highly oriented crystalline grains in films of 100-nm thickness. The structural properties of the film were characterized using high-resolution transmission electron microscopy (HRTEM) and selective-area electron diffraction (SAED). Temperature-dependent magnetization measurements show that the Curie temperature of the film is ~327 K. Angular M-H measurements indicate that the CrTe films have an in-plane easy axis of magnetization along the [0[bar.1]1] direction of GaAs. Index Terms--CrTe, ferromagnetic, molecular-beam epitaxy, zinc-blende.

We investigated the effect of magnetic-electric barriers on electron transport in the two-dimensional electron gas (2DEG) of a Al-GaAs-GaAs heterostructure. It is found that electric potential can be controlled to achieve both spin and charge conductance modulation in this material system, with the requisite condition being the presence of magnetic barriers to break the time reversal symmetry of the system. The use of electrical potential rather than applied magnetic fields as an external control parameter to achieve spin/charge conductance modulation promises a simpler device design for practical realization. Index Terms--Ballistic, device, resonant tunneling, spin-polarized current.

In this paper, we propose an alternative method to improve magnetoresistance by inserting a thin ferromagnetic (FM) layer into the nonmagnetic (NM) spacer of a basic spin-valve (SV) trilayer (FM1-NM-FM1), thus creating a penta-layer SV structure (FM1-NMFM2-NM-FM1). We investigated the effect of increasing the resistivity ([[rho].sub.F2]) of the FM2 on overall magnetoresistance (MR). We performed both analytical and numerical studies on the MR of the current perpendicular-to-plane (CPP) structure using the phenomenological spin drift-diffusion models. For finite [[rho].sub.F2], the MR profile is dependent on the intrinsic conductance polarization ([[alpha].sub.F2]) of FM2. We found that inserting FM2 enhances MR when [[alpha].sub.F2] exceeds a critical value of [[alpha].sub.2C]. It is found that MR can be doubled by inserting a FM layer with high [[alpha].sub.F2], such as the half-metallic [Cr.sub.2]O. We have numerically calculated [MR.sub.max]. and the corresponding [[rho].sub.F20] values for different [[alpha].sub.F2] values. Finally, we studied the effect of spin relaxation on the MR of the CPP SV. Index Terms--Current perpendicular-to-plane (CPP)-GMR, ferromagnetic, magnetoresistance (MR), spin valve (SV).

The use of microphone arrays for video conferences, hands-free mobile telephony and computer applications has created the demand for near-field broadband beamformer design methods. Here, a general broadband beamformer design problem is formulated as a weighted Chebyshev optimization problem, and a method to solve the resulting functionally-constrained problem is presented. The formulation can also be applied to the design of multidimensional digital finite-impulse response (FIR) filters with an arbitrarily specified amplitude and phase. Numerical results that demonstrate the minimax near-field behavior of the designed beamformers are given. Index Terms - Beamforming, Chebyshev optimization, near field.

Several studies are conducted to examine the long range exchange coupling taking place in the zinc-blende CrTe/ZnTe/MnTe trilayer. The shifts exhibited by the magnetic hysteresis loops of the compounds are also analyzed.

The low temperature molecular beam epitaxy technique is employed to explain the antiferromgnetic thickness dependence of the CrTe- MnTe exchange-bias system. The coercivity and the exchange bias field of the system are shown to be completely dependent on the thickness.

Magnetic imaging study of regular hexagonal shaped NiFe elements arranged in different configurations is described. The alternating chirality of the hexagons has disappeared when the interelemental spacing becomes large and the results are understood by the symmetry and direction of the stray field generated by the individual elements.

The optical, magnetic and transport behaviors of [Ge.sub.1-x][Mn.sub.x]Te grown by solid-source molecular-beam epitaxy are examined. The magnetoresistance of [Ge.sub.1-x][Mn.sub.x]Te is isotropic and has displayed a clear hysterestic loop at low temperature, which has resembled that of giant-magnetoresistance granular system in solids.

The magnetic properties of Si doped with transition-metal (TM) using ion implantation are studied. A range of analytical transmission electron microscopy (TEM) methods are used for examining the origin of the ferromagnetic in this system.

A systematic study of the structural and magnetic properties of molecular-beam epitaxial growth of CrTe thin films with different layer thicknesses and Cr/Te flux ratios is reported. The results obtained from high-resolution transmission electron microscopy reveal that a metastable zinc-blende (ZB) phase of CrTe film can be generated with a nominal thickness of 5 nm under suitable growth conditions.

The structural, transport and magnetic behaviors of (Zn,Cr)Te system without additional carrier doping grown by low temperature molecular-beam epitaxy on GaAs (100) substrates are investigated. The results have highlighted the importance of clustering effect in models for the diluted magnetic semiconductor (DMS) system and also the affect of disorder on the Curie temperature.

Byline: K.L. Teo, T.C. Chong In this work, we give a review on the nanoscale cubic-islands growth of SrS and ZnxSr1-xS [abbreviated as (ZnSr)S] thin films by solid-source molecular-beam epitaxy (MBE). Our detailed analyses of scanning electron microscopy (SEM) and atomic force microscopy (AFM) images show that different sizes of SrS islands can be achieved depending on the substrate temperature. Reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD) establish cube-on-cube (001)SrS ' (001)MgO with [001]SrS ' [001]MgO epitaxial relationship. All these results point towards the growth to occur in step-flow mode. When (ZnSr)S is codoped with europium and samarium ions (SrS : Eu, Sm and ZnSrS : Eu, Sm), infrared-stimulated luminescence (ISL) with a peak at 612 nm is observed at room temperature, which is stimulated with infrared light after irradiation with visible light. The ISL results show that the (ZnSr)S system can be developed for erasable and rewritable optical memory.

The growth and magnetic properties of BeTe with Cr doping grown on GaAs(001) substrate at Te-rich condition by solid-source molecular-beam epitaxy is presented. Results show that the ferromagnetic ordering of Be(Cr)Te films could be attributed to precipitations of NiAs C[r.sub.1-[delta]]Te.

A ballistic device model which harnesses the Dresselhaus spin-orbit coupling effect to induce spin polarization [P] is proposed. Calculations for GaAs, GaSb, and InSb show a field enhancement of [P] from peak 2%-3% to 10%-80% near the conduction band.

A device model is produced that couples spin to the crystal field, external magnetic, and transverse electric field E(sub y), such that current j(sub x) transport in the ballistic regime. As E(sub y) modulates j(sub x) and its polarization P at a particular distance y, the model shows that the Landau spin-orbit system could implement the functions of a spin-field effect transistor.

A drift-diffusion transport model to evaluate the spin-injection efficiency eta and magnetoresistance (MR) ratio in a ferromagnetic (FM) metal-semiconductor (SC)-FM metal trilayer structure is presented. The presence of interfacial resistances (IR) at the FM-SC boundary is found to be crucial for generating a large spin splitting of mu, and consequently a high injection efficiency eta.

The hydrostatic pressure dependence of Ge nanocrystals embedded into SiO2 matrix on the quartz-glass substrate by Raman scattering at room temperature is studied. A simple elastic model, which describes the effective pressure transmitted from matrix to the nanocrystals, is used to explain the results.

Two algorithms were created to calculate non-convex curve's upper and lower approximate curves. The algorithms initially entails mapping of non-convex curve into a convex curve with the use of p-power transformation. The inverse of the p-power transformation is taken to allow mapping of the approximate curves into the original space. Such algorithms can be utilized to approximate the non-convex efficient frontiers of bicriteria optimization problems.