Anchoring Properties of Nematic Liquid Crystals Studied Using the Attenuated Total Reflection Method

By using the attenuated total reflection method associated with the excitation of surface plasmons, the tilt angle of the liquid crystal director and its gradient at the surface are measured in a planar nematic cell as a function of the applied voltage. The surface anchoring anisotropy δπ of the liquid crystal and the surface elastic constant k_s, are found to be δπ = 0.288 erg/cm and k_s, = 9·12 × 10^-11 erg, respectively, when the boundary condition suggested by Barbero et al is used. The theoretical and experimental values obtained with this boundary condition and that of Mada are discussed. The results show that the boundary condition proposed by Barbero et al is in better agreement with the experiment.     

A randomized voltage vector switching scheme for three-level powerinverters

In this paper, a feasibility study of a randomized space vector switching scheme for three-level inverters is reported. Based on the traditional space vector concept for pulse width modulation (PWM) inverters, the sequence of the space vector is randomized in this scheme. The overall vector, resulting from the randomization, is mathematically identical to that of the traditional space vector. It has been found that the randomized scheme can effectively spread the switching noise over a wide frequency range and at the same time keep the steady-state link capacitor voltage balanced. The proposed scheme has been implemented in real time in a digital controller and its features have been experimentally confirmed     

Design and Experimental Characterization of Low‐Volume PM10/2.5/1.0 Trichotomous Sampler Inlet

This paper presents the development and laboratory evaluation of a PM10/2.5/1.0 trichotomous sampling inlet that consists of two main parts: a previously designed PM10 size‐selective inlet part and a PM2.5/1.0 two‐stage virtual impactor, which was newly fabricated and attached serially to the PM10 size selective inlet part. Particles are collected in three locations through the trichotomous sampling inlet to provide for not only particle concentration measurements of PM10, PM2.5 and PM1.0, but also those of PM2.5–10 and PM1.0–2.5.     

Bipyridinophane‐containing conjugated polymers modulated with an intramolecular aromatic C?H/π interaction

Bipyridinophane–fluorene conjugated copolymers have been synthesized via Suzuki and Heck coupling reactions from 5,8‐dibromo‐2,11‐dithia[3]paracyclo[3](4,4′)‐2,2′‐bipyridinophane and suitable fluorene precursors. Poly[2,7‐(9,9‐dihexylfluorene)‐co‐alt‐5,8‐(2,11‐dithia[3]paracyclo[3](4,4′)‐2,2′‐bipyridinophane)] ( P7 ) exhibits large absorption and emission redshifts of 20 and 34 nm, respectively, with respect to its planar reference polymer Poly[2,7‐(9,9‐dihexylfluorene)‐co‐alt‐1,4‐(2,5‐dimethylbenzene)] ( P11 ), which bears the same polymer backbone as P7 . These spectral shifts originate from intramolecular aromatic C? H/π interactions, which are evidenced by ultraviolet–visible and ¹H NMR spectra as well as X‐ray single‐crystal structural analysis. However, the effect of the intramolecular aromatic C? H/π interactions on the spectral shift in poly[9,9‐dihexylfluorene‐2,7‐yleneethynylene‐co‐alt‐5,8‐(2,11‐dithia[3]paracyclo[3](4,4′)‐2,2′‐bipyridinophane)] ( P10 ) is much weaker. Most interestingly, the quenching behaviors of these two conjugated polymers are largely dependent on the polymer backbone. For example, the fluorescence of P7 is efficiently quenched by Cu²⁺, Co²⁺, Ni²⁺, Zn²⁺, Mn²⁺, and Ag⁺ ions. In contrast, only Cu²⁺, Co²⁺, and Ni²⁺ ions can partially quench the fluorescence of P10 , but much less efficiently than the fluorescence of P7 . The static Stern–Volmer quenching constants of Cu²⁺, Co²⁺, and Ni²⁺ ions toward P7 are of the order of 10⁶ M^?1, being 1300, 2500, and 37,300 times larger than those of P10 , respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4154–4164, 2006     

An analysis of the coupling of an injection laser diode to a planar LiNbO3waveguide

Calculated butt coupling efficiency between a GaAlAs double heterostructure laser and a single-mode LiNbO3Ti-diffused optical waveguide is presented in this paper as a function of the transverse displacement, the angular alignment, the longitudinal separation between the laser and the waveguide end surfaces, the radiation field of the laser diode and its dependence on the laser diode structure, and the mode profile of the waveguide and its dependence on experimental diffusion parameters. The maximum efficiency is less than 40 percent because of the mismatch between the waveguide mode and the laser radiation, caused primarily by the experimental limitations in their structures. The effect of the reflection of the waveguide end surface on the laser oscillation has also been estimated.     

用离子束混合及快速热处理方法形成钽的硅化物

本文描述用离子束透过钽金属膜进行混合和快速热处理方法来形成钽的硅化物.用溅射方法在P型硅衬底上淀积一层金属钽,然后用砷离子束透过钽金属模进行混合,采用快速热处理后形成了平整的硅化钽薄层.使用厚度为500埃的钽金属膜,得到钽的硅化物薄层电阻为5.5Ω/□.研究了砷离子能量、剂量及钽膜厚度对钽的硅化物薄层电阻的影响.用透射电镜和台阶仪对所形成的硅化钽进行了分析和厚度测量.     

Integrated scheduling of flexible manufacturing systems employingautomated guided vehicles

Centralized and distributed automated guided vehicle system (AGVS) models for materials handling, and the model for part processing are integrated into a single coherent model. This formulation can be used to collectively schedule and control the entire flexible manufacturing system (FMS) as opposed to the traditional separate scheduling of part processing and material handling. The two AGVS models are based on Petri nets and can be directly used in the scheduling method that uses Petri nets for formulation and heuristic search for solution. This method employs a global search to seek the optimal operation of an entire FMS. Scheduling examples are presented and the method compares favorably with the results simulated using heuristic dispatch rules     

A neural network control system with parallel adaptive enhancementsapplicable to nonlinear servomechanisms

In this paper, we present a technique for using an additional parallel neural network to provide adaptive enhancements to a basic fixed neural network-based nonlinear control system. This proposed parallel adaptive neural network control system is applicable to nonlinear dynamical systems of the type commonly encountered in many practical position control servomechanisms. Properties of the controller are discussed, and it is shown that if Gaussian radial basis function networks are used for the additional parallel neural network, uniformly stable adaptation is assured and the approximation error converges to zero asymptotically. In the paper, the effectiveness of the proposed parallel adaptive neural network control system is demonstrated in real-time implementation experiments for position control in a servomechanism with asymmetrical loading and changes in the load     

Enhancement of oxide break-up by implantation of fluorine inpoly-Si emitter contacted p+-n shallow junctionformation

In this study, it is demonstrated that the incorporation of fluorine can enhance poly-Si/Si interfacial oxide break-up in the poly-Si emitter contacted p⁺-n shallow junction formation. The annealing temperature for breaking up the poly-Si/Si interfacial oxide has been found to be as low as 900°C. As a result, the junction depth of the BF₂-implanted device is much larger than that of the boron-implanted device