高精度数字跟踪式压电陶瓷驱动电源设计

设计了一种数字跟踪式复合结构的压电陶瓷驱动电源。采用数字式自适应信号源,驱动高精度运放OP07和高压大电流运放PA04组成复合式放大器,通过合理的相位补偿、保护电路设计和散热计算,实现高精度低漂移的压电陶瓷驱动。     

一种高速声纳实时处理系统的设计与实现

水下声成像技术具有广泛的应用前景,日益得到人们的重视。介绍了一种二维图像声纳的数据采集、实时处理系统。讨论了系统硬件组成以及软件程序设计,使用高性能A/D、FPGA和DSP进行数据采集及实时处理,用以太网进行数据传输。可以实时处理200通道的基元数据,图像刷新率达到20 f/s,为图像声纳提供了一套可行的设计方案。     

Simulations of Supersonic Astrophysical Jets and Their Environments Using Level Set Methods

Computational fluid dynamics simulations using the WENO method and level set method are applied to high Mach number nonrelativistic astrophysical jets, including the effects of radiative cooling. WENO methods introduced in Liu et al. (J. Comput. Phys., 115:200–212, 1994) have allowed us to simulate HH 1-2 astrophysical jets at Mach number much higher than Mach 80 (Ha et al. in J. Sci. Comput. 24:29–44, 2005). Simulations at high Mach numbers and with radiative cooling are essential for achieving detailed agreement with the astrophysical images. Simulations of interaction between astrophysical jet and environment using level set methods are considered in this paper.     

Queue length analysis of batch arrival queues under bilevel threshold control with early set-up

The queue length process of M^X/G/1 queues under bilevel threshold control and early set-up withlwithout server vacations is outlined. The stationary probability generating functions of the queue length distributions under a unified framework are also derived. Also derived are the mean queue length of each system.     

Numerical solutions of time-varying TS-fuzzy-model-based time-delay dynamic equations via orthogonal functions

In this paper, the approach of orthogonal functions is presented to solve the time-varying Takagi–Sugeno (TS) fuzzy-model-based time-delay dynamic equations (time-varying TSFMTDE). The new method simplifies the procedure of solving the time-varying TSFMTDE into the successive solution of a system of recursive formulae only involving matrix algebra. Based on the presented recursive formulae, an algorithm only including straightforward algebraic computation is also proposed in this paper. The new proposed approach is non-iterative, non-differential, non-integral, straightforward, and well-adapted to computer implementation. Hence, the computational complexity is considerably reduced. The first illustrated example shows that the proposed method, based on the orthogonal functions, can obtain satisfactory results. The second illustrated example, for the pendulum time-delay system with the vibration in the vertical direction on the pivot point having a fuzzy parallel-distributed-compensation controller, is given to demonstrate the application of the proposed approach.     

Interactive Lighting Design with Hierarchical Light Representation

Lighting design plays a crucial role in indoor lighting design, computer cinematograph and many other applications. Computer‐assisted lighting design aims to find a lighting configuration that best approximates the illumination effect specified by designers. In this paper, we present an automatic approach for lighting design, in which discrete and continuous optimization of the lighting configuration, including the number, intensity, and position of lights, are achieved. Our lighting design algorithm consists of two major steps. The first step estimates an initial lighting configuration by light sampling and clustering. The initial light clusters are then recursively merged to form a light hierarchy. The second step optimizes the lighting configuration by alternatively selecting a light cut on the light hierarchy to determine the number of representative lights and optimizing the lighting parameters using the simplex method. To speed up the optimization computation, only illumination at scene vertices that are important to rendering are sampled and taken into account in the optimization. Using the proposed approach, we develop a lighting design system that can compute appropriate lighting configurations to generate the illumination effects iteratively painted and modified by a designer interactively.     

H ∞ PID controller design for Lur’e systems and its application to a ball and wheel apparatus

In this paper, we consider the problem of synthesizing proportional-integral-derivative (PID) controllers for a given Lur’e system in the presence of exogenous energy-bounded disturbance. Based on the circle criterion, sufficient conditions for guaranteeing closed-loop absolute stability and achieving disturbance attenuation are given in terms of the multi-objective H _∞ specifications. The results from the earlier work are then used to solve the resulting multi-objective H _∞ PID design problem. It is shown that for a fixed proportional gain, and by sweeping over a variable, the set of admissible integral and derivative gain values can be determined constructively using linear-programming techniques. The proposed synthesis method is used to design a PID controller for the ball and wheel system and the experimental results are presented to show effectiveness of the proposed method.     

Stabilizing static output feedback receding horizon controls for linear discrete time-invariant systems

In this paper, a stabilizing static output feedback receding horizon control (RHC) is proposed for linear discrete time-invariant systems. An inequality condition on the terminal weighting matrices is presented under which the closed-loop stability of static output feedback receding horizon controls is guaranteed. It is shown that the stabilizing static output feedback receding horizon control problem can be represented as a non-linear minimization problem based on linear matrix inequalities (LMIs). An algorithm for solving the presented non-linear minimization problem is proposed. In addition, this result is extended to an arbitrary reference tracking problem that is one of the main features of receding horizon control. Finally, the efficiency of the proposed algorithm is illustrated by numerical examples.     

Translating Singapore architects' environmental awareness into decision making

Construction activity is known to have a major impact on the environment. Construction is a major consumer of a wide range of naturally occurring and synthesized resources. The extraction, processing and utilization of these resources can have various negative impacts on the environment. With increased awareness and knowledge of these impacts, efforts are being made to avoid these adverse effects. Among these is the selection and specification of appropriate materials. This paper studies the level of environmental awareness and knowledge of architects in Singapore when selecting and specifying materials during the design stage. Responses to a questionnaire indicate that the architects are aware of the environmental impacts of building materials, and knowledgeable about possible measures which could help avoid the problems. However, they are not adopting green design approaches. Key policy directions for government, professional bodies, educators and clients are made to enable Singapore architects to apply their knowledge of environmental issues in their design decisions.     

Theoretical study of indoline dyes for dye-sensitized solar cells

Indoline dye sensitizers were designed and studied theoretically to increase molar extinction coefficients in the visible to near infrared region for solar-cell devices. To gain insight into dye sensitizers' structural, electronic, and optical properties, DFT/TDDFT calculations were performed on a series of dye sensitizers derived from the D149. The good agreement between the experimental and TDDFT calculated absorption spectra of the D149 sensitizer allowed us to provide a detailed assessment of the main spectral features of a series of dye sensitizers. Increase in the conjugation length resulted in a more red-shifted spectral response and less positive oxidation potential than that of the D149. The dye with the dimethylfluorene group showed stronger absorption bands due to a large dipole moment. The calculated dipoles for the dye series correlate well with the observed strong absorption bands of the electronic spectra. These results provided useful clues for the molecular engineering of efficient organic dye sensitizers.