两基色、三基色和荧光粉转换白光LED配色研究

根据色度学基本原理,对荧光粉转换白光发光二极管(LED)和两基色、三基色白光LED进行了配色计算,得到了距离理想白光点色度坐标(1/3,1/3)小于0.5%范围内的众多基色组合,同时对光视效能、显色指数和荧光粉转换效率等参数进行了分析,提出了荧光粉转换白光LED和两基色、三基色白光LED的最佳基色组合,并在实验上对荧光粉转换白光LED进行了验证。     

Slow-Scale and Fast-Scale Instabilities in Voltage-Mode Controlled Full-Bridge Inverter

This paper discusses the slow-scale and fast-scale instabilities of a voltage-mode controlled full-bridge inverter which is widely used in AC power supply applications. The main results are illustrated by exact cycle-by-cycle simulations. It is shown that the slow-scale instability is a type of low-frequency instability which manifests itself as a Hopf-type low-frequency oscillation in the whole line cycle, whereas the fast-scale instability is a type of local instability which manifests itself as a period-doubling bifurcation in some intervals of a line cycle. An averaged model and an improved discrete-time model are used to theoretically analyze the slow-scale and fast-scale instabilities, respectively. Finally, experimental results are presented to verify the results from simulations and analysis. Our work has revealed more instabilities which are likely to occur in the inverter, and has provided a convenient means of predicting stability boundaries to facilitate the design of the inverter.     

A Basis-Function Canonical Piecewise-Linear Approximation

This paper proposes a basis-function canonical piecewise-linear (BF-CPWL) function, which can approximate any continuous function using a weighted sum of PWL BFs. The BF-CPWL approximation integrates Breiman's hinging hyperplane model and Julian's high-level canonical PWL approximation into a common theoretical framework. Moreover, an approximation algorithm is developed, which fits and adds the PWL BFs iteratively using a modified Gauss-Newton method. This algorithm guarantees a local convergence, while achieving a good tradeoff between computational simplicity and approximation accuracy. The BF-CPWL approximation can find applications in nonlinear circuit synthesis, dynamic system identification and control.     

Robotic System for Closed-Bore MRI-Guided Prostatic Interventions

This paper reports on the development of a new closed-bore magnetic resonance imaging (MRI) compatible robotic system for image-guided prostatic interventions: ablation, brachytherapy, and biopsy. The first stage of development addresses only laser-based ablation. The robot actuators are ultrasonic motors. The first physical robot prototype was manufactured and tested in the MRI with an ablation tool. The tests covered magnetic resonance (MR) compatibility, tool visualization, and robot control accuracy. Robot tip position error is less than 2 mm at points closer than 0.5 m to the isocenter. A method to control ultrasonic motors for MRI-compatibility is reported.     

PY181 Pigment Microspheres of Nanoplates Synthesized via Polymer‐Induced Liquid Precursors

Organic pigments are important crystalline substances, and their properties and applications rely on size and shape control. Pigment Yellow 181 (PY181) is an industrial azo pigment that is light and weatherfast and suitable for high temperature processing. One disadvantage is its needle‐like shape in the default β‐phase, which makes the pigment difficult to process in industry, e.g., in polymer melts, where a spherical structure would be ideal. Here, we show for the first time, that polymer‐induced liquid precursor structures can be formed even in association to a chemical reaction. Furthermore, it is demonstrated that biomineralization principles can be exploited for the generation of advanced functional materials, such as pigments with novel complex morphology and different properties. Stable PY181 microspheres of nanoplates in the β‐phase were obtained in mixed solvents of water and isopropanol by direct azo coupling under the directing influence of a designed copolymer additive aminobenzoylaminobenzamide‐acetoacetyl‐poly(ethylene imine)‐block‐poly(ethylene glycol) (ABABA‐acetoacetyl‐PEI‐b‐PEG).     

An output-feedback fuzzy approach to guaranteed cost control of vehicle lateral motion

This paper introduces a fuzzy guaranteed cost control approach for automated steering of a highway vehicle. The Takagi–Sugeno (T–S) fuzzy model is utilized to depict the dynamics of nonlinear time-varying lateral system. Based on the fuzzy model, an observer-based fuzzy controller is developed so that without knowing road’s curvature the vehicle can track center of the present lane on a curved highway section. Integrating H_∞ control and optimal control strategies, the fuzzy controller and observer are formulated by solving a minimization problem, which is to minimize a given quadratic performance function. Sufficient conditions to ensure minimum upper bound of the performance function are derived in terms of linear matrix inequalities (LMIs). Therefore, the designing work can be efficiently completed by applying the convex optimization techniques. Verified by computer simulation, the proposed method can perform well in driving safety and ride comfort.     

增益提高型套筒式全差分跨导放大器的设计与分析

提出了一种应用于流水线型模数转换器(ADC)的增益提高型套筒式全差分跨导放大器(OTA)的设计与分析方法.通过ADC的性能要求推导出OTA的设计指标.该设计中OTA的架构由主运放、增益辅助运放及共模反馈电路3部分子电路组成.设计采用SMIC CMOS 0.18mm工艺平台.该设计方法的实验结果表明:1pF负载下,跨导放大器.的直流增益达到145dB,单位增益带宽超过750MHz,相位裕度达到58°.闭环增益为4时,放大器在20ns内稳定到0.05%的精度.     

宽带无线接入系统WiMAX的应用与部署

介绍了宽带无线接入系统WiMAX的关键技术，并与其他接入技术作了比较；阐述了WiMAX的主要应用、组网部署；也指出了WiMAX存在的一些主要问题。     

一种安全的公共认证电子拍卖方案

利用Bit承诺,单向函数和数字签名算法,对一种安全电子拍卖模型进行改进,提出了一种安全、简单、高效的密封式电子拍卖方案.它可以在注册中心离线的情况下,最大程度地缩小拍卖行的权力实现公共认证.同时,该方案不仅能对除中标者外的其他所有投标者的投标价进行保密,而且能有效防止拍卖行不诚实的行为.     

Nonparametric change detection and estimation in large-scale sensor networks

The problem of detecting changes in the distribution of alarmed sensors is considered. Under a nonparametric change detection framework, several detection and estimation algorithms are presented based on the Vapnik-Chervonenkis (VC) theory. Theoretical performance guarantees are obtained by providing error exponents for false-alarm and miss detection probabilities. Recursive algorithms for the efficient computation of test statistics are derived. The estimation problem is also considered in which, after detection is made, the location with maximum distribution change is estimated.