MX345芯片及单片机控制

MX345芯片用于产生模拟信令—CTCSS单音.本文在介绍MX345编码/解码器工作原理的基础上,设计出MX345芯片与单片机的接口电路.最后给出控制软件.     

基于EWB的D/A数模转换器的仿真研究

阐述了D／A转换器的仿真原理，给出了T形电阻网络D／A转换器仿真模型的构造方法，并采用EWB进行了系统仿真，仿真结果表明该方法是合理、可行的。     

高聚合度β-萘磺酸盐缩合物的合成

介绍了用工业萘、硫酸、甲醛为原料，合成高聚合度β-萘磺酸盐甲醛缩合物的工艺过程。试验了不同的萘与甲醛配比、反应时间和催化剂对缩合物核体数的影响，确定了可行的工艺条件。     

A parametric interpolator with confined chord errors, acceleration and deceleration for NC machining

Parametric interpolation has many advantages over linear interpolation in machining curves. Real time parametric interpolation research so far has addressed achieving a uniform feed rate, confined chord errors and jerk limited trajectory planning. However, simultaneous consideration of confined chord errors that respect the acceleration and deceleration capabilities of the machine has not been attempted. In this paper, the offline detection of feed rate sensitive corners is proposed. The velocity profile in these zones is planned so that chord errors are satisfied while simultaneously accommodating the machine's acceleration and deceleration limits. Outside the zone of the feed rate sensitive corners, the feed rate is planned using the Taylor approximation. Simulation results indicate that the offline detection of feed rate sensitive corners improves parametric interpolation. For real time interpolation, the parametric curve information can be augmented with the detected feed rate sensitive corners that are stored in 2×2 matrices.     

浅析燕云十六州的战略价值

后晋天福三年(938年),"儿皇帝"石敬瑭"履约"向契丹割献燕云十六州.从此,中原王朝丧失了抵御北方游牧民族入侵的天然屏障,北方门户大开.宋代,燕云地区的争夺几乎贯穿了十至十二世纪北宋与辽金战争的整个过程.事实上,后人所指的"燕云十六州"与石敬瑭割辽的十六州在名称、时间和地域上有很大的差别;燕云地区内的险峻的山脉、横贯的河流与长城、五关一起构成了其巨大的军事价值;富庶的经济,众多的人口又构成了该地区巨大的经济价值;从历史上看,燕云十六州的归属于中原王朝和北方游牧民族政权双方而言,战略意义重大.     

A quantitative analysis of the effectiveness of laparascopy and endoscopy virtual reality simulators

The increasing use of virtual reality (VR) simulators in surgical training makes it imperative that definitive studies be performed to assess their training effectiveness. Indeed in this paper we report the meta-analysis of the efficacy of virtual reality simulators in (1) the transference of skills from the simulator training environment to the operating room and (2) their ability to discriminate between the experience levels of its users. The task completion time and the error score were the two study outcomes collated and analyzed in this meta-analysis. Sixteen studies were identified from a computer-based literature search (1996-2004). The meta-analysis of the random-effects model (because of the heterogeneity of the data) revealed that training on virtual reality simulators did lessen the time taken to complete a given surgical task as also clearly differentiate between the experienced and the novice trainees. Meta-analytic studies such as the one reported here would be very helpful in the planning and setting up of surgical training programs and for the establishment of reference ‘learning curves’ for a specific simulator and surgical task. If any such programs already exist they can then indicate the improvements to be made in the simulator used such as providing for more variety in their case scenarios based on the state and/or rate of learning of the trainee.     

油田热采注汽管道在线检测技术现状

稠油热采注汽管道由于长期在高温、高压下运行,极易发生各种损伤,如腐蚀、裂纹、材料退化等,极易造成管道承压能力降低,发生失效事故。如何检测出潜在危险性缺陷,判断注汽管道能否继续使用,是保证注汽管道安全运行的关键问题。探讨了高温压力管道在线检测技术发展现状及其应用范围。     

Determination of optimal feedback terminal controllers for general boundary conditions using generating functions

Given a nonlinear system and a performance index to be minimized, we present a general approach to expressing the finite time optimal feedback control law applicable to different types of boundary conditions. Starting from the necessary conditions for optimality represented by a Hamiltonian system, we solve the Hamilton-Jacobi equation for a generating function for a specific canonical transformation. This enables us to obtain the optimal feedback control for fundamentally different sets of boundary conditions only using a series of algebraic manipulations and partial differentiations. Furthermore, the proposed approach reveals an insight that the optimal cost functions for a given dynamical system can be decomposed into a single generating function that is only a function of the dynamics plus a term representing the boundary conditions. This result is formalized as a theorem. The whole procedure provides an advantage over methods rooted in dynamic programming, which require one to solve the Hamilton-Jacobi-Bellman equation repetitively for each type of boundary condition. The cost of this favorable versatility is doubling the dimension of the partial differential equation to be solved.     

汽车排放控制系统中的氧传感器现状及展望

介绍了浓差型(Nernst型)、极限电流型和半导体电阻型等汽车排放控制系统中的氧传感器原理及结构。在综合该领域国内外研究现状的基础上,对氧传感器的发展进行了展望。