TC4钛合金与LD10铝合金感应摩擦焊接头的组织与性能

利用感应电磁场对焊接过程热与物质流动作用,改善异种金属摩擦焊接头的组织与性能。采用光学金相、扫描电镜及室温拉伸实验与对比分析的方法,研究了外加电磁场对弱磁性材料TC4钛合金与LD10铝合金摩擦焊接头焊合区的显微组织、主要合金元素扩散行为及室温力学性能的影响。结果表明:外加电磁场作用使TC4钛合金与LD10铝合金摩擦焊接头铝合金侧动态再结晶区宽度增大;同时,感应电磁场通过影响摩擦副合金材料内部电子密度状态等,促进了摩擦焊接过程中主要合金元素Al和Ti在焊合区的扩散过程,并且提高了TC4钛合金与LD10铝合金摩擦焊接头的拉伸强度。其中,外加电磁场在顶锻保压阶段的影响更为明显。     

Perception of Hand Force in Power Grip for Females

Borg's rating of perceived exertion (RPE) and category ratio (CR‐10) scales are commonly used to quantify perceived muscular exertion for body segments. Twenty females participated in an experiment to study the power grip force at four perceived exertion levels using either dominant or nondominant hand under two posture conditions. It was found that the subjects tended to apply a higher power grip force (100% of perceived maximum voluntary contraction) than the levels they were requested to apply. The power grip forces between dominant and nondominant hands at low hand exertion levels were negligible. The grip forces between the two hands were significantly different when the exertion level was nearly maximal. Linear regression models were established for the subjects to link the relationship between the perceived hand exertion and measured grip force, hand used, and hand/arm posture. All the models were statistically significant (p < 0.0001) with R² values 0.97 or higher. These models provided better estimates in perceived hand exertion for dominant hand than for nondominant hand. A follow‐up experiment was conducted to measure the subjective rating of both the CR‐10 and RPE when a 98 N grip force was applied. It was found that the subjects reported higher exertion levels when they were using the CR‐10 scale than when they were using the RPE scale. © 2011 Wiley Periodicals, Inc.     

管理科学发展的泛系鸟瞰与显微

从泛系理论的视角,运用泛系快深频方法对管理科学各理论学派进行审视,对相关理论进行详细解读,将管理科学与方法看成某种特化的泛系方法与泛系管理哲学,在泛系理法基础上实现某种三大显生(系统,关系,泛对称//泛系真善美禅极值原理)及技术化具体建构的分类对策巧显生.     

基于单片机的小气候信息采集系统便携机设计

农业生产技术的快速发展,迫切需要一种适用于普及的、可靠、有效的针对农田小气候信息参数的实时采集系统,提高人们对作物生长与小气候之间关系的认识,为农业生产服务。本文介绍了基于PIC单片机的小气候信息采集系统便携机部分设计,文中详细描述了小气候信息采集方法和系统软硬件结构。便携机系统实现了包括温湿度、光照度、降雨量、蒸发量、大气压等15种小气候参数的自动、实时监测。通过实践证明该便携机设计合理、性能可靠,作为小气候信息采集系统的主体部分,是适合目前农田小气候信息自动监测的普及型设备。     

An LMI approach to synthesis subject to almost asymptotic regulation constraints

A multi-objective controller synthesis problem is considered in which an output is to be regulated approximately by assuring a bound on the steady-state peak amplification in response to an infinite-energy disturbance, while also guaranteeing a desired level of performance measured in terms of the worst-case energy gain from a finite-energy input to a performance output. Relying on a characterization of the controllers with which almost asymptotic regulation is accomplished, the problem of guaranteeing the desired level of performance is reduced to solving a system of linear matrix inequalities subject to a set of linear equality constraints. Based on the solution of this system, a procedure is outlined for the construction of a suitable controller whose order is equal to the order of the plant plus the order of the exogenous system.     

control with limited communication and message losses

We propose an H^∞ approach to a remote control problem where the communication is constrained due to the use of a shared channel. The controller employs a periodic time sequencing scheme for message transmissions from multiple sensors and to multiple actuators of the system. It further takes into account the information on the random message losses that occur in the channel. An exact characterization for controller synthesis is obtained and is stated in terms of linear matrix inequalities. Furthermore, an analysis on the loss probabilities of the messages to accomplish stabilization is carried out. The results are illustrated through a numerical example.     

高速串行数据通讯电路设计及应用

介绍了Hotlink协议芯片CY7B923/933的性能特点、内部结构、工作原理和工作方式;设计了由CY7B923/933组成的高速串行数据通讯电路,详细讨论了耦合电路、偏置电路、匹配电阻、波形观测等关键性问题;并分别用同轴电缆和双绞线对电路进行了传输速率为330Mpbs的图像数据的传输测试;实验结果表明,传输过程稳定可靠,没有发生解码错误;CY7B923/933芯片可以方便地实现Hotlink协议,非常适用于工作站、服务器、海量存储、图像和视频传输等方面的应用。     

Complex radial basis function networks trained by QR‐decomposition recursive least square algorithms applied in behavioral modeling of nonlinear power amplifiers

In this article, we propose a novel complex radial basis function network approach for dynamic behavioral modeling of nonlinear power amplifier with memory in 3 G systems. The proposed approach utilizes the complex QR‐decomposition based recursive least squares (QRD‐RLS) algorithm, which is implemented using the complex Givens rotations, to update the weighting matrix of the complex radial basis function (RBF) network. Comparisons with standard least squares algorithms, in batch and recursive process, the QRD‐RLS algorithm has the characteristics of good numerical robustness and regular structure, and can significantly improve the complex RBF network modeling accuracy. In this approach, only the signal's complex envelope is used for the model training and validation. The model has been validated using ADS simulated and real measured data. Finally, parallel implementation of the resulting method is briefly discussed. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Controller synthesis with guaranteed closed-loop phase constraints

In this paper, we present an analysis and synthesis approach for guaranteeing that the phase of a single-input, single-output closed-loop transfer function is contained in the interval [−α,α] for a given α>0 at all frequencies. Specifically, we first derive a sufficient condition involving a frequency domain inequality for guaranteeing a given phase constraint. Next, we use the Kalman–Yakubovich–Popov theorem to derive an equivalent time domain condition. In the case where , we show that frequency and time domain sufficient conditions specialize to the positivity theorem. Furthermore, using linear matrix inequalities, we develop a controller synthesis approach for guaranteeing a phase constraint on the closed-loop transfer function. Finally, we extend this synthesis approach to address mixed gain and phase constraints on the closed-loop transfer function.