PLC 控制的榨菜自动包装机控制系统的可靠性研究及其通讯监测

本文着重研究了榨菜自动包装机控制系统的可靠性，并对其运行状态进行通讯监测     

Electrostatic actuation of three-dimensional MEMS mirrors using sidewall electrodes

We propose and demonstrate electrostatic sidewall-electrodes actuation of three-dimensional (3-D) microelectromechanical systems (MEMS) gimbal mirrors. The linearity of the mirror angle dependence on actuation voltage is improved with the sidewall-electrodes actuation. In addition, the undesired spring-softening effect commonly found in electrostatic actuation, where the mirror resonance frequency decreases with increased tilt angle, is significantly reduced. Sidewall actuation enables superior performance of 3-D MEMS mirrors including large pull-in angles, reduced actuation voltages, improved device reliability, and fast switching times.     

Optimal common-mode voltage reduction PWM technique for inverter control with consideration of the dead-time effects-part II: applications to IM drives with diode front end

The main theme of this paper is to demonstrate the applications of the newly developed common-mode voltage reduction pulsewidth-modulation (PWM) technique, which restricts the common-mode voltage to one-third of DC-link voltage, to vector-controlled induction motor drives. As compared to previous common-mode voltage reduction techniques, the presented technique can be applied to the inverter with diode front end and has no adverse effect on the linear modulation range. Therefore, vector-controlled drives using the developed technique for inverter control have a wide speed range. Moreover, the effects of the common-mode voltage reduction PWM technique on speed response for vector-controlled induction motor drives will be fully investigated in this paper. It will be demonstrated by intensive experimental results that speed performance does not deteriorate significantly within the rated speed range.     

Low-temperature X-ray microanalysis of the differentiating vascular tissue in root tips of Lemna minor L

The fracture faces of bulk-frozen tissue offer a number of advantages for the analysis of diffusible elements. They are easy to prepare, remain uncontaminated, and, unlike most frozen-hydrated sections, can be shown to exist in a fully hydrated state throughout examination and analysis. Root tips of Lemna minor briefly treated with a polymeric cryoprotectant are quench frozen in melting nitrogen. Fractures are prepared using the AMRAY Biochamber, lightly etched if necessary to reveal surface detail and carbon coated while maintaining the specimen at 110 K. The frozen-hydrated fracture faces are analysed at 110 K using the P/B ratio method which is less sensitive to changes in surface geometry and variations in beam current. The method has been used to investigate the distribution of seven elements (Na+, Mg⁺⁺, P, S, Cl^?, K+ and Ca⁺⁺) in the developing vascular tissue of the root tip. The microprobe can measure relative elemental ratios at the cellular level and the results from this present study reveal important variations in different parts of the root. The younger, more actively dividing cells, appear to have a slightly higher concentration of diffusible ions in comparison to the somewhat older tissues which have begun to differentiate into what are presumed to be functional vascular elements.     

水资源承载力综合评价的熵权属性识别模型

根据水资源承载力分析的结构特点,在传统多目标分析决策技术的基础上,将熵值法与属性识别模型相结合,建立了基于熵权的属性识别水资源承载力评价模型,应用熵值法来确定权重系数,避免了权重系数确定的主观性问题,用一种新的方法进行水环境承载力评价.结合实际应用的结果表明,其评价结果合理,适用于水环境承载力评价.     

Termination detection for dynamically distributed systems with non-first-in-first-out communication

We propose a new algorithm for detecting termination of distributed systems. The algorithm works correctly whether the system is static or dynamic, whether the interprocess communication is synchronous or asynchronous, and whether the communication channels are first-in-first-out or not. The algorithm requires, in the worst case, O(nm) control messages in all, where n is the number of processes in the system and m is the total number of messages transmitted during the operation of the system. After the system terminates, the algorithm is able to detect the termination using only O(n) control messages; it is optimal if the system concerned is static.     

基于Jack的虚拟环境中一种防止穿越的实现

在虚拟环境下虚拟人手和虚拟物体的交互中,会发生穿越现象。为了解决穿越问题,在人体模型系统Jack的虚拟环境中,根据约束Constraint对象的特点,利用Constraint对象来模拟物体对人手阻挡作用,并利用约束队列实现了对场景中Constraint对象的管理,达到防穿越的效果。     

A general stochastic clustering method for automatic cluster discovery

Finding clusters in data is a challenging problem. Given a dataset, we usually do not know the number of natural clusters hidden in the dataset. The problem is exacerbated when there is little or no additional information except the data itself. This paper proposes a general stochastic clustering method that is a simplification of nature-inspired ant-based clustering approach. It begins with a basic solution and then performs stochastic search to incrementally improve the solution until the underlying clusters emerge, resulting in automatic cluster discovery in datasets. This method differs from several recent methods in that it does not require users to input the number of clusters and it makes no explicit assumption about the underlying distribution of a dataset. Our experimental results show that the proposed method performs better than several existing methods in terms of clustering accuracy and efficiency in majority of the datasets used in this study. Our theoretical analysis shows that the proposed method has linear time and space complexities, and our empirical study shows that it can accurately and efficiently discover clusters in large datasets in which many existing methods fail to run.     

Dynamic characteristic analysis of TBM tunnelling in mixed-face conditions

In this paper, by taking into account the periodically varying mesh stiffness in multiple pinions transmission and the speed–torque characteristics of variable frequency motor drives, the dynamic model for the revolving system of tunnel boring machine (TBM) has been established. Based on the soft ground/hard rock assumption of mixed-face conditions and the analysis of cutting force on each disc cutter and each drag bit, the time-varying excavation torque on the TBM cutterhead in mixed-face tunnelling is obtained. The dynamic excavation torque and cutterhead rotation speed are discussed and compared for TBM tunnelling in several typical mixed-face conditions, which are characterized by the area percentage of soft ground on the excavation face and the uniaxial compressive strength (UCS) of rock. The results show that the excavation torque may run up to a critical value and fluctuate greatly in extremely adverse excavation environments, which may lead to an unexpected TBM stoppage and even a catastrophic failure of the drive motor. To decrease the penetration per revolution in time through applying a lower advance velocity and a higher cutterhead revolution will significantly reduce the excavation torque and effectively avoid such situations.