Operation of brushless doubly-fed machine for drive applications

This paper presents dynamic and steady-state performance of the Brushless Doubly-Fed Machine (BDFM) operating as a variable speed drive. A simple closed-loop control system is used which only requires a speed feedback. The controller is capable of stabilising the machine when changes in speed and torque are applied. The machine starts in cascade mode and then makes a transition to the synchronous mode to reach the desired speed. This will allow a uni-directional converter to be used. The experiments included in this paper were carried out on a 180 frame size BDFM.

Stable operation of the Brushless Doubly-Fed Machine (BDFM)

A simple method of controlling the Brushless Doubly-Fed Machine (BDFM) is presented. The controller comprises two Proportional-Integral (PI) modules and requires only the rotor speed feedback. The machine model and the control system are developed in MATLAB. Both simulation and experimental results are presented. The performance of the system is presented in the motoring and generating operations. The experimental tests included in this paper were carried out on a 180 frame size BDFM with a nested-loop rotor. © 2007 IEEE.

Performance of thin film carbon materials and carbon nanotubes as cold cathodes

The field emissions from three different types of carbon films are studied using a Kiethly voltage-current source-measure unit under computer control. The three types of carbon films are : 1) a-C:H:N deposited using an inductively coupled rf PECVD process, where the N content in the films can be as high as 30 at %; 2) cathodic arc deposited tetrahedral amorphous carbon with embedded regions of carbon nanotube and anion structures and 3) unoriented carbon nanotube films on a porous substrate. The films are formed by filtering a solution of nanotubes dispersed in alcohol through the pores and drying.

Visuomotor feedback gains upregulate during the learning of novel dynamics.

At an early stage of learning novel dynamics, changes in muscle activity are mainly due to corrective feedback responses. These feedback contributions to the overall motor command are gradually reduced as feedforward control is learned. The temporary increased use of feedback could arise simply from the large errors in early learning with either unaltered gains or even slightly downregulated gains, or from an upregulation of the feedback gains when feedforward prediction is insufficient. We therefore investigated whether the sensorimotor control system alters feedback gains during adaptation to a novel force field generated by a robotic manipulandum. To probe the feedback gains throughout learning, we measured the magnitude of involuntary rapid visuomotor responses to rapid shifts in the visual location of the hand during reaching movements. We found large increases in the magnitude of the rapid visuomotor response whenever the dynamics changed: both when the force field was first presented, and when it was removed. We confirmed that these changes in feedback gain are not simply a byproduct of the change in background load, by demonstrating that this rapid visuomotor response is not load sensitive. Our results suggest that when the sensorimotor control system experiences errors, it increases the gain of the visuomotor feedback pathways to deal with the unexpected disturbances until the feedforward controller learns the appropriate dynamics. We suggest that these feedback gains are upregulated with increased uncertainty in the knowledge of the dynamics to counteract any errors or disturbances and ensure accurate and skillful movements.

The performance of closed reactor grade plutonium-thorium fuel cycles in reduced-moderation pressurised water reactors

The production of long-lived transuranic (TRU) waste is a major disadvantage of fission-based nuclear power. Previous work has indicated that TRU waste can be virtually eliminated in a pressurised water reactor (PWR) fuelled with a mixture of thorium and TRU waste, when all actinides are returned to the reactor after reprocessing. However, the optimal configuration for a fuel assembly operating this fuel cycle is likely to differ from the current configuration. In this paper, the differences in performance obtained in a reduced-moderation PWR operating this fuel cycle were investigated using WIMS. The chosen configuration allowed an increase of at least 20% in attainable burn-up for a given TRU enrichment. This will be especially important if the practical limit on TRU enrichment is low. The moderator reactivity coefficients limit the enrichment possible in the reactor, and this limit is particularly severe if a negative void coefficient is required for a fully voided core. Several strategies have been identified to mitigate this. Specifically, the control system should be designed to avoid a detrimental effect on moderator reactivity coefficients. The economic viability of this concept is likely to be dependent on the achievable thermal-hydraulic operating conditions. © 2012 Elsevier Ltd. All rights reserved.

Generalization in Adaptation to Stable and Unstable Dynamics

Humans skillfully manipulate objects and tools despite the inherent instability. In order to succeed at these tasks, the sensorimotor control system must build an internal representation of both the force and mechanical impedance. As it is not practical to either learn or store motor commands for every possible future action, the sensorimotor control system generalizes a control strategy for a range of movements based on learning performed over a set of movements. Here, we introduce a computational model for this learning and generalization, which specifies how to learn feedforward muscle activity in a function of the state space. Specifically, by incorporating co-activation as a function of error into the feedback command, we are able to derive an algorithm from a gradient descent minimization of motion error and effort, subject to maintaining a stability margin. This algorithm can be used to learn to coordinate any of a variety of motor primitives such as force fields, muscle synergies, physical models or artificial neural networks. This model for human learning and generalization is able to adapt to both stable and unstable dynamics, and provides a controller for generating efficient adaptive motor behavior in robots. Simulation results exhibit predictions consistent with all experiments on learning of novel dynamics requiring adaptation of force and impedance, and enable us to re-examine some of the previous interpretations of experiments on generalization. © 2012 Kadiallah et al.

Stabilization of periodic orbits in a wedge billiard

This paper introduces a stabilization problem for an elementary impact control system in the plane. The rich dynamical properties of the wedge billiard, combined to the relevance of the associated stabilization problem for feedback control issues in legged robotics make it a valuable benchmark for energy-based stabilization of impact control systems.

A simple closed aquatic ecosystem (CAES) for space

A closed aquatic ecosystem (CAES) was developed to stud), the effects of microgravity on the function of closed ecosystems aboard the Chinese retrieved satellite and on the spacecraft SHENZHOU-II. These systems housed a small freshwater snail (Bulinus australianus) and an autotrophic green algae (Chlorella pyrenoidosa). The results of the test on the satellite were that the concentration of algae changed little, but that the snails died during the experiments. We then sought to optimize the function of the control system, the cultural conditions and the data acquisition system and carried out an experiment on the spacecraft SHENZHOU-II. Using various sensors to monitor the CAES, real-time data regarding the operation of the CAES in microgravity was acquired. In addition, all on-board Ig centrifuge was included to identify gravity-related factors. It was found that microgravity is the major factor affecting the operation of the CAES in space. The change in biomass of the primary producer during each day in microgravity was larger than that of the control groups. The mean biomass concentration per day in the microgravity group decreased, but that of the control groups increased for several days and then leveled off. Space effects on the biomass of a primary producer may be a result of microgravity effects leading to increasing metabolic rates of the consumer combined with decreases in photosynthesis. (c) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.

Micronutrient niacin addition to enhance biological treatment of textile wastewater

Micronutrients play an important role in biological processes for wastewater treatment. Many industrial wastewaters lack in nutrients required for microbial growth, and this is one of the problems at many activated sludge plants treating them. In this study, the effects of the micronutrient niacin on the COD removal rates of textile wastewater, together with the effect of Mixed Liquor Suspended Solids (MLSS) on niacin, were studied. Certain improvement effects were found on the removal rates of COD, when 0.5 similar to 2.0 mg/L niacin was added to the textile wastewater. The optimal concentration of niacin was 1.0 mg/L, which was continuously added during textile wastewater treatment, and removal rates were 1.31 times compared to those of the control system. The concentration of MLSS was probably one of the factors influencing treatment efficiency, and the biological performance of treatment system could be optimized through micronutrient niacin supplements.

面向ETL过程的数据质量控制系统的设计与实现

ETL过程是一个从分布数据源(包括数据库、应用系统、文件系统等)抽取数据，进行转换、集成和传输，并最终加载到目标系统的过程。传统的ETL过程主要服务于数据仓库(Data Warehouse)，属于企业决策支持系统的一部分。随着数据集成技术的发展和轻量级的数据集成中间件的出现，ETL过程广泛应用于企业数据集成与数据交换系统。在ETL过程中，数据质量控制是一个极为重要的基本组件和功能，它对集成中的数据进行检测、转换、清洗，以防止“脏”数据进入目标系统。在ETL过程中如果缺少对数据质量的有效控制，就会导致数据集成项目无法圆满实现目标或彻底失败。 针对ETL过程中存在的数据质量问题，设计并实现面向ETL过程的数据质量控制系统，是本文研究的重点。论文通过对ETL过程中各阶段可能产生的数据质量问题进行了分类，并对质量控制需求建模，提出一个面向ETL过程的数据质量控制框架，该框架通过对源端数据的分析来指导ETL的设计，通过灵活、可配置、可扩展的数据处理机制实现数据的过滤、转换与清洗，并支持对数据质量处理全过程进行监控。在该框架基础上，论文特别在灵活的数据处理机制、数据分析、数据过滤和数据清洗四个方面进行了探讨。在数据处理机制方面，提出了基于插件元模型的数据处理机制，该机制可以满足用户对数据过滤、数据转换与数据清洗等功能的各种定制需求，并具有较强的可扩展性；在数据分析方面，根据字段类型对数据进行分类统计，并针对大数据量统计分析问题，提出了可自动配置的不同数据统计策略；在数据过滤方面，通过将抽取数据的SQL语句重写的方式，过滤不满足完整性约束的元组；在数据清洗方法方面给出了一种利用统计信息动态确定属性相似度权重的方法，对基于字段的相似记录检测算法的领域无关算法进行了改进，提高了数据检测的准确性。在上述工作基础上，在数据集成中间件OnceDI中设计并实现了数据质量控制系统，并在设计中通过设计模式的应用增强系统的可扩展性。

中药处方配伍监控系统的设计与实现

医院信息系统(hospital information system,HIS)作为医院信息化建设的重要组成部分越来越受到社会的重视,已经进入一个高速发展的阶段。但是作为诊疗过程的一个重要组成部分-药物处方治疗,在HIS中却缺少必要的监控与指导。在HIS标准化推进的同时,更应该对其深度和广度进行研究,结合软件工程的设计思想,基于面向对象的开发方法,设计开发了“中药处方配伍”监控系统,提供了临床用药指导功能,使其作为HIS的一个子系统能够实时的对医生处方进行监控,使临床医药人员记得更多、更准、更细,以降低药源性疾病,提高用药质量,加强用药管理,避免医疗纠纷。

一种分布式转发基站测控系统的研究与实现

布式监测系统(DCS)在许多领域具有重要的应用价值.针对目前分布式监测系统造价高、运行不稳定等问题,该文提出了一种解决方案--基于多种通讯链路的分布式转发基站监测系统.该文详细介绍了阐述了该监测控制系统的工作原理,并对监测控制系统的结构(包括软件的结构和硬件系统的结构)进行了具体地说明,然后详细描述了监控系统软件、硬件以及通讯协议的设计与实现;文章最后,对基于该系统的一个成功应用--无线寻呼基站无人测控系统的实现作了介绍.无线寻呼基站运行实践中所表现出的低成本、高性能的特点进一步验证了该方案的可实施性.