基于SiPESC.OPT的透平低压排汽缸优化设计

针对提高蒸汽透平机组效率的需求,基于SiPESC.OPT集成软件平台,集成SolidWorks,ICEM和CFX等多个软件构建透平低压排汽缸优化设计系统.系统采用参数化建模、三维黏性流体分析和蚁群算法等多种手段,对某型号透平低压排汽缸模型进行优化设计.结果表明,优化后平均压力恢复因数提升188.31%,出口气流不均匀分布因数明显下降.该优化设计系统能有效提高透平低压排汽缸气动性能.     

一种高效的H.264反变换反量化结构设计

在分析H.264反变换反量化算法的基础上,提出了一种高效的H.264反变换反量化硬件结构.在反变换中,采用了一个可重构的一维IDCT变换结构;在反量化中,采用了4个反量化单元的并行结构,并通过LUT取代了占用电路面积大的模运算和除法运算;在整体结构设计中,采用了门控时钟方案和流水线技术.结果表明,本设计可提高系统输出能力和降低硬件功耗,并满足1080i高清码流实时解码的要求.     

The interaction between skill, postures, forces and back pain in wool handling

Wool handling is an important rural occupation where workers process 200 or more fleeces daily, separating them into various quality components. Loads and postures they experience carry substantial risk of low back pain (LBP). Although a formal skill training structure exists, interaction with loads and LBP is unknown. We examined whether skill and LBP influenced trunk postures and loads of 60 wool handlers representing 3 skill levels. LBP prevalence ranged from 20% for junior (lowest skill) to 45% for open class (highest skill) wool handlers. Open class wool handlers demonstrated increased lateral bend and more axially twisted postures, generating greater medio-lateral shear forces and lateral bend and axial twist moments. LBP was associated with open class wool handlers spending more time in severe axially twisted postures. These findings suggest that skill-based training needs to be reviewed to reduce the quantity of axially twisted posture which may help reduce the prevalence of LBP in this workforce.     

The effect of a lower extremity kinematic constraint on lifting biomechanics

Leaning against a stationary barrier during manual materials handling tasks is observed in many industrial environments, but the effects of this kinematic constraint on low back mechanics are unknown. Thirteen participants performed two-handed lifting tasks using both a leaning posture and no leaning posture while trunk kinematics, muscle activity and ground reaction force were monitored. Results revealed that lifting with the leaning posture required significantly less activity in erector spinae (26% vs. 36% MVC) and latissimus dorsi (8% vs. 14% MVC), and less passive tissue moment compared with the no leaning posture. Peak sagittal accelerations were lower when leaning, but the leaning posture also had significantly higher slip potential as measured by required coefficient of friction (0.05 vs. 0.36). The results suggested that the leaning lifting strategy provides reduced low back stress, but does so at the cost of increased slip potential.     

A fuzzy reasoning and fuzzy-analytical hierarchy process based approach to the process of railway risk information: A railway risk management system

Risk management is becoming increasingly important for railway companies in order to safeguard their passengers and employees while improving safety and reducing maintenance costs. However, in many circumstances, the application of probabilistic risk analysis tools may not give satisfactory results because the risk data are incomplete or there is a high level of uncertainty involved in the risk data. This article presents the development of a risk management system for railway risk analysis using fuzzy reasoning approach and fuzzy analytical hierarchy decision making process. In the system, fuzzy reasoning approach (FRA) is employed to estimate the risk level of each hazardous event in terms of failure frequency, consequence severity and consequence probability. This allows imprecision or approximate information in the risk analysis process. Fuzzy analytical hierarchy process (fuzzy-AHP) technique is then incorporated into the risk model to use its advantage in determining the relative importance of the risk contributions so that the risk assessment can be progressed from hazardous event level to hazard group level and finally to railway system level. This risk assessment system can evaluate both qualitative and quantitative risk data and information associated with a railway system effectively and efficiently, which will provide railway risk analysts, managers and engineers with a method and tool to improve their safety management of railway systems and set safety standards. A case study on risk assessment of shunting at Hammersmith depot is used to illustrate the application of the proposed risk assessment system.     

温室远程多参数控制系统的国产化研究

基于国产STC12C5A62S2的温室多参数控制系统的应用技术(包括软硬件设计),该系统通过RS-485总线与PC上位机通信,实现了低成本、多参数、远距离、多节点数据采集与控制的全部国产化。     

溶剂系统的模式识别

通过三层ＢＰ人工神经网络,对溶剂系统进行模式识别。以经规格化自理伯Ｘｔ、Ｘｅ、Ｘｍ、Ｘｎ、Ｘｄ这５个溶剂性质的选择性参数作为判别指标,５类共１９种不同的溶剂作为训练样本,得到最佳网络参数。然后以十我种有代表性的溶剂作为待测样本进行了模式识别。研究结果表明,人工神经网络用于溶剂系统的模式识别,识别结果与实际一致,本文结果有助于色谱分析及分离技术中溶剂的选择。     

Feedforward networks in financial predictions: the future that modifies the present

The main goal of this paper is to show how relatively minor modifications of well-known algorithms (in particular, back propagation) can dramatically increase the performance of an artificial neural network (ANN) for time series prediction. We denote our proposed sets of modifications as the 'self-momentum', 'Freud' and 'Jung' rules. In our opinion, they provide an example of an alternative approach to the design of learning strategies for ANNs, one that focuses on basic mathematical conceptualization rather than on formalism and demonstration. The complexity of actual prediction problems makes it necessary to experiment with modelling possibilities whose inherent mathematical properties are often not well understood yet. The problem of time series prediction in stock markets is a case in point. It is well known that asset price dynamics in financial markets are difficult to trace, let alone to predict with an operationally interesting degree of accuracy. We therefore take financial prediction as a meaningful test bed for the validation of our techniques. We discuss in some detail both the theoretical underpinnings of the technique and our case study about financial prediction, finding encouraging evidence that supports the theoretical and operational viability of our new ANN specifications. Ours is clearly only a preliminary step. Further developments of ANN architectures with more and more sophisticated 'learning to learn' characteristics are now under study and test.     

关于BP算法推导过程与讨论

本文通过对多层神经网络模型的BP算法的推导,讨论用BP算法对网络进行优化后误差精度、网络结构和学习次数之间的关系,最后指出BP算法的不足之处,提出加快学习过程的一些方法和技巧。