织构拉刀的拉削负载特性建模与验证

针对传统圆孔拉削加工负载建模过程不够清晰,负载特性预测误差较大的问题,将拉刀刀齿上的槽定义成一种表面织构槽,综合考虑刀齿上的织构槽参数、拉削面积圆孔效应和拉削过程多齿接触周期特性,建立了较详细的织构拉刀拉削负载计算模型。基于经典刀齿切削负载理论,提出了具有织构槽拉刀的单齿拉削负载模型;考虑工件圆弧孔形状对拉削面积的影响,进一步优化单齿拉削负载模型;考虑由工件长度引起的多齿接触周期特性,得到一般性的织构拉刀拉削负载计算模型。仿真与实验结果表明,提出的模型能较好地预测实际拉削负载。同时也指出,在拉刀刀齿上开设织构槽可以降低拉削负载,但是开设的织构槽数量并非越多越好,而是存在一个最优值。

一种基于实测的自动负载建模算法

负载平衡是影响大规模并行计算效率的一个关键因素,准确的负载建模是负载平衡的基础。提出了一种基于实测的自动负载建模算法。该算法无需用户提供信息,具有良好的理论保证以及近似线性的计算复杂度和完全的并行性。2400个进程上的分子动力学模拟表明,该算法执行速度快,同时能够保证60%以上的负载平衡效率。

基于稀疏学习的微电网负载建模

微电网由负载、储能系统和分布式电源互联集成到能源系统中,微电网系统可以作为一个整体系统与电网并行运行或以孤岛模式运行.负载建模是微电网运行和管理中的一个基本问题.本文着重解决以下两个关键问题:1)协调负载模型结构的合理性和简洁性;2)负载模型参数的校准.与常规负载建模方法不同,本文提出了一类数据驱动建模方法以同时实现负载模型结构选择和参数校准.具体地,该方法从量测数据中稀疏学习静态负载模型和动态负载模型,其关键方法分别来自于稀疏贝叶斯学习方法和交替方向方法,即从一组备选非线性字典函数中稀疏学习最主要的非线性项以平衡数据拟合度并实现模型学习.所提出的方法将机器学习与稀疏表示相结合,旨在对负载模型从物理角度提供机理解释并向配电网系统操作员提供有关负载的动态信息.在孤岛微电网测试系统中验证并评估了所提出的算法.研究测例表明所提出算法从量测数据中实现负载稀疏学习的合理性和对于噪声的鲁棒性.

基于货运列车组的传感网节点负载建模分析

部署于货运列车组的无线传感器网络一般为线性拓扑,汇聚节点位于网络端部.由于网络的中间节点需要承担较多的传输任务,从而易导致能耗不均形成能量空洞,造成网络快速失效.对线型网络节点负载情况进行了建模以分析网络能耗分布,建立了节点和汇聚节点距离与节点负载的关系模型,并通过仿真实验证明了模型的正确性.模型能够在未来应用中对网络布设时的拓扑构建、路由协议定制等起到指导作用.

面向TTCN-3性能测试的负载生成方法

TTCN-3(Testing and Test Control Notation version 3)是一种面向黑盒测试的测试描述与实现语言.随着TTCN-3语言的广泛应用,用户对使用TTCN-3进行性能测试的需求日益强烈.然而,TTCN-3语言没有提供有效的负载描述和产生机制.目前,在使用TTCN-3产生性能测试的负载时,通常需要依靠大量的人工编码.该文提出了一种模型驱动方法以更加有效地支持面向TTCN-3的负载生成.在该方法中,负载指标模型用于刻画负载指标及约束关系;负载剖面模型则能够定义指标的取值及指标值随时间变化的情况.基于这些模型,该文提出的算法能够完成从模型到TTCN-3测试系统的自动转换.TTCN-3测试系统可在负载控制点的支持下得以执行,从而模拟出满足模型描述的负载场景.该文通过案例分析验证了上述方法的有效性和所模拟负载场景的准确性.

高精度超快响应大功率负载的设计与实现

针对传统功率电子产品往往存在着负载响应时间较慢、精确度不高并且测试能力较弱的情况,设计了一种全新的超快响应大功率负载装置,整套装置及系统通过高精度的电子元器件及合理的电路板进行综合设计布局,提升了整套系统的运行稳定性和反应速度,并达到了较高的精度,实现了良好的动态特性及静态特性及新一代高压直流电子负载的基本功能,同时还提供了强大的测试功能和友好的人机界面,适用于各种直流电源或相关设备的测试,能为工程设计和测试提供多种解决方案。

使用智能电表数据进行智能电网负载分析

面向异常用电定位和电力营销模式创新的电力缴费系统的一体化建设对负载预测提出更高的要求。为此,提出了一种基于智能电表数据的随机负荷建模方法。通过对用电量模式进行线性化和聚类处理,将原始智能电表数据简化为加权合并和线性化的用电量曲线,从而实现负载数据的聚类分析。试验结果证明了方法的鲁棒性和准确性。

实用电源(11)

正二十、DC-DC电源三相电机的供电电路1.DC-DC电源的负载问题(1)DC-DC电源的负载——三相电机到此为止,为了简化问题,我们总是把负载理想化为一只电阻器。比如音响中的功率放大器,输出负载为8Ω(或16Ω)。

电流频谱Hurst指数在串联电弧故障检测中的应用

串联电弧故障因故障电流小、随机性强,难以被普通保护电器所检测和切除.本文基于已有的Mayr电弧模型增加了弧柱电感、间隙电容和压控随机开关以模拟电弧高频特性,从而构建了不同类别典型负载的精细化电路模型.实验证实所建负载模型和电弧模型的仿真数据较好拟合了相应的实验结果,在此基础上将仿真波形重构为二维矩阵,提取矩阵奇异值之比作为时域特征;提取02500 Hz内归一化谐波幅值波形的Hurst指数作为频域特征;选取隐层节点数为17的单隐层BP网络实现了串联电弧故障诊断,总体准确率达到93.9%.检测方案在STM32F767平台上运行时间仅19.85 ms,符合UL–1699中实时性指标要求.本文提出的检测方案具有计算量相对较小、特征简洁、准确率高等优势,有助于串联电弧检测和有效辨识的工业应用.

A priority-based dynamic load transfer algorithm for cellular/WLAN integrated networks

For the integration network of a cellular network and a wireless local area network （WLAN）, a priority-based dynamic load transfer （PDLT） algorithm is proposed. The dynamic vertical handoffs by call admission control are jointly determined by the network conditions and the traffic characteristics in combination with the location-condition of mobile terminals. When there is no bandwidth resource available in the cellular network or WLAN, the proposed PDLT algorithm allows an incoming voice call or data call within the overlapping area of the cellular network and the WLAN to be directed to the spare network; meanwhile, by dynamically computing the occupancy of the bandwidth resource, the proposed PDLT algorithm also allows an ongoing voice call or data communication to be transferred to the network with a sufficient bandwidth resource according to the given threshold to balance the number of voice/data calls in the two networks. The analysis results of a two-dimensional Markov model and the simulation results show that the PDLT algorithm can effectively enhance the whole integrated network＇ s traffic, reduce the blocking probability of new calls and increase the data throughput, and thus decrease the response time for various services.

基于硬件与虚拟用户的大型软件性能测试解决方案

关键的负载测试对于降低大型软件的风险至关重要。在实施负载测试的几种方法中,基于硬件与虚拟用户的测试方法的可行性、可实施性都很强。本文以Rational性能测试工具为例,给出了一个基于硬件与虚拟用户的大型软件负载测试解决方案。

AccGecko:面向分布式存储系统的尾延迟SLO保证框架

对于分布式存储系统来说,保证多租户尾延迟服务质量目标(SLO)同时获得较高的资源利用率十分重要。现有租户负载建模方法忽略了突发流量的密集程度,采用间接方法来预测尾延迟,导致系统的资源利用率较低。为了解决上述问题,本文基于密度聚类算法(DBScan),从强度、概率及密集程度3个维度对租户负载突发流量进行建模,直接预测连续突发流量期间请求延迟超限的概率。结合固定速率分配方法,本文设计了尾延迟SLO保证框架AccGecko。相比于已有的工作,AccGecko可以使系统平均多承载66%的租户。

摆动喷管电动伺服系统复合控制方法

针对飞行器摆动喷管电动伺服系统在低气压高温升条件下的控制问题,提出一种复合控制方法。基于LuGre模型对伺服系统的复杂负载力矩进行建模,利用状态观测器和两个dual观测器推导出负载力矩参数自适应律,以期实现对负载力矩随外界条件变化时的拟合。采用自适应反步终端滑模算法,负载力矩估计值进行虚拟力矩补偿,同时解决控制电压与力矩干扰之间不匹配、电机电压扰动及参数变化的问题,理论分析证明所提控制算法对于匹配及非匹配不确定性都具备鲁棒性,能够保证跟踪误差最终一致有界。最后通过仿真及实验,验证了所提方法的有效性。

Load distribution model and voltage static profile of Smart Grid

Voltage profiles of feeders with the connection of distributed generations(DGs) were investigated.A unified typical load distribution model was established.Based on this model,exact expressions of feeder voltage profile with single and double DGs were derived and used to analyze the impact of DG's location and capacity on the voltage profile quantitatively.Then,a general formula of the voltage profile was derived.The limitation of single DG and necessity of multiple DGs for voltage regulation were also discussed.Through the simulation,voltage profiles of feeders with single and double DGs were compared.The voltage excursion rate is 7.40% for only one DG,while 2.48% and 2.36% for double DGs.It is shown that the feeder voltage can be retained in a more appropriate range with multiple DGs than with only one DG.Distributing the total capacity of DGs is better than concentrating it at one point.

Load-balancing data distribution in publish/subscribe mode

To improve data distribution efficiency a load-balancing data distribution LBDD method is proposed in publish/subscribe mode.In the LBDD method subscribers are involved in distribution tasks and data transfers while receiving data themselves.A dissemination tree is constructed among the subscribers based on MD5 where the publisher acts as the root. The proposed method provides bucket construction target selection and path updates furthermore the property of one-way dissemination is proven.That the average out-going degree of a node is 2 is guaranteed with the proposed LBDD.The experiments on data distribution delay data distribution rate and load distribution are conducted. Experimental results show that the LBDD method aids in shaping the task load between the publisher and subscribers and outperforms the point-to-point approach.

Measurement-based approach for identification of static load model of electric power system

The validity of electric power system simulation or prediction models depends on static load model. Measurement- based approach is the unique method to identify them adequately. The measured power depends on both load reaction to supply voltage alteration and random process of load alteration Basically, there is no any universal method that can single out the inherent static load model from experimental data. The paper offers a proprietary technique which is the particular solution of the task. The technique considers the selection of neighboring measurement pairs with the supply voltage altering significantly be-tween them, the exclusion of selected pairs by load power factor and subsequent selection of the inherent static load model presented as the polynomial load model. The usage of the technique to identify static load model at “Fenster” industrial enterprise （in Borisov city） is presented. The ideas considered in the paper can be used for future development of static load model identification methods with the data obtained during both active experiment and in other operating models of electric power systems.

A new support vector machine optimized by improved particle swarm optimization and its application

A new support vector machine （SVM） optimized by an improved particle swarm optimization （PSO） combined with simulated annealing algorithm （SA） was proposed. By incorporating with the simulated annealing method, the global searching capacity of the particle swarm optimization（SAPSO） was enchanced, and the searching capacity of the particle swarm optimization was studied. Then, the improyed particle swarm optimization algorithm was used to optimize the parameters of SVM （c,σ and ε）. Based on the operational data provided by a regional power grid in north China, the method was used in the actual short term load forecasting. The results show that compared to the PSO-SVM and the traditional SVM, the average time of the proposed method in the experimental process reduces by 11.6 s and 31.1 s, and the precision of the proposed method increases by 1.24% and 3.18%, respectively. So, the improved method is better than the PSO-SVM and the traditional SVM.

Analytical solution to rock pressure acting on three shallow tunnels subjected to unsymmetrical loads

According to the interaction of three shallow tunnels with large section, the analytical solution to rock pressure has been derived and discussed. The load model is given when the bilateral tunnels are excavated. According to the model, the stresses of three tunnels and single tunnel are calculated and compared to analyze the distribution characteristics, where the stresses are influenced by controlling factors of clear distance, covering depth and inclination angle of ground surface. The results show that, in general, the bias distribution is more serious. Therefore, it is significant to settle down the load model of three shallow tunnels so as to determine the measure of reinforcement and design the structure of support. The model and results can be used as a theoretical basis in designation and further research of the three shallow tunnels.

Hybrid force control of astronaut rehabilitative training robot under active loading mode

In order to mitigate the effects of space adaptation syndrome(SAS) and improve the training efficiency of the astronauts, a novel astronaut rehabilitative training robot(ART) was proposed. ART can help the astronauts to carry out the bench press training in the microgravity environment. Firstly, a dynamic model of cable driven unit(CDU) was established whose accuracy was verified through the model identification. Secondly, to improve the accuracy and the speed of the active loading, an active loading hybrid force controller was proposed on the basis of the dynamic model of the CDU. Finally, the actual effect of the hybrid force controller was tested by simulations and experiments. The results suggest that the hybrid force controller can significantly improve the precision and the dynamic performance of the active loading with the maximum phase lag of the active loading being 9° and the maximum amplitude error being 2% at the frequency range of 10 Hz. The controller can meet the design requirements.

Theoretical and experimental analyses of casing collapsing strength under non-uniform loading

Failure data from oilfield showed that casings which were designed according to API standards were deformed and collapsed in salt formations. The main reason for decrease in strength may be caused by non-uniform loading(NUL) that was not considered in traditional casing collapsing strength design or that the designing method should be improved and developed. Obviously, the calculation of casing collapse strength is one of the key factors in casing design. However, the effect of NUL on casing collapse strength was generally neglected in the present computational methods. Therefore, a mechanical model which can calculate casing collapse strength under NUL was established based on the curved beam theory of the elasticity and was solved using displacement method. Simultaneously, three anti-collapse experiments were performed on C110 casing under NUL, and the strain and deformation laws of three casings in the process of collapse were obtained by the electrical method. Yield limit of every casing was obtained by analyzing those data. Experimental results are consistent with the results of calculation of new model. It indicates that the model can be used to calculate yield limit loading of casings under NUL.