石油储罐防腐涂料施工策略

在经济不断发展的背景下,石油已经成为不可或缺的能源,其从开采至加工整个过程均需使用储油罐,所以储油罐的防腐质量十分重要,需要使用相应的涂料进行防腐。本文对石油储罐防腐涂料施工策略进行分析,以供参考。     

基于NB分类器重访概率预测的Web缓存替换策略

Web缓存是用来解决网络访问延迟和网络拥塞问题，缓存替换策略直接影响缓存的命中率。为此，提出一种朴素贝叶斯（NB）分类器重访概率预测的Web缓存替换策略；根据用户之前访问日志，通过分区操作提取多项特征来表示每次访问的对象，并构建特征数据集；训练NB分类器，用来确定缓存中对象被再次访问的概率，为对象分配权重；结合LRU策略来合理删除一些对象。仿真结果表明，提出的策略在保证较高命中率的同时有效降低了执行时间。     

Corporate performance of the Seven Brothers of the European energy market: Then there were five

Fifteen years ago, Thomas (2003) found that seven European energy utilities had a strong hold over European energy markets. By 2009, further concentration had occurred, with five large utilities becoming more dominant. However, by 2015, while the market share of these five companies remained intact, their strength was waning. Sales and profits were declining, and their credit ratings suffering. Contributing factors were poor corporate strategy, competition from new entrants, and a shift from large, complex technologies to smaller, decentralised options. The challenge for the Big Five is to embrace new business models and transform themselves into more nimble companies.     

多维不确定性影响下的水期权交易最优策略研究

为解决来水预测不确定性和水价不确定性给用水户带来的风险对冲问题,引入对冲性的水期权交易模式,建立了以用水户期望收益最大为目标的水期权交易模型,得到了最优的期权交易策略应满足的条件,并利用二分法计算得到了最优的期权交易策略,探究了来水不确定性与水价不确定性对期权交易策略的影响。结果表明,来水预测误差和水价的波动越大,用水户的期望收益越大,最优的期权交易策略能有效降低来水预测不确定性和水价不确定性带来的风险。     

Nonlinear optimization strategy based on multivariate prediction capability ratios: Analytical schemes and model validation for duplex stainless steel end milling

Given the complex nature of their phenomena and interactions, industrial processes often have multiple variables of interest, usually grouped into critical-to-quality and critical-to-performance characteristics. These variables often have significant correlations, which make engineering problems multivariate. For this reason, Response Surface Methodology, coupled with multivariate techniques, has been widely used as a logical roadmap for modeling and optimization of the characteristics of interest. However, the variability and prediction capability of the numerical solutions obtained are almost always neglected, reducing the likelihood that numerical results are indeed compatible with observable process improvements. To fill this gap, this paper proposes a nonlinear multiobjective optimization strategy based on multivariate prediction capability ratios. For this, rotated Factor Analysis is used as the multivariate technique for grouping process characteristics and composing capability ratios, so that the prediction variance is taken as the natural variability of the process modeled and the expected value distances to the nadir solutions of the latent variables are taken as the allowed variability. Normal Boundary Intersection method, combined with Generalized Reduced Gradient algorithm, is used as the numerical scheme to maximize the prediction capability of Pareto optimal solutions. To illustrate the feasibility of the proposed strategy, we present a case study of end milling without cutting fluids of duplex stainless steel UNS S32205. Rotatable Central Composite Design, with three cutting parameters, was employed for data collection. Traditional multivariate and proposed approaches were compared. The results demonstrate that the proposed optimization strategy is able to provide solutions with satisfactory prediction capability for all variables analyzed, regardless of their convexities, optimization directions, and correlation structure. In addition, while critical-to-quality characteristics are more difficult to control, they have been favored by the proposed optimization regarding prediction capability, which was a desirable result.     

车辆高速避让路径跟踪控制策略

建立车辆动力学模型,研究车辆在高速避让工况下的路径跟踪控制策略。基于自抗扰控制设计车辆横摆角速度以及道路曲率2种不同的路径跟踪控制器;设计基于车辆偏航位移和偏航角度加权的线性二次最优控制器;对3种控制器控制效果进行仿真验证,分析路径跟踪侧向位移误差、侧向加速度、前轮转向角以及偏航角度变化。越野车实车测试结果表明,路径跟踪控制策略正确。     

国际环境不确定下海外采矿权评估研究

在实物期权理论框架下,基于Black-Schole采矿权评估模型,提出了计量国际环境不确定性的方法以及将其纳入评估模型的途径,以此优化完善海外采矿权评估; 通过一实例验证了本文所述方法的可行性,并依据评估结果进一步分析了投资策略,最后对所提方法的可靠性进行了检验。研究结果显示: ① 采矿权价值来自于矿业权人对矿产资源的开采加工及具有灵活经营的权利,国际环境的不确定变化影响采矿权价值及投资策略。② 矿产品价格升高、价格波动率增加、驻在国矿业行业环境和国家环境变异程度的增加、矿山服务年限的增加,均提高了海外采矿权价值; 但矿产品价格下降、矿山服务年限减少将降低采矿权价值。③ 当矿产品价格持续处于低位时,项目应尽早建设或放弃; 而当价格处于增长或高位时,项目可适当推迟建设。④ 老挝矿业行业环境的变异程度大于该国国家环境的变异程度,前往老挝投资的矿企应重点关注该国涉及矿业投资的法律法规及政策,重点防范行业风险。⑤ 本文所提海外采矿权评估方法是可行、可靠的,具有一定实践意义。     

Recovery planning of industrial robots based on semantic information of failures and time-dependent utility

Industrial robots are required to recover from temporary errors and continue operations under a changing environment. In this paper, we propose a recovery planning system that considers the semantic information behind errors during robotic actions. In order to establish general repair strategies for feasible recovery plans under uncertainties, the proposed system uses a conceptual graph based on case grammar and a Bayesian network that is dynamically constructed according to the semantic information. In addition, we tackle the problem that the wealth of the recovery plan depends on the uncertainty of execution costs against the deadline at the production site. The proposed system controls the decision model by using a time-dependent utility. We demonstrate the effectiveness of the proposed system through simulations of assembly tasks by multiple robots.     

智能数据分区与布局研究

大数据时代,数据规模庞大,由数据进行驱动的应用分析场景日益增多.如何快速、高效地从这些海量数据中提取出用以分析决策的信息,给数据库系统带来重大挑战.同时,现代商业分析决策对分析数据的实时性要求数据库系统能够同时快速处理ACID事务和复杂的分析查询.然而,传统的数据分区粒度太粗,且不能适应动态变化的复杂分析负载;传统的数据布局单一,不能应对现代大量增加的混合事务分析应用场景.为了解决以上问题,“智能数据分区与布局”成为当前的研究热点之一,它通过数据挖掘、机器学习等技术抽取工作负载的有效特征,设计最佳的分区策略来避免扫描大量不相关的数据,指导布局结构设计以适应不同类型的工作负载.首先介绍了智能数据分区与布局的相关背景知识,然后对智能数据分区与布局技术的研究动机、发展趋势、关键技术进行详细的阐述.最后,对智能数据分区与布局技术的研究前景做出总结与展望.