基于马尔科夫链模拟的支持向量机可靠性分析方法

针对实际工程中可靠性分析设计的极限状态方程为隐式的情况,提出了一种基于马尔科夫链模拟的支持向量机可靠性分析方法.所提方法采用改进的马尔科夫链来产生极限状态重要区域上的样本点,再采用支持向量机方法求得相应的函数替代模型来进行可靠性分析.由于马尔科夫链能够自适应的模拟极限状态重要失效区域附近的样本,并且由于采用马尔科夫链备...     

基于改进HMM和Pearson相似度分析的滚动轴承自适应寿命预测方法

基于数据驱动思想,提出了一种相同工况下的滚动轴承寿命预测方法。针对轴承全寿命监测数据,根据K-means聚类算法划分轴承运行状态空间,考虑到隐马尔科夫模型主链为状态链的不足,对状态转移矩阵重新定义,将主链改进为寿命链,建立了基于改进HMM的全寿命状态驻留时间模型;将观测轴承数据、实时与建模数据进行Pearson相似度分析,构造寿命比例调节系数,实现寿命模型参数的动态修正和观测轴承寿命的自适应预测。采用美国辛辛那提大学实验中心轴承试验数据开展了应用研究,通过一组轴承全寿命数据实现了对其它轴承不同阶段及全寿命的预测,与传统的隐马尔科夫模型、灰色模型预测等方法预测结果相比,所提算法兼具较好的预测准确性和模型的泛化性。     

河流中长期水质预测建模与应用

本文论述了如何对河流中长期水质预测进行建模、计算和分析。而且论述了如何采用灰色系统模型和马尔可夫链模型对河流中长期水质进行数学建模和计算。最后,通过对长江宜宾段未来十年水质情况进行预测分析,得出灰色系统模型相比马尔科夫链预测模型在河流中长期水质现状预测中更适用的结论。     

退化串联可修系统瞬态可靠性分析

可修串联系统是一类经典的可靠性模型,在实际工程中较为常见．为满足工程实际需求,所研究的系统由2个部件和1个维修工组成．假设工作时间、维修时间和部件更换时间均服从指数分布,在维修之后系统不能修复如新．系统采用部件故障N次之后将被更新的维修策略．在这些假设下利用几何过程和马尔科夫过程对系统进行建模,再利用半马尔科夫过程和数值积分方法给出系统瞬态可用度和（0,t］时间内故障次数的计算公式．最后给出算例并应用Monte Carlo方法对所得公式进行验证．为进一步研究复杂机械系统的可靠性提供了理论基础．     

核燃料元件中氦气泄漏规律的探讨

本文讨论了核燃料元件中,氦气通过不同标称泄漏率所等效的不同直径的漏孔向大气进行自然泄漏时,其氦气压强随时间变化的规律。通过数学推导,分别得出了氦气通过漏孔时的流动状态为分子流、粘滞流及扩散状态时的计算方程。并给出了元件中氦气通过不同标称泄漏率所等效的不同孔径的漏孔直径的计算公式。     

基于数字孪生技术的"四线一库"自动运维系统建设及应用

数字孪生技术是在信息化平台上,利用三维建模、物联网、人工智能等技术,实现对特定场景下的物理实体、流程或系统的模拟技术.针对电力计量领域中"四线一库"检定流水线故障处理时间长、巡检工作量大等问题,文章介绍了利用数字孪生技术与设备状态预测技术相结合,实现"四线一库"计量检定流水线的全自动无人值守与精益化运维的方法及其系统.在某省电力公司的应用结果表明,在"四线一库"计量检定流水线的数字孪生系统中应用马尔科夫链预测技术可使平均巡检时间下降30％,平均故障处理时间下降30％,能有效提高该类检定流水线的可靠性与高效性.     

基于区块链的医疗临床数据防篡改机制及篡改攻击分析

医疗临床数据的可靠共享机制对提升智慧医疗水平具有重要意义,防篡改机制可为医疗临床数据交互与共享提供保障。本文首先给出了基于区块链的医疗临床数据防篡改机制,然后设计了两种场景来分析医疗临床数据篡改攻击的实施途径,最后对篡改攻击进行建模并基于马尔科夫链进行了分析。本文研究内容对提升医疗临床数据共享安全性以及智慧医疗水平均具有较高的应用价值。     

面向高度时变不确定患者需求的急诊医生周排班方法研究

本文对急诊医生的周计划排班问题进行研究,建立了基于马尔科夫链模型和均匀化方法的系统定量评估方法,并设计禁忌搜索算法对问题加以求解优化。为了减少算法的计算时间,设计了三种算法运算求解加速策略。本文利用上海、武汉等三甲医院的真实数据对算法优化后的医生排班方案与目前实际排班进行了比较,在病人等待时间等多个指标上分析了求解结果的优势。     

马尔科夫跳变系统的时滞依赖L2-L∞滤波设计

本文研究带有时滞的Markov跳变系统的L2-L∞滤波问题，其中跳变参数以离散马尔科夫链的形式给出．设计出满阶与降价的滤波器，使得误差系统满足一定的L2-L∞性能指标．本文时滞依赖的方法，以一系列严格的矩阵不等式的形式给出了滤波器存在的充分条件．并以一种统一的形式给出了滤波器的参数．最后，以一个数值实例验证了结论的有效性。     

基于Petri网的可信连接架构的安全属性分析

为确保可信连接架构(TCA)自身的安全可靠,研究了其安全属性量化问题,分析了其双向用户身份认证和平台认证过程中存在的安全威胁.利用随机Petri网对带有攻击行为的TCA可信网络连接过程进行了建模,该模型用于描述攻击行为和TCA的双向认证过程.以该模型为基础构造了马尔科夫链,通过计算马尔科夫模型的稳定状态概率对TCA的稳定状态机密性和完整性等安全属性进行定量分析.最后给出了一个具体数值评估结果的实例.此研究给出的方法有理论和实用意义.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from