一类五阶Korteweg-de-Vries方程的惟一连续性（英文）

惟一连续性是可积系统的重要性质之一,而初值问题解的性质与初值的光滑性密切相关.本文主要讨论了一类五阶Kd V方程初值问题解的惟一连续性,证明了该初值问题的足够光滑的解,如果在一个非退化的时间区间内具有紧支集,那么该解恒为零.     

分数阶脉冲微分方程初值问题解的存在性

利用Green函数可以将分数阶微分方程初值问题转化为等价的积分方程.近来此方法被应用于讨论非线性分数阶微分方程初值问题解的存在性.本文讨论菲线性分数阶脉冲微分方程初值问题,应用Green函数,将其转化为等价的积分方程,并设非线性项满足Carathéodory条件,利用非紧性测度的性质和M(o)nch,8不动点定理证明解的存在性.     

线性脉冲微分方程初值问题的ω-周期解(英文)北大核心CSCD

本文利用广义常微分方程理论,得到了线性脉冲微分方程的通解公式,并利用ω-周期解的定义和线性代数方程的性质,得到了线性脉冲微分方程初值问题的ω-周期解.     

一个新的推广两分量Camassa-Holm系统的持久性

解的长时间行为是偏微分方程研究中的一个重要问题.在很大程度上,解的性质取决于初值的性质.持久性指当初值满足无穷远处衰减的条件,则方程的解在无穷远处也衰减.在本文中,我们利用权函数估计的方法研究了一个新的推广两分量Camassa-Holm系统初值问题解的持久性,进而给出了最优衰减估计.     

一类带调和势的非线性Klein-Gordon方程的L2-集中性质

Klein-Gordon方程是相对论、量子力学和量子场论中最基本的方程.本文在n维空间中讨论一类带调和势的非线性Klein-Gordon方程的初值问题,在得到其局部解存在性的基础之上,应用能量方法和微分、积分不等式技巧,得到了在一定条件下解的爆破性质,并进一步讨论了解的爆破点与L2-集中性质.     

高阶分数阶微分方程系统的解的注记

分数阶导数在描述不同物质的记忆与遗传性质方面提供了有力的工具.在科学和工程的不同领域,都用分数阶微分方程组来描述动力系统.本文主要探讨分数阶微分方程系统初值问题局部解的存在性与唯一性.对于线性系统,运用Schur分解定理,给出其局部解的存在性与唯一性,并通过举例说明该方法是有效的.对于非线性系统,利用Schauder不动点定理,给出了解的存在性;运用Banach不动点定理,给出了解的唯一性.     

可测系数广义线性常微分方程的周期解（英文）

本文利用ω-周期解的定义和广义常微分方程理论,得到了广义线性常微分方程初值问题的ω-周期解,所得结果是对线性常微分方程周期解的本质推广.     

关于收缩性非线性初值问题多步Runge—Kutta方法的动力特征

讨论了多步Ｒｕｎｇｅ－Ｋｕｔｔａ方法数值求解收缩性非线性初值问题时数值解的动力性质，阐明代数稳定的多步Ｒｕｎｇｅ－Ｋｕｔｔａ方法具有与所求问题的相同的唯一整体吸收平衡点。     

基于系统搜索的容差模拟电路多参数故障诊断

针对容差条件下非线性模拟电路的多参数故障诊断问题,提出一种系统搜索算法求解故障参数,实现故障元件的定位和参数辨识。首先将非线性测试方程的多解求解转化为差分方程的初值问题;然后采用牛顿法迭代生成简单曲线簇,沿曲面方向进行测试方程的解搜索,并通过四阶龙格库塔法计算初值问题的数值解,显著提高方程组解的求解效率,降低漏解的风险;最后将故障集验证转化为容差约束下的线性规划问题求解,实现故障元件定位,并通过实际电路实验验证该算法的有效性。该算法适用于含BJT和CMOS等非线性电路的故障诊断,具有较高的诊断准确度和参数辨识准确度。     

应用谱方法研究管内非牛顿流体的非定常流动

本文研究上随体Ｍａｘｗｅｌｌ流体在水平管内的非定常流动，该问题可归纳为无量纲速度分量的二阶偏微分方程的边初值问题，采用以Ｃｈｅｂｙｓｈｅｖ多项式为基底的谱方法，将该偏微分方程化为二阶常微分方程组的初值问题，采用Ｌａｐｌａｃｅ变换，求得二阶常微分方程组的解析解，文中提出了用谱方法解非定常流动的新方法，并通过在常压力梯度和周期性压力梯度两种情形下的计算结果，与用差分法和Ｋａｎｔｏｒｏｖｉｃｈ变分法求得     

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.……     

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.     

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.     

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