具有非线性传染率的两类传染病模型的全局分析

讨论了两类带有非线性传染率的SIS型和SIRS型传染病模型,得到了各类平衡点存在的阈值条件。借助构造Dulac函数和Liapunov函数,找到了各类平衡点全局渐近稳定的充要条件。     

一类带有毒素生产的恒化器模型的定性分析

讨论了一类带有毒素生产的恒化器模型,获得了模型各类平衡点存在及稳定的充要条件,通过构造Dulac函数和Lyapunov函数和运用极限系统理论,证明了该模型符合竞争排斥原理,并且得到了各类微生物绝灭的完整分析结果。     

一类具有非线性饱和传染力的传染病模型

讨论了一类具有非线性饱和传染力的SIS流行病模型,确定了各类平衡点存在的阈值条件,利用线性化和李亚谱诺夫-拉塞尔的方法,得到了各类平衡点全局稳定性的条件。     

捕食者有病的生态-流行病SIS模型的分析

建立并分析了捕食者具有疾病的生态一流行病SIS模型,讨论了解的有界性。应用特征根法得到了平衡点局部渐近稳定的充分条件,进一步,分析了平衡点的全局稳定性,得到了边界平衡点和正平衡点全局稳定的充分条件。     

一类含确定时滞的流行病模型的研究

讨论了一类含确定时滞的SIS流行病模型,利用李亚普诺夫泛函的方法,得到了无病平衡点和地方病平衡点全局稳定性的结论,揭示了时滞对各类平衡点稳定性的影响。     

具有预防接种的非线性传染率传染病模型的稳定性

本文讨论了一个采取预防接种措施的非线性传染率传染病模型,得到了决定疾病流行与否的阈值θ,当θ>1时,仅存在无病平衡点E0,是渐近稳定的,当θ<1时,存在两个平衡点:无病平衡点E0和地方病平衡点E ,其中无病平衡点E0不稳定。在不考虑免疫的丧失或者不考虑因病死亡的因素的情况下,当θ>1时E0全局渐近稳定;当θ<1时E 全局渐近稳定。     

非线性微分动力系统稳定域计算的波形松弛方法

非线性微分动力系统稳定域计算是在许多领域具有实际应用的问题。本文对非线性微分动力系统稳定域的计算方法进行了总结,通过对稳定域边界流形的全面分析,提出了用波形松弛方法计算稳定域边界流形的思想,给出了计算稳定域边界流形的波形松弛算法。第一步,找出微分动力系统的所有平衡点,确定渐近稳定平衡点稳定域边界上的平衡点;第二步,用微分动力系统的反方向系统确定原系统渐近稳定平衡点稳定域边界上平衡点的稳定流形;第三步,渐近稳定平衡点稳定域的边界是由边界上平衡点和该平衡点稳定流形的并集构成。最后用例子来说明波形松弛方法在计算稳定域边界流形的有效性。     

一类具有交叉传染的流行病接种模型

通过对一类具有交叉传染的流行病接种模型进行分析，借助李雅普诺夫函数和Krasnoselakii技巧，得到结论：若该模型仅存在无病平衡点，则无病平衡点是全局渐近稳定的；若该模型有地方病平衡点存在，则无病平衡点是不稳定的，而正平衡点是渐近稳定的。     

一个捕食者染病、食饵具有阶段结构的生态 - 流行病模型的稳定性

研究了一个捕食者染病且食饵具有阶段结构的生态 - 流行病模型的稳定性,考虑了捕食者对食饵的 Holling-II 型功能性反应函数,并讨论了由捕食者的妊娠期引起的时滞对模型稳定性的影响。通过计算特征方程的特征值,运用 Hurwitz 判定定理,得到了该模型的在平凡平衡点、捕食者灭绝平衡点、无病平衡点和正平衡点的局部稳定性,得到了正平衡点处存在 Hopf 分支的充分条件。通过构造 Lyapunov 泛函,运用 LaSall 不变集原理得到了该模型的平凡平衡点、捕食者灭绝平衡点、无病平衡点和正平衡点全局稳定的充分条件。     

一个具有时滞和捕食者、食饵均具有阶段结构的捕食模型

本文研究一个具有时滞和捕食者、食饵均具有阶段结构的捕食模型的稳定性.首先,通过分析特征方程,运用Hurwitz判定定理,分别给出了该模型的边界平衡点和正平衡点局部稳定的充分条件,并得到了该模型在正平衡点存在Hopf分支的充分条件;其次,运用无穷维动力系统的一致生存定理,得到了该模型持续生存的充分条件;最后,通过构造适当的Lyapunov泛函,运用La Sall不变集原理,分别给出了该模型边界平衡点和正平衡点全局稳定的充分条件.     

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.……     

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.     

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     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.     

新闻(英文)

正China and Greece Sign the Standardization Cooperation Agreement Witnessed by Chinese Premier Li Keqiang and Greek Prime Minister Antonis Samaras,AQSIQ Minister Zhi Shuping and ELOT Chairman and Executive Director Angelos Tolkas signed the SAC-ELOT Standardization Cooperation Agreement.The Agreement is one of the critical cooperation documents signed during Li Keqiang’s visit in Greece,encouraging China and Greece to