热网管道热损失现场测试方法探讨

<正> 国外热网管道热损失测试多半采用热流计、红外测温仪、点温计等测试手段来实现。但现场测试时往往受到风、日照等非稳态影响。为探讨现场测试方法的可行性,采用了热流计法、表面温度法、温差法和焓降法来测量热网管道热损失。a.热流计法:用热流计直接测量管道保温层外表面热损失。b.表面温度法:测量管道保温层外表面温度、环境温度和风速,按对流换热和辐射换热公式来计算管道热损失。c.温差法:根据管道保温层内、外表面温度,内、外径以及实验室测得的保温材料导热系数,按径向一维导热计

假想分子与化学平衡

为了简化在求算有化学反应的气态物质的宏观热力学性质时所用到的概念和方法,本文引进“假想分子”的概念,导出了其化学势μ和绝对活度z=e~(μ/kT)的表达式。这样即可对化学平衡作出全新的物理解释,证明了化学平衡时,反应物的假想分子与生成物的假想分子可用统一的玻尔兹曼分布来表示,从而把有化学反应与无化学反应的体系统一了起来,并且简化了化学平衡时各能态上粒子数的计算方法。

O futuro é a internet gratuita

Consultoria Legislativa - Área XIV - Comunicação Social, Informática, Telecomunicações, Sistema Postal, Ciência e Tecnologia.

Numerical study of bifurcation solutions of spherical Taylor-Couette flow

The steady bifurcation flows in a spherical gap (gap ratio sigma=0.18) with rotating inner and stationary outer spheres are simulated numerically for Re(c1)less than or equal to Re less than or equal to 1 500 by solving steady axisymmetric incompressible Navier-Stokes equations using a finite difference method. The simulation shows that there exist two steady stable flows with 1 or 2 vortices per hemisphere for 775 less than or equal to Re less than or equal to 1 220 and three steady stable flows with 0, 1, or 2 vortices for 1 220

Cauchy singular integral equation method for transient antiplane dynamic problems

In this paper, by use of the boundary integral equation method and the techniques of Green basic solution and singularity analysis, the dynamic problem of antiplane is investigated. The problem is reduced to solving a Cauchy singular integral equation in Laplace transform space. This equation is strictly proved to be equivalent to the dual integral equations obtained by Sih [Mechanics of Fracture, Vol. 4. Noordhoff, Leyden (1977)]. On this basis, the dynamic influence between two parallel cracks is also investigated. By use of the high precision numerical method for the singular integral equation and Laplace numerical inversion, the dynamic stress intensity factors of several typical problems are calculated in this paper. The related numerical results are compared to be consistent with those of Sih. It shows that the method of this paper is successful and can be used to solve more complicated problems. Copyright (C) 1996 Elsevier Science Ltd

Fusion energy-production from a deuterium-tritium plasma in the jet tokamak

Describes a series of experiments in the Joint European Torus (JET), culminating in the first tokamak discharges in deuterium-tritium fuelled mixture. The experiments were undertaken within limits imposed by restrictions on vessel activation and tritium usage. The objectives were: (i) to produce more than one megawatt of fusion power in a controlled way; (ii) to validate transport codes and provide a basis for accurately predicting the performance of deuterium-tritium plasmas from measurements made in deuterium plasmas; (iii) to determine tritium retention in the torus systems and to establish the effectiveness of discharge cleaning techniques for tritium removal; (iv) to demonstrate the technology related to tritium usage; and (v) to establish safe procedures for handling tritium in compliance with the regulatory requirements. A single-null X-point magnetic configuration, diverted onto the upper carbon target, with reversed toroidal magnetic field was chosen. Deuterium plasmas were heated by high power, long duration deuterium neutral beams from fourteen sources and fuelled also by up to two neutral beam sources injecting tritium. The results from three of these high performance hot ion H-mode discharges are described: a high performance pure deuterium discharge; a deuterium-tritium discharge with a 1% mixture of tritium fed to one neutral beam source; and a deuterium-tritium discharge with 100% tritium fed to two neutral beam sources. The TRANSP code was used to check the internal consistency of the measured data and to determine the origin of the measured neutron fluxes. In the best deuterium-tritium discharge, the tritium concentration was about 11% at the time of peak performance, when the total neutron emission rate was 6.0 × 10¹⁷ neutrons/s. The integrated total neutron yield over the high power phase, which lasted about 2 s, was 7.2 × 10¹⁷ neutrons, with an accuracy of ±7%. The actual fusion amplification factor, Q_DT was about 0.15

Crack tip behavior and crack-propagation in ductile materials

Dilatational plastic equations, which can include the effects of ductile damage, are derived based on the equivalency in expressions for dissipated plastic work. Void damage developed internally at the large-strain stage is represented by an effective continuum being strain-softened and plastically dilated. Accumulation of this local damage leads to progressive failure in materials. With regard to this microstructural background, the constitutive parameters included for characterizing material behaviour have the sense of internal variables. They are not able to be determined explicitly by macroscopic testing but rather through computer simulation of experimental curves and data. Application of this constitutive model to mode-I cracking examples demonstrates that a huge strain concentration accompanied by a substantial drop of stress does occur near the crack tip. Eventually, crack propagation is simulated by using finite elements in computations. Two numerical examples show good accordance with experimental data. The whole procedure of study serves as a justification of the constitutive formulation proposed in the text.

Hierarchal structure of the simplified Navier-Stokes equations (SNSE) and its mechanical connotation and application

The hierarchial structure and mathematical property of the simplified Navier-Stokesequations (SNSE) are studied for viscous flow over a sphere and a jet of compressible flu-id. All kinds of the hierarchial SNSE can be divided into three types according to theirmathematical property and also into five groups according to their physical content. Amultilayers structure model for viscous shear flow with a main stream direction is pre-sented. For the example of viscous incompressible flow over a flat plate there existthree layers for both the separated flow and the attached flow; the character of thetransition from the three layers of attached flow to those of separated flow is elucidated.A concept of transition layer being situated between the viscous layer and inviscidlayer is introduced. The transition layer features the interaction between viscous flow andinviscid flow. The inner-outer-layers-matched SNSE proposed by the present author inthe past is developed into the layers matched (LsM)-SNSE.

PICES Press, Vol. 12, No. 2, July 2004

The future of PICES [pdf, 1.7 MB] Paris by day - Symposium on "Quantative ecosystem indicators in fisheries management" [pdf, 0.2 MB] The Bering Sea: Current status and recent events [pdf, 0.4 MB] The state of the western North Pacific in the second half of 2003 [pdf, 0.7 MB] The state of the eastern North Pacific entering spring 2004 [pdf, 0.4 MB] PICES-IFEP Workshop on "In-situ iron enrichment experiments in the eastern and western subarctic Pacific" [pdf, 1.4 MB] Canadian SOLAS/PICES-IFEP session on "Response of the upper ocean to meso-scale iron enrichment" [pdf, 0.3 MB] Fisheries and ecosystem responses to recent regime shifts [pdf, 0.8 MB] PICES Interns [pdf, 0.8 MB] Did a regime shift occur in 1998 around Japan?- Highlights from a symposium addressing this question [pdf, 0.8 MB] The Global Ocean Carbon Observing System - Connecting national programs and regional networks [pdf, 1.7 MB] The North Pacific Ecosystem Metadatabase [pdf, 1.2 MB] International GLOBEC Symposium on "Climate variability and Sub-Arctic marine ecosystems" [pdf, 0.2 MB] PICES Calendar [pdf, 0.2 MB] PICES/GLOBEC Symposium on "Climate variability and ecosystem impacts on the North pacific: A basin-scale synthesis" [pdf, 0.2 MB]

Diário da Constituinte [gravação de vídeo] : [programa n. 156 A]

O Deputado Arnaldo Faria de Sá (PTB-SP) entrega projeto de decisão, que trata do mandato do Presidente Sarney, ao Presidente da Assembleia Nacional Constituinte (ANC), Deputado Ulysses Guimarães (PMDB-SP). O Deputado Octávio Elísio (PMDB-MG) considera que, ao impor ao PFL e ao PMDB o mandato de cinco anos, o Presidente Sarney criou posição sobre a soberania da Assembleia Nacional Constituinte. O Deputado Plínio Arruda Sampaio (PT-SP) afirma que é juridicamente possível tratar como matéria destacada o projeto do constituinte Arnaldo Faria de Sá. O Deputado Asdrubal Bentes (PMDB-PA) apresenta medida que proíbe a reeleição e a ocupação de cargo público para todos os que atingirem os setenta anos de idade. Informações sobre a quantidade de artigos de textos constitucionais em outros países. O Deputado Bernardo Cabral (PMDB-AM) esclarece que a maioria dos países dispõe de Constituição com poucos artigos, sendo o restante tratado em Lei Ordinária. Análise da quantidade de artigos que tiveram as Constituições brasileiras: 179 artigos tinha a Constituição do Império; 91 artigos a da Primeira República; 187 artigos as Constituições de 1934 e de 1937; 218 artigos a de 1946; 217 artigos a de 1967. O projeto atual de Constituição, com 501 artigos, pode virar "um catálogo telefônico" na opinião de alguns políticos. O Deputado Adroaldo Streck (PDT-RS) afirma que há muita coisa no texto que é matéria de Lei Ordinária, não precisa entrar no texto constitucional. O Deputado Bernardo Cabral (PMDB-AM) defende que o texto da Constituição seja sintético, com no máximo 200 artigos.

三峡升船机系统动态响应分析

根据三峡升船机最新设计报告,采用有限元软件ANSYS构建了升船机系统有限元模型,包括承船厢、提升钢索、滑轮组、平衡重、厢内水体、驱动机构和刹车机构;通过数值模拟,对升船机系统进行了模态分析及动态响应研究,内容包括升船机系统的流固耦合模态及其在各种工况(起动、刹车、事故)下的动态响应和影响因素分析,如弹簧刚度、误载水深、阻尼、承船厢的位置等.计算结果表明:对于升船机这样一个复杂系统,该文所建立的有限元模型及数值算法是合理的,其结果可为升船机系统整体设计提供必要的参考.

直接统计模拟位置元方法中的分子表面反射确定论判据

发展的分子表面反射判据，使判断分子是否与某一表面无相撞问题得到了有效的解决。此外，还讨论了分子空间位置坐标的记录方法、分子碰撞对的极限距离、网格自适应等实际模拟技术。与圆球自由分子流准确解和过渡领域贴体网格DSMC模拟结果的比较，证明了上述判据和技术和有效性。