第二代AFBC—CC热力性能初探

第二代ＡＦＢＣ—ＣＣ热力性能初探张娜，蔡睿贤，林汝谋（中国科学院工程热物理研究所）关键词常压流化床，燃煤联合循环，效率，功比符号表Ｄ总压恢复系数Ｔｅ余热锅炉排烟温度Ｂ燃烧室Ｇ流量△增量Ｃ压气机Ｈ焓η效率ｃｃ联合循环Ｈｕ煤气热值π压比ｄ燃气透平出口Ｎ功...     

任意循环的卡诺循环分解

指出任意循环的两种卡诺循环分解的极限都趋于原来的循环，一些献中关于其中一种分解不趋于原循环的证明是欠妥的。     

一类Holling功能性反应模型极限环的唯一性

考虑捕食者无密度制约，食饵具有非线性密度制约的第三类Ｈｏｌｌｉｎｇ功能性反应捕食者－食饵系统．对该系统给出了完整的定性分析，证明了该系统至多有一个极限环，存在极限环的充要条件是正平衡点不稳定．     

Life‐cycle toxicity of dibutyltin to the sheepshead minnow (Cyprinodon variegatus) and implications of the ubiquitous tributyltin impurity in test material

Dibutyltin (DBT) is used in the plastics polymerization process as a catalyst in polyvinyl chloride (PVC) products and is the primary degradation product of tributyltin (TBT), an antifoulant in marine paint. DBT and other organotin compounds make their way into the environment through antifoulants, PVC processing plants, and PVC products maintained in water and water‐handling systems. A flow‐through saltwater life‐cycle toxicity test was conducted to determine the chronic effect of DBT to the sheepshead minnow (Cyprinodon variegatus Lacepede), an estuarine species. Embryos were monitored through hatch, maturation, growth, and reproduction in DBT concentrations of 158, 286, 453, 887, and 1510 µg l^?1. Progeny were monitored for survival as embryos and fry/juveniles, and growth for 30 days post‐isolation. Mean length of parental generation fish was significantly reduced on day 30 at DBT concentrations ≥887 µg l^?1, setting the lowest observable effect concentration (LOEC) at 887 µg l^?1 and the no observable effect concentration (NOEC) at 453 µg l^?1. Fecundity, as egg viability, was significantly reduced at the LOEC. Survival of parental and progeny generation embryos and mean length, wet weight and dry weight of progeny generation juveniles were not significantly affected at concentrations ≤LOEC. TBT, a toxic impurity in DBT reversibly produced in DBT by the process of comproportionation, was also monitored throughout this study. Comparing measured levels of TBT in this study with levels exerting toxic effects in an earlier TBT life‐cycle study with C. variegatus suggests biological responses in this study were likely due to the TBT impurity and not to DBT alone. Results indicate that TBT impurity as low as 0.1% may have a significant influence on the perceived toxicity of DBT and that spontaneous production of TBT in DBT may be the major source of biological toxicity of DBT. Copyright © 2003 John Wiley & Sons, Ltd.     

Plasma Feedback Control System for HL-2A Tokamak

As the limit of time and budget etc, the control system of HL-2A just could be operated in programmed discharge when HL-2A was checked and accepted in 2002. Recent years, many subsystem of HL-2A have been improved in functions and performances. And the demand for experiment of HL-2A is becoming more and more higher in plasma discharge parameters. So it＇s necessary to develop a plasma feedback control system （ FBCS ） which has enough functions and good stability and reliability to satisfy the demand of experiment on HL-2A.     

多元混合工质内复叠节流结合涡流管复合循环的热力分析

针对多元混合工质内复叠节流循环和涡流管的特点 ,提出了一种新的复合循环流程 ,以期达到液氮以下的制冷温度。建立了适当的涡流管热力学模型 ,采用火用分析方法对复合制冷循环各部件进行了分析。在相同的条件下 ,对复合循环和内复叠循环的热力特性进行对比 ,结果表明 ,采用复合循环可以提高整个循环的火用效率 ,完全可能达到液氮以下的制冷温度     

Formulas and representations for cyclic Markovian networks via Palm calculus

We present an extension of the arrival theorem for the output process from a node in closed Markovian networks which we use to obtain simple representations and explicit expressions for the throughput, the distribution of the cycle time, and the joint distribution of interoutput times from a node in single class closed networks with exponential servers. Our approach uses tools from Palm calculus to obtain a recursion on the number of customers in the system. The analysis relies on a non-overtake condition and thus many of the results obtained here apply only to cyclic, single server networks. One of the surprising conclusions of our analysis is that the interoutput times that comprise the cycle time of a customer are (finitely) exchangeable, i.e., that their joint distribution is invariant under permutations. This revised version was published online in June 2006 with corrections to the Cover Date.     

THE POINCAR BIFURCATION OF CUBIC HAMILTONIAN SYSTEMS WITH DOUBLE CENTERS

In this paper, we discuss the Poincare bifurcation of cubic Hamiltonian systems with double centers and prove that the systems may at least generate two limit cycles and at most generate three limit cycles outside the lemniscate after a small cubic perturbation.     

Distribution and cycle of arsenic compounds in the ocean

In order to understand the distribution and the cycle of arsenic compounds in the marine environment, the horizontal distributions of arsenic(V) [As(V)], arsenic(III) [As(III)], monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA) in the Indian Pacific Oceanic surface waters have been investigated. This took place during cruises of the boat Shirase from Tokyo to the Syowa Station (15 November–19 December 1990), of the tanker Japan Violet from Sakai to Fujayrah (28 July–17 August 1991) and of the boat Hakuho-maru from Tokyo to Auckland (19 September–27 October 1992). Vertical distributions of arsenic in the west Pacific Ocean have also been investigated. The concentration of As(V) was found to be relatively higher in the Antarctic than in the other areas. Its concentration varied from 340 ng dm^?3 (China Sea) to 1045 ng dm^?3 (Antarctic). On the other hand, the concentrations of the biologically produced species, MMAA and DMAA, were extremely low in the Antarctic and southwest Pacific waters. Their concentrations in Antarctic waters were 8 ng dm^?3 and 22 ng dm^?3 and those in the southwest Pacific were 12 ng dm^?3 and 25 ng dm^?3. In the other regions the concentration varied from 16 ng dm^?3 (China Sea) to 36 ng dm^?3 (north Indian Ocean) for MMAA and from 50 ng dm^?3 (east Indian Ocean) to 172 ng dm^?3 (north Indian Ocean) for DMAA. As a result, with the exception of Antarctic and southwest Pacific waters, the percentages of each arsenic species in the surface waters were very similar and varied from 52% (east Indian Ocean) to 63% (northwest Pacific Ocean) for As(V), from 22% (northwest Pacific Ocean) to 27% (east Indian Ocean) for As(III) and from 15% (northwest Pacific Ocean) to 21% (north and east Indian Oceans) for the methylated arsenics (MMAA+DMAA). These percentages in Antarctic waters were 97%, 0.2% and 2.8%, respectively, and those in the southwest Pacific Ocean were 97% for As(V)+As(III) and 3% for MMAA+DMAA. The very low concentrations of the biologically produced species in Antarctic waters and that of methylated arsenic in southwest Pacific waters indicated that the microorganism communities in these oceans was dominated by microorganisms having a low affinity towards arsenic. Furthermore, microorganism activity in the Antarctic was also limited due to the much lower temperature of the seawater there. The vertical profile of inorganic arsenic was 1350 ng dm^?3 in surface waters, 1500 ng dm^?3 in bottom waters with a maximum value of 1700 ng dm^?3 at a depth of about 2000 m in west Pacific waters. This fact suggested the uptake of arsenic by microorganisms in the surface waters and the co-precipitation of arsenic with hydrated heavy-metal oxides in bottom waters. The suggested uptake of inorganic arsenic and subsequent methylation was also supported by the profile of DMAA, with a high concentration of about 26 ng dm^?3 in surface water and a significant decrease to a value of 9 ng dm^?3 at a depth of 1000 m.     

活性炭-氨吸附式制冷循环中吸附床的传热传质性能研究

吸附床由6个吸附单元组成,吸附单元为壳管式换热器,吸附工质对是活性炭-氨。利用多孔介质中流体流动的概念,建立一个吸附单元的数学模型,模拟结果与实验结果显示出很好的一致性。同时得出了吸附床内某种平均温度和平均压力的分布规律。