CO2滚动活塞膨胀机膨胀过程模拟计算

膨胀机工作过程模拟是以膨胀机实际工作过程为研究对象,综合各种因素,建立数学模型,利用计算机对模型进行数值求解,分析了膨胀机中工质的主要热力参数以及其能量、质量及功率等变化特性,计算了膨胀机输出功和效率等主要参数,通过分析,揭示了膨胀机的内部工作规律和改进膨胀机性能的途径.     

Saturation of Photoassociation in Cs Magneto-optical Trap

An ultrahigh resolution photoassociation spectrum of caesium atoms in a magneto-optical trap is presented. Hyperfine structure of the excited state molecule is obtained by using the lock-in method based on modulated cold atoms in this spectrum. Amplitude of resonant lines related to the rotational levels increases with photoassociation laser intensity, and saturation effect of photoassociation of cold atoms is observed in our experiment. The saturation intensity of photoassociation is deduced by fitting the experimental data to asaturation model based on scattering theory. Differences among saturation intensities of different rotational progressions in the υ=55 vibrational state of the caesium molecular long-range 0_g^- state have been found.     

A NUMERICAL AND ANALYTICAL STUDY ON A TAIL-FLAPPING MODEL FOR FISH FAST C-START＊

The force production physics and the flow control mechanism of fish fast C-start are studied numerically and theoretically by using a tail-flapping model. The problem is simplified to a 2-D foil that rotates rapidly to and fro on one side about its fixed leading edge in water medium. The study involves the simulation of the flow by solving the two-dimensional unsteady incompressible Navier-Stokes equations and employing a theoretical analytic modeling approach. Firstly, reasonable thrust magnitude and its time history are obtained and checked by fitting predicted results coming from these two approaches. Next, the flow fields and vortex structures are given, and the propulsive mechanism is interpreted. The results show that the induction of vortex distributions near the trailing edge of the tail are important in the time-averaged thrust generation, though the added inertial effect plays an important role in producing an instant large thrust especially in the first stage. Furthermore, dynamic and energetic effects of some kinematic controlling factors are discussed. For enhancing the time-averaged thrust but keeping a favorable ratio of it to time-averaged input power within the limitations of muscle ability, it is recommended to have a larger deflection amplitude in a limited time interval and with no time delay between the to-and-fro strokes. The project supported by the CAS (KJCX-SW-L04)     

Preliminary research on the relationship between long-range correlations and predictability

By establishing the Markov model for a long-range correlated time series (LRCS) and analysing its evolutionary characteristics, this paper defines a physical effective correlation length (ECL) τ, which reflects the predictability of the LRCS. It also finds that the ECL has a better power law relation with the long-range correlated exponent γ of the LRCS: τ= Kexp (-γ/0.3)+Y, (0 < γ < 1) -- the predictability of the LRCS decays exponentially with the increase of γ. It is then applied to a daily maximum temperature series (DMTS) recorded at 740 stations in China between the years 1960--2005 and calculates the ECL of the DMTS. The results show the remarkable regional distributive feature that the ECL is about 10--14 days in west, northwest and northern China, and about 5--10 days in east, southeast and southern China. Namely, the predictability of the DMTS is higher in central-west China than in east and southeast China. In addition, the ECL is reduced by 1--8 days in most areas of China after subtracting the seasonal oscillation signal of the DMTS from its original DMTS; however, it is only slightly altered when the decadal linear trend is removed from the original DMTS. Therefore, it is shown that seasonal oscillation is a significant component of daily maximum temperature evolution and may provide a basis for predicting daily maximum temperatures. Seasonal oscillation is also significant for guiding general weather predictions, as well as seasonal weather predictions.     

2,3-二苯基丙烯酸酯在DTBP/CaCl_2作用下的氧化偶联

多甲氧基菲-9-甲酸及酯是合成娃儿藤生物碱及其类似物的关键中间体。实验发现,以DTBP作为氧化剂,CaCl2存在下,能有效提高分子内氧化偶联合成多甲氧基菲-9-甲酸及酯产率,且反应条件温和,后处理方便,为合成许多重要化合物前体菲提供了一种新的思路。     

用微机实时处理γ射线测量数据的研究

本文介绍了将微机用于实时采集和处理γ射线的测量数据，并讨论了Ｎ个粒子时间间隔所对应的概率分布函数，用微机不仅可以计算出平均值，而且可以实时显示相应的概率分布图形。     

相律应用于电位—PH图的讨论

电位 pH 图亦称 Pourbaix 图,是一种表示水溶液体系的热力学平衡和电化学平衡图,既能说明水溶液中某元素在一定电位和 pH 时的稳定状态,又能说明元素不同价态离子的变化倾向。在湿法冶金,金属腐蚀,矿物地质,分析化学等学科领域均有广泛的应用。人们已经绘制了各种各样的元素-H_2O,金属-非金属-H_2O,金属Ⅰ-金属Ⅱ-非金属-H_2O 等体系的电位-pH 图。     

强降水持续过程对上海市内交通经济损失评估模型初探

通过探讨极端降水与城市道路交通受灾损失之间的关系确定灾损函数曲线,首先构建城市道路积水排尽模型、积水持续时间模型,以及道路积水的经济损失评估模型等理论模型,再引入与道路抗涝能力相关的社会经济因子,最终构建了一个极端降水对道路交通造成经济损失的估算模型.经检验,该模型具有较好的模拟性能和适用性,且所需输入变量少,计算简便,适合地区经济损失的快速评估.从该模型出发,确定了上海地区逐年极端降水降水强度和总过程降水量的阈值,从而提出一个新的极端降水定义方法——随影响因子变化的固定阈值法,该方法突出了极端降水给社会 关键词： 极端降水 极端降水-经济损失模型 阈值