冰风洞试验中水滴的传热传质计算研究

进行冰风洞试验时,出口过冷水滴的参数往往使用风洞来流空气参数进行计算,忽略了真实情况下水滴与空气的传热传质过程,致使试验数据产生偏差,并影响测试结果的可靠性.通过对冰风洞试验中水滴的运动过程进行研究,考察了水滴与空气主流间的传热与传质现象,建立了水滴运动过程中参数变化的控制方程.基于该方程编制了冰风洞水滴粒径温度变化分析软件,计算分析了过冷水滴在行进过程中相关参数的变化曲线,比较了不同初始条件及各参数对水滴温度、直径和速度的影响.结果表明:不同环境下水滴在运动过程中温度、尺寸和速度变化受来流温度、速度、相对湿度和水滴初始温度的影响,呈现出不同的特点,不能忽略水滴状态参数在冰风洞内的变化.     

飞机乘客重量最优布置的一种建模方法

飞机重心对飞行安全至关重要,也影响着飞机的性能。本文给出了乘客重量的定义,分析了飞机纵向重心对飞行性能的影响。通过分析确定了以乘客重量为自变量的约束条件和以实现所有乘客的纵向重心坐标靠近重心后极限为目的的目标函数,建立了考察不同重量的乘客在飞机中的座位最优布置的优化模型,并从理论上说明了优化模型具有最优解。算例结果表明,建立的最优化模型存在最优解,用此模型求解目标函数可行。此模型同样适用于行李箱布置与货物装载。     

Interplanetary Physics Research in China During 2004 - 2005

This brief report summarized the latest advances of the interplanetary physics research in China during the period of 2004-2005, made independently by Chinese space physicists and through international collaboration. The report covers all aspects of the interplanetary physics, including theoretical studies, numerical simulation and data analysis.     

Satellite Measurements of Middle Atmospheric Impacts by Solar Proton Events in Solar Cycle 23

Solar cycle 23 was extremely active with seven of the largest twelve solar proton events (SPEs) in the past forty years recorded. These events caused significant polar middle atmospheric changes that were observed by a number of satellites. The highly energetic protons produced ionizations, excitations, dissociations, and dissociative ionizations of the background constituents in the polar cap regions (>60 degrees geomagnetic latitude), which led to the production of HO_x (H, OH, HO₂) and NO_y (N, NO, NO₂, NO₃, N₂O₅, HNO₃, HO₂NO₂, BrONO₂, ClONO₂). The HO_x increases led to short-lived ozone decreases in the polar mesosphere and upper stratosphere due to the short lifetimes of the HO_x constituents. Polar middle mesospheric ozone decreases greater than 50 % were observed and computed to last for hours to days due to the enhanced HO_x. The NO_y increases led to long-lived polar stratospheric ozone changes because of the long lifetime of the NO_y family in this region. Upper stratospheric ozone decreases of >10 % were computed to last for several months past the solar events in the winter polar regions because of the enhanced NO_y.     

Acceleration of Solar-Energetic Particles by Shocks

Our current understanding of the acceleration of solar-energetic particles is reviewed. The emphasis in this paper is on analytic theory and numerical modeling of the physics of diffusive shock acceleration. This mechanism naturally produces an energy spectrum that is a power law over a given energy interval that is below a characteristic energy where the spectrum has a break, or a rollover. This power law is a common feature in the observations of all types of solar-energetic particles, and not necessarily just those associated with shock waves (e.g. events associated with impulsive solar flares which are often described in terms of resonant stochastic acceleration). Moreover, the spectral index is observed to have remarkably little variability from one event to the next (about 50%). Any successful acceleration mechanism must be able to produce this feature naturally and have a resulting power-law index that does not depend on physical parameters that are expected to vary considerably. Currently, only diffusive shock acceleration does this.     

Dust Environment Modelling of Comet 67P/Churyumov-Gerasimenko

Dust is an important constituent of cometary emission; its analysis is one of the major objectives of ESA’s Rosetta mission to comet 67P/Churyumov-Gerasimenko (C–G). Several instruments aboard Rosetta are dedicated to studying various aspects of dust in the cometary coma, all of which require a certain level of exposure to dust to achieve their goals. At the same time, impacts of dust particles can constitute a hazard to the spacecraft. To conciliate the demands of dust collection instruments and spacecraft safety, it is desirable to assess the dust environment in the coma even before the arrival of Rosetta. We describe the present status of modelling the dust coma of 67P/C–G and predict the speed and flux of dust in the coma, the dust fluence on a spacecraft along sample trajectories, and the radiation environment in the coma. The model will need to be refined when more details of the coma are revealed by observations. An overview of astronomical observations of 67P/C–G is given, because model parameters are derived from this data if possible. For quantities not yet measured for 67P/C–G, we use values obtained for other comets, e.g. concerning the optical and compositional properties of the dust grains. One of the most important and most controversial parameters is the dust mass distribution. We summarise the mass distribution functions derived from the in-situ measurements at comet 1P/Halley in 1986. For 67P/C–G, constraining the mass distribution is currently only possible by the analysis of astronomical images. We find that both the dust mass distribution and the time dependence of the dust production rate of 67P/C–G are those of a fairly typical comet.     

Ptolemy – an Instrument to Measure Stable Isotopic Ratios of Key Volatiles on a Cometary Nucleus

A fundamental goal of cometary studies is to determine the exact relationship between these bodies and the Solar System – the question(s) can be summarised as follows: did comets originate during the same events that spawned the Sun and planets, are they more primitive bodies that record a pre-solar history, or are they interstellar materials collected in relatively more recent times? Now, whatever the origin of comets, it is entirely possible that they could, in part, contain interstellar or pre-solar components – indeed, it seems rather likely in light of the fact that primitive meteorites contain such entities. These particular components are likely to be refractory (dust, macromolecular organic complexes, etc.). Of more relevance to the issues above are the volatile constituents, which make up the bulk of a comet's mass. Since these materials, by their very nature, volatilise during perihelion passage of a comet they can, in some instances, be detected and measured spectroscopically. Perhaps the most useful species for isotopic investigations are C₂, HCN and CN. Unfortunately, spectroscopic measurements can only currently be made with accuracies of ±10 to ±20%. As such it is very often not practical to conclude anything further than the fact that isotopic measurements are compatible with ‘`solar’' values, which tends to imply an origin from the margins of the solar accretion disk. But there is another problem with the spectroscopic measurements – since these are made on gaseous species in the coma (and relatively minor species at that) it is impossible to be certain that these represent the true nuclear values. In other words, if the processes of sublimation, active jetting, and photochemistry in the coma impart isotopic fractionation, the spectroscopic measurements could give a false impression of the true isotope ratios. What is required is an experiment capable of measuring isotopic ratios at the very surface of a comet. Herein we describe the Ptolemy instrument, which is included on the Philae lander as part of the Rosetta mission to 67P/Churyumov-Gerasimenko. The major objective of Ptolemy is a detailed appraisal of the nature and isotopic compositions of all materials present at the surface of a comet.     

一种城市公交车调度的优化方案模型

本文通过对公交线路的客流调查和运营资料数据的修正和深入分析，概括出公交调度中广泛在的3个规律，据此建立多目标优化的数学模型。并得出操作性很强的公并车调度方案。     

灰色预测在MCMQC中的应用

分析了大规模定制生产中的质量控制中灰色预测算法的简单快速的优点和精度不高的缺点,及造成这一现象的本质原因,并提出了改进大规模定制生产灰色质量控制的思路。