The impact of semi-convection and overshooting on the surface abundances in massive stars

We analyse the effects of semi-convection and overshooting on the predicted surface abundances after the first and second dredge-ups in 15 and 20 M Pop. I stars. Overshooting is applied either to the core boundary or to the boundaries of all convective zones. It is shown that the surface abundances are sensitive to the mixing scheme adopted in the interior. The models including semi-convection lead to lower¹²C/¹³C ratios than the other mixing schemes, while models with overshooting predict higher enhancements of sodium at the surface.     

Co2 and Climate: a Geologist's View

Climate is discussed as an integral part of System Earth, determined by a complex interplay of numerous geological, biological and solar processes. The historical and geological record of changing climate and atmospheric CO₂ pressure does not support the current popular vision that this greenhouse gas is the dominant climate controlling agent. When empirically ante post tested against past global climate changes, the forecasts of the climate models mainly based on forcing by atmospheric CO₂ are not borne out. On the other hand, recent studies show that solar variability rather than changing CO₂ pressure is an important, probably the dominant climate forcing factor.     

Simulation of a working process in the pulsejet engine with an aerodynamic valve on the basis of the thermodynamic cycle analysis

A physical and a mathematical model of a working process in the pulsejet engine based on the analysis of the thermodynamic cycle are proposed. The process of self-sustained periodic combustion is connected with special features of elementary processes comprising the cycle, influencing the engine operation and depending on its design parameters. The calculation method is based on the use of fundamental laws of conservation and basic equations of gas dynamics     

低密度小喷管流场的DSMC直接模拟

用ＤＳＭＣ方法数值模拟了低密度轴对小喷管的流场流动，获得了相应的结果，并将所得结果与用差分求解Ｎ－Ｓ方程方法获得的结果进行了对比，二者吻合较好。     

可溶性改性双马来酰亚胺树脂基体的研究

在双马来酰亚胺/二元胺/改性剂A预聚体系中加入环氧丙烯酸树脂,制备了一种可用作耐热复合材料基体的改性双马来酰亚胺树脂。用DSC研究了该树脂基体的反应特性,并制定出了合适的固化工艺参数:改性树脂基体经140℃/1 h 160℃/1 h 180℃/2 h初固化,于220℃/8 h后固化处理,其热变形温度(HDT)为245℃;该树脂与玻璃纤维制备的单向复合材料层压板的室温拉伸强度、弯曲强度和层间剪切强度分别为1 030 MPa、1 600 MPa和92．1 MPa;180℃下测得弯曲强度保持率为67．8%,层间剪切强度保持率为63．2%,用DMA法测得T_g为273℃。     

空空导弹发动机采用少烟复合固体推进剂评述

本文在总结我国空空导弹发动机研制的基础上,分析空空导弹发动机尾喷流对载机的影响.同时,从导弹发动机设计的角度出发,根据国内实际水平,提出采用少烟复合固体推进剂作为今后减少尾喷流对载机影响的主要技术途径.     

关于潜入式SRM冷流模拟试验中相似与模拟问题的探讨

评述了目前ＳＲＭ冷流模拟试验技术的发展，并从相似与模化的基本理论出发，探讨了ＳＲＭ喷管潜入段稳态不可压有加质的湍流流场相似准则，并根据该实验的具体特点，提出了以ＣＴ作为选定量来求解其它相似常数的设想。分析表明，用以高压气源作为冷流模拟气源一般只能近似模拟ＳＲＭ喷管潜入段内流场的流动工况，近似模化必须尽量满足Ｒｅ准则。     

强制偏流喷管的数值仿真

采用薄层Ｎ－Ｓ方程成功地求解了强制流喷管内的三维复杂流场，对通量项和压力项用Ｖａｎ Ｌｅｅｒ发展的矢通量分裂法进行了离散，对离散方程采用线超松弛方法迭代求解，在亚音速与超音速气流共同存在的出口边界分情况进行了处理。计算结果验证了强制偏喷管具有自动补偿外界压力变化的能力，与实验结果基本吻合。     

Satellite fault diagnosis using a bank of interacting Kalman filters

The main objective of this work is development and testing of a detection, isolation, and diagnosis algorithm based on interacting multiple model (IMM) filters for both partial (soft) and total (hard) reaction wheels faults in a spacecraft. This is shown to be accomplished under a number of different faulty mode scenarios for these actuators associated with the attitude control system (ACS) of a satellite. Various operating and faulty conditions due to changes and anomalies in the temperature, the power supply line voltage, and the loss of effectiveness of the torque and the current are considered in each reaction wheel associated with the three axes of the satellite. Once a fault mode is detected and isolated the recovery procedure can subsequently be engaged by invoking appropriate switching control strategies for the ACS. The application of a bank of interacting multiple Kalman filters for detection and diagnosis of anticipated reaction wheel failures in the ACS is described and developed. Compared with other model-based fault detection, diagnosis and isolation(FDDI) strategies developed in the control systems literature, our FDDI strategy is shown, through extensive numerical simulations, to be more accurate and robust with potential for extension to a number of other application areas.     

固体火箭发动机寿命预估的一种考虑

利用弹性－粘弹性对应原理，分析长期贮存固体推进剂药柱由环境温度变化引起的热应力，计算药柱损伤，并对发动机寿命进行预估。理论分析和算法具有普遍性，可供工程设计参考。