2001 Mars Odyssey Mission Summary

The 2001 Mars Odyssey spacecraft, now in orbit at Mars, will observe the Martian surface at infrared and visible wavelengths to determine surface mineralogy and morphology, acquire global gamma ray and neutron observations for a full Martian year, and study the Mars radiation environment from orbit. The science objectives of this mission are to: (1) globally map the elemental composition of the surface, (2) determine the abundance of hydrogen in the shallow subsurface, (3) acquire high spatial and spectral resolution images of the surface mineralogy, (4) provide information on the morphology of the surface, and (5) characterize the Martian near-space radiation environment as related to radiation-induced risk to human explorers. To accomplish these objectives, the 2001 Mars Odyssey science payload includes a Gamma Ray Spectrometer (GRS), a multi-spectral Thermal Emission Imaging System (THEMIS), and a radiation detector, the Martian Radiation Environment Experiment (MARIE). THEMIS and MARIE are mounted on the spacecraft with THEMIS pointed at nadir. GRS is a suite of three instruments: a Gamma Subsystem (GSS), a Neutron Spectrometer (NS) and a High-Energy Neutron Detector (HEND). The HEND and NS instruments are mounted on the spacecraft body while the GSS is on a 6-m boom. Some science data were collected during the cruise and aerobraking phases of the mission before the prime mission started. THEMIS acquired infrared and visible images of the Earth-Moon system and of the southern hemisphere of Mars. MARIE monitored the radiation environment during cruise. The GRS collected calibration data during cruise and aerobraking. Early GRS observations in Mars orbit indicated a hydrogen-rich layer in the upper meter of the subsurface in the Southern Hemisphere. Also, atmospheric densities, scale heights, temperatures, and pressures were observed by spacecraft accelerometers during aerobraking as the spacecraft skimmed the upper portions of the Martian atmosphere. This provided the first in-situ evidence of winter polar warming in the Mars upper atmosphere. The prime mission for 2001 Mars Odyssey began in February 2002 and will continue until August 2004. During this prime mission, the 2001 Mars Odyssey spacecraft will also provide radio relays for the National Aeronautics and Space Administration (NASA) and European landers in early 2004. Science data from 2001 Mars Odyssey instruments will be provided to the science community via NASA’s Planetary Data System (PDS). The first PDS release of Odyssey data was in October 2002; subsequent releases occur every 3 months.     

37kW底盘测功机计算机控制系统

底盘测功机是检验汽车、摩托车输出功率及其相关参数的一种检测设备。本课题利用现代先进的计算机控制技术实现对37kW-CHDY底盘测功机的行驶阻力控制、测试数据自动采集,从而实现摩托车道路工况模拟运转以及整车动力性、燃料经济性等指标的测量。     

混合气体流动的一种数值模拟方法

本文建立一个数值模拟完全气体混合流动的理论模型.该模型首先应用混合气体的Euler方程和每种气体组分的质量分数方程来控制流动.为了消除混合网格内气体组分界面附近出现的非物理振荡,我们假定混合气体的每种组分达到了动力学平衡状态然而尚未达到热力学平衡状态.这种思想导致需要另外给定每种气体组分的总能量方程.为使用高分辨格式来求解这组双曲型偏微分方程并且简化对所需要的Jacobi矩阵的推导,混合气体的压力方程也被耦合起来.Godunov型的波传播方法被采用来离散求解所获得的控制方程.从典型算例结果来看,一维问题的数值解与精确解一致,二维问题的数值解与理论分析一致.这说明本文的理论模型是合理的.     

结构参数对圆转矩形喷管换热的影响

为了解结构参数对圆转矩形内喷管再生冷却换热的影响，设计了多个圆转矩形喷管，考虑了三种结构参数：转方位置、出口高宽比和出口圆角大小的影响。采用有限体积法求解三维可压缩的N-S方程对其内部流动和换热进行了数值模拟。湍流模型采用标准的k-ε双方程模型，壁面附近的流动和传热采用壁面函数法处理，速度与压力的耦合采用SIMPLE算法求解。结果表明：在型面一阶导数连续的情况下，转方位置对圆转矩形内喷管的换热影响不大；出口高宽比对圆转矩形内喷管的换热影响较大，出口高宽比不能太小，否则影响内喷管流场和换热；出口圆角大小影响内喷管周向上的温度分布，圆角太小造成周向温度分布不均匀。     

Dynamics of Coronal Loop Oscillations Recent Improvements and Computational Aspects

We will discuss the observed, heavily damped transversal oscillations of coronal loops. These oscillations are often modeled as transversal kink oscillations in a cylinder. Several features are added to the classical cylindrical model. In our models we include loop curvature, longitudinal density stratification, and highly inhomogeneous radial density profiles. In this paper, we will first give an overview of recently obtained results, both analytically and numerically. After that, we shed a light on the computational aspects of the modeling process. In particular, we will focus on the parallellization of the numerical codes.     

复合材料在DCB试验中的裂纹尺寸效应

在许多关于复合材料Ⅰ型层间断裂韧性试验研究工作中，不同的作者所选取的有效裂纹长度有很大的差异，由此带来试验结果分散程度很大，试验结果无法相互比较等问题。本文对复合材料在Ⅰ型层间断裂ＤＣＢ试验中裂纹的预裂长度、裂纹尖端形状以及裂纹测量误差等问题进行了研究。     

多级涡轮S2流面的变比热气动热力计算方法

针对在多级涡轮流道中沿流动方向燃气温度变化较大这一特点，为了准确反映出温度变化对气动热力计算结果的影响，提出了一种考虑变比热影响的Ｓ２流面的气动热力计算方法。该方法摒弃了传统的定比热气动热力计算公式和由温度、密度确定压力的求解顺序，而是根据导出的变比热计算压力的关系式求解压力，然后用温度和压力计算密度。计算结果显示出本文的算法较传统的未能充分考虑变比热影响的气动热力计算方法可以改善多级涡轮联算时的计算准确度。     

EXPERIMENTAL INVESTIGATION ABOUT THE UNSTEADY AERODYNAMIC CHARACTERISTICS OF WINGS

ＥＸＰＥＲＩＭＥＮＴＡＬＩＮＶＥＳＴＩＧＡＴＩＯＮＡＢＯＵＴＴＨＥＵＮＳＴＥＡＤＹＡＥＲＯＤＹＮＡＭＩＣＣＨＡＲＡＣＴＥＲＩＳＴＩＣＳＯＦＷＩＮＧＳＹｕＸｉｎｚｈｉ；ＹａｎｇＹｏｎｇｎｉａｎ；ＷｕＺｅ（Ａｉｒｃｒａ．ｆｔＥｎｇｉｎｅｅｒｉｎｇＤｅｐａ...     

涡轮叶栅叶型损失的数值模拟方法

给出了一个计算亚、跨音涡轮叶栅叶型损失的数值计算方法。主流采用时间推进有限体积法求解积分型欧拉方程,并采用了局部网格修正技术;附面层采用全隐格式求解有限差分方程;在叶栅出口与远后方均匀流之间进行了叶片尾迹与主流的掺混损失计算。算例表明本文的数值方法可准确地预测涡轮叶栅的叶型损失。     

Effects of polarization and resolution on SAR ATR

Lincoln Laboratory is investigating the detection and classification of stationary ground targets using high resolution, fully polarimetric, synthetic aperture radar (SAR) imagery. A study is summarized in which data collected by the Lincoln Laboratory 33 GHz SAR were used to perform a comprehensive comparison of automatic target recognition (ATR) performance for several polarization/resolution combinations. The Lincoln Laboratory baseline ATR algorithm suite was used, and was optimized for each polarization/resolution case. Both the HH polarization alone and the optimal combination of HH, HV, and VV were evaluated; the resolutions evaluated were 1 ft/spl times/1 ft and 1 m/spl times/1 m. The data set used for this study contained approximately 74 km/sup 2/ of clutter (56 km/sup 2/ of mixed clutter plus 18 km/sup 2/ of highly cultural clutter) and 136 tactical target images (divided equally between tanks and howitzers).