隐身目标电磁散射特性的图形电磁计算方法研究

计算了不同涂覆介质的反射系数,利用图形电磁计算方法计算了平板和圆柱的涂覆不同介质的雷达散射截面,并且为了增加图形电磁计算的通用性引入了归一化因子。结果表明,此计算方法是正确的。     

飞机机翼表面水滴撞击特性计算

根据飞机防冰系统的研制需要，以机翼为对象，对水滴撞击特性的数值计算进行研究，建立了计算模型，研究了计算方法，用相应的计算程序，在广泛的飞行，气象及多种翼型条件下，对水滴撞击特性作了计算，计算结果与国外权威机构公布的数据相比吻合性好，给出了部分计算结果，并对水滴撞击特性计算的应用作了简要分析。     

卫星在轨太阳辐射热流的简化计算方法

针对卫星在轨太阳辐射热流计算过程中计算参数多,计算过程复杂的问题,提出了一种简化的计算方法。该方法在分析卫星、地球和太阳三者之间空间几何关系的基础上,建立了新的计算坐标系,在计算坐标系中对卫星、地球和太阳的位置进行了重新规定,并在此坐标系中推导了卫星太阳辐射热流的计算公式。运用此方法对卫星太阳辐射热流进行分析求解时,轨道参数之间的空间角度关系更为简单,仅需对7个主要参数进行计算,与传统方法相比较计算量减少了约2/3。     

一种复杂表面的平行光辐射传递系数计算方法

提出了复杂表面之间平行光辐射传递系数的一种新型计算方法,克服了蒙特卡洛法在计算平行光辐射系数时存在运算量较大、计算精度难以保证等缺点,并且从计算精度及耗时性两方面对新方法进行了比较分析,计算结果表明新方法在计算精度及耗时性上都要优于蒙特卡洛法。     

远地点发动机推力矢量的极坐标算法

简述了远地点发动机推力矢量测试系统的原理;概述了往次试验数据处理所采用的推力矢量计算方法--“线性组合法”,着重分析其缺点;提出了计算准确度更高的极坐标计算方法,并给出了极坐标法计算举例。     

第二代低阶面元法及在动力短舱上的应用

在气动力设计和计算中,面元法是主要实用计算方法之一。新近发展的第二代低阶面元法实用性强和计算精度较高。本文介绍了该面元法的理论,通过对比早期面元法,着重探讨了第二代低阶面元法的特点及其优越性。运用自行研制的计算程序,对低速动力短舱进行了计算和分析研究,结果表明与国外资料所提供的计算结果吻合得较好。     

收敛无穷计算及其应用

经典计算不能很好地刻画无穷计算的行为.基于形式系统序列及其极限,讨论一类称为收敛无穷计算的问题,旨在建立刻画无穷计算在变化的环境中如何交互与演化以及演化的极限状态的逻辑理论基础.提出了收敛无穷计算的一个逻辑和推理系统,其表达能力超过一阶逻辑.还基于经典计算模型图灵(Turing)机和形式系统序列及其极限,提出了收敛无穷计算的模型,称为过程模式.在极限计算的意义下,其计算能力超过了Turing机和实数机器.讨论了上述研究在数据挖掘中的应用,用收敛无穷计算研究了数据挖掘的极限行为.     

一种敏捷卫星积分时间计算方法

敏捷卫星成像过程中姿态变化灵活,积分时间变化剧烈,传统卫星积分时间计算模型已无法满足精度要求。因此,提出一种改进的积分时间计算模型,在星地斜距计算和摄影点地速计算两方面作了改进。星地斜距计算时利用地表数字高程模型修正理论的斜距值,摄影点地速计算中增加姿态角速度对卫星本体坐标系角速度矢量的影响,并设计了整个算法在星上数管分系统中的实现方案。最后在星载嵌入式环境下进行了仿真计算,并与地面仿真计算结果进行了比对分析。两者比对偏差在0.01‰以内,可以满足相机成像质量要求。     

欧空局1992年各成员国承担的空间预算

欧空局委员会在1991年12月一次公开会议上通过了1992年空间预算,总额为23.6940亿计算单位。预算中一半是用于空间计划,为12.876亿计算单位(包括赫尔墨斯航天飞机预研费,阿里安-4和阿里安-5火箭的费用),余下的用于哥伦布及回收卫星平台(Eureca),为3.2亿计算单位,空间科学(2.664亿计算单位)、通信卫星(2.36亿计算单位)、地球观测(1.855亿计算单位)、微重力0.678亿计算单位、其它开支(0.20亿计算单位)。欧空局工作经费总预算增加了2.531亿计算单位。     

相控阵天线有源单元方向图的计算方法

基于弗洛奎定理给出了一种计算无限相控阵有源单元方向图的方法。与传统的基于有源反射系数的方法不同,这种方法不但可以用于计算功率方向图,而且可以计算场方向图,因此可以计算诸如交叉极化、相位信息等更多的辐射特性。通过数值计算结果与仿真结果的比较验证了方法的正确性。     

Updating of the IRI-1990 with respect to substorms

The method of updating the IRI-1990 model for the effects of large scale travelling ionospheric disturbances (LSTIDs) of the F-region have been established as a result of the statistical analysis of VI sounding data of European- Asian sector for 380 substorms. The effect of a LSTID occurring during a substorm is modelled as an additive correction to the quiet IRI foF2 and hmF2 values which depends on the time since the onset of the substorm and on the maximum AE-index value reached in it. In case of a sequence of substorms the additive corrections ΔfoF2 and ΔhmF2 are taking into account. The method for night-time ionosphere is described in detail, the listing of the FORTRAN-77 computer program is available on the floppy disk. The method is workable as correction to any ionospheric model.     

Detection of the ionospheric disturbances on GPS-TEC using Differential Rate Of TEC (DROT) algorithm

The solar, geomagnetic, gravitational and seismic activities can cause spatial and temporal (hourly, diurnal, seasonal and annual) variabilities of the ionosphere. Main observable ionospheric parameters such as Total Electron Content (TEC) can be used to quantify these. TEC is the total number of electrons on a ray path crossing the atmosphere. The network of world-wide Global Positioning System (GPS) receivers provide a cost-effective solution in estimating TEC over a significant proportion of global land mass. This study is focused on the analysis of the variations of ionosphere over a midlatitude region using GPS-TEC estimates for three Sun Spot Numbers (SSN) periods. The investigation is based on a fast and automatic variability detection algorithm, Differential Rate Of TEC (DROT). The algorithm is tested using literature data on disturbances generated by a geomagnetic activity, a Solar Flare, a Medium Scale Travelling Ionospheric Disturbance (MSTID), a Large Scale TID (LSTID) and an earthquake. Very good agreement with the results in the literature is found. DROT is applied to IONOLAB-TEC estimates from nine Turkish National Permanent GPS Network (TNPGN Active) stations over Turkey to detect the any wave-like oscillations, sudden disturbances and other irregularities during December, March, June, September months for 2010, 2011, 2012 years. It is observed that DROT algorithm is capable of detecting both small and large scale variability due to climatic, gravitational, geomagnetic and solar activities in all layers of ionosphere. The highest DROT values are observed in 2010 during winter months. In higher solar activity years of 2011 and 2012, DROT is able to indicate both seasonal variability and severe changes in ionosphere due to increased number of geomagnetic storms and local seismic activities.     

一种新的四路激光跟踪坐标测量系统的基点标定方法

在激光跟踪三维坐标测量系统中,系统首先要经过标定,才可以进行实际测量。因此系统标定的准确度会直接影响系统最终测量准确度。为了提高标定准确度,提出一种新的标定方法,即利用直线法原理,在优化布局下,采用两路激光干涉仪测量出基点的三维坐标。仿真结果表明目标点相对于基点呈对称分布时,测得的基点坐标准确度比非对称分布时高6到7倍,并通过实验得出了在该优化布局下的基点坐标。     

Signal transduction in T lymphocytes--a comparison of the data from space, the free fall machine and the random positioning machine.

In this paper we discuss the effect of microgravity on T cells and we present the data of studies with two new machines for 0 g simulations. Several experiments in space show that mitogenic T cell activation is lost at 0 g. Immunocytochemistry indicates that such effect is associated with changes of the cytoskeleton. Biochemical studies suggest that the lack of expression of the interleukin-2 receptor is one of the major causes of the loss of activity. In fact, interleukin-2 is the third signal required for full activation. In order to deepen our investigations we are now working with the free-fall machine, FFM, invented by D. Mesland, and with the random positioning machine, RPM, or three-dimensional clinostat, developed by T. Hoson. The FFM produces periods of free-fall lasting approximately 800 ms followed by bounces of 15-30 g lasting 45-60 ms. The RPM eliminates the effect of gravity by rotating biological specimen randomly around two orthogonal axes. While the FFM failed to reproduce the results obtained with T lymphocytes in space, the data from the RPM are in good agreement with those in real microgravity. In fact, the inhibition of the mitotic index in the RPM is 89% compared to static controls. The RPM (as the FFM) can carry markedly larger specimen than the fast rotating clinostat and thus allows to conduct comprehensive studies to select suitable biological objects for further investigations in space.     

辐射变色薄膜剂量计性能测试及加速器应用

本课题的目的是建立用于辐射加工高剂量水平吸收剂量测量的辐射变色薄膜剂量计。通过系统研究,批量制备了以尼龙为基材,副品红氰化物为染料的辐射变色薄膜剂量计。为了验证批制辐射变色薄膜剂量测量的可靠性,选择了国际上应用较广的FWT-60膜及丙氨酸薄膜剂量计与本实验室批制的辐射变色薄膜开展实验室内剂量比对,比对结果均在±4%内符合,归一化偏差En绝对值均小于1。通过在加速器上进一步应用实验表明批制辐射变色薄膜可用于电子束辐照参数测量。     

高值电容标准首次比对实验结果分析

1μF以上电容量值的溯源难度较大,为保证国防系统内高值电容（10μF~10mF）参数的量值统一、准确可靠。北京东方计量测试研究所组织国防系统内四家计量单位首次开展了（10μF~10mF）/100Hz高值电容标准的比对实验,取得了宝贵的实验数据。本文公布了比对结果,并对实验数据进行进一步分析。本次比对以各参加实验室测量结果的加权算术平均值作为参考值,其中权重与各实验室声称的不确定度平方的倒数成比例。实验数据由4家单位共享。     

深空探测下行测距调制度变化的现象和机理分析

文章对统一S波段应答机下行测距调制度随上行信噪比以及工作模式的不同而不同的现象进行了分析,推导出计算公式,并和实测数据进行了比对。实测数据与文中的理论分析的结果是一致的。另外,文章也说明了测距下行调制度变化的具体计算公式将随不同应答机模型不同而不同。在设计计算时,应当对具体的应答机转发模型进行分析,而不能简单引用CCSDS标准所给出的公式。     

The situation in the geostationary ring

For more than 25 years, the practice of reorbiting of a geostationary satellite at the end of its mission in order to protect the geostationary orbit (GEO) environment has been recommended and performed by a number of operators. In recent years, an internationally recognised re-orbiting altitude has been defined by the Inter-Agency Space Debris Coordination Committee (IADC). Based on orbital data contained in the DISCOS database, the situation on the geostationary ring is analysed. In January 2004, from 1036 catalogued objects passing through the geostationary region, 340 are controlled within their allocated longitude slots, 395 are drifting above, below or through GEO, and 140 are in a libration orbit. In the periods 1997–2003, 103 spacecraft reached their end of life; 34 were reorbited in compliance with the IADC recommendation, 35 were reorbited below the minimum recommended altitude, and 34 were abandoned without any end-of-life disposal manoeuvre. Apart from these catalogued objects, the ESA 1-m telescope has observed many smaller debris (down to 10–15 cm) in this orbital region representing a collision risk for GEO spacecraft which is difficult to quantify.     

Do we understand the inner magnetotail dynamics during substorms?

Substorm evolution of the near-Earth (|X|<15 R_E) plasma sheet has been emphasized recently because the inner tail is thought to link closely to the substorm auroral activity in the ionosphere during the early stage of substorms. In this paper, we discuss how the inner tail substorm phenomena during the late substorm growth phase and early expansion phase are accounted for by the two prevailing substorm models, namely, the near-Earth neutral line model and the current disruption model. We find that the late growth phase features are more satisfactorily accounted for by the current disruption model than by the near-Earth neutral line model. In addition, detailed observations on current disruption show evidence inconsistent with the proposed idea of dipolarization being due to plasma flow braking from reconnection in the mid-tail region, which poses a difficulty to the near-Earth neutral line model as well.     

Fading in the HF ionospheric channel and the role of irregularities

It is well known that the ionosphere affects radio wave propagation especially in the high frequency (HF) range. HF radio waves reflected by the ionosphere can reach considerable distances, often with changes in amplitude, phase, and frequency. The ionosphere is a dispersive in frequency and time, bi-refractive, absorbing medium, in which multipath propagation due to traveling irregularities is very frequent. The traveling irregularities undulate the reflecting ionospheric layer, introducing variations in signal amplitude (fading). In this multipath time variant channel fading is mainly considered, even though it is not the sole effect. Echo signals from a single reflection, as in ionospheric vertical sounding (VIS) techniques, are affected by a certain degree of variability even in quiet ionospheric conditions. In this work the behavior of the ionospheric channel is studied and characterized by observing the power variation of received echoes using the VIS technique. Multipath fading was analyzed quantifying the power variation of the signal echo due to irregularities on a temporal scale from 0.5 to 256 s. An experimental set-up derived from an ionosonde was implemented and the analysis was performed employing a special numerical algorithm operating off-line on the acquired time sequence of the signal. The gain-loss of the irregularity shapes are determined in some special cases.