Comparison of the mean quality factors for astronauts calculated using the Q-functions proposed by ICRP,ICRU, and NASA

For the estimation of the radiation risk for astronauts, not only the organ absorbed doses but also their mean quality factors must be evaluated. Three functions have been proposed by different organizations for expressing the radiation quality, including the Q(L), Q(y), and Q_NASA(Z, E) relationships as defined in International Committee of Radiological Protection (ICRP) Publication 60, International Commission on Radiation Units and Measurements (ICRU) Report 40, and National Aeronautics and Space Administration (NASA) TP-2011-216155, respectively. The Q(L) relationship is the most simple and widely used for space dosimetry, but the use of the latter two functions enables consideration of the difference in the track structure of various charged particles during the risk estimation.     

Comptonization efficiencies of the variability classes of GRS 1915 + 105

The Galactic microquasar GRS 1915 + 105 exhibits at least seventeen types of variability classes. Intra and inter class transitions are reported to be observed within seconds to hours. Since the observation was not continuous, these classes appeared to be exhibited in a random order. Our goal is to predict a sequence of these classes. In this paper, we compute the ratio of the photon counts obtained from the power-law component and the blackbody component of each class and call this ratio as the ‘Comptonizing efficiency’ (CE) of that class. We sequence the classes in the ascending order of CE and find that this sequence matches with a few class transitions observed by RXTE satellite and IXAE instruments on board IRS-P3. A change in CE corresponds to a change in the optical depth of the Compton cloud. Our result implies that the optical depth of the Compton cloud gradually rises as the variability class becomes harder.     

An improved neutron transport algorithm for HZETRN

Long-term human presence in space requires the inclusion of radiation constraints in mission planning and the design of shielding materials, structures and vehicles. It is necessary to expose the numerical tools commonly used in radiation analyses to extensive verification, validation and uncertainty quantification. In this paper, the numerical error associated with energy discretization in HZETRN is addressed. An inadequate numerical integration scheme in the transport algorithm is shown to produce large errors in the low energy portion of the neutron and light ion fluence spectra. It is further shown that the errors result from the narrow energy domain of the neutron elastic cross section spectral distributions and that an extremely fine energy grid is required to resolve the problem under the current formulation. Since adding a sufficient number of energy points will render the code computationally inefficient, we revisit the light ion and neutron transport theory developed for HZETRN and focus on neutron elastic interactions. Two numerical methods (average value and collocation) are developed to provide adequate resolution in the energy domain and more accurately resolve the neutron elastic interactions. An energy grid convergence study is conducted to demonstrate the improved stability of the new methods. Based on the results of the convergence study and the ease of implementation, the average value method with a 100 point energy grid is found to be suitable for future use in HZETRN.     

金属长旋转椭球附近偶极子辐射

本文采用严格的麦克斯韦方程组的直接求解法,分析了金属长旋转椭球附近任意位置电偶极子的辐射特性,并得到辐射场量表达式。最后举例对长旋转椭球侧部的偶极子方向图进行了数值计算并由实验证实其结果。     

Radiation efects on MHD stagnation point flow of nano fluid towards a stretching surface with convective boundary condition

The aim of the present paper is to study the numerical solutions of the steady MHD two dimensional stagnation point flow of an incompressible nano fluid towards a stretching cylinder.The effects of radiation and convective boundary condition are also taken into account.The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis.The resulting nonlinear momentum,energy and nano particle equations are simplifed using similarity transformations.Numerical solutions have been obtained for the velocity,temperature and nanoparticle fraction profles.The influence of physical parameters on the velocity,temperature,nanoparticle fraction,rates of heat transfer and nanoparticle fraction are shown graphically.     

空间光学遥感器天然辐射效应数据库研究

空间环境是诱发卫星异常和故障的主要原因之一。光学遥感器作为卫星最重要的有效载荷之一，在空间会受到空间辐射环境的影响。因此在研制光学遥感器的同时，需要同时考虑空间辐射环境因素，文章就空间光学遥感器天然辐射效应数据库的设计和应用进行了介绍。     

质子和电子对光学反射镜辐射效应的研究

研究了能量为E=160keV质子和电子单独及综合辐照作用对两种空间反射镜光学表面的影响。观察到在辐照剂量达到Φ=10×105/cm2后反射镜表面形咸了明显的结构缺陷,并导致某些谱段反射率的降低和成像质量的下降。辐照诱发缺陷的类型及分布特征除与粒子种类和反射镜结构有关外,还依赖于试样的接地方式。质子幅照主要引起反射镜表面膜层的起泡现象;电子辐照则使SiO2保护膜着色;综合辐照的影响复杂,尤其是在接近于空间使用条件的第二种接地方式下,起泡现象和静电效应成为镜面损伤的主要机制。     

The mitigation, management, and survivability of asteroid/comet impact with Earth

The chances that Earth will collide with a significant near earth object (NEO) within the next century are very small, but such a collision is possible, would be catastrophic, and could happen at any time. Much discussion has been devoted to methods of diverting these objects away from Earth through the use of space technology. However, if these efforts are unsuccessful, we would need to implement effective strategies to survive the event, no matter how cataclysmic. To date, disaster management for various impact scenarios has not been addressed (except in novels and Hollywood films). An impact disaster may be many orders of magnitude greater than any disaster the human species has ever experienced. Initially, technology and experience gained in other large-scale disasters will most likely form the foundation of how these impact events will be managed and classified. Given the size and energy of the projectile, the estimated area of damage, and whether impact effects might be localized or global in nature, we can begin to build basic disaster response scenarios, anticipate public health concerns, and formulate questions in need of answers. Questions we must deal with include: what will be required technologically, sociologically, and medically to survive? What types of evacuation plans and warning systems might be required? Capabilities in need of further investigation include: technological protection strategies related to ‘impact winter’, expanded chemical hazard control methodologies, food storage and production, roles of national governments, and international cooperation. Whatever the magnitude and severity of the event, we must reflect on what we know, what capabilities we can apply, develop or adapt, and seriously investigate what might be done to manage it and survive.     

非对称构型多站时差定位系统定位精度分析

以空间四站时差定位系统为例对多站时差定位系统原理进行阐述,推导定位系统的定位精度并分析影响系统定位精度的因素。通过仿真分析多站时差定位系统在不同空间构型、站间距、时差测量误差、位置误差条件下对地面辐射源的定位精度得出:多站时差定位系统的空间构型直接影响定位精度,主辅站间距长度越长定位精度越好;各站位置误差比时差测量误差对定位精度的影响更大;对于多站定位系统出现的非对称空间构型,通过合理的布站优化可以提升对某一固定辐射源的定位精度。     

卫星编队飞行的地球扁率摄动分析

本文研究了地球扁率J2项摄动对卫星编队飞行的影响。首先，给出了编队飞行数学描述，推导了轨道根数和相对运动状态的关系式；然后，将卫星编队的受摄影响分解为整体摄动和相对摄动，分别得到了解析解，重点分析了相对摄动规律。研究结果对卫星编队的设计有一定的参考价值。