Statistical validation of HZETRN as a function of vertical cutoff rigidity using ISS measurements

Measurements taken in Low Earth Orbit (LEO) onboard the International Space Station (ISS) and transit vehicles have been extensively used to validate radiation transport models. Primarily, such comparisons were done by integrating measured data over mission or trajectory segments so that individual comparisons to model results could be made. This approach has yielded considerable information but is limited in its ability to rigorously quantify and differentiate specific model errors or uncertainties. Further, as exploration moves beyond LEO and measured data become sparse, the uncertainty estimates derived from these validation cases will no longer be applicable. Recent improvements in the underlying numerical methods used in HZETRN have resulted in significant decreases in code run time. Therefore, the large number of comparisons required to express error as a function of a physical quantity, like cutoff rigidity, are now possible. Validation can be looked at in detail over any portion of a flight trajectory (e.g. minute by minute) such that a statistically significant number of comparisons can be made. This more rigorous approach to code validation will allow the errors caused by uncertainties in the geometry models, environmental models, and nuclear physics models to be differentiated and quantified. It will also give much better guidance for future model development. More importantly, it will allow a quantitative means of extrapolating uncertainties in LEO to free space. In this work, measured data taken onboard the ISS during solar maximum are compared to results obtained with the particle transport code HZETRN. Comparisons are made at a large number (∼77,000) of discrete time intervals, allowing error estimates to be given as a function of cutoff rigidity. It is shown that HZETRN systematically underestimates exposure quantities at high cutoff rigidity. The errors are likely associated with increased angular variation in the geomagnetic field near the equator, the lack of pion production in HZETRN, and errors in high energy nuclear physics models, and will be the focus of future work.     

尿素法制备氮化物陶瓷材料的研究进展

综述了近年来尿素法制备氮化物陶瓷粉体、涂层、纳米管和陶瓷基复合材料等的研究进展,并对其发展趋势作了展望.     

人工鱼群算法在浮标跟踪阶段的使用优化研究

在对人工鱼群算法进行研究的基础上,结合被动浮标对潜跟踪的实际应用,将人工鱼群算法应用于被动浮标对潜跟踪时的投放优化,对算法的应用、相关参数的选择及其对浮标跟踪效果的影响进行了仿真分析,为被动浮标对潜跟踪使用提供了参考.     

压气机试验器排气节气门控制系统设计

通过调节压气机转速和试验器的进、排气节气门的开度,可以获得所需的压气机气动试验特性。压气机试验器调节系统采用双冗余液压系统、成熟的可编程控制器和适合压气机性能试验特点的控制软件,很好地解决了试验状态控制精度低和试验风险高的问题。该系统的成功应用使试验器的工作效率显著提高,并减少了设备损耗和大量的能源消耗。     

民用飞机空气导管内外温度分布研究

对空气导管内外温度分布进行了研究,建立具体的换热模型并采用两种方法进行了计算,同时还分析了导管布置对空气传热和流动特性的影响。     

GPS scintillation and TEC gradients at equatorial latitudes in April 2006

We use observations of ionospheric scintillation at equatorial latitudes from two GPS receivers specially modified for recording, at a sampling rate of 50 Hz, the phase and the amplitude of the L1 signal and the Total Electron Content (TEC) from L1 and L2. The receivers, called GISTM (GPS Ionospheric Scintillation and TEC Monitor), are located in Vietnam (Hue, 16.4°N, 107.6°E; Hoc Mon, 10.9°N, 106.6°E). These experimental observations are analysed together with the tomographic reconstruction of the ionosphere produced by the Multi-Instrument Data Analysis System (MIDAS) for investigating the moderate geomagnetic storm which occurred on early April 2006, under low solar activity. The synergic adoption of the ionospheric imaging and of the GISTM measurements supports the identification of the scale-sizes of the ionospheric irregularities causing scintillations and helps the interpretation of the physical mechanisms generating or inhibiting the appearance of the equatorial F layer irregularities. In particular, our study attributes to the turning of the IMF (Interplanetary Magnetic Field) between northward and southward direction an important role in the inhibition of the generation of spread F irregularities resulting in a lack of scintillation enhancement in the post-sunset hours.     

星载天线指向机构的润滑

空间机械的润滑不同于地面设备,星载天线指向机构更有其本身的特点,应针对天线指向机构不同组件的工作特点选择最适合的润滑方式。文章对目前空间机械常用的几种润滑方式的机理和优缺点进行了综述,指出了天线指向机构润滑设计应考虑的问题和不同组件可采取的润滑措施。     

便携式红外寻的防空导弹初制导探索

对便携式红外寻的防空导弹的初制导进行了定性研究。根据期望前置角,讨论了导弹发射出筒后的侧向力控制方案,给出了发射时下沉的补偿措施。分析了俄制针式便携式红外寻的防空导弹初制导系统的控制律并进行了讨论。     

氧化铝的直接电镀

讨论了在氧化铝基板上的厚膜应用领域中采取直接电镀的方法。研究了建立在钯涂层、碳涂层和导电聚合物基础上的三种直接电镀的方法，测定和比较了它们与传统电镀／ 化学镀技术的操作步序、电镀速度和膜层结合力等技术指标。     

前放组件高低温测试系统设计

对前放组件高低温测试系统设计开发的背景及意义作了简单介绍,并阐述了系统的组成结构及测量原理;详细地论述了测试系统中标准设备的选取、专用设备和夹具的设计思路,最后对测试系统的接地和屏蔽进行了概括总结。