钛合金表面抗激光涂层损伤特性及热效应影响研究

实验研究了钛合金和高反射型陶瓷涂层材料抗连续型激光烧蚀的损伤及温度分布特性，并从热效应影响角度对比分析了二者在抗激光损伤效果方面的差异性。研究结果表明：相比于钛合金，高反射型陶瓷涂层材料能有效增强钛合金基底抗激光损伤的能力；在同等激光功率密度辐照下，陶瓷涂层材料能有效提升钛合金基底耐受激光辐照的时间长度。实验结果表明该陶瓷涂层材料的激光损伤阈值比钛合金高约5.8倍。实验发现陶瓷涂层温升速率高于钛合金，但由于陶瓷材料具有较高的反射特性，以及良好的热吸收和热传导特性，因此能使由激光辐照产生的热量在其表面较快地扩散，而降低向基底方向传导的程度，最终提升陶瓷涂层的抗激光损伤阈值。     

Estimating the spin axis orientation of the Echostar-2 box-wing geosynchronous satellite

For the first time, the spin axis orientation of an inactive box-wing geosynchronous satellite has been estimated from ground-based optical photometric observations of Echostar-2’s specular reflections. Recent photometric light curves obtained of Echostar-2 over four years suggest that unusually bright and brief specular reflections were occurring twice within an observed spin period. These bright and brief specular reflections suggested two satellite surfaces with surface normals separated by approximately 180°. The geometry between the satellite, the Sun, and the observing location at the time of each of the brightest observed reflections, was used to estimate Echostar-2’s equatorial spin axis orientation coordinates. When considering prograde and retrograde rotation, Echostar-2’s spin axis orientation was estimated to have been located within 30° of either equatorial coordinate pole. Echostar-2’s spin axis was observed to have moved approximately 180° in right ascension, within a time span of six months, suggesting a roughly one year spin axis precession period about the satellite’s angular momentum vector.     

弹道交班自适应算法研究

为实现复合制导不同制导弹道的平滑过渡,用二阶吻合法设计了一不同制导律间的指令交接导引段。建立了自适应弹道交接导引算法的模型。理论分析和仿真结果表明,该算法具较好的弹道过载平滑能力,有一定的应用价值。     

在二元柔壁自适应风洞中利用面元法进行三元模型实验

简要叙述了在西北工业大学二元柔壁自适应风洞中利用面元法进行二元半机翼模型试验的研究情况，分析了面元法的基本思想和部分试验结果。     

Ionospheric behavior of the F2 peak parameters foF2 and hmF2 at Hainan and comparisons with IRI model predictions

Monthly median values of foF2, hmF2 and M(3000)F2 parameters, with hourly time interval resolution for the diurnal variation, obtained with DPS-4 digisonde observations at Hainan (19.4°N, 109.0°E) are used to study the low latitude ionospheric variation behavior. The observational results are compared with the International Reference Ionospheric Model (IRI) predictions. The time period coverage of the data used for the present study is from March 2002 to February 2005. Our present study showed that: (1) In general, IRI predictions using CCIR and URSI coefficients follow well the diurnal and seasonal variation patterns of the experimental values of foF2. However, CCIR foF2 and URSI foF2 IRI predictions systematically underestimate the observed results during most time period of the day, with the percentage difference ΔfoF2 (%) values changing between about −5% and −25%, whereas for a few hours around pre-sunrise, the IRI predictions generally overestimate the observational ones with ΔfoF2 (%) sometimes reaching as large as ∼30%. The agreement between the IRI results and the observational ones is better for the year 2002 than for the other years. The best agreement between the IRI results and the observational ones is obtained in summer when using URSI coefficients, with the seasonal average values of ΔfoF2 (%) being within the limits of ±10%. (2) In general, the IRI predicted hmF2 values using CCIR M(3000)F2 option shows a poor agreement with the observational results. However, when using the measured M(3000)F2 as input, the diurnal variation pattern of hmF2 given by IRI2001 has a much better agreement with the observational one with the detailed fine structures including the pre-sunrise and post-sunset peaks reproduced reasonably well. The agreement between the IRI predicted hmF2 values using CCIR M(30,000)F2 option and the observational ones is worst for the afternoon to post-midnight hours for the high solar activity year 2002. During daytime hours the agreement between the hmF2 values obtained with CCIR M(30,000)F2 option and the observational ones is best for summer season. The discrepancy between the observational hmF2 and that obtained with CCIR M(30,000)F2 option stem from the CCIR M(3000)F2 model, which does not produce the small scale structures observed in the measured M(3000)F2.     

对B2C领域两种营销渠道形式的比较探析

在B2C领域,传统营销渠道与网络营销渠道是一对相互竞争的矛盾。网络营销渠道是新生事物,凭借低成本优势得以迅速成长。传统营销渠道根基雄厚,且更贴近消费者的需求,因此仍吸引着大多数的消费者。网络营销渠道如何进一步发展,传统营销渠道如何吸收新的元素,不对两种营销渠道进行比较,是不能获得满意的答案的,而比较这两者之间的相对劣势比比较它们的优势更能引发思考。     

FY-2气象卫星在轨管理工程测控关键技术(上)

介绍了风云二号(FY—2)地球静止轨道自旋气象卫星工程测控的关键技术。分析了位置保持、姿态确定、星蚀和日凌的原理，给出了位置保持、姿态控制策略和地影、月影、日凌预报算法。并提出了一种检验定姿结果正确性的方法，提供了相应的工程计算参数。这些策略都已成功地用于FY—2卫星的在轨管理工程测控。     

炭/炭复合材料防氧化涂层研究进展

介绍了近两年国内外开发的几种C/C复合材料高性能抗氧化涂层的微观结构和高温氧化行为,表明SiC-Al2O3-莫来石、SiC晶须增韧陶瓷、硅酸钇等涂层1500℃静态空气环境下均具有长时间防氧化能力,部分涂层还具有优良的抗热震性能。其中采用原位形成法制备的硅酸钇涂层具有极佳的抗氧化性能,可在1600℃空气中对C/C复合材料有效保护200 h。此外,还介绍了部分涂层的失效机理,并就C/C复合材料抗氧化涂层下一步研究重点提出一些见解。     

N2O-C2H2火焰原子吸收光谱法测定纯镍中硅含量

为简化纯镍中硅含量的测定过程,提高测量精度,研究了一种N2O-C2H2火焰原子吸收光谱法用于检测。介绍了方法的原理、工作参数和测定条件,并确定最佳工作条件,讨论了燃烧温度、共存离子等干扰因素的影响。实验结果表明,该法的灵敏度高、干扰小、选择性和重现性好,操作简单,分析周期短。其测定结果的相对标准偏差均小于1.0%,标准加入回收率大于97.0%(样本数n=6),可满足实验室仪器分析质量与控制的要求。     

化学镀Ni—P合金等温处理的结构转变

利用电子显微术研究了化学镀Ni—P合金层在260℃等温不同时间的非晶-晶体转变。结果表明,晶体镍首先从非晶态中析出,Ni_3P相亦直接从非晶态中生成,而不经过亚稳过渡相。