空间材料质量损失和易挥发可凝物长期预测方法

文章从基本理论及相应试验两方面详细介绍了欧洲 ESA 空间研究技术中心(ESTEC)材料部建立的空间材料质量损失和易挥发可凝物长期预测的方法,并确认此种预测方法具有极高准确度。     

Diurnal and seasonal variations in long-term changes in the E-layer critical frequency

Long-term changes in the E-layer critical frequency, foE, at three stations of the European region (Juliusruh, Slough and Rome) and also at Moscow and Wakkanai stations are analyzed by the method developed by the authors and described in detail in the previous papers. It is found that Juliusruh and Slough stations demonstrate a well-pronounced change in foE (a trend) during two previous decades. At the same time, the same features of the behavior of the aforementioned trend k(foE) are obtained. The trend is positive and negative in the morning and evening hours, respectively. Similar diurnal behavior of k(foE) is found also for Moscow station but with lower absolute values of the trends. A well-pronounced seasonal behavior of k(foE) is detected at Juliusruh and Slough: the trend is minimal and maximal in the summer period and at the end of fall—beginning of winter, respectively. The maximal amplitude in the morning hours reaches +0.04?MHz per year, whereas the minimal amplitude in evening hours is ?0.06?MHz per year. No systematic changes exceeding by the magnitude 0.01?MHz per year are found for Rome and Wakkanai stations. It is assumed that the observed trends are related to changes (trends) in the meridional wind bringing NO molecules from the auroral oval to lower latitudes.     

An attempt to study long-term variation of sporadic E layers using neural networks

Strong positive correlation between sporadic E layers and the solar activity and the long-term declining trend of Es were found in this paper. Then the feed-forward back propagation neural networks (NNs) were used to simulate the long-term variation of Es at four stations and predict foEs yearly average values. The inputs used for NNs are the yearly mean values of foEs in the daytime of the past ten years and the yearly averaged data of solar 10.7 cm radio flux (F107) of the present year, and the output is the present yearly mean value of daytime foEs. The outputs of trained NNs have high correlation with the desired values and the foEs yearly mean values predicted by NNs have good agreement with the observed data. The results indicate that NNs can make full use of the observed data to simulate the long variation rule of Es. Also, the results confirm the effect of solar activity on Es.     

微电子封装技术及发展趋势综述

随着电子产品小型化、高集成度的发展趋势,电子产品的封装技术正逐步迈入微电子封装时代。本文对微电子封装的关键技术进行了介绍,介绍了芯片互连工艺、典型封装技术和MCM技术。同时,本文对微电子封装技术的发展趋势及应用前景进行了综述。     

国外空间对抗装备技术的发展途径与趋势

空间已成为事关国家安全和利益的战略“制高点”。主要航天国家围绕控制“制高点”,采取不同策略发展空间对抗能力。国外已具备有限的空间对抗实战能力,但是空间对抗装备在世界范围内总体上仍处于技术发展阶段。空间对抗装备技术将在与导弹攻防对抗、网络攻防对抗技术的交叉与叠加中演进升级。预计2030年前后,国外将形成一个比较全面、完整和成熟的空间对抗装备体系。     

Semi-analytical investigations of high area-to-mass ratio geosynchronous space debris including Earth’s shadowing effects

This paper investigates the long-term perturbations of the orbits of geosynchronous space debris influenced by direct radiation pressure including the Earth’s shadowing effects. For this purpose, we propose an extension of our homemade semi-analytical theory [Valk, S., Lemaître, A., Deleflie, F. Semi-analytical theory of mean orbital motion for geosynchronous space debris under gravitational influence. Adv. Space Res., submitted for publication], based on the method developed by Aksnes [Aksnes, K. Short-period and long-period perturbations of a spherical satellite due to direct solar radiation. Celest. Mech. Dyn. Astron. 13, 89–104, 1976] and generalized into a more convenient non-singular formalism. The perturbations accounting for the direct radiation pressure with the Earth’s shadow are computed on a revolution-by-revolution basis, retaining the original osculating Hamiltonian disturbing function. In this framework, we compute the non-singular mean longitude at shadow entry and shadow exit at every orbital revolution in opposition to classical approaches where the singular eccentric anomalies at shadow entry and shadow exit are computed. This new algorithm is developed using non-singular variables. Consequently, it is particularly suitable for both near-circular and near-equatorial orbits as well as orbits which transit periodically around null eccentricities and null inclinations.The algorithm is tested by means of numerical integrations of the equations, averaged over the short periods, including radiation pressure, J₂, the combined Moon and Sun third body attraction as well as the long-term effects of the 1:1 resonance occurring for geosynchronous objects. As an extension of [Valk, S., Lemaître, A., Anselmo, L. Analytical and semi-analytical investigations of geosynchronous space debris with high area-to-mass ratios influenced by solar radiation pressure. Adv. Space Res., doi:10.1016/j.asr.2007.10.025, 2007b], we especially apply our analysis to space debris with area-to-mass as high as 20 m²/kg. This paper provides numerical and semi-analytical investigations leading to a deep understanding of the long-term evolution of the semi-major axis. Finally, these semi-analytical investigations are compared with accurate numerical integrations of the osculating equations of motion over time scales as high as 25 years.     

Long-term changes in indices of geomagnetic activity at the auroral station Sodankylä

Here we compare the traditional analog measure of geomagnetic activity, Ak, with the more recent digital indices of IHV and Ah based on hourly mean data, and their derivatives at the auroral station Sodankylä. By this selection of indices we study the effects of (i) analog vs. digital technique, and (ii) full local-time vs. local night-time coverage on quantifying local geomagnetic activity. We find that all other indices are stronger than Ak during the low-activity cycles 15–16 suggesting an excess of very low scalings in Ak at this time. The full-day indices consistently depict stronger correlation with the interplanetary magnetic field strength, while the night-time indices have higher correlation with solar wind speed. The Ak index correlates better with the digital indices of full-day coverage than with any night-time index. However, Ak depicts somewhat higher activity levels than the digital full-day indices in the declining phase of the solar cycle, indicating that, due to their different sampling rates, the latter indices are less sensitive to high-frequency variations driven by the Alfvén waves in high-speed streams. On the other hand, the night-time indices have an even stronger response to solar wind speed than Ak. The results strongly indicate that at auroral latitudes, geomagnetic indices with different local time coverage reflect different current systems, which, by an appropriate choice of indices, allows studying the century-scale dynamics of these currents separately.     

The accuracy of data from ionosondes for the estimation of hmF2 and the identification of global change in the ionosphere

A long temporal series of simulated ionograms was generated with a superimposed secular variation of −14 km/century on the h_mF2 parameter. These ionograms were interpreted by the automatic scaling program Autoscala. By applying four different empirical formulas, four artificial series of h_mF2 were generated and then processed with the same methods used by other authors for real data sets. Data analysis of the simulated ionograms revealed the artificially imposed long-term trend. These results lead to the conclusion, that regardless of the empirical formula used, the accuracy of h_mF2 from ionosonde measurements would be adequate to observe a long-term trend of −14 km/century.     

Time and spatial variations of the foF2(night)/foF2(day) values

The ratio of daytime and nighttime values of the foF2 critical frequency is analyzed on the basis of the data of 35 ionospheric stations of the eastern hemisphere and 7 stations of the western hemisphere. The analysis confirms the results of Danilov [Danilov, A.D. Variations in the ratio of nighttime and daytime critical frequencies of the F2 layer. Geomagn. Aeronomy, 47 (6), 551–561 (in Russian) 2007; Danilov, A.D. Time and spatial variations in the ratio of nighttime and daytime critical frequencies of the F2 layer, J. Atmos. Sol-Terr. Phys. 70, 1201–1212, 2008.] that after about 1980, a systematic behavior of this ratio with time is observed: an increase with time (a positive trend) or a decrease with time (a negative trend). The sign of this trend is shown to be governed by the signs of the magnetic declination D and magnetic inclination I at the given ionospheric station. This fact makes it possible to assume that the above indicated trend is caused by long-term variations in the zonal component V_ny of the horizontal wind in the thermosphere, the latter component contributing into the vertical drift velocity W.     

当前我国企业承担社会责任情况评估——以电梯企业为例

随着国内外企业社会责任实践的不断推进和深化,行业性社会责任备受关注,企业必须兼顾一般社会责任和行业特色责任。电梯等特种设备行业作为我国重要的制造产业,其社会责任的履行事关企业持续发展与社会和谐稳定。通过对电梯企业社会责任建设情况的评估,提出了未来电梯企业社会责任建设的思路。