Space science education in Egypt and the 2006 solar eclipse

The space science research has been started in Egypt since 1910 by measuring the solar constant as indication of solar radiation at Helwan Observatory. The solar sunspot studies and its influence on the Nile flooding was erected and operated at Helwan as a first solar station in Egypt during 1957. Zeiss-Coude’ refractor was installed in 1964. Astronomy and space science educations started in Egypt at the university level since 1936 at Department of Astronomy and Meteorology of Cairo University. Undergraduate and graduate education in Egypt will be discussed in this work.     

关于Access2000的安全机制解析

Microsoft Access 2000数据库作为常用的桌面数据库软件，在中小型的数据库系统中得到了广泛的应用。针对Access2000安全性能不高，探讨如何设置及提高Access2000的安全性方法。     

A model of foreground emission in UV using GALEX deep observations

Foreground emission, mainly airglow and zodiacal light, is a significant contributor in an ultraviolet observation especially from low earth orbit. Its careful estimation and removal are tedious yet unavoidable processes in the study of diffuse UV radiation and by extension interstellar dust studies. Our analysis of deep GALEX observations show that airglow is not only a function of Sun angle but also a strong function of Solar activity at the time of observation. We present here an empirical model of airglow emission, derived from GALEX deep observations, as a function of 10.7 cm Solar flux and Sun angle. We obtained the model by training machine learning models on the data using a variant of the regression algorithm that is both resilient toward outlier data and sensitive to the complexities of the provided data. Our model predictions across various observations show no loss in generalization as well as good agreement with the observed values. We find that the total airglow in an observation is the sum of a baseline part (AG_c) that depends on the Solar flux and Sun angle, and a variable part (AG_v) that depends on the Sun angle and the time of observation with respect to local midnight. We also find that the total airglow can vary between 85 – 390 photon units in FUV and 80 – 465 photon units in NUV.     

一种基于混合规则的作业车间计划调度方法

针对多品种小批量生产车间计划调度存在的复杂度高、实用性差等问题,在分析车间计划调度相关的任务、资源和约束等要素的基础上,提出了一种基于混合规则的计划调度编制算法,该算法综合考虑了零件差异性、工艺差异性、设备差异性、以及交货期约束等因素,使得该方法具有可行性高、实用性强等特点,较好地满足了离散制造车间的实际需求.     

Science rational for MIERS/IRI collaboration

In this paper, we will shortly highlight some of the aspects that COST Action 296 on Mitigation of Ionospheric Effects on Radio Systems (MIERS) and International Reference Ionosphere (IRI) have in common in an attempt to define science rationale for collaboration between these two international projects.     

Options for mapping foF2

Available long-term and near-real time global and regional maps of foF2 are examined in relation to telecommunication and aeronomy requirements and recommendations are made for the best present-day maps to adopt. In particular, it is shown that current CCIR maps do not meet all requirements and should not necessarily be regarded as standards against which other mappings should be compared.     

Diurnal and seasonal variations of F2 layer characteristics over Irkutsk during the decrease in solar activity in 2003–2006: Observations and IRI-2001 model predictions

The diurnal and seasonal variations of F2 layer characteristics (critical frequency, peak height and bottomside thickness) over Irkutsk, Russia (52.3 N and 104.3 E) are studied by the method of running medians. The comparison with the IRI-2001 model during the decrease in solar activity in 2003–2006 revealed cases of both close agreement and systematic differences between predictions and observations. The systematic difference is not the only reason for disagreement between IRI and observations; there are also intrayear variations which are not associated with seasonal behavior. The period of observation was too short to make conclusions about solar activity dependence of the noon bottomside thickness and the modification of its diurnal behavior with decreasing solar activity.     

Dynamical evolution of high area-to-mass ratio debris released into GPS orbits

A large set of simulations, including all the relevant perturbations, was carried out to investigate the long-term dynamical evolution of fictitious high area-to-mass ratio (A/M) objects released, with a negligible velocity variation, in each of the six orbital planes used by Global Positioning System (GPS) satellites. As with similar objects discovered in near synchronous trajectories, long lifetime orbits, with mean motions of about 2 revolutions per day, were found possible for debris characterized by extremely high area-to-mass ratios. Often the lifetime exceeds 100 years up to A/M ∼ 45 m²/kg, decreasing rapidly to a few months above such a threshold. However, the details of the evolution, which are conditioned by the complex interplay of solar radiation pressure and geopotential plus luni-solar resonances, depend on the initial conditions. Different behaviors are thus possible. In any case, objects like those discovered in synchronous orbits, with A/M as high as 20–40 m²/kg, could also survive in this orbital regime, with semi-major axes close to the semi-synchronous values, with maximum eccentricities between 0.3 and 0.7, and with significant orbit pole precessions (faster and wider for increasing values of A/M), leading to inclinations between 30° and more than 90°.     

Probing solar and stellar interior dynamics and dynamo

Solar and stellar activity is a result of complex interaction between magnetic field, turbulent convection and differential rotation in a star’s interior. Magnetic field is believed to be generated by a dynamo process in the convection zone. It emerges on the surface forming sunspots and starspots. Localization of the magnetic spots and their evolution with the activity cycle is determined by large-scale interior flows. Thus, the internal dynamics of the Sun and other stars hold the key to understanding the dynamo mechanism and activity cycles. Recently, significant progress has been made for modeling magnetohydrodynamics of the stellar interiors and probing the internal rotation and large-scale dynamics of the Sun by helioseismology. Also, asteroseismology is beginning to probe interiors of distant stars. I review key achievements and challenges in our quest to understand the basic mechanisms of solar and stellar activity.     

对等性权利义务下的我国农业补贴法律制度研究

农业、农村经济的发展以及农民收入的增长是关系国家和社会利益的一件大事。在当前我国社会经济发展前提下，根据权利与义务的对等性理念，分析农业的特性，得出农业具有先义务性，存在权利与义务非对等性的现象，以此揭示农业补贴得以存在的本质内涵，即弥补这种先义务性，寻求权利与义务的数量等值。最后得出必须通过建立完善的农业补贴法律制度，达到权利与义务的对等，保证正当权利的实现，使其获得正当利益，最终使社会正义得以体现。