Statistical characteristics of locally generated ESF during equinoctial months over Sanya

Understanding the local generation rate of equatorial spread-F (ESF) is important for forecasting ionospheric scintillation. Using the GPS ionospheric scintillation/TEC and VHF radar data during March-April and September-October from 2010 to 2014, the occurrence of ionospheric scintillation, TEC fast fluctuation, and backscatter plume were studied. Through analyzing the simultaneous occurrence of ionospheric scintillation, TEC fast fluctuation and backscatter plume, the local generation rate of ESF over Sanya was investigated. The results show that the monthly generation rate varies between 0% and 68%. A significant equinoctial asymmetry of local generation rate of ESF can be found in 2010, 2013 and 2014. The local generation rate of ESF increases from 2010 to 2014 during March-April, while it does not have similar trend during September-October. The plasma vertical drift influenced by solar activity has a significant impact on the monthly generation rate. The equinoctial asymmetry of plasma vertical drift may contribute a lot to the equinoctial asymmetry of the generation rate of ESF.     

A multi-objective multi-memetic algorithm for network-wide conflict-free 4D flight trajectories planning

Under the demand of strategic air traffic flow management and the concept of trajectory based operations (TBO),the network-wide 4D flight trajectories planning (N4DFTP) problem has been investigated with the purpose of safely and efficiently allocating 4D trajectories (4DTs) (3D position and time) for all the flights in the whole airway network.Considering that the introduction of large-scale 4DTs inevitably increases the problem complexity,an efficient model for strategic level conflict management is developed in this paper.Specifically,a bi-objective N4DFTP problem that aims to minimize both potential conflicts and the trajectory cost is formulated.In consideration of the large-scale,high-complexity,and multi-objective characteristics of the N4DFTP problem,a multi-objective multi-memetic algorithm (MOMMA) that incorporates an evolutionary global search framework together with three problem-specific local search operators is implemented.It is capable of rapidly and effectively allocating 4DTs via rerouting,target time controlling,and flight level changing.Additionally,to balance the ability of exploitation and exploration of the algorithm,a special hybridization scheme is adopted for the integration of local and global search.Empirical studies using real air traffic data in China with different network complexities show that the pro posed MOMMA is effective to solve the N4DFTP problem.The solutions achieved are competitive for elaborate decision support under a TBO environment.     

新四六级考试和大学英语教学的改革

通过考前辅导和对考试结果的研究分析，发现学生在听读写几个方面都存在普遍性的问题，使我们教师不得不反思我们目前的大学英语课堂教学，并痛下决心，锐意改革，使我们的教学符合时代和社会的要求，提高学生的英语实际综合应用能力，更好地为社会服务。     

TC4半球形锻件成形工艺改进

通过对TC4半球形锻件成形工艺改进,进一步提高并稳定该产品的锻造成品率,经过改进的成形工艺为中小型设备批量生产该类锻件提供了新的方法.     

四色定理论证

用离散数学之图论证明"四色猜想",巧妙而深层次地应用数学归纳法和换色法,解决了肯泊(A.Kempe)百多年前提出"不可避免构形集"中的一个地域有五个邻域的情况的所谓"可约性"问题,同时指出了1890年希伍德(P.Heawood)举出的25阶反例(当时,他以此说明"四色猜想"不成立,而"五色定理"成立)与本文中的一种可换色(即"可约性")的典型实例类同,进而简捷而理想地证明了"四色猜想"是成立的,使"四色定理"得到科学的论证。     

末端区域4D导引的水平轨迹计算方法

末端区域４Ｄ导引首先生成轨迹，然后生成沿该轨迹飞行的高度剖面，合理的速度剖面，最后生成自动引导飞机在规定时间着陆的４Ｄ导引指令。现简要讨论末端区域４Ｄ导引理论，主要推导了生成末端区域４Ｄ导引的首要算法－－水平飞行轨迹的计算方法。数值仿真结果表明，该方法只输入少量的航路点坐标数据和限制参数，就能计算出沿直线和曲线飞行的水平轨迹。     

聚苯胺/NiFe2 O4纳米晶体复合体系的电磁性能研究

分别使用原位掺杂的方法和溶胶-凝胶自燃烧的方法制备了聚苯胺微管以及纳米NiFe2O4晶体；并对聚苯胺微管以及聚苯胺／NiFe2O4和石蜡的复相粉体在8～12GHz频率范围进行了复介电常数和磁导率的测量。结果表明，聚苯胺微管在测试频率范围内为介电损耗材料，当纳米NiFe2O4晶体加入到聚苯胺和石蜡的混合体系时，聚苯胺／NiFe2O4和石蜡的复相粉体混合体系在测试频率范围内同时具有一定的介电损耗和磁损耗，并且其混合体系的微波吸收性能高于单独加入聚苯胺时的微波吸收性能。     

表面再结晶层对DZA定向凝固合金低周疲劳性能影响

针对DZ4定向凝固合金表面再结晶层对材料性能的影响进行了低周疲劳实验研究,并通过岛津SEM伺服疲劳试验机进行表面裂纹实时观察跟踪.研究结果表明,表面再结晶层的存在对材料性能明显产生负面作用,低周疲劳寿命大大降低.不同喷丸强度试件在相同的高温退火条件下形成的再结晶具有不同的再结晶形态,高喷丸强度再结晶更加完全,晶界清晰平直,晶粒有长大的趋势.表层再结晶形态也对疲劳寿命的降低程度以及疲劳微裂纹萌生寿命和裂纹密度有较大的影响.较高喷丸强度形成的再结晶层的试件疲劳寿命降低较少,表面微裂纹萌生较晚,裂纹密度也很低.低喷丸强度试件表面微裂纹大量萌生,密度非常高.再结晶层的晶界开裂是导致表面微裂纹大量萌生的根源,从而导致疲劳寿命大幅度降低.     

X射线脉冲星4U 1538—52 的时间和能谱特性

本文处理分析了EXOSAT卫星对4U1538-524次中能观测资料,并结合其他观测结果对4U1538-52的时间和能谱特性作了分析和解释:中子星自转仍在减慢;能谱为幂律谱,Tenma卫星以后的观测未见Fe发射线;X射线dip现象可解释为一前景星对中子星的遮掩而形成;X射线爆发在不同的轨道位相出现,持续近1小时;在1keV附近似有一发射线。      

激光选区熔化成形Ti6Al4V合金的热处理组织演变机理

激光选区熔化(SLM)Ti6Al4V成形构件需要通过热处理改善其塑性。为探究该过程中的组织特征和演变机理,研究了Ti6Al4V试样固溶时效热处理(910℃/8 h水冷,750℃/4 h炉冷)前后的微观形貌和力学性能。结果表明:沉积态的马氏体α′相尺寸具有层次结构;热处理相变时初生马氏体α′发生分解,小尺寸马氏体α′转变为β相,随后发生β→(α+β)转变,最后得到α相片层和精细(α+β)相结构均匀分布的组织;热处理后材料抗拉强度达1 055 MPa,延伸率提升至16.2%,均优于典型Ti6Al4V合金拉伸性能。采取的热处理技术对Ti6Al4V组织调控成效显著,满足后续工艺要求,可在激光选区熔化成形双相钛合金中推广应用。