Large geomagnetic storms of extreme solar event periods in solar cycle 23

During extreme solar events such as big flares or/and energetic coronal mass ejections (CMEs) high energy particles are accelerated by the shocks formed in front of fast interplanetary coronal mass ejections (ICMEs). The ICMEs (and their sheaths) also give rise to large geomagnetic storms which have significant effects on the Earth’s environment and human life. Around 14 solar cosmic ray ground level enhancement (GLE) events in solar cycle 23 we examined the cosmic ray variation, solar wind speed, ions density, interplanetary magnetic field, and geomagnetic disturbance storm time index (D_st). We found that all but one of GLEs are always followed by a geomagnetic storm with D_st  −50 nT within 1–5 days later. Most(10/14) geomagnetic storms have D_st index  −100  nT therefore generally belong to strong geomagnetic storms. This suggests that GLE event prediction of geomagnetic storms is 93% for moderate storms and 71% for large storms when geomagnetic storms preceded by GLEs. All D_st depressions are associated with cosmic ray decreases which occur nearly simultaneously with geomagnetic storms. We also investigated the interplanetary plasma features. Most geomagnetic storm correspond significant periods of southward B_z and in close to 80% of the cases that the B_z was first northward then turning southward after storm sudden commencement (SSC). Plasma flow speed, ion number density and interplanetary plasma temperature near 1 AU also have a peak at interplanetary shock arrival. Solar cause and energetic particle signatures of large geomagnetic storms and a possible prediction scheme are discussed.     

产业集中度与产业盈利水平关系的研究

基于经济学演化范式的观点和产业的复杂适应系统特征，构建了以目标产业为核心的产业供求关系网络分析框架。在回顾以往产业集中度与利润率关系的研究成果的基础上，利用国内消费类产业集中度与毛利率的相关系数分析，对以往研究结论做了进一步印证。在此基础上，基于对产业供求关系网络的认识，提出将产业集中度与产业盈利水平关系的研究，从目标产业本身扩展到与其密切相关的上下游产业，深入分析产业间集中度差异对产业盈利水平产生的影响。     

谈当代大学生的心理困惑

从社会问题、学习、人际交流、情感四个方面分析了目前在技大学生心理矛盾和困惑的表现及原因。     

政府层级改革:逻辑起点与改革思路

政府层级改革是一个系统工程,不仅涉及行政体制改革而且牵动财政体制改革。只有在进行改革之前找到政府层级改革的根本原因（逻辑起点）,才能保证这一系统工程沿着正确的道路推进。文章从公共产品供给的角度出发,认为政府层级改革的逻辑起点在于供给公共产品,实现公共产品有效供给的政府分级才是合理的政府分级,并针对我国政府分级供给公共产品产生的问题,提出了减少政府层级,扩大下级政府的财政“发言权”,明确界定各级政府的事权和财权,完善转移支付制度等政策建议。     

A new online modelling method for aircraft engine state space model

To overcome the drawbacks of current modelling method for aircraft engine state space model, a new method is introduced. The form of state space model is derived by using Talyor series to expand the nonlinear model that is implicit equations and involves many iterations. A partial derivative calculation method for iterations is developed to handle the influence of iterations on parameters. The derivative calculation and the aerothermodynamics calculations are combined in the component level model with fixed number Newton-Raphson (N-R) iterations. Mathematical derivation and simulations show the convergence ability of proposed method. Simulations show that comparing with the linear parameter varying model and centered difference based state space model, much higher accuracy of proposed online modelling method is achieved. The accuracy of the state space model built by proposed method can be maintained when the step amplitudes of inputs are within 2%, and the responses of the state space model can match those of the component level model when each input steps larger amplitudes. In addition, an online verification was carried out to show the capability of modelling at any operating point and that state space model can predict future outputs accurately. Thus, the effectiveness of the proposed method is demonstrated.     

三层三级民机修理级别经济性分析模型的改进

现代民机产品普遍采用模块化设计，具有多层次特点，相应的维修场所也表现为多个维修级别。现有修理级别分析（LORA）模型在移级维修和报废时，可能存在父单元与其内部封装子单元成本重复累加的问题。引入跟随行为矩阵，对子单元中因父单元层级约束而做出的决策进行标记，能有效地避免父单元与子单元成本被重复计算。在此基础上，考虑实际维修活动中无故障发现事件（NFF）、二次维修等人为因素对LORA决策的影响，建立适用于民机的修理级别分析模型，较已有模型更加真实地反映决策的预计成本，提高了决策的可信度和工程适用性。最后使用混合惩罚函数法将原问题转化为等价的无约束优化问题，采用改进的二进制粒子群算法（BPSO）对多故障模式下的三层三级案例进行仿真优化，验证了该经济性分析模型的合理性和求解算法的有效性。     

Multi- GNSS reflectometry performance evaluation for coastal sea level monitoring: A case study in Antarctic Peninsula

Antarctica is a continent that crucial for studying climate change and its progression across time, as well as analyzing and forecasting local and global change. In this environment, due to the challenges caused by sea-level rise, storm surges, and tsunamis, sustainability is a critical concern, particularly for coastal regions. As a result, the long-term observations that will be conducted in Antarctica are critical for monitoring the adverse impacts of climate change. In recent years, many monitoring approaches, both space, and ground-based are performed to monitor sea/ice level trends in space-based scientific investigations conducted in and around the region. In the study, based on one year of observations from the Palmer GNSS Station, the GNSS Reflectometry technique was used to measure the sea level on the Antarctic Peninsula (PALM). GNSS Station observations were analyzed with a Lomb-Scargle periodogram to monitor sea-level changes, and results were validated with data from a co-located tide gauge (TG). The results show that the correlation between GNSS-R sea-level changes and tidal sea-level changes is found as 0.91.     

基于CNS定位误差的平行航路间隔安全评估

主要对平行航路中基于CNS定位误差的飞行间隔安全评估问题进行了研究。首先分析了CNS定位误差对飞机碰撞风险的影响。其次运用概率论方法得到了CNS定位误差下飞机纵向、侧向和垂直三个方向上的碰撞风险计算模型,并根据模型利用牛顿迭代算法,通过给定某一方向安全目标水平计算CNS定位误差下相应的安全间隔。最后对平行航路三个方向的飞行间隔进行了评估计算,将结果与实际相比较,表明该模型可行。     

用打靶法求解微重力下矩形和旋转对称贮箱内静液面形状

简要介绍了打靶法用于求解带未知参数的非线性二阶常微分方程组问题. 由于微重力环境下矩形和旋转对称贮箱内的静液面形状能够用一个带参数的二阶常微分方程组表示, 因此可用打靶法求解. 利用打靶法求解了微重力下矩形、圆柱形、旋转椭球形以及Cassini贮箱内的静液面形状, 通过大量数值计算可知, 当未知参数初值选取恰当时, 这种方法是快速有效的. 将打靶求解法与其他文献所用的龙格库塔求解法进行比较, 结果表明, 绝大多数情况下采用打靶法效果更好.      

分层次交通运输专业硕士研究生培养探索

随着交通运输专业硕士研究生培养层次的增加,普通硕士、全日制工程硕士和普通工程硕士三种不同类型的硕士研究生培养层次带来了新的研究生培养问题.在分析不同研究生培养目标和培养对象特点的基础上,本文提出了针对普通型硕士研究生的科研强化培养模式,针对全日制工程硕士的实践强化培养模式和针对普通工程硕士的科研认知培养模式.实践证明,分层次有针对性的研究生培养模式受到了学生的欢迎,培养效果正在逐渐显现.