不确定性因素下航班延误波及建模与分析

针对机场终端区日益严重的航班延误,提出了一种基于有色－时间Petri网的不确定性因素下航班延误波及分析模型。模型综合考虑航班运行尾流、跑道运行模式、跑道占用时间等运行安全间隔约束,同时根据连续航班间的信息更新,设计进离场航班序列动态调整流程,并由计算模型可得出航班延误总架次及时间。最后,依据历史延误数据分析得出不确定性因素延误的概率分布。选取上海浦东机场为背景对模型进行仿真验证,仿真结果表明,所构建模型可用于战略阶段的航班延误波及程度与过程的评估。     

Methods to determine stress profile in ALT based on theoretical life models

With the recent products being more reliable,engineers cannot obtain enough failure or degradation information through the design period and even the product lifetime,therefore,accelerated life test(ALT)has become the most popular way to quantify the life characteristics of products.Test design is the most essential topic,such as testing duration,stress profile,data inference,etc.In this paper,a method and procedure based on theoretical life models is proposed to determine the accelerated stress profile.Firstly,the method for theoretical life calculation is put forward based on the main failure mechanism analysis and the theoretical life models.Secondly,the method is provided to determine the accelerated stress profile,including the method to determine the accelerated stress types and the stress range on the basis of the main failure mechanism analysis,the method to determine the acceleration factor and the accelerated stress level based on life quantitative calculation models,and the collaborative analysis method of the accelerated test time while taking the multiple failure mechanisms into consideration.Lastly,the actuator is taken as an example to describe the procedure of the method and the engineering applicability and the validity are verified.     

气密机身纵向裂纹非线性鼓胀因子数值研究

为了研究不同几何参数包括壳半径、壳壁厚度和裂纹长度对鼓胀因子的影响,应用有限元软件ABAQUS,通过几何非线性有限元分析,计算含纵向裂纹无加强柱形壳鼓胀因子的数值,并与现有的经验公式进行对比,同时讨论双轴载荷比对鼓胀因子的影响。结果表明:大部分几何参数对鼓胀因子的数值有显著影响;现有经验公式存在局限性;当双轴载荷比从0.5增长到1.0时,鼓胀影响降低了约20%;当双轴载荷比从0.5降低到0时,鼓胀影响增加了约28%。     

影响分光光度计透射比示值偏差的原因分析

从仪器光路、仪器结构、被测样品性质、检定所用标准器等几个方面对分光光度计透射比示值产生偏差的原因进行了详细的分析。依据这些分析,可有针对性地发现影响透射比示值的各种原因。     

高校英语阅读课教学生态环境研究

从教育生态学的角度来看,英语阅读课的教学是在一个由多种因子构成的生态环境中进行的。按照能否在教学过程中得到控制或调整,本文将这些因子分成可控和不可控两大类,并分析了对于阅读教学影响较大的几种可控因子,包括学习氛围、学校的设施、阅读动机和学习策略等。对这些因子的干预能够改善教学生态环境,提高学生英语阅读的效率。     

管制员信息处理能力模糊评价

信息处理能力是管制员能力和工作负荷的重要组成部分。针对此方面缺乏系统研究的实际，详细分析了管制员信息处理能力的影响因素，给出了评价指标体系，建立了多级模糊评价模型，实现了此能力的量化评价。通过对管制员的具体评价，符合管制员的自身情况，证明了方法的有效性。     

Materials selection for applications in space environment considering outgassing phenomenon

Application of the existing materials selection methods is not much popular in space environment. This is in spite of involvement of the selection process in this field with a wide range of influential factors (e.g. conventional mechanical properties and over 21 space environmental effects). In this paper an introductory road map for employing systematic materials selection methods in the field by engaging the selection process with mechanical properties and only one of the space environmental factors is presented. Here, selected case studies, which are involved with outgassing phenomenon of materials in vacuum condition, highlight the incapability of some of the methods in dealing with such example problems. The study specifically indicates the effectiveness of the most recently introduced method, i.e. Z-transformation, over other existing methods. The results show that considering the mechanical properties of materials in conjunction with the space environmental effects produce much more reliable ranking of the candidate materials. Besides, the results recommend introducing more space environmental aspects in the selection process may produce a better outcome.     

网球初学者正手击球技术难点分析

网球的技术性很强,正手击球是其中最为基本的一项技术。从网球技术动作的生物力学原理以及身体姿势、动作轨迹、动作时间、动作速度、动作速率、动作力量几项动作要素分析了网球正手击球技术动作,帮助网球初学者解析拍面角度的控制、击球点的掌握以及挥拍的轨迹等技术难点,从而建立了清晰的动作概念,促进了正手击球技术的快速掌握。     

陶瓷材料小裂纹的生长与聚合

对陶瓷材料小裂纹的生长与聚合规律进行了试验研究。结果表明由Ｖｉｋｅｒｓ压痕法引入的单个小裂纹的裂纹扩展速率（ｄａ／ｄｔ）随裂尖应力强度因子的增大呈先降后升的Ｖ形特征。理论分析和数据处理均表明这种特征是由压痕法引入的残余应力场的影响所致。试验结果还表明多个小裂纹的生长与聚合规律也与残余应力场密切相关。文中提出的叠加残余应力场模型很好地解释了上述试验结果