摘要：In the 6th edition of the Chinese Space Trajectory Design Competition held in 2014, a near-Earth asteroid sample-return trajectory design problem was released, in which the motion of the spacecraft is modeled in multi-body dynamics, considering the gravitational forces of the Sun, Earth, and Moon. It is proposed that an electric-propulsion spacecraft initially parking in a circular 200-kin-altitude low Earth orbit is expected to rendezvous with an asteroid and carry as much sample as possible back to the Earth in a 10-year time frame. The team from the Technology and Engineering Center for Space Utilization, Chinese Academy of Sciences has reported a solution with an asteroid sample mass of 328 tons, which is ranked first in the competition. In this article, we will present our design and optimization methods, primarily including overall analysis, target selection, escape from and capture by the Earth-Moon system, and optimization of impulsive and low-thrust trajectories that are modeled in multi-body dynamics. The orbital resonance concept and lunar gravity assists are considered key techniques employed for trajectory design. The reported solution, preliminarily revealing the feasibility of returning a hundreds-of-tons asteroid or asteroid sample, envisions future space missions relating to near-Earth asteroid exploration.

摘要：目的:激光诱导火花点火(简称激光点火)是取代传统的靠近缸壁的单点电火花点火以实现稀薄燃烧、提高热效率和改善排放的新型点火方式之一。本文通过对比分析两种点火方式在定容弹中的点火及燃烧过程的压力上升率、最大爆发压力及放热率为激光点火技术在内燃机中的应用提供设计过程的参考依据。创新点:1.同时进行两种点火方式的试验,保证对比研究的准确性;2.激光点火采用532 nm和1064 nm波长的两种激光进行对比;3.直接采用汽油进行研究。方法:通过记录不同当量比的汽油空气混合气在定容燃烧弹内激光点火(532 nm和1064 nm波长)及电火花点火的燃烧过程压力变化:1.对比分析三种点火情况的压力上升率和最大爆发压力;2.通过公式计算,对比分析三种点火情况的放热率。结论:1.532 nm与1064 nm波长激光点火的压力上升率和最大爆发压力都在当量比为1.8时出现最大值,其中532 nm波长激光为39.4 MPa/μs和0.68 MPa,1064 nm波长激光为38.8 MPa/μs和0.67 MPa;而电火花点火的压力上升率和最大爆发压力则在当量比为1.6时出现最大值,分别为38.1 MPa/μs和0.67 MPa;2.激光点火的稀燃极限相对电火花点火对应的当量比更小;3.三种点火类型的放热率规律与压力上升率变化规律一致。

摘要：OBE是成果导向教育理念,在教学过程中坚持以学生为中心、以成果为导向、以持续改进为重点,能够改革传统教学模式,为高职数学提供新的思路。当前,高职数学课堂教学仍然局限于传统教学模式中,教学内容和方法创新性不足,师生互动不充分,导致学习成果转化不充分,教学效果达不到预期。对此,聚焦高职数学课堂教学存在的不足,利用OBE教学理念进行创新设计。并从教学观念、教学方法、教学评价等方面探索创新策略,展开具体的教学实践,促进高职数学课堂教学创新转变,以期获得更高质量的教学成果。

摘要：为研究高强水泥基灌浆料(简称灌浆料)在压力型岩石锚杆内锚结构中的受力特性,采用侧限抗压强度试验和推出试验,探讨了围岩约束作用下灌浆料和围岩强度对灌浆体侧限抗压强度与界面黏结性能的影响规律,提出了界面黏结-滑移模型和极限黏结强度计算式。研究结果表明:围岩约束作用提高了灌浆体的抗压强度,强度增大系数在2.5~4.6之间,该系数随围岩强度增大而增大,随灌浆料强度增大而减小;当围岩强度和灌浆料强度分别增大到60 MPa和80 MPa时,强度增大系数的变化幅度较小;增大围岩和灌浆料强度均能提高界面黏结强度,而围岩强度对黏结强度和界面破坏特征影响更大;黏结界面的黏结-滑移曲线具有上升、快速下降和慢速下降变化特征;提出的界面黏结-滑移模型曲线与实测黏结-滑移曲线吻合良好;提出的极限黏结强度计算式能够反映围岩强度对极限黏结强度的影响规律。

摘要：跨学科主题学习打破学科壁垒,超越简单的内容叠加,走向主题统领的整合与应用。通过Citespace可视化工具梳理近些年跨学科主题学习的相关文献,从发文量、研究机构、关键词等方面分析国内跨学科主题学习的现状,跨学科主题学习研究热点表现为重视学科核心素养发展、学科教学案例设计与学生高阶思维培养,跨学科主题学习发展趋势指向关注学科综合育人、学习模式转变以及数智技术融合。

摘要：本文通过对造型色彩和设计色彩两种课程体系在训练内容及方法上的比较,倡导在色彩基础训练中应注意将学习知识、培养能力、拓宽语汇、提高创造性思维相结合,提出了将"小色稿变调训练法"、"色彩归纳训练法"、"采集重构色彩训练法"、"色彩创意训练法"融入到绘画色彩基础训练之中,改变了过去色彩训练单一的状况,这无疑是对新时期高等师范美术专业色彩基础教学所作的一种新的探索和有益的尝试。

摘要：为解决钢-混组合结构负弯矩区桥面板易开裂等问题,提出将超高性能混凝土(Ultra-high Performance Concrete,UHPC)代替负弯矩区普通混凝土的铺设方案,设计并完成了3片钢-UHPC组合梁的负弯矩区静力加载试验,研究负弯矩区UHPC的裂缝发展规律及内在开裂机理,得到组合梁的裂缝宽度、发展规律等试验数据,并结合黏结滑移分析理论,推导桥面板UHPC的裂缝宽度计算公式。结果表明:UHPC可以提高组合梁负弯矩区的抗裂性能,具有抑制桥面板裂缝发展的能力;增加UHPC桥面板的配筋率能提高组合梁负弯矩区的临界开裂荷载和负弯矩区的抗裂性能,并限制裂缝发展;提出的负弯矩区桥面板UHPC裂缝宽度计算公式的计算值与试验值吻合良好,可用于工程实践。

摘要：为探讨中小跨径桥梁在设计、建造及服役期间中典型的不确定性因素对结构抗震性能的影响,以一座4跨连续小箱梁桥为工程背景,基于OpenSees建立非线性动力模型,分析了地震波不确定性、建模参数不确定性和构件抗震能力不确定性对关键构件地震动响应的影响机理。在此基础上,结合易损性分析理论,探讨了以上不确定性因素在构件易损性曲线的建立过程中的联动效应,进而量化了各类不确定性因素对结构抗震性能分析的影响程度。结果表明:构件的地震滞回曲线的差异主要由建模参数的不确定性造成,而峰值地震响应差异主要由地震动和建模参数的不确定性联合所导致;建模参数的不确定性和构件抗震能力的不确定性均会导致结构失效概率的增加,继而使得部分构件无法满足既定的损伤状态;考虑不确定性因素会增加桥梁系统易损性曲线的失效概率,且随着损伤程度的加深,不确定性的影响也会越大,使分析结果偏差30%以上。

摘要：When modeling wave propagation in infinite space, it is necessary to have stable absorbing boundaries to effectively eliminate spurious reflections from the truncation boundaries. The SH wave equations for Perfectly matched Layers （PML） are deduced and their Crank-Nicolson scheme are presented in this paper. We use the second-, sixth-, and tenth-order finite difference and pseudo-spectral algorithms to compute the spatial derivatives. Two numerical models, a homogeneous isotropic medium and a multi-layer model with a cave, are designed to investigate how the absorbing boundary width and the algorithms determine PML effects. Numerical results show that, for PML, the low-order finite difference algorithms have fairly good absorbing effects when the absorbing boundary is thin, whereas, high-order algorithms always have good absorption when the boundary is thick. Finally, we discuss the reflection coefficient and point out its shortcomings, which is why we use the SNR to quantitatively scale the PML effects,

摘要：The deficiencies of basic particle swarm optimization （bPSO） are its ubiquitous prematurity and its inability to seek the global optimal solution when optimizing complex high-dimensional functions. To overcome such deficiencies, the chaos-PSO （COSPSO） algorithm was established by introducing the chaos optimization mechanism and a global particle stagnation-disturbance strategy into bPSO. In the improved algorithm, chaotic movement was adopted for the particles＇ initial movement trajectories to replace the former stochastic movement, and the chaos factor was used to guide the particles＇ path. When the global particles were stagnant, the disturbance strategy was used to keep the particles in motion. Five benchmark optimizations were introduced to test COSPSO, and they proved that COSPSO can remarkably improve efficiency in optimizing complex functions. Finally, a case study of COSPSO in calculating design flood hydrographs demonstrated the applicability of the improved algorithm.