摘要：目的:为改善高速列车明线运行时的气动性能,提出一种基于近似模型的高速列车头部外形多目标气动优化设计方法。创新点:1.建立包含转向架区域的高速列车参数化模型;2.基于近似模型并结合遗传算法,对高速列车头部外形及转向架区域进行多目标气动优化设计。方法:1.建立包含转向架区域的原始头型高速列车模型(图2和3),并基于CATIA脚本文件和MATLAB自编程序对列车头部外形进行参数化处理;2.通过最优拉丁超立方设计方法在设计空间内对优化设计变量进行采样,并采用计算流体动力学方法对样本点中新头型列车气动性能进行计算;3.基于样本点的列车头型优化设计变量及优化目标(表4),建立优化目标与设计变量之间的近似模型;4.基于近似模型和多目标遗传算法,对高速列车头部外形进行多目标优化设计,选取其中的一个优化头型与原始头型进行比较,并验证横风下优化头型的可行性。结论:1.相较于原始头型列车,无横风时,优化头型列车的整车气动阻力减小2.61%,尾车气动升力减小9.90%;2.横风下,优化头型列车的整车气动阻力减小2.98%,头车气动侧力减小0.24%;3.横风下,优化头型列车的头车气动载荷波动幅值有所减小。

摘要：Because of the complicated interplay between the prefractionator and main distillation column involved,the black-hole problem might occur and prohibit the assignment of four specifications to dividing-wall distillation columns(DWDCs)(e.g., the three main product compositions plus an impurity ratio in the intermediate product), which lowers terribly process flexibility and operability. In this paper, a feed thermal condition adjustment strategy, achieved by the installation of a pre-heater in feed pipeline, is employed to eliminate the black-hole problem and serve to enhance process flexibility and operability. Through the strong influence to the overall mass and energy balance of the DWDC, the feed thermal condition adjustment can alter the interlinking flows between the thermally coupled prefractionator and main distillation column and work effectively to coordinate their relationship. A DWDC separating a benzene, toluene, and o-xylene mixture is chosen to ascertain the feasibility of the philosophy proposed. The static and dynamic studies demonstrate that the feed thermal condition adjustment is an effective way to refine process design and can completely eliminate the black-hole problem and elevate consequently process flexibility and operability.

摘要：This study focused on modifying heat treatment schemes to enhance the mechanical properties of sand cast Al−2Li−2Cu−0.5Mg−0.2Sc−0.2Zr *** three-stage solution treatment schemes((460℃,32 h)+(520℃,24 h)+(530/540/550℃,4/12/24/32 h))and aging temperatures(125,175,225℃)were designed for *** microstructure evolutions were analyzed by optical microscopy(OM),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results showed that the three-stage solution treatment of(460℃,32 h)+(520℃,24 h)+(530℃,12 h)could dissolve most of the secondary *** TEM results illustrated that fineδ'(Al_(3)Li)particles were homogeneously distributed in the matrix after aging at 175℃for 8 h,accompanied by a small amount of lath-shaped S′(Al_(2)CuMg)and plate-like T_(1)(Al_(2)CuLi)*** best comprehensive properties of yield strength of 376 MPa,ultimate tensile strength of 458 MPa and elongation of 4.1%were obtained by the optimal heat treatment scheme((460℃,32 h)+(520℃,24 h)+(530℃,12 h)+(175℃,8 h)).

摘要：In this work,the impact of internal heat integration upon process dynamics and controllability by superposing reactive section onto stripping section,relocating feed locations,and redistributing catalyst within the reactive section is explored based on a hypothetical ideal reactive distillation system containing an exothermic reaction:A + BC + *** state operation analysis and closed-loop controllability evaluation are carried out by comparing the process designs with and without the consideration of internal heat *** superposing reactive section onto stripping section,favorable effect is aroused due to its low sensitivities to the changes in operating *** ascending the lower feed stage,somewhat detrimental effect occurs because of the accompanied adverse internal heat integration and strong sensitivity to the changes in operating *** descending the upper feed stage,serious detrimental effect happens because of the introduced adverse internal heat integration and strong sensitivity to the changes in operating *** redistributing catalyst in the reactive section,fairly small negative influence is aroused by the sensitivity to the changes in operating *** reinforcing internal heat integration with a combinatorial use of these three strategies,the decent of the upper feed stage should be avoided in process *** the conclusions are derived based on the hypothetical ideal reactive distillation column studied,they are considered to be of general significance to the design and operation of other reactive distillation columns.

摘要：With the merits of high energy density,environmental friendliness,and cost effectiveness,lithium-sulfur(Li-S)batteries are considered as one of the most promising next-generation electrochemical storage ***,the notorious polysulfide shuttle effect,which results in low active material utilization and serious capacity fading,severely impedes the practical application of Li-S *** various electrocatalysts to improve the polysulfide redox kinetics has recently emerged as a promising strategy to address the shuttle ***,the electronic structure of the electrocatalysts plays a decisive role in determining the catalytic activity to facilitate the polysulfide ***,reasonably modulating the electronic structure of electrocatalysts is of paramount significance for improving the electrochemical performance of Li-S ***,a comprehensive overview of the fascinating strategies to tailor the electronic structure of electrocatalysts for Li-S batteries is presented,including but not limited to vacancy engineering,heteroatom doping,single atom doping,band regulation,alloying,and heterostructure *** future perspectives and challenges are also proposed for designing high-efficient electrocatalysts to construct high-energy-density and long-lifetime Li-S batteries.

摘要：以长江绿色创意产业园工程为背景,对粘钢加固法的应用领域和结构外包钢加固设计进行了论述,对其施工工艺、钢板下料、打磨、预钻孔型钢骨架组装与焊接、包钢“注胶法”施工、固化养护、面层防腐蚀、防火涂料涂装、外包钢成品保护等方面进行了详细分析,实践证明施工效果良好。

摘要：实验电影的历史最早可以追溯到电影诞生之时,其在技术、形式甚至发行放映等方面的创新也一直为传统电影所吸收和借鉴。本文由实验电影的双重定义切入,以阿彼察邦·韦拉斯哈古电影为例,从形式和观念两个角度研究了阿彼察邦·韦拉斯哈古电影中实验影像的产生背景、发展脉络及其艺术和美学效果,并加入了声音实验方面的研究,全面呈现了实验电影在其形成自己独有的电影语言过程中起到的作用,指出实验电影可以为传统电影在创新方面提供参考和思路。

摘要：A series of novel dihydro-alkylthio-benzyl-oxopyrimidines （S-DABOs） 7a-f have been designed and synthesized with an efficient method. Biological evaluation of their HIV-1 reverse transcriptase inhibitory activities was performed using Nevirapine （NVP） as a reference compound. Among the series, compound 7d shows the highest reverse transcriptase inhibitory activity, which is better than Nevirapine.

摘要：本研究采用时间滞后设计,考察过去20年我国高中生教育效用和教育志向水平的年代和城乡差异,以及二者与个体学业成绩、父母学历之间关系的年代和城乡差异。分别在1999年、2010年、2018年对来自相同的三个地区(包括城市和农村)、相同学校的高中生进行问卷调查,使用协方差分析和回归分析进行数据分析。结果发现:(1)自1999年至2018年,城乡高中生的教育效用都遵循先下降、后回升的变化趋势;在教育志向上,城市高中生无明显变化,而农村高中生教育志向上升并超越城市高中生;(2)高中生教育效用、教育志向受父母学历和学业成绩等微观因素影响,且受年代和城乡宏观社会历史因素调节。相比于其他年份,2010年时成绩较差学生的教育效用更低、2018年时成绩较差学生的教育志向更高;自1999年至2018年,低父母学历对农村高中生教育志向的影响方式由“枷锁效应”转变为“鞭策效应”。我国过去20年的社会变迁使城乡高中生对教育的价值认同发生系统性变化,且宏观社会历史因素的演变改变了教育的价值认同形成的微观机制。

摘要：乳腺癌早期筛查、精准诊断、有效治疗是提高患者生存率的重要因素,而影像学是筛查、诊断、治疗评估的主要手段。基于现有的影像技术,乳腺临床诊治流程虽然已逐步规范化,但在高效灵敏筛查、无创精准诊断以及治疗监测评估等方面仍存在核心局限。例如,传统的医学影像技术存在诊断特异性低、成像速度慢、使用电离辐射或注射造影剂等局限,仍存在重大临床诉求。光声成像作为一项新兴的医学影像技术,可以与传统技术形成优势互补,提供快速(如10~15s完成全乳腺扫描)、高分辨率、信息丰富的医学影像。其光学对比度和声学分辨率使之具备揭示肿瘤微环境结构、功能、分子细节特征的能力。本文简述了光声成像的技术原理和主要设计形态,概述并评价了乳腺肿瘤筛查、诊断和治疗评估领域的代表性光声成像研究。最后讨论了光声成像在乳腺临床上的应用前景,其有望成为继钼靶、超声、核磁共振之后的“第四大”乳腺成像技术。