摘要：目的:流体弹性不稳定性是引起换热器管束振动失效的最主要原因。鉴于目前有关两相横向流诱发管束弹性不稳定性的设计准则尚无一致结论,本文采用空气-水两相流体系,考察不同参数条件下换热器管束的弹性不稳定性。创新点:1.从避免发生弹性不稳定性的角度,确定适宜的管束排列方式和节径比;2.建立基于Connor准则的不稳定常数的确定方法,并提出新的推荐值。方法:1.实验研究两相流的流动条件和管束的几何特征对管束阻尼、振动特性及弹性不稳定性的影响;2.采用建立稳定区图的方法确定不稳定常数的推荐值;3.通过与其他研究成果的对比分析,验证本文推荐的不稳定常数的合理性和可靠性。结论:1.相比于阻力方向,升力方向上的阻尼比更小,也更易发生弹性失稳。2.四种排列管束的稳定性从高到低依次为:正三角形、正方形、转置正方形、转置正三角形。3.对于正方形和正三角形排列管束,推荐不稳定常数为4.0;对于转置正方形和转置正三角形排列管束,当质量阻尼参数小于或等于0.54时,推荐不稳定常数为1.1,反之,则推荐不稳定常数为1.5。

摘要：目的:目前大中型控制阀大多存在结构复杂、驱动能耗大、反应时间慢、振动噪声大、稳定性差和使用寿命短等缺点。基于此,浙江大学相关研究人员组建了特种控制阀研究室,致力于提升控制阀的整体性能和设计水平。研究点:本研究室的主要方向为:1.控制阀内部流动特性分析和新结构设计开发;2.流体目标流量、温度、压力和振动噪声等的智能控制研究;3.适应纳米流体、压缩氢气和高温高压过热蒸汽等新流体介质的智慧控制阀研究。展望:特种控制阀作为超超临界火电机组、核电、石化高压反应和百万吨级乙烯工程等国家重大重点工程的关键零部件之一,将会在内流动机理、新结构开发、新流体介质和智能控制等研究领域得到广泛关注和长足发展。

摘要：大流识别是网络测量中的一项关键基础性工作,目前主流的方法是采用概要型数据结构Sketch快速统计网络流量,进而高效筛选大流.然而,当网络流量发生抖动时,大量分组的急速涌入将导致大流识别精度显著下降.对此,提出一种支持流量抖动的网络大流弹性识别方法RobustSketch.所提方法首先设计基于Sketch循环链的可伸缩小流过滤器,根据实时分组到达速率适应性扩增与缩减其中的Sketch数量,以始终完整记录当前时间周期内所有到达的网络分组,从而确保网络流量抖动出现时仍能精确过滤小流.然后设计基于动态分段哈希的可拓展大流记录表,根据小流过滤器筛选后的候选大流数量适应性增加与减少分段,以完整记录所有候选大流,并保持较高的存储空间利用率.进一步,通过理论分析给出了所提小流过滤器和大流记录表的误差界限.最后,借助真实网络流量样本,对所提大流识别方法RobustSketch进行实验评估.实验结果表明:所提方法的大流识别精确率明显高于现有方法,即使在网络流量抖动时仍能稳定保持在99%以上,而平均相对误差减少了86%以上,有效提升了大流识别的精确性和鲁棒性.

摘要：本文以理科地球物理学专业的"地磁学"课程为例,就课程内容的整合与优化、教学方法与手段的革新等方面进行了探讨。在明确课程教学目标的前提下,通过强化基础理论,增加反映学科发展动态和国内外重大成果的内容,以及添加实践性教学环节来优化课程内容。为了切实提升学生的学习效果,引进先进的教育教学理念和方式,融入课堂教学体系,改进教学质量,从而培养更多的拔尖创新人才。

摘要：Polyl(lactide),PLA,suffers from bitleness and low heat deflection temperature(HDT),which limits its application as an engineering *** this work,poly(L-lactide)/poly(D-lactide)/ethylene-vinyl acetate glycidyl methacrylate random copolymer(PLLA/PDL A/EVM-GMA=1/1/x)composites were prepared by melt blending,and the in situ formed EVM-g PLA copolymers improved the compatibility between PLA and ***,the blends were subjected to a two-step annealing process during compression molding,*** annealing at 120℃ to rapidly form a certain amount of stereocomplex(sc)crystallites as nucleation sites,and then annealing at 200℃ to guide the formation of new *** differential scanning calorimetry(DSC)and wide angle X-ray dffrction(WAXD)measurements confirmed the formation of highly stereocomplexed PLA *** results showed that the PLLA/PDLA blend with 20 wt%of EVM-GMA had a notched impact strength up to 65 kJ/m2 and an elongation at break of 48%,while maintaining a tensile strength of 40 ***,dynamic mechanical analysis(DMA)and heat deflection tests showed that the PLA composite had an HDT up to 142℃ which is 90℃ higher than that of normal PLA *** electron microscopy(SEM)confirmed the fine dispersion of EVM-GMA particles,which facilitated to understand the toughening ***,the highly stereocomplexed PLA composites simultaneously exhibited excellent chemical and hydrolysis ***,these fascinating properties may extend the application range of sc PLA material as an engineering bioplastic.

摘要：教学保障条件信息化是教育信息化的关键要素之一,是提升人才培养质量、推动院校教育信息化发展的重要支撑。本文从构建标准化体系、部署智能化空间、设计功能化布局3个方面,系统地论证并解决了院校教学保障条件建设与应用的理论和实践问题,以标准化体系为依据,以智能化空间和功能化布局为支撑,提出基于网络和信息技术的“三化”教学条件标准体系构建与应用模型,为提升院校办学条件、推动教育信息化进程提供理论参考和实践借鉴。

摘要：We propose and analyze a novel ultra-compact polarization beam splitter based on a resonator cavity in a two-dimensional photonic *** two polarizations can be separated efficiently by the strong coupling between the microcavities and the waveguides occurring around the resonant frequency of the *** transmittance of two polarized light around 1.55µm can be more than 98.6%,and the size of the device is less than 15µm×13µm,so these features will play an important role in future integrated optical circuits.

摘要：The climate variability in global land precipitation is important for the global hydrological *** on the Coupled Model Intercomparison Project Phase 6(CMIP6)historical experiments and the Global Monsoons Model Intercomparison Project(GMMIP)Tier-1 experiments,the spatialtemporal characteristics of global and regional land precipitation long-term climate changes in CAS FGOALS-f3-L are evaluated in this *** comparing these two kinds of experiments,the precipitation biases related to the SSTs are also *** results show that the two experiments could capture the precipitation trend and amplitude to a certain degree compared with *** GMMIP simulations show a higher skill than the historical runs verified by correlation coefficients partly because the observed monthly mean SST was *** the Northern Hemisphere,GMMIP can reproduce the trend and variability in global precipitation,while historical simulations cannot reproduce the trend and ***,both experiments fail to simulate the amplitude of the southern hemisphere summer precipitation *** empirical mode decomposition(EEMD)was applied to compare the simulated precipitation on different time *** sea surface temperature anomaly(SSTA)bias,especially the La Ni?a-type SSTA,is the dominant source of the model bias for simulating interannual precipitation *** authors also emphasize that the response of precipitation anomalies to the ENSO effect varies *** study highlights the importance of the multiannual variability in SSTAs in global and hemispheric precipitation *** ways to improve the simulation of global precipitation for CAS FGOALS-f3-L are also discussed.

摘要：Based on the antiplatelet aggregation mechanism and the bioisosterism principle of the reference drug picotamide, thirteen novel derivatives of arylamide and arylsulfonamide were designed and prepared. The biological activities of these derivatives were investigated. The chemical structures of the target compounds were confirmed by ^1H NMR and IR. The in vitro activities of antiplatelet aggregation of the thirteen target compounds were assessed by Bore＇s method. Compounds 2b and 8h have significant antiplatelet aggregation activities, which are superior to the corresponding activity of Picotamide.

摘要：泰国广告以其明显的艺术风格及足够大的“体量”,在互联网上形成了一个相对独立的系统,形成了一种现象级传播形态:“泰国广告”。它在传播产品和服务信息的同时,关注社会效益、注重正能量的传递,塑造着理想社会形象。文章以塑造“幸福家庭”的泰国广告为案例,从传播内容和艺术特色两个方面进行分析,寻找泰国广告的现象级传播的规律,并进行一定的理论提升。泰国广告作为文化传播的逻辑路径有四个关键点:文化认同是文化对外传播成功的逻辑起点;新媒体技术是泰国广告成功传播的重要因素,但一切创作技巧和手段都是为内容服务的,文化创作坚持以传播经典传统文化、本土优秀文化为重点的“内容为王”的核心要义不能改变,这是文化精品生产必经之路;在“讲什么”及“如何讲”上不断优化讲述的技巧,通过观众喜闻乐见的叙事艺术手法,即文化传播的“战术”,运用化虚为实、化静为动的创新表现形式使故事生动活泼、能看、好看;只有与观众的悲欢离合、喜怒哀乐等感情对接,与观众产生共情、共振等效果的广告作品才能够使观众对产品产生好感,唤醒其潜在的购买欲望,感情共鸣是广告文化传播的目标和逻辑归宿。