摘要：This study proposes a process to obtain an optimal helicopter rotor blade shape for aerodynamic performance in hover flight. A new geometry representation algorithm which uses the class function/shape function transformation （CST） is employed to generate airfoil coordinates. With this approach, airfoil shape is considered in terms of design variables. The optimization process is constructed by integrating several programs developed by author. The design variables include twist, taper ratio, point of taper initiation, blade root chord, and coefficients of the airfoil distribution function. Aerodynamic constraints consist of limits on power available in hover and forward flight. The trim condition must be attainable. This paper considers rotor blade configuration for the hover flight condition only, so that the required power in hover is chosen as the objective function of the optimization problem. Sensitivity analysis of each design variable shows that airfoil shape has an important role in rotor performance. The optimum rotor blade reduces the required hover power by 7.4% and increases the figure of merit by 6.5%, which is a good improvement for rotor blade design.

摘要：The coronary artery calcification score and pericardial fat volume have recently been reported to be strongly associated with the severity and presence of coronary atherosclerosis. However, no studies have explored the outcome of phased progression of atherosclerosis by non-contrast computed tomography in asymptomatic people in China. The population-based cohort study in outcome of phased progression of atherosclerosis in China （PERSUADE）, an observational, longitudinal and prospective cohort study in a target population of healthy sub- jects based in Jidong Oilfield （China）, prospectively analyzes the outcome of phased progression of atherosclerosis by non-contrast computed tomography in healthy population. The results of this study are expected to be of value for utilizing noninvasive imaging combine with tradi- tional cardiovascular risk factors to create a risk stratification and find pertinent biomarkers associated with the outcome of phased progres- sion of atherosclerosis in healthy people, thereby could help to establish a more personalized treatment of clinical practice.

摘要：An investigation of the effect of simplifying bogie regions on the aerodynamic performance of a high-speed train was carried out by studying four train models,to explore possible ways to optimise the train underbody structure,improve the underbody aerodynamic performance,and reduce the aerodynamic *** shear stress transport(SST)k-ωturbulence model was used to study the airflow features of the high-speed train with different bogie regions at Re=2.25×10^(6).The calculated aerodynamic drag and surface pressure were compared with the experimental benchmark of wind tunnel *** results show that the SST k-ωmodel presents high accuracy in predicting the flow fields around the train,and the numerical results closely agree with the experimental *** with the train with simplified bogies,the aerodynamic drag of the train with a smooth surface and the train with enclosed bogie cavities/inter-carriage gaps decreases by 38.2%and 30.3%,respectively,while it increases by 10.8%for the train with cavities but no ***,enclosing bogie cavities shows a good capability of aerodynamic drag reduction for a new generation of highspeed trains.

摘要：High-temperature proton exchange membrane(HT-PEM)fuel cells offer more advantages than low-temperature PEM fuel *** ideal characteristics of HT-PEMs are high conductivities,low-humidity operation conditions,adequate mechanical properties,and competitive *** molecular moieties,such as benzimidazole,benzothiazole,imide,and ether ether ketone,have been introduced to polymer chain backbones to satisfy the application requirements for *** most common sulfonated polymers based on the main chain backbones have been employed to improve the *** group/chain engineering,including the introduction of SO_(3)^(-) on the side chain,grafting,branching,and crosslinking,has been widely applied to HTPEMs to further improve their proton conductivity,thermal stability,and mechanical ***,phosphoric acid-doped polybenzimidazole is the most successful polymer material for application in *** compositing/blending modification methods of polymers are effective in obtaining high PA-doping levels and superior mechanical *** this review,the current progress of various membrane materials used for HT-PEMs is *** synthesis and performance characteristics of polymers containing specific moieties in the chain backbones applied to HT-PEMs are discussed *** modification approaches and their deficiencies associated with HT-PEMs are analyzed and *** and future challenges are also presented.

摘要：Strainburst is one type of rockburst that generally occurs in deep *** this study,the strainburst behaviors of marble specimens were investigated under tunnel-excavation-induced stress condition,and two stress paths were designed,a commonly used stress path in true triaxial unloading rockburst tests and a new test path in which the intermediate principal stress was *** the tests,a high-speed camera was used to record the strainburst process,and an acoustic emission(AE)monitoring system was used to monitor the AE characteristics of *** these two stress paths,all the marble specimens exhibited strainbursts;however,when the intermediate principal stress was varied,the rockburst became more *** obtained results indicate that the intermediate principal stress has a significant effect on rockburst behavior of *** a higher intermediate principal stress before the unloading,more elastic strain energy was accumulated in the specimen,and the cumulative AE energy was higher in the rockburst-induced failure,i.e.,more elastic strain energy was released during the ***,more violent failure was observed:more rock fragments with a higher mass and larger size were ejected outward.

摘要：以甜樱桃‘红灯’为试材,应用选择性扩增微卫星(SAM)法分离、克隆了100个SSR序列,其中81个非重复,可用。加上搜索数据库所获得的1个SSR序列,一共82个序列用于特异引物的设计。仅从69个序列的77个基因座设计出特异引物。合成38对特异引物,对其中的36个基因座进行检测。其中19对引物扩增出相应大小的片段,另外8对引物扩增出非预期片段。最后,以27个甜樱桃种质的基因组DNA为模板,从27对可扩增出带的引物中,筛选出多态性引物24对,获得了24个甜樱桃基因座特异性SSR标记。

摘要：针对目前冲击危险性评价方法的不足,提出了II类开采技术因素,并揭示了该类因素诱发煤岩震动异常并激发灾害发生的内在规律。结果表明,工作面推进度与高能震动事件频率成正比,推进度变化梯度与高能震动事件能量大小成正比,大的变化梯度将增加冲击地压突发的风险;煤层卸压爆破针对巷道两帮冲击启动区,爆破后7~18 h内是解危措施发挥作用的主要时段;巷帮扩修使得围岩从原有的相对稳定变为不稳定状态,扩修进尺过快显著影响煤岩震动异常;工作面停产后恢复生产时期,各能级的微震事件急剧上升,且伴随高能事件发生的危险。II类开采技术因素临时介入,打破原有平衡状态,使得煤岩宏观调整,微观破裂突然无序,激发煤岩冲击事件发生。