高强预腐蚀铝合金单轴拉-拉疲劳断口定量分析

目的通过断口定量分析获得7A09铝合金的疲劳裂纹扩展规律,为7A09铝合金结构的寿命评估提供依据。方法使用EXCO溶液对试验件进行预腐蚀,利用疲劳拉伸机进行疲劳加载直至断裂,使用扫描电镜对疲劳断口进行定量化分析。结果疲劳裂纹在试件的腐蚀坑处萌生,从自由界面附近向纵深发展导致试件的断裂。通过断口分析和Paris公式确定了裂纹的萌生寿命和扩展寿命。结论腐蚀之后的试件裂纹萌生寿命占总寿命的比例下降,当裂纹扩展程度较大之后,受腐蚀影响减轻,得出裂纹扩展速率和应力强度因子的关系。     

TiO2薄膜光催化效果的强化

采用溶胶-凝胶法制备TiO2溶胶,将其涂覆在普通钠钙玻璃上,以TiO2对甲基橙的光分解率探讨TiO2薄膜最佳光催化性能.结果表明,当PEG400的加入量为7%时,TiO2薄膜的光催化性能最强;用锐钛型TiO2粉末二次引发的溶胶提拉制成的薄膜对甲基橙的光催化分解效果有很大的提高;经滴加操作后薄膜的光催化性能有明显改善;各个影响因素最好的组合效果为滴加操作 锐钛型粉体引发 H2SO4超强酸化 La3 掺杂.     

板料弯曲变形应力的滑移线解法

滑移线法作为一种求解塑性成形应力状态的常用方法而被广泛应用。而在板材弯曲中一般采用主应力法求解变形区的应力状态。通过对板料弯曲变形区应力分析 ,根据滑移线理论 ,推导出了变形区的应力分布规律 ,与主应力法求解的结果相同     

滑坡滑动面方程多项式拟合

本文讨论了滑坡的形态特征来确定滑动面分析方法，应用数据分析方法，通过多项式对滑动面方程进行拟合，工程实践证明拟合后的滑动面方程能满足工程要求。     

Effects of Customary Marine Closures on Fish Behavior,Spear‐Fishing Success,and Underwater Visual Surveys

Abstract: Customary management systems (i.e., management systems that limit the use of marine resources), such as rotational fisheries closures, can limit harvest of resources. Nevertheless, the explicit goals of customary management are often to influence fish behavior (in particular flight distance, i.e., distance at which an organism begins to flee an approaching threat), rather than fish abundance. We explored whether the flight distance of reef fishes targeted by local artisanal fishers differed between a customary closure and fished reefs. We also examined whether flight distance of these species affected fishing success and accuracy of underwater visual census (UVC) between customary closed areas and areas open to fishing. Several species demonstrated significant differences in flight distance between areas, indicating that fishing activity may increase flight distance. These relatively long flight distances mean that in fished areas most target species may stay out of the range of spear fishers. In addition, mean flight distances for all species both inside and outside the customary‐closure area were substantially smaller than the observation distance of an observer conducting a belt‐transect UVC (mean [SE]= 8.8 m [0.48]). For targeted species that showed little ability to evade spear fishers, customary closures may be a vital management technique. Our results show that customary closures can have a substantial, positive effect on resource availability and that conventional UVC techniques may be insensitive to changes in flight behavior of fishes associated with fishing. We argue that short, periodic openings of customary closures may allow the health of the fish community to be maintained and local fishers to effectively harvest fishes.     

Channel and Perennial Flow Initiation in Headwater Streams: Management Implications of Variability in Source-Area Size

Despite increasing attention to management of headwater streams as sources of water, sediment, and wood to downstream rivers, the extent of headwater channels and perennial flow remain poorly known and inaccurately depicted on topographic maps and in digital hydrographic data. This study reports field mapping of channel head and perennial flow initiation locations in forested landscapes underlain by sandstone and basalt lithologies in Washington State, USA. Contributing source areas were delineated for each feature using a digital elevation model (DEM) as well as a Global Positioning System device in the field. Systematic source area–slope relationships described in other landscapes were not evident for channel heads in either lithology. In addition, substantial variability in DEM-derived source area sizes relative to field-delineated source areas indicates that in this area, identification of an area–slope relationship, should one even exist, would be difficult. However, channel heads and stream heads, here defined as the start of perennial flow, appear to be co-located within both of the lithologies, which together with lateral expansion and contraction of surface water around channel heads on a seasonal cycle in the basalt lithology, suggest a controlling influence of bedrock springs for that location. While management strategies for determining locations of channel heads and perennial flow initiation in comparable areas could assign standard source area sizes based on limited field data collection within that landscape, field-mapped source areas that support perennial flow are much smaller than recognized by current Washington State regulations.     

新结构传爆药柱多点起爆数值模拟及实验研究

根据冲击波汇聚技术原理及有效装药理论,设计出环锥形传爆药装药结构.用ANSYS/LY-DYNA软件分析起爆点个数对环锥形传爆药柱输出波形的影响,并用多点同步起爆网络起爆环锥形传爆药柱进行实验验证.结果表明,利用多点同步起爆网络起爆环锥形传爆药柱能有效提高传爆药柱的输出威力,起爆点个数对爆轰波形有很大的影响.     

Entrepreneurial motivation: A review of the literature and an agenda for future research

Given the substantial impact that new ventures have on the global economy, understanding what motivates entrepreneurs is of both practical and theoretical importance. Although research on the nature, causes, and consequences of entrepreneurial motivation has grown rapidly, it has evolved in distinct theoretical silos that tend to isolate motives based on the phase of business development (e.g., initiation, growth, and exit) rather than acknowledge that individuals often traverse all these phases and experience multiple types of motivation throughout their entrepreneurial journey. To advance the study of motivation in the fields of entrepreneurship and organizational behavior and provide a means through which these advancements can contribute to our understanding of how motivation drives the start-up, growth, and exiting of businesses, we organize and review the extant literature on entrepreneurial motives based on the phases of the new venture process. In doing so, this article develops a roadmap of the current state of entrepreneurial motivation research and its nomological network and provides suggestions to guide future research in extending our understanding of motivation in the entrepreneurship domain as well as in traditional organizational settings.     

地震液化流滑震害

通过地震液化的震害调查,从土种类、地形条件和坡度、液化土壤的赋存状况、地震能量和流滑的时间与空间分布等方面,简要总结了液化流滑的震害特征和规律,初步分析了液化引起流滑发生的条件、规模、剧烈程度、坡体运动规律以及流滑产生的破坏形式,分析了影响流滑的因素,可供进一步研究等参考。     

基于Seam型裂纹的复合型裂纹起裂角预测的有限元法

目的对处于多轴应力状态下的复合型裂纹起裂角进行预测。方法考虑材料的弹性性能,利用商业有限元软件ABAQUS中的Seam裂纹模拟穿透型裂纹损伤,建立双轴载荷作用下中心带孔边裂纹板的三维有限元模型,通过位移外推法得到裂纹尖端的应力强度因子(Stress Intensity Factor,SIF),并利用求得的SIF基于最大周向应力断裂准则预测孔边裂纹的起裂角。结果通过与相关文献结果进行对比,发现通过该有限元方法计算得到的应力强度因子与文献结果的最大误差在2%以内,预测的裂纹起裂角与文献结果的最大误差在3%以内。结论该有限元方法计算的裂纹起裂角与文献结果一致,因此文中求解复合型裂纹起裂角所使用的有限元方法是可靠有效的。