复合惰气在采空区遗煤中竞争吸附的分子动力学模拟研究*

为明确作用于采空区的复合惰气的竞争吸附,进行不同温度、压力及组分下烟煤对N2、O2、CO2多元气体竞争吸附分子的模拟研究。研究结果表明:当注入压力达到3 MPa后,竞争吸附效果不再明显,为高压注入提供一定的理论基础;随着CO2分压的增大,O2吸附量降低速度逐渐平缓,初步确定最佳注入配比范围为2∶1至3∶1,为进一步结合实际工程中成本等因素确定最佳注入配比提供参考;等量吸附热受吸附条件的影响较小,仅与吸附质本身有关;随着CO2分压的增大,范德华能升高56.9%,分子内能升高78.7%,静电能升高67.2%,CO2对整个系统内的吸附作用强度及吸附量有着较大的影响;随着CO2分压增大,N2竞争吸附能力逐渐弱于O2,竞争吸附能力大小顺序为CO2>O2>N2。     

地铁内楼梯口处全尺寸火灾实验与数值模拟

建立了地铁实体模型，开展了地铁火灾实验研究，测量了站台与站厅之间的楼梯处的速度和温度等火灾参数。同时利用火灾动力学模拟程序软件对地铁站台火灾进行了数值模拟，研究了地铁站台和站厅连接楼梯处温度和烟气速度的变化趋势，并与实验结果作了对比分析，验证了数值模拟结果的有效性。研究结果可为有效控制烟气在地铁中的蔓延和组织人员疏散提供技术支持。     

影响振动环境试验的若干关键技术要点解析

从振动试验方案设计、试验方法和步骤、试验设备选择、振动试验控制方法等几个方面对影响振动试验的关键技术进行了详细的解析;并结合结构动力学阐述了振动试验夹具设计的注意要点。     

Interacting Effects of Phenotypic Plasticity and Evolution on Population Persistence in a Changing Climate

Abstract: Climate change affects individual organisms by altering development, physiology, behavior, and fitness, and populations by altering genetic and phenotypic composition, vital rates, and dynamics. We sought to clarify how selection, phenotypic plasticity, and demography are linked in the context of climate change. On the basis of theory and results of recent empirical studies of plants and animals, we believe the ecological and evolutionary issues relevant to population persistence as climate changes are the rate, type, magnitude, and spatial pattern of climate‐induced abiotic and biotic change; generation time and life history of the organism; extent and type of phenotypic plasticity; amount and distribution of adaptive genetic variation across space and time; dispersal potential; and size and connectivity of subpopulations. An understanding of limits to plasticity and evolutionary potential across traits, populations, and species and feedbacks between adaptive and demographic responses is lacking. Integrated knowledge of coupled ecological and evolutionary mechanisms will increase understanding of the resilience and probabilities of persistence of populations and species.     

WIND DRIVEN RAIN DISTRIBUTIONS AROUND STREET CANOPIES1

ABSTRACT: Wind driven raindrop tracking is used to investigate the microscale redistribution of wind driven rainfalls in street canopies by combining a Eulerian wind flow model and a Lagrangian raindrop tracking model. The former conducts large eddy simulations of the turbulent flows in street canopies, and the latter performs raindrop trajectory calculations by releasing a large number of raindrops into the computational domain. The wind speed model is verified with available wind tunnel measurement. Twenty sets of simulations are carried out for various building configurations and driving rain angles. The simulated results show that the trajectories of smaller raindrops are more slanting and more influenced by the multibuilding perturbed flow field. Impingement of raindrops on the building envelope increases from bottom to top. The height of the front building is a significant factor affecting wind driven rain redistribution. Distinct nonuniform spatial rainfall distributions are found for scenarios with high building configurations and low driving rain angles. The simulated results are further integrated to assess the effect of real raindrop size distributions by weighing the volumetric fraction of a range of drop sizes. There is about 10 percent variation in spatial extent of street canopies. An overall 5 to 17.4 percent increase of the rainfall amount in the upwind zone is observed.     

Effects of life history and reproduction on recruitment time lags in reintroductions of rare plants

Reintroductions are important components of conservation and recovery programs for rare plant species, but their long-term success rates are poorly understood. Previous reviews of plant reintroductions focused on short-term (e.g., ≤3 years) survival and flowering of founder individuals rather than on benchmarks of intergenerational persistence, such as seedling recruitment. However, short-term metrics may obscure outcomes because the unique demographic properties of reintroductions, including small size and unstable stage structure, could create lags in population growth. We used time-to-event analysis on a database of unusually well-monitored and long-term (4–28 years) reintroductions of 27 rare plant species to test whether life-history traits and population characteristics of reintroductions create time-lagged responses in seedling recruitment (i.e., recruitment time lags [RTLs]), an important benchmark of success and indicator of persistence in reintroduced populations. Recruitment time lags were highly variable among reintroductions, ranging from <1 to 17 years after installation. Recruitment patterns matched predictions from life-history theory with short-lived species (fast species) exhibiting consistently shorter and less variable RTLs than long-lived species (slow species). Long RTLs occurred in long-lived herbs, especially in grasslands, whereas short RTLs occurred in short-lived subtropical woody plants and annual herbs. Across plant life histories, as reproductive adult abundance increased, RTLs decreased. Highly variable RTLs were observed in species with multiple reintroduction events, suggesting local processes are just as important as life-history strategy in determining reintroduction outcomes. Time lags in restoration outcomes highlight the need to scale success benchmarks in reintroduction monitoring programs with plant life-history strategies and the unique demographic properties of restored populations. Drawing conclusions on the long-term success of plant reintroduction programs is premature given that demographic processes in species with slow life-histories take decades to unfold.     

啶虫脒在甘蓝和土壤中的残留消解动态研究

采用田间试验及气相色谱检测方法,研究了啶虫脒在甘蓝(Brassica oleracea L.var.capitata L.)和土壤中的残留消解动态.结果表明,啶虫脒在甘蓝和土壤中消解较快.在甘蓝中半衰期为1.4～1.6 d,药后3d消解90%以上;在土壤中的半衰期为1.8～1.9 d,药后7 d消解90%以上.3%啶虫脒可湿性粉剂,45、22.5 g·hm-2,施药2次,药后3、5、7 d苹果和土壤中残留量均小于2 mg·kg-1.