基于渗流-应力耦合分析的野鸡尾尾矿坝稳定性研究

基于渗流场与应力场耦合机理,对柿竹园野鸡尾尾矿坝进行稳定性研究。研究渗流-应力的耦合效应,提出了渗流-应力耦合以及渗流体积力计算的实施方案;建立二维的有限元渗流-应力耦合计算模型,分析了考虑耦合效应时的尾矿坝渗流场、位移场、应力场;最终分析了不同耦合关系对于渗流量、位移场、等效渗透集中力以及应力场的影响。研究结果表明:当前水力条件下,尾矿坝稳定性良好;尾矿坝主要受水平渗透力作用,初期坝坝顶、坝脚以及坝底等处应力集中;尾矿坝的渗流-应力作用不容忽视,不同的耦合关系对于x方向位移、渗透力的预测影响巨大;考虑渗流-应力耦合关系得到的主应力、剪应力以及竖向位移,比不考虑耦合效应时大。     

基于几何参数的优化对双层柱面网壳结构动力性能的影响

以双层柱面网壳为研究对象,采用参数化设计语言APDL对AN SY S进行二次开发,实现了任意跨度双层柱面网壳的自动建模、加载、施加约束及求解。借此平台对柱面网壳结构进行模态和地震反应分析。首先,分析了结构自振特性随几何参数变化的特点,研究了结构的基频随矢跨比和网壳厚度的变化规律,结果表明,当矢跨比在1/3.6~1/5该范围内,结构的整体刚度较大;网壳厚度在1.8~2.1 m时,网壳整体刚度较大;对于矢跨比一定的网壳,随着厚度的增加,杆件的动内力大多增加,横向弦杆的二维与单维动内力比值有所增加,而纵向弦杆的二维与单维动内力则变化不大。然后,对网壳进行不同几何参数下的地震反应分析,给出了最大节点位移和最大杆件轴应力随几何参数变化的时程响应曲线,揭示了这类网壳的地震反应特点。     

Baseline soil levels of PCDD/Fs established prior to the construction of municipal solid waste incinerators in China

In order to determine the baseline contamination by polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in different areas in China, prior to the construction of municipal solid waste incinerators (MSWIs), a total of 32 representative soil samples was collected near 16 incinerators and analyzed for their PCDD/F concentrations. The PCDD/F baseline concentrations in the soil samples ranged from 0.32 to 11.4 ng I-TEQ kg⁻¹ (dry matter), with average and median value of 2.73 and 2.24 ng I-TEQ kg⁻¹ (dry matter), respectively, and a span between maximum and minimum recorded value of 36. The PCDD homologues predominated in 26 out of 32 soil samples, with the ratio (PCDDs)/(PCDFs) ranging from 1.1 to 164; however in the other 6 samples, PCDF homologues were larger, with the same ratio varying from 0.04 to 0.8. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used to examine PCDD/F amount and profile in these soil samples, and their possible associations with known emission sources: in this process 6 really distinct isomer fingerprints were identified. Background PCDD/F levels and profiles were comparable to those found in soils from China and other countries and indicate a rather low baseline PCDD/F contamination of soils. The present data provide the tools for future assessment of a possible impact of these MSWIs.     

BPA暴露对本体和子代胰岛β细胞转录组差异对比分析

双酚A(BPA)作为一种典型的环境内分泌干扰物,与二型糖尿病和肥胖症等代谢类疾病密切相关.在这项研究中,旨在探讨BPA直接暴露以及围产期暴露对本体和子代胰岛β细胞影响的差异,从而实现对不同易感人群的精准预防与治疗.通过对GEO数据库中GSE126297和GSE82175两个数据集进行分析,共筛选出108个共有的差异基因...     

Effects of urban greenspace configuration and native vegetation on bee and wasp reproduction

Pollinator welfare is a recognized research and policy target, and urban greenspaces have been identified as important habitats. Yet, landscape-scale habitat fragmentation and greenspace management practices may limit a city's conservation potential. We examined how landscape configuration, composition, and local patch quality influenced insect nesting success across inner-city Cleveland, Ohio (U.S.A.), a postindustrial legacy city containing a high abundance of vacant land (over 1600 ha). Here, 40 vacant lots were assigned 1 of 5 habitat treatments (T1, vacant lot; T2, grass lawn; T3, flowering lawn; T4, grass prairie; and T5, flowering prairie), and we evaluated how seeded vegetation, greenspace size, and landscape connectivity influenced cavity-nesting bee and wasp reproduction. Native bee and wasp larvae were more abundant in landscapes that contained a large patch (i.e., >6 ha) of contiguous greenspace, in habitats with low plant biomass, and in vacant lots seeded with a native wildflower seed mix or with fine-fescue grass, suggesting that fitness was influenced by urban landscape features and habitat management. Our results can guide urban planning by demonstrating that actions that maintain large contiguous greenspace in the landscape and establish native plants would support the conservation of bees and wasps. Moreover, our study highlights that the world's estimated 350 legacy cities are promising urban conservation targets due to their high abundance of vacant greenspace that could accommodate taxa's habitat needs in urban areas.     

Study of lignocellulosic biomass ignition properties estimation from thermogravimetric analysis

In the last decade, the use of renewable resources has increased significantly in order to reduce the energetic dependence on fossil fuels, as they have an important contribution to the global warning and greenhouse gasses effect. Because of that, research on biofuels has been increased in the last years as its characteristics of use match those of the conventional fuel's: solid biomass can be used instead of coals, and biodiesel could replace diesel. Research on solid biomass ignition properties has been considerably developed because of the amount of industrial accidents related to the treatment and use of solid biomass (self-ignition, dust explosions, etc.). On the other hand, thermogravimetric analysis (TGA) is becoming and important characterization technique as it can be used to determine a wide spectrum of properties, such as kinetics, composition, proximate analysis, etc. This research aims to combine thermal analysis and ignition properties, by using the TGA to obtain the elemental composition of lignocellulosic biomass and compare those results to Minimum Ignition Energy (MIE) values test output, so a relation between composition and MIE can be found.To achieve this aim, biomass samples from different origins have been used: oil palm wastes (empty fruit bunches, mesocarp fiber and palm kernel shell), agricultural wastes (straw chops) and forestry wastes (wood chips and wood powder). Also, raw materials and torrefied biomass were compared. The hemicellulose/cellulose ratio was calculated and compared to different flammability properties, finding out that the greater the ratio and the lower the onset temperature (temperature at which the pyrolysis reaction accelerates), the lower was the minimum ignition energy. From this basis it was possible to define “tendency areas” that grouped the samples whose MIE values were similar. Three tendency areas were found: high minimum ignition energy, medium minimum ignition energy, and low ignition energy.     

Molecular composition of recycled organic wastes,as determined by solid-state 13C NMR and elemental analyses

Using solid state ¹³C NMR data and elemental composition in a molecular mixing model, we estimated the molecular components of the organic matter in 16 recycled organic (RO) wastes representative of the major materials generated in the Sydney basin area. Close correspondence was found between the measured NMR signal intensities and those predicted by the model for all RO wastes except for poultry manure char. Molecular nature of the organic matter differed widely between the RO wastes. As a proportion of organic C, carbohydrate C ranged from 0.07 to 0.63, protein C from <0.01 to 0.66, lignin C from <0.01 to 0.31, aliphatic C from 0.09 to 0.73, carbonyl C from 0.02 to 0.23, and char C from 0 to 0.45. This method is considered preferable to techniques involving imprecise extraction methods for RO wastes. Molecular composition data has great potential as a predictor of RO waste soil carbon and nutrient outcomes.     

Implications of different population model structures for management of threatened plants

Population viability analysis (PVA) is a reliable tool for ranking management options for a range of species despite parameter uncertainty. No one has yet investigated whether this holds true for model uncertainty for species with complex life histories and for responses to multiple threats. We tested whether a range of model structures yielded similar rankings of management and threat scenarios for 2 plant species with complex postfire responses. We examined 2 contrasting species from different plant functional types: an obligate seeding shrub and a facultative resprouting shrub. We exposed each to altered fire regimes and an additional, species‐specific threat. Long‐term demographic data sets were used to construct an individual‐based model (IBM), a complex stage‐based model, and a simple matrix model that subsumes all life stages into 2 or 3 stages. Agreement across models was good under some scenarios and poor under others. Results from the simple and complex matrix models were more similar to each other than to the IBM. Results were robust across models when dominant threats are considered but were less so for smaller effects. Robustness also broke down as the scenarios deviated from baseline conditions, likely the result of a number of factors related to the complexity of the species’ life history and how it was represented in a model. Although PVA can be an invaluable tool for integrating data and understanding species’ responses to threats and management strategies, this is best achieved in the context of decision support for adaptive management alongside multiple lines of evidence and expert critique of model construction and output.     

地下工程建筑企业事故统计分析

事故统计分析是企业安全生产管理中的重要部分.讨论了建筑企业生产安全事故统计分析中遇到的事故分类方法,并对事故统计指标作了分析.以广州市某地下工程有限公司2003-2007年间的原始数据资料为例,对企业事故进行了统计分析,最后提出了改进安全管理的几点意见.     

Water saving effect on integrated water resource management

This study proposes an improved integrated water resource management (IWRM), in which water conservation was analyzed for the entire water use process. A multi-objective optimization method was applied to optimize the IWRM, which investigated the reduction of freshwater consumption and the total water supply cost. Customer's preference for saving water and an end use analysis (EUA) was applied in the water conservation analysis. Taking Tianjin as the study area, a reduction in customer's economic pressure (EP) was utilized to evaluate the degree of the customer's preference for saving water. The results revealed that agriculture had a greater preference for saving water than other sectors, where as the public had the weakest motivation for saving water. Improving the transportation method could contribute 62.1% of the total water savings in the agriculture sector. The optimization of the IWRM demonstrated that the local freshwater savings would be 21.5%, and the total cost for water supplies would decrease by 13%. However, a government subsidy of 87.5 million Yuan would be needed. Additionally, by analyzing the change in the amount of water savings affected by water price, the appropriate water price increase range was suggested to be 1.5–1.7 times the original price.