生物锰氧化物对4种重金属的吸附特性研究

通过培养锰氧化细菌Sphingopyxis sp.4-15,制备生物锰氧化物,研究了生物锰氧化物的结构性质及其在不同影响因素下对4种重金属Cu、Zn、Cr和As的吸附特性。结果表明该生物锰氧化物中含有MnO₂、Mn₃O₄和MnO等晶体锰氧化物,包裹在菌体细胞表面呈现出规则的花球状。其锰主要以高价态的Mn⁴⁺和Mn³⁺形式存在,平均孔径为35.56 nm,比表面积为41.49 m²/g。锰氧化物对重金属的吸附过程受pH值影响,最适pH值为4~6;离子强度对吸附过程干扰较小;升高温度有利于其对Cu和Zn的吸附,而对As的吸附产生抑制;锰氧化物对Cu(Ⅱ)、Zn(Ⅱ)、As(Ⅲ)的吸附在反应360 min时可达到平衡,对Cr(Ⅲ)的吸附在反应5 min内达到平衡;在4种重金属最大初始浓度下,生物锰氧化物对Cu(Ⅱ)、Zn(Ⅱ)、Cr(Ⅲ)、As(Ⅲ)的吸附量依次为:70.184、15.140、9.141、0.089 mg/g,具有较大的重金属吸附容量。     

基于SEM的城市突发事件现场应急指挥能力影响因素分析

为提升城市突发事件现场应急指挥能力,通过分析城市现场应急指挥能力影响因素,构建城市现场应急指挥能力影响因素与突发事件应急指挥效果结构方程模型,并采用SPSS和AMOS软件对北京市现场应急指挥能力进行研究。结果表明:应急指挥统筹决策对应急指挥能力影响相对较大,应急指挥对象影响相对较小;应急指挥体系建设对应急指挥统筹决策影响相对最大,其次是应急信息平台系统。城市应综合考虑各因素间相关关系,有针对性地提高应急指挥能力。     

华北地下水超采区农户节水灌溉技术认知分析——以河北省张家口市沽源县为例

目前我国华北地区面临严重的地下水超采问题,在地下水超采综合治理行动方案中明确提出要加强农业节水,调整农业种植结构。农户节水灌溉技术认知与农业节水效果密不可分,本文以河北省张家口市沽源县269份农户调查为样本,采用结构方程模型探索农户节水灌溉技术认知的内在机理。结果显示：农户个人特征、家庭生产特征、政策宣传特征和农户水资源稀缺性认知的路径系数分别为0.186、0.157、0.469和0.200。表明节水灌溉技术补助、培训和参观高效节水示范区对提升农户节水灌溉技术认知的效果显著。因此,在依靠政府技术资金支持的基础上,发现农户节水灌溉技术认知差异,制定完善的节水灌溉技术宣传推广体系,有利于提高华北地区农户采用节水灌溉技术的积极性。     

黄土丘陵区侵蚀坡面CO2通量空间分异格局驱动机制

以黄土丘陵区不同有机碳水平的完整侵蚀坡面为对象,解析了CO₂通量的空间分异格局驱动因子及过程机制,并构建了CO₂通量的分段测算模型.结果表明：（1）侵蚀导致坡面土壤CO₂通量的空间分异格局,具体表现为沉积区（S）>对照区（CK）>侵蚀区（E）;有机碳水平的提高可以整体促进各部位CO₂通量的增加.（2）侵蚀可导致土壤水分、容重和团聚体稳定性降低,引起土壤养分流失,降低细菌、真菌多样性;沉积则引起相反的现象.侵蚀/沉积过程对土壤温度的影响并不显著.有机碳水平的增加可以有效改善土壤颗粒、土壤水分,增加容重,抑制土壤养分的流失、增加细菌,降低真菌多样性.（3）结构方程模型解析了侵蚀部位、土壤温度、土壤水分、有机碳（SOC）、水溶性碳（DOC）、微生物碳（SMBC）、真菌多样性、细菌多样性对于CO₂通量的多因素耦合驱动机制（R²=77%）,明确了土壤温度、土壤水分、微生物碳为CO₂通量的直接影响因子.在水热双因子模型的基础上,嵌入能够间接表征微生物活性和有效碳底物的C因子,分段（按照坡面侵蚀部位）建立T&M&C模型,可以较为准确地测算侵蚀坡面不同部位CO₂通量（R²>67%）.     

市场一体化的工业污染排放机制:长江经济带例证

采用长江经济带2003~2015年105个城市面板数据,利用动态面板系统GMM方法探讨了市场一体化影响长江经济带工业二氧化硫、工业烟尘以及工业废水的实证结果及中间机制.研究表明：长江经济带各类工业污染物排放都具有动态累积效应以及存在路径依赖问题,市场规模加剧了工业污染排放,第三产业结构比例以及技术水平的提升则降低了各类工业污染排放水平,市场一体化存在影响各类工业污染物排放的规模、结构与技术传导路径.具体地,全样本中,市场一体化对各类工业污染排放物都具有技术中介效应,对于除工业烟尘之外的其他工业污染物排放具有市场规模中介效应,但第三产业结构中介效应不显著;分析区域异质性可知,与中下游地区相比,长江经济带上游地区市场一体化水平偏低,导致其对技术进步的促进不显著,缺乏影响各类工业污染物排放的技术中介效应,另外市场一体化对各地区工业烟尘的排放都具有一定的显著中介效应,至少能够从规模、结构以及技术进步层面找到一条显著的传导路径.本文推测,市场一体化对工业污染排放的影响可能受到了经济发展阶段、地区企业所有权属性、产业结构以及交通基础设施建设等潜在因素影响,而且工业烟尘排放量较大的行业是未来降低长江经济带工业污染排放的政策重点.     

一种新型电磁抛投器仿真设计分析

抛投器广泛应用于多种救援场合,目前抛投器的动力主要有气动式和火药式两种。本文首先介绍了目前抛投器发展现状,根据现有抛投器的技术参数,提出了一种采用电磁力给抛投器提供动力的新方式。接着综合分析三种电磁发射方法,选取线圈型电磁发射方式,根据异步感应式直线电机基本原理和有限元电磁场数值计算理论,利用COMSOL Multiphysics软件建立电磁抛投器结构图和有限元仿真模型,对这种新型电磁抛投器不同抛体金属套材料和不同初、次级空气长度这两个重要结构参数进行仿真分析对比,给电磁抛投器选择了一组优化的结构参数。     

基于三维动力学模型及试验数据重用技术的全箭模态分析

目的在运载火箭设计过程中,获得精确的全箭模态数据,为火箭总体设计提供关键输入参数。方法针对全箭动特性数据的高效高精度获取问题,提出并实践基于三维动力学模型和试验数据重用相结合的模态参数获取方法,包括高精度全箭三维动力学模型建模技术、数据重用技术、多状态模型修正技术、模型综合技术。结果解决了界面连接刚度未知条件下的全箭模态精确预示难题。在设计阶段给出了高精度的动特性数据,分析结果与靶场试验结果比对,一阶弯曲频率误差在2%以内,斜率误差在4%以内,分析结果通过了靶场竖立模态试验验证,最后进一步通过型号首飞成功验证。结论靶场竖立模态试验验证和型号首飞成功验证说明提出的获取全箭动特性参数方法高效可靠。     

Linkages between measures of biodiversity and community resilience in Pacific Island agroforests

Designing agroecosystems that are compatible with the conservation of biodiversity is a top conservation priority. However, the social variables that drive native biodiversity conservation in these systems are poorly understood. We devised a new approach to identify social–ecological linkages that affect conservation outcomes in agroecosystems and in social‐ecological systems more broadly. We focused on coastal agroforests in Fiji, which, like agroforests across other small Pacific Islands, are critical to food security, contain much of the country's remaining lowland forests, and have rapidly declining levels of native biodiversity. We tested the relationships among social variables and native tree species richness in agroforests with structural equation models. The models were built with data from ecological and social surveys in 100 agroforests and associated households. The agroforests hosted 95 native tree species of which almost one‐third were endemic. Fifty‐eight percent of farms had at least one species considered threatened at the national or international level. The best‐fit structural equation model (R² = 47.8%) showed that social variables important for community resilience—local ecological knowledge, social network connectivity, and livelihood diversity—had direct and indirect positive effects on native tree species richness. Cash‐crop intensification, a driver of biodiversity loss elsewhere, did not negatively affect native tree richness within parcels. Joining efforts to build community resilience, specifically by increasing livelihood diversity, local ecological knowledge, and social network connectivity, may help conservation agencies conserve the rapidly declining biodiversity in the region.     

Study on leak-acoustics generation mechanism for natural gas pipelines

In order to figure out the principles of acoustic leak detection for natural gas pipelines, a study on the leak-acoustics generation mechanism is carried out. The aero-acoustics generation mechanism is analyzed and when leakage occurs the wave equations of sonic sources are developed. The leak-acoustics generated by the quadrupole and dipole sonic sources are then simulated to obtain the laws of the acoustic characteristics. The simulation data are compared with the experimental data to verify the simulation accuracy under variable operating conditions. The results show that the quadrupoles and the dipoles generated by turbulent fluctuations cause leak-acoustics; the main component of pressure perturbations acquired by the dynamic pressure sensor is acoustic perturbations; both the simulation method and the experimental method can be applied to study the leak-acoustics generation mechanism of natural gas pipelines.     

Enhancing Avifauna in Commercial Plantations

Abstract:  The occurrence of fauna in commercial plantations is often associated with structural complexity. Through a meta-analysis, we tested whether the structural complexity of plantations could enhance bird species assemblages and whether bird assemblages respond differently depending on taxonomic affiliation, body size, and diet. Our analyses included 167 case studies in 31 countries in which bird assemblages in forests and plantations were compared and 42 case studies in 14 countries in which bird assemblages in plantations of different structural complexity were compared. Species richness, but not abundance, was higher in forests than in plantations. Both species richness and abundance were significantly higher in complex than in structurally simple plantations. Taxonomic representation and body size did not differ between forest and plantations, except that there were fewer insectivorous birds in plantations than in forests. In the comparison of simple versus complex plantations, abundance of all taxonomic and dietary groups was higher in complex plantations. Body size did not affect bird species richness or abundance. Independent of the type of plantation, bird richness and abundance were greater in structurally complex plantations. Enhancing the structural complexity of plantations may mitigate their impact and offer habitat for some native species.