转轮式洗轮机对车轮带泥的冲洗效果

施工车辆车轮带泥是我国道路扬尘污染控制面临的共性和突出问题。为在国内推广使用洗轮机提供技术依据，通过检测工地出口外道路积尘负荷来估算转轮式洗轮机对车轮带泥的冲洗效率，并以该洗轮机作为车轮带泥检测设备，检测和统计北京市车轮带泥量。结果表明，（1）转轮式洗轮机可以将工地出口外100m道路积尘负荷增量由64．4g／m2降至5．9g／m2，转轮式洗轮机对车轮带泥的冲洗效率大于90％；（2）渣土车和混凝土车车轮带泥量的平均值分别为5．1和2．2kg／车；（3）北京市未来车轮带泥量将超过8．8万t／a，施工车辆全部经过转轮式洗轮机冲洗后，车轮带泥量可削减7．9万t／a。建议在相关法律法规中以强制性条款落实施工车辆车轮带泥机械化冲洗要求。     

Modelling the Choice Between Multiple-Use vs. Specialised Forest Management and its Impact on Forest Management Costs

Forests provide ecosystem services, including timber production. In some cases, private forest owners perform management actions in order to enhance the provision of such services, or they may be encouraged by public policies and payments. This paper focuses specifically on the decision to set forest land aside for biodiversity conservation, as part of the more general question of the efficiency of multiple-use vs. specialised management of forest lands. We propose an econometric analysis to identify factors in the set-aside choice and measure the impact of this decision on forest management costs. The results show that the set-aside choice depends on the landowners’ income and motivations related to forest amenities. The choice of specialised management, as reflected in the set-aside decision, has a significant and positive impact on the intensity of management in the remainder of the forest and on management costs. From a policy implications point of view, these results suggest that instruments such as forest certification, subsidies and reverse auctions for conservation will be most likely to attract the interest of those forest owners with personal motivations and forest properties that offer both benefit and cost advantages in opting for such specialised management strategies.

     

Study on microstructure and extinction characteristics of particulate matter in diesel engine fueled with different biodiesels

Environmental Science and Pollution Research - Biodiesel combustion particulate matter (PM) is different from diesel combustion PM in terms of microscopic morphology, which directly affects the...     

水下连接器试压帽结构动态仿真及密封性分析

为解决水下连接器现有力学模型过于简化，预紧力加载不够合理，密封性能分析结果不够准确的问题，基于ABAQUS有限元模拟提出了新的动态接触分析方法，针对水下连接器试压帽双头螺柱结构，探究了安装和试压工况中该结构形式的密封特性及其与等效拧紧力矩的非线性关联。研究结果表明:在塑性失效设计准则范围内，2种工况下密封环的Mises值最大为399.4 MPa；安装工况下，随预紧力的增加，密封环上、下锥面最大接触应力先增大后略微减小；1 145 Nm螺栓拧紧力矩可完成安装工况，并能在试压工况中保证各部件不被弹开；试压工况下，随试验内压的增加，密封环上锥面最大应力缓慢增加，下锥面最大接触应力几乎不变，最终2值近似相等约为850 MPa，密封宽度合理。     

Changes in biomass activity and characteristics of activated sludge exposed to low ozone dose

In this paper, the response mechanism of activated sludge exposed to low-dose ozone at less than 20 mg O₃ g⁻¹ total suspended solids (TSS) was studied by analyzing the changes in sludge activity and the evolution of C, N, P and metals from sludge following ozonation. The intracellular ATP concentration was not affected at less than 5 mg O₃ g⁻¹ TSS and thereafter decreased rapidly to around 60% when the ozone dose increased to 20 mg O₃ g⁻¹ TSS. Similarly, the efficiency of sludge solubilization initially changed a little and then increased rapidly to around 30% at an ozone dose of 20 mg O₃ g⁻¹ TSS. However, the activities of superoxide dismutase and protease decreased immediately upon exposure to ozone. These findings indicate that ozone firstly destroys the floc, leading to the disruption of the compact aggregates, which does not affect cells viability but induces a decrease in enzyme activities. Ozone then attacks the bacterial cells of the sludge, causing a decrease in cells viability. During ozonation, the content of carbon, nitrogen and phosphorus in the sludge matrix decreased, while the content of these elements in the micro-solids and supernatant gradually increased. Most of the released metals from the sludge matrix were found in the micro-solids.     

航空装备研制风险的综合赋权-双基点法评估

为实现对航空预研项目技术风险的定量评估,建立技术风险评价指标体系,建立基于综合赋权和双基点方法的综合评估模型,采用层次分析法(AHP)求得主观权重,熵值赋权法求得客观权重,运用线性规划方法求得对2类权重加权的权值,构造综合权重;使用正负理想点间的投影距离代替传统的相对欧式距离对TOPSIS方法进行改进;实例分析中,通过对某航空预研项目5种不同的方案进行风险评估,得出各方案的优劣度,选出了较为优化的技术方案,该方法可用于指导其他装备研制风险的评估。     

断路器合闸电阻运行可靠性分析及故障诊断技术研究

合闸电阻作为断路器合闸过程中合闸涌流、操作过电压抑制的重要部件,主要应用在 800kV及以上电压等级输电线路与换流变电站交流滤波器场,其特殊的应用环境导致其故障率较均压电容、支撑绝缘件等其他电气部件高。然而,在合闸电阻日常运维与故障诊断过程中,无相应的标准与系统的方法对其是否存在缺陷以及故障后的故障原因进行分析。 本文首先对合闸电阻特性参数与工作原理进行介绍,之后对串联结构断路器与并联结构断路器分别进行运行可靠性与故障诊断技术研究。提出了动态电阻拟合、声振信号检测、绝缘性能测试、热容量测试等断路器运行过程中合闸电阻状态监测方法,以及基于 ICP的合闸电阻堆拼接、应力特性分析、电场仿真等合闸电阻故障诊断方法,最后通过设备解体验证了所提方法在合闸电阻运行状态检测过程中的可行性。     

不同磷肥对水稻铅积累的影响及其机理

采用盆栽实验,研究外源添加过磷酸钙(SSP)、磷酸二铵(DAP)对于铅胁迫下水稻的生长、铅吸收和铅分布的影响.结果表明:在铅胁迫下,水稻根、茎叶、籽粒的生物量随着两种磷肥浓度的增大而增大,以施加DAP的水稻茎和叶生物量增幅最大,分别增加13.77%和44.17%.水稻体内铅大部分分布在细胞壁中,并随铅浓度的增加,两种磷肥提高了细胞壁对铅的固定能力,有效抑制了水稻对Pb的吸收,Pb在水稻体内的分布表现为根茎叶籽粒,其中SSP的效果大于DAP,施加SSP有效地降低了水稻籽粒Pb的含量.