Effect of stress corrosion cracking at various strain rates on the electrochemical corrosion behavior of Mg-Zn-In-Sn alloy

This study is aimed to determine the effect of stress corrosion with low strain rates on the electrochemical properties of alloy electrode. Stress corrosion cracking tests of Mg-Zn-In-Sn alloy in 3.5 wt.% sodium chloride solutions at 25℃ were performed. The effects of the electrochemical properties under the stress corrosion with low strain rates were investigated. The microstructures of cross section were observed by optical microscope. The results showed that the ultimate tensile strengths of Mg-Zn-In-Sn alloy increased and the strain decreased as the strain rates increased. Open circuit potentials (OCP) of Mg-Zn-In-Sn alloy electrode possess stability and the loop currents (LC) were improved with the increasing of stress in the elastic zone. The variation of OCP and LC did not change with the increasing of strain-rate. The microstructure of cross section observing revealed the mechanism of OCP and LC changing.     

基于Gompertz的气象水文装备维修器材消耗量分析与预测

利用由Gompertz曲线推导出的生命周期曲线建立了气象水文装备维修器材消耗-时间模型.计算表明,由Gompertz曲线推导出的生命周期曲线可以较好地反映气象水文装备维修器材消耗量与时间之间的关系,所建模型的预测结果也较好,具有较高的实用性,为探索气象水文装备维修器材消耗规律提供了一种简单有效的科学方法.     

Effect of elevated tropospheric ozone on methane and nitrous oxide emission from rice soil in north India

Physiological changes in crop plants in response to the elevated tropospheric ozone (O₃) may alter N and C cycles in soil. This may also affect the atmosphere-biosphere exchange of radiatively important greenhouse gases (GHGs), e.g. methane (CH₄) and nitrous oxide (N₂O) from soil. A study was carried out during July to November of 2007 and 2008 in the experimental farm of Indian Agricultural Research Institute, New Delhi to assess the effects of elevated tropospheric ozone on methane and nitrous oxide emissions from rice (Oryza sativa L.) soil. Rice crop was grown in open top chambers (OTC) under elevated ozone (EO), non-filtered air (NF), charcoal filtered air (CF) and ambient air (AA). Seasonal mean concentrations of O₃ were 4.3 ± 0.9, 26.2 ± 1.9, 59.1 ± 4.2 and 27.5 ± 2.3 ppb during year 2007 and 5.9 ± 1.1, 37.2 ± 2.5, 69.7 ± 3.9 and 39.2 ± 1.8 ppb during year 2008 for treatments CF, NF, EO and AA, respectively. Cumulative seasonal CH₄ emission reduced by 29.7% and 40.4% under the elevated ozone (EO) compared to the non-filtered air (NF), whereas the emission increased by 21.5% and 16.7% in the charcoal filtered air (CF) in 2007 and 2008, respectively. Cumulative seasonal emission of N₂O ranged from 47.8 mg m⁻² in elevated ozone to 54.6 mg m⁻² in charcoal filtered air in 2007 and from 46.4 to 62.1 mg m⁻² in 2008. Elevated ozone reduced grain yield by 11.3% and 12.4% in 2007 and 2008, respectively. Global warming potential (GWP) per unit of rice yield was the least under elevated ozone levels. Dissolved organic C content of soil was lowest under the elevated ozone treatment. Decrease in availability of substrate i.e., dissolved organic C under elevated ozone resulted in a decline in GHG emissions. Filtration of ozone from ambient air increased grain yield and growth parameters of rice and emission of GHGs.     

嘉山台地电阻率各类变化的判定与分析

本文以嘉山台地电阻率数字化改造后的观测资料为基础,在台址条件、资料质量、干扰因素等方面进行了较为系统的整理,总结了地电阻率观测中的非震现象、典型干扰的变化及影响观测精度的因素,对干扰机制也进行了必要的判断,同时对嘉山台地电阻率的映震效能进行了尝试性的分析,为同类型地电台有效地识别和排除干扰提供参考和借鉴。     

响应突发事件的大型装备应急备件调度模型研究

研究大型装备备件供应网络面临大规模突发事件时的应急备件调度问题。首先采用信息熵理论对应急维修点进行优先度权重排序;其次建立应急响应时间和需求满意度函数,并将量化后的时间满意度和需求满意度以作为模型的目标函数,构建了网络供应状态下应对突发事件的备件调度规划模型;最后以某大型装备企业备件的应急备件调度为例,验证了模型的有效性,给出调度优化方案。     

中国不同发展阶段地区环境可持续性状态与趋势研究

中国不同地区发展水平存在较大的差异．面临的环境问题和可持续发展的优先领域也不同。因此．可持续发展评价与政策制定需要与区域发晨实际相结合。选取上海、德州和固原三个地区作为中国发达、发展中和欠发达地区的代表．选择可操作和可比性强的指标．基子压力-状态-响应模型．构建了环境可持续性趋势系数．对比不同发展水平地区环境发展的状态、趋势和存在的主要问题。得出以下结论：近20年来．虽然中国总体环境保护能力有了一定的提高．但污染物排放压力持续增长．环境质量普遍恶化的趋势没有得到根本改变;上海、德州和固原环境可持续性趋势系数分别为0．82、0．55和0．45．发达地区环境可持续性最强．发展中地区一般．欠发达地区量差;目前我国环境政策领域往往注重经济发展的“两极”：高度发达地区和欠发达地区,本文的研究结果表明。面积占全国67％、人口占全国40％的发展中地区环境问题最为突出。     

广州市不同人群硒摄入量研究

通过酸消解、原子荧光-氢化物发生法测定了广州市市售109种常见食物中硒的含量,结合膳食结构计算了广州市不同人群的每日硒摄入量.结果表明,广州市不同食品硒含量有较大差异,均值为4.97～457.3 μg·kg-1,其中动物性食品硒含量明显高于植物性食品硒含量,硒含量较高的食品有动物内脏、鱼虾类、蛋及蛋制品、猪肉等,均大于150 μg·kg-1.广州市不同人群膳食硒摄入量有明显差别,不同收入人群的摄入量为高收入人群(102.6 μg·d-1)＞中收入人群(83.8 μg·d-1)＞低收入人群(66.6 μg·d-1);老人硒摄入量为73.3 μg·d-1,儿童为44.3 μg·d-1,大学生为86.8 μg·d-1,工人为69.7 μg·d-1;标准人摄入量为98.5 μg·d-1.动物性食品是广州居民硒摄入量的主要来源;其次是大米;蔬菜、水果和豆类及制品等植物性食品贡献很小.广州市不同人群每日硒摄入量处于良好水平.     

板料冲压成形中坯料优化设计方法研究

较为系统地介绍了冲压件坯料的优化设计方法 ,并比较分析了其各自的优缺点。相比于其他方法 ,一步模拟方法效率高、适应面广、功能较强 ,可以在产品的设计之初提供较为丰富的信息。因此 ,对其作了较为详细的论述。实例证明 ,一步模拟法可用于板料成形工艺方案的快速评价及参数优化。     

冲裁零件的交互式几何造型

采用构造体素法(CSG)/边界表示法(Breps)混合式表示模式来完成冲裁零件的几何造型，具有实时显示、高效输入的优点。结合双向循环链表和二叉树这2种数据结构有效表征了包含冲栽件图形几何信息与拓扑信息的数字模型。从而为面向工程的模具CAD／CAPP／CAM集成提供了理论上和技术上的可靠基础。     

盒形件多点常力压边拉深模设计

对盒形件拉深成形 ,提出了在周向多个位置施加压边力的方法 ,且根据常力压边原理 ,用弹簧和橡胶作弹性元件 ,可根据需要在不同位置施加不同的压边力 ,且每个位置的压边力在拉深过程中保持定值。以此设计的模具所提供的压边力 ,更适合复杂零件的成形 ,也更符合拉深工艺对压边力的要求