加强电力需求侧管理的探讨

在目前电力供需严重不平衡的形势下，要加强需求侧管理工作，制定切实可行的峰谷电价措施，并实施科学避峰错峰和计划用电方案，全面落实不同供电能力和负荷水平下的有序用电方案和各项措施，对政府、电力企业或电力用户都是有益的，可以取得多赢的效果。     

工程结算中常见问题及对策建议

阐述工程承包方在工程结算中常遇到的一些问题,在调查研究及分析问题产生原因的基础上,就如何解决工程结算中的问题提出对策与建议。     

Seat tightness of pneumatic cryogenic control valve

Pneumatic cryogenic control valves(PCCV)are designed to meet the special requirements for the large cryogenic helium refrigeration system.Polychlorotrifluoroethylene(PCTFE)is adopted as the flat seal material of the valve seat.The leakage rates and compressive strain of the PCTFE gasket with different sealing stress are tested at both room temperature(293 K)and liquid nitrogen temperature(77 K).After 300 open/close cycles,the experimental results show that the sealing properties of the PCTFE gasket are improved.The leakage rates are about 10-8(293 K)and 10-4(77 K)Pam3 s-1 respectively.Finally,the effects of working pressure on sealing characteristics are discussed.The working pressure has little effect on compressive strain but it has a great influence on leakage rate.The leakage rate is linear with the working pressure of inlet at room temperature,but at liquid nitrogen temperature the leakage rate is linear with the square of the working pressure.     

变频器在电线电缆收线机械电控系统中的应用

本文分析了变频器内置PID调节器的闭环反馈系统的工作原理，应用于电线电缆收线张力恒定系统，配合主从传动点的主从应用宏，达到调节加工速度和张力恒定的要求。     

Mg-4Zn-0.5Er-1Y镁合金板材的组织与力学性能

研究了Mg-4Zn-0.5Er-1Y变形合金轧制板材在经200～380℃,保温0.5～4h退火处理后,合金显微组织的演变及其力学性能的变化规律。结果表明,该合金退火后均出现明显的动态再结晶组织,且晶粒比较细小,基体中存在大量含有稀土元素的第二相,这些第二相在热轧状态下破碎成细小的颗粒,促进了动态再结晶晶粒的异质形核。合金退火处理后的强度较原轧制态降低,但塑性却得到明显的改善。最佳退火温度为350℃,保温0.5h后晶粒尺寸约为8μm,抗拉强度为276MPa,伸长率达到最大为22.5%。经过计算可知,该合金再结晶晶界迁移激活能为22.76kJ/mol,同时建立了该合金再结晶晶粒长大的动力学模型。     

Application of phosphate-containing materials affects bioavailability of rare earth elements and bacterial community in soils

The exploitation and smelting of rare earths can cause serious pollution to the farmland around the mining area. The rare earth elements(REEs) are absorbed by crops and enter the human body through the food chain, which threatens people's health. The effects of four phosphorus-containing materials-calcium superphosphate(SSP), phosphate rock(PR), calcium magnesium phosphate(CMP) and bone charcoal(BC) on rice growth and bacterial community structure in REE mining area of Xinfeng County were studied by pot experiment. The soil solution was collected during rice transplanting and harvest periods respectively, the rice and soil samples were collected and sequenced. The concentrations of water-soluble REEs were measured by inductively coupled plasma mass spectrometry(ICP-MS), and bacteria in soil was deeply sequenced by the Illumina Miseq sequencing platform. PR, CMP and BC promoted the growth of rice, improved the biomass of rice roots, shoots and grains, and significantly reduced absorption and accumulation of REEs in rice roots, shoots and grains. SSP treatment reduced the pH value of soil, significantly improved the concentration of REE solution in soil and improved biomass of rice roots, shoots and grains,and significantly improved the concentration of REEs in grain. The effects of phosphorus-containing materials on the absorption and accumulation of 15 REEs in rice roots, shoots and grains were very different, and significantly influenced the soil bacterial community. SSP reduced richness and diversity of bacteria. CMP improved the diversity of soil bacteria, but reduced their richness. PR and BC treatment improved the richness and diversity of soil bacteria, and significantly increased the abundance of Bacillus. The results showed that adding PR, CMP and BC to soil in the REE mining area of Xinfeng can improve food security and eco-environmental quality, and hence, are potential restorative materials; SSP is not recommended for use in acidic soils.     

绿色施工的节材措施探析

绿色施工是对传统施工方式的改进和革新,也是转变经济发展方式的必然。节约材料是绿色施工实现资源节约的核心,在施工过程中,实现材料节约不仅仅是节约材料,从某种方式上也节约了能源、水资源、土地资源,因此要高度重视材料节约,实现项目经济效益和社会效益的最大化。     

贵阳市GPS连续运行参考站选址分析及经验

介绍了贵阳市GPS连续运行参考站的选址情况及对选址环境测试效果进行分析,确定贵阳市GPS连续运行参考站网建站点,保证贵阳市GPS连续运行参考站网建设的顺利实施。探讨城市GPS连续运行参考站选址中的问题和经验。     

Elucidating the operating behavior of PEM fuel cell with nickel foam as cathode flow field

Metal foam material, which serves as an alternative replacement of the conventional flow distributor of proton exchange membrane(PEM) fuel cell, has been attracting much attention over last few decades. In this work, three-dimensional modeling work for PEM fuel cell containing metal foam as cathode flow distributor has been carried out. The fuel cell performance and operating characteristics of metal foam flow field and conventional parallel flow channel have been compared and discussed.The cell performance has been reasonably validated based on the corresponding experimental tests conducted in this study. The superior performance of PEM fuel cell with metal foam as cathode flow field benefits a lot from the uniform gas flow. The porous metal foam material provides more pathways for the water delivery at the interface of metal foam flow field and gas diffusion layer(GDL), accelerating water removal capability of cathode. Because of the significant oxygen transfer loss in diffusion limited parallel channel, the operation of PEM fuel cell with parallel channel is found to be more sensitive to cathode humidification and oxygen supply at inlet. Due to the more uniform and effective electron transport though the porous electrode, it is possible to use thinner GDL in metal foam PEM fuel cell. It is expected that this study could give a good baseline of operating behavior of PEM fuel cell with metal foam flow distributor.