Mineralogical characteristics and photocatalytic properties of natural sphalerite from China

Different natural sphalerites have a range of photocatalytic properties that can potentially be exploited for environmental remediation purposes. To develop value in the exploitation of sphalerite, samples were collected from 19 ore deposits in China and characterized for their mineralogical and photocatalytic properties. X-ray diffraction (XRD) and electron probe micro analysis (EPMA) measurements indicated that all the natural sphalerites from various localities crystallized in cubic phases with various chemical compositions. The substitution of Fe for Zn ranged from 0.235% to 14.826% by weight, Mn from 0.004% to 4.868%, Cu from 0.009% to 5.529% and Cd from 0.133% to 1.576%. As Fe became more abundant, the color of natural sphalerite darkened, becoming almost black; and higher Fe content was associated with stronger visible light absorption. Photoluminescence spectra showed emission mainly related to S-vacancies and progressively decreasing fluorescence intensity with increasing Fe content. Tests of the photocatalytic degradation of methyl orange indicated that the sample with the highest Cd content but moderate Fe content had the highest photocatalytic activity. Specifically, the degradation of Methyl Orange (30 mg/L) attained 82.11% efficiency under visible light irradiation for 4 hr of natural sphalerite with 4.262% Fe and 1.576% Cd. Overall, the Fe content in sphalerite was found to contribute to the visible light absorption ability and the recombination rate of photo-generated electrons and holes, while substitution by Cd was observed to have a greater effect on the photocatalytic properties. These findings provide a scientific basis for the profitable utilization of base metal resources like sphalerite.     

地级市域工业VOCs排放源产排特性及其控制技术应用现状:以秦皇岛市为例

对秦皇岛市609家工业企业VOCs的源排放和污染控制技术做了调研.结果表明,VOCs排放源排放的气体流量以石油加工、炼焦和核燃料加工业最高(105m3·h-1).其余行业主要集中在103~105m3·h-1之间.各行业源排放的VOCs浓度均小于1 000 mg·m-3,各行业的VOCs排放速率差异性较大,介于50~10 000 g·h-1之间.其中交通运输设备制造业、石油加工、炼焦和核燃料加工业、机械设备制造业、印刷和记录媒介复制业及化学原料和化学制品制造业的排放浓度和排放速率均较高.和国内之前的调查研究相比,秦皇岛市工业企业VOCs的排放水平相对较低.此次调研的609家工业企业中拥有VOCs处理设施的案例共109个.吸附技术应用的占比最大(69%).其次为吸收技术(19%).     

凤眼莲、稻草和污泥制备生物炭的特性表征与环境影响解析

有机废弃物限氧热解制备生物炭可在减缓温室气体排放的同时改善土壤和水体环境质量,但同时生物炭在环境中的应用具有潜在生态毒理风险.因此,在将生物炭大规模应用于各类环境介质前,对其关键物理-化学性质进行系统分析与评价是极为必要的.本文选择对我国水生生态环境危害最大的入侵植物凤眼莲(Eichhornia crassipes)和我国产量最高的农业废弃物稻草,以及市政污水处理厂剩余污泥3种生物质前体,于250~550℃进行低温慢热解,对所制备生物炭的表面形貌、元素组成、矿物形态和一系列关键化学特性进行了全面表征与比较分析.在此基础上,深入探讨了此3类生物炭应用于土壤改良、重金属污染修复和水体富营养化控制的潜力与风险.结果表明,凤眼莲生物炭中K、Ca、Na、Mg含量最为丰富,指示其对于缓解土壤酸化具有重要应用价值,而其中P主要以AlPO_4晶体态存在,水溶性较低,这有利于降低此类生物炭引起水体富营养化的风险;水稻秸秆生物炭阳离子交换量(CEC)相对较高,达到33.7 cmol·kg~(-1),表明其在提高土壤保肥能力和降低重金属生物有效性方面具有较大潜力;SEM-EDX显示,凤眼莲生物炭和稻草秸秆生物炭均具有发达的束筒结构,可优先考虑用于改善土壤通气性;但是,部分生物炭中水溶性Cd、As含量超出安全阈值,表明对有机质前体和热解产物进行严格检测和筛选是实现生物炭在环境与农业中安全利用的必要环节.     

深溪沟电站大坝强震监测系统设计及应用

强震监测是大坝安全监测的重要内容之一,强震监测成果对大坝的安全性和稳定性分析有重要作用。本文根据水电站枢纽工程实际对深溪沟水库大坝强震监测系统设计开展研究,并对仪器的性能指标和数据采集处理分析软件进行了全面阐述。通过深溪沟水电站建设大坝强震监测系统的运行实践,大坝强震监测系统可以在地震发生后短时间内自动获取强震动加速度记录,储存地震波数据,并显示大坝坝体各测点的地震反应过程。强震监测结果进一步验证了设计烈度,为判定震后大坝安全性提供了支持。     

关于未来中国劳动力是否短缺的一个证明

迅速发生的人口转变现象对未来中国社会的各个方面影响深远,经济增长同样受到人口转变的影响.本文以1978-2004年为样本区间.按照2010、2020、2030年劳动力人口预测数,对未来经济增长的4种路径分别进行模拟.通过分析中国经济增长模式和内在源泉.我们发现在未来很长一段时间内,全要素生产率代表的技术进步、劳动力受教育水平的提高和制度变迁等其他因素,都会降低人口转变对未来经济增长可能的影响.由人口转变导致的劳动年龄人口减少不太可能对中国未来年均经济增长7.2%的目标构成较大瓶颈.而有可能的瓶颈应该是资本存羹能否继续维持目前这种高速增长、低效利用的状态.在未来的经济增长中,我们急需改变对资本投入的过度依赖.发挥技术进步和制度改革的力量,以减缓外部冲击对宏观经济的整体影响.     

Performance Enhancement of a Beta Type Rhombic Drive Stirling engine

ABSTRACT

Stirling engines maintain attraction because of their high energy conversion efficiencies. In this study, experimental comparison of a beta-type Stirling engine for two different rhombic-drive mechanisms was presented. In one of the rhombic mechanisms, spur gears were used and the gear shaft was supported in bearings from one side. In the other mechanism, two helical gears were placed on crankshafts and the crankshafts were supported in bearings from both sides. Rhombus lengths of the mechanisms were determined as 66 mm and 80 mm to provide same constant compression ratio of 2.5 for both configurations. Both mechanisms were used in the same beta-type Stirling engine having same cylinder, piston and displacer dimensions. Performance parameters of the engines were evaluated at different helium charge pressures (2–4 bar) and hot-end temperatures (400–600°C). The hot-end of the displacer cylinder was heated by a liquefied petroleum gas (LPG) burner. The engine power increased by 132%, friction losses and gear noses were reduced by supporting the rhombic-drive mechanism from both side and using helical gears. The maximum output torque and power of the engine were obtained as 13.14 Nm at 428 rpm engine speed and 663 W at 800 rpm engine speed, respectively, at 600°C hot-end temperature and 4 bar charge pressure.     

对用近因原则处理工伤认定的思考

近因原则是商业保险中用于区分保险责任和非保险责任的一个被普遍认可的工作原则,工伤认定是确认是否进行工伤保险金给付的前提。针对目前中国工伤认定相关法律不健全的现状,笔者首次提出在工伤认定有关规定的列举法空白处,使用近因原则的建议。有益于完善工伤认定工作。通过分析我国工伤认定有关规定的历史沿革与现行做法,指出现行工伤认定规定不合理之处,如列举未尽的弹性处理不利于员工、严苛的免责条款不利于雇主、雇员野蛮操作零成本降低社会福利,应用近因原则处理过劳死、未经归类的职业病两个案例,弥补现行工伤认定立法缺陷,实践证明,工伤认定中使用近因原则是可行的、合理的、实用的。