基于水足迹理论与物元分析法的水资源紧缺度分析

针对国内水资源紧缺现状,基于水足迹理论建立了水资源紧缺度评价指标,分析确定了相应的评价标准,采用物元分析法对水资源紧缺度进行了量化计算。以江苏省为例绘出了2005~2009年间水足迹评价指标变化的折线图,计算分析了各年的综合关联度,得出了江苏省的水资源紧缺程度,从降低水足迹角度提出了应对水紧缺状态的建议。     

Experimental investigation of bubble behaviors in subcooled flow boiling

The experimental investigation on vapor bubble growth is performed for analyzing subcooled boiling in a vertical annular channel with inner heating surface and upward water flow under atmospheric pressure. Bulk liquid mass flux ranges from 79 kg/m2s to 316 kg/m2s, and subcooling is from 40 K to 60 K. The bubble behaviors from inception to collapse are captured by High-speed photography. The performance of bubble growth recorded by the high-speed photography is given in this paper. The bubble behaviors, effect of the bubble slippage on the heat transfer, and various forces acting on the bubble are discussed.     

An Investigation on Temperature Distribution Within the Substrate and Nozzle Wall in Cold Spraying by Numerical and Experimental Methods

During cold spraying (CS), heat exchange between the hot driving gas and the solid bodies, e.g., spray nozzle and substrate, results in the temperature redistribution within the solid bodies. In this study, numerical and experimental investigations on the heating behavior of the substrate and nozzle wall were conducted to clarify the temperature distribution within the solid bodies in CS. The results show that after heating by the hot gas, the highest temperature presents at the center point of the substrate and decreases toward the substrate back surface and edge. With increasing standoff distance or decreasing inlet temperature, the substrate temperature decreases gradually, but the temperature gradient within the substrate changes little. The numerical results are consistent with the experimental measurements. Besides, it is also found that increasing the substrate size (diameter) can lead to the gradual increment in the substrate temperature. Moreover, the numerical study on the temperature distribution within the nozzle wall reveals that the highest temperature presents at the throat section of the nozzle and that the nozzle material significantly affects the temperature distribution within the nozzle wall.     

俄罗斯天然气工业股份公司的地位及发展战略研究

俄罗斯的天然气储量和产量均位居世界前列,而俄罗斯天然气工业股份公司2011年公布的储量为35.05×1012m3,约占全俄储量的78%;产量为5132×108m3,约占全俄产量的77%。俄气还控制着世界最大的天然气管道运输网络,独家垄断全俄天然气出口经营权,甚至影响着俄天然气工业政策制订到执行的每一个环节。俄气公司还拥有大规模的电力、传媒、金融等资产,同时还经营着航空和铁路运输、无线通讯、IT等业务。由于俄气公司在俄罗斯政治经济生活中的重要地位,使之成为国内经济的晴雨表,更是成为俄罗斯内政外交和能源政治中的重要工具。虽然近年俄气面临诸多挑战,但未能从根本上动摇其在国内外天然气市场的地位。俄气公司未来的发展战略,一是继续强化行业领袖和垄断出口商地位,并扩大综合影响力。为此,2011年俄气公司资本投入达到13277亿卢布,继2010年大幅提高40%之后再次同比提高50.3%。二是以强硬姿态扩大世界天然气市场份额,增量不减价。力求西方市场稳中有升,维持垄断供应商地位;在亚太市场实现突破,获取10%～15%的市场份额;同时遏制中亚国家的出口独立。我国石油企业与俄气公司开展合作,其实质是与俄罗斯国家层面的经济和能源战略的合作。要从更高层面深入分析俄气公司所处的市场地位和战略得失,同时从更广阔和长远的角度考虑我国经济和能源发展状况,寻找相应的对策。     

An electrochemical immunosensor based on chemical assembly of vertically aligned carbon nanotubes on carbon substrates for direct detection of the pesticide endosulfan in environmental water

A glassy carbon substrate was covalently modified with a mixed layer of 4-aminophenyl and phenyl via in situ electrografting of their aryldiazonium salts in acidic solutions. Single-walled carbon nanotubes (SWNTs) were covalently and vertically anchored on the electrode surface via the formation of amide bonds from the reaction between the amines located on the modified substrate and the carboxylic groups at the ends of the nanotubes. Ferrocenedimethylamine (FDMA) was subsequently attached to the ends of SWNTs through amide bonding followed by the attachment of an epitope, i.e., endosulfan hapten to which an antibody would bind. Association or dissociation of the antibody with the sensing interface causes a modulation of the ferrocene electrochemistry. Antibody-complexed electrodes were exposed to samples containing spiked endosulfan (unbound target analyte) in environment water and interrogated using the square wave voltammetry (SWV) technique. The modified sensing surfaces were characterized by atomic force microscopy, XPS, and electrochemistry. The fabricated electrochemical immunosensor can be successfully used for the detection of endosulfan over the range of 0.01-20 ppb by a displacement assay. The lowest detection limit of this immunosensor is 0.01 ppb endosulfan in 50 mM phosphate buffer at pH 7.0.     

灰铁基Cr-n-Al_2O_3复合电刷镀层的性能

采用电刷镀在灰口铸铁表面制备了n-Al2O3掺杂的Cr基复合镀层。通过X射线衍射仪(XRD)、扫描电镜(SEM)、扫描电子显微镜附带能谱仪(EDS)等技术对镀层的晶粒尺寸、截面与表面形貌及n-Al2O3在镀层中的分布进行了表征。此外,利用显微硬度计、磨损试验机、电化学工作站等仪器对镀层的硬度、耐磨性、抗腐蚀性等进行了测试。结果表明:Cr-n-Al2O3复合镀层组织致密无明显缺陷,n-Al2O3均匀地弥散分布于镀层表面;在纳米粒子的弥散强化及细晶强化作用下,复合镀层的硬度相对于纯Cr镀层提高了42.8%,耐磨性也有所提高;此外,n-Al2O3的加入也改善了镀层的耐腐蚀性能。     

A Novel and Highly Efficient Photocatalyst Based on P25–Graphdiyne Nanocomposite

Titania nanoparticles (P25) are successfully chemically bonded with graphdiyne (GD) nanosheets by a facile hydrothermal treatment, to form a novel nanocomposite photocatalyst. The as‐prepared P25–GD nanocomposite exhibits higher photocatalytic activity for degrading methylene blue under UV irradiation than not only P25 and P25–carbon nanotube composite but also the current well‐known P25–graphene composite photocatalysts. Moreover, P25–GD also shows considerable visible‐light‐driven photocatalytic activity, since the formation of chemical bonds between P25 and GD effectively decreases the bandgap of P25 and extends its absorbable light range. The photocatalytic activity of P25–GD can be adjusted by changing the content of GD in composites and the optimized value is about 0.6 wt%. Such a nanocomposite photocatalyst might find potential application in a wide range of fields including air purification and waste water treatment.     

一种谐振式露点测量方法

针对大气湿度测量问题,提出一种基于谐振式的露点测量方法,并设计了一套独立的露点传感装置.利用QCM原理将石英晶体谐振器作为湿敏元件,用半导体制冷器对其进行制冷,使其表面出现结露现象,导致石英晶体谐振器的谐振频率出现突变,以此达到对露点的识别,同时测取结露时刻石英晶体表面的温度,从而获得当前环境下的露点温度.通过实验验证了此方法的可行性与准确性,并将获取的实验数据与实际提供的环境数据进行对比分析,相对湿度误差达到±1.37%RH,此方法具有精度和灵敏度双高的优点,并且成本低、可操作性强.     

PEG-based bioresponsive hydrogels with redox-mediated formation and degradation

A hydrogel which will undergo macroscopic transition responding to redox stimuli is prepared. Mercapto precursors are prepared from 4-armed polyethylene glycol and after deprotection of thiolate anions, they can transform into disulfide crosslinked hydrogels within 3 min by responding to oxidant H₂O₂. Desirable elasticity is exhibited with a wide range of storage modulus from 50 Pa to 14 kPa through rheological investigation. In addition, the hydrogels are found to be hydrolytically stable but degrade within 75 days when exposed to reductant such as glutathione (GSH). So gelation time and degradation behavior can be regulated by concentrations of precursor, oxidant, reductant, temperature, and pH value. Notably, interest arises from the long-period degradation under low GSH concentration of 0.01 mM that is similar to extracellular level, but not the fast disintegration under high concentration intracellular, providing the possibility of “smart” degradation responding to those cell-secreted biomacromolecules during the process of tissue regeneration. Furthermore, both hydrogels and their degradation products show cell viability above 90% culturing with C2C12 cells, representing nontoxic properties. Such a stimuli-responsive degradation strategy will give promising application in tissue repair and regeneration; especially enable the achievement of matching the degradation kinetics with physiological environment.     

CNTs增强Cr基复合电刷镀层的性能

以45号钢为基体,采用电刷镀制备了Cr-CNTs复合镀层。通过X射线衍射仪(XRD)、扫描电镜(SEM)、扫描电子显微镜附带能谱仪(EDS)等技术对镀层的晶粒尺寸,截面与表面形貌及CNTs在镀层表面的分布进行了表征。此外,利用显微硬度计、电化学工作站、磨损试验机等仪器对镀层的硬度、抗腐蚀性、耐磨性等进行了测试。研究结果表明:Cr-CNTs复合镀层组织致密无明显缺陷,CNTs弥散分布于镀层中,在胞状组织的交界处出现了富集;适量CNTs的加入在一定程度上细化了镀层的晶粒;在CNTs弥散强化和细晶强化等作用下,复合镀层的硬度提高了23.8%,腐蚀速率降低了49.2%,而且耐磨性能也得到了显著的改善。