Dynamic propagation velocity of a positive streamer in a 3 m air gap under lightning impulse voltage

Streamers represent an important stage in the initiation of gap discharge. In this work, we used an eight-frame intensified charge-coupled device camera to capture the streamer development process when a lightning impulse voltage of 95%–100% U50% was applied in a 3 m rod–plate gap and the streamer velocity was analyzed. Analysis of the observations shows that streamer velocity can be defined by three stages: rapid velocity decline(stage 1), rapid velocity rise(stage 2)and slow velocity decline(stage 3). The effects of electrode shape, applied voltage and gap breakdown or withstanding on streamer velocity were analyzed. The electrode with a larger radius of curvature will result in a higher initial velocity, and a higher voltage amplitude will cause the streamer to propagate faster at stage 3. Gap withstanding or breakdown has no obvious effect on streamer velocity. In addition, the experimental results are compared with previous results and the statistical characteristics of the primary streamer discharge are discussed.

IGF-ⅠR抑制剂联合西妥昔单抗对人肝癌细胞的体外抑制作用

目的探讨西妥昔单抗与胰岛素样生长因子-Ⅰ受体（IGF-ⅠR）抑制剂aIR3对人肝癌细胞株HepG2细胞的作用。方法选用浓度递增的西妥昔单抗（5-500）mg／mL和aIR3（2．5～250．0）μmol／L，单独或联合作用于HepG2细胞，观察不同时间对细胞增殖的抑制作用以及联用时的两药协同系数。结果单药西妥昔单抗与aIR3对HepG2细胞增殖的抑制作用均呈浓度依赖性与时间依赖性，二药单独作用于HepG2细胞72h最大抑制率分别为42．2％、82．3％，二药联合作用于HepG2细胞72h最大抑制率达91．8％。西妥昔单抗与aIR3不同浓度在各时间点的协同系数均小于1。结论西妥昔单抗和aIR3在体外对HepG2细胞的增殖均具有一定的抑制作用，联合应用时具有明显的协同效应。

土壤气抽提多井方案的数值模拟研究

以存在石油烃污染的北京市某加油站场地为研究对象，设计了土壤气抽提（SⅦ）原位修复系统，应用A1R3D软件对SVE作用下土壤包气带的气压场进行数值模拟,划定以土壤气压强低于或等于101．122kPa的区域为抽气影响区域．模拟结果显示，单井的抽气影响区域不能满足要求；多井抽气时，井间区域土壤气体真空度受多井共同作用，扩大了抽气的影响区域．抽气井不同布置情况下井间距大小对相互作用效果存在影响．研究发现。井间相互作用随着井间距的增大而减小，井间距存在临界值．井间距临界值与抽气井的布置形式相关．对于本研究中的2眼井、3眼井、4眼井情景，此临界值分别在3-5m、5-8m、8-10m区间．超过此临界值时井间相互作用将显著减弱，并导致抽气影响区域不能覆盖整个井间范围．

Ziegler-Natta催化配位聚合反应中AlR_3组分对催化剂活性影响的理论研究

本文采用ASED-MO法对Ziegler-Natta型催化剂催化的α-烯烃聚合过程中AlR_3组分对催化剂活性的影响进行了研究.得到了无AlR_3组分存在和一系列不同AlR_3存在时链增长过程的能量变化和相应的活化能.通过比较看出,AlR_3存在可以明显增强催化剂活性.同时运用分子轨道分析的方法探讨了AlR_3增强催化活性的原因.

烷基铝残液焚烧炉设计与烟气治理

针对烷基铝残液焚烧的烟气特征，分析某烯烃厂焚烧炉燃烧工况及烟气温度、烟气含湿量与风机风量、压头之间关系，专门设计一整套烷基铝残液焚烧和烟气治理系统。

Surface magnetization of siderite mineral

Surface self-magnetization of siderite is achieved by generating ferromagnetic substance on the surface of siderite by adjusting slurry temperature,pH value,stirring rate and reaction time.No addition of any iron-containing reagent is required.The temperature of 60 ℃,NaOH concentration of 0.10 mol/L;stirring rate of 900 r/min and the reaction time of 10 min are the optimal conditions.The results show that the siderite recovery in magnetic separation increased from 26.9% to 88.8% after surface magnetization.Magnetization kinetic equation is expressed as 1 [1(e0.269)]1/3 = Kt.Activation energy for the magnetization reaction is 4.30 kJ/mol.VSM,SEM and XPS were used to characterize the siderite,and results show that the saturated magnetization(rs) of siderite increased from 0.652 to 2.569Am2 /kg,the magnetic hysteresis was detected with a coercive force of 0.976 A/m after magnetization;Fe2P3/2 electron binding energy changed which reflects the valence alteration in iron on the surface and the formation of ferromagnetic Fe3O4.

CES Attended the 3rd China International Air Service Exhibition and Won Good Remarks

Bao peide,Deputy Director of CAAC and other leaders,together with Chen Xiaoning,Director of CAAC Policy Research Office,Chen Haiju,Director General of CAAC Air Administrative Bureau,Deng Youchi,General Manager of CAAC Advertising Company_2 Visiting the CES area in the exhibition hall.Ye Yiagan,President of Eastern Air Group Company and Chairman of CES co.,Ltd.,arraying the exhibition affairs.

Sourcing the merits of 3D integrated air cathodes for highperformance Zn-air batteries by bubble pump consumption chronoamperometry

Zn-air batteries(ZABs)as a potential energy conversion system suffer from low power density(typically≤200 mW·cm^(−2)).Recently,three-dimensional(3D)integrated air cathodes have demonstrated promising performance over traditional twodimensional(2D)plane ones,which is ascribed to enriched active sites and enhanced diffusion,but without experimental evidence.Herein,we applied a bubble pump consumption chronoamperometry(BPCC)method to quantitatively identify the gas diffusion coefficient(D)and effective catalytic sites density(ρEC)of the integrated air cathodes for ZABs.Furthermore,the D andρEC values can instruct consequent optimization on the growth of Co embedded N-doped carbon nanotubes(CoNCNTs)on carbon fiber paper(CFP)and aerophilicity tuning,giving 4 times D and 1.3 timesρEC over the conventional 2D Pt/C-CFP counterparts.As a result,using the CoNCNTs with half-wave potential of merely 0.78 V vs.RHE(Pt/C:0.89 V vs.RHE),the superaerophilic CoNCNTs-CFP cathode-based ZABs exhibited a superior peak power density of 245 mW·cm^(−2) over traditional 2D Pt/C-CFP counterparts,breaking the threshold of 200 mW·cm^(−2).This work reveals the intrinsic feature of the 3D integrated air cathodes by yielding exact D andρEC values,and demonstrates the feasibility of BPCC method for the optimization of integrated electrodes,bypassing trial-and-error strategy.

Synergistic impacts of anthropogenic and biogenic emissions on summer surface O_3 in East Asia

A factor separation technique and an improved regional air quality model （RAQM） were applied to calculate synergistic contributions of anthropogenic volatile organic compounds （AVOCs）,biogenic volatile organic compounds （BVOCs） and nitrogen oxides （NOx） to daily maximum surface O3（O3DM） concentrations in East Asia in summer （June to August 2000）.The summer averaged synergistic impacts of AVOCs and NOx are dominant in most areas of North China,with a maximum of 60 ppbv,while those of BVOCs and NOx are notable only in some limited areas with high BVOC emissions in South China,with a maximum of 25 ppbv.This result implies that BVOCs contribute much less to summer averaged O3DM concentrations than AVOCs in most areas of East Asia at a coarse spatial resolution （1×1） although global emissions of BVOCs are much greater than those of AVOCs.Daily maximum total contributions of BVOCs can approach 20 ppbv in North China,but they can reach 40 ppbv in South China,approaching or exceeding those in some developed countries in Europe and North America.BVOC emissions in such special areas should be considered when O3 control measures are taken.Synergistic contributions among AVOCs,BVOCs and NOx significantly enhance O3 concentrations in the Beijing-Tianjin-Tangshan region and decrease them in some areas in South China.Thus,the total contributions of BVOCs to O3DM vary significantly from day to day and from location to location.This result suggests that O3 control measures obtained from episodic studies could be limited for long-term applications.

Effect of TiO_2 calcination temperature on the photocatalytic oxidation of gaseous NH_3

Carbon-modified titanium dioxide （TiO2） was prepared by a sol-gel method using tetrabutyl titanate as precursor, with calcination at various temperatures, and tested for the photocatalytic oxidation （PCO） of gaseous NH3 under visible and UV light. The test results showed that no samples had visible light activity, while the TiO2 calcined at 400℃ had the best UV light activity among the series of catalysts, and was even much better than the commercial catalyst P25. The catalysts were then characterized by X-ray diffractometry, Brunauer-Emmett-Teller adsorption analysis, Raman spectroscopy, thermogravimetry/differential scanning calorimetry coupled with mass spectrometry, ultraviolet-visible diffuse reflectance spectra, photoluminescence spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy. It was shown that the carbon species residuals on the catalyst surfaces induced the visible light adsorption of the samples calcined in the low temperature range （〈 300℃）. However, the surface acid sites played a determining role in the PCO of NH3 under visible and UV light over the series of catalysts. Although the samples calcined at low temperatures had very high SSA, good crystallinity, strong visible light absorption and also low PL emission intensity, they showed very low PCO activity due to their very low number of acid sites for NH3 adsorption and activation. The TiO2 sample calcined at 400℃ contained the highest number of acid sites among the series of catalysts, therefore showing the highest performance for the PCO of NH3 under UV light.

Simulation of Unsteady State Performance of a Secondary Air System by the 1D-3D-Structure Coupled Method

This paper describes the calculation method for unsteady state conditions in the secondary air systems in gas turbines. The 1D-3D-Structure coupled method was applied. A 1D code was used to model the standard components that have typical geometric characteristics. Their flow and heat transfer were described by empirical correlations based on experimental data or CFD calculations. A 3D code was used to model the non-standard components that cannot be described by typical geometric languages, while a finite element analysis was carried out to compute the structural deformation and heat conduction at certain important positions. These codes were coupled through their interfaces. Thus, the changes in heat transfer and structure and their interactions caused by exterior disturbances can be reflected. The results of the coupling method in an unsteady state showed an apparent deviation from the existing data, while the results in the steady state were highly consistent with the existing data. The difference in the results in the unsteady state was caused primarily by structural deformation that cannot be predicted by the 1D method. Thus, in order to obtain the unsteady state performance of a secondary air system more accurately and efficiently, the 1D-3D-Structure coupled method should be used.