镍海绵浸渍氧化物阴极在北京质子加速器中的应用和研究

描述了北京质子直线加速器（ＢＰＬ）双等离子体源中使用的一种低加热功率镍海绵浸渍氧化物阴极的结构、底金属表面的海绵化处理以及浸渍涂料的制备方法。介绍了该阴极的激活方法和实验结果。讨论了影响氧化物阴极使用寿命的主要因素。该阴极的使用寿命已达２１１０ｈ，可供引出脉冲束流２００ｍＡ。     

Lifetime determination in delayed-coincidence experiments using the differential decay-curve approach

A new method for the analysis of delayed-coincidence lifetime experiments is proposed following the approach of the Differential decay-curve method. Examples of application of the procedure using simulated and experimental data reveal its reliability for lifetimes in the nanosecond and sub-nanosecond range. The procedure is expected to improve the treatment of systematic errors and scarce data. Possible further expansions and practical aspects of the procedure are also discussed.     

Compensation and doping effects in heavily helium-radiated silicon for power device applications

The formation of defects modifying the effective doping concentration of helium-radiated p⁺-n⁻-n⁺ and p⁺-p⁻-n⁺ silicon diodes is analyzed as a function of the annealing temperature. After irradiation with helium at high energy levels and annealing at 220 °C, the probable formation of divacancy clusters increases the number of charged-acceptor states in a space-charge region. Capacitance-Voltage and Spreading-Resistance Profile measurements show that annealing at 350 °C results in the formation of an acceptor-like defect that deep level transient spectroscopy measurements suggest can be tentatively attributed to the V₂O or V₄/V₅ centre. Annealing at 430 °C results in the disappearance of the acceptor-like defect. Instead, pronounced donor formation in a range close to the penetration depth of the helium ions is observed. The influence of these effects on device characteristics is discussed.     

Recovery of minority carrier lifetime in low-cost multicrystalline silicon

Lifetime of minority carriers has been widely identified to be the key material parameter determining the conversion efficiency of pn-junction silicon solar cells. Impurities and defects in the silicon crystal lattice reduce the charge carrier lifetime and thus limit the performance of the solar cells. Removal of impurities by silicon material purification is often contradictory with low cost production of photovoltaic devices. In this paper, we present experimental results of an efficient gettering technique which can be applied to low cost processing of multicrystalline silicon solar cells without any additional process steps or compromises with optimal device design parameters. This technique is based on well-known phosphorous gettering. We have discovered that if the silicon wafers are kept in the furnace after the emitter diffusion at the 700°C, significant improvement in the lifetime will take place. At this temperature the properties of the pn-junction remain unaffected meanwhile many lifetime killers are still mobile. The time needed for this temperature program can be easily modified in order to respond to the material quality variations in substrates originating from different parts of multicrystalline ingot. Better control of lifetime can lead to higher degree of starting material utilization.     

Round robin on accelerated life testing of solar absorber surface durability

As degradation by ageing of solar absorber surfaces was identified to be an important quality factor, the Working Group MSTC (‘Materials in Solar Thermal Collectors') of the IEA-SHCP (International Energy Agency-Solar Heating and Cooling Programme) worked out a general test procedure for accelerated lifetime testing (ALT) of these materials, based on methods established by the former Task X of the IEA SHCP. The qualification test procedure was adopted by ISO and is presently dealt within ISO/TC 180 ‘Solar Energy'. The standard proposal in detail describes a procedure how to test the long-term stability of an absorber surface for the use in flat plate collectors for domestic hot water systems. The collectors service lifetime is assumed to be 25 years, at least. Degradation caused by thermal loads, high humidity and condensation and sulphur dioxide are regarded. In order to examine the feasibility and reproducibility of the test method the Working Group MSTC initiated a round robin test in accelerated life testing of solar absorber surfaces. The test was performed according to the ISO standard proposal dated January 1997. In total, five different industrially manufactured absorber coatings were available to the three participating laboratories. Tests concerning the thermal stability as well as the resistance to high humidity and condensation were performed by all three laboratories. The test for determining absorber surface corrosion resistance to air of high humidity containing sulphur dioxide was carried out by one lab only. The outcome of the round robin test shows very good agreement of the results of the different coatings tested for all of the laboratories. The feasibility and reproducibility of the method was fully confirmed.     

Heteroleptic iridium (III) complexes with three different ligands: Unusual triplet emitters for light-emitting electrochemical cells

Two cationic iridium (III) complexes [Ir(dfppy)(tpy)(bpy)](PF₆) and [Ir(dfppy)(tpy)(phen)](PF₆) bearing three different ligands were tested as triplet emitters for Light-Emitting Electrochemical Cells (LECs). These two phosphorescent materials only constitute the third and fourth examples of triple heteroleptic cationic iridium complexes to be tested in electroluminescent devices. LECs fabricated with this almost unknown class of iridium complex furnished green-emitting devices. Parallel to investigations devoted to electroluminescent properties, photophysical and electrochemical properties of the two new complexes were examined. Density functional theory calculations were also performed to provide insight into the electronic structure of the two emitters.     

00Crl8Nil0N奥氏体不锈钢200 - 600℃高温疲劳性能的研究

试验用00Cr18Ni10N钢（/%:0.018C,0.41Si,1.68Mn,18.18Cr,10.38Ni,0.16N）经1t EAF-AOD-ESR冶炼,锻成Φ30 mm材和1 050℃固溶处理,进行了00Cr18Ni10N钢200～600℃光滑（K_t=1）、缺口（K_t=3）的轴向高周疲劳性能研究,绘制了疲劳S-N曲线、计算了疲劳极限,并对疲劳试样的典型断口进行了SEM观察。结果表明,光滑试样的疲劳极限随试验温度升高而降低,缺口试样的疲劳极限对试验温度变化不敏感。当应力集中系数由K_t=1提高到K_t=3时,00Cr18Ni10N钢的200、400、600℃下10⁷周次条件疲劳极限分别从530、506、410 MPa,降低到323、370、392 MPa。表明在高温下00Cr18Ni10N钢存在疲劳极限对应力集中敏感,且应力集中敏感性随着试验温度的升高而降低。疲劳试样的断口形貌由疲劳源区、疲劳裂纹扩展区和瞬断区组成,疲劳起源于表面加工刀痕的不连续位置,呈韧性断裂特征。     

无线传感器网络分簇路由协议的改进研究

针对无线传感器网络(WSN)中分簇路由协议LEACH算法中簇首分配不均以及簇首与Sink节点直接通信问题进行研究,提出一种基于LEACH成簇思想的分簇路由协议。该算法基于节点剩余能耗和已担任簇首时间选举簇头。簇头间采用贪婪算法形成一条链,在该链中又选出一个簇头,将整个网络的数据融合后转发给基站。MatLab仿真结果显示,改进后的算法在均衡网络节点能耗和网络的生存时间上比LEACH算法有很大提高。     

Influence diagnostics in log-Birnbaum-Saunders regression models with censored data

In this paper we discuss log-Birnbaum-Saunders regression models with censored observations. This kind of model has been largely applied to study material lifetime subject to failure or stress. The score functions and observed Fisher information matrix are given as well as the process for estimating the regression coefficients and shape parameter is discussed. The normal curvatures of local influence are derived under various perturbation schemes and two deviance-type residuals are proposed to assess departures from the log-Birnbaum-Saunders error assumption as well as to detect outlying observations. Finally, a data set from the medical area is analyzed under log-Birnbaum-Saunders regression models. A diagnostic analysis is performed in order to select an appropriate model.     

Improving the estimation of Kendall's tau when censoring affects only one of the variables

This paper considers the estimation of Kendall's tau for bivariate data (X,Y) when only Y is subject to right-censoring. Although τ is estimable under weak regularity conditions, the estimators proposed by Brown et al. [1974. Nonparametric tests of independence for censored data, with applications to heart transplant studies. Reliability and Biometry, 327-354], Weier and Basu [1980. An investigation of Kendall's τ modified for censored data with applications. J. Statist. Plann. Inference 4, 381-390] and Oakes [1982. A concordance test for independence in the presence of censoring. Biometrics 38, 451-455], which are standard in this context, fail to be consistent when τ≠0 because they only use information from the marginal distributions. An exception is the renormalized estimator of Oakes [2006. On consistency of Kendall's tau under censoring. Technical Report, Department of Biostatistics and Computational Biology, University of Rochester, Rochester, NY], whose consistency has been established for all possible values of τ, but only in the context of the gamma frailty model. Wang and Wells [2000. Estimation of Kendall's tau under censoring. Statist. Sinica 10, 1199-1215] were the first to propose an estimator which accounts for joint information. Four more are developed here: the first three extend the methods of Brown et al. [1974. Nonparametric tests of independence for censored data, with applications to heart transplant studies. Reliability and Biometry, 327-354], Weier and Basu [1980, An investigation of Kendall's τ modified for censored data with applications. J. Statist. Plann. Inference 4, 381-390] and Oakes [1982, A concordance test for independence in the presence of censoring. Biometrics 38, 451-455] to account for information provided by X, while the fourth estimator inverts an estimation of Pr(Y_i?y|X_i=x_i,Y_i>c_i) to get an imputation of the value of Y_i censored at C_i=c_i. Following Lim [2006. Permutation procedures with censored data. Comput. Statist. Data Anal. 50, 332-345], a nonparametric estimator is also considered which averages the obtained from a large number of possible configurations of the observed data (X₁,Z₁),…,(X_n,Z_n), where Z_i=min(Y_i,C_i). Simulations are presented which compare these various estimators of Kendall's tau. An illustration involving the well-known Stanford heart transplant data is also presented.