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1.
本文考虑损失函数的估计问题,分别对于球对称分布和均匀分布情形给出了其参数的J-S型估计量的损失之估计,它们满足[1]中提出的条件(Ⅰ)和(Ⅱ).  相似文献   
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Cu@Ag/Bi2Te3 nanocomposites were prepared for the first time by ultrasonic dispersion-rapid freezedrying method combined with spark plasma sintering(SPS).By changing the content of Cu@Ag nanoparticle,we could modulate the temperature dependent thermoelectric properties.The highest ZT value can be obtained at 450 K for 1 vol%Cu@Ag/Bi2Te3,which is benefited from the decoupling of electrical and thermal properties.With the increase of electrical conductivity,the absolute value of Seebeck coefficient lifts while the thermal conductivity declines.Meanwhile,the average ZT value between 300 K and 475 K was 0.61 for 1 vol%Cu@Ag/Bi2Te3,which is much higher than that of pristine Bi2 Te3.Therefore,the decoupling effect of Cu@Ag nanoparticles incorporation could be a promising method to broaden the application of Bi2Te3 based thermoelectric materials.  相似文献   
4.
By using the methods of Picard-Fuchs equation and Riccati equation, we study the upper bound of the number of zeros for Abelian integrals in a kind of quadratic reversible centers of genus one under polynomial perturbations of degree $n$. We obtain that the upper bound is $7[(n-3)/2]+5$ when $n\ge 5$, $8$ when $n=4$, $5$ when $n=3$, $4$ when $n=2$, and $0$ when $n=1$ or $n=0$, which linearly depends on $n$.  相似文献   
5.
本研究采用水热法,以柠檬酸为螯合剂,通过控制n(Sn4+)/n(Sn2+)的数值,合成了由具有丰富氧空位的SnO2纳米晶体组装成的微球。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶红外光谱(FT-IR)、X射线光电子能谱(XPS)及UV-Vis漫反射光谱对SnO2纳米微球进行表征分析,结果表明:在酸性水热条件和柠檬酸的螯合作用下,二氧化锡纳米晶体聚集形成微球;在Sn4+/Sn2+摩尔比例为3:7时,其微球尺寸最小,整体分散性较好;同时适量二价锡离子的掺杂使得该样品氧空位浓度达到最佳,氧空位的存在将使得样品光吸收范围拓展至可见光,因而该样品显示出较强的可见光催化效率,在8 min内完全降解甲基橙。  相似文献   
6.
The corrosion behavior and surface morphology of Ni–SiC composite coatings produced by electrodeposition with the aid of magnetic field were studied. The results of the electrochemical analysis including polarization resistance and potentiodynamic polarization curves showed that a magnetic field of 0.1 T could significantly improve the corrosion resistance of the composite. The electrochemical impedance spectra revealed that a passive layer was formed on the surface of the Ni–SiC coating with the magnetic field. The microstructures of electrodeposited Ni–SiC composite coatings were also examined. More SiC particles were found to be incorporated into the coating with the presence of magnetic field, which was considered to be one of the reasons for the enhancement of corrosion resistance as SiC particles were reported to be corrosion inhibitors. Contribution to special issue “Magnetic field effects in Electrochemistry”  相似文献   
7.
周树兰  赵显  江向平  韩晓东 《结构化学》2012,31(8):1095-1104
The structural,electronic and optical properties of KNbO 3 (KN),NaNbO3(NN)and K05 Na0.5NbO3(KNN) in paraelectric cubic phase were calculated employing the plane-wave pseudopotential method based on density functional theory (DFT).The calculated electronic structures of the three crystals show similar features in the valence bands and the lower conduction bands.However,the structures in higher conduction bands differ markedly due to the effect of Na and K atoms.The calculated optical properties reveal that the features of optical spectrum at low energy are dominated by the transitions from O2p valence bands to Nb 4d conduction bands and those at high energy are related to the transitions to K 4s4p and/or Na 3s3p states.Moreover,the optical constants of KNN are approximately the average of KN and NN at high energy.Therefore,the optical properties of KNN in high energy region can probably be altered by changing the ratio of Na/K.  相似文献   
8.
设X是半自共轭的Banach空间,而A是B(X)的严格循环的交换子代数,考虑算子代数A的一些性质,这些性质与算子代数的自反性有关,而且这些性质为讨论A的自反性提供了理论基础.  相似文献   
9.
利用值分布理论,研究了一类Fermat型复微分-差分方程与复微分-差分方程组,得到有限级超越整函数解的存在条件与具体形式,推广改进了高凌云、刘凯、曾翠萍等人的结果.  相似文献   
10.
成国庆  李玲  唐应辉 《大学数学》2011,27(1):113-117
利用拟生灭过程和矩阵几何解的方法研究了只允许部分服务台异步单重休假的M/M/c排队系统,给出了系统的稳态指标的计算方法和条件随机分解结果,最后指出一些较简单的排队模型是本文的特例.  相似文献   
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