三元Ag-Pd-Pt团簇结构优化

改进了用于模拟二元金属团簇稳定结构的自适应免疫优化算法（称为Tri-AIOA）,并将其应用于三元金属Ag-Pd-Pt团簇的结构优化。对原子数为19的Ag-Pd-Pt团簇的优化结果表明,Tri-AIOA具有较强的优化能力和效率。该方法也被用于模拟原子数为55的Ag_nPd₄₃Pt₁₂（n=1-42）团簇稳定结构,优化结果被分为27个Mackay二十面体结构、4个五折叠饼状结构、以及11个由3个双二十面体面面相连构成的环状结构。优化结果为Ag-Pd-Pt团簇的性质研究提供了理论依据。     

基于簇结构的负载平衡模型—簇平衡

文中针对当前大型的工作站网络环境，提出了一种基于层次式簇组组结构的负载平衡模型ＬＯＢＡＣ。     

一种利用MS软件计算纳米金属团簇熔点的新方法——定向相关函数综合判断法

到目前为止,所报道的利用分子动力学方法计算纳米金属团簇的熔点多采用的是某些特定的软件,这给该领域的研究推广带来了一些不便。MS(Materials Studio)软件是一种通用的商业化软件,已被许多高校和研究机构所使用。利用MS软件计算纳米团簇的熔点,一般采用的是径向分布函数法,判据不够充分。本课题组在前期工作的基础上经摸索发现,定向相关函数随温度变化曲线在熔点附近出现明显的波动,再结合能量温度曲线以及径向分布函数曲线,可以方便地计算出纳米团簇的熔点范围,计算结果与文献经验式计算结果基本一致。本文简要报道了以直径2.12和2.73nm银纳米团簇为例进行研究的结果,希望能和同行们一起分享这种新方法。     

双簇结构DSP的数据Cache优化

数字信号处理常常包含大量数据运算,这使得数据Cache成为影响其性能的关键因素。特别是对于我们研制的双簇VLIW结构YHFrDSP系列处理器,Cache的失效会导致整个内核八条流水线同时停顿。所以,减小Cache失效延迟能给处理器性能带来显著的提升。本文研究的主要问题是如何针对一级数据Cache的读失效操作进行优化,从四个方面进行, 分别为提前发读请求、请求字优先、合并并行失效读和后台处理Snooping。模拟结果表明,采用这些优化措施后,处理器的性能提高了8．36％。     

长期施肥对土壤腐殖质组成的影响

利用微区 (1m2 ) 16年定位试验研究了不同施肥措施在相同气候条件、轮作制度及相同管理措施下对山东省三大主要土类———棕壤、潮土、褐土腐殖质组成的影响。结果表明长期施用化肥可使三种土壤腐殖质各组分积累 ;氮钾肥提高了土壤腐殖酸碳与有机碳的比值 ,降低腐殖酸活性 (提高HA/FA比值 ) ;与单施化肥比较 ,化肥配施有机肥大幅度增加了土壤胡敏素和腐殖酸数量 ,并降低了土壤胡敏素和腐殖酸的比值     

钯栅厚度对气敏MOS晶体管灵敏度的影响

本文介绍了一种Pd栅MOS结构的半导体气敏器件。在叙述Pd栅MOS晶体管气敏机理的基础上,着重讨论了钯栅厚度对器件灵敏度的影响。实验结果证明,Pd栅MOS晶体管的灵敏度随着钯栅厚度的增加而降低。在工作温度不太高的条件下,灵敏度随钯栅厚度的变化基本上不受温度的影响。另外,文中还扼要地阐述了钯栅M0S晶体管的结构、制造技术及器件灵敏度的测试原理和方法。研究结果对于MOS结构的半导体气敏传感器的研制具有重要的意义。     

组合对Ag-Rh双金属团簇熔化行为的影响

采用分子动力学方法,模拟研究了6种不同组合、具有正十面体壳对称构型、原子总数为魔幻数(309)的Ag-Rh双金属团簇的熔化过程。研究金属原子间作用力采用Sutton-Chen多体作用势能模型,初始构象取自半巨正则系综Monte Carlo模拟结果。通过分析模拟所得到的平均单原子势能Ua和等容热容Cv与温度的关系,得出各团簇的熔点,还发现Ag-Rh双金属团簇熔点与团簇中Ag原子数的增加呈近似线性相关。     

基于囊状银钯铂合金的无标记型癌胚抗原免疫传感器的研制

该文将所合成的中空囊状银钯铂合金和壳聚糖（CHIT）修饰于玻碳电极（GCE）表面,利用中空囊状银钯铂合金比表面积大、反应活性位点多、导电能力良好、催化性能优异和吸附能力强等优点将癌胚抗原的抗体（anti-CEA）固定到电极表面,从而制得高灵敏的无标记型癌胚抗原（CEA）免疫传感器。当抗体与抗原发生免疫反应形成复合物时,会降低银钯铂合金的电催化活性并增加传质阻力。采用示差脉冲伏安法（DPV）检测电化学探针铁氰化钾的响应电流信号的减小程度,实现对CEA的检测。实验考察了电极表面的电化学行为,并对免疫传感器的性能进行了研究。在最优的实验条件下检测癌胚抗原的线性范围为0.5-80.0 ng/mL,线性相关系数为0.989 0,检测下限为0.17 ng/mL。     

分簇拓扑结构的水情无线传感器网络

针对水情无线传感器的立体空间中的网络分布问题,建立了无线网络数学模型;基于数学模型中节点与节点间的能量扩散模式,利用该模型研究网络中节点数据传输的能量消耗形式,计算出基于本节点能量消耗模型的LEACH算法所要推举最佳簇头个数;通过分析LEACH算法,提出在水情监测环境立体空间中分布节点且节点所储存能量不同情况下LEACH改进算法,采用轮循机制分别在不同能量储备节点中推举簇头,稳定阶段各个簇头采用星型拓扑与汇聚节点进行数据通信,簇成员与簇头进行数据传输;最后,利用MATLAB对改进算法进行了仿真,结果说明改进后的算法使网络所消耗的能量均匀地分布到各个网络节点上,可以可靠地应用到实际水情监测环境中。     

Metal (Pd, Pt)-decorated carbon nanotubes for CO and NO sensing

Using the first-principles calculations, we investigated adsorption of CO and NO gas molecules on the Pd- and Pt-decorated single-walled carbon nanotube (SWNT). The metal-decorated SWNTs exhibit strong affinity toward the gas molecules. Our results reveal that the CO and NO gas molecules can be chemisorbed on the Pd or Pt atom, accompanying with the large binding energy and significant charge transfer. Adsorption of these gases would affect the electronic conductance of the materials, which can serve as a signal of gas sensor. In particular, adsorption of NO generates the magnetic properties to the metal-decorated SWNT, which can also serve as a sensitive signal for chemical sensors. After adsorption of CO and NO, the changes in binding energy, charge transfer and conductance may lead to the different response in the metal-doped CNT-based sensors. It is expected that these results could provide helpful information for the design and fabrication of the CO and NO sensing devices.     

Sensor properties and surface characterization of the metal-deposited SPR optical fiber sensors with Au,Ag, Cu,and Al

Metal-deposited optical fiber sensors with Cu and Al with a film thickness of 45 nm based on surface plasmon resonance (SPR) were fabricated for the first time. The response curves and the properties of these sensors were investigated with a comparison of those of the sensors with Au and Ag. The reflection properties of thin films of Au, Ag, Cu, and Al due to the SPR phenomenon were also measured and considered. The metal-deposited SPR optical fiber sensors with Au, Ag, and Cu have high sensitivities and good responses. Though the sensor with Al shows a lower sensitivity, it has a wider response range in the refractivity. The response curve of the sensor with Au calculated from SPR theoretical equations agreed well with that obtained by the experiment. However, the response curves of the sensors with Ag, Cu, and Al have the effects of the surface oxide layers. The surface characterization of these metal films by X-ray photoelectron spectroscopy (XPS) showed the presence of oxide layers on the films of Ag, Cu, and Al. A very thin (about 0.3 nm) oxide layer is present on Ag, while thick (about 2 nm) oxide layers are present on Cu and Al.     

Adhesive properties study on the interfaces of AlN and metal of Pd,Ag and Cu

AlN is used as high power LED package material because of its excellent thermal conductivity. But its poor adhesive with metal is not compatible with the later processing sequence. The properties of the bonding between the deposited palladium,silver,copper and the clean Al-terminated (0001) surface of wurtzite AlN are investigated by using the density-functional theory. The results show that the sites of deposited metal atoms on N site are more stable than that on Al site. Relaxations are found at all the s...     

(C_2H)_2M_n(M=Cu、Ag、Au;n=1-4)团簇的密度泛函理论研究

采用密度泛函理论的B3LYP和PBEIPBE方法,对(C_2H)_2M_n(M=Cu、Ag、Au;n=1-4)团簇的结构和性质进行了研究。结果表明:(C_2H)_2M_n(M=Cu、Ag、Au;n=1-4)簇的最稳定结构都是在C_2HM_n(M=Cu、Ag、Au;n=1-4)簇最稳定结构的基础上,又与C_2H自由基相互作用的结果。NBO计算结果表明:银与2个C_2H自由基的相互作用弱于铜和金。(C_2H)_2M_n(M=Cu、Ag、Au;n=1-4)簇最稳定结构的相互作用能均为负值,表明形成的团簇较稳定,并且出现了奇-偶振荡效应(n=1-4),含偶数个IB原子的团簇比含奇数个IB原子的团簇稳定。红外分析表明:(C_2H)_2M_n(M=Cu、Ag、Au;n=1-4)团簇中C_2H自由基的C≡C和C-H键的伸缩振动都发生了红移,随着团簇尺寸的增加(n=1-4),也出现了奇-偶振荡效应。     

(OsB)_n(n=1-6)团簇结构与稳定性的第一性原理研究

基于第一性原理,采用密度泛函理论(DFT)中的广义梯度近似(GGA)对(OsB)_n(n=1-6)团簇各种可能的构型进行了几何结构优化,得出了各团簇的最稳定构型,并对最稳定构型的能量、结合能、二阶能量差分、能隙等性质进行了理论研究。研究结果表明:n=2、3时,体系的基态结构分别为棱形和锅盖形;n=4时,体系的基态结构是对称性为T_d的立方体形状,是本文对称性最高的构型;从n=4开始立方体构型主导着团簇基态结构的生长行为,表明团簇的稳定性不仅与团簇的尺寸大小有关,还与团簇的对称性有关。团簇(OsB)_4的能隙、结合能与能量的二阶差分比邻近的值都大,说明团簇(OsB)_4有较高的稳定性,n=4是团簇的幻数。     

解析金和铂的流动注射-化学发光动力学曲线的研究

本文结合中国地质调查项目,用本实验室编制的自学习人工神经网络解析金和铂的流动注射-化学发光法动力学曲线,提出了一种不需要分离、在线、灵敏地同时测定痕量金和铂的方法。以Luminol-H2O2作化学发光试剂,用阳离子交换树脂在线吸附大多数金属离子的干扰,用EDTA作掩蔽剂消除残余的干扰元素。方法可以校正部分实验误差,对金和铂的模拟混合样品的浓度预测,分析结果的相对误差≤20％。     

Design and performances of immunoassay based on SPR biosensor with Au/Ag alloy nanocomposites

A novel method for detecting human IgG is reported, which is based on Au/Ag alloy nanocomposites for amplifying surface plasmon resonance response. Au/Ag alloy nanocomposites were characterized in detail by transmission electron microscopy (TEM), UV-vis absorption spectroscopy and X-ray photoelectron spectroscopy (XPS). Covalent immobilization of about 24 nm diameter of Au/Ag alloy nanocomposites on the Au film results in a large shift in resonance wavelength, which is due to the increase of the thickness of the sensing membrane, high dielectric constant of Au/Ag nanoparticles, and electromagnetic coupling between Au/Ag alloy nanocomposites and Au film. The SPR biosensor based on Au/Ag alloy nanocomposites exhibits a satisfactory response for human IgG in the concentration range of 0.15-40.00 μg mL⁻¹. While the biosensor based on Au nanoparticles shows a response in the concentration range of 0.30-20.00 μg mL⁻¹ and the biosensor based on Au film shows a response for human IgG in the concentration range of 1.25-20.00 μg mL⁻¹.     

Characterization of porous cubic silicon carbide deposited with Pd and Pt nanoparticles as a hydrogen sensor

Porous 3C-SiC (pSiC) samples with different pore diameters were prepared from polycrystalline n-type 3C-SiC films by electrochemical anodization using a mixture of HF and ethanol as the electrolyte solution. The pSiC surface was chemically modified via the sputtering of Pd and Pt nanoparticles as a hydrogen catalyst. Changes in the resistance were monitored with respect to hydrogen concentrations in the range of 110-410 ppm. The variations in the electrical resistance at the presence of nitrogen diluted with hydrogen demonstrated that Pd and Pt-deposited pSiC samples have the ability to detect hydrogen. Regardless of the catalyst, the 25 nm pore diameter samples exhibited better response and recovery properties than the 60 nm pore diameter samples. It was found that the pore size affects the catalyst reaction and results in changes in the response factor to hydrogen. A large change in resistivity was observed with the Pd catalyst and the hydrogen sensing performance improved at high temperatures.     

Comparison between calculated and measured thermodynamic data of liquid (Ag, Au, Cu)-Sn-Zn alloys

The activity of zinc was measured in a series of liquid alloys in the three ternary systems, Ag-Sn-Zn [94Kar], Au-Sn-Zn [96Kar] and Cu-Sn-Zn [97Pen], with an emf (electromotive for e) method. From these measurements and the slope of the emf vs. temperature (dE/dT) all thermodynamic properties were derived. The experimental values were compared with calculated results. For these calculations four different models were applied and the thermodynamic data of the binary systems, obtained from the literature, were used.     

The effect of cluster size, dimensionality, and the number of clusters on recovery of true cluster structure

An evaluation of four clustering methods and four external criterion measures was conducted with respect to the effect of the number of clusters, dimensionality, and relative cluster sizes on the recovery of true cluster structure. The four methods were the single link, complete link, group average (UPGMA), and Ward's minimum variance algorithms. The results indicated that the four criterion measures were generally consistent with each other, of which two highly similar pairs were identified. The tirst pair consisted of the Rand and corrected Rand statistics, and the second pair was the Jaccard and the Fowlkes and Mallows indexes. With respect to the methods, recovery was found to improve as the number of clusters increased and as the number of dimensions increased. The relative cluster size factor produced differential performance effects, with Ward's procedure providing the best recovery when the clusters were of equal size. The group average method gave equivalent or better recovery when the clusters were of unequal size.