六极装置电场分布及对CH3Cl分子束选态会聚的模拟

通过数值获得的六极装置内部电势分布数值解,拟合得出电势分布公式中的系数,给出各项系数随着装置参数ρ0/r0的变化规律及拟合函数形式,结果表明ρ0/r0=0.5516时,六极装置的电场分布最接近理想六极电场. 对于其它ρ0/r0值时,推导出电势、电场更精确的计算公式. 并利用这些公式,在ρ0/r0不满足最优配置时给出了对CH3Cl分子转动态的会聚所需的实验参数. 这些方法为利用六极装置对分子束会聚和转动态选择的理论模拟及试验提供了更准确的理论依据.     

三维荧光与紫外光谱联合表征样品中猝灭剂赋存状态:以胡敏酸与Fe(Ⅲ)相互作用为例

利用三维荧光-紫外光谱表征了荧光猝灭剂的赋存状态,当样品体系中存在Fe(Ⅲ)的情况下,胡敏酸会发生荧光猝灭现象,而其紫外光谱基本不受影响。考察了胡敏酸荧光强度I值(Ex/Em=300 nm/510nm)和紫外吸光度A值(UV300)的变化,I/A比值越小,说明水样中猝灭剂Fe(Ⅲ)浓度越高。当胡敏酸为10,15和20 mg·L~(-1)时,根据Stern-Volmer公式I/I_0=1-f_c×K_c×[c]/(1+K_c×[c])以及拟合函数I/A=f×[k/(CFe~(3+)+c)+b],拟合得到荧光猝灭常数K_c=1.08~1.15,比例系数f_c=1.10~1.14之间,胡敏酸荧光强度值与吸光度比值(I/A)及铁离子浓度(C_(Fe~(3+))相关曲线系数f=0.83~1.19,k=587.19~612.19,c=0.87~0.92,b=-87.09~-46.36,拟合曲线相关性R~2均为0.99。Stern-Volmer公式描述了Fe(Ⅲ)对胡敏酸荧光的猝灭作用,但实际样品测定时难以获得无猝灭剂时的荧光强度I_0。基于荧光强度I_0与紫外吸光度A之间的内在联系,两者比值I/A与Fe(Ⅲ)浓度c的拟合函数亦可以反映Fe(Ⅲ)对胡敏酸荧光的影响。利用拟合公式预测城市污水厂及纳污河流样品的树脂分离富集液中铁离子浓度,与电感耦合等离子体发射光谱仪实际测量值相比,铁离子浓度较高的情况下(铁离子浓度大于0.4 mg·L~(-1)时)预测结果较好,可以判断猝灭剂的存在及相应浓度。     

McMillan Tc公式的解析推导(Ⅰ)——μ*=0情形

作者在μ^*=0情形,从Eliashberg方程解析地导出如下的T_c公式:T_c=αω_logexp{-b((1+cλ)/λ)},式中α=2γ/π,b=c=1;Inγ=C=0.5772是Euler常数。这个T_c公式只有在T_c=0.36/α(k)以下才是正确的,α是个大于1并随材料而异的常数。我们推测,当T_c超过上述范围后,T_c公式的函数结构很可能不同于McMillan T_c公式,至少α,b和c等参量不再是些不依赖于材料的常数了。 关键词：     

McMillan T_c公式的解析推导(Ⅰ)μ~*=0情形

作者在μ~*=0情形,从Eliashberg方程解析地导出如下的T_c公式: T_c=αω_(10g)exp{-b(1 cλ/λ)}式中α=2γ/π,b=c=1;Inγ=C=0.5772是Euler常数。 这个T_c公式只有在T_c=0.36/α(k)以下才是正确的,α是个大于1并随材料而异的常数。我们推测,当T_c超过上述范围后,T_c公式的函数结构很可能不同于McMillanT_c公式,至少α,b和c等参量不再是些不依赖于材料的常数了。     

三胶子张量算符反常量纲的计算

计算了两个与量子数为J^PC=1^－+的胶球流算符密切相关的三胶子张量算符Ωαβ1=Gαa,μ Gμb,ν Gνβc f_abc和Ωαβ2=gαβ Gσa,μ Gμb,ν Gνc,σ f_abc的重整化矩阵和反常量纲矩阵.     

Al的微观组态与LaNi3.75Al1.25的结构和弹性第一性原理研究

在全电子水平上,采用广义梯度近似密度泛函理论和全势能线性缀加平面波方法并结合二维立方拟合方法,对LaNi3.75Al1.25合金的晶体结构与弹性性质进行了理论研究.计算结果给出合金的晶格常数a=b=0.5137 nm,c=0.4018 nm,Al原子在晶胞中的微观分布为同时占据部分3g和2c等价格位,弹性常数C11+C12=281.2,C13=82.3,C33=227.3,以及体弹性模量B＝124.5、切变模量G＝68.2 GPa.还对态密度、能带结构和电荷密度进行了计算分析,并给出材料LaNi3.75Al1.25的电子线性比热系数23.45 mJ/molK2.     

N(4S)+CH3X(X=Cl、Br)反应机理的理论研究

利用abinitio方法对N(4S)+CH3X(X=Cl、Br)反应进行了理论研究,在MP2/6311+G(d,p)水平上优化得到了反应途径上的反应物、过渡态和产物的几何构型和谐振频率,在MP2/6311++G(3df,2p)和QCISD(T)/6311+G(d,p)水平上进行单点能计算,并用G2MP2方法计算了所有物种的能量.计算结果表明,反应存在三条反应通道:H抽提反应通道a、Cl或Br抽提反应通道b和替代反应通道c.对于N(4S)+CH3Cl反应,a反应通道是主反应通道,b和c反应通道在反应中有少量贡献.对于N(4S)+CH3Br反应,a反应通道是主反应通道,b和c反应通道在反应中有一定的贡献.     

硼组分在BaAl2Si2O8:Eu2+发光材料中的作用

采用高温固相法在弱还原气氛下制备Ba0.955Al2-xBxSi2O8:Eu2+(x=0～0.5)系列荧光粉,研究B3+置换Al3对晶体结构和光谱特性的影响.B3+以类质同相替代BaAl2Si2O8晶格中的Al3+形成部分连续固溶体,随着B3+置换量的增加,晶胞参数a,b,c和晶胞体积V呈线性递减,晶面夹角β呈线性递增.荧光激发光谱位于225～400 nm的宽带谱可拟合成4个峰,表观峰值位于337nm,半峰全宽为96 nm.荧光发射光谱位于370～600nm,可由423 nm和457nm两峰拟合而成,表观峰值位于437nm,两拟合峰峰位均随着B3+置换量的增加呈线性蓝移.     

考虑界面接触热阻的一维复合结构的热整流机理

建立了考虑变截面、变热导率及界面接触热阻效应的组合热整流结构的温度场及热整流系数的理论模型和有限元解.数值算例证明了本文模型及算法的可靠性,进而通过参数影响研究确定了若干几何及材料参数对结构热整流系数的影响规律,揭示界面接触热阻对热整流效果的影响机理.研究结果表明长度比、截面半径变化率、热导率、边界条件温差和界面接触热阻等因素必须通过优化设计才能得到最大的热整流系数,同时界面接触热阻的引入也为调控热整流系数提供了一条新的途径.     

液滴在不同润湿性表面上蒸发时的动力学特性

基于润滑理论,采用滑移边界条件建立了二维液滴厚度的演化模型和移动接触线动力学模型,利用数值计算方法模拟了均匀加热基底上固着液滴蒸发时的动力学特性,分析了液-气、固-气和液-固界面张力温度敏感性对壁面润湿性和液滴动态特性的影响.结果表明,液滴的运动过程受毛细力、重力、热毛细力和蒸发的影响,重力对液滴铺展起促进作用,而毛细力、热毛细力则起抑制作用;通过改变界面张力温度敏感性系数,可使液滴蒸发过程中的接触线呈现处于钉扎或部分钉扎模式,且接触线钉扎模式下的液滴存续时间低于部分钉扎模式;提高液-气与液-固界面张力温度敏感系数均可改善壁面润湿性能,加快液滴铺展速率;而增大固-气界面张力温度敏感系数则导致壁面润湿性能恶化、延缓液滴铺展过程;通过改变固-气界面张力温度敏感系数更有利于调控处于蒸发状态下的液滴运动.     

Analytical solution to the Lipari-Szabo model based on the reduced spectral density approximation offers a novel protocol for extracting motional parameters.

An analytical solution to the Lipari-Szabo model is derived for isotropic overall tumbling. The parameters of the original Lipari-Szabo model, the order parameter S2 and the effective internal correlation time tau(e), are calculated from two values of the spectral density function. If additionally the spectral density value J(0) is known, the exchange contribution R(ex) term can also be determined. The overall tumbling time tau(c) must be determined in advance, for example, from T1/T2 ratios. The required spectral density values are obtained by reduced spectral density mapping from T1, T2, and NOE measurements. Our computer simulations show that the reduced spectral density mapping is a very good approximation in almost all cases in which the Lipari-Szabo model is applicable. The robustness of the analytical formula to experimental errors is also investigated by extensive computer simulations and is found to be similar to that of the fitting procedures. The derived formulas were applied to the experimental 15N relaxation data of ubiquitin. Our results agree well with the published parameter values of S2 and tau(e), which were obtained from standard fitting procedures. The analytical approach to extract parameters of molecular motions may be more robust than standard analyses and provides a safeguard against spurious fitting results, especially for determining the exchange contribution R(ex).     

Evaluation of Expansion Coefficients from Optimal Fitting Parameters for the Analysis of Spectra of Diatomic Molecules and an Application to LiH

To evaluate individual expansion coefficients composing fitting parameters of the Born-Oppenheimer corrections to Dunham's coefficients Y(ij) that have been given analytically with the Delta(B) and Delta(omega) formalism, we examined the consistency of analytic expressions for those corrections with Watson's assertion of the experimental inseparability of nonadiabatic corrections Q(a, b)(r) for a molecule AB. Derived analytic expressions in terms of optimal fitting parameters for the corrections are essential to evaluate individual expansion coefficients. These expressions also reveal redundancies between empirical correction parameters Delta(ij). A method of evaluating nonadiabatic vibrational corrections Q(a, b)(r) and adiabatic corrections S(a, b)(r) separately consistent with Watson's assertion of inseparability is presented and is applied to an analysis of spectral data of LiH. Functions Q(a, b) and S(a, b) for LiH are thus successfully evaluated; S(H, Li)(r) values agree well with those predicted simply by wobble-stretch theory. Experimental values for optimal fitting parameters r(H)(1q) and r(H)(2q) are nearly equal to those of r(Li)(1q) and r(Li)(2q), respectively, in agreement with a theoretical relation r(a)(iq)=r(b)(iq). Copyright 2001 Academic Press.     

Investigation of coulomb and pairing effects using new developed empirical formulas for proton-induced reaction cross sections

We have investigated Coulomb and pairing effects by using new empirical formulas including the new coefficients for (p, α) at 17.9 MeV, (p, np) at 22.3 MeV, and (p, nα) at 24.8 and 28.5 MeV energies. A new formula is obtained by adjusting Levkovskii’s original asymmetry parameter formula and also Tel et al. formula for proton-induced reactions. The new coefficients by using least-squares fitting method for the reactions are determined. In addition, the findings of the present study are compared with the available experimental data.     

Mass and thermal accommodation during gas-liquid condensation of water

In this Letter we report, for the first time, direct and simultaneous determinations of mass and thermal accommodation coefficients for water vapor condensation in air, based on the observation of droplet growth kinetics in an expansion cloud chamber. Our experiments exclude values below 0.85 for the thermal and below 0.4 for the mass accommodation coefficients at temperatures ranging from 250 to 290 K. Both coefficients are likely to be 1 for all studied conditions. Previously available experimental data on the mass accommodation coefficient for water span about 3 orders of magnitude. Our results provide new and firm insight to cloud microphysics and consequently to the global radiative balance.     

Freeze-out conditions in ultrarelativistic heavy-ion collisions

We present recent results on single particle transverse momentum distributions of pions, kaons and protons, measured in CERN Experiment NA44, of 200 AGeV/c S+S and 158 AGeV/c Pb+Pb central collisions. By comparing these data with thermal and transport models, freeze-out parameters like the temperatureT _fo and the chemical potentials (μ _q ,μ _s ) are extracted and discussed.     

Thermal Shift Calculations (Ⅱ): The Theoretical Calculation of R Line Thermal Shift of MgO:Cr3+

By making use of the theory for thermal shift of crystal field spectra of rare earth or transition metalions, taking into account all the contributions adequately, we calculated R line thermal shift of MgO:Cr³⁺ by fitting experimental data. The results show a good agreement with thermal shift experimental data and a series of other experimental data of MgO:Cr³⁺. Values of the most important parameters are calculated theoretically with wavefunctions obtained from diagonalization of complete d³ energy matrices. They are in good agreement with those from fitting experimental data.     

Newly developed semi-empirical formulas for (<Emphasis Type="Italic">p,α</Emphasis>) at 17.9 MeV and (<Emphasis Type="Italic">p,np</Emphasis>) at 22.3 MeV reaction cross-sections

In this study, we have investigated the asymmetry term effect for the (p, α) and (p, np) reaction cross-sections and obtained new coefficients for the (p, α) and (p, np) reaction cross-sections at 17.9 and 22.3 MeV energies. We have suggested semi-empirical formulas including the non-elastic effects of optical model found by fitting two parameters for proton-induced reactions. The coefficients were determined by least-square fitting method. The obtained cross-section formulas with new coefficients have been discussed and compared with the available experimental data.     

A Ubiquitous Thermal Conductivity Formula for Liquids,Polymer Glass,and Amorphous Solids

The microscopic mechanism of thermal transport in liquids and amorphous solids has been an outstanding problem for a long time.There have been several approaches to explain the thermal conductivities in these systems, for example, Bridgman’s formula for simple liquids, the concept of the minimum thermal conductivity for amorphous solids, and the thermal resistance network model for amorphous polymers.Here, we present a ubiquitous formula to calculate the thermal conductivities of liquids and amo...     

Analysis of equation of state and thermodynamic functions for trans-decahydronaphthalene up to 200~MPa and 446~K

This paper develops a modified Tait equation of state(EOS) for trans-decahydronaphthalene with four parameters A,B,V0 and P0 being treated as linear functions of temperature.The coefficients contained in these functions are determined through fitting the experimental compression data in the literature between 293 K and 446 K and at pressures from 10 to 200 MPa.Expressions for the thermal expansivity,isothermal compressibility and thermodynamic quantities are deduced and the numerical results are analytically derived.The numerical results show that the precision of the modified Tait EOS developed in this paper is superior to the EOS in the literature.     

Microscopic transport theory of heavy-ion collisions

Transport equations of the Fokker-Planck type are derived from a master equation for deeply inelastic collisions. Using the method of spectral distributions, the transport coefficients are calculated for symmetric fragmentations. Analytic formulas are given for the memory time, for the energy-drift coefficient and for the diffusion coefficients which correspond to the excitation of the fragments and the transfer of nucleons. These expressions contain parameters of the basic interaction matrix elements only, which describe excitations and transfers. Agreement with experimental data is obtained for reasonable values of these interaction parameters. Production cross-sections are predicted for superheavy nuclei in the deeply inelastic collisions U+U and U+Cf.