不同方式地下爆炸地震耦合效应的数值模拟

通过一种Euler与Lagrange相结合的有限差分法,开展地下爆炸地震耦合效应的数值模拟.比较花岗岩介质中填实和空腔两种爆炸方式在地震耦合效应方面的差异,进一步分析初始空腔大小在填实以及空腔爆炸地震效应中的作用以及空腔爆炸解耦因子随频率的变化特性.计算结果表明,花岗岩介质中完全空腔解耦因子能达到50~60倍.     

La0.7Ca0.3MnO3和CeO2混合块状样品电输运性质及使用分形迭代电阻网络模型的计算模拟

固相反应方法制得的La_0.7Ca_0.3MnO₃ (LCMO)粉末与Ce O₂粉末均匀混合后压块烧结,对其进行了电阻率随温度变化的测量.观察到样品电阻率存在绝缘体-金属转变. 研究了烧结工艺、CeO₂的混合比例与样品的电阻率、结构和表面形貌的关系.结 果表明， 制备工艺对材料性能有相当大的影响，其中较低温度的烧结主要影响小晶粒及其晶粒间界， 而高温长时间烧结将影响大晶粒的形成.利用三维随机电阻网络（RRN）模型和蒙特卡罗方法 对这种混合块状样品的输运性质进行了模拟，模拟中使用了一种新的RRN平均方法.该模型得 到的数值模拟结果与实验结果在定性上是一致的.这说明以RRN模型来理解LCMO(x)-CeO ₂(1-x) 复合体系的导电状况是合理的，提出的随机电阻网络平均方法是合适的 . 关键词： 0.7Ca_0.3MnO₃')" href="#">La_0.7Ca_0.3MnO₃ 绝缘体-金属转变 随 机电阻网络 蒙特卡罗模拟     

Superposition of Fock states via adiabatic passage in a coupled four-level atom－cavity system

We have investigated the behaviour of an atom－cavity system via a stimulated Raman adiabatic passage technique in a four-level system, in which two dark states are present. We find, because of the coherent control field, that a superposition of Fock states can be prepared, even when the cavity is initially not in its vacuum state. This method provides a way to generate arbitrary quantum states of a cavity field.     

Statistical Mechanics Approach for Uniform and Non-uniform Fluid with Hard Core and Interaction Tail

One recently proposed self-consistent hard sphere bridge functional was combined with an exponential function exp(-cr) and a re-normalized indirect correlation function to construct the bridge function for fluid with hard core and interaction tail. In the present approach, the adjustable parameter α was determined by the thermodynamic consistency realized on the compressibility modulus, the re-normalization of the indirect correlation function was realized by a modified Mayer function with the interaction potential replaced by the perturbative part of the interaction potential. As an example, the present bridge function was combined with the Ornstein-Zernike (OZ) equation to predict structure and thermodynamics properties in very good agreement with the simulation data available for Lennard-Jones (L J). Based on the universality principle of the free energy density functional and the test particle trick, the numerical solution of the OZ equation was employed to construct the first order direct correlation function of the non-uniform fluid as a functional of the density distribution by means of the indirect correlation function. In the framework of the density functional theory, the numerically obtained functional predicted the density distribution of LJ fluid confined in two planar hard walls that is in good agreement with the simulation data.     

红外光谱法测定杉木/聚丙烯复合材料中木粉和塑料含量

木塑复合材料(wood plastic composites, WPCs)中木材和塑料的配比影响其性能和价格,传统的热化学方法尚不能快速准确地测定WPCs中木塑配比。为探究红外光谱法定量分析WPCs中木粉和塑料的可行性,以杉木、聚丙烯(PP)以及各种添加剂为原料,经过木粉改性、混料和挤出造粒制备出13种不同杉木含量(9.8%～61.5%)的WPCs。采用KBr压片法对制得的样品进行红外光谱分析,通过对比WPCs、杉木、PP以及其他添加剂的红外谱图,确定杉木特征吸收峰为1 059,1 033和1 740 cm-1,1 377,2 839和841 cm-1表征PP特征峰。建立木粉含量、PP含量和二者特征吸收峰峰高比之间的相关关系,结果表明,木粉含量与I_{1 059}/I_{1 377}和I_{1 033}/I_{1 377}之间均存在极强的线性相关,R2分别为0.992和0.993,PP含量与I_{1 377}/I_{1 740}和I_{2 839}/I_{1 740}之间存在高度线性相关,R2分别为0.985和0.981,形成了杉木/PP复合材料中木粉和PP含量的红外光谱定量分析方法,木粉含量预测方程依次为y=53.297x-9.107和y=55.922x-10.238,PP含量预测方程依次为y=6.828 5x+5.403 6和y=8.719 7x+3.295 8。方法精密性和准确性检验表明,方法可重复性强、准确度高,木粉与塑料含量预测平均相对误差约为5%,与传统热化学方法相比,预测精度有较大提高,更重要的是红外光谱法操作更为简便。该研究为杉木/PP复合材料中木粉及塑料含量的测定提供了一种简便、快速、准确的方法。     

带楔块二维面阵列超声相控阵声场特性分析

开展了带楔块二维面阵脉冲超声相控阵辐射声场特性的研究。将安装在一定角度斜楔块上二维面阵相控阵换能器声场问题简化为液固界面情况进行讨论。以单阵元在液固平界面条件下的辐射声场为基础,推导了聚焦偏转法则,给出了带楔块二维面阵超声相控阵声场计算方法。以检测材料为钢板,安装在倾斜角为36°有机玻璃楔块上的频率为5 MHz、8×8二维面阵相控阵的辐射声场计算为例,分析了在不同偏转角和不同聚焦深度下检测材料中的辐射声场特性。计算结果表明该方法可有效的分析带楔块二维面阵超声相控阵声场特性并用于指导二维超声面阵角束探头的设计。     

运用PLS算法由小麦冠层反射光谱反演氮素垂直分布

文章提出了利用遥感光谱数据反演小麦冠层氮素垂直分布的化学计量学方法,运用偏最小二乘算法(PLS),穷尽测定的小麦田间冠层可见光和近红外光谱不同波长处的冠层光谱反射率及其组合与小麦不同层次的叶绿素、叶片全氮含量之间的关系。通过2001～2002年的建模和2003～2004年的验证试验,求得了用PLS算法对叶片全氮上层、中层、下层垂直分布估算结果的相关性。表明PLS算法能够用于反演作物冠层生物化学参数的垂直分布。运用PLS的小麦氮素垂直分布的估算方法,较以往单一冠层估算方法精度明显提高,对于生产上迫切需求对作物中、下层叶片氮素状况的监测来指导适时和适量施肥具有指导意义。     

Density functional approximation for van der Waals fluids： based on hard sphere density functional approximation

A universal theoretical approach is proposed which enables all hard sphere density functional approximations (DFAs) applicable to van der Waals fluids. The resultant DFA obtained by combining the universal theoretical approach with any hard sphere DFAs only needs as input a second-order direct correlation function (DCF) of a coexistence bulk fluid, and is applicable in both supercritical and subcritical temperature regions. The associated effective hard sphere density can be specified by a hard wall sum rule. It is indicated that the value of the effective hard sphere density so determined can be universal, i.e. can be applied to any external potentials different from the single hard wall. As an illustrating example, the universal theoretical approach is combined with a hard sphere bridge DFA to predict the density profile of a hard core attractive Yukawa model fluid influenced by diverse external fields; agreement between the present formalism's predictions and the corresponding simulation data is good or at least comparable to several previous DFT approaches. The primary advantage of the present theoretical approach combined with other hard sphere DFAs is discussed.     

Optimization of polarization spectroscopy for rubidium D lines

Polarization spectroscopy of the D lines of rubidium atoms is investigated experimentally,especially with different pump powers and cell temperatures.We find that there are four candidate transitions suitable for frequency stabilization,and optimal pump powers and cell temperatures are also presented to obtain a perfect signal with maximal amplitude and slope.The optimal signal is insensitive to the fluctuations of laser power and the temperature,which can enhance the performance of frequency locking.     

Augmented Kierlik-Rosinberg Fundamental Measure Functional andExtension of Fundamental Measure Functional to Inhomogeneous Non-hard Sphere Fluids

From point of view of weighted density procedure, it isguessed that a Percus-Yevick (PY) compressibility excess free energydensity, appearing in the Kierlik--Rosinberg type fundamentalmeasure functional (KR-FMF) and expressed in terms of scaledparticle variables, can be substituted by a corresponding expressiondictated by a more accurate Mansoori-Carnahan-Starling-Leland(MCSL) equation of state, while retaining the original weightingfunctions; it is numerically indicated that the resultantundesirable non-self-consistency between the PY type weightingfunction and MCSL type excess free energy density had no bad effecton the performance of the resultant augmented KR-FMF which, on theone hand, preserves the exact low-density limit of the originalKR-FMF and holds a high degree of pressure self-consistency, on theother hand, improves significantly, as expected, the predictions ofdensity profile of hard sphere fluid at single hard wall contactlocation and its vicinity, and of the bulk hard sphere second orderdirect correlation function (DCF), obtained from functionaldifferentiation. The FMF is made applicable to inhomogeneousnon-hard sphere fluids by supplementing a functional perturbationexpansion approximation truncated at the lowest order with summationof higher order terms beyond the lowest term calculated by the FMFfor an effective hard sphere fluid; the resultant extended FMF onlyneeds second order DCF and pressure of the fluid considered atcoexistence state as inputs, consequently is applicable whether theconsidered temperature is above critical point or below criticalpoint. The extended MCSL-augmented KR-FMF is found to be endowedwith an excellent performance for predictions of density profile andsurface tension by comparing the present predictions of these twoquantities with available computer simulation data for inhomogeneoushard core attractive Yukawa fluid and Lennard-Jones fluid.