Surface second harmonic generation of chiral molecules using three-coupled-oscillator model

Based on the three-coupled-oscillator molecular model we proposed, the relation between the second-order susceptibilities of a chiral film and the molecular hyperpolarizabilities is given. The effect of microscopic parameters on the second-order susceptibilities is simulated numerically and the difference between the efficiencies of s-polarized secondharmonic fields induced by the left- and the right-handed circularly-polarized fundamental beams is discussed. The theoretical basis for studying second-order nonlinear optical properties of the chiral molecular media with a tripod-like structure is provided in this paper.

Should China Allow Couples to Have a Second Child?

China’s family planning policy is back in the spotlight.Guangdong, the country’s most populous province according to the latest population census,has officially applied to the Central Government for permission for it lifting family planning restrictions.If the application is approved,couples in which either the husband or wife is an only child will be allowed to have a second child,according to Zhang Feng, family planning chief in Guangdong.

2-μm single longitudinal mode GaSb-based laterally coupled distributed feedback laser with regrowth-free shallow-etched gratings by interference lithography

We report a type-I Ga Sb-based laterally coupled distributed-feedback（LC-DFB） laser with shallow-etched gratings operating a continuous wave at room temperature without re-growth process. Second-order Bragg gratings are fabricated alongside the ridge waveguide by interference lithography. Index-coupled LC-DFB laser with a cavity of 1500 μm achieves single longitudinal mode continuous-wave operation at 20℃ with side mode suppression ratio（SMSR） as high as 24 dB.The maximum single mode continuous-wave output power is about 10 mW at room temperature（uncoated facet）. A low threshold current density of 230 A/cm^2 is achieved with differential quantum efficiency estimated to be 93 mW/A. The laser shows a good wavelength stability against drive current and working temperature.

A new discipline: ［Non-Classic(N-C) State-field Theory of Thermodynamics (S-F.TOT)a new second law(2nd-law) of thermodynamics(OT),the Law of Coupling (LOC)］［(N-C).(S-F.TOT)New (2nd-law)OT, (LOC)］,expressed as a theoretical flow sheet

In this paper, the mistakes in the traditional first law are pointed out. A new second law of thermodynamics, the law of coupling is mentioned. The Liu's Principle of Free Energy Conservation is stated. And finally a New Discipline is expressed as A THEORETICAL FLOW SHEET.

New Complex Solutions of the Coupled KdV Equations

In this paper,new infinite sequence complex solutions of the coupled Kd V equations are constructed with the help of function transformation and the second kind of elliptic equation.First of all,according to the function transformation,the coupled Kd V equations are changed into the second kind of elliptic equation.Secondly,the new solutions and Bäcklund transformation of the second kind of elliptic equation are applied to search for new infinite sequence complex solutions of the coupled Kd V equations.These solutions include new infinite sequence complex solutions composed by Jacobi elliptic function,hyperbolic function and triangular function.

Positive Solutions for Singular Boundary Value Problems of Coupled Systems of Nonlinear Differential Equations

We establish the existence of positive solutions for singular boundary value problems of coupled systems? The proof relies on Schauder’s fixed point theorem. Some recent results in the literature are generalized and improved.

Dynamic thermo-mechanical coupled response of random particulate composites:A statistical two-scale method

This paper focuses on the dynamic thermo-mechanical coupled response of random particulate composite materials. Both the inertia term and coupling term are considered in the dynamic coupled problem. The formulation of the problem by a statistical second-order two-scale （SSOTS） analysis method and the algorithm procedure based on the finite-element difference method are presented. Numerical results of coupled cases are compared with those of uncoupled cases. It shows that the coupling effects on temperature, thermal flux, displacement, and stresses are very distinct, and the micro- characteristics of particles affect the coupling effect of the random composites. Furthermore, the coupling effect causes a lag in the variations of temperature, thermal flux, displacement, and stresses.

Effects of Second-Order Difference-Frequency Wave Forces on Floating Wind Turbine Under Survival Condition

In this paper, the effects of second-order difference-frequency wave forces on the global motion of an offshore wind turbine system with a large displacement under the survival condition are studied. In this case, the hydrodynamic force is the main force because the blades are feathered to reduce the lifting force. The first-order hydrodynamic forces are calculated by WADAM, while the second-order wave forces are calculated by a customized MATLAB module. Then the hydrodynamic coefficients are transferred to the wind turbine analytical code FAST. Through the comparisons of dynamic responses between the first- and second-order numerical models, it is found that the second-order wave forces significantly influence the motion of floating wind turbine under the survival condition. Moreover, neglecting the second-order force significantly underestimates the tension forces in the mooring lines. © 2017, Tianjin University and Springer-Verlag Berlin Heidelberg.

THEORY AND APPLICATION OF FRACTIONAL STEP CHARACTERISTIC FINITE DIFFERENCE METHOD IN NUMERICAL SIMULATION OF SECOND ORDER ENHANCED OIL PRODUCTION

A kind of second-order implicit fractional step characteristic finite difference method is presented in this paper for the numerically simulation coupled system of enhanced （chemical） oil production in porous media. Some techniques, such as the calculus of variations, energy analysis method, commutativity of the products of difference operators, decomposition of high-order difference operators and the theory of a priori estimates are introduced and an optimal order error estimates in l^2 norm is derived. This method has been applied successfully to the numerical simulation of enhanced oil production in actual oilfields, and the simulation results ate quite interesting and satisfactory.

Second-harmonic generation circular dichroism spectroscopy from tripod-like chiral molecular films

The second-harmonic generation （SHG） circular dichroism in the light of reflection from chiral films of tripod-like chiral molecules is investigated. The expressions of the second-harmonic generation circular dichroism are derived from our presented three-coupled-oscillator model for the tripod-like chiral molecules. Spectral dependence of the circular dichroism of SHG from film surface composed of tripod-like chiral molecules is simulated numerically and analysed. Influence of ehiral parameters on the second-harmonic generation circular dichroism spectrum in chiral films is studied. The result shows that the second-harmonic generation circular dichroism is a sensitive method of detecting chirality compared with the ordinary circular dichroism in linear optics. All of our work indicates that the classical molecular models are very effective to explain the second-harmonic generation circular dichroism of chiral molecular system. The classical molecular model theory can give us a clear physical picture and brings us very instructive information about the link between the molecular configuration and the nonlinear processes.

浮式风力机若干特征动力学问题综述

总结浮式风力机类型及其对应的特征动力学问题,针对浮式风力机气动荷载、水动荷载的计算方法以及结构动力学、控制动力学典型问题进行论述。讨论了气动—水动—结构—伺服耦合分析的难点,重点分析了二阶波浪力、畸形波等非线性波浪荷载、流荷载及涡激运动对浮式风力机特征动力响应的影响。阐述了浮式风力机动力学研究的试验方法、数值仿真方法、样机测试方法,并对模型试验技术的相似理论、气动模型的实现和难点以及数值仿真的频域方法、时域方法和分析工具进行了归纳对比。研究表明:浮式风力机多场、多体耦合动力分析机理及相关技术仍不成熟,气动荷载、高阶非线性波浪荷载耦合模型的建立是动力学问题研究的重点,数值仿真及模型试验是浮式风力机动力响应研究的主要方法,样机测试技术的积累将促进设计标准的完善及浮式风电的产业化发展。

计及电-气双向耦合的综合能源配电网优化重构

综合能源系统是实现电网、气网以及热网等多种能源系统深度融合,利用能量耦合互补等优势提升整个系统能源利用效率的有效形式。为提升综合能源系统优化运行能力,文章首先基于电转气技术与天然气发电技术,构建了的电-气双向耦合综合能源系统总体模型。进而考虑配电网重构技术(Distribution Network Reconfiguration Technology,DNR)中拓扑结构灵活可控这一特性,在配电子系统中引入开关变量、系统运行总费用最低这一目标函数及网络辐射状拓扑结构等约束,建立了配电子系统重构模型。从降低模型求解复杂性的角度,应用二阶锥松弛、乘积变量线性化及分段线性化等方法,将原始综合能源配电网重构非凸非线性模型转化为混合整数二阶锥规划(Mixed Integer Second-Order Cone Programming,MISOCP)问题求解。仿真结果表明,在电-气双向耦合的综合能源系统中应用配电网重构技术,能够降低综合能源系统运行费用,同时有效支撑了配电子系统电压与配气子系统气压。

二阶波浪力对浮式风机系统动力响应的影响研究

文中以OC4-DeepCwind海上浮式风机系统为例,考虑浮式基础运动与气动力之间的耦合,研究了二阶波浪力对浮式风机系统动力响应的影响.结果表明:二阶波浪力增加了浮式基础纵荡和纵摇运动的标准差,而浮式基础纵荡和纵摇对风机气动力有较大的影响,从而使得风轮的推力及功率波动都增大.因此,在风力机系统控制设计及风力机叶片结构设计时,需要充分考虑二阶波浪力的影响.此外,二阶和频力和塔柱一阶固有频率接近,激发了塔柱自振,在设计塔柱时应避开二阶和频力.

二语汉语词汇习得的三维耦合互动模式探析

从多学科视角分析二语汉语词汇学习中所涉及的三个重要的非自主认知维度,即语言知识、社会文化和情感态度。汉语词汇习得的过程就是将这三个维度下的非自主认知元素不断进行认知内化的过程。互动是实现汉语词汇习得的有效途径,包括人际互动和语层互动,两者的结合能够将三维非自主认知元素进行有机联结。人际互动和语层互动的融合可能会产生一种加快词汇认知内化的促进效应,根据汉语学习者最近发展区的预设进行持续性地反馈互动是这种促进效应产生的关键。本文对多语层语境下三维耦合互动的具体实现路径进行了详细阐述。

G蛋白偶联受体(GPCR)腺苷酸环化酶(AcyA)途径介导赭曲霉群体感应现象的机制

赭曲霉(Aspergillus ochraceus)是一种代表性的产毒模式真菌,存在密度依赖性转化的高、低群体密度阈值和携带这种密度信息的群体感应(QS)信号分子--氧脂素。本研究首先基于代表高、低群体密度条件的野生型赭曲霉转录组差异,分析群体密度这一环境条件对赭曲霉行为的影响,结果发现,除了氧脂素代表的细胞通信外,还具有种内对资源的竞争现象,体现在碳代谢。进一步,基于前期实验筛选到负责响应密度信息的膜受体GprC和主要的胞内效应器腺苷酸环化酶(AcyA),构建了基因缺陷型赭曲霉(ΔgprC和ΔacyA)。对比野生型与缺陷型赭曲霉的基因表达及行为差异后发现,GprC-AcyA途径缺陷后不仅中断了密度信息的传递,还直接影响赭曲霉的生命周期。本文研究结果表明,GprC和AcyA作为G蛋白网络的重要枢纽,具有广泛的调控作用,涉及生物过程、细胞组分、分子功能中大部分行为。本研究结果对利用生物手段进行真菌毒素污染的高效、绿色防治具有指导意义。

整体式平箔气体动压止推轴承静特性分析

整体式平箔气体动压止推轴承具备制造工艺简单,承载能力强等优点,其由多个带有独立波箔的轴承扇区组成,但具有一个完整的环形平箔片。为了探究该新型轴承工作机制和静特性,提出相应的静特性分析模型并利用循环边界耦合条件,设置气流入口与出口处压力相等,利用数值仿真分析整体式平箔止推轴承的转速、最小气膜厚度和楔形高度对其静特性的影响,并与相同工作条件下的分离式平箔轴承进行比较。研究结果表明:整体式平箔所设计的轴承在负载情况下平箔片会由楔形-台阶转变为楔形-平端的几何形状,单瓦扇区后缘因变形向上弯曲产生二次收敛间隙,因此形成2个气膜压力峰值,且由于轴承面积较分离式平箔所设计的轴承更大,因此承载能力会更高;由于平箔台阶处存在负压区,因此整体式平箔最优楔形高度区间延后于分离式平箔出现,当楔形高度在50μm左右时,能够达到较高承载能力并且摩擦力矩较小;当增加最小气膜厚度时,其承载能力与摩擦力矩均减小。

Conversion of out-of-phase to in-phase order in coupled laser arrays with second harmonics

A novel method for converting an array of out-of-phase lasers into one of in-phase lasers that can be tightly focused is presented.The method exploits second-harmonic generation and can be adapted for different laser arrays geometries.Experimental and calculated results,presented for negatively coupled lasers formed in a square,honeycomb,and triangular geometries are in good agreement.

基于RCSA和二阶有限差分法的刀尖点频响函数预测研究

铣削系统动态特性参数对切削过程的稳定性起着非常重要的作用,而获取由刀具尖点频响函数表示的该参数是实现无颤振切削的先决条件。基于响应耦合子结构法,将铣削系统划分为主轴刀柄和刀具两个子系统,将刀具子系统进一步细分为刀杆和刀齿两个子系统。综合运用模态锤击实验和二阶有限差分法等辨析方法,考虑旋转响应的主轴刀柄末端频响函数,将铣刀简化为欧拉-伯努利梁,计算出铣刀子结构的频响函数,通过响应耦合获得铣削系统刀尖点频响函数,模型的正确性得到了实验验证。

ON STATE FEEDBACK AND POLE ASSIGNMENT OF THE SECOND ORDER COUPLED SINGULAR DISTRIBUTED PARAMETER SYSTEMS IN HILBERT SPACE

State feedback and pole assignment of the second order coupled singular distributed parameter systems are discussed via functional analysis and operator theory in Hilbert space, in which infinite many poles are changed. The solutions of the problem and the constructive expression of the solutions are given by the generalized inverse of bounded linear operator. This research is theoretically important for studying the pole assignment and stabilization of the singular distributed parameter systems.

硅微陀螺仪正交耦合系数的计算及验证

硅微陀螺仪多采用微机械加工工艺制作,其加工的相对精度较低,从而易产生正交耦合误差,影响陀螺仪的输出。为了优化设计硅微陀螺仪结构,提高其性能,本文建立了陀螺仪正交耦合系数的理论分析模型。首先,利用能量方法推导陀螺仪驱动梁的面内刚度;然后,建立陀螺仪的刚度矩阵;最后,推导了正交耦合系数的理论计算公式。针对本课题组研制的双质量振动式硅微陀螺仪,理论计算出其直接耦合系数为4.74×10-5,二次耦合系数为8.44×10-7。得到的陀螺仪的正交耦合系数为4.75×10-5,与仿真值相差8.7%。分析得到陀螺仪正交耦合系数的最大值为2.18×10-4,与仿真值相差7.9%。最后,实验验证了计算结果的正确性。得到的结果表明,建立的正交耦合系数理论分析模型可为硅微陀螺仪的结构优化设计提供理论依据和实际指导。