钬铝石榴石晶场参数调整

利用比热实验值,对钬铝石榴石（Ho3Al5O12）晶体的晶场参数进行了调整,依此计算了Ho3Al5O12晶体的晶场能谱、Zeeman劈裂能级和波函数. 在外磁场H=0时,分别计算了Ho3Al5O12晶体的总比热、总熵随温度的变化,以及外磁场H=10kOe时该晶体倒数磁化率的温度关系,理论计算结果均与已有实验数据符合较好.该工作为进一步探究该晶体的其它性质奠定了必要的理论基础,对实际生产和科学研究中磁制冷材料的优化选取也具有一定的现实意义.     

Effect of magnetic field on freely moving superconductors in the audio band

The results of studying the magnetomechanical effects in classical superconductors are analyzed. The energy losses are determined, and a number of macroscopic parameters are calculated using a developed model. The studies of superconductors by the method of rotation of a body suspended without contact are described. The results obtained are analyzed, and the values of some parameters are determined.     

Geoacoustic Inversion for Bottom Parameters via Bayesian Theory in Deep Ocean

We develop a new approach to estimating bottom parameters based on the Bayesian theory in deep ocean.The solution in a Bayesian inversion is characterized by its posterior probability density(PPD),which combines prior information about the model with information from an observed data set.Bottom parameters are sensitive to the transmission loss(TL)data in shadow zones of deep ocean.In this study,TLs of different frequencies from the South China Sea in the summer of 2014 are used as the observed data sets.The interpretation of the multidimensional PPD requires the calculation of its moments,such as the mean,covariance,and marginal distributions,which provide parameter estimates and uncertainties.Considering that the sensitivities of shallowzone TLs vary for different frequencies of the bottom parameters in the deep ocean,this research obtains bottom parameters at varying frequencies.Then,the inversion results are compared with the sampling data and the correlations between bottom parameters are determined.Furthermore,we show the inversion results for multifrequency combined inversion.The inversion results are verified by the experimental TLs and the numerical results,which are calculated using the inverted bottom parameters for different source depths and receiver depths at the corresponding frequency.     

一类时变时滞混沌系统的参数辨识方法

时变的未知时滞参数普遍存在于混沌系统中,它使得混沌系统同步控制变得非常困难. 针对时滞混沌系统中参数时变且未知的问题, 提出了一种新颖的辨识方法. 该方法首先将未知时变参数用分段常数函数来近似, 把求解非线性函数的问题转化为参数向量选择问题, 其中分段常数函数的高度向量成为待求解参数向量; 然后推导了目标函数对分段常数高度向量的梯度信息, 结合序列二次规划法求解得最优分段函数; 随着分段数的增加, 最优分段函数将逼近原非线性时变函数. 数值实例结果验证了该方法的有效性.     

受激布里渊散射光脉冲波形的研究

从实验和理论上研究了受激布里渊散射(SBS)光脉冲波形.在Nd∶YAG调Q激光器中实验研究了SBS光脉冲波形随抽运光参数、结构参数和介质参数的变化规律，并利用SBS理论模型进行了数值模拟，实验与数值模拟结果的变化趋势基本一致.结果表明，抽运光能量越小，透镜焦距越短，镜-池间距越长，介质声子寿命越长，SBS光脉冲波形就越不容易出现调制现象.分析和讨论了抽运光参数、结构参数和介质参数对SBS光脉冲波形的影响机理. 关键词： 受激布里渊散射 脉冲波形 抽运光参数 结构参数     

线阵激光二极管侧面抽运Nd∶YAG激光器特性研究

依据四能级系统速率方程 ,推导出了多横模振荡固体激光器输出与输入参量的关系。对二极管抽运固体激光器中线阵激光二极管三向对称侧面抽运结构 ,计算了抽运光强分布 ,并就激光器的阈值抽运功率、近阈值条件下的斜率效率、输出功率和光束质量等与抽运参量的关系 ,进行了数值计算。由计算结果看出 ,线阵激光二极管侧面抽运Nd∶YAG激光器中晶体半径和抽运光束腰半径是影响输出激光功率和光束质量的主要因素 ,并通过在谐振腔中加小孔选模 ,使光束质量得到明显改善。选择了一组三向侧面抽运结构参量进行了实验验证 ,实验结果与理论计算一致。     

索末菲参量对三重微分截面的影响

在前期工作的基础上，对非对称几何条件下波函数中的索末菲参量作了进一步的完善。研究了索末菲参量对三重微分截面（ＴＤＣＳ）产生的影响。用新的索末菲参量计算了低能电子入射离化氢原子的ＴＤＣＳ。所得结果与前期工作及ＣＣＣ（ｃｏｎｖｅｒｇｅｎｔｃｌｏｓｅ－ｃｏｕｐｌｉｎｇ）理论结果进行比较发现：所得结果明显地改善了理论曲线与实验数据的符合程度     

Parameter selection in the Green’s function parabolic equation

The accuracy of the Green’s function parabolic equation (GFPE) has already been confirmed for outdoor sound propagation over flat ground with a slowly varying sound speed profile and/or atmospheric turbulence. However, use of parabolic equation methods for prediction is generally limited to experts because of their dependence on numerous algorithm parameters that have significant impact on the accuracy of prediction. The present work offers a set of GFPE parameters, outlined in Table 1, that will provide accurate results for a variety of physical situations involving atmospheric propagation. The guidelines are found by comparing GFPE results to analytical results for a variety of situations and parameter choices and noting which combinations of parameters lead to accurate (within 3 dB of the analytical solution) results and which do not. A significant source of error in GFPE results is inaccuracy in the starting field or inappropriate starting field selection. The selection criteria for starting field and other parameters are discussed here.     

在超重核区应用Viola-Seaborg公式研究α衰变寿命

在超重核区(Z≥104)使用文献[7—9]给出的3组参数应用Viola-Seaborg公式计算了α衰变寿命,所得结果与实验值进行比较,发现其结果与实验值相差较大。为此,利用最小二乘法分别在重核区和超重核区重新对参数进行了拟合,得到的计算结果与实验值相比符合得较理想,尤其是由超重核得到的参数的结果非常理想。     

红宝石中分子轨道效应和塞曼参数的确定

本文在配位场理论中利用普遍的静电相互作用参数,计算了红宝石吸收线的位置,结果比前人稍有改善。讨论了这些参数与分子轨道的关系,利用了二个共价键参数和自由离子参数,虽然引入的参数很少,但所得结果与上面的计算相近,并定出N_π≌0.92,N_σ≌0.89。计算了推广等效自旋哈密顿中的参数,发现修正项中的g因子是来自四级微扰的贡献,其数量级约为10^-5。得到了红宝石R线的等效哈密顿。     

Response of a plate to a transient pressure wave load

The dynamical behaviour of a Kirchhoff plate under a moving pressure wave is investigated. The results are presented as dynamic amplification factors (DAF). The influence of the load parameters (propagation speed, pressure wave duration) and the plate parameters (slenderness, aspect ratio, damping, etc.) is discussed. Finally results for two examples are presented.     

重频超宽带脉冲干扰低噪声放大器

理论分析和仿真研究了重频超宽带脉冲对低噪声放大器(LNA)的干扰特征,给出了高斯脉冲幅度、脉宽及重频等参数对LNA干扰效果的规律,对工作于40~80MHz频段的接收机LNA开展了相关验证实验。结果表明:干扰特征主要由LNA工作频带和脉冲参数决定;不同脉冲参数对干扰的效果影响不同,脉冲幅值的影响最显著;在验证实验研究的参数范围内,增大高斯脉冲幅度、脉宽和重频均有利于增强对LNA的干扰效果。     

各向异性超常媒质矩形波导的导波特性研究

研究中通过建立和求解填充各向异性超常媒质的矩形波导TE模式和TM模式的波动方程和场分布方程,讨论了各向异性超常媒质矩形波导的有效介电常数、有效磁导率、相位常数以及传输系数与所填充超常媒质本构参数之间的变化关系.研究发现,填充了各向异性超常媒质的矩形波导的导波特性在截止频率之上的频率区域,其导波特性由所填充超常媒质的横向本构参数决定,而与超常媒质的纵向本构参数无关.但是,在截止频率之下的频率区域,该矩形波导的导波特性则由所填充超常媒质的横向本构参数和纵向本构参数共同决定.研究中通过典型的计算实例对所得到的结 关键词： 各向异性 超常媒质 矩形波导 导波特性     

Influence of Control Parameters on the Competition Between Spiral Waves and Target Waves

In this paper we systematically investigate the influence of control parameters on the competition results between spiral waves and target waves. Driving frequency f , amplitude A and injection area n of the input signals are three important parameters and the competition results between spiral waves and target waves are influenced by these three parameters remarkably. Based on these understandings we can control spiral waves effectively by suitable combination these parameters to generate faster target waves. And the effective controllable parameter regions are also studied.     

Design Guideline of Hollow-Core Fibres with Cobweb Cladding Structure

By using a plane wave expansion method, some important cobweb cladding structure are analysed. Taking a dielectric parameters of designing the hollow-core fibre with material PMMA, for example, the tolerance of the parameters is discussed. The results show that the parameters of the structure possess oneself of a regularity and limit, and have a larger tolerance for the structural parameters in fabrication.     

Soret and Dufour effects on MHD non-Darcian mixed convection heat and mass transfer over a stretching sheet with non-uniform heat source/sink

An analysis has been carried out to study the effects of thermal-diffusion and diffusion-thermo on non-Darcian mixed convection heat and mass transfer of an incompressible, electrically conducting fluid over a stretching sheet embedded in a porous medium in the presence of an external magnetic field and non-uniform heat source/sink. Similarity transformations are used to convert highly non-linear partial differential equations into ordinary differential equations. Similarity equations are then solved numerically using shooting algorithm with Runge-Kutta-Fehlberg scheme over the entire range of physical parameters. The effects of various physical parameters on the dimensionless velocity, temperature and concentration profiles are depicted graphically. Present results are compared with previously published work on various special cases of the problem and the results are found to be in very good agreement. Numerical results for local skin-friction, local Nusselt number and local Sherwood number are tabulated for different physical parameters.     

Influence of Control Parameters on the Competition Between Spiral Waves and Target Waves

In this paper we systematically investigate the influence of control parameters on the competition results between spiral waves and target waves. Driving frequency f, amplitude A and injection area n of the input signals are three important parameters and the competition results between spiral waves and target waves are influenced by these three parameters remarkably. Based on these understandings we can control spiral waves effectively by suitable combination these parameters to generate faster target waves. And the effective controllable parameter regions are also studied.     

Adjoint-based sensitivity analysis of flames

Simulation of chemically reacting flows using detailed chemistry introduces a large number of chemistry model parameters. While not all significantly affect the target outcomes of a simulation, the parameters that do are not always known a priori. In order to improve simulations for specified target outcomes, termed quantities of interest (QoIs), the sensitivity of these QoIs to the model parameters are needed. However, evaluating the sensitivities is computationally expensive, especially for complex fuels that may involve many parameters. For these simulations, the forward sensitivity method requires the solution of an additional number of governing equations proportional to the number of parameters. Here, an adjoint sensitivity approach is formulated where the computational cost scales as the number of QoIs and not the number of parameters. Specifically, adjoint equations are derived for laminar, incompressible, variable density reacting flow and applied to hydrogen flame simulations. From the solution of the corresponding adjoint equations, sensitivity of the QoIs to chemistry model parameters is calculated. The one-dimensional simulation results show that the adjoint sensitivity results closely match those of forward sensitivity methods, thus providing validation of the adjoint method. The two-dimensional simulation results indicate the most sensitive parameters for two QoIs, flame tip temperature and NOx emission. For these tests, the adjoint method reduces computational expense compared to forward sensitivity methods by a factor proportional to the number of QoIs over the number of parameters, here 2/172. Such savings can be more drastic for cases that involve complex fuels, such as combustion of jet fuel, requiring thousands of chemistry model parameters. Further, this sensitivity information can be used in development of experiments by pointing out which are the critical chemistry model parameters.     

基于NI-myDAQ数据采集器的混沌电路实验系统

混沌电路是大学物理实验课程中非线性系统教学内容的典型案例,为了提高学生对非线性实验内容的学习效率和自主学习能力,本文设计了一种基于NI-myDAQ数据采集器和LabVIEW软件平台的混沌电路实验系统.该系统可提高混沌参数微小变化的精密性,实时显示并记录不同参数下的混沌现象,能保存相图、时域图和数据.用该系统测量了蔡氏混...     

Scattering parameters of a waveguide cross junction loaded with a metallic post in the center

In this paper, the scattering parameters of a waveguide cross junction loaded with a metallic post in the center are analyzed for the first time by using the Method of Lines. The homogeneous boundary condition of the third kind and curved boundary are introduced in the formulation. Numerical results are in good agreement with the experimental data. The scattering parameters at Ka-band and W-band of the cross junctions loaded with metallic posts of different radii are presented. It is shown from the numerical results that loaded with metallic posts is an effective means for adjusting the network parameters of the waveguide cross junction to satisfy some special requirements in the design of millimeter wave components.