激光脉冲波形优化与材料压缩特性

结合快点火靶丸预压缩涉及的基本物理问题,分析了驱动激光脉冲波形对材料压缩过程的影响,并利用辐射流体力学程序MULTI模拟了不同激光波形下的材料压缩情况。结果表明:通过调节激光脉冲波形,优化激光初始强度、激光强度开始上升时间和上升速度,控制压缩过程中的熵增,可以获得更高的材料压缩度。     

激光脉冲波形优化与材料压缩特性

 结合快点火靶丸预压缩涉及的基本物理问题,分析了驱动激光脉冲波形对材料压缩过程的影响,并利用辐射流体力学程序MULTI模拟了不同激光波形下的材料压缩情况。结果表明:通过调节激光脉冲波形,优化激光初始强度、激光强度开始上升时间和上升速度,控制压缩过程中的熵增,可以获得更高的材料压缩度。     

Variational piecewise constant level set methods for shape optimization of a two-density drum

We apply the piecewise constant level set method to a class of eigenvalue related two-phase shape optimization problems. Based on the augmented Lagrangian method and the Lagrange multiplier approach, we propose three effective variational methods for the constrained optimization problem. The corresponding gradient-type algorithms are detailed. The first Uzawa-type algorithm having applied to shape optimization in the literature is proven to be effective for our model, but it lacks stability and accuracy in satisfying the geometry constraint during the iteration. The two other novel algorithms we propose can overcome this limitation and satisfy the geometry constraint very accurately at each iteration. Moreover, they are both highly initial independent and more robust than the first algorithm. Without penalty parameters, the last projection Lagrangian algorithm has less severe restriction on the time step than the first two algorithms. Numerical results for various instances are presented and compared with those obtained by level set methods. The comparisons show effectiveness, efficiency and robustness of our methods. We expect our promising algorithms to be applied to other shape optimization and multiphase problems.     

Finite element acoustic simulation based shape optimization of a muffler

This paper describes a methodology which combines finite element analysis and Zoutendijk’s feasible directions method for mufflers shape design. The main goal is to obtain the dimensions of the acoustic muffler with the transmission loss (TL), being maximized in the frequency range of interest. The improved four parameters method is used for TL evaluations and the Helmholtz’s equation is solved numerically with the finite element method (FEM). The quadratic triangular finite element meshes are adequately constructed to control the pollution error and the optimization problem is solved using the Zoutendijk’s feasible directions method due to robustness and efficiency for problems with nonlinear constraints. Numeric experiments performed with circular expansion chambers with extended inlet and outlet show results for constrained and unconstrained shape optimization.     

Numerical shape optimization of photoacoustic resonators

The sensitivity of photoacoustic sensors strongly depends on the shape of the acoustical resonator. Up to now, mainly photoacoustic sensors consisting of a number of cylindrical parts have been investigated (cylinder cells, H cells, T cells etc.). In this paper, a numerical shape optimization of the resonator cell of photoacoustic sensors is described. The approach considers all shapes that can be represented by a number of axisymmetrical truncated cones which are connected in a continuous way. In addition, the geometry of the cell is subjected to certain constraints, e.g.  the laser beam should not be blocked during its passage through the cell. The purpose is to maximize the sensor’s signal strength. The acoustic pressure at the position of the microphone represents the objective function and is calculated using an eigenmode expansion combined with a finite element calculation. The solution of a 17-dimensional nonlinear optimization problem is a resonator shape with a substantial quality improvement with reference to the well-known H cell.     

Plasma shape optimization for EAST tokamak using orthogonal method

It is necessary to reduce the currents of poloidal field(PF) coils as small as possible, during the static equilibrium design procedure of Experimental Advanced Superconductive Tokamak(EAST). The quasi-snowflake(QSF) divertor configuration is studied in this paper. Starting from a standard QSF plasma equilibrium, a new QSF equilibrium with 300 kA total plasma current is designed. In order to reduce the currents of PF6 and PF14, the influence of plasma shape on PF coil current distribution is analyzed. A fixed boundary equilibrium solver based on a non-rigid plasma model is used to calculate the flux distribution and PF coil current distribution. Then the plasma shape parameters are studied by the orthogonal method. According to the result, the plasma shape is redefined, and the calculated equilibrium shows that the currents of PF6 and PF14 are reduced by 3.592 kA and 2.773 kA, respectively.     

带有双X型铁心框架的超导MRI磁体的设计

文中对带有双X型铁心框架的MR I用高温和低温超导磁体的设计进行了介绍,包括项目的市场需求、磁体的基本参数和系统热负荷的预设计结果等。     

On the equilibrium equation for a generalized biological membrane energy by using a shape optimization approach

A mechanical equilibrium equation of a vesicle membrane under a generalized elastic bending energy is obtained in this paper. Moreover, the derivation of this equilibrium equation is based on some shape optimization tools. This approach is new and more concise than the tensorial tools used previously for this problem.     

An adjoint method for shape optimization in unsteady viscous flows

A new method for shape optimization for unsteady viscous flows is presented. It is based on the continuous adjoint approach using a time accurate method and is capable of handling both inverse and direct objective functions. The objective function is minimized or maximized subject to the satisfaction of flow equations. The shape of the body is parametrized via a Non-Uniform Rational B-Splines (NURBS) curve and is updated by using the gradients obtained from solving the flow and adjoint equations. A finite element method based on streamline-upwind Petrov/Galerkin (SUPG) and pressure stabilized Petrov/Galerkin (PSPG) stabilization techniques is used to solve both the flow and adjoint equations. The method has been implemented and tested for the design of airfoils, based on enhancing its time-averaged aerodynamic coefficients. Interesting shapes are obtained, especially when the objective is to produce high performance airfoils. The effect of the extent of the window of time integration of flow and adjoint equations on the design process is studied. It is found that when the window of time integration is insufficient, the gradients are most likely to be erroneous.     

基于本征正交分解的气动优化设计外形数据挖掘

气动外形的全局优化设计会产生大量的过程数据,其中隐含的设计知识具有较高的挖掘价值.数据挖掘有助于获取直观、可定性描述的设计知识.本文采用基于本征正交分解的数据挖掘方法从气动优化设计的过程数据中获取设计知识,数据挖掘对象为跨音速压气机转子叶片NASA Rotor 37的优化过程数据,该数据由基于粒子群方法的绝热效率最大化优化设计产生.结果表明:基于本文数据挖掘方法获取的设计知识能够直接反映气动外形的变化规律,为叶片的气动外形设计提供参考;数据挖掘的设计知识成功地验证了优化设计结果的有效性.     

Design and optimization of a nano-antenna hybrid structure for solar energy harvesting application

A novel hybrid structure with high responsivity and efficiency is proposed based on an L-shaped frame nano-antenna(LSFNA) array for solar energy harvesting application. So, two types of LSFNAs are designed and optimized to enhance the harvesting characteristics of traditional simple electric dipole nano-antenna(SEDNA). The LSFNA geometrical dimensions are optimized to have the best values for the required input impedance at three resonance wavelengths of λres = 10 μm,15 μm, and 20 μm. Then the LSFNAs with three different sizes are modeled like a planar spiral-shaped array(PSSA).Also, a fractal bowtie nano-antenna is connected with the PSSA in the array gap. This proposed hybrid structure consists of two main elements:(I) Three different sizes of the LSFNAs with two different material types are designed based on the thin-film metal–insulator–metal diodes that are a proper method for infrared energy harvesting.(II) The PSSA gap is designed based on the electron field emission proposed by the Fowler–Nordheim theory for the array rectification. Finally,the proposed device is analyzed. The results show that the PSSA not only has an averaged 3-time enhancement in the harvesting characteristics(such as return loss, harvesting efficiency, etc.) than the previously proposed structures but also is a multi-resonance wide-band device. Furthermore, the proposed antenna takes up less space in the electronic circuit and has an easy implementation process.     

Design and application of shape memory actuators

The use of shape memory alloys in actuators allows the development of robust, simple and lightweight elements for application in a multitude of different industries. Over the years, the intermetallic compound Nickel-Titanium (NiTi or Nitinol) together with its ternary and quaternary derivates has gained general acceptance as a standard alloy. Even though as many as 99% of all shape memory actuator applications make use of Nitinol there are certain properties of this alloy system which require further research in order to find improvements and new markets: • Lack of higher transformation temperatures in the available alloys in order to open the field of automotive applications (M_f  temperature > 80 °C) • Non-linearity in the electrical resistivity in order to improve the controllability of the actuator, • Wide hysteresis in the temperature-vs.-strain behaviour, which has a signi-ficant effect on both, the dynamics of the actuator and its controllability. Hence, there is a constant strive in the field towards an improvement of the related properties. However, these improvements are not always just alloy composition related. There is also a tremendous potential in the thermomechanical treatment of the material and in the design of the actuator. Significant improvement steps are already possible if the usage of the existent materials is optimized for the projected application and if the actuator system is designed in the most efficient way. This paper provides an overview about existent designs, applications and alloys for use in actuators, as well as examples of new shape memory actuator application with improved performance. It also gives an overview about general design rules and reflects about the strengths of the material and the related opportunities for its application.     

Physical aspects of the shape of electron emission spectra for ferroelectric electrets

A correlation between the specific features of the electron emission spectrum of a ferroelectric electret and the behavior of the potential at the surface of the sample is determined within the theoretical approach proposed. The physical nature of the main features in experimental emission spectra is interpreted in terms of the behavior of the potential relief. It is revealed that the electret charge relaxation affects the spectrum shape due to the bifurcation (branching) of singularities in the spectrum.     

Design and application of core mineral spectrometer

Core mineral spectrometer is one of the advanced and important tools for core digitalization,altered mineral mapping,ore deposits exploring,and ore-searching in surrounding mine and beneficiation process.In this letter,a new core mineral spectrometer(CMS 350)is designed and developed.The basic principle,structural design,function module,key components,data acquisition,and processing methods of CMS 350are introduced.In addition,some applications and results of CMS 350 in Zijin Mining are presented to validate the performance of CMS 350.     

Graphene的物理性质与器件应用

Graphene因其新奇的物理性质和广泛的应用前景已迅速成为国际新材料领域的研究前沿和热点.文章详细介绍了Graphene奇特的物理性质（多体相互作用、量子霍尔效应、双极场效应、弱局域化效应等）,并对其在微纳米器件、分子电子学、自旋电子学等领域的应用进展给出了综述.     

Graphene的物理性质与器件应用

Graphene因其新奇的物理性质和广泛的应用前景已迅速成为国际新材料领域的研究前沿和热点.文章详细介绍了Graphene奇特的物理性质(多体相互作用、量子霍尔效应、双极场效应、弱局域化效应等),并对其在微纳米器件、分子电子学、自旋电子学等领域的应用进展给出了综述.     

Physical mechanisms in divertors and their impact on the core

The magnetic separatrix in a diverted tokamak determines the boundary between closed and open magnetic field lines. Even though the main influences on the physics of SOL and core regions may be different and shift from the plasma-neutral coupling and impurity radiation in the scrape-off layer (SOL) to anomalous plasma transport in the core, the influence of this boundary persists over some width, both into the core region and into the SOL. We give a short review of the progress in the divertor-SOL physics and discuss the links between edge core and SOL plasmas which are likely to have an important role in different edge-plasma phenomena.     

The study of reactive silencers by shape and parametric optimization techniques

The aim of this work is to show the application of shape and parametric optimization techniques in the study of reactive silencers with extended inlet and outlet ducts. Parametric optimization is employed to evaluate the appropriate size of the inlet and outlet ducts. Shape optimization is employed to establish the proper profile of these ducts in order to improve the acoustic features of these mufflers in a specific frequency range. The objective function used in the optimization processes is defined through the average transmission loss (TL) for the desired frequency range. This type of objective function is strongly non-linear and the genetic algorithm, GA, was chosen as a mathematical method for determining the maximum of this function. The Finite Element Method with an axisymmetric formulation along with the modified four-parameter method are used to calculate the TL(ω). The Hermite polynomials were used in the shape optimization in order to obtain local boundary approximations with C¹ continuity. The results showed the optimization efficiency of the inlet ducts profile for acting in specific frequency ranges with gains up to 20 dB with respect to silencers without shape optimization. The numerical analyses agree well with experimental results.     

双包层光纤折射率研究及纤芯结构优化设计

采用Matlab和Comsol建立单模光纤内激光传输模型,对双包层内光纤折射率和纤芯结构对光能量分布的影响进行了理论研究。系统分析了光纤芯径与数值孔径、归一化频率和功率填充因子的关系,依据得到的结果进一步采用多模物理耦合仿真方法对不同类型的单模双包层光纤纤芯的能量分布进行仿真,探索了不同折射率分布情况对纤芯能量分布的影响。计算和仿真结果表明：凹面折射率分布光纤的光斑模场面积最大,单位面积的功率分布最低。针对大功率光纤激光器的应用需求设计了工作波长为1.064 m、纤芯直径为10 m、凹面直径为8 m、数值孔径为0.12的单模凹面折射率双包层光纤,为提高光纤泵浦效率、降低纤芯的能量密度提供了思路。     

Reduction of core in cage protein for application to electron device

For application to floating nanodots gate memory, ferritin core, ferrihydrite nanodot, array was made and reduced to be conductive. Ammonia plasma treatment was employed to reduce the ferrihydrite cores. X-ray photoelectron spectroscopy analysis confirmed that the plasma treated cores embedded in a SiN film are successfully reduced from ferrihydrite to metal iron. It was elucidated that hydrogen radicals or ions in the plasma combine with oxygen atoms in the core and, consequently, the core is reduced to a conductive state. Transmission electron microscope analysis before and after the treatment showed that the reduced core size was smaller than ferrihydrite core by approximately 2 nm, which is consistent with theoretical calculation of the shrink size accompanying core reduction to α-Fe. The plasma treated cores embedded in SiO₂ film are found to be iron oxides, which indicates that the metal iron nanodots are vulnerable to oxygen and easy to be reoxidized.