超导直流能源管道本体结构比较研究

超导直流能源管道本体是实现电力/液化天然气一体化输送的关键部件,承担着能源输送、高效热耦合和主动安全防御等功能。对超导直流能源管道原理验证样机进行了实验测试和仿真分析,获得了稳态运行时的管道沿程温度分布,其中出口温度测量值为95.5 K,仿真计算值为95.18 K。沿程温度分布仿真值和测量值偏差不超过1%,验证了仿真模型的正确性和仿真方法的有效性。基于实验验证的仿真模型和方法,对四种典型的能源管道本体结构进行了仿真分析。对比不同管道结构的温度场和流场仿真结果,获得了各种管道结构的特点,为超导直流能源管道的设计和优化提供了理论指导。     

集中送风式陈列柜的CFD整体模拟

将集中送风式陈列柜的五大部件送风管道、送风结构、陈列柜风幕、回风结构和回风管道结合成为一个整体,采用双流体改进模型进行CFD模拟,分析了CFD模拟的陈列柜温度场分布特性,并与测试结果进行了对比分析。对比分析的结果表明,CFD模拟温度与实测温度十分吻合,说明所采用的CFD整体模拟是成功的。     

电弧射流激励器工作特性仿真研究

为了在高超声速飞行器减阻中达到更好的减阻效果,设计了一种电弧射流等离子体激励器。采用有限元法求解非线性多物理方程,对此电弧射流等离子体激励器的工作特性进行了数值模拟,得到了激励器内部的电势、压力、温度和速度分布,综合分析了进气口气体速度、放电电流、激励器管道半径对电势、压力、温度和速度分布的影响。获得了全面的影响规律,通过仿真结果还得到:电弧射流等离子体激励器可产生最高温度为8638 K、最高速度为655 m/s的等离子体射流。当电流20 A,进气速度0.5 m/s,管道半径2.5 mm时,所需功率最小;当电流20 A,入口气体流速5 m/s,管道半径2.5 mm时,出口处平均温度最高;当电流20 A,进口气体速度10 m/s,管道半径2.5 mm时,出口处平均速度最大。并对仿真得到的放电电压进行了实验验证,在等离子体参数相似的情况下,实验结果与仿真结果吻合较好。     

封闭管道中热耦合效应对激光传输的影响

建立了封闭竖直管道热耦合效应物理模型,采用流固耦合方法,数值模拟了封闭管道中介质气体、光学玻璃之间的热相互作用造成流场分布的变化,研究了热耦合作用对近场波前相差和远场光束质量的影响。数值模拟结果表明,光束质量可以由封闭管道内介质气体温度分布来决定,气体在管道内流动改变温度分布,使得相差分布不断变化,造成远场光束质量的振荡起伏;光学镜与介质气体热相互作用对流场分布有较大影响,尤其是竖直管道底部的光学镜对激光束远场光束质量影响明显。热耦合效应放大了光束质量的变化:当介质模型中光束质量变差,热耦合模型中热耦合效应使光束质量变得更差;当介质模型中光束质量变好,耦合模型中的热耦合作用使光束质量变得更好,即光束质量随着流场分布的变化而振荡。     

矩形管道载氚热磁流体输运特性的数值模拟研究

聚变堆液态金属包层矩形管道中的氚输运过程与磁流体动力学(MHD)流动传热过程耦合在一起，形成了复杂的载氚热磁流体输运特性。基于开发的MHD流动与传热数值模拟程序对矩形管道中液态金属MHD流动传热特性及其氚输运的影响进行了数值模拟。该程序首先求解了动量守恒方程，并与理论解进行了对比验证，然后与能量守恒方程耦合求解，得到了温度影响下矩形管道中的液态金属流场分布，在此基础上对强磁场高核热梯度影响下的氚浓度分布进行了数值模拟，得到了氚浓度在管道中的分布特性。结果显示，液态金属在矩形管道中的流动传热对氚输运过程产生了显著影响。     

架空管道停输介质温度分布的影响因素分析

考虑环境温度、对流换热系数、初始温度和析蜡潜热等因素的影响,研究热油管道停输过程中介质的径向温度场分布及变化规律,对确定安全停输时间具有重要的指导作用。本文建立了架空热油管道停输径向传热物理模型及数学模型,利用FLUENT软件模拟了架空管道停输温降过程特定半径处温度变化过程。该方法能够确定不同半径处原油凝固时刻,为管道维修争取更多的时间。     

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给出了通道插件管道MHD效应的初步实验结果,结果表明：中心区流速分布与数值预测的差别较大,且不同位置的管道截面流速分布不同,在压力平衡孔之间呈周期性变化;宏观的中心区与边缘区流量分配、MHD压降与简化理论预测结果相接近。这些数据将给FCI管道数值分析模型的完善和液态包层设计提供参考。     

基于原油最高温度点变化规律分析停输相变传热

采用分区法数学模型,利用等价比热容法处理析蜡潜热问题,追踪停输相变过程中管道内原油最高温度点位置的变化轨迹,确定管道内原油最终凝固位置,提出管道内原油全凝的判断依据。基于最高温度点位置的变化规律将传热过程分为四个阶段,重点讨论了各阶段中自然对流、潜热释放、传热方式转化对最高温度位置点变化的影响,结合Ra数变化分析了自然对流换热影响从强到弱的变化过程。深入探讨了停输相变过程中管道内固相率的变化及不同位置处原油温降曲线的特点。     

750keV射频四极注入器水冷设计

750 keV,201.25 MHz的射频四极注入器为四杆型,电极长度124 cm,共16个支撑板。根据加速器射频结构设计的结果进行了水冷管道的结构设计,理论分析了管路的流体力学特性和传热学特性。在忽略结构形变的情况下,利用射频计算软件的稳态热分析功能计算了加速腔的温度分布,降低了模拟计算的难度。计算结果表明:加速腔的最大温升控制在1 K以内,水冷系统能够使加速器在适宜的温度下长时间稳定运行,设计结果很好地满足了物理需求。     

核磁共振陀螺中原子气室温度场的研究

为研究核磁共振陀螺中加热机构对原子气室性能的影响,设计了5种典型加热方式。利用有限元分析软件ANSYS建立了原子气室的温度场模型,给出了原子气室表面的稳态温度场分布情况。同时设计了探测精度为0.01℃的测温电路,对原子气室表面不同位置的温度进行监控,获得了不同加热方式下原子气室表面的温度变化情况。将仿真和实验结果进行比较,发现误差在5%之内,验证了仿真模型的正确性。综合仿真和实验结果比较了不同加热方式下原子气室表面温度分布情况,获得了能够使原子气室表面温度分布最均匀的加热方式。     

All-fiber bidirectional passively mode-locked ring laser

We report the design and operation of a novel all-fiber bidirectional passively mode-locked ring laser. An erbium-doped fiber was chosen as the active element in a ring cavity arrangement. A short segment of a fiber taper embedded in carbon nanotubes/polymer composite, acting as a saturable absorber, was used to enable bidirectional mode locking. The laser generates two stable femtosecond pulse trains in opposite directions. A beat note of about 2 MHz, having a bandwidth of less than 2 kHz, is measured when the pulses propagating in opposite directions are (temporally) overlapped at a photodetector. We believe this device will find important applications in precision rotation sensing.     

New methods of measuring thermal and thermoelectric characteristics of substances,particularly semi-conductors on samples of undefined shape

A new method of measuring the thermal and thermoelectric characteristics of materials, especially semi-conductors, is elaborated theoretically and experimentally. Measurements are made in an unstationary regime on large enough samples (e.g. in liquids) but it is also possible to measure by stationary means. The contacts are either probes or linear. An especial advantage of the proposed methods is that they are quick, and, if linear wires are chosen as contacts, all the most important electrical, thermal and thermoelectric characteristics of materials can be measured in the same arrangement even up to high temperatures, and also in the liquid state after melting. In such an arrangement the conduction of heat by convection or radiation has no influence on the measurements.     

A novel interferometric method for contour mapping of optically rough surfaces

A new white light interferometric arrangement for contour mapping of light diffusing but not depolarising surfaces is presented and compared with related electronic speckle and holographic interferometry (ESPI and HI) methods. Using two angles of illumination of the tested surface, and modifying the light beam in the observation pupil it is possible to observe contour fringes with arbitrary sensitivity depending on the geometry of a chosen set-up.     

基于HHT与LSSVM的远区核爆电磁脉冲识别

为实现远区核爆电磁脉冲（NEMP）和闪电电磁脉冲（LEMP）的有效识别,提出一种基于希尔伯特黄变换（HHT）和最小二乘支持向量机（LSSVM）的识别算法。采用希尔伯特黄变换对远区NEMP和LEMP进行分析,利用两种信号的Hilbert谱在不同频带上分布的差异性,选择谱图中两个区域的能量占比作为信号的特征,选择LSSVM作为分类器进行分类识别。实验结果表明,采用能量占比特征可有效识别NEMP和LEMP,且综合识别率可达到98.59%。     

Dependence of the Structural Stability of MCM-41 on the Impregnating Iron Solution

Hyperfine Interactions - The MCM-41 mesoporous material was chosen as support of very small iron oxide particles. To study the preparation conditions that allow to preserve the support structure...     

Plateau borders of smectic liquid crystalline films

We investigate the geometrical properties of Plateau borders in an arrangement of connected smectic A free standing films. The geometry is chosen such that a circular Plateau border surrounds a planar smectic film and connects it with two smectic catenoids. It is demonstrated that, similar to soap films, the smectic film geometry can be described by a negative line tension of the circular contact region. Thus, the equilibrium angle between the films depends upon the liquid content in this region, and with increasing liquid content, deviations from Plateau's rule are observed. The experimental results are qualitatively comparable to soap films. A possible origin of slight quantitative differences is discussed.     

Solving Delay Differential Equations Through RBF Collocation

A general and easy-to-code numerical method based on radial basis functions (RBFs) collocation is proposed for the solution of delay differential equations (DDEs). It relies on the interpolation properties of infinitely smooth RBFs, which allow for a large accuracy over a scattered and relatively small discretization support. Hardy's multiquadric is chosen as RBF and combined with the Residual Subsampling Algorithm of Driscoll and Heryudono for support adaptivity. The performance of the method is very satisfactory, as demonstrated over a cross-section of benchmark DDEs, and by comparison with existing general-purpose and specialized numerical schemes for DDEs.     

Atomistic model of physical ageing in Se-rich As–Se glasses

Thermal, optical, X-ray excited and magnetic methods were used to develop a microstructural model of physical ageing in Se-rich glasses. The glass composition As₁₀Se₉₀, possessing a typical cross-linked chain structure, was chosen as a model object for the investigations. The effect of physical ageing in this glass was revealed by differential scanning calorimetry, whereas the corresponding changes in its atomic arrangement were studied by extended X-ray absorption fine structure, Raman and solid-state ⁷⁷Se nuclear magnetic resonance spectroscopy. Straightening–shrinkage processes are shown to be responsible for the physical ageing in this Se-rich As–Se glass.     

A note on the theory of spin wave resonance in spiral structures

The appearance of two resonant modes of spin waves with different non-zero wave vectors is theoretically predicted for a magnetic arrangement of the type of an antiferromagnetic spiral combined with weak antiferromagnetism in the direction of the spiral axis. A study is made of the question of the Hamiltonian suitable for possible applications of the chosen magnetic arrangement, and the possibility of energetic stability of the considered magnetic structure for two concrete realistic forms of the Hamiltonian is pointed out.The author expresses his sincere thanks for valuable discussions and stimulating comments to Dr. S. Krupika and Dr. J. Loos, P. Novák and I. Veltruský of the Institute of Solid State Physics of the Czechoslovak Academy of Sciences, and to Assoc. Prof. J. Morkowski and Assoc. Prof. L. Kowalewski of the Polish Academy of Sciences and Poznan University.     

Theory and simulation of chain molecules with multiple bonding sites in an associating solvent

Although polyethylene oxide (PEO) is soluble in water, polymethylene oxide (PMO) is not, even though PMO has more association sites. Some suggest this is due to orientation effects in the water hydrogen-bond network. A simulation and theory study of the effect of bonding site density on thermodynamic properties and extent of bonding of a linear flexible chain in a hydrogen-bonding solvent is performed. Predictions from Wertheim's theory are compared against simulation results. Thermodynamic properties and extent of bonding were obtained. The solvent molecules are modeled as hard spheres with four association sites in a tetrahedral arrangement. The chains are flexible and consist of six tangent segments of hard spheres with bonding sites that interact with the solvent molecules. A solvent molecule can also form a bond with a second solvent molecule. The association interaction is modeled with an orientation-dependent square-well. The total number of bonding sites on each chain is varied and the effects studied. This is another test of the theory for the case of mixtures of associating molecules of different sizes. The Metropolis Monte Carlo technique was chosen to perform simulations in the canonical and isothermal–isobaric ensembles. Good agreement was found between theory and simulation.