分布损耗加载回旋行波管多模稳态注波互作用理论与比较证实

基于目前国际上实验研究的均匀介质加载和周期介质加载结构,建立了一种分布式损耗加载回旋行波管(gyro-TWT)多模稳态注波互作用理论.利用这一理论,以TE01模式基波gyro-TWT注波互作用为例,将Ka和W波段的理论结果与实验和软件仿真进行比较,以证实理论的合理性.     

船舶典型结构损耗因子试验及应用研究

损耗因子是衡量系统阻尼特性并决定其振动能量耗散能力的重要参数,对船舶水下噪声预报分析具有重要影响。针对船舶结构特点,选取内底板、舱壁板和甲板等典型结构建立试验模型,基于瞬态衰减法,对船舶典型结构损耗因子进行测试,分析、掌握其特性规律。在此基础上,开展船舶典型结构损耗因子水下噪声预报应用研究,结果表明,损耗因子对船舶水下噪声具有较大影响,进行船舶水下噪声预报时需开展相关损耗因子测试。     

利用多普勒移动衰减法研究46Ti核的激发态能级寿命

原子核的能级寿命直接反映了其内部的结构信息,是核性质研究中一个十分重要的物理参量。本工作报道了依托兰州重离子加速器装置,首次采取多普勒移动衰减法(DSAM)开展的原子核能级寿命测量。采取核反应¹²C(³⁶Ar,2p)来布居⁴⁶Ti的高激发态,利用新组建的大型高纯锗(HPGe)探测器阵列进行符合测量。根据γ能谱分别提取了4⁺、5^-、6^-态的能级寿命,并得到了这些态的跃迁概率。理论上采取大规模组态混合壳模型进行计算,并得出了能级的组态信息。     

超导低电阻接头衰减法测试过程中的拟合偏差控制

超导技术在许多高新技术领域有着广泛而深远的应用前景,其中超导导体接头技术是超导发展过程中必不可少的关键环节之一,快速而又准确地评估低电阻接头显得尤为重要.本文在考虑超导体的E-J特性后,针对目前低电阻接头采用的衰减法测量,计算得出感应电流完整的衰减曲线方程-幂函数方程.对比目前广泛采用的指数方程拟合与采用幂函数方程拟合的偏差,指出采用指数方程代替幂函数方程拟合的必要条件,为接头电阻衰减法测试,尤其是低电阻接头情况下的测量提供参考.     

随机耦合模型中损耗因子的分析与获取

随机耦合模型(RCM)是研究电磁脉冲干扰下波混沌系统中感应电压统计预测的新方法,其中波混沌腔体损耗因子的获取是这种方法使用的关键。从随机耦合模型理论出发,分析了损耗因子对腔体阻抗随频率变化特性的影响,探讨了不同损耗因子下归一化阻抗矩阵的统计特性,提出了使用腔体散射阻抗与辐射阻抗的比值作对照,以快速获取腔体损耗因子的新方法。     

多模干涉器的精确计算及弱限制下的损耗分析

对多模干涉器的模场传播常数和光场分布进行了精确计算,并与解析近似计算结果进行了比较,发现在弱限制条件下出现输出光能量降低的真正原因：一方面是波导支持的导模数量较少,导致高频成分丢失,自映像质量下降,形成大的弥散斑,造成输出耦合损失;另一方面是由于高频辐射模直接辐射带走了一部分能量。该分析结果纠正了传统的模糊观念。     

78Kr高自旋态的形状共存

用熔合蒸发反应 58Ni(2 3Na,3p) (Ein=70 Me V)和 58Ni(2 8Si,α4p) (Ein=1 30 Me V)研究了78Kr的高自旋态 ,用美国劳伦斯伯克利国家实验室的γ球测量了实验中产生的瞬时符合事件,对新发现的一个负宇称带用多普勒位移衰减法对 1 0 0 4 ke V(1 0 -→ 8-)和 873ke V(8-→ 6-)作了多普勒展宽谱线形状测量 .得到了负宇称带 1 0 -态能级的寿命τ=(2 .2± 0 .3) ps,8-态能级的寿命τ=(1 .6± 0 .2 ) ps.故可知此负宇称带呈现长椭形变 ,与正宇称带的扁椭形变形状共存. Doppler shift attenuation lifetime measurements were performed in the 58 Ni( 23 Na,3p) reaction at 70 MeV and 58 Ni( 28 Si, α4p) reaction at 130 MeV. By analyzing the Doppler broadened line shapes of the 1 004 keV(10 -→8 -) negative parity transition in coincidence with depopulating transitions, the lifetime of the 10 - state has been deduced as τ =(2.2±0.3) ps. A similar analysis of 873 keV(8 -→6 -)transition gave values of τ =(1.6±0.2)...     

平行圆柱面导热形状因子的保角变换法

本文采用保角变换将两个平行偏心的等温圆柱面之间的稳态导热变换为同心同轴的圆柱面之间的导热,得到稳态导热情况下偏心圆筒壁、两平行圆柱面以及地下埋管与地面之间等三种实际情况下的导热形状因子,为简化热流量计算提供方便,为对其机理的认识拓展新思路.     

Approximation errors for the measurement of coupling loss factors using the ELD method

In this paper the formulae are developed to predict the approximation error resulted from the use of the energy level difference (ELD) method. The predicted approximation error can then be used to assess the feasibility of the application of the ELD method. The effects of different parameters on the approximation error are analysed and discussed. Two practical applications are presented. Both numerical and experimental results showed that the ELD method could give identical results (from experimental point of view) as other existing methods as long as α_i and β_i are small.     

Tuneability amplification factor and loss of high-contrast composites

The problem of tuneability of nonlinear ferroelectric–dielectric composite materials is addressed. Attention is concentrated on the analysis of the tuneability amplification factor, K, of a composite material, which is introduced as the ratio of the effective tuneability of a composite material to the tuneability of its ferroelectric (tuneable) component. Previously, ferroelectric–dielectric composite materials have been designed with an effective tuneability amplification factor slightly greater than 1 (i.e. 1.1–1.4) [A.K. Tagantsev et al., J. Electroceramics 11 (2003) p.5; A.G. Kolpakov et al., J. Electroceramics 18 (2007) p.129]. It is demonstrated that the tuneability amplification factor can take values significantly greater than 1. Numerical prototypes (structural designs integrated with finite element method tools) of microstructures are presented with K in the range 3 to 30. The effective tuneability of nonlinear composite materials strongly depends on the microgeometry and microtopology of the material and, in general, cannot be described in terms of volume fraction of components of composite material. In the designs presented, the increased tuneability is due to concentration of the high electric field in narrow regions with carefully selected geometry. The problem of loss in ferroelectric–dielectric composite materials is discussed. In the general case, the loss tangent stays between that of the components of the composite. For high-contrast ferroelectric–dielectric composite materials, the effective loss tangent is practically equal to the loss tangent of the ferroelectric.     

样品厚度对稳态法测定不良导体导热系数实验的影响

用稳态法测量了不同厚度橡胶板的导热系数,并分析了实验结果的一致性和正确性.发现当样品厚度较小时测量结果具有更优的一致性,并且更接近于真实值.     

Computing electron energy loss spectra with the Discontinuous Galerkin Time-Domain method

In this work, we demonstrate how to extract electron energy loss spectra of metallic nano-particles from time-domain computations. Specifically, we employ the Discontinuous Galerkin Time-Domain (DGTD) method in order to model the excitation of individual metallic nano-spheres and dimers of spheres by a tightly focussed electron beam. The resulting electromagnetic fields that emanate from the particles act back on the electrons and the accumulated effect determines the electrons’ total energy loss. We validate this approach by comparing with analytical results for single spheres. For dimers, we find that the electron beam allows for an efficient excitation of dark modes that are inaccessible for optical spectroscopy. In addition, our time-domain approach provides a basis for dealing with materials that exhibit a significant nonlinear response.     

瞬发中子密度衰减法计算中子代时间

采用蒙特卡罗程序MCNP计算了西安脉冲堆中子代时间。使用MCNP程序模拟了反应堆瞬发中子通量密度衰减,基于忽略缓发中子项的点堆动力学方程计算出中子代时间。在微次临界下,研究了次临界度、源的分布、计数区域等对西安脉冲堆中子代时间计算结果的影响。计算分析表明：采用瞬发中子密度衰减法计算中子代时间时,微次临界度、源分布、计数区域等对计算结果影响都很小;误差产生的主要原因是忽略缓发中子项的点堆动力学方程并不能较好地反应瞬发中子通量密度的衰减规律。     

瞬发中子密度衰减法计算中子代时间

采用蒙特卡罗程序MCNP计算了西安脉冲堆中子代时间。使用MCNP程序模拟了反应堆瞬发中子通量密度衰减,基于忽略缓发中子项的点堆动力学方程计算出中子代时间。在微次临界下,研究了次临界度、源的分布、计数区域等对西安脉冲堆中子代时间计算结果的影响。计算分析表明:采用瞬发中子密度衰减法计算中子代时间时,微次临界度、源分布、计数区域等对计算结果影响都很小;误差产生的主要原因是忽略缓发中子项的点堆动力学方程并不能较好地反应瞬发中子通量密度的衰减规律。     

电容量及损耗角的一种测量方法

介绍了在微机控制的自动测量装置中采用的双极性电容器的测试方法。这种方法用反相运算放大器微分电路获得与电容器相关的两个工频电压,并通过对它们数字化输入微机内存,最后通过对数字化后的两个周期信号进行处理求得电容量和损耗角正切。     

Isothermal decay method for analysis of thermoluminescence: a new approach

A variant of the isothermal decay method to determine the trap activation energy E in thermoluminescence is put forward. The area under the phosphorescence curve recorded at different temperatures is employed to calculate E by re-arranging the original equations by Randall–Wilkins, Garlick–Gibson and May–Partridge. As an example, the proposed method is applied to calculate E for a real phosphor and compared with other well-established methods.     

非线性耗散对亚稳态系统量子衰变速率的影响

发展了一种快速傅里叶变换路径积分方法，研究非线性耗散系统的量子衰变速率，得到了Bounce轨道的作用量S_B，即衰变速率的指数因子.在系统与环境存在非线性耦合f(x)=tanh［λ(x-x_b)］的情形下，发现其对衰变速率具有抑制作用.指数因子随温度T的关系不再满足S_B=a［1-b(T/T_c)²］法则；与通常的线性耗散情形相比，跨越温度T_c回升，即系统更早地进入穿透区域. 关键词： 量子衰变 非线性耦合 路径积分 快速傅里叶变换