Heat spreading in a thin longitudinal fin

In view of the trend towards higher power densities in ever shrinking geometries, understanding heat spreading fundamentals is gaining importance. In this paper heat spreading in thin longitudinal geometries is considered. This geometry is of practical interest in one-dimensional Cartesian geometries. A characteristic length is derived and it is shown that this has physical significance for the distance that heat spreads, and for the total amount of heat cooled away. Furthermore, it is investigated when “thin” is a viable assumption. The use of the characteristic length is illustrated for the case of a line source cooling to a plate and for the case of the fins of a plate heatsink. The results are compared to numerical simulations. The work is an extension of the authors' earlier work on heat spreading in infinite longitudinal geometries and heat spreading in infinite and finite circular geometries.     

Triangular quad-port multi-polarized UWB MIMO antenna with enhanced isolation using neutralization ring

In this study, a quad-port multi-polarized ultra-wideband (UWB) multiple input multiple output (MIMO) antenna system with a new isolation technique is designed for wireless devices. The antenna structure consists of four triangular monopole elements and neutralization ring (NR) structures. The monopoles are back-to-back positioned in symmetrical and orthogonal arrangement. Therefore, they radiate towards four directions without interference, and thus the diversity performance is improved. A novel NR is formed by combining a rectangular ring and a straight line to reduce the mutual coupling due to interoperation of the elements. Each triangular monopole is fed by 50 Ohm microstrip transmission line (MTL) with a thin strip line for ensuring impedance matching. Antenna performance in terms of impedance bandwidth, current distribution, radiation pattern, peak gain and envelope correlation coefficient (ECC) is also investigated. The MIMO antenna system has 3.1–17.3 GHz impedance bandwidth, 1–5 dBi peak gain variation, less than 0.1 ECC. The results indicate that the proposed antenna has the characteristics of larger UWB bandwidth, high isolation by the NR structure, multi-polarization, uniform gain and quasi-omnidirectional pattern.     

Line intensities of acetylene: New measurements in the 1.5-μm spectral region and global modelling in the ΔP=10 series

Using the Fourier transform spectra of the acetylene molecule recorded near 1.5-μm, the intensities of 111 lines belonging to seven hot bands of the main isotopologue ¹²C₂H₂ have been retrieved by means of a multispectrum fitting procedure. Considering the density of lines in the spectra, and the fact that the measured bands are the weakest observed, the accuracy of the measurements is around 10%. At first stage, an empirical treatment of these data has been performed, leading to the vibrational transition dipole moment squared and some Herman–Wallis coefficients. Then the measured line intensities of this work and collected ones from the literature have been treated simultaneously within the framework of the effective operator approach.     

基于超材料结构实现5.8GHz RFID天线小型化设计

设计出一款可应用于RFID（Radio Frequency Identification）系统的5.8GHz传统矩形微带天线,天线辐射贴片尺寸为15.74mm×11.12mm,天线的回波损耗（S11）的实测结果为-23.276dB。此后,在矩形微带天线基础上进行设计改进,通过分别蚀刻15个超材料结构I型谐振环和6个超材料结构开口谐振环(Split Resonant Ring, SRR),构造出两款新型小型化天线。与传统矩形天线相比,在保持方向性、最大增益等参数性能基本不变的条件下,基于超材料结构的天线辐射贴片尺寸分别为12.44mm×9.12mm 和11.74mm×9.1mm,相比传统矩形天线分别缩小了35.2%和41.82%,辐射贴片小型化效果明显,其回波损耗实测结果分别为-21.83dB 和-15.40dB。     

Metric inequalities for routings on direct connections with application to line planning

We consider multi-commodity flow problems in which capacities are installed on paths. In this setting, it is often important to distinguish between flows on direct connection routes, using single paths, and flows that include path switching. We derive a feasibility condition for path capacities supporting such direct connection flows similar to the well-known feasibility condition for arc capacities in ordinary multi-commodity flows. The condition can be expressed in terms of a class of metric inequalities for routings on direct connections. We illustrate the concept on the example of the line planning problem in public transport and present an application to large-scale real-world problems.     

基于集成技术的二维智能焊缝传感器

本文简述了基于GMR的二维焊缝检测传感器.为解决焊接加工自动化过程中焊缝的跟踪检测,将GMR焊枪悬浮高度传感器、焊缝检测传感器以及相应的微处理器有机集成,从而使传感器实现小型化智能化,减少对工件检测的死区范围.该传感器与自动焊接机组成的焊缝跟踪系统,焊缝跟踪精度高、响应速度块,减少了焊缝轨迹空间捕捉算法的复杂性.     

时域有限差分法对不连续微带线的分析

不连续微带线的特性以前已由几种全波方法计算得到.本文涉及的时域有限差分法(FDTD方法)是一种独立的算法,是计算微波相关器件频域特性较新的方法.本文的目的是验证用FDTD方法分析电路组成元件特性的有效性.     

基于基片集成同轴线的双馈点圆极化天线

提出了一种采用基片集成同轴线(SICL)馈电的双馈点圆极化微带贴片天线。具体通过多馈点法实现圆极化,并通过背腔加载提高增益,增加带宽,减小后瓣,降低互耦,提高天线性能。经过仿真验证,该天线能够在42.42～56.69 GHz之间实现S₁₁<-10 dB(相对带宽为28.8%@51 GHz),在45.26～48.08 GHz之间实现轴比小于3 dB,最大增益8.9 dBi。     

同步光分组交换网核心节点光分组长度分析

研究了同步光分组交换网中光分组长度的设计及其对一些网络性能参数的影响,分别推导了光分组中开销所占比率、时延及光纤延时线长度与光分组长度的关系,并给出各自相应的理论分析和数值解析,为光分组中分组长度的设计做了基础工作。     

用于无线能量传输系统的微带天线设计

本文提出一种用于组成无线能量传输(Wireless Power Transmission,WPT)系统的微带天线结构,并采用基于有限元法的电磁仿真软件(HFSS)对微带天线进行3D建模.在二端口网络分析法的基础上,建立磁耦合共振无线能量传输等效电路模型,求解出系统发生频率分叉现象产生的条件以及最大效率时的频率表达式.基于以上方法,研究本文设计的微带天线传输特性,包括:系统的最优传输效率与耦合距离的关系,工作频率与耦合距离的关系,得出在能量传输距离在50cm左右时,天线的谐振频率为12.5MHz,效率可达63%.微带天线具有很大的结构优势,如与集成电路兼容,成本低,体积相对较小,且工艺相当成熟,易大规模批量生产等优势.因此该设计的平面微带天线可用于无线能量传输系统.