矿用可穿戴翻折结构半模衬底集成空腔天线设计

根据煤矿井下对可穿戴天线的要求,在半模衬底集成空腔天线的基础上,采用折叠结构降低天线主体的宽度,并利用水平放置的馈电探针实现可穿戴天线扁平化,设计了一种矿用可穿戴翻折结构半模衬底集成空腔天线。仿真结果表明,该天线在5GHz处于谐振状态,-10dB带宽约为254 MHz,最大增益为5.4dBi,辐射效率为70%,辐射方向具有较宽的主瓣和较低的背向辐射,且可通过增加上层衬底厚度来增加天线-10dB带宽。     

矿用多频切换半模衬底集成空腔天线设计

根据煤矿井下无线通信和人员实时监控对可穿戴式天线的要求,在半模衬底集成空腔天线的基础上,分析了通过在空腔不同位置添加短接针对谐振频率的影响,并利用可拆卸式的螺丝代替短接针,设计了一种能够实现2.45~3.07GHz多频切换的矿用可穿戴式天线。由导电布、导电缝纫线和皮革衬底组成的天线实物的测试结果与仿真结果一致,验证了该天线设计的可行性。     

屏蔽罩高度对bow-tie天线性能影响的分析

本文研究了一种终端加载的bow-tie天线,计算所加载的电阻值,并改变其屏蔽罩高度,对其辐射特性和驻波比(VSWR),用软件进行了仿真分析,同时进行了实际测试,并将仿真和实验结果进行了对比.结果表明,仿真和实验的结果基本吻合,为今后进一步的研究工作打下了一定的基础.     

一种矿用定向天线设计

设计了一款适用于巷道类狭长受限空间的双臂平面螺旋天线。该天线由4条等角螺旋线构造的2个对称的螺悬臂组成。与传统的全向天线相比,该天线辐射的定向波束可减少无线电波在巷道壁上的反射损耗,圆极化特性可有效减弱巷道内多径效应的影响,双向辐射特性可提高辐射效率。仿真结果表明,工作在2.4GHz频段时,5圈双臂平面螺旋天线的3dB半功率波瓣宽度大于60°,增益大于4dB;10圈双臂平面螺旋天线的3dB半功率波瓣宽度为120°,增益大于6dB。     

矿用湿式除尘器变频调速性能试验研究

针对由于掘进工作面的不断推进导致掘进巷道的压、抽风量比值减小,从而影响湿式除尘器控尘、除尘效果的问题,介绍了通风机变频调速原理,并通过试验的手段得到湿式除尘器风量与频率、风量与功率及除尘效率与频率的关系,为湿式除尘器的风量控制、变频调速区间的确定等提供了依据。     

A general solution of bending cylindrical shell

In this paper a general solution to the bending problem of cylindrical shells is presented with standard fundamental function. It is practicable in the analysis of the bending problem of cylindrical shells with variable rigidities and reinforced ribs under arbitrary complex loads.     

High performance resonant cavity antenna with non‐uniform metamaterial inspired superstrate

The resonant cavity antenna (RCA) is a class of widely used high gain antennas, but usually suffers from narrow impedance bandwidth owing to its strong resonant property, as well as relatively low aperture efficiency because of its non‐uniform electromagnetic (EM) field distribution on the aperture. This article explores enhancing the RCA's impedance bandwidth and aperture efficiency by designing a non‐uniform metamaterial inspired superstrate, on which the metal patches vary their sizes with respect to their distances to the superstrate's center. After optimized by the Genetic Algorithm, the proposed RCA is designed, fabricated and tested. Measured results agree well with simulated ones and show that in comparison with a RCA with a uniform metamaterial inspired superstrate, this work significantly improves the |S ₁₁| < ?10 dB impedance bandwidth from 2.1% to 6.1%, the gain at the working frequency 10 GHz from 19.07 dBi to 20.55 dBi, and correspondingly the aperture efficiency from 50.5% to 71%. A further analysis estimates that due to the non‐uniform metamaterial inspired superstrate, a more homogeneous distribution for both the amplitude and phase of the EM field is observed on the superstrate's aperture.     

A wearable flexible microstrip antenna based on the floating‐ground backplane

In the present study, a wearable coplanar waveguide fed flexible microstrip antenna is proposed, which is based on the floating‐ground backplane. When the antenna is placed on a high‐loss human body, the antenna maintains reasonable impedance matching and exhibits a peak gain of 5.6 dBi. Moreover, the performance of the antenna under different bending radii and crumpling conditions is also analyzed. The simulation and experimental results show that the bending and crumpling have little effect on the impedance bandwidth and radiation pattern of the proposed antenna. Accordingly, it is concluded that the proposed antenna has great robustness. Furthermore, it is found that the proposed floating‐ground backplane structure significantly reduces the backward radiation of the planar antenna and enables the antenna to obtain a very low specific absorption rate (SAR) and increase the antenna gain. It should be indicated that antennas with great robustness, very low SAR, and small size are ideal candidates for wearable applications.     

A novel design of high performance multilayered cylindrical dielectric lens antenna using 3D printing technology

In this work, design and realization of high performance, low‐cost X‐band multilayered cylindrical dielectric lens antenna (MLCDLA) is presented using 3D printing technology. Firstly, MLCDLA is designed and simulated in the complete 3D CST microwave studio (MWS) within the X‐ band as consisting of six layers and being fed through a conventional rectangular waveguide (WR90). These layers are in the form of cylindrical discs having different radii, thicknesses and made of a cheap polylactic acid material. These layers have also varying dielectric constant from 1.2 to 2.7 that are compatible for fused deposition modeling (FDM) based 3D‐printing process. Secondly, a prototype of MLCDLA is produced by using a FDM based 3D‐printer. 3D printed dielectric lens antenna is measured and a good return loss of almost more than 10 dB within the X‐band with a high gain of 16‐18 dBi are achieved as compared with the counterpart alternative designs. Thus, it can be concluded that the proposed novel design and prototyping method not only achieves the high radiation performance characteristics along X‐band but also is a fast, low‐cost, and effective method for prototyping dielectric lens structures for the microwave applications.     

谐波对矿用干式变压器损耗及温升的影响

为了更准确地分析谐波对变压器损耗和温升的影响,首先建立了干式变压器二维结构模型,并对干式变压器的漏磁场与谐波损耗进行了仿真计算,得到干式变压器轴向和径向漏磁场分布规律及谐波损耗与谐波次数、谐波含有率、谐波电流畸变率的关系;然后利用Fluent对干式变压器二维温度场与流体场进行了流固耦合分析,得到干式变压器温升与谐波次数及谐波电流畸变率的关系。仿真结果表明,干式变压器的谐波铜损耗与谐波电流含有率的平方成正比,且当谐波电流含有率一定时,近似与谐波电流次数的平方成正比;而谐波铁损耗与谐波电压含有率的平方成正比,但当谐波电压含有率一定时,谐波铁损耗随谐波次数的增大而减小,并逐渐趋于平缓。     

Numerical study of non-kinematical conical bending with cylindrical rolls

Although desired cones can be manufactured by kinematical conical roll bending, less manufacturing cost is still largely required. This paper presents the modelling and simulation of non-kinematical conical roll bending process with cylindrical rolls. Such process is achieved by using attachments to reduce the velocity on the area close to the top edge of the plate. In contrast with a kinematical conical roll bending machine, the driving outer rolls of a non-kinematical conical roll bending machine are allowed to slide on the plate close to the top edge. The modelling is based on finite element method under ANSYS/LS-DYNA environment. The bent cones obtained from numerical simulations compare well with the desired cones. Numerical simulation investigations show that the adaptive capacity of the model is available within a range of the top–bottom radius ratio of the desired cones between 0.44 and 0.8.