A Novel Beam Design Method for mm Wave Multi-Antenna Arrays with Mutual Coupling Reduction

To overcome the mutual coupling (MC) of multiple antennas in millimeter wave (mmWave) communication systems, a novel beam design method with low complexity is proposed in this paper. Firstly, an equivalent channel model incorporating the effect of MC is analyzed and established, and then an optimal precoding / combiner vector for beamforming is derived. On this basis, by using greedy geometric (GG) algorithm, a novel hybrid beam design method is proposed. Finally, the performance of proposed method is analyzed and compared with other traditional ones. The simulation results show that the proposed method has better suppression of the MC effect as well as lower complexity.

Beam Position and Beam Hopping Design for LEO Satellite Communications

The numbers of beam positions(BPs)and time slots for beam hopping(BH)dominate the latency of LEO satellite communications.Aiming at minimizing the number of BPs subject to a predefined requirement on the radius of BP,a low-complexity user density-based BP design scheme is proposed,where the original problem is decomposed into two subproblems,with the first one to find the sparsest user and the second one to determine the corresponding best BP.In particular,for the second subproblem,a user selection and smallest BP radius algorithm is proposed,where the nearby users are sequentially selected until the constraint of the given BP radius is no longer satisfied.These two subproblems are iteratively solved until all the users are selected.To further reduce the BP radius,a duplicated user removal algorithm is proposed to decrease the number of the users covered by two or more BPs.Aiming at minimizing the number of time slots subject to the no co-channel interference(CCI)constraint and the traffic demand constraint,a low-complexity CCI-free BH design scheme is proposed,where the BPs having difficulty in satisfying the constraints are considered to be illuminated in priory.Simulation results verify the effectiveness of the proposed schemes.

A New Codebook Design Scheme for Fast Beam Searching in Millimeter-Wave Communications

To overcome imperfection of exhaustive based beam searching scheme in IEEE 802.15.3c and IEEE 802.11 ad and accelerate the beam training process, combined with the fast beam searching algorithm previously proposed, this paper proposed a beam codebook design scheme for phased array to not only satisfy the fast beam searching algorithm's demand, but also make good use of the advantage of the searching algorithm. The simulation results prove that the proposed scheme not only performs well on flexibility and searching time complexity, but also has high success ratio.

Beam Line Design of Compact Laser Plasma Accelerator

A compact laser plasma accelerator that is a novel accelerator based on the interaction of ultra-intense laser and plasmas is being built now at Peking University. According to the results of experiments and numerical simulations, a beam line combining the advantages of quadrupole and analyzing magnets is designed to deliver proton beams with energy ranging from 1 to 44MeV, energy spread within ±5% and 10^6-8 protons per pulse. It turns out that the existence of space charge force of protons can be ignored for the increase of transverse and longitudinal envelopes even in the case of 10^9 protons in one pulse. To cope with the challenge to obtain a uniform distribution of protons at the final experiment target in laser acceleration, we manipulate the envelope beam waist in the Y direction to a proper position and obtain a relatively good distribution uniformity of protons with an energy spread of 0-±5%0.

Beam Dynamics Design of a 50 mA D^+ RFQ

A new 973 project was proposed by Peking University and Institute of Modern Physics of Chinese Academy of Sciences recently. The project requires a 50mA, 162.5MHz, cw mode radio frequency quadrupole （FtFO,） to accelerate the D＋ to 1 MeV. In a high-current linear accelerator, the strong space charge effect causes the growth of envelope and emittanee along with heavy beam losses. In the beam dynamics design of this RFQ, beam envelope mismatching is discussed and a matching dynamics method is proposed to minimize the envelope and emittance growth. The influence of limiting current on the beam transmission is discussed and used in the optimization of transverse and longitudinal parameters. After the optimization, the beam transmission efficiency reaches higher than 98%.

Four-Rod RFQ Beam Dynamics Design of PKUNIFTY Upgrade

The Peking University neutron imaging facility (PKUNIFTY), an RFQ-based neutron source, aims at developing industrial applications. During the past 3 y operation, some problems have appeared, such as RF sparking for the RFQ high power operation, full power level instability of RF transmitter, and the misalignment of RFQ electrodes assembling and deformation. The PKUNIFTY upgrade endeavors to adopt a modest inter-voltage beam dynamics design. The new beam dynamics design of 201.5MHz RFQ of PKUNIFTY, which accelerates 35mA of D+ from 50 keV to 2.0MeV at 10% duty factor, is performed. The averaged D+ beam will be about 3 mA. The source will deliver a fast neutron yield of 2.5x10(12) n/s via the deuteron-beryllium reaction, which is about 10 times higher than the current status.

Recent developments in the structural design and optimization of ITER neutral beam manifold

This paper describes a new design of the neutral beam manifold based on a more optimized support system.A proposed alternative scheme has presented to replace the former complex manifold supports and internal pipe supports in the final design phase.Both the structural reliability and feasibility were confirmed with detailed analyses.Comparative analyses between two typical types of manifold support scheme were performed.All relevant results of mechanical analyses for typical operation scenarios and fault conditions are presented.Future optimization activities are described,which will give useful information for a refined setting of components in the next phase.

Optimal Design for Thin-Walled Box Beam Based on Material Strength Reliability

According to the reliability of material strength,the optimal design for the cross sectional size of thin walled box beam was studied.Firstly the cross sectional size as design random variable was determined,then its stochastic nature was researched,with which the objective function is to seek the maximum reliability of the beam under given constraint conditions.This way is not the same as the conventional optimal design for the minimum weight of the material.With establishing the optimal objective,the reliability of the material under conditions of static and fatigue was considered.The corresponding calculated expressions are given.Normally the cross section sizes are fitted to the normal distribution,for the simplification of the design variable,the variation of the section size is assumed as a dependent variable proportional to the mean of the size.The way is different not only with the conventional optimal design but also with the common reliability design.The maximum reliability of material is obtained,meanwhile the area of the cross section is reduced,i.e.,the weight of the material is decreased.

Beam Dynamics and Electromagnetic Design Studies of 3 MeV RFQ for SNS Programme

The physics design of a 3 MeV, 30 mA, 352.2 MHz Radio Frequency Quadrupole (RFQ) is done for the future Indian Spallation Neutron Source (ISNS) project at RRCAT, India. The beam dynamics design of RFQ and the error analysis of the input beam parameters are done by using standard beam dynamics code PARMTEQM. The electromagnetic stu-dies for the two-dimensional and three-dimensional cavity design are performed using computer codes SUPERFISH and CST Microwave Studio. The physics design of RFQ consisting of the beam dynamics design near the beam axis and the electromagnetic design for the RFQ resonator is described here.

STRUCTURE DESIGN OF THE BEIJING SPECTROMETERⅢBEAM PIPE

The Beijing spectrometer Ⅲ （BESⅢ） beam pipe is in the center of the BESⅢ, which is the detector of the upgrade project of Beijing electron and positron collider （BEPC Ⅱ）. Electrons and positrons collide in the BESⅢ beam pipe. According to the demands of the BEPC Ⅱ, a key program of Chinese Academy of Sciences, the BESⅢ beam pipe is designed based on the finite elements analysis. The BESIII beam pipe is installed in the inner cylinder of the BESⅢ drift chamber. As a vacuum tube, the BESIII beam pipe is designed as 1 000 mm in length, 63 mm in inner diameter and 114 mm in outer diameter, respectively. The BESIII beam pipe consists of a central beryllium pipe cooled by EDM-1, the oil No.1 for electric discharge machining, and two extended copper pipes cooled by deionized water （DW）. The three parts are jointed by vacuum welding. Factors taken into account in the design are as follows. ① The wall thickness of the central beryllium pipe should be designed as small as possible to reduce the multi-scattering and improve the particle momentum resolution. And the wall thickness of the extended copper pipe should be designed as large as possible to protect the detectors from the backgrounds. ②The BESⅢ beam pipe must be sufficiently cooled to avoid the damage and prevents its influence to the BESⅢ drift chamber （DC） operation. The inner surface temperature of the DC inner cylinder must be maintained at 293±2 K. ③ The magnetic permeability of the materials used in the BESⅢ beam pipe must be less than 1.05 H/m to avoid large magnetic field distortions. ④ The static pressure of the vacuum chamber of the BESⅢ beam pipe must be less than 800 μPa. The simulating results show that the designed structure of the BESⅢ beam pipe satisfies the requirements mentioned above. The structure design scheme is evaluated and adonted hv the headouarters of BEPCⅡ.

Designs of Two-Element Optical Refracting System to Achieve Uniform Laser Beam Profile

Various specific laser irradiance distribution outputs are needed in many applications. To fulfill this need, a detailed step-by-step design procedure for split refracting system is proposed for three types of laser beams transformation: 1) Annular-uniform-to-uniform;2) Annular-Gaussian-to-uniform;and 3) Gaussian-to-uniform to obtain the required laser irradiance distributions. Mathematical expressions of the two Plano-aspheric surfaces are derived for each type. The proposed designs take into account few important parameters such as the system length, the surfaces radii of curvature, the annular beam starting cone angle, and the beams power ratio. Further, the proposed designs are much better than the ones, which were previously

模块化防屈曲钢板墙抗震性能

考虑经济性和便利性,提出了模块化防屈曲钢板墙及其常用模数,然后基于已有的防屈曲钢板墙的简化计算模型,推导了在不同墙数量情况下,模块化防屈曲钢板墙充分发挥抗震性能时,周边梁的承载力和刚度需求,并提出了周边梁的设计方法.进而,对模块化防屈曲钢板墙和整体墙进行了对比验证试验及其有限元模拟分析.研究结果表明:模块化防屈曲钢板墙能够达到与整体钢板墙相同的抗震性能,且周边梁未发生明显转动和破坏,说明所提出的周边梁设计方法是合理的;在层间位移角为1/50时,防屈曲钢板墙上下周边梁均未进入塑性,且承载力和初始刚度等的有限元值与试验值误差小于6%,从而进一步验证了其抗震性能.

复合材料在汽车防撞梁上的应用研究进展

为促进复合材料在汽车构件中的应用,以汽车保险杠防撞梁为例,对复合材料防撞梁的材料、结构设计以及保险杠内部零件连接的研究进展进行综述。简述了碳纤维、玻璃纤维以及天然纤维等复合材料在汽车防撞梁上的研究进展,介绍了不同结构复合材料防撞梁对于耐撞性能的影响,分析了保险杠内部零件不同连接方式的优缺点。最后提出了汽车复合材料防撞梁的未来发展方向,应注重新型复合材料的开发、防撞梁结构的优化设计以及新型连接方式的研究。

Designing of an Automatic Paraffin Controlling Device for a Beam Well

Aiming at the paraffin-deposition problem of a beam well, the automatic paraffin-controlling device is designed by making use of ratchet-pallet mechanism, cam mechanism and modern designing method. The device has four main functions： paraffin-controlling, paraffin removal, centralizing the pumping rod, and improving the safety of well tubing. This device integrates the advantages of the paraffin control, such as strong magnetic paraffin controlling and mechanical paraffin-cutting. Theoretical analysis shows that this device has fine working reliability. It turns out to be a new device which can solve the paraffin-deposition problem of a beam well economically and efficiently.

双向密肋楼盖的计算及设计探讨

在双向密肋楼盖的设计中采用弹性板对楼板进行计算分析,但与实际密肋楼盖结构相比,常用软件的计算模型在柱帽区域的计算假定存在重复考虑柱帽厚板与框梁重叠区域、板柱连接区与梁柱连接区重叠区域的问题。针对该问题,对密肋楼盖柱帽区域建立了多种不同计算假定的计算模型,分析了各模型对楼盖构件内力的影响,结果表明:考虑这些计算假定上的差异后,会导致与柱帽区域相连接的构件内力计算结果产生极大的变化。设计中应充分关注这些差异带来的影响,避免出现结构安全问题。此外,对密肋楼盖采用将柱帽格构化为等代梁的分析方法,能够避免过高估计柱帽承载能力,计算结果合理,且能方便对柱帽进行配筋设计。

基于MATLAB App Designer的光学干涉实验仿真平台的设计与教学应用

利用MATLAB的App Designer功能,设计了典型光学干涉实验的仿真教学平台,实现了杨氏双缝、劈尖、牛顿环、迈克尔逊、法布里-珀罗干涉5个实验的干涉图样复现,且能展示干涉图样随影响因素的动态变化。该平台可帮助学生更好地理解光学干涉原理,培养学生的逻辑思维和科学创新能力,也有助于在线学习以及混合式课堂教学的开展。

机器学习辅助太赫兹涡旋波超表面快速设计方法

太赫兹涡旋波产生与调控被认为是6G通信、雷达探测、新型传感器的关键技术之一。利用人工超表面产生涡旋波,相较于传统方法具有平面化、集成化、低成本的特点,但是面临复杂的参数设计和分析,需要耗费大量的时间和算力。为此,提出一种机器学习辅助太赫兹涡旋波超表面快速设计方法,通过长短期记忆(Long Short-Term Memory, LSTM)神经网络法快速得到满足相位需求的超单元并进行一体化组阵。利用该方法,设计构筑了三块模数l分别为1、2、3的太赫兹涡旋波超表面,仿真结果表明,设计的太赫兹涡旋波束模式纯度达到80%以上。机器学习辅助太赫兹涡旋波超表面设计方法具备精度高、快速、一体化设计等优点,有望运用于太赫兹幅度、相位、极化、轨道角动量等复杂波束调控领域。

发动机燃油泵附件的管路动力学等效设计及实现

燃油泵附件的管路空间构型复杂,在振动环境试验中直接模拟难以实现。为满足试验要求,采用系统等效缩减/扩展过程(SEREP)方法对管路进行动力学等效设计,选取管路上特定结点为主自由度,并将原管路模型缩减至主自由度模型上,得到缩减质量和刚度矩阵;对子振型矩阵采用SVD分解,使得缩减质量和刚度矩阵进一步简化,得到低阶管路模型的新缩减质量和刚度矩阵参数;提出“质量球—梁弹簧”结构模型,分别用“质量球”和“梁弹簧”来映射缩减的质量和刚度矩阵,进而确定等效设计加工参数;通过实例验证等效设计方法的可行性。结果表明:等效管路与原管路的第一阶频率误差大多在10%以内,满足工程应用要求。

古金赤水河大桥主桥总体设计

古金赤水河大桥主桥为(83.5+173.5+575+173.5+83.5)m半飘浮体系双塔双索面斜拉桥。主梁采用双边主梁断面钢-混组合梁,由工字钢主梁和混凝土桥面板组成,全宽43.8 m,设置裙板抑制主梁涡振。桥塔为下塔柱内收的A形塔,南、北塔塔高分别为217 m和261 m。由于山区超高桥塔塔墩景观效果欠佳,采用超高塔柱无塔墩方案,桥塔采用嵌岩群桩基础;针对山区桥梁养护不便的情况,索塔锚固采用耐候钢钢锚梁;针对剪力钉在拉拔力作用下承载能力降低问题,采用以开孔板连接件为主的钢-混结合构造实现锚梁牛腿壁板与塔壁连接。斜拉索采用公称直径15.20 mm、标准抗拉强度1860 MPa的钢绞线拉索,全桥共4×23对(184根),空间双索面扇形布置。由于斜拉索锚拉板+外置减振阻尼器景观效果不佳,选用全内置减振阻尼器方案。

基于准静态法的船体梁极限强度试验设计方法

为了应对采用传统试验法求解船体梁极限强度问题时存在的成本较高的情况,有必要在开展试验之前进行预设计。针对船体梁极限强度试验预设计问题,采用四点弯曲理论对船体梁极限强度开展试验设计,给出具体的试验工装设计方案和加载方案,并采用准静态法分析该方案在中拱状态下的极限强度。将采用该方法所得计算结果与理想状态下的数值计算结果相对比对比,结果发现误差仅为0.08%,表明该试验设计方案可靠、可行。研究结果可为船体梁极限强度试验的开展提供参考。