Design of Simulation for Time-Division Multiplexing Digital Optimal Frequency Band Transmission System

This paper designs a simulation experiment model of the overall structure of time-division multiplexing digital optimal frequency band transmission system based on MATLAB simulation platform. The parameters of each module in the simulation model are set. The working process and performance of the time-division multiplexing digital optimal band transmission system are simulated. The simulation results show that the digital optimal band transmission system achieves the best transmission receiving conditions and performance, and the designed time-division multiplexing optimal digital band transmission simulation system achieves its functions. The research in this paper will help to improve the level of digital communication technology and to understand the structure of time-division multiplexing digital optimal band transmission system.

Reconstructing early transmission networks of SARS-CoV-2 using a genomic mutation model

The coronavirus disease 2019(COVID-19)pandemic has greatly damaged human society,but the origins and early transmission patterns of the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)pathogen remain unclear.Here,we reconstructed the transmission networks of SARS-CoV-2 during the first three and six months since its first report based on ancestor-offspring relationships using BANAL-52-referenced mutations.We explored the position(i.e.,root,middle,or tip)of early detected samples in the evolutionary tree of SARS-CoV-2.In total,6799 transmission chains and 1766 transmission networks were reconstructed,with chain lengths ranging from 1-9 nodes.The root node samples of the 1766 transmission networks were from 58 countries or regions and showed no common ancestor,indicating the occurrence of many independent or parallel transmissions of SARS-CoV-2 when first detected(i.e.,all samples were located at the tip position of the evolutionary tree).No root node sample was found in any sample(n=31,all from the Chinese mainland)collected in the first 15 days from 24 December 2019.Results using six-month data or RaTG13-referenced mutation data were similar.The reconstruction method was verified using a simulation approach.Our results suggest that SARS-CoV-2 may have already been spreading independently worldwide before the outbreak of COVID-19 in Wuhan,China.Thus,a comprehensive global survey of human and animal samples is essential to explore the origins of SARS-CoV-2 and its natural reservoirs and hosts.

基于湖北输电线路灾情的山火分布特征分析

[目的]利用湖北输电线路山火历史灾情数据对山火分布特征进行分析。[方法]基于2016~2021年湖北省输电线路山火灾情资料,运用数理统计、气候统计和GIS空间叠加方法,对全省输电线路山火时空分布及山火与气象、下垫面、社会人文等影响因子的关系特征进行分析。[结果]时间上,2019年为近几年湖北输电线路山火发生最多的年份,秋冬季是高发季节,其中2月和9月为易发月份;空间上,鄂东地区是山火的频发区域,宜昌及荆门地区为次高发区域。山火与气象关系,大部分山火爆发前1个月降水偏少30%~100%、气温偏高0.5~3℃、湿度偏小3.8%~23%、风速偏大0.1~1.9 m/s。山火与下垫面关系,山火主要发生在耕地,占总数50.32%;山火主要集中在海拔高度150 m以下、坡度6°以下的区域,76.90%的山火发生在阳坡。山火与社会人文关系,山火主要发生在人口密度100~600人/km2的城市圈周边的乡镇及距离道路1.6 km缓冲区的区域。[结论]掌握湖北输电线路山火分布特征,有助于山火风险预警模型指标选取和阈值确定。

矿井无线电波防爆安全发射功率研究

5G,5.5G,WiFi6,WiFi7,UWB,ZigBee等矿井移动通信系统及人员和车辆定位系统等发射的大功率无线电波有点燃瓦斯和煤尘的风险。因此,需要合理设置防爆无线电设备发射的无线电波防爆安全功率阈值,限制防爆无线电设备发射的无线电波功率。欧洲标准CLC/TR 50427:2004《Assessment of inadvertent ignition of flammable atmospheres by radio-frequency radiation-Guide》规定了爆炸性气体环境中无线电波防爆安全接收点火功率阈值,但缺少无线电波防爆安全发射功率阈值的内容。国家标准GB/T 3836.1—2021《爆炸性环境第1部分:设备通用要求》和国际标准IEC 60079-0:2017《Explosive atmospheres-Part 0:Equipment-General requirements》虽然有无线电波防爆安全发射功率阈值的相关规定,但错误地将欧洲标准CLC/TR 50427:2004中的无线电波防爆安全接收点火功率阈值修改为无线电波防爆安全发射功率阈值,大大降低了爆炸性环境中无线电设备所能允许的最大发射功率。由于煤矿井下没有能作为接收天线的起重机这类细长结构物体,且现有矿井无线通信及定位系统工作频率均远大于30 MHz,所以,无线电波防爆安全接收点火功率阈值应为8 W,而不是国家标准GB/T 3836.1—2021和国际标准IEC 60079-0:2017规定的无线电波防爆安全发射功率阈值6 W。在发射天线发射的无线电波能量全部被等效天线吸收的最不利于无线电防爆的传输和耦合情况下,无线电设备工作频率为等效天线谐振频率时,接收点火功率达到最大,为等效天线接收的总功率的一半,即发射功率的一半。在实际工程中,无线传输效率和耦合效率均不会为1,因此,无线电波防爆安全发射功率阈值应是无线电波防爆安全接收点火功率阈值2倍以上。煤矿井下无线电波防爆安全接收点火功率阈值为8 W,因此,煤矿井下无线电波防爆安全发射功率阈值应大于16 W。

Intrinsic physical relationships between rotor modal shapes and instantaneous vibrational energy flow transmission characteristics:Theoretical and numerical analysis and application

The modal vibration of the rotor is the main cause of excessive vibration of the aeroengine overall structure.To attenuate the vibration of the rotor under different modal shapes from the perspective of energy control,the intrinsic physical relationships between rotor modal shapes and instantaneous vibrational energy flow transmission characteristics is derived from the general equation of motion base on the structural intensity method.A dual-rotor-support-casing coupling model subjected to the rotor unbalanced forces is established by the finite element method in this paper.The transmission,conversion and balance relationships of the vibrational energy flow for the rotors in the first-order bending modal shape,the conical whirling modal shape and the translational modal shape are analyzed,respectively.The results show that the vibrational energy flow transmitted to the structure can be converted into the strain energy,the kinetic energy and the energy dissipated by the damping of the structure.The vibrational energy flow transmission characteristics of rotors with different modal shapes are quite different.Especially for the first-order bending modal shape,the vibrational energy flow and the strain energy are transmitted and converted to each other in the middle part of the rotor shaft,resulting in large deformation at this part.To attenuate this harmful vibration,the influences of grooving on the shaft on the first-order bending vibration are studied from the perspective of transmission control of vibrational energy flow.This study can provide theoretical references and guidance for the vibration attenuation of the rotors in different modal shapes from a more essential perspective.

师幼关系对学前儿童自我概念的影响:接受性语言能力和心理弹性的链式中介作用

为探讨师幼关系与学前儿童自我概念的关系,并检验接受性语言能力和心理弹性在其间的中介作用,采用师幼关系量表、接受性语言能力测量、幼儿心理弹性量表和幼儿自我概念量表对911名学前儿童及其教师进行测量和调查。结果表明:1)师幼亲密性和依赖性对学前儿童自我概念具有直接正向预测作用;2)接受性语言能力和心理弹性在师幼亲密性与自我概念之间分别起着部分中介作用,接受性语言能力在师幼依赖性与学前儿童自我概念之间具有部分中介作用;3)接受性语言能力和心理弹性在两种类型师幼关系与学前儿童自我概念之间起着链式中介作用。研究表明,教师与学前儿童建立积极亲密的师幼关系将有助于促进学前儿童自我概念的发展。

重绘“山海”:明胡文焕刻“山海经图”与近世《山海经》的知识重构

在晚明坊刻的书籍史语境下,胡文焕刻“山海经图”一方面以其世俗化的图文形态,勾勒出《山海经》接受史中“到民间去”的重要流脉,另一方面则在与日用类书“诸夷门”等通俗文献的互文中,折射出近世民间视野中关于《山海经》知识的重构方式,并由此为理解早期经典的民间接受与知识传递提供了重要线索。

椭圆函数低通滤波器在机载天线中的应用

以椭圆函数低通滤波器为原型,建立不同形式的宽带低通滤波器,通过HFSS软件对滤波器进行仿真分析。采用不同切向形式工艺降低装配误差对高次模的影响,并通过实际测试数据验证仿真结果的一致性。最终将两种不同形式的滤波器应用于机载天线系统进行业务测试,通过性能及数据对比,选择了一种更适合机载天线系统的宽带低通滤波器,收发隔离度达90 dB以上,为验证滤波器在机载天线中的应用提供了一些思路。

迭代、变迁与再造:有声读物的历史追溯与未来价值

政府工作报告连续10年写入“全民阅读”,有声读物成为数字化时代推动全民阅读的重要渠道。有声读物通过长时间的发展,已经趋于成熟。各时期的有声读物是如何影响社会和受众的?未来会给社会和人们带来哪些可能性?该文从我国有声读物的历史迭代出发,梳理出口语媒介、广播媒介及媒介融合时期有声读物的特点,并聚焦受众参与形式、接受主体及审美态度三方面的变迁,最后从媒介的创新、内容创作的解构及传受关系的重构三个维度构建有声读物未来的价值。追溯有声读物的历史,找准有声读物未来的发展方向,厘清受众的变化,明确有声读物的时代责任,能有效地助力有声读物的未来发展,也能促进全民阅读以更生动的形式开展。

Receptive Anal Intercourse and HIV Infection

Objective: Inform the public that receptive anal intercourse (RAI) is a key transmission route of the human immunodeficiency virus (HIV) epidemic in the United States. Method: The role of receptive anal intercourse (RAI) in this epidemic will be examined using the following approach: 1) Risk comparison of HIV transmission via RAI to the other major routes of transmission. 2) HIV transmission risks of RAI using some of the present risk reduction techniques. 3) HIV infection via anal intercourse among male youth. 4) HIV infection via anal intercourse among women. Results: Of the major transmission routes of HIV, receptive anal intercourse has the highest transmission risk for acquiring HIV infection. RAI is 2 times the risk of needle-sharing during injection drug use (IDU) and 17 times the risk of receptive vaginal intercourse. The estimated per act probability of acquiring HIV from an infected source by the exposure route of RAI is high in most circumstances: 1) Condoms alone only partially reduce the high risk of RAI. With the addition of pre-exposure prophylaxis (PrEP), the risk is further reduced. 2) When one or both partners are infected with a sexually transmitted disease (STD), even with condom use, the risks are very high. With the addition of PrEP the risks are reduced, but RAI still carries significant risks. 3) With exposure to acute HIV (high viral load) the risks of RAI are very high and remain significant even with condom use and PrEP. Anal intercourse often begins in adolescence;both genders are at risk. Conclusion: Public knowledge of the high transmission risks of receptive anal intercourse may likely result in a downward trend of new HIV infections and contribute to ending the epidemic.

Autonomous and Mobile Prototype of Curvature Sensor with Remote Reliable Communication of Spectral Curvature

Through the creation and construction of a curvature sensor of accelerometer type, using the spectral curvature concept or curvature energy that measures curvature in Volts/m3, an autonomous and mobile censorship of curvature sensing with reliable data transmission/reception in real time and remote position is designed and constructed considering the spectra of curvature of the measured curvature energy during the advance of the prototype as the normed measure by with β , a constant rationalized parameter according with the required advance of the mobile device in the control scale of their velocity. Likewise, the sensed curvature data are digitalized through wireless interconnectivity using a HC-05 Module with a programmable device that includes logic blocks whose interconnection and functionality can be configured according to the sensor measure in situs. Also an application is planted to the obtaining of an energy plus due to the curvature that could be used in the displacement of a vehicle.

基于TR-YOLOv5的输电线路多类缺陷目标检测方法

针对复杂环境中输电线路多类缺陷目标的多尺度检测问题,提出一种基于Transformer和感受野模块的YOLOv5输电线路多类缺陷目标检测算法,简记为TR-YOLOv5。首先,搭建了YOLOv5网络,针对复杂背景造成缺陷目标的显著性低,进而影响检测精度的问题,在Backbone部分引入Transformer模块,通过利用多头注意力结构获取特征图像素点间的相关性和全局信息,增强缺陷目标的特征表达能力,从而提升模型检测精度;其次,由于待检测目标受多尺度影响,在Neck部分引入感受野模块提取目标不同尺度的特征,利用空洞卷积增大感受野,为后续PANet结构保留更细致的特征,增强Neck特征融合能力,提高模型对多尺度缺陷目标的检测精度;然后,为了提升预测边框回归精度,引入CIOU函数,进一步提高算法检测精度;最后,利用某电力巡检部门近3年的数据对该算法进行验证。实验结果表明,相比于7种对比算法,本文算法具有较高检测精度的同时具有较好的实时性,其平均检测精度可达95.6%,1280×720分辨率的巡检图像检测速度为125帧/秒。

环保绝缘气体介电强度预测方法评估

为明确各类气体介电强度预测方法的准确性,基于9种气体(N_(2)、CO_(2)、N_(2)O、CF_(4)、SO_(2)F_(2)、c-C_(4)F_(8)、C_(3)F_(8)、C_5F_(10O)和C_(4)F_(7)N)在50 Hz工频交流电场下测得的相对介电强度对5种预测方法进行了评估。结果表明,各方法预测准确性与其给出的可决系数R~2不一致。这主要与其使用的样本数据测试条件不统一、同一气体的相对介电强度不一致有关。当修正上述问题后,各方法准确性得到提升,并与其R~2相符。分子参数的丰富和放电理论的介入可使预测方法准确性提升。使用样本外气体进行验证的方法,其预测结果在修正前后都具有较高的准确性;使用基团贡献法的预测方法也具有上述特性。通过上述评估结果可知,样本中的气体数据需在统一条件下获得,并根据试验条件和样本分子特征确定预测方法的适用范围。放电理论、分子几何特征和新分子参数的引入有助于提高预测模型的准确性。模型验证和基团贡献法可提高预测方法对样本数据的包容性。

多层次传递型内幕交易责任认定的实证考察与理论反思

信息传递与互联网技术的耦合带来传递型内幕交易中传播链条的延长,造成现行推定规则在追究各信息受领主体责任时的局限性,也导致了法律责任在交易端与泄露端间的严重不匹配。应当认识到,泄密人与受密人责任是成立内幕交易责任的两个方面,现行推定规则实则是在泄密人责任成立的基础上对受密人责任的推定。将泄密人违法性具体化为从泄密中获益,受密人交易行为的违法性具体化为对受密人违法的认知,方能揭示内幕交易以获益为核心的违法性本质。身份关系所蕴含的人际利益是信息传递的原动力,在坚持一次推定的基础上,通过分析信息传递过程中各主体间的身份关系,以信息获取便利性与利益一致性为实质审查标准,可以将形式上处于不同传播层级的主体实质认定为同一层级知情人,从而在确保推定事实效力的基础上对内幕交易责任主体实现精准覆盖。

“天问一号”环绕器测控数传通信系统设计与验证

针对“天问一号”火星环绕器最远距离4亿km下的超远距离大动态通信难题,“天问一号”火星环绕器测控数传通信系统通过多天线波束赋形的测控数传一体化技术、多码率自适应收发处理技术、高灵敏度信号捕获技术、超高灵敏度下的电磁干扰抑制技术以及极低温下大口径天线高精度稳定指向技术,实现了对–156 dBm微弱信号的高灵敏度捕获以及大动态下的数据自适应收发,除天体遮挡外全过程100%对地通信链路覆盖和波束覆盖,最远4亿km处对地数传速率达1 Mbps。该项技术已经在“天问一号”火星探测任务中得到了考核和验证,可以为后续深空探测任务中测控数传通信系统的设计与在轨工作提供参考。

电容式微机械超声换能器的水下收发性能

为满足水下超声探测的应用需求,设计了一种采用硅基集成电路制造工艺制备的电容式微机械超声换能器(CMUT)。首先介绍了CMUT的工作原理及其结构参数,然后完成了CMUT的水密封装,最后对封装后CMUT的电容-电压(C-V)特性、发送电压响应级、接收灵敏度与回波信号进行测试。测试结果表明,封装后的CMUT具有良好的C-V特性,电容变化量最大可达313.7 pF,其发送电压响应级最大值为163.83 dB@2 MHz,接收灵敏度最大值为-228.27 dB@1 MHz,因此其在水下环境具备良好的发射超声波与接收超声波的能力。该研究结果为高密度CMUT阵列的设计和封装及水下超声探测提供了理论和应用依据。

嵌入视觉关系掩码的多类别金具检测方法

在对输电线路金具进行检测的过程中,由于受到复杂背景的影响,一些互相遮挡或者特征不明显的金具会隐匿在复杂环境难以精确检测。针对这一问题,提出了基于视觉关系掩码的多类别金具检测模型,通过挖掘和提取输电线路金具之间包含空间信息的视觉关系先验知识,构建视觉关系掩码和视觉关系检测网络,并将先验知识作为辅助信息融入视觉关系模块中,最终实现多类别金具的精确定位与识别。对具有14类金具的数据集进行多种定性和定量实验,结果表明,改进后的模型平均检测精度能提高到76.25%,检测效果也优于其他先进目标检测模型。

心理灵活性代际传递:亲子关系的中介作用和师幼关系的调节作用

本研究采用父母心理灵活性量表、儿童心理灵活性量表、师幼关系量表和亲子关系量表,探究心理灵活性的代际传递作用机制。通过对51个班级的幼儿教师及318名幼儿家长进行问卷调查,多层路径分析结果发现:(1)父母的心理灵活性显著预测幼儿的心理灵活性;(2)亲密亲子关系和冲突亲子关系在父母心理灵活性和幼儿心理灵活性之间起部分中介作用;(3)师幼关系不仅可以调节亲密亲子关系、冲突亲子关系对幼儿心理灵活性的影响,而且可以调节亲密亲子关系、冲突亲子关系对父母心理灵活性与幼儿心理灵活性的中介作用。

高频适用的层状介质电磁场数值模拟

在地球物理勘探中,均匀层状介质电磁场表达式含有汉克尔积分,其核函数可以化简为含有0阶与1阶的贝塞尔(Bessel)函数组合,限于电磁场的复杂特性,大部分层状介质电磁场汉克尔积分不存在解析表达式,且随着其宗量的增大,Bessel函数呈现出快速振荡和慢衰减的特性,由此造成电磁场难以高精度计算,特别是高频和长收发距情况下难度更大。针对这一问题,本文提出一种可适用高低频及长短收发距的全解析积分方法,其基本思想是将层状介质电磁场表达式中的汉克尔积分的系数部分采用二次形函数插值,其单元内插值结果与贝塞尔函数的乘积可推导出解析表达式,然后将所有离散单元叠加求和,从而求得汉克尔积分的数值解,最终实现高精度的层状介质数值模拟。采用含有不同形式贝塞尔函数积分的全空间电磁场表达式对全解析积分算法进行测试,计算结果表明:该算法正确且精度高;本文算法在不同的频率范围与收发距下均具有较高的计算精度,特别在高频与长收发距下,比选取的四种数字滤波算法计算精度高两个数量级以上,具有较强的普适性。