High performance receiving and processing technology in satellite beam hopping communication

Beam-hopping technology has become one of the major research hotspots for satellite communication in order to enhance their communication capacity and flexibility.However,beam hopping causes the traditional continuous time-division multiplexing signal in the forward downlink to become a burst signal,satellite terminal receivers need to solve multiple key issues such as burst signal rapid synchronization and high-per-formance reception.Firstly,this paper analyzes the key issues of burst communication for traffic signals in beam hopping sys-tems,and then compares and studies typical carrier synchro-nization algorithms for burst signals.Secondly,combining the requirements of beam-hopping communication systems for effi-cient burst and low signal-to-noise ratio reception of downlink signals in forward links,a decoding assisted bidirectional vari-able parameter iterative carrier synchronization technique is pro-posed,which introduces the idea of iterative processing into car-rier synchronization.Aiming at the technical characteristics of communication signal carrier synchronization,a new technical approach of bidirectional variable parameter iteration is adopted,breaking through the traditional understanding that loop struc-tures cannot adapt to low signal-to-noise ratio burst demodula-tion.Finally,combining the DVB-S2X standard physical layer frame format used in high throughput satellite communication systems,the research and performance simulation are con-ducted.The results show that the new technology proposed in this paper can significantly shorten the carrier synchronization time of burst signals,achieve fast synchronization of low signal-to-noise ratio burst signals,and have the unique advantage of flexible and adjustable parameters.

Optimization of the Physical Aperture of the Parabolic Reflector Antenna

In fields like astronomy and radar technology, high-gain antennas are required for long-distance communication. Due to its relatively large gain, the use of parabolic antennas has become very popular over time, because they can easily achieve gains of above 30 dB at microwave and higher frequencies. Today, most systems’ success depends on how well the antennas perform. These antennas are available in different types and sizes. Each antenna’s effective area usually has less than the actual physical area of the antenna surface. This means that the unused area of the antenna is massive, and a waste. The aim of the research is to show that the actual physical aperture of a parabolic antenna can be reduced as much as possible to equal the effective area, as given by the antenna formula, thereby saving manufacturing costs, improve the aesthetics. In other words, the focus of this work is to experimentally show that reflector antenna can be made of smaller sizes but better performance. Measurements were taken from different positions from a parabolic antenna, the signal level measured and compared with signal levels for optimal performance.

Translation of Culture-loaded Words in The Golden Cangue under the Perspective of Reception Aesthetics

Good translations play a very important role in cultural exchange.The idea of reception aesthetics think the reader as the center in translation process.This paper will study the translation of culture-loaded words from the perspective of reception aesthetics.It is divided into five parts.The first part mainly introduces the background and theoretical foundation of this paper,the second part introduces the writer’s works,the third part gives examples to analyze the culture-loaded words appearing in The Golden Cangue,the fourth part gives examples of the translation methods,and the fifth part is the conclusion.It aims to provide a reference for the English translation of culture-loaded words.

Response of a hypersonic blunt cone boundary layer to slow acoustic waves with assessment of various routes of receptivity

The hypersonic boundary-layer receptivity to slow acoustic waves is investigated for the Mach 6 flow over a 5-degree half-angle blunt cone with the nose radius of 5.08 mm. The plane acoustic wave interacts with the bow shock, and generates all types of disturbances behind the shock, which may take various routes to generate the boundarylayer unstable mode. In this paper, two routes of receptivity are investigated in detail.One is through the disturbance in the entropy layer. The other is through the slow acoustic wave transmitted downstream the bow shock, which can excite the boundary-layer mode due to the synchronization mechanism. The results show that, for a low frequency slow acoustic wave, the latter route plays a leading role. The entropy-layer instability wave is able to excite the first mode near the neutral point, but its receptivity efficiency is much lower.

Receptivity of hypersonic boundary layer due to fast-slow acoustics interaction

The objective of receptivity is to investigate the mechanisms by which external disturbances generate unsta- ble waves. In hypersonic boundary layers, a new receptivity process is revealed, which is that fast and slow acoustics through nonlinear interaction can excite the second mode near the lower-branch of the second mode. They can generate a sum-frequency disturbance though nonlinear interaction, which can excite the second mode. This receptivity process is generated by the nonlinear interaction and the nonparal- lel nature of the boundary layer. The receptivity coefficient is sensitive to the wavenumber difference between the sumfrequency disturbance and the lower-branch second mode. When the wavenumber difference is zero, the receptivity coefficient is maximum. The receptivity coefficient decreases with the increase of the wavenumber difference. It is also found that the evolution of the sum-frequency disturbance grows linearly in the beginning. It indicates that the forced term generated by the sum-frequency disturbance resonates with the second mode.

ON THE RECEPTIVITY OF PIPE POISEUILLE FLOW WITH A BUMP ON THE WALL UNDER THE PERIODICAL PRESSURE

Asymptotic method was adopted to obtain a receptivity model for a pipe Poiseuille flow under periodical pressure,the wall of the pipe with a bump.Bi_orthogonal eigen_function systems and Chebyshev collocation method were used to resolve the problem.Various spatial modes and the receptivity coefficients were obtained.The results show that different modes dominate the flow in different stages,which is comparable with the phenomena observed in experiments.

Value of Intrauterine Autologous Platelet-Rich Plasma Therapy on Endometrial Receptivity:A Literature Review

Endometrial receptivity is an important factor that influences embryo implantation.Thus,it is important to identify an applicable approach to improve endometrial receptivity in women undergoing assisted reproductive technology.Recently,growing evidence has indicated that intrauterine platelet-rich plasma(PRP)infusion is an effective method to obtain a satisfactory reproductive outcome by increasing endometrial thickness and improving endometrial receptivity.Therefore,the present review aims to outline the possible mechanisms of PRP on endometrial receptivity and summarize the present literature on the effects of PRP therapy in improving endometrial receptivity.

A New Method for Image Tamper Detection Based on an Improved U-Net

With the improvement of image editing technology,the threshold of image tampering technology decreases,which leads to a decrease in the authenticity of image content.This has also driven research on image forgery detection techniques.In this paper,a U-Net with multiple sensory field feature extraction(MSCU-Net)for image forgery detection is proposed.The proposed MSCU-Net is an end-to-end image essential attribute segmentation network that can perform image forgery detection without any pre-processing or post-processing.MSCU-Net replaces the single-scale convolution module in the original network with an improved multiple perceptual field convolution module so that the decoder can synthesize the features of different perceptual fields use residual propagation and residual feedback to recall the input feature information and consolidate the input feature information to make the difference in image attributes between the untampered and tampered regions more obvious,and introduce the channel coordinate confusion attention mechanism(CCCA)in skip-connection to further improve the segmentation accuracy of the network.In this paper,extensive experiments are conducted on various mainstream datasets,and the results verify the effectiveness of the proposed method,which outperforms the state-of-the-art image forgery detection methods.

基于双通路视觉系统的自适应轮廓检测模型

在轮廓检测领域,背景纹理的干扰容易造成轮廓提取不完整。针对这一问题,本文提出了一种基于双通路视觉系统的自适应轮廓检测模型。首先从皮层下通路的信息采集与评估过程出发,对图像整体的显著性进行评估,以此获得轮廓信息的可能性分布;然后采用自适应尺度的高斯导函数对经典视觉通路中感受野的动态特性进行模拟,加强了模型对轮廓细节的捕获;最后在外周抑制算法的基础上,结合像素的空间分布对所有边缘的稀疏性进行度量,更加准确地区分了轮廓和纹理边缘。实验结果表明,本文模型可以有效抑制背景纹理,提升轮廓连续性,具有较好的轮廓检测性能。

超声评估在子宫内膜容受性判定中的应用

目的 探讨经阴道三维超声在子宫内膜容受性判定中的应用价值。方法 回顾性选取昆明市妇幼保健院2022年4月至2023年6月106例拟行辅助生殖者,所有辅助生殖者在妊娠前均接受经阴道三维超声检测,根据临床妊娠与否分为妊娠组(n=48)和未妊娠组(n=58),运用经阴道三维容积探头,记录2组子宫内膜类型、子宫内膜血流分型、子宫内膜容积、妊娠率、子宫内膜及内膜下血流参数[血流指数(flow index,FI)、血管化指数(vascularization index,VI)、及血管-血流指数(vascular fiow index,VFI)]情况。结果 2组在子宫内膜类型、子宫内膜血流分型、子宫内膜容积方面比较,差异有统计学意义(P <0.05);子宫内膜形态A型妊娠率高于C型,子宫内膜血流分型Ⅲ级妊娠率高于型Ⅰ级,差异有统计学意义(P <0.05);2组在子宫内膜及内膜下FI、VI以及VFI方面比较,差异有统计学意义(P <0.05)。结论 经阴道三维超声技术能够有效评估子宫内膜容受性,预测妊娠结局,为临床治疗方案提供重要依据。

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。

基于改进YOLOv5的遥感图像目标检测

目前目标检测技术虽然已经趋于成熟,但是对遥感图像的检测仍存在不少挑战。针对遥感图像的背景复杂、目标尺度差异大、目标方向任意等特点造成目标检测精度低下的问题,提出一种基于改进YOLOv5的遥感图像目标检测算法。首先,构建一种联合注意力的多尺度特征增强网络,充分融合高低层特征,使特征层具有语义信息的同时包含丰富的细节信息,并在融合过程中利用设计的特征聚焦模块帮助模型选择关键特征,抑制无关信息。其次,使用感受野模块(RFB)对融合后的特征图进行更新,扩大特征图的感受野,减少特征信息损失。最后,对目标增加旋转角度,并采用圆形平滑标签将回归问题转化成分类问题,提高遥感目标定位的准确性。在用于航拍图像目标检测的大规模数据集(DOTA)上的实验结果表明,与YOLOv5算法相比,所提算法的交并比(Io U)为0.5和0.5~0.95时的平均精度均值(m AP@0.5和m AP@0.5∶0.95)分别提高了7.3和3.3个百分点,能够明显提高复杂背景下遥感图像目标的检测精度,并改善对遥感目标的漏检和误检情况。

基于Transformer的多尺度遥感语义分割网络

为了提升遥感图像语义分割效果,本文针对分割目标类间方差小、类内方差大的特点,从全局上下文信息和多尺度语义特征2个关键点提出一种基于Transformer的多尺度遥感语义分割网络(muliti-scale Transformer network,MSTNet)。其由编码器和解码器2个部分组成,编码器包含基于Transformer改进的视觉注意网络(visual attention network,VAN)主干和基于空洞空间金字塔池化(atrous spatial pyramid pooling, ASPP)结构改进的多尺度语义特征提取模块(multi-scale semantic feature extraction module, MSFEM)。解码器采用轻量级多层感知器(multi-layer perception,MLP)配合编码器设计,充分分析所提取的包含全局上下文信息和多尺度表示的语义特征。MSTNet在2个高分辨率遥感语义分割数据集ISPRS Potsdam和LoveDA上进行验证,平均交并比(mIoU)分别达到79.50%和54.12%,平均F1-score(m F1)分别达到87.46%和69.34%,实验结果验证了本文所提方法有效提升了遥感图像语义分割的效果。

维生素D与女性生育力及生殖系统疾病的研究进展

维生素D受体在女性生殖器官中广泛表达,维生素D与维生素D受体结合调节体内骨和钙稳态,参与炎症、细胞介导免疫、细胞周期和凋亡等多种信号通路。维生素D对卵泡发育和卵巢储备、子宫内膜容受性有调节作用;维生素D缺乏与多囊卵巢综合征病理进程有关;补充维生素D对预防卵巢早衰、子宫肌瘤、子宫内膜异位症和卵巢癌有重要意义;体内维生素D水平与体外受精结局也有一定相关性。维生素D缺乏是一个主要公共卫生问题,合理补充维生素D,有益于维护女性生殖健康。

基于多尺度特征融合的绝缘子缺陷程度检测

针对绝缘子不同程度缺陷特征相似、像素信息少、不同程度缺陷检测效果不佳的问题,提出了一种基于多尺度特征融合的绝缘子缺陷程度检测网络(multi-scale feature fusion defect degree detection network,MFFD3Net)。该网络采用重构的ResNeSt50架构提高了对绝缘子缺陷程度数据集的特征提取能力。设计了基于反卷积的多尺度特征融合模块,丰富了不同尺寸特征图的表达能力,提高了对不同尺度目标的检测性能。同时,在输入检测模块的浅层特征图后增加多感受野的特征提取模块(receptive field block,RFB),使得更多绝缘子缺陷信息进入有效感受野,对最终特征图产生影响,提升不同程度绝缘子缺陷的检测精度。MFFD3Net在绝缘子缺陷程度数据集上的全类平均精度达到85.02%,其中绝缘子轻微破损与绝缘子轻微闪络小目标的检测精度分别为78.37%、79.98%,能够完成不同程度绝缘子缺陷的识别与定位。因此,该文提出的MFFD3Net对于完善电力系统故障预警、保障电网安全稳定运行具有重要意义。

不当得利法释义学的建构

不当得利法始于罗马法,集大成于德国民法,旨在调整私法上无法律上原因的财产变动,涉及整个私法关系。中国台湾地区不当得利法继受于德国,其法释义学的建构亦主要依靠学说继受。在不当得利法的体系建构上,类型化区分非常关键。当前台湾地区通说采类型说,将不当得利区分为给付型不当得利和非给付型不当得利两大类型。前者旨在调整失败法律交易的财产变动、物权行为无因性理论,与市场私法自治密切相关。后者尤其是权益侵害型不当得利旨在强化对权益的保护,有较广阔的适用领域。通过比较法学说继受、本土判例积累以及学说发展深化,建构不当得利的理论体系并使之精细化,亦是内地不当得利法发展的重要课题。

基于改进U^(2)-Net网络的金属涂层剥落与腐蚀图像分割方法

针对金属涂层缺陷图像分割中存在特征提取能力弱和分割精度低的问题,提出了一种改进的U^(2)-Net分割模型。首先,在U型残差块(RSU)中嵌入改进的增大感受野模块(receptive field block light,RFB_l),组成新的特征提取层,增强对细节特征的学习能力,解决了网络由于感受野受限造成分割精度低的问题;其次,在U^(2)-Net分割模型的解码阶段引入有效的边缘增强注意力机制(contour enhanced attention,CEA),抑制网络中的冗余特征,获取具有详细位置信息的特征注意力图,增强了边界与背景信息的差异性,从而达到更精确的分割效果。实验结果表明,该模型在两个金属涂层剥落与腐蚀数据集上的平均交并比、准确率、查准率、召回率和F_1-measure分别达到80.36%、96.29%、87.43%、84.61%和86.00%,相比于常用的SegNet、U-Net以及U^(2)-Net分割网络的性能都有较大提升。

基于改进SSD模型的柑橘叶片病害轻量化检测模型

针对当前目标检测算法存在模型占比大,对柑橘叶片病害检测速度较慢、精度较低等问题,提出了一种基于改进SSD(single shot multibox detector)的柑橘叶片病害轻量化检测方法。引入了轻量化卷积神经网络MobileNetV2作为SSD网络的骨架,以减小模型规模、提高检测速度。引入感受野模块(receptive field block,RFB)来扩大浅层特征感受野,以提高模型对小目标的检测效果。并引入CA(coordinate attention)注意力机制,以强化不同深度的特征信息,进一步提升柑橘叶片病害的识别精度。结果表明,与VGG16-SSD相比,改进模型(MR-CA-SSD)在柑橘叶片病害检测上平均精度均值(mAP)提升4.4百分点,模型占比减小52.3 MB,每秒检测帧数提升3.15。MR-CA-SSD综合性能也优于YOLOv4、CenterNet、Efficientnet-YoloV3等模型。该改进模型可实现对柑橘叶片病害的快速准确诊断,有助于对病害部位及时精准施药。

接受美学理论视角下英语文学翻译研究

翻译活动是一个“翻译→作品→读者”的线性接受过程,其出发点和落脚点都是读者的接受。从接受美学理论来看,文本意义的实现在于信息接受者的期待视野。基于接受美学理论视角的英语文学作品翻译活动,应关照读者的“期待视野”,关注“未定点”,聚焦如何实现“视野融合”,如此才能有效解决翻译过程中语言和文化的接受性问题,为翻译理论和实践研究拓展空间。

粒细胞集落刺激因子联合他达拉非对薄型子宫内膜患者子宫内膜容受性和妊娠结局的影响

目的探究粒细胞集落刺激因子(G-CSF)联合他达拉非(TD)对薄型子宫内膜(TE)患者子宫内膜容受性和妊娠结局的影响。方法选取2020年5月至2023年3月秦皇岛市第一医院生殖医学科TE患者为研究对象。根据治疗方案不同分为试验组(G-GSF联合TD)和对照组(G-GSF)。比较治疗前和治疗后(内膜转化日)TE患者子宫内膜容受性[子宫内膜厚度(EMT)、子宫内膜容积(EMV)、子宫内膜血流收缩期峰值流速/舒张末期流速(EBF-S/D)、子宫内膜分型、子宫内膜血流分型、子宫动脉搏动指数(AUPI)、子宫动脉阻力指数(AURI)和子宫动脉收缩期峰值流速/舒张末期流速(AU-S/D)];比较两组患者内膜转化日子宫内膜容受性、治疗后妊娠结局[胚胎种植率(EIR)、临床妊娠率(CPR)和早期流产率(ABR)]及治疗期间不良反应发生情况。结果研究共纳入60例患者,每组30例。治疗前,两组患者子宫内膜容受性差异无统计学意义(P>0.05)。与治疗前比较,治疗后两组患者内膜转化日EMT、EMV、A型子宫内膜比例和II型+III型子宫内膜血流比例显著增加(P<0.05),而EBF-S/D、AUPI、AURI和AU-S/D显著下降(P<0.05)。试验组EMT和EMV大于对照组(P<0.05),而EBF-S/D、AUPI、AURI和AU-S/D小于对照组(P<0.05)。与对照组相比,试验组子宫内膜形态、子宫内膜血流分型、EIR、CPR、ABR差异均无统计学意义(P>0.05)。两组患者在治疗期间均未发生不良反应。结论G-CSF联合TD可改善TE患者子宫内膜容受性,安全性较高,但对妊娠结局尚无影响。