半波振子结构在井下5G辐射场中的安全性分析

GB 3836.1-2021《爆炸性环境第1部分设备通用要求》规定,爆炸性环境中射频设备的射频阈功率不得大于6 W,该规定引自欧盟标准,缺乏试验验证,严重制约了5G技术在煤井下的应用。为了重新评价矿井5G通信设备辐射电磁波能量的安全性,分析得出金属结构耦合电磁波产生放电的形式应为低压分断电路电弧放电;分析了金属结构耦合电磁波产生的放电能量,选择最易耦合电磁波的半波振子结构为研究对象,通过比较得出等效半波振子等价直流放电电路产生的放电能量大于等价高频放电电路产生的放电能量,从而将分析金属结构耦合电磁波放电的安全性转换为分析金属结构的等效半波振子天线等价直流放电电路的安全性。选择直流本安电路的安全性判别原则来判断等效半波振子等价直流放电电路的安全性,通过计算放电功率和能量,得出5G射频设备辐射功率不大于10.5 W时,将不会点燃爆炸性的瓦斯气体,因此,可将5G通信系统射频基站的安全辐射功率提高到10.5 W。

SD—OCT黄斑区GCIPLT测量在青光眼诊断中的应用研究

目的探讨黄斑区神经节细胞-内丛状层厚度（ganglioncell-innerplexiformlayerthickness，GCIPLT）在不同阶段青光眼诊断中的应用价值，了解与视功能的关系。方法采用前瞻性系列病例对照研究设计。在同一天内，使用频阈光学相干断层扫描（spectral domain optical coherencetomography，SD-OCT）对入选的63例青光眼患者（青光眼组）及年龄、性别、屈光均匹配的42名正常对照者（正常对照组）分别行视盘及黄斑区扫描，检测黄斑区平均GCIPLT（mGCIPL）、最小GCIPLT（minGCIPLT），上方、颞上、颞下、下方、鼻下、鼻上共6个不同方位的GCIPLT及视盘周围视网膜神经纤维层厚度（retinal nerve fiber layer thickness，RNFLT）。根据青光眼患者的视野损害程度将其进一步分为早期组、中期组及晚期组，分析GCIPLT与RNFLT参数的相关性及其随病情进展的普遍变化规律。同时通过受试者工作特征曲线下面积（area under receiver operating characteristic curve，AROC）分析GCIPLT与RNFLT参数诊断能力大小，通过Pearson相关分析GCIPLT、RNFLT、视野平均缺损值（mean deviation，MD）的相关性。结果青光眼组与正常对照组相比，黄斑GCIPLT各参数值均明显降低（P〈0．01），青光眼早期、中期及晚期组间minGCIPLT、颞下及下方GCIPLT差异均有统计学意义（P〈0．05），随着青光眼程度的加重，各参数均明显降低，差异有统计学意义（P〈0．01）。早期组GCIPLT参数中minGCIPLT具有最大的AROC，为0．819，RNFLT参数中下方RNFLT具有最大的AROC，为0．902，两者比较差异无统计学意义（P〉0．05）。mGCIPLT与视野MD相关系数为0．795，平均RNFLT（mRNFLT）与视野的相关性为0．852，两者差异无统计学意义（P〉0．05）。结论黄斑区GCIPLT参数和RNFLT参数一样，两者具有相似的诊断能力，且与RNFLT参数及视野各指数高度相关。

煤矿5G通信系统安全应用技术研究

针对煤矿5G通信系统安全应用需求,研究了5G核心网侧和无线接入侧的安全应用技术。在核心网侧,采用专网技术和网络切片技术实现不同煤矿业务场景的物理隔离,采用比例公平算法优化切片组内的资源块分配,实现切片资源调度,保障煤矿业务数据安全可靠传输;在无线接入侧,设计天线隔离电路实现基站输出信号本安,并将5G基站的射频阈功率限制在6 W内,杜绝由辐射能量滋生的安全隐患,实现多种煤矿井下终端设备的安全接入。井下测试结果表明,5G基站无线覆盖半径为100 m,覆盖范围内信号强度不低于-100 dB,上传速率不低于520 Mbit/s,平均通信时延为18.56 ms,用户个数为200时用户业务性能提升52.8%,在保证通信系统安全可靠的基础上,满足煤矿业务数据多并发、大容量、高速率和低时延无线通信需求。

Early all-zero blocks detecting method for video coding based on novel threshold

In order to decrease both computational complexity and coding time, an improved algorithm for the early detection of all-zero blocks （AZBs） in H. 264/AVC is proposed. The previous AZBs detection algorithms are reviewed. Three types of transformed frequency-domain coefficients, which are quantized to zeros, are analyzed. Based on the three types of frequencydomain scaling factors, the corresponding spatial coefficients are derived. Then the Schwarz inequality is applied to the derivation of the three thresholds based on spatial coefficients. Another threshold is set on the basis of the probability distribution of zero coefficients in a block. As a result, an adaptive AZBs detection algorithm is proposed based on the minimum of the former three thresholds and the threshold of zero blocks distribution. The simulation results show that, compared with the existing AZBs detection algorithms, the proposed algorithm achieves a 5% higher detection ratio in AZBs and 4% to 10% computation saving with only 0. 1 dB video quality degradation.

应用OROGIN软件对光电效应实验进行分析

在光电效应测量普朗克常量的实验中,利用OROGIN软件分别对零点法、作图法二种方法进行数据采集和图形分析,然后对得出的结果进行分析和讨论。

Rolling element bearing instantaneous rotational frequency estimation based on EMD soft-thresholding denoising and instantaneous fault characteristic frequency

The accurate estimation of the rolling element bearing instantaneous rotational frequency(IRF) is the key capability of the order tracking method based on time-frequency analysis. The rolling element bearing IRF can be accurately estimated according to the instantaneous fault characteristic frequency(IFCF). However, in an environment with a low signal-to-noise ratio(SNR), e.g., an incipient fault or function at a low speed, the signal contains strong background noise that seriously affects the effectiveness of the aforementioned method. An algorithm of signal preprocessing based on empirical mode decomposition(EMD) and wavelet shrinkage was proposed in this work. Compared with EMD denoising by the cross-correlation coefficient and kurtosis(CCK) criterion, the method of EMD soft-thresholding(ST) denoising can ensure the integrity of the signal, improve the SNR, and highlight fault features. The effectiveness of the algorithm for rolling element bearing IRF estimation by EMD ST denoising and the IFCF was validated by both simulated and experimental bearing vibration signals at a low SNR.

Design of 0.5V low-voltage phase and frequency detector for frequency synthesizer in wireless sensor networks

Based on 0.13μm complementary metal-oxide-semiconductor（CMOS） technology,a phase and frequency detector（PFD） is designed with a low supply voltage of 0.5V for frequency synthesizers used in wireless sensor networks（WSNs）.The PFD can compare the frequency and phase differences of input signals and deliver a signal voltage proportional to the difference.Low threshold transistors are used in the circuits since a power supply of 0.5V is adopted.A pulse latched structure is also used in the circuits in order to increase both the detection range of phase errors and the maximum operation frequency.In experiments,a phase error with a range from-358° to 358° is measured when the input signal frequency is 2MHz.The PFD has a faster acquisition speed compared with conventional digital PFDs.When the input signals are at a frequency of 2MHz with zero phase error,the circuits have a power consumption of 1.8[KG＊8]μW,and the maximum operation frequency is 1.25GHz.

Cross validations of radio-frequency interference signature in AMSR-E data using two detection methods

Radio-frequency interference（RFI） detection for low-frequency microwave measurements is an important step before these data are applied to geophysical parameter retrieval or data assimilation. There are several robust techniques to identify the RFI signals, such as the mean/standard deviation method and the normalized principal component analysis method. However, verification of these existing detection methods remains an open issue in the absence of a reliable validation data-set of the ‘true＇ RFI signals. In this paper, a cross-validation scheme using two independent RFI detection methods is proposed to derive the thresholds for identifying the RFI-contaminated data for the Advanced Microwave Scanning Radiometer for Earth Observing System（AMSR-E）. It is shown that the new scheme is effective in the quantitative classification of the RFI signals in the AMSR-E C-and X-band channels over the continents. Strong RFI signals are found to be populated over cities of the United States at AMSR-E C-band, while RFIs at X-band are mainly observed over Europe and Japan.

Spatio-Temporal Adaptive Super-Resolution Reconstruction Model Based on Zemike Moment for Spatial Video Sequences

Video Super-Resolution （SR） reconstruction produces video sequences with High Resolution （HR） via the fusion of several Low-Resolution （LR） video frames. Traditional methods rely on the accurate estimation of subpixel motion, which constrains their applicability to video sequences with relatively simple motions such as global translation. We propose an efficient iterative spatio-temporal adaptive SR reconstruction model based on Zemike Moment （ZM）, which is effective for spatial video sequences with arbitrary motion. The model uses region correlation judgment and self-adaptive threshold strategies to improve the effect and time efficiency of the ZM-based SR method. This leads to better mining of non-local self-similarity and local structural regularity, and is robust to noise and rotation. An efficient iterative curvature-based interpolation scheme is introduced to obtain the initial HR estimation of each LR video frame. Experimental results both on spatial and standard video sequences demonstrate that the proposed method outperforms existing methods in terms of both subjective visual and objective quantitative evaluations, and greatly improves the time efficiency.

A Nonparametric Approach to Foreground Detection in Dynamic Backgrounds

Foreground detection is a fundamental step in visual surveillance.However,accurate foreground detection is still a challenging task especially in dynamic backgrounds.In this paper,we present a nonparametric approach to foreground detection in dynamic backgrounds.It uses a history of recently pixel values to estimate background model.Besides,the adaptive threshold and spatial coherence are introduced to enhance robustness against false detections.Experimental results indicate that our approach achieves better performance in dynamic backgrounds compared with several approaches.

Determination of Threshold for Energy Detection in Cognitive Radio Sensor Networks

The Internet of Things （loT） is called the world＇ s third wave of the information industry. As the core technology of IoT, Cognitive Radio Sensor Networks （CRSN） technology can improve spectrum utilization efficiency and lay a sofid foundation for large-scale application of IoT. Reliable spectrum sensing is a crucial task of the CR. For energy de- tection, threshold will determine the probability of detection （Pd） and the probability of false alarm Pf at the same time. While the threshold increases, Pd and Pf will both decrease. In this paper we focus on the maximum of the difference of Pd and Pf, and try to find out how to determine the threshold with this precondition. Simulation results show that the proposed method can effectively approach the ideal optimal result.

电声系统测量与分析常用的重要技法——快速傅里叶变换(FFT)

文中主要介绍经常用于电声系统测量和分析的重要技法——快速傅里叶变换(FFT,Fast-Fourier Transform),这种技法在不少电声设备、电声部件、扩声系统及声学系统测量中、相关测试与分析软件的平台上经常出现,如SmaartLive软件和Smaart声学工具软件里的几种模式中。了解并掌握这种技法对顺利实施各个电声指标测量、提高测量精度、圆满完成各种电声测试任务极为重要。

A Family of Degenerate Codes for Depolarizing Channels

Quantum degenerate code may improve the hashing bound of quantum capacity. We propose a family of quantum degenerate codes derived from two-colorable graphs. The coherent information of the codes is analyticaJly obtained as a function of the channd noise for the depolarizing channel. We find a new code which has a higher noise threshold than that of the repetition code.

Structures and properties of functional metal iodates

Metal iodates with a lone-pair containing I(V) that is in an asymmetric coordination geometry can form a diversity of unusual structures and many of them are promising new second homonic generation (SHG) materials. They exhibit wide transparency wavelength regions, large SHG coefficients and high optical-damage thresholds as well as moderately high thermal stability. In this paper, the structures and properties of the metal iodates are reviewed. The combination of d0 transition-metal cations with the iodate groups afforded a large number of metal iodates, with cations covering alkali metal, alkaline earth and lanthanide elements. Many of them are noncentrosymmetric (NCS) and display excellent SHG properties due to the additive effects of polarizations from both types of the asymmetric units. Some lanthanide iodates are able to emit strong luminescence in the visible or near-IR regions. The use of transition metal ions with dn (n ≠ 0) electronic configuration into iodate systems can also induce the formation of NCS compounds when the lone pairs of the iodate groups are properly aligned. The dn transition metal cations are normally octahedrally coordinated or in a square-planar coordination geometry. Furthermore, the combination of two different types of lone-pair-containing cations is also an effective strategy to design new SHG materials.