Optimal Energy-Efficient Transmission for Hybrid Spectrum Sharing in Cooperative Cognitive Radio Networks

In order to improve the energy efficiency(EE)in cognitive radio(CR),this paper investigates the joint design of cooperative spectrum sensing time and the power control optimization problem for the secondary user systems to achieve the maximum energy efficiency in a cognitive network based on hybrid spectrum sharing,meanwhile considering the maximum transmit power,user quality of service(QoS)requirements,interference limitations,and primary user protection.The optimization of energy efficient sensing time and power allocation is formulated as a non-convex optimization problem.The Dinkelbach’s method is adopted to solve this problem and to transform the non-convex optimization problem in fractional form into an equivalent optimization problem in the form of subtraction.Then,an iterative power allocation algorithm is proposed to solve the optimization problem.The simulation results show the effectiveness of the proposed algorithms for energy-efficient resource allocation in the cognitive network.

Downlink Resource Allocation for NOMA-Based Hybrid Spectrum Access in Cognitive Network

To solve the contradiction between limited spectrum resources and increasing communication demand,this paper proposes a wireless resource allocation scheme based on the Deep Q Network(DQN)to allocate radio resources in a downlink multi-user cognitive radio(CR)network with slicing.Secondary users(SUs)are multiplexed using non-orthogonal multiple access(NOMA).The SUs use the hybrid spectrum access mode to improve the spectral efficiency(SE).Considering the demand for multiple services,the enhanced mobile broadband(eMBB)slice and ultrareliable low-latency communication(URLLC)slice were established.The proposed scheme can maximize the SE while ensuring Quality of Service(QoS)for the users.This study established a mapping relationship between resource allocation and the DQN algorithm in the CR-NOMA network.According to the signal-to-interference-plusnoise ratio(SINR)of the primary users(PUs),the proposed scheme can output the optimal channel selection and power allocation.The simulation results reveal that the proposed scheme can converge faster and obtain higher rewards compared with the Q-Learning scheme.Additionally,the proposed scheme has better SE than both the overlay and underlay only modes.

Performance Analysis of Wireless Mobile Radio Hybrid(DS/FH) Spread Spectrum Network

By the flexible redefinition of frequency-occupation and frequency-collision event, the frequency-(collision) probability of hybrid(DS/FH) spread spectrum network is analyzed. This probability is based on the simultaneous transmission number threshold and is discussed in synchronous and asynchronous circumstances respectively. And then, the network throughput based on the packet correct reception probability is analyzed. Two models which have finite and infinite population respectively is discussed. At last, the numerical results are given.

Analysis of Charge-Exchange Spectrum during Lower Hybrid Current Drive on HT-7 Tokamak

A perpendicular neutral particle analyzer (NPA) is used on HT-7 tokamak experiment to provide the measurements of neutral particle flux and ion temperature. The measured results were compared with calculated data by Monte-carlo method for ohmic heating. In lower hybrid current drive (LHCD) experiments, the ion heating of LHCD was identified. The chargeexchange neutral particle flux enhanced was observed. The energy spectrum clearly showed a high-energy ions tail. The bulk ion temperature increased by 0.4-0.5 keV after the onset of LHCD. Efficient ion heating of 1 eV. kW-1 was obtained.

The Numerical Calculation and Analysis of the Spectrum of Lower-Hybrid Waves Launched by Grill-Type Antenna on HL-2A

The LHCD antenna that will be used in LH-2A is the original one used in LH-1M, which will be modified. We measured the feature of the antenna, including the reflection of main waveguide, VSWR, the phase shift between the adjacent sub-waveguides and so on. The paper describes the measured results and spectrum calculation based on the measured parameters. From the works we can assess our antennas correctly, which will be useful in LHCD experiment on HL-2A in the years to come.

Near-field characteristics of highly non-paraxial subwavelength optical fields with hybrid states of polarization

The vectorial structure of an optical field with hybrid states of polarization （SOP） in the near-field is studied by using the angular spectrum method of an electromagnetic beam. Physical images of the longitudinal components of evanescent waves are illustrated and compared with those of the transverse components from the vectorial structure. Our results indicate that the relative weight integrated over the transverse plane of the evanescent wave depends strongly on the number of the polarization topological charges. The shapes of the intensity profiles of the longitudinal components are different from those of the transverse components, and it can be manipulated by changing the initial SoP of the field cross-section. The longitudinal component of evanescent wave dominates the near-field region. In addition, it also leads to three-dimensional shape variations of the optical field and the optical spin angular momentum flux density distributions.

Influence of laser on arcs in alternate arcing during laser-twin-arc hybrid welding process

In this study, multi-information including spectrum, high-speed photograph and electrical signal was adopted to explore the coupling mechanism of alternate burning in laser-twin-arc welding process. Laser provides a conductive, stable plasma channel for arcs. Plasma radiation strengthened especially in the center of the arc after hybrid. High temperature plasma erupting from keyhole provides an upward reacting force which can prevent droplet from transfer. The charged particles consisted in high temperature plasma reduce the voltage that maintains arc ignition or burning. The results show that laser can influence the arc shape, prevent droplet transfer, reduce resistivity and stabilize arcs.

A Hybrid Features Based Detection Method for Inshore Ship Targets in SAR Imagery

Convolutional Neural Networks(CNNs)have recently attracted much attention in the ship detection from Synthetic Aperture Radar(SAR)images.However,compared with optical images,SAR ones are hard to understand.Moreover,due to the high similarity between the man-made targets near shore and inshore ships,the classical methods are unable to achieve effective detection of inshore ships.To mitigate the influence of onshore ship-like objects,this paper proposes an inshore ship detection method in SAR images by using hybrid features.Firstly,the sea-land segmentation is applied in the pre-processing to exclude obvious land regions from SAR images.Then,a CNN model is designed to extract deep features for identifying potential ship targets in both inshore and offshore water.On this basis,the high-energy point number of amplitude spectrum is further introduced as an important and delicate feature to suppress false alarms left.Finally,to verify the effectiveness of the proposed method,numerical and comparative studies are carried out in experiments on Sentinel-1 SAR images.

Ethoxycarbonylmethyl Viologen Induced Metal Halide-based Hybrids:Structures,Photoluminescence and Photocurrent Response Behavior

Two new ethoxycarbonylmethyl viologen induced metal halide-based hybrids,(Ae V)(BiI)(DMF)(1)and(Ae V)(CoCl)(2)(AeV=N,N?-bis(ethoxycarbonylmethyl)-4,4?-bipyridinium)have been synthesized and structurally determined by X-ray diffraction method.Under the direction of a new template AeV,the(BiI)tetramer constructed from four edge-sharing BiIoctahedra(for 1)and(CoCl)mono-nuclear(for 2)were obtained.Furthermore,C–H···O and C–H···X(X=I,Cl)hydrogen bonds contribute to the extension of structures from 0-D to 1-D chains.Their energy band gaps of 2.18 and 2.41 eV indicate their semiconductor properties,and the photoluminescence was detected on 1.Interestingly,2 exhibits good photocurrent response behavior.Electronic structure analysis was executed to correlate the structure/property.

PERFORMANCE ANALYSIS OF HYBRID DS SFH/SSMA SYSTEMS OVER MULTIPATH FADING CHANNELS

Hybrid direct sequence and slow frequency hopping spread spectrum multiple access systems (Hybrid DS/SFH SSMA) operating through nonselective slow Rayleigh fading channels was investigated. Multipath and Multiple access interference was taken into account. Expressions of the average error probability for the system were derived. Analytical and numerical results on the average probability of error were presented for the system examined. Random signature sequences and hopping patterns were employed for the system. The numerical results show the effects of the value of M for M ary frequency shift keying (MFSK) modulation and Reed Solomon (RS) coding on the system’s performance. The comparison between RS coded system and noncode system shows that error correction coding is essential to improve the system’s performance.

Spectral parameter-based models for leaf potassium concentration estimation in Ping'ou hybrid hazelnut

Ping′ou hybrid hazelnut is produced by cross cultivation and is widely cultivated in northern China with good development prospects.Based on a field experiment of fertilizer efficiency,the leaf spectral reflectance and leaf potassium(K)concentration were measured with different quantities of K fertilizer applied at four fruit growth stages(fruit setting stage,fruit rapid growth stage,fruit fat-change stage,and fruit near-maturity stage)of Ping′ou hybrid hazelnut in 2019.Spectral parameters that were significantly correlated with leaf K concentration were selected using Pearson correlation analysis,and spectral parameter estimation models of leaf K concentration were established by employing six different modelling methods(exponential function,power function,logarithmic function,linear function,quadratic function,and cubic function).The results indicated that at the fruit setting period,leaf K concentration was significantly correlated with Dy(spectra slope of yellow edge),Rg(reflectance of the green peak position),λo(red valley position),SDb(blue edge area),SDr/SDb(where SDr represents red edge area),and(SDr–SDb)/(SDr+SDb)(P<0.01).There were significant correlations of leaf K concentration with Dy,Rg,SDb,Rg/Ro(where Ro is the reflectance of the red valley position),and(Rg–Ro)/(Rg+Ro)at the fruit rapid growth stage(P<0.01).Further,significant correlations of leaf K concentration with Rg,Ro,RNIR/Green,and RNIR/Blue were obtained at the fruit fat-change period(P<0.01).Finally,leaf K concentration showed significant correlations with Dr,Rg,Ro,SDy(yellow edge area),and SDr at the fruit near-maturity stage(P<0.01).Through a cubic function analysis,regression estimation model of leaf K concentration with highest fitting degree(R2)values at the four fruit growth stages was established.The findings in this study demonstrated that it is feasible to estimate leaf K concentration of Ping′ou hybrid hazelnut at the various phenological stages of fruit development by establishing regression models between leaf K concentration and spectral parameters.

Performance Analysis of Hybrid MAC Protocol for Cognitive Radio Networks

The rapid growth in demand for broadband wireless services coupled with the recent developmental work on wireless communications technology and the static allocation of the spectrum have led to the artificial scarcity of the radio spectrum. The traditional command and control model (Static allocation) of spectrum allocation policy allows for severe spectrum underutilization. Spectrum allocated to TV operators can potentially be shared by wireless data services, either when the primary service is switched off or by exploiting spatial reuse opportunities. This paper describes a hybrid access scheme based on CSMA/CA and TDMA MAC protocols for use in the TV bands. The approach allows secondary users (SU) to operate in the presence of the primary users (PU) and the OPNET simulation and modelling software has been used to model the performance of the scheme. An analysis of the results shows that, the proposed schemes protect the primary user from harmful Interference from the secondary user. In terms of delay, it was found that packet arrival rates, data rates and the number of secondary users have significant effects on delay.

Performance analysis and code recognition for dual N-ary orthogonal hybrid modulation systems

A dual N-ary orthogonal hybrid modulation system is introduced in this paper, which can increase the data rate greatly compared with conventional N-ary orthogonal spread spectrum system, so it can be used for high rate data communication. Then, three code recognition algorithms are presented for dual N-ary orthogonal hybrid modulation system and the analytic bit error rate （BER） performance of the system in additive white Gaussian noise （AWGN） and fiat Rayleigh fading channel is derived. Finally, the computer simulation of the system with three code recognition algorithms is performed, which shows that the simplified maximum a posteriori （MAP） algorithm is the best for the system with a compromise between the performance and the complexity.

高性能YVO_(4)基稀土杂化发光材料的构建及其能量传递机制

采用溶剂热和离子交换两步实验法,以YVO_(4)为无机基质,2-噻吩甲酰三氟丙酮(TTA)为有机配体,构建了具有核壳结构的YVO_(4)∶Eu^(3+)@YVO_(4)∶Eu^(3+)-TTA稀土杂化发光材料,研究了其高效的发光性能和内部的能量传递机制。结果表明,在621nm的监控波长下,YVO_(4)∶Eu^(3+)@YVO_(4)∶Eu^(3+)-TTA稀土杂化发光材料在280~420nm范围内有两个很强的吸收峰(即V-O峰和TTA特征吸收峰)。YVO_(4)基质通过交换作用能量传递,而TTA有机配体通过分子内能量传递,可将吸收的紫外光能量有效地传递给Eu^(3+),从而实现了Eu^(3+)更高效的可见光(红光)发射。

基于变分模态分解和深度多核极限学习机的轴承故障分类

针对轴承故障分类任务中核极限学习机(kernel extreme learning machine,KELM)超参数选择困难、模型运算速度慢的问题,提出一种基于深度混合核极限学习机(deep hybrid kernel extreme learning machine,DHKELM)的轴承故障分类方法,利用天鹰优化算法(aquila optimization algorithm,AO)实现该模型超参数的优化选择。首先,以峰度指数作为鲸鱼优化算法(whale optimization algorithm,WOA)的适应度函数,对变分模态分解(variational mode decomposition,VMD)的相关参数寻优,利用最优参数组合进行VMD分解,得到k个模态分量并求其希尔伯特-黄变换(Hilbert-Huang Transform,HHT)边际谱作为特征数据,将其作为天鹰优化DHKELM分类器的输入,对不同状态的轴承故障进行识别。实验结果表明,KELM,DHKELM,天鹰优化DHKELM三种分类模型故障识别准确率分别为94%,96.67%,98.34%,运算时间分别为0.0631,0.0360,0.0175 s,证明AO-DHKELM识别准确率和运算速度均具有明显优势。

基于DWDM的超100 Gbit/s混合组网分析

【目的】近年来,数据通信量呈爆炸性增长,为了应对高速、高容量数据传输及网络应用场景多样化的需求,超100 Gbit/s密集波分复用(DWDM)混合组网作为一种高效的解决方案逐渐受到关注。文章通过对超100 Gbit/s DWDM混合组网的需求、关键技术及实际案例进行分析,为构建高容量、高效率的通信网络提供了技术支持和指导。【方法】文章首先阐述了网络发展在容量扩展和支持复杂网络设计方面的需求,其次重点介绍了超100 Gbit/s混合组网的关键技术,包括星座图整形、频谱整形和灵活栅格技术等。其中,为支撑混合组网的业务速率设计,提供了一种用于级联掺铒光纤放大器(EDFA)通信系统的光信噪比(OSNR)计算方法,仅利用信道配置信息、发端信号光功率、EDFA的增益及噪声等相关参数,即可计算出整个链路中各个波长的输出OSNR。最后,结合海外某网络案例,根据实际链路OSNR评估情况,合理进行混合速率网络设计,论证了超100 Gbit/s DWDM混合组网在实际工程中的应用效果。【结果】通过应用超100 Gbit/s DWDM混合组网,根据OSNR评估情况灵活配置传输速率和传输带宽,实现了200、600和800 Gbit/s混合速率网络部署,既满足了核心站点的大容量需求,也兼顾了边缘站点的长途大跨度需求,并在3年期间实现了网络的平滑升级和扩容。【结论】实践证明,超100 Gbit/s DWDM组网能够有效提升网络容量、灵活性及频谱资源利用率,同时也为网络的持续演进提供了空间,是推进大容量光传输网络发展的重要手段。

混合式教学模式在天然药物化学结构波谱解析中的应用

随着网络信息技术的快速发展,线上线下混合式教学模式在高校专业课教育中体现出独特的优势。常用的线上线下教学平台包括超星学习通平台、对分易平台、雨课堂等。超星学习通就是这种网络化教学的产物,它极大地改善了传统授课枯燥、单调以及满堂灌的传统模式。波谱解析是一门理论性很强的学科,主要用于天然药物化学中结构的鉴定,其中包含大量的物理学概念既抽象又深奥,传统的教学模式学生大多提不起兴致,上课效果较差。笔者将超星学习通平台应用于波谱解析这门课程,提高了学生的学习热情。主要介绍了超星学习通平台的功能,并以波谱解析这门课程中的紫外光谱章节为例,探讨基于该平台的混合式教学模式在波谱解析教学全过程中的应用。实践表明,超星学习通平台应用于波谱解析教学,可以调动学生的学习积极性,提高学生的学习兴趣,使师生互动更便捷和迅速,对教学效果的改善具有重要意义。

独塔非对称钢-混混合梁斜拉桥抗震性能研究

【目的】研究独塔非对称钢-混混合梁斜拉桥的抗震性能,并探明非对称结构地震响应的差异。【方法】以长沙香炉洲大桥西汊航道桥为依托,采用MidasCivil软件建立非对称钢-混混合梁斜拉桥全桥有限元模型,分别采用反应谱法和非线性时程分析法对其进行地震响应分析,并重点研究了结构非对称性对斜拉桥辅助墩、过渡墩及其桩基抗震性能的影响。【结果】独塔非对称钢-混混合梁斜拉桥的动力特性和地震响应规律呈现出明显的非对称性,非对称布置的两过渡墩和两辅助墩在地震作用下的内力响应存在较大差异,结构的非对称性对横向地震更加敏感,在抗震设计时应予以重视;除两过渡墩桩基外,长沙香炉洲大桥按照静力计算设计的结构尺寸及配筋形式均能满足各工况地震作用下的抗震性能目标;塔身、墩身在横向+竖向地震作用下的安全储备均大于纵向+竖向地震的,桩基在横向+竖向地震作用下的安全储备几乎都小于纵向+竖向地震的;受结构非对称性的影响,边跨的27#过渡墩桩基总是先于主跨的31#过渡墩桩基发生破坏;在横向地震作用下,受群桩承台影响横向各排桩基地震轴力有较大差异。【结论】从经济性和抗震合理性角度出发,应对独塔非对称钢-混混合梁斜拉桥进行差异化的抗震设计,研究成果可为非对称斜拉桥及其他非对称桥梁结构的抗震设计提供有益参考。

基于HDSS构建800 MHz的5G和LTE共覆盖研究与实践

800 MHz频段5G是广覆盖很好选择,但是由于800 MHz频率资源短缺,传统的硬重耕方式舍旧换新,不能适应现网需要并且资源投入较大。而频谱动态共享的技术可以在现有4G网络上快速进行5G部署,实现4G和5G双网并存,并动态扩展演进。该文通过对HDSS的技术的15 MHz HDSS动态频谱共享(15 MHz的NR包含10 MHz的LTE)方案,对共享资源调度、干扰规避、功率配置等关键技术问题进行了分析验证,并对HDSS组网下的多种场景进行了测试,给出了实际配置建议,对实现绿色共享频率资源,4G和5G网络协同、5G的广覆盖等方面具有参考价值。

一种UUV集群的隐蔽水声通信低截获技术

针对当前水下无人航行器(UUV)或水下自主航行器(AUV)集群任务过程中水声通信隐蔽性不足的问题进行研究(简称UUV集群)。首先建立UUV集群的水声隐蔽通信分析模型,明确影响水声通信隐蔽性因素及实现隐蔽通信的技术途径;然后从工程实际的角度给出一种基于时频空及发射功率控制的UUV集群水声隐蔽通信低截获技术实现方法。采用波束定向、宽带混合扩频/编码通信与变步长发射功率控制等综合措施进行水声隐蔽通信系统设计。性能仿真结果表明,上述方法可大大提升UUV集群的水声隐蔽通信低截获性能。