A novel control method for on-off gain and gain tilt of fiber Raman amplifiers

Considering spectrum tilt due to signal-to-signal Raman scattering (SSRS) in backward distributed fiber Raman amplifiers (B-DFRA),an inverse tilted on-off gain profile is adopted to achieve flat net gain.A simple approximate linear relationship of pump power at each wavelength versus on-off gain level and tilt was derived numerically and experimentally so that a novel control method was established.Since there are only 3 pre-determinable constants required for individual pump wave,it is easy to be realized.As an example,maximum errors less than 0.2 and 0.4 dB respectively for average gain and gain tilt were achieved over C+L band in 100-km back-pumped standard single-mode fiber (SMF) experimentally.

Winter wheat yield improvement by genetic gain across different provinces in China

The replacement of winter wheat varieties has contributed significantly to yield improvement worldwide,with remarkable progress in China.Drawing on two sets of data,production yield from the National Bureau of Statistics of China and experimental yield from literature,this study aims to(1)illustrate the increasing patterns of production yield among different provinces from 1978 to 2018 in China,(2)explore the genetic gain in yield and yield relevant traits through the variety replacement based on experimental yield from 1937 to 2016 in China,and(3)compare the yield gap between experimental yield and production yield.The results show that both the production and experimental yields significantly increased along with the variety replacement.The national annual yield increase ratio for the production yield was 1.67%from 1978 to 2018,varying from 0.96%in Sichuan Province to 2.78%in Hebei Province;such ratio for the experimental yield was 1.13%from 1937 to 2016.The yield gap between experimental and production yields decreased from the 1970s to the 2010s.This study reveals significant increases in some yield components consequent to variety replacement,including thousand-grain weight,kernel number per spike,and grain number per square meter;however,no change is shown in spike number per square meter.The biomass and harvest index consistently and significantly increased,whereas the plant height decreased significantly.

Preweaning period is a critical window for rumen microbial regulation of average daily gain in Holstein heifer calves

Background Rumen bacterial groups can affect growth performance,such as average daily gain(ADG),feed intake,and efficiency.The study aimed to investigate the inter-relationship of rumen bacterial composition,rumen fermentation indicators,serum indicators,and growth performance of Holstein heifer calves with different ADG.Twelve calves were chosen from a trail with 60 calves and divided into higher ADG(HADG,high pre-and post-weaning ADG,n=6)and lower ADG(LADG,low pre-and post-weaning ADG,n=6)groups to investigate differences in bacterial composition and functions and host phenotype.Results During the preweaning period,the relative abundances of propionate producers,including g_norank_f_Butyricicoccaceae,g_Pyramidobacter,and g_norank_f_norank_o_Clostridia_vadin BB60_group,were higher in HADG calves(LDA>2,P<0.05).Enrichment of these bacteria resulted in increased levels of propionate,a gluconeogenic precursor,in preweaning HADG calves(adjusted P<0.05),which consequently raised serum glucose concentrations(adjusted P<0.05).In contrast,the relative abundances of rumen bacteria in post-weaning HADG calves did not exert this effect.Moreover,no significant differences were observed in rumen fermentation parameters and serum indices between the two groups.Conclusions The findings of this study revealed that the preweaning period is the window of opportunity for rumen bacteria to regulate the ADG of calves.

Topological laser on square lattice with gain–loss-induced higher-order corner modes

We investigate the higher-order topological laser in the two-dimensional(2D) coupled-cavity array. By adding staggered on-site gain and loss to the 2D Hermitian array with a trivial phase, the system will emerge degenerate topological corner modes, which are protected by bulk band gap. For such a non-Hermitian model, by adjusting the parameters of the system and introducing the pumping into the cavity at the corner, a single-mode lasing with topological protection emerges.Furthermore, single-mode lasing exists over a wide range of pumping strengths. No matter where the cavity is initially stimulated, after enough time evolution, all the cavities belonging to the topological corner mode can emit a stable laser.

A Stroke-Limitation AMD Control System with Variable Gain and Limited Area for High-Rise Buildings

Collisions between a moving mass and an anti-collision device increase structural responses and threaten structural safety.An active mass damper(AMD)with stroke limitations is often used to avoid collisions.However,a strokelimited AMD control system with a fixed limited area shortens the available AMD stroke and leads to significant control power.To solve this problem,the design approach with variable gain and limited area(VGLA)is proposed in this study.First,the boundary of variable-limited areas is calculated based on the real-time status of the moving mass.The variable gain(VG)expression at the variable limited area is deduced by considering the saturation of AMD stroke.Then,numerical simulations of a stroke-limited AMD control system with VGLA are conducted on a high-rise building structure.These numerical simulations show that the proposed approach has superior strokelimitation performance compared with a stroke-limited AMD control system with a fixed limited area.Finally,the proposed approach is validated through experiments on a four-story steel frame.

基于GAIN-LSTM网络的雷达PRI序列还原及识别方法

开展脉冲重复间隔(Pulse Repetition Interval,PRI)模式识别工作是电子支援系统的一项重要任务。现代复杂电磁环境下,受雷达辐射源部署和接收设备本身影响,雷达脉冲丢失率极高,导致分选后PRI序列调制规律被破坏,现有的PRI模式识别方法准确率不足。针对上述问题,从PRI序列还原角度出发,并结合PRI序列本质是时序序列的特点,提出GAIN-LSTM(Generative Adversarial Imputation Nets and Long Short Term Memory)网络架构,其先对丢失脉冲位置进行补全操作,恢复PRI调制规律,然后对还原后PRI序列进行调制模式识别。仿真结果表明,提出的GAIN-LSTM网络架构在脉冲丢失率70%时仍保持95%的正确识别率。

ANovel Non-Isolated Cubic DC-DC Converter with High Voltage Gain for Renewable Energy Power Generation System

In recent years,switched inductor(SL)technology,switched capacitor(SC)technology,and switched inductor-capacitor(SL-SC)technology have been widely applied to optimize and improve DC-DC boost converters,which can effectively enhance voltage gain and reduce device stress.To address the issue of low output voltage in current renewable energy power generation systems,this study proposes a novel non-isolated cubic high-gain DC-DC converter based on the traditional quadratic DC-DC boost converter by incorporating a SC and a SL-SC unit.Firstly,the proposed converter’s details are elaborated,including its topology structure,operating mode,voltage gain,device stress,and power loss.Subsequently,a comparative analysis is conducted on the voltage gain and device stress between the proposed converter and other high-gain converters.Then,a closed-loop simulation system is constructed to obtain simulation waveforms of various devices and explore the dynamic performance.Finally,an experimental prototype is built,experimental waveforms are obtained,and the experimental dynamic performance and conversion efficiency are analyzed.The theoretical analysis’s correctness is verified through simulation and experimental results.The proposed converter has advantages such as high voltage gain,low device stress,high conversion efficiency,simple control,and wide input voltage range,achieving a good balance between voltage gain,device stress,and power loss.The proposed converter is well-suited for renewable energy systems and holds theoretical significance and practical value in renewable energy applications.It provides an effective solution to the issue of low output voltage in renewable energy power generation systems.

Design of a Low Power Low-Noise Amplifier with Improved Gain/Noise Ratio

This work details the development of a broad-spectrum LNA (Low Noise Amplifier) circuit using a 65 nm CMOS technology. The design incorporates an inductive degeneracy circuit, employing a theoretical approach to enhance gain, minimize noise levels, and uphold low power consumption. The progression includes a shift to a cascode structure to further refine LNA parameters. Ultimately, with a 1.8 V bias, the achieved performance showcases a gain-to-noise figure ratio of 16 dB/0.5 dB, an IIP3 linearity at 5.1 dBm, and a power consumption of 3 mW. This architecture is adept at operating across a wide frequency band spanning from 0.5 GHz to 6 GHz, rendering it applicable in diverse RF scenarios.

Joint Beamforming Design for Dual-Functional Radar-Communication Systems Under Beampattern Gain Constraints

The joint beamforming design challenge for dual-functional radar-communication systems is addressed in this paper.The base station in these systems is tasked with simultaneously sending shared signals for both multi-user communication and target sensing.The primary objective is to maximize the sum rate of multi-user communication,while also ensuring sufficient beampattern gain at particular angles that are of interest for sensing,all within the constraints of the transmit power budget.To tackle this complex non-convex problem,an effective algorithm that iteratively optimizes the joint beamformers is developed.This algorithm leverages the techniques of fractional programming and semidefinite relaxation to achieve its goals.The numerical results confirm the effectiveness of the proposed algorithm.

Analysis of the Effects of Maternal Body Mass Index and Gestational Weight Gain on Maternal and Neonatal Outcomes in Twin Pregnancy

Objective:To investigate the effects of maternal body mass index(BMI)and gestational weight gain on maternal and neonatal outcomes in twin pregnancies.Methods:Five hundred cases of twin pregnancies were divided into a low body weight group(68 cases),a normal weight group(355 cases),an overweight group(65 cases),and an obesity group(12 cases)according to the World Health Organization(WHO)Body Mass Index(BMI)classification guidelines Results:Comparison of weight gain during different pregnancies revealed that pregnant women were mainly of low weight and average weight.The higher the BMI before pregnancy,the higher the incidence of excessive weight gain during pregnancy.The incidences of gestational diabetes mellitus(GDM)and premature rupture of membranes in women with low weight gain were significantly higher than those in women with average weight gain and high weight gain(P<0.05).The incidences of gestational hypertension,preeclampsia,and anemia in women with high weight gain were significantly higher than those in women with low weight gain and average weight gain(P<0.05).The incidence of neonatal birth weight,fetal distress,and macrosomia in the high weight gain group was significantly higher than those in the low weight gain and average weight gain groups(P<0.05).The birth weight of newborns in low-weight gain mothers was significantly lower than that of normal-weight gain mothers(P<0.05).Conclusion:Poor maternal and infant outcomes were common in women with insufficient or excessive weight gain during pregnancy.Therefore,for women with twin pregnancies,weight management is crucial to ensure maternal and infant health.

一种前后台结合的Pipelined ADC校准技术

针对Pipelined模数转换器(ADC)中采样电容失配和运放增益误差带来的非线性问题,提出了一种前后台结合的Pipelined ADC校准技术。前台校准技术通过对ADC量化结果的余量分析,补偿相应流水级的量化结果,后台校准技术基于伪随机(PN)注入的方式,利用PN的统计特性校准增益误差。本校准技术在系统级建模和RTL级电路设计的基础上,实现了现场可编程门阵列(FPGA)验证并成功流片。测试结果显示,在1 GS/s采样速率下,校准精度为14 bit的Pipelined ADC的有效位数从9.30 bit提高到9.99 bit,信噪比提高约4 dB,无杂散动态范围提高9.5 dB,积分非线性(INL)降低约10 LSB。

基于人工磁导体的低剖面高增益宽带天线

提出一种基于人工磁导体(Artificial Magnetic Conductor, AMC)的高增益宽带天线,该天线由一个AMC超表面和一个微带贴片天线组成。利用AMC的同相反射特性,将天线的后向辐射反射与前向辐射叠加,从而提升了天线的增益。天线的整体尺寸为0.6λ_(0)×0.6λ_(0)×0.12λ_(0) (λ_(0)为天线谐振频率对应的波长)。测试结果表明,在4.55~6.1 GHz (27.7%)的工作频段内,天线的峰值增益达到8.4 dB。与利用理想电导体(Perfect Electric Conductor, PEC)提升增益的方法相比,其剖面从0.37λ_(0)降低到0.12λ_(0)。该天线剖面低、尺寸小、增益高、成本低廉,可以应用于WLAN波段通信。

AlWCrNiMo高熵涂层的阻扩散性能研究

目的解决NiAlHf涂层和镍基高温合金元素互扩散造成的抗氧化性能衰减问题。方法采用磁控溅射技术在NiAlHf涂层与镍基高温合金N5之间沉积一层AlWCrNiMo高熵涂层作为扩散阻挡层,通过静态高温氧化测试和表征分析来评估涂层性能。结果AlWCrNiMo具有单一的面心立方晶体结构,结构致密且与N5基体、NiAlHf面层结合良好。在1100℃恒温氧化25h后,无扩散障试样(NN)出现了连续的γʹ-Ni3Al贫铝区,而有扩散障试样(NAN)的扩散阻挡层较好地抑制了这种扩散现象。NAN试样的互扩散区+二次反应区(IDZ+SRZ)宽度为19.2µm,远小于NN试样的30µm。然而随着氧化时间的延长,NAN试样的阻挡性能发生衰减。50h之后NAN试样的二次反应区(SRZ)宽度大于NN试样;100h后扩散障被逐渐消耗变薄,200h时彻底分解。结论1100℃恒温氧化25h后,AlWCrNiMo高熵扩散障明显减缓了元素扩散,氧化50 h后,高熵合金中分解的W和Mo元素在一定程度上促进了TCP相的析出。在氧化初期,NAN试样优先实现了暂态氧化铝到稳态氧化铝的转变,为基体提供了良好的保护,其增重明显小于单一NN试样。

On-off控制对高速动车组综合动力学性能的影响分析

利用ADAMS-Matlab联合仿真的方法研究了on-off半主动控制对高速动车组的横向平稳性、运动稳定性和安全性的影响。根据国内某型号高速动车组的参数,利用多体动力学软件ADAMS/Rail建立了满载工况下的单车动车组模型。随后,运用ADAMS-Matlab联合仿真的方法对被动控制和on-off半主动控制条件下的动车组模型进行了仿真分析,仿真考虑了不同运行速度和不同线路条件等工况。最后,分别计算了两种控制条件下高速动车组模型的横向平稳性、运动稳定性和安全性能。从分析结果可知:与被动控制相比,on-off控制下车辆的横向平稳性指标可大幅提升35.5%,但非线性临界速度降低了16.6%,高速运行工况下的安全性指标也严重下降。因此,on-off控制策略在高速动车组上应用时存在严重缺陷,需要对其进行改良方可应用。

基于天棚On-Off控制的磁流变半主动悬架研究

以平行平板流动模型和Bingham模型为理论基础,推导了磁流变减振器的阻尼力计算公式.在车辆悬架动态性能模拟试验台上对磁流变减振器的示功特性和速度特性进行了试验验证.最后基于天棚on-off控制,利用dSPACE搭建了实车试验平台,并进行了实际越野路面的道路试验.试验结果表明:与传统被动悬架对比,磁流变半主动悬架能够很好地抑制车身以及驾驶员座椅的低频共振峰值,降低车身垂向振动幅值,提高车辆行驶平顺性和乘坐舒适性.

一种基于BETA分布抗On-off攻击的信任机制

在无线传感器网络(WSNs)中,加密和认证机制只能预防外部攻击,对于内部攻击的防御,信任管理机制则是一种较好的方法。On-off攻击作为内部攻击的一种,由于其节点信誉值动态调整,具有更大的隐蔽性与攻击性。通过在BETA分布下采用差值判决与趋势分析方法,提出了一种有效抗On-off攻击的信任机制。仿真结果证明该机制能够很好的抵御On-off攻击,且易于实现。

物联网中基于信任抗On-off攻击的自适应安全机制

为了降低静态安全机制中不必要的数据源认证开销和防御信任阈值机制中存在的On-off攻击,在物联网(IoT)环境下提出了一种基于信任的自适应安全机制。首先,根据节点在信息交互中的行为表现建立节点间的信任评估模型,进而给出节点总体信任值的度量方法;然后,对于总体信任值高于信任阈值的节点,采用基于信任的自适应检测算法实时地检测这些节点总体信任值的变化情况;最终,中继节点根据自适应检测的结果决定是否验证接收到的消息。仿真实验结果和分析表明,该机制降低了中继节点的能量开销,同时对物联网中的On-off攻击起到较好的防御作用。

GAINS中重力传感器信息的扰动改正

重力辅助惯性导航系统GAINS(Gravity Aided Inertial Navigation System)是利用地球物理特征信息──重力来完成水下运动载体的辅助惯性导航与定位。为实现重力匹配以校正惯性导航随时间累积的误差,首先必须对重力传感器输出信息进行扰动改正。分析了水下运动状态下重力传感器受到的各种重力扰动,如垂直扰动加速度、水平扰动加速度以及厄特弗斯效应影响所产生的原因,研究了扰动误差模型与INS导航精度之间的关系,并通过计算,提出了可直接以INS输出数据而无需其它外部有源导航信息进行扰动分离的方法。

A Ka Broadband High Gain Monolithic LNA with a Noise Figure of 2dB

A four-stage monolithic microwave integrated circuits （MMIC） low noise amplifier （LNA） operating from 23 to 36GHz is reported using commercially available 0.15μm PHEMT technology. The LNA is self-biased. To achieve a low noise characteristic, careful optimizations of gate width are performed to reduce gate resistance. Absorption circuits and an elaborate bias structure with a resistor-capacitor network are employed to improve stability. Multiple resonance points and negative feedback technologies are used to widen the bandwidth. Measurements show a noise figure （NF） of less than 2.0dB,and the lowest NF is only 1.6dB at a frequency of 31GHz. In the whole operation band,the LNA has a gain of higher than 26dB,and an input return loss and output return loss of more than 11 and 13dB,respectively. The output power at ldB compression gain of 36GHz is about 14dBm. The chip area is 2.4mm ×1mm.