Ultra-wide band gap and wave attenuation mechanism of a novel star-shaped chiral metamaterial

A novel hollow star-shaped chiral metamaterial(SCM)is proposed by incorporating chiral structural properties into the standard hollow star-shaped metamaterial,exhibiting a wide band gap over 1500 Hz.To broaden the band gap,solid single-phase and two-phase SCMs are designed and simulated,which produce two ultra-wide band gaps(approximately 5116 Hz and 6027 Hz,respectively).The main reason for the formation of the ultra-wide band gap is that the rotational vibration of the concave star of two novel SCMs drains the energy of an elastic wave.The impacts of the concave angle of a single-phase SCM and the resonator radius of a two-phase SCM on the band gaps are studied.Decreasing the concave angle leads to an increase in the width of the widest band gap,and the width of the widest band gap increases as the resonator radius of the two-phase SCM increases.Additionally,the study on elastic wave propagation characteristics involves analyzing frequency dispersion surfaces,wave propagation directions,group velocities,and phase velocities.Ultimately,the analysis focuses on the transmission properties of finite periodic structures.The solid single-phase SCM achieves a maximum vibration attenuation over 800,while the width of the band gap is smaller than that of the two-phase SCM.Both metamaterials exhibit high vibration attenuation capabilities,which can be used in wideband vibration reduction to satisfy the requirement of ultra-wide frequencies.

A phenomenological model for plastic flow behavior of rotating band material with a large temperature range

The plastic flow behavior of the rotating band material is investigated in this paper. The rotating band material is processed from H96 brass alloy, which is hardened to a much higher yield strength compared to the annealed one. The dynamically uniaxial compression behavior of the material is tested using the split Hopkinson pressure bar(SHPB) with temperature and strain rate ranging from 297 to 1073 K and500 to 3000 s^(-1), respectively, and a phenomenological plastic flow stress model is developed to describe the mechanical behavior of the material. The material is found to present noticeable temperature sensitivity and weak strain-rate sensitivity. The construction of the plastic flow stress model has two steps. Firstly, three univariate stress functions, taking plastic strain, plastic strain rate and temperature as independent variable, respectively, are proposed by fixing the other two variables. Then, as the three univariate functions describe the special cases of flow stress behavior under various conditions, the principle of stress compatibility is adopted to obtain the complete flow stress function. The numerical results show that the proposed plastic flow stress model is more suitable for the rotating band material than the existing well-known models.

A Novel Polymorphic Topology with Hybrid Control Strategy Based LLC Resonant Converter for Ultra-Wide Input Voltage Range Applications

To realize effective utilization of renewable energy sources,a novel polymorphic topology with hybrid control strategy based LLC resonant converter was analyzed and designed in this paper.By combining the merits of a full bridge LLC resonant converter,three-level half bridge LLC resonant converter,and variable frequency control mode,the converter realizes an intelligent estimation of input voltage by automatically changing its internal cir-cuit topology.Under this control strategy,different input voltages determine different operation modes.This is achieved in full bridge LLC mode when the input voltage is low.If the input voltage rises to a certain level,it operates in three-level half bridge LLC mode.These switches are digital and entirely carried out by the DSP(Digi-tal Signal Processor),which means that an auxiliary circuit is unnecessary,where a simple strategy of software modification can be utilized.Experimental results of a 500W prototype with 100V~600V input voltage and full load efficiency of up to 92%are developed to verify feasibility and practicability.This type of converter is suitable for applications with an ultra-wide input voltage range,such as wind turbines,photovoltaic generators,bioenergy,and other renewable energy sources.

Compact Coplanar Epsilon-Negative Antenna with Ultra-Wide Band Character

In this paper, a compact coplanar epsilon.negative(ENG) antenna is proposed with ultra.wide operation band and small size of 18×11.5 mm2. The proposed antenna is designed based on a coplanar.waveguide(CPW) feeding antenna, and thus the via.free structure is employed to realize the ENG unit cell, which is convenient to tune the frequency of zeroth.order resonance(ZOR) and extends the ZOR bandwidth. The high.order resonant frequencies are achieved and mainly determined by the separate slots that are located between the radiating patch and the ground plane. Adding the left.handed inductance between the radiating patch and ground has slight impact on the high.order resonant frequencies, and then the ultra.wide band is achieved by merging the ZOR bandwidth with the high.order resonant bandwidths. The ground plane primarily works as a matching network for the proposed antenna. Although it generates a low.frequency resonance, the performance is undesirable due to the impedance mismatching. The measured results show that the reflection coefficient, |S11| <.10 d B, is in a wide frequency range from 5.25 to 13 GHz, which covers the upper operation band of UWB communication. Also, the antenna contains relatively stable gains and omni.directional radiation patterns.

ON THE PAR REDUCTION OF MB-OFDM ULTRA-WIDEBAND SIGNALS

The Peak to Average power Ratio (PAR) of a Multi-Band Orthogonal Frequency-Division Multiplexing (MB-OFDM) Ultra-Wide Band (UWB) signals can be substantially larger than that of single carrier or carrier-less ultra-wideband signals. In this letter, a novel PAR reduction scheme for the MB-OFDM UWB system based on spreading and interleaving is proposed. By spreading the coded bits over each subcarrier in corresponding band and interleaving the spread symbols across all bands, the PAR statistics of the MB-OFDM signals can be improved and the PAR is reduced obviously. In the PAR reduction scheme, there is no loss in transmission data rate or Bit Error Rate (BER) performance decreasing. Since the spreading and interleaving operation are implemented by unitary Hadamard sequences and used for an approach to provide the robustness of the UWB system to narrowband interference, there is no additional implementation burden. Simulation results show that the investigated scheme gives the PAR reduction of 3dB compared with that of the original MB-OFDM signals.

Numerical simulation of the coupling of ultra-wide band electromagnetic pulse into landmine by aperture

The modern landmine＇s electronic fuse is susceptible to strong interference or can even be damaged by the ultra-wide band electromagnetic pulse（UWB-EMP）. The finite-difference time-domain（FDTD） method in lossy media with cylindrical coordinates is used to study the interactions of the UWB-EMP with the landmine. First, the coupling of UWB-EMP into the landmine shielding shell through an aperture is numerically simulated. Second, the coupled electromagnetic field of mine shells made of different shielding materials and with apertures of different sizes is plotted. Third, the aperture coupling laws of UWB-EMP into shells are analyzed and categorized. Such an algorithm is capable of effectively preventing ladder similar errors, and consequently improving the calculation precision, and in addition to adopting the message passing interface（MPI） parallel method to divide the total calculating range into more sub-ranges, the overall calculating efficiency is greatly increased. These calculations are surely a constructive reference for modern landmine design against electromagnetic damage.

Mobile Robot Positioning and Tracking Based on Ultra-wideband Technology

To solve the precision self-positioning problem for mobile robot,a positioning program based on ultra-wideband technology was proposed. Ultra-wideband pulse has very high bandwidth; ranging accuracy can achieve centimeter-level theoretically. The mobile robot obtained the distance to the reference node by sending ultra-wideband pulse. According to the geometric relations among the references and the robot,establish equations to calculate the position coordinates. Then Kalman filter algorithm was applied for mobile robot tracking. Simulation results show that robot positioning and tracking based on ultra-wideband technology can achieve indoor and outdoor seamless docking.

Designing a Carbon Nanotube Field-Effect Transistor with High Transition Frequency for Ultra-Wideband Application

Theoretical calculations predict transition frequencies in the terahertz range for the field-effect transistors based on carbon nanotubes, and this shows their suitability for being used in high frequency applications. In this paper, we have designed a field-effect transistor based on carbon nanotube with high transition frequency suitable for ultra-wide band applications. We did this by optimizing nanotube diameter, gate insulator thickness and dielectric constant. As a result, we achieved the transition frequency about 7.45 THz. The environment of open source software FETToy is used to simulate the device. Also a suitable model for calculating the transition frequency is presented.

Evaluation of System Performance of Ultra-Wide Band Jointing in MC Signaling in Correlated Environments

The evaluation of System Performance of UWB (ultra-wide band) jointing in MC (multi-carrier) signaling in correlated environments is presented in the report. The correlated Nakagami-m statistical distribution for the multipath fading model is assumed in this scenario. In fact to establish the model for analyzing in this article is using MC-CDMA (multi-carrier code-division multiple-access) system characterization combined with a UWB scheme. The average BER (bit error rate) is calculated and compared to a special case of previously published results. Studied results from this paper can be implied to approve the system performance for a UWB system combined with a MC-CDMA wireless communication system. It is worth noting that the Nakagami-m distributed fading parameter significantly dominates UWB system performance when it cooperates with MC signaling under a fading environment. Finally, it is worthy of noting that when the SNR (signal-to-noise ratio) at system’s receiver reaches a preset high threshold value, the parameter of power decay ratio effect could be not included.

Angular insensitive nonreciprocal ultrawide band absorption in plasma-embedded photonic crystals designed with improved particle swarm optimization algorithm

Using an improved particle swarm optimization algorithm(IPSO)to drive a transfer matrix method,a nonreciprocal absorber with an ultrawide absorption bandwidth and angular insensitivity is realized in plasma-embedded photonic crystals arranged in a structure composed of periodic and quasi-periodic sequences on a normalized scale.The effective dielectric function,which determines the absorption of the plasma,is subject to the basic parameters of the plasma,causing the absorption of the proposed absorber to be easily modulated by these parameters.Compared with other quasi-periodic sequences,the Octonacci sequence is superior both in relative bandwidth and absolute bandwidth.Under further optimization using IPSO with 14 parameters set to be optimized,the absorption characteristics of the proposed structure with different numbers of layers of the smallest structure unit N are shown and discussed.IPSO is also used to address angular insensitive nonreciprocal ultrawide bandwidth absorption,and the optimized result shows excellent unidirectional absorbability and angular insensitivity of the proposed structure.The impacts of the sequence number of quasi-periodic sequence M and collision frequency of plasma1ν1 to absorption in the angle domain and frequency domain are investigated.Additionally,the impedance match theory and the interference field theory are introduced to express the findings of the algorithm.

车辆涉水智能无线报警装置

针对暴雨天汽车涉深水行驶和停驻浸水易损坏问题,设计了基于NB-IoT通信技术的智能车辆防浸报警装置.装置利用超声波传感器测量车辆涉水深度,可预判水位上升速度,并动态调整测量时间间隔以降低功耗.同时设计了汽车开关检测电路判断车辆驶停状态,当水位深度越限时可本地告警,或通过NB-IoT通信模块远程告警.实验结果表明:该装置可实时准确监测车辆周边水位,提醒司机涉水缓速行驶,并在发生暴雨险情时通知车主及时转移车辆,避免浸水造成经济损失.

双有源桥DC-DC变换器三移相调制及其死区效应分析和补偿

针对双有源桥(DAB)变换器宽电压范围应用,该文研究一种全工况连续、表达形式统一、计算量小的三移相(TPS)调制策略,并分析其功率传输特性及软开关性能。结合工程应用中的非理想因素,对TPS调制不同开关模式下的死区效应及其边界进行研究,给出DAB宽电压范围运行时避免电压跌落和极性反转的约束条件。针对死区引入的移相比损失、软开关范围减小等问题,提出一种基于开关脉冲调整的死区补偿策略以补偿移相比损失,重新获取全工况软开关范围,降低死区引入的附加电流应力及损耗、提升效率。最后通过仿真和实验验证所提策略的有效性。

一种复杂环境下UWB测距误差预测方法

针对复杂室内环境中,多径干扰和视距遮挡影响室内定位精度的问题,提出一种复杂环境下UWB测距误差的预测方法:根据超宽带(UWB)室内定位方法抗干扰能力强、定位精度高的特点,从理论上分析影响超宽带信号测距精度的因素;然后通过模型量化分析每种影响因素对测距误差的影响程度,改进以往通过信道脉冲响应特征分析单一的视距遮挡参数来提高定位精度的补偿算法;最后从数据挖掘和机器学习的角度出发,将多径效应、视距遮挡、标签与基站的距离、标签移动速度、标签与基站天线俯仰角以及气象因素(温度、湿度、压强)等对测距精度造成影响的重要因素作为特征进行分类和归类,并使用梯度提升决策树模型对数据集进行训练和预测。实验结果表明,该模型可以根据当前状态下的组合特征值估计出测距误差值,将当前预测的误差值补偿到测量值上,可以有效提高超宽带室内定位的精度。

Thera-Band弹力带主动运动疗法联合滑囊内注射曲安奈德对肩峰-三角肌下滑囊病变患者肩关节活动度的影响

目的探究Thera-Band弹力带主动运动疗法联合滑囊内注射曲安奈德对肩峰-三角肌下滑囊病变患者肩关节活动度的影响.方法选取我院2018年10月—2020年10月收治的68例肩峰-三角肌下滑囊病变患者为研究对象,随机分为联合组和单一组,每组34例.单一组采用滑囊内注射曲安奈德治疗,联合组采用Thera-Band弹力带主动运动疗法联合滑囊内注射曲安奈德治疗,比较两组治疗前后的疼痛程度、肩关节活动度和肩关节功能障碍程度.结果治疗后,两组的疼痛视觉模拟评分(VAS)、肩关节功能障碍指数量表(SPADI)评分均低于治疗前,且联合组VAS评分、SPADI评分均低于单一组,组间差异有统计学意义(P<0.05).治疗后,两组的肩关节活动度评分均高于治疗前,且联合组评分高于单一组,组间差异有统计学意义(P<0.05).结论采用Thera-Band弹力带主动运动疗法联合滑囊内注射曲安奈德治疗肩峰-三角肌下滑囊病变患者能够提升治疗效果,减轻疼痛,增强肩关节活动度,改善肩关节功能障碍程度.

一种机载甚高频数据广播(VDB)接收机射频前端设计

设计了一种甚高频(VHF)波段接收机,并对接收机的功能性能指标进行优化设计,着重分析了接收通道的动态范围、灵敏度以及本振信号和自动增益控制(AGC)响应时间。测试结果表明,接收机的技术指标与设计结果基本相符,达到了预期要求,具有一定的工程实用价值。

四黄散联合间断垂直钢丝缝合加张力带对髌骨下极骨折患者膝关节活动度及骨折愈合时间的影响

目的:观察四黄散联合间断垂直钢丝缝合加张力带对髌骨下极骨折患者膝关节活动度及骨折愈合时间的影响。方法:选取2021年9月至2022年9月丰城市中医院收治的髌骨下极骨折患者40例,按照随机数字表法分为对照组和试验组,每组20例。两组患者均给予切开复位内固定,对照组给予间断垂直钢丝缝合联合张力带治疗,试验组给予四黄散联合间断垂直钢丝缝合加张力带治疗。观察两组患者术后6周、3个月、6个月、1年及末次随访时膝关节疼痛评分、屈伸活动范围(range of motion, ROM)、Bostman评分、骨折愈合时间、各项临床指标及并发症发生情况。结果:试验组术后6周、3个月、6个月、1年膝关节疼痛评分均低于对照组,差异有统计学意义(P<0.05)。试验组术后6周、3个月、6个月、1年ROM、Bostman评分高于对照组,差异有统计学意义(P<0.05)。试验组术后1年骨折愈合时间、各项临床指标均优于对照组,并发症发生率低于对照组,差异有统计学意义(P<0.05)。结论:四黄散联合间断垂直钢丝缝合加张力带能改善髌骨下极骨折患者膝关节功能,降低术后并发症发生率,促进骨折早日愈合。

基于TWR的WLS和KF融合室内定位方法

超宽带(ultra wide band,UWB)传感器室内定位常通过双向测距法(two-way ranging,TWR)测得基站到待测标签距离,采用三边定位法进行室内定位,但因存在非视距误差等因素影响导致定位精度低且发散,为此本文提出采用加权最小二乘法(weighted least squares,WLS)训练数据集,将其定位结果与卡尔曼滤波相结合进行室内定位。仿真实验结果表明,该方法能够解决经典定位造成较大误差的缺点,定位更快速.

超宽频带范围开关磁阻电机电子干扰信号调制方法

传统的电子干扰信号调制方法,只能对特定频段的干扰信号进行抑制,导致误比特率值较大,因此设计一种超宽频带范围开关磁阻电机电子干扰信号调制方法。构建一个可调的开关磁阻电机电子干扰信号模型。该模型可模拟不同频段和幅度的干扰信号,对干扰信号进行振幅调制,通过改变信号的幅度调整其对电机性能的影响,采用多比特差分检测方法对调制后的信号进行检测。实验结果表明,设计的超宽频带范围开关磁阻电机电子干扰信号调制方法,误比特率明显低于其它两种方法,误比特率最低达0.02,证明该方法的信号调制最佳。

Design and optimization of an ultra-wide frequency range CMOS divide-by-two circuit

A novel toggled flip-flop（TFF） divide-by-two circuit（DTC） and its optimization method based on a large-signal analysis approach are proposed.By reducing the output RC constant in tracking mode and making it large in latching mode,compressing the internal signal swing as well as compensating the current leaked in the latching mode, the operating frequency range is greatly expanded.Implemented in a SMIC 0.13μm RF CMOS process with a 1.2 V power supply,it can work under an ultra-wide frequency band ranging from 320 MHz to 29.6 GHz.Experimental results show that two phase-locked loops（PLLs） with the proposed DTC can achieve in-band phase noise of-94 dBc/Hz @ 10 kHz under 4224 MHz operating frequency and-84 dBc/Hz @ 10 kHz under 10 GHz operating frequency,respectively. The power consumption of the proposed DTC is reduced by almost 50%compared with the conventional counterparts.

Compact Bluetooth/UWB Antenna with Multi-Band Notched Characteristics

A small-sized, low-profile, and planar dual band antenna for Bluetooth (2.4 - 2.484 GHz) and ultra-wideband (UWB) (3.1 - 10.6 GHz) with multi-band notched antennas is presented. Two antennas A and B with different types of slots are used to obtain tri-band notched characteristic. In antenna A notched bands, 5 - 6 GHz for WLAN, and 3.3 - 4 GHz for WiMAX, are achieved using a U-slot in ground structure and in the radiating patch. In antenna B two notched bands at 3.3 - 4 GHz, for WiMAX and 7.2 GHz for C-band satellite communication systems are achieved by using a U-slot in ground structure and a H-shaped slot in the radiating patch. The radiation characteristics of the two antennas are calculated using a commercial EM simulator based on Finite Element Method (FEM) and the Finite Integration Technique (FIT). The two antennas show acceptable gain flatness with stable omnidirectional radiation patterns across the integrated Bluetooth and UWB bands.