Reconfigurable mechanism-based metamaterials for ternary-coded elastic wave polarizers and programmable refraction control

Elastic metamaterials with unusual elastic properties offer unprecedented ways to modulate the polarization and propagation of elastic waves.However,most of them rely on the resonant structural components,and thus are frequency-dependent and unchangeable.Here,we present a reconfigurable 2D mechanism-based metamaterial which possesses transformable and frequency-independent elastic properties.Based on the proposed mechanism-based metamaterial,interesting functionalities,such as ternarycoded elastic wave polarizer and programmable refraction,are demonstrated.Particularly,unique ternary-coded polarizers,with 1-trit polarization filtering and 2-trit polarization separating of longitudinal and transverse waves,are first achieved.Then,the strong anisotropy of the proposed metamaterial is harnessed to realize positive-negative bi-refraction,only-positive refraction,and only-negative refraction.Finally,the wave functions with detailed microstructures are numerically verified.

NIPT-plus筛查染色体MMS的应用评价

目的探讨扩展性无创产前检测(NIPT-plus)在筛查染色体微缺失/重复综合征(MMS)上的应用。方法选取中山大学附属第一医院2018年1月至2020年12月3860例孕妇及2022年10例室间质评样本的NIPT和NIPT-plus检测结果,其中24例孕妇进行染色体微阵列分析(CMA)产前诊断。结果24例孕妇及10例质评样本NIPT-plus游离DNA浓度明显高于NIPT,总测序数据量提高了1.39~1.58倍,有效测序数据量提高了1.20~1.35倍;24例孕妇样本NIPT-plus提示1例18-三体,1例21-三体,2例MMS,NIPT提示1例18-三体,1例21-三体;10例质评样本NIPT-plus提示9例MMS且9号样本同时存在性染色体非整倍体(SCAs),NIPT仅提示1例SCAs。结论在本院系统检测范围内NIPT-plus能有效应用于MMS的筛查,减少出生缺陷。

格洛克19型9 mm手枪射击弹壳痕迹探究

枪弹痕迹形成于枪支装弹、击发和退壳过程中,能够不同程度地反映枪种特征。本文利用显微镜对格洛克19型手枪发射六种国际现役的9 mm北约标准弹(CBC-9mm-15、FC LUGER 9MM、GCED LUGER9mm、WIN LUGER 9MM、CLA 9MM 16、S&B 119×19)的射击弹壳痕迹进行观测、分析。结果表明,不同弹种的同类射击弹壳痕迹特征均具有较好的稳定性和较高的出现率,且实验中射击弹壳的击针头痕迹、击针头孔痕迹、舌痕、抛壳挺痕迹、拉壳钩痕迹、弹壳口扇形刮擦痕迹的形态反映、留痕部位及出现率均反映出该格洛克19型手枪射击痕迹的稳定特征,可为司法实践中枪种鉴别与枪支认定工作提供一定参考。

Gain-Enhanced Metamaterial Based Antenna for 5G Communication Standards

Metamaterial surfaces play a vital role to achieve the surface waves suppression and in-phase reflection,in order to improve the antenna performance.In this paper,the performance comparison of a fifth generation(5G)antenna design is analyzed and compared with a metamaterial-based antenna for 5G communication system applications.Metamaterial surface is utilized as a reflector due to its in-phase reflection characteristic and high-impedance nature to improve the gain of an antenna.As conventional conducting ground plane does not give enough surface waves suppression which affects the antenna performance in terms of efficiency and gain etc.These factors are well considered in this work and improved by using the metamaterial surface.The radiating element of the proposed metamaterial based antenna is made up of copper material which is backed by the substrate,i.e.,Rogers-4003 with a standard thickness,loss tangent and a relative permittivity of 1.524 mm,0.0027 and 3.55,correspondingly.The proposed antenna with and without metamaterial surface operates at the central frequency of 3.32 GHz and 3.60 GHz,correspondingly.The traditional antenna yields a boresight gain of 2.76 dB which is further improved to 6.26 dB,using the metamaterial surface.The radiation efficiency of the proposed metamaterial-based 5G antenna is above 85%at the desired central frequency.

The metamaterial analogue of electromagnetically induced transparency by dual-mode excitation of a symmetric resonator

Electromagnetically induced transparency （EIT） is obtained in a symmetric U-shaped metamaterial, which is at- tributed to the simultaneously excited dual modes in a single resonator under lateral incidence. A large group index accom- panied with a sharp EIT-like transparency window offers potential applications for slowing down light and sensing.

基于ROC曲线分析>5 mm亚实性结节平均CT值及形态学特征在预测肺腺癌浸润程度中的应用效果

目的:探究基于ROC曲线分析>5 mm亚实性结节(SSN)平均CT值及形态学特征在预测肺腺癌浸润程度中的应用效果。方法:选择2021年7月—2023年6月期间在吉林省肿瘤医院进行影像检查且经手术病理证实的SSN患者105例,共计112个结节。依据术后病理检查结果并结合第8版肺癌TNM分期标准将入组患者分为浸润性腺癌组(A组,n=66)和浸润前-微浸润腺癌组(B组,n=39)。收集患者临床资料及影像学资料,在单因素分析结果的基础上进行Logistic分析,再绘制受试者工作特征(ROC)曲线分析对浸润性肺癌的预测价值。结果:两组患者有无吸烟史、结节位置、空泡征、支气管充气征对比差异无统计学意义(P>0.05),两组患者形状、边界、磨玻璃成分平均CT值、相对密度、胸膜凹陷、结节最大直径、肺组织平均CT值、性质、胸膜凹陷对比,差异有统计学意义(P<0.05)。结节最大直径、磨玻璃成分平均CT值是浸润性肺癌的危险因素(P<0.05)。二者联合预测的曲线下面积(AUC)为0.913,灵敏度为81.43%,特异度为92.86%。结论:CT值及形态学特征在预测肺腺癌浸润程度具有较高的应用效果。结节最大直径和磨玻璃成分均CT值是浸润性肺癌的危险因素,二者联合预测具有较高的灵敏度、特异度和准确率。

Reconfigurable metamaterial for asymmetric and symmetric elastic wave absorption based on exceptional point in resonant bandgap

Elastic wave absorption at subwavelength scale is of significance in many engineering applications.Non-Hermitian metamaterials show the ability in high-efficiency wave absorption.However,the single functionality of metamaterials is an important limitation on their practical applications for lack of tunability and reconfigurability.Here,we propose a tunable and reconfigurable non-Hermitian piezoelectric metamaterial bar,in which piezoelectric bars connect with resonant circuits,to achieve asymmetric unidirectional perfect absorption(UPA)and symmetric bidirectional perfect absorption(PA)at low frequencies.The two functions can be arbitrarily switched by rearranging shunted circuits.Based on the reverberation-ray matrix(RRM)method,an approach is provided to achieve UPA by setting an exceptional point(EP)in the coupled resonant bandgap.By using the transfer matrix method(TMM)and the finite element method(FEM),it is observed that a non-Hermitian pseudo-band forms between two resonant bandgaps,and the EP appears at the bottom of the pseudo-band.In addition,the genetic algorithm is used to accurately and efficiently design the shunted circuits for desired low-frequency UPA and PA.The present work may provide new strategies for vibration suppression and guided waves manipulation in wide potential applications.

100 mm×100 mm液相外延碲镉汞薄膜技术进展

昆明物理研究所突破了φ150 mm碲锌镉单晶定向生长技术,实现了100 mm×100 mm碲锌镉衬底的小批量制备,位错腐蚀坑密度(EPD)≤4×10^(4) cm^(-2),沉积相尺寸小于5μm、沉积相密度小于5×10^(3) cm^(-2)。突破了大尺寸碲锌镉衬底表面处理以及大面积富碲水平推舟液相外延技术,实现了100 mm×100 mm大尺寸短波、中波碲镉汞薄膜材料的制备,薄膜表面质量优异,厚度极差优于±1.25μm,组分极差优于±0.0031,是目前国际上报道的最大面积碲锌镉衬底基碲镉汞薄膜材料。该材料为10k×10k及以上亿像素规模红外探测器的研制、4k×4k等规模大面阵红外探测器的量产奠定了坚实的基础。

Self-powered circularly polarized light detector based on asymmetric chiral metamaterials

Circularly polarized light(CPL)has been given great attention because of its extensive application.While several devices for CPL detection have been studied,their performance is affected by the magnitude of photocurrent.In this paper,a self-powered photodetector based on hot electrons in chiral metamaterials is proposed and optimized.CPL can be distinguished by the direction of photocurrent without external bias owing to the interdigital electrodes with asymmetric chiral metamaterials.Distinguished by the direction of photocurrent,the device can easily detect the rotation direction of the CPL electric field,even if it only has a very weak responsivity.The responsivity of the proposed detector is near 1.9 mA/W at the wavelength of 1322 nm,which is enough to distinguish CPL.The detector we proposed has the potential for application in optical communication.

国产超细胆道镜(3mm)在腹腔镜经胆囊管胆道探查、取石中的临床应用

探究在腹腔镜经胆囊管胆道探查、取石中应用国产超细胆道镜(3mm)的效果。方法 收集本院2022年4月至2023年4月住院治疗的胆管结石患者60例,按随机数表分成两组。观察组采用3 mm直径的自制微型胆道镜进行探诊,对照组采用传统的开腹手术,一期缝合。对手术时间,出血量,住院天数, VAS评分等进行观察。结果 治疗组在手术时间、术中出血量及住院天数等方面,与对照组比较,有显著性差别(P<0.05),而观察组的 VAS得分则显著低于对照组(P<0.05)。结论 国产超细胆道镜(3mm)在腹腔镜经胆囊管胆道探查、取石临床疗效及疼痛感均显著低于常规腹腔镜下胆总管探查技术,充分证明国产超细胆道镜已经达到国际先进水平,具有临床推广的价值与意义。

Giant Asymmetric Transmission and Optical Rotation of a Three-Dimensional Metamaterial

We show that giant asymmetric transmission and optical rotation for linear polarizations can be achieved by a chiral three-dimensional metamaterial composed of L-shaped and C-shaped metallic particles. Numerical calcu- lations on the electric field distributions indicate that the coupling between the electric dipolar and quadrupolar resonances in the L- and C-shaped metallic particles contributes to these effects.

鞍钢Φ110 mm圆钢孔型设计与轧制

鞍钢股份有限公司大型总厂连轧生产线设备升级后,采用“箱形-椭圆-圆-椭圆-圆”的孔型系统,完成了Φ110 mm圆钢孔型设计。轧制后,Φ110 mm圆钢平均成材率达到90.31%,外径在109.10~111.05 mm波动,平均椭圆度1.16 mm,满足生产要求。

Approximate CN scheme and its open region problems for metamaterial rotational symmetric simulation

In order to simulate metamaterial rotational symmetric open region problems,unconditionally stable perfectly match layer(PML)implementation is proposed in the body of revolution(BOR)finite-difference time-domain(FDTD)lattice.More precisely,the proposed algorithm is implemented by the Crank-Nicolson(CN)Douglas-Gunn(DG)procedure for BOR metamaterial simulation.The constitutive relationship of metamaterial can be expressed by the Drude model and calculated by the piecewise linear recursive convolution(PLRC)approach.The effectiveness including absorption,efficiency,and accuracy is demonstrated through the numerical example.It can be concluded that the proposed implementation is to take the advantages of the CNDG-PML procedure,PLRC approach,and BORFDTD algorithm in terms of considerable accuracy,enhanced absorption and remarkable efficiency.Meanwhile,it can be demonstrated that the proposed scheme can maintain its unconditional stability when the time step exceeds the CourantFriedrichs-Levy(CFL)condition.

Equivalent electromagnetic parameters for microwave metamaterial absorber using a new symmetry model

Transmission line theory uses the complex nature of permeability and permittivity of a conventional magnetic absorber to evaluate its absorption properties and mechanism. However, because there is no method to obtain the electromagnetic parameters of a metamaterial-absorber integrated layer(composed of a medium layer and a periodic metal array), this theory is seldom used to study the absorption properties of the metamaterial absorber. We propose a symmetry model to achieve an equivalent complex permittivity and permeability model for the integrated layer, which can be combined with the transmission line theory to calculate metamaterial absorption properties. The calculation results derived from both the transmission line theory and the high-frequency structure simulator are in good agreement. This method will be beneficial in practical investigations of the absorption mechanism of a metamaterial absorber.

一种20GHz0.65mm节距CQFP外壳

提出了一种应用频率达20 GHz的0.65 mm节距陶瓷四边引线扁平封装(CQFP)外壳,对高频信号的传输采用共面波导-垂直过孔-共面波导-引线的结构。对成型引线附近的阻抗不连续性进行了分析,通过信号传输引线的非等宽设计,改善了引线部位的阻抗突变,提高了信号的传输带宽。通过板级联合仿真和布线优化,将外壳应用频率提升至20 GHz。利用GSG探针对外壳样品进行测试,实测结果表明,该结构在DC~20 GHz插入损耗优于-1 dB,回波损耗不大于-15 dB。该CQFP外壳通过了机械和环境可靠性试验,可应用于高频高可靠封装领域。

Inverse design of mechanical metamaterial achieving a prescribedconstitutive curve

Besides exhibiting excellent capabilities such as energy absorption,phase-transforming metamaterials offer a vast design space for achieving nonlinear constitutive relations.This is facilitated by switching between different patterns under deformation.However,the related inverse design problem is quite challenging,due to the lack of appropriate mathematical formulation and the convergence issue in the post-buckling analysis of intermediate designs.In this work,periodic unit cells are explicitly described by the moving morphable voids method and effectively analyzed by eliminating the degrees of freedom in void regions.Furthermore,by exploring the Pareto frontiers between error and cost,an inverse design formulation is proposed for unit cells.This formulation aims to achieve a prescribed constitutive curve and is validated through numerical examples and experimental results.The design approach presented here can be extended to the inverse design of other types of mechanical metamaterials with prescribed nonlinear effective properties.

Simulated and experimental studies of a multi-band symmetric metamaterial absorber with polarization independence for radar applications

We develop a simple new design for a multi-band metamaterial absorber(MTMA)for radar applications.Computer Simulation Technology(CST)Studio Suite 2018 was used for the numerical analysis and absorption study.The simulated results show four high peaks at 5.6 GHz,7.6 GHz,10.98 GHz,and 11.29 GHz corresponding to absorption characteristics of 100%,100%,99%,and 99%,respectively.Furthermore,two different structures were designed and compared with the proposed MTMA.The proposed structure remained insensitive for any incident angle and polarization angle from 0°to60°.Moreover,negative constitutive parameters were retrieved numerically.To support the simulated results,the proposed design was fabricated by using a computer numerical control-based printed circuit board prototyping machine and tested experimentally in a microwave laboratory.The absorption mechanism of the proposed MTMA is presented through the surface current and electric field distributions.The novelties of the proposed structure are a simple and new design,ease of fabrication,low cost,durability,suitability for real-time applications and long-term stability given the fabrication technique and non-destructive measurement method and very high absorption.The proposed structure has potential applications in C and X band frequency ranges.

Gelatin-Based Metamaterial Hydrogel Films with High Conformality for Ultra-Soft Tissue Monitoring

Implantable hydrogel-based bioelectronics(IHB)can precisely monitor human health and diagnose diseases.However,achieving biodegradability,biocompatibility,and high conformality with soft tissues poses significant challenges for IHB.Gelatin is the most suitable candidate for IHB since it is a collagen hydrolysate and a substantial part of the extracellular matrix found naturally in most tissues.This study used 3D printing ultrafine fiber networks with metamaterial design to embed into ultra-low elastic modulus hydrogel to create a novel gelatin-based conductive film(GCF)with mechanical programmability.The regulation of GCF nearly covers soft tissue mechanics,an elastic modulus from 20 to 420 kPa,and a Poisson’s ratio from-0.25 to 0.52.The negative Poisson’s ratio promotes conformality with soft tissues to improve the efficiency of biological interfaces.The GCF can monitor heartbeat signals and respiratory rate by determining cardiac deformation due to its high conformability.Notably,the gelatin characteristics of the biodegradable GCF enable the sensor to monitor and support tissue restoration.The GCF metamaterial design offers a unique idea for bioelectronics to develop implantable sensors that integrate monitoring and tissue repair and a customized method for endowing implanted sensors to be highly conformal with soft tissues.

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.

Multi-band asymmetric transmissions based on bi-layer windmill-shaped metamaterial

This study proposes a bi-layer windmill-shaped metamaterial that consists of resonators, with similar shapes, on both sides of a dielectric substrate. In this study, the second layer is rotated clockwise around the substrate normal at 90°and thereafter flipped in the first layer. Due to the introduction of a windmill-like shape, the resonant structures result in new resonant modes and thus can achieve multi-band high-efficiency cross-polarization conversions and asymmetric transmissions(ATs) for a linearly polarized incident plane wave with a maximum asymmetric parameter of 0.72. Depending on the geometric parameters of our windmill-shaped structures, the AT effects can be flexibly modulated in a broad multiband from 160 THz to 400 THz, which has not been reported in previous studies. These outstanding AT effects provide potential applications in optical diodes, polarization control switches, and other nano-devices.