摘要：A compact high-scanning-rate circular-polarized leaky-wave antenna(LWA)based on a meandering substrate integrated waveguide(SIW)with defected ground structures(DGSs)is *** meandering-SIW design is employed to enhance the beam scanning rate,while circular polarization is achieved by etchingπ-shaped slots on the top *** suppress the open stopband at broadside,offset circular DGSs are periodically etched on the ground *** impact on the reflection coefficient and axial ratio is then analyzed through a parametric study.A prototype of the antenna is simulated,fabricated,and *** simulated and measured results indicate a scanning rate of approximately 8.6,with continuous beam scanning from-41°to 59°across the 11.3-12.7 GHz operating *** antenna maintains an axial ratio below 3 dB within the 11.5-12.3 GHz *** design shows promise for use in wireless communication systems,particularly in environments with increasingly limited spectrum resources.

摘要：A compact antenna formed by three concentric split rings for ultra-high frequency(UHF)radio frequency identification(RFID)tag is proposed in this *** antenna is composed of two parts,an outer short-circuited ring modified from a traditional split-ring resonator(SRR)antenna and an inner SRR load,so the antenna can be regarded as a short-circuited ring loaded with *** to the transmission line theory,to conjugate match with the capacitive input-impedance of a tag chip,the length of the short-circuited ring isλg/4 shorter than that of an open-circuited dipole of a traditional SRR antenna,whereλg is the wavelengh of the operating ***,the size of the proposed antenna is more compact than that of the traditional SRR ***,the proposed antenna is simulated and optimized by ANSYS high-frequency structure simulator(HFSS).The impedance,efficiency,and mutual coupling of the fabricated antenna are tested in a reverberation chamber(RC).The results show that the size of the presented antenna is 83%smaller than that of the traditional SRR antenna and the proposed antenna can cover the whole UHF RFID operating frequency band worldwide(840—960 MHz).The measured read range of the tag exhibits maximum values of 45 cm in free space and 37 cm under dense tag environment.

摘要：目的分析评价机器人手术临床应用相关指南或专家共识的方法学质量。方法计算机检索国内外指南网站及电子数据库中关于机器人手术临床应用的指南或专家共识,检索时限为2000年1月1日—2021年12月29日,按照纳入和排除标准进行筛选。2名评价人员采用AGREEⅡ(Appraisal of Guidelines for Research and EvaluationⅡ)工具对指南和专家共识独立进行评价,对2名研究人员的组内相关系数进行一致性检验,并计算指南和专家共识在AGREEⅡ6个领域的得分。结果共纳入34篇文献,其中指南10篇,专家共识24篇。2名研究人员的一致性较好,组内相关系数>0.75。纳入指南和专家共识在AGREEⅡ6个领域(范围和目的、参与人员、制定的严谨性、表达的清晰性、应用性和编辑的独立性)的平均得分分别为81.0%、43.5%、28.2%、81.5%、12.7%和51.7%。结论目前国内外的机器人手术指南在制定的严谨性、应用性和编辑独立性等方面仍有待提高。随着机器人手术的不断开展,建议制定证据等级更高的循证指南和专家共识,以促进机器人手术的规范化应用。

摘要：在C/C复合材料表面采用等离子喷涂ZrB_2基陶瓷涂层是提高复合材料抗氧化性能的理想途径。为有效防止热裂纹的产生、设计性能更优的材料,基于数值模拟,通过合理的模型,采用间接顺序热结构耦合,可预测涂层在沉积过程中由于热失配引起的宏观残余应力的大小和分布。结果表明,径向应力是残余应力的主要表现形式;较厚的粘结层能够有效缓解材料的热物性差异;涂层的厚度为0. 5 mm时能够保证涂层表面不会因为受压而开裂的情况下在界面处的残余应力较小;涂层体系的材质倾向于导热系数较高、热膨胀系数较低的ZrB_2-30%SiC(体积分数)材料,以保证涂层在边缘不会有太大的拉应力而产生翘曲。