The resonant frequency of metamaterials structured with split ring resonator(SRR) meta-atoms is determined primarily through the capacitance and inductance of the individual meta-atoms. Two designs that vary inductanc...The resonant frequency of metamaterials structured with split ring resonator(SRR) meta-atoms is determined primarily through the capacitance and inductance of the individual meta-atoms. Two designs that vary inductance incrementally were modeled, simulated, fabricated, and tested to investigate the role inductance plays in metamaterial designs. The designs consisted of strategically adding sections to the SRR to increase the inductance, but in a manner that minimized capacitance variations. Each design showed a shift in resonant frequency that was proportional to the length of the added section. As the length of each section was increased, the resonant frequency shifted from 2.78 GHz to 2.18 GHz.展开更多
Metasurfaces consisting of subwavelength structures,so-called meta-atoms,have steadily attracted considerable attention for advanced holography due to their advantages in terms of high-resolution holographic images,la...Metasurfaces consisting of subwavelength structures,so-called meta-atoms,have steadily attracted considerable attention for advanced holography due to their advantages in terms of high-resolution holographic images,large field of view,and compact device volume.In contrast to conventional holographic displays using bulky conventional diffractive optical elements,metasurface holography enables arbitrary complex wavefront shaping with a much smaller footprint.In this review,we classify metasurface holography according to the meta-atom design methodologies,which can further expand hologram functionalities.We describe light-matter interactions,particularly in metasurface systems,using the relevant the Jones matrix to rigorously explain modulations of the amplitude,phase,and polarization of light.Six different types of metaatoms are presented,and the corresponding achievable wavefronts that form the holographic images in the far-field are also provided.Such a simple classification will give a straightforward approach to design and further realize advanced metasurface holographic devices.展开更多
针对原子优化算法寻优精度弱且易陷入局部极值的问题,本文从种群多样性、参数适应性和位置动态性角度提出一种融合混沌优化、振幅随机补偿和步长演变机制改进的原子搜索优化算法(improved atom search optimization,IASO),并将其成功应...针对原子优化算法寻优精度弱且易陷入局部极值的问题,本文从种群多样性、参数适应性和位置动态性角度提出一种融合混沌优化、振幅随机补偿和步长演变机制改进的原子搜索优化算法(improved atom search optimization,IASO),并将其成功应用于分类任务。首先,引入帐篷映射(Tent混沌)增强原子种群在搜索空间中的分布均匀性;其次,通过构建振幅函数对算法参数进行随机扰动并加入步长演变因子更新原子位置,以增强算法全局性和收敛性;最后,再将改进算法应用于误差反馈神经网络(BP神经网络)参数优化。通过与6种元启发式算法在20个基准测试函数下的数值实验对比表明:IASO不仅在求解多维基准函数上具有好的寻优性能,且在对BP神经网络参数进行优化时相较于2种对比算法具有更高的分类精度。展开更多
We propose the design of anisotropic metamaterials with cascading meta-atoms.Each meta-atom array behaves as an impedance-tuned interface and dramatically modifies the complex reflection and transmission coefficients....We propose the design of anisotropic metamaterials with cascading meta-atoms.Each meta-atom array behaves as an impedance-tuned interface and dramatically modifies the complex reflection and transmission coefficients.By engineering the frequency-dependent impedances,the reflection phase difference along the two axes of anisotropic metamaterials approximates to a constant in a wide range.We numerically demonstrate the proposed anisotropic metamaterials can accomplish achromatic polarization transformation from 0.5 THz to 3.1 THz.The polarization conversion ratio is higher than 80%,which exhibits excellent agreements with the theoretical calculation.Such design is scalable to other bands and can provide helpful guidance in broadband devices design.展开更多
目的 系统评价雾化吸入乙酰半胱氨酸溶液辅助治疗支气管肺炎的疗效,为临床提供循证参考。方法 计算机检索Cochrane Library,Pubmed,EMbase,CNKI,维普和万方数据库,检索时限均从建库到2017年11月,收集雾化吸入乙酰半胱氨酸溶液辅助治疗...目的 系统评价雾化吸入乙酰半胱氨酸溶液辅助治疗支气管肺炎的疗效,为临床提供循证参考。方法 计算机检索Cochrane Library,Pubmed,EMbase,CNKI,维普和万方数据库,检索时限均从建库到2017年11月,收集雾化吸入乙酰半胱氨酸溶液辅助治疗支气管肺炎的相关研究,对符合纳入标准的研究进行提取资料和质量评价,采用Rev Man 5.3统计软件进行Meta分析。结果 共纳入7项研究,合计448例患者。Meta分析结果显示:雾化吸入乙酰半胱氨酸溶液对支气管肺炎的治疗效果优于对照组,差异有统计学意义〔有效性:OR=4.60,95%CI(2.59,8.16), P <0.00001;显效性:OR=2.53,95%CI(1.80,3.57),P <0.00001〕;在改善临床症状体征和住院时间方面也优于对照组,差异有统计学意义〔体温恢复正常所需的时间:MD=-0.53,95%CI(-0.63,-0.44), P <0.00001;咳嗽消失所需的时间:MD=-1.45,95%CI(-1.87,-1.03), P <0.00001;气促消失所需的时间:MD=-1.13,95%CI(-1.58,-0.68), P <0.00001;肺部啰音消失所需的时间:MD=-1.07,95%CI(-1.62,-0.52), P =0.0002;住院时间:MD=-2.22,95%CI(-3.58,-0.86),P =0.001〕。结论 雾化吸入乙酰半胱氨酸可有效提高支气管肺炎患儿的治疗效果,缩短临床症状、体征消失的时间和住院时间,且安全性较好。但是由于纳入研究的数量和质量限制,以上结论尚待开展更多高质量研究加以验证。展开更多
[目的]系统评价中药雾化吸入辅助治疗呼吸机相关性肺炎的临床疗效及预后情况。[方法]从建库到2021年4月,检索PubMed、Cochrane Library、Web of Science、Clinical Trials、中国知网、维普、万方、中国生物医学文献数据库,纳入中药雾化...[目的]系统评价中药雾化吸入辅助治疗呼吸机相关性肺炎的临床疗效及预后情况。[方法]从建库到2021年4月,检索PubMed、Cochrane Library、Web of Science、Clinical Trials、中国知网、维普、万方、中国生物医学文献数据库,纳入中药雾化吸入辅助治疗呼吸机相关性肺炎的随机对照试验,以临床总有效率、白细胞水平、降钙素原(procalcitonin,PCT)水平、重症监护室(intensive care unit,ICU)住院时间、氧合指数为结局指标,提取并合并数据。使用Cochrane协作网偏倚风险评估工具进行单个研究的质量评价,使用Rev Man 5.4软件进行Meta分析。[结果]最终纳入12篇文献,共计909例。Meta分析结果显示:中药雾化吸入组临床总有效率明显优于对照组[比值比(odds ratio,OR)=4.27,95%可信区间(confidence interval,CI)(2.53,7.20),P<0.00001];中药雾化吸入可以降低白细胞水平[加权均数差(mean difference,MD)=-1.11,95%CI(-1.40,-0.81),P<0.00001];降低PCT水平[MD=-0.49,95%CI(-0.59,-0.40),P<0.00001];缩短ICU住院天数[MD=-2.70,95%CI(-3.13,-2.27),P<0.00001];提高氧合指数[MD=52.07,95%CI(47.44,56.71),P<0.00001]。[结论]中药雾化吸入辅助治疗呼吸机相关性肺炎可提高临床疗效并改善预后,但存在发表偏倚,需进一步验证。展开更多
目的:系统评价雾化吸入多黏菌素辅助治疗呼吸机相关性肺炎的疗效与安全性,为临床治疗提供循证参考。方法:计算机检索Cochrane Library、Embase、PubMed、Web of Science、中国期刊全文数据库、中国生物医学文献数据库、中文科技期刊数...目的:系统评价雾化吸入多黏菌素辅助治疗呼吸机相关性肺炎的疗效与安全性,为临床治疗提供循证参考。方法:计算机检索Cochrane Library、Embase、PubMed、Web of Science、中国期刊全文数据库、中国生物医学文献数据库、中文科技期刊数据库、万方数据库(检索时限均为建库至2021年3月)中关于雾化吸入多黏菌素联合常规治疗(试验组)对比常规治疗(对照组)对呼吸机相关性肺炎的疗效和安全性的随机对照试验(RCT)及队列研究。对符合纳入与排除标准的文献进行资料提取和质量评价后,采用RevMan 5.4软件进行Meta分析。结果:共纳入13项临床研究,包括2项RCT和11项队列研究,共计1066例患者。Meta分析结果显示,试验组患者的临床有效率[OR=1.53,95%CI(1.17,2.00),P=0.002]、微生物清除率[OR=1.46,95%CI(1.11,1.91),P=0.007]均显著高于对照组,差异均有统计学意义;两组患者的全因死亡率[OR=0.88,95%CI(0.68,1.14),P=0.32]、肾功能损害发生率[OR=1.04,95%CI(0.72,1.49),P=0.85]比较,差异均无统计学意义。结论:基于现有临床证据,雾化吸入多黏菌素联合常规治疗能显著提高呼吸机相关性肺炎患者的临床有效率和微生物清除率。但本结论尚需要更多设计严格、长期随访的大样本RCT加以证实。展开更多
Real-time terahertz(THz)imaging offers remarkable application possibilities,especially in the security and medical fields.However,most THz detectors work with scanners,and a long image acquisition time is required.Som...Real-time terahertz(THz)imaging offers remarkable application possibilities,especially in the security and medical fields.However,most THz detectors work with scanners,and a long image acquisition time is required.Some thermal detectors can achieve realtime imaging by using a focal plane array but have the drawbacks of low sensitivity due to a lack of suitable absorbing materials.In this study,we propose a novel photomechanical meta-molecule array by conveniently assembling THz meta-atom absorbers and bi-material cantilevers together,which can couple THz radiation to a mechanical deflection of the meta-molecules with high efficiency.By optically reading out the mechanical deflections of all of the meta-molecules simultaneously,real-time THz imaging can be achieved.A polyimide sacrificial layer technique was developed to fabricate the device on a glass wafer,which facilitates the transmission of a readout light while the THz wave radiates onto the meta-molecule array directly from the front side.THz images and video of various objects as well as infrared images of the human body were captured successfully with the fabricated metamolecule array.The proposed photomechanical device holds promise in applications in single and broadband THz as well as infrared imaging.展开更多
文摘The resonant frequency of metamaterials structured with split ring resonator(SRR) meta-atoms is determined primarily through the capacitance and inductance of the individual meta-atoms. Two designs that vary inductance incrementally were modeled, simulated, fabricated, and tested to investigate the role inductance plays in metamaterial designs. The designs consisted of strategically adding sections to the SRR to increase the inductance, but in a manner that minimized capacitance variations. Each design showed a shift in resonant frequency that was proportional to the length of the added section. As the length of each section was increased, the resonant frequency shifted from 2.78 GHz to 2.18 GHz.
基金Hyundai Motor Group,Grant/Award Number:Hyundai Motor Chung Mong-Koo fellowshipLG Display,Grant/Award Number:LGD-SNU incubation programNational Research Foundation of Korea,Grant/Award Numbers:CAMM-2019M3A6B3030637,NRF-2019R1A2C3003129,NRF-2019R1A5A8080290,NRF-2021R1C1C2004291。
文摘Metasurfaces consisting of subwavelength structures,so-called meta-atoms,have steadily attracted considerable attention for advanced holography due to their advantages in terms of high-resolution holographic images,large field of view,and compact device volume.In contrast to conventional holographic displays using bulky conventional diffractive optical elements,metasurface holography enables arbitrary complex wavefront shaping with a much smaller footprint.In this review,we classify metasurface holography according to the meta-atom design methodologies,which can further expand hologram functionalities.We describe light-matter interactions,particularly in metasurface systems,using the relevant the Jones matrix to rigorously explain modulations of the amplitude,phase,and polarization of light.Six different types of metaatoms are presented,and the corresponding achievable wavefronts that form the holographic images in the far-field are also provided.Such a simple classification will give a straightforward approach to design and further realize advanced metasurface holographic devices.
文摘针对原子优化算法寻优精度弱且易陷入局部极值的问题,本文从种群多样性、参数适应性和位置动态性角度提出一种融合混沌优化、振幅随机补偿和步长演变机制改进的原子搜索优化算法(improved atom search optimization,IASO),并将其成功应用于分类任务。首先,引入帐篷映射(Tent混沌)增强原子种群在搜索空间中的分布均匀性;其次,通过构建振幅函数对算法参数进行随机扰动并加入步长演变因子更新原子位置,以增强算法全局性和收敛性;最后,再将改进算法应用于误差反馈神经网络(BP神经网络)参数优化。通过与6种元启发式算法在20个基准测试函数下的数值实验对比表明:IASO不仅在求解多维基准函数上具有好的寻优性能,且在对BP神经网络参数进行优化时相较于2种对比算法具有更高的分类精度。
基金supported in part by National Science Foundation(NSF)
文摘We propose the design of anisotropic metamaterials with cascading meta-atoms.Each meta-atom array behaves as an impedance-tuned interface and dramatically modifies the complex reflection and transmission coefficients.By engineering the frequency-dependent impedances,the reflection phase difference along the two axes of anisotropic metamaterials approximates to a constant in a wide range.We numerically demonstrate the proposed anisotropic metamaterials can accomplish achromatic polarization transformation from 0.5 THz to 3.1 THz.The polarization conversion ratio is higher than 80%,which exhibits excellent agreements with the theoretical calculation.Such design is scalable to other bands and can provide helpful guidance in broadband devices design.
文摘目的 系统评价雾化吸入乙酰半胱氨酸溶液辅助治疗支气管肺炎的疗效,为临床提供循证参考。方法 计算机检索Cochrane Library,Pubmed,EMbase,CNKI,维普和万方数据库,检索时限均从建库到2017年11月,收集雾化吸入乙酰半胱氨酸溶液辅助治疗支气管肺炎的相关研究,对符合纳入标准的研究进行提取资料和质量评价,采用Rev Man 5.3统计软件进行Meta分析。结果 共纳入7项研究,合计448例患者。Meta分析结果显示:雾化吸入乙酰半胱氨酸溶液对支气管肺炎的治疗效果优于对照组,差异有统计学意义〔有效性:OR=4.60,95%CI(2.59,8.16), P <0.00001;显效性:OR=2.53,95%CI(1.80,3.57),P <0.00001〕;在改善临床症状体征和住院时间方面也优于对照组,差异有统计学意义〔体温恢复正常所需的时间:MD=-0.53,95%CI(-0.63,-0.44), P <0.00001;咳嗽消失所需的时间:MD=-1.45,95%CI(-1.87,-1.03), P <0.00001;气促消失所需的时间:MD=-1.13,95%CI(-1.58,-0.68), P <0.00001;肺部啰音消失所需的时间:MD=-1.07,95%CI(-1.62,-0.52), P =0.0002;住院时间:MD=-2.22,95%CI(-3.58,-0.86),P =0.001〕。结论 雾化吸入乙酰半胱氨酸可有效提高支气管肺炎患儿的治疗效果,缩短临床症状、体征消失的时间和住院时间,且安全性较好。但是由于纳入研究的数量和质量限制,以上结论尚待开展更多高质量研究加以验证。
文摘[目的]系统评价中药雾化吸入辅助治疗呼吸机相关性肺炎的临床疗效及预后情况。[方法]从建库到2021年4月,检索PubMed、Cochrane Library、Web of Science、Clinical Trials、中国知网、维普、万方、中国生物医学文献数据库,纳入中药雾化吸入辅助治疗呼吸机相关性肺炎的随机对照试验,以临床总有效率、白细胞水平、降钙素原(procalcitonin,PCT)水平、重症监护室(intensive care unit,ICU)住院时间、氧合指数为结局指标,提取并合并数据。使用Cochrane协作网偏倚风险评估工具进行单个研究的质量评价,使用Rev Man 5.4软件进行Meta分析。[结果]最终纳入12篇文献,共计909例。Meta分析结果显示:中药雾化吸入组临床总有效率明显优于对照组[比值比(odds ratio,OR)=4.27,95%可信区间(confidence interval,CI)(2.53,7.20),P<0.00001];中药雾化吸入可以降低白细胞水平[加权均数差(mean difference,MD)=-1.11,95%CI(-1.40,-0.81),P<0.00001];降低PCT水平[MD=-0.49,95%CI(-0.59,-0.40),P<0.00001];缩短ICU住院天数[MD=-2.70,95%CI(-3.13,-2.27),P<0.00001];提高氧合指数[MD=52.07,95%CI(47.44,56.71),P<0.00001]。[结论]中药雾化吸入辅助治疗呼吸机相关性肺炎可提高临床疗效并改善预后,但存在发表偏倚,需进一步验证。
文摘目的:系统评价雾化吸入多黏菌素辅助治疗呼吸机相关性肺炎的疗效与安全性,为临床治疗提供循证参考。方法:计算机检索Cochrane Library、Embase、PubMed、Web of Science、中国期刊全文数据库、中国生物医学文献数据库、中文科技期刊数据库、万方数据库(检索时限均为建库至2021年3月)中关于雾化吸入多黏菌素联合常规治疗(试验组)对比常规治疗(对照组)对呼吸机相关性肺炎的疗效和安全性的随机对照试验(RCT)及队列研究。对符合纳入与排除标准的文献进行资料提取和质量评价后,采用RevMan 5.4软件进行Meta分析。结果:共纳入13项临床研究,包括2项RCT和11项队列研究,共计1066例患者。Meta分析结果显示,试验组患者的临床有效率[OR=1.53,95%CI(1.17,2.00),P=0.002]、微生物清除率[OR=1.46,95%CI(1.11,1.91),P=0.007]均显著高于对照组,差异均有统计学意义;两组患者的全因死亡率[OR=0.88,95%CI(0.68,1.14),P=0.32]、肾功能损害发生率[OR=1.04,95%CI(0.72,1.49),P=0.85]比较,差异均无统计学意义。结论:基于现有临床证据,雾化吸入多黏菌素联合常规治疗能显著提高呼吸机相关性肺炎患者的临床有效率和微生物清除率。但本结论尚需要更多设计严格、长期随访的大样本RCT加以证实。
基金This study was funded by the National Natural Science Foundation of China(Grants No.61575003)the China Postdoctoral Science Foundation(Grants Nos.2015M580096 and 2017T100074).
文摘Real-time terahertz(THz)imaging offers remarkable application possibilities,especially in the security and medical fields.However,most THz detectors work with scanners,and a long image acquisition time is required.Some thermal detectors can achieve realtime imaging by using a focal plane array but have the drawbacks of low sensitivity due to a lack of suitable absorbing materials.In this study,we propose a novel photomechanical meta-molecule array by conveniently assembling THz meta-atom absorbers and bi-material cantilevers together,which can couple THz radiation to a mechanical deflection of the meta-molecules with high efficiency.By optically reading out the mechanical deflections of all of the meta-molecules simultaneously,real-time THz imaging can be achieved.A polyimide sacrificial layer technique was developed to fabricate the device on a glass wafer,which facilitates the transmission of a readout light while the THz wave radiates onto the meta-molecule array directly from the front side.THz images and video of various objects as well as infrared images of the human body were captured successfully with the fabricated metamolecule array.The proposed photomechanical device holds promise in applications in single and broadband THz as well as infrared imaging.
