Arising from the proposed Transmission Line(TL) model for ERR and wire structure, a TL model for a metamaterial absorber is proposed. The S-parameters obtained by this TL model demonstrate the same shapes as the simul...Arising from the proposed Transmission Line(TL) model for ERR and wire structure, a TL model for a metamaterial absorber is proposed. The S-parameters obtained by this TL model demonstrate the same shapes as the simulation. An investigation of the TL model and average absorption power densities shows that the metamaterial absorber does not simply convert the electromagnetic wave into thermal energy, but concentrate the electromagnetic wave into a small space where it is finally absorbed. This suggests that the metamaterial absorber can be applied to solar cells for the purpose of light trapping.展开更多
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 ...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.展开更多
In recent years, a great deal of effort has been made to a create terahertz （THz） wave absorber based on metamaterials （MM）. Metamaterials absorbers have a variety of potential applications including thermal emitt...In recent years, a great deal of effort has been made to a create terahertz （THz） wave absorber based on metamaterials （MM）. Metamaterials absorbers have a variety of potential applications including thermal emitters, detector, stealth technology, phase imaging, etc. In this paper, we firstly introduce the basic structure and work principle of the THz MM absorbers, and a transmission line model is developed for devices analysis. To expand the application of THz absorbers, dual-band and broadband THz MM absorbers are designed, fabricated, and measured. At the end of this article, the future development trends of MM absorbers are discussed.展开更多
Acoustic measurements or ultrasonic testing can be strongly affected by reflections or echoes from test tank walls. In order to create a non-reflecting environment equivalent to infinite medium, a pyramidal structured...Acoustic measurements or ultrasonic testing can be strongly affected by reflections or echoes from test tank walls. In order to create a non-reflecting environment equivalent to infinite medium, a pyramidal structured absorber (PSA) can be used to coat the walls of an ultrasonic tank. In this work, we model an array of tetragonal pyramid ultrasonic wave absorbers. This model is based on two coupled first-order equations describing the stress and particle velocity within an isotropic medium. For absorbing media, the Kelvin-Voigt model of viscoelasticity is used. The equations are discretized in 2D using an efficient time-stepping pseudo-spectral scheme that takes in consideration both, the acoustic properties and attenuation characteristics of the composite materials. We then built a 3D printed PSA using a Stratasys Objet500 Connex 3D printer, which allows to combine photopolymers in specific concentrations and microstructures. We designed PSA covering the frequency ranges from 0.5 MHz to 5 MHz and from 1 MHz to 10 MHz, with double homogeneous layer: a core of rubber material with a skin of a variety of elastomers by combining rigid and flexible materials. Each single pyramid contains two major parts: the ground of the pyramid (9.4 mm base × 4.7 mm height, for 0.5 MHz and 4.7 mm base × 2.35 mm height, for 1 MHz) and the body of the pyramid (23.5 mm height, for 0.5 MHZ and 11.75 mm height, for 1 MHz). The measured echo-reduction was greater than 35 dB at the covering frequency range and the transmission loss was estimated by 20 dB. Echoes increase rapidly for frequencies below the minimum frequency of the covering range. The modeling and 3D printing of PSA with different sizes, in a wide range of frequencies, is a cost-effective custom solution for a wide range of applications including for example, radiation force balances, hydrophone mounts and medical ultrasound equipment.展开更多
In this paper we propose an optimal design of ultra-wideband (4 ~ 20 GHz) microwave absorbers consisting of two resistive meta-surface layers of different square patch arrays. Gradient Descent and Genetic Algorithm nu...In this paper we propose an optimal design of ultra-wideband (4 ~ 20 GHz) microwave absorbers consisting of two resistive meta-surface layers of different square patch arrays. Gradient Descent and Genetic Algorithm numerical methods are employed to optimize all the parameters through equivalent transmission line circuit model. The circuit parameters are then implemented by a multilayer including two resistive meta-surfaces of square patch structures. Two types of such absorbing structures, with the total thicknesses close to that of the known theoretical limit, are designed and their performance are verified by full wave electromagnetic simulation.展开更多
目的 探析联合治疗(1064nm/1320nm复合激光溶脂技术+可吸收线雕)对下面部轻度脂肪堆积伴皮肤松弛(cutis laxa,CL)患者的临床效果。方法:回顾性分析本院2021年7月-2023年7月收治的94例下面部脂肪堆积伴CL患者,根据治疗策略差异分为对照组...目的 探析联合治疗(1064nm/1320nm复合激光溶脂技术+可吸收线雕)对下面部轻度脂肪堆积伴皮肤松弛(cutis laxa,CL)患者的临床效果。方法:回顾性分析本院2021年7月-2023年7月收治的94例下面部脂肪堆积伴CL患者,根据治疗策略差异分为对照组(单一可吸收线雕,n=40例)、观察组(1064nm/1320nm复合激光溶脂技术+可吸收线雕,n=54例)。对比两组术后1月、6月患者主观满意度、观察者总体美容改善评分(improvement based on global aesthetic improvement scale,IGAIS)、术后1月不良反应率。结果:观察组术后1月、6月患者满意度评价(94.44%、87.04%)均高于对照组(72.50%、65.00%),差异有统计学意义(P<0.05)。术后1月、6月观察组IGAIS评分均高于对照组,差异有统计学意义(P<0.05)。两组患者均未发生神经损伤、感染、血肿、皮下出血等严重并发症,术后7d患者术区基本消肿。两组术后不良反应发生率(9.26%、7.50%)对比,差异无统计学意义(P> 0.05)。结论:联合治疗(1064nm/1320nm复合激光溶脂技术+可吸收线雕)应用于下面部脂肪堆积伴CL患者中改善效果显著,可有效提高患者满意度,且不良反应发生率较低,值得临床推广。展开更多
基金supported by Major State Basic Research Development Program of China （973 Program ） （No. 2007CB310407） the National Natural Science Foundation of China （No. 60721001 and No. 60801023 ）.
文摘Arising from the proposed Transmission Line(TL) model for ERR and wire structure, a TL model for a metamaterial absorber is proposed. The S-parameters obtained by this TL model demonstrate the same shapes as the simulation. An investigation of the TL model and average absorption power densities shows that the metamaterial absorber does not simply convert the electromagnetic wave into thermal energy, but concentrate the electromagnetic wave into a small space where it is finally absorbed. This suggests that the metamaterial absorber can be applied to solar cells for the purpose of light trapping.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574122 and 51731001)the Fundamental Research Funds for the Central Universities,China(Grant No.kzujbky-2017-k20)the Innovation Special Zone of National Defence Science and Technology,China
文摘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.
基金supported by the National Natural Science Foundation of China under Grant No.61131005Keygrant Project of Chinese Ministry of Education under Grant No.313013+4 种基金National High Technology Research and Development Program of China(863)under Grant No.2011AA010204the New Century Excellent Talent Foundation under Grant No.NCET-11-0068Sichuan Youth S&T Foundation under Grant No.2011JQ0001Specialized Research Fund for the Doctoral Program of Higher Education under Grant No.20110185130002the CAEP THz Science and Technology Foundation under Grant No.CAEPTHZ201207
文摘In recent years, a great deal of effort has been made to a create terahertz （THz） wave absorber based on metamaterials （MM）. Metamaterials absorbers have a variety of potential applications including thermal emitters, detector, stealth technology, phase imaging, etc. In this paper, we firstly introduce the basic structure and work principle of the THz MM absorbers, and a transmission line model is developed for devices analysis. To expand the application of THz absorbers, dual-band and broadband THz MM absorbers are designed, fabricated, and measured. At the end of this article, the future development trends of MM absorbers are discussed.
文摘Acoustic measurements or ultrasonic testing can be strongly affected by reflections or echoes from test tank walls. In order to create a non-reflecting environment equivalent to infinite medium, a pyramidal structured absorber (PSA) can be used to coat the walls of an ultrasonic tank. In this work, we model an array of tetragonal pyramid ultrasonic wave absorbers. This model is based on two coupled first-order equations describing the stress and particle velocity within an isotropic medium. For absorbing media, the Kelvin-Voigt model of viscoelasticity is used. The equations are discretized in 2D using an efficient time-stepping pseudo-spectral scheme that takes in consideration both, the acoustic properties and attenuation characteristics of the composite materials. We then built a 3D printed PSA using a Stratasys Objet500 Connex 3D printer, which allows to combine photopolymers in specific concentrations and microstructures. We designed PSA covering the frequency ranges from 0.5 MHz to 5 MHz and from 1 MHz to 10 MHz, with double homogeneous layer: a core of rubber material with a skin of a variety of elastomers by combining rigid and flexible materials. Each single pyramid contains two major parts: the ground of the pyramid (9.4 mm base × 4.7 mm height, for 0.5 MHz and 4.7 mm base × 2.35 mm height, for 1 MHz) and the body of the pyramid (23.5 mm height, for 0.5 MHZ and 11.75 mm height, for 1 MHz). The measured echo-reduction was greater than 35 dB at the covering frequency range and the transmission loss was estimated by 20 dB. Echoes increase rapidly for frequencies below the minimum frequency of the covering range. The modeling and 3D printing of PSA with different sizes, in a wide range of frequencies, is a cost-effective custom solution for a wide range of applications including for example, radiation force balances, hydrophone mounts and medical ultrasound equipment.
文摘In this paper we propose an optimal design of ultra-wideband (4 ~ 20 GHz) microwave absorbers consisting of two resistive meta-surface layers of different square patch arrays. Gradient Descent and Genetic Algorithm numerical methods are employed to optimize all the parameters through equivalent transmission line circuit model. The circuit parameters are then implemented by a multilayer including two resistive meta-surfaces of square patch structures. Two types of such absorbing structures, with the total thicknesses close to that of the known theoretical limit, are designed and their performance are verified by full wave electromagnetic simulation.
文摘目的 探析联合治疗(1064nm/1320nm复合激光溶脂技术+可吸收线雕)对下面部轻度脂肪堆积伴皮肤松弛(cutis laxa,CL)患者的临床效果。方法:回顾性分析本院2021年7月-2023年7月收治的94例下面部脂肪堆积伴CL患者,根据治疗策略差异分为对照组(单一可吸收线雕,n=40例)、观察组(1064nm/1320nm复合激光溶脂技术+可吸收线雕,n=54例)。对比两组术后1月、6月患者主观满意度、观察者总体美容改善评分(improvement based on global aesthetic improvement scale,IGAIS)、术后1月不良反应率。结果:观察组术后1月、6月患者满意度评价(94.44%、87.04%)均高于对照组(72.50%、65.00%),差异有统计学意义(P<0.05)。术后1月、6月观察组IGAIS评分均高于对照组,差异有统计学意义(P<0.05)。两组患者均未发生神经损伤、感染、血肿、皮下出血等严重并发症,术后7d患者术区基本消肿。两组术后不良反应发生率(9.26%、7.50%)对比,差异无统计学意义(P> 0.05)。结论:联合治疗(1064nm/1320nm复合激光溶脂技术+可吸收线雕)应用于下面部脂肪堆积伴CL患者中改善效果显著,可有效提高患者满意度,且不良反应发生率较低,值得临床推广。
