Based on the transmission line code TLCODE, a 1D circuit model for a transmission- line impedance transformer was developed and the simulation results were compared with those in the literature. The model was used to ...Based on the transmission line code TLCODE, a 1D circuit model for a transmission- line impedance transformer was developed and the simulation results were compared with those in the literature. The model was used to quantify the efficiencies of voltage-transport, energy- transport and power-transport for a transmission-line impedance transformer as functions of ψ （the ratio of the output impedance to the input impedance of the transformer） and Г （the ratio of the pulse width to the one-way transit time of the transformer） under a large scale of m （the coefficient of the generalized exponential impedance profile）. Simulation results suggest that with the increase in Г, from 0 to ∞, the power transport efficiency first increases and then decreases. The maximum power transport efficiency can reach 90% or even higher for an exponential impedance profile （m = 1）. With a consideration of dissipative loss in the dielectric and electrodes of the transformer, two representative designs of the water-insulated transformer are investigated for the next generation of petawatt-class z-pinch drivers. It is found that the dissipative losses in the electrodes are negligibly small, below 0.1%, but the dissipative loss in the water dielectric is about 1% to 4%.展开更多
Completely solving the dissipative dynamics of nonlinear Jaynes-Cumming model is a very difficult task.In our recent work (Phys. Lett. A284 (2001) 156), we just obtained analytical results of the field dissipative dyn...Completely solving the dissipative dynamics of nonlinear Jaynes-Cumming model is a very difficult task.In our recent work (Phys. Lett. A284 (2001) 156), we just obtained analytical results of the field dissipative dynamicsof the nonlinear JCM. In the present paper, employing the perturbative expansion of master equation, we obtain thedensity operator of the system (field +atom). The coherence losses of the system and of the atom are investigated whentwo-photon process is involved. We also study the effect of different atomic initial states and the influence of the fieldamplitude on the atomic coherence loss.展开更多
In this paper,by solving a complex nonlinear Schr6dinger equation,radially symmetric dissipative vortex solitons are obtained analytically and are tested numerically.We find that spatially inhomogeneous nonlinear abso...In this paper,by solving a complex nonlinear Schr6dinger equation,radially symmetric dissipative vortex solitons are obtained analytically and are tested numerically.We find that spatially inhomogeneous nonlinear absorption gives rise to the stability of dissipative vortex solitons in self-defocusing nonlinear medium in the presence of constant linear gain.Numerical simulation reveals the interaction effect among linear gain and nonlinear loss in the azimuthal modulation instabilities of these vortices suppression.Apart from vortex in this media,another noticeable feature of current setup the uniform linear gain indeed affects the stability of is that the steep spatial modulation of the nonlinear absorption can suppress sidelobes effectively and support stable vortex solitons in situations with uniform linear gain.Under appropriate conditions,the vortex solitons can propagate stably and feature no symmetry breaking,although the beams exhibit radical compression and amplification as they propagate.展开更多
电压源换流器型直流输电(voltage source converter based HVDC,VSC-HVDC)应用于大容量功率传输的主要障碍之一是其相对较高的换流器损耗。因而,换流器损耗的准确计算对系统设计、器件参数及冷却装置的选择非常重要。通过分析换流器IGB...电压源换流器型直流输电(voltage source converter based HVDC,VSC-HVDC)应用于大容量功率传输的主要障碍之一是其相对较高的换流器损耗。因而,换流器损耗的准确计算对系统设计、器件参数及冷却装置的选择非常重要。通过分析换流器IGBT器件的开关特性,同时考虑结温、死区效应的影响,提出一种基于曲线拟合理论的通用换流器损耗计算方法。该方法能够有效利用厂家提供的器件特性参数,适合于实际工程应用。在此基础上,分析了正弦脉宽和最小开关PWM两种调制方式下的换流器损耗特性,建立了基于PSCAD/EMTDC的通用的损耗计算模块。展开更多
Background:To compare femtosecond laser-assisted versus conventional phacoemulsification in terms of visual and refractive outcomes,cumulative dissipated energy,anterior chamber inflammation and endothelial cell loss....Background:To compare femtosecond laser-assisted versus conventional phacoemulsification in terms of visual and refractive outcomes,cumulative dissipated energy,anterior chamber inflammation and endothelial cell loss.Methods:In this retrospective cohort study,records of eyes that underwent femtosecond laser-assisted cataract surgery(FLACS)or conventional phacoemulsification(CP)were reviewed.The Victus femtosecond laser(Bausch and Lomb,Germany)was used to carry out corneal incisions,anterior capsulotomy,and lens fragmentation in FLACS procedures.Manifest refraction spherical equivalence(MRSE),uncorrected distance visual acuity(UDVA),corrected distance visual acuity(CDVA),cumulative dissipated energy(CDE),postoperative cells and flare and endothelial cell count data were collected.Subgroup analysis of the visual acuity tests was performed based on the type of intraocular lens implanted(monofocal,monofocal toric,multifocal,multifocal toric,accommodating).Results:A total of 735 eyes were included in the study(296 eyes for the FLACS group and 439 eyes for the CP group).At one year follow-up,120 eyes comprised the FLACS group and 265 eyes for the CP group.MRSE in the FLACS group was−0.16±0.58 D and−0.20±0.52 D in the CP group(P=0.50).UDVA in the FLACS group was 20/25(mean logMAR 0.12±0.13)and 20/25(mean logMAR 0.11±0.13)in the CP group(P=0.48).CDVA was 20/20(mean logMAR 0.03±0.07)in the FLACS group and 20/20(mean logMAR 0.02±0.06)in the CP group(P=0.15).No statistically significant trend was seen for FLACS versus CP by intraocular type for visual acuity.CDE for the different cataract grades ranged from 6.97±5.74 to 29.02±16.07 in the FLACS group and 7.59±6.42 to 35.69±18.30 in the CP group.The FLACS group was significantly lower for post-operative central corneal edema(P=0.05),cells and flare(P=0.01),and endothelial cell loss(P=0.04).Conclusions:Femtosecond laser-assisted cataract surgery and conventional phacoemulsification had similar refractive and visual outcomes.Phacoemulsification energy,anterior ch展开更多
It is a crucial requirement for structure-damping materials to attain both stiffness and damping;unfortunately,the two properties are usually mutually exclusive.This study interestingly demonstrates that introducing N...It is a crucial requirement for structure-damping materials to attain both stiffness and damping;unfortunately,the two properties are usually mutually exclusive.This study interestingly demonstrates that introducing Ni atoms into the interface of carbon nanotube(CNT)reinforced aluminum-matrix composites can defeat the conflict of stiffness versus damping.This originates from the gradient variation of the modulus and energy dissipation in the effective interfacial zone.The rule of mixture is modified by taking the interface contribution into account,and a gradient damping model is proposed to account for the contribution of the interface energy dissipation.Molecular dynamics simulations confirm that the proposed multiscale modulus and damping models can describe the elastic modulus and damping behavior of the composites with different volume fractions and different diameters of CNTS.The gradient interface slip caused by the lattice mismatches and misfit dislocations between Ni-coated CNT and aluminum is one of the pathways for achieving unprecedented levels of the product of stiffness and damping.展开更多
The application of unbonded post-tensioning (PT) in structural walls has led to the development of advanced self-centring (rocking) shear wall systems that has significant advantages, including accelerated constructio...The application of unbonded post-tensioning (PT) in structural walls has led to the development of advanced self-centring (rocking) shear wall systems that has significant advantages, including accelerated construction due to the incorporation of prefabricated elements and segmental construction for different materials (e.g., concrete, masonry, and timber), reduced residual drifts, and little damage upon extreme seismic and wind loads. Concrete, masonry, and timber are often used for the construction of unbonded PT structural wall systems. Despite extensive research since the 1980s, there are no well-established design guidelines available on the shear wall configuration with the required energy dissipation system, joint’s locations and acceptance criteria for shear sliding, confinement, seismic performance factors, PT loss, PT force range and residual drifts of shear walls subjected to lateral loads. In this research a comprehensive state-of-the-art literature review was performed on self-centring shear wall system. An extensive study was carried out to collect a database of 100 concrete, masonry, and self-centring shear wall tests from the literature. The established database was then used to review shear walls’ configurations, material, and components to benchmark requirements applicable for design purposes. The behaviour of concrete, masonry and timber shear walls were compared and critically analysed. The general behaviour, force-displacement performance of the walls, ductility, and seismic response factors, were critically reviewed and analysed for different self-centring wall systems to understand the effect of different parameters including configurations of the walls, material used for construction of the wall (concrete, masonry, timber) and axial stress ratio. The outcome of this research can be used to better understand the behaviour of self-centring wall system in order to develop design guidelines for such walls.展开更多
文摘采用Belov公式计算单元并排式阻性消声器消声量误差较大,为提高计算精度,按以下步骤构建单元并排式消声器消声量计算模型。(1)将消声器划分为角单元、边单元和内部单元等3种基本单元,采用Belov公式计算各基本单元传递损失(Transmission Loss,TL);(2)假设消声器入口端声能均匀分布,根据各基本单元入口端声功率和传递损失计算公式确定其出口端声功率;(3)根据消声器入口端和出口端总声功率得到消声量理论值TLt;(4)将11425 Pa·s/m^(2)作为流阻率基准值,通过有限元仿真得到采用该流阻率多孔吸声材料的消声器消声量仿真值TLs,得到仿真值和理论值的比值K_(1)(即TLs/TLt);(5)通过仿真进一步确定多孔吸声材料流阻率和基准流阻率不同情况下消声器消声量的比值K_(2),拟合获得K_(2)与流阻率σ的关系函数K_(2)(σ);(6)建立单元并排式阻性消声器消声量计算模型TL=TLt·K_(1)·K_(2)(σ)。实测结果表明,根据该模型计算得到的消声器各倍频带传递损失值与实测值绝对误差均小于2 d B,相对误差均小于10%。模型适用于计算采用不同多孔吸声材料、具有不同结构尺寸的单元并排式阻性消声器的消声量。
基金supported by National Natural Science Foundation of China(No.50637010)
文摘Based on the transmission line code TLCODE, a 1D circuit model for a transmission- line impedance transformer was developed and the simulation results were compared with those in the literature. The model was used to quantify the efficiencies of voltage-transport, energy- transport and power-transport for a transmission-line impedance transformer as functions of ψ （the ratio of the output impedance to the input impedance of the transformer） and Г （the ratio of the pulse width to the one-way transit time of the transformer） under a large scale of m （the coefficient of the generalized exponential impedance profile）. Simulation results suggest that with the increase in Г, from 0 to ∞, the power transport efficiency first increases and then decreases. The maximum power transport efficiency can reach 90% or even higher for an exponential impedance profile （m = 1）. With a consideration of dissipative loss in the dielectric and electrodes of the transformer, two representative designs of the water-insulated transformer are investigated for the next generation of petawatt-class z-pinch drivers. It is found that the dissipative losses in the electrodes are negligibly small, below 0.1%, but the dissipative loss in the water dielectric is about 1% to 4%.
基金The project supported by National Natural Science Foundation of China under Grant No.10305002
文摘Completely solving the dissipative dynamics of nonlinear Jaynes-Cumming model is a very difficult task.In our recent work (Phys. Lett. A284 (2001) 156), we just obtained analytical results of the field dissipative dynamicsof the nonlinear JCM. In the present paper, employing the perturbative expansion of master equation, we obtain thedensity operator of the system (field +atom). The coherence losses of the system and of the atom are investigated whentwo-photon process is involved. We also study the effect of different atomic initial states and the influence of the fieldamplitude on the atomic coherence loss.
基金Supported by the National Natural Science Foundation of China under Grant No.11705164the Zhejiang Provincial Natural Science Foundation of China under Grant No.LQ16A040003
文摘In this paper,by solving a complex nonlinear Schr6dinger equation,radially symmetric dissipative vortex solitons are obtained analytically and are tested numerically.We find that spatially inhomogeneous nonlinear absorption gives rise to the stability of dissipative vortex solitons in self-defocusing nonlinear medium in the presence of constant linear gain.Numerical simulation reveals the interaction effect among linear gain and nonlinear loss in the azimuthal modulation instabilities of these vortices suppression.Apart from vortex in this media,another noticeable feature of current setup the uniform linear gain indeed affects the stability of is that the steep spatial modulation of the nonlinear absorption can suppress sidelobes effectively and support stable vortex solitons in situations with uniform linear gain.Under appropriate conditions,the vortex solitons can propagate stably and feature no symmetry breaking,although the beams exhibit radical compression and amplification as they propagate.
文摘电压源换流器型直流输电(voltage source converter based HVDC,VSC-HVDC)应用于大容量功率传输的主要障碍之一是其相对较高的换流器损耗。因而,换流器损耗的准确计算对系统设计、器件参数及冷却装置的选择非常重要。通过分析换流器IGBT器件的开关特性,同时考虑结温、死区效应的影响,提出一种基于曲线拟合理论的通用换流器损耗计算方法。该方法能够有效利用厂家提供的器件特性参数,适合于实际工程应用。在此基础上,分析了正弦脉宽和最小开关PWM两种调制方式下的换流器损耗特性,建立了基于PSCAD/EMTDC的通用的损耗计算模块。
文摘Background:To compare femtosecond laser-assisted versus conventional phacoemulsification in terms of visual and refractive outcomes,cumulative dissipated energy,anterior chamber inflammation and endothelial cell loss.Methods:In this retrospective cohort study,records of eyes that underwent femtosecond laser-assisted cataract surgery(FLACS)or conventional phacoemulsification(CP)were reviewed.The Victus femtosecond laser(Bausch and Lomb,Germany)was used to carry out corneal incisions,anterior capsulotomy,and lens fragmentation in FLACS procedures.Manifest refraction spherical equivalence(MRSE),uncorrected distance visual acuity(UDVA),corrected distance visual acuity(CDVA),cumulative dissipated energy(CDE),postoperative cells and flare and endothelial cell count data were collected.Subgroup analysis of the visual acuity tests was performed based on the type of intraocular lens implanted(monofocal,monofocal toric,multifocal,multifocal toric,accommodating).Results:A total of 735 eyes were included in the study(296 eyes for the FLACS group and 439 eyes for the CP group).At one year follow-up,120 eyes comprised the FLACS group and 265 eyes for the CP group.MRSE in the FLACS group was−0.16±0.58 D and−0.20±0.52 D in the CP group(P=0.50).UDVA in the FLACS group was 20/25(mean logMAR 0.12±0.13)and 20/25(mean logMAR 0.11±0.13)in the CP group(P=0.48).CDVA was 20/20(mean logMAR 0.03±0.07)in the FLACS group and 20/20(mean logMAR 0.02±0.06)in the CP group(P=0.15).No statistically significant trend was seen for FLACS versus CP by intraocular type for visual acuity.CDE for the different cataract grades ranged from 6.97±5.74 to 29.02±16.07 in the FLACS group and 7.59±6.42 to 35.69±18.30 in the CP group.The FLACS group was significantly lower for post-operative central corneal edema(P=0.05),cells and flare(P=0.01),and endothelial cell loss(P=0.04).Conclusions:Femtosecond laser-assisted cataract surgery and conventional phacoemulsification had similar refractive and visual outcomes.Phacoemulsification energy,anterior ch
基金supported by National Natural Science Foundation of China(61304256)Zhejiang Provincial Natural Science Foundation of China(LQ13F030013)+4 种基金Project of the Education Department of Zhejiang Province(Y201327006)Young Researchers Foundation of Zhejiang Provincial Top Key Academic Discipline of Mechanical Engineering and Zhejiang Sci-Tech University Key Laboratory(ZSTUME01B15)New Century 151 Talent Project of Zhejiang Province521 Talent Project of Zhejiang Sci-Tech UniversityYoung and Middle-aged Talents Foundation of Zhejiang Provincial Top Key Academic Discipline of Mechanical Engineering
基金supported by the National Natural Science Foundation of China(Grant Nos.52175095 and 51605172)the Young Top-notch Talent Cultivation Program of Hubei Province of China。
文摘It is a crucial requirement for structure-damping materials to attain both stiffness and damping;unfortunately,the two properties are usually mutually exclusive.This study interestingly demonstrates that introducing Ni atoms into the interface of carbon nanotube(CNT)reinforced aluminum-matrix composites can defeat the conflict of stiffness versus damping.This originates from the gradient variation of the modulus and energy dissipation in the effective interfacial zone.The rule of mixture is modified by taking the interface contribution into account,and a gradient damping model is proposed to account for the contribution of the interface energy dissipation.Molecular dynamics simulations confirm that the proposed multiscale modulus and damping models can describe the elastic modulus and damping behavior of the composites with different volume fractions and different diameters of CNTS.The gradient interface slip caused by the lattice mismatches and misfit dislocations between Ni-coated CNT and aluminum is one of the pathways for achieving unprecedented levels of the product of stiffness and damping.
基金Open Access funding enabled and organized by CAUL and its Member Institutions.
文摘The application of unbonded post-tensioning (PT) in structural walls has led to the development of advanced self-centring (rocking) shear wall systems that has significant advantages, including accelerated construction due to the incorporation of prefabricated elements and segmental construction for different materials (e.g., concrete, masonry, and timber), reduced residual drifts, and little damage upon extreme seismic and wind loads. Concrete, masonry, and timber are often used for the construction of unbonded PT structural wall systems. Despite extensive research since the 1980s, there are no well-established design guidelines available on the shear wall configuration with the required energy dissipation system, joint’s locations and acceptance criteria for shear sliding, confinement, seismic performance factors, PT loss, PT force range and residual drifts of shear walls subjected to lateral loads. In this research a comprehensive state-of-the-art literature review was performed on self-centring shear wall system. An extensive study was carried out to collect a database of 100 concrete, masonry, and self-centring shear wall tests from the literature. The established database was then used to review shear walls’ configurations, material, and components to benchmark requirements applicable for design purposes. The behaviour of concrete, masonry and timber shear walls were compared and critically analysed. The general behaviour, force-displacement performance of the walls, ductility, and seismic response factors, were critically reviewed and analysed for different self-centring wall systems to understand the effect of different parameters including configurations of the walls, material used for construction of the wall (concrete, masonry, timber) and axial stress ratio. The outcome of this research can be used to better understand the behaviour of self-centring wall system in order to develop design guidelines for such walls.
