Resonance effects caused by the photon-electron interaction are a focus of attention in semiconductor optoelectronics,as they are able to increase the efficiency of emission.GaN-on-silicon microdisks can provide a per...Resonance effects caused by the photon-electron interaction are a focus of attention in semiconductor optoelectronics,as they are able to increase the efficiency of emission.GaN-on-silicon microdisks can provide a perfect cavity structure for such resonance to occur.Here we report GaN-based microdisks with different diameters,based on a standard blue LED wafer on a Si substrate.A confocal photoluminescence spectroscopy is performed to analyze the properties of all microdisks.Then,we systematically study the effects of radial modes and axial modes of these microdisks on photon-electron coupling efficiency by using three-dimensional finite-difference time-domain simulations.For thick microdisks,photon-electron coupling efficiency is found to greatly depend on the distributions of both the radial modes and the axial modes,and the inclined sidewalls make significant influences on the axial mode distributions.These results are important for realization of high-efficiency resonant emission in GaN-based microcavity devices.展开更多
Aim: Electron, photon or proton beams are used in radiotherapy for cancer treatment while each one may be used depending on depth and the location of tumor and normal tissues around the treatment target as well as eco...Aim: Electron, photon or proton beams are used in radiotherapy for cancer treatment while each one may be used depending on depth and the location of tumor and normal tissues around the treatment target as well as economic issues. Materials and Methods: In this research, dose distribution by proton was measured by film dosimetry in nasal cavity Plexiglas phantom and Monte Carlo simulation. Then the DVH of treatment target and the posterior of treatment target of different beams were compared. The energies of electron, photon and proton were 9 MeV, 6 MV, and maximum 65 MeV, respectively. Due to a depth of 3.5 cm of CTV (Clinical Target Volume), Modulation Range was between 0 - 3.5 cm and SOBP (Spread-out Bragg Peak) was between 0 - 65 MeV. Results: Comparing the obtained DVH values, 95% dose coverage of target volume for electron, photon, proton and Photon-Electron beams were 88%, 98%, 98%, and 95%, respectively. However, doses above 40% that reached outside the target were 50%, 82%, 5%, and 44%, respectively. Conclusions: The results demonstrate the superiority of proton therapy in nasal cancer due to its better target volume coverage and the less amount of the dose reaching outside the target that is because of dose discharge in a small area and significant dose fall-off after Bragg peak.展开更多
The new phenomena induced by femtosecond lasers lead to the new area of ultrafast science.It is a significantchallenge to explain the phenomena associated with complex non-equilibrium and non-linear processes.Although...The new phenomena induced by femtosecond lasers lead to the new area of ultrafast science.It is a significantchallenge to explain the phenomena associated with complex non-equilibrium and non-linear processes.Althoughthere is a growing body of experimental observation,a comprehensive model remains undeveloped.We reviewthe challenges in understanding the photon absorption stage mainly for the femtosecond ablation of wide bandgap materialsat the intensities of 10^(13)～10^(14) W/cm^2.Major opinions and challenges in ionization mechanisms are presentedby primarily considering multiphoton ionization and avalanche ionization.展开更多
奥氏体不锈钢是不锈钢中产量和用量最大的一种,在石化、核电、食品等众多领域发挥着重要作用,但较低的屈服强度限制了其进一步应用。近年来,高强奥氏体不锈钢的研发已成为不锈钢领域研究热点之一。通过真空冶炼、低温轧制、退火和时效...奥氏体不锈钢是不锈钢中产量和用量最大的一种,在石化、核电、食品等众多领域发挥着重要作用,但较低的屈服强度限制了其进一步应用。近年来,高强奥氏体不锈钢的研发已成为不锈钢领域研究热点之一。通过真空冶炼、低温轧制、退火和时效热处理等工艺制备了屈服强度为676 MPa、抗拉强度为1011 MPa且塑性良好(断后伸长率大于50%)的新型高强高塑性奥氏体不锈钢。时效处理能提高钢的强度,但对耐蚀性的影响及其机理目前尚不明晰。为此,利用SEM(scanning electron microscope)/EBSD(electron back scatter diffraction)、XRD(X-ray diffraction)、XPS(X-ray photoelectron spectroscopy)、TEM(transmission electron microscope)、电化学等方法研究了550℃时效处理对新型奥氏体不锈钢点蚀性能的影响,并探讨了影响机理。结果表明,时效试样的点蚀电位(E_(p))低于未时效试样的,并且随着时效时间的延长,E_(p)逐渐降低,极化电阻(R_(p))逐渐减小,耐点蚀性能缓慢下降;但E_(p)最小也在0.15 V以上,且时效处理对自腐蚀电位和自腐蚀电流密度的影响不明显。此外,时效处理使试样钝化膜中的Cr_(2)O_(3)相对含量低,而NiO、MoO_(3)的相对含量变化不大。这主要是因为,时效处理过程中试样中Cr_(23)C_(6)和NbN等析出相的析出和长大造成了样品中Cr、N元素分布的局部不均匀而导致微区电化学的不均匀,从而使试样的点蚀电位降低以及再钝化能力减弱,而时效处理对影响试样点蚀性能的平均晶粒尺寸、基体相组成等因素无影响。这为开发综合性能更加优异的先进奥氏体不锈钢提供了可能的途径。展开更多
有机-无机杂化钙钛矿太阳能电池(perovskite solar cell, PSC)具有光电转换效率潜力高、成本低、可叠层、可柔性四大核心优势,已成为当前光伏领域的研究热点。经过十余年发展,其认证光电转换效率已达27.0%。围绕有机-无机杂化钙钛矿太...有机-无机杂化钙钛矿太阳能电池(perovskite solar cell, PSC)具有光电转换效率潜力高、成本低、可叠层、可柔性四大核心优势,已成为当前光伏领域的研究热点。经过十余年发展,其认证光电转换效率已达27.0%。围绕有机-无机杂化钙钛矿太阳能电池的大面积制备工艺、柔性钙钛矿电池、钙钛矿/晶硅叠层电池的研究进展,以及有机-无机钙钛矿太阳能电池的稳定性提升策略展开讨论,旨在为有机-无机杂化钙钛矿太阳能电池的产业化发展提供有益的参考。展开更多
基金the National Key R&D Program of China(Grant Nos.2016YFB0400102 and 2016YFB0400602)the National Natural Science Foundation of China(Grant Nos.61674076,61422401 and 51461135002)+2 种基金the Collaborative Innovation Center of Solid State Lighting and Energy-Saving Electronics,Open Fund of the State Key Laboratory on Integrated Optoelectronics(Grant No.IOSKL2017KF03)the Natural Science Foundation for Young Scientists of Jiangsu Province of China(Grant No.BK20160376)the Research Funds from NJU-Yangzhou Institute of Opto-electronics,and the Research and Development Funds from State Grid Shandong Electric Power Company and Electric Power Research Institute.
文摘Resonance effects caused by the photon-electron interaction are a focus of attention in semiconductor optoelectronics,as they are able to increase the efficiency of emission.GaN-on-silicon microdisks can provide a perfect cavity structure for such resonance to occur.Here we report GaN-based microdisks with different diameters,based on a standard blue LED wafer on a Si substrate.A confocal photoluminescence spectroscopy is performed to analyze the properties of all microdisks.Then,we systematically study the effects of radial modes and axial modes of these microdisks on photon-electron coupling efficiency by using three-dimensional finite-difference time-domain simulations.For thick microdisks,photon-electron coupling efficiency is found to greatly depend on the distributions of both the radial modes and the axial modes,and the inclined sidewalls make significant influences on the axial mode distributions.These results are important for realization of high-efficiency resonant emission in GaN-based microcavity devices.
文摘Aim: Electron, photon or proton beams are used in radiotherapy for cancer treatment while each one may be used depending on depth and the location of tumor and normal tissues around the treatment target as well as economic issues. Materials and Methods: In this research, dose distribution by proton was measured by film dosimetry in nasal cavity Plexiglas phantom and Monte Carlo simulation. Then the DVH of treatment target and the posterior of treatment target of different beams were compared. The energies of electron, photon and proton were 9 MeV, 6 MV, and maximum 65 MeV, respectively. Due to a depth of 3.5 cm of CTV (Clinical Target Volume), Modulation Range was between 0 - 3.5 cm and SOBP (Spread-out Bragg Peak) was between 0 - 65 MeV. Results: Comparing the obtained DVH values, 95% dose coverage of target volume for electron, photon, proton and Photon-Electron beams were 88%, 98%, 98%, and 95%, respectively. However, doses above 40% that reached outside the target were 50%, 82%, 5%, and 44%, respectively. Conclusions: The results demonstrate the superiority of proton therapy in nasal cancer due to its better target volume coverage and the less amount of the dose reaching outside the target that is because of dose discharge in a small area and significant dose fall-off after Bragg peak.
基金supported by the National Natural Science Foundation of China(50705009)the 111 project China(B08043)+3 种基金the National“863”project of China(2008AA03Z301)the Changjiang Scholar Program of Chinathe Air Force Research Laboratory USA(FA8650-04-C-5704)the National Science Foundation USA(0423233)
文摘The new phenomena induced by femtosecond lasers lead to the new area of ultrafast science.It is a significantchallenge to explain the phenomena associated with complex non-equilibrium and non-linear processes.Althoughthere is a growing body of experimental observation,a comprehensive model remains undeveloped.We reviewthe challenges in understanding the photon absorption stage mainly for the femtosecond ablation of wide bandgap materialsat the intensities of 10^(13)～10^(14) W/cm^2.Major opinions and challenges in ionization mechanisms are presentedby primarily considering multiphoton ionization and avalanche ionization.
文摘奥氏体不锈钢是不锈钢中产量和用量最大的一种,在石化、核电、食品等众多领域发挥着重要作用,但较低的屈服强度限制了其进一步应用。近年来,高强奥氏体不锈钢的研发已成为不锈钢领域研究热点之一。通过真空冶炼、低温轧制、退火和时效热处理等工艺制备了屈服强度为676 MPa、抗拉强度为1011 MPa且塑性良好(断后伸长率大于50%)的新型高强高塑性奥氏体不锈钢。时效处理能提高钢的强度,但对耐蚀性的影响及其机理目前尚不明晰。为此,利用SEM(scanning electron microscope)/EBSD(electron back scatter diffraction)、XRD(X-ray diffraction)、XPS(X-ray photoelectron spectroscopy)、TEM(transmission electron microscope)、电化学等方法研究了550℃时效处理对新型奥氏体不锈钢点蚀性能的影响,并探讨了影响机理。结果表明,时效试样的点蚀电位(E_(p))低于未时效试样的,并且随着时效时间的延长,E_(p)逐渐降低,极化电阻(R_(p))逐渐减小,耐点蚀性能缓慢下降;但E_(p)最小也在0.15 V以上,且时效处理对自腐蚀电位和自腐蚀电流密度的影响不明显。此外,时效处理使试样钝化膜中的Cr_(2)O_(3)相对含量低,而NiO、MoO_(3)的相对含量变化不大。这主要是因为,时效处理过程中试样中Cr_(23)C_(6)和NbN等析出相的析出和长大造成了样品中Cr、N元素分布的局部不均匀而导致微区电化学的不均匀,从而使试样的点蚀电位降低以及再钝化能力减弱,而时效处理对影响试样点蚀性能的平均晶粒尺寸、基体相组成等因素无影响。这为开发综合性能更加优异的先进奥氏体不锈钢提供了可能的途径。
文摘有机-无机杂化钙钛矿太阳能电池(perovskite solar cell, PSC)具有光电转换效率潜力高、成本低、可叠层、可柔性四大核心优势,已成为当前光伏领域的研究热点。经过十余年发展,其认证光电转换效率已达27.0%。围绕有机-无机杂化钙钛矿太阳能电池的大面积制备工艺、柔性钙钛矿电池、钙钛矿/晶硅叠层电池的研究进展,以及有机-无机钙钛矿太阳能电池的稳定性提升策略展开讨论,旨在为有机-无机杂化钙钛矿太阳能电池的产业化发展提供有益的参考。
