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1.
界面摩擦过程非连续能量耗散机理研究   总被引:3,自引:0,他引:3       下载免费PDF全文
龚中良  黄平 《物理学报》2008,57(4):2358-2362
结合无磨损界面摩擦微观能量耗散机理的复合振子模型,运用量子理论建立了微观能量耗散的量子力学模型.分析表明:在滑动过程中,当界面原子从一种平衡态跳跃至另一种平衡态时,摩擦功以离散形式耗散为界面原子热振子,且界面吸收能量的能力是离散的;高能态界面较低能态界面吸收能量的能力强,表现为易于吸收界面势能.界面原子吸收和释放能量的离散性在宏观上表现为摩擦功耗散的非连续性,为从微观角度解释无磨损界面摩擦状态周期性变化提供了理论基础. 关键词: 摩擦 非连续能量耗散 复合振子模型  相似文献   

2.
 建立了荧光再吸收的蒙特卡罗计算模型,对不同尺寸的Yb3+:ZBLANP玻璃材料的荧光再吸收作用进行了数值计算,给出了由于再吸收作用引起的荧光平均波长红移与界面反射和材料尺寸的关系。对于立方体形状,当材料尺寸较小时由界面全反射引起的荧光平均波长红移量占主要部分;随着尺寸的变大,界面全反射的影响相对变小;材料尺寸在0.1~1.0 cm时,由于荧光再吸收作用导致的荧光平均波长红移量在2.6~5.0 nm范围内。随激发光波长的变化绝对制冷效率和单位长度的制冷功率均存在极大值,荧光平均波长红移使制冷效率明显下降,通过减小材料尺寸、改变材料形状等措施可减小荧光再吸收作用对激光冷却固体的不利的影响。  相似文献   

3.
A1/GaAs界面微结构的慢正电子束研究   总被引:1,自引:0,他引:1  
基于正电子扩散方程,对于线形全吸收型等特殊的界面模型,求得了正电子湮没辐射多普勒展宽S参数与单能慢正电子入射能量E之间函数关系S(E)的解析表达式.测量不同膜厚、不同退火条件下A1/GaAs的S(E),用所得解析式拟合实验数据,发现A1/GaAs界面系统与线形全吸收型界面模型符合得很好.通过拟合,得出了界面S参数S1及其与膜厚和退火温度的关系,由此对界面微结构及其动力学特性作了讨论.  相似文献   

4.
光学薄膜吸收损耗的研究   总被引:1,自引:1,他引:0  
用横向光热偏转技术研究光学薄膜的吸收损耗.结果表明:对ZrO_2、MgF_2、ZnS等单层膜,薄膜-基底界面吸收、空气-薄膜界面吸收以及薄膜体内吸收三者处于同一量级,而对TiO_2、Ta_2O_5、SiO_2等样品,薄膜-基底界面吸收远大于空气-薄膜界面吸收及薄膜体内吸收,是吸收损耗的主要来源.  相似文献   

5.
吸收对垂直腔面发射激光器光学特性的影响   总被引:2,自引:2,他引:0  
采用光学传输矩阵方法,详细分析了反射镜以及键合界面的吸收对垂直腔面发射激光器光学特性的影响. 结果表明,反射镜以及键合界面的吸收对反射镜和垂直腔面发射激光器的反射率和势透射率有较大影响,而对反射镜中心波长处的反射相移以及垂直腔面发射激光器模式的反射相移和模式位置影响很小. 随着反射镜以及键合界面的吸收增大,反射镜中心波长处的反射率逐渐减小,垂直腔面发射激光器的模式反射率变化则是先急剧减小,达到一个极小值,然后再逐渐增大,而反射镜中心波长处以及垂直腔面发射激光器模式处的势透射率则都是迅速降低的. 此外,将有吸收的键合界面离有源区的距离远一些,有利于提高垂直腔面发射激光器模式处的光输出效率.  相似文献   

6.
两种反射膜系的激光热力损伤特性   总被引:1,自引:0,他引:1       下载免费PDF全文
陈发良  胡鹏 《强激光与粒子束》2005,17(11):1610-1616
 在驻波场理论基础上,用表面和界面强吸收理论模型,计算出了激光辐照下两种不同反射膜系中温度场的“多峰”分布特性,分析了激光对薄膜的热力损伤特性、主要破坏模式和阈值条件。结果表明,光学薄膜对激光能量的吸收,主要由驻波场分布及膜层的消光系数决定;膜系表面的杂质吸附层和界面吸收层是膜系的主要能量沉积区,从而在这些界面形成温度场的“多峰”分布,界面因此成为最容易受激光损伤的部分。导致光学薄膜激光损伤的主要模式为膜层熔融和脱落两种。如果膜层中含有杂质,则容易诱导杂质处膜层剥落破坏。  相似文献   

7.
通过时间分辨光谱技术详细地研究了ZnCuInS/ZnSe/ZnS量子点的激子弛豫动力学. 基于速率分布模型,波长依赖的发射动力学表明本征激子、界面缺陷态中的激子、给-受体对态中的激子都会参与量子点的发光过程,整个发光过程主要依赖于给-受体对态发射. 瞬态吸收数据表明激发后本征激子和界面缺陷物种可能会同时出现,在高激发光强下,光强依赖的俄歇复合过程也存在于量子点中  相似文献   

8.
探讨探地雷达正演模拟中,应用广义完全匹配层(GPML)吸收边界条件时的模拟效果.利用时域有限差分(FDTD)法将麦克斯韦方程离散化,再采用Mur超吸收边界条件和GPML吸收边界条件吸收向外的电磁波,模拟充水岩溶的雷达图像;同时,采用GPML吸收边界条件模拟多个圆柱体异常模型和倾斜界面异常模型的探地雷达剖面图像.对模拟结果的分析可知,GPML吸收边界条件可有效地吸收向外的电磁波,其吸收效果优于Mur超吸收边界条件,在探地雷达的应用中可推广应用.  相似文献   

9.
通过溶胶反应在乙醇溶液中合成了60nm的SiO2纳米粒子,将其与聚乙烯咔唑(PVK)共混,得到了不同质量分数的PVK/SiO2复合体系,利用荧光光谱,吸收光谱,研究了PVK/SiO2复合体系的荧光效应,光致发光的研究表明在PVK与SiO2纳米粒子之间存在界面能量传递过程,这种能量传递的必要条件是PVK的发射谱与SiO2纳米粒子的吸收谱有重叠,以上研究表明PVK/SiO2复合体系存在较强的界面效应,是研究有机与无机纳米体系界面效应的良好模型。  相似文献   

10.
研究了12.5 μm长波HgCdTe探测器的吸收层厚度和异质结界面电荷对器件光响应率的影响.分析了吸收层厚度与吸收长度、扩散长度之间的联系,获得了设计最佳吸收层厚度的经验公式.研究结果显示入射光波长超过截止波长时,响应率随吸收层厚度增加单调增加,并逐渐饱和.响应率峰值对应的波长随吸收层厚度增加,有向长波偏移的趋势.最佳吸收层厚度值随少子寿命或入射光波长的增大而增大.同时,研究了衬底、钝化层与HgCdTe材料之间异质界面电荷对光响应率的影响,发现正的界面电荷在衬底异质结界面处形成诱导pn结,对响应率影响显著 关键词: 长波HgCdTe器件 光伏型红外探测器 光响应率 少子寿命  相似文献   

11.
A procedure is given which is to be followed when linking an acoustic finite element model to an absorption model. The procedure ensures both equality of pressure and compatibility of the normal velocity at the interface boundary. It is illustrated and tested by applying it to a one dimensional acoustic absorption system to calculate the absorption coefficient. Good agreement with an exact solution is shown.  相似文献   

12.
A simple model is proposed to take into account secondary X-ray fluorescence and absorption effects near the interface. This model is based on the investigation of the shape change of the first derivative equation that can fit the sigmoidal EDS profile obtained when a high vacuum electron beam passes through the interface of two adjacent materials. The contribution of the photoelectric absorption of primary X-rays (characteristic and Bremsstrahlung) and the secondary fluorescence on the degradation of the X-ray spatial resolution can be easily quantified. The close agreement between the simulated (Monte Carlo simulation using the Casino software) and the experimental data serves to assess the reliability of this developed model.  相似文献   

13.
《Composite Interfaces》2013,20(9):845-861
The stress transfer ability at the fiber–matrix interface of wood fiber composites is known to affect the mechanical properties of the composite. The evaluation of interface properties at the level of individual fibers is however difficult due to the small dimensions and variability of the fibers. The dynamical mechanical properties of composite and constituents, in this case wood fibers and polylactide matrix, was here used together with micromechanical modeling to quantify the stress transfer efficiency at the fiber–matrix interface. To illustrate the methodology, a parameter quantifying the degree of imperfection at the interface was identified by inverse modeling using a micromechanical viscoelastic general self-consistent model with an imperfect interface together with laminate analogy on the composite level. The effect of moisture was assessed by comparison with experimental data from dynamic mechanical analysis in dry and moist state. For the wood fiber reinforced polylactide, the model shows that moisture absorption led to softening and mechanical dissipation in the hydrophilic wood fibers and biothermoplastic matrix, rather than loss of interfacial stress transfer ability.  相似文献   

14.
The indirect laser processing approach (LIBWE) laser-induced backside wet etching allows defined microstructuring of transparent materials at low laser fluences with high quality. The optical and the thermal properties of the solid/liquid interface determine the temperatures and therefore the etching mechanism in conjunction with the dynamic processes at the interface due to the fast heating/cooling rates. The exploration of organic liquid solvents and solutions such as 0.5 M pyrene/toluene results in low etch rates (∼20 nm/pulse). By means of liquid metals as absorber here, demonstrated for gallium (Ga), etch rates up to 600 nm/pulse can be achieved. Regardless of the high etch rates a still smooth surface similar to etching with organic liquid solutions can be observed. A comparative study of the two kinds of absorbing liquids, organic and metallic, investigates the etch rates regarding the fluence and pulse quantity. Thereby, the effect of incubation processes as result of surface modification on the etching is discussed. In contrast to pyrene/toluene solution the metallic absorber cannot decompose and consequently no decomposition products can alter the solid/liquid interface to enhance the absorption for the laser radiation. Hence, incubation can be neglected in the case of the silica/gallium interface so that this system is a suitable model to investigate the primary processes of LIBWE. To prove the proposed thermal etch mechanism an analytical temperature model based on a solution of the heat equation is derived for laser absorption at the silica/gallium interface.  相似文献   

15.
A mathematical model for analyzing laser beam transmission and focusing inside media is developed. The reflection and refraction on the interface between two different media and the absorption inside media are considered. Based on the mathematical model a computer program, which allows us to analyze the focusing and transmission processes of laser beam as well as to obtain the beam parameters and intensity profile inside media, is created.  相似文献   

16.
Spectroscopic measurements in the UV/VIS region show reduced transmission through laser-induced backside wet etching (LIBWE) of fused silica. Absorption coefficients of up to 105 cm−1 were calculated from the transmission measurements for a solid surface layer of about 50 nm. The temperatures near the interface caused by laser pulse absorption, which were analytically calculated using a new thermal model considering interface and liquid volume absorption, can reach 104 K at typical laser fluences. The high absorption coefficients and the extreme temperatures give evidence for an ablation-like process that is involved in the LIBWE process causing the etching of the modified near-surface region. The confinement of the ablation/etching process to the modified near-surface material region can account for the low etch rates observed in comparison to front-side ablation.  相似文献   

17.
单层膜体吸收与界面吸收研究   总被引:2,自引:0,他引:2       下载免费PDF全文
采用热透镜测量方法进行了SiO2和HfO2单层膜的体吸收与界面吸收分离研究.首先推导了光从薄膜侧及基底侧入射时单层膜内的驻波场分布,给出了单一厚度薄膜分离体吸收和界面吸收的计算方程式以及求解薄膜消光系数的方法.利用电子束蒸发工艺制备了半波长光学厚度(λ=1064 nm)的SiO2和HfO2单层膜,通过热透镜的测量数据实际分离了两种薄膜的体吸收和界面总吸收.计算结果表明,对于吸收小至10-6关键词: 驻波场理论 光热技术 薄膜吸收 消光系数  相似文献   

18.
含三聚氰胺多孔材料分层复合介质吸声特性*   总被引:1,自引:1,他引:0       下载免费PDF全文
白聪  沈敏 《应用声学》2019,38(1):76-84
三聚氰胺泡沫材料是一种具有高开孔率的多孔材料,具备优良的吸音、防火隔热及环保性能,可以作为吸声材料与弹性板、空腔介质形成复合结构,在建筑、航空、交通工具等工程领域有广泛的应用。该文基于Biot理论和分层介质在交界面处的不同边界条件,建立非均匀复合介质背衬刚性壁面结构的理论声学模型,详细分析了多孔材料布局对复合结构吸声特性的影响。该文理论模型计算的结果与阻抗实验得到的垂直入射吸声系数基本一致,验证了理论模型的正确性。结果表明:在多孔材料前面增加空气层可以改善高频吸声特性;在多孔材料后面增加空气层可以改善复合结构低频吸声特性。通过合理配置多孔材料,可以在应用需求频段上达到满意的吸声效果。  相似文献   

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