固体激光器

从Yb:YAG的晶体结构、特性出发系统地介绍了Yb,YAG激光器的运转特性。着重阐述了自吸收效应对调谐输出特性的影响,空间烧孔效应对宽度可调激光脉冲产生的限制,以及Yb:YAG激光器可调谐特性和自     

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研究了矩形永磁体的理论计算方法,深入剖析了PIC-MCC处理算法,在粒子模拟软件平台下研制了全三维PIC-MCC模拟算法,并采用该算法数值研究了J-PARC多峰离子源放电特性,分析了J-PARC离子源电子能量沉积过程和体积产生机制,讨论了该离子源在光学特性和设计思路上的优势。结果显示:该离子源能产生空间均匀的负氢离子离子束,且体积负氢离子产生效率较高。     

基于气流调制的封闭空间高声强次声产生方法研究

基于气流调制技术研究了封闭空间高强度次声产生方法。设计了大流量气流调制器,对调制器和赫尔姆霍兹共振腔组成的高声强次声产生装置的声场特性进行了数值仿真,制作出原理装置,并进行了实验测试。从理论上分析了不同调制频率和不同供气压力下调制器出口的声压幅度,分析了次声产生装置不同调制频率的声压幅度,分析了舱内声场的空间分布特性。实验结果表明:气流调制器设计合理、运行平稳,次声产生装置最大能产生161 dB的次声,测试舱声场均匀、声波信噪比较高,实验结果与数值仿真结果基本一致。      

浅谈感应电流的特性及其应用——兼谈楞次定律的创新教学

 众所周知,质量守恒(物质不灭)定律和能量守恒(能量不灭)定律是自然界中的两条普遍适应的最基本的定律。质量守恒(物质不灭)定律在化学问题的研究中得到普遍应用,能量守恒(能量不灭)定律则在物理问题中得到普遍应用。一、感应电流的特性笔者在高中物理电磁感应一章的教学中,应用能量的观点对电磁感应现象进行分析研究,发现、概括和归纳了感应电流的特性,在教学中提出了感应电流的特性这一新概念与新观点:引导学生揭示了感应电流的特性及其具有的物理本质,并归纳出了应用感应电流的特性解决相关问题的方法。应用能量的观点对电磁感应现象进行分析,我们不难发现感应电流具有这样的特性:“感应电流总是要阻碍它本身的产生”。     

外加电场对激光诱导Al等离子体发射光谱的影响

在低压环境下,由Nd:YAG脉冲激光器产生的1.06 μm激光烧蚀金属Al靶产生等离子体,观测了外加电场下其空间分辨发射光谱,并由此分析了谱线相对强度、谱线展宽随外加电压的演化特性.结果发现:原子谱线强度及其半高全宽随外加电压的增加均有明显增大,而离子谱线受外加电压的影响较小.从微观机制上分析推断:外加电场使非稳态等离子体中的电子作定向运动,加剧电子与原子之间的碰撞是上述结果的主要原因.此外,由发射光谱线的Stark展宽计算了等离子体电子密度,并由实验结果讨论电子密度随外加电压的演化特性和空间演化特性.     

光纤光栅中孤子时延特性研究

从光纤光栅慢光产生的物理机理和非线性耦合模方程组,仿真分析了均匀布拉格光栅中光栅孤子传输时的减速特性;利用高速示波器搭建了测量高能量、窄脉冲通过布拉格光纤光栅后时延特性的实验系统,分别测量了由普通单模光纤和高非线性光纤制作的均匀光栅对光脉冲的时延特性.实验结果为:用5 cm长普通单模光纤制作的布拉格光栅可以使在其中传输...     

开孔金属泡沫池内沸腾换热特性研究

常压下用去离子水作为工质,在沸腾池底部单独或两两叠加地放置3种PPI的泡沫金属进行池内沸腾实验研究;分析了不同过热度下的热流密度和不同热流密度下池沸腾的传热系数;对沸腾汽泡在单层或双层泡沫金属表面产生、融合和脱离进行了可视化的研究。实验发现:不同PPI泡沫金属的叠加方式,会影响沸腾传热面积和产生汽泡的核心数,以及汽泡脱离受热壁面的动态特性。本实验为多孔介质池沸腾传热特性研究提供了实验指导和基础数据。     

甘油的黏度对激光等离子体推进的影响

以液体甘油为烧蚀靶材,研究了不同环境温度下超短脉冲激光烧蚀后产生的等离子体的推进特性.实验结果表明:甘油产生的动量和烧蚀压力与环境温度密切相关,其原因是甘油的黏度受温度影响较大.     

GaAs/GaAlAs双异质结发光管退化特性的研究

本文研究了GaAs/GaAlAs双异质结发光管的退化特性。有快、慢二种退化类型。器件的慢退化是由于有源区有暗缺陷(DSD)产生和长大,引起光功率下降。文中研究了老化过程中I-V特性和I-P特性与EL图象的变化规律,并与相同结构的InP/InGaAsP双异质结发光管的退化特性进行了比较,结果表明:它们有着不同的退化机理。     

冲击波在空气和熔石英元件界面传播的超快诊断

基于球面波在弹性介质界面上的反射和折射特性的基本理论,采用超快时间分辨的光学诊断技术,研究了532nm纳秒激光辐照熔石英元件表面产生的冲击波在空气和样品界面的传播特性,获得了冲击波在材料内部传输以及在空气与样品界面反射的时间分辨图像。结果表明:激光脉冲与材料作用在前后表面产生了向体内传输的冲击波,且产生的冲击波在玻璃与空气界面处反射为两个波,即反射波和反射剪切波;反射波和反射剪切波的强度与入射冲击波的入射角有关。     

Applicability of the minimum entropy generation method for optimizing thermodynamic cycles

Entropy generation is often used as a figure of merit in thermodynamic cycle optimizations. In this paper, it is shown that the applicability of the minimum entropy generation method to optimizing output power is conditional. The minimum entropy generation rate and the minimum entropy generation number do not correspond to the maximum output power when the total heat into the system of interest is not prescribed. For the cycles whose working medium is heated or cooled by streams with prescribed inlet temperatures and prescribed heat capacity flow rates, it is theoretically proved that both the minimum entropy generation rate and the minimum entropy generation number correspond to the maximum output power when the virtual entropy generation induced by dumping the used streams into the environment is considered. However, the minimum principle of entropy generation is not tenable in the case that the virtual entropy generation is not included, because the total heat into the system of interest is not fixed. An irreversible Carnot cycle and an irreversible Brayton cycle are analysed. The minimum entropy generation rate and the minimum entropy generation number do not correspond to the maximum output power if the heat into the system of interest is not prescribed.     

The biological characteristics of different generation mesenchymal stem cells cultured in vitro and cocultured with vascular scaffold

Mesenchymal stem cells (MSCs) were used widely as seed cells in tissue engineering blood vessel construction. However, the biological characteristics difference of different generation MSCs in vitro culture is unknown, which laid a foundation for appropriate generation seeded cells selection for tissue engineering blood vessel construction. In this report, MSCs were isolated from SD rat bone marrow and identified by flow cytometry; cell growth curve test, cell surface antigen expression rate detection, cryopreservation resuscitation rate test, CD31 expression rate test, cell cycle analysis, and adhesion difference on vascular scaffold test were performed. The research results indicated that the MSCs shape was spindle and uniform with vigorous growth. CD105 and CD90 factor expression rate reached 82.5 and 84.9%, respectively, and the expression rate of CD45 was only 7.3%. The proliferation capacity of the fourth generation MSCs were more exuberant, with proliferation index as 20.3%; the cell proliferation index of the eighth generation decreased to only 9.1%. The cryopreservation resuscitation rate of the second generation and fourth generation MSCs were both higher than 80%, and the cryopreservation resuscitation rate of the eighth generation MSCs was only about 60%. After the induction for 5 days, MSCs had weak CD31 expression, and with the prolonged induction time, expression increased. All generation MSCs expressed CD31 after being induced for 10 days; however, the CD31 positive expression rate of the second generation, fourth generation, and sixth generation MSCs had significant difference with the eighth generation MSCs. Adhesion rate of MSCs before sixth generation was around 40%, but the adhesion rate of eighth generation MSCs was only about 27%. In all, biological characteristics of different generation MSCs existed certain differences, and especially the eighth generation MSCs aged seriously, whose cell activity decreased significantly. The researchers believed that the MSCs before the sixth generation can maintain excellent properties of MSCs, and can be used as seed cells for vascular tissue engineering.     

Applicability of minimum entropy generation methodto optimizing thermodynamic cycles

Entropy generation is often used as a figure of merit in thermodynamic cycle optimizations. In this paper, it is shown that the applicability of the minimum entropy generation method to optimizing output power is conditional. The minimum entropy generation rate and the minimum entropy generation number do not correspond to the maximum output power when the total heat into the system of interest is not prescribed. For the cycles whose working medium is heated or cooled by streams with prescribed inlet temperatures and prescribed heat capacity flow rates, it is theoretically proved that both the minimum entropy generation rate and the minimum entropy generation number correspond to the maximum output power when the virtual entropy generation induced by dumping the used streams into the environment is considered. However, the minimum principle of entropy generation is not tenable in the case that the virtual entropy generation is not included, because the total heat into the system of interest is not fixed. An irreversible Carnot cycle and an irreversible Brayton cycle are analysed. The minimum entropy generation rate and the minimum entropy generation number do not correspond to the maximum output power if the heat into the system of interest is not prescribed.     

钛宝石激光器端面抽运Nd:YAG陶瓷激光器热沉积理论和实验研究

通过热沉积系数研究在激光提取条件下掺杂原子分数为1.0%的Nd:YAG陶瓷激光器中热沉积问题.热沉积系数定义为热沉积功率与激光器输出功率之比.在理论分析基础上，通过测量激光器斜率效率来间接测定热沉积系数，实验测定的热沉积系数值为0.63.建立激光提取条件下Nd:YAG陶瓷发热模型，讨论了影响热沉积系数的主要因素.结果表明：热沉积系数对Nd:YAG陶瓷的辐射量子效率、交叠效率以及激光提取效率的变化非常敏感.为有效减少介质内热沉积，在激光器优化设计中交叠效率和激光提取效率是需要着重考虑的参数.所得结果可为进一步研究陶瓷激光器中热效应提供参考. 关键词： 热沉积 Nd:YAG陶瓷 固体激光器     

阶跃电压法确定产生寿命和表面产生速度

在分析MOS电容对耗尽的阶跃电压瞬态响应的基础上,本文提出了一种同时确定产生寿命和表面产生速度的方法。用该方法对一些样品进行了测试分析,结果表明该方法是合理的。并且指出,在表面产生与体产生相比较实际上不能忽略时,忽略表面产生的方法将导致测得的产生寿命低于它的真实值。 关键词：     

Recent developments in high power near-infrared super-continuum generation based on photonic crystal fiber

High power supercontinuum generation has witnessed rapid developments during the past few years. The mechanism and the latest achievements in high power supercontinuum generation are reviewed both for the continuous wave pump regime and the pulsed pump regime. The challenges in scaling the average power of supercontinuum generation are analyzed. Some of our works on high power supercontinuum generation are summarized, and perspectives for the future development are discussed.     

Recent Advance of Hydride Generation–Analytical Atomic Spectrometry: Part I—Technique Development

Abstract Hydride generation is the most popular and widely used chemical vapor generation technique and is interesting to analytical chemists as an effective sample introduction method, especially for elemental determination and speciation analysis by analytical atomic spectrometry. The present review provides a literature survey on the hydride generation technique coupled to analytical atomic spectrometry during the past several years, covering the literature on both tetrahydroborate-based hydride generation and non-tetrahydroborate-based hydride generation techniques. Development of other related methods coupled to hydride generation for better analytical performance of analytical atomic spectrometry is included as well.     

基于1149.7标准的测试生成方法研究

单芯片多核设计、片上系统等技术的不断发展为边界扫描技术带来了新的挑战,多扫描拓扑的测试矢量自动生成也成为了研究的重点与热点。基于1149.7标准对测试生成方法进行了研究,包括互连测试矢量、调试应用指令及数据和寄存器配置命令的生成,提出了测试生成的总体框架,以VS2008作为软件平台搭建自动测试生成系统,从数据库中提取目标板信息对寄存器进行配置,生成互连测试矢量或调试数据,最后将生成的信息插入数据库中,在互连测试矢量生成过程中,提出了一种基于边界扫描寄存器的功能来设置网络结点类型的新方法,有效地完成了对复杂网络的测试。     

Verification of numerical simulation method for entropy generation of radiation heat transfer in semitransparent medium

The numerical simulation method of radiative entropy generation in participating media presented by Caldas and Semiao [Entropy generation through radiative transfer in participating media: analysis and numerical computation. JQSRT 2005;96:423-37] is extended to analyze the radiative entropy generation in the enclosures filled with semitransparent media. A discrete ordinates method is used to solve radiative transfer equation and radiative entropy generation. Two different examples are employed to verify the numerical simulation method of radiative entropy generation in the enclosure. Numerical results of dimensionless radiative entropy generation of enclosure are identical to that of entire thermodynamics analysis for the enclosure system. This numerical simulation method can be used in the entropy generation analysis of high-temperature systems such as boilers and furnaces, in which radiation is the dominant mode of heat transfer.     

交互式网格生成技术研究

探讨了分区网格生成的交互方法,包括交互输入、图形显示、网格质量检查、网格求解过程的随机可视控制等问题。在此基础上研制了一种具有交互性能的网格生成系统——BIGG。应用该系统生成的网格实例及流场解表明该交互技术是有效可行的,研制的软件系统提高了生成效率和网格质量。