共查询到19条相似文献,搜索用时 93 毫秒
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高功率光纤端帽是kW级光纤激光器必不可少的器件,而实现光纤端帽的低损耗高强度熔接是其关键技术。由于光纤和大尺寸光纤端帽在直径上的巨大差异,二者的熔接不能通过传统熔接机实现。设计并搭建了光纤端帽熔接系统,掌握了多种尺寸的光纤端帽的熔接工艺,成功用于光纤激光器及光纤合束器的高功率输出。实验上利用单模光端帽实现了3.01kW的激光输出,在未进行主动制冷的情况下温升为7℃/kW。利用多模光纤端帽实现了6.08kW的激光输出,在未进行主动制冷的情况下温升为6℃/kW。 相似文献
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在高功率光纤激光系统中,包层光滤除器能将光纤中包层光滤除以保证输出激光光束质量,光纤端帽通过对输出激光扩束降低输出光纤端面的光功率密度,从而保护光纤端面不受损坏,两者都是高功率光纤激光系统稳定运行的重要核心器件。将包层光滤除器和光纤端帽进行一体化设计,制备了一体化高功率光纤包层光滤除器和光纤端帽并分别应用于20 kW合束系统和单纤系统中,输出功率达到20 kW时,端帽的最高温度约为40℃,温升速率约为0.8℃/kW。 相似文献
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实验研究了高有载品质因数下有无阳极端帽时调谐性能的差异,以及低有载品质因数下,没有阳极端帽时的可调谐相对论磁控管性能。研究结果表明:没有阳极端帽时,可调谐相对论磁控管具有更宽的调谐范围;在高有载品质因数下,可以达到2.52~3.31 GHz的调谐范围,输出功率范围为44~790 MW;低有载品质因数下,调谐范围为2.55~3.05 GHZ,调谐范围内输出功率1~1.7 GW。 相似文献
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基于Stone-Wales缺陷演变理论与分子动力学、Monte Carlo计算方法, 进行了碳纳米管(CNTs)对接成异质结器件的计算模拟.首先, 提出了一种模拟CNTs端帽位置变化的新算法, 并计算模拟了单根CNT的端帽从开口到闭合的过程. Stone-Wales缺陷演变被设计模拟这些端帽变化的跃变过程, 以模拟C–C键的生成与断裂, 而分子动力学则作为跃变后构型弛豫的渐变模拟. 同时, 研究了不同管型CNTs的端帽打开并对接形成异质结的过程.研究结果显示, 对接初期在对接处先产生大量的缺陷, 以促进反应的发生. 这些缺陷趋向于演变成稳定的六元环结构, 或者五元环/七元环的结构, 使异质结趋于稳定.
关键词:
碳纳米管
Monte Carlo
Stone-Wales缺陷
分子动力学 相似文献
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岩石、土壤和沉积物中主成分的ICP-AES测定 总被引:5,自引:0,他引:5
用HNO3-HF-HCIO4分解试样和ICP-AES测定岩石、土壤和沉积物中九种主要成分。方法简便、快速,测量精密度和准确度令人满意。相对标准偏差小于3%,是测定岩石、土壤和沉积物中主成分的比较理想的方法。 相似文献
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岩石含水量是影响岩石物理、化学和力学特性的一个重要指标。在岩土工程、隧道工程等领域,岩石含水量的大小是诱发灾变和病害的关键原因。与传统方法相比,利用近红外光谱(NIRS)特征检测岩石含水量,具有无损、定量的明显优势,其难点和关键是近红外光谱的特征选择。针对该问题,进行了室内实验,研究不同含水量下的岩石近红外光谱的特征选择。特征选择方法中的Filter法,利用样本数据内在的特点,评价特征的重要程度,增强了特征与类的相关性,同时削减了特征之间的相关性,具有复杂度低、直观、效率高、普适性强的优点,符合该研究的数据特点。因此,选用Filter型的依赖性度量法进行特征选择。室内实验中,首先制备11种不同含水量的砂岩试样,并分别采集了前后左右4个测试点处的共计44条近红外光谱曲线;然后,利用一阶导数法对光谱进行预处理,基于此,选择1 400和1 930 nm谱段进行光谱特征分析,并分别提取2个谱段处的峰面积、峰高、半高宽、左肩宽度、右肩宽度、左右肩宽比共计6个初始特征变量;考虑到6个初始特征变量的量纲不同,且变量之间的变化幅度不同,对原始数据进行正规化变换,消除量纲和变化幅度不同带来的影响;接着,根据自变量的筛选原则,去掉自变量之间具有强线性相关的冗余变量;然后,利用依赖性度量法中的统计相关系数作为相关程度的度量标准,分析了初始特征变量之间以及初始特征变量与含水量之间的相关程度,并得到了2个强相关谱段处的最优特征变量;最后,在强相关谱段处分别构建了多元回归模型,并对模型进行了检验分析。研究结果表明:(1)波长1 400和1 930 nm附近的近红外光谱吸收峰特征与岩石含水量有明显相关性;(2)波长1 400 nm处的峰高、右肩宽度、左肩宽度与含水量线性相关性明显;波长1 930 nm处的峰高、右肩宽度与含水量线性相关性明显;(3)多元线性回归模型能够较精确表达含水量与近红外光谱之间的相关性,利用该模型可实现基于近红外光谱特征的含水岩石含水量预测,为利用近红外光谱实现动态监测与评估岩石含水量提供基础建模数据。 相似文献
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为研究含水率对硬岩材料的力学性质和能量损伤的影响规律,对不同含水状态的砂岩开展了单轴压缩试验。结果表明:砂岩试样的峰值应力、弹性模量和脆性指数随着含水率的增大而减小,峰值应变随着含水率的增大而增大;在干燥状态下,砂岩试样在破坏之前未发生明显的塑性变形,表现出显著的脆性破坏,而在饱水状态下,砂岩试样在峰前阶段出现显著的塑性变形,破坏前出现屈服平台;砂岩试样的含水率越大,吸能能力越强,能量吸收率越小,但是能量耗散越显著;砂岩试样的含水率越小,破坏时其损伤变量越大,在干燥状态下砂岩试样的破坏具有较强的冲击倾向性。研究结果可为深部地下工程围岩的稳定性控制提供理论参考。 相似文献
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电热原子吸收法固体加样直接测定高铝岩石中钾 总被引:1,自引:1,他引:0
粉末试样直接原子化是原子吸收中最引人注目的问题之一。不需要什么试剂,因而避免了试剂沾污。固体试样直接原子化,火焰及无火焰原子吸收分析国外时有报导,国内不多见。我们用常规手段,自制加样小舟,石墨粉稀释试样,在次灵敏线用石墨杯直接测定了红柱石、硅线石等高铝岩石中钾。用固定量的标准水溶液加到精确称量的不同重量试样中去的标准加入法作了校正比较。探索了固体试样直接分析的可行性。 相似文献
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An analytical model is developed for the vibration response of a cylindrical machine casing excited by the force arising in a bearing that is assumed to support a rotating shaft. The casing system consists of a bearing housing mounted in a flat circular end cap that is built into a cylindrical casing. The housing is considered to be a rigid trunnion in the center of the end cap (which itself is modeled as a Mindlin plate). The development allows for arbitrary location of the center of mass of the housing and of the plane of action of the exciting force. 相似文献
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ZHAO Chuan SUN Sheng-Sen LI Cheng ZHANG Xiao-Jie HE Kang-Lin AN Qi CHEN Hong-Fang DAI Hong-Liang FENG Chang-Qing HENG Yue-Kun HUANG Ya-Qi HUANG Yan-Ping GUO Jian-Hua LI Wei-Dong LI Xiu-Rong LIU Fang LIU Huai-Min LIU Shu-Bin LIU Shu-Dong LIU Yong MA Xiang MAO Ze-Pu SHAO Ming SUN Yong-Jie SUN Zhi-Jia WU Jin-Jie YANG Gui-An ZHAO Lei ZHU Xing-Wang ZUO Jia-Xu 《中国物理C(英文版)》2011,35(1):72-78
The time calibration for end cap TOF system of BESⅢ is studied in this paper.It has achieved about 110 ps time resolution for muons in dimu events.The pulse height correction using electronic scan curve and the predicted time calculated using Kalman filter method are introduced.This paper also describes the study of using electrons and muous as calibration samples. 相似文献
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赵川 孙胜森 李澄 张晓杰 何康林 安琪 陈宏芳 代洪亮 封常青 衡月昆 黄亚齐 黄燕萍 郭建华 李卫东 李秀荣 刘芳 刘怀民 刘树彬 刘曙东 刘勇 马想 毛泽普 邵明 孙勇杰 孙志嘉 吴金杰 杨桂安 赵雷 朱兴旺 左嘉旭 《中国物理 C》2011,35(1)
The time calibration for end cap TOF system of BESⅢ is studied in this paper. It has achieved about 110 ps time resolution for muons in dimu events. The pulse height correction using electronic scan curve and the predicted time calculated using Kalman filter method are introduced. This paper also describes the study of using electrons and muons as calibration samples. 相似文献
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A spherical cap radiator is one of the important parts of
an underwater wide-beam imaging system. The back radiation of a
traditional spherical cap radiator, which is composed of a vibrating
cap and a rigid baffle, is strong and its far-field directivity
function may fluctuate in big amplitude in the vicinity of the polar
axis. These shortcomings complicate the processing of the reflective
waves received for imaging the targets. In this study, the back
radiation is weakened by adding an acoustic soft material belt
between the vibrating cap and the rigid baffle. And the fluctuation
mentioned above is lowered remarkably by dividing the spherical cap
radiator into many annuluses and a relatively smaller spherical cap,
and by controlling the phase retardations of all elements
appropriately. Furthermore, the numerical experiments are carried
out by the finite element method (FEM) to prove the validity of the
above methods. 相似文献
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We have studied the topological transition of the nonionic micelles of a penta-ethyleneglycol mono n-dodecyl ether (C12E5)/DL-alpha-phosphatidylcholine Dimyristoyl (DMPC) mixture in water by light scattering and viscosity measurements. The topological transition concentration decreases with an increase of the mixing ratio of DMPC to C12E5. The topological transition point is strongly affected by defect energies of the end cap (epsilon(1)) and a threefold junction (epsilon(3)) and is compared with a recent theoretical study. This experimental study shows the first clear evidence for the topological transition in a nonionic micellar system resulting from balancing the defect energies. 相似文献
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Yi Wei Shi Katsumasa Iwai Yuji Matsuura Mitsunobu Miyagi Helena Jelinkova 《Optics & Laser Technology》2006,38(2):107-110
A sealing cap had been proposed as an output device for hollow optical fibers in delivering laser light underwater. Properties of sealing cap were experimentally discussed when used in ablation on soft tissue for Er:YAG laser. A self-cleaning effect of the sealing cap was observed when various targets were used for different laser light power. Debris from pork fat formed a uniform oil layer on the output surface of the cap, and the oil layer is relatively transparent in Er:YAG laser light wavelength band. When the target was pork muscle, almost no debris could attach on the surface of the cap. The self-cleaning effect was more obvious when ablation was conducted underwater because of the protection of the water film between the target and the cap's surface. 相似文献
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The paper deals with the analysts of damping characteristics of a curved composite shaft. The composite shaft consists of an outer elastic curved tube with a similarly curved rod placed inside. The annular space between the tube and the rod is filled with viscoelastic material. The composite shaft is clamped at one end and a concentrated load (varying harmonically) acts on a radial arm fixed to the outer shell at the free end. It is shown that optimum design values exist for maximizing the total damping capacity of the system. It also is indicated that direct use of this method for increasing the damping capacity is not effective, as the damping factor reduces sharply after reaching a maximum value. It is shown how this difficulty can be overcome and how helical springs, possessing considerable damping capacity, can be designed. Sometimes this may help in simplifying the design of vibration isolators which will take the shape of a simple spring only. 相似文献
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Field emission microscopy of adsorption and desorption of residual gas molecules on a carbon nanotube tip 总被引:2,自引:0,他引:2
Field emission of electrons from multiwall carbon nanotubes has been investigated by field emission microscopy (FEM) in ultra-high vacuum. A carbon nanotube, at the end of which at least six pentagons exist to make a closed cap, gives an FEM pattern consisting of bright pentagonal rings if the nanotube surface is clean. Adsorption of residual gas molecules is observed as bright spots in the FEM pattern, giving rise to an abrupt increase in the emission current. Adsorbed molecules seem to reside preferentially on the pentagonal sites where the strong electric field is concentrated. A heat cleaning of the emitter at about 1300 K allows the molecules to desorb, and the nanotube emitter recovers its original clean surface. It has been revealed that the adsorption and desorption of gas molecules are responsible for stepwise fluctuation of the emission current. 相似文献
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Aluminum combustion in a solid rocket motor environment 总被引:5,自引:0,他引:5
A model for prediction of particle radius and oxide cap size/shape versus time for an aluminum particle tracking a stream-tube through a solid rocket motor port has been developed. Following preliminary calculations leading to a postulated flame structure, a quasi-steady model to predict instantaneous consumption of aluminum and generation of condensed oxide (both as a cap on the aluminum particle and as smoke) as a function of instantaneous particle size, ambient conditions, and cumulative amount of oxide in the cap was developed. Finally, this model was imbedded into a framework tracking evolution of particle size, oxide cap size, and ambient conditions, which change as the particle travels along a stream-tube consuming oxidizer and releasing heat. Qualitative agreement was found between predictions and limited observations. 相似文献