Thulium Fiber Laser Ablation of Urinary Stones Through Small-Core Optical Fibers

Complications during laser lithotripsy include optical fiber bending failure resulting in endoscope damage and low irrigation rates leading to poor visibility. Both problems are related to fiber diameter and limited by the holmium:YAG (Ho:YAG) laser (lambda = 2120 nm) multimode beam profile. This study exploits the thulium fiber laser (lambda = 1908 nm) beam profile for higher power transmission through smaller fibers. Thulium fiber laser radiation with 1 ms pulse duration, pulse rates of 10-30 Hz, and 70-mu m-diameter spot was coupled into silica fibers with 100, 150, and 200 mum core diameters. Fiber transmission, bending, and endoscope irrigation tests were performed. Damage thresholds for 100, 150, and 200 mum fibers averaged 40, 60, and > 80 W, respectively. Irrigation rates measured 35, 26, and 15 mL/min for no fiber, and 100 and 200 mum fibers. Thulium fiber laser energy of 70 mJ delivered at 20 Hz through a 100 mum fiber resulted in vaporization and fragmentation rates of 10 and 60 mg/min for uric acid stones. The thulium fiber laser beam profile provides higher laser power through smaller fibers than Ho:YAG laser, potentially reducing fiber failure and endoscope damage, and allowing greater irrigation rates for improved visibility.     

Toward a Germanium Laser for Integrated Silicon Photonics

It has been demonstrated theoretically and experimentally that germanium, with proper strain engineering and n-type doping, can be an efficient light emitter and a gain medium at its direct bandgap within the third optical communication window ($sim$1520–1620 nm). In this paper, we systematically discuss the effect of strain, doping, and temperature on the direct-gap optical gain in germanium. For electrically pumped devices, properties and design guidelines of Ge/Si heterojunction are also analyzed and compared with the results from fabricated Ge/Si heterojunction LEDs.      

不可逆电穿孔微创消融肿瘤技术的研究进展

肿瘤愈发成为人类健康的主要威胁。传统的手术切除、化学治疗存在一定的禁忌症,且易对患者身心造成巨大的伤害,物理消融治疗就是在这种背景下提出的。为此,在简要介绍目前临床应用较广的几种物理消融技术的基础上,由电穿孔现象及其应用出发,着重介绍了率先由我国研究人员提出的不可逆电穿孔消融肿瘤技术的发展历程及研究进展。尽管不可逆电穿孔治疗肿瘤技术的机理尚未完全探明,但该技术由于具有治疗时间短、病人术后恢复快、对正常组织损伤小等优势,且可避免热消融损伤的缺憾,所以已展现出广阔的应用前景。然而,相对于国外的成果迅速转化的优势以及临床快速推进,国内的临床推进相对缓慢,但不可逆电穿孔消融肿瘤方法逐渐为我国工程专家和临床医生所接受,目前亟需汇集技术、临床及资金等各方面力量,将该技术尽快实现成果转化进而推广到临床以造福患者。     

Laguerre Runge--Kutta--Fehlberg Method for Simulating Laser Pulse Propagation in Biological Tissue

An efficient algorithm for solving the transient radiative transfer equation for laser pulse propagation in biological tissue is presented. A Laguerre expansion is used to represent the time dependency of the incident short pulse. The Runge-Kutta-Fehlberg method is used to solve the intensity. The discrete ordinates method is used to discretize with respect to azimuthal and zenith angles. This method offers the advantages of representing the intensity with a high accuracy using only a few Laguerre polynomials, and straightforward extension to inhomogeneous media. Also, this formulation can be easily extended for solving the 2-D and 3-D transient radiative transfer equations.     

钨和氧化钨对银镍触头材料性能的影响

本文对分别掺杂W和WO3两种不同添加剂的银镍触头材料(85%含银量)进行电性能、力学物理性能及微观组织对比分析。在添加剂的成分、颗粒尺寸及分布相同时,两种材料的微观组织、抗拉强度及断后伸长率几乎相同,在显微硬度和接触电阻上略有差别,而在电弧侵蚀和材料转移上有明显区别。相对于WO3而言,W的添加降低了Ag Ni(15)触头材料的较大抗熔焊力出现概率。对于因电弧侵蚀导致的材料损失,添加1.5%的W要比1.5%的WO3低。在电弧作用下掺杂WO3的触头材料表面有较大镍颗粒的团聚,这可能是由于WO3的添加影响了其材料的转移。     

一种高氧化物含量AgCdO触点在GMC交流接触器中的应用

介绍了一种高氧化物含量AgCdO材料的试制,进行了不同内氧化工艺条件下触点材料力学物理性能的比较和分析,选取最佳方案产品在GMC-50三极交流接触器中进行AC-4电性能试验,结果表明,触点在56 000次电寿命内性能可靠,温升满足要求.所研究材料可以达到良好的节银效果.     

AgSnO2的断裂机理及裂纹对触点材料侵蚀过程的影响

本文主要研究了AgSnO2触点材料在使用过程中的裂纹产生机理以及裂纹对材料侵蚀过程的影响。     

银氧化镉材料的欧盟限制政策与其它银金属氧化物电接触材料的发展

本文介绍了欧盟对含镉物质及产品的限制政策，评述了银氧化镉替代材料的发展，建议制定我国的相关政策与标准，以应对发达国家对有关银基电接触材料及相关产品的限制措施。     

反应合成AgSnO2电接触材料的组织与性能研究

采用反应合成技术和传统粉末冶金技术制备银氧化锡(AgSnO2)电接触材料。利用千瓦CO2激光器模仿电弧作用在试样表面产生局部熔化，对AgSnO2块体材料进行抗熔蚀性测试。对AgSnO：块体材料进行电导率测试和X射线衍射分析，对块体材料及冷拉拔的AgSnO2线材进行显微组织分析(扫描电镜、透射电镜)。研究结果表明，采用反应合成技术可以在银基体中合成尺寸细小、界面新鲜的SnO2颗粒，所制备的AgSnO2电接触材料中，微米级的SnO2颗粒系由纳米级的SnO2颗粒聚集而成I反应合成法制备的AgSnOz电接触材料较传统粉末冶金法制备的AgSnO2电接触材料具有更高的导电性和抗熔蚀性；该方法制备的AgSnO2电接触材料由于改变了Ag、SnO2的结合状态使材料的加工性能、导电性能和抗熔蚀性同时得到改善和提高。     

A New Approach in Layer-by-layer Growth of Oxide Materials by Pulsed Laser Deposition

Pulsed laser deposition (PLD) has become thin film deposition technique with increasing prominence. One of the advantages above other techniques is the possibility to growth at relative high background pressures, with a large freedom in choosing the kind of gas. An example is oxygen in the case of high T_c superconductors and giant magnetic resistors. However, the advantage of relative high pressures hinders the use of a number of diagnostics and monitor techniques, like reflective high energy electron diffraction (RHEED). With the introduction of the possibility to use RHEED at standard PLD pressures, it became possible to study the growth of oxide materials under different oxygen and temperature conditions. In this paper we employed this technique on SrTiO₃, which can be grown in different growth modes depending on growth temperature and oxygen pressure during deposition. Applying a modified etch treatment on SrTiO₃ single crystals, a real 2D growth mode could be observed by the homo-epitaxial growth of SrTiO₃, as indicated by RHEED oscillations. In addition to the RHEED oscillations another phenomenon is observed, typical for PLD. The pulsed way of deposition leads to discontinuities in the intensity of the diffracted pattern. This is caused by the mobility of the deposited material from a disordered distribution till an ordered one and leads to a characteristic exponential slope with characteristic relaxation time constants. These time constants give extra information about relaxation, crystallization, and nucleation of the deposited material during growth. Finally, a new approach to deposit these complex oxide materials will be introduced. This, so-called interval deposition, is based upon the results obtained from the intensity oscillations as well as relaxations. The basic idea is to deposit an equivalent of one unit cell of material in such a short time that no coalescence in larger islands can occur, followed by a relaxation time before the next unit cell layer is deposited. This interval deposition leads to an imposed layer by layer growth.     

弧触头烧蚀程度对灭弧室内短路开断过程多物理场的影响

为研究SF6断路器开断过程中弧触头烧蚀程度对灭弧室内多物理场变化的影响,建立了弧触头接触行程分别减小0、5、10和15Smm下灭弧室内开断过程的多物理场耦合仿真模型,获得了短路电流开断过程中灭弧室内温度、气流和电场分布特性。计算结果表明：开断过程中,弧道最高温度出现在弧根处,其值随弧触头烧蚀程度变化不大;随着弧触头烧蚀程度的加剧,SF6气体最高速度不断减小,吹弧效果减弱;最大场强集中在静弧触头端部或动弧触头弧角处,且随弧触头烧蚀程度加剧而畸变更严重。基于此,根据流注理论的气体击穿判据计算了不同弧触头烧蚀程度下SF6介质恢复特性,发现当弧触头接触行程减小15 mm时,临界击穿电压低于瞬态恢复电压,触头间隙可能再次击穿造成电弧重燃。研究结果可为SF6断路器电寿命退化机理提供理论支撑。     

Striation Formation in Ti-doped Y3Al5O12 Fibers Grown by the Laser Heated Floating Zone Method

Microscopic dopant distribution has been investigated in 1mm-diameter single crystal fibers of Ti-doped Y₃Al₅O₁₂ (YAG) grown by a laser heated floating zone (LHFZ) method. In the fibers, a periodic fluctuation in the Ti dopant concentration has been observed along the growth direction, and striations, attributed to variation in dopant concentration, were seen across the diameter of the fiber by two dimensional mapping using an electron probe microanalyser. The dopant concentration was found to vary by as much as 30% from average levels with a spacing of the order of 20m. Microscopic inhomogeneities of Ti are discussed in relation to growth conditions with emphasis on crystal/feed rotation. Effects to minimize segregation effects by annealing are reported.     

Techniques for Polarization-Independent Cross-Phase Modulation in Nonlinear Birefringent Fibers

We present a theoretical, numerical, and experimental investigation of the polarization dependence of cross-phase modulation in nonlinear birefringent fibers. Two new methods are described for producing a polarization-independent spectral shift through cross-phase modulation of a weak probe signal by a copropagating strong optical pulse. The birefringence of the fiber and spectral separation between the pump and probe signals are shown to play a critical role in determining the polarization dependence of the cross-phase modulation process. The methods are experimentally verified in two different highly nonlinear fibers, and are used to achieve polarization-independent optical switching at speeds of up to 160 Gb/s.     

纳秒电脉冲对肝脏组织不可逆电穿孔消融区分布的时域有限差分法仿真

纳秒电脉冲消融是一种新型的电外科手术技术,在肿瘤切除中可以无创或少创器官旁组织,尤其是血管,达到既切除肿瘤,又不伤及周边组织的目的.纳秒电脉冲参数,如脉冲电压、脉冲持续时间、脉冲数、脉冲率等的选择是术前治疗计划设计的关键,术前进行仿真研究对手术设计至关重要.以人体模型Duke为对象,采用人体生物电磁仿真软件平台Sim4...     

中国软磁铁氧体用氧化铁

介绍了中国软磁铁氧体用氧化铁的发展历史和现状，预测了未来的市场需求，并探讨了氧化铁的应用技术问题。     

电力通信中光纤通信设备的维护经验

介绍了光纤通信设备雏护的分类、故障分析方法、告警信号分析以及常用故障的处理方法。     

Pulsed Laser Deposition of Zr1-xCexO2 and Ce1-xLaxO2-x/2 for Buffer Layers and Insulating Barrier in Oxide Heterostructures

We have studied the pulsed laser deposition (PLD) of Zr_1-xCexO₂ and Ce_1-xLa_xO₂-x/2 initially to grow buffer layers for perovskite films deposited on Si, LaAlO₃, SrTiO₃ and MgO and then to produce tunneling barriers for cuprate or manganite heterostructures. On (1 0 0) Si, the deposition of Zr_1-xCexO₂ (x = 0.12) produces a smooth epitaxial layer (R _RMS = 0.25/1m²), which allows the further deposition of high quality YBa₂Cu₃O₇ (Tc 88 K) and La_0.7Sr_0.3MnO₃ films. On the other hand, the use of Ce_1-xLa_xO_2-x/2 (0 x 0.4) makes it possible to match the YBa₂Cu₃O₇ and La_0.7Sr_0.3MnO₃ layers to various substrates. The buffer layers are epitaxially grown with a 45° rotation of the in-plane axes with respect to those of the substrate, and the smoothness is high (R _RMS = 0.25/1m²). In the case of an ultra-thin barrier (2.5 nm) of Ce_1-xLa_xO_2-x/2 sandwiched in a La_0.7Sr_0.3MnO₃, the out-of-plane mismatch of 2 induces distortions at the interface steps, which propagate into the topmost La_0.7Sr_0.3MnO₃ layer. This is in contrast to the case of SrTiO₃ barriers where an ideal crystal continuity in the growth direction is observed.     

线路氧化锌避雷器应用中注意的几个问题

雷击是造成线路跳闸停电事故的主要原因之一,线路避雷器已被证明是有效的防雷措施之一。介绍了线路避雷器应满足的技术性能要求,并提出了线路避雷器安装选点的一般原则及安装中应注意的几个问题。     

冷轧薄板激光焊机激光梁伺服控制的实现

本文针对冷轧薄板激光焊接的控制特点,研究了焊机激光梁的工艺控制流程,并据此提出了实现该动作过程的伺服控制方案.系统主要由西门子S7-400、SIMODRIVE 611U变频器、1FK7交流同步伺服电机等来组成.采用PROFIBUS-3DP通信,保证了参数的快速、准确传递.实现了激光梁伺服控制的快速性和准确性.