Erbium-Doped Zirconia-Alumina Silica Glass-Based Fiber as a Saturable Absorber for High Repetition Rate Q-Switched All-Fiber Laser Generation

We propose and demonstrate a Q-switched erbium-doped fiber laser （EDFL） using an erbium-doped zirconia-alumina silica glass-based fiber （Zr-EDF） as a saturable absorber. As a 16-cm-long Zr-EDF is incorporated into a ring EDFL cavity, a stable Q-switching pulse train operating at 1565？nm wavelength is successfully obtained. The repetition rate is tunable from 33.97？kHz to 71.23？kHz by increasing the pump power from the threshold of 26？mW to the maximum of 74？mW. The highest pulse energy of 26.67？nJ is obtained at the maximum pump power.

Tensile Properties of Fiber Materials under Different Strain Rates

The quasi-static and dynamic tensile tests of aramid and high strength PVA fiber bundles are carried out under a wider range of strain rate by use of MTS (Materials Testing System) and bar-bar tensile impact apparatus. The influences of strain rate on mechanical properties of aramid and high strength polyvinyl alcohol fibers are studied. Micro failure mechanisms of fibers at different strain rates are examined by means of SEM.

Influence of Heating Rate and Calcining Temperature on Properties of 95 Polycrystalline Alumina Fiber

The swung gel fibers were hea, ted to 400 ℃ at 0. .5 ,1, 1.5,2,2.5,3and4 ℃ min^-1 of heating rate, respectivel, and soaked.for 1 h ; then heated to 600 ℃ at 3 ℃ min ^-1 of.heating rate amt soaked for 1 h at last calcined m 1 000, 1 100, 1 200, 1 300, and 1 400 ℃.for 1 h, respectively.

Complete splitting process of steel fiber reinforced concrete at intermediate strain rate

The complete splitting process of steel fiber reinforced concrete(SFRC)at intermediate strain rate was studied by experiment.The basic information of a self-developed SFRC dynamic test system matching with Instron 1342 materials testing machine was given,and the experiment principle and the loading mode of cubic split specimen were introduced.During the experiment,30 cubes of 150 mm×150 mm×150 mm and 36 cubes of 100 mm×100 mm×100 mm,designed and prepared according to C20 class SFRC with different volume fractions of steel fiber(0,1%,2%,3%,4%)were tested and analyzed.At the same time,the size effect of SFRC at intermediate strain rate was investigated.The experimental study indicates that SFRC size effect is not influenced by the loading speed or strain rate.When the steel fiber content increases from 0 to 4%,the splitting strength of SFRC increases from 100%to 261%,i.e.increasing by 161%compared with that of the common concrete.The loading rate increases from 1.33 kN/s to 80.00 kN/s,and the splitting tensile strength increases by 43.55%.

A low-outgassing-rate carbon fiber array cathode

In this paper, a new carbon fiber based cathode — a low-outgassing-rate carbon fiber array cathode — is investigated experimentally, and the experimental results are compared with those of a polymer velvet cathode. The carbon fiber array cathode is constructed by inserting bunches of carbon fibers into the cylindrical surface of the cathode. In experiment, the diode base pressure is maintained at 1×10^（-2） Pa–2×10^（-2） Pa, and the diode is driven by a compact pulsed power system which can provide a diode voltage of about 100 kV and pulse duration of about 30 ns at a repetition rate of tens of Hz.Real-time pressure data are measured by a magnetron gauge. Under the similar conditions, the experimental results show that the outgassing rate of the carbon fiber array cathode is an order smaller than that of the velvet cathode and that this carbon fiber array cathode has better shot-to-shot stability than the velvet cathode. Hence, this carbon fiber array cathode is demonstrated to be a promising cathode for the radial diode, which can be used in magnetically insulated transmission line oscillator（MILO） and relativistic magnetron（RM）.

INFLUENCE OF LOADING RATE ON DYNAMIC FRACTURE BEHAVIOR OF FIBER-REINFORCED COMPOSITES

The effect of loading rate on the dynamic fracture properties and the failure mechanisms of glass fiber-reinforced composite materials under mode I fracture is studied. Dynamic reflective caustic experiments are carried out for two loading rates. By measuring the characteristic dimensions of the shadow spots during the caustic experiments, the dynamic SIFs are calculated for different loading rates. The experimental results indicate that the dynamic fracture toughness Kid increases remarkably with increasing loading rate, and the crack grows faster under the high-velocity impact. Moreover, by examining the crack growth routes and the fracture surfaces, it is shown that the loading rate also greatly affects the failure mechanisms at micro-scale.

Modification of spontaneous emission rate of micrometer-sized light sources using hollow-core photonic crystal fibers

We investigate numerically and experimentally the modification of the spontaneous emission rate for micrometersized light sources embedded in a hollow-core photonic crystal fiber （HCPCF）. The diameter of the light source is deliberately chosen such that they could be easily introduced into the central hole of the hollow-core photonic crystal fiber by capillary force. The photoluminescence from the microparticles is measured by using an inverted microscope in combination with a spectrometer. The modification of the spontaneous emission rate is observed in a wavelength region where there is no band gap. The experimental observations are consistent with the simulation results obtained by the plane wave expansion and finite-difference time-domain techniques.

FACTORS AFFECTING FATIGUE CRACK GROWTH RATES OF FIBER REINFORCED METAL LAMINATES

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基于纤维解离水曲柳压缩解离特征与能量耗散机制研究

目的以水曲柳为研究对象,研究高应变率压缩载荷作用下水曲柳试件的解离特征和能量耗散机制。方法利用压缩加载试验分析应变率、加载方向对受载水曲柳的形态特征影响和动力学特性,并利用弹塑性基本原理分析其受压解离的能量耗散机制。结果解离后径向加载试件主要呈火柴棍状,弦向加载试件主要呈片状,轴向加载试件主要呈不规则块状,试件的解离程度随应变率的增大而增大;当应变率在400~1000 s^(-1)时,水曲柳试件的应力-应变曲线由弹性阶段和屈服后弱线性强化阶段两部分组成;水曲柳试件的屈服强度随应变率的增大而增大,当应变率从400s^(-1)增加到1000s^(-1)时,径向、弦向和轴向加载试件的屈服强度分别增加了0.45倍、1.34倍和0.71倍;木材原料沿径、弦向解离时主要依靠木材细胞的压缩变形来耗散能量,沿轴向解离时主要依靠木材细胞纵向结构的弯曲来耗散能量。结论弦向最易解离,轴向最难解离;水曲柳是一种应变率敏感材料;木材原料径、弦向解离主要依靠压缩变形来耗散能量,轴向解离主要依靠弯曲变形来耗散能量,木材原料解离能够耗散能量的多少主要受加载方向、木材细胞的结构尺寸和力学性能的影响。

一种氧化锌复合物抗菌纺织纤维材料制备及性能测试

为降低抗菌材料生物毒性,提高其抗菌性能,本试验先通过原位还原法制备氧化锌复合物,并以该复合物作为抑菌剂,结合聚酯纤维无纺布制备一种抗菌纺织纤维材料,并研究其性能。试验结果表明,当氧化锌复合物中Cu含量在4.5%以上时,抗菌纺织纤维材料抑菌率基本达到99%,抗菌性能良好;在经过50次2 g/L的AATCC 1993标准洗涤剂洗涤后,抗菌纺织纤维材料抑菌率为97.6%,耐水洗性能良好;在经过12 h、24 h细胞培养后,抗菌纺织纤维材料的细胞相对存活率分别是86.6%、85.1%,生物相容性良好。综上,该抗菌纺织纤维材料综合性能良好,具备应用价值。

Generation of high-energy dual-wavelength domain wall pulse with low repetition rate in an HNLF-based fiber ring laser

The generation of high-energy dual-wavelength domain wall pulse with a low repetition rate is demonstrated in a highly nonlinear fiber （HNLF）-based fiber ring laser. By introducing the intracavity birefringence-induced spectral filtering effect, the dual-wavelength lasing operation can be achieved. In order to enhance the cross coupling effect between the two lasing beams for domain wall pulse formation, a 215-m HNLF is incorporated into the laser cavity. Experimentally, it is found that the dual-wavelength domain wall pulse with a repetition rate of 77.67 kHz could be efficiently obtained through simply rotating the polarization controller （PC）. At a maximum pump power of 322 mW, the 655-nJ single pulse energy in cavity is obtained. The proposed configuration provides a simpler and more efficient way to generate high energy pulse with a low repetition rate.

早熟陆地棉金垦1402脱叶效果的比较研究

[目的]针对早熟陆地棉品种金垦1402,研究棉花叶片形态学指标与药剂脱叶催熟效果的规律研究,为生产中提供脱叶催熟效果优良的早熟机采棉品种提供理论依据。[方法]分析金垦1402不同类型叶片脱叶规律及催熟效果,寻找影响该品种在脱叶剂作用下单株叶片脱落率的重要影响因素。[结果]金垦1402主茎叶、果枝叶、叶枝叶叶量均高于新陆早61号,但脱叶速度、脱叶率均高于新陆早61号,在药后21 d,脱叶效果优于新陆早61号;金垦1402药后单株吐絮铃数较新陆早61号多,且单株吐絮率高,优于新陆早61号;纤维品质指标达到“双31”以上,优于新陆早61号。[结论]金垦1402生育期119 d左右,在喷施脱叶剂后21 d,脱叶效果好,说明该品种属于对脱叶剂敏感型品种;该品种施药后,吐絮率高,纤维品质优。

玄武岩纤维沙漠砂混凝土本构关系及损伤特性研究

为了有效提高沙漠砂资源化利用,研究了玄武岩纤维掺量(0、0.3%、0.4%、0.5%)对沙漠砂混凝土本构关系和损伤特性的影响。结合本构模型拟合了玄武岩纤维沙漠砂混凝土的应力-应变曲线,利用声发射事件数分析了玄武岩纤维沙漠砂混凝土损伤破坏过程,并借助速率过程理论对玄武岩纤维沙漠砂混凝土的损伤程度进行了评估。研究表明:掺入适量的玄武岩纤维(0.4%)可以减小沙漠砂混凝土构件的损坏;Carrerira J模型与试验数据具有较高的吻合度;同时还发现构件在到达峰值应力附近时,声发射事件数会急剧增加;基于速率过程理论以损伤变量D与相对荷载V之间的关系建立的损伤演化曲线,可用来评估玄武岩纤维沙漠砂混凝土的损伤破坏程度。

动载下玄武岩纤维混凝土能量耗散特征与破坏损伤规律

本文基于分离式霍普金森压杆试验装置,在4种不同的应变率下研究了4种不同玄武岩纤维掺量混凝土的破坏行为和能量耗散特征。结果表明:随应变率的增加,不同玄武岩纤维掺量混凝土的分形维数均线性增加,掺入纤维会降低分形维数增长的速率;混凝土的入射能、反射能、耗散能均呈线性增长趋势,透射能呈轻微下降趋势。随纤维掺量的增加,不同应变率下玄武岩纤维混凝土的分形维数先增大后减小,耗散能密度呈先增大后减小再增大的“S”形趋势。随着分形维数的增长,不同玄武岩纤维掺量混凝土的耗散能密度均呈线性增长。当纤维体积分数为0.1%时,混凝土的性能最优,可承受的损伤最大。

不同截面类型玻纤增强PA6的性能

对比研究了扁平玻纤及圆形玻纤增强尼龙6 (PA6)复合材料的力学性能、流动性能、收缩翘曲情况、摩擦性能及线膨胀系数(CLTE)。结果表明,随着玻纤含量增加,扁平玻纤及圆形玻纤增强PA6复合材料力学性能均增加,但熔体流动速率(MFR)降低;相同玻纤含量下,与圆形玻纤相比,扁平玻纤增强PA6复合材料的拉伸强度、弯曲强度及弯曲弹性模量较低,简支梁缺口冲击强度及MFR较高。在玻纤含量30%的条件下,不同扁平玻纤及圆形玻纤增强PA6复合材料性能存在差异,通过收缩率测试分析,扁平玻纤复合材料比圆形玻纤具有更低的收缩率及横纵收缩比,扁平比越高,横纵收缩比越低,翘曲度越小;通过MFR及注塑螺旋线测试,发现扁平玻纤复合材料具有更好流动性、更高流长比,扁平比越高优势越明显,有利于成型加工;通过滑动摩擦测试结果看出,扁平玻纤复合材料具有更低摩擦系数,随着扁平比增大,摩擦系数越低;通过热机械分析检测,扁平玻纤复合材料在垂直流动方向CLTE低于圆形玻纤,且流动方向和垂直流动方向CLTE差异也较小。扁平玻纤增强材料能改善传统圆形玻纤增强体系的一些不足,优化产品性能。

异性纤维清除机的改进与应用

针对目前国内外异性纤维清除机清除效率较低的问题,通过自主研发核心软硬件、采用先进高可靠性元器件和技术措施对异性纤维清除机进行技术改进;详细阐述改进后异性纤维清除机的工作原理、技术参数、安装要点、喷阀参数设置、维护及故障排除措施等,并对改进关键件、改后实际检出率及性价比进行分析。指出:改进后的异性纤维清除机,解决了乱喷误喷、稳定性差、故障率高等问题,识别并检出异性纤维的能力稳定,检出率提高,各单项及综合检出率最高可达88%。

莱赛尔赛络集聚纺纱过程温湿度控制

探讨莱赛尔纤维赛络集聚纺纱过程中的温湿度控制问题。分析了莱赛尔纤维性能,得出莱赛尔纤维在纺纱各工序中的主要加工性能特点和环境温湿度要求。以纺制中高档赛络集聚纺纱线为例,介绍了纺纱主要工序空调控制方法和温湿度参数及各工序半成品回潮率控制范围。认为:莱赛尔纤维纺纱过程应增加预处理工序,需要采用偏大的相对湿度环境,并保证各工序纤维吸湿和放湿过程稳定,以减少静电,保证纤维开松、梳理顺利,减少纺纱断头。

玻璃纤维增强机制砂混凝土力学性能及收缩性能研究

为了解决机制砂性能不稳定、易收缩开裂的问题,提出了一种增强机制砂混凝土性能的方法,即采用耐腐蚀的玻璃纤维进行加固。以不同配合比的玻璃纤维增强机制砂混凝土为研究对象,制作试件共计180个,分别进行了坍落度测试、轴心抗压强度试验、抗折强度试验及收缩试验。通过对比机制砂对替代率和玻璃纤维掺量两个重要因素对玻璃纤维增强机制砂混凝土工作性能、力学性能及收缩性能的影响规律和作用原理,进一步确定机制砂对天然砂的最佳替代率和玻璃纤维最佳掺量,以推动机制砂玻璃纤维混凝土的发展与应用。

PVA-铁尾矿砂混凝土抗折性能研究

为实现固废再生利用,将铁尾矿砂部分替代细骨料并掺入PVA纤维,制备出具有良好和易性的PVA-铁尾矿砂混凝土,通过标准抗折试验研究了不同铁尾矿砂替代率与PVA纤维掺量对混凝土抗折性能的影响。研究表明,PVA纤维掺量为0%和0.1%(质量分数,下同)时试件发生贯通型开裂脆性破坏,而PVA纤维掺量为0.2%和0.3%的试件破坏时裂缝宽度明显减小且未贯通。当铁尾矿砂替代率为30%、PVA纤维掺量为0.3%时,试件跨中挠度和抗折强度均达到最大值,较普通混凝土分别提高了22.04%和6.57%。当铁尾矿砂替代率超过30%时试件抗折强度和跨中挠度会显著下降。与单掺PVA纤维相比,混掺PVA纤维与铁尾矿砂的试件变形能力增强更明显。由XRD谱可知,30%铁尾矿砂替代率下试件中C-S-H凝胶与钙矾石生成量最多,能显著提高材料强度。

中红外掺铒氟化物光纤连续激光器及其数值分析

基于产生3μm中红外激光的Er^(3+)能量转换过程与能级体系,建立了掺铒氟化物光纤激光器的速率方程和传输方程,系统地研究了泵浦结构和光纤长度对输出功率、斜率效率以及腔内泵浦和激光功率分布的影响,为后续的实验提供理论依据。仿真确定了小泵浦功率的光纤激光器理想的光纤长度为4~8 m,最终实验选择4.7 m光纤完成了中红外掺铒氟化物光纤激光器连续激光输出光路的搭建,在泵浦功率为5 W、中心波长为2.797μm处实现了最大功率1.038 W、斜率效率20.4%的连续激光输出。