THEORETICAL AND EXPERIMENTAL STUDY OF POLARIZATION CHARACTERISTICS OF POLARIZATION MAINTAINING FIBER BASED ON WAVELENGTH-SWEEPING MODULATION

We analyze theoretically the polarization characteristics of polarization maintaining fiber and study the basic measurement principles of beat length and polarization extinction ratio of this kind of optical fiber. According, to the dependence of the phase difference between two orthogonally polarized modes (denoted Os HE(11)(x) and HE(11)(y)) transmitted in the polarization maintaining fiber on the light wavelength, we propose the wavelength-sweeping modulation method to measure the beat length and the model birefringence. Based on this technique, the hew length and polarization extinction ratio of the PANDA polarization maintaining fibers (PMFs) (provided by Yangtze Optical Fiber and Cable Company, Wuhan, China) were investigated in detail. Experimental results show good consistent with the theoretical ones. We find that this method shows high measurement precision with the advantages of clear measurement principle and easy to operate. 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1466-1469, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25244

A NEW WAKE OSCILLATOR MODEL FOR PREDICTING VORTEX INDUCED VIBRATION OF A CIRCULAR CYLINDER

This article proposes a new wake oscillator model for vortex induced vibrations of an elastically supported rigid circular cylinder in a uniform current. The near wake dynamics related with the fluctuating nature of vortex shedding is modeled based on the classical van der Pol equation, combined with the equation for the oscillatory motion of the body. An appropriate approach is developed to estimate the empirical parameters in the wake oscillator model. The present predicted results are compared to the experimental data and previous wake oscillator Model results. Good agreement with experimental results is found.

Controlling parameter for wave types of long flexible riser undergoing vortex-induced vibration

Submerged floating tunnel (SFT) is a popular concept of crossing waterways. The failure of the cable may occur due to vortex-induced-vibration (VIV), and the stability of the cable is crucial to the safety of the entire tunnel. Investigation results in recent years show that the vortex-induced vibration of the flexible cables with large aspect ratio reveals some new phenomena, for example, the vortex-induced wave, multi-mode competition, wide band random vibration, which have brought new challenges to the study of vortex-induced vibration of long flexible cables. In this paper, the dimensionless parameter controlling the wave types of dynamic response of slender cables undergoing vortex-induced vibration is investigated by means of dimensional analysis and finite element numerical simulations. Our results indicate that there are three types of response for a slender cable, i.e. standing wave vibration, traveling wave vibration and intermediate state. Based on dimensional analysis the controlling parameter is found to be related to the system damping including fluid damping and structural damping, order number of the locked-in modes and the aspect ratio of cable. Furthermore through numerical simulations and parameter regression, the expression and the critical value of controlling parameter is presented. At last the physical meaning of the parameter is analyzed and discussed.

电子辅照耐高温（电缆用）高分子材料改性的研究

本文以高密度聚乙烯（HDPE）为基料研制出电子辐照耐高温阻燃电线电缆绝缘材料，并对HDPE的辐射交联机制进行了讨论，辐射交联不仅发生在无定形区，结晶区对交联有贡献．对抗氧剂、敏化剂、炭黑、阻燃剂等对材料交联性质的影响做了一些试验，总结出一些规律，尤其对敏化剂在HDPE交联中的作用做了合理的阐述．阻燃剂对材料耐温等级提高很大，而且辐射交联后氧指数有所提高， 研究了HDPE与乙烯一醋酸共聚物（EVA)共混辐照后的一些性 质,EVA对HDPE的改性的有利与不利之处，还进一步探讨了用三元乙丙橡胶(EPDM),硅橡胶、氟材料来提高体系耐温等级和其它性能的办法． 耐高温皿燃线缆材料具有非常广泛的用途，它的耐温等级为135℃,氧指数可达30以上．该成果具有非常广泛的用途，填补了国内空白，为辐射加工产业化做出一定贡献．

Pressure Effects on the Structural, Electronic, and Optical Properties of Si-n@SWCNTs

Well-ordered single, double/four parallel, three/four-strands helical chains, and five-strand helical chain with a single atom chain at the center of Si nanowires (NWs) inside single-walled carbon nanotubes (Si-n@SWCNTs) are obtained by means of molecular dynamics. On the basis of these optimized structures, the structural evolution of Si-n@SWCNTs subjected to axial stress at low temperature is also investigated. Interestingly, the double parallel chains depart at the center and transform into two perpendicular parts, the helical shell transformed into chain, and the strand number of Si NWs increases during the stress load. Through analyzis of pair correlation function (PCF), the density of states (DOS), and the z-axis polarized absorption spectra of Si-n@SWCNTs, we find that the behavior of Si-n@SWCNTs under stress strongly depends on SWCNTs' symmetry, diameter, as well as the shape of Nws, which provide valuable information for potential application in high pressure cases such as seabed cable.

Synthesis and characterization of polyethylene chains grafted onto the sidewalls of single-walled carbon nanotubes via copolymerization

Polyethylene (PE) chains grafted onto the sidewalls of SWCNTs (SWCNT-g-PE) were successfully synthesized via ethylene copolymerization with functionalized single-walled carbon nanotubes (f-SWCNTs) catalyzed by rac-(en)(THInd)(2)ZrCl2/ MAO. Here f-SWCNTs, in which alpha-alkene groups were chemically linked on the sidewalls of SWCNTs, were synthesized by Prato reaction. The composition and microstructure of SWCNT-g-PE were characterized by means of H-1 NMR, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analyses (TGA), field-emission scanning electron microscope (FESEM), and transmission electron microscope (TEM). Nanosized cable-like structure was formed in the SWCNT-g-PE, in which the PE formed a tubular shell and several SWCNTs bundles existed as core. The formation of the above morphology in the SWCNT-g-PE resulted from successfully grafting of PE chains onto the surface of SWCNTs via copolymerization. The grown PE chains grafted onto the sidewall of the f-SWCNTs promoted the exfoliation of the mass nanotubes. Comparing with pure PE, the physical mixture of PE/f-SWCNTs and in situ PE/SWCNTs mixture, thermal stability, and mechanical properties of SWCNT-g-PE were higher because of the chemical bonding between the f-SWCNTs and PE chains.

A moored underwater energy conservation system for profiling measurement

There is a need to obtain the hydrologic data including ocean current, wave, temperature and so on in the South China Sea. A new profiling instrument which does not suffer from the damage due to nature forces or incidents caused by passing ships, is under development to acquire data from this area. This device is based on a taut single point mid-water mooring system. It incorporates a small, instrumented vertically profiling float attached via an electromechanical cable to a winch integral with the main subsurface flotation. On a pre-set schedule, the instrument float with sensors is winched up to the surface if there is no strip passing by, which is defined by an on-board miniature sonar. And it can be immediately winched down to a certain depth if the sonar sensor finds something is coming. Since, because Of logistics, the area can only be visited once for a long time and a minimum of 10 times per day profiles are desired, energy demands are severe. To respond to these concerns, the system has been designed to conserve a substantial portion of the potential energy lost during the ascent phase of each profile and subsequently use this energy to pull the instrument down. Compared with the previous single-point layered measuring mode, it is advanced and economical. At last the paper introduces the test in the South China Sea.

基于无线通信的阀门泄漏检测系统

阀门泄漏的在线监测一直是困扰流程工业的难题,采用传统有线监控方式需要巨大的布线安装成本。本文通过结合无线通信技术和超声检测技术,研究并开发了一种基于无线通信的阀门泄漏检测系统,可极大地降低测控系统的投资和使用成本,通过实时检测阀门的工作状态,及时发现并定位泄漏位置,实现工业生产的节能降耗。

一种新型柔索驱动并联机器人的模型样机

提出一种新型并联机器人机构 ,利用张紧柔索驱动该并联机器人·通过运动学和动力学分析、工作空间分析、轨迹规划、误差分析 ,设计并制作了模型样机本体、驱动与控制模块 ,开发了机器人语言 ,控制模型样机完成指定动作·实验结果表明 ,这种新型并联机器人是可行的 ,适用于轻型机床等设备·该机器人在某一速度范围内工作时 ,会产生较明显的振动 ,并伴有噪声 ,因此要提高机器人的性能还必须设法抑制其振动

自由表面上球形浮体的拖曳运动仿真与试验

浮体在自由表面上的拖曳是一种常见的拖曳形式,由于自由表面上物体的运动情况相当复杂,目前对这种拖曳系统的设计和分析一般采用试验的方法。通过理论分析,对球形浮体在自由表面上的匀速直线拖曳运动建立了数学模型,其中对缆绳的分析采用Ablow-Schechter提出的有限差分模型,对球形浮体的分析采用水动力系数法,整个耦合系统用有限差分方法求解。之后,在拖曳水池进行了试验,试验结果表明,这种方法在拖曳速度比较低的情况下能够模拟真实情况,可以用来指导拖曳系统设计。

光纤微缆对SARV操纵性的影响分析

以新概念小型自治遥控水下机器人SARV及其光纤微缆系统为研究对象,在对光纤微缆进行受力分析的基础上,采用集中质量法建立了光纤微缆的动力学模型。结合作业中SARV载体的实际运动,利用直接计算法分析了不同运动状态下光纤微缆对SARV载体产生的附加力和附加力矩及其对SARV载体操纵性的影响,并提出了合理的操纵建议。为SARV载体端设计光纤微缆释放装置张力控制提供了一定的理论依据,在一定程度上有助于完善SARV控制系统,提高SARV航行的稳定性。

SARV光纤收放装置的控制系统设计与实现

根据小型自治遥控水下机器人SARV的运动特性,研制了光纤微缆收放的控制系统。设计使用了嵌入式QNX软件开发技术,系统稳定可靠。采用系统辨识的方法,获得被控对象的等效数学模型。采用单神经元自适应PID控制器对控制参数进行在线自调节,实现了SARV在水中运动时光纤收放的恒张力控制,满足光纤收放装置的设计要求。

SARV光纤微缆收放系统的研究与设计

通过对光纤微缆的受力分析,结合光纤微缆的特点设计并实现了光纤微缆收放系统.该系统采用恒张力控制收放光纤微缆,使光纤微缆随着水下机器人的运动释放和回收,减小了光纤微缆对水下机器人运动的影响,避免了光纤微缆的缠绕和损伤.

采用普通双绞线远距离传输动力、图像、双向数据的方法

论述了一种在一对普通动力双绞线上实现直流动力、彩色图像和双向数据的远距离实时传输方法,详细介绍了其工作原理、电路设计和试验结果。

水下机器人光纤微缆动力学研究

讨论了水下机器人远程通信光纤微缆的动力学问题,研究分析了在海洋层流条件下水下机器人的运动对光纤微缆张力的影响,在仿真分析的基础上提出了对光纤微缆收放系统的设计要求并给出了概念设计方案。