Scaling laws and internal structure for characterizing electrospun poly[(R)-3-hydroxybutyrate] fibers

Using chloroform/dimethylformamide (CF/DMF) co-solvent, electrospinning of poly[(R)-3-hydroxybutyrate] (PHB) solutions was carried out at ambient temperature. The effects of the applied voltage (V), flow-rate (Q), and solution viscoelastic properties on the Taylor cone, electrified jet, and fiber morphology were investigated. In addition, the electric field developed by the needle-plate electrode configuration was calculated using a finite element analysis to reveal the tip-to-collector (H) effect. Among the processing parameters (V, Q and H), it was found that Q played a key role in determining the jet diameter (d_j) and electrospun fiber diameter (d_f), and scaling laws existed between them, i.e., d_j-Q^0.61 and d_f-Q^0.33. The diameter reduction ratios of D_o/d_j (D_o is the needle diameter) and d_j/d_f were measured as 50-120 and 5-10, respectively; it suggested that major jet stretching took place in the straight electrified jet region, and further chain orientation could be gained by the subsequent process of jet whipping. By changing PHB concentrations from 5 to 15 wt%, the solution viscosity (η_o) was increased from 100 to 4900 cP, whereas the surface tension and solution conductivity remained unchanged; it provided a good model solution to exclusively reveal the η_o effect on the electrospinning process. Our results showed that the η_o-dependence of d_j and d_f also followed simple scaling laws: d_j-η_o^0.06, and d_f-η_o^0.39, with a prefactor depending on the processing variables, mainly the flow-rate. Regardless of the PHB concentrations used, the obtained PHB fibers showed a similar crystallinity fraction of ca. 0.63 and possession of major α-crystals together with a small amount of β-crystals with zigzag chain conformation.     

Studies on jute–asphalt composites

The tensile properties of jute make it a suitable raw material for asphalt overlay (A/O) fabric. In this study, the thermal stability of jute under conditions of asphalt overlaying process was investigated and the compatibility of jute with asphalt was assessed through experimentation on jute–asphalt composites under mechanical and hygral loads. Fourier transform infra red (FTIR) spectroscopic study revealed probable chemical bonding between jute and asphalt. The test for ascertaining the capability of asphalt encasement for protecting jute against biodegradation under enzymatic attack was found positive. A 6‐month hygral treatment, of the jute–asphalt composite, showed significant increase in modulus of the material. The results indicate that although the strength of jute deteriorates by about 10% under asphalt overlaying condition, the overall tensile behavior of jute fabric–asphalt composite material is considerably superior to that of the pure jute fabric, even under biological and extended hygral loading conditions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

A study on dynamic friction of different spun yarns

This article presents the results from a study of yarn-to-yarn (YY) and yarn-to-metal (YM) frictions conducted on ring, rotor, air-jet, and open-end friction (OE friction) spun yarns at different relative speeds and input tensions. The results indicate that the behavior of frictions for YY is different than that of YM. In case of YY friction, OE friction yarn shows maximum friction followed by rotor, air-jet, and ring spun yarns; however, a reverse order is noticed for YM friction. The relative speed and input tension have significant influence on the frictional behavior of spun yarns. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

一种基于FBG和LPG的温控报警模型

文章依据FBG温度传感的原理以及LPG滤波技术,提出了一种新的光纤光栅温度报警模型.用MATLAB对系统所采用的方法进行了模拟,结果表明该系统能满足温度报警的要求.     

OPGW应用问题的探讨

根据多年的光纤复合架空地线(0PGW)应用经验与实践，从0PGW结构及组成、光纤余长、线路配合、金具配套、0PGW安装等方面，对0PGW应用中的若干问题进行详细的探讨。     

Continuous hydrogen evolution from cyclohexanes over platinum catalysts supported on activated carbon fibers

The continuous production of hydrogen from cyclohexanes is achieved effectively using Pt/ACF (ACF = activated carbon fiber) catalysts in a fixed-bed flow reactor. The Pt catalysts are more effective than a Pd/ACF catalyst for the reaction. Besides cyclohexane, methylcyclohexane, 1,4-dimethylcyclohexane, and p-menthane can also be employed as hydrogen source in the reaction system.     

数字分量电视图像的光纤传输实验

介绍了光纤传输数字电视的意义，电视信号分量数字化的标准和优点。利用自行研制的２７０Ｍｂ／ｓ光发射机和光接收机，建立了分量数字电视信号的光纤传输系统，直接传输了１００ｋｍ光纤，系统传输无误码，传输后图像质量不变。光接收机灵敏度达－２９．２４ｄＢｍ，动态范围为１３．５ｄＢ。无压缩电视图像的传输对于远程医疗和演播室间转输节目等有非常实际的意义。     

一种新型的基于LP01模的双模色散补偿光纤

通过计算机模拟发现在可传输双模的三包层色散补偿光纤中如果抑制ＬＰ０２模，而仅传输ＬＰ０１模时能在一个较窄的带宽内产生大于数千ｐｓ／ｎｍ·ｋｍ的负色散，并且具有较大的模场直径、较小的弯曲损耗和偏振模色散，另外还具有较小的温度波长漂移以及同其它色散补偿光纤一样大小的损耗，是一种非常有前途的新型色散补偿光纤     

自聚焦光纤对半导体激光束的准直研究

介绍了一种新颖的利用自聚焦光纤对半导体激光束的准直技术。该方法结构简单、调整方便。实验研究表明其可使大发散角的半导体激光束压缩到0.01º的数量级,适合作半导体激光器的准直元件而运用于精密测试领域。     

差动光栅在精密测试中的应用

提出差动光栅概念,举例说明差动光栅在光纤面板刀口响应测试和材料形变自动监测系统等精密测试中的应用。