The terminal phase of an unconfined hemispherical deflagration

The aerial pressure wave generated by the deflagration of a truly unconfined vapour cloud is known to be composed of a positive (overpressure) part as the flame expands, followed by a negative (underpressure) part, when the deflagration vanishes. Basically, this second part is ignored in safety predictions. The present study proposes an empirical method estimating the amplitude and the duration of the negative part of the wave, provided the mixture, the size of the cloud and the maximum flame velocity be known a priori, or estimated. This method is deduced from spherical piston flow model properties and results of small scale experiments carried out for flame spatial velocities in the range 5 to 200 m/s. Received 4 August 1995 / Accepted 12 December 1995     

中红外光纤技术用于腮腺肿瘤诊断的研究

采用傅里叶变换红外光谱法与中红外光导纤维联用技术对１１例肿瘤，７例正常腮腺和１例舍格伦综合症的红外光谱进行了对比研究。结果发现正常腮腺和舍格伦综合症的红外光谱很相似，而与肿瘤的光谱存在着明显差别，同时也观察到良性与恶性肿瘤的光谱在若干波段处也有所不同．     

Increase in dynamic modulus of nylon 6 fiber in repeated heating and cooling cycles under sinusoidal deformation

The repeated heating and cooling cycles under sinusoidal deformation have been investigated on nylon 6 fibers. The fibers zone-drawn twice at high temperatures were used, which have a crystallinity of 52.2% and a birefringence of 59.4×10^?3. The heating and cooling cycle was performed twice at a frequency of 110 Hz over a temperature range from 0°C to 180°C and 190°C. The crystallinity and birefringence of the treated fiber were 51.7% and 60.7×10^?3, respectively, indicating almost no changes in molecular orientation and crystallinity. However, the dynamic modulus, E′, increased steadily over whole temperature range measured. Finally, the E′ value reached 21 GPa at room temperature and 10 GPa ever at 180°C. The elongation of fiber after two cycles was only about 5%. © 1993 John Wiley & Sons, Inc.     

多层薄膜模型分析光纤光栅的一个新方法

光纤光栅可以看作为周期性高、低折射率相间的多层落膜叠合结构。用波动方法推导了计算这一结构总反射系数的一个新的循环公式。用这一方法计算了均匀光纤光栅布格拉格相位匹配、失配情况和非均匀光纤光栅的反射系数，并将其结果与用耦合波理论、Rouard方法以及基础矩阵方法的结果进行了比较，并检验了这些方法的精度。     

Tensile Characterization of FRP Rods for Reinforced Concrete Structures

The application of FRP rods as an internal or external reinforcement in new or damaged concrete structures is based on the development of design equations that take into account the mechanical properties of FRP material systems.The measurement of mechanical characteristics of FRP requires a special anchoring and protocol, since it is well known that these characteristics depend on the direction and content of fibers. In this study, an effective tensile test method is described for the mechanical characterization of FRP rods. Twelve types of glass and carbon FRP specimens with different sizes and surface characteristics were tested to validate the procedure proposed. In all, 79 tensile tests were performed, and the results obtained are discussed in this paper. Recommendations are given for specimen preparation and test setup in order to facilitate the further investigation and standardization of the FRP rods used in civil engineering.     

Simulation of Ultrashort Laser Pulse Propagation in Silica Fibre by FDTD+

The finite-difference time-domain algorithm is extended to solving the Maxwell's equations with nonlinear terms which include all exact Sellmeier-fitting values in this paper. The results obtained by the presented method are in good agreement with those from experiments, and this method is even better than solving the generalized nonlinear Schrödinger equation by split-step Fourier method. The spectral phase of propagated pulses is also obtained by the presented method, which is important for investigation of single-cycle optical pulse generation via phase compensation of the nonlinear-chirped in silica fibers.     

Dual-order Raman fiber laser with suppressed low-frequency pump-to-stokes RIN transfer

By employing an output-power clamping technique, a dual-order Raman fiber laser (RFL) is theoretically presented with suppressed low-frequency relative-intensity-noise (RIN) transfer from pump sources to both first- and second-order Stokes output. Their powers can be easily tuned in a large dynamic range. Furthermore, the second-order output power can be individually controlled, which makes it flexible to adjust the ratio of the first- to second-order output power. In addition, the stabilization of low-power second-order output is also accomplished in the RFL setup. These properties fit the proposed RFL for use as dual-order pump sources in Raman fiber amplifiers.     

厚二氧化硅光波导薄膜制备及其特性分析

以硅烷和氧化二氮作为反应气体，采用等离子体增强化学气相沉积(PECVD)技术，不使用掺杂，在单晶硅衬底上制备了用于平面光波导的二氧化硅薄膜。研究了薄膜折射率和淀积速率与工艺参量之间的关系，通过棱镜耦合仪、傅里叶变换红外光谱、原子力显微镜等测试手段，分析了薄膜的结构和光学特性。结果表明，实验能快速生长厚二氧化硅薄膜，薄膜表面平整，颗粒度均匀，同时薄膜具有折射率精确可控和红外透射性能好的特点，非常适合制作光波导器件。