Polarization maintaining holey fibers for residual dispersion compensation over S + C + L wavelength bands

We report on a highly birefringent holey fiber for broadband dispersion compensation covering the S, C, and L telecommunication bands i.e. wavelength ranging from 1460 to 1625 nm. The finite element method with circular perfectly matched layer boundary condition is used to investigate the guiding properties. Numerical analysis demonstrates that it is possible to obtain negative dispersion coefficient of about −470 to −850 ps/nm/km over S to L-bands and a relative dispersion slope perfectly matched with single mode fiber (SMF) of about 0.0036 nm⁻¹ at 1550 nm. At the same time birefringence of the order 2.53 × 10⁻² is realized at 1550 nm wavelength. Owing to superior optical properties of the proposed holey fiber, this can be a promising candidate for broadband dispersion compensation and sensing applications.     

Design of single polarization single mode dispersion compensating photonic crystal fiber

In this paper, we present a photonic crystal fiber based on hexagonal structure for improved negative dispersion as well as high birefringence in the telecom wavelength bands. It is demonstrated that it is possible to obtain negative dispersion coefficient of −712 ps/(nm km) and relative dispersion slope (RDS) perfectly match to that of single mode fiber (SMF) of about 0.0036 nm⁻¹ at the operating wavelength 1550 nm. The proposed fiber exhibits high birefringence of the order 2.11 × 10⁻² with nonlinear coefficient about 57.57 W⁻¹ km⁻¹ at 1550 nm. Moreover, it is confirmed that the designed fiber successfully operates as a single mode in the entire band of interest.     

SQUID用于铍材残余应力检测的计算机模拟

依据SMM-601型超导量子干涉显微镜检测部分构建计算模型,采用电磁场有限元方法分析了残余应力引起的非磁性金属材料铍电导率变化对超导量子干涉仪(SQUID)检测信号的影响,并讨论了该方法实际应用于非磁性金属材料残余应力检测的条件和可能性。     

Combined implementing the hole-drilling method and reflection hologram interferometry for residual stresses determination in cylindrical shells and tubes

Main features inherent in simplified approach to residual stresses determination in cylindrical shells and tubes, external diameter of which is not less than 60 mm, by combing the hole-drilling method and reflection hologram interferometry are discussed in detail. Initial experimental information in a form of hole diameter increments in principal stress directions is derived from high-quality reflection holograms recorded near cylindrical objects of intermediate curvature value. Converting measured parameters into required stress values is based on the transition model that corresponds to plane stress conditions of pure membrane type. The technique developed is capable of determining residual stress component values within 5% accuracy in an absence of stress gradients over the probe hole diameter when a type of residual stress field corresponds to the transition model adopted. The accuracy analysis involved is based on matrix formulation of conventionally direct problem and an assumption on a pure membrane character of residual stress field under study for thin-walled shell. Required error estimations in a case of inspecting thick-walled cylindrical tube are obtained by combining the above-mentioned approach and an analogy of reconstructed fringe patterns with actual and artificial interferograms, which follow from drilling blind hole of the same geometrical parameters in thick-walled plates. Experimental verification of the developed approach is founded upon a determination of actual stresses in thin-walled cylindrical shell and obtaining residual stress distributions at the proximity of welded joint in thick-walled cylindrical tube.     

Flow system to gas capture from a nebulized solution

The use of aerosol produced in a nebulization chamber is proposed as an alternative to gas sample capture in flow systems. This paper describes the coupling of a sampling interface with a flow system, for in situ gas monitoring. Aspects related with the behavior of aerosol formation and gas solubilization in liquid drops are discussed. The method is applied to the determination of residual lime in acidic soils. Aliquots of 5.0 ml of 1.0 mol l⁻¹ HCl were mixed with soil samples (1 g). The CO₂ released from these samples was captured by a nebulized aerosol and determined conductivity. The analytical curve from 1.0×10⁻² to 5.0×10⁻² mol kg⁻¹ CaCO₃ was ploted applying the matrix matching approach. This proposition, allowed an increase in the sensibility with detection limit of 6.0×10⁻³ mol kg⁻¹. The precision was good (R.S.D. <3%) for an analytical frequency of 22 determinations per hour. A fair agreement, at 95% confidence level, was found between the results from the proposed method and certified values of the investigated samples.     

Unknown residual solvents identification in drug products by headspace solid phase microextraction gas chromatography-mass spectrometry

Summary A sensitive headspace SPME method for the extraction of residual solvents from pharmaceutical products has been developed and optimized. It was found that minimizing sample and headspace volume has a beneficial effect on extraction efficiency. At the same time the method reproducibility was seriously affected by reducing sample and headspace volume. The added air volume was not found to have any significant influence on method sensitivity. The method showed reproducibilities of less than 10% and detection limits as low as 1 ppb for benzene and dichloromethane. The headspace SPME method is around 1000 times more sensitive than static headspace. The optimized parameters were headspace volume 1.5 mL, sample volume 10 μL, and extraction time 30 min. The method was successfully applied to the identification of unknown residual solvents in three different proprietary active drug substances and was successfully applied to the confirmation of the presence of benzene in a proprietary drug substance. Presented at Balaton Symposium '01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001     

Novel correlations between the critical constants of the noble gases

For any particular fluid, the set of three critical constants (CC) – pressure P_c, temperature T_c and molar volume V_c – has a central importance in defining the physical behaviour of the fluid in the gas and liquid states. However, little attention seems to have been paid in the past to the relations between the CC of different substances. In the present paper, some simple and apparently novel relations have been found between the three CC for the set of four noble gases: Ne, Ar, Kr, Xe. Defining the critical quotient Q_c ≡ RT_c/P_c (where R is the Gas Constant) the correlations may be summarised by the dual equation: (V_c/cm³ mol⁻¹) = 27 + 0.31 (T_c/K) = 3.3 + 0.280 (Q_c/cm³ mol⁻¹), which describes the CC data for the quartet Ne–Xe with an average uncertainty of 0.5%. Regarding the other two noble gases, the two isotopes of the lightest member, ³He and ⁴He, show the deviations from these relations that are expected from quantal effects and their low molar masses; while for the heaviest member, Rn, the correlations enable a value of 145(5) cm³ mol⁻¹ to be estimated for V_c that is not otherwise well defined in the literature. By contrast, and contrary to the general assumption, the second lightest member, Ne, apparently does not show appreciable quantal effects in the area, so that Ne–Xe may be considered together as a group. These correlations are compared with the behaviour of a selection of polyatomic fluids; in these comparisons, the NG dual correlation equation provides a reference line defining the presumed simplest behaviour. This and related areas show a “Residual Volume Effect”, in that extrapolating the equivalent temperature and energy parameters to zero for the state of zero-mass point particles, referred to here as the hypothetical element zeronium (Ze), the system in each case still has a finite intercept; this intercept amounts to essentially 34% of the average volume for the present quartet Ne–Xe, rather than the zero volume expected for this condition.     

Micro–macro approach for the rock salt behaviour

Rock salt is considered as a pure aggregate of halite (mineral NaCl) crystals and its behaviour is investigated by a micro–macro approach. The behaviour of the polycrystalline aggregate is deduced from the properties of the constituent halite crystals. A model for the elastoplastic behaviour of halite crystal has been deduced from experimental data available in the literature. The basic equations of the micro–macro model for the polycrystalline medium and the calculation method are then presented and the elastoplastic behaviour of rock salt is investigated by this method. The hardening effects obtained for the polycrystal are found to be very different from those obtained for FCC metal polycrystals. The differences are explained as a consequence of differences of families of glide systems in these crystals. Finally, the internal stresses in the polycrystal are studied in order to elucidate the origin of cracking and damage of the rock salt.     

On Thermal Contact of Two Axially Symmetric Elastic Solids

A contact problem of two elastic convex and axially symmetric solids heated (or cooled) to temperatures of different values is considered. Pertinent formulae have been derived for relations between the contact pressure, geometrical characteristics of the solids and distributions of heat flux over the contacting region. We have analysed: 1. The problem of the loss of the contact between two solids pressed together with active heat fluxes. We discuss the cases for which the contact of the axially symmetric solids can take the form of a circle, or an annulus. 2. The problem of a paradox when the mathematically well posed contact problem of thermoelasticity leads to a physically unacceptable solution with a region of overlapping materials. Here we discuss a generalization of the cooled sphere paradox. The heat flux functions are continuously differentiable, of constant sign. The conditions have been derived for the cases when the paradox can be avoided.     

局部载荷作用简支板屈曲分析

根据能量原理,引入大挠度Von-Karman方程,求解了应力不连续简支板的屈曲问题,得到了临界载荷和临界应力计算系数.