Weld corrosion in urea synthesis

Corrosion of 316L stainless welds in urea synthesis systems is not due to preferential attack of ferrite, but to dissolution of sigma phase formed from ferrite by successive weld passes. Proper element balancing of 316L filler metal, or welding with Alloy 20 or a high nitrogen 316 weld eliminates this problem.     

Modern techniques in reflectance measurements

In the field of quantitative investigation of microscopic images reflectance measurements with the aid of photoelectric equipment play an important role. Reflectances can be used for the identification of various components in a polished specimen, for chemical analysis and for the determination of the refractive index of a specimen as well as for a determination of the various absorption parameters of reflecting solid material. The parameters involved are: reflectances at given wavelengths, spectral reflectance curves in the visible, UV-, and near IR-spectral range, reflectances of optically anisotropic surfaces at varying orientations of the vibration plane of linearly polarized light, reflectances in air and in an immersion liquid (mainly in standard immersion oil). From spectral curves, quantitative expressions of colour can be derived. Due to improvements in reflectance standard materials and technical design of apparatus the measurements and calculations can be carried out very conveniently, quickly and precisely.     

Open systems interconnection — the teletex-based session protocol: Part 1

Two draft proposals for an international standard for the teletex-based session protocol have now been considered by the ISO. The ECMA 75 protocol has been found to be relatively complex as a result of ECMA having to sort out some weak points within the protocol. S.62, proposed by the CCITT, is quite suitable for the kernel of the session service, but not for the entire service. The paper suggests possible developments towards an international standard, and discusses the specification of the BAS subset. It then examines the services available, and how they operate. A proposal for a standard for service conventions is presented, along with a summary of the parameters of the service elements.     

Analytical and experimental investigations of the vibrations of a hollow blade model of turbines

The practice of using air-cooled blades for the increased efficiency of turbine stage is a recent feature with advanced aero-engines. The objective of the present paper is to describe the results of numerical and experimental investigation of the dynamical behaviour of hollow cross-sectioned blades. The analytical method consists in modelling the blades by means of a finite-element method to determine the natural frequencies and normal modes of a hollow cross-sectioned blade model. Numerical results are compared with experimental values obtained from holographic tests.