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The diffusion of hydrogen adsorbed inside layered MoS2 crystals has been studied by means of quasi- elastic neutron scattering, neutron spin-echo spectroscopy, nuclear reaction analysis, and X-ray photoelectron spectroscopy. The neutron time-of-flight and neutron spin-echo measurements demonstrate fast diffusion of hydrogen molecules parallel to the basal planes of the two dimensional crystal planes. At room temperature and above, this intra-layer diffusion is of a similar speed to the surface diffusion that has been observed in earlier studies for hydrogen atoms on Pt surfaces. A significantly slower hydrogen diffusion was observed perpendicular to the basal planes using nuclear reaction analysis.
Many fluids transported by pipelines are in some sense hazardous. It is therefore often necessary to install leak detection (and locating) systems (LDS), especially due to legal regulations like the "Code for Federal Regulations (CFR) Title 49 Part 195", API 1130 2nd Ed., both for the USA, or the "Technische Regeln für Fernleitungen" (TRFL) (Technical Rules for Pipelines) in Germany. This paper gives a survey of methodologies, methods and techniques for leak detection and locating. The survey starts with some remarks concerning (legal) regulations both for the USA and for Germany. Some few words about externally based systems (due to API 1130 2nd Ed.) follow next. A significant part of the paper deals with internally based systems (also due to API 1130 2nd Ed.) like balancing systems (line balance, volume balance, compensated mass balance etc.), Real Time Transient Model LDS (RTTM-LDS), pressure/flow monitoring and statistical analysis LDS. Different methods for leak locating (gradient intersection method, wave propagation analysis etc.) will also be shown. The presentation of an Extended RTTM approach (E-RTTM) combining advantages of conventional RTTM LDS and statistical analysis follows next, together with the demonstration of applicability by means of two examples, a liquid multi-batch pipeline, and a gas pipeline. Sketching future work and the conclusion conclude the survey.
