High-Sensitivity Raman Gas Probe for In Situ Multi-Component Gas Detection

Multiple reflection has been proven to be an effective method to enhance the gas detection sensitivity of Raman spectroscopy, while Raman gas probes based on the multiple reflection principle have been rarely reported on. In this paper, a multi-reflection, cavity enhanced Raman spectroscopy (CERS) probe was developed and used for in situ multi-component gas detection. Owing to signal transmission through optical fibers and the miniaturization of multi-reflection cavity, the CERS probe exhibited the advantages of in situ detection and higher detection sensitivity. Compared with the conventional, backscattering Raman layout, the CERS probe showed a better performance for the detection of weak signals with a relatively lower background. According to the 3σ criteria, the detection limits of this CERS probe for methane, hydrogen, carbon dioxide and water vapor are calculated to be 44.5 ppm, 192.9 ppm, 317.5 ppm and 0.67%, respectively. The results presented the development of this CERS probe as having great potential to provide a new method for industrial, multi-component online gas detection.

Investigation of multiple Bragg reflections and their possible exploitation

This paper summarizes recent results of an exhaustive experimental study of multiple Bragg reflections accompanying allowed as well as forbidden reflections. The multiple reflection observations were carried out in the frame of Bragg diffraction optics experiments on cylindrically bent perfect single crystals. It has been found that depending on the thickness and curvature of the crystal slabs and the diffraction geometry (reflection, transmission), many strong multiple reflections can be excited which can also be used as a source of highly monochromatic and highly collimated beams for further experiments requiring extremely high resolution.

NOISE PROTECTIVE SCREENS AS MEANS OF OPTIMIZATION OF NOISE MODE

One of factors that negatively influence on an environment is noise. Noise can negatively influence on a health man. Determination of effective measures of noise rotection of workplaces became the aim of our researches. Certainly, that the most more showy measure are the so-called screens. It is significant, it is the most effective entrance of the city. They became the theme of our research. By us were the studied systems of classifications of screens. They are divided depending on such parameters: on the method of action; after a geometrical form; after an outline in a plan; after the method of arranging, on material. Defining advantages or lacks of the two following charts is impossible (id est there is not sense). They are accepted as given. Consideration of frequent is carried out from the source of noise, that it is located in a narrow corridor between an abat-voix and other obstacle. For simplification it is possible to accept the location of source of noise directly on the surface of soil: the point of source of noise is successfully approximated by a location directly on the surface of soil; distance between this surface and very had an actual mestome to the locations, easily yields to the calculation, i always can be a little rather entered in a calculation as an insignificant additional correction. If we consider reflections not from the left, but from the right screen, absolutely adequate formulas can be derived, in which (taking into account the mirror symmetry of geometric construction), the corresponding indexes are simply replaced... At some stage, the multiple reflection stops. This happens when the height of one of the reflection points exaggerates the height of one of the screens. The sound beam has nothing more to reflect, and it enters the space (to the sky). Therefore, when describing each reflection, we provide boundary conditions for its happening. A voice ray falls on a screen, and reflected from a that screen under the same corner q. It is suggested to "delete" a voice ray by us, directing him to sky above an oppositely stand-up screen after the first beating back.