Gas Stratification Research Articles

Clinical risk factors and periventricular leucomalacia.

Two hundred infants of below 1501 g at birth were regularly examined with real time ultrasound using a 7.5 MHz transducer. Abnormalities were categorized as periventricular haemorrhage (PVH) (n = 107) or periventricular leucomalacia (PVL), with or without PVH (n = 52). Of the group with PVL, 25 had the appearances of prolonged flare without cavitation. Prospective assessments of up to 50 potential clinical risk factors were made wherever possible on each infant including stratification of all blood gas and systolic blood pressure data. Multivariate logistic regression analyses confirmed a strong correlation between immaturity and PVH but this was not found in cases of PVL. Independent variables associated with PVL included pneumothorax, maximum bilirubin concentration, surgery, and the proportion of time the infant's PaCO2 remained above 7 kPa. There was a very strong inverse correlation between anaemia and PVL. Systolic blood pressure data were carefully analysed and there was no relation between either hypotension or antepartum haemorrhage and the development of PVL.

Some effects of gas stratification on choked nozzle flows.

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Geology of Subsurface Fluids--Problems and Research Needs: ABSTRACT

Oil and gas occupy the pore spaces of sedimentary rocks in petroliferous basins to the extent of the order of 1 part per 100,000; below shallow depths the remainder of the pore space is filled with water. Hence, oil and gas originate, migrate, and become stably trapped in a rock-water environment. From an initial state of dispersion elementary volumes of oil or gas are driven by physical forces to positions of concentration and entrapment. The direction of these forces is from regions of higher environmental energy for the given fluid to lower--energy regions; and traps for a given fluid are regions of local minimum potential energy. The search for oil and gas thus reduces itself to a search for regions of minimum potentials for these two fluids. These, in turn, depend on the density and state of motion of the ambient water as well as on the geometrical configuration of the rocks. Petroleum geology, to the extent that it is to become a rational, rather than an empirical science, must therefore ultimately be based on a comprehensive knowledge of the mutual relations of the rock-water-oil (or gas) complex. Out of such knowledge, it is seen that the conventional horizontal stratification of gas, oil, the water is true only for the special case of hydrostatics. For the general dynamical case, when the water is in motion, traps for gas and those for oil do not coincide. Furthermore, it is possible for such traps to exist in almost any structural position from the crests of anticlines to the troughs of synclinal basins. End_of_Article - Last_Page 2074------------

The Application of Radiation Measurement Techniques to the Determination of Gas Temperatures in Liquid Propellant Flames

Radiation temperature measurements were made throughout the flame developed within an open-tube combustor using liquid oxygen and a heptane-turpentine mixture as the reactants. The temperature measurement technique applied was the two-color radiation method. Observed absolute temperature measurements did not agree with theoretical equilibrium flame temperatures in most cases. The results can be explained by the existence of one, or a combination of three conditions within the chamber: (a) gas temperature stratification; (b) lack of thermodynamic equilibrium; and (c) optical effects such as selective absorption and scattering of light. These conditions limit measurements to qualitative observations concerning absolute temperatures as a function of flame position and time. In general, gas stratification effects were found to become more pronounced as the flame was made increasingly fuel rich. Flame temperatures were found to vary inversely with the radiation intensity, and fluctuating temperatures were found to exist at a frequency compatible with an acoustical mode of the chamber, even when sound oscillations of the same frequency were not apparent. Very high frequency oscillations of tempera­ ture, emissivity, and radiation were also found.

A suggestive x-ray sign of strangulation in intestinal obstruction.

STRANGULATION is a serious threat to life in intestinal obstruction. When this complication develops, immediate diagnosis and surgical intervention are mandatory to avoid mortality. Proper diagnosis of strangulation requires the integration of history, physical examination, laboratory study, and radiologic signs. It is the purpose of this report to draw attention to certain radiologic features occasionally found in intestinal obstruction which are highly suggestive of strangulation although not commonly recognized. Once a mechanical barrier to the normal passage of fluid and gas along the intestinal tract develops, a sequence of events ensues which produces wellknown signs and symptoms. Associated with these are characteristic radiologic findings which result from the accumulation and stratification of gas and fluid in distended loops of intestine. These include hairpin turns, stepladder arrangement of coils, central distribution of gas and fluid-filled segments of small bowel, and little or no gas distal to the point of obstruction. Great

The Fuel-Bed Tests at Hell Gate Generating Station, 1937-1938

Abstract This paper is a final report on fuel-bed tests at Hell Gate Generating Station and includes some of the conclusions reached in the authors’ study of the data up to this time. The fuel bed of a multiple-retort underfeed stoker is shown to consist of vertical strata parallel to the center lines of the retorts and tuyère stacks in which coking and ignition processes occur along the entire length of the stoker. The actual burning of the carbonized fuel occurs largely by overfeed action in the burning lanes where the temperature and pressure gradients are determined by the rate of primary-air flow, and the gases, rising from the burning lanes, may require the addition of secondary air for complete combustion. It is shown that control of the contour of the fire in operating practice may affect not only the amount of coke blown from the fire and the degree of gas stratification in the boiler passes, but also the severity of treatment to which the stoker iron is subjected.

Recent Developments in the Burning of Anthracite

Abstract The anthracite referred to is that of which at least 95 per cent will pass through a 3/16-in. round-mesh screen and less than 20 per cent through a 3/32-in. round-mesh screen. The coal was burned on Coxe stokers. The paper describes successive furnace designs made at the Amsterdam (N. Y.) steam station of the Adirondack Power and Light Corporation. The boilers are of Babcock & Wilcox design and of 1345 hp. Each boiler has two Coxe stokers. Attempts were made to improve on the customary furnace design to which the following objections are made: (a) tendency to stratification of gases, (b) high carbon content of ash, (c) loss of fines to ashpit and stack, and (d) lack of flexibility. The first experimental furnace had, in addition to the ignition arch, a very short arch over the rear of the grate. With this arrangement improvement, if any, was slight. A three-arch furnace was then built, with better results but with defects due to slagging. A third furnace of two-arch design was finally constructed. Tests reported in the paper show that with the final design stratification can be practically eliminated, as well as ignition troubles, even with low-grade coal. A decided improvement has also been made in the burning of undersizes. Greater capacity was obtained with low-grade coal (60 per cent undersize and 33 per cent ash) in the multiple-arch furnace, where 300 per cent of rating was easily reached, than in the single-arch furnace where 190 per cent was about the limit. The boilers and furnaces are described and illustrated, and a description of the tests with the principal data and results are given in the form of curves.