scholarly journals VI. On the heat dissipated by a platinum surface at high temperatures. Part IV. Thermal emissivity in high-pressure gases

1901 ◽  
Vol 197 (287-299) ◽  
pp. 229-254 ◽  
Keyword(s):  
Atmospheric Pressure ◽  
High Pressures ◽  
Unit Length ◽  
Electrical Energy ◽  
Perfect Gas ◽  
Platinum Surface ◽  
Thermal Emissivity ◽  
The Subject ◽  
Rate Of Cooling ◽  
Energy Dissipated

The question of the heat dissipated by a hot body in gases at ordinary pressures has received considerable attention during recent years. The subject has been experimentally treated in many different ways. The rate of cooling of a body of known specific heat has been directly measured by Dulong and Petit, Narr, Macfarlane, Nichol, Stefan, Brush, Bottomley, Winkelmann, Kundt, and Warburg, Eckerlein, Graetz, &c. By Christiansen’s method, the value of the conductivity has been derived from the fall of temperature per unit length along the axis of a cylinder carrying a constant flow of heat. Schleierm acher, Sala, Ayrton, and others have preferred to measure the quantity of electrical energy dissipated per unit time. These experiments have, however, been carried out at or below the atmospheric pressure, and the question of the heat dissipated in gases at high pressures has rarely been touched upon. From the ordinarily accepted principles of the Kinetic theory of gases, it may be shown that the conductivity of any perfect gas is independent of pressure. The experimental work of Stefan and of Kundt and Warburg has gone far to confirm this law as far as ordinary pressures are concerned. It will be seen, however, that at higher pressures, only a small proportion of the loss of heat is due to conductivity, and the question as to whether the theoretical law is strictly correct, though well worth investigation, is not of primary importance. For the above reasons the present work has been restricted to a study of the total heat dissipated at exceptionally high pressures and temperatures.

On the heat dissipated by a platinum surface at high temperatures. Part IV.—High-pressure gases

1901 ◽  
Vol 68 (442-450) ◽  
pp. 246-247
Keyword(s):  
Experimental Investigation ◽  
High Pressure ◽  
High Temperatures ◽  
High Pressures ◽  
Water Circulation ◽  
Platinum Surface ◽  
The Subject ◽  
Rate Of Cooling

The rate of cooling of a hot body in gases at pressures up to one atmosphere has received considerable attention, but with regard to gases at high pressures practically no data were up to the present available. It was thought therefore that an experimental investigation of the subject might prove of some interest. The experiments were carried out with a horizontal cylindrical radiator contained in a strong steel enclosure, the enclosure being maintained at about 18° C. by a water circulation.

Microstructural Characterization of High-Pressure Oxidized Si1-x Gex /Si Heterolayers

1992 ◽  
Vol 280 ◽  
Author(s):  
N. David Theodore ◽  
Gordon Tam
Keyword(s):  
Heterojunction Bipolar Transistors ◽  
Atmospheric Pressure ◽  
High Pressures ◽  
Microstructural Characterization ◽  
Bipolar Transistors ◽  
Pure Silicon ◽  
Device Structures ◽  
Microstructural Behavior ◽  
Very High

ABSTRACTSiGe alloys have recently been of interest for fabrication of heterojunction bipolar transistors using pre-existing or modified silicon-processing technology. These devices are faster than devices using pure silicon. Because of the interest in developing SiGe device structures, various elements of processing relevant to fabrication of the devices are being investigated. One such element has been the use of thermal oxidation for isolation of SiGe devices. Utilization of the technique requires an understanding of oxidation behavior of SiGe layers under a variety of oxidation conditions. Past studies in the literature have investigated the oxidation of SiGe at atmospheric pressure or at very high pressures (∼650–1300 atmospheres). The present study investigates the wet-oxidation of SiGe structures at intermediate pressures (∼25 atmospheres) and temperatures (∼750°C). Unlike atmospheric oxidation, most of the Ge (from SiGe) remains in the oxidized silicon (SiO2) in the form of GeO2. Occasional segregation of Ge to the oxidizing interface is noted. The microstructural behavior of partially and entirely oxidized structures is presented.

scholarly journals Clinopyroxene Solid Solutions in the CaMgSi2O6 – Ca0,5AlSi2O6 Cross-Section at High P-T Parameters

2020 ◽  
Vol 34 ◽  
pp. 37-54
Author(s):  
S. V. Banushkina ◽  
◽  
A. I. Turkin ◽  
A. I. Chepurov ◽  
◽  
...  
Keyword(s):  
Cross Section ◽  
Solid Solutions ◽  
Atmospheric Pressure ◽  
High Pressures ◽  
Experimental Investigations ◽  
Electric Resistance ◽  
Resistance Furnace ◽  
Mineral Association ◽  
Electric Resistance Furnace ◽  
Piston Cylinder

Clinopyroxenes (Cpx) are one of the main rock-forming minerals, but stoichiometry of their compositions was called into question. In particular, an idea of hypothetical calcium molecule Eskola (CaEs, Ca0,5AlSi2O6) existence was expressed. This minal has structure vacancy and silica excess. Numerous experimental investigations in CMAS-system (CaO-MgO-Al2O3-SiO2) have showed that the question of non-stoichiometric Cpx existence remains open. This paper presents the results of an experimental study of the diopside Di (CaMgSi2O6) – calcium molecule Eskola CaEs (Ca0,5AlSi2O6) cross-section in the CMAS-system. The experiments were carried out in the following pressure and temperature range: P=10-4 – 3,0 GPa; T=966 – 15250C. Experiments at atmospheric pressure (10-4 GPa) were performed on a vertical shaft electric resistance furnace; high-pressure ones were performed on a "piston-cylinder" type apparatus. Samples obtained were analyzed using electron microprobe (EMP), scanning electron microscope (SEM) and Raman spectrometer. Depending on the P-T conditions, the samples contain the following phases: anorthite An, garnet Grt, diopside Di, clinopyroxene Cpx, quartz Qtz (tridymite Tr – for experiments at atmospheric pressure), and glass L. The data array on the composition of clinopyroxenes crystallized in this cross-section with diopside in various associations is generalized and supplemented. Clinopyroxenes were found to form quaternary solid solutions of diopside Di (CaMgSi2O6) – enstatite En (Mg2Si2O6) – calcium molecule Tschermak CaTs (CaAl2SiO6) – calcium molecule Eskola CaEs (Ca0,5AlSi2O6). The CaTs and CaEs minals contents are positively correlated with the amount of aluminum in clinopyroxene, and this relationship is particularly pronounced for CaTs. It is confirmed that clinopyroxenes in this cross-section can contain an excess of silica at both atmospheric and high pressures. Apparently, the cation vacancy that exists in pyroxene structure can participate in ordering processes. As a result the pyroxenes of another structure (not diopside – C2/c-symmetry) can be crystallized from total compositions in the Di-CaEs cross-section. Additional research is needed to support this hypothesis. Besides, at present investigation it was not possible to establish an unambiguous relationship between the Cpx composition and P-T-parameters, since it is also associated with both the mixture initial composition and the mineral association. Further experiments are required to justify any geothermobarometric dependence.

scholarly journals Convolution and deconvolution: two mathematical tools to help performing tests in research and industry

2021 ◽  
Vol 12 ◽  
pp. 6
Author(s):  
Jean-Pierre Fanton
Keyword(s):  
Experimental Data ◽  
Inverse Problem ◽  
Electrical Energy ◽  
Integral Transforms ◽  
Physical Measurement ◽  
Photographic Images ◽  
Test Standards ◽  
Energy Networks ◽  
The Third ◽  
The Subject

The concepts of convolution and deconvolution are well known in the field of physical measurement. In particular, they are of interest in the field of metrology, since they can positively influence the performance of the measurement. Numerous mathematical models and computer developments dedicated to convolution and deconvolution have emerged, enabling a more efficient use of experimental data; this in sectors as different as biology, astronomy, manufacturing and energy industries. The subject finds today a new topicality because it has been made accessible to a large public for applications such as processing photographic images. The purpose of this paper is to take into account some recent evolutions such as the introduction of convolution methods in international test standards. Thus, its first part delivers a few reminders of some associated definitions. They concern linear systems properties, and integral transforms. If convolution, in most cases, does not create major calculation problems, deconvolution on the contrary is an inverse problem, and as such needs more attention. The principles of some of the methods available today are exposed. In the third part, illustrations are given on recent examples of applications, belonging to the domain of electrical energy networks and photographic enhancement.

scholarly journals The determination of the specific heat of superheated steam by throttling and other experiments

1905 ◽  
Vol 76 (509) ◽  
pp. 185-205 ◽  
Keyword(s):  
Specific Heat ◽  
Atmospheric Pressure ◽  
Superheated Steam ◽  
Electrical Energy ◽  
Total Heat ◽  
Saturated Steam ◽  
External Work

In October, 1898, the author commenced experiments, having for their object the determination of the specific heat of superheated steam. At first an attempt was made to obtain this end by measuring the rise in temperature produced in a known quantity of steam by supplying a definite amount of heat in the form of electrical energy, but the experimental difficulties experienced in satisfactorily preventing radiation, in maintaining the rate of flow of steam uniform and in securing a steam supply sufficiently homogeneous and constant as to temperature, proved so great that the attempt on these lines was given up for a time, but returned to later. Then another method was adopted, that of allowing dry saturated steam to expand without doing external work, and observing the resulting change in temperature. This method had been used in preliminary experiments on this subject by Professor Ewing and Mr. Dunkerley, who found that the specific heat of superheated steam at atmospheric pressure, as deduced by this method from Regnault’s values of the "total heat,” was not a constant, as had been previously supposed, but increased with temperature.

scholarly journals Gaseous combustion at high pressures. Part XV.— The formation of nitric oxide in carbonic oxide-oxygen-nitrogen explosions

1933 ◽  
Vol 139 (837) ◽  
pp. 74-83 ◽  
Keyword(s):  
Nitric Oxide ◽  
High Pressures ◽  
Volume Ratio ◽  
Optimum Composition ◽  
Normal Rate ◽  
Secondary Formation ◽  
Spherical Explosion ◽  
Rate Of Cooling ◽  
Hot Products

In previous papers of this series it was shown that the secondary formation of nitric oxide in CO-O 2 -N 2 explosions, when oxygen is present in excess of that required to burn all the carbonic oxide, rapidly increases with the density of the medium, the optimum composition of the medium for the purpose being 2CO + 3O 2 + 2N 2 . The former experiments were carried out, in bombs Nos. 2 and 3, the 7·5 cm. diameter spherical explosion chambers of which were each of 240 c.c. capacity with a surface/volume ratio 0·78, under conditions permitting of no acceleration in the normal rate of cooling down of the hot products from the maximum explosion temperature.

Active sites and states in the heterogeneous catalysis of carbon–hydrogen bonds

2005 ◽  
Vol 363 (1829) ◽  
pp. 879-900 ◽  
Author(s):  
Gabor A Somorjai ◽  
Anderson L Marsh
Keyword(s):  
Surface Structure ◽  
Active Sites ◽  
High Pressures ◽  
Bond Activation ◽  
Co Adsorption ◽  
Molecular Rearrangement ◽  
Platinum Surface ◽  
Bond Dissociation ◽  
Surface Mobility ◽  
Structure Sensitive

C–H bond activation for several alkenes (ethylene, propylene, isobutene, cyclohexene and 1-hexene) and alkanes (methane, ethane, n -hexane, 2-methylpentane and 3-methylpentane) has been studied on the (111) crystal face of platinum as a function of temperature at low (<10 −6  Torr) and high (≥1 Torr) pressures in the absence and presence of hydrogen pressures (≥10 Torr). Sum frequency generation (SFG) vibrational spectroscopy has been used to characterize the adsorbate structures and high pressure scanning tunnelling microscopy (HP-STM) has been used to monitor their surface mobility under reaction conditions during hydrogenation, dehydrogenation and CO poisoning. C–H bond dissociation occurs at low temperatures, approximately 250 K, for all of these molecules, although only at high pressures for the weakly bound alkanes because of their low desorption temperatures. Bond dissociation is known to be surface structure sensitive and we find that it is also accompanied by the restructuring of the metal surface. The presence of hydrogen slows down dehydrogenation and for some of the molecules it influences the molecular rearrangement, thus altering reaction selectivity. Surface mobility of adsorbates is essential to produce catalytic activity. When surface diffusion is inhibited by CO adsorption, ordered surface structures form and the reaction is poisoned. Ethylene hydrogenation is surface structure insensitive, while cyclohexene hydrogenation and dehydrogenation are structure sensitive. n -Hexane and other C 6 alkanes form either upright or flat-lying molecules on the platinum surface which react to produce branched isomers or benzene, respectively.

Collisions through liquid films

1948 ◽  
Vol 44 (4) ◽  
pp. 566-580 ◽  
Author(s):  
F. R. Eirich ◽  
D. Tabor
Keyword(s):  
Plastic Deformation ◽  
Liquid Film ◽  
Metal Surfaces ◽  
High Pressures ◽  
Early Experiment ◽  
Liquid Films ◽  
Metallic Contact ◽  
Dynamic Yield ◽  
Energy Dissipated ◽  
Clean Metal

When impact occurs between clean metal surfaces, plastic flow of the metal usually takes place at the points of real contact, so that the pressures developed are as high as the dynamic yield pressure of the metal concerned. Early experiment show that if the surfaces are covered with a thin film of a highly viscous liquid, the pressures developed and transmitted through the liquid film may be sufficiently great to produce plastic deformation of the metal, even though no metallic contact occurs through the film (1). The existence of these high pressures in the liquid layer means that extremely high rates of flow and shear may be developed in the liquid film, and that the energy dissipated in overcoming viscous flow may lead to an appreciable temperature rise in the liquid. Even in much gentler impacts, where plastic deformation of the metal surfaces does not occur, very high pressures, rates of flow and shear, etc., may be developed in the liquid film. These effects are of great interest in any study of collisions through liquids; they are of particular significance in the study of the mechanism of detonation of liquid explosives by impact.

Problems related to the tests of resistance and strength of military equipment in reduced atmospheric pressure conditions

2019 ◽  
Vol 124 ◽  
pp. 151-159
Author(s):  
Patryk Płochocki ◽  
Mateusz Makarewicz ◽  
Przemysław Simiński
Keyword(s):  
High Altitude ◽  
Working Conditions ◽  
Atmospheric Pressure ◽  
Ambient Pressure ◽  
Air Transport ◽  
Normative Documents ◽  
Military Equipment ◽  
The Subject

This article is about military equipment research in conditions of reduced atmospheric pressure. Reported cases of equipment damage during work at high altitude or air transport show the need to perform research on phenomena occurring during storage, transport and operation of equipment at a reduced ambient pressure. One of the fragments of the article is devoted to the records contained in normative documents regarding the subject of the study. In addition, an exemplary experiment was made, the purpose of which was to illustrate some of the effects associated with the use of the equipment in the above-mentioned working conditions.

scholarly journals Effect of HIP Parameters on the Micro-Structural Evolution of a Single Crystal Ni-Based Superalloy

2011 ◽  
Vol 278 ◽  
pp. 72-77 ◽  
Author(s):  
Inmaculada Lopez-Galilea ◽  
Stephan Huth ◽  
Marion Bartsch ◽  
Werner Theisen
Keyword(s):  
Single Crystal ◽  
Atmospheric Pressure ◽  
High Pressures ◽  
Hot Isostatic Pressing ◽  
Structural Evolution ◽  
Local Deformation ◽  
Local Distribution ◽  
Slow Cooling ◽  
Distribution Of Elements ◽  
Hardened State

For reducing the porosity of single crystal (SX) nickel-based superalloys, Hot Isostatic Pressing (HIP) is used. High pressures of about 100-170 MPa lead to local deformation, which close the pores. However, since HIP also requires high temperatures (1000-1200°C) it has a pronounced effect on the microstructure and the local distribution of elements. This contribution analyses the effect of different HIP treatments on both the microstructure and the segregation of the SX superalloy LEK94 in the as-precipitation-hardened state. In addition, the effects of rapid or slow cooling are analyzed. To distinguish the effect of pressure from those of temperature, the HIPed samples are compared with specimens annealed at atmospheric pressure.

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