Place In Gas Research Articles

Evaluation of mechanical properties of polyethylene for pipes by energy approach during tensile and fatigue tests

Since its introduction in pipe applications more than 40 years ago, polyethylene (PE) has been taking a growing place in gas and water distribution due to its low cost, lightness and good corrosion resistance. Besides, long-term properties have been steadily rising due to the development of novel PE-based materials. The present highest standard is the PE100 class. Several laboratory tests are used to extract design data for long-term failure-type prediction based on stress and time to failure relationship. It remains difficult to assess the relation between creep and fatigue loadings on the one side. On the other side, the manufacturing process of the test specimens influences considerably the obtained performance for viscoelastic materials subjected to working conditions. In present paper, the mechanical properties of high-density polyethylene (HDPE), PE 100 class, for pipes were investigated using experimental techniques. Thermographic technique was used during the static tests in order to identify the maximum stress zone and also during the fatigue tests to study the temperature evolution of the specimen. The aim of this study is the application of the Thermographic Method for the fatigue assessment of PE100.

COSMIC-RAY SPALLATION IN RADIO-QUIET ACTIVE GALACTIC NUCLEI: A CASE STUDY OF NGC 4051

We investigate conditions for and consequences of spallation in radio-quiet Seyfert galaxies. The work is motivated by the recent discovery of significant line emission at 5.44 keV in Suzaku data from NGC 4051. The energy of the new line suggests an identification as Cr I Ka emission, however the line is much stronger than would be expected from material with cosmic abundances, leading to a suggestion of enhancement owing to nuclear spallation of Fe by low energy cosmic rays from the active nucleus. We find that the highest abundance enhancements are likely to take place in gas out of the plane of the accretion disk and that timescales for spallation could be as short as a few years. The suggestion of a strong nuclear flux of cosmic rays in a radio-quiet Seyfert galaxy is of particular interest in light of the recent suggestion from Pierre Auger Observatory data that ultra-high-energy cosmic rays may originate in such sources.

Photoinduced Processes in Heterogeneous Gas−Solid Systems. Temperature Dependence (100−600 K) and Modeling of a Surface Chemical Reaction on Zirconia that Triggers Photophysical Events in the Solid

We report studies on photoinduced processes that take place in gas−solid heterogeneous systems. In particular, we examine the chemical reaction (i.e., chemical relaxation pathway) between hydrogen (or methane) and the surface of ZrO2 particles which occurs after the solid was preirradiated (vacuo or oxygen) and the intrinsic phosphorescence from zirconia had terminated. Introduction of H2 yields an after-glow (light pulse referred as photoinduced chesorluminescence, PhICL) that is caused by chemical interaction between the photoactivated surface of the photocatalyst and the H-containing molecules in the heterogeneous gas−solid system. Unlike hydrogen, methane does not yield a detectable PhICL emission. The PhICL emission for hydrogen decays via biphasic kinetics (τ1 = 0.9 s and τ2 = 10 s; ambient temperature). Reactions were also investigated in the temperature range of 75−600 K. For a nonpreirradiated surface, the H-containing molecules physisorb with binding energy Ephys = 33 kJ mol-1 (0.34 eV) for H2 and 52 kJ mol-1 (0.54 eV) for CH4. After preirradiation of ZrO2, the molecules chemisorb dissociatively yielding free radicals (H• for H2, and CH3• for methane, the other H• is trapped) through an activated process; activation energies Ea = 30 kJ mol-1 (0.31 eV) for H2 and 32 kJ mol-1 (0.33 eV) for CH4 if the process occurs by a Langmuir-type pathway; if the process occurs by an Eley-Rideal mechanism, Ea = 41 kJ mol-1 (0.43 eV) for H2 and 46 kJ mol-1 (0.48 eV) for CH4. The data were modeled through a sequence of differential equations. A mechanism is proposed that involves shallow traps and deep energy traps for electrons to explain the photophysical events triggered by the surface chemical reaction. In essence, surface chemical reactions cause the release of the energy stored during the preirradiation stage of the solid. This results in photoinduced formation of metastable defects in the solid (e.g., Os-•) together with deep electron traps (F centers) that lead to both chemical and physical relaxation of the system.

From Service to Sales: Home Economics in Light and Power, 1920–1940

From Service to Sales: Home Economics in Light and Power, 1920-1940 CAROLYN M. GOLDSTEIN In 1917, the Public Service Electric and Gas Company of NewJer­ sey hired Ada Bessie Swann, a home economist, to develop a pro­ gram educating homemakers about the benefits of gas and electric­ ity. In less than a decade, Swann transformed a set ofsimple cooking demonstrations into a “home service department” offering instruc­ tion in all aspects of “modern housekeeping.” Aimed primarily at adult homemakers who did not have the opportunity to learn home economics in school, Swann’s program ranged from laundry, light­ ing, and cleaning, to food preservation, preparation, and serving. Formats included lecture demonstrations in department stores and before organized groups such as women’s and girls’ clubs, home management and cookery classes at the utility company facilities, and calls at customers’ homes. In addition, through radio programs and individual correspondence, Swann established the New Jersey utility company as a constant presence in the community, available and accessible to all customers and any questions. The large cadre of home economics-trained women she assembled on her staff helped ensure regular contact with homemakers throughout an extensive metropolitan area.1 Swann’s activities typify an emerging group of Dr. Goldstein is a curator in the exhibitions department at the National Building Museum in Washington, D.C. She thanks Anne Boylan, Joan Jacobs Brumberg, Da­ vid Hounshell, Jan Jennings, Ronald Kline, Robin Leidner, Steven Lubar, Harold Platt, Susan Strasser, and Sarah Stage for comments on previous versions of this article. For assistance in refining and reshaping her argument, she is especially grate­ ful to Mark Rose, the Technology and Culture referees, and the editors of this special issue. Much of the writing was supported by a Fellowship in the History of Home Economics and Nutrition from the College of Human Ecology, Cornell University, Ithaca, New York. ’By 1931, Swann had a staff of 1,200 home economists and a radio audience of 18,000 women. See Eloise Davison, “Home Economics Invades Business,” Indepen­ dent Woman 10 (March 1931): 127. On her career at the NewJersey utility, see Ada Bessie Swann, “Home Economics Work with Electric and Gas Utility Companies,” Home Economist and the American Food Journal 6 (November 1928): 317-18; “How NewJersey Electric Company Uses the ‘Home Electrical’ Section of‘Electrical Mer­ chandising’ to Reach the Women’s Clubs,” Electrical Merchandising (hereafter EM)© 1997 by the Society for the History of Technology. All rights reserved. 0040-165X/97/3801-0003$01.00 121 122 Carolyn M. Goldstein professional women who found a place in gas and electric utility companies teaching consumers about the new power sources and businesses about consumers.* 2 This case study of home economists’ role in the distribution of gas and electric power in the 1920s and 1930s opens a window on the complex gender-technology interactions at what Ruth Schwartz Cowan has called “the consumptionjunction.”3 It argues the impor­ tance ofconsidering production and consumption as part of a single process, one in which home economists occupied an important me­ diating location. It also refines historical understanding of the rela­ tionship between technological change and the notion of “separate spheres.” Generations of scholars associated the realms of produc­ tion and consumption with men and women, respectively. They in­ terpreted men as part of the public sphere and women as tied exclu­ sively to the private. Yet in recent years, historians of women have found so much evidence of men and women crossing these suppos­ edly rigid boundaries that they have called into question the entire “separate spheres” concept.4 As a group of female technical profes­ 29 (February 1923): 3094; and Swann, “What of the Future of Home Economics in Utilities,” 1927 speech, Folder: “Speeches, Annual Meetings, Etc.,” Home Econo­ mists in Business, Box 1, American Home Economics Association Archives, Alexan­ dria, Virginia (hereafter AHEA Archives). Active within the home economics profes­ sion, Swann also was a founding member of the Electrical Women’s Round Table, an organization ofwomen employed in the electrical industry which was established in 1923. In 1935 Swann left the Public Service Electric and Gas Company to head up the Home Service Center at Woman...

Nonequilibrium hypersonic flow of gas past a wing of small aspect ratio

It is well known [1] that nonequilibrium physicochemical processes taking place in gases at high temperature influence the gas-dynamic parameters and aerodynamic characteristics of bodies in hypersonic flight. In the present paper, the thin shock layer method [2–4] is used to consider the problem of nonequilibrium hypersonic flow of gas past a wing of small aspect ratio at an angle of attack. It is shown that the flow component of the vorticity is conserved along the streamlines, and this property is exploited to obtain an analytic solution of the equations of the three-dimensional nonequilibrium shock layer. The influence of the disequilibrium on the thickness of the shock layer and the pressure distribution is investigated.

Eighth rank isotropic tensors and rotational averages

Isotropic tensors play an important role in the theory of many physical processes, which take place in gases and liquids. In such systems it is usually necessary to perform a rotational average on products of direction cosines relating the space-fixed and molecular coordinate frames. The average is generally expressible in terms of isotropic tensor. The authors discuss the isotropic tensors of eighth rank, and relations between them are demonstrated. The rotational average of eighth rank is then evaluated in both reducible and irreducible form; the results are applicable to a number of processes, for example optical seventh harmonic generation and four-photon absorption.

An introduction to researches on circuit breaking

This paper is an introduction to the Electrical Research Association's researches on arc rupture which have been in progress since 1922.An introductory section describes the genesis and aims of the research. The problem of circuit breaking is far more complicated than has been generally supposed, and can be solved only by separate study of the numerous variables involved. The apparatus, controls, and general lay-out of the testing station at Carville are described.The investigators aimed at means for preventing the arc from re-striking, rather than attacking the arc when heavy current is flowing, which may cause heavy energy release.It is shown that, in oil switches, the arc is often broken while the contacts are still within the gas bubble, so that, in such cases, arc extinction is not due to the quenching effect of the oil. Experiments have proceeded along two lines: (1) Study of the gas formed and of its arc-rupturing properties as compared with other gases, with a view to its utilization to full advantage in arc rupture; and (2) a study of the best methods of utilizing the good features of oil for like purpose, the general aim being the utilization of each method separately or in combination in improved or new types of design.Novel methods of gas-sampling during arcing are described, and the results are given of gas collection and analysis covering a wide range of currents and powers.The present paper deals mainly with arcing in gas. For given gaseous conditions in the gap between the contacts at current pause, the adequacy of the gap depends on the instantaneous value of the voltage gradient appearing across it at current zero, and it is found that, for arcs in hydrogen, the. length of critical gap is approximately proportional to the sine of the angular displacement between current and “virtual” voltage zeros. This differs radically from Bauer's conclusions. In arcs in oil there are superimposed phenomena, but in general the same law applies.With asymmetrical currents in gas and oil there is a phase-displacement effect which affects the available voltage in addition to the phase angle due to circuit conditions.Experimental results on arc-voltage characteristics are given which indicate that Norberg's application of Steinmetz's formula, if used over the range considered in the present paper, would lead to large errors in the results obtained for arc energy, whereas his experimental results, though few in number, are consistent with the results here described.A formula for arc energy when arcing takes place in gas is developed, based on simplified assumptions arising from experiment and theory. This formula illustrates the great complexity, more especially of certain known features of the time and frequency factors, which may in certain circumstances play a highly important part in affecting arc length and energy production; these appear to have been omitted in the previously published formulæ of Bauer and others.The above work leads to certain practical applications.Certain effects of arc lengthening by mechanical and electromagnetic means are discussed. This section concludes with some description of the principles of operation of a new device for arc rupturing by gas blast, which has been developed as a direct outcome of the investigation of arcing in gas. Models tested show great improvement on recognized methods of arc rupture in oil, and show promise of a satisfactory solution of the problem of arc rupture in gas, which is the main subject of this introductory paper.In spite of the added experimental difficulties due to the presence of oil in oil circuit-breakers, great advance has been made and further details will be given when the patent situation permits.