Research into defectiveness of welded joints of steam pipes operated over a long time

Проведено аналіз пошкоджуваності металу зварних з'єднань паропроводів із Cr–Mo–V теплостійких перлітних сталей, які тривалий час експлуатуються в умовах повзучості та малоциклової втоми. Наведені зварні з'єднання пошкоджуються одночасно порами повзучості та тріщинами втоми. Розглянуто фактори, які викликають пошкоджуваність, а також залежність пошкоджуваності від структури зварних з'єднань і умов експлуатації. Їх пошкоджуваність переважно має крихкий характер

Metastable phases and "metastable" phase diagrams

The work discusses specifics of phase transitions for metastable states of substances. The objects of condensed media physics are primarily equilibrium states of substances with metastable phases viewed as an exception, while the overwhelming majority of organic substances investigated in chemistry are metastable. It turns out that at normal pressure many of simple molecular compounds based on light elements (these include: most hydrocarbons; nitrogen oxides, hydrates, and carbides; carbon oxide (CO); alcohols, glycerin etc) are metastable substances too, i.e. they do not match the Gibbs' free energy minimum for a given chemical composition. At moderate temperatures and pressures, the phase transitions for given metastable phases throughout the entire experimentally accessible time range are reversible with the equilibrium thermodynamics laws obeyed. At sufficiently high pressures (1-10 GPa), most of molecular phases irreversibly transform to more energy efficient polymerized phases, both stable and metastable. These transformations are not consistent with the equality of the Gibbs' free energies between the phases before and after the transition, i.e. they are not phase transitions in "classical" meaning. The resulting polymeric phases at normal pressure can exist at temperatures above the melting one for the initial metastable molecular phase. Striking examples of such polymers are polyethylene and a polymerized modification of CO. Many of energy-intermediate polymeric phases can apparently be synthesized by the "classical" chemistry techniques at normal pressure.Comment: 5 pages, 4 figure

Rhetorical Awareness of Student Writers at an HBCU: A Study of Reflective Responses in the Writing Center

The recent call for replicable, aggregable, and data-driven (RAD) research of writing center effectiveness motivated this study. In writing centers, the primary objective is to improve writers through one-to-one conversations. Improvement in writers, defined here in terms of rhetorical awareness, has proven difficult to measure. In this article, the authors describe how they developed a scale to measure rhetorical awareness, specifically purpose, genre, and audience awareness. Using both discourse and content analyses, they applied the scale to student responses on reflection forms collected over two semesters at an HBCU to see if rhetorical awareness might be observable and measurable. Although the responses of students who visited the center more than once within six months did not show changes in their rhetorical awareness, as the authors had hoped, the results seem to reveal more about the social context than individual students, suggesting that current-traditional pedagogy persists. Aggregating data with this methodology may open new lines of inquiry for researchers of writing and allow them to track trends in discourse on writing.University Writing Cente

Baryonic Regge trajectories with analyticity constraints

A model for baryonic Regge trajectories compatible with the threshold behavior required by unitarity and asymptotic behavior in agreement with analyticity constraints is given in explicit form. Widths and masses of the baryonic resonances on the N and $\Delta$ trajectories are reproduced. The MacDowell symmetry is exploited and an application is given.Comment: 12 pages, 6 figure

Lasing on the D_2 line of sodium in helium atmosphere due to optical pumping on the D_1 line (up-conversion)

A new method is proposed to produce population inversion on transitions involving the ground state of atoms. The method is realized experimentally with sodium atoms. Lasing at the frequency corresponding to the sodium D_2 line is achieved in the presence of pump radiation resonant to the D_1 line with helium as a buffer gas.Comment: 4 pages, 4 figures, Late