Stability analysis of some integrable Euler equations for SO(n)

A family of special cases of the integrable Euler equations on $so(n)$ introduced by Manakov in 1976 is considered. The equilibrium points are found and their stability is studied. Heteroclinic orbits are constructed that connect unstable equilibria and are given by the orbits of certain 1-parameter subgroups of SO(n). The results are complete in the case $n=4$ and incomplete for $n>4$.Comment: 15 pages, LaTeX, minor stylistic changes in v

Further explorations of Skyrme-Hartree-Fock-Bogoliubov mass formulas. III: Role of particle-number projection

Starting from HFB-6, we have constructed a new mass table, referred to as HFB-8, including all the 9200 nuclei lying between the two drip lines over the range of Z and N > 6 and Z < 122. It differs from HFB-6 in that the wave function is projected on the exact particle number. Like HFB-6, the isoscalar effective mass is constrained to the value 0.80 M and the pairing is density independent. The rms errors of the mass-data fit is 0.635 MeV, i.e. better than almost all our previous HFB mass formulas. The extrapolations of this new mass formula out to the drip lines do not differ significantly from the previous HFB-6 mass formula.Comment: 9 pages, 7 figures, accepted for publication in Phys. Rev.

Effect graphite on magnesium diboride superconductivity synthesized by combustion method under argon pressure: Part II

There are many various techniques to synthesize the superconductors based on magnesium diboride. In this paper, we attempted to obtain a superconducting magnesium diboride in a way by using a High-Temperature Centrifuge and investigated how a centrifugal force can be effect on superconducting parameters of MgB2 during solid-state combustion. It was the first superconductor based on magnesium diboride synthesized under the influence of centrifugal force in the high temperature centrifuge during solid phase process. As a result of this research, we could determine that a centrifugal force do not impact considerably on the critical transition temperature of the MgB2 samples (stay at around 37,5 – 38 K). However, it was found that the value of a centrifugal force could effects on the critical current density (Jc) of the samples

Effect graphite on magnesium diboride superconductivity synthesized by combustion method under argon pressure: Part I

Solid-state synthesis of a superconductor based on magnesium diboride doped by graphite microparticles (MgB2@C) at argon atmosphere has been described. The offered method allows the possibility to increase the critical current density of the studied samples at relatively low temperature in the inert environment. The superconducting characteristics of samples critical current density (Jc) and critical transition temperature (Tc) have been measured. The impact of the doping additives on superconducting characteristics of magnesium diboride has been analyzed. The results showed that the best optimal characteristics are for MgB2@3%C that reveals a good critical transition temperature 38,8 K and the higher critical current density 2,7 x 106 A / cm2 at 5 K

Effect graphite on magnesium diboride superconductivity synthesized by combustion method under argon pressure: Part I

Solid-state synthesis of a superconductor based on magnesium diboride doped by graphite microparticles (MgB2@C) at argon atmosphere has been described. The offered method allows the possibility to increase the critical current density of the studied samples at relatively low temperature in the inert environment. The superconducting characteristics of samples critical current density (Jc) and critical transition temperature (Tc) have been measured. The impact of the doping additives on superconducting characteristics of magnesium diboride has been analyzed. The results showed that the best optimal characteristics are for MgB2@3%C that reveals a good critical transition temperature 38,8 K and the higher critical current density 2,7 x 106 A / cm2 at 5 K

A New High Energy Photon Tagger for the H1 - Detector at HERA

The H1 detector at HERA has been upgraded by the addition of a new electromagnetic calorimeter. This is installed in the HERA tunnel close to the electron beam line at a position 8m from the interaction point in the electron beam direction. The new calorimeter extends the acceptance for tagged photoproduction events to the high y range, 0.85 < y < 0.95, and thus significantly improves the capability of H1 to study high energy gamma-p processes. The calorimeter design, performance and first results obtained during the 1996-1999 HERA running are described.Comment: 17 pages, 16 figure

Tagging High Energy Photons in the H1 Detector at HERA

Measures taken to extend the acceptance of the H1 detector at HERA for photoproduction events are described. These will enable the measurement of electrons scattered in events in the high y range 0.85 < y < 0.95 in the 1998 and 1999 HERA run period. The improvement is achieved by the installation of an electromagnetic calorimeter, the ET8, in the HERA tunnel close to the electron beam line 8 m downstream of the H1 interaction point in the electron direction. The ET8 will allow the study of tagged gamma p interactions at centre-of-mass energies significantly higher than those previously attainable. The calorimeter design and expected performance are discussed, as are results obtained using a prototype placed as close as possible to the position of the ET8 during the 1996 and 1997 HERA running.Comment: 13 pages, 13 figure

An Inquiry into the Practice of Proving in Low-Dimensional Topology

The aim of this article is to investigate specific aspects connected with visualization in the practice of a mathematical subfield: low-dimensional topology. Through a case study, it will be established that visualization can play an epistemic role. The background assumption is that the consideration of the actual practice of mathematics is relevant to address epistemological issues. It will be shown that in low-dimensional topology, justifications can be based on sequences of pictures. Three theses will be defended. First, the representations used in the practice are an integral part of the mathematical reasoning. As a matter of fact, they convey in a material form the relevant transitions and thus allow experts to draw inferential connections. Second, in low-dimensional topology experts exploit a particular type of manipulative imagination which is connected to intuition of two- and three-dimensional space and motor agency. This imagination allows recognizing the transformations which connect different pictures in an argument. Third, the epistemic—and inferential—actions performed are permissible only within a specific practice: this form of reasoning is subject-matter dependent. Local criteria of validity are established to assure the soundness of representationally heterogeneous arguments in low-dimensional topology

Risk-oriented approach to ecological safety management at oil refinery

The article considers place and role of the risk-oriented approach in environmental management at enterprises, describes mechanisms for use of risk assessment in environmental management processes and documents, tools for use of risk characteristics in development and implementation of programmes and plans for oil refineries.The study relevance is based on the need to improve the environmental management system of “Orsknefteorgsintez” in line with the plans to include risk-oriented approach in supervisory work, including state environmental supervision.The main goal of the work was development of approaches to risk-oriented environmental management at “Orsknefteorgsintez” based on the health risk assessment from environment pollution, followed by interpretation of gained data and appropriate management decisions.The research was conducted in two stages. The first stage included health risk levels determination resulted from air pollution by “Orsknefteorgsintez”. The results included hygienic studies of human health risk assessment from negative impact by “Orsknefteorgsintez” considering the implementation of the middle-term enterprise development program; and results of comparative analysis of human health risk levels prior to and after operational commissioning of reconstructed objects within the middle-term enterprise development program. The recommendation on human health risk management from the “Orsknefteorgsintez” production facilities (including control and monitoring) are based on the results of the first stage.Risk-oriented improves environmental management systems at enterprises, helps in interactions with government bodies, enhances management decisions in line with environmental legislation and increases environmental-economic investment efficiency

Self-Propagating High Temperature Synthesis of MgB2 Superconductor in High-Pressure of Argon Condition

Magnesium diboride can be synthesized under argon ambient, elevated or high pressures. High-pressure syntheses are promising methods for manufacturing of the bulk MgB2 superconductor material. We have been used high pressure of Ar gas in order to investigate its effect on properties of MgB2 superconductor such as critical temperature and current density. Bulk MgB2 superconductor was synthesized from elemental Mg–B powders in thermal explosion mode of self-propagating hightemperature synthesis (SHS) under argon pressure of 25 atm. XRD pattern of the as-synthesized product indicates an almost complete conversion of the reactants to the MgB2 single phase. Most of the diffractions peaks are related to the MgB2 polycrystalline bulk material. The impurity fraction is less than 24.3% in total sample and identified as MgO and MgB4 secondary phases. The positive effect of pressure of Ar gas during synthesis of MgB2 on critical current density JC has been confirmed. The critical current density of the sample was achieved in high pressure reactor was 3.8×106 A/cm2. A superconducting volume fraction of 16% under a magnetic field of 10 Oe was obtained at 5 K, indicating that the superconductivity was bulk in nature. The succeeded level of superconductor parameters of the highpressure synthesized MgB2 and the possibility to produce a large bulk products make this technology very promising for practical applications