Charge Screening at First Order Phase Transitions

Possibility of structured mixed phases at first order phase transitions is examined with taking into account of charge screening and surface effects. Hadron-quark phase transition in dense neutron star interior is considered, as concrete example.Comment: 15 pages, 1 figur

Effect of Non-uniform Flow on the Ignition and Combustion in Scramjet Combustor

The uniform and nonuniform flow conditions are created at the entry of the combustor by incorporating a Circle to Rectangle Transition duct (CR-Transition duct, for short) in the subsonic and supersonic flows ahead of the combustor. Computational and experimental studies have been carried out on a ramp-cavity based supersonic combustor with supersonic and subsonic transitions. It is observed that the non-uniform three-dimensional flow caused by the presence of the CR-Transition duct, help in ignition of kerosene, while the same could not be achieved with uniform flow at the combustor entry. The experimental and computational investigations are discussed in this paper.Условия однородного и неоднородного потоков создаются введением круглого и прямоугольного соединительных воздухопроводов в дозвуковой и сверхзвуковой потоки перед камерой сгорания. Численные и экспериментальные исследования проводились на основе ramp-cavity со сверхзвуковыми и дозвуковыми соединениями. Установлено, что неоднородный трехмерный поток, вызываемый наличием соединительного воздухопровода, способствует зажиганию керосина, что не достигается при однородном потоке на входе камеры сгорания.Умови однорідного та неоднорідного потоків створюються уведенням круглого та прямокутного з’єднувальних повітропроводів у дозвуковий та надзвуковий потоки перед камерою згоряння. Чисельні та експериментальні дослідження проводились на основі ramp-cavity з надзвуковими та дозвуковими з’єднаннями. Визначено, що неоднорідний тривимірний потік, викликаний наявністю з’єднувального повітропроводу, сприяє запалюванню керосину, чого не можна досягти за однорідного потоку на вході камери згоряння

Sensitivity analysis of the tool for assessing safe manoeuvrability of ships in adverse sea conditions

In 2013, International Maritime Organization (IMO) introduced the Interim Guidelines for determining the minimum propulsion power to maintain the manoeuvrability of ships in adverse conditions. Considering the sufficiency of propulsion system in adverse sea conditions, the European project SHOPERA has developed alternative processes and tools for assessing safe manoeuvrability of ships. The main objective of these procedures is to identify the critical conditions where the vessel maintains its course keeping and manoeuvring ability at the vessel available propulsion power by using basic ship design values as input into the simplified methods proposed. Outcomes of this project were submitted and discussed in the 70th session of IMO’s Marine Environmental Protection Committee. In this paper, a brief description of these new assessment procedures is presented and a sensitivity analysis is conducted. The analysis is performed for a range of different open water propeller and hull resistance characteristics, hull – propeller interaction factors and engine power limit values, investigating the influence of these various performance parameters on the performance of the vessel

Numerical Study of Pulse Detonation Engine with One-step Overall Reaction Model

This paper presents an insight for the study of transient, compressible, intermittent pulsed detonation engine with one-step overall reaction model to reduce the computational complexity in detonation simulations. Investigations are done on flow field conditions developing inside the tube with the usage of irreversible one-step chemical reactions for detonations. In the present simulations 1-D and 2-D axisymmetric tubes are considered for the investigation. The flow conditions inside the detonation tube are estimated as a function of time and distance. Studies are also performed with different grid sizes which influence the prediction of Von-Neumann spike, CJ Pressure and detonation velocity. The simulation result from the single-cycle reaction model agrees well with the previous published literature of multi-step reaction models. The present studies shows that one-step overall reaction model is sufficient to predict the flow properties with reasonable accuracy. Finally, the results from the present study were compared and validated using NASA CEA.Defence Science Journal, Vol. 65, No. 4, July 2015, pp. 265-271, DOI: http://dx.doi.org/10.14429/dsj.65.873

How robust is a 2SC quark matter phase under compact star constraints?

We study the phase structure and equation of state for two-flavor quark matter at low temperature under compact star constraints within a nonlocal chiral quark model. We find that the occurence of a two-flavor color superconducting (2SC) phase is sensitive to variations of both the formfactor of the interaction and the ratio \eta between the coupling constants in the diquark and the scalar meson channels. Our study suggests that for standard values of the coupling ratio 0.5<\eta<0.75 either the 2SC phase does not occur (Gaussian formfactor) or it exists only in a mixed phase with normal quark matter (NQ-2SC) with a volume fraction less than 20 - 40 %, occuring at high baryon chemical potentials \mu_B >1200 MeV and most likely not relevant for compact stars. We also present the relevant region of the phase diagram for compact star applications and obtain that no gapless 2SC occurs at low temperatures.Comment: 19 pages, 9 figures, Subsec.2.5: "Phase diagram" adde

Neutrino Cooling of Neutron Stars. Medium effects

This review demonstrates that neutrino emission from dense hadronic component in neutron stars is subject of strong modifications due to collective effects in the nuclear matter. With the most important in-medium processes incorporated in the cooling code an overall agreement with available soft X ray data can be easily achieved. With these findings so called "standard" and "non-standard" cooling scenarios are replaced by one general "nuclear medium cooling scenario" which relates slow and rapid neutron star coolings to the star masses (interior densities). In-medium effects take important part also at early hot stage of neutron star evolution decreasing the neutrino opacity for less massive and increasing for more massive neutron stars. A formalism for calculation of neutrino radiation from nuclear matter is presented that treats on equal footing one-nucleon and multiple-nucleon processes as well as reactions with resonance bosons and condensates. Cooling history of neutron stars with quark cores is also discussed.Comment: To be published in "Physics of Neutron Star Interiors", Eds. D. Blaschke, N.K. Glendenning, A. Sedrakian, Springer, Heidelberg (2001

Nonlinear ion-acoustic (IA) waves driven in a cylindrically symmetric flow

By employing a self-similar, two-fluid MHD model in a cylindrical geometry, we study the features of nonlinear ion-acoustic (IA) waves which propagate in the direction of external magnetic field lines in space plasmas. Numerical calculations not only expose the well-known three shapes of nonlinear structures (sinusoidal, sawtooth, and spiky or bipolar) which are observed by numerous satellites and simulated by models in a Cartesian geometry, but also illustrate new results, such as, two reversely propagating nonlinear waves, density dips and humps, diverging and converging electric shocks, etc. A case study on Cluster satellite data is also introduced.Comment: accepted by AS

Treatment of post-cholecystectomy biliary strictures with fully-covered self-expanding metal stents - results after 5 years of follow-up

BACKGROUND: Endoscopic treatment of post-cholecystectomy biliary strictures (PCBS) with multiple plastic biliary stents placed sequentially is a minimally invasive alternative to surgery but requires multiple interventions. Temporary placement of a single fully-covered self-expanding metal stent (FCSEMS) may offer safe and effective treatment with fewer re-interventions. Long-term effectiveness of treatment with FCSEMS to obtain PCBS resolution has not yet been studied. METHODS: In this prospective multi-national study in patients with symptomatic benign biliary strictures (N = 187) due to various etiologies received a FCSEMS with scheduled removal at 6-12 months and were followed for 5 years. We report here long-term outcomes of the subgroup of patients with PCBS (N = 18). Kaplan Meier analyses assessed long-term freedom from re-stenting. Adverse events were documented. RESULTS: Endoscopic removal of the FCSEMS was achieved in 83.3% (15/18) of patients after median indwell of 10.9 (range 0.9-13.8) months. In the remaining 3 patients (16.7%), the FCSEMS spontaneously migrated and passed without complications. At the end of FCSEMS indwell, 72% (13/18) of patients had stricture resolution. At 5 years after FCSEMS removal, 84.6% (95% CI 65.0-100.0%) of patients who had stricture resolution at FCSEMS removal remained stent-free. In addition, at 75 months after FCSEMS placement, the probability of remaining stent-free was 61.1% (95% CI 38.6-83.6%) for all patients. Stent or removal related serious adverse events occurred in 38.9% (7/18) all resolved without sequalae. CONCLUSIONS: In patients with symptomatic PCBS, temporary placement of a single FCSEMS intended for 10-12 months indwell is associated with long-term stricture resolution up to 5 years. Temporary placement of a single FCSEMS may be considered for patients with PCBS not involving the main hepatic confluence. TRIAL REGISTRATION NUMBERS: NCT01014390; CTRI/2012/12/003166; Registered 17 November 2009

Statefinder Parameters for Different Dark Energy Models with Variable G Correction in Kaluza-Klein Cosmology

In this work, we have calculated the deceleration parameter, statefinder parameters and EoS parameters for different dark energy models with variable $G$ correction in homogeneous, isotropic and non-flat universe for Kaluza-Klein Cosmology. The statefinder parameters have been obtained in terms of some observable parameters like dimensionless density parameter, EoS parameter and Hubble parameter for holographic dark energy, new agegraphic dark energy and generalized Chaplygin gas models.Comment: 9 pages, no figure, accepted for publication in IJTP. arXiv admin note: text overlap with arXiv:1104.2366 by other author