Spin modulation instabilities and phase separation dynamics in trapped two-component Bose condensates

In the study of trapped two-component Bose gases, a widely used dynamical protocol is to start from the ground state of a one-component condensate and then switch half the atoms into another hyperfine state. The slightly different intra-component and inter-component interactions can then lead to highly non-trivial dynamics, especially in the density mismatch between the two components, commonly referred to as 'spin' density. We study and classify the possible subsequent dynamics, over a wide variety of parameters spanned by the trap strength and by the inter- to intra-component interaction ratio. A stability analysis suited to the trapped situation provides us with a framework to explain the various types of dynamics in different regimes

Approximate method for stress intensity factors determination in case of multiple site damage

A simple and easy to use approximate procedure, for calculating stress intensity factors, was proposed. The procedure was developed based on existing solution for stress intensity factor in the case of two unequal cracks in an infinite plate subjected to remote uniform stress. The solution for this configuration was used for obtaining interaction effect coefficients which take into consideration the increase of stress intensity factor of analyzed crack tip due to interaction with existing adjacent crack. Accuracy and application of suggested procedure were verified through two different computer programs which are based on two different computational methods: finite element method (FEM) with singularity elements and extended finite element method (X-FEM). The analysis of the results has shown that a very good agreement between solutions was achieved, and that this method can provide stress intensity factors with acceptable accuracy

C programs for solving the time-dependent Gross-Pitaevskii equation in a fully anisotropic trap

We present C programming language versions of earlier published Fortran programs (Muruganandam and Adhikari, Comput. Phys. Commun. 180 (2009) 1888) for calculating both stationary and non-stationary solutions of the time-dependent Gross-Pitaevskii (GP) equation. The GP equation describes the properties of dilute Bose-Einstein condensates at ultra-cold temperatures. C versions of programs use the same algorithms as the Fortran ones, involving real- and imaginary-time propagation based on a split-step Crank-Nicolson method. In a one-space-variable form of the GP equation, we consider the one-dimensional, two-dimensional, circularly-symmetric, and the three-dimensional spherically-symmetric harmonic-oscillator traps. In the two-space-variable form, we consider the GP equation in two-dimensional anisotropic and three-dimensional axially-symmetric traps. The fully-anisotropic three-dimensional GP equation is also considered. In addition to these twelve programs, for six algorithms that involve two and three space variables, we have also developed threaded (OpenMP parallelized) programs, which allow numerical simulations to use all available CPU cores on a computer. All 18 programs are optimized and accompanied by makefiles for several popular C compilers. We present typical results for scalability of threaded codes and demonstrate almost linear speedup obtained with the new programs, allowing a decrease in execution times by an order of magnitude on modern multi-core computers.Comment: 8 pages, 1 figure; 18 C programs included (to download, click other and download the source

Approximate method for stress intensity factors determination in case of multiple site damage

A simple and easy to use approximate procedure, for calculating stress intensity factors, was proposed. The procedure was developed based on existing solution for stress intensity factor in the case of two unequal cracks in an infinite plate subjected to remote uniform stress. The solution for this configuration was used for obtaining interaction effect coefficients which take into consideration the increase of stress intensity factor of analyzed crack tip due to interaction with existing adjacent crack. Accuracy and application of suggested procedure were verified through two different computer programs which are based on two different computational methods: finite element method (FEM) with singularity elements and extended finite element method (X-FEM). The analysis of the results has shown that a very good agreement between solutions was achieved, and that this method can provide stress intensity factors with acceptable accuracy

Development of Grid e-Infrastructure in South-Eastern Europe

Over the period of 6 years and three phases, the SEE-GRID programme has established a strong regional human network in the area of distributed scientific computing and has set up a powerful regional Grid infrastructure. It attracted a number of user communities and applications from diverse fields from countries throughout the South-Eastern Europe. From the infrastructure point view, the first project phase has established a pilot Grid infrastructure with more than 20 resource centers in 11 countries. During the subsequent two phases of the project, the infrastructure has grown to currently 55 resource centers with more than 6600 CPUs and 750 TBs of disk storage, distributed in 16 participating countries. Inclusion of new resource centers to the existing infrastructure, as well as a support to new user communities, has demanded setup of regionally distributed core services, development of new monitoring and operational tools, and close collaboration of all partner institution in managing such a complex infrastructure. In this paper we give an overview of the development and current status of SEE-GRID regional infrastructure and describe its transition to the NGI-based Grid model in EGI, with the strong SEE regional collaboration.Comment: 22 pages, 12 figures, 4 table

SPEEDUP Code for Calculation of Transition Amplitudes via the Effective Action Approach

We present Path Integral Monte Carlo C code for calculation of quantum mechanical transition amplitudes for 1D models. The SPEEDUP C code is based on the use of higher-order short-time effective actions and implemented to the maximal order $p$=18 in the time of propagation (Monte Carlo time step), which substantially improves the convergence of discretized amplitudes to their exact continuum values. Symbolic derivation of higher-order effective actions is implemented in SPEEDUP Mathematica codes, using the recursive Schroedinger equation approach. In addition to the general 1D quantum theory, developed Mathematica codes are capable of calculating effective actions for specific models, for general 2D and 3D potentials, as well as for a general many-body theory in arbitrary number of spatial dimensions.Comment: 17 pages, 3 figures, uses cicp.cl

Simultaneous detection of vaccinal and field infectious bursal disease viruses in layer chickens challenged with a very virulent strain after vaccination

Infectious bursal disease virus is an important poultry pathogen. It is distributed worldwide and causes significant economic losses. In this study, a system was adopted for the simultaneous monitoring of vaccine and virulent strains using reverse transcription polymerase chain reaction (RT-PCR). After the decay of maternal antibodies, chickens were vaccinated at the age of 37 days with a virus of intermediate virulence and challenged at 5, 10 and 14 days post vaccination (dpv). The challenge was done with IBDV strain CH/99. Sequencing of the hypervariable region of VP2 has shown that CH/99 belongs to the very virulent group of viruses. The vaccine virus could be found in the bursa of Fabricius, spleen, thymus and bone marrow until 24 dpv. The CH/99 challenge virus was found in the bursa and lymphoid organs when chickens were challenged at 5 and 10 dpv. When challenge was performed at 14 dpv, the pathogenic virus could not be found in the bursa and other lymphoid organs

Application of extended finite element method for fatigue life predictions of multiple site damage in aircraft structure

This paper presents an application of the extended finite element method (XFEM) to the modelling of the propagation of four cracks in a typical aircraft structural configuration. It is a thin plate with three holes subjected to uniform uniaxial tensile stress. Material of the plate is aluminium alloy Al-2024 T3. Short theoretical background information is provided on the XFEM as well as the representation of cracks and the stress intensity factors computation. The accuracy of these computations is verified through super-position based approximate procedure and through finite element method (FEM) with singularity elements. The numerical results illustrate that XFEM is efficient for the simulation of crack propagation in MSD (Multiple Site Damage) without the need to re-mesh during the propagation if the finite element mesh is well defined

Application of extended finite element method for fatigue life predictions of multiple site damage in aircraft structure

This paper presents an application of the extended finite element method (XFEM) to the modelling of the propagation of four cracks in a typical aircraft structural configuration. It is a thin plate with three holes subjected to uniform uniaxial tensile stress. Material of the plate is aluminium alloy Al-2024 T3. Short theoretical background information is provided on the XFEM as well as the representation of cracks and the stress intensity factors computation. The accuracy of these computations is verified through super-position based approximate procedure and through finite element method (FEM) with singularity elements. The numerical results illustrate that XFEM is efficient for the simulation of crack propagation in MSD (Multiple Site Damage) without the need to re-mesh during the propagation if the finite element mesh is well defined

Simulation of crack propagation in titanium mini dental implants (MDI)

Unapređenja u proizvodnji mini dentalnih implantata (MDI) su uglavnom usmerena ka povećanju njihove biokompatibilnosti i, u isto vreme, izdržljivosti i bezbednosti, ali i ka smanjenju njihovih dimenzija u odnosu na postojeće implantate. Međutim, tokom ugradnje MDI-a može doći do njegovog loma ili nastanka prsline koja kasnije može prouzrokovati lom. Da bi se analiziralo širenje prsline u titanijumskom MDI-u, korišćeni su softveri za primenu metode konačnih elemenata (MKE) ANSYS v13 i FRANC3D v5. Korišćenjem FRANC3D programa izmodelirane su prsline različitih veličina i oblika na 3D geometriji MDI-a i izvršeno je simuliranje njihovog širenja. Na osnovu rezultata simulacije izračunat je približan zamorni vek oštećenog MDI-a.Developments in mini dental implants (MDI) manufacturing are aimed at making them more biocompatible and, at the same time, lighter, more durable and simultaneously safer than the existing implants. But, occasionally, during installation the failure of MDI may occur or cracks may appear, which could lead to the later failure of MDI. In order to understand and assess crack growth in titanium MDI, Finite Element (FE) software packages ANSYS v13 and FRANC3D v5 have been used. Using FRANC3D software different crack sizes and shapes have been modeled and simulations of crack propagations in three-dimensional model of MDI have been performed. Based on simulation results, the approximate fatigue life of damaged MDI was calculated