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A soft recovery system is used to arrest a supersonic object over a limited distance in a controlled manner. This may be achieved through ballistic compression of gas. This work explains the motion of a supersonic object passing through a ballistic compression decelerator i.e., pressurized gas column initially sandwiched between two diaphragms. The accompanying mechanics is complex and includes diverse effects such as separation of shock from the supersonic object, travelling shocks, shock reflections, creation of a new shock, emergence and dissolution of contact discontinuities and expansion waves, and shock-shock interactions. In this work, these phenomena have been numerically and experimentally studied. While the method of characteristics was used to solve Euler's equations in continuous regions, jump conditions derived from control volume considerations were used to obtain solutions across discontinuities. In this way, a duly validated finite difference method computer program was developed to analyze the problem. Finally, simulation predictions were validated by conducting experiments on a 7.62 mm soft recovery system tube. Our results showed that, an object having an entry velocity of 880 m/s, left the SRS with a velocity that was lower by 47% from simulation predictions. Further analysis showed that friction between the object and tube was a major contributor to this gap. Post accounting for friction, the difference between numerical analysis and experimental data got reduced to about 5% at most locations, and to 17% at the end of the SRS. We attribute this residual difference between observations and simulations to build up of pressure at a location post passage of shock by it. Our 2-D finite volume study results, which are consistent with earlier research, as well as with our experimental data, show that such a phenomenon is prominent particularly in narrow tubes due to development of significantly thick turbulent boundary layers. [ABSTRACT FROM AUTHOR]

Thread mapping is one of the techniques which allow for efficient exploiting of the potential of modern multicore architectures. The aim of this paper is to study the impact of thread mapping on the computing performance, the scalability, and the energy consumption for parallel dense linear algebra kernels on hierarchical shared memory multicore systems. We consider the basic application, namely a matrix-matrix product (GEMM), and two parallel matrix decompositions (LU and WZ). Both factorizations exploit parallel BLAS (basic linear algebra subprograms) operations, among others GEMM. We compare differences between various thread mapping strategies for these applications. Our results show that the choice of thread mapping has the measurable impact on the performance, the scalability, and energy consumption of the GEMM and two matrix factorizations. [ABSTRACT FROM AUTHOR]

A numerical investigation was carried out to analyze in details the perforation process of target AA5754-O Aluminum plate when subjected to normal impact at low (up to 25 ms − 1 ) and moderate velocities (ranged between 25 − 50 ms − 1 ). A fully coupled elasto-visco-plastic-damage model is implemented into a user-defined material (VUMAT) subroutine for the commercial finite element code ABAQUS/Explicit. The strain rate effect is considered. Comparison between isotropic J 2 and orthotropic Hill yield criteria associated with isotropic and mixed non-linear isotropic/kinematic hardening was conducted. A parametric study of the effect of anisotropy, plate thickness and impactor nose shapes on ballistic limit and petal forming is carried out. A good agreement is found between numerical and experimental results conducted by other researchers. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the response of composite sandwich beams with honeycomb core subjected to low-velocity impact by using a finite-element model implemented in Abaqus/Explicit code. The face-sheets behaviour was modelled through a VUMAT subroutine, in which a failure model based on Hou failure criteria was implemented. The aluminium honeycomb core behaviour was defined as an elastic–plastic material. A series of low-velocity impact tests were carried out to validate the numerical model. Good agreement, in terms of contact-force histories, energy histories, absorbed energy, and failure of the sandwich beam was observed between the experimental data and the numerical results. The contribution of both the face-sheets and the core to the energy absorption process was analysed separately. It was found that the core controlled the energy absorption of the sandwich beams at the lowest impact velocities studied; however, at higher impact velocities the face-sheets were more involved. [Copyright &y& Elsevier]

Abstract: This paper provides FORTRAN subroutines for the calculation of the partially-Correlated quadratic-Speed-Dependent Hard-Collision (pCqSDHC) profile and of its two limits: the quadratic-Speed-Dependent Voigt (qSDV) and the quadratic-Speed-Dependent Hard-Collision (qSDHC) profiles. Numerical tests successfully confirm the analytically derived fact that all these profiles can be expressed as combinations of complex Voigt probability functions. Based on a slightly improved version of the CPF subroutine [Humlicek. J Quant Spectrosc Radiat Transfer 1979;21:309] for the calculation of the complex probability function, we show that the pCqSDHC, qSDHC and qSDV profiles can be quickly calculated with an accuracy better than 10−4. [Copyright &y& Elsevier]

Abstract: This numerical investigation of an advanced Gurson–Tvergaard–Needleman (GTN) model is an extension of the original work of Ben Bettaiebet al. (2011 [18]). The model has been implemented as a user-defined material model subroutine (VUMAT) in the Abaqus/explicit FE code. The current damage model extends the previous version by integrating the three damage mechanisms: nucleation, growth and coalescence of voids. Physically based void nucleation and growth laws are considered, including an effect of the kinematic hardening. These new contributions are based and validated on experimental results provided by high-resolution X-ray absorption tomography measurements. The current damage model is applied to predict the damage evolution and the stress state in a tensile notched specimen experiment. [Copyright &y& Elsevier]

Numerical analysis data in engineering needs the use or development of software that allows creating the graphical representation of functions, among other calculations. In this article a step by step use of Visual Basic 6® and the control PictureBox® are presented as helping tools to draw one or more series in the same graphic, with the same or different length or data quantity for their comparison. The management of rainfall data from a pluviographic station is presented as an example of this successful application. The methodology here presented can be used with Visual Basic 6®, but the process can be codified in other computing languages commonly applied as tools to solve several engineering problems related to the quick inspection of data generation processes. [ABSTRACT FROM AUTHOR]

SUMMARY The popularity of Partitioned Global Address Space (PGAS) languages has increased during the last years thanks to their high programmability and performance through an efficient exploitation of data locality, especially on hierarchical architectures such as multicore clusters. This paper describes UPCBLAS, a parallel numerical library for dense matrix computations using the PGAS Unified Parallel C language. The routines developed in UPCBLAS are built on top of sequential basic linear algebra subprograms functions and exploit the particularities of the PGAS paradigm, taking into account data locality in order to achieve a good performance. Furthermore, the routines implement other optimization techniques, several of them by automatically taking into account the hardware characteristics of the underlying systems on which they are executed. The library has been experimentally evaluated on a multicore supercomputer and compared with a message-passing-based parallel numerical library, demonstrating good scalability and efficiency. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: A number of nonlinear phenomena in many branches of the applied sciences and engineering are described in terms of delay differential equations, which arise when the evolution of a system depends both on its present and past time. In this work we apply the Adomian decomposition method (ADM) to obtain solutions of several delay differential equations subject to history functions and then investigate several numerical examples via our subroutines in MAPLE that demonstrate the efficiency of our new approach. In our approach history functions are continuous across the initial value and its derivatives must be equal to the initial conditions (see Section ) so that our results are more efficient and accurate than previous works. [Copyright &y& Elsevier]

This paper deals with the design of Ni47Ti44Nb9 shape memory alloy (SMA) tightening components. The tightening of an SMA ring on an elastic pipe is analyzed using the finite element code ABAQUS® and a UMAT subroutine developed by the authors to model the specific behavior of Ni47Ti44Nb9 SMA. Main features of the thermomechanical model implemented in this UMAT routine are briefly recalled. Numerical predictions are validated using experimental tightening pressures obtained on a test bed developed in this work. The validation strategy is documented and the results for different ring thicknesses are presented. This finite element tool is then applied to a parametric study of the influence of ridges on the tightening pressure. Eventually, geometrical defects like out of roundness are considered. [ABSTRACT FROM PUBLISHER]

The dqds algorithm computes all the singular values of an n x n bidiagonal matrix to high relative accuracy in O(n²) cost. Its efficient implementation is now available as a LAPACK subroutine and is the preferred algorithm for this purpose. In this paper we incorporate into dqds a technique called aggressive early deflation, which has been applied successfully to the Hessenberg QR algorithm. Extensive numerical experiments show that aggressive early deflation often reduces the dqds runtime significantly. In addition, our theoretical analysis suggests that with aggressive early deflation, the performance of dqds is largely independent of the shift strategy. We confirm through experiments that the zero-shift version is often as fast as the shifted version. We give a detailed error analysis to prove that with our proposed deflation strategy, dqds computes all the singular values to high relative accuracy. [ABSTRACT FROM AUTHOR]

Abstract: This article is concerned with implementing the Arlequin method into the commercial finite element software ABAQUS and demonstrating its versatility in various typical applications. According to the basic idea of the Arlequin method, the particular formulations for the ABAQUS user element are presented. A unified method for calculating coupling matrices is proposed in an obvious and straightforward way. The user element subroutines for coupling two relatively independent models with different or same dimensions are developed. Four numerical examples are considered: One is to demonstrate the coupling of elements with the same element type but different grid density by the Arlequin method, and the other three examples involve different types of elements. The numerical results justify the correctness of the codes developed for the user defined elements as well as the feasibility of the Arlequin method which is successfully integrated into ABAQUS. [Copyright &y& Elsevier]

Abstract: A Python tool for manipulating netCDF files in a parallel infrastructure is proposed. The parallel interface, PyPnetCDF, manages netCDF properties in a similar way to the serial version from ScientificPython, but hiding parallelism to the user. Implementations details and capabilities of the developed interfaces are given. Numerical experiments that show the friendly use of the interfaces and their behaviour compared with the native routines, are presented. [Copyright &y& Elsevier]

Independent component analysis (ICA) problem is often posed as the maximization/minimization of an objective/cost function under a unitary constraint, which presumes the prewhitening of the observed mixtures. The parallel adaptive algorithms corresponding to this optimization setting, where all the separators are jointly trained, are typically implemented by a gradient-based update of the separation matrix followed by the so-called symmetrical orthogonalization procedure to impose the unitary constraint. This article addresses the convergence analysis of such algorithms, which has been considered as a difficult task due to the complication caused by the minimum-(Frobenius or induced 2-norm) distance mapping step. We first provide a general characterization of the stationary points corresponding to these algorithms. Furthermore, we show that fixed point algorithms employing symmetrical orthogonalization are monotonically convergent for convex objective functions. We later generalize this convergence result for nonconvex objective functions. At the last part of the article, we concentrate on the kurtosis objective function as a special case. We provide a new set of critical points based on Householder reflection and we also provide the analysis for the minima/maxima/saddle-point classification of these critical points. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we introduce an implementation of the extended finite element method for fracture problems within the finite element software ABAQUSTM. User subroutine (UEL) in Abaqus is used to enable the incorporation of extended finite element capabilities. We provide details on the data input format together with the proposed user element subroutine, which constitutes the core of the finite element analysis; however, pre-processing tools that are necessary for an X-FEM implementation, but not directly related to Abaqus, are not provided. In addition to problems in linear elastic fracture mechanics, non-linear frictional contact analyses are also realized. Several numerical examples in fracture mechanics are presented to demonstrate the benefits of the proposed implementation. [Copyright &y& Elsevier]

Simulation of polydisperse flows must include the effects of particle–particle interaction, as breakage and aggregation, coupling the population balance equation (PBE) with the multiphase modelling. In fact, the implementation of efficient and accurate new numerical techniques to solve the PBE is necessary. The direct quadrature method of moments, known as DQMOM, is a moment-based method that uses an optimal adaptive quadrature closure and came into view as a promising choice for this implementation. In the present work, DQMOM was implemented in two CFD packages: the commercial ANSYS CFX, through FORTRAN subroutines, and the open-source OpenFOAM, by directly coding the PBE solution. Transient zero-dimensional and steady one-dimensional simulations were performed in order to explore the PBE solution accuracy using several interpolation schemes. Simulation cases with dominant breakage, dominant aggregation and invariant solution (equivalent breakage and aggregation) were simulated and validated against an analytical solution. The solution of the population balance equation was then coupled to the two-fluid model, considering that all particles classes share the same velocity field. Momentum exchange terms were evaluated using the local instantaneous Sauter mean diameter of the size distribution function. The two-dimensional tests were performed in a backward facing step geometry where the vortex zones traps the particles and provides high rates of breakage and aggregation. [Copyright &y& Elsevier]

Abstract: Coastal and regional ocean forecasts can be currently performed on a daily basis due to the advances in numerical techniques and in computational resources. Maintenance of routine forecasts is a demanding task from the point of view of software engineering since it involves a number of new additional tasks difficult to code efficiently in the compiled languages in which ocean models are written. In this contribution, we present a set of free, open-source, portable and fast modules named OOFɛ – Operational Ocean Forecast Python Engine that provide a way to cope with the demanding requirements of routine execution of a regional ocean model written in a compiled language (namely the Regional Ocean Modelling System, ROMS, developed in Fortran) and that make the forecast process possible and fully automatic and robust. [Copyright &y& Elsevier]

Abstract: Computation of exponential modula when using hashing functions such as Karp-Rabin fingerprints can be quite cumbersome especially when the alphabet size is large. In this paper, we show an interesting result which can allow this computation to be done in a very simple and efficient manner. [Copyright &y& Elsevier]