A vehicle routing improvement algorithm comparison of a “greedy” and a matching implementation for inventory routing

Given an initial solution to a vehicle routing problem—(VRP)—we present three heuristic route improvement schemes based on the concept of node interchange between different routes. Three algorithms are presented together with their computational performance when applied to an inventory routing problem for 12 consecutive weekly periods. All three procedures improve the initial solution constructed by a modified Clark and Wright algorithm by over 50% as measured by the change in the value of the objective function. In two of the algorithms a minimum weight matching problem is solved repetitively.     

FPGA implementation of time–frequency analysis algorithms for laser welding monitoring

The on-line monitoring and detection of defects in laser welding is a basic manufacturing requirement in several applicative contexts, as vehicle assembly in automotive production. This work presents the FPGA implementation of time–frequency analysis algorithms as an effective solution compared with pure software implementation based on different modern processors. In particular the proposed FPGA based approach not only satisfies the processing constraints of the considered application, but still offers a high degree of flexibility and modularity.     

Do too many goals impede a program? A case study of enterprise system implementation with multiple interdependent projects

Complex or large information technology (IT) implementations are typically managed as single programs composed of multiple projects. Program managers must be able to manage the interfaces of multiple interdependent projects to realize the goals of an IT implementation. However, the common problems of conflict and poor coordination often hinder the achievement of a program's goals. Part of this difficulty may lie in the structuring of the program goals themselves. Guided by Strategic Consensus Theory (SCT) and Realistic Group Conflict Theory (RGCT), we examine three enterprise system programs to study the relationship between the shared understanding of multiple or single program goals and conflict resolution and the coordination of programs in an attempt to explain a program's successful implementation. We find that a shared goal understanding as suggested by SCT is not sufficient to facilitate essential coordination. However, a superordinate goal as suggested by RGCT appears to resolve any discrepancies. The results imply that goals should be structured as superordinate requirements.     

A posteriori error analysis of a fully-mixed formulation for the Brinkman–Darcy problem

We develop the a posteriori error analysis for a mixed finite element method applied to the coupling of Brinkman and Darcy equations in 3D, modelling the interaction of viscous and non-viscous flow effects across a given interface. The system is formulated in terms of velocity and pressure within the Darcy subdomain, together with vorticity, velocity and pressure of the fluid in the Brinkman region, and a Lagrange multiplier enforcing pressure continuity across the interface. The solvability of a fully-mixed formulation along with a priori error bounds for a finite element method have been recently established in Álvarez et al. ( Comput Methods Appl Mech Eng 307:68–95, 2016). Here we derive a residual-based a posteriori error estimator for such a scheme, and prove its reliability exploiting a global inf-sup condition in combination with suitable Helmholtz decompositions, and interpolation properties of Clément and Raviart–Thomas operators. The estimator is also shown to be efficient, following a localisation strategy and appropriate inverse inequalities. We present numerical tests to confirm the features of the estimator and to illustrate the performance of the method in academic and application-oriented problems.     

Efficient hardware implementation of 8 × 8 integer cosine transforms for multiple video codecs

The current trend of digital convergence leads to the need of the video decoder that should support multiple video standards such as, H.264/AVC, JPEG, MPEG-2/4, VC-1, and AVS on a single platform. In this paper, we present a cost-sharing architecture of multiple transforms to support all five popular video codecs. The architecture is based on a new multi-dimensional delta mapping. Here the inverse transform matrix of the Discrete Cosine Transform (DCT) of AVS, that has the lowest computational unit, is taken as the base to compute the inverse DCT matrices of the other four codecs. The proposed architecture uses only adders and shifters on a shared basis to reduce the hardware cost significantly. The shared architecture is implemented on FPGA and later synthesized in CMOS 0.18 μm technology. The results show that the proposed design satisfies the requirement of all five codecs with a maximum decoding capability of 60 fps of a full HD video. The scheme is also suitable for low-cost implementation in modern multi-codec systems.     

BLAZE™: An implementation of the Smith-Waterman sequence comparison algorithm on a massively parallel computer

We have implemented the Smith and Waterman dynamic programming algorithm on the massively parallel MP1104 computer from MasPar and compared its ability to detect remote protein sequence homologies with that of other commonly used database search algorithms. Dynamic programming algorithms are normally too computer intensive to permit full databases search, however on the MP1104 a search of the Swiss-Prot database takes about 15 s. This nearly interactive speed of database searching permits one to optimize the parameters for each query. Most of the common database search methods (FASTA, FASTDB and BLAST) gain their speed by using approximations such as word matching or eliminating gaps from the alignments which prevents them from detecting remote homologies. By using queries from protein super families containing a large number of family members of diverse similarities, we have measured the ability of each of these algorithms to detect the remotest members of each super family. Using these super families, we have found that the algorithms, in order of decreasing sensitivity are BLAZE, FASTDB, FASTA and BLAST. Hence the massively parallel computers allow one to have maximal sensitivity and search speed simultaneously.     

A comparison of mix models for the Rayleigh–Taylor instability

Four mix models, implemented into an Arbitrary Lagrangian–Eulerian (ALE) multi-physics code, are compared on simulations of the Rayleigh–Taylor instability. The specific models of interest are a mass diffusion model, the $k\text{–}L$ turbulence model, the BHR turbulence model, and a multifluid interpenetration mix model. The bubble growth rates produced by the different models are compared to experimentally determined growth rates. The diffusion model reproduces the characteristic $t^{1/2}$ growth for diffusion processes and therefore does not reproduce instability growth rates, as expected. The $k\text{–}L$ and BHR turbulence models reproduce the nominal instability growth rates at multiple Atwood numbers with a single set of model parameters. The multifluid interpenetration model exhibits diffusion-like behavior and therefore does not reproduce instability growth rates. All four models exhibit Cauchy-like convergence in the mixing layer width with decreasing mesh size, although the multifluid model exhibits both a larger error for a given mesh size and a slower convergence rate than the turbulence models.     

Stability analysis of T–S fuzzy models for nonlinear multiple time-delay interconnected systems

In this paper, the Takagi–Sugeno (T–S) fuzzy model representation is extended to the stability analysis for nonlinear interconnected systems with multiple time-delays using linear matrix inequality (LMI) theory. In terms of Lyapunov’s direct method for multiple time-delay fuzzy interconnected systems, a novel LMI-based stability criterion which can be solved numerically is proposed. Then, the common P matrix of the criterion is obtained by LMI optimization algorithms to guarantee the asymptotic stability of nonlinear interconnect systems with multiple time-delay. Finally, the proposed stability conditions are demonstrated with simulations throughout this paper.     

A Kane’s based algorithm for closed-form dynamic analysis of a new design of a 3RSS-S spherical parallel manipulator

This paper proposes a systematic methodology to obtain a closed-form formulation for dynamics analysis of a new design of a fully spherical robot that is called a 3(RSS)-S parallel manipulator with real co-axial actuated shafts. The proposed robot can completely rotate about a vertical axis and can be used in celestial orientation and rehabilitation applications. After describing the robot and its inverse position, velocity and acceleration analysis is performed. Next, based on Kane’s method, a methodology for deriving the dynamical equations of motion is developed. The elaborated approach shows that the inverse dynamics of the manipulator can be reduced to solving a system of three linear equations in three unknowns. Finally, a computational algorithm to solve the inverse dynamics of the manipulator is advised and several trajectories of the moving platform are simulated.

     

Multisensor comparison of NDVI for a semi‐arid environment in Spain

The joint use of multiresolution sensors from different satellites offers many opportunities to describe vegetation and its dynamics. This paper introduces the concept of a virtual constellation (defined as an ensemble of all Earth Observation satellites in orbit that satisfy common requirements) for agricultural applications and contributes to providing the necessary inter‐sensor calibration methodology for spectral reflectances and NDVI. For this purpose, we performed an observational study, comparing reflectances and the Normalized Difference Vegetation Index (NDVI), from near‐synchronous image pairs of Landsat 7 Enhanced Thematic Mapper Plus (ETM+), as the reference sensor and Landsat 5 Thematic Mapper (TM), IRS 1C/D LISS‐III (LISS), Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), QuickBird, and NOAA Advanced Very High‐resolution Radiometer (AVHRR). Linear relationships were found for the intercalibration of reflectances and NDVI from one sensor to another, for all sensors, provided that some spatial aggregation was performed. The main source of data dispersion in our linear cross‐sensor translation equations is the geolocation uncertainty inherent in the process of geometric correction. Consequently, spatial aggregation always needs to be performed if (different or the same) sensors are to be used to derive time‐series of biogeophysical parameters over heterogeneous areas. The homogenous zone approach developed here is recommended as an excellent tool for deriving robust new cross‐sensor relationships, provided that the selected homogeneous crops cover the full NDVI range. The linear cross‐sensor relationships derived from one image pair were shown to be valid for the whole season and for all areas with similar vegetation and climate.     

A comparison of parallel solvers for the incompressible Navier–Stokes equations

The paper compares coupled multigrid methods and pressure Schur complement schemes (operator splitting schemes) for the solution of the steady state and time dependent incompressible Navier–Stokes equations. We consider pressure Schur complement schemes with multigrid as well as single grid methods for the solution of the Schur complement problem for the pressure. The numerical tests have been carried out on benchmark problems using a MIMD parallel computer. They show the superiority of the coupled multigrid methods for the considered class of problems. Received: 14 October 1997 / Accepted: 11 February 1998     

A first error indicator for micro–macro simulations of viscoelastic fluids having closed-form constitutive equations

An a posteriori error indicator for viscoelastic flow calculations is proposed by the author for a recently introduced method. This new method is derived from the Brownian configuration field approach and can be applied to models for which closed-form expressions already exist. Numerical results are presented in the context of the spectral element method to show the reliability of the error indicator. The benchmark problem of the flow of an Oldroyd-B fluid past a cylinder in a channel is used and we show that this new method is always more accurate than using a constitutive equation.     

The bending strip method for isogeometric analysis of Kirchhoff–Love shell structures comprised of multiple patches

In this paper we present an isogeometric formulation for rotation-free thin shell analysis of structures comprised of multiple patches. The structural patches are C¹- or higher-order continuous in the interior, and are joined with C⁰-continuity. The Kirchhoff–Love shell theory that relies on higher-order continuity of the basis functions is employed in the patch interior as presented in Kiendl et al. [36]. For the treatment of patch boundaries, a method is developed in which strips of fictitious material with unidirectional bending stiffness and zero membrane stiffness are added at patch interfaces. The direction of bending stiffness is chosen to be transverse to the patch interface. This choice leads to an approximate satisfaction of the appropriate kinematic constraints at patch interfaces without introducing additional stiffness to the shell structure. The attractive features of the method include simplicity of implementation and direct applicability to complex, multi-patch shell structures. The good performance of the bending strip method is demonstrated on a set of benchmark examples. Application to a wind turbine rotor subjected to realistic wind loads is also shown. Extension of the bending strip approach to the coupling of solids and shells is proposed and demonstrated numerically.     

KINAL—a program package for kinetic analysis of reaction mechanisms

A program package is provided for analysis of kinetic mechanisms on personal computers. KINAL consists of four programs called DIFF, SENS, PROC and YRED. These require similar input data and use common subroutines. DIFF solves stiff differential equations and SENS computes the local concentration sensitivity matrix. PROC generates the rate sensitivity matrix or the quasi-stationary sensitivity matrix from concentration data or uses a matrix computed by SENS and extracts the kinetic information inherent in sensitivity matrices by principal component analysis. Finally, YRED provides suggestions for the elimination of species from the reaction mechanism.     

An algorithm of contact problems for forming process of thin plates—a numerical analysis for the seaming process of a can

An algorithm of contact problems for processing thin plates is presented. In the seaming process of a can, two thin plates, an end and flange of a can slip each other and repeat contacting and separating, and are deformed by a roll. To analyse such a complex contact problem, an algorithm using penalty forces and maximum displacement control is proposed. A trial analysis of the seaming process with this algorithm is shown in this paper.     

A family of non-conforming elements and the analysis of Nitsche’s method for a singularly perturbed fourth order problem

In this paper we address several issues arising from a singularly perturbed fourth order problem with small parameter ε. First, we introduce a new family of non-conforming elements. We then prove that the corresponding finite element method is robust with respect to the parameter ε and uniformly convergent to order h ^1/2. In addition, we analyze the effect of treating the Neumann boundary condition weakly by Nitsche’s method. We show that such treatment is superior when the parameter ε is smaller than the mesh size h and obtain sharper error estimates. Such error analysis is not restricted to the proposed elements and can easily be carried out to other elements as long as the Neumann boundary condition is imposed weakly. Finally, we discuss the local error estimates and the pollution effect of the boundary layers in the interior of the domain.     

Stability and bifurcation analysis for a model of a nonlinear coupled pitch–roll ship

Using a combination of analytical and numerical methods, the paper studies the stability and bifurcations for a model of a nonlinear coupled pitch–roll ship. The model represents a two-degree-of-freedom system with quadratic coupling subjected to a modulated sinusoidal excitation. Three types of critical points for the bifurcation response equations near the combination resonance in the presence of internal resonance are considered. These points are characterized by a double zero and two negative eigenvalues, a double zero and a pair of purely imaginary eigenvalues, and two pairs of purely imaginary eigenvalues, respectively. For each case, the stability regions for the initial equilibrium solution and the critical bifurcation curves are obtained. The amplitude response curves with respect to detuning/damping parameters for critical bifurcation parameters are obtained for the first two types, and detailed analyses of the eigenvalues of the linearized system for each parametric region are given. For the third type, with the aid of normal form theory, the explicit expressions of the critical bifurcation curves leading to incipient and secondary bifurcations are obtained. Bifurcations leading to 2D, 3D tori and their stability conditions are also investigated. Some new dynamical behaviors are presented for this system.