Explicit Implementation Research Articles

Probabilistic Prediction of Crack Depth Distributions Observed in Structures Subjected to Thermal Fatigue

The application of risk-based technologies not only to in-service inspections but also to the design of components and systems, encompassing a plant life-cycle, is the way to be pursued for the improvement of design of new reactors such as fast breeder reactors. When doing so, it is necessary to develop an analytical method that is capable of estimating failure probabilities without a failure database that can only be established on the long-time accumulation of operational experiences. The prediction method should estimate failure probabilities based on actual mechanisms that cause failure. For this purpose, this study developed a structural reliability evaluation method using probabilistic prediction of crack depth distributions for thermal fatigue, which is one of representative failure modes to be prevented in components of nuclear plants. This method is an extension of probabilistic fracture mechanics approach but is capable of modeling crack initiation, crack propagation, and crack depth density distribution at a given cycle. To verify the methodology, crack depth distribution observed in thermal fatigue test specimens was evaluated, and it was shown that the method could reproduce the observed crack depth distributions fairly well. This is considered to explore the possibility that probabilistic fracture mechanics approach can be verified by experiments, which was deemed impossible so far. Further improvement such as explicit implementation of interaction mechanisms between adjacent cracks will allow this methodology to be applied to the procedure of optimization of in-service inspection planning, as well as to the optimization of safety factors in component design of nuclear plants.

Advance and retreat: tobacco control policy in the U.S. military.

This archival study explored why military tobacco control initiatives have thus far largely failed to meet their goals. We analyzed more than 5,000 previously undisclosed internal tobacco industry documents made public via an online database and additional documents obtained from the U.S. military. In four case studies, we illustrate how pressures exerted by multiple political actors resulted in weakening or rescinding military tobacco control policy initiatives. Our findings suggest that lowering military smoking rates will require health policymakers to better anticipate and counter political opponents. The findings also suggest that effective tobacco control policies may require strong, explicit implementation instructions and high-level Department of Defense support. Finally, policy designers should also consider ways to reduce or eliminate existing perverse incentives to increase tobacco consumption, such as allowing exchange store tobacco sales to fund Morale, Recreation, and Welfare Programs.

Caveats on the implementation of the generalized material point method

The material point method (MPM) is a numerical method for the Solution of problems in continuum mechanics, including Situations of large deformations. A generalization (GMPM) of this method was Introduced by Bardenhagen and Kober (2004) in order to avoid some computational instabilities inherent to the original method (MPM). This generalization leads to a method more akin of the Petrov-Galerkin procedure. Although It is possible to find in the literature examples of the deduction and applications of the MPM/GMPM to specific problems, its detailed Implementation is yet to be presented. Therefore. this paper attempts to describe all steps required for the explicit Implementation of the material point method, Including its generalization. Moreover, some caveats during the implementation are addressed. For example, the setting up of boundary conditions and the steps for the computation of Values at nodes and material points are discussed. The Influences of the time and space discretization are also verified, basing oil numerical analyses. Two strategies for the update of stress. known as Update stress first (USF) and update stress last (USL) are numerically investigated. It is shown that both the order for the computation of boundary conditions and the way that the,rid values are extrapolated have high impact on the accuracy of the Solution. The complete 3D algorithm is detailed and summarized in order to make easier the implementation of the GMPM/MPM.

An algorithm for the Traverso–Swan theorem on seminormal rings

We give an algorithm for an explicit implementation of Traverso–Swan's theorem, saying that a reduced ring A is seminormal if and only if the canonical map: Pic A → Pic A [ x ] is an isomorphism.

A robust and reliable method for detecting signals of interest in multiexponential decays

The concept of rejecting the null hypothesis for definitively detecting a signal was extended to relaxation spectrum space for multiexponential reconstruction. The novel test was applied to the problem of detecting the myelin signal, which is believed to have a time constant below 40 ms, in T2 decays from magnetic resonance imagining of the human brain. It was demonstrated that the test allowed the detection of a signal in a relaxation spectrum by using only the information in the data, thus avoiding any potentially unreliable prior information. The test was implemented both explicitly and implicitly for simulated T2 measurements. For the explicit implementation, the null hypothesis was that a relaxation spectrum existed that had no signal below 40 ms and that was consistent with the T2 decay. The confidence level by which the null hypothesis could be rejected gave the confidence level that there was signal below the 40 ms time constant. The explicit implementation assessed the test's performance with and without prior information where the prior information was the non-negative relaxation spectrum assumption. The test was also implemented implicitly with a data conserving multiexponential reconstruction algorithm that used left invertible matrices and that has been published previously. The implicit and explicit implementations demonstrated similar characteristics in detecting the myelin signal in both the simulated and experimental T2 decays, providing additional evidence to support the close link between the two tests. When the relaxation spectrum was assumed to be non-negative, the novel test required signal to noise ratios (SNRs) approaching 1000 in the T2 decays for detection of the myelin signal with high confidence. When the relaxation spectrum was not assumed to be non-negative, the SNR requirements for a detection with high confidence increased by a factor of 25. The application of the test to a T2 decay from human white matter, measured in vivo with a SNR of 650, demonstrated a solid detection of the signal below 40 ms believed to be due to the myelin water. This study demonstrated the robustness and reliability of extending the concept of rejecting the null hypothesis to relaxation spectrum space. The study also raised serious questions about the susceptibility to false positive detection of the myelin signal of the multiexponential reconstruction algorithms currently in use.

Child Custody in Jewish Law: From Authority of the Father to the Best Interest of the Child

The understanding of Jewish law of the legal rationale of the relationship between parent and child developed gradually. In the first stage, in ancient Jewish law, the dominant tendency was to affirm the authority of the Jewish father over the members of his family. During this period, the idea that parents have a natural responsibility to love their children, care for them and provide for their welfare was less transparent. The main purpose of the rules concerning the relationship between parents and children at this stage was the assertion of the rights and needs of the father of the family.1 Consequently, some of the regulations of ancient Jewish law regarding the relationship between parents and children were not necessarily focused on the best interest of the child and the ideological basis for the legal policy in the sphere of custody in the ancient period was somewhat vague.By contrast, during the second, medieval stage of development of Jewish law on the relationship between parents and children, the ancient supreme principle, of the father's authority over members of his family in all spheres including the sphere of custody of children, was largely replaced by an explicit rule in Jewish law: the best interest of the child is a paramount consideration. Indeed, we could say that the explicit implementation of the principle of best interest of the child in Jewish custody cases is a medieval invention, introduced by Jewish scholars at this period in their child custody verdicts. By contrast to the ancient period, the rules of custody, which had become fully defined at this stage, utilizing this principle, usually favored the mother.

Floquet perturbation theory: Applicability of the finite level approximation in different gauges

The Floquet perturbation theory represents an important technique for studying the response of atoms or molecules exposed to weak monochromatic fields. In this paper, we discuss an explicit implementation of the Floquet perturbation theory starting from different gauge representations of the matter-light Hamiltonian, namely, from the velocity gauge, the length gauge, and the acceleration gauge. Interestingly, the development of the second-order Floquet perturbation theory in different gauges gives rise to formally different quasienergy corrections, whose mutual equivalence is not self-evident. Nevertheless, our derivation shows how the perturbation formulas associated with different gauges can be converted to one another, provided that a complete basis set of the atomic-molecular electronic states has been used. On the other hand, it turns out that an inappropriate basis set truncation employed for a particular gauge (such as, e.g., the two-level approximation applied within the velocity gauge) may sometimes lead toward completely wrong results. This fact should serve as a warning against an uncautious use of various gauge transformations in practical calculations with a finite basis set.

60 GHz wireless communications: Emerging requirements and design recommendations

Multiple GHz of internationally available, unlicensed spectrum surrounding the 60 GHz carrier frequency has the ability to accommodate high-throughput wireless communications. While the size and availability of this free spectrum make it very attractive for wireless applications, 60 GHz implementations must overcome many challenges. For example, the high attenuation and directional nature of the 60 GHz wireless channel as well as limited gain amplifiers and excessive phase noise in 60 GHz transceivers are explicit implementation difficulties. The challenges associated with this channel motivate commercial deployment of short-range wireless local area networks, wireless personal area networks, and vehicular networks. In this paper we detail design tradeoffs for algorithms in the 60 GHz physical layer including modulation, equalization, and space-time processing. The discussion is enhanced by considering the limitations in circuit design, characteristics of the effective wireless channel (including antennas), and performance requirements to support current and next generation 60 GHz wireless communication applications.

Improved Explicit Method for Structural Dynamics

An explicit method, which simultaneously has the most promising advantages of the explicit and implicit methods, is presented. It is shown that numerical properties of the proposed explicit method are exactly the same as those of the constant average acceleration method for linear elastic systems. However, for nonlinear systems, it has unconditional stability for an instantaneous stiffness softening system and conditional stability for an instantaneous stiffness hardening system. This conditional stability property is much better than that of the Newmark explicit method. Hence, the proposed explicit method is possible to have the most important property of unconditional stability for an implicit method. On the other hand, this method can be implemented as simply as an explicit method, and hence, possesses the most important property of explicit implementation for an explicit method. Apparently, the integration of these two most important properties of explicit and implicit methods will allow the proposed explicit method to be competitive with other integration methods for structural dynamics.

A conservative discretization of the Kepler problem based on the L-transformations

Abstract Conservative numerical schemes for the two- and three-dimensional Kepler motion were recently proposed in [Y. Minesaki, Y. Nakamura, Phys. Lett. A 306 (2–3) (2002) 127; Y. Minesaki, Y. Nakamura, Phys. Lett. A 324 (4) (2004) 282]. They are based on Levi-Civita and Kustaanheimo–Stiefel transformations respectively. The schemes preserve all first integrals of Kepler motion: the Hamiltonian function, the angular momentum and Runge–Lenz vector. In the present Letter we extend this approach to the L-transformations (a generalization of Levi-Civita and Kustaanheimo–Stiefel transformations). Thus, we can consider more general family of the conservative numerical schemes for the two- and three-dimensional Kepler motion as well as construct conservative schemes for higher-dimensional Kepler problems. Conservation of the first integrals is proved with the help of L-matrix identities. The proposed numerical scheme permits explicit implementation.

Conservative discretizations of the Kepler motion

Modified vector fields are used to construct high-order conservative discretizations of the three-dimensional Kepler motion. The numerical integrators preserve the Hamiltonian function, the angular momentum and Runge–Lenz vector. In particular, the exact integrator of the Kepler motion is found. The proposed numerical schemes permit explicit implementation.

FULL NEWTON LATTICE BOLTZMANN METHOD FOR TIME-STEADY FLOWS USING A DIRECT LINEAR SOLVER

A full Newton lattice Boltzmann method is developed for time-steady flows. The general method involves the construction of a residual form for the time-steady, nonlinear Boltzmann equation in terms of the probability distribution. Bounce-back boundary conditions are also incorporated into the residual form. Newton's method is employed to solve the resulting system of non-linear equations. At each Newton iteration, the sparse, banded, Jacobian matrix is formed from the dependencies of the non-linear residuals on the components of the particle distribution. The resulting linear system of equations is solved using a direct solver designed for sparse, banded matrices. For the Stokes flow limit, only one matrix solve is required. Two dimensional flow about a periodic array of disks is simulated as a proof of principle, and the numerical efficiency is carefully assessed. For the case of Stokes flow (Re = 0) with resolution 251×251, the proposed method performs more than 100 times faster than a standard, fully explicit implementation.

Hardware Synthesis of Explicit Model Predictive Controllers

The general solution to constrained linear and piecewise linear model predictive control (MPC) has recently been explicitly characterized in terms of piecewise-linear (PWL) state feedback control. This means that a PWL controller can be precomputed using parametric programming, and the exact explicit MPC implementation amounts to the evaluation of a PWL function in the control unit. It has recently been shown that PWL function evaluation can be accelerated by searching a binary tree data structure, leading to highly efficient, accurate, and verifiable software implementation in low-cost embedded control units. In this work, we report hardware synthesis results for this type of PWL control, and show that explicit MPC solutions can be implemented in an application specific integrated circuit (ASIC) with about 20 000 gates, leading to computation times in the microsecond scale. This opens the way for the use of highly advanced control designs such as constrained MPC in small-scale industrial and consumer electronics application areas that are characterized by fast sampling or low cost, including mechatronics, microelectromechanical systems (MEMS), automotive control, power electronics, and acoustics. The main limitation of the approach is that the memory requirements increase rapidly with the problem dimensions

Electron exchange influence on the energy loss of ions in SIMOX structure

In this research report we analyse Rutherford back scattering (RBS) measurements with SIMOX structure and transmission experiments with Si single crystals by means of Monte Carlo simulation code with explicit implementation of impact parameter dependence of the electron transfer and the electronic energy loss processes. Although all the basic experimental characteristics of the ion channelling have been successively reproduced, effects related to the charge pre-equilibrium region turned out to be much smaller than these determined from experiment.

Deformable registration of diffusion tensor MR images with explicit orientation optimization

In this paper, we present a novel deformable registration algorithm for diffusion tensor MR images that enables explicit optimization of tensor reorientation. The optimization seeks a piecewise affine transformation that divides the image domain into uniform regions and transform each region affinely. The objective function captures both the image similarity and the smoothness of the transformation across region boundaries. The image similarity enables explicit orientation optimization by incorporating tensor reorientation, which is necessary for warping diffusion tensor images. The objective function is formulated in a way that allows explicit implementation of analytic derivatives to drive fast and accurate optimization using the conjugate gradient method. By explicitly optimizing tensor reorientation, the algorithm is designed to take advantage of similarity measures comparing tensors as a whole. The optimal transformation is hierarchically refined in a subdivision framework. A comparison with affine registration for inter-subject normalization of 8 subjects shows that the proposed algorithm improves the alignment of several major white matter structures examined: the anterior thalamic radiations, the inferior fronto-occipital fasciculi, the corticospinal/corticobulbar tracts and the genu and the splenium of the corpus callosum. The alignment of white matter structures is assessed using a novel scheme of computing distances between the corresponding fiber bundles derived from tractography.

Extension of a multi-surface plasticity model to two-phase materials

The work reported in this paper is part of the ongoing research on the development of suitable elastic–plastic constitutive models for multiphase materials. This paper is concerned with the application of an elastic–plastic constitutive model based on the Mróz-multi-surface kinematic hardening rule to particulate metal matrix composites (PMMCs). Details of the Mróz-based elastic–plastic constitutive model for PMMCs and its explicit implementation are presented to enhance the applicability of the model for a stress controlled simulation. Comparison between numerical predictions and experimental results is also presented for uniaxial loading and biaxial proportional and non-proportional loading paths. For the load paths tested, reasonable agreement is observed between the numerical and the experimental results.

A new hybrid approach using the explicit dynamic finite element method and thermodynamic law for the analysis of the thermoforming and blow molding processes for polymer materials

In this work, the problem of the modeling of thermoforming and blow molding processes for viscoelastic sheet are considered. To take account of the enclosed gas volume, responsible for inflation of the thermoplastic membrane (which contributes significantly to the strength and stiffness of a thermoplastic structure), we considered thermodynamic approach to express external work in terms of a closed volume. The pressure load is thus deduced from the thermodynamic law of ideal gases. The viscoelastic behavior of the K-BKZ model is considered. The Lagrangian formulation together with the assumption of the membrane theory is used in the explicit dynamic finite element implementation. The numerical validation is performed by comparing the theoretical bubble free inflation with numerical results. Moreover, the influence of the K-BKZ constitutive model on the thickness and stress distribution in the thermoforming of containers is presented. POLYM. ENG. SCI., 46:1554–1564, 2006. © 2006 Society of Plastics Engineers

The Compression of Dark Matter Halos by Baryonic Infall

The initial radial density profiles of dark matter halos are laid down by gravitational collapse in hierarchical structure formation scenarios and are subject to further compression as baryons cool and settle to the halo centers. Here we describe an explicit implementation of the algorithm, originally developed by Young, to calculate changes to the density profile as the result of adiabatic infall in a spherical halo model. Halos with random motion are more resistant to compression than are those in which random motions are neglected, which is a key weakness of the simple method widely employed. Young's algorithm results in density profiles in excellent agreement with those from N-body simulations. We show how the algorithm can be applied to determine the original uncompressed halos of real galaxies, a step that must be computed with care in order to enable a confrontation with theoretical predictions from theories such as ΛCDM.

A Permutation-Translation Simulated Annealing Algorithm for L1 and L2 Unidimensional Scaling

Given a set of objects and a symmetric matrix of dissimilarities between them, Unidimensional Scaling is the problem of finding a representation by locating points on a continuum. Approximating dissimilarities by the absolute value of the difference between coordinates on a line constitutes a serious computational problem. This paper presents an algorithm that implements Simulated Annealing in a new way, via a strategy based on a weighted alternating process that uses permutations and point-wise translations to locate the optimal configuration. Explicit implementation details are given for least squares loss functions and for least absolute deviations. The weighted, alternating process is shown to outperform earlier implementations of Simulated Annealing and other optimization strategies for Unidimensional Scaling in run time efficiency, in solution quality, or in both.

The role of tacit knowledge and the challenges in transferring it: a case study at the Finnish NPPs

Explicit knowledge and implementation of proper IT systems have been of concern of many organisations which recognise the importance of managing knowledge for safety operation and sustainable competitive advantage. Data and document management systems have been implemented to capture, store and distribute explicit knowledge. However, recently also awareness of the existence of tacit knowledge in organisations has arisen. What kind of role does this undocumented knowledge, which the employees have acquired throughout their careers, play in nuclear power plant context? This paper explores the role of tacit knowledge and the challenges related to its transfer at the two Finnish nuclear power plants.