Explicit Implementation Research Articles

Matrix manifolds and the Jordan structure of the bialternate matrix product

The bialternate product of matrices was introduced at the end of the 19th century and recently revived as a computational tool in problems where real matrices with conjugate pairs of pure imaginary eigenvalues are important, i.e., in stability theory and Hopf bifurcation problems. We give a complete description of the Jordan structure of the bialternate product 2A⊙I n of an n×n matrix A, thus extending several partial results in the literature. We use these results to obtain regular (local) defining systems for some manifolds of matrices which occur naturally in applications, in particular for manifolds with resonant conjugate pairs of pure imaginary eigenvalues. Such defining systems can be used analytically to obtain local parameterizations of the manifolds or numerically to set up Newton systems with local quadratic convergence. We give references to explicit numerical applications and implementations in software. We expect that the analysis provided in this paper can be used to further improve such implementations.

Transforming visionary products into realities: constituency-building and observacting in NewsPad

In September 1996, NewsPad—one of the first serious prototypes ever of the portable tablet computer went on show during Edinburgh's iTV96 Conference. The paper recounts and analyses the NewsPad experience and, simultaneously, tells a story of the explicit implementation of the sociotechnical constituencies theoretical approach to guide and inform the innovation process in highly uncertain conditions. The discussion is structured in short sections from the visions and realities of the portable tablet computer to the successful demonstration of the working NewsPad in Edinburgh.

Mental health services--maintaining strategic direction.

AIM AND KEY ISSUES: This article reviews the theoretical basis of strategic management in an attempt to provide managers with a better understanding of the underpinning concepts and consequent actions they need to take to avoid loss of control and ultimate failure. The authors argue that community care for the severely mentally ill is failing and that in part the reason for this perceived failure is a closer allegiance to primary care that has shifted the focus away from mental illness. Such a shift, coupled with poor management and a desire by Community Mental Health Nurses (CMHNs) to retain a broad focus and maintain the 'autonomy' they gain when not held in the gravitational grasp of Consultant Psychiatrists, has resulted in strategic drift. The authors suggest 10 possible reasons to explain why CMHNs currently fail to meet the needs of the severely mentally ill. Among these are a lack of explicit strategic implementation plans, professional ambivalence and self-interest, poor management of resources and conflicting demands from key interest groups. It seems that mental health services in this country have reached the point where resistance to change should be crumbling in the face of perceived failure to deliver the required services. Whilst it could be argued that a major and potent source of internal change is performance gaps, few things force change more than sudden and unexpected information about poor organizational performance.

The impact of legislatively imposed practice guidelines on cesarean section rates: the Florida experience.

Florida legislation implemented in the fall of 1992, unique in the nation, mandated that practice guidelines regarding cesarean section deliveries be disseminated to obstetric physicians. The law also required that peer review boards at hospitals be established to review cesarean deliveries and that the exact dates of implementation of the guidelines be reported to a state agency. To determine the impact of the legislation, we conducted a retrospective analysis of 366,246 total live births occurring in Florida hospitals during 1992 and 1993, before and after formal hospital certification of the implementation of the guidelines. Changes in primary and repeat cesarean rates were analyzed for 108 independent groups of births, controlling for the mother's age, race, payment source, and the timing of the implementation of the guidelines at hospitals. The guideline certification program did not accelerate the consistent but gradual downward trend in cesarean births which had already been evident in the three prior years. The data do suggest that the guideline program may have affected repeat cesareans more than primary cesareans, especially in the first quarter of 1993, immediately after the hospital certification period. Reductions in repeat cesareans involved both Medicaid and commercially insured births, whereas reductions in primary cesareans were found almost exclusively within commercially insured mothers, where the existing rates are highest. Although births with a prior cesarean represent only 12.5% of all births, significant decreases in repeat cesareans were found in groups representing 72.6% of this population. By comparison, significant decreases in primary cesareans were found in groups representing only 36.5% of the births without a prior cesarean. The date of guideline implementation reported by hospitals was not related to any systematic change in observed cesarean section rates. We concluded that the mere dissemination of practice guidelines by a state agency may not achieve either the magnitude or the specificity of the results desired without an explicit and thorough guideline implementation program. Blunt legislative mandates may be ineffective when multiple initiatives are already achieving desired outcomes.

A Numerical Implementation of Kolmogorov's Superpositions

Hecht-Nielsen proposed a feedforward neural network based on Kolmogorov's superpositions f(x i,…,x n)= ∑ q=0 2π Φ q(y q) that apply to all real valued continuous functions f(x 1, …, x n) defined on a Euclidean unit cube of dimension n ≥ 2. This network has a hidden layer that is independent of f and that transforms the n-tuples (x 1, …, x n) into the 2n + 1 variables y q, and an output layer in which f is computed. Kůrková has shown that such a network has an approximate implementation with arbitrary activation functions of sigmoidal type. Actual implementation is, however, impeded by the lack of numerical algorithms for the hidden layer which contain continuous functions of the form y q = Σ n p=1 α p ψ( x p + qa) with constants a and α p. This paper gives an explicit numerical implementation of the hidden layer that also enables the implementation of the output layer. Copyright © 1996 Elsevier Science Ltd

A design for future-oriented government

This article presents a design for future-oriented government. To guide the design, nine criteria are proposed, which include the explicit recognition of future generations and future-oriented issues, explicit implementation of a structured decision-making process, incentives to include people of wisdom, and effective and broad-based citizen participation. The two main elements of the design are the Court of Generations and the Futures Congress, which diagnose the severity of threats to future generations and decide what actions to take, respectively. The Futures Administration provides information system support to these institutions. The Futures Issues Commission and the Coordination/Mediation Service assist the futures-oriented government interact with existing governmental institutions that are more appropriate for addressing everyday concerns. It is hypothesized that major decisions regarding the environment, energy, long-term science and space projects, and agriculture, among other areas, would shift to the Futures Congress from the National Legislature.

Effects of increased cloud-cover on a montane forest landscape

Abstract:Although increased cloud-cover may reduce global temperature response to trace gas emissions, it is an important climatic change from an ecological perspective. For plants, cloud-cover reduces photosynthesis and alters establishment; these effects differ among species. The differential effects may be modified, however, by pattern at the landscape level, such as forest edges. Here we include cloud-cover and the edge effects of a snow avalanche path in a simulation of the dynamics of a montane forest using a spatially explicit implementation of the JABOWA-FORET model. Cloud cover is simulated by a 10% reduction in ambient light. Alternately we forced constant full sunlight, constant mortality for conifers, or both, on a strip of simulated cells in order to maintain an avalanche path. Higher light levels maintained on the path allow the persistence of shade-intolerant species that otherwise decline under a scenario of increased cloud-cover (deciduous proportion on 800 cells changes from 0.19 to 0.11...

Explicit Streamline Diffusion Finite Element Methods for the Compressible Euler Equations in Conservation Variables

The paper concerns the streamline diffusion finite element method applied to one- and two-dimensional gas flow described by the inviscid Euler equations in conservation variables. We point out that the streamline diffusion method is a natural finite element analogue to upstream-type finite difference/volume schemes and in fact constitutes a general framework for a large class of them. We study explicit implementations of the method and derive different choices of stabilizing streamline diffusion matrices; in particular we propose a consistent, fully multidimensional, version. A brief review of the theoretical background to the method is presented, and some numerical results in two dimensions are given.

Stability of explicit navier-stokes procedures using k- ε and k - ε/algebraic reynolds stress turbulence models

A three-dimensional explicit Navier-Stokes procedure has been developed for application to compressible turbulent flows, including rotation effects. In the present work, a numerical stability analysis of the discrete, coupled system of seven governing equations is presented. Order of magnitude arguments are presented for flow and geometric properties typical of internal flows, including turbomachinery applications, to ascertain the relative importance of grid stretching, rotation and turbulence source terms, and effective diffusivity on the stability of the scheme. It is demonstrated through both analysis and corroborative numerical experiments that: (1 ) It is quite feasible to incorporate, efficiently, a two-equation k- ϵ turbulence model in an explicit time marching scheme, provided certain numerical stability constraints are enforced. (2) The role of source terms due to system rotation on the stability of the numerical scheme is not significant when appropriate grids are used and realistic rotor angular velocities are specified. (3) The direct role of source terms in the turbulence transport equations on the stability of the numerical scheme is not significant when appropriate grids are used and realistic freestream turbulence quantities are specified, except in the earliest stages of iteration (a result which is contrary to that generally perceived). (4) There is no advantage to numerically coupling the two-equation model system to the mean flow equation system, in regard to convergence or accuracy. (5) For some flow configurations, including turbomachinery blade rows, it is useful to incorporate the influence of artificial dissipation in the prescription of a local timestep. (6) Explicit implementation of an algebraic Reynolds stress model (ARSM) is intrinsically stable provided that the discrete two-equation transport model which provides the necessary values of k and ϵ is itself stable.

Error Analysis for Pseudodynamic Test Method. I: Analysis

On-line, pseudodynamic tests are becoming increasingly popular for large-scale seismic performance testing of structures. Such tests provide a means of simulating the effect of compliance of the structure on the inertial loads it will experience in the event of an earthquake, without the need to use a shaking table. One of the difficulties encountered is that the results from pseudodynamic tests can be extremely sensitive to measurement and control errors. Error analyses available to date have focused on implementations based on explicit time-integration schemes. Recently, however, researchers have successfully implemented an implicit integration scheme, which will probably become the preferred technique for pseudodynamic testing. An error analysis for this implicit scheme is presented, using a systematic approach. It is shown that the effect of measurement and control errors can in most cases be greatly reduced by a suitable adjustment of the measured displacements at every time step. The reduction in errors for this case is similar to that achieved in the explicit implementation by using the computed instead of the measured displacements.

Relative performance comparisons for the Group Explicit class of methods on MIMD, SIMD and pipelined vector computers

The study of the potentiality and suitability of the Group Explicit (GE) class of methods for parallel computers will be completed with the reporting of some results obtained from the implementation of the Group Explicit with Ungrouped ends (GEU) method on two different types of computer systems: the ICL DAP and the CRAY-1S. Finally, a diagrammatical description of the parallel behaviour on a MIMD system of all the GE schemes experimented with will be presented in comparison with the Standard Explicit method.

A new random-number generator for multispin Monte Carlo algorithms

We develop a novel multispin coded random number generator algorithm to compute bits equal to 1 with probabilityp. Compared to previously used algorithms, this generator is at least equally fast and allows for an arbitrary accuracy of the computed probability without any significant increase in time. An explicit implementation of the algorithm is given for a Cray-1 vector computer, and the modifications for other machines are discussed. Finally, the algorithm is tested by computing the magnetization of the two-dimensional Ising model. The measured speed of the program is 57 million spin-flips per second. The agreement with theoretical values is found to remain very satisfying even when quite close (∼-0.5%) to the critical temperature.

Numerical outflow boundary condition for Navier-Stokes flow calculations by a line iterative method

THIS study investigates the use of explicit/implicit, step/linear space extrapolation as numerical outflow boundary conditions for turbulent flow calculations. The emphasis is on the interplay between the use of curvilinear coordinate systems for complex flow calculation and the semiimplicit line iterative procedure. Both a planar singlechanneled and an annular multichanneled flow configuration were used as test models. It was found that implicit linear space extrapolation needs more computing time and may not yield a unique solution. On the other hand, explicit zero-order space extrapolation appears to be a robust outflow boundary condition since it has the largest stability limit with respect to underrelaxation factors and initial conditions. Contents The present study investigates the use of outflow boundary condition for subsonic viscous flow calculations. The emphasis is on the complex geometry configuration arising from, e.g., modeling gas turbine combustor flows. Modeling these flows requires the use of the curvilinear body-fitted coordinate system to allow proper treatment of the near-wall region as well as to reduce the skewness between the streamlines and the coordinate lines, as discussed in Refs. 1 and 2. This study concentrates on one category of outflow boundary condition, extrapolation in space, since it is easier to implement into a computer code. The merits between the explicit and implicit implementation with respect to the iteration level are investigated. Both single- and multichanneled geometry configurations are used for the numerical experiments. Four outflow boundary conditions have been implemented and tested: 1) Explicit step space extrapolation—using an explicit onesided difference to approximate a zero first derivative along the main flow direction, i.e.,

Dealing with Poor Performance: Supervisor Attributions and the Cost of Responding1

The Green and Mitchell (1979) model of the process by which supervisors diagnose and deal with the causes of subordinates' poor performance is based upon attribution theory. The notion is that the supervisor makes an attribution about the cause of the poor performance and then selects an appropriate response or solution to deal with the problem. Two ways in which this can lead to an inapprorpriate solution are, first, a bias toward making internal attributions and, second, an aversion to using costly, even though appropriate, solutions. This study demonstrates that it is possible to prompt participants to make more external attribution about poor performance. It also demonstrates that whichever attributions they make (either internal or external), the solutions they select to deal with the poor performance are congruent with their attributions provided that the solutions do not have explicit implementation costs associated with them. However, when implementation costs are made explicit, costs influence solution selection and reduce the congruence between the attributions and the selected solutions. The possible implications of this finding for success in dealing with poor performance are discussed.

A Recursive Approach to the Cumulant Method of Calculating Reliability and Production Cost

A new recursive approach to the Cumulant Method used in reliability index (LOLP and EUE) and production cost calculations is presented. The method allows to include any number of cumulants without additional explicit theoretical development or software implementation effort. A continuous probability model that approximates the available generating capacity is also introduced. Together, these two features permit a deeper and more exhaustive investigation of the convergence behavior and accuracy of the method. The results shed new light on when and how the cumulant method can be effectively used.

Delphi: An investigation from a Bayesian viewpoint

This paper presents an analysis of Delphi from a Bayesian point of view and brings to attention several hitherto neglected, but highly relevant findings of research in areas other than Delphi proper. The aim has been to seek avenues of improvement in the Delphi technique. This has led to development of a methodology, which is based on a concept of second order probabilities as a measure of one's fuzzy thinking. The justification of this new methodology lies in explicit recognition and implementation of an optimum, determined by the trade-off between advantages and complexities of hierarchial inference. It is essential that conventional Delphi applications, at the very least, be accompanied by a Turoff-type cross impact analysis. It is indicated that the tremendous potential of Bayesianized Delphi in appropriate situations has remained utapped.