77 research outputs found
Structure of the isotropic transport operators in three independent space variables
Based on the idea of separation of variables, a spectral theory for the three-dimensional, stationary, isotropic transport operator in a vector space of complex-valued Borel functions results in continuous sets of regular and generalized eigenfunctions
Recommended from our members
Preconditioned gradient methods for sparse linear systems for very `large structural` problems
This paper deals with background and practical experience with preconditioned gradient methods for sparse linear systems for `very large` structural problems. The conjugate gradient method with diagonal preconditioning (CG/D) is demonstrated to substantially increase the size of structural problems that can be analyzed, significantly reduce computer storage requirements, and cut computing cost; thus allowing for much more detailed modeling and increased engineering efficiency. For one case for a structural system with 396,087 unknowns, the conjugate gradient method with diagonal preconditioning is demonstrated to be a factor of sixty faster than the direct method. For certain problems, however, the number of iterations required by the CG/D method is excessive and improved methods are needed. A stand-alone iterative solver research computer program was developed to evaluate the merits of various matrix preconditioners. A matrix preconditoner based on a shifted incomplete Cholesky factorization algorithm was demonstrated to be superior to other choices. The stand-alone program incorporates an effective data management strategy which utilizes disk and solid state auxiliary computer storage devices to make it possible to efficiently solve excessively large structural problems on state-of-the-art vector and parallel computers. The background of gradient methods, algorithms for their implementation, and practical experience in their applications to structural problems are presented
Recommended from our members
Coupling 2-D cylindrical and 3-D x-y-z transport computations
This paper describes a new two-dimensional (2-D) cylindrical geometry to three-dimensional (3-D) rectangular x-y-z splice option for multi-dimensional discrete ordinates solutions to the neutron (photon) transport equation. Of particular interest are the simple transformations developed and applied in order to carry out the required spatial and angular interpolations. The spatial interpolations are linear and equivalent to those applied elsewhere. The angular interpolations are based on a high order spherical harmonics representation of the angular flux. Advantages of the current angular interpolations over previous work are discussed. An application to an intricate streaming problem is provided to demonstrate the advantages of the new method for efficient and accurate prediction of particle behavior in complex geometries
Increasing health worker capacity through distance learning: a comprehensive review of programmes in Tanzania
<p>Abstract</p> <p>Background</p> <p>Tanzania, like many developing countries, faces a crisis in human resources for health. The government has looked for ways to increase the number and skills of health workers, including using distance learning in their training. In 2008, the authors reviewed and assessed the country's current distance learning programmes for health care workers, as well as those in countries with similar human resource challenges, to determine the feasibility of distance learning to meet the need of an increased and more skilled health workforce.</p> <p>Methods</p> <p>Data were collected from 25 distance learning programmes at health training institutions, universities, and non-governmental organizations throughout the country from May to August 2008. Methods included internet research; desk review; telephone, email and mail-in surveys; on-site observations; interviews with programme managers, instructors, students, information technology specialists, preceptors, health care workers and Ministry of Health and Social Welfare representatives; and a focus group with national HIV/AIDS care and treatment organizations.</p> <p>Results</p> <p>Challenges include lack of guidelines for administrators, instructors and preceptors of distance learning programmes regarding roles and responsibilities; absence of competencies for clinical components of curricula; and technological constraints such as lack of access to computers and to the internet. Insufficient funding resulted in personnel shortages, lack of appropriate training for personnel, and lack of materials for students.</p> <p>Nonetheless, current and prospective students expressed overwhelming enthusiasm for scale-up of distance learning because of the unique financial and social benefits offered by these programs. Participants were retained as employees in their health care facilities, and remained in their communities and supported their families while advancing their careers. Space in health training institutions was freed up for new students entering in-residence pre-service training.</p> <p>Conclusions</p> <p>A blended print-based distance learning model is most feasible at the national level due to current resource and infrastructure constraints. With an increase in staffing; improvement of infrastructure, coordination and curricula; and decentralization to the zonal or district level, distance learning can be an effective method to increase both the skills and the numbers of qualified health care workers capable of meeting the health care needs of the Tanzanian population.</p
Recommended from our members
Waukegan Station plume
In a previous report on effects of thermal discharges from power plants into the Great Lakes, we stressed the need for a statistical analysis of the spatial and temporal pattern of the thermal plume. The plume pattern is recognized as stochastic in nature and requires statistical analysis. A single realization of the Waukegan Station plume is studied with emphasis on its information content. Areas between isotherms at various depths are computed together with volumes of water in given temperature ranges above ambient; these measurements indicate the extent of the various parts of the plume together with the heat content of each part
Recommended from our members
Flexible cubic spline interpolation
This report describes a simple, efficient, and flexible program for cubic spline interpolation in one dimension, suitable for inclusion in the ANL Subroutine Library and in an interactive timesharing system. Most of the cubic spline programs already available either restrict the boundary conditions to knowledge of the first derivative at both end points, or require the second derivatives to vanish at these points. The program described here removes these restrictions and enables the user to adopt boundary conditions appropriate for his own problem. The advantage is demonstrated for the extreme case of interpolating the function x log (1/x), which has singularities in all its derivatives at x = 0
Recommended from our members
Initial objectives of on-site empirical modelling of thermal plumes: A preliminary evaluation of a river-site and a lake-site thermal plume
This report recommends developing a statistical model to characterize the three-dimensionall pattern of thermal plumes, It indicates the danger of drawing detailed conclusions on the basis of a small number of observations, and emphasizes the need for proper interpretation of empirical measurements, Two reports, on the discharges (1) from the Dresden Power Station into the Illinois River and (2) from Waukegan Station into-Lake Michigan are analyzed. In conclusion, a plan for interpretation of temperature measurements is recommended
Recommended from our members
Angular quadratures for improved transport computations
This paper introduces new octant-range, composite-type Gauss and mid-point rule angular quadrature formulas for neutron and photon transport computations. A generalization to octant-range quadratures is also introduced in order to allow for discontinuities at material interfaces for two- and three-dimensional transport problems which can be modeled with 60-degree triangular or hexagonal mesh subdivisions in the x-y plane
- …