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Hybrid Methods (hybrid + methods)
Selected AbstractsA New Method for Estimating Race/Ethnicity and Associated Disparities Where Administrative Records Lack Self-Reported Race/EthnicityHEALTH SERVICES RESEARCH, Issue 5p1 2008Marc N. Elliott Objective. To efficiently estimate race/ethnicity using administrative records to facilitate health care organizations' efforts to address disparities when self-reported race/ethnicity data are unavailable. Data Source. Surname, geocoded residential address, and self-reported race/ethnicity from 1,973,362 enrollees of a national health plan. Study Design. We compare the accuracy of a Bayesian approach to combining surname and geocoded information to estimate race/ethnicity to two other indirect methods: a non-Bayesian method that combines surname and geocoded information and geocoded information alone. We assess accuracy with respect to estimating (1) individual race/ethnicity and (2) overall racial/ethnic prevalence in a population. Principal Findings. The Bayesian approach was 74 percent more efficient than geocoding alone in estimating individual race/ethnicity and 56 percent more efficient in estimating the prevalence of racial/ethnic groups, outperforming the non-Bayesian hybrid on both measures. The non-Bayesian hybrid was more efficient than geocoding alone in estimating individual race/ethnicity but less efficient with respect to prevalence (p<.05 for all differences). Conclusions. The Bayesian Surname and Geocoding (BSG) method presented here efficiently integrates administrative data, substantially improving upon what is possible with a single source or from other hybrid methods; it offers a powerful tool that can help health care organizations address disparities until self-reported race/ethnicity data are available. [source] Hybrid finite element/volume method for shallow water equationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 13 2010Shahrouz Aliabadi Abstract A hybrid numerical scheme based on finite element and finite volume methods is developed to solve shallow water equations. In the recent past, we introduced a series of hybrid methods to solve incompressible low and high Reynolds number flows for single and two-fluid flow problems. The present work extends the application of hybrid method to shallow water equations. In our hybrid shallow water flow solver, we write the governing equations in non-conservation form and solve the non-linear wave equation using finite element method with linear interpolation functions in space. On the other hand, the momentum equation is solved with highly accurate cell-center finite volume method. Our hybrid numerical scheme is truly a segregated method with primitive variables stored and solved at both node and element centers. To enhance the stability of the hybrid method around discontinuities, we introduce a new shock capturing which will act only around sharp interfaces without sacrificing the accuracy elsewhere. Matrix-free GMRES iterative solvers are used to solve both the wave and momentum equations in finite element and finite volume schemes. Several test problems are presented to demonstrate the robustness and applicability of the numerical method. Copyright © 2010 John Wiley & Sons, Ltd. [source] Hybrid and enhanced finite element methods for problems of soil consolidationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2007X. X. Zhou Abstract Hybrid and enhanced finite element methods with bi-linear interpolations for both the solid displacements and the pore fluid pressures are derived based on mixed variational principles for problems of elastic soil consolidation. Both plane strain and axisymmetric problems are studied. It is found that by choosing appropriate interpolation of enhanced strains in the enhanced method, and by choosing appropriate interpolations of strains, effective stresses and enhanced strains in the hybrid method, the oscillations of nodal pore pressures can be eliminated. Several numerical examples demonstrating the capability and performance of the enhanced and hybrid finite element methods are presented. It is also shown that for some situations, such as problems involving high Poisson's ratio and in other related problems where bending effects are evident, the performance of the enhanced and hybrid methods are superior to that of the conventional displacement-based method. The results from the hybrid method are better than those from the enhanced method for some situations, such as problems in which soil permeability is variable or discontinuous within elements. Since all the element parameters except the nodal displacements and nodal pore pressures are assumed in the element level and can be eliminated by static condensation, the implementations of the enhanced method and the hybrid method are basically the same as the conventional displacement-based finite element method. The present enhanced method and hybrid method can be easily extended to non-linear consolidation problems. Copyright © 2006 John Wiley & Sons, Ltd. [source] Hybrid Framework for Managing Uncertainty in Life Cycle InventoriesJOURNAL OF INDUSTRIAL ECOLOGY, Issue 6 2009Eric D. Williams Summary Life cycle assessment (LCA) is increasingly being used to inform decisions related to environmental technologies and polices, such as carbon footprinting and labeling, national emission inventories, and appliance standards. However, LCA studies of the same product or service often yield very different results, affecting the perception of LCA as a reliable decision tool. This does not imply that LCA is intrinsically unreliable; we argue instead that future development of LCA requires that much more attention be paid to assessing and managing uncertainties. In this article we review past efforts to manage uncertainty and propose a hybrid approach combining process and economic input,output (I-O) approaches to uncertainty analysis of life cycle inventories (LCI). Different categories of uncertainty are sometimes not tractable to analysis within a given model framework but can be estimated from another perspective. For instance, cutoff or truncation error induced by some processes not being included in a bottom-up process model can be estimated via a top-down approach such as the economic I-O model. A categorization of uncertainty types is presented (data, cutoff, aggregation, temporal, geographic) with a quantitative discussion of methods for evaluation, particularly for assessing temporal uncertainty. A long-term vision for LCI is proposed in which hybrid methods are employed to quantitatively estimate different uncertainty types, which are then reduced through an iterative refinement of the hybrid LCI method. [source] A posteriori error estimator for expanded mixed hybrid methods,NUMERICAL METHODS FOR PARTIAL DIFFERENTIAL EQUATIONS, Issue 2 2007Dongho Kim Abstract In this article, we construct an a posteriori error estimator for expanded mixed hybrid finite-element methods for second-order elliptic problems. An a posteriori error analysis yields reliable and efficient estimate based on residuals. Several numerical examples are presented to show the effectivity of our error indicators. © 2006 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 23: 330,349, 2007 [source] Development and Implementation of a Model to Improve Identification of Patients Infected with HIV Using Diagnostic Rapid Testing in the Emergency DepartmentACADEMIC EMERGENCY MEDICINE, Issue 12 2007Jason S. Haukoos MD Objectives Infection with the human immunodeficiency virus (HIV) continues to expand in nontraditional risk groups, and the prevalence of undiagnosed infection remains relatively high in the patient populations of urban emergency departments (EDs). Unfortunately, HIV testing in this setting remains uncommon. The objectives of this study were 1) to develop a physician-based diagnostic rapid HIV testing model, 2) to implement this model in a high-volume urban ED, and 3) to prospectively characterize the patients who were targeted by physicians for testing and determine the proportions who completed rapid HIV counseling, testing, and referral; tested positive for HIV infection; and were successfully linked into medical and preventative care. Methods An interdisciplinary group of investigators developed a model for performing physician-based diagnostic rapid HIV testing in the ED. This model was then evaluated using a prospective cohort study design. Emergency physicians identified patients at risk for undiagnosed HIV infection using clinical judgment and consensus guidelines. Testing was performed by the hospital's central laboratory, and clinical social workers performed pretest and posttest counseling and provided appropriate medical and preventative care referrals, as defined by the model. Results Over the 30-month study period, 105,856 patients were evaluated in the ED. Of these, 681 (0.64%; 95% confidence interval [CI] = 0.60% to 0.69%) were identified by physicians and completed rapid HIV counseling, testing, and referral. Of the 681 patients, 15 (2.2%; 95% CI = 1.2% to 3.6%) patients tested positive for HIV infection and 12 (80%; 95% CI = 52% to 96%) were successfully linked into care. Conclusions A physician-based diagnostic HIV testing model was developed, successfully implemented, and sustained in a high-volume, urban ED setting. While the use of this model successfully identified patients with undiagnosed HIV infection in the ED, the overall level of testing remained low. Innovative testing programs, such as nontargeted screening, more specific targeted screening, or alternative hybrid methods, are needed to more effectively identify undiagnosed HIV infection in the ED patient population. [source] | ||||||||||