Bishay P.L.,University of California at Irvine |
Bishay P.L.,Saint Martins University |
Dong L.,Hohai University |
Atluri S.N.,University of California at Irvine |
Atluri S.N.,King Abdulaziz University
Computational Mechanics | Year: 2014
Conceptually simple and computationally most efficient polygonal computational grains with voids/inclusions are proposed for the direct numerical simulation of the micromechanics of piezoelectric composite/porous materials with non-symmetrical arrangement of voids/inclusions. These are named “Multi-Physics Computational Grains” (MPCGs) because each “mathematical grain” is geometrically similar to the irregular shapes of the physical grains of the material in the micro-scale. So each MPCG element represents a grain of the matrix of the composite and can include a pore or an inclusion. MPCG is based on assuming independent displacements and electric-potentials in each cell. The trial solutions in each MPCG do not need to satisfy the governing differential equations, however, they are still complete, and can efficiently model concentration of electric and mechanical fields. MPCG can be used to model any generally anisotropic material as well as nonlinear problems. The essential idea can also be easily applied to accurately solve other multi-physical problems, such as complex thermal-electro-magnetic-mechanical materials modeling. Several examples are presented to show the capabilities of the proposed MPCGs and their accuracy. © 2014, Springer-Verlag Berlin Heidelberg.
Marenko B.,Saint Martins University
Design Studies | Year: 2015
This article investigates those aspects of computation that concern uncertainty, contingency and indeterminacy. Starting from a critique of current dominant models of computation, and drawing on the philosophical notions of the virtual and the event, uncertainty, contingency and indeterminacy are proposed as virtualities that express the ongoing differentiation of digital matter. On these grounds, the glitch is reframed as an event capable of revealing the potential of the digital in processes of computational making. Ideas concerning the incomputable and non-human intelligence of the algorithm underpin this argument. Finally, it is proposed that intuitive and uncognitive modes of apprehending digital making operate as forms of divination that capture the unprogrammed unfolding of matter. © 2015.
Khaleghi B.,Saint Martins University
PCI Journal | Year: 2015
A semitrailer hit several overhead steel truss members of the Interstate 5 (I-5) bridge over the Skagit River in Washington State, causing the north span to collapse. An emergency design-build contract required reopening of the permanent replacement span within 90 days of notice to proceed. Precast, prestressed concrete decked bulb tees of sand-lightweight concrete and full flexure-shear flange connections kept the weight of the superstructure within 5% of that of the original steel superstructure, allowing the undamaged substructure to be reused. Careful control of the girder geometry maintained vertical clearance over the Skagit River. Temporary posttensioning enabled the girders to resist construction-induced stresses. The replacement span was assembled alongside the existing bridge and skidded into place during a single 19-hour closure of I-5.
Abdelmessih A.N.,Saint Martins University |
Journal of Heat Transfer | Year: 2010
High heat fluxes are encountered in numerous applications, such as on the surfaces of hypersonic vehicles in flight, in fires, and within engines. The calibration of heat flux gauges may be performed in a dual cavity cylindrical blackbody. Insertion of instruments into the cavity disturbs the thermal equilibrium resulting in a transient calibration environment. To characterize the transient heat fluxes, experiments were performed on a dual cavity cylindrical blackbody at nominal temperatures varying from 800°C to 1900°C in increments of 100°C. The pre-insertion, steady state, axial temperature profile is compared experimentally and numerically. Detailed transient thermal models have been developed to simulate the heat flux calibration process at two extreme fluxes: the high flux is 1 MW/m2 and the relatively low is 70 kW/m2. Based on experiments and numerical analysis, the optimum heat flux sensor insertion location as measured from the center partition was determined. The effect of convection (natural and forced) in the blackbody cavity during the insertion is calculated and found to be less than 2% at high temperatures but reaches much higher values at relatively lower temperatures. The transient models show the effect of inserting a heat flux gauge at room temperature on the thermal equilibrium of the blackbody at 1800°C and 800°C nominal temperatures. Also, heat flux sensor outputs are derived from computed sensor temperature distributions and compared with experimental results. The numerical heat flux agreed with the experimental results to within 5%, which indicates that the numerical models captured the transient thermal physics during the calibration. Based on numerical models and all experimental runs the heat transfer mechanisms are explained. © 2010 by U.S. Government.
Doescher M.P.,The University of Oklahoma Health Sciences Center |
Andrilla C.H.A.,University of Washington |
Skillman S.M.,University of Washington |
Morgan P.,Duke University |
Kaplan L.,Saint Martins University
Medical Care | Year: 2014
BACKGROUND:: Estimates of the relative contributions of physicians, physician assistants (PAs), and nurse practitioners (NPs) toward rural primary care are needed to inform workforce planning activities aimed at reducing rural primary shortages. OBJECTIVES:: For each provider group, this study quantifies the average weekly number of outpatient primary care visits and the types of services provided within and beyond the outpatient setting. METHODS:: A randomly drawn sample of 788 physicians, 601 PAs, and 918 NPs with rural addresses in 13 US states responded to a mailed questionnaire that measured reported weekly outpatient visits and scope of services provided within and beyond the outpatient setting. Analysis of variance and χ testing were used to test for bivariate associations. Multivariate regression was used to model average weekly outpatient volume adjusting for provider sociodemographics and geographical location. RESULTS:: Compared with physicians, average weekly outpatient visit quantity was 8% lower for PAs and 25% lower for NPs (P<0.001). After multivariate adjustment, this gap became negligible for PAs (P=0.56) and decreased to 10% for NPs (P<0.001). Compared with PAs and NPs, primary care physicians were more likely to provide services beyond the outpatient setting, including hospital care, emergency care, childbirth attending deliveries, and after-hours call coverage (all P<0.001). CONCLUSIONS:: Although our findings suggest that a greater reliance on PAs and NPs in rural primary settings would have a minor impact on outpatient practice volume, this shift might reduce the availability of services that have more often been traditionally provided by rural primary care physicians beyond the outpatient clinic setting. © 2014 by Lippincott Williams & Wilkins.