Elastoplastic model for hydro-mechanical behavior of unsaturated soils

A coupled elastoplastic constitutive model is presented for describing the hydraulic and mechanical behaviors of unsaturated soils. The model is capable of considering the influence of the irreversible changes in water saturation on the mechanical behavior and in plastic deformation on the hydraulic behavior. The mechanical and hydraulic behaviors are captured using the subloading surface and bounding surface plasticity frameworks, respectively. The coupling between hydraulic and mechanical behaviors is established using the intergranular stress concept in addition to appropriate coupled hardening rules. Attention is also given to the movement of the soil water characteristic curve due to the plastic deformation. Model predictions for some unsaturated soil samples are compared with experimental data, and a reasonable agreement is achieved

A hybrid numerical model for multiphase fluid flow in a deformable porous medium

In this paper, a fully coupled finite volume-finite element model for a deforming porous medium interacting with the flow of two immiscible pore fluids is presented. The basic equations describing the system are derived based on the averaging theory. Applying the standard Galerkin finite element method to solve this system of partial differential equations does not conserve mass locally. A non-conservative method may cause some accuracy and stability problems. The control volume based finite element technique that satisfies local mass conservation of the flow equations can be an appropriate alternative. Full coupling of control volume based finite element and the standard finite element techniques to solve the multiphase flow and geomechanical equilibrium equations is the main goal of this paper. The accuracy and efficiency of the method are verified by studying several examples for which analytical or numerical solutions are available. The effect of mesh orientation is investigated by simulating a benchmark water-flooding problem. A representative example is also presented to demonstrate the capability of the model to simulate the behavior in heterogeneous porous media

Risk factors of blood transfusion in patients undergoing off-pump coronary artery bypass

Normal 0 false false false EN-US X-NONE AR-SA MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Arial; mso-bidi-theme-font:minor-bidi;} Background: One of the most important components of coronary artery bypass graft surgery is need for blood transfusion that increases morbidity and mortality. The aim of this study was to evaluate the factors affecting the need for blood transfusion during off pump coronary artery bypass (OPCAB) surgery."n"nMethods: In this descriptive case control study 923 patients who had undergone OPCAB at Afshar Hospital in Yazd, Iran, from July 2008 to January 2010 were evaluated. The data was gathered from their records and was analyzed."n"nResults: 54% of male and 79% of female patient need blood transfusion. Mean age in patients needed transfusion was 61.58±11.11 years and in other group was 60.27±10.98 years of the patients that needed transfusion (p= 0.08). 563 (61%) of the patients needed transfusion with the average of two units. The need for blood transfusion was higher in female gender (p< 0.0001), low hematocrit (p< 0.0001), diabetes (p< 0.001), hypertension (p< 0.025) and multiple grafts (p< 0.027). There were no significant differences in preoperative hemostasis tests, affection to hyperlipidemia, CVA or renal failure, antiplatelet drug administration and the application of left internal mammary artery between the transfusion and non transfusion groups."n"nConclusion: In this study preoperative hematocrit was most important risk factor in transfusion in patients that underwent OPCAB. Female gender, preoperative low hematocrit, multiple grafts, diabetes and hypertension increased the rate of blood transfusion. According to the high prevalence of blood transfusion in OPCAB, considering factors that affect the transfusion rate is essential