RESUMEN
One of the major abnormalities in the urinary system is vesicoureteral reflux which may allow toxins and bacteria from the bladder to infect and hamper kidney function, thus leading to dialysis or in the critical cases, kidney transplantation. A quantitative analysis to characterize urine flow will further aid our understanding of the ureter and also aid in the design of flow aided devices such as valves and stents to correct reflux conditions. A numerical simulation with fluid-structure interactions [FSI] was introduced and solved to perform the ureteral flow analysis. The incompressible Navier-Stokes equations were used as the governing equations for the fluid and a non-linear hyperelastic model was utilized for the compliant wall. The finite element equations for both the structure and the fluid were solved by the Newton-Raphson iterative method. Recirculation regions formed upside of urine central jet, adjacent to the bolus peak. Separation occurred in the urine flow, behind the moving bolus and ureteropelvic reflux began from that location and extended to the upstream and ureteral inlet. The maximum luminal pressure occurred in the back of bolus during peristalsis. The maximum volumetric flow rate resulted from isolated bolus transportation was measured to be 0.92 mlit/min. Effect of the vital function of ureteropelvic junction in prevention of reflux is inevitable, especially in the beginning of peristaltic wave propagation because of presence of fluid inertial forces. As the future work, we suggest that Patient-specific modeling of ureteral mechanics will be valuable to identify crucial disease conditions and will further aid our understanding of the ureter and also aid in the design of flow aided devices such as valves and stents to correct reflux conditions
RESUMEN
Ergonomic factors in sleep designing system will have direct effects on maintaining the spinal alignment during sleep. Studies show that a mattress with uniform stiffness cannot preserve the spine's natural posture. Using a mattress made of components with different stiffness can be considered as a solution for this problem. In this study, male spinal alignment has been assessed and compared on the hard and soft mattress along with a new type of mattress with different stiffness. The aim of this study was to evaluate the performance of this new type of mattress and determination of specific layout for each volunteer. After obtaining the dimensional survey data, 25 male volunteers were asked to take the side sleeping position on soft and very firm surfaces, with specific stiffness based on a predetermined protocol. The location coordinates of markers installed on the spinous process by optical detection methods were obtained in frontal plane. In the next step, spring-foam elements were arranged in a frame for each volunteer so that their spinal frontal plane can be close to their natural alignment. In side sleeping posture a c formed curvature appeared along the spinal frontal plane on stiff surface due to lack of support of the spine, and on the soft mattress, softness caused further sinking in the area of pelvis and loss of natural posture. But the arrangement of elements with different stiffness [custom made mattresses] maintained the natural posture of spine. The specific layouts for each volunteer were extracted. The results of this study showed that use of mattresses with custom arrangement is an appropriate way for maintaining optimum spinal alignment during sleep. Common mattresses with uniform stiffness do not have the ability to maintain the spine in a natural position during sleep. Determination of specific arrangements for side sleeping posture can help predict layout required for every individual in the future studies without performing a test