Inherent irreversibility impacts on thermal boundary layer flow over a mobile plate with convective surface boundary conditions

Background:The irreversibility impacts on flow and heat transfer processes can be quantified through entropy analysis. It is a significant tool which can be utilized to deduce about the energy losses. The current study investigates the inherent irreversibility impacts during a flow of boundary layer and heat transfer on a mobile plate. Methods:The flow is examined under thermal radiation and convective heat conditions. The fundamental governing equations of flow and heat phenomenonare transmuted into ordinary differential equations by employing similarity transmutations and shooting technique is utilized in order to solve the resultant equations. The temperature and velocity profiles are acquired to reckon Bejan and entropy generation number. Pertinent results are elucidated graphically for the movement of plate and flow in same and opposite directions.Results:A decline in temperature profile is noted with rise in values of Prin both cases when the movement of surface and free stream is in similar and converse directions. A decrease in temperature is observed for both cases with increase inNRwhile with the rise in Biot numbera, the temperature profile also increases. Entropy generation rate near the surface is high in case when surface and free stream are moving in opposite directions as compared to case when they move in same directions.Conclusions:It is observed that irreversibility impacts are more remarkable when the movement of fluid and plate is in opposite direction. Moreover, irreversibility impacts of heat transfer are prominent in free stream region.

Finite Element Analysis on Partially Closed and Fully Opened Aortic Valve / 医用生物力学

Objective To explore the effect of different initial state setting on a valve simulation. Methods Two-dimensional structural models were established with the initial state of the aortic valve being partially closed in one model and fully opened in the other. The time-dependent load was applied to the valve and the vessel wall of the aortic and the ventricle sides. The finite element method was used to study the maximum stress, the length of the joint, and the contact force of the closed aortic valve under two different initial states. Results The stress and contact force of the aortic valve were relatively large at the closed position when the initial state was fully opened. The closure degree of the valve was low, and the variations in stress and closure degree were large during the periodic cycle. The stress and contact force of the valve were relatively small when the aortic valve was partially closed. The closure degree was high, and the variations in stress and closure degree of the aortic valve were small during the periodic cycle. Conclusions In the case of the aortic valve partially closed in the initial state, the stability of the calculation process and the closure degree of the valve were relatively high, which should be given more consideration in numerical simulation. The results can be used to study the mechanical behavior of the valve and the biomechanical mechanism of the aortic root.

Effects of breathing patterns on flow field in upper airway of an OSAHS patient during natural sleep / 医用生物力学

Objective To study the effects of different pressure boundary conditions and breathing patterns on the airflow of upper airway and related physiological status of the obstructive sleep apnea hypopnea syndrome (OSAHS) patient at sleep stage with eupnea and apnea, respectively. Methods The CT scan data of an OSAHS patient during natural sleep in supine position were acquired and used to reconstruct a three-dimensional finite element model of upper airway. Meanwhile the pressure changes in laryngeal cavity of the OSAHS patient were clinically measured and then used as the boundary conditions, and four typical breathing patterns (nasal inhaling and nasal exhaling, nasal inhaling and oral exhaling, oral inhaling and nasal exhaling, oral inhaling and oral exhaling) were considered for computational fluid simulation. Results The airflow of the OSAHS patient during sleep was an unstable, whorled and bidirectional flow, which was significantly affected by pressure boundary conditions and breathing patterns. Compared with nasal breathing, the maximum velocity of airflow by mouth breathing was increased, resulting in an increase of pressure drop in oral cavity, with was about 30% in inspiration and 100% in expiration. Conclusions It is significant to use CT data of an OSAHS patient during natural sleep for model reconstruction and the clinically measured pressure in laryngeal cavity as boundary conditions for finite element simulations, and the results will contribute to understand the characteristics of flow field in upper airway of the OSAHS patient during real natural sleep.

Considerations of Blood Properties, Outlet Boundary Conditions and Energy Loss Approaches in Computational Fluid Dynamics Modeling / 신경중재치료의학

Despite recent development of computational fluid dynamics (CFD) research, analysis of computational fluid dynamics of cerebral vessels has several limitations. Although blood is a non-Newtonian fluid, velocity and pressure fields were computed under the assumptions of incompressible, laminar, steady-state flows and Newtonian fluid dynamics. The pulsatile nature of blood flow is not properly applied in inlet and outlet boundaries. Therefore, we present these technical limitations and discuss the possible solution by comparing the theoretical and computational studies.

Effect of Intensity of Unconditional Stimulus on Reconsolidation of Contextual Fear Memory

Memory reconsolidation is ubiquitous across species and various memory tasks. It is a dynamic process in which memory is modified and/or updated. In experimental conditions, memory reconsolidation is usually characterized by the fact that the consolidated memory is disrupted by a combination of memory reactivation and inhibition of protein synthesis. However, under some experimental conditions, the reactivated memory is not disrupted by inhibition of protein synthesis. This so called "boundary condition" of reconsolidation may be related to memory strength. In Pavlovian fear conditioning, the intensity of unconditional stimulus (US) determines the strength of the fear memory. In this study, we examined the effect of the intensity of US on the reconsolidation of contextual fear memory. Strong contextual fear memory, which is conditioned with strong US, is not disrupted by inhibition of protein synthesis after its reactivation; however, a weak fear memory is often disrupted. This suggests that a US of strong intensity can inhibit reconsolidation of contextual fear memory.

Internal boundary parameters identification of human middle ear with neural network / 医用生物力学

Objective To study the method of internal boundary parameters identification of middle ear.Method The numerical model is created using CT technology.Based on Matlab tools,the neural network for identifying internal boundary is proposed.Result The uniform pressure of 105 dB is applied at the outside of the tympanic membrane,and the harmonic analysis is calculated on the model to take the training samples.The internal condition parameters are identified using the good neural network.Conclusions The investiga-tion shows that the inverse method reveals a fast convergence and a high degree of accuracy.

Internal boundary parameters identification of human middle ear with neural network / 医用生物力学

Objective To study the method of internal boundary parameters identification of middle ear.Method The numerical model is created using CT technology.Based on Matlab tools,the neural network for identifying internal boundary is proposed.Result The uniform pressure of 105 dB is applied at the outside of the tympanic membrane,and the harmonic analysis is calculated on the model to take the training samples.The internal condition parameters are identified using the good neural network.Conclusions The investiga-tion shows that the inverse method reveals a fast convergence and a high degree of accuracy.

Internal boundary parameters identification of human middle ear with neural network / 医用生物力学

Objective To study the method of internal boundary parameters identification of middle ear.Method The numerical model is created using CT technology.Based on Matlab tools,the neural network for identifying internal boundary is proposed.Result The uniform pressure of 105 dB is applied at the outside of the tympanic membrane,and the harmonic analysis is calculated on the model to take the training samples.The internal condition parameters are identified using the good neural network.Conclusions The investiga-tion shows that the inverse method reveals a fast convergence and a high degree of accuracy.

Heat Transfer Boundary Condition Calculation Model of a Fighter Plane Cockpit / 航天医学与医学工程

Objective To establish a complete heat transfer boundary condition model in a cockpit including the inner wall heat transfer boundary condition and the air supply heat transfer boundary condition of the air distribution system. Methods The temperature field in the cockpit was carried out unmerical caculation with above model and the traditional method which was assumed uniform heat flux through walls and flow flux out of each air supply hole individually.An experiment was carried out to prove the caculation accuracy of both methods. Results The comparison between calculation and experiment results shows that the temperature field calculation accuracy of this model was much higher than traditional method’s.This model could indicate the unevenness and the asymmetry of the heat transfer through walls and the air temperature out of air supply holes of air distribution system. Conclusion This model is reasonable and has a good engineering application value.