Simulation of the Cardiovascular Mechanical System Based on Pressure-Flow Model Rest Condition

Non-invasive measurement method has made rapid developments in the field of biomedical engineering. One of research is impedance cardiography (ICG), which provide information of pulsation basic. By knowing this kind of measurement technique, it will assist inspection of the patient's physiological condition with cardiovascular system. This research is aimed to determine the mechanical characteristics of the cardiovascular system in the human body such as a wave graph of pressure, flow, and volume, based on pressure–flow model in rest condition, and analyze the simulation results by implementing state of the physiology cardiovascular disease. To obtain the wave chart that is modeled by the cardiovascular system using a lumped parameter method, formulate the differential equations of the pressure–flow dynamics equation for an incompressible fluid in a segment of a cylindrical elastic tube and simulate the model using the Simulink toolboxes from Matlab R2008b. The simulation with lumped parameter method resulted wave graphics of pressure, flow, and volume of physiological state a person in rest condition, the left ventricular pressure is 120 mmHg , right ventricular pressure is 30 mmHg , left ventricular outflow is 800 mL / sec and volume in the left ventricle is 160 mL . By implementing the simulation have been developed on the physiological state of cardiovascular disease, hypertension occurs when the arteries resistance R3i = 0.61 mmHg × s mL with the pressure of the left ventricle is 145 mmHg. For coronary heart condition, ventricular pressure decreased until 82 mmHg in the value of the coronary arteries resistance is R3o = 0.852 mmHg × s mL. This research assumed heart haves the character of passive because there is no feedback signal that can compensate if the pressure in the systemic circulation is reduced. The research can be concluded that the graph from simulation shows the results are not much different from the reference chart, this results indicates that the equation and the simulation was able to reflect on the human circulatory physiological circumstances. A little different of a graphic simulation result due to differences in the parameters and assumptions used.

Effects of Evaporator and Condenser in the Analysis of Adsorption Chillers

In a survey of the literature from the last 20 years, 20% of the numerical models used to analyze the performance of adsorption chillers assumed the evaporator and condenser were ideal, with a fixed evaporation temperature and condenser temperature, and ignored interactions between the adsorption bed and evaporator/condenser. Even when the interaction with the evaporator and condenser was included, the other 80% of studies modeled the adsorption bed based on the LPM (lumped parameter method), which ignores the geometry effect and contact resistance of the bed, and thus reduces the accuracy of the analysis. As a consequence, these earlier numerical studies overestimated the system performance of the adsorption chiller. In this study, we conducted a refined numerical approach which avoids these limitations, producing estimates in close agreement with experimental results. Compared with our approach, the models with ideal treatment of evaporator and condenser overestimated COP (coefficient of performance) and SCP (specific cooling power) by as much as 16.12% and 24.64%, respectively. The models based on LPM overestimated COP and SCP by 22.82% and 11.28%, compared to our approach.

Analysis and Application of Screens for Acoustic Impedance in a Speaker Box with a Passive Radiator to Decrease Standing-Wave Influence

Micro speakers are playing an increasingly important role with the development of multimedia devices. This study applies the lumped-parameter method, which uses an equivalent circuit to model the electromagnetic and mechanical domains. The acoustic domain is modeled using the finite element method. Based on the analysis tool, the use of a screen is analyzed, and the screen is designed to depress the acoustic resonance in the sound-pressure-level curve and improve the performance. The samples are fabricated, and the experiment verifies the analysis method. The experimental result shows that the peak and dip due to the standing wave are cancelled, and the frequency response is smooth when the screen is used.

Analysis and Design of Helmholtz Protector to Improve High-Frequency Response of Insert Earphone

With the development of multimedia devices, earphones are playing an increasingly important role. This article applies the lumped parameter method using an equivalent circuit to model the electromagnetic, mechanical, and acoustic domains of earphones. Then, parameters are determined according to the dimensions and material properties of earphone parts. On the basis of the analysis tool and determined parameters, a Helmholtz protector is analyzed and designed to improve the high-frequency response. Samples are fabricated, and the experiment verifies the analysis method. The experimental result shows that the peaks at 7 k and 10 k are decreased at 8.05 dB and 7.89 dB. The root means square value of SPL deviation compared with target curve decreased from 9.77 to 4.39. High-frequency response is improved by using the Helmholtz protector.

An improved lumped parameter method for calculating static characteristics of multi-recess hydrostatic journal bearings

This paper proposes an improved lumped parameter method for calculating the static characteristics of multi-recess hydrostatic journal bearings. The improved lumped parameter method can estimate the total pressure distribution in the circumferential direction by introducing control volume in the middle of each inter-recess land, and utilizing the flow continuity equations for each recess and each control volume with the assumption that the pressure distributions are parabolic on the inter-recess land. Then the recess pressure and the fluid film force can be calculated. The calculation accuracy of the improved lumped parameter method and the traditional lumped parameter method is comparatively discussed under different eccentricity ratios and wrap angles of the recess. The results show that the improved lumped parameter method has higher calculation accuracy and wider application range.

Comparison of Multi-Physical Coupling Analysis of a Balanced Armature Receiver between the Lumped Parameter Method and the Finite Element/Boundary Element Method

The balanced armature receiver (BAR) is a product based on multiphysics that enables coupling between the electromagnetic, mechanical, and acoustic domains. The three domains were modeled using the lumped parameter method (LPM) that takes advantage of an equivalent circuit. In addition, the combined finite element method (FEM) and boundary element method (BEM) was also applied to analyze the BAR. Both simulation results were verified against experimental results. The proposed LPM can predict the sound pressure level (SPL) by making use of the BAR parts dimension and material property. In addition, the previous analysis method, FEM/BEM, took 36 h, while the proposed LPM takes 1 h. So the proposed LPM can be used to check the BAR parts’ dimension and material property influence on the SPL and develop the BAR product efficiently.

Dynamic modeling and analysis of the nut-direct drive system

For ball screw feed system, it has been a common practice that screw shaft is typically supported by bearings at both ends and is driven by a servo motor through coupling. However, this drive method has a relative low dynamic rigidity due to the influence of the support bearings. In this study, the nut-direct drive system is proposed, where the screw shaft is fixed at both ends and the screw nut is driven by the hollow servo motor through the bolted flange. In order to analyze the advantages of the nut-direct drive system compared with the classical drive, the dynamic models of the classical drive and the nut-direct drive are established based on lumped parameter method, respectively. According to the lumped parameter method, the influence of the table position, the length of screw shaft, and the nominal diameter of screw shaft on the natural frequency are analyzed. Furthermore, to analyze the influence of the mechanical system on position tracking accuracy, the mechanical systems of the classical drive and the nut-direct drive are integrated into the control system using the same control parameters, respectively. Results indicate that the nut-direct drive has faster responsiveness and better position tracking accuracy compared with the classical drive.