• Journal of Biomedical Engineering Research
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• v.30 no.4
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• pp.294-305
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• 2009

The bio signals essentially have different characteristics in each person. And the main purpose of automatic diagnosis algorithm based on bio signals focuses on discriminating differences of abnormal state from personal differences. In this paper, we propose automatic ECG diagnosis algorithm which discriminates normal heart beats from premature ventricular contraction using optimization of wavelet parameterization to solve that problem. The proposed algorithm optimizes wavelet parameter to let energy of signal be concentrated on specific scale band. We can reduce the personal differences and consequently highlight the differences coming from arrhythmia via this process. The proposed algorithm using ELM as a classifier show high discrimination performance between normal beat and PVC. From the experimental results on MIT-BIH arrhythmia database the performances of the proposed algorithm are 98.1% in accuracy, 93.0% in sensitivity, 96.4% in positive predictivity, and 0.8% in false positive rate. This results are similar or higher then results of existing researches in spite of small human intervention.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.321-326
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• 2006

Vitiated air heater which could supply air of 700K and 6 bar was designed conceptually for the firing test on the ground of the air breathing propulsion engines. This vitiated air heater consists of premixer with air and excessive gas oxygen, mixing head, combustor with gas passage, convergent-divergent nozzle and diffuser. the fuel was natural gas and/or liquefied natural gas. Through computational fluid dynamics, each component of the air heater was analyzed and flame-holding after ignition was investigated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.201-205
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• 2011

In a cryogenic propellant tank the pressurant is contracted due to heat loss and the propellant itself evaporates. On a restartable propulsion system such phenomena are more intensive because the propellant contacts with the pressurant on the larger surface during the coast flight. Such heat and mass transfer phenomena should be considered for estimating the amount of pressurant. On the hypothesis that the heat and mass transfer quasi-equilibrium is achieved during the coast flight, the calculation process of the equilibrium pressure is presented. On the process the amount of loaded helium on the Falcon-1 second stage is calculated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.116-121
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• 2011

Performance of Secondary Injection Thrust Vector Control system is investigated under various secondary injection operating conditions. 3-dimensional converging-diverging nozzle having 8 secondary injection nozzles is used in this numerical study. Total pressure of flow inside the nozzle is about 70bars, and total temperature set to 300K for cold flow simulation. Effect of secondary injection flow rate and injection nozzle configuration is considered in this research. Simulation is conducted with commercial CFD code Ansys Fluent v13. Spalart-Allmaras(1-equation)model is used for turbulence modeling with AUSM+ scheme. Various performance factors as Axial thrust, side force, system specific impulse ratio are considered and explained for system performance evaluation.

• Proceedings of the KOSOMBE Conference
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• v.1995 no.11
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• pp.222-226
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• 1995

인공심장에서의 박출량제어는 전부하에 따른 심박출균형, 심실내 완전충만과 완전구출을 구현하는데 그 목적이 있다. 본 논문에서는 인공심장 내부의 심실간 공간 압력파형을 심박출량의 제어에 활용하였다. 이를 위해서는 심실간 공간의 압력파형을 심실 유입부와 유출부의 혈류량에 대한 정보, 이동작동기의 위치신호와 동기시켜 해석하는 것이 필요하다. 이러한 압력파형의 해석을 바탕으로, 심실간 공간의 음압 크기로 좌,우 심방압을 추정하고 작동기의 좌,우 수축기때 심실간 공간의 음압크기를 비슷하게 유지하도록 작동거리를 제어하면 좌우 심박출 균형을 이룰 수 있음을 확인하였다. 또한, 심실의 완전충만과 완전구출의 실현을 위한 심실 충만 정도를 추정할 수 있게 하는 인자를 제시하였다.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.398-401
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• 1997

The EMG signal of spinal cord injured patient is very feeble because that the information from central nervous system is not sufficiently transmitted to molter neuron or muscle fiber. Therefore the observer can not observe contraction and relaxation movement of muscle from the raw EMG signal. In this paper, we propose the muscle contraction and relaxation pattern analysis method of spinal cord injured patient whose EMG signal is composed of the sum of motor unit action potential train with additive white Gaussian noise and impulsive noise. From the EMG model, we denoise impulsive noise using median filter which is a kind of nonlinear filter and the output of median filter is transformed to wavelet transform domain for denoising additive white Gaussian noise using threshold level removal technique. As a result, we can obtain the clear contraction and relaxation pattern.

• Journal of Biomedical Engineering Research
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• v.33 no.3
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• pp.135-140
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• 2012

Previous investigators have shown that the frequency compression is related to the muscle fatigue and the decreasing conduction velocity of muscle fibers. The aim of the present study was to investigate the relationship between endurance times and frequency parameters such as mean power frequency and median frequency in the surface EMG signal during isotonic contractions. Eight healthy subjects performed voluntary isotonic contractions of biceps Brachii muscle until their endurance times which were determined when the subject could no longer follow the contraction cycle. The regressive slopes of mean power frequency and median frequency were used to describe the frequency compression of the surface EMG signal, and to test the predictability of endurance time. As results of experiment, significant correlations were found between endurance time and the regressive slopes of mean power frequency and mean frequency computed over 50%Tend of endurance time.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.99-103
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• 2003

An analysis of the flow within supersonic turbine cascades is necessary to design and manufacture turbo-pump system. Because of the differences between the specified inlet boundary value and the computed inlet value caused by the far field inlet boundary condition, the computations at desired inlet conditions can not be achieved. So, this paper studied the problem occurred when far field inlet conditions were specified as inlet boundary conditions. And the numerical analyses using Fine Turbo, CFD Program, has been performed and compared with those of experiments when a converging-diverging nozzle or a linear nozzle was located in front of cascades instead of the far field inlet condition.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.197-201
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• 2009

Experiments were conducted to study the transition of shrinking flame disk to flame hole in counterflow diffusion flames. The studies of transition are well described by varying burner diameters, global strain rate and velocity ratio. It is experimentally verified that radial conduction heat loss is affected at even high strain rate flames for appropriately small burner diameters. It is also shown that flame extinction modes are grouped into three and particularly, hole or stripe is observed in sufficiently high strain rate flames. There exists critical radius according to burner diameter which divide flame extinction modes into three parts.

• Proceedings of the IEEK Conference
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• 2009.05a
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• pp.138-140
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• 2009

Hemorrhage shock occupies high rate in trauma patient's mortality and blood pressure is the variance that judges early diagnosis and the effect of remedy. Systolic blood pressure is related to pulse transit time(PTT). PTT means the time that is required to flow from the heart to peripheral artery. PTT is influenced from the length, cross section and stiffness of the blood vessels. It is hard to evaluate the correlation between systolic blood pressure and PTT because they are variable in human body. In this paper, we evaluated the correlation between the systolic blood pressure and PTT in normal and hemorrhage states using standardized rat. PTT is defined as the time differences between the R peak and the peak of pulse wave. The analyzed time differences of ECG and blood pressure are analyzed every 5minutes for 30 seconds when there is before and after bleeding. Before bleeding, systolic blood pressure and PTT are steadily preserved but when the bleeding comes started, systolic blood pressure is declined. However PTT was increased and decreased. Under the circumstance that the standardized rat is controlled by age, the length of the blood vessels, and any disease, it shows that PTT measurement using systolic blood pressure of bleeding is impossible.