• Journal of Mechanical Science and Technology
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• v.17 no.8
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• pp.1203-1210
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• 2003

Emission of ultrasonic vibration to turbulent flow promotes the turbulence generation due to the resonantly oscillating pressure field and thereby induced cavitation. In addition, ultrasonic vibration is well transmitted through water and not dissipated easily so that the micro-bubbles involved in the fluid induce the gaseous cavitation if the bubbles are resonated with the ultrasonic field. In the present study, we found through LDV measurement that the gaseous cavitation induced by ultrasonic vibration to CO$_2$saturated water flow in the rectangular cross-sectioned straight duct enhances turbulence much more than the case of non-ultrasonic or normal ultrasonic conditions without gaseous cavitation. We also found that the fluctuating velocity component induced by emitting the ultrasonic vibration in normal direction of a rectangular channel flow can be redistributed to stream-wise component by the agitation of gaseous cavitation.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.465-472
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• 2003

The main concept of base isolation system is to reduce the member forces by decreasing the earthquake forces transmitted to superstructure instead of the conventional techniques of strengthening the structural members. There are two important advantages in friction pendulum systems. The functions of carrying the vertical load and of providing horizontal stiffness are effectively separated. This results in a more stable system that eliminates the need of a fail-safe mechanism. Friction pendulum systems are less sensitive to variations in the frequency content of ground excitation and tend to limit the intensity of the farce imparted to the superstructure. This study investigates the friction coefficients on the FPS test specimens according to the velocity, bearing pressure and test waveform.

• Proceedings of the KSR Conference
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• 1999.11a
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• pp.163-171
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• 1999

The major source of railway noises is rolling noise caused by the interaction of the wheels and rails. This rolling noise is generated by the roughness of the wheel/rail surface on tangent tack in the absence of discontinuities, such as wheel flats or rail joints. These roughness cause relative vibrations of the wheel and rail at their contact area. The vibrations generated at the contact area are transmitted through the wheel and rail structures, exciting resonances of the wheel and travelling waves ill tile rail. Then these vibrations radiate noise to the wayside. In this paper, we predict the rolling noise radiated from radial/axial motion of the wheel and vertical/lateral motion of the rail using Remington's analytical model and then compare of the predicted sound pressure and measured one. Although there are some inaccuracy in our predication these results show in good agreement between 500 ㎐ and 3150㎐.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.96-97
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• 2020

Polymer modified cement mortar (PCM) is commonly used as a repair material. However, in high-temperature environments such as fire, it is more likely to explode than cement mortar. The polymer is thermally decomposed at a high temperature to form a gas, and the gas remaining inside the structure increases the internal pressure to generate a burst. When an spalling occurs, the coating is peeled off and dropped, and high temperature is transmitted to the inside of the structure. In severe cases, even the reinforcing bar is exposed, which can lead to the collapse of the structural member due to severe loss of strength. In this study, in order to reduce spalling of PCM, a fiber mixing method was selected from the refractory method to find an appropriate blending ratio of fibers and polymers.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.379-385
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• 2012

This paper suggests U-healthcare system for individual health management realizing the gateway, client, and Java-based network server by using the vital signal measuring system and android-based mobile platform. This study realized the vital signal measuring system based on the technology to measure the ECG, oxygen saturation, blood pressure, and respiration, etc. And all the information of measurement was transmitted to the mobile gateway using the 3-bite transmission protocol consisting of headers and data. The data transmitted to the mobile gateway was used to examine the mobile client's personal health indexes through the network server. This paper realized and tested the android-based gateway, client, and the broadcasting network server and verified their validity with simulations and actual humans. As a result, the U-healthcare system suggested was proved to be effective in managing each individual's health from short distance and long distance. And it could examine each individual's health conditions in real-time and was found to be advantageous in that it could secure the guardian's mobility.

• Structural Engineering and Mechanics
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• v.65 no.5
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• pp.587-600
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• 2018

Infill panel is the first element of a building subjected to blast loading activating its out-of-plane behavior. If the infill panel does not have enough ductility against the loading, it breaks and gets damaged before load transfer and energy dissipation. As steel infill panel has appropriate ductility before fracture, it can be used as an alternative to typical infill panels under blast loading. Also, it plays a pivotal role in maintaining sensitive main parts against blast loading. Concerning enough ductility of the infill panel out-of-plane behavior, the impact force enters the horizontal diaphragm and is distributed among the lateral elements. This article investigates the behavior of steel infill panels with different thicknesses and stiffeners. In order to precisely study steel infill panels, different ranges of blast loading are used and maximum displacement of steel infill under such various blast loading is studied. In this research, finite element analyses including geometric and material nonlinearities are used for optimization of the steel plate thickness and stiffener arrangement to obtain more efficient design for its better out-of-plane behavior. The results indicate that this type of infill with out-of-plane behavior shows a proper ductility especially in severe blast loadings. In the blasts with high intensity, maximum displacement of infill is more sensitive to change in the thickness of plate rather the change in number of stiffeners such that increasing the number of stiffeners and the plate thickness of infill panel would decrease energy dissipation by 20 and 77% respectively. The ductile behavior of steel infill panels shows that using infill panels with less thickness has more effect on energy dissipation. According to this study, the infill panel with 5 mm thickness works better if the criterion of steel infill panel design is the reduction of transmitted impulse to main structure. For example in steel infill panels with 5 stiffeners and blast loading with the reflected pressure of 375 kPa and duration of 50 milliseconds, the transmitted impulse has decreased from 41206 N.Sec in 20 mm infill to 37898 N.Sec in 5 mm infill panel.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.3
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• pp.273-280
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• 2012

As changed the clinical environment, the interest on u-Healthcare service and systems has been increased. The ubiquitous healthcare(u-Healthcare) systems are constructed at the integrated environment that consists of various devices and systems basically such as personal health devices(PHDs) measuring body signals, information aggregators gathering the data transmitted from PHDs through wireless technology, and health information systems storing and managing personal health information transmitted from the information aggregators. International standards such as IEEE 11073 and HL7 have been specified for the interoperability of PHDs and health information systems, but the research on u-Healthcare systems that were developed and applied in the real clinical environment by adopting the standards was rarely conducted. Therefore, we developed an u-Healthcare system which can manage personal health information, such as blood glucose, blood pressure, and body composition, based on health information exchange standards. Moreover, we verified the stability of the developed system through clinical trial in patients with endocrine disease at the Kyungpook National University Hospital, and listed problems occurred during clinical trial and found their solutions.

• Journal of Biomedical Engineering Research
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• v.28 no.4
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• pp.569-576
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• 2007

Ventricular Assist Device(VAD) has switched its goal from a short-tenn use for bridge-to-transplantation to a long-tenn use for destination therapy, With this goal, the importance of long-tenn reliability gets more interests and importances, H-VAD is an portable extracorporeal biventricular assist device, and adopts an electro-pneumatic driving mechanism. The pneumatic pressure to pump out blood is generated with compression of bellows, and is transmitted in a closed pneumatic circuit through a pneumatic line. The existing pneumatic VAD adopts a air compressor which can generate stable pressures but has defects such as a noise and a size problem. Thus, it is not suitable for being used as a portable device, These problems are covered with adopting a closed pneumatic circuit mechanism with a bellows which has a small size and small noise generation, but it has defects that improper pneumatic setting causes a failure of adequate flow generation. In this study, the pneumatic pressure regulation system is developed to cover these defects of a bellows-type pneumatic VAD. The optimal pneumatic pressure conditions according to various afterload conditions for an optimal flow rate were investigated and the afterload estimation algorithm was developed, The final pneumatic regulation system estimates a current afterload and regulate the pneumatic pressure to the optimal point at a given afterload condition. The afterload estimation algorithm showed a sufficient performance that the standard deviation of error is 8.8 mmHg, The pneumatic pressure regulation system showed a sufficient performance that the flow rate was stably governed to various afterload conditions. In a further study, if a additional sensor such as ultrasonic sensor is developed to monitor the direct movement of diaphragm in a blood pump part, the reliability would be greatly increased. Moreover, if the afterload estimation algorithm gets more accuracy, it would be also helpful to monitor the hemodynamic condition of patients.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.11 no.1
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• pp.48-60
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• 2007

Palpation of the pulse has been used in Korean traditional medicine since ancient times to assess physical health. Pulse wave contour may be obtained by measuring arterial pressure or blood volume change of skin. The latter is called as Photoplethysmography(PPG) or digital volume pulse(DVP). The PPG signal is measured by a device comprising an infrared light sourece and a photodetector. Although less widely used, this technique deserves further consideration because of its simplicity and ease of use. The contour of the PPG is formed as a result of a complex interaction between the left ventricle and the systemic circulation. It usually exhibits an early systolic peak and an early diastolic peak. the first peak is formed mainly by pressure trasmitted along a direct path from the left ventricle to the finger. The second peak is formed in part by pressure transmitted along the aorta and large arteries to sites of impedance mismatch in the lower body. The contour of the PPG is sensitive to changes in arterial tone and is influenced by ageing and large artery stiffness. Measurements taken directly from the PPG or from its second derivative can be used to assess these properties. In some mathematical approaches, the extraction of periodic components using frequency analysis was tried to analysis of the PPG. But we don't understand yet what kind of factor in the cardiovascular system or human body is related with the respective specific Fourier components of PPG. This review describes the background to measurement principles, representative contour, contour analysis and frequency domain analysis of PPG, and current and future.

• The Korean Journal of Physiology
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• v.9 no.2
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• pp.17-22
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• 1975

Adult nonpregnant female rabbits were subjected to the study of the effects of carbon monoxide inhalation on the uterine motility. Animals were anesthetized with intravenous injection of nembutal, 35 mg/kg, and the uteri were exposed. Polyethylene tubing which had a small hole near the blind tip was inserted in the loop and normal saline was infused at a constant rate of 1.5 ml/min. On the other end of the loop, an outlet of fluid was made. When a peristaltic wave proceeded to the hole, a rise of the pressure was ensued and it was transmitted to the pressure transducer, making an upward deflection of the recording pen on the physiograph. Carbon monoxide, 1,000 ppm in the concentration, was inhaled through a tracheal cannula for 30 minutes, following fresh air for 30 minutes. In some cases, pure oxygen was also supplemented for another 30 minutes. Uterine motility was expressed in terms of the impulse that was the time integral of the pressure and of the frequency of the peristaltic waves. The results obtained were as follows. 1. When 1,000 ppm carbon monoxide was inhaled for 30 minutes, the impulse dropped to $72{\pm}16.5%$ and the frequency to $75{\pm}22.7%$ of the values obtained before the gas administration. 2. By fresh air for 30 minutes, the impulse and the frequency restored to $77{\pm}25.7%$ and $92{\pm}21.1%$, respectively. 3. By the supplement of pure oxygen for 30 minutes, no remarkable improvement were revealed, showing $89{\pm}35.2%$ in the impulse and $91{\pm}10.8%$ in the frequency, respectively. 4. There was an appreciable discrepancy in the recovery courses of the impulse and the frequency, suggesting different mechanisms attributable to the alteration by carbon monoxide inhalation.