• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.4 s.247
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• pp.298-305
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• 2006

The flow around a circular cylinder which oscillates rotationally with a relatively high forcing frequency has been investigated experimentally using flow visualization and hot-wire measurements. Dominant parameters are Reynolds number (Re), oscillation amplitude $({\theta}_A)$, and frequency ratio $F_R=f_f/f_n$, where $f_f$ is the forcing frequency and $f_n$ is the natural frequency of vortex shedding. Experiments were carried out under the conditions of $Re=4.14{\times}10^3,\;{\theta}_A={\pi}/6$, and $0{\leq}F_R{\leq}2$. The effect of frequency ratio $F_R$ on the flow structure of wake was evaluated by measuring wake velocity profile and spectral analysis of hot-wire signal. Depending on the frequency ratio $F_R$, the cylinder wake has 5 different flow regimes. The vortex formation length and vortex shedding frequency are changed significantly before and after the lock-on regime. The drag coefficient was reduced under the condition of $F_R<1.0$ and the maximum drag reduction is about 33% at $F_R=0.8$. However, the drag is increased as $F_R$ increases beyond $F_R=1.0$. This active flow control method can be effective in aerodynamic applications, if the forcing parameters are selected optimally.

• Archives of Plastic Surgery
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• v.33 no.2
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• pp.213-218
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• 2006

As the large defect of peripheral nerve occurs, the autologous nerve graft is the most ideal method but it has many limitations due to donor site morbidities. Various materials have been developed for the nerve defect as the conduits, but none of these materials is satisfactory. Among them, $Gore-Tex^{(R)}$ tube seems to be one of the most ideal nerve conduit materials at peripheral nerve defect. Many researches have focused on finding the neurotrophic factors. It is recently demonstrated that Valproic acid(VPA) has an effect of axonal regeneration as a neurotrophic factor without enzymatic degradation and toxicity problems. The purpose of this study is to evaluate the effect of VPA on the nerve regeneration at the peripheral nerve defect. A 10 mm gap of rat sciatic nerve was made and $Gore-Tex^{(R)}$ tube filled with biceps femoris muscle was placed at the nerve defect site. We let the rat take VPA as drinking water in experimental group and did not give VPA to the control group. We estimated the results as electrophysiologic and histological aspects for 16 weeks after the surgery. The nerve conduction velocity, total myelinated axon count, myelin sheath thickness and mean nerve fiber diameter significantly increased in VPA-treated experimental group when compared to the control (p < 0.05). From the above results, we conclude that VPA promotes the nerve regeneration at the peripheral nerve defect site. It is suggested that $Gore-Tex^{(R)}$ tube filled with skeletal muscle and VPA administration may be a good substitute for autologous nerve graft.

• Journal of Embryo Transfer
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• v.28 no.1
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• pp.63-71
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• 2013

In this study, we used flow a cytometric assay to evaluate plasma membrane integrity and mitochondrial activity in post-thawed sperm that was supplemented with ginsenoside-$Rg_1$. Varying concentrations of ginsenoside-$Rg_1$ (0, 25, 50 and $100{\mu}M/ml$) were used in the extender during cryopreservation to protect the DNA of thawed sperm, thereby increasing the viability and motility rate as evaluated using a computer-assisted sperm analysis (CASA) method. The results derived from CASA were used to compare the fresh, control, and ginsenoside-$Rg_1$ groups. Sperm motility and the number of progressively motile sperm were significantly (p<0.05) higher in the $50{\mu}M/ml$ ginsenoside-Rg1 group ($61.0{\pm}4.65%$) than in the control ($46.6{\pm}7.02%$), $25{\mu}M/ml$ ($46.2{\pm}4.76%$), and $100{\mu}M/ml$ ginsenoside-$Rg_1$ ($52.0{\pm}1.90%$) groups. However, the velocity distribution of post-thawed sperm did not differ significantly. Membrane integrity and MMP staining as revealed using flow cytometry were significantly (p<0.05) higher ($91.6{\pm}0.82%$) in the $50{\mu}M/ml$ ginsenoside-$Rg_1$ group than in the other groups. Here, we report that ginsenoside-$Rg_1$ affects the motility and viability of boar spermatozoa. Moreover, ginsenoside-$Rg_1$ can be used as a protective additive for the suppression of intracellular mitochondrial oxidative stress caused by cryopreservation.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.2 s.42
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• pp.7-15
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• 2005

Numerical analysis model is proposed to predict the dynamic behavior of a single-degree-of-freedom structure that is equipped with hybrid base isolation system. Hybrid base isolation system is composed of friction pendulum systems (FPS) and a magnetorheological (MR) damper. A neuro-fuzzy model is used to represent dynamic behavior of the MR damper. Fuzzy model of the MR damper is trained by ANFIS (Adaptive Neuro-Fuzzy Inference System) using various displacement, velocity, and voltage combinations that are obtained from a series of performance tests. Modelling of the FPS is carried out with a nonlinear analytical equation that is derived in this study and neuro-fuzzy training. Fuzzy logic controller is employed to control the command voltage that is sent to MR damper. The dynamic responses of experimental structure subjected to various earthquake excitations are compared with numerically simulated results using neuro-fuzzy modeling method. Numerical simulation using neuro-fuzzy models of the MR damper and FPS predict response of the hybrid base isolation system very well.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.4
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• pp.457-462
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• 2011

In this study, a simplified design procedure for friction dampers of a multi-story structure in order to reduce seismic response is proposed. To get insight for control effect of the structure with friction dampers is difficult, because of a nonlinear characteristic by a friction damper. Since a control force of a friction damper is influenced by coupling velocity between floors, adjoining modes are coupled. Thus structural response are derived by assuming steady-state response in resonance. As it is impossible that an exact solution is obtained for seismic load, first, a closed form solution can be achieved under harmonic vibration. Second, to convert a three-story building into a single-degree-of-freedom(SDOF) structure, modal analysis is performed. Third, an equivalent damping ratio is derived with utilizing closed form solution. And response reducing factor is proposed by it. Finally, friction force of a damper is designed for using response reducing factor, and then designed dampers are verified for seven seismic data. The nonlinear analysis results confirm the validity of the proposed procedure.

• Archives of Plastic Surgery
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• v.32 no.5
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• pp.613-618
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• 2005

When a large peripheral nerve defect occurs, an autologous nerve graft is the most ideal method of recinstruction. But an autologous nerve graft has many limitations due to donor site morbidities. Many previous focused on finding the ideal nerve conduit. Among them, $Gore-Tex^{(R)}$ has several advantages over other conduits. It can be manipulated to a suitable size, does not collapse easily, and it is a semi- permeable material that contain pores. A round shaped nerve can be newly formed because of its smooth inner surface. The purpose of this study was to evaluate the availability of $Gore-Tex^{(R)}$ tube as a nerve conduit at the peripheral nerve defect in the rat sciatic nerve. The 10 mm nerve gap was made in each group. A $Gore-Tex^{(R)}$ tube filled with skeletal muscle was inserted and autologous nerve graft was harvested, respectively. In the experimental group, we placed a 0.5 mm thickness, $30{\mu}m$ pored, 1.8 mm in diameter and 14 mm length tube with skeletal muscle inserted inside. In the control group, the nerve gap was inserted with a rat sciatic nerve. We estimated the results electrophysiologically and histologically to 16 weeks postoperatively. Results in the nerve conduction velocity, total myelinated axon count, myelin sheath thickness and mean nerve fiber diameter, the experimental group was substantially lower than that of the control group, but the statistic difference was not significant (p<0.05). The morphology was very similar in both groups, microscopically. From the above results, We conclude that $Gore-Tex^{(R)}$ qualifies as an ideal nerve conduit. It is suggested that $Gore-Tex^{(R)}$ tube filled with skeletal muscle may, substitute for an autologous nerve graft.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.5
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• pp.544-549
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• 2006

This research is to introduce about Judgment System for Intelligent Movement(JSIM) that can perform assistance work of human brain. JSIM can order autonomous command and also it can be directly controlled by user. This research assumes that control object is limited to Mobile Robot(MR) Mobile robot offers image and ultrasonic sensor information to user carrying JSIM and it performs guide to user. JSIM having PDA and Sensor-box controls velocity and direction of the mobile robot by soft-computing method that inputs user's command and information that is obtained to mobile robot. Also it controls mobile robot to achieve various movement. This paper introduces wearable JSIM that communicates with around devices and that can do intelligent judgment. To verify the possibility of the proposed system, in real environment, the simulation of control and application problem lot mobile robot will be introduced. Intelligent algorithm in the proposed system is generated by mixed hierarchical fuzzy and neural network.

• Journal of Practical Engineering Education
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• v.10 no.2
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• pp.119-124
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• 2018

Educational equipment that enables the user or device to recognize the indoor position by using the acceleration and angular velocity of the IMU (Inertial Measurement Unit) sensor is introduced. With this educational equipment, various position recognition and tracking algorithms can be learned and creative engineering design works can be realized. The data value of the IMU sensor is transmitted to the MCU (microcontroller unit) through $I^2C$ (Inter-Integrated Circuit), and the indoor position recognition algorithm is applied by processing the data value through the filter and numerical method. It is then designed to use wireless communication to send and receive processed values and to be recognized by the user. As an example using this equipament, the case of "Implementation and recognition of virtual position using computation of moving direction and distance using IMU sensor" is introduced, and various creative engineering design application is discussed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.9
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• pp.827-832
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• 2012

In this paper, we will design the speed measurement board of LEO Satellite's reaction wheel which has two speed measuring methods as M-Method type and T-Method type. therefore we can use the advantage of two methods. and we will verify the availability of design on the on-board computer at the real LEO Satellite(KOMPSAT-3). In the reaction wheels satellite that can change the satellite's attitude is one of the leading drivers by the rotational inertia of the motor will perform attitude control. Reaction methods for detecting wheel rotation speed generated during a certain period T internal reaction wheel tacho pulse counting M-Method to detect wheel speed and wheel tacho pulses are generated by measuring the time between the detection rate can be divided into T-Method. M-method is simple to implement and benefit measurement time is constant, but slow fall in the velocity measurement accuracy is a disadvantage. In contrast, the time between tacho pulses to measure the T-Method to measure the precise speed at low speed and to measure the time delay is small, has the advantage. However, this method also in the actual implementation and the complexity of the operation at different speeds depending on the speed of operation has the disadvantage.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.2
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• pp.202-210
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• 2015

Objectives: The purpose of this study was to examine clean room(C/R) structure, air conditioning and contamination control systems and to provide basic information for identifying a correlation between the semiconductor work environment and workers' disease. Methods: This study was conducted at 200 mm and 300 mm semiconductor wafer fabrication facilities. The C/R structure and air conditioning method were investigated using basic engineering data from documentation for C/R construction. Furthermore, contamination parameters such as airborne particles, temperature, humidity, acids, ammonia, organic compounds, and vibration in the C/R were based on the International Technology Roadmap for Semiconductors(ITRS). The properties of contamination control systems and the current status of monitoring of various contaminants in the C/R were investigated. Results: 200 mm and 300 mm wafer fabrication facilities were divided into fab(C/R) and sub fab(Plenum), and fab, clean sub fab and facility sub fab, respectively. Fresh air(FA) is supplied in the plenum or clean sub fab by the outdoor air handling unit system which purifies outdoor air. FA supply or contaminated indoor air ventilation rates in the 200 mm and 300 mm wafer fabrication facilities are approximately 10-25%. Furthermore, semiconductor clean rooms strictly controlled airborne particles(${\leq}1,000{\sharp}/ft^3$), temperature($23{\pm}0.5^{\circ}C$), humidity($45{\pm}5%$), air velocity(0.4 m/s), air change(60-80 cycles/hr), vibration(${\leq}1cm/s^2$), and differential pressure(atmospheric pressure$+1.0-2.5mmH_2O$) through air handling and contamination control systems. In addition, acids, alkali and ozone are managed at less than internal criteria by chemical filters. Conclusions: Semiconductor clean rooms can be a pleasant environment for workers as well as semiconductor devices. However, based on the precautionary principle, it may be necessary to continuously improve semiconductor processes and the work environment.