• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.2
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• pp.161-169
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• 2011

Two-way slabs reinforced with high-performance steels, which have several practical advantages of a reduction of congestion in heavily reinforced members, savings in the cost of labor and repair, the higher corrosion resistance, and a reduction of construction time, were constructed and tested. The influences of the flexural reinforcement ratio, concentrating the reinforcement in the immediate column region, and using steel fiber-reinforced concrete (SFRC) in the slab on the punching shear resistance and post-cracking stiffness were investigated, and compared with the punching shear test results of the slabs reinforced with conventional steels and GFRP bars. In addition, the strain distribution of flexural reinforcements and crack control were investigated, and the effective width calculating method for the average flexural reinforcement ratio was estimated. The use of high-performance steel reinforcement increased the punching shear strength of slabs, and decreased the amount of flexural reinforcements. The concentrating the top mat of flexural reinforcement increased the post-cracking stiffness, and showed better strain distribution and crack control. In addition, the use of SFRC showed beneficial effects on the punching shear strength and crack control. It was suggest that the effective width should be changed to larger than 2 times the slab thickness from the column faces.

• Korean Journal of Acupuncture
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• v.25 no.3
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• pp.147-166
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• 2008

Objectives : Crohn's disease (CD) is characterized by a chronic relapsing inflammation of the bowel in which proinflammatory cytokines play an important perpetuating role. Methods : Mice (preventive animal model of gliotoxin) were treated with 5 % 2,4,6-trinitrobenzenesulfonic acid (TNBS) at day 1 and day 7. To investigate preventive effects of acupuncture with Gujin at $LI_{11}$, acupuncture was carried out at day -1, day 1, day 3. And, to investigate therapeutic effects, acupuncture with Gujin was carried out at day 3, day 5, day 7. For the data analysis, we checked weight and width of colon, diarrhea, edema, survival rate, changes of body weight, and myeloperoxygenase (MPO) activity. For analysing protein expression, we carried out immunohistochemical staining and Western blot and we analyzed mRNA expression by RT-PCR. Results : Colon of TNBS treated mice was erosive and shortening compared with the colon of control mice and induced damages of colon epithelial cell layer and induced infiltration of immune cells in all layer of colon. Acupuncture of gujin at $LI_{11}$ in preventive mode suppressed macorscopic damages such as erosive and shortening of colon by TNBS and damages of intestinal epithelial cells and infiltration of immune cells in the colon. The average weight of 5 cm distal colon was increased in TNBS treated mice (758${\mu}g$) compared with in control mice (112${\mu}g$) and width of distal colon was also increased in TNBS treated mice (4.9mm) compared with in control mice (1.3mm). Acupuncture with Gujin at $LI_{11}$ in preventive and therapeutic mode suppressed increase of colon weight and width by TNBS. TNBS induced edema of colon and diarrhea and Acupunctured with Gujin at $LI_{11}$ in preventive and therapeutic mode ameliorated these symptom by TNBS. In preventive and therapeutic mode, the effects of acupuncture with Gujin at $LI_{11}$ were increasing the motility, suppressing body weight decreasing, suppressing MPO activity, reducing expressing of TNF-${\alpha}$, IL-1b, and ICAM-1 in colon compared with that by TNBS Conclusions : This study demonstrates that acupuncture with Gujin at $LI_{11}$ represents a potential therapeutic method of Crohn's disease.

• Journal of Power Electronics
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• v.15 no.3
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• pp.660-669
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• 2015

This paper presents a control scheme with a focus on the combination of phase disposition pulse width modulation (PDPWM) and DC capacitor voltage control for a chopper-cell based modular multilevel converter (MMC) for the purpose of eliminating the time-consuming voltage sorting algorithm and complex voltage balancing regulators. In this paper, the convergence of the DC capacitor voltages within one arm is realized by charging the minimum voltage module and discharging the maximum voltage module during each switching cycle with the assistances of MAX/MIN capacitor voltage detection and PDPWM signals exchanging. The process of voltage balancing control introduces no extra switching commutation, which is helpful in reducing power loss and improving system efficiency. Additionally, the proposed control scheme also possess the merit of a simple executing procedure in application. Simulation and experimental results indicates that the MMC circuit together with the proposed method functions very well in balancing the DC capacitor voltage and improving system efficiency even under transient states.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1392-1395
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• 2004

In order to successfully develop attitude and orbit control subsystem(AOCS), AOCS engineer performs hardware selection, controller design and analysis, control logic and interface verification on electrical test bed, integrated system test, polarity test, and finally verification on orbit after launching. Attitude and orbit control subsystem for KOMPSAT-2 consists of standby mode, sun mode, maneuver mode, science mode, and power safe mode to stabilize and to control the spacecraft for performing the mission. The sun mode is usually divided into sun point submode, earth search submode and safe hold submode. The maneuver mode is divided into attitude hold submode and ${\triangle}$ V submode, while the science mode divided into science coarse submode and science fine submode. Moreover, it is added to back-up mode which uses wheels as an actuator for sun mode and maneuver mode. In this paper, we describe the controller design process and the performance of the design results with respect to the sun mode and the maneuver mode based on thrusters as an actuator using on flexible model.

• Journal of Sensor Science and Technology
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• v.27 no.3
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• pp.175-181
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• 2018

In this paper, we introduce a new dimming control method in a visible light communication (VLC) system wherein byteinversion is adopted for flicker-free transmission. In the VLC transmitter, the original and the inverted data were sent sequentially and the remnant time in one period was used for the dimming control of the LED light. In the VLC receiver, only the original data was recovered using the gating signal whose width was the same as the length of the original data. In our experiments, the dimming control ranges were measured to be 22%-53%, 11%-76%, and 5%-88% of the CW LED light when the data rates were 9.6, 19.2, and 38.4 kbps, respectively. In this system, we used a 240-Hz sync pulse whose period was 4.16 ms, which was shorter than the maximum flickering time period of 5 ms that is generally considered to be safe. This configuration is very simple and useful in constructing indoor wireless sensor networks using the flicker-free LED lamps with dimming control capability.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1081-1092
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• 2014

Renewable energy is being spotlighted as the electric power generating source for the next generation. Due to an increase in renewable energy systems in the grid system, their impact on the grid has become non-negligible. Thus, many countries in the world, including Europe, present their own grid codes for grid power conversion devices. In order to experiment with these grid codes, grid fault test equipment is required. This paper proposes both equipment and a control method, which are constructed with a 7-level cascaded H-bridge converter, that are capable of generating various grid faults. In addition, the Pulse Width Modulation (PWM) method for multilevel converters is compared and analyzed. The proposed structure, the control method, and the PWM method are verified through simulation and experimental results.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1400-1404
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• 2005

This paper presents the temperature control of aluminum plate by using Peltier element. Peltier effect is heat pumping phenomena by electric energy as one of the thermoelectric effect. So if current is charged to Peltier element, it absorbs heat from low temperature side and emits heat to high temperature side. In this experiment, Peltier element is used to control the temperature of small aluminum plate with current control and operating cooling fan only while cooling duration. Operating cooling fan only while cooling duration is proper to get more rapid heating and cooling duration. As a result of experiment, it takes about 100sec period to repeating temperature between $35^{\circ}C$ and $70^{\circ}C$ and about 80sec from $40^{\circ}C$ to $70^{\circ}C$ in ambient air temperature $25^{\circ}C$ and while operating cooling fan only in cooling duration. Future aim is to apply this temperature control method in actuating SMHA(special metal hydride actuator) which is applicable in Siver project acting in low frequency range by using Peltier element for heating and cooling.

• International Journal of Aeronautical and Space Sciences
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• v.4 no.1
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• pp.75-87
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• 2003

The primary objective of this study is to demonstrate ground-based experiment for the attitude control of spacecraft. A two-axis rotational simulator with a flexible ann is constructed with on-off air thrusters as actuators. The simulator is also equipped with payload pointing capability by simultaneous thruster and DC servo motor actuation. The azimuth angle is controlled by on-off thruster command while the payload elevation angle is controlled by a servo-motor. A thruster modulation technique PWM(Pulse Width Modulation) employing a time-optimal switching function plus integral error control is proposed. An optical camera is used for the purpose of pointing as well as on-board rate sensor calibration. Attitude control performance based upon the new closed-loop control law is demonstrated by ground experiment. The modified switching function turns out to be effective with improved pointing performance under external disturbance. The rate sensor calibration technique by Kalman Filter algorithm led to reduction of attitude error caused by the bias in the rate sensor output.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.1
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• pp.10-21
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• 2003

During seek operation in disk drives, the recording head is moved toward desired track by seek servo controller and then is settled onto the center of the desired track by settling servo controller. If the head speed at the start of settling servo control is not slow, it may produce overshoot relative to the center of track and thus extend the settling time. The degradation in settling performance will be more severe as the track width becomes smaller for higher density of data storage. We design a new settling servo controller for minimizing settling time based on the pole-zero cancellation. In order to cancel slow poles in settling response, we apply discrete pulse signals to the system in addition to the state feedback control. For exact pole-zero cancellation, we consider the dynamics of power amplifier used for actuator current regulation and the effects of delay in control action. In addition, we present system parameter identification algerian for the robustness of our controller to system parameter variation. In order to demonstrate the practical use of our controller, we present experimental results obtained by using a commercially available disk drive.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.12
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• pp.108-115
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• 2014

Recently, Uninterruptible power supply(UPS) is spotlighted from concern about black out, due to reserve power problem caused by increased power consumption. When fault occurs on the grid, UPS system supplies power to loads instead of the grid. Also, it is an advantage of possible operation as Energy storage system(ESS). Bi-directional power control of AC/DC Pulse width modulation(PWM) converter is essential for grid-connected UPS system. And, mode transfer control has to be performed considering phase and dynamic characteristic under grid condition. In this paper, control of mode transfer and bi-directional power control of AC/DC PWM converter is proposed for UPS system. Also, it is verified by simulation and experimental results.