• Transactions of The Korea Fluid Power Systems Society
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• v.6 no.3
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• pp.10-15
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• 2009

The major system of an agricultural power-shift tractor is the transmission, using power-shift. Because the transmission performance depends on the hydraulic control system, the most important aspect of the optimization is the design of the hydraulic control system. This study was conducted to improve a pressure modulation characteristics of the power-shift transmission hydraulic system. It has been tried to replace an existing pressure modulation method with a digital control by using HSSV(High Speed Solenoid Valve). The performance of the PWM control system in power-shift hydraulic transmission has been evaluated by means of experiment.

• International Journal of Air-Conditioning and Refrigeration
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• v.12 no.3
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• pp.113-122
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• 2004

In case of heat exchangers operating under frosting condition, the thermal resistance and the air-side pressure loss increase with a growth of frost layer. In this paper, a transient characteristic prediction model of the heat transfer for a multi-inverter heat pump with frosting on its surface was presented by taking into account the change of the fin efficiency due to the growth of the frost layer. This dynamic simulation program was developed for a basic air conditioning system composed of an evaporator, a condenser, a compressor, a linear electronic expansion valve, and a bypass circuit. The theoretical model was derived from measured heat transfer and mass transfer coefficients. We also considered that the heat transfer performance was only affected by the decrease of wind flow area. The calculated results were compared with the experimental results for frosting conditions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.1
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• pp.60-64
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• 2004

In this paper, we implemented a real-time remote home monitoring system which we have ported the Linux OS and HTTP(Hypertext Transfer Protocol) web server. The GoAhead web server was ported using by ARM cross compiler. And then we used the analog to digital converter ADC0809 for sensing the vii able input signal at widely separated home. We have implemented linux device driver for ADC(Analog to Digital Convertor) and CGI-C(Common Gateway Interface - C language) application program using Client pull method for monitoring real-time changing data. The factor of monitoring is temperature, intensity of illumination and gas's existence. And this system has ability which check the status of out door and gas valve. We have designed the embedded web server system for home emergency monitoring in low cost.

• Journal of Digital Convergence
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• v.17 no.7
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• pp.265-274
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• 2019

The purpose of this study was to know the difference in pain, sleep, self-care behavior in patients performed by sternotomy and robotic minimally invasive cardiac surgeries. The participants were 64 patients with sternotomy and 64 patients with minimal thoracotomy in heart valve surgeries at a tertiary hospital in Seoul. Data were analyzed using descriptive statistics, ${\chi}^2$ test, paired t-test. with SPSS/WIN(22.0). The participants with minimally invasive thoracotomy felt severe pain than the patients with thoracotomy at post operation day 2 & 5. The severe pain site were the surgical site in both groups. The participants with sternotomy had better sleep than minimally invasive thoracotomy patients. Self-care behavior was higher in the minimally invasive thoracotomy group. Therefore, despite the many advantages of robotic surgery such as rapid recovery and shortening of length of stay in hospital, accurate pain assessment and application of differentiated protocols are needed for the management of pain in the patients with robotic minimally invasive cardiac surgeries. In addition, a structured education program intervention is needed to improve comfort by considering gender, age, and method of operation.

• Journal of Digital Contents Society
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• v.16 no.3
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• pp.483-492
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• 2015

This thesis analysis the CARBO 3000 that is one of a $CO_2$ infuser and improve its effectiveness. The thesis designs H/W and S/W that controls the $CO_2$ infusing mass compared to the CARBO 3000. Specially the designed H/W has a newly CPU, LCD, a flow velocity controller, a solenoid valve and a flow sensor. Also the designed S/W is composed of GUI and the algorithm to control the $CO_2$ infusing mass. The designed and implemented the $CO_2$ Infuser in this thesis is tested for the performance. The commercial measuring sensor is used for the test. The testing results say that the designed and implemented the $CO_2$ Infuser in this thesis is much more accurate compared to the CARBO 3000 on $CO_2$ infusing.

• Journal of Digital Convergence
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• v.13 no.1
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• pp.469-479
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• 2015

Purpose: The purpose of this study is to explore the effect of nursing intervention of aromatherapy hand massage. Method: In order to conduct a meta-analysis, a total of 124 studies were retrieved. From these studies, fifteen studies met the inclusion criteria with a total of 733 participants. And these studies published from January 2004 to July 2013 were included in the journal articles published in Korea. Results: In fifteen studies, Random effect model for the aromatherapy hand massage that 95% confidence level, significant level of p-valve on less than 0.001. Standardized Mean Difference reported systolic blood pressure(d=-9.5320), diastolic pressure(d=-8.8730), pulse(d=-9.1241), anxiety(d=-0.1469), and depression(d=-0.4489) All measurement variables were significantly decreased in the negative direction. Conclusion: This study suggests that aromatherapy hand massage can reduce the level of blood pressure(systolic, diastolic), pulse, anxiety and depression.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.2
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• pp.134-141
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• 2010

Small PEM (Proton Exchange Membrane) fuel cell systems do not require humidification and have great commercialization possibilities. However, methods for controlling small PEM fuel cell stacks have not been clearly established. In this paper, a control method for small PEM fuel cell systems using a dual closed loop with a static feedforward structure is defined and realized using a DSP (Digital Signal Processor). The fundamental elements that need to be controlled in fuel cell systems include the supply of air and hydrogen, water management inside the stack, and heat management of the stack. For small PEM fuel cell stacks operated without a separate humidifier, fans are essential for air supply, heat management, and water management of the stack. A purge valve discharges surplus water from the stack. The proposed method controls the fan using double control loops to quicken transient response of the fan thereby improving the supply rate of air. Feedback control to compensate for the voltage change in fuel cell stack improves the response characteristics in fuel cell to load variations. The feasibility of proposed method was proved by the experiments with a 60W small PEM fuel cell system and operation of a notebook computer using this system.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.979-984
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• 2007

This paper presents a new control mechanism for the proportional pressure control which is accomplished by electro-pneumatic regulator using two PZT actuators. The electro-pneumatic regulator of this study is 2-stage type and consists of two piezoelectric actuators, a controller and a main poppet valve. The piezoelectric actuators are multilayer bender type and are controlled by digital signal. Proportional pressure control technique is very important because that can derive improvement of product quality and driving ability in the pneumatic system. Solenoid actuator method for pressure control is widely used but this actuator has a high power consumption characteristics. So new actuator is required for the energy saving. In this study, PZT actuator for the pressure control was fabricated and experimented instead of the conventional type solenoid actuator. Experiments for the new control mechanism of the elector-pneumatic regulator were operated under the input condition of 0.4[MPa] and it was confirmed that this mechanism has a good control characteristics to the response sensitivity and hysteresis.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1109-1114
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• 2007

This paper presents the road simulator control technology for reproducing the road input signal to implement the real road data. The simulator consists of the hydraulic pump, servo valve, hydraulic actuator and its control equipment. The QFT is utilized to control the simulator effectively. The control system illustrates a tracking performance of the closed-loop controller with low order transfer function G(s) and pre-filter F(s) for a parametric uncertain model. A force controller is designed to communicate the control signal between simulator and digital controller. The efficacy of the QFT force controller is verified through the numerical simulation, in which combined dynamics and actuation of the hydraulic servo system are tested. The simulation results show that the proposed control technique works well under uncertain hydraulic plant system. The conventional software (Labview) is used to make up for the real controller in the real-time basis, and the experimental works show that the proposed algorithm works well for a single road simulator.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.11
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• pp.1069-1076
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• 2007

This paper presents the road simulator control technology for reproducing the road input signal to implement the real road data. The simulator consists of the hydraulic pump, servo valve, hydraulic actuator and its control equipment. The QFT(Quantitative Feedback Theory) is utilized to control the simulator effectively. The control system illustrates a tracking performance of the closed-loop controller with low order transfer function G(s) and pre-filter F(s) for a parametric uncertain model. A force controller is designed to communicate the control signal between simulator and digital controller. Tracking specification is satisfied with upper and lower bound tolerances on the steep response of the system to the reference signal. The efficacy of the QFT force controller is verified through the numerical simulation, in which combined dynamics and actuation of the hydraulic servo system are tested. The simulation results show that the proposed control technique works well under uncertain hydraulic plant system. The conventional software (Labview) is used to make up for the real controller in the real-time basis, and the experimental works show that the proposed algorithm works well for a single road simulator.