• Biomedical Science Letters
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• v.10 no.3
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• pp.237-243
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• 2004

In recent, many cardiac centers have preferred off-pump coronary artery bypass grafting (CABG) to on-pump CABG to prevent the adverse effects of cardiopulmonary bypass. The present study was performed to prove beneficial effects of off-pump CABG. Sixty adult patients scheduled for elective CABG were randomly assigned to On-pump group (n=30) or Off-pump group (n=30). Arterial blood samples were drawn before and after the operation (Pre-OP and Post-OP, respectively) for measuring CBC, prothrombin time, activated thromboplastine time, blood gas analysis, creatine kinase-MB (CK-MB) level, and lactate dehydrogenase (LDH) level. Perioperative parameters including heparin and protamine usages, complications, blood components usages, blood loss, ventilation and ICU-staying time, and hospitalization were also evaluated. Platelet count at Post-OP was high in Off-pump group whereas CK-MB and LDH levels were low compared with On-pump group. Off-pump group had significantly lower heparin and protamine usages, lower total leukocyte count, higher hematocrit and hemoglobin levels, less blood loss, lower usages of blood components, shorter ventilation and ICU-staying time, and lower incidence of pleural effusion than On-pump group. Other variables did not significantly differ between two groups. These results showed that Off-pump CABG was a satisfactory technique with less inflammatory reaction, less cardiac damage, less postoperative complications, and less cost.

• Journal of Korean Society on Water Environment
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• v.21 no.4
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• pp.353-359
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• 2005

This study was conducted to evaluate the operation characteristics with aeration time in intermittent aeration membrane bioreactor. The BOD removal efficiency rate of this process was over than 97% regardless of aeration on/off time. To get over than 82% of nitrogen removal efficiency rate, aeration off time needs more than 70 minutes in reactor. Specific denitrfication rate was 2.68 mg $NO_3-N/gMv/hr$ in 40/80 min aeration on/off time, was 2.6 times more than 60/60 min, and 1.4 times more than 50/70 min in 6,300 mg/L of MLSS concentration. Specific nitrification rate was 1.96 mg $NH_4-N/gMv/hr$ in 50/70 min, was 1.4 times more than 40/80 min, but it was effectded little upon nitrification. Microbial activity was effected little according to aeration on/off time, oxygen demend was reduced according to aeration off time increased and microbial concentration increased. The longer aeration off time become, the higher Extraceller Pollymeric Substance (EPS), 50/70 min and 40/80 min in aeration on/off time was increased 1.6 times and 2.7 times, respectively more than 60/60 min because of increase of operation pressure.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.8
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• pp.1089-1096
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• 2003

An experiment was performed to investigate lift-off, blow-off and combustion characteristics of a lifted coaxial diffusion flame according to fuel jet and air velocity. A jet diffusion flame which is attached on the nozzle rim begins to be lifted with increase of air velocity, and finally becomes blow-off at higher air velocity. In experiment, blow-off limit increased with increase of fuel jet velocity, however lift-off occurred at lower air velocity. Flame structure and combustion characteristics were examined by schlieren photos, temperature distributions and emission concentration distributions. Flame temperature became higher at midstream and its RMS became larger at up and downstream with increase of air velocity. Local NO concentration decreased but $CO_2$concentration increased with increase of air velocity, which shows combustion reaction becomes close to be stoichiometric at higher air velocity in spite of lift-off.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.3
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• pp.868-876
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• 1995

This study deals with a position control of an electro-hydraulic servo system which consist of cylinder and high speed on-off valves operated by microcomputer. The merits of PWM control of hydraulic equipment are the robustness of the high spee on-off valve, its low price and the direct control without D/A converter. In the PWM control of high speed on-off valve, the time lag and switching time existing between the input and output signals of valve are considered as demerit points. To get analytical results, the effects of these demerits have to be clarified in detail. The object of this study is to propose a mathematical model for the behavior of high speed on-off valve and to get analytical results of this system. The dynamic characteristics of this system is examined by digital computer simulation analytically and compared with experimental results to varify the proposed mathematical model.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.820-825
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• 1996

This paper is concerned with effective operating method of pneumatic on-off valves for improving position control accuracy, valve life-time and position settling time using modified pulse width modulation with dead-zone. The pneumatic system using on-off valves studied in this paper has advantage of simple construction and low cost compared with a system with servo-valves. The performance of proposed control system is investigated experimentally for the position control of a pneumatic cylinder using on-off valves. Experimental results show that the proposed algorithm for valve operation can be used to obtain fast and accurate position control and to prevent on-off valves from unnecessary switching.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.6
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• pp.835-841
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• 2011

The humidification is essential for performance enhancement of the electrolysis of PEMFC because proton conductivity depends on hydration of the proton exchange membrane. In this study, the humidification experiment did about On/Off control the humidification and dew condensation for PEMFC by using of the membrane humidifiers. As the results, it was possible to approximation control of the humidity by using of the solenoid valve On/Off control on the membrane humidifier. Also the problem on the dew condensation was resolved by approximation humidity control through solenoid valve On/Off control and the removal of the dew condensation in the flow channel was verified through visualization experiment.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.225-230
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• 2002

Machine of textiles let off is equipment supplying constantly fabrics. Nowdays, as it is replaced band - brake type with hydraulic motor driven type, we looked into characteristic of hydraulic solenoid pilot direction valve(SPDV) for controlling acceleration performance of hydraulic motor. This study deals with controlling the initial speed of textiles let off machine. Finally, to control the initial speed of hydraulic motor, we controlled the adjustment screw of SPDV by a hand. Test which was carried out in the laboratory shows that initial speed of textiles let off could be improved by controlling adjustment screw of SPDV. Also, the results of experiment work were compared with dynamic characteristic of other on/off solenoid direction valve(SDV).

• Land and Housing Review
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• v.8 no.3
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• pp.131-143
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• 2017

Automobiles and parking lots have greatly been increased by the continuous development of new towns and residential districts. There were not enough parking lots; and although there were off-street parking lots available for sale, they were not easily sold. Through a parking regulation, local governments can require parking spaces for more than a certain rate in developing areas. Despite local governments should require parking spaces within the parking demand and regulation, they did not investigate parking demands. Off-street parking spaces are not easy to sell because they don't consider the parking demand. In this study, we analyzed the factors that affect the parking management in order to increase sales of the off-street parking. The factors were "the characteristics of the parking lots", "the accessibility of the off-street parking", and "the traffic environment around off-street parking." We have derived suggestions for these factors. In addition, this study has derived nine variables affecting the parking operation in these three factors, and suggested a logistic regression model and the influence of each factors. According to the analysis, "parking signs" were the most influential. Next were "land uses" and "lanes on road".

• Fashion & Textile Research Journal
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• v.21 no.6
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• pp.743-753
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• 2019

This study investigates differences in demographic characteristics, shopping orientation, perceived risk, and satisfaction after purchase among consumer types. This study classifies consumer types according to their channel transition behaviors between the online and offline channels with a focus on the steps of information research and buying decision in buying decision-making process. The four consumer groups are as follows: off-off type (offline research-offline purchase), on-on type (online research-online purchase), on-off type (online research-offline purchase) and on/off-off type (online and offline research-offline purchase), off-on type (offline research-online purchase) and on/off-on type (online and offline research-online purchase). Data were collected from adults over 20 years old who had bought clothes within one year. The questionnaire was carried out from July, 2019 using a professional internet research panel; in addition, 500 sets of useful data were analyzed by descriptive statistics, factor analysis, reliability analysis, chi-squared test, ANOVA and Duncan-test using SPSS 21.0. The findings showed significant differences among the classified consumer groups for consumer demographics, shopping orientation, perceived risk, and purchase after satisfaction. The results imply that consumers show a variety of channel transition behaviors based on demographic variables, shopping orientation, and perceived risk. Understanding and adapting to consumer purchase behaviors will allow company distribution channels to be effectively managed and eventually increase consumer satisfaction as well as company sales volume.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.3
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• pp.237-243
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• 2016

Recently, technologies that produce biofuels from microalgae are being studied worldwide. It is necessary to significantly reduce the production costs of biofuels from microalgae for economic reasons. In this study, the growth curve of the microalgae was obtained using the batch-culture method, and the specific growth rate was predicted using the regression method. Based on the culture conditions of the estimated specific growth rate, the turbidity of the microalgae in the flat panel photobioreactor (PBR) was measured. Furthermore, an on-off control scheme was applied to the flat panel PBR in order to culture the microalgae continuously on the basis of turbidity. The parameters of the on-off control system were displayed by LabView. The on-off scheme of peristaltic pump was controlled based on the turbidity in the PBR. In addition, the turbidity values of growth curves were compared and analyzed in the continuous culture process using the on-off controller.