• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.535-539
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• 2010

We present a digital dilution chip comprising a $2{\times}6$ array of wells; the chip can be employed to change the dilution ratio as well as to initiate reactions among diluted samples by using the inter-well valve around the well. In previous dilution devices, streams comprising sample and dilution solutions were merged and separated by a branched microchannel. Therefore, the dilution ratio could not be changed until the structure of the branched microchannel was changed. The present device merges and splits the wells filled with sample or dilution solution by controlling inter-well valves around the wells. Thus, it is possible to change the dilution ratio by changing the sequence in which merging and splitting sequence of each well filled with sample or dilution solution. In experiments, we found that the chip could be used to change linear or exponential dilution ratios within an error of 16.7% and to initiate reactions among the samples within a reaction error of 17.7%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.5
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• pp.650-658
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• 1997

Analysis and control of intake charge motion such as swirl and tumble are very important factors in improving the gasoline engine performance. In this paper, single-frame PTV (particle tracking velocimetry) is used to investigate intake tumble patterns in a steady flow test rig of gasoline engine with dual-intake-valve and pent-roof combustion chamber. Intake tumble pattern is quantified in accordance with blockage ratio of TIV (tumble intensifying valve) with single- frame PTv.The view of the instantaneous 2-D velocity field gives a realistic understanding of in-cylinder flow field. Thus it is confirmed that PTV is a effective tool in engine design. In conventional port, two tumble structures appear clearly, and the larger one is observed under the exhaust valve side and the smaller is right below the intake valve side. The larger vorticity is observed in TIV port, thus it is concluded that TIV have an effect on intensified tumble motion in cylinder flow.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.6
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• pp.234-242
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• 1998

It has been demonstrated that the in-cylinder turbulence is enhanced by inclined swirl with a SCV(swirl control valve). The inclined-tumble flow measurement and analysis were performed for various types of intake systems that generated several different combinations of swirl ratio and tumble ratio in the cylinder. Experiments were conducted in a 4-valve optically accessed transparent research engine using a backward-scatter LDV mode under motoring condition at 1,000rpm. The influence of swirl/tumble levels on the characteristics of turbulence was analysed. This study presents experimental results of the inclined-tumble flow structure, including the flow motion phenomena, angular momentum and turbulence intensity.

• Korean Journal of Agricultural Science
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• v.48 no.3
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• pp.597-606
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• 2021

Due to the characteristics of the farmland in Korea, forward and reverse shift is the most used. The fatigue of farmers is caused by forward and reverse shifting with a manual transmission. Therefore, it is necessary to improve the convenience of forward and backward shifting. This study was a basic study on the development of a current control system for forward and reverse shifting of agricultural tractors using proportional control valves and a controller. A test bench was fabricated to evaluate the current control accuracy of the control system, and the stability of the controller was evaluated through CPU (central processing unit) load measurements. A controller was selected to evaluate the stability of the proportional valve controller. The stability evaluation was performed by comparing and analyzing the command current of the controller and the actual current measured. The command current was measured using a CAN (controller area network) communication device and DAQ (data acquisition). The actual current was measured with a current probe and an oscilloscope. The control system and stability evaluation was performed by measuring the CPU load on the controller during control operations. The average load factor was 12.27%, and when 5 tasks were applied, it was shown to be 70.65%. This figure was lower than the CPU limit of 74.34%, when 5 tasks were applied and was judged to be a stable system.

• Journal of Chest Surgery
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• v.54 no.1
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• pp.25-30
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• 2021

Background: Life-long anticoagulant therapy is mandatory for patients who undergo heart valve replacement with implantation of a mechanical prosthesis. The aim of this study was to investigate the effects of a nurse-led patient educational program concerning oral anticoagulant therapy intake after heart valve replacement surgery on patients' knowledge of important parameters of anticoagulant administration. Methods: In this single-center study, 200 patients who underwent surgical implantation of a mechanical prosthesis were divided into 2 groups. The control group received the basic education concerning oral anticoagulants, while the intervention group received a personalized educational program. Results: Personalized education was correlated with a better regulation of therapeutic international normalized ratio (INR) levels and adequate knowledge among patients. Therapeutic levels of INR were achieved in 45% of the patients during the first month, 71% in the third month, and 89% in the sixth month after discharge in the intervention group, compared to 25%, 47%, and 76% in the control group, respectively. Patients' satisfaction with the information was higher in the intervention group than in the control group. The percentage of satisfaction reached 80% for the intervention group versus 37% for the patients of the control group. Conclusion: The implementation of the nurse-led educational programs was associated with improved clinical results and increased adherence to oral anticoagulant treatment.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.242-247
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• 2003

An experimental study presents characteristics of combustion in a combustion chamber by port deactivation valve for economy and emissions standards. In order to use combustion properties data it is necessary to build some data base, which use cylinder pressure sensor, etc. Port deactivation valve has been developed to satisfy requirement of achieving sufficient swirl generation to improve the combustion. A feasibility and necessity of combustion pressure based cylinder spark timing control has been examined. So, this was obtained the Coefficient of Variation(COV) and the mass-burned(MFB). The characteristics of pressure ratio fraction is similar to that of mass-burned fraction. Using the results of the test, the effects of the combustion chamber can be improved combustion stability by port deactivation.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.928-933
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• 2001

EGR(Exhaust Gas Recirculation) is an effective strategy to control nitrogen oxides emissions from diesel engine. The EGR reduces $NO_x$ through lowering the oxygen concentration in the combustion chamber as well as through heat absorption. However, application of EGR system is difficult because of the penalty in fuel consumption and the increase in particulate matter. The engine used for the experimental was a 3-cylinder 0.8-liter turbo-charged light duty diesel engine with an electronic EGR valve. In this study, experiments were performed at variable vehicle speeds and loads on the chassis dynamometer. To evaluate the exhaust emissions with the EGR system testing was performed using cvs-75 mode test procedure. Results of the cvs-75 mode test achieve sufficiently to meet EURO3 standards.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.745-746
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• 2010

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.585-589
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• 2010

It is important for the liquid rocket engine to meet the exact performance requirements in order to guarantee the successful mission of the launch vehicle. Usually, a ground combustion test for the engine is conducted to reduce the performance error and for the tuning. For the gas-generator (GG) cycle engine, this adjustment process can be easily tuned by means of the control valves. A linearized correlation between the process parameters of the control - the combustion chamber pressure and the mixture ratio of engine - and the independent parameter of the control- rotational angle of the control valve - could be suitable to reduce the tuning errors. Also this linearity can reduce the effort for the tuning and make the process more explicit by ensuring a more intuitive control. In this point, we proposed an algorithm in the frame of the in-house-developed program to obtain the control valves' inherent characteristics which satisfy the linearity.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.4
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• pp.67-75
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• 2004

It is essential to develop a transient analysis model for the turbopump-fed type liquid rocket engine development, especially for deriving the number of test and its parameters. In this study we proposed a mathematical model of turbopump-fed type liquid rocket engine, and inspected transient mode changes of a rocket engine according to variations of thrust control valve opening ratio. To verify the results, we solved the same problem with AnaSyn software from Russia, and concluded that the results of transient code we developed deviated within 2% from AnaSyn results. Also, using the transient engine analysis code we showed the possibility to find out the system level design Parameters of the components. For example, we modeled a pressure stabilizer which is used to control the consistency of mixture ratio in the gas generator as forced damping system, and found the stability range of the natural frequency and the damping ratio with the transient engine system analysis code.