• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.1 s.256
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• pp.62-69
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• 2007

Micromanipulator is a device that manipulates an object with high precision. Generally, a parallel-type robot has inherently higher precision than a serial-type robot. In most cases, the use of flexure hinge mechanisms is the most appropriate approach to micromanipulators. The micromanipulator is basically required that have high natural frequency and sufficient workspace. However, previous designs are hard to satisfy the required workspace and natural frequency, simultaneously, because the previous micromanipulators are coupled designs. Therefore, this paper suggests a new design parameter as displacement amplifier and new design procedure based on semi-coupled design in axiomatic design. As a consequence the spatial 3-DOF micromanipulator which is chosen as an exemplary device has natural frequency of 500Hz and workspace of $-0.5^{\circ}{\sim}0.5^{\circ}$. To investigate the effectiveness of the displacement amplifier, simulation and experiment are performed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.1 s.256
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• pp.91-98
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• 2007

Air-conditioners use a spirally coiled capillary tube as an expansion device to enhance compactness of the unit. However, most empirical correlations in open literature were developed for straight capillary tubes without considering coiled effects on the mass flow rate. The objectives of this study are to investigate the flow characteristics of coiled capillary tubes and to develop a generalized correlation for mass flow rate through coiled capillary tubes. The mass flow rates through the coiled capillary tubes and straight capillary tubes were measured by varying operating conditions and tube geometry. The condensing temperatures varied at 40.5, 47.5 and $54.5^{\circ}C$, and subcoolings altered at 3.5, 6.5 and $11.5^{\circ}C$. The mass flow rates of the coiled capillary tubes decreased by 5 to 16% compared with those of the straight capillary tubes at the same operating conditions. An empirical correlation was developed by introducing equivalent length of capillary tube with non-dimensional parameters for coiled shape. The present correlation predicts the data with average and standard deviations of 0.33% and 3.24%, respectively.

• Journal of the Korean Solar Energy Society
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• v.37 no.2
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• pp.13-22
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• 2017

Two-step water splitting thermochemical cycle with $CeO_2/ZrO_2$ foam device was investigated by using a solar simulator composed of 2.5 kW Xe-Arc lamp and mirror reflector. The hydrogen production of $CeO_2/ZrO_2$ foam device depending on heat recovery of Thermal-Reduction step and Water-Decomposition step was analyzed, and the hydrogen production of $CeO_2/ZrO_2$ and $NiFe_2O_4/ZrO_2$ foam devices was compared. Resultantly, the quantity of hydrogen generation increased by 52.02% when the carrier gas of Thermal-Reduction step is preheated to $200^{\circ}C$ and, when the $N_2/steam$ is preheated to $200^{\circ}C$ in the Water-Decomposition step, the quantity of hydrogen generation increased by 35.85%. Therefore, it is important to retrieve the heat from the highly heated gases discharged from each of the reaction spaces in order to increase the reaction temperature of each of the stages and thereby increasing the quantity of hydrogen generated through this.

• Journal of the Korean Society of Industry Convergence
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• v.10 no.2
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• pp.115-122
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• 2007

The MPC(Moisture Protected Computer) system is completely unique. It was recently invented in Korea and it is a technological break-through in the field of computer systems. It will be instrumental in the development of a complete moisture air-tight capability and will work well in field environments. The MPC includes the following: 1) An enclosed design. 2) Moisture proof computer enclosure joints. 3) System dust protection & an impact buffing system. 4) A normal temperature maintenance system when the temperature inside the computer is low. 5) The ability to generate heat and a radiate system inside the computer 6) An automatic power input sensing controller device. 7) A safety device in case of mis-operation. 8) A proper admission procedure for various tests. Because of the above, and as a result of temperature property experiments, there aren't any operational problems. The result of this treatise could provide very important data for verification of cases involving: using strong materials to protect against explosions, searching for ways to make the size and weight small, and for making repairs easier. As a result, it could achieve price and function competitiveness in advanced countries such as the USA and in Europe.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.11
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• pp.1214-1220
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• 2012

Vibration assisted cutting (VAC) is one of the promising methods for precision machining, which has been normally equipped with piezoelectric materials. In this paper, a feasibility of applying magnetostrictive materials to VAC as a cutting device instead of piezoelectric materials was studied. For this, the vibrational characteristics of a magnetostrictive material was investigated with respect to a coil design, a preload, and the effects of a biasing and an exciting magnetic fields. The output strain of a magnetostrictive material is restricted due to an increasing inductive impedance as the exciting frequency increases and the heat of coil, etc. Through the experimental results, it was found that the biasing and the exciting magnetic field affected the output performance significantly but not the preload. In conclusion, the magnetostrictive material could be used only in the low frequency range but not a good candidate for high frequency actuating application.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1484-1485
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• 2008

The control of the number and dimension of nanowires is essential for dielectrophoretic(DEP) nanoscale assembly process. However, it is difficult to control the number of nanowires assembled between the electrodes. We have developed a nanowire diluter device, which consists of a glass substrate with gold electrodes and a PDMS layer with microchannel. The diluter device is fabricated by the conventional and soft lithographies using a SU-8 mold. Nickel nanowires (30${\mu}m$-long) are fabricated by a template-directed electrodeposition process using nanoporous alumina templates. A solution containing nanowires is injected into an inlet whereby pulsed voltages are applied to 16 pairs of electrodes in this experiment. The nanowires are trapped or released depending on the pulsed electric field from inlet to outlet (the channel). Therefore, the number of nanowires can be decreased correspondingly if the fixed frequency at each electrode is decreased from electrode to electrode.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.11
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• pp.1889-1896
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• 2003

In the microfluidic applications, viscous-driven pumping mechanism is a promising one since the viscous effect increases significantly as the size of device decreases, relative to the inertial effect. However, there exist a few drawbacks we have to improve such as low efficiency and small volume flow rate. In the present study, an optimum design synthesis is proposed to enhance the performance characteristics of the micropump with single rotating cylinder. First, the unstructured grid CFD method is described and validated by comparing its results to the previous results. Next, an automated optimum design synthesis tool is constructed by combining the aforementioned CFD analysis model with the mathematical optimization model. This technique is used to improve the performance characteristics of newly designed viscous-driven pump. The presented results show that the fluid dynamic optimization tool is robust and may be applied to other microfluidic device design applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.228-232
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• 2002

The rise throughput and the stability in the device fabrication can be obtained by applying chemical mechanical polishing(CMP) process in 0.18 ${\mu}m$ semiconductor device. However it does have various problems due to the CMP equipment. Especially, among the CMP components, process variables are very important parameters in determining removal rate and non-uniformity. In this paper, We studied the DOE(design of experiment) method for the optimized CMP process. Various process variations, such as table and head speed, slurry flow rate and down force, have investigated in the viewpoint of removal rate and non-uniformity. Through the above DOE results, we could set-up the optimal process parameters.

• Journal of Power System Engineering
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• v.20 no.2
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• pp.32-42
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• 2016

Under part load condition of spark-ignition engine, pumping loss had great effect on engine efficiency. To reduce pumping loss, the study designed spark-ignited engines to make direct spray of gasoline to combustion chamber. In spark-ignited direct-injection engines, ignition probability is important for successful combustion and flame propagation characteristics are also different from pre-mixed combustion. This study designed a visualization testing device to study ignition probability of spark-ignited direct-injection LPG fuel and combustion flame characteristics. This visualization device consists of combustion chamber, fuel supply system, air supply system, electronic control system and data acquisition system. Ambient pressure, ambient temperature and ambient air flow velocity are important parameters on ignition probability of LPG-air mixture and flame propagation characteristics, and the study also found that sprayed LPG fuel can be directly ignited by spark-plug under proper ambient conditions. To all successful cases of ignition, the study recorded flame propagation image in digital method through ICCD camera and its flame propagation characteristics were analyzed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.10 s.253
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• pp.1003-1011
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• 2006

Droplets are ejected onto a substrate through a nozzle by pushing liquids in flow channels of drop-on-demand devices. The behavior of ejection and formation of droplets is investigated to enhance the physical understanding of the hydrodynamics involved in inkjet printing. The free surface phenomenon of a droplet is described using $CFD-ACE^{TM}$ which employs the volume-of-fluid (VOF) method with the piecewise linear interface construction (PLIC). Droplet formation characteristics are analyzed in various flow regimes with different Ohnesorge numbers. The computational results show that the droplet formations are strongly dependent on the physical properties of working fluids and the inlet flow conditions. In addition, the wetting characteristics of working fluids on a nozzle influence the volume and velocity of a droplet produced in the device. This study may provide an insight into how a liquid droplet is formed and ejected in a piezoelectric inkjet printing device.