• Journal of the Korean Ceramic Society
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• v.43 no.7 s.290
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• pp.445-450
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• 2006

The preparation of AlN powder by SHS in the system of $Al-AlN-NH_4Cl$ was investigated in this study. In the preparation of AlN powder, the effect of gas pressure and the composition such as Al, AlF, and additive in mixture on the reactivity were investigated. At 60 atm of the initial inert gas pressure in reactor, the optimum composition for the preparation of pure AlN was 35 wt%Al+5 wt% $NH_4Cl+60wt%$AlN. The AlN powder synthesized in this condition was a single phase AlN with a whisker morphology.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2495-2500
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• 2008

We simulated the mixing characteristics in micro T-channel using Lattice Boltzmann Method. We studied the relation a mixing length and pressure-drop due to inlet and outlet ration in Reynolds number 0.5, Peclet number 500 and Schmidt 1000. The ratio of a down-inlet to up-inlet was $0.5{\sim}1.5$ times, up-inlet to outlet was $1{\sim}3$ times and outlet length was 250 times to up-inlet. The mixing length decrease linearly as outlet ratio decreased, and pressure-drip increase non-linearly. Initial stage of micro channel mixture was fast by down-inlet ratio, however, the mixing length is not influence.

• The KSFM Journal of Fluid Machinery
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• v.20 no.2
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• pp.26-31
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• 2017

In the present study, 20 kW turbine for OTEC with a ejector and a motive pump is designed and performance prediction is implemented by means of CFD. The meridional analysis for initial geometry and CFD for detail design are used to design the turbine. This turbine has about 90.9% efficiency and 28.47 kW power at 15,000 rpm and pressure ratio of 1.53. Homogeneous mixture model is used because two phase flow can be occurred in the turbine. Performance evaluation is carried out and then results are presented by plotting of power, mass flow rate and efficiency as varying pressure ratio and rotational speed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.9
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• pp.104-109
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• 2021

Tactile sensors and integrated circuits that detect external stimuli have been developed for use in various industries. Most tactile sensors have been developed using the MEMS(micro electro-mechanical systems) process in which metal electrodes and strain sensors are applied to a silicon substrate. However, tactile sensors made of highly brittle silicon lack flexibility and are prone to damage by external forces. Flexible tactile sensors based on polydimethylsiloxane and using a multi-walled carbon nano-tube mixture as a pressure-sensitive material are currently being developed as an alternative to overcome these limitations. In this study, a manufacturing process of pressure-sensitive materials with low initial electrical resistance is developed and applied to the fabrication of flexible tactile sensors. In addition, flexible tactile sensors are developed with pressure-sensitive materials dispensed on a substrate with flexible mechanical properties. Finally, a study is conducted on the change in electrical resistance of pressure-sensitive materials according to the modulus of elasticity of the substrate.

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.4
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• pp.27-32
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• 2003

The Performance of micro combustor in various condition was exploited experimentally. Various geometric conditions of combustor were considered to figure out the performance of micro combustor. The micro combustor studied in this study was constant volume with cylindrical shape. Geometric parameters of combustor were defined to be combustor height and diameter. The effect of height was exploited parametrically with the size of 1mm, 2mm and 3mm. The effect of diameter was observed parameterized with 7.5mm and 15mm. Three different combustibles or Stoichiometric mixture of methane/air, hydrogen/air were used. Pressure transition during combustion process was recorded. The maximum pressure by combustion responded favorably with the change of height of combustor and the initial pressure. The flame propagation was visulized using Schlieren method. The flame propagation within combustor was observed when specific conditions such as combustor height and initial pressure over critical value was satisfied.

• Journal of Power System Engineering
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• v.13 no.6
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• pp.13-21
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• 2009

This basic study is required to examine spray or jet behavior depending on fuel phase. In this study, analyses of diesel fuel(n-Tridecane, $C_{13}H_{28}$) spray and natural gas fuel(Methane, $CH_4$) jet under high temperature and pressure are performed by a general-purpose program, ANSYS CFX release 11.0, and the results of these are compared with experimental results of diesel fuel spray using the exciplex fluorescence method. The simulation results of diesel spray is analyzed by using the combination of Large-Eddy Simulation(LES) and Lagrangian Particle Tracking(LPT) and of a natural gas jet is analyzed by using Multi-Component Model(MCM). There are two study variables considered, that is, ambient pressure and injection pressure. In a macroscopic analysis, the higher ambient pressure is, the shorter spray or jet tip penetration is at each time after start of injection. And the higher injection pressure is, the longer spray or jet tip penetration is at each time after start of injection. When liquid fuel is injected, droplets of the fuel need some time to evaporate. However, when natural gas fuel is injected, the fuel does not need time to evaporate. Gas fuel consists of minute particles. Therefore, the gas fuel is mixed with the ambient gas more quickly at the initial time of injection than the liquid fuel is done. The experimental results also validate the usefulness of this analysis.

• Food Science and Biotechnology
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• v.14 no.6
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• pp.747-751
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• 2005

Microencapsulation of pine flavors was investigated to determine the optimum wall material and spray drying condition. ${\beta}$-Cyclodextrin, maltodextrin, and a 3:1 mixture of maltodextrin and gum arabic were evaluated as wall materials. The latter mixture was determined to be the best wall material based on dispersion capacity and flavor yield. Spray drying effectiveness was evaluated using a $3^3$ fraction factorial design and statistical analysis. The optimum operation condition was an inlet air temperature of $175^{\circ}C$, inlet airflow rate of $0.65\;m^3/min$ and atomizing pressure of 180 kPa, which resulted in a 93% flavor yield. The best particle shape observed by SEM was a round globular shape obtained under the above spray drying condition, whereas lower temperatures and higher inlet airflow rates resulted in initial and full collapses, respectively. The round globular shapes remained stable for at least one month.

• Bulletin of the Korean Chemical Society
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• v.13 no.6
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• pp.593-595
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• 1992

To improve the lifetime and output power in a sealed-off $CO_2$ laser, a series of Nd$_{1-x}$Sr$_x$CoO$_3$(x = 0.0, 0.25, 0.40, 0.50, 0.60, 0.75) perovskite-type compounds has been synthesized and used for a cathode material. Using a typical method samples were sintered at 1150$^{\circ}$C and their structures were determined as a cubic form by means of XRD analysis. The degrees of $CO_2$ dissociation were measured by PAS (photoacoustic spectroscopy) with the lapse of time. In the case of $Nd_{0.4}$Sr$_{0.6}$$CoO_3$, which showed the highest catalytic cathode effect, only 7% of the initial $CO_2$ concentration were dissociated at 30 torr of gas mixture and 5 mA of discharge current. The more the gas pressure decreased and the discharge current increased, the more the degree of dissociation occurred. The ability of catalytic cathode to regenerate CO$_2$ in the laser cavity lies in order for x, 0.60 > 0.50 > 0.40 > 0.75 > 0.25 ${\gg}$ 0.0. Except for the case of x = 0.0 the amounts of $CO_2$ dissociation were found to be within 7-15% of the initial $CO_2$ concentration.

• Membrane Journal
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• v.16 no.3
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• pp.204-212
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• 2006

A numerical analysis was carried out for separation of carbon dioxide from carbon dioxide/nitrogen gas mixture by a polyethersulfone hollow fiber membrane which has shown a good stability against plasticization by carbon dioxide and an excellent separation efficiency fur carbon dioxide from its gas mixture. A computer program for carbon dioxide separation was developed using the Compaq Visual Fortran 6.6 software. Governing module equations were thought to be an initial-value problem and the nonlinear ordinary differential equations were simultaneously solved using the Runge-Kutta-Verner fifth-order method. From results of numerical analysis, the carbon dioxide partial pressure of the feed stream, the pressure ratio of the feed side to the permeate side and the feed gas residence time at the inside of a membrane were found to be very important factors to affect the permeation characteristics of carbon dioxide.

• Journal of the Korean Applied Science and Technology
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• v.27 no.3
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• pp.233-239
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• 2010

Supercritical carbondioxide is very effective in removing oils from a variety of seed matrices, devoid of any appreciable amount of phospholipid content. However, the limited solubility of phosphalipids in supercritical carbondioxide leaves behind a potentially valuable by-product in spent seed matrix. Any phospholipid extraction process from the spent matrix must maintain the structure and the quality of phospholipids and must be compatible with the end use of the seed protein meal an animal feed or for human consumption. An initial supercritical carbondioxide extraction of soybean flakes was performed at 32 MPa and $80^{\circ}C$ to extract the oils, leaving the phospholipids in the deflatted soybean flakes, A second step was performed on the defatted soybean flake using $X_{eth}$=0.10, Varying the pressure from 175 MPa to 70.6 MPa and temperature from $60^{\circ}C$ to $80^{\circ}C$. For all supercritical carbon dioxide/ethanol mixture extractions, a fraction rich in phospholipids was obtained. The fractions extracted from defatted soybean flakes were dried and them redissolved in chloroform before HPLC-ELSD analysis. Quantitative and qualitative analysis of phospholipids on soybean seeds, defatted soybean flake, and different extracted phospholipid fractions was carried out, to ascertain the effect of extraction pressure and temperature.