• Textile Coloration and Finishing
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• v.8 no.1
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• pp.56-63
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• 1996

A number of thermotropic liquid crystalline polyurethanes with mesogenic unit were synthesized by polyaddition of a para-type diisocyanate such as 1, 4-phenylene diisocyanate(1,4-PDI) with 4, 4'-bis($\omega$-hydorxyalkoxy) biphenyls($BP{m}$) in DMF. The thermal and liquid crystab line properties were examined by differential scanning calorimetry(DSC), polarized optical microscopy, and wide-angle X-ray scattering(WAXS). Intrinsic viscosities of the polymers exbibited two endothermic peaks correspondinding to phase transitions of melting and isotropization. For example, polyurethane(1,4-PDI/($BP{11}$) ) was found to display a liquid crystalline phase between 177 to 205$^{\circ}C$. In order to know how the hydrogen bonding interaction affects the formation of mesophases in polyurethane 1, 4-PDI/($BP{8}$) / thermal processing FT-IR measurements were carried out. It was found that the stretches regarded as shift to higher frequency region with increasing temperature which showed grdually their liquid crystalline phase

• Aerospace Engineering and Technology
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• v.3 no.1
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• pp.205-212
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• 2004

In this paper, to satisfy the temperature requirement of turbopump-inlet condition, the cooling of cryogenic propellant is performed at the simulated suction-line of the Launch Vehicle. The cooling method is by using gas helium injection. This paper investigates the effect of helium injection on liquid nitrogen, which simulates the liquid oxygen. By using helium injection, subcooling of liquid nitrogen can be achieved and in the condition of v/vL≒0.8min-¹ approximately in four minutes subcooling temperature can be achieved.

• Earthquakes and Structures
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• v.13 no.1
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• pp.67-77
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• 2017

Oil storage tanks are vital life-line structures, suffered significant damages during past earthquakes. In this study, a numerical model for an unanchored vertical vaulted-type tank was established by ANSYS software, including the tank-liquid coupling, nonlinear uplift and slip effect between the tank bottom and foundation. Four actual earthquakes recorded at different soil sites were selected as input to study the dynamic characteristics of the tank by nonlinear time-history dynamic analysis, including the elephant-foot buckling, the liquid sloshing, the uplift and slip at the bottom. The results demonstrate that, obvious elephant-foot deformation and buckling failure occurred near the bottom of the tank wall under the seismic input of Class-I and Class-IV sites. The local buckling failure appeared at the location close to the elephant-foot because the axial compressive stress exceeded the allowable critical stress. Under the seismic input of Class-IV site, significant nonlinear uplift and slip occurred at the tank bottom. Large amplitude vertical sloshing with a long period occurred on the free surface of the liquid under the seismic wave record at Class-III site. The seismic properties of the storage tank were affected by site class and should be considered in the seismic design of large tanks. Effective measures should be taken to reduce the seismic response of storage tanks, and ensure the safety of tanks.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.366-370
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• 2008

Mode analysis is very important for the development of liquid rocket engine in various applications. We developed a mode analysis program for the gas-generator cycle liquid rocket engine by proposing 13 independent equations with 13 independent variables which can be solved by Newton method. As an example we calculated the change of engine operating mode according to the control valve's loss coefficient change located in the gas-generator oxidizer supply line. And we concluded that this program can give basic idea for the mode analysis of gas-generator cycle liquid rocket engine.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.10
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• pp.1-7
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• 2020

In this study, a multichannel gas-liquid microextraction system is designed by integrating the automatic elution of extraction line and multichannel gas-purging liquid phase microextraction. The system uses an injection pump and inert gas to push the extraction solvent to a sample bottle of a gas-phase color autosampler and then implements multichannel gas-liquid microextraction and gas chromatography-mass spectrometry. The system also employs a three-way integrated micro-high-temperature heater, syringe pump, and microflow controller to realize the simultaneous processing of multiple groups of samples, thus improving the sample pretreatment speed and reproducibility and reducing human error. Autoinjection experiments were implemented with polycyclic aromatic hydrocarbon standard samples. The experiments show that the average recovery rate of the system exceeds 70%, and the relative standard among the channels is less than 15%.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.276-281
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• 2001

The KSR-III Main Propulsion System configuration of the liquid oxygen (LOX) feed line is analyzed. This feed line includes a tighter radius and cavitation venturi for flow mass flow-rate passive control. There were concerns that these configurations might generate a great flow distortion at the engine interface. Also both the pressure drop at the feed line and any presence of separation area are a great concern according to the propellant flow. To resolve these issues, a computational fluid dynamic analysis was conducted to determine the flow field in the LOX feed lines.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.84-87
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• 2009

Electrowetting is a versatile tool to handle tiny droplets and forms a backbone of digital microfluidics. Numerical analysis is necessary to fully understand the dynamics of electrowetting, especially in designing electrowetting-based devices, such as liquid lenses and reflective displays. We developed a numerical method to analyze the general contact-line problems, incorporating dynamic contact angle models. The method is based on the conservative level set method to capture the interface of two fluids without loss of mass. We applied the method to the analysis of spreading process of a sessile droplet for step input voltages and oscillation of the droplet for alternating input voltages in electrowetting. The result was compared with experimental data. It is shown that contact line friction significantly affects the contact line motion and the oscillation amplitude. The pinning process of contact line was well represented by including the hysteresis effect in the contact angle models.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.9
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• pp.955-960
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• 2003

In this paper, complex permittivities of reference liquids were measured by a sample holder of terminated slotted coaxial line with a movable probe at mobile communications frequencies. The validity of the liquid measurement system was checked by experimental tests with the reference liquids proposed in IEEE Std 1528-200X.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.2
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• pp.140-145
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• 2001

The tape carrier package(TCD) is one of the most important components in a liquid crystal display(LCD) module. It has a role to transmit electrical signals from a printed circular board(PCB) to a display panel. If TCP is damaged under mechanical shock, the signals can not be transmitted to the panel and as a result, some dead lines are generated on the panel. This kind of phenomenon is commonly called as 'line defects'. In this paper, new structural design concepts of TCP are proposed to guarantee its reliability by using Taguchi's approach and dynamic FE-analysis. The line defects problem of TCP module is solved by replacing the original TCP with the newly designed one.

• Fire Science and Engineering
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• v.13 no.1
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• pp.37-47
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• 1999

The spreading fire of very small floating particles after they are ignited is fast and t therefore dangerous. The research on this area has been limited to experiments and global simulations which treat them as dusts or gaseous fuel with certain concentration well m mixed with air. This research attempted micro-scale analysis of ignition of those particles modeling them as liquid droplets. For the beginning, the in-line array of fuel droplets is modeled by two-dimensional, unsteady conservation equations for mass, momentum, energy and species transport in the gas phase and an unsteady energy equation in the liquid phase. They are solved numerically in a generalized non-orthogonal coordinate. The single step chemical reaction with reaction rate controlled by Arrhenius’ law is assumed to a assess chemical reaction numerically. The calculated results show the variation of temperature and the concentration profile with time during evaporation and ignition process. Surrounding oxygen starts to mix with evaporating fuel vapor from the droplet. When the ignition condition is met, the exothermic reactions of the premixed gas initiate a and burn intensely. The maximum temperature position gradually approaches the droplet surface and maximum temperature increases rapidly following the ignition. The fuel and oxygen concentration distributions have minimum points near the peak temperature position. Therefore the moment of ignition seems to have a premixed-flame aspect. After this very short transient period minimum points are observed in the oxygen and fuel d distributions and the diffusion flame is established. The distance between droplets is an important parameter. Starting from far-away apart, when the distance between droplets decreases, the ignition-delay time decreases meaning faster ignition. When they are close and after the ignition, the maximum temperature moves away from the center line of the in-line array. It means that the oxygen at the center line is consumed rapidly and further supply is blocked by the flame. The study helped the understanding of the ignition of d droplet array and opened the possibility of further research.