• Journal of the Korean Applied Science and Technology
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• v.24 no.3
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• pp.219-232
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• 2007

In T-mixer crystallization, supersaturation is generated by mixing of another solvent or non-solvent in order to reduce the solubility of the compound. Also, T-mixer is a type of continuous crystallization. In order to induce micro-mixing, two solutions were mixed rapidly by T-mixer, which formed high supersaturation. As the results, mean size of HMX crystals decreased with increasing de-supersaturation rate $(R_s)$. Eventually, HMX particles ranging from 0.5 to $5{\mu}m$ can be obtained by T-mixer crystallization. Mixing efficiency in T-mixer increased with increasing $R_s$ values. In T-mixer crystallization without surfactants, homogeneous nucleation was formed when S and $R_s$ was over 54 and $1.6{\times}10^3/sec$. In T-mixer crystallization with surfactants, homogeneous nucleation was formed when S and $R_s$ was over 26 and 7.4/sec.

• Journal of Korean Society for Quality Management
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• v.39 no.2
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• pp.244-255
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• 2011

In this study, we try to evaluate the efficiency of the photonics industry using a data envelopment analysis(DEA) model. We first develope four stage procedures for selecting proper input and output variables which consist of selecting the first candidate variables from literature survey, selecting the second candidate variables through experts' discussion, measuring the partial efficiency of the selected variables based on Tofallis' profiling, and clustering some variables through the rank correlation analysis of partial efficiency proposed by Min and Kim(l998). With this procedure, we select 4 input variables(capital, number of employee, R&D cost, operating cost) and 2 output variables(sales, growth of sales) and then utilize CCR and BCC model to measure efficiencies of 26 photonics companies in Gwangju. Moreover, we perform the reference group analysis to figure out what causes inefficiencies and to provide the desirable values for input and output variables at which inefficient photonics companies become efficient. Finally, we classify 26 photonics companies into three groups such as optical communications, optical applications, and optical sources, and perform the Kruskal-Wallis test to check if there exist some differences between efficiencies of three groups.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12B
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• pp.1754-1757
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• 2001

In this paper, a R-band hybrid amplifier with the coplanar waveguide(CPW) and the photonic bandgap(PBG) structure is designed and fabricated. The PBG and the CPW techniques are simultaneously employed in amplifier to improve the power added efficiency(PAE) and the IMD(Intermodulation Distortion) in R-band. In this paper, the PBG structures are optimized to obtain matching network. The output impedance of amplifier and the input impedance of PBG are matched to minimize the return loss. The PAE and the IMD were improved 15% and 4.5dB compared with the conventional amplifier, respectively.

• The KSFM Journal of Fluid Machinery
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• v.18 no.4
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• pp.5-12
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• 2015

Several working fluids for Organic Rankine Cycle(ORC) were recommended by many researchers. However, the recommended optimal working fluids were not exactly same because the operating conditions of ORC and application were different. The major parameter to select the working fluid for ORC was the temperature of available thermal energy. In this study, low-grade thermal energy was used for the heat source for ORC and the appropriate working fluids were searched among 26 candidate working fluids. The requirements to be a working fluid for ORC were reviewed and the cycle analysis for simple cycle was conducted with $75^{\circ}C$ and $35^{\circ}C$ at the turbine inlet and exit, respectively. R600, R601, toluene were best candidates if the system could work without leaking the working fluid. Next, R236ea, R245ca, R245fa were recommended because they are not inflammable working fluids as well as better efficiency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.11
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• pp.966-977
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• 2015

This paper presents a novel modified coaxial cavity resonator and its application to bandpass filters with compact size and improved quality factor(Q-factor). The proposed resonator is made up of ${\Gamma}-shape$ or curved four inner conductive posts within a single cavity, which provides quadruplet to realize bandpass filter. No metallic walls inside the cavity are required, and thus the utilization efficiency of the cavity space is improved. As a result, the unloaded Q can be approximately 15 % higher in comparison to the conventional coaxial resonator, or more than 35 % volume saving can be achieved while maintaining the similar Q-factor value with the conventional designs. In addition, due to the multiple cross-coupling occurring within the cavity, including the source-to-load coupling, four flexible transmission zeros can be created to realize different filtering functions. Simulations as well as experimental results of four- and eight-pole filters are presented to validate this attractive design concept. Good agreement between measured and computed results is obtained.

• Applied Chemistry for Engineering
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• v.26 no.5
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• pp.563-568
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• 2015

Liquiritin and its aglycone, liquiritigenin are flavonoid found in licorice that show anti-oxidant and anti-aging properties. In this study, ethosomes loaded with hydrophobic liquiritigenin or liquiritin were prepared as a transdermal delivery system. The particle size, entrapment efficiency, and skin permeability of ethosomes were evaluated. Ethosome containing liquiritigenin was stable up to 2 mM and ethosome containing liquiritin was stable up to 0.75 mM concentration. The particle size of ethosomes containing 0.75 mM liquiritigenin and liquiritin was 143.85 and 158.90 nm, respectively and the entrapment efficiency was 47.51 and 54.61%, respectively. The entrapment efficiency was improved with increasing concentrations of drugs. Ethosomes loaded with liquiritigenin or liquiritin were superior in skin permeation ability compared to that of 20% ethanol solution and conventional liposomes. These results suggest that ethosomes containing 0.50 mM liquiritigenin or liquiritin are effective for the skin permeation and may be used as an antiaging and antioxidant ingredient in cosmetic formulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.7
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• pp.1544-1550
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• 2013

In recent years, Container Security Device(CSD) using GPS & GLONASS to improve logistics efficiency are being extensively researched. The purpose of this paper is to examine the performance development antenna usable cargo container security transport. Antenna developed by study were optimized to match logistics environment apply to GPS/GLONASS dual frequency for monitering system. The measure of antenna have confirmation about frequency characteristics each 1575.42MHz, 1602MHz and VSWR is 2:1 measured in return loss -9.54dB. Reliability of this antenna has been verified about GPS/GLONASS through test-operation between the south korea and Russia.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.10
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• pp.97-107
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• 2009

Recent technologies of the car are focused on improving vehicle's fuel efficiency and developing alternative energy sources. These technologies bring on the development of hybrid car. On the other hand, because of short driving distance, low efficiency of charging and high price, energy storage system need to improve the storage capability. It is very important to understand the existing technologies, grasp the existing patent and establish the technical target to improve the energy storage system. In this paper, technology trends of energy storage system of the hybrid car are analyzed. This study was based on the applied and registered patent in Korea, Japan, U.S.A and Europe until December 2008. The analyses are divided into two categories: a battery system and charging system of the hybrid car. The facts of the level of technology, trends of the R&D of leading companies, key patents, blank of the technology were analyzed. Finally the future R&D strategy of hybrid car are established.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.1
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• pp.74-81
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• 2017

A crane is typically used as a means to lift and load equipment or materials. A surface vessel uses a towed object for underwater activity. Such a mechanism for dropping and lifting of equipment is necessary, and is called an overboarding unit. The present study is focused on the overboarding unit used for a crane structure. This paper deals with new overboarding mechanism design and GA-based $MATLAB^{(R)}$ optimization. By using a quadrilateral link mechanism, it is possible to set the constraint function for optimizing the GA method. The optimization with $MATLAB^{(R)}$ is followed by the $SolidWorks^{(R)}$ simulation and verification. When applying the proposed mechanism, the operator is expected to have a big advantage in safety and efficiency of operations. Furthermore, the technology developed in this study will be helpful in similar circumstances and in the proposed mechanism.

• KSBB Journal
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• v.26 no.6
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• pp.533-537
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• 2011

The aim of this study was to develop a new natural preservative system to improve the weak points of natural polyhydric alcohols together with the efficiency of natural plants as a preservative. Polyhydric alcohols (glyceryl caprylate and ethylhexylglycerin) and antimicrobial plants (S. radix, A. nilotica and C. reticulata) were tested using the disc diffusion method and minimum inhibitory concentration (MIC) method for their antimicrobial activity against the common poultry pathogens, respectively. A study of the preservative efficacy of the cosmetic formulations containing the optimized preservative system demonstrated sufficient preservative efficacy against bacteria and eukaryotic test microbes. These results suggest that the natural preservative system including polyhydric alcohol extracts containing natural plants could be incorporated in cosmetic formulations.