• Industrial Engineering and Management Systems
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• v.3 no.2
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• pp.116-122
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• 2004

This paper presents a process plan selection model with multiple objectives. The process plans for all parts should be selected under multiple objective environment as follows: (1) minimizing the sum of machine processing and material handling time of all the parts considering realistic shop factors such as production volume, processing time, machine capacity, and capacity of transfer device. (2) balancing the load between machines. A multiple objective mathematical model is proposed and an evolutionary algorithm with the adaptive recombination strategy is developed to solve the model. To illustrate the efficiency of proposed approach, numerical examples are presented. The proposed approach is found to be effective in offering a set of satisfactory Pareto solutions within a satisfactory CPU time in a multiple objective environment.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.29.4-29.4
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• 2016

The relations between star formation and properties of molecular clouds are studied based on a sample of star forming regions in the Galactic Plane. Sources were selected by having radio recombination lines to provide identification of associated molecular clouds and dense clumps. Radio continuum and mid-infrared emission were used to determine star formation rates, while 13CO and submillimeter dust continuum emission were used to obtain masses of molecular and dense gas, respectively. We test whether total molecular gas or dense gas provides the best predictor of star formation rate. We also test two specific theoretical models, one relying on the molecular mass divided by the free-fall time, the other using the free-fall time divided by the crossing time. Neither is supported by the data. The data are also compared to those from nearby star forming regions and extragalactic data. The star formation "efficiency," defined as star formation rate divided by mass, spreads over a large range when the mass refers to molecular gas; the standard deviation of the log of the efficiency decreases by a factor of three when the mass of relatively dense molecular gas is used rather than the mass of all the molecular gas.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.1
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• pp.33-38
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• 2014

In this work, according to temperature and time of hydrothermal synthesis, the electrochemical properties of $TiO_2$ particle using TTIP based on changing temperature and time in the hydrothermal synthesis were analyzed and optimized temperature and time were derived. When hydrothermal synthesis temperature and time were $200^{\circ}C$ and 1 h, respectively. The fabricated DSSC delivered the best electrochemical properties. In that case, $TiO_2$ particle size was 13.08 nm, electron transport time was $2.34{\times}10^{-3}s$ and recombination time was $4.01{\times}10^{-2}s$. The lowest impedance of $13.52{\Omega}$ and Voc, Jsc, FF is 0.70 V, $1.50mAcm^{-2}$, 65.62%, respectively and corresponding efficiency of 5.34% was considered as the optimal.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.346.2-346.2
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• 2016

The rear side contact recombination in the crystalline silicon solar cell could be reduced by back surface field. We formed polycrystalline silicon as a back surface field through crystallization of amorphous silicon. A thin silicon oxide applied to the passivation layer. We used quasi-steady-state photoconductance measurement to analyze electrical properties with various annealing condition. And, blister formed on surface of wafer during the annealing process. We observed the blister after varied annealing process with wafer of various surface. Shape and density of blister is influenced by various annealing temperature and process time. As the annealing temperature became higher, the average diameter of blister is decreased and total number of blister is increased. The sample with the $600^{\circ}C$ annealing temperature and 1 min annealing time exhibited the highest implied open circuit voltage and lifetime. We predicted that the various shape and density of blister affects the lifetime and implied open circuit voltage.

• Industrial Engineering and Management Systems
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• v.14 no.1
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• pp.11-21
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• 2015

The purpose of this research is to develop algorithms using the Differential Evolution Algorithm (DE) to solve a multi-objective, sources and stages location-allocation problem. The development process starts from the design of a standard DE, then modifies the recombination process of the DE in order improve the efficiency of the standard DE. The modified algorithm is called modified DE. The proposed algorithms have been tested with one real case study (large size problem) and 2 randomly selected data sets (small and medium size problems). The computational results show that the modified DE gives better solutions and uses less computational time than the standard DE. The proposed heuristics can find solutions 0 to 3.56% different from the optimal solution in small test instances, while differences are 1.4-3.5% higher than that of the lower bound generated by optimization software in medium and large test instances, while using more than 99% less computational time than the optimization software.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.481.1-481.1
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• 2014

Dye-sensitized solar cell (DSSC) has been extensively investigated as the next generation energy source. Despite attractive features of simple fabrication process and its economical efficiency, there are some problems such as low efficiency and low long-term stability. Many groups have attempted the proposed way to improve the cell efficiency and long-term stability such as low recombination rate between $TiO_2$ surface and electrolyte, the development of new dye molecules capable of light adsorption as broadly as possible, the fabrication of a solid-state DSSC by replacing the liquid electrolyte, and protective coating on glass. In this work, we confirmed new dye-coating conditions to maximize the dye adsorption between the dye and $TiO_2$ nanoparticle surface. The experiment results coating conditions with the coating temperature of $70^{\circ}C$, the dye concentration of 10 mM and the coating time of 3 min. Conditions have two times, three times cycle the experiment in progress efficiency rises.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.08a
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• pp.121-125
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• 2003

Time-resolved photoluminescence from InGaN/GaN multi-quantum well structures was investigated for two different shapes of square- and trapezoidal wells grown by metal-organic chemical vapor deposition. To compare to the conventional square well structure with a radiative recombination lifetime of 0.170 nsec, the large value of lifetime of 0.540 nsec from trapezoidal well were found at room temperature. This value is similar to the value for GaN host material indicating no confinement effect of quantum well. Furthermore, the high resolution transmission electron microscopy image provides the In clustering effect in the trapezoidal well structure.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.758-761
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• 2009

The electroluminescent devices with the phenylnaphthyldiamine HTMs as the hole-transporting layer were more efficient than that with the biphenyldiamine HTM 1. Particularly, the life-time of the device IV using HTM 2 is about two times longer than that of the reference device III with HTM 1 within the measured current density, indicating more effective recombination at the emitting layer of device IV.

• Transactions on Electrical and Electronic Materials
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• v.4 no.5
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• pp.19-23
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• 2003

Time-resolved photoluminescence from InGaN/GaN multi-quantum well structures was investigated for two different shapes of square-and trapezoidal wells grown by metal-organic chemical vapor deposition. To compare to the conventional square well structure with a radiative recombination lifetime of 0.170 nsec, the large value of lifetime of 0.540 nsec from trapezoidal well were found at room temperature. This value is similar to the value for GaN host material indicating no confinement effect of quantum well. Furthermore, the high resolution transmission electron microscopy image provides the In clustering effect in the trapezoidal well structure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.362-363
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• 2007

The transport property of stabilized amorphous selenium typical of the material used in direct conversion x-ray imaging devices was studied using the moving photo-carrier grating (MPG) technique and time-of-flight (TOF) measurements. For MPG measurement, the electron and hole mobility, and recombination lifetime of a-Se films with arsenic (As) additions have been obtained. For TOF measurement, a laser beam with pulse duration of 5ns and wavelength of 350 nm was illuminated on the surface of a-Se with thickness of $400{\mu}m$.