• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3307-3311
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• 2013

A new fiber optical sensor was developed for the determination of 2,4-dichlorophenol (DCP). The sensor was based on DCP oxidation by oxygen with the catalysis of iron(III) tetrasulfophthalocyanine (Fe(III)PcTs). The optical oxygen sensing film with $Ru(bpy)_3Cl_2$ as the fluorescence indicator was used to determine the consumption of oxygen in solution. A lock-in amplifier was used for detecting the lifetime of the oxygen sensing film by measuring the phase delay change of the sensor head. The different variables affecting the sensor performance were evaluated and optimized. Under the optimal conditions (i.e. pH 6.0, $25^{\circ}C$, Fe(III)PcTs concentration of 0.62 mg/mL), the linear detection range and response time of the sensor are $1.0{\times}10^{-6}-9.0{\times}10^{-6}$ mol/L and 250 s, respectively. The sensor displays high selectivity, good repeatability and stability, and can be used as an effective tool in analyzing DCP concentration in practical samples.

• Korean Journal of Agricultural Science
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• v.45 no.2
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• pp.204-210
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• 2018

Medium chain triglycerides (MCTs) provide polka dot grouper Chromileptes altevelis with a more readily utilizable source of energy than long-chain fatty acids (LCFAs) and significantly elevate the plasma cholesterol level of chickens. As a possible alternative to feed antibiotics, this study investigated the effect of different phase levels of medium chain triglycerides on the growth performance, excreta microflora and blood profiles in broilers. A total of 450 ROSS 308 mixed-sex broilers with an average initial body weight of $49{\pm}0.79g$ (1 day of age) were used in this trial. They were randomly assigned to the following 3 treatments (15 birds / 10 replications): CON (Basal diet); MCT1 (Starter, Grower, Finisher: Basal diet + 0.1%, 0.075%, 0.05% of MCT) and MCT2 (Starter, Grower, Finisher: Basal diet + 0.1%, 0.1%, 0.1% of MCT). The results show that supplementing the diets with different phase levels of MCT did not have a significant impact on the body weight gain (BWG), feed intake (FI) and feed conversion ratio (FCR) during the overall experimental period. Additionally, there were no differences in the blood profiles and excreta microflora among the treatments. However, this study found that the BWG was increased by 2.3%, and the FCR was decreased by 0.6% in the broiler fed MCT1 treatment group during overall experiment phase. Therefore, the results suggest that MCTs could be used as an alternative to growth promoting feed additives. Moreover, further research should be done to evaluate the effect of the different levels of MCTs.

• Journal of Power System Engineering
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• v.22 no.1
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• pp.34-40
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• 2018

In this paper, Performance of 1MW OTEC system using R32 with varying seawater temperature range is studied. Steady state cycle is designed and its output and generation efficiency were 1,014kW and 2.72%, respectively. Compared to dynamic cycle, system performance and change during long term operation is studied. The simulation is performed by decreasing surface seawater temperature from $29^{\circ}C$ to $25^{\circ}C$ with 20 minute of reaction time. Dynamic cycle with same condition applied to steady state cycle and it showed output and efficiency of 1,020kW and 2.75% respectively. Seawater temperature decreased from $29^{\circ}C$ and the vapor fraction of refrigerant decreased below 1 at $28^{\circ}C$. While the vapor fraction was above 1, the turbine output decreased by 0.017kW per second. After the seawater temperature reached $26.2^{\circ}C$, the turbine output decreased by 1.03kW per second. However, Driving the turbine below the saturation temperature caused the occurrence of surging and the influx of liquid refrigerant. When the liquid separator having a capacity of 1.0 m3 was used, the flow into the turbine was confirmed after 5 minutes from the first liquid refrigerant coming into the separator.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.99.1-99.1
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• 2012

The thin-film photovoltaic absorbers (CdTe and $Cu(In,Ga)Se_2$) can achieve solar conversion efficiencies of up to 20% and are now commercially available, but the presence of toxic (Cd,Se) and expensive elemental components (In, Te) is a real issue as the demand for photovoltaics rapidly increases. To overcome these limitations, there has been substantial interest in developing viable alternative materials, such as $Cu_2ZnSnS_4$ (CZTS) is an emerging solar absorber that is structurally similar to CIGS, but contains only earth abundant, non-toxic elements and has a near optimal direct band gap energy of 1.4 - 1.6 eV and a large absorption coefficient of ~104 $cm^{-1}$. The CZTS absorber layers are grown and investigated by various fabrication methods, such as thermal evaporation, e-beam evaporation with a post sulfurization, sputtering, non-vacuum sol-gel, pulsed laser, spray-pyrolysis method and electrodeposition technique. In the present work, we report an alternative aqueous chemical approach based on chemical bath deposition (CBD) method for large area deposition of CZTS thin films. Samples produced by our method were analyzed by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, absorbance and photoluminescence. The results show that this inexpensive and relatively benign process produces thin films of CZTS exhibiting uniform composition, kesterite crystal structure, and some factors like triethanolamine, ammonia, temperature which strongly affect on the morphology of CZTS film.

• Journal of Powder Materials
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• v.25 no.1
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• pp.1-6
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• 2018

Uniform $TiO_2$ blocking layers (BLs) are fabricated using ultrasonic spray pyrolysis deposition (USPD) method. To improve the photovoltaic performance of dye-sensitized solar cells (DSSCs), the BL thickness is controlled by using USPD times of 0, 20, 60, and 100 min, creating $TiO_2$ BLs of 0, 40, 70, and 100 nm, respectively, in average thickness on fluorine-doped tin oxide (FTO) glass. Compared to the other samples, the DSSC containing the uniform $TiO_2$ BL of 70 nm in thickness shows a superior power conversion efficiency of $7.58{\pm}0.20%$ because of the suppression of electron recombination by the effect of the optimized thickness. The performance improvement is mainly attributed to the increased open-circuit voltage ($0.77{\pm}0.02V$) achieved by the increased Fermi energy levels of the working electrodes and the improved short-circuit current density ($15.67{\pm}0.43mA/cm^2$) by efficient electron transfer pathways. Therefore, optimized $TiO_2$ BLs fabricated by USPD may allow performance improvements in DSSCs.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.8
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• pp.1-11
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• 2002

A multi-section DFB-LD shows optical bistability subject to externally injected light signal, then it has potential applications such as wavelength conversion and optical logic gates. In this paper, we have studied the optical bistability in multi-section DFB-LD using split-step time-domain model. It is confirmed that the multi-section DFB-LD, which is excited inhomogeneously, shows bistability. The optical bistable characteristics are investigated when input light is injected into a absorptive region. Simulation results show that multi-section DFB-LD works as a flip-flop depending on the set-reset optical pulse which has a few ns in switching time and a few pj in switching energy, so that it can act as a optical logic device. Besides, if we change the carrier lifetime and the differential gain coefficient, it is expected that the response time of optical output signal can be reduced.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.4
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• pp.211-220
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• 2017

The application of the theoretical model to real assembly lines has been one of the biggest challenges for researchers and industrial engineers. There should be some realistic approach to achieve the conflicting objectives on real systems. Therefore, in this paper, a model is developed to synchronize a real system (A discrete event simulation model) with a theoretical model (An optimization model). This synchronization will enable the realistic optimization of systems. A job assignment model of the assembly line is formulated for the evaluation of proposed realistic optimization to achieve multiple conflicting objectives. The objectives, fluctuation in cycle time, throughput, labor cost, energy cost, teamwork and deviation in the skill level of operators have been modeled mathematically. To solve the formulated mathematical model, a multi-objective simulation integrated hybrid genetic algorithm (MO-SHGA) is proposed. In MO-SHGA each individual in each population acts as an input scenario of simulation. Also, it is very difficult to assign weights to the objective function in the traditional multi-objective GA because of pareto fronts. Therefore, we have proposed a probabilistic based linearization and multi-objective to single objective conversion method at population evolution phase. The performance of MO-SHGA is evaluated with the standard multi-objective genetic algorithm (MO-GA) with both deterministic and stochastic data settings. A case study of the goalkeeping gloves assembly line is also presented as a numerical example which is solved using MO-SHGA and MO-GA. The proposed research is useful for the development of synchronized human based assembly lines for real time monitoring, optimization, and control.

• Journal of the Korean Vacuum Society
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• v.5 no.4
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• pp.348-353
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• 1996

Rapid thermal annealing (RTA) was applied to polycrystalline CdTe thin films evaporated on CdS/ITO/glass substrate and the effect of the annealing temperatures and the atmosphere on physical properties of polycrystalline CdTe thin films and CdTe/CdS solar cell characteristics were studied. Results obtained by EDX showed that the bulk composition of CdTe remained stoichiometric after annealing at $550^{\circ}C$ in the air but the surface composition became Cd-rich. Cross-sectional TEM and micro EDX showed that columnar grains and micro-twins remained even after RTA, however, and the sulfur content in the annealed CdTe (added by sulfur diffusion from CdS during the annealing) was much smaller than that by furnace annealing. Among the investigated RTA temperatures and gas environments, the cell made with CdTe annealed at $550^{\circ}C$ in air showed the best solar energy conversion efficiency.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.1
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• pp.29-33
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• 2020

Despite the same system architecture and operation principle, Advanced Metering Infrastructure (AMI) and Internet of Things (IoT) are recognized as a heterogeneous system. This is due to the different object modeling and communication protocols used in smart meters and sensors. However, data interworking between AMI and IoT is expected to be inevitable in the future. In this paper, we propose Device Language Message Specification (DLMS) to Lightweight Machine to Machine (LwM2M) conversion model. The proposed interworking model can reduce the packet size by 46.5% compared to that of the encapsulation method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.4 s.107
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• pp.351-357
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• 2006

In this paper, a direct $TM_{01}-TE_{11}$ mode converter of circular waveguide which is used the approximated design method of mode conversion between $TM_{01}$ and $TE_{11}$ modes is designed for radiation with the maximum directivity of high power energy into air (rom high power microwave antenna system. The proposed direct $TM_{01}-TE_{11}$ mode converter is calculated and designed with an approximated method for non-linear function about an extended non-constant serpentine type of circular waveguide. Then, the designed mode converter is optimized by length of 200 mm and efficiency above 95% by FIM simulation and achieved short length and high efficiency of the antenna by results of fabricated and measured characteristics.