• Journal of the Korean Institute of Gas
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• v.7 no.2 s.19
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• pp.48-53
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• 2003

This study is to look at the effect for deformation of carbon steel for high-presure pipe, on the AE signals produced by tensile test. Acoustic emission(AE) has been widely used in various fields because of its extreme sensitivity, dynamic detection ability and location of growing defects. We investigated a relationship failure mode and AE signals by tensile test, From the tensile test, we could divide into four ranges of the failure modes of elastic range, yield range, plastic range before $\sigma$u, plastic range after $\sigma$u. And failure behaviors of elastic range, yield range, plastic range before $\sigma$u, plastic range after $\sigma$u could be evaluated in tensile test by AE counts, accumulation counts and time frequency analysis. It is expected to be basic data that can protect a risk according to tensile test and bending of pipe material for pressure vessel, as a real time test of AE.

• Resources Recycling
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• v.20 no.4
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• pp.58-64
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• 2011

Recovery of novel metals such as Au, Ag and Ni from wastes PCB was investigated by slag treatments. The CaO-$Al_2O_3$(-$SiO_2$) and CaO-$SiO_2$-$CaF_2$ slags were employed in the present study. The PCB/Cu ratio is recommended to be lower than unity. The use of CaO-$SiO_2$-$CaF_2$ slag provided the more higher yield of Au, Ag and Ni than the CaO-$Al_2O_3$(-$SiO_2$) slag did, which was mainly due to the lower melting point and the viscosity of $CaF_2$-containing slag. The terminal descending velocity of metal droplets in the slag phase increased with decreasing slag viscosity.

• Resources Recycling
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• v.29 no.1
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• pp.3-16
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• 2020

This work provides an overview of the steel production process, pretreatment and tramp elements of scraps and recycling technology of dust generated from steelmaking process. Steel is the most common metal used by mankind, with the world production of crude steel in 2018 exceeding 1.8 billion tonnes. Recycling of ferrous scraps reduces CO₂ emissions by about 42 % and saves about 60 % of energy, compared to production steel from iron ore. Steel scraps are usually recycled to both an electric arc furnace (EAF), scrap-based steelmaking and the basic oxygen furnace (BOF), in ore-based steelmaking. EAF steelmaking, which uses iron scrap as a main raw material, is changing to an energy-saving type with a device for preheating scrap. Dust generated from the steelmaking process is recycled in various ways in the steel mill to recover iron and zinc.

• Korean Journal of Optics and Photonics
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• v.25 no.2
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• pp.102-107
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• 2014

In this paper the spectra of correlated color temperature (CCT) tunable white light-emitting diode (LED) luminaires, consisting of commercial red, green, blue, and amber LED chips, were optimized to increase color rendering index (CRI), and a special CRI of R9 for deep red color was obtained. To improve the design's accuracy, measured LED spectra were used instead of mathematically modeled ones. Real CCT tunable LED luminaires with CRIs of 87-90 and R9s of 34-93 were fabricated and demonstrated at CCTs of 3000-6000 K.

• Resources Recycling
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• v.30 no.6
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• pp.76-82
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• 2021

The separation of palladium from crude metal, which is obtained from electronic waste using pyrometallurgy was achieved through electrolysis. This was done to recover high-purity copper. The oxidation potentials of these metals are a fundamental part of the analysis of electrolytic separation of palladium and impurity metals. To achieve this, copper, iron, and nickel were dissolved in the electrolyte, and palladium and aluminum were found to be recoverable from anode slime. During the electrolysis for palladium separation, palladium was present in the anode slime and was obtained with a recovery of 97.46 % indicating almost no loss. 4N-grade copper was recovered from the electrodeposition layer at the cathode.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.216-223
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• 2019

Fault detection during production processes is one of the required operational tasks to run production processes both safely and consistently. Unexpected operational events or undetected process faults can have a serious impact on the production systems and subsequently on the final products' quality. In addition, such situations may lead to malfunctions or breakdowns of production processes. To reliably detect such abnormalities, a new one-class classification-based detection scheme has recently been developed The proposed method consists of four steps:1) noise filtering, 2) feature selection, 3) nonlinear representation and 4) outlier detection. The performance of the proposed scheme was demonstrated using the multivariate data obtained from a simulation process. The results have shown that the proposed method produced reliable monitoring results and outperforms any existing methods with an average improvement of 25.4%. The use of proper feature selection in the proposed framework yielded better detection performance.

• Journal of Radiation Protection and Research
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• v.45 no.4
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• pp.154-162
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• 2020

Background: Several studies have reported that wild mushrooms contain high amounts of radioactive cesium (137Cs). After the Fukushima Daiichi Nuclear Power Plant Accident, a significantly high concentration of 137Cs has been detected in wild mushrooms, and their consumption may be the cause of the chronic internal exposure of local consumers to radioactivity. Therefore, an accurate evaluation of the internal radioactivity resulting from mushroom ingestion is needed. Materials and Methods: The 137Cs elution rate through the cooking and digestion stages was evaluated using in vitro experiments. The edible mushroom Pleurotus djamor was taken as a sample for the experiments. The mushrooms were cultivated onto solid media containing 137Cs. We evaluated the internal dose based on the actual conditions using the elution rate data. For various cooking methods, the results were compared with those of other wild edible mushrooms. Results and Discussion: From the elution experiment through cooking, we proved that 25%-55% of the 137Cs in the mushrooms was released during soaking, boiling, or frying. The results of a simulated digestion experiment after cooking revealed that almost all the 137Cs in the ingested mushrooms eluted in the digestive juice, regardless of the cooking method. The committed effective dose was reduced by 20%-75% when considering the dissolution through the cooking process. Conclusion: We found that cooking lowers 137Cs concentration in mushrooms, therefore reducing the amount of radioactivity intake. Besides, since there were differences between mushroom types, we demonstrated that the internal exposure dose should be evaluated in detail considering the release of 137Cs during the cooking stages.

• Journal of Electrochemical Science and Technology
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• v.13 no.2
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• pp.199-207
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• 2022

Lithium-sulfur batteries (LSBs) have emerged as a promising alternative to lithium-ion batteries (LIBs) owing to their high energy density and economic viability. In addition, all-solid-state LSBs, which use solid-state electrolytes, have been proposed to overcome the polysulfide shuttle effect while improving safety. However, the high interfacial resistance and poor ionic conductivity exhibited by the electrode and solid-state electrolytes, respectively, are significant challenges in the development of these LSBs. Herein, we apply a poly (ethylene oxide) (PEO)-based composite solid-state electrolyte with oxide Li₇La₃Zr₂O₁₂ (LLZO) solid-state electrolyte in an all-solid-state LSB to overcome these challenges. We use an electrochemical method to evaluate the degradation of the all-solid-state LSB in accordance with the carbon content and loading weight within the cathode. The all-solid-state LSB, with sulfur-carbon content in a ratio of 3:3, exhibited a high initial discharge capacity (1386 mAh g^-1), poor C-rate performance, and capacity retention of less than 50%. The all-solid-state LSB with a high loading weight exhibited a poor overall electrochemical performance. The factors influencing the electrochemical performance degradation were revealed through systematic analysis.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.3
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• pp.589-602
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• 2024

Thermoelectric generator (TEG) generally do not have high heat conversion efficiencies. The performance of a thermoelectric generator module depends on the shape of the legs as well as the properties of the material and the number of legs. In this study, the leg shapes of thermoelectric elements are modeled into various geometric structures such as cylinder and cube shaped to efficiently harvest waste heat, and the electrical characteristics are compared numerically. The temperature gradient and power generation according to the bridge shape are found to be highest at the existing Cube shape. As a result of comparing the power generation using the cooling effect, the Cone shape was the highest in natural convection and the Hourglass shape was highest in forced convection. Research results confirm that geometry can affect the efficiency of thermoelectric generators.

• Journal of the Korean Society for Heat Treatment
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• v.37 no.2
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• pp.49-57
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• 2024

We investigated the changes in microstructure and surface roughness of the compound layer of GC250D gray cast iron, commonly used in brake discs, during gas nitriding. The gas atmosphere of the nitriding process was controlled with a hydrogen partial pressure of 49.5%, and the process was conducted at a nitriding temperature of 520℃ with various process times. As the nitriding process time of the GC250D material increased, both the depth of hardening and the thickness of the compound layer increased, with a maximum surface hardness of approximately 1265 HV_0.1 was measured. Additionally, the surface roughness increased with the process time. Phase analysis of the compound layer revealed an increase in the proportion of the γ' phase as the nitriding process time increased. Changes in the formation of the compound layer were observed depending on the orientation of graphite within the material, leading to the formation of wedges. Therefore, the increase in surface roughness appears to be attributed to the uneven compounds, the expansion of the compound layer and wedges formed on the surface during the nitriding process.