• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.05a
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• pp.215-216
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• 2012

Emissions of CO₂ occur during the production of cement manufacturing process. During the production of clinker, limestone is mainly calcium carbonate, is heated to produce lime and CO₂ as a by-product. It has a major problem, CO₂ uptake is not considered in concrete carbonation, just focus in CO₂ emission. This study is to develop a simulation model for CO₂ uptakes in concrete structures based on carbonation reduction coefficient considering finishing materials. CO₂ uptakes unit of concrete cubic meter is calculated by CO₂ emissions unit of concrete materials and usage of concrete materials in mix proportion. From the simulation result, CO₂ uptake ratios is 2.04 percent in carbonation models of concrete structure during 40 years.

• Transactions on Electrical and Electronic Materials
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• v.11 no.2
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• pp.49-53
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• 2010

Microstructural origins of leakage current and physical degradation during operation in product-quality AlGaN/GaN high electron mobility transistor (HEMT) devices were investigated using photon emission microscopy (PEM) and transmission electron microscopy (TEM). AlGaN/GaN HEMTs were fabricated with metal organic chemical vapor deposition on semi-insulating SiC substrates. Photon emission irregularity, which is indicative of gate leakage current, was measured by PEM. Site specific TEM analysis assisted by a focused ion beam revealed the presence of threading dislocations in the channel below the gate at the position showing strong photon emissions. Observation of electrically degraded devices after life tests revealed crack/pit shaped defects next to the drain in the top AlGaN layer. The morphology of the defects was three-dimensionally investigated via electron tomography.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.2
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• pp.105-110
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• 2008

Flowable fill is generally a mixture of sand, fly ash, a small amount of cement and water. Sand is the major component of most flowable fill with waste materials. Various materials, including two waste foundry sands(WFS), an anti-corrosive waste foundry sand and natural soil, were used as a fine aggregate in this study. Natural sea sand was used for comparison. The flow behavior, hardening characteristics, and ultimate strength behavior of flowable fill were investigated. The unconfined compression test necessary to sustain walkability as the fresh flowable fill hardens was determined and the strength at 28-days appeared to correlate well with the water-to-cement ratio. The strength parameters, like cohesion and internal friction angle, were determined for the samples prepared by different curing times. The creep test for settlement potential was conducted. The data presented show that by-product foundry sand, an anti-corrosive WFS, and natural soil can be successfully used in controlled low strength materials(CLSM), and it provides similar or better properties to that of CLSM containing natural sea sand.

• Korean Journal of Materials Research
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• v.32 no.2
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• pp.80-84
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• 2022

Copper nanoparticles (CuNPs) are considered of great importance due to their high catalytic and antimicrobial activities. This study focuses on the preparation and characterization of CuNPs, and on their antibacterial/antifungal activities. A copper salt (copper sulfate pentahydrate) as precursor, starch as stabilizing agent, and ascorbic acid as reducing agent were used to fabricate CuNPs. The resulting product was characterized via different techniques such as X-ray diffractrometry (XRD), Fourier Transform Infrared (FTIR) spectroscopy, and Scanning electron microscopy (SEM) to confirm its characteristic properties. Employing the Scherrer formula, the mean crystallite sizes of copper (Cu) and cuprous oxide (Cu₂O) nanocrystals were found to be 29.21 and 25.33 nm, respectively, as measured from the main X-ray diffraction peaks. The functional groups present in the resulting CuNPs were confirmed by FTIR. In addition, the engineered CuNPs showed antibacterial and antifungal activity against tested pathogenic bacterial and fungal strains.

• Journal of Drive and Control
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• v.21 no.1
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• pp.16-21
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• 2024

The yaw gearbox is a key device in a wind power generator that improves power generation efficiency by rotating hundreds of tons (400 to 600 tons) of nacelle so that the blade reaches 90 degrees in the wind direction. Recently, installation sites have been advancing from land to sea as they have become super-large at (8-12) MW to increase the economic feasibility of wind power generators and utilize excellent wind resources, and the target life of large wind power generators is 25 to 30 years. The yaw gearbox of 6 to 12 sets is installed in a very complex place inside the nacelle on the tower with parallels, and it is important to secure the reliability of the yaw gearbox because if a failure occurs after installation, it costs tens to hundreds of times the price of a new product to restore. In this study, equivalent loads were calculated by analyzing failure mode and field data, accelerated life test conditions were established, and a test device was constructed to perform the accelerated life tests and performance tests to ensure the reliability of the gearbox.

• The International Journal of Costume Culture
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• v.8 no.2
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• pp.111-123
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• 2005

In the fashion retail research, the role of fashion salesperson and their job satisfaction have been getting attentions. The purpose of this study was to investigate the elements affecting the job satisfaction of fashion salesperson. A hypothetical path model of job satisfaction of fashion salesperson was developed and tested. Empirical data were collected with a written survey instrument. Data were collected from 150 fashion salespersons during 2001 fall, and finally 101 responses were analyzed. As results of series of regression analysis, final job satisfaction model was identified. Job satisfaction of fashion salesperson was affected by subjective job aptitudity, salary, fashion product knowledge. fashion involvement, and work experience. Managerial implication and research limitation were discussed.

• Natural Product Sciences
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• v.2 no.2
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• pp.96-101
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• 1996

A new natural product, 3,4,8-trihydroxybenzopyranopyran-6,9-dione was isolated from the aqueous ethanolic gall extract of Tamarix aphylla (Tamaricaceae) along with the known phenolics, monodecarboxyellagic acid and brevifolin carboxylic acid as well. The structures have been established by ESI-MS, $^1H$ and $^{13}C$ NMR spectral analysis. Antiinflammatory, antipyretic and ulcerogenic activities determination for both plant (Tamarix aphylla and Phragmites australis) were carried out on aq. ethanolic of extracts.

• Transactions of Materials Processing
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• v.21 no.3
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• pp.195-201
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• 2012

A vacuum ladling die casting system is suggested as a means to obtain a high vacuum level. A high vacuum of 17.8 mmHg is obtained by sealing the inner space of the mould. The sample product is a rear-head housing for an auto-compressor, and the die-casting with 6-cavities was conducted. The flow analysis shows that the filling speed during vacuum ladling is faster than for a non-vacuum system. The air holes in the sample product were too small to be seen with the naked eye in X-ray films. Density tests show that the high vacuum ladling system reduces the internal porosity as much as 57.8% when compared to the non-vacuum system. A defective rate of only 0.17% was found from leak testing. The results of this research prove that the high vacuum die-casting process is useful for manufacturing of aluminium components under high internal pressure.

• International Journal of Concrete Structures and Materials
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• v.4 no.2
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• pp.119-125
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• 2010

In this study, the effects of the fineness modulus of reactive aggregate on ASR expansion and ASR products have been investigated. The reactive aggregate used was metamorphic aggregate originated from Korea. ASR tests were conducted according to accelerated mortar bar test. The morphology and chemical composition of products formed in mortar bars, 5 years after the mortar bar test had been performed, were studied by scanning electron microscopy equipped with energy dispersive spectroscopy. Test results indicated that ASR expansion of mortar bars decrease in linear proportion to the fineness modulus of reactive aggregate. SEM images indicated that mortar bars showed reactive products formed in cement paste, within air voids and within cracks through particles except for the mortar bar with the fineness modulus of 3.25. The EDS analysis of the reactive products showed presence of silica, calcium and sodium, typical of ASR product composition.

• Management Science and Financial Engineering
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• v.6 no.2
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• pp.1-28
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• 2000

Supply chain management issues faced by a manufacturing company are considered in this paper. The supply chain consists of a manufacturing company and its suppliers. The manufacturer produces multiple products with inputs (e.g., raw materials) from the suppliers, but each product needs a different mix of these inputs. The market demand for the products is uncertain. We develop a mathematical model and algorithm, which can help the manufacturer to solve its procurement decision problem: how much of raw material to order from which supplier. The model incorporates such factors as market demand uncertainty, product's input requirement, supplier's as well as manufacturer's capacity, plus other costs comparable with those in a typical newsboy problem. Numerical examples are presented to see the interacting effects among critical parameters and variables.