• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.2
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• pp.78-83
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• 2021

In this study, we prepared NiCo2O4 nanoparticles with large surface area by hydrothermal synthesis. In order to optimize the processing conditions for spinel NiCo2O4 nanoparticles with large surface area, experimental variables including concentration of Ni and Co precursor, reaction time, and temperature for post-heat treatment were evaluated. Optimized conditions for spinel NiCo2O4 with large surface area were [Ni]/[Co] 1:2 ratio, reaction time for 12 h, and post-heat treatment at 400℃. To investigate the feasibility as potential application for glucose sensor, electrochemical tests of the prepared NiCo2O4 nanoparticles in response to glucose was performed, which suggests that the NiCo2O4 can be suitable for a non-enzymatic-based electrochemical glucose sensor based on its high sensitivity and selectivity for glucose detection.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.570-576
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• 2002

Application of the aged Inconel 718 in hydrogen environment is seriously restraint by its high hydrogen embrittlement (HE) sensitivity. m previous researches, we have suggested the possibility and applicability of the laser surface annealing (LSA) process in improving the HE resistance of this alloy. Sequentially, a study on the effects of the precipitates in the Inconel 718 on its HE sensitivity was conducted in this research. Firstly, flat bar specimens were heat-treated to obtain various kinds of precipitation microstructures concerning the ${\gamma}$" phase and the 6 phase. Hydrogen was charged into the specimen by a cathodic charging process. The loss in reduction of area (RA) caused by hydrogen charging was used to assess the HE sensitivity. The HE sensitivity of the alloy was lowered with decreasing the volume fraction of ${\gamma}$". Moreover, it was possible to increase the HE resistance of the aged alloy by dissolving the $\delta$ phase, keeping the strength at the same level as that of the common aged alloy. Thus, we concluded that both the $\delta$ phase and the ${\gamma}$" phase affected the HE sensitivity of Inconel 718. Next, two kinds of notch tensile specimens were fabricated, one kind having $\delta$ phase and the other having no $\delta$ phase. All these specimens were aged via the same aging heat treatment process. The LSA process annealed a thin layer of the notch bottom of each specimen. One specimen of each kind was charged with hydrogen by the cathodic hydrogen charging process. Loss in the notch tensile strength (NTS) caused by hydrogen was used to evaluate the HE sensitivity. It was found that while the HE sensitivity of conventionally aged Inconel 718 was decreased by the LSA process, the HE sensitivity of the $\delta$-free aged Inconel 718 could further be decreased. Therefore, for applications in hydrogen environments, it is possible to fabricate alloys with both good HE resistance and high strength by controlling the precipitation conditions, and to improve HE resistance further via applying the LSA process.

• Environmental and Resource Economics Review
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• v.12 no.4
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• pp.611-635
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• 2003

This study deals with the "Dissemination Stage", the final step in the R&D process consisting of R&DDD($R&D^3$ : Research & Development, Demonstration, Dissemination). At the "Dissemination Stage", the newly configured technical design is compared with other alternatives to come up with the most desirable selection. The assessment conducted at this stage is not a simple procedure. It goes through the complex evaluation process in which various elements including economic effects and technical characteristics are considered. The reason for taking such a complex procedure is that the assessment, selection and application of the desirable technical alternative is critical for the company's competitive edge in every field of industrial sectors, thus influencing its survival and continuous growth. This study reviews the AHP method for assessing technical alternatives of the heat supply system design. And, to show the practical validity of the AHP method, it is applied to the evaluation of waste heat system alternatives in the field of energy supply system technology.

• Journal of Welding and Joining
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• v.33 no.2
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• pp.8-13
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• 2015

This study was carried out to evaluate mechanical properties of the jointed Al6061/HT590 alloys by friction stir welding (FSW). FSW was conducted under the conditions with tool rotating speed of 500 RPM and traveling speed of 300 mm/min., where Ar gas was introduced to prevent the materials from corrosion during the welding process. Electron back-scattering diffraction (EBSD) was used to characterize microstructures such as grain size, misorientation angle and crystal orientation. Evolution of intermetallic compounds in Al6061 during the process were examined in terms of morphology, size and aspect ratio at three distinct zones Al base material, heat affected zone and stir zone, where transmission electron microscope (TEM) was used. It was revealed that FSW gave rise to refinement of grains as well as growth of intermetallic compounds in Al6061. The morphological changes of intermetallic compounds exerted an influence on mechanical properties, resulting in occurrence of fracture in the part of the base material instead of the jointed parts (heat affected zone and stir zone). This study systematically evaluated the microstructural evolutions during the FSW for joining Al6061 with HT590 and their effect on mechanical properties.

• Resources Recycling
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• v.16 no.5
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• pp.25-30
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• 2007

In Korea, reutilization of construction waste is gaining attention as construction waste generated increases continuously. Currently, the concrete waste is simply crushed and used as a low value application such as paving, back filling, etc. To meet the demand of aggregate for construction and the resource efficiently, production of high quality recycled aggregate is necessary. Therefore, in this study, a better process for production of high quality recycled aggregate was developed using combination of heat pretreatment and autogenous milling. Test results showed that the recycled aggregate has a density of $2.5\;g/cm^3$ and a water absorption ratio of 3.0%, which meet the specification of the first class of KS F 2573. Currently, a pilot scale autogenous mill is being constructed and tests will be further conducted to develop a commerce-scale process.

• Journal of Korean Society of Steel Construction
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• v.23 no.4
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• pp.483-491
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• 2011

The fabrication of steel structural members always involves welding process such as flux cored arc welding. Therefore, for the application of structural steels to cold regions, it is a prerequisite to clarify the service temperature of the welded joints in order to ensure the structural integrity of the welded parts. In this study, the Charpy impact test was conducted to evaluate the service temperature of structural steel weld. The Charpy impact test is a commercial quality control test for steels and other alloys used in the construction of metallic structures. The test allows the material properties for service conditions to be determined experimentally in a simple manner with a very low cost. Standard V-notch Charpy specimens were prepared and tested under dynamic loading condition. The service temperatures of the weld metal, HAZ (heat affected zone) and base metal were derived by the absorbed energy and the impact test requirements; thus the applicability of the structural steels to cold regions was discussed in detail.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.335-337
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• 1995

In this study, $Pb(Zr_{0.52}Ti_{0.48})O_3$ ceramic thin films were fabricated from an alkoxide-based by Sol-Gel method. $Pb(Zr_{0.52}Ti_{0.48})O_3$ stock solution was made and spin-coated on the $Pt/SiO_2/Si$ substrate at 4000[rpm] for 30[sec]. Coated specimens were dried at 400[$^{\circ}C$] for 10 [min]. The coating process was repeated 4 times and then heat-treated at 500$\sim$800[$^{\circ}C$], 1 hour. The final thickness of the thin films were about 3000[A]. The crystallinity and microstructure of the thin films were investigated for varing the sintering condition. The ferroelectric perovskite' phases precipitated under the sintering of 700[$^{\circ}C$] for 1 hours. In the $Pb(Zr_{0.52}Ti_{0.48})O_3$ thin films sintered at 700[$^{\circ}C$] for 1 hour, dielectric constant and dielectric loss were 2133, 2.2[%] at room temperature, respectively. $Pb(Zr_{0.52}Ti_{0.48})O_3$ thin film capacitors having good dielectric and electrical properties are expected for the application to the dielectric material of DRAM.

• Food Science and Biotechnology
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• v.18 no.2
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• pp.362-366
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• 2009

This research was conducted to determine the effect of far-infrared ray (FIR) irradiation of grape berries as a potential application for manufacturing grape products with a high amount of antioxidant chemicals. Two grape cultivars, the red grape cv. Campbell Early and the white grape cv. Thompson Seedless, produced increased amounts of crude extracts, in the FIR treatments compared to a non-FIR treatment control with same temperature. However, total phenolic concentrations and antioxidant activity in a 'Campbell Early' increased in the extracts following FIR treatment, whereas those of 'Thompson Seedless' did not increase significantly. High performance liquid chromatography (HPLC) analysis indicated that functional components affecting antioxidant activity were significantly increased in the extract of 'Campbell Early' following FIR treatment. Our results indicate that application of FIR treatment in heat process of grapes increases levels of antioxidative phenolic chemicals and it may help to enhance the availability of antioxidative compounds in various grape food products.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.3
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• pp.257-262
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• 2011

A low capacity generator converted to high capacity of 40m3 is designed and developed in order to use the hydroxy gas in the steel manufacturing process. For efficient design, it is increased from 8 electrode tubes to 10 electrode tubes as well as expanding the diameter of cell integument up to two times bigger, which can increase the amount of hydrogen occurrence per a cell significantly. In addition, circulating pump and pipe, heat exchanger of affiliated SUS material have been used in the circulation of electrolysis catalyst, and circulating cooling section and piping design are also developed. The flame trap is designed into all-in-one suitable check valve in the flow rate of 28-35m3/h and its application is possibly applied in work operation. It is found that the efficiency of generator developed is enhanced substantially up to 84%. It is expected that the application in this field can be expanded significantly by this study.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.6
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• pp.639-643
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• 1997

This paper presents how nonlinear PID control algorithms can be applied on chemical processes for a more stable operation and perfect automation. A pass balance controller is designed to balance the exiting temperatures of a heater and a heat exchange network. The proposed controller has gain-varying integral action and deals with the operational constraints in an efficient manner. Also, the use of a PID gap controller is proposed to maximize energy saving and operation stability and to minimize operator intervention in operation of air fan coolers. The proposed controller adjusts the opening of a louver automatically in such a way that it keeps the air fan pitch position within the desired range. All these nonlinear PID controllers have been implemented on the distributed control system (DCS) for good reliability and operability. Operator acceptance was very high and the implemented controllers have shown good performance and high service factor still now on. The proposed methodology can be directly applied to similar processes without any modification.