• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.128-135
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• 2011

In this study, in order to develop ultra rapid hardening mortar(URHM) for tunnel repairs using bottom ash of low recycle ratio and Admixture as Eco concept, fundamental properties of URHM on temperature condition of construction field were performed. Test result, URHM of three types for fluidity and setting time were as in the following : B > C > A. Those for low temperatures were later than the standard condition. Compressive, bending and bond strength were similar with three types as follow. In compressive strength, initial strength of the low were smaller than the standard but the low in the long-term were similar with the standard. On the contrary to this, bending strength were similar in initial strength but the low in the long-term were smaller than the standard. The low in bond strength was average 35% less than the standard. Length changes was as in the following : A > C > B. the low is two times much as the standard but the case using blast furnace slag particles noticeably reduced length changes. Water absorption coefficient and water vapor resistance were as in the following : C > A > B. In case of URHM added bottom ash, water absorption coefficient and water vapor resistance were increased because bottom ash is porous material.

• Journal of Sensor Science and Technology
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• v.29 no.5
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• pp.293-302
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• 2020

Food safety has emerged as a growing concern for human health in recent times. Consuming contaminated food may lead to serious health problems, and therefore, a system for monitoring food freshness that is both non-detrimental to the quality of food and highly accurate is required to ensure that only high-quality fresh food packages are provided to the customers. This paper proposes a method to monitor and detect food quality using a compact smart sensor tag. The smart tag is composed of three ultra-low-power sensors, which monitor four major indicators of food freshness: temperature, humidity, and the concentrations of ammonia and hydrogen sulfide gases. An RF energy scavenging circuit is integrated into the smart sensor tag to harvest energy from radio waves at a high frequency of 13.56 MHz to supply sufficient power to the tag. Experimental results show that the proposed energy harvester can efficiently obtain energy at a distance of approximately 40 cm from a 4 W reader. In addition, the proposed smart sensor tag can operate without any battery, thereby eliminating the requirement of frequent battery replacement and consequently decreasing the cost. Meanwhile, the freshness of preserved pork is continuously monitored under two conditions--room temperature and refrigerator temperature--both of which are the most common temperatures under which food is generally stored. The food-monitoring experiments are conducted over a period of one week using the proposed battery-less tag. Based on the experimental results, the food assessment is classified into four categories: fresh, normal, low, and spoiled.

• Applied Chemistry for Engineering
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• v.19 no.2
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• pp.236-241
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• 2008

The possibility of silicon oxidation through the aerial-diffusion of active oxygen species has been evaluated. The species originate from the surface of $TiO_2$ exposed by UV. Among process parameters such as UV intensity, substrate temperature and chamber pressure with oxygen, UV intensity was a major parameter to the influence on the oxide growth rate. When 1 kW high pressure Hg lamp was used as a UV source, the growth rate of silicon oxide was 8 times as faster as that of a 60 W BLB lamp. However, as the chamber pressure increased, the growth rate was declined due to the suppression of aerial diffusion of active oxygen species. According to the results, it could be confirmed that the aerial-diffusion of active oxygen species from UV-irradiated photocatalytic surface can be applied to a new method for preparing an ultra-thin silicon oxide at the range of relatively low temperature.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.571-580
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• 2020

In this study, an experimental study on storage media for thermal energy storage system was conducted. For thermal energy storage medium, concrete has excellent thermal and mechanical properties and also has various advantages due to its low cost. In addition, the ultra-high strength concrete reinforced by steel fibers exhibits excellent durability against exposure to high temperatures due to its high toughness and high strength characteristics. Moreover, the high thermal conductivity of steel fibers has an advantageous effect on heat storage and heat dissipation. Therefore, to investigate the temperature distribution characteristics of ultra-high-strength concrete, concrete blocks were fabricated and a heating test was performed by applying high-temperature thermal cycles. The heat transfer pipe was buried in the center of the concrete block for heat transfer by heat fluid flow. In order to explore the temperature distribution characteristics according to different shapes of the heat transfer pipe, a round pipe and a longitudinal fin pipe were used. The temperature distribution at the differnent thermal cycles were analyzed, and the thermal energy and the cumulated thermal energy over time were calculated and analyzed for comparison based on test results.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.479-482
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• 2003

We propose a real time gas monitoring system for classifying various gases with different concentrations. Using thermal modulation of operating temperature of two sensors, we extract patterns of gases from the voltage across the load resistance. We adopt the relative resistance as a pre-processing method and an ART2 neural network as a pattern recognition method. The proposed method has been implemented in a real time embedded system with tin oxide gas sensors, TGS 2611, 2602 and an MSP430 ultra-low power microcontroller in the test chamber.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.142.1-142.1
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• 2016

We present bulk diffusion rates of hydroxide ions in amorphous solid water (ASW) at 135 ~ 160 K. Previous researches showed that the diffusion mechanism of hydroxide is different from one of hydronium ions, and this implies that they have different diffusion rates. In ultra-high vacuum (UHV) chamber, low-energy scattering (LES) was used to measure ion population and temperature-programmed desorption (TPD) was conducted for measuring ASW thicknesses. To determine the diffusion rates, a simple model for $H_2O/NaOH/H_2O$ sandwich films was developed using Fick's second law. The measured surface population of hydroxide ions as a function of time was well fitted to the model, and the rates were well agreed to an Arrhenius equation.

• Applied Science and Convergence Technology
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• v.26 no.3
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• pp.50-51
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• 2017

Strongly correlated electron systems which induce strong electron-electron interaction at ultra-low temperatures have always been an intriguing topic in mesoscopic condensed matter physics. Below 130 mK, a peculiar gap can be found in Al/$SiO_2$/Si:P structured tunnelling devices. The gap survives at the base temperature of more than 1800 gauss (30 mK), contrary to the superconductivity of the top Al electrode, which is completely suppressed above 100 gauss. This outcome implies that the observed gap is induced by Coulomb interaction in the heavily doped Si.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.859-862
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• 2003

Well-aligned multiwall carbon nanotubes (MWCNTs) were prepared at low temperature of 400 $^{\circ}C$ by utilizing a radio frequency plasma-enhanced chemical vapor deposition (rf-PECVD) system. The MWCNTs were treated by an external rf plasma source and an ultra-violet laser in order to modify structural defect of carbon nanotube and to ablate possible contamination on carbon nanotube surface. Structural properties of carbon nanotubes were investigated by using a scanning electron microscopy (SEM), Raman spectroscopy, Fourier transformer Infrared spectroscopy (FTIR) and transmission electron microscope (TEM). In addition, the emission properties of the MWNTs were measured for the application of field emission display (FED) in near future. Various post treatments were found to improve the field emission property of carbon nanotubes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.620-624
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• 1997

Corrugated membranes which are used as a means of liquid- and gas-sealing for a LNG storage tank and provide one of the most reliable primary barrier are the main component of in-ground membrane types for the assurance of high safety. It absorbs large thermal and mechanical deformations caused by ultra low temperature of LNG, -162 .deg.c, the cryogenic liquid and mechanical deformations caused by was carried out on crossing corrugation by commercial F.E code, ANSYS. This paper presents some of results in stress analysis of membranes performed for the purpose to investigate the strength of existing membrane for LNG storage tank designed by IHI,MHI, KHI and KGC expect for Technigaz eariy published. Based on these analytical studies,design criteria were estabilished and SHI original membranes having a high level of safety and fitting to larger capacities were developed.

• Proceedings of the KWS Conference
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• 2003.11a
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• pp.253-255
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• 2003

Commercially pure 1050 aluminum alloy with ultra-fine grain sizes was produced by a friction stir process. The maximum temperature in the friction stir processed zone decreased almost linearly with the tool rotation speed. In the friction stir processed zone, dislocation density was very low and fine equiaxed grains were observed. The grain size decreased with tool rotation speed. It is noteworthy that, for 560 rpm, a grain size decreased to even the submicron level with only the single pass of friction stir process. These fine grains resulted in improvement in hardness of the friction stir processed zone.