• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.47-48
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• 2015

Recycled aggregate used in a site is strong alkali due to calcium hydroxide attached on its surface. Accordingly, many environmental problems arise. Therefore, as basic research to reduce pH of recycled aggregate, this study tries to reduce the strong alkalinity of recycled aggregate by using mixture solution based on sodium phosphate and ammonium chloride. As a result, original aggregate has the strong alkalinity of pH 11.23, whereas pH of recycled aggregate immersed in mixture solution decreased as more mixture rate increased, and mostly pH 9.8 or less was found.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2939-2942
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• 2010

A new high-temperature pH sensor has been successfully developed by reforming the internal reference systems of the pH sensors based on oxygen-ion conducting ceramic membrane. The conventional internal reference system, a mixture of Ni and NiO, has been replaced with partially oxidized Ni powders, where Ni and NiO coexist on the surface of particles, in order to avoid the cumbersome mixing step of Ni and NiO particles. The partially oxidized Ni particles were made by oxidizing Ni under air atmosphere at $600^{\circ}C$ and characterized by X-ray diffraction (XRD) and FTIR spectroscopy. The viability of the pH sensor developed was assessed in boric acid (1000 ppm-B)/ lithium hydroxide (1 to 3 ppm-Li) buffer solutions at $280^{\circ}C$. The pH sensor showed excellent accuracy with a small error less than ${\pm}0.2$ pH units.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.824-827
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• 2000

Fabrication of InP-based photonic devices by dry etch Process is important for clear formation of waveguide mesa structure. We have developed more efficient etch process of the inductively coupled plasma (ICP) with low damages and less polymeric deposits for the InP-based photonic devices than the reactive ion etching (RIE) technique. We report the tendency of etch rate variation by the process parameters of the RF power, pressure, gas flow rate, and the gas mixing ratio. The surface roughness of InP-based waveguide structure was more improved by the light wet etching in the mixed solution of H$_2$SO$_4$:H$_2$O (1:1)

• Korean Journal of Environmental Agriculture
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• v.21 no.3
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• pp.178-188
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• 2002

Constructed wetlands typically cost less to build and operate, and require less energy than standard mechanical treatment technology but they have similar performance to centralized wastewater treatment plants. Therefore, they were constructed especially many in rural areas, where are small villages but not industries. Plantless column tests were performed to investigate the possibility on using zeolite as a filter medium of constructed wetland for the wastewater treatment. Removal efficiency was $COD_{Cr}$ 94.63% T-P 41.41% and $NH_4^+-N$ 99.75% at hydraulic load 314 $L/m^2{\cdot}d$ and filtering height 100 cm filled with a zeolite mixture. This zeolite mixture consisted of 1 : 1 by volume of zeolites in the diameter range of 0.5 to 1 mm and 1 to 3 mm. Accordingly, hydraulic load 314 $L/m^2{\cdot}d$ was considered as optimal. Three zeolite mixtures were used to determine the optimal mixing ratio by volume of a zeolite (A) in the diameter range of 0.5 to 1 mm to a zeolite (B) in the diameter range of 1 to 3 mm 1 : 3, 1 : 1 and only B in A to B by volume were tested at hydraulic load 314 $L/m^2{\cdot}d$ and filtering height 100 cm $COD_{Cr}$ removal efficiency was more than 89% at mixing ratios of 1 : 3 and 1 : 1 in A to B. That of T-P ranged 56.42 to 58.72% and, that of T-N and $NH_4^+-N$ was 87% and 99% regardless of mixing ratios of two zeolites. Removal efficiency was lower at the column filled with only B. Removal efficiency was better at Inter medium filled with mixing ratio 1 : 1 in A to B than with the other mixing ratios. Thus, it was found that the mixture of mixing ratio 1 : 1 in A to B was appropriate far Inter medium of constructed wetland Removal efficiency was higher in down-flow than in up-flow, and all contaminants were removed most in 20 cm filter height near feeding area.

• Journal of the Korea Organic Resources Recycling Association
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• v.2 no.1
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• pp.87-98
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• 1994

Sludge minimization in an water treatment plant can be achieved by optimizing a main water treatment process as well as by enhancing a thickening and a dewatering facilities. In this study, dewatering and drying techniques for reducing the quantity of the water sludge generated from the conventional water treatment plant in the local states were investigated by reducing its water content. Not only the types and dosages of polymers but also the mixing intensity of the mixtures of a concentrated sludge and polymers on the different pH were evaluated for the optimum dewatering conditions of the water sludge. Weight reduction of the water sludge was also tested at a given temperature range. The dewatering efficiency of the water sludge was not affected by the types of polymer but by mixing intensity(GT value) in this study. pH effect on dewaterbility of the water sludge took a major role at the neutral pH range. The optimal polymer dose was 1.5 mg-polymer/g-TSS(about 40mg/L as polymer). Dewaterability was enhanced at a lower mixing intensity(GTbelow 10,000 sec-1). Free water in the void of sludge cake was dried around $100^{\circ}C$, chemical bound water was evaporated around $320^{\circ}C$, and organic material was burned out at the range of 300 to $600^{\circ}C$. Ignition losses of the water sludge were varied 15 to 40 % as the raw water quality. The ignition loss due to the chemical bound water was 10-20% and the loss due to the organic material was 4-20% of the total ignition loss.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.11
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• pp.1027-1033
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• 2013

In this work, a D-band imaging detector has been developed in a 65-nm CMOS technology for high frequency imaging application. The circuit was designed based on the resistive self-mixing of MOSFET devices. The fabricated detector exhibits a maximum responsivity of 400 V/W and minimum NEP of 100 $pW/Hz^{1/2}$ at 145 GHz. The chip size is $400{\mu}m{\times}450{\mu}m$ including the probing pads and a balun, while the core of the circuit occupies only $150{\mu}m{\times}100{\mu}m$.

• 한국신재생에너지학회:학술대회논문집
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• 2005.11a
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• pp.299-306
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• 2005

Anaerobic fermentation of food waste (FW) and waste activated sludge (WAS) for hydrogen production was performed in CSTR (Continuous Stirred tank reactor) under various HRTs and volumetric mixing ratio (V/V) of two substrates, FW and WAS. The specific hydrogen production potential of FW was higher than that of WAS. However, pH drop in the CSTR for hydrogen production from FW was higher than that from WAS. The maintenance of desired pH during fermentative hydrogen production is regarded as the most important operation parameter for the stable hydrogen production. Therefore, when the potential of hydrogen production from FW and better buffer capacity of WAS, the proper mixture of FW and WAS for fermentative hydrogen production were considered as a useful complementary substrate. The maximum yield of specific hydrogen production, 140 mL/g VSS, was found at HRT of 2 day and the volumetric mixing ratio of 20:80 (WAS : FW). The spatial distribution of hydrogen producing bacteria was observed in anaerobic fermentative reactor using fluorescent in situ hybridization (FISH) method.

• Journal of Institute of Convergence Technology
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• v.4 no.2
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• pp.51-54
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• 2014

Energy storage not only reduces the mismatch between supply and demand but also improves the performance and reliability of energy systems. The different forms of energy that can be stored, including mechanical, electrical and thermal energy. Phase change materials (PCM) are latent heat storage materials. A large number of phase change materials (organic, inorganic and eutectic) are available in any required temperature range. We concentrated on eutectic materials and made a eutectic by mixing urea and choline chloride. Heat capacity ($C_p$) is one of the most important properties to be considered when a process is developed using the eutectic and currently DSC (Differential Scanning Calorimetry) has been proved as an effective technique to measure the heat capacity. This study focused on measuring heat capacity ($C_p$) of the mixing urea and choline chloride by DSC.

• Journal of the Optical Society of Korea
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• v.4 no.2
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• pp.75-78
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• 2000

We design a high temperature oven for measuring the saturation intensity of the transition line $4f^ 6/6s^{2 7}7F_0 ↔ 4f^6/6s6p $^1$P(J = 1)$ of the samarium atom. We first constructed a high temperature oven to generate the samarium vapor column and study the thermal characteristics of the oven. The oven is able to operate at a temperature up to about 1400 $^{\circ}C$ and the operation is tested by using several metals with high melting points. We describe two wave mixing experiment with the samarium vapor generated in the high temperature oven and obtain the saturation intensity by analyzing the first diffraction signal.

• Journal of Environmental Science International
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• v.9 no.1
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• pp.81-88
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• 2000

Every year, 1.1 million tons of rice-hull are produced in South Korea by the by-product in pounding rice. But they has mainly been utilized as a fuel, agricultural compost and moisture proofs. So, it's very valuable to use waste rice-hull for activated carbon manufacture. SiO2 content was the highest among inorganics in rice-hull. Therefore, the SiO2 extraction experiments were carried out under the various conditions of pH 9 to 14, reaction time from 2 to 24 hrs and various temperature of 20 to 100℃. The results showed that increase in pH and temperature enhanced SiO2 extraction from the carbonized rice-hull. The surface area of the carbonized rice-hull indicating activated carbon adsorption capacity was very small as 178∼191 m2/g at first. However, it was increased to 610∼675 m2/g when extracted in alkali solution at 100℃. When the mixing rate of carbonized rice-hull and NaOH was 1:1.5, iodine No. and surface area of activated rice-hull during 10 min at 700℃ were 1,650 mg/g and 1837 m2/g, respectively. Subsequently, an activated carbon with specific surface area of 1,300∼1,900m2/g was manufactured in a short contact time of 10∼30 min with a mixing rate of 1:1.5 in carbonized rice-hull and NaOH, and iodine No. and specific surface area increased as the amount of SiO2 removal increased.