• Korean Journal of Agricultural Science
• /
• v.6 no.2
• /
• pp.185-191
• /
• 1979

Compressive and tensile strengths of commonly being used mortar and mortar specially hardened by adding 1%, 2% and 3% of $CaCl_2$ were compared under the different mixing ratio of mortar and ages to investigate the effect of $CaCl_2$ which is being used as a promotor for coagulation and hardness, on the strength of mortar. The results obtained were as follows: 1. The compressive strength of mortar hardened by addition of $CaCl_2$ was higher than that of commonly being used mortar. The highest compressive strength of mortar was obtained when 2% of $CaCl_2$ were added. 2. The tensile strength of mortar, which was made by adding $CaCl_2$ and aged for seven days, was higher than that of commonly being used mortar. The highest tensile strength of mortar was obtained when 1% of $CaCl_2$ was added and aged for 28 days. And the tensile strength of mortar with 2% of $CaCl_2$ was lower than that of commonly being used mortar. 3. When the amount of $CaCl_2$ added was higher than 3%, the mortar was abruptly hardened and thereby occurred crack was considered lowering strength of mortar. 4. The rich mix was effective for the increasing the compressive and tensile strength before seven days of age and less effective after seven days of age. Therefore, the addition of one to two per cent of $CaCl_2$ would be effective for promoting initial strength of mortar during winter season.

• Korean Journal of Microbiology
• /
• v.53 no.3
• /
• pp.200-207
• /
• 2017

A new approach to the solubilization of waste activated sludge (WAS) using alginate-quaternary ammonium complex beads was investigated under controlled mild alkaline conditions. The complex beads were prepared by the reaction of sodium alginate (SA) with 3-(trimethoxysilyl)propyl-octadecyldimethylammonium chloride (TSA) in acid solution, followed by crosslinking with $CaCl_2$. Treatment of WAS with SA-TSA complex beads was effective for enhancing the efficacy of WAS solubilization. The highest value of soluble chemical oxygen demand (SCOD) concentration (3,900 mg/L) was achieved after 10 days of treatment with 30% (v/v) SA-TSA complex beads. The WAS solubilization efficacy of the complex beads was also evaluated by estimating the concentrations of volatile fatty acids (VFAs). The maximum value of VFAs was 2,961 mg/L, and the overall proportions of VFAs were more than 75% of SCOD. The main components of VFAs were acetic, propionic, iso-butyric, and butyric acids. These results suggest that SA-TSA complex beads might be useful for enhancing the solubilization of WAS. The potential use of VFAs as the external carbon substrate for the production of polyhydroxyalkanoate (PHA) by a mixed microbial culture (MMC) was also examined. The enrichment of PHA-accumulating MMC could be achieved by periodic feeding of VFAs generated from WAS in a sequencing batch reactor. The composition of PHA synthesized from VFAs mainly consisted of 3-hydroxybutyrate. The maximum PHA content accounted for 25.9% of dry cell weight. PHA production by this process is considered to be promising since it has a doubly beneficial effect on the environment by reducing the amount of WAS and concomitantly producing an eco-friendly biopolymer.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.16 no.4
• /
• pp.157-161
• /
• 2006

InGaN layers on GaN templated sapphire (0001) substrates were grown by mixed-source hydride vapor phase epitaxy (HVPE) method. In order to get InGaN layers, Ga-mixed In metal and $NH_3$ gas were used as group III and group V source materials, respectively. The InGaN material was compounded from chemical reaction between $NH_3$ and indium-gallium chloride farmed by HCl flowed over metallic In mixed with Ga. The grown layers were confirmed to be InGaN ternary crystal alloys by X-ray photoelectron spectroscopy (XPS). In concentration of the InGaN layers grown by selective area growth (SAG) method was investigated by the photoluminescence (PL) and cathodoluminescence (CL) measurements. Indium concentration was estimated to be in the range 3 %. Moreover, as a new attempt in obtaining InAlGaN layers, the growth of the thick InAlGaN layers was performed by putting small amount of Ga and Al into the In source. We found the new results that the metallic In mixed with Ga (and Al) as a group III source material could be used in the growth process of the In(Al)GaN layers by the mixed-source HVPE method.

• Journal of the Korea Concrete Institute
• /
• v.17 no.3 s.87
• /
• pp.411-418
• /
• 2005

Polymer-modified mortar and concrete are prepared by mixing either a polymer or monomer in a dispersed, or liquid form with fresh cement mortar and concrete mixtures, and subsequently curing, and if necessary, the monomer contained in the mortar or concrete is polymerized in situ. Although polymers and monomers in any form such as latexes, water-soluble polymers, liquid resins, and monomers are used in cement composites such as mortar and concrete, it is very important that both cement hydration and polymer phase formation proceed well the yield a monolithic matrix phase with a network structure in which the hydrated cement phase and polymer phase interpenetrate. In the polymer-modified mortar and concrete structures, aggregates are bound by such a co-matrix phase, resulting in the superior properties of polymer-modified mortar and concrete compared to conventional mortar and concrete. The purpose of this study is to obtain the necessary basic data to develope appropriate latexes as cement modifiers, and to clarify the effects of the monomer ratios and amount of emulsifier on the properties of the polymer-modified mortars using methyl methacrylate-butyl acrylate(MMA/BA) and methyl methacrylate-ethyl acrylate(MMA/EA) latexes. The results of this study are as follows, the water absorption, chloride ion penetration depth and carbonation depth of MMA/BA-modified mortar are lowest. However, they are greatly affected by the polymer-cement ratio rather than the bound MMA content and type of polymer.

• International Journal of Highway Engineering
• /
• v.3 no.4 s.10
• /
• pp.93-103
• /
• 2001

This study focused on the field applicability evaluation of SB latex-modified concrete (LMC) for concrete bridge deck overlay using mobile mixer. The main experimental factors were water-cement ratio(31, 33, 35 37%), latex contents(0, 5, 10, 15, 20%), and fine aggregate ratio(55, 56, 57, 58%) in order to evaluate the workability, mechanical properties, and durability property of LMC. The slump loss, air content, compressive and flexible strength tests were used to evaluate LMC workability and strength properties. Also, the rapid chloride permeability test was used to evaluate the relative permeability of LMC. As a results, the LMC with enough workability and good quality was produced when it was mixed in field using mobile mixer, satisfying the target compressive strength and flexural strength. The required water-cement ratio of LMC for same workability when mixing with mobile mixer was less than that when mixing in laboratory. Increasing the amount of latex produced concrete with increased flexural strength by mobile mixer. The required cement-water ratios for same initial $19{\pm}3cm$ slump were 37% and 33% at laboratory and mobile mixer, respectively. The mobile mixer was accurately calibrated satisfying the required specification.

• Particle and aerosol research
• /
• v.15 no.4
• /
• pp.191-202
• /
• 2019

In this study, performance (particle removal efficiency and breathing resistance) of several commercially available face masks (electrostatic filter masks (KF80 certified), a nanofiber filter mask (KF80 certified), and an uncertified mask) with their filter structure and composition were evaluated. Also, effects of relative humidity (RH) of incoming air, water and alcohol exposure, and reusability on performance of face masks were examined. Monodisperse and polydisperse sodium chloride particles were used as test aerosols. Except the uncertified mask filter, PM_2.5 removal efficiency was found to be higher than 90%, and the nanofiber filter mask had the highest quality factor due to the low pressure drop and high removal efficiency (nanofibers were arranged in a densely packed pore structure and contained a significant amount of fluorine in addition to carbon and oxygen). In the case of the KF80 certified mask, the removal efficiency was little affected when the RH of incoming air increased. When the mask filters were soaked in water, the removal efficiency of mask filters was degraded. In particular, the uncertified mask filter showed the highest removal efficiency degradation (26%). When the mask was soaked in alcohol, the removal efficiency also decreased with the greater degree than the water soaking case. The nanofiber mask filter showed the strongest resistance to alcohol exposure among tested mask filters. During evaluation of reusability of masks in real life, the removal efficiency of certified mask filter was less than 4% for 5 consecutive days (2 hours per day), while the removal efficiency of uncertified mask filter significantly decreased by 30% after 5 days.

• The Korean Journal of Pharmacology
• /
• v.2 no.1 s.2
• /
• pp.49-69
• /
• 1966

For the purpose of stydying the pharmacodynamic action of methemoglobin, the author made the following experiments: 1. Preparation of hemoglobin and methemoglobin solutions: Red cell suspension from rabbit blood was hemolysed with distilled water and then divided into two portions. One portion was dialysed through cellophane paper and made isotonic with the proper amount of sodium chloride. The second portion was treated with sodium nitrite to convert hemoglobin to methemoglobin, dialysed through cellophane paper and made isotonic. 2. The concentration of methemoglobin in solution, plasma and urine was determined by Horecker and Brackette's method, and that of hemoglobin by the cyanmethemoglobin method. 3. The concentration of methemoglobin and hemoglobin in the plasma and urine of rabbits was measured at several intervals of time after infusion of the above samples. 4. The blood pressure and respiration of rabbits were recorded on a kymograph, and the effects of the samples on them were observed. 5. The effects of the samples on the movements of the in-situ heart and the isolated intestine of rabbits were studied. 6. The kidneys of rabbits were excised 4 to 5 hours after injection of the samples, and histopathological examinations were made. These experiments revealed the following results: 1. When methemoglobin solution was allowed to stand in room air, there was no decrease in the concentration of methemoglobin. 2. When methemoglobin solution was mixed with whole blood and incubated at $37^{\circ}C$, the concentration of methemoglobin decteased gradually. 3. After the infusion of methemoglobin and hemoglobin solutions, the rate of disappearance of methemoglobin in the plasma was more rapid than that of hemoglobin in the plasma. The higher the initial concentration in the plasma, the larger was the rate of disappearance of methemoglobin. 4. The rate of disappearance of methemoglobin was exceedingly rapid for 30 minutes after the infusion. 5. The urinary excretion of methemoglobin was more rapid than that of hemoglobin. 6. It would seem that the circulating blood contains substances which are promptly mobilized in the plasma to reduce methemoglobin to hemoglobin. 7. Moderate amounts of methemoglobin solution caused some rise in the blood pressure and a transient acceleration of the respiration of the rabbits. These effects of methemoglobin were milder than those of hemoglobin. 8. The movements of the in-situ heart and the isolated intestine of rabbits were accelerated by methemoglobin. These accelerating effects were milder than those of hemoglobin. 9. In the kidneys of rabbits treated with methemoglobin solution, hyperemia of the glomeruli, cloudy swelling and hemoglobin deposit in the tubular epithelium, hemoglobin casts in the tubular lumina of the proximal tubules, and interstitial congestion were constantly observed. There was no definite difference between the histological findings in the rabbit kidneys injected with methemoglobin, and those injected with hemoglobin solutions.

• Applied Microscopy
• /
• v.33 no.1
• /
• pp.1-16
• /
• 2003

As is well known that N-nitroso-N-methylurethane (NNNMU) causes acute lung injury (ALI) in experimental animals. And ALI caused by NNNMU is very similar to ARDS in human being in its pathology and progress. In its context, we investigated the pathogenetic mechanism of ARDS associated with oxidative stress by neutrophils in Sprague-Dawley rat model of NNNMU-induced ALI. NNNMU had increased lung weight/body weight ratio (L/B ratio), lung myeloperoxidase (MPO) activity, protein content and number of neutrophils in bronchoalveolar fluid (BALF) compared with those of control rat (p<0.001, respectively). In contrast, the amount of pulmonary surfactant in BALF was decreased by NNNMU (p<0.001). Morphologically, light microscopic examination denoted pathological findings such as formation of hyaline membrane, infiltration of neutrophils and perivascular cuffing in the lungs of NNNMU-treated rats. In addition, ultrastructural changes such as the necrosis of endothelial cells, swelling and vacuolization of lamellar bodies of alveolar type II cells, and the degeneration of pulmonary surfactant were identified after treatment of NNNMU. Very interestingly, cerium chloride electron microscopic cytochemistry showed that NNNMU had increased the production of cerrous-peroxide granules in the lung, which signified the increased production of hydrogen peroxide in the lung. Collectively, we conclude that NNNMU causes acute lung leak by the mechanism of neutrophilic oxidative stress of the lung.

• Applied Biological Chemistry
• /
• v.24 no.1
• /
• pp.21-28
• /
• 1981

Brewing method and quality of 15 samples of traditional Kochuzang in Junrabook-do area were investigated. Average combination ratio of glutinous rice: Meju (soybean Koji): red pepper powder was 2 : 0.7 : 1.1. In order to improve the taste of Kochuzang, some amount of natural soysauce was added in the Kochuzang at early stage of fermentation. Average content of sodium chloride was 7.32%; amino nitrogen, 123.3%; total sugar, 31.9%; reducing sugar, 19.4%; ethyl alcohol, 1.13% and the activity of acid protease was 0.07; liquefying amylase, 9.67 and saccharogenic amylase was 15.82. Five samples were selected as excellent Kochuzang through sensory evaluation. These samples were similarly strong in hot and sweet taste with alcoholic flavor, glossy surface and brownish red color.

• Clean Technology
• /
• v.19 no.4
• /
• pp.416-422
• /
• 2013

In environmental friendly aspects, the synthesis of glycerol carbonate from glycerol using carbon monoxide and oxygen gases which were produced in petrochemical plants was studied. The oxidative carbonylation of glycerol under batch reaction system was performed on parameter conditions such as effect of various metals (Cu, Pd, Fe, Sn, Zn, Cr), oxidizing agents, mole ratio of carbon monoxide to oxygen, catalyst amount, solvent types, reaction temperature and time and dehydrating agents. In particular copper chloride catalysts showed the excellent activities, and the glycerol carbonate yields over CuCl and $CuCl_2$ catalysts were the maximum of 44% and 64%, respectively at the following reaction conditions: solvent as nitrobenzene, mole ratio of 1:3:0.15 (glycerol:carbon monoxide:catalyst), mole ratio of 2:1 (carbon monoxide:oxygen), the total pressure of 30 bar at 413 K for 4 hr. It was found that reactivity were significantly different depending on the oxidation number of Cu catalysts, and oxygen plays an important role as oxidizing agents in producing H2O during oxidation reaction after carbonylation of glycerol.