• Journal of Korean Society of Water and Wastewater
• /
• v.35 no.6
• /
• pp.425-436
• /
• 2021

In this study, chemically enhanced steam cleaning(CESC) was applied as a novel and efficient method for the control of organic and inorganic fouling in ceramic membrane filtration. The constant filtration regression model and the resistance in series model(RISM) were used to investigate the membrane fouling mechanisms. For total filtration, the coefficient of determination(R²) with an approximate value of 1 was obtained in the intermediate blocking model which is considered as the dominant contamination mechanism. In addition, most of the coefficient values showed similar values and this means that the complex fouling was formed during the filtration period. In the RISM, R _c/R _f increased about 4.37 times in chemically enhanced steam cleaning compared to physical backwashing, which implies that the internal fouling resistance was converted to cake layer resistance, so that the membrane fouling hardly to be removed by physical backwashing could be efficiently removed by chemically enhanced steam cleaning. The results of flux recovery rate showed that high-temperature steam may loosen the structure of the membrane cake layer due to the increase in diffusivity and solubility of chemicals and finally enhance the cleaning effect. As a consequence, it is expected that chemically enhanced steam cleaning can drastically improve the efficiency of membrane filtration process when the characteristics of the foulant are identified.

• Journal of Microbiology and Biotechnology
• /
• v.28 no.11
• /
• pp.1846-1849
• /
• 2018

Recent human gut microbiome studies have supported that the genus Bifidobacterium is one of the most beneficial bacteria for human intestinal health. To develop a new probiotic strain for functional food applications, fourteen fecal samples were collected from healthy Koreans and the strain BCBR-583 was newly selected and isolated from a 25-year-old Korean woman's fecal sample using the selective medium for Bifidobacterium. Subsequent fructose-6-phosphate phosphoketolase (F6PPK) test and 16S rRNA gene sequencing analysis of the strain BCBR-583 confirmed that it belongs to B. longum subsp. longum. The stress resistance tests showed that it has oxygen and heat tolerance activities (5- and 3.9-fold increase for 24 h at 60 and 120 rpm, respectively; $78.61{\pm}6.67%$ survival rate at $45^{\circ}C$ for 24 h). In addition, gut environment adaptation tests revealed that this strain may be well-adapted in the gut habitat, with gastric acid/bile salt resistance ($85.79{\pm}1.53%$, survival rate under 6 h treatments of gastric acid and bile salt) and mucin adhesion ($73.72{\pm}7.36%$). Furthermore, additional tests including cholesterol lowering assay showed that it can reduce $86.31{\pm}1.85%$ of cholesterol. Based on these results, B. longum BCBR-583 has various stress resistance for survival during food processing and environmental adaptation activities for dominant survival in the gut, suggesting that it could be a good candidate for fermented food applications as a new probiotic strain.

• Journal of Sensor Science and Technology
• /
• v.23 no.4
• /
• pp.266-271
• /
• 2014

Chemical sensors are used in various industrial facilities such high-risk and prevent the leakage of substances, important in life and environmental protection and the safe use of industry, used for management. In particular, high-temperature environments such as power generation equipment of the rotating part due to leakage generated by the various oil, power plants Shut Down, fire, work environment (exposure to various chemical solution and gas leak) and various water, air and soil pollution causes. Thus, over the long term through various channels such as crops and groundwater contamination caused by the slow, serious adverse effect on the ecosystem. In this paper, synthetic lube oil and high pressure hydraulic fluid leakage and immediately detect a new Printed Electronic implementation of technology-based film-type sensors, and its performance test. Thus, industrial accidents and environmental pollution and for early detection of problems, large accidents can be prevented. Experimental results of the synthetic lube oil and high pressure hydraulic fluid solution after the contact time depending on the experiment and the oil solution of the sensor material of the conductive porous PE resistance value by a chemical reaction could be confirmed that rapid increase. Also implemented in the film-type oil sensor electrical resistance change over time of the reaction rate and the synthetic lube oil is about 2 minutes or less, the high pressure hydraulic fluid is less than about 1 minute was. Therefore, more high-pressure hydraulic fluid such as a low volatility synthetic lube oils are the resistance change and the reaction rate was confirmed to be the slowest.

• Korean journal of applied entomology
• /
• v.40 no.4
• /
• pp.321-326
• /
• 2001

Contribution of Wolbachia infection to fitness of a species (developmental time, adult life span, fecundity and ovipositional period) was measured in the susceptible and dicofol-resistant strains of two spotted spider mite, Tetranychus urticae Koch, on miniature roses. Based on ftsZPCR assay, Wolbachia infection was confirmed only in the susceptible strain. The susceptible strain had significantly higher fecundity (eggs/female) and shorter developmental times than the resistant strain. Longer adult life span and ovipositional period were observed in the susceptible strain. Fitness differences were appeared to influence dicofol resistance development. Similar measurements were performed with progeny from two reciprocal $F_1$crosses. Similar to other examples of cytoplasmic incompatibility induced by Wolbachia, subsequent cross between uninfected female and infected male spider mites were different from the other combination: a high egg mortality and a male-biased sex ratio. When the intrinsic rate of natural increase was calculated, the cross between uninfected female and infected male spider mites had a significantly lower rate($0.09\pm$0.01) than did the other combination ($0.20\pm$0.01). These results suggest that the dynamic and evolution of the fitness are closely associated with dicofol resistance and Wolbachia infection in the two spotted spider mites.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.29 no.3
• /
• pp.200-213
• /
• 1993

A model experiment on a midwater rope trawl net which is used in the North Pacific to catch alaska pollack is carried out in the circulating tank to examine the basic efficiency of the net. The prototype is the net used by M/S Hanil(1, 179GT, 2, 700PS), a Korean trawler. The model net was made according to the Tauti's Similarity Law of Fishing Gear in 1/100 scale by considering the condition of the tank. To measure the basic efficiency of the standard model net, the vertical opening and width between some points marked on the net were measured, and the hydrodynamic resistance were determined. Then the constructive conditions of the net were varied as follows and the factors were measured again to compare the efficiency of those nets with that of the standard net(A-1 type) front weight multiplied 1.5 times: A-2 type. buoyancy and depressing force multiplied 1.7 times: A-3 type. front weight multiplied 1.5 times on A-3 type: A-4 type. depressors rigged at ground rope: B type. cod-end stuffed with cashmylon wad: C type. The results obtained can be summarized as follows: 1. The vertical opening at the center of head rope was steeply decreased with the flow velocity increasing and the vertical opening H(m) can be expressed in H=1.2v super(-1.2)(v : flow velocity in m/sec). The width of the net varied a little when the flow velocity was over 0.4m/sec, and the width of net mouth showed about 37% of the distance between the fore tips of net pendant. The shape of net mouth was almost a circle at 0.2m/sec and then steeply flatted elliptically with the flow velocity increasing and the area of mouth S(m super(2)) can be expressed in S=(1.65-2.3v)$\times$10 super(-2). The hydrodynamic resistance of the net increased almost linearly with the flow velocity increasing and the resistance R(kg) can be expressed in R=3.2$\times$d/l$\times$abv. where d/l denotes the mean of d(diameter of netting twine) and l(length of a leg in a mesh) from wing tip to the end of bag-net except cod-end on the side pannel, and a denotes the strectched circumference of the net at the fore end of a meshed part and b the stretched length of the whole net from wing tip to the end of cod-end. 2. In the condition-varied nets, the vertical opening of head rope showed some increase in every type net except the C type, and the increase showed the greatest in the B type by 30~54%, whereas it showed decrease in the C type by 5~10%. Variation of the area of net mouth showed almost the same tendency as the vertical opening and the increase showed the greatest in the B type by 20%, whereas it showed decrease in the C type by 12%. Hydrodynamic resistance showed some increase in every type compared with the standard net, and the rate of increase indicated 5~10% in the A-2, A-3 and A-4 type, 22% in the B type and 3% in the C type.

• Journal of Korean Society of Environmental Engineers
• /
• v.37 no.3
• /
• pp.152-158
• /
• 2015

This paper investigated the membrane fouling potential at the state of passive adsorption which is no permeation with the test modules on COD (Chemical oxygen demand) loading rates, examined the recovery rate and resistance on membrane fouling by three cleaning manners of hydrophobic membrane in a bioreactor. The results showed that high COD loading led to the increase of extra-cellular polymeric substances and filtration resistance. The permeability resistance from 1st day to 63rd day was getting increased, however, the value of permeability resistance after 63th day during the operation period was almost same level at three COD loading rates, it was due that the biomass adhesion on membrane surface at the state of passive adsorption reached to the critical state. Also, the final recovery rates after three cleaning manners were 78%, 72% and 69% at the COD loading concentrations of 250 mg/L, 500 mg/L and 750 mg/L respectively, and then recovery rate by physical cleaning at Run 2 and Run 3 was decreased after 40th day, it proved that biomass cake, which is not easily removed, was formed on the membrane surface because of high COD loading rate and EPS concentration.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.8 no.4
• /
• pp.520-527
• /
• 2020

Hwangtoh is the rich resource that accounts for about 15.0% of the domestic soil, and can be used as the admixture of concrete with Pozzolan characteristics if activated by rapidly freezing after burning with high temperature. In this study, the mortar curbs containing active hwangtoh were produced, based on the mixture for the mortar curbs sold on the market. The substitution rate of active hwangtoh were considered 10.0% and 25.0%, and the test items were selected to compressive and flexural strength tests, freezing/thawing resistance tests, accelerated carbonation tests, and accelerated chloride diffusion tests. In the results of the mechanical performance, it was showed that the highest strength was evaluated in OPC mixture, and the increase in strength was small by the increase of age, which was believed to be due to the fact that most of the strength in each mixture was created in three days of steam curing. The results of the freezing/thawing tests for 28 aged days showed the reduction rate of compressive strength was 85.0% or higher for all specimen, meeting the criteria presented. The accelerated carbonation tests were carried out on the specimen at 28 days of age, and the results showed that the mortar with active hwangtoh had lower carbonation resistance performance than mortar with OPC. The passed charge of each mixture was assessed in accordance with ASTM C 1202 on 28 and 91 aged days. The OPC mixture had "Low" rate and the mortar with active hwangtoh had "Moderate" rate. So it was thought that the mortar with active hwangtoh had appropriate resistance performance for chloride attack.

• Corrosion Science and Technology
• /
• v.20 no.2
• /
• pp.45-51
• /
• 2021

In this work, we describe the effect of pulse anodizing duty ratio on the corrosion resistance of anodic films in magnesium AZ31B. The process involves the application of square pulse potential for a constant period with a duty ratio varying from 40, 60 and 80%. In several samples, a sealing treatment for 30 minutes was conducted after anodization in order to seal the pores available in the anodic layer. After anodizing, the surface morphology of the anodic layer was examined using a scanning electron microscope (SEM Hitachi SU3500). The corrosion characteristics of the sample were evaluated through an open circuit potential (OCP) and potentiodynamic polarization test using potentiogalvanostat. SEM observation shows that the increase of anodization duty ratio (α) results in a more uniform anodic layer, with fewer pores and cracks. The increase of duty ratio (α) decreases the OCP value from approximately -1.475 to about -1.6 Volt, and significantly improves the corrosion resistance of the anodic coating by 68%. The combination of anodization and sealing treatment produces an anodic coating with a very low corrosion rate of 4.4 mpy.

• Journal of Power System Engineering
• /
• v.14 no.6
• /
• pp.83-88
• /
• 2010

The wear behavior of epoxy matrix composites filled with nano sized silica particles is discussed in this paper. Especially, the variation of the coefficient of friction and the wear resistance according to the change of apply load and sliding velocity were investigated for these materials. Wear tests of pin-on-disc mode were carried out and the wear test results exhibited as following ; The epoxy matrix composites showed lower coefficient of friction compared to the neat epoxy through the whole sliding distance. As increasing the sliding velocity the epoxy matrix composites indicated lower coefficient of friction, whereas the neat epoxy showed higher coefficient of friction as increasing the sliding velocity. The specific friction work of both materials were increased with apply load. In case of the epoxy matrix composites, the running in periods of friction were reduced as increase in apply load. The epoxy matrix composites were improved the wear resistance by adding the nano silica particles remarkably. It is expected that the load carrying capacity of the epoxy matrix composites will be improved by increase of Pv factor.

• The Journal of Fisheries Business Administration
• /
• v.41 no.1
• /
• pp.113-128
• /
• 2010

This study is aimed to analyze the economic feasibility of the selective breeding program on the Oliver flounder aquaculture. First of all, in order to evaluate this program, we review the concept and research trend on the selective breeding. The objective of this research is the selective breeding program on the Oliver flounder aquaculture in the Genetics and Breeding Research Center, NFRDI. It was conducted to investigated economic effects of three factors of the selective breeding program on the Oliver flounder aquaculture such as fast growth, disease resistance and increase exports. The results of economic analysis of the selective breeding program on the Oliver flounder aquaculture are as follows; First, there were the significant meaning of the economic effects on the technology of the selective breeding program by fast growth, disease resistance and increase exports. Second, we analyzed in the economic feasibility of the selective breeding program on the Oliver flounder aquaculture from 2004 to 2020, internal rate of return(IRR) was 419%, a benefit-cost ratio was shown to be 24.92, net present value(NPV) was 989,942,464 thousand won, which indicates the economic feasibility of the selective breeding program is very high. Finally, in order to improve the economic feasibility, there is need to be focused on the efficient the selective breeding program on the Oliver flounder aquaculture.