• Membrane Journal
• /
• v.24 no.3
• /
• pp.201-212
• /
• 2014

This study was performed to discover the optimum operation conditions for the advanced water treatment using the ceramic membrane, introduced the first in the nation at the Y water treatment plant (WTP). The result of investigation to find the optimum operation conditions which can continue preserving the filtration performance as well as satisfying both the economics and the water quality is as follows. In the ordinary water quality condition of the Y WTP, the optimum filtration time(the backwash period), which can minimize the production of backwash waste and preserve the membrane performance was examined to be 4.0 hours on basis of institution capacity ($16,000m^3/day$). Examining the recovery rate of TMP from the chemical cleaning (CIP) discovered that the inorganic contaminants, which cause membrane fouling, such as iron, manganese, aluminum, were removed through the acidic cleaning using citric acid, whereas the membrane recovery rate was found to be low. But, on the other hand, the TMP was recovered to the initial value from the alkali cleaning using the NaOCl. Therefore, the main contaminant causing the fouling was determined to be hydrophilic organic compound( biopolymer). The membrane recovery rate is highly influenced by the temperature of the cleaning chemical. That is, the rate increased with increasing temperature.

• Journal of the Mineralogical Society of Korea
• /
• v.31 no.1
• /
• pp.57-65
• /
• 2018

The geology of Hidalgo state in Mexico is formed by a Precambrian metamorphic rock base which discordantly supports a strong Paleozoic sedimentary rock sequence. Triassic-Jurassic and Cretaceous sedimentary rocks overlie the above-mentioned rocks at a discordant angle. These Mesozoic rocks are in turn covered by a Cenozoic structure which is marine at its base. At the top, the structure changes to andesitic and basaltic composition volcanic rocks. And, a great variety of mineral deposits, both metallic and nonmetallic, is present in Hidalgo state. The host rocks of these deposits are also very varied in age from Mesozoic to Tertiary. Mineralization age corresponds to Tertiary in 90% of the area. Hidalgo state occupies as an important place in national silver and manganese production. Main mineral deposits correspond to argentiferous veins hosted in sedimentary rocks. Following in order of importance are lead and zinc, as well as some small iron deposits. There is evidence of tin and molybdenum mineralization, but these deposits have not been exploited because of their low grade and volume. And, Hidalgo state has different types of nonmetallic mineral deposits such as sedimentary, hydrothermal, metamorphic and volcanic origins.

• Ocean and Polar Research
• /
• v.23 no.2
• /
• pp.77-95
• /
• 2001

Temperature, salinity, nutrients, chlorophyll-a, and primary production were measured within the upper 200 m water column in the area around the South Shetland Islands in January, 2000. Surface temperature was relatively high in the Drake Passage north of the South Shetland Islands and low in the northeastern area of the Antarctic Peninsula. In contrast, surface salinity was low in the Drake Passage and increased toward the Antarctic Peninsula, reaching the maximum value in the northeastern area of the Antarctic Peninsula. Surface nutrients were low in the Drake Passage and high in the area near the South Shetland Islands. Surface chlorophyll-a was also low in the Drake Passage and near the Antarctic Peninsula and high in the area of the northern King George Island. The study area could be classified as four geographical zones based on the characteristic shape of the T/S diagrams;the Drake Passage, the Bransfield Strait, the mixed zone, and the Weddell Sea. Each geographical zone showed apparently different physical, chemical, and biological characteristics. Phytoplankton biomass was relatively low in the Drake Passage and the Weddell Sea and high in the Bransfield Strait and the mixed zone. The low phytoplankton biomass in the Weddell Sea could be explained by the low water temperature and deep surface mixing down to 200 m. The high grazing pressure and low availability of iron could be responsible for the low phytoplankton biomass in the Drake Passage.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2002.07a
• /
• pp.25-37
• /
• 2002

The most important industrial application of gamma radiation in characterizing green compacts is the determination of the density. Examples are given where this method is applied in manufacturing technical components in powder metallurgy. The requirements imposed by modern quality management systems and operation by the workforce in industrial production are described. The accuracy of measurement achieved with this method is demonstrated and a comparison is given with other test methods to measure the density. The advantages and limitations of gamma ray densitometry are outlined. The gamma ray densitometer measures the attenuation of gamma radiation penetrating the test parts (Fig. 1). As the capability of compacts to absorb this type of radiation depends on their density, the attenuation of gamma radiation can serve as a measure of the density. The volume of the part being tested is defined by the size of the aperture screeniing out the radiation. It is a channel with the cross section of the aperture whose length is the height of the test part. The intensity of the radiation identified by the detector is the quantity used to determine the material density. Gamma ray densitometry can equally be performed on green compacts as well as on sintered components. Neither special preparation of test parts nor skilled personnel is required to perform the measurement; neither liquids nor other harmful substances are involved. When parts are exhibiting local density variations, which is normally the case in powder compaction, sectional densities can be determined in different parts of the sample without cutting it into pieces. The test is non-destructive, i.e. the parts can still be used after the measurement and do not have to be scrapped. The measurement is controlled by a special PC based software. All results are available for further processing by in-house quality documentation and supervision of measurements. Tool setting for multi-level components can be much improved by using this test method. When a densitometer is installed on the press shop floor, it can be operated by the tool setter himself. Then he can return to the press and immediately implement the corrections. Transfer of sample parts to the lab for density testing can be eliminated and results for the correction of tool settings are more readily available. This helps to reduce the time required for tool setting and clearly improves the productivity of powder presses. The range of materials where this method can be successfully applied covers almost the entire periodic system of the elements. It reaches from the light elements such as graphite via light metals (AI, Mg, Li, Ti) and their alloys, ceramics ($AI_20_3$, SiC, Si_3N_4, $Zr0_2$, ...), magnetic materials (hard and soft ferrites, AlNiCo, Nd-Fe-B, ...), metals including iron and alloy steels, Cu, Ni and Co based alloys to refractory and heavy metals (W, Mo, ...) as well as hardmetals. The gamma radiation required for the measurement is generated by radioactive sources which are produced by nuclear technology. These nuclear materials are safely encapsulated in stainless steel capsules so that no radioactive material can escape from the protective shielding container. The gamma ray densitometer is subject to the strict regulations for the use of radioactive materials. The radiation shield is so effective that there is no elevation of the natural radiation level outside the instrument. Personal dosimetry by the operating personnel is not required. Even in case of malfunction, loss of power and incorrect operation, the escape of gamma radiation from the instrument is positively prevented.

• Journal of Conservation Science
• /
• v.36 no.5
• /
• pp.351-367
• /
• 2020

The pigments of three old and new celestial charts folding screens(『Celestial Chart(Folding Screen)』 and 『Old and New Celestial Charts, Eight-Panel Folding Screen』 of National Folk Museum of Korea and 『Koudou-Nanboku-Ryousouseizu』 of National Diet Library of Japan) were analyzed to estimate their dating. It was estimated that the 『Celestial Charts(Folding Screen)』 was painted using traditional pigments from the Joseon dynasty such as azurite, indigo lake, malachite, atacamite, vermilion, iron oxide, cochineal, gamboge, orpiment, lead white, talc and soot. The green and blue colors of the 『Old and New Celestial Charts, Eight-Panel Folding Screen』 and 『Koudou-Nanboku-Ryousouseizu』 were painted using artificial inorganic pigments such as emerald green and ultramarine blue. These pigments were imported from Europe post the mid-19th century. In the 『Old and New Celestial Chart, Eight-Panel Folding Screen』, only artificial inorganic pigments were used for green and blue colors. However in the 『Koudou-Nanboku-Ryousouseizu』, emerald green and atacamite in green color, and ultramarine blue and indigo lake in blue color were used together. Based on both the results of pigment analysis and the study of star charts and inscriptions, the 『Celestial Charts(Folding Screen)』 was painted post mid-18th century. The 『Koudou-Nanboku-Ryousouseizu』 and 『Old and New Celestial Charts, Eight-Panel Folding Screen』 were painted after green and blue artificial pigments were imported in the mid-19th century. The 『Koudou-Nanboku-Ryousouseizu』 in which both traditional and western artificial pigments were used, can be dated earlier than the 『Old and New Celestial Chart, Eight-Panel Folding Screen』.

• Korean Journal of Community Nutrition
• /
• v.11 no.5
• /
• pp.650-660
• /
• 2006

Recently, according to increase in production of pond snails resulting from the widespread organic farming, organic farmers are showing a lot of interests in the promotion of consumption and extending the market of pond snails. This study was performed to suggest the process of product development of the ready-to-eat pond-snail Mandu as a health food, to show the results of market test of the pilot product, and to investigate the change of the sensory characteristics during storage periods. For the market test of pond-snail Mandu, the survey was developed and delivered to consumers. The questionnaire consisted of 3 parts such as respondents demographic characteristics, customer's perception of pond-snail Mandu before tasting, and customer's perception of that after tasting. And the market test was carried out with university students, welfare institution residents and apartment residents in the Seoul and Gyeonggi areas. As a result of the test, the most important purchasing factors were determined in the order of taste (49.5%), hygienic quality (12.5%), nutritional value (10%) and price (9%). And only 4.2% of respondents selected brand name as an important purchasing factor. After tasting pond-snail Mandu, consumers had suggested the better taste (t=6.986, p<0.000) and price (t=2.082, p<0.05) than those of before tasting. In response to favorable impression of pond-snail Mandu, 54.5% of total respondents evaluated positively. The favorable impressions came from iron-rich Mandu (27.6%), high protein and nutritious Mandu (24.4%), calcium-rich Mandu (17.9%), diet Mandu (13.3%), and delicious Mandu (12.5%) respectively. Sensory characteristics of pond-snail Mandu were evaluated by professional panels in terms of the softness of Mandu skin, chewiness, moistness, toothpacking, color, aroma, saltiness, and degree of plain, taste, and aftertaste. The evaluation of sensory characteristics on a 7-point scale, showed that softness of mandu skin (4.44) and aftertaste (4.11) got a low scores. The statistical difference of the tastes (p>0.05) was not founded by storage period of 7, 14, 21 and 28 days. Based on the result, the improvement of these characteristics are desired in developing the pond-snail Mandu. Research method applied to this study can be useful for developing a new product.

• Economic and Environmental Geology
• /
• v.42 no.4
• /
• pp.301-314
• /
• 2009

The Taebaeksan mineralized province, which is the most important one in South Korea, is rich in zinc-lead-tungsten-iron-copper-molybdenum-silver-gold mineral resources and has a diversity of deposit styles. These deposits principally coexist in time and space with porphyry-related epigenetic deposit such as skarn, hydrothermal replacement, mesothermal vein, and Carlin-like deposits. The magmatic-hydrothermal systems in the Taebaek fold belt is genetically characterized by the Bulguksa subvolcanic rocks(ca. $110{\sim}50\;Ma$) related to northwestward subduction of the paleo-Pacific Plate. The most important zinc-lead deposits in the area are the Uljin, Yeonhwa II and Shinyemi skarn, the Janggun hydrothermal replacement, and the Yeonhwa I intermediate-mixed (skarn/hydrothermal replacement) ones. In the present study, we present a compilation of metal production and mineral assemblage of the zinc-lead deposits. The metal difference of deposit styles in the area indicates a cooling path from intermediate-sulfidation to low-sulfidation state in the polymetallic hydrothermal system, reflecting spatial proximity to a magmatic source.

• Korean Journal of Food Science and Technology
• /
• v.39 no.6
• /
• pp.619-624
• /
• 2007

Sedum sarmentosum, also blown as stonecrop (dolnamul), is a widely consumed herb, and is used as an ingredient in salads in Korea. Unfortunately, sedum is perishable and vulnerable to tissue damage during preservation. Therefore, this feasibility study was performed in order to increase the availability of sedum and increase its value. Various concentrations of sedum extract (0.5-3%) were added to gelatin jelly, and their physicochemical properties were determined. The ascorbic acid content of the sedum jelly increased in proportion to the sedum extract concentration. Calcium content of the sedum jelly was 4 to 28 times higher than that of the control. Contrary to the control, iron was detected in the sedum jelly (0.023-1.031 mg/100 g dry weight). Furthermore, magnesium and potassium levels were higher in the sedum extract groups. There were significant differences (p < 0.05) in greenness (a value) and yellowness (b value) between the control and the sedum extract groups. However, significant differences between the 2% and 3% sedum extract groups were not detected. As sedum extract concentration increased, the pH level of soft jellies (solid state) decreased. Therefore, hardness and gumminess were decreased significantly. These results are in agreement with the sensory evaluation. According to sensory tests, the values for palatability, appearance, and color in the 2% sedum extract group were higher than those of the 0.5-1% and 3% sedum extract groups.

• Journal of Bio-Environment Control
• /
• v.15 no.2
• /
• pp.177-183
• /
• 2006

The summer production of sweet pepper in Korea which cultured in the highland area such as Hapchon is essential for a year-round export, but has the problem, fruits lose easily those marketability. This study was carried out to find changes of fruit quality in response to storage on sweet pepper cultivars in summer. Seven cultivars of sweet peppers, 'Jubilee', 'Plenty', 'Goal', 'Romeca', 'Derby', 'Midas' and 'Maximalia' were obtained iron growers in Hapchon which was highland of 600-800m from sea level and stored at $10^{\circ}C$ with box packing. Fruit quality was evaluated every 4days up to 4weeks. The weight loss of 'Jubilee' was the lowest, that of 'Romeca' was the highest. The firmness of 'Goal' was maintained highly for 4weeks and the red cultivars was higher than those of other color cultivars. The lightness of 'Jubilee' was sensitively affected by storage duration. Seeds of 'Plenty' and 'Derby' were plentifully browned after 4weeks storage. The occurrence of fruit rotting was after 16-204ay storage and those of 'Plenty' and 'Maximalia' were the earliest. The marketability of 'Jubilee' and 'Romeca' maintained by 70% for 16 days was the highest, but most cultivars lost those by 20% after 24days storage. It may be suggested that the marketability of sweet pepper producted in summer can be stored at $10^{\circ}C$ for 2weeks to maintain that of 80%.

• Korean Chemical Engineering Research
• /
• v.46 no.6
• /
• pp.1113-1118
• /
• 2008

Characteristics of reduction properties and carbon deposition of $CuFe_2O_4$ and $Fe_3O_4$ were investigated by using TGA, XRD, SEM, TEM and gas analysis at $900^{\circ}C$. XRD analyses indicated that the reduced $Fe_3O_4$ was composed of Fe, graphite and $Fe_3C$ phases. In contrast, the reduced $CuFe_2O_4$ did not show the graphite or $Fe_3C$ phases. It was observed by SEM analysis that the surface of the $Fe_3O_4$ was completely covered with carbon, after methane partial oxidation. From gas analysis, $CuFe_2O_4$ showed much higher methane conversion and reduction kinetics as compared to the $Fe_3O_4$ under the same reaction conditions and the estimated carbon deposition amounts on the reduced $CuFe_2O_4$ was much lower than those on the reduced $Fe_3O_4$ during the syngas production process. It was found by TEM that carbon on the reduced $Fe_3O_4$ particles has a platelet shape.