• Journal of the Korean Recycled Construction Resources Institute
• /
• v.1 no.1
• /
• pp.89-97
• /
• 2005

Recently, for the problem solution of demand and supply imbalance of fine aggregate due to the shortage of natural fine aggregate resource and the environment regulation on sea sand extraction in the construction field, the studies for the application of recycled fine aggregate using waste concrete are being progressed versatilely. On the other hand, the treatment of fly-ashes that of industrial by-product originated in the steam power plant is discussed by the continuous increasing of origination quantities. In the ease of using fly-ash, advantages are the improvement of workability, viscosity and long-time strength, and the reduction of hydration heat under the early ages, as the admixtures for concrete, but the studies for the application of fly-ash as recycled concrete admixtures are inadequacy. There fore, in this study, through investigating the properties of fresh, hardened and durability according to the replacement of recycled fine aggregate and fly-ash, it is intended to propose the fundamental data for structural application of recycled concrete using recycled fine aggregate and fly-ash. As the result of this study, they arc shown that the engineering properties and durability, in the case of replacement ratio 100% of recycled fine aggregate, arc similar to those of concrete using natural fine aggregate, so it is considered that recycled fine aggregate could be used as the fine aggregate for concrete. Also, the performances of recycled concrete are improved by replacing fly-ash.

• Food Science of Animal Resources
• /
• v.28 no.1
• /
• pp.51-58
• /
• 2008

This study was performed to evaluate the physico-chemical properties of fermented sausages containing probiotic starter cultures (LK-30 plus, Lactobacillus plantarum 155 and 167, and Pediococcus damnosus L12) with reduced fat levels, and to determine the optimum condition for the manufacture of these products. Although low-fat fermented sausages were reduced fat content at the amount of 90% and the ripening time by 1-2 weeks, as compared to regular-fat counterpart, they became harder and had many winkles outside due to the extreme drying. In addition, fat level in fermented sausages affected the composition and shear force values. During ripening, pH, lightness and yellowness values tended to decrease, however, microbial counts of inoculated lactic acid bacteria were increased up to $10^8-10^9cfu/g$ within 3 days and remained constant thereafter. Low-fat fermented sausages had higher microbial counts than regular-fat ones. Although the inoculated probiotic starter cultures alone had the functional properties, such as cholesterol reduction, anti-high blood pressure and antimicrobial activity, they did not have distinctive characteristics in the fermented sausages. Based on these results, the low-fat fermented sausages were successfully manufactured, but a little bit increased fat level and improved functional properties in the fermented sausages would be required to have better quality as compared to regular-fat counterparts.

• Korean Chemical Engineering Research
• /
• v.58 no.1
• /
• pp.84-91
• /
• 2020

The efficiency of the synthetic magnesium silicate used in basic polyols and edible oil purification is evaluated by its purification ability and filtration rate and is affected by the particle size and surface area of magnesium silicate. In this study, it was investigated the change on the particle size of magnesium silicate was influenced by the reaction temperature, injection rate, injection order (Si, Mg) and Mg/Si reaction mole ratio. The synthesized magnesium silicate was compared and analyzed for the synthesis, grinding, and refining processes. In the synthesis process, the reaction temperature and feed rate did not affect the average particle size change of magnesium silicate, while the reaction molar ratio of Mg / Si and the order of injection acted as main factors for the change of average particle size. The average particle size of magnesium silicate increased by 8.7 ㎛ from 54.4 ㎛ to 63.1 ㎛ at Mg injection when Mg molar ratio increased from 0.125 to 0.500, and increased by about 4.8 ㎛ from 47.3 ㎛ to 52.1 ㎛ at Si injection. The average particle size according to the order of injection was 59.1 ㎛ for Mg injection and 48.4 ㎛ for Si injection and the difference was shown 10.7 ㎛, therefore the filtration rate was about 2 times faster under the condition of Mg injection. That is, as the particle size increases, the filtration time is shortened and washing filtration rate can be increased to improve the productivity of magnesium silicate. The cake form of separated magnesium silicate after filtration becomes a solid through drying process and is used as powdery adsorbent through the grinding process. As the physical strength of the dried magnesium silicate increased, the average particle size of the powder increased and it was confirmed that this strength was affected by the reaction molar ratio. As the reaction molar ratio of Mg / Si increased, the physical strength of magnesium silicate decreased and the average particle size after grinding decreased by about 40% compared to the average particle size after synthesis. This reduction of strength resulted in an improvement of the refining ability due to the decrease of the average particle size and the increase of the amount of fine particle after the pulverization, but it resulted in the decrease of the purification filtration rate. While the molar ratio of Mg/Si was increased from 0.125 to 0.5 at Mg injection, the refining ability increased about 1.3 times, but the purification filtration rate decreased about 1.5 times. Therefore, in order to improve the productivity of magnesium silicate, the reaction molar ratio of Mg / Si should be increased, but in order to increase the purification filtration rate of the polyol, the reaction molar ratio should be decreased. In the synthesis parameters of magnesium silicate, the order of injection and the reaction molar ratio of Mg / Si are important factors affecting the changes in average particle size after synthesis and the changes of particle size after grinding due to the changes of compressive strength, therefore the synthetic parameter is an important thing that determines productivity and refining capacity.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.55 no.2
• /
• pp.98-104
• /
• 2010

Excess nitrogen (N) uptake of rice, which could cause much lodging, disease and reduction of rice quality, could be occurred at the paddy field with previous upland condition at which much soil N could be mineralized by soil-drying effect. N fertilizers of 0, 3, and 6 kg N $10a^{-1}$ were applied to early-maturity rice, cultivar Joanbyeo at the paddy field of first and second year after upland condition, and rice growth and nitrogen uptake were investigated to know the increase of rice N uptake at the paddy field with previous upland condition for one-year. Total dry matter (DM) and N uptake of rice at the paddy field with previous upland condition increased more than continuous paddy field. Total DM and N uptake of rice at the paddy field with previous upland condition increased linearly to N fertilizer 6 kg $10a^{-1}$ at the paddy field owing to vigorous growth compared to continuous paddy field. Rice N uptake was higher at the paddy field of the first year than the second year after upland condition in considering N uptake at the plot of no N fertilizer. Vigorous growth at the paddy field with previous upland condition resulted in higher rice yield which was related with high panicle and spikelet, but much N fertilizer as much as 6 kg $10a^{-1}$ at the paddy field with previous upland condition resulted in higher lodging and protein content of brown and milled rice. Particularly, protein content of brown and milled rice increased more when the same N fertilizer was applied two times splitly at transplanting and panicle initiation stage than when N fertilizer was applied one time at transplanting as basal N. N application with under 3 kg $10a^{-1}$ as only basal N was recommended at the paddy field with previous upland condition to obtain high quality rice without lodging.

• Restorative Dentistry and Endodontics
• /
• v.35 no.5
• /
• pp.335-343
• /
• 2010

Objectives: To compared the effect of different levels of moisture of root canal on the sealing ability after filling with four different types of sealer. Materials and Methods: Single-rooted teeth (n = 90) instrumented to and apical size of 0.06 / 45 were randomly assigned to 12 experimental groups (n = 7 per group), positive/negative control groups (n = 3 per group). The teeth of the experimental groups (a. DRY; b. PAPER POINT DRY; c. WET) were obturated with sealer (Group 1-3: Sealapex; Group 4-6: AH plus; Group 7-9: Tubuli-seal; Group 10-12: EndoRez) and warm vertical compaction method. After 7 days in $37^{\circ}C$, 100% humidity, the coronal-to-apical microleakage was evaluated quantitatively using a glucose leakage model. The leaked glucose concentration was measured with spectrophotometer at 1, 3, 7, 14, 21, and 30 days. Data were recorded ad mmol/L and statistically analysed with the two-way ANOVA and Duncan test (p = 0.05). Results: Throughout the experimental period Tubuli-seal/WET (Group 9) showed the highest mean cumulative glucose penetration (178.75 mmol/L), whereas AH plus/DRY (Group 4) had the least (20.78 mmol/L). Conclusions: The results of this study demonstrated that the moisture condition of root canals at the time of obturation and the type of sealer that was used had a significant effect on leakage and sealing ability. Thus drying procedure according to sealer types is a critical step and should not be missed in endodontic treatment.

• Economic and Environmental Geology
• /
• v.54 no.6
• /
• pp.709-716
• /
• 2021

In this study, an adsorbent prepared by natural drying of iron hydroxide-based sludge collected from settling basin at a mine drainage treatment facility located in Gangneung, Gangwon-do was used to remove fluoride in an artificial fluoride solution and mine drainage, and the adsorption characteristics of the adsorbent were investigated. As a result of analyzing the chemical composition, mineralogical properties, and specific surface area of the adsorbent used in the experiment, iron oxide (Fe₂O₃) occupies 79.2 wt.% as the main constituent, and a peak related to calcite (CaCO₃) in the crystal structure analysis was analyzed. It was also identified that an irregular surface and a specific surface area of 216.78 m²·g^-1. In the indoor batch-type experiment, the effect of changes in reaction time, pH, initial fluoride concentration and temperature on the change in adsorption amount was analyzed. The adsorption of fluoride showed an adsorption amount of 3.85 mg·g^-1 16 hours after the start of the reaction, and the increase rate of the adsorption amount gradually decreased. Also, as the pH increased, the amount of fluoride adsorption decreased, and in particular, the amount of fluoride adsorption decreased rapidly around pH 5.5, the point of zero charge at which the surface charge of the adsorbent changes. Meanwhile, the results of the isotherm adsorption experiment were applied to the Langmuir and Freundlich isotherm adsorption models to infer the fluoride adsorption mechanism of the used adsorbent. To understand the thermodynamic properties of the adsorbent using the Van't Hoff equation, thermodynamic constants 𝚫H° and 𝚫G° were calculated using the adsorption amount information obtained by increasing the temperature from 25℃ to 65℃ to determine the adsorption characteristics of the adsorbent. Finally, the adsorbent was applied to the mine drainage having a fluoride concentration of about 12.8 mg·L^-1, and the fluoride removal rate was about 50%.

• Bangmulgwan gwa yeongu (The National Museum of Korea Journal)
• /
• v.1
• /
• pp.36-73
• /
• 2024

The Tomb of Jang Mui located in Bongsan-gun, Hwanghae-do Province has attracted much attention since its first investigation due to the inscribed bricks found there that have allowed the guessing of the name and official title of its occupant and construction date. Inscriptions on these bricks, such as the "Prefect of Daebang Commandery Jang Mui" and the "Mu" (戊, the fifth sign of the Chinese calendar), and "Sin" (申, the ninth sign of the Chinese zodiac), have become the basis for believing the location of the government office of Daebang Commandery to be in Bongsangun, Hwanghae-do Province rather than somewhere in the Hangang River region. From the early days of its investigation, the tomb was suggested as historic remains of the Daebang Commandery along with the Earthen Fortress in Jitap-ri. Inscribed bricks excavated from the Tomb of Jang Mui were featured in several books and articles in the form of photographs and rubbings, leading to a vast body of studies on its construction period and the characteristics of its occupant that drew upon interpretations of the inscriptions. However, the inscribed bricks themselves were not publicly available outside those held in the collection of the University of Tokyo, making it difficult to expect consistent research findings on the types of inscribed bricks and their contents. Following previous studies re-examining the structure of the tomb and the materials used for its construction, most scholars dated the Tomb of Jang Mui to 348, a period after the collapse of Daebang Commandery. However, there is still a lack of adequate examination of the bricks, which account for the majority of the artifacts excavated from the tomb. Among the bricks excavated from most brick chamber tombs, including the Tomb of Jang Mui, only those with inscriptions or designs have been collected. Moreover, among these, only those with inscriptions or designs on the stretcher faces have been documented. Accordingly, the bricks themselves have been notably understudied. This paper intends to reorganize the contents of the inscriptions on eleven types (out of sixty-one pieces) of bricks in the collection of the National Museum of Korea, which make up the majority of the bricks excavated from the Tomb of Jang Mui. It also classified them according to their shapes. Furthermore, it examined the bricks from the Tomb of Jang Mui as architectural materials by focusing on their production techniques, including their forming, drying, and firing. Taking a more specific approach, it then compared the results to other bricks from the second century through the fourth century: those from the brick chamber tombs of the Nangnang and Daebang Commanderies and those from the brick chamber tombs built after Nangnang and Daebang Commanderies were ousted. The examination of bricks from the Tomb of Jang Mui has revealed that these bricks were basically produced using the brick manufacturing techniques of Nangnang, but they incorporated new elements found in bricks from brick chamber tombs or brick-and-stone chamber tombs constructed around the mid-fourth century in terms of their size, the use of lime, and the number of inscribed bricks. This supports the prevailing view that the date of the construction of the Tomb of Jang Mui is 348. The Tomb of Jang Mui sustained the existing brick chamber tomb burial tradition, but its ceiling was finished with stone. It demonstrates a blending of the brick chamber tomb practice of the Nangnang and Daebang Commanderies by using bricks produced based on related techniques, but with new elements such as the addition of a lime layer to the bricks. This fusion reflects the political circumstances of its time, such as the expulsion of the Daebang Commandery and the advance of the Goguryeo Kingdom, leading to diverse interpretations. Given archaeological evidence such as the structure, materials, and location of the tomb, the Tomb of Jang Mui appears to be highly related to the Goguryeo Kingdom. However, the forms of the inscribed bricks and the contents of the inscriptions share similarities with brick chamber tombs constructed during the third and fourth centuries in the Jiangsu and Zhejiang regions in China. Further studies on whether the use of lime was an influence from Goguryeo or a continuation of the Daebang tradition and a comparative examination with contemporaneous stone ceiling tombs will provide a more refined understanding of the Tomb of Jang Mui.

• Korean Journal of Animal Reproduction
• /
• v.24 no.1
• /
• pp.1-18
• /
• 2000

Eighty dairy farms in Palmers ton North area in New Zealand were surveyed on 1) general characteristics (10 Questions), 2) milk yield and feed supplementary (7 questions), 3) reproductive efficiencies (12 questions) and 4) reproductive disorders (12 questions) by mail questions from February to July, 1998. Among those 4 items from 38 dairy farms (47.5%), especially in items 1) and 2), overall dairy farming situation, supplementary feeding and milk yields were surveyed and analyzed for Korean dairy farmers (especially in Cheju island) to have better understanding or higher economical gains. The results were as follows. 1. In dairy experience, 21 (45%) among 38 dairy farms surveyed were answered that farming less than 15 years, 15~19 year, 20~25 years and over 26 years experience were 3 (7.9%), 7 (18.4%), 6 (15.8%) and 5 (13.2%) which generally showed longer experience compare to Korean dairy farming situation. In survey of labour input and business goal of dairy farming, self-managing farms, sharemilkers, unpaid family manpowering farms, manager running farms, farms with hired worker, farms with part time helper and other type was 21 (55.3%), 10 (26.3%), 2 (3.5%), 3 (5.3%), 18 (31.6%), 2 (3.5%), and 1 (1.8%), respectively. 2. Analyzing pasture and tillable land, pasture according to feeding scale (200, 300 and 400 heads) were 56, 90 and 165.3 ha, and tillable lands were 51, 78 and 165 ha which showed some differences among feeding scale. In recording methods in 38 farms replied, 36 (95%) dairy handbook and 23 (70%) dual methods taking farms were higher than that of 10 (26.3%) computer and 15(39.5%) well-recorder methods. 3. Dairy waste processing facilities in environmental field were almost perfect except of metropolitan area, and so no problem was developed in its control so far. Hence, 26 farm (68.4%) of pond system was higher rather than those in 8 (21.2%) of using as organic manure after storing feces of dairy cattle, 1(2.6%) bunker system and 3 (7.9%) other type farms. 4. In milking facilities, 33 farms (86.9%) of Harringbone types were higher than those in 3 (7.9%) of Walkthrough types, 1 (2.6%) of Rotary system and other types. Although the construction facilities was not enough, this system show the world-leveled dairy country to attempted to elevate economic gains using the advantage of climatic condition. 5. In milking day and yearly yield per head, average 275 milking days and 87 drying days were longer than that of 228 average milking days in New Zealand. Annual total milk yield per head and milk solid (ms) was 3,990 kg and approximately 319 kg. Dairy milk solid (ms) per head, milk yield, fat percentage was 1.2 kg, 15.5 kg and average 4.83% which was much higher than in other country, and milk protein was average 3.75%. 6. In coclusion, Palmerstone North has been a center of dairy farming in New Zealand for the last 21 years. Their dairy farming history is 6~9 year longer than ours and the average number of milking cows per farm is 355, which is much greater than that (35) of Korea. They do not have dairy barn, but only milking parlors. Cows are taken care of by family 0.5 persons), are on a planned calving schedule in spring (93%) and milked for 240~280 days a year, avoiding winter. Cows are dried according to milk yield and body condition score. This management system is quite different from that of Korean dairy farms. Cows are not fed concentrates, relying entirely on pasture forages and the average milk yield per cow is 3,500 kg, which is about 1/2 milk yield of Korean dairy farms. They were bred to produce high fat milk with an average of 4.5%. Their milk production cost is the lowest in the world and the country's economy relies heavily on milk production. We Korean farmers may try to increase farming size, decreasing labor and management costs.