• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.21 no.1
• /
• pp.11-15
• /
• 1988

Square slices of sea tangle was dried in constant condition of thickness (1.54mm), air temperature $(50^{\circ}C)$, relative humidity $(30\%)$ and air velocity (0.4m/s). The shrunk surface area and the shrinking rate were investigated. The results obtained are summarized as follows : 1) Comparing the shrinking of transverse section with that of vertical section, the transverse section was proceeded more double shrinkage than vertical section. 2) The shrunk surface area curve showed nearly a linear shrinkage up to 90min of drying time. 3) The shrinking rate was rapidly increased in first falling rate period, and was largest in the early period of second falling rate period.

• Journal of Welding and Joining
• /
• v.5 no.3
• /
• pp.46-52
• /
• 1987

The mechanism of transverse shrinkage for the butt joint weldig of plates is investigated in this paper. It was certified that the compressive plastic strain due to thermal expansion of materials during heating play an important role on the transverse shrinkage. It was also pointed out that the transverse shrinkage has to be treated with the samples of which the shapes are as close to real shapes of welded materials as possible, because the distribution of temperature and relative rigidity of materials during welding have great influence on the transverse shrinkage. The formulas for the calculation of transverse shrinkage were presented and the experiments were carried out in order to verify the formulas. the main results are as follows; 1. For the bead-on-plate welding, the transverse shrinkage in the begining parts of welding is the smallest, the end parts is next and the transverse shrinkage of mid section is the largest. 2. In bead-on-plate welding, the equations presented in this paper concerning transverse shrinkage coincide fairly well with the experimental values generally. 3. Transverse shrinkage increases generally as specific heat input per unit thickness increaes.

• Journal of Welding and Joining
• /
• v.6 no.1
• /
• pp.11-20
• /
• 1988

이 글에서는 Butt joint에서 발생되는 가로수축, 각변형 그리고 bowing의 관찰을 통해 mechanism을 서술하였고, box beam, damper blade, bulk head, ball tank, 그리고 cylindrical column 등 실구조물의 변형문제에 접근하여 변형예측, 측정 data제시, 그리고 그 해석을 통해 구조물의 변형 크기를 인식케 하고, 동일한 구조물의 제작에 guide가 되고자 하였다. 변형에 대해서는 일률적인 방지방법이 없기 때문에 우선은 구조물의 제작시마다 변형의 크기와 향상에 대한 예측과 함께 변형계측이 계속되어 data가 축적된다면 차후 그 이용 및 응용 효과는 지대할 것이다.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.36 no.1
• /
• pp.20-29
• /
• 2009

This study was performed to evaluate the effect of the shrinkage stress induced by polymerization process of several light curing filling materials according to filling methods. High power light curing unit which has a plasma arc lamp was used and filling materials used were Filtek $Z-250^{(R)}$ composite resin, $Dyract^{(R)}$ AP compomer and $Tetric^{(R)}$ Flow flowable composite resin. Cavities were prepared on the permanent molars with width 3 mm, height 3 mm and depth 1.5 mm and the filling materials were filled with 1 step, 2 step layering technique and 3 step oblique filling methods. The results can be summarized as follows; 1. Strain values showed rapid increase from the start of light curing followed by gradual decrease afterwards with time. 2. Although the shrinkage stress value of $Z-250^{(R)}$ were shown to be relatively higher than $Dyract^{(R)}$ AP and $Tetric^{(R)}$ Flow, no statistically significant could be found between tested materials(p>0.05). 3. There were no statistically significant difference between 3 filling methods when using $Dyract^{(R)}$ AP and $Z-250^{(R)}$(p>0.05). 4. There were no statistically significant difference between shrinkage stress values obtained from samples prepared by different filling methods and materials(p>0.05).

• Journal of Korean Society of Forest Science
• /
• v.108 no.3
• /
• pp.341-348
• /
• 2019

In order to reduce the safety risk of forestry operations, this research was conducted to examine the suitability of chainsaw protective pants after repeated laundering, testing four different products that are currently used in hand-held chainsaw operations. Laundering was repeated 10, 20, 30, 40, and 50 times. After washing, we measured the shrinkage ratio of 17 measurement positions mostly affecting the safety of forest operations and suggested the expected safety life cycle of chainsaw protective clothes. The results showed that most of the products have only one measurement position where the standard shrinkage ratio (<6%) was exceeded after 20 washings, and that the lateral direction of measurement positions shrank more than the vertical one. The numbers of repeated launderings and measurement positions were found to be significant factors influencing the shrinkage ratio (p<0.05). In the shrinkage rates for 17 measurement positions, there were significant correlations between five of the measurement positions (a, b, g, j, and n) and the number of repeated launderings (p<0.05). Therefore, the results suggest that about 10 months would be suitable for an adequate safety lifetime for chainsaw protective pants. The relationship between the number of repeated launderings and the measurement positions will be further analyzed in detail to examine the durability of chainsaw protective pants.

• Journal of the Korean earth science society
• /
• v.42 no.2
• /
• pp.185-194
• /
• 2021

A lava dome and sheet lava flow can be observed at the seashore of Aewol, Jeju island. The cylindrical lobes are characterized by a concentric structure consisting of a massive core and radial joints. Columnar joints with different thickness between the upper and lower parts are developed in the sheet lava flow around the rock salt field in Goeomri. The upper part of the columnar joints is uneven in shape, and has a diameter of 120-150 cm. The lower part of the columnar joints is hexagonal and pentagonal in shape, and has a diameter of about 60 cm. The cylindrical lobes can be divided into two groups based on size and shape. One is a megalobe, with a semicircular outline and a maximum diameter of 30 m. The other is a circular lobe with a diameter of less than 10 m. The columns in the radial joints have hexagonal and pentagonal cross sections and gradually increasing diameter, outward from the core, to a size of 80-120 cm at the rim. The concentric structure observed in the cylindrical lavas is attributable to a combination of four factors. The first is a circular crack caused by the decrease of the temperature and density difference between the inside and outside of the cylindrical lava flow. The second is a concentric chisel mark of the radial joints, which formed at the same time as the radial joints. The third is a flow band, which is a trace left in a round passage when lava flows through. The fourth is a vesicular band formed in a cave by gas bubbles escaping from the lava flow.

• Korean Journal of Animal Reproduction
• /
• v.25 no.2
• /
• pp.191-198
• /
• 2001

The purpose of this study was to investigate the effects of embryo sources such as in vivo vs. in vitro produced blastocyst, and culture systems on the membrane permeability and viability of bovine blastocyst following GMP vitrification. To produce in vivo embryos, six cows were superovulated by administration of follicle stimulation hormone (FSH) and prostaglandin $F_{2{\alpha}}$(PG $F_{2{\alpha}}$). in vitro embryos were produced by two different culture systems, oviduct co-culture (OCS) and defined culture system (HECM-6; DCS). Ovaries were picked up at a local slaughterhouse and transported to laboratory in 3$0^{\circ}C$ saline within 2 h. Ovaries were washed with same saline three times and then placed in saline on warm plate adjusted at 3$0^{\circ}C$ during aspiration. The blastocysts produced were assigned for membrane permeability and viability following GMP vitrification. The membrane permeability of blastocysts was checked in 0.5 M sucrose solution on warm plate at 35$^{\circ}C$ for 0, 2, 5 and 7 min, respectively. Then the diameters (width and length) of embryo cytoplasms were measured by a eyepiece meter, and they were converted to their volume by 4/3 $\pi$ $r^3$. The blastocysts were cryopreserved by GMP vitrification method, where they were sequentially placed into vitrification solution before being loaded into GMP vessels and immersed into L$N_2$ within 20 to 25 sec. Post-thaw blastocysts were serially washed in 0.25 and 0.15 M sucrose in HM and TCM-199 for 5 min each, and then cultured in TCM 199 supplemented with 10% FCS for 24 or 48 h. The volume change of in vivo blastocyst at 0, 2, 5 and 7 min (100, 37.1, 34.3 and 31.6%) was significantly more shrunk than those of in vitro blastocysts derived from OCS (100, 59.8, 48.9, 47.9%) and DCS (100, 57.2, 47.3 and 46.9%) (P＜0.05). The viability of post-thaw blastocyst derived from in vivo (93.6%) was also significantly different from those in OCS and DCS (81.9 and 83.6%; P＜0.05). In the present culture system, the morphology of embryos produced in vitro was similar to that of in vivo embryos, but the quality in membrane permeability and post-thaw viability showed a big difference from their sources as in vivo or in vitro derived from OCS and DCS. The results indicated that the quality of in vivo embryos in membrane permeability and post-thaw viability was better than those of in vitro embryos derived from OCS or DCS.

• Journal of the Korean Institute of Traditional Landscape Architecture
• /
• v.35 no.2
• /
• pp.1-14
• /
• 2017

The purpose of this study is to understand the environmental traits and significance of the pond place that appears in historic maps in 'Dongchon(東村)', which is the eastern section within the fortress wall of Hanyang. We reviewed various documents and maps to identify the name of the pond, and of those materials we followed the name provided by official national records and geographical titles to designate it 'Eouidongji Pond(於義洞池).' The results of the research showed, first, that from the standpoint of location and environmental characteristics, that the area of the Eouidongji Pond was an area that contained a pastoral atmosphere within the city. It was located in an area where the waters flowing from the mountains gathered, and the boundaries of the pond would change based on water levels within a plot of land about 2,000pyeong(app. $6,600m^2$) in size. Second, when seen from the perspective of its creation background, the Eouidongji Pond seems to have been a naturally occurring pond which was modified when the water system was managed in the city at the beginning of the dynasty. In addition to its role as a reservoir, it was operated as a lotus pond(蓮池) to offer lotus(蓮) related by-products. With the nearby detached palace being actively used, it seems the pond was managed at the same time. The pond had already been filled in by the early 20th century, and although there were efforts to reconstruct the pond, it was eventually destroyed as the area was included in the site of a school during the colonial period. Third, the Eouidongji Pond was appreciated in many cases by individuals or admired as part of the natural landscape by viewing it from afar. In addition, it provided entry landscape near the road entering Dongchon, and was a location that was easily visited in connection with other nearby pleasure grounds. Through studying the location and environmental characteristics, the background of its creation and destruction, operation and management by time period, usage at the time, and characteristics of scenery appreciation of Eouidongji Pond, the Eouidongji Pond was a pond of high practical value to the nation, as it supplemented the water system in the city and was able to provide lotus harvests for the nation. In addition, from a urban environment perspective, it was a lateral landmark with a large area, as well as an effective boundary. It was an open area that the people of the Hanseong-bu could freely use, and it had a high public value due to its ease of accessibility.