• Ocean and Polar Research
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• v.36 no.2
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• pp.111-119
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• 2014

This study examined the spatial and temporal variation of dissolved inorganic radiocarbon in the East Sea. Five vertical profiles of radiocarbon values were obtained from samples collected in 1999 in three basins (Japan Basin, Ulleung Basin, Yamato Basin) of the East Sea. Radiocarbon values decreased from 63- 85‰ at the surface to about -50‰ with increasing depth (up to 2,000 m) and were nearly constant in the layer deeper than 2,000 m in all basins. Radiocarbon values did not show significant basin-to-basin differences in the surface and the bottom layers. In the intermediate layer (200-2,000 m), however, they decreased in the order of Japan Basin > Ulleung Basin > Yamato Basin, which is consistent with the suggested circulation pattern in the intermediate layer of the East Sea. Radiocarbon was found to have decreased at ~2%/year in the surface water of the East Sea. In contrast, in the interior of the East Sea, radiocarbon values have increased with time in all three basins. In the Central Water, the annual increase rate was about 3.3‰, which is faster than the rates in the Deep and Bottom Waters. The radiocarbon in the Deep and Bottom Waters had increased until mid-1990s, after which time it has been almost constant.

• Journal of Conservation Science
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• v.29 no.4
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• pp.437-444
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• 2013

We studied for the chemical characterizations of the charred residues obtained from the ancient potteries in the Proto-Three Kingdom period from archaeological sites in Joong-do, Chuncheon. Organic components of the charred residues were extracted and analysed using mass spectrometry and infrared spectroscopy. Lipid profiles from these samples were not identified in gas chromatography-mass spectrometry. Bulk stable isotope analyses of charred residues was used to infer an average values of the foods prepared. The average carbon isotope values (${\delta}^{13}C$) of the residues are $-14.7{\pm}2.8$‰ (ranging from -8.7‰ to -18.4‰, n=9), and nitrogen isotope values (${\delta}^{15}N$) are $6.2{\pm}1.1$‰ (ranging from -4.4‰ to -7.6‰, n=9). This is the first approach to analyse charred residues using stable isotopic method in Korea. Charred food residues on the interior surface of archaeological pottery can provide valuable information about pottery use and dietary habits of its population.

• Journal of Welding and Joining
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• v.14 no.3
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• pp.48-57
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• 1996

A study was made to examine the characteristics of base metal and stress relief cracking(SRC) of heat affected zone(HAZ) for HY-100 and Cu-bearing HSLA-100 steels. The Gleeble thermal/mechanical simulator was used to simulate the SRC/HAZ. The details of mechanical properties of base plate and SRC tested specimens were studied by impact test, optical microscopy and scanning electron microscopy. The specimens were aged at $650^{\circ}C$ for HSLA-100 steel and at $660^{\circ}C$ for HY-100 steel and thermal cycled from $1350^{\circ}C$ to $25^{\circ}C$ with a cooling time of $\Delta$t_${800^{circ}C/500^{circ}C}$=21sec. corresponds to the heat input of 30kJ/cm. The thermal cycled specimens were stressed to a predetermined level of 248~600MPa and then reheated to the stress relief temperatures of $570~620^{\circ}C$. The time to failure$(t_f)$ at a given stress level was used as a measure of SRC susceptibility. The strength, elongation and impact toughness of base plate were greater in HSLA-100 steel than in HY-100 steel. The time to failure was decreased with increasing temperature and/or stress. HSLA-100 steel was more susceptible to stress relief cracking than HY-100 steel under same conditions. It is thought to be resulted from the precipitation of $\varepsilon$-Cu phase by dynamic self diffusion of solute atoms. By the precipitation of $\varepsilon$-Cu phase, the differential strengthening of grain interior relative to grain boundary may be greater in the Cu-bearing HSLA-100 steel than in HY-100 steel. Therefore, greater strain concentration at grain boundary of HSLA-100 steel results in the increased SRC susceptibility. The activation energies for SRC of HSLA-100 steel are 103.9kcal/mal for 387MPa and 87.6kcal/mol for 437MPa and that of HY-100 steel is 129.2kcal/mol for 437MPa.

• The Journal of the Korea Contents Association
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• v.13 no.10
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• pp.427-433
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• 2013

The aim of this study was to evaluate the efficacy of bleached tooth with white toothpaste on the whitening effect, microhardness test. Forty-four human interior teeth were randomly assigned to two groups as follows: Group 1 was used general toothpaste as control, Group 2 exposed to white toothpaste at 3 times a day for 3 minutes. The total application time was 4 weeks. After each application, all tooth were washed with distilled water and immersed in artificial saliva. The color change and microhardness were measured using CIELab Color system and microhardness tester. The data were analyzed by student t-test, using SPSS 20.0 statistical computer program (SPSS Inc., USA). The overall color changes (${\Delta}E$) by white toothpaste have a capability of the whitening efficacy by factor of 2.3 times larger compared with general toothpaste. Moreover, the application of white toothpaste did not cause any microhardness reduction on enamel surface.

• Journal of Korea Water Resources Association
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• v.53 no.11
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• pp.951-960
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• 2020

This study investigates the adjustment processes of the rivers after weir removal through laboratory experiments. Delta upstream eroded rapidly by flow at the initial stage of the experiments and the knickpoint migrates upward. Moreover, the knickpoint moves fast upward on the condition of alternate bars. The head cutting in the bed is developed fast at the initial stage. However, the erosion speed in the bed decreases with time. The well developed alternate bars migrates with keeping their shape downstream, and the bars affect the channel downstream to adjust new environments after weir removal. Maximum scouring depth downstream and the migration speed decrease over time after removing the weir. The scouring depth in the channel without alternate bars migrates with speed. However, the depth in the channel with alternate bars migrates slow downstream. The channel with alternate bars, in turn, is adjusted well to the new equilibrium states. The maximum scouring depth migrates downstream with time, and the scouring depth and its migration speed decreases with time. The dimensionless maximum scouring depth decreases with the migration speed of dimensionless maximum scouring depth because the deeply scoured places capture the sediments from upstream and the migration speed is slow as the places are filled with them. The dimensionless maximum scouring depth is shallow as the dimensionless backfilling speed is high. The dimensionless maximum scouring depth decreases rapidly less than 5 of dimensionless backfilling speed. However, the depth decreases slow more than 5 of it.

• Journal of architectural history
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• v.32 no.3
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• pp.7-20
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• 2023

The compositions of ethnic groups in Macau vary with time. Prior to the opening of the port, the majority of the residents in Macau were Chinese people, including those living on land and at sea. After the port was opened, with the increase of Portugal businessmen and missionaries, the population was divided into Chinese people and foreigners (so-called 'Yiren' or 夷人 in Chinese). Chinese people living on land were mainly of Hakka, Fujian, and Cantonese descent. Those living at sea were referred to as 'Tanka People' (named 'Danmin' or 蜑民in Chinese). They lived on floating boats for their entire lives and were similar to the 'drifters' in Japan. Since modern times, many refugees from mainland China and Southeast Asia flooded into Macau due to warfare. The development of industrialization required a larger number of laborers, and some 'coolies' entered Macau in legal or illegal ways, making it a multi-ethnic city. However, the Tanka people were not considered a minority ethnic group under the national ethnic policy of 56 ethnic groups since they did not have an exclusive language and shared dialects in different regions. As the ports inhabited by Tanka people gradually restored foreign trade, the boats and stilt houses used by Tanka people were dismantled to expand the infrastructure area of the ports. Many Tanka people began to live on land and marry people on land, leading to the disappearance of the Tanka group in Macau. The fishing boats and stilt houses used by Tanka people have also disappeared, with only a few remaining in areas such as Pearl River Delta and Hong Kong. This paper examines the natural and social environment of Tanka people in Macau from the Ming and Qing dynasties to the Republic of China, as well as the adaptive changes they adopted for the aforementioned environment in terms of living space and architectural type, on the basis of summarizing the historical activities of Tanka people. Finally, this study provides a layout plan and interior structure of the most commonly used boat for Tanka people from the Ming and Qing dynasties to the Republic of China, with the use of CAD and other technical software, along with reference to written historical documentation, and provides a case study for further research on the architectural history of Macau's inner harbor cities, from anthropological and folklore perspectives.

• Economic and Environmental Geology
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• v.15 no.3
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• pp.123-154
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• 1982

Petrochemical, K-Ar dating, Sand Rb/Sr isotopes, metallogenic zoning, paleomagnetic and geotectonic studies of the Gyongsang basin were carried out to examine applicability of plate tectonics to the post-late Cretaceous igneous activity and metallogeny in the southeastern part of Korean Peninsula. The results obtained are as follows: 1. Bulgugsa granitic rocks range from granite to adamellite, whose Q-Ab-Or triangular diagram indicates that the depth and pressure at which the magma consolidated increase from coast to inland varying from 6 km, 0.5-3.3 kb in the coastal area to 17 km, 0.5-10 kb in the inland area. 2. The volcanic rocks in Gyongsang basin range from andesitic to basaltic rocks, and the basaltic rocks are generally tholeiitic in the coastal area and alkali basalt in the inland area. 3. The volcanic rocks of the area have the initial ratio of Sr^{87}/Sr^{86} varying from 0.706 to 0.707 which suggests a continental origin; the ratio of Rb/Sr changing from 0.079-0.157 in the coastal area to 0.021-0.034 in the inland area suggests that the volcanism is getting younger toward coastal side, which may indicate a retreat in stage of differentiation if they were derived from a same magma. The K_2O/SiO_2 (60%) increases from about 1.0 in the coastal area to about 3.0 in the inland area, which may suggest an increase indepth of the Benioff zone, if existed, toward inland side. 4. The K-Ar ages of volcanic rocks were measured to be 79.4 m.y. near Daegu, and 61.7 m.y. near Busan indicating a southeastward decrease in age. The ages of plutonic rocks also decrease toward the same direction with 73 m.y. near Daegu, and 58 m.y. near Busan, so that the volcanism predated the plutonism by 6 m.y. in the continental interior and 4 m.y. along the coast. Such igneous activities provide a positive evidence for an applicability of plate tectonics to this area. 5. Sulfur isotope analyses of sulfide minerals from 8 mines revealed that these deposits were genetically connected with the spacially associated ingeous rocks showing relatively narrow range of ${\delta}^{34}S$ values (-0.9‰ to +7.5‰ except for +13.3 from Mulgum Mine). A sequence of metallogenic zones from the coast to the inland is delineated to be in the order of Fe-Cu zone, Cu-Pb-Zn zone, and W-Mo zone. A few porphyry type copper deposits are found in the Fe-Cu zone. These two facts enable the sequence to be comparable with that of Andean type in South America. 6. The VGP's of Cretaceous and post Cretaceous rocks from Korea are located near the ones($71^{\circ}N$, $180^{\circ}E$ and $90^{\circ}N$, $110^{\circ}E$) obtained from continents of northern hemisphere. This suggests that the Korean peninsula has been stable tectonically since Cretaceous, belonging to the Eurasian continent. 7. Different polar wandering path between Korean peninsula and Japanese islands delineates that there has been some relative movement between them. 8. The variational feature of declination of NRM toward northwestern inland side from southeastern extremity of Korean peninsula suggests that the age of rocks becomes older toward inland side. 9. The geological structure(mainly faults) and trends of lineaments interpreted from the Landsat imagery reveal that NNE-, NWW- and NEE-trends are predominant in the decreasing order of intensity. 10. The NNE-trending structures were originated by tensional and/or compressional forces, the directions of which were parallel and perpendicular respectively to the subduction boundary of the Kula plate during about 90 m.y. B.P. The NWW-trending structures were originated as shear fractures by the same compressional forces. The NEE-trending structures are considered to be priginated as tension fractures parallel to the subduction boundary of the Kula plate during about 70 m.y. B.P. when Japanese islands had drifted toward southeast leaving the Sea of Japan behind. It was clearly demonstrated by many authors that the drifting of Japanese islands was accompanied with a rotational movement of a clock-wise direction, so that it is inferred that subduction boundary had changed from NNE- to NEE-direction. A number of facts and features mentioned above provide a suite of positive evidences enabling application of plate tectonics to the late Cretaceous-early Tertiary igneous activity and metallogeny in the area. Synthesizing these facts, an arc-trench system of continental margin-type is adopted by reconstructing paleogeographic models for the evolution of Korean peninsula and Japan islands. The models involve an extention mechanism behind the are(proto-Japan), by which proto-Japan as of northeastern continuation of Gyongsang zone has been drifted rotationally toward southeast. The zone of igneous activity has also been migrated from the inland in late-Cretaceous to the peninsula margin and southwestern Japan in Tertiary.