• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.191-191
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• 2008

강유전성 세라믹스 재료로써는 PZT계열의 세라믹재료가 널리 쓰이고 있다. 이는 우수한 유전 및 압전특성을 가지고 있으나, PbO을 다량 함유하고 있어 $1000^{\circ}C$이상에서 PbO가 급격하게 휘발되는 성질 때문에 조성의 변동이 생겨 재현성이 어려우며 이를 방지하기 위하여 PbO를 과잉 첨가시키기 때문에 PbO휘발로 인한 강한 독성이 인체에 유해하고, 비환경 친화적인 물질로 최근에는 환경문제가 대두됨에 따라 대체 또는 보완 할 수 있는 방안에 검토되고 있다. 본 연구는 그 해결책의 한 방안으로 압전특성이 우수한 $(Pb_{0.94}Sr_{0.06})[(Ni_{1/2}W_{1/2})_{0.02}(Mn_{1/3}Nb_{2/3})_{0.07}(Zr_{0.51}Ti_{0.49})_{0.91}]O_3$계 조성을 설계하고 Glass frit(0~1.1 wt%)를 소량 첨가하여 액상 소결 특성을 부여하고 $1000^{\circ}C$ 이하의 저온에서 소결하여 유전 및 압전 특성을 평가하였다. 실험방법은 일반적인 세라믹스 제조공정으로 24시간 ball milling하고 $850^{\circ}C$에서 2시간 하소 후 Glass frit를 소결조제로 소랑 첨가하여 $1000^{\circ}C$ 이하 온도에서 소결을 진행하여 각 소결온도에 따른 유전 및 압전 특성을 평가하였다. 최종 소결된 시편의 밀도와 수축율을 분석하여 최적의 소결온도를 확립하였으며 XRD분석을 통해 perovskite구조를 확인하고 미세구조확인을 위해 SEM으로 관찰하였다. 압전 특성을 평가하였다.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.5
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• pp.315-323
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• 2008

To measure the mineral content of fishes, we collected 177 individuals from 53 fish species from the east (Pohang), west (Gunsan), and south (Tongyeong) coasts of Korea. The mean content of the macro mineral in a 100 g sample taken from the edible portion of each fish was (in descending order): P(207.4 mg), K(169.7 mg), Na(101.6 mg), Ca(44.4 mg), and Mg(30.4 mg). In comparison, the mean content of micro mineral in the fishes was (in descending order): Zn ($8.98{\mu}g/g$), Fe ($5.03{\mu}g/g$), Cu ($0.76{\mu}g/g$), Mn ($0.43{\mu}g/g$), and Ni ($0.08{\mu}g/g$). We could not observe clear regional variation in the mineral content of fish species. With regard to minerals considered essential for humans, the amount of Ca per sample (100 g) was the highest in the Scyliorhinus torazame (465.4 mg), and than followed by Ammodytes personatus (338.0 mg), Dasyatis akajei (267.4 mg), Raja kenojei (248.1 mg), Conger myriaster (174.1 mg), Clupanodon punctatus (86.8 mg), Muraenesox cinereus (81.2 mg), and Engraulis japonica (70.4 mg). The daily average intake of the mineral through the fishes consisted of P (100.6 mg), K (82.3 mg), Na (49.3 mg), Mg (14.8 mg), Zn (0.44 mg), Fe (0.24 mg), Cu (0.04 mg) and Mn (0.02 mg). The respective intakes of macro mineral (P, Mg, Na, Ca, K) from the fishes were about 14.4, 4.2, 3.3, 3.1 and 1.8% of the dietary reference intakes for Koreans (KDRIs) set by the Korean Nutrition Society. In comparison, the respective intakes of micro mineral (Cu, Zn, Fe, Mn) from the fishes were about 4.6, 4.4, 2.4, and 0.6% of the KDRIs.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.5
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• pp.649-655
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• 2013

During welding, the dissimilar metal butt welds of nuclear piping are typically subjected to repair welding in order to eliminate defects that are found during post-weld inspection. It has been found that the repair weld can significantly increase the tensile residual stress in the weldment, and therefore, accurate estimation of the weld residual stress due to repair weld, especially for dissimilar metal welds using Ni-based alloy 82/182 in nuclear components, is of great importance in order to assess susceptibility to primary water stress corrosion cracking. In the present study, the stress distributions of dissimilar metal butt welds in nuclear reactor piping subjected to repair weld were investigated based on detailed nonlinear finite element analyses. Particular emphasis was placed on the variation of the stress distribution in the dissimilar metal butt weld according to the finite element welding analysis sequence for the repair welding process.

• Economic and Environmental Geology
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• v.11 no.4
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• pp.169-182
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• 1978

The Weolagsan area consists of four units; (1) Low grade meta-sediments of the upper members of Ogcheon age unknown group such as Changri (mainly black slate and phyllitic rock), Majeonri (mainly alternation of slate, limestone and chert) and Hwanggangri Formation (pebble bearing phyllitic sediments); (2) Samtaesan Formation of Chosun System of Ordovician; (3) So called meta-volcanics and (4) Weolagsan Granite and its associations which intruded above mentioned meta-sediments and meta-volcanics. This study was focused to know the Woelagsan granite and its metasomatic effects to the country rocks petrographically and petrochemically. According to the field survey, microscopic work and some chemical analysis, the granite is a "normal granite" based on the Streckeisen's classification and belongs to a mass of the Central-zone younger group in Ogcheon geosynclinal belt. The granite metasomatized the country rocks along its northern contact zone. Zone of calcareous and cherty rocks (Majeonri formation) was silicified partly and skarned locally at the contact with the granite. The chemical analysis of the zone show no difinite variations in contents of $SiO_2$ and CaO with the distance from the granite. It seems to be indicated that the silicification of this part was not so metasomatized by the granite body, but thermally affected as much as to be partially remelted in the specific parts of the formations. Meta-volcanic rock zone was slightly chloritized near contact with the granite. Limestone of Samtaesan Formation was silicified and skarned along the contact zone by the granite body. The chemical analysis of the zone show some noticiable changes in compositions of $SiO_2$ and CaO with distance from the granite boundary. It can be imagined that the silicification of this zone was metasomatically originated by Woelagsan Granite. According to chemical analysis on several trace elements, the ratio of Zn/Cr and Ni/Cr are relatively higher than that of Cu/Cr in the above mentioned silicified zones. Generally the variation of these metal elements in the zones tend to be regular with distance from the granite body.

• Journal of Korea Water Resources Association
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• v.49 no.3
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• pp.207-215
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• 2016

In this study, it is analyzed how large scale climate variation has an effect on climate systems over Korea using correlation analysis between climate indices and Intrinsic Mode Functions (IMFs) of precipitation and temperature. For this purpose, the estimated IMFs of precipitation and temperature from the accompanying paper were used. Furthermore, cross correlation coefficients and lag time between climate indices and IMFs were calculated considering periodicities and tendencies. As results, more accurate correlation coefficients were obtained compared with those between climate indices and raw precipitation and temperature data. We found that the Korean climate is closely related with climate variations of $El-Ni{\tilde{n}}o$ in terms of periodicity and its tendency is followed with increasing sea surface temperature due to climate change.

• Natural Product Sciences
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• v.26 no.1
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• pp.50-58
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• 2020

The study was conducted for quantitive determination of macronutrients, micronutrients and heavy metals present in Spilanthes acmella Hutch and Dalz, a traditionally used important medicinal plant. The results illustrated the presence of substantial amounts of essential nutrient elements in different parts of the plant. K and Mg were detected in the range between 36.35 ± 1.01 to 67.78 ± 1.33 g/kg and 2.17 ± 0.13 to 7.02 ± 0.84 g/kg of DWS respectively. While the essential micronutrients Fe, Na, Mn, Zn and Cu were detected in the range between 62.62 ± 12.72 to 856.95 ± 76.61 mg/kg, 365.47 ± 23.84 to 633.03 ± 38.12 mg/kg, 51.66 ± 7.77 to 186.33 ± 13.92 mg/kg, 41.87 ± 2.85 to 53.89 ± 3.79 mg/kg and 18.49 ± 2.07 to 48.71 ± 4.89 mg/kg of DWS respectively. Besides, heavy metals (Cd, Ni and Pb) detected in some of the plant samples were beyond the maximum permissible limit (MPL) of FAO/WHO for herbal medicines. The concentrations of the essential nutrient elements except zinc were significantly different in different parts of the plant (p < 0.001). Further variation in the concentrations of the elements in the plant was observed with respect to seasonal changes and geographical conditions. Nevertheless the findings corroborate ethnomedicinal significance of the plant and signify the possibilibity of utilizing its standardized products for preparation of food supplements as well as multidimensional therapeutic herbal medicines.

• Journal of the korean society of oceanography
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• v.35 no.4
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• pp.179-191
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• 2000

Both acid-leached and residual Pb in surface sediments of the Yellow Sea are analyzed in order to explain the spatial distribution of Pb contents and to determine a major controlling factor of its geographical distribution. Leached and residual Pb contents in surface sediments, which may have a different origin, show mirrored geographical distribution. Sediments with high residual Pb ( ${\sim}$20 ${\mu}$g/g; northeastern sand) contain low leached Pb (6-8 ${\mu}$g/g) while sediments with high leached Pb ( ${\sim}$20 ${\mu}$g/g; central mud) contain low residual Pb. As a result, total Pb shows little variation spatially. The mirrored distribution of both species also leads the grain-size dependence of Pb contents to be unclear although the grain-size dependence of other trace metals (Cr, Co, Ni etc.) has been well reported in this shelf. High leached Pb contents (>15 ${\mu}$g/g) were also observed in sediments off the Changjiang River mouth and off the Kyunggi Bay where they can be interpreted as the results of diagenetic accumulation and anthropogenic pollution, respectively. Residual Pb enriched in sands of the northeastern area might be from K-feldspar, which in turn allows the suggestion that northeastern sands may have originated from coastal erosion of granitic landmass or directly from nearby rivers.

• 한국해양학회지
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• v.25 no.4
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• pp.189-204
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• 1990

In the KODOS (Korea Deep Ocean Study)-89 area, western part of clarion-Clipperton fracture zones in the northeastern equatorial Pacific, magnate nodules and sediments were sampled during the 'Farnella' cruise in Oct., 1989. Bulk chemical and mineralogical analyses have been made on a suit of ferromanganese nodules and sediments to study the origin and distribution pattern of the nodules. The nodules are classified into three groups based on their origin: diagenetic nodules with high Mn/Fe ratio, Cu, Ni, Zn, Mg, todorokite contents and rough surface texture; hydrogenetic nodules with high Fe, Co, vernadite contents and smooth surface texture; and transitional nodules with intermediate characters between diagenetic and hydrogenetic nodules. Study area is divided into four zones according to the origin and abundance of nodules: far north area where nodules are hydrogenetic and intermediate in abundance; north area where nodules are diagenetic and low in abundance; south area where nodules are diagenetic and intermediate in abundance; seamount area where nodules are hydrogenetic and high in abundance. distribution pattern of manganese nodules in the KODOS-89 area seems to be controlled by latitudinal variation of productivity in water column and sea bottom morphology.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.1
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• pp.28-40
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• 2015

This paper aims to address the intelligent active vibration control problem of a flexible rectangular plate vibration involving parameter variation and external disturbance. An adaptive sliding mode (ASM) MIMO control strategy and smart piezoelectric materials are proposed as a solution, where the controller design can deal with problems of an external disturbance and parametric uncertainty in system. Compared with the current 'classical' control design, the proposed ASM MIMO control strategy design has two advantages. First, unlike existing classical control algorithms, where only low intelligence of the vibration control system is achieved, this paper shows that high intelligent of the vibration control system can be realized by the ASM MIMO control strategy and smart piezoelectric materials. Second, the system performance is improved due to two additional terms obtained in the active vibration control system. Detailed design principle and rigorous stability analysis are provided. Finally, experiments and simulations were used to verify the effectiveness of the proposed strategy using a hardware prototype based on NI instruments, a MATLAB/SIMULINK platform, and smart piezoelectric materials.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.1
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• pp.23-32
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• 1999

Deposition is one of the important removal mechanisms for the ambient aerosol, and it also leads to adverse environmental and economic impacts. The purpose of this study was to investigate chemical compositions and spatial distributions of fall-out aerosols. A total number of 340 samples were collected at 35 sampling sites in Suwon area from January to November, 1996. Twelve inorganic elements (Al, Ba, Cd, Cr, K, Pb, Sb, Zn, Cu, Fe, Ni, and V) and eight ionic components ($F^-$, Cl, $NO_3^-$, $SO_4^{2-}$, $Na^+$, $NH_4^+$, $Mg^{2+}$, and $Ca^{2+}$) were analyzed by AAS and IC, respectively. The monthly variation showed that the flux of fall-out particles was increased in the spring season(March, April, and May) and decreased from August to October. Arithmetic mean flux of fall-out particles was 176.8 kg/$ extrm{km}^2$/day during the study period. The fluxes of each chemical species were $SO_4^{2-}$ 12.414, $Ca^{2+}$ 7.369, $NO_3^-$ 5.812, $Cl^-$ 3.566, $NH_4^+$ 3.176, Fe 3.107 kg/$\textrm{km}^2$/day, and so on. By using a kriging analysis, spatial distribution pattern of those fluxes was intensively studied. Total fluxes estimated in Suwon city were 8424.72t/y of fall-out particles, 519.27t/y of $SO_4^{2-}$, 336.79t/y of $Ca^{2+}$,267.34 t/y of $NO_3^+$, 155.36t/y of $Cl^-$, 147.79t/y of Fe.