• International Journal of Oral Biology
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• 제36권3호
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• pp.123-128
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• 2011

The notion that dental amalgam is a potential source of mercury exposure remains a controversial issue. However, there are few epidemiological analyses that have addressed whether this occurs in children. We aimed in our current study to identify the relationship between dental amalgam filling surfaces and the blood mercury levels in a cohort of 711 South Korean children aged between 8-9 years. Oral examinations were conducted to detect the number of amalgam filling surfaces on the teeth of these individuals. Blood samples were also taken from these children to assess the levels of mercury accumulation in the body. The amalgam filling surfaces were classified into four groups based on their number: 0 (n = 368), 1-5 (n = 219), 6-10 (n = 89), and 11+ (n = 35). The blood mercury levels in the children with more than 10 amalgam surfaces was 0.47 ${\mu}g$/L higher on average than those with no amalgam surfaces after adjusting for the frequency of fish or seafood consumption, age, and gender (P < 0.05). We found from our data that a higher number of dental amalgam fillings correlated with a higher blood mercury level in Korean children. Further studies are needed to investigate whether these elevated mercury levels exert neurotoxic or nephrotoxic effects.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제31회 춘계학술대회
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• pp.159-165
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• 2000

In this paper the residual stresses on lubricated sliding surfaces were measured during break-in procedure and up to scuffing by the X-ray diffraction method. The cylinder-on-disk type tribometer was used with the line-contact geometry. Scuffing tests were done using a constant load. In the break-in procedure the loads were increased from very low values in several steps. It was found that the sliding surfaces with break-in represented relatively higher values of residual compressive stresses than those without break-in. The residual stresses below the surfaces showed the small amount of stress increases. The results of scuffing tests with and without break-in showed the same trends as break-in tests did. However, in case of tests with break-in procedure the stresses below the surfaces showed very large increases in the residual compressive stresses. From the tests of break-in and scuffing, it was found that the increases in scuffing lives were related with the increases of residual stresses on the lubricated sliding surfaces with break-in.

• 대한수학회보
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• 제51권3호
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• pp.911-922
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• 2014

In the present article we study a special class of surfaces in the four-dimensional Euclidean space, which are one-parameter systems of meridians of the standard rotational hypersurface. They are called meridian surfaces. We show that a meridian surface has a harmonic Gauss map if and only if it is part of a plane. Further, we give necessary and sufficient conditions for a meridian surface to have pointwise 1-type Gauss map and find all meridian surfaces with pointwise 1-type Gauss map.

• 분석과학
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• 제36권3호
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• pp.121-127
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• 2023

범죄 현장에서 혈액을 찾아 식별하는 것은 신원 확인 및 사건 재구성을 하기 위해 중요한 과정이다. 하지만, 혈액은 어둡거나 다양한 색상의 표면에서 육안으로 관찰하기 어려울 수 있다. Acidic hydrogen peroxide (AHP)는 최근에 발표된 혈액 증강 시약으로, 카메라의 장노출 기능을 사용하면 혈액을 높은 감도로 관찰할 수 있다. 그러나 어둡거나 다양한 색상의 표면에서 기존에 알려진 기법과 비교된 바는 없다. 이를 위해, 어둡거나 다양한 색상의 표면 8 종류에 혈흔족적을 남기고 UV나 IR을 비추면서 관찰/촬영하는 방법, alginate 전사법, leuco rhodamine 6G (LR6G), AHP를 적용하여 비교하였다. 그 결과, AHP는 UV 및 IR 촬영법보다 증강한 혈액과 표면의 contrast가 높았고, alginate 전사법과 달리 모든 표면에서 적용이 가능했다. 또한 LR6G와 마찬가지로 AHP 역시 어둡거나 다양한 색상의 표면에 부착된 혈액을 성공적으로 증강하였다.

• 전기화학회지
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• 제13권4호
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• pp.251-255
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• 2010

We report on the electrocatalytic reduction of hydrogen peroxide at nanoporous gold (NPG) surfaces. Various NPG surfaces with different surface structure were prepared by changing the conditions of electrodeposition for Ag-Au layers such as the concentration ratios of $KAu(CN)_2$ over $KAg(CN)_2$ and deposition charges. The effects of different electrochemical conditions on the electrocatalysis of $H_2O_2$ reduction were investigated. The NPG surfaces exhibited sensitive amperometric responses for $H_2O_2$ reduction, from which calibration plots with higher sensitivity than a bare Au surface were obtained.

• 전자공학회논문지S
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• 제34S권2호
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• pp.63-70
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• 1997

This paper proposes a new algorithm for recognizing polyhedral objects using a single 2-D image. It is base don a new representation scheme having two level hierarchey. In the lower level, geometrical features of each primitive surface are represented using their signatures and the variation of signature due to rotation is represented suing the rotation map. In the higher level, topological features are represented in the inter-surface description table(SDT). Based on the proposed representaton scheme, loer level database searched to find a matching primitive surface. The srotation map determines the degree of rotation as well as the matchness. If all surfaces in a test object find their matching primitive surfaces, its structural information is compared with the SDTs of object models. If primitive surfaces of a test object equal to tha tof certain model and satisfy inter-surfaces relationship in SDT, a test object is recognized as the model.

• Journal of the Korean Wood Science and Technology
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• 제24권4호
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• pp.87-92
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• 1996

When cutting 2.0cm-thick red oak and hard maple with an air-jet-assisted carbon-dioxide laser of 2kW output power, maximum feed speed at the point of full penetration of the beam decreased with increasing the angle between grain and cutting direction. Feed speed averaged 3.75 and 3.38 meters per minute for red oak and hard maple, respectively. Gray-level of laser-cut surfaces were analyzed by image analysis system. The highest gray level of laser-cut surface was obtained when red oak was cut parallel to grain by laser. Surface profiler was used to scan the sawn and laser-cut surfaces. Center line average roughnesses of laser-cut surfaces were higher than those of sawn surfaces. Scanning electron micrographs showed the cell walls which were melted by laser.

• Tribology and Lubricants
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• 제19권2호
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• pp.109-115
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• 2003

Nanotribological characteristics between a Si$_3$N$_4$ AFM tip and hydrophobic thin films were experimentally studied. Tests were performed to measure the nano adhesion and friction in both AFM (atomic force microscope) and LFM (lateral force microscope) modes in various .ranges of normal load. Plasma-modified thin polymeric films were deposited on Si-wafer (100). Results showed that wetting angle of plasma-modified thin polymeric film increased with the treating time, which resulted in the hydrophobic surface and the decrease of adhesion and friction. Nanotribological characteristics of these surfaces were compared with those of other hydrophobic surfaces, such as DLC, OTS and IBAD-Ag coated surfaces. Those of OTS coated surface were superior to those of others, though wetting angle of plasma-modified thin polymeric film is higher.

• 대한기계학회논문집
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• 제17권12호
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• pp.3083-3093
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• 1993

Friction and wear at ceramic coated surfaces of aluminum alloy were experimentally studied using a Ring-on-Block wear test machine. Ceramic materials coated on aluminum alloy surfaces were WC, CrC, $Al_{2}O_{3}$ by a plasma spray; and $Al_{2}O_{3}$,$Al_{2}SiO_{5}$, $Na_{2}B_{4}O_{7}$,$Na_{4}P_{2}O_{7}$, and $Al_{2}O_{3}-ZrO_{2}$ composite coating by an Anodic Spark Depositon. They were tested under the sliding wet contact and compared with aluminum alloys and steels. Test results showed that ceramic coated surfaces, in general, have better anti-wear property than those of aluminum alloys due to increase in the surface hardness ; however, they also showed higher coefficients of friction and changes in wear mechanisms, resulting in brittle fractures.

• Restorative Dentistry and Endodontics
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• 제21권1호
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• pp.218-226
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• 1996

This study was performed to evaluate the possibility of pulpal damage by measuring temperature change occured in dentin according to the thickness of dentin, the time of irradiation and the output of laser energy when the dentin surfaces were irradiated with Nd-YAG laser under water coolant and no water coolant. Sound upper and lower molar teeth were sectioned with 1mm, 1.5mm and 2mm thickness of dentin discs and divided into 4 groups by dentin thiness. 0.5 watt, 1 watt, 1.5 watt and 2 watt-energied beam of pulsed 10 p.p.s of Nd : YAG laser was applied respectively to dentin surfaces for 8 secs and 16 secs when water coolant is used or not.Ant then the temperature changes occurd in dentin were measured at opposite surfaces of laser-irradiated dentin surfaces with digital thermometer. The results were as follow. 1. When the amount of irradiated energy was same, the temperatue changes of dentin were higher as the thickness of dentin discs was thinner(p<0.01). 2. When the amount of irradiated energy and the thickness of dentins were same, The temperature changes of dentin were lower under water coolant than under no water coolant in all groups(p<0.01). 3. With the increase of time of irradiation, the temperature changes of Dentin became higher in all groups and were steeply increased at initial period of irradiation of laser. 4. Under the same thickness of dentin, the temperature changes of dentin became higher as irradiated energy was increased. These results suggest that when the beam of Nd : YAG Laser is irradiated to dential hard tissue, amount of irradiating energy, thickness of dentin, using water coolant must be considered in order to minimize thermal damage of the pulp.