• Corrosion Science and Technology
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• 제9권5호
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• pp.223-232
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• 2010

NiTi alloy has been used for orthodontic wire due to good mechanical properties, such as elastic strength, friction resistance, and high corrosion resistance. Recently, these wire were coated by polymer and ceramic materials for aesthetics. The purpose of this study was to investigate electrochemical characteristics of tooth colored NiTi wire using various instruments. Wires (round type and rectangular type) were used, respectively, for experiment. Polymer coating was carried out for wire. Specimen was investigated with optical microscopy (OM), field emission scanning electron microscopy (FE-SEM) and energy dispersive x-ray spectroscopy (EDS). The corrosion properties of the specimens were examined using potentiodynamic tests (potential range of -1500 ~ 2000 mV) and electrochemical impedance spectroscopy (frequency range of 100 kHz ~ 10 mHz) in a 0.9 % NaCl solution by potentiostat. From the results of polarization behavior, the passive region of non-coated NiTi wire showed largely, whereas, the passive region of curved NiTi wire showed shortly in anodic polarization curve. In the case of coated NiTi wire, pitting and crevice corrosion occurred severely at interface between non-coated and coated region. From the results of EIS, polarization resistance(Rp) value of non-coated round and rectangular NiTi wire at curved part showed $5.10{\times}10^5{\Omega}cm^2$ and $4.43{\times}10^5{\Omega}cm^2$. lower than that of coated NiTi wire. $R_p$ of coated round and rectangular NiTi wire at curved part showed $1.31{\times}10^6{\Omega}cm^2$ and $1.19{\times}10^6{\Omega}cm^2$.

• Corrosion Science and Technology
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• 제15권5호
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• pp.217-225
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• 2016

Linear polarization resistance (LPR) testing of soils has been used extensively by a number of water utilities across Australia for many years now to determine the condition of buried ferrous water mains. The LPR test itself is a relatively simple, inexpensive test that serves as a substitute for actual exhumation and physical inspection of buried water mains to determine corrosion losses. LPR testing results (and the corresponding pit depth estimates) in combination with proprietary pipe failure algorithms can provideauseful predictive tool in determiningthe current and future conditions of an asset. Anumber of LPR tests have been developed on soil by various researchers over the years1), but few have gained widespread commercial use, partly due to the difficulty in replicating the results. This author developed an electrochemical cell that was suitable for LPR soil testing and utilized this cell to test a series of soil samples obtained through an extensive program of field exhumations. The objective of this testing was to examine the relationship between short-term electrochemical testing and long-term in-situ corrosion of buried water mains, utilizing an LPR test that could be robustly replicated. Forty-one soil samples and related corrosion data were obtained from ad hoc condition assessments of buried water mains located throughout the Hunter region of New South Wales, Australia. Each sample was subjected to the electrochemical test developed by the author, and the resulting polarization data were compared with long-term pitting data obtained from each water main. The results of this testing program enabled the author to undertake a comprehensive review of the LPR technique as it is applied to soils and to examine whether correlations can be made between LPR testing results and long-term field corrosion.

• Clinical and Experimental Pediatrics
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• 제55권8호
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• pp.293-296
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• 2012

M$\acute{e}$n$\acute{e}$trier's disease is a rare form of acquired gastropathy characterized by giant rugal folds in the stomach and protein-losing gastropathy. Children with M$\acute{e}$n$\acute{e}$trier's disease tend to follow a benign self-limited course with symptoms typically completely resolving within 2 to 10 weeks in contrast to the chronic course in adults. A 9-year-old girl presented with a history of gradually worsening abdominal distension, increasing body weight, and abdominal pain for 2 weeks. Physical examination on admission indicated periorbital swelling, pitting edema in both the legs, and abdominal distension with mild diffuse tenderness and shifting dullness. Laboratory tests on admission showed hypoalbuminemia, hypoproteinemia, and peripheral eosinophilia. The test result for anti-cytomegalovirus immunoglobulin M was negative. Increased fecal alpha 1 anti-trypsin excretion was observed. Radiological findings showed massive ascites and pleural effusion in both the lungs. On gastroscopy, large gastric folds, erythema, erosion, and exudation were noted in the body and fundus of the stomach. Microscopic findings showed infiltration of eosinophils and neutrophils in the gastric mucosa. Her symptoms improved with conservative treatment from day 7 of hospitalization and resolved completely.

• 한국표면공학회지
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• 제48권6호
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• pp.329-334
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• 2015

The aim of this paper is to determine the proper heat treatment temperature for SDSS tube production without ${\sigma}$-phase precipitation. When Mother steel tube was heat treated at $800^{\circ}C$ temperature, relatively a large amount of ${\sigma}$-phase precipitated and grain refinement of ferrite phase occurred simultaneously. However, in Pilgered and Drawn steel tubes, grain refinement of the ferrite phase did not occur and a small amount of ${\sigma}$-phase precipitated. For all three types of steel tubes, the pitting potential was reduced to 2/5 or less compared with the untreated one and corrosion also occurred in the salt spray test due to the precipitation of ${\sigma}$-phase. When heat treatment temperature was $900^{\circ}C$, grain refinement of the ferrite phase occurred and very little ${\sigma}$-phase precipitated in Pilgered and Drawn steel tubes. But when heat treatment was done at $1,000^{\circ}C$ temperature, all three types of steel tubes had a similar corrosion properties of that of untreated one and also corrosion did not occur in the salt spray test, as ${\sigma}$-phase did not precipitate. Therefore, the optimum heat treatment temperature range is determined to be more than $1000^{\circ}C$ for the SDSS at which corrosion does not occur.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2018년도 춘계학술발표회
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• pp.52-52
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• 2018

Apple (Malus domestica) is one of the most economically important fruits in Korea. But virus infection has decreased sustainable production of apple and caused the serious problems such as yield loss and poor fruit quality. Virus or viroid infection including Apple chlorotic leaf spot virus (ACLSV), Apple stem pitting virus (ASPV), Apple stem grooving virus (ASGV), Apple mosaic virus (ApMV) and Apple scar skin viroid (ASSVd) has been also reported in Korea, furthermore, its damages and economic losses have increased constantly. In our research, we tried to survey virus infection for commercial nursery trees of major apple cultivars, especially dwarfing rootstocks 'M.9' and 'M.26' as well as scions. Trees were collected from 11 locations which have produced a great amount of apple nursery stocks in Korea. Infection degree was investigated in apple cultivars, 'Hongro' and 'Fuji' using RT-PCR method. In the scion of cultivar 'Hongro', infection ratio of ACLSV, ASPV and ASGV were 100%, 81.8% and 100% respectively. In the rootstock of cultivar 'Hongro', infection ratio of ACLSV, ASPV, ASGV and ApMV were 90.9%, 81.8%, 100% and 9.1% respectively. In the scion of cultivar 'Fuji', infection ratio of ACLSV, ASPV and ASGV were 81.8%, 90.9% and 100% respectively. In the rootstock of cultivar 'Fuji', infection ratio of ACLSV, ASPV, ASGV and ApMV were 81.8%, 90.9%, 100% and 9.1% respectively. Infection of ASSVd was not detected in both cultivars. From our results, it was found that most of apple rootstocks and scions had multiple infections by apple viruses which have caused economic damage in fruit production.

• Journal of Forest and Environmental Science
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• 제8권1호
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• pp.51-66
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• 1992

This study was carried out to investigate the micromorphology of vessel wall sculpture such as shape of perforation plate, perforation rim, steepness of perforation plate, occurrence of vestured pit, warty layer and ray-vessel pitting on 13 species of Fagaceae in Korea. The results were summarized as follows ; 1. In the species examined, all sample species except Fagus crenata var. multinervis have simple perforation plate. But Fagus crenata var. multinervis has simple and scalariform perforation plate (it was called to combination perforation plate) in a tree stem. 2. The shapes of perforation rim could be classified into five types; Type A without tail, Type B with small tail on both sides, Type C with long tail on both sides, Type D with tail only one side and Type E with the very short interval between perforations. Among five types, Type Band C have higer frequency of distribution than the others. 3. The steepness of perforation plate measured was about 20 degree on pore zone and 43 degree on outside parts of pore zone. 4. Species with vestured pit were Q. aliena, Q, dentata, Q. variabilis, Fagus crenata var. multinervis, Castanopsis cuspidata var sieboldii, Q. acuta, Q. stenophylla, and Q. glauca. But the extent of vesturing was very slight and vestured pits were observed mainly in ray-vessel pit of some vessel elements. 5. Species with warty layer on the inner surface wall of all vessel elements were Q. acuta, Q. stenophylla, Q. glauca, Fagus crenata var. multinervis and species with warty layer of some vessel elements were Q. aliena, Q, dentata, Q. variabilis, Castanopsis cuspidata var. sieboldii. 6. Species with palisade ray-vessel pit were Q. acuta, Q. stenophylla, Q. glauca, Castanea crenata, Castanea bungeana, Q. aliena, Q. serrata, Q. mongolica, and species with scalariform ray-vessel pit was Fagus crenata var. multinervis and species with oval ray-vessel pit were Q, dentata, Castanopsis cuspidata var sieboldii.

• 한국환경과학회지
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• 제14권7호
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• pp.675-681
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• 2005

A laboratory experiment was performed to investigate phosphorus and nitrogen removal from synthetic wastewater by intermittently aerated activated sludge process packed with aluminum and silver plate. Three continuous experi­mental processes, i. e. an intermittently aerated activated sludge process(Run A), an intermittently aerated activated sludge process with an aluminum and silver plate packed into the reactor(Run B), and a reactor post stage(Run C) were compared. In the batch experiments, the phosphorus removal time in the reactor packed with aluminum and silver plate simultaneously was faster than that of the reactor packed with only an aluminum plate. More phos­phorus was removed with an increase of NaCl concentration. The pitting corrosion of aluminum does not affect the performance of the biological treatment. The total nitrogen removal efficiency in Run B was $57\%\;and\;43.6\%$ at the HRT of 12 and 6 hours respectively. The effluent $PO_{4-}P$ concentration as low as 1.0 mg/L could be ob­tainable through the continuous experiment in Run B at HRT of 6 hours.

• 대한화학회지
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• 제53권5호
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• pp.485-490
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• 2009

0.1 M 중탄산소듐 용액에서 납전극부식에 대한 로소니아, 감초뿌리 및 카로브 추출물수용액의 부식방지작용에 대한것을 정전류극성방법을 사용해 연구하였다. 이들 물질들의 부식방지작용을 지적해주는 것으로 이들 물질들이 존재할 때 부식속도가 감소하는 것이 발견되었다. 부식방지효율은 추출물농도가 증가하면 증가한다. 이들 추출물의 부식방지작용은 납표면에 이들 추출물이 흡착되어 물질 및 하전이동의 장벽을 만들어 나타내는 것으로 설명되었다. 이들 추출물의 납표면에 흡착은 자발적으로 일어나며, Freundlich 등온흡착을 따르는 것으로 발견되었다. 또한, 변전위양극분극법을 사용해 이들 추출물은 염소를 포함한 용액에서 납의 움푹패이게 하는 부식으로부터 잘 보호해주는 것이 발견되었다.

• Corrosion Science and Technology
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• 제6권5호
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• pp.233-238
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• 2007

Due to the occasional occurrence of a localizedcorrosion such as a SCC and pitting in steam generator tubing(Alloy 600), leading to a significant economical loss, an effective repair technology is needed. For a successful electrodeposition inside a tube, many processes should be developed. Among these processes, an anode to be installed inside a tube, a degreasing condition to remove any dirt and grease, an activation condition for a surface oxide elimination, a strike layer forming condition which needs to be adhered tightly between an electroforming layer and a parent tube and a condition for an electroforming layer should be established. Through a combination of these various process condition parameters, the desired material properties can be acquired. Among these process parameters, various material properties including a mechanical property and its variation along with the height of the electrodeposit inside a tube as well as its thermal stability and SCC resistance should be assessed for an application in a plant. This work deals with the material properties of the Ni electrodeposits formed inside a tube by using the anode developed in this study such as the current efficiency, hardness, tensile property, thermal stability and SCC behavior of the electrodeposit in a 40wt% NaOH solution at $315^{\circ}C$. It was found that a variation of the material properties within the entire length of the electrodeposit was quite acceptable and the Ni electrodeposit showed an excellent SCC resistance.

• 대한치과보철학회지
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• 제37권2호
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• pp.256-268
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• 1999

Submerged implants require secondary surgical uncovering of implants after healing period of 3-6 months. In surgical methods, there are surgical scalpel, tissue punch, electro-surgical, and laser-used uncovering, and so forth The objectives of this study are investigation and assessment of 1) thermal change in clinical application for uncovering of HA-coated implant and pure titanium implant irradiated by pulsed Nd-YAG, $CO_2$, and Er-YAG laser. 2) surface change of cover screws aaer irradiation using laser energy. The temperature of apex & side wall of implants were recorded at 10sec, 20sec, 30sec after 30sec irradiation to implant healing screw; 1) pulsed Nd-YAG laser; 2W, 20pps, contact mode 2) $CO_2$ laser; water-infused & non-water infused state, 2.5-3.5W, contibuous mode, noncontact mode 3) $CO_2$ laser ; non-water infused state, 3W, superpulse, noncontact. mode 4) Er-YAG laser; (1) non-water infused state, 10pps, 60mj, contact mode (2) water-infused state, 10pps, 60mj, 80mj, 101mj, contact mode. According to the results of this study, pulsed Nd-YAG laser is not indicated because of increased thermal change and pitting of metal surface of implant cover screw. By contrast, $CO_2$ laser & Er-YAG laser are presumed to indicate because of narrow range of thermal change & near abscence of thermal damage of metal surface. Dental laser is thought to be much helpful to surgical procedure when it is used as optimal power and time condition considering characteristics and indications of each laser. Further research is needed to verify that these techniques are safe and beneficial to implant success.