• 열처리공학회지
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• 제25권5호
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• pp.227-232
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• 2012

Magnesium alloy have good physical properties such as good castability, good vibration absorption, high strength/weight ratios. Despite the desirable properties, the poor resistance of Mg alloy impedes their use in many various applications. Therefore, magnesium alloy require surface treatment to improve hardness, corrosion and wear resistance. Plasma Electrolytic Oxidation (PEO) is one the surface treatment methods to form oxide layer on Mg alloy in alkali electrolyte. In comparison with Anodizing, there is environmental process having higher hardness and faster deposition rate. In this study, the characteristics of oxide film were examined after coating the AZ31 Mg alloy through the PEO process. We changed concentration of sodium aluminate into $K_2ZrF_6$, KF base electrolyte. The morphologies of the coating layer were characterized by using scanning electron microscopy (SEM). Corrosion resistance also investigated by potentiodynamic polarization analysis. As a result, propertiy of oxide layer were changed by concentration of sodium aluminate. Increasing with concentration of sodium aluminate in electrolyte, the oxidation layer was denser and the pore size was smaller on the surface.

• 대한설비공학회지:설비저널
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• 제12권4호
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• pp.252-263
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• 1983

In the briquet-burning hot water boiler the $SO_x$-dew point is calculated and found to be between $130^{\circ}C\;and\;154^{\circ}C$. The corrosion rate depends on the surface temperature and the concentration of the condensate on the surface. The concentration of the condensate is decided acoording to the difference detween $SO_x$-dew point and the surface temperature. When the surface temperature is $80^[\circ}C$, the concentration of the condensate is also high (0.15N). Therefore the high concentration and high temperature promote the high corrosion rate of $14{\times}13^{-3}g/100cm^2{\cdot}hr$ on the SS41 material. On the other hand, when the surface temperatures are $60^{\circ}C\;and\;40^{\circ}C$, the concentrations and the co..sion rates are reduced dramatically to $0.11\;N,\;8.6{\tiems}10^{-3}g/100cm^2{\cdot}hr$ and $5{\tiems}10^{-4}g/100cm^2{\cdot}hr$ respectively.

• Korean Chemical Engineering Research
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• 제52권4호
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• pp.538-543
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• 2014

이산화지르코늄 표면에 흡착되는 금 입자의 분포 또는 그 반대 경우의 분포에 영향을 끼칠 수도 있는 정전기적 상호작용과 금 입자를 코팅한 Glutathione층의 표면물성을 규명하였다. 이를 위하여, 원자힘현미경(AFM)으로 Glutathione 층 표면과 이산화지르코늄표면 사이의 표면힘을 염 농도와 pH 값에 따라 측정하였다. 측정된 힘은 Derjaguin-Landau-Verwey-Overbeek(DLVO) 이론으로 해석되어 표면의 전하밀도와 포텐셜들이 정량적으로 산출되었다. 이 특성들이 염 농도와 pH에 대하여 나타내는 의존성을 질량보존의 법칙으로 기술하였다. pH 8 조건에서 실험으로 산출된 표면 특성의 염 농도 의존성은 이론적으로 예측했던 결과와 일치하는 것으로 관찰되었다. Glutathione 층의 표면이 이산화지르코늄 표면보다 높은 전하밀도와 포텐셜을 갖는 것이 발견되었는데, 이는 Glutathione 층의 이온화-기능-그룹에 기인한 것으로 생각된다.

• 청정기술
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• 제20권2호
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• pp.130-135
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• 2014

지르코니아 표면에 흡착되는 금 입자의 분포 또는 그 반대 경우의 분포에 영향을 끼칠 수도 있는 정전기적 상호작용과 금 입자를 코팅한 메르캡토파이러빅산(mercaptopyruvic-acid)층의 표면물성을 규명하였다. 이를 위하여, 원자힘현미경(atomic force microscope)으로 메르캡토파이러빅산층 표면과 지르코니아표면 사이의 표면힘을 염농도와 pH값에 따라 측정하였다. 측정된 힘은 derjaguin-landau-verwey-overbeek (DLVO) 이론으로 해석되어 표면의 포텐셜과 전하밀도들이 정량적으로 산출되었다. 이 특성들이 염농도와 pH에 대하여 나타내는 의존성을 질량보존의 법칙으로 기술하였다. pH 8 조건에서 실험으로 산출된 표면 특성의 염농도 의존성은 이론적으로 예측했던 결과와 일치하는 것으로 관찰되었다. 메르캡토파이러빅산층의 표면이 지르코니아 표면보다 높은 포텐셜과 전하밀도를 갖는 것이 발견되었는데, 이는 메르캡토파이러빅산 층의 이온화-기능-그룹에 기인한 것으로 생각된다.

• 한국환경과학회지
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• 제22권9호
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• pp.1213-1226
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• 2013

$PM_{10}$ concentration is related to the meteorological variables including to local and synoptic meteorology. In this study the $PM_{10}$ concentrations of Busan in 2007~2011 were analyzed and the days of yellow sand or rainfall which is more than 5 mm were excluded. The sections of $PM_{10}$ concentration were divided according to 10-quantiles, quartiles and 90-quantiles. The 90-quantiles of daily $PM_{10}$ concentration were selected as high concentration dates. In the high concentration dates the daily mean averaged cloudness, mean daily surface wind speed, daily mean surface pressure and PBL height were low and diurnal variation of surface pressure and daily maximum surface temperature were high. When the high $PM_{10}$ dates occurred, the west and south wind blew on the ground and the west wind blew strongly on the 850 hPa. So it seemed that long range transboundary air pollutants made effects on the high concentration dates. The cluster analysis using Hysplit model which is the backward trajectory was made on the high concentration dates. As a result, 3 clusters were extracted and on the short range transboundary cluster the daily mean relative humidity and cloudness were high and PBL height was low.

• Steel and Composite Structures
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• 제18권6호
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• pp.1479-1492
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• 2015

This study evaluated the localized stress condition of the real corroded deck surface of an orthotropic steel bridge because severe corrosion damage on the deck surface and fatigue cracking were reported. Thus, a three-dimensional finite element (FE) analysis model was created based on measurements of the corroded orthotropic steel deck surface to examine the stress level dependence on the corrosion condition. Based on the FE analysis results, it could be confirmed that a high stress concentration and irregular stress distribution can develop on the deck surface. The stress level was also increased by approximately 1.3-1.5 times as a result of the irregular corroded surface. It was concluded that this stress concentration could increase the possibility of fatigue cracking in the deck surface because of the surface roughness of the orthotropic steel bridge deck.

• 한국산업보건학회지
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• 제25권4호
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• pp.465-471
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• 2015

Objectives: An objective of this study is to apply a thermal image camera which shows various color according to temperature of indoor surface for estimating concentration of airborne fungi. Materials and Methods: While wall temperature were monitored by applying the thermal image camera, airborne bacteria as well as air temperature and relative humidity have been measured in lecture room and toilet of university for seven months. Results: Based on the results obtained from this study, the ranges of temperature and airborne fungi concentration were $20{\sim}24^{\circ}C$ and $20{\sim}400cfu/m^3 $ for red image, $17.5{\sim}20^{\circ}C$ and $35{\sim}150cfu/m^3$ for orange image, $15.5{\sim}17.5^{\circ}C$ and $25{\sim}650cfu/m^3$ for sky-blue image, and $13.5{\sim}15.5^{\circ}C$ and $50{\sim}200cfu/m^3$ for blue image, respectively. The color of indoor surface taken shot by thermal image camera showed consistent trend with temperature of indoor surface. There is, however, little correlation between color of indoor surface and airborne fungi concentration(p>0.05). Among environmental factors, relative humidity in indoor air showed a significant relationship with airborne fungi concentration(p<0.05). Conclusions: The more measurement data for proving statistically an association between color of indoor surface and airborne fungi concentration should be provided to easily estimate indoor level of airborne fungi.

• 한국환경과학회지
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• 제15권7호
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• pp.635-642
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• 2006

Present study evaluated the low-temperature destruction of n-hexane and benzene using mesh-type transition-metal platinum(Pt)/stainless steel(SS) catalyst. The parameters tested for the evaluation of catalytic destruction efficiencies of the two volatile organic compounds(VOC) included input concentration, reaction time, reaction temperature, and surface area of catalyst. It was found that the input concentration affected the destruction efficiencies of n-hexane and benzene, but that this input-concentration effect depended upon VOC type. The destruction efficiencies increased as the reaction time increased, but they were similar between two reaction times for benzene(50 and 60 sec), thereby suggesting that high temperatures are not always proper for thermal destruction of VOCs, when considering the destruction efficiency and operation costs of thermal catalytic system together. Similar to the effects of the input concentration on destruction efficiency of VOCs, the reaction temperature influenced the destruction efficiencies of n-hexane and benzene, but this temperature effect depended upon VOC type. As expected, the destruction efficiencies of n-hexane increased as the surface area of catalyst, but for benzene, the increase rate was not significant, thereby suggesting that similar to the effects of the re- action temperature on destruction efficiency of VOCs, high catalyst surface areas are not always proper for economical thermal destruction of VOCs. Depending upon the inlet concentrations and reaction temperatures, almost 100% of both n-hexane and benzene could be destructed, The current results also suggested that when applying the mesh type transition Metal Pt/SS catalyst for the better catalytic pyrolysis of VOC, VOC type should be considered, along with reaction temperature, surface area of catalyst, reaction time and input concentration.

• 지구물리
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• 제8권4호
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• pp.173-185
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• 2005

This study examines the relationships among sea ice concentration, surface air temperature, surface wind, and SST (Sea Surface Temperature) in Bransfield Strait to understand the climatic characteristics and its related sedimentary process there. In analyses of the monthly data, during the austral autumn (Mar., Apr., and May), the frequency of southeasterlies is correlated positively with the sea ice concentration and negatively with the surface air temperature, whereas that of northwesterlies is reverse. These relationships are explained by the process that the southeasterlies of the cold air from the Antarctic Continent affect the ocean current around Bransfield Strait. And then the ocean current makes the sea ice generated in the Weddell Sea drift into the strait. During the spring (Sep., Oct., and Nov.), sea ice concentration and surface air perature are closely correlated with the frequency of northwesterlies with warm air mass. In the some parts of the northern boundary region, the sea ice concentration in Bransfield Strait is positively correlated with the SST during the autumn and spring. Such relationship may rather propel the sea ice melting in proportion to the sea ice concentration during the autumn.

• Elastomers and Composites
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• 제33권1호
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• pp.27-36
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• 1998

The surface of wiper blade(W/B) rubber was chlorinated by chemical treatment method using the hydrochloric acid(HCI) and sodium hypochlorite(NaOCl). From the results of contact angle measurement, friction coefficient measurement, and ATR-IR spectra, the surface characteristics of chlorinated W/B rubber with time of chlorination were studied. Contact angles for W/B rubber with increasing time of chlorination and chlorine concentration were measured for the water and ethylene glycol. From the results, contact angle fell rapidly with increasing time of chlorination and chlorine concentration, reaching a constant value after about 10min. And the wettability of W/B rubber surface by means of chlorination has been improved. For an unchlorinated W/B rubber, the friction coefficient with time of chlorination decreased from 1.27 to 0.20~0.23 on full chlorination. As the results it was considered that abrasion resistance of W/B rubber surface has been also improved. The values of pH and $Cl^-$ ion concentration in a chlorine treatment solution decreased as the extent of chlorination of W/B rubber surface increased. From the results of ATR-IR spectra, it was observed that C=C double band of W/B rubber surface transformed into C-Cl band, but quantitative determination of the extent of chlorination was not feasible because of the complexity of chlorination reactions.