• Child Health Nursing Research
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• 제25권4호
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• pp.487-495
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• 2019

Purpose: We aimed to identify associations between the frequency of electronic cigarette (e-cigarette) use and smoking-related characteristics among adolescent smokers. Methods: We used data from the 14th Korea Youth Risk Behavior Survey. The participants were 3,722 smokers who had smoked cigarettes on at least one day during the past 30 days. The frequency of e-cigarette use was defined as the number of days that participants used e-cigarettes during the past 30 days, and was divided into four categories: 0, 1~2, 3~9, and ${\geq}10$ days. We used the $x^2$ test and multinomial logistic regression to examine the associations between the frequency of e-cigarette use and smoking-related characteristics. Results: Those who attempted to quit smoking, had used a heated tobacco product (HTP) at least once, or initiated e-cigarette use before middle school were more likely to use e-cigarettes for 3~9 days in the past 30 days. More frequent e-cigarette use (${\geq}10$ days) was associated with a higher frequency and greater amount of cigarette use, lifetime HTP use, and earlier initiation of e-cigarette use. Conclusion: Smoking-related characteristics differed by the frequency of e-cigarette use. Therefore, intervention programs targeting adolescent smokers should consider differences in smoking-related characteristics based on the frequency of e-cigarette use.

• 한국화재소방학회논문지
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• 제33권1호
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• pp.1-6
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• 2019

열중량 분석법(TGA)을 이용하여 소방용 합성수지 배관으로 사용되는 CPVC의 활성화 에너지를 측정하였다. 열중량 분석법을 이용한 활성화 에너지는 Kissinger method와 Flynn-Wall-Ozawa method를 이용하여 계산하였다. 활성화 에너지를 계산한 결과 Kissinger method에 의해 128.07 kJ/mol, Flynn-Wall-Ozawa method에 의해 145.60 kJ/mol로 나타났다. Kissinger method와 Flynn-Wall-Ozawa method에 의해 계산된 활성화 에너지의 차이는 해석 방법이 다르다는 점을 감안했을 때 큰 차이가 없다고 판단된다. 향후 가속열화을 이용한 열적 열화평가 및 공기오븐노화시험을 통한 CPVC의 연소특성을 시험하고, 수명을 예측하고자 한다.

• 실내환경 및 냄새 학회지
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• 제17권4호
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• pp.396-403
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• 2018

In this study, volatile organic compounds (VOCs) emitted from printing industries were analyzed, and an inorganic adsorbent, ${\gamma}-alumina$, was selected for the effective control of the VOC emissions. Printing processes commonly require inks, thinners, and cleaners, and they were mixed organic solvents containing aromatic compounds, ketones, and alcohols. Therefore, toluene, methyl ethyl ketone (MEK), and isopropyl alcohol (IPA) were selected as model compounds for this study. The adsorptive properties using ${\gamma}-alumina$ were determined for the model compounds. Both batch isotherm and continuous flow column tests demonstrated that the adsorption capacity of MEK and IPA was 3~4 times higher than that of toluene. The column test performed at an inlet toluene concentration of 100 ppm showed that an 80% breakthrough for toluene was observed after 3 hours, but both MEK and IPA were continuously adsorbed during the same time period. A numerical model simulated that the ${\gamma}-alumina$ could remove toluene at a loading rate of 0.4 mg/min only for a 4-hour period, which might be too short of a duration for real applications. Consequently, lifetime enhancement for ${\gamma}-alumina$ must be implemented, and ozone oxidation and regeneration would be feasible options.

• 대한금속재료학회지
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• 제46권10호
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• pp.652-661
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• 2008

Reduction of NOx in emission gas, improvement of engine efficiency, and extension of warranty period has made demands for developing materials more corrosively resistant to the inner-muffler environments or predicting the lifetime of materials used in muffler more precisely. The corrosion inside muffler has been explained with condensate corrosion mainly though thermal oxidation experiences prior to condensate corrosion. Hence, the aim of this study is to describe how the thermal oxidation affects the corrosion of stainless steel exposed to the inner-muffler environments. Auger electron spectroscopy and electrochemical tests were employed to analyze oxide scale and to evaluate corrosion resistance, respectively. Thermal oxidation has different role of condensate corrosion depending on the temperature: inhibiting condensate corrosion below $380^{\circ}C$ and enhancing condensate corrosion above $380^{\circ}C$. The low temperature oxidation causes to form compact oxide layer functioning a barrier for penetrating condensate into a matrix. Although though thermal oxidation caused chromium-depleted layer between oxide layer and matrix, the enhancement of the condensate corrosion in high temperature oxidation resulted from corrosion-induced crevice formed by oxide scale rather than corrosion in chromium-depleted layer. It was proved by aids of anodic polarization tests and measurements of pitting corrosion potentials. By the study, the role of high temperature oxidation layer affecting the condensate corrosion of stainless steels used as muffler materials was well understood.

• 한국재료학회지
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• 제31권6호
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• pp.331-338
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• 2021

Ti-Al-Si target and Cr-Si target are sputtered alternately to develop a multi-layered nitride coating on a steel mold to improve die-casting lifetime. Prior to the multi-layer deposition, a CrN layer is developed as a buffer layer on the mold to suppress the diffusion of reactive elements and enhance the cohesive strength of the multi-layer deposition. Approximately 50 nm CrSiN and TiAlSiN layers are deposited layer by layer, and form about three ㎛-thickness of multi-layered coating. From the observation of the uncoated and coated steel molds after the acceleration experiment of liquid metal injection casting, the uncoated mold is severely eroded by the adhesion of molten metallic glass. On the other hand, the multi-layer coating on the mold prevents element diffusion from the metallic glass and mold erosion during the experiment. The multi-layer structure of the coating transforms the nano-composite structured coating during the acceleration test. Since the nano-composite structure disrupts element diffusion to molten metallic glass, despite microstructure changes, the coating is not eroded by the 1,050 ℃ molten metallic glass.

• 한국정밀공학회지
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• 제14권2호
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• pp.58-65
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• 1997

Work rolls used in cold rolling mills must have outstanding wear resistance and very little plastic defor- mation. Thus, these rolls require a higher surface hardness and harding to a greater depth. To meet these requirements, the rolls, in general, have basic chemical composition of 0.7 to 1.0% carbon and 1.0 to 5.0% Cr(chromium), plus a small amounts of special elements, and are subjected to intensive water quenching and tempering at low temperature to provide a surface hardness of over 90 shore. This test results are as follows. Deflection and fracture load of 5% Cr material are than those of 3% Cr material and show flat curve from surface to subsurface. It will be clear that 5% Cr work roll has a superior resisti- bility against wear and abrasion comparing with 3% Cr work roll. The improvement of wear and abrasion in 5% Cr work roll will be achieved by the large amount of wpheroidal carbide. In grindability and polish, 5% Cr work roll will be a little inferior comparing with 3% Cr work roll.

• 마이크로전자및패키징학회지
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• 제25권2호
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• pp.25-30
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• 2018

Sn-Pb솔더는 그동안 자동차 전장품에서 많이 사용되어 왔다. 그러나 최근에 환경과 인체에 대한 유해성 때문에 end-of-life vehicle (ELV)과 같은 국제 환경 규제로 인하여 Pb의 사용이 금지되었다. 이러한 이유로 자동차 전장품을 위한 Pb-free 솔더링에 관한 많은 연구들이 보고 되어 왔다. 한편, 자동차의 연료 효율성과 공간 활용을 위하여 유연성과 경량의 특성을 가지는 플렉시블 기판이 자동차 전장품에 사용되고 있다. 자동차 전장품에 대한 Pb-free 솔더 접합부 특성에 관한 연구들이 많이 진행되었음에도 불구하고 자동차의 사용 환경을 고려한 플렉시블 기판 솔더 접합부에 대한 신뢰성 특성에 관한 연구는 아직 부족한 실정이다. 본 연구에서는 organic solderability preservative (OSP) 및 electroless nickel immersion gold (ENIG) 표면처리 된 플렉시블 기판 위 Sn3.0Ag0.5Cu, Sn0.7Cu, Sn0.5Cu0.01Al(Si) 세 가지 Pb-free 솔더 접합부에 대한 특성을 보고 하였다. 솔더 조성과 기판 표면처리에 따른 접합부의 특성 및 신뢰성을 비교 평가 하기 위하여 인장 강도 시험, 열 충격 시험과 반복 굽힘 시험을 진행 하고 그 결과를 분석하였다. OSP 표면처리 된 기판 접합부에 대한 반복 굽힘 시험 결과 세 종류의 솔더 접합부 모두 파괴는 솔더 내부에서 일어 났으며 Sn3.0Ag0.5Cu 솔더의 접합부에서 반복 굽힘 수명이 가장 길게 나타났다.

• Asian Pacific Journal of Cancer Prevention
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• 제13권1호
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• pp.195-198
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• 2012

To date, there was no controlled-study regarding awareness and knowledge of colorectal cancer in the Turkish population. We therefore designed a questionnaire consisting of items related to socio-demographic parameters, medical and family history and questions of awareness and knowledge about colorectal cancer for use in a descriptive cross-sectional study. An interviewer-administered technique was applied and 450 subjects were interviewed in the outpatient clinics at Near East University Hospital. Among all subjects, 337 were found to be eligible for the study group. Exclusion criteria were age below 18 years, any cancer history, family history of colorectal cancer, current colorectal problems, history of any diagnostic or therapeutic interventions for colorectal diseases. All participants stated that they heard about colorectal cancer. When asked about the lifetime risk of colorectal carcinoma, only 25.4% of women and 37.9% of men estimated correctly. Univariate analysis revealed that the total awareness score was significantly correlated with age, marital status, parenthood and fecal occult blood testing history. On multivariate analysis of independent predictors for awareness of colorectal cancer were found to be history of fecal occult blood testing, age and marital status were found to be the most important determinants. As a conclusion, opportunistic screening with fecal occult blood test by physicians from non-gastrointestinal specialties not only helps to reduce the mortality but also increases the awareness of colorectal cancer.

• 한국산학기술학회논문지
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• 제16권7호
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• pp.4398-4404
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• 2015

스테인리스 강판은 동적기계구조물을 제작하기 위한 구조용 재료로 널리 사용된다. 또한 이들을 일체화 시키는 방법으로 가스용접을 많이 사용하게 되는데 가스용접에는 다양한 종류에 의해 구조물을 일체화 시킨다. 따라서 부재와 부재를 연결하는 용접부에 대한 응력분포 및 피로강도평가는 구조물의 건전성 및 수명을 연구하는데 매우 중요한 요소가 된다. 그래서 본 연구에서는 피로시험에 의해서 얻어지는 ${\Delta}P-N_f$ 관계를 유한요소해석법에 의해서 최대주응력으로 ${\Delta}{\sigma}-N_f$ 관계로 나타내어 피로설계기준을 정하였고, 이 결과를 이용해서 확률론적 통계해석기법을 적용해서 가속식을 추정하여 임의의 목표수명을 예측할 수 있는 신뢰성설계기술기법을 제시하고자 하였다.

• 한국재료학회지
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• 제9권1호
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• pp.73-80
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• 1999

The effect of alloy compositions of the bond coating on the plasma sprayed-thermal barrier coatings was investigated. The performance of the coating composed of Rene80/NiCrAl/ZrO$_2$-CeO$_2$-Y$_2$O$_3$ and Rene80/CoNiCrAlY/ZrO$_2$-CeO$_2$-Y$_2$O$_3$was evaluated by isothermal and thermal cyclic test in an ambient atmosphere at 115$0^{\circ}C$. The failure of Rene80/NiCrAl/ZrO$_2$-CeO$_2$-Y$_2$O$_3$ coatings was occurred at the bond coating/ceramic coating interface while Rene80/CoNiCrAlY/ZrO$_2$-CeO$_2$-Y$_2$O$_3$ coating was failed at the substrate/bond coating interface after thermal cyclic test. The lifetime of Rene80/NiCrAl/ZrO$_2$-CeO$_2$-Y$_2$O$_3$coatings was longer than Rene80/CoNiCrAlY/ZrO$_2$-CeO$_2$-Y$_2$O$_3$coating. The oxidation rate of the NiCrAl bond coating examined by TGA was lower than CoNiCrAlY bond coatings. In summary, these results suggest that Rene80/CoNiCrAlY/ZrO$_2$-CeO$_2$-Y$_2$O$_3$system as thermal barrier coating be not suitable considering the durability of the coating layer for high temperature oxidation and thermal stress.