• Structural Engineering and Mechanics
• /
• 제59권5호
• /
• pp.795-802
• /
• 2016

Gas pipelines are types of structures that are highly susceptible to corrosion. Sometimes, the pipes are subjected to a thinning of the wall thickness at the inside or outside wall due to erosion/corrosion. Therefore, it is important to evaluate the strength of the pipes undergoing corrosion to maintain the integrity of the piping systems. The main purpose of this study is to understand failure aspects caused by degradation of metal due to corrosion through. The ASME standard offers a relationship for the yielding pressure of the corroded pipes which was compared with the finite element results. The results demonstrate to obtain accurate results, the ASME relationship is unreliable. Moreover, pitting corrosion must be considered critical more than of other types.

• International Journal of Korean Welding Society
• /
• 제3권1호
• /
• pp.45-50
• /
• 2003

Welding using lasers can be mass-produced in high speed. In the laser welding, performing real-time monitoring system of the welding quality is very important in enhancing the efficiency of welding. In this study, the plasma and molten metal which are generated during laser welding were measured using the UV sensor and IR sensors. The results of laser welding were classified into five categories such as optimal heat input, little low heat input, low heat input, partial joining due to gap mismatch, and nozzle deviation. Also, a system was formulated which uses the measured signals with a fuzzy pattern recognition method which is used to perform real-time evaluation of the welding quality and the defects which can occur in laser welding.

• 환경영향평가
• /
• 제29권4호
• /
• pp.252-271
• /
• 2020

본 연구에서는 대불산업단지 내 14개 지점에서 채취한 도로먼지의 입도, 중금속 성분, 자기특성 등 물리 화학적 특성을 파악하고, 오염도 평가를 통해 주변 환경에 미치는 영향에 대한 고찰을 시행하였다. 도로먼지 내 금속농도는 Fe>Zn>Cu>Pb>Cr>Ni>As>Cd>Hg 순이었으며, 중금속류 오염은 연구지역의 주요 산업 및 교통 활동에 영향을 받은 것으로 나타났다. 도로먼지 내 중금속 원소와 입도와의 상관관계 분석결과는 Fe 및 모든 분석된 원소가 서로 유의한 상관관계를 가지며, 입자크기와는 유의한 음의 상관성을 가짐을 보여주었다(p<0.05). 그러나 큰 금속 입자들의 노면 유입으로 인해 일부 금속의 경우 >1000 ㎛의 입자의 중금속류 농도가 가장 높았으며, 이 분율의 단위면적당 오염부하량이 다른 입도분율보다 높았다. 도로먼지에서 자성입자의 분리 후 Cr, Ni, Cu, Zn, Cd, Pb의 농도 수준이 전체의 85(As)-22(Ni)%로 감소함을 알 수 있었다. 연구지역 도로먼지의 평균 중금속 오염도는 3지역 토양환경 우려기준을 초과하지 않아 우려할 수준은 아닌 것으로 나타났으나, 일부 지점의 경우 Zn 농도 기준을 초과해 재 비산이나 비점오염유출 등을 통해 도로먼지가 주변 환경에 미치는 영향과 효과적 관리방법에 대한 더욱 자세한 연구가 필요한 것으로 판단된다.

• 전기화학회지
• /
• 제22권2호
• /
• pp.69-78
• /
• 2019

리튬 금속 음극은 낮은 환원 전위, 고에너지 밀도로 인해 흑연을 대체할 차세대 음극재로 재조명 받고 있다. 하지만, 충방전시 리튬 금속 표면에서의 반복적인 산화/환원 반응에 의해 리튬 덴드라이트가 형성되며 이로 인해 수명특성이 급격하게 저하되고 더 나아가 내부 단락(Internal Short-circuit)과 같은 안전성 문제로 인해 상용화되기에는 어려운 실정이다. 이를 해결하기 위해 본 연구 그룹에서는 리튬 금속에 미세 패턴을 형성하여 전류 밀도를 제어함으로써 덴드라이트 형성을 제어하였으나, 고전류밀도에서는 리튬 덴드라이트의 형성을 완벽하게 제어할 수는 없었다. 본 연구에서는 미세 패턴화된 리튬 금속 전극에 전해질 첨가제 Vinylene Carbonate(VC)를 도입하여 고율 충방전 시 미세 패턴화된 리튬 금속 전극의 덴드라이트 형성 억제를 극대화하고자 하였다. 미세 패턴화된 리튬 금속 전극과 VC 첨가제의 시너지 효과로 인해 높은 전류 밀도에서의 리튬 덴드라이트가 비교적 치밀하게 형성되는 것을 확인할 수 있었다. 이로 인해 300사이클 동안 88.3%의 용량유지율을 보였으며, 기존의 미세 패턴화된 리튬 금속 전극에 대비하여 수명특성이 약 6배 이상 향상된 것을 확인할 수 있었다.

• 동아시아식생활학회지
• /
• 제16권6호
• /
• pp.717-723
• /
• 2006

Chemical characteristics of soybean oil after deep-frying with potato sticks (200 g, 10% w/w of soybean oil) were studied according to the 34 deep-frying times. After consecutive 34 deep-frying, total polyunsaturated FA contents was gradually decreased while the total saturated FA and trans FA were increased. Acid value and peroxide value were increased while iodine value decreased, respectively. The Hunter $L^{\ast}$ value decreased while each $a^{\ast}\;and \;b^{\ast}b$ value were gradually increased. Electronic nose equipped with 12 metal oxide sensors was used for the discrimination of odor pattern of frying oils against the times of deep-trying. The proportions of 1st and 2nd principal component analysis showed 75.97% and 21.23%, respectively. While 6 among total 12 sensors well responded to discrimination of odor in the repented frying oils, suggesting that the odor pattern of each oil after deep-frying would be discriminated against fresh soybean oil, especially after 14 times. From the results, electronic nose could differentiate the degree of quality deterioration of the repeated deep-frying oils.

• 대한기계학회논문집
• /
• 제17권8호
• /
• pp.2061-2068
• /
• 1993

Condition monitoring technology is of great importance for the maintenance of complex machinery in view of its early monitoring of the abnormal condition and the protection against failure. Several methods have been used for the detection of failure of journal bearings, one of the main elements of mechanical system. The methods most frequently used are vibration and temperature monitoring, but these are unable to monitor the wear conditions exactly. In this study, an ultrasonic measument method, one of the non-destructive testing methods, was introduced as the monitoring technology. Furtermore a pattem recognition method was applied to analyze the ultrasonic signal. The monitoring system using the pattern recognition method is composed of digital signal processing units and uses Hamming net algorithm for the recognition of ultrasonic waves. From the journal bearing wear test, the occurrence of adhesive wear of the white metal in rubbing contact with the shaft was exactly detected by this system, and the wear status of the journal bearing was monitored by measuring the wear thickness.

• 패션비즈니스
• /
• 제13권5호
• /
• pp.121-134
• /
• 2009

The purpose of this study was to analyze the wearing pattern and design preference of shoes for men, and to develop the possibility and strategy of the shoes market for the shoes marketers and manufacturers. In this study, the data obtained from 285 respondents were analyzed by the descriptive statistics. The results from the data were as follows : The most frequent brand among the 45 shoes brand by 285 respondents described in free style was 'Esquire'. The 268 respondents possessed two shoes or more, the most frequent shoes' color was black, and the most preferred brand was 'Kumkang'. The 195 respondents indicated the discomfort of ready-made shoes, The 198 respondents discarded their shoes 'on the reason of worn-out', the 98 respondents indicated that the most important thing in the purchasing point was 'the comfort of shoes' The respondents preferred shoes with 'slip-on type', 'cow leather', 'semi-rounded toe', 'no-metal ornaments', 'moccasin tip', 'leather-sole', and '3cm heel'. Finally, this study proposed that the best strategy for shoes marketers and manufacturers was to upgrade the comfort of shoes by design(line) and the material with functional textures.

• 동아시아식생활학회지
• /
• 제18권1호
• /
• pp.14-21
• /
• 2008

Flavor is one of the most important factors for determining wine characteristics and quality. Flavor pattern of wines(brewed from America, France, Italy, Chile, and Australia) was analyzed by the electronic nose that is equipped with 12 metal oxide sensors. In the results, the flavor pattern of wines was discriminated according to their origins by the principal component analysis(PCA). Each proportion of the first principal component score in the PCA plot was 94.79%(America), 73.62%(France), 99.06%(Italy), 96.74%(Chile), and 96.53%(Australia), respectively. Consequently, the imported wines could be practically differentiated into one from the other origins by volatile properties, suggesting that electronic nose could be successfully used for easy screening and quality evaluation of wines.

• Nuclear Engineering and Technology
• /
• 제47권1호
• /
• pp.115-125
• /
• 2015

Background: Residual stress always exists on any kind of welded area. This residual stress can cause the welded material to crack or fracture. For many years, the hole-drilling method has been widely used for measuring residual stress. However, this method is destructive. Nowadays, electronic speckle pattern interferometry (ESPI) can be used to measure residual stress with or without the hole-drilling method. ESPI is an optical nondestructive testing methods that use the speckle effect. Mechanical properties can be measured by calculation of the phase difference by the variation of temperature, pressure, or loading force. Methods: In this paper, the residual stress on the butt-welded area is measured by using ESPI with a suggested numerical calculation. Two types of specimens are prepared. Type I is made of pure base metal part and type II has a welded part at the center. These specimens are tensile tested with a material test system. At the same time, the ESPI system was applied to this test. Results: From the results of ESPI, the elastic modulus and the residual stress around the welded area can be calculated and estimated. Conclusion: With this result, it is confirmed that the residual stress on the welded area can be measured with high precision by ESPI.

• Transactions on Electrical and Electronic Materials
• /
• 제6권2호
• /
• pp.78-84
• /
• 2005

Standard crystalline solar cells are generally fabricated with the front grid pattern of silver paste contact. We have reported a detailed theoretical analysis of the proposed segmented cross grid line pattern in this paper. This work was carried out for the optimization of spacing and width of grid finger, main busbar and sub-busbar. The overall electrical and optical losses due to front contact were brought down to $10\%$ or even less as compared to the usual loss of $15\%$ or more in the conventional screen printed silver paste technology by choosing proper grid pattern and optimizing the grid parameters. The total normalized power loss for segmented mesh grid with plated metal contact was also observed and the total power loss could be brought down to $10.04\%$ unlike $11.57\%$ in the case of continuous grid and plated contact. This paper is able to outline the limitations of conventional screen printed contact.