• Corrosion Science and Technology
• /
• 제20권3호
• /
• pp.152-157
• /
• 2021

Stainless steel is a metal that does not generate rust. Due to its excellent workability, economic feasibility, and corrosion resistance, it is used in various industrial fields such as ships, piping, nuclear power, and machinery. However, stainless steel is vulnerable to corrosion in harsh environments. To solve this problem, its corrosion resistance could be improved by electrochemically forming an anodized film on its surface. In this study, 316L stainless steel was anodized at room temperature with ethylene glycol-based 0.1 M NH₄F and 0.1M H₂O electrolyte to adjust the thickness of the oxide film using different anodic oxidation voltages (30 V, 50 V, and 70 V) with time control. The anodic oxidation experiment was performed by increasing the time from 1 hour to 7 hours at 2-hour intervals. Corrosion resistance according to the thickness of the anodic oxide film was observed. Electrochemical corrosion behavior of oxide films was investigated through polarization experiments.

• 생태와환경
• /
• 제55권3호
• /
• pp.221-230
• /
• 2022

침입외래식물의 확산은 서식지훼손 및 생물다양성 감소의 가장 중요한 원인 중 하나이며, 본 연구는 생태계교란식물 양미역취의 방제를 위한 기초자료를 확보하기 위해 수행되었다. 양미역취의 생장이 마무리된 10월 길이성장은 대조구 (199±19.96 cm), 1M6 (152±13.41 cm), 2M6U7 (54±3.17 cm), 2M6M7 (45±9.96 cm) 순으로, 양미역취 식물체의 1회 제거보다 2회 제거에서, 2회 제거는 예초/뿌리째뽑기보다 예초 2회 제거처리가 길이성장을 더 효과적으로 억제하는 것으로 나타났다(p<0.001). 식물체 제거에 따른 단위면적 당(m²) 평균밀도는 1M6 실험구 73개체로 대조구 61개체보다 높은 밀도가 관찰되었으며, 6M7실험구 31개체, 2M6U7 실험구 16개체 순으로 나타났다. 식물체 제거에 따른 평균 개화율은 대조구 97±5.77 (%), 1M6 실험구 77±5.77 (%), 2M6M7 실험구 30±10.00 (%), 2M6U7 실험구 0±0.00 (%) 순으로 나타났다(p<0.001). 식물체 제거에 따른 개화율은 지상부 제거 1회보다 2회가 효과적이고, 2회에서 예초와 뿌리째뽑기를 동시에 실시한 방법이 억제효과가 높은 것으로 나타났다. 따라서 가장 효과적인 양미역취 분포 억제방법은 2M6U7이었다.

• 한국세라믹학회지
• /
• 제44권3호
• /
• pp.152-156
• /
• 2007

Tungsten carbide powder was synthesized by SHS (self-propagating high-temperature synthesis). Except $WO_{3}$, each concentration of raw material ($WO_{3},\;Mg,\;NaCl,\;Na_{2}CO_{3},\;C$) was investigated. Final product was characterized by XRD and SEM. X-ray data demonstrated that the $NaCl+Na_{2}CO_{3}$ combined mixture has superiority in the WC formation process. Single phase and submicrometer WC powder was synthesized at the temperature below $1600^{\circ}C$. The role of sodium salts in combustion process was discussed, and chemical mechanism of WC formation was proposed. WC powder prepared by salt-assisted combustion synthesis has a size $0.2{\sim}3\;{\mu}m$ and low agglomeration degree.

• International Journal of Fluid Machinery and Systems
• /
• 제6권3호
• /
• pp.152-159
• /
• 2013

A two-dimensional Darrieus-type hydroturbine system, installed with a wear for flow streams such as small rivers and waterways, has been developed for hydropower utilization of extra-low head less than 2m. There are several problems such as flow rate change and flowing wastes to be solved for its practical use in natural flow streams. In the present study, at first, a design guideline in the case of overflow or bypass flow is shown by using simple flow model. Next, in order to avoid the unexpected obstacles flowing into the hydroturbine, an installation of waste screening system is examined. It is confirmed that the screen is effective with some amount of bypass flow rate, however the output power is remarkably deteriorated.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
• /
• pp.152-152
• /
• 2003

Hg$\sub$l-x/Cd$\sub$x/Te (MCT) was grown by hot wall epitaxy. Prior to the MCT growth, the CdTe (111) buffer layer was grown on the GaAs substrate at the temperature of 590$^{\circ}C$ for 15 min. When the thickness of the CdTe buffer layer was 5 $\mu\textrm{m}$ or thicker, the full width at half maximum values obtained from the x-ray rocking curves were found to significantly decrease. After a good quality CdTe buffer layer was grown, the MCT epilayers were grown on the CdTe (111) /GaAs substrate at various temperatures in situ. The crystal quality for those epilayers was investigated by means of the x-ray rocking curves and the photocurrent experiment The photoconductor characterization for the epilayers was also measured The energy band gap of MCT was determined from the photocurrent measurement and the x composition rates from the temperature dependence of the energy band gap were turned out

• 한국전기전자재료학회논문지
• /
• 제31권3호
• /
• pp.152-155
• /
• 2018

Ultrasonic wave technologies have been widely used in ultrasonic washing machines, ultrasonic surgery, ultrasonic welding machines, ultrasonic sensors, and medical instruments. Ultrasonic surgery can be realized through the cavitation effect of ultrasonic waves. In this study, piezoelectric ceramics were manufactured to achieve the optimum design of a piezoelectric vibrator in a handheld generator for ultrasonic surgery. The best specimen showed the excellent piezoelectric properties of kp＝0.624, Qm＝1,531, and $d_{33}=356pC/N$. Numerical modeling based on the finite element method was performed to find the resonance frequency, the anti-resonance frequency, and the displacement properties of the handheld ultrasonic generator. Maximum displacement was observed in the six-step piezoelectric vibrator at $6.36{\mu}m$.

• 한국정보처리학회:학술대회논문집
• /
• 한국정보처리학회 2017년도 춘계학술발표대회
• /
• pp.152-155
• /
• 2017

본 논문은 지역에 관심이 많은 사용자들이 실시간으로 모바일 웹페이지 형태의 뉴스를 제공 받을 수 있는 시스템을 설계하고 이를 제작하였다. 사용자는 실시간으로 본인이 위치한 지역을 대상으로 종합되어지는 뉴스를 모바일 웹페이지 형태의 오브젝트로 제공받는다. 본 연구를 통해 지역 관심도 향상 및 지역 개발 촉진 및 관광시설 피드백 활성화 효과의 기대가 가능하다.

• Journal of Species Research
• /
• 제6권spc호
• /
• pp.152-163
• /
• 2017

Four feather mite species, Grallobia fulicae (Trouessart, 1885), Grallobia gallinulae Gaud, 1968, Grallolichus proctogamus (Trouessart, 1885) and Megniniella gallinulae (Buchholz, 1869), previously unrecorded in South Korea are reported. Specimens of Grallobia fulicae and Grallolichus proctogamus were collected from the eurasian coot, Fulica atra in Cheongju-si. Grallobia gallinulae and M. gallinulae were found on the common moorhen, Gallinula chloropus in Yesan-gun. The genera Grallobia Hull, 1934, Grallolichus Gaud, 1960 and Megniniella Gaud, 1958 are new records for South Korea. Here, we provide illustrations and morphological descriptions of these four feather mite species as well as the partial sequences of the mitochondrial cytochrome c oxidase subunit I (COI) as DNA barcodes.

• 설비공학논문집
• /
• 제2권3호
• /
• pp.218-225
• /
• 1990

Studies on the performance of a heat pump using non-azeotropic refrigerant mixtures are done. In order to estimate the thermodynamic properties for the selected non-azeotropic refrigerant mixtures including R22/R152a, R22/R142b, R22/R114 and R13B1/R152a, Peng-Robinson equation of state is adopted. The pressure-enthalpy diagram and the temperature-entropy diagram are plotted for each refrigerant mixture. Considerations on the capacity modulation for the heat pump system using refrigerant mixtures are taken into. Results show that when the heating load varies, the possibility for the capacity modulation is found in the heat pump system using a compressor with constant volume flow rate. Under a constant heating capacity condition in the heat pump system, the coefficient of performance increases when the refrigerant mixtures are used. The volume flow rate decreases as the mass fraction of lower boiler increases in this case.

• 설비공학논문집
• /
• 제2권2호
• /
• pp.142-154
• /
• 1990

A theoretical cycle analysis has been performed for a basic heat pump, charged with non-azeotropic refrigerant mixtures, R22/R114 and R13B1/R152a. At first, a procedure is introduced to calculate thermodynamic properties simply and correctly, and the advantages of using refrigerant mixtures are discussed through the cycle analysis. It is shown that by using refrigerant mixtures in the heat pump, several improvements can be made. In comparison with conventional pure refrigerants, the application of refrigerant mixtures results in high reliabilities caused by the extension of the application limit, energetic improvements, and a continuous capacity control. From generalizing various results, the optimum compositions in refrigerant mixtures are also determined. The 30%/70% and 40%/60% compositions are selected for R22/R114 and R13B1/R152a, respectively.