• E2M - 전기 전자와 첨단 소재
• /
• 제9권1호
• /
• pp.18-23
• /
• 1996

The molding pressure is also one of the important parameters in the preparation of HTSC materials by the solid state reaction method. In the present study, changes in structural, electrical and microstructural proper-ties with the molding pressure in YiB $a_{2}$C $u_{3}$ $O_{70{\delta}}$ superconductors have been performed. The investigated molding pressures were 0.5*10$^{3}$ N/c $m^{2}$, 1*10$^{3}$ N/c $m^{2}$, 2*10$^{3}$ n/c $m^{2}$ and 4*10$^{3}$ N/c $m^{2}$. As the molding pressure increased, the anisotropy of the crystal structure decreased and the grains have been grown preferentially in a c-axis direction. Since the size of the grain becomes larger with the decrease of the porosity, denser textures are formed. The results indicated that the critical current density is improved resulting from the enhanced densification due to higher molding pressure. When the molding pressure was between 1*10$^{3}$ N/c $m^{2}$ and 2*10$^{3}$ N/c $m^{2}$, while it did not affect the oxygen deficiency and Tc, the increase of the molding pressure affects remarkably on grain size and densification of the $Y_{1}$B $a_{2}$C $u_{3}$ $O_{7-{\delta}}$. When the molding pressure is larger than 2*10$^{3}$ N/c $m^{2}$, electrical proper-ties are independent on the molding pressure..

• 한국표면공학회지
• /
• 제54권6호
• /
• pp.340-347
• /
• 2021

Among various metal oxide semiconductors, ZnO has an excellent electrical, optical properties with a wide bandgap of 3.3 eV. It can be applied as a photocatalytic material due to its high absorption rate along with physical and chemical stability to UV light. In addition, it is important to control the morphology of ZnO because the size and shape of the ZnO make difference in physical properties. In this paper, we demonstrate synthesis of size-controlled ZnO tetrapods using an atmospheric pressure plasma system. A micro-sized Zn spherical powder was continuously introduced in the plume of the atmospheric plasma jet ignited with mixture of oxygen and nitrogen. The effect of plasma power and collection sites on ZnO nanostructure was investigated. After the plasma discharge for 10 min, the produced materials deposited inside the 60-cm-long quartz tube were obtained with respect to the distance from the plume. According to the SEM analysis, all the synthesized nanoparticles were found to be ZnO tetrapods ranging from 100 to 600-nm-diameter depending on both applied power and collection site. The photocatalytic efficiency was evaluated by color change of methylene blue solution using UV-Vis spectroscopy. The photocatalytic activity increased with the increase of (101) and (100) plane in ZnO tetrapods, which is caused by enhanced chemical effects of plasma process.

• 농업과학연구
• /
• 제45권4호
• /
• pp.601-614
• /
• 2018

Chitosan with a natural antimicrobial property has been introduced to protect horticultural crops from diseases as an environmentally friendly method. The purpose of this study was to investigate the effects of the pre-harvest application of chitosan on growth and quality during the late stage of fruit development and on the simulated marketing of the peach fruit (Prunus persica L.). The application of chitosan with calcium chloride ($100mg{\cdot}L^{-1}$) three times at one week intervals 4 weeks before the harvest significantly increased the fruit weight, changed the fruit shape, and reduced the fruit length/diameter ratio giving the peach fruits a round oblate shape. The calcium treatment contributed to enhancing or maintaining the storage potential by increasing the flesh firmness. However, at higher concentrations of $CaCl_2$, i.e., > $600mg{\cdot}L^{-1}$, the positive effects of the chitosan application were offset, and fruit growth was not affected by calcium alone. The application of the chitosan/calcium mixture delayed fruit softening; however, this effect was shortened when the storage temperature was $20^{\circ}C$ rather than $15^{\circ}C$. The internal quality of the fruit was profoundly affected by the concentration of calcium added to the chitosan, and delayed fruit maturation was observed at a higher concentration of calcium. The pre-harvest application of chitosan with calcium contributes to the enhancement of food safety by inhibiting the occurrence of diseases during postharvest handling. Considering the above results, chitosan has the potential to improve both the yield of peach fruits and their storability. Because chitosan can enhance the freshness and shelf-life of fresh produce, it is necessary to examine its effects on other horticultural crops.

• 정보보호학회논문지
• /
• 제13권1호
• /
• pp.139-146
• /
• 2003

본 논문은 과포화 다변수 방정식을 이용하여 LILI-128 스트림 암호를 분석한다. LILI-128 암호$^{[8]}$ 는 128비트 키를 가진 선형귀환 쉬프트 레지스터 기반의 스트림 암호로 구조를 살펴보면 크게 “CLOCK CONTROL” 부분과 “DATA GENERATION” 부분으로 나뉘어진다. 분석 방법은 “DATA CENERATION” 부분에 사용되는 함수 \ulcorne $r^{d}$ 의 대수적 차수가 높지 못하다는 성질을 이용한다. 간략히 설명하면 차수(K)가 6차인 다변수 방정식을 많이 얻을 수 있고, 이를 7차 (D)의 다변수 방정식으로 확장하여 주어진 변수보다 많은 연립방정식을 얻어 그 해를 구하는 XL 알고리즘을 통해 전수조사보다 빠르게 키정보를 찾을 수 있다. 결과 중 가장 좋은 것은 출력 키수열 2$^{26.3}$비트를 가지고 2$^{110.7}$ CPU 시간을 통해 128비트 키정보를 얻는 것이다.다.

• 한국농공학회논문집
• /
• 제63권2호
• /
• pp.41-50
• /
• 2021

The asphalt pavement industry has introduced the warm-mix asphalt (WMA) as a mean of energy saving and environmentally safe technology, because the WMA mixture can be mixed and compacted at 30℃ lower than conventional hot-mix asphalt (HMA) at 160℃ or higher. The implementation of WMA can be a good option for paving operations for rural road in remote place, not only due to energy saving and environmental issues, but also lower working temperature. Using WMA technology, the cooled-down asphalt mixture can be still compacted to meet the quality requirement in narrow winding rural road in remote places. Therefore, this study is designed to evaluate engineering properties of WMA binders and concretes, which were prepared for rural road pavement. The objective of the study was to evaluate and suggest proper fundamental properties level of the WMA concrete for rural road pavement. The kinematic viscosity test result indicated that the WMA binders used in this study were effective for compaction at lower temperature, i.e., at 115℃, compared to the HMA binder. According to strength property analyses, it was found that the WMA concrete was acceptable for rural road pavement even though it was compacted at 30℃ lower level. Since the deformation strength (SD) of 3.2 MPa was found to satisfy rutting and cracking resistance minimum guidelines, this value was suggested as a minimum SD value for rural road pavement, considering lack of maintenance program for rural area.

• 소성∙가공
• /
• 제31권2호
• /
• pp.51-56
• /
• 2022

In this study, finite element analyses were performed by applying a stress ring and split die design to relieve the tensile stress acting on the die due to high surface pressure during warm-closed forging. The applied material was a yield-ratio-control-steel (YRCS). It was used without quenching or tempering after forging. In the case of stress rings design, the number of stress rings and the tolerance for shrink fit were different. Vertical and horizontal splits were applied for insert die split design. Case 5 die with three stress rings, 0.2 % shrink fit tolerance, and vertical split was selected as an effective die design for tensile stress reduction. Based on die stress reduction analyses, Case 5 die for warm-closed forging was produced and smooth forgeability was secured, making it possible to manufacture forging product of yoke with the required geometry. In addition, controlled cooling using warm forging heat was applied to secure mechanical properties of yokes. When oil cooling was used for direct controlled cooling after warm-closed forging, a relatively uniform Rockwell hardness distribution and high mechanical properties could be obtained.

• 한국축산식품학회지
• /
• 제42권5호
• /
• pp.800-815
• /
• 2022

This study aimed to obtain high Fischer's ratio oligopeptides from goat whey (HFO) and investigate antioxidant property of it. Hydrolysis of goat whey was done with the approach of sequential digestion of pepsin and flavourzyme. With the adsorption of aromatic amino acids by activated carbon, HFO with a Fischer's ratio of 27.070 and a molecular weight of 200-1,000 Da were obtained, and the branched-chain amino acids accounted for 22.87%. Then the antioxidant activity of HFO was evaluated. At the concentrations of 2.0 mg/mL and 0.50 mg/mL, HFO scavenged 77.27% and 99.63% of 1,1-diphenyl-2-picrylhydrazyl and 3-ethylbenzthiazoline-6-sulphonate free radicals respectively. The scavenging rate of HFO against hydroxyl radicals reached 92.31% at the concentration of 0.25 mg/mL. Animal experiments demonstrated that HFO could moderate the changes of malondialdehyde, superoxide dismutase and glutathione peroxidase caused by CCl₄-induced oxidative stress in vivo. This study indicated that HFO from goat whey was capable of oxidation resistance both in vivo and in vitro, which provided a scientific basis for the high-value processing and application of goat milk whey.

• Nuclear Engineering and Technology
• /
• 제54권12호
• /
• pp.4708-4714
• /
• 2022

The novelty in the present search, the Soda-Lime-Silica (SLS) glass waste to prepare free lead glass shielding was used in order to limit the accumulation of glass waste, which requires extensive time to decompose. This also saves on the consumption of pure SiO₂, which is a finite resource. Furthermore, the combining of BaO with Bi₂O₃ into a glass network leads to increased optical properties and improved attenuation. The UV-Visible Spectrophotometer was used to investigate the optical properties and the radiation shielding properties were reported for current glass samples utilizing the PhysX/PDS online software. The optical property results indicate that when BaO content increases in glass structure, the Urbach energy ΔE, and refractive index n increases while the energy optical band gap E_opt decreases. The result of the metallisation criteria (M) revealed that the present glass samples are nonmetallic (insulators). Furthermore, the radiation shielding parameter findings suggest that when BaO was increased in the glass structure, the linear attenuation coefficient and effective atomic number (Z_eff) rose. But the half-value layer HVL declined as the BaO concentration grew. According to the research, the glass samples are non-toxic, transparent to visible light, and efficient radiation shielding materials. The Ba5 sample is considered the best among all the samples due to its higher attenuation value and lower HVL and MFP values, which make it a suitable candidate as transparent glass shield shielding.

• Earthquakes and Structures
• /
• 제26권2호
• /
• pp.131-147
• /
• 2024

Damage caused by an earthquake depends on not just the intensity of an earthquake but also the region-specific construction practices. Past earthquakes in Asian countries have highlighted inadequate construction practices, which caused huge life and property losses, indicating the severe need to strengthen existing structures. Strengthening activities shall be proposed as per the proposed weighting factors, first at the higher weighted members to increase the capacity of the building immediately and thereafter, the other members. Through this study on gravity load-designed (GLD) buildings, relative weights are assigned to each storey and exterior and interior columns within a storey based on their contribution to the energy dissipation capacity of the building. The numerical study is conducted on mid-rise archetype GLD buildings, i.e., 4, 6, 8, and 10 stories with variable storey heights, in the high seismic zones. Non-linear static analysis is performed to compute weights based on energy dissipation capacities. The results obtained are verified with the non-linear time history analysis of 4 GLD buildings. It was observed that exterior columns have higher weightage in the energy dissipation capacity of the building than interior columns up to a certain building height. The damage in stories is distributed in a convex to concave parabolic shape from bottom to top as building height increases, and the maxima location of the parabola shifts from bottom to middle stories. Relative weighting factors are assigned as per the damage contribution. And the sequence for strengthening activities is proposed as per the computed weighting factors in descending order for regular RCC buildings. Therefore, proposals made in the study would increase the efficacy of strengthening activities.

• 지능정보연구
• /
• 제19권3호
• /
• pp.127-139
• /
• 2013

최근 지식기반 사회의 진입과 더불어 지식재산에 대한 관심이 증가하고 있다. 특히 하이테크산업을 이끌고 있는 ICT기업들은 지식재산의 체계적 관리를 위하여 끊임없이 노력하고 있다. 기업의 지적 자본을 대표하는 특허정보가 지속적으로 축적됨에 따라 정량적인 분석이 가능해졌다. 특허정보를 통하여 특허수준부터 기업수준, 산업수준, 국가 수준에 이르기 까지 다양한 수준에서의 분석이 가능하다. 특허정보는 기술 현황을 파악하거나 성과에 미치는 영향을 분석하는데 활용되고 있다. 특허 인용 정보를 활용한 분석은 크게 두 가지로, 인용 횟수를 활용하는 인용지표 분석과 인용관계를 바탕으로 한 네트워크분석으로 나뉜다. 네트워크를 통한 분석은 지식 영향의 흐름을 나타내며, 이를 통하여 기술의 변화를 확인할 수 있을 뿐만 아니라 앞으로의 연구 방향을 예측할 수 있다. 네트워크를 활용한 분석 분야에서는 기업이 차지하는 네트워크상에서의 위치가 기업성과에 미치는 영향을 다각도에서 분석하는 연구가 진행되고 있다. 본 연구에서는 소셜네트워크분석 기법을 활용하여 특허 인용을 기반으로 한 기업 간의 네트워크를 도출하고 특허 인용 네트워크에서 차지하는 기업의 위치적 특성이 기업성과에 미치는 영향을 분석하였다. 이를 위해 미국 S&P500에 등록된 IT 및 통신서비스 기업 가운데 74개 기업을 표본으로 선정하였다. 소셜네트워크분석을 통하여 개별 기업들의 아웃디그리 중심성, 매개 중심성, 효율성(구조적 공백)을 측정하여 네트워크 상에서의 위치적 우위를 나타내는 독립변수로서 이용하였으며, 기업성과 변수로는 순이익을 사용하였다. 실증 분석 결과, 각각의 네트워크 지표는 기업성과인 순이익에 통계적으로 유의한 영향을 미치는 것으로 나타났다. 두 가지 중심성 지표는 기업성과에 정(+)의 영향을 미친 반면, 구조적 공백으로 인한 위치적 우위를 나타내는 효율성은 기업성과에 부정적(-)인 영향을 미치는 것으로 나타났다. 세 가지 네트워크 지표를 동시에 고려할 경우에는 매개 중심성만이 기업성과에 대해 통계적 유의성을 보였다. 분석 결과를 토대로 연구의 발견점을 토의하고 시사점을 논의하였다.