• 한국인터넷방송통신학회논문지
• /
• 제21권3호
• /
• pp.15-21
• /
• 2021

사회의 변화에 따라 범죄들의 수법들도 다양해지며 그 수도 증가하고 있다. 그리고 이러한 현상은 사람의 밀집도가 높은 곳일수록 더 높은 추세를 보인다. 이에 따라 많은 기관에서는 CCTV를 설치함으로써 범죄를 줄이고 결정적 증거를 제공해준다. 그럼에도 불구하고 아직 CCTV를 대상으로 한 영상 조작과 같은 범죄들에 대해서는 그 대처가 미약하다. 이러한 영상의 조작을 방지하기 위해 블록체인 기반의 CCTV 영상 무결성 기법들을 적용하고 있음에도 불구하고, 이들은 전체 영상의 조작 무결성만을 보장할 뿐 영상의 특정 구간이 어떻게 조작되었는지 설명해 주지 못한다. 따라서 본 연구에서는 이러한 문제를 해결하기 위해 블록체인을 기반으로 한 설명 가능 CCTV 영상 무결성 지원 시스템을 제안한다.

• 한국분말재료학회지
• /
• 제28권3호
• /
• pp.246-252
• /
• 2021

The effect of sintering conditions on the austenite stability and strain-induced martensitic transformation of nanocrystalline FeCrC alloy is investigated. Nanocrystalline FeCrC alloys are successfully fabricated by spark plasma sintering with an extremely short densification time to obtain the theoretical density value and prevent grain growth. The nanocrystallite size in the sintered alloys contributes to increased austenite stability. The phase fraction of the FeCrC sintered alloy before and after deformation according to the sintering holding time is measured using X-ray diffraction and electron backscatter diffraction analysis. During compressive deformation, the volume fraction of strain-induced martensite resulting from austenite decomposition is increased. The transformation kinetics of the strain-induced martensite is evaluated using an empirical equation considering the austenite stability factor. The hardness of the S0W and S10W samples increase to 62.4-67.5 and 58.9-63.4 HRC before and after deformation. The hardness results confirmed that the mechanical properties are improved owing to the effects of grain refinement and strain-induced martensitic transformation in the nanocrystalline FeCrC alloy.

• 대한금속재료학회지
• /
• 제46권11호
• /
• pp.747-754
• /
• 2008

Recently, the requirement for the ultra thin copper foil increases with smaller and miniaturized electronic components. Therefore, it is important to examine the surface state of substrate depending on the processing parameter during the anodic oxidation. This study investigated the effect of the various electrolyte concentrations on anodizing of titanium anode prior to copper electrodeposition. Different surface morphology of anodized titanium was obtained at different electrolytic concentration 0.5 M to 3.0 M. In addition, the effect that the surfaces and the electrical characteristics on the electrodeposited copper layer was observed. In this study, surface anodized in the group containing 0.5M $H_2SO_4$ shows more uniform copper crystals with low surface roughness. the surface roughness and sheet resistance for 0.5M $H_2SO_4$ group were $1.353{\mu}m$ and $0.104m{\Omega}/sq$, respectively.

• 대한금속재료학회지
• /
• 제47권9호
• /
• pp.586-590
• /
• 2009

The effects of additives on the surface morphology and physical properties of copper electrodeposited on polyimide(PI) film were investigated here. Two kinds of additives, an activator(additive A) and a leveler(additive B),were used in this study. Electrochemical experiments, in conjunction with scanning electron microscopy(SEM), X-ray diffraction(XRD) and a four-point probe, were performed to characterize the morphology and mechanical characteristics of copper electrodeposited in the presence of the additives. The surface roughness, crystal growth orientation and resistivity could be controlled using various quantities of additive B. High resistivity and lower peel strength were observed on the surface of the copper layer electroplated onto the electrolyte with no additive B. However, a uniform surface, lower resistivity and high flexibility were obtained with a combination of 20 ppm of additive A and 100 ppm of additive B.

• 한국분말재료학회지
• /
• 제28권3호
• /
• pp.221-226
• /
• 2021

We fabricate the non-equiatomic high-entropy alloy (NE-HEA) Fe_49.5Mn₃₀Co₁₀Cr₁₀C_0.5 (at.%) using spark plasma sintering under various sintering conditions. Each elemental pure powder is milled by high-energy ball milling to prepare NE-HEA powder. The microstructure and mechanical properties of the sintered samples are investigated using various methods. We use the X-ray diffraction (XRD) method to investigate the microstructural characteristics. Quantitative phase analysis is performed by direct comparison of the XRD results. A tensile test is used to compare the mechanical properties of small samples. Next, electron backscatter diffraction analysis is performed to analyze the phase fraction, and the results are compared to those of XRD analysis. By combining different sintering durations and temperature conditions, we attempt to identify suitable spark plasma sintering conditions that yield mechanical properties comparable with previously reported values. The samples sintered at 900 and 1000℃ with no holding time have a tensile strength of over 1000 MPa.

• 한국분말재료학회지
• /
• 제29권3호
• /
• pp.219-225
• /
• 2022

An alternative fabrication method for carburizing steel using spark plasma sintering (SPS) is investigated. The sintered carburized sample, which exhibits surface modification effects such as carburizing, sintered Fe, and sintered Fe-0.8 wt.%C alloys, is fabricated using SPS. X-ray diffraction and micro Vickers tests are employed to confirm the phase and properties. Finite element analysis is performed to evaluate the change in hardness and analyze the carbon content and residual stress of the carburized sample. The change in the hardness of the carburized sample has the same tendency to predict hardness. The difference in hardness between the carburized sample and the predicted value is also discussed. The carburized sample exhibits a compressive residual stress at the surface. These results indicate that the carburized sample experiences a surface modification effect without carburization. Field emission scanning electron microscopy is employed to verify the change in phase. A novel fabrication method for altering the carburization is successfully proposed. We expect this fabrication method to solve the problems associated with carburization.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제27권5호
• /
• pp.10-17
• /
• 2022

Inorganic acids such as HCl, HNO₃, and H₂SO₄ have been commonly applied to soil washing of heavy metals-contaminated soil due to their cost-effectiveness. However, implementing the 'Chemical Substance Control Act' requires off-site risk assessment of the chemicals used in the soil washing. Therefore, in this study, organic acids or Fe(III)-based washing agents were evaluated to replace commonly used inorganic acids. Ferric removed heavy metals via H⁺ generated by hydrolysis, which is similar to the HCl used in the control group. Oxalic acid and citric acid were effective to remove Cu, Zn, and Cd from soil. Organic acids could not remove Pb because they could form Pb-organic acid complexes with low solubility. Furthermore, Pb could be adsorbed onto the iron-organic acid complex on the soil surface. Ferric could remove exchangeable-carbonate, Fe-Mn hydroxide, and organic matter and sulfides bound heavy metals (F1, F2, and F3). Organic acids could remove the exchangeable-carbonate and Fe-Mn hydroxide bound metals (F1&F2). Therefore, this research shows that the fractionation of heavy metals in the soil and the properties of washing agents should be considered in the selection of agents in the process design.

• 한국분말재료학회지
• /
• 제29권5호
• /
• pp.399-410
• /
• 2022

Changes in the mechanical properties and microstructure of an IN 939 W alloy according to the sintering heating rate were evaluated. IN 939 W alloy samples were fabricated by spark plasma sintering. The phase fraction, number density, and mean radius of the IN 939 W alloy were calculated using a thermodynamic calculation. A universal testing machine and micro-Vickers hardness tester were employed to confirm the mechanical properties of the IN 939 W alloy. X-ray diffraction, optical microscopy, field-emission scanning electron microscopy, Cs-corrected-field emission transmission electron microscopy, and energy dispersive X-ray spectrometry were used to evaluate the microstructure of the alloy. The rapid sintering heating rate resulted in a slightly dispersed γ' phase and chromium oxide. It also suppressed the precipitation of the η phase. These helped to reinforce the mechanical properties.

• 동서간호학연구지
• /
• 제16권1호
• /
• pp.70-75
• /
• 2010

Purpose: Nursing students face constant threats of blood-borne infections such as HIV, Hepatitis B, and Hepatitis C during their clinical rotation period. This study was done to determine the frequency and risk of the exposure to blood and body fluids. Methods: The data was collected using a questionnaire. Ninety eight junior & senior nursing students were participated in this study. Results: 75.6% of the participants reported more than once during practicum. The exposure occurred most frequently while checking the blood glucose (65.3%). The general ward (45.3%) was the most frequent site for the occurrence of the exposure. However, only eight cases (10.7%) were reported to the medical or nursing personnel in charge. Conclusions: This study shows nursing students are in a great risk of the exposure to blood & body fluid. The risk is highest in the general ward during checking the blood glucose. Thorough education on preventive measures, should be provided to nursing students prior to clinical practium.

• 동서간호학연구지
• /
• 제29권1호
• /
• pp.68-77
• /
• 2023

Purpose: The purposes of this study were to develop a predictive model and evaluate this model of turnover in hospital nurses. Methods: Participants were 1,565 nurses from a tertiary hospital in South Korea. Descriptive statistics and a decision-tree analysis were performed using the SPSS WIN 23.0 program. Results: The turnover groups were presented in eleven different pathways by decision tree analysis. There were three high-risk groups with a higher turnover rate than the average, and eight low-risk groups with a lower turnover rate. Among them, two low-risk groups had a 0% turnover rate. The groups were classified according to general characteristics such as position, period of temporary position, clinical career at last working unit, total clinical career, and period of leave of absence. The accuracy of the model was 83.2%, sensitivity 63.7%, and specificity 98.1%. Conclusion: This predictive model of turnover may be used to screen the turnover risk groups and contribute for decreasing the turnover of hospital nurses in South Korea.