• 한국환경과학회지
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• 제30권6호
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• pp.487-500
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• 2021

To evaluate the geochemical characteristics and assess the pollution in surface sediments of the Nakdong River estuary, two sites adjacent to the estuary bank (Hh1 and Hh2) and one site at the upper part of the estuary bank (Hh3) were investigated. The surface sediments were analyzed for their contents of metals (Cu, Pb, Ni, Cr, Zn, and Al), organic matter (IL, COD, TOC, and TN), and grain size from 2018 to 2020. As a result of the pollution assessment, there was little anthropogenic contamination by most of the metals. The surface sediments in Hh2 had comparatively abundant silt and clay, whereas the other sites were mainly composed of sand. The organic index and contents of organic matter were highest at Hh2. Multivariate statistical analyses (cluster analysis and Pearson correlation analysis) showed that the contents of organic matter and pollution were associated with fine sediment. These results suggest that the geochemical characteristics were changed by the estuary bank built in the research area and that the increase in fine sediment attributable to the low-energy environment resulted in an increase in organic matter pollution.

• 대한금속재료학회지
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• 제47권11호
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• pp.728-733
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• 2009

Cu based amorphous ($Cu_{54}Zr_{22}Ti_{18}Ni_{6}$) powders were deposited onto Al 6061 substrates by cold spray process with different powder preheating temperatures (below glass transition temperature: $350^{\circ}C$, near glass transition temperature: $430^{\circ}C$ and near crystallization temperature: $500^{\circ}C$). The microstructure and macroscopic properties (hardness, wear and corrosion) of Cu based amorphous coating layers were also investigated. X-ray diffraction results showed that cold sprayed Cu based amorphous coating layers of $300{\sim}350{\mu}m$ thickness could be well manufactured regardless of powder preheating temperature. Porosity measurements revealed that the coating layers of $430^{\circ}C$ and $500^{\circ}C$ preheating temperature conditions had lower porosity contents (0.88%, 0.93%) than that of the $350^{\circ}C$ preheating condition (4.87%). Hardness was measured as 374.8 Hv ($350^{\circ}C$), 436.3 Hv ($430^{\circ}C$) and 455.4 Hv ($500^{\circ}C$) for the Cu based amorphous coating layers, respectively. The results of the suga test for the wear resistance property also corresponded well to the hardness results. The critical anodic current density ($i_{c}$) according to powder preheating temperature conditions of $430^{\circ}C$, $500^{\circ}C$ was lower than that of the sample preheated at $350^{\circ}C$, respectively. The higher hardness, wear and corrosion resistances of the preheating conditions of near $T_{g}$ and $T_{x}$, compared to the properties of below $T_{g}$, could be well explained by the lower porosity of coating layer.

• 대한금속재료학회지
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• 제50권9호
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• pp.659-667
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• 2012

Alloy 617 is a Ni-base superalloy and a candidate material for the intermediate heat exchanger (IHX) of a very high temperature gas reactor (VHTR) which is one of the next generation nuclear reactors under development. The high operating temperature of VHTR enables various applications such as mass production of hydrogen with high energy efficiency. Alloy 617 has good creep resistance and phase stability at high temperatures in an air environment. However, it was reported that the mechanical properties decreased at a high temperature in an impure helium environment. In this study, high-temperature corrosion tests were carried out at $850^{\circ}C-950^{\circ}C$ in a helium environment containing the impurity gases $H_2$, CO, and $CH_4$, in order to examine the corrosion behavior of Alloy 617. Until 250 h, Alloy 617 specimens showed a parabolic oxidation behavior at all temperatures. The activation energy for oxidation in helium environment was 154 kJ/mol. The SEM and EDS results elucidated a Cr-rich surface oxide layer, Al-rich internal oxides and depletion of grain boundary carbides. The thickness and depths of degraded layers also showed a parabolic relationship with time. A normal grain growth was observed in the Cr-rich surface oxide layer. When corrosion tests were conducted in a pure helium environment, the oxidation was suppressed drastically. It was elucidated that minor impurity gases in the helium would have detrimental effects on the high-temperature corrosion behavior of Alloy 617 for the VHTR application.

• 대한금속재료학회지
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• 제46권5호
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• pp.321-327
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• 2008

Cu based amorphous ($Cu_{54}Zr_{22}Ti_{18}Ni_6$) coating was produced by cold spraying as a new fabrication process. The microstructure and macroscopic properties of amorphous coating layer was investigated and compared with those of cold sprayed pure Cu coating. Amorphous powders were prepared by gas atomization and Al 6061 was used as the substrate plate. X-ray diffraction results showed that Cu based amorphous powder could be successfully deposited by cold spraying without any crystallization. The Cu based amorphous coating layer ($300{\sim}400{\mu}m$ thickness) contained 4.87% porosity. The hardness of Cu based amorphous coating represented $412.8H_v$, which was correspond to 68% of the hardness of injection casted bulk amorphous material. The wear resistance of Cu based amorphous coating was found to be three times higher than that of pure Cu coating. The 3-point bending test results showed that the adhesion strength of Cu based amorphous coating layer was higher than that pure Cu coating. It was also observed that hard Cu base amorphous particle could easily deform soft substrate by particle collisions and thus generated strong adhesion between coating and substrate. However, the amorphous coating layer unexpectedly represented lower corrosion resistance than pure Cu coating, which might be resulted from the higher content of porosity in the cold sprayed amorphous coating.

• Design & Manufacturing
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• 제17권2호
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• pp.55-61
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• 2023

With femtosecond (fs) laser pulse irradiation on metals, various types of nano- and micro-scale structures can be naturally induced at the surface through laser-matter interaction. Two notable structures are laser-induced periodic surface structures (LIPSSs) and cone/spike structures, which are known to significantly modify the optical and physical properties of metal surfaces. In this work, we irradiate fs laser pulses onto various types of metals, cold-rolled steel, pickled & oiled steel, Fe-18Cr-8Ni alloy, Zn-Mg-Al alloy coated steel, and pure Cu which can be useful for precise molding and imprinting processes, and adjust the morphological profiles of LIPSSs and cone/spike structures for clear structural coloration and a larger range of surface wettability control, respectively, by changing the fluence of laser and the speed of raster scan. The periods of LIPSSs on metals used in our experiments are nearly independent of laser fluence. Accordingly, the structural coloration of the surface with LIPSSs can be optimized with the morphological profile of LIPSSs, controlled only by the speed of the raster scan once the laser fluence is determined for each metal sample. However, different from LIPSSs, we demonstrate that the morphological profiles of the cone/spike structures, including their size, shape, and density, can be manipulated with both the laser fluence and the raster scan speed to increase a change in the contact angle. By injection molding and imprinting processes, it is expected that fs laser-induced surface structures on metals can be replicated to the plastic surfaces and potentially beneficial to control the optical and wetting properties of the surface of injection molded and imprinted products.

• Journal of Ecology and Environment
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• 제47권3호
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• pp.157-167
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• 2023

Background: The most hazardous wastewater sources in the northern part of the Middle Nile Delta, Egypt; receiving a massive amount of agricultural, industrial, and sewage drainage are Kitchener drain which is one of the tallest drainage systems, and Burullus Lake which represents the 2nd largest Egyptian coastal lake. Results: The current work is to determine the abundance and frequency of cyanophytes, chlorophytes, and bacillariophytes and the correlation between them and environmental abiotic components. Among sixty nine microalgal species, 19 species are belong Cyanophyta, 26 belong Chlorophyta and 24 belong Bacillariophyta. Genus Scenedesmus (Chlorophyta) was the most abundant in the study area (13 species), followed by Genus Oscillatoria (9 species) and Genus Navicula (7 species). Nostoc muscorum and Chlorella vulgaris were the most common and recorded in all sites (100% of the locations) under study. The application of the two-way indicator species analysis (TWINSPAN) and detrended correspondence analysis revealed agglomerating of 4 groups (communities) at 4th level of classification and reasonable segregation between these groups. Zinc, cadmium and lead were showed the highest levels (0.26±0.03, 0.26±0.06, and 0.17±0.01 ppm, respectively). Conclusions: The correlation analysis between water and community variables indicated a high negative correlation of total algae richness with nickel (r = -0.936, p < 0.01). Cyanophyta and Bacillariophyta were correlated negatively (r = -0.842, p < 0.01). However, Chlorophyta showed a negative richness with each of Ni and Pb (r = -0.965, -0.873, respectively) on one hand and a high positive correlation was revealed (r = 0.964) with all environmental variables on the other hand.

• International Journal of Computer Science & Network Security
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• 제24권6호
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• pp.200-206
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• 2024

Laser induced breakdown spectroscopy (LIBS) technique has been used for the elemental composition of the soils. In this technique, a high energy laser pulse is focused on a sample to produce plasma. From the spectroscopic analysis of such plasma plume, we have determined the different elements present in the soil. This technique is effective and rapid for the qualitative and quantitative analysis of all type of samples. In this work a Q-switched Nd: YAG laser operating with its fundamental mode (1064 nm laser wavelength), 5 nanosecond pulse width, and 10 Hz repetition rate was focused on soil samples using 10 cm quartz lens. The emission spectra of soil consist of Iron (Fe), Calcium (Ca), Titanium (Ti), Silicon (Si), Aluminum (Al), Magnesium (Mg), Manganese (Mn), Potassium (K), Nickel (Ni), Chromium (Cr), Copper (Cu), Mercury (Hg), Barium (Ba), Vanadium (V), Lead (Pb), Nitrogen (N), Scandium (Sc), Hydrogen (H), Strontium (Sr), and Lithium (Li) with different finger-prints of the transition lines. The maximum intensity of the transition lines was observed close to the surface of the sample and it was decreased along the axial direction of the plasma expansion due to the thermalization and the recombination process. We have also determined the plasma parameters such as electron temperature and the electron number density of the plasma using Boltzmann's plot method as well as the Stark broadening of the transition lines respectively. The electron temperature is estimated at 14611 °K, whereas the electron number density i.e. 4.1 × 10¹⁶ cm^-3 lies close to the surface.

• Nuclear Engineering and Technology
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• 제56권5호
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• pp.1830-1835
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• 2024

The current study aims to study the impacts of the substitution of magnesium with nickel concentrations on physical and γ-ray shielding capacity of magnesium alloys. The density of the magnesium alloys under study is varied from 3.677 g/cm³ to 5.652 g/cm³, with raising the nickel content from 26.7 wt% to 54.8 wt% and reducing the magnesium concentration from 72.6 wt% to 44.2 wt%, respectively. Additionally, the examination of the γ-ray shielding capacity using the Monte Carlo simulation code shows that the substitution of magnesium by nickel content in the magnesium alloys was associated with an enhancement in the γ-ray shielding capacity, where the linear attenuation coefficient for the studied alloys was enhanced by 53.22 %, 52.45 %, and 52.52 % at γ-ray energies of 0.662 MeV, 1.252 MeV, and 1.408 MeV, respectively, with raising the nickel concentration from 26.7 wt% to 54.8 wt%. Simultaneously, the half-value thickness for magnesium alloys was reduced from 2.47 cm to 1.62 cm (at gamma ray energy of 0.662 MeV), from 3.39 cm to 2.22 cm (at gamma ray energy of 1.252 MeV), and from 3.60 cm to 2.36 cm (at gamma ray energy of 1.408 MeV), raising the nickel concentration from 26.7 wt % to 54.8 wt%, respectively. The study shows that the substitution of magnesium for nickel greatly enhanced the radiation shielding capacity of the magnesium alloys.

• 자원환경지질
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• 제27권2호
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• pp.171-180
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• 1994

충남 예산군 및 청양군 일대에 분포하는 시대미상의 초염기성암의 기원을 규명하기 위하여 주성분, 미량성분 및 희토류원소(REE)의 전암분석의 결과를 이용하여 연구하였다. 전암분석결과에 의하면 주성분원소 중 $K_{2}O$와 $Na_{2}O$를 제외한 대부분의 원소들은 후기변질작용에 관계없이 일정한 상관관계를 보여주며, primitive 맨틀의 화학조성과 비교할 때 매우 낮은 $Al_{2}O_{3}$ (<1.5%), CaO (<1%), $TiO_{2}$의 값을 나타내며, 비슷한 Ni의 함량을 가진다. 이점으로 미루어 본역의 암석은 상당한 양의 부분용융 (large degree of partial melting)을 받은 맨틀의 잔여물(residues)로 사료된다. REE의 chondrite normalize value는 (La/Yb)c= 1.1-5.2, (Sm/Eu)c=0.6-1.5 및 (Sm/Yb)c= 1.2-1.6 (dunites=0.53-0.77)의 값을 나타낸다. 대부분의 초염기성암이 LREE가 빈화(depleted)된 $(LREE/HREE)_{c}$ < 1) 특징을 보이는데 반해 이 지역의 초염기성암들은 LREE가 약간 부화(enriched)된 ($(LREE/HREE)_{c}$ <1) REE pattern을 나타낸다. 또한, La-Sm-Yb의 ternary diagram을 살펴보면 이들은 chondrite 의 값과 유사한 primitive한 맨틀의 부분용융 후의 잔여물보다 상당히 La가 부화된 양상을 보이며, alkali basalt의 source가 되는 부화된 맨틀의 부분용융 후의 잔여물과 비슷한 화학조성을 나타내고 있다. 이와같은 현상은 사문암화와 같은 후기변질작용 (late stage alteration), pre-melting composition 이 LREE가 부화된 경우, 혹은 빈화된 mantle의 잔여물과 LREE가 부화되어 있는 어떤 component의 mixing에 의한 부화의 가능성 등을 생각해 보았다. 그 결과, 1) 본역의 암석들은 가장 덜 변질받은 암석들만 분석하였고, MgO와 FeO를 다른 oxides로 나눈값을 도시해본 결과 대부분의 oxide들이 매우 좋은 trend를 보여주므로 후기 변질작용에 의한 LREE의 부화가능성은 희박하다고 생각되며, 2) 본역의 암석을 alkali basalt의 source와 같은 LREE가 부화된 deep mantle source에서 부분용융 후의 잔여맨틀로 생각하기에는 이들이 지표 위로 나타날 수 있는 emplacement mechamism을 설명하기가 불가능하다. 따라서 이러한 점으로 마루어볼 때, 이 지역의 초염기성암의 LREE 부화는 두 가지 component의 mixing에 의한 가능성이 가장 높은것으로 사료된다. 상당한량의 부분용융을 받은, 즉 빈화된 맨틀과 LREE가 부화된 component의 mixing에 의하여 이와같이 LREE가 부화된 특성을 보여주고 있다고 사료된다. Component의 성분으로서는 고압에서 LREE를 많이 함유하는 $H_{2}O$나 $CO_{2}$-rich fluid, 혹은 부화된 맨틀의 low degree of partial melting에 의하여 LREE가 부화된 partial melt일 가능성이 높으며 이들이 올라오면서 빈화된 잔여맨틀과 mixing되면서 본역의 암석과 같이 LREE를 부화시켰다고 사료된다.

• 한국지구과학회지
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• 제25권6호
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• pp.428-442
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• 2004

본 연구는 낙동강 하류역 강하먼지의 조성 특성을 파악하기 위하여, 광구병형 Dust jar를 사용하여 2002년 6월부터 2003년 5월까지 1년간 낙동강 하류역의 5개 지점에서 시료를 채취하였다. 채취된 강하먼지에 함유된 불용성 성분(Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Si, V, Zn) 및 수용성 성분($Cl^-$, $NO_3^-$, $SO_4^{2-}$, $NH_4^+$, $Ca^{2+}$, $K^+$, $MG^{2+}$)들은 ICP/AES, AAS, IC 및 UV를 이용하여 정량하었다. 성분에 대한 지각농축계수를 지역별로 비교한 결과 인위적인 오염원인 Cd, Cu, Pb, Zn에서 10 이상의 높은 값을 보였다. 특히 Pb는 감전동, 원동, 신라대, 삼랑진 및 물금 지점 순으로 감소하는 것으로 조사되었다. 계절별 토양입자의 기여율은 겨울철에 16.3 %로서 가장 높았으며, 1년간 평균 기여율은 11.2%이었다. 계절별[$SO_4^{2-}/NO_3^-$] 당량비는 겨울철(5.12)이 가장 높았고, 가을철(3.30)이 가장 낮게 나타났다. 지역별로는 신라대, 감전동, 물금, 원동 및 삼랑진 순으로, 특히 도심에 인접한 지점의 경우가 높게 나타났으며, 평균 당량비는 4.28이었다. 총 강하먼지에 대한 수용성 이온성분의 총 침적량의 비율은 봄철(71.6%), 여름(61.2%), 가을(49.2%) 및 겨울철(48.6%)의 순으로 나타났으며, 평균은 57.6%이었다. 해염입자의 지역별 기여율 분포는 신라대(34.5%), 감전동(28.3%), 원동(17.3%), 삼랑진(17.2%) 및 물금(13.8%)의 순으로 나타났으며, 평균 기여율은 22.1%로 나타났다.