• 제목/요약/키워드: chemistry education

검색결과 2,005건 처리시간 0.024초

A report on 53 unrecorded bacteria species in Korea in the class Gammaproteobacteria

  • Kanjanasuntree, Rungravee;Cha, Chang-Jun;Cho, Jang-Cheon;Im, Wan-Taek;Kim, Myung Kyum;Jeon, Che-Ok;Joh, Kiseong;Kim, Seung-Bum;Seong, Chi-Nam;Yi, Hana;Lee, Soon Dong;Bae, Jin-Woo;Kim, Wonyong
    • Journal of Species Research
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    • 제8권4호
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    • pp.319-336
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    • 2019
  • During an investigation of unrecorded prokaryotic species in Republic of Korea, a total of 53 bacterial strains belonging to the class Gammaproteobacteria were isolated from soil, seawater, tidal flats, rhizosphere, salt ponds, beach sand, urine, manure, sediment, and animal intestine (Russian grayling butterfly [Hipparchia autonoe], mouse [Mus musculus], and sea bass [Lateolabrax japonicus]). Strains were identified to species using the 16S rRNA gene sequence, showing high similarity (>98.7%) with the closest bacterial species and forming a robust clade in the neighbor-joining phylogenetic tree. The 53 strains of Gammaproteobacteria in this study have not been report previously in Korea. Therefore, we describe 27 genera of 16 families in 7 orders: 13 strains in the order Alteromonadales, 1 strain in the order Chromatiales, 11 strains in the order Enterobacterales, 7 strains in the order Oceanospirillales, 10 strains in the order Pseudomonadales, 8 strains in the order Vibrionales, and 3 strains in the order Xanthomonadales. Gram reaction, strain ID, isolation source, and morphological and basic biochemical characteristics are described for each species.

Enhancement of Electrochemical Activity of Ni-rich LiNi0.8Mn0.1Co0.1O2 by Precisely Controlled Al2O3 Nanocoatings via Atomic Layer Deposition

  • Ramasamy, Hari Vignesh;Sinha, Soumyadeep;Park, Jooyeon;Gong, Minkyung;Aravindan, Vanchiappan;Heo, Jaeyeong;Lee, Yun-Sung
    • Journal of Electrochemical Science and Technology
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    • 제10권2호
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    • pp.196-205
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    • 2019
  • Ni-rich layered oxides $Li(Ni_xCo_yMn_z)O_2$ (x + y + z = 1) have been extensively studied in recent times owing to their high capacity and low cost and can possibly replace $LiCoO_2$ in the near future. However, these layered oxides suffer from problems related to the capacity fading, thermal stability, and safety at high voltages. In this study, we use surface coating as a strategy to improve the thermal stability at higher voltages. The uniform and conformal $Al_2O_3$ coating on prefabricated electrodes using atomic layer deposition significantly prevented surface degradation over prolonged cycling. Initial capacity of 190, 199, 188 and $166mAh\;g^{-1}$ is obtained for pristine, 2, 5 and 10 cycles of ALD coated samples at 0.2C and maintains 145, 158, 151 and $130mAh\;g^{-1}$ for high current rate of 2C in room temperature. The two-cycle $Al_2O_3$ modified cathode retained 75% of its capacity after 500 cycles at 5C with 0.05% capacity decay per cycle, compared with 46.5% retention for a pristine electrode, at an elevated temperature. Despite the insulating nature of the $Al_2O_3$ coating, a thin layer is sufficient to improve the capacity retention at a high temperature. The $Al_2O_3$ coating can prevent the detrimental surface reactions at a high temperature. Thus, the morphology of the active material is well-maintained even after extensive cycling, whereas the bare electrode undergoes severe degradation.

탄소중립과 그린 수소에너지 전환을 위한 PEM 수전해 시스템에서 작동 전압 및 효율의 열역학적 이해 (Understanding Thermodynamics of Operating Voltage and Efficiency in PEM Water Electrolysis System for Carbon Neutrality and Green Hydrogen Energy Transition)

  • 주형국;봉성율;박승용;이창현
    • 전기화학회지
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    • 제26권4호
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    • pp.56-63
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    • 2023
  • 태양, 파도, 바람 등 친환경 재생에너지원을 이용한 전력 생산 기술이 성숙함에 따라 재생에너지 전력의 경제성과 규모 측면에서 빠르게 발전하고 있다. 특히, 전기화학적인 방법으로 수소를 생산하는 기술은 이러한 재생에너지와 효율적으로 연계될 수 있는 방법 중 하나로 주목받고 있다. 수전해 기술은 작동 온도에 따라서 저온(100 ℃ 이하), 중온(300-700 ℃), 고온(700 ℃ 이상) 수전해로 나눌 수 있으며, 에너지 소비량 및 전압 효율 평가는 열역학 법칙에 따라 계산한다. 그러나 수전해 평가에서 열역학적 전압(thermodynamic voltage)과 열중성 전압(thermo-neutral voltage)의 개념이 혼용되어 사용되고 있다. 본 총설에서는 저온 PEM (proton exchange membrane) 수전해 기술을 바탕으로 작동 전압과 효율 평가에 대한 이해를 높이고, 열역학적 전압과 열중성 전압의 차이점을 명확히 하고자 한다.

Surface Engineering of GaN Photoelectrode by NH3 Treatment for Solar Water Oxidation

  • Soon Hyung Kang;Jun-Seok Ha
    • Journal of Electrochemical Science and Technology
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    • 제14권4호
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    • pp.388-396
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    • 2023
  • Photoelectrochemical (PEC) water splitting is a vital source of clean and sustainable hydrogen energy. Moreover, the large-scale H2 production is currently necessary, while long-term stability and high PEC activity still remain important issues. In this study, a GaN-based photoelectrode was modified by an additional NH3 treatment (900℃ for 10 min) and its PEC behavior was monitored. The bare GaN exhibited a highly crystalline wurtzite structure with the (002) plane and the optical bandgap was approximately 3.2 eV. In comparison, the NH3-treated GaN film exhibited slightly reduced crystallinity and a small improvement in light absorption, resulting from the lattice stress or cracks induced by the excessive N supply. The minor surface nanotexturing created more surface area, providing electroactive reacting sites. From the surface XPS analysis, the formation of an N-Ga-O phase on the surface region of the GaN film was confirmed, which suppressed the charge recombination process and the positive shift of EFB. Therefore, these effects boosted the PEC activity of the NH3-treated GaN film, with J values of approximately 0.35 and 0.78 mA·cm-2 at 0.0 and 1.23 VRHE, respectively, and an onset potential (Von) of -0.24 VRHE. In addition, there was an approximate 50% improvement in the J value within the highly applied potential region with a positive shift of Von. This result could be explained by the increased nanotexturing on the surface structure, the newly formed defect/trap states correlated to the positive Von shift, and the formation of a GaOxN1-x phase, which partially blocked the charge recombination reaction.

Testing and evaluation of the corrosion behavior of Aluminum/Alumina bulk composites fabricated via combined stir casting and APB process

  • Abdalkareem Jasim;Ghassan Fadhil Smaisim;Abduladheem Turki Jalil;Surendar Aravindhan;Abdullah Hasan Jabbar;Shaymaa Abed Hussein;Muneam Hussein Ali;Muataz S. Alhassan;Yasser Fakri Mustafa
    • Advances in materials Research
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    • 제12권4호
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    • pp.263-271
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    • 2023
  • In this study, AA1060/Alumina composites were fabricated by combined stir casting and accumulative press bonding (APB). The APB process was repeated up to six press bonding steps at 300Ċ. As the novelty, potential dynamic polarization in 3.5Wt% NaCl solution was used to study the corrosion properties of these composites. The corrosion behavior of these samples was compared and studied with that of the annealed aluminum alloy 1060 and versus the number of APB steps. So, as a result of enhancing influence on the number of APB process, this experimental investigation showed a significant enhancement in the main electrochemical parameters and the inert character of the Alumina particles. Together with Reducing the active zones of the material surfaces could delay the corrosion process. Also, at higher number of steps, the corrosion resistance of composites improved. The sample produced after six number of steps had a low corrosion density in comparison with high corrosion density of annealed specimens. Also, the scanning electron microscopy (SEM), was used to study the corrosion surface of samples.

경작지내(耕作地內) 도시하수(都市下水) Sludge 의 처리(處理)가 작물(作物)중 Cu 및 Pb 함량(含量)에 미치는 영향(影響) (Effects of Municipal Sewage Sludge on Contents of Lead and Copper in Crop Plants.)

  • 김성조;백승화;정동진
    • 한국환경농학회지
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    • 제11권1호
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    • pp.9-19
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    • 1992
  • 도시생활하수의 처리과정에서 얻어지는 sludge를 토양개량제 등으로 토양에 처리하였을 때 토양중에 증가될 수 있는 Cu 및 Pb이 식물체에 홉수 축척되 는 정도를 비교 분석하기 위하여, sludge 를 0, 22. 5, 45. 0, 90.0ton/ha 수준으로 토양에 처리하고 감자, 무우, 배추, 파의 4 종 작물을 pot 재배하여 각 식물체 부위별 Cu 및 Pb 농도를 분석하고 토양중에서의 이블 중금속 농도의 증가와 식물체중의 Cu 및 Pb 함량증가와의 관계를 분석한 결과는 다음과 같다. 1. 토양중 sludge 처리량의 증가는 식물체중의 Cu 및 Pb 함량을 증가시켰다. 2. 작물별 잎중의 Cu 및 Pb 홉수축적량은 무우<쪽파<배추<감자 순으로 중가하였고 Pb의 홉수축적이 Cu보다 높았다. 3. 작물별 뿌리중의 Cu 홉수축적량은 배추<쪽파 <무우<감자 순으로, Pb의 홉수축적량은 무우<배추<쪽파<감자 순으로 많아졌다. 4. 식물체 부위별 Cu 농도가 가장 낮았던 부위 는 무우 잎, 배추 잎과 뿌리, 쪽파의 괴경으로 그 범위가 $6.500{\sim}9.000ppm$ 이었고, Pb은 무우 잎과 뿌리로 $2.563{\sim}13.533ppm$ 이였다. 5. sludge를 토양에 90.0ton/ha 수준으로 처리 하여 재배한 식물체중의 Cu 함량은 sludge를 처리 하지 않은 토양에 재배한 식물체중 함량에 비하여 $0.17{\sim}0.6ppm$배 범위로 흡수축적되었고, Pb 함량은 $0.32{\sim}1.8ppm$배 범위까지 홉수 축적되었다. 6. sludge 처리에 의한 식물체중의 Cu 홉수축적율은 잎에서 $0.34{\sim}2.21ppm$, 인경 및 괴경에서는 $0.28{\sim}1.48ppm$, 뿌리에서 $0.25{\sim}0.80$배였고, Pb의 경우는 잎에서 $1.81{\sim}5.71$, 인경 및 괴경에서 $1.08{\sim}2.44$, 뿌리에서 $1.28{\sim}7.66ppm$1.28-7.66 배의 축적률을 나타냈다.

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Synthesis of Fully Dehydrated Partially Cs+-exchanged Zeolite Y (FAU, Si/Al = 1.56), |Cs45Na30|[Si117Al75O384]-FAU and Its Single-crystal Structure

  • Seo, Sung-Man;Kim, Ghyung-Hwa;Lee, Seok-Hee;Bae, Jun-Seok;Lim, Woo-Taik
    • Bulletin of the Korean Chemical Society
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    • 제30권6호
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    • pp.1285-1292
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    • 2009
  • Large single crystals of zeolite, |$Na_{75}$|[$Si_{117}Al_{75}O_{384}$]-FAU (Na-Y, Si/Al = 1.56), were synthesized from gels with composition of 3.58Si$O_2$ : 2.08NaAl$O_2$ : 7.59NaOH : 455$H_2$O : 5.06TEA : 2.23TCl. One of these, a colorless single-crystal was ion exchanged by allowing aqueous 0.02 M CsOH to flow past the crystal at 293 K for 3 days, followed by dehydration at 673 K and 1 ${\times}\;10^{-6}$ Torr for 2 days. The crystal structure of fully dehydrated partially $Cs^+$-exchanged zeolite Y, |$Cs_{45}Na_{30}$|[$Si_{117}Al_{75}O_{384}$]-FAU per unit cell (a = 24.9080(10) $\AA$) was determined by single-crystal X-ray diffraction technique in the cubic space group Fd $\overline{3}$ m at 294(1) K. The structure was refined using all intensities to the final error indices (using only the 877 reflections with $F_o\;>\;4{\sigma}(F_o))\;R_1$ = 0.0966 (Based on F) and $R_2\;=\;0.2641\;(Based\;on\;F^2$). About forty-five $Cs^+$ ions per unit cell are found at six different crystallographic sites. The 2 $Cs^+$ ions occupied at site I, at the centers of double 6-ring (D6Rs, Cs-O = 2.774(10) $\AA$ and O-Cs-O = 88.9(3) and 91.1(3)$^o$). Two $Cs^+$ ions are found at site I’ in the sodalite cavity; the $Cs^+$ ions were recessed 2.05 $\AA$ into the sodalite cavity from their 3-oxygen plane (Cs-O = 3.05(3) $\AA$ and O-Cs-O = 77.4(13)$^o$). Site-II’ positions (opposite single 6-rings in the sodalite cage) are occupied by 7 $Cs^+$ ions, each of which extends 2.04 $\AA$ into the sodalite cage from its 3-oxygen plane (Cs-O = 3.067(11) $\AA$ and O-Cs-O = 80.1(3)$^o$). The 26 $Cs^+$ ions are nearly three-quarters filled at site II in the supercage, being recessed 2.34 $\AA$ into the supercage (Cs-O = 3.273(8) $\AA$ and O-Cs-O = 74.3(3)$^o$). The 4 $Cs^+$ ions are found at site III deep in the supercage (Cs-O = 3.321(19) and 3.08(3) $\AA$), and 4 $Cs^+$ ions at another site III’ (Cs-O = 2.87(4) and 3.38(4) $\AA$). About 30 $Na^+$ ions per unit cell are found at one crystallographic site; The $Na^+$ ions are located at site I’ in the sodalite cavity opposite double 6-rings (Na-O = 2.578(11) $\AA$ and O-Na-O = 97.8(4)$^o$).

일부 산업장 남성근로자들의 흡연,음주실태에 따른 혈압 및 혈액검사치의 특성 (Properties of Blood Pressure and Routine Laboratory Test Results by the Status of Smoking and Alcohol Intakes in Male Workers)

  • 유창균;정용준;조영채
    • 보건교육건강증진학회지
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    • 제20권1호
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    • pp.131-145
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    • 2003
  • This study was conducted to estimate the incidence and the degree of cigarette smoking and drinking among working men, and then to investigate the effects on blood pressure, various hematological indices and blood chemistry. The sample consisted of 2,287 male workers who had undertaken a general health check-up during the two-year period from January, 2000 to December, 2001. Such factors as blood pressure, blood glucose, lipid profiles, and liver function tests were determined and then analyzed with respect to the subjects smoking and/or drinking status. The major findings from this study are: 1. The drinking and smoking status have shown that 52.7% of participants were in the habit of both drinking and smoking while 11.6% were not associated with either. On the other hand 25.4% were involved only in drinking and 10.2% only in smoking. In the group smoking over 21 cigarettes per day over 30, the age group occupied the largest proportion at 20.1%. 2. Regarding the relationship between smoking and/or drinking status, and blood pressure, hematology and blood chemistry, the smoking and/or drinking group had significantly higher levels of blood pressure, both systolic and diastolic, Hb & Hct, TG, LDL-C, SGOT, and ${\gamma}$-GTP, than the non-smoking and/or non-drinking group. But HDL-C was significantly lower in the smoking group and significantly higher in the drinking group than the non-smoking/non-drinking group. 3. Regarding amount smoked, a larger number of cigarettes per day was significantly associated with the higher levels of blood pressure, systolic and diatolic, TG, TC, LDL-C, Hb, Hct, and ${\gamma}$-GTP. As for the amount druck, an increasing amount of alcohol intake was associated with rising levels of blood pressure, systolic and diatolic, TG, TC, LDL-C, HDL-C, Hb, SGOT, and ${\gamma}$-GTP. 4. Regarding the correlation among all the variables stated above, the smoking and drinking amount was shown to be in the positive correlation with blood pressure, both systolic and diastolic, TG, TC, Hb, and ${\gamma}$-GTP. On the contrary, LDL-C and HDL-C was in a positive correlation only with the amount drunk amount, and Hct only with the amount smoked. 5. As with systolic and diastolic blood pressure, the odds ratio of the smoking group was 2.35 and 2.58 compared to the non-smoking/drinking group. whereas it was 1.47 and 1.75 in the smoking/drinking group. Concerning serum lipids, the smoking/drinking group had 1.97 times the levels of TG in the non-smoking/non-drinking group, though the smoking group had 1.55 times the levels of HDL-C in the non-smoking/non-drinking group. As with liver function test results, the drinking group had 2.50 times and the smoking/drinking group had 4.41 times the levels of ${\gamma}$-GTP in the non-smoking/drinking group. respectively. The above results revealed that smoking and alcohol intake were effected the results of blood pressure and laboratory tests. Specifically, not only the smoking/drinking group but also those only smoking or only drinking were not as desirable as the non-smoking and non-drinking group to the results of blood pressure and laboratory tests.

동해안지역 온천유형별 수리화학적 특성 및 영족기체 기원 (Hydrochemistry and Noble Gas Origin of Various Hot Spring Waters from the Eastern area in South Korea)

  • 정찬호;;김규한;최훈공;;박지선;박충화;이종익;허순도
    • 한국지하수토양환경학회지:지하수토양환경
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    • 제13권1호
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    • pp.1-12
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    • 2008
  • 이 연구는 한반도 동해안 일대에 분포하고 있는 주요 온천에 대하여 화학성분, 안정동위원소, 삼중수소 그리고 헬륨과 아르곤 같은 영족기체의 동위원소 특성을 분석하여 온천유형별 온천수의 지화학적 특성을 밝히고, 영족기체의 기원을 규명하고자 하였다. 이를 위하여 동해안 일대의 6개 온천지에서 11개의 온천수 시료와 14개의 가스시료를 채취하여 분석하였다. 온천수의 수리화학적 특성을 보면 오색탄산온천수를 제외한 모든 온천수의 pH는 $7.0{\sim}9.1$ 범위의 약알카리성 내지 알카리성을 보이며 오색탄산온천의 pH는 5.7의 약산성의 특성을 보였다. 온천수의 토출온도는 $25.7{\sim}68.3^{\circ}C$ 범위를 보였으며 전기전도도는 $202{\sim}7,130{\mu}S/cm$의 넓은 범위로 해운대와 동래온천은 평균 $3,890{\mu}S/cm$으로 높은 값을 보인다. 온천을 용존성분에 따른 분류하면 오색, 척산, 백암, 덕구온천은 소량의 유황가스 함유한 알카리성의 Na-$HCO_3$형으로 분류되고, 해운대와 동래온천은 높은 TDS(총용존고형물질)의 해수형 Na-Cl형을 보인다. 그리고 오색탄산온천은 약산성으로 탄산을 함유한 Na-$HCO_3$형으로 분류된다. 연구지역 온천수의 ${\delta}^{18}O$${\delta}D$값은 각각 $-7.8{\sim}-11.7%o$$-57.3{\sim}86.4%o$의 범위를 보여 온천수가 순환수 기원임을 지시한다. 위도가 높아질수록 낮은 동위원소 조성 값을 보이는 위도효과가 잘 나타난다. 일부 해수형온천수의 삼중수소 함량은 거의 0 TU에 가까운 값을 보여 최소 약 50년 이상 체류한 물임을 알 수 있다. 오색탄산온천수를 제외한 온천수의 $^3He/^4He$ 동위원소비는 $0.1{\times}10^{-6}{\sim}1.1{\times}10^{-6}$ 범위를 보여, 대기-지각 혼합선보다 상위에 분포한다. 이는 온천수내 He 가스가 대부분 대기와 지각기원이며, 일부는 맨틀기원의 He 가스가 부분적으로 존재한다는 것을 의미한다. 판 경계부에 위치한 일본의 온천수내 He가스는 대부분이 맨틀기원으로 알려져 있어 판 경계부에서 떨어진 우리나라의 경우와 뚜렷한 차이를 보인다. 그러나, 오색탄산온천에서는 대기기원 He 동위원소비보다 2.4배 높은 값인 $3.3{\times}10^{-6}$을 보여주어 지하 심부의 맨틀기원의 가스가 지각상부 대수층까지 공급된 것으로 해석된다. 온천수의 $^{40}Ar/^{36}Ar$ 비는 대기기원의 값과 유사한 범위를 보인다.

방사선학과 교육과정 개선을 위한 현 교육과정 평가 (Evaluation of Present Curriculum for Devlopment of Dept. of Radiological Science Curriculum)

  • 강세식;김창수;최석윤;고성진;김정훈
    • 한국콘텐츠학회논문지
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    • 제11권5호
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    • pp.242-251
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    • 2011
  • 시대와 사회적인 변화에 따라서 교육과정은 변화의 요구를 받게 된다. 교육과정의 변화를 요구받는 현시점에서 교과과정을 개선하기 위한 선행단계인 현재의 교과과정을 분석, 평가하고자 한다. 교육전문가 집단의 설문과 현재 방사선학과가 개설되어 있는 21개 대학 중 19개 대학 방사선학과의 교육과정 및 참고문헌을 중심으로 연구하였으며, 연구내용은 방사선사 업무범위와 교과과정, 방사선과학 교육과 교과과정, 디지털과 국제화시대의 교과과정, 방사선과학에 대한 학문적인 발전과 교과과정 등의 내용을 중심으로 연구하였다. 업무범위에서는 혈관조영학 및 중재적검사학은 6 ~ 8개교, 투시영상학은 4개교, 초음파영상학 및 실습은 6개교, 자기공명영상학은 2개교 등에서 미개설된 것으로 나타났다. 기초의학 교과목인 인체생리학, 인체해부학 및 실습, 의학용어 등은 대부분의 대학에서 개설되어 있었으나, 병리학 5개교, 영상해부학 6개교, 임상의학 11개교 등에서 미개설 되어 있는 것으로 나타났다. 기초이공학 교과목 중에서 일반생물학 및 실습은 11개교, 일반물리학 및 실습은 14개교, 일반화학 및 실습은 8개교 등 약 절반정도의 대학에서 개설된 것으로 나타났다. 전공기초에서 디지털화 교과목인 보건전산학, 컴퓨터프로그램밍, PACS 등이 개설된 대학은 4 ~ 5개교에 불과하였다. 방사선과학 교육은 확대된 업무범위를 포함하여, 방사선과학의 학문적 발전과 디지털화 교육 및 국제화 그리고 방사선과학 분야의 미래지향적인 교육의 토대를 마련하기 위해서는 현재 각 대학에서 개설, 운영되고 있는 교과과정은 일정부분 표준화의 필요성을 인식하였으며, 이에 방사선학과 교육과정은 인증제 도입의 필요성을 제시한다.