• Applied Microscopy
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• 제26권4호
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• pp.431-446
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• 1996

This experiment was performed to study the ultrastructural changes of the juxtaglomerular cell of mice following subcutaneous injection of heavy metallic agents. Male mice were divided into normal and experimental groups. The mice were subcutaneouly injected with $HgCl_2$ (2mg, 5mg or 10 mg/Kg/BW) or with $K_{2}Cr_{2}O_7$(5 mg, 10 mg or 20 mg/Kg/BW). Mice were sacrificed on 6 hours, 3 days and 14 days after the injection. Kidneys were fixed in the 2.5% glutaraldehyde-1.5% paraformaldehyde solution, followed by refixation in the 1% osmium tetroxide solution. Dehydrated blocks were embedded in araldite mixture. The sections were cut on a LKB-V ultratome, and ultrathin sections stained with uranyl acetate and lead citrate were observed with JEM 100CX II electron microscope. The results were as follow: 1. Juxtaglomerular cell of the experimental groups showed some alterations, especially in the structures of protein synthesis including dilations and degradations of granular endoplasmic reticula, atrophy of Golgi complex, and numerous free ribosomes in the cytoplasm. 2. Juxtaglomerular cells treated groups showed a number of vacuoles, protogranules and some myelin figures in the cytoplasm, especially in the earlier groups. 3. Juxtaglomerular cells of treated groups, contained a large number of secretory granules showing variable electron densities and pleomorphism in later groups (2 weeks). From the above results, it was concluded that, the mercuric chloride or potassium bichromate induces acute renin release from juxtaglomerular cells of the mice, but many juxtaglomerular cells may secrete prematured secretory granules, or the synthetic system of the cell can not perform normal function.

• 청정기술
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• 제25권3호
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• pp.223-230
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• 2019

본 연구에서는 강원도 5개 지자체에서 발생된 음식물류 폐기물의 특성을 분석하고 메탄가스 발생량을 평가하였다. 시료는 2017년 7월과 9월에 걸쳐 총 2회 채취하였다. 메탄가스 발생가능량을 평가하기 위하여 BMP (biochemical Methane potential) 시험과 원소조성을 이용한 계산방법을 이용하였다. 음식물류 폐기물의 겉보기밀도는 평균 $0.758{\sim}0.850g\;cm^{-3}$, pH는 4.29 ~ 4.75이었다. 물리적 조성 중 주성분은 채소류가 56.43 ~ 72.81%로 가장 높았고, 과일류는 5.31 ~ 8.95%, 곡물류는 1.60 ~ 18.73%, 어육류는 4.47 ~ 12.11%, 여액은 1.76 ~ 3.64%이었다. 평균 수분함량은 69.30 ~ 75.87%, 가연분함량은 22.50 ~ 27.98%, 회분함량은 1.63 ~ 2.48%를 나타내었다. 또한 $BOD_5$는 $17,690.3{\sim}33,154.9mg\;L^{-1}$, $COD_{Cr}$은 $106,212.3{\sim}128,695.5mg\;L^{-1}$, 그리고 $COD_{Mn}$은 $51,266.1{\sim}63,426.3mg\;L^{-1}$의 범위를 보였고 NaCl 함량은 0.81 ~ 1.17%의 범위를 나타내었다. 원소분석 결과 C, H, O, N, S 함량은 각각 44.87 ~ 48.16%, 7.12 ~ 7.57%, 40.13 ~ 43.78%, 3.22 ~ 4.14%, 그리고 0.00 ~ 0.02%를 나타내었다. 음식물류 폐기물의 VS 단위질량당 메탄수율을 살펴보면 BMP 시험에 의한 메탄가스 발생누적량(${0.303{\sim}0.354m_{CH4}}^3\;{kg_{VS}}^{-1}$)은 원소조성과 생분해율을 반영하여 예측한 결과(${0.294{\sim}0.352m_{CH4}}^3\;{kg_{VS}}^{-1}$)와 큰 차이가 없었다.

• 자원환경지질
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• 제28권3호
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• pp.259-269
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• 1995

석탄연소 폐기물 (Pulverised Fuel Ash: PFA)을 17년, 40년 매립 풍화받은 것 그리고 현재 발생하는 신선한 시료등으로 구분 영국내 2개 화력발전소로부터 각각 채취하여 주상용출시험 (Column leaching test)을 실시하였다. 용매는 증류수와 인공합성 침출수의 2가지를 이용하였다. 전자의 경우 풍화 시료의 용출행태를 주로 알아보고자 하였으며 후자의 경우 PFA시료와 용매간의 반응중에 발생하는 2차 물질형성이 폐수처리중 중금속제거에 활용가능성이 있는가를 알아보자고 함이었다. 신선한 시료로부터 매우 높은 함량의 원소방출이 관찰된다. 이는 Ca, Na, K, B, Cr, Li, Mo, Se, 그리고 $SO^{2-}_4$등을 포함한다. 이는 원소들의 분포위치에 관한 정보를 제공하며 이들원소의 입자 표면 수반을 시사한다. 풍화 받은 시료로부터 채취된 용액시료에서는 신선한 시료와는 달리 원소들의 급격한 초기방출은 관찰되지 않으며 비교적 일정함량을 보이며 매우 완만한 농도감소 현상을 보인다. 이는 17년과 40년이라는 매립기간중 표면의 용융성원소들의 방출을 의미하며 입자를 주로 구성하는 유리질물질에 수반되는 부분이 이들 시료에서의 원소방출에 중요한 역할을 하는 것으로 생각된다. 증류수를 이용한 실험결과를 여러가지 침출수배출기준, 음용수기준치 등과 비교시 PFA는 이들 기준에 초과하는 농도를 나타내는바 침출수배출시에는 희석 등의 처리가 필요할 것으로 생각되며 매립시 침출수가 지하수로 유입되지 않도록 하여야할 것으로 보인다. 인공 침출수가 PFA기둥을 통과하며 많은 중금속 - B, Fe, Zn, Hg, Ni, Li, Mo -등이 침출수로부터 제거되며 이 제거정도는 신선한 Drax > 풍화 Drax > 풍화 Meaford 시료의 순이다. 물분석시료를 지구화학 모델링 프로그램인 WATEQ4F를 이용하여 PFA 침출수내의 농도조정물질의 존재여부를 알아본 결과 Ca의 경우 $CaSO_4{\cdot}2H_2O$, Al의 경우 $Al(OH)_3$, Fe는 $Fe(OH)_3$ 등이 PFA침출수내에 각 해당원소의 농도를 제한하는 2차물질로 판단되었다.

• Nuclear Engineering and Technology
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• 제51권4호
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• pp.1069-1074
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• 2019

A novel fabrication method of oxide dispersion strengthened (ODS) steel cladding tubes for advanced fast reactors has been investigated using the cold spray powder-based materials deposition process. Cold spraying has the potential advantage for rapidly fabricating ODS cladding tubes in comparison with the conventional multi-step extrusion process. A gas atomized spherical 14YWT (Fe-14%Cr, 3%W, 0.4%Ti, 0.2% Y, 0.01%O) powder was sprayed on a rotating cylindrical 6061-T6 aluminum mandrel using nitrogen as the propellant gas. The powder lacked the oxygen content needed to precipitate the nanoclusters in ODS steel, therefore this work was intended to serve as a proof-of-concept study to demonstrate that free-standing steel cladding tubes with prototypical ODS composition could be manufactured using the cold spray process. The spray process produced an approximately 1-mm thick, dense 14YWT deposit on the aluminum-alloy tube. After surface polishing of the 14YWT deposit to obtain desired cladding thickness and surface roughness, the aluminum-alloy mandrel was dissolved in an alkaline medium to leave behind a free-standing ODS tube. The as-fabricated cladding tube was annealed at $1000^{\circ}C$ for 1 h in an argon atmosphere to improve the overall mechanical properties of the cladding.

• 대한치과기공학회지
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• 제31권1호
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• pp.55-61
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• 2009

Passive fitting of meso-structure and super-structures is a predominant requirement for the longevity and clinical success of osseointegrated dental implants. However, precision and passive fitting has been unpredictable with conventional methods of casting as well as for corrective techniques. Alternative to conventional techniques, electro discharge machining(EDM) is an advanced method introduced to dental technology to improve the passive fitting of implant prosthesis. In this technique material is removed by melting and vaporization in electric sparks. Regarding the efficacy of EDM, the application of this technique induces severe surface morphological and elemental alterations due to the high temperatures developed during machining, which vary between $10,000{\sim}20,000^{\circ}C$. The aim of this study was to investigate the morphological and elemental alterations induced by EDM process of casting dental gold alloy and non-precious alloy used for the production of implant-supported prosthesis. A conventional clinical dental casting alloys were used for experimental specimens patterns, which were divided in three groups, high fineness gold alloy(Au 75%, HG group), low fineness gold alloy(Au 55%, LG group) and nonprecious metal alloy(Ni-Cr, NP group). The UCLA type plastic abutment patterns were invested with conventional investment material and were cast in a centrifugal casting machine. Castings were sandblasted with $50{\mu}m\;Al_2O_3$. One casting specimen of each group was polished by conventional finishing(HGCON, LGCON, NPCON) and one specimen of each group was subjected to EDM in a system using Cu electrodes, kerosene as dielectric fluid in 10 min for gold alloy and 20 min for Ni-Cr alloy(HGEDM. LGEDM, NOEDM). The surface morphology of all specimens was studied under an energy dispersive X-ray spectrometer (EDS). The quantitative results from EDS analysis are presented on the HGEDM and LGEDM specimens a significant increase in C and Cu concentrations was found after EDM finishing. The different result was documented for C on the NPEDM with a significant uptake of O after EDM finishing, whereas Al, Si showed a significant decrease in their concentrations. EDS analysis showed a serious uptake of C and Cu after the EDM procedure in the alloys studied. The C uptake after the EDM process is a common finding and it is attributed to the decomposition of the dielectric fluid in the plasma column, probably due to the development of extremely high temperatures. The Cu uptake is readily explained from the decomposition of Cu electrodes, something which is also a common finding after the EDM procedure. However, all the aforementioned mechanisms require further research. The clinical implication of these findings is related with the biological and corrosion resistance of surfaces prepared by the EDM process.

• Current Applied Physics
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• 제18권11호
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• pp.1268-1274
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• 2018

We have investigated the effects of chemical rounding (CR) on the surface passivation and/or antireflection performance of $AlO_{x^-}$ and $AlO_x/SiN_x:H$ stack-passivated pyramid textured $p^+$-emitters with two different boron doping concentrations, and on the performance of bifacial n-PERT Si solar cells with a front pyramid textured $p^+$-emitter. From experimental results, we found that chemical rounding markedly enhances the passivation performance of $AlO_x$ layers on pyramid textured $p^+$-emitters, and the level of performance enhancement strongly depends on boron doping concentration. Meanwhile, chemical rounding increases solar-weighted reflectance ($R_{SW}$) from ~2.5 to ~3.7% for the $AlO_x/SiN_x:H$ stack-passivated pyramid textured $p^+$-emitters after 200-sec chemical rounding. Consequently, compared to non-rounded bifacial n-PERT Si cells, the short circuit current density Jsc of 200-sec-rounded bifacial n-PERT Si cells with ~60 and ${\sim}100{\Omega}/sq$ $p^+$-emitters is reduced by 0.8 and $0.6mA/cm^2$, respectively under front $p^+$-emitter side illumination. However, the loss in the short circuit current density Jsc is fully offset by the increased fill factor FF by 0.8 and 1.5% for the 200-sec-rounded cells with ~60 and ${\im}100{\Omega}/sq$ $p^+$-emitters, respectively. In particular, the cell efficiency of the 200-sec-rounded cells with a ${\sim}100{\Omega}/sq$ $p^+$-emitter is enhanced as a result, compared to that of the non-rounded cells. Based on our results, it could be expected that the cell efficiency of bifacial n-PERT Si cells would be improved without additional complicated and costly processes if chemical rounding and boron doping processes can be properly optimized.

• 한국물환경학회지
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• 제18권3호
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• pp.245-251
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• 2002

Reactive dyes waste water, a toxic and refractory pollutant, was treated by an electrochemical method using $Ti/IrO_2$ as anode and Stainless Steel 316 as cathode. In this technique, sodium chloride as an electrolyte was added. A number of experiments were run in a batch system. Artificial samples (reactive blue 19, red 195, yellow 145) were used. Operation parameters, such as supporting electrolyte concentration, current density, pH and sample concentration have been investigated for their influences on COD and color removal efficiencies during electrolysis. After 5 and 90 minites of eletrolysis, color was reduced by 51.5% and 98.9% respectively. Under the condition of current density $10A/dm^2$, NaCl concentration 12mg/l and pH 3, 62.9% of $COD_{Cr}$ was removed after electrolysis for 90 minites. The optimum condition of color removal and COD reduction in this work was found to be the following : pH 3, sodium chloride concentration 20g/l, current density $10A/dm^2$. As a result, we confirmed to be effective to color removal and reduction of refractory organic material.

• 한국표면공학회지
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• 제32권2호
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• pp.144-156
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• 1999

Thermal Barrier Coating with Functional Gradient Materials (FGM-TBC) can play an important role to protect the parts from harmful environments in high temperatures such as oxidation, corrosion, and wear and to improve the efficiency of aircraft engine by lowering the surface temperature on turbine blade. FGM-TBC can increase the life spans of product and improve the operating properties. Therfore, in this study the evaluations of mechanical and thermal properties of FGM-TBC such as fatigue, oxidation and wear-resistance at high temperatures have been conducted. The samples of both the TBC with 2, 3, 5 layers (YSZ/NiCrAlY) to be produced by Air Plasma Spray method (APS) and the bulk TBC with 6 layers to be produced by Plasma Assisted Sintering method (PAS) were used. Furthermore, residual stress, bond strength, and thermal conductivity were evaluated. The average thickness of the APS was 500$\mu\textrm{m}$ to 600$\mu\textrm{m}$ and the average thickness of the PAS was 3mm. The hardness number of the top layer of APS was 750 Hv to 810Hv and that of PAS was 950 Hv to 1440Hv. The $ZrO_2$ coating layer of APS was composed of tetragonal structure after spraying as the result of XRD analysis. As shown in the results of the high temperature wear test, the 3 layer coating of APS had the best wear resistance at $800^{\circ}C$ and the 5 layer coating of APS had the best wear resistance at $600^{\circ}C$. But, these coatings had the tendency of the low-temperature softening at $300^{\circ}C$. The main mechanism of wear was the adhesive wear and the friction coefficient of coatings was increased as increasing the test temperatures. A s results of thermal conductivity test, the ${\Delta}T$ of the APS coating was increased as number of layer and the range of thermal conductivity of the PAS was $800^{\circ}C$ to $1000^{\circ}C$.

• Journal of Veterinary Science
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• 제23권1호
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• pp.9.1-9.11
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• 2022

Background: Escherichia coli, which causes subclinical or clinical mastitis in cattle, is responsible for transmitting antimicrobial resistance via human consumption of raw milk or raw milk products. Objectives: The objective of this study was to investigate the molecular characteristics of 183 E. coli from bulk tank milk of five different dairy factories in Korea. Methods: The molecular characteristics of E. coli such as serogroup, virulence, antimicrobial resistance, and integron genes were detected using polymerase chain reaction and antimicrobial susceptibility were tested using the disk diffusion test. Results: In the distribution of phylogenetic groups, group D was the most prevalent (59.6%) and followed by group B1 (25.1%). The most predominant serogroup was O173 (15.3%), and a total of 46 different serotypes were detected. The virulence gene found most often was fimH (73.2%), and stx1, fimH, incC, fyuA, and iutA genes were significantly higher in isolates of phylogenetic group B1 compared to phylogenetic groups A, B2, and D (p < 0.05). Among 64 E. coli isolates that showed resistance to at least one antimicrobial, the highest resistance rate was observed for tetracyclines (37.5%). All 18 integron-positive E. coli carried the integron class I (int1) gene, and three different gene cassette arrangements, dfrA12+aadA2 (2 isolates), aac(6')-Ib3+aac(6')-Ib-cr+aadA4 (2 isolates), and dfrA17+aadA5 (1 isolate) were detected. Conclusions: These data suggest that the E. coli from bulk tank milk can be an indicator for dissemination of antimicrobial resistance and virulence factors via cross-contamination.

• 대한환경공학회지
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• 제22권10호
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• pp.1799-1808
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• 2000

본 연구에서는 구입이 용이한 황토를 이용하여 축산폐수외 화학적 응집 처리제로서의 적용가능성과 최적 응집조건을 찾고 기존에 사용되어 왔던 고분자 응집제(PAC, PACS, LAS)와 응집성능을 비교하였다. 연구 결과 황토와 생석회의 최적 혼합비율은 3:7이었으며, 이 혼합 응집제의 적정 주입량은 30 g/L이었다. 기존 응집제와 비교실험에서는 loess : lime = 3 : 7의 경우 탁도, SS, BOD, $COD_{er}$, T-P, TKN의 제거효율이 각각 95.8%, 92.5%, 71.6%, 71.1%, 98.2%. 32.5%를 나타내었다. Loess : lime = 3 : 7은 응집제로서 사용할 수 있으며, 생산된 슬러지는 토양개량제로서의 사용 가능성을 확인할 수 있었다.