• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1996년도 제24회 춘계학술대회
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• pp.45-54
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• 1996

The effect of graphite on the frictional characteristics of Cu-based sintered friction materials was studied by pin-on-disk type wear test. A study has been carried out concerning the optimum concentration of graphite in sintered friction material to obtain the minimum wear rate and low friction coefficient . Friction coefficient and wear rate were increased as increasing the content of graphite in the matrix. In the study the optimum concentration of graphite was 19vol % to get the minimum wear rate and optimal frick'ion coefficient.

• 멤브레인
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• 제18권3호
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• pp.250-255
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• 2008

열적, 기계적, 화학적 안정성이 우수한 제올라이트 분리막의 물/에탄올 선택도를 이온교환 실험을 통해 더욱 효과적으로 높이고자 하였다. KA형 제올라이트 분리막을 직접 합성하는 것은 용이하지 않으므로 NaA형 제올라이트 분리막을 합성한 후 이를 다시 이온교환 하여 KA형 제올라이트 분리막을 제조하였다. 공급되는 에탄올의 농도 변화 및 투과 증발실험 온도의 변화가 투과플럭스와 물 선택도에 미치는 영향을 고찰하였다. 이온교환 실험 후 전체 투과플럭스는 감소하였고 물 선택도는 증가함을 관찰할 수 있었다.

• Journal of Microbiology
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• 제34권2호
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• pp.179-183
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• 1996

Streptoccus Pneumoniae (pneumococcus), the most common cause of bacterial pneumonia, has an ample polysaccharide (PS) capsule that is highly antigenic and is the source of PS vaccine. This investigation was undertaken to optimize the culture conditions for the production of capsulard PS by type 1 pneumococcus. Among several culture media, brain heart infusion (BHI) and Casitone based media were found to support luxuriant growth of pneumococcus type 1 at the same level. Because BHI medium is rather expensive and more complex than the Casitone based media, the Casitone based media was uwed to study optimization of the culture condition. The phase of growth which accomodated maximum PS production was logarithmic phase. Concentrations of glucose greater than 0.2% did not ehnahce growth or PS production. Substitution of netrogen sources with other resources or supplementation of various concentrations of metal ion (with the exception of calcium ion) had adverse affects on growth and PS production. On the other hand, low level aeration was beneficial for increased PS production. Addition of 3 mg/1 concentration of methionine, phenylalanine, and threonine were found to enhance growth and PS production. The synerigistic effect of all the favorable conditions observed in pneumococcal growth assays provided a two-fold cummulative increase in capsular PS production.

• 대한환경공학회지
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• 제22권1호
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• pp.33-42
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• 2000

중금속은 토양 내에서 비보존성 화학물질로 작용하므로 흡착에 의해 지연효과가 발생할 수 있고 흡착은 pH에 영향을 받는다고 보고된 바 있다. 그러므로 토양 및 지하수 오염을 예방하고 복구하기 위해서는 다양한 pH조건에서 중금속의 이동형태를 파악하는 것이 중요한 연구과제가 된다. 본 연구에서는 사질토양에서 pH에 따른 중금속의 이동특성을 연구하기 위하여 배치실험과 주상실험올 수행하였다. 배치실험의 경우 초기농도별로 11가지의 $ZnCl_2$ 40 mL 용액과 사질토양 10g을 교반기에서 72시간 반응시켜 평형상태에 도달하게 한 후 용액을 채취하여 Zn, Ca, Mg의 세 가지 양이온을 ICP-AES로 분석하였다. 주상실험은 3가지 pH조건 (7.7, 5.8, 4.1)에서 10 g/L의 KCl과 $ZnCl_2$를 추적자로 사용하여 순간주입 (pulse injection) 형태로 토양시료 상부에 투입한 후 Time Domain Reflectometry (TDR)를 사용하여 10 cm 깊이에서 잔존수농도를, EC-meter와 ICP분석을 통하여 20 cm 깊이의 하부 경계면에서 침출수농도를 분석하였다. 배치실험 결과, Zn은 Ca, Mg와 이온교환의 형태로 흡착이 발생하였고 등온 흡착방정식의 각 모델 (Linear, Freundlich, Langmuir)별로 최저 1.2에서 최고 614.1의 지연계수를 나타냈다. 주상실험에서도 모든 pH조건에서 Zn이온이 이온교환을 하여 흡착이 발생하였으나, 잔존수와 침출수 형태의 파과곡선 모두에서 Zn이용의 첨두농도 도달시간이 K이온과 일치하여 지연효과는 발생하지 않은 것으로 나타났다. 이는 정상류 상태로 부과한 낮은 배경농도의 용탈수내에 Zn보다 강한 이온교환능을 가지는 원소가 존재하지 않아 Zn의 탈착이 발생하지 않았기 때문이다. pH가 낮을수록 Zn는 용액내 수소이온 ($H^+$)의 증가로 치환능이 감소하여 첨두농도가 높게 나타났고, 상대적으로 치환되는 Ca, Mg의 양은 줄어들었다. 따라서 본 연구에 적용된 배치실험과 주상실험의 조건하에서는 Zn이온이 이온교환반응에 의한 흡착이 발생하였으나 지연효과는 발생하지 않았고 가장 낮은 pH에서 첨두농도가 최고 12.7배까지 증가하였다.

• Environmental Engineering Research
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• 제22권1호
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• pp.95-107
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• 2017

Adsorption equilibrium and kinetic behavior of two toxic heavy metals hexavalent chromium [Cr(VI)] and mercury [Hg(II)] on mustard oil cake (MOC) was studied. Isotherm of total chromium was of concave type (S1 type) suggesting cooperative adsorption. Total chromium adsorption followed BET isotherm model. Isotherm of Hg(II) was of L3 type with monolayer followed by multilayer formation due to blockage of pores of MOC at lower concentration of Hg(II). Combined BET-Langmuir and BET-Freundlich models were appropriate to predict Hg(II) adsorption data on MOC. Boyd's model confirmed that external mass transfer was rate limiting step for both total chromium and Hg(II) adsorptions with average diffusivity of $1.09{\times}10^{-16}$ and $0.97m^2/sec$, respectively. Desorption was more than 60% with Hg(II), but poor with chromium. The optimum pH for adsorptions of total chromium and Hg(II) were 2-3 and 5, respectively. At strong acidic pH, Cr(VI) was adsorbed by ion exchange mechanism and after adsorption reduced to Cr(III) and remained on MOC surface. Hg(II) removal was achieved by complexation of $HgCl_2$ with deprotonated amine ($-NH_2$) and carboxyl (COO-) groups of MOC.

• 센서학회지
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• 제8권4호
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• pp.341-346
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• 1999

일반적으로 FET형 전해질 이온 센서는 유리전극에 비하여 여러 가지 장점을 가지고 있으나 드리프트 및 기억효과가 있고 재현성이 부족한 단점을 가지고있어 이온 측정 시스템에 적용한 경우 전체적인 시스템의 신뢰성 저하를 가져온다. 이러한 점을 개선하기 위하여 본 논문에서는 8개의 동종 FET형 전해질 이온 센서 어레이를 사용하여 높은 신뢰성을 가지며 4종류의 이온($H^+$, $Na^+$, $K^+$, $Ca^{2+}$) 농도 측정이 가능한 시스템을 개발하였다. 개발된 측정 시스템은 전자식 스위치를 사용하여 단일의 신호 검출회로로 8개의 센서 신호를 검출하는 방법을 채택하였다. 또한 8개의 센서 신호를 삽입 정렬을 하여 신뢰성이 낮은 센서를 제외시키는 신호 처리 알고리즘을 개발하여 신뢰성을 향상시켰다. 제작된 시스템으로 3종류의 이온($H^+$, $Na^+$, $K^+$) 농도를 측정한 결과 개발된 신호처리 알고리즘은 여러 개의 센서 신호를 단순히 산술 평균을 취하는 방식에 비하여 오차의 범위를 더욱 줄일 수 있는 것으로 나타났으며, 기존의 단채널 방식의 전해질 이온 측정 시스템과 비교해볼 때 우수한 신뢰성을 가짐을 알 수 있었다.

• 환경위생공학
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• 제20권4호통권58호
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• pp.9-20
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• 2005

The purpose of the study was characteristics of secondary pollutants of $PM_{10}$ collected in pocheon between August 2002 and June 2003. The ambient concentrations of $PM_{10}$ mass, 9 water-soluble anions and cations, and 13 bulk composition trace elements were determined from filter samples collected by $PM_{10}$ high volume air sampler(UV-15H, Graseby-Anderson Co., USA). During this period average $PM_{10}$ mass concentration was $83.8{\mu}g/m^3(49.8{\mu}g/m^3\~111.6{\mu}g/m^3)$ in Pocheon. Mechanism for transformation of secondary pollutants by soluble ion components is divided into two categories; $NaNO_3$ type by the reaction of sea salt and $HNO_3$ in the atmosphere, and nitrate salt or phosphate salt type such as $(NH_4)_2SO_4,\;NH_4NaSO_4,\;and\;(NH_4)_2SO_4(2NH_4O_3)$.

• 기술경영경제학회:학술대회논문집
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• 기술경영경제학회 2005년도 통합학술대회 논문집
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• pp.5-28
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• 2005

This paper estimates the effect of networks on innovative performance at the firm level , using Korean Innovation Survey (KIS) dataset Product innovation, product improvement , and process innovation are used as proxies for innovative activity. The explanatory variables such as firm size, market concentration ratio, lagged profitability, foreign ownership, export ratio, firm's age, formal R&D activity, and industrial R&D intensity are yet other considerations. With two year-long (2000 and 2001) data from 1,124 Korean manufacturing firms, we estimated the logistic regression model. The research finding indicates that the external networks have a strong positive effect on innovative output regardless of type of innovation. However, the network effects by partner (other firms or research institutions) vary across the type of innovation. Especially, we found that the user-supplier linkage plays an important role in product ion innovation, product improvement, and process innovation.

• 미생물학회지
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• 제26권1호
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• pp.1-5
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• 1988

The esolation and characterization of a new type II restriction endounclease, BamI, from Bacellus macerans ATCC 8244 were described. BmaI endonuclease was partially purified by procedures of ammonium sulfate fractionation, DEAE-cellulose and phosphocellulose chromatographies. This enzume recognized one site on pBR322 DNA, two sites on Bluescribe DNA, three sites on $\lambda$DNA and no site on SV 40 DNA. The same cleavage patterns for vareius DNAs as PvuI indicated that BamI is an isoschisomer of PvuI whose recognition sequence is 5'-CGATCG-3'. The optimal pH for the BmaI endonuclease activity was about 7.0 and optimal NaCl concentration was about 100mM. Manganese ion could partially replace magnesium as a cofactor, but calcium could not at all.

• 미생물학회지
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• 제12권4호
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• pp.159-179
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• 1974

In order to investigate morphological and cultural characteristics of strains in species, Flammulina velutipes, the author collected isolates of Flammultina velutipes at 49 locations in Korea and cultivated these isolates on the various kinds of solid media. After investigating the cultural characteristics, appeared on the various media, he obtained the following results : 1. The variation of colors in the fruit bodies is connected with the variation of climatic environments(composite effects between mean temperature in January and number of rain days of 1mm and over precipitation). The author, therfore, can find out the trend that brown type is distributed in the midland climatic region and yellow type in the southern climatic regoin. 2. Two types can be classified into several strains respectively : the strain of abundant or insufficient productivity, and strain of selectivity or non-selectivity of media. 3. According to the results of mutual comparison of soluble mycelial proteins by disc electrophoresis using polyacrylamide gels, each type has special common protein fractions(brown type : band located at 26..5mm position from surface of gel, yellow type : band located at 24.5mm position from surface of gel), and each strain has special protein fractions too. Therefore this phenomenon seems to support the results obtained by the above-stated morphological and cultural studies. 4. In the adaptability of strains to the temperature, every strain has the nature of growing in lower temperature(the optimum temperature of 20.deg.C to 25.deg.C) except that YI-1 strain has the optimum temperatue of $25^{\circ}C$-26^{\circ}C. And mycelial growth of every strain is discontinued at $35^{\circ}C.$ 5. In the adaptability of strains to the H-ion concentration, every strain has wide adaptable range of H-ion concentration, and has optimum range of pH 5.5 to 6.6 in mycelial growth excepting YA01, BI-2 and YI-1. 6. In the utility of carbon sources, the mycelial growth of every strain is very poor on the media containing xylose(average diameter of mycelial growth : 18mm), and most strains utilize favorably sucrose(39mm), maltose(37mm) and dextrose(35mm) in mycelial growth. In the utility of nitrogen sources, every strain utilizes favorably organic nitrogens(36 mm)more than inorganic nitrogens (25 mm), and utilizes fully peptone nad asparagine in organic nitrogens. Especially BA-1, BIK-2 and YA-1 strains grow vigorously on each media containing various carbon and nitrogen sources. 7. The characteristic tests of the number of days required for mycelial growth, the number of days requried for sprout of young bodies, the length of stipe and the number of fruit bodies formation seem to be useful methods in the early selection of the strain of the abundant productivity.