• 마이크로전자및패키징학회지
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• 제7권4호
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• pp.1-5
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• 2000

열전반도체 ($Pb_{1-x}Sn_{x}$)Te를 AC통전 가압법으로 제조하여 그물성에 대해서 연구하였다. 균질성 향상과 구성 성분의 휘발방지에 유효한 진동분쇄공정으로 기계적 합금화를 시켰다. Sn 함량이 증가함에 따라 합금화에 요구되는 기계적 합금화 시간이 증가되었다. AC 통전 hot press법으로 873-923 K에서 1~4분간 150 kgf/$\textrm{cm}^2$의 압력으로 소결하였다. 단시간의 소결은 Te의 증발을 억제할 수 있었다. ($Pb_{1-x}-Sn_{x}$)Te 밀도는 소결 시간보다 소결온도에 더 영향을 받았다. Sn첨가량이 10 mol% 이하일때 온도 상승에 따라 p-n전이 현상이 일어났으나 그 이상의 함량에서는 p-type반도성이 그대로 유지됨이 관찰되었다. 열기전력은 500 K, x=0.2일때 250 $\mu$V/K의 최대치론 나타내었다. Sn함량의 증가에 따라 최대치는 낮아졌으며, 그 온도는 고온측으로 이동하였으며, 전기전도도의 최대치는 온도가 상승함에 따라 저하되었다.

• 한국지반환경공학회 논문집
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• 제8권4호
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• pp.47-55
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• 2007

본 연구는 연약지반의 압밀특성을 나타내는 정수중 하나인 압밀계수($C_v$)를 결정하는데 있어 피에조 콘 관입시험(PCPT)결과의 적용성을 평가하고자 양산-물금지역의 연약지반에서 실시된 피에조 콘 관입시험 자료와 같은 지역 44개소에서 시추한 심도별로 총 172개 자연시료를 사용하여 기본적인 실내토질시험(압밀시험, Atterberg 한계시험, 입도분포시험 등)을 실시하였다. 각 시료의 압밀시험결과를 사용하여 Terzaghi(1943) 압밀 이론으로 구한 구속탄성계수(M) 및 압밀계수($C_v$)를 각 시료에 상응하는 현장 흙에서 실시한 피에조 콘 관입시험(PCPT) 결과로 구한 구속탄성계수 및 압밀계수와 비교분석하였다. 압밀시험으로 구한 구속탄성계수는 피에조 콘 관입시험으로 구한 구속탄성계수와 높은 상관성을 보였고 Jones & Rust(1995)가 제안한 경험식으로 계산된 구속탄성계수가 본 연구에서 피에조 콘 관입시험으로 구한 구속탄성계수와 유사한 값을 보였다. 압밀시험으로 구한 압밀계수와 콘 관입시험 결과로 구한 압밀계수는 직선적 관계를 보였고 콘 관입시험 결과로 구한 압밀계수 값은 압밀시험으로 구한 압밀계수 값의 54%정도로 나타났다.

• 한국분무공학회지
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• 제19권4호
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• pp.211-215
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• 2014

The main purpose of this study is to provide basic information of droplet soot generation of decane fuel. To achieve this, this paper presents the experimental results on the decane droplet combustion conducted under various ambient pressure($P_{amb}$), and oxygen concentration($O_2$) conditions. At the same time, the experimental study was conducted in terms of soot volume fraction($f_v$) and its maximum value. Also, visualization of single fuel droplet was conducted by high resolution CCD camera and ambient pressure($P_{amb}$) and oxygen concentration($O_2$) was changed by control system. It was revealed that higher ambient pressure($P_{amb}$), and oxygen concentration($O_2$) enhanced the soot generation and improved the maximum soot volume fraction( $f_v$).

• 응용통계연구
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• 제3권1호
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• pp.89-103
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• 1990

관측치가 불균형을 이룰 때, Nelson(1988)에 의한 균형 관측치에 관한 이론이 확장될 수 있음을 보여 주고 있다. 이 방법을 이용하여 이원 요인 계획법에서의 교호작용항에 대한 통계량을 구하고, 그래프를 이용한 방법을 제시 하였다.

• 한국안전학회지
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• 제30권4호
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• pp.26-31
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• 2015

The purpose of this paper is to measure the induced voltage of the downscaled and simulated overhead ground wire of a 22.9kV-Y distribution line. This study performed a test of the downscaled and simulated distribution line according to whether it is grounded or not and the value of the ground resistance. In order to verify the reliability of the data measured by the test, the data was analyzed using the Minitab 17 program. It was found that the induced voltage of the downscaled and simulated distribution line is influenced by the value of the ground resistance. It was also found that the ground resistance obtained at a certain point is closely related to whether electric poles are grounded or not. The analysis results of the measured test data with a statistical method showed that the Anderson Darling (AD) was analyzed to be the smallest as 0.188 when the ground resistance of the electric poles had been maintained at $10{\Omega}$. In addition, the P value analyzed to be 0.894 which is in the proximity of the theoretical value of 1 and verified the reliability of the test data. It could be seen that the data measured by the downscaled simulation test forms a linear graph. It is thought that if a distribution line is installed in the same manner as the downscaled, simulated distribution line, the mean induced voltage will be reduced and reliability will be increased.

• 대한전기학회논문지
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• 제45권1호
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• pp.1-8
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• 1996

Recently, much attention has been paid to problems which is concerned with voltage instability phenomena and much works on these phenomena have been made. In this paper, by substituting d $P_{k}$ d $e_{k}$ ( $v^{\rarw}$= e +j f) for $P_{k}$ in conventional load flow, direct method for finging the limit of voltage stability is proposed. Here, by using the fact that taylor se- ries expansion in .DELTA. $P_{k}$ and .DELTA. $Q_{k}$ is terminated at the second-order terms, constraint equation (d $P_{k}$ d $e_{k}$ =0) and power flow equations are formulated with new variables .DSLTA. e and .DELTA.f, so partial differentiations for constraint equation are precisely calculated. The fact that iteratively calculated equations are reformulated with new variables .DELTA.e and .DELTA.f means that limit of voltage stability can be traced precisely through recalculation of jacobian matrix at e+.DELTA.e and f+.DELTA.f state. Then, during iterative process divergence may be avoid. Also, as elements of Hessian mat rix are constant, its computations are required only once during iterative process. Results of application of the proposed method to sample systems are presented. (author). 13 refs., 11 figs., 4 tab.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.446-446
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• 2011

One dimensional (1-D) structures of ZnO nanorods are promising elements for future optoelectronic devices. However there are still many obstacles in fabricating high-quality p-type ZnO up to now. In addition, it is limited to measure the degree of the doping concentration and carrier transport of the doped 1-D ZnO with conventional methods such as Hall measurement. Here we demonstrate the measurement of the electronic properties of p- and n-doped ZnO nanorods by the Kelvin probe force microscopy (KPFM). Vertically aligned ZnO nanorods with intrinsic n-doped, As-doped p-type, and p-n junction were grown by vapor phase epitaxy (VPE). Individual nanowires were then transferred onto Au films deposited on Si substrates. The morphology and surface potentials were measured simultaneously by the KPFM. The work function of the individual nanorods was estimated by comparing with that of gold film as a reference, and the doping concentration of each ZnO nanorods was deduced. Our KPFM results show that the average work function difference between the p-type and n-type regions of p-n junction ZnO nanorod is about ~85meV. This value is in good agreement with the difference in the work function between As-doped p- and n-type ZnO nanorods (96meV) measured with the same conditions. This value is smaller than the expected values estimated from the energy band diagram. However it is explained in terms of surface state and surface band bending.

• 한국환경과학회지
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• 제13권2호
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• pp.149-159
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• 2004

In the removal of heavy metals from the mine deposit using electrokinetic processes, the effects of operation under both constant current and constant potential conditions were estimated. The results of soil pH distributions for DDW-20 V and DDW-100 mA cases after the electrokinetic remediation tests were observed. In the former case, soil pH was not much changed and kept to almost constant value just little higher than initial soil pH of 3.52, except near the cathode, which was about pH 5. While in the latter case, soil pHs of anode and the cathode regions were less than pH 3 and about 6, respectively. The electroosmotic flow to the cathode increased rapidly till 10 hrs and decreased steadily and then maintained to constant rate until the end of operation at constant current condition. Electric potential gradient was continuously increased to as much as 34.375 V/cm. At the steady state, values of the apparent electric conductivity for DDW-20 V and DDW-100 mA were around 40 ${\mu}\textrm{s}$/cm and 30 ${\mu}\textrm{s}$/cm, respectively. In the DDW-100mA test, Cu, Cd, and Zn except Pb showed the tendency of moving toward the cathode. While in the DDW-20 V case, it was observed that Cu, Zn, and Pb except Cd were not moved to any directions. The results of the tests demonstrated that the electrokinetic soil remediation process could be operated better under constant current condition than constant electric potential condition.

• 한국미생물·생명공학회지
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• 제18권6호
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• pp.599-606
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• 1990

근해 연안 토양으로부터 Chitinase 활성이 우수한 균주를 분리하여 Aeromonas salmonicida로 동정하였으며, 분리균주의 효소생산 최적조건은 colloidal chitin 1.26, tryptone 2.95, $MgSO_4-7H_20$0.15, $K_2HP0_4$, 0.15, pH8.5, 27'C에서 48시간 진탕배양하였을 때였다. 효소의 정제는 배양액으로부터 ammonium sulfate 침전, affinity adsorption, hydroxylapatite chromatography, gel filtration을 통해 수율 29.7, 정제도 18.5배의 정제효소를 얻었다. 정제된 chitinase의 최적온도와 pH는 $50^{\circ}C$와 7.0이었고 pH 안정성은 pH5.0-9.0 사이였고 $50^{\circ}C$까지 안정하였으며 Km값은 1.276mg/ml, 분자량은 200,000 daltons으로 확인되었다.

• Applied Biological Chemistry
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• 제46권4호
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• pp.367-375
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• 2003

복분자 과육의 농축액을 유산균을 이용하여 발효시킨 후 발효액의 생리활성을 평가하였다. 발효에는 Lactobacillus acidophilus KCCM 32820, L. casei KCCM 12452, Lactococcus lactis subsp. lactis KCCM 40104, Streptococcus thermophilus KCCM 40430을 단독 또는 혼합하여 사용하였으며 접종량은 대수증식기 말기의 배양액을 2%(v/v)가 되도록 첨가하였다. 단독발효의 경우 L. casei의 발효능이 가장 우수하였으며 혼합 starter를 사용하였을 경우에는 L. casei와 L. lactis를 1:1로 혼합하였을 때 가장 우수한 발효능을 나타내었으나 관능검사에 있어서 L. acidophilus와 S. thermophilus를 이용하였을 때 종합적 기호도가 가장 높았다. 발효는 올리고당을 1%(w/v) 첨가하고 pH를 4.0, 발효온도를 $35{\sim}37^{\circ}C$로 하였을 때 $72{\sim}96$시간에서 가장 잘 이루어졌다. 발효액에는 glucose와 fructose가 주요 유리당으로 존재하였고 lactic acid 함량은 698.2 mg/100 g으로 발효전보다 9배 이상 증가하였다. 발효액의 생리활성을 측정한 결과 69%의 전자공여효과를 나타내었으며 아질산염 소거기능은 pH 1.2에서 38.3%, SOD 유사활성과 xanthine oxidase 저해활성은 각각 60.3%와 41.8%의 활성을 나타내었다. 발효액은 Escherichia coli 0-157:H7에 대해서는 17.3%의 생육저해율을 나타내 사용한 검정균 중에서 가장 높은 항균력을 보였으며 Salmonella typhimurium과 Bacillus cereus에 대해서는 각각 8.9%, 9.7%의 생육저해효과를 나타내었고 Staphylococcus aureus에 대해서는 7.2%의 생육저해효과를 나타내었다.