• 한국전기전자재료학회논문지
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• 제18권2호
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• pp.136-141
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• 2005

In this study, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, PCW-PMN-PZT ceramics using Li$_2$CO$_3$, Bi$_2$O$_3$, and CuO as sintering aids were manufactured according to the amount of MnO$_2$ addition. Their microstructural, dielectric and piezoelectric properties were investigated. When the sintering aids were added, specimens could be sintered below 95$0^{\circ}C$, but mechanical qualify factor decreased. Therefore, MnO$_2$ was added excessively to the PCW-PMN-PZT ceramics to increase mechanical quality factor. At the sintering temperature of 95$0^{\circ}C$, the density, dielectric constant($\varepsilon$$_{r}$), electromechanical coupling factor(k$_{p}$), mechanical quality factor(Q$_{m}$) and Curie temperature(T$_{c}$) of 0.1 wt% MnO$_2$ added specimen showed the optimal values of 7.75 g/㎤, 1503, 0.57, 1502, and 337, respectively, for multilayer piezoelectric transformer application.ation.n.

• 한국지능시스템학회논문지
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• 제20권5호
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• pp.624-630
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• 2010

심전도 신호는 일반적으로 200Hz 이상의 주파수로 표본화 되므로 효율적인 저장 및 전송을 위해서는 진단에 중요한 정보를 손실 없이 압축하는 방법이 필요하다. 본 논문에서는 곡률을 이용하여 진단에 중요한 정보인 특징점에 기반한 심전도 신호 압축 방법을 제안한다. 제안한 방식은 심전도 신호의 중요 구성요소인 P, Q, R, S, T파의 특징점이 다른 정점에 비해 곡률 값이 크므로 곡률의 국부적 극값을 이용하여 정점을 추출하였다. 또한 신호의 복원 오차를 최소화하기 위하여 순환적정점 선택 방법에 따른 정점을 특징점으로 추가한다. MIT-BIH 부정맥 데이터베이스에 있는 심전도 신호에 대한 실험을 통하여 선택한 정점들이 심전도 신호의 특징점을 모두 포함하고 있으며, 압축의 효율성도 AZTEC 방식 보다 높다는 것을 확인하였다.

• Journal of Plant Biology
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• 제25권2호
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• pp.83-99
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• 1982

In this study, thirty-two stands in Kwangnung forest located in the central part of Korea were preferentially selected. In each stand, all stems for trees and shrubs were recorded by species and their girths were measured down to 5cm. In addition, several enviromental factors such as field soil pH, field soil moisture, soil compressibility, depth of soil, thickness of litter layer, elevation and basal area were measured. Three soil cores were sampled and various physical and chemcial properties was determined. The vegetational data were subjected to three kinds of multivariate ordination(PO, PCA, RA). The results suggested that Kwangnung forest was consisted of three forest types: coniferous, mixed and broad leaved forest communities. The relation between the stand scores of ordination and several environmental factors were investigated in terms of correlation analysis in order to examine the relationships between the vegetation and certain environmental factors. As a result of this analysis, the amount of sand content in A1 horizon decreased frm the coniferous to broad leaved forest, while maximum field capacity, pore space, exchangeable cations, loss on ignition, soil pH nad the amount of total nitrogen had a tendancy to increase significantly. However, easily soluble phosphorus appeared to have little to do with the forest types. The result of species ordination of centered-standardized PCA suggested that the major successional pathway in Kwangnung forest was; Pinus densifloralongrightarrowQuercus mongolica, Q. serrata, Q. alienalongrightarrowCarpinus laxifloralongrightarrowC. erosa in sequence. This trend is in good agreement with the past studies. In three kinds of ordination (centered PCA, centered-standardized PCA and RA) based on nineteen species and twenty-five stands, the total variances accounted for the first three axes were 77%, 46% and 63% respectively. The estimated beta diversity in Kwangnung forest assumed as a coenocline, was 1.5~1.8 HC. Increasing the effect of the sampling errors on ordination perfermance, this low heterogeneity seems to cause the poor concentration of the total variance. The results from the four kinds of ordination were in good agreement with each other, especially between PO, centered-standardized PCA and RA appeared robust. It seems to be worthy of applying multivariate method for analyzing other forest communities in Korea.

• Journal of Plant Biology
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• 제27권2호
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• pp.61-72
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• 1984

The concept of natural grouping of plant designated as the "Amentiferous" is no longer given serious credence, and many of the families included in this grouping have been dispersed in diverse order. Because a review of taxonomic treatments of amentiferous taxa reveals diverse classifications, it has become necessary to investigate new characteristics and attempt to determine the significance of these characteristics in terms of amentiferous taxonomy. Protein analyses by isoelectrofocusing(IEF) and rocket immunoelectrophoresis(RIE) have proved to be useful in the delicitation of Quercus taxa using pollen extracts from selected taxa. When Quercus pollen extracts were separated by electrophoresis based on their isoelectric points in a stable pH gradient and substrates for estrase activity were stained, ten bands were revealed between pH 5-14. Within Lepidobalanus grouping, a great diversity in the pollen protein zymograms was observed with some segregation corresponding to the designated taxonomic sections. Two taxa of Cyclobalanopsis produced a zymogram that is somewhat similar to taxa included within the section Prinus of Lepidobalanus, and less similar to taxa within the section Cerris of the same subgenus. Three tested taxa of the Cerris are in the similar zymogram each other, being segregable from the taxa of Prinus. Quantitative and qualitative analyses for serological relationships within and among th Quercus were also employed. To calculate the degree of protein similarity, total rocket heights obtained from RIE provided an index of serological correspondence(SC). It is reconfirmed that the Quercus is distantly separated from the Fagus according to SC. Comparative data from rocket number and SC in the tested taxa of Quercus also indicate that Lepidobalanus is separable from Cyclobalanopsis. Within the Lepidobalanus Q. acutissima and Q. acutissima x variabilis are almost homogeneors and distinguishable from the other tested taxa of same subgenus. Although the number of taxa tested has been limited, the overall serological evidence best reflects the classification proposed by Redher(1940) and Melchior (1964), having the genus Quercus subdivided into three subgunera: Erythrobalanus, Lepidobalanus, and Cyclobalanopsis.alanopsis.

• 전력전자학회논문지
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• 제4권4호
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• pp.342-348
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• 1999

본 논문에서는 간단한 제어회로와 반브릿지 PWM 인버터로 구성된 저가의 단상능동전력필터에 대해 기술하고 있다. 이 능동전력필터의 성능을 확인하기 위하여 EMTP 프로그램에 의한 시뮬레이션을 실시하고 프로토타입을 제작하여 실험을 실시하였는데, 그 결과 제안하는 능동전력필터는 단상비선형부하가 발생하는 고조파를 제거하는데 우수한 성능을 갖고 있음을 확인할 수 있었다. 제안된 시스템은 반브릿지 인버터와 단일 전류센서를 사용한 간단한 제어회로로 구성되었기 때문에, 하드웨어 비용이 저렴하고 프러그인 타입으로 제작 가능한 장점을 갖는다.

• 한국전기전자재료학회논문지
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• 제28권3호
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• pp.165-169
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• 2015

In this paper, in order to develop the composition ceramics with the excellent dielectric properties, $Pb(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_{0.09}(Zr_{0.5}Ti_{0.5})_{0.88}O_3$ ceramics were fabricated by the conventional solid-state method. The effects of ZnO addition on their microstructure and piezoelectric properties were systematically investigated. The rhombohedral-tetragonal phase coexistence has been found in the ceramics without ZnO content and then with further increasing ZnO content, specimens exhibited tetragonal phase. The optimized ZnO content formed liquid phase and aided the grain growth of specimens. When 0.4 wt% ZnO was added, the optimal physical properties ($d_{33}=422pC/N$, $d_{31}=161pC/N$, ${\varepsilon}_r=1,905$, $k_p=0.55$, $Q_m=160$) were obtained.

• 한국전기전자재료학회논문지
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• 제23권5호
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• pp.379-382
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• 2010

In this study, in order to develop the lead-free piezoelectric ceramics with high piezoelectric and dielectric properties, $(K_{0.5}Na_{0.5})(Nb_{0.97}Sb_{0.03})O_3$ ceramics were fabricated using a conventional mixed oxide process and their piezoelectric and dielectric characteristics were investigated according to the $K_{5.4}Cu_{1.3}Ta_{10}O_{29}$ addition. $K_{5.4}Cu_{1.3}Ta_{10}O_{29}$ addition enhanced density, electromechanical coupling factor($k_p$) piezoelectric constant $d_{33}$ and mechanical quality factor($Q_m$). At the 0.9 mol% $K_{5.4}Cu_{1.3}Ta_{10}O_{29}$ addition, density, electromechanical coupling factor($k_p$), dielectric constant(${\varepsilon}_r$) and piezoelectric constant($d_{33}$) of specimen showed the optimum values of 0.46, 471, and 148 pC/N, respectively.

• 간호행정학회지
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• 제13권2호
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• pp.184-190
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• 2007

Purpose: This study was undertaken in order to suggest self-leadership as a method for nurses to lower their job stress and enhance their job satisfaction. So the relations among self-leadership, job stress and job satisfaction were studied. Method: The subjects of study were 123 nurses who have been working in 2 general hospitals located in K city. The data were collected by Q & A and analyzed using descriptive statistics, Pearson's correlation coefficient, t-test, and ANOVA on SPSS Program. Result: Nurses got average 3.50, 2.64 and 3.12 points out of 5 in their self-leadership, job stress and job satisfaction respectively. The self-leadership was negatively correlated with job stress (r=-.429, p=<.001) while it is positively correlated with job satisfaction(r=.281, p=<.001). And job stress was negatively correlated with job satisfaction(r=-.574, p=<.001). Job stress had statistically significant differences according to age and marital status. Conclusion: In conclusion self-leadership is correlated with job stress and job satisfaction. It is recommend that hospital managers have to develop methods which enhance self-leadership of nurses.

• 대한수학회지
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• 제44권2호
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• pp.373-391
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• 2007

We study an (n+3)($n\;{\geq}\;7-dimensional$ real submanifold of a (4m+3)-unit sphere $S^{4m+3}$ with Sasakian 3-structure induced from the canonical quaternionic $K\"{a}hler$ structure of quaternionic (m+1)-number space $Q^{m+1}$, and especially determine contact three CR-submanifolds with (p-1) contact three CR-dimension under the equality conditions given in (4.1), where p = 4m - n denotes the codimension of the submanifold. Also we provide necessary conditions concerning sectional curvature in order that a compact contact three CR-submanifold of (p-1) contact three CR-dimension in $S^{4m+3}$ is the model space $S^{4n_1+3}(r_1){\times}S^{4n_2+3}(r_2)$ for some portion $(n_1,\;n_2)$ of (n-3)/4 and some $r_1,\;r_2$ with $r^{2}_{1}+r^{2}_{2}=1$.

• 대한환경공학회지
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• 제29권8호
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• pp.930-937
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• 2007

본 연구에서는 소나무 종류인 Pinus densiflora로부터 채취한 수피를 이용하여 수용액으로부터 구리 제거를 위한 회분식 흡착 실험을 수행하였다. 구리 흡착에 수피의 화학적 처리가 미치는 효과를 알아보기 위해 1 N 수산화나트륨(NaOH)과 1 N 염산(HCl)을 이용하여 전처리하였다. 구리 농도가 100 mg/L이고 pH가 $3\sim6$인 수용액에서 수산화나트륨(NaOH)을 이용한 수피의 화학적 전처리는 구리의 흡착량을 $139\sim184%$ 정도 증가시키는 효과를 나타냈으나, 염산(HCl)을 이용한 수피의 전처리는 구리의 흡착량을 $37\sim42%$ 정도 감소시키는 효과를 나타냈다. 대체적으로 수피에 의한 구리 흡착은 pH $5\sim6$에서 최대 흡착량을 나타내기는 하였으나, 주어진 pH 범위내에서 수용액의 pH가 구리 흡착에 미치는 효과는 크지 않았다. 수피의 구리 흡착은 유사 2차 동역학 모델로 설명이 가능하였으며, 수산화나트륨(NaOH)으로 전처리한 수피의 경우 초기 농도가 100 mg/L에서 2배로 증가함에 따라 유사 2차 동역학 모델식으로부터 계산된 흡착량$(q_e)$은 6.58 mg/g에서 12.77 mg/g로 증가한 반면에 속도 상수$(k_2)$는 0.284 g/mg/min에서 0.014 g/mg/min으로 감소하였다. 수피의 구리 흡착특성은 Langmuir와 Freundlich 등온식에 의해 모두 잘 표현되는 것으로 나타났다. 수피에 존재하는 카르복실산(carboxylic acid, RCOOH)이 구리 이온의 흡착에 관여하는 것이 확인되었으며, 특히 수산화나트륨을 이용하여 전처리한 수피에서 나타나는 구리의 높은 흡착효율은 수피에 존재한 에스테르(ester) 화합물과 카르복실산(carboxylic acid) 화합물이 가수분해되어 생성된 카르복실산 염(sodium carboxylate) 때문인 것으로 판단되었다.