• 한국결정학회지
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• 제12권3호
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• pp.157-161
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• 2001

Pb계 완화형 강유전체인 Pb(Mg/sub ⅓/Nb/sub ⅔/O₃계에서 relaxation 현상과 freezing 거동을 살펴보기위해 낮은 전계에서 측정된 물성들과 강전계 하에서 측정된 물성들을 다양한 주파수 범위에서 비교분석하였다. -40∼90℃의 상전이 온도범위에 걸쳐 1 V/mm의 낮은전계에서 측정된 유전특성의 온도의존성을 구하고 유전이력곡선의 기울기로부터 계산된 유전상수의 온도의존성을 관찰하였다. 이상의 결과와 함께 초전 전류의 온도의존성을 검토한 결과 Vogel-Fulcher 관계식에 비교적 잘 일치되었다. 본 연구를 통하여 일정한 경향을 나타내는 freezing 온도를 산출할 수 있었다.

• Journal of Magnetics
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• 제20권4호
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• pp.342-346
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• 2015

The nuclear magnetic resonance of the $^{23}Na$ nucleus in a $NaBrO_3$ single crystal was investigated at the temperature range of 200 K~410 K. The tendencies of temperature dependence of the nuclear quadrupole coupling for the two magnetically inequivalent Na(I) and Na(II) centers are found to be opposite to each other. The nuclear spin-lattice relaxation mechanism of $^{23}Na$ in the $NaBrO_3$ crystal is investigated, and the result revealed that the Raman process is dominant in the temperature range investigated. The relaxation process of the $^{23}Na$ nuclear spins was well described by a single exponential function in time. The $T_1$ values of the $^{23}Na$ nuclei in the $NaBrO_3$ single crystal decreased with increasing temperature. The calculated activation energy for the $^{23}Na$ is $0.032{\pm}0.002eV$.

• Elastomers and Composites
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• 제50권1호
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• pp.1-6
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• 2015

Polybutadiene rubber (BR) has been well known that its physical and chemical properties are changed when it is exposed to ultraviolet light undergoing photooxidation. In this study, photooxdiation process of BR vulcanizate was investigated using a high pressure mercury lamp used as an outdoor lighting, which has high UV radiation efficiency and reasonable cost. Discoloration and crack formation of photooxdized BR vulcanite surface were examined using an image analyzer. Change of chemical functional groups of BR vulcanite surface by photooxidation was investigated using ATR-FTIR, and variation of the crosslink density with the UV irradiation time was investigated. By increasing the UV irradiation time, the crosslink density steeply increased after a period of time and did not increase any more. Formation of hydroxyl (~OH) and carbonyl (~C=O) groups on the BR vulcanizate surface increased and the1,4-cis unit was converted to the 1,4-trans unit as the photooxidation was proceeded.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.309-314
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• 2009

The unpredicted worldwide oil price makes the energy efficiency technology be more importance than any other period. The small cogeneration system is one of the most representative technology among the energy efficiency technologies, and the Stirling engine cogeneration system has been concerned and investigated due to the preferable characteristics - low toxic emission, low noise and vibration level, and the various form of fuel. A tiny, 1kW of electrical output, gas fueled Stirling engine cogeneration system was investigated. The electrical efficiency and thermal efficiency of the system were measured. The experiment was executed at an independent Stirling engine mode, independent secondary burner mode, and the combined mode. Part load characteristics of the Stirling engine cogeneration system were investigated also. With the efficiency characteristics, the $O_2$ and NOx emission characteristics were measured.

• 한국독성학회:학술대회논문집
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• 한국독성학회 2003년도 춘계학술대회 논문집
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• pp.70-71
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• 2003

Dichlorodiphenyltrichloroethane (DDT), is a widespread environmental pollutant. In this study, we investigated the effect of DDT on testosterone production through aromatase and investigated its molecular mechanism in testicular leydig cell, R2C. We investigated that the effects of DDT on testosterone production and its effects on aromatase activity in R2C cell by radio immunoassay (RIA). (omitted)

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2003년도 추계학술발표회
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• pp.391-394
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• 2003

The applicability of in situ microbial filter or biobarrier technology for the remediation of soil and groundwater contaminated with chlorinated solvents was investigated. The efficiency and rates of reductive dechlorination of chlorinated solvents are known to be highly dependent on hydrogen concentration. In this study, the effect of electron donors on the reductive dechlorination of PCE was investigated using vermicompost (worm casting) and peat as permeable reactive barrier medium The effect of organic acids (lactate, butyrate and benzoate), yeast extract and vitamin $B_{l2}$ on the reductive dechlorination was investigated. Compared to the control (no electron donor added), addition of electron donors stimulated the dechlorinated rate. Among the electron donor treatments, lactate/benzoate amendment exhibited the highest dechlorination rate. Since vermicompost and peat are inexpensive and biodegradable and have high sorption capacity, they could be successfully used as biobarrier media, especially when electron donors (for example, lactate/benzoate) are added.d.

• 한국축산식품학회지
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• 제21권2호
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• pp.97-102
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• 2001

The characteristic fitness of food to each Sa-sang constitution and the relationship between Han-Yeoul characteristics and chemical composition after classifying Samgye-tang ingredients and other food into Ohn-Yeoul-Ryang-Han characteristic were assessed. When the suitable constitution to the each characteristic was investigated after classifying Samgye-tang ingredients and other food into Han, Ryang, Pyound, Ohn and Yeoul of which fitness case for Soeumin was 44∼63% but fitness case for Soyangin and Taeyangin was only 0∼18%. When the relationship between Samgye-tang ingredients and other food classified into Ohn-Yeoul-Ryang-Han and chemical composition of fatty acid, amino acid, vitamin and mineral was investigated, the value of correlation coefficient was extremely low. There was not the relationship between chemical composition and Han-Yeoul classification. Therefore it should be further investigated the relationship between characteristic and chemical composition by additional analysis index.

• 마이크로전자및패키징학회지
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• 제11권4호
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• pp.75-80
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• 2004

In copper metallization, resistivity of copper seed layer is very important. Conventionally MOCVD has been used for this purpose however electroless copper plating is simple process and the resistivity of copper deposit is less than that of copper prepared by MOCVD. In this study electroless copper plating was conducted on different substrate to find optimum conditions of electroless copper plating for electronic applications. To find optimum conditions, the effects and selectivity of activation method on several substrates were investigated. The effects of copper bath composition on morphology were investigated. The effects of pH and stabilizer on deposition rate were also investigated. The optimum pH of the bath was 12 with addition of stabilizer. The resistivity of copper was decreased with addition of stabilizer and alter heat treatment.

• Structural Engineering and Mechanics
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• 제45권5호
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• pp.655-676
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• 2013

In this study, strength reduction factors and inelastic displacement ratios are investigated for SDOF systems with period range of 0.1-3.0 s considering soil structure interaction for earthquake motions recorded on soft soil. The effect of stiffness degradation on strength reduction factors and inelastic displacement ratios is investigated. The modified-Clough model is used to represent structures that exhibit significant stiffness degradation when subjected to reverse cyclic loading and the elastoplastic model is used to represent non-degrading structures. The effect of negative strain - hardening on the inelastic displacement and strength of structures is also investigated. Soil structure interacting systems are modeled and analyzed with effective period, effective damping and effective ductility values differing from fixed-base case. For inelastic time history analyses, Newmark method for step by step time integration was adapted in an in-house computer program. New equations are proposed for strength reduction factor and inelastic displacement ratio of interacting system as a function of structural period($\tilde{T}$, T) ductility (${\mu}$) and period lengthening ratio ($\tilde{T}$/T).

• Structural Engineering and Mechanics
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• 제60권4호
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• pp.595-614
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• 2016

By taking the Runyang Highway Bridge over the Yangtze River with 1490 m main span as example, structural response of the bridge under the horizontal and vertical seismic excitations is investigated by the response spectrum and time-history analysis of MIDAS/Civil software respectively, the seismic behavior and the influence of structural nonlinearity on the seismic response of the bridge are revealed. Considering the aspect of seismic performance, the suitability of employing the suspension bridge in super long-span bridges is investigated as compared to the cable-stayed bridge and cable-stayed-suspension hybrid bridge with the similar main span. Furthermore, the effects of structural parameters including the span arrangement, the cable sag to span ratio, the side to main span ratio, the girder height, the central buckle and the girder support system etc on the seismic performance of the bridge are investigated by the seismic response spectrum analysis, and the favorable earthquake-resistant structural system of suspension bridges is also discussed.