• Fibers and Polymers
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• 제2권2호
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• pp.98-107
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• 2001

The phase transition behavior isothermal micro-phase separation kinetics of polyester-based thermoplastic elastomer were studied using the synchrotron X-ray scattering(SAXS) method. The structural changes occurring during heating period were investigated by determining the changes of the one-dimensional correlation function, interfacial thickness and Porod constant. Based on the abrupt increases of the domain spacing and interfacial thickness, a major structural change occurring well below the melting transition temperature is suggested. Those changes are explained in terms of melting of the thermodynamically unstable hard domains or/and the interdiffusion of the hard and soft segments in the interfacial regions. SAXS profile changes during the micro-phase separation process were also clearly observed at various temperatures and the separation rate was found to be sensitively affected by the temperature. The peak position of maximum scattering intensity stayed constant during the entire course of the phase separation process. The scattering data during the isothermal phase separation process was interpreted with the Cahn-Hilliard diffusion equation. The experimental data obtained during the early stage of the phase separation seems to satisfy the Cahn-Hilliard spinodal mechanism. The transition temperature obtained from the extrapolation of the diffusion coefficient to zero value turned out to be about 147$\pm$$2^{\circ}$, which is close to the order-disorder transition temperature obtained from the Porod analysis. The transition temperature was also estimated from the inveriant growth rate. By extrapolating the inveriant growth rate to zero, a transition temperature of about 145$\pm$$\pm$$2^{\circ}$ was obtained.

• Journal of Pharmaceutical Investigation
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• 제38권6호
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• pp.393-398
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• 2008

A propofol delivery system was prepared using two biocompatible polymeric surfactants, poloxamer 407 and PEG 400. The nanoparticular stability of the micellar system was evaluated in terms of temperature change, storage time and composition. The particle size of the system was slightly increased with elevating temperature from $4^{\circ}C$ to $25^{\circ}C$, but its distribution was unimodal. At $40^{\circ}C$, the system presented a bimodal particle size distribution and the increase in the fraction of particles larger than 15 nm. This result might be due to the expansion of the nanoparticles through micellar swelling at the high temperature. It was found that propofol was gradually come out of the system, stored for a month at three different temperatures (4, 25 and $40^{\circ}C$). The drug loss was apparently dependent on temperature and the system composition. Increasing temperature induced the acceleration of the drug loss of $7{\sim}10%$ at $4^{\circ}C$ and $14{\sim}16 %$ at $40^{\circ}C$. This may be owing to the high diffusivity resulting from the swelling of the hydrophilic surface of the nanoparticle at high temperature. However, the addition of PEG 400 to the system led to the reduction of the drug loss. This result is associated with the previous investigation that PEG coverage decreased diffusion coefficient because of the formation of the denser structure on the surface of nanoparticulate. Nevertheless, the limited amount of PEG, less than 2% (w/v), should be used to prevent the precipitation and discoloration of the system.

• 한국작물학회지
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• 제42권6호
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• pp.766-777
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• 1997

수도 저하발아성에 대한 유전 양상을 구명하여 저온발아성 품종 육성의 기초 자료를 얻고자 숙기가 다른 세 그룹에서 10품종을 선정 '94년에 15일 간격 4시기로 파종 및 이앙을 실시하여 수량한 종자를 '95년 4~5월에 13$^{\circ}C$ 항온 실내 시험과, 건답 직파의 포장 시험으로 저온발아성을 조사하고, 저온발아성 고 1품종, 저 1품종, 중 4품종을 선정 '94 하계에 절영법에 의한 정역이면교잡을 실시하여 얻어진 F$_1$ 교배입을 '95년 5월에 13$^{\circ}C$ 항온에서 저온발아 시험을 실시하여 얻은 결과를 요약하면 다음과 같다. 1. 재배 시기를 달리하여 수량된 종자의 실내 및 포장에서의 저온발아성 분산분석 결과 품종에 따라 재배시기간에 고도의 유의차가 인정되었다. 2. 실내 13$^{\circ}C$ 항온 저온발아계수와 포장의 자연상태 건답직파에서의 출아계수와의 상관분석 결과 고도의 유의한 상관(r=0.5111)이 인정되었다. 3. 조합능력 분석 결과 일반조합능력 및 특정조합능력 모두 고도의 유의성이 인정되었으며, 일반조합능력이 특정조합능력보다 커서 상가적작용이 상위성 작용보다 더 크게 나타났다. 4. 정역차이 분산분석 결과 정역간에 고도의 유의차가 인정되었다. 5. 부친열 공분산/모친열 공분산 Graph에서 6개의 교배열 모두가 모본 효과를 보였으며, Alpha와 Beta 유전 분석 결과, 저온발아성의 정역간 차이는 Alpha 유전의 효과로 나타났다. 6. 평균우성도 분석 결과, 30개 조합 중 17개 조합에서 초월분리를 보였으며, 그 중 9개 조합이 저온발아성이 낮은 쪽으로 초월분리를 보였다.

• 한국재료학회지
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• 제21권4호
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• pp.192-195
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• 2011

The electro-deposition of compound semiconductors has been attracting more attention because of its ability to rapidly deposit nanostructured materials and thin films with controlled morphology, dimensions, and crystallinity in a costeffective manner (1). In particular, low band-gap $A_2B_3$-type chalcogenides, such as $Sb_2Te_3$ and $Bi_2Te_3$, have been extensively studied because of their potential applications in thermoelectric power generator and cooler and phase change memory. Thermoelectric $Sb_xTe_y$ films were potentiostatically electrodeposited in aqueous nitric acid electrolyte solutions containing different ratios of $TeO_2$ to $Sb_2O_3$. The stoichiometric $Sb_xTe_y$ films were obtained at an applied voltage of -0.15V vs. SCE using a solution consisting of 2.4 mM $TeO_2$, 0.8 mM $Sb_2O_3$, 33 mM tartaric acid, and 1M $HNO_3$. The stoichiometric $Sb_xTe_y$ films had the rhombohedral structure with a preferred orientation along the [015] direction. The films featured hole concentration and mobility of $5.8{\times}10^{18}/cm^3$ and $54.8\;cm^2/V{\cdot}s$, respectively. More negative applied potential yielded more Sb content in the deposited $Sb_xTe_y$ films. In addition, the hole concentration and mobility decreased with more negative deposition potential and finally showed insulating property, possibly due to more defect formation. The Seebeck coefficient of as-deposited $Sb_2Te_3$ thin film deposited at -0.15V vs. SCE at room temperature was approximately 118 ${\mu}V/K$ at room temperature, which is similar to bulk counterparts.

• 수산해양기술연구
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• 제28권4호
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• pp.418-429
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• 1992

Recently, many researchers make a great effort to develop high efficient marine diesel engines using low grade heavy oil, and also study substitution fuel oil for engines and boilers. In case of Fisheries Vessels, we need to know that fish oil can be substituted for fuel oil. Therefore, it is studied that evaporation, ignition and combustion phenomena of the single droplet of fish oils (i.e., Sardine fish oil, File fish oil and Alaska pollac oil) on heated plane surface to evaluate appropriateness as substitution oil. Methanol and light oil are tested simultaneously to help the evaluation on these Fish oils. The results are summarized as follows: 1. The type of evaporation and combustion is spherical evaporation in case of methanol and light oil. And fish oil blended with light oil was finished after spherical evaporation happen when high temperature. 2. Ignition of Pure fish oil was shorter than that of fish oil blended with light oil. 3. Heat transferred to droplet could make qualitative comparison by contact diameter of droplet with hot surface as time changes. Life time of droplet according to the change of heated surface temperature was greatly influenced by droplet contact condition on the heated surface. 4. As far as combustion phenomena was concerned, apparent diameter of the fish oil droplet increased after ignition and decreased suddenly by internal boiling of droplet. 5. Three fish oils had similar phenomena on the evaporation, ignition and combustion. 6. Evaporation and combustion feature of fish oil could not be shown by coefficient of evaporation velocity of droplet and coefficient of combustion velocity of droplet.

• Steel and Composite Structures
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• 제43권5호
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• pp.581-601
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• 2022

The main objective of this research work is to investigate the free vibration behavior of annular sandwich plates resting on the Kerr foundation at thermal conditions. This sandwich configuration is composed of two FGM face sheets as coating layer and a porous GPLRC (GPL reinforced composite) core. It is supposed that the GPL nanofillers and the porosity coefficient vary continuously along the core thickness direction. To model closed-cell FG porous material reinforced with GPLs, Halpin-Tsai micromechanical modeling in conjunction with Gaussian-Random field scheme is used, while the Poisson's ratio and density are computed by the rule of mixtures. Besides, the material properties of two FGM face sheets change continuously through the thickness according to the power-law distribution. To capture fundamental frequencies of the annular sandwich plate resting on the Kerr foundation in a thermal environment, the analysis procedure is with the aid of Reddy's shear-deformation plate theory based high-order shear deformation plate theory (HSDT) to derive and solve the equations of motion and boundary conditions. The governing equations together with related boundary conditions are discretized using the generalized differential quadrature (GDQ) method in the spatial domain. Numerical results are compared with those published in the literature to examine the accuracy and validity of the present approach. A parametric solution for temperature variation across the thickness of the sandwich plate is employed taking into account the thermal conductivity, the inhomogeneity parameter, and the sandwich schemes. The numerical results indicate the influence of volume fraction index, GPLs volume fraction, porosity coefficient, three independent coefficients of Kerr elastic foundation, and temperature difference on the free vibration behavior of annular sandwich plate. This study provides essential information to engineers seeking innovative ways to promote composite structures in a practical way.

• 대한화학회지
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• 제40권1호
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• pp.81-86
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• 1996

반도체를 보호하기 위하여 사용하는 반도체 성형 재료로, 현재 주로 사용되고 있는 Epoxy Molding Compound(EMI)의 주성분인 올소 크레졸 노볼락 에폭시 수지의 특성과 성형 재료의 관계를 조사하기 위하여 올소 크레졸 노볼락 에폭시 수지의 분자량과 깊은 관련이 있는 수지의 연화점 변화에 따른 EMC의 물성변화를 살펴보았다. 사용된 epoxy 수지의 연화점은 각각 65.1$^{\circ}C$, 72.2$^{\circ}C$, 83.0$^{\circ}C$ 인 3종을 사용하였으며 연화점 변화에 따른 EMC의 물성변화를 살펴보기 위하여 기계적 물성으로 굴곡 강도와 굴곡탄성율을, 열적 특성 변화를 관찰하기 위하여 열팽창 계수와 열전도도 그리고 유리 전이온도를 각각 측정하였다. 그리고 성형 특성과의 관계를 살펴보기 위하여 스피랄 플로우(Spiral Flow)를 측정하였다, 연화점이 증가함에 따라 굴곡 탄성율과 유리상에서의 열팽창 계수(${\alpha}_1$), 그리고 열전도도는 거의 변화가 없었으나 유리전이온도는 연화점 증가에 따라 증가함을, 스피랄 플로우는 연화점 증가에 따라 감소함을 보여주었다. 이는 에폭시 수지의 분자량이 증가함에 따라 가교밀도가 증가하는 현상에 기인한다고 판단된다. 고무상에서의 여팽창 계수(${\alpha}_2$)와 굴곡강도의 경우는 전이점을 보여주고 있는데, 이는 수지점도 증가에 따른 충전제의 분산성에 기인한 것으로 판단된다.

• 한국재료학회지
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• 제11권4호
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• pp.305-311
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• 2001

PDP용 투명유전체 재료로 사용되는 $PbO-B_2O_3-SiO_2-Al_2O_3$계의 소성과정 중에서 투명전극 (ITO)과의 반응성 및 광학적, 열적, 전기적 특성을 조사하였다. 본 연구에서 유전체막.두께는 12$\mu\textrm{m}$으로, 온도는 550-58$0^{\circ}C$에서 소성한 후 여러 물성을 평가하였다 그 결과로, 유전체와 투명전극(ITO)의 반용에서, In 이온이 유전체층으로 확산이동하였으며, Sn 확산은 거의 발생하지 않았다. 선팽창계수, 유전상수, 유리전이온도,광 투과율은 유전체 조성의 PbO 양에 큰 영향을 받았다. PbO양 증가는 선팽창계수와 유전상수를 증가시킨 반면, 유리전이온도와 광 투과율온 저하시켰다. $Al_2O_3/B_2O_3$ 비가 증가함에 따라서는 선팽창계수는 감소, 유전상수는 증가, 광 투과율은 감소하였으며, 유리 전이점 변화는 거의 나타나지 않았다.

• Advances in nano research
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• 제5권1호
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• pp.27-34
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• 2017

One of the methods of removing cyanide from wastewater is surface adsorption. We simulated the removal of cyanide from a synthetic wastewater in the presence of Titanium dioxide nano-particles absorbent uses VISUAL MINTEQ 3.1 software. Our aim was to determine the factors affecting the adsorption of cyanide from synthetic wastewater applying simulation. Synthetic wastewater with a concentration of 100 mg/l of potassium cyanide was used for simulation. The amount of titanium dioxide was 1 g/l under the temperature of $25^{\circ}C$. The simulation was performed using an adsorption model of Freundlich and constant capacitance model. The results of simulation indicated that three factors including pH, nanoparticles of titanium dioxide and the primary concentration of cyanide affect the adsorption level of cyanide. The simulation and experimental results had a good agreement. Also by increasing the pH level of adsorption increases 11 units and then almost did not change. An increase in cyanide concentration, the adsorption level was decreased. In simulation process, rising the concentrations of titanium dioxide nanoparticles to 1 g/l, the rate of adsorption was increased and afterward no any change was observed. In all cases, the coefficient of determination between the experimental data and simulation data was above 0.9.

• 한국지반공학회논문집
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• 제19권1호
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• pp.229-236
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• 2003

본 연구에서는 우란바톨(Ulanbator)에서 북경(Beijing)사이의 지역에서 샘플링한 동결된 응회암 풍화토의 동적 특성을 규명하기 위해 풍화토와, 글래스비드(glass bead)를 대상으로 온도변화에 따른 초음파 속도를 sing-around 법을 사용하여 측정하였다. 본 실험을 통해 초음파 속도는 온도가 증가함에 따라 감소하였고 초음파 속도와 부동수분 사이에는 선형적인 관계가 존재함을 확인하였다. 또한 동결토의 초음파 실험결과, 종파가 시료의 종류에 크게 영향을 받지 않기 때문에 부동수분과 초음파 속도와의 관계규명에 적합하다고 판단된다.