• Nuclear Engineering and Technology
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• 제38권8호
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• pp.733-752
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• 2006

Severe accidents in PWRs are characterized by a continuously changing geometry of the core due to chemical reactions, melting and mechanical failure of the rods and other structures. These local variations of the porosity and other parameters lead to multi-dimensionnal flows and heat transfers. In this paper, a comprehensive set of multi-dimensionnal models describing heat transfers, thermal-hydraulics and melt relocation in a reactor vessel is presented. Those models are suitable for the core description during a severe accident transient. A series of applications at the reactor scale shows the benefits of using such models.

• Archives of Pharmacal Research
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• 제5권2호
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• pp.61-70
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• 1982

Sulfisoxazole, a chemotherapeutic agent, was microencapsulated with ethylcellulose by means of phase separation form cyclohexane by temperatture change. The size distribution was determined by use of standard sieves and the effect of core to wall ratio was noted. To examine their shapes and usrface characteristics, the microcapsules were observed with a scanning electron microscope. Release of the drug from microcapsules into pH 7.5 buffer medium was studied. The release pattern was found to have similar properties to the release of a drug from an insoluble porous matrix reported. The apparent diffusion coefficient of sulfisoxazole was measured for the transport of the drug from the core of microcapsules into the surronding sink condition. The apparent diffusion coefficient increased with increasing capsule size.

• Advances in environmental research
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• 제4권2호
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• pp.69-81
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• 2015

A new magnetite-silica core/shell nanocomposite ($Fe_3O4@nSiO_2@mSiO_2$) was synthesized and functionalized with trimethylchlorosilane (TMCS). The prepared nanocomposite was used for the removal of diesel oil from aqueous media. The characterization of magnetite-silica nanocomposite was studied by X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission electron microscopy (TEM), surface area measurement, and vibrating sample magnetization (VSM). Results have shown that the desired structure was obtained and surface modification was successfully carried out. FTIR analysis has confirmed the presence of TMCS on the surface of magnetite silica nanocomposites. The low- angle XRD pattern of nanocomposites indicated the mesoscopic structure of silica shell. Furthermore, TEM results have shown the core/shell structure with porous silica shell. Adsorption kinetic studies indicated that the nanocomposite was able to remove 80% of the oil contaminant during 2 h and fit well with the pseudo-second order model. Equilibrium studies at room temperature showed that the experimental data fitted well with Freundlich isotherm. The magnetic property of nanocomposite facilitated the separation of solid phase from aqueous solution.

• Structural Engineering and Mechanics
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• 제69권2호
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• pp.131-143
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• 2019

In this study, the nonlinear vibration analysis of the composite nanoplate is studied. The composite nanoplate is fabricated by the functional graded (FG) core and lipid face sheets. The material properties in the FG core vary in three directions. The Kelvin-Voigt model is used to study the viscoelastic effect of the lipid layers. By using the Von-Karman assumptions, the nonlinear differential equation of the vibration analysis of the composite nanoplate is obtained. The foundation of the system is modeled by the nonlinear Pasternak foundation. The Bubnov-Galerkin method and the multiple scale method are used to solve the nonlinear differential equation of the composite nanoplate. The free and force vibration analysis of the composite nanoplate are studied. A comparison between the presented results and the reported results is done and good achievement is obtained. The reported results are verified by the results which are obtained by the Runge-Kutta method. The effects of different parameters on the nonlinear vibration frequencies, the primary, the super harmonic and subharmonic resonance cases are investigated. This work will be useful to design the nanosensors with high biocompatibility.

• 해양환경안전학회지
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• 제23권7호
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• pp.948-955
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• 2017

현재 해양플랜트용 패널의 주요한 중심재는 다공성재료(미네랄울) 이지만, 뛰어난 차음성능에도 불구하고 환경적인 이유로 이를 대체할 재료가 요구되고 있다. 허니컴 구조는 무게 대비 강도가 우수하여 산업전반에서 많이 쓰이고 있다. 하지만 소음진동 측면에서의 연구는 미미하다. 다공성재료를 대체하기 위한 연구로서 허니컴의 음향학적 연구가 필요하다. 본 논문에서는 허니컴패널을 대칭모드와 비대칭모드의 중첩으로 가정하여 수치해석을 진행하였다. 이러한 이론을 통한 수치해석과 실험결과를 비교하여 수치해석의 신뢰성을 검증하였다. 그리고 수치해석을 통해 허니컴패널의 차음특성을 연구하고 중심재로서의 가능성을 평가하였다. 패널두께를 키울수록 일치주파수가 저주파수로 이동하였다. 셀사이즈와 셀벽의 사이각이 감소함에 따라 차음성능이 개선되었고, 셀벽두께의 경우 증가할수록 차음성능이 향상되었다.

• Structural Engineering and Mechanics
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• 제91권1호
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• pp.75-86
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• 2024

In this paper, the porous metal PM-35 is proposed as the filler material of filled thin-walled tubes (FTTs), and a series of experimental study is conducted to investigate the dynamic behavior and energy absorption performance of PM-35 filled thin-walled tubes under impact loading. Firstly, cylinder solid specimens of PM-35 steel are tested to investigate the impact mechanical behavior by using the Split Hopkinson pressure bar set (SHP); Secondly, the filled thin-walled tube specimens with different geometric parameters are designed and tested to investigate the feasibility of PM-35 steel applied in FTTs by the orthogonal test. According to the results of this research, it is concluded that PM-35 steel is with the excellent characteristics of high energy absorption capacity and low yield strength, which make it a potential filler material for FTTs. The micron-sizes pore structure of PM-35 is the main reason for the macroscopic mechanical behavior of PM-35 steel under impact loading, which makes the material to exhibit greater deformation when subjected to external forces and obviously improve the toughness of the material. In addition, PM-35 steel core-filled thin-wall tube has excellent energy absorption ability under high-speed impact, which shows great application potential in the anti-collision structure facilities of high-speed railway and maglev train. The parameter V0 is most sensitive to the energy absorption of FTT specimens under impact loading, and the sensitivity order of different variations to the energy absorption is loading speed V0>D/t>D/L. The loading efficiency of the FTT is affected by its different geometry, which is mainly determined by the sleeve material and the filling material, which are not sensitive to changes in loading speed V0, D/t and D/L parameters.

• 폴리머
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• 제32권4호
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• pp.328-333
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• 2008

삼투압을 이용한 약물전달시스템은 소화관내의 물이 다공성막을 통하여 시스템 내부로 침투하면 시스템 내부에 있던 삼투압물질과 섞여 삼투압을 발생시키고, 이 삼투압의 힘으로 시스템 내부에 있는 약물을 시스템 외부로 일정한 속도로 방출하는 제제기술이다. 이러한 삼투압을 이용하여 상용화된 대표적인 제품으로 니페디핀을 모델약물로 한 타블렛제형인 Procadia $XL^{(R)}$(Pfizer)과 $Adalat^{(R)}$(Bayer)가 널리 상용화되어 있다. 이번 연구에서는 타블렛 형태의 삼투압정을 유동층코팅 기술을 이용하여 삼투성펠렛으로 제조하였다. 삼투성펠렛은 수팽윤성 고분자와 삼투염을 포함한 시드층, 모델약물인 니페디핀을 포함하는 약물층 그리고 약물의 방출을 조절할 수 있는 다공성막으로 구성되어 있다. 본 연구에서는 다공성막으로 사용되는 초산셀룰로오스(CA)와 $Eudragit^{(R)}$ RS의 구성비와 코팅두께에 따른 약물방출 거동을 확인하였으며, 다공성막의 구성물질인 CA의 비가 증가할수록 또한 다공성막의 코팅두께가 증가할수록 같은 측정시간 때에 약물의 방출이 낮게 나타남을 확인하였다. 약물방출 전후의 펠렛의 형태를 확인하기 위하여 SEM을 측정하였다.

• 지질공학
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• 제28권1호
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• pp.35-45
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• 2018

이미징 기술은 매질 자체의 구조특성 뿐만 아니라 유체의 유동특성을 분석하기 위해 공극규모, 코어규모, 그리고 중급규모에서 다양하게 활용되고 있다. 본 기술보고에서는 코어규모에서 유동실험과 이미징기술을 연계하여 균질매질, 균열매질, 그리고 불균질매질에서의 이산화탄소($CO_2$) 유동 특성과 함께 $CO_2$ 주입시 주입관정 주변에서 발생할 수 있는 염침전 현상, 균질매질과 균열매질에서의 모세관압 평가, 그리고 $CO_2$ 주입이 완료된 이후 나타나는 포획메커니즘 평가 등에 대해 살펴보았다. 이미징기술을 통해 코어내에서 시간에 따른 $CO_2$ 플룸을 이미지화 함으로써 유동특성을 분석할 수 있으며, 특히 균열이 포함된 매질과 불균질한 매질에서의 유동 및 저장특성을 평가할 수 있다.

• 한국세라믹학회지
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• 제48권4호
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• pp.293-297
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• 2011

The thermodynamic behavior of phenolic resin was investigated to verify the relation between the properties of porous ceramics with $ZrO_2$-C system for submerged entry nozzle and the characteristics of phenolic resin with various relative humidity. The green and the sintered density were decreased between 25% and 50% relative humidity, whereas they were gradually enhanced above 50% relative humidity. The highest value of apparent porosity was 20.1% and the minimum compressive strength was 69MPa in the specimen using the powder exposed to 50% relative humidity. As a result of thermal analysis for phenolic resin, the shift of endothermic peak to low temperature and the reduction of exothermic peak were observed, and the peaks corresponded to melting and curing of phenolic resin, respectively. The melting and the curing of phenolic resin generate the change of green density, and it can affect the properties of submerged entry nozzle.

• Nuclear Engineering and Technology
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• 제27권1호
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• pp.1-7
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• 1995

다공성 매질을 통한 방사성 핵종의 콜로이드에 의한 이동을 실험과 새로운 모델을 도입하여 살펴보았다. 본 실험에서는 기존의 컬럼 슬라이스 방법을 개선하기 위하여 비파괴 스캐닝 시스템을 개발하였다. 이 장치를 이용하여 기존의 방법보다 훨씬 많은 핵종이동에 관한 자료를 측정하였다. 중성자조사를 시킨 진흙 입자와 여기에 방사성 핵종을 흡착시켜 콜로이드 입자를 만들었다. 실험결과 콜로이드 입자의 크기 분포에도 불구하고 콜로이드 여과계수는 2개의 그룹으로 명백히 구분되었다. 이를 모사하기 위하여 2개의 파라미터를 이용한 새로운 모델식이 개발되었고, 모델식은 실험결과를 잘 모사하였다. 흡착된 핵종중 $^{137}$Cs은 주로 콜로이드 형태로 이동하였으나 $^{Sr}$ 은 그렇지 않았다.