(A) Study on Stability Evaluation of Pharmaceutical Containers

학위논문(석사) --서울대학교 대학원 :약학과 (약품분석학전공),2009.2.Maste

Hydrodynamics of liquid imbibition in porous media

학위논문 (박사)-- 서울대학교 대학원 : 기계항공공학부, 2015. 2. 김호영.Liquid imbibition in a porous structure is mundanely observed in our daily lives, including such phenomena as water absorption into a sponge, ink imbibition in fibrous paper, a water cleaning process by towel or tissue, etc. In this thesis, we combine experimental observation and theoretical analysis to understand the hydrodynamics of liquid imbibition in porous media. We start with relatively simple two-dimensional (2-D) flows on rough porous surfaces, and then increase the complexity of the structure to eventually understand flows in three-dimensional (3-D) multiscale porous media. We first consider one of the most representative 2-D wicking flows, ink writing, i.e. liquid spreading into porous plates from moving point source. We use hydrophilic microtextured silicon wafers (superhydrophilic substrate) as model paper, capillary tubes as model pens, and various liquids as model inks. We start by focusing on liquid spreading when the source is stationary. Balancing surface tension force and viscous shear force, scaling law of blot spreading with time is derived. We then concentrate on the behaviors of the liquid when the source moves in a constant speed. Employing a simplified schematics delineating the frontal liquid flow from the moving source, geometrical analysis is coupled with aforementioned force balance. The front profile predicted by the scaling analysis shows good agreement with experimental results. Also, considering volume conservation, the line thickness is quantified by parametric analysis and verified by experiments. Next, we focus on the role of pore structure in the dynamics of liquid wicking on 2-D substrate. In experiments, we prepare arrays of pillars of varying height, pitches, diameter, and skewness. Through the macroscopic model, deducing average capillary force and resisting shear force, we derive a scaling law of the liquid propagation, which applies for wide range of structural conditions. Through the microscopic model, we approach the dynamics more rigorously by considering the local pressure drop between consecutive pillars. Separating the microscopic propagation by climbing and sweeping, we derive scaling laws of the spreading dynamics. Comparing results of the macroscopic model and microscopic model, we derive the validation limit of the scaling law of macroscopic model. We then consider flows within the dual sized porous media, the simplest form of multi-porous media. The employed structure consists of parallel substrates with micropillar arrays, separated by a millimetric gap. The flow involves the bulk flow at the millimetric gap and the film flow in the micrometric pores above the bulk. The bulk flow between the superhydrophilic surfaces shows identical behavior to what is observed on smooth substrates, meaning that the bulk flow is independent of the microstructures. The flow of the film emanating from the bulk is affected by the bulk in the beginning, but becomes independent of the bulk flow in the late stages. The entire flow regimes are investigated by scaling analysis and verified by experiments. Also, the moment of the film emanating from the bulk is quantitatively estimated by comparing the rising speeds of bulk and film. Finally, we investigate the flows in porous material of practical importance, cellulose sponge, containing various sized pores. We construct a simple model, delineating unit structure of sponge pores by introducing large void and wall pores of the sponge. We first study the horizontal flow in sponge to understand the flow without gravitational effects. The horizontal liquid propagation distance is found to obey the Washburns rule. We turn to the vertical flow, which shows different flow behaviors depending on the rise height. When the rise height is small so that the large void can be completely saturated, liquid flow behavior is identical to the horizontal flow. Whereas, when the rise height is so large that the large void is saturated but partially. The rise height grows like time to the 1/4. This unusual phenomenon is caused by the non-uniformity of permeability, which is inversely proportional to the square of rise height. The scaling laws for the entire flow dynamics show good agreement with experimental results.Abstract i Contents iv List of Figures vi List of Tables xvi 1 Introduction 1 2 Hydrodynamics of writing with ink 9 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2 Experimental setup . . . . . . . . . . . . . . . . . . . . . . . 10 2.3 Stationary pen . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.4 Moving pen . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.4.1 Frontal shape . . . . . . . . . . . . . . . . . . . . . . 16 2.4.2 Final width . . . . . . . . . . . . . . . . . . . . . . . 17 2.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3 Dynamics of hemiwicking 28 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 3.2 Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 3.3 Macroscopic model of hemiwicking dynamics . . . . . . . . 32 3.4 Microscopic model of hemiwicking dynamics . . . . . . . . . 36 3.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 iv CONTENTS 4 Capillary rise between superhydrophilic substrates 47 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 4.2 Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 4.3 Bulk flow dynamics . . . . . . . . . . . . . . . . . . . . . . . 51 4.4 Bifurcation point . . . . . . . . . . . . . . . . . . . . . . . . 53 4.5 Film flow dynamics . . . . . . . . . . . . . . . . . . . . . . . 56 4.5.1 Early stages . . . . . . . . . . . . . . . . . . . . . . . 59 4.5.2 Late stages . . . . . . . . . . . . . . . . . . . . . . . 60 4.5.3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . 63 5 Hydrodynamics of capillary imbibition in cellulose sponges 65 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 5.2 Sponge model and experimental setup . . . . . . . . . . . . 67 5.3 Horizontal imbibition . . . . . . . . . . . . . . . . . . . . . . 70 5.4 Vertical imbibition . . . . . . . . . . . . . . . . . . . . . . . 73 5.4.1 Early stages . . . . . . . . . . . . . . . . . . . . . . . 73 5.4.2 Late stages . . . . . . . . . . . . . . . . . . . . . . . 74 5.4.3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . 78 6 Concluding remarks 83 6.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 6.2 Future work . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 References 86 A Abstract (in Korean) 91Docto

Surfactant-Directed Mesoporous Beta Zeolite as a Catalyst for Friedel-Crafts Alkylation

Zeolites can be used as catalysts in Friedel-Crafts (FC) alkylation, but in liquid phase reactions, the catalysts have very short lifetimes or very limited turnovers. This seems to be related to diffusion limitations, whereas FC alkylation products are often close to or bigger than zeolite pore apertures. Here, we investigated FC alkylation catalytic performance of beta zeolite having mesoporosity. This zeolite was recently synthesized in our laboratory using a surfactant-type zeolite structure-directing agent. We have investigated the reaction kinetics for benzylation of benzene with benzyl alcohol in the liquid phase, and the effect of the mesopores on the catalytic performance. Further works were performed on the details of the FC alkylation, such as the temperature effects, reactant concentrations, poisoning of the external surfaces of zeolite, in order to improve the catalytic lifetime. This investigation clarified why the zeolites had short catalytic lifetimes in liquid-phase FC alkylation. We provided helpful information to improve the catalytic lifetime

Zeolite with MRE structure and their analogue materials possessing mesopore, and synthesis method thereof

본 발명은 제올라이트의 합성 조성에 특수 설계된 유기계면활성제를 첨가하여 합성한, 5 nm 이하의 두께의 결정성 골격과 그것들의 유기적인 조립에 의해 형성된 2 ~ 50 nm 크기의 메조기공이 규칙적이거나 불규칙적으로 배열된, 신규 MRE 제올라이트 및 그 유사 분자체 물질에 관한 것이다. 덧붙여 본 발명은 탈 알루미늄화, 이온 교환, 그리고 그 외의 다른 후 처리에 의해 활성화되거나 관능화 된 마이크로-메조다공성 분자체 물질 및 그 촉매 활용을 포함하고 있다. 이러한 신규 물질들은 마이크로기공과 메조기공의 위계적인 결합구조로 인하여 외표면적과 기공부피가 비약적으로 증가하였고, 이로 인하여 분자확산이 증진되어 기존의 제올라이트에서 보였던 촉매 및 이온교환 수지의 기능에서 활성이 크게 증가될 것으로 예상된다

다중 이진 클래스 스태킹 앙상블 방법을 이용한 침입탐지 시스템

학위논문(석사) - 한국과학기술원 : 산업및시스템공학과, 2011.2, [ ii, 23 p. ]Today, internet is closely related to our daily life. Internet creates benefits using huge amount of information. But using Internet contains some risks of network attacks, thus, detecting network intrusion becomes a significant issue all over the world. Intrusion Detection System is widely employed for security purpose to detect network attacks. In this thesis, we suggest an intrusion detection system using multiple binary-class stacking ensemble method. Previous studies showed that ensemble of weak classifiers can enhance performance of intrusion detection system. In multi-class problem, certain classifier can accurately classify only specific classes, not entire classes. Thus, we employed classifier which is specialized in only one specific class. Also, we use stacking, one of meta-classification methods, ensemble method to combine base classifiers output predictions. Simulation results show that our proposed framework improves detection rate without increasing false positive rate.한국과학기술원 : 산업및시스템공학과

Metal Alloy Nanoparticles-Supported Porous Material Composites, including the Composite Catalysts and the Fabrication Method Thereof

본 발명에 따른 복합체는 공공 결함을 갖는 메조다공성 무기 지지체 및 메조다공성 무기 지지체에 분산 결착되고 귀금속 원소와 희토류 원소를 포함하는 금속 합금(metal alloy) 나노입자를 포함한다