친수성 실록산을 도입하여 분리 및 재사용성을 향상시킨 자성 나노입자 유도물질 개발 및 정삼투 수처리 적용에 대한 연구

학위논문 (석사)-- 서울대학교 대학원 : 재료공학부, 2013. 2. 곽승엽.Forward osmosis (FO) is an emerging technology for water treatment. Finding of feasible draw solute which is the origin of the driving force for FO is one of the most important challenges of the whole research of FO. High osmotic pressure generation and easy recycling are most required properties of draw solute. Hydrophilic magnetic nanoparticle (HMNP) has full of promise as feasible draw solute. However, gradual decline of osmotic performance after recycling process, caused by particle core aggregation, is one of the major problems of HMNP draw solute. In this work, we have synthesized HMNP capped with hydrophilic siloxane (HS-MNP) for draw solute. Be compared to the carboxylate ligands of conventional HMNP draw solutes, siloxane linkages formed by condensation of hydrophilic trimethoxysilane are considered as a good protector of particle core against aggregation on high strength magnetic fields. Ligands of MNP/oleic acid synthesized by thermal decomposition method were exchanged to hydrophilic siloxane. Two trimethoxysilanes, 2-[methoxy-(polyethyleneoxy)propyl]trimethoxysilane (Silane-PEG) and n-(trimethoxysilylpropyl) ethylenediamine triacetic acid (Silane-COOH), were used as hydrophilic ligands for HS-MNP draw solutes. Physical properties of HS-MNP draw solutes were thoroughly characterized and osmotic pressure generation of HS-MNPs were analyzed by freezing point depression osmometer. HS-MNPs were applied to a batch scale FO to determine the water flux generation. After that, variation of water flux generation and mean particle size of HS-MNPs were measured after 5-times-repeated magnetic recycle. Osmotic pressure and water flux generation of PEG-MNP were 7.6 atm and 2.13 LMH at 0.038 mol/L of ligand concentration. Similarly, osmotic pressure and water flux generation of COOH-MNP were 6.3 atm and 1.81 LMH at same concentration. These results confirm that synthesized HS-MNPs were feasible to apply to the FO water treatment of mild brackish water or wastewater. In addition, water flux generation and particle size PEG-MNP draw solutes were well-maintained by 5-tmies of magnetic recycle. Finally, 0.038 mol/L of PEG-MNP + DI water draw solution was applied to the FO process with a feed solution with 500 ppm of methylene blue. Water flux generation with the feed solution was up to 1.58 LMH. Results of this work shows that HS-MNPs are feasible draw solutes in FO water treatment. Especially, properties of PEG-MNP as draw solute were well-maintained on magnetic recycle, and acceptable to FO water treatment of mild brackish water.1. Introduction ..............................................................1 2. Experimental ...........................................................14 2.1. Materials...............................................................14 2.2. Preparation of hydrophilic siloxane-coated magnetic nanoparticle (HS-MNP) draw solutes.............................15 2.2.1 Step 1: Synthesis of magnetic nanoparticle capped by oleic acid (MNP/oleic acid)..........................................15 2.2.2. Step 2: Ligand exchange reaction for hydrophilic modification of HS-MNPs..............................................16 2.3. Characterization of synthesized HS-MNPs................19 2.3.1. Crystal structure, shape and particle size distribution..................................................................19 2.3.2. Surface modification of hydrophilic siloxane...........20 2.3.3. Osmotic pressure generation................................20 2.4. Forward osmosis (FO) with HS-MNP draw solutes....21 2.4.1. Water permeation test...........................................21 2.4.2. Magnetic recycling and regeneration of HS-MNP draw solutes...............................................................22 2.4.3. Water permeation test with brackish feed solution....22 3. Results and Discussion .................................................................28 3.1. Preparation of hydrophilic siloxane-coated magnetic nanoparticle (HS-MNP)................................................28 3.1.1. Crystal structure, shape and particle size distribution..................................................................28 3.1.2. Surface modification by ligand exchange reaction......................................................................36 3.1.3. Osmotic pressure generation................................46 3.2. FO process with HS-MNP draw solutes....................50 3.2.1. Water flux of HS-MNP draw solutes in FO process..50 3.2.2. Change of water flux and mean particle size in FO process on repeated magnetic recycle...........................53 3.2.3. Water flux of PEG-MNP draw solutes with brackish feed solution................................................................55 4. Conclusions............................................................58 5. References..............................................................62 KOREAN ABSTRACT....................................................67 ACKNOWLEDGEMENT.................................................70Maste

Regression clustering based on boosting approach

학위논문 (석사)-- 서울대학교 대학원 : 통계학과, 2011.8. 김용대.Maste

CBCT를 이용한 상악전치부 후방이동에 따른 상악전치부 치조골 및 치근의 변화 평가

학위논문 (박사)-- 서울대학교 대학원 : 치의과학과 치과교정학 전공, 2012. 8. 백승학.목 적: 본 연구는 최대 고정원을 이용하여 군집(en-masse) 후방 견인 후, 상악전치부 치조골 면적, 수직 치조골 높이, 치근 길이 및 면적의 변화를 평가하기 위함이다. 방 법: 골격성 I급 치아치조전돌 성인 여성 환자 37명을 대상으로, 상악 제1소구치 발거 후, 최대고정원으로 후방 견인을 시행하였다. 치료 전(T1)과 공간 폐쇄 후(T2), 콘빔형 전산화단층사진 (cone beam computed tomograms, CBCT)을 촬영하여, 상악 중절치(N = 66), 상악 측절치 (N = 69), 상악 견치 (N = 69)를 대상으로 개개 치아의 치관 형태와 치아 장축을 기준으로 삼차원 중첩을 시행하였다. 치근의 수직 길이를 3등분하여, 치경부, 중간, 치근단 부위의 치조골 면적 및 치조골 수직 높이, 치근 길이, 치근 면적, 열개(dehiscence)의 유병률을 평가하고 통계처리 하였다. 결 과: 이로부터 다음과 같은 결과를 얻었다. 1.구개측에서 상악 중절치, 측절치, 견치 모두, 모든 영역에서 유의한 치조골 면적의 감소를 보였다. 상악 중절치와 측절치는 견치보다 더 높은 치조골 면적의 감소율을 보였다. 순측에 대한 구개측 치조골 면적 비율은 상악 중절치와 측절치에서 감소하였다. 상악중절치와 측절치는 구개측에서 순측보다 치조골의 수직 높이가 더 크게 감소하였다. 2.상악중절치, 측절치 견치 모두 구개측에서 순측보다 열개(dehiscence)의 유병률이 더 높게 나타났다. 상악 중절치의 순측 열개 유병률과 상악 견치의 설측 열개 유병률이 유의하게 낮았다. 3.상악 중절치, 측절치, 견치 모두 치근 면적 및 치근 길이 감소가 유의하게 나타났으나 치아 간 차이는 없었다. 결 론: 골격성 I급 양악치아치조 전돌 증례에서, 최대 고정원을 이용한 상악 전치부 군집 후방 견인 시, 상악 중절치와 측절치의 구개측 치조골 면적, 수직 치조골 높이, 치근 길이 및 면적의 유의한 감소를 보였다.Objective: To evaluate the changes of alveolar bone area, vertical bone level, root length, and root area of the maxillary anterior teeth after en-masse retraction with maximum anchorage. Materials and Methods: The samples consisted of 37 female adult patients who had Class I dentoalveolar protrusion and were treated by extraction of the first premolars and en-masse retraction with maximum anchorage. Using three-dimensional cone-beam computed tomograms (3D-CBCT) taken before treatment (T1) and after space closure (T2), the maxillary central incisors (N = 66), lateral incisors (N = 69), and canines (N = 69) were superimposed using individual reference planes according to their long axis and clinical crown. Alveolar bone area (ABA) at the cervical, middle, and apical levels, and vertical bone level (VBL), root length (RL), root area (RA), and prevalence of dehiscence (PD) were measured and statistical analyses were performed. Results: On the palatal side, ABA significantly decreased in every level of all maxillary anterior teeth. Maxillary central and lateral incisors exhibited more decrease in the ratio of change in palatal ABA than maxillary canines. Palatal/labial ABA ratios decreased in maxillary central and lateral incisors. They showed greater amounts and ratios of changes in VBL on the palatal side than the labial side. The palatal side showed more PD than the labial side in all maxillary anterior teeth. The lowest percentage of dehiscence was observed in maxillary central incisors on the labial side and in maxillary canines on the palatal side. Root resorption occurred significantly in all maxillary anterior teeth but did not show difference among maxillary central incisors, lateral incisors, and canines. Conclusion: During en-masse retraction with maximum anchorage in cases with Class I dentoalveolar protrusion, the ABA and VBL on the palatal side, RL and RA of the maxillary central and lateral incisors were significantly decreased.I. INTRODUCTION II. REVIEW OF LITERATURE III. MATERIALS AND METHODS IV. RESULTS V. DISCUSSION VI. CONCLUSIONS REFERENCESDocto

Hypodontia Pattern and Genetic Association in Cleft Lip and Palate Patients

Cleft lip and palate (CLP) is one of the most prevalent congenital craniofacial anomalies. It has a significantly greater incidence of dental abnormalities in number, size, shape, and eruption of the teeth. Knout-out mouse model can identify several genes which play an important role in tooth agenesis. Since disruption of these genes has been confirmed to result in tooth agenesis in humans, CLP associated with hypodontia may be the best models for isolated tooth agenesis. According to the studies of dental abnormalities in CLP, the severity of dental defect is known to be influenced by the CLP phenotype. The cumulative data obtained from mouse and human genetic studies indicated that MSX1, PAX9 and AXIN2 are considered as candidate genes in non-syndromic hypodontia, while Shh, Pitx2, Irf6, p63 and EDA pathway genes are involved in syndromic one. We expect that genetic approach of CLP can offer the basis for tooth regeneration and be a new target in hypodontia therapy

Potentials of Computational Fluid Dynamics Technique for Optimization of Water Treatment Process

최근 전 세계적으로 급속하게 확정되고 있는 물 산업은 소비자의 높아지는 요구수준을 만족시키기 위해 정수처리공정의 설계, 운전 및 진단에 보다 진보되고 정교한 기술발전을 필요로 하고 있다. 이러한 요구와 병행하여 특히 각 단위 공정을 물리,화학적으로 깊이 이해하여 원천적인 문제점 발견 및 해결방안을 공정에 재적용 하려는 연구는 그 중요성이 증가되고 있다. 같은 맥락으로 근래 많은 연구자들은 단의 공정내 수리거동과 이에 의거한 수처리 효율과의 관계 규명에 귀추를 주목하고 있다. 한편, 최근 수치해석과 컴퓨터 기술의 발달은 각 단의 공정내의 수리거동을 보다 상세하게 연구할 수 있도록 하였으며, 급기야 1990년대 말부터 전산유체 역학(CFD; Computational Fluid Dynamics)기술을 정수처리 공정에 접목시키려는 연구 시도들이 생겨나게 되었다. 원래 CFD 소프트웨어들은 항공 우주 또는 자동차 설계 분야에서 활발히 개발되어, 항공기 및 자동차주변 공기 흐름을 해석하는데 활용되어왔다. 이후 이러한 소프트웨어들은 기계 및 화학 단위 공정 설계자들이 그 용도를 확장시켜 적용사능 범위를 넓혀 놓았으며, 더욱이, 몇몇 연구자들은 상용 CFD프로그램을 이용하여, 토목, 환경 및 수처리 분야에서도 연구성과를 발표하였다. 이에 본 고에서는 전산유체역학의 정의 및 소개 그리고 적용 사례를 통해 이 기술의 정수 처리공정 적용 가능성에 대해 역설하려 한다