Fabrication and Characterization of Vertically Aligned Graphene Gaps at THz Regime

학위논문 (박사) -- 서울대학교 대학원 : 자연과학대학 물리·천문학부(물리학전공), 2020. 8. 홍성철.In this work a vertically aligned graphene gap array composed of a c opper graphene copper structure was investigated for optical measurements at terahertz regime. The graphene gap array was manufactured by directly synthesizing graphene on the first patterned copper thin film followed by depositing the second copper layer. Structural features of the graphene between the copper thin films were characterized by Cs corrected transmission electron microscope and resonant Raman spectroscopy. The results revealed that the number of layers and the crystallinity of graphene on the copper surface can be controlled by adjusting the synthesis temperature and pre-annealing time in plasma enhanced chemical vapor deposition process. And the gap size can be defined by a multiple of van der Waals distance according to the number of graphene layers. Furthermore, the optical properties of a graphene gap slit array at terahertz regime was investigated by terahertz-time domain spectroscopy. Even though the gap size is a sub-nanometer for single layer graphene gap, the terahertz transmitted amplitude revealed that the fabricated graphene gap slit array is fully functional. The constant normalized terahertz amplitude through the graphene gap slit array in the frequency domain was explained by the graphene treated as treated as a gap materiala gap material with with a complex dielectric constant using analysis of the capacitor model. The results in this work can open a new route for the fabrication techniques and characterization of structural and optical properties in many optical, electronic and optoelectronic applications using two dimensional materials such as hexagonal boron nitride (h BN), molybdenum disulfide (MoS 2 ), and etc.본 연구는 구리-그래핀-구리 구조로 수직으로 정렬된 그래핀 갭 의 테라헤르츠 파 영역 에서 광학 적 특성 을 알아보기 위해 진행 되었다. 그래핀 갭을 갖는 슬릿 배열은 패턴 된 구리 박막 상에 그래핀을 직접 합성한 후 그 위에 두 번째 구리층을 증착함으로써 제조되었다 . 구리 표면에서 합성된 그래핀의 구조적 특징은 구면 수차 보정 투과 전자 현미경 및 공명 라만 분광학에 의해 특성화되었다. 결과는 플라즈마 강화 화학 기상 증착 공정에서 합성 온도 및 사전 열처리 시간을 조정함으로써 구리 표면 상의 그래핀의 층 수 및 결정도를 제어할 수 있음을 밝혀냈다. 또한, 그래핀 갭의 크기는 그리팬 층의 수에 따른 반 데르 발스 거리의 배수에 의해 정해질 수 있음을 확인하였다. 테라헤르츠 파 영역 에서 그래핀 갭 슬릿 배열의 광학적 특성을 조사하기 위해 테라헤르츠-시간영역 분광학을 수행하였다. 갭 크기가 단층 그래핀갭에 대해 서브 나노미터임에도 불구하고 테라헤르츠파 투과 진폭은 제조된 그래핀 갭 슬릿 배열이 테라헤르츠파 영역에서 완전히 작동하는 것을 보여주었다. 테라헤르츠파의 일정한 투과 진폭은 축전기 모델을 이용하여 갭 안에 그래핀을 복소 유전 상수를 갖는 갭 물질로 하여 분석되었다. 이 연구 결과는 육방 정계 질화 붕소 (h(h--BN), BN), 이황화 몰리브덴 (MoS(MoS22) ) 등과 같은 2 차원 물질을 사용하여 광학, 전자 및 광전자 응용 분야에서 구조 제작 기술 및 구조적, 광학적 특성화를 위한 새로운 방법을 제시할 것으로 기대된다.Chapter 1. Introduction 1 1.1 Extraordinary optical transmission 1 1.2 Field enhancement in a nanogap at THz regime 3 1.3 Sub nanometer gap using graphene 5 Chapter 2. Preparation of graphene gap array 7 2.1 Atomic layer lithography for nanogap fabrication 7 2.2 Graphene synthesis by plasma enhanced CVD 11 2.3 Fabrication of a graphene gap array 19 Chapter 3. Structural characterization of graphene gap 28 3.1 Raman measurement of the graphene 28 3.2 Defining the size of the graphene gap 42 Chapter 4. Optical properties of graphene gap array at THz regime 46 4.1 THz-time domain spectrosocpy 46 4.2 Kirchhoff integral and field enhancement 49 4.3 THz transmission for the graphene gap slit array 52 4.4 Complex dielectric constant of graphene in out-of-plane direction at THz regime 57 Chapter 5. Conclusion 63 Bibliography 65 Abstract in Korean 73Docto

중하부 직장암 환자에서 영구장루형성의 예측인자 평가 : 수술전 항문기능에 대한 다기관 코호트연구

학위논문(석사) -- 서울대학교대학원 : 의과대학 의학과, 2023. 2. 강성범.Aim: Preoperative factors predictive of permanent stoma creation were investigated in a long-term follow-up of patients with mid or low rectal cancer. Methods: We included patients who underwent radical resection for mid or low rectal cancer with available data for preoperative anal function measured by manometry and Faecal Incontinence Severity Index questionnaire between January 2005 and December 2015 in three tertiary referral hospitals. A permanent stoma was defined as a stoma present until the patients last follow-up visit or death. Preoperative factors that predicted permanent stoma creation were analysed. Results: Over a median follow-up of 57.4 months (range 12–143 months), a permanent stoma was created in 144/577 (25.0%) patients, including 89 (15.4%) who underwent abdominoperineal resection, one (0.2%) who underwent Hartmanns operation without reversal, 15 (2.6%) with a diverting ileostomy at the time of initial sphincter-preserving surgery without undergoing stoma reversal, and 39 (6.8%) who underwent permanent ileostomy formation after sphincter-preserving surgery. Patients with permanent stoma creation had a shorter tumour distance from the anal verge (P < 0.001), larger tumour size (P = 0.020) and higher preoperative Faecal Incontinence Severity Index score (P = 0.020). On multivariable analysis, tumour distance from the anal verge predicted permanent stoma formation (relative risk 0.53 per centimetre increase; 95% confidence interval 0.46–0.60; P < 0.001) but preoperative anal function did not. Conclusion: Tumour distance from the anal verge was the only preoperative determinant of permanent stoma creation in rectal cancer patients. These data may help mid and low rectal cancer patients understand the need for permanent stoma.목적: 중하부 직장암 환자를 대상으로 장기간 추적관찰하여 영구적인 장루 생성을 예측할 수 있는 수술 전 요인을 알아보고자 하였다. 방법: 2005년 1월부터 2015년 12월까지 3개 3차 병원에서, 수술전 항문압력검사와 변실금 중증도 지수 설문지를 통해 항문 기능에 대한 데이터가 있는 중하부 직장암 환자 중 근치적 절제술을 시행한 환자를 포함했다. 영구 장루는 환자가 마지막으로 방문하거나 사망할 때까지 존재하는 장루로 정의되었다. 영구적인 장루 생성을 예측하는 인자를 수술 전 요인을 이용하여 분석하였다. 결과: 중앙값 57.4개월(12-143개월)의 추적 기간 동안 144/577(25.0%)의 환자에서 영구 장루가 생성되었으며, 이는 첫 수술에서 복회음절제술을 받은 89명(15.4%), 하트만수술을 받은 1명(0.2%)이 포함되었으며, 일시적 장루를 형성했다가 복원하지 못한 15명(2.6%), 첫 수술이후 장루를 다시 형성한 39명(6.8%)을 포함한다. 영구 장루 생성 환자는 항문 가장자리에서 더 짧은 종양 거리(P < 0.001), 더 큰 종양 크기(P = 0.024) 및 더 높은 수술 전 변실금 중증도 지수 점수(P = 0.016)를 보였다. 다변량 분석에서 항문연부터 종양까지 거리는 영구적인 장루 형성을 예측했지만 (상대 위험도 0.53/cm; 95% 신뢰 구간 0.46–0.60; P < 0.001), 수술 전 항문 기능은 통계적으로 유의하지 않았다. 결론: 직장암 환자에서 항문연부터 종양까지 거리는 수술 전 영구적인 장루 생성을 결정하는 유일한 요인이었다. 이러한 데이터는 중하부 직장암 환자가 영구 장루의 필요성을 이해하는 데 도움이 될 수 있다.1. Introduction 1 2. Methods 2 3. Results 4 4. Discussion 7 5. References 11 Tables Table 1 16 Table 2 18 Table 3 19 Table 4 21 Table 5 23 Table 6 25 Figures Figure 1 27 Figure 2 28 Figure 3 29석

The effect of medial open wedge high tibial osteotomy on the patellofemoral joint: comparative analysis according to the preexisting cartilage status

BACKGROUND: Although it has been known that medial open wedge high tibial osteotomy (MOWHTO) would adversely affect the patellofemoral joint, no previous study examined the surgical outcome of MOWHTO according to the preexisting cartilage status of the patellofemoral joint. The aim of this study was to investigate the effect of MOWHTO on the patellofemoral joint with regard to objective and subjective aspects according to the preexisting cartilage status. METHODS: Ninety-two patients who underwent MOWHTO and a following second-look arthroscopic assessment were included in this study. The patients were divided into two groups according to the preexisting cartilage status of the patellofemoral joint: group 1 (International Cartilage Repair Society [ICRS] grade 2 or 3) and group 2 (ICRS grade 0 or 1). Comparative analysis was performed regarding clinical scores, radiographic parameters, and arthroscopic measurements between the two groups. RESULTS: Clinical outcomes showed overall improvement from baseline to the time of second-look operation, with no significant difference between the two groups at each time point. There were no significant differences in radiographic parameters between the two groups. Radiographic grade of patellofemoral osteoarthritis in both groups showed a tendency to progress, without statistical significance. In arthroscopic assessment, the size of the cartilage lesion on the patellofemoral joint increased with time in both groups (P = 0.003), but the degree of change over time between the two groups was not statistically significant. Consistently, there was no significant difference in the frequency of progression of cartilage lesion grade in the patellofemoral joint between the two groups. CONCLUSIONS: MOWHTO would contribute to osteoarthritis progression of the patellofemoral joint regardless of the preexisting cartilage status, without an association with clinical outcomes in short-term follow-up.ope

Do Rotation and Measurement Methods Affect Reliability of Anterior Cruciate Ligament Tunnel Position on 3D Reconstructed Computed Tomography?

Background: The literature has seldom investigated the anterior cruciate ligament (ACL) tunnel position while considering the effect of rotation of 3-dimensional computed tomography (3D-CT) images during measurements. Hypothesis: We hypothesized that (1) measurement of the ACL tunnel position in the femur and tibia through use of 3D-CT is considerably influenced by rotation of the 3D model and (2) there exists a reliable measurement method for ACL tunnel position least affected by rotation. Study Design: Controlled laboratory study. Methods: The 3D-CT images of 30 randomly selected patients who underwent single-bundle ACL reconstruction were retrospectively reviewed. For femoral tunnel assessments, rectangular reference frames were used that involved the highest point of the intercondylar notch and outer margins of the lateral femoral condyle (method 1), the highest point of the intercondylar notch and outer margins of the lateral wall of the intercondylar notch (method 2), and the lowest point of the intercondylar notch and outer margins of the lateral femoral condyle (method 3). For tibial tunnel assessments, rectangular reference frames with the cortical outline at the articular surface of the tibia (method A) and the cortical outline of the proximal tibia (method B) were used. For both femoral and tibial assessments, the tunnel positions at 5°, 10°, and 15° of rotation of the 3D model were compared with that at a neutral position. Results: The values measured by methods 1 and 3 showed significant differences at greater than 5° of rotation compared with the value at the neutral position, whereas method 2 showed relatively consistent results. However, the values measured with both methods A and B showed significant differences at greater than 5° of rotation compared with the value at the neutral position. Conclusion: The tunnel position on 3D-CT images was significantly influenced by rotation during measurements. For femoral tunnel position, measurement with a reference frame using the lateral wall of the intercondylar notch (method 2) was the least affected by rotation, with relatively consistent results. Clinical Relevance: This study demonstrates that measurement using the lateral wall of the intercondylar notch might be a consistent and reliable method for evaluating the ACL femoral tunnel position considering the effect of 3D-CT image rotation during measurements. However, both methods to measure tibial tunnel position described in this study were similarly affected by rotation.ope

Analysis of Potentially Inappropriate Medication Use and Related Factors in Terminal Cancer Patients

학위논문 (석사) -- 서울대학교 대학원 : 약학대학 약학과, 2021. 2. 이주연.Polypharmacy is common in cancer patients by taking not only drugs for cancer treatment, but also drugs for other underlying diseases and supportive care drugs for relieving adverse reactions of chemotherapy. In terminal cancer patients who have 6 to 12 months of life expectancy, the goal of treatment should focus on improving quality of life, such as alleviating the pain caused by cancer-related symptoms and avoiding unnecessary treatment. Nevertheless, it is common for terminal patients to keep taking many drugs that can only benefit from long-term use. Such unnecessary polypharmacy can lead to problems such as drug interaction, adverse reactions, and poor quality of life. STOPPFrail, OncPal are the deprescribing guideline that suggest potentially inappropriate medications (PIMs) to frail patients with a limited life expectancy. The purpose of this study was to identify the frequency of PIM use according to the STOPPFrail and OncPal guideline in terminal cancer patients in South Korea and to analyze related factors. We used two data sources. The one is the data from the 2018 Health Insurance Review and Assessment Service - National Patients Sample (HIRA-NPS) of South Korea and the other was electrical medical records of cancer patients registered hospice care in 2019 at one tertiary hospital. After reviewing the STOPPFrail criteria and the OncPal guideline, we adjusted the criteria for PIMs to applicable level in this study. When we analyze the national patients sample data, patients with death records or previous medical records but no healthcare utilization for more than 6 months are considered as deceased patients. Among them, patients who used opioid analgesics or megestrol, or who had been hospitalized for more than 90 days were defined as the deceased terminal cancer patients. The prescriptions for 3 months prior to the estimated death were reviewed and only the oral medications used for more than 7 days or more were included in the analysis. For patients receiving hospice care at tertiary hospital, we reviewed the prescriptions for one months before and after the hospice consultation request date. A total of 1,558 terminal cancer patients among 1,481921 patients of 2018 national patients sample data were included for analysis. Among them, 1,133 patients (72.7%) used 5 or more medications and 630 patients (40.4%) used 10 or more medications. According to the adjusted PIM criteria, 914 patients (58.7%) used 1 or more PIMs and 210 patients (13.5%) used 3 or more PIMs. The most common categories of PIM were lipid lowering agents (307 patients, 19.7%), proton pump inhibitors (274 patients, 17.6%), hypoglycemic agents (221 patients, 14.2%), alpha-blocker for urinary symptoms (182 patients, 11.7%), H2 receptor antagonist (110 patients, 7.1%). A total of 1243 cancer patients in hospice care at the tertiary hospital were included in the analysis. Among them, 794 patients (63.9%) used 5 or more medications and 312 patients (25.1%) used 10 or more medications. Five hundred and thirty two patients (42.8%) were found that used one or more PIMs and 93 patients (7.5%) were found that used three or more PIMs. The frequent categories of PIM that found in hospice care patients were lipid lowering agents (142 patients, 11.4%), nutritional supplements (133 patients, 10.7%), multivitamins (103 patients, 10.7%), H2 receptor antagonists (95 patients, 7.6%), proton pump inhibitor (91 patients, 7.3%). This study showed that polypharmacy and PIM use according to the predefined guideline in terminal cancer patients were prevalent in real-world practice. These findings suggested that active interventions for pharmacotherapy were necessary for these patients.암환자는 암 치료에 대한 약제뿐 아니라, 다른 기저질환에 대한 치료제와 항암치료에 따른 부작용 증상 완화를 위한 보조약제 등을 함께 투약하여 다약제 사용의 빈도가 높다. 말기 암환자는 암의 종류나 환자의 임상 상태에 따라 6개월에서 12개월의 여명이 예상되는데, 이러한 상황에서 치료는 암 관련된 증상으로 인한 고통을 완화하고 불필요한 치료를 피하는 것과 같이 삶의 질을 향상시키는데 중점을 두어야 한다. 그럼에도 불구하고 말기 환자에서 장기간 복용해야 이익을 얻을 수 있는 약물의 복용을 유지하는 경우가 흔한데, 이러한 불필요한 다약제 사용으로 인해 약물상호작용, 약물 부작용, 환자 삶의 질 저하 등의 문제가 발생할 수 있다. Deprescribing은 더 이상 유익성이 없거나 위해를 야기시킬 수 있는 약의 용량을 감량하거나 중단하는 과정이며, STOPPFrail, OncPal은 기대여명이 얼마 남지 않은 노쇠한 환자에게 잠재적으로 부적절한 약물(potentially inappropriate medication, PIM)을 제시한 deprescribing 가이드라인이다. 본 연구에서는 한국의 말기 암환자에서 STOPPFrail, OncPal 가이드라인에 따른 잠재적 부적절 약물의 사용 현황을 파악하고 관련 인자를 분석하고자 하였다. 2018년 건강보험심사평가원 청구자료와 2019년 서울대학교병원에서 호스피스 상담 의뢰된 암환자의 처방내역을 분석하였다. 일차적으로 잠재적 부적절 약물은 STOPPFrail, OncPal 가이드라인의 항목을 종합하여 본 연구에서 적용 가능한 기준으로 수정하여 선정하였다. 전국민 표본자료에서는 암환자 중에서 사망 기록이 있거나 이전에 진료기록이 있었으나 6개월 이상 청구 내역이 없는 환자를 사망한 환자로 간주하고, 이 중에서 마약성 진통제나 식욕촉진제인 megestrol을 사용한 기록이 있거나 90일 이상 입원한 기록이 있는 환자를 말기 암환자 사망한 것으로 정의하였다. 사망 전 3개월 간의 처방을 분석하였으며, 7일 이상 사용한 경구약 처방을 분석하였다. 서울대학교병원 호스피스 환자 자료에서는 호스피스 상담 의뢰일을 기준으로, 이전 및 이후 한 달 간의 처방내역에서 잠재적 부적절 약물을 분석하였다. 2018년 전국민 표본자료의 총 1,481,921명 중 말기 암환자로 추정되는 1,558명의 처방을 분석한 결과, 1,133명(72.7%)이 5종 이상 약물을 사용하는 것으로 나타났고 이 중 630명(40.4%)는 10종 이상의 약물을 사용하는 것으로 나타났다. 미리 정의한 PIM을 하나 이상 사용한 것으로 확인된 환자는 914명으로 전체의 58.7%를 차지하였으며, 3종 이상 사용한 환자는 210명(13.5%)이었다. 가장 흔한 PIM은 이상지질혈증 치료제(307명, 19.7%), 프로톤펌프억제제(274명, 17.6%), 혈당강하제(221명, 14.2%), 알파차단제(전립선 비대증에 대한, 182명, 11.7%), H2-수용체차단제(110명, 7.1%) 순으로 나타났다. 2019년 서울대학교병원 호스피스 상담 의뢰된 암환자 총 1,243명을 분석한 결과, 794명(63.9%)이 5종 이상 약물을 동시에 사용하는 것으로 나타났고 이 중 312명(25.1%)는 10종 이상 다약제를 사용하였다. PIM을 하나 이상 사용한 것으로 확인된 환자는 532명(42.8%)였고, 93명(7.5%)에서는 3종 이상의 PIMs를 사용하는 것으로 확인되었다. 기대여명이 짧은 암환자에서 가장 흔히 사용된 PIM의 계열은 이상지질혈증 치료제(142명, 11.4%), 영양제(133명, 10.7%), 종합 비타민제(103명, 8.3%), H2 수용체 차단제(95명, 7.6%), 프로톤펌프억제제(91명, 7.3%) 순으로 나타났다. 본 연구 결과, 우리나라 임상 현실에서 여명이 길지 않은 말기 암환자에서 실제로 다약제 사용과 deprescribing의 대상으로 검토가 필요한 잠재적 부적절 약물의 사용이 빈번함을 확인할 수 있었다. 이러한 결과는 이들 환자 대상으로 약물치료에 대한 검토 및 중재가 필요함을 시사한다.1. 서론 1 1.1 연구의 배경 1 1.2 연구의 필요성 5 1.3 연구의 목적 7 2. 연구 방법 8 2.1 연구 자료 8 2.2 연구 대상 11 2.3 분석 기간 설정 33 2.4 결과 변수 35 2.5 PIM 발생 빈도 관련 인자 분석 35 2.6 통계 분석 35 3. 연구 결과 36 3.1 연구 대상자 선정 및 기초 특성 파악 36 3.2 단일 상급종합병원 자료에서 PIM 발생 빈도 분석 42 3.3 건강보험심사평가원 자료에서 PIM 발생 빈도 분석 47 3.4 상급종합병원 자료에서 PIM 발생 빈도 관련인자 분석 51 3.5 심평원 표본 자료에서 PIM 발생 빈도 관련인자 분석 54 4. 고찰 58 5. 결론 69Maste

Efficacy and safety of short-term use of a pelubiprofen CR and aceclofenac in patients with symptomatic knee osteoarthritis: A double-blinded, randomized, multicenter, active drug comparative, parallel-group, phase IV, non-inferiority clinical trial

Introduction: At present, information about clinical efficacy and adverse events of controlled release (CR) form of pelubiprofen, a prodrug of 2-arylopropionic acid with relatively selective effects on cyclooxygenase-2 activity, remains scarce. In this study, we sought to determine non-inferiority of pelubiprofen CR 90 mg/day compared to aceclofenac 200 mg/day regarding clinical efficacy and adverse events after a 4-week course of medication in the patients with symptomatic knee osteoarthritis. Materials and methods: A total of 191 patients were randomly assigned to take either pelubiprofen CR 90 mg (n = 95) or aceclofenac 200 mg (n = 96). The primary outcome variable was non-inferiority of pain reduction between baseline and week 4 when assessed using a 100 mm pain visual analogue scale (VAS). Pelubiprofen was considered non-inferior to aceclofenac if the upper limit of the one-sided 97.5% confidence interval for the difference in terms of pain VAS was above 15 mm (the average change of pain VAS in the pelubiprofen group-pain VAS reduction in the aceclofenac group). Secondary outcome variables were the changes in 100 mm pain VAS at week 2 versus baseline, K-Western Ontario, and McMaster University Arthritis Index (K-WOMAC) changes at weeks 2 and 4 as compared to baseline, patient global assessment at weeks 2 and 4. The frequency and amount of rescue medicine usage at weeks 2 and 4 were also evaluated as the secondary outcome variable. For safety analysis, adverse events, clinical laboratory tests, vital signs, and physical examinations were assessed and conducted at each follow-up visit. Results: At week 4, the pain VAS values were significantly reduced in both groups receiving either pelubiprofen CR 90 mg or aceclofenac 200 mg as compared to the baseline. However, the pelubiprofen group and the aceclofenac group respectively showed the pain VAS changes of -22 and -21.9 in the pre-protocol set and -20.8 and -21.7 in the full analysis set, confirming non-inferiority. The pelubiprofen CR 90 mg showed a reduced incidence of adverse events compared to the aceclofenac 200 mg (p = 0.005). Conclusions: Pelubiprofen CR 90 mg is as effective as aceclofenac 200 mg with reduced adverse events for the treatment of symptomatic knee osteoarthritis.ope

In Vivo Evaluation of the Subject-Specific Finite Element Model for Knee Joint Cartilage Contact Area

In this paper, we present a new validation method for subject-specific finite element (FE) modeling of the knee joint based on in vivo computed tomography (CT) and magnetic resonance imaging (MRI) data. Previously, several FE models have been developed for estimating the mechanical response of joint structures, where direct or indirect in vivo measurement is difficult or impossible. More recently, studies using MRI have provided clear visualization of the motion and deformation of the articular cartilage within the tibiofemoral (TF) joint space. Two methods have been introduced to validate in vivo subject-specific models: alignment of supine MRI with X-ray images and weight-bearing MRI. The size of the contact area between the femur and tibia was determined by computing the area of femoral cartilage that intersected the tibial cartilage. The result showed good agreement between non-weight bearing image aligned with X-ray and weight-bearing MRI images. This study may help to better define the relative importance of modeling validations for the development of subject-specific models.ope

The effects of posterior cruciate ligament deficiency on posterolateral corner structures under gait- and squat-loading conditions: A computational knee model

OBJECTIVES: The aim of the current study was to analyse the effects of posterior cruciate ligament (PCL) deficiency on forces of the posterolateral corner structure and on tibiofemoral (TF) and patellofemoral (PF) contact force under dynamic-loading conditions. METHODS: A subject-specific knee model was validated using a passive flexion experiment, electromyography data, muscle activation, and previous experimental studies. The simulation was performed on the musculoskeletal models with and without PCL deficiency using a novel force-dependent kinematics method under gait- and squat-loading conditions, followed by probabilistic analysis for material uncertain to be considered. RESULTS: Comparison of predicted passive flexion, posterior drawer kinematics and muscle activation with experimental measurements showed good agreement. Forces of the posterolateral corner structure, and TF and PF contact forces increased with PCL deficiency under gait- and squat-loading conditions. The rate of increase in PF contact force was the greatest during the squat-loading condition. The TF contact forces increased on both medial and lateral compartments during gait-loading conditions. However, during the squat-loading condition, the medial TF contact force tended to increase, while the lateral TF contact forces decreased. The posterolateral corner structure, which showed the greatest increase in force with deficiency of PCL under both gait- and squat-loading conditions, was the popliteus tendon (PT). CONCLUSION: PCL deficiency is a factor affecting the variability of force on the PT in dynamic-loading conditions, and it could lead to degeneration of the PF joint.Cite this article: K-T. Kang, Y-G. Koh, M. Jung, J-H. Nam, J. Son, Y.H. Lee, S-J. Kim, S-H. Kim. The effects of posterior cruciate ligament deficiency on posterolateral corner structures under gait- and squat-loading conditions: A computational knee model. Bone Joint Res 2017;6:31-42. DOI: 10.1302/2046-3758.61.BJR-2016-0184.R1.ope

Development of Hybrid Electrochemical Water Treatment System Combined of Deionization and Oxidation

학위논문 (박사)-- 서울대학교 대학원 : 화학생물공학부, 2017. 2. 윤제용.Over recent decades, the lack of available water has been considered as a critical challenge for mankind. Electrochemical water treatment can be a promising alternative due to its high energy efficiency, eco-friendliness and lack of required hazardous chemicals. Capacitive deionization (CDI), electrodialysis (ED) and desalination battery are well-established demonstrations that are successfully converged of materials used for energy storage with electrochemical system for water treatment. These demonstrations accomplish electrochemical deionization by means of the operational principle of energy storage in energy storage systems (e.g., supercapacitors and batteries). Although they provide an energy efficient deionization process, the systems have suffered from the limitations in their systems and materials, attributing to difficulties to find suitable compounds/systems for capturing anions and retain the stability of active material in aqueous system. In this dissertation, it is demonstrated that a novel electrochemical water treatment system combined of deionization and oxidation, and suitable materials for intercalation/deintercalation of cations. First of all, a novel hybrid electrochemical water treatment system consisting of an electrochemical desalination system synchronized with an oxidation process is developed. The hybrid electrochemical water treatment system consists of electrode material for the sodium ion battery as a desalination component and an oxidant generation anode serving the oxidation function. As a primary result, superior desalination capacities of approximately 87 mg g-1 and 36 mg g-1 were accomplished with NaCl concentrations of 35 g L-1 and 3 g L-1, respectively. Moreover, this hybrid system showed a coulombic efficiency in synthetic brackish water (2.79 g L-1 of diverse ions) of approximately 98% and 66% for desalination and oxidation, respectively. Second, a new HCDI system with sodium iron pyrophosphate (Na2FeP2O7) is investigated. The overall deionization performance of Na2FeP2O7 as the electrode capturing cations is demonstrated. The major results of the HCDI system with Na2FeP2O7 showed a superior maximum deionization rate performance (0.08 mg g-1 s-1) with a comparable deionization capacity (30.2 mg g-1) compared to the previous HCDI system with Na4Mn9O18. Furthermore, the analysis of the CDI Ragone plot was applied to investigate the hybrid behavior characteristics, high deionization capacity that originated from the high capacity of Na2FeP2O7 and fast deionization rates resulting from the supercapacitor. Consequently, the novel electrochemical water treatment and electrode materials can contribute to providing a new strategy to overcome the limitations of materials used for capturing anions and discovering their behavior for electrochemical water treatment.1. Introduction 1 1.1. Research Background 1 1.2. Objectives 5 2. Literature Review 7 2.1. Electrochemical Water Treatment System 7 2.1.1. Capacitive Deionization 7 2.1.2. Desalination Battery 16 2.1.3. Hybrid Capacitive Deionization 20 2.2. Materials of Electrochemical Water Treatment for Deionization and Oxidation 24 2.2.1. Materials for Deionization 24 3. Hybrid Electrochemical Water Treatment System for Deionization and Oxidation 33 3.1. Introduction 33 3.2. Experimental 38 3.2.1. Preparation of sodium manganese oxide (Na0.44MnO2) 38 3.2.2. Preparation of blue TiO2 nanotube on meshed Ti substrate (m-Blue TiO2 NTs) 39 3.2.3. Characterization of prepared electrodes 40 3.2.4. Operations of the hybrid system for deionization and oxidant generation 41 3.3. Results and Discussion 43 3.4. Summary 67 4. Na2FeP2O7 as Novel Material for Hybrid Capacitive Deionization 68 4.1. Introduction 68 4.2. Experimental 71 4.2.1. Material synthesis 71 4.2.2. Electrode fabrication 72 4.2.3. Electrochemical characterization 73 4.2.4. Deionization test 74 4.3. Results and Discussion 76 4.4. Summary 98 5. Conclusion 99 References 101 국문초록 114Docto

A Study on Energy Harvesting using Kelvin Water Dropper

학위논문 (석사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2015. 8. 김용권.본 논문에서는 소량의 물로도 고전압의 정전기를 발생시키는 Kelvin water dropper를 에너지 하베스팅에 이용하기 위하여 고전압 저 전하의 정전기 에너지를 저장할 수 있는 에너지 저장 회로를 제안하고 Kelvin water dropper를 이용한 에너지 하베스팅 시스템의 효율을 증대시키기 위한 두 가지 방법을 제시하였다. 또한 이러한 시스템이 가변적인 환경에서도 특정 응용에 맞는 일정한 출력 전압을 낼 수 있도록 전원공급 회로를 도입하였다. Kelvin water dropper가 안정적이고 효율적으로 동작하도록 Kelvin water dropper를 수학적으로 모델링하여 적합한 배치에 대한 시뮬레이션 및 실험을 진행하여 금속 용기와 금속 링 사이의 거리 h 를 3 cm 로 정하였다. 다음으로 Kelvin water dropper에서 발생되는 정전기 에너지를 저장하기 위해 MEMS 스위치를 이용한 에너지 저장회로를 제작 및 시험하였으나 적합성의 문제와 효율성의 문제로 불꽃 방전 간극을 이용한 에너지 저장 회로를 새로이 설계 및 시험하였다. 제작된 에너지 저장 회로를 이용하여 Kelvin water dropper에서 하베스팅을 진행하였을 경우 리터당 32.56 μJ 의 에너지를 수확할 수 있었다. 더 나아가 시스템의 효율 향상을 위해 Paschen의 법칙에 근거한 불꽃 방전 간극을 증가시킴으로써 에너지 저장 효율을 증가시킬 수 있었는데 방전간극이 3 mm 이하일 때에는 에너지 저장 효율이 증가하는 경향을 실험을 통해 확인할 수 있었으나 3 mm 를 초과한 시점에서는 물방울 사이의 반발로 인한 물의 손실로 효율이 감소함을 확인하였다. 또한 Kelvin water dropper의 전압 상승식에서 초당 떨어지는 물방울의 수를 증가시키기 위해 다중 노즐을 도입하였고 그 결과 노즐의 개수만큼의 에너지 충전시간이 감소하였다. 이러한 모든 결과들을 종합하여 3 V 의 출력 전압을 낼 수 있는 전원 공급 회로를 추가하였고, 총 5.84 L 의 물을 사용하여 3 V 의 출력 전압이 1 MΩ 의 부하를 통해 1 s 동안 유지하는 결과를 얻음으로써 시스템의 유효성을 확인하였다. 제안된 Kelvin water dropper를 이용한 에너지 하베스팅 시스템은 적은 양의 물로도 발전이 가능한 친환경 에너지원으로 다양한 환경에서의 에너지 수확에 그 분야를 확장할 수 있을 것으로 기대된다.초록 목차 제 1 장 서 론 1 1.1 연구의 배경 1 1.2 에너지 하베스팅의 연구 동향 4 1.3 Kelvin water dropper 14 1.4 연구의 동기 및 목적 15 1.5 논문의 구성 17 제 2 장 Kelvin water dropper의 이론적 분석과 구성 19 2.1 Kelvin water dropper의 원리 19 2.2 Kelvin water dropper의 구성 24 제 3 장 정전기 에너지를 저장하기위한 에너지 저장회로의 설계와 제작 30 3.1 Paschen곡선에 의한 공기의 절연 파괴 전압 30 3.1.1 Paschen의 법칙 30 3.1.2 수정된 Paschen의 법칙 36 3.2 에너지 저장회로의 설계 38 3.2.1 MEMS switch를 이용한 에너지 저장회로 38 3.2.2 불꽃 방전 간극을 이용한 에너지 저장회로 42 제 4 장 시스템의 효율 향상 방법과 전원공급 회로의 제작 47 4.1 시스템 효율 향상 방법 47 4.1.1 불꽃 방전 간극 47 4.1.2 다중 노즐 55 4.2 전원공급 회로의 제작 59 제 5 장 결론 63 참고문헌 65 Abstract 69Maste