[특별강연]동아시아의 미래, 역사분쟁을 넘어서

고마바 캠퍼스에서 대학원생들을 대상으로 평소에 일본학생들에게 하고 싶었던 얘기를 할 수 있었던 것은 나에게 귀중한 기회였다. 초청해 주신 다카하시 데쓰야(高橋哲也) 선생과 나까지마 다까히로(中島隆博) 선생, 기타가와 사끼코(北川東子)선생, 히데 이시구로(ひて石黑) 선생 네 분께 다시 한번 감사한다. 수업 중에 학생들이 강의를 열심히 듣고 진지한 질문을 많이 해 주어 큰 보람을 느꼈다. 내 강의의 주제는 UTCP(The University of Tokyo, Center for Philosophy)의 역사, 법, 폭력이란 프로젝트에 맞추어 근대한일관계사에서의 법과 폭력으로 정했으며, 이 강의를 통해 강조한 것은 다음과 같다. 즉 일본은 한국을 식민지로 통치하는 동안 근대화 시켜 주었다고 하지만 실제로는 한국의 자력 근대화의 기회를 박탈했던 것이며, 한국병합에 대해서도 일본측에서는 합법이란 주장이 많으나 실제로는 절차상의 탈법이 여러 번 저질러지고 무력으로 한국측을 위협해서 조약을 강제 체결했기 때문에 조약 자체가 성립한 것이라고 보기 어려운 점이 많다는 것을 조약문 하나하나를 함께 보면서 얘기했다

A Study on the Optimization of Linear Equalizer for Low-power Underwater Acoustic Communication

A communication system with low power consumption is required in underwater sensor network because of environmental limitations. For the low-power system, it is necessary to reduce the transmit power, and to optimize the sparse coefficients of equalizer, or the tap length. In this thesis, the method that reduce a computation time by optimizing computation process is proposed to realize low-power underwater acoustic communication system. At first, dependency of decision delay on tap length of linear equalizer was investigated using simulation. According to the result, increasing the tap length resulted in an improvement of MSE performance within a limited range even though tap made system became complicated. Moreover, excessive tap length induced over-estimation effect, thus it make error increase, and system showed the best performance when decision delay of signal sequence had appropriate value. In addition to decide optimal tap length with decision delay, we extracted the MSE-decision delay graph. From the graph, we obtained variance value of the MSE-decision delay, and estimated the optimum decision delay range from the variance value. Also, using the extracted optimal parameters, we performed a simulation. In this simulation, we considered two cases of depth of receiver, 130 and 170m. According to the result, the simulation employing optimal tap length, which is only 33% of maximum tap length, showed a satisfactory performance comparable to simulation employing maximum tap length.제 1 장 서 론 ······························································ 1 제 2 장 수중 음향 통신 채널 특성 ··························· 4 제 2-1절 수중 채널 특성 ······································ 4 제 2-2절 수중 음향 통신 오차 유발 요인 분석 ·· 5 제 2-2-1. 전달 손실 ············································ 6 제 2-2-2. 다중 경로 ············································ 6 제 2-2-3. 도플러 확산 ········································ 7 제 2-2-4. 잡음 ······················································ 8 제 3 장 선형등화기법 ················································· 9 제 3-1절 선형 등화 기법 ······································· 11 제 3-1-1. Zero Forcing 등화 기법 ··················· 14 제 3-1-2. MMSE 등화 기법 ······························ 14 제 3-2절 최적의 탭 길이와 결정 지연 ················ 15 제 3-2-1. 탭 길이에 따른 MSE 변화 분석 ······ 15 제 3-2-2. 결정 지연에 따른 MSE 변화 분석 ·· 19 제 4 장 선형 등화 최적화 기법 제안 ························· 25 제 5 장 모의 실험 및 결과 분석 ······························· 32 제 6 장 해상 실험 결과 및 분석 ······························· 38 제 7 장 결 론 ······························································ 43 참고문헌 ······································································· 4

LiNi0.5Mn1.5O4 양극 피막의 이온 전달 특성

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 화학생물공학부, 2018. 2. 오승모.A high-voltage positive electrode can increase both energy density and output, and thus commercialization is under consideration. However, the mainly used organic electrolytes at present are electrochemically decomposed in the high-voltage region (>4.3 V vs. Li/Li+) to form a concomitant surface film on the positive electrodes, which cause to high resistance in the electrochemical cells. The interface of the electrode is an important key factor that determines not only the resistance itself, but also the reversibility and kinetics of the electrode. Therefore, it is important to understand the ion transport property of the surface film and to study a strategy of overcoming a series of resistances at interfaces based on these studies. At present, there has not been much studied on the physical properties of the positive electrode interface. On the other hand, a relatively large portion of the negative electrode interface is known about its characteristics. Therefore, in this study, it was tried to understand the characteristics of the surface film on positive electrodes, comparing with the properties for the negative electrodes. The surface film on negative electrodes, which is usually referred to solid electrolyte interphase (SEI): it secures excellent passivating ability within initial cycling and transport Li+ ion through its solid matrix to the active materials. Unlike the negative electrode surface film, however, the positive electrode interface has no excellent protecting ability and is rather permeable, so that lithium ions are not transferred through the solid phase, but delivered by the permeability of the liquid electrolyte. In addition, this permeability causes a continuous electrolyte side reaction when the positive electrodes are exposed to a high-voltage condition, because the electrolyte is easily accessible to the electrode surface due to passivating ability flaw of the surface film. It is one of the main deterioration for the high-voltage positive electrode. Second, it was examined the some of fundamental reason for charge transfer resistance at the surface film/electrodes interfaces, and studied how to overcome this resistance. Unlike the SEI on negative electrodes, a phenomenon, in which lithium ions are not densely accumulated on the surface of the high-voltage positive electrode interface was observed. The concentration of redox species at the electrode surface is one of the factors that could determine the rate of charge transfer reaction. It is thus examined that Li+ ion, the redox mediator in lithium-ion batteries, whether it can also influence charge transfer reaction into electrode. It was ascertained that the lithium ion concentration on the electrode surface affects the charge transfer resistance, and the charge transfer reaction was improved by organizing a high concentrated electrolyte based on phenomenon and the permeability. A high concentration electrolyte using a low viscosity solvent improves the charge transfer resistance and improves the lithium insertion rate so that more lithium ions can be delivered from the electrolyte to the electrode active material even at high C-rates. It was further studied to realize this advantage in a real full-cell. It is should be significantly considered to select the counter electrode, which must show fast delithiation property. Considering this point, after positive and negative electrodes, a high-power property is also realized in a full-cell.1. INTRODUCTION 1 2. BACKGROUND 6 2.1. Basic electrochemistry 6 2.1.1. Ionic conductivity 6 2.1.2. Solvation states in low dissociable solution medium 7 2.1.3. Electrochemical charge transfer kinetics 10 2.1.4. Cyclic voltammetry 10 2.2. Electrolytes: Aprotic liquid organic electrolytes 13 2.2.1. Li salts 13 2.2.2. Organic solvents 14 2.3. Active materials 18 2.3.1. Nickel doped lithium manganese spinel (LiNi0.5Mn1.5O4) 18 2.3.2. Graphite 21 2.3.3. Lithium titanate spinel (Li4Ti5O12) 25 2.3.4. Two-phase reaction 28 2.4. Solid Electrolyte Interphase (SEI) 34 3. EXPERIMENTAL 45 3.1. Preparation of electrodes, electrolytes, and electrochemical cells 45 3.1.1. Electrolytes preparation 45 3.1.2. Synthesis of Ni(cyclam)[BF4]2 (Ni(Ⅱ)-cy) 46 3.1.3. Electrodes preparation 47 3.1.4. Fabrication of electrochemical cells 49 3.2. Electrochemical analysis 50 3.2.1. The galvanostatic charging and discharging cycling 50 3.2.2. Alternating current (Ac) impedance 51 3.2.3. Electrochemical quart crystal microbalance (EQCM) 53 3.2.4. Cyclic voltammetry 54 3.3. Surface analysis 55 3.3.1. X-ray photoelectron spectroscopy (XPS) 56 3.3.2. Time of flight-secondary ion mass spectrometry (TOF-SIMS) 56 3.3.3. Transmission electron microscopy (TEM) 58 3.4. Physical properties characterization 58 3.4.1. Viscosity measurement 58 3.4.2. Raman spectroscopy 58 3.4.3. Ion coupled plasma-atomic emission spectroscopy (ICP-AES) 60 3.4.4. X-ray diffraction (XRD) 60 3.4.5. Field emission-scanning electron microscopy (FE-SEM) 61 4. RESULTS AND DISCUSSION 64 4.1. Ion Transport Properties in Surface Films 64 4.1.1. Ionic conductivities of surface films 64 4.1.2. Surface films components 70 4.1.3. Permeability of surface film on LNMO electrode 82 4.1.4. Li+ transport properties in SPI 93 4.2. Charge Transfer Kinetics at Electrode Interface 97 4.2.1. Li+ concentration and charge transfer resistance 97 4.2.2. Highly Li+-concentrated electrolyte design 108 4.2.3. Charge transfer reactions and Li+ insertion rates 118 4.2.4. Delithiation rates 140 4.2.5. Fast discharging in full-cell 143 5. CONCLUSIONS 146 REFERENCES 150 국문 초록 160Docto

Results of Microfracture in the Osteoarthritic Knee with Focal Full-Thickness Articular Cartilage Defects and Concomitant Medial Meniscal Tears

PURPOSE: To evaluate the efficacy of arthroscopic microfracture in patients with focal full-thickness cartilage defects in the osteoarthritic knee. MATERIALS AND METHODS: Seventy-six patients were enrolled in this study. They were divided into group I (n=38) who underwent microfracture plus meniscectomy and group II (n=38) who underwent only meniscectomy. Clinical and radiological evaluations were performed. RESULTS: At the time of the three-year follow-up, a total of five failures (6.6%) were reported: four patients in group I and one in group II. The two groups showed no significant difference in the Lysholm score, the Tegner activity score and the visual analog pain scale score at three years after surgery. However, at the time of the three-month follow-up, group II showed significantly more improvement in the Tegner activity and the visual analog pain score compared with group I. CONCLUSIONS: In the osteoarthritic knee, additional microfracture did not confer any additional benefit to meniscectomy.ope

Endoscopic Carpal Tunnel Release Is Preferred Over Mini-open Despite Similar Outcome: A Randomized Trial

BACKGROUND: The decision to perform endoscopic versus the mini-open carpal tunnel release technique is most likely left to surgeons rather than patients with idiopathic carpal tunnel syndrome. QUESTIONS/PURPOSES: We hypothesized that (1) at 3 months after surgery, the subjective outcomes of endoscopic release, performed on one hand, and mini-incision release, performed on the other, would not differ in patients with bilateral carpal tunnel syndrome; however, (2) each patient would likely prefer one technique over the other for specific reasons. METHODS: Fifty-two patients with bilateral carpal tunnel syndrome had one hand randomized to undergo endoscopic release and the other to undergo mini-incision release. Each patient was assessed with the Boston Carpal Tunnel Questionnaire (BCTQ) and DASH preoperatively and at each followup. Three months after surgery, the patients commented on which technique they preferred and completed a questionnaire regarding the reasons for not preferring the other technique. RESULTS: The mean BCTQ symptom/function score and DASH improved similarly in the endoscopic release group and the mini-incision release group. Thirty-four patients preferred endoscopic release and 13 preferred the mini-incision technique. Scar or pillar pain was the most commonly cited factor in not preferring either technique followed by postoperative pain for the open technique and transient worsening of symptoms for the endoscopic technique. CONCLUSIONS: Despite similar improvements in BCTQ and DASH scores after endoscopic and open techniques at 3 months postoperatively, the majority of our patients preferred the endoscopic technique. The most concerning reason for not preferring the other technique was scar or pillar pain.ope

Posterior Preventive Foraminotomy before Laminectomy Combined with Pedicle Screw Fixation May Decrease the Incidence of C5 Palsy in Complex Cervical Spine Surgery in Patients with Severe Myeloradiculopathy

C5 palsy is a frequent sequela of cervical decompression surgeries for cervical myeloradiculopathy. Although many researchers have suggested various risk factors, such as cord shifting and the correction of lordotic angles, the tethering of the C5 root beneath the narrow foramen is an independent risk factor for C5 palsy. In this study, we tried to investigate different techniques for foramen decompression with posterior cervical fusion and assess the incidence of C5 palsy with each technique depending on the order of foraminal decompression. A combined 540° approach with LMS and uncovertebrectomy was used in group 1. Group 2 combined a 540° approach with pedicle screws and posterior foraminotomy, while posterior approach only with pedicle screws and foraminotomy was used in group 3. For groups 2 and 3, prophylactic posterior foraminotomy was performed before laminectomy. Motor manual testing to assess C5 palsy, the Neck Disability Index (NDI) and the Japanese Orthopedic Association (JOA) scores were determined before and after surgery. Simple radiographs, MRI and CT scans, were obtained to assess radiologic parameters preoperatively and postoperatively. A total of 362 patients were enrolled in this study: 208 in group 1, 72 in group 2, and 82 in group 3. The mean age was 63.2, 65.5, and 66.6 years in groups 1, 2, and 3, respectively. The median for fused levels was 4 for the three groups. There was no significant difference between groups regarding the number of fused levels. Weight, height, comorbidities, and diagnosis were not significantly different between groups. Preoperative JOA scores were similar between groups (p = 0.256), whereas the preoperative NDI score was significantly higher in group 3 than in group 2 (p = 0.040). Mean JOA score at 12-month follow-up was 15.5 ± 1.89, 16.1 ± 1.48, and 16.1 ± 1.48 for groups 1, 2, and 3, respectively; it was higher in group 3 compared with group 1 (p = 0.008) and in group 2 compared with group 1 (p = 0.024). NDI score at 12 months was 13, 12, and 13 in groups 1, 2, and 3, respectively; it was significantly better in group 3 than in group 1 (p = 0.040), but there were no other significant differences between groups. The incidence of C5 palsy was significantly lower in posterior foraminotomy groups with pedicle screws (groups 2 and 3) than in LMS with uncovertebrectomy (group 1) (p < 0.001). Thus, preventive expansive foraminotomy before decompressive laminectomy is able to significantly decrease the root tethering by stenotic lesion, and subsequently, decrease the incidence of C5 palsy associated with posterior only or combined posterior and anterior cervical fusion surgeries. Additionally, such expansive foraminotomy might be appropriate with pedicle screw insertion based on biomechanical considerations.ope