LTE 네트워크에서 단말 간 직접 통신 신호를 이용한 단말 위치추정 기법

학위논문 (석사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2015. 2. 이광복.In this paper, we study a positioning scheme with device-to-device (D2D) communications in LTE networks. Recently, there has been increasing interest in a positioning technique to support location-based services (LBS). Various positioning techniques are supported in LTE networks such as assisted global navigation satellite system (A-GNSS) and observed time difference of arrival (OTDOA). With emerge of D2D communications in LTE networks, positioning technique based on D2D communication attracts growing attention. A-GNSS provides more accurate positioning service than other positioning technique but it is not available in indoor or urban environments. The accuracy of OTDOA and centroid positioning changes due to the surrounding environment, i.e., position of base stations, distances to base stations, and density of neighbor D2D devices. We derive the mathematical analysis to predict the positioning accuracy of centroid positioning based on the gathered information about surrounding environments. Based on the analysis, hybrid positioning scheme, which exploits a strength of OTDOA and centroid positioning is proposed. The proposed hybrid positioning scheme dynamically selects the positioning scheme which is expected to have better performance in accordance with collected information. Numerical results show that the proposed hybrid positioning scheme achieves better performance than conventional positioning schemes for various environments.Abstract ⅰ Contents ⅲ List of Tables ⅳ List of Figures ⅴ Chapter 1 Introduction 1 Chapter 2 System model 3 Chapter 3 Hybrid Positioning Scheme 5 3.1 Information Gathering 5 3.2 Positioning Accuracy Prediction 6 3.2.1. OTDOA Positioning Accuracy Prediction 6 3.2.2. Centroid Positioning Accuracy Prediction 7 3.3 Positioning Scheme Selection 10 Chapter 4 Numerical Results 12 Chapter 5 Conclusion 18 Bibliography 19 초록 20Maste

A Study on the Insulation Diagnosis of Switchboard by Detection of TEV Signals

Switchboard is a major power facility that is equipped for electricity distribution, switching, metering, and diagnosis. The modern society is highly relies on electrical energy and power outage may cause great economic and technical losses. As a result, it is necessary to diagnosis the condition of switchboard to ensure its reliable operation. During the operation of power apparatus such as transformers and circuit breakers, partial discharge(PD) may occur due to electric field concentration or insulation deterioration. Accompanying with PD, the transient earth voltage(TEV) will propagate along the metal or ground surface of switchboard. In this paper, for the purpose of insulation diagnosis of switchboard and related power apparatus, a TEV sensor was designed and fabricated for on-line PD detection. The insulation defects that cause insulation breakdown in switchboard were classified into protrusion on conductor, protrusion on enclosure, and free particle. The simulated TEV experiments were carried out and the characteristics of TEV sensor were analyzed. The fabricated TEV sensor could detect the signal with a frequency range from 1MHz to 100MHz and sample PD signals with a response time less than 8ns. In addition, the detection sensitivity depending on apparent charge and sensor type were studied. It was verified that the sensor with a diameter of 70mm and a thickness of 1mm was optimal for detect PD with a magnitude of 10pC∼100pC. The sensor used for application and evaluation had a sensitivity of 1.2 mV/pC. The electrical detection method specified in KS C IEC 60270 is a reference of PD signal acquisition, however, it can not be used for on-line detection of switchboard. The TEV sensor is a non-electrical method that can obtain same discharge patterns as the electrical method and overcome the limitations of existing method. The TEV sensor proposed in this paper had the optimal detection sensitivity and economic advantage, which can be used for condition monitoring and asset management of switchboards.목 차 i 그림 및 표 목차 ii Abstract iv 제 1 장 서 론 1 제 2 장 이 론 3 2.1 수배전반 3 2.2 절연열화와 부분방전 6 2.3 TEV의 발생원리 19 제 3 장 TEV 센서 23 3.1 설계 및 제작 23 3.2 센서의 특성 평가 31 제 4 장 적용 평가 40 4.1 실험계 40 4.2 TEV의 주파수 스펙트럼 43 4.3 결함별 PRPD 패턴 47 4.4 TEV의 거리 의존성 51 제 5 장 결 론 52 참 고 문 헌 54Maste

A comparison of the masticatory function between two different types of implant supported prostheses and complete denture for fully edentulous patients

STATEMENT OF PROBLEM: The improvement in oral function and comfort from the dental implant appears to depend on the particular type of implant support used with the denture. The number and positioning of implants have an influence on the force transfer and subsequent stress distribution around implants. Nevertheless, a quantitative comparison has not been made between the types of implant prosthesis used with different materials compared to conventional complete denture. PURPOSE: The objective of this study is to assess the masticatory performance, bite force and impact of two different type of implant supported prostheses on oral health-related quality of life compared to conventional complete denture with GOHAI, validated oral-specific health status measures, the sieving method, and the Prescale Dental System. MATERIAL AND METHODS: From the years 1999 to 2006, a total of 30 completely edentulous patients in a single arch were selected from the Yonsei University Dental Hospital, Department of Prosthodontics and Implant Clinic in Seoul, S. Korea. Patients were divided into 3 groups of 10 each. Group HR was restored with fixed-detachable hybrid prostheses with resin teeth. Group FP had fixed dentures with porcelain teeth while Group CD had a complete denture. The masticatory performance was compared between 3 groups. RESULTS: The results showed a significant improvement in oral health-related quality of life with dental implants compared to a conventional denture in GOHAI comparison. Overall, implant prostheses showed a higher masticatory performance (S50) and maximum bite force compared with conventional dentures (P .05). CONCLUSION: Within the limitation of this study, the numbers of implant and material of implant prostheses does not appear to impact patient satisfaction, masticatory performance or bite force.ope

The Drug Release and Antibacterial Effects on Titanium Surface According to Biodegradable Polymer Coating with Antibiotics

Titanium and titanium alloys are the most common materials used for dental and biomedical implants, owing to their biocompatibility and favorable mechanical properties. However infection of the region surrounding a implant by pathogenic microorganisms is a significant factor in implant failure. Currently, a number of studies to create antibacterial surfaces of dental implants and biomaterials are being reported and commercially applied. Prevention and control of microbial colonization of implant surfaces is therefore of considerable interest to the biomedical community. One of the solutions, various biodegradable polymeric drug delivery devices have been developed for the sustained release of a variety of drugs. Among them, fi lms as implantable drug delivery systems have gained growing interest in various applications. The purpose of this study was to confirm the release of antibiotics and antibiotic effects of titanium surface which coated with biodegradable polymer and different concentrations of tetracycline. Anodized titanium specimen (diameter 8 mm, height 2 mm) were coated with poly (lactide) acid solution (1%) containing different concentrations of tetracycline (0.0%: Group I, 0.1%:Group II, 0.5%:Group III, 1.0%: Group IV). The coated specimen’s surface were observed by scanning electron microscope. For the analysis of drug release, the specimens were inserted in distilled water and then the solution was measured for 3 hours, 6 hours , 12 hours , 1 days, 3 days, 7 days, 14 days u sing the ultraviolet spectrometer. Antimicrobial activi ty against Staphylococcus aureous was tested wi th the agar di ffusion method. Scanning electron microscope image showed that polymer coating layers fulfi lled the ti tanium surface. The most of tetracycline released within 6 hours and then continued until 2 weeks. Regarding the antibacterial effect for Staphylococcus aureous, the specimens showed inhibitions of the strain with larger zones for the higher tetracycline concentrationope

Optimization of orbital retraction during endoscopic transorbital approach via quantitative measurement of the intraocular pressure - [SevEN 006]

Background: Increased use of the transorbital approach (TOA) warrants greater understanding of the risk of increased intraocular pressure (IOP) and intraorbital pressure (IORP) due to orbital compression. We aimed to investigate the changes in IOP and IORP in response to orbital retraction in TOA and establish a method for the continuous measurement of intraoperative IORP. Methods: We assessed nine patients who underwent TOA surgery from January 2017 to December 2019, in addition to five cadavers. IORP and IOP were measured using a cannula needle monitor, tonometer, cuff manometer, and micro strain gauge monitor. Results: In all nine clinical cases and five cadavers, increased physical compression of the orbit increased the IOP and IORP in a curvilinear pattern. In clinical cases, when the orbit was compressed 1.5 cm from the lateral margin in the sagittal plane, the mean IOP and IORP were 25.4 ± 5.2 mmHg and 14 ± 9.2 mmH2O, respectively. The IORP satisfactorily reflected the IOP (Pearson correlation coefficient = 0.824, p < 0.001). Conclusion: We measured IOP and IORP simultaneously during orbital compression to gain basic information on pressure changes. In clinical cases, the change in the IOP could be conveniently and noninvasively monitored using continuous IORP measurements.ope

Triggered Electrooculography for Identification of Oculomotor and Abducens Nerves during Skull Base Surgery

Objective: Electrooculography (EOG) records eyeball movements as changes in the potential difference between the negatively charged retina and the positively charged cornea. We aimed to investigate whether reliable EOG waveforms can be evoked by electrical stimulation of the oculomotor and abducens nerves during skull base surgery. Methods: We retrospectively reviewed the records of 18 patients who had undergone a skull base tumor surgery using EOG (11 craniotomies and seven endonasal endoscopic surgeries). Stimulation was performed at 5 Hz with a stimulus duration of 200 μs and an intensity of 0.1-5 mA using a concentric bipolar probe. Recording electrodes were placed on the upper (active) and lower (reference) eyelids, and on the outer corners of both eyes; the active electrode was placed on the contralateral side. Results: Reproducibly triggered EOG waveforms were observed in all cases. Electrical stimulation of cranial nerves (CNs) III and VI elicited positive waveforms and negative waveforms, respectively, in the horizontal recording. The median latencies were 3.1 and 0.5 ms for craniotomies and endonasal endoscopic surgeries, respectively (p=0.007). Additionally, the median amplitudes were 33.7 and 46.4 μV for craniotomies and endonasal endoscopic surgeries, respectively (p=0.40). Conclusion: This study showed reliably triggered EOG waveforms with stimulation of CNs III and VI during skull base surgery. The latency was different according to the point of stimulation and thus predictable. As EOG is noninvasive and relatively easy to perform, it can be used to identify the ocular motor nerves during surgeries as an alternative of electromyography.ope

국내 발생 고병원성조류인플루엔자(H5N8)의 수학적 모델링 및 역학적 분석

학위논문 (박사) -- 서울대학교 대학원 : 수의과대학 수의학과, 2021. 2. 조성범.감염병은 질병 발생 시 사회 경제적 영향이 증가하기에 공중보건학에서 점차 그 중요도가 증가하고 있다. 수학적 모델링을 기반으로 감염병 전파 양상을 이해하고 예측하고자 하는 시도가 계속되고 있다. 이러한 모델들은 특히 공중 보건 정책을 세우는데 있어서 유용한 도구로써 점점 더 인식되고 있다. 고병원성 조류 인플루엔자(highly pathogenic avian influenza; HPAI)는 인간과 조류 사이의 주요 인수공통 감염증으로 2003년 이후 한국에서 지속적으로 발생하고 있다. 특히 H5N8 아형(subtype)에 의한 HPAI는 국내 발생 사례 중 최장기 유행하여 가금 산업에 막대한 경제적 피해를 초래 하였다. 그러므로 새로운 H5N8 아형 바이러스의 유입, 전파 및 확산 측면에서의 연구가 필요하나, 현재까지 H5N1 아형을 대상으로 한 연구만 이루어진 상황이다. 따라서 본 논문은 국내 발생 H5N8 HPAI의 발생 위험 요인, 질병 매개 변수, 그리고 질병 유행 및 확산의 시공간 특성 분석을 통하여 HPAI의 역학적 특성을 조사하였다. 첫 번째로 국내 육용 오리농가에서의 H5N8의 유입 및 발생을 이해하고자 분석 역학 기법인 후향적 환자 대조군 연구(retrospective case-control study)를 사용하여 잠재적인 위험요인(risk factor)을 선정하고 이를 평가하였다. HPAI H5N8에 감염되었던 양성 농장을 환자군(case)으로 선정하고, 선정 농장을 기준 반경 3km내 음성 농가를 대조군(control)으로 대응 추출(matching) 하였다. 단변수 및 다변수 로지스틱 회귀분석(univariable and multivariable logistic regression)을 사용하여 육용 오리 농가에서의 잠재적인 위험요인을 분석하였다. 그 결과 분변 처리 서비스를 이용하지 않는 경우(OR = 27.78), 농장주의 경력이 15년 이상일 경우(OR = 7.91), 7동 이상의 축사를 가진 경우(OR = 6.99), 마지막으로 농장 주변 500m 이내 다른 가금 농장이 존재하는 경우(OR = 6.30)가 그렇지 않은 경우에 비해 교차비가 높은 것으로 확인되었다. 이러한 결과는 우선 육용 오리 농장에서 발생한 HPAI H5N8이 농장 방역, 농장 규모 및 시설, 농장주의 경력과 연관성이 있음을 시사하고 있다. 확인된 위험요인 들을 관리하기 위한 정책을 수립한다면 가금농가에서의 HPAI 발생 위험성을 줄일 수 있을 것이다. 두번째로 수학적 모델링을 사용하여 국내에서 발생했던 HPAI H5N1, H5N8 및 H5N6의 기초 재생산 지수(basic reproduction number; R_0)를 추정하여 각 아형에 따른 가금농가간의 전파력을 조사하였다. R0의 추정은 SIR compartment model을 기반으로 하여, Exponential growth와 Maximum likelihood 모델을 사용하였다. 세가지 subtype H5N1, H5N8, 및 H5N6의 R0 는 각각 1.68-1.95. 1.03-1.83, 1.37-1.60 이었다. Kruskal-Wallis pairwise comparison 결과 H5N8의 평균 감염세대기간(generation time) 이 7.27일로 H5N1의 4.93일보다 통계적으로 유의하게 길다는 결과가 확인되었다. 이러한 결과는 R0가 감염 초기단계의 온도, 가금생산시스템, subtype별 종 특이성 및 방역 정책과 관련되어 있음을 시사하고 있다. 이러한 질병 전파력에 영향을 미치는 요소를 고려할 시 향후 발생할 수 있는 HPAI 아형에 대한 실질적인 질병 통제 전략을 설계할 수 있을 것이다. 세번째로 국내 가금류 농장 발생 H5N8의 시공간적 분포를 분석하여, 농장 간의 전파 메커니즘을 이해하고자 하였으며, 방역 정책이 HPAI의 시공간적 분포에 미치는 영향을 평가하였다. 2014년 1월부터 2016년까지 발생한 H5N8 첫번째 및 두번째 발생 기간에 대한 Global and local 에서의 시공간 상호작용(spatiotemporal interaction)은 각각 space-time K function과 space-time permutation model을 사용하여 분석되었다. 두 발생 기간 모두에서 space-time K function은 3일이내에 40km 이상에서 시공간 상호작용을 나타내었다. Excessive risk attributable value은 거리와 상관없이 그 값을 유지하였습니다. 총 11개의 local 시공간 군집(spatiotemporal cluster)가 확인되었으며, 그 결과 H5N8의 지역적 확산은 양극화 되어 작은 시공간적 군집과 큰 시공간 군집이 동시에 나타났다. 이러한 시공간 상호작용 결과는 한국에서의 HPAI 전염병의 전파가 주로 작은 지역 내에서 단기간 전파된 이후 장거리 점프에 의해 분산되는 것으로 추정된다. 결론적으로 본 연구는 향후 HPAI 통제를 위한 효과적인 방역 정책 수립을 위한 과학적 근거를 제공하기 위하여 세가지 역학적 모델을 사용하였습니다. 국내 발생 H5N8 HPAI에 대하여 역학적 분석을 통해서 가금농장으로 유입될 수 있는 잠재적인 위험요인들을 확인하였다. 또한 수학적 모델링을 사용하여 세 개의 HPAI subtype에 따라 질병 전파력의 차이가 있음을 증명하였다. 국내 발생 H5N8에 대한 시공간적 분석 결과를 볼 때 선제적 살처분, 이동통제 및 가금 차량 이동 추적과 같은 현행 방역 시스템 유지 필요성을 시사한다. 본 연구 결과는 HPAI의 방역 정책 및 HPAI 질병 대응책을 평가하고 보완하는데 있어서 중요한 과학적 근거로써 활용될 수 있고, 해당 연구의 방법론은 향후 국내외에서 발생하는 타 가축유래 인수공통전염병에 대하여 접목이 가능할 것으로 기대된다.Infectious diseases have become important in public health because of their increased socioeconomic impact during epidemics. Attempts are on to understand and predict disease transmission based on mathematical modeling. These models are increasingly being recognized as useful tools for establishing public health policies. Highly pathogenic avian influenza (HPAI) is one of the major zoonoses transmitted from birds to humans and has been an intermittent disease in South Korea since 2003. Among the multiple epidemics, the HPAI subtype H5N8 is the enormous outbreaks resulting in significant damage to the country’s poultry industry. It is, thus, important to study the disease transmission characteristics of the emerging H5N8 subtype in South Korea. However, to date, epidemiological studies have mainly focused on the H5N1 subtype. Therefore, this thesis is aimed to conduct to investigate epidemiologic characteristics of HPAI caused by newly appeared subtypes, including their risk factors, transmissibility, and spatiotemporal dynamics between poultry farms. First, to understand HPAI H5N8 infection, a retrospective case-control study was conducted to identify and evaluate potential risk factors for HPAI H5N8 infection on broiler duck farms. Duck farms with known H5N8 infections were selected as cases; control farms were matched to cases based on location within a 3-km radius. Potential risk factors were analyzed using univariable and multivariable logistic regression. Fecal removal services (OR = 27.78, 95% confident interval (CI) = 3.89–198.80), farm owner’s career (OR = 7.91, CI = 1.69–37.14), large flock size (OR = 6.99, CI = 1.34–37.04), and other poultry farms within 500 m (OR = 6.30, CI = 1.08–36.93) were significantly associated with HPAI (H5N8) outbreaks in the final model. These results indicated that the HPAI H5N8 outbreaks in South Korea were associated with farm owner age, the number of flocks, poultry farm density, and biosecurity. Establishing policies to manage these risk factors may reduce the vulnerability of South Korean poultry farms to HPAI (H5N8) outbreaks. The second study assessed the transmissibility of the HPAI subtypes H5N1, H5N8, and H5N6 in poultry farms by estimating their basic reproduction numbers (R0) through mathematical modeling. R0 calculations used exponential growth and maximum likelihood models based on the susceptible-infected-removed compartment model. The mean R0 for subtypes H5N1, H5N8, and H5N6 were 1.68-1.95, 1.03-1.83, and 1.37-1.60, respectively. Results of Kruskal-Wallis pairwise comparison tests showed that the mean generation time for H5N8 (7.27 days) was significantly longer than that for subtype H5N1 (4.93 days). These findings suggest that the R0 differ by HPAI subtype and might be associated with the temperature during the early stage of the infection, species specificity by viral subtype, and prevention policies. Knowledge of these and other factors affecting transmissibility can be used to design practical disease control strategies for future emergent HPAI subtypes. Finally, H5N8 infections in South Korean poultry farms were analyzed to identify their spatiotemporal distributions, understand the mechanisms of transmission between farms, and evaluate the effectiveness of quarantine policies in addressing outbreaks. The global and local spatiotemporal interactions in the first and second H5N8 epidemics were analyzed using a space-time K function at the national level and a space-time permutation model from 2014 to 2016, respectively. In both epidemics, the space–time K-function analyses revealed significant interactions within three days and up to 40 km distance; excessive risk attributable values (D0) were maintained despite the distance. Eleven local spatiotemporal clusters were identified, and results indicated that the regional spread of H5N8 was polarized between small and large spatiotemporal clusters. This global and local spatiotemporal interaction indicates that the HPAI epidemics in South Korea were mostly characterized by short duration of transmission within a small area and then dispersal by long-range jumps. In conclusion, this study used three epidemiological models to provide a scientific basis for improved effective quarantine policies for HPAI control. Risk factors for the introduction and spread of H5N8 HPAI virus in South Korean poultry farms were identified through analytic epidemiology. Furthermore, differences in disease transmissibility for three HPAI subtypes were demonstrated through mathematical modeling. Results suggest that features of the current quarantine system, such as preemptive depopulation, and the tracking of poultry vehicle movements, need to be continued. The results of this thesis can be used as scientific evidence for evaluating and supplementing HPAI quarantine policies and disease countermeasures. It is also expected that the methodologies used in this thesis can be applied to other infectious zoonosis occurring in South Korea and worldwide.Abstract i Contents iv List of tables vii List of figures viii List of abbreviations x General introduction 1 Literature review 4 1. Analytic epidemiology in infectious disease 4 1.1. Analytic epidemiology 4 1.2. Case-control study and risk factors 6 1.3. Risk factors associated with HPAI outbreaks 7 2. Pathogen epidemiology in infectious disease 9 2.1. Pathogen epidemiology 9 2.2. Mathematical models of infectious disease 11 2.3. Reproduction number study in infectious disease 13 3. Spatial epidemiology in infectious disease 15 3.1. Application of geographical information system to epidemiology 15 3.2. Spatial research approach 17 3.3. Spatiotemporal analysis using clustering 19 4. Avian Influenza 21 4.1. Avian influenza virus 21 4.2. Transmission 23 4.3. HPAI subtype H5N8 outbreaks 25 Chapter 1. Risk factors associated with highly pathogenic avian influenza subtype H5N8 outbreaks on broiler duck farms in South Korea Abstract 30 1.1 Introduction 31 1.2 Material and Methods 34 1.3 Results 40 1.4 Discussion 43 1.5 Conclusions 47 Chapter 2. Estimation of the basic reproduction numbers of the subtypes H5N1, H5N8, and H5N6 during the highly pathogenic avian influenza epidemic spread between farms Abstract 60 2.1 Introduction 61 2.2 Material and Methods 64 2.3 Results 69 2.4 Discussion 72 2.5 Conclusions 77 Chapter 3. Spatiotemporal distribution of highly pathogenic avian influenza subtype H5N8 in South Korea Abstract 85 3.1 Introduction 86 3.2 Material and Methods 88 3.3 Results 93 3.4 Discussion 96 3.5 Conclusions 102 General conclusions 110 Reference 112 Appendix 127 국문 초록 132Docto

영상정보를 이용한 순항미사일 복합항법시스템 설계

학위논문(석사)--서울대학교 대학원 :전기컴퓨터공학부,2006.Maste

모델예측제어 기법을 이용한 무인체 유도

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