모터-프로펠러 로터 시스템의 공력소음 및 심리음향 분석: 회전 속도 변동 모델링 및 청각화

학위논문(박사) -- 서울대학교대학원 : 공과대학 항공우주공학과, 2024. 2. 이수갑.브러시리스 직류 모터 (Brushless direct current motor, BLDCM)-프로펠러 기반의 분산 전기 추진 (Distributed electric propulsion, DEP) 방식을 활용한 무익형 전기 수직 이착륙기 (electric vertical take-off and landing, eVTOL)는 활주로가 필요 없는 고유한 기동과 더불어 비행 안정성, 정숙성의 장점으로 민간 및 군사용도로 다양하게 사용되어 왔다. eVTOL은 물류 및 배송, 수색 및 구조, 군사, 농업, 구조물 검사 등의 분야에서 무인 항공기 (Unmanned aerial vehicle, UAV)에서 도심 항공 교통 (Urban air mobility, UAM)에 이르기까지 다양하게 활용되고 있다. eVTOL이 널리 사용됨에 따라 운용 범위가 인간 거주 지역에 가까워지면서 자연스럽게 소음 문제가 대두되고 있다. 민수용의 경우, 제품의 선호도를 결정하는 중요한 요소가 되기 때문에 비교 우위를 위해서는 저소음화 및 음질 개선이 요구되며, 군수의 경우에는 소음으로 인해 임무 실패의 위험성 방지를 위해 저소음화 및 음질 개선이 요구된다. 게다가, 소음으로 인한 일반 대중들의 수용을 보장하기 위해 저소음화 및 음질 개선 측면의 연구가 필수적이다. 이는 기체 설계 단계에서 인간 인식 기반의 평가를 통해서 개발될 기체의 위해성에 관한 연구의 필요성을 시사한다. eVTOL 소음의 위해성 연구를 위해서는 실제 운용되는 기체에 대한 포괄적인 소음 정보가 요구된다. 하지만, 이 연구가 수행되는 시점에도 개발되고 있는 UAV, UAM에 대한 실제 소음 정보를 획득한다는 것은 명백한 모순이다. 이러한 맹점을 해결하기 위한 효과적인 방법은 예측에 기반한 청각화가 될 수 있다. 기존 회전익기 공력 및 소음에 대한 수치적 예측은 자유 후류 와류 격자 기법 및 전산 유체 역학을 이용하여 연구되어 왔지만, 이러한 중, 고충실도 해석 기법은 요구되는 계산 비용이 높기 때문에 회전 속도 제어 방식의 eVTOL 소음 해석에는 적합하지 않다. 따라서 본 연구는 eVTOL의 주요 소음원인 BLDCM-프로펠러 시스템 소음의 예측 기반의 소음 평가를 목적으로 한다. 이를 위해 BLDCM-프로펠러 시스템의 공력소음 및 심리음향 측면의 연구가 수행되었다. 본 연구에는 다학제 기반의 eVTOL 소음 평가 프레임워크 CONA (Comprehensive multirotor noise assessment)가 사용되었다. CONA 프레임워크는 비행제어, 공기역학, 소음 예측 및 청각화 모듈을 활용해 기존 로터 해석 방법론이 갖는 한계로 해결할 수 없는 eVTOL의 다양한 구성이나 기동에 따른 포괄적인 소음 평가가 가능하다. 추가적으로 본 논문에서는 BLDCM-프로펠러 시스템에서 전형적으로 나타나는 회전속도 (revolutions per minute, RPM)의 확률적이고 주기적인 변동을 모사하기 위한 기법이 적용되었다. 시스템 고유의 노이즈나 외풍으로 인한 확률적인 RPM 변동과 BLDCM의 특성인 오프셋 전류, 전류 진폭의 변화, 자기 밀도의 변화 등으로 발생하는 토크 리플에 의한 주기적인 RPM 변동을 수치적으로 구현하였다. 스펙트럼, 지향성 패턴, 신호 유사성 분석을 통해 물리적 음향 특성에 대한 논의가 이루어졌고, RPM 변동 모델링이 적용되면, BLDCM-프로펠러 시스템 소음의 중, 고주파 톤 소음 예측 성능이 비약적으로 향상되는 효과가 있음을 밝혔다. 더 나아가, RPM 변동 모델링의 효과의 심리음향 측면을 분석하기 위해 주관적 반응 실험과 단기 불쾌감 실험, 두 가지의 실험실 규모의 청감 실험이 수행되었다. 심리음향 실험은 세 가지 유형의 자극 (1. 측정, 2. RPM 변동 모델링이 적용되지 않은 청각화, 3. RPM 변동 모델링이 적용된 청각화)에 대한 논의가 이루어졌다. 주관적 반응 실험에서는 측정과 청각화 (RPM 변동 모델링 적용)가 동일하지는 않지만, 구별할 수 없다는 것을 통계적으로 규명되었다. 단기 성가심 실험에서는 청각화와 측정 모두 성가심이 소음의 라우드니스와 밀접한 관계가 있음을 확인했다. 그리고 측정된 소리와 청각화된 소리 (RPM 변동 모델링 적용)의 %HA (percentage of highly annoyed)가 매우 유사한 경향을 갖는 것을 확인했다. 본 연구는 확률적이고 주기적인 RPM 변동 모델링을 통해 청각화된 BLDCM-프로펠러 시스템 소음이 측정된 소음을 대체할 수 있음을 규명하였다. 이는 미래에 개발될 UAV, UAM 등의 소음 문제에 직접적인 해결 방안 연구에 활용될 수 있다. 우선, 설계 단계에서 가상으로 소음을 미리 청취가 가능하기 때문에 인간의 인지적 평가를 설계 전략 수립에 포함시킬 수 있다. 또한, eVTOL의 다양한 기동과 구성에 따른 포괄적인 소음 평가를 통해 DEP 시스템의 고유의 공력 및 소음 특성을 반영할 수 있는 지표 확립에 기여함으로써, 저소음을 넘어 저성가심 eVTOL 기체 개발에 크게 기여할 것으로 기대된다.Wingless electric vertical take-off and landing (eVTOL) aircraft, utilizing brushless direct current (BLDC) motor (BLDCM) and propeller-driven distributed electric propulsion (DEP), have been employed in numerous civilian and military applications due to their exceptional maneuverability without the need for runways, flight stability, and quietness. eVTOL has a wide range of applications, from unmanned aerial vehicle (UAV) to urban air mobility (UAM), in areas such as logistics and delivery, search and rescue, military, agriculture, and structural inspection. As eVTOL becomes more widely used, their operating ranges are getting closer to human habitation areas, which raises the issue of noise. In civilian usage, noise reduction and sound quality improvement are required for comparative advantage as it is an important factor in determining product preference, and in military usage, noise reduction and sound quality improvement are required to prevent the risk of mission failure due to noise. In other words, research is required to ensure social acceptance. This suggests the need for research on the hazards of vehicles to be developed through human perception-based assessments during the vehicle design phase. Research on the annoyance of eVTOL noise requires comprehensive noise information on actual operational vehicle. However, it is an obvious contradiction to obtain real noise information for UAV and UAM, which are still being developed at the time of this study. Prediction-based auralization can be an effective way to address these limitations. Numerical predictions of rotorcraft aerodynamics and aeroacoustics have traditionally been studied using free-wake vortex lattice method and computational fluid dynamics, but these mid- and high-fidelity analysis approaches are not suitable for eVTOL noise analysis with rotational speed control due to the high computational cost required. Therefore, this study aims to provide a prediction-based noise assessment of BLDCM-propeller system noise, which is a major noise source in DEP systems. For this purpose, the aeroacoustics and psychoacoustic aspects of the BLDCM-propeller system were studied. The comprehensive multirotor noise assessment (CONA), a multidisciplinary based eVTOL noise assessment framework, was used in this study. The CONA framework combines flight control, aerodynamics, noise prediction, and auralization modules to achieve a comprehensive noise assessment of various configurations and maneuvers of eVTOL, which cannot be addressed by traditional rotor analysis methodologies. In addition, techniques have been applied in this thesis to simulate stochastic and periodic fluctuations in revolutions per minute (RPM) typical of BLDCM-propeller systems. The stochastic RPM fluctuations caused by the system's inherent noise and wind gust, and the periodic RPM fluctuations caused by torque ripples due to the BLDCM's characteristics of offset current, changes in current amplitude, and changes in magnetic density were numerically implemented. Discussion of the physical acoustic characteristics through spectral, directivity pattern, and signal similarity analysis was conducted, and it was found that when RPM fluctuation modeling is applied, the mid- and high-frequency tone noise prediction performance of BLDCM-propeller system noise is dramatically improved. Furthermore, two types of laboratory-scale listening experiments, a "subjective response test" and a "short-term annoyance test," were designed and conducted to analyze the psychoacoustic aspects of the effects of RPM fluctuation modeling. Psychoacoustic experiments were discussed for three types of stimuli: 1. measurements, 2. auralization without RPM fluctuation modeling, and 3. auralization with RPM fluctuation modeling. In the subjective response test, it was statistically established that measurement and auralization (with RPM fluctuation modeling) are not identical, but indistinguishable. The short-term annoyance test confirmed that annoyance is strongly related to the loudness of the noise, both auralization and measurement. Finally, the percentage of highly annoyed (%HA) of the measured and auralized sounds (with RPM fluctuation modeling) showed a highly similar trend. This study has shown that auralized BLDCM-propeller system noise can replace measured noise by stochastic and periodic RPM fluctuation modeling. This finding can be applied to the study of direct solutions to noise problems in future UAV and UAM developments. First, human perceptions can be incorporated into design strategies by virtually pre-listening to noise during the design phase. Further, by contributing to the establishment of metrics that can reflect the unique aerodynamic and acoustical characteristics of DEP systems through a comprehensive noise assessment of various eVTOL maneuvers and configurations, it is expected to contribute significantly to the development of low-annoyance eVTOL aircraft beyond low noise.Abstract I Table of Contents IV Nomenclature VI List of Figures X List of Tables XII Chapter 1. Introduction 1 1.1 Background 1 1.1.1 Overview of eVTOL 1 1.1.2 Multirotor type DEP system noise 3 1.2 Previous research on eVTOL noise 7 1.2.1 Uncertain factors of BLDCM-propeller system noise 7 1.2.2 Multidisciplinary analysis (control, aerodynamics, and noise) 8 1.2.3 Laboratory scale listening test 9 1.3 Research objective and scope 10 Chapter 2. CONA framework 13 2.1 Flight simulation 15 2.1.1 Flight control 15 2.1.2 Aerodynamics 19 2.2 Noise prediction and auralization 29 2.2.1 Tone noise 29 2.2.2 Broadband noise 34 Chapter 3. Rotational speed fluctuation modeling 40 3.1 RPM fluctuation modeling 40 3.1.1 Theoretical background 40 3.1.2 Stochastic and periodic RPM fluctuation modeling 43 3.2 BLDCM-propeller system: single rotor type 50 3.2.1 Noise spectrum 52 3.2.2 Noise directivity pattern (Polar) 55 3.3 BLDCM-propeller system: multirotor type 57 3.3.1 Measurement 60 3.3.2 Noise directivity pattern (Azimuthal) 65 Chapter 4. Laboratory scale listening test 68 4.1 Stimulus for listening tests: single rotor type 68 4.1.1 Noise measurement 68 4.1.2 Auralization of BLDCM-propeller system 76 4.2 Subjective response test 82 4.2.1 Test configuration 82 4.2.2 Results and discussions 82 4.3 Short-term annoyance test 88 4.3.1 Test configuration 90 4.3.2 Results and discussions 92 Chapter 5. Conclusions and recommendations 96 5.1 Conclusions 96 5.2 Recommendations for future work 97 Appendix 99 A. Documents for laboratory scale listening test 99 A.1. Notice 99 A.2. Agreement 103 A.3. Questionary: subjective response test 104 A.4. Questionary: Short-term annoyance test 105 B. Description of supplement files 106 B.1. Level A 106 B.1. Level B 107 C. Response of laboratory scale listening test 108 C.1. Response of subjective response test 108 C.2. Response of short-term annoyance test 109 References 113 국문 초록 124박

A study on an optimal configuration for spark-induced breakdown spectroscopy and minerals analysis aimed at planetary analysis

학위논문 (석사) -- 서울대학교 대학원 : 공과대학 협동과정 우주시스템 전공, 2021. 2. 여재익.스파크 유도 플라즈마 분광법 (SIBS)은 전기 스파크를 사용하여 강력한 플라즈마를 유도한 후 원자 방출 스펙트럼 신호를 수집하는 방법이다. 스파크는 고전압과 낮은 전류량으로 인한 전기적 방전으로, 전극 사이의 매질에 인가된 전압이 전극을 둘러싼 주변의 항복 전압보다 높을 때 발생한다. 이 연구는 우주 탐사에 활용되는 기존의 레이저 유도 분해 분광법 (LIBS)를 대체하여 SIBS를 사용할 수 있는지의 가능성을 보기 위해 진행되었다. 과거에는 SIBS를 사용하여 부피가 큰 고체 샘플을 대상으로 실험하는 것이 성공적이지 않았기 때문에, 본 연구에서는 전극 위치 및 전극 재료의 SIBS의 최적화 연구가 수행되었다. LIBS를 사용할 때에 비해 SIBS의 검출 한계 (LOD)가 78에서 20ppm으로 최대 4배 향상되어 있음을 볼 수 있었다. 생성된 플라즈마의 더 높은 에너지로 인해, SIBS에 의한 신호 세기는 동일한 분광계 설정에서 LIBS보다 3 배 정도 높았다. 우주탐사에 활용될 시 필요한 SIBS의 최적화 설정을 위해 전극 재료를 변경하고 전극의 최적 위치를 찾는 연구도 수행되었다.Spark-induced breakdown spectroscopy (SIBS) utilizes an electric spark for inducing a strong plasma for collecting atomic emissions. The spark is an electric discharge characterized by a high voltage and low current, which occurs when the applied voltage between electrodes is higher than the breakdown voltage of the ambient surrounding the electrodes. This study analyses the potential for complementing a compact SIBS over conventional laser-induced breakdown spectroscopy (LIBS) in discriminating rocks and soils for planetary missions. Targeting bulky solids using SIBS has not been successful in the past, and therefore a series of optimizations of electrode positioning and electrode materials was performed in this work. The limit of detection (LOD) was enhanced up to 4 times from when LIBS was used, showing a change from 78 ppm to 20 ppm from LIBS to SIBS. Within the same CCD gate delay time and width, the signal intensity by SIBS was substantially higher than LIBS in three orders of magnitude due to the bigger energy of plasma generated. Changing the electrode material and locating the optimum position of the electrodes were considered for optimizing the current SIBS set up being tested for the planetary origin.목 차 초 록 i 목 차 ii 표 목차 iii 그림 목차 iii 제 1 장 서 론 1 제 2 장 실험 재료 및 방법 4 2.1 샘플 제작과정 4 2.1.1. 광물 샘플 준비 과정 4 2.1.2. 펠렛 샘플 제작과정 6 2.2 실험 원리와 장치 8 2.2.1. 실험 셋업 8 2.2.2. 소형화 SIBS 장치 10 2.2.3. 전극 위치 및 재질에 대한 최적화 실험 셋업 12 제 3 장 실험 결과 15 3.1 고체 샘플 분석에서의 SIBS 활용 15 3.2 검량곡선과 스펙트럼에서의 SIBS와 LIBS 비교 17 3.3 전극 배치 및 재질에 대한 최적화 실험 결과 22 3.4 우주탐사에 활용될 SIBS의 가능성 29 제 4 장 결론 31 참고문헌 32 Abstract 37 표 목차 표 2.1 광물 샘플의 화학적 정보 및 대표 스펙트럼 피크 5 표 2.2 각 실험 샘플과 설정에 따른 여러 유형의 SIBS 셋업 6 표 2.3 사용된 네 가지 전극 재질의 구성 정보 및 녹는점 13 표 3.1 Ca 스펙트럼 라인에서의 SIBS 와 LIBS 의 비교표 21 그림 목차 그림 2.1 고체 샘플을 분석하기 위한 (a) SIBS (b) LIBS 의 실험 도식 10 그림 2.2 실제 제작한 소형 SIBS 장치 11 그림 2.3 소형 MCU 알고리즘에 대한 전기 신호의 시간에 따른 그림 12 그림 2.4 샘플 표면과의 원거리, 전극 간격, 각도 변화 및 펠렛 샘플에 행해진 실험 도식 14 그림 3.1 SIBS 실험 결과로 나온 광물분석 스펙트럼 16 그림 3.2 각 분광 방법으로 실험한 광물 샘플의 방출 스펙트럼 (SIBS : 빨간색, LIBS : 남색) 18 그림 3.3 CaCO3 분석에서의 SIBs 와 LIBS 의 SNR 스펙트럼 19 그림 3.4 Ca II (393.366 nm) 스펙트럼 라인에서의 SIBS 와 LIBS 검량곡선 20 그림 3.5 여러 종류의 다른 전극 재료를 사용하여 파이라이트 (FeS2) 샘플의 플라즈마 방출 스펙트럼 23 그림 3.6 Olivine ((Mg,Fe)2SiO4) 광물 샘플에 대한 전극 간격 거리 실험 (1 ∼ 5 mm) 24 그림 3.7 Aragonite (CaCO3) 광물 샘플에 대한 전극 간격 거리 실험 (1 ∼ 5 mm) 25 그림 3.8 Olivine ((Mg,Fe)2SiO4) 광물 샘플에 대한 원거리 실험 (-1 ∼ 3 mm) 26 그림 3.9 Aragonite (CaCO3) 펠렛 샘플에 대한 전극 간격 거리 실험 (1 ∼ 2 mm) 27 그림 3.10 Olivine ((Mg,Fe)2SiO4) 광물 샘플에 대한 전극 각도 변화 실험 (0 ∼ 60°) 29Maste

A Study on the Influencing Factors of Marine Pollution Control Manpower in Korea Coast Guard

이 논문은 해양오염사고의 대형화와 더불어 재난업무로써 그 비중이 날로 높아지는 해양오염방제업무에 있어서 그 업무를 담당할 방제인력에 영향을 주 는 결정요인을 밝히고자 하는 연구이다 . 조직에서의 인력관리는 인적자원의 수 요와 관련하여 중요한 부분이며, 따라서 적정 수요인력을 산정하는 기준을 마 련하는 것은 필수적이라고 할 수 있다. 그러나 해양경찰청 재난업무에 대해 방제인력의 필요성과 역할은 점차 커져 감에도 불구하고, 아직까지 이와 관련한 다양한 연구가 진행되지 않은 실정이 다. 따라서 현재까지 해양경찰청의 자체 노력의 부족과 더불어, 학계에서도 이 와 관련된 어떠한 연구도 존재하고 있지 않아, 해양오염방제 서비스가 실현될 수 있는 인력의 적정규모는 어느 정도인지를 제안하기 위하여 방제인력 표준정 원 모형을 시험적으로 도출하였다. 2004년부터 2016년까지의 통계 시계열적 수치를 기준으로 한 회귀분석 결과, 해양경찰청 해양오염방제인력에 결정적인 영향요인으로 해양오염 신고건수, 해 양환경관련 민원․신고건수, 방제정 척수, 유회수기 수로 나타났다. 해양오염 발 생건수는 실질적인 기름이 선박 및 육상으로부터 해난, 부주의, 고의, 파손 등 의 원인으로 인해 기름 및 폐기물 등의 오염물질이 바다로 유출된 건수를 의미 하며 해양환경관련 민원 신고건수는 현지 , ․ 대응기관인 해양경찰서의 해양오염방 제과 또는 상황실로 통해 접수된 현장 목격자 또는 행위자의 해양오염 신고를 의미한다. 방제정척수는 해양오염방제를 위해 장비를 갖춘 선박의 수를 말하며, 유회수기는 해양오염 시 기름을 회수하기 위한 장비를 말한다. 따라서 해양경 찰청 해양오염방제인력에 영향요인인 4개의 독립변수를 이용하여 이를 정원모 형으로 제시하면, 아래와 같다. Y(인력수) = 상수 + (B[비표준화 계수]×해양오염사고 발생건수) + (B[비표준화 계수]×해양환경관련 민원․신고 건수) + (B[비표준화 계수]×방제정 척수) + (B [비표준화 계수]×유회수기수) Y(인력수) = 104.969 + (.346×284.6) + (.192×1030.9) + (.081×26.0) + (.168×87.3) 이상의 표준정원모형에 따라 해양경찰청 해양오염 방제인력수를 산정하면 418.15명이 되는 것으로 나타났다. 2004년부터 2016년까지의 정원에 대한 방제인력의 평균 정원수는 268.38명으 로 나타났다. 본 연구의 정원 산정 방식에 따른 표준정원인 418.15명과 비교 할 때 149.77명이 부족하다는 것을 알 수 있으며, 2016년도 해양경찰청 직제에 따 른 법정정원 324명보다 94.15명이 부족하고, 2016년 현원 대비해서는 96.15명이 부족한 현실임을 알 수 있다. 이러한 연구결과는 해양경찰에서 해양오염 방제인력에 결정적으로 영향을 미 치는 독립변수 4가지 요인들을 강화하거나 보완하는 방향으로 국가 방제시스템 을 구축하여야 한다는 점을 시사한다. 본 연구에서 제시한 해양경찰청 해양오염 방제인력 산정지표 개발은 해양오 염 재난업무 분야에서 매우 중요한, 인력과 관련한 논의를 촉진시켜, 활발한 후 속 연구의 밑거름이 될 것이며, 본 연구에서 개발한 지표를 이용하여 실질적으 로 적정 인력을 산출할 수 있는 토대가 될 것으로 사료된다.|The purpose of this study is to identify the influencing factors to determine the proper size of pollution control manpower in Korea Coast Guard, who are in charge of marine pollution control services which are becoming more important these days due to the increasing magnitude of marine pollution disasters and as disaster response services. Manpower management in an organization is an important issue, and the preparation of the criteria for calculating the proper size of the manpower is essential. For this reason, while there have not been any studies or efforts of Korea Coast Guard in this matter so far, the authors experimentally developed a standard model for calculating the proper manpower size, in order to suggest the proper manpower size for marine pollution control within Korea Coast Guard in order to realize marine pollution control services. For this reason, the authors reviewed existing studies related to manpower sizes in order to review the proposed criteria for the manpower size and overviewed the theories on the method to estimate the demands for manpower. Then, the authors analyzed the factors that could statistically be quantified for marine pollution control services and the functional relationship between these factors and the manpower for pollution control, using an empirical and quantitative manner using regression analysis model that calculates the factors for determining the manpower and extracts the manpower calculation model based on the result of such an analysis. For this study, the data from 2004 to 2016, totaling to 13 years, were analyzed. The result of the study showed that the influencing factors to determine an appropriate size of the manpower included the number of marine pollution events, number of reported complaints related to marine environment, and number of pollution control ships, and number of oil skimmeres. The number of marine pollution events meant the number of incidents where actual oil or other waste material spelt from a vessel or a ground facility leaked into the sea, due to a maritime accident, negligence, deliberate actions, or damages. The number of reported complaints related to marine environment means the number of marine pollution reports from the field witnesses or the person who committed the act, received by the situation room or the Department of Marine Pollution Control in a Coast Guard Station, which is a field response organization. The number of pollution control ship is equipped with equipment for the reponse of marine pollution accidents. The number of oil skimmer is equipment to recover oil in case of marine pollution accident. The result of the influencing factors of manpower for marine pollution control in Korea Coast Guard using the calculation model for the pollution control manpower for Korea Coast Guard showed that the standard manpower size was 418.15 persons. Compared to the average size of the manpower from 2004 to 2016, which was 268.38, it indicates that the manpower size is still 149.76 short of the proper size of 418.15. It is also clear that, compared to the legal manpower size for pollution control in 2016, which was 324, the agency still needs 96.14 more persons to be manned properly. Based on these findings, Korea Coast Guard should design the national control system in order to strengthen the four independent variables that affect the marine pollution control personnel. This implication of this study is that a standard manpower size calculation model for pollution control manpower was developed, while there have been scarcely any studies on the proper manpower size for marine pollution control for Korea Coast Guard so far. Therefore, it is difficult to assume that all of the results of this study were valid, and it is the hope of the authors that the experimental study may be used as an opportunity for follow up studies in the future.LIST of Tables ·····························································································ⅲ LIST of Figures ························································································· ··ⅴ Abstract ···································································································· ·ⅸ 제 1 장 서 론 1.1 연구의 배경과 목적··················································································1 1.2 연구의 범위와 방법··················································································6 1.2.1 연구의 대상과 범위···············································································6 1.2.2 연구의 방법························································································· 7 제 2 장 인력규모 산정에 관한 이론적 배경 2.1 인력산정의 중요성과 공무원 인력관리제도 ················································11 2.1.1 적정인력 산정의 중요성·········································································11 2.1.2 공무원 인력과 관련된 국가적 제도분석 ············································· 14 2.2 인력규모 산정에 관한 선행연구··································································28 2.2.1 국가공무원 인력규모에 관한 연구······················································· 28 2.2.2 지방공무원 인력규모에 관한 연구······················································· 32 2.3 인력산정을 위한 연구모형·········································································41 2.3.1 연구의 분석과정 ···················································································41 2.3.2 분석방법 및 분석모형············································································43 제 3 장 해양오염 방제정책과 방제행위자 역할분석 3.1 해양오염방제 실태 ················································································· ·47 3.1.1 한국 해양오염발생 현황분석 ·································································47 3.1.2 해양오염 발생요인과 특성·····································································57 3.2 한국 해양오염 방제정책······································································· ····67 3.2.1 해양오염방제 업무 특성·········································································67 3.2.2 한국 해양오염 방제정책 현황······························································ ·69 3.2.3 한국 해양오염 방제정책의 문제점······················································ ·79 3.3 해양오염방제 인력과 조직 변화추이···························································84 3.3.1 해양오염 방제인력 변화·········································································84 3.3.2 해양오염 방제조직 변화·········································································89 3.4 해양오염방제 행위자 역할분석 ·································································94 3.4.1 해양경찰청···························································································97 3.4.2 지방자치단체························································································98 3.4.3 해양환경관리공단 ················································································101 3.4.4 민간 방제업체······················································································103 제 4 장 해양오염방제인력 영향요인 분석 및 적정규모 산정 4.1 자료수집 방법 및 변수의 조작적 정의···················································· ··105 4.1.1 자료수집 방법·······················································································105 4.1.2 변수의 조작적 정의···············································································109 4.2 해양경찰청 해양오염방제 인력산정····························································114 4.2.1 기술통계 분석·······················································································114 4.2.2 상관분석······························································································120 4.2.3 단순회귀분석························································································127 4.2.4 다중회귀 분석·······················································································129 제 5 장 결 론 5.1 연구의 요약 및 시사점···············································································138 5.2 연구의 한계점···························································································152 참고문헌 ········································································································154 감사의 글 ·······································································································162Docto

Endovascular Drug-Coated Stenting of Basilar Artery Stenosis: A Case Report and Literature Review

Patients with a symptomatic basilar artery stenosis have a poor prognosis and limited therapeutic options. Despite the best medical efforts, there is still a high incidence of stroke. A surgical bypass is technically demanding with a high mortality and morbidity rate. Percutaneous angioplasty still carries a risk of procedure related complication and restenosis. Stenting has been shown to improve the safety and durability of angioplasty in the coronary and peripheral arteries. Recently, stenting of the intracranial arteries has been attempted by some investigators with newer and more trackable stents. We report a case of a basilar artery stenosis that was successfully treated using a drug-coated stent.ope

Endovascular Therapy Combined With Immunosuppressive Treatment for Occlusive Arterial Disease in Patients With Takayasu's Arteritis

PURPOSE: To evaluate the feasibility and efficacy of endovascular therapy combined with immunosuppression for the treatment of arterial occlusive disease in patients with Takayasu's arteritis (TA). METHODS: From January 1998 to June 2003, 25 patients (22 women; age 37.8+/-15.5 years) with TA were treated with angioplasty for symptomatic lesions or with a hemodynamically significant aortic narrowing. The patients with active disease, defined as an increase in inflammatory markers (e.g., erythrocyte sedimentation rate [ESR]), were treated with immunosuppressive agents before intervention. Angioplasty was performed after the ESR had been normalized. RESULTS: In the 25 patients, 58 vascular territories (7 aortic, 9 carotid, 3 vertebral, 11 subclavian, 2 superior mesenteric, 18 renal, 4 iliac, and 4 coronary arteries) were treated with angioplasty only (19 lesions) or with stents (39 lesions). The mean ESR when the vascular lesions were initially diagnosed was 35.6+/-26.2 mm/h, which fell to 18.5+/-7.8 mm/h after immunosuppressive therapy. The endovascular procedure was performed successfully in 52 (90%) of 58 lesions. During the mean 23.7+/-18.4-month follow-up, 9 (17%) treated segments restenosed; 4 were treated with repeat angioplasty. The overall cumulative primary clinical success rate was 82%; secondary clinical success was 90%. CONCLUSIONS: Endovascular therapy for stenotic lesions in patients with TA is safe and effective when disease activity is strictly controlled with immunosuppressive treatment.ope

An Attempt for Combining Microarray Data Sets by Adjusting Gene Expressions

PURPOSE: The diverse experimental environments in microarray technology, such as the different platforms or different RNA sources, can cause biases in the analysis of multiple microarrays. These systematic effects present a substantial obstacle for the analysis of microarray data, and the resulting information may be inconsistent and unreliable. Therefore, we introduced a simple integration method for combining microarray data sets that are derived from different experimental conditions, and we expected that more reliable information can be detected from the combined data set rather than from the separated data sets. MATERIALS AND METHODS: This method is based on the distributions of the gene expression ratios among the different microarray data sets and it transforms, gene by gene, the gene expression ratios into the form of the reference data set. The efficiency of the proposed integration method was evaluated using two microarray data sets, which were derived from different RNA sources, and a newly defined measure, the mixture score. RESULTS: The proposed integration method intermixed the two data sets that were obtained from different RNA sources, which in turn reduced the experimental bias between the two data sets, and the mixture score increased by 24.2%. A data set combined by the proposed method preserved the inter-group relationship of the separated data sets. CONCLUSION: The proposed method worked well in adjusting systematic biases, including the source effect. The ability to use an effectively integrated microarray data set yields more reliable results due to the larger sample size and this also decreases the chance of false negatives.ope

Adenosine triphosphate-based chemotherapy response assay (ATP-CRA)-guided versus empirical chemotherapy in unresectable non-small cell lung cancer

BACKGROUND: We retrospectively compared adenosine triphosphate-based chemotherapy response assay (ATP-CRA)-guided and empirical chemotherapies for unresectable non-small cell lung cancer (NSCLC) in this case-control study. PATIENTS AND METHODS: Unresectable NSCLC patients receiving ATP-CRA-guided platinum-based doublets as first-line therapy were enrolled as cases (n=27; 14 platinum-sensitive and 13 platinum-resistant patients). Performance status, stage, and chemotherapeutic regimen-matched patients receiving empirical chemotherapy were selected from the retrospective database as controls (n=93) in a case to control ratio of approximately 1:3. RESULTS: Response rate and survival (progression-free; overall) in both groups were not significantly different. However, the platinum-sensitive subgroup by ATP-CRA showed a higher response rate than the empirical group (71 versus 38%; p=0.023) with a trend toward longer progression-free survival (8.7 versus 4.8 months for platinum-sensitive versus empirical; p=0.223) and overall survival (not reached versus 12.6 months for platinum-sensitive versus empirical for p=0.134). CONCLUSION: ATP-CRA may be helpful in selecting platinum-responsive patients in unresectable NSCLC. We consider that nonplatinum doublets in platinum-resistant patients by ATP-CRA may be a more adapted approach than platinum-based doublets in future clinical trialsope

Carotid Artery Stenting with Distal Protection Device：Early Experience

Background and Objectives：Carotid artery stenting (CAS) is emerging as a reasonable alternative to carotid endarterectomy, and especially for those patients with comorbidities. However, this endovascular approach has acute complications related to distal embolization. Therefore, the use of protection devices is expected to reduce the risk of embolic strokes during this procedure and to deliver more favorable outcomes. We report here on our early experiences with balloon occlusion and filter type distal protection devices that were used for CAS. Subjects and Methods：CAS was performed on 92 lesions of 73 patients (age：61.0±12.7 years, males：71.2%). Of these patients, 16 patients with 17 carotid lesions underwent CAS using distal protection devices. A balloon occlusion type protection device, PercuSurge GuardWire system, was used for 8 lesions and a filter type, FilterWire EX system, was used for 9 lesions. Procedural and early clinical outcomes including complications were compared between the two groups of patients who underwent CAS with the distal protection (group I) and without the distal protection (group II). Results：Carotid angioplasty and stenting was performed successfully in all the patients. Successful deployment of the protection devices was possible in all 17 carotid lesions. Among the 75 carotid lesions treated without protection device, there were two fatal strokes, one non-fatal major stroke, one minor stroke and five transient ischemic attacks (TIA), whereas one TIA and one non-neurologic death occurred among the 17 lesions treated with the protection device (p=ns). Conclusion：CAS with use of the distal protection device can be performed successfully and safely. Despite the limited experience with the protection devices, our results suggest the use of distal protection device for carotid intervention may reduce acute complications related to distal embolization during the procedure.ope

Comparison of the Naranjo and WHO-Uppsala Monitoring Centre criteria for causality assessment of adverse drug reactions

Background/Aims : Several criteria have been proposed to increase the objectivity, reliability and validity of causality assessment of adverse drug reactions (ADR). We compared the Naranjo probability scale and the World Health Organization- Uppsala Monitoring Centre (WHO-UMC) causality categories to evaluate the validity and clinical usefulness of these criteria. Methods : We evaluated 100 ADR cases with the Naranjo probability scale and the WHO-UMC causality categories. The Spearman rank coefficient was used to determine the correlation of these criteria. The evaluation of the ADR was categorized into four groups for the Naranjo system: definite, probable, possible, and doubtful, and six groups for the WHO‐UMC: certain, probable, possible, unlikely, conditional/unclassified, and unassessable. Results : The criteria used form these two systems showed some differences when compared with the same ADR cases. The Spearman rank coefficient was 0.519 (p<0.001) and the agreement was 55% between the Naranjo probability scale and the WHO-UMC causality categories. The Naranjo probability scale includes measurements for drug concentration, objective evidence of ADR, ADR to previous exposures, responses to placebo, and the dose adjustment of drugs. However, few cases were evaluated for all of these measures. Conclusions : The Naranjo probability scale may be helpful for assessing unexpected ADRs and useful for evaluators with little experience. However, some of the items are not utilized and there are discrepancies when compared with the WHO-UMC causality criteriaope

칼슘 실리케이트 시멘트와 칼슘 실리케이트 계통 실러를 함께 사용 시 치근단 역충전의 질 평가

In apical surgery, retrograde filling is a crucial procedure used to form a hermetic seal at the root-end area. However, it is very technique-sensitive because of limited access and visibility in clinical settings and the difficulty of handling retrograde filling materials. Therefore, the use of calcium silicate–based sealer, which has good flowability and maneuverability, as a retrograde filling material could be expected to improve retrograde filling quality. The aim of this study was to assess the quality of retrograde filling with a combination of calcium silicate cement and calcium silicate–based sealer. Twenty single-rooted, extracted human teeth were instrumented with nickel-titanium instruments and obturated with gutta-percha cones. Root resection at 3 mm from the apex and root-end preparation were performed. The root-end cavities were filled using two different retrograde filling methods (n=10). In group 1, the root-end cavities were filled with Endocem Zr (Maruchi, Wonju, Korea), while in group 2, the root-end cavities were filled with an approximately 1-mm-thick layer of Endoseal MTA (Maruchi) followed by Endocem Zr. Then, the samples were scanned using micro-computed tomography (micro-CT) and three-dimensional images of the samples were reconstructed. The volume of the gap between the tooth structure and the root-end filling materials and the volume of the voids in the filling materials were measured, and the percentages of these volumes were calculated. Data were analyzed using the Mann-Whitney U test at a significance level of 95% to compare the difference in the volume percentage of voids between the two groups. Selected specimens were further observed using scanning electron microscopy (SEM). No significant difference was found between the two groups in the volume percentage of the gaps and internal voids. The SEM examinations showed that the calcium silicate based–sealer applied in the retro-prepared cavity demonstrated good adaptation to the cavity wall and the calcium silicate cement. Within the limitations of this study, the quality of retrograde filling with a combination of calcium silicate cement and calcium silicate–based sealer showed no statistically significant difference from that of retrograde filling with calcium silicate cement only. 치근단 수술 시, 치근단 역충전은 근관 내 세균이 치근단 조직으로 누출되지 않도록 긴밀한 밀폐를 형성한다는 점에서 매우 중요한 과정이다. 하지만 실제 수술 시 제한된 시야와 접근의 어려움, 재료 및 기구 조작의 어려움으로 인해 치근단 역충전은 난이도가 높고, 이로 인해 결함이 발생할 수 있다. 만약 흐름성이 좋고, 적용이 간편한 칼슘 실리케이트 계통 실러를 치근단 역충전 재료로 사용한다면 보다 쉬운 적용 및 양질의 치근단 역충전을 기대할 수 있다. 이 연구의 목적은 칼슘 실리케이트 계통 실러와 칼슘 실리케이트 시멘트를 순차적으로 치근단 와동에 역충전 재료로 적용했을 때 void의 비율을 micro-CT로 측정하여 충전의 질을 평가하는 것이며, 주사전자현미경(SEM)을 사용하여 치아와 재료 간, 서로 다른 재료 간 계면을 관찰하였다. 20개의 사람의 상악 소구치를 근관충전 후 치근단 3mm를 절제한 뒤 초음파 기구를 사용하여 3mm 깊이로 치근단 와동 형성을 시행하였다. 무작위로 두 그룹으로 나누어 첫 번째 그룹은 칼슘 실리케이트 시멘트로 충전하고, 두 번째 그룹은 칼슘 실리케이트 계통 실러를 근단부 와동에 1mm 적용하고, 남은 부위를 칼슘 실리케이트 시멘트로 충전하였다. 이후 micro-CT로 스캔 후 충전재와 근관 벽 사이, 충전재 내부 void의 비율로 나누어 통계적 처리를 시행하였다. 이후 시편은 SEM으로 관찰하였다. 충전재와 근관 벽 사이 void의 비율 (%Vout), 충전재 내 void의 비율(%Vin) 모두 두 번째 그룹에서 상대적으로 적게 나타나지만 두 가지 충전 방법 간 통계적 유의차는 없었다. SEM 이미지에서는 칼슘 실리케이트 계열 실러가 근관 벽 및 칼슘 실리케이트 시멘트와 잘 적합 되는 것이 관찰되지만 칼슘 실리케이트 시멘트 재료 내의 void가 관찰되었다.open석