다중 센서 항법시스템을 위한 연합형 불변 확장칼만필터

학위논문(석사) -- 서울대학교대학원 : 공과대학 항공우주공학과, 2022.2. 박찬국.This thesis presents the federated invariant extended Kalman filter (IEKF) using multiple measurements. IEKF has superior estimation performance compared to EKF through the definition of state variables on matrix Lie group while using the framework of the EKF. The IEKF enables trajectory independent estimation when left- or right-invariant measurements are used with proper invariant error selection. As a result, the IEKF ensures the convergence and accuracy of estimation, even when the estimation error is large. Most IEKF studies assumed the use of single aiding measurement. However, navigation systems often use multiple aiding sensors to improve estimation performance in applications. When left- and right-invariant measurements are used simultaneously, implementing the LIEKF or RIEKF with a centralized filter structure causes some terms of the measurement matrix dependent on the current estimates, which results in IEKF losing its trajectory independent advantage. On the other hand, when a decentralized filter structure, especially a federated filter structure, is applied, the estimation becomes trajectory independent through separate update of each measurement in the local filters. This thesis proposes a fusion method of IEKF using the federated filter structure for simultaneous use of left- and right-invariant measurements. The performance of the proposed fusion method is validated through simulations. The error convergence and accuracy of the proposed method and the centralized IEKF are compared.본 논문에서는 다수의 보정 센서를 사용하는 항법 시스템을 위한 연합형 불변 확장 칼만필터의 구현을 제안한다. 불변 확장 칼만필터는 일반적인 확장 칼만필터의 프레임워크는 그대로 사용하면서 상태변수를 행렬 리 그룹 상에서 정의하여 확장 칼만필터 대비 우수한 추정 성능을 가진다. 좌불변 혹은 우불변 측정치를 사용할 때 이에 적합한 불변 오차 정의를 선택하여 구현한다면 궤적 독립적인 추정이 가능하다. 대부분의 불변 확장 칼만필터에 대한 연구들은 단일 보정 센서의 사용을 가정한다. 그런데 실제 적용에 있어, 항법 시스템은 추정 성능을 향상하기 위해 다수의 보정 센서를 사용하는 경우가 많다. 좌불변 측정치와 우불변 측정치가 모두 사용되는 상황이라면, 중앙집중형 좌불변 확장 칼만필터와 우불변 확장 칼만필터는 모두 추정치에 영향을 받는 측정치 행렬을 사용하게 된다. 이로 인해 불변 확장칼만필터가 갖는 가장 큰 장점인 궤적 독립 특성을 잃는다. 반면에 연합형 필터 구조를 사용하면 각 측정치에 할당된 국소 필터에서 적절한 필터로 각 측정치를 처리할 수 있다. 따라서 이 논문에서는 불변 확장 칼만필터의 연합형 구조 구현을 제안한다. 리 그룹의 성질을 고려하는 적절한 융합 방식을 사용한 구조를 제안하며, 그 성능을 시뮬레이션을 통해 확인한다. 제안한 방식과 중앙집중형 불변 확장 칼만필터를 수렴성과 추정 정확도의 관점에서 비교하였다.Chapter 1 Introduction 1 1.1 Motivation 1 1.2 Objectives and contributions 3 Chapter 2 Related Works 5 2.1 Invariant extended Kalman filter (IEKF) 5 2.2 Federated filter 7 Chapter 3 Framework of invariant EKF 9 3.1 Mathematical preliminaries 9 3.2 States and model 10 3.2.1 Matrix Lie group states 10 3.2.2 Process model 12 3.2.3 Measurement model 15 3.2.4 Adjoint 16 3.3 IEKF for inertial navigation 17 3.3.1 IMU states and error states 17 3.3.2 Process model 20 3.3.3 Measurement model 22 3.3.4 Adjoint transformation 27 Chapter 4 IEKF Using Multiple Measurements 28 4.1 Centralized filter implementation 29 4.1.1 Centralized LIEKF 30 4.1.2 Centralized RIEKF 32 4.2 Federated filter implementation 34 4.2.1 Overall structure 34 4.2.2 Fusion process 39 4.3 Numerical simulations 40 4.3.1 Convergence test 43 4.3.2 Comparison of centralized IEKF and EKF 48 4.3.3 Comparison of IEKF and the proposed method 52 Chapter 5 Conclusion 60 5.1.1 Conclusion and summary 60 5.1.2 Future works 61 Bibliography 62 국문초록 68석

Comparison of urinary hippuric acid, toluene and o-cresol as biological exposure indicies for workers exposed t

산업보건학과/석사[한글] 유기용제는 여러 산업장에서 필수적인 것으로 그 용도가 다양하며 사용량은 점점 증가하고 있다. 특히 톨루엔은 벤젠의 대체물질로 사용량이 증가됨에 따라 많은 작업장에서 이를 취급하고 있는 근로자들의 직업적 노출기회가 매우 높은 상황이다. 본 연구는 톨루엔에 노출되는 근로자들을 대상으로 생물학적모니터링 방법으로서 요중 마뇨산, 요중 톨루엔, 요중 오르토-크레졸과 노출 근로자의 개인별 특성에 따른 차이, 기중 톨루엔 개인 노출 농도와의 상관성, 생체시료의 채취시점에 따른 노출 지표의 차이를 알아보고자 하였으며 결과는 다음과 같다. 첫째, 연구대상자의 개인별 특성(연령, BMI, 안식향산 함유 음식 섭취 여부, 음주, 흡연, 약물복용, 커피 음용)에 따른 생물학적 노출지표 배설 농도에는 요중 마뇨산, 요중 톨루엔, 요중 오르토-크레졸 모두 통계학적으로 유의한 차이가 없었다. 둘째, 기중 톨루엔에 대한 개인 노출농도와 요중 마뇨산은 상관계수가 r=0.596으로 통계적으로 유의한 상관관계가 있었지만(p<0.05), 요중 톨루엔과 요중 오르토-크레졸은 각각 r=-0.051 , r=0.037로 상관관계가 낮고 통계적으로도 유의 하지 않았으며 또한 10ppm미만군에서도 기중 톨루엔 개인 노출농도와 생물학적 노출지표와의 상관성은 세 지표 모두 통계학적으로 유의하지 않았다. 셋째, 기중 톨루엔의 개인 노출 농도에 따른 작업 전 및 작업 후의 생물학적 노출지표의차이는 전체적으로 요중 마뇨산, 요중 톨루엔, 요중 오르토-크레졸 모두 작업 후가 작업 전보다 높게 나왔으며 통계학적으로 유의하였다.(p<0.05). 그러나 농도군별 비교에서 1pp m 미만 군에서는 요중 톨루엔과 요중 오르토 크레졸이 작업 전 및 작업 후의 차이가 통계학적으로 유의하였고 요중 마뇨산은 통계학적으로 유의하지 않았다. 본 연구결과 연구대상자의 개인별 특성(연령, BMI, 안식향산 함유 음식 섭취 여부, 음주, 흡연, 약물 복용, 커피 음용)은 각각의 요중 대사산물 배설에 영향을 주지 않았다. 그러나 작업 전 및 작업 후의 배설량에 차이가있어 작업 종료시의 시료 채취가 노출 평가에중요하였다. 또한 세가지 요중 대사산물중 요중 마뇨산은 기중 톨루엔과 상관성이 높았으나 요중 톨루엔 및 요중 오르토-크레졸은 1ppm의 저 농도군에서 요중 마뇨산을 보완할 수 있는 요중생물학적 노출지표라고 생각되며 앞으로 이에 대한 연구가 더욱 필요하다. [영문] Organic solvents, which are very necessary in many industrial fields, have various uses and are now increasingly consumed. Especially, as toluene is widely used as a substitute material for benzene, the chances of workers' occupational exposure to toluene are becoming higher than ever before. This study was performed to compare the urinary hippuric acid, toluene and o-cresol as indices for biological exposure for workers exposed to toluene in air the statistical differences of various individual characteristics, the correlations between each biological exposure index and the concentration of individual exposure to toluene in air, and the statistical differences of the indices depending on sampling time points. The results of the study are as follows; 1. Factors such as age, BMI, benzoic acid containing foods, alcohol, smoking, drug , coffee did not affect the excretion of urinary hippuric acid, urinary toluene and urinary o-cresol. 2. For urinary hippuric acid, the correlation with the individual exposure concentration to tolune in air was statistically significant (r=0.596, p<0.05) and the correlations for urinary toluence and o-cresol were r=-0.051 and r=0.037, respectively, thus the correlations were not statistically significant and low. Besides in cases lower than 10ppm, the correlation between the concentration of individual exposure to air-toluene and three biological monitoring indicies was not statistically significant. 3. Deffrence of biological exposure indecise in the begining of work and end of shift to indivisual exposure to toluene in air were statistically significant that the urinary hippuric acid, toluene, and o-cresol in end of shift were higher than begining of work. However, in cases lower than 1ppm, deffrence of the urinary toluene and o-cresol were statistically significant in the begining of work and end of shift, but urinary hippuric acid was not. We concluded that, while the individual characteristics(e.g., age, body mass index, benzoic acid containing foods, alcohol, smoking, drug, coffee) did not affect the excretion of urinary hippuric acid, toluene and o-cresol. But excretions changes through the begining of work and the end of shift have the statistical significant, so sampling time at the end of shift was vary important. Although the excretion of urinary hippuric acid showed significant correlation with the exposure to toluene in air, urinary toluene and o-cresol was recommended to be used as a subsidiary index in very low concentration of toluene in air.ope

Case report of renal cell carcinoma in automobile manufacturing factory worker due to trichloroethylene exposure in Korea

BACKGROUND: The aim of this paper was report first case of renal cell carcinoma developed in a worker who worked in an automobile manufacture line which handles trichloroethylene in Korea. CASE PRESENTATION: To clarify the relationship between the onset of renal cell carcinoma in 52-years old male worker and the exposure to trichloroethylene, document studies and work environment measurement were done. Past work environment exposure data were reviewed and medical history and surgery records of the worker were also reviewed. The patient had no personal risk factor related to renal cell carcinoma except for his smoking habit of quarter a pack per day for twenty years, and since trichloroethylene was not part of measurement criteria, past work environment risk assessment data could not verify the exposure. The exposure level is deduced by analyzing material exposure level of work environments which has similar processes in data from revised research of chemical exposure standard and work environment validity assessment. Evaluation Committee of Epidemiologic Survey decided that there are relevant relationship between the exposure and the disease, though we do not have exact data during that period, most experts agree that in every factories they used trichloroethylene without any direction. CONCLUSIONS: From the relevant medical history and the results of the usage of trichloroethylene in the relevant industries, and initial discovery of renal cell carcinoma at health inspection sonogram in 2001, it can be concluded that suggests significant causal relationship between the exposure to trichloroethylene and renal cell carcinoma onset, thus reporting it to be the first domestic case declared to be occupational disease.ope

A Descriptive Study on Violence by Customer against ‘Daeri’ Drivers in Korea

Objectives: The purpose of this study was to research ‘Daeri’ drivers who work for drunken customers as a substitute driver. This was the first study in Korea to investigate assault and verbal abuse experienced while employed as a ‘Daeri’ driver. Methods: In this study, we conducted a survey to investigate people who work as ‘Daeri’ drivers. The survey was performed from September 1 to 7, 2014. The participants were 166 adult men and women who work as full-time ‘Daeri’ drivers. Results: Participants who experienced physical violence and assault from the customers to the point of disturbing safe driving in a year were 36.1% of total respondents. People who experienced verbal abuse to the point of disturbing safe driving in a year totaled 80.4% of respondents. In addition, there were also qualitative research results. Conclusions: Acts that impede safe driving are a danger to both passengers and drivers. By protecting the safety of ‘Daeri’ drivers, we will be able to protect the safety of citizens. Therefore, it is necessary to make an effort to protect ‘Daeri’ drivers from customer violence. Furthermore, it is also necessary to research policy to emplace a legal system that can protect ‘Daeri' drivers.ope

Design of High-Speed Power-Efficient Optical Transmitter With Push-Pull Driving Technique

학위논문(박사)--서울대학교 대학원 :공과대학 전기·정보공학부,2019. 8. 정덕균.Data usage dramatically increases by year due to Internet of Things (IoT) and 5G networks. Even though required data keeps going up, backbone network of wireline such as data center has to transmit and receive data without or less errors. However, electrical wireline interface is difficult to process data for the data surge due to skin effects and dielectric loss in the copper channel at high frequency. Therefore, the significance of high-speed and power-efficient optical links utilizing optical fibers keeps increasing owing to its low loss even delivering data for the long distance. Following this trends, this thesis is focused on transmitter side of optical links. Push-pull driving technique, which is suitable for high-speed and power-efficient network, is proposed and utilized. Based on this technique, 32Gb/s NRZ driver with large output swing, which drives Mach-Zehnder modulator (MZM) or electro-absorption modulator (EAM), has been implemented with the power efficiency of 6.28pJ/b in 65nm CMOS process. It achieves an active area of 0.086mm2. Also, 4-channel HDMI active optical cable (AOC) transmitter chips achieving 12Gb/s per channel is fabricated in 180nm CMOS process using push-pull driving scheme with the total area of 1.62mm2. In the subsequent section, optical transmitters with clocking architecture have been proposed. Vertical-cavity surface-emitting laser (VCSEL), which has low cost for fabrication and high ability for integration, are utilized for clocked optical transmitters. Both forwarded and embedded clocking architectures have been employed for the future optical interface between application-specific integrated circuit (ASIC) and optical links. As a result, 56Gb/s VCSEL PAM-4 transmitter with forwarded clocking and 64Gb/s VCSEL PAM-4 transmitter with embedded clocking have been implemented in 65nm CMOS process. Figure of merits for power efficiency are 2.12pJ/b and 2.69pJ/b, respectively. Both chips occupy the area of 0.133mm2 and 0.278mm2, respectively.다가오는 IoT와 5G 무선망으로 인해 해마다 데이터의 사용량은 급격히 증가하고 있다. 요구되는 데이터의 양이 계속 증가되는 가운데, 유선 망에서는 한정된 자원으로 에러 없이 혹은 적은 에러로 전송을 해야 한다. 하지만, 기존의 유선 네트워크로는 고속 주파수에서의 표피효과와 유전체의 손실로 인해 구리 선에서 데이터를 처리하는 것은 쉽지 않다. 따라서, 장거리를 손실 없이 고속의 데이터를 보낼 수 있는 광섬유를 활용의 중요함은 커지고 있다. 이러한 흐름을 따르며, 본 논문에서는 광통신의 송신부에 초점을 맞추었다. 고속 저전력에 적합한 푸쉬-풀 구동 기술이 제안되고 사용되었다. 해당 기술을 기반으로 큰 스윙을 가지며 6.28pJ/b의 효율성을 가진 32Gb/s 마크-젠더 광 변조기/전계-흡수 광 변조기가 65나노 CMOS 공정으로 설계되었다. 해당 칩은 0.086mm2의 작용면적을 지니고 있다. 또한, 채널당 12Gb/s의 속도를 지닌 4-채널 HDMI AOC 드라이버 역시 180나노 공정을 이용하여 설계하였다. 마찬가지로 푸쉬-풀 구동 기술을 사용했으며 총 면적은 1.62mm2였다. 후속 섹션에서는 클락을 가진 광 송신기가 제안되었다. 값싸고 집적도가 높은 면발광 레이져가 본 섹션에서 이용되었다. 클락 전송형, 클락 내장형 송신기가 차세대 광통신을 위해 적용되었다. 그 결과 56Gb/s 4-레벨 진폭변조가 가능한 면발광 레이저를 구동하는 클락 전송형 광 송신기와 64Gb/s 4-레벨 진폭변조가 가능한 면발광 레이저를 구동하는 클락 내장형 광 송신기가 설계되었다. 전력효율성은 각각 2.12pJ/b와 2.69pJ/b 이며 0.133mm2와 0.278mm2의 작용면적을 갖고 있다. 다가오는 IoT와 5G 무선망으로 인해 해마다 데이터의 사용량은 급격히 증가하고 있다. 요구되는 데이터의 양이 계속 증가되는 가운데, 유선 망에서는 한정된 자원으로 에러 없이 혹은 적은 에러로 전송을 해야 한다. 하지만, 기존의 유선 네트워크로는 고속 주파수에서의 표피효과와 유전체의 손실로 인해 구리 선에서 데이터를 처리하는 것은 쉽지 않다. 따라서, 장거리를 손실 없이 고속의 데이터를 보낼 수 있는 광섬유를 활용의 중요함은 커지고 있다. 이러한 흐름을 따르며, 본 논문에서는 광통신의 송신부에 초점을 맞추었다. 고속 저전력에 적합한 푸쉬-풀 구동 기술이 제안되고 사용되었다. 해당 기술을 기반으로 큰 스윙을 가지며 6.28pJ/b의 효율성을 가진 32Gb/s 마크-젠더 광 변조기/전계-흡수 광 변조기가 65나노 CMOS 공정으로 설계되었다. 해당 칩은 0.086mm2의 작용면적을 지니고 있다. 또한, 채널당 12Gb/s의 속도를 지닌 4-채널 HDMI AOC 드라이버 역시 180나노 공정을 이용하여 설계하였다. 마찬가지로 푸쉬-풀 구동 기술을 사용했으며 총 면적은 1.62mm2였다. 후속 섹션에서는 클락을 가진 광 송신기가 제안되었다. 값싸고 집적도가 높은 면발광 레이져가 본 섹션에서 이용되었다. 클락 전송형, 클락 내장형 송신기가 차세대 광통신을 위해 적용되었다. 그 결과 56Gb/s 4-레벨 진폭변조가 가능한 면발광 레이저를 구동하는 클락 전송형 광 송신기와 64Gb/s 4-레벨 진폭변조가 가능한 면발광 레이저를 구동하는 클락 내장형 광 송신기가 설계되었다. 전력효율성은 각각 2.12pJ/b와 2.69pJ/b 이며 0.133mm2와 0.278mm2의 작용면적을 갖고 있다.Chapter 1 Introduction 1 1.1. Motivation 1 1.2. Thesis Organization 3 Chapter 2 Background of Optical Link 4 2.1. Overview 4 2.2. Basic Principles of Optical Transmission 7 2.3. Basis of Data Center 13 2.4. Design Challenges of Optical Link in Data Center 16 2.4.1. Required Bandwidth of the Data Center Interconnects 16 2.4.2. Power Budget of the Data Center 17 2.4.3. Future Data Center 18 2.5. Basis of Optical Components for Transmitter 20 2.5.1. Modulator 20 2.5.2. VCSEL 22 Chapter 3 High-Speed Optical Driver Implementations With Power-Efficient Push-Pull Driving Scheme 24 3.1. Overview 24 3.2. Push-Pull Technique in Current-Mode Driver 26 3.3. Mach-Zehnder/Electro-Absorption Modulator Driver 29 3.3.1. Previous Works 30 3.3.2. Proposed MZM/EAM Driver 31 3.3.3. Measurement Results 38 3.4. HDMI 4-Channel Driver for AOCs 45 3.4.1 Previous Works 46 3.4.2 Proposed HDMI AOC 49 3.4.3 Measurement Results 56 Chapter 4 High-Speed Clocked Optical Transmitter Implementations With Power-Efficient Techniques 64 4.1 Overview 64 4.2 System Comparison of High-Speed Transmitter 66 4.3 Proposed Clocked Optical Transmitter 70 4.3.1 Previous Works 70 4.3.2 Proposed Forwarded Clocked Optical Transmitter 71 4.3.3 Measurement Results 73 4.3.4 Proposed Embedded Clocked Transmitter 78 4.3.5 Measurement Results 85 Chapter 5 Conclusions 93 Appendix A 95 Bibliography 97 초록 104Docto

(The) design of dress and ornaments applying color cordination to geometrical shape

기계화 문명화된 현대사회에 있어서의 복식디자인은 생활의 향상과 더불어 인간의 자기욕구 충족과 필요성에 의해 보다 실용적이고 세련된 감각의 독창성을 갖는 디자인을 추구하게 되었다. 기하학적인 형태는 이러한 미적인 요구에 보다 충실할 수 있는 합리성·단순성·명확성·객관성등의 요소로 인해 시각전달이 빠르고 설득력과 정돈성이 강한 형태이다. 또한 형태를 창조하는데에 있어 매우 편리하고 합리적인 형태이다. 따라서 본 연구는 이러한 기하학적 형태중 가장 기본적인 형태인 원과 삼각형과 사각형을 설정하여 기하학적 형태의 의미를 분석하여 본인의 기하학적 형태에 대한 인식을 바탕으로 복식디자인에 응용하여 보았다. 단순한 형태이지만 한낱 형태에 그치지 않도록 색채조화를 응용하여 순수성과 자율성을 갖고 있는 새로운 형태와 색채로서의 무한한 개발 가능성을 제시함에 그 목적을 두었다. 이와같은 목적을 위하여 기하학적 형태의 특징 그리고 기하학적 형태의 기본형태인 원과 삼각형과 사각형에 대하여 알아보고, 색채조화에서는 색채 조화의 일반론과 배색의 일반적 개념에 대하여 연구 분석하였다. 이를 토대로하여 8점의 작품을 제작 분석하여 다음과 같은 결론을 얻을 수 있었다. 첫째, 시각은 가장 지각하기 좋은 형태를 좋아한다는 시지각의 필요조건으로서 기하학적 형태의 구조적 간결성은, 오늘날 기계화된 이 시대를 이해하는 형태로서 적합하다고 볼 수 있다. 둘째, 기하학적 형태와 형태의 만남에 있어서 절제있는 구성으로 조형미와 합리성을 가능케 하는 새로운 형태로서 작가의 창조적 의도에 따라 무한히 개발가능한 소재로서 나타났다. 셋째, 울크레이프라는 소재는 탄력성이 있어 주름이 잘 지지 않고 봉제하기 쉬운 직물이므로 평상복으로 적합하며, 같은 색상의 다른 직물과 비교하여 볼 때 염착성이 좋으므로 색채조화의 효과를 더욱 높일 수 있었다. 이와같은 결론을 토대로 복식디자인에 응용함으로서 개성있는 기하학적 형태와 색채조화의 배합으로 새롭게 창조되는 순수한 작품을 시도할 수 있는 기초자료를 제시할 수 있었고, 의류생산업체에 참고자료가 되기를 바란다.;The design of dress and ornaments in the mechanized and civilized modern society got to pursue the aim of modeling nature to have the originality of more practical and refined sense by human own desire satisfactoriness and necessity. Geometrical Shape is the shape that the visual transmission is fast and the persuasion and arrangement nature are strong, by the elements such as rationality, simplicity, clearness, and objectivity etc to be able to be more faithful to this aesthetic demand. In addition, it is very convenient and rational shape in creating the shape. Thus, the purpose of this study is to suggest the infinite development possibility as the new shape to have purity and autonomy, with color harmony in the center, so that even the simple shape may not stop in only shape, by trying to reflect the establishment of circle, triangle and square which are most basic shapes among these geometrical shapes and the analysis of meaning of geometrical shape to the design of dress and ornaments, on the basis of the recognition about my geometrical form. For this purpose, the author tries to examine the general concept of geometrical shape, the feature of geometrical shape, and circle, triangle and square which are the basic elements of geometrical shape, in the theoretical background of geometrical shape, and tries to examine the generality of color harmony, and the base and feeling of coloration, in the color harmony and coloration. On the basis of this, the author could come to the following conclusion by manufacturing and analyzing 8 pieces of works. First, today, the structural conciseness of geometrical shape as the shape to understand this mechanized period is the necessary condition of visual sense that the sense of sight likes the best shape to feel. Then, the geometrical shape can be regarded as what corresponds with this condition, with the stimulus itself. Third, it was the proper method that the mass production is possible, by supplementing the monotony which can be seen in the expression of geometrical shape in the course of manufacture with the color harmony and using the material, woolen fabrics which can be obtained easily. On the basis of this conclusion, by making this study as the moment of start, through the continuous study and effort about future shape and color, more refined and deep work will be able to be created.논문개요 = ⅴ Ⅰ. 서론 = 1 A. 연구의 필요성 = 1 B. 연구의 목적 = 1 Ⅱ. 이론적 배경 = 3 A. 기하학적 형태 = 3 1. 기하학적 형태의 일반적 개념 = 3 2. 기하학적 형태의 특징 = 6 3. 기하학적 형태와 복식디자인 = 8 B. 색채조화와 배색 = 23 1. 색채조화의 일반론 = 23 2. 배색의 일반적 개넘 = 26 Ⅲ. 연구방법 및 절차 = 29 Ⅳ. 결과 = 30 A. 작품제작 배경 = 30 B. 작품 및 해설 = 32 Ⅴ. 결론 및 제언 = 73 참고문헌 = 75 ABSTRACT = 7

The correlation between salivary and serum cortisol concentrations in fire fighters

This studies were measure the cortisol from salivary and serum of fire-fighters, who are relatively always exposed to highly dangerous and unsafe working conditions in which they should bring a fire under control or rescue people in danger situations et cetera, therefore both physically and mentally stressed-out, and comparatively analyzed the correlation between the two cortisol levels. The salivary and serum samples of 133 active fire fighters. These were collected at 8:30am, when leaving for work. The salivary cortisol analysis was carried out with enzyme immunoassay, and the serum cortisol analysis utilized chemiluminescence immunoassay. On the morning of testing, the salivary cortisol concentration was 1.92±0.73(0.51-5.85)㎍/㎗, while the cortisol concentration of serum was 14.93±4.23(4.45~25.85)㎍/㎗. Results were grouped according to ages, smoking, drinking habit, and duly type. Higher smoking and drinking produced a statistically significant increase in salivary and serum cortisol concentration. Cortisol concentrations according to type or duty followed by emergency rescue, fire suppression, rescue, miscellaneous. There is a statistically significant correlation between salivary and serum cortisol concentrations. The results show that a significant correlation between salivary and serum cortisol concentrations exists in fire fighters. It is judged that noninvasive methods salivary cortisol could be used in place of serum cortisol to measure cortisol levels when considering factors such as convenience of sample collection and cost.ope

Autonomic dysfunction of overweight combined with low muscle mass

OBJECTIVE: To examine the relationship between overweight combined with low muscle mass and the cardiac autonomic nervous system using heart rate variability (HRV) in healthy workers. METHODS: A total of 1,150 workers were included, with a mean age of 43.55 ± 11.45 years. The subjects were classified as low muscle mass if their appendicular skeletal muscle mass was below the 50th percentile of the study sample. Similarly, subjects were classified as overweight if their body mass index was above 25 kg/m(2). Electrocardiography recordings were obtained for 5 min, and the time-domain and frequency-domain indices of HRV were analyzed. RESULTS: Compared with the high muscle mass and non-overweight (HMM) group, the low-frequency power and the standard deviation of normal-to-normal intervals were significantly decreased in both the overweight and high muscle mass (OHMM) group and the overweight and low muscle mass (OLMM) group. The significantly decreased high-frequency (HF) power and square root of the mean squared differences of successive differences, which reflects efferent parasympathetic activity, was indicative of reduced parasympathetic modulation in the OHMM and OLMM groups. In addition, the OLMM group had a lower HF power than did the OHMM group. CONCLUSIONS: This study suggests that HRV is reduced in overweight combined with low muscle mass group than overweight and HMM group.ope