• 한국정밀공학회지
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• 제26권4호
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• pp.107-113
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• 2009

In this paper, we studied of measurement the vibration of natural frequency using optical fiber sensor. The boring bar for measurement of vibration in use optical fiber sensor has the advantage of direct measure for the frequency than accelerometer. Because it deal with output value on electrical signal of optical fiber in physical disturbance when it measures the frequency of vibration. The optical fiber sensor measured the vibration of boring bar by the gap in sensing jig while optical fiber just kept contact with boring bar. A prototype system was composed of jig part with gap and optical system part. In this paper, we found out the possibility to measurement of vibration by the gap in use optical fiber.

• 보건교육건강증진학회지
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• 제32권5호
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• pp.73-81
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• 2015

Objectives: We tried to confirm physical activity of 1,000 Kcal per week was a meaningful point in controlling coronary artery disease risks in female older adults. Methods: Participants were 66 female older adults recruited from senior welfare center. Participants were provided with accelerometer (e-step, Kenz, Japan) for measuring daily energy expenditure. Graded exercise test was done for measuring aerobic fitness. Blood glucose and lipid were analyzed. Framingham risk score was calculated based on blood glucose, blood lipid, and smoking. These variables were compared between the group expended more than 1,000 Kcal/week and the group with energy expenditure below 1,000 Kcal/week. Results: The group expended over 1,000kcal/week showed to be superior to the counterpart group in following variables; AC(Abdominal Circumference), %BF, $HR_{rest}$(resting heart rate), $VO_{2peak}$, FBG, LDL-C, TG, BDI-II, QOL, AR(Absolute Risk), RR(Relative Risk). Conclusions: The group expended over 1,000 Kcal/week was likely to have less probability in CAD than group expended less than 1,000 Kcal/week. The result of this study suggests the important role of active daily life that can be replaced with that of regular exercise especially for those who are not available to do structured exercise.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2016년도 춘계학술발표대회
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• pp.953-955
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• 2016

본 논문은 다중 회귀 분석을 이용하여 3축 가속도센서기반의 활동량을 추정하는 방법을 제안한다. 본 연구를 위해 총 59명의 피 실험자가 자체 제작한 활동량계를 착용한 뒤 트레드밀에서 일정한 속도로 걷는/뛰는 동작을 수행한 신호를 수집하였다. 수집한 3축 가속도 신호의 에너지 값에서 사전에 정의한 특징들을 산출한다. 그 다음 각 특징별로 선형, 지수, 로지스틱 회귀 분석을 적용하여 적합도가 높은 특징을 선정한다. 마지막으로 산출된 회귀식들을 사용하여 다중 회귀 분석 방법으로 활동량을 추정한다. 호흡가스 대사 분석기(K4B2)를 착용한 뒤 동일한 방법으로 실험을 수행 하고 제안한 방법과 정확도를 비교한 결과 제안한 방법의 정확도는 86.38 %로 산출되었다. 이는 기존의 Kim 외 3인의 연구결과[1]보다 2.70 %, Actical의 정확도보다 4.31 % 높은 수치이다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.928-929
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• 2017

한국형발사체개발 사업의 일환으로 75톤급 액체로켓엔진이 개발되었다. 액체로켓엔진을 개발하는데 있어 지상연소시험의 수행은 필수적이며, 이를 통해 전체 엔진 시스템에 대한 다양한 검증이 수행될 수 있다. 본 연구에서는 75톤급 액체로켓엔진의 지상연소시험을 수행하고 지상연소시험 중 측정된 진동 신호의 분석에 관하여 개략적인 내용을 기술하였다. 진동 응답 특성 측정 및 분석은 전체 구조물의 건전성 및 구조설계를 검증하는데 있어 매우 중요한 지표로 활용될 수 있다.

• Structural Engineering and Mechanics
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• 제54권6호
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• pp.1245-1266
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• 2015

In this research, the cylindrical absorber made of expanded metal sheets under impact loading has been examined. Expanded metal sheets due to their low weight, effective collapse mechanism has a high energy absorption capacity. Two types of absorbers with different cells angle were examined. First, the absorber with cell angle ${\alpha}=0$ and then the absorber with angle cell ${\alpha}=90$. Experimental Study is done by drop Hammer device and numerical investigation is done by finite element of ABAQUS software. The output of device is acceleration-time Diagram which is shown by Accelerometer that is located on the picky mass. Also the output of ABAQUS software is shown by force-displacement diagram. In this research, the numerical and experimental study of the collapse type, force-displacement diagrams and effective parameters has been investigated. Similarly, the comparison between numerical and experimental results has been observed that these results are matched well with each other. From the obtained results it was observed that the absorber with cell angle ${\alpha}=0$, have symmetric collapse and had high energy absorption capacity but the absorber with cell angle ${\alpha}=90$, had global buckling and the energy absorption value was not suitable.

• 한국산학기술학회논문지
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• 제16권5호
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• pp.3412-3420
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• 2015

스마트폰은 일상생활의 필수 요소가 되었으며, 스마트폰의 내장된 센서는 사용자의 상황인지를 위해 유용하게 활용될 수 있다. 하지만, 동적 상황 인지를 통해 안전 및 사고예방을 위한 연구가 미흡한 상황이다. 본 논문에서는 모바일 디바이스의 가속도 센서, 마이크, GPS 센서를 이용해 위험상황을 동적으로 인지할 수 있는 기법을 제안한다. 본 동적인지기법의 센싱 기법에 대한 아키텍쳐와 프로세스를 제안하며, 아키텍쳐의 적합성을 검증을 위해 모바일 어플리케이션을 개발한다.

• 한국소음진동공학회논문집
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• 제18권1호
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• pp.47-56
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• 2008

This paper presents a detecting technique for the improvement in quality by appling the various vibrational characteristics theory. The object of this study is to objectively point out faulty gear by developing the program which can be used to analyze and predict the vibrational characteristics caused by gear wear, deformation and nick of auto-transmission. The fault detection methods by vibrational signal analysis of gear have been progressed in the various fields of industry. These methods have the advantage of being easy to attach the accelerometer without discontinuance of the structure. But not all the methods are efficient for finding early faults. So in the thesis, we completed development of the inspection system of vibration by appling the most efficient detecting methods and verified the system's reliability through experiments.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2015년도 추계학술발표대회
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• pp.1372-1374
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• 2015

본 논문에서는 농구 경기에서의 대표적 자세 중 Standing shoot, Jump shoot, Pass, Dribble, Lay-up shoot, 총 5가지 자세를 인식하기 위해 각 자세와 3축 가속도 값과의 상관관계를 보여주고 있다. 스마트폰에 내장되어 있는 가속도 센서로부터 데이터를 생성해주는 어플리케이션인 Sensor log를 활용하여 얻은 3축 가속도 값으로 수직, 수평축과 3축 가속도의 크기를 구해 Instance로 사용하였다. 위 데이터는 대표적인 데이터 마이닝 도구인 Weka tool을 이용하여 각 모션과 데이터 값의 상관관계를 확인하였고, 실험 결과 10-fold에서 평균 59.8%를 보였으나 Training set과 Test set의 결과 80.8%를 보였다.

• Journal of Positioning, Navigation, and Timing
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• 제11권4호
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• pp.279-286
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• 2022

In this paper, we designed a software library that produces integrated Global Navigation Satellite System (GNSS) / Inertial Navigation System (INS) navigation information using the raw measurements provided by the GNSS chipset, gyroscope, accelerometer and magnetometer embedded in android smartphone. Loosely coupled integration method was used to derive information of GNSS /INS integrated navigation. An application built in the designed library was developed and installed on the android smartphone. And we conducted field experiments. GNSS navigation messages were collected in the Radio Technical Commission for Maritime Service (RTCM 3.0) format by the Network Transport of RTCM via Internet Protocol (NTRIP). As a result of experiments, it was confirmed that design requirements were satisfied by deriving navigation such as three-dimensional position and speed, course over ground (COG), speed over ground (SOG), heading and protection level (PL) using the designed library. In addition, the results of this experiment are expected to be applicable to maritime navigation applications using smart device.

• Geomechanics and Engineering
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• 제31권3호
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• pp.319-328
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• 2022

Ensuring the integrity of a country's infrastructure is necessary to protect surrounding communities in case of disaster. Embankment dam systems across the US are an essential component of infrastructure, referred to as lifeline structures. Embankment dams are crucial to the survival of life and if these structures were to fail, it is imperative that states be prepared. Southern California is particularly concerned with the stability of embankment dams due to the frequent seismic activity that occurs in the state. The purpose of this study was to create a numerical model of an existing embankment dam simulated under seismic loads using previously recorded data. The embankment dam that was studied in Los Angeles, California was outfitted with accelerometers provided by the California Strong Motion Instrumentation Program that have recorded strong motion data for decades and was processed by the Center for Engineering Strong Motion Data to be used in future engineering applications. The accelerometer data was then used to verify the numerical model that was created using finite element modeling software RS2. The results from this study showed Puddingstone Dam's simulated response was consistent with that experienced during previous earthquakes and therefore validated the predicted behavior from the numerical model. The study also identified areas of weakness and instability on the dam that posed the greatest risk for its failure. Following this study, the numerical model can now be used to predict the dam's response to future earthquakes, develop plans for its remediation, and for emergency response in case of disaster.