• 한국멀티미디어학회논문지
• /
• 제21권5호
• /
• pp.583-591
• /
• 2018

With the development of ICT(Information and Communication Technology), the number of smart devices is rapidly increasing. LBS(Location Based Service) applications that provide user's location based service are used in various fields. There is also a growing demand for indoor precision positioning technology to provide seamless services. In this paper, we propose an indoor positioning system that estimates the location of a smartphone user. The proposed algorithm determines whether the received signal is LOS(Line-of-Sight) or NLOS(Non-Line of-Sight) in order to decrease multipath effect by the indoor environment. The proposed positioning algorithm is very simple and requires only the AP(Access Point) coordinates. In addition, it requires only two APs for estimating the location of a smartphone user. The proposed algorithm is a practically applicable technology without any additional hardware and kernel modification in the smartphone. In the experiment results, the reliability of the positioning system was found to be within 0.83 m.

• Steel and Composite Structures
• /
• 제27권5호
• /
• pp.545-554
• /
• 2018

This study presents a novel method of improving the strength and stiffness of cold-formed steel (CFS) beams. Flexural members are primary members in most of the structures. Hence, there is an urgent need in the CFS industry to look beyond the conventional CFS beam sections and develop novel techniques to address the severe local buckling problems that exist in CFS flexural members. The primary objective of this study was to develop new CFS composite beam sections with improved structural performance and economy. This paper presents an experimental study conducted on different CFS composite beams with simply supported end conditions under four point loading. Material properties and geometric imperfections of the models were measured. The test strengths of the models are compared with the design strengths predicted by using Australian/New Zealand Standard for cold-formed steel structures. Furthermore, to ensure high precision testing, a special testing rig was also developed for testing of long span beams. The description of test models, testing rig features and test results are presented here. For better interpretation of results, a comparison of the test results with a hot rolled section is also presented. The test results have shown that the proposed CFS composite beams are promising both in terms of better structural performance as well as economy.

• 대한공간정보학회지
• /
• 제10권2호
• /
• pp.29-37
• /
• 2002

도로상에서 발생되는 교통사고의 많은 부분이 도로의 선형불량에 기인된다. 이러한 도로의 개량설계를 위하여서는 도로의 선형을 정확히 분석할 필요가 있으며, 도로의 설계도와 주요진의 좌표가 필요하게 된다. 따라서, 본 연구에서는 현재 많이 연구되고 있는 인공위성 중 RTK GPS/GLONASS의 조합에 의하여 획득된 자료를 기존 설계도의 제원을 근거로 하여 위치정밀도를 비교하였다. 연구 결과 관측된 도로선형 자료는 5cm 범위 내에 포함되었으며, 이렇게 재현된 도로의 선형을 평가함으로써 인공위성을 이용한 도로의 선형정보체계를 보다 효율적이고 실용적으로 사용하기 위한 한 접근방법을 제시하고자 한다.

• 대한원격탐사학회지
• /
• 제36권5_3호
• /
• pp.1027-1036
• /
• 2020

본 연구에서는 재해/재난 현장에서 취득한 대용량 무인기 영상으로부터 고정밀 3차원 실감 자료를 신속하게 생성하기 위하여 상용 소프트웨어인 Agisoft Metashape와 클라우드 컴퓨팅 서비스인 Amazon web service를 이용하여 처리하는 방식을 제안하고 성능을 평가하였다. 로컬 컴퓨터를 이용하는 온프레미스 방식, Agisoft사(社)와 Pix4D사(社)에서 제공하는 클라우드 서비스와 비교하여, 항공삼각측량, 3차원 포인트 클라우드 및 DSM 생성, 메쉬 및 텍스처 생성, 정사 모자이크 영상 제작 등의 과정은 비슷한 시간을 소요하였다. 클라우드 방식은 대용량 자료의 업로드와 다운로드 시간을 필요로 하지만 실질적인 현장 처리가 가능하다는 분명한 장점을 보였다. 온프레미스 방식과 클라우드 방식 모두 CPU와 GPU 성능에 따라 처리 시간의 차이가 발생하지만 벤치마크를 통해 확인되는 성능 차이만큼 큰 차이는 발생하지 않았다. 그러나 저성능의 GPU가 탑재된 랩탑 컴퓨터는 지나치게 많은 시간을 소요하여 현장 처리에 적용하기 어려운 것으로 나타났다.

• 한국측량학회지
• /
• 제37권5호
• /
• pp.379-388
• /
• 2019

Recently, a technique for acquiring spatial information data using UAV (Unmanned Aerial Vehicle) has been greatly developed. It is a very crucial issue of the GIS (Geographic Information System) mapping system that passes way point in the unmanned airframe and finally measures the accurate image and stable localization to the desired destination. Though positioning using DGPS (Differential Global Navigation System) or RTK-GPS (Real Time Kinematic-GPS) guarantee highly accurate, they are more expensive than the construction of a single positioning system using a single GPS. In the case of a low-priced single GPS system, the stability of the positioning data deteriorates. Therefore, it is necessary to supplement the uncertainty of the absolute position data of the UAV and to improve the accuracy of the current position data economically in the operating state of the UAV. The aim of this study was to present an algorithm enhancing the stability of position data in a single GPS mode of UAV with multiple GPS. First, the arrangement of multiple GPS receivers through the center of gravity of the UAV were examined. Next, MD (Mahalanobis Distance) is applied to detect instantaneous errors of GPS data in advance and eliminate outliers to increase the accuracy of previously collected multiple GPS data. Processing procedure for multiple GPS reception data by applying the center of the triangular method were presented to improve the position accuracy. Second, UAV navigation systems integrated multiple GPS through configuration of the UAV specifications were implemented. Using the unmanned airframe equipped with multiple GPS receivers, GPS data is measured with the TCM (Triangular Center Method). In addition, UAV equipped with multiple GPS were operated in study area and locational accuracy of multiple GPS of UAV with VRS (Virtual Reference Station) GNSS surveying were compared. The result showed that the error factors are compensated, and the error range are reduced, resulting in the reliability of the corrected value. In conclusion, the result in this paper is expected to realize high-precision position estimation at low cost in UAV using multiple low-cost GPS receivers.

• 한국응급구조학회지
• /
• 제12권3호
• /
• pp.87-98
• /
• 2008

Purpose : This study was designed to figure out the necessity of continuing basic CPR education for the higher grade students of elementary school. The assessment contents were knowledge, practice ability, precision level of CPR skills and continuation of the educational efficiency. Methods : Twenty two students of 4th and 5th grade of elementary school in K city in Chungcheongnam-do were recruited for this study. The study method was a control group of non-synchronized design. A preliminary study was done on October 27 in 2006. The main study was performed from February 14 to May 11 in 2007. The researcher adopted the method of Kyung-hui, Kang (1998) such as awareness, attitude and knowledge in control group, emergency medical technician test protocol, Anne/SkillReporter$^{(R)}$ in case of the basic CPR knowledge. Four times of measures were done in shortly after practicing CPR, 4 weeks after the education, 8 weeks after the education, and 12 weeks after the education. By using SPSS/PC+ (version 12.0), the researcher analyzed the collected data based on frequency, percentage, repeated measurement, ANOVA (analysis of variance), and sidak (multiple comparison - sidak). Results : 1) The confidence of people in the control group in terms of practicing CPR showed a statistically meaningful difference (t = 10.230, p = .000) before/after CPR education. Therefore, hypothesis No.1-1 was accepted. 2) The educational necessity of people in the control group showed no statistically meaningful difference (t = -1.695, p = 0.105) before/after CPR education. Therefore, hypothesis No.1-2 was rejected. 3) The knowledge points of people in the control group showed a statistically meaningful difference (t = -7.731, p = .000) before/after CPR education. Therefore, hypothesis No.2 was accepted. 4) The confidence of people in the control group in terms of practicing CRP showed no meaningful difference (F = 2.789, p = 0.072) as time passed. Therefore, hypothesis No.3 was rejected. 5) The knowledge of people in the control group showed a meaningful difference (F = 9.090, p = .000) as time passed. Therefore, hypothesis No.4 was accepted. 6) The capability of people in the control group in terms of practicing CPR showed a statistically meaningful difference (F = 42.795, p = .000) as time passed. Therefore, hypothesis No.5 was accepted. 7) The precision level of CPR skill of people in the control group showed a statistically meaningful difference (F = 25.198, p = .000) as time passed. Therefore, hypothesis No.6-1 was accepted. 8) The precision level of chest compression skill of people in the control group showed a statistically meaningful difference (F = 5.188, p = .003). Therefore, hypothesis No.6-2 was accepted. Conclusion : In a nutshell, CPR education for the 4th and 5th graders of elementary schools had an influence on their confidence in practicing CPR and on their knowledge. This study showed that as time passed. the educational effect declined in terms of knowledge point, capability of practicing CPR, and the precision level of CRP skill. The results of the study could be postulated into the fact that re-education within 8 weeks after the first education was essential to retaining the educational effect. Therefore, we need to vitalize the CPR education for elementary school students repeatedly on a regular basis in order to continue the educational effect after they were grown-ups and to make them play their roles as a first aider.

• 마이크로전자및패키징학회지
• /
• 제23권3호
• /
• pp.63-67
• /
• 2016

본 논문에서는 폴리머 기반의 유연 기판 위 적층 된 다양한 필름의 굽힘 탄성계수의 간접 측정법을 소개한다. 패키징 기판의 다양한 적층 재료들의 탄성계수는 기계적으로 신뢰성 있는 전자기기 개발에 결정적이지만, 기판과 매우 견고히 접합하고 있는 적층 필름을 온전히 떼어 내어 자유지지형(free-standing) 시편을 만들기 어렵기 때문에 그 측정이 쉽지 않다. 이를 해결하기 위해 본 연구에서는 필름-기판의 복합체 시편에 대한 3점 굽힘을 진행하였고 시편 단면에 면적 변환법(area transformation rule)을 적용한 응력 해석을 수행하였다. 탄성계수를 알고 있는 기판에 대하여, 굽힘 시험으로 얻은 다층 시편의 강성으로부터 필름과 기판의 탄성계수 비를 계산하였으며, 전기 도금 구리 시편을 이용하여 양면 적층, 단면 적층의 두 가지 해석 모델이 실험 평가되었다. 또한 주요 절연체 적층 재료인 prepreg (PPG)와 dry film solder resist (DF SR)의 굽힘 탄성계수가 양면 적층 시편 형태로 측정 되었다. 결과로써 구리 110.3 GPa, PPG 22.3 GPa, DF SR 5.0 GPa이 낮은 측정 편차로 측정 됨으로써 본 측정법의 정밀도와 범용성을 검증하였다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집C
• /
• pp.572-579
• /
• 2001

본 연구에서는 유한요소해석을 통한 와이어 방전가공기의 설계검증을 위하여 두 모델을 선정하여 CAD 패키지 I-DEAS를 이용하여 3차원 유한 요소모델을 모델링한 후 상용 유한요소해석코드인 ABAQUS로 각 모델의 가공위치에 따른 해석을 수행하였다. JW-35A와 JW-60A 두 모델의 상호 비교 타당성 여부를 확인하기 위하여 ${\eta}-factor$ 개념을 이용하였다. 이어 공리적 설계 개념을 도입하여 오차보정을 위한 설계변수들의 선택과 방법이 적절함을 보이고 두 모델의 유한요소해석 결과를 상호 비교하여 구조물의 설계를 검증하고 변형 예측식을 유도하였다. 본 연구를 통해 유도된 변형 예측식 (5)-(6) 형태의 접근방법은 비단 방전가공기 뿐만 아니라 이와 유사한 형태의 공작기계에도 적용 할 수 있을 것이다.

• 전기학회논문지
• /
• 제59권6호
• /
• pp.1150-1158
• /
• 2010

In this paper, a new reliable portable activity monitoring device implemented with the buddhist-style bowing activity and walking step detection algorithm, is presented. In order to monitor the bowing and walking activities, miniaturized 3-axis accelerometer sensor with the sensitivity of 800 mV/g was used. After initial signal conditioning, vector magnitude of accelerometer signals was calculated. Syntactic peak detection method was used in order to feature points. All signal processing algorithms were implemented in ultra-low power microcontroller MSP430 with double precision floating point arithmetic. For evaluation, 19 young man($24.22\pm5.22$ yrs) and woman($22.28\pm2.72$ yrs) were involved. The accuracy of the proposed algorithms were 98.91 %($\pm0.011$) for walking step detection and 98.25 %($\pm0.023$) for buddhist-style bowing activity. Comparing to the commercialized pedometer accuracy, 87.1 %($\pm0.058$), the proposed walking step detection algorithms show more reliable accuracy.

• 한국산학기술학회논문지
• /
• 제7권5호
• /
• pp.852-857
• /
• 2006

본 논문은 디지털 지도를 이용하여 산악지형의 전계강도를 정밀하게 분석하는 방법을 제시한다. 일반적으로 전파의 전계 강도는 직접파와 수평면 반사를 주로 고려하였으나, 산악지역에서는 직접파와 수평면 반사 외에도 산악지형의 수직면에 의한 반사도 고려해야 한다. 이러한 점을 고려하여 산악지형에서 전파를 송신할 때 일어나는 직접파와 수평면 반사파, 산악 지형에 의한 수직면 반사파의 합성 전계를 전파의 편파 특성과 위상 특성을 고려하여 계산한 결과를 제시하였다.