• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.393-395
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• 2013

In modern society, the elderly over 65 years old are increasing due to development of medical technology and improvement of their standard of living. Severe fall of the elderly can lead to death threats. To solve this problem, several algorithms and hardware systems for fall detection have been studied and developed. In this paper, a fall detection system using 3-axial acceleration sensor is presented. In the fall detection system, several types of fall-feature parameters are calculated and then the fall is determined by using them. Using this system, best sensitivity and specificity are 98.3% and 94.7%, respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.5 s.57
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• pp.142-148
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• 2009

This paper is to investigate the fracture behavior characteristics of box culvert and incremental crack width of upper slab for the incremental loading by the 3-axis loading system. In the 3-axes loading system, loading directions are upper side, left and right side which simulate earth pressure and static traffic load. With the incremental load, crack patterns is investigated on the upper slab, left and right wall. Especially, on the upper slab, crack width is measured by crack gage. Based on the experimental results, structural internal force indices of box culvert are estimated quantitatively.

• Journal of Internet Computing and Services
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• v.11 no.1
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• pp.129-141
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• 2010

In this paper, we present a wearable intelligent device based on multi-sensor for monitoring human activity. In order to recognize multiple activities, we developed activity recognition algorithms utilizing an image sensor and a 3-axis accelerometer sensor. We proposed a grid?based optical flow method and used a SVM classifier to analyze data acquired from multi-sensor. We used the direction and the magnitude of motion vectors extracted from the image sensor. We computed the correlation between axes and the magnitude of the FFT with data extracted from the 3-axis accelerometer sensor. In the experimental results, we showed that the accuracy of activity recognition based on the only image sensor, the only 3-axis accelerometer sensor, and the proposed multi-sensor method was 55.57%, 89.97%, and 89.97% respectively.

• Journal of the Korean Magnetics Society
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• v.24 no.1
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• pp.22-27
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• 2014

North indicating azimuth angle sensors have been used in airplanes, ships traditionally and nowadays employed in smart phones. For the azimuth and roll angle measurement of the sensor, 3-axis acceleration sensor was added to the 3-axis magnetic field sensor. In this work, we have constructed a measuring system for the measurement of the magnetic field and the angle uncertainty of the magnetic field sensors. Measuring system could be useful not only in non-magnetic laboratory but also in normal laboratory, we constructed small size of 3-axis Helmholtz coils for the compensation environment magnetic field (Earth magnetic field and magnetic field from building) and the generation of magnetic field for the test of magnetic field sensor. The constructed measuring system could compensate environment magnetic field below 10 nT level and generate 3-dimensional magnetic field with magnitude uncertainty of 0.2 % and angle error of $0.2^{\circ}$ within the volume of ${\pm}30mm$ diameter at center of Helmholtz coils. For the conformation of developed measuring system, We tested commercially available 3-axis magnetometer and heading sensor.

• Journal of Korean Society of Steel Construction
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• v.14 no.1
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• pp.95-104
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• 2002

In this paper, research for dynamic wheel loads of 3-D vehicle model considering tire enveloping model is carried out. Heavy trucks with 2-axles and 3-axles are modeled by 7-d.o.f. and 8-d.o.f., in which contact length of tire and pitching of tandem spring axles is considered. Dynamic equations of vehicle are derived by using the Lagrange's equation and solution of the equation is calculated by 5th Runge-Kutter method. The validity of the developed 3-D vehicle model is demonstrated by comparing the results obtained by the present method and experimental data by Whittemore. The maximum impact factors of tire force are calculated when vehicle models of 8ton and 15ton dump truck are running on the different class roads with 1.0km and on the various step bump.

• International Journal of Highway Engineering
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• v.14 no.2
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• pp.29-36
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• 2012

In this study, frequently passing vehicles with two, three, four, and five axles were chosen through traffic volume analysis in Kyung-In Expressway in order to analyze how the road roughness and vehicle speed affect on the dynamic loads for roads in various vehicle classes. Dynamic loads according to chosen vehicles are estimated by TruckSim program. Dynamic load amplification factor is ratio between dynamic and static loads, and it is also determined for each vehicle classes. From the result of dynamic loads estimated by the dynamic load amplification factor, it is shown that for three-axles vehicle, when IRI is 3.5 and vehicle speed is 100km/hr, asphalt pavements receive additional 36% of static loads in maximum. The analysis of the amplification factor according to each vehicle classes also indicates that the amplification factor increases as the distance between the axles becomes smaller and each axle receives more loads.

• Korean Journal of Applied Biomechanics
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• v.19 no.3
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• pp.549-555
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• 2009

The purpose of this study was to quantify the isokinetic peak torque and range of motion at the shoulder in 8 national male volleyball players who played during the 2008 professional leagues. In this study the strength and range of motion data in the internal rotation(IR) and external rotation(ER) of shoulder joint were measured with isokinetic measurement system(Biodex Inc) and motion analysis system (Simi motion system Inc.) from 3 volleyball players with atrophy of the infrasupinatus and 5 volleyball players without atrophy of the infraspinatus. Peak torques were determined using isokinetic measurement on the shoulder joint rotator at the point of angular velocities of $60^{\circ}$/s. Significant difference was found in the peak torque, IR / ER ratio and the range of motion through assessment of the dominant shoulder between two groups. we recommended functional exercises that improve both external rotators strength and stretching exercise for internal rotation in the dominant side during the prevention programs in volleyball players.

• Journal of Aerospace System Engineering
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• v.12 no.3
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• pp.9-17
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• 2018

For Earth observation, a small satellite camera has relatively weak structural stability compared to medium-sized satellite, resulting in misalignment of optical components due to severe launching and space environments. These alignment errors can deteriorate the optical performance of satellite cameras. In this study, we proposed a 3-axis focus mechanism to compensate misalignment in a small satellite camera. This mechanism consists of three piezo-electric actuators to perform x-axis and y-axis tilt with de-space compensation. Design requirements for the focus mechanism were derived from the design of the Schmidt-Cassegrain target optical system. To compensate the misalignment of the secondary mirror (M2), the focus mechanism was installed just behind the M2 to control the 3-axis movement of M2. In this case, flexure design with Box-Behnken test plan was used to minimize optical degradation due to wave front error. The wave front error was analyzed using ANSYS. The fabricated focus mechanism demonstrated excellent servo performance in experiments with PID servo control.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.112-115
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• 2011

3축 가속도 센서의 활용이 점차 다양화 되면서 3차원 공간에서의 동작 인식에 대한 개발이 늘어나는 추세이다. 본 논문에서는 모바일기기의 동작을 바탕으로 한 3차원 공간에서의 동작 인식 방법을 제안한다. 동작의 인식은 3축 가속도 센서를 이용하며, 3차원 공간을 14가지 방향으로 나누어서 인식 한다. 기존의 연구에서는 3차원 가속도 데이터를 처리하여 동작을 인식하는 여러 가지 방법만을 제안했을 뿐, 3차원 공간을 방향으로 나누어 접근한 시도는 아직까지 없었다. 본 연구의 이러한 시도는 앞으로 모바일기기에서 사용자 인터페이스를 보다 쉽게 이용할 수 있는 방향으로 활용 가능할 것으로 보인다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3066-3073
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• 2009

Joint paths of master and branch pipes are induced mathematically for many kinds of joint patterns between both pipes in 3-axis pipe profile-cutting machines. By compensating them with a kerf width, the real cutting paths are determined, and their CL-data are generated, and the tool paths generated by CL-data are verified by a ghost function. A bevelling of welds is implemented through tilting a cutting torch in the $\beta$-axis direction for 8 sections in the chuck rotation of $\alpha$-axis. A PLC controls simultaneously position and velocity in a real time for $\alpha$, X, $\beta$-axis by loading CL-data generated. We developed the PLC-controlled 3-axis pipe profile-cutting system which can cut a master or branch pipe along the cutting path and simultaneously do a bevelling process.