• 한국멀티미디어학회논문지
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• 제21권8호
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• pp.982-990
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• 2018

In recent years, many wearable devices and mobile apps related to life care have been developed, and a service for measuring the movement during walking and showing the amount of exercise has been provided. However, they do not measure walking in detail, so there may be errors in the total calorie consumption. If the user's behavior is measured by a multi-axis sensor and learned by a machine learning algorithm to recognize the kind of behavior, the detailed operation of walking can be autonomously distinguished and the total calorie consumption can be calculated more than the conventional method. In order to verify this, we measured activities and created a model using a machine learning algorithm. As a result of the comparison experiment, it was confirmed that the average accuracy was 12.5% or more higher than that of the conventional method. Also, in the measurement of the momentum, the calorie consumption accuracy is more than 49.53% than that of the conventional method. If the activity recognition is performed using the wearable device and the machine learning algorithm, the accuracy can be improved and the energy consumption calculation accuracy can be improved.

• Wind and Structures
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• 제21권2호
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• pp.119-158
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• 2015

The characteristics of the coherence functions of X axial, Y axial, and RZ axial (i.e., body axis) wind forces on the Shanghai World Trade Centre - a 492 m super-tall building with section varying along height are studied via a synchronous multi-pressure measurement of the rigid model in wind tunnel simulating of the turbulent, and the corresponding mathematical expressions are proposed there from. The investigations show that the mathematical expressions of coherence functions in across-wind and torsional-wind directions can be constructed by superimposition of a modified exponential decay function and a peak function caused by turbulent flow and vortex shedding respectively, while that in along-wind direction need only be constructed by the former, similar to that of wind speed. Moreover, an inductive analysis method is proposed to summarize the fitted parameters of the wind force coherence functions of every two measurement levels of altitudes. The comparisons of the first three order generalized force spectra show that the proposed mathematical expressions accord with the experimental results well. Later, the influences of coherence functions on wind-induced dynamic responses are analyzed in detail based on the proposed mathematical expressions and the frequency-domain method of random vibration theory.

• 천문학회보
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• 제41권2호
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• pp.62.2-62.2
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• 2016

We present a newly developed algorithm based on a Bayesian method for 2D tilted-ring analysis of disk galaxies which operates on velocity fields. Compared to the conventional ones based on a chi-squared minimisation procedure, this new Bayesian-based algorithm less suffers from local minima of the model parameters even with high multi-modality of their posterior distributions. Moreover, the Bayesian analysis implemented via Markov Chain Monte Carlo (MCMC) sampling only requires broad ranges of posterior distributions of the parameters, which makes the fitting procedure fully automated. This feature is essential for performing kinematic analysis of an unprecedented number of resolved galaxies from the upcoming Square Kilometre Array (SKA) pathfinders' galaxy surveys. A standalone code, the so-called '2D Bayesian Automated Tilted-ring fitter' (2DBAT) that implements the Bayesian fits of 2D tilted-ring models is developed for deriving rotation curves of galaxies that are at least marginally resolved (> 3 beams across the semi-major axis) and moderately inclined (20 < i < 70 degree). The main layout of 2DBAT and its performance test are discussed using sample galaxies from Australia Telescope Compact Array (ATCA) observations as well as artificial data cubes built based on representative rotation curves of intermediate-mass and massive spiral galaxies.

• 한국지능시스템학회논문지
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• 제13권1호
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• pp.70-75
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• 2003

기존 이동로봇의 활발한 연구와 더불어 다양한 형태의 이동로봇이 등장하였다. 이에 본 논문에서는 8축으로 구성된, 총 16 Degree Of Freedom을 가지는 다 관절 뱀 로봇을 제작하였다. 뱀 로봇은 지면과의 진행 마찰력을 고려하여 무동력 바퀴를 사용하였다. 또한 PC Cam과 초음파 센서를 사용하여 각 관절이 움직일 수 있는 Joint Angle을 나타내기 위하여 Target의 색상과 거리를 입력으로 하였다. 뱀 로봇은 머리부분, 몸통 그리고 꼬리부분으로 나뉘어 진행하는 방식을 가지며 PC Cam 을 통해 화면에 보여지는 움직이는 특정 목표물에 대하여 진행을 하며, 진행 중 움직이거나 고정되어있는 Obstacle이 포착될 경우 충돌회피를 통하여 Target을 추종하는 방식을 실험적으로 보이고자 한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.302-309
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• 2009

Nowadays, the construction sites are growing in city every year, so complaints for construction noise have increased more and more. To analyze this noise scientifically, construction noise prediction program was developed in 1998 and 2005 but it is too difficult to apply program in field because there is few soundproof facilities and it can't understand the coordinate system and so on. The aim of this study is to develop noise prediction program to apply in construction sites. For this, the problems of existing program was analyzed and survey was performed to get requestion of field overseer and upgraded program. To get reliability of program, it was compared with sound measurement value in field. As a result, construction sound prediction program have various soundproof facilities data than existing program. It can also analyze multi receiver point at the same time for several construction machinery. Most of all, it is more powerful to set receiver or source in the axis of X, Y, Z. so program user can make use of it easily. An average of difference is -0.9$\sim$1.8dB.

• 대한기계학회논문집A
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• 제27권6호
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• pp.946-953
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• 2003

A FEM-based analytical approach was used to evaluate the multiaxial high cycle fatigue damage of an automotive sub-frame. Elastic Multi Body Simulation (MBS) has been applied in order to determine the multiaxial load histories. The stresses due to these loads have been given by FE computation. These results have been used as the input for the multiaxial fatigue analysis. For the assessment of multiaxial high cycle fatigue damage, the signed von Mises, the signed Tresca, the absolute maximum principal stress and critical plane methods have been employed. In addition, the biaxiality ratio, a$\sub$e/, the absolute maximum principal stress, $\sigma$$\sub$p/ and the angle, $\phi$$\sub$P/, between $\sigma$$\sub$1/ and the local x-axis, have been calculated to evaluate the stress state at each node.

• 한국소음진동공학회논문집
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• 제19권4호
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• pp.409-417
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• 2009

Nowadays, the construction sites are growing in city every year, so complaints for construction noise have increased more and more. To analyze this noise scientifically, construction noise prediction program was developed in 1998 and 2005 but it is too difficult to apply program in field because there is few soundproof facilities and it can't understand the coordinate system and so on. The aim of this study is to develop noise prediction program to apply in construction sites. For this, the problems of existing program was analyzed and survey was performed to get requestion of field overseer and upgraded program. To get reliability of program, it was compared with sound measurement value in field. As a result, construction sound prediction program have various soundproof facilities data than existing program. It can also analyze multi receiver point at the same time for several construction machinery. Most of all, it is more powerful to set receiver or source in the axis of X, Y, Z. so program user can make use of it easily. An average of difference is -0.9~1.8 dB.

• Journal of Computational Design and Engineering
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• 제2권4호
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• pp.261-267
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• 2015

Free-form blades are widely used in different industries, such as aero-engine and steam turbine. Blades that are damaged during service or have production deficiencies are usually replaced with new ones. This leads to the waste of expensive material and is not sustainable. However, material and costs can be saved by repairing of locally damaged blades or blades with localized production deficiencies. The blade needs to be further machined after welding process to reach the aerodynamic performance requirements. This paper outlines an adaptive location approach of repaired blade for model reconstruction and NC machining. Firstly, a mathematical model is established to describe the localization problem under constraints. Secondly, by solving the mathematical model, localization of repaired blade for NC machining can be obtained. Furthermore, a more flexible method based on the proposed mathematical model and the continuity of the deformation process is developed to realize a better localization. Thirdly, by rebuilding the model of the repaired blade and extracting repair error, optimized tool paths for NC machining is generated adaptively for each individual part. Finally, three examples are given to validate the proposed method.

• 한국정밀공학회지
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• 제23권4호
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• pp.183-190
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• 2006

Digital 3D Real Object Duplication System (RODS) consists of 3D Scanner and Solid Freeform Fabrication System (SFFS). It is a device to make three-dimensional objects directly from the drawing or the scanning data. In this research, we developed an office type SFFS based on Three Dimensional Printing Process and an industrial SFFS using Dual Laser. An office type SFFS applied sliding mode control with sliding perturbation observer (SMCSPO) algorithm for control of this system. And we measured process variables about droplet diameter measurement and powder bed formation etc. through experiments. In case of industrial type SFFS, in order to develop more elaborate and speedy system for large objects than existing SLS process, this study applies a new Selective Dual-Laser Sintering (SDLS) process and 3-axis Dynamic Focusing Scanner for scanning large area instead of the existing f lens. In this process, the temperature has a great influence on sintering of the polymer. Also the laser parameters are considered like that laser beam power, scan speed, and scan spacing. Now, this study is in progress to evaluate the effect of experimental parameters on the sintering process.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2003년도 추계학술발표대회 개요집
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• pp.18-20
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• 2003

Optimal processing and system to produce the laser welded tube for one body formed bumper beam are studied. The calculated size of tube is a thickness of 1.4mm, diameter of 105.4mm and length of 2000mm. The tube is shaped from cool rolled high strength steel sheet(tensile strength: 60kgf/$\textrm{mm}^2$ grade). Two roll bending method is the optimal tube shaping process compared to UO-bending, bending on press brake, multi-step continuous roll forming and 3 roll bending methods. Weld quality monitoring and seam tracking along the butt-joint lengthwise to the tube axis are also studied. The longitudinal butt-joint is welded by the $CO_2$ laser welding system equipped with a seam tracker and plasma sensor. The constructed $CO_2$ laser tube welding system can be used for the precision seam tracking and the real-time monitoring of weld quality. Finally, the obtained laser welded tube can be used for one-body formed automobile bumper beam.