• Laser Solutions
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• v.12 no.1
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• pp.19-24
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• 2009

Because of its fast and precise welding performance, laser welding is becoming a new excellent welding method. However, the precise focusing and robust seam tracking are required to apply laser welding to the practical fields. In order to laser weld a type of T joint like a circular pipe on a square pipe, which could be met in the three dimensional structure such as an aluminum space frame, a visual sensor system was developed for automation of focusing and seam tracking. The developed sensor system consists of a digital CCD camera, a structured laser, and a vision processor. It is moved and positioned by a 2-axis motorized stage, which is attached to a 6 axis robot manipulator with a laser welding head. After stripe-type structured laser illuminates a target surface, images are captured through the digital CCD camera. From the image, seam error and defocusing error are calculated using image processing algorithms which includes efficient techniques handling continuously changed image patterns. These errors are corrected by the stage off-line during welding or teaching. Laser welding of a circular pipe on a square pipe was successful with the vision tracking system by reducing the path positioning and de focusing errors due to the robot teaching or a geometrical variation of specimens and jig holding.

• Human Ecology Research
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• v.56 no.2
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• pp.109-122
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• 2018

Cross-border online shopping is an example of non-mobile transnational consumption behavior that has become more popular over the last decade due to the development of technology and transportation. Based on the Theory of Reasoned Action(TRA), this study proposed and tested the hypothesized model that would explain the relationships among consumption beliefs, attitudes toward cross-border online shopping, subjective norms, and purchase intention. Consumption beliefs were measured by global consumption orientation, consumer orientation, and global brand beliefs. In addition, subjective norms included two types: online and offline norms. Descriptive statistics and path analysis were employed for the analysis of the dataset of 174 participants. As a result, the hypothesized model was generally supported. Consistent with the hypothesis, global consumption orientation and global brand beliefs were positively related to positive attitudes toward cross-border online shopping but negatively associated with consumer ethnocentrism. Offline subjective norms positively predicted both the attitudes and purchase intention whereas online subjective norms only predicted purchase intention. The results reflected that TRA was applicable to the intention of cross-border online shopping in a current on-line shopping context. We also discussed the practical applications and limitations of the study.

• Journal of Communications and Networks
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• v.17 no.3
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• pp.231-240
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• 2015

To facilitate the base station planning in high speed railway communication systems, it is necessary to consider the functional relationships between the base station transmit power and space parameters such as train velocity and cell radius. Since these functions are able to present some inherent system properties determined by its spatial topology, they will be referred to as the power-space functions in this paper. In light of the fact that the line-of-sight path persists the most power of the received signal of each passing train, this paper considers the average transmission rate and bounds on power-space functions based on the additive white Gaussian noise channel (AWGN) model. As shown by Monte Carlo simulations, using AWGN channel instead of Rician channel introduces very small approximation errors, but a tractable mathematical framework and insightful results. Particularly, lower bounds and upper bounds on the average transmission rate, as well as transmit power as functions of train velocity and cell radius are presented in this paper. It is also proved that to maintain a fixed amount of service or a fixed average transmission rate, the transmit power of a base station needs to be increased exponentially, if the train velocity or cell radius is increased, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.4
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• pp.462-469
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• 2011

In this paper, we propose a novel hybrid codebook design method which combines DFT matrix based codebook for Rayleigh fading and LOS codebook for direct path. Link-level performances employing hybrid codebook outperform the ones employing the conventional codebooks when K-factor of Rician distribution is 0.28 to 0.99. Moreover hybrid codebook shows good performances over not only Rayleigh channel but also high K's Rician channels.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.912-918
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• 1994

Poor speech intelligibility in an air traffic control room is frequently a result of many, quite different causes and occasionally leads to complaints of the controller personnel. The paper describes a sequence of successful tasks performed in a local control room. The initial measurements included an investigation of the background noise (caused by fans, air condition, computer and radar equipment) and performance checks of the electronic audio and communication equipment with respect to the audio transmission behavior. The spectral composition of the noise as well as the characteristics of the audio communication path between the controllers and the pilots(which showed a loss of spectral information in the audio band due to built-in notch filters for the suppression of control tones) required adaptations of the amplitude behavior of the amplifiers through user adjustable tone controls. The radar console fans, which contributed significantly to the overall noise floor of the room, underwent a substantial reconstruction by replacing the tight mounting with an elastic double suspension, reducing the noise level by 50%. Finally, a possible source of untimely fatigue of the controllers during their working hours has been found in strong spectral components of the noise above the audio band, radiated by numerous video monitors in the control through vibrating components excited by the line frequency of the video signal.

• Journal of Korea Society of Industrial Information Systems
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• v.12 no.4
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• pp.89-96
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• 2007

The amount of home deliveries are increasing day by day owing to the increment of the on-line market. This environment brings along generating many delivery companies and keen competition with each other in its customer hold Therefore, this study aims at the development of a shortest delivery route search demonstration system using Ant Algorithm. The developed system reduces the time consumption significantly in search of delivery path and time of the products for the novice delivery driver as well as experienced driver. Ultimately, the developed system will give the customer reliability and satisfaction, knowing a delivery route in advance.

• The Journal of Korea Robotics Society
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• v.2 no.3
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• pp.234-241
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• 2007

Effective tools which can alleviate the complexity and computational load problem in collision-free motion planning for multi-agent system have steadily been demanded in robotics field. To reduce the complexity, the extended collision map (ECM) which adopts decoupled approach and prioritization is already proposed. In ECM, the collision regions which represent the potential collision of robots are calculated using the computational power; the complexity problem is not resolved completely. In this paper, we propose a mathematical analysis of the extended collision map; as a result, we formulate the collision region as an equation with 5-8 variables. For mathematical analysis, we introduce realistic assumptions as follows; the path of each robot can be approximated to a straight line or an arc and every robot moves with uniform velocity or constant acceleration near the intersection between paths. Our result reduces the computational complexity in comparison with the previous result without losing optimality, because we use simple but exact equations of the collision regions. This result can be widely applicable to coordinated multi-agent motion planning.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.8
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• pp.742-747
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• 2015

The quality of steel plate products is determined by the number of defects and the process problems are estimated by shapes of defects. Therefore pinholes defects of cold rolled steel have to be controlled. In order to improve productivity and quality of products, within each production process, the product is inspected by an adequate inspection system individually in the lines of steelworks. Among a number of inspection systems, we focus on the pinholes detection system. In this paper, we propose an embedded system using FPGA which can detect pinholes defects. The proposed system is smaller and more flexible than a traditional system based on expensive frame grabbers and PC. In order to detect consecutive defects, FPGAs acquire two dimensional image and process the image in real time by using correlation of lines. The proposed pinholes detection algorithm decreases arithmetic operations of image processing and also we designed the hardware to shorten the data path between logics due to decreasing propagation delay. The experimental results show that the proposed embedded system detects the reliable number of pinholes in real time.

• Bulletin of the Society of Naval Architects of Korea
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• v.24 no.4
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• pp.9-18
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• 1987

The hydrodynamic radiation forces acting on a ship travelling in waves have been conventionally treated by strip theories or by direct three dimensional approaches, most of which have been formulated in frequency domain. If the forward speed of a ship varies with time, or if its path is not a straight line, conventional frequency domain analysis can no more be used, and for these cases time domain analysis may be used. In this paper, formulations are made in time domain with applications to some problems the results of which are known in frequency domain. And the results of both domains are compared to show the characteristics and validity of time domain solutions. The radiation forces acting on a three dimensional body within the framework of a linear theory. If the linearity of entire system is assumed, radiation forces due to arbitrary ship motions can be expressed by the convolution integral of the arbitrary motion velocity and the so called impulse response function. Numerical calculations are done for some bodies of simple shapes and Series-60[$C_B=0.7$] ship model. For all cases, integral equation techniques with transient Green's function are used, and velocity or acceleration potentials are obtained as the solution of the integral equations. In liner systems, time domain solutions are related with frequency domain solutions by Fourier transform. Therefore time domain solutions are Fourier transformed by suitable relations and the results are compared with various frequency domain solutions, which show good agreements.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.4
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• pp.375-387
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• 2015

This study investigates an economic and highly efficient power-converter topology and its modulation scheme for 60 kW rapid EV charger system. The target system is a three-phase three-switch buck-type rectifier topology. A new carrier-based PWM scheme, which is characterized by simple implementation using logic gates, is introduced in this paper. This PWM scheme replaces the diode rectifier equivalent switching state with an active switching state to produce the same effective current flowing path. As a result, the distortion of input current during the polarity reversal of capacitor line voltage can be mitigated. The proposed modulation technique is confirmed through simulation verification. The proposed modulation technique and its implementation scheme can expand the operation range of the three-phase three-switch buck-type rectifier with high-quality AC input and capacitor ripple current.