• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.2
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• pp.435-449
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• 2023

The state-of-the-art video-based point cloud compression(V-PCC) has a high efficiency of compressing 3D point cloud by projecting points onto 2D images. These images are then padded and compressed by High-Efficiency Video Coding(HEVC). Pixels in padded 2D images are classified into three groups including origin pixels, padded pixels and unoccupied pixels. Origin pixels are generated from projection of 3D point cloud. Padded pixels and unoccupied pixels are generated by copying values from origin pixels during image padding. For padded pixels, they are reconstructed to 3D space during geometry reconstruction as well as origin pixels. For unoccupied pixels, they are not reconstructed. The rate distortion optimization(RDO) used in HEVC is mainly aimed at keeping the balance between video distortion and video bitrates. However, traditional RDO is unreliable for padded pixels and unoccupied pixels, which leads to significant waste of bits in geometry reconstruction. In this paper, we propose a new RDO scheme which takes 3D-Distortion into account instead of traditional video distortion for padded pixels and unoccupied pixels. Firstly, these pixels are classified based on the occupancy map. Secondly, different strategies are applied to these pixels to calculate their 3D-Distortions. Finally, the obtained 3D-Distortions replace the sum square error(SSE) during the full RDO process in intra prediction and inter prediction. The proposed method is applied to geometry frames. Experimental results show that the proposed algorithm achieves an average of 31.41% and 6.14% bitrate saving for D1 metric in Random Access setting and All Intra setting on geometry videos compared with V-PCC anchor.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.391-396
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• 2009

In this paper, a control algorithm for DC-Link voltage unbalancing compensation of a four-switch inverter for a three-phase BLDC motor drive is proposed. Compared with a conventional six-switch inverter, the split source of the four-switch inverter can be obtained by splitting DC-link capacitor into two capacitors to drive the three phase BLDC motor. The voltages across each of two capacitors are not always equal in steady state because of the unbalance in the impedance of the DC-link capacitors $C_1$ and $C_2$ or the variable current flowed into the capacitor's neutral point in motor control. Despite the unbalance, if the BLDC motor may be run for a long time the voltage across one of the capacitors is more increased. So the unbalance in the capacitors voltages will be accelerated. As a result, The current ripple and torque ripple is increased due to the fluctuation of input current which flows into 3-phase BLDC motor. According to that, the vibration of motor will be increased and the whole system will be instable. This paper presents a control algorithm for DC-Link voltage unbalancing compensation. The sampling from the voltages across each of two capacitors is used to perform the voltage control of DC-Link by using the feedforward controller.

• Journal of Electrical Engineering and Technology
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• v.4 no.2
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• pp.266-271
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• 2009

In this paper, improved direct torque control(DTC) of five-phase induction motor(IM) is proposed. Due to the additional degrees of freedom, five-phase IM drives present unique characteristics. One of them is the ability of enhancing the torque producing capability of the motor. Also five-phase motor drives possess many others advantage compared with the traditional three-phase motor drives. Such as, reducing the amplitude and increasing of frequency of torque pulsation, reducing amplitude of current per phase without increasing the voltage per phase and increasing the reliability. The direct torque control method is advantageous when it is applied to the five-phase IM. Because the five-phase inverter provides 32 space vectors in comparison to 8 space voltage vectors by the three-phase inverter. The 32 space voltage vectors are divided into three groups according to their magnitudes. The characteristics and dynamic performance of traditional five-phase DTC are analyzed and new DTC for five-phase IM is proposed. Therefore, a more precise flux and torque control algorithm for the five-phase IM drives can be suggested and explained. For presenting the superior performance of the pro-posed direct torque control, experimental results is presented using a 32 bit fixed point TMS320F2812 digital signal processor

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.38 no.2
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• pp.27-32
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• 2001

In this paper, the three dimension scanner system employing the parallel camera model is discussed. The camera calibration process and the three dimension scanning algorithm are developed. The laser strip line is utilized for assisting stereo matching. An object being scanned rotates on the plate which is activated by a stepping motor, The world coordinate which is. the measured distance from the camera to the object is converted into the model coordinate. The facets created from the point. cloud of the model coordinate is used for rendering the scanned model by using the graphic library such as OpenGL. The unmatched points having no validate matching points are interpolated from the validate matching points of the vicinity epipolar lines.

• Journal of the Korea Society of Computer and Information
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• v.19 no.11
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• pp.53-61
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• 2014

In this paper, we propose a method using an image received by the depth camera in order to separate the wall in a three-dimensional space indoor environment. Results of the paper may be used to provide valuable information on the three-dimensional space. For example, they may be used to recognize the indoor space, to detect adjacent objects, or to project a projector on the wall. The proposed method first detects a normal vector at each point by using the three dimensional coordinates of points. The normal vectors are then clustered into several groups according to similarity. The RANSAC algorithm is applied to separate out planes. The domain knowledge helps to determine the wall among planes in an indoor environment. This paper concludes with experimental results that show performance of the proposed method in various experimental environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.3C
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• pp.359-367
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• 2004

The postprocessing to remove false minutia is important because the extraction of true minutia affects the performance as a key factor in fingerprint identification system. In this paper, we propose an efficient postprocessing algorithm for removing false minutia among the extracted candidates in a thinned image. The proposed algorithm removes false minutia in three steps by using various information in the acquired fingerprint image: the structural information of minutia (end point and bifurcation), the inherent characteristics of fingerprint, and the quality of acquired images. Under Intel Celeron processor environment with 248${\times}$292 images acquired by optic device, the experiments showed that the proposed algorithm efficiently removed false minutia while preserving true minutia. Moreover, the proposed algorithm takes 0.0154 second, which is very small compared to the time for preprocessing (0.343 second).

• The Journal of the Acoustical Society of Korea
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• v.26 no.4
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• pp.173-181
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• 2007

In this paper, we propose a moving target localization algorithm using acoustic spectrograms. A time-versus-frequency spectrogram provide a information of trajectory of the moving target in underwater. For a source at sufficiently long range from a receiver, broadband striation patterns seen in spectrogram represents the mutual interference between modes which reflected by surface and bottom. The slope of the maximum intensity striation is influenced by waveguide invariant parameter ${\beta}$ and distance between target and sensor. When more than two sensors are applied to measure the moving ship-radited noise, the slope and frequency of the maximum intensity striation are depend on distance between target and receiver. We assumed two sensors to fixed point then form a circle of apollonios which set of all points whose distances from two fixed points are in a constant ratio. In case of three sensors are applied, two circle form an intersection point so coordinates of this point can be estimated as a position of target. To evaluates a performance of the proposed localization algorithm, simulation is performed using acoustic propagation program.

• Geophysics and Geophysical Exploration
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• v.2 no.2
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• pp.86-95
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• 1999

This paper presents an efficient three-dimensional (3-D) modeling algorithm using the extended approximation to an electric field integral equation. Numerical evaluations of Green's tensor integral are performed in the spatial wavenumber domain. This approach makes it possible to reduce computing time, to handle smoothly varying conductivity model and to remove singularity problems encountered in the integration of Green's tensor at a source point. The responses obtained by 3-D modeling algorithm developed in this study are compared with those by the full integral equation for a thin-sheet EM scattering. The extensive analyses on the performance of modeling algorithm are made with the conductivity contrasts and source frequencies. These results show that the modeling algorithm are accurate up to the conductivity contrast of 1:16 and the frequency range of 100 Hz-100 kHz. The extended Born approximation, however, may produce inaccurate results for some source and model configurations in which the electric field is discontinuous across the conductivity boundary. We performed the modeling of a composite model of which conductivity varies continuously and this shows the modeling algorithm developed in this study is efficient for 3-D EM modeling. For a cross-hole source-receiver configuration a composite model of which conductivity varies continuously can be successfully simulated using this algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.8
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• pp.3366-3383
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• 2020

The Poisson point process (PPP) is widely used in wireless network modeling and performance analysis because it can provide tractable results for heterogeneous cellular networks (HetNets) analysis. However, it cannot accurately reflect the spatial distribution characteristics of the actual base stations (BSs). Considering the fact that the distribution of macro base stations (MBSs) is exclusive, the deployment of MBSs is modeled by the Matérn hard-core point process (MHCPP), and the deployment of pico base stations (PBSs) is modeled by PPP. This paper studies the performance of multiantenna HetNets and improves the energy efficiency (EE) of HetNets by optimizing the transmit power of PBSs. We use a simple approximate method to study the signal-to-interference ratio (SIR) distribution in two-tier MHCPP-PPP HetNets and derive the coverage probability, average data rate and EE of HetNets. Then, an optimization algorithm is proposed to improve the EE of HetNets. Finally, three transmission technologies are simulated and analyzed. The results show that multiantenna transmission has better system performance than single antenna transmission and that selecting the appropriate transmit power for a PBS can effectively improve the EE of the system. In addition, two-tier MHCPP-PPP HetNets have higher EE than two-tier PPP-PPP HetNets.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.323-328
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• 2003

A basic design on a flexible riser in a floating type development system for upwelling deep ocean water is presented. In the numerical study, an implicit finite difference algorithm is employed for three-dimensional riser equations. Fluid and geometric non-linearity and bending stiffness are considered and solved by Newton-Raphson iteration. To keep the depth of end point of a flexible and light riser is very important for upwelling deep ocean water in a floating type development system. Weight attached at the end point of the riser in order to keep its intake depth is designed under the strong surface current and the configuration of the riser is predicted. The results of this study can be contributed to the design of the development system in floating type for upwelling deep ocean water.