• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.6
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• pp.3165-3181
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• 2019

Spherical videos, which are also called 360-degree videos, have become increasingly popular due to the rapid development of virtual reality technology. However, the large amount of data in such videos is a huge challenge for existing transmission system. To use the existing encode framework, it should be converted into a 2D image plane by using a specific projection format, e.g. the equi-rectangular projection (ERP) format. The existing high-efficiency video coding standard (HEVC) can effectively compress video content, but its enormous computational complexity makes the time spent on compressing high-frame-rate and high-resolution 360-degree videos disproportionate to the benefits of compression. Focusing on the ERP format characteristics of 360-degree videos, this work develops a fast decision algorithm for predicting the coding unit depth interval and adaptive mode decision for intra prediction mode. The algorithm makes full use of the video characteristics of the ERP format by dealing with pole and equatorial areas separately. It sets different reference blocks and determination conditions according to the degree of stretching, which can reduce the coding time while ensuring the quality. Compared with the original reference software HM-16.16, the proposed algorithm can reduce time consumption by 39.3% in the all-intra configuration, and the BD-rate increases by only 0.84%.

• Journal of the Society of Disaster Information
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• v.20 no.2
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• pp.284-292
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• 2024

Purpose: Compared to general fires of the same size, underground parking lot fires are more likely to cause human and property damage and are not easy for firefighters to extinguish fire and save lives. This study attempted to find out how to secure the evacuation safety of parking lot users based on changes in the evacuation simulation behavior mode applied to evaluate the evacuation safety of the object. Method: Simulation for each CASE was performed using the Pathfinder program. Result: it was found that the higher the reference value, the higher the evacuation time, and Behavior showed an increase in time in SFPE mode rather than Steering mode. Priority was able to confirm an increase in time in priority designation rather than non-priority designation. Conclusion: The Required Safe Egress Time (RSET) for evaluating the evacuation safety of underground parking lots and the building evacuation design to ensure evacuation safety should be evaluated and reflected separately from Simulation's Behaviour Mode and Priority.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.42-49
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• 2014

The gasoline direct injection (GDI) system is considerably spreading in automotive market due to its advantages. Nevertheless, since GDI system emit higher particle matter (PM) due to its combustion characteristics, it is difficult to meet strengthened emission regulation in near future. For this reason, a combined GDI with MPI system, so-called, dual injection (DUI) system is being investigated as a supplemental measure for the GDI system. This paper focused on power and fuel consumption effect by injection mode strategy of DUI system in part load and idle engine operating condition. In this study, port fuel injectors are installed on 2.4 liters GDI production engine in order to realize DUI system. And, at each injection mode, DOE (design of experiment) method is used to optimize engine control parameters such as dual injection ratio, start of injection timing, end of injection timing, CAM position and so on. As a consequence, DUI mode shows slightly better or equivalent fuel efficiency compared to conventional GDI engine on 9 points fuel economy mode as well as MPI mode shows less fuel consumption than GDI mode during idle operation. Furthermore, DUI system shows improvement potential of maximum 2.0% fuel consumption and 1.1% performance compared to GDI system in WOT operating condition.

• Smart Structures and Systems
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• v.32 no.4
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• pp.253-266
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• 2023

The time-reversal method is employed to improve the ability of pipeline defect detection, and a new approach of identifying the pipeline defect depth is proposed in this research. When the L(0,2) mode ultrasonic guided wave excited through a lead zirconate titinate (PZT) transduce array propagates along the pipeline with a defect, it will interact with the defect and be partially converted to flexural F(n, m) modes and longitudinal L(0,1) mode. Using a receiving PZT array attached axisymmetrically around the pipeline, the L(0,2) reflection signal as well as the mode conversion signals at the defect are obtained. An appropriate rectangle window is used to intercept the L(0,2) reflection signal and the mode conversion signals from the obtained direct detection signals. The intercepted signals are time reversed and re-excited in the pipeline again, result in the guided wave energy focusing on the pipeline defect, the L(0,2) reflection and the L(0,1) mode conversion signals being enhanced to a higher level, especially for the small defect in the early crack stage. Besides the L(0,2) reflection signal, the L(0,1) mode conversion signal also contains useful pipeline defect information. It is possible to identify the pipeline defect depth by monitoring the variation trend of L(0,2) and L(0,1) reflection coefficients. The finite element method (FEM) simulation and experiment results are given in the paper, the enhancement of pipeline defect reflection signals by time-reversal method is obvious, and the way to identify pipeline defect depth is demonstrated to be effective.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.1034-1037
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• 2003

In this work, Integral photography with variable focusing lens arrays is proposed. We fabricate two-dimensional liquid crystal lens arrays using cohesion of UV curable polymer and lithography. Applied voltage to the cell alters the effective refractive index of the liquid crystal layer and results in a change of the focal length. By adjusting the focal length, synchronized elemental image array for real or virtual mode is integrated in front of or behind the lens array.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.2
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• pp.152-159
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• 2013

A structural health monitoring(SHM) technique for locating impact position in a composite plate is presented in this paper. The technique employs a single sensor and spatial focusing properties of time reversal(TR) and inverse filtering(IF). We first examine the focusing effect of back-propagated signal at the impact position and its surroundings through simulation. Impact experiments are then carried out and the localization images are found using the TR and IF signal processing, respectively. Both techniques provide accurate impact location results. Compared to existing techniques for locating impact or acoustic emission source, the proposed methods have the benefits of using a single sensor and not requiring knowledge of material properties and geometry of structures. Furthermore, it does not depend on a particular mode of dispersive Lamb waves that is frequently used in the SHM of plate-like structures.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.512-514
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• 2008

In this paper, a new electromagnetic circuit is proposed for an optical pickup actuator with high sensitivity. Contrary to those of conventional actuators, the proposed circuit has two focusing coils which are diagonally placed at the front and rear of a moving part. The configuration which makes the effective length of the focusing coil longer and the moving part lighter, is helpful in increasing the sensitivity of the actuator. However, the asymmetry of the moving part by two focusing coils causes flexible node vibrations in quite low frequency range. This paper shows that the design modification of the moving part for the reconfiguration of mass moment of inertia can reduce the mode vibrations.

• Journal of Biomedical Engineering Research
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• v.20 no.4
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• pp.503-513
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• 1999

A general expression for the beam patterns of various synthetic aperture(SA) techniques was derived based on a unified SA model. This model was used to analyze and compare the performance of existing SA methods. Based on the theoretical studies, we propose a new synthetic aperture technique that is best suitable for the linear-scan imaging. The proposed method enables dynamic tow-way focusing in real imaging so that the B-mode image resolution can be greatly improved. Compared to the conventional focusing technique, the focused beam pattern by the proposed shows the mainlobe width reduced by half and comparable sidelobe levels. Computer simulation results demonstrated the validity of the theoretical analysis and the proposed SA method.

• Journal of Distribution Science
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• v.10 no.11
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• pp.21-30
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• 2012

Purpose - This study aimed to analyze the strategy of late domestic entrants into the Chinese retail market, focusing on the case of Lotte-Mart, given that there are few studies on market entry strategies of domestic retail companies in China. Research Design, data, methodology - The methodology of this paper is a case study approach, focusing on literature reviews and a few interviews. We conducted a survey by disseminating questionnaires and conducting interviews focusing on the Chinese retail market, and analyzed Lotte-Mart's market entry strategy in China. Results - Lotte-Mart chose M&A as the mode of entry, pursuing quick market entry and rapid expansion. It chose small to medium size cities with relatively less competition. Subsequently, Lotte-Mart devoted significant effort towards localization, attempting to organize stores and assorting products to fit the Chinese consumers' preferences. It operated CSR programs to increase its brand awareness and to create a favorable brand image. Conclusions - Lotte-Mart now needs to devise alternative corporate strategies for business expansion and growth. An understanding of the Chinese retail market and the case study analysis of Lotte-Mart's market entry strategy offers significant insights for domestic retail companies looking to expand into China.

• Journal of Biomedical Engineering Research
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• v.30 no.3
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• pp.233-240
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• 2009

Using a spatial compound imaging technique in a medical ultrasound imaging system, the average speed of sound in a medium of interest is measured, and imaging of its distribution is implemented. When the brightness reaches the highest level in an ultrasonic image obtained as the speed of sound used in focusing is varied, it turns out that the focusing has been accomplished satisfactorily and that the speed of sound which has been adopted becomes the sought-after average speed of sound. Because spatial compound imaging provides many different views of the same object, the adverse effect of erroneous speed-of-sound estimation tends to be more severe in compound imaging than in plain B-mode imaging. Thus, in compound imaging, the average speed of sound even in the case of speckled images can be accurately estimated by observing the brightness change due to different speeds of sound employed. Using this new method that offers spatial diversity, we can construct an image of the speed of sound distribution in a phantom embedded with a 10-mm diameter plastic cylinder whose speed of sound is different from that of the background. The speed of sound in the cylinder is found to be different from that of the surrounding medium.