• Korean Journal of Optics and Photonics
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• v.4 no.4
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• pp.487-492
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• 1993

A polarization maintaining fiber optic gyroscope was constructed having an optical loss of about 25 dB. Using the earth rotation rate as a reference, the long term stability of better than $3^{\circ}/hr$ and the rms short term noise of $0.6^{\circ}/hr/{\sqrt{Hz}}$ were obtained.

• Journal of the Korean Mathematical Society
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• v.58 no.2
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• pp.487-499
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• 2021

We prove a decay estimate for oscillatory integrals with Hölder amplitudes and polynomial phases. The estimate allows us to answer certain questions concerning the uniform boundedness of oscillatory singular integrals on various spaces.

• KIPS Transactions on Software and Data Engineering
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• v.3 no.11
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• pp.487-494
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• 2014

This paper focuses on an advanced congestion control scheme for M2M(Machine-to-Machine) communications in 3GPP LTE-A standard. A large number of MTC(Machine-type-Communication) devices try to access to LTE-A networks and send data to the networks all at once. In this characteristics, M2M communications will bring the serious network congestion problems into LTE-A cellular networks. To solve this critical problem, a congestion control mechanism will be required and it has been studied since Rel-10 LTE-A systems based on backoff mechanism for mobility management and session management. In this paper, we briefly introduce the main concept and operation about the congestion control scheme in 3GPP LTE-A standard. Also, simulation results for the basic congestion control and advanced congestion control scheme in MTC communication environment are provided and the improvement direction is considered in future 3GPP LTE-A standard.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.46 no.4
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• pp.487-494
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• 2010

In order to test the applicability of bunker-A in a diesel engine for small-fishing boat, the investigation of the engine performance and the exhaust emission was performed under various conditions of fuel property, intake air pressure and fuel temperature. It was also performed based on IMO NOx Technical code. At high load, the energy consumption rate of bunker-A was lower than that of diesel oil, and the characteristics of exhaust emission of bunker-A were similar to those, and NOx emission rates of both fuels satisfied the IMO NOx emission regulation limits. The energy consumption rate and characteristics of exhaust emission were improved as the intake air pressure was increased, but these were not improved remarkably as the temperature of bunker-A was heated. However, at low load the energy consumption rate, CO emission rate and HC emission rate of bunker-A were higher than those of diesel oil, but NOx emission rates of the fuels were about the same. In addition, at low load the energy consumption rate and CO emission rate of bunker-A were increased as the intake air pressure and the temperature were higher than normal conditions. Accordingly, it is thought that the use of bunker-A in a kind of test engine is possible at high load. On the other hand, it is thought that more research is needed to improve the combustion efficiency under low temperature and low load condition.

• Korean journal of food and cookery science
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• v.27 no.5
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• pp.487-496
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• 2011

The purpose of this study was to understand the interrelationships among customers'perceived values, switching cost, and loyalty to a family restaurant. Based on 328 patrons obtained from empirical research, this study reviewed the reliability and fitness of a research model and verified three hypotheses using the Amos program. The hypothesized relationships were tested in the model simultaneously using a structural equation model (SEM). The proposed model provided an adequate fit to the data, $x^2$=341.01 (df=154), p<0.001, CMIN/df 2.21, GFI 0.91, NFI 0.94, IFI 0.97, TLI 0.96, CFI 0.97, RMSEA 0.06. The results showed that utilitarian values (${\beta}$=0.27) as customers' perceived values elements in a family restaurant, had a positive (+) influence upon switching cost. Switching cost had a significant positive (+) effect on the behavioral loyalty (${\beta}$=0.16) and attitudinal loyalty (${\beta}$=0.16). Hedonic values (${\beta}$= 0.41) and utilitarian values (${\beta}$=0.26) had a positive (+) influence on customer's behavioral loyalty. Additionally, a customers hedonic values (${\beta}$= 0.30) and utilitarian values (${\beta}$=0.32) had a significant positive (+) effect on attitudinal loyalty. Limitations and future research directions are also discussed.

• Journal of Powder Materials
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• v.26 no.6
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• pp.487-492
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• 2019

Titanium dioxide (TiO₂) is a typical inorganic material that has an excellent photocatalytic property and a high refractive index. It is used in water/air purifiers, solar cells, white pigments, refractory materials, semiconductors, etc.; its demand is continuously increasing. In this study, anatase and rutile phase titanium dioxide is prepared using hydroxyl and carboxyl; the titanium complex and its mechanism are investigated. As a result of analyzing the phase transition characteristics by a heat treatment temperature using a titanium complex having a hydroxyl group and a carboxyl group, it is confirmed that the material properties were different from each other and that the anatase and rutile phase contents can be controlled. The titanium complexes prepared in this study show different characteristics from the titania-formation temperatures of the known anatase and rutile phases. It is inferred that this is due to the change of electrostatic adsorption behavior due to the complexing function of the oxygen sharing point, which crystals of the TiO₆ structure share.

• Journal of Broadcast Engineering
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• v.27 no.4
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• pp.487-498
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• 2022

Depth map is an image that contains distance information in 3D space on a 2D plane and is used in various 3D vision tasks. Many existing depth estimation studies mainly use narrow FoV images, in which a significant portion of the entire scene is lost. In this paper, we propose a technique for generating 360° omnidirectional RGBD images from a sparse set of narrow FoV images. The proposed generative adversarial network based image generation model estimates the relative FoV for the entire panoramic image from a small number of non-overlapping images and produces a 360° RGB and depth image simultaneously. In addition, it shows improved performance by configuring a network reflecting the spherical characteristics of the 360° image.

• Geomechanics and Engineering
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• v.35 no.5
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• pp.487-497
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• 2023

Penetration rate (PR) and penetration depth (Pe) are crucial parameters for estimating the cost and time required in tunnel construction using tunnel boring machines (TBMs). This study focuses on investigating the impact of rock strength on PR and Pe through full-scale experiments. By conducting controlled tests on rock-like specimens, the study aims to understand the contributions of various ground parameters and machine-operating conditions to TBM excavation performance. An earth pressure balanced (EPB) TBM with a sectional diameter of 3.54 m was utilized in the experiments. The TBM excavated rocklike specimens with varying uniaxial compressive strength (UCS), while the thrust and cutterhead rotational speed were controlled. The results highlight the significance of the interplay between thrust, cutterhead speed, and rock strength (UCS) in determining Pe. In high UCS conditions exceeding 70 MPa, thrust plays a vital role in enhancing Pe as hard rock requires a greater thrust force for excavation. Conversely, in medium-to-low UCS conditions less than 50 MPa, thrust has a weak relationship with Pe, and Pe becomes directly proportional to the cutterhead rotational speed. Furthermore, a strong correlation was observed between Pe and cutterhead torque with a determination coefficient of 0.84. Based on these findings, a predictive model for Pe is proposed, incorporating thrust, TBM diameter, number of disc cutters, and UCS. This model offers a practical tool for estimating Pe in different excavation scenarios. The study presents unprecedented full-scale TBM excavation results, with well-controlled experiments, shedding light on the interplay between rock strength, TBM operational variables, and excavation performance. These insights are valuable for optimizing TBM excavation in grounds with varying strengths and operational conditions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.4
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• pp.487-493
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• 2010

Most structural analyses are concerned with the deformations and stresses in a body subjected to external loads. However, in many fields, inverse problems have to be interpreted to determine surface tractions or internal stresses from displacements measured on a remote surface. In this study, the inverse processes are studied by using the finite element method for the evaluation of internal stresses. Small errors in the measured displacements often result in a substantial loss of stability of an inverse system. In order to improve the stability of the inverse system, the displacements on a section near the region of the unknown tractions are predicted by using orthogonal basis functions. We use the Gram-Schmidt orthogonal technique to determine two bases for the displacements on a section near the region of the unknown tractions. Advantages over previous methods are discussed by using numerical examples.

• Korean Journal of Human Ecology
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• v.20 no.2
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• pp.487-503
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• 2011

The purpose of this study was to investigate residents' perceptions and attitudes towards Han-Ok based on a study of the characteristics and elements of Han-Ok that experts perceived. For the study, in-depth interviews were conducted and the data of 7 experts and 24 Han-Ok residents were analyzed. The results of the study were as follows. First, the characteristics of spatial arrangements are primarily emphasized and provide emotional stability for the residents. Placement on the ground, a suitable scale, appropriate openings and closures, hierarchical spatial system and a spatial relationship provide a feeling of comfort and protection. Second, the spaces and the materials of Han-Ok are considered the representative elements providing functionality and health. The close relationship between the inside and outside area makes the air naturally circulate and natural materials such as wood, soil, and paper have the function as natural ventilation, heat storage, and in the prevention of various illnesses. Third, residents in modern society put more of a value on experiences of natural environments that are usually impossible in the city. The simple and incomplete characteristics in using color, materials, and form, provide a culture of story telling and a leisurely lifestyle. Fourth, the cold and spatial inconvenience of Han-Ok are solved by partially using modernized equipment and material. The functionality of spatial systems in Han-Ok needs to be promoted in order to change the residents' perceptions of cold in Han-Ok.