• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.9
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• pp.1767-1769
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• 2011

In a CR (cognitive radio) network, channel selection is one of the important issues for the efficient channel utilization. When the CR user exploits the spectrum of primary network, the interference to the primary network should be minimized. In this paper, we propose a spectrum hole prediction based channel selection scheme to minimize the interference to the primary network. To predict spectrum hole, statistic properties of primary user's traffic is used. By using the predicted spectrum hole, channel is selected and it can reduce the possibility of interference to the primary user and increase the efficiency of spectrum utilization. The performance of proposed channel selection scheme is evaluated by the computer simulation.

• Journal of The Korean Society of Integrative Medicine
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• v.7 no.2
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• pp.133-139
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• 2019

Purpose : This study aims to investigate the rating of perceived exertion (RPE) and muscle activity of the inspiratory primary and accessory muscle during breathing exercise with different air hole diameters of the inspiratory muscle trainer (IMT). Methods : The Borg's scale and surface electromyography (EMG) was used to collect data of the RPE and muscle activity of the inspiratory primary the external intercostal (EI) and diaphragm (DIA) and accessory muscles anterior scalene (AS), sternocleidomastoid (SCM), pectoralis major (PM), and upper trapezius (UT) muscles during breathing exercise with different air hole diameters (6 mm, 4 mm, and 2 mm) of the IMT in healthy young male subjects. Results : The RPE and muscle activities of the AS, SCM, and UT are increased significantly in accordance to the decreasing diameter of air hole of air tip in IMT. However, there are no differences in the muscle activities of the PM, EI, and DIA based on differences of diameters of air hole of air tip in IMT. Conclusion : The smaller the diametr of IMT air-hole, RPE and muscle activities of AS, SCM and UT were increased. Therefore, further study would be necessary to investigate the proper intensity and relaxation posture for the exercise protocol to strengthen the inspiratory primary muscles.

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.E
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• pp.45-59
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• 1992

At downstream part of the hydraulic structures such as spiliway or drainage gate, jet flow can occur by gate opening. If stream bed is not hard or bed protection is not sufficient, scour hole will be formed due to high shear stress of the jet flow. We call this primary scour. Once the scour hole is formed, a vortex occurs in it and this vortex causes additional scour. We call this secondary scour. The primary scour proceeds to downstream together with flow direction but the secondary one proceeds to upstream direction opposite to it. If the secondary one continues and reaches to the hydraulic structure, it can undermine the bottom of hydraulic structure and this will lead to failure of structure itself. Thus, it is necessary to know the physical features of the vortex structure in a scour hole, which is the main mechanism of the secondary scour. This study deals with the characteristics of the vortex structure and its shear stress which causes the secondary scour.

• The KSFM Journal of Fluid Machinery
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• v.17 no.2
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• pp.12-23
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• 2014

A parametric study on anti-vortex holes for turbine blade cooling was investigated numerically. Three-dimensional Reynolds-averaged Navier-Stokes equations and shear stress transport turbulence model were used for analysis of anti-vortex film cooling. Validation of numerical results was carried out comparing with experimental data. The cooling performance of anti-vortex holes was assessed by two geometric variables, the ratio of diameters of holes and the lateral distances between the primary hole and anti-vortex hole at blowing ratios of 0.5 and 1.0. The results showed that the spatially-averaged film-cooling effectiveness increases as the ratio of the diameters increases and the distance between the primary hole and anti-vortex hole decreases.

• Journal of Advanced Navigation Technology
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• v.23 no.4
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• pp.322-327
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• 2019

In this paper, we propose first a scheme of grouping spectrum holes that are created in the multiple channels of primary users, and then by using the scheme we enhance quality of service (QoS) of wideband cognitive radio users in cellular cognitive radio networks. In our scheme, spectrum holes created in each primary channel are predicted by Wiener prediction process, and then the predicted spectrum holes happened in the same time are grouped into a group. The wideband cognitive radio users explore the group of spectrum holes to improve their QoS. Simulation results show that their handoff calls dropping rate and initial calls blocking rate are significantly reduced in our scheme, compared to those in the single primary channel.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.101-106
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• 2001

This paper presents experimental results for the confining characteristics of cylinder with center-hole and spiral reinforcements. The experiments have been conducted for the specimens with primary variables i.e., spiral reinforcement ratio and diameter of center-hole which affect the compressive strength and stress-strain relationship. Through this research, it was found that the compressive strength and ductility were increased with the ratio of spiral reinforcement because the lateral expansion of the concrete inside the spiral was restrained by the spiral, but dependent on the size of center-hole.

• The KSFM Journal of Fluid Machinery
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• v.17 no.5
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• pp.5-10
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• 2014

In this paper, the experimental study was carried to investigate the effect of angle of the anti-vortex holes on the film cooling effectiveness on a flat plate. The pressure sensitive paint technique was applied to measure the film cooling effectiveness. Two anti-vortex hole angles of $0^{\circ}$ and $15^{\circ}$ with respect to the primary hole were considered, and the simple cylindrical hole case was also tested. The blowing ratio based on the cylindrical hole was 0.5 and the same flow rate was kept for all anti-vortex hole cases. Results showed that the film cooling effectiveness for the anti-vortex hole cases were much higher than that of the cylindrical case. Among the anti-vortex hole cases, $15^{\circ}$ angle anti-vortex hole case showed higher film cooling effectiveness than that by the $0^{\circ}$ angle anti-vortex hole case.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.3
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• pp.165-171
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• 2003

In a structure, many components are fastened together using bolts, nuts and rivets through drilled holes. Not only do these fastened joints enable easy assembly and dismantling, they are also able to transfer as well as to distribute loads applied onto the structures. The major drawback of such connections, however, is that the fatigue life of the components is reduced by the presence of the hole since the stress concentration around the hole is increased. In addition, the hole drilling process itself may introduce defects or roughness at the surfaces of the hole that may cause further decrease in fatigue performance of the components. For applications where fatigue loadings are important, one way to compensate the decrease in fatigue life of the components is by introduction of beneficial compressive residual stress around the hole using cold working. The material used for this research were A12024-T351 and A17050-T7451 using the primary member of aircraft. We present, In this paper, the characteristics of coldworking by evaluation of the hole expansion ratio, residual stress distribution, and fatigue properties.

• 한국연소학회:학술대회논문집
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• 1999.10a
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• pp.201-207
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• 1999

The combustion characteristics for the low NOx 50 kW-class gas turbine combustor have been experimentally investigated. In order to achieve the premixing and the lean burn combustion, the geometries of the primary zone including premixed chamber were modified from conventional combustor. The centerline profiles of CO and NO concentration, and temperature were measured for the premixed combustors with or without dilution holes in the liner. The effects of the pilot fuel injection rate and air dilution on flame stabilization and pollutant (CO, NO) emission are discussed in detail.

• Journal of Communications and Networks
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• v.16 no.2
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• pp.209-216
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• 2014

Cognitive radio (CR) has been proposed to solve the spectrum utilization problem by dynamically exploiting the unused spectrum. In CR networks, a spectrum selection scheme is an important process to efficiently exploit the spectrum holes, and an efficient channel allocation scheme must be designed to minimize interference to the primary network as well as to achieve better spectrum utilization. In this paper, we propose a multichannel selection algorithm that uses spectrum hole prediction to limit the interference to the primary network and to exploit channel characteristics in order to enhance channel utilization. The proposed scheme considers both the interference length and the channel capacity to limit the interference to primary users and to enhance system performance. By using the proposed scheme, channel utilization is improved whereas the system limits the collision rate of the CR packets.