• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.10B
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• pp.621-629
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• 2007

In cognitive radio (CR) network, the channels are generally classified into either the unavailable channels that are occupied by incumbent users or the available channels that are not occupied. The conventional channel classification scheme may result in poor utilization of spectrum holes since it does not take the spatial relationship between CR node and incumbent users into consideration. In this paper, we propose an efficient channel management scheme for the centralized CR network to maximize the spectrum holes by overcoming the shortcomings of conventional scheme. In addition, we mathematically analyze the effectiveness of proposed scheme. Based on the proposed channel management scheme, we also propose the rendezvous algorithm, which can establish the control channels between base station and CR node under the dynamically changing spectrum environment.

• Land and Housing Review
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• v.2 no.4
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• pp.463-469
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• 2011

LH has installed sashes to the balcony to save energy and increase residential space. Then, it is very difficult to protect a condensation of vapor on the walls in the winter time, because the space is closed and the wall surface temperature becomes very low in a balcony. We have tried to get the optimal thermal design methods to reduce the condensation on the walls. The one of the chosen method is to make holes on the walls, and then the condensation shall be reduce because the dew point temperature will be lower due to the effect of dehumidify. In this case, it is just necessary to find as like that how many holes should be perforated through the wall, what's their size, and where is their positions. In this study, a computational fluid dynamics was applied to analyze the temperature, the pressure and the velocity distribution for an incompressible flow in the balcony spaces. And field tests were also carried out to get the data to compare to the simulation results. Finally the design criteria of the ventilation holes in the balconies was suggested by analysis of the computer simulation models.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.5
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• pp.637-649
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• 1997

Effects of cone angle, pressure-hole orientation and Reynolds number on the five-hole probe calibration have been investigated for eight large-scale conical five-hole probes, which have either perpendicular pressure holes or forward-facing pressure holes for the cone angles of 45 deg, 60 deg, 75 deg and 90.deg. Pitch and yaw angles are changed from -40 deg to +40 deg with an interval of 5 deg, respectively, when the probe Reynolds numbers are 1.77*10$^{4}$, 3.53*10$^{4}$ and 7.06*10$^{4}$. The result shows that larger cone angle results in more sensitive changes in the calibration coefficients. In the case that the cone angle is 45 deg, the pitch-angle and yaw-angle coefficients of the five-hole probe with the perpendicular pressure holes show a very different trend compared with those of the five-hole probe with the forward-facing pressure holes. On the other hand, when the cone angle is more than 60 deg, each calibration coefficient is nearly independent of the pressure-hole orientation. Additionally, the effects of the Reynolds number on the calibration coefficients are also reported in detail.

• 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.

• Journal of Acupuncture Research
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• v.21 no.4
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• pp.31-51
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• 2004

Objective: The propose of this study is to investigate the characteristics of combustion in indirect moxibustion with garlic. Methods: We observed the characteristics of combustion by the variations of the thickness(3mm, 4mm, 5mm) of a slice for indirect moxibustion with garlic and mass(80mg, 100mg, 120mg) of moxa cone and existence of holes. The temperature of indirect moxibustion for garlic insulation with holes was higher than temperature of indirect moxibustion for garlic insulation without holes. Combustions time in the preheating period is about 1 minute, it varies by the existence of holes, the thickness of a slice for indirect moxibustion with garlic, and the density of moxa cone. Results: Maximum temperature of heating period was $38.7{\sim}46.2^{\circ}C$, combustion time in the heating period was 118~164sec and maximum ascending temperature gradient was $0.102{\sim}0.264^{\circ}C/sec$. Retaining period was shorter than heating period and stimulus of heating retains more, because it is higher than body temperature. By this report, indirect moxibustion with garlic is more effective with holes and the appropriate thickness of a slice for indirect moxibustion with garlic is 3.5~4mm. It is appropriate that the diameter of moxa cone is 8mm and height of that is 10mm. With this condition, effective combustion period is 120sec, maximum temperature is $42{\sim}44^{\circ}C$, maximum ascending temperature gradient is $0.14{\sim}0.16^{\circ}C/sec$. It is necessary to study clinical correlations for more accurate quantitative standard.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.4
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• pp.1-7
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• 2013

DME spray characteristics were investigated about varied ambient pressure and fuel injection pressure using the DME common rail fuel injection system when the nozzle holes diameter is varied. The common rail fuel injection system with DME cooling system was used since DME has properties of compressibility and vaporization in atmospheric temperature. The fuel injection quantity and spray characteristics were measured. The spray analysis parameters were spray shape, penetration length, and spray angle at six nozzle holes. Three types of injector were used, the nozzle holes diameter were 0.166 mm (Injector 1), 0.250 mm (Injector 2), and 0.250 mm with enlargement of orifice hole from 0.6 mm to 1.0 mm (Injector 3). The fuel injection pressure was varied by 5MPa from 35 to 70MPa when the ambient pressure was varied 0, 2.5, and 5MPa. When using Injector 3 in comparison to the others, the DME injection quantity was increased 1.69 ~ 2.02 times. Through this, it had the similar low heat value with diesel which was injected Injector 1. Among three types of injector, Injector 3 had the fastest development velocity of penetration length. In case of spray angle, Injector 2 had the largest spray angle. Through these results, only the way enlargement the nozzle holes diameter is not the solution of DME low heat value problem.

• The Journal of the Korea Contents Association
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• v.13 no.10
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• pp.62-70
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• 2013

DIBR(Depth Image Based Rendering) is a kind of view synthesis algorithm to generate images at free view points from the reference color image and its depth map. One of the main challenges of DIBR is the occurrence of holes that correspond to uncovered backgrounds at the synthesized view. In order to cover holes efficiently, two main approaches have been actively investigated. One is to develop preprocessing algorithms for depth maps or parallax maps to reduce the size of possible holes, and the other is to develop hole filling methods to fill the generated holes using adjacent pixels in non-hole areas. Most conventional preprocessing algorithms for reducing the size of holes are based on the smoothing process of depth map. Filtering of depth map, however, attenuates the resolution of depth map and generates geometric distortions. In this paper, we proposes a novel preprocessing algorithm for parallax map to improve the performance of hole-filling by avoiding the drawbacks of conventional methods.

• Journal of Environmental Science International
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• v.10 no.1
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• pp.47-58
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• 2001

According to the results of the groundwater quality investigation about 230 holes all over the country, the groundwater which was in excess of standard grows larger every year and closed holes increased to 23,457 holes in 1997 from 15,724 holes in 1996. This is the major reasons that water quality contamination, shortage of water quantity, increasing of salinity and so on. There are 7 groundwater salinization sources which are condisered as most important on a regional level. And among theses the Cheju Island groundwater salinization sources are (1) halite solution, (2) natural saline groundwater, (3) sea-water intrusion. The method of taking an isotopes is one of research methods of the origin of groundwater salinization and is used in so many studies because it has very high confidence. $^{18O}O, ^2H, ^3H, ^{14}C$ and so on in an isotopes are frequently used in the method of them. Consequently on this study we analyzed major ions and $^3H$ in groundwater, sea-water and rain of the eastern part of cheju island known as contaminated site from long time ago to examine the origin of groundwater salinization. Relation ratios of the major ions versus chloride ion shows similar tendency to sea-water. This indicates that sea-water entered the groundwater layer. And amount of $^3H$ in holes of the land side is higher than of the sea side. Relation of chloride ion versus $^3$H indicates negative character. Therefore we can think that the reason of groundwater salinization of this part is natural saline groundwater and halite solution by relation.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.2
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• pp.87-94
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• 2009

There are several types of compressors which are appropriate for hydrogen gas station. Diaphragm type of compressor is the one of them and it satisfies the requirements for that purpose in terms of maintaining gas purity and making high pressure over 700 bar. The objective of this study is to find an optimal design of oil distribution hole configuration. The number of holes is changed maintaining total cross-sectional area of holes. Five cases(1 hole, 4, 8,16 and 24 holes) were studied through Fluid Structure Interaction(FSI) analysis method. Gas and oil pressure, the deflection and stress of the diaphragm were analysed during compression and suction process respectively. There is no specific difference among the cases during compression. An additional deflection due to the existence of hole was found during suction for all case. But the highest deflection and stress were found in the 1 hole case. It was seen that 60% decrease of stress in magnitude in 24 hole case compare to the 1 hole case.

• Journal of the Korean Vacuum Society
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• v.16 no.5
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• pp.366-370
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• 2007

Nano-scopic holes which are distributed densely and uniformly were fabricated on $SiO_2$ surface. Self-assembling resists were used to produce a layer of uniformly distributed parallel poly methyl methacrylate (PMMA) cylinders in a polystyrene (PS) matrix. The PMMA cylinders were degraded and removed by acetic acid rinsing. Subsequently, PS nanotemplates were fabricated. The patterned holes of PS template were approximately $8{\sim}30\;nm$ wide, 40 nm deep, and 60 nm apart. The porous PS template was used as a dry etching mask to transfer the pattern of PS template into the silicon oxide thin film during reactive ion etching (RIE) process. The sizes of the patterned holes on $SiO_2$ layer were $9{\sim}33\;nm$. After pattern transfer by RIE, uniformly distributed holes of which size were in the range of $6{\sim}22\;nm$ were fabricated on Si substrate. Sizes of the patterned holes were controllable by PMMA molecular weight.