• Journal of Communications and Networks
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• v.12 no.1
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• pp.43-51
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• 2010

IEEE 802.11 defines distributed coordination function (DCF), which is characterized by CSMA/CA and binary exponential backoff (BEB) algorithm. Most modifications on DCF so far have focused on updating of the contention window (CW) size depending on the outcome of own frame transmission without considering freezing periods experienced in the backoff interval. We propose two simple but novel schemes which effectively utilize the number of freezing periods sensed during the current backoff interval. The proposed schemes can be applied to DCF and its family, such as double increment double decrement (DIDD). Saturation throughput of the proposed schemes is analyzed by means of Bianchi's Markovian model. Computer simulation validates the accuracy of the analysis. Numerical results based on IEEE 802.11b show that up to about 20% improvement of saturation throughput can be achieved by combining the proposed scheme with conventional schemes when applied to the basic access procedure.

• Journal of Industrial Technology
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• v.31 no.A
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• pp.33-38
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• 2011

In an express tilting train, side wall insulating the noise from the exterior sound source consists of two parts. One is the layered composite panel including aluminum honeycomb, glass wool and nomex honeycomb. The other is the double glazed window. In this study, sound insulation performance of the two parts is investigated by mass law and experiment. Based on ASTM E2249-02, the intensity sound transmission loss (TL) is measured on the specimens of the two parts. Mass law deviation (MLD) is considered in order to compare the sound insulation performance in respect of weight. Contribution of each part to the sound insulation is analyzed and the sound insulation strategy for the interior noise reduction is investigated.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.3
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• pp.214-223
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• 2004

This study aim to find an appropriate window for classrooms to provide proper sound insulation against aircraft noise and to achieve this goal, measurements were taken of the sound insulation performance of windows with various thicknesses of inner air space and sound absorption materials in the inner air spaces. As a result of this study the improvement of the sound insulation performance of windows(single, double and triple window) was shown through the analysis and the measuring of windows with these characteristics. These results may be applied to the manufacture of window frames and provide basic data for the improvement of the sound insulation performance of windows.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.710-717
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• 2003

This study aim to find an appropriate window for class rooms to provide proper sound insulation against aircraft noise and to achieve this, measurements were taken of the sound insulation performance of windows with varying thicknesses of inner air space and sound absorption materials in the inner air spaces. As a result of (his study the improvement of the sound insulation performance of windows(single , double and triple window) has been shown through the analysis and the measuring of windows with these characteristics. These results may be applied to the manufacture of window frames and provide data lot the improvement of the sound insulation performance of windows.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.3B
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• pp.280-287
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• 2001

본 논문에서는 기존의 LCD MW를 이용한 각 다중화 시스템에서 인접한 수직방향 MW 사이의 crosstalk를 제거하기 위하여 MW의 뒷단에 수직방향으로 주기적으로 서로 다른 초점 길이를 갖는 이중초점 렌즈를 삽입하여 인접한 MW의 기준빔이 서로 다른 공간에 기록되게 함으로써 기준빔의 전자적 제어뿐만 아니라 고밀도의 정보저장 및 복원이 가능한 새로운 공간-각 다중화 기법을 제안하고 이에 대한 광학 실험을 통해 구현가능성을 제시하였다.

• Journal of the Korean Solar Energy Society
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• v.32 no.3
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• pp.50-58
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• 2012

The objective of this study is to evaluate the lighting dimming rates with various parameters of the building skin in a small office. We compared to simulated workplane illuminance and measured workplane illuminance for the base model. After that, the five veriables(the presence of vertical wall in double skin facade, the presence of windowsill, window to wall ratio(WWR), window visible transmittance, the width of double skin facade) were applied to base model, and we analyzed the simulated lighting energy saving rates. The results are listed as below. The simulated workplane illuminance results are similar to the measurement. Simulated illuminance was smaller than measured illuminance by 16.5%(60 lx). In accordance with applicable building skin parameters, lighting energy saving rate results are summarized as follows. Lighting energy saving rate of case1(windowsill height 0.7m) is higher than that of base case(windowsill and vertical wall) by 7.3% and the lighting energy saving rate of case2(no vertical wall) is higher than that of base case by 7.6% and the lighting energy saving rate of case3(no windowsill and vertical wall) is higher than that of base case by 12.4%. The lighting energy saving rate is increased by 2.3%, when window visible transmittance is increased from 70% to 86%. The lighting energy saving rate is increased by 4.6%, when we changed the WWR 70% to 90%. lighting energy savings rate is increased by 6.5%, when the width of double skin facade is reduced from 1m to 0.3m.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1419-1426
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• 2012

The heating and cooling energy load of the KNU plant factory was analyzed using the DesignBuilder. Indoor temperature set-point, LED supplemental lighting schedule, LED heat gain, and type of double skin window were selected as simulation parameters. For the cases without LED supplemental lighting, the proper growth temperature of lettuce $20^{\circ}C$ was selected as indoor temperature set-point together with $15^{\circ}C$ and $25^{\circ}C$. The annual heating and cooling loads which are required to maintain a constant indoor temperature were calculated for all the given temperatures. The cooling load was highest for $15^{\circ}C$ and heating load was highest for $25^{\circ}C$. For the cases with LED supplemental lighting, the heating load was decreased and the cooling load was 6 times higher than the case without LED. In addition, night time lighting schedule gave better result as compared to day time lighting schedule. To investigate the effect of window type on annual energy load, 5 different double skin window types were selected. As the U-value of double skin window decreases, the heating load decreases and the cooling load increases. To optimize the total energy consumption in the plant factory, it is required to set a proper indoor temperature for the selected plantation crop, to select a suitable window type depending on LED heat gain, and to apply passive and active energy saving technology.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.9
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• pp.463-467
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• 2015

The air-bubble sheet has been widely used to wrap fragile products for long-distance transportation. The further usage of the air-bubble sheet as a thermal-insulation material for the reduction of the thermal conductivities of window systems has occurred because of its low price, in addition to its thermal-conductivity properties. In this study, the thermal performances of a variety of commercial air-bubble sheets according to various applications were evaluated. The experiments were performed with single-glazed and double-glazed windows and three types of air-bubble sheets of different air volumes. U-values are used and were calculated for the determination of the thermal performances that are based on the KS F 2278. The maximum decrease of the U-value was measured as 1.092 when a sheet was attached onto the frame of single-glazed window. The square-like air-bubble sheet that contains the largest air volume shows the highest thermal-resistance value. Double layers of the air-bubble sheets show better performances than those of the single layers on both sides of the windows.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.863-868
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• 2008

In accordance with the guidelines on the balcony structure changes in December 2005, most of tenants were moving into apartment housing, expand the balcony, but some large deviation between the price construction costs set of cases, due to overuse and the cause of the dispute, and the housing law amended in 2007 due to price cap system is implemented, the cost of expansion the balcony overdose pointed out that there is set to boost the sale price has been raised. These issues in order to improve the government in January 2008, the "Note costs by the balcony expansion" suggested guidelines to protect the rights of tenants and wants to promote the settlement of the sale price cap system. This study calculated the "Note costs by the balcony expansion" window system based on double or single, high performance insulation window system of the quantitative performance analysis of each type window that purpose.

• Korean Institute of Interior Design Journal
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• v.24 no.4
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• pp.91-98
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• 2015

Double skin façade is known that several features affected the building energy and daylighting performance. That is why the envelope is able to consist of all architectural materials such as glass, aluminum, wood and insulation for vision of residents and workers in buildings. Its specifications is very diverse according to the building designers and building owners. In recent times, visual environment became a major focus and resulted in the development of cutting edge engineering of diverse glazing systems and shading devices by growing interests of friendly environment. Thus this research has evaluated the fluctuations of interior lighting and atmospheric conditions based on double skin facade systems. Especially in terms of daylighting environment as dependent on solar variations, this research provides quantitative analysis of interior lighting conditions and how it affects the living conditions as well as improve the design of interior spaces.