• Journal of Communications and Networks
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• 제13권4호
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• pp.360-366
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• 2011

In this paper, we investigate the problem of power allocation in a heterogeneous network that is composed of a pair of cognitive users (CUs) and an infrastructure-based primary network. Since CUs have only limited effective spectrum-sensing ability and primary users (PUs) are not active all the time in all locations and licensed bands, we set up a new multi-area model to characterize the heterogeneous network. A novel combined interference-avoidance policy corresponding to different PU-appearance situations is introduced to protect the primary network from unacceptable disturbance and to increase the spectrum secondary-reuse efficiency. We use dual decomposition to transform the original power allocation problem into a two-layer optimization problem. We propose a low-complexity joint power-optimizing method to maximize the transmission rate between CUs, taking into account both the individual power-transmission constraints and the combined interference power constraint of the PUs. Numerical results show that for various values of the system parameters, the proposed joint optimization method with combined PU protection is significantly better than the opportunistic spectrum access mode and other heuristic approaches.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제34권7A호
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• pp.548-553
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• 2009

The aim of 4G mobile communication systems is to connect arbitrary devices to high-speed network anytime, anywhere. Cellular system must solve the problem of inter-cell interference caused by frequency reuse for meeting needs of 4G. In this paper, to solve interference problem we propose the algorithm, the so-called Threshold-Based Region Decision (TBRD) and analyze characteristics and performance of the proposed algorithm through simulation. The proposed technique has high applicability and flexibility due to simple construction using only existing UE measurement, and achieves performance improvement through the threshold that can be easily controlled.

• Journal of Advanced Marine Engineering and Technology
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• 제40권10호
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• pp.916-921
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• 2016

It is possible for humans to breathe underwater using dissolved oxygen. However, unlike fish, humans need large amounts of oxygen to breathe underwater. Water generally contains small amounts of dissolved oxygen. To get enough dissolved oxygen from water, great volumes of it should be supplied into a separation device. If exhalation gases are used, the amounts of water supplied into the membrane can be decreased. However, the characteristics of exhalation gases after passage through the separation device need to be investigated. To reuse the exhalation gases, the concentration of carbon dioxide should be decreased. A compressor is needed to supply the exhalation gases because of the high pressure generated in the membrane inlet. However, compressors require a lot of power and are heavy, so it is not proper to get the portable separation device. A system without the compressor is needed. If the pressure of the position mixed from the exhalation is less than atmosphere, the compressor is not needed. In this thesis, characteristics of the gases which are mixed with exhalation gases and separated from water after passing the membrane are investigated. The compositions of carbon dioxide, oxygen, and nitrogen are measured with the gas chromatography. The effects of water and exhalation gas flow rates on characteristics of gases separated from water after the membrane are showed.

• Journal of Convergence for Information Technology
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• 제7권5호
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• pp.111-116
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• 2017

In this paper, we propose a method to measure the complexity of assets when a software component is constructed as a basic asset, a standardized design model is acquired, and a reusable extended asset is designed based on the standardized design model. However, each asset of our proposed asset management system consists of composite assets that combine assets of two domains. So this method can not make accurate measurements. Therefore, the complexity of the overall asset can be measured by reflecting the property value of the basic asset stored under the architecture. In conclusion, it is possible to measure the composite-complexity of a composed asset that is inversely proportional to cohesion and proportional to the cumulative sum of the associated values of each asset in the asset-related design.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.232-235
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• 2017

Scramjet combustor materials are exposed at ultra high temperature over 2000K and severe erosion environment. Inconel alloys are usually applied for combustor material however its mechanical properties are decreased beyond temperature of 1000K so that is impossible for long term operation and reuse. In this study, fiber reinforced ceramic material was used as scramjet combustor material and its feasibility studied. To increase combustion efficiency, regenerative combustor system developed and channel fabrication in composite material also studied.

• Journal of the military operations research society of Korea
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• 제16권2호
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• pp.14-28
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• 1990

The objective of this study is to propose how to acquire through international cooperation the sensitive nuclear technology, so called reprocessing technology. In spite of the need to reuse spent fuel, the transfer of the sensitive technology has been tightly controlled by the nuclear advanced countries due to the fear of nuclear proliferation and, in fact, it would be impossible to secure it by the economic means. In this regard, as a means of acquiring the sensitive nuclear technology, this study proposes the following; 1) President's declaration concerning the peaceful uses of nuclear energy, 2) the establishment and maintenance of national basis through inter-ministerial cooperation, 3) as a confidence building measure, the efforts to strengthen our role in the international nuclear community, and 4) the establishment of the synthetic feedback system to efficiently coordinate. In line with those stated above, this study suggests that it be necessary to invest consistently for developing new technologies and cultivating human resources. Furthermore, this study proposes the necessity to resolve the problems lying ahead by the national consensus achieved through the discussions among the public concerning the sensitive nuclear technology.

• Journal of Environmental Science International
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• 제5권1호
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• pp.51-59
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• 1996

The purpose of this study was to evaluate the partial oxidation of the biological treatment plant effluents using Fenton's reagent as a pretreatment step prior to a tertiary biological oxidation of these effluents. Fenton's reagent was evaluated as a pretreatment process for inhibitory or refractory organics. Based on the Fenton oxidation system, the petrochemical wastewater treatment plant effluent was shown to have significant improvement in toxicity after oxidation with hydrogen peroxide. For example, at ranee of 42 ∼ 184 mg/L COD of petrochemical plant effluents, the COD removal efficiencies were from 38.2% to 60.1% after reaction with hydrogen peroxide 200 mg/L and Fe2+ 100 mg/L and reaction time was 30 minutes. The total TOC reduction were about 15.8∼22.4% with same test condition and difference between the overall removal rate and BOD/COD ratio after Fenton's oxidation estabilished in the biodegradation and otherwise meets the discharge standard or reuse for cooling tower make-up water.

• Journal of the Korean Recycled Construction Resources Institute
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• 제5권1호
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• pp.125-130
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• 2010

It is necessary to re-establish the code and to control the quality of the recycled aggregate itself for ensuring the useability of the recycled aggregate using waste concrete. Generally, adhering mortar cause of the water absorption ratio increment and strength decreased at the surface of the aggregate of the recycled aggregate using waste concrete, thus removing the adhering mortar could increase the useability of the recycled aggregate in the concrete industry. In this study, as a quality control method of the recycled aggregate using waste concrete, the quality characteristic of the recycled aggregate according to the mixing proportion between the recycled and the natural aggregate is obtained Therefore, a system is established to reuse the recycled aggregate in the construction industry.

• KIEAE Journal
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• 제10권5호
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• pp.171-179
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• 2010

Korea owns vast amount of apartment houses no less than those of world prominent countries, but did not pay enough efforts to maintain existing apartment houses and develop policies to reuse them due to growth driven policy of housing supply like construction of new houses. Korea constructed tremendous amount of houses in short period through government led forced house supplying policy, and resulted in excess houses such that present house supply rate happened to be reaching 110%. However, recently there are growing demand of change in housing policy due to social environmental changes like low birth rate and aging of society etc and nationals' demand for improvement of residential quality. When such social changes are demanded and 80% of apartment houses in Korea are less than 20 years old, renovations and remodeling of apartment houses are anticipated to emerge as important matter. In particular, the apartment houses in Seoul and the 1st generation new cities like Bundang and Ilsan etc have passed considerable period of time after construction and require safety measure, it is quite impending to loan programs for the maintenance of existing apartment houses. The objective of this study is to compare and analyze the system of loan programs about apartment houses of Japan, and then to propose to accelerate loan programs about maintenance for apartment houses in korea.

• Journal of Korea Game Society
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• 제10권3호
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• pp.73-82
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• 2010

The Metadata are used for the reuse of core information, distribution and management, protection of copyright and prevention of overlapping investment. Serious game consists of multi-hierarchial multimedia data. And quality information is very important for selection according to the purpose of the game. In this paper, we designed the serious game metadata schema, including multi-media characteristic information and measurable quality information. This study will lay the groundwork for the development of metadata system which can provide serious game users with reliability through quality information, and with compatibility through multi-media characteristic information. Furthermore, we hope this study will be helpful to stable growth in serious game industry.