• 한국통신학회논문지
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• 제34권2A호
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• pp.124-131
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• 2009

Cognitive radio has been proposed to mitigate the spectrum scarcity problem by allowing the secondary users to access the under-utilized frequency bands and opportunistically transmit. Spectrum sensing, as a key technology in cognitive radio, is required to reliably detect the presence of primary users to avoid the harmful interference. However, it would be very hard to reliably detect the presence of primary users due to the channel fading, shadowing. In this paper, we proposed a distributed cooperative spectrum sensing scheme based on conventional DF (decode-and-forward) cooperative diversity protocol. We fist consider the cooperation between two secondary users to illustrate that cooperation among secondary users can obviously increase the detection performance. We then compare the performance of DF based scheme with another conventional AF (amplify-and-forward) protocol based scheme. And it is found that the proposed scheme based on DF has a better detection performance than the one based on AF. After that, we extend the number of cooperative secondary users, and demonstrate that increasing the cooperation number can significantly improve the detection performance.

• 에너지공학
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• 제26권1호
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• pp.68-75
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• 2017

Global warming affects water supply and water resources throughout the world. In many countries, climate change affects significantly on the fresh water resources. Vietnam is exposed mainly, to landslides and floods triggered by tropical storms and monsoon rains, although storm surge, whirlwind, river bank and coastal line erosion, hail rain. In addition to the prevalent drought, there are many major water challenges, including water availability, stress, scarcity and accessibility, because of poor resource management. Fast growth of urbanization, industrialization and population growth, agricultural activities and climate change cause heavy pressure on water quality. Both domestic and industrial wastewater, as well as storm water shares the same drainage. The common facilities for wastewater treatment are not available. Therefore, wastewater is treated only superficially and then discharged directly into rivers and lakes causing serious pollution of surface water environment. In this paper, we reported the severe water crisis and massive green algal blooms formation in Vietnam rivers and lakes. This is the biggest evidence of climate change variations in Vietnam.

• 한국의류학회지
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• 제42권3호
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• pp.486-502
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• 2018

Mass-production caused by industrialization has led to environmental pollution; however, a potential solution to this problem is the Up-cycling fashion design belonging to the sustainable design category. This study analyzed the material characteristics of each brand fashion product by selecting 21 domestic Up-cycling fashion brands. The product types manufactured by domestic Up-cycling fashion brands could be divided into fashion clothing, bag, and fashion accessories. The materials used for each item included special material, waste fiber, waste leather, waste paper, and others. In the results of analyzing the material characteristics into the external characteristics and internal characteristics, the external characteristics included the durability with less abrasiveness and deformation as well as a mixture with other different materials, while the internal characteristics included a story arousing consumers' empathy, and scarcity without the same design due to the limitation of material.

• 한국항공운항학회지
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• 제17권2호
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• pp.52-61
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• 2009

In Korea, there is great lack in jet lease agreements compared to many other countries. Due to such scarcity in numbers of jet lease agreements, problems have never truly surfaced and legal foundation dealing with such issues have not yet been formulated. However, as the globalization is making the world smaller and smaller, the demand for jets will grow. As the Korean aviation industry is expanding tremendously, although very preliminary at this time, the interest and actual execution on private jet lease agreements will grow. The prediction of increase in the private jet ownership is causing the lease industry to be nervous and may require particular preparatory foundation works. Particularly, legal analysis and detailed review maybe necessary to set a precedent with will serve as the grounded rule in the future. It is notable that Vietnam, a country which is believed have a less developed aviation industry than Korea, had already established a specialized jet leasing company, VALC in 2007. Also, when leasing an airplane from a foreign financial institution, it is possible to obtain a government issued guarantee. Therefore, it is urgent for Korea to prepare the legal foundation for the future demands in aviation leasing, as well as private jet leases which in turn would promote national wealth and further develop the financial industry.

• Industrial Engineering and Management Systems
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• 제13권2호
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• pp.193-202
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• 2014

Patients' satisfaction while receiving medical service is affected by whether or not their preferences can be met, including time and physician preference. Due to scarcity of medical resource in China, efficient use of available resources is urgently required. To guarantee the utilization ratio, the scheduling decisions are made after all booking information is received. Two integer models with different objectives are formulated separately, maximizing the degree of satisfaction and revenue. The optimal value of the two models can be considered as the bound of corresponding objectives. However, it is improper to implement any of the extreme policies. Because revenue is a key element to keep the hospital running and satisfaction degree is related to the hospital's reputation, neither the revenue nor the satisfaction can be missed. Therefore, hospitals should make a balance. An integrated model is developed to find out the tradeoff between the two objectives. The whole degree of mismatching that is related to patient satisfaction and other separate mismatching degree are considered. Through a computational study, it is concluded that based on the proposed model hospitals can make their decisions according to service requirement.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2001년도 학술발표회 논문집(I)
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• pp.67-75
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• 2001

Anticipated water scarcity in the first half of this century is one of the most concerned international issues. However, even though the issue has an international impact and world wide monitoring is critical, there are limited number of global estimates at present. In this study, annual water availability was derived from annual runoff estimated by land surface models using Total Runoff Integrating Pathways (TRIP) with 0.5 degree by 0.5 degree longitude/latitude resolution globally. Global distribution of water withdrawal for each sector in the same horizontal spatial resolution was estimated based on country-base statistics of municipal water use, industrial water use, and agricultural intake, using global geographical information system with global distributions of population and irrigated crop land area. The total population under water stress estimated for 1995 corresponded very well with former estimates, however, the number is highly depend on how to assume the ratio how much water from outside of the region can be used for water resources within the region. It suggests the importance of regional studies evaluating the possibility of water intake as well as the validity of the investment for water resources withdrawal facilities.

• 한국농림기상학회:학술대회논문집
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• 한국농림기상학회 2011년도 학술발표회
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• pp.7-10
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• 2011

The semi-arid and arid regions comprise almost 40 percent of the world's land surface. The low and erratic precipitation pattern is the single most significant contributor for limiting crop production in such regions where rainfall is the source for surface, soil and ground water. In a changing climate, the semi-arid and arid regions would increasingly face the challenge of water scarcity. According to the relevant literature; under the assumption of a doubling of the current atmospheric CO2 concentration, irrigation demand was estimated to increase for wheat and to decrease for second crop maize in a Mediterranean environment of Turkey in the 2070s. Crop evapotranspiration would decrease due to stomata closure. Reference evapotranspiration and potential soil evaporation were projected to increase by 8.0 and 7.3%, respectively, whereas actual soil evaporation was predicted to decrease by 16.5%. Drainage losses below 90 cm soil depth were found to decrease mainly due to lesser rainfall amount in the future.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2016년도 학술발표회
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• pp.81-81
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• 2016

가뭄은 국민생활, 경제 등에 막대한 손실을 초래하며, 지역사회 공동체나 사회기능에 심각한 영향을 끼칠 수 있는 재해이다. 가뭄피해 최소화를 위해서는 단기대응, 복구지원 등의 사후대책에서 사전대비 및 예방으로의 정책 전환이 필요하며, 이러한 정책 수립을 뒷받침하기 위해서는 가뭄에 따른 정량적인 피해영향 평가가 우선적으로 필요한 실정이다. 가뭄은 그 지속기간이나 피해양상 및 영향범위 등에 있어 일반 자연재해와는 다른 특성을 지니고 있다. 우선 그 시점과 종점이 모호하고 다른 재해에 비해 장기간에 걸쳐 피해가 누적되며, 가뭄이 해갈된 후에도 장기간 파급효과가 나타날 수 있다. 또한 가뭄이 장기화 될수록 대형복합재난의 형태로 사회전반에 영향을 주기때문에, 영향범위를 설정하고 피해규모를 추정하는 것조차 쉽지 않은 것이 현실이다. 특히 가뭄으로 인한 제한급수, 단수 등의 상황에서 생 공용수의 부족으로 인한 국민생활과 산업의 피해규모 추정과 관련해서는 그 필요성에 비해 연구되거나 적용된 사례가 극히 드물다. 본 연구에서는 국가 가뭄정보분석센터에서 운영 중인 가뭄정보시스템을 통한 가뭄영향평가 정보 생성 및 제공을 위해, 가뭄 영향평가에 대한 국내 외 사례를 조사하고, 생 공용수에 대한 가뭄 피해액 추정 기법을 국민안전처, 국토연구원 등에서 수행된 연구사례와 일본의 갈수에 의한 감 단수피해액 추정기법을 중심으로 검토하였으며, 가뭄정보시스템 구축자료와의 연계 활용 방안에 대해 고찰하였다.

• Geomechanics and Engineering
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• 제9권6호
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• pp.689-707
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• 2015

Progressive increase in population causing land scarcity, which is forcing construction industry to build multistory buildings having underground basements. Normally, basements are constructed for parking facility. This research work evaluates important factors which have caused the collapse of pile-anchor system at under construction five star hotel. 21 m deep excavation is carried out, to have five basements, after installation of 600 mm diameter cast in-situ contiguous concrete piles at plot periphery. To retain piles and backfill, soil anchors are installed as pit excavation is proceeded. Before collapse, anchors are designed by federal highway administration procedure and four anchor rows are installed with three strands per anchor in first row and four in remaining. However, after collapse, system is modeled and analyzed in plaxis using mohr-coulomb method. It is investigated that in-appropriate evaluation of soil properties, additional surcharge loads, lesser number of strands per anchor, shorter grouted body length and shorter pile embedment depth caused large deformations to occur which governed the collapse of east side pile wall. To resume work, old anchors are assumed to be standing at one factor of safety and then system is analyzed using finite element approach. Finally, it is concluded to use four strands per anchor in first new row and five strands in remaining three with increase in grouted and un-grouted body lengths.

• 한국의류산업학회지
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• 제23권4호
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• pp.448-457
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• 2021

This study aimed to identify messages that induce positive product attitudes and purchase intentions among luxury consumers in online luxury sales. Message types elicited from luxury products were classified as quantity-limited, time-limited, sustainability, and personalization. A total of 150 participants were recruited through a Google survey, and all respondents were randomly assigned to respond to one of five stimuli (quantity-limited, time-limited, sustainability, personalization, and control). Participants were informed that they would be engaging in luxury online shopping and read a description about it. Results showed that message attitude, product attitude, and purchase intention were positively formed with the quantity-limited and personalization message types. Furthermore, we discovered the underlying mechanism for quantity-limited and personalization messages increasing favorable message attitudes and it affected the product attitude. Finally, it increased the purchase intention of the product. By confirming purchase intentions according to message types for luxury brands, we have expanded the scope of advertising research to include online luxury sales platforms. Since luxury online shopping is inevitable, this study suggests that the effective use of message types such as quantitylimited and personalization would improve online sales.