• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5A
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• pp.347-354
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• 2009

In this paper, we propose a new transmit diversity technique for multiple-input multiple-output (MIMO) systems to improve the link level performance of open-loop systems. By cyclically applying a predetermined set of preceding weight vectors, artificially induced fluctuation is created to achieve additional diversity gain in flat fading channels. To design the set of the precoding vectors, we exploit the knowledge on the distribution of near optimum Preceding vectors observed in a beamforming scheme based on the rotation transformations. Simulation results demonstrate that the proposed open-loop diversity scheme with an arbitrary number of transmit antennas achieves a full diversity gain with computational complexity comparable to a single-input single-output (SISO) system.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.5
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• pp.131-138
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• 2008

The channel parameters such as RMS delay spread and Doppler frequency have an effect on performance of system. This paper investigates the effect between the Inter-Code Interference (ICI) and the frequency diversity gain in the multi-rate MC-CDMA system. The multi-rate MC-CDMA system has achieved the more variable data rate than the MC-CDMA and moreover it has the better performance than the OFDMA system, because it has achieved the frquency diversity gain. However, the frequency diversity gain and ICI have a trade-off relationship by using the spreading code. Therefore, we have improved the system performance by efficient choice of system parameters. In order to evaluate the effectiveness of the frequency diversify gain and the ICI effect, we perform simulations by altering the Doppler frequency and RMS delay spread.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1C
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• pp.1-8
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• 2009

Cooperative diversity is a novel technique to improve diversity gains, capacity gains, and energy saving. This technique involves multiple terminals sharing resources in order to build a virtual antenna array in a distributed fashion. In this paper, we propose a multi-user cooperative diversity protocol called Relay-assisted Multiple Access Channel(R-MAC) that allows multiple source terminals to transmit their signals simultaneously and the relay terminal forwards the aggregated signal received from the source terminals to the destination terminal. The proposed protocol converts the distributed antenna channels into an effective MIMO channel by exploiting a relay, increasing both diversity gain and system throughput. We investigate the performance of the proposed protocol in terms of outage probability and diversity-multiplexing tradeoff where we assume block fading channel environment. Our simulation results show that the proposed protocol outperforms direct transmission in the high spectral efficiency regime where the conventional cooperative diversity protocols cannot outperform direct transmission.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.11
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• pp.1980-1985
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• 2010

This paper is about design of optimal structure of slot antenna array antenna with inner waveguide in accordance with the slot model, and fabrication of its prototype sample operating at the frequency of 24 GHz. Results of this work can be employed as a useful tool to develop and diversify slot antenna having superior performance and omni-directivity to that of current antenna. The implemented antenna demonstrates ultra-wideband performance for frequency ranges 24 GHz with the relatively high and flat antenna gain of 18.64dBi and low sidelobe levels. In addition, a $2{\times}8$ antenna array for phased-array systems and mm-wave sensor applications is also presented.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3B
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• pp.247-254
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• 2009

Over the last decade multiple-input and multiple-output (MIMO) systems have been actively researched and started to be deployed in wireless communications owing to the significant increase in channel capacity. In this paper, we propose a energy saving MAC protocol in systems by focusing on energy efficiency instead of capacity maximization. We considers the energy consumption together with the tradeoff between reliability (i.e., diversity) and throughput (i.e., multiplexing gain), and dynamically chooses an appropriate number of antennas for transmission. In computing the total energy consumption, we counts circuit energy as well as transmission energy. Naturally the circuit energy consumption is directly proportional to the number of active antennas. Through numerical analysis, we confirm that our power saving MAC scheme for MIMO considerably saves energy consumption compared to conventional capacity maximization schemes that use a fixed number of MIMO channels, for a given outage constraint. Our finding is that the capacity maximizing communication which possibly can be regarded best in terms of energy efficiency gives a different solution from the energy minimizing communication.

• Journal of the International Relations & Interdisciplinary Education
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• v.1 no.2
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• pp.91-101
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• 2021

With the rapid development of the Chinese economy, it is particularly important to strengthen the development of start-up innovation among Chinese university students, that is, public innovation is no longer a slogan.College student start-ups can promote the constant development of society, provide more jobs to society, diversify college students' experiences, and help college students gain experience.However, currently, there are problems such as an imbalance in economic and educational development in China, which affects the aggressiveness of college student start-ups. This study aims to contribute to the development of innovative start-ups in Chinese university students by analyzing the influencing factors of innovative start-ups for college students and presenting solutions.

• International Journal of Contents
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• v.17 no.2
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• pp.1-8
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• 2021

Online streaming wars are intensifying. Netflix is known as the market leader in the streaming business. However, since 2019, Netflix has been losing subscribers in the United States and is at a turning point where it needs to reassess its current position in the market. While Netflix is losing dominance, rivals Amazon Prime and Hulu continue to gain market shares. Studies from Deloitte and PricewaterhouseCoopers indicated a new shift in the streaming landscape caused by the abundance of streaming options and rising subscription costs. Recent surveys showed that consumers are excited about new streaming services, such as Disney +. Nearly two-thirds of consumers intend to terminate or downgrade one or more of their current subscriptions to make room for a new service. Moreover, it seems that consumers want ad-supported options. In Deloitte's latest Digital Media Trends survey, 65% responded that they would watch ads to eliminate or reduce subscription costs. Seventy percent of Hulu's subscribers choose its lower-priced ad-supported plan. NBC recently launched its own streaming service, Peacock, with a free ad-supported option. This opposes Netflix's brand identity of "no ads" and premium differentiation. With increasing pressure from competition and the growing risk of subscriber loss, Netflix needs to diversify its price plans. The company could try implementing the lower-priced mobile-only plan they are currently testing or plan to test in other regions. Netflix should also consider features or benefits for loyal subscribers to maintain a stronger consumer base.

• Journal of Korea Port Economic Association
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• v.27 no.4
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• pp.271-289
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• 2011

Mongolia as a land-locked country, has tried to diversify its foreign trade with European and Asian countries. Recently continual price rise of mineral resources also helps Mongolia have chances to gain her trading partners. Nevertheless, regulations and barriers to exports of Mongolian mineral resources in China and Russia, which are transit countries, are complex and complicated in border crossing and transshipment procedures for transit transport. This paper discusses problems and barriers to economic and efficient logistics systems and transit transport of Mongolian mineral resources, and addresses a proposal of international intermodal transport corridors for improving transit transport, and suggests international cooperation, by applying transit rights of land-locked country. Specifically, it is necessary for Mongolia to search for other international intermodal corridors besides the corridor through the port of Tianjin. It is needed to build an international organization for discussion of affirmation of logistics equipments and improvement of transit procedure in border crossing, and to raise financial feasibility in building a new intermodal corridor.

• Nuclear Engineering and Technology
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• v.45 no.6
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• pp.731-744
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• 2013

Energy security is a topic of high importance to many countries throughout the world. Countries with access to vast energy supplies enjoy all of the economic and political benefits that come with controlling a highly sought after commodity. Given the desire to diversify away from fossil fuels due to rising environmental and economic concerns, there are limited technology options available for baseload electricity generation. Further complicating this issue is the desire for energy sources to be sustainable and globally scalable in addition to being economic and environmentally benign. Nuclear energy in its current form meets many but not all of these attributes. In order to address these limitations, TerraPower, LLC has developed the Traveling Wave Reactor (TWR) which is a near-term deployable and truly sustainable energy solution that is globally scalable for the indefinite future. The fast neutron spectrum allows up to a ~30-fold gain in fuel utilization efficiency when compared to conventional light water reactors utilizing enriched fuel. When compared to other fast reactors, TWRs represent the lowest cost alternative to enjoy the energy security benefits of an advanced nuclear fuel cycle without the associated proliferation concerns of chemical reprocessing. On a country level, this represents a significant savings in the energy generation infrastructure for several reasons 1) no reprocessing plants need to be built, 2) a reduced number of enrichment plants need to be built, 3) reduced waste production results in a lower repository capacity requirement and reduced waste transportation costs and 4) less uranium ore needs to be mined or purchased since natural or depleted uranium can be used directly as fuel. With advanced technological development and added cost, TWRs are also capable of reusing both their own used fuel and used fuel from LWRs, thereby eliminating the need for enrichment in the longer term and reducing the overall societal waste burden. This paper describes the origins and current status of the TWR development program at TerraPower, LLC. Some of the areas covered include the key TWR design challenges and brief descriptions of TWR-Prototype (TWR-P) reactor. Selected information on the TWR-P core designs are also provided in the areas of neutronic, thermal hydraulic and fuel performance. The TWR-P plant design is also described in such areas as; system design descriptions, mechanical design, and safety performance.

• The Journal of the Korea Contents Association
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• v.22 no.9
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• pp.217-233
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• 2022

This study was conducted with the purpose of deriving a revitalization plan by analyzing the factors influencing the characteristics and perception of self-employment and self-employment selection of young people. To this end, discussions on self-employment and the size of workers were reviewed, and the characteristics, determinants, and difficulties of self-employment youth were analyzed based on data from a survey of youth in Seoul and Gyeonggi-do. The support plan proposed through the analysis should first strengthen the program so that the government, local governments, and schools can all gain experience in the practice of developing ideas, producing, and selling based on aptitude and competency to solve youth employment problems. Next, compared to support for technology-based start-ups, there are no suitable programs in the fields of knowledge, manufacturing, and distribution, and there is almost no support for freelancers in which the majority of young people are engaged. Therefore, it is necessary to diversify support projects so that the diversity of young people can be expressed in self-employment. Finally, it was found that entrepreneurship had an important influence on self-employment. However, Korean teenagers do not know what entrepreneurship is and have no experience in education, so they should focus on cultivating entrepreneurship in the regular curriculum and establishing a cultural foundation to foster young leaders with creative ideas and execution.