• 한국정보통신학회논문지
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• 제17권9호
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• pp.1975-1985
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• 2013

우리나라 가계의 통신비는 꾸준히 증가하여 왔다. 이에 따라 이동통신요금의 적정성에 대한 문제가 제기되고 있으나 실효성 있는 해결책은 제시되지 않고 있다. 우리나라의 이동전화보유율은 99%로 세계에서 가장 높고 요금은 상대적으로 비싸다. 이는 근본적으로 정부가 이동통신 3사체제를 유지해오면서 사실상 최저가격제를 용인하고 MVNO의 도입을 늦추었기 때문으로 풀이된다. 정부는 서비스생산비용이 타당하게 반영되는 요금구조로 유도할 수 있으며 시장지분확보만을 위한 마케팅비용을 일정한 범위로 제한할 수 있다. 또 과도하게 복잡한 요금제에 따른 거래비용을 억제함으로써 소비자의 소비선택권을 보장하고 요금부담을 줄일 수 있다. 이동통신요금의 적정화를 위해서는 MVNO의 활성화를 통한 이동통신시장구조의 개선, 마케팅 비용의 적정수준인정을 통한 요금의 인하가 필요하다. 바람직한 시장구조와 정책운용이 뒷받침된다면 이동통신요금은 30%정도의 하향조정은 가능할 것으로 보인다. 이동통신 요금은 데이터 사용량에 따른 종량제를 기본으로 하는 것이 바람직할 것이다.

• ETRI Journal
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• 제32권3호
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• pp.447-456
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• 2010

Asymmetric regulation as applied to mobile termination rates refers to regulatory arrangements in which different mobile operators charge different termination rates, even though the services provided are essentially identical. The asymmetric regulation has been frequently used as a regulatory tool to support new entrants to a mobile market. This paper examines the economic effects of asymmetric regulation of mobile termination rates using a theoretical model and its simulation. The result shows that when there is no noticeable difference in brand loyalty between mobile operators with the high degree of substitutability between services provided by mobile operators, and the costs of new entrants are low, a reduction in the asymmetry of mobile access prices results in an enhancement of consumer welfare. These findings provide positive evidence for the argument that in certain situations asymmetric pricing of mobile access services may be counterproductive for consumer welfare.

• 한국태양에너지학회 논문집
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• 제34권4호
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• pp.123-129
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• 2014

Photovoltaic and fuel cell systems can be used as power source in mobile robots. At this time the photovoltaic system generally generate power in daytime. The starting time of fuel cell is slower than the lithium battery. To compensate for these disadvantages, a battery charge-discharge system is used. Especially the bi-directional converter is used mainly in the charge-discharge method. The controller in a buck converter controls the input voltage of the converter to meet the maximum power point tracking(MPPT) performance. First of all, the simulations of hybrid system for battery charge-discharge system in each step simulated using solar and fuel cell modeling as input source in PSIM. Experiment of the buck and bi-directional converter system is conducted through using photovoltaic/fuel cel simulator(pCube) instead of solar and fuel cell. This hybrid system for battery charge discharge using photovoltaic/fuel cell generates emergency power for the communication system in mobile robot.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2008년도 춘계종합학술대회 A
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• pp.939-942
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• 2008

본 연구에서는 시범서비스 단계에 있는 모바일 RFID 서비스를 품질측면, 가치측면, 만족/불평측면, 충성도 측면을 고려한 평가차원을 개발하고 평가함으로써 관련 이동통신서비스 제공자 및 실무담당자들에게 모바일 RFID 서비스와 관련한 유용한 시사점들을 제공하고자 한다. 본 연구의 목적을 위해 모바일 RFID 시범서비스 경험이 있는 일반 고객들을 대상으로 웹 설문조사를 실시하였으며, 수집된 표본 350부를 본 연구의 분석을 위해 사용하였으며, SPSS 12.0k 툴을 사용하여 모바일 RFID 서비스를 평가하고 고객특성에 따른 차이분석도 실시하였다. 분석결과를 토대로 이동통신 서비스 관련 실무담당자 및 관리자들에게 상용화 이전에 모바일 RFID 서비스 평가결과를 통해 얻을 수 있는 서비스 개선방안 등과 같은 유용한 시사점들을 실증연구를 기반으로 제공하였다.

• 설비공학논문집
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• 제27권6호
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• pp.321-327
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• 2015

This study presents an HFC152a refrigerant air conditioner as an alternative to HFC134a, which is currently used in mobile air conditioning systems. Cool-down performance tests of an HFC152a air conditioning system were conducted and compared to a baseline HFC134a air conditioner. The experimental set-up consisted of a belt-driven compressor, a sub-cooled type condenser, an evaporator, and a block-type thermal expansion valve (TXV). A drop-in test was carried out on the mobile air conditioning system under various vehicle running speeds in a climate-controlled wind tunnel (CWT). Additionally, to optimize the HFC152a air conditioning system, the effects of the TXVs on the performance were studied. The results show that compared to the HFC134a air conditioning system, the refrigerant charge quantity was reduced by approximately 20%, the discharge pressure was reduced by about 350~430 kPa, and the air discharge temperature at vehicle running conditions was $0.5{\sim}1.5^{\circ}C$ lower. In addition, good compressor durability was expected due to the lower compression ratio.

• 디지털산업정보학회논문지
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• 제13권3호
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• pp.53-64
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• 2017

Korean Identification card or driver license is usually used to verify one's identity in Korea. These are also used as an adult certification. Since the form of these ID card is an analog and it needs to be checked with naked eyes, it might be used maliciously. Someone who's got someone else's ID card can do other things. Therefore, it must be reported rapidly when ID card is lost or stolen. The most serious problem might be occurred when they do not recognize and report the loss. They might suffer from pecuniary or mental damage such as opening a mobile phone service, providing loan or credit card, opening a personal checking account, etc. Thus, this study suggests and compares the ways of avoiding these problems. First, the most effective way is to send the authorization code via mobile phones in consideration of build-up period and cost. The person in charge of business processing department using ID card sends the authorization code via registered mobile phone. The owners submits it to the person and their identifications are confirmed. Next effective way is that the person in charge of business processing department using ID card sends text messages via registered mobile phone. Lastly, the most ineffective way is to introduce and implement the electronic ID card ultimately even though it is expensive and takes a long time to build up the system.

• Journal of applied mathematics & informatics
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• 제39권5_6호
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• pp.805-811
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• 2021

Currently, batteries use commonly as energy sources for mobile electric devices. Due to the high density of energy, the energy storage state of a battery is very important information. To know the battery's energy storage state, it is necessary to find out the open state voltage of the battery. The open state voltage calculates with a mathematical model, but the computation of the real time state is complicated and requires many calculations. Therefore, the state observer designs to estimate in real time the battery open-circuit voltage as disturbance including model error. Using the estimated open voltage and applying it to the state estimation algorithm, we can estimate the charge. In this study, we first estimate the open-circuit voltage and design an estimation algorithm for estimating the state of battery charge. This includes errors in the system model and has a robust characteristic to noise. It is possible to increase the precision of the charge state estimation.

• ETRI Journal
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• 제28권6호
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• pp.777-786
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• 2006

Since the introduction of competition in the telecommunication market due to the growth of the interconnection between heterogeneous networks, particularly fixed and mobile networks, the interconnection charge based on traffic-sensitive (TS) and non-traffic-sensitive (NTS) costs has become more important. Although there have been many studies of the public switched telephone network (PSTN), previous studies of TS and NTS costs in mobile networks are very few. In this paper, as a pilot study, we propose three criteria and a procedure for the classification of TS and NTS costs based on mobile systems. The three criteria are the following: function type, investment requirement, and main exhaust driver. Moreover, for a CDMA mobile system, strongly TS, strongly NTS, and mixed components are classified by the proposed criteria and procedure. The proposed criteria, procedure, and classification can provide a systematic and useful guideline to decide the scope of mobile facilities and to determine the terminating cost on mobile networks from fixed networks.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 춘계학술대회 논문집 센서 박막재료연구회 및 광주 전남지부
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• pp.82-85
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• 2008

Polyimide is widely used as a high-temperature insulating material. Space charge distributions in polyimide (PI) films strongly depend upon electric field, temperature, water content and so on. We observed space charge distributions in PI films with various water contents. When a dc field was applied to as-received PI films or water-treated PI films, positive and negative homo space charges were observed near the respective electrodes at 333 K. In dried PI films, the homo space charges were much reduced, and positive and negative hetero space charges in the bulk were clearly observed. The space charge amounts in water-treated PI films were smaller than in as-received ones, while the current density in water-treated PI film was larger than that in as-received one by two or more orders of magnitude. These suggest not only that the charge injection from the electrode is enhanced by absorbed water but also that absorbed water makes carriers mobile. The decay of space charge was also faster in water-treated PI than in as-received or dried one. This also supports the enhancement of apparent mobilities of carriers in PI by absorbed water.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.311-312
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• 2007

Polyimide is widely used as a high-temperature insulating material. Space charge distributions in polyimide (PI) films strongly depend upon electric field, temperature, water content and so on. We observed space charge distributions in PI films with various water contents. When a dc field was applied to as-received PI films or water-treated PI films, positive and negative homo space charges were observed near the respective electrodes at 333 K. In dried PI films, the homo space charges were much reduced, and positive and negative hetero space charges in the bulk were clearly observed. The space charge amounts in water-treated PI films were smaller than in as-received ones, while the current density in water-treated PI film was larger than that in as-received one by two or more orders of magnitude. These suggest not only that the charge injection from the electrode is enhanced by absorbed water but also that absorbed water makes carriers mobile. The decay of space charge was also faster in water-treated PI than in as-received or dried one. This also supports the enhancement of apparent mobilities of carriers in PI by absorbed water.