• Proceedings of the Korean Operations and Management Science Society Conference
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• 2007.11a
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• pp.341-356
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• 2007

We study factors that affect consumers' switching behaviors among service providers in Korean mobile telecommunications service market. For empirical analysis, quarterly time series data from the first quarter of 2004 through the second quarter of 2007 were used. We chose the number of switchers to each mobile service provider in each quarter as dependent variables. Independent variables include acquisition costs per subscriber, which play the role of subsidy to mobile handset, switching costs, time trend, structural change effect, and standby demand effects. Through the empirical analysis, we found that different providers' churn-in customers are affected by different factors. Specifically, the number of chum-in customers into SK Telecom is explained mainly by SK Telecom's customer acquisition costs and standby demand from KTF, while the number of customers switching into KTF is better explained by switching costs from the previous service provider and standby demand from SK Telecom. Those who chose LG Telecom as their new provider, on the other hand, were mainly attracted by LG Telecom's high subscriber acquisition cost.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.12
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• pp.2387-2393
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• 2017

The Moon government, launched in May 2017, regards telecommunication service as part of people's welfare and is trying to save telecommunication costs. However, the direction of policy presented is assessed as symptomatic approach. This is largely attributable to the a partial improvement approach from the framework of the present mobile telecommunication industry. However if we restart from an essential point of view, the result is likely to be much better. The nation's mobile communication costs are not adequate because the government's role was not sufficient. There is a problem with the mobile phone supply chain, the subsidy payment mechanism, and the billing system. Addressing these complex issues requires the establishment of an independent system of handset distribution from telecommunication companies, ban on discriminative subsidies payment, and adoption of volume rate system. Telecommunications Business Act that defines the service charges to normalize the market might be somewhat useful, but the normal application of the Fair Trade Act is more important.

• Journal of Internet Computing and Services
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• v.5 no.3
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• pp.63-72
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• 2004

Recently the range of mobile phone's usage has become more widely since phone has the function of data communication and voice communication. In addition, the request of users who wish to represent their identity on their mobile phones by storing some kinds of multimedia data such as images and melody has increased. There are two different methods for downloading the multimedia data; one method accesses a wireless internet server to download the data and another method downloads the data from PC directly. While the first one requires extra fee for downloading the data, the second method has weakness to modify the original data and it cannot be used in GSM phone yet since it is developed for CDMA phone. In this paper, we introduce a PC-based download application system that enables the users to download multimedia data from PC to GSM phone very easily.

• Journal of Satellite, Information and Communications
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• v.9 no.1
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• pp.102-106
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• 2014

In this paper, we investigate the realistic environment influence on the Hearing-Aid Compatibility(HAC) of the body-held device mock-up with a dual-band antenna. In detail, first, a dual-band internal antenna is designed considering the neighboring objects essential to a real attachable mobile device. This comes to reality by making its mock-up version. Second, the HAC of this device is simulated and measured for 'stand alone', and 'hand-held' cases. Particularly, the electromagnetic simulation of the designed antenna in the real device is verified by the standard measurement. Finally, the evaluated HAC is analyzed in terms of the relations with the bands, the mock-up environment and the hand effect.

• Smart Media Journal
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• v.2 no.3
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• pp.10-16
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• 2013

NFC (Near Field Communication) was developed by SONY, NXP in 2002 and in 2003 respectively. It is one type of standard shore-range wireless communication system which operates in 13.56 MHz frequency band, within 10 cm distance and enables data transfer between devices with maximum rate of 424kbps. Various studies have been done on NFC technology and many handset manufacturers such as Apple, Google, Samsung Electronics Co., are trying to expand their market for new mobile services using this technology. This paper analyses the NFC standard technology, its trends and prospects in chapter II, which is followed by NFC systems and communication method in chapter III, and eventually NFC trends and future views is explained in chapter IV.

• Journal of Information Processing Systems
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• v.4 no.1
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• pp.9-16
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• 2008

This paper describes the design and implementation of a two-tier DBMS for handling massive data and providing faster response time. In the present day, the main requirements of DBMS are figured out using two aspects. The first is handling large amounts of data. And the second is providing fast response time. But in fact, Traditional DBMS cannot fulfill both the requirements. The disk-oriented DBMS can handle massive data but the response time is relatively slower than the memory-resident DBMS. On the other hand, the memory-resident DBMS can provide fast response time but they have original restrictions of database size. In this paper, to meet the requirements of handling large volumes of data and providing fast response time, a two-tier DBMS is proposed. The cold-data which does not require fast response times are managed by disk storage manager, and the hot-data which require fast response time among the large volumes of data are handled by memory storage manager as snapshots. As a result, the proposed system performs significantly better than disk-oriented DBMS with an added advantage to manage massive data at the same time.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.689-697
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• 2007

This thesis suggests ways on how to enhance handset radiation power under head phantom condition. Generally, peak EIRP(Effective Isotropic Radiated Power) is used to measure the radiation performance. TRP is more effective to represent indication of mobile radiation performance in the field than EIRP. In this case, we measure the TRP as an index of radiation power. The factors which effect TRP are antenna length, antenna position, folder angle and ground connection method. More detailed analysis is performed over these items. Significant item is ground connection method between main PCB and folder GND. Using the FPCB we connect main GND to folder GND through the hinge near the antenna. The result is that TRP attenuation is decreased about 5 dB under head phantom condition.

• Journal of electromagnetic engineering and science
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• v.5 no.3
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• pp.132-139
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• 2005

Wireless bio-signal sensing system, which is based on the principle of Doppler radar, can measure a respiration and heart rates with a periodic movement of skin and muscle near the heart. Though the sensing monostatic system using a circulator has been studied, this bistatic system can be improved by using a circular polarized antenna which has a high isolation between transmitter and receiver. In this paper, we measured the bio-signal without the direct contact with the person. The design of each system and experimental results are discussed.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2005.11a
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• pp.431-435
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• 2005

학습과 감정은 지능형 시스템을 구현하는데 있어 가장 중요한 요소이다. 본 논문에서는 강화학습을 이용하여 사용자와 상호작용을 하면서 학습을 수행하고 내부적인 감정모델을 가지고 있는 지능적인 가상 캐릭터를 구현하였다. 가상 캐릭터는 여러 가지 사물들로 이루어진 3D의 가상 환경 내에서 내부상태에 의해 자율적으로 동작하며, 또한 사용자는 가상 캐릭터에게 반복적인 명령을 통해 원하는 행동을 학습시킬 수 있다. 이러한 명령은 인공신경망을 사용하여 마우스의 제스처를 인식하여 수행할 수 있고 감정의 표현을 위해 Emotion-Mood-Personality 모델을 새로 제안하였다. 그리고 실험을 통해 사용자와 상호작용을 통한 감정의 변화를 살펴보았고 가상 캐릭터의 훈련에 따른 학습이 올바르게 수행되는 것을 확인하였다.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.1002-1005
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• 2009

본 논문에서는 GSM/DCS/USPCS/WCDMA대역에서 사용할 수 있는 IFA 형태의 내장형 안테나를 설계하고 이를 제작하였다. 이 안테나는 제한된 공간에서 기본 IFA에 전류 흐름의 상쇄작용을 고려하여 4중 대역을 형성 시켰으며, GSM대역에서 Maximum Gain -1.11dBi ~ 1.29dBi, DCS/USPCS/WCDMA대역에서 -1.15dBi~3.12dBi의 결과를 얻었다. 방사패턴 또한 전방향성에 가까운 특성을 가지고 있으며 전체적으로 효율은 약 3.35% ~ 33.23% 향상됨을 확인할 수 있다.