• Proceedings of the KSME Conference
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.321-325
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• 2007

Recently, demands on thin multi-layer printed circuit boards(PCB) have been rapidly increased with broad spread of personal portable digital appliances such as multi-media. In case of mobile phone, however, the fact that PCBs have low flexural strength might cause defects. The purpose of this study is to improve the flexural strength by substituting the well-known GFRP(glass fiber reinforced plastic) for CFRP(carbon fiber reinforced plastic). Firstly, finite element simulation was carried out using ABAQUS to find out a unique CFRP layer that has a role to sustain the applied forces mainly in PCB. Secondly, three point bending tests were conducted with the newly designed CFRP PCB model to verify the improvement of the flexural strength. Consequently, it is shown that PCB layered with the CFRP on both outer sides of the board can be used to improve the flexural strength effectively.

• Journal of Satellite, Information and Communications
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• 제9권1호
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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.

• Proceedings of the KIPE Conference
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• 전력전자학회 2008년도 하계학술대회 논문집
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• pp.259-261
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• 2008

The electronic products such as laptop PC, cellular phone, robots and etc. need the DC power source. Recently, the secondary battery is frequently used as the portable DC power source and it needs forming process. In this paper, we proposed the bidirectional converter that the battery can be charged with high power factor and the discharged energy is regenerated into AC power source. In the charging mode, the converter acts as the boost rectifier. And the AC input current is controlled in phase with the AC input voltage. As a result, the power factor is improved nearly to unity. In the discharging mode, the DC power of battery wasted in resistor is regenerated to the AC bus line. Finally, the validity of the proposed bidirectional converter is verified by computer simulations and experimentation.

• Journal of Korean Society of Steel Construction
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• 제26권5호
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• pp.375-383
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• 2014

In Seoul, total 166 places of foot-bridges were constructed but a study on correlation between resonance occurrence status by gait vibration and natural frequency by each span and that between span based on structural system and natural frequency is very unsatisfactory in reality. Consequently in this study, time series wave form, power spectrum and natural frequency were analyzed based on resonance occurrence by targeting 65 places of foot-bridges being constructed in Seoul through convenient and simple portable vibration meter.

• Journal of Welding and Joining
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• 제29권3호
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• pp.82-88
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• 2011

With a tendency for the application of thin magnesium alloy plates in portable electronic equipment such as cell phone and notebook PC, there is a requirement to develop a welding technology for the lap welding of these thin magnesium alloy. This paper presents the single pulsed laser welding of AZ31B magnesium alloy. The effects of fiber types and parameters such as peak power and pulse width on laser weldability were investigated. The results show that weld defects, especially solidification crack, were always generated in the weld. These defects couldn't be controlled by the simple square pulse, but could be improved through the application of variable pulse. It is because that variable pulse has effect of solidification delay by dropping peak power gradually.

• Proceedings of the Korea Contents Association Conference
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• 한국콘텐츠학회 2005년도 춘계 종합학술대회 논문집
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• pp.151-155
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• 2005

Telemedicine uses common technologies that provide a conduit for information exchange between physicians nurses and patients. In addition to patient records, medical professionals can obtain vital signs and other reference data through telemedicine applications. also, recent advancement in RF technology and wireless communications has enabled the development of Ubiquitous networks. Mobile telemedicine involves more than just communicating via mobile phone of PDA that sends and receives medical data on Portable Internet. this paper describes the design of a mobile telemedicine PDA prototype based on Embedded Linux that can be used to monitor the medical information using a single board computer(SBC). This system would be very useful for patients with chronic illness, especially in an emergent environment, and for containing medical cost in the aged society.

• Journal of Information Technology Services
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• 제13권3호
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• pp.309-321
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• 2014

Recently, due to the advent of ubiquitous computing and the spread of intelligent portable device such as smart phone, iPad and PDA has been amplified, a variety of services and the amount of information has also increased fastly. It is becoming a part of our common life style that the demands for enjoying the wireless internet are increasing anytime or anyplace without any restriction of time and place. And also, the demands for e-commerce and many different items on e-commerce and interesting of associated items are increasing. Existing collaborative filtering (CF), explicit method, can not only reflect exact attributes of item, but also still has the problem of sparsity and scalability, though it has been practically used to improve these defects. In this paper, using a implicit method without onerous question and answer to the users, not used user's profile for rating to reduce customers' searching effort to find out the items with high purchasability, it is necessary for us to analyse the segmentation of customer and item based on customer data and purchase history data, which is able to reflect the attributes of the item in order to improve the accuracy of recommendation. We propose the method of recommendation system using association rule and weighted preference so as to consider many different items on e-commerce and to refect the profit/weight/importance of attributed of a item. To verify improved performance of proposing system, we make experiments with dataset collected in a cosmetic internet shopping mall.

• Proceedings of the KIEE Conference
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• 대한전기학회 2002년도 하계학술대회 논문집 D
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• pp.2577-2579
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• 2002

In this paper, we describe a CMOS DC-DC converter with a variable output voltage(8-12V @100mA) for a portable battery-operated system applications. The proposed DC-DC converter is used along with a Pulse-Frequency Modulation (PFM) method and consists of a reference circuit, a feedback resistor, a controller, and an internal oscillator. The integrated DC-DC converter with two external passive components(L.C) has been designed and fabricated on a 0.6${\mu}m$ 2-poly, 3-metal CMOS process and could be applied to the Personal Digital Assistants(PDA), Cellular Phone, Laptop Computer, etc.

• Journal of Digital Contents Society
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• 제6권2호
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• pp.131-135
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• 2005

Nowadays, the demand for the wireless technology has gradually increased to support the services of high speed wired internet and also the interest of a mobile terminal convergence has increased. In the next generation, the mobile terminal could merge with the celluar phone, wireless LAN, portable internet, digital multimedia brodcasting, mobile game and sensor(smart-tag and biometrics) through the unified single user interface. Moreover, the system is supported to multi-mode at difference networks, which have variable functions and high performance for available service. Inthis paper, we investigate the minimum requirements and the core technologies of the next generation mobile terminals.

• The Journal of the Acoustical Society of Korea
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• 제19권5호
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• pp.9-12
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• 2000

Voice dialing system can recognize the speaker's command and dial the destinate phone number automatically. Such a system is useful for wireless handsets and portable communication devices. As a personal voice dialing system, all the commands are used to train the HMM for speech recognition based on owner-selected phrases. Its implementation requires much less memory space and computation resource compared to a speaker-independent system. Since only two or three training utterances per command are used in this system, it is difficult to estimate exact state duration distribution to improve the recognition performance. Therefore a post-processor is presented to improve the performance. Experiments which use the database collected through the telephone line showed that the proposed post-processor improves the recognition system performance.