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Choi H.-H.,Korea Electronic Technology Institute
AEU - International Journal of Electronics and Communications | Year: 2015

We propose a new vertical handover scheme that uses cooperative ad hoc nodes, instead of interworking via backhaul, for the fast handover of mobile nodes (MN) in next-generation heterogeneous network environments. An MN requiring a vertical handover requests an adjacent ad hoc node to undertake some of the handover procedures that require latency, such as authentication and registration procedures, and to process them in place of the requested MN before the handover completion. A vertical handover procedure that uses this takeover technique is described in detail and its performance is analyzed by investigating the success probability of takeover. The results confirm that the proposed vertical handover scheme using takeover reduces both connection disruption time and packet loss compared with conventional vertical handover schemes without takeover. © 2015 Elsevier GmbH.

Yang H.-Y.,Honam University | Yang H.-Y.,Regal Beloit | Lim Y.-C.,Chonnam National University | Kim H.-C.,Korea Electronic Technology Institute | Kim H.-C.,Chonnam National University
IEEE Transactions on Industrial Electronics | Year: 2013

This paper presents a single-phase switched reluctance motor (SRM) with skewed stator and rotor so that the acoustic noise and vibration have been significantly reduced. The motor has the same skew angle for both stator and rotor laminations. The main source of acoustic noise and vibration is the rapid change of radial magnetic force along the air gap between the stator and rotor poles. Since the radial force (RF) is most intensified on the stator yoke near the salient poles, the abrupt change of the RF can be mitigated by skewing the stator and/or rotor laminations. Therefore, the RF can be more distributed throughout the stator core, and in turn, the peak value of the RF is reduced. In this paper, the distribution of the RF with respect to the skew angles is analyzed through the finite-element method simulation to design a single-phase SRM with the significantly reduced vibration and noise. Based on the simulation results, prototype motors with three different skew angles (0°, 30°, and 64°) have been constructed and tested, validating that the proposed design is effective in mitigating acoustic noise and vibration. © 1982-2012 IEEE.

Kim K.-S.,Korea Electronic Technology Institute | Yang J.-M.,National NanoFab Center | Ahn J.-P.,Korea Institute of Science and Technology
Applied Surface Science | Year: 2010

Electric current was applied on pure Sn-plated leadframes to evaluate the effects of current-induced stress on the growth of Sn whiskers. The samples were stored at room temperate and 55 °C/85% relative humidity (RH) conditions with an induced current range of 0.1 A to 0.5 A. The samples stored at the room temperature did not grow the whiskers at any of the current conditions until 3000 hrs. As the current flow increased, irregular intermetallic compounds (IMCs) grew at the interface between the Sn finish and Cu substrate. However, various lengths of columnar and bent whiskers were observed under all current conditions, after exposure to 55 °C/85% RH conditions for 1000 hours. At the same temperature, the higher current levels showed longer whiskers than lower current levels. The Sn oxide had the α-SnO2 structure of the rutile phase which was non-uniformly formed on the surface of the Sn finish. The grain size of the SnO2 was estimated to be several nanometers. The SnO2 film was up to a thickness of ∼23 nm on the Sn whisker surface stored at 55 °C/85% RH conditions for 3000 hours. © 2010 Elsevier B.V.

Kim I.,Korea Institute of Machinery and Materials | Chun S.,Korea Electronic Technology Institute
Journal of Electronic Materials | Year: 2011

Silver oxide pastes were formulated from silver oxide powder, silver α-neodecanoate, and solvents, which lowers the sintering temperature of printed silver films to 150°C. In this paper, solvent effects were investigated through the formulation of silver oxide pastes using various solvents with high boiling points such as glycol, ether, and terpineol. Solvent structures such as terminal methyl and alkoxyl groups affected the solubility of silver α-neodecanoate and the swelling of the polydimethylsiloxane (PDMS) blanket. Particularly, higher solubility induced uniform mixing of the silver oxide powder and silver α-neodecanoate, which resulted in higher conductivity after sintering. Glycols and monoalkyl ethers reacted with the silver oxide or silver salt, which deteriorated the pot life of the paste. Among the various candidates, α-terpineol satisfied all the requirements such as printability and stability, exhibiting a solubility of 47.8 g in 100 g of solvent, PDMS swelling of 4.6%, and conductivity of 1.8 × 10 5 S/cm after sintering at 150°C for 30 min. © 2011 TMS.

Korea Electronic Technology Institute | Date: 2014-04-17

This invention defines management protocols for wireless power transfer to multiple devices in Multi-device Wireless Power Management System. Various functions of Multi-device Wireless Power Management System are justified from this invention. The WPT frames and messages which work between the management block of a charger and the management block or the coupler block of a device, or the coupler block of a charger are defined as well to execute various functions. Also the procedures for each functionality are described based on its frames and messages.

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