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Oh E.,Hanseo University | Son K.,University of Southern California | Krishnamachari B.,University of Southern California
IEEE Transactions on Wireless Communications | Year: 2013

In this paper, we investigate dynamic base station (BS) switching to reduce energy consumption in wireless cellular networks. Specifically, we formulate a general energy minimization problem pertaining to BS switching that is known to be a difficult combinatorial problem and requires high computational complexity as well as large signaling overhead. We propose a practically implementable switching-on/off based energy saving (SWES) algorithm that can be operated in a distributed manner with low computational complexity. A key design principle of the proposed algorithm is to turn off a BS one by one that will minimally affect the network by using a newly introduced notion of network-impact, which takes into account the additional load increments brought to its neighboring BSs. In order to further reduce the signaling and implementation overhead over the air and backhaul, we propose three other heuristic versions of SWES that use the approximate values of network-impact as their decision metrics. We describe how the proposed algorithms can be implemented in practice at the protocol-level and also estimate the amount of energy savings through a first-order analysis in a simple setting. Extensive simulations demonstrate that the SWES algorithms can significantly reduce the total energy consumption, e.g., we estimate up to 50-80% potential savings based on a real traffic profile from a metropolitan urban area. © 2002-2012 IEEE.


Patent
Hak Yoon Kim and Hanseo University | Date: 2013-12-16

Disclosed is a hand-foot compound bicycle with a double ratchet, which comprises a handle assembly which comprises a crank handle for generating handle power, and an upper gear to be rotated by rotation of the crank handle; a pedal assembly which comprises a pedal for generating pedal power, and transfers both or either one of the handle power and the pedal power to a rear wheel; and a power transfer unit which comprises a first power transfer gear corresponding to the upper gear, and a second power transfer gear for transferring the handle power from the first power transfer gear to the pedal assembly.


Sung Lim C.,Hanseo University
Journal of Physics and Chemistry of Solids | Year: 2015

Double tungstate KGd1-x(WO4)2:Ho3+/Yb3+ phosphors with doping concentrations of Ho3+ and Yb3+ (x=Ho3++Yb3+, Ho3+=0.05, 0.1, 0.2 and Yb3+=0.2, 0.45) were successfully synthesized by the microwave sol-gel method, and the upconversion mechanisms were investigated in detail. The synthesized particles formed after heat-treatment at 900 °C for 16 h showed a well crystallized morphology with particle sizes of 2-5 μm. Under excitation at 980 nm, the UC intensities of KGd0.7(WO4)2:Ho0.1Yb0.2 and KGd0.5(WO4)2Ho0.05Yb0.45 particles exhibited yellow emissions based on a strong 550-nm emission band in the green region and a strong 655-nm emission band in the red region, which were assigned to the 5S2/5F4→5I8 and 5F5→5I8 transitions, respectively. The Raman spectra of the doped particles indicated the presence of strong peaks at higher frequencies of 764, 812, 904, 984, 1050, 1106, 1250 and 1340 cm-1 induced by the disorder of the [WO4]2- groups with the incorporation of the Ho3+ and Yb3+ elements into the crystal lattice or by a new phase formation. © 2014 Elsevier Ltd. All rights reserved.


NaY1-x(WO4)2:Ho3+/Yb3+ phosphors with doping concentrations of Ho3+ and Yb3+ (x=Ho3++Yb3+, Ho3+=0.05, 0.1, 0.2 and Yb3+=0.2, 0.45) were successfully synthesized by the microwave-modified sol-gel method, and the upconversion of their photoluminescence properties was investigated. Well-crystallized particles showed a fine and homogeneous morphology with particle sizes of 2-5 μm. Under excitation at 980 nm, the UC intensities of NaY0.7(WO4)2:Ho0.1Yb0.2 and NaY0.5(WO4)2 Ho0.05Yb0.45 particles exhibited yellow emissions based on a strong 550-nm emission band in the green region and a strong 655-nm emission band in the red region, which were assigned to the 4S2/5F4→5I8 and 5F5→5I8 transitions, respectively. The Raman spectra of the doped particles indicated the presence of strong disordered peaks at higher frequencies and weak peaks at lower frequencies induced by the incorporation of the Ho3+ and Yb3+ elements into the Y3+ site in the crystal lattice, which resulted in the unit cell shrinkage accompanying the new phase formation of the [WO4]2- groups. © 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.


MMoO 4 (M=Ca, Ba) particles were synthesized by a metathetic reaction in ethylene glycol assisted by cyclic microwave irradiation followed by further heat-treatment. The MMoO 4 (M=Ca, Ba) particles were well crystallized after heat-treatment at 400600 °C for 3 h. The microstructures exhibited fine morphologies with sizes of 0.51 μm and 1.52 μm for the CaMoO 4 and BaMoO 4 particles, respectively. The synthesized MMoO 4 (M=Ca, Ba) particles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The optical properties were examined by photoluminescence emission and Raman spectroscopy. © 2012 Elsevier B.V.


Lim C.S.,Hanseo University
Materials Chemistry and Physics | Year: 2012

CdWO 4 particles were synthesized using a solid-state metathetic reaction assisted by microwave irradiation. Well-crystallized CdWO 4 particles formed at 400-600 °C after 3 h, showing fine and homogeneous morphologies with particle sizes of 1-3 μm. The synthesized CdWO 4 particles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The optical properties were examined by photoluminescence emission and Raman spectroscopy. © 2011 Elsevier B.V. All rights reserved.


Lim C.S.,Hanseo University
Materials Chemistry and Physics | Year: 2013

Er3+-doped BaMoO4 (BaMoO4:Er3+) and Er3+/Yb3+ co-doped BaMoO4 (BaMoO 4:Er3+/Yb3+) particles were successfully synthesized by a cyclic microwave-assisted metathetic (MAM) method, and show fine and homogeneous morphology with particle sizes of 0.5-1 μm. At 980-nm excitation, BaMoO4:Er3+ and BaMoO4:Er 3+/Yb3+ particles exhibited a strong 525-nm emission band and a weak 550-nm emission band in the green region. The Raman spectrum of BaMoO4:Er3+/Yb3+ particles indicated the appearance of additional peaks at higher frequencies (390 and 505 cm -1) and at lower frequencies (218 and 255 cm-1). © 2013 Elsevier B.V. All rights reserved.


Patent
Hanseo University | Date: 2013-05-14

This invention relates to an in-situ remanufacturing method of SCR aged catalyst. More specifically, in case the activity of the catalyst, which is used in selective catalytic reduction (SCR) to remove nitrogen oxides, is decreased, such deactivated catalyst, in this in-situ remanufacturing method, is not to be separated from its related reactor but to be remanufactured in-situ for elimination in this method, which, compared to the one that otherwise includes detachment and transportation to remanufacturing facilities, should prevent potential damage to the catalyst, reduce transportation costs as well as additional enormous costs depending upon unloading and loading of the catalyst and shorten the remanufacturing time. The activity of reclaimed catalyst in this invention is recovered at a level of 95% or more than that of fresh SCR catalyst by rapidly facilitating the in-situ elimination of any contaminant and possesses high economic efficiency as there is no catalyst loss during the process. The reuse of the catalyst which otherwise is to be disposed is also possible, mitigating environmental burden.


Lim C.S.,Hanseo University
Materials Research Bulletin | Year: 2012

Upconversion (UC) photoluminescence of Er 3+ doped CaMoO 4(CaMoO 4:Er 3+) and Er 3+/Yb 3+ co-doped CaMoO 4 (CaMoO 4:Er 3+/Yb 3+) particles was successfully achieved by a cyclic microwave-assisted metathetic (MAM) method, followed by heat-treatment. Well-crystallized UC CaMoO 4:Er 3+/Yb 3+ particles formed after heat-treatment at 600°C for 3 h showed a fine and homogeneous morphology with particle sizes of 1-3 μm. At excitation at 980 nm, CaMoO 4:Er 3+/Yb 3+ particles exhibited a strong 525-nm emission band and a weak 550-nm emission band in the green region, and a weak 655-nm emission band in the red region. The UC intensities of CaMoO 4:Er 3+/Yb 3+ particles were much higher than that of the CaMoO 4:Er 3+ particles. The Raman spectra of CaMoO 4:Er 3+ and CaMoO 4:Er 3+/Yb 3+ particles indicated the detection of additional strong peaks at higher frequencies (618, 575, 492, 420 and 373 cm -1) and at lower frequencies (290 and 234 cm -1). © 2012 Elsevier Ltd. All rights reserved.


Er3+ doped SrMoO4 (SrMoO4:Er3+) and Er3+/Yb3+ co-doped SrMoO4 (SrMoO 4:Er3+/Yb3+) particles were successfully synthesized by a cyclic microwave-assisted metathetic (MAM) route followed by heat treatment. The microstructures exhibited well-defined and homogeneous morphology with particles sizes of 100-500 nm. With excitation at 980 nm, SrMoO4:Er3+ and SrMoO4:Er3+/Yb 3+ particles exhibited a strong 525-nm emission band and a weak 550-nm emission band in the green region and a weak 655-nm emission band in the red region. The Raman spectra of SrMoO4:Er3+ and SrMoO4:Er3+/Yb3+ particles indicated the detection of additional strong peaks at both higher frequencies (564, 524, 456, and 403 cm-1) and lower frequencies (294, 251, and 220 cm -1). © 2013 Elsevier Ltd. All rights reserved.

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