1,652 research outputs found
An Adjustable Scheduling Algorithm for Multi-User MIMO Systems
No full textMultiple Input Multiple Output (MIMO) represents a highly promising technique for 4G communication networks as it uses multiple antennas at the transmitter and receiver to improve the reliability of transmissions and to provide a high data rate. This paper introduces all adjustable scheduling algorithm for-multi-user MIMO systems that call provide an advantageous trade-off solution between throughput maximization and fair resource allocation among users. Specifically, Our algorithm is proposed as a solution to system requirement issues through the flexible control of fairness factors
A Goal Programming Approach for Resource Allocation Considering Client Demands in a Multiuser OFDMA Downlink System
No full textThis study investigates subcarrier and power allocation schemes in an OFDMA downlink system. To consider client demands, a goal programming approach is proposed. The proposed algorithm minimizes the weighted sum of each client's dissatisfaction index. Simulations show that the sum of dissatisfaction indices can be reduced significantly
A new chaotic attractor and its robust function projective synchronization
No full textWe introduce a simple chaotic system that contains one multiplier and one quadratic term. The system is similar to the generalized Lorenz system but is not topologically equivalent. The properties of the proposed chaotic system are examined by theoretical and numerical analysis. An analog chaotic circuit is implemented that realizes the chaotic system for the verification of its attractor. Furthermore, we propose a robust function projective synchronization using time delay estimation. A numerical simulation of synchronization between the proposed system and the Lorenz system demonstrates that the proposed approach provides fast and robust synchronization even in the presence of unknown parameter variations and disturbances. © 2013 Springer Science+Business Media Dordrecht
Tetraphenylimidazole-based excited-state intramolecular proton-transfer molecules for highly efficient blue electroluminescence
No full textAiming for highly efficient blue electroluminesence, we have designed and synthesized a novel class of tetraphenylimidazol-based excited-state intramolecular proton-transfer (ESIPT) molecules with covalently linked charge-transporting functional groups (carbazole- and oxadiazole- functionalized hydroxyl-substituted tetraphenylimidazole (HPI), i.e., HPI-Cbz and HPI-Oxd, respectively). High T-g (ca. 130 degrees C) amorphous films of HPI-Cbz and HPI-Oxd showed and ideal blue-light emission (lambda(max)=462 and 468 nm, Phi(PL) = 0.48 and 0.38) with a large Stokes shift of over 160 nm and a narrow full width at half-maximum of less than 65 nm. Organic light-emitting devices using HPI-Cbz and HPI-Oxd as the emitting layer generated an efficient blue electroluminescence (EL) emission peaking at around 460 nm with excellent CIE coordinates of (x, y) = (0.15, 0.1). A maximum external quantum efficiency of 2.94% and a maximum brightness of 1 229 cd m(-2) at 100 mA cm(-2), as well as a low turn-on voltage of 48.4 V were achieved in this work.
Intrarow Adsorption Structure of Glycine on Ge(100)
No full textThe adsorption structure of glycine on Ge(100) was investigated using scanning tunneling microscopy (STM), density functional theory (DFT) calculations, and high-resolution core-level photoemission spectroscopy (HRCLPES). We found a major adsorption feature of glycine on Ge(100) in the STM images. This feature appeared as a bright protrusion between two dimer rows with a dark adjacent dimer. The position of the bright protrusion located in the middle of the two dimer rows indicates a multibonding adsorption structure. The results of the theoretical calculations confirm that the adsorption structure of glycine on Ge(100) (between two possible multibonding adsorption structures) is an "intrarow O-H dissociated and N dative bonded structure". In the HRCLPES experiments, we found an N 1s peak (at 399.5 eV) and two 0 1s peaks (at 531.1 and 532.0 eV), which represent strong evidence that the adsorption configuration of glycine on Ge(100) is composed of both O-H dissociation and N dative bonding. All our STM, DFT, and HRCLPES results suggest that the adsorption structure of glycine molecules on Ge(100) is an "intrarow O-H dissociated and N dative bonded structure".We thankDr. Chan-CukHwang and Han-
NaHwang for supporting ourHRCLPES experiments at the 7B1
beamline in the Pohang Accelerator Laboratory. This work was
supported by High Risk High Return Project of KAIST and the
Korea Research Foundation (Grant KRF-2005-070-C00063). H.
L. was supported by the Korea Research Foundation Grant
funded by the Korean Government (MOEHRD, Basic Research
Promotion Fund) (KRF-2008-314-C00169)
Confined Optical Fields in Nanovoid Chain Structures Directly Visualized by Near-Field Optical Imaging
No full textLinearly aligned nanovoid chain structures on Au thin films were fabricated on glass substrates. Two-photon excitation imaging techniques using an aperture-type near-field scanning optical microscope revealed localized optical field distributions due to the individual structures. Confined optical fields due to the void chains were observed at each interstitial gap between voids with excitation polarization parallel to the chain axis. Electromagnetic field simulations of dimeric voids qualitatively matched the experimental results. Under excitation polarization perpendicular to the chain axis, only weak optical fields were observed. Further detailed characteristics of localized optical fields in these systems, including those in relation to Babinet's principle in optics, were discussed. Our study may open up new possibilities in molecular sensing and photochemistry
Hybrid Intrusion Forecasting Framework for Early Warning System
No full textRecently, cyber attacks have become a serious hindrance to the stability of Internet. These attacks exploit interconnectivity of networks, propagate in an instant, and have become more sophisticated and evolutionary. Traditional Internet security systems such as firewalls, IDS and IPS are limited in terms of detecting recent cyber attacks in advance as these systems respond to Internet attacks only after the attacks inflict serious damage. In this paper, we propose a hybrid intrusion forecasting system framework for an early warning system. The proposed system utilizes three types of forecasting methods: time-series analysis, probabilistic modeling, and data mining method. By combining these methods, it is possible to take advantage of the forecasting technique of each while overcoming their drawbacks. Experimental results show that the hybrid intrusion forecasting method outperforms each of three forecasting methods
Universal block copolymer lithography for metals, semiconductors, ceramics, and polymers
No full textA universal block copolymer lithography is developed for a broad spectrum of materials including metals, semiconductors, ceramics, and polymers by combining advanced film deposition techniques with block copolymer lithography. The figure presents a nanopatterned platinum film prepared by applying universal block copolymer lithography.We thank G. S. Kim and J.-H. Ahn for assistance with thin film
depositions, and S. S. Bae for assistance with SEM analysis. This
work was supported by the second stage of the Brain Korea 21
Project, the Korea Research Foundation (KRF-2005-003-D00085),
the Basic Research Program of the Korea Science & Engineering
Foundation (R01-2005- 000-10456-0), the Korean Ministry of
Science and Technology, and the Korean Ministry of Science and
Technology and Fundamental R&D Program for Core Technology of
Materials funded by the Korean Ministry of Commerce, Industry and
Energy. Also, this work was partially supported by grants-in-aid for
the National Core Research Center Program from MOST/KOSEF
(No. R15-2006-022-01001-0)
Electronic Structure and Bonding Configuration of Histidine on Ge(100)
No full textThe electronic structures and bonding configuration of histidine on Ge(100) have been investigated with various sam-ple treatments using core-level photoemission spectroscopy (CLPES). Interpretation of the Ge 3d, C 1s, N 1s, and O 1s core level spectra being included in these systems revealed that both the imino nitrogen in the imidazole ring and the carboxyl group in the glycine moiety concurrently participate in the adsorption of histidine on a Ge(100) surface at 380 K. Moreover, we could clearly confirm that the imino nitrogen with a free lone pair in the imidazole group adsorbs on Ge(100) more strongly than the carboxyl group in the glycine moiety by examining systems annealed at various temperatures
Highly entangled hollow TiO2 nanoribbons templating diphenylalanine assembly
No full textWe introduce a biotemplating approach for creating highly entangled hollow TiO2 nanoribbons by combining peptide assembly with an atomic layer deposition process. An aromatic peptide of diphenylalanine was readily assembled into a hierarchical organogel consisting of highly entangled nanoribbons. Unlike ordinary biomaterials, the peptide nanoribbon framework exhibited a high level of thermal stability, such that it may undergo the further functionalization process of vacuum deposition without significant damage to its nanoscale structure. A nanoscale layer of anatase TiO2 was deposited on the nanoribbon framework by means of atomic layer deposition. After pyrolysis, a highly entangled nanotubular TiO2 framework was created successfully. The highly entangled TiO2 architecture exhibited UV-switchable wetting properties.This work was supported by the second stage of the Brain
Korea 21 Project, National Research Laboratory Program
(R0A-2008-000-20057-0), the KAIST EEWS Initiative (No.
EEWS0903, EEWS: Energy, Environment, Water, and
Sustainability), the Fundamental R&D Program for Core
Technology of Materials, and the National Core Research
Center Program (R15-2006-022-01001-0) funded by the Korean
government
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