1,721,155 research outputs found
An Adjustable Scheduling Algorithm for Multi-User MIMO Systems
Full text linkMultiple 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
Full text linkThis 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
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
Aluminium-salen luminophores as new hole-blocking materials for phosphorescent OLEDs
No full textThe organic light-emitting diodes (OLEDs) employing complex [salen((t)Bu)(4)Al(OC(6)H(4)-p-C(6)H(5))] (4) as a hole-blocking layer produced stable green EL emission of Ir(ppy)(3) irrespective of changing current density and showed higher brightness and device efficiency than the BAlq-based device
Highly phosphorescent iridium complexes with chromophoric 2-(2-hydroxyphenyl)oxazole-based ancillary ligands: Interligand energy-harvesting phosphorescence
No full textWe disclose a controlled phosphorescence color tuning in a Series of cyclometalated heteroleptic Ir(III) complexes (Ir(III) bis(2-(2,4-difluorophenyl)pyridinato-C,N-2') (LX)) containing chromophoric 2-(2-hydroxyphenyl)oxazole-derivative ancillary ligands (LX). From a cyclometalated chloride-bridged Ir(III) dimer, three highly emissive cyclometalated heteroleptic Ir(III) complexes were obtained in good yields, each with a different conjugative plane in the chromophoric ancillary ligand (i.e., 2-(2-hydroxyphenyl)-4-methyloxazole, 2-(2-hydroxyphenyl)-6-methylbenzoxazole, and 2-(2-hydroxyphenyl)naphthoxazole). The three Ir(Ill) complexes showed highly efficient greenish blue (500 nm), green (525 nm), and yellow (552 nm) phosphorescence, respectively; a regular ca. 0.11 eV bathochromic shift was observed for each additional phenyl ring fused to the oxazole ring in the ancillary ligand. From the absorption, electrochemical measurements, static and transient photoluminescence (PL), and time-dependent density functional theory (TD-DFT) calculations, it can be concluded that the Ir(Ill) complexes have a single emission center with dual excitation paths. Finally, this characteristic energy-harvesting phosphorescence was further demonstrated in electrophosphorescence devices.
데이터의 특징을 고려한 트리 기반 침입탐지 시스템
No full text학위논문(석사) - 한국과학기술원 : 산업및시스템공학과, 2010.2, [ iv, 42 p. ]Intrusion Detection is a serious global concern. The potential of network intrusion has posed a threat to national security; meanwhile the increasing prevalence of malware and incidents of network intrusions hinder the utilization of the Internet to its greatest benefit and incur significant economic losses to individuals, enterprises and public organizations.
In this thesis, an efficient algorithm for Intrusion Detection System as Tree-based Intrusion Detection System considering Data Features is proposed to enhance the misclassification, detection and false positive rate by considering data features.
Our results show a significant improvement in the misclassification, detection and false positive rate for the most difficult to detect attacks (e.g., Probing). In ours simulation, we used a Neural Network as classifier. This classifier basically shows lower performances than others. Nevertheless, our approach shows the better results in most cases. For that reason, if our approach, Tree-based Intrusion Detection System considering Data Features, is applied to other classifiers ( e.g., Support Vector Machine and Self-Organizing Map ) when design an intrusion detection system, we will get improved results.한국과학기술원 : 산업및시스템공학과
OFDMA 상향링크 시스템의 무선 자원 관리에 관한 연구
No full text학위논문(박사) - 한국과학기술원 : 산업공학과, 2008.2, [ vii, 101 p. ]Orthogonal frequency division multiple access (OFDMA) has been regarded as a very promising technique for high rate transmission. One of the major advantages of OFDMA is a capability to combat the inter-symbol interference. OFDMA has been also shown to be robust against frequency selective fading environment. And OFDMA exploits multiuser diversity in the frequency domain as well as user domain. Thus the radio resource management takes a more important role in OFDMA systems
This study mainly focuses on the radio resource management for OFDMA uplink systems. First, we investigate the system throughput maximization problem. We propose an efficient subcarriers and power allocation algorithm based on Lagrangian relaxation procedure. A greedy algorithm known to be the most efficient algorithm for this problem can provide a high quality near-optimal solution, but has the disadvantage of incurring a long computation time. As this problem should be solved in a real-time environment, computation time is a very important performance measure of algorithms. In this study, a computationally efficient algorithm that provides a nearly identical quality, near-optimal solution as the greedy algorithm but requires less than 10% of the computation time of the greedy algorithm is proposed.
Then, we extend our throughput maximization problem to consider the fairness issue. In this study, to provide the minimum number of subcarriers to users is used for fairness criteria. We proposed a subcarriers and power allocation algorithm which assigns the required number of subcarriers to users. Proposed algorithm outperforms two-phase algorithm in the aspects of throughput and fairness.
We also proposed a subcarrier and power allocation algorithm which guarantees QoS requirement of users. In this study, the QoS requirement is defined as the minimum transmit rates of users. Computer simulations show that proposed algorithm provides better system throughput and fairness among users. In ad...한국과학기술원 : 산업공학과
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