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971.
For the effective mobility management of mobile nodes in Infrastructure-based Mobile Ad Hoc Networks, every mobile node is obliged to send a registration message to the Internet Gateway (IG) periodically. Not only do the registration messages and the additional control messages to establish paths from mobile nodes to the IG to send the registration messages incur a considerable amount of control overhead, but also they impose high traffic congestion on the mobile nodes in the vicinity of the IG which is referred to as the “funneling effect.” The control overhead and the funneling effect make it hard to handle mobility management with little impact on the performance of a routing protocol. Therefore, in this paper we propose a tree-based mobility management approach using a message aggregation technique that employs a novel timing model suitable for tree topology, referred to as a skewed wait time assignment technique, in order to maximize message aggregation. Despite its superior performance, this wait time assignment technique differs from the other techniques in that it does not require clock synchronization over nodes. By resorting to simulations, we show that the proposed approach can significantly alleviate the funneling effect as well as improve the performance of mobility management compared with the Tree-based and Quasi-tree based mobility management schemes. 相似文献
972.
A First‐Cycle Coulombic Efficiency Higher than 100 % Observed for a Li2MO3 (M=Mo or Ru) Electrode
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Jihyun Jang Youngjin Kim Oh B. Chae Taeho Yoon Sang‐Mo Kim Hyun‐seung Kim Hosang Park Prof. Ji Heon Ryu Prof. Seung M. Oh 《Angewandte Chemie (International ed. in English)》2014,53(40):10654-10657
The lithiation/de‐lithiation behavior of a ternary oxide (Li2MO3, where M=Mo or Ru) is examined. In the first lithiation, the metal oxide (MO2) component in Li2MO3 is lithiated by a conversion reaction to generate nano‐sized metal (M) particles and two equivalents of Li2O. As a result, one idling Li2O equivalent is generated from Li2MO3. In the de‐lithiation period, three equivalents of Li2O react with M to generate MO3. The first‐cycle Coulombic efficiency is theoretically 150 % since the initial Li2MO3 takes four Li+ ions and four electrons per formula unit, whereas the M component is oxidized to MO3 by releasing six Li+ ions and six electrons. In practice, the first‐cycle Coulombic efficiency is less than 150 % owing to an irreversible charge consumption for electrolyte decomposition. The as‐generated MO3 is lithiated/de‐lithiated from the second cycle with excellent cycle performance and rate capability. 相似文献
973.
Chan Seo Sehoon Park Youngbae Kim Moongi Ji Hyeon-Seong Lee Yun-Ho Hwang Subin Choi Jeuk Min Song-Jin Oh Sung-Tae Yee Wonjae Lee Man-Jeong Paik 《Biomedical chromatography : BMC》2022,36(3):e5298
This is a metabolomics study for monitoring altered amino acid (AA) and organic acid (OA) metabolism of in eyes from aging an mouse model at 8 and 18 weeks and 18 months. Simultaneous metabolic profiling analysis of OAs and AAs was performed as ethoxycarbonyl/methoxime/tert-butyldimethylsilyl derivatives by gas chromatography–tandem mass spectrometry. A total of 42 metabolites—24 AAs and 18 OAs—were determined and their composition values were normalized to the corresponding mean values of 8-week-old mice as the control group. Then their normalized values were plotted as star graphs, which were distorted and readily distinguishable for each age-related group. Among the 42 metabolites, 18 AAs and 11 OAs were age dependent and significantly different (p < 0.05). Principal component analysis and partial least squares discriminant analysis showed unclear separation between 8- and 18-week-old mice but clear separation between these and 18-month-old mice. In particular, the variable importance in projection scores of 4-hydroxyproline, cis-aconitic acid, glycine, isocitric acid, leucine, pipecolic acid and lysine from partial least-squares–discriminant analysis were higher than 1.3. A heatmap for the classification and visualization of 42 metabolites showed differences in metabolite changes with aging. Altered AA and OA profiles were monitored, which may explain the metabolic disturbance of AA and OA. These findings are related to mitochondrial dysfunctions related to energy metabolism and the impaired antioxidant system in the aging eye. Therefore, the present metabolomics results of the association between physiological states and altered metabolism of AA and OA will be useful for understanding the aging eye and related diseases. 相似文献
974.
Wonsik Nam Seichang Oh Hyunku Joo Jaekyung Yoon 《Journal of solid state chemistry》2011,184(11):2920-2924
The purpose of this study was to develop effective cathodes to increase the production of hydrogen and use the seawater, an abundant resource in the earth as the electrolyte in photoelectrochemical systems. In order to fabricate the Pt/TiO2 cathodes, various contents of the Pt precursor (0–0.4 wt%) deposited by the electrodeposition method were used. On the basis of the hydrogen evolution rate, 0.2 wt% Pt/TiO2 was observed to exhibit the best performance among the various Pt/TiO2 cathodes with the natural seawater and two concentrated seawater electrolytes obtained from single (nanofiltration) and combined membrane (nanofiltration and reverse osmosis) processes.The surface characterizations exhibited that crystal structures and morphological properties of Pt and TiO2 found the results of XRD pattern and SEM/TEM images, respectively. 相似文献
975.
976.
Jae‐Mun Oh Byung‐Do Yang Hyeong‐Ju Kang Yeong‐Seuk Kim Ho‐Yong Choi Woo‐Sung Jung 《ETRI Journal》2015,37(5):961-971
This paper proposes a 250 mV supply voltage digital low‐dropout (LDO) regulator. The proposed LDO regulator reduces the supply voltage to 250 mV by implementing with all digital circuits in a 0.11 μm CMOS process. The fast current tracking scheme achieves the fast settling time of the output voltage by eliminating the ringing problem. The over‐voltage and under‐voltage detection circuits decrease the overshoot and undershoot voltages by changing the switch array current rapidly. The switch bias circuit reduces the size of the current switch array to 1/3, which applies a forward body bias voltage at low supply voltage. The fabricated LDO regulator worked at 0.25 V to 1.2 V supply voltage. It achieved 250 mV supply voltage and 220 mV output voltage with 99.5% current efficiency and 8 mV ripple voltage at 20 μA to 200 μA load current. 相似文献
977.
Seismic ground motion can vary significantly over distances comparable to the length of a majority of highway bridges on multiple supports. This paper presents results of fragility analysis of highway bridges under ground motion with spatial variation. Ground motion time histories are artificially generated with different amplitudes, phases, as well as frequency contents at different support locations. Monte Carlo simulation is performed to study dynamic responses of an example multi-span bridge under these ground motions. The effect of spatial variation on the seismic response is systematically examined and the resulting fragility curves are compared with those under identical support ground motion. This study shows that ductility demands for the bridge columns can be underestimated if the bridge is analyzed using identical support ground motions rather than differential support ground motions. Fragility curves are developed as functions of different measures of ground motion intensity including peak ground acceleration, peak ground velocity, spectral acceleration, spectral velocity and spectral intensity. This study represents a first attempt to develop fragility curves under spatially varying ground motion and provides information useful for improvement of the current seismic design codes so as to account for the effects of spatial variation in the seismic design of long-span bridges. 相似文献
978.
Wireless Microfluidic Systems for Programmed,Functional Transformation of Transient Electronic Devices
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Chi Hwan Lee Seung‐Kyun Kang Giovanni A. Salvatore Yinji Ma Bong Hoon Kim Yu Jiang Jae Soon Kim Lingqing Yan Dae Seung Wie Anthony Banks Soong Ju Oh Xue Feng Yonggang Huang Gerhard Troester John A. Rogers 《Advanced functional materials》2015,25(32):5100-5106
Electronic systems that enable programmable transformation of functional behaviors by remote control or by autonomous responses to user‐defined circumstances create unusual engineering opportunities, where physical changes in the hardware induce desired changes in operation. This paper presents materials and device architectures for technologies of this type, in which localized microfluidic chemical etching of targeted constituent components in the electronics occurs in a sequential, selective manner. Custom circuits that include reconfigurable radio‐powered thermal actuators with analog amplifiers and square waveform generators illustrate the concepts. 相似文献
979.
In Situ Formation of Conductive Metal Sulfide Domain in Metal Oxide Matrix: An Efficient Way to Improve the Electrochemical Activity of Semiconducting Metal Oxide
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In Young Kim Jiyoon Seo Seung Mi Oh Sharad B. Patil Seong‐Ju Hwang 《Advanced functional materials》2015,25(31):4948-4955
A new effective way to improve the electrochemical activity of semiconducting metal oxide is developed by the in situ formation of conductive metal sulfide domain in the metal oxide matrix. The Li0.96Ti1.08S2?Li4Ti5O12 nanocomposites with tunable compositions and electrical properties are synthesized by the reaction of Li4Ti5O12 with CS2 at elevated temperature. The resulting incorporation of conductive Li0.96Ti1.08S2 domain in the Li4Ti5O12 matrix is effective in enhancing the electrical conductivity and electrode activity of semiconducting lithium titanate. As anode materials for lithium ion batteries, the obtained Li0.96Ti1.08S2?Li4Ti5O12 nanocomposites show much greater discharge capacity and better rate characteristics than does the pristine Li4Ti5O12. The usefulness of the present method is further evidenced from the improvement of the electrochemical activity of semiconducting CsTi2NbO7 after the reaction with CS2. The present study clearly demonstrates the in situ formation of conductive metal sulfide domain using CS2 liquid can provide an efficient and universal way to improve the electrode functionality of semiconducting metal oxide. 相似文献
980.
Use of DEA cross-efficiency evaluation in portfolio selection: An application to Korean stock market
We propose a way of using DEA cross-efficiency evaluation in portfolio selection. While cross efficiency is an approach developed for peer evaluation, we improve its use in portfolio selection. In addition to (average) cross-efficiency scores, we suggest to examine the variations of cross-efficiencies, and to incorporate two statistics of cross-efficiencies into the mean-variance formulation of portfolio selection. Two benefits are attained by our proposed approach. One is selection of portfolios well-diversified in terms of their performance on multiple evaluation criteria, and the other is alleviation of the so-called “ganging together” phenomenon of DEA cross-efficiency evaluation in portfolio selection. We apply the proposed approach to stock portfolio selection in the Korean stock market, and demonstrate that the proposed approach can be a promising tool for stock portfolio selection by showing that the selected portfolio yields higher risk-adjusted returns than other benchmark portfolios for a 9-year sample period from 2002 to 2011. 相似文献