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1.
The results of a comprehensive experimental program, aimed at providing a fundamental understanding of the behavior of shear-critical exterior reinforced concrete (RC) joints strengthened with fiber reinforced polymers (FRP) under simulated seismic load, are presented in this study. The role of various parameters on the effectiveness of FRP is examined through 2/3-scale testing of 18 exterior RC joints. Conclusions are drawn on the basis of certain load versus imposed displacement response characteristics, comprising the strength (maximum lateral load), the stiffness, and the cumulative energy dissipation capacity. The results demonstrate the important role of mechanical anchorages in limiting premature debonding, and they provide important information on the role of various parameters, including: area fraction of FRP; distribution of FRP between the beam and the column; column axial load; internal joint (steel) reinforcement; initial damage; carbon versus glass fibers; sheets versus strips; and effect of transverse beams. 相似文献
2.
Costas Chaikalis 《Wireless Personal Communications》2007,41(1):77-97
Reconfiguration concept represents reconfigurable functionalities of the radio interface for mobile radio systems. Particularly
for the physical layer, some possible reconfigurable architectures can be identified. We focus on outer interleaving for turbo
codes, which can improve their performance in flat Rayleigh fading environment. The larger the number of columns in the outer
interleaver, the better is the performance, but with the penalty of more complexity and delay. Furthermore, an incorrect choice
of the number of columns can increase the bit and frame error rates. Therefore, it would be advantageous to reconfigure the
outer interleaver in different operating environments with the optimum number of columns. Using two different data frame lengths,
in this contribution simulation results are presented for the four possible outer block interleaver configurations specified
for the 3GPP mobile standard in the case of flat Rayleigh fading channel. It is shown that different operating environments
require an optimum number of columns in terms of bit error rate and frame error rate performance. Finally, frame fade duration
is considered and the effect of the product of the Doppler frequency with the frame duration on the performance for the four
different 3GPP outer block interleaver configurations is discussed.
Costas Chaikalis was born in Athens, Greece, on March 7, 1973. He received the B.Sc. degree in electrical engineering in 1995 from Technological
Educational Institute of Lamia, Greece. He also received the M.Sc. and Ph.D. degrees from Department of Electronics and Telecommunications,
University of Bradford, Bradford, UK in 1999 and 2003, respectively. During his doctoral studies he worked as a Research Assistant
for Mobile Virtual Center of Excellence (Mobile VCE), Terminals Group, UK. Since 2003, he is a lecturer in the Department
of Electrical Engineering, Technological Educational Institute of Lamia, Greece. His research interests are in all areas of
mobile communications but especially in forward error correction coding, reconfigurable (software radio) architectures, cross
layer architectures and DSP applications. 相似文献
3.
A discrete-time, model-based output feedback control structure for nonlinear processes is developed in the present work. The structure makes use of a closed-loop observer, while at the same time it guarantees that the overall feedback controller possesses integral action. An algebraic transformation is applied on the observer states to insure that the input/output gain of the observer matches the model upon which the static state feedback control law is based. The resulting control algorithm is a two-degree-of-freedom control law, in the sense that the output and the set point are processed in different ways. The control structure is shown not only to have the same properties as the standard model-state feedback structure, but also that it emerges from a model algorithmic control framework. Finally, a simulation example using an exothermic CSTR operating at an open-loop unstable steady state is used to evaluate the closed-loop performance of the proposed method. 相似文献
4.
Vasilios Kelefouras Angeliki Kritikakou Costas Goutis 《The Journal of supercomputing》2014,68(3):1418-1440
In this paper, a new methodology for speeding up Matrix–Matrix Multiplication using Single Instruction Multiple Data unit, at one and more cores having a shared cache, is presented. This methodology achieves higher execution speed than ATLAS state of the art library (speedup from 1.08 up to 3.5), by decreasing the number of instructions (load/store and arithmetic) and the data cache accesses and misses in the memory hierarchy. This is achieved by fully exploiting the software characteristics (e.g. data reuse) and hardware parameters (e.g. data caches sizes and associativities) as one problem and not separately, giving high quality solutions and a smaller search space. 相似文献
5.
The selective catalytic reduction of NO by H2 under strongly oxidizing conditions (H2-SCR) in the low-temperature range of 100–200 °C has been studied over Pt supported on a series of metal oxides (e.g., La2O3, MgO, Y2O3, CaO, CeO2, TiO2, SiO2 and MgO-CeO2). The Pt/MgO and Pt/CeO2 solids showed the best catalytic behavior with respect to N2 yield and the widest temperature window of operation compared with the other single metal oxide-supported Pt solids. An optimum 50 wt% MgO-50wt% CeO2 support composition and 0.3 wt% Pt loading (in the 0.1–2.0 wt% range) were found in terms of specific reaction rate of N2 production (mols N2/gcat s). High NO conversions (70–95%) and N2 selectivities (80–85%) were also obtained in the 100–200 °C range at a GHSV of 80,000 h−1 with the lowest 0.1 wt% Pt loading and using a feed stream of 0.25 vol% NO, 1 vol% H2, 5 vol% O2 and He as balance gas. Addition of 5 vol% H2O in the latter feed stream had a positive influence on the catalytic performance and practically no effect on the stability of the 0.1 wt% Pt/MgO-CeO2 during 24 h on reaction stream. Moreover, the latter catalytic system exhibited a high stability in the presence of 25–40 ppm SO2 in the feed stream following a given support pretreatment. N2 selectivity values in the 80–85% range were obtained over the 0.1 wt% Pt/MgO-CeO2 catalyst in the 100–200 °C range in the presence of water and SO2 in the feed stream. The above-mentioned results led to the obtainment of patents for the commercial exploitation of Pt/MgO-CeO2 catalyst towards a new NOx control technology in the low-temperature range of 100–200 °C using H2 as reducing agent. Temperature-programmed desorption (TPD) of NO, and transient titration of the adsorbed surface intermediate NOx species with H2 experiments, following reaction, have revealed important information towards the understanding of basic mechanistic issues of the present catalytic system (e.g., surface coverage, number and location of active NOx intermediate species, NOx spillover). 相似文献
6.
On the Competitive Ratio for Online Facility Location 总被引:2,自引:0,他引:2
Dimitris Fotakis 《Algorithmica》2008,50(1):1-57
We consider the problem of Online Facility Location, where the demand points arrive online and must be assigned irrevocably
to an open facility upon arrival. The objective is to minimize the sum of facility and assignment costs. We prove that the
competitive ratio for Online Facility Location is Θ
. On the negative side, we show that no randomized algorithm can achieve a competitive ratio better than Ω
against an oblivious adversary even if the demands lie on a line segment. On the positive side, we present a deterministic
algorithm which achieves a competitive ratio of
in every metric space.
A preliminary version of this work appeared in the Proceedings of the 30th International Colloquium on Automata, Languages
and Programming (ICALP 2003), Lecture Notes in Computer Science 2719. This work was done while the author was at the Max-Planck-Institut
für Informatik, Saarbrücken, Germany, and was partially supported by the Future and Emerging Technologies programme of the
EU under contract number IST-1999-14186 (ALCOM–FT). 相似文献
7.
In this work sufficient conditions for uniform input‐to‐output stability and uniform input‐to‐state stability are presented for finite‐dimensional systems under feedback control with zero‐order hold. The conditions are expressed by means of single and vector Lyapunov functions. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
8.
Papazoglou TG Liu WQ Vasiliou A Grassmel R Kalpouzos C Fotakis C 《Applied optics》1996,35(19):3759-3762
Early-arriving photons of 100-fs laser pulses transmitted through highly scattering media have been detected by a streak camera. Because of their partial spatial coherence, they are affected by diffraction from small hidden discontinuities. The experimental data of the patterns are analyzed with Fresnel diffraction theory and then corrected accordingly. Submillimeter hidden objects were scanned and imaged. Diffraction correction resulted in a significantly improved contrast in the hidden object's image. 相似文献
9.
We study here the effect of concurrent greedy moves of players in atomic congestion games where n selfish agents (players) wish to select a resource each (out of m resources) so that her selfish delay there is not much. The problem of “maintaining” global progress while allowing concurrent
play is exactly what is examined and answered here. We examine two orthogonal settings: (i) A game where the players decide
their moves without global information, each acting “freely” by sampling resources randomly and locally deciding to migrate
(if the new resource is better) via a random experiment. Here, the resources can have quite arbitrary latency that is load
dependent. (ii) An “organised” setting where the players are pre-partitioned into selfish groups (coalitions) and where each
coalition does an improving coalitional move. Our work considers concurrent selfish play for arbitrary latencies for the first
time. Also, this is the first time where fast coalitional convergence to an approximate equilibrium is shown. 相似文献
10.
Themis P. Exarchos Markos G. Tsipouras Costas Papaloukas Dimitrios I. Fotiadis 《Knowledge and Information Systems》2009,19(2):249-264
In this paper we present a novel methodology for sequence classification, based on sequential pattern mining and optimization
algorithms. The proposed methodology automatically generates a sequence classification model, based on a two stage process.
In the first stage, a sequential pattern mining algorithm is applied to a set of sequences and the sequential patterns are
extracted. Then, the score of every pattern with respect to each sequence is calculated using a scoring function and the score
of each class under consideration is estimated by summing the specific pattern scores. Each score is updated, multiplied by
a weight and the output of the first stage is the classification confusion matrix of the sequences. In the second stage an
optimization technique, aims to finding a set of weights which minimize an objective function, defined using the classification
confusion matrix. The set of the extracted sequential patterns and the optimal weights of the classes comprise the sequence
classification model. Extensive evaluation of the methodology was carried out in the protein classification domain, by varying
the number of training and test sequences, the number of patterns and the number of classes. The methodology is compared with
other similar sequence classification approaches. The proposed methodology exhibits several advantages, such as automated
weight assignment to classes using optimization techniques and knowledge discovery in the domain of application.
相似文献
Dimitrios I. FotiadisEmail: |