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991.
Ahmad Feyz Dizaji Hossein Ali Sepiani Farzad Ebrahimi Akbar Allahverdizadeh Hasan Ali Sepiani 《Journal of Mechanical Science and Technology》2009,23(8):2299-2307
An initial-boundary value problem that is Duffing’s oscillator with time varying coefficients will be studied. Using Banach’s
fixed-point theorem, the existence of periodic solution of the equation will be predicted. The method applied in this paper
is the Schauder second fixed point theorem, which includes the response of structures under vibratory force systems. As an
example, the dynamics of nonlinear simply supported rectangular thin plate under influence of a relatively moving mass is
studied. By expansion of the solution as a series of mode functions, the governing equations of motion are reduced to an ordinary
differential equation for time development vibration amplitude, which is Duffing’s oscillator. Finally, a parametric study
is developed, after that some numerical examples are solved, and the validity of the present analysis is clearly shown.
This paper was recommended for publication in revised form by Associate Editor Maenghyo Cho
Hossein Ali Sepiani received his B.S. degree in Mechanical Engineering from University of Kashan, Iran, in 2003. He then received his M.S. degree
from University of Tehran, in 2006. Currently, Hossein is continuing his research at University of Tehran. His research interests
include new materials (FGMs, Nano-materials, SMAs, SMPs, etc), Composites (Woven Fabrics and Fiber Metal Laminates), Smart
Materials (Shape Memory Alloy, Magnet/Electro-rheological and Piezoelectric Sensors and Actuators), Intelligent structures
(Structures integrated with smart materials), Vibration and control of Intelligent Structures and their application.
Ahmad Feyz Dizaji got his B.S. degree from University of Tehran, Iran, in 1970. Then he continued his study in U.S. and received his PhD. degree
from Michigan State University in 1983, in Applied Mathematics under the supervision of Professor Shui-ni Chow and Professor
J. Mallet-Paret. Since then he has been a member of the Faculty of Engineering in University of Tehran, teaching mathematics
in both undergraduate and graduate levels. 相似文献
992.
Cyclostationarity-Based Modulation Classification of Linear Digital Modulations in Flat Fading Channels 总被引:3,自引:0,他引:3
Octavia A. Dobre Ali Abdi Yeheskel Bar-Ness Wei Su 《Wireless Personal Communications》2010,54(4):699-717
Modulation classification is an intermediate step between signal detection and demodulation, and plays a key role in various
civilian and military applications. In this correspondence, higher-order cyclic cumulants (CCs) are explored to discriminate
linear digital modulations in flat fading channels. Single- and multi-antenna CC-based classifiers are investigated. These
benefit from the robustness of the CC-based features to unknown phase and timing offset. Furthermore, the latter provides
significant performance improvement due to spatial diversity used to combat the fading effect. Classifier performances are
investigated under a variety of channel conditions. In addition, analytical closed-form expressions for the cyclic cumulant
polyspectra of linearly digitally modulated signals affected by fading, carrier frequency and timing offsets, and additive
Gaussian noise are derived, along with a condition for the oversampling factor to avoid aliasing in the cycle and spectral
frequency domains. 相似文献
993.
Ali R. Yildiz 《The International Journal of Advanced Manufacturing Technology》2013,66(9-12):1319-1326
This paper presents a novel hybrid optimization approach based on teaching–learning based optimization (TLBO) algorithm and Taguchi’s method. The purpose of the present research is to develop a new optimization approach to solve optimization problems in the manufacturing area. This research is the first application of the TLBO to the optimization of turning operations in the literature The proposed hybrid approach is applied to two case studies for multi-pass turning operations to show its effectiveness in machining operations. The results obtained by the proposed approach for the case studies are compared with those of particle swarm optimization algorithm, hybrid genetic algorithm, scatter search algorithm, genetic algorithm and integration of simulated annealing, and Hooke–Jeeves patter search. 相似文献
994.
In the present study, wear properties of A356 unreinforced alloy and composites with different vol.% of boron carbide particles were investigated. It is noted that composites exhibit better wear resistance compared to unreinforced alloy. According to the differences in wear rates of the composites, two separate wear rate were identified as low and high wear rate regimes. A combination of artificial neural network (ANN) and finite element technique (FEM) was implemented in order to predict the composites wear behavior. The FEM method is used for discretization and to calculate the transient temperature field of quenching. It is observed that predictions of ANN are consistent with experimental measurements for A356 composite and considerable savings in terms of cost and time could be obtained by using neural network model. 相似文献
995.
996.
997.
Hamid Chakeri Rohola Hasanpour Mehmet Ali Hindistan Bahtiyar Ünver 《Bulletin of Engineering Geology and the Environment》2011,70(3):439-448
Tunnels are increasingly being excavated in soft ground conditions when services are required in urban environments, and it
is now common to have tunnels crossing at various elevations. As the tunnel excavations are undertaken at different levels,
there will be an interaction which can have a significant influence on stress distributions and consequently deformations
within the tunnels and surface settlement. As multi-layer tunnelling is a three dimensional phenomenon in nature, 3D numerical
solutions must be utilized for perpendicularly crossing tunnels at various levels. This paper reports the investigations into
the changes in stress distribution, deformations and surface settlements which may be expected when the twin Tohid Tunnels
pass beneath the Line 4 metro tunnel in Tehran. 相似文献
998.
Temporal fluctuations of the speckle pattern formed upon backscattering of a laser beam from an interface between gold and nonlinear polymer film have been observed as a function of optical power. The instability can be explained by coupling of laser light to surface plasmons and other guided modes, which experience multiple scattering while propagating in the film along the interface. The speckle pattern produced in this process is extremely sensitive to fluctuations of the scattering potential near the interface. 相似文献
999.
Ayesha Binte Ashfaq Muhammad Qasim Ali Syed Ali Khayam 《Journal in Computer Virology》2011,7(1):63-81
An unprecedented growth in computer and communication systems in the last two decades has resulted in a proportional increase
in the number and sophistication of network attacks. In particular, the number of previously-unseen attacks has increased
exponentially in the last few years. Due to the rapidly evolving nature of network attacks, a considerable paradigm shift
has taken place in the intrusion detection community. The main focus is now on Network Anomaly Detection Systems (NADSs) which
model and flag deviations from normal/benign behavior of a network and can hence detect previously-unseen attacks. Contemporary
NADS borrow concepts from a variety of theoretical fields (e.g., Information theory, stochastic and machine learning, signal
processing, etc.) to model benign behavior. These NADSs, however, fall short of achieving acceptable performance levels as
therefore widespread commercial deployments. Thus, in this paper, we firstly evaluate the performance of eight prominent network-based
anomaly detectors under malicious portscan attacks to identify which NADSs perform better than others and why. These NADSs
are evaluated on three criteria: accuracy (ROC curves), scalability (with respect to varying normal and attack traffic rates,
and deployment points) and detection delay. These criteria are evaluated using two independently collected datasets with complementary
strengths. We then propose novel methods and promising guidelines to improve the accuracy and scalability of existing and
future anomaly detectors. Experimental analysis of the proposed guidelines is also presented for the proof of concept. 相似文献
1000.
In this paper, an adaptive control scheme, based on fuzzy logic systems, for pH control is addressed. For implementation of the proposed scheme no composition measurement is required. Stability of the closed-loop system is established and it is shown that the solution of the closed-loop system is uniformly ultimately bounded and under a certain condition, asymptotical stability is achieved. Effectiveness of the proposed controller is tested through simulation and experimental studies. Results indicate that the proposed controller has good performances in set-point tracking and load rejection and much better than that of a tuned PI controller. 相似文献