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  • Articles  (43,222)
  • 2010-2014  (40,568)
  • 1955-1959  (2,654)
  • Technology  (43,222)
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  • Articles  (43,222)
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  • 1
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    Mechanical and Durability Behaviour of Structural Lightweight Concrete Produced with Volcanic Scoria (2014)
    Springer
    Details
    Publication Date: 2014-12-31
    Description: In this paper, the mechanical and long-term durability behaviour of structural lightweight concrete (LWC) produced with natural lightweight scoria aggregate (LWSA) from the Azores is analysed. Among the properties studied are the compressive and tensile strength, modulus of elasticity, shrinkage, capillary absorption, carbonation and chloride resistance. To this end, a comprehensive experimental study was carried out on different concrete compositions involving common and high-performance structural concrete produced with coarse or coarse and fine volcanic scoria aggregate. Generally, all the mechanical properties worsened with the incorporation of LWSA. It is concluded that the most efficient LWC with LWSA can attain compressive strength up to about 35 MPa. On the other hand, the production of LWC of more than 50 MPa implies a marked reduction in compressive strength for a small reduction in density. The long-term shrinkage increased with the replacement of normal-weight aggregate by LWA and was higher when coarse and fine scoria were used. However, the early age shrinkage can be counterbalanced by the internal curing effect provided by LWSA. The capillary absorption, chloride and carbonation resistance were affected by the high porosity of LWSA. The absence of the outer shell in scoria aggregate and the surface effects during tests can partly explain the lower performance of the LWC. Nevertheless, it is shown that LWC with scoria can be durable, and even for low- to moderate-strength LWC the corrosion induced by carbonation may not be relevant.
    Print ISSN: 1319-8025
    Electronic ISSN: 2191-4281
    Topics: Natural Sciences in General , Technology
    Published by Springer on behalf of The King Fahd University of Petroleum & Minerals.
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  • 2
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    Online Identification Methods of Load Rotary Inertia and Torque in Radar Servo System (2014)
    Hindawi
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    Publication Date: 2014-12-31
    Description: In radar servo system, the load is usually subject to movement and gust, which may cause instability of the system. In this paper, the online identification methods of load rotary inertia and torque in radar servo system are proposed, respectively. The radar servo system is based on synchronous motor. The load rotary inertia of the system is identified online by a disturbance observer. Moreover, a reduced order Luenberger observer is designed to observe the variation of the load torque and velocity online. The simulation models are established to verify the proposed disturbance observer for the load rotary inertia and the reduced order Luenberger observer for the load torque and velocity.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 3
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    Low-Rank Representation for Incomplete Data (2014)
    Hindawi
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    Publication Date: 2014-12-31
    Description: Low-rank matrix recovery (LRMR) has been becoming an increasingly popular technique for analyzing data with missing entries, gross corruptions, and outliers. As a significant component of LRMR, the model of low-rank representation (LRR) seeks the lowest-rank representation among all samples and it is robust for recovering subspace structures. This paper attempts to solve the problem of LRR with partially observed entries. Firstly, we construct a nonconvex minimization by taking the low rankness, robustness, and incompletion into consideration. Then we employ the technique of augmented Lagrange multipliers to solve the proposed program. Finally, experimental results on synthetic and real-world datasets validate the feasibility and effectiveness of the proposed method.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 4
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    Asynchronous Dynamic Output Feedback Control of Switched Time-Delay Systems with Sensor Nonlinearity and Missing Measurements (2014)
    Hindawi
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    Publication Date: 2014-12-31
    Description: The dynamic output feedback control problem for a class of discrete-time switched time-delay systems under asynchronous switching is investigated in this paper. Sensor nonlinearity and missing measurements are considered when collecting output knowledge of the system. Firstly, when there exists asynchronous switching between the switching modes and the candidate controllers, new results on the regional stability and gain analysis for the underlying system are given by allowing the Lyapunov-like function (LLF) to increase with a random probability. Then, a mean square stabilizing output feedback controller and a switching law subject to average dwell time (ADT) are obtained with a given disturbance attenuation level. Moreover, the mean square domain of attraction could be estimated by a convex combination of a set of ellipsoids, the number of which depends on the number of switching modes. Finally, a numerical example is given to illustrate the effectiveness of the proposed method.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 5
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    Residual Probability Function, Associated Orderings, and Related Aging Classes (2014)
    Hindawi
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    Publication Date: 2014-12-31
    Description: The concept of residual probability plays an important role in reliability and life testing. In this investigation, we study further the residual probability order and its related aging classes. Several characterizations and preservation properties of this order under some statistical and reliability operations of monotone transformation, mixture, weighted distributions, and order statistics are discussed. In addition, by comparing the original distribution with its associated equilibrium distribution with respect to the residual probability order, new aging classes of life distributions are proposed and studied. Finally, a test of exponentiality against such classes is derived and sets of real data are used as examples to elucidate the use of the proposed test for practical problems.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 6
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    Image Processing Method for Automatic Discrimination of Hoverfly Species (2014)
    Hindawi
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    Publication Date: 2014-12-31
    Description: An approach to automatic hoverfly species discrimination based on detection and extraction of vein junctions in wing venation patterns of insects is presented in the paper. The dataset used in our experiments consists of high resolution microscopic wing images of several hoverfly species collected over a relatively long period of time at different geographic locations. Junctions are detected using the combination of the well known HOG (histograms of oriented gradients) and the robust version of recently proposed CLBP (complete local binary pattern). These features are used to train an SVM classifier to detect junctions in wing images. Once the junctions are identified they are used to extract statistics characterizing the constellations of these points. Such simple features can be used to automatically discriminate four selected hoverfly species with polynomial kernel SVM and achieve high classification accuracy.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 7
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    Theory and Applications of Fractional Order Systems (2014)
    Hindawi
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    Publication Date: 2014-12-31
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 8
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    The Interval Stability of an Electricity Market Model (2014)
    Hindawi
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    Publication Date: 2014-12-31
    Description: Combined with the electric power market dynamic model put forward by Alvarado, an interval model of electricity markets is established and investigated in this paper pertaining to the range of demand elasticity with suppliers and consumers. The stability of an electricity market framework with demand elasticity interval is analyzed. The conclusions characterizing the interval model provided are derived by constructing a suitable Lyapunov function and using the theory of interval dynamical system in differential equations and matrix inequality theory and so forth. Applying the corollary obtained can judge the system stability by available data about demand elasticity. The obtained results are validated and illustrated by a case example.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 9
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    Effects of Countdown Signals in Red Phase on Drivers: A Comparative Study between Japan and Turkey (2014)
    Hindawi
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    Publication Date: 2014-12-31
    Description: Countdown signals can be found in many countries; however, there are only a few researches that study the impact of the signals on driver behavior. In this study, we focus particularly on the behavior of drivers reacting to countdown signals when the signal shifted from red to green. Although the countdown signal can reduce startup delay, it also causes drivers premature start. This paper determines the factors influencing the behaviors of drivers on startup delay, premature start, and headway due to countdown signals. The analysis results are compared between Japan and Turkey. From our findings, we propose countermeasures to reduce the problems caused by the countdown signals which can be a guideline for implementation or modification of countdown-signalized intersections in many countries in order to increase safety of both drivers and pedestrians as well as drivers’ satisfactions.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 10
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    Effect of Coriolis Force on Bénard–Marangoni Convection in a Rotating Ferrofluid Layer with MFD Viscosity (2014)
    Springer
    Details
    Publication Date: 2014-12-31
    Description: The simultaneous effect of Coriolis force due to rotation and magnetic field dependent (MFD) viscosity on the onset of Bénard-Marangoni convection in a horizontal ferrofluid layer in the presence of a uniform vertical magnetic field is studied. The lower boundary is rigid while the upper free boundary is open to the atmosphere and at which the temperature-dependent surface tension effect is allowed for. The Galerkin technique is employed to extract the critical stability parameters numerically. The results show that the onset of Bénard-Marangoni ferroconvection is delayed with an increase in the MFD viscosity parameter Λ, Taylor number T a , magnetic susceptibility χ and Biot number B i but opposite is the case with an increase in the value of magnetic number M 1 and nonlinearity of fluid magnetization M 3 . Further, increase in M 1 , M 3 and decrease in Λ, T a , χ and B i is to decrease the size of the convection cells. Comparisons of results between the present and the existing ones are made under the limiting conditions and good agreement is found.
    Print ISSN: 0938-0108
    Electronic ISSN: 1875-0494
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Natural Sciences in General , Technology
    Published by Springer
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