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A Alibeigloo - One of the best experts on this subject based on the ideXlab platform.
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thermo electro elasticity solution of functionally graded carbon nanotube reinforced composite cylindrical shell embedded in piezoelectric layers
Composite Structures, 2017Co-Authors: A Alibeigloo, A Pasha A ZanoosiAbstract:Abstract Based on theory of elasticity, static analysis of functionally graded carbon nanotube reinforced composite (FG-CNTRC) cylindrical shell imbedded in piezoelectric sensor and actuator layers under thermo-electro-mechanical load is carried out. Thermo-elastic constants of the CNTRC cylindrical shell is supposed to be independent of temperature difference. In this study, uniformly as well as different cases of functionally graded CNT distribution, along the radial coordinate of host layer is considered. Governing ordinary differential equations are derived by expanding all of quantities in term of axial coordinate and using state Space Technique along the radial direction and then they are solved analytically to compute temperature, stress and displacement fields as well as induced electric voltage in sensor layer. Validity of the present approach is assessed by comparing the obtained numerical results with the available results in literature. Influence of CNT volume fraction, kind of CNT distribution along the radial coordinate, surface thermal, mechanical and electrical boundary conditions on static behavior of hybrid FG-CNTRC cylindrical shell are evaluated.
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three dimensional static and free vibration analysis of carbon nano tube reinforced composite cylindrical shell using differential quadrature method
International Journal of Applied Mechanics, 2016Co-Authors: A Alibeigloo, Haadi JafarianAbstract:In this paper, bending and free vibration analysis of carbon nanotubes reinforced composite (CNTRC) cylindrical shell is carried out using the three-dimensional theory of elasticity. The single-walled carbon nanotubes (SWCNT) reinforcement is either uniformly distributed (UD) or functionally graded (FG) in the thickness direction which, are specified as the cases FG − Δ, FG −∇, FG −♢ and FG-X. Effective material properties of CNTRC cylindrical shell are estimated according to the rule of mixture as well as considering the CNT efficiency parameters. An analytical solution is performed by using Fourier series along the axial coordinate together with state Space Technique along the radial coordinate for the simply supported CNTRC cylindrical shell. Moreover, for CNTRC cylindrical shell with other edges boundary conditions, a semi-analytical solution is accomplished by using differential quadrature method (DQM) along the axial coordinate and state Space Technique along the radial coordinate. Present approach ...
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effect of viscoelastic interface on three dimensional static and vibration behavior of laminated composite plate
Composites Part B-engineering, 2015Co-Authors: A AlibeiglooAbstract:Abstract In this study, static and free vibration analysis of laminated cross-ply rectangular plate with special emphasis on incorporating viscoelastic interface is investigated using three-dimensional theory of elasticity. The laminated plate is assumed to be simply-supported at four edges and is subjected to uniform pressure at the top surface. State Space Technique is used along the plate thickness to investigate the Space dependent behavior where as time dependent behavior can be discussed by solving first order differential equation of sliding displacement at the viscoelastic interfaces. Numerical results depicts that the present method converges rapidly and good agreement is exist between the present results and the published results. Moreover, the effects of elastic and viscous interfaces, time, aspect ratio and length to thickness ratio on the bending and vibration behavior of laminated plate are studied.
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static and free vibration analyses of carbon nanotube reinforced composite plate using differential quadrature method
Meccanica, 2015Co-Authors: A Alibeigloo, Ali EmtehaniAbstract:This work presents bending and free vibration behaviour of carbon nanotubes reinforced composite (CNTRC) plates using the three dimensional theory of elasticity. The single-walled carbon nanotubes reinforcement is either uniformly distributed or functionally graded (FG) along the thickness direction indicated with FG-V, FG-O and FG-X. In the present study the effective material properties of CNTRC plates, are estimated according to the rule of mixture along with considering the CNT efficiency parameters. For the plate with simply supported edges we used Fourier series expansion across the in plane coordinates as well as the state Space Technique across the thickness direction to obtain closed form solution. Since in the case of plate with non-simply supported boundary conditions it is not possible to use Fourier series along the longitudinal and width directions, therefore it should be employed numerical method along the above mentioned coordinates. In this investigation we used semi analytical Technique, differential quadrature method along the in-plane coordinates and state-Space Technique across the thickness direction. Present approach is validated by comparing the numerical results with those published results. Furthermore, effect of types of CNT distributions in the polymer matrix, volume fraction of CNT, edges boundary conditions and width-to-thickness ratio on the bending and free vibration behaviour of FG-CNTRC plate are discussed.
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three dimensional thermoelasticity solution of functionally graded carbon nanotube reinforced composite plate embedded in piezoelectric sensor and actuator layers
Composite Structures, 2014Co-Authors: A AlibeiglooAbstract:Based on theory of elasticity, static behavior of functionally graded carbon nanotube reinforced composite (FG-CNTRC) rectangular host plate attached to thin piezoelectric layers subjected to thermal load and or electric field is studied. It is assumed that temperature gradient does not affect the thermo-elastic constants of the plate. Distribution of CNT is uniformly or functionally graded along the plate thickness. Analytical solutions for the temperature, stress and displacement fields for the FG-CNTRC plate with simply-supported edges are derived by using the Fourier series expansion along in-plane coordinates and state-Space Technique across thickness direction. The present procedure is validated by comparing the numerical results with the available published results. Parametric studies are performed to assess the effects of CNT volume fraction, case of CNT distribution along the thickness direction, surface boundary conditions, applied voltage, aspect ratio and length to thickness ratio on the behavior of FG-CNTRC rectangular plate.
John Bechhoefer - One of the best experts on this subject based on the ideXlab platform.
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two experimental tests of a fluctuation induced first order phase transition intensity fluctuation microscopy at the nematic smectic a transition
Physical Review E, 2002Co-Authors: Anand Yethiraj, Ranjan Mukhopadhyay, John BechhoeferAbstract:We have developed a new, extremely sensitive real-Space Technique (intensity fluctuation microscopy) to probe the order of the nematic-smectic-A (NA) transition. Using this Technique, we show that the NA transition in 4'-n-octyl-4-cyanobiphenyl (8CB) is clearly first order, contrary to calorimetric studies but in agreement with conclusions drawn from front-velocity measurements. We characterize the strength of the discontinuity at the first-order transition by the dimensionless quantity t 0 = (T N A - T * /T * . By precisely measuring t 0 , we have made the first detailed tests of predictions based on the Halperin-Lubensky-Ma (HLM) theory of fluctuation-induced, first-order phase transitions. First, we explore the effect of an external magnetic field on the NA transition. Although modest fields (of order 10 T) are predicted to drive the weakly first-order transition in pure 8CB second order, we observe no such effect; we establish instead that the lower bound on this critical field is 30 T. Likewise, we observe no effect in mixtures of 8CB with its longer chemical homolog 4'-n-decyl-4-cyanobiphenyl (10CB). Second, we examine the dependence of t 0 as a function of 8CB-10CB mixture concentration and find that the data in mixtures with small nematic temperature range are well-fit by the parameters derived by Anisimov et al. based on calorimetric measurements. As we increase the nematic range (by using concentrations closer to pure 8CB), the measured t 0 deviates more and more from the HLM predictions. Smectic fluctuations, which are neglected in the HLM calculation, are an obvious candidate to explain such a discrepancy, but one's naive expectation is that they would reduce t 0 below the HLM levels, whereas the observed values are too large. However, a recent renormalization-group calculation concludes that smectic fluctuations, surprisingly, should indeed increase t 0 , explaining the observations presented here.
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two experimental tests of a fluctuation induced first order phase transition intensity fluctuation microscopy at the nematic smectic a transition
Physical Review E, 2002Co-Authors: Anand Yethiraj, Ranjan Mukhopadhyay, John BechhoeferAbstract:: We have developed a new, extremely sensitive real-Space Technique (intensity fluctuation microscopy) to probe the order of the nematic-smectic-A (NA) transition. Using this Technique, we show that the NA transition in 4'-n-octyl-4-cyanobiphenyl (8CB) is clearly first order, contrary to calorimetric studies but in agreement with conclusions drawn from front-velocity measurements. We characterize the strength of the discontinuity at the first-order transition by the dimensionless quantity t(0)=(T(NA)-T*)/T(*). By precisely measuring t(0), we have made the first detailed tests of predictions based on the Halperin-Lubensky-Ma (HLM) theory of fluctuation-induced, first-order phase transitions. First, we explore the effect of an external magnetic field on the NA transition. Although modest fields (of order 10 T) are predicted to drive the weakly first-order transition in pure 8CB second order, we observe no such effect; we establish instead that the lower bound on this critical field is approximately 30 T. Likewise, we observe no effect in mixtures of 8CB with its longer chemical homolog 4'-n-decyl-4-cyanobiphenyl (10CB). Second, we examine the dependence of t(0) as a function of 8CB-10CB mixture concentration and find that the data in mixtures with small nematic temperature range are well-fit by the parameters derived by Anisimov et al. based on calorimetric measurements. As we increase the nematic range (by using concentrations closer to pure 8CB), the measured t(0) deviates more and more from the HLM predictions. Smectic fluctuations, which are neglected in the HLM calculation, are an obvious candidate to explain such a discrepancy, but one's naive expectation is that they would reduce t(0) below the HLM levels, whereas the observed values are too large. However, a recent renormalization-group calculation concludes that smectic fluctuations, surprisingly, should indeed increase t(0), explaining the observations presented here.
Ariel Tarasiuk - One of the best experts on this subject based on the ideXlab platform.
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chronic upper airway obstruction induces abnormal sleep wake dynamics in juvenile rats
BMC Neuroscience, 2014Co-Authors: Gideon Gradwohl, Nilly Berdugoboura, Yael Segev, Ariel TarasiukAbstract:Traditional scoring of sleep provides little information about the process of transitioning between vigilance-states. We hypothesized that chronic upper airway obstruction (UAO) will lead to sleep instability in the absence of frank obstructed apneas or hypopneas. Using an approach similar to previous reports [1,2] defined a 2-dimensional (2D) state Space Technique (SST) using 2 spectral amplitude ratios calculated by dividing integrated spectral amplitudes at selected frequency bands. We calculated two spectral amplitude ratios by integrating the spectral amplitude over specific frequencies: 0.5-20/0.5-40 Hz for ratio 1 and 0.5-4/0.5-9 Hz for ratio 2. Each second of this ratio was mapped into the 2D state Space, ratio 2 vs. ratio 1 (Figure (Figure1).1). State Space analysis yields wake at low ratio 1 values and SWS at high ratio 1 values. We used the SST to explore whether the abnormal sleep in UAO reflects sleep instability, faster movements, and abnormal transitions between vigilance-states. Figure 1 Spontaneous sleep in rats. Values of wake (W), light slow wave sleep (LSWS), deep slow wave sleep (DSWS) and paradoxical sleep (PS) are shown. We analyzed whole day electroencephalography sleep/wake recordings of UAO and sham control juvenile Sprague-Dawley rats using SST. SST is a non-categorical approach allowing quantitative and unbiased examination of sleep/wake states and state transitions. Measurements of sleep/wake recordings were performed at baseline and following administration of ritanserin (5-HT2 receptor antagonist) the next day to stimulate sleep. UAO rats spent less time in deep (delta-rich) slow wave sleep (SWS) and near transition zones between states. Sleep state transitions were more frequent and rapid in UAO rats, indicating that obstructed animals have more regions where vigilance-states are unstable. The number of microarousals and trajectories from light SWS to wake and vice versa increased in the UAO group. Ritanserin consolidated sleep in both groups by decreasing the number of microarousals and trajectories between wake to light SWS, and increasing deep SWS in UAO.
Anand Yethiraj - One of the best experts on this subject based on the ideXlab platform.
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two experimental tests of a fluctuation induced first order phase transition intensity fluctuation microscopy at the nematic smectic a transition
Physical Review E, 2002Co-Authors: Anand Yethiraj, Ranjan Mukhopadhyay, John BechhoeferAbstract:We have developed a new, extremely sensitive real-Space Technique (intensity fluctuation microscopy) to probe the order of the nematic-smectic-A (NA) transition. Using this Technique, we show that the NA transition in 4'-n-octyl-4-cyanobiphenyl (8CB) is clearly first order, contrary to calorimetric studies but in agreement with conclusions drawn from front-velocity measurements. We characterize the strength of the discontinuity at the first-order transition by the dimensionless quantity t 0 = (T N A - T * /T * . By precisely measuring t 0 , we have made the first detailed tests of predictions based on the Halperin-Lubensky-Ma (HLM) theory of fluctuation-induced, first-order phase transitions. First, we explore the effect of an external magnetic field on the NA transition. Although modest fields (of order 10 T) are predicted to drive the weakly first-order transition in pure 8CB second order, we observe no such effect; we establish instead that the lower bound on this critical field is 30 T. Likewise, we observe no effect in mixtures of 8CB with its longer chemical homolog 4'-n-decyl-4-cyanobiphenyl (10CB). Second, we examine the dependence of t 0 as a function of 8CB-10CB mixture concentration and find that the data in mixtures with small nematic temperature range are well-fit by the parameters derived by Anisimov et al. based on calorimetric measurements. As we increase the nematic range (by using concentrations closer to pure 8CB), the measured t 0 deviates more and more from the HLM predictions. Smectic fluctuations, which are neglected in the HLM calculation, are an obvious candidate to explain such a discrepancy, but one's naive expectation is that they would reduce t 0 below the HLM levels, whereas the observed values are too large. However, a recent renormalization-group calculation concludes that smectic fluctuations, surprisingly, should indeed increase t 0 , explaining the observations presented here.
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two experimental tests of a fluctuation induced first order phase transition intensity fluctuation microscopy at the nematic smectic a transition
Physical Review E, 2002Co-Authors: Anand Yethiraj, Ranjan Mukhopadhyay, John BechhoeferAbstract:: We have developed a new, extremely sensitive real-Space Technique (intensity fluctuation microscopy) to probe the order of the nematic-smectic-A (NA) transition. Using this Technique, we show that the NA transition in 4'-n-octyl-4-cyanobiphenyl (8CB) is clearly first order, contrary to calorimetric studies but in agreement with conclusions drawn from front-velocity measurements. We characterize the strength of the discontinuity at the first-order transition by the dimensionless quantity t(0)=(T(NA)-T*)/T(*). By precisely measuring t(0), we have made the first detailed tests of predictions based on the Halperin-Lubensky-Ma (HLM) theory of fluctuation-induced, first-order phase transitions. First, we explore the effect of an external magnetic field on the NA transition. Although modest fields (of order 10 T) are predicted to drive the weakly first-order transition in pure 8CB second order, we observe no such effect; we establish instead that the lower bound on this critical field is approximately 30 T. Likewise, we observe no effect in mixtures of 8CB with its longer chemical homolog 4'-n-decyl-4-cyanobiphenyl (10CB). Second, we examine the dependence of t(0) as a function of 8CB-10CB mixture concentration and find that the data in mixtures with small nematic temperature range are well-fit by the parameters derived by Anisimov et al. based on calorimetric measurements. As we increase the nematic range (by using concentrations closer to pure 8CB), the measured t(0) deviates more and more from the HLM predictions. Smectic fluctuations, which are neglected in the HLM calculation, are an obvious candidate to explain such a discrepancy, but one's naive expectation is that they would reduce t(0) below the HLM levels, whereas the observed values are too large. However, a recent renormalization-group calculation concludes that smectic fluctuations, surprisingly, should indeed increase t(0), explaining the observations presented here.
Gideon Gradwohl - One of the best experts on this subject based on the ideXlab platform.
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chronic upper airway obstruction induces abnormal sleep wake dynamics in juvenile rats
BMC Neuroscience, 2014Co-Authors: Gideon Gradwohl, Nilly Berdugoboura, Yael Segev, Ariel TarasiukAbstract:Traditional scoring of sleep provides little information about the process of transitioning between vigilance-states. We hypothesized that chronic upper airway obstruction (UAO) will lead to sleep instability in the absence of frank obstructed apneas or hypopneas. Using an approach similar to previous reports [1,2] defined a 2-dimensional (2D) state Space Technique (SST) using 2 spectral amplitude ratios calculated by dividing integrated spectral amplitudes at selected frequency bands. We calculated two spectral amplitude ratios by integrating the spectral amplitude over specific frequencies: 0.5-20/0.5-40 Hz for ratio 1 and 0.5-4/0.5-9 Hz for ratio 2. Each second of this ratio was mapped into the 2D state Space, ratio 2 vs. ratio 1 (Figure (Figure1).1). State Space analysis yields wake at low ratio 1 values and SWS at high ratio 1 values. We used the SST to explore whether the abnormal sleep in UAO reflects sleep instability, faster movements, and abnormal transitions between vigilance-states. Figure 1 Spontaneous sleep in rats. Values of wake (W), light slow wave sleep (LSWS), deep slow wave sleep (DSWS) and paradoxical sleep (PS) are shown. We analyzed whole day electroencephalography sleep/wake recordings of UAO and sham control juvenile Sprague-Dawley rats using SST. SST is a non-categorical approach allowing quantitative and unbiased examination of sleep/wake states and state transitions. Measurements of sleep/wake recordings were performed at baseline and following administration of ritanserin (5-HT2 receptor antagonist) the next day to stimulate sleep. UAO rats spent less time in deep (delta-rich) slow wave sleep (SWS) and near transition zones between states. Sleep state transitions were more frequent and rapid in UAO rats, indicating that obstructed animals have more regions where vigilance-states are unstable. The number of microarousals and trajectories from light SWS to wake and vice versa increased in the UAO group. Ritanserin consolidated sleep in both groups by decreasing the number of microarousals and trajectories between wake to light SWS, and increasing deep SWS in UAO.