ORCID Profile
0000-0003-0062-6436
Current Organisation
Southern University of Science and Technology
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Publisher: SAGE Publications
Date: 18-06-2014
Abstract: In this work, we theoretically revisit the longitudinal permeability of aligned fiber arrays from ordered configuration (i.e. rectangular and staggered arrangements) to random pattern, based on a geometrical scaling rule. The scaling model on the basis of the characteristic length and the characteristic ratio quantifies the flow behaviors more accurately than the widely applied Kozeny-Carman equation. The model for actual fiber arrays composed of randomly located fibers is extended from the ordered case, and the randomness of fiber distribution is realized by the Voronoi tessellation method and quantified by a single parameter. The proposed compact and easy-use model is verified by experimental and numerical results throughout the range of fiber volume fractions (FVFs). The structural parameters, including FVF, fiber packing angle, and randomness of fiber distribution are also extensively analyzed.
Publisher: Informa UK Limited
Date: 02-2001
Publisher: IOP Publishing
Date: 18-08-2017
Publisher: SAGE Publications
Date: 28-07-2016
Abstract: Identification of location and magnitude of impact forces on a rectangular carbon fibre–epoxy honeycomb composite panel has been experimentally investigated through an inverse approach. The dynamic signals captured by a single piezoelectric (PZT) sensor installed on the panel remotely from the impact locations are utilized to identify the impact forces generated by an instrumented hammer. A number of potential impact locations on the panel are assumed to be known a priori. An actual impact is then occurred at one or two of these locations. The objective is to simultaneously identify the location and magnitude of the impact forces using the PZT sensor. The problem is solved through minimization of an extended matrix form of the convolution integral incorporating linear superposition of the responses due to impact at different locations. The under-determined problem is ill-posed and is regularized by Tikhonov and generalized cross validation methods. It is revealed that impact forces occurred at any location among four possible locations can be well identified.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2010
Publisher: Springer Science and Business Media LLC
Date: 18-08-2017
Publisher: Springer Science and Business Media LLC
Date: 19-09-2009
Publisher: American Chemical Society (ACS)
Date: 19-12-2013
DOI: 10.1021/LA4034063
Abstract: Porous materials engineered for rapid liquid absorption are useful in many applications, including oil recovery, spacecraft life-support systems, moisture management fabrics, medical wound dressings, and microfluidic devices. Dynamic absorption in capillary tubes and porous media is driven by the capillary pressure, which is inversely proportional to the pore size. On the other hand, the permeability of porous materials scales with the square of the pore size. The dynamic competition between these two superimposed mechanisms for liquid absorption through a heterogeneous porous structure may lead to an overall minimum absorption time. In this work, we explore liquid absorption in two different heterogeneous porous structures [three-dimensional (3D) circular tubes and porous layers], which are composed of two sections with variations in radius orosity and height. The absorption time to fill the voids of porous constructs is expressed as a function of radius orosity and height of local sections, and the absorption process does not follow the classic Washburn's law. Under given height and void volume, these two-section structures with a negative gradient of radius orosity against the absorption direction are shown to have faster absorption rates than control s les with uniform radius orosity. In particular, optimal structural parameters, including radius orosity and height, are found that account for the minimum absorption time. The liquid absorption in the optimized porous structure is up to 38% faster than in a control s le. The results obtained can be used a priori for the design of porous structures with excellent liquid management property in various fields.
Publisher: Elsevier BV
Date: 02-2012
Publisher: Elsevier BV
Date: 2015
Publisher: ASMEDC
Date: 2008
Abstract: Structural health monitoring (SHM) plays a significant role in terms of fatigue life and damage accumulation prognostics. SHM for structures with complex geometry are much more practical in engineering applications. In this paper, complex aluminium alloy structures with “U” shape section were evaluated in terms of both finite element method (FEM)- and experiment-based Lamb wave analysis for the purpose of damage detection and identification. In the FEM-based analysis, three-dimensional finite element model was established to simulate the propagation behavior of Lamb wave in the structures. On the other hand, in the experiments, piezoelectric (PZT) wafers, functioning as both actuator and sensor, were used to generate Lamb waves propagating in the structures and collect the Lamb wave signals from the complex structures. Quantitative relationship between crack location and the reflection coefficient was constructed by taking advantage of continuous wavelet transform (CWT) and Hilbert transform (HT), which are based on the collected Lamb wave signals. Furthermore, the differences between simulated and experimental results in respect of crack severity evaluation and the reasons were discussed.
Publisher: Elsevier BV
Date: 09-2018
Publisher: Elsevier BV
Date: 05-2006
Publisher: Elsevier BV
Date: 12-2018
Publisher: Elsevier BV
Date: 12-2019
DOI: 10.1016/J.JMBBM.2019.103372
Abstract: Shape memory polyurethanes (SMPU) have been of great interest in biomedical applications because of their unique ability to recover a primary shape by external actuation. This advantage can allow for easy suture and minimum tissue damage caused by surgery. Since SMPU suffer from low stiffness and low strength, carbon fibres have been widely used to reinforce SMPU, and their shape memory properties have been investigated using thermomechanical tensile tests. In reality, however, bending situations are more common than tensile situations, such as human skulls. In this study, carbon fibre reinforced SMPU (CF/SMPU) composites were studied as promising cranial implants that can offer shape memory properties, shape flexibility and high strength. First, the basic properties of pristine SMPU and CF/SMPU composites were characterised, including glass transition temperature (T
Publisher: Elsevier BV
Date: 08-2005
Publisher: SAGE Publications
Date: 07-07-2015
Abstract: This article presents the development of a quantitative method for identifying interfacial delamination in composite laminates. Splitting and merging occur as Lamb waves pass through the delamination. It is demonstrated from the dispersion curve of Lamb waves that the group velocities of A 0 and S 0 modes in the sub-laminates above and below the delamination area are different when the delamination interface is not at the thickness center of a symmetrical layup laminate. Changes in the time of flight (ToF) of A 0 and S 0 modes are caused by the parallel propagation of Lamb waves. Based on those changes in the ToF, delamination size can be evaluated even though the delamination location through the thickness is not pregiven. Numerical and experimental studies are conducted to assess this method. Continuous wavelet transform is applied to extract the ToF of A 0 mode waves from the overlapped signals. Mode conversion is illustrated for the interaction of Lamb waves and delamination. The sensitivity and applicability of the proposed method are validated numerically and experimentally in two asymmetric layup composite laminates. The limitation of this method for symmetric layup composite laminates is analyzed and a potential improvement approach is further discussed.
Publisher: Elsevier BV
Date: 12-1998
Publisher: World Scientific Pub Co Pte Lt
Date: 10-03-2014
DOI: 10.1142/S0217979214500568
Abstract: The initial stress is induced during film formation and is partially counterbalanced through curvature changes. Therefore, it is commonly evaluated by the measured residual stress. Initial stress may directly affect the film formation rather than residual stress in progressively deposited films. In the present work, we introduced a multiple layer model for progressively deposited films to obtain a quantitative solution for estimating the initial stress. The results showed that residual stress in the last layer is equal to the initial stress when layer number approaches infinity. In particular, the initial stress, σ i in deposited film could be determined using the equation, σ i = σ St /β, in which σ St is the averaged residual stress in films calculated by Stoney formula and β is the correction factor. The value of β varied between 0 and 1, depending on relative modulus and relative thickness of film and substrate. Finally, using element birth and death technique, a finite element model was presented to verify the analytical multiple layer model. Good agreement was obtained between the analytical and FE results.
Publisher: IEEE
Date: 2005
Publisher: Elsevier BV
Date: 07-2013
Publisher: Elsevier BV
Date: 10-2004
Publisher: Elsevier BV
Date: 11-2016
Publisher: Elsevier BV
Date: 05-2020
Publisher: Elsevier BV
Date: 2012
Publisher: American Physical Society (APS)
Date: 12-05-2014
Publisher: Elsevier BV
Date: 04-2017
Publisher: Elsevier BV
Date: 2018
Publisher: Elsevier BV
Date: 10-2002
Publisher: ASMEDC
Date: 2008
Abstract: Different from the mostly concerned Lamb wave-based damage detection for thin plates, this paper presents a diagnosis procedure on thick steel beams with thickness of 34 mm. The diagnosis strategy and specimens were first described, and some parameters, such as the frequency and the number of cycles of the diagnostic waveform, were discussed. Based on finite element method (FEM) simulation, the experiment configuration was addressed, results from which show good similarity between the outcomes from the simulations and those from the experiments. Wavelet transform was further used to process the acquired Lamb wave signals for the purpose of damage detection and localization. Meanwhile, the velocity of the Lamb waves was calculated, illustrating that the fundamental anti-symmetric (A0) Lamb wave mode was excited in this case. The results demonstrate that Lamb waves can also be applied to some thick structures for the purpose of structural health monitoring.
Publisher: Elsevier BV
Date: 07-2007
Publisher: Elsevier BV
Date: 2008
Publisher: Elsevier
Date: 2013
Publisher: IOP Publishing
Date: 27-11-2013
Publisher: Elsevier BV
Date: 10-2017
Publisher: Elsevier BV
Date: 09-2015
Publisher: Elsevier BV
Date: 02-2014
Publisher: Elsevier BV
Date: 12-2012
Publisher: Informa UK Limited
Date: 2003
Publisher: Elsevier BV
Date: 08-2015
Publisher: Elsevier BV
Date: 10-2020
Publisher: Wiley
Date: 02-2002
Publisher: Elsevier BV
Date: 03-2013
Publisher: Springer International Publishing
Date: 29-11-2016
Publisher: Elsevier BV
Date: 10-2009
Publisher: Trans Tech Publications, Ltd.
Date: 06-2013
DOI: 10.4028/WWW.SCIENTIFIC.NET/KEM.558.25
Abstract: Damage detection using guided waves in the inspection of tapered sandwich structures with high density foam core (Dyvinicell HP100) is investigated. Characterisation of the fundamental symmetric and anti-symmetric Lamb wave modes is carried out in terms of their velocity and magnitude variation as they encounter a change in the thickness of a composite sandwich plate, aiming at optimising the mode selection to improve the capability and increase the sensitivity of guided waves in inspection of tapered sandwich structures. In addition, an imaging algorithm based on time reversal is developed to detect multiple debonding and artificial damage in tapered sandwich panels based guided waves from an active sensor network. The correlation coefficients between the original and reconstructed time reversal signals are calculated to define a damage index for in idual sensing paths, which are used later in the fusion process, identifying the presence of damage in the monitoring area enclosed by the active sensor network. The results confirm that the incident wave signals and their reconstructed time-reversed counterparts can be used to accurately detect the debonding/damage in tapered sandwich structures.
Publisher: SAGE Publications
Date: 1195
DOI: 10.1177/002199839603000201
Abstract: A new effective crack growth model (ECGM) is developed to evaluate residual strength of composite laminates with circular holes. When the local normal stress reaches the tensile strength of the unnotched laminate, damage is assumed to initiate and it propagates with increase of the applied load. The damage is modelled by a fictitious crack with cohesive stress acting on the crack surfaces and the damage growth is simulated by extension of the fictitious crack and reduction of the cohesive stress with crack opening. The apparent fracture energy (G:) is used to define the relationship between the unnotched strength and the critical crack opening. Based on the equilibrium condition, an iterative technique is developed to evaluate the applied load required to produce the damage growth. The residual strength of notched composite laminates is defined by the unstable point of the applied load with damage growth. AS4-carbon/948A1 epoxy [0/90] 4s , and [0/±45/90] 2s , composite laminates were manufactured and residual strength tests were conducted for composite laminates with various hole diameters and specimen widths. Effect of the damage increment on the convergence of the residual strength was investigated and the stress redistribution with damage growth in the composite laminates was discussed. The residual strength predicted from the new model correlates well with experimental data for the different laminate configurations.
Publisher: Springer Science and Business Media LLC
Date: 12-2003
Publisher: Springer Science and Business Media LLC
Date: 02-2004
Publisher: ASME International
Date: 27-12-2013
DOI: 10.1115/1.4026174
Abstract: In the present work, nanoindentation experiments were carried out to characterize the localized transfer film layer (TFL) on a steel disk, which resulted from a sliding contact of the latter against a polymer composite pin. It was found that the hybrid nanocomposites filled with both nanoparticles and traditional tribo-fillers were more effective to form durable TFLs on the steel counterpart, associated with desirable tribological properties of the sliding system, i.e., a low friction coefficient and a low wear rate. By studying the load-displacement behavior of polymeric TFLs on metallic substrates, the thickness of TFLs could be estimated, thus, allowing the comparison of TFLs formed under different sliding conditions in a quantitative way. Based on the experimental data, the effects of TFLs on the tribological performance of polymer composites were further discussed in terms of a “transfer film efficiency factor” λ, which was calculated by the ratio of the average thickness of the TFL to the surface roughness of the steel counterpart. The factor mainly considered the relative contributions of the TFL and the metallic counterface to the wear process of the polymer-on-metal system. Accordingly, the wear rate and the friction coefficient of the sliding system could be analyzed as a function of the transfer film efficiency factor, resulting in a Stribeck type diagram. The analyses provided new insight into the role of TFLs in polymer tribology.
Publisher: Elsevier BV
Date: 2010
Publisher: Trans Tech Publications Ltd.
Date: 09-02-2008
Publisher: Elsevier BV
Date: 05-2007
Publisher: Informa UK Limited
Date: 03-2007
Publisher: Springer Science and Business Media LLC
Date: 23-04-2010
Publisher: Informa UK Limited
Date: 2005
Publisher: Elsevier BV
Date: 12-2003
Publisher: Informa UK Limited
Date: 12-05-2020
Publisher: American Chemical Society (ACS)
Date: 04-12-2012
DOI: 10.1021/NN303904Z
Abstract: This study demonstrates that large-size graphene oxide (GO) sheets can impart a tremendous positive impact on self-alignment, electrical conductivity, and mechanical properties of graphene papers. There is a remarkable, more than 3-fold improvement in electrical conductivity of the papers made from ultralarge GO sheets (with an average area of 272.2 μm(2)) compared to that of the small GO counterpart (with an average area of 1.1 μm(2)). The corresponding improvements in Young's modulus and tensile strength are equally notable, namely 320% and 280%, respectively. These improvements of bulk properties due to the large GO sheets are correlated to multiscale elemental and structural characteristics of GO sheets, such as the content of carboxyl groups on the GO edge, C/O ratio and Raman D/G-band intensity ratio of GO on the molecular-scale, and the degree of dispersion and stacking behavior of GO sheets on the microscale. The graphene papers made from larger GO sheets exhibit a closer-stacked structure and better alignment as confirmed by the fast Fourier transform analysis, to the benefits of their electrical conductivity and mechanical properties. The molecular dynamics simulation further elucidates that the enhanced intersheet interactions between large GO sheets play a key role in improving the Young's modulus of GO papers. The implication is that the said properties can be further improved by enhancing the intersheet stress transfer and electrical conduction especially through the thickness direction.
Publisher: Informa UK Limited
Date: 03-10-2013
Publisher: Elsevier
Date: 2015
Publisher: SAGE Publications
Date: 11-09-2011
Abstract: An integration of time-reversal Lamb wave signals from a sensor network and a damage diagnostic imaging algorithm is developed to identify dual notches in an aluminum plate. The time reversibility of Lamb waves for one wave propagation path in an aluminum plate is investigated using dynamic finite element analysis (FEA). A time-reversal-based damage index (DI) is calibrated by correlation of the reconstructed waveform and the original activated tone burst, when the fundamental symmetric (S 0 ) mode alone is reversed or when both the S 0 mode and the fundamental antisymmetric (A 0 ) mode are reversed. Simulation results demonstrate that the calibrated DI is almost identical for the time reversal of single or multiple Lamb modes. On the basis of the time reversibility of Lamb waves, dual notches in an aluminum plate are identified using the damage diagnostic imaging algorithm in the experiment. With the availability of time-reversal-based DI for in idual sensing paths on the aluminum plate, the probability values for the presence of dual notches are estimated in the inspected area enclosed by the sensor network. Identification results demonstrate that the integrated approach with time-reversal Lamb waves and the damage diagnostic imaging algorithm is independent of additional benchmark signals, and it can be used confidently to locate multiple instances of damage.
Publisher: Elsevier BV
Date: 07-2004
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 08-2012
DOI: 10.2514/1.J051274
Publisher: IEEE
Date: 2003
Publisher: SAGE Publications
Date: 10-02-2014
Abstract: The propagation properties of ultrasonic waves in rebar-reinforced concrete beams were investigated and their ability for damage identification was demonstrated. Rectangular piezoelectric ceramics were attached at the exposed ends of the rebar to monitor the wave transmission along the rebar with and without simulated corrosion, which was introduced in the form of partial removal of material from the rebar. Experimental testing demonstrated that the presence of concrete had a significant influence on the propagation characteristics of guided waves along the rebar. In consideration of the inevitable discrepancies in different concrete beams due to in idual specimen preparation and sensor installation, the time-reversal process was applied to identify the damage. A damage index was defined based on the correlation coefficient between the actuated and the reconstructed wave signals. Wavelet transform was applied to overcome the wave conversion difficulty and to reduce the noise in the captured wave signals. Damage of different sizes was introduced and then was correlated with the damage index. Enlarging the damage size resulted in an increase in the level of distortion in the reconstructed wave signals, and consequently, a higher damage index was obtained. The results demonstrate the efficiency of the time-reversal process in identifying damage in rebar-reinforced concrete structures.
Publisher: Elsevier BV
Date: 2005
Publisher: Wiley
Date: 22-09-2010
DOI: 10.1002/PEN.21790
Publisher: Elsevier BV
Date: 05-2000
Publisher: IOP Publishing
Date: 17-05-2006
Publisher: Elsevier BV
Date: 08-2006
Publisher: Elsevier BV
Date: 09-2012
Publisher: Elsevier
Date: 2008
Publisher: Informa UK Limited
Date: 17-08-2015
Publisher: Elsevier BV
Date: 12-1999
Publisher: Wiley
Date: 16-07-2010
DOI: 10.1002/PEN.21663
Publisher: Elsevier BV
Date: 05-2017
Publisher: Elsevier BV
Date: 09-2013
Publisher: Elsevier BV
Date: 08-2019
Publisher: Wiley
Date: 08-01-2002
DOI: 10.1002/APP.10189
Publisher: Elsevier BV
Date: 06-2018
Publisher: World Scientific Pub Co Pte Lt
Date: 09-2020
DOI: 10.1142/S0219455420420043
Abstract: Simultaneous estimation of both the location and force history of an impact applied on a lattice truss core sandwich panel is inversely carried out utilizing velocity signals collected by means of a scanning laser Doppler vibrometer. The algorithm assumes that several impact forces are exerted concurrently on a number of specified locations on a panel, provided that the magnitude of all impact forces but one is actually equal to zero. This condition equates to a scenario where an impact occurs at only one location. The purpose is therefore to detect the actual impact location among all potential locations, together with its force history, through minimizing error functions. Two algorithms, the one-to-one (even-determined) approach and the superposition approach, are considered. The one-to-one approach solves the reconstruction problem independently for each pair of impact and measurement points. However, in the superposition approach, the impact forces at all potential locations are concurrently reconstructed through a single matrix equation. It is shown that the one-to-one approach fails to detect the true impact location while the superposition approach recognizes the actual impact location based on some qualitative evaluating criteria. Adopting the superposition approach, for a problem with four possible impact locations, two scenarios one with four and one with 12 measurement points, are investigated. It is observed that the additional measurement points do not necessarily enhance the efficiency and accuracy of the proposed method. It is found that different arrangements of measuring points lead to identification of the location and the magnitude of the impact force, though the use of four evenly distributed measurement points seems to be most effective in simultaneous identification of the location and magnitude of the impact force. Further, a quantitative index based on the concept of similarity search for time-series using wavelet transformation is proposed and it is demonstrated that the index can successfully identify the true impact force location in a fully automated way.
Publisher: Walter de Gruyter GmbH
Date: 02-2006
DOI: 10.3139/146.101221
Abstract: Ultrafine grained magnesium alloy was synthesized via mechanical milling of AZ91 chips. Mechanical property measurement revealed enhanced yield strength of 470 MPa after mechanical milling. The increase in yield strength is associated with reduction in grain size which restricts twining and dislocation gliding. The present investigation demonstrates that magnesium alloys can be cost-effectively recycled through the process of mechanical milling.
Publisher: SPIE
Date: 02-04-2012
DOI: 10.1117/12.924070
Publisher: Elsevier BV
Date: 02-2007
Publisher: Elsevier BV
Date: 05-2002
Publisher: Elsevier BV
Date: 05-2018
Publisher: American Chemical Society (ACS)
Date: 08-02-2010
DOI: 10.1021/AM9008727
Abstract: We successfully synthesized hyperbranched poly(triazole)s by in situ click polymerization of diazides 1 and triyne 2 monomers on different metal surfaces (copper, iron, and aluminum) and characterized their adhesive properties. Optimizations were performed to obtain high adhesive strength at different temperatures by analyzing the effects of curing kinetics, annealing temperature and time, catalyst, monomer ratio, surface conditions, alkyl chain length of diazides 1, etc. The adhesive bonding strength with metal substrate is 2 orders of magnitude higher than similar hyperbranched poly(triazole)s made by click polymerization and clearly higher than some commercial adhesives at elevated temperatures. With the same conditions, adhesives prepared on aluminum and iron substrates have higher adhesive strength than those prepared on copper substrate, and an excess of triyne 2 monomer in synthesis has greater adhesive strength than an excess of diazide 1 monomer. Tof-SIMS experiment was employed to understand these phenomena, and the existence of an interphase between the polymer and metal surface was found to be critical for adhesive bonding with thicker interphase (excess of triyne 2 monomer) and the higher binding energy between polymer atoms and substrate atoms (e.g., aluminum substrate) generating the higher bonding strength. In addition, the light-emitting property of synthesized polymers under UV irradiation can be used to check the failure mode of adhesive bonding.
Publisher: Elsevier BV
Date: 09-2014
Publisher: Elsevier BV
Date: 1996
Publisher: American Chemical Society (ACS)
Date: 19-05-2006
DOI: 10.1021/JP057228Z
Abstract: Polystyrene (PS) sphere films with loosely packed arrays were prepared by plasma etching of closely packed PS sphere arrays. The size of PS spheres can be efficiently reduced with plasma etching, and surface topography can be manipulated by controlling the initial PS sphere size and the time of plasma exposure. These surfaces with loosely packed arrays provide a well-characterized model system for studying water repellency behavior. It was found that the surface hydrophobicity could be systematically tailored due to the well-defined and controlled surface topography. Sphere size and the interparticle distance between two adjacent spheres are critical factors in determining the water repellency behavior of the surface. A model based on the Cassie theory was proposed to elucidate the effect of surface topography on hydrophobicity, and the predicted contact angles agree well with the experimental results.
Publisher: Elsevier BV
Date: 12-2011
Publisher: Elsevier BV
Date: 10-2008
Publisher: Wiley
Date: 03-02-2010
DOI: 10.1002/POLB.21942
Publisher: Springer Science and Business Media LLC
Date: 22-05-2009
Publisher: Springer Science and Business Media LLC
Date: 13-08-2010
Publisher: Springer Science and Business Media LLC
Date: 14-05-2010
Publisher: Springer Science and Business Media LLC
Date: 11-03-2010
Publisher: Informa UK Limited
Date: 10-09-2010
Publisher: Elsevier BV
Date: 08-2016
Publisher: Elsevier BV
Date: 04-2011
Publisher: Elsevier BV
Date: 24-01-2000
Publisher: Wiley
Date: 2005
DOI: 10.1002/PC.20062
Publisher: IOP Publishing
Date: 14-07-2009
Publisher: Informa UK Limited
Date: 02-01-2015
Publisher: SAGE Publications
Date: 09-06-2011
Abstract: A Time-of-Flight (ToF)-based interrogation with a single PZT actuator—sensor pair in the pulse-echo configuration for locating and quantifying dual damage in woven laminated beams was investigated through experiments. By applying the Hilbert transform, the ToF and the reflection coefficient are extracted from each damage-induced energy component as damage-sensitive features for identifying the location and severity of damage. The resolution and limitation of this ToF-based interrogation with a single PZT actuator—sensor pair in the pulse-echo configuration for identification of multiple damage are discussed. The results demonstrated that the damage identification algorithm based on the comparison of energy spectra of Lamb wave signals captured in different states has the capability of identifying dual damage in beam-like composite structures.
Publisher: Trans Tech Publications, Ltd.
Date: 12-11-2012
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMM.217-219.130
Abstract: A conductive silicone rubber (SR) composite, filled with both carbon nanotubes (CNT) and carbon black (CB) is prepared by a simple ball milling method. Because of the good dispersion and synergistic effects of CNT and CB, the SR composite shows improvement in mechanical properties. As well, due to the assembly of conductive pathways generated by the CNT and CB, the nanocomposite becomes highly conductive at a comparatively low concentration, with very high sensitivity for tensile and compressive stress. These outstanding properties show that the SR composite has potential applications in tensile and pressure sensors.
Publisher: Springer Science and Business Media LLC
Date: 1994
DOI: 10.1007/BF00624486
Publisher: Springer Science and Business Media LLC
Date: 07-07-2015
Publisher: IOP Publishing
Date: 25-09-2003
Publisher: AIP Publishing LLC
Date: 2016
DOI: 10.1063/1.4942339
Publisher: Elsevier BV
Date: 09-2006
Publisher: SAGE Publications
Date: 26-08-2009
Abstract: The propagation characteristics of Lamb waves activated and collected by an active piezoelectric sensor network in a carbon fibre (CF)/epoxy (EP) composite panel of five stiffeners were investigated. In particular, attenuation and dispersion of Lamb waves induced by reinforced stiffeners were evaluated, and angular dependence of propagating velocity of Lamb waves in the composite structure was studied. The interaction between Lamb wave modes and damage (a through-thickness hole) was subsequently examined. An inverse algorithm based on correlations between the digital damage fingerprints (DDFs) of wave signals in the benchmark and damaged structures was developed for damage identification. DDFs extracted from the captured wave signals were used to achieve efficient data compression for the calculation of correlation coefficients. Different combinations of actuator—sensor paths were used to estimate the location of damage. The results confirm that the proposed algorithm is able to identify damage in such a complex composite structure.
Publisher: IOP Publishing
Date: 15-07-2010
Publisher: AIP Publishing
Date: 09-06-2014
DOI: 10.1063/1.4882057
Abstract: A single-layer porous structure composed of packed particles is designed to achieve the fastest capillary flow under gravity. The minimum flow time for a fixed flow distance is determined by dynamic competition between capillary pressure, gravity, and viscous effects, all of which have different sensitivities to local microstructures of the porous system. Optimal structural parameters are found that account for the minimum flow time in the single-layer porous medium. The theoretical results obtained can be used for the optimization of porous architectures, achieving excellent liquid management properties.
Publisher: Elsevier BV
Date: 2011
Publisher: Elsevier BV
Date: 11-2015
Publisher: Elsevier BV
Date: 06-2014
Publisher: Elsevier BV
Date: 02-2018
Publisher: Elsevier BV
Date: 02-2021
Publisher: Elsevier
Date: 2013
Publisher: Springer Science and Business Media LLC
Date: 06-07-2016
Publisher: Elsevier BV
Date: 03-2007
Publisher: Springer Science and Business Media LLC
Date: 2002
Publisher: Elsevier BV
Date: 10-2018
Publisher: SAGE Publications
Date: 30-07-2008
Abstract: An inverse analysis based on the artificial neural network technique is introduced for effective identification of crack damage in aluminum plates. The concepts of digital damage fingerprints and damage parameter database, which are prerequisites for neural network developing and training, are presented. Parameterized modeling for finite element analysis and an information mapping approach are applied to constitute the damage parameter database cost-effectively. The generalization performance of the neural network is examined by a process of `leave-one-out' cross-validation and erse factors are discussed, based on which the optimization of the neural network architecture is evaluated. The capability of this inverse approach is assessed by two crack cases from experiments, with good accuracy obtained in damage parameters (central position, size, and orientation).
Publisher: Elsevier BV
Date: 08-2006
Publisher: SPIE
Date: 12-04-2017
DOI: 10.1117/12.2258232
Publisher: Elsevier BV
Date: 02-2012
Publisher: SAGE Publications
Date: 27-10-2009
Abstract: Most current studies of guided-wave-based damage detection have been conducted on thin plate-like structures. This article presents a study of damage identification based on activated ultrasonic waves in a thick steel beam. The diagnosis procedure, with key parameters such as excitation frequency and cycle number of the diagnostic waveform, is elaborated in relation to beam dimension as well as pulse-echo itch-catch configurations of PZT active sensors attached to the beam. Finite element simulation was conducted to characterize wave propagation in the beam, and the signals of wave propagation were experimentally measured the results show good agreement with outcomes of the simulation. To aid damage identification, the group velocity of the guided wave was calculated using the envelope of the signal, which was obtained by Hilbert transform. The results for damage location and severity assessment demonstrate that the guided-wave-based damage identification approach can also be applied to certain thick structures for the purpose of structural health monitoring.
Publisher: SAGE Publications
Date: 10-11-2009
Abstract: An algorithm based on correlation analysis was adopted to estimate the probability of the presence of damage in aluminum plates using Lamb wave signals from an active sensor network. Both finite element analysis and experimental evaluations were presented. The Shannon entropy optimization criterion was applied to calibrate the optimal mother wavelet and the most appropriate continuous wavelet transform scale for signal processing. The correlation coefficients for in idual sensing paths between the present state (with damage) and the reference state (without damage) were calculated, and the probability of the presence of damage in the monitoring area enclosed by the active sensor network was estimated to identify the damage. A concept of virtual sensing paths (VSPs) was proposed to enhance the performance of the algorithm by increasing the number of sensing paths in data fusion. The results identified using both simulation and experimental Lamb wave signals from different groups of sensing paths at different central frequencies agreed well with the actual situations, demonstrating the potential of the correlation-based algorithm with the application of VSPs for identification of damage in structures.
Publisher: Elsevier BV
Date: 08-2013
Publisher: Trans Tech Publications, Ltd.
Date: 06-2013
DOI: 10.4028/WWW.SCIENTIFIC.NET/KEM.558.260
Abstract: Fatigue crack growth in metallic plates was monitored using Lamb waves which were generated and captured by surface-mounted piezoelectric wafers in a pitch-catch configuration. Instead of directly pinpointing signal segments to quantify wave scattering caused by the existence of crack damage and related severity, principal component analysis (PCA), as an efficient approach for information compression and classification, was undertaken to distinguish different structural conditions due to fatigue crack growth. For this purpose, a variety of statistical parameters in the time domain as damage indices were extracted from the wave signals. A series of contaminated counterparts with different signal-to-noise ratios were also simulated to increase the statistical size of the data set. It was concluded that PCA is capable of reducing the dimensions of a complex set of original data, whose information can be represented and highlighted by the first few principal components. With the assistance of PCA, the different structural conditions attributable to crack growth can be classified.
Publisher: Hindawi Limited
Date: 2015
DOI: 10.1155/2015/168392
Abstract: Application of nanofibers has become an emerging approach to enhance filtration efficiency, but questions arise about the decrease in Quality factor (QF) for certain particles due to the rapidly increasing pressure drop. In this paper, we theoretically investigate the QF of dual-layer filters for filtration of monodisperse and polydisperse nanoparticles. The inverse problem of air filtration, as defined in this work, consists in determining the optimal construction of the two-layer fibrous filter with the maximum QF. In comparison to a single-layer substrate, improved QF values for dual-layer filters are found when a second layer with proper structural parameters is added. The influences of solidity, fiber diameter, filter thickness, face velocity, and particle size on the optimization of QF are studied. The maximum QF values for realistic polydisperse particles with a lognormal size distribution are also found. Furthermore, we propose a modified QF (MQF) accounting for the effects of energy cost and flow velocity, which are significant in certain operations. The optimal MQF of the dual-layer filter is found to be over twice that of the first layer. This work provides a quick tool for designing and optimizing fibrous structures with better performance for the air filtration of specific nanoparticles.
Publisher: Elsevier BV
Date: 11-2018
Publisher: Elsevier BV
Date: 10-2007
Publisher: Elsevier BV
Date: 06-2016
Publisher: Springer Science and Business Media LLC
Date: 09-02-2010
Publisher: Elsevier BV
Date: 03-2007
Publisher: Informa UK Limited
Date: 03-04-2015
Publisher: Elsevier BV
Date: 07-2002
Publisher: Elsevier BV
Date: 07-2018
Publisher: Elsevier BV
Date: 09-2001
Publisher: SPIE
Date: 09-08-2013
DOI: 10.1117/12.2027564
Publisher: Elsevier BV
Date: 04-2017
Publisher: American Chemical Society (ACS)
Date: 07-05-2014
DOI: 10.1021/LA500479E
Abstract: When capillary flow occurs in a uniform porous medium, the depth of penetration is known to increase as the square root of time. However, we demonstrate in this study that the depth of penetration in multi-section porous layers with variation in width and height against the flow time is modified from this diffusive-like response, and liquids can pass through porous systems more readily in one direction than the other. We show here in a model and an experiment that the flow time for a negative gradient of cross-sectional widths is smaller than that for a positive gradient at the given total height of porous layers. The effect of width and height of local layers on capillary flow is quantitatively analyzed, and optimal parameters are obtained to facilitate the fastest flow.
Publisher: Elsevier BV
Date: 10-2005
Publisher: IOP Publishing
Date: 30-04-2010
Publisher: Elsevier BV
Date: 09-2015
Publisher: Informa UK Limited
Date: 2003
Publisher: Elsevier BV
Date: 10-2013
Publisher: Wiley
Date: 11-2007
Publisher: Elsevier BV
Date: 09-2017
Publisher: Elsevier BV
Date: 2001
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7CP04838F
Abstract: NVERE is a versatile choice for optimizing potential energy through large deformation and capable of finding more stable equilibrium configurations.
Publisher: Elsevier BV
Date: 05-2001
Publisher: Elsevier BV
Date: 07-2005
Publisher: Elsevier BV
Date: 09-2005
Publisher: Elsevier BV
Date: 06-2019
DOI: 10.1016/J.MSEC.2019.02.032
Abstract: As one of the promising smart materials, polyurethane-type shape memory polymers (SMPU) have been extensively investigated as potential biomedical implant materials. However, the hydrophobicity and bio-inertness of SMPU are major problems for biomedical applications. We applied plasma immersion ion implantation (PIII) to increase surface wettability and enable one-step covalent, functionalisation of SMPU with biological molecules to create a tuneable, biocompatible surface. The changes of surface properties due to PIII treatment in nitrogen plasma were determined by measurements of morphology, contact angle, surface energy, and nanoindentation. Collagen attachment on SMPU with and without PIII treatment was measured by Attenuated total reflectance-Fourier transform infrared (ATR-FTIR). To investigate in vivo biocompatibility, SMPU with/without PIII and with/without collagen were subcutaneously implanted in mice. SMPU implants with surrounding tissue were collected at days 1, 3, 7, 14 and 28 to study acute/subacute inflammatory responses at histopathological and immunohistochemical levels. The results show that PIII treatment improves wettability and releases residual stress in the SMPU surfaces substantially. Covalent attachment of collagen on PIII treated SMPU in a single step incubation was demonstrated by its resistance to removal by rigorous Sodium Dodecyl Sulfonate (SDS) washing. The in-vivo results showed significantly lower acute/subacute inflammation in response to SMPU with PIII treatment + collagen coating compared to untreated SMPU, collagen coated untreated SMPU, and PIII treated SMPU, characterised by lower total cell numbers, macrophages, neovascularisation, cellular proliferation, cytokine production, and matrix metalloproteinase production. This comprehensive in vivo study of PIII treatment with protein coating demonstrates that the combination of PIII treatment and collagen coating is a promising approach to enhance the biocompatibility of SMPU, facilitating its application as an implantable biomaterial.
Publisher: Elsevier BV
Date: 02-2004
Publisher: Elsevier
Date: 2000
Publisher: IOP Publishing
Date: 07-09-2007
Publisher: Elsevier BV
Date: 03-2021
Publisher: Elsevier BV
Date: 03-2016
Publisher: SAGE Publications
Date: 04-06-2009
Abstract: A probabilistic damage diagnostic algorithm based on correlation analysis was investigated to locate single or multiple damage. To highlight the changes in signals corresponding to the presence of damage, digital damage fingerprints (DDFs) were extracted from the captured Lamb wave signals. The algorithm was validated through experimental studies where dual artificially introduced notches in an aluminum plate were successfully located using the constructed images of the probability of the presence of damage. Damage identification using either the captured wave signals or their DDFs agreed well with the actual situations. The concept of virtual sensing paths (VSPs) was proposed to enhance the performance of the algorithm. The results demonstrated that the correlation-based algorithm with the applications of DDFs and VSPs was capable of identifying multiple damage in plate-like structures.
No related grants have been discovered for Lin Ye.