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Small-diameter artery disease is the most common clinical occurrence, necessitating the development of small-diameter artificial blood vessels. In this study, seven types of poly(-caprolactone)-cellulose acetate (PCL-CA) composite nanofiber membranes were prepared with different proportions of PCL and CA. The adhesion and growth of Mc3t3-e1 cells were considered to confirm the in vitro cytocompatibility of PCL-CA membranes. A smooth stainless-steel mandrel with a diameter of 4 mm was used to roll up the prepared nanofiber membranes to produce the tubular scaffold with 50 °C hot water. The tubular scaffolds were subjected to axial and circumferential tensile tests. The mechanical performance of the PCL-CA tubular scaffold could be improved by increasing the layers. In addition, the burst pressure (BP) of the tubular scaffolds was increased with the layers, and the BPs of six-layer (2380 ± 36.8 mmHg) and eight-layer (3720 ± 80.5 mmHg) tubular scaffolds were much higher than that of the human saphenous vein (2000 mmHg). The compression shape memory performances of the PCL-CA tubular scaffold with different layers were also investigated to simulate and analyze the contraction and expansion of tubular scaffolds. The experimental results showed that the compression strain of the tubular scaffold in the diameter direction reached 35%, and the ultimate shape recovery rate reached 87%. However, the shape fixity rate and shape recovery rate increased, demonstrating that the optimum number of layers can improve the compression shape memory performance of the tubular scaffold. The results of this study, including comprehensive morphological and mechanical properties and cytocompatibility, indicated the potential applicability of PCL-CA tubular scaffolds as tissue engineering grafts.

Developing three-dimensional (3D) woven composites using various woven structures is important in the advanced composite research field. In this study, carbon-fiber 3D woven textile-reinforced epoxy–resin composites using four different woven structures (such as 2.5D, 3D-a, 3D-b, and 3D-c) were designed and fabricated based on a dobby-weaving loom, and vacuum-assisted resin transfer molding technology. In these 3D woven structures, part of weft insertions serves as binder yarns with a special weft interlock structural design, different weft-to-binder yarn ratios are obtained. Out-of-plane quasistatic three-point bending tests and dynamic low-velocity drop-weight impact tests were conducted on these woven composites to study the effect of woven structure on their flexural performance. Nondestructive ultrasonic C-scan and X-ray microcomputed tomography were applied to characterize the failure modes of the post impacted composites. We found that woven structures affect the flexural performance and failure mode of the developed composites, these structures with lower in-plane and binder yarn waviness exhibited higher quasistatic–flexural performance; 3D-c structure with serious in-plane yarn waviness combined with through-thickness binder yarn path exhibited superior impact resistance than other structures and survived more from composite through-thickness cracks and binder yarn breakage failures. Proper structural design is a key to improving flexural performance in specific engineering applications.

Stability of explicit FDTD algorithm is limited by the established relationship which results in computation duration unacceptable in certain circumstances. To enhance the development of FDTD algorithm, unconditionally stable scheme is implemented to overcome such problem, especially for the open region simulation. Here, for bandpass simulation of anisotropic magnetized ferrite material, complex envelope (CE) method and its modified scheme are employed into the implementation. Generally speaking, the proposed scheme incorporates the alternating direction implicit (ADI) with the CE method during the simulation obtaining the bandpass ADI form in perfectly matched layer (PML) regions. Meanwhile, the proposed scheme establishes the bandpass calculation method of constitutive relationship in ferrite material regions. Such method can also be employed into the unmagnetized isotropic materials and other media. Through ferrite slab model and ferrite waveguide structure, accuracy, absorption and efficiency are demonstrated in the bandpass open region simulation numerically. The proposed scheme can not only benefit an impressive performance but also maintain both of stability and accuracy with decrement of iteration steps which can be proved to be an unconditionally stable implementation. Meanwhile, it also alleviates time increment problem within implicit schemes of small time steps. Thus, benefits of the proposed scheme can be summarized from the following categories: 1) Enhanced absorption and efficiency for the ADI procedure. 2) Decrement of duration with a small time step. 3) Bandpass form inside the magnetized ferrite material. 4) Extensively employment in different kinds of materials.

A theoretical model considering the interface shear deformation is developed to investigate the bending properties of graphene substrates coated with nano-film. This paper presents a closed-form solution for predicting the bending properties of graphene substrates coated with nano-film. Based on the proposed model, we investigate the effects of the interface shear stiffness and the boundary conditions on the bending properties of graphene substrates. A parameter study was carried out analyzing the mechanical behaviors of the graphene substrates. As a result, a parametric study is conducted to show the importance of interface shear transfer mechanisms. The interface shear stress and the deflection of the graphene substrates are largely affected by the interface shear stiffness, the concentrated load position and the boundary conditions of loading. Restraint against bending deflection of graphene nanoribbons coated with nanofilm under the lateral load can be easily investigated using the present theory. The theoretical investigation on the bending behavior provides a useful reference for understanding the interfaces shear deformation in graphene substrates.

Due to the unique nonreciprocal characteristic, ferrite exhibits anisotropic behaviour in electric performance. Owing to such special phenomenon, it is difficult to efficiently analyse and simulate...

For bandpass simulation of nonreciprocal devices with fine and complex structures, hybrid implicit–explicit (HIE) perfectly matched layer (PML) which is incorporated with the higher order concept and complex envelope (CE) method is proposed in finite-difference time-domain (FDTD) lattice. The proposed implementation shows advantages in terms of efficiency, accuracy, and absorption. The effectiveness is demonstrated through the simulation and measurement of ferrite circulator. Through numerical results, the proposed scheme can obtain considerable efficiency and enhanced absorption. From the measurement results, it can be seen that the proposed scheme impacts entire performance in bandpass nonreciprocal simulation.

Small-diameter artificial blood vessels have always faced the problem of thrombosis. In this research, three types of poly(-caprolactone)-cellulose acetate (PCL-CA) composite nanofiber membranes were prepared by various collectors to make into a tubular scaffold with a 4.5-mm diameter. The collector consisted of two sizes of stainless steel wire mesh large-mesh (LM) and small-mesh (SM), respectively. There is also a random flat (RF) that acts as the third type collector. The nanofiber membrane's surface structure mimicked the collectors' surface morphology, they named LM, SM and RF scaffolds. The water contact angles of RF and LM scaffolds are 126.5° and 105.5°, and the distinct square-groove construction greatly improves the contact angle of LM. The tubular scaffolds' radial mechanical property test demonstrated that the large-mesh (LM) tubular scaffold enhanced the strain and tensile strength; the tensile strength and strain are 30 % and 148 % higher than that of the random-flat (RF) tubular scaffold, respectively. The suture retention strength value of the LM tubular scaffold was 103 % higher than that of the RF tubular scaffold. The cytotoxicity and antithrombogenicity performance were also evaluated, the LM tubular scaffold has 88 % cell viability, and the 5-min blood coagulation index (BCI) value was 89 %, which is much higher than other tubular scaffolds. The findings indicate that changing the tubular scaffold's surface morphology cannot only enhance the mechanical and hydrophilic properties but also increase cell survival and antithrombogenicity performance. Thus, the development of a small-diameter artificial blood vessel will be a big step toward solving the problem on thrombosis. Furthermore, artificial blood vessel is expected to be a candidate material for biomedical applications.

Based upon the approximate Crank–Nicolson (CN) algorithms and the higher order (HO) concept, unconditionally stable perfectly matched layer (PML) implementations are proposed for electromagnetic problems in the finite-difference time-domain (FDTD) lattice. The approximate CN algorithms include the CN direct-splitting (CNDS) and CN approximate-factorization-splitting (CNAFS). The proposed schemes take advantage of the approximate CN algorithms in terms of eliminating the Courant–Friedrichs–Levy stability condition and maintaining the computational accuracy. By introducing the HO concept to the PML formulation, the absorbing performance can be enhanced during the simulation. Furthermore, to cope with the existence of half-time-step problems in simulating the anisotropic magnetized plasma, a modified ADE method is proposed at the integer time step. Thus, the modified ADE method can be directly employed in the approximate CN algorithms. Numerical examples and experiments are carried out to demonstrate the effectiveness, efficiency, and performance. Through the results, it can be observed that the computational efficiency and absorbing performance can be significantly improved. Meanwhile, it can be concluded that the CNAFS-PML and CNDS-PML algorithms show higher accuracy and considerable efficiency, respectively, when the time step surpasses far beyond the CFL condition.

By incorporating higher order formulation with perfectly matched layer (PML) implementation, unconditionally stable computationally efficient locally one-dimensional (LOD) algorithm with improved absorption is proposed for simulating ground penetrating radar and its open region problems in finite-difference time-domain (FDTD) algorithm. To take advantages of these methods, the proposed implementation shows characteristics of maintaining considerable accuracy, enhancing computational efficiency and improving the entire absorption. These above-mentioned advantages are illustrated through the ground penetrating radar related problem in open regions. It can be concluded from the calculation results that the proposal shows advantages of higher order formulation, PML implementation and LOD procedure which are efficient in remarkable accuracy, considerable efficiency and improved absorption with increment of CFLNs. Meanwhile, the simulation results also indicate that the proposal is an unconditionally stable procedure with the dissatisfaction of Courant-Friedrichs-Levy stability condition.

For the simulation of gyrotropic plasma structure with fine geometry details along a single direction in open regions, the hybrid implicit-explicit (HIE) algorithm with improved absorbing boundary condition is modified based on the finite-difference time-domain (FDTD) algorithm. More precisely, incorporating the perfectly matched layer (PML) formulation, the higher order concept and the HIE procedure, the proposed implementation shows its significant superiority in terms of efficiency, accuracy and absorption. To simulate the unique anisotropic characteristic inside the gyrotropic plasma regions, the bilinear transform (BT) method is employed during the calculation. The effectiveness can be further demonstrated theoretically and numerically. Through the results, it can be concluded that the proposed scheme exhibits remarkable behaviors in the gyrotropic plasma open region problems. It can not only obtain considerable accuracy compared with the theoretical solution but also receive better absorption and efficiency compared with the published work. In addition, the results also indicate that the proposed scheme can maintain the stability of the algorithm with dissatisfaction of the Courant-Friedrichs-Levy condition between time step and mesh size.

By incorporating the complex envelope (CE) method and the higher order concept, unconditionally stable perfectly matched layer (PML) is proposed based on the Crank–Nicolson approximate-factorization-splitting (CNAFS) algorithm to simulate the bandpass problems in finite-difference time-domain lattice. The proposed algorithm has the advantages of the CNAFS algorithm, higher order PML concept, and CE method in terms of improving efficiency, enhancing absorbing performance, and simulating bandpass problems. A patched antenna model is carried to investigate effectiveness and efficiency.

Composite structure of graphene sheet coated with nano film will be newly developed type structural materials. Hence, the mechanical properties of interface layer between graphene sheet and coating materials is crucial to fabricate the graphene nanoribbons (GNRs) when subjected to thermal loading. In present study, the thermal stress of GNRs with coating nano film is investigated using a proposed model. In the analytical approach, the interface between GNRs and coating materials is considered as a bounding connection by van der Waals (vdW) forces. The normal stress and the shear stress in the interface are obtained by the explicit closed form solution of governing equation for GNRs coated by nano film. The result shows that the maximum shear stress occurs always at the free edge, and much larger than the normal stress. The shear stress in the interface does not change sign, but the normal stress can change from the compression to the tensile, or inverse variation.

In this study, an analytical model is proposed to investigate the sound transmission loss through multi-walled plates with air layers or decompression air layers, under the diffuse incidence field. Using the present approach, the influences of various parameters, such as the wall thickness, the decompressed air and the thickness of air space, on the sound transmission loss through are simulated and discussed in detail. It is seen that, due to the wave frequency of mass-air-mass resonance between double-walled glass plates, the sound transmission loss of the plates can be improved at low frequency range. The sound transmission loss tends to increase with decreasing air pressure because the sound is not transmitted through vacuum space. The design method can be used to investigate the effect of various geometric and material parameters on the sound transmission loss. The advantage of the simulation procedure is easily used for designing the layer structures with different parameter to improve the sound insulation effect.

The elastic modulus of nanowires can be measured by resonant frequency method, in which the elastic modulus is determined using the classical theory of beam deflection. However, the measurement accuracy of the elastic modulus obtained from the resonant frequency can be largely affected by theoretical models and boundary conditions. In the present paper, a theoretical model is developed by considering nonlocal interactions and boundary condition effects of cantilever support. Based on the proposed model, we investigate the influence of nonlocal parameter and elastic foundation on the elastic modulus of carbon nanotubes (CNTs). The results show that the resonant frequency of CNTs is affected by the clamped cantilever condition. Support stiffness and clamped length of CNTS cannot be ignored in determining the elastic modulus of CNTs, especially for CNTs with low stiffness support. After considering the boundary conditions, the influence of cantilever support on the frequency is effectively removed, and the elastic modulus can be precisely determined by measuring the resonant frequency.

In light of the rapid increasing demand for high-precision ultrasonic technologies for damage detection in composite structures, it is necessary to give a further study on the ultrasonic attenuation characteristics, with consideration of the combined effects of material anisotropy and viscoelasticity, and the frequency characteristics of the individual attenuation component. In the present paper, based on the time-domain finite element analysis of ultrasonic wave propagation in a two-layered fiber/matrix composite material, a new method is presented. In the method, by means of extracting the individual attenuation components (viscoelastic attenuation, scattering attenuation due to interface defects, and energy dissipation at the interface) from the overall attenuation respectively, the variation behavior of them with material anisotropy and viscoelasticity, and incident wave frequency, are quantitatively evaluated. The change of proportion of individual attenuation components in overall attenuation under different conditions are also investigated. From the results, the energy loss at the interface is always a major part in ultrasonic attenuation characteristics. Each attenuation component shows frequency dependence, especially the viscoelastic attenuation and energy dissipation at the interface. The simulation results also clarified the detailed effect mechanism of material viscoelasticity and anisotropy on the attenuation characteristics, which will encourage the further development of attenuation measurements for damage detection in composite structures.

In using graphene sheets (GSs) to design nanoscale devices or nanostructure elements, it is very important to understand the properties of these elements against various mechanical loading conditions. The aim of this study is to investigate the impact response of double layer graphene sheets (DLGSs) on elastic foundations when they are subjected to low-velocity impact by nanoparticles. The analytical model is based on general continuum mechanics theory, which considers that a layer stack of two individual GSs is bound together by van der Waals (vdW) forces, and the interaction of DLGSs embedded to elastic foundations is modeled based on the Winkler model. The result shows that elastic foundation materials have a significant effect on the impact characteristics of GSs. The impact response of GSs subjected to nanomass has exceedingly short times with picoseconds order. This investigation may be helpful in engineering design of using GSs as nanostructure elements for nanoelectromechanical system (NEMS).

For overcoming the Courant-Friedrich-Levy (CFL) stable condition and maintaining the stability of the algorithm, unconditionally stable implementation is proposed for the simulation of anisotropic gyrotropic plasma in bandpass open region problems. To be more accurately, the proposed implementation is based on the complex envelope method, higher order concept, perfectly matched layer formulation and Crank-Nicolson Direct-Splitting procedure which shows advantages over them including accuracy, efficiency and absorption. The gyrotropic plasma with unique anisotropic characteristic can be simulated by the modified approach. For the further illustration of effectiveness, several numerical examples are introduced. Through the results and comparison with previous work, it can be concluded that the entire performance which includes accuracy, efficiency and absorption can be significantly improved. In addition, the mesh size can be no longer limited by the CFL condition rather than the computational accuracy which shows considerable potential in numerical simulation of fine structures. Meanwhile, the time step can be obtained according to the maximum frequency rather than bandwidth resulting in the exponential decrement of running time.

To prevent the heat generated by UV radiation from destroying the UV-shielding materials, zinc oxide/polyurethane composite membranes (ZnO/PU composite membranes) were synthesized via a simple solution casting method, where ZnO nanoparticles were firstly synthesized using a hydrothermal method with an eco-friendly reducing agent. Synthesized ZnO nanoparticles (240 nm) were symmetrical pyramid structured that efficiently reflect and absorb the full-length UV radiation. ZnO/PU composite membranes with various ZnO contents were acquired to obtain the optimal ZnO content with full-length UV-shielding properties. The result exhibits that the fabricated membranes with 6 wt% (based on PU weight) of ZnO content process full-length UV-shielding capability with high transmittance . The fabricated composite membranes were exposed under UV radiation at 60 °C for 12 days, confirming that the ZnO/PU composite membranes have high temperature stable UV-shielding properties. The composite mem branes provide a potential direction for fabricating materials with high temperature stable UV-shielding properties.

An analytical solution is proposed for the low velocity impact response of laminated plates with an elastic medium layer. In the theoretical model, the medium materials between laminated plates are considered to be a spring model with elastic constants. The influences of impactor parameters such as velocity and mass on the impact response are investigated based on the proposed model and a numerical simulation. The simulation result shows that the impact response of two-layer laminated plates is quite different when a medium layer is inserted into the laminated plates. Impact loads acting on the laminated plate significantly decrease due to deformation energy absorption by the elastic medium layer in laminated plates.

Carbon nanotubes (CNTs) can be used as atomic force microscope (AFM) probes since they are ideal tip materials with a small diameter, high aspect ratio, and stiffness. In this study, a model of CNTs clamped in an elastic medium is proposed as nanoscale force sensing AFM probes. The relationship between vibration frequency and axial force of the CNT probe clamped in an elastic medium is analyzed based on the Euler-Bernoulli beam model and the Whitney-Riley model. The clamped length of CNTs, and the elastic modulus of elastic medium affect largely on the vibration and the buckling stability of a CNT AFM probe. The result showed that the sensitivity to vibration increases as the applied loads increase. The critical load in which the vibration frequency decreases rapidly, moving to large ones with decreasing ratio of length to diameter of CNTs. The theoretical investigation on the vibration frequency of CNT loaded in the axial direction would give a useful reference for designing a CNT used as a nano-force sensor.