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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 the ferrite material. Here, an alternative scheme is proposed for the bandpass ferrite finite-difference time-domain simulation. This algorithm is carried out which is based on approximate Crank–Nicolson procedure and incorporated with the complex method and higher-order formulation. The ferrite material can be calculated by the modified auxiliary differential equation approach according to the bandpass sampling theorem. The introduction of numerical example validates the effectiveness. As shown in the results, the proposed scheme can take advantage of these methods which can be demonstrated from the aspect of accuracy, efficiency and absorption. In addition, the proposed scheme can solve the time increment problem caused by the solution of tri-diagonal matrices during the simulation of implicit algorithms. [ABSTRACT FROM AUTHOR]

In this paper, an alternative algorithm for simulating metamaterials under a narrow bandpass condition is proposed. To calculate metamaterial regions with unique double negative property, the Drude model is used to solve the constitutive relationship. The effectiveness of the proposed algorithm over existing methods is demonstrated in terms of accuracy, efficiency, and simulation of absorption. For the numerical example, a metamaterial slab with a dipole antenna model is introduced. Compared with previous works, the numerical results indicate that the proposed algorithm is considerably efficient and simulates absorption. Most importantly, the algorithm can maintain stability and reduce simulation duration. [ABSTRACT FROM AUTHOR]

Abstract: Hollow poly(aniline-co-pyrrole)–Fe3O4 (HPAP–Fe3O4) nanospheres with significant electromagnetic properties were successfully prepared via the oxidative polymerization of a mixture of aniline and pyrrole in the presence of a magnetic fluid, using a non-ionic surfactant as a template. The products were characterized by field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray powder diffraction, thermogravimetric analysis and X-ray photoelectron spectroscopy. The electromagnetic (EM) and microwave absorbing properties of the nanocomposites were also investigated. The HPAP–Fe3O4 nanospheres exhibit superparamagnetic properties, and the conductivity increases with Fe3O4 content. The reflection loss evaluation based on the absorbing wall theory at 2mm thickness shows that the reflection loss is reinforced in the frequency range of 0.5–10GHz by the presence of Fe3O4 nanoparticles, and the frequency of minimum reflection loss shifts to a higher value with increasing Fe3O4 content. HPAP–Fe06 exhibits the best microwave absorbing property between 0.5 and 10GHz. [Copyright &y& Elsevier]

Abstract: In this paper, a facile synthesis process is proposed to prepare multiwalled carbon nanotubes/magnetite (MWCNTs/Fe3O4) hybrids. The process involves two steps: (1) water-soluble CNTs are synthesized by one-pot modification using potassium persulfate (KPS) as oxidant. (2) Fe3O4 is assembled along the treated CNTs by employing a facile hydrothermal process with the presence of hydrazine hydrate as the mineralizer. The treated CNTs can be easily dispersed in aqueous solvent. Moreover, X-ray photoelectron spectroscopy (XPS) analysis reveals that several functional groups such as potassium carboxylate (–COOK), carbonyl (–Cdroxyl (–C–OH) groups are formed on the nanotube surfaces. The MWCNTs/Fe3O4 hybrids are characterized with respect to crystal structure, morphology, element composition and magnetic property by X-ray diffraction (XRD), transmission electron microscopy (TEM), XPS and superconducting quantum interference device (SQUID) magnetometer. XRD and TEM results show that the Fe3O4 nanoparticles with diameter in the range of 20–60nm were firmly assembled on the nanotube surface. The magnetic property investigation indicated that the CNTs/Fe3O4 hybrids exhibit a ferromagnetic behavior and possess a saturation magnetization of 32.2emu/g. Further investigation indicates that the size of assembled Fe3O4 nanoparticles can be turned by varying experiment factors. Moreover, a probable growth mechanism for the preparation of CNTs/Fe3O4 hybrids was discussed. [Copyright &y& Elsevier]

Abstract: Shape memory alloys (SMAs) possess both sensing and actuating functions due to their shape memory effect, pseudo-elasticity, high damping capability and other remarkable characteristics. Combining the unique properties of SMAs with other materials can create intelligent or smart composites. In this paper, epoxy resin composites filled with Ni–Ti alloy short fibers were developed. Microstructure was observed using digital HF microscope. The dynamic mechanical properties were investigated by measuring the first vibration mode of clamped cantilever beams and by dynamic mechanical analysis (DMA). Moreover, the natural frequency of SMA composites was predicted theoretically. As a result, the temperature dependency of vibration property and DMA characteristics is affected largely due to the addition of SMA short fibers. The vibrational characteristics of SMA composites can be improved by the addition of small amounts of SMA short fibers. The addition of 3.5wt.% of SMA short fiber content to epoxy resin resulted in the maximum increment in both natural frequency and storage modulus. This suggested that there exists an optimum SMA fiber content for vibration characteristics. [Copyright &y& Elsevier]

Abstract: Shape memory alloys (SMAs) possess both sensing and actuating functions due to their shape memory effect, pseudo-elasticity, high damping capability and other remarkable properties. Combining the SMAs with other materials can create intelligent or smart composites by utilizing the unique properties of SMAs. In this paper, epoxy resin composites filled with NiTi alloy short fibers and particles were fabricated and their mechanical properties investigated. Owing to the addition of SMA fillers, the flexural rigidity of SMA/epoxy composites increases. Especially, the storage modulus increases remarkably with increasing filler content in the high temperature region. The experimental results show that the addition of just 3.5% of SMA fillers to epoxy resin resulted in a remarkable increment of storage modulus, which is six times as large as that of epoxy bulk (ER3). The storage modulus reaches the maximum at the SMA phase transformation temperature of approximate 120°C. The loss factor of SMA/ER3 composites increases with the increment of SMA filler contents. Based on the Halpin–Tsai theory, moreover, a model for the laminated plates with SMA fillers is presented to predict the dynamic mechanical properties. Compared to the experimental results, reasonable prediction of the dynamic behavior is obtained based on the present models. [Copyright &y& Elsevier]

The finite‐difference time‐domain (FDTD) algorithm shows disadvantages in bandpass signal simulation with fine structures along a single direction. The reason is that FDTD algorithm exists the Courant–Friedrichs–Levy (CFL) condition and bases on the lowpass‐sampling theorem. Based on the numerical implementation, hybrid implicit‐explicit procedure and complex envelope method are introduced. As a full‐wave simulation method, higher order concept is incorporated into perfectly matched layer (PML) formulation for improving absorption at boundaries of the lattice. For unmagnetized plasma simulation, piecewise linear recursive convolution method is modified according to the bandpass signal. Through numerical example, the proposed algorithm shows considerable performance during the entire simulation which can be concluded from several aspects: (1) It takes advantages of higher order concept which shows enhanced absorption. (2) The proposed algorithm can overcome the CFL condition and maintain stability with the increment of time steps. (3) It shows considerable efficiency and accuracy in simulating structures with fine details along a single direction. (4) It can alleviate time increment problem among implicit algorithms with lower CFL numbers. [ABSTRACT FROM AUTHOR]

Stability of explicit finite-difference time-domain (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 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; and 4) extensively employment in different kinds of materials. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Symmetrical pyramid-shaped ZnO reflect and absorb full-length UV radiation.. • PU prevents the agglomeration of ZnO to achieve long-term use.. • ZnO/PU composite membranes have full-length UV-shielding properties.. • ZnO/PU composite membranes have high temperature stable UV-shielding properties. [ABSTRACT FROM AUTHOR]

Piezoelectric composite hydrogels have been developed as interfaces connecting biological organs and electronic devices owing to their flexibility, biocompatibility, and electromechanical behavior, which enable the conversion of environmental stimuli into electronic signals. This study presents a multifunctional hydrogel that is soft, deformable, conductive, and piezoelectric. Using water as solvent and ZnO carbon nanotube (CNT) modified polyvinyl alcohol/agar/tannin as active ingredient, a one-pot green solution mixing method was used to prepare piezoelectric hydrogel with multi-network structure. The T5C5Z4 composite hydrogel designed in this paper has excellent performance in the sensing test, and can also clearly and accurately generate signals for slight movements of body parts. The T5C5Z4 composite hydrogel also has stable piezoelectric performance. In this paper designs a 100 g ball with a radius of 10 mm that falls freely from different heights and contacts with composite water (6 cm*3 cm*4 mm) to output different electrical signals, and the output voltage also increases with the height with increasing. The composite hydrogel has also been demonstrated as a sensing-detectable, piezoelectrically stimulated flexible bioelectronic materials. [Display omitted] [ABSTRACT FROM AUTHOR]

The use of machine vision methods has rapidly developed for detecting product defects, but it remains challenging to identify shape and color defects as well as the assembly relationship of parts due to occlusion between components and changes in assembly structures. This paper proposed a method for detecting saw chain assembly defects based on residual networks and knowledge coding to achieve parts segmentation and identification of assembly defects. Firstly, we design an adaptive segmentation algorithm for saw chain parts, which uses the Hough transform to locate rivets and completes the image segmentation based on the inherent assembly features between parts. Secondly, A trained ResNet (Residual Network) based deep learning model was used to identify the individual defects of saw chain parts, in which the transfer learning method was used to improve the detection speed of individual defects. Finally, a parallel inference method based on a knowledge encoding matrix is proposed for detecting part defects and constructing a sparse matrix to locate assembly defects. Evaluating the proposed method in building a saw chain testing platform. Results show that the proposed method can achieve real-time and high-precision detection requirements in different application scenarios. The detection accuracy on individual and assembly defects reaches 94.2% and 89.2%, respectively, which is better than the current state-of-the-art object detection models. Assembly defect detection methods are an important reference for inspecting other types of simple assemblies in the industry. [ABSTRACT FROM AUTHOR]

To prevent CuNPs oxidation, we studied their interaction between graphene oxide (GO) sheets, forming CuNPs@GO composites via a liquid-phase reduction method, and resulting sandwich structures. The limited GO interlayer distance controls the size of CuNPs (∼ 10 nm diameter) during the reduction process. The large surface area of GO sheets provide enough space for CuNPs against their aggregation. To confirm the sandwich structure can protect CuNPs from oxidation, the air stability and high-temperature stability of CuNPs@GO composites were evaluated. The result shows that the composites exhibit no oxidation sign following exposure to dry air for at least 21 weeks or 90 °C. Simultaneously, the synthesized composites show long-term stable conductivity. This sandwich structure composites provide a potential research direction for fabricating CuNPs with high antioxidant stability and long-term stable conductivity. • GO sheets cover CuNPs forming sandwich composites. • The diameter of CuNPs is about 10 nm. • Composites exhibit no signs of oxidation exposed to dry air for at least 21 weeks. • Composites show long-term stable conductivity. • Heating the composites at 90 °C for 30 min, the CuNPs exhibit no signs of oxidation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this work, silver nanoparticles/graphene oxide nanoscroll composites (Ag/GO nanoscroll composites) were fabricated by a one-step method at room temperature. The GO sheets were cut into pieces by the silver nanoparticles (AgNPs) due to their catalytic activity, and then the GO pieces rolled up resulting from the intermolecular hydrogen bonds. Transmission electron microscope images show that the Ag/GO nanoscroll composites have open-ended tubular hollow structures. The Escherichia coli (E. coli) was used to evaluate the antibacterial activity of synthesized nanoscroll composites. After against the E. coli for 3 days, the inhibition rate of Ag/GO nanoscroll composites can still up to 99.99%. This attributes to the open-ended tubular hollow structures, providing abundant channels and space to prevent AgNPs from aggregating and oxidizing. The result exhibits that the Ag/GO nanoscroll composites have the potential for long-lasting antibacterial activity. So, the Ag/GO nanoscroll composites can be applied in antibacterial materials for long-lasting use. Schematic illustration of the silver nanoparticles/graphene oxide nanoscroll composites synthesis process. Image 1 • Ag/GO nanoscroll composites are synthesized by a one-step method. • The cut pieces of GO were rolled up by the force of intermolecular hydrogen bonds. • The size of silver nanoparticles is from 4 to 10 nm. • The obtained composites have the potential for long-lasting antibacterial activity. [ABSTRACT FROM AUTHOR]

By incorporating a complex envelope (CE) method, higher order formulation, and approximate Crank–Nicolson (CN) procedure, unconditionally stable complex frequency shifted perfectly matched layer (CFS-PML) implementation is proposed for anisotropic gyrotropic plasma bandpass simulation in open region problems. More precisely, the CE based higher order CN approximate-factorization-splitting (AFS) PML implementation is introduced to terminate the unbounded finite-difference time-domain (FDTD) lattice. The proposed implementation can not only improve computational efficiency but also enhance the absorption at boundaries during the whole bandpass simulation. Numerical examples which include plasma slab models and ridge waveguide structures are introduced to further demonstrate accuracy, absorption, and efficiency. It can be concluded in the results that our proposal can achieve considerable performance in modeling bandpass signals, improving computational efficiency, enhancing absorption, and maintaining remarkable accuracy. Meanwhile, it can be observed that the proposed implementation is stable when the time step surpasses far beyond the Courant–Friedrichs–Lewy condition. [ABSTRACT FROM AUTHOR]

[Display omitted] • An effective pathway for recycling end-of-life batteries. • A hybrid device achieved self-charging in situ and storing hydro-energy. • Provide a high voltage of 1.5 V within 20 s by simply adding a tap water drop. • Increasing device lifespan by controlling the redox reactions and self-corrosion. • The vertical device exhibits considerable potential for practical applications. Aluminum–air (Al–air) battery-inspired water-movement-based devices have emerged as promising candidates for green conversion because of their high specific energy and theoretical voltage. However, the self-corrosion of Al remains a huge barrier to hinder their large-scale applications. This study developed a novel hybrid device by merging an Al–air battery and a solid-state hydrocapacitor using a graphene sheet/carbon particles (GSCP) composite anode. A plant fiber layer separated the Al electrode from the poly(vinyl alcohol)/phosphoric acid electrolyte, which could greatly reduce Al self-corrosion. Additionally, the all-solid-state working condition of the device prevented negative leakage or undesirable deformation of the electrolyte when not in use. Moreover, the microporous GSCP electrode was synthesized through a green, cost-effective, and nonhazardous process by compositing exfoliated graphene with micro/nano-sized carbon particles processed from recovered spent battery parts. Remarkably, it could achieve a high-level open-circuit voltage of 1.5 V by simply dropping small-scale water droplets and daily repeating for over a month. Simultaneously, the stored energy was maintained for approximately 2.8 h due to water evaporation. Simply stacking cells in an array could amplify the output to power commercial devices. As a breakthrough, the device successfully operated as a human-breathing transducer. To explain the operational principle, a possible model based on the capillarity, ion diffusion, and streaming potential mechanisms was proposed and discussed comprehensively. This novel hybrid device provides considerable insight for future water-movement-based devices and small portable/wearable electronics and facilitates the development of green energy conversion systems. [ABSTRACT FROM AUTHOR]

The 3-D carbon fiber reinforced resin matrix composite tubes were designed and formed via a type of novel braiding-winding-pultrusion processing technique. The effects of temperature environments (lower, normal and high temperature) on the axial compressive mechanical responses and damage behaviors of novel 3-D braiding-winding-pultrusion composite (BWPC) tubes were investigated. It was found that the BWPC tubes combined with three forming process features has a complex compression failure mode. The CT image was show that the fiber damage methods of braiding, winding and pultrusion layer were different, and the structural design of the tubes directly affects the axial bearing capacity. The axial quasi-static compression failures of tubes were the flowering failure of petals at one end. The fiber fracture and fiber block falling off was more apparent when under the lower temperature environment. The research also indicated that, when the temperature exceeds 180 °C, the resin softening and stratification will be destroyed. [Display omitted] [ABSTRACT FROM AUTHOR]

System incorporated (SI) direct-splitting (DS) algorithm is proposed to efficiently simulate periodic nonuniform structures in open regions. Based on the digital signal processing technique, the proposed algorithm cannot only maintain the calculation stability with the enlargement of time steps but also tighten the finite-difference time-domain (FDTD) implementation. An alternative periodic boundary condition (APBC) algorithm is proposed according to the unconditionally stable SIDS algorithm to analyze the periodic structures. To calculate multiscale nonuniform domains, domain decomposition (DD) method is proposed to discretize the entire computational domain into several sub-regions according to the SIDS algorithm. Furthermore, higher order perfectly matched layer (PML) is incorporated with the proposed algorithm for the boundary termination in open regions. Periodic nonuniform metamaterial structure is employed as an example to demonstrate the efficiency, absorption and accuracy. Through comparison with the other algorithms, the proposed algorithm can receive the most considerable performance from each aspect. By employing the proposed APBC algorithm, sparse matrix can be converted to tri-diagonal matrix which alleviates the time increment problem in periodic structures calculation. Through introducing the proposed domain decomposition method, size of nonuniform domains can be reduced compared with the uniform discretization which leads to the decrement of simulation duration and resources. [ABSTRACT FROM AUTHOR]

Dynamic behaviors of double-walled carbon nanotubes (DWCNTs) embedded to elastic foundation under a moving nanoparticle are studied based on the nonlocal elasticity theory. The DWCNTs embedded an elastic medium are considered as two-scale shell model coupled with the van der Waals (vdW) interaction between two adjacent nanotubes. The elastic medium surrounding DWCNTs is formulated as Winkler spring model. Using the proposed models and solutions, we investigate the influences of various parameters on the mechanical properties, such as the nanoparticle delivery, the elastic foundation, and nonlocal coefficient. The dynamic response of DWCNTs depends largely by the moving velocity of nanoparticle, the stiffness of the elastic medium, and the nonlocal coefficient. The results show that increasing constant of elastic medium causes deceases in the dynamic deflection of DWCNTs due to the improved stiffness property. The influence of the nonlocal scaling parameter on the dynamic response of the flexural displacement is enhanced with increasing nanoparticle velocity. [Display omitted] • An analysis model of DWCNTs under a moving nanoparticle is proposed to investigate the dynamic response. • The DWCNTs are considered as double shell nanotubes coupled with the vdW force. • Winkler spring model is used for modeling the connection between DWCNTs and medium foundations. • Closed-form solutions are derived to investigate the effects of various parameters on the dynamic response. [ABSTRACT FROM AUTHOR]

Silver (Ag) nanoparticles fabricated by chemical reduction process were grafted onto the surface of carbon nanotubes (CNTs) to prepare hybrid nanocomposites. The Ag/CNT hybrid nanomaterials were characterized using transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The Ag/CNT hybrid nanomaterials were then loaded in paraffin wax, and pressed into toroidal shape with thickness of 1 mm to evaluate their complex permittivity and complex permeability by scattering parameters measurement method in reflection mode using vector network analyzer. The reflection loss of the samples was calculated according to the transmission line theory using their measured complex permittivity and permeability. The minimum reflection loss of the Ag/CNT hybrid nanocomposite sample with a thickness of 1 mm reached 21.9 dB (over 99 % absorption) at 12.9 GHz, and also exhibited a wide response bandwidth where the frequency bandwidth of the reflection loss of less than −10 dB (over 90 % absorption) was from 11.7 to 14.0 GHz. The Ag/CNT hybrid nanocomposite with thickness of 6 mm showed a minimum reflection loss of ~−32.1 dB (over 99.9 % absorption) at 3.0 GHz and was the best absorber when compared with the other samples of different thickness. The reflection loss shifted to lower frequency as the thickness of the samples increased. The capability to modulate the absorption band of these samples to suit various applications in different frequency bands simply by manipulating their thickness indicates that these hybrid nanocomposites could be a promising microwave absorber. [ABSTRACT FROM AUTHOR]

Abstract: In this work, wave propagation characteristics of double-layer graphene sheets (DLGSs) are investigated using nonlocal Mindlin–Reissner plate theory. The vibrational modes are divided into in-phase mode and anti-phase mode, which is a special feature of DLGSs. The wave propagation behaviors in DLGSs in the in-phase mode and anti-phase mode are different. Cutoff frequency and escape frequency are analyzed in this study. In particular, the escape frequencies with different nonlocal parameters are less than that obtained from nonlocal Timoshenko beam theory and different between the in-phase mode and anti-phase mode. This is because shear forces consider the nonlocal effects in nonlocal Mindlin–Reissner plate theory, but do not consider the nonlocal effects in nonlocal Timoshenko beam theory. Thus, the present work will provide a better representation of wave propagation in DLGSs and will have implications in their application as electromechanical oscillators. [Copyright &y& Elsevier]

Double-layer graphene sheets (DLGSs) have potential applications as nanoelectromechanical systems (NEMS) resonators due to their specific carrier spectrum of electrons. In this study, analysis of the vibration modes of NEMS resonators using simply supported circular DLGSs has been undertaken based on nonlocal thin plate theory. Considering the properties of DLGSs, the vibration mode of circular DLGSs can be divided into an in-phase mode (IPM) and an anti-phase mode (APM). The range of resonance frequencies in the IPM is much larger than in the APM because of the influence of van der Waals forces. Nonlocal effects significantly influence the resonance frequency of circular DLGSs in higher vibration modes and at lower aspect ratios. [ABSTRACT FROM AUTHOR]

Abstract: Graphene nanoribbons (GNRs), the finite-wide counterparts of crystalline graphene sheets, have been potential materials used in nano-devices because of their excellent electronic, thermal and mechanical properties. In this work, a theoretical analysis of nonlocal elasticity theory for the free vibrational characteristics of embedded double-layer GNRs (DLGNRs) is proposed based on continuum and Winkler spring models. We find two types of vibrational modes, in-phase mode (IPM) and anti-phase mode (APM). The results show that the vibrational properties of DLGNRs show different behaviors in IPM and APM. The natural frequencies of DLGNR embedded in an elastic matrix are significantly influenced by nonlocal effects, the aspect ratio of DLGNRs and the Winkler foundation modulus. [Copyright &y& Elsevier]

Abstract: The mechanical stability of graphene nanoribbons (GNRs) is an important mechanical property to study, when GNRs are used as components in sensors or other nanodevices. In this paper, nonlocal effects are considered in a continuum model based theoretical analysis of the critical buckling stress of cantilevered double-layer GNRs (DLGNRs) that are subjected to an axial compressive load. The results show that the nonlocal effect has an inverse relationship with the buckling stress, and the nonlocal effect decreases with increasing aspect ratio of DLGNRs. Moreover, to the best of our knowledge this is the first report that, for DLGNRs in anti-phase modes, lower buckling mode can endure higher buckling stress because of van der Waals (vdW) interaction. [Copyright &y& Elsevier]

Abstract: A novel one-step process using potassium persulfate (KPS) as oxidant is proposed in this paper to prepare water-soluble single-walled carbon nanotubes (SWNTs). The process without the need for organic solvents and acids is a low-cost, eco-friendly, facile method. Morphology observation by atomic force microscopy (AFM) indicates that the KPS-treated SWNTs were effectively debundled without obvious shortening in their length. The functional groups and thermal stability of the treated SWNTs were analyzed by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). XPS results show that several functional groups such as potassium carboxylate (–COOK), carbonyl (–Cdroxyl (–C–OH) groups were formed on the surfaces of the SWNTs, while the TGA results reveal that the quantity of the functional groups can reach to approximately 20%. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) have attracted considerable attention as nanomechanical resonators because of their exceptional mechanical properties and nanoscale dimensions. In this study, a novel CNT-based probe is proposed as an efficient nanoforce sensing nanomaterial that detects external pressure. The CNT probe was designed to be fixed by clamping tunable outer CNTs. By using the mobile-supported outer CNT, the position of the partially clamped outer CNT can be controllably shifted, effectively tuning its resonant frequency. This study comprehensively investigates the modeling and vibration analysis of gigahertz frequencies with loaded CNTs used in sensing applications. The vibration frequency of a partially clamped CNT probe under axial loading was modeled using continuum mechanics, considering various parameters such as the clamping location, length, and boundary conditions. In addition, the interaction between external forces and CNT resonators was investigated to evaluate their sensitivity for force sensing. Our results provide valuable insights into the design and optimization of CNT-based nanomechanical resonators for high-performance force sensing applications.

Hydrogen is the most environmentally friendly and cleanest fuel that has the potential to supply most of the world's energy in the future, replacing the present fossil fuel-based energy infrastructure. Hydrogen is expected to solve the problem of energy shortages in the near future, especially in complex geographical areas (hills, arid plateaus, etc. ) and harsh climates (desert, ice, etc. ). Thus, in this report, we present a current status of achievable hydrogen fuel based on various scopes, including production methods, storage and transportation techniques, the global market, and the future outlook. Its objectives include analyzing the effectiveness of various hydrogen generation processes and their effects on the economy, society, and environment. These techniques are contrasted in terms of their effects on the environment, manufacturing costs, energy use, and energy efficiency. In addition, hydrogen energy market trends over the next decade are also discussed. According to numerous encouraging recent advancements in the field, this review offers an overview of hydrogen as the ideal renewable energy for the future society, its production methods, the most recent storage technologies, and transportation strategies, which suggest a potential breakthrough towards a hydrogen economy. All these changes show that this is really a profound revolution in the development process of human society and has been assessed as having the same significance as the previous industrial revolution., Competing Interests: The authors declare that they have no known competing financial interests., (This journal is © The Royal Society of Chemistry.)

Small-diameter artificial blood vessels are increasingly being used in clinical practice. However, these vessels are prone to thrombus, and it is necessary to improve blood compatibility. Surface coating is one of the commonly used methods in this regard. Inspired by the biomimicry of mussels, the use of deposition technology to obtain coating coverage on the surface of fibers has significantly piqued the interest of researchers recently. In this study, tubular scaffolds consisting of a composite of poly(caprolactone), cellulose acetate, and tannic acid (TA) were electrospun, and then the scaffolds were treated with different Fe(III) solutions (iron(III) chloride hexahydrate (FeCl 3 ' 6H 2 O)) to obtain four tubular scaffolds: F0, F5, F15, and F45. According to scanning electron microscopy (SEM) and field emission-SEM results, TA/Fe(III) complex is coated on the fiber of the scaffold after post-treatment; the fiber surface morphology changes with different Fe(III) concentrations. This provides designability to the performance of tubular scaffolds. The tensile strength of the F5 tubular scaffold (3.33 MPa) is higher than that of F45 (3.14 MPa), while the strain (83.9%) of the F45 tubular stent was 2.26 times that of the F5 (37.2%). In addition, cytotoxicity and antithrombotic performance were evaluated. The test results show that surface TA/Fe(III) coating treatment can affect the cytotoxicity and anticoagulation performance of the scaffold surface. The biomimetic TA/Fe(III) coating of mussels used in this study improves the performance of artificial blood vessels.

Carbon-based nanomaterials, including carbon nanotubes (CNTs) and graphene sheets (GSs), have garnered considerable research attention owing to their unique mechanical, physical, and chemical properties compared with traditional materials. Nanosensors are sensing devices with sensing elements made of nanomaterials or nanostructures. CNT- and GS-based nanomaterials have been proved to be very sensitive nanosensing elements, being used to detect tiny mass and force. In this study, we review the developments in the analytical modeling of mechanical behavior of CNTs and GSs, and their potential applications as next-generation nanosensing elements. Subsequently, we discuss the contributions of various simulation studies on theoretical models, calculation methods, and mechanical performance analyses. In particular, this review intends to provide a theoretical framework for a comprehensive understanding of the mechanical properties and potential applications of CNTs/GSs nanomaterials as demonstrated by modeling and simulation methods. According to analytical modeling, nonlocal continuum mechanics pose small-scale structural effects in nanomaterials. Thus, we overviewed a few representative studies on the mechanical behavior of nanomaterials to inspire the future development of nanomaterial-based sensors or devices. In summary, nanomaterials, such as CNTs and GSs, can be effectively utilized for ultrahigh-sensitivity measurements at a nanolevel resolution compared to traditional materials.

Hybrid nanocomposites of silver nanoparticles and multiwalled carbon nanotubes (AgNPs/MWCNTs) were successfully synthesized by a green one-step method without using any organic solvent. The synthesis and attachment of AgNPs onto the surface of MWCNTs were performed simultaneously by chemical reduction. In addition to their synthesis, the sintering of AgNPs/MWCNTs can be carried out at room temperature. The proposed fabrication process is rapid, cost efficient, and ecofriendly compared with multistep conventional approaches. The prepared AgNPs/MWCNTs were characterized using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The transmittance and electrical properties of the transparent conductive films (TCF_Ag/CNT) fabricated using the prepared AgNPs/MWCNTs were characterized. The results showed that the TCF_Ag/CNT film has excellent properties, such as high flexible strength, good high transparency, and high conductivity, and could therefore be an effective substitute for conventional indium tin oxide (ITO) films with poor flexibility.

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.

Evaluation of impact characteristics of carbon nanomaterials is very important and helpful for their application in nanoelectromechanical systems (NEMS). Furthermore, disclination lattice defects can generate out-of-plane deformation to control the mechanical behavior of carbon nanomaterials. In this study, we design novel stable wavy graphene sheets (GSs) using a technique based on origami and kirigami to control the exchange of carbon atoms and generate appropriate disclinations. The impact characteristics of these GSs are evaluated using molecular dynamics (MD) simulation, and the accuracy of the simulation results is verified via a theoretical analysis based on continuum mechanics. In the impact tests, the C 60 fullerene is employed as an impactor, and the effects of the different shapes of wavy GSs with different disclinations, different impact sites on the curved surface, and different impact velocities are examined to investigate the impact characteristics of the wavy GSs. We find that the newly designed wavy GSs increasingly resist the kinetic energy (KE) of the impactor as the disclination density is increased, and the estimated KE propagation patterns are significantly different from those of the ideal GS. Based on their enhanced performance in the impact tests, the wavy GSs possess excellent impact behavior, which should facilitate their potential application as high-impact-resistant components in advanced NEMS.

Highly regulated Fe 3 O 4 -polyelectrolyte-modified polyaniline (Fe 3 O 4 -PE@PANI) hollow sphere nanocomposites were successfully synthesized using an electrostatic self-assembly approach. The morphology and structure of the Fe 3 O 4 -PE@PANI nanocomposites were characterized using field-emission scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray powder diffraction, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The results showed that the as-prepared nanocomposites had well-defined sizes and shapes, and the average size is about 500 nm. The assembly process was investigated. Magnetization measurements showed that the saturation magnetization of the nanocomposites was 38.6 emu g -1 . It was also found that the Fe 3 O 4 -PE@PANI nanocomposites exhibited excellent reflection loss abilities and wide response bandwidths compared with those of PANI hollow spheres in the range 0.5-15 GHz. The Fe 3 O 4 -PE@PANI nanocomposites are, therefore, promising for microwave absorption applications.

In this paper, a theoretical analysis of the radial breathing mode (RBM) of carbon nanotubes (CNTs) subjected to axial pressure is presented based on an elastic continuum model. Single-walled carbon nanotubes (SWCNTs) are described as an individual elastic shell and double-walled carbon nanotubes (DWCNTs) are considered to be two shells coupled through the van der Waals force. The effects of axial pressure, wave numbers and nanotube diameter on the RBM frequency are investigated in detail. The validity of these theoretical results is confirmed through the comparison of the experiment, calculation and simulation. Our results show that the RBM frequency is linearly dependent on the axial pressure and is affected by the wave numbers. We concluded that RBM frequency can be used to characterize the axial pressure acting on both ends of a CNT.