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At present, China’s energy distribution and economic development are extremely unbalanced. In order to make rational use of resources, China has promoted the “west to East power transmission” and “north to South Power Transmission” pattern. HVDC transmission has obvious advantages in this long-distance transmission, but there are some shortcomings in the traditional LCC-HVDC system. Therefore, a new system LCL-HVDC is proposed. Firstly, some advantages of the system are introduced; secondly, LCC-HVDC and LCL-HVDC models are built in Simulink, in which the current distortion rate of valve side winding of converter transformer is measured; finally, compared with LCC-HVDC, the loss of LCL-HVDC converter transformer is studied by using method 2 recommended by IEEE standard, and the kn value of the new system is calculated.

This work proposes an approach to fabricate flexible transparent ultraviolet (UV)-shielding membrane by casting method, which uniformly disperses pristine zinc oxide nanoparticles (NPs) in low-density polyethylene (LDPE). The critical conditions for film fabrication, such as casting temperature, LDPE concentration in the solution, dissolution time, NP concentration, and post hot press cooling processes, are systematically studied. It is found that the casting temperature needs to be close to the melting temperature of LDPE, namely, 115°C, so that transparent film formation without cracks can be guaranteed. NP agglomerates are suppressed if the polymer concentration is controlled below 6%. For good dispersion of NPs, LDPE has to be swelled or unentangled enough in the solution (close to 200 h dissolution time), and then the NP agglomerates can be diminished due to the diffusion of the NPs into the polymer gel (322 h dissolution time). When the NPs are well-dispersed in the LDPE film, the film can completely shield UV light while allowing high transmissivity for the visible light. As the concentration of NPs in the film increases from 4 to 6%, the transmissivity of the film decreases, the tensile strength increases, and the tensile failure strain decreases.

(Li1+, Al3+) co-doped Ni0.5Zn0.5Fe2O4 ferrites, Ni0.5-xZn0.5-xLixAlxFe2O4 (x = 0.000, 0.025, 0.050 and 0.100), were synthesized by the sol-gel auto-combustion method. X-ray diffraction (XRD), field emission scanning electronic microscope (FESEM), vibrating sample magnetometer (VSM) and LCR meter were used to investigate the structural, magnetic and dielectric properties. Results of XRD and SEM indicate that both doping amount and calcination temperature play significant roles in crystal structure and grain growth. Also, it can be observed that the saturation magnetization and the coercivity change in a noticeable manner. The Ni0.475Zn0.475Li0.025Al0.025Fe2O4 ferrite sintered at 1200 °C has a relatively low coercivity value (62.93 Oe) and the largest saturation magnetization (110.95 emu/g). Besides, dielectric behavior is also improved by Li1+ and Al3+ co-doping.

Rapid developments in the electric industry have promoted an increasing demand for lithium resources. Lithium in salt lake brines has emerged as the main source for industrial lithium extraction, owing to its low cost and extensive reserves. The effective separation of Mg2+ and Li+ is critical to achieving high recovery efficiency and purity of the final lithium product. This paper summarizes Mg2+/Li+ separation materials and methods in the field of lithium recovery from salt lake brines. The review begins with an introduction to the global distribution and demand for lithium resources, followed by a description of the materials used in various separation techniques, including precipitation, adsorption, solvent extraction, nanofiltration membrane, electrodialysis, and electrochemical methods. A comparison, analysis, and outlook of such methods are comprehensively discussed in terms of principles, mechanisms, synthesis/operation, development, and industrial applications. We conclude with a presentation of challenges and insights into the future directions of lithium extraction from salt lake brines. A combination of the advantages of various materials is the most logical step toward developing novel methods for extracting lithium from brines with high separation selectivity, stability, low cost, and environmentally friendly characteristics.

(Li1+, Zn2+ and La3+) co-substituted NiFe2O4 ferrite ceramics (Ni0.8-xZnxLi0.1La0.1Fe2O4, x = 0.0, 0.2, 0.4, 0.6, 0.8) were prepared by the sol-gel auto-combustion method. The structural properties were investigated by X-ray diffraction and field emission scanning electronic microscope techniques. Vibrating sample magnetometer and LCR meter were used to probe magnetic and dielectric properties. A relatively high value of saturation magnetization (105.94 emu/g) can be achieved in Ni0.4Zn0.4Li0.1La0.1Fe2O4 sample sintered at 1100 °C. In addition, the soft magnetic properties are also enhanced due to a reduced coercivity value. Also, dielectric behavior is improved and all the results show that co-substitution with Li1+, Zn2+ and La3+ ions as well as modulation via Zn2+ ions has a great impact on the properties of Ni ferrites.

Although many kinds of flexible piezoelectric materials have been developed, there were few reports on flexible multifunctional nanofibers for energy harvesting. In this study, we prepared multifunctional nanofibers from lead zirconate titanate particles and shape memory polyurethane by electrospinning. The resulting nanofibers had both piezoelectric and shape memory effects. To improve the dispersion, lead zirconate titanate particles were modified by silane coupling agents. The lead zirconate titanate/shape memory polyurethane nanofibers were used to harvest energy from sinusoidal vibrations, and the lead zirconate titanate 80 wt% sample produced voltages of 120.3 mV (peak-to-peak). Taking advantage of the shape memory effect, the lead zirconate titanate/shape memory polyurethane nanofibers can be easily deformed into desired shapes and revealed the potential for realizing energy harvesting in complex structures.

This work performs a detailed theoretical analysis for low-concentration solar thermophotovoltaic (STPV) system with both solar absorber and thermal emitter made of previously-developed selective metafilms along with a cavity reflector for performance enhancement. When paired with an InGaAsSb cell, the initial metafilm structure shows an STPV system efficiency of 7.1% at 50 suns, where about half of the incident solar energy is lost through the thermal emission from the top surface of the absorber according to energy loss analysis. In order to enhance the STPV system performance, the metafilm layer thicknesses of the solar absorber and those of the thermal emitter are optimized at 50 suns, increasing the STPV system efficiency from 7.1% to 10.2%. Moreover, a cavity reflector above the absorber is considered to recycle the infrared photons emitted from the top surface of the absorber. The effects of the size and the reflectivity of the cavity reflector on the efficiency are discussed. The results show that, the efficiency of the optimized metafilm based STPV system at 50 suns can be increased from 10.2% to 17.4% with a cavity made of ideal reflectors.

g-C 3 N 4 with uniformly porous structure is very attractive owing to its special surface and interface properties in photocatalytic field. Herein, uniformly porous sulfur doped C 3 N 4 /carbon dot (S-C 3 N 4 /C-dot) composite with narrow pore size distribution was successfully synthesized via a facile one-step calcination of S-C 3 N 4 precursor with the prefabricated C-dot, rather than employing any other template materials. Experiments found, it was the C-dot that served as the pore-forming agent via its own oxidation into gaseous products, and ratio of C-dot in the raw material played a key role in controlling the crystal structure, morphology and photocatalytic property of the final products. With the optimum ratio, the obtained S-C 3 N 4 /C-dot composite exhibited a superior activity in antibiotics degradation compared with pure S-C 3 N 4 , which was attributed to the unique pore structure, large specific surface area, strong visible light absorption and less recombination of electron-hole pairs. In addition, trapping experiments and intermediate product analyses were also carried out to understand the antibiotics removal mechanism and pathways. This study is very helpful to deeply understand the function of C-dot decoration, and declare the great potential of g-C 3 N 4 in practical water purification.

This study puts forward a new way to produce montmorillonite immobilized bimetallic nickel-iron nanoparticles by dry in-situ hydrogen reduction method in the non-liquid environment, which effectively inhibits the oxidation of iron and nickel during the synthesis process and improves the reactivity of the material. The degradation of 4-Chlorophenol (4-CP) was investigated to examine the catalytic activity of the material. The morphology and crystal properties of the montmorillonite-templated Fe/Ni bimetallic particles were explored by using scanning electron microscopy, transmission electron microscopy, X-ray diffraction studies, and energy dispersive X-ray spectroscopy analysis. Results suggest that Fe and Ni particles were homogeneously dispersed on the montmorillonite. The optimization of Ni content and reduction temperature over the degradation of 4-CP was also studied. The introduction of Ni intensely improved the degradation of 4-CP and reached over 90% when Ni content was 28.5%. The degradation rate increased significantly with the increase of reduction temperature and showed maximum activity at the reduction tempreature of 800 °C. This study offers a new method to fabricate montmorillonite immobilized Fe/Ni bimetallic nanoparticles in the non-liquid environment and the composites exhibited high degradation activity to chlorinated organic compounds.

Multi-scale permutation entropy (MPE) has been proven to be an effective nonlinear dynamic analysis tool for complexity and irregularity evaluation of rolling bearing. Nevertheless, MPE still has some issues that need to be addressed. First, the coarse grained process used in MPE will shorten the length of time series and result in mode information loss, especially for short time series. Second, different patterns of a symbol cannot be distinguished by permutation entropy and MPE. Inspired by the thought of composite coarse graining and weighted permutation entropy, the composite multi-scale weighted permutation entropy (CMWPE) methodology is proposed in this paper. Compared with MPE, CMWPE preserves much more useful information by adding the weighted factor and using composite coarse graining to optimize the process of coarse-gained time series, where multiple time series information is considered for the same scale factor. The simulation synthetic signals are used to demonstrate the effectiveness of CMWPE and the results show that CMWPE has less dependence on data length and the estimated entropy values are much more stable than the other existing methods. Based on CMWPE, a new intelligent fault diagnosis scheme for rolling bearing is proposed with combination of extreme learning machine. Finally, the proposed fault diagnosis method is applied to two diagnostic cases of rolling bearing and the results verified the effectiveness and superiority of the proposed approach to MPE and MWPE.

Composite masterbatches of polyphenylene sulfide (PPS) with functionalized graphene nanoplatelets (GNPs) were prepared by melt blending via a twin-screw extruder. The structure and morphology of composite masterbatches were characterized by scanning electron microscopy and X-ray diffraction analysis. The PPS/functionalized GNPs composite fibers were then manufactured by a self-made spinning equipment via melt spinning. The oxidation resistance and other properties of PPS composite fibers were also examined. The results showed that the pure PPS fibers exhibited smooth surface, whereas the surface of PPS/functionalized GNPs composite fibers was rough. The addition of functionalized GNPs could be acted as heterogeneous nucleating agents to improve the crystallization and increase the degree of crystallinity. The retention rate of breaking strength of PPS/functionalized GNPs composite fibers could maintain up to 85% after the oxidation treatment. The improvement in the oxidation resistance of PPS/functionalized GNPs composite fibers is the results of comprehensive effects characterized by the X-ray photoelectron spectroscopy analyses. The addition of functionalized GNPs could limit the damage of the C–S group and retard the generation of sulfuryl groups (–SO–) during the oxidation treatment. The chemical combination of the elements sulfur (S) and oxygen (O) could also be restricted, thus weakening the oxidation activity.

Nature employs supramolecular self-assembly to organize many molecularly complex structures. Based on this, we now report for the first time the supramolecular self-assembly of 3D lightweight nanocellulose aerogels using carboxylated ginger cellulose nanofibers and polyaniline (PANI) in a green aqueous medium. A possible supramolecular self-assembly of the 3D conductive supramolecular aerogel (SA) was provided, which also possessed mechanical flexibility, shape recovery capabilities, and a porous networked microstructure to support the conductive PANI chains. The lightweight conductive SA with hierarchically porous 3D structures (porosity of 96.90%) exhibited a high conductivity of 0.372 mS/cm and a larger area-normalized capacitance (Cs) of 59.26 mF/cm2, which is 20 times higher than other 3D chemically cross-linked nanocellulose aerogels, fast charge-discharge performance, and excellent capacitance retention. Combining the flexible SA solid electrolyte with low-cost nonwoven polypropylene and PVA/H2SO4 yielded a high normalized capacitance (Cm) of 291.01 F/g without the use of adhesive that was typically required for flexible energy storage devices. Furthermore, the supramolecular conductive aerogel could be used as a universal sensitive sensor for toxic gas, field sobriety tests, and health monitoring devices by utilizing the electrode material in lightweight supercapacitor and wearable flexible devices.

Empirical mode decomposition (EMD) is an effective tool for breaking down components (modes) of a nonlinear and non-stationary signal. Recently, a newly adaptive signal decomposition method, namely extreme-point weighted mode decomposition (EWMD), was put forward to improve the performance of EMD, in particular, to resolve the over- or undershooting issue associated with the large amplitude variations. However, similar to EMD, EWMD also suffers the mode mixing problem caused by intermittence or noisy signals. In this paper, inspired by complementary ensemble EMD (CEEMD), a noise-assisted data analysis method called partial ensemble extreme-point weighted mode decomposition (PEEWMD) is proposed to eliminate the mode mixing problem and enhance the performance of EWMD. In the proposed PEEWMD method, firstly white noises in pairs are added to the targeted signal and then the noisy signals are decomposed using the EWMD method to obtain the intrinsic mode functions (IMFs) in the first several stages. Secondly, permutation entropy is employed to detect the components that cause mode mixing. The residual signal is obtained after the identified components are separated from the original signal. Lastly, the residual signal is fully decomposed by using the EWMD method. The proposed PEEWMD method is compared with original EWMD, ensemble EWMD (EEWMD) and CEEMD using simulated signals. The results demonstrate that PEEWMD can effectively restrain the mode mixing issue and generates IMFs with much better performance. Based on that the PEEWMD and envelope power spectrum based fault diagnosis method was proposed and applied to the rubbing fault identification of rotor system and the fault diagnosis of rolling bearing with inner race. The result indicates that the proposed method of fault diagnosis gets much better effect than EMD and EWMD.

Highly aligned nonwoven vapor grown carbon fibre (VGCF) based polyurethane (PU) fibrous membrane (VGCF@PUFM) was fabricated by rotation spinning based on DMF-H2O exchange for directional microwave shielding. This VGCF@PUFM showed obviously different electrical conductivity and mechanical strength in parallel and perpendicular directions. Variational microwave shielding effectiveness (SE) could be observed by changing the rotation angles of VGCF@PUFM with vibrational direction of electromagnetic (EM) wave. There was the shielding difference more than 10 dB (above 20 dB in 0°, below 8 dB in 90°). Greater shielding effectiveness could be expected by enhancing the anisotropy of electrical conductivity of the VGCF@PUFM. In addition, oriented alignment of VGCF in fibre is promising for further improvement of the electrical conductivity in fibre direction.

In this paper, a Dual-Equal-Collision-Probability-Curve (DECPC) method is proposed for spacecraft close-range safe proximity considering complex shapes. The Equal-Collision-Probability-Curve (ECPC) method models the spacecraft as spheres and the complex shape of the main spacecraft deteriorates the safety performance of the space mission. In terms of this problem, the DECPC method is proposed to generate the collision avoidance maneuvers in the presence of complex shape. Furthermore, the geometrical shape of the main spacecraft is assumed to consist of one big main circle and some small gaps in this paper. Then, the big main circle generates the repulsive force and the gaps engenders the attractive force. Combing the repulsive force with the attractive force, the ultimate avoidance force is achieved. Subsequently, an improved Linear Quadratic Regular (ILQR) is designed to track the reference trajectory and the stability of the overall close-loop control system is proved by the Lyapunov-based method. Numerical simulations are performed in a close-range operation environment and verify the validity of the proposed DECPC avoidance method with the ILQR controller.

Herein we present our research on generation of silver nanoparticles (AgNPs) on cellulose nanofibers by thermal treatment and DMF as reducing agents. The cellulose (CE) nanofibers were prepared by deacetylation of electrospun cellulose acetate (CA) nanofibers which were subsequently silver coated using AgNO3 followed by thermal and DMF induced reduction processes. The samples were characterized with scanning electron microscopy (SEM), Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and antibacterial assays. Effect of these methods on mechanical properties, thermal stabilities (DTA analysis) and swelling of the CE nanofibers were also studied. Both the processes were effective and efficient in generation of AgNPs on CE nanofibers with higher contents and very good spatial distributions. The XRD, XPS and TEM results evidenced formation metallic AgNPs. TEM images depicted the CE nanofibers highly decorated with spherical AgNPs. The DMF induced process generated AgNPs with comparatively larger sizes. The antibacterial results confirmed excellent antibacterial performance of the CEAgNPs against S. aureus and E. coli. The CEAgNP nanofibers well decorated with AgNPs having good spatial distribution and excellent antibacterial performance suggests CEAgNPs as promising candidate for efficient antimicrobial activities.

Currently available synthetic grafts demonstrate moderate success at the macrovascular level, but there are still challenges at small vascular scale (inner diameter of less than 6 mm). In this paper, silk fibroin (SF)/polyurethane (PU)/SF three-layer drug carrier nanofibrous tubes were developed for blood vessel repair with several advantages over existing designs. Our design consisted of a bionic three-layer microtube that was synthesized from the drug carrier SF and oligomeric proanthocyanidin nanofibers as the inner layer, PU nanofibers as the middle layer, and SF nanofibers as the outer layer. The results suggested that these three-layer tubes are attractive biocompatible materials for use as vascular grafts.

Herein we present our research on a novel three phase antibacterial wound dressing prepared from carbon nanotubes, silver nanoparticles (AgNPs) and polyvinyl alcohol nanofibers. The AgNPs were generated on carbon nanotubes surfaces to synthesize carbon nanotubes-AgNP nanoparticles which were added into the polyvinyl alcohol nanofibers prior to electrospinning to prepare PVA/carbon nanotubes-AgNP composite nanofibers. All characterizations confirmed the three phase nanofiber architecture. Owing to growth of AgNPs on carbon nanotubes surfaces and embedding into PVA nanofibers the wound dressings are proposed for sustained and safer wound healing applications. The antibacterial test results confirmed excellent bactericidal and prolonged bacterial growth inhibition properties of the nanocomposites which suggest their suitability as sustained antibacterial wound dressing biomaterial.

A novel ternary nanocomposite of Fe3O4 functionalized porous biomass carbon decorated by aligned polyaniline (A-PANI/Fe3O4/PBC) was successfully fabricated by hydrothermal and in situ oxidative polymerization. The morphology and structure of the composite was characterized by X-ray diffraction, fourier transform infrared spectra, scanning electron microcopy, transmission electron microscopy, X-ray photoelectron spectra and vibrating sample magnetometer. The microwave absorbing properties of A-PANI/Fe3O4/PBC composite were investigated in the frequency of 2–18 GHz. The results indicated that the A-PANI/Fe3O4/PBC composite possess excellent microwave absorbing performance, and the minimum reflection loss can be up to −44.8 dB at 10.67 GHz, effective absorbing bandwidth (RL

Multi-layer graphene oxide (MLGO) coated shape memory polyurethane (MLGO@SMPU) with different layers was fabricated by multiple dipping for adjustable shape memory switching devices. The MLGO, which stacked together in parallel, evenly covered the surface of the SMPU. Stress strain testing indicated that the coating of GO improved the mechanical strength of these MLGO@SMPU composites in the stretching stage below the strain of approximately 6%. Adhesive force testing suggested that the first GO layer could adhere well to the SMPU surface, but the interaction force between GO layers was weak. The angle recovery ratio and time, bending recovery force, and angle fixity ratio of these MLGO@SMPU composites were evaluated using homemade evaluation apparatus. Results indicated that with the increase of GO layers from one to five layers, the MLGO@SMPU gave an angle recovery ratio reduced to 83.2%, recovery time decreased to 7.6 s, bending recovery force increased to 18.3 mN, and angle fixity ratio decreased to 83.3%. This novel and straightforward approach of dipping graphene oxide onto shape memory substrates for adjustable recovery ratio, time and force has the potential to be applied to smart switching devices including sensors and actuators.

Silver nanoparticles (AgNPs) are effective antimicrobial agents however excess release of silver causes argyria and argyrosis. An strategy to avoid these detrimental side effects is immobilization of AgNPs on several organic and inorganic substrates. Herein, we propose immobilization of AgNPs on TiO2 nanoparticles by an environmentally green process subsequently incorporating the TiO2/AgNP into cellulose acetate (CA) nanofiber matrix. The TiO2/AgNP nanocomposite particles were prepared by coating TiO2 nanoparticles with polydopamine hydrochloride followed by a treatment in AgNO3 solution. Subsequently, the TiO2/AgNP nanocomposites were added into CA solution and electrospun to fabricate CA/TiO2/AgNP composite nanofibers. The samples were characterized by XRD, TEM, XPS, SEM, EDX, FTIR and antibacterial assays. Synthesis of TiO2/AgNP and its loading into CA nanofibers was confirmed by XRD, XPS, TEM and EDX analysis. SEM images indicated regular morphology of the nanofibers. The antibacterial test results confirmed CA/TiO2/AgNP composite nanofibers having excellent antibacterial performances for 36 h and substantial bacterial growth inhibition for 72 h.

We present our research on dyeability of polyacrylonitrile (PAN) nanofibers following ultrasonic dyeing method. Although PAN has been extensively utilized in textile apparel, sportswear, upholstery and home furnishing, however, coloration of PAN nanofibers has not yet been reported. PAN is a compact fiber while the nanofiber structure makes it more difficult to color PAN nanofibers. PAN is generally dyed with basic dyes and dyeing is carried out in acidic conditions, while the dyeing process takes about two hours at boiling temperature. A systematic study on dyeability of PAN nanofibers will extend its use in textile apparel industry. Thus, we used ultrasonic energy and first time conducted our research on dyeability of electrospun PAN nanofibers using disperse dyes. Dyeing process parameters such as dyeing time, temperatures and concentrations of dyes were optimized. Ultrasonic dyeing of PAN nanofibers was compared with its conventional dyeing as well. Affect of ultrasonic dyeing on the morphology, chemical state, crystallographic structure and mechanical strength of PAN nanofibers has been studied. PAN nanofiber samples were characterized by SEM, FTIR, XRD and tensile strength tests. The results revealed 80 °C and 60 min as optimum temperature and time for ultrasonic dyeing of PAN nanofibers. The ultrasonic dyeing does not affect morphology, chemical and crystalline structure of the PAN nanofibers while it improves their mechanical strength. Our research suggests dyeability of PAN nanofibers with disperse dyes by ultrasonic method and their subsequent use in textile apparels.

Herein we present our research on synthesis of silver nanoparticles (AgNPs) on cellulose nanofibers (CN) by a facile procedure using dopamine hydrochloride (Dopa), as reducing agent. The CN were produced by deacetylation of electrospun cellulose acetate (CA) nanofibers. The CN were then treated with 2 mg/mL of Dopa in 1 M Tris HCl buffer (pH 8.5) followed by soaking in 150 mM AgNO3 solution for generation of AgNPs. The samples were characterized with SEM, XRD, FESEM, EDX, XPS, TEM, FTIR analysis and antibacterial assays. Synthesis of AgNPs was confirmed by XRD, XPS and TEM analysis. The TEM images demonstrated CNAgNP samples well decorated with AgNPs. Sizes of the spherical AgNPs, calculated by Debye–Scherrer method, were 20 nm. Antibacterial test results confirmed excellent bacterial growth inhibition properties of CNAgNP on agar plates and in liquid medium against E. coli and S. aureus strains. The relative cell viability (CFU/mL) test results demonstrated excellent bactericidal potential of the CNAgNP samples against the tested strains. The CNAgNP prepared by an environmentally benign process would thus be a promising nano-biocomposite for antibacterial applications.

Shape memory driving thickness adjustable graphite (G) micro-flakes@shape memory polyurethane (G@SMPU) sponge was fabricated by two-step dipping separately in G-dispersed aqueous solution and SMPU/THF solution for high-performance microwave shielding. The sponge exhibited an ultrahigh G loading ratio (G/sponge, wt/wt) up to 490 wt%. For the first time, dipping coating of SMPU onto the sponge was proposed, and the obtained G@SMPU sponge exhibited a good recovery effect at least above 90% after thorough compression. And also, the thickness could be adjusted by utilizing its shape memory property. For microwave shielding, G-9@SMPU and G-18@SMPU sponges achieved the shielding effectiveness over 20 and 30 dB, respectively. Moreover, varying thickness or compressing repeatedly even up to 100 times would not obviously decrease the shielding effect of the G@SMPU sponge. This suggests the steady distribution and adhesion of G micro-flakes inside the three-dimensional sponge substrate due to the fixing of SMPU.

The squared envelope spectrum (SES) is one of the most effective methods in rolling element bearing fault diagnosis. Being a technique based on demodulation, the success of SES depends highly on the extraction of information caused by the bearings fault. Therefore, a preprocessing step of choosing an optimal frequency band (OFB), before the implementation of the SES, is absolutely needed and should always be taken prior. Fast kurtogram (FK), as the most commonly used method targeting resonance frequency band which is excited by the bearing fault, is applied as the benchmark tool for the selection of the OFB. However, recent theoretical works show that the kurtosis used as the criterion for OFB selection was both sensitive to the impulsiveness and cyclostationarity, which means irrelevant impulsive and cyclostationary components are able to mislead the kurtosis based OFB selection techniques and subsequently bring great difficulties in bearing fault diagnosis. To tackle this problem, in this paper, a novel statistical model parameter-based method, called Distcsgram, is proposed as a substitution to the traditional FK technique so that an OFB can be selected with the least influences from the irrelevant cyclostationary and impulsive interferences. Together with the SES, the Distcsgram is explained and validated in both simulation and experimental studies. Furthermore, through the comparisons with the traditional methods, the superiority of the proposed method over those traditional methods for the diagnosis of rolling element bearing is proved.

In this study, a new design method for a three-dimensional hollow structure woven fabric was proposed and the effect of cellular size on the cushioning property of the fabric-reinforced polyurethane elastomer composite was investigated. The fabric structure was analyzed from a cross-section view and the theoretical equations for the warp and weft yarns were proposed, using the fabric layer and cellular size as parameters. Nine kinds of fabrics with different layers and cellular size were fabricated with a Jacquard loom and reinforced with polyurethane elastomer to yield fabric composites. Then the effect of cellular size on the cushioning property of the fabric composites was discussed. The results showed that upon increasing the cellular size, the cellular fabric composite exhibited lower compression resistance. Moreover, the stress at a strain of 65% and the energy absorbed in the loading process were increased with decreasing cellular size. Moreover, the compression resilience was also changed with the cellular size. It can be concluded that the cellular size had an important effect on the cushioning property of the fabric composite, which can be considered as a design parameter for cushion material based on its usages.

A novel degumming approach by using steam treatment is proposed to minimize water pollution and consumption in silk wet processing. Sericin removal of Bombyx mori silk fibers was carried out with pressurized steam. The degumming ratio, fine structure and physical properties of the degummed silk fibers as well as energy efficiency were investigated to elucidate the degumming effects of steam treatment. Compared to the conventional neutral soap and sodium carbonate (Na2CO3) degumming methods, sericin can be removed by steam treatment without any chemicals, and the degumming ratio as well as physicochemical properties of the degummed silk fibers maintained at a desirable level. Energy efficiency and cost analysis showed that steam degumming is more energy-efficient and economical than the conventional chemical degumming methods. Results showed that steam treatment is a feasible silk degumming method with the benefits of reduction in water pollution and energy consumption.

Polycyclic aromatic hydrocarbons (PAHs) as polar organic pollutants, their potential harm to the environment has caused widespread concern. This study describes a simple method to prepare modified aerobic granular sludge (AGS) by hydroxypropyl-β-cyclodextrin (HP-β-CD). Using HP-β-CD modified AGS as the adsorbent, the removal of specific PAHs: Fluoranthene (Fla) reached 95% comparing to 80% of the unmodified AGS. The removal of Fla was related to initial concentration, temperature and ion concentration (Na

In this study, we investigated the potentials of nanomaterials to enhance anaerobic ammonium oxidation (anammox) process, in terms of nitrogen removal, microbial enrichment, and activity of key enzymes. Graphene nanosheets (GNs) and γ-Fe2O3 nanoparticles (NPs) were selected due to their catalytic functions as conductive material and electron shuttles, respectively. The obtained results revealed that the optimum dosage of GNs (10 mg/L) boosted the nitrogen removal rate (NRR) by 46 ± 3.1% compared to the control, with maximum NH4+-N and NO2−-N removal of 86.5 ± 2.7% and 97.1 ± 0.5%, respectively. Moreover, hydrazine dehydrogenase (HDH) enzyme activity was augmented by 1.1-fold when using 10 mg/L GNs. The presence of GNs promoted the anammox granulation via enhancement of hydrophobic interaction of extracellular polymeric substances (EPS). Regarding the use of γ-Fe2O3 NPs, 100 mg/L dose increased NRR by 55 ± 3.8%; however, no contribution to HDH enzyme activity and a decrease in EPS compositions were observed. Given that the abiotic use of γ-Fe2O3 NPs further resulted in high adsorption efficiency (~92%), we conclude that the observed promotion due to γ-Fe2O3 NPs was mainly abiotic. Moreover, the 16S rRNA analysis revealed that the relative abundance of genus C. Jettenia (anammox related bacteria) increased from 11.9% to 12.3% when using 10 mg/L GNs, while declined to 8.3% at 100 mg/L γ-Fe2O3 NPs. Eventually, nanomaterials could stimulate the efficiency of anammox process, and this promotion and associated mechanism depend on their dose and composition.

Flexible strain sensors have shown great application value in wearable devices. In the past decades, researchers have spent numerous efforts on developing high-stretchability, excellent dynamic durability, and large linear working range flexible strain sensors and shaped a series of important research results. However, the viscoelasticity of the elastic polymer is always a big challenge to develop a flexible sensor. Here, to overcome this challenge, we developed a novel self-repairing carbon nanotubes/ethylene vinyl acetate (CNTs/EVA) fiber strain sensor prepared by embedding the CNTs on the surface of the swollen shape memory EVA fiber via the ultrasonic method. The CNTs/EVA fiber strain sensors responded with significant results, with high stretchability (190% strain), large linear working range (up to 88% strain), excellent dynamic durability (5000 cycles), and fast response speed (312 ms). In addition, the permanently damaged conductive network of the strain sensors, caused by the viscoelasticity of elastic polymer, can restore above the transforming temperature of the shape memory CNTs/EVA fiber. Moreover, the performance of the restored strain sensors was almost as same as that of the original strain sensors. Furthermore, human health monitoring tests show that the CNTs/EVA fiber has a broad application prospect for human health monitoring in wearable electronic devices.

A facile method for fabricating intelligent microwave absorber of vapor grown carbon fibers/Polydimethylsiloxane-epoxy resin shape memory composites (VGCFs/PDMS-SMEP) was proposed to deliver intelligently tunable and broadband microwave absorption performance. The maximal absorption intensity was regulated by varying the deformation of the composites driven by the superior shape memory property of SMEP, where practical the minimum reflection loss (RLmin) reaches −55.7 dB at 16.0 GHz with the thickness of 2.0 mm. The effective absorption bandwidth (EAB) reached 9.8 GHz, which covered the whole applied frequency range (8.2–18.0 GHz). The intelligent microwave absorption performance of the sample was attributed to robust conductive loss and dielectric loss enhanced by the dipole relaxations and multi-reflections. Thus, VGCFs/PDMS-SMEP composites serves as the key that really opens up opportunity for the application as flexible, shape memory and tunable high performance broadband microwave absorption absorber in frontiers such as wearable electronic devices, chips protection, stealth technology and information security.

Solar-thermal energy conversion performance of a selective metafilm absorber is characterized by a lab-scale experimental setup under multiple solar concentrations.

An equal-collision-probability-curve (ECPC) method is developed in this paper to address the problem of safe spacecraft proximity maneuvers. Considering the uncertainties’ influence, the ECPC, which represents the curve of equal-collision-probability-points in the space around the target spacecraft, is firstly established. It is optimal to maneuver along the gradient direction of the ECPC, which is the fastest change in the ECPC. To calculate this direction, a novel auxiliary function, which has the same gradient direction as the collision probability function, is proposed. Compared to traditional collision probability functions, the proposed function does not contain transcendental elements and hence the computational burden can be greatly decreased while maintaining the necessary accuracy. Then, the safe close-range proximity maneuver generated by ECPC method can be implemented along the estimated gradient direction. Analytical validation is performed to assess the use of such collision avoidance scheme for safety critical operations. Furthermore, an improved Linear Quadratic Regulator (LQR) is designed to track the reference trajectory and a Lyapunov-based analysis verifies the stability of the overall closed-loop system. Numerical simulations show that the novel ECPC method is more computationally efficient than traditional methods while maintaining the same accuracy. Moreover, the novel scheme can be easily validated to guarantee the safety of the mission.

Metal-organic frameworks (MOFs) as catalysts for the activation of peroxymonosulfate (PMS) to remove recalcitrant organic contaminants has been well reported, however, the separation of MOFs from the solution is difficult because of their powder state, which limits their applications. In the present study, zeolitic imidazole framework (ZIF) materials, ZIF-9 and ZIF-12 were pioneered to load on cellulose aerogels, and the hybrid aerogels as metal catalysts to effectively activate PMS for Rhodamine B (RB), tetracycline hydrochloride (TC) and p-nitrophenol (PNP) degradation. The hybrid aerogels/PMS system could remove PNP about 90% in 1 h, which hard to remove from water. The pH value of the solution had no effect on the degradation process, which demonstrated that the hybrid aerogels had excellent pH tolerance. In addition, the mechanism of PNP degradation was investigated by electron paramagnetic resonance (EPR) and free radical trapping methods. The results showed that PMS could effectively activate by hybrid aerogels to produce sulfate radicals (SO4 −), hydroxyl radicals ( OH), and revealed that SO4 − play a key role in degradation. The most important feature of hybrid aerogels is can be easily separated from the solution. The obtained results showed that the hybrid aerogels exhibit excellent recyclability, with no significant effect on degradation. The prepared hybrid aerogels are green, environmentally friendly with high catalytic efficiency. Further, the outstanding degradation of PNP demonstrates the promising prospects of hybrid aerogels as advanced oxidation process (AOP) catalysts.

Nowadays, photothermal agents have attained considerable attention in nanomedicine for the treatment of cancer after chemotherapy, surgery, biological therapy and radiotherapy. In this work, we showed a sericin-based, simple approach for synthesis of sericin functionalized reduced graphene oxide (SRGO) with low cytotoxicity and photo thermal efficiency. During the synthesis, the GO is deoxygenated in situ and functionalized by sericin, a low-cost, silk protein and concurrently forms SRGO. The subsequent SRGO disperse well in water with higher biocompatibility because of the decoration of sericin on graphene sheets. The prepared SRGO exhibited a good photothermal capacity with near-infrared laser irradiation (808 nm) for efficient killing of HeLa cells. Further, the synthesized SRGO could act as a promising material for photo thermal therapy applications in future.

MgxCo1-xFe2O4 ferrites were prepared by the sol-gel method and sintered from 1100 °C to 1300 °C. The microstructures, magnetic and dielectric properties have been investigated. XRD patterns demonstrated that the samples have a single spinel phase with cubic symmetry. Mg2+ doping expands the lattice parameter slightly. The grain size increases with increasing sintering temperature but decreases with Mg2+ doping. The saturation magnetization value decreases from 64.26 emu/g to 26.05 emu/g with the increasing Mg2+ concentration from x = 0.2 to x = 1.0. And the coercivity of the samples also decreases from 0.32 kOe to 0.15 kOe. The dielectric results showed that the behavior of dispersion appeared at the low frequency, which can be attributed to the space charge polarization. And the dielectric constant increases with the increasing grain size. All the results indicated that the Mg2+ doping has a significant influence on the properties of CoFe2O4.

Over recent years, researchers have noticed that recovery rates of shape memory composites (SMCs) would vary due to the addition of fillers. So far, although several superficial reasons are discussed, a thorough analysis has not been presented yet probably due to the absence of a microscopic mechanism of SMCs. Here, a molecular mechanism of SMCs is clarified by identifying the differences lying in molecular motions of shape memory polymers and SMCs. On the basis of the molecular mechanism of SMCs, both a positive effect and a negative effect of fillers on recovery rates are revealed. Because interfaces between fillers and matrices play a decisive role in the two effects of fillers, several experiments are designed to verify the role of interfaces. The experimental results prove that the interfaces are benefit and harmful for recovery rates at the same time. Moreover, the results are able to qualitatively predict that the recovery rates of SMCs would increase or decrease with more addition of fillers.

A class of functional composites are compounded by piezoelectric particles and shape memory polymers, and the resultant composites perform both shape memory effect and piezoelectric effect. Although many kinds of piezoelectric composites have been developed, few papers report the effect of interfacial bonding between fillers and matrices on piezoelectric performances. Here, two groups of samples are investigated to clarify the role of interfaces in piezoelectric performances and permittivity properties. The experimental results testify that the samples with poor interfaces exhibit lower relative permittivity and are unable to show usable piezoelectric effect. The piezoelectric effect critically depends on interfacial bonding. Compared with pristine shape memory polymers, interfaces efficiently improve thermodynamics but influence the glass transition temperature very little. Moreover, shape recovery rates all reach at least 95% in the third cycle, even though decrease with the addition of fillers because of increasing interfaces.

To combine the piezoelectric effect and shape memory effect, various kinds of smart composites are developed through compounding lead zirconate titanate (PZT) particles with average diameters of 400 nm and shape memory polyurethane (SMPU) matrices. Compared with pristine SMPU, the resulting composites are enhanced by more than 133% in the maximum recovery stresses. Additionally, the film actuators made from these composites can generate 1 nm resolution displacements without any control method in a common laboratory environment when the step voltage signals are applied to them. This feature partly profits from the softness of SMPU matrices which, to some extent, protects PZT particles from ambient noise. Moreover, taking the advantage of shape memory effect easily deforms the film actuators into a variety of designed shapes. As a consequence, the shaped actuators are able to produce many more displacements while the positioning errors remain the same. The displacements of the “U” type actuator and the “Z” type actuator are respectively 18 nm (about 4.7 times displacement of the corresponding film actuator) at 840 V and 75 nm (about 13.3 times displacement of the corresponding film actuator) at 600 V. The proposed smart composites strongly show the potential to lower the requirements of nanopositioning and reduce costs.

Herein, we first time present our research on ultrasonic dyeing of polyurethane (PU) nanofibers. The PU nanofibers were fabricated by electrospinning process and were subsequently dyed following exhaust method using sonication. The two disperse dyes selected were a low-energy disperse dye (CI Disperse Blue 56) and a high-energy disperse dye (CI Disperse Red 167:1). The ultrasonic energy was used to achieve higher color build-up on PU nanofibers. The temperature/time (T/T) diagram of proposed dyeing process has been suggested; dyeing time and dyeing temperature were optimized. Color build-up properties (measured in terms of K/S values), dye fixation (%), and color fastness properties were studied in detail. The samples were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and mechanical strength measurements. The results show 70 °C and 40 min as optimum dyeing temperature and time, respectively. The SEM, FTIR, and XRD results did not show any significant effect of ultrasonic dyeing on morphology, chemical, and crystallographic structure of PU nanofibers. Color fastness results revealed excellent light fastness, very good washing, and hot pressing fastness of both dyes.

In this work, five different metal-oxide additives (metal = Ba, Co, Fe, Li, and Mn) were examined as sintering aids and SiO2 impurity scavengers for Ce0.8Sm0.2O1.9 (SDC). 2 mol% additives were loaded into the SDC with ∼150 ppm (moderately impure) and ∼2000 ppm (highly impure) SiO2. Ba-, Co-, Fe- and Mn-oxides showed comparative sintering-aid effect on both moderately- and highly-impure SDC specimens, but the sintering-assisting effect of Li-oxide was completely neutralized in highly impure SDC. Regarding electrical property, the deleterious effect of 2000 ppm SiO2 impurity on the grain-boundary conduction of SDC can be effectively alleviated by adding Ba-, Co-, Fe-, or Mn-oxides. Microstructure analysis revealed that Ba-oxide reacted directly with SiO2 and consequently enhanced grain-boundary conduction. By contrast, with the addition of Co-, Fe-, and Mn-oxides, the improved grain-boundary conductions of impure SDC were related to the scavenging reactions between Si, Ca (another original impurity) and Sm components.

Charged nanocellulose (NC) with a high aspect ratio (larger than 100) extracted from animal or bacterial cellulose and chemical cross-linked NC aerogels have great promising applicability in material science, but facile fabrication of such NC aerogels from plant cellulose by physical cross-linking still remains a major challenge. In this work, carboxylated cellulose nanofiber (CNF) with the highest aspect ratio of 144 was extracted from wasted ginger fibers by a simple one-step acid hydrolysis. Our approach could easily make the carboxylated CNF assemble into robust bulk aerogels with tunable densities and desirable shapes on a large scale (3D macropores to mesopores) by hydrogen bonds. Excitingly, these CNF aerogels had better compression mechanical properties (99.5 kPa at 80% strain) and high shape recovery. Moreover, the CNF aerogels had strong coagulation–flocculation ability (87.1%), removal efficiency of MB dye uptake (127.73 mg/g), and moderate Cu2+ absorption capacity (45.053 mg/g), which were due...

Barium titanate/graphene oxide/polyurethane (BTO@GO@PU) composite membranes for microwave absorption were designed and fabricated by mechanical-blending of BTO and GO in PU medium, followed by mold formation. The cross section morphology of the BTO@GO@PU membrane indicated that the BTO nanoparticles with 450 nm average diameter are successfully incorporated into the PU matrix. Mechanical tensile measurement showed that, as the amount of BTO nanoparticles increased from 5 wt% to 20 wt%, the elastic modulus of the corresponding membrane increased up to 23.0 MPa elongation with the elongation above 450 %. Microwave absorption property of the BTO@GO@PU membranes were evaluated by measuring its reflection loss in the frequency range of 0.1-18 GHz. With the addition of BTO up to 20 wt%, the maximum absorptivity of the composite reached up to 51 %. This is attributed to the dielectric loss of BTO nanoparticles.

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.

The development of biocompatible nanocomposites for biomedical applications such as drug release has attracted increasing attention in recent years. In this work, electrospun membranes composed of polycaprolactone (PCL) and shellac were fabricated because PCL has favorable mechanical and biological properties, such as high biocompatibility and biodegradability. Meanwhile, shellac is biocompatible and non-toxic; as a result, the fabricated membranes are attractive for controlled drug delivery. Here, PCL/shellac/PCL nanofiber membranes were treated by ethanol vapor to improve their properties for use in drug delivery applications. Salicylic acid was loaded in the drug delivery system as a model drug, and three PCL/shellac/PCL membrane configurations were investigated. Ethanol vapor treatment increased the tensile strength, flexibility, and transparency of the membranes. Both the tensile strength and drug release properties of the membranes strongly depended on the ratio of PCL to shellac.

In this paper, electrically actuated shape memory composites were prepared by compounding shape memory polyurethane (SMPU) with conductive antimony-doped tin oxide/TiO2 (ATO/TiO2) whiskers. The resultant composites, ATO/TiO2/SMPU, can be activated by electric voltages because of heating Joule and enhancement of heating efficiency by the conductive network resulting from the overlaps of whiskers. In addition to conductivity, ATO/TiO2/SMPU composites featured lighter color than most electroactive shape memory composites, which exhibit black color due to the addition of carbon materials. The composites exhibited uniform electrical resistance and rapid heat transfer performances. When the composites with 50 wt% ATO/TiO2 whiskers were used in a switch electric circuit as the switch, the circuit can turn off within 30 s. ATO/TiO2 whiskers improved Young's moduli by at least 390% and recovery stresses by more than 250% compared with pristine SMPU. Although the recovery rates were unsatisfactory in the first test cycle, composites with 40 wt% ATO/TiO2 whiskers and 50 wt% ATO/TiO2 whiskers still showed recovery rates higher than 96% and 94% in the third cycle, respectively. Keywords: Electrical actuation, Shape memory composite, Switch, Electric circuit, Morphing performance

This work presents a facile and practical preparation method of cellulose-based bioadsorbent modified by hyperbranched polyethyleneimine (hPEI) using glutaraldehyde cross-linking in heterogeneous system for various dyes removal. The grafting of hPEI with a large molecular structure was achieved efficiently according to the FTIR and XPS analysis. The adsorption properties of the cellulose-based bioadsorbent for anionic reactive yellow X-RG (XRG), cationic bright yellow M-7G (M7G), nonionic disperse brown S-3RL (DB 3) were explored. The kinetics curve was well fitted with pseudo-second-order model, and the equilibrium data well suited Langmuir model with maximum adsorption capacity of 571.43 mg g−1 for M7G, 581.40 mg g−1 for DB 3 and 970.87 mg g−1 for XRG. Compared with other bioadsorbents reported previously, the cellulose-based bioadsorbent could be facilely prepared and simultaneously exhibited enhanced removal for dyes. Therefore, this work will help accelerate the study of scale production of bioadsorbent for treatment of textile effluents.

Mn1−xZnxFe2O4 (x = 0.2–0.8) ferrite samples were successfully prepared by the sol–gel method. X-ray diffraction study reveals that single cubic spinel phase was formed in Mn1−xZnxFe2O4 samples. The SEM micrographs revealed that the microstructures change significantly with different Zn2+ doping concentration and sintering temperature while the grain size grow up to 9.48 μm for Mn0.6Zn0.4Fe2O4 sample sintered at 1100 °C. Further, the dielectric and magnetic measurements indicated that both Zn2+ doping and sintering temperature could affect both electrical and magnetic parameters such as dielectric constant and saturation magnetization in a great manner. The Mn0.6Zn0.4Fe2O4 sample sintered at 1100 °C for 8 h is found to show the largest Ms value (77.30 emu/g) in this work. These results indicate that Zn2+ doping or sintering temperature can adjust the microstructures, dielectric and magnetic properties of Mn1−xZnxFe2O4 ferrites.

In this study, nanoscale bimetallic particles (Ni/Fe) were prepared by a simultaneous ball milling and in situ chemical deposition process (B&C) with high dechlorination activity for 4-chlorophenol (4-CP). The results suggest that the introduction of Ni significantly improved the dechlorination of 4-CP. The dechlorination activity of Ni/Fe-B&C (kobs = 0.168 min−1) was increased significantly with a lengthening of the milling time and showed maximum activity at the milling time of 4 h. Bimetals prepared with the incorporation of Ni into Fe can quickly and completely dechlorinate 4-CP within 90 min reaction time. The dechlorination activity was mainly attributed to the synergistic effects of Ni and Fe. The dechlorination rate was increased with increasing Ni–Fe dosage but decreased with increasing solution pH and 4-CP concentration. Ni/Fe-B&C catalyst could be reused 10 times at pH below 5.0. This approach could offer great opportunities for both research and industrial applications to eliminate chlorinated organic pollutants.

Membrane bioreactor with non-woven fabric membranes (NWMBR) is developing into a suitable method for anaerobic ammonium oxidation (anammox). As a carrier, non-woven fabric membrane divided total biomass into biofilm and suspended flocs gradually. Total nitrogen removal efficiency was maintained around 82.6% under nitrogen loading rate of 567.4mgN/L/d after 260days operation. Second-order substrate removal and Stover-Kincannon models were successfully used to simulate the nitrogen removal performance in NWMBR. High-throughput sequence was employed to elucidate the underlying microbial community dynamics. Candidatus Brocadia, Kuenenia, Jettenia were detected to affirm the dominant status of anammox microorganisms and 98.2% of anammox microorganisms distributed in biofilm. In addition, abundances of functional genes (hzs, nirK) in biofilm and suspended flocs were assessed by quantitative PCR to further investigate the coexistence of anammox and other microorganisms. Potential nitrogen removal pathways were established according to relevant nitrogen removal performance and microbial community.