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Recent research shows that flexoelectricity may prominently affect the electromechanical coupling responses of elastic dielectrics at the nanoscale. From the perspective of devices design, it is urgent to know how the input parameters affect the electromechanical coupling behaviors of flexoelectric nanostructures. In this work, global sensitivity analysis is applied to elastic dielectric nanoplates to decompose the attribution of each of the parameters. Meanwhile, the existing hierarchical regression is found not suitable for simultaneously evaluating the multicollinearity and high dimensionality problems, when global sensitivity analysis of flexoelectric nanostructures is obtained combining polynomial chaos expansion (PCE). In order to overcome the above issues, the following strategies is proposed: 1) First, an adaptive sparse scheme is employed to build the sparse PCE. The number of terms of the PCE is decreased through choosing the most related polynomials with respect to a given model output. 2) Then, the hierarchical regression can be carried out iteratively via combining with the adaptive-sparse scheme. 3) Finally, the Sobol sensitivity indices are calculated through using these procedures. Further, Sobol sensitivity indices reveal that the thickness is the decisive input parameter that strongly affects the buckling and vibration responses of the flexoelectric nanoplate; the flexoelectric coefficients is the next key parameter that affect the buckling and vibration responses of flexoelectric nanoplate. Our finding also demonstrates that the influence of the flexoelectric coefficient is much stronger than that of the piezoelectric coefficient, which revealed the domination of the flexoelectric effect in ultra-thin piezoelectric nanostructures.

It is difficult to investigate the hydrogen-bonding dynamics of hydrogen-disordered ice VI. Here, we present a comparative method based on our previous study of its counterpart hydrogen-ordered phase, ice XV. The primitive cell of ice XV is a 10 molecule unit, and the vibrational normal modes were analyzed individually. We constructed an 80 molecule supercell of ice VI to mimic the periodic unit and performed first-principles density functional theory calculations. As the two vibrational spectra show almost identical features, we compared the molecular translation vibrations. Inspired by the phonon analysis of ice XV, we found that the vibrational modes in the translation band of ice VI are classifiable into three groups. The lowest-strength vibration modes represent vibrations between two sublattices that lack hydrogen bonding. The highest-strength vibration modes represent the vibration of four hydrogen bonds of one molecule. The middle-strength vibration modes mainly represent the molecular vibrations of only two hydrogen bonds. Although there are many overlapping stronger and middle modes, there are only two main peaks in the inelastic neutron scattering (INS) spectra. This work explains the origin of the two main peaks in the far-infrared region of ice VI and illustrates how to analyze a hydrogen-disordered ice structure.

We successfully synthesize six kinds of functional conjugated microporous polymer (CMP) containing amino, hydroxyl, carboxyl and ester groups by a Sonogashira–Hagihara coupling reaction. These CMPs exhibit type-I nitrogen gas sorption isotherms, and their pore widths are approximately 1.28–1.86 nm with a relatively narrow pore size distribution that is attributed to microporous structures. By blending CMPs with TiO2 under solvothermal conditions, TiO2 is uniformly coated onto the surfaces of the CMPs, and CMP/TiO2 nanocomposites are synthesized successfully. The novel nanocomposites show excellent photocatalytic properties for the degradation of organic pollutants, such as methylene blue, ciprofloxacin and tetracycline, under visible light. The degradation rate of organic pollutants is higher than 96.8%, and after 5 recycling cycles, the degradation efficiency is still more than 93%. The effects of the different functional groups of CMPs on the photocatalytic properties are discussed for the first time. CMP/TiO2 with carboxyl groups show the smallest band gap, highest photocurrent intensity and lowest resistance compared to those of nanocomposites with amino, hydroxyl and ester groups. This result may be caused by the high electronegativity of carboxyl groups, which enhances the charge transfer rate. The photocatalytic mechanism of the CMP/TiO2 nanocomposites is investigated, and the superoxide anion (·O2−) is the main active species in the photocatalytic degradation process.

This work presents the dynamic response of piezoelectric and flexoelectric Euler–Bernoulli beams subjected to mechanical loads by means of Green’s functions. Exact solutions in closed form for the electromechanical coupling behaviors are derived. The present solutions will reduce to those of classical piezoelectric beam models by neglecting the flexoelectric effect. Numerical results for a $${\text {BaTiO}}_{3}$$ cantilever show that the tip deflection of the beam will be separated when the beam thickness reduces to one micrometer; therefore, pure mechanical experiments can be used to determine the flexoelectric effect by a bending test under different electrical boundary conditions. In addition, the dynamic output voltage under open-circuit condition and the dynamic output charge under short-circuit condition are dominated by the flexoelectric effect. The dynamic output voltage and charge become negligible when the beam thickness reduces to one micrometer. By reducing the length–thickness ratio or introducing the effective piezoelectric coefficient, the electric response can be more easily detected at microscale. These results demonstrate that the flexoelectric effect can be strong enough to dominate the electromechanical coupling behavior, coordinating with the ‘ever green’ trend to miniaturization, and the flexoelectric effect can be applicable for energy harvesters, sensing, and others.

A comprehensive design methodology is required to maximize the power capacity, the efficiency, and the power density of medium-frequency transformer (MFT), while complying with material, insulation, leakage inductance, and temperature limits. Different from the previous work, an analytical expression for the optimum conductor size of rectangular litz-wire conducting harmonic currents, which ensures best use of the available copper is proposed. A method to tune the leakage inductance with different winding configurations is presented. An insulation design scheme considering the influence of short-term power frequency sinusoidal wave and long-term square wave voltage excitations is put forward. Method to acquire the optimal dimension of fin array heat exchanger under forced air-cooling condition is presented. On this basis, the design methodology is established using the multiobjective nondominated sorting genetic algorithm II. A 1 kV, 200 kVA, 10 kHz nanocrystalline core MFT is designed and prototyped for a 10 kV, 2.5 MW solid-state transformer. The optimal design achieves an efficiency of 99.45%, a power density of 8 MW/m3, and a forced air-cooling temperature of 62 °C.

In order to further develop efficient ultraviolet light-driven photocatalysts for environmental application, α-zirconium phosphate (α-ZrP) and carbon nitride (C3N4) were synthesized, respectively. Then, C3N4–ZrP compositing nanomaterials were prepared by compositing α-ZrP nanocrystals and C3N4 with different mass ratios. C3N4–ZrP compositing nanomaterials were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results illustrated that α-ZrP and C3N4 were successfully composited, and the polarization of the compositing nanomaterials was reduced compared with raw materials. The photocatalytic performances of C3N4–ZrP compositing nanomaterials with different mass ratios were studied by photodegradation of RhB under ultraviolet irradiation. All of the degradation rates of the C3N4–ZrP compositing nanomaterials system were achieved more than 90% after 18 min. When the mass ratio of C3N4–ZrP compositing nanomaterials is 2:1, the degradation efficiency achieved 99.95%, which is more efficient than other tested mass ratios. The result indicated the possibility of utilizing C3N4–ZrP compositing nanomaterials for environmental pollutants degradation.

Two-dimensional (2D) network polymers with nano-sized pores are generally insoluble, and therefore, it is difficult to determine their molecular structures and to fabricate their membranes. Soluble...

This paper carries out the transient behaviors of a thin rectangular plate considering different boundary conditions, Pasternak foundation, and thermal environment simultaneously. The governing differential equations of the system are derived by employing the Kirchhoff’s classical plate theory and Hamilton’s principle. This paper proposes a novel semi-analytical methodology, which integrates Laplace transform, the one-dimensional differential quadrature method, Fourier series expansion technique, and Laplace numerical inversion to analyze plates’ transient response. The proposed method can obtain dynamic response of the rectangular efficiently and accurately, which fills the gap of transient behaviors in semi-analytical method. A comparison between semi-analytical results and numerical solutions from the publication on this subject is presented to verify the method. Specifically, the results also agree well with the data generated by the Navier’s method. The convergence tests indicate that the semi-analytical algorithm is a quick convergence method. The effects of various variables, such as geometry, boundary conditions, temperature, and the coefficients of the Pasternak foundation, are further studied. The parametric studies show that geometry and temperature change are significant factors that affect the dynamic response of the plate.

Given the increasing concern regarding the global decline in rare earth reserves and the environmental burden from current wet-process recycling techniques, it is urgent to develop an efficient recycling technique for leftover sludge from the manufacturing process of neodymium–iron–boron (Nd–Fe–B) sintered magnets. In the present study, centerless grinding sludge from the Nd–Fe–B sintered magnet machining process was selected as the starting material. The sludge was subjected to a reduction–diffusion (RD) process in order to synthesize recycled neodymium magnet (Nd2Fe14B) powder; during this process, most of the valuable elements, including neodymium (Nd), praseodymium (Pr), gadolinium (Gd), dysprosium (Dy), holmium (Ho), and cobalt (Co), were recovered simultaneously. Calcium chloride (CaCl2) powder with a lower melting point was introduced into the RD process to reduce recycling cost and improve recycling efficiency. The mechanism of the reactions was investigated systematically by adjusting the reaction temperature and calcium/sludge weight ratio. It was found that single-phase Nd2Fe14B particles with good crystallinity were obtained when the calcium weight ratio (calcium/sludge) and reaction temperature were 40 wt% and 1050 °C, respectively. The recovered Nd2Fe14B particles were blended with 37.7 wt% Nd4Fe14B powder to fabricate Nd–Fe–B sintered magnets with a remanence of 12.1 kG (1 G = 1 × 10−4 T), and a coercivity of 14.6 kOe (1 Oe = 79.6 A·m−1), resulting in an energy product of 34.5 MGOe. This recycling route promises a great advantage in recycling efficiency as well as in cost. Keywords: Nd–Fe–B grinding sludge, Recycled sintered magnets, Calcium reduction–diffusion, Rare-earth-rich alloy doping

For liquid water in the far-infrared spectrum, phonons of molecular vibrations constitute two bands with a narrow gap at around 30 meV. Interestingly, there are two distinct peaks for ice in this g...

Highly crystalline α-zirconium phosphate (α-ZrP) nanoparticles were synthesized and exfoliated into nanosheets, and then the hydrophilic nanosheets were modified into hydrophobic nanosheets with octadecyltrichlorosilane (OTS). Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis were applied to confirm the morphology and chemical structure of the nanosheets. Contact angle measurement was conducted to explore the wettability alteration of the hydrophobically modified α-ZrP nanosheets, and the result showed that the wettability of the core was changed into hydrophobicity. When ZrP-OTS nanosheets were injected during water-flooding, a Pickering emulsion will be formed. The droplet diameters and viscosities of the Pickering emulsions were measured. The hydrophobically modified α-ZrP nanosheets were applied in low-permeability sandstone cores and various concentrations were tested. The injectivity of the hydrophobically modified α-ZrP nanosheets was also studied and the result indicated that the nanosheets exhibit good injectivity. The mechanisms for enhancing oil recovery by utilizing hydrophobic α-ZrP nanosheets were analyzed: forming Pickering emulsions and increasing the viscosity of the displacing phase. Forming emulsions and increasing the viscosity of the flooding phase can enhance the microdisplacement efficiency, while good injectivity can also enhance the macrodisplacement efficiency. The result indicated the possibility of using hydrophobically modified α-ZrP nanosheets for enhancing oil recovery in a low-permeability reservoir.

The hydrogen-disordered structure of ice, Ic, makes it difficult to analyze the vibrational normal modes in the far-infrared region (i.e., the molecular translation band). To clarify the origin of the energy-splitting of hydrogen bond vibrations in this area, a 64-molecule supercell was constructed and calculated using first-principles density functional theory. The results were in good agreement with inelastic neutron scattering experiments and our previous study of a hydrogen-ordered ice Ic model. Assisted by analytic equations, we concluded that the origin of the two hydrogen bond peaks in real ice Ic is consistent with that of hydrogen-ordered ice Ic: the peaks originate from two kinds of normal mode vibration. We categorize the four peaks in the far-infrared region recorded from inelastic neutron scattering experiments as the acoustic peak, the superposition peak, the two-hydrogen bond peak and the four-hydrogen bond peak. We conclude that the existence of two intrinsic hydrogen bond vibration modes represents a general rule among the ice family, except ice X.

For high-performance mixed-matrix membranes (MMMs), it is crucial to design gas transport channels in fillers to rationally manipulate the structure-property relationship. In this study, the novel porous organosilicon nanotubes (PSiNTs) were incorporated into Pebax to prepare MMMs for biogas purification (CO2/CH4 separation). After comparing the separation performance of MMMs containing PSiNTs and MMMs containing non-porous organosilicon nanotubes (SiNTs)，it can be found that the porous structure on wall of organosilicon nanotubes had a significant effect on the improvement of the gas permeability. In addition, the amino-modified PSiNTs (N-PSiNTs) were prepared and introduced into membranes to significantly enhance the CO2 permeability and CO2/CH4 selectivity. Firstly, the porosity of N-PSiNTs afforded rapid gas transport channels in MMMs and intensified the diffusion mechanism, increasing the CO2 permeability. Secondly, the reversible reaction between amino groups and CO2 in MMMs intensified the facilitated transport mechanism, increasing the CO2/CH4 selectivity. In particular, the Pebax-N-PSiNTs with 0.5 wt% and 1 wt% N-PSiNTs exhibited the optimal separation performance, which surpassed 2008 upper bound and were superior to the MMMs incorporated with other kinds of nanotubes.

The counter-gravity casting methods have been developed to remove the casting defects of Mg based alloys. However, the effects of different counter-gravity casting methods on the microstructure and mechanical properties have not been studied in detail. ZM5 alloys were prepared by gravity casting, low-pressure casting and counter-pressure casting, respectively. The mechanical properties, microstructure and fracture morphologies were examined and compared by means of optical microscopy, scanning electron microscopy methods and tensile testing. Results show that casting defects such as gas pore, shrinkage porosity and cavity can be eliminated by counter-pressure casting. The grain size of α-Mg is decreased signifi cantly by counterpressure casting. Moreover, the precipitated particles are more uniform and fi ner in the counter-pressure casting sample. As a result, the mechanical properties of the alloys are greatly improved. The tensile strength and elongation of the samples by counter-pressure casting are 285 MPa and 13.9%, respectively, which are much higher than those of the low pressure casting and gravity casting.

Summary Interfacial polymerization (IP) is a platform technology for ultrathin membranes. However, most efforts in regulating the IP process have been focused on short-range H-bond interaction, often leading to low-permselective membranes. Herein, we report an electrostatic-modulated interfacial polymerization (eIP) via supercharged phosphate-rich substrates toward ultra-permselective polyamide membranes. Phytate, a natural strongly charged organophosphate, confers high-density long-range electrostatic attraction to aqueous monomers and affords tunable charge density by flexible metal-organophosphate coordination. The electrostatic attraction spatially enriches amine monomers and temporally decelerates their diffusion into organic phase to be polymerized with acyl chloride monomers, triggering membrane sealing and inhibiting membrane growth, thus generating polyamide membranes with reduced thickness and enhanced cross-linking. The optimized nearly 10-nm-thick and highly cross-linked polyamide membrane displays superior water permeance and ionic selectivity. This eIP approach is applicable to the majority of conventional IP processes and can be extended to fabricate a variety of advanced membranes from polymers, supermolecules, and organic framework materials., Graphical abstract, Highlights • Electrostatic-modulated interfacial polymerization is proposed for the first time • Electrostatic attraction regulates the spatial-temporal distribution of amine monomers • Monomer regulation leads to reduced thickness and enhanced cross-linking of membrane • Ultrathin and highly cross-linked polyamide membrane displays superior permselectivity, Supramolecular Materials; Materials Science; Materials Chemistry; Materials Synthesis; Polymers

The growth in aerosol particles caused by water uptake during increasing ambient relative humidity alters the physical and chemical properties of aerosols, which then affects public health, atmospheric chemistry, and the Earth’s climate. The temporal resolution and sensitivity of current techniques are not sufficient to measure the growth dynamics of single aerosol nanoparticles. Additionally, the specific time required for phase transition from solid to aqueous has not been measured. Here, we describe a label-free photonic microscope that uses the Bloch surface waves as the illumination source for imaging and sensing to provide real-time measurements of the hygroscopic growth dynamics of a single aerosol (diameter

Efficient olefin/paraffin separation is a grand challenge because of their similar molecular sizes and physical properties, and is also a priority in the modern chemical industry. Membrane separation technology has been demonstrated as a promising technology owing to its low energy consumption, mild operation conditions, tunability of membrane materials, as well as the integration of physical and chemical mechanisms. In this work, inspired by the physical mechanism of mass transport in channel proteins and the chemical mechanism of mass transport in carrier proteins, recent progress in channel‐based and carrier‐based membranes toward olefin/paraffin separations is summarized. Further, channel‐based membranes are categorized into membranes with network structures and with framework structures according to the morphology of channels. The separation mechanisms, separation performance, and membrane stability in channel‐based and carrier‐based membranes are elaborated. Future perspectives toward membrane‐based olefin/paraffin separation are proposed., Recent progress in channel‐based and carrier‐based membranes toward olefin/paraffin separations is summarized. Further, channel‐based membranes are categorized into membranes with network structures and with framework structures according to the morphology of channels. The separation mechanisms, separation performance, and membrane stability in channel‐based and carrier‐based membranes are elaborated. Future perspectives toward membrane‐based olefin/paraffin separation are proposed.

Conjugate heat transfer of air and steam in a rectangular channel with 90° ribs along two opposite walls was investigated experimentally and numerically. The stainless steel test section was 80 mm × 40 mm × 2.5 mm and the ribs were 80 mm × 2.5 mm × 2.5 mm with 25 mm between ribs. The tests investigated the effects of coolant mass flow rate (the corresponding Reynolds numbers in the range of 10,000-50,000) on the conjugate heat transfer enhancement with the ribs. Two conjugate heat transfer calculation methods with different models were developed. For the first model (CHT-Q model) solid domain was viewed as a uniform internal heat source with the adiabatic exterior surfaces, while for the second model (CHT-T model) the outwall temperature was specified by the fitting polynomials of measured data with the zero internal heat. Comparisons between the experimental and numerical results showed that the SST k–ω turbulence model was more suitable for the conjugate heat transfer in such channels. Regardless of numerical error, an approximation of heat loss was specified by the successive trial calculations of the CHT-Q model, while a relatively accurate heat loss was evaluated by the post-processing of the CHT-T calculation. Local heat transfer coefficient can be determined accurately by the quantified heat loss of test system. The critical impact of conjugate heat transfer was demonstrated. Furthermore, the steam coolant compared to air exhibited a higher heat transfer performance by 12–25% for both the ribbed and smooth walls at the same Reynolds number.

Flexible power packs combining a flexible photovoltaic part with a wearable all-solid-state supercapacitor as the self-sustaining energy system to power wearable device have attracted great interest due to the increasing demands for green energy and the tendency for multi-functionalization in electronics industry. To meet this energy requirement, we report an asymmetric all-solid-state supercapacitor, then integrate with commercial flexible solar cells to develop a self-sustaining power pack. In view of comfort for wearable electronics, cotton-textile radiation-proof clothes commonly used for pregnant woman cloth (PWC) are selected as the flexible substrate to construct wearable energy storage devices, which have the properties of flexible, green, renewable, breathable and excellent conductivity. Experimental tests demonstrate that the wearable asymmetric supercapacitors with high power density and relatively large energy density, fast charge/discharge capability, light-weight, excellent reliability and flexibility can enable the solar energy captured from the environment to afford a continuous and stable output of electric power and diminish the solar energy fluctuations. The supercapacitor is assembled with the Co–Ni layered double hydroxides (Co-Ni LDH) nanosheets as the positive electrode and the FeOOH as the negative electrode. Furthermore, the fabricated self-sustaining power pack as the energy source can continuously power the press sensor for monitoring the human physiological signals regardless of the sunlight fluctuation, demonstrating its potential usage in future wearable and portable electronic devices.

Nowadays, intelligent piezoelectric materials are widely used in transducer devices and aerospace structures. To investigate the dynamic behaviour of a functionally graded piezoelectric material (FGPM) cylindrical panel, a semi-analytical approach by introducing the Laplace transform, differential quadrature method, state space approach and Durbin’s numerical inversion of Laplace transform is presented. The accuracy of this method is validated by comparing the results with the published literature and by ANSYS under various boundary conditions. Convergence studies showed the proposed approach has a quick convergence rate with growing sample point numbers and increasing layer numbers. The analysis of initial electric potential on the outer surface and bottom surface indicated that when the plus and minus signs of two sides are opposite, the value of central electric potential will decrease. Under simply supported condition, if FG index γ increases, the deflection amplitude of the panel will increase, while the electric potential amplitude decreases. Moreover, the amplitude of displacements along the radial direction becomes larger when the central angle increases, but the period time decreases at the same time. The proposed method fills a gap of 3-D semi-analytical investigations for the dynamic behaviour of FGPM cylindrical panels in different boundary conditions.

The polycrystal CuO curved nanowires on Cu mesh were synthesized by a facile alkalization method. This visible light-driven CuO curved nanowires were observed to have highly sensitivity for non-enzymatic ethanol sensing in solution and fast antibacterial property under flashlight irradiation. In order to reveal the mechanism of polycrystal CuO curved nanowires, the comparison between polycrystal CuO nanowires and single-crystal CuO nanowires were investigated based on the analysis of the morphology, nanostructure, theoretical modeling and photoelectrochemical performance. As a result, the highest photocurrent densities were obtained by polycrystal CuO curved nanowires, as the facet heterojunction in curved nanowires played a key role, which existed in the interface between facets CuO (111) and CuO (110) resulting in the effectively separation of photoelectron-holes, thereby increasing of the charge carrier density. Herein, the CuO curved nanowires were assembled as a photoelectrochemical sensor to detect the low concentration ethanol ranging from 10 to 100 nM, and then showed a highly sensitivity. The fast antibacterial performance of CuO curved nanowires was found to completely kill 107 CFU ml−1 E. coli under flashlight irradiation in 20 min. The proposed CuO curved nanowires electrode with self-cleaning performance can be ideal for monitoring the low concentration ethanol in real-time at room temperature as photoelectrodes.

As a promising alternative to the toxic PbTe-based thermoelectric materials, eco-friendly SnTe has attracted considerable attention. Here, we use a facile solvothermal method to in-situ synthesize MXene/SnTe nanocomposites. Comprehensive characterization results indicate that the incorporation of two-dimensional MXene in SnTe matrix can suppress Sn vacancies to result in a reduced carrier concentration and induce abundant MXene/SnTe interfaces, which simultaneously optimizes the electrical and thermal transport properties. As a result, with the optimized MXene content, the maximum figure of merit of ∼0.63 ​at 823 ​K is obtained in SnTe with 0.6 ​wt% MXene, which shows a 60% enhancement compared to pristine SnTe. This work explores a new strategy to introduce two-dimensional MXene into SnTe-based materials with improved thermoelectric properties, which can inspire new pathways into designing and synthesizing high-performance thermoelectric materials.

Reduced graphene oxide (Ni/rGO) decorated by metallic Ni nanoparticles (NPs) was firstly fabricated through in situ thermal decomposition and subsequent reduction in 5% H2/N2 gas at 600 °C, and then Au NPs were loaded on the surface of the as-prepared Ni/rGO. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM) were used to characterize the Ni-decorated rGO and Ni/rGO@Au nanocomposites. The results show that both Ni and Au NPs are highly dispersed on rGO, and Ni/rGO@Au possesses excellent activity toward the conversion of 4-nitrophenol into 4-aminophenol in the presence of NaBH4, showing almost four orders of magnitude higher activity parameter κ (9.7 × 10−2 s−1mg−1) than Ni/rGO (1.1 × 10−5 s−1mg−1), though Ni/rGO has a better performance in the catalytic conversion of 4-NP. In the meantime, the Ni/rGO@Au can be easily recycled by an external magnetic field and the conversion of 4-nitrophenol at the 8th cycle is still close to 95%.

Flexoelectricity becomes remarkable in nanoscale dielectrics where strong strain gradients are expected. The effect of flexoelectricity on elastic plane waves propagating in nanoscale layered phononic crystals is discussed in the current work. The fundamental governing equations and boundary conditions are derived from the virtual work principle. Detailed calculations are performed for nanoscale two-layered and three-layered phononic crystals using the transfer matrix method. Numerical results indicate that phononic crystals possess frequency pass bands and stop bands. For nanoscale layered phononic crystals, flexoelectricity increases the middle frequency regardless of the thickness ratio, whereas the flexoelectric effect on the bandwidth depends on the thickness ratio, which implies that there is an optimal thickness ratio to maximize the bandwidth. In addition, the middle frequency and bandwidth decrease with an increase in the unit cell thickness if the thickness ratio is fixed. Hence, considering the flexoelectric effect on band structures of nanoscale phononic crystals may provide guidance in manipulating elastic wave propagation and facilitate potential applications in phononic crystal devices.

It was reported that a scanning tunneling microscopy (STM) study observed the adsorption geometry of a water monomer and a tetramer on NaCl(100) film. Based on first-principles density functional theory (DFT), the adsorption behavior of water on the NaCl surface was simulated with CASTEP code. The results showed that the water monomer almost lay on the NaCl(001) surface with one O–H bond tilted slightly downward. This was quite different from the STM observations. In fact, the experimental observation was influenced by the Au(111) substrate, which showed an upright form. A recent report on observations of two-dimensional ice structure on Au(111) substrate verified our simulations. However, the water tetramer formed a stable quadrate structure on the surface, which was consistent with observation. The intermolecular hydrogen bonds present more strength than surface adsorption. The simulations presented a clearer picture than experimental observations.

Substrate, a typical ultra-slender aluminum alloy structural components with a large aspect ratio and complex internal structure, was traditionally manufactured by re-assembly and sub-welding. In order to realize the monoblock casting of the substrate, the Pro/E software was utilized to carry out three-dimensional (3D) modeling of the substrate casting, and the filling and solidification processes were calculated, as well as the location and types of casting defects were predicted by the casting simulation software Anycasting. Results of the filling process simulation show that the metal liquid is distributed into each gap runner evenly and smoothly. There is no serious vortex phenomenon in the mold cavity, and the trajectory of the virtual particles is clear. Results of the solidification process simulation show that shrinkage cavities mainly appear at the junction of gap runners and the rail surface of the substrate. The average deformation is 0.6 mm in X direction, 3.8 mm in Y direction, and 8.2 mm in Z direction. Based on the simulation results, the casting process of the substrate was optimized, and qualified castings were successfully produced, which will provide a reference for the casting process design of other ultra-slender aluminum alloy structural components.

Due to abundant nanoscale pores developed in shale, gas flow in shale presents a complex dynamic process. This paper summarized the effects from effective stress increase, shale matrix shrinkage, gas slippage and Knudsen diffusion on the gas permeability change in shale during shale gas recovery. With the reduce in gas pressure, effective stress increase leads to the decline of the permeability in an exponential form; the permeability increases due to the shale matrix shrinkage induced by gas desorption; appearances of gas slippage and Knudsen diffusion cause an additional increase in the gas permeability particularly in small pores at low pressures. In addition, some reported models evaluating the shale permeability were reviewed preliminarily. Models considering these four effects may be potentially effective to evaluate the gas permeability change in shale.

Imaging and tracking three-dimensional (3D) nanoscale organizations and functions of live cells is essential for biological research but it remains challenging. Among different 3D super-resolution techniques, 3D structured illumination microscopy (SIM) has the intrinsic advantages for live-cell studies; it is based on wide-field imaging and does not require high light intensities or special fluorescent dyes to double 3D resolution. However, the 3D SIM system has developed relatively slowly, especially in live imaging. Here, we report a more flexible 3D SIM system based on two galvanometer sets conveniently controlling the structured illumination pattern's period and orientation, which is able to study dynamics of live whole cells with high speed. We demonstrate our microscope's capabilities with strong optical sectioning and lateral, axial, and volume temporal resolution of 104 nm, 320 nm and 4 s, respectively. We do this by imaging nanoparticle and microtubule organizations and mitochondria evolution. These characteristics enable our galvanometer-based 3D SIM system to broaden the accessible imaging content of SIM-family microscopes and further facilitate their applications in life sciences.

Natural gas hydrates are ice-like crystalline materials formed from natural gas and clathrate ice under high pressure and low temperature. Ice XVI, the first S-II type clathrate ice produced in the lab, was simulated by first-principles density functional theory with the CASTEP code. A 34-molecule supercell was built to mimic the hydrogen-disordered structure. The vibrational spectra were calculated as a reference for inelastic neutron scattering (INS), infrared (IR) absorption, and Raman scattering experiments. Two kinds of H-bond vibration modes corresponding to two different bond strengths were found in our previous studies. In this paper, the statistics of distribution calculated by integrating these two kinds of modes was found to match the phonon density of states (PDOS) very well. We confirmed that the two basic types of H-bonds also appeared in clathrate ice XVI. The typical normal modes were analyzed to illustrate the dynamic process of lattice vibrations.

A typical vibrational spectrum in the ice phase has four separate bands: Translation, libration, bending, and stretching. Ice X, the final ice phase under high pressure, shows an exotic vibrational spectrum. Based on harmonic approximation, an ideal crystal of ice X has one peak, at 998 cm&minus, 1, for Raman scattering and two peaks, at 450 cm&minus, 1 and 1507 cm&minus, 1, for infrared absorption in this work. These three characteristic peaks are indicators of the phase transition between ice VII and VIII and ice X. Despite many experimental and theoretical works on ice X, only this study has clearly indicated these characteristic peaks in the region of the IR band. The phonon density of states shows quite different features than ice VIII, which could be verified by inelastic neutron scattering in the future. The dynamic processes of 15 vibrational normal modes are discussed and the typical hydrogen bonds are missing.

Under different ambient temperatures, the thermal aberration certainly affects the imaging quality of infrared multi-spectral camera. Therefore, an athermalized model of infrared multi-spectral cameras is established, and in this model the ambient infrared multispectral camera is equivalent to a separated dual-lens optical system. In the case of the fixed focal length, the influence of the back focal length on the change of the focal power of the front lens and back lens is analyzed. Now, the variation range of the front and rear lens interval is assumed to be restricted. When the back focal length is smaller than the focal length, the ratio of the absolute value of the focal power of the front lens to the absolute value of the focal power of the back lens decreases with the back focal length increasing. The material of the front lens and the back lens have a longer interval on the thermogram. When the back focal length is greater than the focal length, the scenario becomes exactly opposite. Combined with the judgment method of the positive value and negative value of the focal power on the thermogram, the selection range of materials is constrained by the positive value, negative value, and absolute value of focal power, thus realizing the rapid selection of the optical materials. This method is used to design an athermalized infrared multispectral camera with a waveband of 8–14 μm, a focal length of 50 mm, and an F number of 1.4 in a range from –40 ℃ to +60 ℃. Through the simulation analysis, the value of the athermalized infrared multispectral camera, at the Nyquist frequency of 30 lp/mm reaches 0.39, which is close to the diffraction limit; the root mean square radius of the diffuse spot is smaller than the Airy spot radius of 19.17 μm; the axial aberration is less than 0.02 mm, and the design results show that this method can make the long back-focus infrared optical system maintain stable imaging quality in a large temperature range. The SF6 gas is detected experimentally, and the experimental results demonstrate the excellent optical performance of the system.

The hexafluorophosphate type ionic liquids, as one kind of functionalized ionic liquids, have a good application prospect in many fields. In this work, a series of diimidazole hexafluorophosphate ionic liquids with different carbon chain lengths (CnDIMF, n = 1, 2, 3, 4, 5, 6) were synthesized and characterized, so as to find the influence of cation on their structure and properties. The results showed that these products are needlelike or lamellar crystals, and their solubility and thermal stability were similar, but there are significantly different in their melting points and crystal structures. They were insoluble in non-polar or weak polar solvents, while have good solubility in polar aprotic solvents. Surprisingly, they could exhibit the temperature-controlled characteristics in methanol and water. These products have a good thermal stability up to 300 °C, and their decomposition temperature also slightly increases from 360 to 395 °C with the increase in the spacer chain length. The melting points of them are above 120 °C, which increased with the decrease of molecular weight if they belong to the same crystal system. Crystallography data showed that two cationic 1-vinylimidazolium were bound to the both sides of alkyl group, and the two imidazole rings were crystallographically dependant plane, and their structure changed from a semi-capsule with a close angle to a linear with a wide angle between the two imidazole rings. The study and determination of these properties, especially the temperature-controlled performance, is interesting and can afford reliable reference for future applications.

High-performance membrane materials are urgently demanded for efficient membrane-based biogas upgrading. Polyelectrolytes with convertible ionic groups, spontaneously forming interconnected facilitated transport pathways for gas molecules via microphase separation, exhibit promising potential in membrane-based separation. However, there is a great challenge to further enhance the gas permeability and selectivity simultaneously due to the limited microphase separation and low free volume generated by the strong interaction between ionic groups. Herein, we demonstrate a novel strategy to construct the tunable hollow quaternary ammonium (-N+(CH2CH3)3) clusters with good CO2 affinity via sacrificial template method in quaternized polysulfone (QAPSf) membranes for achieving the fast transport of CO2. The templates (POSS) induce the formation of –N+(CH2CH3)3 clusters through forced microphase separation in the membranes and then are etched away to generate hollow CO2-philic clusters to increase the fractional free volume in membranes and thus improve CO2 diffusion. After that, the B(OH)4- as counterions by ion exchange endow the hollow CO2-philic clusters with high CO2-facilitating ability, which simultaneously enhance the CO2 permeability and CO2/CH4 selectivity. The resultant QAPSf-B(POSS-2) membrane exhibits superior separation performance with an optimal permeability of 1113 Barrer and a CO2/CH4 gas selectivity of ~45, i.e. 334% and 73% higher than the pristine QAPSf membrane, respectively, breaking the trade-off between permeability and selectivity and surpassing the Robeson 2008 upper-bound.

This study investigated the pore structure and its effects on mechanical properties of lightweight cellular concrete (LCC) in order to understand more and detailed characteristics of such structure. As part of investigation, environment scanning electron microscopes (ESEM) and industrial high-definition (HD) macro photography camera were separately used to capture and compare images of specimens. Physical properties of the pore structure, including pore area, size, perimeter, fit ellipse, and shape descriptors, were studied based on the image processing technology and software applications. Specimens with three different densities (400, 475, and 600 kg/m3) were prepared in the laboratory. Firstly, the effects of density on the characteristics of pore structure were investigated, furthermore, mechanical properties (compressive strength, modulus of elasticity and Poisson&rsquo, s ratio, flexural strength and splitting tensile strength of LCC) were tested. The relationships among pore characteristics, density, and mechanical properties were analyzed. Based on the results obtained from the lab test&mdash, comparisons made between specimens with high-densities and those with low-densities&mdash, it was found significant variability in bubble size, thickness, and irregularity of pores. Furthermore, the increase of density is accompanied by better mechanical properties, and the main influencing factors are the thickness of the solid part and the shape of the bubble. The thicker of solid part and more regular pores of LCC has, the better mechanical properties are.

Extending SPs and BSWs for microscopy leads to imaging artifacts, which are removed by using azimuthal rotation illumination., Surface plasmon resonance microscopy (SPRM) with single-direction illumination is a powerful platform for biomedical imaging because of its wide-field, label-free, and high-surface-sensitivity imaging capabilities. However, two disadvantages prevent wider use of SPRM. The first is its poor spatial resolution that can be as large as several micrometers. The second is that SPRM requires use of metal films as sample substrates; this introduces working wavelength limitations. In addition, cell culture growth on metal films is not as universally available as growth on dielectric substrates. Here we show that use of azimuthal rotation illumination allows SPRM spatial resolution to be enhanced by up to an order of magnitude. The metal film can also be replaced by a dielectric multilayer and then a different label-free surface-sensitive photonic microscopy is developed, which has more choices in terms of the working wavelength, polarization, and imaging section, and will bring opportunities for applications in biology.

In this paper, a new method is proposed for super-resolution imaging of non-fluorescent samples. This approach is based on the intensity difference between confocal image and negative confocal image, which are simultaneously acquired at one sample scanning. In order to get these two different images simultaneously, the sample was illuminated by two different focused spots from the same laser source: the doughnut spot and the solid spot. The effectiveness of the label-free difference microscopy based on parallel detection was validated by experiments on some samples including 80 nm gold beads, 100 nm silver nanowires, and Blu-ray DVD without fluorescent dyes. By subtraction of the reflected light intensity from the sample, the final resolution of the image without deconvolution was enhanced about 1.6 times compared with confocal imaging. This technique can be applied to surface topography detection of metallographic or other non-fluorescent materials.

Using a first-principles density functional theory method, we calculated the vibrational spectrum of ice XIII. In combination with spectroscopic experiments, we demonstrated that the two characteristic hydrogen bond (H-bond) peaks in the translational region of ice V (the hydrogen-disordered counterpart of ice XIII) recorded by inelastic neutron scattering originate from two basic H-bond vibrational modes. We first observed this phenomenon when studying ice Ic and then confirmed it when studying ice XIV, XVI, and XVII. This study of high-pressure ice XIII supports our theory that two basic H-bond modes exist as a general rule among the ice family. The “isolated O–H vibration modes” found by Whale et al. when studying ice XV are also discussed in this work.

Image scanning microscopy based on pixel reassignment can improve the confocal resolution limit without losing the image signal-to-noise ratio (SNR) greatly [C. J. R. Sheppard, “Super-resolution in confocal imaging,” Optik 80(2) 53–54 (1988). C. B. Müller, E. Jörg, “Image scanning microscopy, “Phys. Rev. Lett. 104(19) 198101 (2010). C. J. R. Sheppard, S. B. Mehta, R. Heintzmann, “Superresolution by image scanning microscopy using pixel reassignment,” Opt. Lett. 38(15) 2889–2892 (2013)]. Here, we use a tailor-made optical fiber and 19 avalanche photodiodes (APDs) as parallel detectors to upgrade our existing confocal microscopy, termed as parallel-detection super-resolution (PDSR) microscopy. In order to obtain the correct shift value, we use the normalized 2D cross correlation to calculate the shifting value of each image. We characterized our system performance by imaging fluorescence beads and applied this system to observing the 3D structure of biological specimen.

The design of laminated glazing for blast resistance is significantly complicated by the post-crack behaviour of glass layers. In this research, a novel numerical method based on a semi-analytical energy model is proposed for the post-crack behaviour of crazed panes. To achieve this, the non-homogenous glass cracks patterns observed in literature experimental and analytical work was taken into consideration. It was assumed that, after the glass crazing, further deformations would occur in the cracked edge areas, whilst the central window surface would remain largely undeformed. Therefore, different internal work expressions were formulated for each zone and were then combined in the overall model. The resulting differential equation was then solved numerically. The results obtained were compared with data from four experimental full-scale blast tests for validation. Three of these blast tests (Tests 1–3) were presented previously (Hooper et al., 2012) on 1.5 × 1.2 m laminated glazing samples made up with two 3 mm glass layers and a central 1.52 mm PVB membrane, using a 15 and 30 kg charge masses (TNT equivalent) at 13–16 m stand-off. The fourth blast test (Test 4) was conducted on a larger 3.6 × 2.0 m pane of 13.52 mm thickness, using a 100 kg charge mass (TNT equivalent) at a 17 m stand-off. All blast tests employed the Digital Image Correlation (DIC) technique to obtain 3D out-of-plane deflections and strains. The proposed analytical method reproduced the experimental deflection profiles, with the best estimates obtained for the more severe loading cases. Reaction forces were also compared with experimental estimates. The predictive ability of the proposed method could permit more accurate designs to be produced rapidly, improving structures resistance to such loadings.

Flexoelectricity, representing the coupling between electrical polarizations and strain gradients, should be taken into account in the analysis of electromechanical responses of nanostructures where large strain gradients are expected. In this paper, we will explore the influence of flexoelectricity on the electromechanical coupling behavior of a simply supported piezoelectric nanoplate by using the Kirchhoff plate theory. The governing equations and corresponding boundary conditions are deduced from Hamilton’s principle, and the analytical solutions are obtained for the deflection and natural frequency. The results indicate that the deflections predicted by the present model are smaller than those calculated by the classical one which only considers piezoelectricity, while the frequencies exhibit the opposite trend. In addition, the flexoelectric effect is more prominent for thinner plates; the differences of the deflections or frequencies between the two models are gradually diminishing with an increase in the plate thickness. The current work may contribute to the understanding of the higher-order electromechanical coupling mechanism. Moreover, the modified plate model can be utilized to accurately design novel piezoelectric nanoplate-based sensors in nanoelectromechanical systems.

GO-F127-RFP composite was prepared by none covalent bond of π-π-stacking, and the properties were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), field-emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), drug loading content, antibacterial activity and cytotoxicity assay. The results show that GO-F127-RFP composite is successfully prepared, and the carrier GO-F127 can load more drug RFP than other carriers, GO-F127-RFP composite has the antibacterial ability and GO-F127-RFP can lower the cytotoxicity of RFP, which make it a talent lung targeted system for curing tuberculosis (TB).

The pile foundations below approach slab in a semi-integral abutment jointless bridge (SAJB) that requires high flexibility to accommodate the horizontal cyclic deformation of approach slab generated by the girder&rsquo, s thermal expansion and contraction as well as earthquake action. In this paper, reactive powder concrete (RPC) and reinforce concrete (RC) micro piles were designed and fabricated. The shaking table tests on dynamic response of micro piles-soil interaction were conducted to investigate the dynamic response characteristics such as the strain time history of pile-soil system, the bending moment, and the deformation of piles. The maximum strain response of piles was observed at the buried depth of 4.2 D (D is the diameter of pile). Meanwhile, the maximum bending moments of RPC and RC piles appear at the depth of 0.64 D and 0.42 D, respectively, under the dynamic load excitation, and the peak horizontal deformation of piles were observed at pile head. It is found that the bending moment and the strain response of the RPC pile are larger than that of the RC micro pile, and increased by 40% and 98%, respectively. The RPC micro pile has better crack resistance, higher ductility, and flexural rigidity than that of the RC pile, and it can be widely used as pile foundations in SAJBs for the earthquake area.