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Compressed hydrogen tanks are now widely used for onboard hydrogen storage in fuel cell vehicles (FCVs). However, because of the high storage pressure and the low thermal conductivity of carbon fibre reinforced polymer (CFRP), the emptying of such tanks during driving or emergency release can cause a significant temperature decrease and result in an in-tank gas temperature below the low safety temperature limit of −40 °C even in warm weather. Once the gas temperature within the tank is lower than −40 °C, the sealing elements at the boss of the tank may fail, and glass transition of the polymer liner of the type IV tank may occur; both can cause hydrogen leakage and severe safety problems. In this paper, the heat transfer correlations, thermodynamic analyses, computational fluid dynamics (CFD) simulations, experimental studies, and thermal management methods associated with the emptying process of compressed hydrogen tanks are comprehensively reviewed. Future research directions on this topic are suggested.

Highly conductive, conformable and gel-free electrodes are desirable in human electrophysiology. Besides, intimately coupling with human skin, wearable strain sensors can detect numerous physiological signals, such as wrist pulse and breath. In this study, a multilayer graphene nanosheet film (MGNF) with high conductivity was prepared by the Marangoni self-assembly for using in tattoo dry electrodes (TDEs) and in a graphene tattoo strain sensor (GTSS). Compared to commercial Ag/AgCl gel electrodes, TDEs have lower skin-electrode contact impedance and could detect human electrocardiogram for 24-hour wearing more accurately as well as electromyogram. Through designing a slim serpentine ribbon structure, a resistance-type GTSS, without deterioration even after 2000 cycles, is well demonstrated for human wrist pulse and breath sensing. With the advantages of high conductivity and conformability, MGNF provides support to fabricate low-cost, customizable, and high-performance electronic tattoos for human electrophysiology and strain sensing.

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.

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.

The application of optical microscopy in four-dimensional (spatial and temporal) super-resolution imaging poses challenges because of the requirement of a long acquisition time or high illumination intensity. In this paper, we introduce simultaneous two-angle axial ratiometry (STARII) for

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...

We report on the design and implementation of an integrated dual-color stimulated emission depletion (STED) microscopy and fluorescence emission difference (FED) microscopy. This highly integrated system combines the respective advantages of STED and FED microscopies, enabling acquisition of super-resolution STED images with specific fluorophores and high laser power, or resolution-enhanced FED imaging for ordinary fluorescent dyes and other materials with moderate demand for laser power. The functional integration enables researchers to select the more appropriate microscopy according to practical scenario and requirements, giving full play to their respective strengths and satisfying the imaging demands maximally. The system’s resolution is characterized by dual-color imaging of fluorescent particles. Its practical applicability is verified through imaging various kinds of samples, including several fixed cells stained with different organic dyes and a given organic material—organometallic halide perovskite.

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.

We propose a novel parallelized fluorescence lifetime imaging microscopy (FLIM) method based on photon reassignment with a detector array and time-correlated single photon counting (TCSPC) array. The detector array composed of seven avalanche photon diodes (APDs) substitutes for original pinhole and detector to constitute an imaging scanning microscopy (ISM) system. The introduction of parallel detection can solve the pile-up effect caused by the dead-time in TCSPC measurement, which can enhance the effective photon detection efficiency and notably increase the fluorescence lifetime imaging speed. More importantly, the resolution and signal–noise ratio (SNR) can be enhanced based on photon reassignment. The simulation results embody the superiority of our FLIM system, and the experiments with different samples validate the improvement of the resolution and speed of fluorescence lifetime imaging. The experiment results show that the resolution of our method is enhanced by a factor of 1.5 and the imaging speed can be at least increased by a factor of 2.5 compared with conventional confocal TCSPC FLIM system. We envision that the proposed FLIM method based on parallel detection will allow for super-resolution fluorescence lifetime real-time imaging of live cell.

The exploration of energy conversion and storage devices for wide-temperature operation is presently a grand challenge. Herein, the single-crystalline integrated energy-storage units based on highly-oriented 4H-SiC nanochannel arrays (NCAs) were fabricated via an improved electrochemical anodic oxidation technique from 4H-SiC wafers. The as-prepared SiC NCAs electrode exhibits an areal capacitance of 14.8 mF cm−2 at 10 mV s−1, which is the highest for SiC electrodes ever reported and also 6-fold higher in comparison to that of SiC nanowire array electrode (NWAs, 2.32 mF cm−2). Moreover, the resultant 4H-SiC NCAs exhibit an extremely stable cycling performance in aqueous electrolytes, with higher than 95% retention of initial capacitance regardless of being serviced under low, high or cross-fade temperatures for 11 000 charge–discharge cycles, demonstrating that they are nearly full-featured for robust wide-temperature operation.

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.

Different from piezoelectricity which is restricted to certain materials, flexoelectricity is a universal electromechanical coupling in all dielectrics. In this work, mechanical energy harvester models were developed based on Timoshenko laminated beam theory, in which the flexoelectric and piezoelectric mechanisms were discussed. For a three-layered energy harvester in parallel configuration, the mechanical vibration energy can be converted into electrical energy due to flexoelectricity, and for the three-layered energy harvester in series configuration, the energy conversion is enhanced by the flexoelectricity. Resonance frequency shifts were observed in the calculations due to flexoelectricity and external circuit resistance. It is found that the electromechanical coupling displayed from the electrical responses versus resonance frequency and resistance. The energy conversion for the three-layered energy harvester system was found to be increased with the decrease in the laminated beam thickness. The energy conversion calculated for different numbers of layers also indicates that laminated energy harvester systems excel single-layered energy harvesters. This work therefore might help in designing flexoelectricity-based energy harvesters.

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.

An analytical method and a semi-analytical method are proposed to analyze the dynamic thermo-elastic behavior of structures resting on a Pasternak foundation. The analytical method employs a finite Fourier integral transform and its inversion, as well as a Laplace transform and its numerical inversion. The semi-analytical method employs the state space method, the differential quadrature method (DQM), and the numerical inversion of the Laplace transform. To demonstrate the two methods, a simply supported Euler–Bernoulli beam of variable length is considered. The governing equations of the beam are derived using Hamilton's principle. A comparison between the results of analytical method and the results of semi-analytical method is carried out, and it is shown that the results of the two methods generally agree with each other, sometimes almost perfectly. A comparison of natural frequencies between the semi-analytical method and the experimental data from relevant literature shows good agreements between the two kinds of results, and the semi-analytical method is validated. Different numbers of sampling points along the axial direction are used to carry out convergence study. It is found that the semi-analytical method converges rapidly. The effects of different beam lengths and heights, thermal stress, and the spring and shear coefficients of the Pasternak medium are also investigated. The results obtained in this paper can serve as benchmark in further research.

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.

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.

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.

In order to predict the absorbing properties of absorbing material effectively in theory, effective media theory was applied to reduce the effective electromagnetic parameters of several composite absorbing agents under different volume ratio. The comparison with experimental data shows that this method can well forecast the absorbing properties of absorbing material. For practical absorbing agent and penetrating agent, this method can compute the optimal proportioning and material thickness.

In this paper, a new anti-vibration bearing is proposed to mitigate vertical train-induced vibrations to improve the vibration environment around the elevated urban rail transit. A scale model test is carried out to verify the vibration reduction effect of a new anti-vibration bearing. Test result shows that vibration amplitudes of new anti-vibration bearing at the upper and lower plates are smaller than those of steel bearing while the electromagnetic vibrator is working on the test model. The whole insertion loss of anti-vibration bearing is 13.49 dB, which is 5.32 dB larger than that of steel bearing. For most frequency components, the new anti-vibration bearing can reduce more vibrations than the steel bearing in the vertical direction. Therefore, this kind of bearing is effective to isolate the vertical vibration.

The use of zirconia crown has attracted considerable attention due to its good mechanical and optimal biocompatility. The white color of zirconia does not allow for perfect aesthetic characteristics though. Colorized zirconia blocks with Pr6O11, Er2O3and Fe2O3gradient concentration and the shade stability were investigated. Chromatic values of the samples were presented in CIELab system, and the shade stability was evaluated by color comparison of samples in the same group. The value of L* from 68.2-84.0, a* from-1.8-5.9, and b* from 18.6-33.2 can be obtained. These values can be comparable to the Vita 3D master system. The E between the samples of every group was below 2.2. The results showed that by adding combined oxides of gradient concentration could reproduce the tooth-like color of zirconia ceramics, and the shade stability was satisfied.

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.

In this paper, recent progress in polymer white light-emitting materials and devices published until April 2012 was reviewed according to the kinds of the materials and devices. The polymer light-emitting materials were reviewed by the classification of small-molecule-doped polymer type, polymer blend type, polymer doped small molecule type, molecule-dispersed polymer type, dye-terminated polymer type, and excimer white EL polymer type. The polymer light-emitting devices were reviewed by the classification of fabricating PWLED through the multilayer device and improving efficiency through the multilayer device. The relationship between the structures of materials or devices and properties was the main content during review. At last, some scientific problems and developing trends on PWLED are discussed.

This paper presents a research on skin effect’s influence on the current density distribution of Cu/barrier layer and Cu/cap layer interfaces of copper interconnects’ via vicinities. A two-level Cu-interconnect structure in different positional relationships with the ground plane is discussed. Through the three-dimensional (3D) finite element simulation of the interconnect structure, the variations of current density on three important surface areas are obtained when skin effect is significant, showing that the current density in the three surface areas near the via has been strongly influenced by current crowding and skin effect. So in many cases the influence of skin effect on via top and via bottom failures of Cu interconnects under high frequencies can not be ignored.

In order to improve absorbing properties of material effectively, enhance the ability of attenuating electromagnetic wave, and at the same time, make the impedance matching with air to the most extent, this paper mixed ferrite magnetism microwave-absorbing agents with semiconductor particulates. We got the effective EM parameter of the mixture using effective EM parameter model, and then analyzed absorption properties. As the result, it figured out the cubage proportion and conductance of semiconductor particulates based on the resistance matching principle. Through calculating the reflection ratio、impedance matching characteristic and attenuation coefficient of the material, it is proved that mixing ferrite magnetism microwave-absorbing agents with semiconductor particulate which has less permittivity could reduce real complex permittivity and increase imaginary complex permittivity of the composite material. It was able to enhance the ability of attenuating electromagnetic wave, improve absorbing properties, and meanwhile do not destroy the impedance matching characteristic with air.

In order to compare the absorbing properties of different microwave-absorbing agents and their mixture, this paper has selected two typical microwave-absorbing agents which respectively are carbon fiber resistance microwave-absorbing agents and ferrite magnetism microwave-absorbing agents, and took them as monolayer absorbing materials. Then used MG formula to calculate the effective electromagnetic parameter of their mixture under different proportion at X band, and finally analyzed their absorbing properties separately. Then through contrasting the impedance matching characteristic and attenuation coefficient of the materials, it is proved that adding carbon fiber in ferrite can not improve absorption properties. Although the ability of attenuating electromagnetic wave would be enhanced when resistance materials and magnetism materials are blend with each other, doping will destroy the materials’ impedance matching characteristic because most resistance materials have high permittivity. It makes reflection strengthen and can not improve absorbing properties.

Microwave diffraction behavior of microwave absorbing ceramics was investigated by numerical calculation, and effective electro-magnetic parameters of the ceramics was obtained by comparing the diffraction behavior with that of homogeneous material. Then, the calculated results were compared with the results of effective medium models, aiming to investigate the applicability of these models. The obvious difference between these results were pointed out, also discussed is the possible reason for this difference.

Fujian Provincial Natural Science Foundation [2009J05157, 2009H0043]; National Natural Science Foundation of China [60807029]; Xiamen University

In order to keep the temperature of Light emitting diode (LED) lamp below some limitation, a finned plain-plate heat-pipe was presented and numerically investigated to predict heat transfer performance under natural convection. Two kinds of fin configurations were studied. It is found that 30° is the worst orientation for the fin configuration with the tops of every other two channels covered, while the worst orientation is around 60° for the fin configuration with channel tops opened. The thermal conductivity of fin material only has mild effect on the cooling capacity with 7 % difference when its thermal conductivity varies from 50 to 200 W/(m·k). The latter configuration has better thermal performance than the former at the same orientation, especially at relatively low inclined angle.

Backlights based on white LEDs have significant advantages for liquid crystal display(LCD) such as good optical property,low power dissipation,long lifetime,high contrast,simple drive system and so on.However,not all LEDs are suitable for light source of backlights.The influence of liquid panel and different white LEDs on color gamut are investigated.Results showed that,to obtain high color gamut,LCD pannel and the corresponding LED light source are needed.Due to the mixed crest,2-band LEDs which used for illumination only achieved 75.2% NTSC gamut.Then for 3-band LEDs,as its crests are independent relatively,it could obtained 84.2% color gamut.

Prefabricated glass fiber posts are widely used; however, their shape cannot be changed and they can be unsuitable for severely damaged teeth with wide root canals. This clinical report describes a procedure for restoring a severely damaged anterior tooth with a customized 1-piece glass fiber post and core, fabricated using a CAD/CAM system. This 1-piece glass fiber post and core adapts better to the root canal than a prefabricated glass fiber post, and reduces the cement layer thickness. Furthermore, it does not require the use of a composite resin foundation. (J Prosthet Dent 2010;103:330–333)

In order to reveal the mechanism of extrusion forming for large-scale aluminum alloy seamless pipe, in this research the rigid-viscous plastic finite element method was used to analyze the effect of the technological parameters of the aluminum alloy pipe extrusion process, consistent with the use requirements.

An optically fixed photorefractive correlator is presented, where two-centre non-volatile holographic recording is employed to write and fix the matched filter in doubly doped LiNbO3 crystals. This correlator shows good correlation characteristics and insensitivity to the writing beam during readout. It can be used in cases requiring stability and not requiring modification for a long period and it is refreshed optically when new information needs to be registered.

In this paper, a phenomenon of polarization introduced by shock waves is experimentally studied. Although this phenomenon has been reported previously in the community of physics, this is the first time to link it to flexoelectricity, the coupling between electric polarization and strain gradients in dielectrics. As the shock waves propagate in a dielectric material, electric polarization is thought to be induced by the strain gradient at the shock front. First, we control the first-order hydrogen gas gun to impact and generate shock waves in unpolarized bulk barium titanate (BT) samples. Then, a high-precision oscilloscope is used to measure the voltage generated by the flexoelectric effect. Based on experimental results, strain elastic wave theory, and flexoelectric theory, a longitudinal flexoelectric coefficient of the bulk BT sample is calculated to be μ 11 = 17.33 × 10 − 6 C/m, which is in accord with the published transverse flexoelectric coefficient. This method effectively suppresses the majority...

Due to the electromechanical coupling effect, mechanical energy can be converted into electrical energy in certain materials. A theoretical framework is established to investigate the circuit voltage, electric power of nanoscale mechanical energy harvesting, in which the mechanical vibration energy was converted into electrical energy by piezoelectric and flexoelectric effects. Analytical solutions for the maximum electric potential, circuit voltage and electric power generated in bent BaTiO3 (BT), ZnO nanowires (NWs) and Pb(Mg1/3Nb2/3)O3 (PMN) nanofilms (NFs) were derived. Static and dynamic analyses are conducted to obtain the fundamental information of these mechanical energy harvestings. Different from the previous studies, the flexoelectric-mechanism are included in the fundamental mechanical frameworks. The maximum electric potential generated in the BT, ZnO NWs and PMN NF is found to be enhanced by flexoelectricity in the static case, meanwhile the circuit voltage and electric power are dramatic enhanced by flexoelectricity when the geometric dimensions shrinks to dozens of nanometers. The mechanical limitation condition is employed to calculate the practical maximum electric potential, circuit voltage and electric power. This work tries to provide a comprehensive understanding of the mechanical energy harvesting capability of these nanoscale structures and provide valuable information for designing flexoelectricity-based nanogenerator devices.

Carbon fiber-reinforced polymer composites (CFRPs) are good candidates in enhancing the blast resistant performance of vulnerable public buildings and in reinforcing old buildings. The use of CFRP in retrofitting and strengthening applications is traditionally associated with concrete structures. Nevertheless, more recently, there has been a remarkable aspiration in strengthening metallic structures and components using CFRP. This paper presents a relatively simple analytical solution for the deformation and ultimate strength calculation of hybrid metal-CFRP beams when subjected to pulse loading, with a particular focus on blast loading. The analytical model is based on a full interaction between the metal and the FRP and is capable of producing reasonable results in a dynamic loading scenario. A nonlinear finite element (FE) model is also developed to reveal the full dynamic behavior of the CFRP-epoxy-steel hybrid beam, considering the detailed effects, that is, large strains, high strain rates in metal, and different failure modes of the hybrid beam. Experimental results confirm the analytical and the FE results and show a strong correlation.

We propose and experimentally investigate a new scheme capable of suppressing light-induced scattering by periodical incoherent erasure during every non-volatile holographic recording cycle in photochromic LiNbO3:Fe:Mn crystals. The results demonstrate that the scattering noise is suppressed effectively, and the final diffraction efficiency of the fixed grating is significantly enhanced, rather than decreased, by about 30% compared with the conventional recording procedure. The period of the recording and incoherent erasure cycle is theoretically calculated and experimentally optimized.

The Kukhtarev two-center model for photochromic doubly doped LiNbO3:Fe:Mn crystals is both numerically and analytically solved for the recording sensitivity and the fixed nonvolatile space-charge field. An optimal prescription for material doping and oxidation/reduction processing is found, which requires that the crystal should be strongly oxidized together with a suitable Mn density with respect to the Fe density. Experiments performed with an oxidized crystal and a reduced crystal prove the prediction.

Lower electromagnetic backscattering from concrete pavement as its smooth surface results the much darker image feature when exposures to imaging radar when compared with rough surface such as vegetation. In this paper, exploratory research on radar cross-section enhancement of concrete specimens with composite scatterer consisted of fiberglass reinforced plastics and trihedral corner reflector (FRP-TriCR) buried is presented. Scattering properties of concrete specimen, corner reflector, concrete specimen mixed with corner reflectors and with FRP-TriCR buried are numerical simulation based on the model of finite difference-time domain (FD-TD) in lossy dielectric with perfect matched layer (PML) in z-direction and period boundary conditions(PBC) in x,y-direction. In the conditions of given incident wave and dielectric coefficient of concrete specimen, the monostatic RCS of concrete specimen with FRP-TriCR buried is -5.6 dBsm and the average is -10.6 dBsm when theta is 30 to 60 degree, which increase much when compared to concrete specimen mixed trihedral corner reflector ( monostatic RCS is -12.3 dBsm, the average is -15.8 dBsm from theta = 30 to theta = 60 degree). It is much more important that FRP-TriCR scatterer is independence of moisture of concrete. On the other hand, the transmission characteristic of infrared radiation has been changed because of cavity structure, which is possible for compatibility for camouflage.