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A fretting wear model of rough surface that conforms to the actual situation is established to accurately reveal the wear mechanism of the connection structure. In the ABAQUS software, the UMESHMOTION subroutine and the energy dissipation model are used to simulate the fretting wear of double rough surfaces. The new model, a single rough surface model, and a smooth model are compared to analyze the differences between them. In addition, the influence of surface roughness, material, and friction coefficient on the fretting wear of rough surfaces is systematically explored through finite element simulation. The results show that the reliability of the model has been verified through Hertz’s theory and experiments. The stress and wear of the contact surface are more realistically reflected by the double roughness model. Besides, with the increase of surface roughness and material rigidity and the decrease of friction coefficient, the wear of the double rough surface model becomes more severe. The research work provides a theoretical basis for the design and performance prediction of the connection structure.

Optical combination lock is a combination of mechanical combination lock and MEMS technology, which can effectively reduce the size of the combination lock. The mechanism of MEMS optical combinatio...

Thin-walled plastic parts are susceptible to deformation during injection molding. Using the example of a notebook battery cover, optimization of the injection mold design and injection process parameters was performed with Moldflow software, which resulted in about 69% reduction of the deformations. Moreover, the uneven material shrinkage during the injection process has been shown to be the main cause of deformations of thin-walled plastic parts.

Heterostructures are an important class of materials with desirable size, morphology, and functionality because of their promising applications in biosensor and photonic communication device. However, no such technology of synthesizing heterojunctions is as convenient as electric welding. Particularly, synthesizing heterojunctions with large lattice‐mismatch has been subjected to a great challenge. Herein, the hybrid heterojunction structures are obtained by in situ chemical transformation from fluoride to oxyfluoride via a laser irradiation‐welding approach (LIWA). Single NaYbF4:Ho3+@YbOF:Ho3+ heterojunctions with unique morphologies including hollow spheres, lollipops and sponge‐like plates, are successfully prepared by deliberate control over precursor particles and light welding parameters. These unique luminescent heterojunctions can not only integrate distinctive properties of fluoride and oxide, but also exhibit the unprecedented convenience for color tunability. This work provides an ultrafast LIWA for the fabrication of lattice‐mismatched heterojunctions in seconds, and LIWA allows tunable laser parameters to control the microstructures and characteristics of heterojunctions for widespread applications.

To assess a precast concrete vibrating table, a system mechanics model was established by using the transverse vibration theory of thin plates. The model was then simplified as a stiffened plate structure according to the structural characteristics of a vibration platen. Specifically, the vibration mode functions of the vibration platen were established by utilizing a two-dimensional beam function method in which the maximum kinetic energy and maximum strain energy of the vibration platen were derived. Additionally, the Rayleigh-Ritz method based on the displacement variation principle was utilized to analyze the natural frequency and mode shapes of the vibration platen. A comparison between the theoretical calculation results and the finite element simulation results indicated that the established vibration mode functions can appropriately reflect the mechanical behavior of the vibration platen, which verified the correctness of the analysis method for the inherent characteristic of the vibration platen and provided a preliminarily theoretical basis for the performance improvement of a precast concrete vibrating table.

Among the patterning technologies for organic thin-film transistors (OTFTs), the fabrication of OTFT electrodes using polymer templates has attracted much attention. However, deviations in the electrode alignment occur because the coefficient of thermal expansion (CTE) of the polymer template is much higher than the CTE of the dielectric layer. Here, a novel dry-blending method is described in which SiO2 nanoparticles are filled into a grooved silicon template, followed by permeation of polydimethylsiloxane (PDMS) into the SiO2 nanoparticle gaps. The SiO2 nanoparticles in the groove are extracted by curing and peeling off PDMS to prepare a PDMS/SiO2 composite template with a nanoparticle content of 83.8 wt %. The composite template has a CTE of 96 ppm/°C, which is a reduction by 69.23% compared with the original PDMS template. Finally, we achieved the alignment of OTFT electrodes using the composite template.

Establishing an accurate and effective stiffness model of the elastic contact surface is the basis for further modeling and analysis of machine tool dynamics. In this paper, a new elastic contact stiffness model is proposed that considers the bulk substrate deformation and modifies the Greenwood and Williamson microcontact model (GW model) of rough surfaces. Based on the Hertz contact theory and fixed-point iteration method, a single asperity contact model is created to analyze the effects of bulk substrate deformation and coating materials. To make the contact stiffness model more accurate and effective, two aspects are improved: One is to introduce the triangular distribution function to make the asperity heights distribution more consistent with the actual machined surface, and the other is to correct the defects in the micro-contact process. Comparing the finite element simulation results with the modal test data, the correctness of the proposed contact stiffness model is verified. The simulation results reveal the influence of distribution function, surface roughness and coating material on the contact characteristics of the joint surface.

The V-shaped electro-thermal MEMS actuator model, with the human error factor taken into account, is presented in this paper through the cascading ANSYS simulation model and the Fuzzy mathematics calculation model. The Fuzzy mathematics calculation model introduces the human error factor into the MEMS actuator model by using the BP neural network, which effectively reduces the error between ANSYS simulation results and experimental results to less than 1%. Meanwhile, the V-shaped electro-thermal MEMS actuator model, with the human error factor included, will become more accurate as the database of the V-shaped electro-thermal actuator model grows.

A new model to accurately obtain the contact stiffness of the mechanical joint surface is established, which satisfies the continuous smooth contact characteristics of the asperity and also considers the influence of the asperity interaction. In order to satisfy the continuous and smooth contact characteristics of the asperity, the interpolation interval of the Hermite polynomial function is improved to make the asperity contact stiffness curve smoothly transition in the elastic, elastoplastic and completely plastic stages. Further, the contact situation of the joint surface considering the asperity interaction is explored through micro-contact analysis and mechanism research. Finally, using statistical principles, the microscopic contact model is extended to the entire joint surface, and the contact stiffness model of the joint surface is established. The simulation results show that the asperity stiffness model satisfies the continuous smooth contact characteristics. Surface roughness is the main factor that affects the contact stiffness, and the influence of the asperity interaction cannot be ignored.

Upconversion (UC) micro/nanomaterials have enabled many promising applications owing to their unique near-infrared to visible emission characteristics. However, some practical applications are limited by the static and invariant emission colours and patterns of UC materials. Here, we demonstrated a novel dynamic UC luminescence pattern and luminescent heterogeneous spatial distribution mediated by laser irradiation. Interestingly, the distinct red dumbbell pattern was submerged gradually by moving the green stripes from the excitation position at one end of a microtube to the other end along the length direction when elevating the power density of excitation light. The underlying reason for the dynamic luminescence patterns obtained by power density controlling was explored, and a mechanism based on an in situ oxidation reaction on NaYbF4:Ho3+ UC microcrystals was revealed. The oxidation reaction between O2 and NaYbF4:Ho3+ microcrystals was induced by increasing excitation power density and irradiation duration leading to a lattice-mismatched NaYbF4 and YbOF heterojunction. This unique heterojunction architecture not only modifies the profiles and colours of the luminescent patterns, but also separates the processes of light–light conversion and light–heat conversion in time and space. These studies have provided a deeper insight into the local in situ oxidation mechanisms of fluoride crystals and offered a novel route toward the tuning of UC luminescence using a heterojunction.

This work aims to make a comparative analysis on the unbalanced discharging phenomenon for the battery packs with series/parallel configurations due to the temperature difference among the cells. A theoretically-based model is developed for the battery pack and the constant power discharging processes are simulated by the model. At the constant temperature difference, lowering operating temperature increases the divergence among the cell terminal voltages for the series pack and the cell discharging currents for the parallel pack. Increasing the temperature differences decreases the dischargeable energy of the series battery pack, while it affects little on that of the parallel. At the same temperature difference, the cell energy differences within the parallel battery pack are 5~10 times higher than that within the series, which makes the temperature uniformity claim of the parallel battery pack is higher than that of the series.

This paper provides a comprehensive study on the zero potential method for restriction of the crosstalk-based measurement error in network resistor arrays. We introduce four circuits with different architectures based on the zero potential method to comparatively study the effect of the switches on-resistance on the measurement error. Moreover, the effect of the operational amplifiers with different specifications on the measurement error will be investigated. The results show that the measurement error introduced by the onresistance of the switches can be effectively suppressed by inserting a buffer between the sensing elements and the switches on each driven electrode, and utilizing the virtual ground of the trans-impedance amplifier on each scanned electrode. We will show that, the efficiency of the circuits on elimination of the measurement error may be improved by employing high precision operational amplifiers.

Purpose The purpose of this paper is proposed a new structure design for high performance accelerometer. Design/methodology/approach An improved sensitivity structure considering sensitivity, natural frequency and cross-axis sensitivity is established and realized. The proposed structure was designed to improve the trade-off between the sensitivity and the natural frequency of piezoresistive accelerometer and eliminate the lateral sensitivity effect by the specific configuration, which is made possible by incorporating slots into the eight-beam structure. The mechanical model and its mathematical solution are established for calculating the sensitivity and natural frequency behavior of the designed structure. The developed sensor is fabricated on the n-type single-crystal silicon wafer and packaged for experiment. The accelerometer prototype was tested in the centrifugal machine and dynamic calibration system. Findings The experimental results show that the sensitivity of the designed sensor is 0.213 mV/(Vg) and the natural frequency of the sensor is 14.22 kHz. Compared with some piezoresistive accelerometers in literatures, the designed sensor possesses a suitable characteristic in sensitivity, natural frequency and transverse effect, which allows its usage in measuring high frequency vibration signals. Originality/value The accelerometer with slotted eight-beam structure shows a good performance in the static and dynamic experiments and can be used in measuring high frequency vibration signals.

The changes of the wettability of the solid surfaces have attracted massive attention due to their important practical implications in numerous fields. As a new subject, the research on the wettability under the different environments is still in its early stage. So the fundamental research must be performed for the practical applications under different environments. However, it is seldom that the comprehensive wettability of a surface in air, in water and in oil has been reported. In this paper, the authors investigated the wettability of the stainless steel mesh coated with polyurethane in the above three different environments. The surface of the uncoated mesh was found to be hydrophobic in air, but the surface of the coated mesh was superhydrophilic in air. More interestingly, the surfaces of the coated meshes were superoleophilic in water and superhydrophobic in oil. Due to the coated meshes with these wettabilities were fabricated via a facile two-step method, the presented method may be adopted for large-scale industrial production, in various fields, such as icing prevention or the oil-field industry.

A flexible mechanical deformation test system, which is a combination of the microwave and the flexible film, is proposed. The system consists of a U-shaped microwave resonator, coaxial transmission line, and PDMS flexible substrate. Microwave signals are generated from the vector network analyzer and loaded to the coaxial transmission line and then coupled to the U-shaped resonator through the coupling loop. The resonator works at the gigahertz band with the test range from 3 GHz to 40 GHz. The resonant frequency of the resonator can be adjusted by changing the shape of PDMS, and the related signals can be detected by using the S11 parameter of the microwave. The response time of the U-shaped resonator is less than 20 ms, and the sensitivity on the curved surface is 12.5 Hz/nm.

An microwave-cavity antenna was designed to manipulate the spin state in diamond. It consists of an Ω antenna and a microwave cavity with the thickness of 0.35mm and Q-value of 65. The microwave intensity increased 12 times than that of the Ω antenna. The size of homogeneity area is 25πmm2 and the heterogeneity is less than 2.3%. Hence, more spin structures in large-sized diamonds with high concentration can be homogeneous excited. As applied in the spin-based magnetometer, the sensitivity increased 13 times, and noise reduced to 0.5nT/Hz1/2. It proves a way to develop the high sensitive spin-based sensors.

Hematite (α-Fe2O3) nanofibers were fabricated using the electro-spinning technique and followed by an annealing process in air. The crystalline structure and morphology of the nano-fibers were studied using XRD, SEM, Raman spectra and high-resolution TEM. Zero-field-cooled (ZFC), field-cooling (FC) and field heated (FH) type temperature dependence of magnetization curves of α-Fe2O3 nanofibers are measured in the temperature range 15–390 K. Two kinds of magnetization steps were observed in the temperature dependence of magnetization curves, one is at 300 k which is very weak and the other is in the temperature range of 245–257 K with large thermal hysteresis (12 K). The tiny step at 300 K can be attributed to normal Morin transition in α-Fe2O3 and this was suppressed by the consequent α- to β- phase transition, which caused the pronounced step in the temperature dependence of magnetization curves. This α- to β- phase transition in Fe2O3 nanofibers was further confirmed by in situ TEM observations. This is the first study to describe novel α- to β-phase transition upon cooling.

Lanthanide doped β-NaYF4 micro/nanocrystals have attracted extensive attentions for various applications by taking advantage of their ability to convert near-infrared into high-energy visible or ultraviolet emission. However, to date, achieving efficient photon upconversion (UC) and distinct far-field luminescent patterns of emission light in UC phosphors is still a fundamental challenge. Here, we report the utilization of the microrod cavity waveguide arrays with the concave top/bottom surfaces to manipulate energy flux and significantly enhance UC processes. By enhancing incident light harvesting and changing Yb3+ concentration, directional luminescence amplification and chrysanthemum-shaped luminescent pattern with various colors can be achieved relative to its disorderly microrod counterpart stackings. This design delineates a strategy of energy flux manipulation to converge a low-power incident light beam into a photonic hotspot of high field intensity and amplify the UC processes resulting in directional luminescence and stereoscopic luminescent patterns.

The joint surfaces have a significant effect on the behavior of mechanical structures. Strong demand exists for the development of a model that can include the contact characteristics of joint surfaces. In this article, a new contact model considering asperity interaction and surface waviness is proposed. The roughness and waviness of the surface are separated by the Fourier series, and a contact model for an asperity is first established to obtain the displacement caused by asperity interaction. The joint surface is then treated as the contact between a rough surface and a smooth waviness to obtain a new model which considers asperity interaction and surface waviness. Simulation results show that when the normal load is fixed, the contact deformation decreases with the increasing radius of the waviness peak, but increases with the increasing surface roughness. In addition, asperity interaction will lead to a lower contact stiffness and a larger real contact area. Compared with other models, the results obtained from the proposed model are closer to the experimental results.

A technique in which a polydimethylsiloxane (PDMS) template is used to assemble silicon oxide nanoparticles is proposed herein. The PDMS substrate was first constructed in a series of casting steps and a copper mask was then made with a laser marking system. Silicon oxide nanoparticles were generated by a modified Stober method. A PDMS substrate covered by the copper mask was then coated with a metal Au layer via sputtering to form the PDMS template. Finally, the silicon oxide nanoparticles were spin-coated on the PDMS template. Because the PDMS template consists of highly hydrophobic PDMS and less hydrophilic Au patterns, the nanoparticles undergo a dual dewetting process on the PDMS template to form an annular distribution around the borders of the Au patterns.

A strain-type three-component table dynamometer is presented in this paper, which reduces output errors produced by cutting forces imposed on the different milling positions of a workpiece. A sensor structure with eight parallel elastic beams is proposed, and sensitive regions and Wheastone measuring circuits are also designed in consideration of eliminating the influences of the eccentric forces. To evaluate the sensor decoupling performance, both of the static calibration and dynamic milling test were implemented in different positions of the workpiece. Static experiment results indicate that the maximal deviation between the measured forces and the standard inputs is 4.58%. Milling tests demonstrate that with same machining parameters, the differences of the measured forces between different milling positions derived by the developed sensor are no larger than 6.29%. In addition, the natural frequencies of the dynamometer are kept higher than 2585.5 Hz. All the measuring results show that as a strain-type dynamometer, the developed force sensor has an improved eccentric decoupling accuracy with natural frequencies not much decreased, which owns application potential in milling process monitoring.

Due to the power instability and field non-uniformity of radio frequency (RF), microwave (MW) and laser signals, inhomogeneous broadening of spin magnetic resonance line causes the absorption to decrease in a nuclear resonance system, which can reduce the sensitivity of spin-based sensing and testing technology. In this paper, we propose and design a double solenoid coil RF resonance antenna structure. The nearly uniform RF field density is produced by the two solenoid coil antenna structures that are parallel to the symmetry axis. The size of the uniformity in the center region of double solenoid coil RF resonance antenna structure is about π×375 mm2 × 10 mm. And the non-uniformity is less than 0.9%. Comparing with a single straight wire antenna and the single solenoid coil RF resonance antenna structure, the uniformity is improved by about 56.889 times and 42.889 times, respectively. At the same time, based on the near-field mutual inductance coupled resonance effect, the intensities of RF field in the center region of the two-solenoid coil antenna structure is enhanced. Comparing with the single solenoid coil antenna structures, it is enhanced by about 1.587 times. And the equivalent sensitivity of the silicon vacancy color center spin based sensor is enhanced by about 4.833 times. In the experiment, an optical detection magnetic resonance measurement system based on the spin magnetic resonance effect of silicon vacancy color center in single crystal SiC is built. Comparing with the single straight wire antenna and the single solenoid coil RF resonance antenna structure, the contrast of the silicon vacancy color center spin magnetic resonance signals of the double solenoid coil RF resonance antenna structure increases about 6 times and 2.4 times, respectively. The sensitivity of the spin-based sensor is increased by 4.833 times and 2.071 times through using the modulation and demodulation method, and the noise decreases by 8 times and twice. Hence, based on this double solenoid coil RF resonance antenna structure, the sensitivity of the silicon vacancy spin sensor can be improved. Combined with chip manufacturing technology of SiC wafer, it proves to be a potential approach to developing the high precision, chip scale spin sensor devices and measurement technology.

The measured frequency response functions (FRFs) are directly used to identify the bolted joint properties. However, the noise effect and the matrix inverse operations create ill-posed problems, and a small noise level may cause the identified result to be faulty. A sensitivity method is developed to avoid the ill-posed problems for identification of the dynamic parameters of bolted joints in this paper. To calculate the sensitivity of stiffness and damping for bolted joints, the sensitive values are used to determine the frequency ranges before the identification. Then, the equivalent stiffness and damping of bolted joints are identified by FRFs method in this range. All results of simulation and experiment show that the proposed method can improve significantly the identification accuracy. Additionally, the sensitivity method can be used to avoid an ill-posed problem by eliminating ill-posed FRFs in some frequency range before identification.

We demonstrate a method for fabricating nanoparticles in a line at the top of silver wrinkled structures by tilting the substrate. The center of gravity of the colloidal droplets was moved backward, resulting in a small volume of droplets at the front of the colloidal droplet. The droplet rapidly evaporated, and the nanoparticles that remained formed lines of highly ordered nanoparticles. The distance between the nanoparticles changed after stretching the PDMS substrate due to the Poisson effect. An optimal plasma effect was achieved by controlling the distance between the nanoparticles. Finally, the Surface-Enhanced Raman Scattering (SERS) effects of CV and R6G molecules in water were determined, and the detection limit was 10−20 M. This method provides an extremely high sensitivity SERS substrate for the detection of biomolecules.

Hollow europium-doped yttrium orthovanadate (YVO4:Eu3+) microspheres were fabricated via a sodium dodecyl sulfate (SDS)–polyethylene glycol (PEG)-assisted hydrothermal technique. The as-synthesized hollow YVO4:Eu3+ microspheres were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectroscopy (PL). The obtained results showed that the morphology and size of the hollow microspheres have a strong dependence on the hydrothermal reaction time of the YVO4:Eu3+ powders. It is believed that the SDS–PEG clusters perform a function of dual soft-template that results in a unique template-induced secondary assembly in the one-pot synthesis of hollow YVO4:Eu3+ microspheres. The photoluminescence measurement revealed that the YVO4:Eu3+ powders with a spherical hollow shape have better red luminescence compared to the YVO4:Eu3+ solid microspheres. As a result, the controlled synthesis of hollow YVO4:Eu3+ microspheres not only has a great theoretical significance in studying the three-dimensional control and selective synthesis of inorganic materials but also benefits the potential applications based on hollow YVO4:Eu3+ microspheres owing to reducing the usage of expensive rare-earth elements.

Polydimethylsiloxane (PDMS) is a widely used inexpensive, non-toxic material which has many advantages. But it is generally considered that PDMS does not adhere to the other substrates without the special treatments due to its low surface energy. However, in this paper, it is the first time that we found that the PDMS adhered on the silicon dioxide substrate to form an adhesive layer only by the routine cast molding process. The mechanism of the PDMS adhesion on the silicon dioxide substrate during the process was illustrated in detail. The smooth, thin, transparent, hydrophobic and selective PDMS adhesion layer can be used as a functional coating to improve the special performances of the micro/nano devices. Finally, as an example, a facile approach is proposed to realize the superhydrophobic surfaces by combining the SiO2 microstructure with the PDMS adhesion layer.

In this paper, the low-frequency band gap mechanism of torsional vibration is investigated for a kind of light elastic metamaterial (EM) shafts architecture comprised of a radial double-period element periodically as locally resonant oscillators with low frequency property. The dispersion relations are calculated by a method combining the transfer matrix and a lumped-mass method. The theoretical results agree well with finite method simulations, independent of the density of the hard material ring. The effects of the material parameters on the band gaps are further explored numerically. Our results show that in contrast to the traditional EM shaft, the weight of our proposed EM shaft can be reduced by 27% in the same band gap range while the vibration attenuation is kept unchanged, which is very convenient to instruct the potential engineering applications. Finally, the band edge frequencies of the lower band gaps for this light EM shaft are expressed analytically using physical heuristic models.

The supporting technology of five-axis CNC machine is establishing virtual machining platform, correcting NC program and process simulation and optimization, which can make the efficient machining technology come true. Taking non-orthogonal 5-axis CNC machine tools DMC70ev as the object, NC machining simulation platform based on the VERICUT was constructed. Taking surface machining for example, the optical design mathematical model based on constant volume removal rate and constant chip thickness optimum method was established and the toolpath optimization was carried out. The research result has realized five-axis process simulation of NC machining and the verification of NC program correctness, which improves the processing efficiency and quality, the application level, quality of NC machining technology for enterprises, and it will promote the development of modern manufacturing technology.