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This paper proposes a novel way of preparing a PZT thick film micro vibrator using the electrohydrodynamic jet (E-Jet) printing technique. Initially, a micro piezoelectric vibrator was simulated and designed for obtaining optimized structure, which has a total thickness of less than 600 µm. Subsequently, the PZT thick film element was directly printed on the elastic body using the E-Jet printing. This method avoids the glue fabrication process involved in the bulk piezoelectric fabrication, thus avoiding the limits of voltage drops, isolating and absorbing amplitude usually occurred in the vibrator having glue interface. It was observed that B02 and B03 modes were generated at frequencies of 29.74 and 79.14 kHz, respectively, and the amplitudes of B02 and B03 modes were 406 and 176 nm, respectively. The error between the simulation and test result in the B03 modal is only 0.35%, which indicates the accuracy of the simulation analysis and the fabrication process. The PZT thick film traveling-wave micro vibrator successfully realized bidirectional rotation of a rotor, with a maximum speed of 681 rpm, which also shows a linear relationship between excitation voltage and rotary speed. This paper provides an effective method for preparing a micro piezoelectric vibrator for MEMS ultrasonic devices, which simplifies the manufacturing process and enhances the performance of the piezoelectric vibrator.

Electrohydrodynamic jet (E-Jet) printing is a promising manufacturing technique for micro-/nano-patterned structures with high resolution, high efficiency and high material compatibility. However, further improvement of the necking ratio of the E-Jet is still limited by the focusing principle. Moreover, ink viscosity is limited to values well below 90 mPa s owing to the high probability of nozzle blockage. Here, we propose a microtip focused electrohydrodynamic jet (MFEJ) printing to overcome these limitations. This technique uses a solid microtip with a radius of curvature (ROC) of several micrometers rather than a hollow nozzle, which is very simple and highly efficient to prepare and can effectively avoid nozzle clogging problems even with high-viscosity printing ink. High-resolution patterns in diverse geometries were printed using different inks with a wide range of viscosities (8.4–3500 mPa s). Nanodroplets with an average diameter of 73 nm were achieved. Moreover, nanofibers with a diameter of 30 nm were obtained using a 4 μm ROC microtip and the necking ratio was as high as 266 : 1. To the best of our knowledge, this is the smallest droplet or fiber diameter directly obtained via E-Jet printing to date without further physical or chemical processing. This MFEJ printing technique can improve printing resolution at the nanoscale, significantly enlarge the material applicability and effectively avoid nozzle clogging for the fabrication of nanodevices.

The consensus of most recent researches is that rich training data which includes more different object forms in different situations is beneficial to improve the performance of deep networks. Deep learning is very dependent on data diversity. So, we provide a novel and principle method called adaptive adversarial example generating network (AAEGN) to generate examples with occlusions for object detection. AAEGN can generate occlusion examples which are rare in current dataset and are difficult to localize and classify. Compared to the traditional adversarial network for the example generation, AAEGN employs several innovations to simplify the architecture of adversarial network and improve the example generation and training speed. What’s more, AAEGN can adjust the hyper-parameters of the adversarial network in the process of training adaptively. The results of our experiments show that using AAEGN to train Fast-RCNN pipeline can get a 1.8% boost on VOC2007 dataset and 3.8% boost on VOC2012 dataset.

Object detection refers to the classification and localization of objects within an image by learning their diversified features. However, the existing detection models are usually sensitive to the important features in some local regions of the object. The existing algorithms cannot learn the diversified features regarding to each region effectively, which limit the performance of the model to a certain range. In this paper, we propose a novel and principle method called Multi-region Occlusion Example Generating (MOEG) to guide the detection model in fully learning the features of the various regions of the object. MOEG can generate completely new occlusion examples and it enables our detection model to learn the features of the remaining regions in the object by blocking the important regions in the proposal. It is a general method to generate occlusion examples and it can be implemented to most mainstream region-based detectors very easily such as Fast-RCNN and Faster-RCNN. Our experimental results indicate a \(2.4\%\) mAP boost on VOC2007 dataset and a 4.1% mAP boost on VOC2012 dataset compared to the Fast-RCNN pipeline. And as datasets become larger and more challenge, our method MOEG become more effective as demonstrated by the results on the MS COCO dataset.

Electrohydrodynamic jet (E-Jet) printing is a powerful technique for micro/nanostructure fabrication with high resolution and efficiency. However, conventional E-Jet printing are still limited in printing accuracy and ink adaptability due to the nozzle clogging effect. In this paper, we develop a nano-tip focused electrohydrodynamic jet (NFEJ) method to print high-resolution structures. The Ni cantilever nanoprobes with nanoscale radius of curvature (ROC) on their tips were manufactured by a facile and scalable method using silicon template and micro-electroforming technique. Scanning electron microscope was used to analyse the micromorphology of the silicon template with inverted pyramid pits, which was obtained from anisotropic wet etching of silicon. Electroforming mold was obtained by photolithography and plasma etching which divide the top side of Ni film into isolated cantilever pits. Ni cantilever nanoprobes with an average tip ROC of about 48 nm were achieved by the subsequent micro electroforming process. High-resolution droplets array with an average diameter of about 890 ± 93 nm were printed by the NFEJ printing head equipped with these Ni nanoprobes, which verified the practicality of the developed Ni nanoprobes for NFEJ printing.

Controlled printing of biodegradable and bioresorbable polymers at desired 3D scaffold is of great importance for cell growth and tissue regeneration. In this work, a novel electrohydrodynamic jet 3D printing technology with the resultant effect of electrohydrodynamic force and thermal convection was developed, and its feasibility to fabricate controllable filament composite scaffolds was verified. This method introduces an effective thermal field under the needle to simultaneously enhance the ink viscosity, jetting morphology controllability and printing structure solidify. The fabrication mechanisms of thermal convection on jetting morphology and printed structures feature were investigated through theoretical analysis and experimental characterization. Under optimized conditions, a stable and finer jet was formed; then with the use of this jet, various 3D structures were directly printed at a high aspect ratio ~30. Furthermore, the PCL/PVP composite scaffolds with the controllable filament diameter (~10 μm) which is closed to living cells were printed. Cell culture experiments showed that the printed scaffolds had excellent cell biocompatibility and facilitated cellular proliferation in vitro. It is a great potential that the developed electrohydrodynamic jet 3D printing technology might provide a novel approach to directly print composite synthetic biopolymers into flexibly scale structures for tissue engineering applications.

A method based on OEMD (Orthogonal Empirical Mode Decomposition) and the theory of time-frequency entropy was applied to detect different rail fastener conditions. The original vertical vibration acceleration response of rail under different fastening conditions was obtained from outdoor experiment. The OEMD method was used to get orthogonal IMFs (Intrinsic Mode Functions) of the original vibration signal. The Hilbert time-frequency spectrum was then obtained based on the orthogonal IMFs and corresponding entropy was calculated and compared. The results show that the method is available to detect different rail fastener conditions.

Direct methanol fuel cell (DMFC), with benefits such as high energy efficiency, quick start capability and instantaneous refueling, is a promising power source to meet the ever-increasing power demand for portable electronic products. In this paper, a novel CO2-driven fuel-feed device was produced and equipped in a passive 8-cell DMFC twin-stack for long-term operation. It was shown that this fuel-feed device was capable of supplying methanol solution continuously in response to the change in discharging current of the stack. Stainless steel sheet was photochemically etched as current collectors based on MEMS techniques. Series interconnections between two neighbor cells were realized in banded configuration which avoided the external connection. TiN-plated mesh was placed between current collector and membrane electrode assembly (MEA), which was used to lessen the internal resistance of the stack. A peak power density of 16.9 mW cm−2 was achieved with 4 M methanol at ambient temperature and passive operation. The stack equipped with the fuel feed device successfully powered a sensor node for 39 h with the consumption of 80 ml of 4 M methanol.

This paper presents the design, microfabrication and characterizations of a silicon based, single-cell μDMFC demonstrator for micro/portable electrical power applications. The flow field plates of the fuel cell were made on 2“silicon wafers utilizing wet-etching and sputtering techniques. The fuel cell was assembled in an epoxy-based packaging process. Results show that a lower internal ohmic resistance of the fuel cell can be achieved with a thicker current collecting layer (CCL). Influence of the operating conditions on the μDMFC performance was also investigated. It was found that 2M methanol can yield a better fuel cell performance because it provided a better compromise between the methanol crossover and mass transportation during operation. On the other hand, a 4-time increase of the peak power density of the fuel cell was achieved by increasing the methanol temperature from 20°C to 80°C.

Micro Direct Methanol Fuel Cell (μDMFC) is a kind of newly developed power sources, which effective apparatus for its performance evaluation is still in urgent need at present. In this study, a testing system was established for the purpose of testing the continuous working performance such as micro flux and temperature of μDMFC. In view of the temperature controlling for micro-flux liquid fuel, a heating block with labyrinth-like single pass channel inside for heating up the methanol solution was fabricated. A semiconductorrefrigerating chip was utilized to heat and cool the liquid flow during testing procedures. On the other hand, the two channels of a high accuracy double-channel syringe pump that can suck and pump in turn so as to transport methanol solution continuously was adopted. Based on the requirements of wide-ranged temperature and micro flux controlling, the solenoid valves and the correlative component were used. A hydraulic circuit, which can circulate the fed methanol cold to hot in turn, has also been constructed to test the fatigue life of the μDMFC. The automatic control was actualized by software module written with Visual C++. Experimental results show that the system is perfect in stability and it may provide an important and advanced evaluation apparatus to satisfy the needs for real time performance testing of μDMFC.

A longitudinal force loading instrument for rails was developed to simulate the longitudinal temperature force of the rail of a ballastless track under different rail temperatures. The instrument comprised the rail, an end-fixing device, a temperature force application device, and concrete foundation. This instrument could simulate the longitudinal stress distribution of the rail under different rail temperature changes and analyze the correlation between the natural frequencies of the rail and the longitudinal stress generated by temperature variation. The result of the longitudinal stress distribution exhibits good agreement with the simulation results. In addition, the result of the dynamic characteristics of the rail demonstrates good agreement with the former conclusions. This experimental instrument can be potentially developed into a powerful tool for researching the rail features of a ballastless track under different temperature forces.

A novel, compact gap-flow heat exchanger (GFHE) using heat-transfer fluid (HTF) was developed in this paper. The detail design of the GFHE coaxial structure which forms the annular gap passage for HTF is presented. Computational fluid dynamics simulations were introduced into the design to determine the impacts of the gap width and the HTF flow rate on the GFHE performance. A comparative study on the GFHE heating rate, with the gap widths ranged from 0.1 to 1.0 mm and the HTF flow rates ranged from 100 to 500 ml/min, was carried out. Results show that a narrower gap passage and a higher HTF flow rate can yield a higher average heating rate in GFHE. However, considering the compromise between the GFHE heating rate and the HTF pressure drop along the gap, a 0.4 mm gap width is preferred. A testing loop was also set up to experimentally evaluate the GFHE capability. The testing results show that, by using 0.4 mm gap width and 500 ml/min HTF flow rate, the maximum heating rate in the working chamber of the as-made GFHE can reach 18 °C/min, and the average temperature change rates in the heating and cooling processes of the thermal cycle test were recorded as 6.5 and 5.4 °C/min, respectively. These temperature change rates can well satisfy the standard of IEC 60068-2-14:2009 and show that the GFHE developed in this work has sufficient heat exchange capacity and can be used as an ideal compact heat exchanger in small volume desktop thermal fatigue test apparatus.

In this paper, a simulation-based optimization methodology combining the Response Surface Method (RSM) and a newly developed Ant Algorithm is introduced. An approximate function between the chief packaging parameters and the maximum value of the equivalent stress in the solder joints has been built. Finally, the better solution of the chief packaging parameters is obtained from Ant Algorithm.

A three-dimensional ballastless track model was established using a finite element method to simulate the rail condition before and after rail break. The distribution of the rail longitudinal stress was analyzed under certain thermal stress. In addition, experiments were also conducted in order to validate the simulation results using rail longitudinal stress test equipment. It was found that the simulation results agreed reasonably well with the experimental results. The tests show that the simulation results could correctly predict the longitudinal stress distribution in the rail. Finally, rail longitudinal stress distributions under different thermal stress were calculated using this model; this is helpful for future application to determine when and where there may be a rail break.