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This paper studied the combined effect of anode and cathode current collectors on the behavior of water and methanol crossover in micro direct methanol fuel cells (μDMFC). A two-phase, two-dimensional, isothermal model was built to analyze the mass transport behavior in the membrane electrolyte assembly (MEA). The results show that the distribution of methanol exhibits uniform concentration feature over the anode porous area with the asymmetric anode and cathode current collectors. Also, lower water content gradient across the membrane is found. Comparing experiments were conducted to verify the simulation results. Two passive μDMFCs were fabricated and tested. The cells presents almost the same performance at relatively low methanol concentration. However, an increase of 10% cell performance (from 27.5 mW.cm-2 for symmetric current collectors to 30.3 mW.cm-2 for asymmetric current collectors) at 5 mol.L-1 methanol solution was observed. This reveals that the couple of asymmetric current collectors induced the methanol to distribute uniformly and largely suppressed the water and methanol crossover.

To meet a high-precision accelerometer resistance of temperature, humidity and other external noise, a new multi-ring cascade optical accelerometer structure is designed. The micro-ring resonator on the cantilever beam based on the photo-elastic effect and the contrast are fabricated with the same manufacturing process and size, which can effectively meet the consistency of the contrast and test micro-ring resonator on the cantilever. The one resonance point curve will split into two under the acceleration, thus the acceleration value can be obtained by detecting the wavelength of the two resonant points. By testing the cascade race-track shaped micro-ring resonator at different temperatures, the Q=104, the test requirement of cascade race-track shaped micro-ring accelerometer in different environments is greatly met. The design can be widely applied to the occasions of penetration system with high impact, strong vibration and so on. And the anti-noise and anti-jamming features of the integrated miniaturized high-sensitivity MOEMS sensors are realized.

Microsphere resonator is widely studied for the high quality factor Q and small mode volume. Aimed at the sensor applications, the resonant point tracking and locking method is proposed for measuring the resonant frequency shift. To avoid external noises, such as air flow and vibration, spot-packaged coupling structure is adopted. The robustness of microsphere-taper coupling unit is greatly improved. And this lays a foundation for resonant point tracking and locking. By employing modulation method, the demodulation signal is obtained. To lock the laser frequency to resonant point, PID circuits will adjust the center frequency of laser until the intensity of demodulation signal becomes zero. In the experiment, resonant tracking and locking is realized on the rotating platform with rotation rate 2 r/s.

In the paper, it demonstrates highly integrated tenth-order filters in silicon-on-insulator (SOI). The micro-ring resonators have a small radius of 5μm and a very large free spectral range ~ 18nm at 1.55μm communication band. For through port responses, the grating and the high-order optic filters with ten coupled micro-ring resonators are designed and demonstrated, and grating responding well matches with the experiment resonators. Devices are patterned with electron-beam lithography (EBL). And 2μm SiO2 layer is covered on the silicon waveguide, thus reducing the propagation loss in micro-ring resonators.

A continue-wave cavity ring down experimental system is established surrounding the micro-sphere cavity. In the experiments of measuring micro-spheres cavity quality factor (Q) upon the system, it is found that photoelectric detectors with different response characteristic have different response to the optical signal which is shut off rapidly. The vibration noise caused by changes of external environment, meanwhile, can be transformed following the change of photoelectric detector properties. With the build of photoelectric detector response model, the mean-square deviation of repeated experiments under the same conditions is used for charactering level of the error caused by vibration noise. The influence of vibration noise to photoelectric detector is discussed in detail, and further analyzes the effect for the cavity ring down time extraction. Then the optimal photoelectric detector (Newfocus1434, 15V/W) is selected to optimize the experimental system. The level of error caused by vibration noise has been decreased from 0.191ns to 1.562ps. Finally, the Q value of micro-sphere cavity is calculated according to fitted value of cavity ring down time, and the experimental correctness is verified by the line-width law.

Along with the rapid development of science and technology, and due to the special advantage of laser communication, such as big traffic and good secrecy, the application of optical communication is more and more wide. One of key technologies is the structure design of receiving system. In this paper, a structure of receiving system for optical communication based on Cassegrain system is introduced. Consist of the support structure of primary mirror and secondary mirror, adjustment structure of secondary mirror, structure design of reflectors, etc. FEM is used to analyze the distortion of primary mirror which is based on this structure. The distortion is caused by pressure, self-weight and temperature change, etc. And the stress deformation of primary mirror tube is analysed particularly. Analysis and test results demonstrate that the design project is reasonable.

This paper describes the effects of the microsphere-taper coupling structure from the external libration Sound, especially the impact on the coupling distance. Here two solutions have been proposed. One approach is to cover the system with a insulation shield. The other is to integrate the coupling structure with the ultraviolet glue. The results show that both measures are viable. The packaged microsphere-taper coupling structure is entirety separated from the nonego, making the structure not be disturbed by the external libration sound. In the subsequent experimentation, the packaged structure will have a good prospect.

In this paper, silicon-based micro direct methanol fuel cells (µDMFCs) with different anode structures were designed and investigated experimentally, the current collectors were fabricated using micro-electromechanical system (MEMS) technology. a novel encapsulation method was also designed using PDMS. The study of the effect of different anode flow fields suggested that the serpentine flow field has the optimal performance. The experimental results also revealed that an open ratio of around 47% led to the best cell performance, a maximum of power density of 13.2 mW/cm2 was achieved with 1.0 M methanol solution.

The existing studies based on 2-dimension cutting model are partial investigations on tool wear. In order to get close to the true cutting conditions, the Lagrangian thermo-viscoplastic cutting simulations were conducted and the tool wears were predicted under different cutting speeds using 3-dimension finite element models. The simulation results indicate that when the cutting speed increases the cutting forces will reduce accordingly while the wear depth will be deeper. As a result, different factors should be considered at the same time when the speed range is selected. This study has shown that the finite element method is a valuable approach to understand the tool wear mechanism in machining and the influences of different cutting speeds.

Two 3-D finite element models of coated tool and uncoated tool were established using the finite element code DEFORM-2D based on the updated Lagrangian formula. And their machinability on high speed orthogonal machining was simulated and compared. The investigation results indicate that the coated tool has higher surface temperature and lower inside temperature compared with the uncoated tool. Moreover, the cutting forces of the model using coated tool are lower than that using uncoated tool.

Miniaturization is a worldwide trend in manufacturing industry. Though lithography has been introduced to meet the basic needs, the technology is limited by its process complexity and the parts geometry to be produced. This research attempted to overcome the above obstacles by applying laser machining approaches on general 3D micro-parts. The machining model is based on a layer-by-layer concept. Experimental verification was made on a 1mm stainless steel sheet by applying a diode-pumped Nd:YVO4 laser with Q-switch option. Three main parameters: power, repetition rate and the speed of laser process were set to optimize the process quality. In the research round holes with the diameter ranging from 10 μm to 30 μm were drilled. The following step was the machining of a sloped groove with the area size of 100 μm × 100 μm for validation.

Epitaxial MgO thin films were deposited on Si(100) substrate by atmospheric-pressure metalorganic chemical vapor deposition for using as buffer layers. Ba0.6Sr0.4TiO3 thin films were prepared on MgO/Si(100) substrate by sol-gel technique. The independence of crystallinity on annealing temperature was investigated. The Ba0.6Sr0.4TiO3 (BST) thin films are crystallized in preferential (100) orientation after post-deposition annealing at 850°C and 950°C for 2h in air, respectively. Rutherford backscattering spectroscopy analysis confirmed that both the BST and MgO films have stoichiometric composition.

This paper analyzes the changes of cutting force, cutting temperature, and cutting-tool wear in the process of precision cutting. All these factors are considered in the test on GCr12, Cr12 and 45 steels. This test uses the sub-dry cutting method with green-air cooling and a little additive. Furthermore, it discusses the feasibility of sub-dry cutting on the basis of a comparison with other cutting methods

A new approach for power system frequency estimation is proposed. The approach consists of two stage adaptive notch filters. The first stage eliminates harmonics and enhances the fundamental waveform. After the down-sampled processing, the second stage produces an accurate estimate of the fundamental frequency. The notch filter is based on all-pass filter with an efficient lattice structure and is simple to realize. Simulation is presented to demonstrate the effectiveness of the algorithm.

In this study, the effect of SiC powder characteristic on the rheological properties of the feedstock was investigated. It was found that the viscosity of the feedstock decreased with the increase of the particle size. For the binary powder mixtures, the viscosity of the feedstock decreased with the increase of the particle size ratio of the larger particle to finer particle, which is attributed to the increase of the tap density of the powder.