相对于电阻应变式测力传感器,国内电容式力传感器的可靠性与制造工艺还有许多方面需要改进和提高.主要介绍了陶瓷电容式力传感器中一种力敏元件在产品化过程中涉及的结构设计、关键材料选择以及生产制作工艺等方面的要求.实践表明:该陶瓷电容力敏元件的性能和可靠性都达到了大批量生产的要求,为进一步研制更多厚膜电容式测力传感器创造了基础和条件.

This article proposed and discussed a kind of sigma-delta A/D converter for load cell signal acquisition, which uses improved charge balance technique. The traditional charge balance sigma-delta A/D converter is stable if and only if the magnitude of the input signal current is less than one half the magnitude of the reference current, which limits the accuracy improvement of load cell. This article examined the stability of an improved version of the charge balance sigma-delta A/D converter. The proposed converter can be designed to be stable for input signals as large as the reference, which is helpful to improve load cell’s measurement accuracy.

传感器是提升我国精准农业产业化水平的关键技术之一.在整个精准农业生产周期中,称重传感器在其中每个环节都有潜在的应用领域,文中从精准农业实施的4个不同阶段:土地准备、精准播种、作物管理、精准收获,对称重传感器在精准农业装备中应用和研究现状进行了总结.在此基础上,进一步分析了当前称重传感器在精准农业实际应用中亟待解决的3个主要关键问题:可靠性、稳定性和动态测量精度.最后,对解决这些问题背后所涉及的关键共性技术,包括敏感机理、制造工艺和计测技术等作了进一步阐述.

A novel design is proposed for highly sensitive surface-plasmon-resonance sensors.The sensor is based on a microstructured optical fiber with two layers of annular-shaped holes.A gold layer is deposited on the inner surface of the second hole-layer,in which the holes have several micrometers thickness in size,facilitating analyte infiltration and metal layer deposition.In the first layer of holes,the sector-ring-shaped arms,used as supporting strips,are utilized to tune the resonance depth of the sensor.Numerical results indicate that the sensor operation wavelength can be tuned across the C+L-band.The spectral sensitivity of 1.0·104nm·RIU-1order of magnitude and a detection limit of 1.0·10-4RIU order are demonstrated over a wide range of analyte refractive index from 1.320 to 1.335.

In order to study elastohydrodynamic lubrication characteristics of cylindrical roller under heavy load and unsteady state, a testing machine is designed for measuring line contact film thickness and shape according to optical interference principle. The experimental apparatus is mainly made of glass block reciprocating motion systems, ball or roller rolling rotation system, loading system, speed control systems, lighting systems and image acquisition system. Moving parts is formed by the slider-crank mechanism. Specimen is accompanied by a pair of floating trial roller bearing. Specimen load is applied by leverage. The entrainment velocity of roller is approximate sinusoidal variation during a cycle. Experiment interference image is satisfactory, can provide reliable experimental data for future research.

We propose a design of a low loss terahertz polarization splitter based on a dual-core terahertz fiber with crossed dielectric strips in the fiber cross section. Low transmission loss is realized by extending the mode field to the air holes adjacent to the solid material. An 11.4-cm-long terahertz polarization splitter is obtained with the extinction ratio better than −15dB and a bandwidth of 16μm.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

We propose the design of a low-loss suspended core terahertz fiber with rectangular-shaped dielectric strips in the fiber cross section. The finite element method is used to analyze the characteristics of the suspended core terahertz fiber. Terahertz wave in a frequency range from 0.74 similar to 0.95 THz is efficiently confined in the suspended core region with a total loss lower than 0.086 dB/cm (similar to 0.02 cm(-1)). Meanwhile, any contact on the surface of this fiber will not disturb the field and induce additional losses. A 3.36-cm-long terahertz polarization splitter derived from this fiber with a transmission loss less than 0.89 dB, is also numerically demonstrated. A bandwidth of 0.032 THz at the center frequency of 1 THz with an extinction ratio better than -20 dB is obtained.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Design strategies for high-sensitivity refractive index sensors based on the principle of wavelength-selective resonant coupling in dual-core photonic crystal fibers are presented. Phase matching at a single wavelength can be achieved between an analyte-filled microstructured core and a small core with a down-doped rod or one small air hole in the center, thus enabling selectively directional resonant-coupling between the two cores. The transmission spectra of the output light presents a notch at the index-matched wavelength, yielding a resonant wavelength depending on the refractive index of the analyte. Numerical simulations demonstrate that both of the two proposed sensors can be used for highly sensitive detection of low-index analyte. In particular, the configuration realized by introducing the fiber with a small air hole in one core can be used to the detection of the analyte index around 1.33 and the sensitivity reach to 1.2×10(4) nm per refractive index unit (RIU). In addition, the detection limit is as low as 2.5×10(-7) RIU at n(a)=1.33.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Hydrogenated nanocrystalline silicon thin films were prepared on Corning 7059 glasses by plasma enhanced chemical vapor technique with radio frequency and direct current bias stimulation. The surface topography and microstructure of sample were characterized with atomic force microscopy and X‐ray diffraction. The mechanical properties of the samples were investigated by TriboIndenter nanosystem. The elastic modulus E and hardness H of samples were calculated by means of Oliver and Pharr analysis method. The results show that with increasing the indentation depth from 70 to 180 nm, the maximum applied load Pmax increases from 500 to 2000 µN, while the elastic modulus E dives to 25 from 45 GPa, and the hardness H decreases from 4.9 to 3.8 GPa. After complete unloading, some plastic deformations occur on the films' surface and with the increase of the indentation depth, they become more obvious. This phenomenon is mainly connected with the film's growth mechanism. In this paper, we did an investigation and a discussion in detail about this phenomenon. Copyright © 2011 John Wiley & Sons, Ltd.

The ultra-structures of Zaocys dhumnades’s ventral scale surface were observed by the AFM (Atomic Force Microscopy), at the same time, the frictional properties between ventral scale and the stainless steel ball under different load, different velocity and different lubrication condition were investigated by mode UMT-2 of Universal Micro Materials Tester. The results show that ultra-structure of Zaocys dhumnades’s ventral scale surface is comprised of periodically arrayed micro-fibers and micro-pits, there are micro-pits at its bottom. The frictional resistance on the ventral scale surface is low under the dry friction, whose average frictional coefficient is 0.064, and the friction coefficient increases under the water or oil lubrication, while it decrease with load and velocity increase under different conditions. The reasons of the low friction resistance of ventral scale are its surface ultra-structure, hydrophobic and lower shearing strength. The investigative results provide theoretical proof of reducing adhesion and resistance for frictional surface of bionics fabrication.

In this paper, p-type hydrogenated nanocrystalline (nc-Si:H) films were prepared on corning 7059 glass by plasma-enhanced chemical vapor deposition (PECVD) system. The films were deposited with radio frequency (RF) (13.56 MHz) power and direct current (DC) biases stimulation conditions. Borane (B2H6) was a doping agent, and the flow ratio eta of B2H6 component to silane (SiH4) was varied in the experimental. Films' surface morphology was investigated with atomic force microscopy (AFM); Raman spectroscopy, X-ray diffraction (XRD) was performed to study the crystalline volume fraction X-c and crystalline size d in films. The electrical and optical properties were gained by Keithly 617 programmable electrometer and ultraviolet visible (UV-vis) transmission spectra, respectively. It was found that: there are on the film surface many faulty grains, which formed spike-like clusters; increasing the flow ratio g, crystalline volume fraction Xc decreased from 40.4% to 32.0% and crystalline size d decreased from 4.7 to 2.7 nm; the optical band gap E-g(opt) increased from 2.16 to 2.4 eV. The electrical properties of p-type nc-Si:H films are affected by annealing treatment and the reaction pressure. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.

This study presents a systematic investigation of the thermodynamic properties of free and gamma-Al2O3-supported size-controlled Pt nanoparticles (NPs) and their evolution with decreasing NP size. A combination of in situ extended x-ray absorption fine-structure spectroscopy (EXAFS), ex situ transmission electron microscopy (TEM) measurements, and NP shape modeling revealed (i) a cross over from positive to negative thermal expansion with decreasing particle size, (ii) size- and shape-dependent changes in the mean square bond-projected bond-length fluctuations, and (iii) enhanced Debye temperatures (D-circle minus, relative to bulk Pt) with a bimodal size- dependence for NPs in the size range of similar to 0.8-5.4 nm. For large NP sizes (diameter d > 1.5 nm) D-circle minus was found to decrease toward D-circle minus of bulk Pt with increasing NP size. For NPs <= 1 nm, a monotonic decrease of D-circle minus was observed with decreasing NP size and increasing number of low-coordinated surface atoms. Our density functional theory calculations confirm the size- and shape-dependence of the vibrational properties of our smallest NPs and show how their behavior may be tuned by H desorption from the NPs. The experimental results can be partly attributed to thermally induced changes in the coverage of the adsorbate (H-2) used during the EXAFS measurements, bearing in mind that the interaction of the Pt NPs with the stiff, high-melting temperature gamma-Al2O3 support may also play a role. The calculations also provide good qualitative agreement with the trends in the mean square bond-projected bond-length fluctuations measured via EXAFS. Furthermore, they revealed that part of the D-circle minus enhancement observed experimentally for the smallest NPs (d <= 1 nm) might be assigned to the specific sensitivity of EXAFS, which is intrinsically limited to bond-projected bond-length fluctuations.

Hydrogenated nanocrystalline silicon thin films were deposited with high hydrogen dilution ratio by plasma enhanced chemical vapor deposition technique. The effects of high hydrogen dilution on the surface topography and mechanical properties of the films were studied with atomic force microscopy and TriboIndenter nano indenter. The results indicate that the average grain size in films deposited with high hydrogen dilution is about 3.18 ± 0.02 nm. The surface roughness and densification of the films decrease with the increase of hydrogen dilution ratio at certain range, resulting in the enhancement of the elastic modulus E and hardness H. Oppositely, the increase of hydrogen dilution can increase the surface roughness induced by the increase of the cavities on the film surfaces, and lead to the decrease of the elastic modulus and hardness correspondingly. In this paper, the detailed analysis and discussion were carried out to investigate the mechanism of the observed phenomena.

The effects of laser shock processing on the residual stresses of the LY2 aluminium alloy samples with elliptical spot (long axis length, 12 mm; short axis length, 3 mm) were experimentally investigated, and the effects of the overlapping rate on the residual stresses were simulated using the Abaqus software. The simulated residual stresses were basically in agreement with the measured data, and the relationship between the magnitude and uniformity of residual stress and the overlapping rate was also addressed. Results show that the largest stress magnitudes are located on the top surface of the sample, and the greatest uniformity is achieved by the overlapping of elliptical laser spots. The overlapping rate is critical for the uniformity of the residual stress across the surface. Within a certain impact number range of one to four times, increasing the shocked number can increase the magnitude of residual stress near the surface but not effectively increase the plastically affected depth.

We propose a novel photonic crystal fiber refractive index sensor which is based on the selectively resonant coupling between a conventional solid core and a microstructured core. The introduced microstructured core is realized by filling the air-holes in the core with low index analyte. We show that a detection limit (DL) of 2.02×10⁻⁶ refractive index unit (RIU) and a sensitivity of 8500 nm/RIU can be achieved for analyte with refractive index of 1.33.

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

Adhesion is a peculiar phenomenon of micro/nano-machine.When the strength of the component's material meets the demand,the adhesion and friction in the micro/nano-machines are the main cause of their failure.To overcome or reduce adhesion has become the hotspot in the micro/nano-electromechanical systems(MEMS/NEMS) research field.The adhesion issue in the micro/nano-machines is introduced.The mechanisms of adhesion and various adhensive models used in adhesive contact are analyzed.The micro/nano-machines' design principle of anti-adhesion using surface energy method and asperity integral method is illustrated.Various anti-adhesion methods such as release dry processes,real contact area reducing,and surface energy reducing,are presented.