To investigate the functioning mechanism of cruise altitude on transportation and discharging dynamics of onboard fire-extinguishants, a numerical model coupling the vaporization and flowing process is established for the Halon 1301-N2 multi-component two-phase flow inside the onboard fire-extinguishing system based on computational fluid dynamics. Flowing and transportation parameters are simulated and compared for Halon 1301 at 0 m, 3000 m, 6000 m and 12000 m. Moreover, the peak discharging fluid pressure, velocity and density are also analyzed to evaluate the impact of altitude on discharging dynamics of Halon 1301. Notably, the maximum discharging velocity at 3000 m, 6000 m and 12000 m are reduced by 4 %, 9 % and 15 % relative to that at 0 m; the maximum discharging fluid pressure and density at 12000 m are respectively reduced by 32 % and 12 % relative to those at 0 m. High altitude is unraveled to inhibit the vaporization of Halon 1301 and lower the discharging efficiency at the pipeline outlet, consequently lowering the diffusion efficiency and effective concentration of Halon 1301 in the protected area and further weakening the fire-suppression effectiveness. The unveiled insights afford guidance for the optimization of fire-extinguishing systems to improve the fire-fighting capability of airplanes at high altitudes.

Micro-scale gas lubrication has been studied for several decades, with extensive research on non-equilibrium flow effects like velocity slip and thermal creep. However, the Knudsen maximum effect in micro-scale gas lubrication has not been reported yet. To address this, we analyzed the load capacity characteristics of slider bearings with ultra-thin film gas lubrication equations derived from the linearized Boltzmann-Bathnagar-Gross-Krook model equation (Fukui-Kaneko lubrication model) under the condition of constant bearing number. Our study reveals that there exists a maximum value of load capacity for slider bearings when the reference Knudsen number is about unity. This happens because the dimensionless mass flowrate of micro-scale gas flows has a minimum value when the reference Knudsen number approaches unity. Understanding the Knudsen maximum effect is crucial when designing micro-nano devices related to gas lubrication, as it implies that there exists an optimum clearance for maximum load capacity.

It is very crucial to solve Reynolds equation quickly and accurately using the numerical methods in the research field of fluid lubrication. For the static Reynolds equation of self-acting gas journal bearings, the typical solution algorithm of the finite difference method is put forward and a new solution algorithm of the finite difference method is proposed. The typical solution algorithm discretizes the transformed Reynolds equation directly and the quadratic equation in one variable of the pressure can be obtained. Different from the typical solution algorithm, the both sides of the transformed Reynolds equation are firstly divided by the term of PH3 and then discretized in the new solution algorithm, thus the linear equation about the pressure can be obtained. Secondly, the Reynolds equation is solved numerically with the same parameters and the pressure distribution of gas bearings is obtained. Finally, the numerical solution from the new solution algorithm can be obtained with less number of iterations and the less computing time under the different computational grids and bearing numbers. Therefore, the new solution algorithm of the finite difference method is superior to the typical solution algorithm of the finite difference method.

提出和发展了适用于液体(水)环境的光热微驱动技术及光热微驱动机构(OTMA).建立了水环境中OTMA膨胀臂在激光照射下的光热膨胀模型,基于有限元分析推导出膨胀臂的温升分布公式,并对长度1080μm、宽度90μm的膨胀臂在4 mW激光照射下的温升分布进行了仿真,理论研究表明了液体环境中光热微驱动技术的可行性.设计与微加工制作了一种对称型OTMA,在波长520 nm、功率可调的激光照射下,首次实现了液体环境中的光热微驱动,实验结果表明膨胀臂的光热偏转量随激光功率的增大而增加.进一步开展了在波长520 nm、有效功率4 mW、频率可调的激光脉冲照射下的光热微驱动实验,结果表明,对称型OTMA在频率0.9 Hz～16.4 Hz的激光脉冲照射下具有良好的动态响应,驱动量(偏转量)振幅在2.6μm～3.7μm之间变化,随激光脉冲频率的增大而减小.理论研究及实验曲线趋势表明,适当增大激光功率、提高激光脉冲频率,在液体环境中实现更大偏转量、更高频率的光热微驱动是完全可行的.本文研究拓展了液体环境中的光热微驱动技术,为微光机电系统及微纳米技术领域的应用提供了新的方法与途径.

In order to prevent the failure of the white balance algorithm of color digital reflection microscope and improve the accuracy of color acquisition, a colorimetric characterization method based on non-RAW data is proposed. First, a nonlinearity correction model based on power function is established by using the neutral patches of the color card. The non-RAW data is converted into the data linearly related to the scene radiance. Then, the colorimetric characterization model is established. Finally, experiments are conducted to test the accuracy of colorimetric characterization model before and after correction of non-RAW data, and the influence of luminance change of light source on nonlinearity correction model and the accuracy of colorimetric characterization is analyzed. The results show that the corrected non-RAW data will improve the accuracy of colorimetric characterization, and the improvement effect is especially obvious for the linear colorimetric characterization model. At the same time, the luminance change of the light source will cause the variation of the nonlinear correction model as well as the accuracy of colorimetric characterization, but when the luminance change is not sharp, the general nonlinear correction model can be used.

Digital cameras usually build a colorimetric characterization model through target samples, which, however, will affect the mapping between the cameras' response values and the colorimetric values. The existing selection methods for target samples ignore the generality of target samples, namely that the colorimetric characterization model built based on the optimized target samples should be applicable to any color samples. Therefore, we proposed an optimization method of colorimetric characterization targets for the digital cameras based on uniform color samples. First, uniform color samples were selected from the spectral reflectance of extensive real objects. Then, the colorimetric characterization model was combined to optimize the target samples among the uniform color samples. The results show that the optimization of target samples is subject to the data type and the colorimetric characterization model. Consequently, different optimized target samples are obtained, and the optimized target samples outperform the typical target samples in terms of colorimetric characterization. In addition, for the RAW data, an increase in the number of target samples does not necessarily improve the accuracy of a linear colorimetric characterization model, while for the sRGB data, more target samples will be beneficial for enhancing the performance of a polynomial colorimetric characterization model.

This paper presents microscopic research on properties of asymmetric optothermal microactuator (OTMA) with different lever ratios. A theoretical model is established on the basis of thermal flux theorem to describe the increase in temperature induced by laser irradiation and thermal expansion of OTMAs' expansion arms. The increases in temperature of three asymmetric OTMAs with total lengths/lever ratios of 540 mu m/7.2, 1,080 mu m/7.2, 1,080 mu m/14.4 were simulated under irradiation of 2.8 mW laser beam, which revealed that a similar increase in temperature will distribute on three expansion arms, with maximum the temperature increase of 82.73, 87.67, and 88.03 degrees C, respectively. Due to these increases in temperature, the arms expand longitudinally and thus the OTMAs are capable of deflecting laterally with enlarged deflection amplitudes. To obtain optimized deflecting properties, three OTMAs with aforementioned lever ratios are further microfabricated and experimented using an optical microscopic observation and measuring system combined with a charge-coupled device. The experimental results show that these OTMAs can be directly actuated by laser beam and acquire maximum deflections of 6.8, 7.2, and 11.4 mu m when only 2.8 mW laser power is employed. In addition, it is demonstrated that, although doubling the lever ratio of OTMA does not correspondingly generate twofold deflection, the deflection amplitude can significantly increase with the increase in the lever ratio. With their characteristic elegances, the OTMAs are expected to be practically applied in the micro-electromechanical system and the micro-opto-electromechanical system.

This paper proposes and studies the characteristics of a laser-driven optothermal microactuator (OTMA) directly operated in water. A theoretical model of optothermal temperature rise and expansion is established, and simulations on a 1000 µm long OTMA are conducted, revealing that its arm is able to expand and contract in response to the laser pulses in a water environment. Microactuating experiments are further carried out using a microfabricated OTMA. The results demonstrate that the OTMA can be practically actuated in water by a 650 nm laser beam and that the OTMA’s deflection amplitude increases linearly with laser power. When irradiated by laser pulses with 9.9 mW power and 0.9–25.6 Hz frequencies, the OTMA achieves deflection amplitude ranging from 3.9 to 3.2 µm, respectively. The experimental results match well with theoretical model when taking the damping effect of water into account. This research may be conducive to developing particular micro-electromechanical systems or micro-optoelectromechanical devices such as underwater optothermal micromotors, micro-pumps, micro-robots, and other underwater microactuators.

High dynamic range (HDR) technology has become a new trend of the development of digital microscopes. Currently, due to the high computational complexity, the HDR video cannot be processed and displayed in real-time. Based on REC.2020 high definition (HD) standard, it is feasible and stable to generate the HDR video flow in real-time using GPU accelerated processing. The experimental results show that the presented algorithm not only provides a stable real-time HDR video flow, but also improves the performance of the recovered video in both detail and color, which has overcome the limitation in processing speed and quality of the traditional HDR imaging technology.

This article proposes to develop a WiFi-controlled portable atomic force microscope (AFM). The AFM consists of a horizontal probe, controlling circuits, digital to analog (D/A) and analog to digital (A/D) interfaces, a microcomputer (Raspberry Pi, RPi), and a laptop. The proposed AFM uses a pocket-size power supply to drive the controlling circuits, the D/A and A/D interfaces, as well as the RPi that constructs network hotspots and generates scanning signals. With special design and integration of the whole system, both of the AFM probe and electronic controlling system are portable. At a distance of 50 m from the proposed AFM, experiments in the constant height mode and the constant force mode are conducted to evaluate its performance. The results show that this WiFi-controlled AFM has a maximum scan range of 3.6 x 3.6 mu m(2) with nanometer order resolution. Meanwhile, it achieves satisfactory image contrast, stability, and repeatability. Compared with conventional AFMs, the AFM proposed in this paper no longer relies on commercial AC mains supply or high-voltage DC power supply, and realizes WiFi-controlled AFM scanning and imaging in 50 m or farther without wire or network cable connection to a laptop or a desktop computer. Given credits to these features, WiFi-controlled AFMs are expected to own a wider range of application, especially in isolated environments, outdoor researches, or even fieldwork investigations.

The degradation of optical microscopic imaging is space-variant, and how to fast restore optical degraded image remains a special problem. Based on point spread function (PSF) estimation under each field of view (FOV), a L0 gradient-constrained image restoration method is proposed to solve optical degradation in microscopic imaging. Firstly, the whole scene is segmented into several different regions according to different FOV. The PSFs for each region are estimated from modulation transfer function (MTF) measured in advance. Secondly, a penalty function is designed using L0 gradient constraint to deblur the degraded images of each sub-FOV. Finally, a weighted stitching approach is used to stitch the restored images of multiple FOV (m-FOV). Experimental results indicate that the m-FOV analysis could well solve the problem of space-variant degradation. Compared with the other methods, both subjective and objective evaluation results prove that the L0 norm idea could rapidly and effectively restore the degraded image. The approach could be well applied to a real product.

研究开发了虚实一体的原子力显微镜实验系统,由AFM原理演示及模拟扫描软件系统、AFM模拟演示探头系统和AFM实验仪器装置等部分组成.开展了AFM实验背景的介绍、相关原理的仿真演示、AFM操作的模拟训练、AFM模拟扫描成像实验数据的测量及相关的实验研究.实现了对学生进行创新思维、操作技能、知识整合等各种层次的训练,并建立了"回顾历史、触摸现在、遇见未来"的四维空间物理实验教学模式,具有低成本、多功能和高效率等特点.该虚实一体的AFM实验系统已在我校得到很好的推广与应用.

This paper proposes and studies symmetric optothermal microactuators (OTMAs) which are directly controlled by a laser beam. Based on the principle of thermal flux, a theoretical model is established to describe the laser-induced temperature rises and optothermal expansions of the OTMAs' expansion arms. Temperature rise distributions of the arms with lengths of 590, 990, and 2260 μm are simulated separately, which reveals that, under 2 mW laser irradiation, the maximum temperature rises are invariably less than 75.9°C. Simulations are also made to consider optothermal expansions of the arms caused by laser irradiation, which turns out that expansion increases considerably when the arm's length increases from 250 to 1000 μm, while insignificantly between 1250 and 2500 μm. Under a laser beam of 2 mW power, experiments on three microfabricated OTMAs have been further conducted, which demonstrate that the OTMAs are capable of generating maximum deflections of 7.3, 11.3, and 13.6 μm, and that the growth of deflection is comparatively obvious in the case when the total length changes from 750 to 1200 μm, while insignificant for the range between 1200 and 2380 μm. With regard to simulations and experiments, it has been proved that the OTMAs are capable of implementing direct laser-controlled microactuation in which only about 2 mW laser power is demanded. Moreover, it has been proved that twofold total length or arm length does not correspondingly result in doubling the deflection, nor the expansion. Therefore, total length/expansion arm's length around or less than 1200/1000 μm is more appropriate for obtaining satisfactory characteristics of OTMAs, which may be potentially applied in MEMS/MOEMS and micro-/nano-technology.

提出了一种基于嵌入式系统和WiFi无线控制的接触模式原子力显微镜（AFM）系统。该AFM系统直接由迷你型移动电源给扫描与反馈电路及嵌入式系统等供电;嵌入式系统由微型电脑树莓派和微小型AD＆DA模块构成,通过WiFi与笔记本电脑实现无线数据通信。利用这一方法,成功研发了无线控制式AFM系统,并开展了微纳米样品的扫描成像实验。实验结果表明,该AFM系统的横向分辨率达到纳米量级,纵向分辨率达到0.1nm,最大扫描范围为3.6μm×3.6μm。该系统的显著特点是无需交流市电供电,无需直流高压电源,也无需与计算机之间的线缆连接,可在约100m远处通过无线控制的方式实现AFM的扫描成像。这一新型AFM系统,不仅能够在微纳米技术的常规领域得到应用,而且在野外考察、隔离环境、真空条件、气体氛围环境及星际探测等特殊领域具有广阔的应用前景。

The dynamic properties of optothermal microactuator (OTMA) are theroretically and experimentally reported under pulsed laser irradiation.A dynamic model for describing optothermal temperature rise and optothermal expansion of the expansion arm is established.The formulas of dynamic expansion and its amplitude are also derived,based on which the relationships among the expansion,expansion amplitude and the laser pulse frequency are obtained through Matlab simulations.An asymmetric optothermal microactuator (A-OTMA) with length of 700μm is designed and microfabricated.Experiments are carried out under pulsed laser with power of 2 mW and frequency of 2-18 Hz.The dynamic actuating of the A-OTMA is monitored by microscopic imaging system and is further analyzed using motion analysis software.The experimental results show that the A-OTMA can periodically deflect with the same frequency of laser pulse,and both of the maximum deflection and deflection amplitude decrease as the frequency increases,matching with the trends of theoretical curves quite well.It is also proved that the A-OTMA is capable of acquiring maximum deflection amplitude of 14.9 μm (at 2 Hz) and maximum response frequency up to 18 Hz.This work can provide technical foundation for practical applications of optothermal microactuator in the fields of micro opto-electro-mechanical system (MOEMS) and micro/nano-technology.

Optical imaging degradation is one of the most important factors for image quality in digital optical microscopic imaging. Combined with the digital microscopic imaging system and optical objective lens measurement, a fast gradient constrained restoration method is proposed based on point spread function estimation under different fields. By measuring the modulation transfer function of objective lens, the point spread function is obtained with different fields. A novel restoration approach is designed with the L0gradient constraint as a regularized term. Meanwhile, the weight image stitching method is designed for the restoration of multiple fields. The image data with different objective lens are tested, and the evaluation methods are used for assessing the results. The results show that the gradient constrained microscopic imaging quality improvement method with the objective lens measurement is suitable for microscopic imaging system for its good restored effect and high computational efficiency, it takes only1. 62sfor the image size of 2048pixel×1536pixel.

This paper proposes a method of a symmetric optothermal microactuator (S-OTMA) directly driven by laser pulse. Based on the principle of thermal flux, a dynamic model is established describing the laser-induced optothermal temperature rise and optothermal expansion of the S-OTMA's expansion arm. The dynamic optothermal expansion and the relationship between the expansion amplitude and laser pulse frequency are simulated, indicating that the expansion arm expands and reverts periodically with the same frequency of the laser pulse, and that the expansion amplitude decreases with the increase of laser pulse frequency. Experiments have been further conducted on a micro-fabricated S-OTMA under a laser pulse of 3.3 mW power and 2-18 Hz frequency. It is shown that the S-OTMA can periodically deflect in accordance with the same frequency of the laser pulse, with a maximum response frequency of at least 18 Hz. The maximum deflection (vibration) amplitude is measured to be 13.7 mu m (at 2 Hz), and the amplitude decreases as the frequency increases. Both the theoretical model and experiments prove that the S-OTMA is capable of implementing direct laser-controlled microactuation in which only similar to 3 mW laser power is demanded. Furthermore, bi-directional actuation of the optothermal microactuator (such as S-OTMA) can be easily achieved by alternately irradiating either arm of the microactuator. This work may broaden the applications of the S-OTMA, as well as optothermal microactuators in MEMS/MOEMS and micro/nano-technology.

This paper reports the dynamic modelling and experimental study of an asymmetric optothermal microactuator (OTMA). According to the principle of thermal flux, a theoretical model for instantaneous temperature distribution of an expansion arm is established and the expression of expansion increment is derived. Dynamic expansion properties of the arm under laser pulse irradiation are theoretically analyzed indicating that both of the maximum expansion and expansion amplitude decrease with the pulse frequency increasing. Experiments have been further carried out on an OTMA fabricated by using an excimer laser micromachining system. It is shown that the OTMA deflects periodically with the same frequency of laser pulse irradiation. Experimental results also prove that both OTMA’s maximum deflection and deflection amplitude (related to maximum expansion and expansion amplitude of the arm) decrease as frequency increases, matching with the theoretical model quite well. Even though the OTMA's deflection decrease at higher frequency, it is still capable of generating 8.2μm maximum deflection and 4.2μm deflection amplitude under 17Hz/2mW laser pulse irradiation. This work improves the potential applications of optothermal microactuators in micro-opto-electro-mechanical system (MOEMS) and micro/nano-technology fields.

An extended Reynolds equation based on the regularised 13 moment equations and lubrication theory is derived for gas slider bearings operating in the early to upper transition regime. The new formulation performs well beyond the capability of the conventional Reynolds equation modified with simple velocity-slip models. Both load capacity and pressure distribution can be reliably predicted by the extended Reynolds equation and are in good agreement with available direct simulation Monte Carlo data. In addition, the equations are able to provide both velocity and stress information, which is not conveniently recovered from available kinetic models. Tests indicate that the equations can provide accurate data for Knudsen numbers up to unity but, as expected, begin to deteriorate afterwards.

An extended slip velocity boundary condition is derived from the regularized 13 moment equations firstly. Different from the existing slip velocity boundary condition, the slip coefficients of the extended one are not fixed, which will change with the wall accommodation coefficient and the Knudsen number of the gas flow. Using the extended slip velocity condition, an improved modified Reynolds equation for thin-film gas lubrication is established. From solving the improved modified Reynolds equation, the pressure distribution of the slider gas bearing is obtained and has a better agreement with that from the direct simulation Monte Carlo method under different pitch angles and wall velocities. It is found that the improved modified Reynolds equation can predict a more accurate pressure distribution of the slider gas bearing than the Fukui and Kaneko’s lubrication model from the linearized Boltzmann equation in the near transition regime.