Automatic measurement of three-phase contact angles in pore throats based on digital images

With the help of digital image processing technology, an automatic measurement method for the three-phase contact angles in the pore throats of the microfluidic model was established using the microfluidic water flooding experiment videos as the data source. The results of the new method were verified through comparing with the manual measurement data.On this basis, the dynamic changes of the three-phase contact angles under flow conditions were clarified by the contact angles probability density curve and mean value change curve. The results show that, for water-wetting rocks, the mean value of the contact angles is acute angle during the early stage of the water flooding process, and it increases with the displacement time and becomes obtuse angle in the middle-late stage of displacement as the dominant force of oil phase gradually changes from viscous force to capillary force. The droplet flow in the remaining oil occurs in the central part of the pore throats, without three-phase contact angle. The contact angles for the porous flow and the columnar flow change slightly during the displacement and present as obtuse angles in view of mean values, which makes the remaining oil poorly movable and thus hard to be recovered. The mean value of the contact angle for the cluster flow tends to increase in the flooding process, which makes the remaining oil more difficult to be recovered. The contact angles for the membrane flow are mainly obtuse angles and reach the highest mean value in the late stage of displacement, which makes the remaining oil most difficult to be recovered. After displacement, the remaining oils under different flow regimes are just subjected to capillary force, with obtuse contact angles, and the wettability of the pore throat walls in the microfluidic model tends to be oil-wet under the action of crude oil.

Three-Dimensional Study of the Effect of the Angle of Incidence of a Magnetic Field on the Electrical Power and Conversion Efficiency of a Polycrystalline Silicon Solar Cell under Multispectral Illumination

A three-dimensional approach to the effect of magnetic field incidence angle on electrical power and conversion efficiency is performed on a front-illuminated polycrystalline silicon bifacial solar cell. A solution of the continuity equation allowed us to present the equations of photocurrent density, photovoltage and electric power. The influence of the angle of incidence of the magnetic field on the photocurrent density, the photovoltage and the electric power has been studied. The curves of electrical power versus dynamic junction velocity were used to extract the values of maximum electrical power and dynamic junction velocity and to calculate those of conversion efficiency. From this study, it is found that the conversion efficiency values increase with the angle of incidence of the magnetic field.

Optimization of the forearm angle for arm wrestling using multi-camera stereo digital image correlation: A preliminary study

This study analyzes the function of different muscles during arm wrestling and proposes a method to analyze the optimal forearm angle for professional arm wrestlers.We built a professional arm-wrestling platform to measure the shape and deformation of the skin at the biceps brachii of a volunteer in vivo during arm wrestling.We observed the banding phenomenon of arm skin strain during muscle contraction and developed a model to evaluate the moment provided by the biceps brachii.According to this model,the strain field of the area of interest on the skin was measured,and the forearm angles most favorable and unfavorable to the work of the biceps brachii were analyzed.This study demonstrates the considerable potential of applying DIC and its extension method to the in vivo measurement of human skin and facilitates the use of the in vivo measurement of skin deformation in various sports in the future.

Evaluation of the Anterior Chamber Angle Structures in Perinatal Infants Using a Wide-Field Digital Fundus Camera

Objective This study aimed to evaluate the ability of a digital fundus camera to observe the development of the anterior chamber angle(ACA)in premature infants.Methods Forty-eight eyes of preterm infants(n=48)were examined by a digital fundus camera to observe the development of the ACA.ACA grading was performed based on the visualization of the anterior chamber structures according to the Scheie Angle Depth Evaluating System.Results ACA images from all 48 infants were successfully acquired using RetCam3.The corrected gestational age ranged from 30 weeks to 49 weeks,which covered the period from 2 months preterm to>2 months post-term.As the corrected gestational age increased,the corrected gestational age grading was significantly decreased.The mean corrected gestational ages of the infants corresponding to the ACA classification from grade IV to grade 0 were 32.75±1.89,37.20±1.30,39.75±2.38,40.56±2.24,and 44.23±2.14 weeks,respectively,which were all significantly different(P<0.05).The regression analysis showed a linear correlation between the grading of the ACA and the corrected gestational age(R2=0.724,P=0.0001).Conclusion The ACA of a full-term newborn can be fully detected and evaluated by a digital fundus camera.For premature infants,part of the ACA is not visible physiologically;however,it should not be misdiagnosed as angle closure or a narrow angle.

Strip silicon waveguide for code synchronization in all-optical analog-to-digital conversion based on a lumped time-delay compensation scheme

An all-optical analog-to-digital converter （ADC） based on the nonlinear effect in a silicon waveguide is a promising candidate for overcoming the limitation of electronic devices and is suitable for photonic integration. In this paper, a lumped time-delay compensation scheme with 2-bit quantization resolution is proposed. A strip silicon waveguide is designed and used to compensate for the entire time-delays of the optical pulses after a soliton self-frequency shift （SSFS） module within a wavelength range of 1550 nm-1580 nm. A dispersion coefficient as high as -19800 ps/（km.nm） with ＋0.5 ps/（km.nm） variation is predicted for the strip waveguide. The simulation results show that the maximum supportable sampling rate （MSSR） is 50.45 GSa/s with full width at half maximum （FWHM） variation less than 2.52 ps, along with the 2-bit effective- number-of-bit and Gray code output.

The digital anatomic study of the changing regularity of thoracic pedicle screw channels in different transverse screw angle

Objective To investigate the changing regularity of thoracic pedicle screw channel (PSC) in different transverse screw angle(TSA).Methods CT scan images of thoracic vertebrae of a healthy adult ware digitally analyzed by Mimics 10.01

Machine Vision Based Measurement of Dynamic Contact Angles in Microchannel Flows

When characterizing flows in miniaturized channels, the determination of the dynamic contact angle is important. By measuring the dynamic contact angle, the flow properties of the flowing liquid and the effect of material properties on the flow can be characterized. A machine vision based system to measure the contact angle of front or rear menisci of a moving liquid plug is described in this article. In this research, transparent flow channels fabricated on thermoplastic polymer and sealed with an adhesive tape are used. The transparency of the channels enables image based monitoring and measurement of flow variables, including the dynamic contact angle. It is shown that the dynamic angle can be measured from a liquid flow in a channel using the image based measurement system. An image processing algorithm has been developed in a MATLAB environment. Images are taken using a CCD camera and the channels are illuminated using a custom made ring light. Two fitting methods, a circle and two parabolas, are experimented and the results are compared in the measurement of the dynamic contact angles.

Effect of Incidence Angle of Magnetic Field on the Performance of a Polycrystalline Silicon Solar Cell under Multispectral Illumination

The aim of this work is to investigate, with a three-dimensional steady-state approach, the effect of the incidence angle of a magnetic field on the performance of a polycrystalline silicon solar cell under multispectral illumination. The magneto-transport and continuity equations of excess minority carriers are solved to find the expression of the density of excess minority carriers and the related electrical parameters, such as the photocurrent density, the photovoltage and the electric power, of a grain of the polycrystalline silicon solar cell. The influence of the incidence angle of the magnetic field on the diffusion coefficient, the short-circuit photocurrent density, the open-circuit photovoltage and the electric power-photovoltage is studied. Then, the curves of the electric power-photovoltage is used to find the maximum electric power allowing to calculate, according to the incidence angle of the magnetic field, the fill factor and the conversion efficiency. The study has shown that the increase of the incidence angle of the magnetic field from 0 rad to π/2 rad, can reduce the degradation of the performance of solar cells.

72 MHz/54 MHz SAMPLING RATE CONVERSION SYSTEM OF HDTV STUDIO SIGNAL

Sampling rate conversion finds great use in the area of multirate signal processing, communications system, speech processing system, etc. In this paper, we describe a structure of 72 MHz/54 MHz sampling rate conversion system which is applied to HDTV system. First, we discuss the theoretical model of a 4/3 conversion scheme and then design the hardware structure implemented in parallel and illustrate the subsystem structure in detail. Finally, the phase diagrams are presented to show the relations between the clocks.

Crack Detection in Pipes with Different Bend Angles Based on Ultrasonic Guided Wave

Pipeline plays an indispensable role in process industries,because the progressing crack-like defects of in it may result in serious accidents and significant economic losses.Therefore,it is essential to detect the cracks occurred in pipelines.The axial crack-like defects in elbows with different angle are inspected by using the T(0,1)mode guided waves,in which different configurations including 45°,90°,135°and 180°(straight pipe)are considered respectively.Firstly,the detection sensitivity for different defect location is experimentally investigated.After that,finite element simulation is used to explore the propagation behaviors of T(0,1)mode in different bend structures.Simulation and experiment results show that the crack in different areas of the elbow can affect the detection sensitivity.It can be found that the detection sensitivity of crack in the middle area of the elbow is higher compared to the extrados and intrados of the elbow.Finally,the mode conversion is also investigated when the T(0,1)crosses the bend,and the results show that bend is a key factor to the mode conversion phenomenon which presents between the T(0,1)mode and F(1,2)mode.

换热翅片几何量数字化测量技术研究及在智能制造中的应用

为解决换热翅片开窗角度的数字化测量问题,研究了面向换热器智能制造产线的翅片几何量参数测量装置。该装置采用激光轮廓传感器进行非接触测量,对获取的多组原始轮廓数据进行数据剔除和取均值预处理,将处理后的数据逐点求导以识别兴趣测量区域,在各兴趣测量区域采用定长逐点步进的方式进行最小二乘拟合运算,选取最优拟合线段进行夹角计算,可自动实现对翅片8个开窗角度及3个长度参数的测量,设计了基于JSON的数据交互格式实现与制造执行系统的数据对接。实验结果表明:装置角度测量最大允许误差(MPE)为±0.5°,具备数字化测量及数据交互能力,测量精度满足企业质控需求。

职业教育数字化转型视角下专业群建设策略研究

数字化转型正在推动社会全面变革。数字化时代的到来,使职业教育面临数字化转型的机遇和挑战。数字化转型不仅会改变职业教育的教学方式和内容,也对职业教育的专业群建设提出了新的要求。基于职业教育数字化转型的视角,分析数字化转型对职业教育专业群建设的影响,并从专业动态调整、师资队伍建设、在线资源库建设等方面提出专业群建设的有效策略。

客户数字化转型与企业营运资金管理效率——基于竞争侵占与约束防御的双重视角

无论在企业管理实践中,还是从已有文献来看,客户数字化转型对企业营运资金管理效率表现出促进还是抑制,仍未形成一致结论。文章采用中国深沪A股上市企业披露的前五大客户数据,探讨客户数字化转型对企业营运资金管理效率的溢出效应与作用机理。基准检验发现,客户数字化转型降低了企业营运资金管理效率,说明数字溢出存在负外部性。作用渠道检验发现,竞争侵占与约束防御是客户数字化转型影响企业营运资金管理效率的两大渠道,即客户数字化转型催生的数字溢出通过降低企业相对议价能力、降低企业应收账款回收率、加剧企业专用资产套牢风险、加大企业商业信用供给以及扩大企业存货储备规模进而降低了企业营运资金管理效率,说明数字溢出具有竞争约束特征。异质性检验发现,当客户集中度较低、企业规模较大、企业风险承担能力较强时,数字溢出的竞争约束特征得到缓解。研究结论解释了客户数字化转型是否能够提升企业营运资金管理效率的争议,发现了客户数字化转型引致的数字溢出具有竞争约束特征,并提供了企业克服数字溢出负外部性的理论指导,具有理论价值和现实意义。

基于FPGA的多通道温度采编装置设计

针对飞行试验中对设备温度测量的需求,设计了一种适用于飞行测试的高精度多通道温度采编装置。设计以FPGA构建信号采集处理系统,采用AD8227和AD590来实现信号的调理和温度冷端补偿,通过标准RS422协议实现16路温度信号传输,并采取线性拟合的方式对输出进行非线性校正,提高了系统准确率和稳定性。测试结果表明,测温电路全量程内最大测量误差为±0.083%F.S.。经过测试验证,该方案传输过程无丢帧零误码,系统运行高效、可靠。

火炮角度参数计量装置关键技术研究与设计

针对现有手段无法满足火炮角度参数对高精度计量的需求,研究提出一种进一步提高火炮角度计量精度的方法,采用正、余弦函数电路及数字—舷角变换电路设计制作了18位高精度数字—舷角转换器,采用D/A转换、电机转速及传动比例换算的方式模拟角度、角速度信号,并制作基于该技术的火炮角度参数计量装置,通过实验验证了该装置的准确性。

基于机载多角度InSAR技术的复杂地形高精度DEM重建方法

干涉合成孔径雷达(Interferomtric Synthetic Aperture Radar,InSAR)是全天时、全天候获取三维地表信息重要的技术手段。机载InSAR系统具有机动灵活、多角度获取数据的优势,可以高效率、高精度获取数字高程模型(Digital Elevation Model,DEM)数据。但是,在地形复杂区域,InSAR侧视成像易在地形陡峭区域形成较大范围的阴影和严重的叠掩现象,阴影和叠掩区域在SAR图像上体现为信息的丢失,从而导致DEM数据大面积无效数据的存在,严重影响DEM数据的质量及应用。针对这一问题,本文提出了基于机载多角度InSAR技术的复杂地形高精度DEM重建方法,基于考虑地形起伏的机载多角度InSAR数据获取任务规划设计,最大程度的避免阴影和叠掩导致的无效数据;基于高精度InSAR数据处理,保证每个角度DEM数据精度的高度一致性;基于快速多角度DSM数据融合与滤波处理,实现多角度InSAR体制复杂地形DEM高精度重建。本文以四川省西部山区大坡度、非连续等复杂地形为例,基于本文提出的方法,利用3个角度InSAR数据融合处理,生成了高精度DEM数据,试验结果表明,本文提出的方法获取复杂地形DEM数据高程均方根误差为0.6 m,同时,数据有效率大于99%。

基于FPGA的单光子时间数字转换器设计

针对单光子计数器对高速飞行光子时间测量的高分辨率要求,传统的TDC在时间测量上存在误差较大的不足。本文设计了一种利用FPGA内部逻辑延迟单元Carry4级联构建延迟链的TDC。该方法首先使用子链平均的方式进行数据采样,避免数据“气泡”。其次,结合码密度测试和bin-by-bin校准将各级延迟单元宽度校准至接近均匀宽度,提高系统的测量精度。最后,通过Vivado软件仿真并烧录至ZYNQ7000进行板级测试,实验结果表明,该TDC能够在3 ns的动态时间范围内实现时间分辨率10.91 ps,差分非线性(DNL)范围为[-0.75,1.01]LSB,积分非线性(INL)范围为[-1.74,2.19]LSB。

基于纯硬件电路的轴角-数字解码系统研究

针对旋转变压器解码系统需要软硬件协同合作及系统结构复杂的问题,提出了一种基于纯硬件电路的轴角-数字解码系统,主要包括解调模块和解算模块。解调模块基于与激励信号同步的脉冲信号控制采样/保持电路来得到低频的解调信号;为避免使用AD转换、昂贵的压控振荡器等复杂硬件,解算模块采用了负反馈结构,主要基于计数器实现,通过正余弦LUT查找表将计数值转换为旋转变压器角度的线性输出,计数值表示解算角度;当解算角度与实际角度不一致时,解算模块会控制计数值增加或者减少,直到解算角度与实际角度一致。为验证该方法的有效性,在Matlab/Simulink中搭建系统模型进行多工况仿真验证,结果表明,纯硬件解码方法在角度阶跃变化、匀速变化及系统存在噪声时均能稳定正常工作,并且误差不超过0.2°,响应时间不超过2 ms,优于常规软件解码方法。最后进一步制作了验证板卡进行了实物验证,验证结果表明该系统具有较好的稳定性及精度。

沉浸美学视野下宋画山水的数字化转变

宋画的数字化美学体现在解构与重组中,主要从形式上的二维到三维的转变;叙事上的消解与转换;体验中的五感融合与沉浸这三点体现。本文以宋画中的山水画为主,从宋画与沉浸美学的关系入手,结合案例分析宋画在数字化过程中的转变与呈现,以沉浸美学的视角探究宋画本身可被活化的因素,希望能为其他中国传统绘画数字化提供参考,为文化与技术结合作出有意义的探讨。