基于应变式双参数倾斜仪的设计

为精确测量桩体在施工过程的倾斜角度,介绍一种基于电阻应变计式的双参数倾斜仪,阐述了倾斜仪的结构设计和工作原理;推导出倾斜角和方位角的数学模型。对放大电路及其信号变换电路进行硬件设计和软件编程。实验结果表明倾斜角在±10°范围内,其测量精度为0.04°;方位角在0°～360°范围内,其测量精度为2.253°,可以满足桩基础施工的技术要求。     

双冠醚钠离子选择电极的研制

本文用新合成的2—氯—4,6—双(4′—亚氨基苯并—12—冠—4)三嗪(以下简称双冠醚)作电活性物质,制成钠离子选择电极。其电极性能、线性范围:10°～5×10~(-5)M,斜率为55±1mv,对Li~+、NH_4~+、Mg~(2+)、Zn~(2+)和Ca~(2+)的选择系数分别为7.7×10~(-2)、1.1×10~(-2)、8.4×10~(-4)、4.0×10~(-4)和4.6×10~(-4)。     

温差电传感器在温差监测中的应用

<正>半导体材料与一般金属温差电材料相比,具有大得多的温差电动势率和小的导热率以及小的电阻率。对于通常用于检测温差的传感器来说,这是一些很重要的特性。性能较佳的n-Bi_2Te_3·Se_2Te_3材料,具有如下的数据:热导率为1.4×10~(-2)W/cm·°C;电阻率为 1.1×10~(-3)Ω·cm;温差电动势率为210μV/°C。p-     

基于CORDIC算法的360°角度传感器的设计

一维霍尔板型角度传感器无法测量0～360°的角度,采用4个霍尔器件的联合测角技术和CORDIC算法可实现0～360°范围内的角度测量。文章详细描述了4个霍尔器件联合测角技术的测角原理及实现算法,并引入了符号幅值表示法,即先利用正弦和余弦的幅值进行0°～90°范围内的反正切CORDIC运算,再根据正弦和余弦正负号(符号)的不同组合实现角度从0°～90°到0°～360°的映射。Modelsim平台仿真验证了该方法的准确度和精度,仿真误差小于0.01%,实测总误差不大于0.05°。     

直接和间接的笔倾斜输入性能对比

越来越多的笔式设备通过增加笔倾斜输入来提高其输入能力。但在直接输入设备和间接输入设备上执行笔的倾斜操作时,由于操作环境和视觉反馈的不同,往往会导致操作性能产生差异。本研究以探索笔倾斜输入在直接设备和间接设备上的性能差异为目的,以实证手段考察在两种设备上获取不同角间距下的不同笔倾斜目标时的操作速度、稳定性和准确性,讨论导致直接设备和间接设备笔倾斜性能不同的原因,并提出适用的角间距和倾斜目标位置。实验结果表明,在直接设备和间接设备上操作笔倾斜角时,在操作速度上直接设备优于间接设备,但在稳定性和准确性上,间接设备优于直接设备。20°的角间距对两种设备来说都呈现较好的性能,若需要在更小角间距内完成目标选择操作,在间接设备上的效果更好。最后,对两种设备的用户使用习惯进行了总结,为基于笔倾斜角的用户界面设计提供了帮助和参考。     

一种扫描式热金属探测器的研制

为了满足自动化钢铁生产的要求,根据红外探测原理研制了一种新型的扫描式热金属探测器。对研制过程中扫描转镜的设计、光电接收器的选取、信号处理电路的设计原理做出了详细的分析,并给出了集扫描与聚焦系统于一体的柱面扫描镜的扫描角计算公式,为扫描系统的设计提供了理论依据。研制出的热金属探测器的视场角可达2°×20°,仪器的发现概率大于0.95,虚报率小于10-6,抗干扰能力强,该仪器能够在恶劣的环境条件下正常工作。     

基于摆扫反射镜的大视场成像像移模型

为实现大视场技术指标,建立了一种基于摆镜转动的摆扫成像模型;通过对摆扫成像与推扫成像模式的比较,分析得出当横滚角等于摆镜转角的2倍时,摆扫成像能够实现与推扫成像小姿态时相同的视场;经过实验验证,在横滚角为2°、4°、6°、8°、10°时,文章的方法与推扫成像模型像移相对误差在1%以内,偏流角大小相对误差在0.001%以内,两种方法保持了较好的一致性,保证了模型的合理性与正确性;此外,该模型还可以通过实时地控制摆镜的转动来实现穿航方向上的对地的扫描成像,进而实现大视场、宽幅盖对地成像,减小回访周期,提高空间相机对地成像的工作效率。     

声表面波压力传感器

论述了声表面波压力传感器的工作原理及设计方法,报导了研究结果:传感器在0～100kPa范围内具有良好的线性;其中一阶压力灵敏度为0.55×10~(-9)/(Pa·cm~(-2))。     

微型压力传感器

<正> 美国ENDEVCO公司最近推出两种新式微型压力传感器,是专为航空和航天、汽车及工业上设计的。8510B/C-M5和8530B/C-M5型压力传感器具有耐用、体积小以及灵敏度高的特点,它有M5的公制螺纹,端面直径仅为3.8mm。8510B/C-M5型是压差传感器,使用范围为6.89×10~3Pa至1.38×10~7Pa。8530B/C-M5型是绝对压力传感器,其使用范     

一种用于智能机械手测距觉的PVDF 超声传感器

研制了一种高灵敏度、宽频带及广开角的智能机械手测距觉PVDF超声传感器.其通频带为10~52kH _2(—6dB),宽频带内接收电压灵敏度为69.7dB.指向性广开角为±30°.论述了其结构设计、宽带原理、基本性能及应用实例.研究结果可供设计智能机械手距离觉传感器时参考.     

Non-body-fitted Cartesian-mesh simulation of highly turbulent flows using multi-relaxation-time lattice Boltzmann method

This paper presents a lattice Boltzmann method (LBM) based study aimed at numerical simulation of highly turbulent and largely inclined flow around obstacles of curved geometry using non-body-fitted Cartesian meshes. The approach features (1) combining the interpolated bounce-back scheme with the LBM of multi-relaxation-time (MRT) type to enable the use of simple Cartesian mesh for the flow cases even with complex geometries; and (2) incorporating the Spalart–Allmaras (SA) turbulence model into LBM in order to represent the turbulent flow effect. The numerical experiments are performed corresponding to flows around an NACA0012 airfoil at Re=5×10⁵ and around a flat plate at Re=2×10⁴, respectively. The agreement between all simulation results obtained from this study and the data provided by other literature demonstrates the reliability of the enhanced LBM proposed in this paper for simulating, simply on Cartesian meshes, complex flows that may involve bodies of curved boundary, high Reynolds number, and large angle of attack.     

An implicit method for three dimensional viscous flow with application to cones at angle of attack

An iteration method for solving the implicit difference equations associated with three nonlinear parabolic differential equations is derived and analyzed. The method is applied to the high Reynolds number viscous flow around a cone at high angle of attack. The requirements which must be met to ensure convergence of the iterations are obtained. In addition, an analysis of the stability of the difference equations is presented and discussed. The numerical results are compared with experimental data for a 10° cone at 12° angle of attack, and a 5·6° cone at 8° angle of attack. The agreement is very good.     

Liquid flow through a diverging microchannel

In this work, experiments and three-dimensional numerical calculations of fluid flow through diverging microchannels were carried out with the aim of bringing out differences between flow in uniform and nonuniform passages. Deionized water was used as the working fluid in the experiments where the effects of mass flow rate (8.33 × 10^?6 to 8.33 × 10^?5 kg/s), microchannel hydraulic diameter (118–177 µm), length (10–30 mm) and divergence angle (4°–16°) on pressure drop were studied. The results are analyzed in detail with the help of numerical data. The pressure drop exhibits a linear dependence on the mass flow rate, whereas it is inversely proportional to the divergence angle and square of the hydraulic diameter. The pressure drop increases anomalously at 16°, suggesting that flow reversal occurs between 12° and 16°, which agrees with the corresponding value at the conventional scale. For the purpose of predicting pressure drop using straight microchannel theory, an equivalent hydraulic diameter was defined. It is observed that the equivalent hydraulic diameter, located at one-third of the diverging microchannel length from the inlet, becomes mostly independent of the mass flow rate, microchannel hydraulic diameter, length and divergence angle. The pressure drop for a diverging microchannel becomes equal to an equivalent hydraulic diameter uniform cross-section microchannel, suggesting that conventional correlations for straight microchannels can also be applied to diverging microchannels. The data presented in this work are of fundamental importance and can help in optimization of diffuser design used for example in valveless micropumps.     

嵌入式大气数据系统人工智能算法及故障诊断

嵌入式大气数据传感(FADS)系统由于其诸多优势成为现在战斗机设计中的关键技术之一。开发了基于BP(反向传播)人工神经网络的FADS算法和基于随机森林算法的故障识别与处理算法。该嵌入式大气数据系统算法以迎角和马赫数为分段依据,分别计算大气数据。故障识别则采用随机森林算法自动识别出故障测压点,在将故障测压点剔除后,采用不含故障点压强的组合预测各大气数据。采用飞行数据测试开发FADS系统算法,结果表明：该算法计算大气参数较为准确,迎角误差小于0.2°,侧滑角误差小于0.3°,马赫数误差小于0.0105,静压误差小于300 Pa。采用单个测压点故障的压强组合测试了故障识别与容错算法的性能,测试结果显示该算法能够准确识别出故障测压点压强,采用的飞行曲线测试中准确度达到100%,且各大气数据计算精度可达上述无故障压强时的精度,有效降低了故障压强对FADS系统算法计算精度的影响。     

初始条件对滑阀性能影响的数值研究

对流体通过滑阀的阶跃响应进行了数值解析计算.分别在静止流体和稳定流体的初始条件下,给出了压力差为阶跃变化时液流通过滑阀的流线图.讨论了初始条件和压力差对射流角、流量,流量系数和雷诺数等的影响,做出了不同初始条件下,射流角、流量,流量系数及雷诺数与压力差的关系图.数值计算的结果表明,当压力差大于临界值时,由于初始条件的不同,将导致两个迥然不同的射流流动.在初始条件为静止流体的情况下,其射流角、流量,流量系数和雷诺数比初始条件为稳定流体的情况下的对应值小.     

Design and simulation of passive micromixers based on capillary

Three-dimensional passive micromixers made by clamping capillaries in different directions and angles are presented in this paper. This type of mixers is easier to fabricate than the multi-layer passive mixers, and is the firstly proposed capillary-based micromixer. Simulations have been conducted for the flow and mass transport through the 3D-twisted compression–expansion microchannels. The simulations show that, compared to the T-mixer with the same cross-sectional perimeter, the 3D capillary mixers proposed in this paper can significantly enhance mixing. The 3D-twisted compression–expansion mixers with different clamping angles are analyzed. The results show that capillaries with clamping angle of 90°, 45–90° and 45° exhibit different mixing mechanism. The 45-mixer presents the best mixing enhancement by reducing 90.8?% of the mixing length with only 57?%extra pressure drop in transporting the liquids to those of the T-mixer when the clamping cross-section of 0.6?mm?×?0.2?mm, clamping interval of 1?mm, and the Peclet number of 3,000 are applied to all designed mixers.     

A numerical study of the unsteady leading edge separation bubble on an oscillating airfoil

A preliminary study of unsteady leading edge separation bubbles on a NACA 0012 airfoil is undertaken using a finite difference procedure. In this preliminary study the interaction between the viscous and inviscid flow field is neglected. Prior to applying the procedure to the study of the leading edge bubble several calculations are performed, to assess the accuracy of the numerical procedure. These test cases include stagnation point flow, flow about a circular cylinder, and flow over an oscillating flat plate. Calculations are then carried out for flow over the leading edge of a NACA 0012 airfoil oscillating in pitch between 9° and 21° incidence at chord Reynolds numbers of 1.0 × 10⁶ and 2.5 × 10⁶. The results show that for the flow conditions considered, a small leading edge separation bubble is present throughout the entire motion cycle. The bubbles are predicted to move forward and decrease in size as the incidence increases. The results also indicate that the viscous flow in the leading edge region is quasi-steady and that the bubble height is inversely proportional to the Reynolds number. Even with the neglect of interaction, the predicted leading edge bubble behavior is in qualitative agreement with experimental data, indicating that the approach taken should be a feasible method of studying leading edge bubble dynamics and dynamic stall provided that the procedure is extended to include interaction effects.     

二维水翼超空化状态下流体动力特性数值仿真

基于均匀多相流假设,建立了二维水翼自然超空化流动的多相流CFD模型。运用Navier—Stokes方程加k-ε两方程湍流模型对NACA0012水翼的超空化流动进行了数值仿真。分别研究了固定空化数和固定攻角时,超空化状态下水翼的流体动力参数的特性和空泡形态的变化。仿真结果表明：水翼表面流体动力系数随来流攻角和空化数的增大而增大,压力中心沿弦向和展向的位置随着攻角变化,空泡尺寸随空化数的增大而减小,整个流场的流动可分为两个区域,前部对应附着空泡区,后部对应汽液两相流动区,并改进了性能,对速度梯度有较大的改善。     

Incompressible flow calculations with a consistent physical interpolation finite volume approach

The computation of incompressible three-dimensional viscous flow is discussed. A new physically consistent method is presented for the reconstruction for velocity fluxes which arise from the mass and momentum balance discrete equations. This closure method for fluxes allows the use of a cell-centered grid in which velocity and pressure unknowns share the same location, while circumventing the occurrence of spurious pressure modes. The method is validated on several benchmark problems which include steady laminar flow predictions on a two-dimensional cartesian (lid driven 2D cavity) or curvilinear grid (circular cylinder problem at Re = 40), unsteady three-dimensional laminar flow predictions on a cartesian grid (parallelopipedic lid driven cavity) and unsteady two-dimensional turbulent flow predictions on a curvilinear grid (vortex shedding past a square cylinder at Re = 22,000).