CMM Probing Accessibility in a Single Slot

This study presents a novel mathematical method for resolving the accessibility of a through slot when using coordinate measuring machines. The proposed method considers the actual shape of a probe consisting of a motor column, a stylus, and a probe tip. Also derived herein is a mathematical method to derive the feasible probe orientation of the measurement point in the bottom of a slot using a geometrical relationship between the probe and the slot.     

An experimental setup for studying specular reflection of hard γ quanta

An experimental setup is described on which the fact of specular reflection of hard γ quanta (E _γ ≤ 5 MeV) from a smooth amorphous surface has been experimentally established. Specular reflection is observed at sliding incidence of γ quanta onto a reflecting surface at angles of a few thousandths of a degree. The setup is composed of a microtron, a system of electron transportation to a bremsstrahlung target, the bremsstrahlung target generating an intense directed flux of electron bremsstrahlung γ quanta), a guiding system forming a ribbon beam of γ radiation with a width of ～1 cm and a thickness of ≈20 μm, a reflector (a liquid mercury surface or a glass plate), and a detection system containing the counting and spectrometric detectors located at a distance of 120 m from the bremsstrahlung target. Some experimental results are presented.     

A CO2 tracer-gas method for local air leakage detection and characterization

A method for local measurement of air leakage rate is presented that can be used to accurately and quickly assess leakage rates across a surface, such as around a valve or hatch in a pressurized gas tank or a window in a building. The method uses a small local enclosure with constant volume placed about a region on the structure under investigation (e.g., a window), which is depressurized and injected with a small concentration of carbon dioxide as a tracer gas. The time variation of the pressure and carbon dioxide concentration inside the enclosure are monitored and used to quantify the leakage flow rate as a function of pressure difference. This method uses a small enclosure with internal mixing so that a quasi-steady-state condition is quickly achieved. Because of the small size of the enclosure, advanced data processing techniques are necessary to reduce uncertainty in determination of the rate of change of the carbon dioxide concentration that arises from sensor variability. Results of a laboratory demonstration of the proposed leakage detection and characterization device are reported for the problem of leakage through a circular hole in a plate with prescribed pressure differences. Experimental results from the laboratory tests are found to be in excellent agreement with results of a numerical simulation of leakage flow through a hole, as well as predictions from a number of empirical equations for this problem found in the literature.     

Calculation of the induction of a constant magnetic field created in a ferromagnet by an attachable electromagnet

On the grounds of the numerical calculation of the induction of a magnetic field excited in a ferromagnet by scanners in the form of Π-shaped and solenoidal electromagnets, it is established that the Π-shaped type provides a deeper penetration of a magnetic field into a ferromagnet and its better localization in a specified volume. The induction of a magnetic field appearing under the action of a Π-shaped scanner in a ferromagnet decreased with an increase in both the thicknesses of the ferromagnet and the gap between the magnetic conductor of a scanner and the surface of a material and also depended slightly on changes in its width; a maximal scanner winding current exists, above which the induction of a magnetic field in a material changes slightly.     

The interaction between two wearing surfaces I: Copper sliding on Cu-Be and Cu-Be sliding on Cu-Be

The work reported in this paper is an investigation of the interaction of the two components of a wear system with reference to the physical properties of both components. Copper sliding on Cu-Be and Cu-Be sliding on Cu-Be were studied using a ball-on-disc machine, Auger spectroscopy and microhardness measurements. The two systems are found to be qualitatively similar classic examples of severe wear. The wear of a Cu-Be disc sliding under a copper ball is, however, greater than the wear of a Cu-Be disc sliding under a Cu-Be ball. This is attributed to work hardening of the copper ball resulting from an interaction between the two wearing surfaces. Microhardness measurements show that the surface of a Cu-Be ball and a Cu-Be disc are not work hardened during a wear experiment. The surface of a copper ball is work hardened, however, and becomes significantly harder than the wear scar on a Cu-Be ball. As a result the Cu-Be disc wears at a faster rate when sliding under a copper ball than it does when sliding under a Cu-Be ball.     

Theoretical foundations of ultrasonic nondestructive testing of multilayer articles manufactured from composites with rubbery coatings: II. Scattering of elastic waves at flaws involving poorly glued joints between plastic layers and between a plastic layer and a rubbery coating

The second part of this study is devoted to the solution of the following problems: (i) excitation of plate modes with a lumped force applied to the plate’s surface, (ii) scattering of a bending wave at a small crack parallel to the plate’s surface, and (iii) scattering at a flaw involving a poorly glued joint between a rubbery coating and a plastic layer. The final formulas and numerical dependences for calculating the parameters of a crack or a cleavage are presented. A mathematical model that describes the scattering of waves by flaws in a multilayer article made from a plastic composite material has been developed.     

Decrease in the operating gas pressure in an ion source

The results of use of a cold hollow cathode with a multipole magnetic field in a duoplasmatron-type ion source are described. The operating parameters of a duoplasmatron with the developed cathode and a duoplasmatron with a cold hollow two-cylinder cathode are compared. It is shown that the use of a cathode with a multipole magnetic field offers additional possibilities of reducing the operating gas pressure in an ion source and contributes to an increase in both the current and the phase density of the ion-beam current at the output of a charged-particle source and to a decrease in the phase volume of this beam.     

A broadband Fourier transform microwave spectrometer based on chirped pulse excitation

Designs for a broadband chirped pulse Fourier transform microwave (CP-FTMW) spectrometer are presented. The spectrometer is capable of measuring the 7-18 GHz region of a rotational spectrum in a single data acquisition. One design uses a 4.2 Gsampless arbitrary waveform generator (AWG) to produce a 1 mus duration chirped pulse with a linear frequency sweep of 1.375 GHz. This pulse is sent through a microwave circuit to multiply the bandwidth of the pulse by a factor of 8 and upconvert it to the 7.5-18.5 GHz range. The chirped pulse is amplified by a traveling wave tube amplifier and broadcast inside the spectrometer by using a double ridge standard gain horn antenna. The broadband molecular free induction decay (FID) is received by a second horn antenna, downconverted, and digitized by a 40 Gsampless (12 GHz hardware bandwidth) digital oscilloscope. The second design uses a simplified pulse generation and FID detection scheme, employing current state-of-the-art high-speed digital electronics. In this spectrometer, a chirped pulse with 12 GHz of bandwidth is directly generated by using a 20 Gsampless AWG and upconverted in a single step with an ultrabroadband mixer. The amplified molecular emission is directly detected by using a 50 Gsampless digital oscilloscope with 18 GHz bandwidth. In both designs, fast Fourier transform of the FID produces the frequency domain rotational spectrum in the 7-18 GHz range. The performance of the CP-FTMW spectrometer is compared to a Balle-Flygare-type cavity-FTMW spectrometer. The CP-FTMW spectrometer produces an equal sensitivity spectrum with a factor of 40 reduction in measurement time and a reduction in sample consumption by a factor of 20. The CP-FTMW spectrometer also displays good intensity accuracy for both sample number density and rotational transition moment. Strategies to reduce the CP-FTMW measurement time by another factor of 90 while simultaneously reducing the sample consumption by a factor of 30 are demonstrated.     

A method for measuring and calibrating resistive microtorque of a mechanical microcounter

This paper reports a technique for measuring the calibrating resistive input torque of a micro counter and gearbox assembly. The technique presented uses a hairspring (with a quantifiable output torque) to drive the input shaft to a mechanical counter and gearbox assembly in order to determine its resistive torque. The angular displacement of this spring, a parameter needed to compute the torque, is measured using a combination of a laser diode and a monolithic one-dimensional position sensitive device (PSD). This study includes the steps undertaken to develop it from a concept to functional prototype and interpretation of the results it yields. Tests show that in principle the use of a hairspring and PSD is a viable method of measuring micro-torque.     

The influence of preamplifiers on the piezoelectric sensor's dynamic property

A charge amplifier or a voltage amplifier can be used as a signal conditioning circuit between a piezoelectric element and a meter or a data acquisition board. The outputs of the piezoelectric sensor are in an open-circuit state and a short-circuit state if a voltage amplifier and a charge amplifier are used, respectively. When the electrodes are in different states, the piezoelectric element has rather different stiffness and thus different sensor resonant frequency. This phenomenon is theoretically analyzed in detail and validated by a carefully designed experiment. The results indicate that a much wider range of working frequency is achieved when a voltage amplifier is used.     

Determination of the velocity and size of bubbles in two-phase flows by using a laser doppler anemometer

Natural oscillations of a spherical interface between a gas and a liquid in a bubble are registered. A possibility of measuring the geometric parameters of stationary and moving particles of the disperse phase by a laser Doppler anemometer is demonstrated. A method for simultaneous determination of the size and velocity of a bubble or a droplet in a two-phase flow is developed. The mean sizes of a group of bubbles settled on a ruler are compared: the results are obtained by two independent methods, i.e., by analyzing the image and by processing the Doppler signal containing information about the natural oscillations of the spherical interface between the media. A possibility of using a laser Doppler anemometer for simultaneous measurements of the velocity and size of bubbles or droplets in a two-phase flow is confirmed.     

基于XeF(C-A)放大器的混合(固态/气态)超高功率飞秒激光系统

提出了基于前端发生器和终端放大器,使用光泵浦XeF(C-A)激活介质的太瓦级混合激光器(THIA00)系统.前端发生器由长532 nm的连续激光泵浦的钛宝石飞秒脉冲振荡器,脉冲展宽机构,532 nm的脉冲激光泵浦的再生多通道放大器,衍射光栅压缩器和二次谐波发生器(KDP)组成.其光束输出参数为:脉冲持续时间50 fs,...     

Automated fixture configuration using projective geometry approach

The geometric and topological specification of a workpiece boundary is usually represented in a specific data format in a CAD database. To retrieve a set of workpiece data, to analyse its shape in addition to the machining requirements, and to determine the proper fixture configuration accordingly, are not trivial tasks when a part has a complicated shape. The real challenge is to recognise and synthesise the shape of a workpiece from its data representation. Consequently, the decision for fixturing can be made when the shape of a workpiece and the relationship of the shape and the fixturing configuration can be derived by a systematic methodology. In this paper, a projective spatial occupancy enumeration (PSOE) approach is applied as a representational and manipulating scheme for developing algorithms in automatic fixture configuration. The workpiece is projected onto the working plane of the fixture baseplate. A 2D projection is defined as a matrix of cells which can represent a workpiece with an arbitrary shape. Using a discrete search based upon the matrix of cells, the fixture types and their locations are generated according to a set of heuristic algorithms. This work is a generalisation and extension of previous works for prismatic parts. The same methodology is equally applicable in general robot grasping.     

套式钻模的应用研究

在各种长度和直径的圆柱体或空心圆柱体的外圆柱面上沿横截面圆周方向钻削,有较高的位置精度要求且呈多层均匀分布或多层非均匀分布或螺旋均匀分布或螺旋非均匀分布的孔和螺纹孔的方法进行了研究,重点介绍了长度与外径比＆gt;5的圆柱体或空心圆柱体。研究发现,目前常见的固定式钻模、回转分度式钻模、移动式钻模、翻转式钻模和盖板式钻模都不是最佳选择,因为它们的钻模板均为长方体,与圆柱面不能完全配合,导致夹紧元件和定位元件的结构复杂,形式单一且制造周期长,成本高,夹紧钻模的方式单一。套式钻模的钻模板为空心圆柱体,空心圆柱体的独特之处是使套式钻模可与圆柱面完美配合,夹紧元件和定位元件的结构简单,形式灵活且制造周期短,成本低,夹紧钻模的方式灵活,从而使其成为在各种长度和直径的圆柱体或空心圆柱体的外圆柱面上钻削各种排列组合方式的孔和螺纹孔的最佳选择。     

智能气体识别仪的研究

智能气体识别仪用以识别气体种类,它具有学习识别多种气体的功能。本文介绍了仪器的工作原理、特点及仪器的硬件和软件构成。     

液力变矩器-机械无级变速器自动变速汽车综合控制策略研究

针对采用液力变矩器作为汽车起步和低速行驶时的调速装置,金属带无级变速传动为高速行驶时调速装置的双状态无级自动变速汽车,在液力变矩器台架试验的基础上,建立了双状态无级自动变速汽车的动力学仿真模型和金属带无级变速传动系统的综合控制策略,分析了分段加速行驶过程中,汽车液力变矩器和金属带无级变速器速比的变化规律,为开发设计双状态无级自动变速汽车提供理论依据。     

Microwave atomic force microscopy imaging for nanometer-scale electrical property characterization

We introduce a new type of microscopy which is capable of investigating surface topography and electrical property of conductive and dielectric materials simultaneously on a nanometer scale. The microwave atomic force microscopy is a combination of the principles of the scanning probe microscope and the microwave-measurement technique. As a result, under the noncontact AFM working conditions, we successfully generated a microwave image of a 200-nm Au film coating on a glass wafer substrate with a spatial resolution of 120 nm and a measured voltage difference of 19.2 mV between the two materials.     

脉冲激光测距中高精度时间间隔测量方法的研究

高精度时间间隔测量对脉冲激光测距系统具有重要意义,为此提出了一种新的高精度时间间隔测量方法。该方法在FPGA中实现了脉冲计数法、多相采样法和延迟链法的结合。采用脉冲计数法对被测时间间隔进行“粗值”测量,保证大的动态测量范围。利用FPGA内部锁相环产生N路同频率,相位均匀分布的时钟信号作为计数时钟,基于等精度测频原理,将被测时间间隔的测时分辨率提高到Tclk/N。利用FlipFlop锁存器形成延时链,对被测信号与相邻计数时钟的时间间隔进一步量化。该方法解决了传统多相采样技术中倍频次数高则相移分辨率降低的问题,在不增加计数时钟和有限延迟链数量的前提下,得到较高测时分辨率。测试结果表明,该时间间隔测量模块不但可以实现大的动态测量范围,而且测时过程相对较短,具有较高测时精度。     

Actuation of a robotic fish caudal fin for low reaction torque

In this paper, a novel caudal fin for actuating a robotic fish is presented. The proposed caudal fin waves in a vertical direction with a specific spatial shape, which is determined by a so-called shape factor. For a specific shape factor, a traveling wave with a vertical phase difference is formed on a caudal fin during fin motion. It will be shown by the analysis that the maximum reaction torque at the joint of a caudal fin varies depending on the shape factors. Compared with a conventional plate type caudal fin, the proposed fin with a shape factor of 2π can eliminate the reaction torque perfectly, while keeping the propulsion force unchanged. The benefits of the proposed fin will be demonstrated by experiments.     

A method for detecting tool wear on a CNC lathe using a doppler radar detector

Installing a non-contact in-process tool wear detection system on a computer numerical control lathe can help prevent product defects and improve product quality without impacting product cycle time. Many methods have been proposed for non-contact in-process tool wear detection. In particular, a recent international patent application describes a method for measuring the torque in a rotating axle using a high-frequency wireless transmitter/receiver and a vibrating string. The method has reportedly been used to detect cutting on a manual lathe. The authors present a new method for measuring tool wear using a high-frequency wireless transmitter/receiver alone, without a vibrating string. The high-frequency transmitter/receiver apparently responds to metal-metal contact noise rather than, or more strongly than, to signals generated by a vibrating string. The findings could help bring automated tool wear monitoring systems closer to the level of performance needed for practical use in industry.