三维远场涡流探头的设计与应用研究

设计了一种新型三维远场涡流探头，通过其远场耦合特性确定了合适的屏蔽结构。以油田采油钢管为检测对象，对管壁的对称缺损和不对称缺损进行了对比检测实验，结果表明：新型探头可确定缺损的三维位置，既适用于大管径管道测量，又适用于小管径管道测量，适用性较高。     

Development of an air velocity and flow measurement system by using a novel circular disc

In this paper, development of a sensor using a circular disc for air velocity measurement based on the drag force equation is proposed. The air velocity measurement sensor is basically designed with a load cell in order to determine the drag force. The circular disc is used for creating a drag force, and by using load cell, the drag force that acts on the circular disc is measured. As the circular disc's drag coefficient can be considered constant at Reynolds numbers between 10³ and 10⁶, it can be possible to obtain the explicit equation of drag force. The remaining components of drag force equation are obtained by measurement. The proposed air velocity measurement sensor is characterized by wind tunnel measurements. All measurements were performed in an ISO/IEC 17025 accredited calibration laboratory – the Wind Tunnel of Turkish State Meteorological Service. The characterization measurements were performed at air velocities between 1 m/s and 20 m/s. The correction factors were calculated and a calibration curve for the proposed air velocity measurement sensor was obtained. The calibration curve's linearity was higher than 0.99 and a comparison the results from a Micromanometer with Pitot-Tube shows that for the designed working range, the sensor has an acceptable performance for time-averaged air velocity measurements according to the requirements of the World Meteorological Organization.     

Miniature conductivity wire-mesh sensor for gas-liquid two-phase flow measurement

A miniature conductivity wire-mesh sensor for gas-liquid two-phase flow measurement in small channels is presented. The sensor design is similar to the conventional wire-mesh sensor for larger flow cross sections with wire electrodes stretched across the flow channel in two adjacent planes and with perpendicular wire orientation between planes. Conductivity measurement is performed by special electronics which consecutively applies bipolar voltage pulse excitation to the sender wires and measures electrical current flow in the wire crossings at the receiver wires. The new design is based on printed circuit board technology. A prototypical sensor made of 2×16 stainless steel wires each of 50 μm diameter was manufactured and applied to two-phase flow measurement inside the mixing chamber of an effervescent atomizer. Accuracy of the sensor was studied for static liquid distributions using microphotography and for dynamic two-phase flow by comparison of wire-mesh sensor data with radial gas fraction profiles obtained from X-ray microtomography measurements.     

Triaxial joint moment estimation using a wearable three-dimensional gait analysis system

We developed a wireless sensor system composed of a mobile force plate system, three-dimensional (3D) motion sensor units and a wireless data logger. Triaxial joint moments of the ankle, knee and hip joints were calculated using measurements of the sensor system. The accuracy of the joint moment estimation is validated against results obtained from the reference measurement system composed of a camera based motion analysis system and force plates. Triaxial joint moments measured by the sensor system showed normalized root mean square error (NRMSE) and correlation coefficient (R) of less than 22% and more than 0.80 in comparison with the stationary system.     

Operative Calibration Methodology of a TDR Sensor for Soil Moisture Monitoring under Irrigated Crops

Time domain reflectometry (TDR) is more and more frequently used for soil water content measurements in replacement of other techniques as neutron probe. Such observations that can be continuously collected on dataloggers are convenient for monitoring water fluxes under irrigated crops. Though relationships to calculate volumetric water content from analysis of TDR signal and collected data are published in literature or given by manufacturers for different commercialized devices, the results are not satisfactory for many soils and specific calibrations are required. In replacement of the traditional calibration method, two rapid operative computer assisted methods are proposed. The first one is based on drip moistening of a cylindrical sample of disturbed dry soil in which a TDR sensor is vertically embedded. The second one uses the same cylindrical sample wetted close to saturation in which a TDR sensor is inserted step by step during measurements. The data from the two methods were fitted using second degree models. These results are in good agreement with conventional calibration method or gravimetric field measurements of soil water content. Utilization of short time step TDR measurements for monitoring soil water storage under a furrow irrigated corn shows consistent observations with water applications or uptakes by crop. Field comparison with neutron probe and gravimetric measurements corroborate the need of a specific calibration for the soil studied in this paper though its clay content is about 20%.     

Performance tests of a new non-invasive sensor unit and ultrasound electronics

Industrial applications involving pulsed ultrasound instrumentation require complete non-invasive setups due to high temperatures, pressures and possible abrasive fluids. Recently, new pulser-receiver electronics and a new sensor unit were developed by Flow-Viz. The complete sensor unit setup enables non-invasive Doppler measurements through high grade stainless steel. In this work a non-invasive sensor unit developed for one inch pipes (22.5 mm ID) and two inch pipes (48.4 mm ID) were evaluated. Performance tests were conducted using a Doppler string phantom setup and the Doppler velocity results were compared to the moving string target velocities. Eight different positions along the pipe internal diameter (22.5 mm) were investigated and at each position six speeds (0.1–0.6 m/s) were tested. Error differences ranged from 0.18 to 7.8% for the tested velocity range. The average accuracy of Doppler measurements for the 22.5 mm sensor unit decreased slightly from 1.3 to 2.3% across the ultrasound beam axis. Eleven positions were tested along the diameter of the 48.4 mm pipe (eight positions covered the pipe radius) and five speeds were tested (0.2–0.6 m/s). The average accuracy of Doppler measurements for the 48.4 mm sensor unit was between 2.4 and 5.9%, with the lowest accuracy at the point furthest away from the sensor unit. Error differences varied between 0.07 and 11.85% for the tested velocity range, where mostly overestimated velocities were recorded. This systematic error explains the higher average error difference percentage when comparing the 48.4 mm (2.4–5.9%) and 22.5 mm (1.3–2.3%) sensor unit performance. The overall performance of the combined Flow-Viz system (electronics, software, sensor) was excellent as similar or higher errors were typically reported in the medical field. This study has for the first time validated non-invasive Doppler measurements through high grade stainless steel pipes by using an advanced string phantom setup.     

真空微电子传感器研究及进展

介绍真空微电子传感器的研究和发展概况,着重叙述了真空微电子压力传感器和真空微电子磁传感器的发展,并就其研究、发展和应用前景阐述了个人的观点。     

Comparison of water measurement results in polyol ester‐based lubricating fluids determined by the coulometric karl fischer method and a thin‐film polymer capacitive water sensor

Field samples of MIL‐PRF‐23699 and DOD‐L‐85734, both polyol ester‐based fluids, were evaluated for water concentration by the coulometric Karl Fischer (KF) method according to ASTM D 6304 and with a prototype thin‐film polymer capacitance‐based sensor at Naval Air Systems Command (NAVAIR). The NAVAIR KF results showed a consistent negative bias, 190 ppm on average, compared to the results obtained with the water sensor. Since the calibration of the water sensor was performed by the sensor manufacturer using a different KF instrument and reagent/co‐solvent system, the ∼190 ppm negative bias probably reflects the difference in KF results between sensor manufacturer and NAVAIR. A limited round robin test, involving several laboratories using different instruments, reagents, solvents, and techniques, showed that water concentrations determined by the KF method can vary significantly from laboratory to laboratory. A larger round robin test was conducted to assess more accurately the variability in water measurement results. The results of the two round robin tests show that the particular KF instrument, reagents/solvents, and procedures being utilised by the various participating laboratories lead to a KF measurement variability of 20–30% for polyol ester‐based lubricating fluids. The results show that it is possible to obtain ∼190 ppm difference, observed between the water sensor and KF measurements at NAVAIR, between two laboratories. The results of the round robin tests showed a maximum repeatability of 9%. The significant difference between the repeatability and reproducibility indicates that there is potential for improved reproducibility of KF measurements through standardisation of, for example, instrument type, reagent/solvent system, test method, and laboratory procedure. Further work is required to determine the optimum KF test parameters for polyol.     

Effectiveness of rotatable sensor to improve image accuracy of ECT system

This paper presents a new design of rotatable sensor for ECT systems that can be mounted on a multi-phase flow installation. In order to attest how the performance of the sensor is affected by the rotatable frame, the effectiveness of the rotatable sensor is analyzed in terms of SNR (Signal-to-Noise Ratio) and image accuracy, which is dependent on the number of independent measurements, the image reconstruction strategy and the size of the mesh. The results confirm that with a sensor equipped with 16 electrodes, the optimum number of rotation steps is 3 in order to get the best compromise in terms of image accuracy and image reconstruction time. Results also show that this configuration achieves results similar to a classical sensor equipped with 32 electrodes.     

Two degree of freedom PID based inferential control of continuous bioreactor for ethanol production

This article presents the development of inferential control scheme based on Adaptive linear neural network (ADALINE) soft sensor for the control of fermentation process. The ethanol concentration of bioreactor is estimated from temperature profile of the process using soft sensor. The prediction accuracy of ADALINE is enhanced by retraining it with immediate past measurements. The ADALINE and retrained ADALINE are used along with PID and 2-DOF-PID leading to APID, A2PID, RAPID and RA2PID inferential controllers. Further the parameters of 2-DOF-PID are optimized using Non-dominated sorted genetic algorithm-II and used with retrained ADALINE soft sensor which leads to RAN2PID inferential controller. Simulation results demonstrate that performance of proposed RAN2PID controller is better in comparison to other designed controllers in terms of qualitative and quantitative performance indices.     

Computer support in tribology - experiments and database

As in all other areas of research today, so in tribology, computers play an important role. The exact analysis of tribological systems needs finite element methods (FEM) for calculation. Analysis of worn surfaces by SEM, AUGER, ESCA, XRS and the interpretation and documentation of measurements is performed with computers. The new approach to the basis of tribology by the use of scanning tunnelling microscopy (STM) and lateral force microscopy (LFM) would not be possible without computers. This paper points out the opportune tasks for computers in tribological simulation tests, such as complex test cycles, long time runs, automatic sensor calibration, measurements of fast varying signals, control and correction of mutual influences, and mentions the databases TRIBO (Tribology Index) for literature and Tribocollect for tribological data.     

Influence of part material and sensor adjustment on the quality of digitised point-clouds using conoscopic holography

Conoscopic holography is an interferometric measurement technique commonly used for non-contact surfaces digitising in quality assessment, in-process inspection and reverse engineering. Among other factors, accuracy of measurements provided by this technology is influenced by the surface optical properties. Parameters such as laser power (P) or frequency of acquisition (F) are commonly used to adjust the sensor until a quality indicator of the signal acquired (Signal-to-Noise-Ratio) is maximised. Nevertheless, measurements taken under this adjusting criterion does not necessarily ensure the most accurate results from a metrological point of view. Taking this into account, the present work proposes two additional indicators to analyse the influence of sensor setting parameters on the quality of digitised point-clouds for different metals and polymers. Digitising tests have been performed on flat specimens of each material by means of a conoscopic holography sensor integrated on a Coordinate Measuring Machine. In order to meet an optimal scanning of each material, the study provides a series of recommendations about adjustment of the sensor as well as the most suitable indicator to be used in each case.     

Vehicle classification with single multi-functional magnetic sensor and optimal MNS-based CART

To take advantages of magnetic sensor technology in terms of cost, size, weight, power consumption and wireless communication, a wireless multi-functional magnetic sensor was designed and developed. Then, a novel method with single multi-functional magnetic sensor and optimal Minimum Number of Split-sample (MNS)-based Classification and Regression Tree (CART) algorithm was proposed in this paper to classify on-road vehicles. The sensor was deployed on the road to acquire real-time vehicle waveform data. The decision tree model based on CART algorithm was used to execute on-line vehicle classification in the sensor node. Eight speed-independent time-domain waveform features were extracted as the model inputs. This paper trained the decision tree model by using vehicle samples derived from the multi-functional magnetic sensor and pruned the optimal decision tree with a Minimum Error Pruning (MEP) rule to obtain an optimal pruning tree which is more robust to new samples. Some experiments were implemented by different sample sets and classification methods. The results showed that the proposed method achieved on-line vehicle classification in the sensor node. For the field sample sets with two vehicle classes, the average accuracy rates of test samples were 88.9% and 94.4% in the original samples and swapping samples respectively. Besides higher accuracy, the method also has a better sample robustness, which is easy to classify new samples. The comparison results of current methods also showed that the proposed method has some advantages in aspects of accuracy rate, sample robustness and execution time.     

The application of convergent beam electron diffraction (CBED) analysis on transformation‐induced plasticity (TRIP) steels

Convergent beam electron diffraction (CBED) in transmission electron microscopy (TEM) was applied to determine local carbon concentrations in low‐carbon transformation‐induced plasticity (TRIP) steels. High‐order Laue‐zone (HOLZ) lines were experimentally obtained for comparison with simulation results. A new procedure for calculating carbon content is thus proposed. Retained austenite (RA) is classified into three types by morphology; the relationship between the carbon content and the corresponding RA morphology is discussed based on CBED results. Furthermore, results of X‐Ray diffractometry measurements are also used for comparison.     

Evaluation of system models for an endoscopic fringe projection system

To be able to perform inline inspection of complex geometries, which exhibit for example undercuts or internal structures, a new endoscopic micro fringe projection system has been developed. It is designed to perform areal measurements for tool inspection inside the limited space of metal forming presses by employing flexible image fibers to couple the measurement system’s camera and projector to a compact sensor head. The projector features a laser light source and a digital micro-mirror device to generate high-contrast fringe patterns. To increase the depth of field of the sensor heads, custom gradient-index lenses have been designed as an approximation to the Scheimpflug principle. Challenges arise for both calibration and phase measuring algorithms from the optics, as well as from the reduction in resolution introduced by the fiber bundles. This paper presents an evaluation of two different system models for the endoscopic fringe projection system, which are based on the pinhole camera model and a black box model. An automated calibration process, which gathers the calibration data for two calibration algorithms that are robust to artifacts introduced by the optical path, is demonstrated. Based on a comparison of measurements, differences between the two modeling approaches are discussed. Finally, results of measurements of a demonstrational metal forming tool are shown as an application example.     

基于TDLAS和ICL的紧凑中红外痕量气体探测系统

为了实现基于可调谐激光吸收光谱技术的高检测灵敏度、低功耗、小型中红外痕量气体传感器设计,结合锑化镓(GaSb)ICL和紧凑型多反射气体吸收气室(MPC)研制了基于不同结构传感光学核的两个小型TDLAS传感系统。两个传感光学核的总功率消耗为3.7 W,并通过探测甲烷(CH4)和甲醛(CH2O)分别验证了双层结构和单层结构系统的性能。实验结果表明:CH4和CH2O系统的检测灵敏度分别为5.0nL/L和3.0nL/L,测量精度分别为1.4nL/L和1.0nL/L。此外,相同配置情况下将两种结构系统应用于甲、乙烷(C2H6)同步检测,通过对校园环境中甲、乙烷进行连续66h的监测试验,验证了设计的紧凑型中红外痕量气体检测系统能够稳定有效地工作,基本满足目前民用气体测量的稳定可靠、精度高、抗干扰能力强等要求。     

A high-temperature drop calorimeter for studying substances and materials in the solid and liquid states

The design of an automated isothermal drop calorimeter, which is intended for specific-heat and enthalpy measurements and studying phase transformations in solid and liquid materials in a wide temperature range from room temperature to 2300 K, is described. The distinctive features of the unit consists in the location of the temperature sensor directly in a sample, the use of a mechanical lock for the dropping and lower opening screens of the ampoule, as well as a special gateway. The above factors provide the possibility to carry out measurements at an arbitrary initial temperature of the calorimeter unit and considerably increase the efficiency of the calorimeter. To determine its efficiency, measurements of sapphire enthalpy were performed at temperatures of 575–1275 K. The measurement results differ from the reference data of the National Institute of Standards and Technologies (United States) by 0.05%.     

Comparison between wire-mesh sensor and ultra-fast X-ray tomograph for an air–water flow in a vertical pipe

A comparison between ultra-fast X-ray CT and a wire-mesh sensor is presented. The measurements were carried out in a vertical pipe of 42 mm inner diameter, which was supplied with an air–water mixture. Both gas and liquid superficial velocities were varied. The X-ray CT delivered 263 frames per second, while the wire-mesh sensor was operated at a frequency four times higher. Two different gas injectors were used: four orifices of 5 mm diameter for creating large bubbles and gas plugs and a sintered plate with a pore size of 100 μm for generating a bubbly flow. It was found that the wire-mesh sensor has a significantly higher resolution than the X-ray CT. Small bubbles, which are clearly shown by the wire-mesh sensor, cannot be found in the CT images, because they cross the measuring plane before a complete scan can be performed. This causes artifacts in the reconstructed images, instead. Furthermore, there are large deviations between the quantitative information contained in the reconstructed tomographic 2D distributions and the gas fractions measured by the sensor, while the agreement is very good when the gas fraction is obtained by a direct evaluation of the X-ray attenuation along the available through-transmission chords of the tomography set-up. This shows that there is still potential for an improvement of the image reconstruction method. Concerning the wire-mesh sensor it was found that the gas fraction inside large bubbles is slightly underestimated. Furthermore, a significant distortion of large Taylor bubbles by the sensor was found for small liquid velocities up to 0.24 m/s. This effect vanished with growing superficial water velocity.     

Wavelet excited measurement of system transfer function

This article introduces a new method, which is referred to as the wavelet excitation method (WEM), for the measurement of the system transfer function. Instead of commonly used impulse or sine wave excitations, the method uses a sequential excitation by biorthogonal symmetric wavelets. The system transfer function is reconstructed from the output measurements. In the WEM the signals can be designed so that if N different excitation sequences are used and the excitation rate is f, the sampling rate of the analog-to-digital converter can be reduced to f/N. The WEM is especially advantageous in testing systems, where high quality impulse excitation cannot be applied. The WEM gave consistent results in transfer function measurements of various multistage amplifiers with the linear circuit analysis (SPICE) and the sine wave excitation methods. The WEM makes available new high speed sensor applications, where the sampling rate of the sensor may be considerably lower compared with the system bandwidth.     

Calculation of concentration depth profiles in electron probe microanalysis

Based on a multiple reflection model, the concentration depth profiles of gold diffused into a silver substrate are determined. To conclude the structure of the sample from the measured intensity of radiation, an accurate correction procedure is necessary. A new model was developed for this purpose. Since the new electron probe microanalysis (EPMA) correction procedure is also valid for tilted samples, measurements with different geometries could be performed. The different angles of incidence and take-off angles allow for a better comparison of theory with experiment. One advantage of the applied multiple reflection model is that it can be extended comparatively easily with the analysis of layered specimens. Measurements of some specimens with one layer on a substrate are reported. The mean deviation of calculated thicknesses is about 10%. To calculate depth profiles, gold was evaporated with physical vapor deposition on silver foils. The thicknesses of evaporated gold films were 50 and 100 nm. Then the specimens were annealed at a temperature of approximately 400°C. Finally, the concentration depth profiles were quantified with EPMA. The shape of the profiles was derived from a simple diffusion model valid for the samples under consideration. To check the shape of the functions obtained, a comparison with measurements by secondary ion mass spectrometry was performed.