High-speed non-intrusive measurements of fuel velocity fields at high-pressure injectors

Using a single high-speed camera and a frequency modulated laser, a novel approach is presented for fast velocity field measurements in unsteady spray flows. The velocity range is from zero up to several 100 m/s, which requires a high measurement rate and a large dynamic. Typically, flow measurements require to seed tracer particles to the fluid. A paradigm shift to seeding-free measurements is presented. The light scattered at the phase boundaries of the fluid droplets is evaluated. In order to validate the high-speed measurement system, a detailed uncertainty analysis is performed by means of measurements as well as simulations. Thereby, variations of the scattered light intensity, which are based on the high temporal velocity gradients, are found to be the main contribution to the uncertainty. The eventually measurement results, obtained at a measurement rate of 500 kHz, exhibit spray velocities ranging from 0 m/s up to 400 m/s in less than 1 ms, and the detection of unsteady and irregular flow phenomena with a characteristic time of several μs is achieved. This demonstrates the high measurement rate, the high temporal resolution and the large measurement range of the proposed high-speed measurement system.     

A new subdivision method for grating-based displacement sensor using imaging array

A new subdivision method for grating-based displacement sensor was proposed in the present study, which takes advantages of imaging array's high resolution and pixels’ good uniformity in the space. In this method, the magnified grating image is received by imaging array and grating pitch is directly subdivided by pixels, which is quite different from that moiré fringe is subdivided by complex subsequent circuits in moiré-type displacement sensor. The displacement is statistically calculated by using the whole grating image, which greatly eliminates the errors arising from illumination, electrical signals’ fluctuation, grating defect, and so on. Therefore, the subdivision method is easy to obtain signal with high signal-to-noise ratio, insensitive to some external factors, and able to attain high measurement precision with low cost. In this paper, the principle of subdivision method was illuminated, the systemic resolution was theoretically discussed, the measurement precision was experimentally checked, and the uncertainty of measurement was analyzed. The subdivision system consisted of the grating with 20-μm pitch and the CMOS image sensor with the pixels of 1280×1024 had the resolution of 0.04 μm, and the maximum displacement error was less than 0.4 μm, which has been tested in the Abbe comparator platform.     

A mid-infrared carbon monoxide sensor system using wideband absorption spectroscopy and a single-reflection spherical optical chamber

A mid-infrared carbon monoxide (CO) sensor system based on a dual-channel differential detection method was developed using a broadband light source in the 4.60 µm wavelength region and a single-reflection spherical optical chamber with ∼0.373 m absorption path length. CO detection was realized by targeting the wideband strong absorption lines within 4.55–4.65 µm. A dual-channel pyroelectric detector as well as a self-developed digital signal processor (DSP) based orthogonal lock-in amplifier was employed to process CO sensing signal. A minimum detection limit of ∼0.5 ppm in volume (ppmv) was achieved with a measurement time of 6 s, based on an Allan deviation analysis of the sensor system. The response time (1000 → 0 ppmv) was determined to be ∼7 s for the CO sensor operation. Due to the characteristics of low detection limit, fast response time and high cost performance, the proposed sensor has relatively good prospect in coal-mining operation.     

Geometric and magnetic properties of Co/Pd system

We measured geometric and magnetic properties of Co films on the Pd(1 1 1) surface by X-ray photoelectron diffraction (XPD), X-ray magnetic circular dichroism (MCD) at the Co L_2,3 edge, and the surface magneto-optical Kerr effect (SMOKE) measurements. Co thin films are found to grow incoherently with fcc island structure on the smooth Pd(1 1 1) substrate. Comparison of MCD and SMOKE measurements of Co thin films grown on rough and smooth Pd(1 1 1) surfaces suggests that perpendicular remnant magnetization and Co orbital moment are enhanced by the rough interface. Pd capping layer also induces perpendicular orbital moment enhancement. These observations indicate the influence of hybridization between Co 3d and Pd 4d at the interface on the magnetic anisotropy.     

Atomic surface diffusion on Pt nanoparticles quantified by high-resolution transmission electron microscopy

Aberration-corrected high-resolution transmission electron microscopy allows for the delocalization-free observation of atomic motions on metallic surfaces and thus enables measurements of the diffusion of single atoms on the surfaces of nanoscopic objects such as nanoparticles. Using this recently introduced method, the diffusion coefficient for surface self-diffusion of Pt nanoparticles is determined through the fluctuating occupation of the particle's atomic columns. This diffusion coefficient is determined to lie in the range D ∼ (10⁻¹⁷ … 10⁻¹⁶) cm²/s.     

Single image rectification of thermal images for geometric studies in façade inspections

This work presents a photogrammetric technique that provides geometric and thermal information about building façades. It uses low cost and portable scale bars, specially designed for thermal imaging, and processing software based on single image rectification. Image rectification corrects the original photo displacement due to the projection and perspective, and radial distortions introduced by the lens of the camera.The technique is tested by comparing laser scanning and thermal data. Seven segments of different orientation and length are selected for the measurement. Accuracy tests show errors between 44 mm and 151 mm. Precision values range between 22 mm and 61 mm for a maximum length of 7259 mm. The accuracy and precision results obtained for the technique open the possibility of extending its use to building inspection tasks.     

Passive IR field gradient detection of thermal objects in active Fresnel zones

A dual element Passive-Infrared (PIR) sensor is used with a rotating slit aperture to map a narrow scanning beam on the sensing elements through each lens of a Fresnel lens array. The stimuli generated due to each thermal object fall in the active Fresnel zones in a certain direction based on their locations and temperature variations on the surfaces of the sources. These signals are used to analyze the signatures of stationary thermal objects, their slight movements and thermal field gradient changes of the source surfaces provided the object projected area is less than the area of the active zone. Pattern matching is performed using Dynamic-Time-Warping (DTW) algorithm on STFT reduced length time vectors. The object space is divided into m-active zones that correspond to the Fresnel zones in a Fresnel lens array. Within passive IR region from each of the active zones, the system identifies not only the heat intensity changes but also detects the slight movement of the thermal source. The efficiency of the system is dependent on the number of active Fresnel zones and the angular separation between them. This single node PIR sensor system is designed to cover an angular view of ∼10° × 80° while horizontal Field of View (FOV) is divided into 4 active Fresnel zones. Generally costly Thermal-IR camera is used for thermal analysis. Our system is comparatively less costly and active coverage zones are easily configurable by increasing number of Fresnel lenses.     

Spatially variant regularization of lateral displacement measurement using variance

The purpose of this work is to confirm the effectiveness of our proposed spatially variant displacement component-dependent regularization for our previously developed ultrasonic two-dimensional (2D) displacement vector measurement methods, i.e., 2D cross-spectrum phase gradient method (CSPGM), 2D autocorrelation method (AM), and 2D Doppler method (DM). Generally, the measurement accuracy of lateral displacement spatially varies and the accuracy is lower than that of axial displacement that is accurate enough. This inaccurate measurement causes an instability in a 2D shear modulus reconstruction. Thus, the spatially variant lateral displacement regularization using the lateral displacement variance will be effective in obtaining an accurate lateral strain measurement and a stable shear modulus reconstruction than a conventional spatially uniform regularization. The effectiveness is verified through agar phantom experiments. The agar phantom [60 mm (height) × 100 mm (lateral width) × 40 mm (elevational width)] that has, at a depth of 10 mm, a circular cylindrical inclusion (dia. = 10 mm) of a higher shear modulus (2.95 and 1.43 × 10⁶ N/m², i.e., relative shear modulus, 2.06) is compressed in the axial direction from the upper surface of the phantom using a commercial linear array type transducer that has a nominal frequency of 7.5-MHz. Because a contrast-to-noise ratio (CNR) expresses the detectability of the inhomogeneous region in the lateral strain image and further has almost the same sense as that of signal-to-noise ratio (SNR) for strain measurement, the obtained results show that the proposed spatially variant lateral displacement regularization yields a more accurate lateral strain measurement as well as a higher detectability in the lateral strain image (e.g., CNRs and SNRs for 2D CSPGM, 2.36 vs 2.27 and 1.74 vs 1.71, respectively). Furthermore, the spatially variant lateral displacement regularization yields a more stable and more accurate 2D shear modulus reconstruction than the uniform regularization (however, for the regularized relative shear modulus reconstructions, slightly accurate, e.g., for 2D CSPGM, 1.51 vs 1.50). These results indicate that the spatially variant displacement component-dependent regularization will enable the 2D shear modulus reconstruction to be used as practical diagnostic and monitoring tools for the effectiveness of various noninvasive therapy techniques of soft tissue diseases (e.g., breast, liver cancers). Application of the regularization to the elevational displacement will also increase the stability of a three-dimensional (3D) reconstruction.     

Electric current measurement using fiber-optic curvature sensor

A novel fiber-optic curvature sensor, which can measure curvature directly, has been developed in recent years. The electric current measurements system based on fiber-optic curvature sensor and electromagnetic principle is developed. A fiber-optic curvature sensor is bonded to a thin-walled cantilever and two circular magnet targets with the same parameters are configured at the tip of the cantilever symmetrically. In this case, the throughput of the sensor will be changed due to the bending deformation of cantilever, which is proportional to the electromagnetic force caused by measured electric current. Direct and alternate characteristics of the proposed measurement system are studied experimentally. The results show that the measurement errors are within the range of ±5.5 mA and the corresponding accuracy is within 1% at the current measurement range from −300 mA to 300 mA, which indicate the feasibility of the proposed measurement system.     

Temperature self-compensation fiber-optic pressure sensor based on fiber Bragg grating and Fabry–Perot interference multiplexing

A high performance multiplexed fiber-optic sensor consisted of diaphragm-based extrinsic Fabry–Perot interferometer (DEFPI) and fiber Bragg grating (FBG) is proposed. The novel structure DEFPI fabricated with laser heating fusion technique possesses high sensitivity with 5.35 nm/kPa (36.89 nm/psi) and exhibits ultra-low temperature dependence with 0.015 nm/°C. But the ultra-low temperature dependence still results in small pressure measurement error of the DEFPI (0.0028 kPa/°C). The designed stainless epoxy-free packaging structure guarantees the FBG to be only sensitive to temperature. The temperature information is created to calibrate the DEFPI's pressure measurement error induced by the temperature dependence, realizing effectively temperature self-compensation of the multiplexed sensor. The sensitivity of the FBG is 10.5 pm/°C. In addition, the multiplexed sensor is also very easy to realize the pressure and the temperature high-precise high-sensitive simultaneous measurement at single point in many harsh environmental areas.     

Quantitative determination of subsurface defects in a reference specimen made of Plexiglas by means of lock-in and pulse phase infrared thermography

Lock-in and pulse phase infrared thermography measurement techniques have been exploited for quantitative assessment of subsurface defects in a reference specimen made of Plexiglas. Radiometric thermal images were post-processed using a contrast approach in the frequency domain, allowing defect depth to be resolved with a combined standard uncertainty of about 5% for thicknesses up to 3.6 mm. Conversely, significant radial heat diffusion next to the boundary of the discontinuities made accurate sizing of deeper subsurface defects more difficult, resulting in a combined standard uncertainty of about 17% for a 10 mm diameter flat-bottomed hole of 3.6 mm deep. The obtained results demonstrate the potentiality of active thermography as a fast, powerful contactless NDE measurement tool.     

Effects of driving frequency of longitudinal transducer on the vibration characteristics of a stepped plate

The flexural vibration characteristics of a stepped plate, driven at its center by different frequency of longitudinal transducer with a certain area are investigated. The variation in the nodal circle, fundamental frequency and displacement distribution of the stepped plate are calculated by using finite element method (FEM) under different driving frequencies. The results show that the fundamental frequency and nodal circle of the flexural-vibration stepped plate (FVSP) increase with an increase in the driving frequency of the longitudinal vibration ultrasonic transducer (LVUT), before the second-order flexural vibration occurs. When the driving frequency is f = 28 kHz, the displacement amplitude of the stepped plate can achieve the maximum, and the nodal circle radius of the stepped plate is 2.61 cm which fits evenly the edge of stepped profile. Meanwhile, the directivity and radiation efficiency of the FVSP would be greatly improved in a special driving frequency. The conclusions agree with the experimental ones and are significant for both design and applications of the stepped plate.     

Enhancement of oxygen surface kinetics of SrTiO3 by alkaline earth metal oxides

The kinetics of oxygen incorporation into semiconducting metal oxides such as strontium titanate are of particular interest for an application as a fast resistive-type oxygen sensor operating at high temperatures (T > 600 °C), e.g. in automotive exhaust gas monitoring.Based on a frequency-domain analysis of the response signal (resistance R) obtained from an electrically contacted sample exposed to a modulated oxygen partial pressure pO₂ in a fast kinetic measurement setup, the surface transfer controlled response behaviour of undoped and Fe-doped SrTiO₃ single crystals with thicknesses in the order of d = 45–125 μm was investigated with regard to the effect of thin PVD layers with alkaline earth (Ca, Sr, Ba) metal oxide compounds.The results of this electrical characterisation are compared with results obtained from ¹⁸O tracer exchange experiments and subsequent depth profile analysis by secondary ion mass spectrometry (SIMS). Both the electrical measurements and the ¹⁸O self-diffusion experiments revealed an enhancement of oxygen surface exchange kinetics in the case of all three alkaline earth metal oxides investigated.     

A thin film magnetic field sensor of sub-pT resolution and magnetocardiogram (MCG) measurement at room temperature

We developed a very sensitive high-frequency carrier-type thin film sensor with a sub-pT resolution using a transmission line. The sensor element consists of Cu conductor with a meander pattern (20 mm in length, 0.8 mm in width, and 18 μm in thickness), a ground plane, and amorphous CoNbZr film (4 μm in thickness). The amplitude modulation technique was employed to enhance the magnetic field resolution for measurement of the high-frequency field (499 kHz), a resolution of 7.10×10^?13 T/Hz^1/2 being achieved, when we applied an AC magnetic field at 499 kHz. The phase detection technique was applied for measurement of the low frequency field (around 1 Hz). A small phase change was detected using a dual mixer time difference method. A high phase change of 130°/Oe was observed. A magnetic field resolution of 1.35×10^?12 T/Hz^1/2 was obtained when a small AC field at 1 Hz was applied. We applied the sensor for magnetocardiogram (MCG) measurement using the phase detection technique. We succeeded in measuring the MCG signal including typical QRS and T waves, and compared the MCG with a simultaneously obtained conventional electrocardiogram (ECG) signal.     

Fabry–Pérot cavities based on chemical etching for high temperature and strain measurement

In this paper, two hybrid multimode/single mode fiber Fabry–Pérot (FP) cavities were compared. The cavities fabricated by chemical etching are presented as high temperature and strain sensors. In order to produce this FP cavity a single mode fiber was spliced to a graded index multimode fiber with 62.5 μm core diameter. The Fabry–Pérot cavities were tested as a high temperature sensor in the range between room temperature and 700 °C and as strain sensors. A reversible shift of the interferometric peaks with temperature allowed to estimate a sensitivity of 0.75 ± 0.03 pm/°C and 0.98 ± 0.04 pm/°C for the sensor A and B respectively. For strain measurement sensor A demonstrated a sensitivity of 1.85 ± 0.07 pm/μ? and sensor B showed a sensitivity of 3.14 ± 0.05 pm/μ?. The sensors demonstrated the feasibility of low cost fiber optic sensors for high temperature and strain.     

High-performance modulation-doped AlGaAs/InGaAs thermopiles for uncooled infrared FPA application

Novel thermopile based on modulation doped AlGaAs/InGaAs heterostructures is proposed and developed for the first time, for uncooled infrared FPA (Focal Plane Array) image sensor application. The high responsivity with the high speed response time are designed to be 4900 V/W with 110 μs under the 2 μm design rule. Based on integrated HEMT–MEMS technology, the 32 × 32 matrix FPA is fabricated to demonstrate its enhanced performances by black body measurement. The technology presented here demonstrates the potential of this approach for low-cost uncooled infrared FPA image sensor application.     

Membrane cleaning with ultrasonically driven bubbles

A laboratory filtration plant for drinking water treatment is constructed to study the conditions for purely mechanical in situ cleaning of fouled polymeric membranes by the application of ultrasound. The filtration is done by suction of water with defined constant contamination through a membrane module, a stack of five pairs of flat-sheet ultrafiltration membranes. The short cleaning cycle to remove the cake layer from the membranes includes backwashing, the application of ultrasound and air flushing. A special geometry for sound irradiation of the membranes parallel to their surfaces is chosen. Two frequencies, 35 kHz and 130 kHz, and different driving powers are tested for their cleaning effectiveness. No cleaning is found for 35 kHz, whereas good cleaning results are obtained for 130 kHz, with an optimum cleaning effectiveness at moderate driving powers. Acoustic and optic measurements in space and time as well as analytical considerations and numerical calculations reveal the reasons and confirm the experimental results. The sound field is measured in high resolution and bubble structures are high-speed imaged on their nucleation sites as well as during their cleaning work at the membrane surface. The microscopic inspection of the membrane surface after cleaning shows distinct cleaning types in the cake layer that are related to specific bubble behaviour on the membrane. The membrane integrity and permeate quality are checked on-line by particle counting and turbidity measurement of the permeate. No signs of membrane damage or irreversible membrane degradation in permeability are detected and an excellent water permeate quality is retained.     

Low frequency properties of micro power generator using a gold electroplated coil and magnet

Micro power generating devices were fabricated by using a gold electroplated coil and a permanent magnet. The electrical power was generated when the magnet reciprocated on the fabricated electroplated coil. The output power was increased as a function of vibration frequency. A measurement system, which convert a rotational motion of a motor into a linear motion, was designed and fabricated. The purpose of this work is to develop the micro power generating devices which convert the ambient vibration or oscillating energy into useful electrical energy. With changing vibration frequency from 0.5 to 8 Hz, the generated power increased linearly. The generated voltage was 106 mV at 3 Hz and 198 mV at 6 Hz. After using the step up circuit, the measured voltage was 81 mV at 3 Hz and 235 mV at 6 Hz. From above the frequency of about 4.5 Hz, the gain obtained by using the quadrupler circuit becomes larger than the loss without using that circuit.     

Power absorbed during whole-body fore-and-aft vibration: Effects of sitting posture,backrest, and footrest

Although the discomfort or injury associated with whole-body vibration cannot be predicted directly from the power absorbed during exposure to vibration, the absorbed power may contribute to understanding of the biodynamics involved in such responses. From measurements of force and acceleration at the seat, the feet, and the backrest, the power absorbed at these three locations was calculated for subjects sitting in four postures (feet hanging, maximum thigh contact, average thigh contact, and minimum thigh contact) both with and without a rigid vertical backrest while exposed to four magnitudes (0.125, 0.25, 0.625, and 1.25 m s^?2 rms) of random fore-and-aft vibration. The power absorbed by the body at the supporting seat surface when there was no backrest showed a peak around 1 Hz and another peak between 3 and 4 Hz. Supporting the back with the backrest decreased the power absorbed at the seat at low frequencies but increased the power absorbed at high frequencies. Foot support influenced both the magnitude and the frequency of the peaks in the absorbed power spectra as well as the total absorbed power. The measurements of absorbed power are consistent with backrests being beneficial during exposure to low frequency fore-and-aft vibration but detrimental with high frequency fore-and-aft vibration.     

Novel atmospheric extinction measurement techniques for aerospace laser system applications

Novel techniques for laser beam atmospheric extinction measurements, suitable for manned and unmanned aerospace vehicle applications, are presented in this paper. Extinction measurements are essential to support the engineering development and the operational employment of a variety of aerospace electro-optical sensor systems, allowing calculation of the range performance attainable with such systems in current and likely future applications. Such applications include ranging, weaponry, Earth remote sensing and possible planetary exploration missions performed by satellites and unmanned flight vehicles. Unlike traditional LIDAR methods, the proposed techniques are based on measurements of the laser energy (intensity and spatial distribution) incident on target surfaces of known geometric and reflective characteristics, by means of infrared detectors and/or infrared cameras calibrated for radiance. Various laser sources can be employed with wavelengths from the visible to the far infrared portions of the spectrum, allowing for data correlation and extended sensitivity. Errors affecting measurements performed using the proposed methods are discussed in the paper and algorithms are proposed that allow a direct determination of the atmospheric transmittance and spatial characteristics of the laser spot. These algorithms take into account a variety of linear and non-linear propagation effects. Finally, results are presented relative to some experimental activities performed to validate the proposed techniques. Particularly, data are presented relative to both ground and flight trials performed with laser systems operating in the near infrared (NIR) at λ = 1064 nm and λ = 1550 nm. This includes ground tests performed with 10 Hz and 20 kHz PRF NIR laser systems in a large variety of atmospheric conditions, and flight trials performed with a 10 Hz airborne NIR laser system installed on a TORNADO aircraft, flying up to altitudes of 22,000 ft.