Several Tens Of Millimeters Research Articles

Precise Positioning of Primary System of Geodetic Points by GNSS Technology in Railway Operating Conditions

This article deals with the analysis of the accuracy of the geodetic real-time GNSS measurement procedure used in railway operating conditions in the Czech Republic. The purpose was to determine to what extent the operating conditions affect the accuracy of the measurement result and whether an accuracy of standard deviation σx,y = 5 mm in the horizontal plane could be achieved. The use of geodetic GNSS equipment with an IMU unit was also tested. The accuracy obtained in operational conditions is compared with the accuracy obtained on a calibration base using the same measurement procedure. The consistency between the accuracy of the primary system (satellite-based) and the secondary system (terrestrially measured by the traverse method) is also discussed. The analysis includes the issue of residual inhomogeneities of the uniform transformation key when converted to the Czech national coordinate system S-JTSK. It is shown that a homogeneous accuracy in coordinate standard deviation better than σx,y = 5 mm can be achieved. The results indicate that the accuracy under operational conditions is two–three times worse than the accuracy achieved by the same procedure under ideal conditions on a calibration base. This is due to the non-ideal observing conditions, i.e., horizon occlusion by overlays, surrounding vegetation and multipath effects. It has been shown that the effect of multipath can be reduced by repeating short observations 3–4 h apart. Older GNSS instruments using an IMU unit in combination with an electronic compass (eCompass) are at risk of a systematic bias of up to several tens of millimeters, which can be detected by rotating the antenna by 180°. The current uniform transformation key used in the Czech Republic for the conversion of GNSS coordinates into the national system has residual geometric inhomogeneities (p = 0.90 to 10 mm/km, sporadically up to 20 mm/km), which metrologically deteriorate the results of the calculation of the terrestrially measured secondary system inserted into the GNSS measured primary system. Achieving homogeneous accuracy in coordinate standard deviation in a horizontal plane better than σx,y = 5 mm has been demonstrated in non-ideal railway operating conditions with increased risk of multipath. The innovative aspect of the approach used is that it simplifies and thus increases the efficiency of the measurement with respect to the availability of GPS, GLONASS, Galileo and BeiDou satellites, as well as reducing the effect of multipath on the noise by repeating the measurement procedure.

Detection of Individual Microbubbles by Burst-Wave-Aided Contrast-Enhanced Active Doppler Ultrasonography.

We propose burst-wave-aided, contrast-enhanced, active Doppler ultrasonography for visualizing lymph vessels. This technique forces ultrasound contrast agents (UCAs) to move using the acoustic radiation force induced by burst waves with low amplitude while suppressing their destruction. Using a flow phantom, we measured the average, decrease rate of echo intensity [i.e., pulse intensity integral (PII)], and the velocity of individual contrast agents, which directly affects the performance of imaging and tracking contrast agents under stationary flow conditions. Comparison with pulse-inversion Doppler without exposure to the burst wave demonstrated that the velocity of the contrast agents could be enhanced up to several tens of millimeters per second by the effect of the burst wave, maximizing the echo intensity extracted by a clutter filter. The contrast ratio (CR), defined as the ratio of the contrast echo to the phantom echo outside the channel, did not change appreciably, even when the lower cut-off velocity of the clutter filter was increased up to 10 mm/s. This implies a better robustness against the motion of the tissue. In addition, the performance for detecting contrast agents (i.e., echo intensity) was superior or similar to that of pulse-inversion Doppler, even in undesirable conditions where the flow had a velocity component in the opposite direction to that of the acoustic radiation force. The echo intensity was lower or the same as that in pulse-inversion Doppler, demonstrating the potential for suppressing the destruction of contrast agents and enabling long-term observations. From these results, we expect that the proposed method will be beneficial for visualizing lymph vessels.

Fast modal reconstruction of large plane wavefronts from sparse measurements using Shack-Hartmann sensors.

A concept for the fast measurement and reconstruction of optical wavefronts using Shack-Hartmann sensors (SHSs) is presented. For wavefronts with a diameter at the scale of several tens of millimeters, hundreds of measurements with an SHS may be necessary to cover the wavefront. In the proposed concept, a few SHSs are used to measure about 2% of the entire wavefront, providing sufficient measurement data for its successful reconstruction. The small number of SHSs mounted in parallel makes the concept suitable for time-critical applications. A simulation analysis is performed, and an experimental validation of the concept is presented, demonstrating that the wavefront can be reconstructed with an RMS error of about 100nm.

Experimental investigation of the effective point of measurement for plane-parallel chambers used in electron beam dosimetry.

In this study, the effective point of measurement (EPOM) for plane-parallel ionization chambers in clinical high-energy electron beams was determined experimentally. Previous studies have reported that the EPOM of plane-parallel chambers is shifted several tens of millimeters downstream from the inner surface of the entrance window to the cavity. These findings were based on the Monte Carlo (MC) simulation, and few experimental studies have been performed. Thus, additional experimental validations of the reported EPOMs were required. In this study, we investigated the EPOMs of three plane-parallel chambers (NACP-02, Roos and Advanced Markus) for clinical electron beams. The EPOMs were determined by comparing the measured percentage depth-dose (PDD) of the plane-parallel chambers and the PDD obtained using the microDiamond detector. The optimal shift to the EPOM was energy-dependent. The determined EPOM showed no chamber-to-chamber variation, thereby allowing the use of a single value. The mean optimal shifts were 0.104±0.011, 0.040±0.012, and 0.012±0.009cm for NACP-02, Roos, and Advanced Markus, respectively. These values are valid in the R50 range from 2.40 to 8.82cm, which correspond to 6-22 MeV. Roos and Advanced Markus exhibited similar results to those of the previous studies, but NACP-02 showed a larger shift. This is probably due to the uncertainty of the entrance window of NACP-02. Therefore, it is necessary to carefully consider where the optimal EPOM is located when using this chamber.

Thickness Measurement at High Lift-Off for Underwater Corroded Iron-Steel Structures Using a Magnetic Sensor Probe

Infrastructure facilities that were built approximately half a century ago have rapidly aged. Steel sheet piles, the inspection object in this study, are severely corroded, resulting in cave-in damages at wharfs. To solve such a problem, non-destructive inspection techniques are required. We previously demonstrated plate thickness measurement using extremely low-frequency eddy current testing. However, when the steel sheet piles are located in water, shellfish adhere to their surface, causing a lift-off of several tens of millimeters. Therefore, this large lift-off hinders the thickness measurement owing to fluctuations of magnetic signals. In this study, sensor probes with different coil diameters were prototyped and the optimum size for measuring steel sheet piles at high lift-off was investigated. Using the probes, the magnetic field was applied with a lift-off range from 0 to 80 mm, and the intensity and phase of the detected magnetic field were analyzed. Subsequently, by increasing the probe diameter, a good sensitivity was obtained for the thickness estimation with a lift-off of up to 60 mm. Moreover, these probes were used to measure the thickness of actual steel sheet piles, and measurements were successfully obtained at a high lift-off.

In Situ Visualization of the Hydrogen Distribution in an Fe Sheet Under Corrosion Conditions Using Polyaniline

High-strength steels are known to be susceptible to hydrogen embrittlement. Even small amounts of hydrogen which enter the high-strength steels under corrosion conditions could cause the hydrogen embrittlement. In order to elucidate the mechanism of hydrogen entry in corrosive environments, and to prevent the corrosion-induced hydrogen embrittlement, the simultaneous analysis of the corrosion behavior and the hydrogen entry is required. Some techniques, such as scanning Kelvin probe force microscope, have been reported for visualizing the hydrogen distribution in metals with a high spatial resolution. However, it is still challenging to visualize the hydrogen distribution of an observation area of several tens of millimeters with high spatial and temporal resolutions. In this study, we succeeded the visualization of the distribution of hydrogen entering a pure Fe sheet immersed in a NaCl aqueous solution using a conductive polymer.A pure Fe sheet (99.5 %) was used as a specimen. The Fe sheet was electrically polished in a mixed solution of perchloric acid and acetic acid. The thickness of the Fe sheet was 0.4 mm after the polishing. In order to visualize the hydrogen distribution in the Fe sheet, a polyaniline (PANI) layer was formed on one side of the Fe sheet. It was reported that the PANI layer changes its color owing to the reaction with atomic state hydrogen in Fe sheets.1 To enhance the sensitivity of the PANI layer to hydrogen, a Ni interfacial layer was formed between the PANI layer and the Fe sheet. The PANI layer was formed on the Ni interfacial layer through electrolytic polymerization at a constant voltage of 1 V in a 0.5 M H2SO4-0.5 M aniline aqueous solution. On the other side (bare Fe side) of the Fe sheet, an electrode area of 1 cm × 1 cm was prepared using a resin. Only the bare Fe side was immersed in a 0.1 M NaCl aqueous solution. In addition to the open-circuit potential measurements, the corrosion behavior was observed in situ using a digital camera during the corrosion test. The PANI layer was exposed to air without contacting the NaCl solution. During the corrosion test, the color of the PANI layer was observed in situ using another digital camera. It was confirmed that the small amount of hydrogen entering the Fe sheet due to corrosion can be visualized using the PANI layer. The distribution of hydrogen that entered the Fe sheet was analyzed based on the color distribution of the PANI layer. The in situ simultaneous observation of the corrosion behavior and the hydrogen entry revealed that the hydrogen entry was promoted on the dissolved area of the Fe sheet in the NaCl solution. Reference H. Kakinuma, S. Ajito, T. Hojo, M. Koyama, E. Akiyama, Adv. Mater. Interfaces, 2101984 (2022).

Application of Inertial and GNSS Integrated Navigation to Seabird Biologging

The study demonstrates the versatility of integration of inertial navigation and global navigation satellite system (GNSS) with its unique application to seabird biologging. Integrated navigation was originally developed in the field of aerospace engineering, which requires accurate and reliable position, velocity, and attitude information for the guidance and control of aircraft and spacecraft. Due to its high performance and recent progress of sensor development, integrated navigation has been widely used not only in aerospace but also in many fields represented by land and marine vehicles. One of its ultimate applications under the constraint on the size and power consumption of devices is this study. Seabird biologging involves attaching a logging device onto a seabird for scientific purposes to understand its biomechanics, behavior, and so on. Design restrictions for the device include several tens of grams mass, several tens of millimeters in length, and several tens of milliamperes of power consumption. It is more difficult to maintain the accuracy of such a device than applications to an artificial vehicle. This study has shown that integrated navigation is a feasible solution for such extreme applications with two examples: biologging for wandering albatrosses and great frigatebirds. Furthermore, it should be stressed that the navigation captured the world’s first data of their detailed trajectories and attitudes in their dynamic and thermal soarings. For completeness, the navigation algorithm, simulation results to show the effectiveness of the algorithm, and the logging devices attached to bird are also described.

Characteristics of plasma window with various channel diameters for accelerator applications.

Plasma window is a feasible device as an atmosphere-vacuum interface, which can withstand energetic particle beams. It is, however, essential to enlarge the diameter to several tens of millimeters for actual beam passing in the accelerator applications. The pressure separation performance and discharge voltage V current I characteristics should be investigated in detail to design the plasma window for each purpose. Therefore, a cascade arc discharge device with a diameter of up to 20 mm was developed, and its characteristics as a function of diameter were examined. As a result, with an increase in the channel diameter, the discharge pressure that was achieved decreased, whose values were smaller compared with the values by the prediction formula, assuming the viscous gas flow with a constant plasma temperature. It showed that the bulk plasma temperature for the larger discharge channel was low because of the low-current density over the channel. Furthermore, the transition of the V-I slope was observed with an increase in the diameter.

A Magneto-Armored Warm-Solenoid Based System for K-Band Gyrodevices

A magneto-armored system for a new generation of technological complexes based on CW K-band gyrotrons (28–50 GHz), which operate on the main cyclotron resonance with an output power of 25–30 kW or higher, was developed and experimentally tested. The possibility of creating a homogeneous (better than 0.5%) sector of the magnetic field in the region of the electron–wave interaction with a length of several tens of millimeters has been demonstrated. Optimization of the configuration, shapes, and material that were used for the ferromagnetic screens for solenoids with copper windings and working-hole diameters of several tens of millimeters made it possible to obtain record values of constant magnetic fields with respect to the power consumption. For the operating mode with a uniform section of 65 mm and a magnetic-field induction of 1.03 T, the power consumption of the solenoid was 12.5 kW, which makes it possible to significantly (by ~1.5 times) increase the efficiency of the complex as a whole when using a gyrotron with a full radiation efficiency of nearly 50%, which is significantly superior to the existing analogues.

3D RECONSTRUCTION OF INNER STRUCTURE OF RADIOACTIVE SAMPLES UTILIZING GAMMA TOMOGRAPHY.

Unique 3D tomography apparatus was built and successfully tested in Research Centre Rez. The apparatus allows three-dimensional view into the interior of low-dimension radioactive samples with a diameter up to several tens of millimeters with a betterresolution then 1mm3 and is designed to detect domains with different levels of radioactivity. Structural inhomogeneities such as cavities, cracks or regions with different chemical composition can be detected using this equipment. The SPECT scanner has been successfully tested on several samples composed of a 3-mm radionuclide source located eccentrically within homogeneous steel bushings. To detect fine cracks inside a small sample, an ultrafine scan of the sample was carried out in the course of 24hours with a 0.5-mm longitudinal and transverse step and 18° angular step. The exact location and orientation of a fine crack artificially formed inside a sample has been detected.

Piezoelectric Micromachined Ultrasonic Transducers with a Cost-Effective Bottom-Up Fabrication Scheme for Millimeter-Scale Range Finding

This study proposes a novel piezoelectric micromachined ultrasonic transducer (PMUT), fabricated on a metal foil. Using a bottom-up, cost-effective micromachining technique, the PMUTs made of electrodes, a piezoelectric film, or electrode-sandwiched structures with versatile patterns were implemented on a large-area foil thinner rather than regular paper. The proposed microfabrication facilitated the PMUT to be able to generate ultrasonic waves with fundamental and harmonic resonances. The fourth-order resonances of the fabricated PMUT functionally operated at an ultrasonic spectrum of approximately 30 kHz as an ultrasonic emitter. The developed PMUT was paired with a microelectromechanical system (MEMS) microphone module for range-finding applications in the range of several tens of millimeters. A signal-processing scheme was developed to extract the representative pattern from the acquired signals that were emitted and received. The pattern enabled finding the distance between the PMUT and the microphone using time-of-flight and strength-variation technology. The developed PMUT-microphone pair demonstrated its range-finding performance, displaying an error of less than 0.7% using the time-of-flight method.

Highly accurate, absolute optical encoder using a hybrid-positioning method.

An absolute optical encoder with nanometric positioning repeatability is introduced and investigated. The encoder consists of an improved scale grating and a compact two-probe reading head. The scale grating contains multiple unevenly spaced distance marks that are superimposed onto grating grooves. The two probes, which are located in the sensor head, read the marks and the grating grooves to determine the position and displacement simultaneously. For one of the two probes, a mask with the same code design with the marks on the scale grating generates a pulse signal to locate the position of the marks approximately-with an accuracy of less than about half a grating period (0.5μm). For the other probe, light beams are configured for grating interferometry to measure displacement with nanometer-scale resolution. In this Letter, high-quality sinusoidal signals of grating interferometry are used to accurately locate the marks on the scale grating, with stable 100-subdivision phase information. The testing results show that the positioning repeatability can reach 10nm for a motion range of several tens of millimeters.

Development of discrete frequency swept laser for 2D single-shot pseudo comb interferometry

We propose a discrete frequency swept laser with sufficient sweep repetition rate (SRR) of 10 kHz order for 2D single-shot pseudo comb interferometry, in which the shutter speed of 2D imaging sensor is operated at 10 μs order. The proposed light source can overcome the limited SRR in 1 kHz order of the conventional discrete frequency swept lasers, which are not adequate for 2D single-shot pseudo comb interferometry. The proposed light source with a frequency step of approximately 200 GHz and an SRR of 29 kHz is demonstrated, showing an effectiveness for the axial range expansion of 2D single-shot industrial profilometry and tomography in several tens of millimeters.

Highly compact fiber Fabry-Perot interferometer: A new instrument design.

This paper presents the design, construction, and characterization of a new optical-fiber-based, low-finesse Fabry-Perot interferometer with a simple cavity formed by two reflecting surfaces (the end of a cleaved optical fiber and a plane, reflecting counter-surface), for the continuous measurement of displacements of several nanometers to several tens of millimeters. No beam collimation or focusing optics are required, resulting in a displacement sensor that is extremely compact (optical fiber diameter 125 μm), is surprisingly tolerant of misalignment (more than 5°), and can be used over a very wide range of temperatures and environmental conditions, including ultra-high-vacuum. The displacement measurement is derived from interferometric phase measurements using an infrared laser source whose wavelength is modulated sinusoidally at a frequency f. The phase signal is in turn derived from changes in the amplitudes of demodulated signals, at both the modulation frequency, f, and its harmonic at 2f, coming from a photodetector that is monitoring light intensity reflected back from the cavity as the cavity length changes. Simple quadrature detection results in phase errors corresponding to displacement errors of up to 25 nm, but by using compensation algorithms discussed in this paper, these inherent non-linearities can be reduced to below 3 nm. In addition, wavelength sweep capability enables measurement of the absolute surface separation. This experimental design creates a unique set of displacement measuring capabilities not previously combined in a single interferometer.

Self-Correcting Magnetic Tracking in Dynamic Medical Environments

We propose a novel self-correcting tracking technique that can minimize the dynamic distortion during magnetic tracking. In our method, the magnetic field distortion is estimated through field expansion and then minimized in an iterative tracking procedure. Sparse sensor arrays are designed to measure the spatial gradient tensors of the magnetic field for our method. Numerical results demonstrate that the tracking error caused by field distortion could be reduced from several tens of millimeters to below 2 mm.

Three-dimensional welding residual stresses evaluation based on the eigenstrain methodology via X-ray measurements at the surface

In order to assure structural integrity for operating welded structures, it is necessary to evaluate crack growth rate and crack propagation direction for each observed crack non-destructively. Here, three dimensional (3D) welding residual stresses must be evaluated to predict crack propagation. Today, X-ray diffraction is used and the ultrasonic method has been proposed as non-destructive method to measure residual stresses. However, it is impossible to determine residual stress distributions in the thickness direction. Although residual stresses through a depth of several tens of millimeters can be evaluated non-destructively by neutron diffraction, it cannot be used as an on-site measurement technique. This is because neutron diffraction is only available in special irradiation facilities. Author pays attention to the bead flush method based on the eigenstrain methodology. In this method, 3D welding residual stresses are calculated by an elastic Finite Element Method (FEM) analysis from eigenstrains which are evaluated by an inverse analysis from released strains by strain gauges in the removal of the reinforcement of the weld. Here, the removal of the excess metal can be regarded as non-destructive treatment because toe of weld which may become crack starters can be eliminated. The effectiveness of the method has been proven for welded plates and pipes even with relatively lower bead height. In actual measurements, stress evaluation accuracy becomes poorer because measured values of strain gauges are affected by processing strains on the machined surface. In the previous studies, the author has developed the bead flush method that is free from the influence of the affecting strains by using residual strains on surface by X-ray diffraction. However, stress evaluation accuracy is not good enough because of relatively poor measurement accuracy of X-ray diffraction. In this study, a method to improve the estimation accuracy of residual stresses in this method is formulated, and it is shown numerically that inner welding residual stresses can be estimated accurately from the residual strains measured by X-ray diffraction.

Channel Modeling and Capacity Analysis for Electromagnetic Wireless Nanonetworks in the Terahertz Band

Nanotechnologies promise new solutions for several applications in the biomedical, industrial and military fields. At the nanoscale, a nanomachine is considered as the most basic functional unit which is able to perform very simple tasks. Communication among nanomachines will allow them to accomplish more complex functions in a distributed manner. In this paper, the state of the art in molecular electronics is reviewed to motivate the study of the Terahertz Band (0.1-10.0 THz) for electromagnetic (EM) communication among nano-devices. A new propagation model for EM communications in the Terahertz Band is developed based on radiative transfer theory and in light of molecular absorption. This model accounts for the total path loss and the molecular absorption noise that a wave in the Terahertz Band suffers when propagating over very short distances. Finally, the channel capacity of the Terahertz Band is investigated by using this model for different power allocation schemes, including a scheme based on the transmission of femtosecond-long pulses. The results show that for very short transmission distances, in the order of several tens of millimeters, the Terahertz channel supports very large bit-rates, up to few terabits per second, which enables a radically different communication paradigm for nanonetworks.

Nineteenth and Twentieth Century Changes in Sea Level

Following the Last Glacial Maximum (25,000–20,000 years ago), sea level rose at rates on the order of several tens of millimeters per year at times, and increased overall by over 130 m. However, melting of the great ice sheets was largely complete by 6,000 years ago, and it is believed that sea level did not rise significantly again until recently. The rates of sea level change during the last few centuries and in recent decades can be measured in units of millimeters per year and are particularly important in understanding present-day climate change. We now have a range of techniques with which sea level changes can be measured and thus studied more intensively than before, as a global average and in each region. This article introduces each of the main data sets and presents the primary research findings. It is hoped that a greater understanding of the reasons for past observed sea level change, discussed elsewhere in this issue, will lead to better estimation of the changes likely to occur in the future

Atmospheric-pressure cold plasma jet for medical applications

An atmospheric-pressure plasma jet operated with air is presented. The plasma jet device is composed of a porous alumina dielectric element, an outer electrode, and a hollow inner electrode. Microdischarges in the porous alumina evolve to form a plasma jet that reaches lengths up to several tens of millimeters as the flow rate of the working gas increases. The discharge characteristics were investigated by measuring the voltage and current waveforms and by observing the optical emissions. Sterilization of Escherichia coli ( E. coli) was carried out as an example for medical applications of the plasma jet. E. coli cells were completely removed after exposure to the air-plasma jet, even at an exposure time of less than 60 s.

2A2-J04 インテリジェントロボットハンドの研究開発 : Pick and Placeの達成

To achieve a skillful operation like the human being by robot hand, an interaction with the vision and the tactile sense is indispensable. To consider the safe and certain grasping operation by the robot hand, we proposed use of proximity sensor which can detect the several tens of millimeters from finger-tip surface and tactile sensor. And we call such a robot hand an "intelligent robot hand" and develop this. This time, we propose the control method of internal force based on CoP(center of pressure) tactile sensor for the achievement of grasping by three fingers and confirmed utility of the proposal method by the experiments.