Acceleration Calibration Research Articles

Acceleration calibration method for the drop test of radioactive package based on the rebound of specimen

Acceleration calibration method for the drop test of radioactive package based on the rebound of specimen

Development and Calibration of a Three-Directional High-Energy Particle Detector for FY-3E Satellite

According to the characteristics of the LEO space particles radiation environment of China’s Fengyun No. 3 (FY-3) polar-orbiting meteorological satellites, in order to monitor the characteristics, and space–time distribution of charged particle radiation in the orbit space, it is proposed to install a three-directional high-energy particle detector (HEPD) in the three vertical orthogonal directions of FY-3E, so as to carry out the energy spectrum and flux observation of high-energy protons and electrons in the three directions of the satellite, namely, −X, +Y, and −Z. The on-orbit detection data acquired by these payloads can be used for space environment modeling and solar-terrestrial physics research, and provide data sources for operational space environment weather warning and forecasting. Through the ground accelerator calibration experiment and simulation analysis of the three-directional HEPDs developed in the flight model phase, the experimental results show that all the HEPDs’ measured values meet the requirements for technical indexes, such as the detection energy range (high-energy protons: 3–300 MeV; high-energy electrons: 0.15–5.7 MeV), energy span accuracy (<15%), flux accuracy (<15%), and sensitivity (<5% (ΔN/N)).

Primary Low-g Shock Acceleration Calibration Using Laser Interferometry

The current situation of low g shock is introduced with three types of shock exciters described. The measuring theory and system set-up using laser interferometry is explained in accordance with ISO 16063-13 with the emphasis on key technology of signal demodulation algorithm and air-bearing shock exciter based on collision. According to calibration results, the primary shock calibration system can achieve expanded uncertainty of 1%,k=2, in the acceleration range from 20m/s2 to 10000m/s2 and pulse duration from 0.5ms to 10ms.

Acceleration and Deceleration Parameter Calibration of Tunnel Entrance Based on the Naturalistic Driving Test of Passenger Car

The precise calibration of acceleration and deceleration parameters is crucial for improving the accuracy of operating speed prediction and analysis tools at tunnel entrances. Therefore, acceleration and deceleration data of passenger car captured from 20 drivers at 30 tunnel entrances were collected from 200 m outside to 200 m inside the tunnel portal and averaged across four study zones. The results show that, first, the distribution of deceleration rates based on speed differs from that of acceleration rates based on speed in all zones. Second, significant differences in the probability density distribution of deceleration were found between each zone ( p < 0.001 ), but differences in acceleration could not be found between any zones ( p > 0.05 ). Third, the feature values (breakpoints) of the acceleration/deceleration cumulative frequency curves were located near the 95th percentile, differing from the traditional 85th percentile found with the extant model. The feature values of acceleration in the four zones coincided at 0.5 m/s2 and those of deceleration were 0.93, 0.85, 0.70, and 0.47 m/s2 under zones 1–4, respectively. This study provides accurate feature values of acceleration and deceleration for modelling an updated tunnel entrance operating speed prediction model.

Deep J-Sense: Accelerated MRI Reconstruction via Unrolled Alternating Optimization.

Accelerated multi-coil magnetic resonance imaging reconstruction has seen a substantial recent improvement combining compressed sensing with deep learning. However, most of these methods rely on estimates of the coil sensitivity profiles, or on calibration data for estimating model parameters. Prior work has shown that these methods degrade in performance when the quality of these estimators are poor or when the scan parameters differ from the training conditions. Here we introduce Deep J-Sense as a deep learning approach that builds on unrolled alternating minimization and increases robustness: our algorithm refines both the magnetization (image) kernel and the coil sensitivity maps. Experimental results on a subset of the knee fastMRI dataset show that this increases reconstruction performance and provides a significant degree of robustness to varying acceleration factors and calibration region sizes.

Comparative study of different response spectra based on isolated structures

In order to study the influence of different design response spectra on the internal force of the isolated structure, the response spectra of the “Code for Seismic Design of Buildings” (Abbreviated as SD), the response spectra of “Design Standards for Seismic Isolation of Buildings” (draft for comments)(Abbreviated as ID) and the response spectra based on pseudo acceleration calibration(Abbreviated as PA) are analyzed. Compared with SD response spectra, ID response spectra adopts the (1/T) attenuation mode in the long period, which reduces the value of the earthquake influence coefficient in the long period of the response spectrum. At the same time, there is no overshoot phenomenon in ID response spectra. This paper presents the response spectrum basic on structural elastic displacement. PA response spectra considers the influence of different sites on the long-period structure, and adds the characteristic period corresponding to different sites. The calculation shows that compared with the calculation result of SD response spectra, the floor shear force calculated by ID is reduced, and the reduction ratio is between 31% and 36%. Compared with the floor shear force obtained by using PA response spectra, the reduction ratio is between 19% and 29%.

“Warm liquid” detector for measuring dose profiles from ionizing radiation

The use of “warm liquid” tetramethylsilane (TMS) in ionization chambers for measuring dose profiles in water phantoms to prepare the accelerator for a proton therapy session is relevant. One of the promising areas of radiation therapy is proton therapy. To increase the conformality of proton therapy, it is important to know exactly the dose distributions from the energy release of the proton beam in the water phantom before conducting a proton therapy session. A television-type detector (TTD), which measures the profiles of the Bragg peak by the depth of the beam in the water phantom, helps to increase the accuracy of the dose distribution knowledge. To accurately determine the profile of the Bragg peak by the beam width in the water phantom, an additional method is proposed that will allow TTD to quickly determine the profile by the width of the Bragg peak in on-line mode. This prefix to the TTD will improve the quality of summing up the therapeutic beam-thanks to accurate knowledge of the profile by width, and therefore the formed high-dose distribution field will correspond to the irradiated volume in the patient and will increase the conformality of irradiation. The additional prefix to the TTD is designed on an organosilicon “warm liquid” and represents a high-precision ionization chamber with coordinate sensitivity along the width of the water phantom. The fully developed technology for obtaining “warm liquid” TMS allows creating both microdosimeters for proton therapy and detectors for measuring “dose profiles” in water phantoms during accelerator calibration. The considered prefix to the TTD detector - the calibrator meter of the dose field (KIDP) - can also be used independently of the TTD and with great accuracy measure the dose profiles of the Bragg peak in the water phantom, both in depth and width. KIDP can also be used to measure the outputs of secondary “instantaneous” neutrons and gamma quanta emitted from the water phantom orthogonally to the direction of the proton beam.

Beam energy measurement on LINAC-200 accelerator and energy calibration of scintillation detectors by electrons in range from 1 MeV to 25 MeV

Abstract Accurate determination of the energy of LINAC-200 fast electrons was performed using several photonuclear reactions carried out on natural Indium after conversion of electron energy in bremsstrahlung in thick Tungsten target. Natural Indium was used as an activation detector and the ratios of saturation activities R( 113m In)/R( 115m In), R( 114m In)/R( 115m In) and R(111In)/R ( 115m In) were used as a measure of the endpoint energy of the bremsstrahlung beam (and energy of electrons striking the bremsstrahlung target as well). Energy dependence of the three ratios of saturation activities were determined by using the bremsstrahlung produced by electrons accelerated by Microtron to the energies known with accuracy not worse than 0.1 MeV. Three types of scintillation detectors (LaBr3:Ce, BGO and plastic) were calibrated using electrons having energies from 1.17 MeV to 25 MeV. In low energy region photoelectrons produced by 60 Co gamma radiation in the detector itself were used, as well as high energy electrons (from 11 MeV to 25 MeV) accelerated by LINAC-200.

A two-DOF model-based input prediction for high-shock accelerometer calibration

This article describes a two-degree-of-freedom (two-DOF) model-based input prediction method in the frequency domain for the comparison of high-shock acceleration calibration facilities. The current measurand for transferring the unit is the shock sensitivity as the relationship between the peak values of the accelerometer output quantity and the acceleration. The common transfer standards applied in shock calibration facilities in the range up to 100 km s−2 are piezoelectric-based transducers with a first resonance close to, or within, the spectrum of the exciting shock. This leads to the effect that the provided is, technically speaking, only valid for shocks of the same spectral composition, resulting in unpleasantly high uncertainties in high-shock measurements. This is thus not feasible if applied to shocks of differing spectral composition.A parametrized two-DOF model is capable of describing the transfer standard and allows the prediction of the applied input excitation with unprecedented accuracy. A method for the parameter identification and input prediction in the frequency domain and the results for two transfer standards are presented.

Experimental study of a fiber Bragg grating accelerometer for seismic measurement

This paper presents a fiber Bragg grating accelerometer prototype for seismic applications, including accelerometer scheme, calibration method and accelerometer resonance frequencies. The acceleration calibration and measurements were obtained from the laser beam deflection method. A series of experiments were carried out and results shows an accelerometer sensitivity of 8.07 mV/g (where 1g= 9.81 m/s2) at 0.5 Hz and 2.63 mV/g at 50 Hz, the measured range scale goes from 0 to 35 m s-2.

Primary High Acceleration Calibration System at NIM

Currently the maximum acceleration range of primary vibration calibration cannot meet the requirement of secondary vibratoin calibration and vibration testing field. In some special vibration test field, the accelerometers are required to be calibrated up to 4900 m/s2 or more, but the maximum acceleration of primary vibratoin calibration capability is normlly 100 m/s2. In order to meet the high acceleration traceability requirement, a primary high acceleration calibration system has been set up in National Institute of Metrology. Two high acceleration exciters based on resonance amplification are used to produce high acceleration vibration. In order to impove the maximum acceleration of the resonator, a simple clamped-clamped beam is used, only the clamped ends are excited by a shaker to reduce the damping. The phase control method are used to track the resoant frequency. A primary vibration measuring system was set up according to ISO 16063-11. The experimental results show that the maximum acceleration of this vibratoin calibration system can reach more than 10000 m/s2.

Fiber optically coupled radioluminescence detectors: A short review of key strengths and weaknesses of BCF-60 and Al2O3:C scintillating-material based systems in radiotherapy dosimetry applications

Radiotherapy technologies have improved for several decades aiming to effectively destroy cancerous tissues without overdosing surrounding healthy tissues. In order to fulfil this requirement, accurate and precise dosimetry systems play an important role. Throughout the years, ionization chambers have been used as a standard detector for basic linear accelerator calibrations and reference dosimetry in hospitals. However, they are not ideal for all treatment modalities: and limitations and difficulties have been reported in case of (i) small treatment fields, (ii) strong magnetic field used in the new hybrid MRI LINAC/cobalt systems, and (iii) in vivo measurements due to safety-issues related to the high operating voltage. Fiber optically coupled luminescence detectors provide a promising supplement to ionization chambers by offering the capability of real-time in vivo dose monitoring with high time resolution. In particular, the all-optical nature of these detectors is an advantage for in vivo measurements due to the absence of high voltage supply or electrical wire that could cause harm to the patient or disturb the treatment. Basically, fiber-coupled luminescence detector systems function by radiation-induced generation of radioluminescence from a sub-mm size organic/inorganic phosphor. A thin optical fiber cable is used for guiding the radioluminescence to a photomultiplier tube or similar sensitive light detection systems. The measured light intensity is proportional to dose rate. Throughout the years, developments and research of the fiber detector systems have undergone in several groups worldwide. In this article, the in-house developed fiber detector systems based on two luminescence phosphors of (i) BCF-60 polystyrene-based organic plastic scintillator and (ii) carbon-doped aluminum oxide crystal (Al2O3:C) are reviewed with comparison to the same material-based systems reported in the literature. The potential use of these detectors for reference-class dosimetry in radiotherapy will be discussed with a particular emphasis on uses in small and large MV photon fields.

Acceleration and Deceleration Calibration of Operating Speed Prediction Models for Two-Lane Mountain Highways

AbstractIn this study, to calibrate the acceleration/deceleration rates in operating speed prediction models, driving tests were performed on two-lane mountain highways using passenger cars, and co...

Automatic calibration process for optimal control of clutch engagement during launch

ABSTRACTLaunching a vehicle is related to changing acceleration. High acceleration is desired for sporty driving behavior, however, jerk as change of acceleration and change of jerk are major sources of discomfort. Modern double-clutch transmissions allow to shape the acceleration transition by controlling the torque transmitted by the clutch, which is why the question arises about an optimal transition law for the acceleration and optimal calibration of automatic transmissions. A bi-criterion optimization problem is formulated to account for both sportiness and comfort, where the latter criterion is defined as deviation from an ideal acceleration transition. For finding such an optimal transition, another tri-criterion optimization problem is set up and solved analytically. The calibration of the transmission TCU is then performed in a SIL (Software-in-the-Loop) environment where results demonstrate the validity of the proposed approach.

Dynamic Modeling and Calibration of the Acceleration Sensor Based on System Identification Theory

In the process of acceleration dynamic measurement, the measurement results have quite large dynamic errors, due to the resonance of acceleration sensors. Using the system identification theory and combining with the dynamic calibration experimental data of acceleration calibration system based on Hopkinson bar, the dynamic model of the sensor is deduced, the dynamic compensation filter is designed. Simulation results show that the compensation filter can broaden the work band effectively. It improves the system dynamic response speed by nine times and advances the measuring accuracy of the test system.

A primary standard for low-g shock calibration by laser interferometry

This paper presents a novel implementation of a primary standard for low-g shock acceleration calibration by laser interferometry based on rigid body collision at National Institute of Metrology, China. The mechanical structure of the standard device and working principles involved in the shock acceleration exciter, laser interferometers and virtual instruments are described. The novel combination of an electromagnetic exciter and a pneumatic exciter as the mechanical power supply of the standard device can deliver a wide range of shock acceleration levels. In addition to polyurethane rubber, two other types of material are investigated to ensure a wide selection of cushioning pads for shock pulse generation, with pulse shapes and data displayed. A heterodyne He–Ne laser interferometer is preferred for its precise and reliable measurement of shock acceleration while a homodyne one serves as a check standard. Some calibration results of a standard acceleration measuring chain are shown in company with the uncertainty evaluation budget. The expanded calibration uncertainty of shock sensitivity of the acceleration measuring chain is 0.8%, k = 2, with the peak acceleration range from 20 to 10 000 m s−2 and pulse duration from 0.5 to 10 ms. This primary shock standard can meet the traceability requirements of shock acceleration from various applications of industries from automobile to civil engineering and therefore is used for piloting the ongoing shock comparison of Technical Committee of Acoustics, Ultrasound and Vibration (TCAUV) of Asia Pacific Metrology Program (APMP), coded as APMP.AUV.V-P1.

A Novel Angular Acceleration Sensor Based on the Electromagnetic Induction Principle and Investigation of Its Calibration Tests

An angular acceleration sensor can be used for the dynamic analysis of human and joint motions. In this paper, an angular acceleration sensor with novel structure based on the principle of electromagnetic induction is designed. The method involves the construction of a constant magnetic field by the excitation windings of sensor, and the cup-shaped rotor that cut the magnetic field. The output windings of the sensor generate an electromotive force, which is directly proportional to the angular acceleration through the electromagnetic coupling when the rotor has rotational angular acceleration. The mechanical structure and the magnetic working circuit of the sensor are described. The output properties and the mathematical model including the transfer function and state-space model of the sensor are established. The asymptotical stability of the sensor when it is working is verified by the Lyapunov Theorem. An angular acceleration calibration device based on the torsional pendulum principle is designed. The method involves the coaxial connection of the angular acceleration sensor, torsion pendulum and a high-precision angle sensor, and then an initial external force is applied to the torsion pendulum to produce a periodic damping angle oscillation. The angular acceleration sensor and the angle sensor will generate two corresponding electrical signals. The sensitivity coefficient of the angular acceleration sensor can be obtained after processing these two-channel signals. The experiment results show that the sensitivity coefficient of the sensor is about 17.29 mv/Krad·s2. Finally, the errors existing in the practical applications of the sensor are discussed and the corresponding improvement measures are proposed to provide effective technical support for the practical promotion of the novel sensor.

The Calibration Method of a Large Six-Axis Force Sensors

Based on the accelerator calibration method of six-axis force sensors, the system of static calibration for a large six-axis force sensor is build, The accelerator calibration method are introduced detail. the designed six-axis force sensor in multi-dimensional accelerators field is calibrated and the result is well used. the system of static calibrations a contraption, which is smart cheap and practicality.

Interdevice baseline signal magnitude variability of the ActivPAL3 activity monitor

The aim of this study was to evaluate the interdevice variability in baseline signal magnitude of the ActivPAL3 (PALTechnologies, Glasgow, UK) activity monitor. Twenty consecutively numbered ActivPAL3 triaxial physical activity monitors were assessed for baseline signal magnitudes oriented in the X (vertical standing), Y (side lying), and Z (lying flat) planes. Data was recorded for 60s in each orientation and the three orthogonal axes were analysed for baseline signal magnitude each orientation. Our batch of devices demonstrated approximately 6.6% difference in raw acceleration calibration values compared to manufacturer specifications. Analysis of interdevice variability revealed three devices which exhibited baseline signal variability greater than 1.96SD of the group mean. The impact of interdevice variability in baseline signal magnitude on data collection is unknown, however, supports the argument in the literature for the systematic checking of interdevice variability as routine maintenance.

Analysis of a free‐running synchronization artifact correction for MV‐imaging with aSi:H flat panels

Solid state flat panel electronic portal imaging devices (EPIDs) are widely used for megavolt (MV) photon imaging applications in radiotherapy. In addition to their original purpose in patient position verification, they are convenient to use in quality assurance and dosimetry to verify beam geometry and dose deposition or to perform linear accelerator (linac) calibration procedures. However, native image frames from amorphous silicon (aSi:H) detectors show a range of artifacts which have to be eliminated by proper correction algorithms. When a panel is operated in free-running frame acquisition mode, moving vertical stripes (periodic synchronization artifacts) are a disturbing feature in image frames. Especially for applications in volumetric intensity modulated arc therapy (VMAT) or motion tracking, the synchronization (sync) artifacts are the limiting factor for potential and accuracy since they become even worse at higher frame rates and at lower dose rates, i.e., linac pulse repetition frequencies (PRFs). The authors introduced a synchronization correction method which is based on a theoretical model describing the interferences of the panel's readout clocking with the linac's dose pulsing. Depending on the applied PRF, a certain number of dose pulses is captured per frame which is readout columnwise, sequentially. The interference of the PRF with the panel readout is responsible for the period and the different gray value levels of the sync stripes, which can be calculated analytically. Sync artifacts can then be eliminated multiplicatively in precorrected frames without additional information about radiation pulse timing. For the analysis, three aSi:H EPIDs of various types were investigated with 6 and 15 MV photon beams at varying PRFs of 25, 50, 100, 200, and 400 pulses per second. Applying the sync correction at panels with gadolinium oxysulfide scintillators improved single frame flood field image quality drastically [improvement of the signal-to-noise ratio (SNR) up to 66.1 dB for 6 MV and 66.0 dB for 15 MV]. Also for the EPID with a caesium iodide scintillator, the noise for the lower PRFs could be reduced (SNR at 6 MV of up to 56.3 dB and at 15 MV up to 46.7 dB). However, the simplistic readout interference model fails at higher PRFs, where image lag and ghosting effects due to trapped charges in the thin film transistor and scintillator postglowing require additional corrections. The presented free-running sync correction method improves SNR of single frames and enables imaging applications, like low-dose rate imaging at increased image frame rates (e.g., to track moving gold fiducials in the lung). Adaptive image guided radiotherapy protocols become even feasible in VMAT plans. Also simultaneous kilovolt and MV imaging applications can benefit from new possibilities of MV scatter removal in x-ray images.