Acceleration Calibration Research Articles

Start and acceleration optimization of a parallel hybrid electric vehicle

The main issues relating to hybrid electric vehicle (HEV) emissions are starting and transient air-fuel ratio (AFR) control. The idle-cancelling function of an HEV will postpone the catalyst activation at cold start. So it is vital to confine the start emission to a much lower level. The conventional transient fuel also dramatically deteriorates emissions. The start and transient acceleration control strategies were developed on a uni-axis integrated starter–generator (ISG) parallel HEV. The optimization of each stage of the start process was realized. The start parameters of the engine controller (ECU) and vehicle controller (VCU) were determined by analysing unsuccessful starts. The results show that the engine starts smoothly without much speed overshoot. The AFR is superior to that of the prototype vehicle. At warming-up start and hot start there is also a smooth transition from ambient oxygen ratio to stoichiometric AFR. The concept is introduced of ‘fast’ and ‘slow’ torque to ISG boost acceleration. The conventional engine fuel wetting effect is overcome by ISG boost. The engine transient fuel and acceleration fuel compensation (AFC) for vehicle acceleration were replaced by ISG transient torque and continuous torque. The ISG boost acceleration calibration was completed and validated the result that the transient AFR was optimized without sacrificing vehicle drivability or acceleration performance. Both ISG start and ISG boost acceleration are effective approaches to solve the problem of HEV emission.

Discrimination between Upstairs and Downstairs Based on Accelerometer

An algorithm for the discrimination between human upstairs and downstairs using a tri-axial accelerometer is presented in this paper, which consists of vertical acceleration calibration, extraction of two kinds of features (Interquartile Range and Wavelet Energy), effective feature subset selection with the wrapper approach, and SVM classification. The proposed algorithm can recognize upstairs and downstairs with 95.64% average accuracy for different sensor locations, i.e. located on the subject's waist belt, in the trousers pocket, and in the shirt pocket. Even for the mixed data from all sensor locations, the average recognition accuracy can reach 94.84%. Experimental results have successfully validated the effectiveness of the proposed method.

衝撃加速度を用いた加速度計校正のラウンドロビンテスト―国家標準にトレーサブルな衝撃加速度校正システムの開発―

Shock acceleration measurement is widely carried out in a variety of applications such as air-bag control of automobiles or drop testing of mobile instruments, in which accelerometers are a key device to evaluate human safety or product reliability. However, despite the fact that accelerometers have the non-linear sensitivity in relation to frequency and acceleration level, many Japanese private laboratories calibrate accelerometers by the means of comparison calibration in which each reference is traceable to different oversea national standards. Since it is difficult for comparison calibration to evaluate the non-linear characteristic, we developed the shock acceleration calibration system with Japanese time and length standards for primary calibration. In order to enhance the reliability of shock acceleration measurement, it is essential to confirm the equivalence of accelerometer's calibration results between primary and comparison calibrations. So, a round robin test was executed among the National Institute of Advanced Industrial Science and Technology (AIST) and the three Japanese private laboratories. The calibration results among the four laboratories were matched within a difference of 0.17% and En value of 0.58. Also, the non-linear characteristic did not affect the calibration results on the experimental condition of this round robin test.

Calibration of vibration pick-ups with laser interferometry: part IV. Development of a shock acceleration exciter and calibration system

Measuring shock acceleration with peak accelerations ranging from 200 to 5000 m s−2 is a significant concern for mechanical or electrical applications in industries. To precisely calibrate accelerometers using shock acceleration, we developed a shock acceleration calibration system at the National Metrology Institute of Japan. In the calibration system, the shock acceleration exciter generates shock acceleration using rigid-body collisions between three metallic bars inside an air bearing. The pick-up to be calibrated is fixed on an edge surface of the third metallic bar so that the pick-up moves together with the metallic bar. The displacement of the pick-up is measured by a He–Ne laser interferometer with traceable voltage, length and time standards. The sensitivity of the pick-up is evaluated by analysing signals from the accelerometer and laser interferometer. We describe the calibration procedure, the specification of the shock acceleration calibration system and the uncertainty in the shock-acceleration calibration. The shock acceleration calibration result has the expanded uncertainty of roughly 1.0% with a coverage factor 2 and is comparable to the vibration acceleration calibration result with an En value below 0.3.

Calibration of solid state nuclear track detector CR-39 with monoenergetic protons

用北京师范大学2×1.7MV串列加速器和400 kV高压倍加器产生的20—1020 keV单能质子束对CR-39固体核径迹探测器进行了刻度.为了保证质子的单能性和固体核径迹探测器上径迹密度不能超过106/cm2的要求，对两台加速器分别采用了不同方法控制质子辐照数量.在串列加速器上采用了狭缝加转盘的方法，在高压倍加器上采用了100 ns单次高压脉冲扫描束流的方法，既保持了质子的单色性，又达到了质子注量小于106/cm2的

High-precision Radiocarbon Dating with Accelerator Mass Spectrometry and Calibration of Radiocarbon Ages

High-resolution as well as high-precision age estimation is particularly important for Quaternary research to realize its main aim of better understanding of global environmental changes of the past and realistic prediction of the changes in the near future. Among several dating methods that are applicable to Quaternary samples, radiocarbon (14C) dating has been commonly used since its development in late 1940s.A new 14C detection technique, accelerator mass spectrometry (AMS), has been developed since 1977. The method directly detects and counts 14C atoms, instead of counting β-ray emitted in the decay of 14C, and therefore requires only a few mg of carbon for 14C measurements. Nowadays, AMS 14C dating is widely used and more than sixty AMS 14C facilities are in operation in the world. In Japan, eight facilities for AMS 14C dating have been in use since 2004.As one of the eight AMS 14C measurement systems in Japan, the Nagoya University AMS group has started routine 14C measurements with the firstly introduced Tandetron AMS system since 1983 and also with the secondly established Tandetron AMS since 1999. The second system has an excellent performance of the standard deviation (one sigma) of the 14C/12C ratios of around ±0.2% to ±0.4% (±17-±30 14C yrs) and that of the corresponding 13C/12C ratios of ±0.03% to ±0.07%, as are tested for HOxII targets. By using this AMS system, we are now trying to provide accurate ages to the Quaternary events. Briefly discussed in this article are, (1) a consistency test of the established IntCal98 and IntCal04 14C data sets with the 14C-concentration records in Japanese tree rings ; (2) programs of high accuracy and precision age estimation by 14C wiggle matching techniques for wood samples ; (3) investigations of 14C reservoir effect for marine samples from the Japanese Archipelago.

Precise measurement of the differential cross section from the O16(α,α)O16 elastic reaction at 165° and 170° between 2.4 and 6.0MeV

Non-Rutherford cross section for elastic scattering of α particles from oxygen has been measured for energies between 2.4 and 6.0MeV at commonly used backscattering angles of 165° and 170°. High precision in energy has been obtained with a 2MV Tandetron accelerator, with precise and stable energy calibration. The choice of a thin Ta2O5∕Ta∕C standard increased the sensitivity and reduced systematic errors due to the geometry. Precise data for energy, width, and ratio to Rutherford of the resonances have been extracted from nuclear shell models, and excitation levels of Ne20 have been deduced. The well-known resonance ER=3031.7±0.5keV and the narrow and intense resonance ER=5375.5±0.5keV, not included in cross-section libraries, have been applied for surface oxygen analysis in thin WCN∕SiO2∕Si multilayer samples, with improved depth resolution by optimizing the measuring geometry.

Ionization chamber dosimetry of small photon fields: a Monte Carlo study on stopping-power ratios for radiosurgery and IMRT beams

Absolute dosimetry with ionization chambers of the narrow photon fields used in stereotactic techniques and IMRT beamlets is constrained by lack of electron equilibrium in the radiation field. It is questionable that stopping-power ratio in dosimetry protocols, obtained for broad photon beams and quasi-electron equilibrium conditions, can be used in the dosimetry of narrow fields while keeping the uncertainty at the same level as for the broad beams used in accelerator calibrations. Monte Carlo simulations have been performed for two 6 MV clinical accelerators (Elekta SL-18 and Siemens Mevatron Primus), equipped with radiosurgery applicators and MLC. Narrow circular and Z-shaped on-axis and off-axis fields, as well as broad IMRT configured beams, have been simulated together with reference 10 × 10 cm2 beams. Phase-space data have been used to generate 3D dose distributions which have been compared satisfactorily with experimental profiles (ion chamber, diodes and film). Photon and electron spectra at various depths in water have been calculated, followed by Spencer-Attix (Δ = 10 keV) stopping-power ratio calculations which have been compared to those used in the IAEA TRS-398 code of practice. For water/air and PMMA/air stopping-power ratios, agreements within 0.1% have been obtained for the 10 × 10 cm2 fields. For radiosurgery applicators and narrow MLC beams, the calculated sw,air values agree with the reference within ±0.3%, well within the estimated standard uncertainty of the reference stopping-power ratios (0.5%). Ionization chamber dosimetry of narrow beams at the photon qualities used in this work (6 MV) can therefore be based on stopping-power ratios data in dosimetry protocols. For a modulated 6 MV broad beam used in clinical IMRT, sw,air agrees within 0.1% with the value for 10 × 10 cm2, confirming that at low energies IMRT absolute dosimetry can also be based on data for open reference fields. At higher energies (24 MV) the difference in sw,air was up to 1.1%, indicating that the use of protocol data for narrow beams in such cases is less accurate than at low energies, and detailed calculations of the dosimetry parameters involved should be performed if similar accuracy to that of 6 MV is sought.

The effects of radiotherapy treatment uncertainties on the delivered dose distribution and tumour control probability.

Uncertainty in the precise quantity of radiation dose delivered to tumours in external beam radiotherapy is present due to many factors, and can result in either spatially uniform (Gaussian) or spatially non-uniform dose errors. These dose errors are incorporated into the calculation of tumour control probability (TCP) and produce a distribution of possible TCP values over a population. We also study the effect of inter-patient cell sensitivity heterogeneity on the population distribution of patient TCPs. This study aims to investigate the relative importance of these three uncertainties (spatially uniform dose uncertainty, spatially non-uniform dose uncertainty, and inter-patient cell sensitivity heterogeneity) on the delivered dose and TCP distribution following a typical course of fractionated external beam radiotherapy. The dose distributions used for patient treatments are modelled in one dimension. Geometric positioning uncertainties during and before treatment are considered as shifts of a pre-calculated dose distribution. Following the simulation of a population of patients, distributions of dose across the patient population are used to calculate mean treatment dose, standard deviation in mean treatment dose, mean TCP, standard deviation in TCP, and TCP mode. These parameters are calculated with each of the three uncertainties included separately. The calculations show that the dose errors in the tumour volume are dominated by the spatially uniform component of dose uncertainty. This could be related to machine specific parameters, such as linear accelerator calibration. TCP calculation is affected dramatically by inter-patient variation in the cell sensitivity and to a lesser extent by the spatially uniform dose errors. The positioning errors with the 1.5 cm margins used cause dose uncertainty outside the tumour volume and have a small effect on mean treatment dose (in the tumour volume) and tumour control.

A new detector for the measurement of the energy spectrum of cosmic ray nuclei in the TeV region

A new instrument for direct measurements of the individual energy spectra of heavy cosmic-ray nuclei in the energy range from 10 11 to several 10 14 eV shall be described. The instrument performance is discussed, using first results from a 28-hour balloon flight and from an accelerator calibration.

Assessment of physics quality assurance in United States radiotherapy facilities and comparison with American College of Radiology Standard for Radiation Oncology Physics for External Beam Therapy

We have assessed radiation therapy physics quality assurance (QA) elements in the United States and compared the results with the Patterns of Care Study (PCS) Consensus Guidelines for Treatment Planning and the American College of Radiology (ACR) Standard for Radiation Oncology Physics for External Beam Therapy. Data were obtained during PCS site visits to 73 facilities randomly selected from the 1,321 radiation therapy facilities in the United States: 21 academic, 26 hospital, and 26 freestanding. The following is a representative sample of results. The estimated national averages for facilities having QA programs for treatment planning systems, simulators, accelerators, film processors, and blocking systems are 44%, 79%, 94%, 62%, and 55%, respectively. Only 63% of facilities obtain an independent check of their accelerator calibrations from a source outside the facilities obtain an independent check of their accelerator calibrations from a source outside the facility. Twenty-six percent of facilities surveyed did not have in vivo dosimetry capability. These results and others in the study were compared with PCS consensus guidelines and ACR standards, This is the first such study performed in the United States, and the results establish a baseline for future studies. A recommendation for a comprehensive national physics QA study is based on deficiencies found in this study and the implementation of new technologies in radiation therapy.

The gamma-ray telescope Gamma-1

The telescope ‘Gamma-1’ is designed to investigate cosmic gamma rays in the energy range from 50 MeV to 5000 MeV. The geometrical sensitive area of the telescope amounts to 1500 cm2, the angular resolution in each direction is equal to 1.2° at the energy 300 MeV and is about 20′ when including a coded mask in the telescope, the energy resolution changes from 70% at 100 MeV to 35% at 550 MeV. The characteristics of the telescope and its systems have been determined by the Monte-Carlo method as well as by accelerator calibrations. Discrete sources at the intensity level of 10−7 quanta cm−2 s−1 may be recorded in a year of observations with the gamma-ray telescope ‘Gamma-1’ with a source location accuracy of ≈ 10 arc min.

A silicon surface barrier telescope for solar energetic particle analysis

The characteristics and accelerator calibration results of a laboratory model of a heavy ion detector telescope developed to identify energetic solar particles and low energy cosmic rays by the ΔE− E method are presented.

Search for heavy long-lived particles in high-energy cosmic rays

We present the results of an experimental search for energetic particles which arrive at sea level delayed with respect to the shower front, with an order of magnitude greater exposure than previous experiments. The experiment was sensitive to showers from cosmic rays between ${10}^{5}$ and ${10}^{7}$ GeV per nucleus. Events with signals greater than 20 equivalent particles and delayed more than 20 ns were observed and studied. A four-dimensional Monte Carlo simulation of cosmic-ray showers combined with accelerator calibration data showed that the observed events as well as previously reported observations of this type can be accounted for by rare fluctuations in signals from low-energy hadrons in the air shower. No evidence for the existence of heavy long-lived particles in air showers was found. We set an upper limit to the flux of these particles at the 90% confidence level of 1.4\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}12}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$${\mathrm{sr}}^{\mathrm{\ensuremath{-}}1}$${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$.

The observation of the galactic anticenter region by the balloon borne gamma-ray telescope Natalya-I

This paper presents the results of measurements of gamma radiation with energies above 5 MeV, from the galactic anticenter region. The balloon-borne gamma ray telescope “Natalya-I”, was launched on 6 November, 1980 from the Tata Institute of Fundamental Research's Balloon Facility (Hyderabad, India) and reached ceiling altitude of 35 km. The results on the accelerator calibration of the telescope, using a “tagged” gamma ray beam are also presented.

Phosphorus activation neutron dosimetry and its application to an 18‐MV radiotherapy accelerator

Neutron fluxes and dose rates in and near the 18-MV x-ray beam of a Therac-20 accelerator were determined with measured activities from the nuclear reactions 31P(n, rho)31Si (fast neutrons) and 31P(n, gamma)32P (thermal neutrons), published cross sections, and neutron energy spectra from Monte Carlo calculations. Measurements were made in the patient plane in air and at a 10-cm depth in a tissue-similar phantom, and in a plane containing the x-ray target. Orthophosphoric acid solution was identified as a suitable and convenient phosphorus dosimeter material. In the 31P activation method, fluxes and dose rates are determined as the product of measured saturation activity per 31P atom and a conversion factor, which depends on the shape of the assumed neutron spectrum. For fast neutrons, which deliver most of the dose, the accuracy error in the saturation activity determinations was shown to be approximately less than 25%. An inconsistency resulting from neglect of the accelerator's adjustable collimator in the Monte Carlo calculations was demonstrated between the measured saturation activities and the theoretical neutron spectra. The maximum neutron dose equivalent rate observed was 5.9 mSv/Gy of x-ray absorbed dose at the accelerator calibration point. Surface dose equivalent rates of the present study are less than those of fluxmeter and remmeter studies at sites outside Therac-20 treatment fields by as much as factors of 2.4 and 2.8, respectively. The phantom study showed that at 18 MV internally produced neutrons have a negligible effect on the neutron field within the patient.

EOSCOR III, a High Energy Solar Neutron Detector

A light weight high energy neutron detector has been developed for the observation of 20-150 MeV solar flare neutrons on a long duration Sky Anchor balloon flight. It consists of two 1 m2 plastic scintillators separated by a 1 m time-of-flight path to detect the protons from n-p scattering and 12C(n, pX) interactions in the upper scintillator. Adiabatic isochronous light pipes view the scintillators. Time-of-flight and pulse height analysis are used to measure the proton velocity, to discriminate against albedo events, and to separate the slower moving protons from Compton electrons. The Monte Carlo efficiency calculations are compared with accelerator calibration results using mono-energetic neutrons. Some results from short duration high altitude balloon observations are presented.

Thermal iron ions in high speed solar wind streams: Detection by the IMP 7/8 energetic particle experiments

The first measurements of the abundance of iron ions in high speed (> 600 km s−1) solar wind streams have been made with the NOAA/JHU Energetic Particles Experiments (EPE) on IMP 7/8. The identification of iron ions is quantitatively established using 4 years of observations and heavy ion accelerator calibrations of detectors similar to those flown on the spacecraft. Preliminary estimates of the Fe/H ratio are within a factor of 2 of the adopted coronal abundance (5 × 10−5), and there is some evidence that Fe/H may remain approximately constant within a given stream. In the peaks of fast streams (700 < V < 800 km s−1), about 50 iron ion counts are obtained every 20 s, offering the possibility of studying the Fe/H ratio with ∼ 1 m time resolution in high speed streams throughout the decline of Solar Cycle 20 and the rise of Solar Cycle 21.

Linear accelerator calibration monitor with a memory.

A calibration monitor has been designed for measuring the constancy of linear accelerator or cobalt unit output between full calibrations. This monitor is battery operated, light-weight and slides into the shadow tray attachment on a linear accelerator or cobalt unit for easy setup. It provides a digital readout of the dose delivered, and a consistency check can be made in less than two minutes. The precision of the monitor, determined by cobalt-60 irradiations over a 2 1/2 period, is +/- 0.6% (standard deviation). The monitor also retains the dose reading in a CMOS digital counter indefinitely, hence it can be used in the same fashion as mailed thermoluminescent dosimeters (TLD) for calibration checks at remote facilities without the complicated readout procedures associated with TLD. The monitor can be mailed to a remote facility, positioned without ambiguity, and irradiated; and the reading can be verified on return to the originating center simply by pressing a switch. The monitor can easily be set up to carry out a "blind" check in which the reading obtained is not known to the remote facility.

(p,n) threshold measurements for accelerator calibration and the problem of Q-value deductions

The self-consistent values for the thresholds of a number of (p,n) reactions, obtained by Overley et al. from their calibration of the analysing magnet of the Yale MP Tandem accelerator, are examined in the light of more recent work on absolute threshold measurements. A revised set of values, appropriate for accelerator calibrations, is derived. Problems in converting these results to reliable Q-values and mass differences, because of possible systematic errors due to resonance effects in the (p,n) reactions close to the true thresholds, are discussed.