Short Acceleration Research Articles

Transverse Dynamics for Super-Rapid Acceleration in Circular High-Energy Particle Accelerators

A new particle acceleration concept had been presented to realize a short acceleration time of µs to produce high-energy muons in circular accelerators. The acceleration method is also expected to accelerate heavy-mass particles with large momentum spread: protons, deuterons, and various heavy ions. It is most important to develop a beam injection method into a main accelerator and to investigate the vertical motion of particles, especially for heavy ion acceleration. The outlines of beam injection method and beam focusing method to solve the vertical divergence problem, which causes the beam loss, are shown in this paper. In addition, a new compact magnet system, which produces magnetic field like a quadrupole field for beam focusing especially in wide aperture accelerators, is also described here.

Lipid suppression via double inversion recovery with symmetric frequency sweep for robust 2D-GRAPPA-accelerated MRSI of the brain at 7 T.

This work presents a new approach for high‐resolution MRSI of the brain at 7 T in clinically feasible measurement times. Two major problems of MRSI are the long scan times for large matrix sizes and the possible spectral contamination by the transcranial lipid signal. We propose a combination of free induction decay (FID)‐MRSI with a short acquisition delay and acceleration via in‐plane two‐dimensional generalised autocalibrating partially parallel acquisition (2D‐GRAPPA) with adiabatic double inversion recovery (IR)‐based lipid suppression to allow robust high‐resolution MRSI. We performed Bloch simulations to evaluate the magnetisation pathways of lipids and metabolites, and compared the results with phantom measurements. Acceleration factors in the range 2–25 were tested in a phantom. Five volunteers were scanned to verify the value of our MRSI method in vivo. GRAPPA artefacts that cause fold‐in of transcranial lipids were suppressed via double IR, with a non‐selective symmetric frequency sweep. The use of long, low‐power inversion pulses (100 ms) reduced specific absorption rate requirements. The symmetric frequency sweep over both pulses provided good lipid suppression (>90%), in addition to a reduced loss in metabolite signal‐to‐noise ratio (SNR), compared with conventional IR suppression (52–70%). The metabolic mapping over the whole brain slice was not limited to a rectangular region of interest. 2D‐GRAPPA provided acceleration up to a factor of nine for in vivo FID‐MRSI without a substantial increase in g‐factors (<1.1). A 64 × 64 matrix can be acquired with a common repetition time of ~1.3 s in only 8 min without lipid artefacts caused by acceleration. Overall, we present a fast and robust MRSI method, using combined double IR fat suppression and 2D‐GRAPPA acceleration, which may be used in (pre)clinical studies of the brain at 7 T. © 2015 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd.

Sparse-grid, reduced-basis Bayesian inversion

Abstract We analyze reduced basis (RB for short) short acceleration of recently proposed sparse Bayesian inversion algorithms for partial differential equations with uncertain distributed parameter, for observation data subject to additive, Gaussian observation noise. Specifically, Bayesian inversion of affine-parametric, linear operator families on possibly high-dimensional parameter spaces. We consider “high-fidelity” Petrov–Galerkin (PG) discretizations of these countably-parametric operator families: we allow general families of inf–sup stable, PG Finite-Element methods, covering most conforming primal and mixed Finite-Element discretizations of standard problems in mechanics. RB acceleration of the high-dimensional, parametric forward response maps which need to be numerically solved numerous times in Bayesian inversion is proposed and convergence rate bounds for the error in the Bayesian estimate incurred by the use of RB are derived. As consequence of recent theoretical results on dimension-independent sparsity of parametric responses, and preservation of sparsity for holomorphic–parametric problems, we establish new convergence rates of greedy RB compressions for both, the parametric forward maps as well as for the countably-parametric posterior densities which arise in Bayesian inversion. We show that the convergence rates for the RB compressions of the parametric forward maps as well as of the countably-parametric, sparse Bayesian posterior densities are free from the curse of dimensionality and depend only on the sparsity of the uncertain input data. In particular, we establish the quadratic convergence of the RB compression for the posterior densities with respect to that for the parametric forward maps. Numerical experiments for linear elliptic, affine-parametric model problems in two space dimensions with hundreds of parameters are reported which confirm that the proposed adaptive sparse grid reduced basis algorithms indeed exploit sparsity of both, the parametric forward maps as well as the Bayesian posterior density.

Towards highest peak intensities for ultra-short MeV-range ion bunches.

A laser-driven, multi-MeV-range ion beamline has been installed at the GSI Helmholtz center for heavy ion research. The high-power laser PHELIX drives the very short (picosecond) ion acceleration on μm scale, with energies ranging up to 28.4 MeV for protons in a continuous spectrum. The necessary beam shaping behind the source is accomplished by applying magnetic ion lenses like solenoids and quadrupoles and a radiofrequency cavity. Based on the unique beam properties from the laser-driven source, high-current single bunches could be produced and characterized in a recent experiment: At a central energy of 7.8 MeV, up to 5 × 108 protons could be re-focused in time to a FWHM bunch length of τ = (462 ± 40) ps via phase focusing. The bunches show a moderate energy spread between 10% and 15% (ΔE/E0 at FWHM) and are available at 6 m distance to the source und thus separated from the harsh laser-matter interaction environment. These successful experiments represent the basis for developing novel laser-driven ion beamlines and accessing highest peak intensities for ultra-short MeV-range ion bunches.

Attonewton force detection using microspheres in a dual-beam optical trap in high vacuum

We describe the implementation of laser-cooled silica microspheres as force sensors in a dual-beam optical dipole trap in high vacuum. Using this system we have demonstrated trap lifetimes exceeding several days, attonewton force detection capability, and wide tunability in trapping and cooling parameters. Measurements have been performed with charged and neutral beads to calibrate the sensitivity of the detector. This work establishes the suitability of dual beam optical dipole traps for precision force measurement in high vacuum with long averaging times, and enables future applications including the study of gravitational inverse square law violations at short range, Casimir forces, acceleration sensing, and quantum opto-mechanics.

“Measurement and Analysis of Indian Road Drive Cycles for Efficient and Economic Design of HEV Component”

Drive cycle pattern is different for different countries which depends on their traffic density, road condition and driver discipline. Drive cycle influences HEV`s components design, sizing and their ratings. Standard drive cycle data doesn't reveal much information to determine efficient and economic design of HEV`s components. In this research paper measurement and analysis of real time Indian road drive cycles (IRDC) are carried out for urban roads, state highway, national highway and express Highway where vehicles have their most run. Real time drive cycle data will expose impact of driver’s skills, traffic, road conditions and short acceleration / deceleration period, which can be represented on drive cycle chart. Analysis of IRDC in terms of rate of acceleration and deceleration, top speed, average speed with road length and analysed mathematically to find energy and power required for acceleration, normal operation and energy harvested during deceleration. Based on information from IRDC HEV`s components initial size are estimated. Initial estimated size is optimized to make HEV`s components design more efficient and economic. Teaching and learning based optimization algorithm (TLBO) and Multi objective genetic algorithm (MOGA) are used to optimize HEV`s components. Constraint of optimization algorithm are like engine and motor rating should be selected such that it has effective top speed with enough acceleration capability and can run enough distance to reach destination according to Indian urban, state, national and express highway pattern where cities are very closed compared with other countries and its regeneration component design should able to harvest maximum deceleration energy. For economic operation of HEV’s, running cost in terms of Rs. / Km. should be minimum.

Universality in ant behaviour.

Prediction for social systems is a major challenge. Universality at the social level has inspired a unified theory for urban living but individual variation makes predicting relationships within societies difficult. Here, we show that in ant societies individual average speed is higher when event duration is longer. Expressed as a single scaling function, this relationship is universal because for any event duration an ant, on average, moves at the corresponding average speed except for a short acceleration and deceleration at the beginning and end. This establishes cause and effect within a social system and may inform engineering and control of artificial ones.

Satellite tagging and biopsy sampling of killer whales at subantarctic Marion Island: effectiveness, immediate reactions and long-term responses.

Remote tissue biopsy sampling and satellite tagging are becoming widely used in large marine vertebrate studies because they allow the collection of a diverse suite of otherwise difficult-to-obtain data which are critical in understanding the ecology of these species and to their conservation and management. Researchers must carefully consider their methods not only from an animal welfare perspective, but also to ensure the scientific rigour and validity of their results. We report methods for shore-based, remote biopsy sampling and satellite tagging of killer whales Orcinus orca at Subantarctic Marion Island. The performance of these methods is critically assessed using 1) the attachment duration of low-impact minimally percutaneous satellite tags; 2) the immediate behavioural reactions of animals to biopsy sampling and satellite tagging; 3) the effect of researcher experience on biopsy sampling and satellite tagging; and 4) the mid- (1 month) and long- (24 month) term behavioural consequences. To study mid- and long-term behavioural changes we used multievent capture-recapture models that accommodate imperfect detection and individual heterogeneity. We made 72 biopsy sampling attempts (resulting in 32 tissue samples) and 37 satellite tagging attempts (deploying 19 tags). Biopsy sampling success rates were low (43%), but tagging rates were high with improved tag designs (86%). The improved tags remained attached for 26±14 days (mean ± SD). Individuals most often showed no reaction when attempts missed (66%) and a slight reaction–defined as a slight flinch, slight shake, short acceleration, or immediate dive–when hit (54%). Severe immediate reactions were never observed. Hit or miss and age-sex class were important predictors of the reaction, but the method (tag or biopsy) was unimportant. Multievent trap-dependence modelling revealed considerable variation in individual sighting patterns; however, there were no significant mid- or long-term changes following biopsy sampling or tagging.

MAGNETIC RECONNECTION TURBULENCE IN STRONG GUIDE FIELDS: BASIC PROPERTIES AND APPLICATION TO CORONAL HEATING

A current sheet susceptible to the tearing instability is used to drive reconnection turbulence in the presence of a strong guide field. Through nonlinear gyrokinetic simulations, the dependencies of central quantities such as the heating rate on parameters like collisionality or plasma β are studied, revealing that linear physics tends to predict only some aspects of the quasi-saturated state, with the nonlinear cascade responsible for additional features. For the solar corona, it is demonstrated that the kinetic heating associated with this type of turbulence agrees quantitatively with observational volumetric heating rates. In the context of short particle acceleration events, the self-consistent emergence of plasmoids or flux ropes in the turbulent bath is found to be important: ubiquitously occurring merger events of these objects cause strong bursts in the heating rate, the timescale of which is consistent with nanoflare observations. Furthermore, anisotropy of the temperature fluctuations is seen to emerge, hinting at a new means of generating coronal ion temperature anisotropy in the absence of cyclotron resonances.

The examination of different tests for the evaluation of the efficiency of the eggbeater kicks.

The eggbeater kick presents an important basic technical skill in water polo. The aim of this study was to examine some different tests in order to recommend the best ones for the evaluation of the eggbeater kick. Twenty eight young male water polo players performed one test (squat jump) on land and ten tests in water: tethered swimming with legs only, using alternating and simultaneous eggbeater kicks, jumps out of water from basic and vertical (arms vertically above the head) position, water start and swimming two meters and swimming horizontally with legs only five meters with a flying start. The differences between tests were checked by executing dependent t-tests, while Pearson‘s correlation coefficients were calculated to evaluate the correlation between different parameters. Results showed that when performing alternate eggbeater kicks greater average forces were produced by the water polo players when compared to consecutive simultaneous eggbeater kicks. However, a short time maximal acceleration of the body in the vertical and horizontal plane was greater when the single simultaneous kick was performed. It was determined that horizontal swimming using legs only and a squat jump were less useful for the evaluation of the eggbeater kick. Therefore, the recommendation was to measure the average force of successive alternating eggbeater kicks, the height of the jump out of the water from the basic position and the water start and swim over a distance of 2 meters.

Velocity-Toughening and Crack Speed Oscillations in the Dynamic Fracture of PMMA Plates

To study the propagating behavior of a dynamic crack in brittle materials, an experimental technique was developed that measures the propagation speed of a fast crack in a preloaded brittle strip. The specimen is a rectangular PMMA plate clamped by two heavy steel fixtures that are attached to a MTS test machine. After the specimen was tensile loaded to a prescribed load level, a sharp crack was initiated at the middle point on one side of the specimen. Due to the brittleness of the material, the crack propagates quickly across the specimen. The propagation velocity of the crack was measured by using the equally spaced conductive lines that were painted on the specimen surface before the tests. High speed video camera was also used for monitoring the propagation behavior of the cracks. The experimental results show that for each preloaded plate, the crack arrives at a steady velocity v0 after a short acceleration stage. In the steady stage crack propagation is in self-similar state. The steady velocity of the crack was found to be an increasing function of the energy Gc stored in the preloaded strip, which means that the material has a "velocity-toughening" property. When the crack speed exceeds a threshold, the crack exhibits apparent speed oscillations. This speed oscillation corresponds to the occurrence of the periodic grooves on the fractured surface. Further increase of the preload results in the bending, micro branching, and full bifurcations of the crack paths.

Design study of electron cyclotron resonance-ion plasma accelerator for heavy ion cancer therapy

Electron Cyclotron Resonance-Ion Plasma Accelerator (ECR-IPAC) device, which theoretically can accelerate multiple charged ions to several hundred MeV with short acceleration length, has been proposed. The acceleration mechanism is based on the combination of two physical principles, plasma electron ion adiabatic ejection (PLEIADE) and Gyromagnetic Autoresonance (GYRAC). In this study, we have designed the proof of principle machine ECR-IPAC device and simulated the electromagnetic field distribution generating in the resonance cavity. ECR-IPAC device consisted of three parts, ECR ion source section, GYRAC section, and PLEIADE section. ECR ion source section and PLEIADE section were designed using several multi-turn solenoid coils and sextupole magnets, and GYRAC section was designed using 10 turns coil. The structure of ECR-IPAC device was the cylindrical shape, and the total length was 1024 mm and the maximum diameter was 580 mm. The magnetic field distribution, which maintains the stable acceleration of plasma, was generated on the acceleration center axis throughout three sections. In addition, the electric field for efficient acceleration of electrons was generated in the resonance cavity by supplying microwave of 2.45 GHz.

A New Method for Feedback on the Quality of Chest Compressions during Cardiopulmonary Resuscitation

Quality of cardiopulmonary resuscitation (CPR) improves through the use of CPR feedback devices. Most feedback devices integrate the acceleration twice to estimate compression depth. However, they use additional sensors or processing techniques to compensate for large displacement drifts caused by integration. This study introduces an accelerometer-based method that avoids integration by using spectral techniques on short duration acceleration intervals. We used a manikin placed on a hard surface, a sternal triaxial accelerometer, and a photoelectric distance sensor (gold standard). Twenty volunteers provided 60 s of continuous compressions to test various rates (80–140 min−1), depths (3–5 cm), and accelerometer misalignment conditions. A total of 320 records with 35312 compressions were analysed. The global root-mean-square errors in rate and depth were below 1.5 min−1 and 2 mm for analysis intervals between 2 and 5 s. For 3 s analysis intervals the 95% levels of agreement between the method and the gold standard were within −1.64–1.67 min−1 and −1.69–1.72 mm, respectively. Accurate feedback on chest compression rate and depth is feasible applying spectral techniques to the acceleration. The method avoids additional techniques to compensate for the integration displacement drift, improving accuracy, and simplifying current accelerometer-based devices.

Control of seeding phase for a cascaded laser wakefield accelerator with gradient injection

We demonstrated experimentally the seeding-phase control for a two-stage laser wakefield accelerator with gradient injection. By optimizing the seeding phase of electrons into the second stage, electron beams beyond 0.5 GeV with a 3% rms energy spread were produced over a short acceleration distance of ∼2 mm. Peak energy of the electron beam was further extended beyond 1 GeV by lengthening the second acceleration stage to 5 mm. Time-resolved magnetic field measurements via magneto-optical Faraday polarimetry allowed us to monitor the processes of electron seeding and acceleration in the second stage.

Metabolic states in athletes during alternate intense muscular activity

The dynamics of metabolic states in athletes during alternate intense muscular activity was studied. In a laboratory, highly trained athletes (cyclists and speed skaters) performed tests on a bicycle ergometer at the level of the critical power and maximal oxygen consumption. In two additional series of experiments, each of the subjects performed tests at the level of critical power with initial acceleration of 28% of the maximal duration of the 45- and 108-s exercises. During the exercise when the subjects worked at critical power, a succession of metabolic phases was observed: the initial lag period, rapid exponential growth to the level of critical power, subsequent maintenance of the critical power, and, finally, functional disorders of aerobic metabolism, along with increasing local fatigue. We found that a short (no more than 10 s) initial acceleration at the level of power equal to the 45-s maximal exercise is the most efficient for performance at the level of critical power maintenance; this acceleration stimulates the development of aerobic metabolism and does not lead to depletion of anaerobic resources or considerable local exhaustion at the end of the performance.

Precomputed acceleration noise for improved rigid-body sound

We introduce an efficient method for synthesizing acceleration noise -- sound produced when an object experiences abrupt rigid-body acceleration due to collisions or other contact events. We approach this in two main steps. First, we estimate continuous contact force profiles from rigid-body impulses using a simple model based on Hertz contact theory. Next, we compute solutions to the acoustic wave equation due to short acceleration pulses in each rigid-body degree of freedom. We introduce an efficient representation for these solutions -- Precomputed Acceleration Noise -- which allows us to accurately estimate sound due to arbitrary rigid-body accelerations. We find that the addition of acceleration noise significantly complements the standard modal sound algorithm, especially for small objects.

Precomputed acceleration noise for improved rigid-body sound

We introduce an efficient method for synthesizing acceleration noise -- sound produced when an object experiences abrupt rigid-body acceleration due to collisions or other contact events. We approach this in two main steps. First, we estimate continuous contact force profiles from rigid-body impulses using a simple model based on Hertz contact theory. Next, we compute solutions to the acoustic wave equation due to short acceleration pulses in each rigid-body degree of freedom. We introduce an efficient representation for these solutions -- Precomputed Acceleration Noise -- which allows us to accurately estimate sound due to arbitrary rigid-body accelerations. We find that the addition of acceleration noise significantly complements the standard modal sound algorithm, especially for small objects.

Failure Diagnosis of a Gear Box by Recurrences

The recurrence analysis method is used in the mechanical diagnosis of a gear transmission system using time domain data. The recurrence is a natural behavior of a periodic motion system, which tells the state of the system, after running some time, and will approach a certain past state. In this paper, some statistical parameters of recurrence qualification analysis are extensively evaluated for the use of mechanical diagnosis, based on fairly short acceleration time series; recurrence results are compared with those obtained from Fourier analysis, and the identification procedures for the failure gear transmission by recurrences is also presented. It is found that, using only fairly short time series, some statistical parameters in quantification recurrence analysis can give clear-cut distinction between a healthy and damaged state.

The Effect of Assisted and Resisted Sprint Training on Acceleration and Velocity in Division IA Female Soccer Athletes

This investigation evaluated the effects of a 4-week, 12-session training program using resisted sprint training (RST), assisted sprint training (AST), and traditional sprint training (TST) on maximal velocity and acceleration in National Collegiate Athletic Association (NCAA) Division IA female soccer athletes (n = 27). The subjects, using their respective training modality, completed 10 maximal effort sprints of 20 yd (18.3 m) followed by a 20-yd (18.3 m) deceleration to jog. Repeated measures multivariate analyses of variance and analyses of variance demonstrated significant (p < 0.001) 3-way interactions (time × distance × group) and 2-way interactions (time × group), respectively, for both velocity and acceleration. Paired t-tests demonstrated that maximum 40-yd (36.6-m) velocity increased significantly in both the AST (p < 0.001) and RST (p < 0.05) groups, with no change in the TST group. Five-yard (4.6-m), 15-yd (13.7 m), 5- to 15-yd (4.6- to 13.7-m) acceleration increased significantly (p < 0.01) in the AST group and did not change in the RST and TST groups. Fifteen- to 25-yd (13.7- to 22.9-m) acceleration increased significantly (p < 0.01) in the RST group, decreased significantly (p < 0.01) in the AST group, and was unchanged in the TST group. Twenty-five to 40-yd (22.9- to 36.6-m) acceleration increased significantly (p < 0.05) in the RST group and remained unchanged in the AST and TST groups. It is purposed that the increased 5-yd (4.6-m) and 15-yd (13.7-m) accelerations were the result of enhanced neuromuscular facilitation in response to the 12-session supramaximal training protocol. Accordingly, it is suggested that athletes participating in short distance acceleration events (i.e., ≤15 yd; ≤13.7 m) use AST protocols, whereas athletes participating in events that require greater maximum velocity (i.e., >15 yd; > 13.7 m) should use resisted sprint training protocols.

Erratum: Interpretation of ultrafast pump-probe terahertz experiments in the time domain: How to exploit two-dimensional correlations [Phys. Rev. B83, 205111 (2011)

These errors do not at all affect the results and conclusions presented in Ref. 1. In the remainder of this Erratum, we provide a physical interpretation of Eq. (1), which expresses the differential field E in terms of the excited population, the driving field E0, and the Green function G (the response of a charge to an infinitely short acceleration). In Eq. (1), t represents the time at which the differential field E is probed, and t − τ represents the time at which the pump beam (assumed infinitely short) excites the sample. The differential field vanishes whenever the probe precedes the pump (τ < 0). The electric far field produced by a sheet of phased oscillators is proportional to the oscillators’ current. In Eq. (1), the current is calculated as a temporal integral over all velocity contributions Ġ due to infinitely short accelerations (δ kicks) exerted by the driving field E0. For a given value of the integration variable t′, the δ kick occurs at time t − t′, and the driving field exerts a force on the charge proportional to E0(t − t ′). The charge responds to this force with a velocity proportional to Ġ. At time t, which is a time lapse t′ later than the δ kick, the velocity of the charge is proportional to Ġ(t ′). The interpretation of Eq. (1) is more complicated when the excited population decays in time. Figure 1 shows three population profiles as a function of time. For a decaying population (continuous line), the population at time t is a subpopulation of that at time t − t′. Hence, the population of charges giving rise to the differential field at time t is a FIG. 1. (Color online) The three times for Eq. (1). The differential field is evaluated at time t. The charge is accelerated by the driving field at time t − t′. The population is created by the pump pulse at time t − τ . Three population profiles are depicted: an exponentially decaying profile (continuous line), a constant profile (dashed line), and a growing profile (dotted line).