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Journal articles on the topic 'Acceleration'
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1
Rosi, Giuseppe A., and David E. Rival. "Entrainment and topology of accelerating shear layers." Journal of Fluid Mechanics 811 (December 6, 2016): 37–50. http://dx.doi.org/10.1017/jfm.2016.716.
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A constantly accelerating circular plate was investigated towards understanding the effect of non-stationarity on shear-layer entrainment and topology. Dye visualizations and time-resolved particle image velocimetry measurements were collected for normalized accelerations spanning three orders of magnitude. Increasing acceleration acts to organize shear-layer topology. Specifically, the Kelvin–Helmholtz instabilities within the shear layer better adhered to a circular path and exhibited consistent and repeatable spacing. Normalized starting-vortex circulation was observed to collapse with increasing acceleration, which one might not expect due to increased levels of mixing at higher instantaneous Reynolds numbers. The entrainment rate was shown to increase nonlinearly with increasing acceleration. This was attributed to closer spacing between instabilities, which better facilitates the roll-up of fluid between the shear layer and vortex core. The shear-layer organization observed at higher accelerations was associated with smaller spacings between instabilities. Specifically, analogous point-vortex simulations demonstrated that decreasing the spacing between instabilities acts to localize and dampen perturbations within an accelerating shear layer.
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Ashanina, I. A., Yu D. Kluchevskaia, S. M. Polozov, and V. I. Rashchikovd. "Optimization of electrodynamic characteristics of the linear electron accelerator at an energy 8–50 MeV with injection from an electron source based on cluster plasma systems." Seriya 3: Fizika, Astronomiya, no. 1_2023 (June 2, 2023): 2310402–1. http://dx.doi.org/10.55959/msu0579-9392.78.2310402.
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One of the key problems of contemporary accelerator physics has been an increase of the rate of the energy gain in linear electron accelerators. The physical limits of the accelerating field intensity for the normal and superconducting accelerating structures have been practically reached; therefore, new acceleration schemes are being considered, primarily acceleration in plasma and wakefield acceleration. It is suggested to consider an opportunity using of a bunch generated in a laser-plasma channel for injection into a traditional metal structure. It has been shown that an electron source based on a cluster plasma can generate a short (from 0.1 to 1.0 ps) electron bunch with an energy of several hundred keV, which makes it possible to consider such a source as an alternative to a photocathode. Next, the beam must be captured in the acceleration mode and accelerated up to an energy of 50 MeV with the possibility of energy tuning. The features of such accelerator, the features of the electron bunch capturing in the acceleration mode, and the possible values of the energy spectrum in such a system will considered. The features of such a source, including the possible energy spectrum, the features of the electron bunch capturing with an extremely wide spectrum in the acceleration mode, as well as the electrodynamic characteristics of the accelerating structures are considered in the paper. The beam dynamics simulation was carried out using the BEAMDULAC package developed at the Department of Electrophysical Facilities of the National Research Nuclear University MEPhI. The main results of the optimization of electrodynamic characteristics of the accelerating structures was also reported.
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Ashanin, Ilya A., Yulia D. Kluchevskaia, Sergey M. Polozov, and Vladimir I. Rashchikov. "Linear electron accelerator for energy 8-50 MeV with injection from an electron source based on cluster plasma systems." Vestnik of Saint Petersburg University. Applied Mathematics. Computer Science. Control Processes 18, no. 4 (2022): 443–86. http://dx.doi.org/10.21638/11401/spbu10.2022.403.
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For many years, one of the key problems of modern accelerator physics has been an increase of the rate of the energy gain in RF linear electron accelerators. The physical limits of the accelerating field intensity for metallic accelerating structures have been practically reached; therefore, new acceleration schemes are being considered, primarily acceleration in plasma and wakefield acceleration. The second aim is the generation of ultrashort (100 fs and less) electron bunches, for which RF photoguns are traditionally used. In this case, for RF photoguns, a serious problem that limits the intensity of electrons in a bunch is the influence of the own space charge during emission and acceleration in the near-cathode region, where the beam is weakly relativistic and the influence of the space charge on its dynamics plays the determinative role. The possibility of using a plasma cathode source as an injector for RF accelerator will considered. In the future, this may make it possible to bypass the limitations inherent in RF photoguns (sufficient influence of the space charge on the beam dynamics in the near-cathode region) and acceleration in the laser-plasma channel (low electron capture coefficient in the acceleration mode, wide energy spectrum - 10% or more at energies of tens and hundreds of megaelectrons). It is proposed to develop a combined accelerator in which a bunch generated in a laser-plasma channel is injected into a traditional metal structure. It is supposed that could be possible to generate a short (from 0.1 to 1.0 ps) electron bunches with an energy of several hundred kiloelectrons, which will make it possible to consider such source as an alternative to the photocathode. Next, the beam must be captured in the acceleration mode in a normally conducting section and accelerated to an energy of 50 MeV with the possibility of energy tuning. The features of such accelerator, the features of the electron bunch capturing in the acceleration mode, and the possible values of the energy spectrum in such a system will considered.
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Golovanov, A. A., E. N. Nerush, and I. Yu Kostyukov. "Radiation reaction-dominated regime of wakefield acceleration." New Journal of Physics 24, no. 3 (2022): 033011. http://dx.doi.org/10.1088/1367-2630/ac53b9.
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Abstract We study electron acceleration in a plasma wakefield under the influence of the radiation-reaction force caused by the transverse betatron oscillations of the electron in the wakefield. Both the classical and the strong quantum-electrodynamic (QED) limits of the continuous radiation reaction are considered. For the constant accelerating force, we show that the amplitude of the oscillations of the QED parameter χ in the radiation-dominated regime reaches an equilibrium value determined only by the magnitude of the accelerating field, while the averaged over betatron oscillations radiation reaction force saturates at a value smaller than the accelerating force and thus is incapable of stopping acceleration. We find the parameters of the electron bunch and the plasma accelerator for which reaching such a regime is possible. We also study effects of the dephasing and the corresponding change of the accelerating force over the course of acceleration and conclude that the radiation-dominated regime is realized both in cases of single-stage acceleration with slow dephasing (usually corresponding to bunch-driven plasma accelerators) and multi-stage acceleration with fast dephasing (corresponding to the use of laser-driven accelerators).
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Lin, Hongxiang, Tianfa Liao, Xiaohui Wei, Wenyuan Wang, Juan Du, and Yaoxuan Zhi. "Study of a Graphene Surface Plasmon Polariton-Based Dielectric Laser Accelerator." Photonics 12, no. 4 (2025): 292. https://doi.org/10.3390/photonics12040292.
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Due to their high breakdown threshold and acceleration gradient, dielectric laser accelerators (DLAs) have become an important technical direction of accelerator miniaturization. In this study, an electron accelerator scheme based on graphene surface plasmon polaritons (SPPs) is proposed. The grating was designed to be etched on the silica surface in the simulation, and a layer of graphene was modeled to cover the surface of the medium. The incident laser light in the simulation was configured to be coupled by the grating to generate surface plasmon polaritons (SPPs) on the graphene surface. According to the simulation results, a relatively large acceleration channel aperture and long acceleration length could be formed on the graphene surface using a mid-infrared laser; this provides a technical solution for increasing the beam current of a DLA. A 53.375 THz laser was incident on the surface of the accelerating structure to carry out tracking calculations on a 10 MeV electron beam. For the 100 μm accelerating structure, an energy gain of 0.105 MeV was achieved, and the acceleration gradient reached 1.05 GeV/m.
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Łagowski, P., T. Stańczyk, E. Szumska, et al. "Influence of road conditions on the values of longitudinal acceleration during braking of a tourist coach." IOP Conference Series: Materials Science and Engineering 1247, no. 1 (2022): 012004. http://dx.doi.org/10.1088/1757-899x/1247/1/012004.
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Abstract The paper aims to analyse the longitudinal acceleration of a tourist coach on various road pavements. As part of the experimental research, braking tests were carried out at a speed of 30 km/h and acceleration to a speed of 30 km/h. The tests were carried out on four types of pavement, i.e. dry and wet asphalt and dry and wet concrete. The article describes the impact of road conditions on the braking and acceleration performance on selected road pavement types. To increase the reliability of the test results, ten tests were carried out for each tested pavement. Based on the test results, graphs of braking decelerations and accelerations during accelerating the vehicle as a function of time. This allowed for statistical analysis of the recorded decelerations and accelerations.
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FEOLI, ANTONIO. "MAXIMAL ACCELERATION OR MAXIMAL ACCELERATIONS?" International Journal of Modern Physics D 12, no. 02 (2003): 271–79. http://dx.doi.org/10.1142/s0218271803002706.
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Long, Gary. "Acceleration Characteristics of Starting Vehicles." Transportation Research Record: Journal of the Transportation Research Board 1737, no. 1 (2000): 58–70. http://dx.doi.org/10.3141/1737-08.
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Acceleration characteristics of starting vehicles are needed for many transportation analysis and design purposes involving driveways, turning bays, intersecting streets, traffic signals, railroad crossings, simulation software, and so forth. Constant acceleration is sometimes assumed, or AASHTO Green Book values based on piecewise-constant accelerations are sometimes adopted. However, continuing research has shown that linearly decreasing acceleration rates better represent both maximum vehicle acceleration capabilities and actual motorist behavior. It is not acceleration that usually is constant during speed changes; it is the rate of change in acceleration. The evolution of AASHTO acceleration values for design is traced, and the literature is reviewed for pertinent field observations. Linearly decreasing acceleration (and some deceleration) model parameters are calibrated for various sets of observational and design data. Despite published results from thousands of field measurements, the values selected for design were found to be based mostly on vehicle performance capabilities, with conjecture about how many of these capabilities are normally used by drivers. Design accelerations were found to deviate substantially from observed accelerations. At the start of motion, observed accelerations were about 15 percent faster for passenger cars and 45 percent faster for SU (single unit) trucks than design accelerations. As speed increased, observed accelerations dropped three to four times faster than design accelerations for these vehicles. Observed accelerations for WB-15 trucks began 40 percent to 75 percent slower than design accelerations, and they were considerably slower than the values in the Green Book for trucks at railroad crossings. Voids in the available information base are identified. Linearly decreasing design acceleration rates for motorists operating different classes of vehicles in different design situations are recommended, and revisions for Green Book parameters and charts are suggested. The recommended acceleration model greatly simplifies acceleration parameters but implies using different acceleration relationships for different design speeds instead of one for all.
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Cui, Jian, Satoshi Iwase, Tadaaki Mano, Naomi Katayama, and Shigeo Mori. "Muscle sympathetic outflow during horizontal linear acceleration in humans." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 281, no. 2 (2001): R625—R634. http://dx.doi.org/10.1152/ajpregu.2001.281.2.r625.
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To elucidate the effects of linear acceleration on muscle sympathetic nerve activity (MSNA) in humans, 16 healthy men were tested in a linear accelerator. Measurements of MSNA, electrocardiogram, blood pressure, and thoracic impedance were undertaken during linear acceleration. Sinusoidal linear acceleration with peak values at ±0.10, ±0.15, and ±0.20 G was applied in anteroposterior (±Gx, n = 10) or lateral (±Gy, n = 6) directions. The total activity and burst rate of MSNA decreased significantly during forward, backward, left, or right linear accelerations. The total activity of MSNA decreased to 50.5 ± 6.9, 52.5 ± 4.4, 71.2 ± 9.6, and 67.6 ± 8.2% from the baselines (100%) during linear accelerations with peak values at ±0.20 G in the four directions, respectively. These results suggest that dynamic stimulation of otolith organs in horizontal directions in humans might inhibit MSNA directly in order to quickly redistribute blood to muscles during postural reflexes induced by passive movement, which supports the concept that the vestibular system contributes to sympathetic regulation in humans.
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Konstantinov, Stanislav. "Linear acceleration of protons on a backward wave (Bogomolov’s accelerator)." Physics & Astronomy International Journal 6, no. 3 (2022): 105–7. http://dx.doi.org/10.15406/paij.2022.06.00261.
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The article proposes to consider fundamentally new way of accelerating charged particles: linear acceleration (LA) of protons on a backward wave (Professor Bogomolov's Accelerator). The article discusses the advantages and scope of the new accelerator. The European Strategic Group (ESG) is considering fundamentally new projects to create more efficient and less expensive accelerators and colliders for research.
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DaSilva, Carlos M., and Jonas Gabrielsson. "Entrepreneurial Acceleration: Exploring Accelerator Programs." Academy of Management Proceedings 2018, no. 1 (2018): 12509. http://dx.doi.org/10.5465/ambpp.2018.12509abstract.
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Saif, Farhan, and Inam Ur Rehman. "Acceleration Modes in Fermi Accelerator." Journal of Russian Laser Research 34, no. 6 (2013): 515–22. http://dx.doi.org/10.1007/s10946-013-9383-2.
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TRBOJEVIC, D., M. BLASKIEWICZ, and E. FOREST. "CROSSING RESONANCES IN A NON-SCALING FFAG." International Journal of Modern Physics A 26, no. 10n11 (2011): 1852–64. http://dx.doi.org/10.1142/s0217751x11053249.
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There are many possible applications for the non-scaling Fixed Field Alternating Gradient (NS-FFAG): accelerating non-relativistic ions, ion cancer therapy, proton drivers, accelerator driven subcritical reactors, heavy radioactive ions, recirculating linacs, and etc. They are confronted with two significant challenges: first is crossing integer resonances as the tunes vary with energy, and that the required fast acceleration has not yet been achieved in practice. An example of a small 30–250 MeV NS-FFAG proton accelerator is used to study both problems. After an introduction, the second chapter shows theoretical predictions for the emittance blow up from crossing the integer resonances. In the third part, the lattice of the ring is briefly described. The fourth chapter describes the "phase jump" a method for fast proton acceleration, while in the chapter five a six dimensional simulations of acceleration is described, ending with conclusions.
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Bingham, R. "Particle acceleration by electromagnetic waves." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 366, no. 1871 (2008): 1749–56. http://dx.doi.org/10.1098/rsta.2007.2183.
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We consider the symmetry in the interaction of photons and electrons, which has led to a common description of electron and photon accelerations; effects such as photon Landau damping arise naturally from such a treatment. Intense electromagnetic waves can act as a photon mirror to charged particles. The subsequent acceleration is equivalent to the photon pulse accelerating electrons. During the interaction or reflection process, the charged particle can emit bursts of radiation similar to the radiation emitted from the particles during wave breaking of plasma waves.
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JEON, HYEONG-MIN, JI-WON KIM, YURI KWON, JAE-HOON HEO, EUI-BUM CHOI, and GWANG-MOON EOM. "UPPER BODY ACCELERATIONS DURING LOCOMOTION IN DIFFERENT AGE GROUPS AND GENDERS." Journal of Mechanics in Medicine and Biology 17, no. 07 (2017): 1740026. http://dx.doi.org/10.1142/s0219519417400267.
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Aim: The purpose of this study is to measure the acceleration of upper body (pelvis, shoulder and head) during walking and to investigate whether the acceleration patterns differ among age groups and genders. Methods: Twenty-nine old subjects and thirty young subjects participated in this study. Tri-axial accelerations were measured on the back of upper body (head, shoulder and pelvis). Subjects performed two trials of walking on a treadmill in their own comfortable speeds. Three-way ANOVA (repeated measures) was carried out for the root mean square of each directional acceleration with age, gender and sensor position as independent factors. Results: Age effect was significant on the RMS accelerations of the transverse plane. In the anteroposterior direction, the pelvis acceleration was greater in the younger group, while the head acceleration was greater in the older group ([Formula: see text]). In the mediolateral direction, the pelvis acceleration was comparable between age groups but the shoulder and head accelerations were greater in the older group ([Formula: see text]). The overall accelerations were greater in men than in women ([Formula: see text]). The phase-delay and attenuation of shoulder acceleration relative to the pelvis acceleration was smaller for the elderly in AP and ML directions ([Formula: see text]). Normalization of RMS accelerations by height, weight and leg length did not affect the age differences but negated the gender differences. Discussion: Greater head acceleration in older subjects were related to less attenuation of acceleration in the upper body, which may affect the sensory systems in the head and deteriorate balance control during locomotion.
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Abraczinskas, Alicia, Ardyn Olszko, Christine Beltran, et al. "A Comparison of Nonhuman Primate Injuries in Horizontal Versus Vertical Sled +Gz (Head-to-Foot) Impact Accelerations." Military Medicine 186, Supplement_1 (2021): 610–18. http://dx.doi.org/10.1093/milmed/usaa354.
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ABSTRACT Introduction Accelerative events commonly expose military pilots to potentially injurious + Gz (axial, caudal to cranial) accelerations. The Naval Biodynamics Laboratory exposed nonhuman primates (NHPs) to + Gz loading in two subject orientations (supine or upright) to assess the effect of orientation and accelerations associated with injury at accelerations unsafe for human participation. Materials and Methods Archived care records, run records, and necropsy and pathology reports were used to identify acceleration-related injuries. Injuries were categorized as central nervous system (CNS), musculoskeletal (MSK) system, or thoracic (THR). The occurrence of injuries relative to corresponding peak sled acceleration (PSA) and subject orientation were compared. A t-test was applied within each injury category to test for a significant difference in mean PSA between orientations. Results For all 63 + Gz runs conducted, PSA ranged between 6 and 86 G. Of these runs, 17 (6 supine, 11 upright) resulted in acceleration-related injury. The lowest PSAs associated with injury for supine and upright were 69.8 G and 39.6 G, respectively. Individual injury occurrences for supine runs (CNS [n = 5], MSK [n = 6], and THR [n = 6]) occurred at/above 75.7 G, 69.8 G, and 69.8 G, respectively. For upright runs, injury occurrences (CNS [n = 3], MSK injuries [n = 9], and THR injuries [n = 6]) occurred at/above 60.1 G, 39.6 G, and 50.5 G, respectively. The applied t-test showed significant difference between the mean orientation accelerations within each category. Injuries to supine NHPs included compression fracture, organ damage, brain hemorrhage, spinal cord hemorrhage, cervical hemorrhage, paresis/paraplegia, and THR bruising, whereas injuries to upright NHPs included compression fracture, organ damage, spinal cord hemorrhage, paresis/paraplegia, THR bruising, and difficulty breathing. Conclusions Axial loading to supine occupants produced more CNS injuries, whereas upright produced more MSK injuries. Both orientations produced equal THR injuries. NHP injuries reported reflected those reported following human + Gz acceleration events, highlighting the importance of orientation during acceleration to mitigate injury for next generation equipment design and testing.
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Ogata, Atsushi, and Kazuhisa Nakajima. "Recent progress and perspectives of laser–plasma accelerators." Laser and Particle Beams 16, no. 2 (1998): 381–96. http://dx.doi.org/10.1017/s0263034600011654.
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Recent progress in laser-plasma accelerators has matured a concept of particle acceleration as a possible next-generation particle accelerator promising ultrahigh accelerating gradients in a compact size. Four major concepts of laser-plasma accelerators—the plasma beat wave accelerator, the laser wakefield accelerator, the self-modulated laser wakefield accelerator, and the plasma wakefield accelerator—are reviewed on accelerator physics issues and experiments demonstrating the basic mechanisms of their concepts. As a perspective to the future practical application, a design of 5-TeV linear colliders based on the laser wakefield accelerator is discussed.
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Ovchinnikova, Anna, and Tatyana Topoleva. "The regional accelerator as a driver for the development of an innovative environment and technological entrepreneurship." SHS Web of Conferences 116 (2021): 00053. http://dx.doi.org/10.1051/shsconf/202111600053.
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Development of the innovative economy in Russia predetermines the need to adapt to new challenges and global economic trends. World experience demonstrates the effectiveness of the acceleration mechanism in supporting innovative projects, expanding the network interaction of the elements of innovative ecosystems, and accelerating the implementation of breakthrough ideas. The existing imbalance in the socio-economic development of the Russian regions, the differentiation of their resource potentials determine the search for institutional solutions that activate the innovation process. The conceptual and methodological basis for acceleration platforms and foreign and domestic experience of business accelerators are analyzed. The stages of change management in the context of acceleration logic are systematized. These are hackathon, foresight, acceleration, project development. The article substantiates the expediency of acceleration of innovations in the Udmurt Republic as an institutional element of the innovative environment that meets the specifics of the military-industrial complex, the declared diversification of defense industries and actualization of the request to increase the share of high-tech civilian products in the total volume. The mission and goals of the accelerator and the main program stages are described. The graphical model of a regional accelerator is presented. It integrates key elements of the innovation environment. The result is stimulation of the innovation process, support of the technological entrepreneurship, strong regional innovative competencies, qualitative growth of project activities, which will significantly increase the level of competitiveness of regional enterprises and the role of the region in the global economic system.
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Liu, Zhi Xin, Yue Zhang, and Ming Jiang Wei. "Prediction on Vehicle Crash Acceleration Based on Circle of Constant Acceleration Method." Applied Mechanics and Materials 380-384 (August 2013): 51–54. http://dx.doi.org/10.4028/www.scientific.net/amm.380-384.51.
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Vehicle crash acceleration was essential for automotive passive safety analysis. Especially in CAE analysis and sled test, B-pillar lower accelerations are considered as vehicle acceleration and often used as crash pulse to reproduce the real crash conditions. But for frontal offset impact, the magnitudes and directions of the B-pillars lower accelerations were significantly different,which made the selection of vehicle acceleration very complicate. In this paper,a prediction algorithm based on Circle of Constant Acceleration method that can calculate the acceleration of any point on vehicle was presented. And then it is verified with the full scale impact data. The results show that both the trend of the acceleration curves and the curve peak of the calculated value have a strong consistency with the measured value.
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Prasad, R., R. Singh, and V. K. Tripathi. "Effect of an axial magnetic field and ion space charge on laser beat wave acceleration and surfatron acceleration of electrons." Laser and Particle Beams 27, no. 3 (2009): 459–64. http://dx.doi.org/10.1017/s0263034609990127.
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AbstractThe presence of an axial magnetic field in a laser beat wave accelerator enhances the oscillatory velocity of electrons due to cyclotron resonance effect leading to higher amplitude of the ponderomotive force driven plasma wave, and higher energy of accelerating electrons. The axial magnetic field inhibits the transverse escape of electrons and thus causes a growth of the interaction length. The surfatron acceleration of electrons also shows a similar enhancement. A surfatron transverse magnetic field deflects the electrons parallel to the phase fronts of the accelerating wave keeping them in phase with it. However, the electron continues to move away radially.
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Shen, Yi, Yi Liu, Pan Dong, et al. "A Pulsed Synchronous Linear Accelerator for Low-Energy Proton." Laser and Particle Beams 2022 (November 9, 2022): 1–7. http://dx.doi.org/10.1155/2022/2836767.
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A low-energy proton accelerator named pulsed synchronous linear accelerator (PSLA) is proposed and developed at the Institute of Fluid Physics, which is driven by unipolar-pulsed high voltages. Pulsed-accelerating electric fields and low-energy ion beams are precisely synchronized on temporal and spatial positions for continuous acceleration. The operating mode and the features of the PSLA are introduced. At present, the feasibility of a low-energy proton PSLA has been verified in principle. An average accelerating gradient up to 3 MV/m for protons is achieved.
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Price, N. S. C., N. A. Crowder, M. A. Hietanen, and M. R. Ibbotson. "Neurons in V1, V2, and PMLS of Cat Cortex Are Speed Tuned But Not Acceleration Tuned: The Influence of Motion Adaptation." Journal of Neurophysiology 95, no. 2 (2006): 660–73. http://dx.doi.org/10.1152/jn.00890.2005.
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We studied neurons in areas V1, V2, and posteromedial lateral suprasylvian area (PMLS) of anesthetized cats, assessing their speed tuning using steps to constant speeds and acceleration and deceleration tuning using speed ramps. The results show that the speed tuning of neurons in all three cortical areas is highly dependent on prior motion history, with early responses during speed steps tuned to higher speeds than later responses. The responses to speed ramps are profoundly influenced by speed-dependent response latencies and ongoing changes in neuronal speed tuning due to adaptation. Acceleration evokes larger transient and sustained responses than subsequent deceleration of the same rate with this disparity increasing with ramp rate. Consequently, there was little correlation between preferred speeds measured using speed steps, acceleration or deceleration. From 146 recorded cells, the proportion of cells that were clearly speed tuned ranged from 69 to 100% across the three brain areas. However, only 13 cells showed good skewed Gaussian fits and systematic variation in their responses to a range of accelerations. Although suggestive of acceleration coding, this apparent tuning was attributable to a cell's speed tuning and the different stimulus durations at each acceleration rate. Thus while the majority of cells showed speed tuning, none unequivocally showed acceleration tuning. The results are largely consistent with an existing model that predicts responses to accelerating stimuli developed for macaque MT, which showed that the responses to acceleration can be decoded if adaptation is taken into account. However, the present results suggest future models should include stimulus-specific adaptation and speed-dependent response latencies.
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Martı´nez, Jose´ Marı´a Rico, and Joseph Duffy. "Forward and Inverse Acceleration Analyses of In-Parallel Manipulators." Journal of Mechanical Design 122, no. 3 (1998): 299–303. http://dx.doi.org/10.1115/1.1288360.
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Simple expressions for the forward and inverse acceleration analyses of a six degree of freedom in-parallel manipulator are derived. The expressions are obtained by firstly computing the “accelerator” for a single Hooke-Prismatic-Spheric, HPS for short, connector chain in terms of the joint velocities and accelerations. The accelerator is a function of the line coordinates of the joint axes and of a sequence of Lie products of the same line coordinates. A simple expression for the acceleration of the prismatic actuator is obtained by forming the Klein form, or reciprocal product, with the accelerator and the coordinates of the line of the connector chain. Since the Klein form is invariant, the resulting expression can be applied directly to the six HPS connector chains of an in-parallel manipulator. As a required intermediate step, this contribution also derives the corresponding solutions for the forward and inverse velocity analyses. The authors believe that this simple method has applications in the dynamics and control of these in-parallel manipulators where the computing time must be minimized to improve the behavior of parallel manipulators. [S1050-0472(00)01303-9]
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Shuklinov, Serhii, Anatoly Uzhva, Mikhail Lysenko, Anastasia Tishenko, and Yevgeniya Novikova. "Maximum automobile acceleration." Automobile transport, no. 49 (December 24, 2021): 13–22. http://dx.doi.org/10.30977/at.2219-8342.2021.49.0.02.
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Problem. The disadvantage of current dependences for determining the acceleration indicators at engine maximum brake power and driving tire-to-surface friction coefficients is that they are adequate only if the engine and transmission parameters provide power input to the drive wheels rolling without slipping regardless to speed. To eliminate this drawback, it is necessary to take into account that the power input to the drive wheels depends on the engine shaft speed, and therefore on the speed of the vehicle when accelerating. Goal. The purpose of the work is to further develop the theory of the automobile by improving the dependencies that allow determining the automobile acceleration rates and assessing the nature of its acceleration process from the design factors. Methodology. The approaches taken to achieve this goal are based on laws of physics, theoretical mechanics and the theory of automobile. Results. Analytic dependences for determining maximum and limiting automobile acceleration when speeding up depending on its design factors and speed have been improved. Dependences for determining the range of drive wheel slipping on the automobile speed when accelerating and the limiting automobile acceleration under the condition of its pitch stability have been obtained. When studying the automobile acceleration process theoretically it was found that the developed dependences allow determining the nature of automobile movement and assessing the influence of its design factors on the acceleration indicators. Originality. The obtained dependences for determining the maximum and limiting acceleration, the range of driving speeds with wheel slip when automobile accelerating allowed us to clarify the idea of the nature of movement during acceleration and the influence of automobile design factors on the acceleration indicators. Practical value. The obtained dependences can be used in designing new and improving racing cars such as dragsters, and analysing the dynamics of the vehicle when accelerating with full fuel delivery and determining the nature of driving tire-to-surface friction depending on the driving speed.
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Boroushak, Neda, Hasan Khoshnoodi, and Mostafa Rostami. "Investigation of the Head’s Dynamic Response to Boxing Punch Using Computer Simulation." Montenegrin Journal of Sports Science and Medicine 10, no. 1 (2021): 31–35. http://dx.doi.org/10.26773/mjssm.210305.
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Head injuries are dangerous injuries that are common in combat sports. Nevertheless, the mechanisms of concussion in sport have are not precisely known. Thus, this study aimed to investigate the dynamic response of the head based on linear and rotational accelerations in boxing using computer simulation. The ADAMS software model was used to determine the linear and rotational acceleration of boxing’s straight punch. The peak linear acceleration, average linear acceleration, peak rotational acceleration, and average rotational acceleration resulted from the straight punch to head were obtained: 75 g, 20 g, 4036 rad/s², 1140 rad/s², respectively; the impact times were 30 ms and 3 ms, respectively. The comparison of acceleration tolerance thresholds of head injury and obtained results of this study showed the rotational acceleration only leads to head injury. Furthermore, it is biomechanically improbable that the head would be moved only translationally or rotationally as a result of a straight punch. Therefore, both rotational and linear accelerations should be observed together for future studies.
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Morozov, Sergey, Konstantin Kuzmin, Igor Pavlov, Vladimir Reut, and Vladimir Vershinin. "Klystron bunching with sustained electron acceleration in agriculture." E3S Web of Conferences 175 (2020): 11002. http://dx.doi.org/10.1051/e3sconf/202017511002.
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This article discusses klystron bunching with post-acceleration, when bunchers are placed in front of the accelerating tube, and the electronic seals previously formed during the acceleration are ungrouped. The processes of acceleration and bunching of relativistic electron beams can be combined when placing the cavity resonators of the klystron buncher in the gaps between the electrodes of the accelerating tube. In this case, the grouping process occurs in accelerating gaps.
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Ebrahim, N. A., and S. R. Douglas. "Acceleration of particles by relativistic electron plasma waves driven by the optical mixing of laser light in a plasma." Laser and Particle Beams 13, no. 1 (1995): 147–71. http://dx.doi.org/10.1017/s0263034600008910.
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Electron acceleration by relativistic electron plasma waves is studied by theory and particle simulations. The maximum acceleration that can be obtained from this process depends on many different factors. This paper presents a study of how these various factors impact on the acceleration mechanism. Although particular reference is made to the laser plasma beatwave concept, the study is equally relevant to the acceleration of particles in the plasma wakefield accelerator and the laser wakefield accelerator.
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Ma, Kemao, and Xiaoyu Zhang. "A Novel Guidance Law with Line-of-Sight Acceleration Feedback for Missiles against Maneuvering Targets." Mathematical Problems in Engineering 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/983751.
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Terminal guidance law design and its implementation are considered for homing missiles against maneuvering targets. The lateral acceleration dynamics are taken into account in the design. In the guidance law design, the line-of-sight acceleration signals are incorporated into the acceleration reference signals to compensate for the targets’ maneuvers. Then the commanded accelerations are designed and the convergent tracking of the lateral accelerations to these signals is proven theoretically. In the guidance implementation, a linear high-gain differentiator is used to estimate the line-of-sight rates and the line-of-sight acceleration signals. To avoid the magnifying effects of higher order differentiation, a practical design of commanded accelerations is given to realize approximate tracking of the lateral accelerations to the given reference signals. Simulation is conducted for both cases with and without measurement noises. The simulation results justify the feasibility of the design and the implementation.
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Maslov, Vasyl I., Denys S. Bondar, and Ivan N. Onishchenko. "Investigation of the Way of Phase Synchronization of a Self-Injected Bunch and an Accelerating Wakefield in Solid-State Plasma." Photonics 9, no. 3 (2022): 174. http://dx.doi.org/10.3390/photonics9030174.
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The electron acceleration, in a laser wakefield accelerator, controlled through plasma density inhomogeneity is studied on a basis of 2.5-dimensional particle-in-cell simulation. The acceleration requires a concordance of the density scale length and shift of the accelerated electron bunch relative to wake bubble during electron acceleration. This paper considers the excitation of a wakefield in plasma with a density equal to the density of free electrons in metals, solid-state plasma (the original idea of Prof. T. Tajima), in the context of studying the wakefield process. As is known in the wake process, as the wake bubble moves through the plasma, the self-injected electron bunch shifts along the wake bubble. Then, the self-injected bunch falls into the phase of deceleration of the wake wave. In this paper, support of the acceleration process by maintaining the position of the self-injected electron bunch using an inhomogeneous plasma is proposed. It is confirmed that the method of maintaining phase synchronization proposed in the article by using a nonuniform plasma leads to an increase in the accelerating gradient and energy of the accelerated electron bunch in comparison with the case of self-injection and acceleration in a homogeneous plasma.
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Akram, Javed, Khalid Naseer, Inam-ur Rehman, and Farhan Saif. "Acceleration of Material Waves in Fermi Accelerator." Mathematical Problems in Engineering 2009 (2009): 1–8. http://dx.doi.org/10.1155/2009/246438.
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Cold Atoms bouncing on modulated atomic mirror exhibits acceleration and dynamical localization subject to modulated strength. We explain characteristics of acceleration and define control parameters in terms of effective Planck's constant. We show that the effective Planck's constant plays a vital role in limiting classical-like overall linear growth of the variance of accelerated atoms with time. For large values of the effective Planck's constant the atomic quantum acceleration is seized as localization window overlaps the accelerated window.
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Quintero-Illera, José Luis, Fabio Nevado, Raúl Zarzuela-Martín, Roberto López-Del Campo, and Víctor Cuadrado-Peñafiel. "Impact of Acceleration and Acceleration-Initial Speed Profiles on Team Success in LaLiga." Applied Sciences 15, no. 8 (2025): 4344. https://doi.org/10.3390/app15084344.
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Acceleration and Acceleration-Initial Speed Running are important factors in soccer performance. The aims of the study were (a) analyze by playing position the acceleration-initial speed (AS0) profile and (b) analyze the relevance of the number of accelerations > 3 m·s−2 according to final league position. The subjects (n = 309) from the Spanish First Division during the 2021–2022 and 2022–2023 seasons were classified in six positions: Central Defenders (CD), Full Backs (FB), Central Midfielders (CM), Offensive Midfielders (OF), Wingers (W), and Forwards (F). A total of 6180 match observations were recorded using the Mediacoach System. The parameters analyzed were accelerations > 3 m·s−2 and AS0 profile variables, maximal theoretical acceleration (A0Int), and maximal theoretical initial running speed (S0Int). The AS0 profile was calculated using a linear regression model. Welch’s analysis of variance (ANOVA) revealed a consistent relationship between the A0Int variable of the AS0 profile and team success in CM, FB, and W positions. Moreover, the successful teams for CD, CM, FB, OM, and W positions showed a statistically higher number of accelerations > 3 m·s−2 than unsuccessful teams. In conclusion, these findings suggest the importance of enhancing acceleration abilities, particularly for lower-performing teams, to achieve the physical standards of successful teams.
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Baganov, A. P., V. G. Butov, G. V. Nosov, M. G. Nosova, S. V. Sinyaev, and V. A. Solonenko. "AN ELECTROMAGNETIC CATAPULT FOR LAUNCHING HEAVY UAVs (DRONES) FROM SMALL VESSELS." Vestnik Tomskogo gosudarstvennogo universiteta. Matematika i mekhanika, no. 71 (2021): 25–34. http://dx.doi.org/10.17223/19988621/71/3.
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The paper presents the results of mathematical modeling of the operation of a novel electromagnetic catapult design. The main elements of the latter are a single-section multi-rail accelerator with a metal armature and a pulsed energy source based on the powerful pulsed MHD generator and current-increasing transformer. The possibilities of such a scheme for accelerating bodies weighing 7 tons to speeds of about 150 km/h at a maximum permissible acceleration of 15 g are investigated. The mathematical model describes the coordinated operation of the device, starting with connecting of the pulsed MHD generator in idle mode to the primary winding of the transformer and up to the moment when the drone accelerates to a given takeoff speed. Using the proposed model, the efficiency of the electromechanical energy conversion in the developed catapult scheme is tested. The parameters of the main elements of the device, namely the length of the acceleration section of the catapult and the maximum acceleration of the drone, are determined.
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Comisso, Luca, Glennys R. Farrar, and Marco S. Muzio. "Ultra-High-Energy Cosmic Rays Accelerated by Magnetically Dominated Turbulence." Astrophysical Journal Letters 977, no. 1 (2024): L18. https://doi.org/10.3847/2041-8213/ad955f.
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Abstract Ultra-high-energy cosmic rays (UHECRs), particles characterized by energies exceeding 1018 eV, are generally believed to be accelerated electromagnetically in high-energy astrophysical sources. One promising mechanism of UHECR acceleration is magnetized turbulence. We demonstrate from first principles, using fully kinetic particle-in-cell simulations, that magnetically dominated turbulence accelerates particles on a short timescale, producing a power-law energy distribution with a rigidity-dependent, sharply defined cutoff well approximated by the form f cut E , E cut = sech ( E / E cut ) 2 . Particle escape from the turbulent accelerating region is energy dependent, with t esc ∝ E −δ and δ ∼ 1/3. The resulting particle flux from the accelerator follows dN / dEdt ∝ E − s sech ( E / E cut ) 2 , with s ∼ 2.1. We fit the Pierre Auger Observatory’s spectrum and composition measurements, taking into account particle interactions between acceleration and detection, and show that the turbulence-associated energy cutoff is well supported by the data, with the best-fitting spectral index being s = 2.1 − 0.13 + 0.06 . Our first-principles results indicate that particle acceleration by magnetically dominated turbulence may constitute the physical mechanism responsible for UHECR acceleration.
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Aubol, Kevin G., Jillian L. Hawkins, and Clare E. Milner. "Tibial Acceleration Reliability and Minimal Detectable Difference During Overground and Treadmill Running." Journal of Applied Biomechanics 36, no. 6 (2020): 457–59. http://dx.doi.org/10.1123/jab.2019-0272.
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Measurements of tibial acceleration during running must be reliable to ensure valid results and reduce errors. The purpose of this study was to determine the reliability and minimal detectable difference (MDD) of peak axial and peak resultant tibial acceleration during overground and treadmill running. The authors also compared reliability and MDDs when peak tibial accelerations were determined by averaging 5 or 10 trials. Tibial acceleration was measured during overground and treadmill running of 19 participants using a lightweight accelerometer mounted to the tibia. Peak axial and peak resultant tibial accelerations were determined for each trial. Intraclass correlation coefficients determined within-session reliability, and MDDs were also calculated. Within-session reliability was excellent for all conditions (intraclass correlation coefficients = .95–.99). The MDDs ranged from 0.6 to 1.4 g for peak axial acceleration and from 1.6 to 2.0 g for peak resultant acceleration and were lowest for peak axial tibial acceleration during overground running. Averaging 10 trials did not improve reliability compared to averaging 5 trials but did result in small reductions in MDDs. For peak axial tibial acceleration only, lower MDDs indicate that overground running may be the better option for detecting small differences.
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Roehrich, Shania, T. Brock Symons, Paula Parker, and Jennifer Bunn. "Ratio of accelerations to decelerations in Women’s division I lacrosse." Scientific Journal of Sport and Performance 3, no. 4 (2024): 556–64. http://dx.doi.org/10.55860/rdhp6227.
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This study analyzed the differences by position in acceleration, deceleration, and the ratio of accelerations to decelerations in drills and quarters of games (Q1-Q4). Data were collected in 23 female collegiate lacrosse athletes (20.8 ± 1.5 years, 168.3 ± 6.1 cm), consisting of ten midfielders, five defenders, and eight attackers. Drills were categorized as: stickwork (SW), small-sided games (SSG), warm-up (WU), active recovery (AR), individual skills (IS), scrimmage, and conditioning. AR (0.31 ± 0.09 accelerations/min) and WU (0.47 ± 0.07 accelerations/min) showed the lowest number of accelerations, and conditioning and SW were the highest (>1.0 accelerations/min). Conditioning showed the highest demand for decelerations (0.37 ± 0.14 decelerations/min) and AR and WU had the fewest (0.10 ± 0.04 decelerations/min). AR, IS, SW, and WU all had higher acceleration/deceleration ratios (4:1 to 5.7:1) than the remaining drill types (p = .000 - .050, 3:1-4:1). Q1 had a higher acceleration demand (0.72 ± 0.52 accelerations/minute) than the remaining three quarters (0.57 - 0.67 accelerations/min). The game demand in decelerations was approximately 0.20 decelerations/minute across all quarters and the acceleration/deceleration ratio was approximately 4:1, with the exception of defenders in Q1 who had 6:1 ratio. There is a large demand for accelerations in field lacrosse with no positional differences, and training should be devoted towards this skill.
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Ali Khan, A., T. Bakeyev, M. Göckeler, et al. "Accelerating Hasenbusch's acceleration of Hybrid Monte Carlo." Nuclear Physics B - Proceedings Supplements 129-130 (March 2004): 853–55. http://dx.doi.org/10.1016/s0920-5632(03)02733-6.
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Hayajneh, Mohammad R., Mohammad H. Garibeh, Ahmad Bani Younes, and Matthew A. Garratt. "Unmanned Aerial Vehicle Path Planning Using Acceleration-Based Potential Field Methods." Electronics 14, no. 1 (2025): 176. https://doi.org/10.3390/electronics14010176.
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Online path planning for UAVs that are following a moving target is a critical component in applications that demand a soft landing over the target. In highly dynamic situations with accelerating targets, the classical potential field (PF) method, which considers only the relative positions and/or velocities, cannot provide precision tracking and landing. Therefore, this work presents an improved acceleration-based potential field (ABPF) path planning method. This approach incorporates the relative accelerations of the UAV and the target in constructing an attractive field. By controlling the acceleration, the ABPF produces smoother trajectories and avoids sudden changes in the UAV’s motion. The proposed approach was implemented in different simulated scenarios with variable acceleration paths (i.e., circular, infinite, and helical). The simulation demonstrated the superiority of the proposed approach over the traditional PF. Moreover, similar path scenarios were experimentally evaluated using a quadrotor UAV in an indoor Vicon positioning system. To provide reliable estimations of the acceleration for the suggested method, a non-linear complementary filter was used to fuse information from the drone’s accelerometer and the Vicon system. The improved PF method was compared to the traditional PF method for each scenario. The results demonstrated a 50% improvement in the position, velocity, and acceleration accuracy across all scenarios. Furthermore, the ABPF responded faster to merging with the target path, with rising times of 1.5, 1.6, and 1.3 s for the circular, infinite, and helical trajectories, respectively.
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Jaarsveld, H. W. L. van, H. J. Grootenboer, and J. De Vries. "Accelerations due to impact at heel strike using below-knee prosthesis." Prosthetics and Orthotics International 14, no. 2 (1990): 63–66. http://dx.doi.org/10.3109/03093649009080323.
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The acceleration in the sagittal plane of the prosthetic tube at heel strike in normal walking was measured in five healthy amputees with their definitive below-knee prosthesis, every subject using six different prosthetic feet, wearing sport shoes as well as leather shoes. The experiments were carried out in the rehabilitation centre “Het Roessingh”, Enschede, The Netherlands. Maximum accelerations were extracted from the acceleration-time-signal. Mean acceleration maxima of all subjects were calculated for each foot-shoe combination to eliminate the individual influence of the subjects. In the axial direction the maximal accelerations demonstrate a clear difference among the prosthetic feet and the shoes, while in dorsoventral (tangential) direction the. inter-individual variation in the acceleration extremes dominates the difference between the types of footwear. In comparison with non-amputees the magnitude of the maximal axial acceleration at heel strike does not differ significantly.
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GAI, W., J. G. POWER, and C. JING. "Short-pulse dielectric two-beam acceleration." Journal of Plasma Physics 78, no. 4 (2012): 339–45. http://dx.doi.org/10.1017/s0022377812000037.
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AbstractWe are exploring a new parameter space of the two-beam acceleration (TBA) scheme based on an ultra-short (~20 ns) rf pulse in a dielectric TBA. All two-beam accelerators (TBAs) use an electron drive beam to generate high-power rf in a decelerator and extract this power to drive an accelerating structure to high gradient. Typically, the rf pulse is on the order of hundreds of ns or greater in order to maintain good rf-to-beam efficiency. However, recent scaling arguments show that the rf breakdown threshold improves with decreasing rf pulse length, so it desirable to find a way to run at short-pulse length with good efficiency. In this paper, we discuss how we chose the design parameters of a short-pulse TBA for a TeV linear collider module. We then present plans for an experimental program to demonstrate TBA at Argonne wakefield accelerator (AWA) facility including high-power rf generation, high-gradient acceleration, and staging.
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Hidding, Bernhard, Ralph Assmann, Michael Bussmann, et al. "Progress in Hybrid Plasma Wakefield Acceleration." Photonics 10, no. 2 (2023): 99. http://dx.doi.org/10.3390/photonics10020099.
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Plasma wakefield accelerators can be driven either by intense laser pulses (LWFA) or by intense particle beams (PWFA). A third approach that combines the complementary advantages of both types of plasma wakefield accelerator has been established with increasing success over the last decade and is called hybrid LWFA→PWFA. Essentially, a compact LWFA is exploited to produce an energetic, high-current electron beam as a driver for a subsequent PWFA stage, which, in turn, is exploited for phase-constant, inherently laser-synchronized, quasi-static acceleration over extended acceleration lengths. The sum is greater than its parts: the approach not only provides a compact, cost-effective alternative to linac-driven PWFA for exploitation of PWFA and its advantages for acceleration and high-brightness beam generation, but extends the parameter range accessible for PWFA and, through the added benefit of co-location of inherently synchronized laser pulses, enables high-precision pump/probing, injection, seeding and unique experimental constellations, e.g., for beam coordination and collision experiments. We report on the accelerating progress of the approach achieved in a series of collaborative experiments and discuss future prospects and potential impact.
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Polozov, Sergey M., and Vladimir I. Rashchikov. "Simulation studies of beam dynamics in 50 MeV linear accelerator with laser-plasma electron gun." Cybernetics and Physics, Volume 10, 2021, Number 4 (December 31, 2021): 260–70. http://dx.doi.org/10.35470/2226-4116-2021-10-4-260-270.
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Conventionally, electron guns with thermionic cathodes or field-emission cathodes are used for research or technological linear accelerators. RF-photoguns are used to provide the short electron bunches which could be used for FEL’s of compact research facilities to generate monochromatic photons. Low energy of emitted electrons is the key problem for photoguns due to high influence of Coulomb field and difficulties with the first accelerating cell simulation and construction. Contrary, plasma sources, based on the laser-plasma wakefield acceleration, have very high acceleration gradient but rather broad energy spectrum compared with conventional thermoguns or field-emission guns. The beam dynamics in the linear accelerator combines the laser-plasma electron source and conventional RF linear accelerator is discussed in this paper. Method to capture and re-accelerate the short picosecond bunch with extremely broad energy spread (up to 50 %) is presented. Numerical simulation shows that such bunches can be accelerated in RF linear accelerator to the energy of 50 MeV with output energy spread not higher than 1 % .
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Andonian, Gerard, Nathan Burger, Nathan Cook, et al. "Drive Bunch Train for the Dielectric Trojan Horse Experiment at the Argonne Wakefield Accelerator." Instruments 8, no. 2 (2024): 28. http://dx.doi.org/10.3390/instruments8020028.
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The recently demonstrated concept of the plasma photocathode, whereby a high-brightness bunch is initialized by laser ionization within a plasma wakefield acceleration bubble, is informally referred to as Trojan Horse wakefield acceleration. In a similar vein, the dielectric Trojan Horse concept incorporates a dielectric-lined waveguide to support a charged particle beam-driven accelerating mode and uses laser initiated ionization of neutral gas within the waveguide to generate a witness beam. One of the advantages of the dielectric Trojan Horse concept is the reduced requirements in terms of timing precision due to operation at a lower frequency. In this paper, we present experimental results on the generation and characterization of a four-bunch drive train for resonant excitation of wakefields in a cylindrical dielectric waveguide conducted at the Argonne Wakefield Accelerator facility. The results lay the foundation for the demonstration of a plasma photocathode scheme within a dielectric wakefield accelerating structure. Modifications to improve capture efficiency with improved beam transmission are suggested as well.
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Uhm, Han S. "Acceleration gradient of a plasma wakefield accelerator." Applied Physics Letters 92, no. 8 (2008): 081505. http://dx.doi.org/10.1063/1.2887877.
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Sasser, Jordan, Fernando Montalvo, Rhyse Bendell, P. A. Hancock, and Daniel S. McConnell. "Exploring the Effect of Virtual Robot Acceleration on Perceived Competitiveness/ Cooperativeness, Animacy, and Intelligence." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 64, no. 1 (2020): 1595–99. http://dx.doi.org/10.1177/1071181320641382.
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Prior research has indicated that perception of acceleration may be a direct process. This direct process may be conceptually linked to the ecological approach to visual perception and a further extension of direct social perception. The present study examines the effects of perception of acceleration in virtual reality on participants’ perceived attributes (perceived intelligence and animacy) of a virtual human-like robot agent and perceived agent competitive/cooperativeness. Perceptual judgments were collected after experiencing one of the five different conditions dependent on the participant’s acceleration: mirrored acceleration, faster acceleration, slowed acceleration, varied acceleration resulting in a win, and varied acceleration resulting in a loss. Participants experienced each condition twice in a counterbalanced fashion. The focus of the experiment was to determine whether different accelerations influenced perceptual judgments of the observers. Results suggest that faster acceleration was perceived as more competitive and slower acceleration was reported as low in animacy and perceived intelligence.
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YEO, K., B. G. KIM, and C. LEE. "On the near-wall characteristics of acceleration in turbulence." Journal of Fluid Mechanics 659 (July 23, 2010): 405–19. http://dx.doi.org/10.1017/s0022112010002557.
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The behaviour of fluid-particle acceleration in near-wall turbulent flows is investigated in numerically simulated turbulent channel flows at low to moderate Reynolds numbers, Reτ = 180~600). The acceleration is decomposed into pressure-gradient (irrotational) and viscous contributions (solenoidal acceleration) and the statistics of each component are analysed. In near-wall turbulent flows, the probability density function of acceleration is strongly dependent on the distance from the wall. Unexpectedly, the intermittency of acceleration is strongest in the viscous sublayer, where the acceleration flatness factor of O(100) is observed. It is shown that the centripetal acceleration around coherent vortical structures is an important source of the acceleration intermittency. We found sheet-like structures of strong solenoidal accelerations near the wall, which are associated with the background shear modified by the interaction between a streamwise vortex and the wall. We found that the acceleration Kolmogorov constant is a linear function of y+ in the log layer. The Reynolds number dependence of the acceleration statistics is investigated.
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Gu, Xiao Long, Dong Xiang, Peng Zhi Huang, and Yue Xiu Li. "An Optimization Design Method for the Acceleration and Deceleration Curves of Detachable Ropeway." Advanced Materials Research 774-776 (September 2013): 199–206. http://dx.doi.org/10.4028/www.scientific.net/amr.774-776.199.
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It will influence the comfort and safety of passengers when the cabins accelerating and decelerating in the detachable ropeway station. A dynamic model was built for the acceleration and deceleration process of detachable ropeway. And the optimal S acceleration and deceleration curves were designed. Then a physical model of detachable ropeway was built and imported into Adams to make a motion simulation. In order to ensure a small swinging angle when the cabins accelerating or decelerating to a constant velocity, it was compared with the swinging angle and swing in the condition of uniform acceleration and uniform deceleration. And the swinging angle and swing were reduced clearly in the condition of S acceleration and deceleration curves. It can greatly improve the comfort and safety of passengers under the S acceleration and deceleration curves.
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Liu, Xing, Ziheng Dai, Qi Wang, and Zhanpeng Li. "Computing Acceleration of Medical Image Processing Based on Multi-Accelerator Heterogeneous Systems." ACM SIGAPP Applied Computing Review 25, no. 1 (2025): 16–24. https://doi.org/10.1145/3727257.3727259.
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Medical image processing (MIP) can make the medical diagnosis more accurate and efficient. However, the operating process of MIP involves many computationally-intensive tasks, which results in a long computational time for MIP. To optimize the processing time of MIP, many research works use the heterogeneous computing architecture (HCA) to accelerate MIP. These works are effective. However, most of them focus on single-accelerator HCA (SA-HCA), which commonly consists of one CPU plus one kind of accelerators, but pay less attention to the multi-accelerator HCA (MA-HCA) such as CPU/FPGA/NPU or CPU/GPU/FPGA/NPU. Considering different accelerators are suitable for executing different tasks, a MA-HCA can theoretically achieve better computing performance than a SA-HCA. Therefore, this paper aims to design a MA-HCA dedicated to MIP to enhance the acceleration performance of MIP. First, a series of representative MIP algorithms are selected, and the work of accelerating these algorithms by using Huawei's Ascend neural processing unit (NPU) is investigated. Then, the NPU acceleration mechanism is integrated with the FPGA and GPU acceleration strategies to build a MA-HCA dedicated to MIP, and a unified programming model for this MA-HCA is also designed. To evaluate the performance of the proposed MA-HCA, the execution time and energy cost of various MIP algorithms on different SA-HCAs and MA-HCA are measured, and the results show that the MA-HCA presented in this paper can significantly improve the acceleration performance while still maintaining low power consumption.
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Krupych, O., V. Banha, N. Veremeychyk, and S. Krupych. "Investigation of accelerations of branch shaking and walnut fruit separation." Mehanization and electrification of agricultural, no. 10(109) (2019): 101–9. http://dx.doi.org/10.37204/0131-2189-2019-10-9.
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Purpose. Improvement of the efficiency of technical means for shaking walnut fruits due to the rationale for the marginal accelerations of branch shaking and fruit separation. Methods. The basic principles of conducting a field experiment using modern measuring equipment for measuring acceleration in the tree crown, as well as methods of planned experiment and statistical data processing were used. Results. The acceleration of the skeletal branches shaking at the point of capture, the acceleration of fruit separation and the values of the coefficient of transfer of accelerations from the place of application of the exerting force to the point of suspension of the fetus are investigated. The separation of the fruits from the branches occurs due to the force caused by the oscillation of the points of suspension of the fruits, in the process of transmission to the skeletal branches of the first or second orders of excitatory effort. In these circumstances, the point of suspension of the fetus receives marginal acceleration, which breaks the fruit with or without fertilization in the case of full maturity. The acceleration of the separation and shaking of nuts in fertilization are 3.5 and 4.5 times higher, respectively, than for nuts without fertilization. The transfer of accelerations from the place of application of the force of effort is carried out on the crown of the skeletal branch and is characterized by the coefficient of transfer of accelerations. This coefficient largely depends on the placement of the fruit in the crown relative to the location of the transfer of the force and the size and mass parameters of the elements of the skeletal branches (branches of different orders). The acceleration of the separation and shaking of the fruit with open and closed fertilization was established. Conclusions. The acceleration of the separation and shaking of walnuts depends on the degree of ripeness of the fruit, the size parameters of the skeletal branches and the distance of the capture of the branch the diameter of the skeletal branch at the base and the place of application of the force of the force. For fruits with fertilization, the acceleration of separation and shaking are 189.4–255.7 m/s2 and 164.3–349.4 m/s2, respectively, and for nuts in open fertilization – 51.91–68.1 m/s2 and 45.76–72.76 m/s2. The coefficient of acceleration depends on the location of the fruit in the crown relative to the location of the transfer of the force and size-mass parameters of the elements of the skeletal branches (branches of different orders). Both attenuation and acceleration gain were established, which is indicated by the transmission coefficient, which is fixed in the range of 0.59–1.41. Keywords: walnuts, fruit skeletal branch, acceleration, shaking of fruits, separation of fruits, coefficient of transmission of accelerations
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Galletti, Mario, Maria Pia Anania, Sahar Arjmand, et al. "Advanced Stabilization Methods of Plasma Devices for Plasma-Based Acceleration." Symmetry 14, no. 3 (2022): 450. http://dx.doi.org/10.3390/sym14030450.
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Towards the next generation of compact plasma-based accelerators, useful in several fields, such as basic research, medicine and industrial applications, a great effort is required to control the plasma creation, the necessity of producing a time-jitter free channel, and its stability namely uniformity and reproducibility. In this Letter, we describe an experimental campaign adopting a gas-filled discharge-capillary where the plasma and its generation are stabilized by triggering its ignition with an external laser pulse or an innovative technique based on the primary dark current (DC) in the accelerating structure of a linear accelerator (LINAC). The results show an efficient stabilization of the discharge pulse and plasma density with both pre-ionizing methods turning the plasma device into a symmetrical stable accelerating environment, especially when the external voltage is lowered near the breakdown value of the gas. The development of tens of centimeter long capillaries is enabled and, in turn, longer acceleration lengths can be adopted in a wide range of plasma-based acceleration experiments.
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Ma, Li Jie, Xi Bin Wang, and Yong Feng Li. "Influence of Cutting Parameters on Vibration Acceleration in Micro-End-Milling." Applied Mechanics and Materials 457-458 (October 2013): 439–42. http://dx.doi.org/10.4028/www.scientific.net/amm.457-458.439.
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In order to reveal the change rule of vibration acceleration during micro-end-milling straight groove, the single-factor and orthogonal experiments are employed to confirm the influence of milling parameters on vibration acceleration. On this basis, the relation equation between milling parameters and vibration accelerations is built. The result show that, the vibration acceleration along the width of groove is bigger than that of feed direction and it will increase rapidly with the improve of cutting speed; the predicted result of vibration acceleration is in good accordance with test result, therefore the relation equation can be used to predict vibration acceleration.