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A vibration energy harvester is typically composed of a spring–mass system with an electromagnetic or piezoelectric transducer connected in parallel with a spring. This configuration has been well studied and optimized for harmonic vibration sources. Recently, a dual-mass harvester, where two masses are connected in series by the energy transducer and a spring, has been proposed. The dual-mass vibration energy harvester is proved to be able to harvest more power and has a broader bandwidth than the single-mass configuration, when the parameters are optimized and the excitation is harmonic. In fact, some dual-mass vibration energy harvesters, such as regenerative vehicle suspensions and buildings with regenerative tuned mass dampers (TMDs), are subjected to random excitations. This paper is to investigate the dual-mass and single-mass vibration harvesters under random excitations using spectrum integration and the residue theorem. The output powers for these two types of vibration energy harvesters, when subjected to different random excitations, namely force, displacement, velocity and acceleration, are obtained analytically with closed-form expressions. It is also very interesting to find that the output power of the vibration energy harvesters under random excitations depends on only a few parameters in very simple and elegant forms. This paper also draws some important conclusions on regenerative vehicle suspensions and buildings with regenerative TMDs, which can be modeled as dual-mass vibration energy harvesters. It is found that, under white-noise random velocity excitation from road irregularity, the harvesting power from vehicle suspensions is proportional to the tire stiffness and road vertical excitation spectrum only. It is independent of the chassis mass, tire–wheel mass, suspension stiffness and damping coefficient. Under random wind force excitation, the power harvested from buildings with regenerative TMD will depends on the building mass only, not on the parameters of the TMD subsystem if the ratio of electrical and mechanical damping is constant.

For many years, laser-driven ion acceleration, mainly proton acceleration, has been proposed and a number of proof-of-principle experiments have been carried out with lasers whose pulse duration was in the nanosecond range. In the 1990s, ion acceleration in a relativistic plasma was demonstrated with ultra-short pulse lasers based on the chirped pulse amplification technique which can provide not only picosecond or femtosecond laser pulse duration, but simultaneously ultra-high peak power of terawatt to petawatt levels. Starting from the year 2000, several groups demonstrated low transverse emittance, tens of MeV proton beams with a conversion efficiency of up to several percent. The laser-accelerated particle beams have a duration of the order of a few picoseconds at the source, an ultra-high peak current and a broad energy spectrum, which make them suitable for many, including several unique, applications. This paper reviews, firstly, the historical background including the early laser-matter interaction studies on energetic ion acceleration relevant to inertial confinement fusion. Secondly, we describe several implemented and proposed mechanisms of proton and/or ion acceleration driven by ultra-short high-intensity lasers. We pay special attention to relatively simple models of several acceleration regimes. The models connect the laser, plasma and proton/ion beam parameters, predicting important features, such as energy spectral shape, optimum conditions and scalings under these conditions for maximum ion energy, conversion efficiency, etc. The models also suggest possible ways to manipulate the proton/ion beams by tailoring the target and irradiation conditions. Thirdly, we review experimental results on proton/ion acceleration, starting with the description of driving lasers. We list experimental results and show general trends of parameter dependences and compare them with the theoretical predictions and simulations. The fourth topic includes a review of scientific, industrial and medical applications of laser-driven proton or ion sources, some of which have already been established, while the others are yet to be demonstrated. In most applications, the laser-driven ion sources are complementary to the conventional accelerators, exhibiting significantly different properties. Finally, we summarize the paper.

The paper presents the analysis of turbulent coherent structures found in a turbulent boundary layer subjected to zero, favourable and adverse pressure gradient. The analysis of the shape of conditionally averaged traces of u and v velocity components obtained by VITA (Variable Interval Time Averaging) technique based on signals recorded by X-wire probe allows to detect four types of coherent structures. The paper documents a presence of coherent vortical structures of positive or negative vorticity moving upward and downward. It is shown also that the acceleration and deceleration of the mean streamwise velocity, due to the pressure gradient, modifies the vortex convection velocity magnitude and the angle. This effect is clearly seen especially for the adverse pressure gradient flow, where Q events in first and fourth quadrants are enhanced near the wall.

In this paper, we propose a new method of assessing the condition of existing short- and medium-span reinforced/prestressed concrete bridges based on vibration monitoring data obtained from a public bus. This paper not only describes details of a prototype monitoring system that uses information technology and sensors capable of providing more accurate knowledge of bridge performance than conventional ways but also shows a few specific examples of bridge condition assessment based on vehicle vibrations measured by using an in-service public bus equipped with vibration measurement instrumentation. This paper also describes a sensitivity analysis of deteriorating bridges based on simulation of the acceleration response of buses conducted by the "substructure method" employing a finite element model to verify the above bridge performance results. The main conclusions obtained in this study can be summarized as follows: (1) Because the vibration responses of passenger vehicles, such as buses, have a good linear relationship with the vibration responses of the target bridges, the proposed system can be used as a practical monitoring system for bridge condition assessment. (2) The results of sensitivity analysis performed by the substructure method show that bus vibration responses are useful for evaluating target bridge performance. (3) The proposed method was applied to a network of real bridges in a local area to evaluate its effectiveness. The results indicate that the proposed method can be used to prioritize the repair/strengthening works of existing bridges based on various vibration information in order to help bridge administrators establish rational maintenance strategies.

In this paper, we incorporate new parameters into a cellular automaton traffic flow model proposed in our previous paper [Jin et al. 2010 J. Stat. Mech. 2010 P03018]. Through these parameters, we adjust the anticipated velocity and the acceleration threshold separately. It turns out that the flow rate of synchronized flow mainly changes with the anticipated velocity, and the F → S phase transition feature mainly changes with the acceleration threshold. Therefore, we conclude that the acceleration threshold is the major factor affecting the F → S phase transition.

Uniformity of heavy ion beam (HIB) illumination is one of key issues in HIB inertial confinement fusion (HIF) in order to compress a fuel sufficiently and release fusion energy effectively. In this paper a new mitigation method of the Rayleigh-Taylor (R-T) instability growth is presented to make a HIF target robust against a non-uniform implosion. In this study a new mitigation method of the R-T instability growth is proposed based on an oscillating perturbed acceleration, which can be realized by a rotation or oscillation of the HIB illumination axis onto a fuel pellet. The R-T instability analyses and fluid simulations demonstrate that the oscillating acceleration reduces the R-T instability growth significantly. In this paper a baseline steady acceleration g0 is perturbed by a perturbed oscillating acceleration ?g, which is spatially non-uniform and oscillates in time (g0 >> ?g). An example result shows an 84% reduction of the R-T instability growth. In the analytical work two stratified inviscid fluids are treated under the perturbed oscillating acceleration. The linear analysis shows that the R-T instability growth rate does not change from the standard expression of ?. However, the R-T instability growth is strongly affected and mitigated by the oscillating acceleration; The transverse velocity of w is derived at the interface of the two stratified fluids. The R-T instability is induced by ?g. The result presents that the perturbed oscillating acceleration reduces the R-T instability growth significantly depending on the magnitude of the HIB oscillation frequency.

Super intense laser light (> 1020 W/cm2) is able to sweep preplasma over short times and compress the preplasma density gradient typically generated by the prepulse of today's high-intensity, high energy laser systems. Hot electron generation at steep plasma density gradients has been studied in a previous paper [Kemp et al., Phys. Rev. Lett. (2008)], which identified a mode of hot electron acceleration that is characterized by the formation of low-density shelf in front of the target. In this paper, we study the direct interaction mode, which appears after the shelf plasma interaction. We propose an analytical model to describe the absorption, explain electron energy spectra, and identify the parameter regime where the direct interaction mode becomes important.

Thanks to miniaturisation, it is today possible to imagine self-powered systems that use vibrations to produce their own electrical energy. Many energy-harvesting systems already exist. Some of them are based on the use of electrets: electrically charged dielectrics that can keep charges for years. This paper presents an optimisation of an existing system and proves that electret-based electrostatic energy scavengers can be excellent solutions to power microsystems even with low-level ambient vibrations. Thereby, it is possible to harvest up to 200\muW with vibrations lower than 1G of acceleration (typically 50\mumpp at 50Hz) using thin SiO2 electrets with an active surface of 1 cm^{2} and a mobile mass of 1g. This paper optimises such a system (geometric, electrostatic and mechanical parameters), using FEM (Finite Element Method) software (Comsol Multiphysics) and Matlab to compute the parameters and proves the importance of such an optimisation to build efficient systems. Finally, it shows that the use of electrets with high surface potential is not always the best way to maximise output power., This is an author-created, un-copyedited version of an article accepted for publication in Smart Materials and Structures. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it

This paper describes a new approach using mobile sensor networks for structural health monitoring. Compared with static sensors, mobile sensor networks offer flexible system architectures with adaptive spatial resolutions. The paper first describes the design of a mobile sensing node that is capable of maneuvering on structures built with ferromagnetic materials. The mobile sensing node can also attach/detach an accelerometer onto/from the structural surface. The performance of the prototype mobile sensor network has been validated through laboratory experiments. Two mobile sensing nodes are adopted for navigating on a steel portal frame and providing dense acceleration measurements. Transmissibility function analysis is conducted to identify structural damage using data collected by the mobile sensing nodes. This preliminary work is expected to spawn transformative changes in the use of mobile sensors for future structural health monitoring.

Electromagnetic (EM) energy harvesting seems to be one of the most promising ways to power wireless sensors in a wireless sensor network. In this paper, FR4, the most commonly used PCB material, is utilized as a mechanical vibrating structure for EM energy harvesting for body-worn sensors and intelligent tire sensors, which involve impact loadings. FR4 can be a better material for such applications compared to silicon MEMS devices due to lower stiffness and broadband response. In order to demonstrate FR4 performance and broadband response, three moving magnet type EM generator designs are developed and investigated throughout the paper. A velocity-damped harvester simulation model is first developed, including a detailed magnetic model and the magnetic damping effects. The numerical results agree well with the experimental results. Human running acceleration at the hip area that is obtained experimentally is simulated in order to demonstrate system performance, which results in a scavenged power of about 40 mu W with 15 m s(-2) acceleration input. The designed FR4 energy scavengers with mechanical stoppers implemented are particularly well suited for nearly periodic and non-sinusoidal high-g excitations with rich harmonic content. For the intelligent tire applications, a special compact FR4 scavenger is designed that is able to withstand large shocks and vibrations due to mechanical shock stoppers built into the structure. Using our design, 0.4 mW power across a load resistance at off-resonance operation is obtained in shaker experiments. In the actual operation, the tangential accelerations as a result of the tire-road contact are estimated to supply power around 1 mW with our design, which is sufficient for powering wireless tire sensors. The normalized power density (NPD) of the designed actuators compares favorably with most actuators reported in the literature.

This paper presents validation methods for assessing the accuracy and precision of motion-sensing device (i.e. accelerometer) measurements. The main goals of this paper were to assess the accuracy and precision of these measurements against a gold standard, to determine if differences in manufacturing and assembly significantly affected device performance and to determine if measurement differences due to manufacturing and assembly could be corrected by applying certain post-processing techniques to the measurement data during analysis. In this paper, the validation of a posture and activity detector (PAD), a device containing a tri-axial accelerometer, is described. Validation of the PAD devices required the design of two test fixtures: a test fixture to position the device in a known orientation, and a test fixture to rotate the device at known velocities and accelerations. Device measurements were compared to these known orientations and accelerations. Several post-processing techniques were utilized in an attempt to reduce variability in the measurement error among the devices. In conclusion, some of the measurement errors due to the inevitable differences in manufacturing and assembly were significantly improved (p < 0.01) by these post-processing techniques.

This special issue on laser and plasma accelerators illustrates the rapid advancement and diverse applications of laser and plasma accelerators. Plasma is an attractive medium for particle acceleration because of the high electric field it can sustain, with studies of acceleration processes remaining one of the most important areas of research in both laboratory and astrophysical plasmas. The rapid advance in laser and accelerator technology has led to the development of terawatt and petawatt laser systems with ultra-high intensities and short sub-picosecond pulses, which are used to generate wakefields in plasma. Recent successes include the demonstration by several groups in 2004 of quasi-monoenergetic electron beams by wakefields in the bubble regime with the GeV energy barrier being reached in 2006, and the energy doubling of the SLAC high-energy electron beam from 42 to 85 GeV. The electron beams generated by the laser plasma driven wakefields have good spatial quality with energies ranging from MeV to GeV. A unique feature is that they are ultra-short bunches with simulations showing that they can be as short as a few femtoseconds with low-energy spread, making these beams ideal for a variety of applications ranging from novel high-brightness radiation sources for medicine, material science and ultrafast time-resolved radiobiology or chemistry. Laser driven ion acceleration experiments have also made significant advances over the last few years with applications in laser fusion, nuclear physics and medicine. Attention is focused on the possibility of producing quasi-mono-energetic ions with energies ranging from hundreds of MeV to GeV per nucleon. New acceleration mechanisms are being studied, including ion acceleration from ultra-thin foils and direct laser acceleration. The application of wakefields or beat waves in other areas of science such as astrophysics and particle physics is beginning to take off, such as the study of cosmic accelerators considered by Chen et al where the driver, instead of being a laser, is a whistler wave known as the magnetowave plasma accelerator. The application to electron--positron plasmas that are found around pulsars is studied in the paper by Shukla, and to muon acceleration by Peano et al. Electron wakefield experiments are now concentrating on control and optimisation of high-quality beams that can be used as drivers for novel radiation sources. Studies by Thomas et al show that filamentation has a deleterious effect on the production of high quality mono-energetic electron beams and is caused by non-optimal choice of focusing geometry and/or electron density. It is crucial to match the focusing with the right plasma parameters and new types of plasma channels are being developed, such as the magnetically controlled plasma waveguide reported by Froula et al. The magnetic field provides a pressure profile shaping the channel to match the guiding conditions of the incident laser, resulting in predicted electron energies of 3GeV. In the forced laser-wakefield experiment Fang et al show that pump depletion reduces or inhibits the acceleration of electrons. One of the earlier laser acceleration concepts known as the beat wave may be revived due to the work by Kalmykov et al who report on all-optical control of nonlinear focusing of laser beams, allowing for stable propagation over several Rayleigh lengths with pre-injected electrons accelerated beyond 100 MeV. With the increasing number of petawatt lasers, attention is being focused on different acceleration regimes such as stochastic acceleration by counterpropagating laser pulses, the relativistic mirror, or the snow-plough effect leading to single-step acceleration reported by Mendonca. During wakefield acceleration the leading edge of the pulse undergoes frequency downshifting and head erosion as the laser energy is transferred to the wake while the trailing edge of the laser pulse undergoes frequency up-shift. This is commonly known as photon deceleration and acceleration and is the result of a modulational instability. Simulations reported by Trines et al using a photon-in-cell code or wave kinetic code agree extremely well with experimental observation. Ion acceleration is actively studied; for example the papers by Robinson, Macchi, Marita and Tripathi all discuss different types of acceleration mechanisms from direct laser acceleration, Coulombic explosion and double layers. Ion acceleration is an exciting development that may have great promise in oncology. The surprising application is in muon acceleration, demonstrated by Peano et al who show that counterpropagating laser beams with variable frequencies drive a beat structure with variable phase velocity, leading to particle trapping and acceleration with possible application to a future muon collider and neutrino factory. Laser and plasma accelerators remain one of the exciting areas of plasma physics with applications in many areas of science ranging from laser fusion, novel high-brightness radiation sources, particle physics and medicine. The guest editor would like to thank all authors and referees for their invaluable contributions to this special issue.

This paper presents a novel calibration algorithm to be used with a gyro-free inertial measurement unit (GF-IMU) based on the use of linear accelerometers (AC). The analytical approach can be implemented in two calibration procedures. The first procedure (P-I) is articulated in the conduction of a static trial, to compute the sensitivity and the direction of the sensing axis of each AC, followed by a dynamic trial, to determine the AC locations. By contrast, the latter procedure (P-II) consists in the calculation of the previously indicated calibration parameters by means of a dynamic trial only. The feasibility of the two calibration procedures has been investigated by testing two GF-IMUs, equipped with ten and six bi-axial linear ACs, with an ad hoc instrumented double-pendulum apparatus. P-I and P-II were compared to a calibration procedure used as a reference (P-REF), which incorporates the AC positions measured with an optoelectronic system. The experimental results we present in this paper demonstrate that (i) P-I is able to determine the calibration parameters of the AC array with a higher accuracy than P-II; (ii) consequently, the errors associated with translational (a0 ? g) and rotational () acceleration components for the two GF-IMUs are significantly greater using P-II than P-I and (iii) the errors in (a0 ? g) and obtained with P-I are comparable with the ones obtainable by using P-REF. Thus, the proposed novel algorithm used in P-I, in conjunction with the double-pendulum apparatus, can be globally considered a viable tool in GF-IMU calibration.

It is important for space research to study the behavior of fluids such as liquid oxygen and liquid hydrogen under weightless conditions (microgravity). In addition, since 1991 some magnetic ground-based stations have allowed compensating gravity and meeting space conditions. Magnetic devices allow low-cost microgravity experiments with unlimited time. The goal of these techniques is to reach the same or better conditions (residual acceleration of the studied fluid) than those during parabolic flights. In this paper, several specific distributions of the magnetic field are determined. These distributions allow compensating gravity by means of axisymmetric coils (solenoids). This paper introduces several distributions of the residual forces useful for different kinds of microgravity experiments.

Based on the fact that the electronic throttle angle effect performs well in the traditional car following model, this paper attempts to introduce the electronic throttle angle into the smart driver model (SDM) as an acceleration feedback control term, and establish an extended smart driver model considering electronic throttle angle changes with memory (ETSDM). In order to show the practicability of the extended model, the next generation simulation (NGSIM) data was used to calibrate and evaluate the extended model and the smart driver model. The calibration results show that, compared with SDM, the simulation value based on the ETSDM is better fitted with the measured data, that is, the extended model can describe the actual traffic situation more accurately. Then, the linear stability analysis of ETSDM was carried out theoretically, and the stability condition was derived. In addition, numerical simulations were explored to show the influence of the electronic throttle angle changes with memory and the driver sensitivity on the stability of traffic flow. The numerical results show that the feedback control term of electronic throttle angle changes with memory can enhance the stability of traffic flow, which shows the feasibility and superiority of the proposed model to a certain extent.

This paper presents a novel flocking algorithm based on a memory-enhanced disturbance observer. To compensate for external disturbances, a filtered regressor for the double integrator model subject to external disturbances is designed to extract the disturbance information. With the filtered regressor method, the algorithm has the advantage of eliminating the need for acceleration information, thus reducing the sensor requirements in applications. Using the information obtained from the filtered regressor, a batch of stored data is used to design an adaptive disturbance observer, ensuring that the estimated values of the parameters of the disturbance system equation and the initial value converge to their actual values. The result is that the flocking algorithm can compensate for external disturbances and drive agents to achieve the desired collective behavior, including virtual leader tracking, inter-distance keeping, and collision avoidance. Numerical simulations verify the effectiveness of the algorithm proposed in the present study.

We propose a new method to detect gravitational waves, based on spatial coherence interferometry with stellar light, as opposed to the conventional temporal coherence interferometry with laser sources. The proposed method detects gravitational waves by using two coherent beams of light from a single distant star measured at separate space-based detectors with a long baseline. This method can be applied to either the amplitude or intensity interferometry. This experiment allows for the search of gravitational waves in the lower frequency range of $10^{-6}$ to $10^{-4}$ Hz. In this work, we present the detection sensitivity of the proposed stellar interferometer by taking the detector response and shot and acceleration noises into account. Furthermore, the proposed experimental setup is capable of searching for primordial black holes and studying the size of the target neutron star, which are also discussed in the paper., 12 pages, 7 figures

As the current aspect, the nonstructural components (NSCs) linked with the structures are more affected during the seismic motion. It causes not only loss of the economy but also affected life. The various codal provision has been available for minimizing the damages of primary components, but for NSCs, a minimal requirement is functional. So that more investigation is required for understating the behavior of NSCs during the seismic motion. The research aims to understand the behavior of acceleration demand on NSCs in a building. Structures subjected to inertia forces due to earthquakes experience damage of nonstructural components (NSC). The inertia force acting the NSCs are related to acceleration amplification factor. For obtaining the peak horizontal floor acceleration with respect to tectonic ground motion, these factors are used. In this paper, mathematical models of the acceleration amplification factor defined as the peak floor acceleration with respect to peak ground acceleration, given by previous researchers, has been compared. For this 2,4,6,8 and 10 storey moment-resisting frame models considering 29 ground motion data ranging between 0.1g to 0.2g, is analyzed using linear time history method. The supports of the models are considered fixed. The ETABS software is used for the analysis of the models. To analyses the models, the modal mass participation ratio plays a significant role. ASCE 7-05 defines that the structure should be investigated and designed when the model mass participation ratio is equal to or more than 90 per cent. Based on the results, a comparison of the reported models is made. There is a strong need for further research to refine the models for the realistic prediction of acceleration amplification factor.

Acceleration sensor is usually used to test the performance of equipment under high-acceleration vibration. It is widely used in aero-engine, steam turbine and other equipment working in high-acceleration vibration environment. Calibration is an important means to ensure the accuracy and reliability of the measurement results of the acceleration sensor. Aiming at the conventional intermediate frequency (IF) calibration system using many instruments and complicated operation, this paper designs a resonant high-acceleration calibration system based resonant beam. The system amplifies the acceleration amplitude through the resonance of the resonant beam at the natural frequency, thereby generating high-acceleration values to calibrate the sensor. Then the vibration control algorithm of the calibration system is optimized, and the stability of the system is verified through experiments. Finally, the communication between the upper and lower computers is carried out in the vibration control system and the laser measurement system, and the metrological traceability is realized. The experimental results show that the system can effectively calibrate the sensitivity amplitude and phase of high-acceleration sensor in the frequency range of 100-2148 Hz and the acceleration range of 50-11853 m/s2. This calibration system is of great significance to the research on the calibration of IF acceleration sensor.

One of the goals in the SDGs that a region must achieve is 100% sanitation access. Sanitation is considered to have a significant impact on the quality of public health, both in rural and urban areas. The city of Bandung as a city with a high-density level has a big challenge in resolving sanitation matters. Acceleration efforts are needed to improve sanitation access in the city of Bandung which is still low so that it can realize open defecation free (ODF) for every urban village in the city of Bandung. This paper aims to provide a logical framework in the form of efforts that can be made to increase ODF in the city of Bandung. By collecting secondary data, interviews and FGDs as well as the highest and best use approach, the results show that the most important thing is to encourage the community to realize the need for a septic tank through community based total sanitation triggering (STBM) activities, connecting household wastewater channels to PDAM Sewerage, construction of small and large-scale communal septic tanks / IPAL and construction of “Gendong” pipelines, especially those in riverbank areas.

Due to the industrial development and the growing modernity, the elevator systems have become indispensable in many multi-story buildings. When electrical elevators are employed to transport people, riding comfort becomes a very important issue, especially when high-speed elevators are used in high-rise buildings. The elevator systems should provide a good stop accuracy and excellent levels of ride comfort. Passengers experience some problems that affect their comfort such as vibration and jerk that occur when travelling between elevator floors especially when starting and stopping the cabin. To minimize the effects of these problems, the cabin must be driven in such a way as to ensure smooth operation and smooth starting and stopping. Therefore, there is a need to control the voltage and frequency of the electric motor that drives the elevator cabin. This paper introduces a look at the different types of variable speed drives and how they’re used in electric elevator systems, discussing current systems as well as recent development in the field. Therefore, a variable-speed design that provides smooth movement is needed to include a smooth ride, accurate leveling, and a large number of start and stop operations First, some basic principles in driving systems, such as load curves and driving speed/torque, as well as their relationship to stability, are discussed; reference curve generation; speed curve profiling of the elevator system to achieve smooth transmission. The latest study in this topic reached the implementation of an elevator prototype driven by permanent magnet linear synchronous motor (PMSLM) loaded by 24kg. The motor was controlled by voltage frequency drive (VFD) programmed with offline S-curve to get a smooth start and smooth stop for the elevator cabin and constant travel speed with the least jerk possible, estimated by 88% compared the that without using the driver.

An economical and effective method to measure displacement is to integrate the acceleration signal. Because of the zero drift in the acceleration sensor, there will be a trend term in the process of acceleration secondary integration, which will cause some errors in displacement measurement. In this paper, several methods of acceleration signal processing with zero drift are given, and the advantages and disadvantages of these methods as well as the applicable occasions are analysed, which have important reference value for selecting reasonable methods in dealing with engineering problems.

The Fourier amplitude spectrum of acceleration will drop rapidly in the high frequency range. Anderson and Hough quantitatively studied the attenuation law of the acceleration Fourier spectrum above the corner frequency, and proposed the high-frequency attenuation parameter Kappa ( ) to describe this phenomenon. It has important applications in the field of engineering earthquakes, and is widely used by seismologists and engineers in the work of ground motion simulation and attenuation relations. Based on the Anderson method, this paper proposed a method of first smoothing the Fourier acceleration spectrum with a 0.4 Hz Parzen window and then fitting the solution value. The Fukushima earthquake data from Japan’s KiK-net seismic network on February 13, 2021 was used to verify the reliability of the method. The results showed that when the width of the Parzen window was set to 0.4 Hz, the calculation accuracy of the value was effectively improved.

In this paper, the asynchronous induction coil gun is selected as the object of study, and its working principle is firstly briefly introduced, then the mathematical model is established by using the knowledge of electromagnetism, and then the MAXWELL component of ANSYS analysis software is used to simulate the velocity change curve of the projectile in the time domain under different conditions by combining static analysis and transient analysis, which reveals the relationship between the armature The relationship between structural parameters such as armature material, armature axial length, armature position, armature inner diameter and armature outer diameter and projectile end velocity is revealed, and the influence of several structural parameters on the acceleration performance of coil gun launcher is summarized and analyzed, and the optimized design principles of armature are summarized according to the obtained conclusions to provide theoretical references for practical applications.

In conventional linear accelerators, the beam is accelerated with a synchronous harmonic of the radio frequency field where the electric field component is collinear with the beam direction. This approach requires the design of complex accelerating structures, especially for low-energy heavy ions. If the beam motion were sustainably coupled to transverse electromagnetic fields, this could significantly simplify the accelerating structure design, and even allow acceleration with free-space waves. However, despite the long history of the proposed concept for accelerating low-velocity ion beams, it has not found practical application, partially because of the complexity of the technical design. In this paper, we present a practical design approach for this undulator-based accelerator for low-energy heavy-ions, reminiscent of the inverse free electron laser operating principle, but in a different parameter space.

In traditional heavy truck design process, a large number of real vehicle tests are required to evaluate the ride comfort of the heavy truck. This not only increases the R&D costs but also prolongs the R&D cycle, which brings great inconvenience. This paper establishes a three-dimensional digital model in Adams/car based on the relevant parameters of a hybrid heavy truck. The ride comfort with different speeds was tested on B-level random roads and A-level impulsive roads, and the maximum body vibration acceleration of the heavy truck when driving on A-level impulse roads, weighted root mean square value of acceleration of driving seat vibration when driving on a B-level random road are obtained with different speeds. These values reflect the impact on human comfort and health when driving, provide a theoretical basis for the subsequent optimization design and greatly save manpower and material resources.

With the development of the industrial internet, the comprehensive application of big data, the internet of things and artificial intelligence are becoming quietly extensive, and they connect physical things to the digital world tightly. Being smart and intelligent has become one of the most important directions of future social development. As an agent, robots will be widely utilized in every corner of society, and the robot era has come quietly. This paper mainly studies how to let the robot walk according to the prescribed route as a person. Our innovation points are as follows: Firstly, compared with the traditional packaging robot, the steering gear of the legs is similar to that of normal people, and the hands, arms, and heads can also cooperate in the march, just like normal people. Tracking, individual turns, and special gestures can be achieved. Under the combined action of the threshold, CCD, sensor, and 12 steering gear, the robot can complete the patrol walk at a fast speed.

The process of gear shifting in vehicles automatic transmissions is considered in the paper as the shock interaction of transmission elements. Two mathematical models are proposed and considered for simulation the gear shifting processes. Computer simulation of the models’ movement during acceleration of a vehicle, as well as modes of low - and high-frequency gear shift cycling (self-oscillations of the output shaft of the gearbox) is carried out. Methods for decreasing the amplitude of the gearbox output shaft oscillations caused by the impact nature of gear shifting are proposed.

In this paper, it is shown that microparticles can be effectively neutralised in the (spatial) plasma afterglow of an inductively coupled plasma. A key element in the reported experiments is the utilisation of a grounded mesh grid separating the plasma bulk and the ‘shielded’ plasma afterglow. Once particles—being injected in and charged by the inductively coupled plasma—had passed this mesh grid, the plasma was switched off while the particles continued to be transported under the influence of both flow and gravity. In the shielded spatial plasma afterglow region, the particle charge was deducted from their acceleration in an externally applied electric field. Our experiments demonstrate that all particles were neutralised independently of the applied electric field magnitude. The achieved neutralisation is of primary importance for the further development of plasma-assisted contamination control strategies as well as for a wide range of other applications, such as colourimetric sensing, differential mobility analysers, and medical applications.

Objective Activity energy expenditure (EE) plays an important role in healthcare, therefore, accurate EE measures are required. Currently available reference EE acquisition methods, such as doubly labeled water and indirect calorimetry, are complex, expensive, uncomfortable, and/or difficult to apply on real time. To overcome these drawbacks, the goal of this paper is to propose a model for computing EE in real time (minute-by-minute) from heart rate and accelerometer signals. Approach The proposed model, which consists of an original branched model, uses heart rate signals for computing EE on moderate to vigorous physical activities and a linear combination of heart rate and counts per minute for computing EE on light to moderate physical activities. Model parameters were estimated from a given data set composed of 53 subjects performing 25 different physical activities (light-, moderate- and vigorous-intensity), and validated using leave-one-subject-out. A different database (semi-controlled in-city circuit), was used in order to validate the versatility of the proposed model. Comparisons are done versus linear and nonlinear models, which are also used for computing EE from accelerometer and/or HR signals. Main results The proposed piecewise model leads to more accurate EE estimations ([Formula: see text], [Formula: see text] and [Formula: see text] J kg-1 min-1 and [Formula: see text], [Formula: see text], and [Formula: see text] J kg-1 min-1 on each validation database). Significance This original approach, which is more conformable and less expensive than the reference methods, allows accurate EE estimations, in real time (minute-by-minute), during a large variety of physical activities. Therefore, this model may be used on applications such as computing the time that a given subject spent on light-intensity physical activities and on moderate to vigorous physical activities (binary classification accuracy of 0.8155).

With the development of laser technology, laser-driven proton acceleration provides a new method for proton tumor therapy. However, it has not been applied in practice because of the wide and decreasing energy spectrum of laser-accelerated proton beams. In this paper, we propose an analytical model to reconstruct the spread-out Bragg peak (SOBP) using laser-accelerated proton beams. Firstly, we present a modified weighting formula for protons of different energies. Secondly, a theoretical model for the reconstruction of SOBPs with laser-accelerated proton beams has been built. It can quickly calculate the number of laser shots needed for each energy interval of the laser-accelerated protons. Finally, we show the 2D reconstruction results of SOBPs for laser-accelerated proton beams and the ideal situation. The final results show that our analytical model can give an SOBP reconstruction scheme that can be used for actual tumor therapy.

A new electron acceleration mechanism of the superposed laser acceleration which was proposed in a paper [Jpn. J. Appl. Phys. 30 (1991) L1887] is reexamined by numerical analyses and analytical work in order to obtain a scaling law for this mechanism, and to check beam quality and the diffraction effect of laser. In this mechanism, electrons are accelerated by means of two superposed laser beams in which a longitudinal electric field is produced. The numerical analyses show that the acceleration gradient can be 1∼10 GeV/m or more depending on the laser parameter employed, when this mechanism is employed appropriately in an acceleration system. In this paper the following important results are obtained: 1) The scaling law is derived in the analytical work and it is numerically reproduced. 2) An electron beam should be collimated well in order to be accelerated well. 3) The diffraction effect of laser beams has a great influence on the electron acceleration. Under the influence of the diffraction, electrons may not be accelerated at all. Drift tubes which lead electrons to only the acceleration region may be required for effective acceleration.

The paper describes the gravity acceleration sensor (GAS) design, the technical characteristics of which provide an increase in the static transfer constant of the GAS, the ability to determine the current static transfer constant of the GAS, reducing the level of noise effects in the output signal of GAS. The acceleration vector components from the side of a moving vehicle add a noise to the gravity vector components. These investigations give an answer how to obtain of GAS’s desired metrological features by the developing of new GAS based on pendulous integrating gyroscopic accelerometer. The presented material can be seen as an example of how to explore a gyro system mechanics and how to develop new gyro systems structure. The presented methods and the sequences of expressions can be used in master’s and bachelor’s disciplines in the field of applied mechanics, instrument development and automatic control.

The paper describes the results of the efficiency analysis of the simulation model of light commercial vehicle GAZ GAZelle NEXT. The efficiency of the model is confirmed by comparing the results of field test and calculation studies of controllability. The model is built in the MSC ADAMS/Car software package. It accounts for the mass-inertial characteristics of sprung and unsprung masses; the model of the suspension system simulates the kinematics and elasto-kinematics of the suspension and steering control, as well as elastic and damping elements. The tire model simulates vertical stiffness and damping, the slip stiffness depends on the vertical load, the longitudinal slip coefficient and the lateral angle of tire relative to the contact surface. The assessment was made by comparing the data obtained experimentally and by calculation. The test is conducted using the Fishhook method applied by NHTS for the vehicle stability analysis. The resulting errors are analyzed based on relative and absolute error values. When analyzing lateral acceleration and yaw rate deviations, the mathematical statistical tools are employed: average deviation, dispersion, root-mean-square deviation. The discrepancy between the results and the deviation of the average values does not exceed 10%. Minor deviations and scatter of results shows the efficiency of the simulation model and that this model can be employed for simulating the curvilinear motion of light commercial vehicles and assessment of their controllability and stability characteristics.

The floating offshore wind turbine (FOWT) may have significant displacement and acceleration of the hub caused due to the wind-wave interaction. In this paper, a simplified cascaded analysis of the FOWT is presented in order to obtain a preliminary estimate of the responses of the hub using an iterative frequency domain technique. In order to carry out the analysis, the masses of the nacelle and rotor are lumped at the top of the hub, which is discretized into elements. At the base of the hub, two interface degrees of freedom consisting of a rotation and a translation is considered, which connect the two subsystems, namely, the hub and the floating body (spar). Both the wave and fluctuating components of the wind are considered as a random process represented by their power spectral density functions. The two subsystems are analyzed separately, and the interaction effect is incorporated through an iterative process. Using the above method of analysis, a FOWT having a 90m tall tower is analyzed under two random sea states, namely, 12m-18s and 5m-10s. Two mean wind velocities, namely, 12m/s and 20m/s are taken at the reference height of 10m. The results of the study indicate that significant absolute peak displacement and acceleration at the top of the hub may take place, requiring due attention to the safety of the design of FOWT.

Throughout their construction period and service lifespan, the piers of bridges that built in earthquake zones are susceptible to abrupt earthquake. Thus, during their design period, all the possible circumstances must be taken into consideration because they are strategic infrastructures. Basically, the piers can be considered as the major part of the bridges. This paper presents an experimental work to investigate how the earthquakes influence on the seismic behavior of the selected concrete bridge piers. Physical modeling principals were applied to prepare three models of piers and table of shaking (1-g tests). The piers models were tested under 0.8g waveform for three cases, a rectangular pier constructed on a saturated cohesionless layer of soil, a hexagonal pier constructed over a saturated cohesionless layer and a circular pier installed on saturated cohesionless layer. The obtained results involved the time-acceleration measurement from the accelerometers throughout the shacking, the dynamic earth pressure, and the seismic displacement piers models. Basically, the obtained results of the experiments revealed that the acceleration amplification enhanced greatly at the pier top. The seismic displacement increased sharply because of the strong motion. The rectangular pier exhibited the highest values of the dynamic earth pressure.

This paper proposes a method of designing an affordable, universal Computer Numerically Controlled (CNC) machine for the use by hobbyists and university laboratories. The machine combines the functions of a 3 to 4-axis milling machine and of a 3D printer. We discuss the major factors contributing to manufacturability and dimensional accuracy of the produced parts, and make several suggestions that aim to maximize the cost effectiveness of the machine’s design. A methodology is developed for optimizing the machine’s rigidity and dimensional accuracy by selecting the proper off-the-shelf components. A calculation that follows the proposed method starts when the required level of accuracy and the machining speed is specified; the result of such a calculation is the overall design of the CNC machine, a bill of materials, and the cost estimate. The design can be optimized for cost, weight, or other parameters. The model presently accounts for the forces generated by the cutting action, the acceleration of machine components, and the associated simple bending moments. The future work in this area relates to the improvement of the proposed method and mathematical model to account for the twisting moments, friction, and vibration.

This paper presents the development of an artificial neural network (ANN) model for rolling element bearings fault classification that uses features extracted from acceleration data collected during run-to-failure experiments. The presented approach initially employs a wavelet decomposition method for signal denoising and subsequently relies on a Fourier transform to analyse the acceleration signal in the frequency domain. Several features that correspond to the entire signal range as well as to specific frequency bands are then extracted and used as inputs in the ANN model, which is trained to identify three different operational states, namely, no fault, inner race fault and outer race fault. The developed ANN model is validated using experimental data from the publicly available dataset provided by the Center of Intelligent Maintenance Systems (IMS) of the University of Cincinnati. The results show that the trained ANN model has a classification accuracy of 90.2% in the training data and 100% in the test data.

At present, sEMG-based gesture recognition requires vast amounts of training data; otherwise it is limited to a few gestures. Objective. This paper presents a novel dynamic energy model that decodes continuous hand actions by training small amounts of sEMG data. Approach. The activation of forearm muscles can set the corresponding fingers in motion or state with movement trends. The moving fingers store kinetic energy, and the fingers with movement trends store potential energy. The kinetic energy and potential energy in each finger are dynamically allocated due to the adaptive-coupling mechanism of five-fingers in actual motion. Meanwhile, the sum of the two energies remains constant at a certain muscle activation. We regarded hand movements with the same direction of acceleration for five-finger as the same in energy mode and divided hand movements into ten energy modes. Independent component analysis and machine learning methods were used to model associations between sEMG signals and energy modes and expressed gestures by energy form adaptively. This theory imitates the self-adapting mechanism in actual tasks. Thus, ten healthy subjects were recruited, and three experiments mimicking activities of daily living were designed to evaluate the interface: (1) the expression of untrained gestures, (2) the decoding of the amount of single-finger energy, and (3) real-time control. Main results. (1) Participants completed the untrained hand movements (100/100, p < 0.0001). (2) The interface performed better than chance in the experiment where participants pricked balloons with a needle tip (779/1000, p < 0.0001). (3) In the experiment where participants punched a hole in the plasticine on the balloon, the success rate was over 95% (97.67 ± 5.04%, p < 0.01). Significance. The model can achieve continuous hand actions with speed or force information by training small amounts of sEMG data, which reduces learning task complexity.

A gantry crane presents a control problem with ten state variables. The undamped swinging of the load has led earlier researchers to apply cumbersome control strategies. The essence of pragmatic control is gleaned from autopilot designs of half a century ago. The control is designed as a set of ‘nested loops’, where the innermost loop takes the form of a velocity loop wrapped around a motor to give crisp velocity control. Target values are derived from states in the outer loops, to be applied to a succession of inner loops. These target values are subjected to constraints. Thus in the case of the crane, the horizontal position of the load can be considered to be the two outermost variables. In this study, from the load position error, two target velocity components are calculated and subjected to limits. The velocity error leads in turn to a target acceleration of the load and subsequently, to the target displacement that takes place between the horizontal coordinates of the hoist and the load. In this paper, the pragmatic control technique is demonstrated with the aid of a JavaScript and MATLAB software programs using a state-space model.

The paper analyzes the design features of a small technological spacecraft justifying the choice of design parameters and modeling the functioning of the spacecraft in terms of micro-acceleration requirements. These requirements are imposed in order to successfully implement gravitationally sensitive technological processes, determine the possibility and feasibility of their implementation and regulate the choice of design parameters, structural layout diagram and executive bodies of the orientation and motion control system of a small technological spacecraft. The experience of designing, creating and operating medium-class technological spacecraft is generalized and analyzed. Common points and differences are identified and discussed. The approaches proposed in the work and the results obtained can be used in the design of small technological spacecraft.

Thin-walled cold-formed steel (TWCFS) structures have a great application prospect and are widely adopted in low-rise residential constructions due to great mechanical and economical properties. Since TWCFS member has low flexural rigidity and is hard to weld, it is rarely used in bridge engineering. In Poyang Lake Wetland of Jiangxi Province, China, a TWCFS footbridge was built. In this paper, Serial tests including static loading test, natural frequency test and pedestrian comfort test were conducted. At the same time, finite element analysis (FEA) models were built with Midas/Civil software. The data shows that although natural frequency is far greater than the range of pedestrian walking frequency and will not lead to the resonance of bridge, the peak acceleration under crowd load reflects poor pedestrian comfort. The structure was modified for improving pedestrian comfort and the results after modification verify that the comfort can be ensured.

In this paper a multibody dynamic model of a wheeled tractor-front-end loader system with pneumatic boom suspension is created. A front-end loader was designed and manufactured to validate the dynamic model and to conduct proving ground tests. Comparisons of some simulation results with the measured data revealed that the proposed dynamics model can well describe the vibrations of the tested compact wheel loader. In addition, the results of tests for RMS acceleration and spectral densities at different speeds are presented.

Bearing defect is a major factor in failure of rotating machinery. As a defect is detected the machinery is shut down as soon as possible to avoid catastrophic damage. Therefore, it is important to monitor the condition of bearings and to predict its remaining useful life. Six run to failure datasets are provided by pronostia laboratory to build prognostics models and to estimate the remaining useful life of eleven remaining bearings acceleration vibration signals have been gathered during the experiment. Vertical and horizontal acceleration was measured by two accelerometer mounted on the bearing housing. Support vector regression was proposed as a tool to develop the bearing remaining useful life. It is known that the method is affected by outliers because there are possibilities that outliers were selected as support vectors. Some robust support vector regression have been proposed. However, empirical study of robustness of support vector regression for bearing acceleration vibration has not yet been studied. This paper proposes a graphical exploration to study the robustness of support vector regression of bearing acceleration vibration. The results shows that the graphical approach can be used as a tool for preliminary study of robustness of support vector regression for bearing vibration acceleration.

The dynamic monitoring for the scene of the engineering vehicle dynamic load of the vibration was performed. By developing a subroutine of ABAQUS DLOAD to simulate the process of vehicle traffic, the characteristics of vehicle vibration transmission in soil was analyzed. Based on three different indicators: displacement, acceleration and vibration level, the influence of different speeds and different weights of the vehicle vibration on the surrounding soil and reasonable control distance was analyzed. This paper provides reference and guidance to avoid the influence of traffic dynamic load when designing and constructing.

The paper is devoted to the analysis of non-steady combustion and detonation in aqueous solutions foamed with the hydrogen-oxygen gaseous mixture. The processes of flame acceleration and transition to detonation are studied experimentally and numerically. Based on complex analysis, the effect of cumulative compression of the reactive gaseous mixture inside collapsing bubbles is proposed to be the mechanism of detonation formation and its further self- sustained propagation. Flame propagation through the foam leads to the compression waves generation. Under the action of compression waves, the gas bubble collapses, and states with high energy densities are achieved inside the bubble. As a result, the ignition inside the bubble takes place that represents a basic mechanism of detonation formation and propagation.

With the development of MEMS capacitive accelera-tion sensor to a higher measurement range (tens of thousands of g or even hundreds of thousands of g), the failure of the device microstructure under extreme mechanical impact has become a key factor restricting its performance improvement. Existing research mainly focuses on material stress failure and device structure optimization. Aiming at the failure of micro structure under impact, a simulation model of impact response of micro structure is established in this paper. Based on the existing over stress failure and device structure optimization, the stress failure effect and short-circuit failure effect of MEMS capacitive acceleration sensor under strong impact are proposed, and the influence rules of the two failure mechanisms on the sensor limit range and sensitivity are obtained. At the same time, the optimization design of the key structural parameters of the sensor is discussed.

The mountainous area is wide in the western region of China, and there are many seismic zones. Due to the two factors, there are more and more slope projects in the western region, and the influence of earthquake also need to be considered into the relevant researches on anchored slope. The damage to the slope under the earthquake has attracted the attention of researchers, Therefore, there are many studies on slope support under the seismic action. However, there is little research on the influence of seismic intensity on the slopes supported with pre-stressed anchored-frame structures. This paper based on an engineering example in the northwest loess area, taking into account the synergy of the frame-anchor-soil, a three-dimensional finite element model of the slope system with pre-stressed anchored-frame structure under the seismic action was established. The dynamic response of the supported slope was calculated by the finite element software ADINA, and the impact of different seismic intensities on the slope displacement, acceleration, axial force of anchor, and earth pressure are analyzed

The objectives on identifying all the links’ position in a flat lever mechanism within the considered time period, as well as determining the values of displacements, speeds and accelerations for the mechanism’s characteristic points are applied in engineering calculations in the course of the mechanisms designing process. Conducting kinematic analysis using the graphoanalytic method is a fairly accurate and visual method in training, but it is quite time-consuming and contains a lot of routine operations. This paper demonstrates a solution enabling to significantly reduce the number of routine operations by creating a dynamic block for the mechanism’s initial position with the parametric dependencies setting up. Designing is performed in the AutoCAD environment. This solution will help to quickly and accurately build a set of the flat lever mechanism links’ positions and display the characteristic curves for angular coordinates "φ" and time “t”. The algorithm for creating such a block, as well as the features of working with parametric models are described. The proposed method allows to introduce the research elements in studying the discipline “Theory of mechanisms and machines”. By imposing dimensional and geometric constraints, one can trace their influence on changing kinematic diagrams of the path, speed and acceleration.