We cannot hear the vibrations that are made by waving our hands in the air because they are too slow. The slowest vibration our human ears can hear is 20 times a second. That would be a very low sound. The fastest vibration we can hear is 20, times per second, which would be a very high sound. Animals can hear different frequencies from humans.
Cats can hear even higher frequencies than dogs, and porpoises can hear the fastest vibrations of all up to , times per second. It takes 3 different vibrations to hear a sound, since sound is made when things vibrate or wiggle :. When sound waves move through the air, each air molecule vibrates back and forth, hitting the air molecule next to it, which then also vibrates back and forth. The individual air molecules do not "travel" with the wave. They just vibrate back and forth.
When the vibrations are fast high frequency , you hear a high note. When vibrations are slower, you hear a lower note. Describe how sound is produced. How many different vibrations are needed to hear a sound? All objects have the potential to vibrate. Can we hear all of them? The first rigid body is loaded by the harmonic moment , where and p are the amplitude and frequency of the external moment, correspondingly.
Equivalent external and internal damping, having coefficients and , are taking into account in appropriate cross-sections. Substituting 3 into the boundary conditions 2 we obtain the following set of ordinary nonlinear differential equations with a retarded argument for unknown functions and.
Nonlinear equations 4 are solved numerically by means of the Runge-Kutta method. In the case of the local nonlinearities having the hard characteristic, , such equations can be solved numerically with zero or nonzero initial conditions. It should be pointed out that ordinary differential equations with shifts in the arguments of unknown functions have an attention in the literature, eg.
The aim of the numerical analysis is to study the possibility of occurrence of irregular vibrations in discrete-continuous systems considered. The three first natural frequency for linear the system are and. Cases when solutions are harmonic vibrations with the period equal to the period of the external loading are presented in Fig. They are given for large damping having coefficients equal and show the effect of the parameter with and the effect the amplitude of the external moment with. Nonlinear effects are observed in the first three resonant regions, similarly to other results given in [5].
Especially, it is seen that in the third resonant region nonlinear effects have the form of amplitude jumps. Two amplitude jumps are observed. They correspond to zero and nonzero initial conditions, respectively. From diagrams in Fig. It appears that distances of jumps increase also with the decrease of damping, [5]. Further numerical results are presented in Figs.
They concern the amplitude of the external moment equal and , however small damping, i. In Fig. In bifurcations diagrams periods of the solutions are taken into account. From Fig. The effective vibration value is recorded daily. Several times higher vibrations were observed at irregular intervals; their causes were sought, and the relation between the steam generator vibrations measured at the bottom of its vessel and the feedwater pressure was established.
The source of the vibrations was found to be in the feedwater tract of the steam generator. The feedwater tract is described and its hydraulic characteristics are given. Vibrations were measured on the S02 valve. It is concluded that vibrations can be eliminated by reducing the water pressure before the control valves and by replacing the control valves with ones with more suitable control characteristics.
Non-stationary random vibration analysis of a 3D train-bridge system using the probability density evolution method. Rail irregularity is one of the main sources causing train-bridge random vibration. A new random vibration theory for the coupled train-bridge systems is proposed in this paper. First, number theory method NTM with 2N-dimensional vectors for the stochastic harmonic function SHF of rail irregularity power spectrum density was adopted to determine the representative points of spatial frequencies and phases to generate the random rail irregularity samples, and the non-stationary rail irregularity samples were modulated with the slowly varying function.
A case study was presented in which the ICE-3 train travels on a three-span simply-supported high-speed railway bridge with excitation of random rail irregularity. The results showed that compared to the Monte Carlo simulation, the PDEM has higher computational efficiency for the same accuracy, i.
Additionally, the influences of rail irregularity and train speed on the random vibration of the coupled train-bridge system were discussed. The response characteristics of vibration -sensitive saccular fibers in the grassfrog, Rana temporaria. The response characteristics of saccular nerve fibers in European grassfrogs Rana temporaria subjected to dorso-ventral, Hz sinusoidal vibrations were studied.
Only 4 fibers out of a total of did not respond to the vibrations. No behavioral role of a vibration receptor has been demonstrated in the grassfrog. These fibers were very vibration -sensitive. The synchronization thresholds at Hz varied from below 0.
In contrast to earlier results, all these fibers had low-pass characteristics with respect to acceleration and responded maximally at 10 and 20 Hz. Application of the pothole DAF method to vehicles traversing periodic roadway irregularities.
This paper is a sequel to the work discussed in Pesterev et al. Journal of Sound and Vibration , in press. In that paper, it was suggested that the technique to determine the effect of a local road surface irregularity on the dynamics of a vehicle modelled as a linear multi-degree-of-freedom system relies on the so-called pothole dynamic amplification factor DAF , which is a complex-valued function specific to the irregularity shape.
This paper discusses the companion problem of how to determine the DAF function for an irregularity represented as a superposition of simpler ones. Another purpose of this paper is to demonstrate the application of the pothole DAF functions technique to finding a priori estimates of the effect of irregularities with a repeated structure.
Specifically, we solve the problem of finding the conditions under which the dynamic effect of two identical potholes located one after another is greater than that due to the single pothole. We also find the estimate for the number of periods of a periodic irregularity that are sufficient in order to consider the oscillator response as steady state. The discussions are illustrated by numerical examples.
Control of chaotic vibration in automotive wiper systems. Chaotic vibration has been identified in the automotive wiper system at certain wiping speeds. This irregular vibration not only decreases the wiping efficiency, but also degrades the driving comfort. The purpose of this paper is to propose a new approach to stabilize the chaotic vibration in the wiper system.
The key is to employ the extended time-delay feedback control in such a way that the applied voltage of the wiper motor is online adjusted according to its armature current feedback. Based on a practical wiper system, it is verified that the proposed approach can successfully stabilize the chaotic vibration , and provide a wide range of wiping speeds.
Directory of Open Access Journals Sweden. Full Text Available Dynamics of magnetic field-aligned small-scale irregularities in the electron concentration, existing in the F-layer ionospheric plasma, is investigated with the help of a mathematical model.
The plasma is assumed to be a rarefied compound consisting of electrons and positive ions and being in a strong, external magnetic field. In the applied model, kinetic processes in the plasma are simulated by using the Vlasov-Poisson system of equations. The system of equations is numerically solved applying a macroparticle method. The time evolution of a plasma irregularity , having initial cross-section dimension commensurable with a Debye length, is simulated during the period sufficient for the irregularity to decay completely.
The results of simulation indicate that the small-scale irregularity , created initially in the F-region ionosphere, decays accomplishing periodic damped vibrations , with the process being collisionless. With the recent emergence of large-scale knowledge dis- covery, data mining and social network analysis, irregular applications have gained renewed interest.
Classic cache-based high-performance architectures do not provide optimal performances with such kind of workloads, mainly due to the very low spatial and temporal locality of the irregular control and memory access patterns.
In this paper, we present a multi-node, multi-core, fine-grained multi-threaded shared-memory system architecture specifically designed for the execution of large-scale irregular applications, and built on top of three pillars, that we believe are fundamental to support these workloads.
First, we offer transparent hardware support for Partitioned Global Address Space PGAS to provide a large globally-shared address space with no software library overhead. Second, we employ multi-threaded multi-core processing nodes to achieve the necessary latency tolerance required by accessing global memory, which potentially resides in a remote node.
Finally, we devise hardware support for inter-thread synchronization on the whole global address space. We first model the performances by using an analytical model that takes into account the main architecture and application characteristics.
We describe the hardware design of the proposed cus- tom architectural building blocks that provide support for the above- mentioned three pillars.
Finally, we present a limited-scale evaluation of the system on a multi-board FPGA prototype with typical irregular kernels and benchmarks. The experimental evaluation demonstrates the architecture performance scalability for different configurations of the whole system.
The response of guinea pig primary utricular and saccular irregular neurons to bone-conducted vibration BCV and air-conducted sound ACS. This study sought to characterize the response of mammalian primary otolithic neurons to sound and vibration by measuring the resting discharge rates, thresholds for increases in firing rate and supra-threshold sensitivity functions of guinea pig single primary utricular and saccular afferents.
Neurons with irregular resting discharge were activated in response to bone conducted vibration BCV and air conducted sound ACS for frequencies between Hz and Hz. The location of neurons was verified by labelling with neurobiotin. Many afferents from both maculae have very low or zero resting discharge, with saccular afferents having on average, higher resting rates than utricular afferents.
For BCV stimulation: utricular and saccular neurons show similar low thresholds for increased firing rate around 0. There is a steep increase in rate change threshold for BCV frequencies above Hz. The suprathreshold sensitivity functions for BCV were similar for both utricular and saccular neurons, with, at low frequencies, very steep increases in firing rate as intensity increased.
For ACS stimulation: utricular and saccular neurons can be activated by high intensity stimuli for frequencies from Hz to Hz with similar flattened U-shaped tuning curves with lowest thresholds for frequencies around Hz. The average ACS thresholds for saccular afferents across these frequencies is about dB lower than for utricular neurons. The suprathreshold sensitivity functions for ACS were similar for both utricular and saccular neurons. Phase-locking at low frequencies e.
Scintillations associated with bottomside sinusoidal irregularities in the equatorial F region. Multisatellite scintillation observations and spaced receiver drift measurements are presented for a category of equatorial F region plasma irregularities characterized by nearly sinusoidal waveforms in the ion number density. The observations were made at Huancayo, Peru, and the measurements at Ancon, Peru, associated with irregularities observed by the Atmospheric- Explorer -E satellite on a few nights in December Utilizing ray paths to various geostationary satellites, it was found that the irregularities grow and decay almost simultaneously in long-lived patches extending at least km in the east-west direction.
Full Text Available To study the characteristics of the coupling vibration between a maglev vehicle and its track beam system and to improve the performance of the levitation system, a new type of vibration test bench was developed. Take a single maglev frame as the study object; simulation of the coupling vibration of the maglev vehicle, levitation system, and track beam were achieved. In addition, all types of real track irregularity excitations can be simulated using hydraulic actuators of the test bench.
To expand the research scope, a simulation model was developed that can conduct the simulation research synergistically with the test bench. Based on a dynamics model of the test bench, the dynamics simulation method determined the influence on the levitation control performance of three factors: the track beam support stiffness, the track beam mass, and the track irregularity.
By combining the test bench and the dynamics model, experiments can be guided by the simulation results, and the experimental results can validate the dynamics simulation results. Irregular applications are characterized by irregular data structures, control and communication patterns. Novel irregular high performance applications which deal with large data sets and require have recently appeared.
Unfortunately, current high performance systems and software infrastructures executes irregular algorithms poorly. Only coordinated efforts by end user, area specialists and computer scientists that consider both the architecture and the software stack may be able to provide solutions to the challenges of modern irregular applications.
On the stick-slip vibration in the suspension of a freight wagon. Full Text Available Damping based on the dry friction is frequently in suspensions of the freight wagons. The paper presents some aspects of vertical vibration of freight wagons. It uses a simple model considering that the vehicle was reduced to a mass suspended on a wheel, moving at constant speed on a rigid track with harmonic irregularity.
Stick-slip vibration can occur due to the friction and it is characterized by sudden changes in the wheel acceleration affecting the ride quality. The paper shows the influence of stick-slip vibration on the wheel-rail dynamic force.
This study explored four hypotheses: a the relationships among rapid automatized naming RAN and processing speed PS to irregular word, non-word, and word reading; b the predictive power of various RAN and PS measures, c the cognitive correlates that best predicted irregular word, non-word, and word reading, and d reading performance of…. The upper ionosphere of Mars contains a variety of perturbations driven by solar wind forcing from above and upward propagating atmospheric waves from below.
As irregular structure gives rise to off-vertical echoes with excess propagation time, the diffuseness of ionospheric echo traces can be used as a diagnostic tool for perturbed reflection surfaces. The observed properties of diffuse echoes above unmagnetized regions suggest that ionospheric irregularities with horizontal wavelengths of tens to hundreds of kilometers are particularly enhanced in the winter hemisphere and at high solar zenith angles.
Given the known inverse dependence of neutral gravity wave amplitudes on the background atmospheric temperature, the ionospheric irregularities probed by MARSIS are most likely associated with plasma perturbations driven by atmospheric gravity waves.
Though extreme events with unusually diffuse echoes are more frequently observed for high solar wind dynamic pressures during some time intervals, the vast majority of the diffuse echo events are unaffected by varying solar wind conditions, implying limited influence of solar wind forcing on the generation of ionospheric irregularities. Combination of remote and in situ measurements of ionospheric irregularities would offer the opportunity for a better understanding of the ionospheric dynamics at Mars.
Proceedings of the national conference on exploring the frontiers of vibrational spectroscopy: abstracts. Spectroscopy has played and is playing a very important role as it is one of the most efficient methods of molecular structure studies with the help of which direct information about the chemical compounds can be obtained.
Spectroscopy has its contribution in a number of branches in areas such as medicine, industry, environment, agriculture, power, construction, forensic analysis both criminal and civil cases , etc. Vibrational spectroscopic Infrared and Raman techniques have demonstrated potential to provide non-destructive, rapid clinically relevant diagnostic information.
Raman and infrared spectroscopy enable the biochemical signatures from biological tissues to be extracted and analyzed there by advancing the treatment of cancer. Advancement in instrumentation has allowed the development of numerous infrared and Raman spectroscopic methods. Infrared spectroscopy is tremendously used in the fields of pharmaceuticals. Raman spectroscopy is used in condensed matter physics, biomedicinal fields for tissue analysis and chemistry to study vibrational , rotational, and other low-frequency modes in a system.
Keeping in mind the fast development: in the Spectroscopy, we have planned to organize a national level conference for 2 days on ' Exploring the Frontiers of Vibrational Spectroscopy' to bring out the tremendous potential of various Spectroscopic techniques available at the global level.
Papers relevant to INIS are indexed separately. In a recent paper, we presented a phase screen theory for the spectrum of intensity scintillations when the refractive index irregularities follow a two-component power law [Carrano and Rino, DOI: More recently we have investigated the inverse problem, whereby phase screen parameters are inferred from scintillation time series.
This is accomplished by fitting the spectrum of intensity fluctuations with a parametrized theoretical model using Maximum Likelihood ML methods. The Markov-Chain Monte-Carlo technique provides a-posteriori errors and confidence intervals. We refer to this fitting as Irregularity Parameter Estimation IPE since it provides a statistical description of the irregularities from the scintillations they produce. In this talk, we explore some new opportunities for remote sensing ionospheric irregularities afforded by IPE.
Statistical characterization of irregularities and the plasma bubbles in which they are embedded provides insight into the development of the underlying instability. In a companion paper by Rino et al. IPE can be used to reconcile multi-frequency scintillation observations and to construct high fidelity scintillation simulation tools. In space-to-ground propagation scenarios, for which an estimate of the distance to the scattering region is available a-priori, IPE enables retrieval of zonal irregularity drift.
In radio occultation scenarios, the distance to the irregularities is generally unknown but IPE enables retrieval of Fresnel frequency. A geometric model for the effective scan velocity maps Fresnel frequency to Fresnel scale, yielding the distance to the irregularities. Using an integrative perspective drawn from vocational psychology and migration studies, this article explores the lives of irregular migrants, which represents a unique aspect of work-based migration.
Irregular migrants are those individuals who travel from regions without much work to states that offer some means of employment, without formal…. Star formation histories of irregular galaxies. Exploring the vibrational fingerprint of the electronic excitation energy via molecular dynamics. A Fourier-based method is presented to relate changes of the molecular structure during a molecular dynamics simulation with fluctuations in the electronic excitation energy.
The method implies sampling of the ground state potential energy surface. Subsequently, the power spectrum of the velocities is compared with the power spectrum of the excitation energy computed using time-dependent density functional theory. Peaks in both spectra are compared, and motions exhibiting a linear or quadratic behavior can be distinguished.
The quadratically active motions are mainly responsible for the changes in the excitation energy and hence cause shifts between the dynamic and static values of the spectral property. Moreover, information about the potential energy surface of various excited states can be obtained. The procedure is illustrated with three case studies. The first electronic excitation is explored in detail and dominant vibrational motions responsible for changes in the excitation energy are identified for ethylene, biphenyl, and hexamethylbenzene.
The proposed method is also extended to other low-energy excitations. Finally, the vibrational fingerprint of the excitation energy of a more complex molecule, in particular the azo dye ethyl orange in a water environment, is analyzed. Star Formation in Irregular Galaxies.
Examines mechanisms of how stars are formed in irregular galaxies. Formation in giant irregular galaxies, formation in dwarf irregular galaxies, and comparisons with larger star-forming regions found in spiral galaxies are considered separately. Steacy, Laura M. Models of irregular word reading that take into account both child- and word-level predictors have not been evaluated in typically developing children and children with reading difficulty RD. Full Text Available A novel hybrid method, which simultaneously possesses the efficiency of Fourier spectral method FSM and the applicability of the finite element method FEM, is presented for the vibration analysis of structures with elastic boundary conditions.
The FSM, as one type of analytical approaches with excellent convergence and accuracy, is mainly limited to problems with relatively regular geometry. The computational domain of general shape is divided into several subdomains firstly, some of which are represented by the FSM while the rest by the FEM. Then, fictitious springs are introduced for connecting these subdomains. Sufficient details are given to describe the development of such a hybrid method. Numerical examples of a one-dimensional Euler-Bernoulli beam and a two-dimensional rectangular plate show that the present method has good accuracy and efficiency.
Further, one irregular -shaped plate which consists of one rectangular plate and one semi-circular plate also demonstrates the capability of the present method applied to irregular structures.
Development of S-wave portable vibrator ; S ha potable vibrator shingen no kaihatsu. An S-wave portable vibrator to serve as a seismic source has been developed for the purpose of applying the shallow-layer reflection method to the study of the soil ground. The author, et al. The experimentally constructed S-wave vibrator consists of a conventional P-wave vibrator and an L-type wooden base plate combined therewith.
Serving as the monitor for vibration is a conventional accelerometer without any modification. The applicability test was carried out at a location where a plank hammering test was once conducted for reflection aided exploration , and the result was compared with that of the plank hammering test.
As the result, it was found that after some preliminary treatment the results of the two tests were roughly the same but that both reflected waves were a little sharper in the S-wave vibrator test than in the plank hammering test. A computationally efficient software application for calculating vibration from underground railways. The PiP model is a software application with a user-friendly interface for calculating vibration from underground railways. This paper reports about the software with a focus on its latest version and the plans for future developments.
The software calculates the Power Spectral Density of vibration due to a moving train on floating-slab track with track irregularity described by typical values of spectra for tracks with good, average and bad conditions. The latest version accounts for a tunnel embedded in a half space by employing a toolbox developed at K.
Leuven which calculates Green's functions for a multi-layered half-space. Full Text Available The paper herein examines the geometric filtering effect coming from the axle base of a railway vehicle upon the vertical vibrations behavior, due to the random irregularities of the track.
For this purpose, the complete model of a two-level suspension and flexible carbody vehicle has been taken into account. Following the modal analysis, the movement equations have been treated in an original manner and brought to a structure that points out at the symmetrical and anti-symmetrical decoupled movements of vehicle and their excitation modes. There has been shown that the geometric filtering has a selective behavior in decreasing the level of vibrations , and its contribution is affected by the axle base magnitude, rolling speed and frequency range.
National Aeronautics and Space Administration — Proposed effort is to use vibration to propel a small, self-contained device through unconsolidated loose, granular material, such as regolith. Small scale robotic Health care for irregular migrants: pragmatism across Europe: a qualitative study.
Dauvrin, M. Background Health services in Europe face the challenge of delivering care to a heterogeneous group of irregular migrants IM. There is little empirical evidence on how health professionals cope with this challenge. This study explores the experiences of health professionals providing care to IM in. Thanks to new massive IFU surveys like MaNGA, we can now characterize the gas and stellar kinematics of thousands of galaxies in the local universe, enabling statistical analyses on the frequency of disturbed kinematics, their origin, and their impact on their host galaxies.
We present a census of kinematics in MaNGA using a modified version of the Radon transform to map radial variations in kinematic position angles PA. We discuss the frequency of kinematically irregular disks, and describe commonly observed patterns in radial PA profiles. In order to constrain the drivers of these kinematic signatures, we analyze how they correlate with galaxy mass, environment, star formation history, and gas-phase metallicity.
Report of workshop on vibration related to fluid in atomic energy field. This is the fourth workshop on the vibration related to fluid in atomic energy field of Yayoi research group. This time, two topics were taken up. One is edgetone phenomena and the liquid surface vibration phenomena due to flow.
Another is the introduction of the experience in light water reactors. This paper presents an architecture template for next-generation high performance computing systems specifically targeted to irregular applications. We start our work by considering that future generation interconnection and memory bandwidth full-system numbers are expected to grow by a factor of In order to keep up with such a communication capacity, while still resorting to fine-grained multithreading as the main way to tolerate unpredictable memory access latencies of irregular applications, we show how overall performance scaling can benefit from the multi-core paradigm.
At the same time, we also show how such an architecture template must be coupled with specific techniques in order to optimize bandwidth utilization and achieve the maximum scalability. We propose a technique based on memory references aggregation, together with the related hardware implementation, as one of such optimization techniques. We explore the proposed architecture template by focusing on the Cray XMT architecture and, using a dedicated simulation infrastructure, validate the performance of our template with two typical irregular applications.
Our experimental results prove the benefits provided by both the multi-core approach and the bandwidth optimization reference aggregation technique. Capture of irregular satellites at Jupiter.
The irregular satellites of outer planets are thought to have been captured from heliocentric orbits. The exact nature of the capture process, however, remains uncertain. We examine the possibility that irregular satellites were captured from the planetesimal disk during the early solar system instability when encounters between the outer planets occurred. Here we find that the current instability models present favorable conditions for capture of irregular satellites at Jupiter as well, mainly because Jupiter undergoes a phase of close encounters with an ice giant.
We show that the orbital distribution of bodies captured during planetary encounters provides a good match to the observed distribution of irregular satellites at Jupiter. The capture efficiency for each particle in the original transplanetary disk is found to be 1. This is roughly enough to explain the observed population of jovian irregular moons.
Irregular Migrants and the Law. A survey and interview covering respondents was conducted between July and June to ascertain the real situations surrounding irregular migrants in Malaysia, which is one of the major host countries of international migrants from developing nations.
The policy on foreign workers was formulated in the mids to deal with the large number of irregular migrants and their This study adopts digital photography to monitor bridge dynamic deflection in vibration. Firstly, a digital camera is used to monitor the bridge in static as a zero image. Then, the digital camera is used to monitor the bridge in vibration every three seconds as the successive images.
Results show that the average measurement accuracies are 0. The maximal deflection of the bridge is 7. Digital photography used in this study can assess the bridge health through monitoring the bridge dynamic deflection in vibration. The deformation trend curves depicted over time also can warn the possible dangers. Real-time model predictive controller MPC implementation in active vibration control AVC is often rendered difficult by fast sampling speeds and extensive actuator-deformation asymmetry.
If the control of lightly damped mechanical structures is assumed, the region of attraction containing the set of allowable initial conditions requires a large prediction horizon, making the already computationally demanding on-line process even more complex. Model Predictive Vibration Control provides insight into the predictive control of lightly damped vibrating structures by exploring computationally efficient algorithms which are capable of low frequency vibration control with guaranteed stability and constraint feasibility.
Interference between vibration -to-translation and vibration-to-vibration energy transfer modes in diatomic molecules at high collision energies. An explicit time dependent approach for simultaneous VT and VV energy transfer in diatom--diatom collisions is explored using the exponential form of ladder operators in the solution of the Schroedinger equation of motion. The collision of two hydrogen molecules is chosen to illustrate the extent of interference between VT and VV modes among various vibrational states.
The occurrence of the coupling appears to be nearly universal in vibrational transitions at such energies. Exceptions to the coupling have been discussed. Full Text Available Irregularly -shaped bridges are usually adopted to connect the main bridge and ramps in urban overpasses, which are under significant flexion-torsion coupling effects and in complicated stress states.
In irregular -shaped bridge design, the parameters such as ramp radius, bifurcation diaphragm stiffness, box girder height, and supporting condition could affect structural performance in different manners. In this paper, the influence of various parameters on three indices, including maximum stress, the stress variation coefficient, and the fundamental frequency of torsional vibration , is investigated and analyzed based on orthogonal test method.
Through orthogonal analysis, the major influence parameters and corresponding optimal values for these indices are achieved. Combining with the analytic hierarchy process AHP, the hierarchical structure model of the multi-indices orthogonal test is established and a comprehensive weight analysis method is proposed to reflect the parameter influence on overall mechanical properties of an irregularly -shaped bridge.
Influence order and optimal values of parameters for overall mechanical properties are determined based on the weight of factors and levels calculated by the comprehensive weight analysis method. The results indicate that the comprehensive weight analysis method is superior to the overall balance method, which verifies the effectiveness and accuracy of the comprehensive weight analysis in the parameter optimization of the multi-indices orthogonal test for an irregularly -shaped bridge.
Optimal parameters obtained in this paper can provide reference and guidance for parameter control in irregularly -shaped bridge design. Full Text Available The paper describes the numerical simulation of the vertical random vibration of train-slab track-bridge interaction system by means of finite element method and pseudoexcitation method.
Each vehicle is modeled as four-wheelset mass-spring-damper system with two-layer suspension systems. The rail, slab, and bridge girder are modeled by three-layer elastic Bernoulli-Euler beams connected with each other by spring and damper elements.
The equations of motion for the entire system are derived according to energy principle. By regarding rail irregularity as a series of multipoint, different-phase random excitations, the random load vectors of the equations of motion are obtained by pseudoexcitation method. Taking a nine-span simply supported beam bridge traveled by a train consisting of 8 vehicles as an example, the vertical random vibration responses of the system are investigated.
Firstly, the suitable number of discrete frequencies of rail irregularity is obtained by numerical experimentations. Secondly, the reliability and efficiency of pseudoexcitation method are verified through comparison with Monte Carlo method. Thirdly, the random vibration characteristics of train-slab track-bridge interaction system are analyzed by pseudoexcitation method.
Analysis of micro vibration in gas film of aerostatic guide way based on molecule collision theory. Full Text Available Micro vibration of the aerostatic guide way has a significant impact on its dynamic characteristics and stability, which limits the development of pneumatic component. High pressure gas molecules have been collided with the supporting surface and the internal surface of the throttle during the flow process.
Variable impulse of the surfaces aside for the gas film are affected by the changes of impulse which formed irregular impact force in horizontal and vertical direction. Micro- vibration takes place based on the natural frequency of the system and its frequency doubling.
In this paper, the vibration model was established to describe the dynamic characteristics of the gas film, and the formation mechanism of micro vibration in the film is defined. Through the simulation analysis and experimental comparison, formation mechanism of the micro vibration in the gas film is confirmed.
It was proposed that the micro vibration of gas film can be produced no matter whether there is a gas chamber or not in the throttle. Under the same conditions, the micro vibration of the guide way with air chamber is greater than that without any chamber. The frequency points of the vibration peaks are almost the same, as well as the vibration pattern in the frequency domain.
Strategic Analysis of Irregular Warfare. Irregular Migration in Jordan, The first concerns irregular labour migrants and has been approached by using figures showing the socio-economic profile of non Jordanians working in Jordan and, additionally, unemployment in Jordan. This is done by assuming close similarities between legal and irregular labour migrants.
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