Theoretical Analysis Of Dynamics Research Articles

Ligand effect on Ru-centered species toward methane activation.

Ligands have been known to profoundly affect the chemical transformations of methane, yet significant challenges remain in shedding light on the underlying mechanisms. Here, we demonstrate that the conversion of methane can be regulated by Ru centered cations with a series of ligands (C, CH, CNH, CHCNH). Gas-phase experiments complemented by theoretical dynamic analysis were performed to explore the essences and principles governing the ligand effect. In contrast to the inert Ru+, [RuC]+, and [RuCNH]+ toward CH4, the dehydrogenation dominates the reaction of ligand-regulated systems [RuCH]+/CH4 and [RuCHCNH]+/CH4. In active cases, CH acts as active sites, and regulates the activation of CH4 assisted by the "seemingly inert" CNH ligand.

DYNAMIC ANALYSIS OF THE FOOTBRIDGE EXPOSED TO PEDESTRIAN LOADING

The submitted paper is dealing with the phenomenon of the human induced vibration caused by walking pedestrians. Pedestrians naturally work as a source of a periodic load, which is typically in the resonance range with some of the natural frequencies of the crossed footbridge. Typical pacing frequency of the normal walk is close to 2 Hz. Unfortunately, the most of footbridges have some of the natural frequencies in the range 1.5 – 3 Hz. These values can be easily reached by pedestrians, which could lead to the uncomfortable level of the structural vibration as could be seen at the Millennium bridge in London. In the submitted paper, we are going to subject the footbridge, acting as the simply supported beam, to the theoretical dynamic analysis. The dynamic analysis will be divided into the modal analysis and the force vibration analysis, which is accomplished by the modal decomposition method. This approach allows us to execute direct integration of the independent equations of motion. Total number of these modal equations is significantly less than number of equations directly assembled by the Finite element method. The pedestrians will be mathematically described by the periodic shifting force with constant velocity of motion.

Study of the Ground Reaction Force Induced by Swaying or Bobbing People and its Dynamic Effect on Loaded Structures

The core of the submitted article is in the modeling of bobbing people for describing the action of qualified vandals, who try to achieve an excessive level of vibration by their periodic sway in the knees while they are not losing contact between the footbridge deck and their feet. The DLF models, which already exist, provide particular coefficients only for specific pacing frequencies. On the other hand, our study presents DLF coefficients as a continuous function for frequencies in the range of 1 Hz – 3 Hz. The newly presented DLF model is based on the measurement of 15 random people and compared with the experimental data. Each of these people was measured by a force plate in the frequency range of 1 Hz – 3 Hz. Since we know who exactly was present during the experiment, we also monitored the contact forces produced by these people at frequencies identical to some natural frequencies of the footbridge according to the experimental setup. These measured forces were used directly as the input into the calculation process and compared with the experiment too. Subsequent dynamic calculations of the forced vibration were carried out by Modal Decomposition Method. This method requires a mode shape as one of the inputs, these mode shapes were calculated by the Subspace Iteration Method using commercial software Dlubal RFEM 5.03. Numerical integration of the equations of motion (forced vibration analysis) was done by self-written MATLAB codes and routines. At the end of the article, we summarize the results of theoretical dynamic analysis obtained by theoretical modeling of these vandals. The main outcomes are in the determination of the continuous functions for DLFs and their phase angles based on the experimental results. These values are crucial e.g. for designers, who need to compute the response of a footbridge or a grandstand which could be excited by swaying or bobbing vandals or spectators. Obtained and evaluated continuous functions for DLFs were compared by literature where researchers presented some DLFs for discrete sets of frequencies, which produced a good level of accordance.

A New Theoretical Dynamic Analysis of Ship Rolling Motion Considering Navigational Parameters, Loading Conditions and Sea State Conditions

Despite the IMO’s efforts and the large quantity of research carried out over the years concerning the sudden loss of stability in fishing vessels, and even the damage done to merchant fleets due to cargo shifting, accidents with very relevant consequences continue to occur. This paper can be considered as a continuation of the recent research of authors which was carried out with ships in static conditions, with pure beam seas and without resistance. The aim of the present research is to provide a reference for ships’ operators to improve the ship’s behavior and seakeeping, to alter the ship’s loading conditions or the navigational parameters (heading and speed), and even be aware of the time available to carry out these modifications before reaching dangerous situations. For this, all sea state conditions were mathematically modelled for, including the ship’s rolling motion both in static and in realistic and dynamic conditions, with the waves influencing the vessel by coming from any direction. Relevant results of easy comprehension for ships’ operators are shown in each of the models, which were validated with a representative real case study.

Dynamic behavior of axially moving web in multi-span roll-to-roll microcontact printing system

This article presents theoretical dynamic analysis of a vibrating axially moving web of a multi-span / multi-roll microcontact printing system and experimental measurements of the system’s frequency response. A unique lab-scale microcontact printing machine with high-speed web handling capabilities is used. The axially moving web is modeled as a string and as a membrane. Then, numerical results of both models are compared with experimentally obtained response. The experiment is run for both case of constant axial speed and varying axial speed with time. Although both models are in good agreement with the experimental results, the values of frequencies obtained from the string model are found to be in closer agreement with those obtained from the experimental findings. It is found that increasing the web tension and decreasing the axial web speed increase the system’s frequency.

Theoretical analysis of equatorial near-inertial solitary waves under complete Coriolis parameters

An investigation of equatorial near-inertial wave dynamics under complete Coriolis parameters is performed in this paper. Starting from the basic model equations of oceanic motions, a Korteweg de Vries equation is derived to simulate the evolution of equatorial nonlinear near-inertial waves by using methods of scaling analysis and perturbation expansions under the equatorial beta plane approximation. Theoretical dynamic analysis is finished based on the obtained Korteweg de Vries equation, and the results show that the horizontal component of Coriolis parameters is of great importance to the propagation of equatorial nonlinear near-inertial solitary waves by modifying its dispersion relation and by interacting with the basic background flow.

Theoretical Analysis of Dynamics of Kinesin Molecular Motors.

Kinesin is a typical molecular motor that can step processively on microtubules powered by hydrolysis of adenosine triphosphate (ATP) molecules, playing a critical role in intracellular transports. Its dynamical properties such as its velocity, stepping ratio, run length, dissociation rate, etc. as well as the load dependencies of these quantities have been well documented through single-molecule experimental methods. In particular, the run length shows a dramatic asymmetry with respect to the direction of the load, and the dissociation rate exhibits a slip–catch–slip bond behavior under the backward load. Here, an analytic theory was provided for the dynamics of kinesin motors under both forward and backward loads, explaining consistently and quantitatively the diverse available experimental results.

Effect of the Presence of Basements on the Vibration Period and Other Seismic Responses of R.C. Frames

The soil-structure interaction (SSI) of R. C. building frames including basements below ground level has been the subject of extended research, mostly in the form of theoretical dynamic analysis. There are different issues concerned with this type of work, as e.g. the location of the base of the structure. Usually, the base of the structure in dynamic analysis or according to the codes is the level at which the lateral displacement is zero. According to this definition, and with the presence of basement floors and the soil mass below, the ground level may not be the base of the structure. The soil stiffness around basement walls has a great effect on the lateral displacement of the basement floor. Another issue is the effect of the presence of the basement floors on the dynamic behavior of the structure. A third issue is the effect of the soil around the basement walls and the soil mass below the foundation in general, which is known as the SSI. In this paper, 3-dimensional regular building frames subjected to seismic loading are analyzed using SAP2000 software. The first frame is a 5-floor, 3-D frame without including the soil mass below the raft foundation and without a basement floor. The second frame is the same frame with a basement floor and with consideration of the soil mass below the raft foundation and around the walls of the basement floor. The third frame is the same frame with consideration of the soil mass below the raft foundation but without the basement floor. Results of the seismic time history analysis and UBC97 response spectrum analysis are presented and discussed.

Dynamic Analysis of an Existing Arch Railway Bridge According to Eurocodes

AbstractModern regulations concerning railway bridges are based on the approach of structural dynamics, which is described in PN-EN standards. This paper presents the results of theoretical dynamic analysis of the HSLM-A train set loading on the structure of a pre-stressed concrete arch bridge - the first railway bridge of its type which was built in Poland (completed in 1959). The recommendations of PN-EN have been followed and modal analysis was carried out to define the sensitivity of the structure to chosen eigenforms. Additionally the paper presents a course of calculations and the conclusions obtained from the analysis of displacements, accelerations, and bending moments induced in the structure through a simulated passage of a high-speed train in the context of the requirements of PN-EN Standards. The conclusions from the current calculations can be used for dynamic analysis of bridges of similar structural solutions.

Human-Induced Vertical Vibration of the Footbridge across Opatovicka Street

The presented article is focused on a theoretical dynamic analysis of the footbridge across the Opatovicka street in Prague, which acts as a simply supported beam. The structure was loaded by an ordinary pedestrian traffic, synchronous runners and vandals. The ordinary traffic was simulated by the Monte Carlo method as a stream of moving periodic forces with stochastic parameters. The synchronous runners and vandals were modeled as a combination of biomechanical models of human body, which influenced the structure vibration only passively, and driving forces, which loaded the structure in the contact points between the human body models and the structure. The driving force was the time – dependent function based on decomposition to the Fourier’s Series and periodic triangle function. The obtained theoretical results are compared with experimental data.

Rocking instability of free-standing statues atop slender cantilevers under ground motion

This paper deals with the dynamic response of free-standing statues on the top surface of slender elastically supported cantilevers subjected to horizontal ground motion. Given that there is no link between the base of the statue and the top surface of the monolithic cantilever the statue is in equilibrium in the vertical direction under its own weight. Attention is focused on the determination of the minimum amplitude ground acceleration which leads to the rocking (overturning) instability of the statue whose mass and rotatory inertia are a priory known. It is assumed that the friction between the base of the statue and the top surface of the cantilever is sufficiently large to prevent sliding so that rocking prevails. After simulating the statue by a rigid block freely supported on the top surface of the elastically restrained monolithic cantilever, a theoretical dynamic analysis of the cantilever–rigid block system under horizontal ground motion is comprehensively presented. Two modes of overturning instability of the free standing rigid block are discussed: instability without or with impact. Criteria for overturning instability of the rigid block associated with the minimum amplitude ground acceleration which leads through the vanishing of the angular velocity to an escaped motion in the phase-plane portrait, are properly assessed.

과속방지턱 설치규격 검토를 위한 동역학적 분석

This study was conducted to evaluate the characteristics of installation dimensions of speed control humps based on the theoretical dynamic analyses. The field surveys of speed control humps were performed first to compare their sizes with those suggested in the installation standard. Then, the displacement response spectra under impact loads were obtained using the single degree of freedom models where the vehicle and human were assumed to combine completely. The analysis results showed that the human perception became larger as the width and height of the humps increased, but the extremely higher uncomfortableness should be avoided. In addition, the ratio between the width and height should be considered when the humps are designed and installed because the ratio governs the vertical acceleration magnitude.

Propagating Waves in the Steel, Moment-Frame Factor Building Recorded during Earthquakes

Wave-propagation effects can be useful in determining the system identification of buildings such as the densely instrumented University of California, Los Angeles, Factor building. Waveform data from the 72-channel array in the 17-story moment-resisting steel frame Factor building are used in comparison with finite- element calculations for predictive behavior. The high dynamic range of the 24-bit digitizers allows both strong motions and ambient vibrations to be recorded with reasonable signal-to-noise ratios. A three-dimensional model of the Factor building has been developed based on structural drawings. Observed displacements for 20 small and moderate, local and regional earthquakes were used to compute the impulse response functions of the building by deconvolving the subbasement records as representative input motions at its base. The impulse response functions were then stacked to bring out wave-propagation effects more clearly. The stacked data are used as input into theoretical dynamic analysis simulations of the building’s response.

Dynamic Behavior of an Elastic/Pyroelectric Composite Hollow Sphere Under Thermal Environments

Theoretical dynamic analysis is developed for a composite hollow sphere constructed of elastic and pyroelectric layers subjected to spherically symmetric thermal loads. By introducing an unknown time function in terms of the charge equation of electrostatics for the pyroelectric layer, the solution for the mechanical field, in which the unknown time function is involved, is obtained directly in the time domain by the method of superposition, state space method as well as the separation of variables method. By employing the prescribed electric potential boundary conditions, the unknown time function is finally determined by solving a second kind Volterra integral equation. The transient responses for uniformly heated steel/CdSe composite hollow sphere are presented.

Complex Motion of Elastic Systems

This paper addresses issues of the theoretical dynamic analysis of elastic links making large relative translational and rotational motions. Mathematical models and analysis techniques for elastic vibrations of such systems are described. Examples of applied problems are adduced

New experimental technique for the study and analysis of solid particle erosion mechanisms

A theoretical dynamic analysis of a new laboratory technique is presented for the study of solid particle erosion mechanisms of brittle, ductile, and semi-ductile materials. Samples mounted on a rotating disk were air-blasted by erodent particles. The rotating disk movement allows the reduction or increase of the relative particle tangential velocity. Also, the system enables the users to separately study the effect of the particle velocity components, normal and tangential, on the erosion rates and mechanisms. In addition to the separation of the normal and tangential velocities effects of the erodent particles, this technique introduces a radial motion of the particles with respect to the samples. A theoretical dynamic analysis of the system demonstrated that the erosive effect of the radial motion is negligible during the contact period between the particles and samples. An additional advantage of this technique is that it provides erosion rate values at very low angles of impact and at high particle velocities. The air-blasting–rotating disc system enhances our ability to study the erosion acting mechanisms. To show the benefits of this system, erosion tests at very low angles of impact and at high velocities were conducted using alumina as abrasive particles. S-glass, aluminum, and epoxy resin representing brittle, ductile, and semi-ductile materials were selected for this study and their erosion rates as a function of the particle angle of impingement and particle velocity were determinated.

Experience in Railway Track Testing for Validation of Theoretical Dynamic Analysis

The objective of this paper is to present some experimental approaches in dynamic testing of the railway track structure. The load - deflection track characteristics are particularly important in the design, in the evaluation of serviceability of concrete-sleepers tracks, and to improviding data for computer modelling of the track dynamic behaviour and the dynamic vehicle/track interaction analyses. Thus, results of theoretical dynamic analyses of the track structure must be verified and compared with obtained experimental results. The herein presented track testing for validation of dynamic analyses can give many useful indications concerning the evaluation of the superstructure behaviour.

The influence of grinding process on forced vibration damping in headstock of grinding wheel of cylindrical grinder

The paper describes theoretical analysis of dynamics of system: machine–tool–workpiece for cylindrical plunge grinding. The functional as well as mathematical model of grinder equipped with hydrostatic bearing of grinding wheel spindle and hydrostatic slideways has been presented in the paper. Simulations based on that model allow qualitative investigation of grinding force characteristics and its influence on forced vibrations in grinder. Results of simulation supported the thesis, that grinding force significantly influences the forced vibration damping of headstock of grinding wheel.

Theoretical analysis of dynamics of four-bar beat-up mechanism of a loom

During the design of a beat-up mechanism, problems arise in its evaluation with respect to the individual parameters. These problems are related, mainly, to the influence of absolute values of the parameters (such as the angle of weft insertion, the swing angle of the sley with the reed, the structure of the mechanism, the space available, etc.) on the correct and smooth functioning of the mechanism as a whole. This paper deals with a method for the rapid and easy study of the effect of various parameters on the dynamic characteristics of the designed mechanism. A mathematical model has been formulated using Lagrange's equation of type II. This model takes into account the mass-related parameters of the mechanism, joints between its members, technological stress and the non-linearity of the effect of this stress in the system because of the design clearance and transfer function of the mechanism.

Dynamic Analysis of a Fibre-Optic Ring Resonator Excited by a Sinewave-Modulated Laser Diode

This article describes a theoretical dynamic analysis of a fibre-optic ring resonator (FORR) when excited by a sinusoidally-modulated laser diode (LD). The results are given for different conditions of the resonator, namely, modulating frequency, amplitude modulation index, power coupling coefficient of coupler, loop delay time τ and the phase angle between FM and AM response of the LD. When the modulation frequency fm exceeds a limiting value, such that fmτ is greater than about 0.0002, the output response deviates from steady state and exhibits an oscillatory behaviour with overshoots. Also, when the value of fmτ becomes greater than one, the response does not show any resonance in the ring and the output approximates to the intensity modulation of the LD. An unknown FM characteristic of a given LD can be determined from the ring resonator response.