Study on vibration isolation performance of elastic coupling under longitudinal excitation

According to longitudinal vibration differential equations of ship propulsion shafting, deduced transfer matrix of propeller, uniform shaft segment and thrust bearing which composed propulsion shafting. Given longitudinal vibration natural frequency of propulsion shafting using the transfer matrix solver, and compared with finite element simulation results to verify the accuracy of the finite element model. Then analysis the effect of elastic coupling axial stiffness on modal frequencies of shafting longitudinal vibration and vibration isolation performance through simulation. Results show that: elastic coupling can effectively isolate the propulsion shafting vibration transmitted to the propulsion motor; when the axial stiffness ratio of thrust bearing and elastic coupling is greater than 50, the impact of elastic coupling axial stiffness on longitudinal vibration natural frequency of propulsion shafting and acceleration level and axial displacement of thrust bearing is very small; when the stiffness ratio is greater than 100, the elastic coupling can achieve better vibration isolation effect

THREE CONDITIONS LYAPUNOV EXPONENTS SHOULD SATISFY

ABSTRACT In contrast to the unilateral claim in some papers that a positive Lyapunov exponent means chaos, it was claimed in this paper that this is just one of the three conditions that Lyapunov exponent should satisfy in a dissipative dynamical system when the chaotic motion appears. The other two conditions, any continuous dynamical system without a fixed point has at least one zero exponent, and any dissipative dynamical system has at least one negative exponent and the sum of all of the 1-dimensional Lyapunov exponents id negative, are also discussed. In order to verify the conclusion, a MATLAB scheme was developed for the computation of the 1-dimensional and 3-dimensional Lyapunov exponents of the Duffing system with square and cubic nonlinearity. KEYWORDS: Lyapunov exponent, chaos, three conditions, Duffing system INTRODUCTION Recently, chaotic motions that arise from the nonlinearity of dissipative dynamical systems have received a great concern in both physical and non-physical fields. The most striking feature of chaos is the unpredictability of the future despite a deterministic time evolution. This unpredictability is a consequence of the inherent instability of the solutions, reflected by what is called sensitive dependence on initial conditions. The tiny deviations between the initial conditions of all the trajectories are blown up after a short time. A more careful investigation of this instability leads to two different, although related, concepts. One is the loss of information related to unpredictability, quantified by the Kolmogorov-Sinai entropy. The other is a simple geometric one, namely, that nearby trajectories separate very fast, or more precisely, separate exponentially over time. The properly averaged exponent of this increase is the characteristics for th

Evaluation on a Personalized Mobile Advertising System: a Comparative Approach

Along with the high proliferation of mobile phones and other mobile devices, research on the use of short messaging service&#;SMS&#; to access customers through their handheld devices has gained much attention, which is termed as mobile advertising. In order to make the best use of mobile advertising to benefit companies and customers becomes more emergent. One of the most important and successful factor that will bring more positive attitudes towards mobile advertising and induce customers to behave positively is personalization, which has been confirmed in many prior studies. Therefore, it’s necessary and essential for researchers to design an effective system capable of recommending personalized mobile advertising to mobile users. The purpose of this paper is to fulfill this task. We present such a kind of personalized mobile advertising system based on Bayesian Network. Then, we brought out a thorough evaluation of our system in a laboratory environment. Experimental results showed better performance of our system in furnishing personalized mobile advertising than conventional method (random advertising)

Delay-Dependent Finite-Time H

Delay-dependent finite-time H∞ controller design problems are investigated for a kind of nonlinear descriptor system via a T-S fuzzy model in this paper. The solvable conditions of finite-time H∞ controller are given to guarantee that the loop-closed system is impulse-free and finite-time bounded and holds the H∞ performance to a prescribed disturbance attenuation level γ. The method given is the ability to eliminate the impulsive behavior caused by descriptor systems in a finite-time interval, which confirms the existence and uniqueness of solutions in the interval. By constructing a nonsingular matrix, we overcome the difficulty that results in an infeasible linear matrix inequality (LMI). Using the FEASP solver and GEVP solver of the LMI toolbox, we perform simulations to validate the proposed methods for a nonlinear descriptor system via the T-S fuzzy model, which shows the application of the T-S fuzzy method in studying the finite-time control problem of a nonlinear system. Meanwhile the method was also applied to the biological economy system to eliminate impulsive behavior at the bifurcation value, stabilize the loop-closed system in a finite-time interval, and achieve a H∞ performance level

Study of distribution of remaining oil in West Block of the Third District in North Saertu

Identifying remaining oil distribution is an essential study at the Third District in North Saertu of the West Block in Daqing Oilfield. This field is known as a flooding fine potential tapping demonstration zone, characterized by a long-developing history and complex well history. Based on tectonic features and sedimentary characteristics of the study area, the methods of facies controlled reservoir 3D geological modeling and numerical simulation are used in the process of establishing the geological 3D static model. In this paper, we summarized the causes and distribution law of remaining oil in the study area by using the method of fine reservoir numerical simulation to provide a reliable basis for the development and adjustment of the oil field. In combination with fine exploration such as water drive fracturing, water plugging, reperforating and injection-production segment, the recoverable reserves recovery rate could be effectively increased. Estudio de la distribución del remanente de petróleo en el bloque oriental del tercer distrito, en el norte de Sartu, China ResumenLa identificación de la distribución del remanente de petróleo es un estudio esencial en el tercer distrito del norte de Sartu, que corresponde al bloque occidental del campo petrolífero de Daqing. Este campo es conocido como una zona ejemplar para aprovechar el potencial de explotación por inundación y que se caracteriza por una historia compleja y de largo desarrollo de sus pozos. Con base a las características tectónicas y sedimentarias del área de estudio se utlilizaron los métodos de modelado geológico 3D en depósitos con facies controladas y la simulación numérica en el proceso de establecer el modelo geológico 3D estático. En este artículo se establecen las causas y la ley distributiva del remanente de petróleo en el área de estudio a través del método de simulación numérica de depósitos de alta resolución que provea una base fiable para el desarrollo y ajuste del campo petrolero. Con la combinación de métodos de exploración como la fractura dirigida con agua, taponamiento acuático, reperforación y segmentos de inyección-producción, el índice de recuperación de reservas podría incrementar efectivamente

Bremsstrahlung spectrum data for thick Al, Ti, Zr, Mo, and W targets by keV electron impact

The data presented in this paper are related to the research paper entitled “Bremsstrahlung spectra produced by kilovolt electron impact on thick targets” [1]. The dataset includes our measured bremsstrahlung spectra on Al, Ti, Zr, Mo, and W thick targets at 5, 10, 15, 20, and 25 keV electron impact. In this paper we present the experimental method and make the dataset publicly available to enable extended analyses or reuse. The dataset is available on mendeley data public repository at http://dx.doi.org/10.17632/5zx3459bj3.1 Keywords: Electron impact, Bremsstrahlung, Thick targe

DETC2009-86535 NUMERICAL STUDY ON THE APPLICATION OF CHAOS IN LINE SPECTRUM REDUCTION

ABSTRACT The application of chaos method in line spectrum reduction is numerically studied. The nonlinear dynamics and the power flow transmissibility of a two-degree-of-freedom vibration isolation system with nonlinear spring are analyzed. The dynamic behavior distribution chart of the system is obtained. Cascades of bifurcation of the system with different excitation amplitude are also gained. The isolation effectiveness is analyzed from the point of view of energy. The numerical results show that the reduction of the line spectrum in chaotic state is much greater than that in non-chaotic state

Research on MRD Parametric Model Based on Magic Formula

In order to get a better description to the nonlinear characteristics of magnetorheological dampers, the magic formula is introduced into the general method of parametric modelling of magnetorheological dampers to propose a new parameterized model called magic formula-hysteresis loop model (MFM). The new model is simple in structure, the physical meaning of each parameter is clear, and the parameter identification is convenient. The fitting and experimental data of MFM and the phenomenon model under different conditions are applied for error analysis and comparison. The results show that the errors of MFM are more accurate and have better fitting and experimental data under different working conditions, which also have better adaptability and versatility