Equipment Representations for Shock Calculations: Time Domain Dirichlet to Neumann Maps

1995 ◽  
Author(s):  
Paul E. Barbone
Keyword(s):  
Time Domain ◽  
High Frequency ◽  
Large Scale ◽  
Dynamic Simulations ◽  
Naval Vessel ◽  
System Parameters ◽  
Equivalent Time ◽  
Modal Density ◽  
Modal Summation ◽  
High Modal Density

Abstract Large scale dynamic simulations can often be simplified by appropriately replacing large portions of the domain by a Dirichlet to Neumann, or DtN map (Givoli, 1992). Here we consider the problem of representing a dynamical subsystem, a piece of equipment aboard a naval vessel for example, in terms of an equivalent time domain DtN map. The exact DtN map is computed as a modal summation. The exact map is then approximated in both the low and high modal density regimes. The approximate DtN in the high modal density limit is computed utilizing fuzzy-structures concepts recently developed by Pierce, Sparrow and Russel (1993) and others. The resulting DtN map depends on just two easily determined system parameters: the total mass and the high-frequency stiffness.

Power Flow and Energy Sharing between an Oscillator and a Continuous Receiver Structure

2011 ◽  
Vol 189-193 ◽  
pp. 1914-1917
Author(s):  
Lin Ji
Keyword(s):  
High Frequency ◽  
Power Flow ◽  
Energy Analysis ◽  
Statistical Energy Analysis ◽  
Coupled Subsystems ◽  
Modal Density ◽  
Vibration Problems ◽  
Energy Sharing ◽  
High Modal Density ◽  
Vibration Modeling

A key assumption of conventional Statistical Energy Analysis (SEA) theory is that, for two coupled subsystems, the transmitted power from one to another is proportional to the energy differences between the mode pairs of the two subsystems. Previous research has shown that such an assumption remains valid if each individual subsystem is of high modal density. This thus limits the successful applications of SEA theory mostly to the regime of high frequency vibration modeling. This paper argues that, under certain coupling conditions, conventional SEA can be extended to solve the mid-frequency vibration problems where systems may consist of both mode-dense and mode-spare subsystems, e.g. ribbed-plates.

High-Frequency Vibration Analysis of Thin Plate Based on B-Spline Wavelet on Interval Finite Element Method

2016 ◽  
Author(s):  
Jia Geng ◽  
Xingwu Zhang ◽  
Xuefeng Chen ◽  
Xiaofeng Xue
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Dynamic Analysis ◽  
Frequency Domain ◽  
Thin Plate ◽  
Finite Element Methods ◽  
High Frequency ◽  
Numerical Example ◽  
Modal Density ◽  
High Modal Density

For the dynamic analysis of thin plate bending problems, the Finite Element Methods (FEMs) are the most commonly used numerical techniques in engineering. However, due to the deficiency of low computing efficiency and accuracy, the FEMs can’t be directly used to effectively evaluate dynamic analysis of thin plate with high modal density within low-high frequency domain. In order to solve this problem, the Wavelet Finite Element Methods (WFEMs) has been introduced to solve the problem by improving the computing efficiency and accuracy in this paper. Due to the properties of multi-resolution, the WFEMs own excellently high computing efficiency and accuracy for structure analysis. Furthermore, for the destination of predicting dynamic response of thin plate within high frequency domain, this paper introduces the Multi-wavelet element method based on c1 type wavelet thin plate element and a new assembly procedure to significantly promote the calculating efficiency and accuracy which aim at breaking up the limitation of frequency domain when using the existing WFEMs and traditional FEMs. Besides, the numerical studies are applied to certify the validity of the method by predicting state response of thin plate within 0∼1000Hz based on a special numerical example with high modal density. According to the literature, the frequency domain between 0 to 1000Hz contains the low-high frequency domain aiming at the numerical example. The numerical results show excellent agreement with the reference solutions captured by FEM and analytical expressions respectively. Among these, it is noteworthy that the relative errors between the analytical solutions and numerical solution are less than 0.4% when the dynamic response involved with 1000 modes.

Fast Time Domain Integral Equation Solvers for Large-Scale Electromagnetic Analysis

2004 ◽  
Author(s):  
Eric Michielsssen ◽  
Weng C. Chew ◽  
Jianming Jin ◽  
Balasubramaniam Shanker
Keyword(s):  
Integral Equation ◽  
Time Domain ◽  
Large Scale ◽  
Electromagnetic Analysis ◽  
Fast Time ◽  
Domain Integral ◽  
Time Domain Integral Equation

scholarly journals Optimizing the Frequency Capping: A Robust and Reliable Methodology to Define the Number of Ads to Maximize ROAS

2021 ◽  
Vol 11 (15) ◽  
pp. 6688
Author(s):  
Jesús Romero Leguina ◽  
Ángel Cuevas Rumin ◽  
Rubén Cuevas Rumin
Keyword(s):  
High Frequency ◽  
Large Scale ◽  
Low Frequency ◽  
Digital Marketing ◽  
Optimal Frequency ◽  
Novel Technique ◽  
Maximum Threshold

The goal of digital marketing is to connect advertisers with users that are interested in their products. This means serving ads to users, and it could lead to a user receiving hundreds of impressions of the same ad. Consequently, advertisers can define a maximum threshold to the number of impressions a user can receive, referred to as Frequency Cap. However, low frequency caps mean many users are not engaging with the advertiser. By contrast, with high frequency caps, users may receive many ads leading to annoyance and wasting budget. We build a robust and reliable methodology to define the number of ads that should be delivered to different users to maximize the ROAS and reduce the possibility that users get annoyed with the ads’ brand. The methodology uses a novel technique to find the optimal frequency capping based on the number of non-clicked impressions rather than the traditional number of received impressions. This methodology is validated using simulations and large-scale datasets obtained from real ad campaigns data. To sum up, our work proves that it is feasible to address the frequency capping optimization as a business problem, and we provide a framework that can be used to configure efficient frequency capping values.

High Frequency Vibration Analysis of Automotive Body Panels with Damping Materials

2010 ◽  
Vol 36 ◽  
pp. 293-296
Author(s):  
Yoshio Kurosawa ◽  
Takao Yamaguchi
Keyword(s):  
High Frequency ◽  
Large Scale ◽  
The Body ◽  
Viscoelastic Damping ◽  
Fe Model ◽  
Test Results ◽  
Automotive Body ◽  
Modal Damping ◽  
Practical Tool ◽  
Damping Materials

We have developed a technique for estimating vibrations of an automotive body structures with viscoelastic damping materials using large-scale finite element (FE) model, which will enable us to grasp and to reduce high-frequency road noise（200～500Hz）. In the new technique, first order solutions for modal loss factors are derived applying asymptotic method. This method saves calculation time to estimate modal damping as a practical tool in the design stages of the body structures. Frequency responses were calculated using this technique and the results almost agreed with the test results. This technique can show the effect of the viscoelastic damping materials on the automotive body panels, and it enables the more efficient layout of the viscoelastic damping materials. Further, we clarified damping properties of the automotive body structures under coupled vibration between frames and panels with the viscoelastic damping materials.

Effects of large-scale clouds of ionosphericirregularities on the propagation of high-frequency radiowaves

1998 ◽  
Vol 60 (17) ◽  
pp. 1687-1694 ◽  
Author(s):  
N.T. Afanasiev ◽  
A.A. Zheonykh ◽  
V.I. Sazhin ◽  
M.V. Tinin ◽  
M.K. Ivelskaya
Keyword(s):  
High Frequency ◽  
Large Scale
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