Vehicle Model Calibration in the Frequency Domain and its Application to Large-Scale IRI Estimation

2017 ◽  
Vol 12 (3) ◽  
pp. 446-455 ◽  
Author(s):  
Boyu Zhao ◽  
◽  
Tomonori Nagayama ◽  
Masashi Toyoda ◽  
Noritoshi Makihata ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Transfer Function ◽  
Frequency Domain ◽  
Large Scale ◽  
High Efficiency ◽  
Unscented Kalman Filter ◽  
Frequency Domain Analysis ◽  
Vertical Acceleration ◽  
Improved Method ◽  
Vehicle Model

A smartphone-based Dynamic Response Intelligent Monitoring System (iDRIMS) was developed to conduct road evaluations with high efficiency and reasonable accuracy [1]. iDRIMS estimates the International Roughness Index (IRI) based on vehicle responses measured with an iOS application, which obtains three-axis acceleration, angular velocity, and GPS with accurate sampling timing. However, the robustness and accuracy was limited. In this paper, the iDRIMS was improved mainly by employing frequency domain analysis. The algorithm consists of two steps. First, a half car (HC) model was selected as the vehicle model, and vehicle parameters were identified through driving tests over a portable hump of known size. In contrast to the previous approach of parameter identification in the time domain using Unscented Kalman Filter, the parameters were optimized to minimize the difference between the simulation and measured hump responses in the frequency domain, using a genetic algorithm. Then, IRI was estimated by measuring the vertical acceleration responses of ordinary vehicles. The measured acceleration was converted into the acceleration root mean square (RMS) of the sprung mass of a standard quarter car (QC) by multiplying a transfer function. The transfer function, estimated through the simulation of the identified HC model, as opposed to QC model in previous approaches, reflected the vehicle pitching motions and sensor installation location. The RMS was further converted to IRI based on the correlation between these values. Numerical simulation was conducted to investigate the performance in terms of various driving speeds and sensor locations. The experiment was conducted at a 13 km road by comparing three types of vehicles and a profiler. Inaccurate IRI estimation at the speed change section was experimentally investigated and compensated. Furthermore, the improved method was applied to 72 vehicles that were driven more than 180,000 km per year. A data collection and analysis platform was built, which successfully collected and analyzed large-scale data with high efficiency. The results from both numerical simulation and real case application show that the improved method accurately estimates IRI with high robustness and efficiency.

scholarly journals Impact of mild orthostatic stress on aortic-cerebral hemodynamic transmission: insight from the frequency domain

2017 ◽  
Vol 312 (5) ◽  
pp. H1076-H1084 ◽  
Author(s):  
Jun Sugawara ◽  
Tsubasa Tomoto ◽  
Tomoko Imai ◽  
Seiji Maeda ◽  
Shigehiko Ogoh
Keyword(s):  
Transfer Function ◽  
Frequency Domain ◽  
Systemic Vascular Resistance ◽  
Vascular Resistance ◽  
Low Frequency ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Slow Oscillations ◽  
Transfer Function Gain ◽  
The Brain

High cerebral pressure and flow fluctuations could be a risk for future cerebrovascular disease. This study aims to determine whether acute systemic vasoconstriction affects the dynamic pulsatile hemodynamic transmission from the aorta to the brain. We applied a stepwise lower body negative pressure (LBNP) (−10, −20, and −30 mmHg) in 15 young men to induce systemic vasoconstriction. To elucidate the dynamic relationship between the changes in aortic pressure (AoP; estimated from the radial arterial pressure waveforms) and the cerebral blood flow velocity (CBFV) at the middle cerebral artery (via a transcranial Doppler), frequency-domain analysis characterized the beat-to-beat slow oscillation (0.02–0.30 Hz) and the intra-beat rapid change (0.78–9.69 Hz). The systemic vascular resistance gradually and significantly increased throughout the LBNP protocol. In the low-frequency range (LF: 0.07–0.20 Hz) of a slow oscillation, the normalized transfer function gain of the steady-state component (between mean AoP and mean CBFV) remained unchanged, whereas that of the pulsatile component (between pulsatile AoP and pulsatile CBFV) was significantly augmented during −20 and −30 mmHg of LBNP (+28.8% and +32.4% vs. baseline). Furthermore, the relative change in the normalized transfer function gain of the pulsatile component at the LF range correlated with the corresponding change in systemic vascular resistance ( r = 0.41, P = 0.005). Regarding the intra-beat analysis, the normalized transfer function gain from AoP to CBFV was not significantly affected by the LBNP stimulation ( P = 0.77). Our findings suggest that systemic vasoconstriction deteriorates the dampening effect on the pulsatile hemodynamics toward the brain, particularly in slow oscillations (e.g., 0.07–0.20 Hz). NEW & NOTEWORTHY We characterized the pulsatile hemodynamic transmission from the heart to the brain by frequency-domain analysis. The low-frequency transmission was augmented with a mild LBNP stimulation partly due to the elevated systemic vascular resistance. A systemic vasoconstriction deteriorates the dampening effect on slow oscillations of pulsatile hemodynamics toward the brain.

Spatial Frequency Domain Analysis of Heat Transfer in Microelectronic Chips With Applications to Temperature Aware Computing

2007 ◽  
Author(s):  
Keivan Etessam-Yazdani ◽  
Hendrik F. Hamann ◽  
Mehdi Asheghi
Keyword(s):  
Transfer Function ◽  
Spatial Frequency ◽  
Frequency Domain ◽  
Thermal Power ◽  
Three Dimensional ◽  
Heat Removal ◽  
Frequency Domain Analysis ◽  
Heat Diffusion ◽  
The Impact ◽  
Spatial Frequency Domain

In this paper we present a novel analytical approach for obtaining the thermal transfer function of multi-layer chips in the spatial frequency domain. The behavior of the transfer function is used to address a number of key issues such as 1) the appropriate power granularity required for microarchitecture thermal-power analysis, and 2) the impact of packaging and cooling solutions on heat removal from chip hotspots. The merit of the presented method is in 1) simplicity, such that even for rather complicated multi-layer structures the analysis takes only a fraction of a second, and 2) accuracy, because the approach is based on the exact solution of three-dimensional heat diffusion equations.

scholarly journals Frequency Domain Analysis of Cerebral Blood Flow Velocity and its Correlation with Arterial Blood Pressure

1998 ◽  
Vol 18 (3) ◽  
pp. 311-318 ◽  
Author(s):  
Terry Bo-Jau Kuo ◽  
Chang-Ming Chern ◽  
Wen-Yung Sheng ◽  
Wen-Jang Wong ◽  
Han-Hwa Hu
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Transfer Function ◽  
Flow Velocity ◽  
Frequency Domain ◽  
Blood Flow Velocity ◽  
Low Frequency ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Arterial Blood

We applied frequency domain analysis to detect and quantify spontaneous fluctuations in the blood flow velocity of the middle cerebral artery (MCAFV). Instantaneous MCAFV of normal volunteers was detected using transcranial Doppler sonography. Spectral and transfer function analyses of MCAFV and arterial blood pressure (ABP) were performed by fast Fourier transform. We found the fluctuations in MCAFV, like ABP, could be diffracted into three components at specific frequency ranges, designated as high-frequency (HF, 0.15 to 0.4 Hz), low-frequency (LF, 0.04 to 0.15 Hz), and very low-frequency (VLF, 0.016 to 0.04 Hz) components. The HF and LF components of MCAFV exhibited high coherence with those of ABP, indicating great similarity of MCAFV and ABP fluctuations within the two frequency ranges. However, it was not the case for the VLF component. Transfer function analysis revealed that the ABP-MCAFV phase angle was frequency-dependent in the LF range ( r = −0.79, P < 0.001) but not in the HF range. The time delay between LF fluctuations of ABP and those of MCAFV was evaluated as 2.1 seconds. We conclude that in addition to traditional B-wave equivalents, there are at least two different mechanisms for MCAFV fluctuations: the HF and LF fluctuations of MCAFV are basically secondary to those of ABP, and cerebral autoregulation may operate efficiently in LF rather than HF range. Frequency domain analysis offers an opportunity to explore the nature and underlying mechanism of dynamic regulation in cerebral circulation.

Meshfree Method in Geophysical Electromagnetic Prospecting: The 2D Magnetotelluric Example

2017 ◽  
Vol 15 (02) ◽  
pp. 1750084 ◽  
Author(s):  
Yanju Ji ◽  
Tingzhe Huang ◽  
Wanyu Huang ◽  
Liangliang Rong
Keyword(s):  
Numerical Simulation ◽  
Large Scale ◽  
High Efficiency ◽  
Interpolation Method ◽  
Rapid Development ◽  
Linear Equations ◽  
Meshfree Method ◽  
Physical Parameters ◽  
Traditional Methods ◽  
Calculation Results

As an important supplement and development of traditional methods, the meshfree method has received a great deal of attention in the field of engineering calculation, and has been successfully used to solve many problems which traditional methods have difficulty in solving. However, the application of meshfree method is relatively less in the area of geophysics. In this paper, we apply the meshfree method to the numerical simulation of geophysical electromagnetic prospecting, taking the 2D magnetotelluric as an example and deduce the corresponding meshfree radial point interpolation method (RPIM) equivalent linear equations in detail. The high-efficiency and accurate solutions of large-scale sparse linear equations are solved by the quasi-minimal residual method based on Krylov subspace. The optimal values of the shape parameters are given by numerical experiments. The correctness of the meshfree method is verified by a layered model. The root mean square error of the calculation results is no more than 0.35%, its accuracy is superior to the finite element method. We also compare the meshfree solution with FEM solution by calculating an inclined vein body model, and the calculation results are in good agreement. A continuously changing fault model and undulating terrain model which traditional methods have difficulty in simulating are respectively calculated, the sectional profiles of the apparent resistivity accurately reflect the trend of the anomalies. The meshfree method does not require the complicated mesh generation, and the physical parameters are loaded at a series of points, thus it is especially suitable for the calculation of the complex geological models. With the rapid development of computational science, the meshfree techniques will certainly become a new robust numerical simulation method in geophysical electromagnetic prospecting.

scholarly journals Eigenstrain Boundary Integral Equations with Local Eshelby Matrix for Stress Analysis of Ellipsoidal Particles

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Hang Ma ◽  
Cheng Yan ◽  
Qing-hua Qin
Keyword(s):  
Numerical Simulation ◽  
Computational Model ◽  
Large Scale ◽  
High Efficiency ◽  
Boundary Integral Equations ◽  
Three Dimensional ◽  
Solution Procedure ◽  
Boundary Integral ◽  
Ellipsoidal Particles ◽  
Reinforced Materials

Aiming at the large scale numerical simulation of particle reinforced materials, the concept of local Eshelby matrix has been introduced into the computational model of the eigenstrain boundary integral equation (BIE) to solve the problem of interactions among particles. The local Eshelby matrix can be considered as an extension of the concepts of Eshelby tensor and the equivalent inclusion in numerical form. Taking the subdomain boundary element method as the control, three-dimensional stress analyses are carried out for some ellipsoidal particles in full space with the proposed computational model. Through the numerical examples, it is verified not only the correctness and feasibility but also the high efficiency of the present model with the corresponding solution procedure, showing the potential of solving the problem of large scale numerical simulation of particle reinforced materials.

A Simplified Method to Obtain Subway Vibration Load Based on Analysis in Frequency Domain

2012 ◽  
Vol 256-259 ◽  
pp. 1195-1200
Author(s):  
Jing Bo Liu ◽  
Xiao Bo Zhang ◽  
Dong Dong Zhao ◽  
Wen Hui Wang
Keyword(s):  
Numerical Simulation ◽  
Frequency Domain ◽  
Ground Vibration ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Vibration Test ◽  
Vibration Load ◽  
Simplified Method ◽  
Vibration Problems

To obtain reasonable subway vibration load is the key to many subway vibration problems. This paper uses a simplified method to determine subway vibration load in frequency domain analysis, based on ground vibration test induced by subway traveling and numerical simulation of soil-subway model. The operating steps are explained and one example for calculating subway vibration load is given. The result shows that this method is a certain degree of effective in analysis of ground vibration problems, since that it relies on ground vibration test. The operating steps of this method are simple, and also the method can reflect characteristic of randomness of subway vibration.

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