Determination of Ultrasound Phase Velocity in Trabecular Bone Using Time Dependent Phase Tracking Technique

2005 ◽  
Vol 128 (1) ◽  
pp. 24-29 ◽  
Author(s):  
Wei Lin ◽  
Erik Mittra ◽  
Yi-Xian Qin
Keyword(s):  
Fourier Transform ◽  
Phase Velocity ◽  
Fast Fourier Transform ◽  
Ultrasound Velocity ◽  
Time Dependent ◽  
New Method ◽  
Phase Tracking ◽  
Tracking Technique ◽  
Ultrasound Signal

Ultrasound velocity is one of the key acoustic parameters for noninvasive diagnosis of osteoporosis. Ultrasound phase velocity can be uniquely measured from the phase of the ultrasound signal at a specified frequency. Many previous studies used fast Fourier transform (FFT) to determine the phase velocity, which may cause errors due to the limitations of FFT. The new phase tracking technique applied an adaptive tracking algorithm to detect the time dependent phase and amplitude of the ultrasound signal at a specified frequency. This overcame the disadvantages of FFT to ensure the accuracy of the ultrasound phase velocity. As a result, the new method exhibited high accuracy in the measurement of ultrasound phase velocity of two phantom blocks with the error less than 0.4%. 41 cubic trabecular samples from sheep femoral condyles were used in the study. The phase velocity of the samples using the new method had significantly high correlation to the bulk stiffness of the samples (r=0.84) compared to the phase velocity measured using fast Fourier transform FFT (r=0.14). In conclusion, the new method provided an accurate measurement of the ultrasound phase velocity in bone.

A Fast Method for Solving Contact Plasticity in a Half Space

2011 ◽  
Author(s):  
Zhanjiang Wang ◽  
Xiaoqing Jin ◽  
Shuangbiao Liu ◽  
Leon M. Keer ◽  
Jian Cao ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Residual Stresses ◽  
Fast Fourier Transform ◽  
Half Space ◽  
Three Dimensional ◽  
New Method ◽  
Fast Method ◽  
Discrete Convolution ◽  
Influence Coefficients ◽  
The One

This paper presents a new method of contact plasticity analysis based on Galerkin vectors to solve the eigenstresses due to eigenstrain. The influence coefficients relating eigenstrains to eigenstresses thus can be divided into four terms the one due to the eigenstrains in the full space, others due to the mirrored eigenstrains in the mirror half space. Each term can be solved fast and efficient by using the three-dimensional discrete convolution and fast Fourier transform (DC-FFT) or the three-dimensional discrete correlation and fast Fourier transform (DCR-FFT). The new method is used to analyze the contact plastic residual stresses in half space.

Higher order exponential split operator method for solving time-dependent Schrödinger equations

1992 ◽  
Vol 70 (2) ◽  
pp. 555-559 ◽  
Author(s):  
André D. Bandrauk ◽  
Hai Shen
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Operator Method ◽  
Computation Time ◽  
Time Dependent ◽  
Schrodinger Equations ◽  
Schrödinger Equations ◽  
Exponential Form ◽  
Operator Solution ◽  
Split Operator

A new method of splitting exponential operators is proposed for the exponential form of the operator solution to the time-dependent Schrödinger equation. The method is shown to hold for any desired accuracy in the time increment. A comparison of different algorithms is made as a function of accuracy and computation time. Keywords: splitting operator, Fast Fourier Transform (FFT), Schrödinger equations.

scholarly journals Cloud Determination of All-Sky Images under Low-Visibility Conditions

2009 ◽  
Vol 26 (10) ◽  
pp. 2172-2181 ◽  
Author(s):  
Juan Huo ◽  
Daren Lu
Keyword(s):  
Numerical Simulation ◽  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Aerosol Optical Depth ◽  
Image Features ◽  
Threshold Method ◽  
Integrated Method ◽  
Low Visibility ◽  
Key Factor

Abstract The threshold method is commonly used to determine cloud in a sky image. This paper evaluates the method by numerical simulation and shows that the aerosol optical depth (AOD) is a key factor that influences the accuracy. Particularly when the visibility is low, a single threshold method is inappropriate. To improve the accuracy of cloud determination from low-visibility sky images, an integrated cloud-determination algorithm is presented that is based on the fast Fourier transform, symmetrical image features, and threshold methods. The preliminary comparison tests show that the new integrated method improves the ability to determine cloud under lower-visibility conditions.

scholarly journals Empirical Analysis of Traffic Bottleneck at Beijing Expressways

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Sheng Jin ◽  
Dianhai Wang ◽  
Dongfang Ma
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Traffic Flow ◽  
Survey Data ◽  
Traffic Management ◽  
Time Dependent ◽  
Control Line ◽  
Flow Parameters ◽  
Data Gap ◽  
Ramp Control

The expressways in Beijing are confronted with more serious traffic congestions. Based on the survey data obtained from the typical sections at the expressways, the time dependent characteristics of traffic flow parameters were analyzed in detail and the data gap was found in this paper. The Fast Fourier Transform (FFT) method is proposed to transfer the data of traffic flow parameters for describing the fluctuation characteristics of traffic flow. Two methods of identification, the graph method and the control line method, were proposed as to the change time of traffic bottleneck forming and dissipating. The findings in this paper have already been applied in traffic management and ramp control at the expressways in Beijing.

scholarly journals An ultrasound based technique for the determination of poultry egg quality

2010 ◽  
Vol 56 (No. 1) ◽  
pp. 26-32 ◽  
Author(s):  
M. Aboonajmi ◽  
A. Akram ◽  
T. Nishizu ◽  
N. Kondo ◽  
S.K. Setarehdan ◽  
...  
Keyword(s):  
Phase Velocity ◽  
Room Temperature ◽  
Egg Quality ◽  
Sampling Rate ◽  
Storage Period ◽  
Egg Laying ◽  
Ultrasound Signal ◽  
Non Destructive ◽  
Haugh Unit

The present study investigates the possibility of the non-destructive prediction of the main quality indices of commercial eggs by calculating the ultrasound phase velocity within the egg material. The phase velocity of the ultrasound signal in the egg material was determined by analysing the recorded ultrasound signals using the Fast Fourier Transform. Three hundred commercial eggs (Boris Brown, 33 weeks age) from the first day of egg laying were purchased from a farm and divided in two groups. The first group was kept at the room temperature (22–25°C) and the second group was kept in a refrigerator (5°C). Every week, 25 eggs from both the room and the refrigerator were first submitted to the non-destructive ultrasound test at weekly basis at the room temperature. Immediately after testing, the air cell, the thick albumen heights, the Haugh unit and the yolk index of the eggs were also determined destructively for the comparison purposes. The results were analysed to find any possible correlation between the computed ultrasonic phase velocity and the destructive parameters, during a storage period of five weeks. The tests were carried out using an ultrasound beam with a frequency of 150 kHz with a sampling rate of 2.5 Gs/S on the eggs under a controlled temperature situation. Significant differences between the means of the destructive analysis on different days of the eggs storage were found using ANOVA. The results showed that the phase velocity significantly differs between the eggs stored at the room temperature and those stored in the refrigerator. It was found that the phase velocity decreased as the storage time of the eggs increased in three consecutive weeks.  

Sign in / Sign up

Export Citation Format

Share Document