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A novel model for diffusion based release kinetics using an inverse numerical method

MEDICAL ENGINEERING & PHYSICS 2011年第8期33卷 893-899页

作者： Mohammadi, Hadi Herzog, Walter Univ Calgary Fac Kinesiol Human Performance Lab Calgary AB Canada

We developed and analyzed an inverse numerical model based on Fick's second law on the dynamics of drug release. In contrast to previous models which required two state descriptions of diffusion for long- and short-term release processes, our model is valid for the entire release process. The proposed model may be used for identifying and reducing experimental errors associated with measurements of diffusion based release kinetics. Knowing the initial and boundary conditions, and assuming Fick's second law to be appropriate, we use the methods of Lagrange multiplier along with least-square algorithms to define a cost function which is discretized using finite difference methods and is optimized so as to minimize errors. Our model can describe diffusion based release kinetics for static and dynamic conditions as accurately as finite element methods, but results are obtained in a fraction of CPU time. Our method can be widely used for drug release procedures and for tissue engineering/repair applications where oxygenation of cells residing within a matrix is important. (C) 2011 IPEM. Published by Elsevier Ltd. All rights reserved.

关键词： Finite element method Finite difference method least square algorithm Continuum model Computational mechanics Numerical scheme Diffusion Release kinetics

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Loss-of-excitation analysis and protection for pumped-storage machines during starting

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IET RENEWABLE POWER GENERATION 2016年第1期10卷 71-78页

作者： Li, Bin Duan, Zhitian Wang, Xin Wu, Jianzhong Tianjin Univ Key Lab Smart Grid Minist Educ Tianjin 300072 Peoples R China Tianjin Elect Power Co Customer Serv Ctr Tianjin 300010 Peoples R China Cardiff Univ Inst Energy Cardiff Sch Engn Cardiff CF24 3AA S Glam Wales

The reversible synchronous machines in a pumped station are put into operation frequently for effective operation of the hydro pumped-storage system. The detection of loss-of-excitation (LOE), which is a common failure for synchronous machines, must be guaranteed not only in normal operation, but also under starting and other possible operation conditions. A model of pumped-storage units under the starting condition was developed using the SimPowerSystems in Matlab/Simulink. The simulation results and real tests of a pumped-storage power plant in northeast China were presented. The LOE characteristics during starting were analysed for the first time. Since the frequency of voltage and current runs up gradually from zero to the rated frequency during starting, conventional LOE protections based on impedance under the rated frequency have to be disabled during starting. For this reason, a novel LOE protection was developed based on the R-L time-domain model and the least-square algorithm. Theoretical analysis and simulation tests demonstrate that the proposed LOE protection method is correct and valid.

关键词： synchronous machines pumped-storage power stations starting time-domain analysis least mean squares methods power system protection pumped storage machine reversible synchronous machine pumped station hydro pumped-storage system loss-of-excitation starting condition SimPowerSystems pumped storage power plant LOE protection R-L time-domain model least square algorithm

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A NUMERICAL TECHNIQUE TO EVALUATE THE FLEXURAL STIFFNESS OF LONG BONES AFFECTED BY CRACKS AND POROSITY

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JOURNAL OF MECHANICS IN MEDICINE AND BIOLOGY 2011年第1期11卷 131-148页

作者： Mohammadi, Hadi Bahramian, Fereshteh Mequanint, Kibret Rizkalla, Amin Univ Western Ontario Biomed Engn Grad Program London ON N6A 5B9 Canada Univ Western Ontario Dept Chem & Biochem Engn London ON N6A 5B9 Canada

Bone maintains its structure through a constant process of resorption and formation, in a process called bone remodeling. An imbalance in this process caused by disease, abnormal mechanical demands, or fatigue may predispose bone to fracture injuries. Increase in bone resorption can increase the number of surface cracks and structural porosity of the bone and thus change its stiffness properties. In this study, a computational technique is proposed to investigate the stiffness properties in long bones based on dynamic responses. As the first attempt, defects such as porosity and cracks are detected based on changes in stiffness properties of the sample. The least square algorithm and the finite element method are used as tools in this study. The Wilson-theta numerical method is employed to generate artificially experimental results for acceleration vectors. The data obtained from the artificial experiment is later employed to the proposed computational investigation model as raw data.

关键词： Finite element method finite difference method least square algorithm long bones dynamic response

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Applying adaptive prediction to sea-water quality measurements

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EXPERT SYSTEMS WITH APPLICATIONS 2009年第3期36卷 6773-6779页

作者： Hatzikos, E. Hatonen, J. Bassiliades, N. Vlahavas, I. Fournou, E. Aristotle Univ Thessaloniki Dept Informat Thessaloniki 54124 Greece Inst Educ Technol Dept Automat Thessaloniki Greece Univ Sheffield Dept Automat Control & Syst Engn Sheffield S10 2TN S Yorkshire England Inst Educ Technol Dept Gen Sci Thessaloniki Greece

This study explores the possibility of using adaptive filters to predict sea-water quality indicators such as water temperature, pH and dissolved oxygen based on measurements produced by an under-water measurement set-up. Two alternative adaptive approaches are tested, namely a projection algorithm and a least squares algorithm. These algorithms were chosen for comparison because they are widely used prediction algorithms. The results indicate that if the measurements remain reasonably stationary, it is possible to make one-day ahead predictions, which perform better than the prediction that the value of a certain quality variable tomorrow is going to be equal to the value today. (C) 2008 Elsevier Ltd. All rights reserved.

关键词： Projection algorithm least square algorithm One-day ahead prediction

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A rectilinear Gaussian model for estimating straight-line parameters

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JOURNAL OF VISUAL COMMUNICATION AND IMAGE REPRESENTATION 2014年第2期25卷 510-520页

作者： Zhu, Hongjun Gao, Chao Guo, Yongcai Shao, Yanhua Chongqing Univ Minist China Key Lab Optoelect Technol & Syst Educ Chongqing 400030 Peoples R China

For characterizing straight lines in defocused images, a rectilinear Gaussian model (RGM) is proposed. Based on this model, a novel method for estimating the parameters of straight lines is presented. This method, called gray-scale least square (GLS) method, directly deals with gray-scale image data without requiring any preprocessing and hence no additional noise is introduced. Furthermore, the method is able to simultaneously estimate four parameters of straight lines by performing the algorithm only once, while two parameters can be typically estimated by traditional method. Besides this, all parameters are given in closed-form solution. In order to illustrate the effectiveness of RGM and the GLS method, the experiments are performed on a set of artificial images and natural images. The experimental results show that the GLS method outperforms the traditional method from the point of view of sensitivity to noise and accuracy of parameter estimation. (C) 2013 Elsevier Inc. All rights reserved.

关键词： Gaussian model Parameter estimation Straight lines least square algorithm Ridge edge Straight-line parameters Feature description Defocused lines

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Leader-follower tracking in lipschitz nonlinear multi agent systems under undirected graph with noisy sinusoidal motion of the leader

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EVOLVING SYSTEMS 2024年第2期15卷 555-573页

作者： Ghasemzadeh, Seyyed Vahid Safarinejadian, Behrouz Shiraz Univ Technol Dept Elect Engn Modarres Blvd Shiraz 715555313 Iran

A distributed control protocol is proposed in this paper for tracking a leader with a sinusoidal motion path considering an undirected communication graph. A multi-agent system (MAS) is considered in which the dynamics of all agents and the leader are nonlinear and contaminated with noise. Firstly, we assume that the states of the leader and all of the agents are measurable without noise. In this case, graph theory, Lyapunov approach and Lasalle principle are used to design a distributed control protocol for nonlinear MASs to follow the leader with nonlinear dynamics. Next, it is supposed that the leader has a sinusoidal motion and its neighbor followers observe the leader with noise. Therefore, the parameters of measured signal including amplitude, frequency and phase are unknown. In this way, a novel algorithm called Integral Linear least square (ILLS) is proposed to estimate unknown parameters of sinusoidal behavior of the leader which is contaminated by noise, accurately. Next, a distributed control algorithm is designed for multiagent systems with Lipschitz nonlinearities under undirected graph to track the estimated states of the leader with noisy sinusoidal motion. Finally, numerical simulations illustrate the effectiveness of the proposed algorithms.

关键词： Multi agent Leader tracking Graph theory Lyapunov approach Lasalle principle least square algorithm

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Improving finite element results in modeling heart valve mechanics

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART H-JOURNAL OF ENGINEERING IN MEDICINE 2018年第7期232卷 718-725页

作者： Earl, Emily Mohammadi, Hadi Univ British Columbia Sch Engn Fac Sci Appl Heart Valve Performance Lab Okanagan Campus Kelowna BC V1V 1V7 Canada

Finite element analysis is a well-established computational tool which can be used for the analysis of soft tissue mechanics. Due to the structural complexity of the leaflet tissue of the heart valve, the currently available finite element models do not adequately represent the leaflet tissue. A method of addressing this issue is to implement computationally expensive finite element models, characterized by precise constitutive models including high-order and high-density mesh techniques. In this study, we introduce a novel numerical technique that enhances the results obtained from coarse mesh finite element models to provide accuracy comparable to that of fine mesh finite element models while maintaining a relatively low computational cost. Introduced in this study is a method by which the computational expense required to solve linear and nonlinear constitutive models, commonly used in heart valve mechanics simulations, is reduced while continuing to account for large and infinitesimal deformations. This continuum model is developed based on the least square algorithm procedure coupled with the finite difference method adhering to the assumption that the components of the strain tensor are available at all nodes of the finite element mesh model. The suggested numerical technique is easy to implement, practically efficient, and requires less computational time compared to currently available commercial finite element packages such as ANSYS and/or ABAQUS.

关键词： Finite element method finite difference method least square algorithm continuum mechanics numerical methods

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Optimal control and parameters design for the fractional-order vehicle suspension system

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JOURNAL OF LOW FREQUENCY NOISE VIBRATION AND ACTIVE CONTROL 2018年第3期37卷 456-467页

作者： You, Hao Shen, Yongjun Xing, Haijun Yang, Shaopu Shijiazhuang Tiedao Univ Dept Mech Engn 17 Bei Er Huan Dong Rd Shijiazhuang 050043 Hebei Peoples R China

In this paper the optimal control and parameters design of fractional-order vehicle suspension system are researched, where the system is described by fractional-order differential equation. The linear quadratic optimal state regulator is designed based on optimal control theory, which is applied to get the optimal control force of the active fractional-order suspension system. A stiffness-damping system is added to the passive fractional-order suspension system. Based on the criteria, i.e. the force arising from the accessional stiffness-damping system should be as close as possible to the optimal control force of the active fractional-order suspension system, the parameters of the optimized passive fractional-order suspension system are obtained by least square algorithm. An Oustaloup filter algorithm is adopted to simulate the fractional-order derivatives. Then, the simulation models of the three kinds of fractional-order suspension systems are developed respectively. The simulation results indicate that the active and optimized passive fractional-order suspension systems both reduce the value of vehicle body vertical acceleration and improve the ride comfort compared with the passive fractional-order suspension system, whenever the vehicle is running on a sinusoidal surface or random surface.

关键词： Fractional-order derivatives optimal control least square algorithm Oustaloup filter algorithm

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A new physical parameter identification method for shear frame structures under limited inputs and outputs

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ADVANCES IN STRUCTURAL ENGINEERING 2021年第4期24卷 667-679页

作者： Liu, Jing-Liang Yu, An-Hua Chang, Chia-Ming Ren, Wei-Xin Zhang, Jing Fujian Agr & Forestry Univ Sch Transportat & Civil Engn Fuzhou Peoples R China Natl Taiwan Univ Dept Civil Engn Taipei Taiwan Shenzhen Univ Sch Civil & Traff Engn Nanhai Ave 3688 Shenzhen Peoples R China Hefei Univ Technol Sch Civil & Hydraul Engn Tunxi Rd 193 Hefei 230009 Peoples R China

A new physical parameter identification method with a name of EKPF-LS is proposed for shear frame structures under limited inputs and outputs by a combination of extended Kalman particle filter (EKPF) and least square (LS) algorithm. The basic principle of EKPF-LS is to establish the proposed distribution function of the particle filter through EKF-LS. In this method, EKPF is introduced to get rid of the restriction of Gaussian white noise model and reduce the linearization error caused by EKF. Meanwhile, LS is utilized to address the problem of unmeasured excitation estimations. The effectiveness and accuracy of the proposed EKPF-LS method is verified by a numerical example of a four-story hysteretic shear frame under an earthquake excitation and an experimental test of a four-story shear type frame using Gaussian white noise and sine sweep signal as excitations, respectively. Gaussian colored noises are then added to the solved and measured response signals in the numerical example and experimental test, respectively. The results demonstrate that the proposed method can identify the stiffness of shear frame structures effectively and is superior to the existed EKF-LS approach when the structural system is nonlinear structural system or Colored noise model.

关键词： extended Kalman particle filter least square algorithm physical parameter limited input and output shear frame structure

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Controlling of lower-order dead system by implementing adaptive RST algorithm

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INTERNATIONAL JOURNAL OF MODELLING IDENTIFICATION AND CONTROL 2021年第4期39卷 272-278页

作者： Guo, Yanzhu Xian Railway Vocat & Tech Inst Xian Shaanxi Peoples R China

Since the advent of time, humankind has made numerous technological advancements. Every system built is indeed time-varying in nature as well as nonlinear, and they tend to vary with time. The dead or slow system tends to vary at a slow rate. To control such a system, we implemented an RST-based control algorithm that can track the output of the unknown system and control it with minimal error. (tau) is a quantity measured in time and it is a time-varying parameter for the lower order system, this is the parameter that will change with time and in turn change an entire system response. Previously applied control parameters might not be suitable to control the system. Therefore, this study introduces a novel mechanism that combines the least squares (LS) algorithm with RST. LS used to track the changes occurring in the system with time and thus change the control parameter to complement the changes that occurred in the system. The proposed algorithm design of a slow time-varying system is compiled and simulated in MATLAB. It is compared with the conventional PID controller and it tracks the signal faster with the same amount of work force. It shows better performance more robust and effective than the PID controller.

关键词： RST control algorithm slow time-varying system dead systems least square algorithm adaptive control self-tuning regulator

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