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作者： Carvalho, André Rui Dantas University of Victoria

学位级别：master

This thesis presents a simulation model for the dynamics of the human hand for application to an anthropomorphic prosthesis. The Articulated Body algorithm (ABA) algorithm was selected to model the dynamics of a tree type robotic structure. The ABA is a numerical Newton-Euler based algorithm that solves the forward dynamics (obtaining the joint accelerations from the applied torques and forces) for a joint-link model. The main advantage of this algorithm resides in the analysis of the system link by link rather than the entire system analysis. This feature enables the implementation of a computationally efficient code and makes the algorithm generic enough to be applied to almost any robotic structure, with minimal additional effort. Furthermore, as the basic algorithm only handles serial structures, it was modified to include the effect of the gravity, loads on the end-effector, elasticity and damping at the joints, the generalization to tree-type structures, and, finally, the inclusion of impact analysis

关键词： Robotics Biomechanics numerical algorithm Robot Simulation UVic Subject Index Sciences and Engineering Engineering Mechanical engineering

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numerical Study of Inverse Problems of Nonscattering Anisotropic Shell Theory

Numerical Study of Inverse Problems of Nonscattering Anisotr...

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2012 3rd International Conference on Applied Mechanics and Mechanical Engineering(ICAMME 2012)

作者： Alekseev Gennady Lobanov Aleksey Grenkin Gleb Far Eastern Federal University Institute of Applied Mathematics FEB RAS

The inverse problems are formulated for generalized Helmholtz equation describing propagation of acoustics waves in inhomogeneous anisotropic medium. These problems are connected with constructing nonscattering shells filled with anisotropic fluid. For solving the inverse problems we apply the nonlinear optimization techniques. Based on this approach we formulate the general control problem for the Helmholtz equation under consideration. The control problem consists of minimization of a suitable cost functional depending on the state(acoustic pressure) and unknown functions(controls). The optimality system for the general control problem is derived, the sufficient conditions for data which provide a local stability and uniqueness of control problems under study for concrete tracking-type cost functionals are discussed. The efficient numerical algorithm of solving control problem under study based on Newton's method of solving nonlinear equations and finite element for Helmholtz boundary value problems is proposed.

关键词： Acoustics anisotropic media inverse problems control problems optimality system numerical algorithm cloaking shells

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Thermophysical aspects of magnetized Williamson fluid flow subject to both porous and non-porous surfaces: A Lie symmetry analysis

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CASE STUDIES IN THERMAL ENGINEERING 2021年 28卷

作者： Rehman, Khalil Ur Shatanawi, Wasfi Abodayeh, Kamaleldin Prince Sultan Univ Dept Gen Sci Riyadh 11586 Saudi Arabia Air Univ Dept Math PAF Complex E-9 Islamabad 44000 Pakistan China Med Univ China Med Univ Hosp Dept Med Res Taichung 40402 Taiwan Hashemite Univ Fac Sci Dept Math POB 330127 Zarqa 13133 Jordan

The present outcomes on thermally magnetized flow fields by way of symmetry analysis will assist the research community to examine fluid dynamics, particular structures of fluids, and their interaction with the homogeneous porous mediums. The new scaling group of transformations is offered rather than using so-called transformations from existing literature to better narrate the thermal fluid interaction with the porous magnetized medium. Symmetry analysis is carried to find the physical quantities at the surface by executing (i) Slip and non-Slip flow fields (ii) Porous and non-porous mediums (iii) Magnetized and non-Magnetized flow fields. Such collective physical effects result in a complicated mathematical differential system. For the solution purpose firstly the concerned scaling group of transformations is obtained by using symmetry analysis and such transformations are used to covert the differential system into an ordinary differential system. The ultimate differential system is solved by using the shooting method along with RK scheme. The observations are shared with the help of line graph study and tabular forms. It is concluded that for the porous and non-porous mediums, resistance towards fluid declines as the Weissenberg number enhances whereas the heat transfer normal to both porous and non-porous surfaces increases as thermal diffusivity declines.

关键词： Thermally magnetized fluid Symmetry analysis Porous surface Slip flow numerical algorithm

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Optimalizace toku grafem

Optimalizace toku grafem

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作者： Popovič, Viktor Charles University of Prague

When it comes to maximization of effectively or minimizing of cost, optimization represents the key activity. There is a number of practical examples that can be implemented into Theory of Graphs and subsequently optimized. This thesis includes the introduction to transportation problem where the consumer demand is met by the lowest price. Also there is maximum flow problem which is to transfer maximum of commodity (petroleum, gas...) through the network where each edge has a capacity restriction. We will also look into the alternative situations where we will maximize the flow along with minimizing of cost. To resolve these problems we will establish numeric algorithms like distribute method, labeling algorithm, shortest augmented path algorithm, and Preflow-Push algorithms. We will also illustrate functionality on example which confirm appropriate application of algorithms and differences among them.

关键词： Graph optimal flow numerical algorithm

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A statistical approach in enhancing the volume prediction of ellipsoidal ham

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JOURNAL OF FOOD ENGINEERING 2021年 290卷 110186-110186页

作者： Gan, Y. S. Wei, Lan Han, Yiming Zhang, Chenyu Huang, Yen-Chang Liong, Sze-Teng Natl Taipei Univ Nursing & Hlth Sci Res Ctr Healthcare Ind Innovat Taipei Taiwan Xiamen Univ Malaysia Sch Elect & Comp Engn Jalan Sunsuria Sepang Selangor Malaysia Natl Univ Tainan Dept Appl Math Tainan Taiwan Feng Chia Univ Dept Elect Engn Taichung Taiwan

In literature, there exist many attempts to determine the surface area and volume of an irregular object using automated image processing techniques. This paper expanded previous work on predicting the volume of ellipsoidal hams by using both image processing techniques and numerical methods. Novel algorithms were proposed to improve the prediction accuracy and robustness of the volume estimation mechanism. Particularly, the work focused on the ham's position in the horizontal viewpoint. An industrial robotic arm was utilized to lift the ham object and rotate it at a fixed controlled speed to maximize data consistency. Then, a Mask Region-based convolutional neural network approach was used to extract the ham object's features. Experiments were conducted on 16 newly collected ham datasets. In this paper, performance comparisons between this and the previous work were reported and detailed analyses presented. Particularly, three numerical algorithms (i.e., based on the minor axis, Y-direction, and k-nearest neighbor) were introduced to enhance volume prediction in the two databases. The new algorithm exhibited a 27% higher performance than that of the previous work's algorithm. Related theoretical and conceptual frameworks were discussed to further provide evidence and insights on the proposed mechanism.

关键词： Mask R-CNN Ham numerical algorithm Volume

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Application of the Maximum Entropy Method for Determining a Sensitive Distribution in the Renewable Energy Systems

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JOURNAL OF ENERGY RESOURCES TECHNOLOGY-TRANSACTIONS OF THE ASME 2015年第4期137卷 042006-042006页

作者： Yari, Gholamhossein Farsani, Zahra Amini Iran Univ Sci & Technol Sch Math Tehran *** Iran

In the field of the wind energy conversion, a precise determination of the probability distribution of wind speed guarantees an efficient use of the wind energy and enhances the position of wind energy against other forms of energy. The present study thus proposes utilizing an accurate numerical-probabilistic algorithm which is the combination of the Newton's technique and the maximum entropy (ME) method to determine an important distribution in the renewable energy systems, namely the hyper Rayleigh distribution (HRD) which belongs to the family of Weibull distribution. The HRD is mainly used to model the wind speed and the variations of the solar irradiance level with a negligible error. The purpose of this research is to find the unique solution to an optimization problem which occurs when maximizing Shannon's entropy. To confirm the accuracy and efficiency of our algorithm, we used the long-term data for the average daily wind speed in Toyokawa for 12 yr to examine the Rayleigh distribution (RD). This data set was obtained from the National Climatic Data Center (NCDC) in Japan. It seems that the RD is more closely fitted to the data. In addition, we presented different simulation studies to check the reliability of the proposed algorithm.

关键词： hyper Rayleigh distribution Lagrange multipliers maximum copula maximum entropy method numerical algorithm renewable energy systems wind speed probability distribution

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A continuous fracture front tracking algorithm with multi layer tip elements (MuLTipEl) for a plane strain hydraulic fracture

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JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING 2022年第0期217卷

作者： Dontsov, E. V. ResFrac Corp 555 Bryant St 185 Palo Alto CA 94301 USA

The problem of a plane strain hydraulic fracture propagating in a layered formation is considered. Fracture toughness, in-situ stress, and leak-off coefficient are assumed to vary by layer, while the elastic properties are kept constant throughout the domain for simplicity. The purpose of this study is to develop a numerical algorithm based on a fixed mesh approach, which is able to solve the above problem accurately using elements which can even be larger than the layer size. In order to do this, the concept of fictitious tip stress is first introduced for determining the fracture front location. In this technique, an additional stress is applied to the tip element to suppress the opening and to mimic the width corresponding to the actual fracture front location. A theoretical basis for this concept has been established and it is further calibrated for piece-wise constant elements. Once the ability to track the crack front location is developed, the effect of layers is included by varying properties as a function of front location. Several numerical examples benchmarking the numerical solution, as well as highlighting capabilities of the algorithm to tackle multiple thin layers accurately are presented.

关键词： Hydraulic fracturing numerical algorithm Thin layers Plane strain

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Variational assimilation of mean daily observation data for the problem of sea hydrothermodynamics

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RUSSIAN JOURNAL OF numerical ANALYSIS AND MATHEMATICAL MODELLING 2017年第3期32卷 187-195页

作者： Parmuzin, Eugene I. Agoshkov, Valery I. Zakharova, Natalia B. Shutyaev, Victor P. RAS Inst Numer Math Moscow 119333 Russia Moscow Inst Phys & Technol Dolgoprudnyi 141700 Moscow Region Russia

The mathematical model of hydrothermodynamics of the Baltic Sea is considered with the pole moved to a neighbourhood of St. Petersburg in order to improve the horizontal resolution in the Gulf of Finland. The problem of variational assimilation of mean daily data for sea surface temperature (SST) is formulated and studied for the given type of calculation grid of this model. A new algorithm of solution of the inverse problem for reconstruction of the heat flux on the interface of two media is proposed on the base of variational assimilation of satellite observation data. Results of numerical experiments are presented for reconstruction of heat fluxes in the problem of variational assimilation of mean daily observations of SST data.

关键词： Variational assimilation numerical algorithm determination of heat fluxes sea surface temperature

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I?m stuck! How to efficiently debug computational solid mechanics models so you can enjoy the beauty of simulations

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EUROPEAN JOURNAL OF MECHANICS A-SOLIDS 2023年 97卷

作者： Comellas, Ester Pelteret, Jean-Paul Bangerth, Wolfgang Univ Politecn Cataluna Dept Phys Rambla St Nebridi 2 Terrassa 08222 Barcelona Spain Colorado State Univ Dept Math Dept Geosci Ft Collins CO 80524 USA

A substantial fraction of the time that computational modellers dedicate to developing their models is actually spent trouble-shooting and debugging their code. However, how this process unfolds is seldom spoken about, maybe because it is hard to articulate as it relies mostly on the mental catalogues we have built with the experience of past failures. To help newcomers to the field of material modelling, here we attempt to fill this gap and provide a perspective on how to identify and fix mistakes in computational solid mechanics *** this aim, we describe the components that make up such a model and then identify possible sources of errors. In practice, finding mistakes is often better done by considering the symptoms of what is going wrong. As a consequence, we provide strategies to narrow down where in the model the problem may be, based on observation and a catalogue of frequent causes of observed errors. In a final section, we also discuss how one-time bug-free models can be kept bug-free in view of the fact that computational models are typically under continual *** hope that this collection of approaches and suggestions serves as a "road map"to find and fix mistakes in computational models, and more importantly, keep the problems solved so that modellers can enjoy the beauty of material modelling and simulation.

关键词： Computational solid mechanics Material modelling Constitutive model Finite element method Debugging numerical implementation numerical algorithm

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Composite material design of two-dimensional structures using the homogenization design method

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INTERNATIONAL JOURNAL FOR numerical METHODS IN ENGINEERING 2001年第9期50卷 2031-2051页

作者： Fujii, D Chen, BC Kikuchi, N Univ Michigan Dept Mech Engn & Appl Mech Ann Arbor MI 48109 USA

Composite materials of two-dimensional structures are designed using the homogenization design method. The composite material is made of two or three different material phases. Designing the composite material consists of finding a distribution of material phases that minimizes the mean compliance of the macrostructure subject to volume fraction constraints of the constituent phases, within a unit cell of periodic microstructures. At the start of the computational solution, the material distribution of the microstructure is represented as a pure mixture of the constituent phases. As the iteration procedure unfolds, the component phases separate themselves out to form distinctive interfaces. The effective material properties of the artificially mixed materials are defined by the interpolation of the constituents. The optimization problem is solved using the sequential linear programming method. Both the macrostructure and the microstructures are analysed using the finite element method in each iteration step. Several examples of optimal topology design of composite material are presented to demonstrate the validity of the present numerical algorithm. Copyright (C) 2001 John Wiley & Sons, Ltd.

关键词： composite material homogenization method topology optimization microstructures numerical algorithm

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