[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

From the Publisher: 
The accessible presentation of this book gives both a general view of the entire computer vision enterprise and also offers sufficient detail to be able to build useful applications. Users learn techniques that have proven to be useful by first-hand experience and a wide range of mathematical methods. A CD-ROM with every copy of the text contains source code for programming practice, color images, and illustrative movies. Comprehensive and up-to-date, this book includes essential topics that either reflect practical significance or are of theoretical importance. Topics are discussed in substantial and increasing depth. Application surveys describe numerous important application areas such as image based rendering and digital libraries. Many important algorithms broken down and illustrated in pseudo code. Appropriate for use by engineers as a comprehensive reference to the computer vision enterprise.

Computer vision : a modern approach = 计算机视觉 : 一种现代的方法

A paradigm shift is taking place in medicine from using synthetic implants and tissue grafts to a tissue engineering approach that uses degradable porous material scaffolds integrated with biological cells or molecules to regenerate tissues. This new paradigm requires scaffolds that balance temporary mechanical function with mass transport to aid biological delivery and tissue regeneration. Little is known quantitatively about this balance as early scaffolds were not fabricated with precise porous architecture. Recent advances in both computational topology design (CTD) and solid free-form fabrication (SFF) have made it possible to create scaffolds with controlled architecture. This paper reviews the integration of CTD with SFF to build designer tissue-engineering scaffolds. It also details the mechanical properties and tissue regeneration achieved using designer scaffolds. Finally, future directions are suggested for using designer scaffolds with in vivo experimentation to optimize tissue-engineering treatments, and coupling designer scaffolds with cell printing to create designer material/biofactor hybrids.

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Porous scaffold design for tissue engineering

In this paper we develop a new constitutive law for the description of the (passive) mechanical response of arterial tissue. The artery is modeled as a thick-walled nonlinearly elastic circular cylindrical tube consisting of two layers corresponding to the media and adventitia (the solid mechanically relevant layers in healthy tissue). Each layer is treated as a fiber-reinforced material with the fibers corresponding to the collagenous component of the material and symmetrically disposed with respect to the cylinder axis. The resulting constitutive law is orthotropic in each layer. Fiber orientations obtained from a statistical analysis of histological sections from each arterial layer are used. A specific form of the law, which requires only three material parameters for each layer, is used to study the response of an artery under combined axial extension, inflation and torsion. The characteristic and very important residual stress in an artery in vitro is accounted for by assuming that the natural (unstressed and unstrained) configuration of the material corresponds to an open sector of a tube, which is then closed by an initial bending to form a load-free, but stressed, circular cylindrical configuration prior to application of the extension, inflation and torsion. The effect of residual stress on the stress distribution through the deformed arterial wall in the physiological state is examined. The model is fitted to available data on arteries and its predictions are assessed for the considered combined loadings. It is explained how the new model is designed to avoid certain mechanical, mathematical and computational deficiencies evident in currently available phenomenological models. A critical review of these models is provided by way of background to the development of the new model.

https://hal.archives-ouvertes.fr/hal-01297725/document

A new constitutive framework for arterial wall mechanics and a comparative study of material models

Constitutive relations are fundamental to the solution of problems in continuum mechanics, and are required in the study of, for example, mechanically dominated clinical interventions involving soft biological tissues. Structural continuum constitutive models of arterial layers integrate information about the tissue morphology and therefore allow investigation of the interrelation between structure and function in response to mechanical loading. Collagen fibres are key ingredients in the structure of arteries. In the media (the middle layer of the artery wall) they are arranged in two helically distributed families with a small pitch and very little dispersion in their orientation (i.e. they are aligned quite close to the circumferential direction). By contrast, in the adventitial and intimal layers, the orientation of the collagen fibres is dispersed, as shown by polarized light microscopy of stained arterial tissue. As a result, continuum models that do not account for the dispersion are not able to capture accurately the stress–strain response of these layers. The purpose of this paper, therefore, is to develop a structural continuum framework that is able to represent the dispersion of the collagen fibre orientation. This then allows the development of a new hyperelastic free-energy function that is particularly suited for representing the anisotropic elastic properties of adventitial and intimal layers of arterial walls, and is a generalization of the fibre-reinforced structural model introduced by Holzapfel & Gasser (Holzapfel & Gasser 2001 Comput. Meth. Appl. Mech. Eng. 190, 4379–4403) and Holzapfel et al. (Holzapfel et al. 2000 J. Elast. 61, 1–48). The model incorporates an additional scalar structure parameter that characterizes the dispersed collagen orientation. An efficient finite element implementation of the model is then presented and numerical examples show that the dispersion of the orientation of collagen fibres in the adventitia of human iliac arteries has a significant effect on their mechanical response.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsif.2005.0073

Hyperelastic modelling of arterial layers with distributed collagen fibre orientations

Cartilage from the medial femoral condyle of chicken was sectioned and imaged using second harmonic generation
microscopy. Using image analysis techniques based on the Fourier transform we derived quantitative threedimensional
data of the fiber direction and dispersion of the collagen fiber network in the superficial layer. These
data can be used directly in biomechanical models to enhance the fidelity of these models.

Extracting quantitative biomechanical parameters for cartilage from second harmonic generation images

Changes in the microstructure of the human aortic adventitia under biaxial loading investigated by multi-photon microscopy.

Human aortas are three-layered fibrous composites assembled by a ground matrix and embedded families of dispersed collagen fibers. The microstructural arrangement of the collagen fibers alters due to diseases such as aneurysms. We review a general dispersion model that is required to describe the mechanical response of a variety of collagenous tissues such as aortic walls considering three structural and three material parameters. The dispersion model is used to capture the remarkable differences in the microstructure and mechanics of healthy and aneurysmatic aortas. Related modeling/simulation of an aortic dissection is provided using the recently developed phase-field approach. An energy-based anisotropic failure criterion is used to numerically simulate the evolution of the crack phase-field in a simple shear test. Model parameters are provided and numerical results agree favorably with the experimental findings. Finally, an aortic clamping simulation is described by considering the individual aortic layers, residual stresses, nonsymmetric blood pressure after clamping, patient-specific data and damage-induced inelastic phenomena, i.e., stress softening and permanent deformations.

Microstructure and Mechanics of Human Aortas in Health and Disease

Modeling cardiac function is an important task to increase the understanding of the physiological response of the heart and to determine how complex structural heart components influence the biomechanical behavior of the heart. In this communication a coupled model of orthotropic ventricular myocardium is presented using fiber and sheet orientations that is matching regionally measured experimental data. This approach generates a more realistic and homogenized stress distribution when compared to a model with a generic fiber and sheet orientation. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)

Gerhard Holzapfel

Papers

Extracting quantitative biomechanical parameters for cartilage from second harmonic generation images

Changes in the microstructure of the human aortic adventitia under biaxial loading investigated by multi-photon microscopy.

Microstructure and Mechanics of Human Aortas in Health and Disease

A Coupled Model for the Left Ventricle Including Regional Differences in Structure

Mechanical stress in abdominal aneurysm: influence of GEOMETRY and material anisotropy