[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

Soft tissues are diverse biological materials in which the cells are separated by extracellular material. They connect, support, and protect our body and form structures such as organs. Soft tissues include blood vessels, heart tissues, ligaments, tendons, skin or articular cartilage just to name a few. Soft tissues are complex fiber-reinforced composite structures. In a microscopic sense they are non-homogeneous materials because of their composition. Most of them exhibit an anisotropic behavior because of their embedded fibers, which tend to have preferred directions. The tensile response of soft tissues is nonlinear stiffening and the tensile strength depends on the strain rate. In contrast to hard (mineralized) tissues such as bones, soft tissues may experience large

Computational Biomechanics of Soft Biological Tissues: Arterial Walls, Hearts Walls, and Ligaments

Modeling of damage-induced softening for arterial tissues

Collagen fiber bundles are important constituent parts of biological soft tissues, such as tendons, blood vessels and skin. The single collagen fibers within a bundle have a certain crimp that determines the bundle's stretching characteristic, which is of particular interest in mechanobiology. A thorough understanding of the complex interrelations between mechanical factors and the associated biological responses may help to improve diagnostics, which allow disease and injury to be treated earlier. We present a method to obtain the relative stretching characteristics (RSC) of collagen (fibrous) bundles based on the analysis of microscopic tissue images. We show, how the orientation statistics of local orientations in a bundle can be directly related to the RSC. The von Mises distribution (VMD) - a circular probability distribution is used to describe the 2D orientation statistics. The k parameter of the VMD is used to obtain the mean stretching and the probability density function (PDF) of the bundles' RSC is identified.

Estimating the stretching characteristics of fiber bundles in microscopic images

Collagen fibers are prominent constituents of many soft tissues. The fibers are able to carry load along their fiber axis, and, therefore, their structural arrangement renders the mechanical behavior of biological tissue anisotropic. In some tissues, e.g., blood vessels, tendons and ligaments, the fibers form fiber bundles. Structure-based biomechanical models of soft tissues strongly rely on a clear understanding of the underlying collagen fiber bundle structure and require precise quantitative structural information. The paper presents a novel fiber bundle model that satisfactorily explains the observed bundle structure and reveals meaningful parameters for bundle characterization. The model is capable of describing a wide variety of natural bundle structures. It is shown that the identified bundle parameters can be extracted from real histological images using computer vision algorithms. The generative nature of the model allows the creation of artificial fiber bundle images with characteristics very similar to real images.

Gerhard Holzapfel

Papers

Computational Biomechanics of Soft Biological Tissues: Arterial Walls, Hearts Walls, and Ligaments

Modeling of damage-induced softening for arterial tissues

Estimating the stretching characteristics of fiber bundles in microscopic images

Modeling and characterizing collagen fiber bundles

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