다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

http://mech.spbstu.ru/images/b/bd/Potyondy_Cundall_2004_A_bonded-particle_model_for_rock.pdf

A bonded-particle model for rock

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Properties Of Concrete

Modeling of the evolution of distributed damage such as microcracking, void formation, and softening frictional slip necessitates strain-softening constitutive models. The nonlocal continuum concept has emerged as an effective means for regularizing the boundary value problems with strain softening, capturing the size effects and avoiding spurious localization that gives rise to pathological mesh sensitivity in numerical computations. A great variety of nonlocal models have appeared during the last two decades. This paper reviews the progress in the nonlocal models of integral type, and discusses their physical justifications, advantages, and numerical applications.

Nonlocal integral formulations of plasticity and damage: Survey of progress

Application of bacteria as self-healing agent for the development of sustainable concrete

Fracture simulations of concrete using lattice models : computational aspects

In this paper a numerical model is presented for simulating fracture in heterogeneous materials such as concrete and rock. The typical failure mechanism, crack face bridging, found in concrete and other materials is simulated by use of a lattice model. The model can be used at a small scale, where the particles in the grain structure are generated and aggregate, matrix and bond properties are assigned to the lattice elements. Simulations at this scale are useful for studying the influence of material composition. In addition the model seems a promising tool for simulating fracture in structures. In this case the microstructure of the material is not mimicked in detail but rather the lattice elements are given tensile strengths which are randomly chosen out of a certain distribution. Realistic crack patterns are found compared with experiments on laboratory-scale specimens. The present results indicate that fracture mechanisms are simulated realistically. This is very important because it simplifies the tuning of the model.

Simple lattice model for numerical simulation of fracture of concrete materials and structures

In this paper experimental evidence of fracture toughening of concrete and mortar through a mechanism called crack face bridging is presented. The classical explanation for softening of concrete, viz. the formation of a zone of discontinuous microcracking ahead of a continuous macrocrack seems only partially true. Instead, crack face bridging in the wake of the macrocrack tip seems a physically sounder explanation. The crack face bridges are flexural ligaments between ovelapping crack tips. The failure of the flexural ligaments occurs in a stable and controlled manner because the two overlapping crack tips shield each other. The cohesive stress over the macrocrack is directly related to the size of the crack face bridges, which depends on the heterogeneity of the material. The typical failure mechanism can be simulated using a simple numerical lattice model. First the grain structure of the material is generated either by manual methods or by adopting a random generator. Secondly a tringular lattice of brittle breaking beam elements is projected on the grain structure. Aggregate, matrix and bond properties are assigned to the lattice elements at the respective locations, and a simple algorithm allows for crack growth simulation. The main conclusion is that the crack patterns and the associated load-deformation response are largely governed by the properties of the constituents. The bond between aggregates and matrix is the weakest link in the system, and variation of this parameter leads to profoundly different crack patterns.

Experimental and numerical analysis of micromechanisms of fracture of cement-based composites

The self-healing behavior of a series of pre-cracked fiber reinforced strain hardening cementitious composites incorporating blast furnace slag (BFS) and limestone powder (LP) with relatively high water/binder ratio is investigated in this paper, focusing on the recovery of its deflection capacity. Four-point bending tests are used to precrack the beam at 28 days. For specimens submerged in water the deflection capacity can recover about 65-105% from virgin specimens, which is significantly higher compared with specimens cured in air. Similar conclusion applies to the stiffness recovery in water cured specimens. The observations under ESEM and XEDS confirmed that the microcracks in the specimens submerged in water were healed with significant amount of calcium carbonate, very likely due to the continuous hydration of cementitious materials. The self-healing cementitious composites developed in this research can potentially reduce or even eliminate the maintenance needs of civil infrastructure, especially when repeatable high deformation capacity is desirable, e.g. bridge deck link slabs and jointless pavements. © 2009 Elsevier Ltd. All rights reserved.

Erik Schlangen

Papers

Application of bacteria as self-healing agent for the development of sustainable concrete

Fracture simulations of concrete using lattice models : computational aspects

Simple lattice model for numerical simulation of fracture of concrete materials and structures

Experimental and numerical analysis of micromechanisms of fracture of cement-based composites

Self-healing behavior of strain hardening cementitious composites incorporating local waste materials