scholarly journals The Meso-Structural Characteristics of Crack Generation and Propagation during Rock Fracturing

Minerals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 94
Author(s):  
Yanbo Zhang ◽  
Guangyu Gao ◽  
Shaohong Yan ◽  
Xulong Yao ◽  
Xiangxin Liu ◽  
...  
Keyword(s):  
Crack Extension ◽  
Structural Characteristics ◽  
Rock Fracture ◽  
Ct Scanning ◽  
Initial Distribution ◽  
Three Dimensions ◽  
Rock Fracturing ◽  
Underground Engineering ◽  
Cyclic Loading And Unloading ◽  
Crack Generation

Meso-structure is an important factor affecting the characteristics of rock fracture. To determine the factors influencing the internal meso-structural characteristics upon the crack generation and extension, rock samples were tested under uniaxial cyclic loading and unloading and examined using computed tomography (CT) scanning. CT scanning was used to visualize and investigate the entire process of fracture source generation and its development in three dimensions, and finally the location information of the fracture source was determined. The mineral composition and structure along the fracture path inside the specimen were studied by using a polarizing microscope, and the evolution of fracture propagation around mineral particles was revealed based on its mineralogical characteristics. Results indicate that based on the fracture source around different rock meso-structure types, the initial fracture source can also be divided into different types, namely, the primary porosity type, the micro-crack type, and the mineral grain type. The strength characteristics of mineral grains can determine whether the crack extends around the gravel or through it. The hard grains at the crack-tip promote the transformation of tensile stress to shear stress, which lead to the change in the direction of crack extension and bifurcation. The spatial shape of the cracks after rock fracture is related to the initial distribution of minerals and is more complicated in areas where minerals are concentrated. The crack extension around gravel particles also generates a mode of failure, affecting large grains with gravel spalling from the matrix. The findings provide a study basis for identifying the potentially dangerous areas and provide early warning for the safety of underground engineering construction operations.

scholarly journals A Typological Classification for Assessing Farm Sustainability in the Italian Bovine Dairy Sector

2021 ◽  
Vol 13 (13) ◽  
pp. 7097
Author(s):  
Margherita Masi ◽  
Yari Vecchio ◽  
Gregorio Pauselli ◽  
Jorgelina Di Pasquale ◽  
Felice Adinolfi
Keyword(s):  
Structural Characteristics ◽  
Dairy Farms ◽  
Three Dimensions ◽  
Structural Relationships ◽  
Analysis Technique ◽  
The Social ◽  
European Policies ◽  
Farm Sustainability ◽  
Social Environmental ◽  
Cluster Analysis Technique

Italy is among the most important countries in Europe for milk production. The new European policies encourage a transition towards sustainability and are leading European dairy farms to follow new trajectories to increase their economic efficiency, reduce their environmental impact, and ensure social sustainability. Few studies have attempted to classify dairy farms by analyzing the relationships between the structural profiles of farms and the social, environmental, and economic dimensions of sustainability. This work intends to pursue this aim through an exploratory analysis in the Italian production context. The cluster analysis technique made it possible to identify three types of dairy farms, which were characterized on the basis of indicators that represented the three dimensions of sustainability (environmental, social, and economic sustainability) and the emerging structural relationships based on the structural characteristics of the dairy farms. The classification made it possible to describe the state of the art of the Italian dairy sector in terms of sustainability and to understand how different types of farms can respond to the new European trajectories.

Empirical Research on Topological Characteristics of Air Traffic Situation Network

2015 ◽  
Vol 744-746 ◽  
pp. 1975-1979
Author(s):  
Hong Yong Wang ◽  
Rui Ying Wen ◽  
Yi Fei Zhao
Keyword(s):  
Traffic Control ◽  
Structural Characteristics ◽  
Air Traffic ◽  
Clustering Coefficient ◽  
Three Dimensions ◽  
Node Degree ◽  
Traffic Situation ◽  
Network Connection ◽  
Local Sector ◽  
Topological Characteristics

A method for description of structural characteristics of air traffic situation based on the theory of complex network was proposed. This method characterizes the air traffic situation from three dimensions, including single aircraft, local sector, and overall sector. We selected the routinely-recorded flight data in an air traffic control sector within China's airspace in 2013. With the aircrafts in the sector regarded as nodes, and with the between-aircraft proximity relations as edges, we constructed an undirected and unweighted aircraft network. The results show that network node degree can distinguish the key aircraft in the sector; the network connection rate reflects the proximity of aircrafts; the clustering coefficient identifies the presence of high-density aircraft group.

scholarly journals Correlational Analytical Characterization of Energy Dissipation-Liberation and Acoustic Emission during Coal and Rock Fracture Inducing by Underground Coal Excavation

Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2382 ◽  
Author(s):  
Pengfei Shan ◽  
Xingping Lai ◽  
Xiaoming Liu
Keyword(s):  
Acoustic Emission ◽  
Energy Dissipation ◽  
Axial Stress ◽  
Rock Fracture ◽  
Quantitative Relationship ◽  
Dissipated Energy ◽  
Release Mechanism ◽  
Rock Fracturing ◽  
Dissipation Energy ◽  
Energy Parameters

This paper uses an acoustic emission (AE) test to examine the energy dissipation and liberation of coal and rock fracture due to underground coal excavation. Many dynamic failure events are frequently observed due to underground coal excavation. To establish the quantitative relationship between the dissipated energy and AE energy parameters, the coal and rock fracturing characteristics were clearly observed. A testing method to analyze the stage traits and energy release mechanism from damage to fracture of the unloading coal and rock under uniaxial compressive loading is presented. The research results showed that the relevant mechanical parameter discreteness was too large because the internal structures of the coal and rock were divided into multiple structural units (MSU) by a few main cracks. The AE test was categorized into four stages based on both the axial stress and AE event parameters: initial loading stage, elastic stage, micro-fracturing stage, and post-peak fracturing stage. The coal and rock samples exhibited minimum (maximum) U values of 60.44 J (106.41 J) and 321.19 J (820.87 J), respectively. A theoretical model of the dissipation energy during sample fracturing based on the AE event energy parameters was offered. The U decreased following an increase in ΣEAE-II/ΣEAE.

Brain imaging in epilepsy

2019 ◽  
Vol 19 (5) ◽  
pp. 438-443 ◽  
Author(s):  
John S Duncan
Keyword(s):  
Brain Imaging ◽  
Epilepsy Surgery ◽  
Single Photon ◽  
Photon Emission ◽  
Ct Scanning ◽  
Three Dimensions ◽  
Epileptic Focus ◽  
Emission Computed Tomography ◽  
Positron Emission ◽  
Cerebral Pathology

Brain imaging with MRI identifies structural cerebral pathology that may give rise to seizures. The greatest yield is from MRI at 3T using epilepsy protocols, and reported by expert neuroradiologists who possess the full clinical data. X-ray CT scanning has a role in assessing patients with seizures in the context of an acute neurological illness. Identifying a relevant structural lesion with MRI is fundamental in the consideration of epilepsy surgery; it is crucial to establish if a lesion is relevant to the epilepsy or not. If no lesion is identified, developmental MRI and image processing may identify a subtle abnormality. Positron-emission tomography (PET) and single-photon emission computed tomography (SPECT) may identify focal functional abnormalities that infer the location of an epileptic focus. Functional MRI is useful for localising eloquent cortex, and tractography delineates crucial white matter tracts, so that these may be avoided in epilepsy surgery. Reviewing data in three dimensions aids visualisation of structural relationships and helps surgical planning.

Linearized oscillations of a vortex column: the singular eigenfunctions

2014 ◽  
Vol 741 ◽  
pp. 404-460 ◽  
Author(s):  
Anubhab Roy ◽  
Ganesh Subramanian
Keyword(s):  
Critical Radius ◽  
Piecewise Linear ◽  
Three Dimensional ◽  
Vortex Sheet ◽  
Initial Distribution ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Rankine Vortex ◽  
Parallel Flows ◽  
Lord Kelvin

AbstractIn 1880 Lord Kelvin analysed the linearized inviscid oscillations of a Rankine vortex as part of a theory of vortex atoms. These eponymously named neutrally stable modes are, however, exceptional regular oscillations that make up the discrete spectrum of the Rankine vortex. In this paper, we examine the singular oscillations that make up the continuous spectrum (CS) and span the entire base state range of frequencies. In two dimensions, the CS eigenfunctions have a twin-vortex-sheet structure similar to that known from earlier investigations of parallel flows with piecewise linear velocity profiles. The vortex sheets are cylindrical, being threaded by axial lines, with one sheet at the edge of the core and the other at the critical radius in the irrotational exterior; the latter refers to the radial location at which the fluid co-rotates with the eigenmode. In three dimensions, the CS eigenfunctions have core vorticity and may be classified into two families based on the singularity at the critical radius. For the first family, the singularity is a cylindrical vortex sheet threaded by helical vortex lines, while for the second family it has a localized dipole structure with radial vorticity. The presence of perturbation vorticity in the otherwise irrotational exterior implies that the CS modes, unlike the Kelvin modes, offer a modal interpretation for the (linearized) interaction of the Rankine vortex with an external vortical disturbance. It is shown that an arbitrary initial distribution of perturbation vorticity, both in two and three dimensions, may be evolved as a superposition over the discrete and CS modes; this modal representation being equivalent to a solution of the corresponding initial value problem. For the restricted case of an initial axial vorticity distribution in two dimensions, the modal representation may be generalized to a smooth vortex. Finally, for the three-dimensional case, the analogy between rotational flows and stratified shear flows, and the known analytical solution for stratified Couette flow, are used to clarify the singular manner in which the modal superposition for a smooth vortex approaches the Rankine limit.

Heat Induced Fracturing of Rock in an Existing Uniaxial Stress Field

1985 ◽  
Vol 50 ◽  
Author(s):  
J. I. Mathis ◽  
O. Stehpansson ◽  
B. Bjarnason ◽  
H. Hakami ◽  
A. Herdocia ◽  
...  
Keyword(s):  
Large Scale ◽  
Failure Time ◽  
Rock Fracture ◽  
Failure Process ◽  
Uniaxial Stress ◽  
Time To Failure ◽  
Rock Breakage ◽  
Rock Fracturing ◽  
Thermal Failure ◽  
Thermal Fracturing

AbstractThe thermal fracturing of rock has been the object of several research projects, notably for initial rock breakage in mining [4] as well as crushing [6] In addition, the process has been studied carefully in regards to the storage of radioactive waste underground where rock fracturing could lead to a loss of radioactivity confinement. The Stripa Project, a project concerning large scale testing of procedures for underground storage of nuclear waste, probably has dealt most thoroughly with this subject by theoretical studies and in-situ heater testing in an attempt to describe the thermal failure process in rock [13]This project was designed to test the agreement between theoretical and actual rock fracture times of a rock block, loaded with a physical as well as a thermal load. Laboratory testing consisted of physically loading center-drilled cubes of rock, 0.3 m on a side, uniaxially from 0 to 25 MPa. These were then thermally loaded with a nominal 3.7 kW (factory rating) cylindrical heater until failure occurred. This time to failure was recorded for comparison with a direct mathematical and a finite element solution. For both cases, calculations were performed at specific time-steps and an estimated failure time calculated from the compiled results.

scholarly journals X-ray micro-CT scanning reveals temporal separation of male harm and female kicking during traumatic mating in seed beetles

2017 ◽  
Vol 284 (1856) ◽  
pp. 20170550 ◽  
Author(s):  
Liam R. Dougherty ◽  
Leigh W. Simmons
Keyword(s):  
Callosobruchus Maculatus ◽  
Ct Scanning ◽  
Three Dimensions ◽  
Micro Ct ◽  
Temporal Separation ◽  
X Ray ◽  
Seed Beetle ◽  
Proximate Mechanisms ◽  
Fitness Consequences ◽  
Seed Beetles

In the seed beetle Callosobruchus maculatus , the male intromittent organ is covered in sharp spines that pierce the female copulatory tract wall during mating. Although the fitness consequences of traumatic mating are well studied in this species, we know much less about how the male and female genitalia interact during mating. This is partly due to the fact that genital interactions occur primarily inside the female, and so are difficult to observe. In this study, we use X-ray micro-CT scanning to examine the proximate mechanisms of traumatic mating in C. maculatus in unprecedented detail. We show that this technique can be used to identify female tissue damage before the melanization of wound sites. We visualize the positioning of the male intromittent organ inside the female copulatory tract during mating, and show how this relates to tract wounding in three dimensions. By scanning pairs flash-frozen at different times during mating, we show that significant tract wounding occurs before the onset of female kicking. There is thus some degree of temporal separation between the onset of wounding and the onset of kicking, which supports recent suggestions that kicking is not an effective female counter-adaptation to reduce copulatory wounding in this species. We also present evidence that the sharp teeth protruding from the female tract wall are able to pierce the spermatophore as it is deposited, and may thus function to aid sperm release.

scholarly journals Assessment of the remains in historic urban area based on spatial prototype

2020 ◽  
Author(s):  
Guangtong Xu ◽  
◽  
Yi He ◽  
Keyword(s):  
Urban Area ◽  
Urban Areas ◽  
Structural Characteristics ◽  
Assessment System ◽  
Three Dimensions ◽  
Conservation Strategy ◽  
Spatial Problem ◽  
Constituent Elements ◽  
Relationship Of ◽  
Historic City

Like most historic and cultural cities in China, the historic urban area of JingMen city is facing a typical spatial problem of fragmentation and fuzzification. This study is focused on exploring a method for evaluating the existing values of historic urban area based on spatial prototype. As a built-up relationship of historic city, spatial prototype has habitual structural characteristics and formal modulus. It is the inherent logic and order rules behind the scattered historic environment, providing a clue to understand the spatial characteristics and a basis for guiding the construction and conservation in historic urban areas. Three criteria, the resolution of historical elements, the integrity of historical structure and the renewal potential of associated plots, were selected to construct the assessment system. These three dimensions are linked to the spatial prototype and its constituent elements, as well as the transformation relationship in ancient and present day. The results showed that historic urban areas have changed from a holistic city to different existing types dominated by their historic structure elements. Finally, a constructive conservation strategy should be adopted to enhance the integrity of historic urban area based on the trace of spatial prototype and evaluation results.

scholarly journals Experimental Study on Mechanical Properties of Deep Buried Granite under Different Confining Pressures

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Jun Zhao ◽  
Tan Zhang
Keyword(s):  
Cyclic Loading ◽  
Confining Pressure ◽  
Surrounding Rock ◽  
Underground Engineering ◽  
Failure Characteristics ◽  
Deformation And Failure ◽  
Cyclic Loading And Unloading ◽  
Confining Pressures ◽  
Crack Damage Stress ◽  
Loading And Unloading

Brittle failure of hard rock poses a serious threat to the stability of surrounding rock in deep underground engineering. In order to study the deformation and failure characteristics of deep buried granite under high confining pressure cyclic loading and unloading, MTS815 electro-hydraulic servo rock test system was used to conduct cyclic loading and unloading tests under confining pressures of 15 MPa, 35 MPa, 45 MPa, and 55 MPa, and the corresponding stress-strain curves and deformation failure characteristic curves were obtained. The experimental results show the follows: (1) under the same confining pressure, the peak strength, crack initiation stress, crack damage stress, and Poisson’s ratio of the specimens under cyclic loading and unloading are larger than those under conventional triaxial loading and unloading, and the unloading elastic modulus is smaller than that, under conventional triaxial compression; (2) the results show that, under different confining pressures, the granite samples show obvious brittle failure characteristics, the elastic modulus and crack initiation stress increase first and then decrease with the confining pressure, the peak strength and crack damage stress of the samples increase linearly with the confining pressure, and Poisson’s ratio increases first and then remains unchanged with the confining pressure; (3) under the two kinds of stress conditions, the macroscopic failure of the samples is mainly shear failure. The deformation and failure law of granite samples revealed in this study has significant reference value for the selection of rock mass mechanical model of surrounding rock stability of underground engineering, the formulation of surrounding rock support countermeasures, and the evolution law of mechanical parameters with damage variables.

scholarly journals Study on Connectivity Mechanism and Robustness of Three-Dimensional Pore Network of Sandstone

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Guannan Liu ◽  
Xiaopeng Pei ◽  
Dayu Ye ◽  
Feng Gao ◽  
Zongqing Zhou ◽  
...  
Keyword(s):  
Porous Media ◽  
Path Length ◽  
Structural Characteristics ◽  
Three Dimensional ◽  
Ct Scanning ◽  
Pore Network ◽  
Structural Features ◽  
Average Path Length ◽  
Microscopic Mechanism ◽  
Complex Network Theory

As one of the most prevalent porous media, rock contains a large number of pore throats of varying size and shape. It is essential to analyze the complex pore network structure and to define the network structural features to reveal the microscopic mechanism of the rock permeability. In this paper, based on the complex network theory and CT scanning technology, sandstone is used as an example to study the structural characteristics of the rock network with different porosities. The results show that the structural characteristics of the sandstone seepage network are consistent with BA scale-free network, whose average path length increases with the size of the network. At the same time, the porosity of the sandstone is strongly influenced by the number of throat in the rock pore network. Furthermore, our analysis concludes that a few pores with a large number of connections contribute significantly to the overall connectivity of the sandstone seepage network. Removing the ‘hub’ pores increased the average path length of the entire network by 27.63-37.26%, which could not be achieved by randomly removing method. While the sandstone seepage network has better fault tolerance and robustness to external random attacks, this study provides a new approach to study the mechanisms of fluid storage and migration in porous media.

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