Defects in Materials: Their Characterization and Simulation.

1990 ◽  
Vol 209 ◽  
Author(s):  
Colin G. Windsor
Keyword(s):  
Point Defects ◽  
Uranium Oxide ◽  
Computer Modelling ◽  
Experimental Characterization ◽  
Dynamic Measurements ◽  
Stress Concentrations ◽  
Copper Clusters ◽  
Materials Research ◽  
Complementary Nature ◽  
And Control

ABSTRACTMaterials research does not necessarily need to eliminate defects, but rather to characterize them, and to understand and control their effects. In most cases chacterization of defects means making structural or dynamic measurements of their properties. To understand these measurements in order to predict material and defect properties outside the range of the measurements is a much harder problem. Ideally a theory is required. However in the materials examples considered in this review, point defects in uranium oxide, copper clusters in steel, grain boundary aggregations, and stress concentrations, a true analytic theory is beyond our capabilities. Here computer modelling is often able to make the progress needed. This review considers the complementary nature of experimental characterization and computer simulation in our understanding of defects in materials.

scholarly journals Mechanism and Prevention and Control of Mine Earthquake in Thick and Hard Rock Strata considering the Horizontal Stress Evolution of Stope

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Ming Zhang ◽  
Xuelong Hu ◽  
Hongtao Huang ◽  
Guangyao Chen ◽  
Shan Gao ◽  
...  
Keyword(s):  
Hard Rock ◽  
Design Method ◽  
Horizontal Stress ◽  
Prevention Measures ◽  
Stress Concentrations ◽  
Estimation Model ◽  
Working Face ◽  
Mining Design ◽  
And Control ◽  
Rock Strata

This study investigated the mechanism, prevention measures, and control methods for earthquake disasters typically occurring in mines with thick and hard rock strata. A mine stope with large faults and thick hard rock strata in Hebei Province was taken as the background study object. Then, theoretical analysis and numerical simulation methods were adopted in conjunction with field monitoring to explore how horizontal stress evolves in the thick and hard hanging roofs of such mines, potentially leading to mining earthquakes. Then, based on the obtained results, a mining design method was proposed to reduce the horizontal stress levels of earthquake mitigation. The results showed that, under the control of large faults, semiopen and semiclosed stopes with thick hard rock strata are formed, which cause influentially pressurized and depressurized zones during the evolution of the overburden movements and horizontal stress. It was determined that the stress concentrations mainly originated from the release and transfer of horizontal stress during the rock fractures and movements in the roof areas, which were calculated using a theoretical estimation model. The horizontal stress concentrations formed “counter torques” at both ends of the thick and hard strata, which prevented the support ending due to tensile failures. As a result, the limit spans were increased. This study proposed a mining strategy of using narrow working faces, strip mining processes, and reasonable mining speeds, which could effectively reduce horizontal stress concentrations and consequently prevent and control mining earthquakes. This study’s research results were successfully applied to the mining practices in working face 16103.

Interfaces Part I: Structure, Chemistry, Electronic Properties

MRS Bulletin ◽  
1990 ◽  
Vol 15 (9) ◽  
pp. 21-26 ◽  
Author(s):  
Dieter Wolf ◽  
Sidney Yip
Keyword(s):  
Electronic Properties ◽  
Atomic Level ◽  
Critical Element ◽  
Semiconductor Interfaces ◽  
Technological Advances ◽  
Technology Applications ◽  
Materials Research ◽  
Surface Modification Techniques ◽  
Hostile Environments ◽  
And Control

Some of the most important properties of materials in high-technology applications are strongly influenced or even controlled by the presence of solid interfaces. For example, interfaces are the critical element in fiber-reinforced structural ceramics with mechanical properties not even imagined a decade or two ago. The entire electronics industry is based on the fascinating electrical properties of semiconductor interfaces, with ceramic-semiconductor, metal-semiconductor and metal-ceramic interfaces playing critical roles as well. Other examples are surface modification techniques, designed to enhance the corrosion resistance of materials in hostile environments or tailored for tribological or catalytic applications. In contrast to their enormous technological importance, our basic understanding of even the simplest interfaces, such as free surfaces and grain boundaries, is rudimentary at best. It is increasingly recognized, however, that truly significant technological advances can be achieved by a better understanding and control of interfacial processes.To draw attention to the tremendous opportunites that lie ahead in this lively area of materials research, some recent promising developments in the atomic-level understanding of solid interfaces are highlighted in this issue and in the October issue of the MRS BULLETIN. The theme common to ail the articles in the September and October issues lies in the atomic-level insights that have been gained. While this issue of the BULLETIN focuses on structure, chemistry and some electronic properties of crystalline interfaces, the October issue will be devoted to their mechanical and high-temperature behavior.

Australian Defence Applications of Advanced Smart Materials Research

2010 ◽  
Vol 654-656 ◽  
pp. 2079-2082
Author(s):  
Christine M. Scala ◽  
Matthew E. Ibrahim ◽  
Alan R. Wilson ◽  
Darren P. Edwards ◽  
V. Tan Truong
Keyword(s):  
Smart Materials ◽  
Severe Plastic Deformation Processing ◽  
Technology Readiness ◽  
Artificial Muscles ◽  
Smart Materials And Structures ◽  
Ultrafine Grained ◽  
Materials Research ◽  
Ultrafine Grained Materials ◽  
And Control ◽  
Maritime Air

This paper overviews some recent S&T innovations in smart materials and structures at the Australian Defence Science and Technology Organisation (DSTO) under a Corporate Enabling Research Program (CERP) on Signatures, Materials and Energy. The CERP program includes development and transitioning of technology across the maritime, air and land domains, with the major focus of the smart materials program component being to increase the safety, availability and maintainability of Defence assets. Three specific examples are provided of the smart materials and structures program, ranging across the spectrum of technology readiness from new concept phase to technology transitioning, viz.: (i) Advances in smart sensing for prognostics-based platform management; (ii) Fabrication of nanostructured and ultrafine grained materials through top-down severe plastic deformation processing of bulk materials; (iii) Innovative application of carbon nanotubes/conducting polymers as artificial muscles for low-power propulsion and control of small autonomous underwater systems. In each case, the DSTO effort is underpinned by strong university or industry linkages to deliver challenging interdisciplinary S&T.

Point Defects, Diffusion and Gettering in Silicon

1997 ◽  
Vol 469 ◽  
Author(s):  
U. Gösele ◽  
D. Conrad ◽  
P. Werner ◽  
Q.-Y. Tong ◽  
R. Gafiteanu ◽  
...  
Keyword(s):  
Point Defects ◽  
Diffusion Processes ◽  
Silicon On Insulator ◽  
Intrinsic Point Defects ◽  
The Status ◽  
Long Time ◽  
Effective Diffusivities ◽  
And Control ◽  
Soi Substrates ◽  
Measurement And Control

ABSTRACTThe status of our knowledge on intrinsic point defects and diffusion mechanisms is reviewed. Special attention is given to the question of the possible role of carbon in influencing effective diffusivities of intrinsic point defects and the resulting consequences for the values of vacancy and self-interstitial thermal equilibrium concentrations and diffusivities. It is pointed out that we might have to deal with the unfortunate situation that the effective diffusivities of intrinsic point defects might be influenced already by a carbon concentration which is below the detection limit and therefore not amenable to measurement and control. Whereas dopant diffusion processes have been modeled and simulated for a long time the first attempts to quantitatively simulate various gettering processes have just started as will be described in the paper. Finally, the subject of microcrack formation in hydrogen implanted silicon will be dealt with as used for the so-called “smart-cut” process for fabricating silicon-on-insulator (SOI) substrates with thin and uniform silicon layers by wafer bonding. Presently no quantitative treatment of this fascinating hydrogen agglomeration phenomenon is available.

Numerical Simulation and Backfilling Materials Research on Coal Spontaneous Combustion of Thick Seam Large-Scale Top-Caving Region in Resources Conformity Coal Mine

2012 ◽  
Vol 524-527 ◽  
pp. 317-320
Author(s):  
Bo Tan ◽  
Yuan Gang Jiang ◽  
Chao Nan He ◽  
Jing Chang ◽  
Ya Qi Luo
Keyword(s):  
Numerical Simulation ◽  
Process Model ◽  
Large Scale ◽  
Spontaneous Combustion ◽  
Combustion Process ◽  
Fire Control ◽  
Coal Spontaneous Combustion ◽  
Thick Seam ◽  
Materials Research ◽  
And Control

This paper aimed at fire control in thick seam large-scale top-carving region. On the basis of coal and oxygen compounding theory, theoretical analysis, numerical simulation and experiment are combined, and a coal spontaneous combustion process model is built according to fluid mechanics and control theory. By studying and testing on top-carving coal spontaneous combustion process, conclusion is drawn that spontaneous combustion area is the largest in partly-closed region, followed by unclosed region. A totally closed baffle leads to the smallest spontaneous combustion area and the smallest possibility of fire. With local materials in a certain condition, new, cheap backfilling materials are developed. Thus provide theoretical basis for study on the forecasting and prevention of thick seam large-scale top-carving coal spontaneous combustion.

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