scholarly journals Model of long-term seismogenesis

2001 ◽  
Vol 44 (1) ◽  
Author(s):  
F. Evison ◽  
D. Rhoades
Keyword(s):  
Crack Formation ◽  
Shear Fracture ◽  
Critical Phenomenon ◽  
Initial Crack ◽  
Graphical Technique ◽  
Scaling Principle ◽  
Precursory Seismicity ◽  
Precursory Phenomena ◽  
Major Crack

A three-stage faulting model explains the observed quantitative relations between long-term precursory seismicity, mainshocks and aftershocks. Seismogenesis starts with the formation of a major crack, culminates in the corresponding major fracture and earthquake, and ends with healing. Crack formation is a self-organised critical phenomenon, and shear fracture is a delayed sequel to crack formation. It is postulated that the major crack generates a set of minor cracks, just as, later, the major fracture generates a set of minor fractures. Fracturing of the minor cracks raises the average seismicity level. By Mogi’s uniformity criterion, the major earthquake is delayed until the minor fractures have healed and the stress-field has regained relative uniformity. In accord with the scaling principle, the model applies at all magnitude levels. The size of any given initial crack determines the scale of the ensuing seismogenic process. A graphical technique of cumulative magnitude analysis gives a quantitative representation of the seismicity aspects of the model. Examples are given for large earthquakes in a region of continental collision and a subduction region. The principle of hierarchy is exemplified by the seismogenesis of a M 5.9 mainshock occurring entirely within the precursory stage of a M 7.0 mainshock. The model is capable of accommodating a variety of proposed shorter-term precursory phenomena.

scholarly journals The Dimensional Stability and Durability of Acrylic Resins for the Injection of Cementitious Systems

2020 ◽  
Vol 4 (1) ◽  
pp. 75
Author(s):  
C. S. Paglia ◽  
A. Krattiger
Keyword(s):  
Dimensional Stability ◽  
Crack Formation ◽  
General Increase ◽  
Acrylic Resins ◽  
Material Stiffness ◽  
Cent Relative Humidity ◽  
Term Basis ◽  
Cyclic Variations ◽  
Cementitious Systems

The dimensional stability and durability of Acrylamide- and Methacrylate-based acrylic resins have been studied. The dimensional stability was characterized by measuring the volume expansion of samples immersed in water for a period up to 240 days or by exposing the samples to 23oC and 50 per cent, 90 per cent relative humidity and by monitoring the shrinkage. The durability was investigated by exposing the resins to cyclic variations of temperature in air and in water. The resins generally exhibit a significant volume change up to 160 per cent of the initial volume when immersed in water or exposed to a relatively dry atmosphere (23oC and 50 per cent). A general increase in the material stiffness and/or crack formation on the surface of the resin is observed. On a long-term basis, the durability of the resins may significantly vary with occasionally a partial or complete deterioration of the some resins. A general better dimensional stability and durability is observed for the Methacrylate-based resins as compared to the Acrylamide-based resins.

scholarly journals Compression and Shear Fracture Analysis of Boundary Cracks Containing Water in Rock

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Zhensheng Yang ◽  
Fulin Li ◽  
Tianran Ma
Keyword(s):  
Stress Intensity ◽  
Friction Coefficient ◽  
Stress Intensity Factors ◽  
Underground Mining ◽  
Shear Fracture ◽  
Water Environment ◽  
Initial Crack ◽  
Open Boundary ◽  
Shear Stresses ◽  
Intensity Factors

In order to conserve the water resource during underground mining, the fracture and mechanical properties of rock are important for the stability of water-resisting layers, especially for the fracture behavior of boundary cracks containing water in rock. Considering the swelling of rock under water environment and the influence of water on rock, the stress intensity factors of modes I and II are derived for boundary cracks in rock under compressive and shear stresses. The cracks are divided into the closed and open states. The effects of the crack inclination angle, friction coefficient between crack surfaces, and initial crack length on stress intensity factors are also taken into account. The stress intensity factors for closed and open boundary cracks are verified by numerical and physical experiments, respectively, and the deviation of the results is within 5%. It is shown that pore pressure has different effects on the relationship between stress intensity factor and friction coefficient under different lateral pressures. The effect of water on crack propagation is mainly due to the deterioration of the fracture toughness of the rock. It is found that the critical coefficient λc is a key parameter to determine whether the boundary crack propagates in rock under compression-shear stress. Further studies should be performed to apply the present fracture theory to rock mass or water-resisting layers.

Self-Irradiation of Monazite Ceramics: Contrasting Behavior of PuPO4 and (La,Pu)PO4 Doped with Pu-238

2004 ◽  
Vol 824 ◽  
Author(s):  
Boris E. Burakov ◽  
Maria A. Yagovkina ◽  
Vladimir M. Garbuzov ◽  
Alexander A. Kitsay ◽  
Vladimir A. Zirlin
Keyword(s):  
Radiation Damage ◽  
Crack Formation ◽  
Alpha Decay ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
Deep Blue ◽  
Long Term Storage ◽  
First Time ◽  
Term Storage

AbstractTo investigate the behavior of monazite during accelerated radiation damage, which simulates effects of long term storage, 238Pu-doped polycrystalline samples of (La,Pu)PO4 and PuPO4 were synthesized for the first time ever and studied using powder X-ray diffraction (XRD) analysis and optical microscopy. The starting precursor materials were obtained by precipitation of La and (or) Pu from their aqueous nitrate solutions followed by calcination in air at 700°C for 1 hour, cold pressing, and sintering in air at 1200-1250°C for 2 hours. The 238Pu contents in ceramic samples measured using gamma spectrometry were (in wt.% el.): 8.1 for (La,Pu)PO4 and 7.2 for PuPO4. The (La,Pu)PO4 monazite remained crystalline at ambient temperature up to a cumulative dose of 1.19 × 1025 alpha decays/m3. In contrast, the PuPO4 monazite became nearly completely amorphous at a relatively low dose of 4.2 × 1024 alpha decays/m3. Swelling and crack formation due to the alpha decay damage was observed in the PuPO4 ceramic. Also, under self-irradiation this sample completely changed color from initial deep blue to black. The (La,Pu)PO4 monazite was characterized by a similar change in color from initial light blue to gray, however, no swelling or crack formation have so far been observed. The results of this study allow us to conclude that the radiation damage behavior of monazite strictly depends on the chemical composition. The justification of monazite-based ceramics as actinide waste forms requires additional investigation.

Effect of Uncertainties on the Reliability of Fatigue Damaged Systems

2004 ◽  
Author(s):  
Francisco L. Silva-Gonza´lez ◽  
Ernesto Heredia-Zavoni
Keyword(s):  
Fracture Mechanics ◽  
Failure Modes ◽  
Crack Size ◽  
Initial Crack ◽  
Wave Forces ◽  
Scale Parameters ◽  
Uncertain Variables ◽  
Mechanics Model ◽  
Distribution Of Stress

Fluctuating stresses and strains due to wave forces cause accumulated fatigue damage in tubular joints of marine platforms. Considering the uncertainties in the loads, material properties, initial crack sizes, and stress intensity factors, etc., may affect significantly the reliability assessment of marine jacket platforms. In this paper, we assessed the effect of uncertainties about such fatigue variables on the time evolution of the reliability of series and parallel systems considering correlation between failure modes. The fracture mechanics Paris-Erdogan model is used to model crack growth and a FORM method is used for computing the safety index. The uncertain variables analyzed are: initial crack size, material parameters C and m in the fracture mechanics model and the shape and scale parameters of the Weibull density function used for the long-term distribution of stress range.

AN ANALYSIS OF THE DAMAGE TOLERANCE OF LIGHT AIRCRAFT LANDING GEAR

2013 ◽  
Vol 37 (4) ◽  
pp. 1147-1159 ◽  
Author(s):  
Pu-Woei Chen ◽  
Shu-Han Chang ◽  
Jyun-Yuan Siao
Keyword(s):  
Life Cycle ◽  
Damage Tolerance ◽  
Life Time ◽  
Initial Crack ◽  
Landing Gear ◽  
Finite Element Software ◽  
Aircraft Landing ◽  
Aircraft Landing Gear ◽  
The Relationship

This study uses the finite element software, FRANC2D, and the life-time analysis software, AFGROW, to perform simulation analyses of the damage tolerance of the landing gear of light aviation vehicles. This study explores the effect that the initial crack positions and different materials have on the life cycle of landing gear under long-term loads. This study also compares the relationship between stress intensity factors and crack growth for four types of aluminum alloys, titanium alloy and alloy steel. The relationship between residual strength and life cycle, in the presence of existing cracks, is also investigated.

scholarly journals Earthquake forecasting, public policy and earthquake forecasting

1979 ◽  
Vol 12 (4) ◽  
pp. 328-333
Author(s):  
G. J. Lensen
Keyword(s):  
Public Policy ◽  
Public Awareness ◽  
Earthquake Forecasting ◽  
Short Term ◽  
The Public ◽  
Prone Area ◽  
Socio Economic Impact ◽  
Civil Defence ◽  
Precursory Phenomena

The geodetic, geophysical and seismological approaches to earthquake forecasting are summarised and illustrated with examples of precursory phenomena, which can be categorised into long term, intermediate term, short term and imminent. The results from at least two, but preferably more, disciplines are needed to reliably identify a precursory phase before a forecast can be made. The socio-economic impact of earthquake forecasting on business and the community is discussed and it is recommended that for at least the present such forecasts should not be made public. Instead Civil Defence and related exercises should be held in several areas including the "prone" area, in a realistic manner, ensure that manpower is organised, equipment etc. upgraded, and public awareness sharpened in order to reduce the imminent effects on safety both in public and at home. Once the public has gained confidence, not only in the reliability of such forecasts, but more specifically confidence in the authorities concerned, and once their preparedness has become an accepted fact, only then will a public forecasting have a beneficial effect.

VEGF kinase inhibitors: how do they cause hypertension?

2009 ◽  
Vol 297 (1) ◽  
pp. R1-R5 ◽  
Author(s):  
Pankaj Bhargava
Keyword(s):  
Kinase Inhibitors ◽  
Critical Phenomenon ◽  
Term Treatment ◽  
Vascular Endothelial ◽  
Preclinical Models ◽  
Long Term Treatment ◽  
Vegf Pathway ◽  
The Subject ◽  
Endothelial Growth Factor

Neoangiogenesis is a critical phenomenon enabling the growth and metastasis of tumors, and inhibitors of neoangiogenesis have been recently added to the armamentarium of anticancer therapies available for clinical use. Dysregulated signaling through the vascular endothelial growth factor (VEGF) pathway has been implicated as a key mediator of neoangiogenesis in tumors. Agents that block signaling through the VEGF pathway demonstrated tumor shrinkage in preclinical models and were therefore developed as anticancer therapies for use in humans. VEGF kinase inhibitors are being used in the treatment of a wide variety of cancers, and recent studies have shown that patients will likely require long-term treatment with these agents. Hypertension has emerged as a frequent side effect associated with agents that block signaling through the VEGF pathway. A thorough understanding of the mechanisms underlying hypertension is crucial to developing appropriate therapeutic strategies for treating hypertension associated with VEGF kinase inhibitors. Several recent studies have advanced our understanding of the pathophysiology of hypertension associated with VEGF kinase inhibitors and will be the subject of this review.

scholarly journals Impact of severe cracked germanium (111) substrate on aluminum indium gallium phosphate light-emitting-diode’s electro-optical performance

Open Physics ◽  
2016 ◽  
Vol 14 (1) ◽  
pp. 253-260
Author(s):  
Luruthudass Annaniah ◽  
Mutharasu Devarajan
Keyword(s):  
Crack Formation ◽  
Light Emitting Diode ◽  
Temperature Cycle ◽  
Optical Performance ◽  
Light Emitting ◽  
Indium Gallium ◽  
Reliability Performance ◽  
Product Specification ◽  
Gallium Phosphate

AbstractCracked die is a serious failure mode in the Light Emitting Diode (LED) industry – affecting LED quality and long-term reliability performance. In this paper an investigation has been carried out to find the correlation between severe cracked germanium (Ge) substrate of an aluminum indium gallium phosphate (AlInGaP) LED and its electro-optical performance after the Temperature Cycle (TC) test. The LED dice were indented at several bond forces using a die bonder. The indented dice were analysed using a Scanning Electron Microscope (SEM). The result showed that severe cracks were observed at 180 gF onward. As the force of indentation increases, crack formation also becomes more severe thus resulting in the chipping of the substrate. The cracked dies were packaged and the TC test was performed. The results did not show any electro-optical failure or degradation, even after a 1000 cycle TC test. Several mechanically cross-sectioned cracked die LEDs, were analysed using SEM and found that no crack reached the active layer. This shows that severely cracked Ge substrate are able to withstand a −40°C/+100°C TC test up to 1000 cycles and LED optical performance is not affected. A small leakage current was observed in all of the cracked die LEDs in comparison to the reference unit. However, this value is smaller than the product specification and is of no concern.

scholarly journals Suitability of Boulder Marl and Marsh Clay as Sealing Substrates for Landfill Capping Systems—A Practical Comparison

Geosciences ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 356 ◽  
Author(s):  
Steffen Beck-Broichsitter ◽  
Horst Gerke ◽  
Rainer Horn
Keyword(s):  
Laser Scanning ◽  
Crack Formation ◽  
Three Dimensional ◽  
Soil Cores ◽  
Test Results ◽  
Size Dependent ◽  
Proctor Test ◽  
Very High ◽  
Shrinkage Behavior

The effects of compaction on soil shrinkage behavior need to be considered for engineering long-term durable mineral liners of landfill capping systems. For this purpose, a new three-dimensional laser scanning device was coupled with a mathematical-empirical model to simultaneously determine the shrinkage behavior of a boulder marl (bm) and a marsh clay (mc). Therefore, both materials were precompacted in 200 soil cores (100 cm3) on the basis of the Proctor test results with five different degrees of compaction (bm1-bm5; mc1-mc5). Thus, the shrinkage behavior, intensity, and tendency were determined during a standardized drying experiment. The volume shrinkage index was used to describe the pore size dependent shrinkage tendency and was classified as high to very high (11.3–17.7%) for the marsh clay and medium (5.3–9.2%) for the boulder marl. Additionally, only the boulder marl (bm2), compacted up to 88% of Proctor density, could be installed as landfill bottom liner in drier locations if the local matric potentials did not exceed the previously highest observed drying range (i.e. values below −300 hPa), to avoid crack formation and generation.

scholarly journals The distinctiveness of measuring interlaminar fracture toughness by the mode I method

2007 ◽  
Vol 61 (2) ◽  
pp. 79-82
Author(s):  
Isidor Djordjevic ◽  
Milan Gordic ◽  
Danijela Pesikan ◽  
Momcilo Stevanovic
Keyword(s):  
Fracture Toughness ◽  
Carbon Fibre ◽  
Crack Formation ◽  
Resin Composite ◽  
Initial Crack ◽  
Test Material ◽  
Mode I ◽  
Interlaminar Fracture Toughness ◽  
Interlaminar Fracture ◽  
Epoxy Resin Composite

Practical problems in measuring the interlaminar fracture toughness by the mode I method were pointed out in this paper. Unidirectional carbon fibre/epoxy resin composite was used in the experiments (as the test material). The composite was obtained by curing commercial Hexcel ply 6376 in a mould. The techniques of initial crack formation, solving problems of applying the correct stress on the specimen and the precise registering of crack growth were proposed. The reliability of suggested method was assessed by evaluating the dispersion of the results obtained, as well as by comparison with the literature data.

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