Plastic Dynamics and Brittle vs. Ductile Failure in Noncrystalline Solids

1998 ◽  
Vol 539 ◽  
Author(s):  
M.L. Falk
Keyword(s):  
Ductile Failure ◽  
Continuum Theory ◽  
Scale Theory ◽  
Rate Dependent ◽  
Brittle Ductile Transition ◽  
Macro Scale ◽  
Crack Dynamics ◽  
Dynamic Brittle Fracture ◽  
Viscoplastic Solid ◽  
The Relationship

AbstractWe simulate fracture in two amorphous solids with different inter-particle potentials. These small changes in potential result in significant changes in dissipation near the crack tip. While one might expect these effects to arise from a change in flow stress, measurements reveal this is not the case. To understand why, we consider the relationship between crack dynamics, rate-dependent plasticity, and molecular-level structures in the glassy solid. In particular we discuss the macro-scale continuum theory of dynamic brittle fracture in a viscoplastic solid developed by Freund and Hutchinson and the meso-scale theory of viscoplasticity proposed by Falk and Langer. We further consider a simplified model on the molecular scale as a first-step toward the construction of first-principles models of dynamic plasticity and the brittle ductile transition in noncrystalline materials.

Confirming the continuum theory of dynamic brittle fracture for fast cracks

Nature ◽  
10.1038/16891 ◽  
1999 ◽  
Vol 397 (6717) ◽  
pp. 333-335 ◽  
Author(s):  
Eran Sharon ◽  
Jay Fineberg
Keyword(s):  
Brittle Fracture ◽  
Continuum Theory ◽  
Dynamic Brittle Fracture ◽  
The Continuum

An implicit algorithm for a rate-dependent ductile failure model

2008 ◽  
Vol 104 (8) ◽  
pp. 083526 ◽  
Author(s):  
Q. H. Zuo ◽  
Jeremy R. Rice
Keyword(s):  
Ductile Failure ◽  
Failure Model ◽  
Implicit Algorithm ◽  
Rate Dependent

scholarly journals Heart Rate Dependency and Inter-Lead Variability of the T Peak – T End Intervals

2020 ◽  
Vol 11 ◽  
Author(s):  
Irena Andršová ◽  
Katerina Hnatkova ◽  
Martina Šišáková ◽  
Ondřej Toman ◽  
Peter Smetana ◽  
...  
Keyword(s):  
Heart Rate ◽  
Three Dimensional ◽  
Rate Dependency ◽  
Rate Dependent ◽  
Heart Rate Correction ◽  
Ecg Leads ◽  
Relationship Of ◽  
The Relationship ◽  
Vector Magnitude

The electrocardiographic (ECG) assessment of the T peak–T end (Tpe) intervals has been used in many clinical studies, but several related physiological aspects have not been reported. Specifically, the sources of the Tpe differences between different ECG leads have not been systematically researched, the relationship of Tpe duration to underlying heart rate has not been firmly established, and little is known about the mutual correspondence of Tpe intervals measured in different ECG leads. This study evaluated 796,620 10-s 12-lead ECGs obtained from long-term Holters recorded in 639 healthy subjects (311 female) aged 33.8 ± 9.4 years. For each ECG, transformation to orthogonal XYZ lead was used to measure Tpe in the orthogonal vector magnitude (used as a reference for lead-to-lead comparisons) and to construct a three-dimensional T wave loop. The loop roundness was expressed by a ratio between its circumference and length. These ratios were significantly related to the standard deviation of Tpe durations in different ECG leads. At the underlying heart rate of 60 beats per minute, Tpe intervals were shorter in female than in male individuals (82.5 ± 5.6 vs 90.0 ± 6.5 ms, p < 0.0001). When studying linear slopes between Tpe intervals measured in different leads and the underlying heart rate, we found only minimal heart rate dependency, which was not systematic across the ECG leads and/or across the population. For any ECG lead, positive Tpe/RR slope was found in some subjects (e.g., 79 and 25% of subjects for V2 and V4 measurements, respectively) and a negative Tpe/RR slope in other subjects (e.g., 40 and 65% for V6 and V5, respectively). The steepest positive and negative Tpe/RR slopes were found for measurements in lead V2 and V4, respectively. In all leads, the Tpe/RR slope values were close to zero, indicating, on average, Tpe changes well below 2 ms for RR interval changes of 100 ms. On average, longest Tpe intervals were measured in lead V2, the shortest in lead III. The study concludes that the Tpe intervals measured in different leads cannot be combined. Irrespective of the measured ECG lead, the Tpe interval is not systematically heart rate dependent, and no heart rate correction should be used in clinical Tpe investigations.

scholarly journals Effectiveness of Flexible Dam Operation and Sediment Replenishment at Managawa Dam, Japan

2018 ◽  
Vol 13 (4) ◽  
pp. 691-701 ◽  
Author(s):  
Katsumi Matsushima ◽  
Makoto Hyodo ◽  
Noriyuki Shibata ◽  
Yoshihiro Shimizu ◽  
◽  
...  
Keyword(s):  
Flood Pulse ◽  
Demonstration Project ◽  
Scale Analysis ◽  
Management Options ◽  
Ecological Processes ◽  
Fluvial Systems ◽  
Macro Scale ◽  
Dam Operation ◽  
The Impact ◽  
The Relationship

A field demonstration project on flexible dam operation at the Managawa dam in the Kuzuryu River Basin has been implemented since 2000. The goal is to restore flow and sediment regimes in the Managawa River, which flows along the Ono-city and is located below the dam. Flexible dam operation stores inflow discharge into a reservoir, which generally uses part of the flood control capacity and appropriately discharges the stored water to the river, also known as the “flood pulse,” for restoring dynamic fluvial systems and the resulting ecological processes. In addition, other options have been carried out in combination with flexible dam operation, for example, sediment replenishment since 2003 and channel rehabilitation since 2007. This article reveals the positive impacts and effectiveness of flexible dam operation, sediment replenishment, and channel rehabilitation, and discusses challenges and future prospects toward translating the field demonstration project into dam management on the ground level. First, we classified reach types to identify the impact of various management options, e.g., flexible dam operation, sediment replenishment, and channel rehabilitation. These management options can influence respected reaches. We conducted a macro-scale analysis to understand the relationship between the aforementioned management options and dynamic fluvial systems, addressing changes in gravel riverbed, vegetation, and habitat types (riffles and pools). Second, a micro-scale analysis was conducted to understand the relationship between the management option and changes in attached algae to sediment and macro-invertebrates, etc. The results show the effectiveness of the middle-scale flood pulse to restore dynamic fluvial systems, increase habitat diversity, and sustain ecological processes. Furthermore, we discussed the impacts of such options on the flow and sediment regimes in Managawa River and revealed that flexible dam operation reduces the occurrence of low flow and midscale floods. It was also revealed methods such as sediment replenishment and channel rehabilitation play an important role in increasing the effectiveness of the middle-scale flood pulse and restoring dynamic fluvial systems, even though sediment replenishment is not sufficient to restore sediment regimes (i.e., bring then back to pre-dam conditions).

Correlation of wear and work in dual pivoted jaw crusher tests

2018 ◽  
Vol 234 (3) ◽  
pp. 334-349
Author(s):  
Juuso Terva ◽  
Kati Valtonen ◽  
Pekka Siitonen ◽  
Veli-Tapani Kuokkala
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Mass Loss ◽  
Lower Amount ◽  
Jaw Crusher ◽  
Rate Dependent ◽  
Sliding Motion ◽  
The Relationship

A laboratory sized jaw crusher with uniform movement of the jaws, the dual pivoted jaw crusher, was used to determine the relationship between wear and work. Wear was concentrated on the jaw plates opposing each other and was measured as mass loss of the specimens. Work was measured directly from the force and displacement of the instrumented jaw, which allowed work to accumulate only from the actual crushing events. The tests were conducted with several jaw geometries and with two motional settings, where the relation of compressive and sliding motion between the jaws was varied. The tests showed that the relation between wear and work was constant in many of the tested cases. In certain tests with larger lateral and faster contact speed, wear occurred at relatively lower amounts of work. This behavior was more definite when the relation of wear and work was investigated using modified Archards wear equation. The results indicate that the lower amount of needed work could stem from the material reaching a dynamic situation, where the flow stress becomes increasingly strain-rate dependent.

A Review of The Sundanese Scale Theory

2022 ◽  
Vol 21 (2) ◽  
pp. 318-329
Author(s):  
Mariko Sasaki ◽  
Juju Masunah
Keyword(s):  
19Th Century ◽  
Performing Arts ◽  
Educational Institutions ◽  
West Java ◽  
Scale Theory ◽  
The 19Th Century ◽  
The Relationship

This article aims to discuss Kusumadinata’s scale theory in Sundanese music which has been taught in educational institutions in West Java, Indonesia. According to Kusumadinata’s scale theory, sorog and pelog are scales derived from salendro scale in gamelan salendro performance. In my previous research, I investigated three genres of Sundanese performing arts which have existed since the Hindu era, namely goong renteng, pantun, and tarawangsa. The results indicate that the pelog scale has independently existed since the Hindu era. Then, I analyzed the phenomenon that occurs in the gamelan salendro performance, i.e., its melody (rebab and vocals) conventionally modulate into scale ‘like sorog’, occasionally into scale ‘like pelog’. In contrast, the instruments of gamelan are in the salendro scale. However, the analysis on the sorog in the previous research was not enough, so that in this paper, I will focus on the sorog. To find out the relationship between melody (vocal and rebab) and gamelan instruments, I examined the actual performances of gamelan salendro and wayang golek purwa. It became clear that the salendro scale derives four types of sorog. The findings of this study indicate that sorog has existed since the 19th century by this phenomenon, and the scale now called sorog is a scale derived from salendro.

Transient responses and continuous behavior of active smooth muscle during controlled stretches

1982 ◽  
Vol 242 (3) ◽  
pp. C146-C158 ◽  
Author(s):  
R. A. Meiss
Keyword(s):  
Steady State ◽  
Smooth Muscles ◽  
Muscle Length ◽  
Initial Slope ◽  
Stretch Rate ◽  
Rate Dependent ◽  
Upward Slope ◽  
Length Changes ◽  
State Force ◽  
The Relationship

Controlled length changes were imposed on mesotubarium superius and ovarian ligament smooth muscles from the reproductive tracts of female rabbits in constant estrus. Stretches of up to 35% of the muscle length were applied during isometric contraction, relaxation, and steady-state force levels. Force was continuously monitored and was plotted as a function of length. During constant velocity stretches there was an initial steep rise in force, a rapid downward deviation from the initial slope, and a long region with a constant upward slope. Stretches made during contraction showed smaller initial rises in force and steeper linear portions than did identical comparison stretches made during relaxation. The value of the slope was independent of the prior developed force, but it did depend on whether the muscle was contracting or relaxing. During contraction and steady-state force levels, the slope was independent of the stretch rate, but it was strongly rate dependent during relaxation. Changes in the stretch rate during stretch caused associated changes in muscle force; the relationship was curvilinear and was exaggerated during relaxation. The findings are placed in the context of a sliding-filament--cross-bridge hypothesis.

Ischemia-induced and reperfusion-induced arrhythmias: importance of heart rate

1989 ◽  
Vol 256 (1) ◽  
pp. H21-H31 ◽  
Author(s):  
M. Bernier ◽  
M. J. Curtis ◽  
D. J. Hearse
Keyword(s):  
Heart Rate ◽  
Coronary Occlusion ◽  
Ischemia And Reperfusion ◽  
Rate Of Development ◽  
Rate Dependent ◽  
Rat Hearts ◽  
Wide Range ◽  
The Right ◽  
The Relationship ◽  
Isolated Rat

The relationship between heart rate and ischemia-induced and reperfusion-induced arrhythmias was studied using 573 isolated rat hearts. Hearts (12/group), subjected to 7 min of coronary occlusion and 10 min reperfusion, were paced at 300, 330, 360, 390, 420, 480, or 540 beats/min. Pacing either throughout the experiment or during ischemia alone led to a rate-dependent increase in the incidence of reperfusion-induced ventricular fibrillation (VF) from 25% in the unpaced hearts to greater than 90% when the rate was 420 beats/min or higher. However, pacing during reperfusion alone did not increase the incidence of reperfusion-induced VF. In separate hearts, the right atrium was removed to permit examination of both low and high rates (167 +/- 2, 240, 336 +/- 3, or 480 beats/min throughout the experiment) over a wide range of durations of occlusion (3, 5, 7, 10, 15, 20, or 40 min). Ischemia-induced VF incidence was critically dependent on heart rate, low rates being protective. During reperfusion, the incidence of VF was also highly rate dependent if reperfusion was initiated within 10 min of the onset of ischemia (ranging from 8% when rate was 167 +/- 2 beats/min to 100% when rate was 480 beats/min) but was unrelated to heart rate when reperfusion occurred at later times (ranging from 33 to 50% when ischemia duration was 40 min). Heart rate can therefore influence susceptibility to ischemia- and reperfusion-induced arrhythmias, probably as a result of an effect on the rate of development of ischemic injury.

Comparison of Interfacial and Continuum Models for Dynamic Fragmentation Analysis

2018 ◽  
Author(s):  
Bahador Bahmani ◽  
Philip Clarke ◽  
Reza Abedi
Keyword(s):  
Damage Model ◽  
Compressive Load ◽  
Stochastic Field ◽  
Damage Models ◽  
Coupled Equations ◽  
Rate Dependent ◽  
Fracture Simulation ◽  
Microstructure Effects ◽  
Dynamic Brittle Fracture ◽  
Final System

The microstructural design has an essential effect on the fracture response of brittle materials. We present a stochastic bulk damage formulation to model dynamic brittle fracture. This model is compared with a similar interfacial model for homogeneous and heterogeneous materials. The damage models are rate-dependent, and the corresponding damage evolution includes delay effects. The delay effect provides mesh objectivity with much less computational efforts. A stochastic field is defined for material cohesion and fracture strength to involve microstructure effects in the proposed formulations. The statistical fields are constructed through the Karhunen-Loeve (KL) method. An advanced asynchronous Spacetime Discontinuous Galerkin (aSDG) method is used to discretize the final system of coupled equations. Application of the presented formulation is shown through dynamic fracture simulation of rock under a uniaxial compressive load. The final results show that a stochastic bulk damage model produces more realistic results in comparison with a homogenizes model.

scholarly journals The Feedback Response of Escherichia coli rRNA Synthesis Is Not Identical to the Mechanism of Growth Rate-Dependent Control

2000 ◽  
Vol 182 (2) ◽  
pp. 536-539 ◽  
Author(s):  
Justina Voulgaris ◽  
Dmitry Pokholok ◽  
W. Mike Holmes ◽  
Craig Squires ◽  
Catherine L. Squires
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Gene Dosage ◽  
Rrna Synthesis ◽  
Rate Dependent ◽  
Nucleoside Triphosphates ◽  
The Relationship ◽  
Mechanism Of Growth

ABSTRACT Growth rate-independent rrn P1 promoter mutants were tested for their ability to respond to changes in rrn gene dosage. Most were found to be normal for the feedback response. In addition, cellular levels of the initiating nucleoside triphosphates remained unchanged when the rrn gene dosage was altered. These results suggest that the feedback response cannot be the mechanism for growth rate-dependent control of rRNA synthesis and that the relationship between these two processes may be more complicated than is currently understood.

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