Linkage between static and cyclic liquefaction of loose sand with a range of fines contents

2012 ◽  
Vol 49 (8) ◽  
pp. 891-906 ◽  
Author(s):  
Md.A.L. Baki ◽  
M.M. Rahman ◽  
S.R. Lo ◽  
C.T. Gnanendran
Keyword(s):  
Cyclic Loading ◽  
Void Ratio ◽  
Strain Softening ◽  
State Parameter ◽  
Past Research ◽  
Underlying Mechanism ◽  
Fines Content ◽  
Wide Range ◽  
Static Instability ◽  
Effective Stress Ratio

The underlying mechanism of static and cyclic liquefaction of loose contractant sandy soil is unstable behaviour associated with deviatoric strain-softening. Such unstable (strain-softening) behaviour has been referred to as static or cyclic instability depending on whether the loading condition is monotonic or cyclic. Past research into linkage between static instability and cyclic instability of sand with fines is based largely on comparing monotonic and one-way cyclic loading behaviour of specimens of the same void ratio and fines content. In this article, the authors attempt to link the condition that defines triggering of cyclic instability to that of static instability of specimens of different void ratios and fines contents. This is achieved by the proposed concept of equivalent granular state parameter. Two specimens are considered as equivalent if they have the same equivalent granular state parameters at the start of undrained shearing. The effective stress ratio at triggering of static instability can be used to predict impending cyclic instability of an equivalent specimen of different fines content and void ratio. This linkage between static and cyclic instability was evaluated for a wide range of fines contents, initial mean effective stresses, and types of cyclic loading. The last factor includes symmetrical and nonsymmetrical two-way cyclic loading.

Effects of fines on liquefaction behaviour in well-graded materials

2017 ◽  
Vol 54 (10) ◽  
pp. 1460-1471 ◽  
Author(s):  
Katherine A. Kwa ◽  
David W. Airey
Keyword(s):  
Critical State ◽  
Soil Mechanics ◽  
State Parameter ◽  
Triaxial Tests ◽  
Particle Sizes ◽  
Graded Materials ◽  
Fines Content ◽  
Cyclic Resistance ◽  
Wide Range ◽  
Soil Behaviour

This study uses a critical state soil mechanics perspective to understand the mechanics behind the liquefaction of metallic ores during transport by ship. These metallic ores are transported at relatively low densities and have variable gradings containing a wide range of particle sizes and fines contents. The effect of the fines content on the location of the critical state line (CSL) and the cyclic liquefaction behaviour of well-graded materials was investigated by performing saturated, standard drained and undrained monotonic and compression-only cyclic triaxial tests. Samples were prepared at four different gradings containing particle sizes from 9.5 mm to 2 μm with fines (<75 μm) contents of 18%, 28%, 40%, and 60%. In the e versus log[Formula: see text] plane, where e is void ratio and [Formula: see text] is mean effective stress, the CSLs shifted upwards approximately parallel to one another as the fines content was increased. Transitional soil behaviour was observed in samples containing 28%, 40%, and 60% fines. A sample’s cyclic resistance to liquefaction depended on a combination of its density and state parameter, which were both related to the fines content. Samples with the same densities were more resistant to cyclic failure if they contained higher fines contents. The state parameter provided a useful prediction for general behavioural trends of all fines contents studied.

The Uncertain Self: How Self-Concept Structure Affects Subscription Choice

2019 ◽  
Vol 46 (5) ◽  
pp. 887-903 ◽  
Author(s):  
Jennifer Savary ◽  
Ravi Dhar
Keyword(s):  
Past Research ◽  
Underlying Mechanism ◽  
The Self ◽  
Self Concept ◽  
Identity Change ◽  
Exercise Regimen ◽  
Wide Range ◽  
Product Choices ◽  
The Stability

Abstract Whether it is clothing, meals or an exercise regimen, consumers purchase a wide range of goods on a recurring basis using a subscription model. While past research indicates that people continue to subscribe to these services even when they rarely use them, no work to date has examined how identity considerations affect preferences in this domain. Building on research on signaling and self-concept structure, we propose that quitting an ongoing subscription can threaten the stability of the self-concept by signaling a change in identity. Consumers who are uncertain about their self-concept (i.e., low self-concept clarity) and motivated to maintain a stable self-concept are thus more likely to keep unused subscriptions than those who are more certain. In support of the underlying mechanism, we demonstrate that self-concept clarity affects choices only for identity-relevant subscription choices, and that it affects choices for subscriptions, but not one-shot product choices that are a weaker signal of identity. Finally, because signing up for a new subscription also signals an identity change that can threaten the stability of the self, consumers with low self-concept clarity are also less likely to subscribe to a new service compared to those with more certain self-concepts.

TIME TO THE END OF PRIMARY CONSOLIDATION (EOP) OF SOFT CLAYEY SOILS: CONCERNING THE EFFECT OF ATTERBERG’S LIMIT AND CYCLIC LOADING HISTORY

2019 ◽  
Vol 128 (2B) ◽  
pp. 29-41
Author(s):  
Trần Thanh Nhàn
Keyword(s):  
Cyclic Loading ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Clayey Soils ◽  
Loading History ◽  
Cyclic Shear ◽  
Wide Range ◽  
Primary Consolidation ◽  
Time Required

In order to observe the end of primary consolidation (EOP) of cohesive soils with and without subjecting to cyclic loading, reconstituted specimens of clayey soils at various Atterberg’s limits were used for oedometer test at different loading increments and undrained cyclic shear test followed by drainage with various cyclic shear directions and a wide range of shear strain amplitudes. The pore water pressure and settlement of the soils were measured with time and the time to EOP was then determined by different methods. It is shown from observed results that the time to EOP determined by 3-t method agrees well with the time required for full dissipation of the pore water pressure and being considerably larger than those determined by Log Time method. These observations were then further evaluated in connection with effects of the Atterberg’s limit and the cyclic loading history.

scholarly journals Beyond cultural and geographical proximity: delving into the factors that influence the dynamics of academic relationships between students in higher education

2021 ◽  
Author(s):  
José-Vicente Tomás-Miquel ◽  
Jordi Capó-Vicedo
Keyword(s):  
University Students ◽  
Academic Research ◽  
Past Research ◽  
Academic Networks ◽  
Level Data ◽  
Wide Range ◽  
Specific Stage ◽  
The University ◽  
Proximity Dimensions ◽  
Shed Light

AbstractScholars have widely recognised the importance of academic relationships between students at the university. While much of the past research has focused on studying their influence on different aspects such as the students’ academic performance or their emotional stability, less is known about their dynamics and the factors that influence the formation and dissolution of linkages between university students in academic networks. In this paper, we try to shed light on this issue by exploring through stochastic actor-oriented models and student-level data the influence that a set of proximity factors may have on formation of these relationships over the entire period in which students are enrolled at the university. Our findings confirm that the establishment of academic relationships is derived, in part, from a wide range of proximity dimensions of a social, personal, geographical, cultural and academic nature. Furthermore, and unlike previous studies, this research also empirically confirms that the specific stage in which the student is at the university determines the influence of these proximity factors on the dynamics of academic relationships. In this regard, beyond cultural and geographic proximities that only influence the first years at the university, students shape their relationships as they progress in their studies from similarities in more strategic aspects such as academic and personal closeness. These results may have significant implications for both academic research and university policies.

Using time domain reflectometry in triaxial testing

2000 ◽  
Vol 37 (6) ◽  
pp. 1325-1331
Author(s):  
J LH Grozic ◽  
M E Lefebvre ◽  
P K Robertson ◽  
N R Morgenstern
Keyword(s):  
Cyclic Loading ◽  
Water Content ◽  
Time Domain ◽  
Void Ratio ◽  
Time Domain Reflectometry ◽  
Volumetric Water Content ◽  
Degree Of Saturation ◽  
Triaxial Testing ◽  
Empirical Correlations ◽  
Static And Cyclic Loading

Time domain reflectometry (TDR) can be used to determine the volumetric water content of soils. This note describes the utilization of a TDR miniprobe in triaxial testing. The TDR performance was examined with a series of tests that not only proved its reliability but also resulted in two empirical correlations. Using these correlations, the degree of saturation and volumetric water content during triaxial testing could be determined. The TDR was then put to use in a laboratory program designed to investigate the response of loose gassy sand under static and cyclic loading. Because of the TDR measurements it was possible to determine the degree of saturation and void ratio of the gassy specimens. The TDR miniprobe proved to be accurate, simple to use, and inexpensive to build.Key words: time domain reflectometry, TDR, triaxial testing, gassy, unsaturated.

Evaluation of Belleville Springs and Damping Through Static Cyclic Loading “Hysteresis” for pVARD Optimization: Part-I

2021 ◽  
Author(s):  
Abdelsalam Abugharara ◽  
Stephen Butt
Keyword(s):  
Data Analysis ◽  
Cyclic Loading ◽  
Dynamic Compression ◽  
Range Data ◽  
Compression Tests ◽  
Rotary Drilling ◽  
Static Compression ◽  
Drilling Performance ◽  
Wide Range ◽  
Compression Hysteresis

Abstract One unconventional application that researchers have been investigating for enhancing drilling performance, has been implemented through improving and stabilizing the most effective downhole drilling parameters including (i) increasing downhole dynamic weight on bit (DDWOB), (ii) stabilizing revolution per minutes (rpm), (iii) minimizing destructive downhole vibrations, among many others. As one portion of a three-part-research that consists of a comprehensive data analysis and evaluation of a static compression hysteresis, dynamic compression hysteresis, and corresponding drilling tests, this research investigates through static cyclic loading “Hysteresis” of individual and combined springs and damping the functionality of the passive Vibration Assisted Rotary Drilling (pVARD) tool that could be utilized towards enhancing the drilling performance. Tests are conducted on the two main pVARD tool sections that include (i) Belleville springs, which represent the elasticity portion and (ii) the damping section, which represents the viscous portion. Firstly, tests were conducted through static cyclic loading “Hysteresis” of (i) a mono elastic, (ii) a mono viscus, and (iii) dual elastic-viscus cyclic loading scenarios for the purpose of further examining pVARD functionality. For performing static compression tests, a calibrated geomechanics loading frame was utilized, and various spring stacking of different durometer damping were tested to seek a wide-range data and to provide a multi-angle analysis. Results involved analyzing loading and displacement relationships of individual and combined springs and damping are presented with detailed report of data analysis, discussion, and conclusions.

Thermal Response of a Viscoelastic Rod Under Cyclic Loading

1974 ◽  
Vol 41 (1) ◽  
pp. 229-233 ◽  
Author(s):  
S. Mukherjee
Keyword(s):  
Cyclic Loading ◽  
Thermal Response ◽  
Time History ◽  
Thermomechanical Coupling ◽  
Large Strains ◽  
Driving Frequency ◽  
Wide Range ◽  
History Of ◽  
Complex Young’S Modulus ◽  
Viscoelastic Rod

Thermal response of a viscoelastic rod under cyclic loading is discussed by determining the stresses and temperature in a viscoelastic rod insulated on its lateral surface and driven by a sinusoidal stress at one end. Temperature dependence of the complex Young’s modulus of the rod and the effect of thermomechanical coupling are included in the analysis. A method of finite differences is used to directly determine the steady-state stresses and temperature without obtaining the complete time history of the process. The iterative algorithm used is very efficient and converges rapidly for a wide range of driving stress amplitudes and frequencies. It is found that rapid rise of temperature to dangerous levels occurs for relatively low values of driving stress amplitudes, especially if the driving frequency is close to one of the critical frequencies of the rod. Drastic softening of the rod leads to large strains. Thus failure of the rod could occur at low values of the driving stress.

scholarly journals Apamin Enhances Neurite Outgrowth and Regeneration after Laceration Injury in Cortical Neurons

Toxins ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 603
Author(s):  
Hyunseong Kim ◽  
Jin Young Hong ◽  
Junseon Lee ◽  
Wan-Jin Jeon ◽  
In-Hyuk Ha
Keyword(s):  
Phospholipase A2 ◽  
Neurite Outgrowth ◽  
Cortical Neurons ◽  
Neurological Diseases ◽  
Minor Component ◽  
Underlying Mechanism ◽  
Bee Venom ◽  
Dependent Manner ◽  
Neuroprotective Effects ◽  
Wide Range

Apamin is a minor component of bee venom and is a polypeptide with 18 amino acid residues. Although apamin is considered a neurotoxic compound that blocks the potassium channel, its neuroprotective effects on neurons have been recently reported. However, there is little information about the underlying mechanism and very little is known regarding the toxicological characterization of other compounds in bee venom. Here, cultured mature cortical neurons were treated with bee venom components, including apamin, phospholipase A2, and the main component, melittin. Melittin and phospholipase A2 from bee venom caused a neurotoxic effect in dose-dependent manner, but apamin did not induce neurotoxicity in mature cortical neurons in doses of up to 10 µg/mL. Next, 1 and 10 µg/mL of apamin were applied to cultivate mature cortical neurons. Apamin accelerated neurite outgrowth and axon regeneration after laceration injury. Furthermore, apamin induced the upregulation of brain-derived neurotrophic factor and neurotrophin nerve growth factor, as well as regeneration-associated gene expression in mature cortical neurons. Due to its neurotherapeutic effects, apamin may be a promising candidate for the treatment of a wide range of neurological diseases.

scholarly journals Robust Rhythmogenesis in the Gamma Band via Spike Timing Dependent Plasticity

2020 ◽  
Author(s):  
Gabi Socolovsky ◽  
Maoz Shamir
Keyword(s):  
Mean Field ◽  
Rhythmic Activity ◽  
Gamma Oscillations ◽  
Underlying Mechanism ◽  
Spike Timing ◽  
Gamma Band ◽  
Fine Tuning ◽  
Spike Timing Dependent Plasticity ◽  
Dependent Plasticity ◽  
Wide Range

Rhythmic activity in the gamma band (30-100Hz) has been observed in numerous animal species ranging from insects to humans, and in relation to a wide range of cognitive tasks. Various experimental and theoretical studies have investigated this rhythmic activity. The theoretical efforts have mainly been focused on the neuronal dynamics, under the assumption that network connectivity satisfies certain fine-tuning conditions required to generate gamma oscillations. However, it remains unclear how this fine tuning is achieved.Here we investigated the hypothesis that spike timing dependent plasticity (STDP) can provide the underlying mechanism for tuning synaptic connectivity to generate rhythmic activity in the gamma band. We addressed this question in a modeling study. We examined STDP dynamics in the framework of a network of excitatory and inhibitory neuronal populations that has been suggested to underlie the generation of gamma. Mean field Fokker Planck equations for the synaptic weights dynamics are derived in the limit of slow learning. We drew on this approximation to determine which types of STDP rules drive the system to exhibit gamma oscillations, and demonstrate how the parameters that characterize the plasticity rule govern the rhythmic activity. Finally, we propose a novel mechanism that can ensure the robustness of self-developing processes, in general and for rhythmogenesis in particular.

scholarly journals Consistency and variability between cultures during toddlers’ naturalistic play

2019 ◽  
Author(s):  
Bria Long ◽  
Patrick Wong ◽  
Michael C. Frank ◽  
Eva Lai ◽  
Peggy Chan ◽  
...  
Keyword(s):  
Empirical Studies ◽  
Past Research ◽  
The United States ◽  
Free Play ◽  
Wide Range ◽  
Wide Variability ◽  
Play Behaviors ◽  
Audio Data ◽  
Video And Audio ◽  
Guided Play

Play is a universal behavior that is thought to be a critical way for children to learn a wide range of motor, social, and language skills. Empirical studies of play have borne out some of the predictions of classical theories, showing that children preferentially engage with surprising stimuli, will play in order to learn, and generally show a similar progression of increasingly-complex play behaviors through infancy. Past research has also characterized the types of support and guidance that parents offer during guided play with their child, as distinguished from individual free play. However, most of these studies come from Western nations, and relatively few cross-cultural comparisons have been made, despite observations of wide variability in cultural play traditions. The goal of this study is to examine the variability and consistency of play behaviors in a large sample of 1–2-year-old children—a critical period in the development of play behaviors—in two cultural contexts: the United States and Hong Kong. Our investigation covers both individual and guided play, with measures related to joint attention, stereotypical play behaviors, language use, and types of support offered by caregivers during guided play. This rich, annotated corpus of video and audio data also provides an important resource for research on early play.

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