A One-Dimensional, Two-Phase Flow Model for Taylor Impact Specimens

1991 ◽  
Vol 113 (2) ◽  
pp. 228-235 ◽  
Author(s):  
S. E. Jones ◽  
P. P. Gillis ◽  
J. C. Foster ◽  
L. L. Wilson
Keyword(s):  
Wave Speed ◽  
Second Phase ◽  
Plastic Wave ◽  
Two Phase ◽  
Strain Rate Effects ◽  
One Dimensional ◽  
Rate Effects ◽  
Taylor Impact ◽  
Dynamic Yield ◽  
Two Phases

In this paper, a simple theoretical analysis of an old problem is presented. The analysis is more complete than earlier versions, but retains the mathematical simplicity of the earlier versions. The major thrust is to separate the material response into two phases. The first phase is dominated by strain rate effects and has a variable plastic wave speed. The second phase is dominated by strain hardening effects and has a constant plastic wave speed. Estimates for dynamic yield stress, strain, strainrate, and plastic wave speed during both phases are given. Comparisons with several experiments on OFHC copper are included.

scholarly journals XCOVNet: Chest X-ray Image Classification for COVID-19 Early Detection Using Convolutional Neural Networks

2021 ◽  
Author(s):  
Vishu Madaan ◽  
Aditya Roy ◽  
Charu Gupta ◽  
Prateek Agrawal ◽  
Anand Sharma ◽  
...  
Keyword(s):  
Image Classification ◽  
Second Phase ◽  
Two Phase ◽  
X Ray ◽  
The Neural Network ◽  
Rapid Spread ◽  
Chest X Ray ◽  
Polymerase Chain ◽  
Two Phases ◽  
Active Patients

AbstractCOVID-19 (also known as SARS-COV-2) pandemic has spread in the entire world. It is a contagious disease that easily spreads from one person in direct contact to another, classified by experts in five categories: asymptomatic, mild, moderate, severe, and critical. Already more than 66 million people got infected worldwide with more than 22 million active patients as of 5 December 2020 and the rate is accelerating. More than 1.5 million patients (approximately 2.5% of total reported cases) across the world lost their life. In many places, the COVID-19 detection takes place through reverse transcription polymerase chain reaction (RT-PCR) tests which may take longer than 48 h. This is one major reason of its severity and rapid spread. We propose in this paper a two-phase X-ray image classification called XCOVNet for early COVID-19 detection using convolutional neural Networks model. XCOVNet detects COVID-19 infections in chest X-ray patient images in two phases. The first phase pre-processes a dataset of 392 chest X-ray images of which half are COVID-19 positive and half are negative. The second phase trains and tunes the neural network model to achieve a 98.44% accuracy in patient classification.

Modeling Rate Effects and Cyclic Loads With the Pressuremeter

1988 ◽  
Vol 110 (3) ◽  
pp. 196-202
Author(s):  
P. J. Cosentino ◽  
J.-L. Briaud ◽  
T. A. Terry
Keyword(s):  
Viscoelastic Model ◽  
Field Tests ◽  
Second Phase ◽  
Cyclic Loads ◽  
Rate Effects ◽  
Load Effects ◽  
Consistent Method ◽  
Repetitive Loading ◽  
Soil Modulus ◽  
Two Phases

A relatively new tool, the cone pressuremeter (CPMT), was used in order to evaluate its usefulness in predicting the effects on soil due to various rates of loading and to repetitive loading. Field tests were conducted in two phases. The first phase included 24 CPMT tests, at the Texas A&M University research annex, which were designed to show 1) if the CPMT could be used to predict the effects on the soil due to both rate effects and repetitive loads; and 2) if the CPMT should be inserted into a prebored hole to the desired test depth or if the CPMT should be driven to the desired test depth. The soils at the research annex were a clay and a sand. The second phase included 32 CPMT tests at three sites throughout the state of Texas. Two of the sites were clay and the third site was sand. The CPMT test used at these sites was devised so that both rate effect and cyclic effect could be determined from a single test. Rate effects on the soil modulus were modeled using a viscoelastic model of the form EstEso=ttto−ncrp(1) while repetitive load effects on the soil modulus were modeled using a power law of the form EsNEs1=N−n(2) It was concluded that a single CPMT test could be used to model both rate effects and cyclic effects on the soil modulus and that the most consistent method of inserting the probe was to place it in a prebored hole. It was also concluded that a linear relationship exists between the exponents n in both modeling equations and the normalized CPMT stress level.

A Metamorphic Erectable Cell Restraint (MECR)

2012 ◽  
Author(s):  
Gregory H. Teichert ◽  
Quentin T. Aten ◽  
Melanie Easter ◽  
Sandra Burnett ◽  
Larry L. Howell ◽  
...  
Keyword(s):  
Compliant Mechanism ◽  
Genetic Research ◽  
Second Phase ◽  
Two Phase ◽  
Electromechanical Systems ◽  
Metamorphic Mechanism ◽  
Two Phases ◽  
Phase Motion

This paper introduces a metamorphic erectable cell restraint (MECR) to provide cell restraint in genetic research. A micro-electromechanical systems (MEMS) metamorphic mechanism with two phases of motion was designed to grasp individual embryos about their midplane. The first phase of motion lifts a compliant gripper approximately 40 μm (about half the diameter of an embryo). The gripper then closes in the second phase to grasp the embryo. The metamorphic mechanism includes compliant mechanism components which are analyzed here. A microscale prototype was fabricated from polysilicon and used to demonstrate the mechanism’s two phase motion.

scholarly journals Magnetic relaxation and the Taylor conjecture

2015 ◽  
Vol 81 (6) ◽  
Author(s):  
H. K. Moffatt
Keyword(s):  
Magnetic Field ◽  
Initial Phase ◽  
Magnetic Relaxation ◽  
Magnetic Energy ◽  
Magnetic Pressure ◽  
Second Phase ◽  
One Dimensional ◽  
Induction Equation ◽  
Two Phases ◽  
The Magnetic Field

A one-dimensional model of magnetic relaxation in a pressureless low-resistivity plasma is considered. The initial two-component magnetic field $\boldsymbol{b}(\boldsymbol{x},t)$ is strongly helical, with non-uniform helicity density. The magnetic pressure gradient drives a velocity field that is dissipated by viscosity. Relaxation occurs in two phases. The first is a rapid initial phase in which the magnetic energy drops sharply and the magnetic pressure becomes approximately uniform; the helicity density is redistributed during this phase but remains non-uniform, and although the total helicity remains relatively constant, a Taylor state is not established. The second phase is one of slow diffusion, in which the velocity is weak, though still driven by persistent weak non-uniformity of magnetic pressure; during this phase, magnetic energy and helicity decay slowly and at constant ratio through the combined effects of pressure equalisation and finite resistivity. The density field, initially uniform, develops rapidly (in association with the magnetic field) during the initial phase, and continues to evolve, developing sharp maxima, throughout the diffusive stage. Finally it is proved that, if the resistivity is zero, the spatial mean $\langle (\boldsymbol{b}\boldsymbol{\cdot }\boldsymbol{{\rm\nabla}}\times \boldsymbol{b})/b^{2}\rangle$ is an invariant of the governing one-dimensional induction equation.

SenU-PTM: a novel phrase-based topic model for short-text topic discovery by exploiting word embeddings

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Heng-Yang Lu ◽  
Yi Zhang ◽  
Yuntao Du
Keyword(s):  
Latent Dirichlet Allocation ◽  
Topic Model ◽  
Second Phase ◽  
Word Embeddings ◽  
Two Phase ◽  
Content Type ◽  
Short Text ◽  
Topic Discovery ◽  
Two Phases ◽  
Sense Unit

PurposeTopic model has been widely applied to discover important information from a vast amount of unstructured data. Traditional long-text topic models such as Latent Dirichlet Allocation may suffer from the sparsity problem when dealing with short texts, which mostly come from the Web. These models also exist the readability problem when displaying the discovered topics. The purpose of this paper is to propose a novel model called the Sense Unit based Phrase Topic Model (SenU-PTM) for both the sparsity and readability problems.Design/methodology/approachSenU-PTM is a novel phrase-based short-text topic model under a two-phase framework. The first phase introduces a phrase-generation algorithm by exploiting word embeddings, which aims to generate phrases with the original corpus. The second phase introduces a new concept of sense unit, which consists of a set of semantically similar tokens for modeling topics with token vectors generated in the first phase. Finally, SenU-PTM infers topics based on the above two phases.FindingsExperimental results on two real-world and publicly available datasets show the effectiveness of SenU-PTM from the perspectives of topical quality and document characterization. It reveals that modeling topics on sense units can solve the sparsity of short texts and improve the readability of topics at the same time.Originality/valueThe originality of SenU-PTM lies in the new procedure of modeling topics on the proposed sense units with word embeddings for short-text topic discovery.

scholarly journals Mathematical modelling of elastoplasticity at high stress

2012 ◽  
Vol 468 (2148) ◽  
pp. 3842-3863 ◽  
Author(s):  
P. D. Howell ◽  
H. Ockendon ◽  
J.R. Ockendon
Keyword(s):  
Mathematical Model ◽  
Wave Propagation ◽  
Elastic Wave ◽  
Wave Speed ◽  
High Stress ◽  
Plastic Wave ◽  
Simple Mathematical Model ◽  
One Dimensional ◽  
Plastic Compression ◽  
Elastoplastic Wave

This study describes a simple mathematical model for one-dimensional elastoplastic wave propagation in a metal in the regime where the applied stress greatly exceeds the yield stress. Attention is focused on the increasing ductility that occurs in the over-driven limit when the plastic wave speed approaches the elastic wave speed. Our model predicts that a plastic compression wave is unable to travel faster than the elastic wave speed, and instead splits into a compressive elastoplastic shock followed by a plastic expansion wave.

Viscous–elastic–plastic modelling of one-dimensional time-dependent behaviour of clays

1989 ◽  
Vol 26 (2) ◽  
pp. 199-209 ◽  
Author(s):  
J.-H. Yin ◽  
J. Graham
Keyword(s):  
Strain Rate ◽  
Constitutive Models ◽  
Constitutive Modelling ◽  
Time Dependent ◽  
Creep Tests ◽  
Strain Rate Effects ◽  
One Dimensional ◽  
Elastic Plastic ◽  
Constant Rate ◽  
Rate Effects

Increased attention has recently been directed towards the influence of time and strain-rate effects on the behaviour of clays in one-dimensional (1-D) laboratory consolidation. The improved understanding coming from these studies must now be incorporated into improved constitutive models that can be used for analysis of foundation settlements. This paper presents a 1-D model for stepped loading using a new concept for establishing "equivalent times" during time-dependent straining. This model is then developed into a general constitutive equation for continuous loading. The model uses three parameters, λ, κ, and ψ, that can be easily found using conventional oedometer tests.The general model has been used to develop analytical solutions for creep tests, relaxation tests, constant rate of strain (CRSN) tests, and tests with constant rate of stress (CRSS). Results from three different clays have been used to examine the validity of the model. Key words: consolidation, constitutive modelling, elastic-plastic, viscous, time, creep, strain rate, relaxation.

Anti money laundering using a two-phase system

2015 ◽  
Vol 18 (3) ◽  
pp. 304-329 ◽  
Author(s):  
Tamer Hossam Moustafa ◽  
Mohamed Zaki Abd El-Megied ◽  
Tarek Salah Sobh ◽  
Khaled Mohamed Shafea
Keyword(s):  
Money Laundering ◽  
False Positive ◽  
Phase System ◽  
Second Phase ◽  
Two Phase ◽  
Content Type ◽  
Risk Scoring ◽  
Two Phases ◽  
Clear Shift ◽  
Monitoring Phase

Purpose – This paper aims to compete and detect suspicious transactions that can lead to detecting money laundering cases. Design/methodology/approach – This paper presents a plan-based framework for anti-money laundering systems (PBAMLS). Such a framework is novel and consists of two phases, in addition to several supporting modules. The first phase, the monitoring phase, utilizes an automata approach as a formalism to detect probable money laundering. The detection process is based on a money laundering deterministic finite automaton that has been obtained from the corresponding regular expressions which specify different money laundering processes. The second phase is STRIPS-based planning phase that aims at strengthening the belief in the probable problems discovered in the first (monitoring) phase. In addition, PBAMLS contains several supporting modules for data collection and mediation, link analysis and risk scoring. To assess the applicability of PBAMLS, it has been tested using different cases studies. Findings – This framework provides a clear shift of anti-money laundering systems (AML) from depending heuristic and human expertise to making use of a rigorous formalism to accomplish concrete decisions. It minimizes the possibilities of false positive alarms and increases the certainty in decision-making. Practical implications – This framework enhances the detection of money laundering cases. It also minimizes the number of false-positive alarms that waste the investigators’ efforts and time; it decreases the efforts presented by the investigators. Originality/value – This work proposes PBAMLS as a novel plan-based framework for AML systems.

scholarly journals Research of One-Dimensional Consolidation of Clays Considering Their Rehological Properties

2019 ◽  
Vol 2 (4) ◽  
pp. 395
Author(s):  
Chen Zhuo ◽  
Deng JinGen ◽  
Yu Baohua ◽  
Weng Haoyang ◽  
Wang Jie ◽  
...  
Keyword(s):  
Strain Theory ◽  
System Level ◽  
Model Parameters ◽  
Strain Rate Effects ◽  
One Dimensional ◽  
Proposed Model ◽  
Rate Effects ◽  
Mathematical Equations ◽  
Primary Consolidation ◽  
Creep Constitutive Model

The paper concerns the influence of time and strain-rate effects on the clays in one-dimensional consolidation under constant effective stress. An improved creep constitutive model is deduced, by analyzing the stress-strain theory developed by yin and sekiguchi. Treating the sample as a single system and applying the boundary conditions at the system level, differential mathematical equations to the consolidation problem of clays are obtained. The proposed differential mathematical equations have advantages in their ability to (i) not clarify the primary consolidation and secondary consolidation deformation. The error in calculating consolidation deformation which is caused by the argument about end of primary consolidation can be avoided. (ii) obtain the model parameters easily. How to achieve parameters by experiment is described in detail in the paper. (iii) be programmed and solved readily for the finite difference description of the problem. Results from clays have been used to examine the validity of the model. It is shown that the proposed model can describe the consolidation of clays well.

Sign in / Sign up

Export Citation Format

Share Document