47,668 research outputs found
Heterogeneous Cross-Project Defect Prediction using Encoder and Transfer Learning
Heterogeneous cross-project defect prediction (HCPDP) aims to predict defects in new software projects using defect data from previous software projects where the source and target projects have some different metrics. Most existing methods only find linear relationships in the software defect features and datasets. Additionally, these methods use multiple defect datasets from different projects as source datasets. In this paper, we propose a novel method called heterogeneous cross-project defect prediction using encoder and transfer learning (ETL). ETL uses encoders to extract the important features from source and target datasets. Also, to minimize negative transfer during transfer learning, we used an augmented dataset that contains pseudo-labels and the source dataset. Additionally, we have used very limited data to train the model. To evaluate the performance of the ETL approach, 16 datasets from four publicly available software defect projects were used. Furthermore, we compared the proposed method with four HCPDP methods namely EGW, HDP&#x005F;KS, CTKCCA and EMKCA, and one WPDP method from existing literature. The proposed method on average outperforms the baseline methods in terms of PD, PF, F1-score, G-mean and AUC.</p
Electro-Magnetic Earthquake Bursts and Critical Rupture of Peroxy Bond Networks in Rocks
We propose a mechanism for the low frequency electromagnetic emissions and
other electromagnetic phenomena which have been associated with earthquakes.
The mechanism combines the critical earthquake concept and the concept of crust
acting as a charging electric battery under increasing stress. The electric
charges are released by activation of dormant charge carriers in the oxygen
anion sublattice, called peroxy bonds or positive hole pairs (PHP), where a PHP
represents an with ,
i.e. an in a matrix of of silicates. We propose that PHP are
activated by plastic deformations during the slow cooperative build-up of
stress and the increasingly correlated damage culminating in a large
``critical'' earthquake. Recent laboratory experiments indeed show that
stressed rocks form electric batteries which can release their charge when a
conducting path closes the equivalent electric circuit. We conjecture that the
intermittent and erratic occurrences of EM signals are a consequence of the
progressive build-up of the battery charges in the Earth crust and their
erratic release when crack networks are percolating throughout the stressed
rock volumes, providing a conductive pathway for the battery currents to
discharge. EM signals are thus expected close to the rupture, either slightly
before or after, that is, when percolation is most favored.Comment: 17 pages with 3 figures, extended discussion with 1 added figure and
162 references. The new version provides both a synthesis of two theories and
a review of the fiel
Scaling of Fracture Strength in Disordered Quasi-Brittle Materials
This paper presents two main results. The first result indicates that in
materials with broadly distributed microscopic heterogeneities, the fracture
strength distribution corresponding to the peak load of the material response
does not follow the commonly used Weibull and (modified) Gumbel distributions.
Instead, a {\it lognormal} distribution describes more adequately the fracture
strengths corresponding to the peak load of the response. Lognormal
distribution arises naturally as a consequence of multiplicative nature of
large number of random distributions representing the stress scale factors
necessary to break the subsequent "primary" bond (by definition, an increase in
applied stress is required to break a "primary" bond) leading up to the peak
load. Numerical simulations based on two-dimensional triangular and diamond
lattice topologies with increasing system sizes substantiate that a {\it
lognormal} distribution represents an excellent fit for the fracture strength
distribution at the peak load. The second significant result of the present
study is that, in materials with broadly distributed microscopic
heterogeneities, the mean fracture strength of the lattice system behaves as
, and scales as as the lattice system size, , approaches
infinity.Comment: 24 pages including 11 figure
Development of a Transferable Reactive Force Field of P/H Systems: Application to the Chemical and Mechanical Properties of Phosphorene
ReaxFF provides a method to model reactive chemical systems in large-scale
molecular dynamics simulations. Here, we developed ReaxFF parameters for
phosphorus and hydrogen to give a good description of the chemical and
mechanical properties of pristine and defected black phosphorene. ReaxFF for
P/H is transferable to a wide range of phosphorus and hydrogen containing
systems including bulk black phosphorus, blue phosphorene, edge-hydrogenated
phosphorene, phosphorus clusters and phosphorus hydride molecules. The
potential parameters were obtained by conducting unbiased global optimization
with respect to a set of reference data generated by extensive ab initio
calculations. We extend ReaxFF by adding a 60{\deg} correction term which
significantly improves the description of phosphorus clusters. Emphasis has
been put on obtaining a good description of mechanical response of black
phosphorene with different types of defects. Compared to nonreactive SW
potential [1], ReaxFF for P/H systems provides a huge improvement in describing
the mechanical properties the pristine and defected black phosphorene and the
thermal stability of phosphorene nanotubes. A counterintuitive phenomenon is
observed that single vacancies weaken the black phosphorene more than double
vacancies with higher formation energy. Our results also show that mechanical
response of black phosphorene is more sensitive to defects for the zigzag
direction than for the armchair direction. Since ReaxFF allows straightforward
extensions to the heterogeneous systems, such as oxides, nitrides, ReaxFF
parameters for P/H systems build a solid foundation for the reactive force
field description of heterogeneous P systems, including P-containing 2D van der
Waals heterostructures, oxides, etc
Overview of the theoretical relations between necking and strain localization criteria.
Many criteria have been developed during last decades to predict diffuse or localized necking and shear banding. The lack of confrontation of these models with each other on relevant applications makes their choice difficult for the designer. It is proposed to reformulate these plastic instability criteria in an unified framework, to compare their theoretical bases to establish links between them and then to highlighten their limitations. In the case of diffuse necking, a comparison is made between the criteria based on bifurcation analysis and on those based on maximum force principle for elastic-plastic materials. In the case of localized modes, it is shown that the predictions of the Marciniak – Kuczynski approach, based on a multizone model, tend to those of the loss of ellipticity criterion when the initial defect size tends to zero (no initial defect introduced). In the case of elasto-viscoplastic behavior, an approach based on a linear stability analysis is mentioned
Structures and transitions in bcc tungsten grain boundaries and their role in the absorption of point defects
We use atomistic simulations to investigate grain boundary (GB) phase
transitions in el- emental body-centered cubic (bcc) metal tungsten. Motivated
by recent modeling study of grain boundary phase transitions in [100] symmetric
tilt boundaries in face-centered cu- bic (fcc) copper, we perform a systematic
investigation of [100] and [110] symmetric tilt high-angle and low-angle
boundaries in bcc tungsten. The structures of these boundaries have been
investigated previously by atomistic simulations in several different bcc
metals including tungsten using the the {\gamma}-surface method, which has
limitations. In this work we use a recently developed computational tool based
on the USPEX structure prediction code to perform an evolutionary grand
canonical search of GB structure at 0 K. For high-angle [100] tilt boundaries
the ground states generated by the evolutionary algorithm agree with the
predictions of the {\gamma}-surface method. For the [110] tilt boundaries, the
search predicts novel high-density low-energy grain boundary structures and
multiple grain boundary phases within the entire misorientation range.
Molecular dynamics simulation demonstrate that the new structures are more
stable at high temperature. We observe first-order grain boundary phase
transitions and investigate how the structural multiplicity affects the
mechanisms of the point defect absorption. Specifically, we demonstrate a
two-step nucleation process, when initially the point defects are absorbed
through a formation of a metastable GB structure with higher density, followed
by a transformation of this structure into a GB interstitial loop or a
different GB phase.Comment: 40 pages, 19 figure
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