Fracture simulation using a nonlocal particle model

Extensive researches have been done to simulate crack initialization, propagation, branching, and coalesce from different engineering disciplines. Various numerical methods have been developed, which can be generally grouped into two categories: the continuum-based methods and the discontinuous approaches. For cracking problems, the classical finite element method (FEM) uses mesh matching and remeshing techniques which is computationally very expensive. The cohesive elements does not require very dense mesh near the crack tip region, but usually requires the crack path as a priori knowledge for the computational efficiency. eXtended FEM (XFEM) treats the discontinuity via level sets method and enrich the crack tip elements with analytical solution for the stress or displacement from linear elastic fracture mechanics. Arbitrary crack branching and coalesce is still challenging in the XFEM framework. The discontinuous approaches, such as lattice spring models and peridynamics, can handle fracture problems very efficiently. No additional criteria are needed as the crack growth is a natural outcome of the system evolution. As the elongation of the connecting bonds exceeds the critical value, it breaks and the crack propagates automatically. However, there are some other issues with the discontinuous approaches, such as restriction on effective Poisson’s ratio and crack path preference. A Volume-Compensated Particle Method (VCPM) was proposed by Chen et al. to solve these issues within the discontinuous framework. In the VCPM, both pairwise and nonlocal potentials are used to describe interactions among particles. One unique issue in the regular lattice particle method is the directional preference of the crack propagating path due to the regular lattice topology. The objective of this study is to investigate a general formulation using the VCPM concept to eliminate/reduce the crack path preference in the fracture simulation

Learning from Noisy Crowd Labels with Logics

This paper explores the integration of symbolic logic knowledge into deep neural networks for learning from noisy crowd labels. We introduce Logic-guided Learning from Noisy Crowd Labels (Logic-LNCL), an EM-alike iterative logic knowledge distillation framework that learns from both noisy labeled data and logic rules of interest. Unlike traditional EM methods, our framework contains a ``pseudo-E-step'' that distills from the logic rules a new type of learning target, which is then used in the ``pseudo-M-step'' for training the classifier. Extensive evaluations on two real-world datasets for text sentiment classification and named entity recognition demonstrate that the proposed framework improves the state-of-the-art and provides a new solution to learning from noisy crowd labels.Comment: 12 pages, 7 figures, accepted by ICDE-202

Unified framework for microstruture evolution and property quantification

In this study, a novel unified framework for the study of both microstructural evolution and the mechanical property quantification is proposed. The multistate Potts model is used to simulate the microstructural evolution, whereas a volume-compensated particle method (VCPM) is used for the mechanical property quantification of the steady state microstructure. The VCPM proposed by Chen and colleagues was originally developed for the investigation of the fracture phenomenon of solid materials. The model was also successfully extended to study the elastoplastic properties of solids by introducing a volume conservation scheme. In the VCPM framework, the domain of interest is discretized into regular unit cells according to the triangle and square packing for 2D and simple cubic, body centered cubic and face-centered cubic packing for 3D. Both local pair-wise and nonlocal multibody potential are proposed to account for the interactions between particles. The multistate Potts models have been used extensively to model a variety of microstructural phenomena, such as the grain growth in a single or multiple-phase system, recrystallization, solidification, and many others. The space-filling array of regular cells is used to represent the Potts domain which is the same as the one used in VCPM. The microstructure evolves such that the system Hamiltonian is minimized. To consider different external effects on the states of the microstructure, different energy terms can be introduced into the system Hamiltonian, such as surface energy to account for the interface effect and strain energy for the grain orientation. Once the final steady state is obtained using the multistate Potts model, usually some other techniques, such as FEM, are used to calculate the effective properties of the microstructural system. It requires the mapping between the FEM meshes and the microstructure. The mapping is very difficult, especially for the interface mapping when the microstructure is very complex. In this study, the VCPM is coupled with the multistate Potts model to simulate the microstructural evolution and quantify the effective mechanical properties of the system within one framework. No mapping between these two models is required since they share the same underlying domain structures. The nonlocal potential proposed in VCPM is introduced into the multistate Potts model as an alternative of the original strain energy term. By doing this, effective simulation of the microstructure evolution for multiple-phase materials can be achieved. Given the final microstructure, the VCPM simulation is carried out to calculate the effective properties of the obtained system

Enabling Quality Control for Entity Resolution: A Human and Machine Cooperation Framework

Even though many machine algorithms have been proposed for entity resolution, it remains very challenging to find a solution with quality guarantees. In this paper, we propose a novel HUman and Machine cOoperation (HUMO) framework for entity resolution (ER), which divides an ER workload between the machine and the human. HUMO enables a mechanism for quality control that can flexibly enforce both precision and recall levels. We introduce the optimization problem of HUMO, minimizing human cost given a quality requirement, and then present three optimization approaches: a conservative baseline one purely based on the monotonicity assumption of precision, a more aggressive one based on sampling and a hybrid one that can take advantage of the strengths of both previous approaches. Finally, we demonstrate by extensive experiments on real and synthetic datasets that HUMO can achieve high-quality results with reasonable return on investment (ROI) in terms of human cost, and it performs considerably better than the state-of-the-art alternatives in quality control.Comment: 12 pages, 11 figures. Camera-ready version of the paper submitted to ICDE 2018, In Proceedings of the 34th IEEE International Conference on Data Engineering (ICDE 2018

Electric-field-induced strong enhancement of electroluminescence in multilayer molybdenum disulfide.

The layered transition metal dichalcogenides have attracted considerable interest for their unique electronic and optical properties. While the monolayer MoS2 exhibits a direct bandgap, the multilayer MoS2 is an indirect bandgap semiconductor and generally optically inactive. Here we report electric-field-induced strong electroluminescence in multilayer MoS2. We show that GaN-Al2O3-MoS2 and GaN-Al2O3-MoS2-Al2O3-graphene vertical heterojunctions can be created with excellent rectification behaviour. Electroluminescence studies demonstrate prominent direct bandgap excitonic emission in multilayer MoS2 over the entire vertical junction area. Importantly, the electroluminescence efficiency observed in multilayer MoS2 is comparable to or higher than that in monolayers. This strong electroluminescence can be attributed to electric-field-induced carrier redistribution from the lowest energy points (indirect bandgap) to higher energy points (direct bandgap) in k-space. The electric-field-induced electroluminescence is general for other layered materials including WSe2 and can open up a new pathway towards transition metal dichalcogenide-based optoelectronic devices

Linear Coupling of Transverse Betatron Oscillations. Dynamic Stability and Invariants of Motion

Based on the technique of the discrete one-turn transfer maps, the problem of linear coupling between horizontal and vertical betatron oscillations in an accelerator has been treated exactly and entirely in explicit form. The stability region in the fractional part of the horizontal and the vertical betatron tune space as a function of the linear coupling strength, has been obtained, and the increment/decrement of the horizontal and the vertical betatron oscillations in the case of the linear sum resonance has been shown to be approximately equal to the half of the coupling strength. The normal form parameterization of the one-turn linear map with horizontal-to-vertical coupling has been developed in detail in the spirit of the Edwards and Teng formalism. The motion in the normal mode in the new normal form coordinates is decoupled implying that two independent Courant-Snyder invariants exist, which have been found explicitly.Comment: 10 pages, 3 figure

Data-driven input-to-state stabilization with respect to measurement errors

We consider noisy input/state data collected from an experiment on a polynomial input-affine nonlinear system. Motivated by event-triggered control, we provide data-based conditions for input-to-state stability with respect to measurement errors. Such conditions, which take into account all dynamics consistent with data, lead to the design of a feedback controller, an ISS Lyapunov function, and comparison functions ensuring ISS with respect to measurement errors. When solved alternately for two subsets of the decision variables, these conditions become a convex sum-of-squares program. Feasibility of the program is illustrated with a numerical example.Comment: Submitted for peer review on 31 March 2023. To appear in the Proceedings of the 62nd IEEE Conference on Decision and Control, 13-15 December 2023, Singapor