53,142 research outputs found
Online Tool Condition Monitoring Based on Parsimonious Ensemble+
Accurate diagnosis of tool wear in metal turning process remains an open
challenge for both scientists and industrial practitioners because of
inhomogeneities in workpiece material, nonstationary machining settings to suit
production requirements, and nonlinear relations between measured variables and
tool wear. Common methodologies for tool condition monitoring still rely on
batch approaches which cannot cope with a fast sampling rate of metal cutting
process. Furthermore they require a retraining process to be completed from
scratch when dealing with a new set of machining parameters. This paper
presents an online tool condition monitoring approach based on Parsimonious
Ensemble+, pENsemble+. The unique feature of pENsemble+ lies in its highly
flexible principle where both ensemble structure and base-classifier structure
can automatically grow and shrink on the fly based on the characteristics of
data streams. Moreover, the online feature selection scenario is integrated to
actively sample relevant input attributes. The paper presents advancement of a
newly developed ensemble learning algorithm, pENsemble+, where online active
learning scenario is incorporated to reduce operator labelling effort. The
ensemble merging scenario is proposed which allows reduction of ensemble
complexity while retaining its diversity. Experimental studies utilising
real-world manufacturing data streams and comparisons with well known
algorithms were carried out. Furthermore, the efficacy of pENsemble was
examined using benchmark concept drift data streams. It has been found that
pENsemble+ incurs low structural complexity and results in a significant
reduction of operator labelling effort.Comment: this paper has been published by IEEE Transactions on Cybernetic
Study of a Dynamic Cooperative Trading Queue Routing Control Scheme for Freeways and Facilities with Parallel Queues
This article explores the coalitional stability of a new cooperative control
policy for freeways and parallel queuing facilities with multiple servers.
Based on predicted future delays per queue or lane, a VOT-heterogeneous
population of agents can agree to switch lanes or queues and transfer payments
to each other in order to minimize the total cost of the incoming platoon. The
strategic interaction is captured by an n-level Stackelberg model with
coalitions, while the cooperative structure is formulated as a partition
function game (PFG). The stability concept explored is the strong-core for PFGs
which we found appropiate given the nature of the problem. This concept ensures
that the efficient allocation is individually rational and coalitionally
stable. We analyze this control mechanism for two settings: a static vertical
queue and a dynamic horizontal queue. For the former, we first characterize the
properties of the underlying cooperative game. Our simulation results suggest
that the setting is always strong-core stable. For the latter, we propose a new
relaxation program for the strong-core concept. Our simulation results on a
freeway bottleneck with constant outflow using Newell's car-following model
show the imputations to be generally strong-core stable and the coalitional
instabilities to remain small with regard to users' costs.Comment: 3 figures. Presented at Annual Meeting Transportation Research Board
2018, Washington DC. Proof of conjecture 1 pendin
Designing Dirac points in two-dimensional lattices
We present a framework to elucidate the existence of accidental contacts of
energy bands, particularly those called Dirac points which are the point
contacts with linear energy dispersions in their vicinity. A generalized
von-Neumann-Wigner theorem we propose here gives the number of constraints on
the lattice necessary to have contacts without fine tuning of lattice
parameters. By counting this number, one could quest for the candidate of Dirac
systems without solving the secular equation. The constraints can be provided
by any kinds of symmetry present in the system. The theory also enables the
analytical determination of k-point having accidental contact by selectively
picking up only the degenerate solution of the secular equation. By using these
frameworks, we demonstrate that the Dirac points are feasible in various
two-dimensional lattices, e.g. the anisotropic Kagome lattice under inversion
symmetry is found to have contacts over the whole lattice parameter space.
Spin-dependent cases, such as the spin-density-wave state in LaOFeAs with
reflection symmetry, are also dealt with in the present scheme.Comment: 15pages, 9figures (accepted to Phys. Rev. B
A dual-mass capacitive-readout accelerometer operated near pull-in
A mechanical two-mass configuration and a readout circuit for a single-axis capacitive-readout accelerometer with ΣΔ force-feedback is presented. The system reduces electrical and quantisation input-referred noise through the use of negative springs, reduced gaps in the readout capacitors and maximised readout voltage. A theoretical analysis and simulation results are discussed
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