9,479 research outputs found
Quantification of three-dimensional orthodontic force systems of T-loop archwires
Objective:
To demonstrate the three-dimensional (3D) orthodontic force systems of three commercial closing T-loop archwires using a new method and to quantify the force systems of the T-loop archwires.
Materials and Methods:
An orthodontic force tester (OFT) and a custom-made dentoform were developed to measure force systems. The system simulated the clinical environment for an orthodontic patient requiring space closure, which included measurement of three force components along, and three moment components about, three clinically defined axes on two target teeth. The archwires were attached to the dentoform and were activated following a standard clinical procedure. The resulting force system was measured using the OFT.
Results:
The force systems of the T-loops on the teeth were 3D. Activation in one direction resulted in force and moment components in other directions (side effects). The six force and moment components as well as the moment-to-force ratios in the clinically defined coordinate system were quantified.
Conclusions:
The commercial archwires do not provide force systems for pure translation. Quantification of the force system is critical for the selection and design of optimal orthodontic appliances
Scaling in directed dynamical small-world networks with random responses
A dynamical model of small-world network, with directed links which describe
various correlations in social and natural phenomena, is presented. Random
responses of every site to the imput message are introduced to simulate real
systems. The interplay of these ingredients results in collective dynamical
evolution of a spin-like variable S(t) of the whole network. In the present
model, global average spreading length \langel L >_s and average spreading time
_s are found to scale as p^-\alpha ln N with different exponents.
Meanwhile, S behaves in a duple scaling form for N>>N^*: S ~ f(p^-\beta
q^\gamma t'_sc), where p and q are rewiring and external parameters, \alpha,
\beta, \gamma and f(t'_sc) are scaling exponents and universal functions,
respectively. Possible applications of the model are discussed.Comment: 4 pages, 6 Figure
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Revisiting the Collinear Data Problem: An Assessment of Estimator \u27Ill-Conditioning\u27 in Linear Regression
Linear regression has gained widespread popularity in the social sciences. However, many applications of linear regression have been in situations in which the model data are collinear or ‘ill-conditioned.’ Collinearity renders regression estimates with inflated standard errors. In this paper, we present a method for precisely identifying coefficient estimates that are ill-conditioned, as well as those that are not involved, or only marginally involved in a linear dependency. Diagnostic tools are presented for a hypothetical regression model with ordinary least squares (OLS). It is hoped that practicing researchers will more readily incorporate these diagnostics into their analyses.Accessed 17,081 times on https://pareonline.net from June 18, 2008 to December 31, 2019. For downloads from January 1, 2020 forward, please click on the PlumX Metrics link to the right
Electronic Structure in Gapped Graphene with Coulomb Potential
In this paper, we numerically study the bound electron states induced by long
range Coulomb impurity in gapped graphene and the quasi-bound states in
supercritical region based on the lattice model. We present a detailed
comparison between our numerical simulations and the prediction of the
continuum model which is described by the Dirac equation in (2+1)-dimensional
Quantum Electrodynamics (QED). We also use the Fano's formalism to investigate
the quasi-bound state development and design an accessible experiments to test
the decay of the supercritical vacuum in the gapped graphene.Comment: 5 page, 4 figure
Thermodynamics of spin-orbit-coupled Bose-Einstein condensates
In this paper we develop a quantum field approach to reveal the thermodynamic
properties of the trapped BEC with the equal Rashba and Dresselhaus spin-orbit
couplings. In the experimentally-feasible regime, the phase transition from the
separate phase to the single minimum phase can be well driven by the tunable
temperature. Moreover, the critical temperature, which is independent of the
trapped potential, can be derived exactly. At the critical point, the specific
heat has a large jump and can be thus regarded as a promising candidate to
detect this temperature-driven phase transition. In addition, we obtain the
analytical expressions for the specific heat and the entropy in the different
phases. In the single minimum phase, the specific heat as well as the entropy
are governed only by the Rabi frequency. However, in the separate phase with
lower temperature, we find that they are determined only by the strength of
spin-orbit coupling. Finally, the effect of the effective atom interaction is
also addressed. In the separate phase, this effective atom interaction affects
dramatically on the critical temperature and the corresponding thermodynamic
properties.Comment: 8 pages, 6 figure
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