Asymmetric Deviation Research Articles

Study of atomic arrangements and charge distribution on Si(0 0 1) surfaces with the adsorption of one Ge atom by DFTB calculations

Density Functional Tight Binding (DFTB) calculations are performed to study atomic arrangements and charge distribution of Si(0 0 1) surfaces with one Ge atom adsorbate. For these Ge/Si(0 0 1) systems, the initial height between the Ge atom and the surface, and the adsorption position being relative to the Si dimers on the surfaces, have influences on the stable structures of the Ge atom on the Si surface. Firstly, two reconstructed Si(0 0 1) surfaces including c(4 × 2) and p(2 × 2) are obtained. Then, the Ge atom is placed on these two reconstructed surfaces. The calculations show the following results. For these dimers formed on the two Si(0 0 1) surfaces, dimer’s bond length, and the buckling angle between the dimer and the surface have apparent differences as well as the charge distribution of these two surfaces. The Ge atom prefers to be located at two positions of the dimer: the outside top position of one atom of the dimer and the bridge position of this dimer. In these systems, the Ge atom always loses charges, and the charge transfer is found between atoms of one Si dimer. The asymmetric deviation of the two atoms in the dimer greatly affects the structure and charge distribution of Ge atom and the dimer.

Shape of LOSVDs in Barred Disks: Implications for Future IFU Surveys

Abstract The shape of line-of-sight velocity distributions (LOSVDs) carries important information about the internal dynamics of galaxies. The skewness of LOSVDs represents their asymmetric deviation from a Gaussian profile. Correlations between the skewness parameter (h 3) and the mean velocity ( ) of a Gauss–Hermite series reflect the underlying stellar orbital configurations of different morphological components. Using two self-consistent N-body simulations of disk galaxies with different bar strengths, we investigate correlations at different inclination angles. Similar to previous studies, we find anticorrelations in the disk area, and positive correlations in the bar area when viewed edge-on. However, at intermediate inclinations, the outer parts of bars exhibit anticorrelations, while the core areas dominated by the boxy/peanut-shaped (B/PS) bulges still maintain weak positive correlations. When viewed edge-on, particles in the foreground/background disk (the wing region) in the bar area constitute the main velocity peak, whereas the particles in the bar contribute to the high-velocity tail, generating the correlation. If we remove the wing particles, the LOSVDs of the particles in the outer part of the bar only exhibit a low-velocity tail, resulting in a negative correlation, whereas the core areas in the central region still show weakly positive correlations. We discuss implications for IFU observations on bars, and show that the variation of the correlation in the disk galaxy may be used as a kinematic indicator of the bar and the B/PS bulge.

Influence of asymmetrical drawing radius deviation in micro deep drawing

Nowadays, an increasing demand for small metal parts in electronic and automotive industries can be observed. Deep drawing is a well-suited technology for the production of such parts due to its excellent qualities for mass production. However, the downscaling of the forming process leads to new challenges in tooling and process design, such as high relative deviation of tool geometry or blank displacement compared to the macro scale. FEM simulation has been a widely-used tool to investigate the influence of symmetrical process deviations as for instance a global variance of the drawing radius. This study shows a different approach that allows to determine the impact of asymmetrical process deviations on micro deep drawing. In this particular case the impact of an asymmetrical drawing radius deviation and blank displacement on cup geometry deviation was investigated for different drawing ratios by experiments and FEM simulation. It was found that both variations result in an increasing cup height deviation. Nevertheless, with increasing drawing ratio a constant drawing radius deviation has an increasing impact, while blank displacement results in a decreasing offset of the cups geometry. This is explained by different mechanisms that result in an uneven cup geometry. While blank displacement leads to material surplus on one side of the cup, an unsymmetrical radius deviation on the other hand generates uneven stretching of the cups wall. This is intensified for higher drawing ratios. It can be concluded that the effect of uneven radius geometry proves to be of major importance for the production of accurately shaped micro cups and cannot be compensated by intentional blank displacement.

Localized slow light phenomenon in symmetry broken terahertz metamolecule made of conductively coupled dark resonators

We demonstrate a localized slow light phenomenon in a symmetry broken metamolecule (MM) of conductively coupled dark resonators at a terahertz band. Under a dark-mode excitation condition, the single mode resonance becomes dual modes by breaking the uniaxial symmetry of MM. Thus, a transparency window exists in between dual modes. An interaction of V-shaped plasmonic antenna-type (VA) resonances results in a plasmon-induced transparency (PIT) when the asymmetric deviation is below 13 μm. A maximum 25.9 ps group-delay of incident THz pulse is observed at the transparency window. When the asymmetric deviation is beyond 13 μm, one excitation pathway switches from VA resonance to the inductor-capacitor (LC) resonance, which dominates the high-frequency side-mode. Then, the PIT effect transfers to the PIT-like behavior and the slow light phenomenon vanishes. The aforementioned discovery allows for a speed modulation of slow light via symmetry breaking in MM.

Reconstruction of Monte Carlo replicas from Hessian parton distributions

We explore connections between two common methods for quantifying the uncertainty in parton distribution functions (PDFs), based on the Hessian error matrix and Monte-Carlo sampling. CT14 parton distributions in the Hessian representation are converted into Monte-Carlo replicas by a numerical method that reproduces important properties of CT14 Hessian PDFs: the asymmetry of CT14 uncertainties and positivity of individual parton distributions. The ensembles of CT14 Monte-Carlo replicas constructed this way at NNLO and NLO are suitable for various collider applications, such as cross section reweighting. Master formulas for computation of asymmetric standard deviations in the Monte-Carlo representation are derived. A correction is proposed to address a bias in asymmetric uncertainties introduced by the Taylor series approximation. A numerical program is made available for conversion of Hessian PDFs into Monte-Carlo replicas according to normal, log-normal, and Watt-Thorne sampling procedures.

Broadband terahertz plasmon-induced transparency via asymmetric coupling inside meta-molecules

We reported a broadband terahertz (THz) plasmon-induced transparency (PIT) phenomenon owing to asymmetric coupling in between the bright-and-dark resonators in meta-molecules (MMs). Each MM contains a cut-wire resonator and a couple of identical size and gap opposite-directed U-shaped resonators in mirror symmetry. An upside displacement of cut-wire induces an asymmetric deviation of cut-wire away from the X-axis in the MMs. Then, the PIT effect occurs due to the asymmetric coupling of dark resonators. The width of the transparency window extends monotonically with the deviation increasing. A picosecond-scale group delay of the THz wave is found at the transparent windows. The distribution of surface currents and electric energy reveals that the asymmetric coupling between cut-wire and U-shaped resonators results in an energy transfer from surface plasmon (SP) oscillations to the inductive-capacitive (LC) oscillation due to the local symmetry breaking in structures of MMs. A couple of counteract SPs cause the transparency window, while the LC resonance gives rise to the side modes in the THz frequency spectrum. Furthermore, the LC oscillations of side modes take place in between the cut-wire and the local area of the U-shaped resonators, which leads to a magnetic dipole momentum. The displacement of cut-wire leads to an asymmetric distribution of magnetic momentum in MMs, which extends the width of the transparency window. Our experimental findings present a new approach to develop broadband slow-light devices in the THz frequency range.

Phase-structured illumination as a tool to detect nanometer asymmetries

Phase-structured illumination is investigated as a possible extension of scatterometric measurement methods for silicon line gratings. This is done by means of rigorous simulations. Special emphasis is put on the capability of this approach to detect nanoscale fabrication asymmetries such as sidewall angles, bottom rounding, and floor tilt. The studied setup features a focused spot (numerical aperture=0.7), i.e., scanned over the sample, while analyzing the phase distribution in the image plane. This phase distribution can be accessed via holographic imaging. The results are compared to conventional nonstructured illumination. It is shown that by employing phase structuring, the resulting phase changes are larger, even if only symmetric deviations are considered. For asymmetric deviations, phase-structured illumination provides much higher sensitivity and better capability to detect the sign of the asymmetry.

Error correction for rotationally asymmetric surface deviation testing based on rotational shears.

We present a practical method for absolute testing of rotationally asymmetric surface deviation based on rotation averaging, additional compensation, and azimuthal errors correction. The errors of angular orders kNθ neglected in the traditional multiangle averaging method can be reconstructed and compensated with the help of least-squares fitting of Zernike polynomials by an additional rotation measurement with a suitable selection of rotation angles. The estimation algorithm adopts the least-squares technique to eliminate azimuthal errors caused by rotation inaccuracy. The unknown relative alignment of the measurements also can be estimated through the differences in measurement results at overlapping areas. The method proposed combines the advantages of the single-rotation and multiangle averaging methods and realizes a balance between the efficiency and accuracy of the measurements. Experimental results show that the method proposed can obtain high accuracy even with fewer rotation measurements.

Asymmetric nonlinear mean reversion in real effective exchange rates: A Fisher-type panel unit root test applied to Sub-Saharan Africa

This study investigates the nonlinear data generating processes of real effective exchange rates in a panel of Sub-Saharan African countries; the region with the highest transportation costs, trade barriers in international arbitrage and frequent central bank intervention in the foreign exchange market, which are plausible main sources of nonlinear and asymmetric deviations from purchasing power parity. By means of Monte Carlo simulations, we use the empirical distributions of the exponential smooth transition autoregressive (ESTAR), and the asymmetric ESTAR data generating processes to test for mean reversion in monthly real effective exchange rates. We then apply Fisher's inverse chi-square test that combines the observed significance levels of independent univariate unit root tests to test for panel unit roots. The findings suggest that once nonlinearities and asymmetries are taken into account, there is more evidence in favor of the purchasing power parity hypothesis.

On business cycle fluctuations in USA macroeconomic time series

This study employs eighteen USA macroeconomic time series variables to investigate possible existence of asymmetries in business cycle fluctuations in the series. Detection of asymmetric fluctuations in economic activity is important for policymakers since effective monetary policy relies on asymmetric business cycle fluctuations in all the series. The asymmetric deviations from the long-term growth trend in each of the series are modeled using regime switching models and artificial neural networks. The results based on nonlinear switching time series models reveal strong evidence of business cycle asymmetries in most of the series. The results based on in-sample approximations from artificial neural networks show statistically significant evidence of asymmetries in all the series. Similar results are obtained when jackknife out-of-sample approximations from artificial neural networks are used. Thus, the study results show statistically significant evidence of asymmetries in all the series which indicates that business cycle fluctuations in the series are asymmetric, thus alike. Therefore, the impact of monetary policy shocks on the output and the other macroeconomic variables can be anticipated using nonlinear models only. The results on asymmetric business cycle fluctuations in real GDP are in line with recent studies but in sharp contrast with Balke and Fomby (1994).

Dental arch changes associated with rapid maxillary expansion: A retrospective model analysis study.

Introduction:Transverse deficiency of the maxilla is a common clinical problem in orthodontics and dentofacial orthopedics. Transverse maxillary deficiency, isolated or associated with other dentofacial deformities, results in esthetic and functional impairment giving rise to several clinical manifestations such as asymmetrical facial growth, positional and functional mandibular deviations, altered dentofacial esthetics, adverse periodontal responses, unstable dental tipping, and other functional problems. Orthopedic maxillary expansion is the preferred treatment approach to increase the maxillary transverse dimension in young patients by splitting of the mid palatal suture. This orthopedic procedure has lately been subject of renewed interest in orthodontic treatment mechanics because of its potential for increasing arch perimeter to alleviate crowding in the maxillary arch without adversely affecting facial profile. Hence, the present investigation was conducted to establish a correlation between transverse expansion and changes in the arch perimeter, arch width and arch length.Methods:For this purpose, 10 subjects (five males, five females) were selected who had been treated by rapid maxillary expansion (RME) using hyrax rapid palatal expander followed by fixed mechanotherapy (PEA). Pretreatment (T1), postexpansion (T2), and posttreatment (T3) dental models were compared for dental changes brought about by RME treatment and its stability at the end of fixed mechanotherapy. After model measurements were made, the changes between T1–T2, T2–T3 and T1–T3 were determined for each patient. The mean difference between T1–T2, T2–T3 and T1–T3 were compared to assess the effects of RME on dental arch measurements. Results are expressed as mean ± standard deviation and are compared by repeated measures analysis of variance followed by a post-hoc test. Arch perimeter changes are correlated with changes in arch widths at the canine, premolar and molar regions.Results:The intercanine arch width increased by 2.9 mm, inter first premolar width increased by 3.2 mm, inter second premolar width increased by 4.6 mm, intermolar width increased by 4.4 mm, arch perimeter increased by 3.2 mm, arch length decreased by 1.8 mm from pretreatment to posttreatment. There is a strong positive correlation of arch perimeter with intercanine width (r2 = 0.99), interpremolar width (r2 = 0.99) and intermolar width (r2 = 0.98), indicating that there is a significant increase in arch perimeter with increase in arch width at the canine, premolars and molar regions.Conclusion:Findings of this study demonstrate that there was a significant increase in the intercanine, inter first premolar, inter second premolar intermolar arch width and arch perimeter from pretreatment to postexpansion, which was stable at the end of fixed mechanotherapy (PEA). There was a nonsignificant decrease in arch length from pretreatment to postexpansion that further decreased nonsignificantly from postexpansion to posttreatment.

Error-immune Algorithm for Absolute Testing of Rotationally Asymmetric Surface Deviation

Based on Zernike polynomial fitting, we propose an algorithm believed to be new for interferometric measurements of rotationally asymmetric surface deviation of optics. This method tests and calculates each angular surface by choosing specified rotation angles with lowest error. The entire figure can be obtained by superimposing these sub-surfaces. Simulation and experiment studies for verifying the proposed algorithm are presented. The results show that the accuracy of the proposed method is higher than single-rotation algorithm and almost comparable to the rotation-averaging algorithm with fewer rotation measurements. The new algorithm can achieve a balance between the efficiency and accuracy.

基于有限元法的面形反演模型

In order to inversed compute the optical element surface profile using the finite element method and the surface shape interference test results, the composition of interference test results was decomposed, and the testing principles of the rotational averaging method were analysised. The feasibility of using simplified geometrical model to caculate the deformation of an optical element with arbitrary given surface shape was discussed. Surface profile inversion model was proposed based on finite element method. A finite element analysis model was then presented based on surface-surface contact modeling. A plane mirror supported by three rigid spheres as the simulation and experimental model, the rotationally asymmetrical surface deviation was quantitative analysis using the numerical method presented in this paper and the N-step rotational averaging method. The obtained results show that the root mean square of rotationally asymmetric surface is 2.933 nm obtained through numerical method and the root mean square of rotationally asymmetric surface is 2.75 nm obtained through N-step rotational averaging method. Subtracted result of the two rotationally saymmetric surface show that the root mean square of the subtraction are 6.31% of the numerical method result and 6.73% of the N-step rotational averaging method result. Finally, comparing the optical element surface profile computed by proposed inversion model with the surface profile tested by N-step rotational averaging method. Results show that the root mean square of optical element surface profile are 3.535 nm and 3.351 nm respectively. Subtracted result of the two surface profile show that the root mean square of the subtraction are 11.67% of the inversiong result and 11.06% of the result tested by N-step rotational averaging method. The proposed inversion model is accurate and reliable.

Optimized absolute testing method of shift-rotation

The absolute testing method of shift-rotation that combines the traditional N-position method and Zernike polynomial fitting has been commonly employed in surface metrology. It preserves the high spatial frequency of the surface deviation with the N-position method to obtain the rotationally asymmetric surface deviation, but it suffers the kNθ order angular terms errors missed by the N-position method when it calculates the rotationally symmetric surface deviation with the Zernike rotationally symmetric polynomial fitting method. An optimized absolute testing method of shift-rotation is presented in this paper. It considers the missing kNθ order errors when the equations of the rotationally symmetric surface deviation are solved. As a result, it is more accurate than the traditional method. Experimental absolute results of spherical surfaces are given.

Asymmetries in Cost-Volume-Profit Relation: Cost Stickiness and Conditional Conservatism

Cost-volume-profit (CVP) analysis is based on a linear model of earnings behavior. However, recent research documents two potential sources of asymmetry in earnings: cost stickiness and conditional conservatism. We examine the implications of these asymmetries for CVP analysis and develop an “asymmetric CVP” (ACVP) framework incorporating both phenomena. ACVP estimates for Compustat/CRSP data reveal dramatic deviations from the standard CVP model (attributed to both stickiness and conservatism). These asymmetric deviations lead to major conceptual revisions in CVP analysis and have a large impact on various CVP benchmarks.

Simple and rapid data-reduction method with pixel-level spatial frequency of shift-rotation method

Absolute testing methods are commonly employed in surface metrology to calibrate the reference surface deviation and obtain the absolute deviation of the surface under test. A simple and reliable data-reduction method of absolute shift-rotation method with rotational and translational measurements is presented here, which relies on the decomposition of the surface deviation into rotationally asymmetric and symmetric components. The rotationally asymmetric surface deviation can be simply obtained by classical N-position averaging method. After that, the two-dimensional problem of estimating the other rotationally symmetric surface deviation can be simplified to a one-dimensional problem, and it can be directly calculated out with pixel-level spatial frequency based on several measurements of different translations in one same direction. Since that no orthogonal polynomials fitting, such as Zernike polynomials, is required in the calculation, the data reduction of the method is simple and rapid. Experimental absolute results of spherical surfaces are given.

Absolute subaperture testing by multiangle averaging and Zernike polynomial fitting method

A method to obtain the absolute shape of a large plane or sphere surface in the subaperture testing with multiangle averaging and Zernike polynomial fitting method is proposed. The subaperture data obtained by the interferometer contain not only the test mirror deviation but also the reference surface deviation. The reference surface deviation has become the main limit of the subaperture testing accuracy. To correct the deviation, the measurements are made so that the reference deviation could be eliminated by rotational asymmetric deviation and the rotational symmetric deviation. This technique can get not only the full absolute shape of the large mirrors, but also the reference surface shape. Experimental results have been given to verify the effectiveness of this method. (C) 2013 Society of Photo-Optical Instrumentation Engineers (SPIE)

Misestimating Betting Behavior: The Role of Negative Asymmetries in Emotional Self Prediction

This paper addresses the role of negative asymmetries in emotional self-prediction by looking at the extent to which individuals misestimate their own betting behavior in sequential gambles. In a series of three experimental studies, we demonstrate that losses lead to higher than planned bets whereas bets are on average carried over after gains. Such asymmetric deviations from the plan emerge (1) when monetary and non-monetary incentives are used, and (2) when participants face fair and unfair gambles. The asymmetry is based on people's inability to predict how much the negative emotions generated by a bad experience (e.g. the loss) will influence them to put more effort (e.g. bet more) than planned in an attempt to re-establish a homeostatic state in the prospect of a good experience (e.g. winning).

Functional changes following distraction osteogenesis treatment of asymmetric mandibular growth deviation in unilateral juvenile idiopathic arthritis: a prospective study with long-term follow-up

In juvenile idiopathic arthritis (JIA), temporomandibular joint involvement is a frequent complication leading to deficient mandibular growth. Occurring unilaterally this will give rise to mandibular and maxillary asymmetry that will affect the soft tissue and the muscles and result in complex dentofacial anomaly. In the case of severe dentofacial malformation, orthognathic surgery is the only treatment option. Vertical osseodistraction of the mandibular ramus has been suggested as a means of rectifying the mandibular growth deviation and soft-tissue problems. Whether such treatment introduces dysfunctional side effects of the temporomandibular joint and muscles has been debated and concern has been raised that treatment impairs the patient's mouth opening capacity and mandibular movement. The present study prospectively evaluated 23 patients with JIA and mandibular asymmetry caused by unilateral temporomandibular joint arthritis. The authors found a clinical effect on the asymmetry with only minor subjective complaints and limited objective changes in functional parameters.

Method to test rotationally asymmetric surface deviation with high accuracy

We have proposed a new absolute method to test rotationally asymmetric surface deviation. Relying on the high accuracy of Zernike polynomial fitting with least-squares algorithm for the low-frequency component and preserving the high-frequency component with the averaging method, the new method can guarantee the high accuracy of the measurement result with fewer rotational measurements compared to the traditional multiangle averaging method. It realizes a balance between the accuracy and efficiency of the measurements. It has been verified by experiments; the root mean square (rms) of residual figure between the two methods is ∼0.6 nm. Meanwhile, the new method can suppress environmental noise introduced in measurement results well.