Symmetric Contour Research Articles

How asymmetric islands become symmetric.

Scanning tunneling microscopy reveals that sputtering of the Au(110) surface results in the formation of vacancy islands with a broken mirror symmetry. These islands exhibit two types of steps on opposite sides: a lower energy (111) step and a higher energy (331) step. We analyze the thermal fluctuations and especially the kink distribution of such vacancy islands. Despite the broken symmetry, which they adopt internally, these islands show a symmetric average outer contour. Their coarsening proceeds via a variety of pathways, often leading to new, symmetric structures, with exclusively (111) steps. The lowest energy vacancy configuration is a bound pair of two vacancy lines or islands.

Contour symmetry detection: the influence of axis orientation and number of objects

Participants discriminated symmetrical from random contours connected by straight lines to form part of one- or two-objects. In experiment one, symmetrical contours were translated or reflected and presented at vertical, horizontal, and oblique axis orientations with orientation constant within blocks. Translated two-object contours were detected more easily than one, replicating a “lock-and-key” effect obtained previously for vertical orientations only [M. Bertamini, J.D. Friedenberg, M. Kubovy, Acta Psychologica, 95 (1997) 119–140]. A second experiment extended these results to a wider variety of axis orientations under mixed block conditions. The pattern of performance for translation and reflection at different orientations corresponded in both experiments, suggesting that orientation is processed similarly in the detection of these symmetries.

Figure-Ground Assignment of Stereo-Defined Contours Affects the Ease of Symmetry and Translation Detection

When figure - ground assignment reverses for a given contour, convexities along it become concavi- ties, and vice versa. Baylis and Driver (1995 Journal of Experimental Psychology: Human Perception and Performance21 1323 – 1342) examined the possible implications of this effect for the perception of symmetry between contours. Using contrast reversal to determine figure - ground assignment, they argued that the ease of detecting symmetry between two contours depends on whether convexities along them match following figural assignment. However, their results might be attributed to the contrast polarity of individual edges instead. We used random-dot stereograms to vary figure - ground assignment for edges while holding contrast polarity constant. By placing the areas on either side of each contour at various depth planes, conditions were created in which the convex parts yielded for related contours either matched or mismatched following figural assignment. Particular depth arrangements which yielded matching convex parts for symmetrical contours yielded mismatching parts for translated contours, and vice versa. The results confirmed that the relative ease of symmetry-detection versus translation-detection depends on the convex parts yielded for each contour following figural assignment. These findings suggest that the perception of symmetry between contours arises only after they have been assigned to a figure on one of their sides, and is based on a higher-level interpretation of each contour in terms of convex parts, rather than lower-level properties of the image.

Appearance of new lines and change in line shape in the IR spectrum of a NaV2O5 single crystal at a spin-Peierls transition

New lines are observed in the infrared spectrum of a crystal due to unit-cell doubling at a spin-Peierls transition (in NaV2O5). The change in the shape of the spectral lines at the spin-Peierls transition is recorded. A contour characteristic of a Fano resonance is observed above the transition temperature T sp and the standard symmetric contour is observed below T sp . We attribute this effect to the opening of a gap in the magnetic-excitation spectrum at the spin-Peierls transition.

Microsurgical correction of facial contour in congenital craniofacial malformations: the marriage of hard and soft tissue.

The correction of facial asymmetry in complex craniofacial malformations presents a challenging problem for reconstructive surgeons. Deficiencies of both the facial skeleton and the overlying soft tissue must be addressed to achieve the optimal reconstructive result. We present our experience with a minimum of 1-year follow-up over a 5-year period with 19 patients who initially underwent standard facial skeletal reconstruction and subsequently required microsurgical soft-tissue reconstructions for final correction of facial contour. From July of 1989 to June of 1994, 19 patients with craniofacial malformations underwent microsurgical correction of facial contour using 21 free flaps. The underlying malformations included 15 hemifacial microsomias, 2 orbitofacial clefts, 1 congenital temporomandibular joint ankylosis with micrognathia, and 1 Tessier no. 30 (lower midline mandibular) cleft. Sixteen patients had previous facial skeletal correction using craniofacial techniques. Age at operation ranged from 6 to 27 years. Twenty-one microvascular flaps were used on the 19 patients: 19 deepithelialized parascapular flaps, 1 superficial inferior epigastric flap, and 1 fibula with soleus muscle and large skin paddle for a severe Tessier no. 30 facial cleft with severe micrognathia. Of the 15 patients with hemifacial microsomia, 10 were treated with parascapular fasciocutaneous flaps, 3 with parascapular flaps with bone, 1 with a parascapular flap with teres major muscle for additional bulk, and 1 with a superficial inferior epigastric flap. Complications were two limited hematomas drained at the bedside and a partial skin paddle slough of the fibula flap. Correction of facial contour in complex craniofacial malformations is possible using microsurgical techniques. These free flaps "camouflage" the underlying skeletal deformity that persists despite traditional skeletal reconstruction while restoring symmetrical facial contour. We recommend the marriage of both skeletal and microsurgical soft-tissue reconstructions to achieve the optimal aesthetic result for craniofacial contouring in these challenging patients.

Rotary ultrasonic motor utilizing contour and flexural vibrations of a rectangular thick plate

AbstractA method of vibration analysis for an ultrasonic motor using asymmetric flexural vibrations and symmetric contour vibrations of a thick rectangular plate is given. An investigation of the symmetricity of the flexural vibrations using the Rayleigh quotient is used to derive an expression for the resonant frequency of the same flexural mode and the similarity ratio of the vibration plate thickness and contour dimensions. The possibility of estimating the resonant frequency of a rectangular plate of different dimensions is then confirmed experimentally.With the contour vibration mode with small displacements at the middle and large displacements at the ends, the middle side constrained is analyzed. The vibration plate was an SUS304 rectangular plate with a PZT plate attached; as in the case of the PZT rectangular plate, it is confirmed experimentally that shear stress can be neglected. When allowance is made for machined holes in the vibration plate (such as screw holes), a value close to the measurement value is still obtained.

Labial hypertrophy: A new surgical approach

Study Objective: To develop a new technique for labioplasty with the goal of decreased scar formation, decreased vulva pain, and dyspareunia.Design: We present a simple surgical approach to labial reduction in two young women. We performed a wedge resection of the excess labial tissue after first identifying and preserving the main arterial supply to each labia.Results: After surgical correction, the patients had excellent cosmetic results with smooth symmetrical contours, minimal scarring, and relief from symptoms.Conclusions: Hypertrophy of the labia minora is a frequently overlooked problem in young women. In general, gynecologists have been reluctant to surgically remove the excess tissue. We present a new approach to labioplasty that is safe and can be performed easily in symptomatic patients.

Shape from texture and contour by weak isotropy

A unified framework for shape from texture and contour is proposed. It is based on the assumption that the surface markings are not systematically compressed, or formally, that they are weakly isotropic. The weak isotropy principle is based on analysis of the directional statistics of the projected surface markings. It builds on several previous theories, in particular by Witkin [25] and Kanatani [15]. It extends these theories in various ways, most notably to perspective projection. The theory also provides an exact solution to an estimation problem earlier solved approximately by Kanatani. The weak isotropy principle leads to a computationally efficient algorithm, WISP, for estimation of surface orientation. WISP uses simple image observables that are shown to be direct correlates of the surface orientation to compute an initial approximate estimate in a single step. In certain simple cases this first estimate is exact, and in experiments with natural images it is typically within 5° of the final estimate. Furthermore, a proof is given that a rotationally symmetric contour of order three or higher is weakly isotropic. Hence, the WISP algorithm will without modification recover the orientation of any such contour from a perspective view of it.

Rotary Ultrasonic Motor Using Symmetric Contour Vibration of Rectangular Plate

By restraining the center point in the side of a rectangular plate, symmetrical contour vibration can be excited which has nodal points at the centers of the sides. If this contour mode is used instead of the longitudinal mode in an ultrasonic motor, the vibrator can be fixed at the center of the side and will withstand high rotor pressure.

Influence of dynamic spectral information on rate-dependent vowel perception

Earlier research has shown that listeners adjust their identification of spectrally adjacent tense and lax vowels according to the speaking rate of the surrounding sentence. This study attempted to determine whether these rate effects could be reduced if test stimuli more closely resembled natural speech. Two synthetic /æ/–/eh/ series were created: (1) covarying F1 and F2 with syllable duration (i.e., stimuli with more /æ/-like formants were also longer in duration); (2) covarying formant frequencies with syllable duration and with formant frequency contours (i.e., stimuli with more /æ/-like formants and duration had more symmetrical formant contours.) Stimuli from these series were embedded in fast and slow sentence contexts. In series (1), listeners identified more stimuli as /æ/ in fast sentences, showing rate-dependent perception of this tense-lax contrast, replicating Gottfried etal. [Phonetica 47, 155–172 (1990)]. However, in series (2) (with appropriate formant contours—symmetrical for /æ/ and longer offglide for /eh/), listeners showed no significant effect of rate. These results suggest that sentence rate may primarily affect vowel identification when important dynamic acoustic information is absent from the syllable itself.

Finite precision design of optimal linear phase 2-D FIR digital filters

An algorithm is proposed for the design of optimal two-dimensional finite impulse response (2-D FIR) digital filters with finite wordlength and linear phase. This algorithm associates linear programming and a branch-and-bound technique for which two strategies are compared. A large number of examples are presented which show the efficiency of the method for the design of 2-D FIR filters with different specifications and sizes, up to 9*9 in the case of a circularly symmetric contour and up to 13*13 for diamond-shaped filters. Two different types of quantization are also considered.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Phosphorescence excitation spectroscopy in supersonic jets. The lowest triplet state of pyrazine

Motivated principally by dynamic issues, we have observed and assigned the laser-induced phosphorescence excitation spectrum of pyrazine in the collision-free environment of a supersonic jet. The origin of the lowest triplet state (T1) lies at 26 820 cm−1 and exhibits a symmetric parallel-type rotational contour, confirming that this state is 3B3u (nπ*) with an equilibrium geometry that is similar to those of the S0 (1Ag) and S1 (1B3u , nπ*) states. Thirty vibrational bands were also observed in the ∼4000 cm−1 interval between the T1 and S1 origins. Of these, the 13 lower energy bands all exhibit parallel-type contours and may be assigned as T1←S0 transitions, principally involving totally symmetric modes. The 17 higher energy bands exhibit both parallel and perpendicular contours and may be assigned as S1←S0 hot band transitions, some involving nontotally symmetric modes. No evidence for a second, ππ* triplet state lying below the S1 origin is found, nor is there any evidence for rapid relaxation of any of the zero-order T1 levels at a resolution of ∼1 cm−1. We conclude from these and other available spectroscopic data on the isolated molecule that the intersystem crossing dynamics of S1 pyrazine is governed by the interaction of the two largely nested potential surfaces, S1 and T1, zero–order nπ* states that appear to differ primarily in the extent to which they interact vibronically with other zero-order states in manifolds of the corresponding multiplicity.

Optimal trusses transmitting a force to a given contour in creep conditions

The method of contours of complete non-uniqueness, developed by Markiewicz and Życzkowski, is extended to cover the optimization of two-bar trusses under creep conditions. An arbitrarily inclined concentrated force should be transmitted to a symmetric foundations contour. Tangency of this contour to a certain contour from the family of contours of complete non-uniqueness determines the optimal solution. The constraints refer to creep buckling and creep rupture of individual bars. Three different formulations are discussed: minimization of the volume, maximization of the force and maximization of the life-time of the truss.

Symmetrical contours of deep level EL2 in liquid encapsulated Czochralski GaAs

We have determined the isoconcentration contours of the deep level EL2 across 3-in.-diam, semi-insulating GaAs crystals grown by the liquid encapsulated Czochralski technique. The contours are essentially fourfold symmetric at the seed end of the crystals. The symmetrical pattern is independent of the melt stoichiometry and the relative direction of crystal and crucible rotation. EL2 distributions in the tail of the same crystals are often of lower symmetry. The results support a native defect model for EL2 in which the formation of the defect is enhanced by stress in the crystal.

Correction to "Symmetrical Sequence Contours: A Method for Bench-Testing Negative Sequence Detecting Relays"

Correction to "Symmetrical Sequence Contours: A Method for Bench-Testing Negative Sequence Detecting Relays"

Symmetrical sequence contours: A method for bench-testing negative sequence detecting relays

Symmetrical Components is a topic which even a graduate electrical engineer, who took a course on the subject, may not completely understand. Workers who maintain protective relays may have little knowledge of Symmetrical Components. The result of this unfamiliarity may be that relays such as those which respond to negative sequence voltages are never again tested properly, or readjusted to a more desireable setting, after leaving the manufacturer. The intent of this paper is to present a method of bench-testing negative sequence detecting devices by individuals who possess little knowledge of Symmetrical Components.

Extensional vibrations of rectangular crystal plates

A system of one-dimensional equations governing the extensional (contour) modes of vibrations in rectangular crystal plates is derived from the Cauchy–Voigt two-dimensional equations of extensional motion of anisotropic, elastic plates. The system of equations is further divided into two groups of equations governing, separately, the symmetric (contour extensional) and antisymmetric (contour shear) modes of vibrations, by setting the elastic stiffness coefficients γ15 = γ35 = 0 in order to neglect the coupling effect between the two groups. Closed form solutions of contour extensional vibrations are obtained for rectangular crystal plates satisfying the traction-free conditions at four edges. Dispersion relation and frequency equation are obtained in explicit form for the first three contour extensional modes. Resonance frequencies, for various contour extensional modes, are computed as a function of the length-to-width ratio (a/c) of plates. Predicted results are compared with the detailed measurements for rectangular GT cuts with close agreement. Two-dimensional vibration patterns have also been calculated at resonances for different values of a/c ratio.

Longitudinal modes of a cavity ring resonator

An analysis is made of the polarizations, spatial field distribution, and frequency spectrum of longitudinal (axial) modes of a cavity ring resonator with an arbitrary configuration of the axial contour. Use is made of the integral equation method based on the Huygens-Fresnel principle. It is shown that in the longitudinal mode case it is possible to decouple the equations governing the polarization and spatial field distribution. The two-dimensional integral equation for the field distribution has inseparable variables. Its solution is found on a reference plane which intersects normally the axial contour at an arbitrarily selected point. It is found that the equal-amplitude curves on the reference plane are ellipses and—in contrast to the planar resonator case—the directions of the principal axes of these ellipses need not coincide with the directions of the principal curvatures of the wave fronts. The important case of a four-mirror with a symmetric axial contour is discussed in detail.

Thermographic "edge sign" in breast carcinoma.

Thermographic patterns of the breast, both qualitatively and quantitatively, lack specificity in differentiating malignant from benign disease. The recognition of an additional parameter, described herein as the “edge sign,” is considered important for it is the thermographic representation of skin retraction. In some instances, a loss of the symmetrical smooth contour of the normal breast resulting in a localized segment of flattening can be appreciated more readily on the thermogram than by visual observation during a physical examination. Thermography as a preliminary screening procedure serves to identify women who are at high risk for breast cancer, and the combination of an abnormal thermal pattern and the “edge sign” emphasizes the need for additional investigation.

Relaxation treatment of molecular stark broadening

The Liouville operator formalism is applied to the development of a relaxation theory treatment for the electronic Stark broadening of molecular electronic-vibrational system spectral lines. The results are applied to the broadening in the Schumann-Runge system of O 2 at temperatures 3000°K ⪕ T ⪕ 18 000°K and a relative density of one. A comparison is made with the quantum impact theory, and it is found that agreement is good at the upper end of the temperature range. There is deviation at other temperatures since the relaxation theory predicts a shift width ratio varying about as T −2/3 . In all cases considered the theory predicts a symmetrical dispersion contour.