Arc Size Research Articles

Trends of Dental Arc Variation in a Young Adult Male Population and Their Meaning in the Concept of Occlusion

To describe the variation of shape and size of dental arcs the method of principal components was applied. 27 measurements of every dental cast made from 50 young adult males with good occlusion were made, and the following parameters were calculated: 7 widths, 5 left chords, 5 right chords, 5 sagittal lengths (calculated as orthogonal to corresponding width) and 5 angles. Different sets of features were analyzed for both arcs together and for each arc separately. Three independent analyses by the method of principal components show a good description of the main trend of dental arc shape and size variation and a difference between the growth and variation of frontal and distal parts of the arcs. They also describe the variations of occlusion. The trends of dental arc variation ascertained help us to understand the nature of malocclusions and the causes of their preservation in evolution.

Factors determining the efficacy of alpha-helical antimicrobial peptides.

A database of alpha-helical antimicrobial peptides (AMP) was established and their minimum inhibitory concentrations (MIC) were compared with their physiochemical characteristics in an attempt to establish those features that determine efficacy. There is no significant difference in AMP sensitivity between Gram-positive and Gram-negative bacteria but fungi did require higher concentrations to achieve the same degree of growth inhibition. For antibacterial peptides there appears to be a positive correlation between MIC and hydrophobic arc size and a negative correlation between MIC and net charge.

Analytical Surface Roughness Parameters of a Theoretical Profile Consisting of Elliptical Arcs

The closed‐form solutions of surface roughness parameters for a theoretical profile consisting of elliptical arcs are presented. Parabolic and simplified approximation methods are commonly used to estimate the surface roughness parameters for such machined surface profiles. The closed‐form solution presented in this study reveals the range of errors of approximation methods for any elliptical arc size. Using both implicit and parametric methods, the closed‐form solutions of three surface roughness parameters, R t , R a , and R q , were derived. Their dimensionless expressions were also studied and a single chart was developed to present the surface roughness parameters. This research provides a guideline on the use of approximate methods. The error is smaller than 1.6% when the ratio of the feed and major semi‐axis of the elliptical arc is smaller than 0.5. The closed‐form expressions developed in this study can be used for the surface roughness modeling in CAD/CAM simulations.

Vestibular evidence for the evolution of aquatic behaviour in early cetaceans

Early cetaceans evolved from terrestrial quadrupeds to obligate swimmers, a change that is traditionally studied by functional analysis of the postcranial skeleton. Here we assess the evolution of cetacean locomotor behaviour from an independent perspective by looking at the semicircular canal system, one of the main sense organs involved in neural control of locomotion. Extant cetaceans are found to be unique in that their canal arc size, corrected for body mass, is approximately three times smaller than in other mammals. This reduces the sensitivity of the canal system, most plausibly to match the fast body rotations that characterize cetacean behaviour. Eocene fossils show that the new sensory regime, incompatible with terrestrial competence, developed quickly and early in cetacean evolution, as soon as the taxa are associated with marine environments. Dedicated agile swimming of cetaceans thus appeared to have originated as a rapid and fundamental shift in locomotion rather than as the gradual transition suggested by postcranial evidence. We hypothesize that the unparalleled modification of the semicircular canal system represented a key 'point of no return' event in early cetacean evolution, leading to full independence from life on land.

OPTIMIZATION OF WELD BEAD DIMENSIONS IN GTAW OF ALUMINUM–MAGNESIUM ALLOY

The Gas Tungsten Arc Welding (GTAW) process is frequently used in welding of aluminum alloys, because of its possible heat input control. This control can be utilized through a good selection of the process variables, which in turn results in optimizing the bead dimensions. The object of this investigation was to study the effect of TIG process parameters on weld bead dimensions. Suitable combinations of tungsten electrode parameters and process variables can lead to optimum GTAW bead dimensions. With alternative current (AC) polarity, a weld bead may be formed between two 3-mm thick pieces of 5005 aluminum–magnesium alloy sheets. The effect of electrode diameter, vertex angle, and the welding current and speed on the bead dimensions were investigated. Results revealed that the rate of increase of bead width with current increase is greater than that produced by decreasing travel speed, and means that the bead width can be controlled more efficiently by welding current rather than by welding speed. For example, bead width can be reduced by half by increasing the welding travel speed three times, whereas it can be doubled when the current has is doubled. In contrast, bead depth is found to be more sensitive to welding speed rather than to the welding current. One of the important results of the present investigation was that the average heat-affected zone width decreased as the welding current and/or speed increased. On the other hand, it was found that the influences of electrode diameter and apex angle on the bead width were similar to their effects on the arc size. The bead width was found to decrease with an increase in the electrode diameter to a certain extent, and increase slightly with an increase of the apex angle.

Analysis of the impedance spectra of short conductive fiber-reinforced composites

The presence of small amounts of short conductive fibers in a composite of finite matrix conductivity results in the subdivision of the one matrix impedance arc into two separate low and high frequency arcs in the complex impedance plane. These features are attributable to a “frequency-switchable” interfacial impedance on the fiber surfaces, rendering them insulating at DC and low AC frequencies, but conducting at intermediate frequencies. A combination of physical simulations (single wires in tap water) and pixel-based computer modeling was employed to investigate the roles of fiber pull-out, debonding, and orientation on the impedance response of fiber-reinforced composites. The ratio of the low frequency arc size to the overall DC resistance (γ-parameter) is sensitive to pull-out and/or debonding, especially when a fiber just barely makes contact with the matrix. The γ-parameter is also quite sensitive to fiber orientation with respect to the direction of the applied field. Ramifications for the characterization of cement, ceramic, and polymer matrix composites are discussed.

Spectroscopic measurements of radial distribution of electron density and temperature in a plasma

A set of spectroscopic measurements in a high-voltage circuit breaker has been performed in order to evaluate the radial distribution of the electron density and temperature in a section of the arc, and their time evolution in the last half-period of the current before the arc extinction. The measurements have been made at various values of effective current and at two different distances from the fixed electrode. The arc sizes have also been evaluated. A spectroscopic device has been built based on two very fast bi-dimensional CCD detectors, providing observations in the visible range with simultaneous spectral resolution of 0.1 nm, spatial resolution lower than 0.5 mm and time resolution down to with a frame every 0.5 ms over a total observing time of about 10 ms. The lines S II 5453.8 A and F I 6348.5 A have been observed and the Abel inversion has been performed. By measuring the intensity ratio of the two lines, the temperature has been measured and through their Stark broadening the density has been evaluated. The experimental set-up is shown, the arc modelling and the procedure used to obtain the results are presented, the equations are discussed and their physical conditions of validity, particularly the LTE and the condition of small optical depth, are verified. The main results achieved, concerning the arc size, the maximum values of electron density and temperature, at various test currents, and their radial profiles in a section of the arc, are reported.

Plasma diagnostics in a metal vapor vacuum arc ion source (abstract)

We have developed a metal vapor vacuum arc ion source, which was used for film deposition. Based on this source, some experimental diagnostics of plasma parameters are presented in this paper. Characters of vacuum arc cathode spots, including number, size, motion, and lifetime, are studied using a high-speed photograph technique. Substrate bias voltage dependence of plasma microparameters, such as electron density and electron energy, are measured by a Langmuir probe measurement system. In conclusion, some discussion of experimental results are also presented.

Prebreakup arcs: A comparison between theory and experiment

We have developed a model describing the structure of a prebreakup arc based on an ionospheric Cowling channel and its extension into the magnetosphere. A coupled two‐circuit representation of the substorm current wedge is used which is locally superimposed on both westward and eastward electrojets. We find that brighter, more unstable prebreakup arcs are formed in the premidnight (southwest of the Harang Discontinuity) than in the postmidnight (northeast of the Harang Discontinuity) sector. This contributes to the observed prevalence of auroral activity in the premidnight sector. Also, our model predicts that the north‐south dimensions of the current wedge in the ionosphere should vary from a few kilometers at an invariant latitude (Λ) of 62° to hundreds of kilometers above Λ = 68°. Comparison of the model results with the extensive observations of Marklund et al. (1983) for a specific arc observed just after onset shows good agreement, particularly for the magnitude of the polarization electric field and the arc size. We conclude that this agreement is further evidence that the substorm breakup arises from magnetosphere‐ionosphere coupling in the near magnetosphere and that the steady state model developed here is descriptive of the breakup arc before inductive effects become dominant.

Dimensionless relations for predicting arc size in a generator

The Rosa et al. (1988) theory for arc behavior in a boundary layer is presently simplified and nondimensionalized in order to clarify the dependence of arc size on the various operating conditions, as well as to facilitate the correlation of experimental data and its extrapolation to full-scale hardware. The dimensionless law derived can predict arc size on the electrode walls of an MHD device; the predictions obtained agree with both experimental data and the results of a more complex numerical model.

The Mammalian Dentition, a 'Tangled' View

Detailed knowledge of the mammalian dentition has increased enormously during the past few decades, yet the general view of the dentition has changed very little. Synthetic work connecting knowledge from different areas is possible and holds great promise, even if the synthesis is tangled and incomplete. The natural milieu for such a synthesis is the evolutionary framework. Important components of the tangle, as it appears at present, are identified and briefly discussed, mainly from a functional and palaeontological point of view. Such components arc size in relation to function and growth, the dynamics of the masticatory machinery during chewing, and especially its changes during ageing and during evolutionary history, enamel structure in relation to wear and stress, and problems of growth, homology and phylogcny. Rccognition of evolutionary constraints is possible and useful.

Electric arc behavior in a boundary layer

The objective of this work is to understand how the size of an arc on the electrode of a magneto-hydrodynamic (MHD) generator or accelerator depends on operating parameters such as boundary-layer shape and current density. Arc size has an important bearing on device lifetime and performance. A boundary layer in an MHD device is a region of exceedingly steep gradients including, in particular, the gradient of electrical conductivity. A theory relating arc size to the characteristics of these gradients is developed and compared with behavior observed in various MHD devices, most recently that in the Component Development and Integration Facility in Butte, Montana. 32 references.

The ARC Mantle

Through differntial (Wollastoferometric) inter- erometric diagnostics, the radial distributions of temperature and air particle density (at various times within a current pulse) within the arc mantle, and the timewise distributions of arc size and mantle thickness have been obtained in the region upstream of the throat in a single flow orifice nozzle interrupter. Effects of metal vapor were also determined using upstream electrode tips of graphite, copper-tungsten, and copper.

Switching and Fault-Close Design and performance of Loadbreak Separable Connectors at 21.1 kV/36.6kV

Development of a full three-phase rated 21.1kV/36.6kV loadbreak separable connector system presents a design challenge in the area of switching and fault-close. Increased strikeover distance, higher arc energy and size constraint of an operable connector system require design features that pushed the state of the art relative to designs presently used for 8.3kV/14.4kV and 15.2kV/26.3kV connector systems. This paper discusses a design incorporating these features and presents performance data showing the high level of reliability achieved.

Switching and Fault-Close Design and Performance of Loadbreak Separable Connectors at 21.1kV/36.6kV

Development of a full three-phase rated 21.1kV/36.6kV loadbreak separable connector system presents a design challenge in the area of switching and fault-close. Increased strikeover distance, higher arc energy and size constraint of an operable connector system require design features that pushed the state of the art relative to designs presently used for 8.3kV/14.4kV and 15.2kV/26.3kV connector systems. This paper discusses a design incorporating these features and presents performance data showing the high level of reliability achieved.

Observations of Filaments at Centimeter and Millimeter Wavelengths

At cm and mm wavelengths, the quiescent prominences seen on the disk appear as depressions in brightness temperature that are well correlated with Ha dark filaments. In a large number of cases, the sizes of the radio and optical filaments are similar. However, in some cases, the radio filaments have been found to be broader and to persist longer than their optical counterparts. Undisputed examples of broadening have been provided by Kundu and McCullough (1972) at 9 mm (2;5 arc size compared to Ha size of 0;5), and by Kundu et al. (1978) at 5 wavelengths between 0.4 and 11 cm (with half-power beam widths of 017-5’) of a filament whose undeconvolved angular size, 2;2 × 2;7, greatly exceeded the 0;5 × 0;5 nize of the enclosed Ha filament. Specific examples of persistance have been provided by Kundu (1972) and by Kundu and Lantos (1977) who observed 3.5 mm ‘disparition bursque’ events. In the two events, Ha filaments were observed to lie. within the contours of a radio depression; after the Ha filaments disintegrated, the radio depression persisted, though with reduced contrast The depressions reach temperatures below the background of up to 400 K at mm-λ and ~ 1000-5000 K at cm-λ. These values correspond to brightness temperatures of ~ 6000 K at mm-λ and 7000-14000 K at cm-λ.

The DC Arc in a Supersonic Nozzle Flow

The boundary layer integral method at its second level of approximation has been used to study the DC arc in a supersonic nozzle flow. It is shown that with the inclusion of the arc momentum balance, the critical point of the flow is, generally, not the sonic point of the external flow. The speed, at which a disturbance propagates relative to the external flow, is in general supersonic and is dependent on the arc conditions. The arc model is capable of predicting the axial electric field, the arc size and the axial pressure distribution as a function of current. For affinely related nozzles, the solution is determined by a parameter N, which is related to zt, the stagnation condition and the nominal current density at the throat (I/At). Numerical results are given for a particular nozzle shape although the method of analysis is general. Practical implications as regards nozzle design for a gas blast circuit breaker are briefly discussed.

The effective drag width of short moving arcs in argon

Previous experiments have shown that short arcs rotating between ringshaped electrodes in a radial magnetic field move at a speed which is controlled by aerodynamic drag on the arc column when the pressure is above 1-2 atm. For these conditions it is possible to calculate an effective average arc size (which includes a drag coefficient) transverse to the direction of motion. Measurements have been made which enable the change in this effective arc size due to (a) arc speed, (b) arc current, (c) inter-electrode spacing and (d) gas pressure to be estimated for arcs moving in argon at a pressure of 3 atm. These changes are shown for arc speeds up to 80 m sec-1, arc currents up to 700 A and for spacings up to 1 cm, and it is suggested that electrode material introduced by vapour jets may be a significant factor.

溶接現象に関する界面張力理論(第3章)

Assuming that the contact angle of mother drop upon the surface of penetration is a constant value θ0, the pulling force acting on the contact line of the mother drop was calculated, by which the oscillation of the mother drop was caused. It was concluded as follows.(1) Defining the X-and Y-component of pulling force due to the interfacial tension acting upon ds part along the depressed contact line of the mother drop within the surface of penetration as dFX and dFYdFS=γS⋅dY, dFY=γY⋅dX, γX=γ(cosθ0 cos θg+sinθ0 sin θg/cos α)γY=γ cos θ0/cos θgwhere θg; angle of inclination of the surface of penetration at point Pα; angle between the contact line and equi-depth contour line at point P(2) Using the above equation, there is found a strong pulling force acting upon the contact line near the point where it starts to deviate from the melting line of the surface of penetration, which tends to pull back the drop to the melting line.(3) If the depressed contact line of mother drop starts to displace itself, the movement is accelerated by the digging action of arc upon the bare surface of mother plate.(4) The interaction between these forces and the digging action of arc brings about an oscillation of the mother drop and a displacement of exposed surface of mother plate, which results in uniform penetration. The shape of penetration depends on the strength of arc force or size of depressed part of mother drop.