Continuous Planar Research Articles

Optimum Placement of Vibration Control Actuators in Planar Structures Using Voronoi Diagram.

A method determining the optimum placement of vibration control actuators using the Voronoi diagram was proposed focusing on the continuous planar structures. The entire plane is partitioned by a Voronoi diagram which consists of the same number of polygons as that of vibration control actuators. The objective function consisting of the locations of actuators and vibration mode amplitude is minimized for optimization. The location of actuators obtained by the proposed method was found to have effective vibration control capability through finite-element response analyses.

Convergence and Continuity Criteria for Discrete Approximations of the Continuous Planar Skeleton

It has been proposed recently that the skeleton of a shape can be computed using the Voronoi diagram of a discrete sample set of the shape boundary. This method avoids many of the complications encountered when computing the skeleton directly from an image because it is based on a continuous-domain model for shapes. In order to make better use of this new approach, it is necessary to establish a bridge between the continuous domain skeleton and its approximation obtained from the discrete boundary sample set. In this paper, the skeleton and Voronoi diagram formulations are briefly reviewed and elaborated upon to establish criteria for the functions to be continuous. Then the new continuity results are related to the discrete sample set model in order to establish conditions under which the skeleton approximation converges to the exact continuous skeleton.

Convergence and Continuity Criteria for Discrete Approximations of the Continuous Planar Skeleton

Convergence and Continuity Criteria for Discrete Approximations of the Continuous Planar Skeleton

Electronic properties of the ordered delafossite-type superoxides YCuO2+ delta.

Electronic-structure calculations have been carried out on the ordered delafossite-type superoxides ${\mathrm{YCuO}}_{2+\mathrm{\ensuremath{\delta}}}$ (0.5\ensuremath{\le}\ensuremath{\delta}\ensuremath{\le}0.7) that Cava et al. have synthesized recently by inserting interstitial O into the triangular Cu planes of ${\mathrm{YCuO}}_{2}$. The results exhibit a unique feature where each interstitial O inserts two half-filled, cluster-derived ${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ ``impurity levels'' into the \ensuremath{\sim}2.7-eV semiconductor gap of ${\mathrm{YCuO}}_{2}$. These levels evolve into half-filled ``impurity bands'' as adjacent clusters are corner-linked to form continuous one-dimensional (1D) linear (\ensuremath{\delta}\ensuremath{\approxeq}1/2) and 2D planar (\ensuremath{\delta}\ensuremath{\approxeq}2/3) networks that may exhibit interesting transport and magnetic properties.

Statistical Theory of Surface Tension and Molecular Orientations in Nematic Liquid Crystals. III. On Hard Flat Walls

The surface tension of nematic liquid crystals on a hard flat wall is calculated in the mean field approximation assuming that the molecules are non-polar rigid rods and interacting via attractive dispersion forces as well as hard-core repulsions. It is found that the isotropic part of the dispersion force prefers the normal molecular orientation at the wall surface, while the excluded volume effects due to the hard-core repulsions between the wall and molecules and among the molecules both promote the planar alignment on the surface. Possible orientational phase transitions on the wall are predicted to be either a discontinuous planar to normal transition or continuous planar to tilted transition as the temperature is lowered. Therefore, the former type of transition observed really in cyanobiphenyls can be well explained.

Tunable far-infrared laser spectroscopy of van der Waals bonds: thejkc= 10← 00Σ bending vibration of Ar-14NH3

Hyperfine resolved spectra have been measured for the Ar-NH3 complex over the range 21–28 cm-1 using a tunable far-infrared laser in combination with a continuous planar supersonic jet. Twenty-three transitions are assigned to the lowest Σ-bending vibration (v 0 = 26·470633(77)cm-1) from the (asymmetric) inversion level of the Σ, j k c = 00 internal rotor state of NH3 to the Σ, (10) symmetric inversion level. A nearly free-rotor model is used to deduce the zeroth-order intermolecular vibrational energy-level diagram and corresponding selection rules, which are used in assigning the spectra. All evidence obtained in this study supports the contention of Nelson et al. that NH3 is an inverting nearly free rotor in this T-shaped complex.

Tunable far infrared laser spectroscopy of van der Waals bonds: Vibration–rotation–tunneling spectra of Ar–H2O

The first high resolution spectra of a rare gas–H2O cluster have been observed using a tunable far infrared laser to probe the vibration–rotation–tunneling levels of Ar–H2O formed in a continuous planar supersonic jet. The high sensitivity of this spectrometer facilitated extensive measurements of two perpendicular subbands which are assigned to transitions from the ground state to the upper component of a hydrogen exchange tunneling doublet (c-type) at 21 cm−1, and to vb1 =1+ (b-type) at 25 cm−1, the lower tunneling component of a bending vibration which is perpendicular to the tunneling coordinate. The tunneling splitting is shown to be in the range 2.5–7 cm−1 and the lower tunneling component of the excited bending vibration lies between 39 and 43 cm−1 above the ground state of the complex. The experimentally determined center-of-mass separation (Rc.m. =3.75 Å) and harmonic stretching force constant (ks =0.0134 mdyn/Å) are compared to those of related first and second row hydrides. The large amplitude motions occurring within this complex make it difficult to establish its structure.

Shaped patterns from a continuous planar aperture distribution

A pattern synthesis procedure is developed for a planar aperture with a circular boundary. A (Ø-symmetric continuous distribution is assumed and required to produce a flat-topped beam with controlled ripple, surrounded by ring side lobes of controlled height. With M filled-in nulls in the shaped region, there are 2M solutions for the aperture distribution. Sampling can yield the excitation of a circular grid planar array. Linear stretching extends the results to an elliptical boundary.

Tunable far-infrared laser spectroscopy in a planar supersonic jet: The Σ bending vibration of ArH 35Cl

The lowest Σ bending vibration (0200) of ArH35Cl has been observed near 23.6 cm−1 from P(23) to R(17), in a continuous planar jet expansion using a tunable far-infrared laser. A least-squares analysis has been performed to determine the centrifugal distortion constants for the ground and excited states, which will greatly facilitate the determination of an accurate intermolecular potential surface.

Novel calcium-doped yttrium-iron-garnet thermistor bolometer in a planar and continuous bridge configuration

A new material, calcium-doped-yttrium iron garnet (Ca:YIG), which proves very promising in room-temperature thermistor bolometer applications, has been used to construct a continuous planar bridge structure which works as a thermistor bolometer detector (YIGTB). Experimental results concerning the electrical response of the bridge as a function of the position of the incident laser light beam are in perfect agreement with those predicted by computer simulation. Since the Ca:YIG has a relatively low thermal capacity and is highly adsorbing from the visible to the infra-red, YIGTB has proved highly responsive and faster than other commercial thermistors.

Domain Nucleation in Magnetic Thin Films by Localized Fields Produced by Thin Stripline

The nucleation of reversed domains has been studied by means of the Kerr magnetooptical apparatus for a continuous planar film subjected to an easy direction local dc field produced by a microstripline and a hard direction homogeneous dc field. From the observed domain patterns, the mode of the domain nucleation is categorized into the following two types, depending on the intensity of the hard direction field. For the small hard direction fields, the domain nucleation takes place uniformly over all the area covered by the stripline. For the large hard direction fields, the nucleation takes place nonuniformly in the area under the stripline so that the island-shaped reversed domains appear at almost equal spacings along the stripline. These interesting phenomena associated with the domain nucleation are understood clearly on the basis of the one-dimensional model.

Optimal heat pipe heat exchanger design

Abstract A typical heat pipe heat exchanger with continuous planar fins and a staggered equilateral triangular pitch of the tubes is subject to optimization from the point of view of the ratio heat flow/weight and heat transfer effectiveness. Different optimization procedures are explained in detail and numerical results are given in the application. The procedures are as follows. 1. A. If hot and cold fluid mass flow velocities in the minimum free flow areas are given, one obtains the maximum of the ratio heat flow, Q /mass, M for optimal values of fin density and equilateral triangular pitch. The ratio of evaporator to condenser lengths observes a relation which allows Q/M to be permanently at its peak with respect to the dimensionless saturation temperature. 2. B.1. One obtains the maximum of the ratio heat flow/evaporator mass for optimal fin and triangular pitches. 2. One selects the cold fluid mass flow velocity G 2 so as to obtain equality between evaporator and condenser fin side heat transfer coefficients. The optimal pitches found at the evaporator also lead to the maximum of heat flow/condenser mass. 3. There is an optimal value of the ratio of evaporator to condenser lengths which ensures Q/M to be a maximum with respect to the dimensionless saturation temperature. 3. C.1. As B.1.2. G 2 remains variable. A condenser with maximal heat exchanger heat transfer effectiveness is “linked” to the optimized evaporator. One obtains the ratio of evaporator to condenser lengths and the ratio of hot and cold fluid heat capacities as optimal functions of G 2 . 4. D.1. As B.1.2. G 2 remains variable. The ratio of evaporator to condenser lengths is selected from the condition: Q/M maximum with respect to the dimensionless saturation temperature. It follows that this ratio becomes an optimal function of G 2 . The ratio of the heat capacities is derived as an optimal function of G 2 too. The heat flow value, the number of tubes in a row and the number of rows do not affect optimization results. The optimization procedures presented in this paper may be used, with adequate transformations, for other heat pipe heat exchanger configurations.

The internal structure of nephrite: experimental and computational evidence for the coexistence of multiple-chain silicates within an amphibole host

Ultra-structural variations in samples of nephrite jade have been elucidated by a combination of high resolution electron microscopy, which explores local structure in a direct, ‘real space’ manner, and computational procedures using the so-called ‘multislice’ approach which enables the image generated under a given set of electron-optical conditions to be calculated as a function both of unit cell content and of specimen thickness. Microanalyses by electron-stimulated X-ray emission and by optical diffractometry (of micrographs) were also used. Planar faults on (010) occur frequently in nephrite. These are of several distinct kinds, all of which have been characterized. The host amphibole, consisting of double chains of linked SiO 4 tetrahedra, is shown frequently to accommodate triplechain lamellae which are coherently attached to the double-chain matrix on (010) planes. These triple-chain faults may occur in isolated fashion, but sometimes are arranged recurrently, in a disordered manner, within the amphibole host. The nephrite may also accommodate extended regions of a new, triple-chain mineral structure, the maximum observed width of this coexistent phase being ca. 340 A. Other planar faults, composed of regions with chain widths ranging from one to six SiO 4 tetrahedra, have been detected and fully identified on the basis of the correspondence between theoretically calculated and observed images. Detailed structural drawings for the continuous planar faults, as well as others that are described, are given. It is shown that edge-sharing of tetrahedra probably occurs close to the termini of certain types of discontinuous fault and that, in other cases of defect termination, screw-type dislocations may be incorporated to preserve the strain-free, structural regularity of the host. It has not yet proved possible, with currently available in situ X-ray microanalytical techniques, to assign chemical compositions to the new structural types that have been brought to light by this study.

The thermal activation of magnetic domain walls from continuous and discontinuous planar pinning sites

Abstract It is shown that thermally activated escape of a 180° domain wall, from a continuous planar pin, is possible in a magnetic field that is less than the absolute-zero coercive field. The model treated assumes a pinning force that depends on the square of the wall displacement. A thermally activated blister can form in a critical field that is less than the coercive field, and may then peel away allowing the wall to escape. A generalized solution for the blister energy is developed which can be scaled to fit the magnetic constants of different materials. An expression for the coercive field is derived which depends linearly on temperature (if the basic magnetic parameters of the pin and matrix are temperature-independent). An expression for a magnetic viscosity parameter is also derived. At a sufficiently high temperature, a discontinuous planar pin will behave as though it is continuous. The criterion is that the area of the discontinuous fragments must exceed a value proportional to T−½ .

Energy losses of protons moving in the planar channel

Abstract The average energy losses of channeled protons have been studied, both experimentally and theoretically, as a function of dechanneling depth in the planar channel of a W single crystal. The experimental values for the average losses have been obtained from normalized energy spectra of backscattered protons when the crystal planar channel is aligned with the beam. The theoretical description is based on the use of the approximation for continuous planar potentials and on the calculated variation of the mean energy of the transverse motion of particles with depth.

The application of rotational switching model to a cylindrical magnetic film and continuous planar film

A numerical method is presented to extend the coherent rotation model to the study of the dynamic switching behavior of continuous magnetic films for a nonuniformly distributed applied field. This field seriously affects the switching behavior of the film. Infinite planar films and cylindrical films with an applied magnetic field produced by a hairpin word strap are used as examples. The induced voltage from magnetic films is found to be very sensitive to the wave shape of the applied magnetic field as well as to the rise time and amplitude of the field. The calculations also include the bandwidth-limited sense system, which attenuates and distorts the induced voltage. A comparison with an experimental voltage from a cylindrical film was made. Also, the magnetostatic field distributions along the hard direction are determined for the static condition when torques on the magnetization approach zero.

Adjacent element magnetic coupling in continuous film memories

Experimental measurements demonstrate that in magnetic film memory geometries employing continuous planar films, film strips, or plated wires, word line to word line coupling is enhanced by the presence of the intervening magnetic material. Rotation of the magnetization under a word line neighboring a driven word line can be several times greater than that which would occur for mechanically defined elements. Appropriately placed keepers can drastically reduce this interaction. The interaction is most severe for thick, low H K film material and tight element spacing. Theoretical analysis and experimental results show that for typical keepered geometries, the magnetic field inside the magnetic material decreases approximately exponentially with the distance from the driven word line. The attenuation constant α can be conveniently determined from the material parameters and element dimensions by calculating the series and shunt reluctance per unit length.

Ferromagnetic Resonance in Single-Crystal Nickel Films

Ferromagnetic resonance measurements have been carried out on single-crystal nickel films obtained by epitaxial evaporation on NaCl under various evaporation conditions. Resonance measurements on thin films by previous investigators have yielded anomalous values of 4πM which have tentatively been attributed to stress in the films. In this paper it is shown that there is a second factor which must be taken in consideration to explain the shift in resonance peak. Films that were grown at high temperatures (400°C) and in good vacuum (10−10 mm Hg) exhibited an apparent saturation magnetization only 60–70% of the bulk value. This is in accord with the results of ferromagnetic resonance experiments of Kuriyama et al., who attempted to explain their results by the presence of large tensile stresses in the films. However, electron microscope studies of films grown under the above conditions indicated that the films formed discrete, well-separated islands of nickel. The observed particle sizes are such that the demagnetizing factor perpendicular to the film is 60–70% of the value for a continuous planar film. This implies that the shift in the resonance peak was caused not by stresses but by a lowering of the demagnetizing field resulting from the discrete particle growth. To further substantiate this, continuous films grown at lower temperatures (300°C) and in technical vacuum (10−5 mm Hg) exhibited a magnetization approximately 60% higher than the bulk material values. X-ray diffraction indicated the presence of large compressive stresses in these films. That the increased magnetization was induced by these compressive stresses was convincingly shown by the decrease of the saturation magnetization to bulk value when the stress was relieved by the introduction of water vapor into the cavity. No such change in the external field at resonance was observed for the discontinuous films under a similar exposure to water vapor.