Showing papers on "Tilt (optics) published in 1984"

The effect of a grain boundary structural transformation on sliding in -tilt zinc bicrystals

Abstract: The effect of temperature on grain boundary sliding has been studied for tilt boundary, which is slightly off the 56–6° /σ9 near-coincidence orientation relationship. For a 16–5° low-angle tilt boundary, no change in the temperature dependence was observed over the entire test temperature range up to the melting point, and the activation energy for sliding is similar to those for high-angle grain boundaries below Tc. It...

Effect of Pelvic Tilt on Standing Posture

Abstract: Low back dysfunction is associated in many cases with lumbar lordosis, and tilting the pelvis posteriorly is often recommended for therapeutic purposes. The influence of pelvic tilt on the spinal curves has not been studied. The purpose of this study was to use an objective noninvasive method to determine the effect of the pelvic tilt on the spinal curves in the sagittal plane. Thirty-two healthy subjects and 15 patients with chronic low back dysfunction (CLBD) were studied. Patients with CLBD and healthy subjects were instructed in performing active anterior and posterior pelvic tilt maneuvers, first in the supine and then in the standing position. Comparisons between the Patient Group and the Healthy Group were made for several variables representing the severity of spinal curves, pelvic orientation, hip orientation, and knee orientation. A computerized system, the Iowa Anatomical Position System, was used to obtain coordinates of external body surface landmarks from which pelvic tilt measurements were determined. The results showed that the voluntary pelvic tilt did not alter the thoracic spinal curve. For both the Healthy Group and the Patient Group, the lumbar curve was altered by the pelvic tilt: anterior tilt increased the depth of the lumbar curve and posterior tilt decreased the depth of the lumbar curve. The amount of pelvic tilt was the same whether knees were extended or flexed approximately 10 degrees. Pelvic tilt also tended to influence the orientation of the head and other parts of the body.

A simply constructed extreme-tilt holder for the Philips eucentric goniometer stage

Abstract: SUMMARY A simple single-tilt holder has been constructed for the eucentric goniometer stage of the Philips EM 400. This holder is also compatible with the EM 300 series stages. The main improvements are as follows: unlimited tilt range using ‘25°’ polepiece configuration; secure gripping of all types of specimen grids by an easily operated micro-clamp; elimination of shading effects by the holder at high tilt angles; and reduction of potential sources of astigmatism at high tilt angles.

Subaperture optical system testing.

Abstract: Full aperture optical system wave-front accuracy obtainable from single or. multiple subaperture wave-front measurements is analytically determined and illustrated with numerical examples. Insight gained from the analytic derivation and confirmed by the examples shows the effect of subaperture size, placement, and accuracy. The analysis also demonstrates that accurate full aperture aberrations (except tilt) can be estimated even with large uncertainty in relative subaperture tilt.

Dispersion Relation of Optical Eigen Modes in Chiral Smectic C by 4×4 Matrix Method

Abstract: Dispersion relations of optical eigen modes (OEM's) in Sm C* are calculated by the 4×4 matrix method. The first order reflection region (full pitch band) consists of only a total reflection region. The structure of the second order reflection region, corresponding to that of the first order in cholesterics, strongly depends on the tilt angle of Sm C* and the propagation direction of OEM's. For a tilt angle smaller or larger than that of light propagation, the reflection region splits into three or consists of a single region with a structure.

The temperature dependence of liquid‐crystal tilt angles

Abstract: The temperature behavior of various liquid crystals has been studied on obliquely evaporated SiOx (α°) layers. The structure of such layers is discussed and the competition between the effects of two inherent anisotropies of these layers is indicated as the possible origin of the observed temperature dependence of the tilt angle. Attention is also paid to the structure of liquid‐crystal layers close to the nematic to isotropic transition temperature (clearing point). Experimental results for tilt angles as a function of temperature have been adapted to a two‐torque model, which is suggested by the above considerations. This allows comparison between the structural data for SiOx and the parameters from the two‐torque model. It is found that indeed one of the directions of preference is connected roughly with the columnar axis of the SiOx.

The Tilt of the Leading Edge of Mesoscale Tropical Convective Lines

Abstract: The tilt with height of the leading edge of seven mesoscale convective lines in GATE is determined by two independent methods. When averaged over time and along the line axis, the tilt is found to he surprisingly shallow, between 20 and 35 degrees from the horizontal. This is distinct from the slopes of the individual towers, which can be much steeper. The line leading-edge slope corresponds to the ratio of the vertical to horizontal velocity, relative to the line motion, of “representative” embedded convective cores.

Anticlockwise Rotation, Eccentricity and Tilt Angle of the Wind Hodograph. Part II: An Observational Study

Abstract: Following the theory of Kusuda and Alpert (Part I), expressions for the eccentricity and tilt angle of the surface-wind hodograph at different latitudes are derived as functions of the amplitude and phase shift of the horizontal thermal force and also of some reasonable frictional parameter. Further, analyses of 47 hodographs in Washington, Oregon and California give the observed tilt angles, eccentricities and senses of rotation. The tilt angle is nearly linearly dependent on latitude. Eccentricities are in general high (0.9–1) and higher friction leads usually to higher eccentricity. However, eccentricity may sometimes be very small giving a circular hodograph) even with high friction and also very high with low friction; the latter case is primarily due to a phase shift between the horizontal thermal forces. It is shown that although in general the frequency of ACR (anticlockwise rotation) hodographs decrease northward in the Northern Hemisphere, lower friction may lead to a minimum in ACR fre...

The effects of dipole tilt on the structure of the magnetosphere

Abstract: The structure of the magnetosphere as a function of dipole tilt was studied by using a global magnetohydrodynamics (MHD) model. We show here that the cusp current sheet in the MHD model is related to the tail current sheet and that the calculated shape and positions of the tail current sheet are consistent with observations. In addition, we discuss the difference between the MHD model and the Chapman-Ferraro type model which manifests as a function of tilt angle.

Tilt stability of arbitrary aspect ratio ion rings

Abstract: A study is made of the low‐frequency tilt stability of finite aspect ratio field‐reversed ion rings. A new analytic‐numerical method is described which overcomes the large‐aspect‐ratio assumption of previous analytical treatments. The method involves the numerical evaluation of the Vlasov time history integrals for the ring particles using orbits determined numerically in numerically calculated self‐consistent equilibria. The method is applied to the tilt stability of fat, noncircular cross‐section rings. The condition for tilt instability is found to be of the form ωz>kΩ, where the parameter k varies from 0.7 to 1.0 for the cases studied, and where ωz is the mean axial betatron frequency and Ω is the mean toroidal circulation frequency. For weak rings (field‐reversal factor δ=Bself/Bex≤1), k approaches unity, whereas for strong rings (δ≊2), k≊0.7. As a given ring is elongated axially it is found that ωz decreases, while Ω changes relatively little. A saturation mechanism is proposed whereby tilt unstable...

Optical Surface Evaluation

Abstract: The finite element analysis of mirrors is now common practice. The results of such an analysis is the vector displacement of a great number of grid points within the mirror. Evaluation and interpretation of the raw data is difficult, even when represented as contour plots. It is more convenient from an optical engineer's viewpoint to describe the total deformation in terms of its components: tilt, defocus, and common aberrations. A NASTRAN post-processing program is described which performs a least squares fit of Zernike polynomials to a deformed surface.© (1984) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Specimen manipulating mechanism for charged-particle beam instrument

Abstract: A tilt stage that tilts about Y axis perpendicular to the optical axis of an electron beam which is called "the Z axis" herein is mounted to the front cover of a specimen chamber. A Z-axis stage capable of moving in the direction of Z axis and an X-axis stage capable of moving in the direction of X axis perpendicular to Y and Z axes are mounted on the tilt stage. A specimen holder for holding a specimen can be located at any desired position relative to the electron beam by the movements of these stages. Two driving shafts are disposed concentrically about the Y axis, i.e., their common axis. Driving mechanisms for independently driving the driving shafts along the Y axis are mounted to the front cover of the specimen chamber. The movements of the driving shafts are transmitted to the Z-axis stage and the X-axis stage via two levers whose pivots are supported on the tilt stage.

Tilt steering equipment

Abstract: In a tilt steering equipment including a main bracket mounted to a vehicle body; an upper bracket with a steering wheel, which is pivoted at the main bracket around a tilt center; and a driving means supported by the main bracket to tilt the upper bracket against the main bracket, the driving means in fixed to the main bracket and has a drive center spaced from the tilt center and an engaging pin which rotates around the drive center. The upper bracket has an engaging slotted hole in which the engaging pin is inserted. According to the tilt steering equipment of this invention, the drive center of the driving means is spaced from the tilt center. Therefore, it is easy to assemble the equipment with high accuracy and a smaller torque is enough to tilt the upper bracket to the main bracket.

Optical pickup apparatus for recorded information with tilt indication

Abstract: An optical pickup apparatus for reading information recorded on a recording medium, having an optical pickup device and a tilt servo control system for adjusting the angular position of the pickup device, the tilt servo control system comprising a deviation detection means including a light emitting means and a light receiving means, for detecting a deviation of the angle between an axis of the reading light from the optical pickup device and the surface of the recording medium from a right angle and generating a deviation detection signal, and a tilt drive mechanism connected to the optical pickup device, driven by a tilt drive signal generated from the deviation detection signal. The apparatus is characterized by a means for opening the servo loop of the tilt servo system when the light beam from the light emitting means has approached a portion of the recording medium in which no recording tracks are provided.

An Analysis of Temperature Effect in a Finite Journal Bearing with Spatial Tilt and Viscous Dissipation

Abstract: The analysis presented herein deals with the evaluation of the pressure, velocity, and temperature profiles in a finite-length plane journal bearing. The geometry of the case under study consists of a spatially tilted shaft. The two-dimensional Reynolds equation accounts for the variation of the clearance gap h with x and z and is used to model the pressure field. The latter is solved for a variety of shaft tilt angles and then used to calculate the two-dimensional flow field. Finally, the flow field is used in the energy equation to solve for the film temperature profile, when the effect of viscous dissipation is taken into account.

Venetian blind with selective tilt limiting

Abstract: A venetian blind which may have a conventional head rail, tilt rod, ladder tapes and slats, wherein a framework is mounted in the head rail and rotatably passes the tilt rod, an arm extends generally radially from the tilt rod for rotation with the latter, and a pair of stop members are selectively positionable relative to the framework in the path of arm movement for limiting arm rotation in opposite directions. The slats may be provided with reflective and absorptive surfaces to cooperate with the limiting positions of tilt for reflecting and absorbing heat in accordance with the seasons or other desiderata.

Effect of Twin/Tilt on the Growth of Graphite

Abstract: The effect of twin/tilt initiated in the process of graphite growth making the graphite curling and change from flake to vermicular and spheroidal is discussed. With the developing of the solidification process, the modifying elements enrich in the front of solid-liquid interface, the amount of twin defects in the graphite increases, its tilt fashion changes and the graphite formed varies from flake to vermicular and spheroidal. The modifying elements promote the formation of twin/tilt. When the modifying elements are insufficient for spheroidizing, the tilt orientation of twins is changeable, and the graphite formed is twisted. When the modifying elements are sufficient enough, the tilt orientation of twins becomes singular, and the graphite formed tends to be round. According to the energy and kinetics consideration of the formation of twin/tilt boundary, it is predicted that the twin plane would firstly adopt (10Tm), especially the (10T2) plane. This result coincides well with the experimental observations. It is proposed that the formation of SG can be divided into two steps: growth of graphite nucleus into spherulite by twin/tilt mechanism and brancing on it in a spiral mode.

Zero-Coma Condition For Decentered And Tilted Secondary Mirror In Cassegrain/Nasmyth Configuration

Abstract: The tolerance on decentering and tilt of the secondary mirror of a Cassegrain/Nasmyth telescope is considerably broadened when the zero-coma condition is applied, the limit being set by the allowable residual coma and tilt of the focal surface. The dependency of field tilt on decollimation is defined. A simple set of steps for effective collimation of a telescope is outlined, along with practical engineering recommendations concerning the Ritchey-Chretien (R-C) astigmatism corrector and focal surface subsystem. It is shown that when the proper engineering degrees of freedom are provided, essentially ideal R-C imagery can be obtained over the original optical design field, even in the presence of relatively large angular errors in the optical axes of the primary and secondary mirrors. The specific example given is the case of the proposed University of Texas 7.6 m telescope.

Electron beam instrument

Abstract: Under certain conditions, the electron beam from the electron gun of an electron microscope is deflected by deflecting means in such a way that the beam impinges on one point on a filmy crystalline specimen at a specific tilt angle while the direction of the tilt is rotated, to obtain an electron micrograph of the specimen In the conventional astigmatism correcting device, however, the rotation of the direction of the tilt makes it impossible to correct the astigmatism of the objective lens of the microscope which forms such an electron micrograph In the instrument according to the present invention, astigmatism correcting signals synchronized with the rotation of the direction of the tilt are supplied to the astigmatism correcting device so that the obtained electron micrograph may be unaffected by the astigmatism of the objective lens despite the periodic rotation of the direction of the tilt

Method for reading deformation images on electrophotographic media

Abstract: A method for reading deformation images recorded on electrophotographic media involving scanning of an image surface and measuring microscopic surface tilt in a reflected beam. In one embodiment, the deformation image is scanned telecentrically and in another embodiment the surface is scanned with a beam at angles to the surface. By intercepting the retroflected beam and measuring the deviation of the reflected beam from the scanning center, a number of proportional-to-surface tilt is found. By then electrically integrating over neighboring regions, an electrical or optical pattern, reimaging the deformation image, may be constructed.

Optical system for viewing a scene

Abstract: An optical system comprises a number of optical elements arranged in a housing. The housing may be fixed to the underside of an airship. The system corrects for picture tilt. The housing comprises a first fixed portion, a second portion rotatable relative to the first portion around an axis XX', and a third portion rotatable relative to the second portion around an axis YY' orthogonal to XX'. The combination of the rotating motions of the portions B and C of the housing render it possible to rotate the line of sight of the optical system through more than one half-circle.

A simple shaker table for seismometer calibration

Abstract: A unique and simple shaker table (shake table or shaking table), designed, constructed, and installed at the Hawaii Institute of Geophysics, has proven to be a valuable aid in testing and calibrating short period seismometers, as well as ocean bottom and ocean sub-bottom seismometer/tilt meter packages. It consists of a platform suspended in a stairwell by a single elastic cord (10 m extended length) driven by GeoSpace HS-10 geophones. Platform motion is monitored by orthogonal reference geophones and tilt meters. The relatively low natural periods of the platform, about 1.9 sec vertical and 6.5 sec horizontal, provide sufficient isolation from local vibrations that calibration can be made near operational amplitudes. Vertical or horizontal driver geophones can be driven by a commercial signal generator or white noise generator, or from magnetic tape output. The table can also be tilted with respect to the drivers to determine tilt tolerances and to calibrate tilt meters. A Hewlett-Packard 3582-A spectrum analyzer, used to analyze both reference and output signals, provides near real-time system cabibration and is an efficient means for investigating parasitic system resonances. The analyzer can also provide a white noise signal source to the driver geophones.

Tilt lockout system for tilt-cab trucks

Abstract: Disclosed is a tilt lockout system for tilt-cab trucks which extends the shock absorber and spring assemblies adjacent the tilt axis to their maximum strokes prior to initiation of the tilt cycle and locks them in that position throughout the tilt cycle.