Pure Axial Rotation Research Articles

A survey of solar concrete shell collectors for parabolic troughs

Concrete shell collectors offer an alternative to conventional parabolic trough collectors. The principle design concept is derived from existing barrel rooves that effectively bridge large spans in halls or buildings with minimum material usage. The concrete troughs merge the bearing structure and mirroring surface to just one shell of a few centimeters. They are made of high-strength concrete and track the sun via pure axial rotation or lateral movements that avoid any lifting works. In the present contribution, basic constraints in materials, geometry, and static calculation are derived and converted into a framework of possible designs. This contribution thereby presents a survey of concepts that range from small-scale prototypes to full-scale realizations of 140 m2 apertures and large-aperture concepts with a 10 m width. Design concepts with bearing and drive systems as well as optimization-based form findings are introduced to elaborate shells of minimum weight with solid sections, stiffeners, and hollow cores.

Computational Design of a Family of Light-Driven Rotary Molecular Motors with Improved Quantum Efficiency.

Two new light-driven molecular rotary motors based on the N-alkylated indanylidene benzopyrrole frameworks are proposed and studied using quantum chemical calculations and nonadiabatic molecular dynamics simulations. These new motors perform pure axial rotation, and the photochemical steps of the rotary cycle are dominated by the fast bond-length-alternation motion that enables ultrafast access to the S1/S0 intersection. The new motors are predicted to display a quantum efficiency higher than that of the currently available synthetic all-hydrocarbon motors. Remarkably, the quantum efficiency is not governed by the topography (peaked versus sloped) of the minimum-energy conical intersection, whereas the S1 decay time depends on the topography as well as on the energy of the intersection relative to the S1 minimum. It is the axial chirality (helicity), rather than the point chirality, that controls the sense of rotation of the motor.

Biomechanical Analysis of Torsion and Shear Forces in Lumbar and Lumbosacral Spine Segments of Nonchondrodystrophic Dogs

To determine stiffness and load-displacement curves as a biomechanical response to applied torsion and shear forces in cadaveric canine lumbar and lumbosacral specimens. Biomechanical study. Caudal lumbar and lumbosacral functional spine units (FSU) of nonchondrodystrophic large-breed dogs (n=31) with radiographically normal spines. FSU from dogs without musculoskeletal disease were tested in torsion in a custom-built spine loading simulator with 6 degrees of freedom, which uses orthogonally mounted electric motors to apply pure axial rotation. For shear tests, specimens were mounted to a custom-made shear-testing device, driven by a servo hydraulic testing machine. Load-displacement curves were recorded for torsion and shear. Left and right torsion stiffness was not different within each FSU level; however, torsional stiffness of L7-S1 was significantly smaller compared with lumbar FSU (L4-5-L6-7). Ventral/dorsal stiffness was significantly different from lateral stiffness within an individual FSU level for L5-6, L6-7, and L7-S1 but not for L4-5. When the data from 4 tested shear directions from the same specimen were pooled, level L5-6 was significantly stiffer than L7-S1. Increased range of motion of the lumbosacral joint is reflected by an overall decreased shear and rotational stiffness at the lumbosacral FSU. Data from dogs with disc degeneration have to be collected, analyzed, and compared with results from our chondrodystrophic large-breed dogs with radiographically normal spines.

A new algorithm to model the dynamics of 3-D bonded rigid bodies with rotations

In this paper we propose a new algorithm to simulate the dynamics of 3-D interacting rigid bodies. Six degrees of freedom are introduced to describe a single 3-D body or particle, and six relative motions and interactions are permitted between bonded bodies. We develop a new decomposition technique for 3-D rotation and pay particular attention to the fact that an arbitrary relative rotation between two coordinate systems or two rigid bodies can not be decomposed into three mutually independent rotations around three orthogonal axes. However, it can be decomposed into two rotations, one pure axial rotation around the line between the centers of two bodies, and another rotation on a specified plane controlled by another parameter. These two rotations, corresponding to the relative axial twisting and bending in our model, are sequence-independent. Therefore all interactions due to the relative translational and rotational motions between linked bodies can be uniquely determined using such a two-step decomposition technique. A complete algorithm for one such simulation is presented. Compared with existing methods, this algorithm is physically more reliable and has greater numerical accuracy.

The effects of substrate rotation on thermal plasma chemical vapor deposition of diamond

The effects of substrate rotation on the chemical vapor deposition (CVD) of diamond is investigated utilizing a Triple Torch Plasma Reactor (TTPR) activation source. Diamond deposition experiments are conducted with an Ar–H 2–CH 4 plasma gas mixture at reduced pressures. Substrate rotation is achieved by means of a variable speed DC gear motor used to rotate the substrate shaft. Rotation of the substrate during deposition, as well as rotation and offsetting the substrate axis from the converging plasmajet axis, is found to increase the average mass deposition rate as well as the average area of deposit when compared to a stationary substrate. Film and crystal size uniformity of the deposit are found to be enhanced, and deposit roughness decreased by rotating, and rotating plus offsetting the substrate when compared to a stationary substrate. Rotational speed and offsetting the substrate results in negligible differences compared to pure axial rotation. The effect of rotation on substrate temperature is believed to be more significant than the effect of substrate rotation on plasma fluid dynamics.

A spherical rotation coordinate system for the description of three-dimensional joint rotations.

Three-dimensional joint rotations in human movement analysis have been mainly described by Euler/Cardan angles. Due to sequence dependence, each combination of three Euler/Cardan angles defines a single pattern of joint rotation. When the rotation pattern is unknown, it needs to be considered using a particular sequence of Euler/Cardan angles to represent joint rotations. In this paper a spherical rotation coordinate system is developed for describing three-dimensional joint rotations using a method of rotation involving two steps: a long axis rotation and a pure axial rotation. Two angles of the classical spherical coordinate system--longitude and latitude--are used to describe long axis rotations in this newly proposed coordinate system. The spherical rotation coordinate system uses a radial rotation angle to describe pure axial rotation of a limb segment whereas the classical spherical coordinate system uses a radial displacement to describe motion of a point. An application of the spherical rotation coordinate system is given to define three-dimensional rotations of the glenohumeral joint. A mathematical proof shows that the long axis rotation and axial rotation are sequence independent. Two numerical examples are investigated which demonstrate that the spherical rotation angles can be uniquely determined in both forward and inverse kinematics without considering sequences rotations.

The Distal Radioulnar Joint in Relation to the Whole Forearm

The functional anatomy of the distal radioulnar joint was studied in relation to the whole forearm, using three fresh-frozen, above-elbow amputation specimens. The specimens demonstrate how the proximal and distal radioulnar joints together form a bicondylar joint of special character. The proximal "condyle," the radial head, rotates axially, whereas the distal "condyle," the ulnar head, is fixed with respect to rotation. The ordinary articulation of a bicondylar joint (pure axial rotation) is thereby changed into pronation-supination. Axial rotation is preserved proximally, while distally the radius swings around the ulnar head. The mobile radius is distally attached to the stable ulnar head by the dorsal and volar radioulnar ligaments, the dorsal ligament being tight for stabilization in supination and the volar ligament being tight in pronation. The ulnar head also serves as a keystone, carrying the load of the radius. Removal of the ulnar head allows the radius to "fall in" towards the ulna, with narrowing of the interosseous space.

Axial Rotation in the Lumbar Spine and Gaping of the Zygapophyseal Joints

Axial rotation and zygapophyseal joint gaping was studied using 12 human lumbar spines from individuals ranging in age from 14 to 75 years. Using weight and pulley tests and manipulative testing in a torque apparatus, the movement produced by twisting the spine was found not to be pure axial rotation, but rather movement coupled with various combinations of lateral bending and flexion or extension. This motion may not be possible in testing an individual mobile segment. The twisting movements of the spine do not normally produce gaping of the zygapophyseal joints. These joints adapt to the axial rotation by the compliance of their articular cartilages and the movement of fat pads in and out of the joint capsule. Hypermobility appears to be associated with evidence of damage to part of the mobile segment, suggesting that the hypermobility (gaping) at a joint could be due to instability caused by injury.

The outer core rotation about an inclined axis from geomagnetic secular variations (Mitteilungen des Zentralinstituts für Physik der Erde, Nr. 1832)

AbstractNon‐axisymmetric motions of the outer core of the Earth are important for the dynamo problem and the excitation of the decade variations of the polar motion. The components of the vector of a rigid rotation of the outer core about an inclined axis were estimated by a first‐order approximation of the frozen‐ field theory of the geomagnetic secular variation from 1903.5 to 1975.5. The trends and quasi‐periodic constituents of these quantities were computed. It was shown that the position and time behaviour of the rotational pole of the outer core differ considerably from the well‐know co‐ordinates of the dipole axis. Some periods of the equatorial components of the rotational vector are comparable with those of the axial component previously derived for a pure axial rotation. Additionally, the time behaviour of the pole path shows events like the well‐known Markowitz wobble but naturally with other extent. These and other results suggested that the investigations are worth to be continued in future by some physical interpretations.