Transverse plane

About: Transverse plane is a research topic. Over the lifetime, 17069 publications have been published within this topic receiving 194059 citations. The topic is also known as: axial plane.

Parametric instability of a rotor-bearing system with two breathing transverse cracks

Abstract: When the rotor rotates at a constant speed, the transverse crack opens and closes alternatively, due to gravity, and thus a “breathing effect” occurs. This variance in shaft stiffness is time-periodic, and hence a parametrically excited system is expected. The parametric excitation from the time-varying stiffness causes instability and severe vibration under certain operating conditions. Current research mostly focused on the rotor with single transverse crack. There are few studies on the multi-cracked rotor system. In fact, the interaction between the multiple parametric excitations with various phasing and amplitude, which are induced by the multiple breathing transverse cracks, would make the instability behavior of the system differ distinctly from that of the single cracked rotor system. Moreover, how the instability regions change with various crack breathing mechanisms should also be investigated. Thus, the parametric instability of a rotor-bearing system with two breathing transverse cracks is studied in the paper. First, the finite element equations of motion are established for the cracked rotor system. Two types of crack breathing mechanisms, of which one is more accurate (new) and the other is empirical (old), are adopted in the finite element formulation. Then, a generalized Bolotin's method is introduced for determining the boundaries of the primary and secondary instability regions. Based upon these, instability analysis for a practical used rotor-bearing system with single and two cracks are conducted, respectively. The instability regions induced by the single transverse crack with new and old breathing mechanisms are compared with each other. For the two-cracked rotor system, the variations of the unstable boundaries with crack depths, orientation angles and positions are observed and discussed in detail. It is shown from the results that the dynamic instability of the two-cracked rotor-bearing system indeed have some unique features that differ from that of the single cracked rotor system.

Normal shoulder: MR imaging.

Abstract: Relatively poor spatial resolution has been obtained in magnetic resonance (MR) imaging of the shoulder because the shoulder can only be placed in the periphery of the magnetic field. The authors have devised an anatomically shaped surface coil that enables MR to demonstrate normal shoulder anatomy in different planes with high spatial resolution. In the axial plane, anatomy analogous to that seen on computed tomographic (CT) scans can be demonstrated. Variations in scapular position (produced by patient positioning) may make reproducibility of sagittal and coronal plane images difficult by changing the relationship of the plane to the shoulder anatomy. Oblique planes, for which the angle is chosen from the axial image, have the advantage of easy reproducibility. Obliquely oriented structures and relationships are best seen in oblique plane images and can be evaluated in detail.

On the theory of plane stress

Abstract: The classical theory of plane stress is concerned with a thin elastic plate subjected to edge forces which deform it so that there is no normal displacement of its middle plane. This theory may be obtained from the exact three dimensional linear theory of elasticity for homogeneous and isotropic materials, by neglecting some of the compatibility equations and assuming that the shear and normal stresses, transverse to the middle plane of the plate, vanish and the remaining stresses are independent of z, the coordinate normal to this mid-plane. Hence, the relationship between the two theories is shown by systematically deriving from the exact theory the differential equations and boundary conditions of plane stress. Each stress component is expanded in a power sertes in the plate thickness, h, and equated to determine the expansion coefficients. The plane stress theory appears as the zeroth order interior problem, the solutions of which supply a first approximation to the three- dimensional stress distribution. The expansion procedure also provides three- dimensional corrections to the plane stress theory. (N.W.R.)

Suppression of transverse proton beam divergence by controlled electron cloud in laser-plasma interactions

Abstract: In this paper, suppression of a transverse proton divergence is focused by using a controlled electron cloud. When an intense short pulse laser illuminates a foil plasma target, first electrons are accelerated and they form a strong electrostatic field at the target surface, then ions are accelerated by the strong field. When a target has a hole at the opposite side of the laser illumination, an electron cloud is limited in transverse direction by a neutral plasma at the protuberant part. The proton beam is accelerated and also controlled by transverse shaped electron cloud, and consequently the transverse divergence of the proton beam is suppressed. In 2.5-dimensional particle-in-cell simulations, the transverse shape of the electron cloud is controlled well and the transverse proton beam divergence is suppressed successfully; the transverse emittance is improved by about 28% compared with that in a conventional slab target.