Strong Stiffness Research Articles

Large-band reduction of magnetic vibrations of induction machines with "breaking-of-impedance" interface

Magnetic vibration of induction machines is reduced, on a large-frequency band, with a breaking-of-impedance interface between stator core and frame. This device is designed with strong tangential stiffness and low radial stiffness. Two-dimensional finite-element (FE) dynamic response is proposed. It is based firstly on experimental determination of magnetic forces with search coils on a half polar pitch on the stator bore. Secondly, all characteristics of windings are determined versus temperature and frequency and homogenized with a linear mixing law. Thirdly, a FE modal analysis is optimized on the target function based on experimental natural frequencies, in order to identify the equivalent mechanical parameters of wound slots.

Impedance Charactheristics of Human Finger Joints.

This paper describes impedance characteristics of human finger joints. Five joints of thumb and index finger are taken into consideration one by one our experiment. While subject keeps the joint angle of the finger to which the moment of rotation is applied as initial condition, small external disturbance is given to the finger joint. From the time trajectories of the joint angle and the moment of rotation caused by the disturbance, impedance parameters of each joint are estimated. Inertia of finger joint depends on position from MP joint or root of finger, and MP joints of thumb and index finger have large viscosity and stiffiness. Especially, MP joint of thumb has very strong stiffness compared with all joints of index finger, and it plays an important roll for stable gripping motions. On the other hand, DIP joint of index finger has small viscosity and stiffness, which is appropriate to perform active probing motion based on touch sense of fingertips. Moreover, we investigate how initial moment of rotation has influence on impedance of the finger joints. It is shown that stiffness of each joint increases in proportion to the initial moment of rotation.

Characteristics of Human Fingertips in Shearing Direction.

This paper describes characteristics of human fingertips in shearing directions. In the experiment, the shearing force is applied on the thumb, middle, or little finger. Stiffness and viscosity parameters are estimated using Kelvin-Model. Considering contact area, the thumb has the strongest stiffness among the three fingers, and middle and little fingers have the same stiffness. The stiffness depends on the direction of the shearing force. The stiffness in the direction from nail to first joint of finger is stronger than that in the perpendicular direction. As the normal force of gripping increases, the shearing stiffness and viscosity increase without regard to the loading rate of the shearing force. The shearing stiffness has an upper Iimit value, and the viscosity par unit area keeps constant. Moreover, the strain rate of the fingertips is investigated, and it is found that the normal force of gripping affects the stiffness of the fingertips.

ステップ状せん断荷重に対する指先のインピーダンス特性

This paper describes characteristics of human fingertips in shearing directions. In the experiment, the shearing force is applied on the thumb, middle, or little finger. Stiffness and viscosity parameters are estimated using Kelvin-Model. Considering contact area, the thumb has the strongest stiffness among the three fingers, and middle and little fingers have the same stiffness. The stiffness depends on the direction of the shearing force. The stiffness in the direction from nail to first joint of finger is stronger than that in the perpendicular direction. As the normal force of gripping increases, the shearing stiffness and viscosity increase without regard to the loading rate of the shearing force. The shearing stiffness has an upper Iimit value, and the viscosity par unit area keeps constant. Moreover, the strain rate of the fingertips is investigated, and it is found that the normal force of gripping affects the stiffness of the fingertips.

“Snapping” Torsional Response of an Anisotropic Radially Loaded Rotor

A rotor system with two orthogonal lateral and two angular (torsional) degrees of freedom is considered. The rotor has asymmetry of the lateral stiffness and is laterally loaded with a constant radial force and a rotating unbalance. Constant driving and load torques are applied to the rotor. The important part of the research includes an analysis of “snapping” action, when, during rotation, the rotor experiences a peak of torsional acceleration. This occurs when the “strong stiffness” axis of the anisotropic rotor passes under the axis of the sideload. The numerical simulation of the analytical model exhibits a snapping (accelerated) torsional response of the rotor at twice synchronous frequency (2×), and it is especially pronounced at 1× and 2× torsional resonances. The snapping response can initiate a rotor crack in the area of stress concentration, can stimulate existing crack propagation, and can be a cause of the coupling failure. The analytical results are obtained by the Averaging Method application. They confirm the numerical results and show the possibility of combination resonance occurrences. The synchronous dynamic stiffness for the frequency range around 1× lateral resonance is analytically obtained. The specific shape of the quadrature dynamic stiffness component can serve as a shaft crack indicator and can be used for early detection of a lateral crack on the rotor.

Oscillation stability of levitated HTSC in inhomogeneous magnetic field

The stability of the horizontal and vertical oscillations of anisotropic high- T c superconductors (HTSC's) in an inhomogeneous magnetic field has been investigated. The oscillation amplitude of the levitated HTSC's was measured as function of the external force frequency and amplitude. The resonant oscillations of the levitated superconductors were observed for external field frequencies from 20 to 40 Hz. It is demonstrated that the system consisting of a superconductor, a coil and four permanent magnets has strong stiffness. This behavior is described with the general theory of oscillations.

Magnetic field effects on the computed flow over a Mars return aerobrake

A numerical algorithm is developed to calculate the electromagnetic phenomena simultaneously with the fluid flow in the shock layer over an axisymmetric blunt body in a thermal equilibrium, chemical nonequilibrium environment. The flowfield is solved using an explicit time-marching, first-order spatially accurate scheme. The electromagnetic phenomena are coupled to the real-gas flow solver through an iterative procedure. The electromagnetic terms introduce a strong stiffness, which was overcome by using significantly smaller time steps for the electromagnetic conservation equation. The technique is applied in calculating the flow over a Mars return aerobrake vehicle entering the Earth's atmosphere. For the case where no external field is applied, the electromagnetic effects have little impact on the flowfield. With the application of an external magnetic field of 0.05 to 0.1 T, the solution indicates an increase in stagnation line shock standoff distance, wall pressure, and radiative heat transfer and a decrease in convective heat transfer.

Diffusion bonded matrix of high gradient magnetic filter

For improving the performance of high gradient magnetic filter (HGMF) used in steel mill process waste water treatment, a new filtering medium of diffusion bonded matrix has been developed. This new matrix has an excellent high filtering efficiency for feebly paramagnetic particles, and also has strong structural stiffness that prevents the matrix from compaction and the flow-out of fine wool fractions, which are serious defects in the conventional stainless wool matrix.

Self-trapped states of electrons in dense fluids

The conditions which lead to electron self-trapping, in a material, are theoretically investigated. The theory is developed for the simple case of a dense fluid, composed of a single kind of atom, obeying the ideal gas equation of state, and interacting with an electron as a system of hard-sphere scatterers. Possible generalizations are noted. A static continuum approximation and statistical considerations define configurations in which atoms feel no net force, electron states are obtained for these configurations, and, then, stability is investigated. The theory developed is shown to reduce to the case first investigated by Toyozawa, in the limit of small distortions (from the average configuration in the absence of the electron). The material-electron coupling constant depends on the average density, and since the stiffness of the materials is shown to be the external pressure, both may be continuously and independently varied experimentally. The results, for arbitrary distortions, lead to stable self-trapping and metastable quasifree electrons for strong coupling, weak stiffness; stable quasifree electrons and unstable self-trapping for weak coupling, strong stiffness; and metastable self-trapping in a limited intermediate regime. The different regimes are delimited quantitatively. The theoretical importance of this work resides in the fact that the generally used adiabatic approximation can only be justified for system states near stable or metastable configurations. The experimental consequences of changes in the stability of configurations are dramatic changes in some properties. For example, the observed electron-drift-mobility plunge in fluid helium is shown to be strongly correlated with the predicted transition of self-trapped states to stability.

On the Küntscher's Nail to be fixed in the Marrow

Recently the Kuntscher's nail is used a good deal, as it has the strong stiffness and fixes both bones enough.The ventical direction of the nail is 30% stronger than the horizontal and in fracture the stiffness of the bone to be fixed by the nail is equivalent the nail itself regardless of the depth of the head of it, so it is unnecessary to strike the head in one bone too deeply.The three-wings nail is 20% lighter, 30% weaker than the Kuntscher's nail of the same grade.

RIGOR MORTIS AND THE INFLUENCE OF CALCIUM AND MAGNESIUM SALTS UPON ITS DEVELOPMENT

Calcium salts hasten and magnesium salts retard the development of rigor mortis, that is, when these salts are administered subcutaneously or intravenously. When injected intra-arterially, concentrated solutions of both kinds of salts cause nearly an immediate onset of a strong stiffness of the muscles which is apparently a contraction, brought on by a stimulation caused by these salts and due to osmosis. This contraction, if strong, passes over without a relaxation into a real rigor. This form of rigor may be classed as work-rigor (Arbeitsstarre). In animals, at least in frogs, with intact cords, the early contraction and the following rigor are stronger than in animals with destroyed cord. If M/8 solutions-nearly equimolecular to "physiological" solutions of sodium chloride-are used, even when injected intra-arterially, calcium salts hasten and magnesium salts retard the onset of rigor. The hastening and retardation in this case as well as in the cases of subcutaneous and intravenous injections, are ion effects and essentially due to the cations, calcium and magnesium. In the rigor hastened by calcium the effects of the extensor muscles mostly prevail; in the rigor following magnesium injection, on the other hand, either the flexor muscles prevail or the muscles become stiff in the original position of the animal at death. There seems to be no difference in the degree of stiffness in the final rigor, only the onset and development of the rigor is hastened in the case of the one salt and retarded in the other. Calcium hastens also the development of heat rigor. No positive facts were obtained with regard to the effect of magnesium upon heat vigor. Calcium also hastens and magnesium retards the onset of rigor in the left ventricle of the heart. No definite data were gathered with regard to the effects of these salts upon the right ventricle.