Non-uniform Mass Distribution Research Articles

Tactile sensing of density uniformity in powder beds after die filling

The use of tactile sensors has been explored as a novel means of assessing density uniformity of powders in molding dies prior to compaction. Nonuniform mass distribution after the die filling process was detected as gradients in the transmitted pressure by a tactile sensor located at the bottom of the die. The effect of process variables on fill uniformity was determined by comparing the coefficients of variation of transmitted pressure distributions. Direct measurements of the density uniformity after compaction were consistent with the trends in pressure distribution measured by the tactile sensor. Thus, this work demonstrates the feasibility of using tactile sensors as a quality assessment, process development, or training tool in dry pressing operations.

Exact Solutions to A Class of Structure-Equipment Systems

Exact solutions are presented for the mean-square responses of a class of complex structure-equipment systems under dynamic loads. The complex systems consist of an n -story building with each floor supporting a branch of an equipment system. The structure-equipment systems are precisely decomposed into n subsystems whose degrees-of-freedom are only dependent on the degrees-of-freedom in each branch equipment. These results can be used to evaluate the accuracy of existing approximate techniques, to better understand the dynamic characteristics of multituned structure-equipment systems, and to study the dynamic interaction between any two branches of the equipment system. Three illustrative examples indicate that there exists an optimum design damping of the equipment anchorage in such a complex system to suppress its vibration level. Advantage can also be taken of a nonuniform mass distribution in the equipment system to further reduce its vibration. The dynamic interaction between two branch equipment is...

ゾウリムシは重力を感じているか‐ゾウリムシの重力走性のメカニズム

In order to get an insight into the cellular mechanisms for the integration of the effects of gravity,we investigated the gravitactic behaviour in Paramecium. There are two main categories for the model of the mechanism of gravitaxis; one is derived on the basis of the mechanistic properties of the cell (physical model) and the other of the physiological properties including cellular gravireception (physiological model). In this review article, we criticized the physical models and introduced a new physiological model. Physical models postulated so far can be divided into two; one explaining the negative gravitactic orientation of the cell in terms of the static torque generated by the structural properties of the cell (gravity-buoyancy model by Verworn, 1889 and drag-gravity model by Roberts, 1970), and the other explaining it in terms of the dynamic torque generated by the helical swimming of the cell (propulsion-gravity model by Winet and Jahn, 1974 and lifting-force model by Nowakowska and Grebecki, 1977). Among those we excluded the possibility of dynamic-torque models because of their incorrect the oretical assumptions. According to the passive orientation of Ni2+-immobilized cells, the physical effect of the static torque should be inevitable for the gravitactic orientation. Downward orientation of the immobilized cells in the course of floating up in the hyper-density medium demonstrated the gravitactic orientation is not resulted by the nonuniform distribution of cellular mass (gravity-buoyancy model) but by the for-aft asymmetry of the cell (drag-gravity model). A new model explaining the gravitactic behaviour is derived on the basis of the cellular gravity sensation through mechanoreceptor channels of the cell membrane. Paramecium is known to have depolarizing receptor channels in the anterior and hyperpolarizing receptors in the posterior of the cell. The uneven distribution of the receptor may lead to the bidirectional changes of the membrane potential by the selective deformation of the anterior and posterior cell membrane responding to the orientation of the cell in the gravity field; i.e. negative- and positive-going shift of the potential due to the upward and downward orientation, respectively. The orientation dependent changes in membrane potential with respect to gravity, in combination with the close coupling of the membrane potential and the ciliary locomotor activity, may allow the changes in swimming direction along with those in the helical nature of the swimming path; upward shift of axis of helix by decreasing the pitch angle due to hyperpolarization in the upward-orienting cell, and also the upward shift by increasing the pitch angle due to depolarization in the downward-orienting cell. Computer simulation of the model demonstrated that the cell can swim upward along the “super-helical” trajectory consisting of a small helix winding helically an axis parallel to the gravity vector, after which the model was named as “super-helix model”. Three-dimensional recording of the trajectories of the swimming cells demonstrated that about a quarter of the cell population drew super-helical trajectory under the unbounded, thermal convection-free conditions. In addition, quantitative analysis of the orientation rate of the swimming cell indicated that gravity-dependent orientation of the swimming trajectory could not be explained solely by the physical static torque but complementarily by the physiological mechanism as proposed in the super-helix model.

Isochoric heat capacity Cv at the critical point of SF6 under micro- and earth-gravity

Abstract As a consequence of the diverging compressibility, earth-bound experiments near the gas-liquid critical point suffer extremely from the strong influence of gravity. Caloric measurements, in particular of the heat capacity Cv, are inevitably affected by local changes of the density throughout the volume. Experimental results thus rather represent some integral average over all density and temperature variations than a thermodynamic point of state. The first measurements of Cv under micro-gravity conditions for the fluid SF6 near the critical state conducted during the German Spacelab Mission D1 in Oct./Nov. 1985 are reported here. Due to the surprising μg-results, the influence of gravity and equilibration have subsequently been investigated. By numerical simulation of the equilibration process, it became evident that the flattening of the Cv-curves observed could be caused by a non-uniform mass distribution and the slow mass diffusion process.

The quantisation of non-relativistic strings with arbitrary mass and charge densities

The authors present a method for extending charged point particles into strings, within a non-relativistic framework. This method allows a discussion of models with a non-uniform mass and charge distribution, such as strings with quark-like endpoint masses. The form factor associated with a ground-state charged string is calculated, which shows a rapid fall-off with momentum transfer. The authors discuss the question of the second-quantisation of such models.

Vibrations of a transversely nonuniform basilar membrane in the mammalian cochlea

It is shown that high-Q amplitude-coordinate response curves (sharp tuning) can be obtained in a linear hydromechanical model of the cochlea if the nonuniform transverse stiffness and mass distribution in the basilar membrane partition is taken into account.

Stress and strain behavior of low grammage spot in paper during elongation.

Mechanical behavior of a relatively weak spot in paper during deformation was investigated by the finite element method. Significant stress and strain concentrations could be found when the spot was located outermost in the rectangular specimen. Thicker spots connected crosswise to the defect showed a remarkable reinforcing effect on the mechanical response of the thin spot, while they contributed rather negatively if arranged lengthwise. Paper has a non-uniform distribution of mass, and stress and strain of a certain spot may result from a complicated combination of the mechanical phenomena.

Eigenanalysis of the Rigid Body Motion Effect on Elastic Systems

In this paper, the influence of rigid body motion on the behavior of a vibrating elastic system is treated by the development of a difference eigenvalue problem. The maximum possible changes in eigenfrequencies due to removal of constraints are obtained by the employment of the bound approach [1, 2]. As an application to a structural system the Rayleigh-Ritz procedure is employed for constructing the difference eigenvalue problem. Discussion of the use of the method for various types of engineering problems is outlined. An example of a free vibration analysis of a simply supported beam in plane motion with a nonuniform mass and elasticity distribution is solved. A comparison between computer calculations and previously published results is presented.

Electromagnetic-gravitational energy systems

Two methods axe considered to “tap” the earths' rotational energy. This ancient “collapsed gravitational energy” exceeds the earth-lunar binding energy. One involves an orbiting “electromagnetic-gravitational” coupling system whereby the earth's rotation, with its nonuniform mass distribution, first uses gravity to add orbital energy to a satellite, similar to a planetary “flyby.rd The second stage involves enhanced satellite “drag” as current-carrying coils withdraw the added orbital energy as they pass through the earth's nonuniform magnetic field. A second more direct method couples the earth's rotational motion using conducting wires moving through the noncorotating part (ionospheric current systems) of the geomagnetic field. These methods, although not immediately feasible, are considerably more efficient than using pure gravitational coupling to earth-moon tides.

Influence of mass distribution on the stability of rods in the presence of polygenic forces

In this paper, the influence of a non-uniform mass distribution on the stability behaviour of a rod subjected to follower forces is investigated. It is assumed that the mass contributes to the dead load of the system but does not affect the bending stiffness of the rod. Using Pfluger's rod as an example, it is shown that although there will always be instability by divergence, additional instability by flutter is possible depending on the way the mass is distributed. Specifically, a condition is studied which ensures the absence of flutter instability. Coresponding conclusions are drawn for a rocket type rod system.