Memory metal actuator

A mechanical actuator can be constructed by employing a plurality of memory metal actuator elements in parallel to control the amount of actuating force. In order to facilitate direct control by digital control signals provided by a computer or the like, the actuating elements may vary in stiffness according to a binary relationship. The cooling or reset time of the actuator elements can be reduced by employing Peltier junction cooling assemblies in the actuator

Grow rich and clean up later? International assistance and the provision of environmental quality in low- and middle-income countries

This paper deals with the question whether low- and middle-income countries that are politically better integrated into the international system are able to provide higher levels of environmental quality than could be expected only according to their national income levels. Using time-series cross-section regression analysis of 110 countries for the period 1950-1999 it can be shown that those countries that have signed and ratified more environmental treaties, have significantly lower SO2 emissions than countries that are less integrated into the international system. However, in contrast to theoretical predictions democratic low- and middle-income countries despite their stronger integration into the international system exhibit higher SO2 emissions indicating lower environmental quality than autocratic countries. --

Retinally stabilized differential resolution television display

A remote television viewing system employing an eye tracker is disclosed, wherein a small region of the image appears in high resolution, and the remainder of the image appears in low resolution. The eye tracker monitors the position of the viewer's line of sight. The eye tracker position data is transmitted to the remote television camera and control. Both the remote camera and television display are adapted to have selectable high-resolution and low resolution raster scan modes. The position data from the eye tracker is used to determine the point at which the high-resolution scan is to commence. The video data defining the observed image is encoded in a novel format, wherein in each data field, the data representing the position of the high resolution region of predetermined size appears first, followed by the high resolution zone video data and then the low-resolution region data. As the viewer's line of sight relative to the displayed image changes, the position of the high resolution region changes to track the viewer's line of sight

Instabilities of Relativistic Stars

Recent developments on the rotational instabilities of relativistic stars are reviewed. The article provides an account of the theory of stellar instabilities with emphasis on the rotational ones. Special attention is being paid to the study of these instabilities in the general relativistic regime. Issues such as the existence relativistic r-modes, the existence of a continuous spectrum and the CFS instability of the w-modes are discussed in the second half of the article.Comment: 41 pages, 12 figures, Proceedings of the 25th John Hopkins Workshop, Florenc

Positive representations of C0(X)C_0(X). I

We introduce the notion of a positive spectral measure on a $\sigma$-algebra, taking values in the positive projections on a Banach lattice. Such a measure generates a bounded positive representation of the bounded measurable functions. If $X$ is a locally compact Hausdorff space, and $\pi$ is a positive representation of $C_0(X)$ on a KB-space, then $\pi$ is the restriction to $C_0(X)$ of such a representation generated by a unique regular positive spectral measure on the Borel $\sigma$-algebra of $X$. The relation between a positive representation of $C_0(X)$ on a Banach lattice and -- if it exists -- a generating positive spectral measure on the Borel $\sigma$-algebra is further investigated; here and elsewhere phenomena occur that are specific for the ordered context.Comment: There is now a direct proof of the existence of a generating regular positive spectral measure in the case of KB-spaces, without resorting to the Banach space theory. References to the existing literature on the Banach space case have been added, and perspectives for future research are now given. 24 pages, to appear in Ann. Funct. Ana

On the r-mode spectrum of relativistic stars in the low-frequency approximation

The axial modes for non-barotropic relativistic rotating neutron stars with uniform angular velocity are studied, using the slow-rotation formalism together with the low-frequency approximation, first investigated by Kojima. The time independent form of the equations leads to a singular eigenvalue problem, which admits a continuous spectrum. We show that for $l=2$, it is nevertheless also possible to find discrete mode solutions (the $r$-modes). However, under certain conditions related to the equation of state and the compactness of the stellar model, the eigenfrequency lies inside the continuous band and the associated velocity perturbation is divergent; hence these solutions have to be discarded as being unphysical. We corroborate our results by explicitly integrating the time dependent equations. For stellar models admitting a physical $r$-mode solution, it can indeed be excited by arbitrary initial data. For models admitting only an unphysical mode solution, the evolutions do not show any tendency to oscillate with the respective frequency. For higher values of $l$, it seems that in certain cases there are no mode solutions at all.Comment: Major revision, corrected results concerning realistic equations of state, now 17 pages, 11 figures, MNRAS typesettin

Multi-fingered robotic hand

A robotic hand is presented having a plurality of fingers, each having a plurality of joints pivotally connected one to the other. Actuators are connected at one end to an actuating and control mechanism mounted remotely from the hand and at the other end to the joints of the fingers for manipulating the fingers and passing externally of the robot manipulating arm in between the hand and the actuating and control mechanism. The fingers include pulleys to route the actuators within the fingers. Cable tension sensing structure mounted on a portion of the hand are disclosed, as is covering of the tip of each finger with a resilient and pliable friction enhancing surface