Finger Configurations Research Articles

Multicomponent Convection

In two early reviews of this subject (Turner 1973, 1974), the phenomena described were adequately covered by the name double-diffusive convection. They were treated as generalizations of the process of thermal convection in a thin fluid layer, which arise when spatial variations of a second component with a different molecular diffusivity are added to the thermal gradients ; the term thermohaline convection was introduced to describe the heat-salt system. The experimental and theoretical results then available could be described in terms of the differential diffusion of two components acting so as to release potential energy from a component that is heavy at the top, even though the net density decreases upward. It was also shown that the form of the resulting motions depends on whether the driving energy comes from the component having the higher or lower diffusivity. Where one layer of fluid is placed above another (denser) layer having different properties, two basic types of convective instabilities arise, in the diffusive and finger configurations. These are illustrated in Figures 1 and 2, respectively. In both cases, the double-diffusive fluxes can be much larger than the vertical transport in a single-component fluid because of the coupling between and convective processes. The main development of these ideas since 1974 has occurred in the field of oceanography, with interactions between theoreticians, laboratory experimenters, and sea-going oceanographers playing a vital role. The field has also broadened considerably, with new applications becoming ap­ parent in addition to those outlined by Turner (1974). A rather personal historical review of the subject was presented by Huppert & Turner (198 1a), in which they emphasized the importance of transfer of information from

Kinematic and Force Analysis of Articulated Mechanical Hands

This paper deals with several of the basic concepts in the kinematics of mechanical hands. Several different types of finger contacts are modeled and used in a number synthesis of three-fingered hands. Screw theory is used to show which finger configurations allow complete immobilization of the gripped object relative to the fingers, and also allow for the manipulation of the object by the fingers while maintaining the grasp. Shown in this paper is how to determine the forces applied by the fingers on the object, and also how to compute the velocities of the fingers and the object. The analysis developed in this paper is shown to lead to a hand with three fingers, each with three turning joints, and having friction contacts with an object at three separate points.

Finger joint force predictions related to design of joint replacements

The results of previously published studies of the forces transmitted across human finger joints differ significantly. This paper contains a critical review of the previous work and describes and analyses a new model of index finger pinch. The new model has been used to analyse a range of finger configurations from pulp to tip pinch, and incorporates the most recent information about tendon moment arms and directions, the relative magnitudes of the intrinsic muscle tensions, and the way that these forces are distributed within the finger. Muscle and joint force predictions from this model have been used in a discussion of the validity of previously-published results.