Summary Power is becoming an increasingly important concern for large supercomputer centers. However, to date, there have been a dearth of studies of power usage ‘in the wild’—on production supercomputers running production workloads. In this paper, we present the initial results of a project to characterize the power usage of the three Top500 supercomputers at Los Alamos National Laboratory: Cielo, Roadrunner, and Luna (#15, #19, and #47, respectively, on the June 2012 Top500 list). Power measurements taken both at the switchboard level and within the compute racks are presented and discussed. Some noteworthy results of this study are that (1) variability in power consumption differs across architectures, even when running a similar workload and (2) Los Alamos National Laboratory's scientific workload draws, on average, only 70–75% of LINPACK power and only 40–55% of nameplate power, implying that power capping may enable a substantial reduction in power and cooling infrastructure while impacting comparatively few applications. Copyright © 2013 John Wiley & Sons, Ltd.

The geometric approach to the quasistatic analysis of elastic systems of rigid bodies can be used to model a wide variety of situations. The modular dextrous hand is used as a model to explain the difference between elastic systems and elastic networks, define and compute the stiffness of the elastic system, and show how holonomic constraints can be handled in this framework. Geometry of the space of all elastic systems with holonomic constraints is described by the Lagrangian planes in the displacement-force space. It is shown how coordinates can be chosen to simplify the interpretation of the stiffness and compliance matrices. Quasistatic grasp stability is analyzed by an application of the Lagrange-Dirichlet principle.>

A generalized spring associates potential energy with each position and orientation of a rigid body. The stiffness of such a spring can be represented by a 6 × 6 symmetric matrix. This matrix can be brought to a normal form by a particular choice of the coordinate frame. Analogous but independent results hold for compliance matrices. These results, obtained by using a Lie group approach, also extend the concept of the remote center of stiffness to generic generalized springs.