Andrew B. Mansfield

A Regime Diagram for Autoignition of Homogeneous Reactant Mixtures with Turbulent Velocity and Temperature Fluctuations

A theoretical scaling analysis is conducted to propose nondimensional criteria to predict weak and strong ignition regimes for a compositionally homogeneous reactant mixture with turbulent velocity and temperature fluctuations. This leads to a regime diagram that provides guidance on expected ignition behavior based on the thermo-chemical properties of the mixture and the flow/scalar field conditions. The analysis extends the original Zeldovich’s theory by combining the turbulent flow and scalar characteristics in terms of the characteristic Damköhler and Reynolds numbers of the system, thereby providing unified and comprehensive understanding of the physical and chemical mechanisms controlling autoignition. Estimated parameters for existing experimental measurements in a rapid compression facility show that the regime diagram predicts the observed ignition characteristics with good fidelity.

FlexDex™: A Minimally Invasive Surgical Tool With Enhanced Dexterity and Intuitive Actuation

This paper presents the design and fabrication of a novel minimally invasive surgical (MIS) tool — FlexDex™ — that provides enhanced dexterity, intuitive actuation, and natural force feedback in a cost-effective compact package. These attributes are accomplished by means of a fundamentally new MIS tool design paradigm that employs a tool reference attached to the surgeon’s arm, and utilizes a virtual center at the tool input that coincides with the surgeon’s wrist. The resulting physical configuration enables a highly intuitive one-to-one mapping of the surgeon’s arm and hand motions at the tool input to the end-effector motions at the tool output inside the patient’s body. Furthermore, a purely mechanical design ensures low-cost, simple construction, and natural force feedback. A functional decomposition of the proposed design paradigm and associated physical configuration is carried out to identify key modules in the system. This allows for the conceptual and detailed design of each module, followed by system-level integration. The key innovative aspects of the tool design include a three-dimensional parallel-kinematic virtual center mechanism, a decoupled 2DoF end-effector design, and the associated transmissions system.Copyright