Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 30 for “"Contact Geometry"”.
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Orderability and rigidity in contact geometry
<p>We study the existence of positive loops of contactomorphisms on a Liouville-fillable contact manifold (&Sgr;, ξ = ker(α)). Previous results (see [1]) show that a large class of Liouville-fillable contact manifolds admit contractible positive loops. In contrast, we show that for any …
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A study of fretting fatigue incorporating sharp corner contact geometry.
Fretting fatigue occurs when components are in contact and subjected to cyclic loads or vibrations. The following research programme investigates the fretting fatigue phenomenon using a specific flat contact geometry encompassing sharp comers. The pressure distribution at the contact interface is …
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A Tourist's Account of Characteristic Foliations on Convex Surfaces in 3-D Contact Geometry
… begin with a rapid introduction to the theory of contact topology, first spending more time than you would probably want on developing the notion of contact manifold before launching right into the thick of the theory. The tools of characteristic foliations and convex surfaces are introduced next, …
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Investigation of the finite element method for computing wheel/rail contact forces in steady curving
… include such nonlinear effects as two-point contact, creep force saturation, and rail flexibility. The usual approximation concerning the contact geometry is that the Iocalized wheel and rail curvatures at the center of the contact patch are constant throughout the contact patch. This …
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Nonlinear Investigation of the Use of Controllable Primary Suspensions to Improve Hunting in Railway Vehicles
… friction-creep characteristics of the wheel-rail contact geometry. Hunting can lead to severe ride discomfort and eventual physical damage to wheels and rails. A comprehensive study of the lateral stability of a single wheelset, a single truck, and the complete rail vehicle has been performed. …
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Manipulation of unknown objects via contact configuration regulation
… objects through the regulation of an object's contact configuration: the location, geometry, and mode of all contacts between the object, robot, and environment. A contact configuration constrains the forces and motions that can be applied to the object. As such, the ability to predict and …
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A computational approach to the prediction of wheel wear profiles
… model based upon the work done in the wheel/rail contact patch is used to predict wheel wear profiles. The effects of train dynamic response, random rail alignment and the non-linearity of wheel/rail contact geometry are included The distribution of contact patch work is obtained by discretized …
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Vision-based proprioception and tactile sensing for soft robots
… elastomer surface to encode deformation and contact geometry in one image. To co-design hardware and perception, we develop a simulation pipeline that couples finite-element deformation with physics-based optical rendering, enabling design optimization and training data generation. The …
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Robust proprioceptive grasping with a soft robot hand
… resistive force sensors on the fingertips for contact detection and resistive bend sensors for measuring the curvature profile of the finger. The curvature sensors can be used to estimate the contact geometry and thus to distinguish between a set of grasped objects. With one data point from …
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Prediction of wheel wear profiles by analytical methods
… three fundamental steps. First, the wheel/rail contact geometry is characterized. Contact points, Herzian contact patch area and creep coefficients are determined as functions of the wheelset lateral position. Second, a time history of the wheelset positions and velocities is determined from a …
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Realtime state estimation for contact manipulation
… state estimation system to recover the pose and contact state of an object relative to its environment. The capability to make such estimations is important for a controller to adequately react to uncertainties in a manipulation task. We propose a framework that combines tactile and visual …
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Infrared measurements of surface temperatures during oscillating/fretting contact with ceramics
… generated by friction during osculating/fretting contact were measured using an infrared microscope coupled to a digital data acquisition system developed at Virginia Polytechnic Institute and State University. The contact geometry consisted of a stationary test specimen loaded against a vibrating …
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Interactive Touch for Manipulation
… with our physical world and inevitably make contact with various objects. Touch provides contact geometry and forces information during interactions, which can be challenging to observe from vision due to occlusions or inherent limitations. This thesis will focus on how to let robots leverage …
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A Study of Heat Transfer Through Periodically Contacting Surfaces
… the interface between two solids which make contact and then separate periodically. The cycle of contact and separation is continuous and the quasi-steady state only is considered. The system chosen as the model for study comprised two identical solid bars, arranged with their longitudinal …
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Visuo-Tactile Perception for Dexterous Robotic Manipulation
… allows extracting geometric information from contacts which is a task-independent feature. By learning to map tactile observations to contact shapes, we show robots can reconstruct accurate 3D models of objects, which can later be used for pose estimation. We build on the idea of using …
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A study of fretting fatigue in aircraft components
… relevant to aircraft components. The basic contact mechanics for fretting fatigue in a sphere-plane contact geometry are reviewed. Various elastic criteria for predicting fretting failure are discussed; selected fretting maps created from one of these - the modified Crossland criterion -- …
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Low-voltage organic transistors with high transconductance
… implementation of the multi-finger source/drain contacts. The transistors based on dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) exhibited low turn-on voltage and a.c. transconductance around 30 to 60 µS. Transistor amplifiers based on such transistors exhibited voltage gain approaching …
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Imaging Single-Electron Charging in Nanostructures by Low-Temperature Scanning Force Microscopy
… This advantage is apparent in the single-contact geometry of the gold nanoparticles, but also demonstrated on CNTs.
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MEMS relays for make-break power switching applications : {111} silicon etched planar electrical contacts
… feature { 111}-plane silicon-etched electrical contacts. The { 111}-plane contacts provide travel of 30-80 [mu]m, which prevents arcing. Their oblique geometry introduces contact wipe, which is known to enhance the contact reliability. Further, the contact geometry allows for an enhanced …
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Imaging and Understanding Atomic-Scale Adhesion and Wear: Quantitative investigations Using in situ TEM
… (AFM). However, AFM lacks direct access to the contact geometry and structure. In this thesis, nanoscale adhesion and wear tests were performed inside of a transmission electron microscope (TEM), enabling real-time in situ interrogation of the contact in vacuum. Quantitative data was extracted …
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