Improved micro-contact resistance model that considers material deformation, electron transport and thin film characteristics

This paper reports on an improved analytic model forpredicting micro-contact resistance needed for designing microelectro-mechanical systems (MEMS) switches. The originalmodel had two primary considerations: 1) contact materialdeformation (i.e. elastic, plastic, or elastic-plastic) and 2) effectivecontact area radius. The model also assumed that individual aspotswere close together and that their interactions weredependent on each other which led to using the single effective aspotcontact area model. This single effective area model wasused to determine specific electron transport regions (i.e. ballistic,quasi-ballistic, or diffusive) by comparing the effective radius andthe mean free path of an electron. Using this model required thatmicro-switch contact materials be deposited, during devicefabrication, with processes ensuring low surface roughness values(i.e. sputtered films). Sputtered thin film electric contacts,however, do not behave like bulk materials and the effects of thinfilm contacts and spreading resistance must be considered. Theimproved micro-contact resistance model accounts for the twoprimary considerations above, as well as, using thin film,sputtered, electric contact

Biophysical Studies of Rab GTPase Membrane Binding

Rab proteins are the largest subfamily of the Ras superfamily of small GTPases, with more than 60 known members, that are involved in a multitude of different processes regulating membrane traffic. Rab proteins cycle between the cytosol and association with membranes, whereby each Rab exhibits a characteristic and specific subcellular localisation. It remains obscure how Rab proteins, in spite of high sequence and structure identity, distinguish between different membranes in the cell with such specificity. Membrane biophysical properties, such as stored curvature elastic stress and bending rigidity, are increasingly found to be determinants for protein recruitment and activity, and other Ras related proteins have recently been shown to exhibit sensitivity towards lipid species and elastic membrane properties. In this study Rab membrane binding is for the first time correlated to membrane bending rigidity, suggesting that biophysical properties of lipid membranes may play a role in the regulation of Rab targeting. Furthermore, all Rab proteins tested were observed to bind membranes in the absence of other protein factors, questioning the function of protein targeting factors for the Rab membrane recruitment process. Another aspect of Rab membrane interaction is Rab extraction from membranes by GDI. A large scale in vitro screening of 17 Rab proteins revealed a broad range of extractability from membranes with GDI. No correlation was found between extractability and the C-terminal prenylation motif, and no difference in extractability was observed in direct comparison of the extraction potential with GDIα and β. However, Rab proteins that exhibited low extractability from membranes are involved in secretory processes, suggesting a functional correlation to extractability. Furthermore, Rab40c as the first mammalian Rab protein to date was shown to be palmitoylated

Analysis and interpretation of airborne electromagnetic and magnetic data

In this research, I focused on processing and modeling of TDEM and aeromagnetic data acquired during the same survey, with the aim of exploring the possibilities for a joint interpretation of these different datasets. My research involved both methodological advances and applications to real dataset. In particular, I will show two case studies, both located in Canada. The first one, is related to Broken Evil prospect in Ontario. This region hosts some of the richest mineral deposits of Canada (especially volcanic massive sulfide deposits). The second one is related to Drybones bay in Northwest Territories, where in 1994 a completely underwater kimberlite structure was discovered. The interpretative results of the TDEM and magnetic data reveal that the sensitivity of the two methods may differ with respect to the investigated geological structures. This would imply a certain difficulty in setting up a true joint inversion algorithm to interpret these two data types simultaneously that would be valid in all the studied cases. However, results show how with different resolution and depth of investigation, in the studied areas the cooperation of the TDEM and aeromagnetic data can lead to a better understand of the structures at depth

Numerical and experimental analysis on microbubble generation and multiphase mixing in novel microfluidic devices

In this study, a novel K-junction microfluidic junction and a conventional cross-junction were investigated numerically and experimentally for microbubble generation and multiple fluids mixing. In the K-junction, liquid solutions were injected into the junction via three liquid inlet channels, along with inert nitrogen gas supplied via the gas inlet channel, to periodically generate microbubbles in a controlled manner at the outlet channel. Numerical simulations based on Finite Volume method and Volume of Fluid (VOF) technique and experiments of both the K-junction and the cross-junction were conducted. The effect of parameters such as contact angle, surface tension, viscosity, gas pressure and gas-liquid flow ratios on the microbubble size distribution was investigated. The process of microbubble generation, obtained through high speed camera imaging and the numerical simulation, has shown good agreement in both junctions as well as the influence of viscosity and gas-liquid flow ratios for the K-junction and cross-junction. It was indicated that parameters like solution viscosities, gas-to-liquid flow ratios, gas inlet pressure, and their combination have a significant influence on the microbubble diameter, which was found to be in the range of 70-240 µm when using micro capillaries of 100 µm inner diameter. The multiple fluids mixing study was investigated by using two or three different polymer solutions for the cross-junction and the K-junction respectively in simulations and experiments. It can be seen that the mixing process obtained from simulations agrees well with experimental results and chaotic mixing was found in the mixing area of the K-junction, with higher mixing efficiency than the cross junction. Fluorescent images of microbubbles generated by using polymer solutions with dyes inside have shown the devices’ potential of encapsulating fluorescent dyes and polymers on the shell of bubbles and could be adopted as a method to encapsulate active pharmaceutical ingredients for potential applications in drug delivery

NASA Tech Briefs, August 1992

Topics include: Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences

Measurement of the cosmic-induced neutron yield at the Modane underground laboratory

Muon-induced neutrons (µ-ind. n\u27s) are an important background source for Dark Matter searches, e.g. EDELWEISS at Laboratoire Souterrain de Modane (LSM). Within this work, a data set of 313 µ-ind. n\u27s at LSM was collected. Using Geant4 and a calibrated detector response model, the absolute neutron rate is reproduced within 15% and agrees within the uncertainties. This work demonstrates that Geant4 can reliably model the production of µ-ind. n\u27s once a detailed model is implemented

Rotordynamic Instability Problems in High-Performance Turbomachinery, 1988

The continuing trend toward a unified view is supported with several developments in the design and manufacture of turbomachines with enhanced stability characteristics along with data and associated numerical/theoretical results. The intent is to provide a continuing impetus for an understanding and resolution of these problems. Topics addressed include: field experience, dampers, seals, impeller forces, bearings, and compressor and rotor modeling

Prediction of Robot Execution Failures Using Neural Networks

In recent years, the industrial robotic systems are designed with abilities to adapt and to learn in a structured or unstructured environment. They are able to predict and to react to the undesirable and uncontrollable disturbances which frequently interfere in mission accomplishment. In order to prevent system failure and/or unwanted robot behaviour, various techniques have been addressed. In this study, a novel approach based on the neural networks (NNs) is employed for prediction of robot execution failures. The training and testing dataset used in the experiment consists of forces and torques memorized immediately after the real robot failed in assignment execution. Two types of networks are utilized in order to find best prediction method - recurrent NNs and feedforward NNs. Moreover, we investigated 24 neural architectures implemented in Matlab software package. The experimental results confirm that this approach can be successfully applied to the failures prediction problem, and that the NNs outperform other artificial intelligence techniques in this domain. To further validate a novel method, real world experiments are conducted on a Khepera II mobile robot in an indoor structured environment. The obtained results for trajectory tracking problem proved usefulness and the applicability of the proposed solution

Neural Extended Kalman Filter for State Estimation of Automated Guided Vehicle in Manufacturing Environment

To navigate autonomously in a manufacturing environment Automated Guided Vehicle (AGV) needs the ability to infer its pose. This paper presents the implementation of the Extended Kalman Filter (EKF) coupled with a feedforward neural network for the Visual Simultaneous Localization and Mapping (VSLAM). The neural extended Kalman filter (NEKF) is applied on-line to model error between real and estimated robot motion. Implementation of the NEKF is achieved by using mobile robot, an experimental environment and a simple camera. By introducing neural network into the EKF estimation procedure, the quality of performance can be improved