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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

A Constitutive Model for the Mechanical Behavior of Single Crystal Silicon at Elevated Temperature

Moon, H.-S., Anand, Lallit, Spearing, S. Mark 01 1900 (has links)
Silicon in single crystal form has been the material of choice for the first demonstration of the MIT microengine project. However, because it has a relatively low melting temperature, silicon is not an ideal material for the intended operational environment of high temperature and stress. In addition, preliminary work indicates that single crystal silicon has a tendency to undergo localized deformation by slip band formation. Thus it is critical to obtain a better understanding of the mechanical behavior of this material at elevated temperatures in order to properly exploit its capabilities as a structural material. Creep tests in simple compression with n-type single crystal silicon, with low initial dislocation density, were conducted over a temperature range of 900 K to 1200 K and a stress range of 10 MPa to 120 MPa. The compression specimens were machined such that the multi-slip <100> or <111> orientations were coincident with the compression axis. The creep tests reveal that response can be delineated into two broad regimes: (a) in the first regime rapid dislocation multiplication is responsible for accelerating creep rates, and (b) in the second regime an increasing resistance to dislocation motion is responsible for the decelerating creep rates, as is typically observed for creep in metals. An isotropic elasto-viscoplastic constitutive model that accounts for these two mechanisms has been developed in support of the design of the high temperature turbine structure of the MIT microengine. / Singapore-MIT Alliance (SMA)
2

Experimental Investigation and Modeling of Scale Effects in Micro Jet Pumps

Gardner, William Geoffrety January 2011 (has links)
<p>Since the mid-1990s there has been an active effort to develop hydrocarbon-fueled power generation and propulsion systems on the scale of centimeters or smaller. This effort led to the creation and expansion of a field of research focused around the design and reduction to practice of Power MEMS (microelectromechanical systems) devices, beginning first with microscale jet engines and a generation later more broadly encompassing MEMS devices which generate power or pump heat. Due to small device scale and fabrication techniques, design constraints are highly coupled and conventional solutions for device requirements may not be practicable. </p><p>This thesis describes the experimental investigation, modeling and potential applications for two classes of microscale jet pumps: jet ejectors and jet injectors. These components pump fluids with no moving parts and can be integrated into Power MEMS devices to satisfy pumping requirements by supplementing or replacing existing solutions. This thesis presents models developed from first principles which predict losses experienced at small length scales and agree well with experimental results. The models further predict maximum achievable power densities at the onset of detrimental viscous losses.</p> / Dissertation
3

Network processors and utilizing their features in a multicast design

Diler, Timur 03 1900 (has links)
Approved for public release, distribution is unlimited / In order to address the requirements of the rapidly growing Internet, network processors have emerged as the solution to the customization and performance needs of networking systems. An important component in a network is the router, which receives incoming packets and directs them to specific routes elsewhere in the system. Network processors and the associated software control the routers and switches and allow software designers to deploy new systems such as multicasting forwarder and firewalls quickly.This thesis introduces network processors and their features, focusing on the Intel IXP1200 network processor. A multicast design for the IXP1200 using microACE is proposed. This thesis presents an approach to building a multicasting forwarder using the IXP1200 network processor layer-3 forwarder microACE that carries out unicast routing. The design is based on the Intel Internet exchange architecture and its active computing element (ACE). The layer-3 unicast forwarder microACE is used as a basic starting point for the design. Some software modules, called micoblocks, are modified to create a multicast forwarder that is flexible and efficient. / Lieutenant Junior Grade, Turkish Navy

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