Mechanical Engineering Commons^™

Electron Transport In E X B Devices, Emily C. Fossum

Dissertations, Master's Theses and Master's Reports - Open

A Hall thruster, an E × B device used for in-space propulsion, utilizes an axial electric field to electrostatically accelerate plasma propellant from the spacecraft. The axial electric field is created by positively biasing the anode so that the positivelycharged ions may be accelerated (repelled) from the thruster, which produces thrust. However, plasma electrons are much smaller than ions and may be accelerated much more quickly toward the anode; if electrons were not impeded, a "short circuit" due to the electron flow would eliminate the thrust mechanism. Therefore, a magnetic field serves to "magnetize" plasma electrons internal to the thruster …

Decentralized Or Centralized Production : Impacts To The Environment, Industry, And The Economy, Abigail R. Clarke-Sather

Dissertations, Master's Theses and Master's Reports - Open

Since product take-back is mandated in Europe, and has effects for producers worldwide including the U.S., designing efficient forward and reverse supply chain networks is becoming essential for business viability. Centralizing production facilities may reduce costs but perhaps not environmental impacts. Decentralizing a supply chain may reduce transportation environmental impacts but increase capital costs. Facility location strategies of centralization or decentralization are tested for companies with supply chains that both take back and manufacture products.

Decentralized and centralized production systems have different effects on the environment, industry and the economy. Decentralized production systems cluster suppliers within the geographical market region …

Micro-Fabrication Of Bio-Mems Based Force Sensor To Measure The Force Response Of Living Cells, Varun Gouthaman

Dissertations, Master's Theses and Master's Reports - Open

Understanding how a living cell behaves has become a very important topic in today’s research field. Hence, different sensors and testing devices have been designed to test the mechanical properties of these living cells. This thesis presents a method of micro-fabricating a bio-MEMS based force sensor which is used to measure the force response of living cells. Initially, the basic concepts of MEMS have been discussed and the different micro-fabrication techniques used to manufacture various MEMS devices have been described. There have been many MEMS based devices manufactured and employed for testing many nano-materials and bio-materials. Each of the MEMS …

Immobilizing Bacteriorhodopsin On A Single Electron Transistor, Karl A. Walczak

Dissertations, Master's Theses and Master's Reports - Open

As awareness of potential human and environmental impacts from toxins has increased, so has the development of innovative sensors. Bacteriorhodopsin (bR) is a light activated proton pump contained in the purple membrane (PM) of the bacteria Halobacterium salinarum. Bacteriorhodopsin is a robust protein which can function in both wet and dry states and can withstand extreme environmental conditions. A single electron transistor(SET) is a nano-scale device that exploits the quantum mechanical properties of electrons to switch on and off. SETs have tremendous potential in practical applications due to their size, ultra low power requirements, and electrometer-like sensitivity.

The main …

Hall-Effect Thruster-Cathode Coupling : The Effect Of Cathode Position And Magnetic Field Topology, Jason D. Sommerville

Dissertations, Master's Theses and Master's Reports - Open

Hall-effect thruster (HET) cathodes are responsible for the generation of the free electrons necessary to initiate and sustain the main plasma discharge and to neutralize the ion beam. The position of the cathode relative to the thruster strongly affects the efficiency of thrust generation. However, the mechanisms by which the position affects the efficiency are not well understood. This dissertation explores the effect of cathode position on HET efficiency. Magnetic field topology is shown to play an important role in the coupling between the cathode plasma and the main discharge plasma. The position of the cathode within the magnetic field …

Afrc Translation Experiments For Space Propulsion, Carrie S. Niemela

Dissertations, Master's Theses and Master's Reports - Open

No abstract provided.