Steven Johnston

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A quantum mechanical description of particle propagation on the discrete spacetime of a causal set is presented. The model involves a discrete path integral in which trajectories within the causal set are summed over to obtain a particle propagator. The sum-over-trajectories is achieved by a matrix geometric series. For causal sets generated by sprinkling(More)
In this paper we present the features of a new physical device prototyping platform called Microsoft .NET Gadgeteer along with our initial experiences using it to teach computer science in high schools. Gadgeteer makes it easy for newcomers to electronics and computing to plug together modules with varied functionality and to program the resulting system's(More)
Dilute nitride films with a roughly 1 eV band gap can be lattice-matched to gallium arsenide and germanium, and therefore could become a critical component in next-generation multijunction solar cells. To date most dilute nitride solar cells have been plagued with poor efficiency, due in large part to short diffusion lengths. This study focuses on two(More)
Thin-film CdS is used as a window layer in most of the current thin-film polycrystalline device technologies including absorbers based on cadmium telluride (CdTe) and copper indium selenide (CIS) and copper indium gallium se-lenide (CIGS). Device performance has been linked to the deposition technique and posttreatment of the CdS layer. Here we used the(More)
Contactless measurement of important semiconductor parameters has become a popular trend of current semiconductor technology. Here we will describe an improved version of radio frequency photoconductive decay (RFPCD) operating in the ultra-high frequency (UHF) region. This work will show that the improved technique is capable of measuring samples ranging in(More)
Time series data has been exploited for use with Case Based Reasoning (CBR) in many applications. We present a novel application of CBR that combines intelligent tutoring using Augmented Reality (AR) and prediction. The MonitAR system, presented in this paper, is intended for use as an intelligent guidance system for astronauts conducting complex procedures(More)
In this paper, we present an approach to detecting novel cyber attacks though a form of program diversification, similar to the use of n-version programming for fault tolerant systems. Building on extensive previous and ongoing work by others on the use of code clones in a wide variety of areas, our Functionally Equivalent Variants using Information(More)
Vacuum Circuit Breakers (VCBs) are commonly applied to the primary circuit to switch ladle melt furnace (LMF) transformers in melt shop applications that support rolling mill operations. Because of the well-documented phenomenon of switching transients induced on the line of the furnace transformer due to the opening and closing of the VCB, most LMFs in(More)
Vacuum circuit breakers are commonly applied to the primary circuit to switch Ladle Melt Furnaces (LMF) transformers in melt shop applications which support rolling mill operations. Because of the well documented phenomenon of switching transients induced on the line of the furnace transformer due to the opening and closing of the vacuum circuit breaker(More)