Ion engine thrust vector study, phase 2 Quarterly report

Performance prediction for expected thrust misalignment in electron bombardment ion thruste

Ion engine thrust vector study

Probability of thrust vector misalignment in ion thrustor arra

A redundant arithmetic CORDIC system with a unit scale factor

The CORDIC algorithm for the calculation of trigonometric functions has traditionally suffered from two problems; speed, and the necessity to pre-scale the inputs. The speed problem is overcome to a large extent by the introduction of redundant number systems which have been shown by others. Here we show a new CORDIC system which has a unit scale factor that can be ignored. The unit scale factor is achieved by rotating the vector in 3 dimensional space in a manner which scales its projection onto the X-Y plane by the reciprocal of the overall scale factor. This new technique takes the same number of cycles as the standard CORDIC algorithm, with only marginally slower cycle times than the redundant system of Takagi. The system is shown to be entirely compatible with redundant number system implementations of the CORDIC algorithm

Predicting the cache miss ratio of loop-nested array references

The time a program takes to execute can be massively affected by the efficiency with which it utilizes cache memory. Moreover the cache-miss behavior of a program can be highly unpredictable, in that small changes to input parameters can cause large changes in the number of misses. In this paper we present novel analytical models of the cache behavior of programs consisting mainly of array operations inside nested loops, for direct-mapped caches. The models are used to predict the miss-ratios of three example loop nests; the results are shown to be largely within ten percent of simulated values. A significant advantage is that the calculation time is proportional to the number of array references in the program, typically several orders of magnitude faster than traditional cache simulation methods

From Animaculum to single-molecules : 300 years of the light microscope

Although not laying claim to being the inventor of the light microscope, Antonj van Leeuwenhoek (1632-1723) was arguably the first person to bring this new technological wonder of the age properly to the attention of natural scientists interested in the study of living things (people we might now term 'biologists'). He was a Dutch draper with no formal scientific training. From using magnifying glasses to observe threads in cloth, he went on to develop over 500 simple single lens microscopes (Baker & Leeuwenhoek 1739 Phil. Trans. 41, 503-519. (doi:10.1098/rstl.1739.0085)) which he used to observe many different biological samples. He communicated his finding to the Royal Society in a series of letters (Leeuwenhoek 1800 The select works of Antony Van Leeuwenhoek, containing his microscopical discoveries in many of the works of nature, vol. 1) including the one republished in this edition of Open Biology. Our review here begins with the work of van Leeuwenhoek before summarizing the key developments over the last ca 300 years, which has seen the light microscope evolve from a simple single lens device of van Leeuwenhoek's day into an instrument capable of observing the dynamics of single biological molecules inside living cells, and to tracking every cell nucleus in the development of whole embryos and plants

Lunar lander conceptual design

This paper is a first look at the problems of building a lunar lander to support a small lunar surface base. A series of trade studies was performed to define the lander. The initial trades concerned choosing number of stages, payload mass, parking orbit altitude, and propellant type. Other important trades and issues included plane change capability, propellant loading and maintenance location, and reusability considerations. Given a rough baseline, the systems were then reviewed. A conceptual design was then produced. The process was carried through only one iteration. Many more iterations are needed. A transportation system using reusable, aerobraked orbital transfer vehicles (OTV's) is assumed. These OTV's are assumed to be based and maintained at a low Earth orbit (LEO) space station, optimized for transportation functions. Single- and two-stage OTV stacks are considered. The OTV's make the translunar injection (TLI), lunar orbit insertion (LOI), and trans-Earth injection (TEI) burns, as well as midcourse and perigee raise maneuvers

Ion engine thrust vector study Quarterly report

Ion beam current and direction changes due to electrode misalignment, and analysis of electrode temperature distribution and thermal stresses in ion engine thrust vecto

Story-Making: A Narrative Pedagogy For Transformative Christian Faith

Thesis advisor: Thomas H. GroomeThe mid-twentieth century upsurge in scholarship on the methodological and conceptual importance of narrative for theology - established in the work of H.R. Niebuhr, Hans Frei and Stephen Crites inter alia - was a watershed moment for narrative pedagogy in Christian religious education. By and large, narrative approaches have however tended to privilege one form of narrative embodiment - literary (or discursive narratives) - over action (or non-discursive narratives). This dissertation points to the equivocal and pluriform nature of narrativity, and its codification in much more than oral and written textuality. I extend it to refer to a distinct competency for establishing a meaningful world (or ethos) to inhabit, which congeals in varied forms of human expression including our lived narratives. Narrative competency allows us to understand ourselves as persons and communities in (synchronic) relationship with the rest of creation, as well as in (diachronic) relation with persons and communities from the past and in the anticipated future. I propose a narrative pedagogy for transformative faith based on the concept of story-making, which draws on this expanded understanding of narrativity. My story-making approach is grounded in Christian praxis that aims to establish the experiential matrix that, through the working of God's grace, invites and aids the re-storying of the learner's life. Story-making also has as its vision narrative historic praxis that incarnates in social action the understanding that human subjectivity is lived in responsible agency in the present, retrieving the memory of suffering and possibility from the past, in the hope of a more just future. This dissertation is inspired by the Caribbean heritage of survival and grace-filled possibility, but ultimately extrapolates for universal wisdom. It is sustained by a belief that Christian religious education is about forming disciples with agency for furthering the Great story of the reign of God in history and society. The creative, even poetic, enterprise of Caribbean existence is iconic of this existential challenge that remains ubiquitous for life in the modern globalized economy.Thesis (PhD) — Boston College, 2013.Submitted to: Boston College. Graduate School of Arts and Sciences.Discipline: Religious Education and Pastoral Ministry

Dynamic character recognition using hidden Markov models

Hidden Markov Model theory is an extension of the Markov Model process. It has found uses in such areas as speech recognition, target tracking and word recognition. One area which has received little in the way of research interest, is the use of Hidden Markov Models in character recognition. In this paper the application of Hidden Markov Model theory to dynamic character recognition is investigated. The basic Hidden Markov Model theory is reviewed, and so are the algorithms associated with it. A quick overview of the dynamic character recognition process is considered. Then three types of describing characters are considered, position, inclination angle of small vectors and stroke directional encoding using a Freeman code. A system using each of these descriptions, using Hidden Markov Models in the comparison stage, is described. It is recognised that experiments using the different encoding systems have to be carried out to check the validity of this chosen method

The Viterbi algorithm

This paper is a tutorial introduction to the Viterbi Algorithm, this is reinforced by an example use of the Viterbi Algorithm in the area of error correction in communications channels. Some extensions to the basic algorithm are also discussed briefly. Some of the many application areas where the Viterbi Algorithm has been used are considered, including it's use in communications. target tracking and pattern recognition problems. A proposal for further research into the use of the Viterbi Algorithm in Signature Verification is then presented, and is the area of present research at the moment