Henri Temianka Correspondence; (davenport)

This collection contains material pertaining to the life, career, and activities of Henri Temianka, violin virtuoso, conductor, music teacher, and author. Materials include correspondence, concert programs and flyers, music scores, photographs, and books.https://digitalcommons.chapman.edu/temianka_correspondence/1792/thumbnail.jp

Henri Temianka Correspondence; (davenport)

This collection contains material pertaining to the life, career, and activities of Henri Temianka, violin virtuoso, conductor, music teacher, and author. Materials include correspondence, concert programs and flyers, music scores, photographs, and books.https://digitalcommons.chapman.edu/temianka_correspondence/1790/thumbnail.jp

Program: Featured Lecture, An Uneasy Relationship: The Church in a Post-Modern World.

Program for the Twelfth Annual William M. Green Distinguished Christian Lecture Program with featured lecturer Dr. David Davenport, President of Pepperdine University

Using the distribution of cells by dimension in a cylindrical algebraic decomposition

We investigate the distribution of cells by dimension in cylindrical algebraic decompositions (CADs). We find that they follow a standard distribution which seems largely independent of the underlying problem or CAD algorithm used. Rather, the distribution is inherent to the cylindrical structure and determined mostly by the number of variables. This insight is then combined with an algorithm that produces only full-dimensional cells to give an accurate method of predicting the number of cells in a complete CAD. Since constructing only full-dimensional cells is relatively inexpensive (involving no costly algebraic number calculations) this leads to heuristics for helping with various questions of problem formulation for CAD, such as choosing an optimal variable ordering. Our experiments demonstrate that this approach can be highly effective.Comment: 8 page

Program Verification in the presence of complex numbers, functions with branch cuts etc

In considering the reliability of numerical programs, it is normal to "limit our study to the semantics dealing with numerical precision" (Martel, 2005). On the other hand, there is a great deal of work on the reliability of programs that essentially ignores the numerics. The thesis of this paper is that there is a class of problems that fall between these two, which could be described as "does the low-level arithmetic implement the high-level mathematics". Many of these problems arise because mathematics, particularly the mathematics of the complex numbers, is more difficult than expected: for example the complex function log is not continuous, writing down a program to compute an inverse function is more complicated than just solving an equation, and many algebraic simplification rules are not universally valid. The good news is that these problems are theoretically capable of being solved, and are practically close to being solved, but not yet solved, in several real-world examples. However, there is still a long way to go before implementations match the theoretical possibilities

A "Piano Movers" Problem Reformulated

It has long been known that cylindrical algebraic decompositions (CADs) can in theory be used for robot motion planning. However, in practice even the simplest examples can be too complicated to tackle. We consider in detail a "Piano Mover's Problem" which considers moving an infinitesimally thin piano (or ladder) through a right-angled corridor. Producing a CAD for the original formulation of this problem is still infeasible after 25 years of improvements in both CAD theory and computer hardware. We review some alternative formulations in the literature which use differing levels of geometric analysis before input to a CAD algorithm. Simpler formulations allow CAD to easily address the question of the existence of a path. We provide a new formulation for which both a CAD can be constructed and from which an actual path could be determined if one exists, and analyse the CADs produced using this approach for variations of the problem. This emphasises the importance of the precise formulation of such problems for CAD. We analyse the formulations and their CADs considering a variety of heuristics and general criteria, leading to conclusions about tackling other problems of this form.Comment: 8 pages. Copyright IEEE 201

Choosing a variable ordering for truth-table invariant cylindrical algebraic decomposition by incremental triangular decomposition

Cylindrical algebraic decomposition (CAD) is a key tool for solving problems in real algebraic geometry and beyond. In recent years a new approach has been developed, where regular chains technology is used to first build a decomposition in complex space. We consider the latest variant of this which builds the complex decomposition incrementally by polynomial and produces CADs on whose cells a sequence of formulae are truth-invariant. Like all CAD algorithms the user must provide a variable ordering which can have a profound impact on the tractability of a problem. We evaluate existing heuristics to help with the choice for this algorithm, suggest improvements and then derive a new heuristic more closely aligned with the mechanics of the new algorithm

A near real-time algorithm for flood detection in urban and rural areas using high resolution Synthetic Aperture Radar images

A near real-time flood detection algorithm giving a synoptic overview of the extent of flooding in both urban and rural areas, and capable of working during night-time and day-time even if cloud was present, could be a useful tool for operational flood relief management and flood forecasting. The paper describes an automatic algorithm using high resolution Synthetic Aperture Radar (SAR) satellite data that assumes that high resolution topographic height data are available for at least the urban areas of the scene, in order that a SAR simulator may be used to estimate areas of radar shadow and layover. The algorithm proved capable of detecting flooding in rural areas using TerraSAR-X with good accuracy, and in urban areas with reasonable accuracy

Acholi Clan, Ethnic, and National Identities in Post-Conflict Northern Uganda: A Case Study in Koch Goma Sub-County, Nwoya District

the following essay, the researcher will explore the clan, ethnic, and national identities of the Acholi people in the context of post-conflict northern Uganda. The researcher will first describe and interpret the meaning of these identities to Acholi people he interviewed during his research, and then he will analyze them in the post-conflict, socio-cultural context of northern Uganda. During a research period of four weeks, the researcher spent a total of twelve days in Koch Goma Sub-Country, Nwoya District conducting one-on-one interviews. During this time, the researcher was able to interview eighteen people. Data was collected and analyzed qualitatively as well as against the background of theoretical arguments from scholars of anthropology, sociology, and psychology. Unfortunately, the small population size of participants makes the extrapolation of patterns found within the data collected difficult, especially due to the under-representation of educated women in the population size. Furthermore, many of the people of Koch fled to Gulu or Banyoro land during the conflict, an uncontrollable variable that makes it more difficult to generalize these findings to all Acholi. Hence, these findings are presented as a case study of Koch Goma Sub-County. Aside from understanding the meaning of clan, ethnic, and national identities to the Acholi interviewed, several themes became apparent: the Acholi of Koch Goma feel a sense of collective shame as a result of the conflict; the conflict has also affected how some Acholi view themselves as members of their clan and Uganda. Furthermore, protection and social utility is a major factor in determining which identity an individual expresses more over others. Lastly, travelling and interacting with the “other”—someone from another clan, tribe, or nation—affects the way in which an individual defines his identities