The Faculty Notebook, September 2011

The Faculty Notebook is published periodically by the Office of the Provost at Gettysburg College to bring to the attention of the campus community accomplishments and activities of academic interest. Faculty are encouraged to submit materials for consideration for publication to the Associate Provost for Faculty Development. Copies of this publication are available at the Office of the Provost

Improved micro-contact resistance model that considers material deformation, electron transport and thin film characteristics

This paper reports on an improved analytic model forpredicting micro-contact resistance needed for designing microelectro-mechanical systems (MEMS) switches. The originalmodel had two primary considerations: 1) contact materialdeformation (i.e. elastic, plastic, or elastic-plastic) and 2) effectivecontact area radius. The model also assumed that individual aspotswere close together and that their interactions weredependent on each other which led to using the single effective aspotcontact area model. This single effective area model wasused to determine specific electron transport regions (i.e. ballistic,quasi-ballistic, or diffusive) by comparing the effective radius andthe mean free path of an electron. Using this model required thatmicro-switch contact materials be deposited, during devicefabrication, with processes ensuring low surface roughness values(i.e. sputtered films). Sputtered thin film electric contacts,however, do not behave like bulk materials and the effects of thinfilm contacts and spreading resistance must be considered. Theimproved micro-contact resistance model accounts for the twoprimary considerations above, as well as, using thin film,sputtered, electric contact

En la medida de lo imposible [As far as impossible]

The following document presents my dissertation composition. The work is written for eight performers, including flute, clarinet, saxophone, French horn, percussion, violin, viola, and Double Bass. The duration of the piece is approximately sixteen minutes, in a single movement. This composition explores forms of discontinuity within continuous textures, and includes particular theatrical and staging elements

In what sense can instruments and bodies be said to form spaces?

My recent work is an exploration of the physical and conceptual mechanisms that interface people with instruments. Central to this investigation is a conception of the performer/instrument assemblage as a symbiosis of two parallel and interdependent systems: one – the performer – moves through space established by the other – the instrument. Each system possesses its own intrinsic properties and characteristics; each possesses capacities to affect and be affected by one another. The music emanates from this contiguous interaction. Instrument surface is understood as a compositional resource itself, a topological façade, defined by ordinal distances, that guides gestures along its contours. Within these fluctuating constellations of spatial coordinates, I consider all the relevant ways a body can move, and establish some general combinatory rules that inform the convergence of forces within the body. The traditional subjects of compositional contemplation such as form, duration, dynamic, etc. are not attributing features to the work per se but emerge as results from spatiotemporal relations of (bodily) movement’s correspondence with (instrumental) surface and mechanism. This liberation of movement is understood as a liberation of timbre, and the inherent indeterminacy of this relationship is embraced. As such, I would hypothesize that sound is, to an extent, freed from the subtractive tendencies of perception that might otherwise subvert it into generalized typological categories. Once liberated from the imagination, sound can bypass the brain and directly engage the nervous system

A Performance Guide to Glenn Kotche\u27s Monkey Chant

Solo percussionist and composer Glenn Kotche has achieved international fame with his experimental percussion-based music, collaborating with and composing for renowned contemporary music ensembles such as the Kronos Quartet, Band on a Can All-Stars, So Percussion, and Eighth Blackbird. One of his most celebrated compositions in recent years is Monkey Chant, which combines acoustic and electronic elements in a solo multiple percussion setting. Written and premiered in 2006, Kotche was inspired to compose Monkey Chant after listening to original field recordings in Bali from the Nonesuch Explorer Series. Found in these recordings is the popular Balinese music and dance drama known as Kecak. Monkey Chant showcases, through percussion, the intricate vocal patterns and recounting of the Ramayana Epic featured in Balinese Kecak. This monograph serves as an informational performance guide for Monkey Chant that simplifies and resolves performance questions and issues. It provides a contextual setting for the work with a brief biography of Glenn Kotche, including his musical influences and inspiration for the composition. Balinese Kecak is examined as well as the Hindu Ramayana tale as it relates to Kotche’s composition, revealing the function for its compositional form. This document also clarifies and details preparatory procedures for collecting and building the unique instruments required, also detailing schematics for electronic audio equipment and setup. Lastly, there is an analysis of compositional style and form, offering optional solutions to performance obstacles

Designing and Composing for Interdependent Collaborative Performance with Physics-Based Virtual Instruments

Interdependent collaboration is a system of live musical performance in which performers can directly manipulate each other’s musical outcomes. While most collaborative musical systems implement electronic communication channels between players that allow for parameter mappings, remote transmissions of actions and intentions, or exchanges of musical fragments, they interrupt the energy continuum between gesture and sound, breaking our cognitive representation of gesture to sound dynamics. Physics-based virtual instruments allow for acoustically and physically plausible behaviors that are related to (and can be extended beyond) our experience of the physical world. They inherently maintain and respect a representation of the gesture to sound energy continuum. This research explores the design and implementation of custom physics-based virtual instruments for realtime interdependent collaborative performance. It leverages the inherently physically plausible behaviors of physics-based models to create dynamic, nuanced, and expressive interconnections between performers. Design considerations, criteria, and frameworks are distilled from the literature in order to develop three new physics-based virtual instruments and associated compositions intended for dissemination and live performance by the electronic music and instrumental music communities. Conceptual, technical, and artistic details and challenges are described, and reflections and evaluations by the composer-designer and performers are documented

Finding Music in Chaos: Designing and Composing with Virtual Instruments Inspired by Chaotic Equations

Using chaos theory to design novel audio synthesis engines has been explored little in computer music. This could be because of the difficulty of obtaining harmonic tones or the likelihood of chaos-based synthesis engines to explode, which then requires re-instantiating of the engine to proceed with sound production. This process is not desirable when composing because of the time wasted fixing the synthesis engine instead of the composer being able to focus completely on the creative aspects of composition. One way to remedy these issues is to connect chaotic equations to individual parts of the synthesis engine instead of relying on the chaos as the primary source of all sound-producing procedures. To do this, one can create a physically-based synthesis model and connect chaotic equations to individual parts of the model. The goal of this project is to design a physically-inspired virtual instrument based on a conceptual percussion instrument model that utilizes chaos theory in the synthesis engine to explore novel sounds in a reliable and repeatable way for other composers and performers to use. This project presents a two-movement composition utilizing these concepts and a modular set of virtual instruments that can be used by anyone, which can be interacted with by a new electronic music controller called the Hexapad controller and standard MIDI controllers. The physically-inspired instrument created for the Hexapad controller is called the Ambi-Drum and standard MIDI controllers are used to control synthesis parameters and other virtual instruments

Timbral Learning for Musical Robots

abstract: The tradition of building musical robots and automata is thousands of years old. Despite this rich history, even today musical robots do not play with as much nuance and subtlety as human musicians. In particular, most instruments allow the player to manipulate timbre while playing; if a violinist is told to sustain an E, they will select which string to play it on, how much bow pressure and velocity to use, whether to use the entire bow or only the portion near the tip or the frog, how close to the bridge or fingerboard to contact the string, whether or not to use a mute, and so forth. Each one of these choices affects the resulting timbre, and navigating this timbre space is part of the art of playing the instrument. Nonetheless, this type of timbral nuance has been largely ignored in the design of musical robots. Therefore, this dissertation introduces a suite of techniques that deal with timbral nuance in musical robots. Chapter 1 provides the motivating ideas and introduces Kiki, a robot designed by the author to explore timbral nuance. Chapter 2 provides a long history of musical robots, establishing the under-researched nature of timbral nuance. Chapter 3 is a comprehensive treatment of dynamic timbre production in percussion robots and, using Kiki as a case-study, provides a variety of techniques for designing striking mechanisms that produce a range of timbres similar to those produced by human players. Chapter 4 introduces a machine-learning algorithm for recognizing timbres, so that a robot can transcribe timbres played by a human during live performance. Chapter 5 introduces a technique that allows a robot to learn how to produce isolated instances of particular timbres by listening to a human play an examples of those timbres. The 6th and final chapter introduces a method that allows a robot to learn the musical context of different timbres; this is done in realtime during interactive improvisation between a human and robot, wherein the robot builds a statistical model of which timbres the human plays in which contexts, and uses this to inform its own playing.Dissertation/ThesisDoctoral Dissertation Media Arts and Sciences 201

Ontology of music performance variation

Performance variation in rhythm determines the extent that humans perceive and feel the effect of rhythmic pulsation and music in general. In many cases, these rhythmic variations can be linked to percussive performance. Such percussive performance variations are often absent in current percussive rhythmic models. The purpose of this thesis is to present an interactive computer model, called the PD-103, that simulates the micro-variations in human percussive performance. This thesis makes three main contributions to existing knowledge: firstly, by formalising a new method for modelling percussive performance; secondly, by developing a new compositional software tool called the PD-103 that models human percussive performance, and finally, by creating a portfolio of different musical styles to demonstrate the capabilities of the software. A large database of recorded samples are classified into zones based upon the vibrational characteristics of the instruments, to model timbral variation in human percussive performance. The degree of timbral variation is governed by principles of biomechanics and human percussive performance. A fuzzy logic algorithm is applied to analyse current and first-order sample selection in order to formulate an ontological description of music performance variation. Asynchrony values were extracted from recorded performances of three different performance skill levels to create \timing fingerprints" which characterise unique features to each percussionist. The PD-103 uses real performance timing data to determine asynchrony values for each synthesised note. The spectral content of the sample database forms a three-dimensional loudness/timbre space, intersecting instrumental behaviour with music composition. The reparameterisation of the sample database, following the analysis of loudness, spectral flatness, and spectral centroid, provides an opportunity to explore the timbral variations inherent in percussion instruments, to creatively explore dimensions of timbre. The PD-103 was used to create a music portfolio exploring different rhythmic possibilities with a focus on meso-periodic rhythms common to parts of West Africa, jazz drumming, and electroacoustic music. The portfolio also includes new timbral percussive works based on spectral features and demonstrates the central aim of this thesis, which is the creation of a new compositional software tool that integrates human percussive performance and subsequently extends this model to different genres of music

Experimental investigation of productivity, specific energy consumption, and hole quality in single-pulse, percussion, and trepanning drilling of IN 718 superalloy

Laser drilling is a high-speed process that is used to produce high aspect ratio holes of various sizes for critical applications, such as cooling holes in aero-engine and gas turbine components. Hole quality is always a major concern during the laser drilling process. Apart from hole quality, cost and productivity are also the key considerations for high-value manufacturing industries. Taking into account the significance of improving material removal quantity, energy efficiency, and product quality, this study is performed in the form of an experimental investigation and multi-objective optimisation for three different laser drilling processes (single-pulse, percussion, and trepanning). A Quasi-CW fibre laser was used to produce holes in a 1 mm thick IN 718 superalloy. The impacts of significant process parameters on the material removal rate (MRR), specific energy consumption (SEC), and hole taper have been discussed based on the results collected through an experimental matrix that was designed using the Taguchi method. The novelty of this work focuses on evaluating and comparing the performance of laser drilling methods in relation to MRR, SEC, and hole quality altogether. Comparative analysis revealed single-pulse drilling as the best option for MRR and SEC as the MRR value reduces with percussion and trepanning by 99.70% and 99.87% respectively; similarly, percussion resulted in 14.20% higher SEC value while trepanning yielded a six-folds increase in SEC as compared to single-pulse drilling. Trepanning, on the other hand, outperformed the rest of the drilling processes with 71.96% better hole quality. Moreover, optimum values of parameters simultaneously minimising SEC and hole taper and maximising MRR are determined using multi-objective optimisation