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In this dissertation I argue that creativity should be understood as a situated and distributed process. As I develop my approach to understanding creativity over the course of this dissertation, three core claims emerge: 1) that the creative powers of particular agents are constituted within the concrete circumstances (both social and material) in which they are situated, 2) that the creative process itself unfolds across networks of associating actors, and 3) that these networks of associating actors include nonhumans of diverse sorts as active participants in the creative process. Understanding the creative process in this way distinguishes my approach from the ways in which creativity has traditionally been understood, which I argue are marked by a deep Cartesianism. This Cartesianism manifests itself in the way that creativity is predominantly studied and conceived of as a cognitive process that occurs within the minds of individuals. Because creativity is seen to occur within the minds of individuals, and because these minds are seen to function autonomously of their context, there is a resulting lack of attention to how the creative process is shaped by and extended out into the material and social environment. Furthermore, because creativity is understood to be solely a manifestation of human agency and human intentions, the active role of nonhumans in the creative process has not been taking into account. Drawing upon literature within feminist epistemology, cognitive science, science and technology studies, disability theory, and situated action theory, I argue that to better understand creativity, we must consider the creative process as it occurs within particular social and material environments, as it is distributed across diverse networks of actors, and as it is shaped in essential ways by nonhuman actors. It is only by considering creativity in its context, out in the world and in the interactions between things, that we can get an adequate understanding of the creative process. / Philosophy

<p> The quasi-steady state optimization of a single tubular fixed bed chemical reactor with a slowly decaying catalyst is considered. The optimal choice of temperature T(z,t) distributed in both the space of the reactor and in chronological time is sought so as to maximize the total amount of reaction in a fixed given period of time. A single irreversible reaction is considered with a rate expressible as a product of separate functions of temperature, activity and conversion. The rate of catalyst decay is also a product of separate functions of temperature and activity but independent of conversion. Upper and lower bounds are placed on the permitted temperature. Theoretical characterization of the optimal policy is obtained using Sirazetdinov and Degtyarev's maximum principle derived for first-order partial differential equations and the influence of the ratio of reaction activation energy to catalyst deactivation energy on the derived optimal policy is indicated. Numerical calculations are presented to illustrate the optimal policies.</p> / Thesis / Doctor of Philosophy (PhD)

Computational grids and other heterogeneous, large-scale distributed systems require more powerful and more flexible authorization mechanisms to realize fine-grained access-control of resources. Computational grids are increasingly used for collaborative problem-solving and advanced science and engineering applications. Usage scenarios for advanced grids require support for small, dynamic working groups, direct delegation of access privileges among users, procedures for establishing trust relationships without requiring organizational level agreements, precise management by individuals of their privileges, and retention of authority by resource providers. Existing systems fail to provide the necessary flexibility and granularity to support these scenarios. The reasons include the overhead imposed by required administrator intervention, coarse granularity that only allows for all-or-nothing access control decisions, and the inability to implement finer-grained access control without requiring trusted application code. PRIMA, the model and system developed in this research, focuses on management and enforcement of fine-grained privileges. The PRIMA model introduces novel approaches that can be used in place of, or in combination with existing access control mechanisms. PRIMA enables the users of a system to manage access to their own assets directly without the need for, and costs of intervention by technical personnel. System administrators benefit from more flexible and fine-grained definition of access privileges and policies. A novel access control decision and enforcement model with support for legacy applications has been developed. The model uses on-demand account leasing and implements expressive enforcement mechanisms built on existing low-overhead security primitives of the operating systems. The combination of the PRIMA components constitutes a comprehensive security model that facilitates highly dynamic authorization scenarios and increases security through least privilege access to resources. In summary, PRIMA mechanisms enable the use of fine-grained access rights, reduce administrative costs to resource providers, enable ad-hoc and dynamic collaboration scenarios, and provide improved security service to long-lived grid communities. / Ph. D.

The simulation of physical-layer communication systems often requires long execution times. This is due to the nature of the Monte Carlo simulation. To obtain a valid result by producing enough errors, the number of bits or symbols being simulated must significantly exceed the inverse of the bit error rate of interest. This often results in hours or even days of execution using a personal computer or a workstation. Reconfigurable devices can perform certain functions faster than general-purpose processors. In addition, they are more flexible than Application Specific Integrated Circuit (ASIC) devices. This fast yet flexible property of reconfigurable devices can be used for the simulation of communication systems. However, although reconfigurable devices are more flexible than ASIC devices, they are often not compatible with each other. Programs are usually written in hardware description languages such as Very High Speed Integrated Circuit (VHSIC) Hardware Description Language (VHDL). A program written for one device often cannot be used for another device because these devices all have different architectures, and programs are architecture-specific. Distributed computing, which is not a new concept, refers to interconnecting a number of computing elements, often heterogeneous, to perform a given task. By applying distributed computing, reconfigurable devices and digital signal processors can be connected to form a distributed reconfigurable simulator. In this paper, it is shown that using reconfigurable devices can greatly increase the speed of simulation. A simple physical-layer communication system model has been created using a WildForce board, a reconfigurable device, and the performance is compared to a traditional software simulation of the same system. Using the reconfigurable device, the performance was increased by approximately one hundred times. This demonstrates the possibility of using reconfigurable devices for simulation of physical-layer communication systems. Also, an middleware architecture for distributed reconfigurable simulation is proposed and implemented. Using the middleware, reconfigurable devices and various computing elements can be integrated. The proposed middleware has several components. The master works as the server for the system. An object is any device that has computing capability. A resource is an algorithm or function implemented for a certain object. An object and its resources are connected to the system through an agent. This middleware system is tested with three different objects and six resources, and the performance is analyzed. The results shows that it is possible to interconnect various objects to perform a distributed simulation using reconfigurable devices. Possible future research to enhance the architecture is also discussed. / Ph. D.

DAVAs are distributed active and passive devices that can be numerically modelled to provide optimum control of low frequency (< 1000 Hz) mean square velocity and sound power radiation. A numerical model of a multi-DAVA system was developed using the Rayleigh-Ritz method coupled to a hierarchical finite element set (p-method). The numerical model was validated and used to optimize DAVA configurations using lightweight treatments (< 10 % the weight of the base plate weight). The optimizations were performed using genetic algorithms implemented in parallel. They were used to minimize, either passively or actively, the mean square velocity and sound power radiation of different plates having arbitrary boundary conditions (free, simply supported or clamped). Some optimization were also used to determine the optimum number of DAVAs needed, as well as to compare DAVA attenuations with attenuations obtained from optimum Active Constraining Layer Damping (ACLD) treatments. Preliminary results on the passive minimization of the mean square velocity of a simply supported plate with three devices showed that DAVA treatments produce better attenuations than ACLD treatments in the frequency range of interest [2-1000 Hz], and these increased attenuations were due in part to the better capabilities of DAVA treatments to tackle the plate first bending modes. Apart from the free plate, which showed anyway a very low baseline sound transmission, excellent attenuations were obtained both passively and actively for minimizing the mean square velocity and sound power radiation of the simply supported and clamped plates. Following, numerical studies of a DAVA treatment around the optimum solution showed that changing the DAVA top plate stiffness resulted in decreased attenuation, while increasing the DAVA foam layer loss factor increased the attenuation, and decreasing the foam loss factor resulted in decreased attenuation. Finally, by varying the area of the single optimum DAVA that passively minimizes the sound power of the plate, it has been shown that both smaller/lighter and larger/heavier DAVA treatments lead to decreased passive attenuation upon the optimum single DAVA passive solution. Finally, experimental results have further validated the DAVA numerical model, and DAVA treatments have shown excellent passive and active experimental attenuations over various flexible plate structures. / Ph. D.

Modern embedded systems---autonomous vehicle-to-vehicle communication, smart cities, and military Joint All-Domain Operations---feature increasingly heterogeneous distributed components. As a result, existing communication methods, tightly coupled with specific networking layers and individual applications, can no longer balance the flexibility of modern data distribution with the traditional constraints of embedded systems. To address this problem, the investigation herein presents a domain-specific language, designed around the Representational State Transfer (REST) architecture, most famously used on the web. Our language, called the Communication Language for Embedded Systems (CLES), supports both traditional point-to-point data communication and management and allocation of decentralized distributed processing tasks. To meet the traditional constraints of embedded execution, CLES' novel runtime allocates processing tasks across a heterogeneous network of embedded devices, overcoming limitations from other modern distribution methods: centralized task management and limited operating system integration. CLES was evaluated with performance micro-benchmarks, implementation of distributed stochastic gradient descent, and application to the design of versatile stateless services for vehicle-to-vehicle communication and military Joint All-Domain Command and Control (JDAC). From this evaluation, it was determined that CLES meets the data distribution needs of realistic cyber-physical embedded systems. / Master of Science / As computers become smaller, cheaper, more powerful, and energy efficient, they are increasingly used in cyber-physical systems such as planes, trains, and automobiles, as well as large-scale networks such as power plants and smart cities. The field of embedded computing is facing new challenges involving the communication and coordination of large numbers of different devices. Some of the software challenges within embedded device communications are: flexibility both in ability to run on different devices and use different communication links such as cellular, Wi-Fi, or Bluetooth, performance constraints of low-power embedded devices, latency and reliability to ensure safe operations, and the schedule and cost of development. To address these challenges, this thesis presents a new programming language, designed around the Representational State Transfer (REST) architecture, most famously used in HTTP to drive the web. Our language, called the Communication Language for Embedded Systems (CLES), supports both traditional point-to-point data communication designed to prioritize latency and reliability, as well as a standalone application or runtime that can be run on an embedded device to accept requests for processing tasks. CLES and its supporting Software Development Kit (SDK) is designed to allow for quick and cost effective development of flexible low-latency device to device communications and large scale distributed processing on embedded devices.