The ultimate goal in the manufacturing of a part is to achieve an economic production plan with precision and accuracy in the first attempt at machining. A physics-based comprehensive modeling of the machining processes is a fundamental requirement in identifying optimal cutting conditions which result in high productivity rates without violating accuracy throughout the part production process. This thesis presents generalized virtual simulation and optimization strategies to predict and optimize performance of milling processes up to 3-axis. Computationally efficient mathematical models are introduced to predict milling process state variables such as chip load, force, torque, and cutting edge engagement at discrete cutter locations. Process states are expressed explicitly as a function of helical cutting edge - part engagement, cutting coefficient and feedrate. Cutters with arbitrary geometries are modeled parametrically, and the intersection of helical cutting edges with workpiece features are evaluated either analytically or numerically depending on geometric complexity. The dynamics of generalized milling operations are modeled and the stability of the process is predicted using both time and frequency domain based models. These algorithms enable rapid simulation of milling operations in a virtual environment as the part features vary. In an effort to reduce machining time, a constraint-based optimization scheme is proposed to maximize the material removal rate by optimally selecting the depth of cut, width of cut, spindle speed and feedrate. A variety of user defined constraints such as maximum tool deflection, torque/power demand, and chatter stability are taken into consideration. Two alternative optimization strategies are presented: pre-process optimization provides allowable depth and width of cut during part programming at the computer aided manufacturing stage using chatter constraint, whereas the post-process optimization tunes only feedrate and spindle speed of an existing part program to maximize productivity without violating physical constraints of the process. Optimized feedrates are filtered by considering machine tool axes limitations and the algorithms are tested in machining various industrial parts. The thesis contributed to the development of a novel 3-axis Virtual Milling System that has been deployed to the manufacturing industry. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

GetWork nace para atender tres segmentos de mercado enlazados entre sí. En primer lugar, empresas que necesiten cubrir plazas dentro de su equipo de trabajo y buscan a los profesionales más capacitados y sobretodo que les aseguren la creación de valor con su permanencia, atendiendo una problemática como la rotación de personal, y crecimiento dentro de la empresa. Por otro lado, profesionales con dificultades para encontrar el trabajo soñado, o simplemente con dificultades para integrarse al mercado laboral. Ante ello, GetWork garantiza apoyo y asesoría completa, inducción en diversos temas, consejos para la elaboración de CVs y presentación personal, etc. La meta final es que los profesionales se unan a empresas en las que puedan establecerse en una relación de beneficio mutuo. Por último, empresas dedicadas a la educación y capacitaciones para profesionales que se encuentran en la búsqueda de empleo, o que desean mejorar sus habilidades y aptitudes para alcanzar mayores rendimientos en sus centros de trabajo. Para ello, GetWork le sirve de ventana a estas instituciones para darse a conocer por medio de publicidad y conseguir nuevos clientes que eventualmente crearán valor no solo para las empresas en las que laboran, sino también para nosotros incrementado las posibilidades de nuestro servicio. / GetWork was created to serve the three following market segments: companies, users and institutions dedicated to education and training. First place, companies, with open jobs openings who look for the most qualified professionals and above all to ensure the creation of value with their retention. Also, GetWork helps professionals with difficulties to find jobs, land an adequate job opportunity. GetWork guarantees full support and advice, induction on various topics, advices for the preparation of resume and personal presentation, etc. The ultimate goal is for professionals to join companies in which they can establish a mutually beneficial relationship. Finally, GetWork aids companies dedicated to education and training professionals who want to improve their skills and abilities to achieve higher performance in their workplaces. For this, GetWork serves as a link to these institutions to become known through advertising and increase their posibilities for networking. / Trabajo de investigación

One of the oft cited reasons for virtual environments is that they provide experiences with places one would never be able to visit and to perform tasks that would otherwise be dangerous, or inaccessible. The ability to become transported to another environment, such that you think you are "there," is known as presence. Existing presence literature focuses largely on the sensory aspects of virtual environment experiences. However, there is more to experience than what is sensed. This dissertation investigates the theoretical components of holistic experiences in virtual environments. In order to explore the relationship between experiential design and presence, a new evaluation tool was needed. This ultimately led to the development of the Virtual Experience Test. To validate the Virtual Experience Test, an experiment was designed that utilized subjective evaluations regarding game-play in the commercial game Mirror's Edge. Measures of experiential design, flow, and presence were taken and the relationships between the measures analyzed. The results of this research showed that environments utilizing holistic designs result in significantly higher presence. Furthermore, this study produced a validated measure of holistic experience that designers could use to evaluate their virtual environments.

Conventional analysis of atmospheric data includes three-dimensional desktop-computer displays. One disadvantage is that it can reduce the ability to zoom in and see small-scale features while concurrently viewing other faraway features. This research intends to determine if using virtual environments to examine atmospheric data can improve a meteorologist's ability to analyze the given information. In addition to possibly enhancing small-scale analysis, virtual environments technology offers an array of possible improvements. Presented is the theory on developing an experiment to establish the extent to which virtual environments assist meteorologists in analysis. Following is the details of an implementation of such an experiment. Based on the quantitative results obtained, the conclusion is that immersion can significantly increase the accuracy of a meteorologist's analysis of an atmospheric data set.

No description available.

No description available.

A Distributed Virtual Environment (DVE) system provides a shared virtual environment where physically separated users can interact and collaborate over a computer network. More simultaneous DVE users could result in intolerable system performance degradation. We address the three major challenges to improve DVE scalability: effective DVE system performance measurement, understanding the controlling factors of system performance/quality and determining the consequences of DVE system changes. We propose a DVE Scalability Engineering (DSE) process that addresses these three major challenges for DVE design. DSE allow us to identify, evaluate, and leverage trade-offs among DVE resources, the DVE software, and the virtual environment. DSE has three stages. First, we show how to simulate different numbers and types of users on DVE resources. Collected user study data is used to identify representative user types. Second, we describe a modeling method to discover the major trade-offs between quality of service and DVE resource usage. The method makes use of a new instrumentation tool called ppt. ppt collects atomic blocks of developer-selected instrumentation at high rates and saves it for offline analysis. Finally, we integrate our load simulation and modeling method into a single process to explore the effects of changes in DVE resources. We use the simple Asteroids DVE as a minimal case study to describe the DSE process. The larger and commercial Torque and Quake III DVE systems provide realistic case studies and demonstrate DSE usage. The Torque case study shows the impact of many users on a DVE system. We apply the DSE process to significantly enhance the Quality of Experience given the available DVE resources. The Quake III case study shows how to identify the DVE network needs and evaluate network characteristics when using a mobile phone platform. We analyze the trade-offs between power consumption and quality of service. The case studies demonstrate the applicability of DSE for discovering and leveraging tradeoffs between Quality of Experience and DVE resource usage. Each of the three stages can be used individually to improve DVE performance. The DSE process enables fast and effective DVE performance improvement. / Ph. D.

Virtual reality (VR) involves an attempt to create an illusion that the user of the VR system is actually present in a synthetic (usually computer-generated) environment. Little is known about how various system parameters affect the illusion of presence in a virtual environment (VE). In particular, there seem to be very little quantitative data on which to base VR system design decisions. Also, while presence (or immersion) in VEs is a primary goal of VR, not much is known about how this variable affects task performance. The goal of this research was to provide a ratio-scale measure of perceived presence in a VE, to explore the effects of a number of environmental parameters on this measure and construct empirical models of these effects, and to relate perceived presence to user performance. This was done by manipulating eleven independent variables in a series of three experiments. The independent variables manipulated were scene update rate, visual display resolution, field of view, sound, textures, head-tracking, stereopsis, virtual personal risk, number of possible interactions, presence of a second user, and environmental detail. Participants performed a set of five tasks in the VE and rated perceived presence at the end of each set using the technique of free-modulus magnitude estimation. The amount of time spent in the VE was also recorded. The results indicate that the VR system parameters manipulated and analyzed in this research did affect participants' subjective feeling of presence in the VE. Field of view, sound, and head-tracking showed the largest effects. Other significant effects found were those of visual display resolution, texture-mapping, stereopsis, and the presence of a second user. Free-modulus magnitude estimation worked well as a measure of perceived presence. A positive relationship was found between perceived presence and task performance, but this relationship was relatively weak. Second-order empirical models were constructed that predicted perceived presence with moderate success and, with less success, task performance. / Ph. D.

No description available.

ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / One of the core philosophies of the integrated Network Enhanced Telemetry (iNET) project is to leverage standard networking technologies whenever possible to both reduce development cost and to allow standard networking applications to function. This also provides the best long-term scalability to new unforeseen applications, much as the Internet has grown through its open standards. Unfortunately, the radio frequency (RF) channel characteristics do not fully lend themselves to the typical physical layer approaches utilized by IP technologies. As such, the iNET program has developed a specialized communication link management control. But, combining this specialized link management approach with the standardized IP infrastructure on the range and test article provides some challenges. The program has chosen a method to encapsulate the special concepts within a set of components that together (at their boundaries) form a classic router. Construction of this router is quite unique in that portions of it are geographically separate: antenna sites, test article, and mission control room. This paper describes the construction of what the program calls a "virtual router" and explains the performance issues that required it.