As population increases and urbanization occurs, watershed management will be critical in the protection of water resources in North Central Texas. By 2040, Denton County will nearly double its 2010 population. The Upper Hickory Creek Watershed lies west of Denton and empties into Lake Lewisville. Lake Lewisville provides drinking water for Denton, Dallas, and other neighboring cities. Mitigation of non-point source pollutants as a result of urban and agricultural practices is essential to protecting Lake Lewisville water resources. A common best management practice used to mitigate pollutants is the protection of riparian ecotones that occupy river corridors; however, recent agricultural and urban practices are diminishing these ecosystems and their services. In this paper, the riparian buffer delineation equation (RBDE) is used to assess the current state of Upper Hickory Creek Watershed to aid in the monitoring of the riparian buffers along stream corridors. While the RBDE was used as pre-assessment tool for the riparian buffer effectiveness in the watershed, a new form of the equation was used to evaluate riparian buffer improvement potential (BP) in conjunction with Denton County parcel data to provide insights into buffer effectiveness and identify areas for improvement on a landowner scale.

A packet buffer for the protocol processor is a large memory space that holds incoming data packets for an application. Data packets for each application are stored in the form of FIFO queues in the packet buffer. Packets are dropped when the buffer is full. An efficient buffer management algorithm is required to manage the buffer space among the different FIFO queues and to avoid heavy packet loss. This thesis develops a simulation model for the packet buffer and studies the performance of conventional buffer management algorithms when applied to packet buffer. This thesis proposes a new buffer management algorithm, Dynamic Algorithm with Different Thresholds (DADT) to improve the packet loss ratio. This algorithm takes advantage of the different packet sizes for each application and proportionally allocates buffer space for each queue. The performance of the DADT algorithm is dependent upon the packet size distribution in a network traffic load. Three different network traffic loads are considered for our simulations. For the average network traffic load, the DADT algorithm shows an improvement of 6.7 % in packet loss ratio over the conventional dynamic buffer management algorithm. For the high and actual network traffic loads, the DADT algorithm shows an improvement of 5.45 % and 3.6 % in packet loss ratio respectively. Based on the simulation results, the DADT algorithm outperforms the conventional buffer management algorithms for various network traffic loads.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 78-85). Also available on the World Wide Web.

Over the past few years, researchers have directed a significant amount of effort towards realizing tunable all-optical devices using nonlinear optical methods. It is now possible to exercise dynamic control of the group velocity of light traveling through a wide variety of material systems. The slow and fast light refer to situations in which the group velocity íg of an optical pulse through a dispersive material can be made to be smaller and larger, respectively, than the phase velocity vp = c/n. This ability could overcome the remaining challenge in current optical networks of storing and manipulating an optical signal directly in optical domain so as to avoid a bottleneck due to optical-to-electrical (O/E) and electrical-to-optical (E/O) conversions. The overall purpose of the dissertation is to study novel slow-light systems that provide controlled generation of large pulse delays relative to the pulse width with minimal pulse shape distortion by optimally design resonance profiles of such systems. The system design studies utilize several measures of performance such as the fractional delay, power throughput, and signal distortion under the limited system resource constraints. To this end, powerful data fidelity metrics are required to quantify the performance of tunable delay devices. Here, a new framework for measuring an information velocity and throughput is described and implemented using Shannon mutual information concepts. This new technique is used to investigate trends, trade-offs, and limits in slow light devices, which are physically sensible and in good agreement with analyses obtained using a conventional eye-opening(EO) metric. Using these information-theoretic and/or conventional metrics, we present the quantifying performance of gain-based stimulated Brillouin scattering (SBS) system in optical fibers as well as optical passive devices such as Fabry-Perot, fiber Bragg gratings, and ring resonators. It is shown that combining the SBS gain medium with these passive devices can compensate their respective disadvantages and thus increase delay performance without using additional resource of SBS pump power. The results show the possibility of achieving a fractional delay up to 10 at a signal bandwidth up to tens of GHz.

This dissertation examines the “buffer effect,” an important but understudied feature of computer-mediated communication (CMC). Research on the buffer effect posits that CMC venues provide a buffering “screen” that users can literally and figuratively hide behind. The buffer can make people feel more comfortable during interactions, and is theorized to be especially relevant in contexts where self-presentation is threatened. This study employs transgressions as ideal sites for examining the buffer effect because of the high level of threatened self-presentation involved therein. The current project tests whether people perceive different levels of a buffer in different channels of communication, and how the buffer effect is related to other widely studied features of CMC, such as interactivity, synchronicity, and social presence. It also tests outcomes of the buffer effect for both senders and receivers of transgressive messages. Specifically, it posits that the buffer effect is beneficial to senders of transgressive messages, and is detrimental to receivers of those messages. Furthermore, in the context of transgressions, the amount of responsibility that a person takes for the transgression is a factor that influences how others perceive the situation. Therefore, the current study also considers receivers' perceptions of the level of responsibility the sender accepts, and specifically posits that senders' higher levels of responsibility are associated with positive outcomes for receivers. The dissertation is comprised of two studies. In Study One, participants responded to a survey to test their perceptions of the buffer effect and of other features of CMC in various channels. Participants also responded to a hypothetical situation to indicate how the buffer effect influences outcomes when sending a transgressive message. Study Two employed an experimental procedure to test how senders and receivers perceive the buffer effect in actual interactions, as well as how senders' acceptance of responsibility affects outcomes for receivers. Half of the participants were assigned the role of sender and were trained to provide a transgressive message to the receiver. Specifically, senders were trained to say that they had to leave the experiment early without completing the study, rendering the receiver ineligible for course credit. Both the channel (i.e., face-to-face, instant messaging, text messaging) and the senders' level of responsibility (i.e., low/high) were manipulated. Results suggested that the buffer effect manifests in different levels for various channels of communication, such that face-to-face environments provide the lowest buffer, followed by video chat, social networking sites, instant messaging, and email. Text messaging provides the highest buffer. The buffer effect is negatively related to other features of CMC (i.e., synchronicity, interactivity, and social presence) for low-buffer channels, and is either positively or not significantly related to these features in high-buffer channels. Results also suggest that the buffer effect is associated with benefits for senders in both hypothetical and actual interactions, but does not affect receivers' outcomes. Receivers' perceptions of the level of responsibility that senders accept affects receivers' outcomes, but only within environments with a low and moderate buffer. These results extend research on CMC and on transgressive communication. Results also offer practical implications for how people might elect to use channels and modify the content of their message when communicating a transgression to a friend.

In this thesis new methods are presented to achieve performance enhancement in wireless cooperative networks. In particular, techniques to improve diversity gain, throughput and minimise the transmission delay are described. A buffer-aided amplify-and-forward max-link relay selection scheme for both symmetric and asymmetric channels is introduced. This approach shows that the max-link scheme is most effective over the traditional max-SNR scheme when the source-to-relay and relay-to-destination links are symmetric. The closed form expressions for the outage probability and average packet delay of the proposed scheme under both symmetric and asymmetric channel configurations is derived. The diversity order and the coding gain of the AF max-link scheme is analytically provided. Then a novel relay selection scheme with significantly reduced packet delay is proposed. Both the outage performance and average packet delay of the proposed scheme are analysed. The analysis shows that, besides the diversity and coding gains, the proposed scheme has average packet delay similar to that of a non buffer-aided relay system when the channel SNR is sufficiently high thereby. A novel buffer-aided link selection scheme based on network-coding in a multiple hop relay network is proposed. Compared with existing approaches, the proposed scheme significantly increases the system throughput. This is achieved by applying data buffers at the relays to decrease the outage probability and using network-coding to increase the data rate. The closed-form expressions of both the average throughput and packet delay are derived. The proposed scheme has not only significantly higher throughput than both the traditional and existing buffer-aided max-link scheme, but also smaller average packet delay than the max-link scheme. A decode-and-forward buffer-aided relay selection for the underlay cognitive relay networks in the presence of both primary transmitter and receiver is presented. A novel buffer aided relay selection scheme for the cognitive relay network is proposed, where the best relay is selected with the highest signal-to-interference-ratio among all available source-to-relay and relay-to-destination links while keeping the interference to the primary destination within a certain level. A closed-form expression for the outage probability of the proposed relay selection scheme is obtained. Finally, A novel security buffer-aided decode-and-forward cooperative wireless networks is considered. An eavesdropper which can intercept the data transmission from both the source and relay nodes is considered to threaten the security of transmission. Finite size data buffers are assumed to be available at every relay in order to avoid having to select concurrently the best source-to-relay and relay-to-destination links. A new max-ratio relay selection policy is proposed to optimise the secrecy transmission by considering all the possible source-to-relay and relay-to-destination links and selecting the relay having the link which maximises the signal to eavesdropper channel gain ratio. Two cases are considered in terms of knowledge of the eavesdropper channel strengths: exact and average gains, respectively. Closed-form expressions for the secrecy outage probability for both cases are obtained. The proposed max-ratio relay selection scheme is shown to outperform one based on max-min-ratio relay scheme.

Este trabalho propõe um método de análise do trade-off entre o buffer de capacidade de produção e o buffer de estoque, necessários para garantir o bom desempenho de um sistema sujeito a variações de demanda. A análise envolve a definição de um sistema de produção e a construção de um modelo de simulação. A simulação é realizada num sistema formado por uma única estação de trabalho, com mix de 10 produtos, controlados por um sistema kanban, que é considerado por muitos autores inadequado para operar em ambientes cuja demanda não é estável. Os resultados mostram que o buffer de capacidade proporciona vantagens operacionais e de custo ainda que sujeito a maiores níveis de variação de demanda. / This research proposes a method to analyze the trade-off between the production capacity buffer and the inventory buffer, required to guarantee high performance levels in a system with demand variation. The analysis involves a production system delineation and the development of a simulation model. The system simulated is a single-stage production system, with mix of ten products, controlled by a kanban system, which is classified by several authors as not recommended in environments with unstable demand. The results indicate that the production capacity buffer enables operational and cost advantages, even if the production system is under higher demand variation.

Area exploration and information gathering are one of the fundamental problems in mobile robotics. Much of the current research in swarm robotics is aimed at developing practical solutions to this problem. Exploring large environments poses three main challenges. Firstly, there is the problem of limited connectivity among the robots. Secondly, each of the robots has a limited battery life which requires the robots to be recharged each time they are running out of charge. Lastly, the robots have limited memory to store data. In this work, we mainly focus on the memory and energy constraints of the robot swarm. The memory constraint forces the robots to travel to a centralized data collection center called sink, to deposit data each time their memory is full. The energy constraint forces the robots to travel to the charging station called dock to recharge when their battery level is low. However, this navigation plan is inefficient in terms of energy and time. There is additional energy dissipation in depositing data at the centralized sink. Moreover, ample amount of time is spent in traveling from one end of the arena to the sink owing to the memory constraint. The goal is that the robots perform data gathering in the least time possible with the optimal use of energy. Both the energy and time spent while depositing data at the sink act as an additional overhead cost to this goal. In this work, we propose to study an algorithm to tackle this scenario in a decentralized manner. We implement a dynamic task allocation algorithm which accomplishes the goal of exploration with data gathering by assigning roles to robots based on their memory buffer and energy levels. The algorithm assigns two sets of roles, to the entire group of robots, namely: Role A is the data gatherer, a robot which does the task of workspace exploration and data gathering, and Role B is data relayer, a robot which does the task of data transportation from data gatherers to the sink. By this division of labor, the robots dynamically decide which role to choose given the contradicting goals of maximizing data gathering and minimizing energy loss. The choice of a robot to perform the task of data gathering or data relaying is the key problem tackled in this work. We study the performance of the algorithm in terms of task distribution, time spent by the robots on each task and data throughput. We analyze the behavior of the robot swarm by varying the energy constraints, timeout parameter as well as strategies for relayer choice. We also test whether the algorithm is scalable.

This dissertation examines the “buffer effect,” an important but understudied feature of computer-mediated communication (CMC). Research on the buffer effect posits that CMC venues provide a buffering “screen” that users can literally and figuratively hide behind. The buffer can make people feel more comfortable during interactions, and is theorized to be especially relevant in contexts where self-presentation is threatened. This study employs transgressions as ideal sites for examining the buffer effect because of the high level of threatened self-presentation involved therein. The current project tests whether people perceive different levels of a buffer in different channels of communication, and how the buffer effect is related to other widely studied features of CMC, such as interactivity, synchronicity, and social presence. It also tests outcomes of the buffer effect for both senders and receivers of transgressive messages. Specifically, it posits that the buffer effect is beneficial to senders of transgressive messages, and is detrimental to receivers of those messages. Furthermore, in the context of transgressions, the amount of responsibility that a person takes for the transgression is a factor that influences how others perceive the situation. Therefore, the current study also considers receivers' perceptions of the level of responsibility the sender accepts, and specifically posits that senders' higher levels of responsibility are associated with positive outcomes for receivers. The dissertation is comprised of two studies. In Study One, participants responded to a survey to test their perceptions of the buffer effect and of other features of CMC in various channels. Participants also responded to a hypothetical situation to indicate how the buffer effect influences outcomes when sending a transgressive message. Study Two employed an experimental procedure to test how senders and receivers perceive the buffer effect in actual interactions, as well as how senders' acceptance of responsibility affects outcomes for receivers. Half of the participants were assigned the role of sender and were trained to provide a transgressive message to the receiver. Specifically, senders were trained to say that they had to leave the experiment early without completing the study, rendering the receiver ineligible for course credit. Both the channel (i.e., face-to-face, instant messaging, text messaging) and the senders' level of responsibility (i.e., low/high) were manipulated. Results suggested that the buffer effect manifests in different levels for various channels of communication, such that face-to-face environments provide the lowest buffer, followed by video chat, social networking sites, instant messaging, and email. Text messaging provides the highest buffer. The buffer effect is negatively related to other features of CMC (i.e., synchronicity, interactivity, and social presence) for low-buffer channels, and is either positively or not significantly related to these features in high-buffer channels. Results also suggest that the buffer effect is associated with benefits for senders in both hypothetical and actual interactions, but does not affect receivers' outcomes. Receivers' perceptions of the level of responsibility that senders accept affects receivers' outcomes, but only within environments with a low and moderate buffer. These results extend research on CMC and on transgressive communication. Results also offer practical implications for how people might elect to use channels and modify the content of their message when communicating a transgression to a friend.

On-site sewage systems, such as septic tank-absorption trenches, are used by approximately 20 000 people who live within the catchments that supply Sydney??s drinking water. These systems discharge sewage, treated to varying degrees depending on the system type and level of maintenance, to the environment. This can result in contamination of drinking water supplies if systems are not designed or managed appropriately. The aim of the project was to develop a methodology to define appropriate buffer distances between on-site sewage systems and waterways in Sydney??s drinking water catchments, to ensure the protection of drinking water quality. Specific objectives included: identifying the current status of on-site sewage management; assessing the effluent quality and treatment performance of septic tanks, aerated wastewater treatment systems (AWTS) with disinfection and an amended material sand mound; and development of an appropriate methodology for delineating buffer distances and assessing development applications. Viruses were used as a focus for delineating the buffer distances due to their mobility and robustness in the environment, and the potential health consequences of their presence in drinking water. A Quantitative Microbial Risk Assessment (QMRA) model was developed to calculate the cumulative impact of the on-site sewage systems in the Warragamba catchment based on data from literature and experiments, with consideration of virus loads from sewage treatment plants within the catchments. The model enabled consideration of what was a tolerable impact in terms of the resulting infections within the community. The QMRA the tolerable loads of viruses from the Warragamba catchment were 108 viruses per year in raw water and 104 viruses per year in treated water. A log reduction method was developed to facilitate individual site development assessments. This method was compared to other management approaches to development assessment: fixed minimum buffer distances of 100m, reducing failure rates to zero, and the use of a preferred system. Each of these methods had a limit for how much they could reduce virus loads to the catchment due to either failure or short buffer distances at some sites. While the log reduction method is limited by the failure rates, the method provides a quantitative measure of risk by which maintenance inspections can be prioritised.