Made available in DSpace on 2014-06-12T18:32:22Z (GMT). No. of bitstreams: 2 arquivo8543_1.pdf: 1297134 bytes, checksum: 7faa5a0659773d4b7963a19daf8ad9ac (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2005 / Uma equação integral não linear do tipo mista Volterra - Fredholm descrevendo a propagação espacial de uma epidemia é desenvolvida e analisada. Uma atenção especial é dada ao efeito hair-trigger, onde demonstramos o Teorema do Threshold Pandêmico de Kendall. Outro enfoque importante é o problema das ondas viajantes, onde analisamos como as soluções da equação integral se aproximam da distribuição final. A referência principal do trabalho é o artigo [1] Thresholds and travelling waves for the geographical spread of infection", de O. Diekmann

This thesis presents a case study that investigates a large Distributed Denial of Service (DDoS) attack and how it affected speed tests observed by the crowd-based speed test application Bredbandskollen.  Furthermore, the thesis also investigates the possibility of using crowd-based speed tests as a method to detect a DDoS attack. This method has very low overhead which makes it an interesting complement to other methods. This thesis also shows that there was a significant deviation in the number of measurements during the DDoS attack considered in the case study compared to the year average. Furthermore, the measurements of the peak day of the attack had a higher average download speed than the year average. Whereas the higher download speed observation at first may appear non-intuitive, we briefly discuss potential explanations and how such positive anomalies could potentially be used to detect attacks. Detecting DDoS attacks early can lead to earlier recognition of network problems which can aid Internet Service Providers (ISPs) in maintaining the availability of their networks.

Complex networks is an interdisciplinary research area which focuses on the study of properties of complex systems that have many functional or structural subunits. Community detection algorithms are one of the major approaches to analyse complex networks with multilevel or overlapping community structures. This research work focuses on constructing a novel community detection approach for simplification of a given complex demographic network. The general process of the abstraction from concrete problems as well as the general definition of communities have not been well defined and all the existing methods are derived from specific backgrounds, leaving the reliabilities in other fields open to ques- tion. This specificity of the existing methods reveals the need for a general approach for community definition and detection. Here, we devise a general procedure to find community structures in concrete problems by classifying the concrete networks into two basic types: Transmission networks and Similarity networks. The relation among nodes in transmission networks are constructed by material transmission and the ones in similarity network are constructed by the similarity in properties of the nodes. We show that both the types can be represented based upon an unified graph model. Based on the model, we propose a generic approach, Relation Strength Measurement (RSM), to define the communities. We have demonstrated that the Effective Resistance Function (ERF), from the Klein and Randic’s electrical network model, is applicable for quantifying the relation among nodes. We have also introduced a community threshold parameter (CP) based on which, the RSM algorithm categorizes the network nodes into communities. We have compared the performance of our algorithm with other well known community detection methods. The simulation results show that the algorithm accurately obtains the division of community structure both in real-world and synthetic networks.

Foliage feeding insects like fall armyworm (FAW) [Spodoptera frugiperda (J. E. Smith)], granulate cutworm (GCW) [Feltia subterranean (F.)], velvetbean caterpillar (VBC) [Anticarsia gemmatalis (Hübner)] and corn earworm (CEW) [Helicoverpa zea (Boddie)] in peanut (Arachis hypogaea (L.)) and their effects on canopy defoliation and the resultant yield loss is outdated and essentially non-existent in Mississippi. With the expansion of peanuts throughout the state since 2012, growers struggle to manage foliageeeding pests in peanut. The lack of current information regarding insect pressure and economic injury levels is troublesome; especially with newer, high yielding, disease resistant cultivars. Research was required to understand how peanuts respond to complete canopy removal at different times during the growing season. Consequently, we evaluated the severity of canopy defoliation causing significant levels of yield loss during key physiological growth periods. This information will assist growers and extension personnel streamline management decisions for canopy defoliation in peanut throughout Mississippi.

Introduction. Exercise and head-out water immersion (HOI) have consistently reported an increase in central blood volume associated with the cephalad shift in blood volume. This causes an increase in left ventricular end diastolic volume and greater stroke volume during exercise compared to exercise in air at similar metabolic costs. In contrast, the metabolic response, specifically, blood lactate accumulation during exercise combined with HOI has yielded varying results depending on the mode of exercise. At present it appears that during exercise at similar metabolic costs, cycle ergometry exercise augments plasma lactate over treadmill running while HOI reduces the plasma lactate response to cycle ergometry exercise. The interaction between treadmill running and HOI appears less certain. Thus, we tested the hypothesis that running on a treadmill on land would result in a lesser accumulation of lactate than during HOI treadmill running. Methods. Eleven subjects' lactate thresholds were determined while running at a 0% grade at increasing speeds on a treadmill on land or during HOI on an underwater treadmill in a randomized cross-over design. Exercise tests were separated by a minimum of 3 days. Lactate concentrations were expressed in mM• kg-1 H2O after correcting for plasma solid concentration. During exercise changes in plasma volume were calculated from changes in hematocrit and hemoglobin. Lactate threshold was estimated from a log-log plot of lactate concentration (mM• kg-1 H2O) as a function of relative oxygen consumption (ml O2•min-1•kg-1 BW). Results. The energy cost and heart rate response to running at speeds between 5.5 and 7.5 mph was similar for land and HOI. During treadmill running on land, plasma volume decreased by 6.4 ± 4.0% at a speed of 7.5 mph. The decrease in plasma volume was significantly greater during HOI and averaged 18.7 ± 1.7% (p <0.05) at 7.5 mph. Plasma lactate was higher at any given treadmill speed ≥ 5.5 mph during HOI compared to land (p <0.05). Lactate threshold during HOI running (21.8 ± 1.6 mM• kg-1 H2O) was lower (p <0.05) than during running on the land treadmill (27.0 ± 1.6 mM• kg-1 H2O). Discussion. HOI running resulted in a consistent shift to the left (rise in plasma lactate occurred at a lower ) in the lactate threshold and elevated plasma lactate concentration at speeds between 5.5-7.5 mph despite similar metabolic and HR responses to the exercise.

This thesis is separated into two parts: threshold graphs and inertia sets. First we present an algorithmic approach to finding the minimum rank of threshold graphs and then progress to counting the number of threshold graphs with a specific minimum rank. Second, we find an algorithmic and more automated way of determining the inertia set of graphs with seven or fewer vertices using theorems and lemmata found in previous papers. Inertia sets are a relaxation of the inverse eigenvalue problem. Instead of determining all the possible eigenvalues that can be obtained by matrices with a specific zero/nonzero pattern we restrict to counting the number of positive and negative eigenvalues.

No / Contrast constancy is the ability to perceive object contrast independent of size or spatial frequency, even though these affect both retinal contrast and detectability. Like other perceptual constancies, it is evidence that the visual system infers the stable properties of objects from the changing properties of retinal images. Here it is shown that perceived contrast is based on an optimal thresholding estimator of object contrast, that is identical to the VisuShrink estimator used in wavelet denoising.

No / A sinusoidal grating can be viewed as a series of light and dark bars. Here we measure the contrast discrimination thresholds for light and dark bars individually, and find that the contrast discrimination thresholds for the whole sinusoid can be explained as ideal summation of the light and dark bar thresholds. We propose a model for light bar, dark bar, and sinusoidal contrast discrimination which involves local light adaptation and multiplicative noise. The model accounts for the data very well, and also accounts for contrast discrimination of light and dark edges.

<p> This thesis is principally concerned with the performance of the phase-locked FM demodulator under conditions of interference in comparison to the conventional FM demodulator. The linear no interference performance of the phase-locked oscillator is well known, however this aspect is included in the interests of completeness and reference.</p> <p> Mechanisms tor threshold effects in the phase-locked and conventional FM demodulator are discussed and compared. It is shown theoretically and experimentally that the noise threshold is reduced in the phase-locked FM demodulator by virtue of the limits of Ψi (t) being restricted by the noise bandwidth of' the feedback loop. Fall off in baseband signal level in the presence of noise was seen to be a function of θ(t) and (S/N)IF.</p> / Thesis / Master of Engineering (MEngr)

This is a site-driven project located in my hometown of Lewiston, Maine, a point along the Androscoggin River.  Driving over the bridge as a child, I was intrigued by the waterfall, but it always seemed unattainable; the mills and abandoned buildings prevented access.  When my dad said that the last mill burned down at Great Falls in 2009, I was saddened but knew this provided a new opportunity for the community. This project is not about placing a building, but rather intervening and creating a conversation with the existing landscape by framing and experiencing its beauty. This project is an exploration of redefining entry, thresholds and pathways, as well as interlocking public and private spaces.  The design process was not linear; one question always led to another.  The program evolved over time, as I became more acquainted with the water, ruins and topography of the site.  My hope was that I would add a chapter to the site story of Great Falls and inspire future development for the community. / Master of Architecture