Non-perturbative models of intermittency in edge turbulence

A theory of the probability distribution function (PDF) tails of the blob density in plasma edge turbulence is provided. A simplified model of the fast convective radial transport is used. The theoretically predicted PDF tails corroborate earlier measurements of edge transport, further confirming the strongly non-Gaussian feature of edge transport. It is found that increasing the cross sectional spatial scale length ($L_x$ and $L_y$) of the blob results in larger transport whereas increasing the toroidal scale length ($L_z$) decreases the PDF. The results imply that the PDF decreases for larger blob speed $v_b$.Comment: 19 pages, 2 figure

A Trail Hiker: A Historic Memoir of an Appalachian Trail Thru-Hiker

Table of contents only

ASPHALT PAVEMENT PRESSURE DISTRIBUTIONS USING TEKSCAN MEASUREMENT SYSTEM

As a nation that depends so heavily on its infrastructure, the United Statescontinually seeks to better maintain the investment that it has made in its roadways.Asphalt pavements make up the majority of the paved roadways in the United States andultimately contribute to the bulk of the expense of highway maintenance. The goal ofthis research was to develop a means for taking a simple measurement of pressure atvarious interfaces on and within an asphalt pavement structure in an effort to directlyassess the damaging effects of different wheel loadings. It is well known that everincreasing wheel loads and other unusual wheel loading conditions are detrimental to theeffort of maintaining the roadways. The results of the data can be compared to the classicempiricalistic and mechanistic approaches to asphalt pavement design and analysis, aswell as the more modern finite-element computer modeling programs. The Tekscanmeasurement system, which utilizes a very thin matrix based pressure sensitive sensor,has been deemed applicable for measuring pavement pressures. Various types of wheelloadings have been considered throughout this study. It was determined that the type oftire, tire inflation pressure, applied load, and the asphalt itself all have an effect on theresultant pressures on the surface of and within an asphalt pavement structure. Thisresearch may contribute to the understanding of pressure distributions at the tire/asphaltinterface depending on the type of tire, adjustments in tire inflation pressure, and varyingthe wheel load. The results may lead to a better understanding of pressure distributions atvarying depths within an asphalt pavement structure. The ability to quantify thesevariables could assist designers when analyzing and designing asphalt pavements

Influence of Habitat Heterogeneity on Small Mammals in the Central Platte River Valley, Nebraska

Although the loss of prairie is substantial across the extent of its historic range, large portions of native rangeland still remain throughout Nebraska. It is critical that resource managers and private landowners manage rangelands in a manner that will enhance ecosystem integrity by using techniques that provide disturbance regimes. Heterogeneity based management, such as patch-burn grazing and rest-rotation grazing, can be used as a conservation tool to increase biodiversity within management units and at a landscape level. Heterogeneity-based management has received much attention in the literature within the past decade, but there has been little focus on how these management systems influence small mammal communities. I trapped small mammals and surveyed vegetation structure among rangelands during 2009 and 2010 at the Platte River Whooping Crane Maintenance Trust in the Central Platte River Valley, Nebraska to determine the influence of structural heterogeneity on small mammals. Vertical height, litter depth, bare ground, and standing dead vegetation were different among burn units during both years. My data indicated no difference in grasses, forbs, or litter cover among burn units for either year. I used the significant variables in a direct gradient analysis to identify which variables were critical in determining small mammal species presence. The species identified with vegetation variables for 2009 but not 2010 suggested there were other variables not considered in my study. Species diversity measurements indicated the recently disturbed burn units had the lowest small mammal diversity and the undisturbed burn units had the greatest diversity. Community similarity was highest among similar burn units, which indicated that small mammal communities were similar among similar burn units during 2009 and 2010. Resource managers should recognize that alternative grazing systems that create a mosaic of vegetation structure can provide evolutionary processes necessary for prairie ecosystem function. Small mammals play a crucial role in grassland ecosystems and by using heterogeneity-based management, small mammal diversity increased which can lead to a healthier ecosystem

Self-Configuring Neural Networks

Neural Networks are an effective means of classifying data; however they are usually purpose built applications that are created for classifying a single data set. Programming a neural network can be a time consuming and sometimes error prone process. To alleviate both of these problems a self-configuring multilayer perceptron model was used to create and train neural networks. This application can take any training data set that is linearly or nonlinearly separable as input, then create the needed neural network structure and train itself, thus saving programmers\u27 time and effort. The software has been tested with several data sets including sample data sets, the Iris data set, and the MARSI data set. The results indicate that once the network is created and trained, it can be used to effectively classify data from many data sets

Does Retrieving a Memory Insulate It Against Memory Inhibition? A Retroactive Interference Study

Several recent studies suggest that an initial retrieval attempt imbues retrieved memories with special resilience against future interference and other forgetting mechanisms. Here we report two experiments examining whether memories established through initial retrieval remain subject to retrieval-induced forgetting. Using a version of a classical retroactive interference design, we trained participants on a list of A-B pairs via anticipation—constituting a form of retrieval practice. After next training participants on interfering A-C pairs, they performed 0-12 additional A-C anticipation trials. Because these trials required retrieval of A-C pairs, they should function similarly to retrieval practice in paradigms establishing retrieval-induced forgetting. We observed robust evidence that retroactive interference generalizes to final memory tests involving novel, independent memory probes. Moreover, in contrast to practicing retrieval of A-C items, their extra study failed to induce cue-independent forgetting of the original B items. Together, these findings substantiate the role of retrieval-related inhibitory processes in a traditional retroactive interference design. Importantly, they indicate that an initial retrieval attempt on a competitor does not abolish retrieval-induced forgetting, at least not in the context of this classic design. Although such an attempt may protect against inhibition in some circumstances, the nature of those circumstances remains to be understood

CAN NOSTALGIA DEFEND AGAINST STEREOTYPE THREAT?

Stereotype threat causes individuals to perform worse on tasks when they are made aware of a task-relevant negative stereotype for a group to which they belong. Prior research has demonstrated that this effect has been alleviated by using a number of methods including changing test context or bolstering the stereotyped group. One method of bolstering the threatened group is through a self-affirmation of preferred character traits. Nostalgia is a sentimental longing for the past, which has been shown to provide many benefits to an individual, both personally and socially. Research has shown that when told to recall a nostalgic memory, participants are said to have greater access to self-affirming characteristics. The present study was performed in an attempt to utilize nostalgic recollection to directly ameliorate the negative effects of stereotype threat. The study provided participants with a selection of gender identification using gendered images, followed by an instruction which was used as the stereotype threat elicitation. Participants were then randomly assigned to one of three memory conditions — nostalgic, ordinary, and none — and were asked to recall and describe the appropriate memory. Participants then completed a hard math test using 26 sample GRE items. Multiple hypotheses were not supported. Some significant results are described. Probable null contributors, implications, and future directions are explored. Keywords: Stereotype threat, nostalgia, gender, self-affirmatio

Friction Pull Plug and Material Configuration for Anti-Chatter Friction Pull Plug Weld

A friction pull plug is provided for use in forming a plug weld in a hole in a material. The friction pull plug includes a shank and a series of three frustoconical sections. The relative sizes of the sections assure that a central one of the sections defines the initial contact point between the hole's sides. The angle defined by the central one of the sections reduces or eliminates chatter as the plug is pulled into the hole

The momentum flux probability distribution function for ion-temperature-gradient turbulence

There has been overwhelming evidence that coherent structures play a critical role in determining the overall transport in a variety of systems. We compute the probability distribution function (PDF) tails of momentum flux and heat flux in ion-temperature-gradient turbulence, by taking into account the interaction among modons, which are assumed to be coherent structures responsible for bursty and intermittent events, contributing to the PDF tails. The tail of PDF of momentum flux R = 〈vxvy〉 is shown to be exponential with the form exp{−ξR3/2}, which is broader than a Gaussian, similar to what was found in the previous local studies. An analogous expression with the same functional dependence is found for the PDF tails of heat flux. Furthermore, we present a detailed numerical study of the dependence of the PDF tail on the temperature and density scale lengths and other physical parameters through the coefficient ξ