Now showing items 21-40 of 6376

• #### A Computer Simulation Of Auroral Arc Formation

Recent satellite measurements have revealed two intriguing features associated with the formation of auroral arcs. The first is that an auroral arc is produced by a sheet of electrons accelerated along a geomagnetic field-aligned potential drop, and the second is that these electrons carry a field-aligned, upward directed electric current. In order to explain these measurements, a self-consistent, time dependent, computer simulation of auroral arc formation has been developed. The simulation demonstrates for the first time that a stable V-shaped potential structure, called an auroral double layer, develops spontaneously as a result of an ion shielded electron current sheet interacting with a conducting ionosphere. The double layer accelerates current-carrying electrons into the upper atmosphere at auroral energies. The double layer potential depends critically on the drift speed of the current-carrying electrons and on the temperature of the ambient shielding ions. Localized double layers occur near the ionosphere when the geomagnetic field is assumed to be uniform, but when a converging magnetic field is introduced, the double layer becomes extended due to the presence of an additional population of electrons trapped between the magnetic mirror and the double layer potential. The simulated auroral current sheet is subject to auroral curl and fold type deformations due to unstable Kelvin-Helmholtz waves. The previous incompletely understood auroral fold producing mechanism is described.
• #### A Concept To Assess The Performance Of A Permafrost Model Run Fully Coupled With A Climate Model

Soil-temperatures simulated by the fully coupled Community Climate System Model LCM version 3.0 (CCSM3) are evaluated using three gridded Russian soil-temperature climatologies (1951-1980, 1961-1990, and 1971-2000) to assess the performance of permafrost and/or soil simulations. CCSM3 captures the annual phase of the soil-temperature cycle well, but not the amplitude. It provides slightly too high (low) soil-temperatures in winter (summer) with a better performance in summer than winter. In winter, soil-temperature biases reach up to 6 K. Simulated near-surface air temperatures agree well with the near-surface air temperatures from reanalysis data. Discrepancies in CCSM3-simulated near-surface air temperatures significantly correlate with discrepancies in CCSM3-simulated soil-temperatures, i.e. contribute to discrepancy in soil-temperature simulation. Evaluation of cloud-fraction by means of the International Satellite Cloud Climatology project data reveals that errors in simulated cloud fraction explain some of the soil-temperature discrepancies in summer. Evaluation by means of the Global Precipitation Climatology Centre data identifies inaccurately-simulated precipitation as a contributor to underestimating summer soil-temperatures. Comparison to snow-depth observations shows that overestimating snow-depth leads to winter soil-temperature overestimation. Sensitivity studies reveal that uncertainty in mineral-soil composition notably contributes to discrepancies between CCSM3-simulated and observed soil-temperature climatology while differences between the assumed vegetation in CCSM3 and the actual vegetation in nature marginally contribute to the discrepancies in soil-temperature. Out of the 6 K bias in CCSM3 soil-temperature simulation, about 2.5 K of the bias may result from the incorrect simulation of the observed forcing and about 2 K of the bias may be explained by uncertainties due network density in winter. This means that about 1.5 K winter-bias may result from measurement errors and/or model deficiencies. Overall, the performance of a permafrost/soil model fully coupled with a climate model depends partly on the permafrost/soil model itself, the accuracy of the forcing data and design of observational network.

• #### A Description Of The Relationship Between Process Management And The Quality Schools Model In Three Rural Alaska School Districts

This study, conducted as part of a cohort of four, included three districts that follow the Quality Schools Model of educational reform. It used a mixed methods research paradigm to describe how one particular reform evaluation criterion, process management, is believed to be important and to be in practice as a part of the Quality Schools Model (QSM). Process management is the pertinent techniques and tools applied to a process to implement and improve process effectiveness. In this study, I sought to answer four research questions that are fully described in Chapter 3. Three of these questions explored stakeholders' perceptions about the importance of process management in contrast to their perceptions about the extent to which process management was actually in practice in the studied districts. The results of the analysis of the responses showed that there were few significant differences among the respondents. However, stakeholders' perception about the extent to which process management was actually in practice varied significantly with their job classification, but did not vary significantly with either their level of educational work experience or their years of experience with the QSM. Question four of this research was common to the cohort and explored the interrelationship of the seven Malcom Baldrige in Education Criteria in the three districts. The Malcom Baldrige in Education Criteria are a method to evaluate the quality of a school district. The cohort used structural equation modeling (SEM) to answer this question. The data supported a model that shows general agreement with the hypothesized model that is included with the Baldrige literature. While this research was specific to the QSM, others who are pursuing systemic educational reform should consider the implications. They are: holistic educational reform is dependent on well established processes; leadership does not have a direct influence on results; a school district's shared vision must be comprehensive to allow optimum learning conditions through the effective establishment of coproduction; and Total Quality Management practices should be included as a way to ensure staff does its best.
• #### A Descriptive Analysis Of Yakutat Tlingit Musical Style.

Ninety-nine songs from Yakutat, Alaska were analyzed in an effort to determine a musical style of the Gulf Coast Tlingit. Songs were grouped into seven categories from which general trends of style were deduced. Analysis, which was based on the transcriptions of David P. McAllester, included interval distribution, range, tone systems, weighted scales, melodic contour, tempo, duration and rest values, drumming patterns, formal structure, and song length. The transcriptions and data for drumming patterns, formal structure and song length were provided by McAllester in "Under Mount Saint Elias: The History and Culture of the Yakutat Tlingit," by Frederica de Laguna, 1972, Smithsonian Contributions to Anthropology, Volume 7, Washington, D.C: Smithsonian Institution Press. Stylistic differences in the areas of interval distribution, range, tone systems, weighted scales, melodic contour, and tempo were discovered between the two largest categories, the traditional Sib Potlatch songs and the songs of more recent composition called Haida Mouth songs. <p>
• #### A Detailed Structural Analysis Across A Regional Unconformity, Forks Of The Canning River, Franklin Mountains, Northeastern Brooks Range, Alaska

Structural analysis on the northern flank of the 'Franklin Mountains anticlinorium,' northeastern Brooks Range, Alaska, addressed the geometry and sequence of structures, and the deformational mechanics of the Franklinian and Ellesmerian sequences, which are separated by a sub-Mississippian unconformity. The anticlinorium is comprised of two horses of Franklinian sequence rocks in a Cenozoic north-vergent duplex thrust system. South-dipping pre-Mississippian slaty cleavage may have been a plane of preferred failure during ramp formation. Above the unconformity, the Kekiktuk Conglomerate remained attached to pre-Mississippian rocks, deforming with them beneath a roof thrust in the Mississippian Kayak Shale. Increased shear stress and overburden pressure beneath overthrust Franklinian sequence rocks may have led to local detachment near the unconformity surface. Above the Kayak Shale, progressive detachment folding and thrust faulting occurred in the Lisburne and Sadlerochit Groups as a result of emplacement of the two underlying horses. <p>
• #### A fully two-dimensional flux-corrected transport algorithm for hyperbolic partial differential equations

Numerical solutions of the hyperbolic partial differential equation, $\partial p\over\partial t$ + $\vec\nabla \cdot (p\vec u)$ = 0, will generally encounter the difficulties of large diffusion and oscillations near steep gradients or discontinuities. The method of Flux-Corrected Transport (FCT) developed by Boris and Book has conquered these difficulties for the one-dimensional case. Motivated by this one-dimensional FCT algorithm, a fully two-dimensional FCT algorithm is developed in this present work. This fully two-dimensional FCT algorithm is a two-step procedure: (1) the transport scheme, and (2) the antidiffusion scheme. The second step of the procedure could also be replaced by an application of the one-dimensional antidiffusion algorithm in the x direction and the y direction separately. The stability, phase shift errors and positivity for the fully two-dimensional transport scheme are analyzed. Test results are presented. The possibility of the extension of the FCT method to three dimensions are discussed.
• #### A Geobotanical Analysis Of Circumpolar Arctic Vegetation, Climate, And Substrate

The objective of the research presented in this dissertation was to better understand the factors controlling the present and potential future distribution of arctic vegetation. The analysis compares the Circumpolar Arctic Vegetation Map (CAVM) with circumpolar data sets of environmental characteristics. Geographical information system (GIS) software was used to overlay the CAVM with a satellite index of vegetation (normalized difference vegetation index, NDVI) and environmental factors that are most important in controlling the distribution of arctic vegetation, including summer temperature, landscape age, precipitation, snow cover, substrate chemistry (pH and salinity), landscape type, elevation, permafrost characteristics, and distance to sea. Boosted regression tree analysis was used to determine the relative importance of different environmental characteristics for different vegetation types and for different regions. Results of this research include maps, charts and tables that summarize and display the spatial characteristics of arctic vegetation. The data for arctic land surface temperature and landscape age are especially important new resources for researchers. These results are available electronically, not only as summary data, but also as GIS data layers with a spatial context (www.arcticatlas.org). The results emphasize the value and reliability of NDVI for studying arctic vegetation. The relationship between NDVI and summer temperatures across the circumpolar arctic was similar to the correlated increases in NDVI and temperature seen over the time period of satellite records. Summaries of arctic biomass based on NDVI match those based on extrapolation from ground samples. The boosted regression tree analysis described ecological niches of arctic vegetation types, demonstrating the importance of summer temperatures and landscape age in controlling the distribution of arctic vegetation. As the world continues to focus on the Arctic as an area undergoing accelerated warming due to global climate change, results presented here from spatially explicit analysis of existing arctic vegetation and environmental characteristics can be used to better understand plant distribution patterns, evaluate change in the vegetation, and calibrate models of arctic vegetation and animal habitat.
• #### A Maritime Sense Of Place: Southeast Alaska Fishermen And Mainstream Nature Ideologies

This thesis portrays Southeast Alaska fishermen's 'senses of place' on the sea, elicited through interviews. The distinctiveness of a fishing culture, and the demands and opportunities of the occupation and environment, result in a relationship to place different from the majority society. Themes discussed include being at home on the sea, the environment as a basis for occupational choice, territorial flexibility, preference for wild nature, and wild nature produces exploitatable surpluses. The variability of the environment affects patterns of learning, models of nature, and values in inter-personal interactions. Relationship to 'place' is found to be central to the culture, but as the area becomes identified by outsiders as "wilderness," national environmental organizations and others regard fishermen as 'out of place'. Differences from modern Western society in relationship to 'place' and 'nature', highlighted by the Glacier Bay National Park case, are proposed to explain negative perceptions of these fisheries. <p>
• #### A Mechanical Evaluation Of Alaskan White Spruce

This project serves to demonstrate the usefulness of Alaskan White Spruce as a construction material. This is done through the development of allowable strength values for design purposes. Such values allow engineers to design structures using Alaskan White Spruce, increasing the usefulness of the wood species.<p> The mechanical properties of Alaskan White Spruce are investigated. Summaries of the mechanical properties and of subsequently developed allowable structural design values are given. Included are discussions of the Alaskan White Spruce species, general wood behavior, mechanical testing of wood, statistical data analysis, and allowable property development. Results are compared against the work of other researchers. Appendices of test data are given.<p> Test results and subsequent data analysis indicate Alaskan White Spruce possesses strength similar to Douglas-Fir/Larch lumber and higher strength than Spruce/Pine/Fir type lumbers. This indicates that Alaskan White Spruce may have considerable worth as a construction material. <p>
• #### A Mechanism For Current Sheet Thinning In The Growth Phase Of Magnetospheric Substorms

The thinning of the near-Earth current sheet during the growth phase of magnetospheric substorms is a fundamental problem of space physics. It is a characteristic of the slow, steady evolution of the magnetosphere during the growth phase, during which the bulk kinetic energy of the solar wind is transformed into and stored as magnetic field energy in the magnetotail lobes. The thin near-Earth current sheet at the end of the growth phase provides the conditions for the onset of the expansion phase, and is fundamentally important to understand the physical mechanism for the onset of the rapid evolution during which the stored energy is released. I propose that current sheet thinning occurs because of the evacuation of a 'magnetic flux reservoir' in the near-Earth magnetotail by convection to replace magnetic flux that is eroded on the dayside by magnetic reconnection. My hypothesis is able to predict basic properties of current sheet thinning, such as the location, temporal evolution, and dynamics of this process. I examined this new mechanism both conceptually and quantitatively. My conceptual considerations enabled the prediction of the location and duration of current sheet thinning. This location is largely independent of the detailed state of the magnetosphere. I examined this mechanism quantitatively through the use of a three-dimensional ideal MHD simulation. I was able to predict the duration of the growth phase by considering the time needed to deplete our proposed 'magnetic flux reservoir.' The simulation demonstrates the global increase of the current density in this reservoir, despite the removal of magnetic flux---which one would otherwise expect to lead to a decrease of current---as well as even greater local amplifications of the current density. The simulation results are even more significant because the model does not include other effects of the real magnetosphere that contribute to a further increase of the tail current. The increase in current density and thinning are found to be consistent with the amount of flux removed from the system. In addition, I have found a new explanation for the very thin bifurcated current sheets that have been reported in recent publications.
• #### A Methodology For Intelligent Honeypot Deployment And Active Engagement Of Attackers

The internet has brought about tremendous changes in the way we see the world, allowing us to communicate at the speed of light, and dramatically changing the face of business forever. Organizations are able to share their business strategies and sensitive or proprietary information across the globe in order to create a sense of cohesiveness. This ability to share information across the vastness of the internet also allows attackers to exploit these different avenues to steal intellectual property or gather information vital to the national security of an entire nation. As technology advances to include more devices accessing an organization's network and as more business is handled via the internet, attackers' opportunities increase daily. Honeypots were created in response to this cyber warfare. Honeypots provide a technique to gather information about attackers performing reconnaissance on a network or device without the voluminous logs obtained by the majority of intrusion detection systems. This research effort provides a methodology to dynamically generate context-appropriate honeynets. Administrators are able to modify the system to conform to the target environment and gather the information passively or through increasing degrees of active scanning. The information obtained during the process of scanning the environment aids the administrator in creating a network topology and understanding the flux of devices in the network. This research continues the effort to defend an organization's networks against the onslaught of attackers.
• #### A Multiple Stable Isotope Study Of Steller Sea Lions And Bowhead Whales: Signals Of A Changing Northern Environment

The North Pacific and Arctic marine realm is currently experiencing dramatic environmental changes as a result of global climate change. Stable isotope analysis of western arctic bowhead whales (WABW, Balaena mysticetus ) and Steller sea lions (SSL, Eumetopias jubatus) were conducted to examine the influence of these changes on life history characteristics (migration and foraging) of these marine mammals. WABW baleen plates were analyzed for their stable oxygen and hydrogen isotope composition (delta 18O and deltaD) and were compared to the delta18O and deltaD in water and zooplankton prey along their seasonal migratory route. The delta18O and deltaD varied along the baleen (8 to 18�; -180 to -80�, respectively) and corresponded to stable isotopic differences in zooplankton from the winter (Bering Sea) and summer (eastern Beaufort Sea) habitats of WABW. Baleen delta18O and deltaD confirmed the seasonal annual migration of WABW and were subsequently compared to historical sea ice concentrations (SIC). This illustrated that WABW migration patterns appeared to have altered concomitant with changes in SIC. Years with a higher SIC (colder climate regimes) correlated with the largest difference in deltaD between winter and summer in WABW baleen during the period from 1972 to 1988. For a similar time period (1955 to 2000), the feeding ecology of SSL was also examined by analyzing the stable carbon and nitrogen isotope compositions (delta13C and delta 15N, respectively) of archived SSL bone and tooth collagen. Both delta 15N and delta13C varied greatly with location and sample year (14.6 to 20.5�; - 16.7 to -11.8�, respectively), with a significant change in delta13C observed around the 1976 regime shift. Bottom-up processes may have limited growth of SSL populations throughout this region over time, with animals focusing their foraging on offshore regions to mitigate this environmental change. Stable isotope analyses of historical samples of WABW (baleen) and SSL (bone and tooth collagen) both illustrated that recent environmental changes influenced the ecology (migration and feeding) of these marine mammals in the recent past.
• #### A Narrative Study Of The Lived Experience Of Contemporary American Women In Intimate Relationships With Men Who Have Chronic Low Back Pain

Everyone experiences pain to one degree or another, but pain that has outlived its usefulness in assisting the body to avoid injury, and causes other physical and emotional complications, is known as chronic pain. In American medicine, chronic pain is described as that which persists longer than six months and is not relieved by standard medical care. Chronic pain usually leads to a spectrum of other physical and emotional complications, including sleep disturbance, loss of appetite, and severe depression, among many others. Creating and maintaining relationships with others takes effort and energy, and this is especially true in a marital relationship. Marriage between two able-bodied people is challenging enough, so the added variable of chronic pain forms new dimensions of relationship difficulty that must be addressed.