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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Analysis and forecasts of 300 hPa divergence associated with severe convection using ETA-212 and MM5 model data

Lisko, Scott C. 03 1900 (has links)
Approved for public release, distribution is unlimited / This study investigates severe weather events occurring in the Midwest, Central, and Northeastern United States from May through September 2004. Severe weather events are pinpointed using tornado and hail reports and correlating them with NEXRAD radar data to determine maximum intensity of the event. Severe storms that occur within 30 minutes of a model forecast hour are catalogued for further investigation. Once these events are diagnosed, ETA-212 and MM5 model data is regridded, centered on the storm. Divergence values at 300 hPa are extracted from the model data for each storm event. These storms are then grouped in three ways: all storms, tornadic storms, and hail producing storms. The averaged maximum divergence values from the ETA-212 for each group are examined from the 0 hour analysis through the 21 hour forecast. From these averaged divergence values, a matrix of recommended divergence threshold values is derived. For the MM5 data, a subset of storms is examined. The MM5 and ETA-212 are run on an identical set of storms, and the divergence forecasts are compared. / Captain, United States Air Force
22

Lexical Stress Features Affecting the Recognition of English Loanwords in Korean by Native English Hearers

Lee, Yunhyun 04 November 2017 (has links)
Unlike some Asian languages (e.g., Korean), English has lexical stress manifested by four acoustic features: duration, intensity, F0 (pitch), and vowel quality. Lexical stress has been known to have significant influences on native English speakers’ recognition of spoken words. According to Cutler (2015), lexical stress has both suprasegmental and segmental features: Suprasegmental features include duration, intensity, and F0 while vowel quality is considered a segmental feature. However, it is still unclear which lexical features are more responsible for spoken word recognition. This study examined which features, suprasegmental features or vowel quality of English, are a more significant influencer in spoken word recognition using English loanwords in Korean, which lack the prominence of any syllable realized by these features. Additionally, this study investigated the claimed advantage of the strong-weak stress pattern over a weak-strong pattern. To that end, two experiments were conducted. First, a parallel acoustic comparison was made between disyllabic English words and their corresponding English loanwords in Korean in order to investigate whether Korean has lexical stress features similar to those of English. 10 Korean and 10 English native speakers read 20 disyllabic words: the English loanwords in Korean by Korean participants and the source English words by American participants. The results showed that the differences of acoustic values between the syllables of the English words were significantly larger than those of the English loanwords. That is, the relative prominence of the stressed syllable over the unstressed syllable in English was not found in Korean. Additionally, the results indicated that Korean does not have a reduced vowel such as /ə/ in English, which is a critical feature of English vowel quality. In Experiment II, 16 English loanwords were used to create three versions of a spoken word recognition experiment, which was administered using the online survey platform, Qualtrics. Each version had a different type of manipulation: unmanipulated English loanwords, English loanwords with suprasegemental manipulation or English loanwords with vowel quality manipulation. 117 American English hearers identified the spoken words of one of the versions assigned to them; their success rates and reaction times (RT) were recorded. A binominal regression test was used for the analysis of success rates, and the Kruskal-Wallis H test for the response times. The results indicated that as far as success rates are concerned, both suprasegmental features and vowel quality play a role in recognizing spoken English words. However, when these two features were compared, vowel quality seemed to be a much stronger player. As for stress patterns, no significant differences were found in success rates across the three sets of manipulation. Moreover, this study did not find any significant difference in RTs either across the three manipulation sets or the two stress patterns. This study offered many applied implications in ESL, especially for teaching English pronunciation in Korea.
23

Streaming Video in Wireless Networks : Service and Technique / Strömmande video i trådlösa nätverk : tjänst och teknik

Montelius, Fredrik, Larsson, Oscar January 2001 (has links)
The purpose of this thesis is to present an attractive service for the third generation mobile network that includes streaming video. A prototype application for this service is to be built. The technique behind streaming video is to be presented so that it comes clear what kind of problems and solutions that are associated with streaming. Finally, a platform for streaming video is to be tested and evaluated through different channels. The attractive service presented in this thesis is MMS - Multimedia Messaging Service. Today's popular SMS is evolving beyond text to multimedia. Multimedia will be part of the next generation messaging service called MMS, which will, in an advanced shape, include streaming video. MMS is expected to be a successful service for the next generation?s cell phones. The WAP Forum and the 3GPP industry groups are responsible for standardizing MMS. The standard defines an MMS architecture, which has a number of key elements that interact with each other. The prototype application that was built is called mVideo Messaging and is an MMS that is built on the basis of the MMS standard. The kernel of the prototype is a platform from PacketVideo that makes it possible to stream video over wireless networks. Theories and tests makes it clear that the parameters affecting the video quality can be found at the source/target while coding and compressing, as well as at the streaming-channel. At the channel there are above all three network problems - packet loss, end-to-end delay and delay jitter. To deal with these matters, new protocols have been developed. At the source/target it is important use an efficient compression scheme. MPEG-4 is a new compression scheme that suits very well for streaming video through wireless channels. MPEG- 4 make use of scalability, is object oriented, and is optimized for streaming between 9,6 kbps and 4 Mbps. The service proposed in this thesis as a future service for 3G is practicable. It is also shown that the service can be built using the technology of today.
24

Streaming Video in Wireless Networks : Service and Technique / Strömmande video i trådlösa nätverk : tjänst och teknik

Montelius, Fredrik, Larsson, Oscar January 2001 (has links)
<p>The purpose of this thesis is to present an attractive service for the third generation mobile network that includes streaming video. A prototype application for this service is to be built. The technique behind streaming video is to be presented so that it comes clear what kind of problems and solutions that are associated with streaming. Finally, a platform for streaming video is to be tested and evaluated through different channels. </p><p>The attractive service presented in this thesis is MMS - Multimedia Messaging Service. Today's popular SMS is evolving beyond text to multimedia. Multimedia will be part of the next generation messaging service called MMS, which will, in an advanced shape, include streaming video. MMS is expected to be a successful service for the next generation?s cell phones. </p><p>The WAP Forum and the 3GPP industry groups are responsible for standardizing MMS. The standard defines an MMS architecture, which has a number of key elements that interact with each other. The prototype application that was built is called mVideo Messaging and is an MMS that is built on the basis of the MMS standard. The kernel of the prototype is a platform from PacketVideo that makes it possible to stream video over wireless networks. </p><p>Theories and tests makes it clear that the parameters affecting the video quality can be found at the source/target while coding and compressing, as well as at the streaming-channel. At the channel there are above all three network problems - packet loss, end-to-end delay and delay jitter. To deal with these matters, new protocols have been developed. At the source/target it is important use an efficient compression scheme. MPEG-4 is a new compression scheme that suits very well for streaming video through wireless channels. MPEG- 4 make use of scalability, is object oriented, and is optimized for streaming between 9,6 kbps and 4 Mbps. </p><p>The service proposed in this thesis as a future service for 3G is practicable. It is also shown that the service can be built using the technology of today.</p>
25

Qualification et amélioration de la précision de systèmes de balayage laser mobiles par extraction d’arêtes / Edge-based accuracy assessment and improvement of mobile laser scanning systems

Poreba, Martyna 18 June 2014 (has links)
Au cours de ces dernières décennies, le développement de Systèmes Mobiles de Cartographie, soutenu par un progrès technologique important, est devenu plus apparent. Il a été stimulé par le besoin grandissant de collecte d'informations géographiques précises sur l'environnement. Nous considérons, au sein de cette thèse, des solutions pour l'acquisition des nuages de points mobiles de qualité topographique (précision centimétrique). Il s'agit, dans cette tâche, de mettre au point des méthodes de qualification des données, et d'en améliorer sur les erreurs systématiques par des techniques d'étalonnage et de recalage adéquates.Nous décrivons une démarche innovante d'évaluation de l'exactitude et/ou de la précision des relevés laser mobiles. Celle-ci repose sur l'extraction et la comparaison des entités linéaires de la scène urbaine. La distance moyenne calculée entre les segments appariés, étant la distance modifiée de Hausdorff, sert à noter les nuages par rapport à des références existantes. Pour l'extraction des arêtes, nous proposons une méthode de détection d'intersections entre segments plans retrouvés via un algorithme de RANSAC enrichi d'une analyse de composantes connexes. Nous envisageons également une démarche de correction de relevés laser mobiles à travers un recalage rigide fondé, lui aussi, sur les éléments linéaires. Enfin, nous étudions la pertinence des segments pour en déduire les paramètres de l'étalonnage extrinsèque du système mobile. Nous testons nos méthodes sur des données simulées et des données réelles acquises dans le cadre du projet TerraMobilita. / Over the past few decades, the development of land-based Mobile Mapping Systems (MMS), supported by significant technological progress, has become more prominent. It has been motivated by the growing need for precise geographic information about the environment. In this thesis, we consider approaches for the acquisition of mobile point clouds with topographic quality (centimeter-level accuracy). The aim is to develop techniques for data quality assessment and improvement. In particular, we eliminate the systematic errors inherent to an MMS data using appropriate calibration and registration methods.We describe a novel approach to assess the accuracy and/or the precision of mobile laser point clouds. It is based on the extraction and comparison of line features detected within the urban scene. The computed average distance between corresponding pairs of line segments, taking advantage of a modified Hausdorff distance, is used to evaluate the MMS data with respect to a reference data set. For edge extraction, we propose a method which relies on the intersections between planes modelled via the RANSAC algorithm refined by an analysis of connected components. We also consider an approach to correct point clouds using a line-based rigid registration method. Finally, we study the use of line segments for estimating the boresight angles of a land-based mobile mapping system. We apply our methods to synthetic data and to real data acquired as part of the TerraMobilita project.
26

Electron heating in collisionless shocks observed by the MMS spacecraft

Svensson, Martin January 2018 (has links)
Shock waves are ubiquitous in space and astrophysics. Shocks transform directed particle flow energy into thermal energy. As the major part of space is a collisionless medium, shocks in space physics arises through wave-particle interactions with the magnetic field as the main contributor.The heating processes are scale dependent. The large scale processes governs the ion heating and is well described by magnetohydrodynamics. The small scale processes governs the electron heating lies within the field of kinetic plasma theory and is still today remained disputed. A step towards the answer for the small scale heating would be to measure the scale, in order to relate it to a known instability or other small scale processes.The multi-spacecraft NASA MMS spacecraft carries several high resolute particle and field instruments enabling almost instantaneous 3D particle measurements and accurate measurements of the magnetic field. Also the separation between the four MMS spacecraft is as small as &lt; 8km for a certain mission phase. This allows for new approaches when determining the scale which for shocks has not been possible before when using data from previous multi-spacecraft missions with spacecraft separation much larger. The velocity of the shock is large compared to the spacecraft,thus the shock width cannot be directly measured by each spacecraft. Either a constant velocity has to be estimated or we could use gradients of a certain parameter between the spacecraft as the shock flows over them. The usage of gradients is only possible with MMS as all the spacecraft could for MMS be within the shock simultaneously. The change for a parameter within the shockis assumed to be linear between the spacecraft and measurements. It is also assumed that the gradient of the parameter maximizes in the shock normal direction. Using these assumptions two methods have been developed. They have the same working principles but are using two or four spacecraft for linear estimation at each measurement point. From the gradient and parametric data the shock ramp width could then be found. The parameter used in this thesis is the electron temperature. The methods using one, two and four spacecraft were tested using electron temperature data from different shock crossings. Two problems with the gradient methods were found from the results, giving false data for certain time spans. To avoid these problems, the scale of the electron temperature gradient was determined for roughly half the shock ramp. It was found using the two and four spacecraft methods that an assumption of constant velocity for the shock speed is an uncertain assumption. The shock speed varies over short time scales and in the shock crossings analysed the constant velocity estimations were generally overestimated. From the two and four spacecraft methods roughly half of the temperature rise in the shock ramp occurred over 10.8km or 12.4 lpe. This is almost a factor of two greater than previous scale estimates using Cluster data and a multi-spacecraft timing method for shock speed estimation.From the results it is concluded that the methods when using gradients between spacecraft has some restrictions. They can only be used for MMS data, requires quasi-perpendicular high Mach number and will give false results if the temperature is disturbed by interacting hot plasma clouds. However, even though we have these limitations for the tested gradient methods, they were found better and more reliable compared to previous methods for shock scaling.
27

Analýza trajektorie mobilních mapovacích platforem / Analysis of trajectory of mobile mapping platforms

Centový, Radoslav January 2017 (has links)
The diploma thesis deals with possibilities of tracing the trajectory of mobile mapping systems in order to compare their accuracy. This thesis discusses the individual components of the mobile mapping device that were used in its construction. The thesis contains the results of the experiments that were performed on individual test.
28

Orientation of plasma jet fronts in the Earth's magnetotail

Silverhult, Atlas January 2023 (has links)
This project aims to investigate the orientation of plasma jet fronts in Earth's magnetotail using multi-spacecraft measurement data. The orientations are estimated by applying minimum variance analysis (MVA) and multi-spacecraft timing analysis for finding normal vectors to the jet fronts as they pass over the spacecraft. An agreement between the two analysis methods is found when applied to a data set of fronts. The obtained results are compared to measurements of the ion bulk velocities of the fronts, where a discrepancy is found. Limitations of the analysis are addressed and alternative approaches are presented. / I detta projekt undersöks riktningen hos fronter till plasma-jetstrålar i jordens magnetsvans genom analysering av mätdata från en samling rymdfarkoster. Riktningarna uppskattas genom att applicera minimum variance analysis (MVA) samt multi-spacecraft timing för att hitta normalvektorer till fronterna som passerar rymdfarkosterna. De två metoderna uppnår liknande resultat när de tillämpas på en uppsättning fronter. De erhållna normalvektorerna jämförs även med riktningen av uppmätta jonhastigheter från rymdfarkosterna där en tydlig skillnad förekommer. Begränsningar av analysmetoden påpekas och förslag på alternativa tillvägagångssätt läggs fram.
29

Verification of a Computational Aeroacoustics Code Using External Verification Analysis (EVA)

Ingraham, Daniel 14 June 2010 (has links)
No description available.
30

Mobiliųjų paslaugų portalų technologijų tyrimas / Research of mobile portals technologies

Najulis, Mindaugas 03 June 2005 (has links)
Information technologies and mobile telecommunications rapidly enter our personal and social life. Mobile phone is no longer luxury – it has become a necessity. Growing volumes of the mobile services has caused a need to expand the mobile service employment opportunities in the Internet portals. Today’s portals, created using the means, offered by software manufacturers, employ exclusively the mobile Internet service, thanks to which the users can see and manage the necessary information and process of the portal at any time and from anywhere. The problem is related with the fact that mobile Internet services are still expensive in Lithuania. Therefore one should look for cheaper ways to reach and manage portal information. In order to solve this problem one can consider the SMS and MMS message sending, suggested by mobile technologies. Basic aim of the work is to create an entertainment portal, rendering the user both various Internet entertainments (e.g. Internet acquaintances, games), and mobile entertainment (e.g. sending messages, logos, melodies, animations and games for mobile phone) as well as a wide range of mobile services to be used to obtain and to manage the portal information. In the work I describe: portal evolution, classification and creation measures („BroadVision Portal“, „IBM WebSphere Portal for Multiplatforms v5.x“, „Sun One Portal Server v6.0“, „Red Hat Enterprise Portal Server“, „Microsoft SharePoint® Portal Server 2003“, „ORACLE 9ias Portal“, „PHP:... [to full text]

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