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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.
1

Ship airwakes in waves and motions and effects on helicopter operation

Dooley, Gregory M. 01 May 2019 (has links)
This thesis focuses on the effects of wave-induced motions on the airwake of a ship and on the operation of a helicopter in the airwake. While the topic is broad, efforts are concentrated on understanding fundamentals of the ship’s airwake structure at varying Reynolds (Re) numbers without motions, using available experimental data for validation of the computational fluid dynamics (CFD) methodology used, and on studying the effects of waves and motions on the airwake of a ship and a helicopter operating above a ship’s flight deck in full-scale. The static ONR Tumblehome (ONRT) ship geometry with a solid boundary representative of the free surface is simulated at three different Re numbers, 3.2x104, 1x106, and 1.3x108. Validation is performed against experimental measurements at model-scale Re=1x106. Full-scale simulations of the ONRT are carried out in head winds and regular waves approximately equivalent to conditions seen at sea states 3 and 6. Effects of waves and motions are isolated for both sea states using simulations with combinations of waves and motions, waves and no motions, no waves with motions, and no motions or waves. A triple velocity decomposition is conducted in order to quantify changes in the airwake due to motions and waves. The operation of rotorcraft in the ONRT airwake is analyzed using one-way and two-way coupling approaches. The one-way coupling approach uses the velocity field data from the full-scale ONRT simulations and disk actuator theory to calculate thrust fluctuations for three different rotor sizes. The results of the one-way coupling approach show that the smallest rotor is much more affected by small scale turbulence, while small scale fluctuations are filtered out by larger rotor diameters. In the two-way coupling approach, a helicopter based on the Sikorsky SH-60 hovering above the flight deck is simulated, including explicitly moving grids to discretize the main rotor, tail rotor, and fuselage. This method captures the effects of the interaction between the rotor downwash and the ONRT airwake. The study shows that for the mild conditions of sea state 3 the motions have little effect on the airwake behavior. At sea state 6 the airwake behavior is significantly altered, which is reflected in the resulting forces on the helicopter body operating in this condition.
2

Dinaminė interneto sąsaja įmonių klientų-ryšių valdymo sistemoms patobulinti / Dynamic Web interface for improvement of enterprise customer relationship management systems

Junčis, Aurimas 28 January 2008 (has links)
Darbe nagrinėjamas antros kartos (Web 2.0 ) interneto atsiradimas, jam būdingos naujos technologijos ir pasikeitę reikalavimus interneto sistemoms. Pastebimas augantis poreikis darbui su dideliais duomenų kiekiais, naudojant paprastą naršyklę. Iškeliamas tikslas padidinti CRM sistemų dinamiškumą, išplečiant jas raiškių interneto programų savybėmis ir sudarant rekomendacijas esamoms sistemoms patobulinti. Detaliau aptariamas technologijų rinkinys, pavadintas Ajax (Asynchronous JavaScript and XML ), kuris leidžia kurti dinamiškus interneto puslapius (sistemas). Pateikiamas dinamiškos sistemos scenarijų apibrėžimas ir sudaromos RIA taikomųjų programų savybių pritaikymo CRM ir kitoms organizacijų sistemoms rekomendacijos. / This work is concentrated on creation of dynamic web systems. Web 2.0 brings new requirements to internet based systems (web pages). Users needs to work with large amounts of data (information) using simple web browser are increasing very fast. So there is a problem when we need to represent this data on web page. We need dynamic systems (pages) to do it fast ant easy to operate. Dynamic system (page) is internet based system (web page), which most functions are using Ajax (asynchronous communication with server). The real experimental system to increase a dynamism of Customer Relationship Management systems by extending them with Rich Internet Applications characteristics is created and analyzed. Recommendations to improve similar existing CRM systems are made.
3

The use of offline simulation tools to estimate ship-helicopter operating limitations / De l'utilisation des outils de simulation pour l'estimation des limites d'appontage des hélicoptères

Pereira Figueira, José Márcio 16 November 2017 (has links)
Les limitations d’atterrissage des hélicoptères ne sont pas valables dans l'environnement à bord d’un navire. Il n'existe aucune méthodologie approuvée de l'analyse ou de la simulation pour évaluer la compatibilité des hélicoptères-navires et préparer les essais de qualification hélicoptères-navires. Dans ce contexte, le présent travail présente le développement et l'analyse d'une méthodologie hors ligne pour déterminer les limites opérationnelles hélicoptères-navires, SHOLs, en fonction des prédictions d’un modèle de pilote humain. Pour cela, des essais pilotés par des humains sont effectués au simulateur de l’ONERA, Salon de Provence. Sur la base des résultats de ces tests, une méthodologie innovante est validée pour déterminer la limitation de la charge de travail de pilotage, à partir des mesures des déplacements des contrôles d'hélicoptère. En outre, sont validés des modifications innovantes sur un modèle de pilote humain pour pouvoir suivre les trajectoires souhaitées et fournir le même niveau d'activité aux contrôles qu'un véritable pilote. Un ensemble de critères objectifs, correspondant aux marges de sécurité, s'ajoute aux critères subjectifs, correspondant aux limitations de la charge de travail du pilote. Une routine de simulation hors ligne, appelée SholSim, est programmée pour réaliser des simulations avec le modèle pilote et vérifier l'acceptabilité des conditions de vol, selon les critères subjectifs et objectifs. Par conséquent, le présent travail présente la première estimation, dans la littérature, des SHOLs entièrement obtenus à partir d'outils hors ligne, basés uniquement sur les prédictions de modèle pilote. / Helicopter land-based limitations are not valid in the shipboard environment. There is no analytical or simulated approved methodology for evaluating shipboard helicopter compatibility issues and preparing for at-sea flight tests. In this context, the present work presents the development and analysis of an offline methodology to determine the Ship-Helicopter Operating Limitations, SHOLs, based on pilot model predictions. For this, pilot-in-the-loop simulation trials are performed at the engineering fixed-base simulation facility of ONERA, Salon de Provence. Based on these test results, an innovative methodology is proposed and validated to determine the safe pilot workload limitation, from the measurements of the helicopter control displacements. In addition, it is proposed and validated innovative modifications on a classical pilot model enabling to follow complex predefined desired trajectories and provide the same level of control activity of a real pilot. A set of objective criteria, corresponding to the safety margins, is established in addition to the subjective criteria, corresponding to the safe pilot workload limitations. An offline simulation routine, so-called SholSim, is coded to run all models and verify the acceptability of the flight conditions, according to the subjective and objective criteria. Therefore, the present work presents the first estimation, in the literature, of the SHOLs fully obtained from offline tools, based only on pilot model predictions. The proposed methodology is promising, confirmed by predicting coherent limits when compared to the ones defined by the pilot-in-the-loop simulation trials.
4

Konceptdriven designforskning för dynamisk applikationsanvändning : En studie för att främja användarupplevelsen av dynamiska applikationsförslag baserat på plats och tid / Concept-driven design research for dynamic application use : a study to facilitate the user experience of dynamic application suggestions based on location and time

Helge, Isak, Larsson, Christoffer January 2019 (has links)
Den mobila användningen har ökat ordentligt de sista tio åren och smarttelefonen har blivit en viktig del av många människors vardag. Applikationer används i vår vardag och användningen av dessa kan reflektera vår vardag, dock så är gränssnittet på smarttelefonen statiskt och förändrar sig inte beroende på användarens plats och tid. Syftet med studien är att undersöka om användarupplevelsen går att främja med hjälp av en dynamisk hemskärm på en smarttelefon utifrån användarens plats och tid. Detta gjordes med hjälp av konceptdriven designforskning drivet av följande frågeställning: “Hur kan ett designkoncept av en dynamisk hemskärm på en smarttelefon teoretiskt förankras och konceptualiseras baserat på användarens plats och tid i syfte att främja användarupplevelsen? Konceptet grundar sig i tidigare forskning och resultatet blev ett koncept för dynamiska applikationsförslag som bemöttes av sju deltagarna som deltog i studien. Enligt deltagarna har konceptet en potential att minska stressen då navigering till rätt applikation underlättas. Konceptet var också enkelt att förstå men frågan kring integritet och säkerhet delade deltagarna. I resultatet presenteras designkonceptet som bygger på tidigare forskning samt kritiken från studiens deltagare. Konceptet har en potential och kan utforskas vidare från många olika perspektiv. / The mobile usage has increased considerably in the last ten years and the smartphone has become an important part of many people's everyday lives. Applications are used in our everyday life and the use of these can reflect our everyday lives, however, the interface on the smartphone is static and does not change depending on what context the user are in. The purpose of this study is to investigate whether the user experience can be favoured by a dynamic home screen on a smartphone based on the user's location and time. This was accomplished with the help of concept-driven design research driven by the following research question: "How can a design concept of a dynamic home screen on a smartphone be theoretically anchored and conceptualized based on the user's place and time in order to favour the user experience? The concept is based on previous research and the result was a concept for dynamic application suggestions that were met seven participants who participated in the study. According to the participants, the concept has the potential to reduce stress as navigation to the right application is facilitated. The concept was also easy to understand but the question of integrity and security shared the participants. In the result, the design concept is presented, which is based on previous research and the criticism from the study's participants. The concept has great potential and can be explored further from many different perspectives.

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