• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 269
  • 111
  • 90
  • 36
  • 26
  • 24
  • 21
  • 16
  • 7
  • 6
  • 6
  • 3
  • 3
  • 3
  • 3
  • Tagged with
  • 737
  • 140
  • 138
  • 131
  • 101
  • 90
  • 87
  • 82
  • 81
  • 68
  • 67
  • 64
  • 63
  • 63
  • 62
  • 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.
341

Multiple Simultaneous Specification Attitude Control of a Mini Flying-wing Unmanned Aerial Vehicle

Markin, Shael 12 January 2011 (has links)
The Multiple Simultaneous Specification controller design method is an elegant means of designing a single controller to satisfy multiple convex closed loop performance specifications. In this thesis, the method is used to design pitch and roll attitude controllers for a Zagi flying-wing unmanned aerial vehicle from Procerus Technologies. A linear model of the aircraft is developed, in which the lateral and longitudinal motions of the aircraft are decoupled. The controllers are designed for this decoupled state space model. Linear simulations are performed in Simulink, and all performance specifications are satisfied by the closed loop system. Nonlinear, hardware-in-the-loop simulations are carried out using the aircraft, on-board computer, and ground station software. Flight tests are also executed to test the performance of the designed controllers. The closed loop aircraft behaviour is generally as expected, however the desired performance specifications are not strictly met in the nonlinear simulations or in the flight tests.
342

Multiple Simultaneous Specification Attitude Control of a Mini Flying-wing Unmanned Aerial Vehicle

Markin, Shael 12 January 2011 (has links)
The Multiple Simultaneous Specification controller design method is an elegant means of designing a single controller to satisfy multiple convex closed loop performance specifications. In this thesis, the method is used to design pitch and roll attitude controllers for a Zagi flying-wing unmanned aerial vehicle from Procerus Technologies. A linear model of the aircraft is developed, in which the lateral and longitudinal motions of the aircraft are decoupled. The controllers are designed for this decoupled state space model. Linear simulations are performed in Simulink, and all performance specifications are satisfied by the closed loop system. Nonlinear, hardware-in-the-loop simulations are carried out using the aircraft, on-board computer, and ground station software. Flight tests are also executed to test the performance of the designed controllers. The closed loop aircraft behaviour is generally as expected, however the desired performance specifications are not strictly met in the nonlinear simulations or in the flight tests.
343

How to improve the inbound flow of an manufacturing company : Analyzing and refining the Customer-driven Purchasing method

Hedén, Eric, Tiedemann, Fredrik January 2014 (has links)
Purpose: The purpose of this research is to analyze the CDP-method in order to develop and refine the method. The method is developed and presented in Bäckstrand (2012), with the aim to strengthen the competitiveness of manufacturing companies. Someone outside of the development context has never, until now and to the researchers knowledge, refined the method. Methodology: A multiple case study with four companies where used. The empirical data collected within the study where used to evaluate the CDP-method and to refine the method. The presented improvement is based on the empirical data and conceptual models developed from theory. Findings: Three improvements were developed. The first of them changed step 8 of the method, the second can´t be tied to a single step and is therefore an overall suggestion, whereas the third provides a new type of analysis within step 6 of the method. Research limitations: The research was conducted at companies where the CDP-method was already implemented. An implementation at a new company could possibly reveal another type of empirical data, which could be interpreted in a different way. The researchers have also detected areas that couldn’t be investigated within this research, these are identified and left for further research. Theoretical implications: Results from this thesis connect the classification of supply risk by Kraljic (1983) with supply chain strategy by Fisher (1997) to enable a new type of analysis. Furthermore, theory within the standardization and over-specification (e.g. Burt, Petcavage & Pinkerton, 2010; Geldeman & van Weele, 2002) is introduced and incorporated in the CDP-method. A third implication is a reinforced focus on strategy in combination with the CDP-method, which is based on theory regarding strategic alignment (e.g. Gattorna & Walter, 1996; Hines, 2004). Managerial implications: The new analysis should, together with the CDP-method as a whole, strengthen adopting companies supply chain and improve internal and external communication. Originality/value: This thesis provides a new set of analysis in the CDP-method that could benefit practitioners.
344

Formal relationships in sequential object systems

Kerfoot, Eric D. January 2010 (has links)
Formal specifications describe the behaviour of object-oriented systems precisely, with the intent to capture all properties necessary for correctness. Relationships between objects, and in a broader sense the relationship between whole components, may not be adequately captured by specifications. One critical component of specifications having a role in relationships are invariants which define a constraint between multiple objects. If an object's invariant relies on external objects for its conditions, correct operations which abide by their specifications modifying these external objects may violate the constraint. Such an invariant defines a relationship between multiple objects which is unsound since it does not adequately describe the responsibilities which the objects in the relationship have to each other. The root cause of this correctness loophole is the failure of specifications to capture such relationships adequately as well as their correctness requirements. This thesis addresses this shortcoming in a number of ways, both for individual objects in a sequential environment, and between concurrent components which are defined as specialized object types. The proposed Colleague Technique [29] defines sound invariants between two object types using classical Design-by-Contract [35] methodologies. Additional invariant conditions introduced through the technique ensure that no correct operation may produce a post-state which does not satisfy all invariants satisfied by the pre-state. Relationships between objects, as well as their correct specification and management, are the subjects of this thesis. Those relationships between objects which can be described by invariants are made sound with the Colleague Technique, or the lightweight ownership type system that accompanies it. Behavioural correctness beyond these can be addressed with specifications in a similar manner to sequential systems without concurrency, in particular with the use of runtime assertion checking [11].
345

Att vara eller inte vara: En definitionsfråga : Om rekryteringskonsulters tolkning och definition av personliga egenskaper i en kravspecifikation

Erlandsson, Elin, Svensson, Emmie, Thune, Simon January 2017 (has links)
Syfte: Uppsatsens syfte är att tillföra förståelse och kunskap för hur rekryteringskonsulter arbetar med att definiera och bedöma personliga egenskaper som inkluderas i en kravspecifikation. Vidare vill vi kartlägga de verktyg som rekryteringskonsulter använder för att utföra denna bedömning. En större förståelse för dessa processer och begrepp kan skapa ökad medvetenhet och i förlängningen professionalisering av både företag och rekryterare, och framför allt i kommunikationen dem emellan.Metodik: Vi har använt oss av en deduktiv ansats och en kvalitativ forskningsmetod. Vi har utfört elva kvalitativa och semistrukturerade intervjuer med elva personer aktiva inom rekryteringsbranschen.Resultat: Vi har uppmärksammat att rekryteringskonsulter finner en svårighet med att definiera de personliga egenskaperna i en kravspecifikation. Orsakerna har preciserats bero på en kommunikationsbrist mellan rekryteringskonsult och kundföretag. En bristande kommunikation resulterar i att definitionen av de personliga egenskaperna inte är överensstämmande mellan parterna, vilket försvårar rekryterarens arbete med att finna den rätta medarbetaren. Vi har kommit fram till att ett fysiskt möte skapar möjligheten för rekryteringskonsult och kundföretag att nå en god kommunikation. Den goda kommunikationen har i sin tur visats vara det verktyg som minskar risken för att en tolkningsvariation ska uppstå. / Purpose: The purpose of the essay is to provide an understanding and knowledge of how recruitment consultants work to define and assess personal qualities that are included in a requirement specification. Furthermore, we want map the tools that recruitment consultants uses to perform this assessment. A greater understanding of these processes and concepts can create an increased awareness and, in the long run, professionalization of both companies and recruiters, especially in the communication between them.Method: We have used a deductive and qualitative research approach. We conducted eleven qualitative and semi-structured interviews with people working within the recruitment industry.Conclusion: We have seen that recruitment consultants find it difficult to define the personal characteristics found in a requirement specification. The reasons are clarified to be due to the lack of communication between the recruitment consultant and the customer. A lack of communication results in the fact that the definition of the personal characteristics is not consistent between the parties, which significantly complicates the recruitment consultant’s work to find the right employee. We have therefore come to the conclusion that a physical meeting creates the opportunity for recruitment consultants and customers to achieve a good communication. The good communication has, in turn, been shown to be the way to reduce the risk of a definition variation.
346

Genetic mechanisms behind cell specification in the Drosophila CNS

Baumgardt, Magnus January 2009 (has links)
The human central nervous system (CNS) contains a daunting number of cells and tremendous cellular diversity. A fundamental challenge of developmental neurobiology is to address the questions of how so many different types of neurons and glia can be generated at the precise time and place, making precisely the right connections. Resolving this issue involves dissecting the elaborate genetic networks that act within neurons and glia, as well as in the neural progenitor cells that generates them, to specify their identities. My PhD project has involved addressing a number of unresolved issues pertaining to how neural progenitor cells are specified to generate different types of neurons and glial cells in different temporal and spatial domains, and also how these early temporal and spatial cues are integrated to activate late cell fate determinants, which act in post-mitotic neural cells to activate distinct batteries of terminal differentiation genes. Analyzing the development of a specific Drosophila melanogaster (Drosophila) CNS stem cell – the neuroblast 5-6 (NB5-6) – we have identified several novel mechanisms of cell fate specification in the Drosophila CNS. We find that, within this lineage, the differential specification of a group of sequentially generated neurons – the Ap cluster neurons – is critically dependent upon the simultaneous triggering of two opposing feed-forward loops (FFLs) within the neuroblast. The first FFL involves cell fate determinants and progresses within the post-mitotic neurons to establish a highly specific combinatorial code of regulators, which activates a distinct battery of terminal differentiation genes. The second loop, which progresses in the neuroblast, involves temporal and sub-temporal genes that together oppose the progression of the first FFL. This leads to the establishment of an alternative code of regulators in late-born Ap cluster neurons, whereby alternative cell fates are specified. Furthermore, we find that the generation and specification of the Ap cluster neurons is modulated along the neuraxis by two different mechanisms. In abdominal segments, Hox genes of the Bithorax cluster integrates with Pbx/Meis factors to instruct NB5-6 to leave the cell cycle before the Ap cluster neurons are generated. In brain segments, Ap cluster neuron equivalents are generated, but improperly specified due to the absence of the proper Hox and temporal code. Additionally, in thoracic segments we find that the specification of the Ap cluster neurons is critically dependent upon the integration of the Hox, Pbx/Meis, and the temporal genes, in the activation of the critical cell fate determinant FFL. We speculate that the developmental principles of (i) feed-forward combinatorial coding; (ii) simultaneously triggered yet opposing feed-forward loops; and (iii) integration of different Hox, Pbx/Meis, and temporal factors, at different axial levels to control inter-segmental differences in lineage progression and specification; might be used widely throughout the animal kingdom to generate cell type diversity in the CNS.
347

A framework for an adaptive early warning and response system for insider privacy breaches

Almajed, Yasser M. January 2015 (has links)
Organisations such as governments and healthcare bodies are increasingly responsible for managing large amounts of personal information, and the increasing complexity of modern information systems is causing growing concerns about the protection of these assets from insider threats. Insider threats are very difficult to handle, because the insiders have direct access to information and are trusted by their organisations. The nature of insider privacy breaches varies with the organisation’s acceptable usage policy and the attributes of an insider. However, the level of risk that insiders pose depends on insider breach scenarios including their access patterns and contextual information, such as timing of access. Protection from insider threats is a newly emerging research area, and thus, only few approaches are available that systemise the continuous monitoring of dynamic insider usage characteristics and adaptation depending on the level of risk. The aim of this research is to develop a formal framework for an adaptive early warning and response system for insider privacy breaches within dynamic software systems. This framework will allow the specification of multiple policies at different risk levels, depending on event patterns, timing constraints, and the enforcement of adaptive response actions, to interrupt insider activity. Our framework is based on Usage Control (UCON), a comprehensive model that controls previous, ongoing, and subsequent resource usage. We extend UCON to include interrupt policy decisions, in which multiple policy decisions can be expressed at different risk levels. In particular, interrupt policy decisions can be dynamically adapted upon the occurrence of an event or over time. We propose a computational model that represents the concurrent behaviour of an adaptive early warning and response system in the form of statechart. In addition, we propose a Privacy Breach Specification Language (PBSL) based on this computational model, in which event patterns, timing constraints, and the triggered early warning level are expressed in the form of policy rules. The main features of PBSL are its expressiveness, simplicity, practicality, and formal semantics. The formal semantics of the PBSL, together with a model of the mechanisms enforcing the policies, is given in an operational style. Enforcement mechanisms, which are defined by the outcomes of the policy rules, influence the system state by mutually interacting between the policy rules and the system behaviour. We demonstrate the use of this PBSL with a case study from the e-government domain that includes some real-world insider breach scenarios. The formal framework utilises a tool that supports the animation of the enforcement and policy models. This tool also supports the model checking used to formally verify the safety and progress properties of the system over the policy and the enforcement specifications.
348

Evaluace jazyků pro tvorbu chování inteligentních virtuálních agentů / Evaluation of languages for creating intelligent virtual agent behaviors

Vykouk, Ondřej January 2013 (has links)
There are dozens of formalisms specialized programming intelligent virtual agents (IVA). However, there is lack of an evaluation, which would provide the designer of a new agent with an overview of their usability in real-world applications. The goal of this study was evaluation of selected formalisms in order to identify their shortcomings and suggesting improvements. These improvements would allow the designer more accurate control of the IVA's behavior. Evaluation of formalisms was designed based on real-world scenarios and their implementation in different formalisms using the platform Pogamut 3. One of the formalisms is Jason (AgentSpeak language interpreter) and it was connected to that platform as a part of this thesis. During the implementation of the scenarios were identified some problems which make creating the behavior of intelligent virtual agents harder. For these problems was proposed solution in the form of action selection mechanism (ASM) prototype and the basic methodology for designing agents with this ASM. The results of this study could be a starting point for more advanced action selection mechanism, which would allows more precise control of the behavior of intelligent virtual agents. Powered by TCPDF (www.tcpdf.org)
349

Transcriptional and epigenetic control of gene expression in embryo development

Boija, Ann January 2016 (has links)
During cell specification, temporal and spatially restricted gene expression programs are set up, forming different cell types and ultimately a multicellular organism. In this thesis, we have studied the molecular mechanisms by which sequence specific transcription factors and coactivators regulate RNA polymerase II (Pol II) transcription to establish specific gene expression programs and what epigenetic patterns that follows. We found that the transcription factor Dorsal is responsible for establishing discrete epigenetic patterns in the presumptive mesoderm, neuroectoderm and dorsal ectoderm, during early Drosophila embryo development. In addition, these different chromatin states can be linked to distinct modes of Pol II regulation. Our results provide novel insights into how gene regulatory networks form an epigenetic landscape and how their coordinated actions specify cell identity. CBP/p300 is a widely used co-activator and histone acetyltransferase (HAT) involved in transcriptional activation. We discovered that CBP occupies the genome preferentially together with Dorsal, and has a specific role during development in coordinating the dorsal-ventral axis of the Drosophila embryo. While CBP generally correlates with gene activation we also found CBP in H3K27me3 repressed chromatin. Previous studies have shown that CBP has an important role at transcriptional enhancers. We provide evidence that the regulatory role of CBP does not stop at enhancers, but is extended to many genomic regions. CBP binds to insulators and regulates their activity by acetylating histones to prevent spreading of H3K27me3. We further discovered that CBP has a direct regulatory role at promoters. Using a highly potent CBP inhibitor in combination with ChIP and PRO-seq we found that CBP regulates promoter proximal pausing of Pol II. CBP promotes Pol II recruitment to promoters via a direct interaction with TFIIB, and promotes transcriptional elongation by acetylating the first nucleosome. CBP is regulating Pol II activity of nearly all expressed genes, however, either recruitment or release of Pol II is the rate-limiting step affected by CBP. Taken together, these results reveal mechanistic insights into cell specification and transcriptional control during development. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p><p> </p>
350

Development of an Indoor Cultivation Product for Restaurant Environments : Developing a Product Specification and Creating a Product Concept using User-Centered Design

Holmqvist, Sofia, Svensson, Moa January 2019 (has links)
In today’s society there is a growing awareness of where food is produced and there is a trend to use locally grown produce in restaurants. One way for restaurants to differentiate themselves is to grow the produce inside the restaurant. This thesis has the aim on identifying the problems and user needs for an indoor cultivation solution and developing a new indoor cultivation product that solves the identified problems and meet the user needs. To achieve this aim, a usercentered design approach was utilised and the following three research questions were answered: How can the needs of the user be translated into a product specification for indoor cultivation in restaurants? What are the functionality, usability, and construction requirements for an indoor cultivation product in a restaurant? What product concept can be designed to grow classic herbs in restaurants based on the needs of the user? To identify the needs interviews were performed with the users. The needs were then translated, together with the company’s needs, into a product specification. This was done in two steps, identifying the metrics and setting values. Some of the most important requirements are that a hydroponic system is used, that the product is easy to clean and is moveable. The product development process was iterative and included different ideation, development and evaluation methods. The users were involved in some of the evaluation methods to give input on the final design. Their opinion, together with evaluations based on the product specification, were used when choosing the final concept Lärad. Lärad uses a circulating hydroponic system and have three separate growing containers each containing 16 plants. The growing containers can be pulled out to enable easy access of the plants. Both the water system and the LED grow lights, that replaces natural sunlight, are controlled automatically to minimise the users’ involvement. To test the concept, to see how well the product specification is fulfilled, both a CAD model and a functional prototype were created. The results from the tests were, even at the concept stage, that 97% of all the tested requirements were fulfilled which shows that the concept is suitable for indoor cultivation in a restaurant environment. Some further work that includes refining the design and optimising for production will be needed to launch the product.

Page generated in 0.0278 seconds