1,039 research outputs found
Quality Assurance in Agile Distributed Software Teams
No full textThis report is written as part of the graduation of master of science in computer science, information architecture, at the Delft university of technology, the Netherlands. I started this research when an opportunity presented itself for a case study in Mauritius. It was not the trip abroad what interested me but the case to lift a team to a higher level of software quality. During my research I got more interested in software quality assurance. Especially because I noticed that on many of the developer’s priority lists, it has a low priority. Software quality assurance is often observed as an obligation instead of a handy tool. My true motivation for this research was to see if I could change this. In this research the challenge was to develop a newapproach for quality assurance within agile distributed development environments. The research was started as follow-up of several interviews performed with experts in the area of software development in which the opportunities in the field were observed. The research presented in this report can be of value for all software development engineers, with orwithout expertise in quality engineering. The research might particularly be relevant if searching for structured approaches for improving software processes or products. Next to these specific groups, anyone who is interested in software quality (assurance), agile (distributed) approaches or the challenges in these, can obtain relevant and interesting information from this report. For the guidance I experienced during my thesis I would like to thank Rini van Solingen, my mentor at the University and Toine Hurkmans, who acted as mentor at Exact Software. I would further like to thank Exact Software for the opportunity of conducting a case study and in special the Titan, Research and System team for their cooperation. Further thanks goes to Sander Kruger and Global Edge Software who offered the opportunity for performing the orientating case study.Electrical Engineering, Mathematics and Computer ScienceSoftware Engineerin
Globally Distributed Agile Release Trains
No full textSAFe is a framework that applies both agile and lean practices for developing software. The current trend is that increasingly more organizations develop their software in a globally distributed setting. Although SAFe is being deployed in such a setting, SAFe was not originally developed for such a setting but for a co-located setting. Therefore, this research investigates the application of SAFe in globally distributed settings. Five problems are discovered that can be expected to fail when SAFe is applied in distributed settings: incorrect execution of SAFe, language barriers, time zone differences, increased communication effort, and inefficient communication tools. Given these problems, four SAFe elements are identified that can be expected to fail when SAFe is applied in distributed settings: the PI planning, the inspect & adapt meeting, the DevOps team, and the system team. Finally, a customization of SAFe for distributed settings is proposed. This customization is focused on solving the discovered problems for the elements identified to fail.Electrical Engineering, Mathematics and Computer ScienceSoftware TechnologyInformation Architecture trac
Control design for two-bladed wind turbines
No full textIn the past decades wind energy has evolved into a mature source of sustainable energy such that onshore wind turbines have become cost competitive with other fossil-based energy sources. Onshore wind energy, however, faces social resistance and a lack of available locations. Offshore wind energy, on the other hand, offers vast amounts of suitable locations and less social resistance, but is still rather expensive compared to other energy sources. In order to reduce the costs of offshore wind energy, new wind turbine opportunities are considered. One such opportunity can be found in two-bladed wind turbines, which offer several advantages over its conventional three-bladed counterpart. Whereas control for three-bladed wind turbines has been extensively explored and discussed in literature, this is not the case for two-bladed wind turbines. Therefore, in this thesis, various structured controller approaches, with the aim to reduce the turbine loads, of two-bladed wind turbines are proposed, designed, and evaluated.Delft Center for Systems and ControlMechanical, Maritime and Materials Engineerin
Visualization of SysML Project Meta-Model Architecture and Evolution
No full textLarge and complex projects, such as infrastructure, often require the collaboration of multiple parties and disciplines, where an structured interdisciplinary methodology is necessary: Systems Engineering. This field traditionally relied on a document based approach, but is currently transitioning to a model based variant, with the Systems Modeling Language as one of its main standards. Visual modeling platforms, such as Enterprise Architect, allow to design and construct models in SysML. However, these tools lack proper measurement and visualization functionality to deal with project specific meta-model architectures. To overcome these limitations a software tool was developed using the extract-abstract-present paradigm: VoSMA. Also, multiple measurements were developed applying the Goal-Question-Metric approach, and different visualization methodologies were explored to present this information. Three SysML tunnel projects were analyzed as test case studies to assess the usefulness and correctness of the generated data, and multiple feedback sessions were conducted with experienced systems engineers. The results are very promising and indicate that the data generated may greatly benefit project development. Based on the results of the evaluation and the achieved progress, some suggestions and possible future directions were provided at the end of this study.Computer ScienceDepartment of Software and Computer TechnologyElectrical Engineering, Mathematics and Computer Scienc
Feedforward Learning Control for Individual Blade Pitch Control of Modern Two-Bladed Wind Turbines
No full textWind is arguably the most promising source of sustainable energy. However, it is still considered to be an expensive option compared to fossil fuels. Recent developments have achieved significant cost reductions and increased the reliability on wind energy. The main reason for this has been the application of innovative and effective control strategies. All turbine designs over time have been involved in reducing the overall cost of energy by either maximizing energy yield or minimizing the effect of loads to increase the life of the wind turbine. Minimizing the effect of loads is the main focus in this thesis. Control strategies currently used in the industry involve changing the pitch angle for each individual blade to reduce the loads and are called Individual Blade Pitch Control (IPC). However, this strategy causes considerable wear and tear to the large pitch bearings in the wind turbines due to high frequency pitch control action. Thus, control strategies which not only reduce loads, but also provide smoother pitch control action are investigated in this report. It is observed that periodic loads faced by the blades of the wind turbine can be represented by a limited number of parameters such as rotor speed, they are slowly changing and more importantly, account for much of the fatigue causing loads. Thus, this thesis report focuses on applying suitable control strategies to primarily reduce periodic loads. Moreover, since the loads are periodic and slowly varying, the use of basis functions as the input space of a feedforward controller can result in smoother pitch activity. The aforementioned strategy has previously been applied on the ``\emph{Smart Rotor}'' concept which is a mechanism where each blade is equipped with trailing edge flaps similar to an airplane wing to change the lift profile of the blade to reduce loads. This strategy has been successfully applied to the \acs{IPC} mechanism and has resulted in lower pitch activity. The control methodology applied to IPC discussed above is a feedforward controller which consists of parametrized basis functions. The algorithm discussed involves a learning technique where the control parameters are calculated through successive correction in each trial period by ensuring that the wind turbine does not repeat its ``mistakes''. Consequently, the feedforward control is adaptive as it can adjust the controller parameters to compensate for changes in plant dynamics during operation. However, since the controller is based on a model linearized for a particular set of operating conditions such as wind speed, the performance of the controller deteriorates during turbulent wind conditions. Additionally, since it takes a few revolutions for the control parameters to converge and that if the rotor speed changes during this time, the parameters calculated are no longer optimal.Delft Center for Systems and ControlMechanical, Maritime and Materials Engineerin
Customer Involvement in Distributed Requirements Engineering
No full textThe graduation project is run as an internship at software company Exact. The company wants to reduce the time to market for their products. To achieve this objective, Exact wants to adopt agile development and is aiming towards the implementation of a development process that is both globally distributed and Scrum-like. The project’s goal in this objective is to design and validate a process, with which a set of product requirements is engineered and in parallel the products design is being developed at at least two distributed locations. This process needs to iterate between these locations, but at the same time it needs to work towards a non-ambiguous, concrete and focused backlog with which development can do their work. Based on interviews and constraints, the project was scoped down to focus on the verification of requirements with customers. After research in this area, a prototype is created and tested, which should establish a feedback loop on conceptual requirements items in a virtual community. The test results have led to a set of recommendations for customer involvement in a distributed requirements engineering process.Software TechnologyElectrical Engineering, Mathematics and Computer Scienc
Antagomir-mediated silencing of endothelial cell specific microRNA-126 impairs ischemia-induced angiogenesis
No full textMicroRNAs are negative regulators of gene expression that play a key role in cell-type specific differentiation and modulation of cell function and have been proposed to be involved in neovascularization. Previously, using an extensive cloning and sequencing approach, we identified miR-126 to be specifically and highly expressed in human endothelial cells (EC). Here, we demonstrate EC-specific expression of miR-126 in capillaries and the larger vessels in vivo. We therefore explored the potential role of miR-126 in arteriogenesis and angiogenesis. Using miR-reporter constructs, we show that miR-126 is functionally active in EC in vitro and that it could be specifically repressed using antagomirs specifically targeting miR-126. To study the consequences of miR-126 silencing on vascular regeneration, mice were injected with a single dose of antagomir-126 or a control 'scramblemir' and exposed to ischemia of the left hindlimb by ligation of the femoral artery. Although miR-126 was effectively silenced in mice treated with a single, high dose (HD) of antagomir-126, laser Doppler perfusion imaging did not show effects on blood flow recovery. In contrast, quantification of the capillary density in the gastrocnemius muscle revealed that mice treated with a HD of antagomir-126 had a markedly reduced angiogenic response. Aortic explant cultures of the mice confirmed the role of miR-126 in angiogenesis. Our data demonstrate a facilitary function for miR-126 in ischemia-induced angiogenesis and show the efficacy and specificity of antagomir-induced silencing of EC-specific microRNAs in vivo. © 2009 Foundation for Cellular and Molecular Medicine/Blackwell Publishing Ltd
SOLAR 12-month European results: Randomized switch trial of CAB plus RPV vs. oral BIC/FTC/TAF
No full textSOLAR 12-month European results: Randomized switch trial of CAB plus RPV vs. oral BIC/FTC/TAF
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