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Sökning: hsv:(TEKNIK OCH TEKNOLOGIER) hsv:(Annan teknik) hsv:(Övrig annan teknik) > Licentiatavhandling

  • Resultat 1-10 av 182
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  • Löfgren, Johan, 1983 (författare)
  • Observing Sea Level Using Reflected Global Navigation Satellite System Signals
  • 2011
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Sea-level rise due to global warming is predicted to have a large impact on human society, especially for populations living in coastal regions and on islands. It is therefore of great importance to monitor the sea level and to increase the understanding of the local hydrodynamic and meteorological responses to a global sea-level rise.Presented in this thesis is a technique to measure local sea level using Global Navigation Satellite System (GNSS) signals. This GNSS-based tide gauge acquires both the directly received GNSS signals and the GNSS signals that are reflected off the sea surface, using standard geodetic GNSS receivers. With the directly received signals the installation measures land-surface height changes, whereas the reflected signals are used to measure sea-surface height changes. Both measurements are done with respect to the Earth's centre of mass. By combining these observations it is possible to estimate the local sea level, which is directly related to the volume of the ocean.Several GNSS-based tide gauge campaigns have been carried out at the Onsala Space Observatory (OSO) on the west coast of Sweden. Today the installation is still in place and continues to record GNSS data with a sampling frequency of 1 Hz. In this thesis, data from the campaigns are analysed in a post-processing mode with an in-house developed software. Sea-level estimates are produced with a temporal resolution from 5 s to 20 min and compared to independent sea-level observations from stilling well gauges located approximately 18 km south and 33 km north of OSO. The results for three months of GNSS-derived sea level show an agreement, with respect to the stilling well gauge sea level, with typical root-mean-square differences of better than 6 cm and correlation coefficients of higher than 0.95.Additionally, using an ocean-tide analysis of three months of sea-level observations from the GNSS-based tide gauge, it was possible to determine several tidal components, i.e., M2, S2, N2, O2, and M4. The amplitudes and phases show reasonable agreement with the ones derived from one year of stilling well gauge sea-level data.
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  • Abrahamsson, Per, 1985 (författare)
  • Continuum modeling of particle flows in high shear granulation
  • 2012
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • High shear granulation is an important process in the pharmaceutical industry. The aim of the process is to produce granules with specific properties, like size and hardness, from powder mixtures. The properties of the granules are determined by the flow field in the mixer. The most common approach taken to modeling the flow includes tracking the forces on each individual particle and resolving each occurring collision. This gives detailed information but the computational cost restricts this use to small-scale equipment. Continuum modeling of particle flows means that averages are made to form a continuous flow rather than tracking individual entities. The problem that arises in this procedure is to correctly describe the transfer rates of mass and momentum in the system. The focus of the present work is on evaluating the previously used continuum model and investigating other possible techniques that have not yet been used in this application. Results show that the continuum model currently being used has a promising parameterization for describing the overall effect on the flow field due to the particle property changes that occur during granulation. The model is, however, not capable of adequately resolving the flow field in the important regions close to the walls and the impeller where the particle volume fraction is high. When solving these regions, the theory used at present suffers a strong spatial resolution dependence on the solution. The present theory is developed for low particle loadings. A critical review was made to investigate available modifications to the modeling framework for high volume fraction granular flows. Although there is no full solution to the problem the investigation shows that promising improvements to the theory are available.
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  • Acevedo Peña, Carlos Gonzalo (författare)
  • Developing Inclusive Innovation Processes and Co-Evolutionary Approaches in Bolivia
  • 2015
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The concept of National Innovation Systems (NIS) has been widely adopted in developing countries, particularly in Latin American countries, for the last two decades. The concept is used mainly as an ex-ante framework to organize and increase the dynamics of those institutions linked to science, technology and innovation, for catching-up processes of development. In the particular case of Bolivia, and after several decades of social and economic crisis, the promise of a national innovation system reconciles a framework for collaboration between the university, the government and the socio-productive sectors. Dynamics of collaboration generated within NIS can be a useful tool for the pursuit of inclusive development ambitions. This thesis is focused on inclusive innovation processes and the generation of co-evolutionary processes between university, government and socio-productive sectors. This is the result of 8 years of participatory action research influenced by Mode 2 knowledge-production and Technoscientific approaches. The study explores the policy paths the Bolivian government has followed in the last three decades in order to organize science, technology and innovation. It reveals that Bolivia has an emerging national innovation system, where its demand-pulled innovation model presents an inclusive approach. Innovation policy efforts in Bolivia are led by the Vice-Ministry of Science and Technology (VCyT). Moreover, NIS involves relational and collaborative approaches between institutions, which imply structural and organizational challenges, particularly for public universities, as they concentrate most of the research capabilities in the country. These universities are challenged to participate in NIS within contexts of weak demanding sectors.  This research focuses on the early empirical approaches and transformations at Universidad Mayor de San Simón (UMSS) in Cochabamba. The aim to strengthen internal innovation capabilities of the university and enhance the relevance of research activities in society by supporting socio-economic development in the framework of innovation systems is led by the Technology Transfer Unit (UTT) at UMSS. UTT has become a recognized innovation facilitator unit, inside and outside the university, by proposing pro-active initiatives to support emerging innovation systems. Because of its complexity, the study focuses particularly on cluster development promoted by UTT. Open clusters are based on linking mechanisms between the university research capabilities, the socio-productive actors and government. Cluster development has shown to be a practical mechanism for the university to meet the demanding sector (government and socio-productive actors) and to develop trust-based inclusive innovation processes. The experiences from cluster activities have inspired the development of new research policies at UMSS, with a strong orientation to foster research activities towards an increased focus on socio-economic development. The experiences gained at UMSS are discussed and presented as a “developmental university” approach. Inclusive innovation processes with co-evolutionary approaches seem to constitute an alternative path supporting achievement of inclusive development ambitions in Bolivia. 
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  • al-Dbissi, Moad, 1994 (författare)
  • Developments toward a novel methodology for spent nuclear fuel verification
  • 2022
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • One of the tasks in nuclear safeguards is to regularly inspect spent nuclear fuel discharged from nuclear power reactors and verify the integrity of it, so that illegal removal and diversion of radioactive material can be promptly discovered. In the current project, which is a collaboration between Chalmers University of Technology and SCK CEN, a novel methodology for non-intrusive inspection of spent nuclear fuel is under development. The methodology consists of two main steps: 1) neutron flux and its gradient are measured inside spent nuclear fuel assemblies using small neutron detectors; and 2) the measurements are processed using an Artificial Neural Network (ANN) algorithm to identify the number and location of possible fuel pins that have been removed from the fuel assemblies and/or replaced with dummies. The use of small neutron detectors simplifies the inspection procedure since the fuel assemblies are not moved from their storage position. In addition, the neutron flux gradient measurements and its processing with the ANN algorithm have the potential for more detailed results. Different aspects have been investigated for the development of the methodology. For the first step of the methodology, the concept of a new neutron detector has been studied via Monte Carlo simulations and it relies on the use of optical fiber-mounted neutron scintillators. The outcome of the computational study shows that the selected detector design is a viable option since it has a suitable size to be introduced inside a fuel assembly and can measure neutron flux gradients. Then, experimental work has been carried out to test and characterize two optical fiber-based neutron scintillators that can be used to build the detector, with respect to detection of thermal neutrons and sensitivity to gamma radiation. For the second step of the methodology, a machine learning algorithm based on ANN is studied. At this initial stage, a simpler problem has been considered, i.e., an ANN has been prepared, trained and tested using a dataset of synthetic neutron flux measurements for the classification of PWR nuclear fuel assemblies according to the total amount of missing fuel, without including neutron flux gradient measurements and without localizing the anomalies. From the comparison with other machine learning methods such as decision trees and k-nearest neighbors, the ANN shows promising performance.
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7.
  • Alavian Ghavanini, Farzan, 1978 (författare)
  • Toward Carbon based NEMS
  • 2009
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • A systematic analysis and assessment of carbon nanotube (CNT) based NEMS switches is presented and their features are compared to typical complementary metal-oxide-semiconductor (CMOS) performance parameters. It is shown that CNT-based switches with considerably smaller leakage current compared to CMOS switches can be realized. These switches demonstrate very small standby-power dissipation.This thesis also pays special attention to the future integration of carbon based NEMS with mainstream circuitry. It is our belief that the adoption of novel nanotechnologies are closely tied to their successful integration with CMOS technology, not only to benefit from its versatility and maturity but also to be able to present an added value to the full-fledged platform. This thesis demonstrates a relatively low temperature direct current plasma enhanced chemical vapor deposition (dc PECVD) process capable of growing vertically aligned carbon nanofiber-like structures with negligible deterioration of bulk CMOS transistors’ functionality.A main feature of this thesis is the toolbox composed of analytical and computational components to design and simulate a single-pair VACNF based system. Nanoelectromechanical devices based on this building block have been fabricated. The inherent discharging problem of dc PECVD synthesis method is addressed and resolved. Moreover, two different methods are proposed to extract the Young’s modulus of the synthesized vertically aligned carbon nanofibers.
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8.
  • Ali, Mohammad, 1982 (författare)
  • On Automotive Roadway Departure Prevention
  • 2010
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Traffic accidents cause a huge amount of injuries and fatalities each year. Active safety systems assist the driver in critical traffic situations and thus contributes in reducing the amount of injuries and fatalities in traffic. This thesis deals with active safety from a system and control perspective. The thesis outlinesfundamental physical limitations in a vehicle's dynamicalcapabilities and further discusses some of the existing active safety systems. Moreover, several methods for assessing the driver and vehicle's ability to avoid an accident are developed and presented. Such methods can be used in an active safety system in order to motivate autonomous interventions that assist the driver. The methods are based on vehicle and driver mathematical models and have been shown to be able to predict lane departures or vehicle instability. The methods are demonstrated on a roadway departure application but are general and can be extended to a wide range of active safety applications through adjustments in the modeling.
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9.
  • Altunay, Maria, 1992 (författare)
  • Narratives of energy incumbents - Unravelling perspectives on municipal electric utilities
  • 2022
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The dominant narrative in sustainability transitions studies frames electric utilities as incumbents and “villains” who hinder the diffusion of niche innovations (Johnstone et al., 2017; Turnheim and Sovacool, 2020). This behavior is in line with the conception of incumbent actors as part of the dominant sociotechnical regime (Geels, 2002, 2006a), painting the picture of incumbents with a broad brush and limiting nuance. However, several authors have made attempts to illustrate heterogeneity among incumbents and that some can take on proactive roles in advancing niche innovation (Altunay et al., 2021; Ampe et al., 2021; Apajalahti et al., 2018; Berggren et al., 2015; Stalmokaitė and Hassler, 2020). The purpose of this licentiate thesis is to advance this inquiry by unravelling the narratives of electric utilities as incumbents in energy transitions. Three narratives are explored through a synthesis of two qualitative case studies of Swedish electric utilities’ engagement with solar photovoltaics. The thesis is organized along two core questions: how electric utilities engage with this emerging technology at the level of business models and collaborations, and why they choose to engage in certain ways, investigating internal and external drivers. The findings show that most electric utilities engage with solar photovoltaics through a variety of business models and collaborations, depending on a combination of firm-internal factors (i.e., organizational goals, business logics, and resources) and external factors (i.e., the task environment, the institutional environment, and the industry regime). The study illustrates the need for extending dominant narratives, as it shows that electric utility incumbents can support niche innovations, display niche and regime characteristics simultaneously, and react heterogeneously to similar external pressures. As a result, this thesis contributes to pluralizing incumbencies within sustainability transitions.
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  • Andersson, Anna, 1974- (författare)
  • A framework supporting the collaboration between the logistics- and the product development process
  • 2007
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In the competitive environment of today’s global markets, the demands of customers are increasing. They expect to get the best product at the lowest price with immediate availability. Logistics, including transportation, inventory maintenance, order processing, purchasing, warehousing, materials handling, packaging, customer service standards, and product scheduling must continuously be developed to meet the challenges of the market. The globalization, with longer distances to customers and suppliers, and the progressing trend of outsourcing are examples of why the importance of logistics has increased over the last few years.A considerable part of the final product cost is frozen during the early product development phases. In the early phases of the product development process, the cost of making design changes is low compared to making changes later in the product development process. The product development decisions made in the early phases of the product development process have considerable impact on future manufacturing and logistics activities as well.The objective of this research project is to develop a framework supporting the collaboration between the logistics- and the product development process. To do this, it has been essential to analyze which parameters influence the efficiency of the logistics process and the interface between the logistics- and the product development process. Also, to investigate how the logistics department can be integrated earlier in the product development process has been of interest. This has been done through both a theoretical review and also through a number of case studies.The result and conclusion of this project is a framework that gives support for what to focus on, how to collaborate, in which phases collaboration is meaningful, and which persons need to be involved in the different product development phases. Working as the framework suggests will, hopefully, give closer collaboration between the logistics- and the product development process than without this supportive framework. The expectation of the collaboration is an earlier integration of the logistics department in the product development process and through this influence and increase the efficiency of the logistics process.
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