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- Gustafsson, Mattias, 1972-
(författare)
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Evaluation of energy conserving measures in buildings connected to a district heating system : case studies in Gävle, Sweden
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- When different energy conserving measures are implemented for reducing energy use in buildings and the buildings are connected to district heating systems, it is important that an overall system analysis is made which takes into account the effects of total change of energy use due to the energy conserving measures.The method applied in this thesis uses hourly production data for the different production units in the district heating system in Gävle, Sweden. The merit order of the different production units is dependent on the electricity spot market price. To calculate the merit order, hourly data for the electricity price is used. The marginal production unit can then be determined for each hour of the investigated year.This thesis analyzes five different energy conserving measures in a multi-dwelling building regarding how they affect the marginal production units in the district heating system. For CO2 emission evaluations, two different combinations of heat and electricity conserving measures are compared to installation of an exhaust air heat pump. This thesis also analyzes how the configuration of the electric meter affects the measured amount of self-consumed and produced excess electricity for a single-family house and for two multi-dwelling buildings of different sizes.The results show that the use of electricity is the most important objective to consider. The increased use of electricity for operation of the heat pump contributes to an increase of global CO2 emissions and the electricity produced by the solar photovoltaic installation contributes to a decrease of global CO2 emissions.The results also show that the configuration of the electric meter is important for the single-family house but negligible for the multi-dwelling buildings. The amount of produced excess electricity is high for all buildings, which means that the economic value of produced excess electricity is important for a profitable installation.
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- Karlsson, Lisa, 1980-
(författare)
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Differentiation of Human Dermal Fibroblasts : a New Tool in Vascular Tissue Engineering
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Tissue engineering is an expanding field, which focuses on the development of func-tional substitutes for damaged tissues. A limitation in this field is difficulties with obtaining autologous cells. Recent research has shown the presence of cells with multilineage-potential within the connective stroma of the skin. In line with this, a potential plasticity inherent in human dermal fibroblasts has been demonstrated. The overall aim of this study was to investigate if human dermal fibroblasts can be used as a cell source for vascular tissue engineering. Differentiation towards an endothelial cell-like phenotype was induced by culturing dermal fibroblasts in endothelial growth medium. By utilizing in vitro cell culture models, the capacity of different types of serum and serum constituents in inducing a phenotypic shift in fibroblasts was investi-gated. To clarify the mechanisms behind this phenotypic shift and to eliminate the risk of having growth of residual endothelial cells in the cultures, both normal dermal fibroblasts and single-cell clone fibroblasts were used. Our results demonstrated that presence of human serum caused fibroblasts and single-cell clone fibroblasts to express vWf, to incorporate fluorochrome-labeled low-density lipoprotein, and to start form-ing capillary-like networks. As an initial step in using these cells in tissue engineering, their ability to endothelialize a surface in vitro was studied. Cells cultured in either fibroblast or endothelial growth medium were seeded on scaffolds. Differentiation was confirmed by western blotting and immunohistochemistry using antibodies directed towards vWf, ve-cadherin, eNOS, and bradykinin receptor B2. The results revealed that endothelial differentiated fibroblasts cultured on scaffolds showed histological resem-blance to endothelial cells, and expressed molecules indicative of an endothelial phenotype. In conclusion, the results presented in this study indicate a possibility to induce differentiation of human dermal fibroblasts towards an endothelial cell-like phenotype. Consequently, these data suggests that human dermal fibroblast may be a novel cell source for vascular tissue engineering.
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- Karlsson, Magnus, 1977-
(författare)
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Low profile antennas for UWB
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The number of wireless communication applications increases steadily, leading to the competition for currently allocated frequency bands. Pressure on authorities around the world to permit communication in higher and wider frequency ranges to achieve higher wireless capacity than those existed in the past has resulted in several new specifications. The federal communications commission (FCC) in USA has unleashed the band 3.1-10.6 GHz for ultra-wideband radio (UWB) communication. The release has triggered a worldwide interest for UWB. Capacity issues in form of data rate and latency have always been a bottleneck for broadened wireless-communication usages. The new communication systems like UWB require higher spectral efficiency than what is normally utilized with traditional antenna techniques. The interest for compact consumer electronics is growing in the meantime, creating a demand on efficient and low profile antennas which can be integrated on a printed circuit board. In this thesis, some methods to extend the spectral efficiency and other antenna parameters associated with wide band usages are developed and discussed. Furthermore, methods on how to enhance the performance when one antennaelement is not enough are studied as well.
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- Liu, Yu, 1991-
(författare)
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A Data-centric Internet of Things Framework Based on Public Cloud
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The pervasive application of Internet of Things (IoT) has been seen in many aspects in human daily life and industrial production. The concept of IoT originates from traditional machine-to-machine (M2M) communications which aimed at solving domain-specific and applicationspecific problems. Today, the rapid progress of communication technologies, the maturation of Internet infrastructures, the continuously reduced cost of sensors, and emergence of more open standards, have witnessed the approaching of the expected IoT era, which envisions full connectivity between the physical world and the digital world via the Internet protocol. The popularity of cloud computing technology has enhanced this IoT transform, benefiting from the superior computing capability and flexible data storage, let alone the security, reliability and scalability advantages.However, there are still a series of obstacles confronted by the industry in deployment of IoT services. First, due to the heterogeneity of hardware devices and application scenarios, the interoperability and compatibility between link-layer protocols, sub-systems and back-end services are significantly challenging. Second, the device management requires a uniform scheme to implement the commissioning, communication, authorization and identity management to guarantee security. Last, the heterogeneity of data format, speed and storage mechanism for different services pose a challenge to further data mining.This thesis aims to solve these aforementioned challenges by proposing a data-centric IoT framework based on public cloud platforms. It targets at providing a universal architecture to facilitate the deployment of IoT services in massive IoT and broadband IoT categories. The framework involves three representative communication protocols, namely WiFi, Thread and Lo-RaWAN, to enable support for local, personal, and wide area networks. A security assessment taxonomy for wireless communications in building automation networks is proposed as a tool to evaluate the security performance of adopted protocols, so as to mitigate potential network flaws and guarantee the security. Azure cloud platform is adopted in the framework to provide device management, data processing and storage, visualization, and intelligent services, thanks to the mature cloud infrastructure and the uniform device model and data model. We also exhibit the value of the study by applying the framework into the digitalization procedure of the green plant wall industry. Based on the framework, a remote monitoring and management system for green plant wall is developed as a showcase to validate the feasibility. Furthermore, three specialized visualization methods are proposed and a neuron network-based anomaly detection method is deployed in the project, showing the potential of the framework in terms of data analytics and intelligence.
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- Ni, Zhongjun, 1992-
(författare)
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A Digitalization Framework for Smart Maintenance of Historic Buildings
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Smart maintenance of historic buildings involves integration of digital technologies and data analysis methods to help maintain functionalities of these buildings and preserve their heritage values. However, the maintenance of historic buildings is a long-term process. During the process, the digital transformation requires overcoming various challenges, such as stable and scalable storage and computing resources, a consistent format for organizing and representing building data, and a flexible design to integrate data analytics to deliver applications.This licentiate thesis aims to address these challenges by proposing a digitalization framework that integrates Internet of Things (IoT), cloud computing, ontology, and machine learning. IoT devices enable data collection from historic buildings to reveal their latest status. Using a public cloud platform brings stable and scalable resources for storing data, performing analytics, and deploying applications. Ontologies provide a clear and concise way to organize and represent building data, which makes it easier to understand the relationships between different building components and systems. Combined with IoT devices and ontologies, parametric digital twins can be created to evolve with their physical counterparts. Furthermore, with machine learning, digital twins can identify patterns from data and provide decision-makers with insights to achieve smart maintenance.Papers I-III have shown that data can be reliably collected, transmitted, and stored in the cloud. Results of Paper IV indicate that a digital twin that depicts the latest status of a historic building can be created and fed with real-time sensor data. The insights discovered from the digital twin provide facts for improving the indoor climate to achieve both heritage conservation and human comfort. Papers V and VI have shown that deep learning methods exhibit strong capabilities in capturing tendency and uncertainty in building energy consumption. Incorporating future information that determines energy consumption is critical for making multi-horizon predictions. Moreover, changes in the operating mode of a building and activities held in a building bring more uncertainty in energy consumption and deteriorate the performance of point forecasts. Overall, this thesis contributes to the field of preservation of historic buildings by proposing a comprehensive digitalization framework that integrates various advanced digital technologies to provide a holistic approach to achieve smart maintenance of historic buildings.
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