lnu.sePublications
Change search
Refine search result
1 - 7 of 7
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Olsson, Jörgen
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering. SP Technical Research Institute of Sweden.
    Low Frequency Impact Sound in Timber Buildings: Simulations and Measurements2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    An increased share of construction with timber is one possible way of achieving more sustainable and energy-efficient life cycles of buildings. The main reason is that wood is a renewable material and buildings require a large amount of resources. Timber buildings taller than two storeys were prohibited in Europe until the 1990s due to fire regulations. In 1994, this prohibition was removed in Sweden.

        Some of the early multi-storey timber buildings were associated with more complaints due to impact sound than concrete buildings with the same measured impact sound class rating. Research in later years has shown that the frequency range used for rating has not been sufficiently low in order to include all the sound characteristics that are important for subjective perception of impact sound in light weight timber buildings. The AkuLite project showed that the frequency range has to be extended down to 20 Hz in order to give a good quality of the rating. This low frequency range of interest requires a need for knowledge of the sound field distribution, how to best measure the sound, how to predict the sound transmission levels and how to correlate numerical predictions with measurements.

        Here, the goal is to improve the knowledge and methodology concerning measurements and predictions of low frequency impact sound in light weight timber buildings. Impact sound fields are determined by grid measurements in rooms within timber buildings with different designs of their joist floors. The measurements are used to increase the understanding of impact sound and to benchmark different field measurement methods. By estimating transfer functions, from impact forces to vibrations and then sound pressures in receiving rooms, from vibrational test data, improved possibilities to correlate the experimental results to numerical simulations are achieved. A number of excitation devices are compared experimentally to evaluate different characteristics of the test data achieved. Further, comparisons between a timber based hybrid joist floor and a modern concrete floor are made using FE-models to evaluate how stiffness and surface mass parameters affect the impact sound transfer and the radiation.

        The measurements of sound fields show that light weight timber floors in small rooms tend to have their highest sound levels in the low frequency region, where the modes are well separated, and that the highest levels even can occur below the frequency of the first room mode of the air. In rooms with excitation from the floor above, the highest levels tend to occur at the floor levels and in the floor corners, if the excitation is made in the middle of the room above. Due to nonlinearities, the excitation levels may affect the transfer function in low frequencies which was shown in an experimental study. Surface mass and bending stiffness of floor systems are shown, by simulations, to be important for the amount of sound radiated.

        By applying a transfer function methodology, measuring the excitation forces as well as the responses, improvements of correlation analyses between measurements and simulations can be achieved

  • 2.
    Lindblad, Fredrik
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Market structure and economic status for firms producing single-family houses in Sweden2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The gradually changing behavior of the population, towards urbanization, ledto an increased shortage of available housing. This development has resultedin a serious issue in Sweden, where too few firms are providing solutions formulti-family houses in wood. Potential firms that could fill this increasingdemand are those in the single-family house industry. Yet, these firms mightface considerable problems with productivity, predominately derived fromincreasing production costs and inadequate production development.Developing these firms are associated with long-term investments, whichis investigated by evaluating the industry structure for sellers, highlightingthe financial and market situation within their industry. These factors aregrowing in importance due to the current market concentration, where morefirms are required to focus on product development driven by the demand toprefabricate wooden elements, volumes or modules in an industrialized way.This thesis studies Swedish firms producing wooden single-familyhouses, with the aim to investigate their possibilities to enter the woodenmulti-family house industry in Sweden.Investigations will be conducted by applying Altman’s Z’ value, riskposition model, the Herfindahl-Hirschman index, the Herfindahl-Hirschmannumber equivalent, productivity ratio model for profitability and finally amodel measuring market Concentration Ratio.Results show that the industry tends towards perfect competition with toomany firms involved, i.e. firms mainly have to compete by prices. Further,firms are grouped into three zones; risk, grey or safe zone. The levels withinthese zone show a reduction of firms in the red zone over time. Related to thecurrent risks, many firms have promising positions to invest in productdevelopment towards wooden multi-family houses, in addition to theircurrent products, even though firm productivity has declined during thestudied time frame. The results that the investigated firms have goodpossibilities gaining a competitive advantage by diversifying into thegrowing wooden multi-family house industry.

  • 3.
    Toll, Daniel
    Linnaeus University, Faculty of Technology, Department of Computer Science.
    Measuring Programming Assignment Effort2016Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Students often voice that the programming assignments are hard and that they spend a lot of time on solving them. Is this true; are we giving them too hard assignments and how much and what do they spend the time on? This is what we want to gain insight to. We constructed a tool that records programming sessions with finer granularity than the existing solutions. The tool has recorded 2643 programming sessions from students. Using that data we found that students spend only 15% of their time writing code, and that on average 40% of their programming effort is spent reading and navigating. We also estimate the time spent outside of the tool to be almost 20%. The increased detail in the recordings can be used to measure the effect of programming source code comments, and we found that the effect of both helpful and redundant comments increases the reading time but did not help to reduce the students writing effort. Finally, we used the tool to examine the effects of an improved programming assignment and found that the total effort was not reduced.

  • 4.
    Parsland, Charlotte
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Study of the activity of catalysts for the production of high quality biomass gasification gas: with emphasis on Ni-substituted Ba-hexaaluminates2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The fossil hydrocarbons are not inexhaustible, and their use is not without impact in our need of energy, fuels and hydrocarbons as building blocks for organic materials. The quest for renewable, environmentally more friendly technologies are in need and woody biomass is a promising candidate, well provided in the boreal parts of the world. To convert the constituents of wood into valuable gaseous products, suitable for the end use required, we need a reliable gasification technology. But to become an industrial application on full scale there are still a few issues to take into account since the presence of contaminants in the process gas will pose several issues, both technical and operational, for instance by corrosion, fouling and catalyst deactivation. Furthermore the downstream applications may have very stringent needs for syngas cleanliness depending on its use. Therefore, the levels of contaminants must be decreased by gas cleanup to fulfil the requirements of the downstream applications.

    One of the most prominent problems in biomass gasification is the formation of tars – an organic byproduct in the degradation of larger hydrocarbons. So, tar degrading catalysts are needed in order to avoid tar related operational problems such as fouling but also reduced conversion efficiency. Deactivation of catalysts is generally inevitable, but the process may be slowed or even prevented. Catalysts are often very sensitive to poisonous compounds in the process gas, but also to the harsh conditions in the gasifier, risking problems as coke formation and attrition. Alongside with having to be resistant to any physical and chemical damage, the catalyst also needs to have high selectivity and conversion rate, which would result in a more or less tar-free gas. Commercial tar reforming catalysts of today often contain nickel as the active element, but also often display a moderate to rapid deactivation due to the causes mentioned.

  • 5.
    Olsson, Tobias
    Linnaeus University, Faculty of Technology, Department of Computer Science.
    Towards Pattern Based Architectural Conformance Checking2016Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Patterns are a source of knowledge when architecting software systems. They provide abstract and time-tested solutions that show how a system should be structured to achieve needed qualities. However, when developing software there is a chance that small mistakes are introduced in the source code. Over time, these mistakes can accumulate and break the structure of the pattern and its qualities are lost. There are methods that can help find such errors, but none of these provide a pattern abstraction. In this work, we describe a method that raises the level of abstraction from checking individual dependencies to checking key dependencies in the pattern. We implement our method, apply it to check the Model-View-Controller pattern. We show that the method can find architectural problems in real source code and examine how removal of detected erosions affects the source code. We conducted an experiment in a software project setting to determine if using the method affects the number of architectural problems. Some project teams were randomly assigned to use a software service that automated our method. It checked how well their implementation conformed to Model-View-Controller every time they updated the source code. The experiment showed that developers that used the tool had significantly fewer detected architectural problems during the course of the project. Our method makes conformance checking easier to use. This might help increase the adoption of conformance checking in industry.

  • 6.
    Håkansson Ramberg, Maria
    Linnaeus University, Faculty of Arts and Humanities, Department of Languages.
    Was bewerten Lehrer?: Die Bedeutung grammatischer und lexikalischer Faktoren bei der Benotung von Schülertexten im Fach Deutsch als Fremdsprache2016Licentiate thesis, monograph (Other academic)
  • 7.
    Ahlgren, Fredrik
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Waste heat recovery in a cruise vessel2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In three studies of a cruise ship the author has investigated waste heat recovery (WHR)from exhaust gases using an organic Rankine cycle (ORC), and also mapped the energyand exergy flows within the ship. Data were collected from the ship’s machinerysystem for a total extent of one year, and this data were used for simulations andenergy calculations. An off-design analysis was made and an ORC was simulated andoptimised with regards to the ship’s operating conditions. The ORC working fluid wasoptimised in terms for maximum electrical production in the off-design condition. Theoff-design analysis showed that the ship speed and power consumption was far fromits original design. The results indicate that there is a potential for significant savingsby using an organic Rankine cycle for waste heat recovery. The energy and exergyanalysis gave a better understanding of the energy flows and showed that the singlelargest exergy destruction occurs in the ship’s diesel engines.

1 - 7 of 7
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf