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  • 401.
    Assarsson, Felix
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Håkansson, Fredrik
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Guide till ATEX: Framställning av ett virtuellt verktyg för arbete med ATEX hos Plåt och spiralteknik AB2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    I detta arbete har vi fördjupat oss i ATEX-direktiven för att undersöka hur Plåt och spiralteknik ABs arbete på området kan förbättras. I dagsläget säljer företaget ATEX-godkänd utrustning periodvis men anser att deras kunskaper om ATEX inte är tillräckliga för att tillgodose alla kunders behov. Målet med detta arbete var att ta fram en manual för de regler kring explosionsförebyggande föreskrifter som gäller företagets produkter. Detta arbete har resulterat i en manual i form av en lathund för arbete med ATEX anpassad för PSTs verksamhet.

  • 402.
    Assarsson, Jakob
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Eskilsson, Mattias
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Arbetsberedningar och Egenkontroller i produktionen: Work preparations and quality controls in production2009Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    I byggproduktionen behövs noggranna förberedelser för att undvika störningar och kvalitetsfel. En form av styrnings- och planeringsverktyg är arbetsberedningar och egenkontroller som vi i detta examensarbete har undersökt. Syftet har varit att se hur de fungerar och att finna förbättringsmöjligheter för dem. I arbetet gjordes en intervjustudie som visade att anställda på Peab tycker att arbetsberedningarna är ett mycket bra hjälpmedel i produktionen och att användandet fungerar ganska bra i nuläget. Enligt medarbetarna finns det dock mycket som kan utvecklas och förbättras. På företaget tycker personalen även att egenkontrollerna är något bra men själva användandet fungerar inte särskilt bra ute i produktionen.

     

    För att förbättra och utöka användandet av arbetsberedningarna krävs att tjänstemännen får en ökad förståelse och vilja att använda dem. När det gäller egenkontrollerna är det däremot hantverkarnas inställning som är bekymret, de ser inte kontrollen som något viktigt utan mer som ett moment som ödslar deras tid. Studien visar att egenkontrollen, om den används på rätt sätt, kan öka hantverkarnas engagemang och få dem att ta större ansvar för det de utför.

  • 403.
    Assofi, David
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Bijelic, Petar
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Ventilationseffektivisering i skolbyggnader: 2014Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Studien går ut på att jämföra tre olika styrsystem för ventilation, nämligen CAV (Constant Air Ventilation), VAV (Variabel Air Ventilation) och DCV (Demand Controlled Ventilation). Dessa styrsystem ställs mot varandra i tre olika lokaltyper, med syfte att identifiera det mest energieffektiva styrsystemet. Ett syftet med studien är också att upptäcka vid vilka flöden det lönar sig att arbeta med VAV- och DCV-styrsystemen.

  • 404.
    Aster, Maximilian
    Linnaeus University, Faculty of Technology, Department of Computer Science.
    Repackaging Web Pages2013Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Current trends in the market of Web-enabled devices are moving the focus from desktop web pages to pages optimised for a set of other devices like smartphones or tablets. Within this thesis an approach is introduced, able to adapt and automatically transform web pages and even the web applications logic flow into a new kind of representation, specifically for a certain target group. Therefore a general process is defined to describe the various phases that have to be gone through to transform or repackage a website. It serves as the basis for the solution, which was built as part of this thesis, and incorporates state of the art concepts and methods from various fields of Web Science. The implemented artefacts demonstrate how an appropriate architecture looks like and what additional possibilities open up.

  • 405.
    Attila, Dioszegi
    et al.
    Jönköping University, Dept of Mechanical Engineering/Component Technology.
    Elmquist, Lennart
    Jönköping University, Dept of Mechanical Engineering/Component Technology.
    Orlenius, Jessica
    Jönköping University, Dept of Mechanical Engineering/Component Technology.
    Dugic, Izudin
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Defect Formation of Grey Cast Iron2009Conference paper (Refereed)
    Abstract [en]

    Cast iron is one of the oldest technical alloys used for creating objects. Foundrymen from the very beginning ofcasting was fighting to avoid casting defects. In the beginning a successfully performed casting was associated withwitchcraft. Cast component producers suffer yearly substantial expanses due to rejecting or repairing castings. Thepresent work will summarize research efforts to understand formation mechanisms of defects, performed incollaboration with Swedish foundries during the last years. The presented work will focus on defects, specific castingof gray iron components. Studied defects are gas porosity, shrinkage porosity and metal expansion penetration.Novell experimental set up has been developed or existing methods has been improved to study defect formationmechanisms. Today we can realize that casting without defects are possible only by approaching the defect formationmechanism with multidisciplinary science.

  • 406.
    Augustino, Daudi Salezi
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Adjei Antwi-Afari, Bernard
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Parameterized Modelling of Global Structural Behaviour of Modular Based Two Storey Timber Structure2018Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The global stiffness behaviour of modular-based two storey timber structures was studied under prescribed horizontal displacements at the upper corners of the volume modules. To be able to study this behaviour, a numerical finite element model was created in Abaqus. A parametric study was performed in which the geometry and spring stiffness of joints were varied until the enough stiff module was attained for safe transfer of shear forces through the module structure. The FE-model was parameterized to have possibility to vary positions of door and window openings in the volume modules. These openings had influence on the global structural behaviour of the two storey module structure since the side wall with two openings showed less reaction forces at its top corner point A compared to the other wall point B. In addition, the module#3 was assigned with small spring stiffness in x-direction representing friction in the joint between the volume modules. This was done without uplift plates and angle brackets. The findings showed that there was significant slipdeformation between the volume modules and small reaction forces at points A and B. The spring stiffness value in x-direction was varied until large value was obtained which resulted in overall shear deformations of the walls in both volume modules. When the angle bracket and the uplift plates were introduced between the modules when small spring stiffness along the joint between the volume modules was used, the results showed that most of the shear forces were transferred through the angle brackets instead of the fastener joints between the modules. Moreover, the results showed that the reaction forces at the points A and B increased when the angle brackets were assigned in the module. Furthermore, the results also showed that uplift plates used in the model worked well for simulations with low vertical spring stiffness between the modules.

  • 407.
    Augustsson, Jesper
    et al.
    Linnaeus University, Faculty of Technology, Department of Informatics.
    Salomonsson, Peter
    Linnaeus University, Faculty of Technology, Department of Informatics.
    Gamification - Samspelet mellan människor och IT: Undersökning av spelmekanismers motivationshöjande effekter2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This bachelor thesis is a study to investigate the game mechanics in a selected training application. The study aims to create a greater understanding of why people get motivational effects with the help of information technology. This will be done by examining the users of the example Nike + to find out what features they consider giving them a motivating effect and thus describe the game mechanics these include.

     

    The study uses a qualitative approach to carryout interviews with the users of our example Nike+. The interview questions are based in theory of the field Gamification and previous research on the topic.

     

    The result shows that there are several different game mechanics implemented in Nike +, which has a positive impact on users. The result strengthens the game mechanics informants set positively towards making running a fun form of exercise as well as increased training frequency of our informants.

  • 408.
    Augustsson, Joacim
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Larsson, Gustaf
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Styrning av stegmotor för robot med NICompactRIO2009Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report deals about controlling and regulating stepping motors and PM-motors by using thegraphical programming language NI Labview, with hardware NI CompactRIO and NI DAQ-USB.The implementation has been done by controlling a robot with a for the task built system, controllinga PM-motor by PWM and a own created controller.

  • 409.
    Augustsson, Tina
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Söderberg, Emma
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Sandgärdsgatan, Växjö: - En attraktivare gågata2006Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In the outskirts of Växjö many shoppingmalls are vastly expanding which in time could pose a threat to the city centre. Växjö city is, in shoppingaspects dominated by one main street, Storgatan. To achieve a more competitive central part of the city and complex street network, a widening of the center would be preferred. Closest at hand for a widening of the city centre is the paralell pedestrian street Sandgärdsgatan, which today is thought of as a backstreet. Our project is to propose examples on how to turn Sandgärdsgatan into a more attractive pedestrian street. Research have been carried out in the form of literaturestudies, interviews and polls aswell as fieldtrips to various urban environments. The proposals we have created include everything from remodelling and general restorations to street markets and placarding. The main proposals aside from being presented in text are also visualised in drawings whilst smaller changes are only mentioned in text.

  • 410.
    Avander, Alexander
    et al.
    Linnaeus University, Faculty of Business, Economics and Design, Linnaeus School of Business and Economics.
    Robertsson, Erik
    Linnaeus University, Faculty of Business, Economics and Design, Linnaeus School of Business and Economics.
    Batch size policy: A case study of the production site in Hillerstorp 2011Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Abstract

     

    Master Degree Project. Business Administration and Economics Programme, Linnaeus University, Logistics, 4FE05E, Spring 2011.

    Authors: Alexander Avander and Erik Robertsson

    Supervisor: Peter Berling

     

    Title: Batch size policy Thule Vehicle Solutions - A case study in Hillerstorp

     

    Background: The Company has currently no clear batch size policy and batch sizes are an area that has been recognized with potential earnings within the company. A project to map two flows (a high volume and a low volume) and suggest a new cross functional batch size policy has been initiated.

     

    Purpose: The purpose of this project is to, with the help of a current state map, propose a new cost effective and cross functional batch size policy for the business unit car accessories and compare this to the present batch size policy to show possible earnings.  

     

    Method: This project uses a qualitative approach to show the effect of batch sizes with data supplied from the Thule Sweden AB and researched through the Linnaeus University’s recourses. 

     

    Findings: Thule Vehicle Solutions should be able to remove several inventories that have been caused by a batch size policy where whole pallets are preferred. A batch size policy where one batch size is used to the semi-finished inventory and another size, part of first batch size, from that inventory until the finished-goods inventory has been suggested as a cross functional batch size policy. This suggestion has been tested and in four different versions was found more cost effective than the current policy. Using smaller batch sizes in the suggested batch size policy decreased inventory levels and lead times. However, the current, larger batch size was more optimal as the holding costs are low and the set up costs are high.

     

    Key words: Batch size, batch size costs, cross functional, inventory control, lean management, production flow, supply chain integration, transportation costs, value stream mapping. 

  • 411.
    Avdan, Tayfun
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Circular Product Design: Developing (dis/re)assembly oriented methodology towards product end-of-life2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis aims at developing a (dis/re)assembly oriented methodology towards product end-of-life. Particular focus in this thesis is on the circularity of furniture via design for (dis/re)assembly. The main motivation behind this study was the need for a method to evaluate the (dis/re)assembly options of furniture designs to be able to facilitate repair, reuse, remanufacturing, refurbishing, or recycling.

    The study draws upon relevant theories and prior research on Circular product Design, Design for EoL, Design for Environment, and Design for (Dis)assembly of vehicles, electrical and elocronic equipments, whitegoods, as well as office furniture, though relatively limited.

    The proposed methodology determines major aspects of design for (dis/re)assembly to be taken in to consideration in the early stages of product development. It further provides a set of parameters that are relevant to cabinet type and upholstery furniture group.

    The study involves a variety of qualitative research methods that are embedded in an interactive research conduct with the engagement of different stakeholders that are charged with the task of product development at Ikea of Sweden (IoS), the collaborator of this study. 

    The proposed methodology is implemented on three selected furniture designs in a pilot study. The results of the study, above all, suggest that (dis/re)assemblability of a product is a strategic choice that needs to be made at early phases of product development, namely the design phase. Two particular features of the furniture groups, upon which this study focuses, emerges as factors having negative impact on the disassemblability of products: first, wooden frame sofas with respect to their complex structure and connectivity of componants and, second, permanent joints with respect to their destructive impact on the product.

    The study concludes that it is feasible to develop and implement a potentially comprehensible method to evaluate the ease of disassembly of furniture products and to design for disassembly. The proposed methodology in this study is a contribution to support product design for disassembly towards product circularity.

  • 412.
    Avdic, Armin
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Larsson, Daniel
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Korrigering av sågplacering: En flervariabel tidsdiskret reglering av sågplacering i ett sågverk2016Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Det här arbetet handlar om sågreglering i syfte att förbättra precisionen i sågningen. I dagens sågverk är utrustningen modern men sättet att bestämma korrigeringsvärden för bandsågar är omodernt. Arbetet innehåller analys, programmering samt kalkylering. En del i arbetet består av att finna störningar i sågprocessen och eliminera störningarna med hjälp av sågkorrigering. Mätningen sker med en noggrannheten på en tiondels millimeter. En algoritm som korrigerar sågarna för bästa möjliga resultat har implementerats i PLC och Excel. Denna algoritm ger ett snabbt svar för korrigeringsvärdet.

  • 413.
    Axelsson, Erik
    et al.
    University of Kalmar, Kalmar Maritime Academy.
    Ringborg, Mårten
    University of Kalmar, Kalmar Maritime Academy.
    Katodiskt Korrosionsskydd: Hur fungerar katodiskt korrosionsskydd ombord på fartyg?2008Independent thesis Basic level (professional degree), 5 credits / 7,5 HE creditsStudent thesis
    Abstract [en]

    The idea for this exam paper arose under our onboard training periods. Under these periods we understood that the knowledge in cathodic corrosion protection was poor among the engine personal. We have also made a minor survey among marine engineers to see how the knowledge in this area is onboard. The survey shows that our hypothesis on the level of knowledge corresponded to a large extent. Further reason why we studied this area is that we wanted to deepen us in this subject, when our own experience only was to write numbers from a display. Our main question has been how cathodic corrosion protection work at ships. In order to answer this question, we conducted literature studies in the subject. The theoretical knowledge we have gathered from internet and books. The practical knowledge we have gained from previous training periods and during onboard training on MS Silja Galaxy in December 2008 to January 2009.

  • 414.
    Axelsson, Johanna
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Lacalendola, Stefania
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Kulturarvets själ och karaktär jämlik för alla: en studie om till- och frångänglighet i Kalmar residens2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This analysis has been conducted to show that it is possible to combine accessibility, accessible evacuation and cultural heritage buildings, in this case especially Kalmar residence, without distorting the building. 

    The study was performed as a case study. By studying laws, regulations and rules as well as interviewing experts and comparing solutions with other buildings, the residence will become accessible. The aim of this work is to deliver a solution proposal. This proposal should also be used as an inspiration for future projects of similar complex types. 

    The study has come to the conclusion that there is a need for more laws and rules on accessible evacuation and that accessibility is an aspect that should be taken more into consideration in cultural heritage buildings. It is important that everyone can take part in society on an equal basis. 

  • 415.
    Axelsson, Johannes
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    WAN-optimering för sjöfarten: En möjlighet att effektivisera datakommunikationen till sjöss2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Shipboard operations have become more reliant of data communication and many of the duties on board may be facilitated if the crew can access information stored elsewhere. The broadband connection between ship and shore is mostly done via satellite communication where long distances and limited data rate results in inefficient data communication. This study examines network optimization and the performance improvement this can have regarding slow WAN connections via satellite. The survey showed that the biggest issue with data communication via satellite is the signal delay caused by the long transmission distance which means that there will be performance degradation for data traffic and users will experience the data communication as slow. To solve this there is equipment that enhances the performance of the connection and handles the data communication by implementing various techniques. To investigate how much the performance improvement can be this study carried out a number of experiments with network optimization equipment.  The experiments evaluated file transfer with and without network optimization. The results show that the network optimization gives a major performance improvement regarding file transfer.

  • 416.
    Axelsson, Magnus
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Emissioner av växthusgaservid gödsling av granungskog isödra Sverige2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    BAG leads to a greater forest growth, which could have a positive influence on thecarbon balance. To increase our understanding of the effect fertilization have ongreenhouse gas emissions, this study have examined the respiration of a juvenilespruce forest on the estate of Toftaholm (57°0'N; 14°3'E), where the soil-texturewas manly sand-moraine with a medium humidity, with main focus on theemissions of methane and nitrous gas. The results indicated a small increase innitrous gas and a continued net binding of methane independent of amount offertilization. The small increase in greenhouse-gas indicates a continuation withincreased amount of fertilization. For operational productivity with an amount offertilization (150khN/Ha and year) no significance could be determent.

  • 417.
    Axelsson, Therese
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Hur följs kraven på tillgänglighet vid nybyggande av bostäder?: - En studie av utvalda bostadsprojekt i tre närliggande kommuner2008Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this study is to find out how housebuilding meets the demands of availability for people with some sort of disability. The rules and demands of availability are stated in Boverkets byggregler, BBR and the Swedish standard, SS 91 42 21:2006 (publ.5). The projects in this study are compared to the rules and demands of BBR and SS 91 42 21:2006 (publ.5). The rapport studies three different house projects in three different municipalities and the result shows that only three of these nine projects meet the demands of availability for disabled people.

  • 418.
    Axén, Evelina
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Jonasson, Ida
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Bulleråtgärder vid kapsåg2006Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This project is about noise reduction of a cross cut saw at ProfilGruppen Extrusions AB, Åseda. The problems with the sound level depend on the structure-borne sound that generates in the long profiles. To lower the sound level have press clamp constructions been developed which reduce and further attends have been suggested.

    Attempts and comperative measurings of the sound level have been evaluated. The results of the comperative measurings with viscoelastic plastic as damping element display certain damping. The damping can in all probability become larger using a thicker damping element.

  • 419.
    Ayob, Kibret
    Linnaeus University, Faculty of Technology, Department of Informatics.
    Varumärkesstrategi på webben: Tillämpning av användarcentrerad design för positionering på webben2015Independent thesis Basic level (degree of Bachelor), 180 HE creditsStudent thesis
    Abstract [en]

    Purpose: Corporations experience difficulties positioning themselves on the web as a result of not developing their websites in a way that is inline with their overall business strategy. The purpose of this study is to explore how corporations should apply design strategy, based on a user-centered design perspective, to support their overall business strategy on the web.

    Originality/value: This study has identified a knowledge gap in terms of how corporations define and apply design strategy in order to support their overall business strategy on the web.

    Methodology: This study aims to research the application of design strategy by creating a prototype through the use of a user-centered design process. This was done by interviewing experts as well as evaluating websites, in order to explore the domain of a car manufacturers retailers, which was based on the corresponding strategy of leading the visitor to the car manufacturers offerings that are represented by the retailers and their websites. This data collection was the foundation in the creation of a persona and context scenarios that was translated into identified needs that represented the products design strategy. The design strategy in turn was the foundation for the creating phase of the user-centered design process, where iterative design lead to refining framework sketches and an interactive prototype.

    Findings and conclusion: The study which resulted in an interactive prototype shows that user-centered design, which applies design strategy by defining the corporations and the users goals and needs, is an alternative that allows for structured refinement to the point that the website fulfills its design strategy. The results also show that depending on how well the domain exploration is executed as well as how well the design strategy is defined will affect the resulting website and to what extent it fulfills its purpose, whether it’s is still a prototype or if it’s the end result.

  • 420.
    Azman, Ahmet
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Meradi, Sabra
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Development of an engraving machineby designing a protection cabin for laser marking2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The “Development of an existing engraving machine by designing a protection cabin for laser marking”project consists of the achievement of a protection cabin for a marking laser by applying the theory and the experience acquired during the courses in Mechanical Engineering program. Degree project is made with the Maskinteknik i Oskharsham AB by the Mechanical Engineering student, Ahmet Azman and Sabra Meradi. This protection cabin is design for the Deckel GK 21 engraving machine that company already bought it several years ago. The safety requirements for laser protection cabin shown in IEC and ISO standard will be observed. The design process explained in the GETTING DESIGN RIGHT: A

    Systems Approach book will be followed to achieve this project. Six steps of this method are followed: Define the problem, Measure the needs and set targets, Explore the design space, Optimize design choices, Develop the architecture, Validate the project.

  • 421.
    Azmat, Janty
    Linnaeus University, Faculty of Technology, Department of computer science and media technology (CM).
    Performance Evaluation of Node.js on Multi-core Computing Systems2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Since JavaScript code that is executed by the Node.js run-time environment is run in a single thread without really utilizing the full power of multi-core systems, fairly new approaches attempt to solve this situation. Some of these approaches are considered well publicly tested and are widely used at the time of writing this document. The objectives for this study are to check which ones of these approaches achieve the better scalability in accordance to the number of handled requests, and to what extent those approaches utilize the multi-core power compared to the raw Node.js environment with the normal CPU scheduling.

  • 422. Azoulay, M
    et al.
    Carlsson, Bo
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Chemical Substances for Heat-of-Sorption Storage - Thermodynamic Data for some Solid/Gas Phase Dissociation Reactions1982Report (Other academic)
  • 423.
    Azurdia Meza, Cesar Augusto
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Jon Mohamadi, Yaqub
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Implementation of the LMS Algorithm for Noise Cancellation on Speech Using the ARM LPC2378 Processor.2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    On this thesis project, the LMS algorithm has been applied for speech noise filteringand different behaviors were tested under different circumstances by using Matlabsimulations and the LPC2378 ARM Processor, which does the task of filtering in realtime. The thesis project is divided into two parts: the theoretical and practical part.

    In the theoretical part there is a brief description of the different aspects of signalprocessing systems, filter theory, and a general description of the Least-Mean-SquareAdaptive Filter Algorithm.

    In the practical part of the report a general description of the procedure will besummarized, the results of the tests that were conducted will be analyzed, a generaldiscussion of the problems that were encounter during the simulations will be mention,and suggestion for the problems will be given.

  • 424.
    Backlund, Johan
    et al.
    Linnaeus University, Faculty of Engineering and Technology, Kalmar Maritime Academy.
    Nordberg, Robin
    Linnaeus University, Faculty of Engineering and Technology, Kalmar Maritime Academy.
    Ny elektrisk installation på Sjöfartshögskolans ångpanna: Ett projekt från planering till utförande2013Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Abstract

    Kalmar Maritime Academy has a boiler that is used for educating marine engineers, technicians and service engineers. The boiler is used to provide students with training in programming of the control system and also to gain practical knowledge of the control equipment. The original electrical installation for the control and monitoring system was impractically designed, where a switching of cable connections in the system was required when changing between different exercises. There were also absences of real documentation for the installation. Due to these circumstances, the Maritime Academy’s planned expansion of the facility was deemed to be too complicated in its current state. The purpose of our assignment was to develop a solution for a new electrical installation for the boiler and also the practical implementation of this new installation. The goal was for the operator to easily be able to operate the boiler and also to simplify the changeover between the different types of exercises without having to reconnect any cables. The electrical installation would also get a new look with a new housing that would better represent a modern electrical installation. To achieve the objectives for the assignment a project method was chosen, which is preferred when planning and for completion of a specific task. The result of this project where a new electrical installation to the Maritime Academy’s steam boiler that has an improved safety, better ease of use for the operator and has a new modern design.

  • 425. Bader, Thomas K.
    Adaptability and Structural Design of Stadia2008Book (Other academic)
    Abstract [en]

    The aim of this master's thesis is to analyse recent developments in the design of stadia. In particular, the aim to make stadia adaptable in terms of use led to new challenges for the structural design. On one side, in order to increase event days per year, there are multi-purpose stadia for various sports, as well as for non-sporting events. Movable structures for seating tiers, pitches, and roofs developed for stadia that are suitable for various events. The design of these structures is discussed in this thesis. On the other side, major events require stadia with pre-determined capacities, which may be unsuitable for a long-term use. For this purpose, demountable structures for spectator accommodation are used to increase the capacity just temporary for the duration of a major event. Furthermore, general concepts for the structural design of stands and roofs are discussed. In addition, case studies of recent developments for major events, multi-purpose stadia, and stadia in the UK are analysed. Due to a study in the UK, there are British guidelines discussed in this thesis.

  • 426.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Mechanical properties of sound and of deteriorated softwood at different length scales: Poromicromechanical modeling and experimental investigations2011Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Due to its natural origin and its inherent heterogeneities, mechanical properties of wood are highly anisotropic and show a broad variability, not only between different wood species, but also within a tree. Similar to other biological materials, the wood mi- crostructure is well organized and hierarchically structured from the annual rings visible to the naked eye down to the wood polymers cellulose, hemicellulose, and lignin at the nanometer-scale. This thesis aims at a deeper understanding of the role of different hi- erarchical levels and their corresponding physical and chemical characteristics in relation to mechanical properties of sound wood and of deteriorated wood. This is achieved by means of micromechanical modeling and experimental analyses.

    This thesis starts with the re-formulation of an existing micromechanical model for the elastic behavior and elastic limit states of wood in the framework of poromechanics. The mechanical role of cell wall water at different hierarchical levels is investigated by means of this model. In a broader sense, the developed model allows to investigate the transition of eigenstresses from the cell wall to the softwood level. Moreover, this poromicromechanical model forms the basis for subsequent consideration of a microscopic failure criterion for lignin for the derivation of softwood failure stresses. The suitability of the modeling approach is underlined by a satisfactory agreement of the model-predicted failure stresses with experimental results of biaxial strength tests on Norway spruce.

    As a result of partly considerably different microstructural characteristics, Common yew exhibits exceptional mechanical properties compared to other softwood species. The re- lationship between microstructure and stiffness properties of Common yew and Norway spruce is investigated by means of the poromicromechanical model and mechanical tests across various length scales. Moreover, this offers the opportunity of a broader model validation. The influence of differences in microfibril angle of the S2 cell wall layer and in mass density between yew and spruce is found to be more dominant than the influence of differences in the annual ring characteristics.

    The suitability of the poromicromechanical model to predict changes in mechanical prop- erties upon fungal decay is demonstrated. For this purpose, relationships between mi- crostructure and mechanical properties of deteriorated wood are experimentally explored. Changes in mechanical properties and in the microstructure, measured at pine wood samples after standard wood durability tests using one brown rot fungus (Gloeophyl- lum trabeum) and one white rot fungus (Trametes versicolor), are presented. Transverse stiffnesses are revealed to be more sensitive to degradation than longitudinal stiffness, particularly as a result of pronounced degradation of hemicelluloses. Moreover, ultrason- ically derived anisotropy ratios of elastic stiffnesses allow to identify certain degradation mechanisms of the two considered fungi. The experimental campaign is complemented by micromechanical modeling. For this purpose, the micromechanical model is extended to take into account degradation-specific microstructural characteristics. 

  • 427.
    Bader, Thomas K.
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Bocquet, Jean-Francois
    ENSTIB/LERMAB, University of Lorraine, France.
    Schweigler, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Lemaitre, Romain
    ENSTIB/LERMAB, University of Lorraine, France.
    Numerical modeling of the load distribution in multiple fastener connections2018In: Design of Connections in Timber Structures: A state-of-the-art report by COST Action FP1402/WG3 / [ed] Carmen Sandhaas, Jorgen Munch-Andersen, Philipp Dietsch, Aachen: Shaker Verlag, 2018, p. 221-239Chapter in book (Refereed)
  • 428.
    Bader, Thomas K.
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Bocquet, Jean-Francois
    University of Lorraine, France.
    Schweigler, Michael
    Vienna University of Technology, Austria.
    Lemaitre, Romain
    University of Lorraine, France.
    Numerical modeling of the load distribution in multiple fastener joints2017In: International Conference on Connections in Timber Engineering – From Research to Standards: Proceedings of the Conference of COST Action FP1402 at Graz University of Technology / [ed] Reinhard Brandner, Andreas Ringhofer & Philipp Dietsch, Graz: Verlag der Technischen Universität Graz , 2017, p. 136-152Conference paper (Refereed)
    Abstract [en]

    Numerical modeling approaches, for the determination of load distribution in laterally loaded joints, as well as for the assignment of stiffness properties of joints for the structural analysis, are summarized in this contribution. The effect of the nonlinearity and the load-to-grain orientation dependence of connection slip, of elastic deformation in the surrounding wood matrix, and of the deviation between load and displacement direction are discussed. Comparison of various models demonstrates the pronounced effect of the load-to-grain orientation dependence and the nonlinearity in connection slip on the load distribution, particularly in case of moment loading. The effect of elastic deformation in the wood matrix on the load distribution increases with increased size of joints, even more pronounced when joints are loaded by a shear force perpendicular to the grain. In case of normal force loading, the non-uniform load distribution due to elastic deformation in the wood matrix reduces rapidly with increased relative joint displacement. Pros and cons of the modeling approaches as well as necessary input data are discussed in relation to the design process and European standardization.

  • 429. Bader, Thomas K.
    et al.
    Braovac, Susan
    Fackler, Karin
    Hofstetter, Karin
    Stiffness Properties of the Archaeological Oak Wood from the Oseberg Ship2011In: Cultural Heritage Preservation.EWCHP - 2011: Proceedings of the European Workshop on Cultural Heritage Preservation. Berlin, Germany, September 26 to 28, 2011, Fraunhofer IRB Verlag, 2011, p. 164-170Conference paper (Refereed)
  • 430.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Braovac, Susan
    University of Oslo, Norway.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Microstructure-Stiffness Relations of the Ancient Oak Wood from the Oseberg Ship2010In: International Workshop on "Modeling Mechanical Behavior of Wooden Cultural Objects", Krakow, 2010, p. 22-23Conference paper (Other academic)
  • 431.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Dastoorian, Foroogh
    Vienna University of Technology, Austria ; University of Tehran, Iran.
    Ebrahimi, Ghanbar
    University of Tehran, Iran.
    Unger, Gerhard
    Vienna University of Technology, Austria.
    Lahayne, Olaf
    Vienna University of Technology, Austria.
    Hellmich, Christian
    Vienna University of Technology, Austria.
    Pichler, Bernhard
    Vienna University of Technology, Austria.
    Combined ultrasonic-mechanical characterization of orthotropic elastic properties of an unrefined bagasse fiber-polypropylene composite2016In: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 95, p. 96-104Article in journal (Refereed)
    Abstract [en]

    Use of wood-fiber plastics for construction purposes calls for comprehensive understanding of their anisotropic mechanical properties. As a respective contribution, we here report the first-ever complete elasticity characterization of an orthotropic bagasse fiber polypropylene composite, requiring identification of nine independent constants. For this purpose, we carry out characterization in principal material directions. Six diagonal stiffness tensor components are quantified based on ultrasonic longitudinal and shear wave velocity measurements; and three diagonal compliance tensor components are identified as the inverses of three Young’s moduli derived from unloading regimes of quasi-static uniaxial compression tests. Combination of all measurement data in the framework of orthotropic linear elasticity provides access to all off-diagonal stiffness and compliance tensor components, opening the door to quantifying six Poisson’s ratios. 

  • 432.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    de Borst, Karin
    University of Glasgow, UK.
    Poroelastic properties of hardwood at different length scales2013In: Poromechanics V: proceedings of the fifth Biot Conference on Poromechanics, July 10-12, 2013, Vienna, Austria / [ed] Christian Hellmich, Bernhard Pichler, Dietmar Adam, Reston: American Society of Civil Engineers (ASCE), 2013, p. 1830-1836Conference paper (Other academic)
    Abstract [en]

    Hardwoods show a very complex, hierarchically organized microstructure. Slight structural differences at various length scales bring about a huge variety of hardwood species. This motivates the development of a micromechanical model for hardwood. Since differences in the microstructure of the material can be considered in the model, it offers the opportunity to explain the variability of mechanical properties of the whole class of hardwood. The micromechanical model is formulated in the framework of poroelasticity. In this contribution, poroelastic properties at different length scales of the material are discussed. Validation of the micromechanical model is based on an extensive experimental database covering elastic properties and microstructural characteristics of different temperate and tropical hardwood species. Exemplary parameter studies demonstrate the ability of the model to study the contribution of specific microstructural characteristics to the load transfer and the deformation characteristics of wood. 

  • 433.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    de Borst, Karin
    University of Glasgow, UK.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Micromechanical modeling of Common yew and Norway spruce2013In: Proceedings in Applied Mathematics and Mechanics: PAMM, ISSN 1617-7061, E-ISSN 1617-7061, Vol. 13, no 1, p. 185-186Article in journal (Refereed)
    Abstract [en]

    In this contribution, a micromechanical modeling approach in the framework of poromechanics is adopted to study structure-stiffness relations of two quite different species, namely spruce and yew, in detail. In particular, microstructural specialties of yew and spruce are assessed. A dominant influence of the cellulose content and its orientation on the stiffness of the cell wall is revealed, while on the macroscopic scale, density is found to be the governing microstructural characteristic for elastic properties.

  • 434.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    de Borst, Karin
    University of Glasgow, UK.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Micromechanical Modeling of Wood: Multiscale Modeling and Model Validation2013Conference paper (Other academic)
    Abstract [en]

    Due to its natural origin and its inherent heterogeneities, mechanical properties of wood are highlyanisotropic and show a broad variability, not only between different wood species, but also within a tree [1].Similar to other biological materials, the wood microstructure is well organized and hierarchically structuredfrom the annual rings visible to the naked eye down to the wood polymers cellulose, hemicellulose, andlignin at the nanometer-scale. The aim of the research conducted at the Institute for Mechanics of Materialsand Structures is a deeper understanding of the role of different hierarchical levels and their correspondingphysical and chemical characteristics in relation to mechanical properties of softwood and hardwood. This isachieved by means of micromechanical modeling and experimental analyses at various length scales.

    A micromechanical model provides the opportunity to predict poroelastic properties of softwood andhardwood tissues at different hierarchical levels from microstructural and compositional data [1,2]. Thehierarchical organization of wood is mathematically represented in a multiscale model. Effective poroelasticproperties are predicted by means of continuum micromechanical approaches (self-consistent method andMori-Tanaka method), the unit cell method, and laminate theory. These approaches are extended to accountfor water-induced eigenstresses within representative volume elements and repetitive unit cells, which aresubsequently upscaled to the macroscopic wood level.

    Verification of the micromechanical model for softwood and hardwood with a comprehensive experimentaldataset, shows that it suitably predicts elastic properties at different length scales under the assumption ofundrained conditions [3,4]. Moreover, Biot tensors, expressing how much of the cell wall water-induced porepressure is transferred to the boundary of an overall deformation-free representative volume element (RVE),and Biot moduli, expressing the porosity changes invoked by a pore pressure within such an RVE can bestudied at different length scales. Consequently, the relevance and the contribution of specificmicrostructural characteristics to the load transfer and the deformation characteristics in case of moisturechanges in wood can be studied. Besides the scientific interest in structure-function-relationships, theseinvestigations are motivated by the growing importance of wood as building material.

  • 435.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Esser, Gerold
    Vienna University of Technology, Austria.
    Hochreiner, Georg
    Vienna University of Technology, Austria.
    The Historical Roof Structure of the Leopold Wing of the Vienna Hofburg Palace: Structural Assessment2015In: Proceedings of the International Conference on Structural Health Assessment of Timber Structures (SHATIS'15), 2015Conference paper (Refereed)
    Abstract [en]

    In this case study, the structural behaviour of the historic roof structure of the “Leopold Wing”, part of the Hofburg, the Vienna Imperial Palace, is assessed. The current appearance of the roof is a consequence of several adaptions and extensions of the original structure that dates back to the 17th century. The main part of the roof was reconstructed in the early 1670s following a disastrous fire in February 1668. The structure had the shape of an M-roof consisting of two adjacent gable roofs. Probably in the 19th century, the centre part was closed, creating a mansard roof over the entire width of the building. Basically, the geometry of the structure is symmetric with respect to the middle wall. However, since the position of the middle wall is partly asymmetric, also the roof structure becomes asymmetric. Herein, the influence of the building history on the load-deformation behaviour of the roof structure is investigated. Therefore, structural analyses of the original M-roof and of the mansard roof are performed. The modelling of the historic roof structure is based on a deformation-accurate survey. In addition, the influence of the nonlinear, compliant behaviour of connections on the load-deformation behaviour of the timber structure is taken into account. A considerable influence of the connection slip on the deformation of the structure becomes obvious from the analysis. Consequently, consideration of the nonlinear behaviour of the joints reveals a realistic load transfer within the structure. The addition of structural elements caused additional dead loads, which increase long-term deformations.

  • 436.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    de Borst, Karin
    University of Glasgow, UK.
    Shear stiffness and its relation to the microstructure of 10 European and tropical hardwood species2017In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, no 2, p. 82-91Article in journal (Refereed)
    Abstract [en]

    In this study, shear stiffness properties of 10 different hardwood species and their relation to the corresponding species-specific microstructure are investigated. For this purpose, shear stiffness of 10 different hardwood species is experimentally measured by means of ultrasonic testing. In addition, a micromechanical model for hardwood is applied in order to illustrate the influence of certain microstructural characteristics such as mass density and volume fractions of vessels and ray cells on the shear stiffness. Comprehensive microstructural and mechanical data from previous investigations of the same hardwood material support the interpretation of the microstructure–shear stiffness relationships. Mass density was confirmed to be the dominant microstructural characteristic for shear stiffness. Also, ultrasound shear wave propagation velocity increases with density, particularly in the radial-tangential (RT) plane. In addition to density, comparably higher shear stiffness GLR can be explained by comparably higher ray content and lower vessel content. As for GLT, a ring porous structure seems to lead to higher shear stiffness as compared to a diffuse porous structure. For this shear stiffness, vessel and ray content were found to have a less impact. Also, the rolling shear stiffness GRT was found to be higher for a diffuse porous structure than for a ring porous one. Moreover, the data supports that ray cells act as reinforcements in the RT plane and lead to higher GRT

  • 437. Bader, Thomas K.
    et al.
    Hofstetter, Karin
    Technische Universität, Austria.
    Pilzabbau von Holz: Quantifizierung des Steifigkeitsverlusts auf Basis von mikromechanischen Überlegungen2010In: Wiener Holzschutztage 2010: 25. - 26. November 2010, Wien, Wien: Wiener Holzschutztage , 2010, Vol. 28, p. 50-55Conference paper (Other academic)
    Abstract [de]

    Pilzbefall bewirkt eine Zersetzung des Materials durch Mikroorganismen und damit unweigerlich auch eine Veränderung des mechanischen Verhaltens von Holz. Die Auswirkung der mikrostrukturellen Änderungen auf makroskopisch beobachtbare mechanische Materialkennwerte wie Steifigkeit und Festigkeit lassen sich mittels Mehrskalenmodellierung abschätzen und quantifizieren. Die Eignung solcher Mehrskalenmodelle als Prognosewerkzeuge für Dauerhaftigkeitsbetrachtungen wurde im WoodWisdom-Netzwerk „WoodExter“ im Rahmen eines umfangreichen Testprogramms untersucht. Es wurde dabei sowohl ein Braunfäule verursachender Pilz (Gloephyllum trabeum) als auch ein Weißfäule verursachender Pilz (Trametes versicolor) verwendet. Die Vorgehensweise sowie die gewonnenen Einblicke und Erkenntnisse sind in diesem Beitrag zusammengefasst. Nach einer Kurzbeschreibung der hierarchischen Struktur von Holz und deren Modifikation durch Pilze folgt ein Abriss über die verwendeten Verfahren der Mehrskalenmodellierung. Der Schwerpunkt liegt in der Präsentation der Ergebnisse sowie der experimentellen Validierung des Modells durch Vergleich von Messwerten mit zugehörigen Modellvorhersagen. Schließlich werden im Ausblick mögliche Anwendungen der Modellierung skizziert. 

  • 438.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Alfredsen, Gry
    Norwegian Forest and Landscape Institute, Norway.
    Bollmus, Susanne
    Georg-August-University of Göttingen, Germany.
    Changes in microstructure and stiffness of Scots pine (Pinus sylvestris L) sapwood degraded by Gloeophyllum trabeum and Trametes versicolor Part II: Anisotropic stiffness properties2012In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, no 2, p. 199-206Article in journal (Refereed)
    Abstract [en]

    Fungal decay considerably affects the macroscopic mechanical properties of wood as a result of modifications and degradations in its microscopic structure. While effects on mechanical properties related to the stem direction are fairly well understood, effects on radial and tangential directions (transverse properties) are less well investigated. In the present study, changes of longitudinal elastic moduli and stiffness data in all anatomical directions of Scots pine (Pinus sylvestris) sapwood which was degraded by Gloeophyllum trabeum (brown rot) and Trametes versicolor (white rot) for up to 28 weeks have been investigated. Transverse properties were found to be much more deteriorated than the longitudinal ones. This is because of the degradation of the polymer matrix between the cellulose microfibrils, which has a strong effect on transverse stiffness. Longitudinal stiffness, on the other hand, is mainly governed by cellulose microfibrils, which are more stable agains fungal decay. G. trabeum (more active in earlywood) strongly weakens radial stiffness, whereas T. versicolor (more active in latewood) strongly reduces tangential stiffness. The data in terms of radial and tangential stiffnesses, as well as the corresponding anisotropy ratios, seem to be suitable as durability indicators of wood and even allow conclusions to be made on the degradation mechanisms of fungi.

  • 439.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Alfredsen, Gry
    Norwegian Forest and Landscape Institute, Norway.
    Bollmus, Susanne
    Georg-August-University of Göttingen, Germany.
    Microstructure and stiffness of Scots pine (Pinus sylvestris L) sapwood degraded by Gloeophyllum trabeum and Trametes versicolor Part I: Changes in chemical composition, density and equilibrium moisture content2012In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, no 2, p. 191-198Article in journal (Refereed)
    Abstract [en]

    Fungal degradation alters the microstructure of wood and its physical and chemical properties are also changed. While these changes are well investigated as a function of mass loss, mass density loss and changes in equilibrium moisture content are not well elucidated. The physical and chemical alterations are crucial when linking microstructural characteristics with macroscopic mechanical properties. In the present article, a consistent set of physical, chemical and mechanical characteristics is presented, which were measured on the same sample before and after fungal degradation. In the first part of this two-part contribution, elucidating microstructure/stiffness-relationships of degraded wood, changes in physical and chemical data are presented, which were collected from specimens of Scots pine (Pinus sylvestris) sapwood degraded by Gloeophyllum trabeum (brown rot) and Trametes versicolor (white rot) for up to 28 weeks degradation time. A comparison of mass loss with corresponding mass density loss demonstrated that mass loss entails two effects: firstly, a decrease in sample size (more pronounced for G. trabeum), and secondly, a decrease of mass density within the sample (more pronounced for T. versicolor). These two concurrent effects are interrelated with sample size and shape. Hemicelluloses and cellulose are degraded by G. trabeum, while T. versicolor was additionally able to degrade lignin. In particular because of the breakdown of hemicelluloses and paracrystalline parts of cellulose, the equilibrium moisture content of degraded samples is lower than that in the initial state.

  • 440.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Keunecke, Daniel
    ETH Zürich, Switzerland.
    Microstructure–Stiffness Relationships of Common Yew and Norway Spruce2012In: Strain, ISSN 0039-2103, E-ISSN 1475-1305, Vol. 48, no 4, p. 306-316Article in journal (Refereed)
    Abstract [en]

    Yew (Taxus baccata L.) exhibits among conifers a unique macroscopic elastic behaviour. For example, it shows a comparatively low longitudinal elastic modulus related to its comparatively high density. We herein explore the microstructural origin of these peculiarities, aiming at the derivation of microstructure–stiffness relationships. We measure stiffness properties of yew at different hierarchical levels and compare them to corresponding stiffnesses of Norway spruce (Picea abies [L.] Karsten). Cell wall stiffness is investigated experimentally by means of nanoindentation in combination with microscopy and thermogravimetric analysis. On the macroscopic level, we perform uniaxial tension and ultrasonic tests. Having at hand, together with previously reported stiffnesses, a consistent data set of mechanical, chemical and physical properties across hierarchical levels of wood, we discuss influences of microstructural characteristics at different scales of observation. Moreover, a micromechanical model is applied to predict trends of effects of the microstructure on the investigated stiffness properties. On the cell wall level, particularly, the amount of cellulose and its orientation – which was earlier reported to be distinctly different for yew and spruce – result in differences between the two considered species. On the macroscopic scale, model predicted effects of the annual ring structure on transverse stiffness and shear stiffness are found to be smaller than effects of the microfibril angle and mass density.

  • 441.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Hellmich, Christian
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    From lignin to spruce: Poromechanical upscaling of wood strength2011In: 2010 MRS Fall Meeting: Symposium V/NN/OO/PP – Soft Matter, Biological Materials and Biomedical Materials—Synthesis, Characterization and Applications / [ed] A.J. Nolte, K. Shiba, R. Narayan, D. Nolte, Warrendale, Pennsylvania, USA: Materials Research Society, 2011, Vol. 1301, p. 75-80Conference paper (Other academic)
    Abstract [en]

    Wood strength is highly anisotropic, due to the inherent structural hierarchy of the material. In the framework of a combined random-periodic multiscale poro-micromechanics model, we here translate compositional information throughout this hierarchy into the resulting anisotropic strength at the softwood level, based on “universal” elastic properties of cellulose, hemicelluloses, and lignin, and on the shear strength of the latter elementary constituent. Therefore, derivation of the elastic energy in a piece (representative volume element – RVE) of softwood, stemming from homogeneous macroscopic strains prescribed in terms of displacements at the boundary of the RVE and from pressure exerted by water filling the nanoporous space between the hemicelluloses-lignin network within the cell walls, with respect to the shear stiffness of lignin, yields higher order strains in the lignin phase, approximating micro-stress peaks leading to local lignin failure. Relating this (quasi-brittle) failure to overall softwood failure (or strictly speaking, elastic limit of softwood) results in a macroscopic microstructure-dependent failure criterion for softwood. The latter satisfactorily predicts the biaxial strength of spruce at various loading angles with respect to the grain direction. The model also predicts the experimentally well-established fact that uniaxial tensile and compressive strengths, as well as the shear strength of wood, depend quasi-linearly on the cell water content, but highly nonlinearly on the lumen porosity. 

  • 442.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Hellmich, Christian
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Homogenization and Localization in a Multiscale Microporomechanical Model for Wood Strength2009Conference paper (Other academic)
  • 443.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Hellmich, Christian
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Multiscale Microporomechanics Model for Estimation of Elastic Limit States of Softwood Materials2009Conference paper (Other academic)
  • 444.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Hellmich, Christian
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Multiscale Microporomechanics of Softwood: Applications and Experimental Model Validation2010In: IV European Conference on Computational Mechanics (ECCM 2010), Paris, France: European Community on Computional Methods in Applied Sciences (ECCOMAS), 2010Conference paper (Other academic)
  • 445.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Hellmich, Christian
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    On the Relevance of Lignin Failure for Softwood Strength: a Poromicromechanical Approach2011In: XI International Conference on Computational Plasticity - Fundamentals and Applications, Barcelona: International Center for Numerical Methods in Engineering (CIMNE), 2011Conference paper (Other academic)
  • 446.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Hellmich, Christian
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Poromechanical scale transitions of failure stresses in wood: from the lignin to the spruce level2010In: Zeitschrift für angewandte Mathematik und Mechanik, ISSN 0044-2267, E-ISSN 1521-4001, Vol. 90, no 10-11, p. 750-767Article in journal (Refereed)
    Abstract [en]

    Wood strength is highly anisotropic, due to the inherent structural hierarchy of the material. In the framework of a combined random-periodic multiscale poro-micromechanics model, we here translate compositional information throughout this hierarchy into the resulting anisotropic strength at the softwood level, based on “universal” elastic properties of cellulose, hemicellulose, and lignin, and on the shear strength of the latter elementary constituent. Relating, through elastic energy-derived higher-order strains in a poromechanical representative volume element, the (quasi-)brittle failure of lignin to overall softwood failure, results in a macroscopic microstructure-dependent failure criterion for softwood. The latter satisfactorily predicts the biaxial strength of spruce at various loading angles with respect to the grain direction. The model also predicts the experimentally well-established fact that uniaxial tensile and compressive strengths, as well as the shear strength of softwood, depend quasi-linearly on the cell water content, but highly nonlinearly on the lumen porosity.

  • 447.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Hellmich, Christian
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    The poroelastic role of water in cell walls of the hierarchical composite “softwood”2010In: Acta Mechanica, ISSN 0001-5970, E-ISSN 1619-6937, Vol. 217, no 1, p. 75-100Article in journal (Refereed)
    Abstract [en]

    Wood is an anisotropic, hierarchically organized material, and the question how the hierarchical organization governs the anisotropy of its mechanical properties (such as stiffness and strength) has kept researchers busy for decades. While the honeycomb structure of softwood or the chemical composition of the cell wall has been fairly well established, the mechanical role of the cell wall water is less understood. The question arises how its capability to carry compressive loads (but not tensile loads) and its pressurization state affect mechanical deformations of the hierarchical composite “wood”. By extending the framework of poro-micromechanics to more than two material phases, we here provide corresponding answers from a novel hierarchical set of matrix-inclusion problems with eigenstresses: (i) Biot tensors, expressing how much of the cell wall water-induced pore pressure is transferred to the boundary of an overall deformation-free representative volume element (RVE), and (ii) Biot moduli, expressing the porosity changes invoked by a pore pressure within such an RVE, are reported as functions of the material’s composition, in particular of its water content and its lumen space. At the level of softwood, where we transform a periodic homogenization scheme into an equivalent matrix-inclusion problem, all Biot tensor components are found to increase with decreasing lumen volume fraction. A further research finding concerns the strong anisotropy of the Biot tensor with respect to the water content: Transverse components increase with increasing water content, while the relationship “longitudinal Biot tensor component versus volume fraction of water within the wood cell wall” exhibits a maximum, representing a trade-off between pore pressure increase (increasing the longitudinal Biot tensor component, dominantly at low water content) and softening of the cell wall (reducing this component, dominantly at high water contents). Soft cell wall matrices reinforced with very stiff cellulose fibers may even result in negative longitudinal Biot tensor components. The aforementioned maximum effect is also noted for the Biot modulus.

  • 448.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Muszynski, Lech
    Oregon State University, USA.
    Integrative Method for Micromechanical Characterization of Wood in Steel-Dowel Connections2012In: COST Action FP 0802: Experimental and Computational Micro-Characterization Techniques in Wood Mechanics, Edinburgh, UK, 2012, p. 100-101Conference paper (Other academic)
  • 449.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Muszynski, Lech
    Lederer, Wolfgang
    Eberhardsteiner, Josef
    Imaging the Micromechanical Response of Wood in Steel-Dowel Connections2013Conference paper (Other academic)
  • 450.
    Bader, Thomas K.
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology. TU Wien, Austria.
    Schweigler, M.
    TU Wien, Austria.
    Hochreiner, Georg
    TU Wien, Austria.
    Eberhardsteiner, Josef
    TU Wien, Austria.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Serrano, Erik
    Lund University, Sweden.
    Integrative Research for an Enhanced Design of Dowel Connections2015In: Proceedings of the EUROMECH Colloquium 556 on Theoretical, Numerical, and Experimental Analyses in Wood Mechanics, 2015Conference paper (Refereed)
6789101112 401 - 450 of 4029
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