lnu.sePublikasjoner
Endre søk
Begrens søket
1234567 101 - 150 of 2878
Referera
Referensformat
• apa
• ieee
• modern-language-association-8th-edition
• vancouver
• Annet format
Fler format
Språk
• de-DE
• en-GB
• en-US
• fi-FI
• nn-NO
• nn-NB
• sv-SE
• Annet språk
Fler språk
Utmatningsformat
• html
• text
• asciidoc
• rtf
Treff pr side
• 5
• 10
• 20
• 50
• 100
• 250
Sortering
• Standard (Relevans)
• Forfatter A-Ø
• Forfatter Ø-A
• Tittel A-Ø
• Tittel Ø-A
• Type publikasjon A-Ø
• Type publikasjon Ø-A
• Eldste først
• Nyeste først
• Disputationsdatum (tidligste først)
• Disputationsdatum (siste først)
• Standard (Relevans)
• Forfatter A-Ø
• Forfatter Ø-A
• Tittel A-Ø
• Tittel Ø-A
• Type publikasjon A-Ø
• Type publikasjon Ø-A
• Eldste først
• Nyeste først
• Disputationsdatum (tidligste først)
• Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
• 101.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
MDSS: ett beslutsstödsystem för kostnadseffektivare underhållsåtgärder  Del IV:2:22011Inngår i: Bättre produktivitet : tidning för PLAN och regionala produktivitetsföreningar : med plan-nytt, ISSN 1402-1145, nr 2, s. 24-Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
• 102.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Med färre dyra stopp kan produktionen räddas kvar2004Inngår i: Dagens industri, ISSN 0346-640X, nr 0607Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
• 103.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Mycket att tjäna på tillståndsbaserat underhåll2005Annet (Annet (populærvitenskap, debatt, mm))
• 104.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
On establishing cost-effective condition-based maintenance: Exemplified for vibration-based maintenance in case companies2012Inngår i: Journal of Quality in Maintenance Engineering, ISSN 1355-2511, E-ISSN 1758-7832, Vol. 18, nr 4, s. 401-416Artikkel i tidsskrift (Fagfellevurdert)

Purpose

– The purpose of this paper is to develop the steps required for establishing and running cost-effective condition-based maintenance (CBM) exemplified for vibration-based maintenance (VBM) and compared with real implementations in case companies.

Design/methodology/approach

– The study is based on published knowledge and experience within condition monitoring (CM) and CBM, and three case studies.

Findings

– The study has shown that all three case companies are in a big need for systematic procedures for doing right things right, in the right time cost-effectively (establishing and running a cost-effective CBM).

Research limitations/implications

– The paper focuses on development of cost-effective CBM exemplified for VBM. Also, the case companies belong to three branches: paper and pulp mills, energy producer and engineering manufacturing. The case companies have different levels in applying CBM/VBM, experience and knowledge in CM and CBM.

Practical implications

– Systematic procedures for establishing CBM/VBM policy are developed, motivated and discussed in a way which enables the user to establish and run CBM/VBM policy cost-effectively.

Originality/value

– The steps of establishment of CBM/VBM provide a unique model for companies to establish and run cost-effective maintenance its originality.

• 105.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Onödigt underhåll kostar företagen stora pengar2002Annet (Annet (populærvitenskap, debatt, mm))
• 106.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Prediction of the vibration level when monitoring rolling element bearings in paper mill machines2001Inngår i: International Journal of COMADEM, ISSN 1363-7681, Vol. 4, nr 2, s. 19-26Artikkel i tidsskrift (Fagfellevurdert)

Rolling element bearings in paper mill machines are considered in this paper due to their critical role in the machine function. In general, the cost-effectiveness of a vibration-based maintenance policy mainly depends on the technical and economic effectiveness of the vibration monitoring system, i.e. software, hardware, and personnel, being used. In this paper, a model for predicting the vibration level of rolling element bearings in paper mills is developed. In the model, a combination of bearing vibration history, current condition and data from operating conditions is used to predict the vibration level of a bearing during a near future.

The factors influencing the condition of rolling element bearings during operation are discussed. These factors are related partly to operating and environmental conditions and partly to previous changes in the condition of the bearing. The operating life of a bearing is divided into four phases characterised by their vibration behaviour. One of the important conclusions is that a mechanistic model would be more appropriate than other models for predicting the vibration level of a rolling element bearing and describing the deterioration process, which are needed to achieve better understanding of the bearing vibration behaviour.

• 107.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Prediction of the vibration level when monitoring rolling element bearings in paper mills machines1998Konferansepaper (Fagfellevurdert)
• 108.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Review of maintenance concepts1999Konferansepaper (Fagfellevurdert)
• 109.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Selection of a cost-effective vibration based monitoring system1994Konferansepaper (Fagfellevurdert)
• 110.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Strategies for Maintenance Cost-effectiveness2010Inngår i: E-maintenance / [ed] Kenneth Holmberg, London: Springer, 2010, 1, s. 297-344Kapittel i bok, del av antologi (Fagfellevurdert)

To survive hard international competition, it is necessary for many producing companies to enhance their competition positions by, for example, reducing production costs and maintaining and improving product quality to increase the profit margin. In order to achieve these strategic goals, strategies for making maintenance more profitable are developed, introduced and discussed in this chapter. These strategies are all developed as software modules included by an innovatively new maintenance decision support system (MDSS). Also, theoretical backgrounds are introduced, and software prototypes for making the application of any of the tools on a daily basis easier and more cost-effective are developed and discussed, and their functionalities are tested. MDSS consists of three toolsets, where each toolset consists of one to three tools that can be used for different objectives and applications. It is designed to support maintenance and production engineers to achieve dynamic and cost-effective maintenance decisions. The latter will be discussed in Chapter 13. MDSS software prototype can be utilised for several objectives, such as, to:

• enhance the accuracy of maintenance decisions;

• simulate and select the most cost-effective maintenance solution, i.e., the best investment in maintenance;

• identify and prioritise problem areas; and

• map, monitor, analysis, follow up and assess maintenance contribution in company profit.

• 111.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
System för underhållsstöd gör det lättare välja lönsammaste underhåll2011Annet (Annet (populærvitenskap, debatt, mm))
• 112.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
The impact of the lack of real-time measurements of performance parameters on vibration-based maintenance1999Konferansepaper (Fagfellevurdert)
• 113.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
The Rockets1983 (oppl. 1)Bok (Fagfellevurdert)
• 114.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Tillämpning av PBI inom ämnet systemekonomi2001Rapport (Annet vitenskapelig)
• 115.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Total quality maintenance: An approach for continuous reduction in costs of quality products1996Inngår i: Journal of Quality in Maintenance Engineering, ISSN 1355-2511, E-ISSN 1758-7832, Vol. 2, nr 3, s. 4-20Artikkel i tidsskrift (Fagfellevurdert)

The common thread in achieving and maintaining high Overall Equipment Effectiveness, OEE, is the availability of improved manufacturing processes capable of producing quality products without interruption. Implementing Just In Time, JIT, philosophy demands healthy processes. Any interruption of the line caused by any equipment malfunction or failure will result in a major disruption of output or even line or factory shutdown. Thus, an effective maintenance program should be evolved to provide the required availability of machinery and output quality. A new concept of condition-based maintenance, Total Quality Maintenance, TQMain, is presented. It aims to maintain not only machinery but all the elements constituting a manufacturing process, e.g. production/operation, environmental condition, personnel, methods, material, quality control. TQMain is a result of establishing a common database through integrating the maintenance program with other plant programs to form an overall plant Information Technology, IT-system. Identifying and ‘eliminating’ quality deviations and failure causes at early stages, and extensive use of data feedback are the suggested tools to accomplish continuous improvements and to assure high quality products.

• 116.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Total Time on Test, TTT-plots for Condition Monitoring of Rolling Element Bearings in Paper Mills2003Inngår i: International Journal of COMADEM, ISSN 1363-7681, Vol. 6, nr 2, s. 27-32Artikkel i tidsskrift (Fagfellevurdert)

When using vibration-based maintenance, it is easier to detect damage in rolling element bearings. But the damage severity and risk of bearing's failure, if no maintenance action such as replacement is done, can not be assessed accurately. When the vibration level of a rolling element bearing is increasing or it is close to (or greater than) a predetermined replacement level, the assessment of the probability of a bearing’s failure enhances the decision making process. Thus, at each vibration measurement occasion a decision has to be made regarding whether the bearing needs to be maintained and how urgent it actually is.

The paper describes a graphical method for both assessing the probability of failure of damaged rolling element bearing and predicting the residual of its effective life. It uses history of the bearing in question and life statistics as well as the vibration levels at failure/condition-based replacements of past bearings of the same design or of very similar performance and duties. This method is based on the concept of Total Time on Test, TTT-plot. The application of TTT-plot on age and condition-based maintenance techniques are discussed and described by two examples. This graphical method is developed from previous work by the author and others.

• 117.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Totalt kvalitetsunderhåll (TKU): Ett koncept för kvalitetssäkring och förbättring till minskande kostnader1999Inngår i: Konferensen vinnande ledarskap: den 9-10 februari 1999 på svenska mässan congress i Göteborg, 1999, s. 171-176Konferansepaper (Annet vitenskapelig)
• 118.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Vibration-based maintenance and common database: Effectiveness and benefits1998Konferansepaper (Fagfellevurdert)
• 119.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Växjö universitet utvecklar underhållsverktyg2005Inngår i: Industriprojekt, nr 6, s. 30-32Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
• 120.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Damscus University.
A Model to Identify and Prioritise the Causes behind Losses in Company profit: Application Example2010Inngår i: Damascus University Journal, ISSN 1999-7302, Vol. 26, nr 2, s. 35-45Artikkel i tidsskrift (Fagfellevurdert)

A production process includes several sub-processes (working areas) that are responsible for performing the different tasks required to accomplish the mission of the process. Thus, it is important to avoid a shortage of resources, unplanned stoppages and idle times that may arise. The problem addressed in this paper is: How should maintenance be considered in conjunction with plant activities, such as production, quality and personnel competence for easily and effectively identifying and quantifying company losses in profitability and eliminating underlying causes? In this paper, the interactions between major working areas have been introduced and discussed. The major result achieved in this study is the development of a new model (Maintenance Function Deployment (MFD), for an easy and effective identification and quantification of company losses in profitability. Four matrixes have been used for developing MFD model for effectively integrating maintenance with production, competence and quality. An application example is conducted to demonstrate the possibility of applying the model and its potential for enhancing production processes profitably. The main conclusion is: applying MFD gives an enormous opportunity to continuously maintain the quality of the working areas under consideration, which makes MFD one of the company’s objective-driven tools for enhancing its profitability and competitiveness.

• 121.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Lund University.
Selection the most efficient maintenance-approach using fuzzy multiple criteria decision-making2000Konferansepaper (Fagfellevurdert)
• 122.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK. Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Selecting and Improving the most Cost-effective Maintenance Policy: A Model2004Konferansepaper (Fagfellevurdert)
• 123.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK. Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
The economic importance of maintenance planning when using vibration-based maintenance2001Rapport (Annet vitenskapelig)
• 124.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
A Model for More Accurate Maintenance Decisions2010Inngår i: Engineering Asset Management: Proceeding of the Fourth World Congress on Engineering Asset Management (WCEAM) 2009 / [ed] Dimitris Kiritsis, Christos Emmanouilidis, Andy Koronios, and Joseph Mathew, Springer, 2010, s. 7-14Konferansepaper (Fagfellevurdert)

It is usual when using CM technology for assessing the state of a component and planning maintenance actions using predetermined levels for warnings and replacements. The replacement of a damaged component is usually done at lower or higher than the predetermined level, which both means losses. This is because the probability of doing replacements just at the predetermined level is negligibly small. The accuracy in the assessment of the condition of a component has big technical and economic impact on the output of the machine, production process and consequently company profitability and competitiveness. The higher the accuracy in assessing the condition of a component yields higher probability of avoiding failures and planning maintenance actions at low costs. In this paper, techniques for assessing the state of a component using both mechanistic and other statistical approaches are considered. This paper also applies Cumulative Sum (CUSUM) Chart for identifying the time of damage initiation and reducing false alarms.  Techniques for assessing the probability of failure of a component and its residual life, and predicting the vibration level at the next planned measuring opportunity or planned stoppage are introduced, discussed, computerised and tested. The problem addressed is: How is it possible to increase the accuracy of assessing the condition of a component? The major result achieved is; development of a model for more accurate assessment of the condition of a component/equipment through combining different approaches. The main conclusion that can be drawn is; applying the model, it is possible to enhance the accuracy of assessment of the condition of a component/equipment and consequently maintenance decision since the integrated model provides comprehensive and relevant information in one platform.

• 125.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
Dynamic and Cost-effective Maintenance Decisions2010Inngår i: E-maintenance / [ed] Kenneth Holmberg, London: Springer, 2010, 1, s. 345-390Kapittel i bok, del av antologi (Fagfellevurdert)

In general, all the elements involved in a production process, such as tools, machinery, methods, competence and working environment are exposed to changes. Thus, to maintain and improve company profitability and competitiveness, it is necessary to reduce losses through maintaining and improving the quality of the elements involved in the production process. Therefore, the maintenance strategy applied should be dynamic to be suited for all these changes cost-effectively. In producing companies, the accuracy of maintenance decisions is essential for reducing economic losses generated due to unnecessary stoppages in companies of intensive capital investment where stoppage time is expensive, especially in paper and pulp mills, refineries, power stations and engineering manufacturing. Therefore, it is necessary for maintenance and production managers to have a system providing the data required to achieve dynamic and cost-effective maintenance decisions.

In this chapter, the new maintenance decision support system (MDSS) for achieving dynamic and cost-effective maintenance decisions developed in Chapter 12 is tested and discussed. The developed system is MIMOSA compatible, consists of three toolsets and five software modules for performing six services to achieve different objectives, e.g.:

1. higher accuracy of maintenance decisions;

2. selection of the most cost-effective maintenance solutions;

3. identification and prioritisation of problem areas and assessment of losses in production time; and

4. mapping, follow up and assessment of maintenance cost-effectiveness (maintenance savings and profit) to achieve continuous and cost effective improvement.

• 126.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Effektivare underhåll när rätt åtgärd görs i rätt tid2010Inngår i: Husbyggaren, nr 3, s. 20-22Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
• 127.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Maintenance Solutions for Continuous & Cost-effective Improvement of Wind Turbine Performance2012Inngår i: Workshop on Advanced Maintenance Engineering, Services and Technology (A-Mest'12), 2012Konferansepaper (Fagfellevurdert)

Enhancement of company competitiveness and profitability demands continuous, high quality and trouble free production. Technical specifications and the condition of a wind turbine depend on the quality and condition of its significant components, which usually have the biggest impact on production continuity, - cost per KW and the environment. These necessitate intelligent technologies for maintaining the quality of significant components. Thus, it would be mandatory to select the most informative condition monitoring (CM) system and most cost-effective maintenance policy. In this paper, wind turbine problems are specified and described, available maintenance and CM techniques are discussed, and a maintenance solution with clearly specified objectives are suggested, discussed and the potential results are outlined in the end.

• 128.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Benchmarking of maintenance performance: A case study in two manufacturers of furniture2001Konferansepaper (Fagfellevurdert)
• 129.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK. Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
A database model for monitoring and assessing technical and financial impacts of maintenance on the production process2004Konferansepaper (Fagfellevurdert)
• 130.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Effectiveness of vibration-based monitoring systems in paper mills: Two case studies1997Inngår i: COMADEM '97: 10th international congress and exhibition on condition monitoring and diagnostic engineering management, vol. 1 / [ed] Jantunen, E; Holmberg, K; Rao, RBK, 1997, s. 48-57Konferansepaper (Fagfellevurdert)

The effectiveness of vibration-based monitoring, (VBM), system may be measured in terms of reduced stoppage rates and increased use of potential bearing life. Analysis of data from roller bearings at two paper mills suggests that greater bearing lives can be safely achieved by increasing the accuracy of the vibration data, This paper relates bearing failures to the observed vibration spectra and their development over the bearings' lives. The literature was found mainly to confirm the author's analysis. A systematic approach which describes the performance and objectives of the studies is discussed. Explanations of the mechanisms behind some frequent modes of early failure and ways to avoid them are suggested. it is shown theoretically, and partly confirmed by the analysis of unfortunately incomplete data from two paper mills over manly years, that accurate prediction of remaining bearing life requires (a) enough vibration measurements, (b) numerate records of operating conditions, (c) better discrimination between frequencies in the spectrum and (d) correlation of (b) and (c). This is because life prediction depends on precise knowledge about primary, harmonic and side band frequency amplitudes and their development over time, Much money could be saved because some policies-utilise as little as half of the bearing's potential life.

• 131.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Salford Univeristy.
A Conceptual Model for Fault Detection and Decision Making for Rolling Element Bearings in Paper Mills2001Inngår i: Journal of Quality in Maintenance Engineering, ISSN 1355-2511, E-ISSN 1758-7832, Vol. 7, nr 3, s. 192-206Artikkel i tidsskrift (Fagfellevurdert)

Rolling element bearing failures in paper mill machines are considered in relation to their critical role in the machine function. The use of expensive, sophisticated and highly automated equipment and machines and the intention to achieve higher quality products, longer machine life, higher machinery effectiveness and safer operating processes were the main driving force motivating efforts to improve maintenance concept during the last 50 years. In this paper, a conceptual model that integrates the available condition information, the deterministic models used in condition monitoring based upon mechanical theory and the probabilistic models used in the area of operational research is developed and its applicability is discussed. This models covers fault detection of a mechanical component such as a rolling element bearing, prediction of its vibration level in the near future, assessment of the probability of failure of a component over a finite period of time of interest.

• 132. Alonso-Saez, Laura
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för naturvetenskap, NV.
Leucine-to-carbon empirical conversion factor experiments: does bacterial community structure have an influence?2010Inngår i: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 12, nr 11, s. 2988-2997Artikkel i tidsskrift (Fagfellevurdert)

The suitability of applying empirical conversion factors (eCFs) to determine bacterial biomass production remains unclear because seawater cultures are usually overtaken by phylotypes that are not abundant in situ. While eCFs vary across environments, it has not been tested whether differences in eCFs are driven by changes in bacterial community composition or by in situ environmental conditions. We carried out seawater cultures throughout a year to analyse the correlation between eCFs and bacterial community structure, analysed by catalysed reporter deposition fluorescence in situ hybridization. Gammaproteobacteria usually dominated seawater cultures, but their abundance exhibited a wide range (25–73% of cell counts) and significantly increased with inorganic nutrient enrichment. Flavobacteria were less abundant but increased up to 40% of cells counts in winter seawater cultures, when in situ chlorophyll a was high. The correlations between eCFs and the abundance of the main broad phylogenetic groups (Gamma-, Alphaproteobacteria and Flavobacteria) were significant, albeit weak, while more specific groups (Alteromonadaceae and Rhodobacteraceae) were not significantly correlated. Our results show that the frequent development of the fast-growing group Alteromonadaceae in seawater cultures does not strongly drive the observed variations in eCFs. Rather, the results imply that environmental conditions and the growth of specific phylotypes interact to determine eCFs.

• 133. Alonso-Saéz, Laura
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för naturvetenskap, NV. Marine Biological Section, University of Copenhagen, 3000 Helsingør, Denmark .
Role for urea in nitrification by polar marine Archaea2012Inngår i: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 109, nr 44, s. 17989-17994Artikkel i tidsskrift (Fagfellevurdert)

Despite the high abundance of Archaea in the global ocean, their metabolism and biogeochemical roles remain largely unresolved. We investigated the population dynamics and metabolic activity of Thaumarchaeota in polar environments, where these microorganisms are particularly abundant and exhibit seasonal growth. Thaumarchaeota were more abundant in deep Arctic and Antarctic waters and grew throughout the winter at surface and deeper Arctic halocline waters. However, in situ single-cell activity measurements revealed a low activity of this group in the uptake of both leucine and bicarbonate (<5% Thaumarchaeota cells active), which is inconsistent with known heterotrophic and autotrophic thaumarchaeal lifestyles. These results suggested the existence of alternative sources of carbon and energy. Our analysis of an environmental metagenome from the Arctic winter revealed that Thaumarchaeota had pathways for ammonia oxidation and, unexpectedly, an abundance of genes involved in urea transport and degradation. Quantitative PCR analysis confirmed that most polar Thaumarchaeota had the potential to oxidize ammonia, and a large fraction of them had urease genes, enabling the use of urea to fuel nitrification. Thaumarchaeota from Arctic deep waters had a higher abundance of urease genes than those near the surface suggesting genetic differences between closely related archaeal populations. In situ measurements of urea uptake and concentration in Arctic waters showed that small-sized prokaryotes incorporated the carbon from urea, and the availability of urea was often higher than that of ammonium. Therefore, the degradation of urea may be a relevant pathway for Thaumarchaeota and other microorganisms exposed to the low-energy conditions of dark polar waters.

• 134.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
A Study Of Multipath Wave Propagation Using Nero2d and FFT2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave

In this report, the Fast Fourier Transform is described briefly. An implementation, inthe form of the Fortran code four1, is tested to verify the accuracy. A two-ray modelfor wave propagation above a flat earth is discussed. The case with AM modulation isimplemented in a Mathematica script. Calculations of the surface current density, withthe program NERO, are made to test the accuracy. The transient scattering from a PECcylinder is studied by means of the code run_nero that runs NERO repeatedly. From aspectrum calculated in this way, the impulse response is obtained by Fourier inversion.

• 135.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för naturvetenskap, NV.
Jämförelse mellan olika serologiska markörer för diagnostik av celiaki2010Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave

• 136.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för naturvetenskap, NV.
The Influence of Training on Preferences2010Inngår i: 7th International Conference on Natural Sciences andTechnologies for Waste and Wastewater Treatment,Remediation, Emissions Related to Climate, Environmentaland Economic Effects / [ed] Kaczala F et.al., Kalmar: Linnéuniversitetet , 2010, s. 676-683Konferansepaper (Annet vitenskapelig)

Any organisation or company that want to bring about a change in the process, procedures or internal organisation encounters the issue of training the staff. Training is commonly used to increase dedication in specific issues for example environmental issues, energy saving or enhancing the overall competence of the staff.

When working with environmental- or energy issues, the attitude of the employees is often considered one of the most important factors for the outcome.

In this paper two different studies are compared. In both studies training has been included as a background factor in a conjoint analysis study.

The first study concerns preferences for new materials, in this case advanced high strength steel. The respondents were asked to rank eight alternative steel containers and the results, (preferences) were compared to any previous training the individual respondent had.

The same procedure was taken in study number two where employees at a paper & pulp industry was asked to rank eight alternative processes with different environmental impacts. Also here the respondents were asked to state any previous training and the preferences was compared to previous training.

It has not been possible to show any significant connection between preferences in a specific issue and training in the same area. However, it would be interesting to use the method to measure the effect of training on preferences before and after a specific training session.

• 137.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för naturvetenskap, NV.
Luleå Tekniska Universitet.
Studies of preferences as an extra dimension in system studies2011Inngår i: World Renewable Energy Congress – Sweden, 8–13 May, 2011Linköping, Sweden: Volume 7, Industrial Energy Efficiency / [ed] Bahram Moshfegh, Linköping: Linköping University Electronic Press, 2011, s. 1732-1739Konferansepaper (Fagfellevurdert)

Industrial energy systems are complicated networks where changes in one process influence itsneighboring processes. The network complexity increases if production/use of bio fuel is introduced in anexisting system. Process integration can be a useful tool to study such systems and thus avoid sub optimization.However, changes in an industrial complex do not only influence the technical values of energy and materialefficiency. The social impact is also important and sometimes is comparable to that of technical factors.A process integration project has recently been carried out for a paper mill in northern Sweden with a side viewon future expansion with a bio refinery. An activity to study the social impacts were included through a Conjointanalysis, a stated preference method that combines statistics and interviewing technique.The results indicate that the participants are divided in four groups, the largest group focusing on a change in theprocess towards a bio refinery, the second largest focusing on the local environment. The third and fourth groupboth look at the local forestry, one group wanting to increase local forest production, and one rejecting anincrease.

• 138.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för naturvetenskap, NV.
Linnéuniversitetet, Fakultetsnämnden för hälsa, socialt arbete och beteendevetenskap, Institutionen för pedagogik, psykologi och idrottsvetenskap, PPI.
Miljöpreferenser och intressentanalyser ur ett miljöperspektiv2012Bok (Annet vitenskapelig)

Handbok som beskriver olika metoder för att ta reda på och analysera vilken inställning människor har till miljön.

En viktig knut att lösa för att kunna nå hållbar utveckling är varför människor beter sig på ett sätt trots att de egentligen vet att de borde bete sig på ett annat sätt. Människors beteende när det gäller miljöfrågor beror på många bakomliggande faktorer och för att nå den hållbara utvecklingen måste vi ge människor möjlighet att bli bekväma med beteenden som är bra för miljön. En viktig pusselbit för att nå dit är att veta hur individer och grupper ställer sig till olika strategiska miljöfrågor. Sådan kunskap kan användas för att anpassa informationskampanjer, skräddarsy utbildningspaket eller undanröja faktorer som riskerar att omintetgöra miljöarbetet.

Metoderna som beskrivs i den här handboken kan användas inom många fler områden än miljö, t.ex. inom marknadsföring eller för att identifiera kunskaps- eller informationsluckor bland den egna personalen eller för att undersöka attityder och synsätt hos olika intressentgrupper.

Handboken är framtagen inom forskningsprogrammet Stålkretsloppet och utgiven av Linnéuniversitetet i Kalmar med stöd från Jernkontoret och Mistra.

• 139.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
Testkrets för lavingenombrott för högspännings diod2012Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave

High frequency power converters are used for both consumer products and in industrial power plants. In some industrial applications, a very high output voltage can be obtained. A transformer gives a high voltage in the secondary, which is then rectified by diodes. High voltage diodes are important components in the rectifier to withstand tough work so that the transformer supplying the desired high voltage.

Alstom in Växjö is working with Air Pollution Control Equipment. They develop marketing and executing projects with advanced systems and products for smoke gas cleaning to power plants and the industry. The objective is to minimize the risk of negative impact on the environment. In Växjö, Alstom also has a large unit for service, which also consists of several local offices covering all parts of the country.

Another important facility in Växjö is Alstom's global research and development center, where new environmental solutions and technologies are tested in large scale format. The test center has a long tradition of environmental control systems, but during the past decade the center has been one important platform for the development of Alstom’s products for carbon particle separation (electrostatic filter). These electrostatic filters use diodes as the main component of a high frequency transformer. The diodes must be specially designed to withstand high voltages. The development of the Alstom invented a new type of power diode.  The idea is that the diode is withstand of 10kV in the reverse direction.

The goal of this work is based on building a facility to test the new diode and see how the diode works with high voltage in the reverse direction condition.

• 140.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Wind energy system reliability and maintainability, and operation and maintenance strategies2010Inngår i: Wind energy systems: optimising design and construction for safe and reliable operation, Cambridge: Woodhead Publishing Limited, 2010, nr 10, s. 303-328Kapittel i bok, del av antologi (Fagfellevurdert)

This chapter discusses the reliability, operation and maintenance strategies for wind power systems. It examines the role of systems engineering in optimising the aspects of a system relating to reliability, supportability and maintainability. It considers various maintenance approaches and the role of proper maintenance practices in providing a secure and reliable energy supply at the right cost. It discusses the importance of identifying and understanding the relevant cost factors associated with wind power systems, based on lifecycle costing and using relevant performance measures to help select a cost-effective maintenance approach. It then reviews some efforts aimed at improving the design, production, construction, operation and maintenance of wind power systems. Finally, some future trends are discussed in the areas of operation and maintenance of wind power systems.

• 141.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
A Differentiable Approach to Stochastic Differential Equations: the Smoluchowski Limit Revisited2012Doktoravhandling, med artikler (Annet vitenskapelig)

In this thesis we generalize results by Smoluchowski [43], Chandrasekhar[6], Kramers, and Nelson [30]. Their aim is to construct Brownian motion as a limit of stochastic processes with differentiable sample paths by exploiting a scaling limit which is a particular type of averaging studied by Papanicolao [35]. Their construction of Brownian motion differs from the one given by Einstein since it constitutes a dynamical theory of Brownian motion. Nelson sets off by studying scaled standard Ornstein-Uhlenbeck processes. Physically these describe classical point particles subject to a deterministic friction and an external random force of White Noise type, which models perpetuous collisions with surrounding(water) molecules. Nelson also studies the case when the particles are subject to an additional deterministic nonlinear force. The present thesis generalizes the work of Chandrasekhar in that it deals with finite dimensional α-stable Lévy processes with 0 < α < 2, and Fractional Brownian motion as driving noises and mathematical techniques like deterministic time change and a Girsanov theorem. We consider uniform convergence almost everywhere and in $L^2$-sense. In order to pursue the limit we multiply all vector fields in the cotangent space by the scaling parameter including the noise. For α-stable Lévy processes this correspondsto scaling the process in the tangent space, $v_{t}$, $t\geq 0$, according to $\beta v_{t}=v_{\beta^{\alpha}t}$. Sending β to infinity means sending time to infinity. In doing so the noise evolves with a different speed in time compared to the component processes. For α≠2, α-stable Lévy processes are of pure jump type, therefore the approximation by processes having continuous sample paths constitutes a valuable mathematical tool. α-stable Lévy processes exceed the class studied by Zhang [46]. In another publication related to this thesis we elaborate on including a mean-field term into the globally Lipschitz continuous nonlinear part of the drift while the noise is Brownian motion, whereas Narita [28] studied a linear dissipation containing a mean-field term. Also the classical McKean-Vlasov model is linear in the mean-field. In a result not included in this thesis the scaling result of Narita [29], which concerns another scaling limit of the tangent space process (velocity) towards a stationary distribution, is generalized to α-stable Lévy processes. The stationary distribution derived by Narita is related to the Boltzmann distribution. In the last part of this thesis we study Fractional Brownian motion with a focus on deriving a scaling limit of Smoluchowski-Kramers type. Since Fractional Brownian motion is no semimartingale the underlying theory of stochastic differential equations is rather involved. We choose to use a Girsanov theorem to approach the scaling limit since the exponent in the Girsanov denvsity does not contain the scaling parameter explicitly. We prove that the Girsanov theorem holds with a linear growth condition alone on the drift for 0 < H < 1, where H is the Hurst parameterof the Fractional Brownian motion.

• 142.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
Nelson-type Limits for α-Stable Lévy Processes2010Licentiatavhandling, med artikler (Annet vitenskapelig)

Brownian motion has met growing interest in mathematics, physics and particularly in finance since it was introduced in the beginning of the twentieth century. Stochastic processes generalizing Brownian motion have influenced many research fields theoretically and practically. Moreover, along with more refined techniques in measure theory and functional analysis more stochastic processes were constructed and studied. Lévy processes, with Brownian motionas a special case, have been of major interest in the recent decades. In addition, Lévy processes include a number of other important processes as special cases like Poisson processes and subordinators. They are also related to stable processes.

In this thesis we generalize a result by S. Chandrasekhar [2] and Edward Nelson who gave a detailed proof of this result in his book in 1967 [12]. In Nelson’s first result standard Ornstein-Uhlenbeck processes are studied. Physically this describes free particles performing a random and irregular movement in water caused by collisions with the water molecules. In a further step he introduces a nonlinear drift in the position variable, i.e. he studies the case when these particles are exposed to an external field of force in physical terms.

In this report, we aim to generalize the result of Edward Nelson to the case of α-stable Lévy processes. In other words we replace the driving noise of a standard Ornstein-Uhlenbeck process by an α-stable Lévy noise and introduce a scaling parameter uniformly in front of all vector fields in the cotangent space, even in front of the noise. This corresponds to time being sent to infinity. With Chandrasekhar’s and Nelson’s choice of the diffusion constant the stationary state of the velocity process (which is approached as time tends to infinity) is the Boltzmann distribution of statistical mechanics.The scaling limits we obtain in the absence and presence of a nonlinear drift term by using the scaling property of the characteristic functions and time change, can be extended to other types of processes rather than α-stable Lévy processes.

In future, we will consider to generalize this one dimensional result to Euclidean space of arbitrary finite dimension. A challenging task is to consider the geodesic flow on the cotangent bundle of a Riemannian manifold with scaled drift and scaled Lévy noise. Geometrically the Ornstein-Uhlenbeck process is defined on the tangent bundle of the real line and the driving Lévy noise is defined on the cotangent space.

• 143.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
Differentiable Approximation by Solutions of Newton Equations Driven by Fractional Brownian Motion.Manuskript (preprint) (Annet vitenskapelig)

We derive a Smoluchowski-Kramers type scaling limit for second order stochastic differential equations driven by Fractional Brownian motion.We show a Girsanov theorem for the solution processes with respect to corresponding Fractional Ornstein-Uhlenbeck processes which are Gaussian. This reveals existence of weak solutions as well as a weak scaling limit. Subsequently the results are strengthened.

• 144.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM. Department of Statistics, University of Warwick, CV4 7AL, UK.
Nelson-type Limit for a Particular Class of Lévy Processes2010Inngår i: AIP Conference Proceedings; 1232 / [ed] Andrei Yu. Khrennikov, AIP , 2010, Vol. 1232, s. 189-193Konferansepaper (Annet vitenskapelig)

Brownian motion has been constructed in different ways. Einstein was the most outstanding physicists involved in its construction. From a physical point of view a dynamical theory of Brownian motion was favorable. The Ornstein-Uhlenbeck process models such a dynamical theory and E. Nelson amongst others derived Brownian motion from Ornstein-Uhlenbeck theory via a scaling limit. In this paper we extend the scaling result to α-stable Lévy processes.

• 145.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM. Department of Statistics, Warwick University.
Smoluchowski-Kramers Limit for a System Subject to a Mean-Field DriftManuskript (preprint) (Annet vitenskapelig)

We establish a scaling limit for autonomous stochastic Newton equations, the solutions are often called nonlinear stochastic oscillators,where the nonlinear drift includes a mean field term of Mckean type and the driving noise is Gaussian. Uniform convergence in $L^{2}$ sense is achieved by applying $L^{p}$-type estimates and the Gronwall Theorem.The approximation is also called Smoluchowski-Kramers limit and is a particular averaging technique studied by Papanicolaou. It reveals an approximation of diffusions with a mean-field contribution in the drift by diffusions with differentiable trajectories.

• 146.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
Förberedelse till modernisering av styrsystem för produktion av processvatten2012Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave

På kraftvärmeverket Allöverket I Kristianstad produceras processvattnet i en anläggning som heter totalavsaltningen. I denna anläggning som består ut av två identiska linjer låter man det inkommande vattnet passera genom jonbytare för att byta ut de oönskade jonerna i vattnet emot mer önskade. Anledningen till att man gör detta är att de oönskade jonerna i vattnet ger beläggningar på turbinen. När jonbytarna blivit mättade så måste de återställas till sin ursprungliga form. Detta sker genom att det startas ett regenereringsprogram, som består av ett antal steg så som backspolning, kemikalieintag och fyra olika spolningar. Det finns gränsvärden för vilken ledningsförmåga samt vilken halt av kisel vattnet skall ha för att få levereras men det finns endast mätning av ledningsförmåga kopplat till styrsystemet vilket gör att man får styra anläggningen efter olika tider. Till styrsystemet är det kopplat ett antal centrifugalpumpar och magnetventiler samt mätutrustning för mätning av ledningsförmåga. I totalavsaltningen sitter det ett Siemens S5 styrsystem som styr anläggningen efter vattenmängd, ledningsförmåga och olika tider för sekvenserna. Alla de styrande funktionerna sitter på ett styrskåp ute i fabriken. Siemens systemet är gammalt och omodernt och skall därför bytas ut emot ett ABB 800xA system. Detta system används redan på operatörsstationerna i manöverrummet för att styra andra delar av fabriken. Med denna studie så har jag tagit fram en ny funktionsbeskrivning av totalavsaltningen. Funktionsbeskrivningen består ut av funktionsdiagram som beskriver hur programmet styr anläggningen idag. Till funktionsbeskrivningen har jag också gjort en ny teknisk beskrivning samt reviderat det processchema som finns över anläggningen för att all dokumentation skall hänga samman.

• 147.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
Frisörer och frisörlärares syn på gesällbrevsmomentens användbarhet2010Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
• 148.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
Underhåll och övervakning av distributionstransformatorer2012Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave

Följande projekt går i korthet ut på att avgöra om användning av kylsystemet i en transformatorstation är relevant, om det minimerar temperaturhöjningen orsakad av effektförlusterna som transformatorn avger. Arbetet ska resultera i förslag på val av transformatorer samt beskriva dess egenskaper. Vidare vill vi finna lösningar kring problemet med överhettning i transformatorstationerna och att de generella kraven såsom låg ljudnivå och tillräcklig ventilation (för att ta bort den värmeförlust som de inre komponenterna avger) skall uppfyllas.  För att kunna ge olika förslag på val av transformator i transformatorstationerna har vi på Holtab AB utfört olika beräkningar som visar skillnad för pris, kvalitet, livslängd och egenskaper (effektförluster, energiförluster).

• 149.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
online assignment submission2011Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave

The main goal of this thesis is to design and implement online assignment submission and provide an interface use for uploading test program (Nant script file) by instructors, who would be able to evaluate assignments automatically.

The system provides an interface for testing assignments such that they can be plugged in by the teachers.  This testing could invoke a compiler and make a test-run of the compiled code and check the result or test for plagiarism, existence of certain documents or simply check the file type (extension).

The most obvious advantage offered by online assignment submission is that it offers faster transmission of assignments than using traditional way by using online system. The interface use to invoke different testing program by teachers, So Save the time and cost for teachers by enabling them to put up a fast response for students as well as increasing the quality of the feedback provided to students.

Keywords: UML (Unified Modeling Language), Nant (Not Ant), OSS (online assignment Submission), Script file, DotNet2005.

• 150.
Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för naturvetenskap, NV.
Exposure models for contaminated soil: Examples from 3 countries2010Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave

Exposure assessments can be made for contaminated soil to get information about how the human health may be affected. They are used in many different countries and may differ from each other, either dramatically or minimal. This study was conducted to examine how these differences appear between three countries' exposure assessments. The countries chosen were Sweden, the Netherlands and the United States and the purpose was to see how the difference appears between the structure, parameters, thresholds, calculations, etc. to be abl e to discuss which of the models are perceived to give the best picture of reality. The discussion was focused on the Swedish assessment model. The results show that there are differences between models and that they sometimes refer to the fact that their model is based on other models. Many parameters used, such as body weight, are not justified and there are manyuncertainties associated with the use of these models. The sources they use to justify the parameters and their values are not always relevant and updated. Uncertainty always follows with these kinds of calculations, but some of the uncertain can be reduced, as shown in this study.

1234567 101 - 150 of 2878
Referera
Referensformat
• apa
• ieee
• modern-language-association-8th-edition
• vancouver
• Annet format
Fler format
Språk
• de-DE
• en-GB
• en-US
• fi-FI
• nn-NO
• nn-NB
• sv-SE
• Annet språk
Fler språk
Utmatningsformat
• html
• text
• asciidoc
• rtf