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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
301

Misturas de madeira de Eucalyptus grandis x Eucalyptus urophylla, Eucalyptus globulus e Pinus taeda para produção de celulose Kraft através do Processo Lo-Solids® / Mixtures of Eucalyptus grandis x Eucalyptus urophylla, Eucalyptus globulus and Pinus taeda wood chips for the production of kraft pulp through Lo-Solids® process

Ana Gabriela Monnerat Carvalho Bassa 01 February 2007 (has links)
Este estudo teve como objetivo verificar os efeitos de misturas de madeiras de Eucalyptus grandis x Eucalyptus urophylla, Eucalyptus globulus e Pinus taeda na eficiência do processo Lo-Solids® e características das polpas celulósicas visando a diferenciação das propriedades dos papéis resultantes. Foram avaliados os comportamentos das madeiras, quanto aos parâmetros: densidade básica, composição química, polpação Lo-solids®, características químicas das polpas celulósicas, características das fibras das polpas celulósicas e testes físicos. Os mesmos parâmetros foram avaliados nas misturas entre as espécies, realizadas da seguinte forma: Eucalyptus grandis x Eucalyptus urophylla e Pinus taeda nas proporções de 10 a 50% de Pinus taeda, Eucalyptus globulus e Pinus taeda nas proporções de 10 a 50% de Pinus taeda e Eucalyptus grandis x Eucalyptus urophylla e Eucalyptus globulus nas proporções de 10 a 50% de Eucalyptus globulus. Para as misturas entre os Eucalyptus e o Pinus taeda, o número kappa das polpas celulósicas aumentou gradativamente, conforme a proporção de Pinus taeda aumentava na mistura, sendo que os números kappa variaram entre 17,9 e 22,1. Para atingir os números kappa desejados no trabalho, foi necessário ajustar a carga alcalina (álcali efetivo entre 19,3 e 21,3 % expresso como NaOH) e o fator H (entre 970 a 1420). Os resultados das análises indicaram uma tendência de queda dos rendimentos bruto e depurado e da viscosidade da polpa celulósica, dos teores de ácidos hexenurônicos, da solubilidade em NaOH 5%, do número de fibras por grama, da drenabilidade e do índice de tração e estouro, com o aumento da participação de Pinus taeda nas misturas. Em contrapartida, foram observadas tendências de aumento dos teores de lignina total na polpa, do comprimento e da largura das fibras, do coarseness, do índice de rasgo e do consumo específico de madeira à medida que a participação de Pinus taeda aumenta nas misturas. Nas misturas entre o Eucalyptus grandis x Eucalyptus urophylla e o Eucalyptus globulus, os números kappa variaram entre 17,9 e 18,6 e foram observadas tendências de queda dos rendimentos bruto e depurado, da viscosidade da polpa celulósica, do teor de lignina total e do coarseness, com a adição de Eucalyptus globulus ao Eucalyptus grandis x Eucalyptus urophylla. Para os parâmetros solubilidade em NaOH 5%, número de fibras por grama, drenabilidade, índices de tração, alongamento e estouro foram verificadas tendências de aumento com o aumento da proporção de Eucalyptus globulus nas misturas. Com base nos resultados obtidos, a adição de até 10% de fibra de Pinus taeda aos Eucalyptus pode melhorar a qualidade da polpa para os parâmetros índice de rasgo e drenabilidade. Essas características permitem maiores velocidades de operação das máquinas secadoras de polpa celulósica e máquinas de papel e consequentemente conduzem a uma maior produção. Plantas produtoras que desejam a produção de um tipo de celulose diferenciada, com elevada resistência ao rasgo, incremento da produção, ou ainda a produção de papéis especiais, de baixa gramatura, devem considerar a adição de pequenas proporções de Pinus taeda aos Eucalyptus. / The objective of this study was to evaluate the possibility of cooking mixtures between the species Eucalyptus grandis x Eucalyptus urophylla, Eucalyptus globulus and Pinus taedafor the production of kraft pulp with specific characteristics. The three species were analyzed for their wood density, chemical composition, Lo-solids® pulping, the chemical characteristics of the pulp, characteristics of its fibers and physical tests. The same parameters were evaluated in the mixtures between the species that were made up as: Eucalyptus grandis x Eucalyptus urophylla and Pinus taeda in the proportion of 10 to 50% of Pinus taeda, Eucalyptus globulus and Pinus taeda in the proportion of 10 to 50% of Pinus taeda and Eucalyptus grandis x Eucalyptus urophylla and Eucalyptus globulus in the proportion of 10 to 50% of Eucalyptus globulus. For the mixtures between the Eucalyptus and the Pinus taeda, the pulp kappa numbers increased as the proportion of Pinus taeda increased in the pulps, varying from 17.9 to 22.1. In order to reach the target kappa number it was necessary to adjust the alkali charge applied (from 19.3 to 21.3 %NaOH as effective alkali) and the H factor (between 970 and 1420). The results indicated a downward trend in total yield and screened yield values, in pulp viscosity, in the hexenuronic acid content, in solubility in NaOH 5%, in the number of fibers per gram of pulp, in the drainability and strength and burst indices, with the increasing proportion of Pinus taeda in the pulps. As the proportion of Pinus taeda increased in the pulps an increase was noticed for the parameters total lignin content in the pulp, length and width of the fibers, coarseness and tear indices. In the mixtures between Eucalyptus grandis x Eucalyptus urophylla and Eucalyptus globulus the kappa number varied from 17.9 to 18.6. Eucalyptus grandis x Eucalyptus urophylla performed performed better in pulping as it needed a lower alkali charge and had a higher pulp yield and pulp viscosity. Hence, in the Eucalyptus mixtures a downward trend was noticed in the values for pulp yield and pulp viscosity with an increasing proportion of Eucalyptus globulus. Falls in total lignin content in the pulp and in the coarseness were also observed as the proportion of Eucalyptus globulus increased. For the parameters solubility in NaOH 5%, number of fibers per gram of pulp, drainability, strength and burst indices an increase was noticed as the proportion of Eucalyptus globulus increased in the pulps. In conclusion, the addition of up to 10% of Pinus taeda to Eucalyptus can increase pulp quality for the tear index and drainability parameters, making pulp and paper mills faster at drying pulp, or speeding up the paper machines, resulting in higher productivity. These mixtures also allow the production of tailor-made pulp and special papers.
302

Hastighetsbaserad styrketräning : En strukturerad komparativ litteraturstudie om träningseffekterna mellan olika metoder av hastighetsbaserad styrketräning och dess förhållande till traditionell procentbaserad styrketräning / Velocity based training : A structured comparative literature study regarding the training effects of different velocity based training methods and their relationship to traditional percentage-based strength training

Dahlgren, Ida, Strandgren, Mathias January 2021 (has links)
Introduktion: Hastighetsbaserad styrketräning är en metod där rörelsehastighet används för att styra träning, samt monitorera träningsintensitet och volym. Metoden har vuxit fram som ett komplement till traditionellt procentbaserad styrketräning. Syfte: Syftet med litteraturstudien var att undersöka effekterna mellan olika metoder av hastighetsbaserad styrketräning och dess förhållande till traditionell procentbaserad styrketräning. Metod: En strukturerad litteratursökning genomfördes i de vetenskapliga databaserna PubMed och SPORTDiscus med de primära sökorden; velocity-based training, percentage based training och training effect. En ytterligare sökning genomfördes i referenslistorna bland de artiklar som uppfyllde inklusionskriterierna. Resultat: Litteraturstudien visade att hastighetsbaserad styrketräning medförde liknande styrkeökningar som traditionell procentbaserad styrketräning. Hastighetsbaserad styrketräning medförde större ökningar i hopphöjd jämfört med traditionell procentbaserad styrketräning. Ingen av interventionerna medförde träningseffekter på sprintförmåga. Konklusion: Hastighetsbaserad styrketräning verkar vara lika effektivt för att utveckla maximal styrka men effektivare för att utveckla hoppförmåga jämfört med traditionellt procentbaserad styrketräning. Hastighetsbaserad styrketräning med lägre procentuell hastighetsförlust verkar vara fördelaktigt för att utveckla hoppförmåga medan högre procentuell hastighetsförlust verkar vara fördelaktigt för att utveckla muskelhypertrofi. / Introduction: Velocity based training refers to a method where movement velocity is used to regulate strength training and monitor training intensity and volume. In addition, velocity based training could be considered as a complementary method to traditional percentage based training. Purpose: The aim of the literature review was to investigate the effects of different velocity based training methods and their relationship to traditional percentage based training. Method: A structured literature search was conducted in the scientific databases PubMed and SPORTDiscus with the following search terms; velocity-based training, percentage based training and training effect. A further search was conducted in the reference list among articles that met the inclusion criteria. Results: The literature review shows that velocity based training leads to similar gains in maximal strength as traditional percentage based training. However, velocity based training leads to greater gains in jump height compared to traditional percentage based training. Sprint ability showed no clear outcome following any of the interventions. Conclusion: Velocity based training seems to be just as efficient in developing maximal strength but more efficient in developing explosive strength such as jump height compared to traditional percentage based training. In addition, velocity based training with lower velocity loss thresholds may be more beneficial to improve jump height, whilst higher velocity loss threshold may be more beneficial to develop muscle hypertrophy.
303

Vergleichende Untersuchungen zu KWK-Systemen im Leistungssegment bis 30 kW elektrischer Leistung

Werner, Claudia 17 December 2004 (has links)
Interessante Optionen in der dezentralen Energieversorgung ergeben sich mit dem Einsatz von erdgasbetriebenen Gas-Otto-Motor-, Mikrogasturbinen-, Stirlingmotor- und PEMFC-Modulen. In dem Zusammenhang ist zu beachten, dass die Nutzungsmöglichkeiten dieser KWK-Systeme auch durch die elektrischen und thermischen Bedarfswerte und -strukturen der zu versorgenden Objekte bestimmt werden. Der Schwerpunkt dieser Arbeit ist, neben einer experimentellen und theoretischen Untersuchung ausgewählter KWK-Module, die vergleichende Bewertung von KWK-Anwendungen in der Hausenergieversorgung. Am Beispiel der Energieversorgung von Modell-Siedlungen nach VDI 2067-7 wird der stationäre Betrieb der untersuchten KWK-Module im bi- und polyvalenten Einsatz nachgebildet und bilanziert. Zur Bewertung der KWK-Konzepte erfolgt ein Vergleich zu einer konventionellen Energieversorgungsstrategie mit getrennter Bereitstellung elektrischer und thermischer Energie. Als Indikatoren zur Beurteilung der dezentralen Energieversorgungsvarianten dienen definierte energetische, ökologische und ökonomische Faktoren. Im Rahmen von Simulationsanalysen wird die Bedeutung der Integrations- und Einsatzweise der KWK-Module untersucht. Ein Variantenvergleich der Energieversorgungsstrategien verdeutlicht, welche Einsatzmöglichkeiten der KWK-Module für die untersuchte Struktur der Hausenergieversorgung beim gegenwärtigen Stand der Technik zweckmäßig sind.
304

Thermally insulating carbon foams from carbonized kraft lignin / Värmeisolerande kolskum från karboniserat kraftlignin

Hernodh Svantesson, Isabelle January 2021 (has links)
Kolmaterial, såsom kolfibrer och kolskum, används som värmeisolatorer i applikationer vid höga temperaturer. För närvarande härleds dessa material från fossilbaserade källor, vilket tyder på ett behov av att hitta alternativa kandidater baserade på förnybara källor. Detta examensarbete undersökte möjligheten att använda kraftlignin som ett förnyelsebart startmaterial för framställning av kolskum med värmeisoleringsegenskaper. Två kraftligniner av barrträd med olika molekylvikter och ett kraftlignin av lövträd användes. De tre kraftligninerna karboniserades vid 1000°C efter att ha blandats i olika förhållanden och kombinationer (formuleringen av råmaterialet). Formuleringen av råmaterialet påverkade densiteten och porositeten hos de erhållna materialen, vilket i sin tur ledde till skillnader i kompressionsstyrkan och värmeledningsförmågan hos de erhållna kolskummen. Kolskummen hade olika värmeledningsförmåga (0,11-0,35 W/mK), porositet (80,55-97,53%) och densitet (0,08-0,42 g/cm3). För skummet med den högsta densiteten uppskattades krossstyrkan till cirka 10,03 MPa vilket är jämförbart med kommersiellt använda kolskum för högtemperaturisolerande applikationer. Kolskummens värmeledningsförmåga var inom omfånget för kommersiellt använda kolskum för högtemperaturapplikationer. Detta arbete visar möjligheten att tillverka kolskum från 100% kraftlignin som har liknande egenskaper som kommersiellt tillgängliga termiska isoleringsmaterial för högtemperaturapplikationer. / Carbon materials, such as carbon fibres and carbon foams, are used as thermal insulators in high-temperature applications. At present, these materials are derived from fossil-based sources, which suggests a need of finding alternatives candidates based on renewables. This thesis work investigated the possibility of using kraft lignin as a renewable starting material for the preparation of carbon foams with thermal insulation properties. Two softwood kraft lignins with different molecular weights and a hardwood kraft lignin were used. The three kraft lignins were carbonized at 1000°C after being mixed in different ratios and combinations (precursor formulation). The precursor formulation affected the density and porosity of the obtained materials, which in turn led to differences in compression strength and thermal conductivity of the carbon foams derived. The obtained carbon foams had different thermal conductivities (0.11-0.35 W/mK), porosity (80.55-97.53%) and density (0.08-0.42 g/cm3). For the foam with the highest density, the crushing strength was estimated to approximately 10.03 MPa which is comparable to commercially used carbon foams for high-temperature insulating applications. The thermal conductivity of the prepared carbon foams was in the range of commercially used carbon foams for high-temperature applications. This work demonstrates the possibility of preparing carbon foams from 100% kraft lignin which has properties similar of commercially available insulating materials for high-temperature applications.
305

Washing efficiency in the pulp mill : An evaluation of the washing efficiency in SCA Munksund's pulp mill / Tvätteffektivitet i massabruket - En utvärdering av tvätteffektiviteten i SCA Munksundsmassabruk

Malmberg, Malin January 2023 (has links)
Munksunds pappersbruk är ett integrerat massa- och pappersbruk som består av två fiberlinjer, en barr- och en lövlinje där båda kokarna är kontinuerliga med efterföljande tvättsteg. En kartering av COD (eng. Chemical Oxygen Demand) och natrium utfördes för båda linjerna för att utvärdera tvätteffektiviteten. COD anger hur mycket syre som krävs för att bryta ned det kvarvarande organiska materialet och natrium används som en indikator på tvättförlusten av kokkemikalierna. Karteringen utfördes genom att analysera in- och utgående flöden vid varje tvättsteg, exklusive kokarna. En förenklad metod användes, där tre flöden analyserades och den fjärde beräknades genom flödes- och massbalanser. Modellen som användes för att beskriva tvätteffektiviteten för respektive utrustning var tvättutbytet Y, som erhölls genom en massbalans. Studien visade att halten COD och Natrium minskar mest från början för respektive linje och når ett gränsvärde runt 8,2 kg COD/adt och 6,6 kg Na/adt för barrlinjen, respektive 8,5 kg COD/adt och 4,8 kg Na/adt för lövlinjen, där ytterligare substans inte kan tvättas bort. Båda linjerna tvättar likvärt med avseende på COD, men lövlinjen tvättar bättre med avseende på natrium. I det sista tvättsteget hade båda fiberlinjerna eliminerat 98% av den inkommande COD-mängden med massan från kokarna. Vidare hade barrlinjen eliminerat 86% och lövlinjen 93% med avseende på natrium i det sista tvättsteget. Utvärderingen av de olika tvättutrustningarna visade att DD-filtret i lövlinjen var effektivast både med avseende på COD och natrium, följt av PO-pressen. På barrlinjen var filter 1 mest effektivt med avseende på COD och natrium. / A mapping of COD (Chemical oxygen demand) and sodium will be done to evaluate the different washing steps. COD describe the amount of oxygen needed to dissolve the organic matter left in the pulp and sodium is used as an indicator of the washing loss of the cooking chemicals. The in- and outgoing streams of the washing steps was analyzed to examine the efficiency. A simplified method was applied where three streams were analyzed and the fourth was calculated through flow-and mass balances. The model used to describe the wash efficiency in this study was the wash yield, which can be obtained by mass balances. The study showed that the content of COD and sodium decreased most in the beginning and reaches a limit value of 8,2 kg COD/adt and 6,6 kg Na/adt in the softwood pulp line and 8,5 kg COD/adt and 4,8 kg Na/adt in the soft wood pulp line, where no more content could be removed. Both pulp lines washed efficient with aspect of COD, but the hardwood pulp line washed more efficient in the aspect of natrium compared to the softwood pulp line. In the last washing step, both pulp lines had removed 98% of the ingoing COD from the digester. With aspect to natrium the softwood pulp line had removed 86% and the hardwood pulp line 93% in the last washing step. The evaluation of the different washing equipment showed that the DD-filter in the hardwood pulp line was the most efficient with aspect of both COD and Sodium, followed by the PO-press. In the softwood pulp line, filter 2 was the most efficient regarding both COD and Sodium. The flow- and mass balances turned out to be complicated at some of the washing steps, especially around the Q1-press in the hardwood pulp line and press 1-3 and filter 2 in the softwood pulp line. The reason for this could be that different functional chemicals are added before the Q1-press, which was not considered in this study, additional causes could be unidentified flows that affect the balances. The study was limited to only analyze three streams and calculate the fourth, an analyze of all the streams would give a more accurate result. However, the study provides a good overview of the wash efficiency in the pulp mill.
306

Compassion Energy: Att finna kraft till att vårda - ur ett sjuksköterskeperspektiv

Carlsson, Matilda, Johansson, Hilda January 2024 (has links)
Bakgrund: God vård kännetecknades av medlidande. Sjuksköterskors yrke innebar möten med både glädje och sorg. Flertalet faktorer kunde leda till att sjuksköterskor drabbades av compassion fatigue. Patienters välbefinnande främjades av sjuksköterskors medlidande. Syfte: Beskriva hur sjuksköterskor finner kraft till att vårda. Metod: En allmän litteraturöversikt genomfördes. Tolv artiklar valdes, varav nio kvalitativa och tre kvantitativa. Resultat: Närvarande chefer och kollegor var en viktig faktor för att sjuksköterskor fann kraft till att vårda. Det var viktigt för sjuksköterskor att få chans till kompetensutveckling och möta utmaningar på arbetet. Arbetserfarenhet visade sig ha en positiv påverkan på hur sjuksköterskor fann kraft till att vårda. Många sjuksköterskor upplevde ett kall och en inneboende vilja att vårda som en bidragande faktor som ökade kraften till att vårda. Det var viktigt med återhämtning samt att värna om sig själv för att sjuksköterskor skulle behålla kraften till att vårda. Slutsats: Genom en arbetsplats med närvarande och förstående chefer där kunskap och samarbete fungerade bra främjades sjuksköterskors kompetensutveckling. Detta i kombination med inre vilja att vårda, arbetserfarenhet och återhämtning bidrog till kraft att vårda. Genom att sjuksköterskor hade kraft till att vårda kunde en vård präglad av medlidande ges. / Background: Good care should be recognized as compassion. The nursing profession involved encounters with both joy and sorrow. Many factors could lead nurses to experience compassion fatigue. Patients’ well-being was enchanted by nurses’ compassion. Aim: To describe how nurses find strength to provide care. Method: A general literature review was performed. Twelve articles were chosen, nine qualitative and three quantitative. Result: Present supervisors and colleagues were important factors for nurses’ strength to care. It was important for nurses to get the opportunity for knowledge and competence development and to meet challenges at work. Work experience was found to have a positive influence on how nurses found strength to care. Many nurses experienced a vocation and an inherent will to care as a contributive factor that increased the strength to care. It was important with self-care and recovery for the nurses to keep the strength to care. Conclusion: Trough a workplace with present and understanding supervisors and where knowledge and collegial cooperation worked well, nurses’ competence development was promoted. This in combination with inherent will to care, work experience and recovery contributed to the strength to care. Because nurses had the strength to care, care characterized by compassion could be given.
307

Hårdare utsläppskrav för medelstora förbränningsanläggningar : En utredning om MCP-direktivets relevans, innebörd och konsekvenser för Mälarenergi och dess anläggningar.

Jansson, Andreas January 2016 (has links)
EU har beslutat om ett nytt direktiv som innebär hårdare krav för mellanstora förbränningsanläggningar. Detta direktiv innebär hårdare utsläppskrav och när dessa nya gränser skall efterföljas 2025 eller 2030 är Mälarenergi ett företag som kommer att drabbas. Detta arbete har gått ut på att ta reda på vad detta direktiv kommer att få för konsekvenser för Mälarenergis 24 stycken spetslastpannor. Arbetet har gått ut på att sammanställa befintliga underlag för att kunna besvara frågan om vad direktivet kommer att få för inverkan. Direktivet behandlar stoft, NOx och SOx och där mätningar tidigare har genomförts har de granskats. Utredningen har kunnat visa på att av dessa 24 pannor är det 2 pannor som ej kommer klara gränsvärdena för stoft. På dessa två pannor har ytterligare mätningar genomförts och resultatet har verifierats. Dessutom genomfördes en gasanalys av ett Fourier transform infrared spectroscopy av en panna samt en energibalansberäkning. Det finns olika metoder för att minska stoften på dessa pannor men de varierar i pris. Exempel på detta är att installera elektrofilter eller slangfilter, men kostnaden uppgår till över 800 000kr i investeringskostnader. Ett alternativ är ett additiv som heter Kaolin, där undersökningar har visat att till en kostnad av ca 45000 kr per år torde stofthalten kunna minskas till under gränsvärdena. En energibalansberäkningen har genomförts och visar på att pelletspannan i Kungsör har en verkningsgrad på 91% vilket stämmer överrens med vad leverantören anger. / This thesis work was initiated because of the EUs new MCP-directive that puts pressure on plants for heat and power production with an maximum input effect from 1 to 50 MW. Mälarenergi is one of the companies that are going to feel the pressure of this new directive. When the directive becomes Swedish law and the new limits are set to be followed, in 2025 or 2030, the allowed emissions for NOx, SOx and dust will be a lot stricter than they are today. This thesis has studied all the 24 different peak-load-boilers that the company has and tried to figure out which of these boiler will be having problem with the new directive. Information about the different plants has been gathered and summarized, previous measurements checked and where more information was needed, own measurements have been conducted. The conclusion is that two boiler will not fulfill the demands in regards of dust emissions. These results has been checked using own measurements of dust and also analyzing the gas using an Fourier transform infrared spectroscopy. The costs for improving the dust cleaning has been summarized and it starts at 800 000 SEK for a textile filter or even more for an electrofilter. There is a possibility to add Kaolin to the fuel at an expense of 45 000kr per year. However this method has never been tried in large scale.
308

Operation dependent costs of non-optimal hydropower production : Effects on the operational pattern of the Small Lule River

Lännevall, Joel January 2016 (has links)
In the present electrical market there is an increasing penetration of intermittent energy sources. Several studies have examined its effect on the planning of hydropower operation and the conclusion is that an increasing intermittent production is likely to result in a more variable hydropower operation, utilising a wider span of operational set points. The wear of a hydropower unit is generally at a minimum when operated close to best efficiency and increases when operating at higher or lower set points. This study introduces a method to calculate an operation dependent cost (ODC) function for an arbitrary hydropower unit or unit combination based on vibration measurements and operational data. The method is tested in a case study where an ODC is implemented in Akkats, located in the Small Lule River in order to evaluate its effect on operational pattern, profitability and balancing contribution. The results show that the implemented ODC mainly affects Akkats. For an increasing ODC, Akkats is operated closer to the best point of efficiency and the operational pattern gets less variable and the effect gets more apparent the lower the spot price. Akkats ability to follow the spot price is reduced, decreasing the earning per produced energy with a few percent­ages. Akkats balancing contribution decreases significantly more, due to a less variable operational pattern. The study compares the reduced ODC to the reduced spot income and concludes that the wear cost in Akkats has to be above 1,21 €/MWh in order to be economically feasible to include in the planning. The operational pattern for the simulated river is close to unchanged at highest price hours but during lower price hours an increasing ODC results in an increased production, due to an increasing mean flow and changed operational pattern in Akkats. More production during low prices hours results in a decreasing profitability for all plants along the river. The balancing contribution is close to unchanged in all plants except Akkats, since the production still follows the same pattern.
309

On the Interrelation Between Kraft Cooking Conditions and Pulp Composition

Gustavsson, Catrin January 2006 (has links)
In the early 1990’s, a lot of work was focused on extending the kraft cook to a low lignin content (low kappa number). The driving force was the need to further reduce the environmental impact of the bleaching, as less delignification work would be needed there. However, the delignification during the residual phase of a kraft cook is very slow and, due to its poor selectivity, it is a limiting factor for the lignin removal. If the amount of lignin reacting according to the residual phase could be reduced, it would be possible to improve the selectivity of the kraft cook. In the work described in this thesis, special attention has been given to the activation energy of the slowly reacting residual phase of a kraft cook on softwood raw material and to the influence of different cooking parameters on the amount of the residual phase lignin. The activation energy of the residual phase delignification of the kraft cook was shown to be higher than that of the bulk phase delignification. In order to decrease the amount of residual phase lignin, it was essential to have a high concentration of hydrogen sulphide ions when cooking with a low hydroxide concentration. It was also important to avoid a high sodium ion concentration when cooking with low hydroxide and low hydrogen sulphide ion concentrations. Furthermore, it was demonstrated that dissolved wood components had a positive effect on the delignification rate in the bulk phase of a kraft cook. The influence of different cooking parameters in the extended softwood kraft process on the bleachability (i.e. the ease with which the pulps can be bleached to a target brightness) of the manufactured pulp was also investigated. If variations in bleachability were seen, an attempt would also be made to find chemical reasons to explain the differences. It was difficult to establish clear relationships between the chemical structures of the residual lignin and the bleachability of the pulp. However, it was seen that the higher the content of β-aryl ether structures in the residual lignin after cooking, the better was the QPQP*-bleachability. In the middle/end of the 1990’s, the focus moved from extended cooking to efficient utilisation of the wood raw material, e.g. by interrupting the kraft cook at higher kappa number levels and choosing appropriate cooking conditions to maximise the cooking yield. A high cooking yield often leads to a somewhat higher hexenuronic acid (HexA) content of the pulp at a given kappa number. Therefore additional attention was devoted to how the HexA content and carbohydrate composition were affected, e.g. by a set of cooking parameters. Performing these studies it was also important to investigate the effects of a low HexA (after cooking) strategy on such vital factors as the cooking yield, the bleachability and the yellowing characteristics of the pulp obtained. It proved to be difficult to significantly reduce the HexA content in a kraft pulp by altering the cooking conditions for both softwood and the hardwood Eucalyptus Globulus. A reduction in HexA content can be achieved by extending the cook to lower kappa numbers, or by using a high hydroxide concentration, a low hydrogen sulphide concentration or a high sodium ion concentration. However, neither of these strategies is attractive for industrial implementation since they would result in an extensive loss of yield, viscosity and strength. / <p>QC 20100825</p>
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Röda skynken : om hur sättet vi pratar om elever påverkar sättet vi pratar med elever / Red rags : how the manner in which we talk about pupils effects the manner in which we talk with pupils

Hedgrund, Jesper, Westberg, Lotta January 2017 (has links)
Vår tanke med att skriva en essä är att reflektera över oss själva i vår roll som fritidslärare. Vi har varsin egenupplevd berättelse där vi båda forskar i bägges berättelser parallellt i essän. Syftet är att undersöka hur sättet vi pratar om elever påverkar sättet vi pratar med elever och om detta då även påverkar hur vi pratar om och med kollegor. Vi har en föreställning om att en negativ samtalskultur om elever skapar en negativ bild av elever, vilket i sin tur skapar negativa elever som leder till en negativ verksamhet. Undersökningens temaområden är språk, ansvar och reflektionen som verktyg. Vi lyfter upp hur språket skapar och formar bilder, uppfattningar och innebörder som påverkar hur vi ser på det vi benämnt. Vi tar upp metaforens betydelse, fördomens positiva sida och hur kulturen kring positivt och negativt kan påverka våra handlingar. Ansvaret vi fritidslärare ständigt har, ser vi som en viktig del i den värld vi är med och skapar. Många av våra val kräver vårt ansvarstagande. Vi kan inte skylla på någon annan. Vi alla har ansvaret. Hur vi gör påverkar, oavsett hur vi gör. Hela essän tar upp och problematiserar våra tankar genom reflektionen som verktyg. Reflektion anser vi ger oss bredare syn, insikter och förståelse av hur vi tillsammans kommer vidare i vår utveckling som fritidslärare. / Our intention with this essay is to reflect on our role as leisure-time pedagogues. Our research has its starting points in two separate but similar stories from our workplaces. The purpose of this research is to investigate how the manner in which we talk about pupils effects the manner in which we talk with pupils. We believe a negative culture of talking about pupils creates a negative picture of pupils. This creates negatively minded pupils which leads to a negative work environment. The theme of this essay contains concepts such as speech, responsibility and reflection as a tool. We show how speech manufactures images, views and meanings of things which effects how we perceive them. We write about the use and abuse of metaphor, the negative side but also the neglected positive side of prejudice as well as the negative aspects of a positive conversation-culture and the positive aspects of a negative conversation-culture. We see the constant responsibility we as leisure-time pedagogues have as a crucial part in the world we are a part of and at the same time create. We can not blame anyone else for our actions. We are all accountable. What we do effects, always. The essay has an undertone of the urge and need for reflection. We feel reflection gives a wider view and greater understanding of how we can progress in our development as leisure-time pedagogues.

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