• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 159
  • 155
  • Tagged with
  • 315
  • 295
  • 291
  • 38
  • 30
  • 27
  • 27
  • 27
  • 24
  • 18
  • 18
  • 16
  • 16
  • 15
  • 14
  • 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.
31

Ekologisk status på Stäholmsbäcken : Enligt EU:s vattendirektiv

Wiman, Helena, Vesa, Minna January 2009 (has links)
Detta examensarbete skrivs på uppdrag av länsstyrelsen i Västmanland, som vill ha en ekologisk statusbedömning av Stäholmsbäcken. En ekologisk statusbedömning enligt EU:s vattendirektiv utförs i tre delar, biologiska, kemiska och hydromorfologiska kvalitetsfaktorer. Den biologiska delen bestod i att på en provplats ta fem prover på bottenfaunan med hjälp av handhåvsmetoden. Djuren artbestämdes och därefter gjordes indexberäkningarna ASPT, DJ-index och MISA. De biologiska kvalitetsfaktorerna fick ett otillfredsställande resultat. DJ-indexets resultat var sämst och fick därmed styra, one out – all out. Normalt går man inte vidare till nästa steg, som är de kemiska kvalitetsfaktorer, utan ser på vilka förbättringsåtgärder som ska genomföras. I detta examensarbete undersöktes även de båda andra kvalitetsfaktorerna. Den kemiska delen bestod av bestämning av näringsämnen i vattendraget och den hydromorfologiska delen bestod av bland annat identifiering av vandringshinder, vägövergångar, diken, markanvändningen i närmiljön och i delavrinningsområdet. De kemiska och de hydromorfologiska testerna styrkte resultatet i och med att det också blev otillfredsställande. Förklaringen till detta är att både närmiljön och avrinningsområdet är starkt påverkat av jordbruket. För att förbättra Stäholmsbäckens status bör skyddszoner och/eller en våtmark anläggas.
32

Jämförande livscykelinventering

Selamis, Henrik January 2010 (has links)
No description available.
33

Solceller för flerbostadshus : En teknisk rapport för HFAB

Ivarsson, Johanna January 2011 (has links)
This examination paper is about the potential for Solar cells on apartment blocks. The technology with using solar cells for manufacturing electricity, has been on the market for a while, but recently the new installations of solar cells has increased. Solar cells are suited for placements on buildings but are expensive to obtain. The municipal real-estate company is interested in solar cells but wants to know more before they invest in the technology. This report contains an account of the solar cell and a guide to how a connection to the grid is accomplished. The report even contains suggestions of where the solar cells can be located and an estimate of annual production of electricity on a building. The outcome of the report is that there are good prerequisites for solar cells on apartment blocks and it shows the real- estate company as an environmental-thinking corporation.
34

Effects of hydraulic load on nitrate removal in surface-flow constructed wetlands

Khan, Imran January 2011 (has links)
Abstract Constructed wetlands had been widely used as economical and environment friendly treatment systems for agriculture runoff in southwest Sweden to limit the transport of nutrients to Kattegat, thereby aiding in the effort of abating eutrophication. The extensive use and acceptance of wetlands as treatment systems had been an incentive to develop performance models. Even recent studies showed that first order models are inadequate to guide the design of constructed wetlands, these are still commonly used. The main assumption of such models is tested here, which states that the removal rate of pollutant(s) is proportional to concentration in a constructed wetland. For this purpose experimental wetlands in Plonninge near Halmstad (southwest of Sweden) were selected and divided into two groups (9 each). They were fed with different hydraulic loads achieving 4 and 8 days residence times. The data obtained from the analysis of total nitrogen and nitrate were tested with first order equations and found that these models are sufficient to describe the nitrate removal in nitrate rich experimental wetlands. Key words: constructed wetlands, hydraulic load, first order kinetic models, eutrophication, nitrogen removal / Abstrakt Anlagda våtmarker har i stor utsträckning använts så ekonomisk och miljövänlig behandling av system för jordbruk avrinning i sydvästra Sverige för att begränsa transporten av näringsämnen till Kattegatt och därmed hjälpa till i ansträngningarna på att avta övergödning. Den omfattande användningen och acceptansen av våtmarker som behandling systemen hade ett incitament att utveckla prestanda modeller. Även senare studier visade att första order modellerna är otillräckliga för att vägleda designen av konstgjorda våtmarker är dessa fortfarande vanliga. Det viktigaste antagandet om sådana modeller testas här, som säger att avverkning av föroreningar (s) är proportionell mot koncentrationen i en konstruerad våtmark. För detta ändamål experimentella våtmarker i Plönninge utanför Halmstad (sydväst om Sverige) valdes ut och delades i två grupper (9 vardera). De matades med olika hydrauliska belastningar uppnå 4 och 8 dagar uppehållstid. De data som erhållits från analysen av totalkväve och nitrat testades med första ordningens ekvationer och fann att dessa modeller är tillräckliga för att beskriva nitrat bort i nitrat rika experimentella våtmarker. Nyckelord: anlagda våtmarker, hydraulisk belastning, första ordningens kinetiska modeller, övergödning, kväverening
35

Miljöeffekter vid ändrad ytbehandling på ITT Water & Wastewater

Beckeman, Klara January 2008 (has links)
ITT Water & Wastewater (före detta ITT Flygt) tittar på att eventuellt genomföra en förbättring av ytbehandlingen av deras pumpar för att eliminera de rostangrepp pumparna utsätts för idag. Examensarbetets uppgift är här att analysera och beskriva miljöeffekterna av de nya ytbehandlingsmetoderna som företaget undersöker.Målet med studien är att få fram ett underlag och en rekommendation om vilken ytbehandlingsmetod företaget bör välja ur miljösynpunkt.De olika metoder som studerats är: • Järnfosfatering + ED-lackering • Zinkmanganfosfatering + ED-lackering • Oxsilan + ED-lackering Dessa metoder har jämförts med nollalternativet, vilket innebär att samma metod som tillämpas idag fortsätter att användas.Miljöeffekterna som studerats för de olika metoderna är: • utsläpp till luft och vatten • avfall • energi Av de tre nya metoderna samt nollalternativet är Oxsilan följt av ED-lackering det alternativ som ger minst påverkan på miljön. Metoden har inga utsläpp av flyktiga organiska ämnen till luft, inget farligt avfall bildas och det avfall som ändå bildas är litet. Metoden har även lägre energiåtgång än de andra studerade metoderna. 2008:Nr 2 Teknik / ITT Water & Wastewater will perhaps change the surface treatment method of the pumps to improve the elimination of the rust attacks the pumps get affected by today. The task for this degree project is to analyze and describe the effects of the environment caused by the new surface treatment methods the company investigates.The aim with the project is to develop groundwork and a recommendation on which of the surface treatment ITT Water & Wastewater should choose from an environmental point of view.The methods that have been studied are: • Iron phosphatising + electro coating • Zinc manganese phosphatising + electro coating • Oxsilan + electro coating These methods have been compared to the no-action alternative, which means today’s process continuing unchanged.The studied effects on the environment of the different methods are: • Emission to air and water • Waste • Energy From the three new methods and the no-action alternative, Oxsilan followed by electro coating is the alternative that causes least effects of the environment. The method has no emissions of VOC to air, it doesn´t cause any hazardous waste and the waste created is a small amount. The energy consumption is also less than for the other studied methods.
36

Technique and human perception of intermittent air velocity variation

Wigö, Hans January 2005 (has links)
<p>Objectives. The main objective of the present thesis was to evolve a controlled intermittent velocity field and to examine the impact of this type of dynamic indoor climate on human’s psychology and physiology. The prediction was that intermittent velocity variation could provide occupants with the desired cooling without causing draught and that this intermittent change of the indoor climate would influence peoples’ affect and cognitive performance.</p><p>Methods. All experiments were performed in a classroom-like environment where groups of subjects were exposed to a temperature increase and step changes in air velocity. The changes or intermittent variations in air velocity consisted of elevated speed during five minutes, which were repeated three times. To reduce the influence of individual thermal preferences all measures were collected twice and the statistical analyses were based on the change scores in these measures.</p><p>Results. The obtained results showed that, intermittent velocity variation may provide occupants with the desired cooling without causing draught. Subjects exposed to velocity variations were significantly less affected by the temperature rise in the room, compared to the control group. Moreover, the method reduced the expected increase of occupants who perceived the temperature condition as uncomfortable. The findings concerning air movements demonstrate that very few perceived the condition as draughty, after being exposed to the three high velocity pulses.</p><p>The results concerning affect showed a significant effect on high activation, in the temperature range 21 - 24<sup>o</sup>C when the velocity variations made the subjects rate the temperature as slightly lowered over time, they kept their level of activation. In the higher temperature interval, 25 - 27<sup>o</sup>C, unactivated unpleasantness increased and activated pleasantness decreased significantly more in subjects in the constant velocity condition than it did for subjects in the velocity variation condition. In sum, all results concerning affect, the significant ones and tendencies point in the same direction. Subjects exposed to velocity variation report changes, over time, indicating higher activation and more positive feelings.</p><p>No differences in cognitive performances were shown between the air velocity conditions. However, a tendency to a significant result (p = 0.10) in an attention task was shown, indicating that subjects in the velocity variation condition increased their speed in a short-term memory search, compared to subjects in the constant velocity condition.</p><p>In the temperature range 21- 24<sup>o</sup>C, where the perception of the room temperature was measured at 0, 5 and 10 minutes respectively after the last high velocity period, the difference in MTV scores between the two groups, did decrease over time. Ten minutes after the last pulse the difference in MTV scores between the two groups was not significant. This suggests that the high velocity period should be repeated every10 to 15 minutes to keep the expected rise in subjects who judged the thermal conditions as uncomfortable down.</p><p>The skin temperature was not affected neither by the rise in ambient temperature (from 21 to 24<sup>o</sup>C over 80 minutes) nor the periods (3 x 5 minutes) of high velocity. A consequence of this result is that the human temperature regulation system permitted an increased heat loss during the high velocity pulse, and hence a reduction of the body’s internal stored heat. For uncovered body parts the increase in heat loss was 20 % during the high velocity pulse. Summarised over the whole exposure time the three pulses produced a total energy loss that was only 2 % higher compared to constant low velocity.</p>
37

Technique and human perception of intermittent air velocity variation

Wigö, Hans January 2005 (has links)
Objectives. The main objective of the present thesis was to evolve a controlled intermittent velocity field and to examine the impact of this type of dynamic indoor climate on human’s psychology and physiology. The prediction was that intermittent velocity variation could provide occupants with the desired cooling without causing draught and that this intermittent change of the indoor climate would influence peoples’ affect and cognitive performance. Methods. All experiments were performed in a classroom-like environment where groups of subjects were exposed to a temperature increase and step changes in air velocity. The changes or intermittent variations in air velocity consisted of elevated speed during five minutes, which were repeated three times. To reduce the influence of individual thermal preferences all measures were collected twice and the statistical analyses were based on the change scores in these measures. Results. The obtained results showed that, intermittent velocity variation may provide occupants with the desired cooling without causing draught. Subjects exposed to velocity variations were significantly less affected by the temperature rise in the room, compared to the control group. Moreover, the method reduced the expected increase of occupants who perceived the temperature condition as uncomfortable. The findings concerning air movements demonstrate that very few perceived the condition as draughty, after being exposed to the three high velocity pulses. The results concerning affect showed a significant effect on high activation, in the temperature range 21 - 24oC when the velocity variations made the subjects rate the temperature as slightly lowered over time, they kept their level of activation. In the higher temperature interval, 25 - 27oC, unactivated unpleasantness increased and activated pleasantness decreased significantly more in subjects in the constant velocity condition than it did for subjects in the velocity variation condition. In sum, all results concerning affect, the significant ones and tendencies point in the same direction. Subjects exposed to velocity variation report changes, over time, indicating higher activation and more positive feelings. No differences in cognitive performances were shown between the air velocity conditions. However, a tendency to a significant result (p = 0.10) in an attention task was shown, indicating that subjects in the velocity variation condition increased their speed in a short-term memory search, compared to subjects in the constant velocity condition. In the temperature range 21- 24oC, where the perception of the room temperature was measured at 0, 5 and 10 minutes respectively after the last high velocity period, the difference in MTV scores between the two groups, did decrease over time. Ten minutes after the last pulse the difference in MTV scores between the two groups was not significant. This suggests that the high velocity period should be repeated every10 to 15 minutes to keep the expected rise in subjects who judged the thermal conditions as uncomfortable down. The skin temperature was not affected neither by the rise in ambient temperature (from 21 to 24oC over 80 minutes) nor the periods (3 x 5 minutes) of high velocity. A consequence of this result is that the human temperature regulation system permitted an increased heat loss during the high velocity pulse, and hence a reduction of the body’s internal stored heat. For uncovered body parts the increase in heat loss was 20 % during the high velocity pulse. Summarised over the whole exposure time the three pulses produced a total energy loss that was only 2 % higher compared to constant low velocity. / QC 20111221
38

Miljöeffekter vid ändrad ytbehandling på ITT Water & Wastewater

Beckeman, Klara January 2008 (has links)
<p>ITT Water & Wastewater (före detta ITT Flygt) tittar på att eventuellt genomföra en förbättring av ytbehandlingen av deras pumpar för att eliminera de rostangrepp pumparna utsätts för idag. Examensarbetets uppgift är här att analysera och beskriva miljöeffekterna av de nya ytbehandlingsmetoderna som företaget undersöker.Målet med studien är att få fram ett underlag och en rekommendation om vilken ytbehandlingsmetod företaget bör välja ur miljösynpunkt.De olika metoder som studerats är:</p><p>• Järnfosfatering + ED-lackering</p><p>• Zinkmanganfosfatering + ED-lackering</p><p>• Oxsilan + ED-lackering</p><p>Dessa metoder har jämförts med nollalternativet, vilket innebär att samma metod som tillämpas idag fortsätter att användas.Miljöeffekterna som studerats för de olika metoderna är:</p><p>• utsläpp till luft och vatten</p><p>• avfall</p><p>• energi</p><p>Av de tre nya metoderna samt nollalternativet är Oxsilan följt av ED-lackering det alternativ som ger minst påverkan på miljön. Metoden har inga utsläpp av flyktiga organiska ämnen till luft, inget farligt avfall bildas och det avfall som ändå bildas är litet. Metoden har även lägre energiåtgång än de andra studerade metoderna.</p><p>2008:Nr 2 Teknik</p> / <p>ITT Water & Wastewater will perhaps change the surface treatment method of the pumps to improve the elimination of the rust attacks the pumps get affected by today. The task for this degree project is to analyze and describe the effects of the environment caused by the new surface treatment methods the company investigates.The aim with the project is to develop groundwork and a recommendation on which of the surface treatment ITT Water & Wastewater should choose from an environmental point of view.The methods that have been studied are:</p><p>• Iron phosphatising + electro coating</p><p>• Zinc manganese phosphatising + electro coating</p><p>• Oxsilan + electro coating</p><p>These methods have been compared to the no-action alternative, which means today’s process continuing unchanged.The studied effects on the environment of the different methods are:</p><p>• Emission to air and water</p><p>• Waste</p><p>• Energy</p><p>From the three new methods and the no-action alternative, Oxsilan followed by electro coating is the alternative that causes least effects of the environment. The method has no emissions of VOC to air, it doesn´t cause any hazardous waste and the waste created is a small amount. The energy consumption is also less than for the other studied methods.</p>
39

Combined solar and pellet heating systems : Study of energy use and CO-emissions

Fiedler, Frank January 2006 (has links)
<p>In this study 4 solar and pellet heating systems have been studied with the help of annual dynamic simulations. Two of the systems comprised a pellet stove and two systems were solar combisystems; one with a store integrated pellet burner, the other with a separate pellet boiler.</p><p>The aim was to evaluate their thermal performance and their CO-emissions. The systems have been modelled based on lab measurements of the single system components. The used models allow a detailed study of the dynamic behaviour of the systems.</p><p>The stove systems have the least primary energy consumption provided the auxiliary electricity is taken into account with a conversion factor of 100%. If the auxiliary electricity is taken into account with a conversion of 40% and/or the systems are placed in the heated area the combisystems need less or a similar amount of primary energy.</p><p>Modulating combustion power reduces the number of starts and stops and for most pellet units this reduces the total CO emissions. The obtained annual CO emissions are higher than the values obtained from the standard test methods. It was shown that the average emissions under realistic annual conditions were greater than the limit values of two Eco-labels.</p><p>The system performance can be significantly improved by a proper control of the pellet heater and by sizing the pellet heater according to the size of the peak space heating demand.</p><p>Based on these findings from the simulations two prototypes of a combined solar and pellet heating system has been designed, built and tested; one for the lab and one that has been installed in a demonstration house. The system is very compact and is suitable for detached houses with no heating room or little space for a heating room.</p>
40

Amalgam and Mercury in the Dental Setting and the Efficiency of Amalgam Separators

Jacobsson-Hunt, Ulla January 2007 (has links)
<p>Mercury is the only metal that is in liquid form at room temperature and it has over the years been used in various combinations to extract gold, in measuring devices, medicaments, paper industry, batteries and fluorescent lights as well as in dentistry as dental amalgam. Dental amalgam is a mixture of 50 % mercury and 50% of an alloy consisting of silver, tin, copper and zink particles and has been used in dentistry for many years. The environmental effect of mercury release into the sewer from dental practices and clinics, and the inability of the wastewater treatment plants to remove it from the sludge lead to the introduction of amalgam separators in Sweden in 1980. The ISO standard 11143 regulates the efficacy of the amalgam separators, which should be at a 95% level, but is based on a laboratory test rather than a clinical evaluation.</p><p>This study looks at the available amalgam separators in use in four areas of Sweden, Uppsala, Stockholm, Östergötland and Skåne and compares their clinical efficiency. The clinical efficiency ranged between 75 to 95%, with most units below the 90% mark. In Östergötland a new improved separator is being tried, the Capere unit, which is based on finely ground pine bark treated with a chelator sensitive to all metals and used in conjunction with a cotton filter and a regular amalgam separator. This was shown to be superior to the other separators, with a 99, 9% removal of even the smallest amalgam particles and ionic mercury from the wastewater before leaving the clinic. Otherwise, combining more than one amalgam separator of the brands available on the Swedish market did not improve the efficiency of them.</p>

Page generated in 0.0268 seconds