Freshwater ecosystems are some of the most threatened on the planet. Efforts to conserve, restore, or otherwise manage large rivers and the services they provide are hindered by limited understanding of the functional dynamics of these systems. This shortcoming is especially evident with regard to trophic structure and energy flow. In this study I use natural abundances of carbon and nitrogen isotopes to examine patterns of energy flow and food-chain length of large-river food webs characterized by different landscape-scale hydrologic features. Ten locations along an approximately 500 km stretch of the Upper Paraná River Basin, Brazil, provided the setting for this work. Carbon derived from C3 plants and phytoplankton were the dominant energy sources across all webs, but relative contributions differed among landscape types (low-gradient river, high-gradient river, river stretches downstream of reservoirs, and reservoirs). Increases in food chain length corresponded with higher relative importance of phytoplankton derived carbon, likely due to size-structured effects of the phytoplankton-zooplankton-secondary consumer trophic link. River impoundment corresponded with decreased ecological and economic efficiency of fisheries production, an important ecosystem service provided by many tropical rivers.

The aim of this project is to make an energy flow survey of Ljusdal’s municipality. The reason for the energy flow survey is to discover possibilities to utilize and refine the energy resources locally, and use the information from this survey as a base for further discussions about the energy situation in Ljusdal’s municipality. As it is today the raw material is transported to other municipalities for processing and then bought back, e.g. biomass is transported to other municipalities where they make pellets which are sold back to consumers in Ljusdal’s municipality. A local upgrading of the raw material will probably create more job opportunities in the municipality and it will probably also lead to a higher profit than just selling the raw material. The target groups for this study are the local (and regional) politicians and entrepreneurs, primarily in Ljusdal but also in other similar municipalities. Mainly bioenergy is handled in this thesis. Other energy sources e.g. hydroelectricity is handled just briefly, flows and use of electricity are described briefly for different parts of the municipality and types of consumers. To perform the energy flow survey, information about now used, and possible future, energy resources was collected in order to find out the energy quantities used per year, for different users, and the energy flows. Unexploited energy sources, and energy sources that have the potential to be increased, like forest and arable land was also included. Investigations about the wind potential are also carried out. The energy use of the consumers, divided into energy carriers, is mapped. Larger companies and institutions, particularly those with energy related business are asked about their future plans. Energy suppliers are also asked where they buy and sell energy in order to make an energy flow survey. The energy needs for different types of buildings were also considered in this energy flow survey. In order to do that, information about the numbers of buildings in the municipality and also the average energy usage, for different types of buildings e.g. apartments and single family houses, are collected from different sources. The flows of bioenergy across the municipality border are also investigated in order to be able to see where it comes from and where it goes. Nearby municipalities, projects nearby Ljusdal’s municipality, that may have an impact in the field of energy in Ljusdal’s municipality are also briefly handled. The energy flows, in and out of the municipality, were put into maps from the municipality’s Geographic Information System (GIS) in order to get a good overview of the energy flow, supply and use. Based on the gathered information, project ideas are suggested, and calculations are done to determine if biogas production, from household waste and sludge, could be a better option than today’s waste management where the waste is being transported to a nearby municipality for incineration, a service that Ljusdal’s municipality also have to pay for. The results from the calculations show that the total amount of energy that could be extracted from the annual produced biogas would reach about 1.9 GWh. The biogas could e.g.be used as a fuel in the district heating plants in the municipality. By using locally produced products a decreased import of energy carriers, e.g. light fuel oil, would be expected. The conclusions that could be drawn from this study are that a lot of biomass is produced in Ljusdal’s municipality, which is mainly exported in the form as raw material. Large amounts of hydroelectricity is produced in Ljusdal’s municipality, about 60% of the electricity is being exported. Wind mappings show that there are some areas of national interest for electricity production through wind power in the municipality. A deregulated European electricity market will probably lead to an increased electricity price, this in combination with the green certificate would lead to a more profitable electricity production through wind power and areas that are not of national interest at present could probably be of national interest in the future. There are also a large potential to increase the amount of biomass from the forestry remainings. Another potential energy source is the arable land where it probably would be possible to grow e.g. hemp for an energy conversion purpose. In Ljusdal’s municipality, there are possibilities in the field of energy which no one takes advantage of at present. / Syftet med detta projektarbete är att kartlägga energiflödet inom-, samt till och från Ljusdals kommun, i första hand bioenergi men även andra energiformer som t.ex. elektricitet behandlas översiktligt. Anledningen till denna energiflödesanalys är att upptäcka möjligheter att bearbeta och förädla biomassan lokalt. I dagens läge lämnar stora mängder av råmaterial kommunen för förädling utanför kommunens gränser, detta leder till förlorade arbetstillfällen i kommunen. Ett exempel på detta är att råmaterial i form av sågspån transporteras från Ljusdals kommun till en annan kommun där sågspånen förädlas till pellets som i sin tur säljs tillbaka till konsumenter i Ljusdals kommun. En lokal förädling av biomassan skulle förmodligen kunna leda till nya arbetstillfällen inom kommunens gränser samt en högre avkastning än att bara sälja råmaterialet obearbetat. Målgruppen för denna studie är lokala och regionala politiker och entreprenörer, i första hand i Ljusdals kommun, men också i liknande glesbygdskommuner med stora arealer skog och andra former av biobränslen. För att genomföra denna energiflödesanalys samlades information, angående i nuläget använda samt framtida energikällor, in med avsikt att uppskatta de kvantiteter, och olika typer av energi som omvandlas och används årligen av olika typer av konsumenter. Denna information tillhandahölls av bl.a. statistiska central byrån – SCB, kommunens energirådgivare, energibolag, större energikrävande företag samt bostads företag. Antalet enfamiljshus och flerfamiljs hus i kommunen samt antalet boende i kommunen kartlades för att kunna beräkna, enligt schabloner, de energimängder som förbrukades årligen i bostadssektorn. Även transport- och industrisektorn undersöktes med avseende på dess energianvändning. Flödet av biomassa i kommunen samt över dess gränser analyserades med avsikt på att klargöra vilka mängder som lämnar, respektive stannar kvar inom kommunen. Även projekt i närliggande kommuner analyserades översiktligt för att se om de hade någon nämnbar inverkan på Ljusdals kommuns energiproduktion1 och energianvändning. Slutsatserna som kan dras från denna analys är i korthet att stora mängder av biomassa produceras inom Ljusdals kommuns gränser och transporteras bort i form av råmaterial, som förädlas utanför kommunens gränser. Ett sätt att eventuellt skapa fler jobbtillfällen samt se till att en större del av vinsten från biomassan stannar kvar inom kommunens gränser är att lokalt bearbeta biomassan. Inom kommunen produceras också en stor del vattenkraft där ungefär 60 % exporteras och resterande används inom kommunen, möjlighet till utökad elproduktion bör vara möjlig genom byggnation av vindkraftsparker eftersom det finns områden som är av nationellt intresse för vindkraftsproduktion. Något mer som talar för en ökad lönsamhet inom elproduktion via vindkraft är den avreglerade Europeiska elmarknaden som förmodligen kommer att leda till ökade elpriser, en annan faktor är elcertifikaten, som erhålls för varje MWh producerad med förnyelsebara källor t.ex. vindkraft eller biomassa eldat kraftvärmeverk. Biogas motsvarande ungefär 2 GWh årligen bör också kunna utvinnas ur sopor, gödsel från bondgårdar och energigrödor. Detta kräver dock investeringar i rötningsanläggningar och ytterligare utredningar angående detta föreslås göras. En markant ökad produktion av biobränsle från skogsbruket bör också vara möjlig. Den globala ökningen av invånare i kombination med en strävan efter minskad produktion av fossila bränslen resulterar i en ökad efterfrågan av förnyelsebara bränslen, denna ökade efterfrågan leder i sin tur till ett ökat pris för dessa bränslen. Dessutom har ett antal länder skrivit på Kyoto avtalet, vilket innebär i korthet att dessa länder måste minska sina koldioxidutsläpp. Dessa faktorer kan tolkas som indikationer på att det kommer att bli en ökad användning av biobränslen. Problemet med detta scenario är att, aven i ett nationellt perspektiv, mängden av tillgänglig biomassa är begränsad om den skulle utgöra baslasten för energiproduktionen. Detta faktum öppnar nya möjligheter för kommuner med en låg befolkningstäthet i kombination med stora skogsarealer. Ljusdals kommun är en glest befolkad kommun med ungefärligen 19 400 invånare, det finns 10 100 bostäder i kommunen varav 3 700 är lägenheter och resterande är enfamiljshus. Den totala arealen av kommunen uppgår till 5 640 km2, befolkningstätheten uppgår till fyra invånare per kvadrat kilometer. Arealen per capita i kommunen är väldigt hög, vilket innebär att det finns stora mängder biomassa tillgänglig då stordelen av kommunen består av skog. Syftet med denna analys är att få en bättre översikt över dagens situation inom detta område. En bättre översikt skulle kunna hjälpa politiker och entreprenörer att se nya möjligheter inom detta område, vilket skulle kunna innebära fler arbetstillfällen inom kommunen.

Bythotrephes longimanus is an invasive, macroinvertebrate from Eurasia that was introduced into the Great Lakes region in the mid 1980s. Bythotrephes introductions into lake ecosystems have resulted in substantial changes in zooplankton communities, including declines in species richness, abundance, biomass and production. Changes in zooplankton communities may alter the quantity and quality of prey to other predators such as cisco (Coregonus artedii), a pelagic forage fish. Here, I conduct a current day comparison of cisco populations to determine if prey consumption by cisco differs in the presence of Bythotrephes, and whether changes in diet result in energetic consequences (changes in growth and condition) for cisco. Effects of Bythotrephes on native zooplankton communities have resulted in substantial changes in the variety and proportion biomass of zooplankton and macroinvertebrate prey types in cisco stomachs, which have in turn modified growth of cisco. Cisco taken from invaded lakes achieve greater total lengths but changes in condition were not detected. This effect may be driven by improved growth in the second and subsequent growing seasons, suggesting that growth consequences for young fish (that do not feed on Bythotrephes) are different than for older individuals. Length-at-structure age data indicate that by the end of the first growing season (age 1) cisco achieve comparable total body lengths in invaded and reference lakes, suggesting that food consumption by young cisco remains unchanged by Bythotrephes. Alternatively, young cisco forage may be reduced in the presence of Bythotrephes, resulting in decreased survival and similar growth among individuals that survive to age 1. In contrast, despite changes in the zooplankton community; growth of older fish (≥ age 2) was enhanced in lakes that have Bythotrephes. Improved growth among older cisco (≥ age 2) in invaded lakes may be related to the presence of a newly attainable, high energy prey source (Bythotrephes). Alternatively, enhanced growth may be explained by lower competition due to reduced recruitment of young cisco (≤ age 1) in invaded lakes. Increased knowledge regarding the effects of Bythotrephes on growth of cisco is important in furthering our understanding of its impact on lake ecosystems. / Thesis (Master, Biology) -- Queen's University, 2010-04-28 22:46:07.756

Acid mine drainage (AMD) is a significant environmental issue worldwide, which often causes severe contamination and marked species losses in receiving streams. However, little is known about how this stress alters food webs and ecosystem function. I conducted a literature review, which revealed that AMD-impacted streams generally had depauperate benthic communities dominated by a few tolerant species and impaired ecosystem processes. Next, using survey and experimental-based approaches, I investigated food web structure and energy flow in these highly stressed streams, which typically have low pH (< 3), high concentrations of dissolved metals (Al, Fe), and substrata coated with metal hydroxide precipitates, on the South Island, New Zealand. Inputs of AMD caused substantial loss of consumers and reduced the overall number of links between species generating small and simplified food webs, with few invertebrates and no fish. Comparative analysis of food webs from a survey of 20 streams with either anthropogenic or natural sources of acidity and metals, indicated that anthropogenic sources had a stronger negative effect on food web properties (size, food chain length, number of links); an effect driven primarily by differences in consumer diversity and diet. However, the presence of fewer trophic levels and reduced trophic diversity (detected using isotopic metrics), were common structural attributes in AMD-impacted webs along a pH gradient, regardless of impact level. Furthermore, complementary dietary analyses of consumer gut contents and stable isotope signatures (δ13C and 15N) confirmed that primary consumers fed generally on basal resources and that there were few predatory interactions, which reflected low densities of small-bodied chironomids. This suggests that food quantity was unlikely to limit primary consumers but that reduced prey availability may be an additional stressor for predators. In these radically re-structured food webs, trophic bottlenecks were generated at the primary consumer level and energy flow to higher consumers was disrupted. However, streams still retained some limited function, including slow leaf litter breakdown, which provided detrital resources and supported the small food webs. Overall, my findings have furthered our understanding of these highly stressed stream ecosystems by providing new insights into interactions among species and trophic levels that structure food webs and enable function.

This mixed methods status study examined 32 fourth grade students’ conceptual understandings of energy flow through ecosystems prior to instruction and 40 eighth grade students’ conceptual understandings of the same topic after five years of daily standards-based instruction in science. Specific ecological concepts assessed related to: 1) roles of organisms; 2) the sun as the original energy source for most ecosystems; and 3) interdependency of organisms. Fourth and eighth grade students were assessed using the same three-tiered forced-choice instrument, with accompanying tasks for students to defend their forced-choice selections and rate their level of confidence in making the selections. The instrument was developed for the study by a team of researchers and was based on similar tasks presented in the research literature. Distractor options were embedded in each assessment task using common non-scientific ideas also reported in the research literature. Cronbach’s alpha values at or greater than .992 for each task indicated inter-rater consistency of task answers, and Rasch analysis was employed to establish the reliability of the instrument. Qualitative and quantitative analyses were employed to assess the data. Constant comparative methods were employed to analyze students’ written responses, which were coded and grouped into emerging themes. These themes were further developed to characterize students’ conceptual understandings. Student open responses also were scored and coded by a team of researchers using a rubric to identify level of scientific understanding. Quantitative analyses included Rasch analysis used to normalize survey data. Independent samples t-tests were then employed to compare students’ forced-choice responses to their written responses and to the confidence ratings, as well as to compare fourth and eighth grade students’ responses. Findings indicated that eighth grade students generally outperformed the fourth grade on both the forced-choice and written responses, but both groups demonstrated conceptual difficulties in all three topics assessed. Thus, results from the current study support the assertion that students’ understanding of concepts related to energy flow in ecosystems is not at the expected level according to national science education standards and frameworks. Conceptual difficulties identified in the study are discussed along with implications and curricular recommendations.

No description available.

A major challenge to cold regions hydrology and northern water resources management lies in predicting runoff dynamically in the context of warming-induced changes to the rates and patterns of ground thaw and drainage. Meeting this challenge requires new knowledge of the mechanisms and rates of ground thaw and their implications to water drainage and storage patterns and processes. The study carries out to evaluate the concept of energy-based runoff in the perspective of ground heat flux, soil thaw and liquid moisture content, tortuosity of snow-free area, preferential flow and discharge of the hillslope. Based on field measurements, coupled energy and water flow is simulated in the Area of Interest (AOI) with a half-hour time interval by the distributed hydrological model, GEOtop. In the field, the saturated hydraulic conductivity varies exponentially between the superficial organic layer and the underlying mineral layer. In the simulation, the parameters of the soil physical properties are input by fourteen uneven layers below the ground surface. Starting from the initially frozen state, the process of soil thaw is simulated with dynamic variables such as soil liquid moisture and ice content, hydraulic conductivity, thermal conductivity and heat capacity. The simulated frost table depths are validated by 44-point measurements and the simulation of point soil temperature is also compared to data measured in an excavated soil pit. As a result, the frost table topography is dominated by both the snow-free pattern and the energy fluxes on the ground surface. The rate and magnitude of runoff derived from snow drift and the ice content of frozen soil is greatly influenced by the frost table topography. According to the simulation, the frost table depth is closely regressed with the ground surface temperature by a power function. As soil thawing progresses, ground heat flux reduces gradually and the rate of soil thaw becomes small when the frost table descends. Along with the snow-free area expanding, the average soil moisture of the AOI increases prior to that time when the average frost table is less than 25 cm deep. The snow-free patches expand heterogeneously in the AOI, which causes the spatial and temporal variation of hydraulic conductivity due to the non-uniform frost table depth. According to the simulation, the transit time of the flow through the AOI decreases to the shortest span on May 13 with the average frost table of 10 cm. Before this date, the time lag between snowmelt percolation and slope runoff is about 8-10 hours; while after this date, the time lag is no more than 5 hours. The pattern of the preferential flow in the AOI highly depends on the frost table topography. When the snow-free patches are widely scattered and the average frost table is between 0 and 10 cm, the preferential flow paths are inhibited. With soil thaw progresses, the preferential flow paths are prominent with the largest single contributing area occurring when the average frost table is between 10 cm to 15 cm. When the average frost table reaches 25 cm, the importance of preferential flow is not apparent, and matrix flow prevails.

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Efficient and reliable energy generation capability is vital to any country's economic growth. Many strategic, tactical and operational decisions take place along the energy supply chain. Shortcomings in South Africa's electricity production industry have led to the development of an energy ow simulator. The energy ow simulator is claimed to incorporate all significant factors involved in the energy ow process from primary energy to end-use consumption. The energy ow simulator thus provides a decision support system for electric utility planners. The original aim of this study was to develop a global optimisation model and integrate it into the existing energy ow simulator. After gaining an understanding of the architecture of the energy ow simulator and scrutinising a large number of variables, it was concluded that global optimisation was infeasible. The energy ow simulator is made up of four modules and is operated on a module-by-module basis, with inputs and outputs owing between modules. One of the modules, namely the primary energy module, lends itself well to optimisation. The primary energy module simulates coal stockpile levels through Monte Carlo simulation. Classic inventory management policies were adapted to fit the structure of the primary energy module, which is treated as a black box. The coal stockpile management policies that are introduced provide a prescriptive means to deal with the stochastic nature of the coal stockpiles. As the planning horizon continuously changes and the entire energy ow simulator has to be re-run, an efficient algorithm is required to optimise stockpile management policies. Optimisation is achieved through the rapidly converging cross-entropy method. By integrating the simulation and optimisation model, a prescriptive capability is added to the primary energy module. Furthermore, this study shows that coal stockpile management policies can be improved. An integrated solution is developed by nesting the primary energy module within the optimisation model. Scalability is incorporated into the optimisation model through a coding approach that automatically adjusts to an everchanging planning horizon as well as the commission and decommission of power stations. As this study is the first of several research projects to come, it paves the way for future research on the energy ow simulator by proposing future areas of investigation. / AFRIKAANSE OPSOMMING: Effektiewe en betroubare energie-opwekkingsvermoë is van kardinale belang in enige land se ekonomiese groei. Baie strategiese, taktiese en operasionele besluite word deurgaans in die energie-verskaffingsketting geneem. Tekortkominge in Suid-Afrika se elektrisiteitsopwekkingsindustrie het tot die ontwikkeling van 'n energie-vloei-simuleerder gelei. Die energie-vloei-simuleerder vervat na bewering al die belangrike faktore wat op die energie-vloei-proses betrekking het van primêre energieverbruik tot eindgebruik. Die energie-vloei-simuleerder verskaf dus 'n ondersteuningstelsel aan elektrisiteitsdiensbeplanners vir die neem van besluite. Die oorspronklike doel van hierdie studie was om 'n globale optimeringsmodel te ontwikkel en te integreer in die bestaande energie-vloeisimuleerder. Na 'n begrip aangaande die argitektuur van die energievloei- simuleerder gevorm is en 'n groot aantal veranderlikes ondersoek is, is die slotsom bereik dat globale optimering nie lewensvatbaar is nie. Die energie-vloei-simuleerder bestaan uit vier eenhede en werk op 'n eenheid-tot-eenheid basis met insette en uitsette wat tussen eenhede vloei. Een van die eenhede, naamlik die primêre energiemodel, leen dit goed tot optimering. Die primêre energiemodel boots steenkoolreserwevlakke deur Monte Carlo-simulering na. Tradisionele voorraadbestuursbeleide is aangepas om die primêre energiemodel se struktuur wat as 'n swartboks hanteer word, te pas. Die steenkoolreserwebestuursbeleide wat ingestel is, verskaf 'n voorgeskrewe middel om met die stogastiese aard van die steenkoolreserwes te werk. Aangesien die beplanningshorison deurgaans verander en die hele energie-vloei-simulering weer met die energie-vloei-simuleerder uitgevoer moet word, word 'n effektiewe algoritme benodig om die re-serwebestuursbeleide te optimeer. Optimering word bereik deur die vinnige konvergerende kruis-entropie-metode. 'n Geïntegreerde oplossing is ontwikkel deur die primêre energiemodel en die optimering funksie saam te voeg. Skalering word ingesluit in die optimeringsmodel deur 'n koderingsbenadering wat outomaties aanpas tot 'n altyd-veranderende beplanningshorison asook die ingebruikneem en uitgebruikstel van kragstasies. Aangesien hierdie studie die eerste van verskeie navorsingsprojekte is, baan dit die weg vir toekomstige navorsing oor die energie-vloeisimuleerder deur ondersoekareas vir die toekoms voor te stel.

I samband med EU-direktivs mål att reducera energikonsumtionen med 20 % fram till år 2020 har kraven i Boverkets byggregler skärpts för energianvändningen i Sverige. Dessa krav håller den totala energiförbrukningen i sektorn bostäder och service på jämn nivå trots att det sker en ständig ökning av antalet bostäder.   Syftet med detta arbete är att undersöka om det finns möjlighet till att minimera energiförluster i infästningen mellan inspända balkonger och bjälklaget. Detta utfördes för att ge samtliga aktörer inom byggbranschen en uppfattning om hur stor inverkan en optimering av de oftast försummade detaljerna i ett projekt har.   Glasfiberförstärkta polymerplaster (GFRP) isolerar ca 120 gånger bättre än konstruktionsstål och klarar samtidigt av att ta upp dragkrafter i en betongkonstruktion om de formas som armeringsstänger. Från ett urval har flera GFRP produkter granskats där ComBAR har valts att studeras och kontrolleras som en ersättningsprodukt för stålarmering i balkonginfästningar. ComBAR uppfyller samtliga konstruktionskrav för att fungera som armering i betong och har egenskaper som är att föredra framför stål vilket även gör den användbar i flera andra konstruktionsdelar i en byggnad eller anläggning.   Utförandet av beräkningar och analyser är indelat i tre delar som är analys av byggstatik för att bestämma den erforderlig armering i balkonginfästningen, simulering av energiflöde mellan balkongen och bjälklaget samt ekonomisk kalkyl för att uppskatta avkastningstiden. I den ekonomiska kalkylen knyts resultaten ihop från analysen av byggstatik och beräkning av energiflödet för att sedan kunna avgöra om en investering är lönsam.   Ur resultaten från analysen av byggstatik som består av handberäkningar och simuleringar i beräkningsprogrammen Concrete Beam och FEM-Design kan vi dra slutsatsen att det behövs en armeringsstång mindre av ComBAR än stål för att bära upp balkongen i studien. Ur statisk synpunkt är det lämpligt att använda glasfiberbaserade armeringsstänger i balkonginfästningen. Energiflödesberäkningarna har utförts i programmet Comsol för att erhålla ett noggrant resultat på energiflödet igenom infästningen. Återbetalningstiden på över 100 år för det pris som ComBAR ligger på i dagsläget anses inte vara rimligt och det behövs en halvering av priset innan det kan komma på tal att användas.

In this dissertation we have studied nearield phenomena in dipole radiation. We have studied first the energy flow patterns of the radiation emitted by an electric dipole located in between parallel mirrors. The field lines of the Poynting vector have intricate structures, including many singularities and vortices. For a dipole parallel to the mirror surfaces, vortices appear close to the dipole. Vortices are located where the magnetic field vanishes. Also, a radiating electric dipole near the joint of two orthogonal mirrors is considered, and also here we find numerous singularities and vortices in the energy flow patterns. We have also studied the current density in the mirrors. Next we have studied the reflection of radiation by and the transmission of radiation through an interface with an  -near-zero (ENZ) material. For p polarization, we find that the reflection coefficient is -1, and the transmission coefficient is zero for all angles of incidence. The transmitted electric field is evanescent and circularly polarized. The transmitted magnetic field is identically zero. For s polarization, the transmitted electric field is s polarized and the transmitted magnetic field is circularly polarized. The next topic was the study of the force exerted on the dipole by its own reflected field near an ENZ interface. We found that, under certain circumstances, it could be possible that the dipole would levitate in its reflected field. This levitation is brought about by evanescent reflected waves. Finally, power emission by an electric dipole near an interface was considered. We have derived expressions for the emitted power crossing an interface. The power splits in contributions from traveling and evanescent incident waves. We found that for an ENZ interface, only evanescent dipole waves penetrate the material, but there is no net power flow into the material.