期刊文献+
共找到71篇文章
< 1 2 4 >
每页显示 20 50 100
Development of Perverse Environmental Subsides for Sheep Production in Iceland
1
作者 Olafur Arnalds 《Agricultural Sciences》 2019年第9期1135-1151,共17页
Sheep production in Iceland is heavily subsidized with a part of the payments tied to land condition and compliance with sustainable land use according to a Quality Management System (QMS). A large proportion of the r... Sheep production in Iceland is heavily subsidized with a part of the payments tied to land condition and compliance with sustainable land use according to a Quality Management System (QMS). A large proportion of the rangelands used for sheep grazing are public lands. The paper is based on Land Improvement Plans (LIP’s) and Soil Conservation of Iceland (SCSI) correspondence obtained by appeal under the Information Act. The results show that “green payments” are made for use of land that fails to meet the criteria given for such payments, based on the extent of barren areas, active soil erosion, and vegetation condition. Strong formal objections by the SCSI about the content and implementation of QMS have been ignored. It is further shown that the land use section of the QMS (L-QMS) is non-transparent and not well scientifically grounded. The use of the term “sustainable land use” is confounded when used to justify the use of collapsed ecosystems. The LIP’s show high to extreme grazing intensities on land in poor condition, thus further defying ideas for green subsidy schemes. The investigation reveals serious conflicts between environmental and agricultural sectors, at agency and ministerial levels, which is enhanced by incoherent legislation structures. It is vital to reconstruct the green subsidies for sheep farming in Iceland, based on science and best available information with a much broader stakeholder participation than at present, involving multi-sectoral agencies and scientists, NGO’s, communities, the general public, and land users. 展开更多
关键词 AGRICULTURAL SUBSIDIES Agro-Environmental SLM Land Condition SHEEP GRAZING
下载PDF
Recent Ventures in Interdisciplinary Arctic Research:The ARCPATH Project 被引量:1
2
作者 Astrid E.J.OGILVIE Leslie A.KING +9 位作者 Noel KEENLYSIDE François COUNILLON Brynhildur DAVIÐSDÓTTIR Níels EINARSSON Sergey GULEV Ke FAN Torben KOENIGK James R.MCGOODWIN Marianne H.RASMUSSON Shuting YANG 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2024年第8期1559-1568,共10页
This paper celebrates Professor Yongqi GAO's significant achievement in the field of interdisciplinary studies within the context of his final research project Arctic Climate Predictions: Pathways to Resilient Sus... This paper celebrates Professor Yongqi GAO's significant achievement in the field of interdisciplinary studies within the context of his final research project Arctic Climate Predictions: Pathways to Resilient Sustainable Societies-ARCPATH(https://www.svs.is/en/projects/finished-projects/arcpath). The disciplines represented in the project are related to climatology, anthropology, marine biology, economics, and the broad spectrum of social-ecological studies. Team members were drawn from the Nordic countries, Russia, China, the United States, and Canada. The project was transdisciplinary as well as interdisciplinary as it included collaboration with local knowledge holders. ARCPATH made significant contributions to Arctic research through an improved understanding of the mechanisms that drive climate variability in the Arctic. In tandem with this research, a combination of historical investigations and social, economic, and marine biological fieldwork was carried out for the project study areas of Iceland, Greenland, Norway, and the surrounding seas, with a focus on the joint use of ocean and sea-ice data as well as social-ecological drivers. ARCPATH was able to provide an improved framework for predicting the near-term variation of Arctic climate on spatial scales relevant to society, as well as evaluating possible related changes in socioeconomic realms. In summary, through the integration of information from several different disciplines and research approaches, ARCPATH served to create new and valuable knowledge on crucial issues, thus providing new pathways to action for Arctic communities. 展开更多
关键词 Recent Ventures in Interdisciplinary Arctic Research:The ARCPATH Project
下载PDF
Polariton lasing in Mie-resonant perovskite nanocavity
3
作者 Mikhail A.Masharin Daria Khmelevskaia +12 位作者 Valeriy I.Kondratiev Daria I.Markina Anton D.Utyushev Dmitriy M.Dolgintsev Alexey D.Dmitriev Vanik A.Shahnazaryan Anatoly P.Pushkarev Furkan Isik Ivan V.Iorsh Ivan A.Shelykh Hilmi V.Demir Anton K.Samusev Sergey V.Makarov 《Opto-Electronic Advances》 SCIE EI CAS CSCD 2024年第4期27-42,共16页
Deeply subwavelength lasers(or nanolasers)are highly demanded for compact on-chip bioimaging and sensing at the nanoscale.One of the main obstacles for the development of single-particle nanolasers with all three dime... Deeply subwavelength lasers(or nanolasers)are highly demanded for compact on-chip bioimaging and sensing at the nanoscale.One of the main obstacles for the development of single-particle nanolasers with all three dimensions shorter than the emitting wavelength in the visible range is the high lasing thresholds and the resulting overheating.Here we ex-ploit exciton-polariton condensation and mirror-image Mie modes in a cuboid CsPbBr3 nanoparticle to achieve coherent emission at the visible wavelength of around 0.53μm from its ultra-small(≈0.007μm3 or≈λ3/20)semiconductor nanocav-ity.The polaritonic nature of the emission from the nanocavity localized in all three dimensions is proven by direct com-parison with corresponding one-dimensional and two-dimensional waveguiding systems with similar material parameters.Such a deeply subwavelength nanolaser is enabled not only by the high values for exciton binding energy(≈35 meV),re-fractive index(>2.5 at low temperature),and luminescence quantum yield of CsPbBr3,but also by the optimization of po-laritons condensation on the Mie resonances with quality factors improved by the metallic substrate.Moreover,the key parameters for optimal lasing conditions are intermode free spectral range and phonons spectrum in CsPbBr3,which govern polaritons condensation path.Such chemically synthesized colloidal CsPbBr3 nanolasers can be potentially de-posited on arbitrary surfaces,which makes them a versatile tool for integration with various on-chip systems. 展开更多
关键词 nanolaser PEROVSKITE POLARITON Mie resonance EXCITON-POLARITON
下载PDF
Natural history of heartburn:A 10-year population-based study 被引量:2
4
作者 Linda Bjork Olafsdottir Hallgrimur Gudjonsson +1 位作者 Heidur Hrund Jonsdottir Bjarni Thjodleifsson 《World Journal of Gastroenterology》 SCIE CAS CSCD 2011年第5期639-645,共7页
AIM: To study the natural history and prevalence of heartburn at a 10-year interval, and to study the effect of heartburn on various symptoms and activities. METHODS: A population-based postal study was carried out.... AIM: To study the natural history and prevalence of heartburn at a 10-year interval, and to study the effect of heartburn on various symptoms and activities. METHODS: A population-based postal study was carried out. Questionnaires were mailed to the same age- and gender-stratified random sample of the Icelandic population (aged 18-75 years) in 1996 and again in 2006. Subjects were classified with heartburn if they reported heartburn in the preceding year and/or week, based on the definition of heartburn. RESULTS: Heartburn in the preceding year was reported in 42.8% (1996) and 44.2% (2006) of subjects, with a strong relationship between those who experienced heartburn in both years. Heartburn in the precedingweek was diagnosed in 20.8%. There was a significant relationship between heartburn, dyspepsia and irritable bowel syndrome. IndMduals with a body mass index (BMI) below or higher than normal weight were more likely to have heartburn. Heartburn caused by food or beverages was reported very often by 20.0% of subjects. CONCLUSION: Heartburn is a common and chronic condition. Subjects with a BMI below or higher than normal weight are more likely to experience heartburn. Heartburn has a great impact on daily activities, sleep and quality of life. 展开更多
关键词 HEARTBURN FOLLOW-UP Questionnaire study EPIDEMIOLOGY
下载PDF
Waste Biomass Gasification Simulation Using Aspen Plus: Performance Evaluation of Wood Chips, Sawdust and Mixed Paper Wastes 被引量:3
5
作者 Sahar Safarian Christiaan Richter Runar Unnthorsson 《Journal of Power and Energy Engineering》 2019年第6期12-30,共19页
Biomass is one of the most widely available energy sources and gasification is a thermal conversion process where biomass is transformed into a fuel gas with a gasifying agent. In this paper by using ASPEN Plus, a new... Biomass is one of the most widely available energy sources and gasification is a thermal conversion process where biomass is transformed into a fuel gas with a gasifying agent. In this paper by using ASPEN Plus, a new steady state simulation model for down draft waste biomass gasification was developed. The model that is stoichiometric equilibrium-based is proposed to be used for optimization of the gasifier performance. Prediction accuracy of the model is validated by comparing with available experimental and modeling results in other literature. Then the model is used for comparative analysis of the gasification performance of sawdust, wood chips and mixed paper wastes. In the model, the operating parameters of temperature and equivalence ratio (ER) have been varied over wide range and their effect on syngas composition, syngas yield, low heating value (LHV) of syngas and cold gas efficiency (CGE) has been investigated. Raise in temperature increases the production of CO and H2 which leads to higher syngas yield, LHV and CGE. However, increasing ER decreases the production of CO and H2 which results lessens in LHV and CGE but syngas yield continuously increases because more oxygen is available for biomass reactions at high ER. The optimal values of CO and H2 mole fraction and CGE of sawdust, wood chips and mixed paper wastes are located at 900&degC, 1000&degC and 1000&degC, respectively and ER range is between 0.20 - 0.35 regardless of the kind of biomass which is used as the feedstock. 展开更多
关键词 WASTE Biomass GASIFICATION SIMULATION Model GASIFIER Performance WASTE to Energy
下载PDF
Sub-Recent Sexual Populations of Limnocythere inopinata Recorded for the First Time from>3500 m Altitude on the Tibetan Plateau 被引量:2
6
作者 ZHANG Wanyi Steffen MISCHKE +2 位作者 ZHANG Chengjun ZHANG Huirong WANG Peng 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2015年第3期1041-1042,共2页
The central and northwestern Tibetan Plateau region,also called"Qiangtang Plateau"(30°27'25"-35°39'13"N,83o41'14"-95°10'46"E),is the highest and largest arcticalpine area of the Earth coveri... The central and northwestern Tibetan Plateau region,also called"Qiangtang Plateau"(30°27'25"-35°39'13"N,83o41'14"-95°10'46"E),is the highest and largest arcticalpine area of the Earth covering approximately 600,000km^2 with altitude ranging from 4600 to 5100 m a.s.l.(Song et al.,2012,Fig.1). 展开更多
关键词 Sub-Recent Sexual Populations of Limnocythere inopinata Recorded for the First Time from>3500 m Altitude on the Tibetan Plateau
下载PDF
Checkpoint inhibitor-induced hepatotoxicity:Role of liver biopsy and management approach 被引量:1
7
作者 Fernando Bessone Einar Stefan Bjornsson 《World Journal of Hepatology》 2022年第7期1269-1276,共8页
Immunological checkpoint inhibitors(ICIs)have revolutionized therapy of many different malignanices.Concomitant immune-mediated adverse effects are common and can affect many organs such as the skin,lungs,gastrointest... Immunological checkpoint inhibitors(ICIs)have revolutionized therapy of many different malignanices.Concomitant immune-mediated adverse effects are common and can affect many organs such as the skin,lungs,gastrointestinal and endocrine organs as well as the liver.Liver injury has been reported in 3%-8%of patients with grade III-IV hepatitis in retrospective studies.The liver injury is characterized by hepatocellular injury resembling autoimmune hepatitis biochemically but not immunologically as patients with ICI induced hepatoxicity rarely have auto-antibodies or IgG elevation.The role for liver biopsy(LB)in patients with suspected liver injury due to ICIs is controversial and it is not clear whether results of a LB will change clinical management.LB can be helpful when there is diagnostic uncertainty and pre-existing liver disease is suspected.Although there are no distinctive histological features,the finding of granulomas and endothelitis may suggest a specific type of hepatitis induced by ICIs.The natural history of hepatotoxicity of ICI therapy is not well known.Recent studies have demonstrated that 33%-50%of patients improve spontaneously with discontinuation of ICIs.In patients with jaundice and/or coagulopathy corticosteroids are used.The high doses of corticosteroids with 1-2 mg/kg/d of methylprednisolone recommended by the oncological societies are controversial.Recently it has shown that initial treatment with 1 mg/kg/d provided similar liver tests improvement which was also associated with a reduced risk of steroid-induced adverse effects in comparison with higher-dose regimens.Secondary immunosuppression mostly with mycophenolate mofetil has been reported to be helpful. 展开更多
关键词 HEPATOTOXICITY Checkpoint inhibitors BIOLOGICS HEPATITIS Drug-induced liver injury Liver biopsy
下载PDF
Techno-Economic Analysis of Power Production by Using Waste Biomass Gasification 被引量:1
8
作者 Sahar Safarian Runar Unnthorsson Christiaan Richter 《Journal of Power and Energy Engineering》 2020年第6期1-8,共8页
Energy recovery from waste biomass can have significant impacts on the most pressing development challenges of rural poverty and environmental damages. In this paper, a techno-economic analysis is carried out for elec... Energy recovery from waste biomass can have significant impacts on the most pressing development challenges of rural poverty and environmental damages. In this paper, a techno-economic analysis is carried out for electricity generation by using timber and wood waste (T & WW) gasification in Iceland. Different expenses were considered, like capital, installation, engineering, operation and maintenance costs and the interest rate of the investment. Regarding to revenues, they come from of the electricity sale and the fee paid by the Icelandic municipalities for waste collection and disposal. The economic feasibility was conducted based on the economic indicators of net present value (NPV) and discounted payback period (DPP), bringing together three different subgroups based on gasifier capacities, subgroup a: 50 kW, subgroup b: 100 kW and subgroup c: 200 kW. The results show that total cost increases as the implemented power is increased. This indicator varies from 1228.6 k€ for subgroups a to 1334.7 k€ for subgroups b and 1479.5 k€ for subgroups c. It is worth mentioning that NPV is positive for three subgroups and it grows as gasifier scale is extended. NPV is about 122 k€ (111,020 $), 1824 k€ (1,659,840 $) and 4392 k€ (3,996,720 $) for subgroups a, b and c, respectively. Moreover, DPP has an inversely proportional to the installed capacity. It is around 5.5 years (subgroups a), 9.5 months (subgroups b) and 6 months (subgroups c). The obtained results confirm that using small scale waste biomass gasification integrated with power generation could be techno-economically feasible for remote area in Iceland. 展开更多
关键词 Waste Biomass Gasification Techno-Economic Analysis Power Production Waste to Energy
下载PDF
Paravertebral Block for Post-Operative Analgesia after Breast Cancer Surgery, Effects of Adding Morphine: Double Blind, Randomised Clinical Trial 被引量:1
9
作者 Gudmundur Bjornsson Astridur Johannesdottir +1 位作者 Bjarni Valtysson Gisli HSigurdsson 《Open Journal of Anesthesiology》 2013年第2期116-121,共6页
Introduction: Thoracic paravertebral block (PVB) block is frequently used in breast cancer surgery for postoperative pain management. Adding opioids to local anaesthetics has been shown to have beneficial effects duri... Introduction: Thoracic paravertebral block (PVB) block is frequently used in breast cancer surgery for postoperative pain management. Adding opioids to local anaesthetics has been shown to have beneficial effects during epidural analgesia. Our hypothesis was that adding morphine to bupivacaine for PVB would improve analgesia provided by this procedure. Methods: 60 patients (25 - 75 years) undergoing elective surgery for breast cancer were randomly assigned to one of two groups. Both groups received a single injection thoracic paravertebral block;group BAM with 20 ml 0.5% bupivacaine, epinephrine and morphine while group BA received identical block except morphine was given subcutaneously. All patients had general anaesthesia. Results: Severity of pain and nausea was low in both groups. Pain scores remained below 20/100 after the first 2 hours throughout the 72 hours of the study. There was no significant difference between the groups in pain scores, consumption of additional morphine or nausea scores. Shoulder mobility was also very good in both groups. Conclusion: Thoracic paravertebral block with bupivacaine and epinephrine was associated with good postoperative analgesic effects and low incidence of nausea and vomiting. The addition of morphine to the local anaesthetic solution in paravertebral block did not have any additional analgesic effects. 展开更多
关键词 Thoracic Paravertebral Block BUPIVACAINE EPINEPHRINE MORPHINE Breast Cancer
下载PDF
Performance Investigation of Biomass Gasification for Syngas and Hydrogen Production Using Aspen Plus 被引量:1
10
作者 Sahar Safarian Runar Unnthorsson Christiaan Richter 《Open Journal of Modelling and Simulation》 2022年第2期71-87,共17页
This study presents a reliable model using Aspen Plus process simulator capable of performing a sensitivity analysis of the downdraft gasification linked to hydrogen production unit. Effects of key factors, including ... This study presents a reliable model using Aspen Plus process simulator capable of performing a sensitivity analysis of the downdraft gasification linked to hydrogen production unit. Effects of key factors, including gasification temperature and steam to biomass ratio (SBR) on the syngas composition, calorific value of syngas and hydrogen production are discussed and then the optimal conditions for maximum hydrogen production are extracted. The model is validated by experimental and other modeling data and found to be in great agreement. The sensitivity analysis results obtained by only using air as gasification agent indicate that higher temperatures are favorable for a product gas with higher hydrogen content and calorific value. Moreover, steam consumption as gasifying agent leads to increasing the hydrogen content and heating value of the syngas compared to the use of air as gasification agent. Finally, the results show that the optimal conditions to have the highest value of hydrogen output from sawdust downdraft gasification are 800&#730C as gasifier temperature and 0.6 for SBR. 展开更多
关键词 Biomass Gasification SYNGAS HYDROGEN SIMULATION Parametric Analysis
下载PDF
Iceland: a window on North-Atlantic divergent plate tectonics and geologic processes
11
作者 Freysteinn Sigmundsson Kristjan Scemundsson 《Episodes》 SCIE 2008年第1期92-97,共6页
Opening of the North Atlantic about 60 million years ago was associated with massive basaltic volcanism, now found on both sides of the Atlantic Ocean. Divergence of the North American and Eurasian plates since then h... Opening of the North Atlantic about 60 million years ago was associated with massive basaltic volcanism, now found on both sides of the Atlantic Ocean. Divergence of the North American and Eurasian plates since then has formed the ocean floor in the North Atlantic, with the Mid-Atlantic Ridge marking the present day plate boundary. Iceland is the only large sub-aerial portion of the ridge. These unique conditions provide a "window" on divergent plate tectonics and related geologic processes, some of the main features of which are described and explained in this paper: The geological record in Iceland reaches back into late Tertiary and is particularly notable for the interplay of rift-volcanism and glaciation during the last three million years of rapid climate change. 展开更多
关键词 板块构造学 大西洋 冰岛 地质构造
下载PDF
Glucosamine increases the expression of YKL-40 and osteogenic marker genes in hMSC during osteogenic differentiation
12
作者 Ramona LIEDER Sigrídur Thóra REYNISDOTTIR +7 位作者 Finnbogi THORMÓDSSON Chuen-How NG Jon Magnús EINARSSON Jóhannes GÍSLASON Jóhannes BJORNSSON Sveinn GUDMUNDSSON Pétur Henry PETERSEN Olafur Eysteinn SIGURJONSSON 《Natural Products and Bioprospecting》 CAS 2012年第2期87-91,共5页
Human mesenchymal stem cells(hMSC)can be expanded in vitro and differentiated towards osteogenic,chondrogenic or adipogenic lineages,making them an attractive source for tissue engineering and regenerative medicine.Ch... Human mesenchymal stem cells(hMSC)can be expanded in vitro and differentiated towards osteogenic,chondrogenic or adipogenic lineages,making them an attractive source for tissue engineering and regenerative medicine.Chitinase-like-proteins(CLPs)belong to the family 18 glycosyl hydrolases and are believed to play a role in inflammation and tissue remodelling.The aim of this study was to determine the effect of the aminosugar glucosamine on the expression of the CLP YKL-40 during osteogenic differentiation of hMSC.Glucosamine did not affect multipotency of hMSC nor proliferation rate of undifferentiated hMSC.YKL-40 was expressed during both expansion of undifferentiated hMSC and during osteogenic differentiation.A slight but non-significant increase in YKL-40 expression was observed with glucosamine,accompanied by a pH-dependent delay in mineralization.However,glucosamine induced higher expression of osteogenic marker genes. 展开更多
关键词 YKL-40 mesenchymal stem cells osteogenic differentiation chitinase-like-protein
下载PDF
Benchmark Integral Cross Sections for Electron Impact Excitation of the n=2 States in Helium
13
作者 M.HOSHINO H.KATO +6 位作者 D.SUZUKI H.TANAKA I.BRAY D.V.FURSA S.J.BUCKMAN O.INGLFSSON M.J.BRUNGER 《Plasma Science and Technology》 SCIE EI CAS CSCD 2010年第3期348-352,共5页
In this paper, we present integral cross sections (ICS) for electron impact excitation of the n = 2 levels in helium in the impact energy range of 23.5 eV to 35 eV. The ICS of each final state, 2^3S, 2^1S, 2^3P and ... In this paper, we present integral cross sections (ICS) for electron impact excitation of the n = 2 levels in helium in the impact energy range of 23.5 eV to 35 eV. The ICS of each final state, 2^3S, 2^1S, 2^3P and 2^1P, has been determined by integration of the angular differential cross sections (DCS) over all of 0° to 180°, where those DCS were obtained from both our previous experiments and the extrapolation using the convergent close coupling calculation. The present experimental ICS for the optically allowed 21P transition state are also compared with those obtained from the BE f-scaling method. Very good agreement between the experimental and BE f-scaled 21P ICSs is generally found in the measured impact energy region. 展开更多
关键词 low energy electron impact electronic excitations HELIUM
下载PDF
Design and Analysis of Experiments Linking on-line Drilling Methods to Improvements in Knowledge
14
作者 Gunnar Stefansson Anna Helga Jonsdottir 《Journal of Statistical Science and Application》 2015年第3期63-73,共11页
An on-line drilling system, the tutor-web, has been developed and used for teaching mathematics and statistics. The system was used in a basic course in calculus including 182 students. The students were requested to ... An on-line drilling system, the tutor-web, has been developed and used for teaching mathematics and statistics. The system was used in a basic course in calculus including 182 students. The students were requested to answer quiz questions in the tutor-web and therefore monitored continuously during the semester. Data available include grades on a status exam conducted at the beginning of the course, a final grade and data gathered in the tutor-web system. A classification of the students is considered, using the data gathered in the system; a Good student should be able to solve a problem quickly and get it right, the "diligent" hard-working Learner may take longer to get the right answer, a guessing (Poor) student will not take long to get the wrong answer and the remaining (Unclassified) apparent non-learning students take long to get the wrong answer, resulting in a simple classification GLUP. The (Poor) students were found to show the least improvement, defined as the change in grade from the status to the trmal exams, while the Learners were found to improve the most. More detailed analyses indicate that improvements in knowledge are best predicted as quadratic responses to the number of items requested and the time spent on each item. The results are used to demonstrate how further experiments are needed and can be designed as well as to indicate how a system needs to be further developed to accommodate such experiments. 展开更多
关键词 统计学 统计方法 统计调查 应用
下载PDF
History of Geology in Norden
15
作者 Bjoern Sundquist Ilmari Haapala +2 位作者 Jens Morten Hansen Geir Hestmark Sigurdur Steinthorsson 《Episodes》 SCIE 2008年第1期185-192,共8页
The Nordic countries of Denmark, Finland, Iceland, Norway, and Sweden have been closely connected for many centuries, not least from a geological point of view. Scientific cooperation as well as contentions have been ... The Nordic countries of Denmark, Finland, Iceland, Norway, and Sweden have been closely connected for many centuries, not least from a geological point of view. Scientific cooperation as well as contentions have been common. The earliest known records of "geological" treatises are from the 16th century, but especially in the 18th century, when the natural sciences flourished all over Europe, Nordic scholars were in the forefront in geochemistry, mineralogy, and paleontology. This was also the century when "geology" started to be taught at the universities, and science academies were founded in Norden, adding greatly to "geological" studies. In the 19th century, like in so many other countries, national geological survey organizations and geological societies were founded. In Norden, geological research has long traditions within mineralogy and ore geology, paleontology and stratigraphy, tectonics and structural geology. During the last century, focus has turned also to Quaternary and glacial geology, igneous and metamorphic petrology, geochemistry, micropaleontology, petroleum geology, sedimentology, marine geology, geophysics, geochronology, and research related to geothermal energy and deposition of radioactive waste products. In many of these research areas, Nordic geoscientists have contributed greatly over the years to the development of the science of geology. 展开更多
关键词 地质学 北欧国家 地球化学 矿物学
下载PDF
Katla volcano in Iceland, potential hazards and risk assessment
16
作者 Jónas Elíasson 《Natural Science》 2014年第3期99-107,共9页
Katla in Iceland is one of the famous volcanoes of the world for the ferocity of the eruptions and associated j?kulhlaups. The major potential hazards are the j?kulhlaup floods that can hit three different floodplains... Katla in Iceland is one of the famous volcanoes of the world for the ferocity of the eruptions and associated j?kulhlaups. The major potential hazards are the j?kulhlaup floods that can hit three different floodplains, an associated tsunami that can harass the south coast of Iceland and a volcanic ash cloud that endangers civil aviation on an unknown scale. The eruption probabilities in Katla and the two others known eruption sectors of the Myrdalsj?kull glacier are reassessed and a 2013 risk curve for the next eruption in Katla is found. The probability of tsunami heights is estimated and the risk from other tsunami sources in the Atlantic Ocean is included. For the danger to aviation, two classes of eruption are defined: an EYF (EYjaFjallaj?kull) eruption class that does not produce volcanic plumes that are dangerous for air traffic in Europe, and another stronger class, the KAT (KATla) class, producing plumes that most likely are dangerous for air traffic in Europe. Overall probabilities for an EYF class eruption in next year and a KAT class eruption in the next 5 years are estimated. 展开更多
关键词 HAZARD PROBABILITY VOLCANIC ERUPTION Risk Assessment
下载PDF
Hydrodynamic Assessment of Increasing the Energy Efficiency of Trawler Propulsion with a Draft Tube
17
作者 Jonas Eliasson Elias B. Eliasson Halldor S. Eliasson 《Open Journal of Fluid Dynamics》 2015年第2期139-144,共6页
The economy of the fishing industry is suffering from high fuel prices. Considerable efforts are invested in methods to increase the energy efficiency of fishing vessels and reducing the oil consumption per kilo of ca... The economy of the fishing industry is suffering from high fuel prices. Considerable efforts are invested in methods to increase the energy efficiency of fishing vessels and reducing the oil consumption per kilo of catch that may be as high as 0.6 to 0.7 liter oil per kilo catch. It is primarily the fact that sailing and fishing are on two very different speeds that cause these high fuel consumptions. This is called the two-speed problem and it is the trawlers that are hit hardest by it. The essence of the two-speed problem is that a hydraulic efficiency of only 28% can be expected in trawling speed, when it would be 67% if the ship is sailing at optimum speed all the time. Hydrodynamical analysis shows that an average hydraulic efficiency of only 41% can be expected for a trawler. There is no simple remedy for this, but it is possible to use a technology developed in the hydropower industry, i.e. a draft tube, or a diffuser, to recover energy that would otherwise be lost when trawling. A draft of tube the same length as the propellers diameter could mean fuel savings of 10%, a draft tube twice as long 20%. The difficulty is to find a way to get the draft tube out of the water during sailing with a vessel-specific mechanical design that is not a part of the fluid dynamics of the problem and not discussed in the paper. 展开更多
关键词 TRAWLER Energy Efficiency HYDRODYNAMIC Assessment Fuel ECONOMY Draft Tube
下载PDF
Fluid Mechanics of Intrusives
18
作者 Jónas Elíasson 《International Journal of Geosciences》 2013年第10期9-14,共6页
The fluid mechanics of dike emplacement are analyzed using the translatory wave theory. The stress strain relations in the host rock are assumed linear and the fracture resistance of the host rock is assumed small. Th... The fluid mechanics of dike emplacement are analyzed using the translatory wave theory. The stress strain relations in the host rock are assumed linear and the fracture resistance of the host rock is assumed small. The resulting model is a flowing dyke progressing upwards to the surface with constant speed and a very small side slope. Apart from the topmost section, the form of the dyke is very close to the static form corresponding to the magma pressure in a no-flow situation. Two scales are found that control the flow, a width scale and a composite stiffness parameter for the host rock, representing the properties of the rock and the magma such as elasticity and viscosity. The theory explains a number of special features for dykes that are already known by researchers. It also adds two new points, the most interesting being that the composite stiffness of the rock can be estimated from field observations of the downwards widening angle of the dyke. 展开更多
关键词 INTRUSION MAGMA Flow Translatory WAVE ROCK STRESS
下载PDF
Olkaria Geothermal Power Plants, Kenya: Preliminary Evaluation of Mercury Emission to the Atmosphere
19
作者 G.N. Wetang'ula 《Journal of Environmental Science and Engineering》 2011年第11期1414-1426,共13页
At Olkaria (Kenya) geothermal energy has been used since 1981, to generate electricity and now there are currently 3 plants with a nominal capacity of 205 MW. Preliminary measurement and evaluation of possible mercu... At Olkaria (Kenya) geothermal energy has been used since 1981, to generate electricity and now there are currently 3 plants with a nominal capacity of 205 MW. Preliminary measurement and evaluation of possible mercury (Hg) emission from two plants has been investigated. Potential atmospheric Hg emission has been determined based on an existing model for estimating the transport of mercury along geothermal fluid flow streams as pertains to energy recovery and conversion from liquid dominated geothermal reservoirs. Hg concentrations, addition, retention and release rates were calculated at a number of locations in the geothermal power plants based on the plant operating parameters and steam flow process (turbine, condenser, non-condensable gas ejector, and cooling tower). Potential Hg emission rates through plume range from 0.455 g/h to 2.17 g/h, or 10-30 mg/h per MWe. The emission per hour per MWe is 130-300 times lower compared to Hg levels reported for 88 MWe five operating geothermal power plants around Mt. Amiata area in Italy. These emissions are coupled with a release of 1.07 kg/h per MW of hydrogen sulphide (HzS). The potential Hg release rates to the environment will depend greatly on the concentration of HzS in the system. Any higher HzS contents may reduce solubility of rig in the brine hence making it to be available in the steam. The volatile Hg may travel with the non-condensable gases as Hg vapour. 展开更多
关键词 Olkaria geothermal steam MERCURY cooling system atmospheric emission oxidation.
下载PDF
New model for dispersion of volcanic ash and dust in the troposphere
20
作者 Jonas Eliasson 《International Journal of Geosciences》 2020年第8期544-561,共18页
Dispersion of volcanic ash and dust is traditionally modeled as advection and Gaussian diffusion. This is the tradition in treating smoke stack plumes. About 100 meters above earth the velocity profile may disintegrat... Dispersion of volcanic ash and dust is traditionally modeled as advection and Gaussian diffusion. This is the tradition in treating smoke stack plumes. About 100 meters above earth the velocity profile may disintegrate, diffusion coefficients become rather unpredictable and stratified flow occur. It is suggested that gravitational flattening may be the main cause of dispersion in dust plumes above the turbulent boundary layer. A dust plume in between two layers of small temperature difference has a certain carrying capacity of dust. The corresponding mass loading can be estimated from the temperature difference between the layers above and beneath the plume. Such dust plumes will be forced to jettison a load they may have in excess of this carrying capacity;this may be seen as streak fallout from the plume. In the same time, the plume will be subjected to gravitational flattening to the sides, in addition to any diffusion if there is any. The plume width resulting from the flattening may be estimated from the temperature difference. This can explain the behavior of plumes like the plume from the Eyjafjallaj<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">?</span></span></span></span></span>kull 2010 in absence of diffusion. In the long run diffusion and gravitational flattening will cause different developments of the plume width. Gravitational flattening and streak fallouts are important elements from plume physics not included in most plume models. It is concluded that modelling dust plumes with diffusion and ordinary fallout only;can cause serious errors in the model, the simulated plumes will become too big. <span style="font-family:;" "="">To avoid them, the new model should be included in dust models in the same manner as the turbulent diffusion, <i>i.e.</i> as a sub grid model. Then, the plume model only needs to include horizontal turbulent diffusion of the same order of magnitude as the vertical one.</span> 展开更多
关键词 Dust Plume Gravitational Dispersion Load Capacity Streak Fallout
下载PDF
上一页 1 2 4 下一页 到第
使用帮助 返回顶部