Search results for "Coal"
showing 10 items of 354 documents
Families of ICIS with constant total Milnor number
2021
We show that a family of isolated complete intersection singularities (ICIS) with constant total Milnor number has no coalescence of singularities. This extends a well-known result of Gabriélov, Lazzeri and Lê for hypersurfaces. We use A’Campo’s theorem to see that the Lefschetz number of the generic monodromy of the ICIS is zero when the ICIS is singular. We give a pair applications for families of functions on ICIS which extend also some known results for functions on a smooth variety.
Fire frequency during the Holocene in central Latvia, northeastern Europe
2021
Fire is today a pan-European issue and is expected to be more salient because of climate and land use changes. Even though natural and anthropogenic fires have shaped forest composition and landscape characteristics since the last glacial retreat from northeastern Europe, fire frequency is an understudied topic. To address this issue, we analysed macroscopic charcoal (>160 μm) from two sediment sequences located in the central and littoral parts of Lake Bricu (central Latvia) revealing the fire frequency during the Holocene. The chronology of the analysed sediment sequences is based on spheroidal fly-ash carbonaceous particles and accelerator mass spectrometry radiocarbon dating. Macroscop…
Structure alteration of a sandy-clay soil by biochar amendments
2014
The aim of the present study was to investigate structure alterations of a sandy-clay soil upon addition of different amounts of biochar (f bc ). All the f bc samples were analyzed by high energy moisture characteristic (HEMC) technique and 1H nuclear magnetic resonance (NMR) relaxometry. HEMC was applied in order to evaluate aggregate stability of biochar-amended soil samples. 1H NMR relaxometry experiments were conducted for the evaluation of the pore distributions through the investigation of water dynamics of the same samples. The HEMC technique revealed improvement in aggregate stability through measurements of the amount of drainable pores and the stability ratio. The latter increased…
Bio-coal, torrefied lignocellulosic resources – Key properties for its use in co-firing with fossil coal – Their status
2012
Abstract Bio-coal has received generous amounts of media attention because it potentially allows greater biomass co-firing rates and net CO2 emission reductions in pulverised-coal power plants. However, little scientific research has been published on the feasibility of full-scale commercial production of bio-coal. Despite this, several companies and research organisations worldwide have been developing patented bio-coal technologies. Are the expectations of bio-coal realistic and are they based on accepted scientific data? This paper examines strictly peer-reviewed scientific publications in order to find an answer. The findings to date on three key properties of torrefied biomass are pres…
Quantitative Estimation of Major and Trace Elements in Coals of the Benue Trough, Nigeria
2013
The concentrations of major and trace elements in ash residues of coals of the Benue Trough, Nigeria have been determined by electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry, respectively. Major and trace element determination in rocks by fusion on an iridium strip heater followed by electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry is extended here to coal ash, and the accuracy of the method is evaluated by including an Argonne Premium Coal reference sample in each analysis program. Si and Al are the major elements detected in the coal ashes. An assessment using worldwide concentration ranges of trace elements in coal ash…
New national and regional bryophyte records, 65
2021
Pseudoamblystegium subtile (Hedw.) Vanderp. & Hedenäs. CONTRIBUTORS: R. Gabriel, M. Kubová, C. Sérgio and I. Soares Albergaria. PORTUGAL, AZORES: Terceira Island, Angra do Heroísmo, municipal garden ‘Jardim Duque da Terceira’, 38° 39′ 24.0′′N, 27°13′ 05.99′′W, 31 m a.s.l, on the base of a shrub, in acidic conditions, 7 April 2017, leg. Michaela Kubová s.n. (AZU). A new understanding of the pleurocarpous moss species Pseudoamblystegium subtile was proposed by Vanderpoorten and Hedenäs (2009). The new genus is separated from the other Amblystegiaceae primarily due to its phylogenetic consistency and is characterised by the possession of leaves with a very short nerve, and erect capsules (Vand…
The Impact of Climate, Resource Availability, Natural Disturbances and Human Subsistence Strategies on Sicilian Landscape Dynamics During the Holocene
2022
This paper presents a multidisciplinary summary of the most recent discoveries and hypotheses concerning factors driving the human subsistence economy and landscape shaping in Sicily during the Holocene. A number of scientific papers have recently pointed out the key role played by paleogeography, resource (water, food) availability and natural disturbances (volcanic eruptions, tsunamis) in local human activities. Modern anthropology and archaeology increasingly use biological remains (e.g. soils, bones, wood, plant macroremains, pollen) to better understand how human communities managed to survive and spread. Likewise, refined reconstructions of past human demographic fluxes and socio-econ…
Techno-economic analysis of integrated processes for the treatment and valorisation of neutral coal mine effluents
2020
Abstract The disposal of highly-concentrated neutral coal mine effluents into the environment constitutes a severe threat to the natural ecosystem. This work proposes and compares five novel treatment chains to purify the effluent and recover raw materials. The chains present different combinations of pre-treatment and concentration technologies. In all cases, the solution sent to the concentration step is concentrated up to saturation to recover water and sodium chloride. Concerning the technical performances, the treatment chains are compared in terms of total energy demand and salt recovery. Furthermore, the economic feasibility assessment is performed via a novel global parameter, i.e. …
Valorisation of SWRO brines in a remote island through a circular approach: Techno-economic analysis and perspectives
2022
Nowadays, small remote islands rely heavily on desalination technologies to overcome freshwater scarcity. Unfortunately, these technologies are accompanied by the production of brines which can affect the receiving water bodies i.e., the aquatic ecosystem. Yet, it is extremely appealing how such brines constitute an abundant source of valuable raw materials (such as magnesium). In this work, a novel hybrid system is introduced to capture the value of seawater reverse osmosis (SWRO) brines produced in the minor Sicilian island of Pantelleria. The “Minimal Liquid Discharge” (MLD) process consists of: (i) Nanofiltration NF (separation of bivalent from monovalent ions), (ii) Mg Reactive Crystal…
A Reinforcement Learning Approach for User Preference-aware Energy Sharing Systems
2021
Energy Sharing Systems (ESS) are envisioned to be the future of power systems. In these systems, consumers equipped with renewable energy generation capabilities are able to participate in an energy market to sell their energy. This paper proposes an ESS that, differently from previous works, takes into account the consumers’ preference, engagement, and bounded rationality. The problem of maximizing the energy exchange while considering such user modeling is formulated and shown to be NP-Hard. To learn the user behavior, two heuristics are proposed: 1) a Reinforcement Learning-based algorithm, which provides a bounded regret and 2) a more computationally efficient heuristic, named BPT- ${K}…