89 research outputs found
Citation chain aggregation: An interaction model to support citation cycling
No full textThis is the postprint version of the conference paper.Citation chaining is a powerful means of exploring the academic literature. Starting from just one or two known relevant items, a
naïve researcher can cycle backwards and forwards through the citation graph to generate a rich overview of key works, authors and journals relating to their topic. Whilst online citation indexes
greatly facilitate this process, the size and complexity of the search space can rapidly escalate. In this paper, we propose a
novel interaction model called citation chain aggregation (CCA). CCA employs a simple three-list view which highlights the
overlaps that occur between the first-generation relations of known relevant items. As more relevant articles are identified, differences in the frequencies of citations made by or to unseen articles provide strong relevance feedback cues. The benefits of this technique are illustrated using a simple case study
Local knowledge, exploitation, and conservation of the African golden cat Caracal aurata in Central Cameroon
No full textThe data contains the responses from a questionnaire survey. Data were collected in local communities in Cameroon using Kobocollect, to assess the knowledge of the locals on the African golden cat.
The questions are listed in the first row and the following rows contain the answers of each participant. The first 13 columns contain socio-demographic questions and the remaining contain specific questions related to the African golden cat knowledge and exploitation.
No abbreviation is used in the dataset except YCF (Council Forest of Yoko); MDNP (Mpem et Djim National park); 1 (Yes), 0(NO)812
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STUDY OF Salmo GENUS (PISCES, SALMONIDAE) ON THE BALKAN PENINSULA
No full textU radu autor osporava stajalište K o t t e l a t a (1997) te K o t t e l a t a i F r e y h o f a (2007) da na dijelovima Balkanskoga poluotoka, posebice u Ohridskome jezeru, postoje neke vrste roda Salmo: Salmo aphelios Kottelat, 1997; Salmo balcanicus (Karaman, 1927); Salmo farioides (Karaman, 1938); Salmo labrax Pallas, 1814; Salmo letnica (Karaman, 1924); Salmo lumi Poljakov, Filipi i Basho, 1958; Salmo macedonicus (Karaman, 1924); Salmo montenigrinus (Karaman, 1933); Salmo pelagonicus Karaman, 1938; Salmo peristericus Karaman, 1938; Salmo taleri (Karaman, 1932). Većinu je tih vrsta uveo od dr. Stanko Karaman, autor koji je po broju opisanih vrsta europskih slatkovodnih riba na drugome mjestu, odmah iza Carla Linnaeusa. Prema autoru, proturječno je formalnoj logici da u jednoj malenoj te oligotrofnoj mikronastambi kakva je Ohridsko jezero i u kojoj ne postoji faktor geografske izolacije budu formirane čak četiri vrste pastrva, kao i to da slijev Vardara nastanjuju tri vrste pastrva, dok je kod nekih drugih vrsta u geografski odvojenim sljevovima, u kojima postoji faktor geografske izolacije, razvoj "zaustavljen". Njegove tvrdnje da je u biti riječ o populacijama jedne te iste vrste Salmo trutta (Linnaeus, 1785) vrlo su plastične glede mikroekoloških uvjeta te fenotipskih manifestacija. Autor svoje tvrdnje potkrepljuje svojim te rezultatima drugih znanstvenika dobivenima proučavanjem ekologije i sistematike potočne pastrve u tekućim i stajaćim mikronastambama, nakon razdvajanja jedne prijašnje cjelovite u dvije nove: rijeka Radika te akumulacija Mavrovo (Republika Makedonija). Osim toga, autor navodi da je neprihvatljiva upotreba terminologije imanentne antropogenom faktoru u području druge znanstvene discipline u kojoj takav faktor ne postoji (agronomija - rasa te biologija - prirodna selekcija).Author disputes the position of the authors K o t t e l a t (1997) and K o t t e l a t & F r e y h o f (2007) about the existence of several species belonging to the Salmo genus in some parts of Balkan Peninsula: Salmo aphelios Kottelat, 1997; Salmo balcanicus (Karaman, 1927); Salmo farioides (Karaman, 1938); Salmo labrax Pallas, 1814; Salmo letnica (Karaman, 1924); Salmo lumi Poljakov, Filipi & Basho, 1958; Salmo macedonicus (Karaman, 1924); Salmo montenigrinus (Karaman, 1933); Salmo pelagonicus Karaman, 1938; Salmo peristericus Karaman, 1938; Salmo taleri (Karaman, 1932). Majority of those species were described by dr. Stanko Karaman, the author who is, regarding the number of described species of European freshwater fishes, on the second place, just behind Carl Linnaeus. It is hardly believable that four trout species were formed in a small and oligotrophic microhabitat like Ohrid Lake, or three species in the Vardar River, knowing that the factor of geographic isolation doesn’t exist in either of the habitats. The author’s position is that all of these species are actually just types of one, highly plastic regarding the micro ecological conditions and phenotypic manifestations, species: Salmo trutta (Linnaeus, 1785). The author supports his opinion by his own results, as well the results of other scientists, obtained through studies of ecology and taxonomy of the brown trout in fluent and still water microhabitats. Also the author suggests that it is unacceptable to apply the terminology immanent to the anthropogenic factor in a sphere of another scientific area where such factor doesn't exist (agronomy-race and biology-natural selection)
African golden cat and serval in forest–savannah transitions in Cameroon
No full textFirst paragraph: African golden cats (Caracal aurata Temminck, 1827; hereafter, ‘golden cat’) occur in the forests and forest–savannah mosaics (hereafter, ‘FSM’) of West and Central Africa (Bahaa-el-din et al., 2015). Another medium-sized wild felid, the serval (Leptailurus [Caracal] serval Schreber, 1776), occurs in well-watered savannah and long-grass environments that are widespread across sub-Saharan Africa (Figure 1a; Thiel, 2019). Golden cats and servals are closely related felids (Johnson et al., 2006), deriving from a common ancestor approximately 5.4 million years ago (O’Brien & Johnson, 2007). They are known to be sympatric only within a small portion of their collective geographic range, including in the Central African Republic (Hickisch & Aebischer, 2013), in the FSM of the western Congo Basin (Henschel et al., 2014) and in Uganda (Mills et al., 2019)
A comparison of two fully coupled codes for integrated dynamic analysis of floating vertical axis wind turbines
No full textThis paper presents a comparison of two state-of-the-art codes that are capable of modelling floating vertical axis wind turbines (VAWTs) in fully coupled time-domain simulations, being the HAWC2 by DTU and the SIMO-RIFLEX-AC code by NTNU/MARINTEK. The comparative study focusses on the way aerodynamics, hydrodynamics and structural dynamics are treated for DeepWind’s 5MW Darrieus rotor mounted on a modified OC3 spar platform. The relevant modelling differences are described, followed by an introduction to the spar VAWT concept and selected load cases. Isolation of the aerodynamic model is achieved using an equivalent rigid land-based VAWT in steady wind-only environments. The added complexity in SIMO-RIFLEX-AC’s aerodynamic model has shown to increase aerodynamic torque at tip-speed ratios above 2.5. Differences in the hydrodynamic and structural models were brought forward through fully coupled analyses in turbulent wind and irregular wave climates. It is found that the simplified mooring system in HAWC2 introduces a 2P yaw response (1P in SIMO-RIFLEX-AC), stronger motion coupling in surge-heave and a largely reduced mooring line tension since the dynamics of mooring lines are not considered. Indications are given that a higher tower mode is excited by 4P aerodynamic loading; an effect that is significantly stronger in HAWC2.Wind Energ
Design of a Steel Pontoon-type Semi-submersible Floater Supporting the DTU 10MW Reference Turbine
No full textIn recent years, offshore wind energy has experienced a huge development. Floating wind turbines may become competitive for water depth larger than 50m. However, high cost is still the main challenge for the offshore wind industry. Floating offshore designs provides the possibility to carry large wind turbines to reduce the cost per MWh. In this thesis, a pontoon-type semi-submersible platform has been designed to support the DTU 10MW reference wind turbine. The initial design is made though upscaling of an existing 5MW semi-submersible platform design. The design is then checked against buoyancy, stability, hydrodynamic and strength criteria. In addition a spread catenary mooring system has been designed based on the catenary theory. Further tests show that clump weight might be needed to balance the strength and stiffness of the mooring lines. Floating wind turbine models with different levels of complexity have been established and studied through the thesis. In addition, viscous drag force and second order wave force have been implemented. Finally the SIMO-RIFLEX-AeroDyn model is established, and extensive numerical tests have been performed to check the model. The modelling of blades, hub, nacelle and shaft has been found to be difficult and will result in some difficulties in eigenfrequency prediction of the wind turbine. It is also found that the blade pitch controller can excite large platform pitch resonant motion at above rated wind speeds, which could be possibly solved by reducing the PI gains of the controller. Finally, time domain coupled dynamic analysis of the floating wind turbine system is performed by the SIMO-RIFLEX-AeroDyn code. Characteristic responses of the semi-submersible floating wind turbine are studied and compared to those of the land-based wind turbine. It is found that platform motions have limited influence on the aerodynamic performance of the wind turbine. Besides, operating at rated wind speed is found to produce the largest blade and tower bending moments for both land-based and floating wind turbines. For the floating wind turbine, resonant surge and pitch motions could be excited by turbulent wind under operational conditions which will dominate the response. Second order wave force has some influences on the surge and pitch resonant responses, but these influences are small comparing to those of turbulent wind. However, second order wave force could be important for the study of heave motion, which is wave force dominated even under turbulent wind conditions.Offshore and Dredging Engineering / European Wind Energy Master program Offshore Engineering trackMarine & Transport TechnologyMechanical, Maritime and Materials Engineerin
Numerical Simulation for Installation of Jacket Foundation of Offshore Wind Turbines
No full textA large contribution to the overall project costs of an offshore wind farm originates from the transport and installation of the substructures. A better understanding of the operational limits that apply for the installation helps to improve the project execution and thus reduces costs. It is important to analyze in which sea states the installation can be carried out safely. A coupled analysis model consisting of a vessel the jacket and couplings is implemented in SIMO. Time domain simulations of the the lowering and landing process of a jacket substructure are carried out for a jack-up and a floating vessel. Based on operational criteria a workability analysis is performed and the limiting sea states are determined. The jacket substructure needs to be lowered into pre-installed foundation piles and the jacket motions are thus limited to a certain threshold in order for the installation to be successful. The jack-up vessel is fixed and consequently there are no crane tip motions. The jacket is thus only excited by waves and the motions are small enough for the jacket to successfully enter the foundation piles for all investigated sea states. The floating vessel is excited by waves and the vessel motions lead to larger motions in the jacket too. The jacket does therefore not always enter the foundation piles. The success rate depends on the wave period and decreases for larger wave periods, close to the excitation periods of the vessel. While the floating vessel is only suited for operations in small wave periods the jack-up vessel was able to operate in all investigated sea states.Offshore EngineeringHydraulic EngineeringCivil Engineering and Geoscience
Continued availability and sale of pangolins in a major urban bushmeat market in Cameroon despite national bans and the COVID-19 outbreak
No full textFirst paragraph: Bushmeat (or ‘wild meat’, defined as the meat of wild animals) is a major source of protein for rural people across sub-Saharan Africa (Ingram et al., 2021), yet some species suffer unsustainable levels of exploitation often to meet the demands of increasing urban populations (Coad et al., 2019; Wilkie et al., 2016). As in the rest of Central Africa, Cameroon has a long history of bushmeat consumption and trade (Bahuchet & Ioveva, 1999; Randolph, 2016). Pangolins (Family: Manidae) have been one of the many groups of species exploited as they are highly valued for food and, in some countries, used as traditional remedies (Soewu et al., 2020). Pangolin meat is favoured for its taste and it remains commonly offered for sale in Cameroonian markets and restaurants (Ingram et al., 2018; Nguyen et al., 2021). Furthermore, Cameroon has become one of the major export countries for the illegal trade in pangolin scales from Africa to Asia (Ingram et al., 2019a), to supply the market for Asian traditional medicines, for example in traditional Chinese medicine (Wang et al., 2020). All African pangolin species are now considered to have declining population trends (Ingram et al., 2019b; Nixon et al., 2019; Pietersen et al., 2019a, 2019b)
Semi-blind adaptive beamforming for high-throughput quadrature amplitude modulation systems
No full textA semi-blind adaptive beamforming scheme is proposed for wireless systems that employ high-throughput quadrature amplitude modulation signalling. A minimum number of training symbols, equal to the number of receiver antenna arrays elements, are first utilised to provide a rough initial least squares estimate of the beamformer's weight vector. A concurrent constant modulus algorithm and soft decision-directed scheme is then applied to adapt the beamformer. This semi-blind adaptive beamforming scheme is capable of converging fast to the minimum mean-square-error beamforming solution, as demonstrated in our simulation study
Increased Carotid Thickness in Subjects with Recently-Diagnosed Diabetes from Rural Cameroon
No full textPMCID: PMC3423396This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
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