337 research outputs found
A new doubly discrete analogue of smoke ring flow and the real time simulation of fluid flow
Modelling incompressible ideal fluids as a finite collection of vortex
filaments is important in physics (super-fluidity, models for the onset of
turbulence) as well as for numerical algorithms used in computer graphics for
the real time simulation of smoke. Here we introduce a time-discrete evolution
equation for arbitrary closed polygons in 3-space that is a discretisation of
the localised induction approximation of filament motion. This discretisation
shares with its continuum limit the property that it is a completely integrable
system. We apply this polygon evolution to a significant improvement of the
numerical algorithms used in Computer Graphics.Comment: 15 pages, 3 figure
Damage detection and location in woven fabric CFRP laminate panels
The need for multifunctional carbon fibre composite laminates has emerged to improve the reliability and safety of carbon fibre composite components and decrease costs. The development of an electrical selfsensing system for woven fabric carbon fibre composite laminate panels which can detect and locate damage due to impact events is presented. The electrical sensing system uses a four probe electrical resistance method. Two different sensing mats are investigated, the main difference between them are the surface area of the electrodes and the distance between the electrodes. To investigate the damage sensitivity of the sensing system for woven fabric carbon fibre composite laminate panels, panels are produced with various thicknesses from 0.84 to 3.5âŻmm and are impacted at energies from 1 to 10âŻJ to generate barely visible impact damage. Damage is detected using global electrical resistance changes, the changes in electrical resistance vary depending on carbon fibre volume fraction, spacing distance between the sensing electrodes in the sensing mats, the surface area of the electrodes, damage size, and damage type; it is found that the thicker the panel, the less sensitive the electrical resistance system is. The effect of the surface area of the sensing electrodes is high on the electrical resistance baseline, where the baseline increases by up to 55% when the surface area of the sensing electrodes increases from 100âŻmm2 to 400âŻmm2; while spacing distance between electrodes has a greater effect on damage sensitivity of the electrical resistance sensing system than the surface area of the sensing electrodes
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Macromineral and trace element concentrations and their seasonal variation in milk from organic and conventional dairy herds
To study the effects of dairy production system on milk macromineral and trace element concentrations, milk samples were collected monthly in 2019 from 43 conventional and 27 organic farms. Organic milk contained more Ca (1049.5 vs. 995.8 mg/kg), K (1383.6 vs. 1362.4 mg/kg), P (806.5 vs. 792.5 mg/kg) and Mo (73.3 vs. 60.6 ÎŒg/kg) but less Cu (52.4 vs. 60.6 ÎŒg/kg), Fe (0.66 vs 2.03 mg/kg), Mn (28.8 vs. 45.0 ÎŒg/kg), Zn (4.51 vs. 5.00 mg/kg) and Al (0.32 vs. 1.14 ÎŒg/kg) than conventional milk. Significant seasonal variation was observed in all determined mineralsâ concentrations. Milk I concentration was not consistently affected by production system, whereas organic milk contained less I in June and July than conventional milk. Dietary factors contributing to different milk mineral concentrations between production systems included intakes of maize silage, dry-straights and oils (higher in conventional diets), and pasture, clover and wholecrop (higher in organic diets)
Measuring Market Liquidity Risk - Which Model Works Best?
Market liquidity risk, the difficulty or cost of trading assets in crises, has been recognized as an important factor in risk management. Literature has already proposed several models to include liquidity risk in the standard Value-at-Risk framework. While theoretical comparisons between those models have been conducted, their empirical performance has never been benchmarked. This paper performs comparative back-tests of daily risk forecasts for a large selection of traceable liquidity risk models. In a 5.5 year stock sample we show which model provides most accurate results and provide detailed recommendations which model is most suitable in a specific situation
European youth care sites serve different populations of adolescents with cannabis use disorder. Baseline and referral data from the INCANT trial
Background: MDFT (Multidimensional Family Therapy) is a family based outpatient treatment programme for adolescent problem behaviour. MDFT has been found effective in the USA in adolescent samples differing in severity and treatment delivery settings. On request of five governments (Belgium, France, Germany, the Netherlands, and Switzerland), MDFT has now been tested in the joint INCANT trial (International Cannabis Need of Treatment) for applicability in Western Europe. In each of the five countries, study participants were recruited from the local population of youth seeking or guided to treatment for, among other things, cannabis use disorder. There is little information in the literature if these populations are comparable between sites/countries or not. Therefore, we examined if the study samples enrolled in the five countries differed in baseline characteristics regarding demographics, clinical profile, and treatment delivery setting.Methods: INCANT was a multicentre phase III(b) randomized controlled trial with an open-label, parallel group design. It compared MDFT with treatment as usual (TAU) at and across sites in Berlin, Brussels, Geneva, The Hague and Paris.Participants of INCANT were adolescents of either sex, from 13 through 18 years of age, with a cannabis use disorder (dependence or abuse), and at least one parent willing to take part in the treatment. In total, 450 cases/families were randomized (concealed) into INCANT.Results: We collected data about adolescent and family demographics (age, gender, family composition, school, work, friends, and leisure time). In addition, we gathered data about problem behaviour (substance use, alcohol and cannabis use disorders, delinquency, psychiatric co-morbidity).There were no major differences on any of these measures between the treatment conditions (MDFT and TAU) for any of the sites. However, there were cross-site differences on many variables. Most of these could be explained by variations in treatment culture, as reflected by referral policy, i.e., participants' referral source. We distinguished 'self-determined' referral (common in Brussels and Paris) and referral with some authority-related 'external' coercion (common in Geneva and The Hague). The two referral types were more equally divided in Berlin. Many cross-site baseline differences disappeared when we took referral source into account, but not all.Conclusions: A multisite trial has the advantage of being efficient, but it also carries risks, the most important one being lack of equivalence between local study populations. Our site populations differed in many respects. This is not a problem for analyses and interpretations if the differences somehow can be accounted for. To a major extent, this appeared possible in INCANT. The most important factor underlying the cross-site variations in baseline characteristics was referral source. Correcting for referral source made most differences disappear. Therefore, we will use referral source as a covariate accounting for site differences in future INCANT outcome analyses
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Mineral concentrations in bovine milk from farms with contrasting grazing management
Thirty conventional and 24 organic dairy farms were divided into equal-number within system groups: high-pasture, standard-pasture and low-pasture groups. Milk samples were collected monthly for 12 consecutive months. Milk from high-pasture organic farms contained less fat and protein than standard- and low-pasture organic farms, but more lactose than low-pasture organic farms. Pasture, concentrate feeds intakes and the contribution of non-Holstein breeds were the key drivers for these changes. Milk Ca and P concentrations were lower in standard-pasture conven-tional farms than the other conventional groups. Milk from low-pasture organic farms contained less Ca than high- and standard-pasture organic farms, while high-pasture organic farms produced milk with the highest Sn concentration. Differences in mineral concentrations were driven by the contribution of non-Holstein breeds, feeding practices, and grazing activity; due to relatively low numerical differences the subsequent impact on consumersâ mineral intakes would be minor
Corporate Social Responsibility Strategies of Spanish Listed Firms and Controlling Shareholdersâ Representatives
This article aims at analyzing how controlling shareholdersâ representatives on boards affect
corporate social responsibility (CSR) strategies (disclosing CSR matters) in Spain, a context
characterized by high ownership concentration, one-tier boards, little board independence, weak
legal protection for investors, and the presence of large shareholders, especially institutional
shareholders. Furthermore, among controlling shareholdersâ representatives, we can distinguish
between those appointed by insurance companies and banks and those appointed by mutual funds,
investment funds, and pension funds. The effect of these categories of directors on CSR strategies
is, therefore, also analyzed. Our findings suggest that controlling shareholdersâ representatives
have a positive effect on CSR strategies, as do directors appointed by investment funds, pension
funds, and mutual funds, while directors appointed by banks and insurance companies have no
impact on CSR strategies. This analysis offers new insights into the role played by certain types
of directors on CSR strategies
New Mediterranean biodiversity records (March 2016)
In this Collective Article on âNew Mediterranean Biodiversity Recordsâ, we present additional records of species found
in the Mediterranean Sea. These records refer to eight different countries mainly throughout the northern part of the basin, and
include 28 species, belonging to five Phyla. The findings per country include the following species: Spain: Callinectes sapidus
and Chelidonura fulvipunctata; Monaco: Aplysia dactylomela; Italy: Charybdis (Charybdis) feriata, Carcharodon carcharias,
Seriola fasciata, and Siganus rivulatus; Malta: Pomacanthus asfur; Croatia: Lagocephalus sceleratus and Pomadasys incisus;
Montenegro: Lagocephalus sceleratus; Greece: Amathia (Zoobotryon) verticillata, Atys macandrewii, Cerithium scabridum,
Chama pacifica, Dendostrea cf. folium, Ergalatax junionae, Septifer cumingii, Syphonota geographica, Syrnola fasciata, Oxyu-
richthys petersi, Scarus ghobban, Scorpaena maderensis, Solea aegyptiaca and Upeneus pori; Turkey: Lobotes surinamensis,
Ruvettus pretiosus and Ophiocten abyssicolum. In the current article, the presence of Taractes rubescens (Jordan & Evermann,
1887) is recorded for the first time in the Mediterranean from Italy. The great contribution of citizen scientists in monitoring
biodiversity records is reflected herein, as 10% of the authors are citizen scientists, and contributed 37.5% of the new findings.peer-reviewe
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