			Home About us Contact

Bench Mark (bench + mark)

Distribution by Scientific Domains

Earth and Environmental Science	40%

Selected Abstracts

Mathematical modelling of fire development in cable installations

FIRE AND MATERIALS, Issue 4 2001
P. Van Hees
In 1996 DG XII of the European Commission (Research and Development) approved a 3 year project on the fire performance of electrical cables. Within this FIPEC project, a major part of the work involved correlation and mathematical modelling of flame spread and heat release rate in cable installations. The FIPEC project has developed different levels of testing ranging from a small-scale, cone calorimeter test procedures developed for cables and materials, a full-scale-test procedure based on the IEC 60332-3, but utilizing HRR and SPR measurements, and a real scale test conducted on model cable installations. Links through statistical correlations and mathematical fire modelling between these levels were investigated and the findings are presented in this paper. These links could form the scientific foundations for standards upon which fire performance measurements can be based and for new fire engineering techniques within fire performance based codes. Between each testing level correlation, numerical and mathematical models were performed. All of the models were based on the cone calorimeter test method. The complexity of the models varied from correlation models to advanced physical pyrolysis models which can be used in CFD codes. The results will allow advanced prediction of cable fires in the future. Also a bench mark was established for the prediction of cable performance by means of data obtained from the constituent materials. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Analysis of the trophy sport fishery for the speckled peacock bass in the Rio Negro River, Brazil

FISHERIES MANAGEMENT & ECOLOGY, Issue 2 2008
M. H. HOLLEY
Abstract, The middle portion of the Rio Negro River in Brazil near the equator supports a popular recreational sport fishery for speckled peacock bass, Cichla temensis (Humboldt). The objective of this study was to determine the effect of fishing mortality on this population. Fish were collected from sport-fishing (n = 72) and commercial (n = 103) catches and otoliths were aged to estimate longevity, growth and natural mortality. Recreational anglers in this region seek to catch, then release, larger speckled peacock bass; and fish larger than 62 cm standard length (SL) (about 4.5 kg) served as a bench mark to assess the potential impact of subsistence and commercial harvest on the abundance of larger fish in the sport fishery. Time of opaque band formation on otoliths generally coincided with the dry season (November to April); these bands appeared to form once per year, but formation was highly variable. Speckled peacock bass grew to 62 cm SL on average in 6.4 years, but some fish obtained this size in 4,5 years. Maximum age was 9 years, but most fish were less than 7 years. Instantaneous annual natural mortality (M) estimated from maximum size, longevity and growth ranged from 0.19 to 0.44. Simulation modelling predicted that exploitation rates of fish >25 cm SL similar to the estimated natural mortality rates would reduce the abundance of fish >62 cm by 67,89% compared with no harvest. Even modest exploitation rates of 5% and 10% would result in approximately 30,50% reduction, respectively, of these larger fish. Abundance of large speckled peacock bass that sustains the sport fishery is susceptible to low rates of exploitation in this remote region of Brazil. [source]

Dispersion in non-ideal packed beds

AICHE JOURNAL, Issue 2 2010
U. M. Scheven
Abstract This work reanalyzes published time series dispersion traces (Han et al., AIChE J. 1985;31:277,288) from step input tracer passages recorded at different locations along the length of a packed bed filled with monodisperse solid spheres. The intrinsic dispersivity and sample dependent dispersion are separated by imposing a heuristic model where coarse grained axial advection velocities vary in a plane perpendicular to the flow but not along the direction of flow. The derived intrinsic dispersivity agrees with the predicted value (Scheven et al., Phys Rev Lett. 2007;99:054502-1,054502-4). It serves as a bench mark for different implementations of simulations coupling Stokes flow and diffusion in random geometries, and for experimental tests of injection and packing methods. Conceptually, a well defined and fittable effective dispersivity is introduced in an analytical framework describing dispersion data obtained in non-ideal packed beds, where elution profiles cannot be fitted to the solution of the one dimensional advection diffusion equation. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

Commercial assessment of growth and mortality of fifth-generation Sydney rock oysters Saccostrea glomerata (Gould, 1850) selectively bred for faster growth

AQUACULTURE RESEARCH, Issue 12 2009
Michael C Dove
Abstract The Sydney rock oyster Saccostrea glomerata (Gould, 1850) industry acquired hatchery-produced spat selected for faster growth for the first time in January 2004. Selectively bred and non-selected (Control) spat produced concurrently were used to compare performance when grown under commercial conditions. Spat were distributed to farmers in seven estuaries in New South Wales. Individual farmers cultivated these oysters using their own techniques and growth and mortality were recorded quarterly. At each site, the two oyster types were cultivated using the same culture method, location and density. Growth was compared when oysters were 27 months of age. At this time, selectively bred oysters were significantly larger and heavier than Control oysters. The same result was obtained when oysters were compared at the point in time when selectively bred oysters had reached 50 g at each site. No significant difference was found for cumulative mortality between the selectively bred oysters and Control oysters across all sites. However, the seven sites had significantly different levels of cumulative mortality. Overall, the performance of selectively bred oysters was superior to the Control oysters and selectively bred oysters reached the 50 g bench mark within 29.3 months when averaged across all sites. [source]

Distribution of endosulfan in water, sediment and fish from Warri river, Niger delta, Nigeria

AFRICAN JOURNAL OF ECOLOGY, Issue 1 2010
Lawrence Ikechukwu Ezemonye
Abstract This article presents the first attempt to quantify the levels and distribution pattern of endosulfan, an organochlorine pesticide in surface water, sediment and fish (Chrysichthys furcatus and Tilapia zilli). The samples were collected from three stations (Ovwian, Ekakpamre and Ovu) of Warri River in the western Niger Delta of Nigeria in 2006 during the dry and wet seasons (January,August). A total of 96 samples made up of 24 samples each for water, sediment and fish were analysed in this study. The pesticide levels were analysed using high performance liquid chromatography (HPLC model CECIL 1010) to elucidate its distribution in various environmental compartments. The ranges of concentrations of the pesticide in the matrices were: 0.01,9.23 ,g/l (water), 0.06,11.98 ,g/gdw (sediment), 0.01,15.06 ,g/gdw (Chrysichthys furcatus) and 0.01,1.80 ,g/gdw (Tilapia zilli). From this result, decreasing order of occurrence of the pesticide is as follows: fish > sediment > water. The concentrations observed in fish (Chrysichthys furcatus) were higher than the levels observed in sediment and water suggesting bioaccumulation of the pesticide by the fish. Spatial variations occurred with downstream stations having statistically higher concentrations in all matrices at P < 0.05. Seasonal variations occurred with higher concentrations in dry season for water and sediment only, while the fish species had higher concentrations in the wet season. The observed values of endosulfan were above the ecological bench marks (0.02 ,g/l) recommended by Nigeria Environmental Protection Agency and European Union. They were also relatively higher than those in previous studies on the Nigerian environment, an observation that calls for regular monitoring of the Niger Delta water bodies. Résumé Cet article présente le premier essai de quantifier les teneurs et le schéma de distribution de l'endosulfan, un pesticide organochloré, dans l'eau de surface, les sédiments et les poissons (Chrysichthys furcatus et Tilapia zilli). Les échantillons ont été récoltés en 2006 dans trois stations (Ovwian, Ekakpamre et Ovu) de la rivière Warri, dans le delta occidental du Niger, au Nigeria, pendant les saisons des pluies et sèche (janvier et août). Un total de 96 échantillons furent prélevés et analysés, à savoir 24 échantillons pour l'eau, pour les sédiments et pour les deux espèces de poissons. La teneur en pesticide a été analysée par la chromatographie en phase liquide à haute performance (HPLC modèle Cecil 1010) pour connaître sa distribution dans les différents compartiments environnementaux. La concentration du pesticide dans les matrices était de 0,01,9,23 ,g/l (eau), 0.06,11.98 ,g/gMS (sédiment), 0,01,15,06 ,g/gMS (Chrysichthys furcatus) et 0,01,1,80 ,g/gMS (Tilapia zilli). De ces résultats, nous pouvons dire que l'ordre d'occurrence du pesticide est le suivant: poissons > sédiment >eau. Les concentrations observées chez le poisson Chrysichthys furcatusétaient plus élevées que celles des sédiments et de l'eau, ce qui suggère une bio-accumulation du pesticide dans le poisson. Il y avait aussi des variations spatiales: les stations situées en aval avaient des concentrations statistiquement plus grandes dans toutes les matrices àP < 0,05. Il y avait des variations saisonnières, et les concentrations étaient plus élevées en saison sèche pour l'eau et les sédiments seulement, alors que les deux espèces de poissons présentaient une teneur plus élevée en saison des pluies. Les teneurs en endosulfan constatées étaient plus élevées que les normes écologiques (0,02 ,g/l) recommandées par l'Agence de protection environnementale du Nigeria et par l'Union européenne. Elles étaient aussi relativement plus élevées que celles décelées lors d'études antérieures de l'environnement au Nigeria, observation qui appelle à un suivi régulier des étendues d'eau du delta du Niger. [source]