Thematische Bibliographien / Successioni numeriche

Auswahl der wissenschaftlichen Literatur zum Thema „Successioni numeriche“

Autor: Grafiati

Veröffentlicht am 26. Juli 2024

Zuletzt aktualisiert am 27. Juli 2024

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Zeitschriftenartikel zum Thema "Successioni numeriche"

Winkler, Dániel. „Ecological Succession of Breeding Bird Communities in Deciduous and Coniferous Forests in the Sopron Mountains, Hungary“. Acta Silvatica et Lignaria Hungarica 1, Nr. 1 (01.01.2005): 49–58. http://dx.doi.org/10.37045/aslh-2005-0004.

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The relationship between breeding bird communities and different phases of secondary succession of deciduous (sessile oak – Quercus petraea) and coniferous (spruce – Picea abies) forests in the Sopron Mountains was studied. The bird censi have been carried out in 5 different successional stages using the “double-visit fixed-radius point count technique”. A total of 38 bird species were encountered. There are typical bird communities to order to different stages of forest succession, containing unique bird species or species appearing predominantly in that successional stage. The study has shown structural changes in breeding bird communities during the succession. Bird species richness, density and diversity showed the same trends. Their numerical values were the lowest in the clear-cut areas with young (1-2 year old) plantations, and the highest in the mature stands. After a starting increase (shrub stage) there is a slight decline (10-12 year old stands) because of the canopy closure of the young trees. Further decrease can be observed in the low pole stands, as these habitats are no longer appropriate for species nesting in shrubs and not yet suitable for the hole-nesting ones. Species richness, density and diversity were lower in early pole and older spruce stands than in the corresponding oak stands.

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Monga, Priyanka, Madhav Kumar, Vandana Prasad und Yogesh Joshi. „Palynostratigraphy, palynofacies and depositional environment of a lignite-bearing succession at Surkha Mine, Cambay Basin, north-western India“. Acta Palaeobotanica 55, Nr. 2 (01.12.2015): 183–207. http://dx.doi.org/10.1515/acpa-2015-0010.

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Abstract The paper reports palynology and palynofacies studies of lignite-bearing sediments exposed in an opencast mine succession at Surkha, Bhavnagar District, in the coastal region of Gujarat, India. The study examined the relationships between the palynoflora, sedimentary organic matter and environment at the time of deposition of lignite and associated sediments. Based on dinoflagellate cyst biostratigraphy, the sedimentary succession is dated as early Eocene (Ypresian). Palynofacies studies helped reveal the palaeoenvironmental fluctuations. The dominance of angiosperm pollen grains, freshwater algae, microthyraceous fungi and a large share of land debris in the lower part of the succession suggests a freshwater swamp environment of deposition for the basal lignite facies. Two cenozones - Matanomadiasulcites maximus and Lakiapollis ovatus - were identified in the lower lignite facies, determined from the dominance of these pollen grains in the palynological assemblages. The presence of angiosperm pollen grains and pteridophyte spores in the carbonaceous shale horizon above the lignite facies indicates a change in the depositional regime from freshwater swamp to lagoonal. This was identified as the Arecipites wodehousei cenozone due to its numerical abundance in the assemblage. Dinoflagellate cyst abundance and diversity, and microforaminiferal test linings along with well-sorted terrestrial debris in the mudstone in the upper part of the succession suggest a more open marine estuarine type of depositional environment. The Homotryblium complex along with Cordospheridium fibrospinosum, Kenleyia sp., and Thalassiphora pelagica dinoflagellate cysts are the main representatives of this zone, determined as the Homotryblium tenuispinosum cenozone. The changing depositional settings (freshwater swamp-lagoonal-estuarine) along the vertical succession indicate a marine transgression in this region. Results from palynological studies of early Palaeogene successions of the Cambay and Kutch basins correlate well with the present findings.

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Ma, Wei, Shen Lei, Yujun Sun und Jason Grabosky. „Forest succession in post-agricultural Larix olgensis plantations in northeast China“. Journal of Forestry Research 31, Nr. 6 (11.07.2019): 2495–505. http://dx.doi.org/10.1007/s11676-019-00960-7.

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Abstract In order to understand the management of regional vegetation, numerical classification and ordination are widely used to investigate community distribution and vegetation features. In particular, two-way indicator-species analysis programs (TWINSPAN) classifies plots and species into different groups. De-trended correspondence analysis (DCA) and canonical correspondence analysis (CCA) reflects the relationship between community and site conditions. Afforestation with Larix olgensis Herry. Plantations is a suitable restoration strategy on post-agricultural fields in the Lesser Khingan Mountains. The results of this study show how these plantations develop over time to establish a reliable pathway model by measuring and clarifying the succession process. Twenty-eight L. olgensis plantations along a 48-year chronosequence of afforestation were investigated with a quadrat sampling method. Species composition, community structure attributes of diversity, and site conditions were analyzed. Communities were classified by TWINSPAN into five successional stages: immature, juvenile, mid-aged, near-mature and mature. Classifications were validated by DCA and CCA analysis. Site conditions such as soil and litter thickness, soil organic matter, soil density, and pH were measured. Successional stages varied in community composition and species population, accompanied by time from afforestation and a gradient of site conditions. This gradient showed changes in vegetation occurrence and diversity coinciding with changes in soil conditions. The study showed that L. olgensis plantations had marked predominance in growth and were associated with improved soil fertility and the formation of a stable plant community.

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Salugin, A. N. „NUMERICAL MODELING OF SUCCESSIONAL TRANSITIONS IN AGROECOLOGY“. Rossiiskaia selskokhoziaistvennaia nauka, Nr. 1 (2020): 62–65. http://dx.doi.org/10.31857/s2500-2627-2020-1-62-65.

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Salugin, A. N. „Numerical Modeling of Successional Transitions in Agroecology“. Russian Agricultural Sciences 46, Nr. 2 (März 2020): 187–91. http://dx.doi.org/10.3103/s1068367420020172.

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Fischer, Martin H., und Richard A. Mills. „A spatial perspective on numerical concepts“. Behavioral and Brain Sciences 31, Nr. 6 (Dezember 2008): 651–52. http://dx.doi.org/10.1017/s0140525x08005670.

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AbstractThe reliable covariation between numerosity and spatial extent is considered as a strong constraint for inferring the successor principle in numerical cognition. We suggest that children can derive a general number concept from the (experientially) infinite succession of spatial positions during object manipulation.

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Chang, Li, Yuanqing He, Taibao Yang, Jiankuo Du, Hewen Niu und Tao Pu. „Analysis of Herbaceous Plant Succession and Dispersal Mechanisms in Deglaciated Terrain on Mt. Yulong, China“. Scientific World Journal 2014 (2014): 1–13. http://dx.doi.org/10.1155/2014/154539.

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Ecological succession itself could be a theoretical reference for ecosystem restoration and reconstruction. Glacier forelands are ideal places for investigating plant succession because there are representative ecological succession records at long temporal scales. Based on field observations and experimental data on the foreland of Baishui number 1 Glacier on Mt. Yulong, the succession and dispersal mechanisms of dominant plant species were examined by using numerical classification and ordination methods. Fifty samples were first classified into nine community types and then into three succession stages. The three succession stages occurred about 9–13, 13–102, and 110–400 years ago, respectively. The earliest succession stage contained the association ofArenaria delavayi +Meconopsis horridula. The middle stage contained the associations ofArenaria delavayi + Kobresia fragilis,Carex capilliformis +Polygonum macrophyllum,Carex kansuensis, and alsoPedicularis rupicola. The last stage included the associations ofKobresia fragilis + Carex capilliformis,Kobresia fragilis,Kobresia fragilis+Ligusticum rechingerana, andKobresia fragilis + Ligusticum sikiangense. The tendency of the succession was from bare land to sparse vegetation and then to alpine meadow. In addition, three modes of dispersal were observed, namely, anemochory, mammalichory, and myrmecochory. The dispersal modes of dominant species in plant succession process were evolved from anemochory to zoochory.

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Catelli, Marika, Angelica Di Domenico, Carlo Mina und Monica Treppiedi. „Alla scoperta dei numeri che ci circondano“. Didattica della matematica. Dalla ricerca alle pratiche d’aula, Nr. 11 (18.05.2022): 69–94. http://dx.doi.org/10.33683/ddm.22.11.4.

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L’articolo presenta dei percorsi didattici finalizzati all’apprendimento numerico in prima elementare, attraverso la ricerca e la conoscenza dei numeri con cui i bambini si confrontano nella quotidianità. I percorsi sono incentrati su attività di scoperta, di stampo laboratoriale e ludico, che hanno la finalità di promuovere le competenze numeriche di base, fondamentali per questo anno scolastico, proponendo anche sviluppi per ampliare e consolidare tali apprendimenti anche negli anni scolastici successivi. Per ogni percorso, vengono presentati alcuni possibili legami con i materiali creati all’interno del progetto MaMa – Matematica per la scuola elementare, che possono aiutare il docente per la progettazione di tali percorsi, consentendo di alternare attività di scoperta, concrete e manipolative, con momenti di riflessione e allenamento.

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CHERRUAULT, Y. „Some numerical methods for resolution of non-linear integral equations“. MAUSAM 36, Nr. 3 (06.04.2022): 319–22. http://dx.doi.org/10.54302/mausam.v36i3.1924.

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We suggest several methods which bring back the resolution of non-linear integral equations to a succession of linear integral equations or to a linear algebraic system. All these methods have been tested numerically.

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Blajer, W. „Aircraft program motion along a predetermined trajectory Part II. Numerical simulation with application of spline functions to trajectory definitions“. Aeronautical Journal 94, Nr. 932 (Februar 1990): 53–58. http://dx.doi.org/10.1017/s0001924000022430.

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Aspects of numerical simulation of aircraft program flight along a predetermined trajectory are presented. An emphasis is laid on the problem of describing the required trajectory by means of a succession of defined points. A spline function method is used for interpolation and smoothing routines. Some numerical illustrations of aircraft trajectory flight simulation (only planar motion) are demonstrated and discussed.

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Dissertationen zum Thema "Successioni numeriche"

Markensten, Hampus. „Climate Effects on Phytoplankton Biomass and Functional Groups“. Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Universitetsbiblioteket [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6029.

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Chan, Terence. „Phytoplankton dynamics in a seasonal estuary“. University of Western Australia. Centre for Water Research, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0089.

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[Truncated abstract] The Swan River is a highly seasonal estuary in the south-west of Western Australia. Salinity may vary from fresh to marine at various times throughout the estuary, depending mostly on the intensity of freshwater discharge. There are occasional problematic dinoflagellate blooms which have spurred investigation of the dynamics of the phytoplankton community. The objective of this research was to examine how phytoplankton biomass and species' successions are influenced by the multiple variables in the aquatic ecosystem, and, if possible, to determine the dominant factors ... Comparisons of phytoplankton nutrient limitation simulations with experimental observations from field bioassays require further investigation, but reinforce findings that nutrients may only limit phytoplankton biomass when there is a convergence of favourable hydrological and hydrodynamic conditions. The Swan River estuary has undergone substantial hydrological modifications from pre-European settlement. Land clearing has increased freshwater discharge up to 5- fold, while weirs and reservoirs for water supply have mitigated this increase and reduced the duration of discharge to the estuary. Nutrient loads have increased approximately 20-fold from pre-European levels. The individual and collective impacts of these hydrological changes on the Swan River estuary were examined using the hydrodynamic-ecological numerical model. The simulation results indicate that despite increased hydraulic flushing and reduced residence times, increases in nutrient loads are the dominant perturbation, producing increases in the frequency and biomass of blooms by both estuarine and freshwater phytoplankton. By comparison, changes in salinity associated with altered seasonal freshwater discharge have a limited impact on phytoplankton dynamics. Reductions of nutrient inputs into the Swan River estuary from its catchment will provide a long-term improvement in water quality but manipulations of freshwater discharge have the potential to provide a provisional short-term remediation measure allowing at least partial control of phytoplankton bloom potential and eutrophication.

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Bücher zum Thema "Successioni numeriche"

Raiola, Joe, und Raffaele Monaco. Successioni e Serie Numeriche. Independently Published, 2019.

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Lezioni di Matematica -Programma triennio scuole superiori, vol.2-. Autopubblicato, 2023.

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Bartkowicz, Leszek. Tekstura drzewostanów naturalnych w polskich parkach narodowych na tle teorii dynamiki lasu. Publishing House of the University of Agriculture in Krakow, 2021. http://dx.doi.org/10.15576/978-83-66602-20-5.

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The aim of the study was to compare a patch-mosaic pattern in the old-growth forest stands developed in various climate and soil conditions occurring in different regions of Poland. Based on the assumption, that the patch-mosaic pattern in the forest reflect the dynamic processes taking place in it, and that each type of forest ecosystem is characterized by a specific regime of natural disturbances, the following hypotheses were formulated: (i) the patches with a complex structure in stands composed of latesuccessional, shade-tolerant tree species are more common than those composed of early-successional, light-demanding ones, (ii) the patch-mosaic pattern is more heterogeneous in optimal forest site conditions than in extreme ones, (iii) in similar site conditions differentiation of the stand structure in distinguished patches is determined by the successional status of the tree species forming a given patch, (iv) the successional trends leading to changes of species composition foster diversification of the patch structure, (v) differentiation of the stand structure is negatively related to their local basal area, especially in patches with a high level of its accumulation. Among the best-preserved old-growth forest remaining under strict protection in the Polish national parks, nineteen research plots of around 10 ha each were selected. In each plot, a grid (50 × 50 m) of circular sample subplots (with radius 12,62 m) was established. In the sample subplots, species and diameter at breast height of living trees (dbh ≥ 7 cm) were determined. Subsequently, for each sample subplot, several numerical indices were calculated: local basal area (G), dbh structure differentiation index (STR), climax index (CL) and successional index (MS). Statistical tests of Kruskal- Wallis, Levene and Generalized Additive Models (GAM) were used to verify the hypotheses. All examined forests were characterized by a large diversity of stand structure. A particularly high frequency of highly differentiated patches (STR > 0,6) was recorded in the alder swamp forest. The patch mosaic in the examined plots was different – apart from the stands with a strongly pronounced mosaic character (especially subalpine spruce forests), there were also stands with high spatial homogeneity (mainly fir forests). The stand structure in the distinguished patches was generally poorly related to the other studied features. Consequently, all hypotheses were rejected. These results indicate a very complex, mixed pattern of forest natural dynamics regardless of site conditions. In beech forests and lowland multi-species deciduous forests, small-scale disturbances of the gap dynamics type dominate, which are overlapped with less frequent medium-scale disturbances. In more difficult site conditions, large-scale catastrophic disturbances, which occasionally appear in communities formed under the influence of gap dynamics (mainly spruce forests) or cohort dynamics (mainly pine forests), gain importance.

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Buchteile zum Thema "Successioni numeriche"

Biollay, Yves, Amel Chaabouni und Joachim Stubbe. „Successioni, serie numeriche e limiti“. In UNITEXT, 139–56. Milano: Springer Milan, 2007. http://dx.doi.org/10.1007/978-88-470-0676-8_7.

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Canuto, Claudio, und Anita Tabacco. „Confronto locale di funzioni. Successioni e serie numeriche“. In UNITEXT, 129–74. Milano: Springer Milan, 2014. http://dx.doi.org/10.1007/978-88-470-5723-4_5.

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Canuto, Claudio, und Anita Tabacco. „Confronto locale di funzioni. Successioni e serie numeriche“. In UNITEXT, 127–69. Milano: Springer Milan, 2005. http://dx.doi.org/10.1007/88-470-0400-4_5.

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Canuto, Claudio, und Anita Tabacco. „Confronto locale di funzioni. Successioni e serie numeriche“. In UNITEXT, 127–69. Milano: Springer Milan, 2008. http://dx.doi.org/10.1007/978-88-470-0872-4_5.

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Imai, Yota, Yasunori Muto und Mahito Kamada. „Change in Floodwater Retention Function of a Paddy Field Due to Cultivation Abandonment in a Depopulating Rural Region in Japan“. In Ecological Research Monographs, 161–73. Singapore: Springer Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-6791-6_10.

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AbstractFlood control concept at watershed scale is used as an adaptation strategy for climate change; rainwater and floodwater should be stored in forests and agricultural lands in the watershed, rather than relying on only river systems; and paddy fields are important ecosystems for floodwater retention. The abandonment of paddy cultivation, however, is increasing year after year in Japan due to depopulation in rural regions. Through two-dimensional numerical inundation analysis, we evaluated the negative effects of topographical changes after abandonment on the floodwater retention function. The bipolarization of the inundation depth is apparent in the current topography. The areas with deepwater inundation are wider, particularly in the most downstream areas, whereas in the past, areas with shallow water were widely distributed. The peak water level in the current land use is 0.4 m higher than in the past. After the peak level is achieved, the water level decreases in a shorter time in the present land use than in the past. Owing to hydraulic changes after the abandonment of rice cultivation, the risk of flooding disasters for people living downstream has increased. To maintain floodwater retention function, one of the regulating services, by artificial wetlands, such as paddy fields, continuous management is essential to prevent vegetation succession. Thus, it is important to provide incentives for local people to perform the daily maintenance activities.

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„2.3. Numerical Age Control for the Miocene-Pliocene Succession at Lothagam, a Hominoid-bearing Sequence in the Northern Kenya Rift“. In Lothagam, 43–64. Columbia University Press, 2003. http://dx.doi.org/10.7312/leak11870-004.

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Odin, G. S. „Chapter E5c Numerical age calibration of the Campanian-Maastrichtian succession at Tercis les Bains (landes, france) and in the Bottaccione Gorge (Italy)“. In Developments in Palaeontology and Stratigraphy, 775–82. Elsevier, 2001. http://dx.doi.org/10.1016/s0920-5446(01)80068-6.

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Ganghoffer, Jean-François. „Mechanical Models of Cell Adhesion Incorporating Nonlinear Behavior and Stochastic Rupture of the Bonds“. In Handbook of Research on Computational and Systems Biology, 599–627. IGI Global, 2011. http://dx.doi.org/10.4018/978-1-60960-491-2.ch027.

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The rolling of a single biological cell is analysed using modelling of the local kinetics of successive attachment and detachment of bonds occurring at the interface between a single cell and the wall of an ECM (extracellular matrix). Those kinetics correspond to a succession of creations and ruptures of ligand-receptor molecular connections under the combined effects of mechanical, physical (both specific and non-specific), and chemical external interactions. A three-dimensional model of the interfacial molecular rupture and adhesion kinetic events is developed in the present contribution. From a mechanical point of view, this chapter works under the assumption that the cell-wall interface is composed of two elastic shells, namely the wall and the cell membrane, linked by rheological elements representing the molecular bonds. Both the time and space fluctuations of several parameters related to the mutual affinity of ligands and receptors are described by stochastic field theory; especially, the individual rupture limits of the bonds are modelled in Fourier space from the spectral distribution of power. The bonds are modelled as macromolecular chains undergoing a nonlinear elastic deformation according to the commonly used freely joined chains model, while the cell membrane facing the ECM wall is modelled as a linear elastic plate. The cell itself is represented by an equivalent constant rigidity. Numerical simulations predict the sequence of broken bonds, as well as the newly established connections on the ‘adhesive part’ of the interface. The interplay between adhesion and rupture entails a rolling phenomenon. In the last part of this chapter, a model of the deformation induced by the random fluctuation of the protrusion force resulting from the variation of affinity with chemiotactic sources is calculated, using stochastic finite element methods in combination with the theory of Gaussian random variables.

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Konferenzberichte zum Thema "Successioni numeriche"

He, Shuling, Dejiang Kong, Jingjun Yang, Lingfa Ma und Yuwei Chang. „Numerical Simulation Of Wetland Ecological Vegetation Restoration And Succession Based On Gis Grid“. In 2020 5th International Conference on Smart Grid and Electrical Automation (ICSGEA). IEEE, 2020. http://dx.doi.org/10.1109/icsgea51094.2020.00135.

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Farrell, Thomas, Hannah Cothren, Laura J. Crossey, Carol Dehler, John R. Foster, James W. Hagadorn, Karl E. Karlstrom, Fred A. Sundberg, Mark D. Schmitz und Mark Webster. „NUMERICAL CALIBRATION OF WESTERN LAURENTIAN CAMBRIAN STRATIGRAPHIC SUCCESSIONS INTO THE GLOBAL GEOLOGIC TIME SCALE“. In GSA Connects 2021 in Portland, Oregon. Geological Society of America, 2021. http://dx.doi.org/10.1130/abs/2021am-368486.

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Chaouachi, Frej, und Ali Zghal. „Study of the Stress Contact Spur Gear, Using the Numerical Asymptotic Method and the Classical Contact Law“. In World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-63038.

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This work is a contribution to optimize the size of gears, by studying the variations of spur gear contact stress. The formulation is based on the virtual work principal and the classical contact law. Such contact problem is non-linear and is generally treated through the Newton-Raphson’s method, which is a robust method but nevertheless requires high computational resources. In this work and as an alternative the used methodology jointly applies the asymptotic numerical method and the finite element method that is a good compromise between efficiency and computational resources. It consists in rewriting the different dependent variables as an asymptotic development which transforms a non-linear problem into a succession of linear ones. The contact is formulated by Hertz theory which assimilate teeth contact to a contact between two cylinders; by applying the classical contact law we take into account the real geometry profile of the teeth.

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Escalona, José L., Juana M. Mayo und Jaime Domínguez. „A New Numerical Method for the Dynamic Analysis of Impact Loads in Flexible Beams“. In ASME 1997 Design Engineering Technical Conferences. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/detc97/vib-4207.

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Abstract The aim of this investigation is to compare the classical St. Venant’s solution of the axial impact on flexible rods with the numerical result from a finite element computational procedure involving component mode synthesis. A new technique developed to simulate impacts is used to this end. The impacts treated are those mainly governed by the propagation of elastic waves along the complete flexible body. Local effects at the vicinity of the contact surfaces are neglected. The phenomenon of succession of impacts is analytically proved, a second period of contact is found in a particular case. A numerical method is developed to solve the collision based on the theoretical solution. This technique is able to identify the elastic waves which travel along the rod and a force balance is continuously made to yield the contact stress and the velocity of the surfaces in contact. Numerical solution shows an excellent agreement between the numerically obtained displacements histories with the theoretical results. The capability of the eigenvectors to describe the wave propagation is analysed as well as the effect of the elements boundaries.

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Proano, Erik S., und Bertrand Rollin. „Numerical Study of Hydrodynamic Instabilities in Converging Geometry“. In ASME 2017 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fedsm2017-69557.

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This work presents simulations of a heavy gas, SF6, immersed within a light gas, air, under the effect of a converging shock wave. Upon interaction of the shock wave with the perturbed interface between air and SF6, Richtmyer-Meshkov instability (RMI) and, later, Rayleigh-Taylor instability (RTI) take place. More precisely, a succession of RMI and RTI occurs due to multiple shock and rarefaction waves, and gives rise to mixing between the heavy and light fluids. The problem of hydrodynamic instability-induced mixing in converging geometry is particularly relevant to engineering applications such as the process of nuclear fusion by the inertial confinement approach. This study is motivated by the need to better understand the relation between the initial perturbations at the interface between the fluids and the development of the instabilities and mixing in a converging geometry. Using the Flash Code, a PPM hydrodynamic solver developed by the ASC center at the University of Chicago [1], this study focuses on the growth rate of instabilities and the subsequent mixing associated with various carefully designed initial interfacial perturbations in the implosion configuration described above. In cylindrical geometry, comparisons between the growth of high and low frequency single mode perturbations are presented. It is found that at later times, after RMI and RTI take place, the width of the mixing layer is the largest for the low-wavenumber initial interface perturbation. Also, simulations show that the SF6 target with the highest wavenumber perturbation presents the most mixing at the later times but the lowest wavenumber initial interface perturbation presents the most mixing before reshock.

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Krovvidi, Sai C., M. Ramulu und Per G. Reinhall. „Numerical Study of the Percussive Riveting Process: Initial Results“. In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-11544.

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Abstract Percussive riveting is a dependable assembly method that produces high-quality joints in the aerospace industry. Its successful application is derived from its ease to implement in an assembly floor environment. The rivets are formed on the shank end of the rivet using a forming tool like a bucking bar and the head is constrained and impacted with a rapid succession of hits using a pneumatic gun with a special purpose die head. The rivet forms an interference fit joint because of the residual compressive stresses that are set up in the circumferential direction due to plastic flow of rivet material. These compressive stresses are balanced by tensile stresses in the skin and stiffener bulk material. Compressive stresses in the longitudinal direction help keep the skins pressed together. Research studies focused on the dynamics modeling of the percussive riveting process for robotic automation have not delivered an understanding of the temporal evolution of stress and strain fields in the vicinity of the rivet and the rivet hole. These studies aimed to produce joints of equal strength using automated assembly process compared with the manual assembly process. No modeling efforts have been published up to this point in time. This understanding is important in order to produce joints of predictable strength. A simulation effort for an unstiffened percussive riveting stackup assembly will be undertaken to study the trends of beneficial compressive residual stresses and strains within the bucked rivet. It is our goal to eventually estimate joint strength for prescribed sets of joint assembly parameters. The domain of interest will be restricted to few inches from the rivet axis.

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Cavalli, Stella C. P., Cristiane Cozin, Fausto A. A. Barbuto und Rigoberto E. M. Morales. „Analysis of Numerical Simulation of Gas-Liquid Slug Flow Using Slug Tracking Model“. In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-52031.

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The distribution of the interfaces in gas-liquid two-phase flows in pipes can assume several shapes. Amongst those shapes, the slug flow pattern stands out as the most common one and occurs quite often in oil and gas production due to the flow rates and geometries used. This pattern is characterized by the succession of the so-called unit cells, that is, a flow structure composed of an aerated liquid slug and an elongated bubble surrounded by a liquid film. Due to its complexity, the study and understanding of this pattern’s behaviour becomes very important. The main methodologies used to describe slug flows are the steady-state one-dimensional models, based on the slug unit concept, and the transient approach, which takes the flow intermittence into account. The slug tracking model is one such transient approach, which considers slugs and elongated bubbles as separated bodies and analyzes the evolution along the flow and the interaction between those bodies. Whenever this model is numerically implemented, its initial conditions are important parameters that affect the results. The goal of this article is to study the influence of the initial conditions on slug flow simulation using the slug tracking model. A computer program written in Fortran95 using a slug tracking model to provide the characteristic parameters of slug flows such as the bubble and slug lengths and void fraction in the bubble region was built and used. The results were compared to experimental data and showed the important role the initial conditions play on the computational simulation of slug flow.

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Trinh, Cuong, Dimiter Zlatanov, Matteo Zoppi und Rezia Molfino. „A Geometrical Approach to the Inverse Kinematics of 6R Serial Robots With Offset Wrists“. In ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/detc2015-47950.

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The computation of the joint-angle values of a 6R serial manipulator for a given end-effector pose is more difficult for architectures lacking the conventional spherical wrist. Despite this added complexity, such arms have increasingly gained acceptance as they provide better dexterity for a number of tasks. The paper presents a geometric-analysis method for the inverse kinematics of a robot with an offset wrist. The sought postures are shown to correspond to the roots of four separate univariate trigonometric equations for the sixth joint angle. A standard numerical solver is applied to derive all sets of possible real solutions. By back-substitution, all the remaining angular variables are found in succession. Two particular arm designs are considered and full sets of solutions are obtained by the discussed approach. The method is easy to implement and can be applied to various 6R serial robots.

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Toft, Adam, und John Sharples. „The Delivery of Technical Training Within the European Style Project“. In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97087.

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The STYLE project considers structural integrity for lifetime management of non-reactor pressure vessel components of nuclear power plant. The project is funded under the seventh European Commission framework programme. A broad objective of the project is to assess, optimise and develop application of advanced tools for structural integrity assessment of reactor coolant pressure boundary components other than the reactor pressure vessel. One aspect of the STYLE project is intended to address the issue of succession planning within the European nuclear industry. With many key technical experts now approaching retirement it is essential to progress the technical expertise of those at an earlier stage of their career in the industry. The paper describes how technical training has been delivered as an integral part of the STYLE project to support retention of the current level of technical capability in future. Diverse aspects of training are described. These include participation in experimental work, numerical modelling and simulation, application of engineering assessment procedures, leak-before-break, probabilistic fracture mechanics and materials behaviour. An illustrative case study is described, in which trainees received practical instruction in the essential steps for technical justification of a leak-before-break argument.

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Jolgam, Shaban A., Ahmed R. Ballil, Andrzej F. Nowakowski und Franck C. G. A. Nicolleau. „Simulations of Compressible Multiphase Flows Through a Tube of Varying Cross-Section“. In ASME 2012 11th Biennial Conference on Engineering Systems Design and Analysis. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/esda2012-82370.

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The simulation of multiphase compressible flows through high pressure nozzles is presented. The study uses the developed numerical approach. There are many important engineering applications which are concerned with multiphase flows and convergent-divergent nozzles. This work presents the developed extension of the model and numerical algorithm based on the so called parent model earlier introduced by Saurel and Abgrall [Saurel, R. and Abgrall, R., A Multiphase Godunov Method for Compressible Multifluid and Multiphase Flows, J. Comput. Phys. 150 (1999), 425–467]. This model which consists of conservation laws for each phase complemented with the volume fraction evolution equation is modified by adding a source term to simulate area variation. The model is strictly hyperbolic and non-conservative due to the existence of non-conservative terms. The model is able to deal with compressible and incompressible flows. Moreover, it can deal with mixtures and pure fluids, where each fluid has its own pressure and velocity. The presence of velocity and pressure relaxation terms in the governing equations has made the velocity and pressure relaxation processes essential to tackle the boundary conditions at the interface. The interface separating phases is considered as a numerical diffusion zone in this method. The model is solved using an efficient Eulerian numerical method. A second order Godunov-type scheme with approximate Riemann solver is used to enable capturing of a physical interface by the resolution of the Riemann problem. The solution is obtained by splitting the hyperbolic part and source terms parts in the numerical algorithm. The source terms, including relaxation parts of the model, are tackled in succession using Strang splitting technique. The governing equations are solved at each computational cell using the same numerical algorithm for the whole domain including the interface. The main aim of this work has been to study different flow regimes with respect to pressure boundary conditions through the numerical solutions of single and multiphase flows. The performance of the programme has been verified via well established benchmark test problems for multiphase flows.

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