Search results for "Drag"

Frictional Drag Mechanisms between Polymer-Bearing Surfaces

2001

The fundamental features of friction between two polymer-bearing surfaces in relative sliding motion are investigated by molecular dynamics simulation. Adsorbed and grafted polymers are considered in good and bad solutions. The solvent is not treated explicitly but indirectly in terms of a Langevin thermostat. In both systems, we observe shear thinning that is attributed to an orientation of the radius of gyration along the sliding direction. This effect is particularly strong for surfaces bearing polymer brushes. In this case, the shear stresses are mainly determined by the degree of the interpenetration of brushes.

All-Polish Andragogical Journals in the Interwar Period (1918–1939)

2020

In the article, the author attempts to show the role of andragogical journals in popularizing adult education in the Interwar period. Six Polish journals of nationwide circulation are characterized, as they reflected the socio-ideological profile of the state and the organizations which published them. In their columns, theoretical and methodological studies which facilitated work with adults were presented. Their major task was to support teachers and educators in their school and outside-school work with adult learners. The basis for preparing the present text was an analysis of the content of the periodicals. W tekście podjęto próbę ukazania roli czasopism andragogicznych w upowszechnian…

«Men dere øver på det hjemme?» : realiseringen av det delte oppdragermandat: en fortolkende studie av kommunikativ praksis i barnehagens foreldresamt…

2016

Masteroppgave pedagogikk - Universitetet i Agder 2016 Det primære pedagogiske mandat, hovedansvaret for barnas oppdragelse, ligger hos foreldrene (Evenshaug & Hallen, 1997). Samtidig skal barnehagen i samarbeid med hjemmet «fremme læring og danning som grunnlag for allsidig utvikling» (barnehageloven, 2006, § 1). Denne kvalitative studien belyser hvordan hjem og barnehage i foreldresamtalen kommuniserer angående oppdragelse. Det empiriske materialet består av åtte foreldresamtaler og etterfølgende intervjuer med foreldre. Med utgangspunkt i Habermas’ (1984) teori om kommunikativ handling, fortolker jeg pedagogers og foreldres bruk av strategisk og kommunikativ handling. Videre drøfter jeg h…

Obrazy patriotyczne we współczesnej andragogice

2019

The unusual hydrodynamical behaviour of freshwater oncolites

1997

Algal concretions are frequent in calcareous environments, occuring as individual particles (oncolites) that are easily transported during floods. Several parameters have been measured and calculated for a population of 127 particles from French streams. These oncolites have a high porosity (mean 42.7%) and a low density (mean 1.65), in respect to quartz and calcite. Oncolites have a settling velocity 1.5 times lower than that of quartz grains with the same nominal diameter. The computation of multiple correlations results in a classification in terms of decreasing efficiency: shape coefficients (Corey, ψ, and SI of Sneed and Folk), nominal diameter, density, edge sharpness and roughness. A…

Risk of Local Extinction of Odonata Freshwater Habitat Generalists and Specialists

2014

Understanding the risk of a local extinction in a single population relative to the habitat requirements of a species is important in both theoretical and applied ecology. Local extinction risk depends on several factors, such as habitat requirements, range size of species, and habitat quality. We studied the local extinctions among 31 dragonfly and damselfly species from 1930 to 1975 and from 1995 to 2003 in Central Finland. We tested whether habitat specialists had a higher local extinction rate than generalist species. Approximately 30% of the local dragonfly and damselfly populations were extirpated during the 2 study periods. The size of the geographical range of the species was negati…

150 years of rowing faster: what are the sources of more and more speed?

2015

Rowing has a 150 yr+ competitive history. Examining results from historic races like Oxford-Cambridge (established 1829) and the world championships (established 1893) reveals a linear increase in boat speed by 2-3% per decade. Boat velocity increases if propulsive power is increased and/or power losses are reduced. Over time, the propulsive power capacity of elite rowers has increased. Part of this increase is a result of recruiting athletes from a population that has become taller (1-3 cm per decade) and heavier. Modern world class rowers are typically 190-200 cm tall and weigh 90-100 kg. However, physical capacity does not scale directly with body dimensions but conforms instead to biolo…

Familias reconstituidas: el cuestionamiento de los roles tradicionales parentales encarnados en las madres y las madrastras

2019

Yhteisövoimainen oppimisprosessi : substantiivinen teoria aikuisten ryhmässä oppimisen kokemuksista

2018

The aim of this study was to build a conception as well as a substantive theory of adult learners’ group learning. The framework for this study is andragogy, which places the life context of adult learners at the center of the learning process (Knowles 1990). This study has been carried out using grounded theory as a research methodology. Hermeneutics offers a broad scientific paradigm for the understanding of group learning as a phenomenon, whereas grounded theory offers a concrete tool for analyzing data and developing a substantive theory. In this approach, the theory emerges gradually in open interaction between a researcher and the data (Glaser 1992). The informants for this study were…

Validity of a novel device for indoor analysis of cyclists' drag area

2021

Cyclists need to measure aerodynamic resistance accurately and reliably, as well as economically. Devices such as Notio Aerostick, an equipment device that includes one pitot tube, have appeared for this purpose. The aim of this study is, therefore, to test the reliability and degree of agreement in the evaluation of the CdA (coefficient of aerodynamic drag), assessed by means of the Notio Aerostick compared to the Virtual Elevation (VE) and Martin mathematical models.Seventeen professional cyclists rode in a 250-metre-long velodrome covered with a concrete surface with their own time trial bikes. Each cyclist completed three rides of 15 laps at constant speed for the evaluation of the CdA,…