Beginning Of XXth Century Research Articles

Experimental investigation of a free-surface turbulent jet with Coanda effect

The deviation of a jet from the straight direction due to the presence of a lateral wall is investigated from the experimental point of view. This flow condition is known as Coanda jet (from the Romanian aerodynamicist Henry Marie Coanda who discovered and applied it at the beginning of XXth century) or offset jet. The objective of the work is to detail the underlying mechanisms of such a phenomenon aiming to use it as a flow control method at polluted river flows mouth. To do this, a large laboratory free-surface tank with an incoming channel has been set up and velocity field measurements are performed by Optical Flow methods (namely Feature Tracking). Preliminary tests on the well-known free jet configuration without any marine structure (i.e. lateral wall) are performed to allow comparison with free jet scaling and self-similar solutions. The presence of the free-surface gives rise to centerline velocity decay which is lower than in free unbounded plane or circular jets due to the vertically limited ambient fluid entrainment. In the second part of the paper, the effect of a lateral wall on the jet configuration is examined by placing it at different lateral distances from the jet outlet. The resulting velocity fields clearly show an inclined Coanda jet with details which seems to depend on the lateral wall distance itself. The analysis of self-similarity along the inclined jet direction reveals that for wall distances larger than 5 jet widths this dependence almost disappears.

Polish Society of Education and Charity and Polish Club in Mohylew in the years 1906-1910. Fragments to history of education, charity and Polish organizations in Belorussia in the beginning of XXth century

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Un siècle de Hautes Pressions : Développements technologiques et scientifiques

A century of high pressure: technological and scientific developments. This paper is devoted to the development of high pressures during approximately one century and the main scientific domains concerned by such a development. Roughly three main periods have been considered: (i) the early period at the beginning of XXth century (1900 → 1970), the second period (1970 → 2005) taking into account some important technical developments (the high pressure vessels with a large volume, the diamond anvil cell associated with the laser heating…), and a prospective concerning, on the basis of recent results, the possible developments during the next 10 years. The early period was mainly characterized by some industrial problems: the improvement of the mechanical properties of alloys and consequently the requirement for performant cutting and machining tools (leading to the diamond synthesis), the synthesis of ammonia (initiated both by the development of explosives and the requirement of fertilisers), the preservation of foods (correlated to a new organization of the Society), the elaboration of single crystals characterized by specific physical properties with functional properties for the development of some industrial sectors (telecommunications, computer science…). The more recent period (1970–2005) has been characterized by the development of new performant tools able to improve the development of scientific domains (diamond-anvil-cell and Geosciences, Belt-type, multi-anvils and toroid equipments and the Chemistry of Materials, high pressure vessels and Food-Science…). During these last years roughly three main tendances have been observed: (i) the investigation of researches at extreme (P, T) conditions, (ii) the improvement of researches involving mild (P, T) conditions mainly in liquid phase (hydrothermal and solvothermal synthesis), (iii) the development of high pressures in Biology and Biotechnology. During the next years the extension of high pressure level and also the development of the next scientific domains would improve research involving different planets. In parallel the development of chemical reactions in mild P, T conditions in a liquid phase would allow to prepare new hybrid nano-systems at the interface between inorganic and organic chemistry, inorganic and biological chemistry or new supramolecular systems. The applications of high pressures in Biotechnology – due in particular to the low energy conveyed by pressure – would lead to new research domains or industrial processes involving either the inactivation of pathogen microorganisms with the development of new vaccines or the domain of the proteins…

Le dinamiche del paesaggio forestale: evoluzione temporale del bosco di neoformazione sui pascoli di Corte Pogallo - Parco nazionale della Val Grande (VB)

The aim of the present study was to investigate forest expansion, dynamics and recolonization of former crop lands, fallows and hayfields in a mountainous area (Corte Pogallo - 777 m s.l.m.) located within Val Grande National Park (VB - Italy). The site has been characterized by mountainous forests for ages, until the beginning of XXth century, when a timbering company was settled there. The whole area has been hardly deforested until the 1960, when the settlement has been completely abandoned. By matching historical (1954, 2000) aerial photographs with several test plots on the ground, the dynamic evolution of the area at the study site was analyzed using a multi-scale sampling method. To assess the stand structure, two transects were established starting from the crop fields (occurring at the valley floor) up to the beech coppice stand (occurring along the mountain slope). A mixed composition of pioneer forest species and fruit trees was found at the ecotone, while pioneer species became more and more dominant along the slope up to the beech coppice stand (the former forest margin before abandonment). Using a GIS software, pinpoint sample data and historical aerial photographs were combined and compared. Maps of land-use change revealed that forests have recolonized about 71% of the former crop area since the last fifty years (1954-2000).

The households of Serbia at the dawn of third millennium: Socio-demographical analysis

Side by side with tumultuous social processes in the end of XXth century great demographical changes have been taking place in Serbia, such as: the decline of nuptiality and fertility, postponement of family formation into older ages of life course of individuals, the rise of: extramarital births as well as adolescent pregnancies and live births, the spread of one-parent households, particularly of lone mothers, and divorces. Besides that, the main feature of the demographic development of Serbia has been increased mobility of population, namely migrations of highly educated professionals to the West ("brain drain") and forced migration of refugees and internally displaced persons to Serbia, as a consequence of armed conflicts in its surroundings and at Kosovo and Metohija. All the above-mentioned demographical changes caused the precomposition of households, as profound associations of population, where its biological and socio-economical reproductions take place. The information of last census of population of Serbia in 2002 indicate that according to the features of family and households, Serbia has approached the countries of Central and Eastern Europe, that are forerunning in the process of post-socialistic transformation and European integrations. Common characteristics of all those countries are: decrease of universality and popularity of marriage delay of childbearing, continuation of earlier demographic tendencies: of low natality, depopulation and aging of population. All those processes have contributed to the transformation of prevailing forms of households, i.e. decline of nuclear family units and the rise of single person households households of aged persons, as well as single-parent ones. As to the Serbia the demographic differences between its separate parts: Vojvodina and central Serbia, have been fading for the first time in its history, owing to previous socio-demographic developments starting from the beginning of XXth century, as well as to the above actual ones, in the period between last two censuses.

Serbian intellectuals and world in historical prospect

In this work author intends to give review of cultural orientation prevailing among Serbian intellectuals within historical scope since beginning of XXth Century, in the period between the world wars, and since Second World War until to our time. Thus is possible to mark three periods first, when serbian intellectuals attended European universities were spreading ideas from most developed countries; second, when cultural orientation was reduced on the connections with France, and third, after Second World War, when chief orientation was towards Soviet Union. Opening to the rest of the world begins in the sixties. In all three periods one can find many representative personalities of cultural life.

The targovistean cultural cocieties from the end of XIXth century and the beginning of XXth century

The targovistean cultural cocieties from the end of XIXth century and the beginning of XXth century

Russian school contribution to the birth and development of neotectonics

Study of young tectonic movements began at the end of XIXth century and is connected with the names of scientists from various countries. A valuable contribution to development of this branch of science was made by Russian school beginning with works by M. V.Lomonosov in the XVIII century. In XIX century this trend was successfully developed by A. P.Karpinsky, A. P.Pavlov, at the beginning of XXth century - V. A.Obruchev, N. I.Andrusov, A. D.Arkhangelsky, A. L.Reingard. Study of neotectonics in the USSR spread especially widely in the Soviet period (20–40ies) owing to industrial development of the country. Works by V. A.Obruchev, G. F.Mirchink and other Soviet scientists of that period contributed much to formation of a new branch of science — neotectonics.

Heur et malheur de la géographie régionale

French regional geography was successfull with agrarian and regional movements, at the beginning of XXth century. When these movements decayed, regional geography lost its finality. This geography only became a subject for school, because it had no theorical basis and because applications did not exist. Now, it seems that regionalization and regionalism have not allowed regional geography to become a scientific subject.