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Remote sensing-based evapotranspiration (ET) algorithms developed in recent years are well suited for estimating evapotranspiration and its spatial trends over time. In this paper the application of energy balance methods in South Africa is reviewed, showing that the Surface Energy Balance Algorithm for Land (SEBAL) model is the most widely used, but highlighting the potentials of the Surface Energy Balance System (SEBS) model. The SEBS model is then reviewed in the international literature and lessons learned from South African examples are expanded upon. The SEBS model has been extensively used for teaching and training purposes and has been applied in research projects across many different environ ments. However, there are discrepancies in the reported accuracy of the SEBS model due to known model sensitivities. It is therefore recommended that any further research using the SEBS model in South Africa should be limited to agricultural areas where accurate vegetation parameters can be obtained, where high resolution imagery with low sensor zenith angles is available, and where canopy cover is complete.

Improving public spaces is a strategy of great importance for the successful future of our cities and their communities. The potential of places for citizen communication is often underestimated as stimulus for growth and development of urban communities and therefore public spaces are underused. The article analyses socioeconomic and psychological effects of architectural arrangement of traditional public spaces in modern perspective as areas for social interaction between different neighbourhood and citizen groups in an urban community, based on case examples of two cities: Vilnius in Lithuania and Weimar in Germany. Analysis of changing spatial composition and principles of social functioning are directly dependent on socio-political system of each different historical period and represent the chronological evolution of the present architectural appearance of the presented urban squares. The importance of local urban territorial communities is underlined in the article as they are the most important social entities for identifying the needs of local residents and in many cases are ready to take over the responsibility for re-arrangement of the public spaces adjacent to their areas of residence. Based on a careful observation of public activities on going in the analysed urban squares in Vilnius and in Weimar, the principles of planning, functionality and spatial arrangement are analysed in the aspect of facilitation of social interactions on going or potentially possible in these spaces. The research identifies planning and spatial arrangement models that could facilitate the preferred ways of social interactions and generate the better overall aesthetical and functional quality of those places.

Auf jeder, allgemeinen Fl~ehe dritten Grades lieges bekanntlich 27 gerade Listen, und zwar sind dieselben so vertheilt, dass sieh dutch jede Gerade 5 Ebenen legen lasses, deren jede soeh zwei weitere Gerade der Fl~che enth~ilt. Drei so is ether Ebene liegende gerade Listen bilden nun im Allgemeinen ein Dreieek, und sat bet speeiellen Fliiehen durchsehneiden sieh dieselben in einem Punkte. Die Betrachtung dieser besonderen F1Rehen nun ist tier Zweck der sachstehesden Abhandlung. Dieselbe beginst mit ether allgemeinen Untersuehung derjenigen Fl~ehes drittes Grades, auf desert sieh einmal drei gerade Listen is einem Punkte schneiden; sie wesdet sieh dann vorzugsweise den Fiiichen zu, auf welches dieser Fall sechsma2 eintritt, und schliesst mit einer Betrachtung yon 3 speeiellen Fl~ehen der letzteren Art. Literaturnaehweise kosnten nut an wenigen Stellen beigeFtigt werden, da dem Verfasser ausser den allgemeinen Werken fiber Fl~ches dritt,en Grades yon Cremona und Sturm und ausser Salmon's analytiseher Geometrie des Raumes fCir seine speeielle Arbeit nut die Abhandlung yon CI e b s c h: ~Ueber die Anwendnng der qtmdratisehen Substitution auf die Gleiehungen f~inften Grades und die geometrisehe Theorie des ebenen 'Fiinfseits" (Bd. IV der mathematischen Annalen) zu Gebote stand. In der letzteren ist abet nur yon ether ganz speciellen der zu behandeln= den Fl~iches, der sogena.nnten Diagonalfliiehe, die Rede. Wenn sic]~ auf irgend ether ~'liiche drei geq'ade Linien in r

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