Search results for " Geometry"
showing 10 items of 2294 documents
Organotin(IV) azido and mixed azidothiocyanato complex anions; A Mössbauer and vibrational spectroscopic study
1975
Abstract Tetraphenylarsonium and tetramethylammonium salts of the complex anions Ph 3 Sn(N 3 ) − 2 , Ph 3 Sn(N 3 )(NCS) − , Me 2 Sn(N 3 ) 2− 4 and Ph 2 Sn(N 3 ) 2 (NCS) 2− 2 have been synthesized, and the solid state configuration of the complex anions has been studied by Mossbauer and vibrational spectroscopies. Trigonal bipyramidal structures are advanced for the Ph 3 Sn IV derivatives, with equatorial SnC 3 and apical pseudohalide ligands, while the R 2 Sn IV compounds are assumed to be trans -octahedral species. The NCS − ligands are observed to be N-bonded to Sn IV . Conductance and PMR (for the Me 2 Sn IV compound) data suggest the presence of the complex anions also in solution phase…
Potentiometric study of the formation of hydroxo complexes of [Cu(terpy)]2+. Synthesis and crystal structure of [Cu(terpy) (H2O)](CF3SO3)2
1992
Two complexes of formula [Cu(terpy)(H2O)](CF3SO3)2 (1) and [Cu(terpy)(OH)]BPh4 (2) (terpy=2,2′∶6′,2″-terpyridine and BPh4=tetraphenylborate anion) have been synthesized and characterized by spectroscopic techniques. The x-ray crystal structure of (1) has been determined by x-ray diffraction. The structure is made up of [Cu(terpy)(H2O)]2+ mononuclear cations plus semi-coordinated CF3SO3 − anions. The coordination geometry around the copper atom is approximately elongated tetragonal octahedral. The oxygen atom of water and the three nitrogen atoms of terpy occupy the equatorial sites whereas the apical ones are filled by trifluoromethanesulphonate oxygen atoms. The formation of hydroxo comple…
Cost-driven framework for progressive compression of textured meshes
2019
International audience; Recent advances in digitization of geometry and radiometry generate in routine massive amounts of surface meshes with texture or color attributes. This large amount of data can be compressed using a progressive approach which provides at decoding low complexity levels of details (LoDs) that are continuously refined until retrieving the original model. The goal of such a progressive mesh compression algorithm is to improve the overall quality of the transmission for the user, by optimizing the rate-distortion trade-off. In this paper, we introduce a novel meaningful measure for the cost of a progressive transmission of a textured mesh by observing that the rate-distor…
FISICA QUANTISTICA E FUNZIONI MENTALI SUPERIORI III
2010
Questo saggio riprende alcuni concetti di anatomia comparata e di fisiologia, sviluppati in una mia precedente ricerca dal titolo Termodinamica, campi quantici e funzioni mentali. Il fine è di chiarire alcuni punti controversi posti dall’analisi scientifica, in riguardo a teoremi di neuro anatomia e di neurofisiologia. Il filosofo Heiddegger H. riteneva che il pensiero umano non può affidarsi interamente all’indagine scientifica, traducendo in schemi ed in formule la vivente realtà della natura, sia fisica che biologica. La ricerca scientifica si basa su un sapere rigoroso e preciso, altamente dimostrativo che può competere con la matematica, ritenuta la scienza delle scienze. Nonostante ci…
FISICA QUANTISTICA E FUNZIONI CEREBRALI SUPERIORI (II)
2010
Data una semplice perturbazione, il processo lineare tende a rimanere leggermente alterato. Data la stessa perturbazione, un processo non lineare tende a tornare al suo punto di partenza. Huygens C. (fisico olandese del XVI sec.) inventò l’orologio a pendolo e la disciplina classica della dinamica. S’imbatté in uno dei grandi esempi di questa forma di regolazione. Huygens notò che vari orologi a pendolo, appoggiati contro una parete stavano oscillando in modo perfettamente sincronizzato. Sapeva che gli orologi non potevano essere così precisi. Huygens ipotizzò che gli orologi fossero coordinati da vibrazioni trasmesse attraverso la parete. Al presente, il fenomeno è definito agganciamento d…
FISICA QUANTISTICA E FUNZIONI CEREBRALI SUPERIORI.
2010
Geometric and conceptual knowledge representation within a generative model of visual perception
1989
A representation scheme of knowledge at both the geometric and conceptual levels is offered which extends a generative theory of visual perception. According to this theory, the perception process proceeds through different scene representations at various levels of abstraction. The geometric domain is modeled following the CSG (constructive solid geometry) approach, taking advantage of the geometric modelling scheme proposed by A. Pentland, based on superquadrics as representation primitives. Recursive Boolean combinations and deformations are considered in order to enlarge the scope of the representation scheme and to allow for the construction of real-world scenes. In the conceptual doma…
Mesh connectivity compression using convection reconstruction
2007
International audience; During a highly productive period running from 1995 to about 2002, the research in lossless compression of 3D meshes mainly consisted in a hard battle for the best bitrates. But for a few years, compression rates seem stabilized around 1.5 bit per vertex for the connectivity coding of usual meshes, and more and more work is dedicated to remeshing, lossy compression, or gigantic mesh compression, where memory and CPU optimizations are the new priority. However, the size of 3D models keeps growing, and many application fields keep requiring lossless compression. In this paper, we present a new contribution for single-rate lossless connectivity compression, which first …
The su(2|1) Model of Electroweak Interactions and Its Connection to NC Geometry
2002
I review the su(2|1) model of electroweak interactions which is essentially based on the super Lie algebra su(2|1), thus incorporating both usual gauge fields and Higgs fields in one generalized Yang-Mills field. Special emphasis is put on the natural appearance of spontaneous symmetry breaking and other appealing features of the model like generation mixing. Also the connection of the model to noncommutative geometry is briefly discussed.
A remark on hyperplane sections of rational normal scrolls
2017
We present algebraic and geometric arguments that give a complete classification of the rational normal scrolls that are hyperplane section of a given rational normal scrolls.