Fractures commonly existing in rocks flow on their elastic properties and hence on velocity of seismic waves propagating in the rock mass. This relation allows to use seismic methods to determine the fracture density and the orientation of fracture sets. This paper presents results of the research which concern directional changes of dynamic elastic moduli in sedimentary and igneous rocks from south part of Poland. These moduli depend on density of the rock matrix as well as density and orientation of cracks and flow on seismic wave velocity. The seismic equipment Terraloc MK6 (ABEM) was used for the measurements of seismic wave velocity in the surface layers of rock mass. The research was made along precise oriented radial seismic profiles. P-waves and S-waves ve locities were established from recorded seism ograms. The values of P and S waves velocity allowed to calculate values of dynamic elastic moduli for all profiles. The results were presented on diagrams of azimuth distribution of elastic moduli, and diagrams of dynamic elastic moduli versus P - wave velocity. The diagrams showed an anisotropy of elastic properties of the investigated rocks. The maximal values of moduli agree with maximal values of velocity and also with orientation of main crack sets or potential directions of weakening of rock mass. Obtained results point that the seismic methods allow to assign the directions of weakening of rocks what can be for example use during preliminary designing, constructing and exploitation of tunnels., Iwona Stan - Kleczek and Adam F. Idziak., and Obsahuje bibliografické odkazy
Hoci najznámejšou technickou aplikáciou kvapalných kryštálov v dnešnej dobe sú kvapalno-kryštalické monitory, kvapalné kryštály sú viac než len ploché obrazovky, aj keď vďaka nim sa dostali do povedomia verejnosti. Výskum v oblasti kvapalných kryštálov však nabral nový smer. Svetový výskum sa odvracia od displejov a zameriava sa na nové možnosti ich využitia, a to na štúdium kompozitných systémov na báze kvapalných kryštálov nielen pre ich technické aplikácie, ale aj na ich využitie v biotechnológiách., Nowadays, the major technical application of liquid crystals is their widespread use in liquid crystal displays. However, even though flat screens have drawn these materials to the public attentions they are much more than just flat screens. Academic liquid crystal science has shown a clear trend of moving away from display research during the last few years. Currently, scientists focus on different topics such as for instance new possible uses in optics, nano-/micro-manipulation, novel composites and biotechnology. This article demonstrates such a development of composite systems containing magnetic nanoparticles in liquid crystalline matrices., Natália Tomašovičová., and Obsahuje bibliografii
Odpor mnoha magnetických materiálů výrazně závisí nejen na velikosti, nýbrž i na směru magnetizace. Průmyslově se tento jev využívá v senzorech citlivých na magnetické pole, mezi něž v nedávno minulé době patřila i velká část světové produkce čtecích hlav počítačových pevných disků. Teoretické modely této anizotropní magnetorezistence ovšem zatím zdaleka nedosáhly uspokojivé úrovně a shody s experimenty bez fitovacích parametrů se podaří dosáhnout jen výjimečně. Skupina takových poměrně úspěšných modelů se v posledních letech rozrostla o další položku - zředěný magnetický polovodič (Ga,Mn)As., Electric resistance of many magnetic materials depends significantly both on strength and direction of its magnetization. Magnetic field sensors belong to the typical industrial applications of this phenomenon and until recently these included also a major part of the world production of read heads in computer hard-drives. Theoretical models of this anisotropic magnetoresistance, however, have never reached a completely satisfactory level and so far it has been only rarely possible to achieve a decent agreement with experiments without any fit parameters. Few years ago, the family of such relatively successful models could welcome a new member that concerns a dilute magnetic semiconductor (Ga, Mn)As., Karel Výborný., and Obsahuje bibliografii