Simple and accurate models based on adaptive-network-based fuzzy inference system (ANFIS) to compute the physical dimensions of open supported coplanar waveguides are presented. The ANFIS is a class of adaptive networks which are functionally equivalent to fuzzy inference systems. Four optimization algorithms, hybrid learning, simulated annealing, least-squares, and genetic, are used to determine optimally the design parameters of the ANFIS. When the performances of ANFIS models are compared with each other, the best results are obtained from the ANFIS models trained by the hybrid learning algorithm. The results of ANFIS are compared with the results of the conformal mapping technique, the rigorous spectral-domain hybrid mode analysis, the improved spectral domain approach, the synthesis formulas, a full-wave electromagnetic simulator IE3D, and experimental works realized in this study.
This historically oriented study is dedicated to the German naturalist, mathematician and philosopher Ehrenfried Walther von Tschirnhaus (1651–1708) and aims to introduce his main philosophical-logical work, Medicina mentis. After a biographical overview, from which important connections emerge, the article sets out and comments upon his four empirical principles, which provide an overview of the philosophical theory of knowledge. The key theme of his main work is the art of invention (ars inveniendi) and the concept of science as applied algebra, which was an obvious influence on Tschirnhaus’s epistemology and logic. The thinking of this philosopher engages with the work of Descartes, Spinoza, Geulincx and Gassendi, with which – like Leibniz – he tries to harmonize. Although Tschirnhaus’s approach is in many regards dependent on other thinkers, he stands out for his appreciation of the controlled imagination in science and experimentation. The four empirical principles, then, emphasize inner experience and an a posteriori approach. and Tato historicky zaměřená studie je věnována německému přírodovědci, matematikovi a filosofovi Ehrenfriedu Waltheru von Tschirnhausovi (1651–1708) s cílem představit jeho hlavní filosoficko-logické dílo Medicina mentis. Po biografickém přehledu, z něhož vyplývají důležité souvislosti, jsou vyloženy a komentovány jeho čtyři empirické principy, které poskytují průřez filosofovou teorií poznání. Klíčovým tématem tohoto spisu je umění objevovat (ars inveniendi) a pojetí vědy jako aplikované algebry, které přirozeně ovlivnilo Tschirnhausovu epistemologii i logiku. Myšlení tohoto filosofa zpracovává podněty z díla Descarta, Spinozy, Geulincxe a Gassendiho, které se – podobně jako Leibniz – snaží harmonizovat. Přestože je Tschirnhausova koncepce v mnohém závislá na jiných myslitelích, vyniká oceněním kontrolované obrazotvornosti v oblasti vědy a experimentu. Čtyři empirické principy pak kladou důraz na vnitřní zkušenost a přístup a posteriori.
Experimental measurement is performed on a simple fibre-mass system: a moving mass coupled with the frame by a fibre. Dynamic response of the mass is measured. The same system is numerically investigated by means of a simple multibody model. The influence of the model parameters on the coincidence of results of experimental measurements and of simulations are evaluated. The simulations aim is to create a phenomenological model of a fibre, which will be utilizable in fibre modelling in the case of more complicated mechanical or mechatronic systems. and Obsahuje seznam literatury
Polymer materials exhibit a high ductility. Determination of the yield strain as well as the break (ultimate) strain is usually done on the basis of tensile tests performed on standard samples and evaluated for normalizhed measured length, supposing the homogeneous material deformation along the sample axis. This experimental approach does not take into account the plastic strain concentration ii small neck area during the final deformation phase before the sample rupture, what is typical for the plastics behavior. Application of so defined material characteristic in the case of Finite element metod (FEM) analyses of real constructions made of TSCP plastics (typical semi-crystal polymer) led to significantly conservative (smaller) values of ultimate loads compared to the measured ones. A special experimental method making use of high-speed camera has been developed to determine the strain in defined small area of local strain concentration being also in correlation with the FEM element size. Application of the more realistic (higher local) break strain value in the case of FEM analyses of real TSCP constructions led to much better agreement between the calculated and measured stiffness and ultimate load values.
The friction conditions at the top of a mobile bed are discussed for flows in the upper-plane-bed regime, i.e. for the flows with values of the bed Shields parameter larger than approximately 0.6. A special attention is devoted to flows of the bed Shields parameter bigger than 2. Experimental data for flows at high bed shear are collected from literature and new data are added from own measurements of flows of a 1.36-mm sand slurry in the 100-mm pipe loop of the Institute of Hydrodynamics. The database represents flows of very different solids and covers friction conditions within a broad range of Shields parameters up to the maximum value of about 23. The paper analyses the data in order to evaluate a relationship among the equivalent roughness of the top of the bed and other relevant parameters. A semi-empirical formula is proposed that relates the equivalent roughness to the bed Shields parameter, the ratio of flow velocity and particle settling velocity, and the ratio of flow hydraulic radius and particle diameter. The formula is applicable primarily to flows of combined load (contact- and suspended loads together). and Příspěvek se zabývá mechanismem tření na povrchu erodovatelného dna za podmínek horního režimu pohybu splavenin nad plochým dnem, to jest při hodnotách Shieldsova parametru větších než přibližně 0,6. Zvláštní pozornost je věnována proudění při Shieldsově parametru větším než 2. Z literatury byla sebrána experimentální data pro proudění za vysokých smykových napětí, ke kterým byla přidána nová data z vlastních měření s pískem velikosti středního zrna 1,36 mm v potrubí průměru 100 mm trubního okruhu Ústavu pro hydrodynamiku AV ČR. Databáze obsahuje výsledky měření pro částice různých vlastností v širokém rozsahu hodnot Shieldsova parametru až do hodnoty okolo 23. Příspěvek analyzuje data za účelem stanovení závislosti hydraulické drsnosti povrchu sedliny na ostatních parametrech proudění. Je navržen semiempirický vztah, který předpokládá závislost hydraulické drsnosti na Shieldsově parametru, poměru rychlosti proudění k usazovací rychlosti částic a poměru hydraulického poloměru průtočného profilu k velikosti částic. Tento vztah se doporučuje především pro proudění nesoucí jak dnové splaveniny, tak suspendované částice.
A new physical laboratory for students of Physical engineering and nanotechnology study programme is based on experiments from the field of modern physics and on advanced imaging techniques with nanometre scale resolution. The experiments and their interpretation form base for study of the modern physics and nanotechnology. and Experimentální sestavy z oblasti moderní fyziky a zobrazovacích technik s nanometrovým rozlišením tvoří základ nové výukové laboratoře pro studenty oboru Fyzikálního inženýrství a nanotechnologie. Experimenty a jejich interpretace představují základní pilíře při studiu moderní fyziky a nanotechnologií.
At the modernization of the ŠKODA 22 Tr low-floor articulated trolleybus a different type of an articulated joint and a different type of driving axles were used in its construction besides other changes. During test drives with the modernized trolleybus, which were focused on the driving stability of the vehicle, a large roll of the rear section appeared. A suitable structural solution for reducing the rear section roll angle of the modernized trolleybus was the using of a rear section stabilizer bar. The stabilizer effect on dynamic properties of the vehicle and a suitable bar diameter were determined on the basis of the results of the computer simulations with the trolleybus multibody models. The text drives focused on the vehicle driving stability were performed again with the loaded real trolleybus, in the structure of which the designed rear section stabilizer bar was applied. On the basis of computer simulations of the test drives with the trolleybus multibody models the correctness of the experimantal-simulation approach used for the stabilizer bar structural design was verified. and Obsahuje seznam literatury