Magnetoresistance of composites based on graphitic discs and cones

We have studied the magnetotransport of conical and disc-shaped nanocarbon particles in magnetic fields |B| ≤ 9 T at temperatures 2 ≤ T ≤ 300 K to characterize electron scattering in a three-dimensional (3D) disordered material of multilayered quasi 2D and 3D carbon nanoparticles. The microstructure of the particles was modified by graphitization at temperatures of 1600 and 2700 °C. We find clear correlations between the microstructure as seen in transmission electron microscopy and the magnetotransport properties of the particles. The magnetoresistance measurements showed a metallic nature of samples and positive magnetoconductance which is a signature of weak localization in disordered systems. We find that the magnetoconductance at low temperatures resembles quantum transport in single-layer graphene despite the fact that the samples are macroscopic and 3D, consisting of stacked and layered particles, which are randomly oriented in the bulk sample. This graphene-like behaviour is attributed to the very weak interlayer coupling between the graphene layers

Modelovanie bunkových štruktúr robotizovaných systémov

Pre zvýšenie efektívnosti technického rozvoja je nutná automatizácia inžinierskej práce. I keď je to široká oblasť systémov, automatizácia sa stává technologickým podkladom produkcie a projektovania (CAD, CAP, CAx), v špecializovaných oblastiach je potrebný ďalší vývoj. Dôležitým stupňom programového vývoja produktov je modelovanie a riešenie problému. Všeobecnými princípmi pri tvorbe geometrických modelov objektov sú vložené do príloh na poli modelu štruktúr výrobných systémov. Výhody: Využitie pri navrhovaní štruktúr výrobných systémov. Vhodnosť pre automatizované systémy, systémi s ľudskou obsluhou, alebo kombinované systémy. Zvýšenie presnosti modelovania oproti doteraz najviac používaným metódam. Zhoda so systematickým vývojom: tvorba modelu databázy (predmetov výroby, elementov výrobného systému, štruktúr výrobných systémov), využitie parametrického modelu databázy (predmetov výroby, elementov výrobného systému, štruktúr výrobných systémov). Pre modelovanie bunkových štruktúr výrobných systémov s robotmi, kde je navrhnutý nový princip riešenia topologického spojenia. Tento príspevok popisuje návrh modelu riešenia.For increasing the efficiency of technical progress is necessary to automate the engineer's work. Although there is a wild area of using the systems of automated constructing, technological background of production and projecting (CAD, CAP, CAx), in specialized areas is necessary an additional progress. Important stage of software products development is modeling a solved problem. Common additions in the field of creating geometrical models of objects are showed into the additions in the field of modeling of the structure of production systems. Advantages: Exploitation in the projection of structures of production systems. Applicability for automated systems, for systems with man attendance, or to combinations of them, too. Increase of the accuracy of the modeling against to the most of yet used methods. Accordance of methodical progress: in creating model databases (objects of produce, elements of production systems, structures of production systems), in the using of parametrical model databases (objects of produce, elements of production systems, structures of production systems). For the modeling of the cell structures of production systems with robots were designed a new principle of solving topological relations. This paper describes the suggested model of solution

Aplikácia kognitivného modelu vizuálnej pozornosti v automatizovanej montáži

Zásobovacie zariadenia a podsystémy v štruktúrach montážnych systémov majú významné postavenie. Technickú zložitosť klasických zásobovacích zariadení a podsystémov je možné eliminovať pružnými programovateľnými automatizovanými zariadeniami. Informácie o spomínanom objekte zabezpečované senzorovými modulmi sa spracovávajú v riadiacom systéme zariadenia resp. na vyššej úrovni riadenia montážneho systému. Spracované informácie sú distribuované ako riadiace informácie výkonným jednotkám a prvkom, ktoré vykonávajú príslušné funkcie. Riadiace systémy programovateľných zásobovacích zariadení a podsystémov plnia viaceré funkcie napr. spracovanie informácií od senzorových jednotiek a modulov, správne vyhodnotenie polohy súčiastky a určenie postupu činnosti výkonných jednotiek a prvkov, distribúcia výkonných inštrukcií pohonovým jednotkám, atď. Programové vybavenie založené na využívaní kognitívneho modelu vizuálnej pozornosti charakterizuje nový prístup k riešeniu uvádzaných problémov. Pri vizuálnom vnímání scény obsahujúcej rôzne objekty a pre potrebu interakcie s určitým cieľovým objektom nachádzajúcim sa v tejto scéne je nutné aby systém upriamil svoju pozornosť na tento (cieľový) objekt. Tento mechanizmus je jedným z principiálnych prvkov videnia a podobne ako mnoho biologicky motivovaných systémov je veľmi výhodne využiteľný v praxi. Navrhovaný model je implementáciou mechanizmu vizuálnej pozornosti vo vytvorenom počítačom simulovanom prostredí.Logistic devices and sub - systems in the structures of assembly systems have significant position. Technical complexity of classical devices and sub - systems can be decreased by using of flexible programmable automated devices. Information's about objects provided by sensor modules are handled in processing system of the device, respective on the higher level of the assembly system. Executed information is distributed like processing information to executive units and elements. Control systems of programmable supply devices and sub - systems take handle of many functions, for example: processing information from sensor devices and modules, right calculating of the bearing of the component, distributing of executive instructions to actuating units, and many others. Software accessories based on the using of cognitive model of visual attention featured a new way of solving former problems. By visual reception the scenes contains miscellaneous objects and for the demand of the interaction with the target object is necessary that the system is need to be focused to this object. This mechanism is one of the pricipally elements of vision, and like many biologically motivated systems is very useful in practice. Designed model is an implementation of the mechanism of visual attention in the computer created simulation environment

Zvyšovanie oteruvzdornosti bórom nasycovaných vrstiev ocelí 15 230 a 17 246

In presented paper we described studies of resistance of selected material in abrasive wear tests. A surface of tested materials was remelted using TIG method and the layer of borax and B4C in water suspension at the surface. Based on tests results, we found out, that the B4C as a boron source is more suitable compare to borax when saturating remelting surface layer, with more significant impact on relative abrasive wear resistance of selected steel 15 230 and 17 246.V našom príspevku popisujeme štúdium odolnosti vybraných materiálov v skúškach abrazívneho opotrebenia. Povrchová vrstva testovaných materiálov bola pretavená metódou TIG s bóraxom a B4C vo vodnej suspenzii. Na základe výsledkov skúšok sme zistili, že B4C ako zdroj bóru je vhodnejší ako bórax pri nasycovaní pretavovanej vrstvy, s výraznejším vplyvom na pomernú oteruvzdornosť oboch vybraných ocelí 15 230 aj 17 246

Utjecaj projektnih parametara uređaja za horizontalno cijepanje drva na silu cijepanja

The article deals with the influence of the shape of the splitting wedge on the size and course of splitting force. Today maximum effort is made to search for and use of energy saving solutions in every industry. Such solutions can include a change of the form of the longitudinal splitting wedge for splitting logs. The core of this problem is the experimental detection of powers, followed by analising the individual effects. For this purpose, an experimental device was designed. The base of equipment consists of a mobile horizontal splitter, which is well adapted to capture the process of splitting force in splitting logs. According to the results, the type of wood was the most influencal factor, followed by wood diameter and splitting wedge. When comparing the average values that were generated from repeated measurements, it is possible to follow the reduction of splitting force. The results showed that the splitting force was reduced by approximately 13 % when comparing splitting wedge No. 1 (simple) and No. 2 (refracted). When comparing splitting wedges No. 1 (simple) and No. 3 (concave), it can be observed that the splitting force was reduced by more than 50 %. The experiment also confirmed the effect of different anatomical structures of different species of wood on various physical and mechanical properties of such wood and hence also on the splitting force in splitting wood.U članku se govori o utjecaju oblika klina za cijepanje drva na veličinu i smjer sile cijepanja. U današnje vrijeme ulažu se veliki napori u pronalaženje i primjenu novih riješenja za uštedu energije u svim industrijama. Jedno od takvih rješenja može predviđati i promjenu oblika klina za uzdužno cijepanje trupaca. Za taj problem važno je eksperimentalno odrediti snagu te analizirati pojedinačne utjecajne parametre. Za tu svrhu izrađen je eksperimentalni uređaj za cijepanje drva. Baza opreme sastoji se od mobilnoga horizontalnog razdjelnika, koji je dobro prilagođen praćenju procesa cijepanja i sile za cijepanje trupaca. Rezultati su pokazali da najveći utjecaj na silu cijepanja ima vrsta drva, zatim promjer drva i, na kraju, oblik klina za cijepanje. Usporedbom prosječnih vrijednosti dobivenih ponovljenim mjerenjima može se pratiti smanjenje sile cijepanja. Rezultati su pokazali smanjenje sile cijepanja za oko 13 % ako usporedimo cijepanje uz pomoć klina 1 (jednostavni) i klina 2 (slomljeni). Usporedimo li klinove za cijepanje broj 1 (jednostavni) i broj 3 (konkavni), može se uočiti smanjenje sile cijepanja za više od 50 %. Eksperiment je također potvrdio utjecaj anatomske građe različitih vrsta drva na fizikalna i mehanička svojstva drva, a time i na silu cijepanja pri obradi drva cijepanjem

Utjecaj promjenjivog koraka zubi kružnih pila na snagu za poprečno rezanje drva

The article deals with the influence of irregular tooth pitch on energy consumption of cross-cutting wood. In this article, the effect was assessed of feeding velocity and parameters of saw blade on the cutting power Pc of spruce (Picea Abies), pine (Pinus Sylvestris) and beech (Fagus Silvatica) wood during sawing with a guided circular saw. For the research, two types of circular saw blades were used, one of them having irregular tooth pitch. The circular saw blades had sintered carbide inserts with a diameter of D = 350 mm and the same number of teeth. The feed velocities were vf = 4, 8,12 m∙min-1 and revolutions n = 3000 min-1. The results showed that the circular saw blades with irregular tooth pitch have higher energy consumption than the circular saw blades with regular tooth pitch. The highest cutting power Pc was shown in the case of beech. It was also shown that energy consumption is increasing linearly with increasing feed velocity.U radu se prikazuje istraživanje utjecaja promjenjivog koraka zubi kružnih pila na potrošnju energije pri poprečnom rezanju drva. Analiziran je utjecaj posmične brzine, parametara lista pile i vrste drva na snagu rezanja (Pc). Eksperiment je proveden piljenjem drva smreke (Picea abies), bora (Pinus sylvestris) i bukve (Fagus silvatica) vođenom kružnom pilom. Za istraživanje su rabljena dva lista kružnih pila, od kojih je jedan imao promjenjivi korak zubi. Oba su lista kružnih pila imala oštrice od sinteriranih karbidnih umetaka, promjer lista D = 350 mm i jednak broj zubi. Primijenjene su tri posmične brzine: 4, 8 i 12 m∙min-1, a broj okretaja radnog vratila iznosio je n = 3000 min-1. Rezultati su pokazali da je potrošnja energije kružnih pila s promjenjivim korakom zubi veća od potrošnje energije kružnih pila s jednakim korakom zubi. Najveća snaga rezanja Pc zabilježena je pri piljenju bukve. Uočeno je da se potrošnja energije linearno povećava s povećanjem posmične brzine