National Repository of Grey Literature 9 records found  Search took 0.01 seconds. 
Adhesion improvement between bitumen and mineral aggregate:theoretical principles and their impact on pavement structure lifetime
Trejbal, J. ; Demo, Pavel ; Nežerka, V. ; Sveshnikov, Alexey ; Valentová, T. ; Valentin, J.
Influence of nanomaterial-based adhesion promoters on maximizing of intermolecular interactions between bitumen and aggregate surfaces was studied. Topological and physico-chemical properties were described and it is shown that presence of promoters increases adhesion about 18%.
Plasma treatment impact on physical and chemical properties of polymeric fibers
Hlůžek, R. ; Prošek, Z. ; Trejbal, J. ; Fládr, J. ; Potocký, Štěpán
Presented work focuses on chemical and physical properties of plasma modified polymeric macro-fibers. Polyethylene terephthalate (PET) and polypropylene (PP) fibers having approx. 300 mu m in diameter were modified using cold oxygen plasma in order to achieve their surface changes needed for durable bond and adhesion with cement matrixes. A duration of plasma modification differed between 5 to 480 seconds, where an effect of the treatment was examined. Fiber surfaces chemical changes were researched via wettability measurement with demineralized water (the measurement was repeated immediately and after 1, 7 and 30 days to find out the changes stability). Physical changes were studied by means of weight balance (determination of weight loss) and tensile strength tests. It was found that wettability was enhanced significantly - up to two times, while mechanical properties of treated fibers decreased only slightly.\n
Performance of cement composites reinforced with surface-modified polypropylene micro-fibers
Antoš, J. ; Dejdar, L. ; Trejbal, J. ; Prošek, Zdeněk
This paper focuses on the mechanical properties investigation of cement pastes reinforced with surface treated polymer fibers. The cement matrix was composed of Portland cement (CEM I 42.5 R, w/c ratio equal to 0.4). Two polypropylene fiber types (micro-and macro-fibers) were used as randomly distributed and oriented reinforcement in volume amount of 2 %. The fibers were modified in the low-pressure inductively coupled cold oxygen plasma in order to enhance their surface interaction with the cement matrix. The investigated composite mechanical properties (load bearing capacity and response during loading) were examined indirectly by means of four-point bending mechanical destructive tests. A response of loaded samples containing treated fibers were compared to samples with reference fibers. Moreover, cracking behavior development was monitored using digital image correlation (DIC). This method enabled to record the micro-cracks system evaluation of both fiber reinforced samples.\n
Wettability enhancement of polymeric and glass micro fiber reinforcement by plasma treatment
Trejbal, J. ; Šmilauer, V. ; Kromka, Alexander ; Potocký, Štěpán ; Kopecký, L.
Plasma treatments were used to modify surface properties of polyethylene terephthalate (PET) and glass micro fibers, to improve their wettability. PET fibers, having diameter of 400 μm, and glass fibers (14 μm) were exposed to low pressure oxygen plasma. A direct horizontal optical method was used for contact angle measurements on fiber surfaces submerged into distilled water. Surface morphology changes before and after treatment were characterized by scanning electron microscopy. Finally, cement paste specimens reinforced with PET and lime-based mortars reinforced with glass fibers were made and after 28 days of mixture curing tested by four-point bending tests. After oxygen plasma treatment contact angles decreased by 60 % on PET fibers and by 25 % on glass fibers in comparison with untreated fibers. Next, SEM images revealed the significant surface damages of PET fibers and minor damages of glass fibers. Both four-point tested samples reinforced with treated fibers exhibited the maximum bending strength loss about to 10 to 20 percent compared to samples with untreated reinforcement.
Making the Land Cultural
Michálková, Kateřina ; Trejbal, Jan (referee) ; Ambrůz, Jan (advisor)
Cultural Landscape Drinkers for cattle For my bachelor thesis I chose the topic which is dealing with the landscape and man's relationship to it. The selected area is unused rural landscape with almost no use at this moment. The project, among other things deals with the design of site-specific objects, sometimes land art installation. Javorníky valley, between the villages Bohuslavice u Zlína and Salaš, was consisted of a small fields. In 70s they built a fence around the valley with a drinkers inside and they began graze a cattle. Field were changed into pasture for several years . But already in the 80s was pasture canceled and cultural quality of the valley began to deteriorate. Present day, the area is primarily for hunting, cultivated by local Hunting Association. The result looks that the valley is overgrown, most of the meadows are not to mowed and the forest is expanding. The journey disappears. No one other is interested in the local landscape, and is here just a fewwho are attend it. My project uses construction of drinkers which are deployed in the valley. A concrete blocks with metal structures can serve as a basis for sculptural and architectural objects. Places in the landscape that have lost their meaning can be reused. And hopefully it will help to attract the people back into the landscape.
Impact of the international economic and financial crisis on the U.S. position in international trade
Rozkydálková, Šárka ; Štěrbová, Ludmila (advisor) ; Trejbal, Jindřich (referee)
The aim of this thesis is to evaluate changes in the foreign trade of the United States in connection with the international economic and financial crisis. First chapter contains brief description of the U.S. economy from macroeconomic perspective, foreign direct investments and exports and imports. Second chapter includes United States' foreign trade and international relations. Third chapter describes the U.S. administration's response to the crisis. Fourth and last chapter summarizes history and changes in international trade with chosen trading partners in recent years. As these partners I have chosen EU, China and members of NAFTA agreement.
EU-USA Trade relations
Štěpánková, Jana ; Štěrbová, Ludmila (advisor) ; Trejbal, Jindřich (referee)
The aim of this bachelor thesis is to analyse trade relations between the EU and the USA in area of trade in goods, services and capital. Briefly describe the development of trade and characterize current situation affected by the crisis. The first chapter deals with general characteristic of the European Union and the United States including their position in the international trade environment. The second part outlines legal basis of their trade relations. The third chapter is devoted to the trade between states, especially the development of the trade balance.There is also outlined the trade relations between the Czech Republic and the USA and subsequently bilateral trade in goods, services and capital.
Export opportunities in the Czech Republic before and after the year 1990
Svatoňová, Petra ; Štěrbová, Ludmila (advisor) ; Trejbal, Jindřich (referee)
The aim of the thesis is to compare export opportunities before and after the year 1990. The year 1990 is characterized as a landmark describing decay of the imaginary border between East and West, beginning of the disintegration of the USSR, the development of liberalisation and globalisation. This thesis deals with the development of the internatinal trade in the Czech Republic including summaries of export relationships inside and outside RVHP, commodity structure of export, pro-export tools, czech state institutions supporting export, development of sectoral opportunities, changes in the list of priority countries, but also new current opportunities for Czech entrepreneurs together with their existing successes.

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1 Trejbal, Jiří
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