Mechanické vlastnosti oceli DC01 tvářené metodou DRECE

The main goal of the paper is a review of current achieved results given by processing of steel DC01 by DRECE (Dual Rolls Equal Channel Extrusion) forming process, whose prototype equipment has been put in service in the end of 2009 at VŠB – Technical University of Ostrava, Faculty of Mechanical Engineering and Department of Mechanical Technology. The paper analyses the effect of the DRECE forming process on the mechanical properties and deep – drawing sheet metal formability of the steel DC01.Příspěvek uvádí současné výsledky ze zpracování oceli DC01 tvářecím procesem DRECE, jehož prototype byl na konci roku 2009 uveden do provozu pod záštitou VŠB – Technické university Ostrava, Fakulty strojní, Katedry mechanické technologie. Příspěvek analyzuje vliv tvářecí metody DRECE na mechanické vlastnosti a hlubokotažnost oceli DC01

Wood - structural material, its structure and mechanical properties

Cílem práce bude rozdělení dřeva z rozličných hledisek. Zejména pak s ohledem na jeho makroskopickou stavbu, mikroskopickou stavbu (rostlinná buňka, typy dřevních buněk, anatomická stavba), jeho chemické složení, fyzikální vlastnosti (hustota, tepelné vlastnosti, vlhkost, zvukové a elektrické vlastnosti) a mechanické vlastnosti dřeva (pevnost, tvrdost, technologické vlastnosti).The aim of proposed work is focused on the classification of wood using several different perspectives. Especially, with focus on its macro-, micro-structure (plant cell, wood cell and anatomical structure), chemical composition, physical properties (density, thermal properties, moisture, sound and electrical) and mechanical properties (strength, hardness and technological properties).

Wikipedie a Polytematický strukturovaný heslář: Wikipedia and Polythematic Structured Subject Heading System

Prezentace nejprve představuje PSH, jeho vlastnosti, účel a způsoby aktualizací. Poté se zaměřuje na vybrané společné vlastnosti PSH a Wikipedie

Photovoltaic properties of molecules with internal charge transfer

Práce je zaměřena na studium donor-akceptorových molekul s vnitřním přenosem náboje z hlediska jejich použití v organických solárních článcích. V práci bude studován vliv změny chemické struktury těchto molekul na optické a optoelektrické vlastnosti. Dále budou z těchto materiálů připraveny solární články a studováno jejich fotovoltaické chování.The work is focused on the study of donor-acceptor molecules with internal charge transfer in terms of their use in organic solar cells. The work will be studied the effect of changes in the chemical structure of these molecules on the optical and optoelectronic properties. Furthermore, based on these materials prepared solar cells and photovoltaic studied their behavior.

Possible roles, positions, factors and components of dairying in organic farming – a rewiev, mapping, survey and comparison in the Czech Republic

The full-value experiment is questionable in evaluation organic dairying. It is problem to do a trial under comparable conditions for comparison of organic and conventional farming because of legislative reasons and necessity of long period of such event. Most of comparisons are carried out as practice descriptive observations and any of them has been carried out about milk production. That is main reason, why the aim of this work is to carry out a opening of monitoring of some production conditions and results of bio-dairying in the Czech Republic (CR). The quality aspects of sources, procedures and products are main topics of solution of projects about organic farming philosophy, in particular in solution of organic dairy foodstuff chain. There were choosen twelve organic dairy farms (survey II, 2006) for more detail research of production conditions according to results of exploratory questionnaire (2006, survey I, n = 85 pieces of questionnaire and 58 organic farms, which practicise dairying) in the CR. The climatology characteristics of selected organic dairy farms were as follows: (I) 562±149 m above sea level on the average (from 270 to 970 m a. s. l.); (II) 571.0±69.9 m above sea level, mean year temperature 6.0±1.1 ºC and average year rainfall sum 843.0±184.3 mm. It is clear according to previously mentioned figures that the organic (ecology) dairy farming is realized mostly in the mountain or sub-mountain areas (less favourable areas, LFAs) as compared to climatic conditions of CR mean profile. The results of investigation of organic farm (E) and breeder conditions and dairy cow health state, reproduction performance and milk quality in organic farms (I data file) as compared to conventional dairy cow herds (K) were: milk yield (E) was 14.2±3.4 kg of milk/cow/day on average and 5165±1112 kg/cow/year; E farms have 50 % free stables, some of them as different untraditional modifications (mostly in herds with low number of dairy cows); it is necessary to increase this amount for welfare improvement in the future; there are 52 % of binding stables in K herds; there (E) is high occurrence frequency of can milking equipments (46.4 %); there are 5.4 % cases of hand milking, 21.4 % of pipeline milking equipments and 26.8 % of milking parlours; there (K) are 3 % of can milking equipments, 50 % of pipeline milking equipments and 47 % of milking parlours; the average organic herd has 60±91 heads it means about 1/3 of K herd in the CR; geometrical average (xg) of organic herd size is 17 heads; daily milk deliveries were 1318±1475 kg in summer and 976±1368 kg in winter season (there is too high variability in the mentioned indicators); breed structure of E herds is 59.8 % of Bohemian Spotted cattle, 18.8 % of Holstein (H), 12.5 % of Jersey breed; H breed is dominating 47.5 % in K herds; average ratio of excluded milk (for secretion disorders or treatment) is 2.99 % in E herds and 4.6 % in K herds (P<0.01); also there (E) is lower occurrence of clinical mastitis 0.53±1.97 %; service period is 124.3 days in K and 98.7±46,1 days in E herds on average (P<0.01); there (E) is better insemination index 1.66±0.45 in comparison to K herds 2.07 (P<0.01); there is longer longevity as duration of production life of dairy cows in E herds (6.02 lactations, „about 141 % better”) in comparison to K herds (2.50 lactations, P<0.01); milk quality showed the average total mesophilic bacteria count (CPM) 36.0±26.8 ths. CFU/ml in organic farms (E), which is comparable to the conventional farms (K); somatic cell count (PSB) was 192±87 ths./ml in E herds and 256 ths./ml in K herds, which is in connection with the lower ratio of milk exclusion from delivery in E herds; an occurrence of residues of inhibitory substances (RIL) was not reported in E herds, which is more advantageous in comparison to the K herds (0.16 %) and it could be an impact of lowered antibiotica drug use; the average fat and lactose contents (T; 4.05±0.19 %) and (L; 4.83±0.15 %) are well comparable with K farms and the results show on higher energy deficiency in E herd nutrition. The water quality (II) is necessary in dairying as well. Drinking water is necessary for health of animals (their watering) and for milk quality (milking equipment sanitation) as well. Drinking water is asked in dairy farms by legislation. The E farm water quality: the nitrate level varied in the range from 1.63 to 28 mg/l with average 10.5 mg/l in ecological farms and standard limit 50 mg/l was not exceeded; the levels of nitrite and ammonia ions were mostly under detection limit of method; legislative limit <0.5 mg/l was not exceeded by nitrite and once by ammonia ions 0.81 mg/l. The microbiological indicators are more sensitive of course. In total the limits were exceeded 7× u in coliform bacteria, 3× in streptococci and Escherichia coli was confirmed 3× (in comparison to demand 0). Therefore it is necessary to take care of incidental water source sanitation. The effect of origin of water source (communal water pipes or own well in the organic farm area) which was used in the organic farming (II) was: the more marked result differences were not observed between own wells (S) and communal water supply (V) in E farms; an exception was stated in insignificantly better results of hygienic indicators of communal supply; therefore it is necessary to put the higher importance on sanitation of own water sources. There were identified eight own wells and four communal supply. E. g. nitrate levels were a little higher for wells 11.7 > 8.2 mg/l. The nitrites were not different. Chemical oxygen consumption was 0.45 and 0.52 mg/l. The more expressive differences were identified in chlorides, sulphates and Mg: 8.33 and 3.02 mg/l; 27.9 and 16.8 mg/l; 18.9 and 3.5 mg/l

Hybrid Composites Combining Short Deformable Fibers and Particulate Fillers in Polymeric Matrix

Tato diplomová práce se zabývala vlivem přídavku krátkých houževnatých polyvinylalkoholových vláken do dimetakrylátových matric na mechanické vlastnosti kompozitních materiálů. Dále byly do matric přidány mikro- nebo nano-plniva. Bylo studováno, jak přídavek krátkých vláken a plniva do matrice ovlivňuje mechanické vlastnosti výsledných, tzv. hybridních kompozitních materiálů. Kompozitní materiály byly charakterizovány pomocí diferenční kompenzační fotokalorimetrie (DPC), termogravimetrické (TGA) a dynamicko-mechanické (DMA) analýzy. Morfologie lomových ploch byly sledovány pomocí skenovací elektronové (SEM) a konfokální laserové (CLSM) mikroskopie. Byly změřeny moduly pružnosti a pevnosti, stanoveny kritické hodnoty faktoru intenzity napětí a hnací síly trhliny a také viskoelastické vlastnosti kompozitních materiálů. Na mechanické vlastnosti kompozitních materiálů má vliv nejen typ plniva/výztuže, ale i vlastnosti matrice. Tyto vlastnosti závisí také na způsobu vytvoření polymerní sítě během světlem iniciovaného vytvrzování. Z tohoto důvodu byly určeny polymerační tepla, stupně konverze a maximální polymerační rychlosti směsí dimetakrylátových monomerů.In this work, the effect of adding short deformable polyvinylalcohol fibers into dimethacrylate resins on mechanical properties of composite materials was investigated. Furthermore, micro- or nano-fillers were added into the matrix. The effect of filler/short fibers combination on mechanical properties of so-called hybrid composites was studied. Composites were characterized by differential compensation photocalorimetry (DPC), termogravimetric (TGA) and dynamic mechanical (DMA) analysis. The fracture surfaces were examined using scanning electron (SEM) and confocal laser (CLSM) microscopy. Elastic modulus and strength, the critical value of stress intensity factor and strain energy release rate and the viscoelastic properties of composite materials were measured. The mechanical properties of composite materials are affected not only by the type of filler/reinforcement, but also by properties of the matrix. These properties also depend on the way of network formation during photo-initiated polymerization. For this reason, heat of polymerization, degree of conversion and the maximum polymerization rate of mixture of dimethacrylate monomers were determined.

Od kompozitních materiálů ke slabé konvergenci

Matematické modelování kompozitních materiálù využívá tzv. homogenizaci, při které heterogenní materiál s jemnou periodickou strukturou nahradíme homogenním materiálem, který má z makroskopického hlediska stejné vlastnosti. Matematický přístup spočívá ve studiu posloupnosti řešení parciálních diferenciálních rovnic s periodickými koeficienty se zmenšující se periodou. Homogenizace umožňuje počítat makroskopické vlastnosti materiálu z vlastností jednotlivých složek a jejich geometrického uspořádání. Koeficienty se zmenšující se periodou studované při homogenizaci nekonvergují (ani bodově ani v normě), konvergují však slabě. článek je zaměřen na tuto slabou konvergenci a její vlastnosti. Příjemnou vlastností je kompaktnost: každá omezená posloupnost funkcí obsahuje slabě konvergentní podposloupnost. Nepříjemnou vlastnost í je však nemožnost přechodu k limitě způsobené ztrátou informace ve slabé limitě. Pokračování tohoto článku se bude zabývat řešením tohoto problému

Design of planar antenna structures from metamaterials

V této práci jsou studovány základní principy metamateriálů, které vykazují v mikrovlnné technice nezvyklé vlastnosti jako je záporná permitivita či permeabilita. Jsou zde popsány typy a vlastnosti antén tvořených metamateriály.The thesis deals with basic principles of metamaterials, which exhibit unusual properties in microwave applications (e.g., negative permittivity and permeability). Different type of metamaterial antennas and parameters of such antennas are described in the thesis.