Belt conveyor

Cílem této bakalářské práce je, se zabývat návrhem pásového dopravníku na přepravu forem dle zadání práce. V úvodu práce je popsán hlavní přehled a rozdělení pásových dopravníků. Druhá část práce se zabývá konstrukčním řešením pásového dopravníku a popisem jeho hlavních částí. Závěrečná část práce, tj. hlavní, zahrnuje funkční výpočet, určení hlavních rozměrů podavače, návrh pohonu a pevnostní výpočet hnací hřídele. Všechny výpočty a konstrukční postupy jsou v souladu s normou ČSN. Práce je doložena výkresovou dokumentací zadaných částí pásového dopravníku.The aim those baccalaureate project is, belt conveyer deal with suggesstion on transportation forms in accordance with project setting. The general summary and division of belt conveyors are described at the beginning of the Bachelor thesis The second part of project with constructive solution of belt conveyor and description of its main elements The final part of project, quasi main, includes functional calculation, determination of the chief proportions hodman, proposal drive and strenght calculation driving shafting. All calculations and constructional progresses conform to norm CSN. Work is documented graphical documentation engaged part belt conveyer.

Effectiveness of dentin pre-treatment on bond strength of two self-adhesive resin cements compared to an etch-and-rinse system: an in vitro study

Statement of problem It has been shown that selective etching improves the bond strength of some self-adhesive resin cements to enamel. The same has yet to be determined with dentin pre-treatment. Purpose To evaluate the tensile bond strength of two self-adhesive resin cements after two dentin surface pre-treatments, and also to analyze the cement/dentin interface. Material and Methods One hundred and twelve human third molars were extracted. The teeth were distributed into seven groups (n = 16). Maxcem Elite Chroma (MAX) (Kerr, Scafati, Italy) and Relyx U200 (RLX) (3M ESPE, Neuss, Germany) were used without pre-treatment or with two dentin pre-treatments (polyacrylic acid or phosphoric acid). A conventional etch-and-rinse (EAR) luting cement, NX3 Nexus (NX3) (Kerr, Scafati, Italy), was used as an external control group. Before testing, all specimens were stored in distilled water for 24 hours. Three specimens from each group were prepared for scanning electron microscopy observation (SEM). A tensile bond strength test (TBS) was performed for the remaining samples. The data were statistically analyzed using the Kruskal–Wallis test and Pairwise comparisons using the Wilcoxon rank sum test. Results MAX without pre-treatment and with phosphoric acid etching attained statistically similar bond strengths to NX3 (P > 0.05). There was a statistical difference (P = 0.00488) between RLX without pre-treatment (5.62 MPa) and NX3 (10.88 MPa). Phosphoric acid pre-treatment increases the bond strength values of RLX to a strength that is comparable to NX3 (P > 0.05). The lowest tensile bond strength (TBS) was attained after the application of polyacrylic acid with MAX (1.98 MPa). No statistical differences were found between the RLX bond strength values after polyacrylic acid treatment and RLX without pre-treatment or NX3 (P > 0.05). SEM observations disclosed an enhanced potential of the self-adhesive cements to infiltrate into dentin tubules and form resin tags when applied after phosphoric acid pre-treatment. The failure mode was dominantly adhesive. Conclusions On dentin, the self-adhesive resin cement MAX might be an effective alternative to conventional resin cement. Etching the dentin with phosphoric acid does not have a negative effect on the bond strength of MAX to dentin. On the other hand, phosphoric acid improved the bond strength of RLX when compared to EAR cement

Modification of Polyamides Properties by Irradiation

Princip ozařování spočívá ve schopnosti vysoké energie radiace produkovat v materiálech kationty, anionty a volné radikály, což vede ke změnám řady vlastností ozařovaných materiálů. V článku je prezentováno porovnání mechanických vlastností ozářeného a neozářeného polyamidu PA6 a PA 6.6, neplněného a plněného 30% skelných vlákenThe principle of the radiation processing is the ability of the high energy of radiation to produce reactive cations, anions and free radicals in materials which leads to changes of materials properties. A comparison of the mechanical properties of natural and irradiated polyamide PA6 and PA 6.6 (Unfilled and filled by 30% of GF) is presented in this articl

Optimized system of installation for producing voids of shape-specific part molds

Inovační řešení se týká zařízení k výrobě dutin forem tvarově specifických dílců jako jsou např. kostní náhrady a implantáty. Optimalizovaná soustava zařízení obsahuje vstupní zařízení pro vstup dat digitálního 3D modelu daného dílce, s ním propojený SW modul k zaformování tohoto digitálního modelu a připojené zařízení 3D tisku, rapid prototyping, reálného negativního modelu tvarových desek formy rozdělených dělící rovinou. Součástí soustavy zařízení je dále navazující subsystém zařízení pro galvanoplastiku skořepiny tvarové dutiny a finalizaci formy. Vstupním digitálním 3D modelem může být produkt 3D skenování, rentgenového nebo tomografického zpracování. Hlavním přínosem optimalizované soustavy zařízení je urychlení výroby dutin fortem tvarově specifických dílců a snížení nákladů na výrobu takových forem.Inovative solution relates to the equipment for the production of cavities of shape-specific components such as bone substitutes and implants. Optimized system of equipments contents above all an input device for data input which is an 3D digital model of workpiece | product of 3D scanning, X-ray, tomographic processing |, an appropriate SW modul and connected 3D print equipment | rapid prototyping |. The main benefit of this solution is considered the production to accelerate and the reduction of the production costs of such specific forms

Tensile behaviour of modified PBT by radiation cross-linking

Radiation processing of polymers is a well-established and economical commercial method of precisely modifying the properties of polymers. The industrial applications of the radiation processing of plastics and composites include polymerization, cross-linking, degradation and grafting. Radiation processing mainly involves the use of either electron beams from electron accelerators or gamma radiation from Cobalt-60 sources. The PBT Polybutylene terephthalate was used in this research and the tensile behaviour was investigated at the ambient temperature. Results demonstrate that PBT has higher values of tensile strength and E-modulus with the increased irradiation dose and it has decreased elongation at break. This behaviour leads to the expansion of these materials in the automotive and electrical industry