DEVELOPMENT OF A CUTTING TOOL FOR COMPOSITES WITH THERMOPLASTIC MATRIX

Fibre reinforced thermoplastic composites (FRTC) are becoming an increasingly important material for a wide range of applications. Thus, the demand for high performance tools for machining of this material is increasing. The main goal of the presented research results is to decrease cutting costs during trimming operations of thin plates and to increase the quality of machined composite materials by suitable shape, geometry and material of the cutting tool and by suitable cutting conditions. Statistical methods were used in order to obtain the control factors (cutting conditions) which are the most important for machining FRTC. Subsequently, an optimal adjustment of cutting conditions was identified. The paper is a brief summary of the cutting tool development. It includes important parts of tests and their results as well as some interesting findings implicit in experiments and measuring

Concurrent Design of Railway Vehicles by Simulation Model Reuse

This paper describes a concurrent design approach to railway vehicle design. Current railway vehicles use many different concepts that are combined into the final design concept. The design support for such systems is based on reusing components from previous design cases. The key part of the railway vehicle design concept is its simulation model. Therefore the support is based on support for reuse of previous simulation models. The simulation models of different railway component concepts are stored using the methodology from the EU CLOCKWORK project. The new concept usually combines stored components

Research on influence of cyclic degradation process on changes of structural adhesive bonds mechanical properties

ArticleThe paper deals with an influence of a cyclic degradation process on changes of a shear tensile strength of single lap-shear adhesive bonds and their elongation according to ČSN EN ISO 9142. Five one-component structural adhesives used in a construction of car body works were used within the research. The degradation of adhesive bonds is a significant factor which influences a quality and a service life of adhesive bonds exposed to environment. A main requirement in production companies is not only reaching satisfactory initial mechanical properties but namely ensuring a reliability and a safety of adhesive bonds during their usage. These reasons show a great importance of adhesive bonds tests either directly in the operating environment or by a simulation of operating conditions in laboratories. The degradation process of adhesive bonds worsens mechanical properties of not only the bond itself but also of the bonded material. This process is progressing and it is usually permanent and irreversible. It is a change of mechanical and physical properties which can endanger a safety and a reliability of parts, prospectively of the whole equipment. It can leads up to a complete failure of its function in the extreme case. A temperature, a moisture, a direct contact with water and chemicals or an atmospheric corrosion belong among the most serious degradation agents. It is important to take into regard time of the processes influence at the same time which can act either independently or concurrently when their effects grow stronger. From that reason the adhesive bonds were exposed to the cyclic degradation process according to the standard ČSN EN ISO 9142. Subsequently, the adhesive bonds mechanical properties were tested on universal testing machine and by means of SEM analysis (TESCAN MIRA 3). Results of mechanical tests proved a fall of the shear tensile strength of single lap-shear adhesive bonds after 42 cycles of the degradation process of 12.8 to 21.7%. The bond strength fall was gradual and it showed a linear trend at some adhesives. Other adhesives showed a significant fall after the exposition to the degradation process after which the strength fall stabilized

Texture Analysis of the Retinal Nerve Fiber Layer in Fundus Images via Markov Random Fields

Abstract-This paper describes method for analysis of the texture created by retinal nerve fibers (RNF) via Markov Random Fields. The Causal Autoregressive Random (CAR) model is used to create a feature vector describing the changes in texture due to losses in RNF layer. It is shown that features based on CAR model can be used for discrimination between healthy and glaucomatous tissue using simple linear classifier. The classification error is slightly below 4% for the tested dataset

Tight Binding Hamiltonians and Quantum Turing Machines

This paper extends work done to date on quantum computation by associating potentials with different types of computation steps. Quantum Turing machine Hamiltonians, generalized to include potentials, correspond to sums over tight binding Hamiltonians each with a different potential distribution. Which distribution applies is determined by the initial state. An example, which enumerates the integers in succession as binary strings, is analyzed. It is seen that for some initial states the potential distributions have quasicrystalline properties and are similar to a substitution sequence.Comment: 4 pages Latex, 2 postscript figures, submitted to Phys Rev Letter

Resistance to Antibiotics in Strains of Staphylococcus spp., Enterococcus spp. and Escherichia coli Isolated from Rectal Swabs of Pigs

The study aimed at determining the level of resistance of selected bacterial species (Staphylococcus spp., Enterococcus spp., Escherichia coli) isolated from rectal swabs of pigs to antimicrobial agents. The tested strains were isolated from piglets aged 7 to 30 days. Bacterial species were identified by standard microbiological techniques and susceptibility to antibiotics was determined quantitatively by the standard microdilution method. Resistance of the Staphylococcus aureus strain to oxacillin was confirmed by detection of the mecA gene and PBP2a. A total of 115 Staphylococcus spp. isolates were collected. In the case of Staphylococcus aureus, the methicillin-resistant strain (MRSA) was identified. Moreover, higher frequency of coagulase-negative staphylococci with minimum inhibitory concentration of oxacillin ≥ 0.5 mg/l was noticed. Inducible resistance to clindamycin in the Staphylococcus hominis strain was also detected. The strains of Enterococcus spp. (61 isolates) exhibited high resistance to tetracycline (98.5%), erythromycin (86.8%) and chloramphenicol (54.4%). Vancomycin-resistant enterococci were not isolated. In the case of Escherichia coli strains (111 isolates), higher frequency of resistant strains to tetracycline (81.1%) and ampicillin (62.2%) was documented. Resistance to fluoroquinolones and production of broad-spectrum β-lactamases was not noticed. The presented study may be considered as a pilot project assessing the prevalence of resistant bacteria in piglets kept on a single farm. It demonstrated the presence of resistant strains of Staphylococcus spp., including one MRSA strain, Enterococcus spp. and Escherichia coli. These strains may be present as a result of postnatal colonization with both bacterial microflora of dams and environmental microflora

VLIV FOTODYNAMICKÉ TERAPIE NA CYTOMECHANIKU NÁDOROVÉ BUNĚČNÉ LINIE HELA

Během posledních desetiletí byla k zobrazování detailních struktur biologických preparátů používána zejména elektronová mikroskopie (EM). Ačkoliv nám EM poskytuje vysoké rozlišení; zobrazovat vzorky bez fixace a barvení není zcela jednoduché a je tímto limitováno. Jak se ale ukazuje, mikroskopie atomárních sil (AFM) se zdá být vhodným nástrojem nejen pro zobrazení biologických struktur, ale i k jejich manipulaci s nimi v nativním stavu a v přirozeném prostředí. Navíc nám poskytuje přesné morfologické a mechanické informace v reálném čase a v nanorozlišení. Moderní AFM přístroj pracuje s pikonewtonovou silovou interakcí s povrchem preparátu, což nám umožňuje provádět detailní studie mofrologických charakterizací biologického vzorku a popisy interakcí hrot-vzorek. Jako biologický objekt byla vybrána HeLa buněčná linie (nádor děložního hrdla virového původu), která je citlivá vůči fotodynamické terapii za současného využití ftalocyaninového senzitizeru. Pro detekci změn v buněčné kultuře byly použity dva různé mikroskopy atomárních sil: Bioscope Catalyst od firmy Bruker a Ntegra AURA od firmy NT-MDT jako nástroj pro detekci mechanických změn po terapii. Naše práce má za úkol upozornit na jednu z aplikací mikroskopie atomárních sil - mechanickou charakterizaci buněk před a po poškození fotodynamickou terapií, která může mít výhledově velký přínos v diagnostice různých onemocnění

Minimizing energy below the glass thresholds

Focusing on the optimization version of the random K-satisfiability problem, the MAX-K-SAT problem, we study the performance of the finite energy version of the Survey Propagation (SP) algorithm. We show that a simple (linear time) backtrack decimation strategy is sufficient to reach configurations well below the lower bound for the dynamic threshold energy and very close to the analytic prediction for the optimal ground states. A comparative numerical study on one of the most efficient local search procedures is also given.Comment: 12 pages, submitted to Phys. Rev. E, accepted for publicatio