Rational Generalized Offsets of Rational Surfaces

The rational surfaces and their offsets are commonly used in modeling and manufacturing. The purpose of this paper is to present relationships between rational surfaces and orientation-preserving similarities of the Euclidean 3-space. A notion of a similarity surface offset is introduced and applied to different constructions of rational generalized offsets of a rational surface. It is shown that every rational surface possesses a rational generalized offset. Rational generalized focal surfaces are also studied

MODELLING AND SIMULATION OF ELECTROPNEUMATIC POSITIONING SYSTEM INCLUDING THE LENGTH OF PNEUMATIC LINES

This paper presents a mathematical model of electropneumatic positioning system including the length of pneumatic lines for the determination of flow and pressure in unsteady operating modes. A simulation model is developed to study the dynamic processes in an electropneumatic positioning system. Simulation of the mathematical models of the screw compressor, proportional directional valve, pneumatic lines, pneumatic cylinder and PID controller were designed in “MatLab Simulink”. The simulation models of the transients in the electropneumatic positioning system at different line lengths from 1m and 10m with stepwise variation of the input setpoint are simulated developed. Graphical comparison is made of the obtained experimental results and simulation model influence of the pneumatic line length on the dynamics of the electropneumatic positioning system are made

Chemical Stability of New Acyclovir Analogues with Peptidomimetics

In the search for new and effective prodrugs against the herpes simplex virus, a series of acyclovir analogues with a thiazole ring containing amino acids (glycine, alanine, valine, leucine) has been investigated. The chemical stability of some of the compounds containing different residues was studied at pH 1 and pH 7.4 at a temperature of 37°C. An HPLC method was developed for quantification of the unchanged ester concentration

MODELLING AND SIMULATION OF DYNAMIC PROCESSES OF PNEUMATIC LINES

The paper presents the simulation of dynamic processes of pneumatic lines using the program "SIMULINK" from the product " MatLab". Simulation is a process of forming, preparing and entering a mathematical model in a computational environment and obtaining the results of the calculations performed in this environment. The mathematical model of the pneumatic line to be simulated is according to previously presented equations. For the simulation of the dynamic processes, various real parameters of the dimensions and lengths of the pneumatic lines with the corresponding coefficients are introduced into the model. The simulation of the transient responses was carried out with stepwise variation and sinusoidal input signal supplied by the set point device and pneumatic line lengths of 1 m, 5 m and 10 m. The simulation output data were output to the interface in the form of graphs showing the dependence of the observed quantities, the input and output pressure through the pneumatic line, and the input and output flow rates. From the mathematical model and the experiments performed, it can be concluded that the transient responses in the simulations correspond to the dynamic processes of pneumatic lines of different lengths

Performance evaluation of data delivery approaches for wireless sensor networks

AbstractWireless sensor networks are expected to revolutionize our abilities in sensing and controlling the physical environment. Power conservation is a primary research concern for these networks, due to the limited energy resources of the sensor nodes. In this paper we study the data delivery approaches, suitable for hierarchical cluster based wireless sensor networks. A radio energy dissipation model is used to evaluate the energy, needed for both intra-cluster and inter-cluster communication. Based on the results we analyze the performance of various combined data delivery approaches. Additionally we study the impact of the base station location and the number of sensor nodes on the energy dissipation and the network lifetime

Post-stall hysteresis and flow field unsteadiness on an NACA 0012 airfoil

The current study was conducted to understand flow field unsteadiness associated with static stall hysteresis on an NACA 0012 airfoil at Rec = 1.0 × 10^6. Unsteady pressure measurements were acquired to evaluate the performance of the airfoil, and a hysteresis loop was identified in the vicinity of the airfoil Cl,max. Two fundamentally different flow regimes were observed at post-stall angles of attack for the airfoil during the upstroke and downstroke branches of the hysteresis loop. A Fourier analysis of the surface pressure distributions was used to attribute the flow field unsteadiness to a low-frequency, high-amplitude oscillation across the leading-edge region during the upstroke, along with a regular bluff-body shedding frequency across the separated region of the airfoil. The low-frequency oscillations were observed to be more dominant for the upstroke branch, while the bluff-body shedding process was more dominant in the downstroke branch. The flow field unsteadiness was observed to become more energetic at lower post-stall angles of attack. In addition, time-resolve particle image velocimetry data were acquired across the leading-edge region of the airfoil to qualitatively and quantitatively describe the unsteadiness in the flow. These data were used to link the low-frequency oscillations across the leading edge of the airfoil during the upstroke to a quasi-periodic surging of the flow, which was also associated with an advancing and retreating of the separation location across the surface

Issues Associated with Genetic Diversity Studies of the Liver Fluke, Fasciola Heptica (Platyhelminthes, Digenea, Fasciolidae)

Space scienc

Measurement of Casein Micelle Size in Raw Dairy Cattle Milk by Dynamic Light Scattering

The particle size of milk influences its microstructure and defines the qualities of dairy products, such as colloidal stability and texture. Moreover, differences in casein micelle size may affect milk processing, especially cheese making. Hence, the size of casein micelle is an important characteristic of raw milk and determines the yield of dairy products. The aim of the present research is to estimate the casein micelle size in the raw milk of dairy cattle by dynamic light scattering. The obtained results may be used for genetic elaboration of the breed, as well as to increase the competitiveness of the milk industry by selection of animals with higher casein micelle size

STUDY OF THE ENERGY POTENTIAL OF RENEWABLE ENERGY SOURCES IN THE REGION OF GABROVO FOR USE IN HYBRID WIND-PHOTOVOLTAIC STAND-ALONE SYSTEM

This paper presents the measurements conducted for two periods (winter and summer) in the region of Gabrovo, Bulgaria for solar radiation and wind conditions using the digital measuring equipment. The aim is to evaluate  and predict the possible production of electricity from already installed low power hybrid system. The conclusion is that a combination of a wind generator and a photovoltaic system in the hybrid system for independent power supply has a good economic effect and allows fuller use of energy from renewable sources.This paper presents the measurements conducted for two periods (winter and summer) in the region of Gabrovo, Bulgaria for solar radiation and wind conditions using the digital measuring equipment. The aim is to evaluate  and predict the possible production of electricity from already installed low power hybrid system. The conclusion is that a combination of a wind generator and a photovoltaic system in the hybrid system for independent power supply has a good economic effect and allows fuller use of energy from renewable sources