Gabriela Demian

Effect of the manufacturing parameters on the structure of nitrogen-doped carbon nanotubes produced by catalytic laser-induced chemical vapor deposition

Nitrogen-containing carbon nanotubes (CNx-NTs), with a relatively high level of nitrogen doping were prepared by the catalytic laser-induced CVD method. The nanotubes were catalytically grown directly on a silicon substrate from C2H2/NH3 gaseous precursors. X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) give firm evidence for the nitrogen doping. As determined by XPS, the N concentration for the prepared CNx-NTs increases from 3.6 to 30.6 at.% with increasing ammonia concentration and pressure. TEM images indicate that the nanotubes are bamboo like. As the nitrogen content increases, there is a transition from the bamboo shape with few defects and little distortion to a corrugated structure with a much larger number of defects. Raman spectroscopy revealed that with increasing nitrogen concentration, there is more disorder and defects, together with an increase in ID/IG ratio. By energy-filtering TEM, a higher N concentration was found on the outer amorphous nanolayer than in the compartment core of the nanotubes.

Studies to Determine Optimal Parameters for the Ultrasonic Bonding of Copper Wires

In the paper is investigated a method of ultrasonic connection of copper wires so that its joining has a higher mechanical strength. Copper wires connection analysis was carried out by destructive methods such as breaking strength of wire testing or metallographic testing. The purpose of the paper is to identify optimal parameters for ultrasonic welding of copper wires.

Multi-Criteria Decision-Making Tools for Selection Photovoltaic Modules

This paper presents aplying a multi-criteria decision methods to evaluate an optimum photovoltaic module for the construction of a solar park. In this work, seven number of alternative of photovoltaic modules and four criteria for selection is used for the optimal solution. The result from the research demonstrate which of the analyzed PV modules is the most convenient to be used for construction of a solar park.

Optimization for Materials Selection and its Importance in a Management Performance

The complexity and importance of the management activities, and implicitly decision-making activities requires in the current period, the use of modern techniques and methods, very well scientifically founded. A power plant management activity involves making decisions based wealth of information and often involve the most varied criteria: technical, economic, environmental and others. Using methods of multi-criteria decision becomes an indispensable decision factor. In this paper, we apply such a method for prioritizing namely Onicescu method in solving the problems as the optimal choose of materials for the realization of thermal to a superheater. Are analyzed three materiale10CrMo9-10, 13CrMo4-5, 16Mo3 taking into account criteria such as technical resistance duration, creep limit, cost and others.

Studies Regarding the Influence of Cutting Regime on Vibration and Noise Pollution in a Parts Processing

This paper presents the results of experimental research of the authors in terms of overall vibration behavior MUSD (machine tool, tool-device) during processing by removing metal on a pump body on a CNC milling and boring machine. At the research conducted in this direction were considered mechanical vibration measurements occurred during the processing of various operations of the technological process in parallel with noise measurements. These experimental research in determining the direction of vibration occurring in machining process led to some conclusions about the interdependence between the intensity and quality cutting data processing carried out and the influence of noise pollution produced.

Studies Regarding Photovoltaic Solar Energy Potential on Pristol Area, Mehedinti County

The paper makes an assessment of the long term solar resource for the location of a photovoltaic solar park in the Pristol, Mehedinti County, Romania. Reference data and observations in the proximity of the solar park location were limited, and the analysis was based on a Typical Meteorological Year (TMY) Meteonorm developed to represent the behavior of the solar resource at the site of Photovoltaic Solar Park. The level of Global Horizontal Irradiance (GHI) was evaluated as 1376 kWh/m2/year, while values for direct normal irradiance (DNI) and diffuse horizontal irradiance (DHI), the resulting values were 1553 kWh/m2/year and 606 kWh/m2/year, respectively, provided for long-term behavior.

Effect of Laser Process Parameters on the Surface Absorbtivity

Hardening laser surface offers new possibilities for the enhancement of the mechanical resistance of superficial layers. Essential for the laser treatment processes is the efficiency at which the incident laser power is coupled into the work piece. The aim of the work was to study the effect of some factors such as spot shape, beam angle of incidence and surface coating on the steel surface absorptivity. Samples made of carbon steel were laser processed using a CW CO2 - 1,2 kW laser unit. Different process parameters (beam power, spot dimension and traverse speed), were used. The microstructure of laser hardened layers which have been investigated by optical microscopy. The mechanical characterization of the layers has been done by hardness measurements. Correlation has been established between the structure of the laser-processed layers and the process parameters.