Bacau, Romania

University of Bacau
Bacau, Romania

The Vasile Alecsandri University of Bacău is a public university in Romania, located in Bacău. It was named in honor of the poet Vasile Alecsandri. Wikipedia.

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Olaru I.,University of Bacau
IOP Conference Series: Materials Science and Engineering | Year: 2017

This paper analyzes several types of cooling agents, their properties and how they can be chosen for a better heat dispersion resulting from the cutting process. An excessive heat in the cutting zone leads to excessive wear of the cutting tools, that leading finally to additional costs of their acquisition and due to wear is reached in cutting process more irregular surfaces. The coolant chosen can be a combination of different cooling fluids from the most simple and inexpensive to more complex, the difference between them being more appropriately cool the processing area. The fluid flow parameters of coolant can be influenced by the nature of the fluid or fluids used, the geometry of the nozzle in order to achieve a better dispersion of the lubricant on the area to be processed. A smaller amount of fluid is important in terms of the economy lubricant, because some of these lubricants are quite expensive. A minimal quantity of lubricant (MQL) may have a better impact on the environment and the health of the operator because the coolants in contact with overheated machined surface may develop a substantial amount of these gases that are not always beneficial to health. © Published under licence by IOP Publishing Ltd.

Caliman R.,University of Bacau
IOP Conference Series: Materials Science and Engineering | Year: 2017

The purpose of this paper is to highlight a number of factors that influence the physical-mechanical and tribological characteristics of sintered composite materials. Such factors are grouped generally in two categories: technological parameters (pressure compacting, sintering temperature, sintering duration, heat treatment) and the receipt of sintered composite materials. In this paper is presented a program of experiments developed both in composite materials sintered polymer matrix (non-metallic) and in the metal matrix (eg., Al) which was prepared in advance a methodology original production and research for this particular type of materials. The experiments have focused development and testing of a number of 14 polymer composite and 5 composite sintered Al base, in both situations armed with carbon fiber in various forms. Tribological tests followed the establishment of the coefficient of friction and wear rate of the sliding speed at the constant values (v = 7.2 mm/s) and the normal load (N = 8 daN) and for different orientations of the fibers to the direction of sliding: normal (N type), parallel (P) and antiparallel-perpendicular (AP type). © Published under licence by IOP Publishing Ltd.

Stan G.,University of Bacau
IOP Conference Series: Materials Science and Engineering | Year: 2017

Flexible automation is used more and more in various production processes, so that both machining itself on CNC machine tools and workpiece handling means are performed through programming the needed working cycle. In order to obtain a successful precise positioning, each motion degree needs a certain deceleration before stopping at a programmed point. The increase of motion speed of moving elements within the manipulators structure depends directly on deceleration duty quality before the programmed stop. Proportional valves as well as servo-valves that can perform hydraulic decelerations are well known, but they feature several disadvantages, such as: high price, severe conditions for oil filtering and low reliability under industrial conditions. This work presents a new deceleration system that allows adjustment of deceleration slope according to actual conditions: inertial mass, speed etc. The new solution of hydraulic decelerator allows its integration to a position loop or its usage in case of positioning large elements that only perform fixed cycles. The results being obtained on the positioning accuracy of a linear axis using the new solution of the hydraulic decelerator are presented, too. The price of the new deceleration system is much lower compared to the price of proportional valves or servo-valves. © Published under licence by IOP Publishing Ltd.

Caliman R.,University of Bacau
IOP Conference Series: Materials Science and Engineering | Year: 2017

This paper contains an analysis of the factors that have an influence on the tribological characteristics of the composite material sintered with metal matrix reinforced with carbon fibers. These composites are used generally if it's needed the wear resistant materials, whereas these composites have high specific strength in conjunction with a good corrosion resistance at low densities and some self-lubricating properties. Through the knowledge of the better tribological properties of the materials and their behavior to wear, can be generated by dry and the wet friction. Thus, where necessary the use of high temperature resistant material with low friction between the elements, carbon fiber composite materials are very suitable because they have: mechanical strength and good ductility, melting temperature on the higher values, higher electrical and thermal conductivity, lower wear speed and lower friction forces. For this purpose, this paper also contains an experimental program based on the evidence of formaldehyde resin made from fiber reinforced Cu-carbon with the aim to specifically determine the volume of fibers fraction for the consolidation of the composite material. In order to determine the friction coefficient and the wear rates of the various fiber reinforced polymer mixtures of carbon have been used special devices with needle-type with steel disc. These tests were conducted in the atmosphere at the room temperature without external lubrication study taking into consideration the sliding different speeds with constant loading task. © Published under licence by IOP Publishing Ltd.

Ardeleanu E.-R.,University of Bacau
Proceedings of the Romanian Academy Series A - Mathematics Physics Technical Sciences Information Science | Year: 2016

We study a system of nonlinear hyperbolic equations, with nonlocal boundary conditions, arising in the modeling of cell growth. The basic model introduced in [7] is completed with a parabolic equation simulating the effect of a treatment introduced in the cell system. The mechanism described is based on experimental evidence for tumoral cells. The aim of the paper is to prove the well-posedness of the system under certain conditions on the parameters. © 2016, Editura Academiei Romane. All rights reserved.

Radu M.C.,University of Bacau | Cristea I.,University of Bacau
Materials and Manufacturing Processes | Year: 2013

The effects of four working parameters, namely tool diameter, tool vertical step, feed rate, and spindle speed on the dimensional accuracy, surface roughness, and microstructure of parts processed by SPIF were experimentally investigated. The parts were made from carbon steel (DC01), stainless steel (304), and aluminium (A1050). Two geometries were tested - a conic and a prismatic shape. The results were statistically processed by using the ANOVA technique. It was highlighted that the working parameters have contradictory influence on the analyzed quality characteristics of parts and only a proper combination of them could lead to the expected results. © 2013 Copyright Taylor and Francis Group, LLC.

Adrian M.L.,University of Bacau
Applied Mechanics and Materials | Year: 2013

In small and medium batch series manufacturing the small tool and workpiece changing time is one of the main objectives to follow in obtaining high productivity. These auxiliary times are defined as the times consumed with preparing and changing the next tool or workpiece to follow the machining process, times that usually overlap the machining process. For this purpose machining centres are equipped with an automatic tool changer system and an automatic pallet changer system. The palletizing systems imply eliminating the times consumed with the alignment, fixing and clamping of the workpieces, these systems consisting of several mechanisms: the pallet, the automatic pallet changing mechanism, the positioning mechanism and the pallet clamp/unclamp mechanism. In this paper we present an general overview of the automatic pallet changing mechanisms used both in flexible manufacturing systems and machining centres. © (2013) Trans Tech Publications, Switzerland.

Mocanu M.,University of Bacau
Complex Analysis and Operator Theory | Year: 2011

We prove a Poincaré inequality for Orlicz-Sobolev functions with zero boundary values in bounded open subsets of a metric measure space. This result generalizes the (p, p)-Poincaré inequality for Newtonian functions with zero boundary values in metric measure spaces, as well as a Poincaré inequality for Orlicz-Sobolev functions on a Euclidean space, proved by Fuchs and Osmolovski (J Anal Appl (Z. A. A.) 17(2):393-415, 1998). Using the Poincaré inequality for Orlicz-Sobolev functions with zero boundary values we prove the existence and uniqueness of a solution to an obstacle problem for a variational integral with nonstandard growth. © 2010 Birkhäuser / Springer Basel AG.

Stefanescu I.A.,University of Bacau
Scientific Study and Research: Chemistry and Chemical Engineering, Biotechnology, Food Industry | Year: 2015

The aim of present study was to characterize the bioaccumulation capacity of heavy metals by Bacillus megaterium from phosphogypsum waste. The Bacillus megaterium strain (BM30) was isolated from soil near the phosphogypsum (PG) dump. For the bioaccumulation quantification produced by BM30 strain were used three experimental treatments respectively with 2, 6 and 10 g·L-1 PG. Cellular biomass samples were collected punctually at ages corresponding to the three stages of the development cycle of the microorganism: exponential phase, stationary phase and decline phase and the heavy metals concentrations were measured by atomic absorption spectroscopy. The bioaccumulation yields in cell biomass, relative to the total amount of analyte introduced in the reaction medium were between 20 - 80 %, the lowest value was recorded by Cu and highest by Mn. The study results indicated that the isolated strain near the dump PG, BM30, bioaccumulate heavy metals monitored in cell biomass in the order Cu > Fe > Zn = Mn. © 2015 ALMA MATER Publishing House, “VASILE ALECSANDRI” University of Bacău. All rights reserved.

Hazi A.,University of Bacau | Hazi G.,University of Bacau
Applied Thermal Engineering | Year: 2014

In this paper, a comparative study of indirect photovoltaic thermal solar-assisted heat pump systems for water heating in industry is presented. The solutions to achieve a system with a steam ejector heat pump and a system with a mechanical compression heat pump integrated in a paper mill are proposed. The mathematical models are developed and used to evaluate the performance of these systems for the Bacau, Romania climatic conditions. A numerical study highlights the energy, exergy and economic efficiency of each system for the different operating hot water temperatures supplied. The obtained results show that an increase in the hot water temperature leads to a decrease in the energy, exergy and economic performance and that in an industrial company with continuous operation, the best solution is a photovoltaic thermal system with a steam ejector heat pump. © 2014 Elsevier Ltd. All rights reserved.

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