Volume 20, No. 2 (2014)
Articles
APPLICATION OF THE FLOCCULATION PROCESS FOR THE MUNICIPAL SEWAGE SLUDGE TREATMENT
JESSICA ALCARAZ(1), MARINE RIDOIRE(1), MIRELA PANAINTE-LEHĂDUȘ(2), MARIANA TURCU (1, 3), NARCIS BÂRSAN(2), DANA CHIŢIMUŞ(2), OANA IRIMIA(2)
All municipal sewage treatments using classic treatment chain create an amount of organic sludge. The stabilization/neutralization of them is essential before any conditioning or reuse. For agronomical recycling or energy-giving optimization, the sludge needs to correspond to some standards. That's why, it exist several treatment of stabilization, packaging and water extraction of sludge. This study deals with sludge chemical conditioning by flocculation process. In the first hand, the flocculation process allows to break up colloidal aversion between particles in sludge. This process is possible by charge neutralization thanks to synthetic or natural organic flocculation which is often cationic since the ionic force of sludge particle usually is negative and the flocculants can be used with lowest dose than common coagulant like aluminum sulfate or ferric chloride. Thanks to laboratory experiments by analysis of several doses of synthesis cationic flocculants, it has been possible to get performance on total suspended solids (TSS), by spectrophotometry measurement and consistency of sludge cake. Graphical analyses allow making comparison between some organic cationic flocculants and select the best one for this type of sludge and the kind of treatment used. The aim is to improve quality of sludge, quantity of filtrated volume, and quality of water.
COLLAPSE BEHAVIOR OF DYNAMICALLY CRASHED HEXAGONAL THIN WALLED STRUCTURES WITH MULTI-CELL CROSS-SECTION GEOMETRY
VLAD ANDREI CIUBOTARIU(1)
In previous studies, the cross-section geometries were either single cell (circular, prismatic) or multi-cell structures with identical cell properties. In the present research the collapse characterization of multi-cell structures consisting of three different types of cell formation defined by either two wide or two narrow angles separating the ladders is conducted. The shape characteristics of interest sum up the layout of the interior walls and their constraints over the outer structure walls. To study the control of cross-section geometry over the crashing mechanism, local or global progressive buckling response, energy absorption and crash load for the structures in discussion FEA simulations of the impact were performed.
THE VARIATION OF THE STRESSES IN THE AREA OF DIAMETER CHANGE IN GAS PIPELINES
MARCU FRĂŢILĂ
The paper presents an analysis of the variation of stresses at a gas pipeline in a geometric discontinuity zone of the diameter. The analysis was performed by assimilating the pipe area with variable diameter with an axially symmetric structure loaded with internal pressure. Stresses were determined using the method of moments, theory for axially symmetrical structures. The analysis was performed according to a set of parameters that define the geometry of a joining between a conical frustum and a cylinder and the loading mode with internal pressure. Efforts and stresses were determined in the meridian direction and in the circumferential direction adjacent coatings combining the two axially symmetries.
EXPERIMENTAL ANALYSIS OF THE INFLUENCE OF BALLSCREW STIFFNESS ON THE POSITIONING PRECISION OF KINEMATIC FEED CHAINS USED ON CNC MACHINE TOOLS
MARIAN FUNARU(1), GHEORGHE STAN(1)
Recent trends in the machine tools domain have focused on improving the manufacturing performances by increasing the feed rates and acceleration values. In this context, the stiffness of the constructive elements which form the mechanical part of the kinematic feed chains need to be studied in order to determine the machine tool dynamic behavior. This study plays a very important role in the correct dimensioning of the feed chain structure and in establishing an optimum control law for the closed-loop system. The present paper presents an experimental study which demonstrates the influence of the whole kinematic feed chain stiffness on the positioning precision of the moving table. Experimental tests were carried out on a test bed which uses the indirect position measuring system, in which case all the external disturbances affecting the mechanical part are found in the values of the positioning precision parameters.
IDENTIFICATION OF THE MAIN PHYSICO-CHEMICAL PROPERTIES INFLUENCING THE QUALITY OF THYME (SATUREJA HORTENSIS)
SIMONA GHINITA CONSTANTIN(1), MIRELA PRAISLER(1), GABRIELA IORDĂCHESCU(1)
Thyme (Satureja hortensis) is a popular spice for food, which is also often used as a medicine for various ailments. This paper presents an artificial intelligence method applied for the objective determination of the most important physico-chemical variables affecting the quality of thyme, i.e. Principal Component Analysis (PCA). The results show that the main properties which significantly influence the nutritional value of thyme are moisture (MOIST), dry matter content (DRYM), protein content (PROT) and, to a lesser extent, carbohydrate content (CARB). Humidity is strongly and negatively correlated with the latter three variables. The main variable that ensures the similarity between the thyme samples having the same geographical origin is the monosodium glutamate content, which generates its delicious (umami) taste.
MUNICIPAL WASTE MANAGEMENT IN LIMETE, MONT AMBA DISTRICT OF KINSHASA, DEMOCRATIC REPUBLIC OF THE CONGO
HOLY HOLENU MANGENDA(1,2) VALENTIN NEDEFF(2), KAKESE KUNYIMA(1), NARCIS BARSAN(2), EMILIAN MOȘNEGUȚU(2), CLAUDIA TOMOZEI(2)
In Kinshasa in general and in the commune of Limete in particular, the problem of waste management have become an important concern. Significant problems with the waste management are very common in the majority of the streets. The analysis from this study shows that all visited landfills are uncontrolled and not respect any regulations on management of urban solid waste. These discharges show a lack of enforcement of waste management policies without participation of the population in the resolve of the waste management problems. Most landfills are located in residential areas, along rivers, along public units, even school routes, hospitals and churches. This study reveals the major problem in the waste management in the commune of Limete. This is a negatively aspect of the low implication of the authorities, noncooperation of the population caused mainly by the precarious information.
SIMULATION BY MEANS FINITE ELEMENTS OF A PREVENTIVE ANTI-ICING SYSTEM FOR WIND TURBINE BLADES
P. MUÑOZ VELASCO(1), L. MUÑOZ VELASCO(2), M.P. MORALES ORTIZ(3), M.A. MENDÍVIL GIRO(2), M.C. JUÁREZ CASTELLÓ(2), J.A. RUIZ BERMEJO(4)
This paper describes the results of a research project undertaken under a research contract with the company DERSA, entitled “Development of a blade anti-icing system for conventional wind turbine models applicable to operational installations”. The goal of the project was developing and analyzing a system which must prevent the build-up of ice on the outer surface of buildings and must be able to melt it under extreme conditions. The idea is to apply the system to existing wind turbines, so the project starts with numerous conditioning factors and limitations. The chosen system operation has been analyzed using the ANSYS computer application.
RESEARCH ON THE STRUCTURE AND CHEMICAL COMPOSITION OF SOME STRAINS OF VEGETABLE CROPS
GELU NUȚU(1), IOAN BĂISAN(2)
This paper presents the results from the analysis of the structure and chemical composition of 15 strains of crops subjected to cutting operation. The experiments consisted of EDAX analysis (Energy Dispersive X - ray Analysis) for identifying the chemical composition of the samples and a microscope electron scanning to obtain the structure -sectional evidence. The results may be related to resistance to cutting of stems, in order to establish correlations between these and their chemical composition, but also for later use of them as plant debris.
FREON COOLING MINISYSTEM USING CIRCULAR MICRO-CHANNELS
LILIANA PĂTULEANU(1), IOAN-COZMIN MANOLACHE-RUSU(1), TIBERIU BURDAN(1), FLORIN ANDRONIC(1), IVAN RADION(1)
The necessity of a higher data processing speed was crucial for the advances in computer science. There were created processors that needed increasingly more power, so that new methods were discovered and more complex systems were created in order to solve the cooling issue. In this paper, there are presented the trials performed on a mini refrigeration plant that used mechanical compression of Freon’s, designed to cool electronic components like microprocessors, microcontrollers, graphic stations, or in the case of local cooling in diverse areas such as bioengineering, optics and nanotechnologies. The refrigeration system was constructed as an experimental set-up and consists of the following: two mini heat exchangers, working both as a condenser and a vaporizer, which are made of circular micro channels, a refrigeration compressor, lamination valve which contains a circular nano channel and a micro filter. The experimental determinations have proven that, although such a system contains a small quantity of Freon, of the order of milligrams, it reaches temperatures of -44 C.
THE EFFECT OF PLANT GROWTH-PROMOTING RHIZOBACTERIA ON MOBILITY OF TOXIC ELEMENTS FROM PHOSPHOGYPSUM AND IMPLICATION ON HUMAN EXPOSURE
IOANA-ADRIANA STEFANESCU(1)
This study investigated the effects of a plant growth- promoting rhizobacteria on soil treated with phosphogypsum (PG) as the mineral additive. The indigenous bacterial strain was isolated from PG polluted soil and identified as Bacillus megaterium, which is able to stimulate plant growth under heavy metals stress conditions. There were nine treated soils with three replicates: (1) control (without PG and inoculums (I) application); (2) control with inoculums (without PG application); (3) - (9) PG application (1, 2, 3, 4, 6, 8 and 10%) equivalent to 10 - 220 t ha−1. The objectives of this study consisted on monitoring the heavy metals levels (Cu, Fe, Zn, Mn) in the body of soybean (Glycine max) and evaluation of the human health risk. This work demonstrates that PG-BM30 coupling effect in the soil on seed germination, seedling growth, biomass accumulation and heavy metals bioaccumulation do not exhibit risk to human health.