Volume 20, No. 3 (2014)
Articles
MODELLING AND SIMULATION OF SEPARATION OF COWPEA AND IMPURITIES IN A PNEUMATIC CLEANER WITH COUNTER-FEED
ADEWOLE A. ADERINLEWO(1), ABDULGANIYU O. RAJI(2)
Mathematical models were developed to study the displacements of cowpea and impurities particles and to predict cleaning efficiencies during separation in a vertical pneumatic cleaner. The predicted horizontal displacements were plotted against the vertical displacements at different angles of injection and air velocities. The plots showed that at a particular air velocity the amount of impurities that are removed from cowpea increased as the angle of injection increased. Experimental studies also confirm that cleaning efficiencies increased as the angle of injection increased at a particular air velocity. There was a high correlation between the predicted and experimental cleaning efficiency.
RISK MANAGEMENT PLANNING WITHIN ROMANIAN COMPANIES
COSTEL CEOCEA(1), LUMINITA BIBIRE(2), ADRIAN STELIAN GHENADI(2)
This paper presents a study that used a quantitative research methodology, approach. The main research method at which it was appealed was based on a questionnaire survey, but there were interviews, observations and study of companies’ documents. Questionnaires were simultaneously distributed to managers from 101 enterprises in Romania, covering companies throughout the country, in all major areas of activity in order to meet the criterion of representativeness. Following an analysis of the responses received, the authors have highlighted conclusions on risk management planning in the Romanian companies.
RISKS FOR THE CAREER DEVELOPMENT OF THE YOUNG ENGINEERS UNDER THE CONDITIONS OF ECONOMIC STAGNATION: A CASE STUDY FOR THE UNIVERSITY OF RUSE
OGNYAN DINOLOV(1), NICOLAY MIHAILOV(1)
The trends in the number of applicants and of the admission of students in engineering specialties in the University of Ruse, Bulgaria are analyzed in this work. It is found that the admission of students constantly decreases throughout the considered period (2009-2013). The structure of the main sectors of the economy of the North-Central Region of Bulgaria, particularly Ruse District, is reviewed. The largest share is of the sector of the Mechanical Engineering followed by the Chemical Industry sector. The risk of inefficient use of financial and human resources, caused by the economic stagnation, is indicated. S-O, S-T, W-O and W-T strategies for reducing the adverse effect of the economic, social, demographic and other factors are synthesized using SWOT analysis. This will helps politicians, decision makers and managers to overcome the risk for the career development of the young engineers in Ruse region, and in Bulgaria. The obtained results can be used in building, designing and implementing strategies to overcome the investigated problems.
NEW PORTFOLIO RISK OPTIMISATION METHOD FOR STRONGLY DEPENDENT ASSETS
PIOTR FRYDRYCH(1), ROMAN SZEWCZYK(1)
New market time series Multiplexed Hysteretic Threshold Autoregressive (MHTAR) model was developed to test the correlation between assets stability, which is the basis of MPT theory and other portfolio optimisation methods. New approach to risk optimisation was presented, which can efficiently lower risk for strongly dependent assets. Developed Random Trading Signals Multiplexing (RTSM) method enables diversification of risk for any portfolio and increase safety for assets with low liquidity.
TEXTURAL AND MORPHOLOGICAL CHARACTERIZATION OF COPPER(II)-EXCHANGED ROMANIAN CALCIUM BENTONITE
ANA-MARIA GEORGESCU(1,2), GHEORGHE BRABIE(3), ILEANA DENISA NISTOR(1), CLAUDE PENOT(2), FRANÇOISE NARDOU(2)
Romanian calcium bentonite was modified by copper(II) ion-exchange, by varying the copper precursors (chloride, sulphate) and synthesis parameters (pH, temperature, time). The quantification of the Cu(II) ions was carried out by atomic absorption spectrophotometer. The modified bentonites were characterized by textural analysis (specific surface area by the Brunauer-Emmett-Teller method (BET) and by nitrogen adsorption/desorption isotherm), structural composition (X-ray diffraction (XRD)) and morphological analysis (scanning electron microscopy (SEM)). Analysis of the nitrogen adsorption/desorption isotherm shows that ion exchanged bentonites, not only contain mesopores, but micropores in larger quantities too. The values of the specific surface area increased by about 20 m2/g compared with raw bentonite, but the interlamellar distance values do not vary substantially. Scanning electron micrographs were acquired to demonstrate changes in the texture of the clay before and after ion exchange.
PREDICTION OF WEAR AND FRICTION COEFFICIENT OF BRAKE PADS DEVELOPED FROM PALM KERNEL FIBRES USING ARTIFICIAL NEURAL NETWORK
IKPAMBESE KUMADEN KUNCY(1), ASHWE ABUGH(1), TULEUN LIVINUS TYOVENDA(1)
Artificial neural network prediction of wear rate and friction coefficient of brake pads developed from palm kernel fibres (PKF) was carried out in this study. Major input parameters including materials formulation, manufacturing conditions, and operating conditions were introduced into the neural model while wear rate and friction coefficient were the outputs. The network architecture of LM12 [4-3]2 2 was selected for predicting the wear rate and coefficient of friction. The predicted wear rate and friction coefficient using ANN models were compared with the measured values using some statistical indicators. Results showed that the ANN predicted accurately the wear rate and friction coefficient of the developed automotive brake pads.
ASSESSMENT OF SOME PHYSICAL FACTORS AND DESIGN FEATURES OF ROTORS IN THERMAL EFFECTS CAUSED BY CENTRIFUGATION
ALEXEI MAFTULEAC(1)
In separating the components of highly dispersed heterogeneous systems, use is made of centrifuges with very high rotation velocities, this leading to samples heating. The said above is due to the friction of the rotor against the air from the centrifuge chamber to the movement of heating from centrifuge engine towards the samples and to compression of samples liquid. However, heating of samples sensible to temperature can generate in these samples the intensification of some uncontrolled chemical processes. This paper is devoted to the investigation of the increase of centrifuged samples temperature depending on the time and relative centrifugal acceleration for model-samples (water and glycerine) using two constructively different types of rotors. The obtained results can be taken into account when elaborating some more rigorous methods for studying finely-dispersed heterogeneous systems.
POSSIBILITIES TO DETERMINING THE SOLID PARTICLE TRAJECTORIES ON AN OSCILLATING SEPARATION SCREEN
EMILIAN MOȘNEGUȚU(1), VALENTIN NEDEFF(1), OVIDIU BONTAŞ(2), NARCIS BÂRSAN(1), DANA CHIŢIMUȘ(1)
To understand the process of separating on the sieve of a solid particles heterogeneous mixture has to be known, first of all, the solid particle movement on the working surface. Therefore, in this article is presented a method for determining these characteristics. The working methodology was based on the processing of some video recordings used to obtain some numerical data for the solid particle movement on the oscillating surface, respectively the values for all three axes OX, OY and OZ. These parameters were used to calculate both the speed and acceleration of the solid particle.
POSSIBILITIES FOR THE TREATMENT OF WASTEWATER FROM PRIMARY PETROLEUM CLARIFIERS
CASEN PANAITESCU(1), MARIUS GABRIEL PETRESCU(1), RODICA BUCUROIU(1)
Wastewater from the oil industry treatment is very difficult to achieve in an uniform matter. Therefore, pre-treatment steps are often required in order to reduce the compounds’ elimination and to determine which treatment cannot be eliminated in the biological stage. Application of a pre-treatment process eliminates certain compounds with specific microorganisms that do not fit with the activated sludge. In this paper, the details of this solution were studied. It was established a reduction of the benzene concentration from 82.23 mg/L to 18.04 mg/L, toluene 3.08 mg/L to 1.15 mg/L, xylene at 4.1 mg/L to 3.1 mg/L and naphthalene 7.08 mg/L to 4.96 mg/L. Experiments have shown a decrease of the polycyclic aromatic hydrocarbons concentration below the limit of detection of the device.
ASPECTS REGARDING VALORIFICATION OF NATURAL FIBROUS MATERIALS FROM TEXTILE AND LEATHER INDUSTRY FOR COMPOSITE MATERIALS
NATALIA POPA(1), DAMIAN TIMOFTE(1), GHEORGHE VOICU(1), ION DURBACA(1), MAGDALENA–LAURA TOMA(1)
Technological aspects regarding sustainable development concept and considerations on creating textile products with high added value from recycled fibres as combed and carded yarns, woven fabric waste, hosiery and leather waste. The paper offers some ways to reuse wastes from leather industry and presents some physical characteristics of some composite materials based on PVC mixed with different concentrations of leather wastes, before and after forced ageing.