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Machining process modeling has been an active endeavor for more than a century and it has been reported to be able to predict industrially relevant process outcomes. Recent advances in the fundamental understanding of material behavior and material modeling aids in improving the sustainability of industrial machining process. In this work, the flow stress behavior of C45E steel is modeled by modifying the well-known Johnson-Cook model that incorporates the dynamic strain aging (DSA) influence. The modification is based on the Voyiadjis-Abed-Rusinek (VAR) material model approach. The modified JC model provides the possibility for the first time to include DSA influence in chip formation simulations. The transition from continuous to segmented chip for varying rake angle and feed at constant cutting velocity is predicted while using the ductile damage modeling approach with two different fracture initiation strain models (Autenrieth fracture initiation strain model and Karp fracture initiation strain model). The result shows that chip segmentation intensity and frequency is sensitive to fracture initiation strain models. The Autenrieth fracture initiation strain model can predict the transition from continuous to segmented chip qualitatively. The study shows the transition from continuous chip to segmented chip for varying feed rates and rake angles for the first time. The study highlights the need for material testing at strain, strain rate, and temperature prevalent in the machining process for the development of flow stress and fracture models.
Ashwin Moris Devotta; P. V. Sivaprasad; Tomas Beno; Mahdi Eynian. Predicting Continuous Chip to Segmented Chip Transition in Orthogonal Cutting of C45E Steel through Damage Modeling. Metals 2020, 10, 519 .
AMA StyleAshwin Moris Devotta, P. V. Sivaprasad, Tomas Beno, Mahdi Eynian. Predicting Continuous Chip to Segmented Chip Transition in Orthogonal Cutting of C45E Steel through Damage Modeling. Metals. 2020; 10 (4):519.
Chicago/Turabian StyleAshwin Moris Devotta; P. V. Sivaprasad; Tomas Beno; Mahdi Eynian. 2020. "Predicting Continuous Chip to Segmented Chip Transition in Orthogonal Cutting of C45E Steel through Damage Modeling." Metals 10, no. 4: 519.
In this study, the flow stress behavior of ferritic-pearlitic steel (C45E steel) is investigated through isothermal compression testing at different strain rates (1 s−1, 5 s−1, and 60 s−1) and temperatures ranging from 200 to 700 °C. The stress-strain curves obtained from experimental testing were post-processed to obtain true stress-true plastic strain curves. To fit the experimental data to well-known material models, Johnson-Cook (J-C) model was investigated and found to have a poor fit. Analysis of the flow stress as a function of temperature and strain rate showed that among other deformation mechanisms dynamic strain aging mechanism was active between the temperature range 200 and 400 °C for varying strain rates and J-C model is unable to capture this phenomenon. This lead to the need to modify the J-C model for the material under investigation. Therefore, the original J-C model parameters A, B and n are modified using the polynomial equation to capture its dependence on temperature and strain rate. The results show the ability of the modified J-C model to describe the flow behavior satisfactorily while dynamic strain aging was operative.
Ashwin Moris Devotta; P. V. Sivaprasad; Tomas Beno; Mahdi Eynian; Kjell Hjertig; Martin Magnevall; Mikael Lundblad. A Modified Johnson-Cook Model for Ferritic-Pearlitic Steel in Dynamic Strain Aging Regime. Metals 2019, 9, 528 .
AMA StyleAshwin Moris Devotta, P. V. Sivaprasad, Tomas Beno, Mahdi Eynian, Kjell Hjertig, Martin Magnevall, Mikael Lundblad. A Modified Johnson-Cook Model for Ferritic-Pearlitic Steel in Dynamic Strain Aging Regime. Metals. 2019; 9 (5):528.
Chicago/Turabian StyleAshwin Moris Devotta; P. V. Sivaprasad; Tomas Beno; Mahdi Eynian; Kjell Hjertig; Martin Magnevall; Mikael Lundblad. 2019. "A Modified Johnson-Cook Model for Ferritic-Pearlitic Steel in Dynamic Strain Aging Regime." Metals 9, no. 5: 528.
Machining parameters needed for stable, high-performance high-speed machining could be found using mathematical models, but these models need accurate measurements of modal parameters of the machining system. In-process modal parameters, however, can slightly differ from those measured offline and this can limit the applicability of simple measurement methods such as impact hammer tests. To study and extract the in-process modal parameters, mathematical models are used to define a few key dimensionless parameters and establish their relationships with each other and the modal parameters. Based on these relationships, the modal parameters are extracted using two analytical methods, the two-point method (TPM), and the regression method (RM). As shown with experimental studies, the RM performs well in the extraction of the modal parameters and while being much faster than the existing iteration-based methods, it provides stability lobe predictions that match well the experimental results. Furthermore, it is noted that the natural frequency parameter is estimated with much higher relative precision compared to that of damping ratio and the modal stiffness parameters.
Mahdi Eynian. In-process identification of modal parameters using dimensionless relationships in milling chatter. International Journal of Machine Tools and Manufacture 2019, 143, 49 -62.
AMA StyleMahdi Eynian. In-process identification of modal parameters using dimensionless relationships in milling chatter. International Journal of Machine Tools and Manufacture. 2019; 143 ():49-62.
Chicago/Turabian StyleMahdi Eynian. 2019. "In-process identification of modal parameters using dimensionless relationships in milling chatter." International Journal of Machine Tools and Manufacture 143, no. : 49-62.
Understanding the influence of the cutting edge geometry on the development of cutting forces during the milling process is of high importance in order to predict the mechanical loads on the cutting edge as well as the dynamic behavior on the milling tool. The work conducted in this study involves the force development over the entire engagement of a flute in milling, from peak force during the entry phase until the exit phase. The results show a significant difference in the behavior of the cutting process for a highly positive versus a highly negative cutting edge geometry. The negative edge geometry gives rise to larger force magnitudes and very similar developments of the tangential and radial cutting force. The positive cutting edge geometry produces considerably different developments of the tangential and radial cutting force. In case of positive cutting edge geometry, the radial cutting force increases while the uncut chip thickness decreases directly after the entry phase; reaching the peak value after a certain delay. The radial force fluctuation is significantly higher for the positive cutting edge geometry. The understanding of such behavior is important for modelling of the milling process, the design of the cutting edge and the interactive design of digital applications for the selection of the cutting parameters.
A. Agic; Mahdi Eynian; J.-E. Ståhl; T. Beno. Dynamic effects on cutting forces with highly positive versus highly negative cutting edge geometries. International Journal on Interactive Design and Manufacturing (IJIDeM) 2018, 13, 557 -565.
AMA StyleA. Agic, Mahdi Eynian, J.-E. Ståhl, T. Beno. Dynamic effects on cutting forces with highly positive versus highly negative cutting edge geometries. International Journal on Interactive Design and Manufacturing (IJIDeM). 2018; 13 (2):557-565.
Chicago/Turabian StyleA. Agic; Mahdi Eynian; J.-E. Ståhl; T. Beno. 2018. "Dynamic effects on cutting forces with highly positive versus highly negative cutting edge geometries." International Journal on Interactive Design and Manufacturing (IJIDeM) 13, no. 2: 557-565.
The ability to minimize vibrations in milling by the selection of cutting edge geometry and appropriate cutting conditions is an important asset in the optimization of the cutting process. This paper presents a measurement method and a signal processing technique to characterize and quantify the magnitude of the vibrations in an end milling application. Developed methods are then used to investigate the effects of various cutting edge geometries on vibrations in end milling. The experiments are carried out with five cutting edge geometries that are frequently used in machining industry for a wide range of milling applications. The results show that a modest protection chamfer combined with a relatively high rake angle has, for the most of cutting conditions, a reducing effect on vibration magnitudes. Furthermore, dynamics of a highly positive versus a highly negative cutting geometry is explored in time domain and its dependency on cutting conditions is presented. The results give concrete indications about the most optimal cutting edge geometry and cutting conditions in terms of dynamic behavior of the tool.
A. Agic; M. Eynian; J.-E. Ståhl; T. Beno. Experimental analysis of cutting edge effects on vibrations in end milling. CIRP Journal of Manufacturing Science and Technology 2018, 24, 66 -74.
AMA StyleA. Agic, M. Eynian, J.-E. Ståhl, T. Beno. Experimental analysis of cutting edge effects on vibrations in end milling. CIRP Journal of Manufacturing Science and Technology. 2018; 24 ():66-74.
Chicago/Turabian StyleA. Agic; M. Eynian; J.-E. Ståhl; T. Beno. 2018. "Experimental analysis of cutting edge effects on vibrations in end milling." CIRP Journal of Manufacturing Science and Technology 24, no. : 66-74.
Chatter vibrations encountered in machining can degrade surface finish and damage the machining hardware. Since chatter originates from unstable interaction of the machining process and the machining structure, information about vibration parameters of the machining structure should be used to predict combinations of cutting parameters that allow stable machining. While modal test methods, for example those with impact hammers, are widely used to identify structural parameters; the need for sophisticated test equipment is prohibitive in their use. Furthermore, dynamic properties of critical components of a machine tool may change as they get affected by cutting loads, material removal and spindle rotation. Recently few algorithms have been proposed that identify the in-process dynamic parameters by frequency measurements, thus avoiding these problems. In this paper, some of these algorithms are reviewed and their capabilities and limitations in processing am experimental data set are compared and discussed.
Mahdi Eynian; Martin Magnevall; Stefan Cedergren; Anders Wretland; Mikael Lundblad. New methods for in-process identification of modal parameters in milling. Procedia CIRP 2018, 77, 469 -472.
AMA StyleMahdi Eynian, Martin Magnevall, Stefan Cedergren, Anders Wretland, Mikael Lundblad. New methods for in-process identification of modal parameters in milling. Procedia CIRP. 2018; 77 ():469-472.
Chicago/Turabian StyleMahdi Eynian; Martin Magnevall; Stefan Cedergren; Anders Wretland; Mikael Lundblad. 2018. "New methods for in-process identification of modal parameters in milling." Procedia CIRP 77, no. : 469-472.
The choice of milling cutter geometry and appropriate cutting data for certain milling application is of vital importance for successful machining results. Unfavorable selection of cutting conditions might give rise to high load impacts that cause severe cutting edge damage. Under some circumstances the radial depth of cut in combination with milling cutter geometry might give unfavorable entry conditions in terms of cutting forces and vibration amplitudes. This phenomenon is originated from the geometrical features that affect the rise time of the cutting edge engagement into workpiece at different radial depths of cut. As the radial depth of cut is often an important parameter, particularly when machining difficult-to-cut materials, it is important to explore the driving mechanism behind vibrations generation. In this study, acceleration of the workpiece is measured for different radial depths of cut and cutting edge geometries. The influence of the radial depth of cut on the dynamical behavior is evaluated in time and frequency domains. The results for different radial depths of cut and cutting geometries are quantified using the root mean square value of acceleration. The outcome of this research study can be used both for the better cutting data recommendations and improved tool design.
A. Agic; Mahdi Eynian; S. Hägglund; J. -E. Ståhl; T. Beno. Influence of radial depth of cut on entry conditions and dynamics in face milling application. Journal of Superhard Materials 2017, 39, 259 -270.
AMA StyleA. Agic, Mahdi Eynian, S. Hägglund, J. -E. Ståhl, T. Beno. Influence of radial depth of cut on entry conditions and dynamics in face milling application. Journal of Superhard Materials. 2017; 39 (4):259-270.
Chicago/Turabian StyleA. Agic; Mahdi Eynian; S. Hägglund; J. -E. Ståhl; T. Beno. 2017. "Influence of radial depth of cut on entry conditions and dynamics in face milling application." Journal of Superhard Materials 39, no. 4: 259-270.
Titanium’s Ti6Al4V, alloy is an important material with a wide range of applications in the aerospace industry. Due to its high strength, machining this material for desired quality at high material removal rate is challenging and may lead to high tool wear rate. As a result, this material may be machined with worn tools and the effects of tool wear on machining quality need to be investigated. In this experimental paper, it is shown how drills of various wear levels affect the cutting forces, surface quality and burr formation. Furthermore, it is shown that high cutting forces and high plastic deformation, along with high temperatures that arise in cutting with worn tools may lead to initiation of microscopic cracks in the workpiece material in proximity of the drilling zone.
Mahdi Eynian; Kallol Das; Anders Wretland. Effect of tool wear on quality in drilling of titanium alloy Ti6Al4V, Part I: Cutting Forces, Burr Formation, Surface Quality and Defects. High Speed Machining 2017, 3, 1 -10.
AMA StyleMahdi Eynian, Kallol Das, Anders Wretland. Effect of tool wear on quality in drilling of titanium alloy Ti6Al4V, Part I: Cutting Forces, Burr Formation, Surface Quality and Defects. High Speed Machining. 2017; 3 (1):1-10.
Chicago/Turabian StyleMahdi Eynian; Kallol Das; Anders Wretland. 2017. "Effect of tool wear on quality in drilling of titanium alloy Ti6Al4V, Part I: Cutting Forces, Burr Formation, Surface Quality and Defects." High Speed Machining 3, no. 1: 1-10.
Drilling of Ti6Al4V with worn tools can introduce superficial and easily measured features such as increase of cutting forces, entry and exit burrs and surface quality issues and defects. Such issues were presented in the part I of this paper. In part II, subsurface quality alterations, such as changes of the microstructure and microhardness variation is considered by preparing metallographic sections and measurement, mapping of the depth of grain deformation, and microhardness in these sections. Drastic changes in the microstructure and microhardness were found in sections drilled with drills with large wear lands, particularly in the dry cutting tests. These measurements emphasize the importance of detection of tool wear and ensuring coolant flow in drilling of holes in titanium components.
Kallol Das; Mahdi Eynian; Anders Wretland. Effect of tool wear on quality in drilling of titanium alloy Ti6Al4V, Part II: Microstructure and Microhardness. High Speed Machining 2017, 3, 11 -22.
AMA StyleKallol Das, Mahdi Eynian, Anders Wretland. Effect of tool wear on quality in drilling of titanium alloy Ti6Al4V, Part II: Microstructure and Microhardness. High Speed Machining. 2017; 3 (1):11-22.
Chicago/Turabian StyleKallol Das; Mahdi Eynian; Anders Wretland. 2017. "Effect of tool wear on quality in drilling of titanium alloy Ti6Al4V, Part II: Microstructure and Microhardness." High Speed Machining 3, no. 1: 11-22.
Amir Parsian; Martin Magnevall; Tomas Beno; Mahdi Eynian. Sound Analysis in Drilling, Frequency and Time Domains. Procedia CIRP 2017, 58, 411 -415.
AMA StyleAmir Parsian, Martin Magnevall, Tomas Beno, Mahdi Eynian. Sound Analysis in Drilling, Frequency and Time Domains. Procedia CIRP. 2017; 58 ():411-415.
Chicago/Turabian StyleAmir Parsian; Martin Magnevall; Tomas Beno; Mahdi Eynian. 2017. "Sound Analysis in Drilling, Frequency and Time Domains." Procedia CIRP 58, no. : 411-415.
Ashwin Devotta; Tomas Beno; Raveendra Siriki; Ronnie Löf; Mahdi Eynian. Finite Element Modeling and Validation of Chip Segmentation in Machining of AISI 1045 Steel. Procedia CIRP 2017, 58, 499 -504.
AMA StyleAshwin Devotta, Tomas Beno, Raveendra Siriki, Ronnie Löf, Mahdi Eynian. Finite Element Modeling and Validation of Chip Segmentation in Machining of AISI 1045 Steel. Procedia CIRP. 2017; 58 ():499-504.
Chicago/Turabian StyleAshwin Devotta; Tomas Beno; Raveendra Siriki; Ronnie Löf; Mahdi Eynian. 2017. "Finite Element Modeling and Validation of Chip Segmentation in Machining of AISI 1045 Steel." Procedia CIRP 58, no. : 499-504.
Amir Parsian; Martin Magnevall; Mahdi Eynian; Tomas Beno. Time domain simulation of chatter vibrations in indexable drills. The International Journal of Advanced Manufacturing Technology 2016, 89, 1209 -1221.
AMA StyleAmir Parsian, Martin Magnevall, Mahdi Eynian, Tomas Beno. Time domain simulation of chatter vibrations in indexable drills. The International Journal of Advanced Manufacturing Technology. 2016; 89 (1-4):1209-1221.
Chicago/Turabian StyleAmir Parsian; Martin Magnevall; Mahdi Eynian; Tomas Beno. 2016. "Time domain simulation of chatter vibrations in indexable drills." The International Journal of Advanced Manufacturing Technology 89, no. 1-4: 1209-1221.
A. Agic; O. Gutnichenko; Mahdi Eynian; J.-E. Stahl. Influence of Cutting Edge Geometry on Force Build-up Process in Intermittent Turning. Procedia CIRP 2016, 46, 364 -367.
AMA StyleA. Agic, O. Gutnichenko, Mahdi Eynian, J.-E. Stahl. Influence of Cutting Edge Geometry on Force Build-up Process in Intermittent Turning. Procedia CIRP. 2016; 46 ():364-367.
Chicago/Turabian StyleA. Agic; O. Gutnichenko; Mahdi Eynian; J.-E. Stahl. 2016. "Influence of Cutting Edge Geometry on Force Build-up Process in Intermittent Turning." Procedia CIRP 46, no. : 364-367.
Study of the vibration frequencies at different cutting conditions is an alternative to the use of impact hammer test for identification of natural frequencies of the machining structure and calculation of stability lobe diagrams. Vibration frequencies not only depend on the natural frequencies of the structure, but also they are dependent on the spindle speed, damping ratio of the structure and the depth of cut. Ignoring these additional parameters would lead to errors in identification of the natural frequencies of the system and considerable deviation of the calculated stability lobe diagrams from actual cutting tests. In this study modified Nyquist method is used to investigate the effects of spindle speed, depth of cut and damping ratio of the structure on vibration frequencies. The quality of frequency prediction is compared to linear and nonlinear time domain simulations and machining experiments.
Mahdi Eynian. Prediction of vibration frequencies in milling using modified Nyquist method. CIRP Journal of Manufacturing Science and Technology 2015, 11, 73 -81.
AMA StyleMahdi Eynian. Prediction of vibration frequencies in milling using modified Nyquist method. CIRP Journal of Manufacturing Science and Technology. 2015; 11 ():73-81.
Chicago/Turabian StyleMahdi Eynian. 2015. "Prediction of vibration frequencies in milling using modified Nyquist method." CIRP Journal of Manufacturing Science and Technology 11, no. : 73-81.
Mahdi Eynian. Vibration frequencies in stable and unstable milling. International Journal of Machine Tools and Manufacture 2015, 90, 44 -49.
AMA StyleMahdi Eynian. Vibration frequencies in stable and unstable milling. International Journal of Machine Tools and Manufacture. 2015; 90 ():44-49.
Chicago/Turabian StyleMahdi Eynian. 2015. "Vibration frequencies in stable and unstable milling." International Journal of Machine Tools and Manufacture 90, no. : 44-49.
Mahdi Eynian. Frequency Domain Study of Vibrations above and under Stability Lobes in Machining Systems. Procedia CIRP 2014, 14, 164 -169.
AMA StyleMahdi Eynian. Frequency Domain Study of Vibrations above and under Stability Lobes in Machining Systems. Procedia CIRP. 2014; 14 ():164-169.
Chicago/Turabian StyleMahdi Eynian. 2014. "Frequency Domain Study of Vibrations above and under Stability Lobes in Machining Systems." Procedia CIRP 14, no. : 164-169.
Holes are made in many industrial parts that need screws, pins or channels for passing fluids. The general method to produce holes in metal cutting is by drilling operations. Indexable insert drills are often used to make short holes at a low cost. However, indexable drills are prone to vibrate under certain circumstances, causing vibrations that affect tool life. Therefore, a good prediction of cutting-forces in drilling is important to get a good description of the cutting process for optimization of tool body and insert design. Reliable simulations of dynamic forces also aid in prediction of chatter vibrations that have significant effects on the quality of the manufactured parts as well as the tool life. In this paper, a mechanistic approach is used to model the cutting-forces. Cutting-force coefficients are identified from measured instantaneous forces in drilling operations. These coefficients are used for simulating torque around drill-axis, axial force and cutting-forces in the plane perpendicular to drill-axis. The forces are modeled separately for peripheral and central insert, which results in a detailed description of the cutting-forces acting on each insert. The forces acting on each insert are estimated by dividing the cutting edges into small segments and the cutting-forces acting on each segment are calculated. The total forces are predicted by summation of the forces acting on each segment. Simulated torque and forces are compared to measured cutting-forces for two different feeds. A good agreement between predicted and experimental results, especially in torque and axial-force, is observed
Amir Parsian; Martin Magnevall; Tomas Beno; Mahdi Eynian. A Mechanistic Approach to Model Cutting Forces in Drilling with Indexable Inserts. Procedia CIRP 2014, 24, 74 -79.
AMA StyleAmir Parsian, Martin Magnevall, Tomas Beno, Mahdi Eynian. A Mechanistic Approach to Model Cutting Forces in Drilling with Indexable Inserts. Procedia CIRP. 2014; 24 ():74-79.
Chicago/Turabian StyleAmir Parsian; Martin Magnevall; Tomas Beno; Mahdi Eynian. 2014. "A Mechanistic Approach to Model Cutting Forces in Drilling with Indexable Inserts." Procedia CIRP 24, no. : 74-79.
During milling of thin-walled components, chatter vibrations give rise to process issues. These include dimensional inaccuracy, damaged and scrap parts, and damaged cutting tools. This, in turn, leads to loss of production time with increasing cost as a consequence. This paper identifies the force profile during a single cut milling process. It focuses on the exit and post-exit behavior of the cut and discusses the process dynamics. The force profiles of various tool-to-workpiece positions are analyzed as regards the exit and post exit phases. A standard on-the-market cutter and a specially designed zero rake cutter are used in the investigation. Finally, a time-domain simulation of the force is performed and compared to the experimental results. The study concludes that a small change in exit angle may result in a considerable improvement in cutting behavior. In addition, the tool position should be chosen so that the cutter exits in the least flexible direction possible for the workpiece.
B. Wanner; Mahdi Eynian; T. Beno; L. Pejryd. Cutter Exit Effects during Milling of Thin-Walled Inconel 718. Advanced Materials Research 2012, 590, 297 -308.
AMA StyleB. Wanner, Mahdi Eynian, T. Beno, L. Pejryd. Cutter Exit Effects during Milling of Thin-Walled Inconel 718. Advanced Materials Research. 2012; 590 ():297-308.
Chicago/Turabian StyleB. Wanner; Mahdi Eynian; T. Beno; L. Pejryd. 2012. "Cutter Exit Effects during Milling of Thin-Walled Inconel 718." Advanced Materials Research 590, no. : 297-308.
Recent developments in the Aerospace industry have led to thin-walled, reduced-weight engine designs. Due to demands in manufacturing, production speeds and material removal rates (MRR) have increased. As component wall thickness gets thinner, the consequence oftentimes is an increase in chatter vibrations. This paper suggests that a correctly chosen tool-to-workpiece offset geometry may lead to a robust and chatter-free process. The results show the differences in force response for three geometries while varying the overhang of the workpiece. This is part of a concerted effort to develop a robust methodology for the prediction of chatter vibrations during milling operations of thin-walled Aerospace components. This paper outlines certain robust machining practices. It also analyzes the criticality of the choice of offset between tool and workpiece during milling setup as well as the effects that the entry and exit of cut have on system vibrations.
B. Wanner; Mahdi Eynian; T. Beno; L. Pejryd. Milling Strategies for Thin-Walled Components. Advanced Materials Research 2012, 498, 177 -182.
AMA StyleB. Wanner, Mahdi Eynian, T. Beno, L. Pejryd. Milling Strategies for Thin-Walled Components. Advanced Materials Research. 2012; 498 ():177-182.
Chicago/Turabian StyleB. Wanner; Mahdi Eynian; T. Beno; L. Pejryd. 2012. "Milling Strategies for Thin-Walled Components." Advanced Materials Research 498, no. : 177-182.
Bertil Wanner; Mahdi Eynian; Tomas Beno; Lars Pejryd. Process stability strategies in milling of thin-walled Inconel 718. THE 4TH MANUFACTURING ENGINEERING SOCIETY INTERNATIONAL CONFERENCE (MESIC 2011) 2012, 1 .
AMA StyleBertil Wanner, Mahdi Eynian, Tomas Beno, Lars Pejryd. Process stability strategies in milling of thin-walled Inconel 718. THE 4TH MANUFACTURING ENGINEERING SOCIETY INTERNATIONAL CONFERENCE (MESIC 2011). 2012; ():1.
Chicago/Turabian StyleBertil Wanner; Mahdi Eynian; Tomas Beno; Lars Pejryd. 2012. "Process stability strategies in milling of thin-walled Inconel 718." THE 4TH MANUFACTURING ENGINEERING SOCIETY INTERNATIONAL CONFERENCE (MESIC 2011) , no. : 1.