Robust Design and Capability Evaluation of a Tribo ... - IEEE Xplore

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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 47, NO. 3, MAY/JUNE 2011

Robust Design and Capability Evaluation of a Tribo-Aerodynamic Charging Process for Fine Particles Lucian Dascalescu, Fellow, IEEE, Mihai Bilici, Student Member, IEEE, Ciprian Dragan, Adrian Samuila, Member, IEEE, Youcef Ramdani, and Amar Tilmatine, Senior Member, IEEE Abstract—Robustness and capability are critical issues for the industrial application of any novel electrostatic process. The aim of this paper is double: show how an experimental design methodology can contribute to assessing the robustness of a given triboaerodynamic charging process and validate a procedure for evaluating the capability of two tribo-aerodynamic chargers with respect to the specific requirements of electrostatic separation applications. The results of three fractional factorial experimental designs performed on starch and flour powders, in two devices similar to the triboguns employed for electrostatic powder coating, demonstrate that the tribo-aerodynamic charging is robust with respect to the three main control variables of the process: the injection and vortex pressures of the air in the pneumatic circuit and the material feed rate. The capability indexes computed for both the straight- and spiral-type tribocharges were satisfactory. Index Terms—Capability, charge measurement, experimental design, robustness, statistic process control, triboelectricity.

I. I NTRODUCTION

T

RIBOCHARGING of particulates is one of the less explored areas of applied electrostatics in spite of numerous industrial applications ranging from powder coating to mineral processing and waste treatment [1]–[3]. In recent years, the tribocharging studies have been associated to the R&D of new Manuscript received October 27, 2010; accepted November 26, 2010. Date of publication March 10, 2011; date of current version May 18, 2011. Paper 2010-EPC-431, presented at the 2010 Industry Applications Society Annual Meeting, Houston, TX, October 3–7, and approved for publication in the IEEE T RANSACTIONS ON I NDUSTRY A PPLICATIONS by the Electrostatic Processes Committee of the IEEE Industry Applications Society. L. Dascalescu, M. Bilici, and C. Dragan are with the Electrostatics of Dispersed Media Research Unit, Electrohydrodynamics Group, PPRIME Institute, UPR 3346, Centre National de la Recherche Scientifique-University of Poitiers-ENSMA, University Institute of Technology at Angoulême, 16021 Angoulême Cedex, France (e-mail: [email protected]; [email protected]; [email protected]; [email protected]). A. Samuila is with the High-Intensity Electric Fields Research Laboratory, Technical University of Cluj-Napoca, 40020 Cluj-Napoca, Romania, and also with the Electrostatics of Dispersed Media Research Unit, Electrohydrodynamics Group, PPRIME Institute, UPR 3346, Centre National de la Recherche Scientifique-University of Poitiers-L’Ecole Nationale Supérieure de Mécanique et d’Aérotechnique, University Institute of Technology at Angoulême, 16021 Angoulême Cedex, France (e-mail: [email protected]). Y. Ramdani is with the University Djillali Liabes of Sidi-Bel-Abbes, 22000 Sidi-Bel-Abbes, Algeria. A. Tilmatine is with the University Djillali Liabes of Sidi-Bel-Abbes, 22000 Sidi-Bel-Abbes, Algeria, and also with the Electrostatics of Dispersed Media Research Unit, Electrohydrodynamics Group, PPRIME Institute, UPR 3346, Centre National de la Recherche Scientifique-University of PoitiersENSMA, University Institute of Technology at Angoulême, 16021 Angoulême Cedex, France (e-mail: [email protected]). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TIA.2011.2126011

electrostatic separation applications, particularly in the recycling industry [4]–[6]. For each application, identification of the optimal operating conditions has been a crucial issue [7]–[11], and the experimental design methodology has proved to be an effective way to address it [12], [13]. Robustness testing is also critical for implementing a new application [14], as it assesses to what extent the performance of the process remains satisfactory even when some influential factors are allowed to vary. The objective is to minimize the system sensibility to small difficult-to-avoid changes in certain control factors [15], [16]. In spite of several recent studies on the experimental modeling of tribocharging processes [17]–[19], no standard procedure is available for identifying the factors that should be better controlled for the process to be claimed robust. Therefore, the first aim of this paper is to show how the robustness of a tribo-aerodynamic charging process can be assessed by using the experimental design methodology. The second objective is to validate a procedure for evaluating the capability of the tribochargers to satisfy the users’ requirements. Indeed, no matter how robust a process is, its outcome may vary because of changes in factors other than those controlled by the operator. Small variations in the size of the particles or changes in the ambient conditions may modify the charge exchanged by triboelectric effect and alter the quality of the final product. Since the pioneer works of Shewhart [20], the statistical process control methodology has been widely used for detecting nonconforming products by monitoring the process through samples. The statistical analysis of the samples prompts the adjustments to be made to the process in order to keep it within the specifications. In this paper, variability in the charge of starch and flour powders at the output of a compressed-air tribocharging device similar to those employed for electrostatic coating is quantified by the so-called “capability index” [21]. A device having a high capability index will constantly respect the charge level imposed by a given application. Control charts [22] may be used to represent the variations in the charge at the outlet of the tribocharging device and make easier the control of the process in order to maintain or improve its capability. II. M ATERIALS AND M ETHOD A. Experimental Setup The experimental setup consists of a custom-designed triboaerodynamic charging device provided with means to control

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DASCALESCU et al.: DESIGN AND CAPABILITY EVALUATION OF TRIBO-AERODYNAMIC CHARGING PROCESS

Fig. 1.

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Schematic representation of the experimental setup for the study of tribo-aerodynamic charging of fine powders.

Fig. 2. Charge ΔQ accumulated in the collecting bag, as displayed on the frontal panel of the VI (the experiment was performed with 1 g of aleurone [24], [25], with the interval of time between two measurements being Δt = 2 s).

the charge by adjusting the air pressure in different circuits (Fig. 1), a solid aerosol generator (model SAG 410, TOPAS GmbH, Dresden, Germany), a modified Faraday cage connected to a digital electrometer (model 6514, Keithley Instruments), and a personal computer for data acquisition and processing. The charging device is similar to those employed for electrostatic coating [23], but the Teflon tribogun was replaced by straight or spiral copper pipes that are 1.5 m in length. The injection pressure pinj determines the particle speed through the tribocharger and the energy of particle–wall impacts, while the vortex pressure pvor controls the turbulence of the motion. The powder concentration in the transport air is controlled by adjusting the feed rate M of the solid aerosol generator. Based on the results of a composite experimental design conducted as indicated in [13] for wheat bran tissues [24], [25], the optimum operation point for this paper was set at pinj = 3.5 bar, pvor = 0.5 bar, and M/Mmax = 0.8. In order to simulate small variations of the factors around this point, the limits of the experimental domain for robustness assessment were established as follows: 3.4 bar ≤ pinj ≤ 3.6 bar, 0.4 bar ≤ pvor ≤ 0.6 bar, and 0.75 ≤ M/Mmax ≤ 0.85. The relative humidity of ambient air was RH = 48.5% ± 4.5% at a temperature of 20.5 ◦ C ± 1.5 ◦ C.

The charge measurement data were acquired during up to 180 s of steady-state operation of the tribocharging device. The virtual instrument (VI) developed in LabView environment [26], [27] controlled the grounding of the electrometer input at regular intervals of time Δt. In this way, it displayed the charge ΔQ (in nanocoulombs) accumulated every time interval Δt (in seconds) in the modified Faraday pail, as shown in Fig. 2. In a distinct experiment, for each material (starch or flour, with more than 90% of the particles having a diameter of less than 50 μm), the mass M of particles in the collected bag was measured after 3 min of continuous operation for three values of the potentiometer of the aerosol generator: M/Mmax = 0.75, 0.80, and 0.85. Thus, it was possible to calculate the average feed rate m (in grams per second) for each test as well as the charge/mass ratio Q/M [nC/g] = ΔQ/(mΔt).

(1)

B. Robustness Assessment Robustness testing is usually the last experiment to be carried out before the industrial release of a new process [28]. Its aim is to ascertain that the response is not sensitive to small changes

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in the factors around the set point. In case nonrobustness is detected, the experiment should indicate how to regulate the factors (alter their bonds) for the outcome to remain within given specifications. As each factor is explored within a narrow range, a linear model is likely to be the most appropriate choice for robustness testing [29]. Such a model would provide an adequate answer to the question which factors should be better controlled so that process robustness may be claimed. Fractional factorial designs are recommended for robustness testing, as they fit linear models [30]. With such models, the response y of the process is expressed as a function of e factors ui (i = 1, . . . , e) y = f (ui ) = c0 + ci ui . (2)

TABLE I L OWER LSL AND U PPER U SL S PECIFICATION L IMITS OF THE T RIBOCHARGING P ROCESS FOR VARIOUS M ATERIALS AND C HARGERS

TABLE II C HARGE /M ASS R ATIOS C ALCULATED F ROM THE R ESULTS OF T HREE F RACTIONAL FACTORIAL E XPERIMENTAL D ESIGNS (I, II, AND III)

A normalized centered value can be defined for each factor ui xi = (ui − uic )/Δui = u∗i

(3)

where uic = (ui max + ui min )/2

Δui = (ui max − ui min )/2. (4)

With these notations, the response function becomes ai xi y = f (xi ) = a0 +

(5)

(6)

C. Capability Evaluation Process capability studies distinguish between conformance to control limits (U CL = upper control limit and LCL = lower control limit) and conformance to specification limits (U SL = upper specification limit and LSL = lower specification limit). Specifically, control limits characterize the inherent variability in a process, whereas specification limits define acceptable product characteristics. The difference between the upper and lower specification limits defines the interval of tolerance (IT ). The inherent variability of a process, as defined by the control limits, must be well within this interval of tolerance. The capability index Cm is defined as [21], [31] Cm = IT /(6σ) = (U SL − LSL)/(6σ)

1 Xi n i=1 n

Xm =

where xi takes the value −1 for the minimum input value ui min and +1 for the maximum input value ui max . For the three factors considered in this paper, i.e., x1 = p∗inj , x2 = p∗vor , and x3 = m∗ , the model is y = a0 + a1 p∗inj + a2 p∗vor + a3 m∗ .

where

(7)

where σ is the standard deviation of the process characteristic being monitored. In most cases, σ is replaced in the aforementioned formula by an estimation given by the following formula: n (Xi − Xm )2 (8) s = i=1 n−1

(9)

is the mean of n measured values Xi , i = 1, . . . , n. The capability index shows how well a machine is able to meet specifications. The higher the value of the index, the more capable the machine: Cm < 1 (unsatisfactory), 1 < Cm < 1.33 (low capability), 1.33 < Cm < 1.66 (medium capability), and Cm > 1.66 (high capability). This index considers only the spread of the characteristic in relation to specification limits, assumed to be two-sided. The performance index Cmk takes into account the position of Xm with respect to the two specification limits [21] U SL − m m − LSL Cmk = min , . (10) 3s 3s These two indexes should be jointly employed in order to accurately assess the capability of a process. A higher capability index can be achieved by reducing the variation in the process. The effect of shifting the mean of the process toward the target is an increase of the performance index. In this paper, the interval of tolerance was chosen as 50% of the maximum charge that could be expected to be obtained with a given device for a certain material (Table I). III. R ESULTS AND D ISCUSSION A. Robustness Assessment The results of three series of experiments are given in Table II. The flour-charging experiments were performed at higher feed rates but at similar injection and vortex pressures. The flow is more turbulent in spiral pipes, which may explain the better charging of starch in case II, when compared to case I (more particle-to-wall collisions). Flour seems to charge


TABLE III E VALUATION OF THE E FFECTS U SING S TUDENT ’ S T EST FOR THE T HREE F RACTIONAL FACTORIAL E XPERIMENTAL D ESIGNS (I, II, AND III)

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The same indexes, calculated for a second series of measurements carried out under rigorously similar conditions, were Cm = IT /(6σ) = 25/(6 × 1.82) = 2.3

(14)

Cmk = (Qav − LSL)/(3σ) = (33.4 − 25)/(3 × 1.82) = 1.55

(15)

which are also higher than 1.33 (i.e., the process has a medium capability). In order to take into account the uncertainty related to the limited number N of measurements employed for the computation of the standard deviation, these values should be divided by the so-called “confidence coefficient” kc . For N = 50, this coefficient is kc = 1.2, and the recalculated values of Cm and Cmk for the two series of measurements are more than starch, but the higher levels of Q/m in case III as compared to case II may be also related to the modification of the turbulent flow due to the increase of m. When compared to the experimental error (i.e., the standard deviation of the three measurements carried out in the central point of the experimental design), the effects of the three factors, calculated with MODDE 5.0 software [32] and listed in Table III, are nonsignificant according to the Student’s test neither for the starch nor for the flour in spiral copper tribochargers, which means that the process is robust. For starch in straight copper pipes (case I in Tables II and III), the feed rate m is the only statistically significant effect. The charge/mass ratio Q/m decreased with the increase of m Q/m [nC/g] = 873.25 + 24.25p∗inj + 27.25p∗vor − 61.75m∗ . (11) The increase of the feed rate m diminishes the probability of particle–wall collisions in the straight pipe. This phenomenon occurs in the spiral pipe too, but its effect is weaker. However, in most actual situations, the variation of the feed rate m around the set point is likely to be much smaller than the simulated one. Therefore, the tribo-aerodynamic charging could be considered as robust with respect to this factor too. B. Capability Evaluation Based on the results of the first series of 50 measurements recorded for starch in a straight pipe (Table IV; p∗inj = 3.5 bar; p∗vor = 0.5 bar; m∗ = 17.5 mg/s), the capability index of the tribocharging is Cm = IT /(6σ) = 25/(6 × 1.02) = 4.08.

(12)

With the average charge Qav = 33.5 nC being closer to the lower specification limit (LSL), it is recommended to calculate also the performance index Cmk = (Qav − LSL)/(3σ) = (33.3 − 25)/(3 × 1.02) = 2.71. (13) Both Cm and Cmk are excellent.

Cm(1) = 3.4 Cmk(1) = 2.26 Cm(2) = 1.91 Cmk(2) = 1.27 (16) respectively, which are still satisfactory. For the starch in the spiral pipe (Table V), Cm and Cmk calculated with (7) and (10) are Cm = 30/(6 × 3.47) = 1.44 Cmk = (60 − 45.1)/(3 × 3.47) = 1.42.

(17) (18)

Divided by 1.2, these indexes become less than 1.33, which means that the capability is quite low. The flow in the spiral pipe is more turbulent, which leads to larger amounts of charge, but the variability also increases. The capability indexes of flour in the spiral pipe (Table VI) are slightly better Cm = 100/(6 × 5.51) = 3.02 Cmk = (200 − 161)/(3 × 5.51) = 2.35.

(19) (20)

There are two reasons for this: the larger flow rates and the longer intervals between the measurements are likely to reduce the fluctuations in the recorded charge values. Considering a smaller number N of measurements is not a good option for the evaluation of the capability of this process. Based on the first ten values of charge measurements in Table V, the index Cm computed with (7) would be Cm = 30/(6 × 1.082) = 4.62

(21)

which is an excellent figure even after division with the confidence coefficient kc = 1.65, corresponding to N = 10. With the values in positions 21–30 of the same series of measurements Cm = 30/(6 × 4.54) = 1.09

(22)

a result according to which the process is not capable, as 1.09/1.65 < 1. This example clearly shows that, when relying on a smaller number N of measurements, the calculation of the capability indexes Cm and Cmk may lead to erroneous conclusions, even when correcting them by using the “confidence coefficient” kc .

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TABLE IV T WO S ERIES OF 50 M EASUREMENTS FOR E VALUATING T RIBOCHARGING C APABILITY OF S TARCH IN A S TRAIGHT C OPPER P IPE (m = 17.5 mg/s; Δt = 2 s)

TABLE V S ERIES OF 50 M EASUREMENTS FOR E VALUATING T RIBOCHARGING C APABILITY OF S TARCH IN A S PIRAL C OPPER P IPE (m = 17.5 mg/s; Δt = 2 s)

TABLE VI S ERIES OF 50 M EASUREMENTS FOR E VALUATING T RIBOCHARGING C APABILITY OF F LOUR IN A S PIRAL C OPPER P IPE (m = 30 mg/s; Δt = 3 s)

With virtual instrumentation available for performing the measurements, there is no reason to reduce N . However, in the situations when the measurements are done manually, the reduction of the number of measurements and the increase of the time interval Δt are inevitable. IV. C ONCLUSION In this paper, the following conclusions have been drawn. 1) Virtual instrumentation facilitates data acquisition and processing related to both robustness and capability studies of tribocharging processes. 2) Experimental design methodology has proven its effectiveness in assessing the robustness of the triboaerodynamic charging process described in this paper. Small difficult-to-avoid changes in the pressure of the

injection or vortex air do not alter the efficiency of the tribocharging. 3) The capability indexes of the tribo-aerodynamic charging process are satisfactory with respect to the specific requirements of triboelectrostatic separators. 4) The charge measured in the spiral pipe is systematically higher than that in the straight pipe of the same length and diameter. This points out the importance of a propitious design of the tribocharger to favor the particle–wall collisions. 5) The two products tested in this paper charge positively in copper pipes. The feasibility of the electrostatic separation of a starch–flour mixture will depend on the outcome of particle–particle collisions. In case the particles will acquire larger amounts of charge in such collisions than in their impacts with the walls, the spiral-type tribocharger


could be effectively used for the electrostatic separation of such pulverulent mixtures.

ACKNOWLEDGMENT The authors would like to thank A. Archambaud, J. Dumonteil, G. Petit, and B. Pradeau for the contributions in part of the experimental work reported in this paper. R EFERENCES [1] G. Touchard, M. Benmadda, P. Humeau, and J. Borzeix, “Static electrification by dusty gas flowing through polyethylene pipes,” Int. Phys. Conf. Ser., vol. 85, pp. 97–102, 1987. [2] A. G. Bailey, “Charging of solids and powders,” J. Electrostat., vol. 30, pp. 167–179, May 1993. [3] J. R. Mountain, M. K. Mazumder, R. A. Sims, D. L. Wankum, T. Chasser, and P. H. Pettit, Jr., “Triboelectric charging of polymer powders in fluidization and transport processes,” IEEE Trans. Ind. Appl., vol. 37, no. 3, pp. 778–784, May/Jun. 2001. [4] J. H. Hughes, Electrostatic Particle Charging—Industrial and Health Care Applications. New York: Wiley, 1997. [5] B. A. Kwetkus, “Particle triboelectrification and its use in the electrostatic separation process,” Part. Sci. Technol., vol. 16, no. 1, pp. 55–68, 1998. [6] I. I. Inculet, G. S. P. Castle, and J. D. Brown, “Electrostatic separation of plastics for recycling,” Part. Sci. Technol., vol. 16, no. 1, pp. 91–100, 1998. [7] I. Geisler, H. J. Knauer, and I. Stahl, “Electrostatic separator for classifying triboelectrically charged substance mixtures,” U.S. Patent 6 011 229, Jan. 4, 2000. [8] G. Dodbiba, A. Shibayama, T. Miyazaki, and T. Fujita, “Electrostatic separation of the shredded plastic mixtures using a tribo-cyclone,” Magn. Elect. Separation, vol. 11, no. 1, pp. 63–92, Feb. 2002. [9] J. M. Stencel, J. L. Schaefer, J. K. Neathery, H. Ban, and D. Finseth, “Electrostatic particle separation system, apparatus, and related method,” U.S. Patent 6 498 313, Dec. 24, 2002. [10] J. Wei and M. J. Realff, “Design and optimization of free-fall electrostatic separators for plastic recycling,” AIChE J., vol. 49, no. 12, pp. 3138–3149, Dec. 2003. [11] J. Wei and M. J. Realff, “Design and optimization of drum-type electrostatic separators for plastics recycling,” Ind. Eng. Chem. Res., vol. 44, no. 10, pp. 3503–3509, May 2005. [12] L. Calin, L. Caliap, V. Neamtu, R. Morar, A. Iuga, A. Samuila, and L. Dascalescu, “Tribocharging of granular plastic mixtures in view of electrostatic separation,” IEEE Trans. Ind. Appl., vol. 44, no. 4, pp. 1045– 1051, Jul./Aug. 2008. [13] S. Das, K. Medles, A. Mihalcioiu, R. Beleca, C. Dragan, and L. Dascalescu, “Factors that influence the tribocharging of pulverulent materials in compressed-air devices,” J. Phys., Conf. Ser., vol. 142, no. 1, p. 012077, 2009. [14] L. Dascalescu, A. Samuila, A. Mihalcioiu, S. Bente, and A. Tilmatine, “Robust control of electrostatic separation processes,” IEEE Trans Ind. Appl., vol. 41, no. 3, pp. 715–720, May/Jun. 2005. [15] R. K. Roy, Design of the Experiments Using Taguchi Approach. 16 Steps to Product and Process Improvement. New York: Wiley, 2001. [16] D. C. Montgomery, Design and Analysis of Experiments, 6th ed. New York: Wiley, 2004. [17] L. Dascalescu, K. Medles, S. Das, M. Younes, L. Caliap, and A. Mihalcioiu, “Using design of experiments and virtual instrumentation to evaluate the tribocharging of pulverulent materials in compressed-air devices,” IEEE Trans. Ind. Appl., vol. 44, no. 1, pp. 3–8, Jan./Feb. 2008. [18] C. Dragan, A. Samuila, D. Iancu, M. Bilici, and L. Dascalescu, “Factors that influence the tribo-charging of insulating ducts in suction-type dilute-phase pneumatic transport systems,” J. Electrostat., vol. 67, no. 2/3, pp. 184–188, May 2009. [19] C. Dragan, M. Bilici, S. Das, and L. Dascalescu, “Triboelectrostatic phenomena in suction-type dilute-phase pneumatic transport system,” IEEE Trans. Dielectr. Elect. Insul., vol. 16, no. 3, pp. 661–667, Jun. 2009. [20] D. C. Montgomery, Introduction to Statistical Quality Control. New York: Wiley, 1996. [21] N. L. Johnson and S. Kotz, Process Capability Indices. London, U.K.: Chapman & Hall, 1993.

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[22] Y. Wu and W. H. Moore, Quality Engineering Product and Process Optimization. Dearborn, MI: Amer. Supplier Inst., 1986. [23] Tribojet JR 106, Sames Technologies, Meylan, France, 2004. [24] Y. Hemery, X. Rouau, C. Dragan, M. Bilici, R. Beleca, and L. Dascalescu, “Electrostatic properties of wheat bran and its constitutive layers: Influence of particle size, composition, and moisture content,” J. Food Eng., vol. 93, no. 1, pp. 114–124, Jul. 2009. [25] L. Dascalescu, C. Dragan, M. Bilici, R. Beleca, Y. Hemery, and X. Rouau, “Electrostatic bases for separation of wheat bran tissues,” IEEE Trans. Ind. Appl., vol. 46, no. 2, pp. 659–665, Mar./Apr. 2010. [26] LabView. Measurements Manual, National Instruments, Austin, TX, 2000. [27] A. Mihalcioiu, L. Dascalescu, S. Das, K. Medles, and R. Munteanu, “Virtual instrument for statistic control of powder tribo-charging processes,” J. Electrostat., vol. 63, no. 6–10, pp. 565–570, Jun. 2005. [28] K. Medles, A. Tilmatine, M. Younes, S. Flazi, and L. Dascalescu, “Set point identification and robustness testing of electrostatic separation processes,” IEEE Trans. Ind. Appl., vol. 43, no. 3, pp. 618–626, May/Jun. 2007. [29] N. L. Frigon and D. Mathews, Practical Guide to Experimental Design. New York: Wiley, 1996. [30] L. Eriksson, E. Johansson, N. Kettaneh-Wold, C. Wikstöm, and S. Wold, Design of Experiments. Principles and Applications. Umeaa, Sweden: Umetrics, 2000. [31] K. Medles, K. Senouci, A. Tilmatine, A. Bendaoud, A. Mihalcioiu, and L. Dascalescu, “Capability evaluation and statistic control of electrostatic separation processes,” IEEE Trans. Ind. Appl., vol. 45, no. 3, pp. 1086– 1094, May/Jun. 2009. [32] User Guide to MODDE, Umetrics, Umea, Sweden, 2005.

Lucian Dascalescu (M’93–SM’95–F’09) received the Dipl. Eng. degree (with first-class honors) from the Faculty of Electrical Engineering, Technical University of Cluj-Napoca, Cluj-Napoca, Romania, in 1978, the Dr. Eng. degree in electrotechnical materials from the “Politehnica” University of Bucharest, Bucharest, Romania, and the Dr. Sci. degree and the “Habilitation à Diriger de Recherches” diploma in physics from the University “Joseph Fourier,” Grenoble, France. His professional carrier began at CUG (Heavy Equipment Works), Cluj-Napoca. In 1983, he moved to the Technical University of Cluj-Napoca as an Assistant Professor, later becoming an Associate Professor of electrical engineering. From October 1991 to June 1992, he received a research fellowship at the Laboratory of Electrostatics and Dielectric Materials, Grenoble, where he returned in January 1994, after one year as an Invited Research Associate and Lecturer at Toyohashi University of Technology, Toyohashi, Japan, and three months as a Visiting Scientist at the University of Poitiers, Poitiers, France. For four years, he taught a course on electromechanical conversion of energy at the University Institute of Technology, Grenoble. In September 1997, he was appointed Professor of electrical engineering and automated systems and Head of the Electronics and Electrostatics Research Unit, University Institute of Technology, Angoulême. Since 1999, he has been the Head of the Department of Management and Engineering of Manufacturing Systems. He is currently the Head of the Electrostatics of Dispersed Media Research Unit, which is part of the EHD Group, PPRIME Institute, CNRS—University of Poitiers—ENSMA, IUT, Angoulême, France. He has been invited to lecture on the electrostatics of granular materials at various universities and international conferences in China (1988), Poland (1990), USA (1990, 1997, 1999, and 2008), Japan (1993 and 2009), France (1993 and 2008), Great Britain (1998), Romania (1999, 2004, and 2006), Canada (2001), Belgium (2002), and Algeria (2005, 2006, and 2009). He is the author or coauthor of more than 130 papers and is the author of several textbooks in the field of electrical engineering and ionized gases. He is the holder of 15 patents. Prof. Dascalescu is a Fellow of IEEE Industry Applications Society (IAS) and a member of the Electrostatics Society of America, the Electrostatics Society of Romania, Société des Electriciens et Electroniciens (SEE), and Club Electrotechnique, Electronique, Automatique (EEA) France. He is also the Vice Chair of the IEEE France Section, and the Past Chair and Technical Program Chair of the Electrostatic Processes Committee of the IAS.

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Mihai Bilici (S’08) received the Dipl. Eng. degree in electrical engineering from the Technical University of Cluj-Napoca, Cluj-Napoca, Romania, in 2008, and the M.S. degree in industrial systems and electrical engineering from the University of Poitiers, Poitiers, France, in 2009, with a research scholarship financed by the Poitou-Charentes Regional Council, France. During his engineering studies, he spent three months at the University Institute of Technology, Angoulême, France, with an Erasmus Student Mobility scholarship financed by the European Union. He is currently preparing a Ph.D. thesis which is jointly sponsored by the Technical University of Cluj-Napoca and the University of Poitiers. His research work is focused on the development of novel electrostatic separation technologies for fine granular mixtures.

Youcef Ramdani was born in Sidi-Bel-Abbes, Algeria, in 1952. He received the Dipl.Eng. degree in electrical engineering from the University of Science and Technology, Oran, Algeria, in 1972, and the Ph.D. degree from the University of Bordeaux, Bordeaux, France, in 1989. He is currently a Professor of electrical engineering at the Institute of Electrical Engineering, University Djillali Liabes of Sidi-Bel-Abbes, SidiBel-Abbes, Algeria, where he teaches electric field theory and electronics. Since July 2000, he has been the Director of the Interaction Réseaux Electrique Convertisseurs Machines Laboratory, University Djilali Liabes of Sidi-Bel-Abbes, where he was also the Head of the Department of Electrical Engineering. His current research interests include electrostatics and high-frequency electronics.

Ciprian Dragan received the Dipl.-Ing. degree from the Technical University of Cluj-Napoca, ClujNapoca, Romania, in 2006, the M.S. degree from the Université de Poitiers, Poitiers, France, in 2007, with a dissertation on the triboelectrostatic phenomena in pneumatic transport systems, and the Ph.D. degree from the Université de Poitiers, Poitiers, France. He defended his Ph.D. thesis on October 21, 2010. He is currently with the University Institute of Technology, Angoulême. His technical fields of interest include experimental and numerical modeling of tribocharging of granular and pulverulent materials, electrostatic measurements, and virtual instrumentation.

Amar Tilmatine (M’08–SM’09) received the Dipl.-Eng. degree in electrical engineering and the Magister (Dr. Eng.) degree from the University of Science and Technology, Oran, Algeria, in 1988 and 1991, respectively, and the Dr. Sci. degree from the University University Djilali Liabes of Sidi-Bel-Abbes, Sidi-Bel-Abbes, Algeria, in 2005. Since 1991, he has been teaching electric field theory and high-voltage techniques in the Department of Electrical Engineering, University Djillali Liabes of Sidi-Bel-Abbes, where he is currently a Professor and the Head of the Electrostatics and High-Voltage Engineering Research Unit of the Interaction Réseaux Electrique Convertisseurs Machines Laboratory. From November 2002 to November 2005, he was the Chairman of the Scientific Committee with the Department of Electrical Engineering, University Djillali Liabes of Sidi-Bel-Abbes. Since 2001, he has been an Invited Scientist with the Applied Electrostatics Research Unit, University Institute of Technology, Angoulême, France, where he works on a joint research project on new electrostatic separation technologies and has visited at least once a year. His other research interests include high-voltage insulation and gas discharges.

Adrian Samuila (M’08) received the M.S. degree in electrical engineering and the Dr.Eng. degree in electrical technologies from the Technical University of Cluj-Napoca, Cluj-Napoca, Romania, in 1980 and 1997, respectively, and the Dr.Sci. degree in physics from the University of Grenoble, Grenoble, France, in 1997. He was a Research and Development Engineer in industry for ten years. He is currently with the Technical University of Cluj-Napoca, where he was a Lecturer and an Associate Professor and, since 2005, has been a Professor in the Electrical Engineering Department. In 1994, 1996, and 1997, he received research scholarships from the Laboratory of Electrostatics and Dielectric Materials, Grenoble, France, where he studied the action of high-intensity electric fields on granular materials. He is the coauthor of more than 70 papers in the field of electrostatic separation of granular mixtures, showing a special interest for the study of particle charging phenomena: corona discharge, triboelectrostatic effects, and electrostatic induction. Since 2002, he has been a Visiting Associate Professor at the University Institute of Technology, Angoulême, France. Dr. Samuila was the Secretary of the First Annual Meeting of the Electrostatics Society of Romania, organized in 1995 by the High Intensity Electric Fields Laboratory, Technical University of Cluj-Napoca, Romania.