N° 28 – July 2011 Italian Journal of Pure and Applied Mathematics ISSN 2239-0227 EDITOR-IN-CHIEF Piergiulio Corsini Editorial Board Saeid Abbasbandy Antonino Giambruno Ivo Rosenberg Reza Ameri Furio Honsell Paolo Salmon Luisa Arlotti James Jantosciak Maria Scafati Tallini Krassimir Atanassov Tomas Kepka Kar Ping Shum Malvina Baica David Kinderlehrer Alessandro Silva Federico Bartolozzi Andrzej Lasota Sergio Spagnolo Rajabali Borzooei Violeta Leoreanu Hari M. Srivastava Carlo Cecchini Mario Marchi Marzio Strassoldo Gui-Yun Chen Donatella Marini Yves Sureau Domenico Nico Chillemi Angelo Marzollo Carlo Tasso Stephen Comer Antonio Maturo Ioan Tofan Irina Cristea Jean Mittas Aldo Ventre Mohammad Reza Darafsheh M. Reza Moghadam Thomas Vougiouklis Bal Kishan Dass Petr Nemec Hans Weber Bijan Davvaz Vasile Oproiu Yunqiang Yin Alberto Felice De Toni Livio C. Piccinini Mohammad Mehdi Zahedi Franco Eugeni Goffredo Pieroni Fabio Zanolin Giovanni Falcone Flavio Pressacco Paolo Zellini Yuming Feng Vito Roberto Jianming Zhan F O R U M EDITOR-IN-CHIEF Franco Eugeni Vito Roberto Dipartimento di Metodi Quantitativi per l'Economia del Territorio Dipartimento di Matematica e Informatica Piergiulio Corsini Università di Teramo, Italy Via delle Scienze 206 - 33100 Udine, Italy [email protected] [email protected] Department of Civil Engineering and Architecture Via delle Scienze 206 - 33100 Udine, Italy Giovanni Falcone Ivo Rosenberg [email protected] Dipartimento di Metodi e Modelli Matematici Departement de Mathematique et de Statistique viale delle Scienze Ed. 8 Université de Montreal 90128 Palermo, Italy C.P. 6128 Succursale Centre-Ville VICE-CHIEF [email protected] Montreal, Quebec H3C 3J7 - Canada [email protected] Yuming Feng Violeta Leoreanu College of Math. and Comp. Science, Chongqing Three-Gorges University, Paolo Salmon Wanzhou, Chongqing, 404000, P.R.China Dipartimento di Matematica [email protected] Università di Bologna MANAGING BOARD Piazza di Porta S. Donato 5 Antonino Giambruno 40126 Bologna, Italy Dipartimento di Matematica e Applicazioni [email protected] Domenico Chillemi, CHIEF via Archirafi 34 - 90123 Palermo, Italy Piergiulio Corsini [email protected] Maria Scafati Tallini Irina Cristea Dipartimento di Matematica Furio Honsell "Guido Castelnuovo" Furio Honsell Dipartimento di Matematica e Informatica Università La Sapienza Violeta Leoreanu Via delle Scienze 206 - 33100 Udine, Italy Piazzale Aldo Moro 2 - 00185 Roma, Italy Elena Mocanu [email protected] [email protected] Livio Piccinini James Jantosciak Kar Ping Shum Flavio Pressacco Department of Mathematics Faculty of Science Brooklyn College (CUNY) The Chinese University of Hong Kong Norma Zamparo Brooklyn, New York 11210, USA Hong Kong, China (SAR) [email protected] [email protected] EDITORIAL BOARD Tomas Kepka Alessandro Silva MFF-UK Dipartimento di Matematica Saeid Abbasbandy Sokolovská 83 "Guido Castelnuovo" Dept. of Mathematics, Imam Khomeini International University, 18600 Praha 8,Czech Republic Università La Sapienza Ghazvin, 34149-16818, Iran [email protected] Piazzale Aldo Moro 2 - 00185 Roma, Italy [email protected] [email protected] David Kinderlehrer Reza Ameri Department of Mathematical Sciences Sergio Spagnolo Department of Mathematics Carnegie Mellon University Scuola Normale Superiore University of Tehran Pittsburgh, PA15213-3890, USA Piazza dei Cavalieri 7 - 56100 Pisa, Italy Tehran, Iran [email protected] [email protected] [email protected] Andrzej Lasota Hari M. Srivastava Luisa Arlotti Silesian University Department of Mathematics and Statistics Department of Civil Engineering and Architecture Institute of Mathematics University of Victoria Via delle Scienze 206 - 33100 Udine, Italy Bankova 14 Victoria, British Columbia [email protected] 40-007 Katowice, Poland V8W3P4, Canada [email protected] [email protected] Krassimir Atanassov Centre of Biomedical Engineering, Bulgarian Academy of Science Violeta Leoreanu Marzio Strassoldo BL 105 Acad. G. Bontchev Str. Faculty of Mathematics Department of Statistical Sciences 1113 Sofia, Bulgaria Al. I. Cuza University Via delle Scienze 206 - 33100 Udine, Italy [email protected] 6600 Iasi, Romania [email protected] [email protected] Malvina Baica Yves Sureau University of Wisconsin-Whitewater Mario Marchi 27, rue d'Aubiere Dept. of Mathematical and Computer Sciences Università Cattolica del Sacro Cuore 63170 Perignat, Les Sarlieve - France Whitewater, W.I. 53190, U.S.A. via Trieste 17, 25121 Brescia, Italy [email protected] [email protected] [email protected] Carlo Tasso Federico Bartolozzi Donatella Marini Dipartimento di Matematica e Informatica Dipartimento di Matematica e Applicazioni Dipartimento di Matematica Via delle Scienze 206 - 33100 Udine, Italy via Archirafi 34 - 90123 Palermo, Italy Via Ferrata 1- 27100 Pavia, Italy [email protected] [email protected] [email protected] Ioan Tofan Rajabali Borzooei Angelo Marzollo Faculty of Mathematics Department of Mathematics Dipartimento di Matematica e Informatica Al. I. Cuza University Shahid Beheshti University Via delle Scienze 206 - 33100 Udine, Italy 6600 Iasi, Romania Tehran, Iran [email protected] [email protected] [email protected] Antonio Maturo Aldo Ventre Carlo Cecchini University of Chieti-Pescara, Department of Social Sciences, Seconda Università di Napoli, Fac. Architettura, Dip. Cultura del Progetto Dipartimento di Matematica e Informatica Via dei Vestini, 31 Via San Lorenzo s/n Via delle Scienze 206 - 33100 Udine, Italy 66013 Chieti, Italy 81031 Aversa (NA), Italy [email protected] [email protected] [email protected] Gui-Yun Chen Thomas Vougiouklis School of Mathematics and Statistics, Jean Mittas Democritus University of Thrace, Southwest University, 400715, Chongqing, China École Polytéchnique de l'Univ. Aristote de Thessaloniki School of Education, [email protected] Departement des Sciences 681 00 Alexandroupolis. Greece Physiques et Mathematiques [email protected] Domenico (Nico) Chillemi 54622 Thessaloniki, Greece Executive IT Specialist, IBM Software Group Hans Weber IBM Italy SpA Dipartimento di Matematica e Informatica Via Sciangai 53 – 00144 Roma, Italy M. Reza Moghadam Via delle Scienze 206 - 33100 Udine, Italy [email protected] Faculty of Mathematical Science [email protected] Ferdowsi University of Mashhadh Stephen Comer P.O.Box 1159 - 91775 Mashhad, Iran Yunqiang Yin Department of Mathematics and Computer Science [email protected] School of Mathematics and Information Sciences, The Citadel, Charleston S. C. 29409, USA East China Institute of Technology, Fuzhou, Jiangxi [email protected] Petr Nemec 344000, P.R. China Czech University of Life Sciences, Kamycka’ 129 [email protected] Irina Cristea 16521 Praha 6, Czech Republic Department of Civil Engineering and Architecture [email protected] Mohammad Mehdi Zahedi Via delle Scienze 206 - 33100 Udine, Italy Department of Mathematics, Faculty of Science [email protected] Vasile Oproiu Shahid Bahonar, University of Kerman Faculty of Mathematics Kerman, Iran Mohammad Reza Darafsheh Al. I. Cuza University [email protected] School of Mathematics, College of Science 6600 Iasi, Romania University of Tehran [email protected] Fabio Zanolin Tehran – Iran Dipartimento di Matematica e Informatica [email protected] Livio C. Piccinini Via delle Scienze 206 - 33100 Udine, Italy Department of Civil Engineering and Architecture [email protected] Bal Kishan Dass Via delle Scienze 206 - 33100 Udine, Italy Department of Mathematics [email protected] Paolo Zellini University of Delhi, Delhi - 110007, India Dipartimento di Matematica [email protected] Goffredo Pieroni Università degli Studi Dipartimento di Matematica e Informatica Tor Vergata, via Orazio Raimondo Bijan Davvaz Via delle Scienze 206 - 33100 Udine, Italy (loc. La Romanina) - 00173 Roma, Italy Department of Mathematics, [email protected] [email protected] Yazd University, Yazd, Iran [email protected] Flavio Pressacco Jianming Zhan Dept. of Economy and Statistics Department of Mathematics, Hubei Institute for Nationalities Alberto Felice De Toni Via Tomadini 30 Enshi, Hubei Province,445000, China Faculty of Engineering 33100, Udine, Italy [email protected] Udine University [email protected] Via delle Scienze 206 - 33100 Udine, Italy [email protected] ITALIAN JOURNAL OF PURE AND APPLIED MATHEMATICS – N. 28-2011 i Professor Emeritus Ioannis Mittas In memoriam In April 2012, Professor Emeritus Ioannis Mittas passed away. He was born in 1921 in Veria, Greece and he received his B.S. in Mathematics from Aristotle University of Thessaloniki and Ph.D in Mathematics from the National Technical University of Athens in 1970. In 1973, he was elected Professor, Chair of Advanced Mathematics, Faculty of Engineering Aristotle University of Thessaloniki, where he served till his retirement in 1985, occupying important posts including that of the Dean of the Faculty; straight after his retirement he was awarded the title of Professor Emeritus. He was a member of a numerous societies and member of the editorial committee of several journals. He was awarded The National Resistance 1941-1944 Medal for his participation in the resistance during the German Occupation of Greece. Professors Mittas's contribution to hyperstructure theory was pioneering as he published numerous papers in several journals and proceedings among which his most famous paper Hypergroupes canoniques, Math.