[1] Univ Teknol Malaysia, Malaysia Japan Int Inst Technol, Takasago Thermal Environm Syst Lab, Kuala Lumpur 54100, Malaysia
[2] Univ Putra Malaysia UPM, Inst Math Res, Serdang 43400, Selangor, Malaysia
[3] Univ Putra Malaysia UPM, Fac Sci, Dept Math & Stat, Serdang 43400, Selangor, Malaysia
[4] Babes Bolyai Univ, Dept Math, Cluj Napoca 400084, Romania
[5] Acad Romanian Scientists, 3 Ilfov St, Bucharest 050044, Romania