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Performance Investigation of Cascade Refrigeration System Using CO2 and Mixtures
Nourheine Jemni,Mouna Elakhdar,Ezzedine Nehdi,Lakdar Kairouani 대한설비공학회 2015 International Journal of Air-Conditioning and Refr Vol.23 No.3
This paper presents reports on simulation and comparative analysis of single stage vapor compression refrigeration system and cascade systems using carbon dioxide, hydrocarbons (HCs) and CO2/HCs mixture. Thermodynamic parameters of fluids are given using the software REFPROP 9.0. To select the most suitable HCs, three criteria have been fixed: Tc, Tt and Tb. It is found that the HCs chosen in low-stage are propane, propylene and ethane and those for the high-stage are propane, propylene and isobutane. The fraction mixture in the two loops has been varied and results are compared with single stage and cascade systems using CO2 and R22. The fraction xCO2 is varied in the two loops. Results are compared for single and cascade systems using CO2 and R22. For the single stage system, we find for xCO2 =0.5, an improvement of COP of 14% for CO2/propane mixture and 36% for the CO2/propylene mixture. It is found that for xCO2 = 0.3, cascade system using propane/CO2 and propylene/CO2 mixtures presents a COP lower than that of cascade system using pure CO2. About of 70% of unfriendly fluids like CFCs and HCFCs can be replaced with CO2, without affecting the performance of cascade refrigeration systems.
Pedagogically-Driven Courseware Content Generation for Intelligent Tutoring Systems
Hend Ben Hadji,Ho-Jin Choi,Mohamed Jemni 한국지능시스템학회 2012 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.12 No.1
This paper describes a novel approach to adaptive courseware generation. This approach adopts its structure from existing intelligent tutoring systems and introduces a new component called pedagogical scenario model to support pedagogical flexibility in the adaptation process of courseware generation system. The adaptation is carried out using Dynamic Constraint Satisfaction Problem framework, which is a variant of classical Constraint Satisfaction Problem, to deliver courseware tailored to individual learner. Such a framework provides a high level of expressiveness to deal with the particular characteristics of courseware generation problem. Further, it automatically designs a sound courseware satisfying the design constraints imposed by the domain, the pedagogical scenario and learner models.
Pedagogically-Driven Courseware Content Generation for Intelligent Tutoring Systems
Hadji, Hend Ben,Choi, Ho-Jin,Jemni, Mohamed Korean Institute of Intelligent Systems 2012 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.12 No.1
This paper describes a novel approach to adaptive courseware generation. This approach adopts its structure from existing intelligent tutoring systems and introduces a new component called pedagogical scenario model to support pedagogical flexibility in the adaptation process of courseware generation system. The adaptation is carried out using Dynamic Constraint Satisfaction Problem framework, which is a variant of classical Constraint Satisfaction Problem, to deliver courseware tailored to individual learner. Such a framework provides a high level of expressiveness to deal with the particular characteristics of courseware generation problem. Further, it automatically designs a sound courseware satisfying the design constraints imposed by the domain, the pedagogical scenario and learner models.
Mohamed Brayek,Zied Driss,Mohamed Ali Jemni,Ali Damak,Mohamed Salah Abid 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.1
Combustion characteristics and emission in spark-ignition engines could be enhanced using hydrogen as supplementary fuel. However, its production, storage, and introduction in the combustion chamber face several challenges. To overcome the necessity of a storage device, a conventional electrolyser was used to produce a hydrogen-oxygen mixture (hydroxygen). The produced hydroxygen bubbles are characterized by their macro and nanometric size. In the present work, gasoline was on top of the water in the electrolyser. Therefore, hydroxygen nanobubbles are diffused in both water and gasoline. Combustion analysis was carried out for different engine speeds. An improvement in brake torque and a reduction in fuel consumption, HC, CO, and CO 2 emissions have been witnessed in the engine during test performance. However, the emission analysis shows a slight increase in NO x emission. Finally, this disadvantage could be neglected compared to the improvements that come with the use of hydroxygen nanobubble gasoline blends.