Esmail A M Mokheimer, Fahad Mohammed Majhoud Alzahrani , Mohamed Habib

كلية الهندسة-جامعة الملك فهد للبترول والمعادن · السعودية

The stringent regulations of harmful gases and pollutants, such as nitrogen oxides, lead to the use of alternative fuels in order to lower these emissions. Hydrogen is one of the cleanest fuels. When burnt with oxidizer, it produces water and no other harmful emissions. Thus, it has the potential to become a major contributor to a near-zero emission future. However, currently, technology limitations, mostly associated with storage and transportation, limit its use in a wide range. A very promising alternative is synthetic gas (syngas), which is composed mainly of hydrogen (H2) and carbon monoxide (CO). Lean premixed (LPM) combustion of syngas can be one of the most promising technologies for increased combustion efficiency and reduced emissions. In this thesis, LPM syngas combustion characteristics have been studied numerically. LPM syngas laminar flames are modeled in zero- and one-dimensional forms using a detailed chemistry model (GRI-Mech. 3.0) to understand their most important basic properties, namely adiabatic flame temperature, laminar flame speed, and NO emissions. An emphasis has been given to the importance of syngas reaction mechanisms by studying some of the available reduced chemical mechanisms and how accurate they are in predicting the basic properties of LPM syngas laminar flames studied. Finally, LPM syngas combustion in a real geometry lab-scale swirl-stabilized combustor is modeled using computational fluid dynamics (CFD) to study the effect of swirl number, syngas composition, and equivalence ratio on flame characteristics and emissions. The adiabatic flame temperature of syngas was observed to increase with equivalence ratio, operating pressure, and preheat temperature, and decrease with hydrogen volume percent in syngas. The laminar flame speed increased with increasing equivalence ratio, hydrogen content in the syngas and preheat temperature, and decreased with increasing operating pressure. The NO production was also observed to increase with increasing equivalence ratio and preheat temperature. However, it decreased with increasing hydrogen in the syngas mixture. As the operating pressure increased, NO formation decreased at low equivalence ratios, and increased at high equivalence ratio. At very lean conditions, the NO predictions by the GRI-Mech. 3.0 were highly under-predicted by the reduced mechanisms. Different combination of these factors resulted in varying degree of discrepancy by the mechanisms understudy. It can be concluded that there is a need for developing more robust chemical mechanisms that could predict LPM syngas flames properties, especially at high preheat temperatures and operating pressures. In addition, experimental data for the effect of pressure on H2/CO laminar flame speeds with air (O2+N2) as the oxidizer is required and will be helpful for validating the developed kinetic models for syngas oxidation at high pressures. For the swirl-stabilized flames, the swirl geometry was found to have a significant effect on the different flame properties. The different strength levels of gases recirculation resulted in different values of flame temperature. The flame was found to be shorter for high swirl numbers. This gave higher residence time of combustion products, which reduced CO emissions. On the other hand, the higher capability of hydrogen to ignite and burn increased the flame temperature and NOX levels locally. Increasing H2/CO ratio resulted in higher flame temperatures, shorter flame lengths, and weaker reverse flow associated with the inner recirculation zones. In addition, upstream flame propagation (flashback phenomenon) occurred beyond H2 = 50%. Higher NOX emissions and lower CO and CO2 emissions resulted from increasing H2/CO ratio. The equivalence ratio was found to have the most significant influence on flame temperature and emissions. Undesirable levels of NO were observed for equivalence ratios beyond φ=0.6, while undesirable levels of CO were recorded for equivalence ratios below φ=0.6. Moreover, increasing equivalence ratio caused CO2 emissions to increase.

محمد بن العارية, حمزة لمعلم, يحي عطى الله

كلية العلوم الاقتصادية، التجارية وعلوم التسيير-جامعة أحمد دراية - أدرار · الجزائر

نهدف من خلال هذه الدراسة إلى معرفة أثر الإنفاق الضريبي على الحصيلة الضريبية ولمعرفة هذا الثأثر قمنا بتحليل وتقييم تكلفة الإعفاءات الجبائية و مقارنتها بالحصيلة الضريبية، وخلصنا إلى أن هناك أثر سلبي لتكلفة النفقات على إيرادات الجبائية لمديرية الضرائب بولاية أدرار.

احمد عيد, عبير فاروق منصور, محي الدين العسالي

كلية الدراسات العليا-جامعة النجاح الوطنية · فلسطين

With increment the number of infections resistance to antibiotics and life threatening causes many researchers work on developing alternative approaches and manufacturing new drug delivery systems to traverse the disadvantages of the conventional antibiotics. The aim of this study was to encapsulate the ciprofloxacin HCl in three different surfactants such as anionic surfactant (Sodium Lauryl Sulfate), cationic surfactant (Cetrimide) and nonionic surfactant (Tween 20). The encapsulation may in one hand help improving penetration behavior of the ciprofloxacin and on the other hand reduce the used doses. The other vital role of this research was the formulation of three stable encapsulated topical dosage forms (ciprofloxacin HCl gels) in order to treat topical infections. The encapsulation of ciprofloxacin HCl lead to successful conspicuous increasing in ciprofloxacin loading with potentially more soluble pattern. Fortunately, the in vitro release results revealed that about almost 90% of the loaded ciprofloxacin HCl was released at pH 5.5 in the first 2 hours. The prepared three gels differentiated as stable, clear and homogeneous formulation with good rheology characteristics. Moreover, improvement in the results of the antibacterial activity manifest that the newly encapsulated ciprofloxacin had better antibacterial activity against S. aureus and P. aeruginosa than ciprofloxacin alone.

رشيد الجودي, فاطمة الزهراء الوكيلي

كلية الطب والصيدلة-جامعة محمد الخامس بالرباط · المغرب

AOUF Zakaria, C. SELADJ

كلية التكنولوجيا-جامعة أبو بكر بلقايد - تلمسان · الجزائر

Dans ce travail de recherche nous étudions l’influence de lathermodiffusion sur la convection naturelle dans une cavité verticale poreuse,saturé par un mélange binaire gazeuse de méthane et n-butane. L’analye dece phénomène est controlé par la distribution de la masse volumique demélange, les lignes de courants et les isoconcentarions.En fonction du facteur de séparation, la perméabilité optimale du milieuporeux a été identifié. Aussi, nous étudions l’effet d’une fracture sur laséparation des mélanges. Les résultats obtenus font apparaître l’influence durapport de perméabilités, la taille de la fracture, l’inclinaison, et sa positionsur la convection thermosolutal en présence de l’effet soret.

صليحة بوصينة, عمي سعيد حمزة

كلية العلوم الاقتصادية والتجارية وعلوم التسيير-جامعة غرداية · الجزائر

تهدف هذه الدراسة إلى إبراز دور الخزينة في المؤسسة المالية غير المصرفية الشركة الوطنية للتأمينات، وذلك من خلال معرفة نظام تسيير الخزينة في المؤسسة محل الدراسة باستخدام المنهج التحليلي وهذا بتحليل القوائم المالية المقدمة من طرف الشركة بالإضافة إلى حساب أهم المؤشرات المالية وقد خلصت هذه الدراسة إلى أن تسيير خزينة الشركة كان له تأثير إيجابي على الأداء المالي في بعض السنوات كما توصلت الدراسة إلى أن الشركة حققت توازنا ماليا لابأس به خلال الفترة المدروسة من خلال تحقيق نتائج إيجابية.

Kamal Hisham Soubra, يوسف ابو جودة

الجامعة الأمريكية في بيروت · لبنان

Tomato yellow leaf curl geminivirus (TYLCV), a whitefly transmitted virus, is the major limiting factor for profitable tomato production especially in the Fall growing season on the Lebanese coast. Therefore, thirty six tomato varieties-lines were tested

عبدالعزيز بن عبدالرحمن المحمود, محمد بن سليمان بن محمد الخضيري

المعهد العالي للقضاء-جامعة الإمام محمد بن سعود الإسلامية · السعودية

Maher Maghalsah, Omran Abu Shammala, محمد إبراهيم الحسني

جامعة بوليتكنك فلسطين · فلسطين

Increasing of energy consumption in residential buildings recently has received a significant concern onthe thermal performance of buildings. Reducing energy consumption resulting from the heating andcooling demands of a building and limiting heat loss or gain can play a main role in buildings' savingenergy. The thermal insulation of building walls has a significant impact on energy conservation. In thisstudy, a group of models was developed to achieve the best thermal performance for the external walls ofresidential buildings. Composite wall models enhanced with selected insulation materials have been thermally examined in the extreme conditions in the Mediterranean region to determine the impact of theused materials on the thermal performance of buildings envelopes and energy consumption, withvalidating results through FLUENT software. The study’s methodology is based on two main stages, analyzing the wall models, and evaluating the most effective thermal performance and the developed onesusing FLUENT software based on the location of the insulation layer, thickness, and thermal behavior. The second is investigating heating and cooling loads during winter and summer via Design Builder software. The study showed that using Phase Change Material (PCM) insulation materials in the building wall composition has a significant impact on the thermal performance of the building envelope, thermal heat transfer, temperature distribution, and on heating and cooling loads. The heat transfer calculations appeared that the average temperature of the internal surface of the wall can be reduced significantly by almost (1.5-3.5) °C in the summer and by almost (2-6.5) °C in winter when applying Paraffin in an appropriate thickness and location within extreme conditions compared to the system without aninsulation layer. The energy calculations of heating and cooling loads obtained showed a reduction inenergy demand when using PCM. The saving of heating energy in January was 35.5%, whereas the saving of cooling energy in August was 41.9%. Moreover, the reduction amount of annual energy load was 3013.57kWh with a saving of 40.1% and the payback period was 2.5 years.

زهير يوسف عليوي, دعـاء مهدي فرحان عذاب المياحي

كلية التربية-جامعة القادسية · العراق