Enhancing flame flashback resistance against Combustion Induced Vortex Breakdown and Boundary Layer Flashback in swirl burners

Swirl combustors have proven to be effective flame stabilisers over a wide range of operation conditions thanks to the formation of well-known swirl coherent structures. However, their employment for lean premixed combustion modes while introducing alternative fuels such as high hydrogenated blends results in many combustion instabilities. Under these conditions, flame flashback is considered one of the major instability problems that have the potential of causing considerable damage to combustion systems hardware in addition to the significant increase in pollutant levels. Combustion Induced Vortex Breakdown is considered a very particular mode of flashback instability in swirling flows as this type of flashback occurs even when the fresh mixture velocity is higher than the flame speed, a consequence of the interaction between swirl structures and swirl burner geometries. Improvements in burner geometries and manipulation of swirling flows can increase resistance against this type of flashback. However, increasing resistance against Combustion Induced Vortex Breakdown can lead to augmentation in the propensity of another flashback mechanism, Boundary Layer Flashback. Thus, this paper presents an experimental approach of a combination of techniques that increase Combustion Induced Vortex Breakdown resistance, i.e. by repositioning a central injector and using central air injection, while simultaneously avoiding Boundary Layer Flashback, i.e. by changing the wall boundary layer characteristics using microsurfaces on the nozzle wall. Results show that using these techniques together has promising potentials regarding wider stable operation for swirl combustors, enabling them to burn a broader variety of fuel blends safely, while informing developers of the improvements obtained with the combined techniques

The Aesthetics of Form and Theme in the Products of Qajar Ceramics

لقد أصبح من البديهيات اعتبار الشكل نوعا من (ملحق زخرفي) يوفر قيمة ترفيهية جمالية بينما كانت عملية الإرشاد التي ترتبط بالمضمون تسير قدما وفق ماهو مخطط لها, لقد أضحى الشكل الوعاء الذي يصب فيه المضمون، ونظريا كان الوعاء ذاته قادرا على استقبال مضامين عدة, فإذا حدث تغيير في الشكل كان ذلك استجابة لمقتضيات المضمون. هذا يدل على قوة الترابط بين الشكل والمضمون في المنجز الفني الجمالي, الذي بان أثره في الفنون القاجارية، المتمثلة بالخزفيات التي مثلت البعد الجمالي على المستويين (الشكل والمضمون) من هنا جاءت الدراسة (جماليات الشكل والمضمون في نتاجات الخزف القاجاري) التي تضم أربعة فصول: خصص الفصل الأول منها لبيان مشكلة البحث التي تم تلخيصها في إمكانية الإجابة على السؤال الآتي: ما هي جماليات الشكل والمضمون في نتاجات الخزف القاجاري؟ وتضمن الفصل الأول الإشارة إلى أهمية البحث والحاجة إليه، وتحديد أهم المصطلحات، وتضمن هذا الفصل أيضاً هدف البحث بـ: (تعرف جماليات الشكل والمضمون في نتاجات الخزف القاجاري)، وتضمن الفصل حدود البحث بدراسة الأعمال الفنية القاجارية، ضمن المدة الزمنية(1779-1925م). أما الفصل الثاني فقد خصص للإطار النظري وأهم المؤشرات، حيث تضمن مبحثين: عني أولها بتقصي مفهوم الجمال، والآخر بدراسة الشكل والمضمون في الفن, أما الفصل الثالث فقد تضمن إجراءات البحث تم فيها تحديد مجتمع البحث البالغ عدده (15) عملاً, وعينة البحث وطريقة اختيارها مع أداة تحليل العينة وتحديد منهج البحث (المنهج الوصفي) ومن ثم تحليل عينة البحث المتكونة من (3) نماذج، في حين خصص الفصل الرابع لاستعراض النتائج والاستنتاجات والتوصيات، ومن أهم النتائج: ومن أهم النتائج التي توصلت إليها هذه الدراسة: ان لجمالية الشكل والمضمون في مشاهد الخزف القاجاري, سمتين:- أ- بانت جمالية الشكل والمضمون عبر التحول من نظام شكلي سابق إلى نظام بنائي جديد وفق رؤية جديدة, تحكمها آليات بناء (عناصر: خط, أون, انسجام) وعلاقات وأهم الاستنتاجات: إستمرار الفن في هذه المدة على نهج وخصائص الفن الإسلامي وفق مبدأ التسطيح. ظهور طابع البهرجة والتزويق والزهور, الذي بان أثرها على الأزياء. وأعقبها التوصيات والمقترحات فقائمة المصادر والمراجع.  It has become axioms to consider the shape as a kind of (a decorative accessory) that provides an aesthetic entertainment value, while the guidance process that is related to the content was moving forward according to what was planned. A change in form occurred in response to the requirements of the content. This indicates the strength of the interrelationship between form and content in the aesthetic artistic achievement, which has shown its impact in the Qajar arts, represented by the ceramics that represented the aesthetic dimension on both levels (form and content) from here came the study (the aesthetics of form and content in the products of Qajar ceramics), which includes four chapters, The first chapter is devoted to clarifying the research problem, which is summarized in the possibility of answering the following question: What are the aesthetics of form and content in the products of Qajar ceramics? The first chapter also included a reference to the importance of the research and the need for it, and the identification of the most important terms. (1779-1925 AD). As for the second chapter, it was devoted to the theoretical framework and the most important indicators, as it included two chapters, the first of which examined the concept of beauty, and the other was a study of form and content in art. With the sample analysis tool and defining the research method (descriptive approach) and then analyzing the research sample consisting of (3) models, while the fourth chapter is devoted to reviewing the results, conclusions and recommendations, and the most important results are: Among the most important findings of this study: 1.The aesthetics of form and content in the Qajar ceramic scenes have two characteristics: A- She showed the aesthetics of form and content through the transformation from a previous formal system to a new structural system according to a new vision, governed by building mechanisms (elements: line, on, harmony) and relationships and the most important conclusions: 1.Art continued in this period on the approach and characteristics of Islamic art according to the principle of flatness. 2.The appearance of glamor, adornment and flowers, which showed its effect on fashion. Followed by recommendations and suggestions, a list of sources and references

Medium-Term Results After Treatment of Recalcitrant Lateral Epicondylitis A Prospective, Randomized Study Comparing Open Release and Radiofrequency Microtenotomy

Background: Recalcitrant lateral epicondylitis (elbow extensor–origin tendinosis) is a common cause of elbow pain with many treatment options. In the present study, the medium-term results after open release and radiofrequency microtenotomy are reported. Hypothesis: Microtenotomy would provide long-term pain relief that was as good as the open release method. Study Design: Prospective, randomized trial. Methods: Twenty-four patients randomized to either open release or microtenotomy were assessed after 5 to 7 years. Clinical examination and dynamic infrared thermography (DIRT) of both elbows were performed preoperatively and at the medium-term follow-up. Magnetic resonance imaging (MRI) of both elbows was performed at the medium-term follow-up. Results: Significant pain reduction was found using a visual analog scale (VAS) at the medium-term follow-up in both groups compared with the preoperative assessment (P < .005). The Mayo Elbow Performance Score (MEPS) increased significantly in both groups (P < .01). The improvement in grip strength was not significant in either group. There was no significant difference between the groups in terms of VAS, strength, and the MEPS. On the DIRT examinations, there were significantly fewer hot spots at the medium-term follow-up than preoperatively (P ¼ .0067, both study groups together). The MRI examinations revealed grade II changes in the operated elbow in 1 patient in each group at the medium-term follow-up, while all the other MRI examinations revealed a normal tendon. Conclusion: In this prospective, randomized trial with a medium-term follow-up, the results were similar after surgical release and microtenotomy in patients with recalcitrant lateral epicondylitis. The hypothesis was thus verified. Keywords: tendinosis; epicondylitis; microtenotomy; infrared thermograph