Hydrodynamics study of the bubble columns with intense vertical heat-exchanging tubes using gamma-ray computed tomography and radioactive particle tracking techniques

Understanding the hydrodynamics of bubble columns with and without vertical heat-exchanging tubes is a necessity for the proper design, scale-up, and operation of these reactors. To achieve this goal, systematic experiments were performed to visualize and quantify the influence of the presence of vertical internal tubes on the gas holdup distributions and their profiles, axial liquid velocity, and turbulent parameters (i.e., normal and shear stresses; turbulent kinetic energy) by using advanced gamma-ray computed tomography (CT) and radioactive particle tracking (RPT). In this study, the experiments were conducted in 6- and 18-inch bubble columns with an air-water system as the working fluid, under a wide range of superficial gas velocities (5-45 cm/s). Three configurations of vertical internals (i.e., hexagonal, circular without a central tube, and circular with a central tube plus vertical internals), as well as the vertical internals sizes, were examined in this study. These three configurations were designed to cover 25% of the column\u27s cross-sectional area (CSA) to represent the percentage of the covered area utilized in the Fischer-Tropsch process. Reconstructed CT images reveal that the configurations of the vertical internal tubes significantly impacted the gas holdup distribution over the CSA of the column. Additionally, the bubble column equipped with 1-inch vertical internals exhibited a more uniform gas holdup distribution than the column with 0.5-inch internals. Moreover, a remarkable increase in the gas holdup values at the wall region was achieved in the churn turbulent flow regime due to the insertion of vertical internals inside the column. Furthermore, pronounced peaks of the gas holdup and axial liquid velocity were observed in the inner gaps between the vertical internals --Abstract, page iv

Catalytic utilization of carbon dioxide as renewable feedstock for production of chemicals and fuels

The utilization of CO2 as a renewable feedstock for producing commodity chemicals and fuels is an interesting challenge to explore new concepts and opportunities in catalysis and industrial chemistry. This sustainable approach not only leads to production of useful chemicals, but also has the potential to mitigate anthropogenic CO2 emissions to the atmosphere. CO2 itself is a sustainable and inexhaustibly available carbon source, however, it is inextricably linked to its inherent inertness. It is a thermodynamically stable molecule (ΔGf = -394.01 kJ.mol-1) with high oxidation state, hence, reactions of CO2 must be combined with a high-energy reactant to gain a thermodynamic driving force. It has been shown that catalytic reaction is the best strategy to address this challenge. Although several processes for production of urea, methanol, and salicylic acid have been developed through CO2 utilization, many of them rely on extremes of temperature and pressure to work. Owing to the growing energy demand and increasing atmospheric carbon dioxide (CO2) concentration, it is desirable to identify effective hydrocarbon transformation reactions in tandem with CO2 conversion. Research on direct transformation of light paraffins -such as methane, ethane and propane into light olefins -such as ethylene and propylene and aromatics has gained considerable importance recently because of its potential large-scale implementation for production of fine chemicals, pharmaceuticals, plastics and liquid fuels from C1-C4 hydrocarbons in the shale gas. The catalytic conversion of propane into propylene in the presence of CO2 as a soft oxidant opens opportunities to simultaneously reduce CO2 to CO and convert paraffin into value-added products --Abstract, page iv

Effect of Interlayer Coating Thickness on the Hardness and Adhesion for the Tungsten Carbide Cutting Tool

تم دراسة تأثير سمك الطبقة البينية لطلاء N((Al,Ti على الخواص الميكانيكية للطلاء في عدة القطع باعتماد خاصيتي الصلادة والالتصاق .فقد تم طلاء عدة القطع باستخدام نترات الالمنيوم التيتانيوم N(AlTi) بنسب قياسية Al0.67Ti0.33 في نظام قوس كاثودي(PVD). وقد تم استخدام كل من اختبار روكويل وفكرز لقياس الصلادة والالتصاق. وقد اظهرت النتائج ان اعلى صلادة لطلاء N((Al,Ti عند سمك 5.815µm بينما اعلى التصاق عند سمك 3.089µm وعلى العكس من ذلك فان اقل صلادة ظهرت عند 2.717µm في حين اقل التصاق ظهر عند 5.815µm. عموما فان طلاء N (AlTi)عند سمك 5.815 يعتبر فعال اذ انه يعطي اعلى صلادة واقل التصاق , وسبب انخفاض الالتصاق له علاقة بتأثير تشكيل الجسيمات الصغير(MPs) التي لها تأثير مباشر على الصلادة لان (MPs) تظهر اساسا على السطح ووجودها في الواجهة محدود جدا بالإضافة الى ذلك فان انشاء طبقة Ti اولية لتقليل الفصل بين الطبقات(التضمين) له تأثير كبير على الالتصاق ولكن ليس له تأثير على تركيب السطح. ولهذين السببين وتأثير جهد الحيز الكهربائي فان النتائج المعروضة في هذه الدراسة اظهرت اختلاف طفيف مع البحوث المنشورة الاخرى. ان تكوين طبقة (Al,TiN)  تتميز على ما يبدو بإظهار واحدة من النتائج المهمة التي تبين التكوين النهائي لطبقاتN) Al,Ti) بالنسب (Al0.62Ti0.38) قريبة جدا من الهدف الاساسي لهذه الدراسة (Al0.67Ti0.33).The thin film of the (Al,Ti)N coating is studied with the aid of two parameters: hardness and adhesion.  These parameters are very close to each other; however, in deposition field they could be interpreted differently.  Several coatings of (Al,Ti)N layers are developed on tungsten carbide insert using the standard commercial Al0.67Ti0.33 cathodes in cathodic arc plating system(PVD). The influence of coating layer thickness on the mechanical properties of the coatings was investigated via two parameters: hardness and adhesion are characterized by the Rockwell tester Vickers tester.  The measurements reveal that the highest hardness appears for the (Al,Ti)N thickness of 5.815 µm while the highest adhesion appears at a thickness of 3.089 µm.  At the opposite extreme, the lowest hardness appears at 2.717 µm and the lowest hardness at 5.815 µm. Overall, the (Al/Ti) N coating of the thickness of 5.815 µm is controversial as it exhibits the highest hardness and the lowest adhesion. This result could be related to the effect of the formation of the micro-particle (MPs) which has a direct effect on the hardness because these MPs appear mainly on the surface and their presence at the interface is very limited.  In addition, the creation of Ti buffering layer to reduce the delamination has its major effect on the adhesion but has no effect on the morphology of the surface.  For these two reasons and the effect of the bias voltage, the results presented in this paper might show slight differences with other published papers.  The composition of the (Al,Ti)N layer is characterized and, seemingly, it shows one important result which is showing that the ultimate composition of the (Al,Ti)N layer (Ti0.62Al0.38) is very close to the original target used in this study (Al0.67Ti0.33)

Statistical Modeling for the Characteristics of Open Graded Friction Course Asphalt

 الطبقات النفاذة الاحتكاكية هي نوع خاص من الخلطات التي تستعمل كطبقة نهائية فوق سطح الخلطات الاعتيادية حيث ازداد استخدامها حول العالم وذلك لخواصها العديدة مثل الاحتكاك، السلامة، والفوائد البيئية، الخ. تضمن هذا البحث بعض الخواص المختبرية المختارة للخلطات النفاذة تم اختيارها للتحليل الاحصائي والتي تعتمد على مدخلات تصميم الخلطة. قوة الشد الغير مباشرة (ITS)، وحساسية الماء (TSR)، والنفاذية (K) اختيرت للخواص الميكانيكية، والديمومة، والحجمية، على التوالي، وهذه الخواص تمثل المتغيرات التابعة لكل موديل احصائي. حيث ان نوع المادة المالئة كغبار الركام الاعتيادي والسمنت البورتلاندي الاعتيادي (CMF, OPC)، نسبة الاسفلت (BC)، ونسبة البوليمر المضاف (SBS) تمثل المتغيرات المستقلة لكل الموديلات الاحصائية. الموديلات الاحصائية المتولدة توفر اداة تنبا قابلة للتحقق حيث كانت قيم R² هي 0.781 ،0.821, 0.820، على التوالي للموديلات الاحصائية المتولدة، كما أنها ساعدت على قياس أهمية كل متغير مستقل. على سبيل المثال، نوع المادة المالئة يؤثر بشكل كبير على خصائص حساسية الماء، حيث كان مقدار ارتباط 0.752). من خلال هذه الدراسة نكتشف أن التحليل الاحصائي هي اداة تنبا قابلة التحقق لوصف خصائص وأداء الخلطات النفاذة الاحتكاكية من حيث الخصائص الحجمية والميكانيكية والمتانة.An open-graded friction course (OGFC) is a special type surface layer of traditional Dense Graded Hot Mix Asphalts (DGHMA) pavement that is increasingly being used around the world due to its various benefits, such as, frictional, safety and environmental, etc. In this research, selective laboratory OGFC properties were statistically modeled depends on mix design inputs for two purposes or aims; mix inputs significant and prediction the OGFC properties according mix inputs.  Principally, Indirect Tensile Strength (ITS), water sensitivity (TSR), and permeability (K) were selected from mechanical, durability, and volumetric properties, respectively as an output property; they represent the dependent variables for each model. While, fillers as conventional mineral filler or Ordinary Portland Cement (CMF, or OPC), binder content (BC), and polymer content (SBS) are represented inputs or the independent variables for all models. The generated models offered a vital achievable tool for prediction (e.g., their R² are 0.781, 0.82 1and 0.820, respectively, for the mentioned model’s properties), also it helped to scale the significant of each independent variable (e.g., filler type significantly affect water sensitivity properties, its correlation was 0.752). This study reveals that the statistical modeling is achievable and offers a dynamic tool to describe the characteristics and performance of OGFC mixture in term volumetric, mechanical and durability properties

RELATIONSHIP BETWEEN TYPES OF REWARDS AND JOB SATISFACTION OF EMPLOYEES: EVIDENCE FROM KHYBER PAKHTUNKHWAH

The main objectives of this research study were to gauge theprevailing level of job satisfaction amongst employees. Furthermore to find an association among the levels of rewards (task significance, task involvement, task autonomy, organizational rewards, social rewards) and job satisfaction of employee’s doing jobs in private sector organizations in Khyber Pakhtunkhwah. 240 employees of five private sector universities and eight private sector banks participated in this study. A Cronbach’s Alpha, Multiple Regression and Pearson Correlation are used to test the proposed hypothesis.The findings reveal that there exists significant and positiveassociation between job satisfaction and rewards (task involvement, task autonomy and task significance). The results show that job satisfaction is insignificantly associated with organizational rewards and social rewards. The findings of this research and their implication for future research are also discussed

Big Data Analytics: A Survey

Internet-based programs and communication techniques have become widely used and respected in the IT industry recently. A persistent source of "big data," or data that is enormous in volume, diverse in type, and has a complicated multidimensional structure, is internet applications and communications. Today, several measures are routinely performed with no assurance that any of them will be helpful in understanding the phenomenon of interest in an era of automatic, large-scale data collection. Online transactions that involve buying, selling, or even investing are all examples of e-commerce. As a result, they generate data that has a complex structure and a high dimension. The usual data storage techniques cannot handle those enormous volumes of data. There is a lot of work being done to find ways to minimize the dimensionality of big data in order to provide analytics reports that are even more accurate and data visualizations that are more interesting. As a result, the purpose of this survey study is to give an overview of big data analytics along with related problems and issues that go beyond technology

Functionalized Multi-Walled Carbon Nanotube/Cellulose Acetate Mixed Matrix Membrane For CO2/N2 Separation

Carbon dioxide (CO2), as one of the major atmospheric contributors to the Earth's greenhouse effect has been rising extensively since the industrial revolution. One promising means of lowering the emission of CO2 is to develop highly efficient and robust membranes that are capable of selective CO2. Karbon dioksida (CO2) adalah salah satu penyumbang utama kepada kesan rumah hijau kepada bumi, yang kuantitinya kian meningkat sejak revolusi industri. Salah satu cara untuk mengurangkan pelepasan CO2 adalah dengan menghasilkan membran yang cekap dan mantap yang mampu menapis mengikut kememilihan CO2