The impact of heat exchanging internals on hydrodynamics of bubble column reactor

In this study, the impact of configuration and size of vertical heat exchanging internals in bubble columns on gas holdup, specific gas-liquid interfacial area, bubble chord length, and bubble rise velocity were investigated. Three different configurations of internals, each covering 25% of the column\u27s cross-sectional area, were used to simulate the heat exchanging tubes utilized in the F-T process. The First configuration is a circular-like arrangement of 0.5 inch diameter vertical rods, whereas the second is a hexagonal-like arrangement of 0.5 inch diameter vertical rods. The third configuration is also a circular arrangement but of 1 inch diameter vertical rods used to examine the effect heat exchanging tubes diameter on the hydrodynamics. The experiments were carried out in a 14 cm inner diameter Plexiglas bubble column using air-water system, at superficial gas velocities in the range of 0.02 to 0.45 m/s, measured based on free cross-sectional area of the column available for fluid flow. 4-point optical fiber probe technique was used to collect the diameter profiles of the hydrodynamic parameters. In comparison to bubble column without internals, the obtained result showed that the configuration of the internals significantly affect the hydrodynamics and also the flow resistance inside the column. Steeper gas holdup and specific interfacial area profiles observed when the 0.5 inch circular arrangement internals is used. A distinct asymmetrical radial profiles of gas holdup and specific interfacial area were obtained when the hexagonal arrangement is used. The 1 inch internals enhanced the gas holdup and specific interfacial area near to the wall regions. In the churn turbulent regime, Bubbles chord length and bubbles rise velocity were found to be larger with the presence of internals when compared to bubble column without internals --Abstract, page iv

Experimental Investigation of Condensation Heat Transfer Characteristics of R-134a Vapor in Horizontal Heat Exchanger

قدم هذا البحث دراسة تجريبية لمعامل انتقال الحرارة وانحدار الضغط خلال تكثيف مائع ثنائي الطور في حالة جريان لمائع التثليج R-134a في مقطع أنبوب مكثف لمنظومة تبريد تحت ظروف تشغيل مختلفة. الاستقصاء العملي والنظري اعتمد ظروف اختبار تم تحديدها، للفيض الحراري 17-10)) كيلوواط\متر مربع، الفيض الكتلي (63-42) كغم\متر مربع. ثانيه، نسبة الجفاف للبخار (0.03-1) ودرجة حرارة التشبع للمائع من (44 الى (49 درجة مئوية. الاختبارات العملية نفذت باستخدام جهاز فحص يتضمن مقطع فحص لمحاكاة مبادل حراري من نوع الانبوب المتداخل مبرد بالماء والذي صمم ونفذ خلال الدراسة الحالية. أظهرت النتائج العملية وجود تأثير واضح للفيض الحراري والفيض الكتلي على قيم معامل انتقال الحرارة. قيم معامل انتقال الحرارة قد ازدادت مع زيادة الفيض الحراري والفيض الكتلي ضمن ظروف الاختبار المحددة، حيث كانت نسبة التحسين في معامل انتقال الحرارة بحدود 47% و14% لقيم الفيض الحراري والفيض الكتلي الأعلى نسبيا على التوالي. نسبة التحسين في معامل انتقال الحرارة كانت بحدود 51% و43% لقيم درجة حرارة التشبع ونسبة الجفاف للمائع 45.47˚C و0.88   على التوالي مقارنة بالقيم الأخرى عند ظروف تشغيل ثابته. انحدار الضغط كان اعلى بحدود 12% و 49% لقيم الفيض الكتلي والفيض الحراري الأعلى نسبيا على التوالي. تم التثبت من نتائج الدراسة الحالية من خلال المقارنة مع نتائج النماذج النظرية وكذلك مع نتائج دراسة مشابهه وقد أظهرت المقارنة توافق مقبول.An experimental investigation of refrigerant R-134a two-phase flow condensation heat transfer coefficient and pressure drop in condenser tube section of refrigeration system under different operating conditions is presented. The experimental and theoretical investigations are based on test conditions in range of 10 -17 kW/m2 for heat flux, 42-63 kg/m2s for mass flux, vapor quality 1-0.03 and saturation temperature 44 to 49˚C. The experimental tests are conducted on test rig supplied with a test section to simulate the water cooled double pipe heat exchanger, which is designed and constructed in the present work. “The experimental results have revealed that, the heat flux and mass flux have significant impacts on the heat transfer coefficient. “The heat transfer coefficient was increased with increase in heat flux and mass flux at prescribed test conditions, where the enhancement in heat transfer coefficient was about 47% and 14% for relatively higher heat flux and mass flux, respectively. “The enhancement in the heat transfer coefficient was about 51% for relatively lower saturation temperature 45.97˚C and 43% for higher vapor quality 0.88 compared to other values at constant test conditions. “The pressure drop was higher in the range of 12% and 49% for relatively higher mass flux and heat flux respectively. “The present work results have validated by comparison with predictive models and with similar research work results and the comparison has revealed  an acceptable agreement

Bank stock returns and macroeconomic variables: Empirical evidence from selected ASEAN countries

The aim of this study is to examine the effect of macroeconomic variables on bank stock returns in ASEAN. The panel data were retrieved from the DataStream and World Bank data archive, consisting of 58 banks from six countries (Malaysia, Indonesia, Singapore, Thailand, Philippines, and Vietnam) for the period 2004 to 2014. The bank stock return index is used as a proxy for bank stock return while proxies for macroeconomic variables are money supply, interest rate, inflation, and foreign exchange rate. By applying pooled OLS regression analysis, the results show that money supply has negative impact on bank stock returns, indicating that changes in money supply is a major signal for change in stock price because it has a direct influence on stock market and an indirect influence on bond market based on the adjustment of interest rates. Inflation also has negative significant influence on bank stock returns, implying that negative inflation –real activity induced the relationship through the money demand theory and the quantity theory of money. Foreign exchange rate has a positive significance influence on bank stock returns, indicating that the foreign exchange exposures of ASEAN banks have influenced their stock returns since most part of the stock returns are sensitive to the changes in exchange rates during the periods. Meanwhile, interest rate is insignificant with bank stock returns, implying that interest rate sensitivity does not exert a significant impact on the common stock of the banks, which could be caused by the effect of wealth distribution triggered by unexpected inflation when banks hold nominal assets and nominal liabilities. It is recommended that ASEAN banks should involve in various off-balance sheet activities and implement effective and efficient approaches of risk management which reduce their exposure to fluctuations in macroeconomic factor

Radiological Findings in Sputum Positive and Sputum Negative Tuberculous Infected Patients: A Comparative Study

Background: Tuberculous infection is a long term chest spoiling which is initiated by mycobacterial bacilli. Tuberculosis implants in higher than the one third from all cases of passing in the nineteenth and twentieth centuries, and it causes infection in about one third over the world. Those best and the majority conclusive system in the finding from claiming lung tuberculous infection is sputum sample, also Ziehl Neelsen staining for a few successive samples. For smear negative furthermore actually smear positive cases, radiographic features would supportive clinched alongside illness finding. Aim of this study: This study need been carried to look at radio-logical findings done for sputum positive, also sputum negative tuberculosis patients. Patients and Methods: This cross sectional ponder might have been conveyed out in Baghdad teaching hospital in respiratory specialized clinic in about 1st of January to September of 2016 .there are 79 patients were enrolled in this study that diagnosed as pulmonary tuberculosis according to WHO criteria for diagnosis of pulmonary TB in which 52 patients were diagnosed as sputum positive TB and 27 patients diagnosed as sputum negative but culture positive  all the participant in this study should have postero-anterior chest x-ray and should be interpreted by at least two specialized radiological professional independently and sputum smear examined by bacteriologist expert  . Results: In our study the chest x-ray finding (calcification, hilar lymphadenopathy, apical infiltrations, mediastinal widening, bronchiectasis and cavity) more visible findings in sputum positive patients than sputum negative pulmonary TB, which are statistically significant P value <0.05.While (reticulonodular infiltrations, lung fibrosis, pleural effusion and miliary shadowing) are more visible findings in sputum negative patients than sputum positive lung TB patients which are statistically insignificant P value >.05. Conclusions: the chest x-ray finding (calcification, hilar lymphadenopathy, apical infiltrations, mediastinal widening, bronchiectasis and cavity) more visible findings in sputum positive patients than sputum negative pulmonary TB, While (reticulonodular infiltrations, lung fibrosis, pleural effusion and miliary shadowing) are more visible findings in sputum negative. Keywords tuberculosis (TB),  sputum negative, sputum positive.

Classification of stress based on speech features

Contemporary life is filled with challenges, hassles, deadlines, disappointments, and endless demands. The consequent of which might be stress. Stress has become a global phenomenon that is been experienced in our modern daily lives. Stress might play a significant role in psychological and/or behavioural disorders like anxiety or depression. Hence early detection of the signs and symptoms of stress is an antidote towards reducing its harmful effects and high cost of stress management efforts. This research work thereby presented Automatic Speech Recognition (ASR) technique to stress detection as a better alternative to other approaches such as chemical analysis, skin conductance, electrocardiograms that are obtrusive, intrusive, and also costly. Two set of voice data was recorded from ten Arabs students at Universiti Utara Malaysia (UUM) in neural and stressed mode. Speech features of fundamental, frequency (f0); formants (F1, F2, and F3), energy and Mel-Frequency Cepstral Coefficients (MFCC) were extracted and classified by K-nearest neighbour, Linear Discriminant Analysis and Artificial Neural Network. Result from average value of fundamental frequency reveals that stress is highly correlated with increase in fundamental frequency value. Of the three classifiers, K-nearest neighbor (KNN) performance is best followed by linear discriminant analysis (LDA) while artificial neural network (ANN) shows the least performance. Stress level classification into low, medium and high was done based of the classification result of KNN. This research shows the viability of ASR as better means of stress detection and classification

Enhancing methanol electro-oxidation by double oxide incorporation with platinum on carbon nanotubes

Name taken from "public.pdf"Electro-oxidation of methanol was investigated on platinum catalyst supported on a double oxide nanocomposite support of tin oxide and carbon-doped titanium dioxide. The Pt-SnO2-C-/CNTs electro catalyst demonstrated about 20% and 44% percent higher forward peak current density than Pt-SnO2/CNTs and E-TEK, respectively. The kinetics of formation of the oxygenated species (-OH) groups was dramatically enhanced upon doped titanium dioxide incorporation. This leads to a much lower onset potential of adsorbed CO oxidation. Doping by carbon in the titanium dioxide makes the oxide support electrically conductive. Shifting in Pt oxidation state was noted, which refers to the influence of the metal oxide incorporation with platinum on the CNTs. The purpose of the coating is to avoid corrosion at high potentials and enhance the durability of the catalyst in an acidic medium. Therefore, the oxide coating was the key factor for the enhanced stability of the Pt catalyst and for the increase of current density during methanol electro-oxidation

Anaerobic Bacteria Associated with Periodontitis

Oral bacteria are highly associated with oral diseases, and periodontitis is a strongly prevalent disease, presenting a substantial economical burden. Furthermore, there is a strong association between periodontal bacteria and other diseases, such as cardiovascular disease, rheumatoid arthritis, or diabetes, so it becomes clear that efficient periodontal cure would be of good medical benefit to general health. Periodontally, Healthy loci show a low number of bacteria which are cultivable by individual sulcus, 102–103 microorganisms with almost Gram-positive microbiota, including Streptococcus and Actinomyces species. In gingivitis, it is characterized by an increased bacterial number, 104–105 microorganisms by periodontal sulcus, besides an increased diffusion of Gram negative bacteria (15–50%).The increased number of oral bacteria could be associated with the decreased role of the innate and adaptive immunity; so, this chapter will focus on the most prevalent bacteria associated with the oral disease on the one hand and the role of innate immunity and adaptive immunity (Interleukin 1 Beta Il-1β and Tumor necrosis factor-alpha TNF-α) in oral diseases on the other hand

Developing a novel method for making metal oxide nanocoatings for electrocatalysis applications

In this dissertation, a new and novel technique to synthesize conformal films of metal oxides on top of nanoscale substrates in different geometries such as carbon nanotubes, carbon black particles, and iron oxide nanoparticles was developed. The coating technique is based on principles of condensing water molecules from an organic solvent, heptane, onto nanoscale substrates after oversaturating the heptane above its water saturation limit. When metal oxide precursors are introduced into the heptane dispersed with the nanoscale substrates, they diffuse to the surface of the substrates and react with the water film on their surface to form metal oxide nanocoatings. Due to the high surface tension between the water film and the heptane, the condensed water film takes a conformal shape on the substrates with minimum roughness, which also leads to producing uniform metal oxide coatings. This new coating technique is termed condensed layer deposition, or CLD. Various metal oxides were successfully made, such as TiO2, Nb2O5, and Al2O3 on various substrates, such as carbon black (CB), carbon nanotubes (CNTs), carbon nanofibers (CNFs), iron oxide particles (IOPs), and TiO2. By removing the carbon supports (CB, CNTs, CNFs), Nb2O5 nanoshells, TiO2 nanotubes and Al2O3 porous nanotubes have been obtained. It was found that the CLD technique can produce fluffy coatings with a high specific surface area of [approximately] 310 m2/g, when a large molecule size of organic precursor such as titanium terta-isopropoxide is used. The surface hydrophilicity was observed to increase by increasing the water ratio. Subsequently, a fluffy TiO2 coating on CNTs was made with tin oxide and used as a support for platinum nanoparticles for ethanol electrooxidation and for oxygen reduction reaction (ORR). The catalyst has shown a much higher ethanol mass activity peak of 560 mA/mg(Pt) than Pt/C (Pt on CB) which showed 296 mA/mg(Pt). In addition, the catalyst has a current density by over 2.2 times of that in Pt/C at 600 mV after 0.5 hours in durability test. In ORR, a remarkable improvement in ORR onset potential was achieved at 930 mV vs. RHE in 0.5 M sulfuric acid electrolyte. The mass activity was 2.66 times that of Pt/C at 900 mV. The same fluffy TiO2/CNTs was used to support platinum and iridium for methanol electrooxidation. Pt-Ir/C-TiO2/CNTs has shown a significant improvement in the anodic to the cathodic current ratio with a 5.6-fold increase. The i-t curve showed a high stability at 0.5 V after 3600 seconds by 12.5 times. On the other hand, Nb2O5 coating of 5 nm on CB was used for the oxygen reduction reaction. Electrochemical tests showed only a 1.7% activity loss after 5000 cycles, demonstrating an excellent durability of the electrocatalyst. Compared to the electrocatalyst without niobium oxide coating, it shows a 25 mV improvement in half-wave potentials, indicative of a better kinetics. The 5 nm Nb2O5 on CB was coupled with tin oxide supporting platinum toward methanol electrooxidation. Pt-TNb/C (tin and niobium oxide support) showed 2.7 A/mg(Pt) in mass activity at 0.8 V vs. Ag/AgCl which is better than most studies reported in the literature. Moreover, the Pt-TNb/C showed 0.0% loss after 1000 cycles in electrolyte containing 1.0 M CH3OH, whereas, Pt-Nb/C (niobium oxide support) and Pt/C suffered 21% and 30% loss, respectively. The chronoamperometry results showed the catalyst has a high CO tolerance after testing for 2 hours with a remarkable stability.Includes bibliographical references (pages 148-173)

International business and the political environment: an exploratory study: "comparative study of Iraqi, Saudi oil trade"

This paper is a Master thesis for the master’s program in International studies in the Department of Sociology and Public Policies at ISCTE University. As the title indicates, the aim of this thesis is to explore what is the political environment and present the concept of international business, and the impact of those works on the political environment by setting the theoretical context and draw that context from a comparative analysis of the historical context of the Iraqi and Saudi oil trade and their impact on the political environment of the stakeholders. The research questions are: What is the concept of the political environment and its components?; Does international business have an impact on the political environment?; How has the Iraqi and Saudi oil trade affected the political environment of these countries?; In order to answer the questions and fulfill the aim of this paper, a qualitative research method has been chosen. The study is mainly based on secondary sources such as textbooks, articles, magazines, and newspapers as well as internet resources. In making the comparative analysis Examination of different historical stages of oil trade and for two different regions and the extent of theoretical convergence of theoretical concepts with the practical realism derived from the events of those stages. This proves the argument of this theory and completed it and how its practical impact on the political environment. The conclusion drawn from the study is that international business affects the political environment and its elements, and the theoretical results coincide with the results of the analysis of the practical experience derived from the historical context of a century, that the Iraqi and Saudi oil trade as one of the international business influenced the political environment of stakeholders, They drew their political behavior, which was reflected in the internal political situation and international relations, which in turn reflected on the security of stakeholders, whether in the form of political risks or development processes for those countries.Este artigo é uma dissertação de mestrado para o programa de mestrado em Estudos Internacionais no Departamento de Sociologia e Políticas Públicas da Universidade Iscte. Como o título indica, o objetivo desta tese é explorar o que é o ambiente político e apresentar o conceito de negócios internacionais e o impacto desses trabalhos no ambiente político, definindo o contexto teórico e extrair esse contexto de uma análise comparativa. do contexto histórico do comércio de petróleo iraquiano e saudita e seu impacto no ambiente político das partes interessadas. As questões de pesquisa são: Qual é o conceito do ambiente político e seus componentes?; Os negócios internacionais têm impacto no ambiente político?; Como o comércio de petróleo do Iraque e da Arábia Saudita afetou o ambiente político desses países?; A fim de responder às questões supracitadas e cumprir o objetivo deste trabalho, optou-se por um método de pesquisa qualitativa. O estudo baseia-se principalmente em fontes secundárias, como livros didáticos, artigos, revistas e jornais, bem como recursos da Internet. Ao fazer a análise comparativa Análise de diferentes estágios históricos do comércio de petróleo e para duas regiões diferentes e a extensão da convergência teórica de conceitos teóricos com o realismo prático derivado dos eventos dessas etapas. Isso prova o argumento dessa teoria e a completou e como seu impacto prático no ambiente político A conclusão tirada do estudo é que os negócios internacionais afetam o ambiente político e seus elementos, e os resultados teóricos coincidem com os resultados da análise da experiência prática derivada do contexto histórico de um século, que o comércio de petróleo iraquiano e saudita como um dos negócios internacionais influenciou o ambiente político das partes interessadas, Eles desenhou seu comportamento político, o que se refletiu na situação política interna e relações internacionais, que por sua vez refletiu sobre a segurança das partes interessadas, seja na forma de riscos políticos ou processos de desenvolvimento para esses países

Effect of Wood Waste as A Partial Replacement of Cement, Fine and Coarse Aggregate on Physical and Mechanical Properties of Concrete Blocks Units

Wood waste has been used in concrete in 19th century. Its light-weight and cost effectiveness are main recognized characteristics. To reduce the environmental burden, nowadays developed countries have opportunities to use wood waste in concrete construction. This research presents experimental program results on mechanical and physical properties of ninety-six specimens of concrete blocks units. The experimental program concluded three groups of mixes plus the control mix. In Group 1 and Group 2, sawdust waste has been used as a partial replacement of 10%, 15%, 20%, 25% and 30% by volume of cement and sand respectively. In Group 3, wood waste aggregate has been used as a partial replacement of 10%, 15%, 20%, 25% and 30% by volume of coarse aggregate. The specimens were conditioned for 28-days at 80±5% Relative humidity and 24±2°C and tested. Slump, compressive strength, water absorption, dry density, porosity and thermal conductivity tests have been conducted. The compressive strength of concrete blocks units decreased due to the effect of sawdust waste and wood waste aggregate by increasing the replacement ratio instead of cement, sand and coarse aggregate. The results showed the mixes of group1 and group2 produced structural concrete blocks units at 20% replacement ratio of sawdust waste instead of cement and sand respectively. Also, the results showed that light-weight concrete blocks units can be obtained at a 25% and 30% replacement ratio in all groups with satisfactory compressive strength. The optimum replacement ratio was about 20% in the three groups so that physical and mechanical properties were satisfactory. This may be considered a solution not only to the problem of the environment but also to the problem of economics in the design of buildings