Heat transfer characteristics and entropy generation for wing-shaped-tubes with longitudinal external fins in cross-flow

Sayed Ahmed E. Sayed Ahmed,Osama M. Mesalhy,Mohamed A. Abdelatief 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.6

A numerical study is conducted to clarify heat transfer characteristics, effectiveness and entropy generation for a bundle of wingshaped-tubes attached to Longitudinal fins (LF) at downstream side. The air-side Re a ranged from 1.8 x 10 3 to 9.7 x 10 3 . The fin height (h f ) and fin thickness (δ) have been changed as: (2 mm ≤ h f ≤ 12 mm) and (1.5 mm ≤ δ ≤ 3.5 mm). The analysis of entropy generation is based on the principle of minimizing the rate of total entropy generation that includes the generation of entropy due to heat transfer and friction losses. The temperature field around the wing-shaped-tubes with (LF) is predicted using commercial CFD FLUENT 6.3.26 software package. Correlations of Nu a , St a , and Bejan number (Be), as well as the irreversibility distribution ratio (Φ) in terms of Re a and design parameters for the studied bundle are presented. Results indicated that, installing fins with heights from 2 to 12 mm results in an increase in Nu a from 11 to 36% comparing with that of wing-shaped tubes without fins (NOF). The highest and lowest values of effectiveness (ε) at every value of the considered Re a range are occurred at h f = 6 mm and (NOF), respectively. The wing-shaped-tubes heat exchanger with h f = 6 mm has the highest values of (ε), efficiency index (η) and area goodness factor (G a ) and also the lowest values of Φ and hence the best performance comparing with other arrangements. The minimum values of Φ are occurred at h f = 6 mm. (Be) decreases with increasing Re a for all studied h f . The heat transfer irreversibility predominates for (1800 ≤ Re a ≤ 4200) while the opposite is true for (6950 < Re a ≤ 9700). δ has negligible effect on Nu a and heat transfer irreversibility. Comparisons between the experimental and numerical results of the present study and those, previously, obtained for similar available studies showed good agreements.

Determining Dimensions of Job Satisfaction among Employees: Evidence from Commercial Bank Industries in Bangladesh

Md. Sayed UDDIN(Md. Sayed UDDIN ),Md. Atikur RAHAMAN(Md. Atikur RAHAMAN ),Wasib Bin LATIF(Wasib Bin LATIF ) 한국유통과학회 2023 The Journal of Asian Finance, Economics and Busine Vol.10 No.2

Since the banking industry relies so heavily on strong customer-staff interactions, measuring employee job satisfaction has become a critical problem. To achieve benefits for both individuals and organizations, it is crucial to foster and ensure employee job satisfaction. The main objective of this study is to determine the influencing factors of employees’ job satisfaction in commercial banks in Bangladesh. This study focused on some significant factors such as employee empowerment, job security, management support, and attractive compensation in an organization. In terms of research purpose, non-probability convenience sampling has been used, and the study is quantitative in nature. For data collection purposes, an online survey questionnaire was prepared based on previously published articles. The targeted population was the bank employees of commercial banks in Bangladesh where the final sample size was n = 200. For analyzing the collected data, SPSS 26.0 version has been used to test the study model and the proposed hypotheses. This study also shows that employee empowerment, job security, management support, and attractive compensation have positive and significant effects on employees’ job satisfaction at the workplace. Finally, this study has offered some extraordinary directions and implications for future research on commercial bank authorities in Bangladesh.

Separation axioms in (L,M)-fuzzy topology (L,M)-fuzzy convexity spaces

Osama Rashed Sayed,EL-Sayed EL-Sanousy,Yaser Hassanein Ragheb Sayed 원광대학교 기초자연과학연구소 2021 ANNALS OF FUZZY MATHEMATICS AND INFORMATICS Vol.21 No.1

In this paper, we dene r-L-fuzzy closed convex sets and r-L-fuzzy closed neighbourhoods in an (L, M)-fuzzy topology (L, M)-fuzzy convexity spaces. Also, r-L-fuzzy neighbourhood separation properties r- L-FNSi were studied where i = f0, 1, 2, 3, 4g. In addition, we also study the invariance or otherwise of these separation properties under subspace and product.

Alleviation of salt stress in  Triticum aestivum by biopriming with  Phanerochaete chrysosporium

Hanan El-Sayed Dief,El-Sayed A. Hashem,Salwa Fawzan,Ashraf S. A. El-Sayed 한국작물학회 2021 Journal of crop science and biotechnology Vol.24 No.1

Wheat is one of the most important cereals, vital basic crop in Egypt, covering approximately 32.6% of the total winter land. However, sensitivity to abiotic stress especially salinity is one the major current hurdles that reduce the global yield of this crop. Plant biopriming with fungi is the recent technology that might alleviate the salt stress eff ect. Thus, the objective of this work was to examine the eff ect of Triticum aestivum grains biopriming with Phanerochaete chrysosporium on the response of wheat to salt stress. From the physiological and biochemical parameters, biopriming of wheat grains with P. chrysosporium significantly alleviates the salt stress and markedly increases the growth parameters, photosynthetic pigments and osmolytes (soluble sugars, soluble protein and proline) contents. In addition, it alleviates the oxidative damage, as indicated by the lower accumulation of malondealdehyde and increasing the activity of antioxidant enzymes; superoxide dismutase, catalase, and ascorbate peroxidase in wheat seedlings. Results indicate the potential of using P. chrysosporium biopriming for reducing the deteriorating eff ects of salinity.

Surface enamel remineralization by biomimetic nano hydroxyapatite crystals and fluoride ions effects

Sayed Reza Shaffiey,Sayedeh Fatemeh Shaffiey 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.2

The use of specific remineralizing agents in toothpastes may help to prevent caries and treat human enamel. In this study,applied nanotechnologies were used to develop toothpastes with remineralizing properties. Hydroxyapatite nanocrystals, withsize, morphology, chemical composition comparable with that of enamel, were synthesized by wet chemical method. Theremineralizing effect was studied with a scanning electron microscopy (SEM) of enamel previously demineralized. The SEMimages demonstrated differences in micro surface at each step. The rate of remineralization seems to be compatible with thedevelopment of toothpastes with remineralizing effect. In conclusion, toothpaste containing nano-sized hydroxyapatite has thepotential to remineralize an incipient caries lesion. In addition, the use of fluoride in toothpaste contains nano- hydroxyapatitemight promote formation of nano fluoro hydroxyapatite in enamel surface.

Investigation of cake deposition on various parts of the surface of microfiltration membrane due to fouling

Sayed Siavash Madaeni,Masoud Rahimi,Mahdiah Abolhasani 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.1

The accumulation of deposited layer on membrane surface in cross-flow microfiltration was investigated. This study provides a basis for elucidation of the membrane segments with superior tendency for cake deposition due to fouling. A commercially available GVWP membrane was fouled with a colored (blue indigo suspension in water) feed. The deposition pattern or fouling tendency was obtained using a digital camera, scanning electron microscope (SEM)and image analysis. The effects of feed concentration, transmembrane pressure and cross-flow velocity on cake deposition were investigated. In the early stages of the filtration trials, cake deposition was increased from the commencement portion (feed inlet) towards the furthermost part (concentrate outlet) of the membrane surface. However, at the completion of filtration, no pronounced difference was realized between cake deposition in the median and end parts of the membrane. Computational fluid dynamics (CFD) modeling of the membrane was carried out to predict the fouling behavior in various segments of the membrane at different operating conditions. The results of CFD modeling are in acceptable agreement with the experimental data. Accomplishment of the membrane sections with higher tendency for accumulation of foulants may provide a basis for manipulation of conditions to diminish the buildup of fouling deposition in the proposed segments. This results in lower cake deposition on vital parts to minimize the overall fouling.

Effectiveness of meta-models for multi-objective optimization of centrifugal impeller

Sayed Ahmed Imran Bellary,Afzal Husain,Abdus Samad 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.12

The major issue of multiple fidelity based analysis and optimization of fluid machinery system depends upon the proper constructionof low fidelity model or meta-model. A low fidelity model uses responses obtained from a high fidelity model, and the meta-model isthen used to produce population of solutions required for evolutionary algorithm for multi-objective optimization. The Pareto-optimalfront which shows functional relationships among the multiple objectives can produce erroneous results if the low fidelity models are notwell-constructed. In the present research, response surface approximation and Kriging meta-models were evaluated for their effectivenessfor the application in the turbomachinery design and optimization. A high fidelity model such as CFD technique along with the metamodelswas used to obtain Pareto-optimal front via multi-objective genetic algorithm. A centrifugal impeller has been considered as casestudy to find relationship between two conflicting objectives, viz., hydraulic efficiency and head. Design variables from the impellergeometry have been chosen and the responses of the objective functions were evaluated through CFD analysis. The fidelity of each metamodelhas been discussed in context of their predictions in entire design space in general and near optimal region in particular. Exploitationof the multiple meta-models enhances the quality of multi-objective optimization and provides the information pertaining to fidelityof optimization model. It was observed that the Kriging meta-model was better suited for this type of problem as it involved less approximationerror in the Pareto-optimal front.

Prolonged semen incubation alters the biological characteristics of human spermatozoa

Sayed Abbas Datli Beigi,Mohammad Ali Khalili,Ali Nabi,Mohammad Hosseini,Abolghasem Abbasi Sarcheshmeh,Mojdeh Sabour The Korean Society for Reproductive Medicine 2022 Clinical and Experimental Reproductive Medicine Vol.49 No.4

Objective: The present study assessed the biological characteristics of human spermatozoa at different time intervals (0, 1, 1.5, and 2 hours) after incubation at 37℃. Methods: Twenty-five normozoospermic semen samples were incubated at 37℃. Incubation was performed at four time intervals of 0 (after liquefaction), 1, 1.5, and 2 hours. The samples were evaluated for sperm parameters at each time interval. Results: The rate of sperm progressive motility decreased at 1.5 hours compared to 0 hours as well as 2 hours compared to 1 hour and 0 hours. The rate of non-motile spermatozoa also decreased after 2 hours compared to after 0 hours. No significant changes were observed in sperm viability (p=0.98) and non- progressive motility (p=0.48) at any time intervals. Abnormal sperm morphology increased at 1.5 hours of incubation time (p<0.001). No significant changes were observed in DNA fragmentation at 1 hour compared to 0 hours (median [interquartile range]: 19.5 [4] vs. 19 [4]), as well as at 1.5 hours compared to 1 hour (20 [5]). However, a significant increase in DNA fragmentation was observed at 1.5 hours compared to 0 hours. The mitochondrial membrane potential decreased remarkably after 1 hour of incubation time. No significant differences were observed in the acrosome reaction or malonaldehyde levels at any time point (p=0.34 and p=0.98, respectively). Conclusion: The incubation of normozoospermic samples before use in assisted reproductive technology should be less than 1.5 hours to minimize the destructive effects of prolonged incubation time on general and specific sperm parameters.

Centrifugal Impeller Blade Shape Optimization Through Numerical Modeling

Sayed Ahmed Imran Bellary,Abdus Samad 한국유체기계학회 2016 International journal of fluid machinery and syste Vol.9 No.4

Surrogate model based shape optimization methodology to enhance performance of a centrifugal pump has been implemented in this work. Design variables, such as blade number and blade angles defining the pump impeller blade shape were selected and a three-level full factorial design approach was used for efficiency enhancement. A threedimensional simulation using Reynolds-averaged Navier Stokes (RANS) equations for the performance analysis was carried out after designing the geometries of the impellers at the design points. Standard k-ε turbulence model was used for steady incompressible flow simulations. The optimized impeller incurred lower losses by shifting the trailing edge towards the impeller pressure side. It is observed that the surrogates are problem dependent and most accurate surrogate does not deliver the best design always.

Underutilized Crops

Sayed Azam-Ali,Max Herriman,Giva Kuppusamy,Kumar Katya,Hyeonho Yun,Sungchul C. Bai 한국수산과학회 양식분과 2014 한국수산과학회 양식분과 학술대회 Vol.2014 No.7