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.

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.

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.

PWM Control Techniques for Single-Phase Multilevel Inverter Based Controlled DC Cells

Sayed, Mahmoud A.,Ahmed, Mahrous,Elsheikh, Maha G.,Orabi, Mohamed The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.2

This paper presents a single-phase five-level inverter controlled by two novel pulse width modulation (PWM) switching techniques. The proposed PWM techniques are designed based on minimum switching power loss and minimum total harmonic distortion (THD). In a single-phase five-level inverter employing six switches, the first proposed PWM technique requires four switches to operate at switching frequency and two other switches to operate at line frequency. The second proposed PWM technique requires only two switches to operate at switching frequency and the rest of the switches to operate at line frequency. Compared with conventional PWM techniques for single-phase five-level inverters, the proposed PWM techniques offer high efficiency and low harmonic components in the output voltage. The validity of the proposed PWM switching techniques in controlling single-phase five-level inverters to regulate load voltage is verified experimentally using a 100 V, 500 W laboratory prototype controlled by dspace 1103.

Stiffened Trapezoidally-Corrugated Plates in Open-Section Shear Walls

Sayed Behzad Talaeitaba,Farshid Khamseh,Mohammad Ebrahim Torki 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.5

The enhancement in the nonlinear mechanical behavior of steel shear walls under the eff ect of perforated trapezoidal corrugated steel plates is addressed herein. The shear wall in conjunction with the trapezoidal plates was simulated with a 1/2 geometric scale in ABAQUS subjected to lateral loads through a Rik’s procedure. Each model was fi rst exposed to opening excised at the middle and corner doors as well as at the window places to evaluate the reduction level in the stress bearing capacity. Then, stiff eners in the form of box and plate sections were utilized in each case, where the latter proved more effi cacious in terms of stress level and energy absorption increase. The eff ect of stiff ness, refl ected through that of the thickness of stiff eners, was then evaluated in every confi guration. This eff ect was quantifi ed through the limit load and energy absorption parameter, which was observed to be signifi cant in all cases. The two parameters reached, respectively, 106 and 166% for the middle door, 100 and 151% for the corner door, and 102 and 132% for the window openings (with respect to those for the solid wall). Ultimately, the optimization factor was evaluated, representing the ratio of the stiff ener cross section to the opening area that corresponds to strength and energy absorption equivalent with those in the solid wall.

Computational fluid dynamics modeling of hydrogen production in an autothermal reactor: Effect of different thermal conditions

Sayed Reza Shabanian,Masoud Rahimi,Amin Amiri,Shahram Sharifnia,Ammar Abdulaziz Alsairafi,정재학,김우경 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.11

A numerical model was developed and validated to simulate and improve the reforming efficiency of methane to syngas (CO+H2) in an autothermal reactor. This work was undertaken in a 0.8 cm diameter and 30 cm length quartz tubular reactor. The exhaust gas from combustion at the bottom of reactor was passed over a Ru/γ-Al2O3 catalyst bed. The Eddy Dissipation Concept (EDC) model for turbulence-chemistry interaction in combination with a modified standard k-ε model for turbulence and a reaction mechanism with 23 species and 39 elementary reactions were considered in the combustion model. The pre-exponential factors and activation energy values for the catalyst (Ru) were obtained by using the experimental results. The percentage of difference between the predicted and measured mole fractions of the major species in the exhaust gas from combustion and catalyst bed zones was less than 5.02% and 7.73%,respectively. In addition, the results showed that the reforming efficiency, based on hydrogen yield, was increased with increase in catalyst bed’s thermal conductivity. Moreover, an enhancement of 4.34% in the reforming efficiency was obtained with increase in the catalyst bed wall heat flux from 0.5 to 2.0 kW/m2.

Adaptive Resource Allocation in Mobile Ad Hoc Computational Grids

Sayed Chhattan Shah,Wan Sik Choi 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10

Two key components contribute to task completion time: execution cost and communication cost. The communication cost is induced by data transfers from one task to another residing on separate nodes. To reduce communication cost, interdependent tasks are allocated to closely located nodes. However, once tasks are allocated, nodes can move within a Grid. The node mobility within a Grid can increase communication distance and may result into multi-hop communication between nodes executing dependent tasks. The multi-hop communication increases communication cost and thus task completion time. In order to avoid multi-hop communication between dependent tasks, we have developed an adaptive and distance-based resource allocation scheme which exploits the characteristics of an application and nodes, and applies migration heuristics to reduce communication cost. The scheme is validated in a simulated environment using various workloads and parameters.

High surface area-activated carbon from Glycyrrhiza glabra residue by ZnCl2 activation for removal of Pb(II) and Ni(II) from water samples

Sayed Zia Mohammadi,Hooshang Hamidian,Zahra Moeinadini 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.6

A high-surface-area activated carbon was prepared by chemical activation of Glycyrrhiza glabra residuewith ZnCl2 as active agent. Then, the adsorption behavior of Pb(II) and Ni(II) ion onto produced activatedcarbon has been studied. The experimental data were fitted to various isotherm models. According toLangmuir model, the maximum adsorption capacity of Pb(II) and Ni(II) ions were found to be 200 and166.7 mg g-1, respectively, at room temperature. Kinetic studies showed the adsorption processfollowed pseudo second-order rate model. High values of intra-particle rate constants calculated showsthe high tendency of activated carbon for removal of Pb(II) and Ni(II) ions.

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.