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Analysis of Flow-Induced Vibrations in a Heat Exchanger Tube Bundle Subjected to Variable Tube Flow Velocity

Hafeez Akmal, Khushnood Shahab, Nizam Luqman Ahmad, Usman Muhammad, Rashid Muhammad Mohsin, Khan Hassan Farid, Ayub Muhammad, Qadir Adeel

Advances in Science and Technology. Research Journal

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2023

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Vol. 17, no 2

279--288

EN

Tube bundles of shell and tube-type heat exchangers often fail because of vibrations produced in tubes due to flow. The turbulence in the flow is the primary cause of vibrations in the tubes. In this study, a tube positioned in the third row of the tube bundle was considered to determine the vibrational response of the heat exchanger tubes. The tube bundle was parallelly arranged in a triangular (60°) configuration having a pitch to diameter (P/D) ratio of 1.44. The internal tube flow velocity ranges from 0 to 0.371 m/s and the shell side velocity ranges from 0.5 m/s to 2 m/s. The experimentation shows that the amplitude of vibration without flow inside the tube is less as compared to the amplitude with the flow. Furthermore, as the velocity of internal tube flow escalates; the amplitude of tube vibrations tends to escalate as well even when the shell side flow velocity is kept constant. The data points from experiments tend to reside in the unstable region of the stability map and particularly on the map’s left side, although the tube shows stable vibration behaviour as confirmed by the experimental results. Thus, further, development can be done by modifying the theoretical models to predict the realistic stability behaviour of tubes with internal tube flow.

2

Reuse in Contemporary Software Engineering Practices – An Exploratory Case Study in A Medium-sized Company

Chen Xingru, Badampudi Deepika, Usman Muhammad

e-Informatica Software Engineering Journal

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2022

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Vol. 16, nr 1

art. no. 220110

EN

Background: Software practice is evolving with changing technologies and practices such as InnerSource, DevOps, and microservices. It is important to investigate the impact of contemporary software engineering (SE) practices on software reuse. Aim: This study aims to characterize software reuse in contemporary SE practices and investigate its implications in terms of costs, benefits, challenges, and potential improvements in a medium-sized company. Method: We performed an exploratory case study by conducting interviews, group discussions, and reviewing company documentation to investigate software reuse in the context of contemporary SE practices in the case company. Results: The results indicate that the development for reuse in contemporary SE practices incurs additional coordination, among other costs. Development with reuse led to relatively fewer additional costs and resulted in several benefits such as better product quality and less development and delivery time. Ownership of reusable assets is challenging in contemporary SE practice. InnerSource practices may help mitigate the top perceived challenges: discoverability and ownership of the reusable assets, knowledge sharing and reuse measurement. Conclusion: Reuse in contemporary SE practices is not without additional costs and challenges. However, the practitioners perceive costs as investments that benefit the company in the long run.

3

Reporting Consent, Anonymity and Confidentiality Procedures Adopted in Empirical Studies Using Human Participants

Badampudi Deepika, Fotrousi Farnaz, Cartaxo Bruno, Usman Muhammad

e-Informatica Software Engineering Journal

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2022

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Vol. 16, nr 1

art. no. 220109

EN

Background: Empirical studies involving human participants need to follow procedures to avoid causing harm to the subjects. However, it is not always clear how researchers should report these procedures. Aim: This study investigates how researchers report ethical issues in the software engineering journal publications, particularly informed consent, confidentiality, and anonymity. Method: We conducted a literature review to understand the reporting of ethical issues in software engineering journals. In addition, in a workshop, we discussed the importance of reporting the different ethical issues. Results: The results indicate that 49 out of 95 studies reported some ethical issues. Only six studies discussed all three ethical issues. The subjects were mainly informed about the study purpose and procedure. There are limited discussions on how the subjects were informed about the risks involved in the study. Studies reported on how authors ensured confidentiality have also discussed anonymity in most cases. The results of the workshop discussion indicate that reporting ethical issues is important to improve the reliability of the research results. We propose a checklist based on the literature review, which we validated through a workshop. Conclusion: The checklist proposed in this paper is a step towards enhancing ethical reporting in software engineering research.

4

Numerical analysis of the compositional graded quaternary barrier AlGaN-based ultraviolet-C light-emitting diode

Malik S., Usman Muhammad, Hussain M., Munsif M., Khan S., Rasheed S., Ali S.

Opto-Electronics Review

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2021

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Vol. 29, No. 3

80--84

EN

The compositional graded quaternary barriers (GQBs) instead of ternary/conventional quantum barriers (QBs) have been used to numerically enhance the efficiency of AlGaN-based ultraviolet light-emitting diode (LED). The performance of LED with GQBs is examined through carrier concentrations, energy band diagrams, radiative recombination, electron and hole flux, internal quantum efficiency (IQE), and emission spectrum. As a function of the operating current density, a considerable reduction in efficiency droop is observed in the device with composition-graded quaternary barriers as compared to the conventional structure. The efficiency droop in case of a conventional LED is ~77% which decreased to ~33% in case of the proposed structure. Moreover, the concentration of electrons and holes across the active region in case of the proposed structure is increased to ~156% and ~44%, respectively.

5

Design of compact ultra-wideband monopole semi-circular patch antenna for 5G wireless communication networks

Usman Muhammad, Alsaif Haitham, Chughtai Muhammad Tajammal, Asif Sajid Mehmood

Przegląd Elektrotechniczny

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2019

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R. 95, nr 4

223--226

EN

This paper presents , a novel design of semi-circular patch antenna for Ultra-wideband (UWB) wireless communication systems. The monopole is compact with structure size of 25x25 mm2 and thickness of 1.6 mm. It has been fabricated on a FR-4 substrate with relative permittivity of Ɛr=4.4. The designed antenna has an ultrawide bandwidth, from 3GHz to 11.5 GHz based on -10dB criteria, which covers the entire UWB allocated by FCC for such applications. Also, the design shows high performance in terms of impedance match between feeding line and radiator. Radiation pattern results have been studied at all resonant frequencies (3 GHz to 11.5 GHz) and they have almost omni directional pattern. The monopole has been fabricated and experimentally measured for verification and both simulation and experimental results show good agreement. The overall antenna gain is 1.8 dBi with bandwidth of 125% for UWB. Therefore, the simulated and measured results confirm that the antenna satisfies the requirements for ultra-wideband applications. Design, simulation, and optimization process have been completed using industrial simulation software called High Frequency Structural Simulator (HFSS).

PL

W artykule opisano projekt półokrągłej anteny szerokopasmowej do systemów WiFi. Antena ma powierzchnię 25x25 mm i grubość 1.6 mm. Psamo częstotliwościowe antent jest od 3 GHz do 11.5 GHz. Symulacje I pomiary potwierdziły przydatność tej antny do pasma UWB.

6

Investigation of the Effects of the Incident Flow Angle on Vibration Behavior in Heat Exchanger Tube Bundle

Usman Muhammad, Khushnood Shahab, Nizam Luqman Ahmad, Tanveer Waqas, Shafi Ahmad, Ayub Muhammad, Khan Hassan Farid, Rustam Behzad

Advances in Science and Technology. Research Journal

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2019

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Vol. 13, no 2

186--194

EN

An experimental study on the incident flow angle effects on the vibration behavior was carried out on aluminum tube in parallel triangular tube bundle with P/D ratio of 1.375. Fluid elastic instability is the most fatal mechanism from all the vibration mechanisms and therefore must be dealt with a lot of attention. Experiments were performed on low speed water tunnel with the velocity of water ranges from 0.3 m/s to 0.7 m/s. The experiments were designed in a unique way to study the effects of incident flow angle on the vibration behavior. The monitored tube was mounted flexibly in an array of rigid tubes. The experiments were conducted on a flexible tube for different velocities ranging from 0.3 m/s to 0.7 m/s with different array rotated angles (0 to 90 degrees). It was observed that the vibration level was significantly high at 75 degree configuration as compared to other rotated angle configurations. It was also observed that the damping response is dispersed with all positive values, indicating that there is no instability in the tube.