University of Dar es Salaam Research Repository

The Research Repository of University of Dar es Salaam (UDSM) is the online/digital collection of research and publications from University of Dar es Salaam. The Research Repository UDSM collects preserves and makes available publications and conference papers, journals, books and other outputs created by UDSM researchers. Participation in UDSM Research Repository helps to ensure that publications are more visible and highly cited.

 

Recent Submissions

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Power/Hydrogen Optimal Stochastic Scheduling Considering Frequency Regulation Markets
(IEEE, 2022-11-28) Amirhossein, Khazali; Roozbeh, Torkzadeh; Chamorro, H. R.; Peter, Makolo; Vijay, K. Soo
This paper presents a novel optimal offering framework to incorporate hydrogen system potential for frequency regulation goals. Furthermore, the presented model considers the possibility of submitting bids for a day-ahead hydrogen market. To harness the uncertainty of AGC (automatic generation control) signals, the problem is formulated as a two-level stochastic programming approach where in the first stage, the day-ahead market is cleared, and in the second stage, which is related to the real-time market, the up and down capacities of the hydrogen system are determined for each hour. The results indicate that the presented model is able to maximize the income of the integrated power/hydrogen system by determining the optimal scheduling of each of these devices and increase the income of the system by taking advantage of the frequency regulation market and dedicating a capacity of the electrolyzer and fuel cell to this market.
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Flexible Synthetic Inertia Optimization in Modern Power Systems
(IMDB, 2024-01-26) Makolo, Peter; Zamora, Ramon; Perera, Uvini; Lie, Tek Tjing
Increasing the replacement of conventional synchronous machines by non-synchronous renewable machines reduces the conventional synchronous generator (SG) inertia in the modern network. Synthetic inertia (SI) control topologies to provide frequency support are becoming a new frequency control tactic in new networks. However, the participation of SI in the market of RES-rich networks to provide instant frequency support when required proposes an increase in the overall marginal operation cost of contemporary networks. Consequently, depreciation of operation costs by optimizing the required SI in the network is inevitable. Therefore, this paper proposes a flexible SI optimization method. The algorithm developed in the proposed method minimizes the operation cost of the network by giving flexible SI at a given SG inertia and different sizes of contingency events. The proposed method uses Box’s evolutionary optimizer with a self-tuning capability of the SI control parameters. The proposed method is validated using the modified New England 39-bus network. The results show that provided SIs support the available SG inertia to reduce the RoCoF values and maintain them within acceptable limits to increase the network’s resilience.
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Kavenuke, P., & Kinyota, M. (2023). Gender Inequalities in Higher Education in Tanzania: Investigating theInfluence of Parents’ Socio-Economic Status. Paper in Education and Development, 41(2), 39-57.
(UDSM, 2023-12-31) KINYOTA MJEGE; PATRICK SEVERINE KAVENUKE
This study investigated the extent to which gender inequality manifests in higher education in Tanzania. Furthermore, through a gendered lens, the study investigated the influence of parents’ socioeconomic status on gender inequality among students who major in STEM and teacher education programmes. The study used a sample of 1714 students across four higher education institutions. It was found that gender is an aspect that forms inequality. For instance, the study revealed that gender differences were reflected in our sample, where female students were underrepresented in both STEM majors and teacher education majors. Also, parents’ education, occupation, educational background (in STEM), and income are some of the socioeconomic statuses that reinforce gender inequality. Finally, the implications for future research and policy are discussed.
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Nonlinear anisotropic diffusion methods for image denoising problems: Challenges and future research opportunities
(Elsevier, 2023-03-01) Maiseli, Baraka
Nonlinear anisotropic diffusion has attracted a great deal of attention for its ability to simultaneously remove noise and preserve semantic image features. This ability favors several image processing and computer vision applications, including noise removal in medical and scientific images that contain critical features (textures, edges, and contours). Despite their promising performance, methods based on nonlinear anisotropic diffusion suffer from practical limitations that have been lightly discussed in the literature. Our work surfaces these limitations as an attempt to create future research opportunities. In addition, we have proposed a diffusion-driven method that generates superior results compared with classical methods, including the popular Perona–Malik formulation. The proposed method embeds a kernel that properly guides the diffusion process across image regions. Experimental results show that our kernel encourages effective noise removal and ensures preservation of significant image features. We have provided potential research problems to further expand the current results.
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Overview of optimal operations of renewable energy power systems in microgrid and virtual power plants
(Elsevier, 2023-11-23) Mushi, Aviti Thadei; Mnkeni, Godwin Elinazi; Justo, Jackson John; Mwasilu, Francis Avilus; Mwinyiwiwa, Bakari Mohamedi Mfaume
Renewable energy sources (RES) in microgrids and virtual power plants are considered to be the backbone of these power systems. The RESs have been shown recently to reduce the costs per kWh by 85% in South Africa, some viability to electrify airport in Tanzania [1,2], and rural villages [2 4] Some reported case studies show that investing in the same project five years later has a great impact on running costs [5] and can improve electrification rates as some other technologies can [6 8]. The RESs in microgrid configuration are considered to be the most costeffective power solutions to meet the load requirements of people that live in rural areas [9,10].