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  Subjects -> SCIENCES: COMPREHENSIVE WORKS (Total: 374 journals)
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Momona Ethiopian Journal of Science
Number of Followers: 5  

  This is an Open Access Journal Open Access journal
ISSN (Print) 2073-073X - ISSN (Online) 2220-184X
Published by African Journals Online Homepage  [261 journals]
  • Coating Properties of Alkyd Resin, Epoxy Resins and Polyurethane Based
           Nanocomposites: A Review

    • Authors: Ikhazuagbe H Ifijen, Nyaknno U Udokpoh, Gregory E Onaiwu, Eribe M Jonathan, Esther U Ikhuoria
      Pages: 1 - 31
      Abstract: The uniqueness of alkyd resin, epoxy resin, and polyurethane nanocomposites has brought prominent recognition to the field of heavy-duty coating materials. This is expected due to the collaborative features of nano-sized materials such as the high surface area to volume ratio, great functionality per-unit space, extremely small sizes with high density, and that of alkyd resin, epoxy resin, and polyurethane (biodegradability, great gloss retention, adaptability, flexibility, durability, good drying properties, and weathering resistance). The objective of this review was to analyze the extent and currency of research and the development of alkyd, epoxy, and polyurethane nanocomposites in coating applications. Some of the several types of modifications discussed in this review are the incorporation of varying types of nanoclay and metal nanoparticles materials into alkyd resins, the incorporation of carbon nanotubes, MGel-graphene oxide (GO)/gelatin (MGel), Ni (II) Complex-Zeolite and starch-modified nano-ZnO into epoxy resin and the incorporation of (Rb2Co(H2P2O7)2.2H2O), modified nanoparticles of ZnO, diminished graphene oxide (dGO) into polyurethane and their effects on coating applications. The various studied modifications resulted in nanocomposite end-products with much improved properties. However, there are several challenges to the development of nanocomposites that need urgent attention. Some of the challenges discussed are the difficulty involved in transforming fabricated nanocomposites from laboratory to commercialized scale, the capital-intensive nature of synthesizing large nanopowder, etc.
      PubDate: 2022-10-22
      DOI: 10.4314/mejs.v14i1.
      Issue No: Vol. 14, No. 1 (2022)
       
  • Pumped Hydro- Energy Storage System in Ethiopia: Challenges and
           Opportunities

    • Authors: Dawit Abay Tesfamariam, Asfafaw T Hailesialssie, Muyiwa S Adaramola
      Pages: 32 - 47
      Abstract: The shares of RE sources are rising because of global warming concerns and the depletion of fossil fuels. However, due to its intermittent nature sustainable power supply depends on the proper energy mix and energy storage. By 2025, Ethiopia has planned to export 24 TWh of energy. Accordingly, its power generation is incorporating different RE sources dominated by hydropower. This paper has reviewed the global up-to-date status of PHES and Ethiopia’s current energy situation and potential PHES. The objective of this paper is to show Ethiopia’s potential for PHES and serve as a “Green Battery’’ for the East Africa Power Pool (EAPP). The review shows that PHES can easily replace backup diesel generators used as a backup during a blackout.  Moreover, it showed the Policy barrier for energy storage in the Ethiopian National Energy Policy proclaimed in 1994 and its 2012 updated policy. Thus, Ethiopia’s energy policies need to consider PHES in its energy storage strategy while expanding its generation.  
      PubDate: 2022-10-22
      DOI: 10.4314/mejs.v14i1.
      Issue No: Vol. 14, No. 1 (2022)
       
  • Investigations on Tribological Performance of Sisal Fiber Reinforced
           Polypropylene Composites

    • Authors: Temesgen Berhanu Yallew, Mulubrhan Mokonen, Tsegay Tesfay
      Pages: 48 - 61
      Abstract: There has been an increase in global interest in the development of natural fiber-reinforced composites. Natural fibers extracted from plants are receiving more attention from researchers, scientists, and academics due to their use in polymer composites and their environmentally friendly nature and sustainability. Recently, sisal fiber-reinforced polymer composites have been used in a variety of engineering applications like aerospace, automotive, marine, and other mechanical components, where tribological properties are of prime consideration. In this endeavor, experiments have been conducted to determine the tribological behavior of sisal fiber-reinforced polypropylene composite. Pin-on-disc wear tests have been conducted on specimens at various combinations of sliding velocities (1-3 m/s), sliding distances (1000-3000 m), and applying normal loads (10-30N). Using Response Surface Method (RSM), a mathematical model has been developed to predict the friction and wear loss behavior of the sisal fiber-reinforced polypropylene (PP) composites. To ensure the validity of the developed model, the Analysis of variance (ANOVA) technique has been applied. Important process parameters and material variables that exert significant influence on sliding wear loss have been determined with the help of systematic experimentation. Scanning Electron Microscope (SEM) has been used to probe morphological observation of the worn surface. Results revealed that the highest volumetric wear loss has been recorded at the highest values of applied load and this has been supported by the morphological study demonstrated by the scratches, as well as wider and deeper plowing marks on the worn surfaces.
      PubDate: 2022-10-22
      DOI: 10.4314/mejs.v14i1.
      Issue No: Vol. 14, No. 1 (2022)
       
  • Improved Receiver Design Concepts for Parabolic Dish Direct Solar Cooking
           Systems

    • Authors: Austin P Theu, Cuthbert Z M Kimambo
      Pages: 62 - 80
      Abstract: In developing countries, solar cooking technology is considered one of the key measures in dealing with deforestation and environmental pollution.  However, their adoption and utilization have been insignificant due to social, cultural, and technical challenges, among others. For parabolic dish direct solar cookers, one of the critical and most important components of the system is a receiver since its performance greatly affects the entire system. This paper presents part of the findings of the study which investigated the prospects of improving the technical performance of parabolic dish direct solar cooking systems by focusing on the identification of prospective heat loss reduction mechanisms on the receiver. The study identified the Insulated (IR), Air-filled (AFR), and Oil-filled (OFR) receivers with Base Circular Rings (BCR) as alternatives to the Conventional Receiver (CR) System. Tests were conducted using procedures and protocols given by the American Society for Agricultural Engineers (ASAE). The test results showed that the average power developed by the systems was 185 W for the IRBCR system, 90 W for the OFRBCR system, 92 W for the AFRBCR system, and 118 W for the CR system. The standardized cooking power for a temperature difference of 50oC, PS (50), was 291 W for the IRBCR system, 11 W for the OFRBCR system, 272 W for the AFRBCR system, and 142 W for the CR system. The results further revealed that the overall efficiencies were 23% for the IRBCR system, 9% for the OFRBCR system, 12% for the AFRBCR system, and 18% for the CR system. The receiver efficiencies were found to be 27% for a system with IR, 11% for a system with OFR, 14% for a system with AFR, and 21% for a system with CR. The study concluded that the performance improved when the system with the IR was used while the magnitudes of the performance parameters of the AFR and OFR were lower than the CR system.
      PubDate: 2022-10-22
      DOI: 10.4314/mejs.v14i1.
      Issue No: Vol. 14, No. 1 (2022)
       
  • Measurement of Radionuclides Concentration and Radiological Health
           Assessment of Some Selected Table Waters in Ilorin

    • Authors: Orosun M M, Fabowale P A, Akinyose F C, Oluyide S F, Umakha M, Olaniyan T, Oduh V O
      Pages: 81 - 94
      Abstract: In order to ensure radiation monitoring and protection, an investigation and assessment of radiological risks that may be associated with the consumption of table waters commonly consumed in Ilorin, Nigeria, was carried out. The activity concentration level of 238U, 232Th, and 40K was determined using thallium activated 3˝×3˝ [NaI(TI)] detector connected to ORTEC 456 amplifier. The radiological risks due to the consumption of the samples were then estimated. The highest annual effective dose (AED) values were obtained from VW and the minimum was obtained from UW water. The AED decreases in the order VW>HW>IW>MW>DW>UW. This implies that VW water constitutes more radiation exposure followed by HW, IW, MW, DW, and then UW Water. The values estimated for MW, DW, and UW water were all lower than the world average value of 1 mSv/y and hence pose no serious radiation hazard. While the values estimated for VW, IW, and HW waters were slightly higher than the recommended threshold value, suggesting a possible risk of radiation exposure to customers. The Excess Lifetime Cancer Risks corroborated the findings of the AED, implying that the probability of developing cancer is high for most of the water samples. Since the values of the estimated hazard parameters were mostly higher than the recommended limits for all age groups, it is recommended that public water system should be monitored and efforts should be made to educate and enlighten the public on radiation exposure, its health effects, and remedial actions necessary to reduce radionuclides concentration in drinking water.
      PubDate: 2022-10-22
      DOI: 10.4314/mejs.v14i1.
      Issue No: Vol. 14, No. 1 (2022)
       
  • Age and growth of gilthead sea bream (Sparus aurata Linnaeus, 1758) from
           Northern Aegean Sea (Turkey)

    • Authors: Özgür Cengiz
      Pages: 95 - 106
      Abstract: The age and growth of gilthead sea bream (Sparus aurata Linnaeus, 1758) were studied in the present study. A total of 126 specimens were collected from commercial fishmongers during the period between January 2015 and December 2015 from the northern Aegean coasts of Turkey. Fork length and the total weight of aged specimens ranged from 29.5 to 48.0 cm and from 425.00 to 2100.00 g, with a mean of 38.5 cm and 101.23 g, respectively. The length-weight relationship was estimated as W = 0.0053FL3.03 (R2 = 0.95). The von Bertalanffy growth equations were computed as 𝐿∞ = 52.8 cm, k = 0.29 year-1, 𝑡0 = -1.25 year for all samples. The growth performance index (𝛷′) was found as 2.91. There is no study on the biology of the species for the northern Aegean Sea. Therefore, this study provides valuable information for the species in this area.
      PubDate: 2022-10-22
      DOI: 10.4314/mejs.v14i1.
      Issue No: Vol. 14, No. 1 (2022)
       
 
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