Research Articles [CoCSE]
https://dspace.nm-aist.ac.tz/handle/20.500.12479/35
2024-03-28T20:53:02ZSuitability of Vermiculite and Rice Husk Ash as Raw Materials for Production of Ceramic Tiles
https://dspace.nm-aist.ac.tz/handle/20.500.12479/2473
Suitability of Vermiculite and Rice Husk Ash as Raw Materials for Production of Ceramic Tiles
Abeid, Said; Park, Seungyong
The challenging issues in ceramic tiles are low mechanical strength, thermal discomfort and high production costs. And in most efforts to improve strength, emphasis has been placed on minimization of quartz content in the ceramic tiles formula. This is due to β-α phase inversion of quartz which occurs at 573°C during cooling resulting to the development of stresses which initiate fracture and affects the strength of the final body. The objective of this work was to evaluate the possibility of using vermiculite and rice husk ash (RHA) in the composition of ceramic tile body. Initially, a typical ceramic body composed of the mixture of vermiculite and RHA batched with clay, feldspar, quartz and kaolin was prepared. Ceramic bodies were then obtained from this ceramic mixture by pressing samples at a forming pressure of 35MPa. These bodies were then fired at 1180°C in a laboratory furnace and finally the changes in the physical and mechanical properties caused by the introduction of vermiculite and RHA were tested and evaluated. The chemical composition of the raw samples was analyzed by X-ray fluorescence (XRF) while the phase composition was investigated using X-ray diffraction (XRD). The morphology of the powdered samples was studied by using Scanning electron microscopy (SEM). The bulk density and open porosity of the sintered ceramic bodies were evaluated using Archimedes ‘principle while the flexural rupture strength was determined by the three point bending test method. The major chemical compounds in vermiculite raw sample were SiO2, Al2O3 and Fe2O3 while RHA sample was found to contain mainly SiO2. From the XRD analysis, vermiculite sample had crystalline vermiculite while RHA sample had amorphous silica at low temperature below 900°C and crystallized (tridymite) above 900°C. The results from physical and mechanical properties tests show that with addition of vermiculite and RHA, the percentage of porosity, water absorption and linear shrinkage were increasing while the bulk density and bending strength of the fired ceramic bodies decreased. Among the studied compositions tile bodies made from a blend containing 20% wt. vermiculite and 5% wt. RHA were found to have the best properties for ceramic tiles applications. For this combination the percentage of porosity, water absorption and linear shrinkage were 12.08%, 7.60% and 3.29% while the bulk density and bending strength were 1.88 g/cm3 and 18.84 MPa respectively. These values were close to the required standards of wall and floor tiles.
This research article was published in the International Journal of Materials Science and Applications, Volume 7, Issue 2, 2018
2018-02-03T00:00:00ZComputer Science Education in Selected Countries from Sub-Saharan Africa
https://dspace.nm-aist.ac.tz/handle/20.500.12479/2466
Computer Science Education in Selected Countries from Sub-Saharan Africa
Bainomugisha, Engineer; Bradshaw, Karen; Ujakpa, Martin; Nakatumba-Nabende, Joyce; Nderu, Lawrence; Mduma, Neema; Kihoza, Patrick; Irungu, Annette
Computer Science education in sub-Saharan Africa has
evolved over the past decades. The number of institutions
offering distinct undergraduate programs has grown, thus
increasing the number of students enrolling in the computer
science discipline. Several computer science degree programs
have emerged with one of the objectives being to satisfy the
growing demand for local talent and skills. In this paper, we
provide a snapshot of the evolution of undergraduate computer
science education in selected countries in Sub-Saharan Africa
over the past 20+ years and an overview of the developments
in computer science education and observed trends. The
setup of educational institutions in Africa and the operational
context requires unique modalities for the design and delivery
of computer science education that meets the demands of the
industry, amongst others. This paper provides insights into
the best practices in the computer science curricula in the
selected countries, as well as an overview of the pedagogical
and delivery approaches to computer science education. The
paper highlights case studies from institutions in the selected
countries, namely Uganda, South Africa, Ghana, Tanzania,
and Kenya with a consolidated summary of the current and
emerging challenges and opportunities in all these countries.
The paper concludes by providing persectives on the future
landscape of computer science in Sub-Saharan Africa.
This research article was published in ACM Inroads, Volume 15, Issue 1, 2024
2024-02-20T00:00:00ZModeling the SBC Tanzania Production-Distribution Logistics Network
https://dspace.nm-aist.ac.tz/handle/20.500.12479/2445
Modeling the SBC Tanzania Production-Distribution Logistics Network
Dzupire, Nelson; Nkansah-Gyekye, Yaw; Mirau, Silas
The increase in customer expectation in terms of cost and services rendered, coupled with competitive business environment and uncertainty in cost of raw materials have posed challenges on effective supply chain engineering making it essential to do cost-benefit analysis before making final decisions on production, distribution logistics. This paper provides a conceptual model that provide guidance in supply chain decision making for business expansion. It presents a mathematical model for production-distribution of an integrated supply chain derived from current operations of SBC Tanzania Ltd which is a major supply chain that manages products' distribution in whole of Tanzania. In addition to finding the optimal cost, we also carried out a sensitivity analysis on the model so as to find ways in which the company can expand at optimal cost, while meeting customers' demands. Genetic algorithms is used to run the simulation for their efficient in solving combinatorial problems.
A research article was submitted to Mathematical Theory and Modeling Volume 4
2017-07-01T00:00:00ZMathematical modeling of COVID-19 transmission dynamics between healthcare workers and community
https://dspace.nm-aist.ac.tz/handle/20.500.12479/2444
Mathematical modeling of COVID-19 transmission dynamics between healthcare workers and community
Masandawa, Lemjini; Mirau, Silas; Mbalawata, Isambi
Corona-virus disease 2019 (COVID-19) is an infectious disease that has affected different groups of humankind
such as farmers, soldiers, drivers, educators, students, healthcare workers and many others. The transmission
rate of the disease varies from one group to another depending on the contact rate. Healthcare workers are
at a high risk of contracting the disease due to the high contact rate with patients. So far, there exists no
mathematical model which combines both public control measures (as a parameter) and healthcare workers
(as an independent compartment). Combining these two in a given mathematical model is very important
because healthcare workers are protected through effective use of personal protective equipment, and control
measures help to minimize the spread of COVID-19 in the community. This paper presents a mathematical
model named SWE 𝐼𝑠
𝐼𝑎HR; susceptible individuals (S), healthcare workers (W), exposed (E), symptomatic
infectious (𝐼𝑠
), asymptomatic infectious (𝐼𝑎
), hospitalized (H), recovered (R). The value of basic reproduction
number 𝑅0
for all parameters in this study is 2.8540. In the absence of personal protective equipment 𝜉 and
control measure in the public 𝜃, the value of 𝑅0 ≈ 4.6047 which implies the presence of the disease. When 𝜃
and 𝜉 were introduced in the model, basic reproduction number is reduced to 0.4606, indicating the absence
of disease in the community. Numerical solutions are simulated by using Runge–Kutta fourth-order method.
Sensitivity analysis is performed to presents the most significant parameter. Furthermore, identifiability of
model parameters is done using the least square method. The results indicated that protection of healthcare
workers can be achieved through effective use of personal protective equipment by healthcare workers and
minimization of transmission of COVID-19 in the general public by the implementation of control measures.
Generally, this paper emphasizes the importance of using protective measures.
A research article was submitted to Results in Physics Volume 29, October 2021
2021-10-01T00:00:00Z