Optimisation of Operational Parameters of a Spiral Classifier Using Design of Experiment (DOE)

Abstract Classifying Mn Ore to improve upon the grade and the properties has become a crucial activity for the Mn industry since it increases the market value of the ore. Ghana Manganese Company (GMC) has renovated their oxide washing plant by integrating it with a spiral classifier to make a batch system operating process. Particle size of <3.35mm (Mn grade of 43-47%) obtained from the primary section of the plant served as feed to the classifier and with the plant condition (i.e. at 60 min washing time, 30 rev/min speed of spirals and feed tonnage of 6 t), Mn grade of 49% was achieved. This paper focused on the optimisation of some selected operational parameters of the classifier to obtain a Mn grade >50% using Design of Experiment (DOE). Series of test works were designed using the DOE for the classifier using the constraints of washing time (30-90 min), speed of spirals (20-40 rev/min) and feed tonnage (6-9 t). The outcome of the test work after simulation showed that all the selected parameters had a great influence on Mn grade. The spiral speed and feed tonnage correlated negatively to the Mn grade with washing time correlating positively. Operating the spiral classifier at a feed rate, spiral speed and washing time of 6 t, 25 rev/min, and 30 min, respectively, yielded Mn grade of 53%. A Confirmatory test using the established conditions gave a Mn grade of 53%, which is a 4% increment in the previous Mn grade which was 47%. The outcome of the studies is the new established operational conditions which is adhered to by the plant, producing a manganese concentrate grade ranging between 52-54%.   Keywords: Design of Experiment (DOE), Spiral Classifier, Grade, Manganes

Market orientation of entrepreneurial university distance education and sustainable competitive advantage relationships: The mediating role of employee engagement

To be competitive in the distance education service delivery market, the need for a strategic approach by managers of these institutions to manage the increased competition cannot be compromised. Despite the available past and current studies on market orientation, the impact of market orientation on firms in the context of distance education is yet to be explored. Additionally, given the COVID crisis, the increasing reliance on distance education has resulted in a dynamic and turbulent environment in which market orientation assumes even greater importance. This study seeks to examine the mediating role of employee engagement in the link between market orientation and sustainable competitive advantage. Using the multistage sampling technique, 375 respondents were selected, consisting of key management and staff of a certain university's distance education programme. Analytically, partial least squares structural equation modelling (PLS-SEM) was used to address the various hypotheses of the study. Both customer and competitor orientations were found to have a significant positive effect on the university's sustainable competitive advantage. The study's outcomes will help shape policy and practise in distance education

Book Reviews

This issue of the CJAS includes reviews of two important books: The Mind of Africa by William Abraham, that was recently re-issued in paperback, and Building the Nation: Seven Notable Ghanaians, edited by Mercy Akrofi- Ansah and Esi Sutherland-Addy. We think that these commentaries provide critical illumation of these important texts, and we are grateful to Professor Emeritus Ivan Addae-Mensah, and Drs Amoah-Boampong and Richmond Kwesi for their thoughtful reflections

Detection of Weak D (Du) Phenotype among Rh-D Negative Males and Females in Kumasi, Ghana

Weak Rh D phenotypes are very frequent in Africans. They are capable of causing alloimmunization in Rh D-negative individuals. Some weak Ds may elude routine typing using direct agglutination techniques. This study aimed at determining the prevalence of weak D phenotype among Rhnegatives, using indirect antiglobulin technique. A total of 400 donors between the ages of 16 and 35 years who were grouped by the blood bank were randomly sampled over a period of 2 months. Three hundred and sixty nine (92.25%) were typed as Rh D-positive and 31 (7.75%) RhD-negative. Two (6.45%) of the Rh D-negative donors were weak D positive while 29 (93.55%) were weak D negative. Among the males 25 (9.43%) were Rh D-negative and 240 (90.57%) RhD-positive. Two (8%) of the 25 males were weak D positive. Among the females, 6 (4.44%) were Rh D-negative and 129 (95.56%) RhD- positive. This implies that, there are people in Kumasi with weak D phenotype which cannot be detected by the direct monoclonal anti-D agglutination. Consequently, indirect antiglobulin test may be indicated for such individuals typed Rh D-negative. This study has shown the need for a comprehensive policy on appropriate testing of donors and newborns, and management of Rh D-negative mothers in the Region. This should include weak D testing of all Rh Dnegative blood donors before transfusion in Rh D-negative patient. Keywords: Rhesus D, weak Rh D, indirect antiglobulin test, Kumasi-Ghana Journal of Science & Technology (Ghana) Vol. 28 (3) 2008: pp. 34-4

Assessment of the mediating effects of external integration on manufactury firms operational performance

Purpose: The purpose of this study was to assess both the direct effect of supply chain integration on firm’s operational performance and the mediating effect of external integration (customer integration and supplier integration) on the relationship between internal integration and operational performance among manufacturing firms. Design/methodology/approach: Quantitative survey research design was adopted. A total of thirty (30) manufacturing firms were sampled using cluster sampling. The data was collected using questionnaires from 317 employees in the procurement, account and administration units of the 30 manufacturing firms. Structural Equation Modeling was used to analyze the direct and mediation relationships. Findings: The results showed that the relationship between internal integration and operational performance was significantly mediated by external integration. It was established that operational performance could only be achieved when manufacturing firms’ managers pay critical attention to internal and external integration. A Significant positive relationship also exists between supplier integration and operational performance as well as customer integration and operational performance. Originality/value: The unique contribution of the current study is the assessment of the mediating effect of external integration constructs (customer integration and supplier integration) as the mediating variable on internal integration and operational performance

Audit of documentation accompanying referred maternity cases to a referral hospital in northern Ghana: a mixed-methods study.

BACKGROUND: Effective referral of maternity cases, which cannot be managed at the primary healthcare level, with detailed referral forms is important for reducing possible delays in the provision of higher-level healthcare. This is the first study to audit documentation or referral forms that accompany referred maternity cases to a referral hospital in the northern region of Ghana. MATERIALS AND METHODS: This study employed an explanatory sequential mixed-method design, starting with a quantitative review of referral forms that accompanied all patients referred to four units (antenatal, antenatal emergency, labour and neonatal intensive care) of a referral hospital in northern Ghana. In-depth interviews were held with the heads of the four units afterwards. Descriptive statistics were computed for the quantitative data. The qualitative data was subjected to content analysis. Integration of the data occurred at the data interpretation/discussion level. RESULTS: A total of 217 referral forms were analysed. Nearly half of the cases were referred from the Tamale Metropolis (46.5%) and 83.9% were referred for advanced care, whilst 8.3% were referred due to a lack of medical logistics and equipment such as oxygen and skilled personnel (6%). Completion rates of the referral forms were as follows: < 50% completion (n = 81; 37.3%), 50-75% completion (n = 112; 51.6%) above 75% completion (n = 24; 11.1%). Some of the handwriting were not legible and were quite difficult to read. The key informants stated that incomplete forms sometimes delay treatment. The head of the antenatal care unit at the referral hospital suggested professional development sessions as a strategy for supporting clinicians to fill the forms as expected. CONCLUSION: The Ghana Health Service should conduct regular audits, develop job aides and provide incentives for health professionals who accurately complete referral forms. Completing forms and digitizing health records can help ensure further efficiencies in the health information system and sustain good maternity referral documentation practices

Green Supply Chain Management and Environmental Performance: The moderating role of Firm Size

This study examined the impact of internal and external green supply chain practices on environmental performance among construction firms. The study used the quantitative survey research design in its methodology. A total of 217 employees were sampled from fifty (50) construction firms. Structural Equation Modeling was used to analyze the data. The results showed that green design does not have a significant positive relationship with environmental performance. However, green design has a positive impact on external green practices namely green purchasing and green construction. Green purchasing and green construction have direct positive relationships with environmental performance. Green design through external green practices have a significant positive relationship with environmental performance. The study found that firm size moderates the relationship between green design, through external green supply chain practices and environmental performance among construction firms

Supply chain integration and operational performance in health institutions: A structural model for mediation effects

This study has examined the impact of supply chain integration on operational performance among health institutions. The study assessed the direct, indirect and mediated effects of supply chain integration on operational performance among health institutions in Ghana using the Structural Equation Modelling (SEM). In this research, the quantitative descriptive survey research design was used. A total of twenty (20) health institutions were sampled from an accessible population of thirty (30) using the simple random sampling technique. A total of two hundred and fifty-four (254) employees and managers from the health institutions were sampled using the stratified sampling technique. For direct effects, the findings of the study have shown that internal integration positively impacts external integration (customer and supplier integration). Direct positive relationships exist between internal integration and operational performance as well as supplier integration and operational performance. A non-significant relationship exists between customer integration and operational performance. For mediation effects, supplier integration significantly mediates the relationship between internal integration and operational performance, while customer integration does not significantly mediate the relationship between internal integration and operational performance among the health institutions in Ghana. The study has managerial implications for health institutions in strengthening their supplier and customer integrations through advanced database systems to enhance their operational performance

Effect of Formaldehyde Treatment on Bacteria-Infected Hatching Eggs of Gallus gallus domesticus Linnaeus, 1758

The effectiveness of formaldehyde egg disinfection is well documented in literature despite its reported toxicity. This study focused on the need for an optimum formaldehyde concentration (FC) that significantly reduces microbial load with minimal damaging effect on egg viability and hatchability. Using a true experimental design, bacterial load on formaldehyde-treated (FT) and control groups of eggs and hatchability were compared. Gram-staining and biochemical tests identified five bacterial species: Escherichia coli, Enterobacter sp., Bacillus cereus, Staphylococcus aureus and Micrococcus sp. with the two coliform bacteria, E. coli and Enterobacter sp., dominating. Comparison of median differences of bacterial load on eggs before and after formaldehyde treatment by Wilcoxon Signed-Rank Test showed marginal significance in bacterial load reduction (Z = -2.016, P = 0.044). This difference was observed for bacterial load between the control group (CG) and the FT group with FC 30/20 ml/g (U = 3.0, P = 0.047). The hatchability of the CG differed significantly from four FT groups of eggs with FC 30/20 ml/g showing the highest level of significance [χ² (1) = 14.71; P = 0.0001]. A FC of 30/20 ml/g produced the best domestic fowl egg disinfection compared to other FCs and hatchability decreased with increasing formalin volume