Statistics and Operations Research
Permanent URI for this community
Statistics and Operations Research
Browse
Browsing Statistics and Operations Research by Title
Now showing 1 - 12 of 12
Results Per Page
Sort Options
- ItemA Proportional Hazard model to establish factors that are significant in child survival.(IOSR, 2014) Musizvingoza, R.; Mwembe, D.; Nyamugure, P.This study addresses important issues affecting under-five mortality in Zimbabwe. The objective of this research is to establish factors that are significantly impacting on child survival and to determine the survival rate of children under the age of five years. Cox regression and Kaplan-Meier estimator were used for data analysis. Child survival was significantly influenced by two predictor variables, breastfeeding and immunisation status (p< 0.05). The Hazard ratios for variable breastfeeding and immunisation are 2.806 and 4.778 respectively. The survival functions for the children indicate a high survival rate especially in children who are well breastfed and those who are fully immunised. This study supports health policy interventions that enhance child survival. Immunisation and breastfeeding should be encouraged among mothers to enhance child survival.
- ItemApplication of Network Reconstruction Algorithm to Compute Maximum Flow for Water Supply Network: A Case Study of the City of Bulawayo, Zimbabwe(Universal Wiser Publisher, 2023-12-13) Tawanda, T.; Kumar, S.; Kumar, S.; Nyamugure, P.Determining the maximum flow value in Water Supply Networks (WSN) is a common problem that is being faced by many cities during and after designing of WSN. In this article, the network reconstruction (NR) algorithm is applied to compute the maximum flow value for the city’s WSN based on the actual data. The city of Bulawayo has been selected for the following reasons, availability of research data, the city is facing severe water shedding and several studies have focused only on other issues such as alternative water sources, leakage detection and demand forecasting. The goal of this study is to determine the maximum flow value from the sources to the reservoirs. The results have revealed that the computed maximum flow value is within the estimated range of 110,000 cubic meters to 190,000 cubic meters. Dam sensitivity analysis were considered to determine the sources to give maintenance priority before the rain season. Several recommendations were suggested to improve the water supply situation.
- ItemApplication of the Equipment Replacement Dynamic Programming Model in Conveyor Belt Replacement: Case Study of a Gold Mining Company(MCSER Publishing, 2015-02) Zvipore, David C.; Nyamugure, P; Maposa, D; Lesaoana, MasekaAs assets age, they generally deteriorate, resulting in rising operating and maintenance costs and decreasing salvage values. In this paper a comprehensive Dynamic Programming-based optimisation solution methodology is used to solve the equipment replacement optimisation problem on the replacement of conveyor belts at a Gold Mining company in Zimbabwe. Given a mining setup with one and two-year old conveyor belts the ultimate objective is to keep or replace the conveyor belt such that the overall cost of material handling is minimised within a five-year period. The findings reveal that this mining system should replace conveyor belts yearly. It is concluded that, an equipment replacement policy for conveyor belts is a necessity in a mining system so as to achieve an optimal contribution to the economic value that a mining system may accrue within a period of time.
- ItemDeterminants of house prices using spatial analysis: the case for Bulawayo(NUST, 2023) Mupondo, N.C.; Ncube, B.; Mupondo, A.; Nemahwe, S.C.The factors affecting house prices are crucial to Zimbabwe’s property organisation, and they necessitate an understanding of market trends and patterns in the housing industry. The primary goal of this research is to investigate the correlations between house prices and the factors that influence them to develop a model that can forecast house prices in Bulawayo. This study uses exploratory data analysis and spatial regression approaches to analyse factors affecting house prices in Bulawayo to understand how much housing costs are influenced by the availability of health services and retail stores. How does the distance to schools and the central business district (CBD) affect property prices, as well as the size of the land and the physical environment? To attain these goals, spatial analysis and local regression parameter estimates were used. The study found that many variables have both positive and negative effects on house prices across space and that the spatial lag model is the best fit for predicting house values in Bulawayo.
- ItemDevelopment and performance evaluation of a web-based feature extraction and recognition system for sheet metal bending process planning operations(Taylor and Francis, 2021-02-14) Murena, E.; Mpofu, K.; Ncube, A.T.; Makinde, O.; Trimble, J.A.; Wang, X.V.Sheet metal bending manufacturing companies require changeable and adaptable process planning systems to shorten the production cycle time and reduce operations costs. This is due to globalisation and the rapid change in market demands for sheet metal products. In light of this, this paper proposes a web-based feature extraction and recognition system. The system would ensure automated planning of various processes used by a bending machine to produce varieties of sheet metal products. The algorithms were implemented using C++ to produce the geometric and feature models used to extract, and recognise the bending features in various CAD files acquired from literature. Five (5) CAD files of various sheet metals were utilised to test the functionality of this system. The results from the feature recognition process have proven to be precisely what the user has designed and saved in the model file. Bend radius and bend angle. Finally, the developed system is able to transform a STEP file into a feature model and display the 3D CAD model within the least time. It is a cost-efficient standalone system that provides data storage, allows collaboration and data sharing. can be used anywhere where there is internet access.
- ItemForecasting stock prices on the Zimbabwe Stock Exchange (ZSE) using Arima and Arch/Garch models.Research Academy of Social Sciences.(Research Academy of Social Sciences, 2014) Mutendadzamera, S.; Mutasa, Farikayi K.The main thrust of this study is to find out whether the stock prices on the ZSE can be predicted using ARIMA and ARCH/GARCH models. The ZSE currently does not have a model that predicts stock price movements. Thus this study attempts to explore econometrics models to predict future stock prices on the Zimbabwe Stock Exchange (ZSE) selected counters. Stock price data is differenced and tested for stationarity using KPSS test and the Augmented Dickey Fuller test. The final models are found to be Econet Wireless, ARIMA(1,1,0), Dairiboard, ARIMA(1,1,0), Delta, ARIMA(1,1,1), SeedCo, ARIMA(1,1,1) and Old Mutual, ARIMA(1,1,0). The GARCH(1,1 model for all the counters forecast better than ARIMA models considering the minimum deviations of the forecasted values from the actual ones. This is because the ARCH/GARCH models incorporate new information and analyses the series based on conditional variances where users can forecast future values with up to date information. Old Mutual had the best ARIMA model with the lowest error where as Dairiboard had the best GARCH model as shown by the minimum Schwarz criterion value of 1.365. We conclude that GARCH(1, 1) model outperforms ARIMA models in modeling stock prices in this study.
- ItemA node merging approach to the transhipment problem(Springer Publishers, 2015) Tawanda, TrustIn this paper, a new approach for solving transhipment model as a transportation model is developed and illustrated. The objective is to expose the transhipment problem to algorithms and methods that are transportation problem (TP) based. The principle of this method consists in merging source nodes with transhipment nodes, through utilization of all possible combination connections, transportation costs are summed up respectively. A numerical example is used to illustrate the approach. The least cost method (LCM) is used to solved the TP resulted from a transformed transhipment problem. Linear programming (LP) models are used as proof of correctness, thus we solve the original transhipment model as an LP problem. This study revealed that solutions from LCM are the same as that of LP formulated from the original transhipment model.
- ItemNon‑parametric quantile regression‑based modelling of additive efects to solar irradiation in Southern Africa(Scientific Reports, 2024) Masache, A.; Maposa, D.; Mdlongwa, P.; Sigauke, C.Modelling of solar irradiation is paramount to renewable energy management. This warrants the inclusion of additive effects to predict solar irradiation. Modelling of additive effects to solar irradiation can improve the forecasting accuracy of prediction frameworks. To help develop the frameworks, this current study modelled the additive effects using non-parametric quantile regression (QR). The approach applies quantile splines to approximate non-parametric components when finding the best relationships between covariates and the response variable. However, some additive effects are perceived as linear. Thus, the study included the partial linearly additive quantile regression model (PLAQR) in the quest to find how best the additive effects can be modelled. As a result, a comparative investigation on the forecasting performances of the PLAQR, an additive quantile regression (AQR) model and the new quantile generalised additive model (QGAM) using out-of-sample and probabilistic forecasting metric evaluations was done. Forecasted density plots, Murphy diagrams and results from the Diebold–Mariano (DM) hypothesis test were also analysed. The density plot, the curves on the Murphy diagram and most metric scores computed for the QGAM were slightly better than for the PLAQR and AQR models. That is, even though the DM test indicates that the PLAQR and AQR models are less accurate than the QGAM, we could not conclude an outright greater forecasting performance of the QGAM than the PLAQR or AQR models. However, in situations of probabilistic forecasting metric preferences, each model can be prioritised to be applied to the metric where it performed slightly the best. The three models performed differently in different locations, but the location was not a significant factor in their performances. In contrast, forecasting horizon and sample size influenced model performance differently in the three additive models. The performance variations also depended on the metric being evaluated. Therefore, the study has established the best forecasting horizons and sample sizes for the different metrics. It was finally concluded that a 20% forecasting horizon and a minimum sample size of 10000 data points are ideal when modelling additive effects of solar irradiation using non-parametric QR.
- ItemScheduling village heads in enhancing conflict resolution and peace building in a rural community(Academic Journals publishers, 2015-10-20) Mwembe, DesmondThis study assessed the effectiveness of village heads in Simatelele Ward, Binga District in resolving conflicts in Zingozo village. The study was from April 2012 to June 2013. Four village heads were sampled using a simple random sampling technique and four types of conflicts common to all the four selected village heads were taken. A mathematical model was developed to assign village heads to cases they can resolve and improve their effectiveness. The four types were divorce cases, conflict of interest, witchcraft and domestic violence. The principle behind was to assign each village head to a single case to resolve so that the overall effectiveness of the village heads at community level is maximized. Ten observations were made per village head per case. The results indicated that, on average, if the village heads resolve the conflicts the same way they are currently doing, they will be 69% effective. The collaborative approach as suggested by the research indicated that the effectiveness of the village heads in resolving conflicts will increase by 14% translating to approximately 9 cases out of 10 being resolved. It concludes that the collaborative approach improves the effectiveness of village heads in resolving conflicts hence its recommendation.
- ItemTrain Schedule Optimization: A Case Study of the National Railways of Zimbabwe(Research Academy of Social Sciences, 2014) Nyamugure, P.; Swene, S.D.; Chiyaka, E.T.; Mutasa, F.K.The locomotive assignment problem involves assigning a set of locomotives to each train in a pre-planned train schedule so as to provide sufficient power to pull them from their origins to their destinations. An integrated model that determines the set of active and deadheaded locomotives for each train, light travelling locomotives and train-to-train connections is presented. The model explicitly considers consist-busting and consistency. A Mixed Integer Programming (MIP) formulation of the problem that contains about 92 integer variables and 56 constraints is presented in the study. Three models are discussed for assigning locomotives to wagons and coaches and the results are compared amongst the models themselves and compared to the existing scenario at National Railways of Zimbabwe (NRZ). The models generally improve the number of saved locomotives and number of used locomotives. The Locomotive Assignment Model (LAM) solution obtained showed savings of over 70 locomotives, which translates into savings of over one-hundred thousand dollars weekly.
- ItemA Two-Product Inventory Model with a Joint Ordering Policy(Hindawi Publishing Corporation, 2013-10-12) Masache, A.Inventory is one of themost visible and tangible aspects of doing business.This is the reason whymost problems of a business often end up in inventory. Most inventory studies focus on a single type of product or item such that optimality decisions are arrived at for that single product. In this study, we create a scenario where two types of products are considered in such a way that there exists a joint ordering policy. A continuous review inventory model was developed but ended up with a single period review model for simplicity reasons.We tried to exhaust all main cost elements and fed them into the model in addition to investigating the possible limitations that may constrain the whole decision making process. Six constraints were found and a mathematical programming model was developed. We further went on to prove that the mathematical inventory-programming model developed minimises the total inventory cost in such a scenario.
- ItemValidation of the DigComp tool and evaluation of the level of digital literacy skills among Zimbabwean in-service secondary school teachers(POTRAZ/RCZ, 2024) Dabengwa, I.M.; Moyo, Sibonile; Gashirai, T.B.; Makaza, D.; Makoni, P.; Pasipamire, N.; Chademana, G.K.; Mufudzi, M.; Mandaza, D.; Mapfumo, S.