SEMI-STOCHASTIC MIXTURE MODEL FOR PREDICTING THE RATE OF ROAD CARNAGES IN KENYA

In this paper we consider the problem of modeling and predicting the rate of road carnage in Kenya inthe presence of randomly changing road conditions. In the literature review, accident prediction ratemodels are typically regression models and discrete time series models. We study such models andexamine their strengths and weaknesses and propose a Semi-stochastic Mixture Model to describethe relation between the highway accidents and the road environment dynamics.The aim of theresearch paper is to propose a model that captures both the deterministic and stochastic nature ofroad parameters to explain the cause of high rate of road accidents in Kenya. We apply the proposedmodel to a simulated data set for the local condition. Our analysis from show that apart from annualaverage daily traffic (AADT), road curvature is an important component of road carnage.Keywords: Road system, Semi-stochastic mixture model, road curvature, road carnage,Simulation

Application of Queuing Theory to Vehicular Traffic on Nakuru Total Road Stretch

 Nations strive to avoid losing revenue and human lives through long traffic snarl ups and frequent accidents on the roads. For this reason Considerations must be made to increase the number of lanes or even better to change from a single carriage to more robust dual carriages. However number of lanes and dual carriage alone serve no purpose for the accidents frequencies and traffic snarl ups that appear to defy even the most modern and sophisticated highway designs. Service time for traffic using such roads would need to be improved. Clearly therefore a numerical model is necessary for the road designers and developers to help understand road improvement demands. In this paper we establish the queue model for the Nakuru – Salgaa road Stretch and test the model with real data from the Case Study. Data is collected between the Soil- junction and the Total junction. We derive the arrival rate, service rate, utilization rate and the probability of Bulking using the M/M/1 queuing model. It is estimated that the arrival rate at the Soil- junction is 37 vehicles per minute and at total junction the service rate is 44 Vehicles per minute this does not march the dwindle service rates in section that are now black spots. The average number of vehicles on single road stretch is on average 15 per minute with some sections recording a high of 40 vehicles per minute and the utilization of the sections of stretch is on average 0.8. The benefit of performing the queue analysis for the road stretch is finally discussed and recommendations provided. 

Risk of Injection-Site Abscess among Infants Receiving a Preservative-Free, Two-Dose Vial Formulation of Pneumococcal Conjugate Vaccine in Kenya.

There is a theoretical risk of adverse events following immunization with a preservative-free, 2-dose vial formulation of 10-valent-pneumococcal conjugate vaccine (PCV10). We set out to measure this risk. Four population-based surveillance sites in Kenya (total annual birth cohort of 11,500 infants) were used to conduct a 2-year post-introduction vaccine safety study of PCV10. Injection-site abscesses occurring within 7 days following vaccine administration were clinically diagnosed in all study sites (passive facility-based surveillance) and, also, detected by caregiver-reported symptoms of swelling plus discharge in two sites (active household-based surveillance). Abscess risk was expressed as the number of abscesses per 100,000 injections and was compared for the second vs first vial dose of PCV10 and for PCV10 vs pentavalent vaccine (comparator). A total of 58,288 PCV10 injections were recorded, including 24,054 and 19,702 identified as first and second vial doses, respectively (14,532 unknown vial dose). The risk ratio for abscess following injection with the second (41 per 100,000) vs first (33 per 100,000) vial dose of PCV10 was 1.22 (95% confidence interval [CI] 0.37-4.06). The comparator vaccine was changed from a 2-dose to 10-dose presentation midway through the study. The matched odds ratios for abscess following PCV10 were 1.00 (95% CI 0.12-8.56) and 0.27 (95% CI 0.14-0.54) when compared to the 2-dose and 10-dose pentavalent vaccine presentations, respectively. In Kenya immunization with PCV10 was not associated with an increased risk of injection site abscess, providing confidence that the vaccine may be safely used in Africa. The relatively higher risk of abscess following the 10-dose presentation of pentavalent vaccine merits further study

Data-Based Mechanistic Modeling of Flow-Concentration Dynamics of Non-Point Source Pollution: A Case of Upper Vaal Water Management Area

This study aimed at applying the Data Based Mechanistic (DBM) modelling approach to develop a simple, parsimonious and discernable Flow-Concentration (F-C) model that can be partitioned into the various identifiable pathways associated with the pollutant at the catchment scale. An attempt was made to model the occurrence of acid mine drainage (AMD) in the Vaal River by using an indicator water quality parameter (sulphate concentration). The optimal Instrumental Variable (IV) methods of identifying and estimating discrete and continuous-time transfer function models as implemented in the CAPTAIN MATLAB® Toolbox were applied to the time series data in order to identify the appropriate model. A discernable F-C model was developed of three parallel pathways: the “quick-route” depletion pathway with a residence time months; a “slow-route” build-up pathway with a residence time months and a direct term component pathway regressed in 9 months. The resulting model showed that it is possible to use the DBM modelling approach to address the problem of representing the potential lag between polluting activity and its effect as well as provide more salient information about the system dynamics. This kind of information (i.e. the residence times and the advective time delays in the system) could prove useful for the catchment managers in making informed decisions including laying out remediation measures. Keywords: Flow-Concentration Modelling, Non-Point Source Pollution, Data Based Mechanistic Modelling, Transfer Function models, Water Quality, Flow Pathway

Turbidity removal: Gravel and charcoal as roughing filtration media

Roughing filtration is an important pre-treatment process for wastewater, because it efficiently separates fine solid particles over prolonged periods, without the addition of chemicals. For this study, a pilot plant was designed at Delmas Coal Mine in the Mpumalanga province of South Africa. The design and sizing of the pilot plant was guided by Wegelin's design criteria. Gravel was used as a control medium because it is one of the most commonly used roughing filter media and because it was used in developing the criteria. We compared the performance of gravel as a filter medium to that of another locally available material, charcoal, for the removal of turbidity in wastewater. The pilot plant was monitored continuously for 90 days from commissioning until the end of the project. The overall performance of the roughing filter in turbidity removal, using gravel or charcoal, was considered efficient for the pre-treatment of waste water. Charcoal performed slightly better than gravel as a filter medium for the removal of turbidity, possibly because charcoal has a slightly higher specific surface area and porosity than gravel, which could enhance sedimentation and other filtration processes, such as adsorption, respectively

Pilot scale study of anaerobic treatment of food waste using ambient and solar heated digesters

ABSTRACTFood waste (FW) is high in nutrients and has gained global attention as an ideal substrate for bioenergy recovery through anaerobic digestion (AD). Ambient digesters have been widely used because of their ease of installation, low cost, and low energy input. However, to improve biogas production sustainably, there is a need to consider reactor heating using renewable energy such as solar. This study sought to apply psychrophilic and mesophilic biodigester temperatures for FW treatment. For ambient digestion, a complete-mix flexible biodigester, named STH-1000A, covered in a greenhouse structure was operated between 24 and 32 °C. A prototype complete-mix tank biodigester, named VUT-1000C, was designed and operated at mesophilic conditions of 37 °C through solar geyser heating. VUT-1000C produced 1200 L of biogas per day while STH-1000A 150 L/day. VUT-1000C and STH-1000A generated up to 1.8 and 0.4 kWh of electricity, respectively. The power balance showed that VUT-1000C used 68% of its power production and STH-1000A consumed 398%. Digester heating using solar geyser is a novel and promising technique for achieving mesophilic condition leading to improved biogas production