EFFECT OF MAGNETIC FIELD AND SLIP VELOCITY ON THIRD GRADE BLOOD FLOW AND HEAT TRANSFER THROUGH A STENOSED ARTERY.

In this study, we considered the effect of magnetic field and slip velocity on blood flow and heat transfer through a stenosed artery using a third grade fluid model. The solution techniques employed are based on Galerkin weighted residual and Newton Raphson methods. Analytical expression for the flow velocity, temperature profile, volume flow rate, wall shear stress and resistance to flow were obtained and the results are presented graphically. The numerical simulation carried out reviewed that higher value of slip velocity significantly increased the flow velocity, flow rate, and wall shear stress but reduced the flow resistance and heat transfer rate while flow velocity, flow rate and shear stress gradually decreased with increased value of the magnetic field parameter but increased the flow resistance and heat transfer rate. Other parameter that enhance the flow velocity are the pressure gradient, shear thinning and Reynold number while that of heat transfer rate are the shear thinning, third grade parameter and Eckert number. Finally, it is reviewed from the results that the effect of slip velocity is more noticeable compare to that of magnetic field effect. Keywords: Stenosed artery, Slip Velocity, Magnetic Field, Pressure Gradient, Eckert number, Reynold number, Shear thinning

Development of a Pseudo-Closed Loop Solar Collector Sun Tracking System with Optimized Set-Point Paths for Flat Plate Payload

This paper provides the theoretical framework for the development of a pseudo-closed loop solar tracking system incorporating a microcontroller for a flat payload, where the outputs of the system (the slope and the azimuth angles of the payload) are observed and the set-points for the system are to be optimally computed by the microcontroller. It also presents, from literature, the equations and models solar angles and incident angles for the development of the optimum set point path for the tracking, and gives the outline of the signal flow plan, as well as the corresponding flowchart, for the tracking system’s components interaction. The concept would provide a cheaper and simpler alternative to dual axis solar tracking incorporating solar sensors. The models presented here are adaptable to any geographical location in Nigeria and globally

Analysis, modeling and control of cascaded NPC/H bridge inverter for high power quality grid connection

Abstract: The cascaded NPC/H- bridge inverter is first analyzed by establishing a new switching model based on a derived control law. From the developed switching model, a general model is obtained using state space technique. A new and accurate average model is developed using abc to dqo transformation technique. Finally small signal model is obtained by linearizing all the state variables around their quiescent operating points. The small signal model is used to study the effects of various control feedback variables on the dynamic performance of the Grid connected system. Feedback control scheme is designed to improve the dynamic response of the system. The system with the proposed control technique also achieves sinusoidal grid voltage and current output with low THD which is a preferred characteristic for any power injected to the grid. Simulation results are provided to validate the analytical model

BRIDGING THE GAP BETWEEN OLD AND NEW TECHNOLOGY: CONSIDERATION OF INDIGENOUS KNOWLEDGE IN MAIZE PESTS MANAGEMENT PRACTICES IN NIGERIA

Conventional pests management practices are carried out mainly through extensive exposure to chemicals (pesticides) used in agricultural production. The overall ailing effects of these chemical based products to the environment and human health are some of the challenges which appeal to look for alternative farming practices that would minimize the use of pesticides in agricultural production. It is against this background that this study was carried out to determine the perception of the effectiveness of indigenous and organic maize pest management practices among maize farmers in Oyo state in order to bridge the gap between the old and new technology and determine the relationship that will enhance the development of ecological organic agriculture (EAO). A well structured interview schedule was used to solicit for information from the 150 respondents using a systematic sampling technique. Frequency, percentage, Chi-square and Pearson Product Moment Correlation (PPMC) were used to describe and analyze the data generated. The farmers’ level of awareness on indigenous and organic maize pests management practices was high at (58%) level and the respondents level of utilization was also high at (61.3%) level, with a favourable perception about the effectiveness of indigenous and organic maize pests management practices and some of these practices are; cultural practices through the use of hoes and cutlasses, the use of traps, practice of bush fallow, early planting, crop rotation, mixed cropping system and biological pest control. Furthermore, Pearson Product Moment Correlation(PPMC) results showed that there is no significant relationship between some selected socio- economic characteristics age (r =0.091, p=0.270), year of formal education (r =0.010, p=0.903), farming experience ( r =0.128, p =0.120), family size (r =0.072, p=0.380), average income per month (r =0.056, p= 0.499) and the perception of the effectiveness of indigenous and organic maize pest management practices in the study area. The results of the study revealed that farmers’ level of awareness and utilization of indigenous and organic maize pest management practices was high and this is good for sustainable development EOA. The farmers perceive indigenous knowledge and organic system to mean the same and better option for against conventional farming system. Improvement of information on indigenous best practices to merge with EOA system for maize pest management through adequate extension services is eminent to enhance sustainable health of food and farmers

Biosorptive removal of cobalt (II) ions from aqueous solution by Amaranthus hydridus L. stalk wastes

The objective of this study was to investigate the possibility of using Amaranthus hybridus L. stalk as an alternative to high cost commercial adsorbent materials for the removal of Co (II) from aqueous solution. The experiment was carried out by batch method at 33°C. The influence of pH, contact time and initial metal ion concentration were evaluated. It was observed that pH had marked effect on the Co (II) uptake. The optimum contact time between the adsorbent and the adsorbate was found to be 90 min. Maximum adsorption was obtained at pH 5. Freundlich models were used to correlate equilibrium data on sorption of Co (II) ion at 33°C and pH 5, and different coefficients were calculated. The data generated, fitted well with Freundlich adsorption model. The biomass was successfully used for removal of cobalt (II) ion from synthetic aqueous solution and the technique appears industrially applicable and viable.Key words: Biosorption, cobalt, aqueous solution, Amaranthus hydrides

Modification of Thermal Hydraulic Transient Models for the Miniature Neutron Source Reactor

A modified Miniature Neutron Source Reactor (MNSR) model dealing with transient thermal hydraulic problem is presented. The model based on lumped parameter method is adopted in this work to numerically solve a system of coupled algebraic and differential equations governing heat transfer in MNSR, using MATLAB solver for variable order method in stiff differential equations and Differential-Algebraic equations, coupled with Maple soft. The simulated results obtained from the model were generally in agreement when compared with reactor operation data recorded from 0 to 270 minutes during experiments. Radiating energy of Fuel and clad and heat transferred at the gap or clearance were taken in to account. Fuel and clad temperatures as well as various temperatures at different sections of the reactor were predicted with the model, in addition to the effect of the installed chiller on the reactor coolant

Fuzzy Logic Based Controller for Maintaining Human Comfort within Intelligent Building System

This paper presents an intelligent control approach for air handling unit (AHU) which is an integral part of heat, ventilation, and air conditioning (HVAC) system. In the past years various control design for HVAC have been proposed as this system remarkably consumes very high energy. But most of the proposed designs were focused on the control flow of heat-transfer medium such as chilled or heated water while the importance of the efficient mixture of outdoor and indoor enthalpies is sometimes ignored. These enthalpies invariably determine the best strategy to overcome thermal load in a controlled environment to satisfy human comfort, hence a control design strategy must be able to efficiently regulate the flow and mixture of outdoor and indoor enthalpies by a proper control of AHU dampers and fans. This approach requires sensors to measure temperature and relative humidity of both outdoor and indoor environments. However, unpredictable level of disturbances coming from many sources including heat generated by occupants, electrical items and air leaking and the continuous changes of outdoor enthalpy makes it difficult to model the process. Consequently, conventional controllers are not suitable, hence the use of fuzzy logic controller (FLC) is proposed in this paper. This proposed controller operates in a master and slave control loop so as to control the AHU dampers and fans with adjustable output membership function whilst at the same time a scaling-factor method is used to drive the master operation. To implement the proposed system, a small scale prototype has been designed and fabricated. This prototype is an AHU model which consists of ductwork, temperature and humidity sensors, dampers, air cooling and heating systems. A small box is used as a conditioning space in which a room temperature is measured. The control algorithm is programmed using National Instrument (NI) LabVIEW and executed using NI FieldPoint. Experimental results reveal that proper control of AHU dampers and fans is an effective and practical means to satisfy human comfort with minimum energy consumption

A cascaded hybrid inverter with improved dc-link voltage control for grid connected systems

Abstract: This paper presents investigation of a new Phase shifted PWM technique with improved harmonic suppression. A novel balance circuit for DC – link voltage balance of two three level legs connected back – to back is designed and tested. Combined with the individual voltage control, a complete voltage controller is developed for a cascaded nine level hybrid model with two cells. Robustness of the proposed algorithm under varying operating conditions and modulation indices is verified by simulation

Machine condition monitoring and fault diagnosis using spectral analysis techniques

There is need to continuously monitor the conditions of complex, expensive and process-critical machinery in order to detect its incipient breakdown as well as to ensure its high performance and operating safety. Depending on the application, several techniques are available for monitoring the condition of a machine. Vibration monitoring of rotating machinery is considered in this paper so as develop a selfdiagnosis tool for monitoring machines’ conditions. To achieve this a vibration fault simulation rig (VFSR) is designed and constructed so as to simulate and analyze some of the most common vibration signals encountered in rotating machinery. Vibration data are collected from the piezoelectric accelerometers placed at locations that provide rigid vibration transmission to them. Both normal and fault signals are analyzed using the singular value decomposition (SVD) algorithm so as to compute the parameters of the auto regressive moving average (ARMA) models. Machine condition monitoring is then based on the AR or ARMA spectra so as to overcome some of the limitations of the fast Fourier transform (FFT) techniques. Furthermore the estimated AR model parameters and the distribution of the singular values can be used in conjunction with the spectral peaks in making comparison between healthy and faulty conditions. Different fault conditions have been successfully simulated and analyzed using the VFSR in this paper. Results of analysis clearly indicate that this method of analysis can be further developed and used for self-diagnosis, predictive maintenance and intelligent-based monitoring