Heat exchanger is a device that exchange the heat between two fluids of different temperatures that are separated by a solid wall. The temperature gradient or the differences in temperature facilitate this transfer of heat. In General, temperature control system has the characteristics of non-linearity, large inertia and time variability. It is difficult to overcome the effects of these factors and get the satisfactory results by using the normal PID controller. Therefore, the PI, FOPID, FUZZY and IMC are the controllers implemented in this paper to control the output temperature of the heat exchanger system. The PI, FOPID, FUZZY and IMC are the controllers are compared, based on their overshoot and settling time the conclusions are given using simulation results. As a future work FOPID controller tuned using genetic algorithm will be implemented in this paper later for better effective temperature control over other controllers.
Keywords: - Internal model based controller, PID controller, Fuzzy controller and Shell and tube heat exchanger system.
This paper presents a Factor Analysis (FA) carried out on the responses of the four major construction parties to the questionnaire. Involved are:management, employer's association, employees, and Construction Trade Union. Underlying the dimension (factors) of the responses data for the four parties are compared and findings are discussed. The influence of various contextual factors on some of these relationships and perceptions between/among the four major construction parties is investigated. A number of essential dimensions of workplace variables are identified which form the basis for developing both conceptual and research model. A significant understanding of group'sinsights of workplace communication and industrial relations(IR) is obtained. The purpose of factor analysis is to develop factors which identity the major dimensional differences within the data set. Finally, the study investigates the statistical reliability of the sample data; a reliability scale assessment indicates that results obtained from the statistical analysis are indeed valid.
Keywords: Satisfaction, Management, Employer's Association, Non-Management Employees and Union
The research correlated physical and mechanical properties with penetration rate of drilling in some typical limestone quarries in Ogun State, Nigeria. The work was carried out using the field data and rock samples collected from the two locations [Sagamu (A) and Ewekoro (B)]. Field data were used for the determination of penetration rate while rock samples were used for the laboratory analysis. The result of modal analysis from the thin section shows that sample A has the mineralogical composition of 79.5% calcite, 13.5% quartz and 7.0% opaque while sample B has 77.5% calcite, 17.0% quartz and 5.5% opaque. The average density, porosity and rebound hardness of samples from locations A and B as determined in the laboratory are 2.68g/cm3, 3.08%, 32.3 and 2.71g/cm3, 3.06%, 35.1 respectively. The result of Uniaxial Compressive Strength (UCS) as estimated from the correlation chart between average density and Schmidt hardness shows that location A has average strength of 61.8 MPa while B has 72.4 MPa. The point load strength index for location A has an average value of 1.6 MPa and B has an average value of 1.8 MPa while the tensile strength as estimated from point load strength index for A is 2.5 MPa and B is 2.7 MPa. The penetration rate as determined from field data shows that location A has an average penetration rate of 0.7 m/min and location B has an average penetration rate of 1 m/min. Statistical model was developed using Statistical Package for Social Sciences (SPSS) software and the result shows that there is a strong correlation between penetration rate and porosity, rebound hardness value and density. The result also shows that the porosity, rebound hardness value and UCS have negative influence on penetration rate while density has positive influence on penetration rate.
Keywords: - Characterization, limestone, physical properties, strength properties, correlation, penetration rate.
This paper reports the development of a Time-Series based outage forecast model on electrical power distribution feeder lines in the Molete District of the network of the Power Holding Company of Nigeria (PHCN) within the city of Ibadan in Nigeria. A five-year(1999-2003) monthly outage data (in hours per month) gathered on the feeder lines was analyzed with the Time-series analysis program in the statistical software package Systat to generate the autocorrelation and the model parameters. These parameters are: smoothing coefficient, Trend coefficient, seasonality index and standard error of the forecast. The models were developed using the parameters. The models were then used to obtain a 24-month outage forecast figures and plots for each of the ten feeder lines. The results indicate that seasonal factors influenced the monthly outage on the feeder lines with the forecast figures rising to their peaks within the rainny season months of June to August while the minimum forecast figures occur during the dry season period which is from November to February on each feeder line. The outage hours on the feeder lines increased with the lengths of the lines with the outage forecast figures rising to as much as 392 hours per month and 328 hours per month respectively on CRIN and Ring-Road, the two longest feeder lines, in the rain season while they were as low as 51.6 hours per month and 64.77 hours per month respectively on Black-House and Best-Oil, the two shortest feeder lines within the same period.
Key Words: - Distribution feeder lines, time-series, autocorrelation plots, autoregressive moving average (ARMA), model parameters, monthly outage forecast models.
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