Durability of Concrete Containing PFA-GGBS By-products

Ground Granulated Blast-furnace Slag (GGBS) and Pulverised Fuel Ash (PFA) were used to replace up to 60% of Portland cement (PC) in concrete. The testing program of the concrete included the determination of the consistency of fresh concrete, the measurement of the density and compressive strength of the hardened products cured for up to 56 days and the evaluation of their durability via visual inspections and strength loss calculations after the freeze and thaw cycles. The results showed that the blend proportion and type had affected the consistency of the fresh concrete. Replacing the PC with 20% for PFA or 40% for GGBS had similar performances as the control mix. The durability of concrete subject to freeze and thaw had little effect on the concrete specimens. It was observed that the concrete without blends suffered the worst, resulting in chips along the edges of the cube and scaling of the faces compared to mixes with 20% GGBS and 20% PFA which resulted in increased durability. However, blended concrete exhibited more loss in strength compared to the concrete without cement blends

Effects of Sodium Iso-butyl Xanthate Dosage on the Froth Flotation of Bead Milled Middle Group 1-3 PGM Ore Blend

An investigation was carried out to determine the effects of collector concentration on the grade and recovery in the flotation of middle group 1-3 Platinum Group Metal (PGM) ore mixture. The ore mixture pulp at a relative density of 1.29 was subjected to “bead milling” test, particle size distribution analysis and the 55% passing 75 µm was froth floated at 180, 200 and 220 g/t dosages of sodium isobutyl xanthate (SIBX) and 30 and 80 g/t of Senfroth and Sendep 30D frother and depressant, respectively. The results obtained indicated the predominance of the <38 µm PGM values in the ore and confirmed the need for tertiary milling for better liberation of the PGMs. The grade of the PGM concentrate obtained when dosing at 200 g/t of sodium isobutyl xanthate was highest at 94 g/t and gave the lowest recovery of 53%. The 180 g/t SIBX dosage resulted in highest PGM recovery of 70% and lowest grade of 84 g/t, while dosing at 220 g/t SIBX gave average PGM grades of 90 g/t and recoveries of 60%. The results obtained thus showed that that an SIBX dosage of 180 g/t SIBX would be appropriate when higher recoveries are targeted, while 200 g/t dosage will yield higher grade

An Optimal Multi-System Control Measure Using the Approach of Conjugate Gradient Algorithm (CGA)

In this paper we examine the application of the classical conjugate gradient method to queue theory. The parameters of the symmetric definite positive linear operator of a quadratic cost functional were obtained from the various characteristic features of a multi-channel queue system. The outcome was tested with numerical values and a comparison was made for systems with two, three and four service points. The numerical computations were carried out in a Maple 14 environment. The results obtained validate previous work done with a singlechannel syste

Numerical Comparison of Line Search Criteria in Nonlinear Conjugate Gradient Algorithms

One of the open problems known to researchers on the application of nonlinear conjugate gradient methods for addressing unconstrained optimization problems is the influence of accuracy of linear search procedure on the performance of the conjugate gradient algorithm. Key to any CG algorithm is the computation of an optimalstep size for which many procedures have been postulated. In this paper, we assess and compare the performance of a modified Armijo and Wolfe line search procedures on three variants of nonlinear CGM by carrying out a numerical test. Experiments reveal that our modified procedure and the strong Wolfe procedures guaranteed fast convergence

DEVELOPMENT OF A RECHARGEABLE ELECTRONICALLY CONTROLLED MOTORISED WHEELCHAIR FOR DISABLED AND ELDERLY PEOPLE

The physically challenged, old-age people, and most paralysed patients need means of transportation from place to place to ease their movement. The earlier available wheelchairs are manually driven that need extra effort of either the physically challenged or an assisting person to move. Nowadays, the level of communication and socialization strongly depends on easy access to mobile transportation. &nbsp;This paper presents a developed motorized wheelchair that facilitates movement of physically challenged people both in the hospital and in their home by taking into account aesthetics, low cost, ease on maintenance with market competitive advantage using locally sourced materials. The developed wheelchair is designed to work for 3 hours under a maximum load of 90 kg with navigation buttons. A working efficiency of 65 % was obtained under full operation. This design brings a new competition into the wheelchair market and gives more comfort to the physically challenged peoples’ mobility than the existing manually driven one

N-Nitrosation of dimethylamine hydrochloride and its toxicology in the wistar rats fed different levels of dietary protein

The present study investigated the in vivo and in vitro effects of orally administered sodium nitrite (NaNO2) and dimethylamine hydrochloride (DMA–HCL) on liver of rats fed ad libitum with high protein diet (64%), normal protein diet (27%) and low protein diet (3.5%). Thirty Male Wistar rats were divided into three groups and kept for four weeks. Group one was given high protein diet, group two was given a normal protein diet, group three was given low protein diet, all the groups were administered with 3mg NaNO2 and 20mg DMA-HCL/kg, using the application of spectrophotometric analysis, centrifugation, histolopathology, enzymatic as well as colorimetric methods. Liver function test, showed significant elevations (P < 0.05) in the AST, ALT, ALP and GGT activities in all the groups compared with the control animals. The histopathology examination exhibited periportal necrosis. Following UV exposure after in vitro incubation of rat liver microsomal plus soluble fraction with NaNO2 plus DMA-HCL, nitrite concentration in the rats fed high protein was highest 4.033 and 0.470 μg/ml, compared to the control rats which was 0.052 and 0.00192 μg/ml before and after UV irradiation. Nitrite loss was significant (p<0.05) before and after UV exposure in all the groups, indicating that the UV-light has degraded the nitrosamine precursors, thereby inhibiting possible nitrosation. The study has revealed that in rats, a high protein diet enhances N-Nitrosation of dimethylamine hydrochloride, liver derangement and the metabolisms in vivo and in vitro of the resultant compound