Current Issue : July - September Volume : 2013 Issue Number : 3 Articles : 8 Articles
The previous efforts toward single period inventory problem with price-dependent demand only investigate the optimal order quantity to minimize the total inventory costs; however, there is no method in the literature to avoid unwanted costs due to the deviation between the actual demand and the previously estimated demand. To fill this gap, the present paper supposes that stochastic demand rate with normal distribution is sensitive to the selling price; this means that increasing the selling price would decrease the demand rate and vice versa. After monitoring the consumption trend within a section of the period, a new selling price is implemented to change the demand rate and reduce the shortage or salvage costs at the end of the period. Three functions were suggested to represent the demand rate as a function of selling price, and the numerical analysis was implemented to solve the proposed problem. Finally, an illustrative numerical example was solved for different configurations in order to show the advantages of the proposed model. The results revealed that there is a significant improvement in the system costs when price revision is considered....
This paper studies the effect of inflation and customer returns on joint pricing and inventory control for deteriorating items. We\r\nadopt a price and time dependent demand function, also the customer returns are considered as a function of both price and\r\ndemand. Shortage is allowed and partially backlogged. The main objective is determining the optimal selling price, the optimal\r\nreplenishment cycles, and the order quantity simultaneously such that the present value of total profit in a finite time horizon is\r\nmaximized. An algorithm has been presented to find the optimal solution. Finally, we solve a numerical example to illustrate the\r\nsolution procedure and the algorithm....
The number of stock keeping units (SKUs) possessed by organizations can easily reach quite a few. An inventory management policy for each individual SKU is not economical to design. ABC analysis is one of the conventionally used approaches to classify SKUs. In the classical method, the SKUs are ranked with respect to the descending order of the annual dollar usage, which is the product of unit price and annual demand. The few of the SKUs that have the highest annual dollar usage are in group A and should be taken into account mostly; the SKUs with the least annual dollar usage are in group C and should be taken into account least; the remaining SKUs are in group B. In this study, we proposed fuzzy c-means (FCM) clustering to a multicriteria ABC analysis problem to help managers to make better decision under fuzzy circumstancse. The obtained results show that the FCM is a quite simple and an easily adaptable method to inventory management....
We consider stabilizing first-order systems with time delay. The set of all stabilizing proportional-integral PI controllers are determined using an extension of the Hermite-Biehler theorem. The time delay is approximated by a second-order Pad�© approximation. For uncertain plants, with interval type uncertainty, robust stabilizing PI controllers are determined....
Surface mechanical attrition treatment (SMAT) was applied to the samples of a type AISI 304 stainless steel in order\r\nto induce grain refinement as well as formation of twins. Transmission electron microscopy and X-ray diffraction\r\nanalysis results showed that the average grain size at the surface of the SMATed sample was about 10 nm. The\r\nuntreated and SMATed samples were then welded using a one-pass gas tungsten arc procedure. The heat-affected\r\nzone (HAZ) of the samples was examined by optical microscopy and corrosion tests. Results of the double loop\r\nelectrochemical potentiokinetic reactivation tests showed that the degree of sensitization in the HAZ for the\r\nSMATed sample was very low as compared to that of the untreated one. The pre-SMATed sample was resistant to\r\nintergranular corrosion. This is mainly due to the formation of high density of twins which are not prone to carbide\r\nprecipitation because of their regular and coherent atomic structure and extreme low grain boundary energy as\r\ncompared with those of other grain boundaries....
The quest for the use of ICT in teaching and learning mathematics has been emphasized. This study investigates the competency of secondary school mathematics teachers on the use of ICT. It also examines the influence of gender on teachers� perceived self efficacy. Questionnaires were distributed to a total of one hundred (100) teachers (50 male and 50 females) in Bwari Area Council of Federal Capital Territory, Abuja Nigeria, who were asked to indicate their level of competence in the use of ICT. The validity of the questionnaire was approved by three experts in the field. The Cronbach�s alpha reliability coefficients were 0.91, 0.83, 0.79 and 0.88 for experience of using computers, level of competency in basic computer operations, competency in using computer software and total score respectively. Percentage analysis showed that 72% of the teachers do not have the required experience in the use of computers, computer basic operations and the use of application software. The chi-square analysis indicated no significant difference between male and female teachers� competence in the use of computers, computer basic operations and the use of application software. It is recommended that teachers should go extra mile in improving themselves as the professional development training provided by the government has proved inadequate. Pre-service teachers should be given basic and advanced training on the use of ICT....
Divalent metals cations present in injection\r\nwater can significantly influence the performance of alkaliââ?¬â??\r\nsurfactantââ?¬â??polymer (ASP) flooding. These cations such as\r\ncalcium and magnesium react with the added chemicals to\r\nform their insoluble salts as precipitations. In this paper, an\r\nin situ precipitation inhibitor known as sodium acrylate is\r\nused to overcome the precipitation problems prevalent with\r\nASP flooding. Fluidââ?¬â??fluid compatibility tests were performed\r\nto examine the performance of the in situ precipitation\r\ninhibitor using hard brine having large quantity of\r\ndivalent metal cations. The effect of the precipitation\r\ninhibitor on interfacial tension was also investigated using\r\nvarious inhibitor concentrations. The in situ precipitation\r\ninhibitor showed an excellent performance in preventing\r\ncalcium and magnesium precipitations and the solutions\r\nremained clear for 45 days at 80 C. Further, as the\r\ninhibitor concentration increased to an optimal value, an\r\nultra-low interfacial tension of 0.04 mN/m could be\r\nachieved. The advantage of the in situ inhibitor is the use of\r\nhard brines without the need for softening the injection\r\nwater....
This work experimentally examines the cocurrent\r\nflow of oil and water in moderately oil-wet smoothwalled\r\nsingle fractures. The focus of our investigation is on\r\nstudying the effects of varying fracture aperture and flow\r\nrate ratios on relative permeability to oil and water. The\r\nphase distribution and flow regimes within the fracture\r\nwere closely monitored and found to vary with the flow\r\nrate ratio and total flow rate, and appeared to have a direct\r\nimpact on the relative permeability. Experimental relative\r\npermeability data exhibited variations in shape indicating\r\nthe effects of fracture aperture and flow ratios. Also, the\r\ndata show the effects of oilââ?¬â??water phase interference, and\r\nphase saturation changes on the relative permeabilities for\r\neach fracture configuration. A couple of two-phase relative\r\npermeability models, namely, viscous coupling model, and\r\nhomogenous single-phase approach, were tested against the\r\nexperimental relative permeability data. This work provides\r\ninsight into the nature of two-phase flow in a single\r\nfracture and could help in better modeling of more complex\r\nfracture networks....
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