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Journal : International Journal of Computing Science and Applied Mathematics-IJCSAM

Optimal Control of Multi-Supplier Inventory Management with Lead Time Darsih Idayani; Subchan Subchan
(IJCSAM) International Journal of Computing Science and Applied Mathematics Vol. 6 No. 1 (2020)
Publisher : LPPM Institut Teknologi Sepuluh Nopember

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Abstract

In the current global competition, companies are required to save money in order to survive. One of the expenses that can be reduced is the cost of inventory control. To minimize these costs, we require a proper planning and management of the inventory. Ordering supplies should be performed at a certain time period, especially with uncertain demand. As such, the company must determine when to order at the suppliers and how many should be ordered. So there will be no excess inventory in the warehouse because of too much ordering or because of the inventory cannot meet demand due to late or too little order to suppliers. Consequently, in this research, a quadratic cost functional is used as the objective function in multi-supplier inventory management problem with different lead time. Optimal control theory, LQR (Linear Quadratic Regulator) is used to solve this problem. According to the simulation, we conclude that the smaller weight resulted in more optimal inventory cost.
Stability and Bifurcation Analysis of Time Delayed Prey-Predator System with Holling Type-III Response Function Nur Aina Maziun; Subchan Subchan
(IJCSAM) International Journal of Computing Science and Applied Mathematics Vol. 6 No. 2 (2020)
Publisher : LPPM Institut Teknologi Sepuluh Nopember

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Abstract

Interaction between prey and predator is a recurring event that occurs continuously and the presence of both can mutually affect each other’s population. This paper discusses the stability and bifurcation analysis of time delayed prey-predator system with Holling type-III response function incorporating a prey refuge. Holling type-III response function is used because the availability of the prey in nature is decreasing. Time delay represents the time for predators to find another prey population when the available population is decreasing. Dynamic analysis is used to study the influence of a given response function. The equilibrium point and stability analysis of the model with and without time delay has been calculated and analyzed. Model analysis under the influence of time delay and coefficient of competition among predators shows an indication of Hopf bifurcation in the neighborhood of the co-existing equilibrium point.
Safety Verification of Uncertain Max-Plus-Linear Systems Aditya Putra Pratama; Subchan Subchan; Dieky Adzkiya
(IJCSAM) International Journal of Computing Science and Applied Mathematics Vol. 4 No. 2 (2018)
Publisher : LPPM Institut Teknologi Sepuluh Nopember

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Abstract

In this work, we discussed the verification of autonomous uncertain Max-Plus-Linear (uncertain MPL) systems with respect to safety property by using the reachability analysis approach. More precisely, given an uncertain MPL system, a nonempty set of initial conditions, a time horizon and an unsafe set, we want to determine whether the state can reach the unsafe set within the given time horizon. If the unsafe set is reachable, then the system is not safe. Otherwise, the system is safe. Our approach uses the piecewise affine representation of MPL systems to compute the reachable sets exactly.