International Journal of Inventory Research (8 papers in press)
Analysis of the Robustness of a Single-Tier Pipeline Inventory Model
by Anthony White, Michael Censlive
Abstract: This paper examines the conditions necessary to specify a robust element of a supply chain using control theory and proposes a new robustness criterion clearly separating robustness from resilience. Algebraic analysis, using the Mikhailov criterion to determine robustness, yields simple criteria for an automatic pipeline with variable inventory and order based production control system (APVIOBPCS) model. Models implemented with either exponential delays or finite delays are found to be completely robust
A new robustness measurement criterion is defined and applied to a case study of RAM manufacture. Results show that the continuous model of an APVIOBPCS system with an exponential delay has a wider allowable range of process delay time than other models and the range of permissible delay is sufficient to cope with a substantial increase in process delay time while retaining adequate performance and stability. Use of nonlinear inventory generally reduces the robustness range.
The techniques used here can also determine the effects of other parameters on robustness.
Keywords: Robustness; APVIOBPCS; control theoretic models; continuous system; discrete system; Mikhailov criterion.
Inclusion of Two-warehouse production prototype for deteriorating inventory Items in Payments
by Nirakar Niranjan Sethy, Nini Maharana, Ameeya Kumar Nayak, Soumya Swayamjyoti
Abstract: In this study an inventory model is proposed for deteriorating items considering two separate warehouses, as own warehouse (OW) of finite dimension and the rented warehouse (RW) for keeping the extra elements higher than the specified accommodation of the OW in practice. A lower deterioration rate is provided by the RW compared to OW due to its better preserving amenity. Also, the holding cost per unit in OW is lower compared to RW. In this paper an inventory model is considered for deteriorating items with inclusion of a two-warehouse management with linear demand rate and delay in payment. The objective of this work is to obtain the best fit replenishment strategies with minimization of the total inventory cost. Numerical experiments are conducted with the developed mathematical model considering various parameters such as order, units and year. A sensitivity analysis is made to obtain optimal solutions with the change of parametric values with time.
Keywords: Inventory management; Two-ware house; Replenishment strategies; Sensitivity analysis.
A Production Stock Model for a Distributed Deteriorating Product with both Price and Time Dependent Demand Rate under Inflation and Late Paying Allowing Shortages
by M. Dhivya Lakshmi, P. Pandian
Abstract: This paper develops a production stock model for deteriorating products with shortages under the effect of inflation and late paying in which demand is a function of selling price and time. In this article, the model is considered with different deterioration distributions and various time dependent holding costs. This model aids in maximising the total inventory cost by finding the two production periods, the consumption period and the shortage period. Numerical example is presented to understand the developed model. Also, the effect of changes in different parameters on the optimal total cost is graphically presented
Keywords: inventory model; production; deterioration; shortages; inflation; permissible delay in payments; total profit.
Innovative approach of Stock- linked demand dependent Production Inventory Model with Decline Deterioration
by R.P. Tripathi, Sachin Mishra
Abstract: In this study, an economic production quantity (EPQ) model is established in favor of failing commodities. Demand rate of an item is considered to be stock induced. In this developed model manufacture rate is measured to be larger relative to demand rate. Mathematical model is offered to locate best possible cycle time and entire inventory cost. Algebraic example is provided to authenticate the model projected in this study. Sensitivity examination is demonstrated with the variation of dissimilar parameters.
Keywords: Stock- linked demand; deterioration; production; inventory; cycle timernrn.
Location pricing to effectively reduce inventory repositioning: The car rental industry
by Kuangnen Cheng, Hui-Ping Chen
Abstract: Inventory repositioning or pooling to efficiently align demand and supply is a strategic tool widely used in the car rental industry. This technique produces optimal results when demand is negatively correlated between locations within a pool. In practice, effective pricing decisions are expected to complement capacity adjustment, so activities of inventory repositioning can be minimized. Although matching demand increases profit, inventory repositioning unavoidably increases cost; thus, this investigation explores a different aspect of inventory repositioning, namely, effectiveness. The study utilizes live pricing data from the U.S. car rental industry, an industry where price is a major differentiator in the market, to detect whether any unwarranted inventory repositioning activity can be removed. Hypotheses are formulated to test whether discrete pricing between weekdays and weekends indeed exists within each pool. Consequently, if rivals do not follow this dogma of discrete pricing strategy, then there must be some invaluable insights. This exploration reveals numerous unforeseen factors such as the size of a rival, the volume of the demand, the destination character (leisure vs. business city) and a constant exorbitant daily rental rate, etc. make inventory repositioning ineffective. Ultimately, an effective repositioning model is proposed.
Keywords: Car rental industry; complementary demand; dynamic pricing; flexible capacity; inventory repositioning.
Two-echelon supply chain inventory model with variable lead time and ramp-type demand for deterioration item under bi-level credit period
by Dipak Barman, Barun Das
Abstract: Here a two-echelon supply chain inventory problem consisting vendor and buyer is considered for deteriorating item. In the system, buyer receives an opportunity of trade credit from vendor and simultaneously buyer offers a credit period to the customers. The buyers inventory model includes stochastic lead time following normal distribution and buyer sells the item to the customer with more realistic ramp-type demand rate. Vendor produces the goods to maintain the supply to buyer. The purpose of this study is to minimize the total cost for different sub-cases. The problem is optimized through the soft computing technique namely, genetic algorithm and different type of convexity has been tested here. Finally, this model is discussed with numerical examples.
Keywords: Vendor-buyer integrated inventory system; stochastic lead time; ramp-type demand; deterioration; bi-level credit policy; genetic algorithm.
Scheduling Period Inventory Model with Weibull Deteriorating for Crisp and Fuzzy
by Yasmien Morsy, Hala Fergany, Omnia Gawdt
Abstract: Two different cases of the probabilistic scheduling period inventory model for deteriorating items are discussed. The deterioration rate follows the Weibull distribution with two-parameter with varying and constrained expected deteriorating cost, when the demand during any scheduling period is a random variable and without shortage. The first case when the total cost components are considered to be crisp values, and the other case when the costs are considered as trapezoidal fuzzy numbers. Also, some special cases are deduced. To illustrate the proposed model in the crisp case and the fuzzy case, a numerical example was added.
Keywords: Deterioration; Deterministic lead time; Scheduling period; Trapezoidal fuzzy numbers; Weibull distribution of two-parameter.
Special Issue on: Digital Innovations in Inventory and Supply Chain Management
RFID Based Smart Inventory System Suitable for All Businesses
by Mrudula Amirapu, Rajendran Eshwari, H.M. Nischitha, N.J. Prajwal, K.P. Lakshmi
Abstract: This paper details the design and development of an RFID-based prototype inventory system. The system comes with a user-friendly graphical user interface and is built to track and monitor the movement of items, and maintain detailed (timestamped) audit logs on item removal, replenishment, and every user action. While authorised access to the store is achieved through RFID tags, this system uses an automatic servo motor-based locking mechanism to secure the items in the inventory store. The system is configured to identify and authenticate two user profiles administrator and end user. The administrator (in charge of the inventory) typically has permissions to monitor and update the inventory, while the end user is only able to view the contents of the inventory through the web GUI, and place/replace items in the store. This system has been developed to be scalable to suit inventory applications across business entities, educational institutions such as colleges and schools and even homes. This RFID-based inventory system comprises mainly of an inventory store that has RFID tagged items/goods, and an RFID reader that tracks them.
Keywords: inventory system; passive RFID; active RFID; Raspberry Pi.