scholarly journals Investing in Lead-Time Variability Reduction in a Quality-Adjusted Inventory Model with Finite-Range Stochastic Lead-Time

2008 ◽  
Vol 2008 ◽  
pp. 1-13 ◽  
Author(s):  
Farrokh Nasri ◽  
Javad Paknejad ◽  
John Affisco
Keyword(s):  
Lead Time ◽  
Variance Reduction ◽  
Inventory Model ◽  
Time Variability ◽  
Defective Items ◽  
Reduction Model ◽  
Time Variance ◽  
Total Inventory ◽  
Truncated Normal ◽  
The Impact

We study the impact of the efforts aimed at reducing the lead-time variability in a quality-adjusted stochastic inventory model. We assume that each lot contains a random number of defective units. More specifically, a logarithmic investment function is used that allows investment to be made to reduce lead-time variability. Explicit results for the optimal values of decision variables as well as optimal value of the variance of lead-time are obtained. A series of numerical exercises is presented to demonstrate the use of the models developed in this paper. Initially the lead-time variance reduction model (LTVR) is compared to the quality-adjusted model (QA) for different values of initial lead-time over uniformly distributed lead-time intervals from one to seven weeks. In all cases where investment is warranted, investment in lead-time reduction results in reduced lot sizes, variances, and total inventory costs. Further, both the reduction in lot-size and lead-time variance increase as the lead-time interval increases. Similar results are obtained when lead-time follows a truncated normal distribution. The impact of proportion of defective items was also examined for the uniform case resulting in the finding that the total inventory related costs of investing in lead-time variance reduction decrease significantly as the proportion defective decreases. Finally, the results of sensitivity analysis relating to proportion defective, interest rate, and setup cost show the lead-time variance reduction model to be quite robust and representative of practice.

scholarly journals Multi-Objective Inventory Model with Lead-Time and Defective Items

2019 ◽  
Vol 9 (2) ◽  
pp. 2415-2420
Keyword(s):  
Lead Time ◽  
Inventory Model ◽  
Inventory Problem ◽  
Defective Items ◽  
Multi Objective ◽  
Deterministic Demand ◽  
Decision Making Problem ◽  
Holding Cost ◽  
Total Inventory

Inventory problem are generally classified under decision making problem where lead time plays an important role in performance and services to customers during supply and placement of order of an item orders can be placed in shorter lead time with higher price or in longer lead time with lower cost. In this paper we have formulated multi-objective inventory model with one objective of minimizing the total inventory cost and other objective of maintaining the quality of the product by discarding the defective items. The model involved the deterministic demand, lead time dependent lead time cost, holding cost, ordering cost and inspection cost for inspecting defective items. The techniques of priority goal programming and genetic algorithm are applied and the results are compared. The sensitivity analysis is explained due to restriction in cost parameter. The model is finally illustrated with a numerical example.

scholarly journals Inventory model for deteriorating items with negative exponential demand, probabilistic deterioration and fuzzy lead time under partial back logging

2020 ◽  
Vol 30 (3) ◽  
Author(s):  
Nabendu Sen ◽  
Sumit Saha
Keyword(s):  
Inventory Management ◽  
Lead Time ◽  
Probability Distributions ◽  
Optimal Strategies ◽  
Inventory Model ◽  
Deteriorating Items ◽  
Optimal Time ◽  
Inventory Cost ◽  
Total Inventory ◽  
Negative Exponential

The effect of lead time plays an important role in inventory management. It is also important to study the optimal strategies when the lead time is not precisely known to the decision makers. The aim of this paper is to examine the inventory model for deteriorating items with fuzzy lead time, negative exponential demand, and partially backlogged shortages. This model is unique in its nature due to probabilistic deterioration along with fuzzy lead time. The fuzzy lead time is assumed to be triangular, parabolic, trapezoidal numbers and the graded mean integration representation method is used for the defuzzification purpose. Moreover, three different types of probability distributions, namely uniform, triangular and Beta are used for rate of deterioration to find optimal time and associated total inventory cost. The developed model is validated numerically and values of optimal time and total inventory cost are given in tabular form, corresponding to different probability distribution and fuzzy lead-time. The sensitivity analysis is performed on variation of key parameters to observe its effect on the developed model. Graphical representations are also given in support of derived optimal inventory cost vs. time.

scholarly journals Inventory record inaccuracy – The impact of structural complexity and lead time variability

Omega ◽  
2017 ◽  
Vol 68 ◽  
pp. 123-138 ◽  
Author(s):  
Salvatore Cannella ◽  
Roberto Dominguez ◽  
Jose M. Framinan
Keyword(s):  
Lead Time ◽  
Structural Complexity ◽  
Time Variability ◽  
The Impact

scholarly journals Imperfect production supply chain model considering price-sensitive demand and quantity discounts under free distribution approach

2020 ◽  
Author(s):  
Hemapriya S ◽  
uthayakumar R
Keyword(s):  
Lead Time ◽  
Optimal Solution ◽  
Chain Model ◽  
Quantity Discounts ◽  
Order Quantity ◽  
Defective Items ◽  
Free Distribution ◽  
Supply Chain Model ◽  
Precautionary Measures ◽  
The Impact

During production process, we may experience with some imperfect things disregarding every single precautionary measures. The imperfect things are each of two dismissed promptly at the season of production or reworked and sold as great ones or customers are given plenty discount to keep up the generosity of the organization. This article considers about this practical circumstances and includes price-sensitive demand. As production propels, we have defective items as a part of result. The customer’s demand is pretended to be price-sensitive dependent to increment the quantity of offers, and the vendor offers a quantity discount to persuade the buyer to purchase more amounts. Here, the lead time demand follows a free distribution. Therefore, the integrated model is used to find the optimizing values for the total number of shipments, order quantity, safety factor and retail price. An efficient iterative algorithm is designed to obtain the optimal solution of the model numerically and sensitivity analysis table formulate to show the impact of different parameter.

scholarly journals Managing slow-moving item: a zero-inflated truncated normal approach for modeling demand

2020 ◽  
Vol 6 ◽  
pp. e298
Author(s):  
Fernando Rojas ◽  
Peter Wanke ◽  
Giuliani Coluccio ◽  
Juan Vega-Vargas ◽  
Gonzalo F. Huerta-Canepa
Keyword(s):  
Decision Analysis ◽  
Lead Time ◽  
Multiple Linear Regression Model ◽  
Inventory Model ◽  
Statistical Distribution ◽  
Intermittent Demand ◽  
Suggested Approach ◽  
Service Companies ◽  
Truncated Normal ◽  
Slow Moving

This paper proposes a slow-moving management method for a system using of intermittent demand per unit time and lead time demand of items in service enterprise inventory models. Our method uses zero-inflated truncated normal statistical distribution, which makes it possible to model intermittent demand per unit time using mixed statistical distribution. We conducted numerical experiments based on an algorithm used to forecast intermittent demand over fixed lead time to show that our proposed distributions improved the performance of the continuous review inventory model with shortages. We evaluated multi-criteria elements (total cost, fill-rate, shortage of quantity per cycle, and the adequacy of the statistical distribution of the lead time demand) for decision analysis using the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). We confirmed that our method improved the performance of the inventory model in comparison to other commonly used approaches such as simple exponential smoothing and Croston’s method. We found an interesting association between the intermittency of demand per unit of time, the square root of this same parameter and reorder point decisions, that could be explained using classical multiple linear regression model. We confirmed that the parameter of variability of the zero-inflated truncated normal statistical distribution used to model intermittent demand was positively related to the decision of reorder points. Our study examined a decision analysis using illustrative example. Our suggested approach is original, valuable, and, in the case of slow-moving item management for service companies, allows for the verification of decision-making using multiple criteria.

scholarly journals Model Persediaan Pemasok-Pembeli Dengan Produk Cacat Dan Kecepatan Produksi Terkontrol.

2016 ◽  
Vol 15 (2) ◽  
pp. 103
Author(s):  
NELITA PUTRI SEJATI ◽  
WAKHID AHMAD JAUHARI ◽  
CUCUK NUR ROSYIDI
Keyword(s):  
Sensitivity Analysis ◽  
Production Rate ◽  
Lead Time ◽  
Demand Uncertainty ◽  
Lot Size ◽  
Defective Items ◽  
Total Cost ◽  
Joint Economic Lot Size ◽  
Demand Rate ◽  
The Impact

Penelitian ini mengembangkan model persediaan Joint Economic Lot Size (JELS) pada pemasok tunggal pembeli tunggal untuk jenis produk tunggal dengan mempertimbangkan produk cacat dan tingkat produksi terkontrol. Tingkat permintaan pada pembeli bersifat stokastik. Pengiriman dilakukan dari pemasok ke pembeli dalam ukuran lot pengiriman yang sama dan lead time pengiriman bersifat tetap. Produk cacat yang ditemukan oleh pembeli pada saat inspeksi disimpan secara sementara di gudang pembeli hingga pengiriman berikutnya tiba untuk selanjutnya produk cacat dikembalikan kepada pemasok. Fungsi tujuan dari model ini adalah meminimasi total biaya persediaan gabungan pemasok pembeli dengan variabel keputusan, yaitu frekuensi pengiriman, periode review, dan tingkat produksi. Analisis sensitivitas dilakukan untuk melihat pengaruh perubahan parameter-parameter tertentu terhadap model. Hasil yang didapatkan dari analisis sensitivitas menunjukkan bahwa total biaya persediaan gabungan sensitif terhadap perubahan nilai parameter persentase produk cacat, ketidakpastian permintaan, dan permintaan. In this paper, we consider a joint economic lot size (JELS) model consisting of single vendor single buyerwith single product. We intend to study the impact of defective items and controllable production rate onthe model. The demand in buyer side is assumed to be stochastic. The delivery of lot from vendor to buyer is conducted under equal size shipment and the lead time is assumed to be constant. The defective items founded by the inspector in buyer side are carried in buyer’s storage until the next shipment and will be returned to the vendor. The goal of the proposed model is to determine optimal delivery frequency, review period and production rate by minimizing the joint total cost. A sensitivity analysis is performed to show the impact of the changes of the decision variables on model’s behavior. The result from the sensitivity analysis shows that the joint total cost is sensitive to the changes of defect rate, demand uncertainty and demand rate. 

scholarly journals Impact of Imperfect Quality Items on Inventory Management for Two Warehouses with Shortages

2020 ◽  
Vol 5 (5) ◽  
pp. 869-885
Author(s):  
Aastha . ◽  
Sarla Pareek ◽  
Leopoldo Eduardo Cárdenas-Barrón ◽  
Mandeep Mittal
Keyword(s):  
Inventory Management ◽  
Storage Capacity ◽  
Inventory Model ◽  
Optimal Order ◽  
Defective Items ◽  
Imperfect Quality ◽  
Inspection Process ◽  
Total Profit ◽  
The Cost ◽  
The Impact

Generally, the majority of the inventory models work on the concept that overall units produced must be perfect in terms of quality and that the storage capacity of the warehouse is unlimited. In fact, under realistic conditions, it is not possible to manufacture products with complete perfection. Furthermore, there are always some limits associated with storage capacity of the warehouse. This paper formulates an inventory model that considers the impact of imperfect quality items and shortages. The cost of storage in rented warehouse (RW) is greater than own warehouse (OW) due to fact there are better preservation facilities in RW. This work considers that defective items are completely withdrawn after the inspection process. The purpose of this inventory model is to establish the optimal order quantity and backorder size that maximize the total profit. Some numerical examples are solved, and a sensitivity analysis is included.

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