• An efficient solution method to design the cost-minimizing platform portfolio

      Van den Broeke, Maud; Boute, Robert; Cardoen, Brecht; Samii, Behzad (European Journal of Operational Research, 2017)
      To offer a wide product variety to customers in a cost-efficient way, companies have introduced platforms, defined as a base from which different products can be derived. We consider a product portfolio, consisting of a set of end products, where each product has a set of attributes (features), which can have different levels requested by the customers. We present a model to support companies in designing the cost-minimizing platform portfolio, consisting of a set of platforms, from which these products can be derived. Each platform has a set of technical design parameters, which can have different levels. The required parameter levels in the platform's design depend on the attribute needs of the products derived from the platform. Our model gives guidance to what extent the platforms should be under-designed, over-designed or the same with regard to the products (and its attribute levels) derived from them. The model quantifies the impact of these platform portfolio decisions on the relevant operational costs. Given the complexity of this problem for large-scale instances, we develop two fathoming rules to improve computational efficiency. These fathoming rules can be used in different solution algorithms. We illustrate their applicability in a branch-and-bound, simulated annealing and genetic algorithm. We demonstrate the value of our model and solution method with a practical case of a high-tech screen manufacturing company, that wants to design the cost-minimizing platform portfolio from which their product portfolio can be derived.
    • An inventory reservation problem with nesting and fill rate based performance measures

      Samii, Behzad; Pibernik, Richard; Yadav, Prashant (International Journal of Production Economics, 2011)
    • Evaluation of product-platform decisions based on total supply chain costs

      Van den Broeke, Maud; Boute, Robert; Samii, Behzad (International Journal of Production Research, 2015)
      Over the past decades, several companies have introduced product platforms in the design of their products in order to produce a large product variety in a cost-efficient way. However, for some companies, the introduction of platforms ended up being more costly than expected, leading them to reconsider their platform decisions. In this paper, we develop a model to support companies in determining (1) how many platforms to develop, (2) which platforms to develop and (3) which products to derive from which platforms. The model takes into account the impact of these product-platform decisions on a company's relevant supply chain activities and costs. The model shows how the optimal product-platform decisions depend on the trade-off between the costs of platforms versus the costs of customising these platforms to final product variants. We propose a simulated annealing algorithm to solve large problem instances within reasonable time. The practical validity of our model is shown through its application in a global technology company specialised in the development and production of medical screens.
    • Impact of nested inventory allocation policies in a newsvendor setting

      Samii, Behzad (International Journal of Production Economics, 2016)
      We model an inventory management setting in which the decision maker first uses newsvendor model to decide on the amount of ordered perishable inventory for a fixed consumption period, based on the best available forecast of demand at the time of ordering. After a relatively long lead time, the consumption period starts and she has to assign the received inventory to two priority customer classes given the -newly updated- rate of arrival of each class. The assignment of inventory requires two simultaneous decisions: 1) the reservation quantity for the high priority class and 2) the choice of inventory allocation mechanism (Standard Nesting SN or Theft Nesting TN), to minimize the expected units short of the high priority class while minimizing the wasted inventory at the end of the fixed consumption period. We assume that some partial information about the bottom line impact of a shortage in high priority customer class compared to the other can be conjectured. For both inventory allocation mechanisms, we then calculate the monetary benefit for all feasible reserved quantities to identify the optimal reserved quantity. We derive closed form expressions for the expected number of units short in each demand class under SN and TN allocation mechanisms. We showcase the management of electricity smart meter inventory in a multi-year implementation project consisting of multiple fixed consumption periods. Numerical experiments and graphical interpretations feature the optimum allocation policy and the cost minimizing reserved quantity under such policy.
    • Reservation and allocation policies for influenza vaccines

      Samii, Behzad; Pibernik, Richard; Yadav, Prashant; Vereecke, Ann (European Journal of Operational Research, 2012)
      This research investigates the impact of alternative allocation mechanisms that can be employed in the context of vaccine inventory rationing. Available vaccine inventory can be allocated to arrivals from high priority (target groups such as healthcare professionals) and low priority (non-target groups) demand classes using Partitioned Allocation (PA), Standard Nesting (SN), and Theft Nesting (TN). In any one of the mechanisms, a part of the available inventory is reserved for the exclusive use of the high priority demand class. They differ, however, in how the unreserved portion of the inventory is utilized: Under PA, demand from the high (low) priority class consumes only the reserved (unreserved) quantity. Under SN, demand from the high priority class first consumes the reserved quantity; once and if this quantity is exhausted, high priority demand competes with low priority demand for the remaining inventory. Under TN the sequence of allocation is reversed: both demand classes first compete for the unreserved inventory. Once this portion of inventory is exhausted, high priority demand is fulfilled from the reserved inventory and low priority demand is rejected. We develop service level (probability of fulfilling the entire demand) and fill rate (fraction of demand fulfilled) expressions for all three allocation mechanisms. Based on these expressions, numerical analyses are conducted to illustrate which allocation mechanism a health planner should choose depending on the availability of vaccines, and how the health planner should set the reserved quantity for the high priority class. We observe that (1) there exist certain conditions under which one of the allocation mechanisms outperforms the others and (2) this effect is determined by the decision maker’s choice of the performance measure.
    • The impact of supply chain resilience on the business case for smart meter installation

      Samii, Behzad; Meyers, Kris; ümit, Hakan (The Electricity Journal, 2014)
      To produce realistic cost benefit assessments for the rollout of electricity smart meters, financial and operational decision-makers can collaborate using the framework of operational excellence and supply chain resilience. Strategies of product standardization, installation cost unification, onsite uncertainty reduction, and binding investments deferral not only reduce electricity supply chain vulnerabilities but also provide considerable cost reduction and resource optimization.