Adaptive inventory policies

The case study on Vinyl Acetate Process, developed in Chapter 10, demonstrates the benefit of solving a process design and plantwide control problem based on the analysis of the reactor/separation/recycles structure. In particular, it is demonstrated that the dynamic behavior of the chemical reactor and the recycle policy depend on the mechanism of the catalytic process, as well as on the safety constraints. Because low per pass conversion of both ethylene and acetic acid is needed, the temperature profile in the chemical reactor becomes the most important means for manipulating the reaction rate and hence ensuring the plant flexibility. The inventory of reactants is adapted accordingly by fresh reactant make-up directly in recycles. 

Other actors (e.g., the Toxic Release Inventory [TRI] program in the United States and corresponding EU policies), althongh the accuracy of information provided in those schemes have often been qnestioned. There is however a lack of schemes that brings relevant information to private citizens (Dalhammar and Nilsson, 2005). Similarly, few schemes are well adapted to the needs of professional pnrchasers. 

At steady state the chemical species must enter and leave the plant in a manner that satisfies perfectly the material balance. If chemical reactions are present, the make-up policy of the reactants must fulfil the stoichiometry of various chemical reactions. However, in practice the material balance of components has always a dynamic character. When several reactants are involved, not all can be fed on flow control. Firstly, because of inherent measurement errors and variability of raw materials, the reactants cannot be exactly counted in the stoichiometric ratio. Secondly, the reaction conditions are not constant. Accumulation will take place, and over longer period could lead to dysfunctions or even to plant upset. Somewhere in the plant the inventory of the reactants and products should be measured or estimated, and the make-up policy adapted accordingly. 

Now consider an inventory/distribution network, also known as a supply chain. Each node in the network represents a stocking location. Suppose a base-stock control policy is followed at each node. With the discussion above, we can adapt the standard decomposition approach in analyzing queueing networks to study this inventory network. 

For retailers (e.g., Amazon), leadtime performance is purely determined by the structure and execution of inventory and distribution policies. But for firms that also manufacture or assemble products (e.g., Dell), the production function is also a driver of performance. Of course, all of the usual methods for achieving manufacturing efficiency (lean, agile, cellular manufacturing, etc.) are relevant to e-commerce settings. As we have noted above, modular product architectures and assemble-to-order production systems are particularly well-adapted to supporting quick-response manufacturing with which to support an e-commerce system. Since the issues of speed, variety, quality and flexibility were clearly priorities prior to the advent of e-commerce, research that addresses these remains relevant but has not been radically affected by the Internet. 

To summarize, we propose a so-called MMSE forecast adaptive base-stock policy. This policy employs the Kalman filter technique to calculate minimum mean square error (MMSE) forecasts of future demands at the beginning of each period. A fixed safety stock 7 set at the beginning of the planning horizon, is then added to the MMSE forecast to form the target level /3t for this period. Then, the following rule is applied if the current inventory position is lower than the target level, an order is placed to fill this gap otherwise, no order is placed. The advantage of our policy is that it is intuitive and easily implementable. But, not less importantly, it can be tailored for use in information-rich supply chains, for which the characterization of optimal policies is virtually impossible. 

In his first model, named locally-managed inventory (LMI) system, Aviv (2002a) studies a supply chain structure in which the members of the supply chain do not share their observations of explanatory market signals (the J-variables). Inventory is managed according to the installation-based MMSE adaptive base-stock policy, with target levels... 

This chapter examines behavioural adaptation that arises as a consequence of road safety-related policy. Through the consideration of real-world examples, as well as previous research in the area, an inventory of policy features that predicts behavioural adaptation is proposed. The ultimate goal of the chapter is to provide guidance to policymakers and road safety practitioners on how to minimise, or at least predict and manage, behavioural adaptation to road safety policy. By acknowledging its potential and anticipating its effects, road safety policymakers can make the most informed and valuable decisions that maximise a road safety policy s benefit to the whole conununity. 

The aim of this chapter is to present and discuss examples of behavioural adaptation to road safety policy countermeasures, including those that relate to the vehicle ( safer vehicles ) and the road user ( safer road users ). Examples relating to safer roads are included in Chapter 7, and so are not repeated here. Based on these examples, an inventory of policy features that are predictive of behavioural adaptation is proposed. The chapter concludes with recommendations regarding best practices in policy implementation, which, along with evidence-based research, policymakers can use to not only guide policy planning efforts, but to limit the extent and impact of any associated behavioural adaptation. 

INVENTORY OF POLICY CHARACTERISTICS TO CONSIDER WHEN ESTIMATING THE LIKELIHOOD FOR BEHAVIOURAL ADAPTATION... 

It is clear that, based on the evidence, the effectiveness of road safety policies would be more accurately estimated if the potential for behavioural adaptation was considered during the planning stages. Several authors (Bjprnskau, 1994 Cacciabue and Saad, 2008 Elvik, 2002 Hedlund, 2000 OECD, 1990 Rudin-Brown and Noy, 2002) have identified factors, or qualities, of intended policy countermeasures that seem to affect how likely it is that behavioural adaptation will develop as a consequence to their introduction. Consideration of these factors together with the examples presented above allows the development of a comprehensive list, or inventory, of those features that may be predictive of whether, and to what extent, behavioural adaptation to a road safety policy decision will occur (see below). Although precise measurement of the forms and degree of behavioural adaptation to road safety policies and countermeasures is generally not possible (Elvik, 2002), policymakers can... 

Burchell, R. W., Listokin, D. (1981). The adaptive reuse handbook Procedures to inventory, control, manage and reemploy surplus municipal properties. New Bmnswick, NJ Center for Urban Policy Research. 

Furthermore, one-time costs are incurred in this scenario through the need for intensive coordination efforts on the part of both supply chain players to jointly discuss and adapt the stock management policy. This involves analyses of historic consumption data, amongst others. In a further step, the involved employees in the planning departments would need to be familiarised with the new inventory management policy. All in all, one-off labour and administrative costs amoxmting to 0.02 % and 0.01 % = 0.0002, afj j = 0.0001) are likely to be incurred according... 

The determination of the balance sheet and P L items carried out for C and the subsequent creation and calculation of the different matrices and vectors must now also be performed in principle for C2. However, this step is abbreviated at this point, since the effects of the examined SCI at company C2 relate predominantly to one-time costs produced by the work required to revise and adapt the inventory management policy. This amount is given as roughly 0.05 % of the administrative costs (a , = 0.0005). 

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