Vinaya Shukla

Bullwhip and backlash in supply pipelines.

‘Bullwhip’ is the phenomenon experienced in practice, signifying the propagation and amplification of orders as they pass upstream in a supply chain pipeline. ‘Bullwhip’ creates uncertainty for managers who then create stock and/or maintain excess capacity leading to increased total costs. A well known descriptor of the phenomenon is the MIT Beer Game simulation. We use the Beer Game to describe and explore a different phenomenon we term the ‘backlash’ effect. This is the resulting impact of the ‘bullwhip’ effect on shipments downstream. The two effects described have analogue with amplitude pressure wave propagation (‘bullwhip’) and reflection (‘backlash’) in physical systems such as flow ducts. We use the Fourier transform method to describe the ‘bullwhip’ propagation and ‘backlash’ reflections. We conclude that the ‘backlash’ effect occurs due to the ready availability of capacity in the whole supply chain and inventory in the final echelon.

Zero-sum and frontier trade-offs: an investigation on compromises and compatibilities amongst manufacturing capabilities

This paper examines well-accepted methodologies and rationales used to assert the presence/absence of trade-offs and compatibilities between manufacturing capabilities, and comparisons are made with respect to more recent theoretical developments. By means of a detailed analysis of a representative framework, important limitations and inconsistencies are identified. The proposal for the existence of zero-sum and frontier trade-offs intends to resolve some of those issues. Generally speaking, zero-sum trade-offs are identified by a statistically significant and negative correlation. On the other hand, frontier trade-offs are predicted to be observed after some level of compatibility between different capabilities is achieved. This means that, apart from widely-used probabilistic methodologies such as linear regression/correlation analysis, subsequent deterministic approaches and rationales need to be applied in order to acknowledge the potential existence of frontier trade-offs. These and other implications are discussed in light of previous studies, and suggestions for future research are offered.

Performance improvements seen through the lens of strategic trade-offs

Performance improvement and competitive advantage are closely related but different concepts. However, the strategic operations management field has often used them interchangeably/equivalently in previous investigations involving Wickham Skinner’s strategic trade-offs model and related theories. In this study, the relationship between these concepts is clarified by means of thought experiments, which are developed on the basis of methodologies, approaches and rationales used in previous studies. It is logically established that utilising measures of improvement along individual performance criteria is inadequate when testing the trade-offs model’s core implications, because these, as per Skinner, only apply in comparisons involving market-leading performance in those criteria (realisation of competitive advantage). The incompleteness of approaches such as linear regression/correlation analysis and like methodologies for such studies is also demonstrated. In short, our research attempts to clarify some misconceptions that are prevalent when performance improvements, market-leading performance and strategic trade-offs are investigated and debated. Venues for future research are offered.

The impact of capacity constraints on supply chain dynamics

Supply chains face varied disturbances which affect their efficiency and customer service provision. An endemic disturbance which has a significant impact on both upstream as well as downstream supply chain operations arises from capacity constraints in one or more echelons. This study uses a dynamic simulation model of the Beer Game (four echelon production distribution system) to investigate the impact of these constraints on the dynamics of supply chain variables. Shipping constraints on the distribution echelons (retailer, wholesaler and distributor) and production constraints on the factory are individually applied on the supply chain and the order, shipment and net inventory profiles obtained are explained. Profiles are subsequently clustered to identify cluster membership patterns associated with the location of a constrained echelon in the chain for which a related look up table has been suggested.

Green supply chain management: the case of the construction sector in the United Arab Emirates (UAE)

Abstract Restraining the negative environmental impacts of the construction sector constitutes one of the major challenges of the twenty-first century. However, efforts to address it have been largely fragmented. With environmental consequences of a construction project typically dispersed across its life cycle, i.e. from design through to end-of-life, greening this sector requires a supply chain wide focus inclusive of all key stages and stakeholders; also, all relevant aspects such as the nature of green practices implemented and associated drivers, barriers and performance implications need to be considered. This forms the focus of the present study where a comprehensive, green supply chain management oriented understanding of the construction sector is developed through the context of the UAE construction sector, and incorporating inputs from all key stakeholders, i.e. Developers, Architects/Consultants, Contractors and (material) Suppliers. The study contributes to improving the efficiency and effectiveness of greening of the construction sector.

Rogue seasonality in supply chains: an investigation and a measurement approach

Purpose – Shukla et al (2012) proposed a signature and index to detect and measure rogue seasonality in supply chains, but which however, were not effectively validated. The authors have sought to investigate rogue seasonality using control theory and realistic multi echelon systems and rigorously validate these measures, so as to enable their application in practice. The paper aims to discuss these issues. Design/methodology/approach – Frequency domain analysis of single echelon and simulated four echelon Beer game system outputs are used in the investigation, with the simulation incorporating realistic features such as non-linearities from backlogs and batching, hybrid make to order-make to stock ordering system and the shipment variable. Lead time, demand process parameters, ordering parameters and batch size are varied in the simulation to rigorously assess the validity of the index. Findings –The signature based on the cluster profiles of variables, specifically whether the variables cluster together with or away from exogenous demand, was validated. However, a threshold for the proportion of variables that could be clustered with exogenous demand and the system still being classified as exhibiting rogue seasonality, would require to be specified. The index, which is derived by quantifying the cluster profile relationships, was found to be a valid and robust indicator of the intensity of rogue seasonality, and which did not need any adjustments of the kind discussed for the signature. The greater effectiveness of the frequency domain in comparison to time for deriving the signature and index was demonstrated. Practical implications – This work enables speedy assessment of rogue seasonality in supply chains which in turn ensures appropriate and timely action to minimize its adverse consequences. Originality/value – Detailed and specific investigation on rogue seasonality using control theory and Beer game simulation and rigorous validation of the signature and index using these methods.

Detecting disturbances in supply chains: the case of capacity constraints

Purpose The ability to detect disturbances quickly as they arise in a supply chain helps to manage them efficiently and effectively. The purpose of this paper is to demonstrate the feasibility of automatically and therefore quickly detecting a specific disturbance, which is constrained capacity at a supply chain echelon. Design/methodology/approach Different supply chain echelons of a simulated four echelon supply chain were individually capacity constrained to assess their impacts on the profiles of system variables, and to develop a signature that related the profiles to the echelon location of the capacity constraint. A review of disturbance detection techniques across various domains formed the basis for considering the signature-based technique. Findings The signature for detecting a capacity constrained echelon was found to be based on cluster profiles of shipping and net inventory variables for that echelon as well as other echelons in a supply chain, where the variables are represented as spectra. Originality/value Detection of disturbances in a supply chain including that of constrained capacity at an echelon has seen limited research where this study makes a contribution.

Environmental supply chain management in the construction sector: theoretical underpinnings

ABSTRACT Environmental implications of a product/project are typically spread across its supply chain, from design through to end-of-life. This is particularly acute for construction sector because of the inherent nature and complexity of its supply chain. The sector, therefore, could benefit from the application of environmental supply chain management (ESCM), a systematic and integrated approach towards restraining the adverse environmental impacts emanating from the supply chain. Unfortunately, uptake of ESCM in construction vis-à-vis other sectors is limited and fragmented. This formed the motivation, which using 39 interviews across 20 firms in the UAE construction sector, provide systemic insights on the various facets of ESCM namely, core and facilitating environmental practices, internal and external drivers (pressures/motives) and barriers/challenges affecting environmental practices’ implementation, and relevant environmental performance measures across different firm types and stakeholders with the support of several established/emerging theories. The findings is expected to enhance the application of ESCM in construction.

Sensing endogenous seasonality in the case of a coffee supply chain

ABSTRACT Rogue seasonality, or endogenously generated cyclicality (in variables), is common in supply chains and known to adversely affect performance. This paper explores a technique for sensing rogue seasonality at a supply chain echelon level. A signature and index based on cluster profiles of variables, which are meant to sense echelon-level generation and intensity of rogue seasonality, respectively, are proposed. Their validity is then established on echelons of a downstream coffee supply chain for five stock keeping units (SKUs) with contrasting rogue seasonality generation behaviour. The appropriateness of spectra as the domain for representing variables, data for which is daily sampled, is highlighted. Time-batching cycles which could corrupt the sensing are observed in variables, and the need to therefore filter them out in advance is also highlighted. The knowledge gained about the echelon location, intensity and time of generation of rogue seasonality could enable timely deployment of specific mitigation actions.