Efficient heuristics for dynamic lot sizing

Dynamic lot sizing heuristics commonly implemented in standard MRP software perform well under conditions of systematic demand only. A survey and numerical test of methods proposed in the literature shows that techniques are available which cope efficiently with both systematic and erratic demand. The paper discusses theoretical and practical ramifications of the dynamic lot sizing problem, surveys heuristics published in the U.S. and West German literature, reports summarily on the findings of extensive simulation experiments involving these heuristics, and, as a conclusion from analytical and numerical results, proposes an algorithm which enhances performance under conditions of erratic demand.     

RESILIENT ECOLOGY AND LANDSCAPE SYSTEMS OF THE FENGXINGLONG ECOLOGICAL PARK,SANYA

In the past 30 years, Sanya has developed into a high-density city with fragmented ecosystems and bottlenecked urban development. In April 2015, the Ministry of Housing and Urban-Rural Development proposed “Ecological Restoration and Urban Remediation” for Sanya and prioritized the Sanya and Linchun Rivers — two rivers that run through the central city — as core causes. The Fengxinglong Ecological Park project is located at the junction of the two rivers in downtown and its surroudings are occupied for various land uses. Diversified urban interfaces, abundant green space, and numerous ecological contradictions make the site critical for the remediation and restoration of waterways in Sanya. Through a series of resilient landscape design interventions, Fengxinglong Ecological Park catches, stores, and purifies rainwater to reduce river pollution and flooding disasters in addition to offering recreational funtions. As a valuable “urban sponge” and comprehensive resilient ecological park, it has helped restore the historic ecosystem and realized the intensive use of resources.     

Coordination of replenishment activities†

Extensive research on the Economic Lot Scheduling Problem (ELSP), and on related topics, has produced powerful techniques originally designed to solve quite specific (coordination) problems. This paper emphasizes the omni-presence of coordination issues in multi-item inventories, characterizes them as problems of staggering and/or clustering replenishment activities or events, and shows how ELSP techniques combine to form a pertinent and fairly comprehensive methodology. A numerical example illustrates the use of one particularly powerful tool (powers of two) in stabilizing replenishment workloads.