Reengineering Legacy Embedded Systems
Systems that require reengineering are a fact of life in both the commercial and military arenas. The authors have developed a systematic methodology based on virtual prototyping, with accompanying tools and libraries, for rapidly upgrading electronic systems.
Rapid re-engineering of embedded real-time systems via cost-benefit analysis with K-level diagonal search
This paper formulates a problem of embedded real-time system re-engineering and presents a systematic solution. Embedded real-time system re-engineering is defined as an understanding and alteration of a legacy system to guarantee newly imposed performance requirements. The performance requirements may include a real-time throughput and an input-to-output latency. The proposed approach is based on bottleneck analysis and nonlinear optimization. The inputs to the approach include a system design specified with a process network accompanied by task graphs and task schedules, and a new real-time throughput requirement specified as a system's period constraint. The output is a set of scaling factors that represent the ratios of performance upgrades for processing elements. The solution approach works in two steps. First, it identifies bottleneck processes by estimating process latencies and by analyzing resource sharing among processes. It then derives a set of linear constraints from the new throughput requirement for bottleneck processes. Second, it formulates an integer nonlinear optimization problem and solves it for scaling factors with an objective of minimizing the hardware upgrade cost. Resultant scaling factors are used for cost-effective upgrades of processing elements. To efficiently find feasible solutions, we propose the k-level diagonal search algorithm which runs in a polynomial time with respect to the number of processing elements. Simulation results also confirm this assertion.
On the use of the Hardening Soil Small Strain model in geotechnical practice
This article highlights the importance of using advanced constitutive soil models in numerical modelling as daily geotechnical practice. In this context, the Hardening Soil (HS) model is presented as the most advanced soil model implemented in the ZSoil finite element code. The article recalls the basic features of the HS model and it explains their role in numerical simulations. The role of pre-failure non-linear behaviour of soils is also discussed. An application of the HS model is illustrated on typical geotechnical problems such as retaining wall excavation, tunnel excavation and undrained loading followed by consolidation.