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A new design of a reconfigurable multirotor is developed by employing a novel active–passive motor scheme. The scheme is based on quadrotor configuration with four additional motors placed in coaxial setup along a single axis. This unconventional design seeks to improve the general response of the system and increase the payload carrying capacity of the aerial vehicle. This paper presents an extensive mathematical model to establish the stability of the design, along with simulation and various real time tests. Simulation of the mathematical model with a proportional–integral–derivative (PID) controller shows the stability and responsiveness of the system in different configurations. Throttle response is also compared for different configurations. Finally, preliminary experimental test results with a prototype employing the same design are discussed. It is analytically and experimentally a stable system with a general improvement in throttle response. [ABSTRACT FROM AUTHOR]

The article presents a closure to energy metrics for the assessment of water distribution system. Topics include a summary on how energy flows vary temporally and spatially in water distribution systems, the goal of nomenclature and energy breakdown proposed in the paper, and the convenience of bringing attention to the coincidence in the metrics.

Operational performance in residential construction production systems is assessed based on measures such as average house-completion time, number of houses under construction, lead time, and customer service. These systems, however, are prone to nonuniformity and interruptions caused by a wide range of variables such as inclement weather conditions, accidents at worksites, fluctuations in demand for houses, and rework. The availability and capacity of resources therefore are not the sole measures for evaluating construction production systems capacity, especially when rework is involved. The writers' aim is to investigate the effects of rework timeframe and frequency/length on tangible performance measures. Different call-back timeframes for rework and their impact on house-completion times are modeled and analyzed. Volume home-building was chosen as the industry sector studied in the research reported in this paper because it is a data-rich environment. The writers designed several experiments to model on time, late, and early call-back timeframes in the presence of rework with different length and frequency. Both mathematical modeling and discrete-event simulation were then used to compare and contrast outputs. The measurements showed that the average completion time is shorter in systems interrupted by frequent but short rework. In other words, a smaller downstream buffer between processes is required to avoid work starvation than those systems affected by infrequent but long interruptions. Early call-backs for rework can significantly increase the number of house completions over the long run. This indicates that there is an opportunity for the mass house-building sector to improve work practice and project delivery by effectively managing rework and its related variables. The research reported in this paper builds on the current body-of-knowledge by applying even-flow production theory to the analysis of rework in the residential construction sector, with the intention of ensuring minimal disruption to construction production process and improving productivity. [ABSTRACT FROM AUTHOR]