Measurement of through-the-thickness variations of mechanical properties in SA508 Gr.3 pressure vessel steels using ball indentation test technique

The through-the-thickness variations of mechanical properties in SA508 Gr.3 pressure vessel steels were measured using the automated ball indentation (ABI) test technique. Key mechanical properties, such as the yield strength, ultimate strength, flow curve and hardness, were evaluated from indentation load-depth curves. The mechanical properties measured were location-dependent and the steepest gradients in the distributions of the mechanical properties appeared in the near-surface regions. The maximum through-the-thickness variations of the mechanical properties were in the range of 5–20% and they depended on the manufacturing process as well as the original wall thickness. It was concluded that the through-the-thickness variations in the mechanical properties were mainly caused by the location-dependent cooling rate during water quenching in the quality heat treatment which consisted of water quenching and tempering.     

Cooperative Hybrid‐ARQ Protocols: Unified Frameworks for Protocol Analysis

Cooperative hybrid‐automatic repeat request (HARQ) protocols, which can exploit the spatial and temporal diversities, have been widely studied. The efficiency of cooperative HARQ protocols is higher than that of cooperative protocols because retransmissions are only performed when necessary. We classify cooperative HARQ protocols as three decode‐and‐forward‐based HARQ (DF‐HARQ) protocols and two amplified‐and‐forward‐based HARQ (AF‐HARQ) protocols. To compare these protocols and obtain the optimum parameters, two unified frameworks are developed for protocol analysis. Using the frameworks, we can evaluate and compare the maximum throughput and outage probabilities according to the SNR, the relay location, and the delay constraint. From the analysis we can see that the maximum achievable throughput of the DF‐HARQ protocols can be much greater than that of the AF‐HARQ protocols due to the incremental redundancy transmission at the relay.     

Extraction and Regularization of Various Building Boundaries with Complex Shapes Utilizing Distribution Characteristics of Airborne LIDAR Points

This study presents an approach for extracting boundaries of various buildings, which have concave boundaries, inner yards, non‐right‐angled corners, and nonlinear edges. The approach comprises four steps: building point segmentation, boundary tracing, boundary grouping, and regularization. In the second and third steps, conventional algorithms are improved for more accurate boundary extraction, and in the final step, a new algorithm is presented to extract nonlinear edges. The unique characteristics of airborne light detection and ranging (LIDAR) data are considered in some steps. The performance and practicality of the presented algorithm were evaluated for buildings of various shapes, and the average omission and commission error of building polygon areas were 0.038 and 0.033, respectively