Embedded devices built on microcontroller units (MCUs) power a vast array of safety- and performance-critical applications. Contrary to the long-held belief that resource-constrained embedded devices avoid dynamic allocations, recent studies show that heap use is actually common. Therefore, embedded software written in C/C++ is prone to temporal memory safety violations. The lock-and-key mechanism is a well-established defense for temporal memory safety. For high performance, recent studies embed keys directly in the unused high-order bits of 64-bit pointers, but this approach has been considered infeasible on MMU -less embedded devices. In this paper, we propose ELK, an effective lock-and-key technique for temporal memory safety on embedded devices in ARMv8-M. ELK observes that only the low-order bits of a 32-bit pointer are needed to access on-chip SRAM. Thus, ELK embeds keys in the unused middle-range bits of 32-bit pointers and stores locks inline with objects through size-aligned allocation that leverages ARMv8-M hardware features. Evaluating the ELK prototype shows geometric mean runtime overheads of 3.9% and 7.4 % on the BEEBs and MiBench2, respectively. The memory overhead, which represents the increase in peak heap usage, ranges from 0.1 % to 2.6 % across six heap-intensive applications. On the Juliet test suite, ELK detects all 180 temporal memory safety violations with zero false positives.

A comprehensive review of 3-D/4-D-printed reconfigurable metasurfaces (RMSs) is presented in this article. A metasurface (MS) demonstrates exceptional abilities for electromagnetic (EM) wave molding beyond that offered by conventional planar interfaces, and RMS provides MS with more diverse EM wave-control capabilities. RMSs are categorized by the type of external stimulus used for reconfiguration, such as electrical RMS, fluidic RMS, mechanical RMS, and thermal RMS. To implement these RMSs, it is important to understand the design and fabrication requirements as well as the EM characteristic of each RMS, including its advantages and disadvantages. In particular, except for electrical RMS, RMSs require complex 3-D structures or special materials that are difficult to implement with conventional subtractive manufacturing methods such as printed-circuit-board manufacturing. Recently, advanced 3-D/4-D printing technology has achieved high fabrication freedom and meets the design and fabrication requirements of each type of RMS. In this article, we introduce representative RMSs with the development of 3-D/4-D printing technology and materials. Furthermore, current issues of RMSs based on 3-D/4-D printing technology and future directions are described.

In this paper, we present a spatial resolution reduction transcoding architecture for H.264/AVC with a low-complexity compensation technique. A fast motion vector re-estimation based on a k-means clustering algorithm is proposed for efficiently determining a motion vector and a reference frame. A motion vector refinement technique is used to further improve the rate-distortion performance without additional high complexity. The proposed method significantly reduces the motion vector estimation complexity up to 10 times while the loss of rate distortion performance is negligible with a decrease of 0.1dB in BD-PSNR and 3% increase in the BD-RATE.