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For an efficient multimode low-density parity-check (LDPC) decoder, most hardware resources, such as permutators, should be shared among different modes. Although an LDPC code constructed based on a Reed–Solomon (RS) code with two information symbols is not quasi-cyclic, in this paper, we reveal that the structural properties inherent in its parity-check matrix can be adopted in the design of configurable permutators. A partially parallel architecture combined with the proposed permutators is used to mitigate the increase in implementation complexity for the multimode function. The high check-node degree of a high-rate RS-LDPC code leads to challenges in the efficient implementation of a high-throughput decoder. To overcome this difficulty, the variable nodes have been partitioned into several groups, and each group is processed sequentially in order to shorten the critical-path delay and hence increase the maximum operating frequency. In addition, shuffled message-passing decoding is adopted, since fewer iterations can be used to achieve the desired bit-error-rate performance. In order to demonstrate the usefulness of the proposed flexible-permutator-based architecture, one single-mode rate-0.84 decoder and two multimode decoders whose code rates range between 0.79 and 0.93 have been implemented. These decoders can achieve multigigabit-per-second throughput. Using the proposed architecture to support lower rate RS-LDPC codes, e.g., rate-0.568 code, is also investigated. [ABSTRACT FROM PUBLISHER]

The dynamic rheology of a complex granular material system strongly depends on the imposed stress state. However, drawing a clear physics based picture of dynamic granular flow is challenging due to the heterogeneous nature of granular materials, as well as the overwhelming difficulties in carrying out dynamic experiments. Here, pressure-shear plate impact (PSPI) is utilized to load a granular boron carbide ceramic in a multi-axial fashion with strain rates on the order of 105 s − 1 and pressure levels ranging from 1 to 3 GPa. Comparisons between the shear flow stresses and the superimposed normal stress indicate a strong pressure dependence in the constitutive response, along with an effective friction coefficient measured to be around 0.16. Both the normal and shear stress-strain relations are obtained. Granular boron carbide shows a highly compressible behavior with a significant amount of volume compaction achieved as the result of the large uniaxial normal strain. Due to the compaction, the estimated granular wave speed increases with density. Microstructure characterization of the deformed particles shows that fracture and amorphization are active deformation mechanisms besides the grain-grain frictional interactions and particle rearrangement. This study will contribute to the development of integrative modeling for behavior of granular boron carbide at ultra-high strain rates and confinement pressures. [ABSTRACT FROM AUTHOR]