Robust image transmission over energy-constrained time-varyingchannels using multiresolution joint source-channel coding

We explore joint source-channel coding (JSCC) for time-varying channels using a multiresolution framework for both source coding and transmission via novel multiresolution modulation constellations. We consider the problem of still image transmission over time-varying channels with the channel state information (CSI) available at (1) receiver only and (2) both transmitter and receiver being informed about the state of the channel, and we quantify the effect of CSI availability on the performance. Our source model is based on the wavelet image decomposition, which generates a collection of subbands modeled by the family of generalized Gaussian distributions. We describe an algorithm that jointly optimizes the design of the multiresolution source codebook, the multiresolution constellation, and the decoding strategy of optimally matching the source resolution and signal constellation resolution “trees” in accordance with the time-varying channel and show how this leads to improved performance over existing methods. The real-time operation needs only table lookups. Our results based on a wavelet image representation show that our multiresolution-based optimized system attains gains on the order of 2 dB in the reconstructed image quality over single-resolution systems using channel optimized source coding     

Continuous error detection (CED) for reliable communication

Block cyclic redundancy check (CRC) codes represent a popular and powerful class of error detection techniques used almost exclusively in modern data communication systems. Though efficient, CRCs can detect errors only after an entire block of data has been received and processed. In this work, we exploit the “continuous” nature of error detection that results from using arithmetic codes for error detection, which provides a novel tradeoff between the amount of added redundancy and the amount of time needed to detect an error once it occurs. We demonstrate how this continuous error detection framework improves the overall performance of communication systems, and show how considerable performance gains can be attained. We focus on several important scenarios: 1) automatic repeat request (ARQ) based transmission; 2) forward error correction (FEC frameworks based on (serially) concatenated coding systems involving an inner error-correction code and an outer error-detection code; and 3) reduced state sequence estimation (RSSE) for channels with memory. We demonstrate that the proposed CED framework improves the throughput of ARQ systems by up to 15% and reduces the computational/storage complexity of FEC and RSSE by a factor of two in the comparisons that we make against state-of-the-art systems     

Equipment for remote recording of cracks in materials and welded joints

A plasma-arc welding technique is designed for joints with the technological beads necessary to fasten flanges in thin-walled large-sized cylindrical and spherical constructions. A high-temperature plasma-gas stream penetrating down to the bottom of the bath damages the oxide film when welding aluminium products.     

Conflicts and support strategies in clashes in 2 groups of crab-eating monkeys formed from individuals with differing social status by birth

Two groups of captive macaques (M. fascicularis) were studied at the Primatological Laboratory, Kassel University, Germany. One group (D) included the animals born to high-ranking mothers, another (H) comprised those whose mothers were low-ranking. The first group was a despotic community in which conflicts occurred mainly between single individuals, and the male leader was the controlling animal. The second group was an egalitarian community split into two mutually hostile subgroups; the conflicts were less severe, and the male leader could control only his own subgroup.