Nested Lattice Codes for Gaussian Relay Networks with Interference

In this paper, a class of relay networks is considered. We assume that, at a node, outgoing channels to its neighbors are orthogonal, while incoming signals from neighbors can interfere with each other. We are interested in the multicast capacity of these networks. As a subclass, we first focus on Gaussian relay networks with interference and find an achievable rate using a lattice coding scheme. It is shown that there is a constant gap between our achievable rate and the information theoretic cut-set bound. This is similar to the recent result by Avestimehr, Diggavi, and Tse, who showed such an approximate characterization of the capacity of general Gaussian relay networks. However, our achievability uses a structured code instead of a random one. Using the same idea used in the Gaussian case, we also consider linear finite-field symmetric networks with interference and characterize the capacity using a linear coding scheme.Comment: 23 pages, 5 figures, submitted to IEEE Transactions on Information Theor

Effects of Nonuniform Fiber Geometries on the Microstructural Fracture Behavior of Ceramic Matrix Composites

Microstructural fracture behavior of a ceramic matrix composite (CMC) with nonuniformly distributed fibers is studied in the presentation. A comprehensive numerical analysis package to study the effect of nonuniform fiber dimensions and locations on the microstructural fracture behavior is developed. The package starts with an optimization algorithm for generating representative volume element (RVE) models that are statistically equivalent to experimental measurements. Experimentally measured statistical data are used as constraints while the optimization algorithm is running. Virtual springs are utilized between any adjacent fibers to nonuniformly distribute the coated fibers in the RVE model. The virtual spring with the optimization algorithm can efficiently generate multiple RVEs that are statistically identical to each other. Smeared crack approach (SCA) is implemented to consider the fracture behavior of the CMC material in a mesh-objective manner. The RVEs are subjected to tension as well as the shear loading conditions. SCA is capable of predicting different fracture patterns, uniquely defined by not only the fiber arrangement but also the specific loading type. In addition, global stress-strain curves show that the microstructural fracture behavior of the RVEs is highly dependent on the fiber distributions

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?????? ??????????????? PI ???????????? cross-linking??? ?????? ????????? ????????? ?????? ????????? ???????????????. ?????? pH ???????????? PI ???????????? polymer??? degradation?????? ?????? ???????????? ????????? ???????????? ???????????? ??????. ?????? ????????? ???????????? ????????? TMC-MPD ????????? ????????? PI ???????????? cross-linking??? ???????????????. ???????????? cross-linking??? ???????????? ?????? FT-IR, ????????? ??????, TGA, ????????? XPS????????? ???????????????. Cross-linking??? ???????????? ????????? ?????? ???????????? ???????????? ?????? MgSO4??? feed ???????????? ????????? filtration ????????? ???????????????, 50% ?????? ????????? ?????? ?????? ?????? ???????????? ??? filtration ????????? ???????????? ?????? ????????? ???????????? ???????????? ???????????? ???????????????

Transmit Optimization for Relay-Based Cellular OFDMA Systems

Abstract—This paper considers a broadband cellular orthog-onal frequency-division multiple-access (OFDMA) system with relay nodes operating in decode-and-forward and half-duplex mode. Two transmit resource allocation problems for sum-rate maximization are formulated for such a system. The first one is the optimization of subcarrier allocation with predetermined power assignment for each subcarrier, and the other is the joint optimization of power and subcarrier allocation. Since these problems can’t be solved easily in direct forms, we make continuous relaxation and solve the dual problems using a subgradient method. Numerical results show that a remarkable increment in sum-rate is achieved, with the aid of relay nodes and sophisticated resource allocation, compared to a system without relay nodes. I

Chemical and surface engineered superhydrophobic patterned membrane with enhanced wetting and fouling resistance for improved membrane distillation performance

Application of membrane distillation (MD) is still in its emerging stage due to membrane wetting and fouling issues. In this study, an anti-wetting and anti-fouling superhydrophobic patterned membrane was prepared utilizing patterned templet surface and subsequent chemical modifications with fluorine-based polymer. A uniform patterned polyvinylidene fluoride-co-chlorotrifluoroethylene (PVDF-CTFE) membrane was prepared using a template having a specific surface structure. It was found that the patterned membrane with a hierarchical microstructure was more hydrophobic than that with a flat surface. Long-term performance of the patterned membrane was determined through direct contact membrane distillation (DCMD). Results showed that such patterned membrane exhibited wetting resistance for a longer time compared to a pristine membrane. However, the patterned membrane showed rapid flux decline during a fouling test due to deposition of foulants such as humic acid (HA), alginate acid (AA), and bovine serum albumin (BSA). To overcome the fouling issue, a patterned membrane was chemically modified with 1H, 1H-perfluorooctyl methacrylate (FOMA) known to possess a low surface energy. After surface modification with FOMA, the superhydrophobic patterned membrane showed good stability in terms of water flux and salt rejection for more than 7 days in DCMD without wetting or fouling issue. Results of this study indicates the capability of a superhydrophobic patterned MD membrane for generating maximum water flux with excellent anti-fouling and wetting resistance properties