Poly[μ-aqua-μ4-terephthalato-strontium]

In the title compound, [Sr(C8H4O4)(H2O)]n, the SrII atom exhibits coordination number eight, with six O atoms from four carboxylate groups (two bidentate and two monodentate) of terephthalate ligands and two water O atoms. The SrO8 polyhedra are linked into inorganic chains by sharing three coplanar O atoms. These inorganic chains are extended along the b axis to form layers in the ab plane by O—C—O linking. Parallel layers are connected by terephthalic groups, forming a three-dimensional framework. O—H⋯O hydrogen-bonding inter­actions are observed

The 3D finite element analysis of cold wave impact effect

AbstractIn April, 1999, Guangdong Changsha arch dam application new technique of MgO-Admixed concrete arch dam without transverse joints, Changsha arch dam is only 90 d complete high 55.5 m, 31000 m3 concrete dam body, the reservoir filling and power generation, is initiative at home and abroad in the history of arch dam. In January 2000, downstream dam surface appear fine cracks, crack width only 0.2–0.3 mm, depth 1.3–4.2 m, all did not throughout the dam upstream face. With the hyperbolic model based on MgO-admixed concrete and APDL language, 3 d finite element in simulation analysis, cleared that design conditions of the stress of MgO-admixed concrete compensation accord with the stress state of conventional arch dam structure. Downstream dam surface crack and using the MgO-mixed concrete dams of new technology without necessarily linked. Before to the stationary temperature field in the dam, the role of heat preservation measures template made of polystyrene foamed plastic board for stress improvement is significant. Cold wave impact cracks appear to great effect, worsened the dam stress state greatly, and put the dam in a high stress state. The original design dam stress state is not ideal, crack resistance caused by concrete quality of dam project is reduced, especially heat preservation measures is invalid during the cold wave impact, caused cracks of ChangSha dam. 1–2 mm tiny cracks of Changsha arch dam used under no harmful effects. Concrete crack resistance of Changsha arch dam is improved greatly after dam grouting, the main performance indexes is also improved obviously, and dam is used has been more than 12 years under safety operation. The analysis of cold wave impact provides important basic material to promote the new technology application, and reference value to similar projects

Reconfigurable Distributed Antennas and Reflecting Surface: A New Architecture for Wireless Communications

Distributed Antenna Systems (DASs) employ multiple antenna arrays in remote radio units to achieve highly directional transmission and provide great coverage performance for future-generation networks. However, the utilization of active antenna arrays results in a significant increase in hardware costs and power consumption for DAS. To address these issues, integrating DAS with Reconfigurable Intelligent Surfaces (RIS) offers a viable approach to ensure transmission performance while maintaining low hardware costs and power consumption. To incorporate the merits of RIS into the DAS from practical consideration, a novel architecture of ``Reconfigurable Distributed Antennas and Reflecting Surfaces (RDARS)'' is proposed in this paper. Specifically, based on the design of the additional direct-through state together with the existing high-quality fronthaul link, any element of the RDARS can be dynamically programmed to connect with the base station (BS) via fibers and perform the connected mode as remote distributed antennas of the BS to receive or transmit signals. Additionally, RDARS also inherits the low-cost and low-energy-consumption benefits of fully passive RISs by default configuring the elements as passive to perform the reflection mode. As a result, RDARS offers flexible control over the trade-off between distribution gain and reflection gain to enhance performance. The ergodic achievable rate under the RDARS architecture is analyzed and closed-form expression with meaningful insights is derived. The theoretical analysis and simulation results prove that the RDARS achieves a higher achievable rate than both DAS and RIS. A RDARS prototype with 256 elements is built for real experiments which shows that the RDARS-aided system can achieve an additional 21% and 170% throughput improvement over DAS and RIS-aided systems, respectively.Comment: 13 pages, 9 figure