In this paper, we explore the characteristics of a concrete block as a communication medium with piezoelectric transducers. Lead zirconate titanate (PZT) is a piezoceramic material used in smart materials intended for structural health monitoring (SHM). Additionally, a PZT based smart aggregate (SA) is capable of implementing stress wave communications which is utilized for investigating the properties of an SA based concrete channel. Our experiments characterize single-input single-output and multiple-input multiple-output (MIMO) concrete channels in order to determine the potential capacity limits of SAs for stress wave communication. We first provide estimates and validate the concrete channel response. Followed by a theoretical upper bound for data rate capacity of our two channels, demonstrating a near-twofold increase in channel capacity by utilizing multiple transceivers to form an MIMO system. Our channel modeling techniques and results are also helpful to researchers using SAs with regards to SHM, energy harvesting and stress wave communications.
In this study, we employed multitemporal InSAR (Interferometric Synthetic Aperture Radar) (MT-InSAR) to detect spatial and temporal ground deformations over the whole Tianjin region in the North China Plain area. Twenty-five ascending Sentinel-1A terrain observation by progressive scans (TOPS) synthetic aperture radar (SAR) scenes covering this area, acquired from 9 January 2016 to 8 June 2017, were processed using InSAR time series analysis. The deformation results derived from Sentinel-1A MT-InSAR were validated with continuously operating reference stations (CORS) at four sites and four stations of the Crustal Movement Observation Network of China (CMONOC). The overall results show good agreement, demonstrating the suitability of applying Doris with Sentinel-1A data to high-resolution monitoring of surface deformation. Significant deformation variations have been observed in different parts of Tianjin. These gradually increased from the central part of the metropolitan area to the nearby suburbs. The deformation rate of the main urban area is well-balanced and it is also relatively linear, with uplifting rates ranging from 0 to 20 mm/yr. However, due to the diversity of the geological conditions and anthropogenic activities, remarkable signs of subsidence were found in several parts of Tianjin. In particular, the south-western part of Wuqing District and western part of Beichen District showed subsidence rates of up to −136 mm/yr. We also found that, in addition to groundwater over-exploitation and lithological characteristics, additional factors also influence ground subsidence, including dynamic loads (e.g., railways), static loads (e.g., urban construction), and groundwater recharging.
This work studies the design of linear precoders for cooperative multi-cell MIMO downlink systems with finite alphabet inputs. Traditionally, multi-cell MIMO downlink precoder designs rely on Gaussian input assumption, which may lead to performance loss when the true inputs admit discrete non-Gaussian symbols. In this work, we present optimized precoders by maximizing weighted sum rate (of finite-alphabet-input) under a set of single basestation power constraints. Specifically, we propose a simple gradient algorithm for general multi-cell MIMO downlink channel and a block diagonalization gradient algorithm while supporting interference cancellation.
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