Experimental Study on Water Absorption by Concrete Damaged by Uniaxial Loading

Cracking of concrete, which may be induced by several mechanisms, such as shrinkage, thermal effect, and loading, plays an important role in the deterioration of reinforced concrete structures because they provide additional pathways for water and aggressive agents, for example, chlorides, to penetrate into concrete. To well understand the transport properties of cracked/damaged concrete is essential for predicting its long-term durability. In general, water acts as the medium for agents to move into concrete, and water penetration by capillary absorption is more common for the real concrete structures since concrete is rarely saturated. As a result, absorption of water is regarded as the dominant factor for the ingress of aggressive substances. This article presents an experimental investigation on capillary absorption of concrete after being subjected to various loading patterns and levels. The sorptivity is chosen as a parameter to describe the rate of water moving into concrete since it can characterize the tendency of cementitious material to absorb and transmit water by capillary mechanism. A series of water absorption experiments were conducted on the concrete samples after they were subjected to uniaxial compressive or tensile loading. Three load levels, 70, 80, and 90%, of the corresponding compression and tension loading capacity were considered. An improved gravimetrical test equipment was used to measure the cumulative water content absorbed by concrete at the given time of exposure. The results show that mechanical loading, compression, or tension, has an important influence on water absorption property of concrete. The rate of capillary absorption of loading-damaged concrete can be raised up to two times of sound concrete samples for the ranges of load level studied

How Does the Low-Rank Matrix Decomposition Help Internal and External Learnings for Super-Resolution

Wisely utilizing the internal and external learning methods is a new challenge in super-resolution problem. To address this issue, we analyze the attributes of two methodologies and find two observations of their recovered details: 1) they are complementary in both feature space and image plane, 2) they distribute sparsely in the spatial space. These inspire us to propose a low-rank solution which effectively integrates two learning methods and then achieves a superior result. To fit this solution, the internal learning method and the external learning method are tailored to produce multiple preliminary results. Our theoretical analysis and experiment prove that the proposed low-rank solution does not require massive inputs to guarantee the performance, and thereby simplifying the design of two learning methods for the solution. Intensive experiments show the proposed solution improves the single learning method in both qualitative and quantitative assessments. Surprisingly, it shows more superior capability on noisy images and outperforms state-of-the-art methods

Experimental Investigation on Capillary Water Absorption in Discrete Planar Cracks

Water movement is responsible for the deterioration of concrete and concrete structures, especially when distributed microcracks exist because cracks can facilitate the ingress of aggressive agents. Experiment was carried out on capillary water absorption by discrete planar cracks to clarify the effect of crack width on the transport speed of water by crack. The granite samples were used to create parallel and smooth cracks with purpose to avoid rehydration of the cement-based materials. Two granite blocks were applied to joint by glue for artificially fabricating a single parallel crack by means of ultra thin steel disc with various thicknesses of 50, 100, 150 and 200 mm. The capillary absorption test was conducted on the specimens according to the gravimetric method recommended in ASTM C1585. Mass of absorbed water by the single discrete crack was measured. It was found that the cumulative water mass of specimen generally increases with an increase of crack width for the ranges studied. The cumulative water mass rapidly increases for the initial stages of water absorption test while at later stages the rate of absorbed water is slowed down apparently

Distributed resilient filtering of large-scale systems with channel scheduling

summary:This paper addresses the distributed resilient filtering for discrete-time large-scale systems (LSSs) with energy constraints, where their information are collected by sensor networks with a same topology structure. As a typical model of information physics systems, LSSs have an inherent merit of modeling wide area power systems, automation processes and so forth. In this paper, two kinds of channels are employed to implement the information transmission in order to extend the service time of sensor nodes powered by energy-limited batteries. Specifically, the one has the merit of high reliability by sacrificing energy cost and the other reduces the energy cost but could result in packet loss. Furthermore, a communication scheduling matrix is introduced to govern the information transmission in these two kind of channels. In this scenario, a novel distributed filter is designed by fusing the compensated neighboring estimation. Then, two matrix-valued functions are derived to obtain the bounds of the covariance matrices of one-step prediction errors and the filtering errors. In what follows, the desired gain matrices are analytically designed to minimize the provided bounds with the help of the gradient-based approach and the mathematical induction. Furthermore, the effect on filtering performance from packet loss is profoundly discussed and it is claimed that the filtering performance becomes better when the probability of packet loss decreases. Finally, a simulation example on wide area power systems is exploited to check the usefulness of the designed distributed filter