Evaluation of concrete bridge deck overlays

Overlay systems have been used by many states for the protection of bridge decks, but the premature delaminations and failures have been observed in many cases. A comprehensive study was recently defined to investigate overlay performance in collaboration with the West Virginia Department of Transportation-Division of Highways (WVDOH).;As part of a comprehensive program, the present study is concerned with the properties of several types of overlay mixtures and the interface bond strengths between them and substrate concrete. All the materials used are of interests to WVDOH. Both fresh and hardened concrete properties of seven different overlay types were characterized. Four of the seven were selected for the study of interface bond strength, which included latex modified concrete, silica fume modified concrete, fiber-reinforced concrete and slag modified concrete. With these four selected overlays, statistical design of experiments were conducted for the evaluation of the influences on bond strength of four factors: aggregate types, surface preparations, use of bonding slurry, and substrate age using a recently developed direct shear test apparatus.;Results show that except for bonding slurry, all the parameters had strong influence on shear bond strength. The results of this study will serve the purpose of screening and selection of overlays from a large number of variables, and will finally help to develop guidelines by WVDOH for future implementations of concrete overlays in the field

The Ecological Role of Roadside Stormwater Ponds - Potential to Support Biodiversity

The increased recognition that roads may impair the aquatic environment and ecosystems has led to a shift from conventional drainage systems toward blue-green solutions such as stormwater ponds. Research on blue-green stormwater solutions has until now mainly focused on water quantity and quality. The aim of this study was to explore the ability of highway stormwater ponds to provide suitable habitats and support, especially macroinvertebrate biodiversity, and to identify the key environmental variables that affect biological community composition and the number of taxa, utilizing data at regional and global scales. Ultimately, this research informs design recommendations for stormwater systems that simultaneously provide multiple ecosystem services.The results of this thesis indicate that larger ponds are better for supporting aquatic biodiversity due to a more heterogeneous environment and the ability to dilute pollutants. Also, the presence of other ponds in the vicinity of the stormwater ponds can facilitate the movement of invertebrates between ponds through increased connectivity. An apparent negative effect of pollution levels on the macroinvertebrate community composition was observed, but not on the biodiversity measured as the number of taxa or Shannon index. The analyses based on the datasets identified using both morphology and DNA metabarcoding demonstrated that DNA metabarcoding captured and identified more than twice the number of taxa compared to morphological identification. Application of DNA metabarcoding greatly increases the number of species identified at each sampling site, thereby providing more accurate information regarding the way the ponds function and how they are affected by management. Subsequently, the differences in the macroinvertebrate community composition between different types of ponds were compared at the regional and global scale. The results indicated that environmental characteristics, especially conductivity and pH, were different between different types of ponds. Alpha and gamma diversity were similar or even higher in manmade ponds compared to natural ponds due to very different macroinvertebrate communities. Moreover, generally ponds exhibited high levels of spatial heterogeneity, which subsequently enhances gamma diversity.In summary, stormwater ponds have the potential to provide suitable habitats to foster biodiversity. When such systems are created, larger ponds should be built to provide more heterogeneous habitat and dilute harmful pollutants. Additional ponds should also be created in the vicinity of the ponds, thereby promoting aquatic biodiversity through higher connectivity. Although stormwater ponds accumulate pollutants due to their primary functions, this pollution retention process creates a unique environment within the stormwater ponds, which are more suitable for taxa that are moderately to strongly tolerant to pollutants and that may not be found in natural ponds. In this way, stormwater ponds constitute an option in the areas along the highway so that they could combine water treatment properties with providing a suitable habitat for aquatic organisms

Universal spin-Hall conductance fluctuations in two dimensions

We report a theoretical investigation on spin-Hall conductance fluctuation of disordered four terminal devices in the presence of Rashba or/and Dresselhaus spin-orbital interactions in two dimensions. As a function of disorder, the spin-Hall conductance $G_{sH}$ shows ballistic, diffusive and insulating transport regimes. For given spin-orbit interactions, a universal spin-Hall conductance fluctuation (USCF) is found in the diffusive regime. The value of the USCF depends on the spin-orbit coupling $t_{so}$, but is independent of other system parameters. It is also independent of whether Rashba or Dresselhaus or both spin-orbital interactions are present. When $t_{so}$ is comparable to the hopping energy $t$, the USCF is a universal number $\sim 0.18 e/4\pi$. The distribution of $G_{sH}$ crosses over from a Gaussian distribution in the metallic regime to a non-Gaussian distribution in the insulating regime as the disorder strength is increased.Comment: to be published in Phys. Rev. Lett., 4 figure

The Coupling Coordination Degree Measurement of Society-Economy-Ecosystem of Regional National Forest Park in Heilongjiang Province

In order to estimate the comprehensive benefits brought by forest parks to the society, economy, and ecology of a certain area, this paper innovatively constructed a social-economic-ecological composite system of forest parks in Heilongjiang Province. The entropy method is used to determine the weight of each index, the coupling coordination degree model is used to analyze the coupling and coordination degree of the social, economic, and ecological benefits of forest parks in Heilongjiang Province from 2010 to 2018. In addition, the LSTM neural network model is used to predict the development trend of the coupling coordination degree of the composite system from 2019 to 2021. Research shows that from 2010 to 2018, the forest park composite system was in a state of "high coupling and low coordination" for a long time; from 2019 to 2021, it is predicted that the degree of coupling of the composite system will decrease slightly and the degree of coordination will increase