444 research outputs found
Corrosion of Q235 Carbon Steel in Seawater Containing Mariprofundus ferrooxydans and Thalassospira sp.
Iron-oxidizing bacteria (IOB) and iron-reducing bacteria (IRB) can easily adhere onto carbon steel surface to form biofilm and affect corrosion processes. However, the mechanism of mixed consortium induced carbon steel corrosion is relatively underexplored. In this paper, the adsorptions of IOB (Mariprofundus ferrooxydans, M. f.), IRB (Thalassospira sp., T. sp.) and mixed consortium (M. f. and T. sp.) on surface of Q235 carbon steel and their effects on corrosion in seawater were investigated through surface analysis techniques and electrochemical methods. Results showed that local adhesion is a typical characteristic for biofilm on surface of Q235 carbon steel in M. f. and mixed consortium media, which induces localized corrosion of Q235 carbon steel. Corrosion rates of Q235 carbon steel in different culture media decrease in the order: rM.f. > rmixed consortium > rT.sp. > rsterile. The evolution of corrosion rate along with time decreases in M. f. medium, and increases then keeps table in both T. sp. and mixed consortium media. Corrosion mechanism of Q235 carbon steel in mixed consortium medium is discussed through analysis of surface morphology and composition, environmental parameter, and electrochemical behavior
Local Averaging Helps: Hierarchical Federated Learning and Convergence Analysis
Federated learning is an effective approach to realize collaborative learning
among edge devices without exchanging raw data. In practice, these devices may
connect to local hubs instead of connecting to the global server (aggregator)
directly. Due to the (possibly limited) computation capability of these local
hubs, it is reasonable to assume that they can perform simple averaging
operations. A natural question is whether such local averaging is beneficial
under different system parameters and how much gain can be obtained compared to
the case without such averaging. In this paper, we study hierarchical federated
learning with stochastic gradient descent (HF-SGD) and conduct a thorough
theoretical analysis to analyze its convergence behavior. In particular, we
first consider the two-level HF-SGD (one level of local averaging) and then
extend this result to arbitrary number of levels (multiple levels of local
averaging). The analysis demonstrates the impact of local averaging precisely
as a function of system parameters. Due to the higher communication cost of
global averaging, a strategy of decreasing the global averaging frequency and
increasing the local averaging frequency is proposed. Experiments validate the
proposed theoretical analysis and the advantages of HF-SGD.Comment: 42 pages, 13 figure
Impacts of salinity parameterizations on temperature simulation over and in a hypersaline lake
In this paper, we introduced parameterizations of the salinity effects (on heat capacity, thermal conductivity, freezing point and saturated vapor pressure) in a lake scheme integrated in the Weather Research and Forecasting model coupled with the Community Land Model (WRF-CLM). This was done to improve temperature simulation over and in a saline lake and to test the contributions of salinity effects on various water properties via sensitivity experiments. The modified lake scheme consists of the lake module in the CLM model, which is the land component of the WRF-CLM model. The Great Salt Lake (GSL) in the USA was selected as the study area. The simulation was performed from September 3, 2001 to September 30, 2002. Our results show that the modified WRF-CLM model that includes the lake scheme considering salinity effects can reasonably simulate temperature over and in the GSL. This model had much greater accuracy than neglecting salinity effects, particularly in a very cold event when that effect alters the freezing point. The salinity effect on saturated vapor pressure can reduce latent heat flux over the lake and make it slightly warmer. The salinity effect on heat capacity can also make lake temperature prone to changes. However, the salinity effect on thermal conductivity was found insignificant in our simulations. © 2015, Chinese Society for Oceanology and Limnology, Science Press and Springer-Verlag Berlin Heidelberg
Unconventional Flatband Line States in Photonic Lieb Lattices
Flatband systems typically host "compact localized states"(CLS) due to
destructive interference and macroscopic degeneracy of Bloch wave functions
associated with a dispersionless energy band. Using a photonic Lieb
lattice(LL), we show that conventional localized flatband states are inherently
incomplete, with the missing modes manifested as extended line states which
form non-contractible loops winding around the entire lattice. Experimentally,
we develop a continuous-wave laser writing technique to establish a
finite-sized photonic LL with specially-tailored boundaries, thereby directly
observe the unusually extended flatband line states.Such unconventional line
states cannot be expressed as a linear combination of the previously observed
CLS but rather arise from the nontrivial real-space topology.The robustness of
the line states to imperfect excitation conditions is discussed, and their
potential applications are illustrated
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