Adaptive Optimizers with Sparse Group Lasso for Neural Networks in CTR Prediction

We develop a novel framework that adds the regularizers of the sparse group lasso to a family of adaptive optimizers in deep learning, such as Momentum, Adagrad, Adam, AMSGrad, AdaHessian, and create a new class of optimizers, which are named Group Momentum, Group Adagrad, Group Adam, Group AMSGrad and Group AdaHessian, etc., accordingly. We establish theoretically proven convergence guarantees in the stochastic convex settings, based on primal-dual methods. We evaluate the regularized effect of our new optimizers on three large-scale real-world ad click datasets with state-of-the-art deep learning models. The experimental results reveal that compared with the original optimizers with the post-processing procedure which uses the magnitude pruning method, the performance of the models can be significantly improved on the same sparsity level. Furthermore, in comparison to the cases without magnitude pruning, our methods can achieve extremely high sparsity with significantly better or highly competitive performance. The code is available at https://github.com/intelligent-machine-learning/dlrover/blob/master/tfplus.Comment: 24 pages. Published as a conference paper at ECML PKDD 2021. This version includes Appendix which was not included in the published version because of page limi

Simulation of Electrochemical Impedance Spectra of Solid Oxide Fuel Cells Using Transient Physical Models

A general electrochemical impedance spectroscopy ͑EIS͒ modeling approach by directly solving a one-dimensional transient model based on physical conservation laws was applied for simulating EIS spectra of an anode-supported solid oxide fuel cell ͑SOFC͒ button cell consisting of Ni-yttria-stabilized zirconia ͉Ni-scandia-stabilized zirconia ͑ScSZ͉͒ScSZ͉lanthanum strontium manganate ͑LSM͒-ScSZ multiple layers. The transient SOFC model has been solved for imposed sinusoidal voltage perturbations at different frequencies. The results have then been transformed into EIS spectra. Six parameters had to be tuned ͑three for the cathode and three for the anode͒ and have been estimated using data from a symmetric cathode cell and from a button cell. The experimental and simulated EIS spectra were in good agreement for a range of temperatures ͑750-850°C͒, of feed compositions ͑mixture of H 2 /H 2 O/N 2 ͒, and of oxidants ͑air and oxygen͒. This approach can help in interpreting EIS spectra, as illustrated by identifying the contribution of transport limitation. Fuel cell electrochemical systems are usually complex and are governed by coupled physicochemical processes such as chemical and electrochemical reactions, charge transport, and mass transport. 1,2 Because polarization curves can only provide a general description of the cell performance, electrochemical impedance spectroscopy ͑EIS͒ has become widely used in fuel cell research and development because it involves a relatively simple electrical measurement that gives detailed information about the fuel cell system, from mass-transport properties, chemical reaction rates, and dielectric properties to defects, microstructure, compositional influences, etc. 3 In this dynamic technique, usually a voltage perturbation is applied to a system and the amplitude and phase shift of the resulting current response are measured. Measurements can be conducted over a wide range of frequencies, resulting in the construction of impedance spectra. 5 Although the approach is useful and quite powerful, it often has limitations such as: 1. The approach can lead to ambiguities in data interpretations because the equivalent circuits are seldom unique except for only the simplest circuits. An equivalent circuit involving several circuit elements could often be rearranged in various configurations while still yielding the same impedance. 2. Detailed physical and chemical processes in the system cannot be predicted by equivalent-circuit models. For instance, the effects of current distributions and concentration distributions cannot be taken into account when interpreting data from equivalent-circuit models. 3. The measured system could only be approximated by circuit elements when assuming linear response of the system. The impedance is supposed to be independent of the amplitude of the applied signals. However, the electrochemical system could be highly nonlinear, especially for sinusoidal perturbations with high amplitudes. It was suggested that nonlinear EIS ͑NLEIS͒ measurements have several potential advantages. To investigate solid oxide fuel cell ͑SOFC͒ electrode reaction kinetics, Miterdorfer and Gauckler 7-9 used a state-space model ͑SSM͒, which is widely used in control theory for solving complex differential equations. Bieberle and Gauckler 5 studied in depth elementary electrochemical reactions in SOFC anode by both experimental and SSM approaches. To simulate the electrochemical impedance spectra, the models were solved directly through the SSM approach. Bessler 10 presented a computational method for simulating EIS spectra based on transient numerical simulations of the reaction system. The impedance was then calculated in the time domain from the simulated periodic response of the system, maintaining its full nonlinear response. This method has been further validated by detailed modeling studies on SOFC EIS spectra achieved from gas-transport processes. 11 Gewies et al. 12 also applied this method on Ni/yttria-stabilized zirconia ͑YSZ͒ cermet anodes. Zhu and Kee 13 developed a time-accurate model to analyze EIS spectra in anode-supported button cells with internal methane reforming. This model represented significant advantages regarding physical conservation laws, porous media transport within the electrode, and heterogeneous chemistry reactions mechanisms, all of those being solved in the time domain. However, the spatial variations of ion and electron transport throughout the electrode structures were not considered. In this paper, a general approach for EIS spectra simulation is applied by solving a comprehensive set of coupled transient models based on physical conservation laws. This simulation approach is illustrated by considering a transient model of an anode-supported SOFC button cell consisting of Ni-YSZ͉Ni-scandia-stabilized zirconia ͑ScSZ͉͒ScSZ͉LSM-ScSZ multiple layers. The simulation results of the EIS spectra were then compared to the measured EIS spectra under various conditions to prove the validity of both the transient model and the EIS simulation approach. Experimental Testing cell.-The anode-supported SOFC button cell used in this study consisted of a Ni/YSZ anode support layer ͑680 m͒, a Ni/ScSZ anode active interlayer ͑15 m͒, a ScSZ thin-film electrolyte layer ͑20 m͒, and a lanthanum strontium manganate ͑LSM͒/ ScSZ cathode layer ͑15 m͒. 14,1

Research progress in the removal of fluoride ions from mine water by adsorption method

Fluoride ions are widely distributed in surface rivers and groundwater bodies in China, especially in the mining areas along the Yellow River in the western Yellow River basin that there is a widespread problem of excessive fluoride in the mine water, which poses a potential threat to the local ecological environment and human health. The status quo of fluoride pollution in China is mostly at a low concentration pollution level, which leads to it difficult to remove efficiently through conventional water treatment technologies. The adsorption method is considered to be an effective way to remove low concentration fluoride ions because of its high adsorption efficiency and convenient operation. The research status of fluoride removal by commonly used adsorption materials such as carbon based, minerals, metals and metal organic frameworks (MOFs) was reviewed and summarized before summarizing the influence of different factors on the fluoride removal efficiency and adsorption mechanism of these adsorption materials. Then the application effect and operation cost of adsorption method in mine water treatment were emphatically analyzed, and the development direction of adsorption method in the treatment of low concentration (<10 mg/L) and high water content fluorine-containing mine water was prospected. In general, there are still some deficiencies in the study of fluoride removal by adsorption. In terms of adsorption mechanism, it should be further investigated from three aspects which includes the characteristics of adsorption materials, the occurrence form of fluoride ions and the interaction mechanism between adsorption materials and fluoride ions. For the engineering application of adsorption method, the demand of engineering application should be regarded as the guidance. Based on the above discussion, the research and development direction of removing fluoride ions from mine water by adsorption method is proposed, which is to focus on the development of low cost and high efficiency environment-friendly modified adsorbents based on natural/waste (ore) and carbon-based, aluminum-based or other new polymer adsorption materials under the principle of clarifying local policies and water quality and quantity. In addition, it is necessary not to improve the selective adsorption performance of the modified adsorbent for fluoride ions, but also to ensure the stability, economy and safety of the adsorbent in the whole life cycle of preparation, processing, production and recycling, thereby improving its competitiveness of the adsorption method in the actual application of fluoride containing wastewater and enhancing the application potential of the adsorption method

Numerical Investigation of Compressive Stress and Wettability Effects on Fluid Transport in Polymer Electrolyte Membrane Fuel Cell Porous Layers

The performance of polymer electrolyte membrane fuel cells (PEMFCs) is greatly influenced by the residual water content generated during the cell operation. A comprehensive understanding of water management at the interfacial regions of PEMFC components is critical for elevating the efficiency of PEMFCs. Herein, the liquid transport and accumulation at the interfacial region of 2D microporous layer (MPL) and catalyst layer (CL) are investigated numerically, considering the effects of compression stress, porosity, and wettability. The numerical scheme is assembled by finite element method (for interfacial contact mechanics) and lattice Boltzmann method (for multiphase flow and permeability calculation). Different levels of compression stress derived from fuel cell assembly pressure are applied on the MPL/CL components, which consequently lead to variations in the pore size distribution and porosity change of the MPL/CL. The results highlight the importance of considering porosity change in the compression process, where increasing compression stress significantly decreases the liquid saturation in the MPL and interfacial gap region. Additionally, strong hydrophobicity can alleviate the heterogeneity of liquid accumulation at the MPL/CL interfacial region. The liquid and gas relative permeability are also investigated to assess the liquid drainage and fuel supply efficiency with different compression stress.</p

A Modified Weber Number Capturing the Bouncing–Wetting Transition of Droplet Impact on Rough Surfaces

Abstract In this work, the effects of surface properties on bouncing–wetting transition of water droplet impacting rough surfaces in the Weber number (We) range from 18 to 221 are experimentally investigated. The correlation between impact outcomes and We is examined with an empirical function, and an impact outcome transition from bouncing to no bouncing is identified with the increase of We. The results suggest that a higher surface area ratio promotes the bouncing to no bouncing transition on sample surfaces used in this study. To quantify the effects of surface wetting area on the transitions of droplet impact regimes, a modified Weber number, We*, is proposed by taking the actual surface area into account. Results show that the regime transitions of droplet impact on samples of different surface area ratios can be unified by the We*. This study reveals the significance of actual surface area and the resultant adhesion force on the droplet impact dynamics on random rough surfaces

Influence of multiscale surface roughness on permeability in fractures

International audienceWe systematically study the role of surface roughness in fluid flow through rough fractures using direct numerical simulations. Random rough fractal surfaces are generated with different relative roughness, which are then decomposed using the wavelet analysis method. Different frequencies of surface topological information is filtered in a level-by-level procedure, while the large-scale waviness remains approximately unchanged. To explore the effects of surface roughness across a spectrum of length scales, simulations are carried out for each approximation level under different flow conditions and fracture spacing. Our results reveal the impact of relative roughness and roughness details at different length scales on the non-linear flow behavior due to inertia associated with formation of eddy flows. We further propose an error index to describe the relative error in permeability induced by limited resolution in surface profile description. Our analysis shows that the relative error in permeability from surfaces under different levels of approximation and relative roughness can be well described by the proposed index for a wide range of flow conditions and fracture apertures. This study provides insights into the role of multi-scale roughness on the fluid flow through rough fractures

Review on the purification mechanism of mine water by coal mine underground reservoir

The purification effect of coal mine groundwater reservoir on mine water mainly lies in the water-rock coupling between the rock mass and mine water.This paper systematically reviews the research methods of water-rock coupling in coal mine underground reservoirs, and presents the characterization methods of water quality and physicochemical properties of rock samples.It employs static simulation, dynamic leaching, cycle purification simulation and other tests to explore the purification regulation of mine water in coal mine underground reservoir, uses numerical simulation to obtain the selective adsorption trend of ions in the reaction process, and combines Piper three-line diagram, Gibbs model and correlation analysis to reveal the mechanism of water-rock coupling.The purification effect and research progress of suspended solids, specific ions and organic matter in coal mine underground reservoirs are discussed.The paper shows that underground reservoir of coal mine has a certain purification effect on mine water, and the purification effect of specific ions is mainly related to filtration and adsorption.Three research directions of coal mine underground reservoir purification technology in the future are proposed: ①developing large-scale and low-cost treatment technologies for underground mine water based on water-rock coupling purification, ②developing a "three-in-one" water quality control technology for coal mine underground reservoirs coupled with multiple water treatment technologies, and ③exploring the underground storage and resource utilization technology of concentrated salt wastewater for the future studies of water-rock coupling

Composition and Geochemical Characteristics of Pyrite and Quartz: Constraints on the Origin of the Xinjiazui Gold Deposit, Northwestern Margin of the Yangtze Block, China

The Xinjiazui gold deposit, a newly discovered deposit, is situated in the northwestern margin of the Yangtze Block, China. The source and genesis of gold mineralization are poorly understood. It is urgent to use the H&ndash;O isotopic composition of quartz and geochemistry of pyrite to evaluate the origins of the Au and ore-forming fluids of this deposit. Three types of pyrite were identified, including synsedimentary framboidal pyrites (Py0), the directional arrangement of pyrites in pre-mineralization stage (Py1), and euhedral coarse-grain pyrites in the quartz&ndash;sulfide veins of the mineralization stage (Py2). The As content in Py2 is relatively higher than Py0 and Py1, indicating that the ore-forming fluids are strongly enriched in As. The &delta;34S values of Py2 (+5.50&ndash;+13.34&permil;) overlap with the S1&ndash;2M phyllite (+7.25&permil;&ndash;+8.70&permil;). This result is consistent with the Pb isotopic composition of Py2, showing that the source of ore-forming materials was derived from the S1&ndash;2M phyllite. Meanwhile, the variations in quartz&rsquo;s H and O isotopic composition suggest that the ore-forming fluids were derived originally from metamorphic fluid. Additionally, the Au mineralization is strictly controlled by the shear zone. Above all, we would like to classify the Xinjiazui deposit as an orogenic gold deposit

Tribocorrosion behaviors of TiSiCN nanocomposite coatings deposited by high power impulse magnetron sputtering

High-performance coatings originated in ingenious coating designs and advanced preparation techniques are expected to fulfill imperious demands in propulsion, bearings and mechanical seals, etc in marine systems for seawater lubrication. In this work, TiSiCN nanocomposite coatings were deposited by high power impulse magnetron sputtering at a power of 4–8 kW. As power is increased, TiSiCN coatings possess nanocrystalline (TiN, TiC, TiCN)/amorphous (Si _3 N _4 , SiC, sp ^2 -C) nanocomposite structure without distinctly preferred orientation. The highest hardness (H) of 43 GPa and effective Young’s modulus (E*) of 360 GPa were achieved at 8 kW, while the highest H/E* of 0.123 and H ^3 /E* ^2 of 0.61 appear at 7 kW due to refined nano-grains, uniform distribution, high surface/interface integrity and fully dense microstructure. Rockwell C adhesion level increased from HF2 at 4 kW to HF1 at 8 kW. TiSiCN coatings with high H, H/E*, H ^3 /E* ^2 and adhesion exhibit high open circuit potential of −0.07 V, low friction coefficient of 0.25 and specific wear rate of 4.78 × 10 ^−5 mm ^3 N ^−1 m ^−1 , resulting from mild abrasive wear without the occurrence of pitting corrosion in 3.5 wt.% NaCl aqueous solution. Moreover, cycling tribocorrosion tests revealed that passive films possess strong abilities of regeneration and self-repairation on sliding contact surface