Effect of cerium salt-activated ceria on the UV degradation resistance of waterborne epoxy coatings

"The author can not apply the abstract because of system's error. Please check it in the WORD version. Thank you

Accelerated ABAB/Push-Pull Methods for Distributed Optimization over Time-Varying Directed Networks

This paper investigates a novel approach for solving the distributed optimization problem in which multiple agents collaborate to find the global decision that minimizes the sum of their individual cost functions. First, the $AB$/Push-Pull gradient-based algorithm is considered, which employs row- and column-stochastic weights simultaneously to track the optimal decision and the gradient of the global cost function, ensuring consensus on the optimal decision. Building on this algorithm, we then develop a general algorithm that incorporates acceleration techniques, such as heavy-ball momentum and Nesterov momentum, as well as their combination with non-identical momentum parameters. Previous literature has established the effectiveness of acceleration methods for various gradient-based distributed algorithms and demonstrated linear convergence for static directed communication networks. In contrast, we focus on time-varying directed communication networks and establish linear convergence of the methods to the optimal solution, when the agents' cost functions are smooth and strongly convex. Additionally, we provide explicit bounds for the step-size value and momentum parameters, based on the properties of the cost functions, the mixing matrices, and the graph connectivity structures. Our numerical results illustrate the benefits of the proposed acceleration techniques on the $AB$/Push-Pull algorithm

Geometric Convergence of Distributed Heavy-Ball Nash Equilibrium Algorithm over Time-Varying Digraphs with Unconstrained Actions

We propose a new distributed algorithm that combines heavy-ball momentum and a consensus-based gradient method to find a Nash equilibrium (NE) in a class of non-cooperative convex games with unconstrained action sets. In this approach, each agent in the game has access to its own smooth local cost function and can exchange information with its neighbors over a communication network. The proposed method is designed to work on a general sequence of time-varying directed graphs and allows for non-identical step-sizes and momentum parameters. Our work is the first to incorporate heavy-ball momentum in the context of non-cooperative games, and we provide a rigorous proof of its geometric convergence to the NE under the common assumptions of strong convexity and Lipschitz continuity of the agents' cost functions. Moreover, we establish explicit bounds for the step-size values and momentum parameters based on the characteristics of the cost functions, mixing matrices, and graph connectivity structures. To showcase the efficacy of our proposed method, we perform numerical simulations on a Nash-Cournot game to demonstrate its accelerated convergence compared to existing methods

Distributed Stochastic Optimization with Gradient Tracking over Time-Varying Directed Networks

We study a distributed method called SAB-TV, which employs gradient tracking to collaboratively minimize the sum of smooth and strongly-convex local cost functions for networked agents communicating over a time-varying directed graph. Each agent, assumed to have access to a stochastic first-order oracle for obtaining an unbiased estimate of the gradient of its local cost function, maintains an auxiliary variable to asymptotically track the stochastic gradient of the global cost. The optimal decision and gradient tracking are updated over time through limited information exchange with local neighbors using row- and column-stochastic weights, guaranteeing both consensus and optimality. With a sufficiently small constant step-size, we demonstrate that, in expectation, SAB-TV converges linearly to a neighborhood of the optimal solution. Numerical simulations illustrate the effectiveness of the proposed algorithm

Optimal Workload Allocation for Distributed Edge Clouds With Renewable Energy and Battery Storage

This paper studies an optimal workload allocation problem for a network of renewable energy-powered edge clouds that serve users located across various geographical areas. Specifically, each edge cloud is furnished with both an on-site renewable energy generation unit and a battery storage unit. Due to the discrepancy in electricity pricing and the diverse temporal-spatial characteristics of renewable energy generation, how to optimally allocate workload to different edge clouds to minimize the total operating cost while maximizing renewable energy utilization is a crucial and challenging problem. To this end, we introduce and formulate an optimization-based framework designed for Edge Service Providers (ESPs) with the overarching goal of simultaneously reducing energy costs and environmental impacts through the integration of renewable energy sources and battery storage systems, all while maintaining essential quality-of-service standards. Numerical results demonstrate the effectiveness of the proposed model and solution in maintaining service quality as well as reducing operational costs and emissions. Furthermore, the impacts of renewable energy generation and battery storage on optimal system operations are rigorously analyzed

CrowdCache: A Decentralized Game-Theoretic Framework for Mobile Edge Content Sharing

Mobile edge computing (MEC) is a promising solution for enhancing the user experience, minimizing content delivery expenses, and reducing backhaul traffic. In this paper, we propose a novel privacy-preserving decentralized game-theoretic framework for resource crowdsourcing in MEC. Our framework models the interactions between a content provider (CP) and multiple mobile edge device users (MEDs) as a non-cooperative game, in which MEDs offer idle storage resources for content caching in exchange for rewards. We introduce efficient decentralized gradient play algorithms for Nash equilibrium (NE) computation by exchanging local information among neighboring MEDs only, thus preventing attackers from learning users' private information. The key challenge in designing such algorithms is that communication among MEDs is not fixed and is facilitated by a sequence of undirected time-varying graphs. Our approach achieves linear convergence to the NE without imposing any assumptions on the values of parameters in the local objective functions, such as requiring strong monotonicity to be stronger than its dependence on other MEDs' actions, which is commonly required in existing literature when the graph is directed time-varying. Extensive simulations demonstrate the effectiveness of our approach in achieving efficient resource outsourcing decisions while preserving the privacy of the edge devices

Nash equilibrium seeking over digraphs with row-stochastic matrices and network-independent step-sizes

In this paper, we address the challenge of Nash equilibrium (NE) seeking in non-cooperative convex games with partial-decision information. We propose a distributed algorithm, where each agent refines its strategy through projected-gradient steps and an averaging procedure. Each agent uses estimates of competitors' actions obtained solely from local neighbor interactions, in a directed communication network. Unlike previous approaches that rely on (strong) monotonicity assumptions, this work establishes the convergence towards a NE under a diagonal dominance property of the pseudo-gradient mapping, that can be checked locally by the agents. Further, this condition is physically interpretable and of relevance for many applications, as it suggests that an agent's objective function is primarily influenced by its individual strategic decisions, rather than by the actions of its competitors. In virtue of a novel block-infinity norm convergence argument, we provide explicit bounds for constant step-size that are independent of the communication structure, and can be computed in a totally decentralized way. Numerical simulations on an optical network's power control problem validate the algorithm's effectiveness

A Bandit Approach to Online Pricing for Heterogeneous Edge Resource Allocation

Edge Computing (EC) offers a superior user experience by positioning cloud resources in close proximity to end users. The challenge of allocating edge resources efficiently while maximizing profit for the EC platform remains a sophisticated problem, especially with the added complexity of the online arrival of resource requests. To address this challenge, we propose to cast the problem as a multi-armed bandit problem and develop two novel online pricing mechanisms, the Kullback-Leibler Upper Confidence Bound (KL-UCB) algorithm and the Min-Max Optimal algorithm, for heterogeneous edge resource allocation. These mechanisms operate in real-time and do not require prior knowledge of demand distribution, which can be difficult to obtain in practice. The proposed posted pricing schemes allow users to select and pay for their preferred resources, with the platform dynamically adjusting resource prices based on observed historical data. Numerical results show the advantages of the proposed mechanisms compared to several benchmark schemes derived from traditional bandit algorithms, including the Epsilon-Greedy, basic UCB, and Thompson Sampling algorithms

Methods for constructing VS30 maps from geology, borehole and topography data

The average shear wave velocity in the upper 30 meters of a soil profile (VS30) is used in building codes to separate sites into classes for the purpose of earthquake engineering design. In this paper, a method of Thompson E.N. and Wald D.J. (2012) was applied to build a VS30 map of Ho Chi Minh city using, many different data such as geologic, topographic and shear wave velocities derived from the Standard Penetration Test (SPT) data of 104 boreholes. The VS30 values are mainly within two ranges of 0 -180 m/s and 180 - 240 m/s corresponding to two site classes of type D and C, respectively, according to the soil classification in Vietnam Construction Code TCVN 9386:2012. The site class of type C is mainly distributed in the districts located in the northern area of Ho Chi Minh city, while the soft soil with VS30 180 m/s is concentrated in the south of the city. This result shows that this method can reduce the uncertainty of VS30 map by up to 11.4% relative to the topography slope-only approach. Moreover, the average topographic slope of Ho Chi Minh city area is about 0.0024. It implies that Ho Chi Minh city area is in a stable continental region, which is suitable to apply ground motion prediction equations developed for seismic stable regions for the purpose of seismic hazard assessment. Our study is a prerequisite for the wide application of this method to build VS30 maps for other areas in Vietnam.ReferencesAbrahamson, N., Atkinson, G., Boore, D.M., Bozorgnia, Y, Campbell, K., Chiou, B., Idriss, I.M., Silva, W., and Youngs, R., 2008. Comparisons of the NGA ground-motion relations. Earthquake Spectra 24(1), 45-66.Allen, T. I. and Wald D. J., 2009. On the Use of High-Resolution Topographic Data as a Proxy for Seismic Site Conditions (VS30). Bull. Seism. Soc. Am., 99(2A), 935-943.Borcherdt, R. D., 1994. Estimates of site-dependent response spectra for design (methodology and justification). Earthquake Spectra 10, 617-654.Bozorgnia, Y., N. A. Abrahamson, L. Al Atik, T. D. Ancheta, G. M. Atkinson, J. W. Baker, A. Baltay, D. M. Boore, K. W. Campbell, B. S.-J. Chiou, et al., 2014. NGA-West2 research project, Earthquake Spectra, 30(3), 973-987.Bui Thi Nhung and Nguyen Hong Phuong, 2015. Local site classification for the urban region of Hanoi city. Journal of Sciences of the Earth, 33(4), 690-694 (in Vietnamese).Bui Van Duan, Ha Thi Giang, Nguyen Anh Duong, and Pham Dinh Nguyen, 2015. About factors related to the occurrence of earthquakes in the Song Tranh 2 hydropower area in period 2011-2014. Journal of Sciences of the Earth, 37(3), 228-240 (in Vietnamese).Building Seismic Safety Council, 2015. Recommended Seismic Provisions for New Buildings and Other Structures, Part 1: Provisions, Part 2: Commentary. Report No. FEMA P-1050-1, Federal Emergency Management Agency, Washington, D.C., 515p.CEN, 2004. EN 1998-1:2004, Eurocode 8: Design of structures for earthquake resistance - Part 1: General rules, seismic actions and rules for buildings. European committee for standardization, Brussels, Belgium.Cat Nguyen Hung et al., 2009. Seismic microzoning of Ho Chi Minh city. Final report of scientific research funding program supported by Ho Chi Minh City Goverment (in Vietnamese).Imai, T., 1977. P and S wave velocities of the ground in Japan. Proceeding of IX International Conference on Soil Mechanics and Foundation Engineering, 2, 127-132.International Code Council, 2009. 2009 IBC International Building Code, Country Club Hills, Illinois, 730p.Lee, C. T. and B. R. Tsai, 2008. Mapping VS30 in Taiwan. Terr. Atmos. Ocean. Sci., 19, 671-682, doi: 10.3319/TAO.2008.19.6.671(PT).Nguyen Anh Duong, T. Sagiya, F. Kimata, D. T. Tran, Q. H. Vy, C. C. Duong, X. B. Nguyen, and D. X. Nguyen, 2013. Contemporary horizontal crustal movement estimation for northwestern Vietnam inferred from repeated GPS measurements, Earth Planets Space, 65(12), 1399-1410, doi:10.5047/eps.2013.09.010.Nguyen Hong Phuong and Pham The Truyen, 2014. Probabilistic seismic hazard assessment for the South Central Vietnam. Vietnam J. Earth Sci., 36(4) 451-461.Nguyen Ngoc Hoa (editor), Duong Van Cau, Dang Ngoc Phan, Doan Sinh Huy, Hoang Ngoc Ky, Le Minh Thuy, Nguyen Van Quang, Truong Cong Duong, 1995. Geological and mineral map of Vietnam on a scale of 1:200.000 (Ho Chi Minh city sheet; C 48 - XI). Geological Survey of Vietnam, Hanoi (in Vietnamese).Nguyen Sinh Minh, Pham Dinh Nguyen et al., 2014. Seismic hazard assessment for the expanded Hanoi city, establishing of detail seismic zoning map for Ha Dong, Son Tay, Hoa Lac areas by scaled 1:25.000, building of database of ground motion features according to the above maps. Final report of scientific research funding program supported by Hanoi City Goverment (in Vietnamese).Petersen, M., Stephen Harmsen, Charles Mueller, Kathleen Haller, James Dewey, Nicolas Luco, Anthony Crone, David Lidke, and Kenneth Rukstales, 2007. Documentation for the Southeast Asia Seismic Hazard Maps. Administrative Report September 30, 2007, U.S. Geological Survey, Reston, Virginia.Phan Trong Trinh, 2012. Neo-tectonics and contemporary geodynamics in Vietnam sea area and adjacency. Publishing House for Science and Technology, Hanoi, 330p (in Vietnamese).Phan Trong Trinh, Ngo Van Liem, Nguyen Van Huong, Hoang Quang Vinh, Bui Van Thom, Bui Thi Thao, Mai Thanh Tan, Nguyen Hoang, 2012. Late Quaternary tectonics and seismotectonics along the Red River fault zone, North Vietnam. Earth-Science Reviews, 114(3), 224-235.Phan Trong Trinh, Hoang Quang Vinh, Nguyen Van Huong, Ngo Van Liem, 2013. Active fault segmentation and seismic hazard in Hoa-Binh reservoir, Vietnam. Cent. Eur. J. Geosci, 5(2), 223-235.Romero, S., and Rix, G.J., 2001. Regional Variations in Near-Surface Shear Wave Velocity in the Greater Memphis Area. Engineering Geology 62, 137-158.Simons, W. J. F., A. Socquet, C. Vigny, B. A. C. Ambrosius, S. Haji Abu, Chawat Promthong, C. Subarya, D. A. Sasito, S. Matheussen, P. Morgan, and W. Spakman, 2007. A decade of GPS in Southeast Asia: Resolving Sundaland motion and boundaries, J. Geophys. Res., 112, B06420, doi:10.1029/2005JB003868.Thompson, E.M and Wald D.J., 2012. Developing VS30 Site-Condition Maps by Combining Observations with Geologic and Topographic Constraint. The 15th World Conference on Earthquake Engineering: September 24-28, 2012, Lisbon, Portugal. USGS Publications Warehouse.Toro, G. R., Abrahamson, N. A. and Schneider, J. F., 1997. Engineering Model of Strong Ground Motions from Earthquakes in the Central and Eastern United States. Seismological Research Letters, 68(1), 41-57.Tran Thi My Thanh, Nguyen Le Minh, Vi Van Vung and Kojiro Irikura, 2014. Values for peak ground acceleration and peak ground velocity using in seismic hazard assessment for Song Tranh 2 hydropower region. Vietnam J. Earth Sci., 36(4), 462-469.Tran Thi My Thanh, Vi Van Vung, Hiroe Miyake and Kojiro Irikura, 2015. Simulated fround motion of the earthquake on Octorber 22nd, 2012, M4.6 at Song Tranh 2 dam area. Journal of Sciences of the Earth, 37(3), 241-251 (in Vietnamese).Vietnam Construction Code TCVN 9386:2012, 2012. Design of structures for earthquake resistances. Hanoi, 288p (in Vietnamese).Vu Trong Tan et al., 2010. Application of seismic borehole methods and establishing the calculating procedure of elastic parameters to serve for foundation structures and seismic resistant construction in Ho Chi Minh City and neighboring provinces. Final report of R-RD scientific research funding program supported by Ministry of Natural Resources and Environment (in Vietnamese).Wald, D. J. and Trevor I. Allen, 2007. Topographic Slope as a Proxy for Seismic Site Conditions and Amplification. Bull. Seism. Soc. Am., 97(5), 1379-1395.Wills, C.J. and Clahan, K.B., 2006. Developing a Map of Geologically Defined Site-Condition Categories for California. Bull. Seism. Soc. Am., 96(4A), 1483-1501.Yong, A., Hough, S.E., Abrams, M.J., Cox, H.M., Wills, C.J., and Simila, G.W., 2008. Site Characterization Using Integrated Imaging Analysis Methods on Satellite Data of the Islamabad, Pakistan, Region. Bull. Seism. Soc. Am., 98(6), 2679-2693.Yong, A., Hough, S.E., Iwahashi, J., and Braverman, A., 2012. A Terrain-Based Site-Conditions Map of California with Implications for the Contiguous United States. Bull. Seism. Soc. Am., 102(1), 114-128

Effect of Polypyrrole on the Electrical, Dielectric and Mechanical Properties of Waterborne Epoxy Coatings

In this context, conducting composite based on waterborne epoxy system and polypyrrole (PPy) was investigated. The polypyrrole was synthesized by chemical oxidation polymerization. Its morphology and chemical structure were confirmed by using field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). Then, PPy was well-dispersed in the epoxy coating and had a good compatibility with the matrix. The effects of PPy on dielectric, electrical and mechanical properties of epoxy/PPy composites was examined. The dielectric constant and electrical conductivity of the coatings increased with addition of PPy fillers. Over to 15 wt. % of PPy loading, the volume resistivity of samples slightly decreased from 6.7 × 1010 to 1.5 × 1010 Ω cm. In contrast, the presence of PPy diminished both impact and abrasion resistance of the epoxy/PPy composites, down to 160 kg cm and 10.2 L/mil, respectively, but they stayed acceptable for the coatings. The results reveal that the epoxy containing polypyrrole is suitable for various electrical and dielectric applications