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Micromechanical modeling of damping behavior in vibration-reducible cementitious composites
No full textRecently, some microparticles have been proven to be effective in improving the damping performance of cementitious composites, which is described by the damping loss factor. Related studies have analyzed damping loss factors of cementitious composites with microparticles to determine optimum mixing proportion, but no efficient numerical analysis method is available for cementitious composites with microparticles. In this study, the micromechanical three-phase model and finite element (FE) strain energy were applied to cementitious composites reinforced with hollow sphere and flake-shaped microparticles. These methods have been widely used with fiber composites but never used with microparticle-reinforced composites. The three-phase model was used here to estimate the damping loss of microparticles, and FE strain energy method was used to analyze the damping loss factor of microparticle-reinforced cementitious composites with the damping loss factor from the three-phase model. This research highlights that the FE strain energy method can be an effective method for estimating the damping loss factor of cementitious composites with different types of microparticles at various volume fractions of fillers with less than 0.1% the least square error between the experimental and simulation results
Multiplicity results of solutions to the double phase anisotropic variational problems involving variable exponent
No full textAim of this paper is to discuss the existence of multiple so-lutions to double phase anisotropic variational problems for the case of a combined effect of concave-convex nonlinearities. Especially the super -linear (convex) term to the given problem substantially fulfills a weaker condition as well as Ambrosetti-Rabinowitz condition. To achieve these results, we apply the variational methods such as the famous mountain pass theorem and Ekeland's type variational principle when an energy functional corresponding to our problem satisfies the compactness con-dition of the Palais-Smale type. In particular, we establish several ex-istence results of a sequence of infinitely many solutions by employing the Cerami compactness condition. The key tools for obtaining these results are the fountain theorem and the dual fountain theorem
Photoelectrochemical Epoxidation of Cyclohexene on an ??-Fe2O3 Photoanode Using Water as the Oxygen Source
No full textThis study developed a safe and sustainable route for the epoxidation of cyclohexene using water as the source of oxygen at room temperature and ambient pressure. Here, we optimized the cyclohexene concentration, volume of solvent/water (CH3CN, H2O), time, and potential on the photoelectrochemical (PEC) cyclohexene oxidation reaction of the alpha-Fe2O3 photoanode. The alpha-Fe2O3 photoanode epoxidized cyclohexene to cyclohexene oxide with a 72.4 +/- 3.6% yield and a 35.2 +/- 1.6% Faradaic efficiency of 0.37 V vs Fc/Fc+ (0.8 VAg/AgCl) under 100 mW cm-2. Furthermore, the irradiation of light (PEC) decreased the applied voltage of the electrochemical cell oxidation process by 0.47 V. This work supplies an energy-saving and environment-benign approach for producing value-added chemicals coupled with solar fuel generation. Epoxidation with green solvents via PEC methods has a high potential for different oxidation reactions of value-added and fine chemicals
Graphene-Encapsulated Bifunctional Catalysts with High Activity and Durability for Zn-Air Battery
No full textCarbon-based electrocatalysts with both high activity and high stability are desirable for use in Zn-air batteries. However, the carbon corrosion reaction (CCR) is a critical obstacle in rechargeable Zn-air batteries. In this study, a cost-effective carbon-based novel material is reported with a high catalytic effect and good durability for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), prepared via a simple graphitization process. In situ growth of graphene is utilized in a 3D-metal-coordinated hydrogel by introducing a catalytic lattice of transition metal alloys. Due to the direct growth of few-layer graphene on the metal alloy decorated 3d-carbon network, greatly reduced CCR is observed in a repetitive OER test. As a result, an efficient bifunctional electrocatalytic performance is achieved with a low ?E value of 0.63 V and good electrochemical durability for 83 h at a current density of 10 mA cm(-2) in an alkaline media. Moreover, graphene-encapsulated transition metal alloys on the nitrogen-doped carbon supporter exhibit an excellent catalytic effect and good durability in a Zn-air battery system. This study suggests a straightforward way to overcome the CCR of carbon-based materials for an electrochemical catalyst with wide application in energy conversion and energy storage devices
Max-Min Fairness Beamforming With Rate-Splitting Multiple Access: Optimization Without a Toolbox
No full textWe propose a max-min fairness (MMF) design method in a multi-antenna downlink network, where rate-splitting multiple access (RSMA) is adopted. A main aim in the considered MMF problem is providing uniformly good rates to users, by carefully controlling the rate of each private and common message, respectively. Solving this problem is challenging since multiple optimization variables, i.e., beamforming vectors and common message portions, are intricately intertwined in a non-tractable objective function. To resolve these obstacles, we first split a whole problem into two stages. In the first stage, we identify beamforming vectors given common message portion by exploiting the LogSumExp (LSE) approximation technique and the novel generalized power iteration (GPI) framework. In the second stage, we determine common message portions under fixed beamforming vectors. Iterating these two stages, we jointly design beamforming vectors and common message portion accordingly. Via simulations, we demonstrate that our method outperforms existing other frameworks in terms of the minimum rate, while requiring extremely small computational complexity
Feasibility of electricity generation based on an ammonia-to-hydrogen-to-power system
No full textThe transition from centralized electricity generation to distributed electricity, such as fuel cell power plants, is one of the promising strategies for decarbonization in the energy sector. However, the operation of hydrogen fuel cells could be problematic because liquefaction or compression processes for hydrogen storage are energy intensive and require high maintenance costs. In addition, if hydrogen in fuel cell-based power plants is supplied via natural gas steam reforming, direct carbon emissions to the atmosphere are caused. Therefore, this study investigates an ammonia-based electricity generation system through the sequential conversion of ammonia to hydrogen and hydrogen to power. This system can replace inefficient and costly hydrogen storage with the existing infrastructure of ammonia and reduce carbon emissions by using ammonia instead of hydrocarbon feedstock. With an ammonia price from the conventional production way, the system shows an electricity generation price in the range of 0.227-0.261 USD per kW h and a carbon intensity of 0.80-1.44 kgCO(2)-eq per kW h which are not feasible at present. Because ammonia price and emissions during production are the most significant factors for the feasibility of the system, five different scenarios considering various ammonia production pathways are established. Based on the scenario analysis, the feasible conditions and countries in terms of both economic and environmental aspects are identified. In the most optimistic scenario, the electricity generation price and carbon intensity are calculated to be 0.134-0.150 USD per kW h and 0.16-0.28 kgCO(2)-eq per kW h respectively, and the system can be competitive in 40 countries out of 134 countries
Utilization of methanol and ethanol for 3,3 '-bis(indolyl)methane synthesis through activation of peroxymonosulfate over a copper catalyst
No full textA greener and simple catalytic system is developed for the synthesis of biologically important 3,3 '-bisindolyl(methanes) (BIMs) using C1 and C2 alcohols as the carbon source for the bridging methylene group. The reaction occurred under very mild and environment friendly conditions without the requirement of any toxic solvents. The low cost CuO-peroxymonosulfate (CuO-PMS) system allows the reaction to be highly efficient, resulting in very good product yield
How to Avoid Misinterpreting Experimental Data for Thermally Activated Processes
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R4N+ and Cl??? stabilized ??-formamidinium lead triiodide and efficient bar-coated mini-modules
No full textThe higher thermodynamic stability of formamidinium lead triiodide (FAPbI3) in the yellow non-perovskite (8-phase) than the black perov-skite (a-phase) at room temperature causes spontaneous a-phase to 8-phase transition. Stabilization of a-FAPbI3 by alloying the perovskite composition is limited by band gap broadening and halide segregation. Furthermore, commercial PSCs require coating methods suitable for large-area modules. Herein, we report a-phase stabilization of FAPbI3 without band gap broadening using R4N+ cations and Cl- anions. Subsequently, high-efficiency perovskite so-lar mini-modules (PSMs) were fabricated using a bar-coating process with simultaneous defect passivation and hole-transport promotion which exhibited a maximum power conversion efficiency (PCE) of 21.23% (certified 20.33%, 36.4-cm2 area). The PCE in the 1-cm2 area fabricated by bar-coating was 23.24% (certified 22.79%, the highest in those fabricated by scalable bar-coating method). Furthermore, the encapsulated PSM retained 93% of its initial PCE, even after 870 h under continuous one-sun illumination