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Calcined paper mill lime mud as an activator in GGBFS-based cementless UHPC
No full textThis study investigates the potential use of calcined lime mud as an activator in the development of a sustainable, ground granulated blast furnace slag (GGBFS)-based cementless UHPC. The effects of the calcination temperature (550 ??C to 850 ??C) of lime mud and its weight percentage in the UHPC mixture were evaluated with various tests, such as compressive strength, isothermal calorimeter, and thermogravimetric analysis. Microstructural changes and pore size distribution were also analyzed using XRD, FTIR, and MIP. The results showed that calcined lime mud can be an effective activator in the UHPC mix, and its mechanical properties are influenced by the calcination temperature and weight percentage. The addition of 10% calcined lime mud enhanced the compressive strength of the UHPC up to 150 MPa without negatively affecting its microstructural and hydration characteristics, suggesting that calcined lime mud has the potential to be used as a sustainable alternative to CaO in GGBFS-based cementless UHPC
Valorization of waste concrete powder (WCP) through silica fume incorporation to enhance the reactivity and hydration characteristics
No full textThe aim of this study is to utilize the bulk proportion of waste concrete powder (WCP) as cementitious material in the fabrication of binder, and to investigate the impact of silica fume on the reactivity and hydration characteristics of thermomechanical activated WCP. A 29 Silicon Nuclear Magnetic Resonance (NMR) analysis confirmed the presence of reactive silica in the activated WCP. Various blends were prepared with a 50%???80% substitution of type CEM I 52.5 N cement. The combination of activated WCP and silica fume improved the reactivity of the binder blend and achieved a compressive strength comparable to cement. Mineralogical analysis revealed the development of secondary C???S???H gels in mixtures containing silica fumes and activated WCP, which is the result of a secondary hydration reaction between portlandite and reactive silica. The use of life cycle analysis software for the replacement of 60 wt % of cement with activated WCP was found to reduce carbon dioxide emissions by 80.42% due to the use of less cement, an environmentally friendly WCP activation process, even when considering the addition of 10% silica fume. This innovative approach not only enhances WCP reactivity and mechanical strength but also significantly contributes to the reduction of carbon emissions. By elucidating the formation mechanisms and environmental benefits, this study paves the way for a more eco-conscious and efficient construction methodology, promoting the vision of a greener future
Absolute nodal coordinate formulation - Multilevel finite element framework for the nonlinear multi-scale multibody dynamic analysis of composite structures
No full textIn this paper, a multi-scale modeling approach for the dynamic response of flexible multibody system made of composite material is suggested using the absolute nodal coordinate formulation (ANCF) - multilevel finite element (FE2) method. On many occasions, the analysis of composite structures requires a multi-scale modeling approach. FE2 method is one of the famous multi-scale modeling methods. And it is a versatile computational homogenization approach that is commonly applicable to many different materials. Because the present FE2 is capable of computing the mechanical response at two different scales simultaneously, ANCF element will be used at the macroscopic scale. And the microscopic RVE at each macroscopic integration point will be obtained by the finite element method. Since ANCF element uses only the absolute nodes and gradients, the mass matrix will be constant. Due to such characteristics, when combined with FE2, the linearization process will become easier compared against the existing formulation. And Coriolis or centrifugal force will not need to be considered in the dynamic formulation. Therefore, computational cost will be reduced, and the relevant algebraic manipulation will become simplified. Several numerical examples are presented to demonstrate the improved accuracy and diminished computational cost of the present suggestion
Efficient MAPbI3-based perovskite solar cells exceeding 21% efficiency via aging treatment
No full textRecently, the demand for large-area and high-efficiency perovskite solar cells (PSCs) has increased, and a twostep process for high-efficiency large-area PSCs is actively being studied. However, the two-step process is still less efficient than the one-step antisolvent dripping process owing to the poor interdiffusion of organic components. In this study, a perovskite layer using a hybrid deposition method in which an excess of methylammonium iodide (MAI) solution is reacted with thermally evaporated PbI2 is reported. The perovskite film quality is improved by reacting unreacted residual PbI2 with excess MAI by applying daily electrical stress and aging for 60 days in a glovebox. The best PSC exhibits a PCE of 21.1 %, the highest reported power conversion efficiency among PSCs based on the two-step hybrid deposited MAPbI3 perovskite, with a large enhanced opencircuit voltage of 1.21 V and fill factor of 80.8 %. Moreover, using the solvent pre-heat treatment method, the reaction of unreacted PbI2 with MAI is accelerated, and the aging time of PSCs is shortened from 60 to 7 days, showing a PCE value of 20.7 %. Furthermore, we present a large-area PSC with a PCE of 19.4 %, indicating that the PCE can be improved through the hybrid deposition method
Hydrogel-anchoring electrodes for relieving impacts of bubbles for overall hydrazine splitting
No full textPost-synthetic modifications in metal-organic frameworks for high proton conductivity
No full textA myriad of metal ions and organic linkers can be used to produce metal-organic frameworks (MOFs) with varied functionalities, porosities, and dimensionalities. Such diversity has garnered significant research interest, particularly in leveraging MOFs as proton conductors for fuel cells. One effective approach involves introducing guest molecules into MOF pores. These molecules serve either as proton carriers or as proton-conducting media through potential hydrogen bonding networks. This review offers an organized overview of key methodologies historically employed to achieve superprotonic conductivity in MOFs. The article systematically categorizes these tactics into three primary groups: guest molecule encapsulation, modulation at metal-coordination sites, and ligand functionalization. We succinctly discuss the roles of proton carriers, conducting media, and the overall MOF framework, emphasizing the significance of each strategy's application. In conclusion, we provide insights into the future development of MOFs as proton conductors, rooted in the categorization and conceptual understanding of these strategies
Improving Electroluminescence of Two-Coordinate Au(I) Complexes: Insights into Steric and Electronic Control
No full textThis research elucidates the effects of structural modulations on electroluminescent Au(I) complexes, shedding light on factors governing radiative and nonradiative processes. A series of Au(I) complexes, fortified with ortho-substituents in carbene and amido ligands, are subjected to rigorous structural, photophysical, and quantum chemical investigations, which unveil distinct structural and electronic effects exerted by the ligands. The investigations reveal that nonradiative processes are governed primarily by the energy-gap law. Radiative processes are observed to have a weak correlation with the mutual interactions of the molecular orbitals of carbene and amido ligands. Rather, it is discovered that an accumulation of the negative charge in the Au 5d orbital in the excited state decelerates radiative processes. The effectiveness of these findings is substantiated through the larger external quantum efficiency of electroluminescence devices employing the Au(I) complex, in comparison to those based on the archetypical Au(I) complex and the organic thermally activated delayed fluorescent molecule. These compelling revelations underscore the untapped potential of Au(I) complexes in the advancement of electroluminescence technology and advocate for continued investigations into the intriguing domain of ligand structural control. Molecular factors that control photoluminescence efficiencies of two-coordinate Au(I) complexes involve the emission energy and the charge in the Au 5d-orbital.imag
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No full textDepartment of Mathematical SciencesFrom the end of 2019, COVID-19 occurred by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Wuhan, China. As the number of confirmed cases worldwide has increased exponentially, the World Health Organization (WHO) declared COVID-19 a pandemic on March 11, 2020. As of August 8, 2020, there are 14,562 confirmed cases and 304 deaths in Korea. As the number of covid 19 confirmed cases increases, economic and cultural losses increase, so it is important to predict the number of confirmed cases well and establish policies. As the number of infected cases increases, covid 19 search query volume also increases, hence this will be applied to predicting the number of infected cases. The parameters: infection rate, recovery rate, and death rate were obtained using the SIRD equation. Among them, the infection rate and covid 19 search query volume data are combined to make an input value of LSTM suitable for time series prediction. Using the output obtained using LSTM as a new infection rate, substitute it into the SIRD ode equation to obtain infected data. Comparing the case when the query was added and the case when the query was not added, unlike expected the case without the query predicted the infected data better. In the future, rather than adding web data to parameter values, we will try to pursue the direction of transforming the SIRD model itself so that wed data can be included.ope
An autopsy study of hollow fiber and multibore ultrafiltration membranes from a pilot-scale ultra high-recovery filtration system for surface water treatment
No full textThe organic fouling characteristics of hollow fiber ultrafiltration (HFUF) and multibore ultrafiltration (MBUF) mem-branes from long-term ultrafiltration (UF) membrane systems were systemically investigated in this study. The objec-tive was to obtain insights into the fouling behavior of dissolved organic matter (DOM) in a pilot-scale ultra-high-recovery membrane filtration system (p-UHMS) used for surface water treatment. The pilot system consisted of a series of two different UF membranes (1st stage: polyvinylidene fluoride (PVDF) HFUF and 2nd stage: polyethersulfone (PES) MBUF). It was designed to feed the HFUF concentrate to the MBUF membranes to achieve >= 99.5 % total water recov-ery for surface water treatment, as these advances might enhance the production efficiencies of drinking water. The experimental results confirmed that hydrophobic DOM controlled the formation of HFUF membrane organic fouling, whereas hydrophilic DOM, including polysaccharide-like and protein-like matter, promoted MBUF membrane fouling. These opposing trends were attributed to the hydrophilic characteristics of the MBUF membrane surfaces (contact angle: PVDF = 90-130 degrees and PES <= 80 degrees), which reduced the hydrophobic interactions between the UF membrane sur-faces and foulants. The performance declines of the MBUF membrane due to fouling layer formation was considerably severer than those of the HFUF membrane, decreasing total permeate water in the p-UHMS. Moreover, the quantity of the desorbed MBUF membrane foulants via 0.1 N NaOH was roughly 7.2 times larger than that of the desorbed HFUF membrane foulants through 0.1 N NaOH, indicating that alkaline-based cleaning agent could much more efficiently recover the performance of the fouled MBUF membranes. Hence, adequate cleaning strategies using alkaline-based agent for the MBUF membrane appeared to be essential for preventing the performance deterioration of the p-UHMS