Existence and multiplicity of non-zero solutions for the Neumann problem via spherical maxima

In this paper, we are interested inthe existence and multiplicity of non-zerosolutions for a two-point boundary value problems subject to Neumannconditions. Our approach is based on a result on spherical maxima sharing the same Lagrange multiplier that was established recently by Ricceri

Infinitely many weak solutions for a fourth-order equation on the whole space

The existence of infinitely many weak solutions for a fourth-order equation on the whole space with a perturbed nonlinear term is investigated. Our approach is based on variational methods and critical point theory

Comparison of Paraquat Herbicide Removal from Aqueous Solutions using Nanoscale Zero-Valent Iron-Pumice/Diatomite Composites

Paraquat is the most important herbicide of the bipyridyl group. The aim of the present study was to compare the removal of paraquat herbicide from aqueous solutions using nanoscale zero-valent iron-pumice/diatomite composites. In this study, nZVI was supported with diatomite and pumice. Scanning electron microscopy (SEM) analysis, X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectrometry (FTIR), and specific surface area tests (BET) were used to evaluate the properties of nanoadsorbents. The residual concentration of paraquat in aqueous solution was detected by high-performance liquid chromatography (HPLC). Then, the effects of different variables including the pollutant concentration, contact time, temperature, adsorbents (D-nZVI and P-nZVI) dose, and pH, were investigated in a lab scale batch system. The results showed that the optimal pH for both processes was 3.74. In optimal conditions, the efficiencies of D-nZVI and P-nZVI were 92.76% and 85.28%, respectively. In addition, isotherm and adsorption kinetics studies indicated that P-nZVI follows the Langmuir and Freundlich isotherm models, and D-nZVI follows the Langmuir isotherm model, and both processes follow pseudo-second-order kinetics. The results indicated that the synthesized nanoparticles were suitable for removing paraquat from aqueous solutions. Both adsorbents were found to be very effective in removing similar compounds at ambient temperature in a short time

Effects of initial wettability and different surfactant-silica nanoparticles flooding scenarios on oil-recovery from carbonate rocks

Initial wettability of rock surfaces plays a crucial role in displacement efficiency during core flooding experiments. In this study, linear alkylbenzene sulfonic acid (LABSA) and silica nanoparticles (NPs) were utilized as enhanced oil recovery (EOR) agents to improve oil recovery from carbonate rock samples. Prior to the core flooding experiments, effects of the presence of LABSA and SiO2 NPs on oil-water interfacial tension (IFT), wettability alteration, and surfactant adsorption on the rock surfaces were evaluated. The results of IFT/contact angle measurements showed that by adding 0.03 wt% LABSA, the IFT, and contact angle reduced from the initial values of 36.9 mN/m and 115.6° ± 0.2° to 8.3 mN/m and 100.3° ± 0.4°, respectively. Furthermore, incorporating SiO2 NPs (0.1 wt%) into the system causes a further decrease in IFT value (dropped to 2.2 mN/m), along with a substantial reduction in contact angle (final contact angle after 6 h soaking into the solution was measured as 64.8° ± 0.3°). In addition, surfactant loss due to the adsorption on the rock surfaces decreased up to 35% in the presence of SiO2 NPs (0.1 wt%). Moreover, various core flooding scenarios in carbonate plugs with different initial wettability conditions were conducted, and the performance of the EOR agents in enhancing oil recovery from oil-wet and water-wet core samples in the secondary and tertiary mode of flooding was evaluated. The outcomes revealed that the injection of a combination of chemicals, containing LABSA (0.03 wt %) and SiO2 (0.1 wt%) in the secondary mode leads to the highest ultimate oil recovery from sister carbonate core samples

Feasibility of large amounts biogas production from garbage bioliquid

Aims: One of the best available alternatives to face the energy and environment problem is to tend renewable energies. The main aim of this study is producing biogas from garbage bioliquid (leachate). Materials and Methods: This study was conducted at wide range of organic loading rate (OLR = 0.93–25 g COD l‑1 d‑1) by varying hydraulic retention times (HRT = 23 and 12 hsr) and initial COD of 1.85–25 g l‑1. pH variations, COD, SCOD, rbCOD and VFAs degradation, biogas and methane production were considered in this study. Results: The COD removal efficiencies were in the range of 76–81% depending on loading rates applied. The maximum volumetric methane production rate (VMPR) of 5.7 l CH4 l‑1 d‑1 was achieved at the OLR of 19.65 g COD l‑1 d‑1. About 85% of removed COD during the biodegradation was converted to methane. Conclusion: The results have shown that the anaerobic sequencing batch reactor (ASBR) reactor could be an appealing option for changing composting leachate into useable products such as biogas and other energy‑rich compounds, which may play a serious role in meeting the world’s ever‑increasing energy requirements in the future

The Interactive Impact of Building Diversity on the Thermal Balance and Micro-Climate Change under the Influence of Rapid Urbanization

Numerous cities face the serious problems of rapid urbanization and climate change, especially in recent years. Among all cities, Wuhan is one of the most affected by these changes, accompanied by the transformation of water surfaces into urban lands and the decline of natural ventilation. This study investigated the impact of surface urban heat island enlargement (SUHI) and block morphology changes in heat balance. Accordingly, the interactive impact of building diversity with major building forms (low-rise, mid-rise, and high-rise) on thermal balance and microclimate changes under the influence of urban land expansion at the residential block scale was studied. To investigate the heat balance changes by air temperature intensification and air movement reduction, a long-term and field observational analysis (1980–2018) coupled with computational fluid dynamic simulation (CFD) was used to evaluate the impact of building diversity on thermal balance. Outcomes show that urban heat island intensity (UHII) increased by 2 ℃ when water surfaces in urban areas decreased; consequently, there was a deterioration in the air movement to alleviate UHII. Thus, the air movement declined substantially with UHII and SUHI enlargement, which, through increased urban surfaces and roughness length, will become worse by 2020. Furthermore, the decline in air movement caused by the transformation of urban water bodies cannot contribute to the heat balance unless reinforced by the morphology of the urban blocks. In the design of inner-city blocks, morphological indicators have a significant impact on microclimate and heat balance, where increasing building density and plot ratio will increase UHII, and increasing water surfaces will result in an increase in urban ventilation. Lastly, a substantial correlation between air temperature and relative humidity was found, which, together with the block indicators, can help control the air temperature and adjust the urban microclimate