Search Results (91)

Aiming at the lightweight design of a bridge-shed integration structure, this paper presents a three-layered absorbing system in which a part of the sand cushion is replaced by expanded polystyrene (EPS) geofoam and the reinforced concrete (RC) protective slab is arranged above the sand cushion to enhance the composite system’s safety. A three-dimensional Smoothed Particle Hydrodynamics–Finite Element Method (SPH-FEM) coupled numerical model is developed in LS-DYNA (Livermore Software Technology Corporation, Livermore, CA, USA, version R13.1.1), with its validity rigorously verified. The dynamic response of rockfall impacts on the shed slab with composite cushions of various thicknesses is analyzed by varying the thickness of sand and EPS materials. To optimize the cushion design, a specific energy dissipation ratio (SEDR), defined as the energy dissipation rate per unit mass (η/M), is introduced as a key performance metric. Furthermore, the complicated interactional mechanism between the rockfall and the optimum-thickness composite system is rationally interpreted, and the energy dissipation mechanism of the composite cushion is revealed. Using logistic regression, the ultimate stress state of the reactive powder concrete (RPC) slab is methodically analyzed, accounting for the speed and mass of the rockfall. The results are indicative of the fact that the composite cushion not only has less dead weight but also exhibits superior impact resistance compared to the 90 cm sand cushions; the impact resistance performance index SEDR of the three-layered absorbing system reaches 2.5, showing a remarkable 55% enhancement compared to the sand cushion (SEDR = 1.61). Additionally, both the sand cushion and the RC protective slab effectively dissipate most of the impact energy, while the EPS material experiences relatively little internal energy build-up in comparison. This feature overcomes the traditional vulnerability of EPS subjected to impact loads. One of the highlights of the present investigation is the development of an identification model specifically designed to accurately assess the stress state of RPC slabs under various rockfall impact conditions. Full article

The impacts of backwater due to large dam construction on flow may lead to navigation or flood control problems in curved rivers. This study conducted flume experiments to investigate the effects of backwater on the velocity distribution characteristics of a 90-degree bend. The experimental results show that the backwater degree (η, defined as the ratio of flow depth under backwater to that under non-backwater conditions) has significant impacts on the three-dimensional velocity distribution in the bend. The depth-averaged velocities decrease with increasing backwater degree, and the deflection degrees of depth-averaged velocities are found to be highly related to the backwater degree and cross-sectional position. In this experimental setup, the mean cross-sectional velocity decreases by 67.2% as η increases from 1.00 to 3.64 for Q = 35 L/s; 63.7% as η increases from 1.00 to 3.26 for Q = 52 L/s; and 60.1% as η increases from 1.00 to 2.80 for Q = 52 L/s. The maximum values of transversal and vertical velocities near the riverbed gradually shift to the inner bank as the backwater degree increases at the 45° cross section. The center of the high transversal velocity area shifts about 0.1 m toward the inner bank as the backwater degree increases from 1.00 to 3.26 for Q = 52 L/s, which can reduce the erosion of the riverbed near the outer bank. In the current study, we also demonstrate that the growth and decay processes of secondary flow cells under backwater conditions are similar to those under non-backwater conditions. However, the scales and positions of the secondary flow cells change continuously with different backwater degrees. From the entrance to the exit of the bend, the secondary flow intensity first increases, and then decreases, with its maximum values occurring at the 45° cross section. The findings detailed in this manuscript provide insights for navigation channel design in reservoir backwater zones. Full article

In this work, Aspen Plus was used to simulate a sorption-enhanced steam methane reforming (SE-SMR) process in a fluidized bed reformer using a Ni-based catalyst and CaO as a sorbent for CO₂ removal from the reaction environment. The performances of the process in terms of the outlet gas hydrogen purity (y_H2), methane conversion (X_CH4), and hydrogen yield (η_H2) were investigated. The process was simulated by varying the following different reformer operating parameters: pressure, temperature, steam/methane (S/C) feed ratio, and CaO/CH₄ feed ratio. A clear sorption-enhanced effect occurred, where CaO was fed to the reformer, compared with traditional SMR, resulting in improvements of y_H2, X_CH4, and η_H2. This effect, in percentage terms, was more relevant, as expected, in conditions where the traditional process was unfavorable at higher pressures. The presence of CaO could only partially balance the negative effect of a pressure increase. This partial compensation of the negative pressure effect demonstrated that the intensification process has the potential to produce blue hydrogen while allowing for less severe operating conditions. Indeed, when moving traditional SMR from 1 to 10 bar, an average decrease of y_H2, X, and η by −16%, −44%, and −41%, respectively, was recorded, while when moving from 1 bar SMR to 10 bar SE-SMR, y_H2 showed an increase of +20%, while X_CH4 and η_H2 still showed a decrease of −14% and −4%. Full article

In today’s data-driven business landscape, effective customer segmentation is crucial for enhancing engagement, loyalty, and profitability. Traditional clustering methods often struggle with datasets containing both numerical and categorical variables, leading to suboptimal segmentation. This study addresses this limitation by introducing a novel application of Factor Analysis of Mixed Data (FAMD) for dimensionality reduction, integrated with K-means and Agglomerative Clustering for robust customer segmentation. While FAMD is not new in data analytics, its potential in customer segmentation has been underexplored. This research bridges that gap by demonstrating how FAMD can harmonize mixed data types, preserving structural relationships that conventional methods overlook. The proposed methodology was tested on a Kaggle-sourced retail dataset comprising 3900 customers, with preprocessing steps including correlation ratio filtering (η ≥ 0.03), standardization, and encoding. FAMD reduced the feature space to three principal components, capturing 81.46% of the variance, which facilitated clearer segmentation. Comparative clustering analysis showed that Agglomerative Clustering (Silhouette Score: 0.52) outperformed K-means (0.51) at k = 4, revealing distinct customer segments such as seasonal shoppers and high spenders. Practical implications include the development of targeted marketing strategies, validated through heatmap visualizations and cluster profiling. This study not only underscores the suitability of FAMD for customer segmentation but also sets the stage for more nuanced marketing analytics driven by mixed-data methodologies. Full article

Accurately simulating wave breaking is crucial for modeling hydrodynamics over steep coral reef slopes, yet it remains a challenge for Boussinesq-type models like FUNWAVE-TVD. The model’s standard hybrid breaking mechanism, triggered by a fixed free surface elevation-to-depth ratio ($\eta /d>0.8$), often lacks physical sensitivity to local slope and wave conditions prevalent in reef environments and suffers from inaccuracies associated with using η as a direct proxy for wave height (H). This study introduces and validates a novel, enhanced hybrid breaking module within FUNWAVE-TVD, specifically designed to overcome these limitations on steep slopes. The core novelty lies in the synergistic implementation of two key components: (1) replacing the fixed threshold with a dynamic, physically-based criterion derived from the Modified Goda formula (MGO) by Rattanapitikon and Shibayama, which calculates the breaking wave height ($H_b$) based on local depth, slope, and deep-water wavelength; and (2) developing and applying a practical method, using the wave vertical asymmetry relationship proposed by Yu and Li, to dynamically convert the calculated $H_b$ into an equivalent breaking surface elevation threshold (${\eta }_b$). This derived dynamic threshold (${\eta }_b/d$) is then used to trigger the model’s existing switch from Boussinesq to Nonlinear Shallow Water Equations (NSWE), allowing for energy dissipation via shock-capturing while retaining the physical basis of the MGO criterion. The performance of this enhanced module was rigorously evaluated against five laboratory experiments of regular waves breaking on impermeable slopes ranging from mild (1:10) to extremely steep (1:1), contrasting results with the original FUNWAVE-TVD. The modified model demonstrates significantly improved accuracy (model skill increases ranging from 10.16% to 42.49%) compared to the original model for breaking location and wave height prediction on steeper slopes ($m\ge 1:6$). Conversely, tests on the 1:1 slope confirmed the inherent limitations of the MGO criterion itself under surging breaker conditions ($m\ge 1:2.3$), highlighting the applicability range. This work provides a validated methodology for incorporating slope-aware, dynamic breaking criteria effectively into hybrid Boussinesq models, offering a more robust tool for simulating wave processes on steep reef topographies. Full article

In this work, we present a study on the thermal/transport properties of a novel deep eutectic solvent (DES) obtained by using N-methyltrifluoroacetamide (FNMA) as the hydrogen bond donor (HBD) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as the hydrogen bond acceptor (HBA). The binary phase diagram, thermal stability, flammability, viscosity and ionic conductivity of the as-prepared DESs were investigated at atmospheric pressure. The binary phase diagram shows a range of eutectic molar ratios (x_LiTFSI = 0.2~0.33), with the lowest deep eutectic temperature of −84 °C. At x_LiTFSI = 0.2 (i.e., FNMA:LiTFSI = 4:1 and denoted as DES-4:1). The as-prepared DES composition exhibits high thermal stability (onset temperature of weight loss = 78 °C), a low viscosity (η = 48.9 mPa s at 25 °C), relatively high ionic conductivity (σ = 0.86 mS cm⁻¹ at 25 °C) and non-flammability. The transport properties, including ionic conductivity and viscosity, as a function of temperature are in accordance with the Vogel–Fulcher–Tammann (VFT) equations. With increasing molar ratio of HBD vs. HBA, the viscosity decreases, and the ionic conductivity increases at a given temperature between 25 °C and 80 °C. The roughly equal pseudo-activation energies for ion transport and viscous flow in each composition imply a strong coupling of ion transport and viscous flow. Walden plots indicate vehicular transport as the main ion transport mechanism for the DES-4:1 and DES-3:1 compositions; meanwhile, it was confirmed that the ionic conductivity and viscous flow are strictly coupled. The present work is expected to provide strategies for the development of wide-temperature-range and safer electrolytes with low salt concentrations. Full article

The performance analysis of a 10 kW_p rooftop grid connected solar photovoltaic (PV) system located in Sagolband, Imphal, India has been studied for 5 years. The key technical parameters such as array yield ($Y_A$), reference yield ($Y_R$), final yield ($Y_F$), capacity utilization factor (CUF), PV system efficiency (${\eta }_{Sys}$), and performance ratio (PR) were used to investigate its performance. In this study, the experimentally measured results of the system’s performance for the five years (i.e., July 2018 to June 2023) were compared with the predicted results, which were obtained using PVsyst V7.3.0 software. The measured energy generation in 5 years (including 40 days OFF due to inverter failure on 17 June 2019 because of a surge, which was resolved on 27 July 2019) was 58,911.3 kWh as compared to the predicted 77,769 kWh. The measured daily average energy yield was 3.2 kWh/kW_p as compared to the predicted 4.2 kWh/kW_p. It can be seen that there was a large difference between the real and predicted values, which may be due to inverter downtime, local environmental variables (e.g., lower-than-expected solar irradiation and temperature impacts), and the possible degradation of photovoltaic modules over time. The measured daily average PR of the system was 70.71%, and the maximum occurred in the months of October, November, December, and January, which was almost similar to the predicted result. The measured daily average CUF of the system was 13.36%, and the maximum occurred in the months of March, April, and May. The measured daily average system efficiency was 11.31%. Moreover, the actual payback was 4 years and 10 months, indicating strong financial viability despite the system’s estimated lifespan of 25 years. This study highlights the importance of regular maintenance, fault detection, and better predictive modelling for more accurate energy projections, and also offers an understanding of real-world performance fluctuations. Full article

Effective mass, the portion of an athlete’s mass contributing to a punch, is a key biomechanical factor influencing punching strength in boxing. This study examines its relationship with punch mechanics, impulse dynamics, and body composition, identifying techniques that maximize effective mass and enhance force transfer efficiency. Thirty trained male boxers performed jab, cross, lead hook, and rear hook punches while punching force and limb acceleration were measured using an AMTI MC12-2K force plate and Noraxon Ultium EMG sensors. Effective mass was calculated as the ratio of peak force to fist acceleration at impact. Statistical analysis compared punching techniques and examined correlations with body composition and training experience. Straight punches (jab, cross) exhibited significantly higher effective mass than hooks (KW-H = 235.24; p < 0.001; η² = 0.468), despite hooks generating greater peak forces. Cross punches had the highest effective mass (31.17 ± 16.20 kg), followed by jabs (30.39 ± 15.09 kg). No significant correlation was found between effective mass and body composition or training tenure, suggesting technique is more critical than absolute body mass. These findings highlight the importance of optimizing linear punch mechanics and impulse-to-acceleration synchronization in training to enhance effective mass transfer and striking performance. Full article

Powder-fueled ramjets show great potential due to their unique advantages. How to further improve ramjet performance through methods such as fuel improvement is also an important focus. In this paper, a 14 km, Ma 3.0, ground test of a powder-fueled ramjet using boron–aluminum composite powder fuel (B–Al composite powder fuel) was conducted. The feasibility and combustion performance of B–Al composite powder fuel were verified. Under the condition of an air–fuel ratio of 19.39, the ramjet achieved independent self-sustaining combustion for 10 s, and the characteristic exhaust velocity efficiency (${\eta }_c^{*}$) reached 81.84%. Through SEM-EDS, XRD, and XPS, this study systematically analyzed the surface morphology, composition, and chemical state of the wall deposits in the combustion chamber after the test. The combustion behavior of the B–Al composite powder fuel in the ramjet was clarified. The composite powder fuel could be converted into smaller and more combustion-favorable reaction basic units during the combustion process. However, the imbalance and unevenness of Al and B in the combustion reaction and the non-reaction or reaction termination of B particles remain significant issues. This study shows that B–Al composite powder fuel has a good application basis and potential, and provides experimental data support for the subsequent improvement and optimization of the B–Al composite powder fuel system. Full article

The properties of EVA copolymers with various vinyl acetate (VA) contents were compared, with EVA 206 (6 wt.% VA) and EVA 212 (12 wt.% VA) having the same melt flow indices of 2 g/10 min. The impact of electron irradiation at levels of 60, 120, and 180 kGy was studied. Four testing methods were employed as follows: wide-angle X-ray diffraction (WAXD); differential scanning calorimetry (DSC); dynamic mechanical analysis (DMA), using a high-temperature frequency sweep at 150 °C; and gel content analysis. The amount of crystalline phase was determined by WAXD and DSC. Copolymers with a higher VA content (EVA 212) had lower crystallinity. The increase in the amorphous phase allows for the greater movement of radicals, enabling them to react and form cross-links. The effects of the VA content, radiation dose, and frequency on dynamic mechanical properties were investigated by DMA. The DMA analysis focused on the shear storage modulus $G^{\prime }$, damping factor $\tan \delta$, and complex viscosity ${\eta }^{*}$. After irradiation, the damping factor $\tan \delta$ decreased with an increasing VA content, indicating improved elasticity and a higher degree of cross-linking. A gel content analysis was used to calculate the parameters of the Charlesby-Pinner and Charlesby–Rosiak equations, which help with the determination of the relationship between cross-linking and chain scission. The ratio of cross-linking to scission $G\left(X\right)/G\left(S\right)$ was higher for the EVA with a higher VA content (EVA 212). Due to a higher VA content (12 wt.%), EVA 212 exhibits more efficient network formation. Full article

The windage loss in impeller back gap and labyrinth seal cavities significantly impacts the aerodynamic performances of supercritical carbon dioxide (sCO₂) compressors. To accurately calculate windage loss, essential factors affecting the skin friction coefficients C_f,d (disk-type gap) and C_f,s (shaft-type gap), including Reynolds number Re, pressure ratio π, and radius ratio η, are investigated in this paper. The flow characteristics of the gap are analyzed and prediction models are proposed. The results indicate that both C_f,d and C_f,s decrease with increasing Re and grow with π and η, attributable to expanded high-vorticity regions caused by enhanced flow instability and larger vortices. The leakage flow rate m is unchanged for Re < 10⁶ since the fluid can flow into the impeller back gap, and slightly decreases for Re ≥ 10⁶ due to the centrifugal force and the inhibition effect of the vortices filling inlet regions. Moreover, the m grows with π and η due to a larger pressure difference and through-flow area. Maximal relative deviations of 6.23% and 6.83% can satisfy the requirements for calculating accurate windage loss in the impeller back gap and labyrinth seal cavities, which help the primary design of sCO₂ compressors. Full article

This paper introduces a novel mathematical model designed to determine combustion characteristics across the length of the combustion zone, underpinned by logical theoretical foundations and demonstrating notable alignment with experimental findings. The model facilitates the calculation of combustion efficiency based on inlet flow parameters (temperature, pressure, velocity, length, porosity, and air excess ratio), achieving efficiencies beyond conventional limits (η = 0.98–0.99) and reaching high values (η = 0.999–0.9999), which is crucial for optimizing low-emission combustors. Verification of the mathematical model was conducted through a dual approach: experimental validation and computational fluid dynamics (CFD) simulations. Comparative analysis revealed a high degree of consistency among theoretical predictions, CFD results, and experimental data, particularly for temperature and combustion efficiency distributions along the combustor length. This robust agreement affirms the model’s accuracy, reliability, and utility in advancing combustion research and developing efficient, low-emission combustors. Full article

Molybdenum disulfide (MoS₂) is a promising catalyst for hydrogen evolution through water electrolysis with low cost and high efficiency, but its hydrogen evolution performance can be further improved. Using sodium molybdate (Na₂MoO₄·2H₂O) and thiourea (NH₂CSNH₂) as raw materials, MoS₂ was prepared by the hydrothermal method. Ni-doped MoS₂(Ni-MoS₂) was prepared by using nickel dichloride dihydrate (NiCl₂·2H₂O) as a Ni source and doping Ni into MoS₂ by the hydrothermal method. Under the conditions of different temperatures (190 °C, 200 °C, and 210 °C) and different Ni doping molar ratios (2%, 3%, and 4%), the optimum temperature and doping ratio of the prepared materials were explored by conducting a hydrogen evolution reaction (HER) by the electrolysis of water. The results showed that the optimum preparation temperature was 200 °C and the optimum molar ratio of Ni doping was 3%. Graphene oxide (GO) was obtained by oxidation of graphite (G), and then Ni-MoS₂/GO was prepared by the hydrothermal method with Ni-MoS₂ and GO. The performance of HER was tested. The materials were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), and X-ray photoelectron spectroscopy (XPS). The results show that the composite Ni-MoS₂/GO has good HER performance, which is better than that of MoS₂ or Ni-MoS₂. In 0.5 M H₂SO₄ solution, the η₁₀ is as low as 196 mV, the Tafel slope is 122 mV/dec, the C_dl is 13.98 mF/cm², and it has good stability. The enhancement of electrocatalytic activity is mainly due to the doping of a small amount of Ni, which increases the defects of the catalyst and forms more active sites. GO improves the conductivity of the material. Ni doping and GO compounding promote the HER performance of MoS₂. Full article

This paper details the enhancement of the optoelectronic properties of Cu-(In, Ga)-Se₂ (CIGSe) solar cells through a two-segment process in the ultraviolet (UV)–visible spectral range. These include fine-tuning the DC sputtering power of the absorber layer (ranging from 20 to 40 W at segment I) and thoroughly checking the trace micro-chemistry composition of the absorber layer (CdS, ZnO/CdS, ZnMgO/CdS, and ZnMgO at segment II). After segment I of treatment, the optimal 30 W CIGSe absorber layer (i.e., with a 0.95 CGI ratio) can be obtained, it can be seen that the Cu-rich film exhibits the ability to significantly promote grain growth and can effectively reduce its trap state density. After the segment II process aimed at replacing toxic CdS, the optimal metal alloy (Zn_0.9Mg_0.1O) composition (buffer layer) achieved the highest conversion efficiency (η) of 8.70%, also emphasizing its role in environmental protection. Especially within the tunable bandgap range (2.48–3.62 eV), the developed overall internal and external quantum efficiency (IQE/EQE) is significantly improved by 13.15% at shorter wavelengths. A photovoltaic (PV) module designed with nine optimal CIGSe cells demonstrated commendable stability. Variation remained within ±5% throughout the 60-day experiment. The PV modules in this study represent a breakthrough benchmark toward a significant advance in the scientific understanding of renewable energy. Furthermore, this research clearly promotes the practical application of PV modules, harmonizes with sustainable goals, and actively contributes to the creation of eco-friendly communities. Full article

Faced with a global consensus on net-zero emissions, the use of clean fuels to entirely or substantially replace traditional fuels has emerged as the industry’s primary development direction. Alcohol–hydrogen fuels, primarily based on methanol, are a renewable and sustainable energy source. This research focuses on energy sustainability and presents a boiler fuel blending system that uses methanol–hydrogen combinations. This system uses the boiler’s waste heat to catalytically decompose methanol into a gas mostly consisting of H₂ and CO, which is then co-combusted with the original fuel to improve thermal efficiency and lower emissions. A comparative experimental study considering natural gas (NG) blending with hydrogen and dissociated methanol gas (DMG) was carried out in a small natural gas boiler. The results indicate that, with a controlled mixed fuel flow of 10 m³/h and an excess air coefficient of 1.2, a 10% hydrogen blending ratio maximizes the boiler’s thermal efficiency (${\eta }_t$), resulting in a 3.5% increase. This ratio also results in a 1% increase in NOx emissions, a 25% decrease in HC emissions, and a 5.66% improvement in the equivalent economics ($e_s$). Meanwhile, blending DMG at 15% increases the boiler’s ${\eta }_t$ by 3%, reduces NOx emissions by 13.8% and HC emissions by 20%, and improves the $e_{s }$ by 8.63%. DMG, as a partial substitute for natural gas, outperforms hydrogen in various aspects. If this technology can be successfully applied and promoted, it could pave a new path for the sustainable development of energy in the boiler sector. Full article