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2025
The yield of photovoltaic hydrogen production systems is influenced by a number of factors, including weather conditions, the cleanliness of photovoltaic modules, and operational efficiency. Temporal variations in weather conditions have been shown to significantly impact the output of photovoltaic systems, thereby influencing hydrogen production. To address the inaccuracies in hydrogen production capacity predictions due to weather-related temporal variations in different regions, this study develops a method for predicting photovoltaic hydrogen production capacity using the long short-term memory (LSTM) neural network model. The proposed method integrates meteorological parameters, including temperature, wind speed, precipitation, and humidity into a neural network model to estimate the daily solar radiation intensity. This approach is then integrated with a photovoltaic hydrogen production prediction model to estimate the region’s hydrogen production capacity. To validate the accuracy and feasibility of this method, meteorological data from Lanzhou, China, from 2013 to 2022 were used to train the model and test its performance. The results show that the predicted hydrogen production agrees well with the actual values, with a low mean absolute percentage error (MAPE) and a high coefficient of determination (R2). The predicted hydrogen production in winter has a MAPE of 0.55% and an R2 of 0.985, while the predicted hydrogen production in summer has a slightly higher MAPE of 0.61% and a lower R2 of 0.968, due to higher irradiance levels and weather fluctuations. The present model captures long-term dependencies in the time series data, significantly improving prediction accuracy compared to conventional methods. This approach offers a cost-effective and practical solution for predicting photovoltaic hydrogen production, demonstrating significant potential for the optimization of the operation of photovoltaic hydrogen production systems in diverse environments.- Book : 18(3)
- Pub. Date : 2025
- Page : pp.543-543
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2025
The cement-based materials widely used in infrastructure construction, such as bridges and ports, are subjected to seawater erosion and medium erosion during their service life, and their durability has always been a concern. The diffusion coefficient of chloride ions is an important indicator in the research of cement-based materials’ durability, and the pore structure is one of the most fundamental reasons affecting the diffusion behavior of chloride ions. In this paper, Mercury intrusion porosimetry (MIP), Nuclear magnetic resonance (NMR), and Nitrogen adsorption method (NAD) were used to analyze the pore structures of mortars with different volume fractions of sands. The relationship between mortar pore structure and chloride ion diffusion coefficient was established to predict its chloride ion diffusion coefficient. It may provide a new idea for studying the durability of cement-based materials. Results indicated that similar to cement paste, the pore structure of mortar satisfied the fractal characteristics of solid phase within a certain range of pores. The most probable gel pore diameter of mortars with different sand volume fractions was about 4 nm, while the most probable capillary pore diameter was approximately 46 nm, and the critical pore diameter was ranging from 50 to 60 nm. MIP results indicated that with the increase in sand volume fraction (ϕagg), the total porosity (fmip) of the mortar decreased, satisfying the relationship of fmip = 0.1859 − 0.0789ϕagg. However, the porosity of the matrix (fbase) increased with the increase in sand volume fraction, which was due to the introduction of more interfaces by the addition of aggregates. The effective chloride ion diffusion coefficient (Dcp,base) of the matrix can be obtained by fitting. Based on this, the interface transition zone (ITZ) and the cement matrix were comprehensively considered as a whole fractal phase. The predicted value of the chloride ion diffusion coefficient obtained by the Mori–Tanaka homogenization method was in good agreement with the results obtained from rapid chloride migration (RCM) experiments, and the maximum error between the simulated and experimental values did not exceed 11%. This finding can provide new ideas for accurately predicting the chloride ion diffusion coefficient of mortar and even concrete.- Book : 15(3)
- Pub. Date : 2025
- Page : pp.383-383
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2025
AbstractMandibles represent a key evolutionary innovation that enabled jawed vertebrates to adapt and diversify in response to a range of food sources. Using a phylogenetic comparative approach, we explore the phenotypic disparity and mechanical properties of the lower jaw in Pelagiaria, a morphologically diverse but relatively small clade of open-ocean fishes which are hypothesized to have radiated near the Cretaceous/Paleogene (K/Pg) mass extinction event. We found that body elongation and diet are not significantly correlated with jaw shape, but that habitat depth and tooth type are. Mechanical advantage (MA) is significantly correlated with mandible shape, with jaw-closing MA being most strongly correlated. Pelagiarian jaw shapes fall broadly into six morphotypes, of which two show significantly higher closing MA than other groups, despite differing substantially in shape. The high morphological disparity of pelagiarian mandible shape was established very early in their evolutionary history, and high levels of disparity have been maintained over tens of millions of years; this is consistent with the hypothesis that Pelagiaria represents an ancient adaptive radiation. Our results demonstrate both the mechanical and morphological diversity of the pelagiarian mandible and highlight the crucial role that morphological diversification has played in the trophic radiation of this clade.- Book : ()
- Pub. Date : 2025
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2025
Treatment with radiotherapy in pregnant women may occur due to some critical conditions. The dose given during the treatment process is not only received by the patient but can also be absorbed by the fetus which can affect its growth. Moreover, the radiation target is near the fetus such as the lung. This study aims to determine the dose distribution to the fetus with variations in fetal age (trimester 1, 2, and 3), beam energy, field size, and fetal distance to the target location (lung). The entire simulation utilized the Monte Carlo-based software EGSnrc-DOSXYZnrc which produced a 3-dimensional dose distribution on the virtual phantom. The simulated virtual phantom is a box with a size of 40×40×40 cm3 containing several materials, namely water, tissue, and lung. The size of the fetus is varied according to trimesters 1, 2, and 3. The beam is in the form of monoenergetic photons with energies of 3 MeV and 5 MeV emitted from above with a source to surface distance (SSD) of 48 cm. The field size was set at 5×5 cm2 and 8×8 cm2 on the phantom surface. The beam axis was located at a distance of 5 cm and 3 cm from the fetus. The results showed that the four variations performed affected the fetal dose, where the fetal dose increased considerably when the field size was enlarged and the beam axis was closer to the fetal position. The increase in fetal dose is also influenced by the increase in fetal age and beam energy. Meanwhile, the location of the beam below the lung causes an increased dose to the fetus due to the closer position of the beam to the fetus.- Book : 8(1)
- Pub. Date : 2025
- Page : pp.328-339
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2025
Abstract
As the magnetic confinement fusion community prepares for the next generation of fusion devices and burning plasmas, there is still a question of whether fast ions (FIs) will drive MHD instabilities, causing significant redistribution or even loss of FIs, thereby leading to reduced plasma performance and possibly threatening the integrity of the first wall. In this paper, we explore the existence and stability of Toroidicity-induced Alfven Eigenmodes (TAEs) in the >100 MW, Q ∼ 9 − 11 DT-fusion power “Primary Reference Discharge” (PRD) of the SPARC tokamak; the PRD has a relatively low on-axis alpha pressure, βα0 ≈ 0.6%, due to the high magnetic field strength, B0 = 12.2 T. A scan in toroidal mode number is performed in the vicinity of the estimated “most unstable” modes, n ≈ 5−20, with the linear eigenvalue code NOVA-K and nonlinear initial-value code MEGA. Both codes identify the same (even) n = 10 TAE located near q = 1 with frequency f ≈ 360 kHz and alpha drive γ/ω ≈ +0.6%. While MEGA evaluates this mode to be marginally unstable for the nominal alpha pressure, NOVA-K instead identifies a higher frequency (odd) n = 10 TAE as marginally destabilized; different evaluations of radiative damping are likely the cause of this discrepancy. These results indicate that AEs may be only marginally unstable for the highest performing SPARC PRD, at least for the q profile explored here. They also serve as a starting point for further scans, inclusion of FIs from auxiliary heating systems, and exploration of AE-induced FI transport, as well as a guide for diagnostic measurements of these n ≈ 10 AEs- Book : ()
- Pub. Date : 2025
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2025
- Book : Volume 17()
- Pub. Date : 2025
- Page : pp.41-49
- Keyword :
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2025
The multipole interference (MPI) effect plays pivotal roles in the formation of electromagnetic responses in various settings. In the optics regime, it has been realized typically through the Mie resonance that necessitates high‐index, deep‐subwavelength‐scale dielectric resonators that are challenging to fabricate. Herein, a new, diffraction‐based MPI scheme that can be realized with low‐index, mesoscale dielectric structures is demonstrated. It is verified that this “diffractive MPI” concept by realizing various MPI states using micrometric polymeric cuboids fabricated by soft‐lithography. Subsequent analyses reveal that the MPI states with a distinct near‐zero forward scattering (NZFS) characteristic played crucial roles in shaping the cuboid's transmission spectrum. A hitherto unreported NZFS state, which exhibits a unique, “trifolium” radiation pattern, is also identified. The spectral position of such NZFS states turns out to be strongly dependent on the cuboid's geometry. By combining these results, the diffractive NZFS formation is related to the important phenomena of induced transparency and structural color generation.- Book : ()
- Pub. Date : 2025
- Page :
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2025
Abstract
Hot axions, thermally produced in the Early Universe, would contribute to dark radiation and are thus subject to present and future constraints from N
eff. In this paper we quantify the contribution to N
eff and its uncertainty in models with axion-gluon couplings from thermal dynamics above the QCD transition. In more detail, we determine the leading-order thermal axion production rate for axion momenta of the order of the temperature adopting three different schemes for the incorporation of the collective dynamics of soft gluons. We show how these three schemes extrapolate differently into the regime of softer axion production, thus giving us a first quantitative handle on the theory uncertainty of the rate. Upon solving the Boltzmann equation, we find that this theory uncertainty translates to an uncertainty of order 0.002 for the contribution to N
eff prior to the QCD crossover. The uncertainty from common momentum-averaged approximations to the Boltzmann equation is smaller. We also discuss how QCD transition dynamics would need to be integrated into our results and we show how existing rate determinations in the literature based on gauge-dependent resummations are problematic.- Book : 2025(1)
- Pub. Date : 2025
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2025
Heat transfer enhancement from tube bank in cross flow with air can be
achieved for energy saving by enhancing the flow turbulence nature. Adding
splitter plates (SPs) to the tubes? trailing edges, besides, increasing the
heat transfer surface?s roughness are proposed options to enhance the flow
turbulence. However, few literatures are available to discuss this,
moreover, almost all available Computational Fluid Dynamics (CFD) models
employ Reynolds-Averaged Navier-Stokes (RANS) turbulence models and away
from using Large Eddy Simulation (LES). Accordingly, this work was presented
to compare the employing of RANS and LES turbulence models for such problems
at low Reynolds numbers. Toward this objective, a complete 3D CFD model
consisting of seven rows of tubes in flow direction is developed without
using any symmetrical boundary conditions. The present study includes the
impact of the Remax range (500 to 4500), for three surface relative
roughnesses: ks/D of 0, 0.01, and 0.02. The local turbulence and heat
transfer characteristics are discussed. The findings confirmed that the two
proposed options for heat transfer enhancement succeeded in doubling it. LES
is superior to RANS models in resolving a wide spectrum scale of flow
eddies. The results are useful in designing more efficient heat exchangers,
especially at low Reynolds number.- Book : (00)
- Pub. Date : 2025
- Page : pp.26-26
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2025
Coal resource extraction and utilization are essential for sustainable development and economic growth. This study integrates a pseudo-triaxial mechanical loading system with low-field nuclear magnetic resonance (NMR) to enable the preliminary visualization of coal’s pore-fracture structure (PFS) under mechanical stress. Pseudo-triaxial and cyclic loading–unloading tests were combined with real-time NMR monitoring to model porosity recovery, pore size evolution, and energy dissipation, while also calculating the fractal dimensions of pores in relation to stress. The results show that during the compaction phase, primary pores are compressed with limited recovery after unloading. In the elastic phase, both adsorption and seepage pores transform significantly, with most recovering post-unloading. After yield stress, new fractures and pores form, and unloading enhances fracture connectivity. Seepage pore porosity shows a negative exponential relationship with axial strain before yielding, and a logarithmic relationship afterward. The fractal dimension of adsorption pores decreases during compaction and increases afterward, while the fractal dimension of seepage pores decreases before yielding and increases post-yielding. These findings provide new insights into the flow patterns of methane in coal seams.- Book : 9(2)
- Pub. Date : 2025
- Page : pp.93-93
- Keyword :
