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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
- Keyword :
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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
- Page :
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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
- Page :
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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
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2025
- Book : ()
- Pub. Date : 2025
- Page :
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2025
- Book : ()
- Pub. Date : 2025
- Page : pp.100720-100720
- Keyword :
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2025
- Book : 607()
- Pub. Date : 2025
- Page : pp.155657-155657
- Keyword :
