• Book : 603()
• Pub. Date : 2025
• Page : pp.155451
• Keyword :

• Book : 603()
• Pub. Date : 2025
• Page : pp.155432
• Keyword :

• Book : 603()
• Pub. Date : 2025
• Page : pp.155422
• Keyword :

Abstract

In this paper, a frequency selective surface (FSS) for n41, n78, n257, n258, n260, and n261 bands electromagnetic interference (EMI) shielding is proposed using a deep learning method. The size of the FSS unit cell is 4.8 mm (0.071$ \lambda _{0} $), where$ \lambda _{0} $is the wavelength corresponding to the cutoff frequency of the −10 dB stopband where the n41 and n78 bands are located. This FSS exhibits three key characteristics. Firstly, it possesses ultrawideband capability, with a stopband frequency range of 23.922-40.023 GHz and a relative bandwidth reaching 50.4%. Secondly, it effectively shields against electromagnetic radiation in multiple 5 G bands, including n41, n78, n257, n258, n260, and n261. Thirdly, it demonstrates high selectivity, with a very narrow transition band of only 0.405 GHz between the passband and the stopband. To validate the designed FSS, a prototype of this structure was first fabricated for experimentation. The experimental results show that the measured S21 is highly consistent with the simulated S21. Secondly, the unit cell array of FSS is placed above the monopole antenna for co-simulation. It can be observed that after placing the FSS, the intensity of electromagnetic radiation propagating in space is significantly reduced by up to more than 90%. Therefore, the proposed FSS can be effectively applied for EMI shielding in 5 G bands.

• Book : 58(1)
• Pub. Date : 2025
• Page : pp.015110
• Keyword :

Abstract

Purpose

This study aims to assess how T2 heterogeneity biases IMPULSED‐derived metrics of tissue microstructure in solid tumors and evaluate the potential of estimating multi‐compartmental T2 and microstructural parameters simultaneously.

Methods

This study quantifies the impact of T2 relaxation on IMPULSED‐derived microstructural parameters using computer simulations and in vivo multi‐TE IMPULSED MRI in five tumor models, including brain, breast, prostate, melanoma, and colon cancer. A comprehensive T2 + IMPULSED method was developed to fit multi‐compartmental T2 and microstructural parameters simultaneously. A Bayesian model selection approach was carried out voxel‐wisely to determine if the T2 heterogeneity needs to be included in IMPULSED MRI in cancer.

Results

Simulations suggest that T2 heterogeneity has a minor effect on the estimation of d in tissues with intermediate or high cell density, but significantly biases the estimation of with low cell density. For the in vivo animal experiments, all IMPULSED metrics except are statistically independent on TE. For B16 tumors, the IMPULSED‐derived exhibited a notable increase with longer TEs. For MDA‐MB‐231 tumors, IMPULSED‐derived showed a significant increase with increasing TEs. The T2 + IMPULSED‐derived of all five tumor models are consistently smaller than .

Conclusions

The findings from this study highlight two key observations: (i) TE has a negligible impact on IMPULSED‐derived cell sizes, and (ii) the TE‐dependence of IMPULSED‐derived intracellular volume fractions used in T2 + IMPULSED modeling to estimate and . These insights contribute to the ongoing development and refinement of non‐invasive MRI techniques for measuring cell sizes.

• Book : 93(1)
• Pub. Date : 2025
• Page : pp.96-107
• Keyword :

Abstract

Purpose

Radiotherapy treatment planning (RTP) using MR has been used increasingly for the abdominal site. Multiple contrast weightings and motion‐resolved imaging are desired for accurate delineation of the target and various organs‐at‐risk and patient‐tailored planning. Current MR protocols achieve these through multiple scans with distinct contrast and variable respiratory motion management strategies and acquisition parameters, leading to a complex and inaccurate planning process. This study presents a standalone MR Multitasking (MT)-based technique to produce volumetric, motion‐resolved, multicontrast images for abdominal radiotherapy treatment planning.

Methods

The MT technique resolves motion and provides a wide range of contrast weightings by repeating a magnetization‐prepared (saturation recovery and T2 preparations) spoiled gradient‐echo readout series and adopting the MT image reconstruction framework. The performance of the technique was assessed through digital phantom simulations and in vivo studies of both healthy volunteers and patients with liver tumors.

Results

In the digital phantom study, the MT technique presented structural details and motion in excellent agreement with the digital ground truth. The in vivo studies showed that the motion range was highly correlated (R² = 0.82) between MT and 2D cine imaging. MT allowed for a flexible contrast‐weighting selection for better visualization. Initial clinical testing with interobserver analysis demonstrated acceptable target delineation quality (Dice coefficient = 0.85 ± 0.05, Hausdorff distance = 3.3 ± 0.72 mm).

Conclusion

The developed MT‐based, abdomen‐dedicated technique is capable of providing motion‐resolved, multicontrast volumetric images in a single scan, which may facilitate abdominal radiotherapy treatment planning.

• Book : 93(1)
• Pub. Date : 2025
• Page : pp.108-120
• Keyword :

• Book : 239()
• Pub. Date : 2025
• Page : pp.115507
• Keyword :

Abstract

In this paper, both semi-analytical method and numerical simulation is applied to investigate the hydrodynamic behavior of large arrays of point-absorber wave energy converters (WECs). To analyze wave interactions among multiple WECs within an array, a semi-analytical model is developed based on the potential flow theory and the matched eigen-function expansions method. The fluid domain is divided into two kinds of regions: interior regions underneath the cylinders and an exterior region surrounding all the cylinders. The matched eigen-function expansions method is employed to solve the radiation potential problem in each domain, and the hydrodynamic coefficients and motion response of the cylinders in the array are evaluated. To validate the accuracy of the semi-analytical method, wamit is adopted to simulate the wave energy park numerically and compared with the results by the semi-analytical model. The hydrodynamic characteristics and power absorption performance of the WECs within the wave energy park are analyzed. The power performance of a wave energy park is studied as functions of layout geometry, incident wave direction, and separation distance between WECs respectively. Finally, multi-objective particle swarm optimization based on a surrogate model is used to optimize the layout of wave energy array.

• Book : 147(4)
• Pub. Date : 2025
• Page : pp.042001
• Keyword :

• Book : 226()
• Pub. Date : 2025
• Page : pp.112285
• Keyword :

• Book : 226()
• Pub. Date : 2025
• Page : pp.112256
• Keyword :