In Silico Study on Tumor-Size-Dependent Thermal Profiles inside an Anthropomorphic Female Breast Phantom Subjected to Multi-Dipole Antenna Array

Electromagnetic hyperthermia as a potent adjuvant for conventional cancer therapies can be considered valuable in modern oncology, as its task is to thermally destroy cancer cells exposed to high-frequency electromagnetic fields. Hyperthermia treatment planning based on computer in silico simulations has the potential to improve the localized heating of breast tissues through the use of the phased-array dipole applicators. Herein, we intended to improve our understanding of temperature estimation in an anatomically accurate female breast phantom embedded with a tumor, particularly when it is exposed to an eight-element dipole antenna matrix surrounding the breast tissues. The Maxwell equations coupled with the modified Pennes’ bioheat equation was solved in the modelled breast tissues using the finite-difference time-domain (FDTD) engine. The microwave (MW) applicators around the object were modelled with shortened half-wavelength dipole antennas operating at the same 1 GHz frequency, but with different input power and phases for the dipole sources. The total input power of an eight-dipole antenna matrix was set at 8 W so that the temperature in the breast tumor did not exceed 42 °C. Finding the optimal setting for each dipole antenna from the matrix was our primary objective. Such a procedure should form the basis of any successful hyperthermia treatment planning. We applied the algorithm of multi for multi-objective optimization for the power and phases for the dipole sources in terms of maximizing the specific absorption rate (SAR) parameter inside the breast tumor while minimizing this parameter in the healthy tissues. Electro-thermal simulations were performed for tumors of different radii to confirm the reliable operation of the given optimization procedure. In the next step, thermal profiles for tumors of various sizes were calculated for the optimal parameters of dipole sources. The computed results showed that larger tumors heated better than smaller tumors; however, the procedure worked well regardless of the tumor size. This verifies the effectiveness of the applied optimization method, regardless of the various stages of breast tumor development.     

In-situ construction of CdS@ZIS Z-scheme heterojunction with core-shell structure: Defect engineering,enhance photocatalytic hydrogen evolution and inhibit photo-corrosion

Designing the core-shell structure and controlling defect engineering are desirable for improving the performance and stability of semiconductor photocatalysts. Herein, CdS nanorods covered with ultra-thin ZnIn₂S₄ nanosheets, named as CdS@ZnIn₂S₄-S_V (CdS@ZIS-S_V), was synthesized through the strategy of constructing core-shell structure and regulating vacancies. The core-shell structure can confine Cd²⁺ and S^2? locally around CdS instead of rapidly diffusing into the solution, thereby inhibiting photo-corrosion. The abundant S vacancies can capture photogenerated electrons and promote the separation of electron-hole pairs, thereby preventing the oxidation of S^2? by the holes. In addition, Z-Scheme heterojunction structure helps the effective separation of electron-hole pairs. Notably, the hydrogen production rate of CdS@ZIS-S_V reached 18.06 mmol g^?1 h^?1, which was 16.9 and 19.6 times than pristine CdS (1.16 mmol g^?1 h^?1) and ZIS (0.92 mmol g^?1 h^?1), respectively. Photoelectric Characterization (PEC), Scanning Kelvin Probe (SKP), UV–vis diffuse reflectance spectra (UV–Vis DRS), Finite-Difference Time-Domain (FDTD) explain the electron transfer mechanism and the reason for the enhanced photocatalytic activity. This work has guiding significance for the preparation of photo-catalysts with high activity and inhibiting photo-corrosion by adjusting S vacancies.     

电磁脉冲对埋地电缆耦合的FDTD仿真分析

以有限埋地电缆为研究对象,依据电磁场理论和时域有限差分法建立了物理分析模型.采用多区域FDTD方法对埋地电缆进行分析,通过编程计算出仿真结果,该结果与实测数据比较一致,验证了该方法的正确性.     

基于高阶FDTD(2,4)与MNA混合方法求解导弹系统线缆的瞬态电磁脉冲耦合效应

提出一种高阶时域有限差分与改进节点分析的混合方法,计算弹载系统内线缆的强电磁脉冲耦合效应问题。将线与路通过混合单端口模型进行拆分,有效实现了基于线缆分析的FDTD(2,4)与基于电路方程的MNA法独立快速求解。同时,通过采用分布源等效的方式,将外场引入到电报方程组,使得求解更加简便有效。数值算例表明了该方法的高效率及高精度。     

Modal analysis of ultra-compact channel filters based on race-track photonic crystal ring resonators

A new channel drop filter (CDF) is proposed based on a race-track photonic crystal ring resonator composed of square-lattice cylindrical silicon rods in air. By using a two-dimensional finite-difference, time-domain numerical technique, the modal behavior of two representative CDFs, parallel and perpendicular, has been analyzed. The analyses include the impact of additional scatterer size, scatterer amount and their position on the performance of proposed CDFs, such as drop efficiency and quality factor (Q). For the parallel CDF, about 130 spectral Q and 99% drop efficiency can be optimally achieved at 1363?nm channel with 0.145 periodicity scatterer size, whereas for the perpendicular one, about 180 spectral Q and 99% drop efficiency can be optimally obtained at 1366?nm channel with 0.165 periodicity scatterer size. By increasing the number of scatterers, the efficiency of both configurations can be enhanced. No obvious variation is obtained by changing the scatterer position.     

一种提高内存使用效率的时域有限差分算法

证明了即使在无源区域,局部一维时域有限差分法(LOD-FDTD)所给出的电磁场量也不满足零散度关系,推导了该散度关系的具体表达式。基于该非零散度关系和麦克斯韦旋度方程,将LOD-FDTD法与减缩时域有限差分法(R-FDTD)相结合,得到一种新的局部一维减缩时域有限差分法(LOD-R-FDTD)。该方法不仅具有LOD-FDTD方法的优势,计算公式简单,消除了CFL稳定条件对时间步长的限制,而且与LOD-FDTD相比平均节约了1/3内存使用量。通过仿真计算与其他方法对比,证明了LOD-R-FDTD方法的准确性和有效性。     

基于图形处理器的时域有限差分算法研究

如何提高时域有限差分算法(FDTD)的运算效率一直是FDTD数值运算研究的核心问题之一.针对近年来图形处理器(GPU)运算能力的高速增长及GPU通用运算概念提出的背景,对GPU加速FDTD运算的潜力与研究现状进行了总结,并对GPU加速FDTD运算的并行实现原理进行了阐述,通过将其与其他典型硬件加速方式进行比较,指出了G...     

基于时域有限差分法舰载活动设备电磁场分析

舰载活动设备产生的电磁干扰因无法采用传统的舰船消磁技术消除而需准确评估。以舰载火炮为例,采用时域有限差分法分析了舰载火炮在姿态改变时的电磁场特性变化。为提高建模精度,引入平均电参数对金属设备进行建模。通过坐标变换,提出了修正的差分方程对金属设备与Yee网格不重合的边缘部分进行模型修正。通过算例对比验证了算法的有效性。仿真结果表明:舰载火炮在姿态改变时电场有0.6~3.8 V/m的变化,磁场有0.0016~0.01 A/m的变化,这类电磁场变化对舰船电磁兼容性的影响不容忽视。     

非均匀传输线间的串扰研究

应用时域有限差分法对非均匀传输线间的串扰耦合进行分析。基于细线散射的时域有限差分法分析非均匀结构时,采用阶梯式均匀传输线模型,对非均匀传输线进行分段逼近。针对不等长、线径变化、非平行线和交叉线4种情况分析其参数变化对串扰的影响。研究表明：不等长电缆超出部分长度对串扰耦合幅度影响较小,对谐振频率影响较大;电缆线径的变化对其串扰耦合影响较小;非平行线和交叉线的角度对电缆间串扰的影响较大。     

同轴馈电耦合微带天线的MPSTD-FDTD分析

将多区域时域伪谱(MPSTD)与时域有限差分(FDTD)相结合的混合算法应用于同轴馈电耦合微带天线的分析,该混合算法充分发挥两种时域算法的优越性,对同轴馈电耦合微带天线进行了准确建模与快速分析,数值仿真验证了该算法的有效性和准确性。