Optics and Laser Technology最新文献_第5页

Hydrogen diffusion in liquid and boiling alumina by laser ablation towards a carbon-free aluminum production 通过激光烧蚀在液态和沸腾氧化铝中扩散氢气，实现无碳铝生产

IF 4.6 2区物理与天体物理 Q1 OPTICS

Optics and Laser Technology

Pub Date : 2024-10-17 DOI: 10.1016/j.optlastec.2024.111935

Lucas-Brian Christen , Masataka Watanabe , Hiroto Yamakami , Hokuto Sekine , Kimiya Komurasaki , Hiroyuki Koizumi

The Hall-Héroult process is the main production process of aluminum, which consumes carbon electrodes to reduce alumina (Al₂O₃) to aluminum, while releasing the by-product carbon-dioxide (CO₂). To overcome this issue and work towards a green transformation, laser reduction of Al₂O₃ has been proposed as a carbon-free aluminum production method. By irradiating a continuous-wave laser onto the Al₂O₃ surface, micro-sized aluminum particles are precipitated on the surface. Furthermore, the use of hydrogen as an ambient gas has shown the appearance of pores beneath to the surface, which furthermore contain aluminum particles. In this study, the correlation between the internal pore structure through hydrogen diffusion and the aluminum production on laser-irradiated Al₂O₃ is investigated. The pore structure is furthermore maximized in terms of volume by rotating the Al₂O₃ target during laser irradiation. Using a hydrogen atmosphere at 0.9 bar, the diffusion of hydrogen depending on the laser fluence and its effect on the formation of pores is examined. The rotating speed of a 20 mm diameter target size is varied between 2 rpm and 4 rpm. The laser power is constant at 1.5 kW with a spot radius of 1.22 mm to 3 mm. Results show a successful increase of the pore volume by a factor of 20 considering the change from an argon to a hydrogen atmosphere under otherwise equal conditions. The abundance of Al particles in the pores is validated through scanning electron microscopy (SEM). The aluminum particle precipitation inside of the pores shows a directional behavior, as the particles are exclusively found at the bottom of the pores. The existence of aluminum particles in the pores concludes an increase of precipitated particles by increasing the pore volume as performed in this study.

霍尔-赫鲁特工艺是铝的主要生产工艺，它消耗碳电极将氧化铝（Al2O3）还原成铝，同时释放出副产品二氧化碳（CO2）。为了克服这一问题，实现绿色转型，有人提出了激光还原 Al2O3 这种无碳铝生产方法。通过将连续波激光照射到 Al2O3 表面，在其表面析出微小的铝颗粒。此外，使用氢气作为环境气体后，表面下方出现了气孔，其中还含有铝颗粒。本研究探讨了通过氢气扩散形成的内部孔隙结构与激光辐照 Al2O3 产生铝之间的相关性。在激光辐照过程中，通过旋转 Al2O3 靶件，孔隙结构的体积进一步增大。在 0.9 巴的氢气环境中，研究了氢的扩散取决于激光通量及其对孔隙形成的影响。直径为 20 毫米的靶的旋转速度在每分钟 2 转和 4 转之间变化。激光功率恒定为 1.5 千瓦，光斑半径为 1.22 毫米至 3 毫米。结果表明，在其他条件相同的情况下，从氩气环境改为氢气环境，孔隙体积成功增加了 20 倍。通过扫描电子显微镜（SEM）验证了孔隙中铝颗粒的丰度。孔隙内的铝颗粒析出具有方向性，因为铝颗粒只出现在孔隙底部。孔隙中存在铝颗粒的结论是，通过增加孔隙容积可以增加析出颗粒的数量，正如本研究中所做的那样。

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引用次数: 0

Ultraviolet time-gated active-imaging digital image correlation: A novel solution for ultra-high temperature deformation measurement 紫外线时间门控主动成像数字图像相关性：超高温变形测量的新型解决方案

IF 4.6 2区物理与天体物理 Q1 OPTICS

Optics and Laser Technology

Pub Date : 2024-10-17 DOI: 10.1016/j.optlastec.2024.111971

Liping Yu , Ning Lu , Kefei Lu , Xuefeng Zou , Bing Pan

Active-imaging digital image correlation (DIC) based on monochromatic illumination and optical bandpass filtering provides a simple and effective approach to measure the surface deformation of test materials and structures at elevated temperatures. However, when the sample temperature exceeds 2000 °C or strong thermal radiation from heating elements is present, the current active-imaging strategy fails to effectively suppress the massive thermal radiation from the heated sample and heating elements. Here, we present an ultraviolet (UV) time-gated active-imaging technique that employs a gated single-photon camera to significantly reduce exposure time and a UV bandpass filter to block most thermal radiation. This combination of UV bandpass filtering in the spectral domain and time-gated imaging at UV wavelengths in the time domain suppresses the enormous thermal radiation from the heated sample and heating source to a negligible level compared with the active illumination. Real-world validations, including full-field thermal deformation measurement of a Ni-based alloy sample, thermal strain measurement at 2800 °C, and tensile strain measurement at 2500 °C of carbon-carbon composite material samples, verified the performance of the proposed method. Beyond its current applications, the ultraviolet time-gated active-imaging DIC method holds promise as a powerful tool for characterizing the thermo-mechanical properties of materials and structures in extremely high-temperature environments.

基于单色照明和光学带通滤波器的主动成像数字图像相关技术（DIC）为测量高温下测试材料和结构的表面变形提供了一种简单有效的方法。然而，当样品温度超过 2000 °C 或存在来自加热元件的强热辐射时，当前的主动成像策略无法有效抑制来自加热样品和加热元件的大量热辐射。在这里，我们提出了一种紫外线（UV）时间门控主动成像技术，该技术采用门控单光子照相机来大幅缩短曝光时间，并使用紫外线带通滤波器来阻挡大部分热辐射。光谱域的紫外带通滤波器和时域紫外波长的时间门控成像相结合，将来自加热样品和加热源的巨大热辐射抑制到与主动照明相比可以忽略不计的水平。实际验证，包括镍基合金样品的全场热变形测量、2800 ℃ 下的热应变测量以及碳碳复合材料样品 2500 ℃ 下的拉伸应变测量，都验证了所提方法的性能。除了目前的应用外，紫外时间门控主动成像 DIC 方法有望成为表征材料和结构在极高温环境下的热机械特性的有力工具。

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引用次数: 0

Reconstruction method of 128 × 256 array single photon Lidar based on multi-domain stability feature fusion 基于多域稳定性特征融合的 128 × 256 阵列单光子激光雷达重建方法

IF 4.6 2区物理与天体物理 Q1 OPTICS

Optics and Laser Technology

Pub Date : 2024-10-17 DOI: 10.1016/j.optlastec.2024.111970

Le Ma , Jianfeng Sun , Xianhui Yang , Jie Lu , Wei Lu , Xin Zhou , Hongchao Ni

Under low-light conditions, random light distribution and non-uniform pixel sensitivity reduce both the correlation and differences among pixels, while unstable intensity information significantly impairs the detection capability of Geiger-mode avalanche photodiode (GM-APD) arrays. To address these challenges, a method based on multi-domain stability feature fusion is proposed. This approach utilizes a distance layer decomposition model to break down the global problem into localized sub-problems, effectively suppressing background noise through the fusion of stable features. Additionally, the Multi-scale Algorithm (MSA) was enhanced to selectively recover missing pixels and improve target reconstruction while preserving details. In imaging experiments conducted on targets under low-light conditions at night within remote, complex scenes, when the photon number was 0.0068 per pixel, the proposed method improved the Peak Signal-to-Noise Ratio (PSNR) of the reconstructed images by more than 12 dB compared with the Non-local MSA. It significantly promotes the development of GM-APD lidar for all-time applications.

在弱光条件下，随机光分布和不均匀的像素灵敏度会降低像素间的相关性和差异，而不稳定的强度信息会严重影响盖革模式雪崩光电二极管阵列（GM-APD）的检测能力。为了应对这些挑战，我们提出了一种基于多域稳定性特征融合的方法。该方法利用距离层分解模型将全局问题分解为局部子问题，通过融合稳定特征有效抑制背景噪声。此外，还增强了多尺度算法（MSA），以有选择性地恢复缺失像素，在保留细节的同时改进目标重建。在对夜间低照度条件下偏远复杂场景中的目标进行的成像实验中，当每个像素的光子数为 0.0068 时，与非局部 MSA 相比，提出的方法将重建图像的峰值信噪比（PSNR）提高了 12 dB 以上。这极大地促进了全时应用的 GM-APD 激光雷达的发展。

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引用次数: 0

Transfer Matrix Method with Gouy Phase Shift correction applied to a High Numerical Aperture fiber-to-fiber optical coupling analysis 将带有 Gouy 相移校正的转移矩阵法应用于高数值孔径光纤到光纤耦合分析

IF 4.6 2区物理与天体物理 Q1 OPTICS

Optics and Laser Technology

Pub Date : 2024-10-17 DOI: 10.1016/j.optlastec.2024.111886

Wender G. Daniel , Gilliard N. Malheiros-Silveira

In this paper, we present the transmittance and reflectance study of the optical coupling between two High Numerical Aperture (HNA) fibers using a new model based on the Transfer Matrix Method (TMM). The TMM is corrected by the effects of the Gouy phase shift and the mode overlap is used in the material between the fibers to calculate the coupling loss. The coupling is also simulated using the Eigenmode Expansion (EME) method, and these numerical results are compared with experimental ones. The Gaussian beam nonparaxial field equations are used to evaluate the phase of the light in the coupling region and to obtain the effective refractive index of the wave between the fiber facets. Our TMM approach produced results close to experimental ones. Our model is, at least, two orders of magnitude faster than a commercial solver, and easy to coding; highlighting this approach’s importance as a transmittance/reflectance simulation tool.

本文采用基于传输矩阵法（TMM）的新模型，对两根高数值孔径（HNA）光纤之间的光耦合进行了透射率和反射率研究。TMM 根据 Gouy 相移的影响进行了修正，并利用光纤间材料的模式重叠来计算耦合损耗。此外，还使用特征模式展开（EME）方法对耦合进行了模拟，并将这些数值结果与实验结果进行了比较。高斯光束非同轴场方程用于评估耦合区域的光相位，并获得光纤面之间波的有效折射率。我们的 TMM 方法得出的结果与实验结果接近。我们的模型至少比商用求解器快两个数量级，而且易于编码；突出了这种方法作为透射/反射模拟工具的重要性。

引用次数: 0

Extremely efficient, high beam quality second harmonic generation using a thin-disk regenerative amplifier 使用薄盘再生放大器生成极高效、高光束质量的二次谐波

IF 4.6 2区物理与天体物理 Q1 OPTICS

Optics and Laser Technology

Pub Date : 2024-10-16 DOI: 10.1016/j.optlastec.2024.111963

Sizhi Xu , Yubo Gao , Xing Liu , Zuoyuan Ou , Fayyaz Javed , Xingyu He , Haotian Lu , Junzhan Chen , Chunyu Guo , Cangtao Zhou , Qitao Lue , Shuangchen Ruan

We report on a second harmonic generation (SHG) 5.79 ps, 1 MHz green laser system based on a 145 W homemade Yb:YAG picosecond thin-disk regenerative amplifier. To achieve an extremely efficient SHG process, we employed the spatial–temporal nonlinear unidirectional pulse propagation equation (UPE) to optimize the efficiency in high-power picosecond lasers. The lengths of lithium triborate (LBO) crystals, infrared laser intensities, and crystal temperatures were systematically optimized. The resulting 515 nm laser generates an average power of 107.7 W with the highest conversion efficiency of 75 % and a near-diffraction-limited beam quality, with an M² factor of 1.14. To the best of our knowledge, it is the highest conversion efficiency achieved based on a high-power thin-disk laser to date. Furthermore, with the third-harmonic generation at 343 nm, the laser system achieved 65 W of average power and 44.8 % of conversion efficiency.

我们报告了基于 145 W 自制 Yb:YAG 皮秒薄盘再生放大器的 5.79 ps、1 MHz 二次谐波发生 (SHG) 绿激光系统。为了实现极其高效的 SHG 过程，我们采用了时空非线性单向脉冲传播方程 (UPE)，以优化高功率皮秒激光器的效率。我们对三硼酸锂（LBO）晶体的长度、红外激光强度和晶体温度进行了系统优化。最终产生的 515 nm 激光器平均功率为 107.7 W，最高转换效率为 75 %，光束质量接近衍射极限，M2 因子为 1.14。据我们所知，这是迄今为止基于大功率薄盘激光器实现的最高转换效率。此外，利用波长为 343 nm 的三次谐波发生，该激光系统实现了 65 W 的平均功率和 44.8 % 的转换效率。

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引用次数: 0

Numerically efficient coherent mode representations for partially coherent beams with separable phases 具有可分离相位的部分相干光束的高效相干模式数值表示法

IF 4.6 2区物理与天体物理 Q1 OPTICS

Optics and Laser Technology

Pub Date : 2024-10-16 DOI: 10.1016/j.optlastec.2024.111950

Milo W. Hyde IV , Carolina Rickenstorff

We present a method to numerically compute the coherent mode representations (CMRs) for partially coherent beams with separable phases. This special class of random light field has the ability to self-focus and is resistant to turbulence-induced degradation, making it potentially useful in applications such as optical communications. We validate our method by generating (in simulation) two such sources from the literature using their computed CMRs. Lastly, we conclude with a summary of our approach and a discussion of applications.

我们提出了一种方法，用于数值计算具有可分离相位的部分相干光束的相干模式表示（CMR）。这种特殊的随机光场具有自聚焦能力，并能抵抗湍流引起的衰减，因此在光通信等应用中具有潜在的用途。我们通过（模拟）生成文献中的两个此类光源，并使用其计算出的 CMR 验证了我们的方法。最后，我们总结了我们的方法并讨论了其应用。

引用次数: 0

Infrared dim-small target detection via chessboard topology 通过棋盘拓扑结构进行红外微小目标探测

IF 4.6 2区物理与天体物理 Q1 OPTICS

Optics and Laser Technology

Pub Date : 2024-10-16 DOI: 10.1016/j.optlastec.2024.111867

Bingbing Dan , Zijian Zhu , Yuxing Wei , Dongxu Liu , Meihui Li , Tao Tang

In infrared dim-small target detection, large background group and small clutter group are the key components. However, existing methods usually consider the detection progress in the original image space, which limits the separability of the target from the two components and leads to missed detection and false alarms. In response to this issue, we propose an innovative infrared dim-small target detection method via chessboard topology, which mines potential differences, such as distribution density and scale trends in the topological space. Specifically, the core of our approach lies in the construction of the chessboard topology space, where each ”point set” serves as a basic unit that is a mapping result of pixels in the original image space. The chessboard’s horizontal divisions are based on the scale space, where pixels undergo multiscale transformations to emphasize scale invariance at smaller scales, resulting in rows that capture scale variation trends. Meanwhile, the vertical divisions are based on the gray space, with pixels rearranged to accentuate gray level variations, thereby forming columns that highlight distribution density disparities. To separate the target pixels, we design two complementary strategies for pixel scoring within the chessboard topological space. The first,

s c o r e S

, evaluates pixel consistency across multiple scales, aiming to eliminate inconsistent pixels that often represent false positives. The second,

s c o r e L

, focuses on measuring the density level of point sets to enhance target visibility by filtering out pixels within less dense point sets. The final detection results are derived from the dot product of these two scores, ensuring a robust differentiation of small targets from background and noise. Comprehensive experiments demonstrate that the proposed method achieves better performance than baselines in six real infrared dim-small target scenarios. The code is publicly available at https://github.com/D-IceIce/IRSTD-ChessboardTopology.

在红外暗小目标检测中，大背景组和小杂波组是关键组成部分。然而，现有方法通常考虑原始图像空间中的检测进度，这就限制了目标与这两部分的可分离性，导致漏检和误报。针对这一问题，我们提出了一种通过棋盘拓扑结构进行红外微小目标检测的创新方法，该方法可挖掘拓扑空间中的潜在差异，如分布密度和尺度趋势。具体来说，我们方法的核心在于构建棋盘拓扑空间，其中每个 "点集 "作为一个基本单元，是原始图像空间中像素的映射结果。棋盘的横向划分基于尺度空间，其中像素经过多尺度变换，以强调较小尺度上的尺度不变性，从而形成捕捉尺度变化趋势的行。同时，纵向划分基于灰度空间，像素经过重新排列以突出灰度变化，从而形成突出分布密度差异的列。为了分离目标像素，我们在棋盘拓扑空间内设计了两种互补的像素评分策略。第一种，scoreS，评估像素在多个尺度上的一致性，目的是消除经常代表假阳性的不一致像素。第二种方法是 scoreL，侧重于测量点集的密度水平，通过过滤掉密度较低的点集中的像素来提高目标的可见度。最终的检测结果来自这两个分数的点乘积，从而确保从背景和噪声中稳健地区分小目标。综合实验证明，在六种真实的红外昏暗-小目标场景中，所提出的方法比基线方法取得了更好的性能。代码可在 https://github.com/D-IceIce/IRSTD-ChessboardTopology 公开获取。

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引用次数: 0

Optimizing the output power of CW Ti:sapphire laser by stable region analysis and adjustment impact observation 通过稳定区域分析和调整影响观测优化 CW Ti:sapphire 激光器的输出功率

IF 4.6 2区物理与天体物理 Q1 OPTICS

Optics and Laser Technology

Pub Date : 2024-10-16 DOI: 10.1016/j.optlastec.2024.111946

Yingjie Ma , Xinxiu Zhou , Yutong Wang , Pengyu Zhang , Jingcheng Shang

With the in-depth research on light-atom interaction, there is a demand for improved performance in output power, noise, beam quality, stability and tunability of continuous-wave Ti:sapphire lasers. Based on the ABCD matrix model and combine with the latest numerical simulation results of Ti: sapphire crystal, the effect of cavity parameters on the stable region of the four-mirror ring resonant cavity is analyzed, and the output characteristics of the Ti:sapphire laser under different pump spot sizes, transmittance of output coupler mirrors, and pump power are measured and discussed. The experimental discovery of a “double-peak” power phenomenon is attributed to the movement of the pump focusing mirror, which is caused by variations in the focusing positions of the pump beam along the x and y directions within the crystal. This work further confirms the correlation between the optimal transmittance of output couplers and the applied pump power. By applying the “3σ” criterion and assessing class A uncertainty in our measurements, we ensure the reliability of our findings and offer valuable insights for the design optimization of tunable Ti:sapphire lasers, contributing to the advancement of laser technology in precision research.

随着光-原子相互作用研究的深入，人们对连续波钛蓝宝石激光器的输出功率、噪声、光束质量、稳定性和可调谐性等性能提出了更高的要求。基于 ABCD 矩阵模型并结合最新的钛蓝宝石晶体数值模拟结果，分析了腔参数对四镜环形谐振腔稳定区的影响，并测量和讨论了不同泵浦光斑尺寸、输出耦合镜透射率和泵浦功率下钛蓝宝石激光器的输出特性。实验中发现的 "双峰 "功率现象归因于泵浦聚焦镜的移动，而泵浦光束在晶体内沿 x 和 y 方向的聚焦位置变化则导致了这种移动。这项工作进一步证实了输出耦合器的最佳透射率与应用泵浦功率之间的相关性。通过应用 "3σ "标准和评估测量中的 A 级不确定性，我们确保了研究结果的可靠性，并为可调谐钛：蓝宝石激光器的设计优化提供了有价值的见解，从而推动了激光技术在精密研究领域的发展。

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引用次数: 0

Wide-range linearly estimation of blood flow with low sampling frequency using laser speckle contrast imaging 利用激光斑点对比成像技术，在低采样频率下对血流进行宽范围线性估算

IF 4.6 2区物理与天体物理 Q1 OPTICS

Optics and Laser Technology

Pub Date : 2024-10-15 DOI: 10.1016/j.optlastec.2024.111943

Kai Jing Shang , Yuan Yuan , Hong Li Liu , Wei Nan Gao , Yong Bi , Yi Hao Chen , Yang Yu

Laser speckle contrast imaging (LSCI) is a real-time, non-invasive imaging technique widely used for visualizing blood flow in biomedical applications. Likely, LSCI method can be applied to the myocardial coronary artery to monitor the evolution of blood flow on spatial and temporal scales, which is of large-size inner diameter, higher flow rate, and has thicker vascular walls. In this paper, we aim to measure wide-range blood flow rate linearly under static scattering noise. We elaborate on the differences between temporal and spatial static scattering parameter that are typically ignored but can result in inaccurate measurements of blood flow through phantom experiments. It is the first time, to our best of knowledge, that the maximum linear range can be measured up to 616 mm/s with 20 Hz sampling frequency. When the blood flow is covered by cardiac vascular tissue, the maximum linear blood flow range can be up to 92.4 mm/s with 100 Hz sampling frequency. Besides, we compared uniform light with ring-shaped light and demonstrated that the latter can increase penetration depth, thereby extending the linear range and reducing oscillations in the curve. Those results will greatly lower the expense of LSCI device while improving performance, and benefit future big animal clinical medical research, especially in monitoring the spatiotemporal evolution of coronary arteries in coronary artery bypass grafting (CABG) surgery.

激光斑点对比成像（LSCI）是一种实时、无创成像技术，广泛应用于生物医学领域的血流可视化。由于心肌冠状动脉内径大、流速高、血管壁厚，因此激光斑点对比成像方法可以应用于监测心肌冠状动脉血流在空间和时间尺度上的演变。本文旨在线性测量静态散射噪声下的宽范围血流量。我们阐述了时间静态散射参数和空间静态散射参数之间的差异，这些参数通常被忽视，但通过模型实验会导致血流测量不准确。据我们所知，这是第一次用 20 Hz 采样频率测量最大线性范围可达 616 mm/s。当血流被心脏血管组织覆盖时，100 Hz 采样频率下的最大线性血流范围可达 92.4 mm/s。此外，我们还对均匀光和环形光进行了比较，结果表明后者可以增加穿透深度，从而扩大线性范围并减少曲线的振荡。这些成果将在提高性能的同时大大降低 LSCI 设备的成本，有利于未来的大动物临床医学研究，特别是在冠状动脉搭桥术（CABG）手术中监测冠状动脉的时空演变。

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引用次数: 0

Theoretical and experimental study of the transmission of Laguerre-Gaussian vortex beams in thyroid tissue 拉盖尔-高斯涡流束在甲状腺组织中传输的理论和实验研究

IF 4.6 2区物理与天体物理 Q1 OPTICS

Optics and Laser Technology

Pub Date : 2024-10-15 DOI: 10.1016/j.optlastec.2024.111918

Kangle Yong , Lu Yang , Yamei Luo , Ling Yang

This paper presents both experimental and theoretical research on the transmission properties of Laguerre-Gaussian (LG) vortex beams in thyroid tissue. LG vortex beams with higher topological charges

m

have a greater ability to preserve their vortex characteristics in biological tissue turbulence. The scintillation index of vortex beams is lower than that of Gaussian beams, and scintillation index decreases as the topological charge increases. The experimental results demonstrated that the attenuation coefficient

μ_{t}

of normal thyroid tissue is higher than that of thyroid cancer tissue. For example, the vortex beam with

m = 4

exhibits an attenuation coefficient of 102.44

{m m}^{- 1}

when the laser is transmitted through normal thyroid tissue, while the

μ_{t}

is 92.08

{m m}^{- 1}

when the laser is transmitted through thyroid cancer tissue. The attenuation coefficient

μ_{t}

decrease with higher values of fractal dimension

D

and refractive index

n

, and also decreases as correlation length

l_{c}

decrease. The parameters

D

and

l_{c}

exert a significant influence on the attenuation coefficient.

本文介绍了拉盖尔-高斯（LG）涡旋束在甲状腺组织中传输特性的实验和理论研究。拓扑电荷 m 越高的 LG 涡旋束在生物组织湍流中保持其涡旋特性的能力越强。涡旋光束的闪烁指数低于高斯光束，闪烁指数随着拓扑电荷的增加而降低。实验结果表明，正常甲状腺组织的衰减系数μt高于甲状腺癌组织。例如，当激光穿过正常甲状腺组织时，m=4 的涡旋光束的衰减系数为 102.44 mm-1，而当激光穿过甲状腺癌组织时，μt 为 92.08 mm-1。衰减系数μt随分形维数D和折射率n值的增大而减小，并随相关长度lc的减小而减小。参数 D 和 lc 对衰减系数有显著影响。

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引用次数: 0