提交时间： 2024-04-19
摘要： HL-3装置高参数运行需要提升中性束注入加热能力。根据HL-3装置二号中性束注入束线7MW/120keV的总体设计要求，建立了基于8饼线圈的注入器偏转磁体3D模型。利用电磁场模拟软件CST Studio计算了中性束注入束线中性化出口不同能量的不同离子束经过偏转磁体偏转180°的励磁电流对应关系，模拟了偏转磁体使主要残留离子偏转180°励磁电流下的偏转轨迹及产生的磁场分布。在模拟分析结果的基础上完成了磁体的工程设计、加工和测试。偏转磁体的磁场测试结果表明，测试值与 CST 计算值的偏差约3%，达到注入器偏转磁体设计要求。
分类： 其他 分类： 其他 提交时间： 2024-04-25
摘要： Radio-loud quasars (RLQs) are known to produce excess X-ray emission, compared to radio-quiet quasars (RQQs) of the same luminosity, commonly attributed to jet-related emission. Recently, we found that the HeII EW and $\alpha_{\rm{ox}}$ in RQQs are strongly correlated, which suggests that their extreme-ultraviolet (EUV) and X-ray emission mechanisms are tightly related. Using 48 RLQs, we show that steep-spectrum radio quasars (SSRQs) and low radio-luminosity ($L_{\rm R}$) flat-spectrum radio quasars (FSRQs) follow the $\alpha_{\rm ox}$--HeII EW relation of RQQs. This suggests that the X-ray and EUV emission mechanisms in these types of RLQs is the same as in RQQs, and is not jet related. High-$L_{\rm R}$ FSRQs show excess X-ray emission given their HeII EW by a factor of $\approx$ 3.5, which suggests that only in this type of RLQ is the X-ray production likely jet related.
分类： 核科学技术 >> 粒子加速器 提交时间： 2024-04-25
摘要： 摘要：目的：放疗过程中的锥形束CT(cone beam CT，CBCT)可为患者提供更精确的靶区定位，但由于散射线多造成的对比度低、噪声大、伪影大等，导致影像质量较差，在实时放疗中无法用于剂量计算。本研究旨在使用Unet、CyclaGAN和CGAN等三种深度学习网络生成基于CBCT的合成CT(sCTs)，研究并对比三种sCTs的图像质量。方法：使用78例前列腺癌患者的CBCT和计划CT(pCTs)数据，进行预处理后，其中63例为训练集，10例为测试集，5例为验证集，分别训练和评估基于三种模型的图像质量。使用平均绝对误差(MAE)、平均误差(ME)、均方误差(MSE)、峰值信噪比(PSNR)、结构相似性(SSIM)和空间非均匀性(SNU)等影像评估指标以及频域信息进行评估。结果：在三种模型中，cGAN模型在各个指标上都表现出最优的性能。在全局条件下的图像质量方面，平均MAE降低到7.77HU, MSE降低到4.99，PSNR提高到54.95，SSIM提高到96%。结论：应用深度学习方法可以大幅修正CBCT的HU值并生成对应高质量的sCT，针对前列腺癌的病人，CGAN模型生成的sCT拥有更好的影像质量，使用该模型生成基于CBCT的sCT可以为前列腺癌放疗靶区剂量计算提供。
分类： 图书馆学、情报学 >> 图书馆学 提交时间： 2024-05-04
摘要： 【目的】针对现有的多标签文本情绪分类算法难以建模和利用情绪间语义关联性的问题，提出一种基于自注意力机制的情绪关联性建模的多标签文本情绪分类方法。【方法】本文提出基于自注意力机制的情绪关联性建模的多标签文本情绪分类神经网络（AttEmoNet），通过自注意力情绪关联模块建模情绪标签自身的语义及相似性，并使用基于大规模预训练模型的文本编码器用于编码输入文本为语义向量，最后通过神经网络计算文本语义向量和情绪语义向量的匹配度，从而实现更加精准的情绪类别识别。【结果】通过在NLPCC2014和GoEmotions两个公开数据集上的对比实验验证AttEmoNet的有效性。结果表明，AttEmoNet的文本情绪分类性能相比于基线方法Random、cnsenti、SVM和BERT均有显著提升。相比于现有最优基线方法，AttEmoNet的分类精准度Precision最高提升13.33%，召回率Recall最高提升21.80%，F1得分F1-score提升12.74%。同时AttEmoNet建模的情绪语义关联矩阵有良好的可解释性，证明其具有较好的建模情绪语义的能力。【局限】大语言模型的出现为多标签文本情绪分类打开了全新的思路，未来将结合AttEmoNet与大语言模型各自的优势以实现更加精准、高效的多标签文本情绪分类算法。【结论】本文提出一种基于自注意力机制的情绪关联性建模的多标签文本情绪分类神经网络，提升了文本情绪模型的情绪语义及其关联性建模的能力以及情绪识别的性能，并通过在两个公开数据集上的对比实验验证了研究的有效性。
提交时间： 2024-04-18
摘要： 喷淋雾化被广泛应用于核动力设备中，以保证其安全稳定运行。喷淋时，部分液滴会撞击设备壁面，以液膜的形式进行扩展和演变。基于 Fluent DPM-to-VOF 进行了液滴射流撞壁研究，使用两液滴滴落过程实验图像验证了模拟方法的准确性，研究了液滴射流注入速度、入射角度对壁面液膜形态的影响规律，得到了液滴溅射率随入射条件的变化情况，并分析了液滴撞击壁面时重力、表面张力、速度分量等对液膜形态扩展过程、液滴溅射率的影响。研究发现，增大注入速度能加大对液膜的扰动，液膜与壁面的接触面积显著增大，液膜区宽度和高度增加；增大入射角度对液膜形态的改变影响较大，体现在液膜区宽度增加和液膜区高度减小，液膜表面稳定性减低。溅射率随着注入速度和入射角度的增大而增大，其中，入射角度对溅射率的影响更大。
提交时间： 2024-04-19
摘要： 本文介绍了基于分压供电模式的TH2103A型速调管阳极电流的测量和保护系统，分析了该供电模式下阳极电流的特点：阳极电流会出现流入或流出速调管阳极过大的情况。介绍了阳极电流的测量电路的原理和供电模式，阳极保护电路的原理和实施方案，以及在运行过程中对阳极电流的测量和保护系统进行了验证，证明该供电模式下阳极电流测量和保护系统的有效性和可靠性。本文所述供电模式和测量保护电路对基于TH2103A型束调管的运行和维护具有重要参考意义。
提交时间： 2024-04-24
摘要： 中国科学院高能物理研究所第二台硼中子俘获治疗（Boron Neutron Capture Therapy, BNCT02）加速器主要由1台离子源、1条低能束流传输线、1台射频四极加速器和3条高能束流传输线组成。为了保障BNCT02加速器的安全运行，设计了基于横河PLC和实验物理及工业控制系统（Experimental Physics and Industrial Control System，EPICS）软件工具包的机器保护系统。为了提高可靠性和安全性，该系统采用了冗余设计，由两套完全独立且主要输入、输出信号一致的子系统构成。测试结果表明，BNCT02加速器机器保护系统的响应时间小于1.6ms，且具有稳定可靠性高的特点，满足BNCT02加速器运行的需要。
分类： 核科学技术 >> 粒子加速器 提交时间： 2024-04-25
摘要： HVE-400注入机是专用的低能加速器离子注入设备，主要用于半导体材料的硼磷参杂工艺。注入机的离子源及引出偏转系统处于高电位，而相应控制系统处于地电位，控制信号与高压端各参数的测量反馈信号需要在地电位与高电位之间通过光纤进行传输，以隔离高压。因光纤传输控制与监测系统年久老化不能稳定工作而进行升级改造。改造采用无线数字传输模式取代多路光纤传输，具有高压隔离功能；利用先进的分散集中控制方式代替原有的分散式单点控制方式，将所有的控制与监测功能集中到工控计算机上进行数字化操作与显示。计算机控制监测系统还设计了两种方式离子质量数软件计算功能。升级改造后，注入机高压平台控制与监测系统具有无线化、数字化、集中控制、操作简单方便等特点。
分类： 核科学技术 >> 核科学技术其他学科 提交时间： 2024-04-25
摘要： 复杂岩性井段对密度测井数据精度要求很高，传统的计算模型不能很好的满足此时的高精度要求。为此提出利用机器学习回归预测模型提高密度测井曲线的精度，考虑到XGBoost模型的过拟合问题，基于SSA算法改进XGBoost进而提出了SSA-XGBoost密度预测模型。采用蒙特卡罗模拟双探测器密度测井仪器，获取不同密度地层数据以验证该模型的预测效果。利用SSA算法优化SVR、RFR和LSTM参数，构建SSA-SVR、SSA-RFR和SSA-LSTM模型预测模拟地层密度，并使用量化评价指标和泰勒图模型对比分析各个模型的预测性能。此外，还分析了不同预测模型对实际密度测井数据的预测效果。结果表明SSA-XGBoost模型的预测精度高于传统脊-肋图模型，在实际密度测井数据处理中具有广阔的应用前景。
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： we investigate the transmission of probe laser beam in a coupled-cavity system with polaritons by using standard input-output relation of optical fields, and proposed a theoretical schema for realizing a polariton-based photonic transistor. On account of effects of exciton-photon coupling and single-photon optomechanical coupling, a probe laser field can be either amplified or attenuated by another pump laser field when it passes through a coupled-cavity system with polaritons. The Stokes and anti-Stokes scattered effect of output prober laser can also be modulated. Our results open up exciting possibilities for designing photonic transistors.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： The miniaturization and mobility of computer vision systems are limited by the heavy computational burden and the size of optical lenses. Here, we propose to use a ultra-thin diffractive optical element to implement passive optical convolution. A division adjoint opto-electronic co-design method is also proposed. In our simulation experiments, the first few convolutional layers of the neural network can be replaced by optical convolution in a classification task on the CIFAR-10 dataset with no power consumption, while similar performance can be obtained.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Diffraction gratings with high upward diffraction efficiency and large effective length are required for chip-scale light detection and ranging. In this paper, we propose a diffraction grating based on a multilayer silicon nitride waveguide, which theoretically achieves an upward diffraction efficiency of 92$\%$, a near-field effective length of 376 $\mu m$ and a far-field divergence angle of 0.105$^{\circ}$ at a wavelength of 850 nm. The diffraction grating has a high tolerance to process variations based on Monte Carlo Analysis. When the conditions are $\pm$5$\%$ layer thickness variation, $\pm$50 nm lithographic variation and $\pm$20 nm wavelength drift, more than 71$\%$ of the grating samples have a diffraction efficiency higher than 80$\%$, and 100$\%$ of the samples have an effective length larger than 200 $\mu m$ (corresponding to a far-field divergence <0.2$ ^{\circ}$). Furthermore, the near-field effective length of the grating with an upward diffraction efficiency above 90$\%$ can be adjusted from hundreds of microns to centimeters by changing the etching layer thickness and the grating duty cycle. This diffraction grating has potential application in optical sensing and imaging from visible to near-infrared wavelengths.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Electromagnetic spins, including longitudinal and transverse ones, have been playing important roles in light-matter interactions. Here, we formulate a unified equation to uncover the physical origins and topological properties of longitudinal and transverse spins in a generic electromagnetic field. The equation reveals universally that the transverse spin is locked with the kinetic momentum and originated from the transverse inhomogeneities of field, whereas the helix-dependent longitudinal spin orients parallel to the local wavevector. Remarkably, a hidden extraordinary helix-dependent transverse spin possessing helix-dependent spin-momentum locking is discovered and the number of locking states consistent with the nontrivial topological spin Chern number. Furthermore, this spin which determines the inverted helical components is related to the Berry curvature closely. The findings, which are demonstrated experimentally by measuring the three-dimensional spin components in the focusing configuration, will deepen the understanding the underlying physics of spins and open an avenue for chiral quantum optical applications.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Polarization vectors of light traveling in a coiled optical fiber rotate around its propagating axis even in the absence of birefringence. This rotation was usually explained due to the Pancharatnam-Berry phase of spin-1 photons. Here, we use a purely geometric method to understand this rotation. We show that similar geometric rotations also exist for twisted light carrying orbital angular momentum (OAM). The corresponding geometric phase can be applied in photonic OAM-state-based quantum computation and quantum sensing.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Optical forces in the near fields have important applications in on-chip optical manipulations of small particles and molecules. Here, we report a study of optical force and torque on small particles induced by the optical polarization singularities of a gold cylinder. We show that the scattering of the cylinder generates both electric and magnetic C lines (i.e., lines of polarization singularities) in the near fields, and the C lines can induce complex force and torque on a dielectric/magnetic particle. The force and torque manifest dramatic spatial variations with interesting symmetry properties, providing rich degrees of freedom for near-field optical manipulations. The study, for the first time to our knowledge, uncovers the effect of optical polarization singularities on light-induced force and torque on small particles. The results contribute to the understanding of chiral light-matter interactions and can find applications in on-chip optical manipulations and optical sensing.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： How migratory birds can find the right way in navigating over thousand miles is an intriguing question, which much interested researchers in both fields of biology and physics for centuries. There several putative proposals that sound intuitively plausible all remain contested so far because those hypothesis-models of magnetoreceptor to sense geomagnetic field need either extremely high sensitivity or humankind-like intelligence to guide. Here we explore theoretically that the birds can navigate to their destination through an entirely new scenario to sense the geomagnetic field. Our proposal is based on separate peaks of the resonance-fluorescence spectrum of a four-level system derived from the ferric sulfide cluster which exists in a protein complex (Drosophila CG8198) of migratory birds. As the separation of spectral peaks contains information about geomagnetic field at both current location and birthland, the change of such separation cues the bird to choose a right direction to move and double-resonance emerges once arrived the destination. Our theoretical mechanism can explain previous experiments on the disorientation of migratory birds caused by oscillating magnetic field naturally and more precisely. This work provides insight to explain migratory navigation and motivates possible manmade practical devices.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Narrow linewidth laser(NLL) of high frequency stability and small form factor is essential to enable applications in long range sensing, quantum information and atomic clocks. Various high performance NLL have been demonstrated by Pound-Drever Hall(PDH) lock or self injection lock(SIL) of a seed laser to a vaccum-stabilized FP cavity of ultrahigh quality factor(Q). However they are often complicated lab setups due to the sophisticated stabilizing system and locking electronics. Here we report a compact NLL of 68mL volume, realized by SIL of a diode laser to a miniature FP cavity of 7.7x108 Q and 0.5mL volume, bypassing table-size vaccum, thermal and vibration isolation. We characterized the NLL with a self-delayed heterodyne system, the Lorentzian linewidth reaches 60mHz, and the integrated linewidth is ~80Hz. The frequency noise performance exceeds that of commercial NLLs and the best reported hybrid-integrated NLL realized by SIL to high Q on-chip ring resonators. Our work marks a major step toward a field-deployable NLL of superior performance utilizing ultra-high Q FP cavity.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Conventional coherent absorption occurs only when two incident beams exhibit mirror symmetry with respect to the absorbing surface, i.e., the two beams have the same incident angles, phases, and amplitudes. In this work, we propose a more general metasurface paradigm for coherent perfect absorption, with impinging waves from arbitrary asymmetric directions. By exploiting excitation of unidirectional evanescent waves, the output can be fixed at one reflection direction for any amplitude and phase of the control wave. We show theoretically and confirm experimentally that the relative amplitude of the reflected wave can be tuned continuously from zero to unity by changing the phase difference between the two beams, i.e. switching from coherent perfect absorption to full reflection. We hope that this work will open up promising possibilities for wave manipulation via evanescent waves engineering with applications in optical switches, one-side sensing, and radar cross section control.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Lingya Yu
Zengbo Wang
Lizhou Xu
Liyang Yue
Bing Yan
Igor V. Minin
Oleg V. Minin
Baidong Wu
Yiduo Chen
摘要： Photonic hook (PH) is a new type of artificial self-bending beam focused by a dielectric particle-lens with a curved waist smaller than the wavelength, which has the potential to revolutionize mesoscale photonics in many applications, e.g., optical trapping, signal switching, imaging, etc. In this paper, we discover a new mechanism that the highly curved PHs can be realised by the light interaction with the fully or partially metal-coated microchannels. The generated W-shaped and J-shaped PHs have bending angles exceeding 80-degree. Compared to other PH setups, the proposed design has a larger range to flexibly control the bending angle through the coating process and can be easily integrated with the established microfluidic systems.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： We show that the time-averaged Poynting vector in parity-time (PT ) symmetric coupled waveguides is always positive and cannot explain the stopped light at exceptional points (EPs). In order to solve this paradox, we must accept the fact that the fields E and H and the Poynting vector in non-Hermitian systems are in general complex. Based on the original definition of the instantaneous Poynting vector, a formula on the group velocity is proposed, which agrees perfectly well with that calculated directly from the dispersion curves. It explains not only the stopped light at EPs, but also the fast-light effect near it. This investigation bridges a gap between the classic electrodynamics and the non-Hermitian physics, and highlights the novelty of non-Hermitian optics.
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