分类： 农、林、牧、渔 >> 农、林、牧、渔业科学其他学科 提交时间： 2024-07-17 合作期刊: 《智慧农业（中英文）》
摘要： ［目的/意义］炭疽病（anthracnose）作为油茶生长过程中重要的病害，其严重程度的精准判定对于精准 施药和科学管理具有重大意义。本研究提出了一种改进YOLACT（You Only Look At CoefficienTs） 分级模型Camel⁃ lia-YOLACT，旨在实现对油茶叶片炭疽病感染严重程度的自动、高效判定。［方法］首先在YOLACT主干网络部 分使用Swin-Transformer来进行特征提取。Transformer架构的自注意力机制拥有全局感受野及移位窗口等特性，有 效地增强了模型的特征提取能力；引入加权双向特征金字塔网络，融合不同尺度的特征信息，加强模型对不同尺 度目标的检测能力，提高模型的检测精度；在激活函数的选择上，采用非线性能力更强的HardSwish激活函数替 换原模型的ReLu激活函数。由于HardSwish在负值区域不是完全截断，对于输入数据中的噪声具有更高的鲁棒性， 自然环境下的图像有着复杂的背景和前景信息，HardSwish的鲁棒性有助于模型更好地处理这些情况，进一步提升 精度。［结果和讨论］采用迁移学习方式在油茶炭疽病感染严重程度分级数据集上进行实验验证。消融实验结果表 明，本研究提出的Camellia-YOLACT模型的mAP75为86.8%，较改进前提升5.7%；mAPall为78.3%，较改进前提升 2.5%；mAR为91.6%，较改进前提升7.9%。对比实验结果表明，Camellia-YOLACT在精度和速度方面表现均好于 SOLO （Segmenting Objects by Locations），与Mask R-CNN算法相比，其检测速度提升了2倍。在室外的36组分级 实验中进一步验证了Camellia-YOLACT模型的性能，其对油茶炭疽病严重程度的分级正确率达到了94.4%，K值 平均绝对误差为1.09%。［结论］本研究提出的Camellia-YOLACT模型在油茶叶片和炭疽病病斑分割上具有较高的 精度，能够实现对油茶炭疽病严重程度的自动分级，为油茶病害的精准防治提供技术支持，进一步推动油茶炭疽 病诊断的自动化和智能化。
分类： 农、林、牧、渔 >> 农、林、牧、渔业科学其他学科 提交时间： 2024-07-17 合作期刊: 《智慧农业（中英文）》
摘要： ［目的与意义］ 梯田作为农业生产的关键要素之一，其面积估算对于农业政策制定、土地规划和资源管 理至关重要。为解决复杂的地形条件、种植环境导致传统遥感数据和监测方法难以开展梯田自动化提取问题，探 索一种利用深度学习技术在高分辨率遥感影像中精准提取梯田面积的方法。［方法］以休耕期梯田高分六号影像构 建语义分割数据集，同时提出一种改进的DeepLab v3+模型。该模型使用轻量级网络MobileNet v2作为骨干网络， 为了同时兼顾局部细节和全局语境，使用多尺度特征融合（Multi-scale Feature Fusion module, MSFF） 模块代替空 洞空间金字塔池化（Atrous Spatial Pyramid Pooling, ASPP） 模块，利用扩张率依次增大的空洞卷积级联模式改善信 息丢失的问题。此外，对浅层特征和深层特征使用坐标注意力机制以加强网络对于目标的学习。［结果与讨论］ 利用红、绿和近红外波段组合方式在梯田提取的精度和效果上表现最佳。相比于原始DeepLab v3+网络，精确率、 召回率、F1评分和交并比指标分别提升4.62%、2.61%、3.81%和2.81%。此外，与UNet和原始DeepLab v3+相比， 改进的DeepLab v3+在参数量上和浮点运算数有着更为优越的性能，其参数量仅为UNet的28.6%和原始DeepLab v3+的19.5%，同时浮点运算数仅为UNet和DeepLab v3+的1/5。这不仅提高了计算效率，也使得改进后的模型更适 用于资源有限或计算能力较低的环境中。［结论］深度学习在高分辨率遥感影像梯田识别中具有较高的精度，有利 于为梯田精细化监测和管理提供参考依据。
分类： 农、林、牧、渔 >> 农、林、牧、渔业科学其他学科 提交时间： 2024-07-17 合作期刊: 《智慧农业（中英文）》
摘要： ［目的/意义］耕地识别是农业遥感的重要应用领域之一，但现阶段深度学习等人工智能方法在中国西南 丘陵区遥感识别的研究应用深度仍然不够，识别精度有待提升。［方法］为了快速、精确地获取耕地面积、分布等 信息，基于高分辨率的高分六号（GF-6） 遥感影像，运用UNet++、DeeplabV3+、UNet与PSPNet等新型深度学习 模型对四川省绵阳市三台县耕地信息进行识别，并对各深度学习模型、传统机器学习方法——随机森林法及新型 土地覆盖产品SinoLC-1的识别精度进行对比分析，以期深入探索深度学习方法在地物遥感识别领域的应用前景。 ［结果和讨论］深度学习模型在F1分数、整体精度（Overall Accuracy, OA）、Kappa系数等精度评价指标的表现上， 相比于传统机器学习方法和新型土地覆盖产品均有显著提升，精度提升幅度分别可达20%和50%；其中添加了密 集跳跃连接技术的UNet++模型的识别效果最好，其F1分数、交并比（Intersection over Union, IoU）、平均交并比 （Mean Intersection over Union, MIoU）、OA 值和 Kappa系数值分别为0.92、85.93%、81.93%、90.60%和0.80。应用 UNet++模型对2种由仅光谱特征以及光谱+地形特征两种不同特征构建的影像进行耕地提取，光谱+地形特征模型 的IoU、OA和Kappa 3个指标比仅光谱特征模型分别提高了0.98%、1.10%和0.01。［结论］深度学习技术在应用于 高分辨率遥感影像中的耕地识别方面展现出显著的实用价值，融合光谱和地形特征可以实现信息互补，能进一步 改善耕地的识别效果。本研究可为相关部门更好地管理和利用耕地资源、推动农业可持续发展提供技术支撑。
分类： 农、林、牧、渔 >> 农、林、牧、渔业科学其他学科 提交时间： 2024-07-17 合作期刊: 《智慧农业（中英文）》
摘要： ［目的/意义］叶球是结球甘蓝的重要部分，其生长发育对田间管理至关重要。针对叶球分割识别存在大 田背景复杂、光照不均匀和叶片纹理相似等问题，提出一种语义分割算法UperNet-ESA，旨在能快速、准确地分 割田间场景中结球甘蓝的外叶和叶球，以实现田间结球甘蓝的智能化管理。［方法］首先，采用统一感知解析网络 （Unified Perceptual Parsing Network, UperNet） 作为高效语义分割框架，将主干网络改为先进的ConvNeXt，使得模 型在提升分割精度的同时也能具有较低的模型复杂度；其次，利用高效通道注意力机制（Efficient Channel Atten⁃ tion, ECA） 融入特征提取网络的各阶段，进一步捕捉图像的细节信息；最后，通过将特征选择模块（Feature Se⁃ lection Model, FSM） 和特征对齐模块（Feature Alignment Model, FAM） 集成到特征金字塔框架中，得到更为精确的 目标边界预测结果。［结果和讨论］在自制结球甘蓝图像数据集上进行实验，与目前主流的UNet、PSPNet和Deep⁃ labV3+语义分割模型相比，改进UperNet方法的平均交并比为92.45%，平均像素准确率为94.32%，推理速度为 16.6 f/s，能够达到最佳精度-速度平衡效果。［结论］研究成果可为结球甘蓝生长智能化监测提供理论参考，对甘 蓝产业发展具有重要的应用前景。
分类： 生物学 >> 植物学 >> 应用植物学 提交时间： 2024-07-17 合作期刊: 《广西植物》
摘要： 为探究湄公锥（Castanopsis mekongensis）叶的化学成分及其α-葡萄糖苷酶抑制活性，该研究以湄公 锥叶70%甲醇提取物为研究对象，选用多种现代分离材料对其开展系统的分离纯化，综合运用NMR 和MS 等波谱分析方法鉴定所得化合物结构，并对分离得到的化合物使用PNPG 法筛选其降糖活性。结果表明：（1） 从湄公锥叶中分离出17 个化合物，分别鉴定为湄公锥A（1）、没食子酸（2）、3,4 二羟基苯甲酸（3）、丁香 酸（4）、3,4-二羟基苯甲酸甲酯（5）、没食子酸甲酯（6）、鞣花酸（7）、龙胆酸5-O-β-D-木糖苷（8）、3-O- 没食子酰基莽草酸（9）、2,3-O-(S)-六羟基二苯基吡喃葡萄糖（10）、木麻黄鞣质（11）、5-desgalloylstarchyurin （12）、芦丁（13）、山奈酚3-O-芸香糖苷（14）、槲皮素-3-O-(6′′-O-没食子酰基-β-D-吡喃葡萄糖苷）（15）、 槲皮素-3-O-(6′′-O- 没食子酰基-β-D- 吡喃半乳糖苷） （ 16 ） 、 quercetin-3-O-β-D-glucopyranoside(3′→O-3′′)quercetin-3-O-β-D-galactopyranoside（17）。其中化合物1 为新化合 物，所有化合物皆为首次从湄公锥植物中分离得到。（2）药理试验结果显示，化合物3、9、10、11、12、14、 17 比阳性对照阿卡波糖展示更强的α-葡萄糖苷酶抑制活性。本研究结果丰富了湄公锥的化学成分，明确了其 降糖活性成分，为后续降糖相关产品开发提供了理论依据。
分类： 农、林、牧、渔 >> 农、林、牧、渔业科学其他学科 提交时间： 2024-07-17 合作期刊: 《智慧农业（中英文）》
摘要： ［目的/意义］农事行为活动识别对设施蔬菜生产精准化调控有着重要意义，在一定程度上可以通过查看 农事操作的时间、操作过程是否合理来减少因农事行为不当导致产量下降。为了解决农事行为识别方法中由于黄 瓜叶片和设施遮挡导致识别准确率不高的问题，提出一种名为SlowFast-SMC-ECA （SlowFast-Spatio-Temporal Ex⁃ citation、Channel Excitation、Motion Excitation-Efficient Channel Attention）的农事活动行为识别算法。［方法］该算 法主要基于SlowFast模型，通过改进Fast Pathway和Slow Pathway中的网络结构来提高对于农事活动中手部动作特 征和关键特征的提取能力。在Fast Pathway中，引入多路径激励残差网络的概念，通过在信道之间插入卷积操作来 增强它们在时域上的相互关联性，从而更好地捕捉快速运动信息的细微时间变化。在Slow Pathway中，将传统的 Residual Block替换为ECA-Res结构，以提高对通道信息的捕获能力。这两项改进有效地加强了通道之间的联系， 提升了特征之间的语义信息传递，进而显著提升了农事行为识别的准确率。此外，为了解决数据集中类别不均衡 的问题，设计了平衡损失函数（Smoothing Loss），通过引入正则化系数，平衡损失函数可以有效地处理数据集中 的类别不均衡情况，提高模型在各个类别上的表现。［结果和讨论］改进的SlowFast-SMC-ECA模型在农事行为识 别中表现出良好的性能，各类行为的平均识别精度达到80.47%，相较于原始的SlowFast模型有约3.5%的提升。 ［结论］本研究在农事行为识别中展现出良好的性能。这对农业生产的智能化管理和决策具有重要意义。
分类： 医学、药学 >> 临床医学 提交时间： 2024-07-16 合作期刊: 《中国全科医学》
摘要： 背景 前蛋白转化酶枯草溶菌素 9（PCSK9）对脂质代谢起到重要调节作用，急性心肌梗死患者血浆PCSK9 水平的影响因素尚未完全阐明。目的 了解急性心肌梗死患者血浆 PCSK9 水平的影响因素。方法 连续纳入2010—2018 年于北京大学第一医院心血管内科入院诊断为急性心肌梗死的患者。基线信息采集患者入院时的电子病历系统中的现病史、既往史、体格检查相关信息，检测基线血浆 PCSK9 水平。影响因素分析采用单因素及多因素线性回归模型，通过 LASSO 法进行筛选并纳入多因素线性回归模型。结果 共入选 996 例急性心肌梗死患者，其中 37 例患者因留存血样容量不足无 PCSK9 检测结果，共 959 例患者纳入分析，PCSK9 水平为 543.1（425.4，692.1）ng/mL。多因素回归分析结果显示，性别是影响急性心肌梗死患者 PCSK9 水平最大的因素（标准化回归系数为 13%），其余对PCSK9 水平影响较大的因素依次为：心房颤动病史（标准化回归系数为 9%）、白细胞计数（标准化回归系数为 7%）及血尿酸水平（标准化回归系数为 7%）。结论 在急性心肌梗死患者中，性别、心房颤动病史、白细胞计数及血尿酸水平与血浆 PCSK9 水平显著独立相关。
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： 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： 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.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Traditional lasers function using resonant cavities, in which the round-trip optical path is exactly equal to an integer multiple of the intracavity wavelengths to constructively enhance the spontaneous emission rate. By taking advantage of the enhancement from the resonant cavity, the narrowest sub-10-mHz-linewidth laser and a $10^{-16}$-fractional-frequency-stability superradiant active optical clock (AOC) have been achieved. However, a laser with atomic spontaneous radiation being destructively inhibited in an anti-resonant cavity, where the atomic resonance is exactly between two adjacent cavity resonances, has not been reported. Herein, we experimentally demonstrate inhibited stimulated emission and termed it an inhibited laser. Compared with traditional superradiant AOCs, which exhibit superiority in terms of the high suppression of cavity noise, the suppression of the cavity-pulling effect of an inhibited laser can be further improved by a factor of $(2F/pi)^2$, i.e., 2.07 in this work, which was improved from 26 to 53 times. This study will guide further development of AOCs with better stability, and thus, it is significant for quantum metrology and may lead to new research in the laser physics and cavity quantum electrodynamics fields.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Resampling by interpolation is the traditional method to process sample in nonunform sampling Fourier transform spectrometer. Nonuniform discrete Fourier transform is an alternative to interpolation that has not been overlooked before. With the aid of experiment, we systematically compare the NUFFT method with resampling by interpolation FFT method in nonuniform sampling Fourier transform spectrometer. We found that NUFFT is comparable to interpolation in spectral profile and spectral noise levels and is better in spectral amplitudes. We also found that It has significant advantage in under-sampling and anti-aliasing property which is offered by the unique non-periodic nature of nonuniform sampling. It is faster and consumes less computer memory in our python implementation. Overall, we found that NUFFT is superior to traditional interpolation method with mostly better performances as well as additional capabilities.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Xiao Sun
Song Liang
Weiqing Cheng
Shengwei Ye
Yiming Sun
Yongguang Huang
Ruikang Zhang
Jichuan Xiong
Xuefeng Liu
John H. Marsh
Lianping Hou
摘要： We report an AlGaInAs multiple quantum well integrated source of polarization controlled light consisting of a polarization mode converter PMC, differential phase shifter(DPS), and a side wall grating distributed-feedback DFB laser. We demonstrate an asymmetrical stepped-height ridge waveguide PMC to realize TE to TM polarization conversion and a symmetrical straight waveguide DPS to enable polarization rotation from approximately counterclockwise circular polarization to linear polarization. Based on the identical epitaxial layer scheme, all of the PMC, DPS, and DFB laser can be integrated monolithically using only a single step of metalorganic vapor phase epitaxy and two steps of III V material dry etching. For the DFB-PMC device, a high TE to TM polarization conversion efficiency 98% over a wide range of DFB injection currents is reported at 1555 nm wavelength. For the DFB-PMC-DPS device, a 60 degree rotation of the Stokes vector was obtained on the Poincar\'e sphere with a range of bias voltage from 0 V to -4.0 V at IDFB is 170 mA.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Light-matter coupling strength and optical loss are two key physical quantities in cavity quantum electrodynamics (cQED), and their interplay determines whether light-matter hybrid states can be formed or not in chemical systems. In this study, by using macroscopic quantum electrodynamics (mQED) combined with a pseudomode approach, we present a simple but accurate method which allows us to quickly estimate the light-matter coupling strength and optical loss without free parameters. Moreover, for a molecular emitter coupled with photonic modes (including cavity modes and plasmon polartion modes), we analytically and numerically prove that the dynamics derived from the mQED-based wavefunction approach is mathematically equivalent to the dynamics governed by the cQED-based Lindblad master equation when the Purcell factor behaves like Lorentzians.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： One of the fundamental challenges in nanophotonics is to gain full control over nanoscale optical elements. The precise spatiotemporal arrangement determines their interactions and collective behavior. To this end, DNA nanotechnology is employed as an unprecedented tool to create nanophotonic devices with excellent spatial addressability and temporal programmability. However, most of the current DNA-assembled nanophotonic devices can only reconfigure among random or very few defined states. Here, we demonstrate a DNA-assembled rotary plasmonic nanoclock. In this system, a rotor gold nanorod can carry out directional and reversible 360 degree rotation with respect to a stator gold nanorod, transitioning among 16 well-defined configurations powered by DNA fuels. The full-turn rotation process is monitored by optical spectroscopy in real time. We further demonstrate autonomous rotation of the plasmonic nanoclock powered by DNAzyme-RNA interactions. Such assembly approaches pave a viable route towards advanced nanophotonic systems entirely from the bottom-up.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Lee-Huang-Yang (LHY) fluids are an exotic quantum matter dominated purely by quantum fluctuations. Recently, the three-dimensional LHY fluids were observed in ultracold atoms experiments, while their low-dimensional counterparts have not been well known. Herein, based on the Gross-Pitaevskii equation of one-dimensional LHY quantum fluids in two-component Bose-Einstein condensates, we reveal analytically and numerically the formation, properties, and dynamics of matter-wave structures therein. Considering a harmonic trap, approximate analytical results are obtained based on variational approximation, and higher-order nonlinear localized modes with nonzero nodes are constructed numerically. Stability regions of all the LHY nonlinear localized modes are identified by linear-stability analysis and direct perturbed numerical simulations. Movements and oscillations of single localized mode, and collisions between two modes, under the influence of different initial kicks are also studied in dynamical evolutions. The predicted results are available to quantum-gas experiments, providing a new insight into LHY physics in low-dimensional settings.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： The key component of nanoplasmonics is metals. For a long time, gold and silver have been the metals of choice for constructing plasmonic nanodevices because of their excellent optical properties. However, these metals possess a common characteristic, i.e., their optical responses are static. The past decade has been witnessed tremendous interest in dynamic control of the optical properties of plasmonic nanostructures. To enable dynamic functionality, several approaches have been proposed and implemented. For instance, plasmonic nanostructures can be fabricated on stretchable substrates or on programmable templates so that the interactions between the constituent metal nanoparticles and therefore the optical responses of the plasmonic systems can be dynamically changed. Also, plasmonic nanostructures can be embedded in tunable dielectric materials, taking advantage of the sensitive dependence of the localized surface plasmon resonances on the neighboring environment. Another approach, which is probably the most intriguing one, is to directly regulate the carrier densities and dielectric functions of the metals themselves.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： We propose and study an efficient photonic CDE method using MZI-based coherent optical matrix multiplication. It improves the compensation performance by about 60% when the tap-length is limited, and only 50% taps of the theoretical value is needed for photonic CDE with 1-dB penalty.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Mingming Feng
Baoqing Zhang
Haotian Ling
Zihao Zhang
Yiming Wang
Yilin Wang
Xijian Zhang
Pingrang Hua
Qingpu Wang
Aimin Song
Yifei Zhang
摘要： Plasma frequency is the spectral boundary for low-loss propagation and evanescent decay of surface plasmon polariton (SPP) waves, which corresponds to a high cut-off phenomenon and is typically utilized for identifying SPPs. At terahertz (THz) frequencies, a metal line with periodic metallic grooves can mimic the conventional optical SPPs, which is referred to as designer SPPs. Theoretically, the plasma frequency of THz SPPs decreases as the groove depth increases. Here, by replacing the metallic grooves with graphene sheets, dynamically sweeping SPP plasma frequency is demonstrated for the first time. The metal-graphene hybrid structure comprises a metal line with periodic graphene grooves, a thin-layer ion gel for gating graphene, and metallic tips for uniforming gate field. As the chemical potential changes, the average conductivity of graphene is modulated so that the effective depth of the graphene grooves changes, which sweeps the plasma frequency of THz SPPs consequently. Both simulated and experimental data demonstrate a red shift of plasma frequency from 195 to 180 GHz at a low bias from -0.5 to 0.5 V. The proposed structure reveals a novel approach to control the on/off status of SPP propagation in the THz range.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Vortex beam carrying orbital angular momentum (OAM) is disturbed by oceanic turbulence (OT) when propagating in underwater wireless optical communication (UWOC) system. Adaptive optics (AO) is used to compensate for distortion and improve the performance of the UWOC system. In this work, we propose a diffractive deep neural network (DDNN) based AO scheme to compensate for the distortion caused by OT, where the DDNN is trained to obtain the mapping between the distortion intensity distribution of the vortex beam and its corresponding phase screen representating OT. The intensity pattern of the distorted vortex beam obtained in the experiment is input to the DDNN model, and the predicted phase screen can be used to compensate the distortion in real time. The experiment results show that the proposed scheme can extract quickly the characteristics of the intensity pattern of the distorted vortex beam, and output accurately the predicted phase screen. The mode purity of the compensated vortex beam is significantly improved, even with a strong OT. Our scheme may provide a new avenue for AO techniques, and is expected to promote the communication quality of UWOC system.
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