To reduce the computational complexity and time consumption of intraframe prediction in high-efficiency video coding (HEVC), an improved algorithm for intraframe prediction mode fast selecting in HEVC based on the size of the prediction units (PUs) is proposed. For the maximum size of PUs, the statistical probability is used to hierarchically set the candidate modes into the rough mode decision (RMD) process. For other PUs, candidate modes are set by extracting the texture direction in two different ways into the RMD process. We use the pixel gradient for the 32×32 and 16×16 PUs and use pixel value deviation for the 8×8 and 4×4 PUs to extract the texture direction; therefore, fewer modes are selected to calculate and reduce the time taken by the RMD process. Experimental results show that the proposed algorithm reduces the encoding time by approximately 32.2% on average with only a 0.86% increase in code rate in comparison with HM16.9. In compared with the existing algorithms, the proposed algorithm further reduces the coding time and produces better coding quality.

Face image optimization has important significance for face recognition in intelligent monitoring system. In the case of multi-face tracking in video, there are problems such as tracking error and inability to add and cancel the tracker in time. This paper proposes a face clustering method replacing the face tracking method to obtain face images of the same person, and a face image quality evaluation method to select a face image with good face pose and good image quality from a large number of multi-pose face images of the same person. First, the face detection from the video frame is performed, and then the residual network is used to extract the facial features for face clustering. Finally, the normalized mean value is computed as the weight coefficient of corresponding evaluation index for each type of face after clustering. Consequently, a comprehensive evaluation index is constructed to optimize the face image. Experiments show that face clustering can effectively obtain the same face image, and the constructed face image quality comprehensive evaluation index can effectively select a better face image from the same face images.

Herein, a dehazing algorithm based on a full convolution regression network is proposed to solve the overexposure and color distortions caused by current dehazing algorithms. The regression network is based on an end-to-end system and comprises two parts, feature extraction and feature fusion, to which a foggy image is first subjected, then regressed into a coarse transmittance map and optimized by the guide filter. The atmospheric physical scattering model is used to invert a fog-free image , which is then enhanced via contrast limit adaptive histogram equalization (CLAHE) to obtain a clear image that is more suitable to human vision. The proposed algorithm can avoid problems such as overexposure and color distortion post dehazing, retain complete details, and provide a better dehazing effect.

To address the issue of the sparsity of image text data and the limitation of traditional image features, this study proposes an image annotation algorithm that combines a convolutional neural network (CNN) and a topic model. Herein, a Dirichlet topic model is used to model text data on image training sets and generate text topic distribution and text topic label distribution, which reduces the dimension and sparsity of image text data. Considering the sparse distribution of image text topic, the CNN is used to extract high-level visual image features, and the loss function is improved to reconstruct the CNN. Multiple classifiers are constructed based on the high-level visual image features and corresponding multi-text topics to perform multi-label classification learning on image text topics and obtain the text-topic distribution of image. Finally, the text-topic distribution and text-topic label distribution are combined to calculate the probability of the image label. Based on the contrast experiment on Corel5K and IAPR TC-12 image annotation datasets, the proposed algorithm effectively improves the performance of image annotation.

Aiming at the loss of information and edge blurring during texture recovery using super-resolution technology based on convolution neural networks, we combine dense block and squeeze module to learn the mapping from low-resolution to high-resolution in an end-to-end manner. The dense block structure formed by the fusion of dense connection utilizes context information of image region effectively. The squeeze module amplifies valuable global information selectively and suppresses the useless features. The multiple 1×1 convolution layer structures in the image reconstruction section reduce the dimension of the previous layers, and speed up the calculation while reducing the loss of information. Processing the original image directly shortens the training time, and the optimization of convolution layers and filters reduces the computational complexity significantly.

The rapid development and application of unmanned aerial vehicles (UAVs) not only bring convenience to the society, but also pose serious threats to public security, personal privacy, and military security. Therefore, rapid and accurate detection of unknown UAV becomes increasingly important. In addition, in UAV detection technology, the method based on machine vision has the advantages of low cost and simple configuration. This paper proposes an optimized YOLOv3 (You Only Look Once version3) based detection and recognition method for low altitude and fast moving UAV. The residual network and multi-scale fusion are used to optimize the network structure of the original YOLO, and the O-YOLOv3 network is proposed. The training and testing are carried out using the real filmed UAV dataset. The experimental results show that the average precision of the optimized method is better than that of the original method, and the detection speed meets the real-time requirement.

Since the spherical-deconvolution (SD)-based intravoxel fiber-orientation distribution (FOD) estimation method is highly sensitive to noise, a non-convex regularized SD method is proposed. It constructs a non-convex spatial regularization based on the FOD similarity between neighboring voxels and resolves the non-convex regularized SD problem using the modified Richardson-Lucy algorithm. The simulated results based on data in two tensors model and HARDI (high-angular-resolution diffusion imaging) model show that, compared with the conventional SD and total-variation regularized SD methods, the proposed method generates FODs with a lower mean angular error (reduced by 52% and 9%, respectively) and exhibits better noise immunity and detail preservation of the fiber orientations.

Aiming at the problem of insufficient sweep range of the swept source used in the existing swept source optical coherence tomography (SS-OCT), a Fourier domain mode-locking(FDML) high-speed broadband swept source based on a quantum dot semiconductor optical amplifier (QD-SOA) and a quantum well semiconductor optical amplifier (QW-SOA) in parallel is studied. The output characteristics of two types of SOA are studied, and the QW-SOA with a center wavelength of 1310 nm and the QD-SOA with a center wavelength of 1280 nm are placed in parallel in the fiber annular cavity. A high-speed broadband swept source is developed combined with FDML. The sweep range is 318 nm, the full width at half maximum is 110 nm, the sweep speed is 101 kHz, the average output optical power is 7.8 mW, and the instantaneous linewidth is less than 0.1 nm, respectively.

In the person reidentification system, the retrieved person image will have large posture differences, complex changes in perspectives, and misalignment of person images in the detection frame. In order to solve these problems, a reidentification algorithm is proposed,which can directly use the key point information of the human body for person image alignment and extract multi-granularity features based on this alignment. First, the posture prediction model is used to locate the key points of the human skeleton, and the person image is directly aligned according to the extracted skeleton key points, and then the multi-granularity features are extracted from the person image. The evaluation phase uses posture information combined with multi-granularity features for similarity matching. The experiment is carried out only using the identity(ID) loss function on the three public datasets of Market1501, CUHK03, and DukeMTMC-reID. The results show that the proposed algorithm has certain advantages.

In order to improve the accuracy of point cloud reconstruction for automatic drive sweeping robots, a simultaneous localization and mapping (SALM) algorithm based on graph optimization is proposed. First, the extended Kalman filter is used to fuse the information of GPS, inertial measurement unit (IMU) and odometer to get the current position. Second, the point cloud transformation relationship is obtained based on 3D-NDT registration. Finally, by constructing point clouds as map nodes, GPS and ground parameters as edge constraints, the back-end optimization is carried out by constructing a map optimization model. The point cloud posture is constructed as a map node, and the real-time laser point cloud data, fusion location information and ground parameters are used as edge constraints, and solve the optimum position and posture of point clouds. The results show that comparing with mapping algorithms that just based on laser data, the proposed algorithm can improve the mapping results of point cloud environment and improve the mapping accuracy. The correctness and efficiency of the strategy in this paper is verified.

In order to predict the microstructure process parameters of the microlens array glass during molding, a finite element analys is model of the microlens array is established using the advanced nonlinear finite element software MSC.Marc in this study. The array optical elements with different microstructural widths are divided into several groups. The influence of the microstructural height of each group of the chalcogenide array optical elements on the equivalent von Mises stress is calculated by the finite element analysis model; subsequently, we obtain the influences of chalcogenide glass microlens array structures with the same microstructural width and different microstructural heights on the equivalent von Mises stress after the molding. The maximum equivalent von Mises stress of array optical elements with the same microstructural width and different microstructural heights is fitted, and the trend of equivalent von Mises stress is analyzed to obtain the ratio of the microstructural height to the width of the chalcogenide glass Ge23Se67Sb10 array optical elements suitable for molding. The simulation results show that the lower the microstructural height is, the lower the equivalent von Mises stress is. The equivalent von Mises stress of the chalcogenide glass microlens array increases gradually from the center to the edge and is the highest at the edge. When the ratio of the microstructural height to the width is greater than 0.322, the equivalent von Mises stress generated by the molding increases greatly.

As an important part of modern optics and photonics, nonlinear optics plays a significant role in both research and application. However, at the micrometer and nanometer scales, the nonlinear optical response of a material is generally weak owing to the inherent nonlinear susceptibility and limited interaction length of the material; this restricts the development of integrated nanoscale nonlinear optoelectronic devices. In recent years, by taking advantage of the ability of surface plasmons to confine the electromagnetic field into a subwavelength volume, researchers have observed the nonlinear optical effects in the micro/nano-structures under the weak excitation light. This has gradually led to the formation of a new research field: nonlinear plasmonics. Different from previous review articles that have focused more on the nonlinear optical properties of the plasmonic metal nanostructures, in this paper, we emphasize the recent progress of nonlinear optical effects in hybrid metal-dielectric systems. First, we introduce the related properties and theoretical background of plasmonics and nonlinear optics; then, we summarize researches related to nonlinear optical enhancement effects in zero-dimensional hybrid systems, nonlinear effects in one-dimensional hybrid systems, nonlinear plasmonics in two-dimensional graphene, respectively. Finally, we discuss future research directions in the field of nonlinear plasmonics and significant opportunities and challenges.

Metasurface is a two-dimensional metamaterial with subwavelength thickness, which can effectively regulate the near-field radiation of electromagnetic waves. Transformation optics supplies a theoretical method to control the propagation of an electromagnetic wave by changing the electromagnetic parameters of an artificial material. In particular, the general relativity phenomena in curved spacetime can be emulated via the transformation optics concept. We introduce the experimental work on the analogy of gravity by exploiting a metasurface waveguide, and simulate the cosmic string as a one-dimensional topological defect generated during the early inflation of the universe, as well as the definite photonic deflection in the nontrivial space of cosmic string. Furthermore, by including the material loss, the symmetry breaking of photonic modes can be used to mimic the phase transition of the Higgs vacuum eld. This paper summarizes the research status and combines the current research basis to analyze the research prospects and development trends of metasurface.

Photoelectric conversion of surface plasmon-induced hot electrons has recently attracted considerable attention as it shows great potential in applications such as highly efficient photodetection, solar cells, and catalytic reactions. The quick transfer and collection of plasmon-induced hot electrons can effectively avoid energy loss caused by relaxation, recombination, and trapping, thereby improving the efficiency and speed of photoelectric conversion. More importantly, plasmon-induced hot electron transfer contributes towards a photoresponse that is beyond the bandgap limit of semiconductors, providing an effective approach for infrared photodetection. In addition to noble metals, heavily doped semiconductors have attracted significant attention owing to their tunable localized surface plasmon resonance in the infrared region of the electromagnetic spectrum. This review focuses on the fundamental mechanism of the excitation and transfer of plasmon-induced hot electrons and the research progress of infrared photodetection based on hot-electron transfer. Furthermore, the current problems and challenges in this field are discussed in order to provide guidance for the design of high-performance devices based on plasmon-induced hot-electron transfer.

In this paper, we attempt to review and sort out the development of two typical types of plasmonic-sensing-on-fiber-tip technologies, and discuss the focus for future work and potential values for application. The first type is surface plasmon resonance (SPR) sensing structures, especially surface plasmon cavities, integrated on optical fiber end-facets. They can be applied to small volumes of samples and achieve biomolecule sensing in a dip-and-read manner. They can also be inserted into narrow spaces for ultrasound endoscopy. In the future, how to solve the problem of low content detection in complex crude samples while upholding the core values of convenience and rapidness, is the critical challenge for fiber SPR sensor development in order to find real application values in medical diagnosis and agriculture product inspection. On the other hand, to greatly improve SPR devices' sensitivities to acoustic signals is the key to achieving fiber SPR hydrophone arrays with high application values. The second type is plasmonic antennas integrated on tapered optical fibers' apexes. Combined with scanning probe microscopy technologies, these probe devices render high precision and dynamic tuning of plasmonic antennas, and high resolution scanning microscopy by using plasmonic hotspots to strongly interact with and map the samples. In the future, through innovative research on the antenna probes and the to-be-measured quantities, the scope of physical and chemical phenomena that can be characterized is expected to be further expanded, and the characterization performance is expected to significantly improve.

The coupling of light and free electron oscillation on the surface of the metal micro-nano structures results in surface plasmon resonance, exhibiting the local structure of the light field at the sub-wavelength scale, and effectively enhances the interaction between the light and material. Further, the development of research on the photothermal effect of plasmons is reviewed. Subsequently, the mechanism and regulation of photothermal transformation assisted by plasmons are summarized. The regulation and application of the photothermal effect of plasmons in solar vapor generation are introduced. On the one hand, the improvement of the heat utilization rate from block heating to interface heating is studied; on the other hand, the improvement of light absorption efficiency from single frequency absorption to wide spectrum absorption is also studied. Finally, the challenges and opportunities of the photothermal effects of equivalent ionizers are discussed.

The photon extraction efficiency of the organic light-emitting devices (OLEDs) is considerably low because of the presence of various light-trapping modes. The power conversion efficiency of organic photovoltaics (OPVs) is also unsatisfactory because of the incomplete light absorption induced by the low diffusion length of the organic active materials which limit the thickness of active layer. An effective method to improve the efficiency of the organic optoelectronic devices is to use the metal plasmonic micro/nano-structures for regulating the light-field distribution. This review article summarizes the recent advances in light-field manipulation induced by the metallic subwavelength structures in organic optoelectronic devices. Furthermore, the principles and strategies for enhancing the light extraction in OLEDs and light harvesting in OPVs, are discussed in this study.

Localized-surface-plasmonic (LSP) nanostructures can efficiently collect light propagating in free space and converge it onto nanoscale “hot spots” in the near-field region, enabling efficient excitation of molecules. Conversely, spectral information about molecules in the hot spots can be “broadcast” to the far field. This process is accompanied by the enhancement of light absorption, radiation, scattering, light force, resonance migration, and photothermal effects. The rich phenomena associated with LSP nanostructures have resulted in a series of applications in the field of sensing, including surface-enhanced infrared-absorption spectroscopy, surface Raman spectroscopy, surface fluorescence spectroscopy, LSP refractive-index sensors, nano-optical tweezers, and LSP matrix-assisted laser desorption/ionization. However, the complexity of LSP behavior also makes it difficult for researchers to understand the mechanisms and applications of this field. For this reason, we review and sort out all types of LSP sensors from the perspectives of both theory and applications. For example, the eigenmode theory based on the quasi-static approximation provides a unified analytical theoretical framework for all kinds of LSP-related phenomena. We provide a brief review of the progress and challenges of various related applications, including Raman scattering, infrared absorption, fluorescence, refractive-index sensing, and laser desorption/ionization, to provide a clear and concise overview for researchers in this field.

According to the generation mechanism of electromagnetic (EM) phase, electromagnetic metasurfaces can be divided into resonance-based metasurfaces using resonance response of microstructures and geometric-phase metasurfaces using anisotropic response of microstructures. In comparison with the resonance-based metasurfaces, geometric-phase metasurfaces have attracted much attention in recent years because of their non-dispersion, polarization dependence, and easy fabrication. This study presents an overview of the development of geometric-phase metasurfaces from the principle and method of their free modulation of EM waves to their extraordinary wavefront manipulation abilities in both the far- and near-field regions. Finally, we also present three typical applications enabled by geometric-phase metasurfaces, including highly efficient meta-hologram, vortex beam generator/detector, and flat achromatic metalens.

The nanolaser based on surface plasmon polariton (SPP) can reduce the light source size by several orders of magnitude, which combines with surface plasmon waves to confine its transmission within nanoscale, breaks through the diffraction limit to match the size of the electronic devices and finally realizes the miniaturization and low power consumption of an entire optical interconnection system. This paper briefly describes the basic principle of SPP, summarizes the recent research progress on SPP nanolasers, and introduces in detail their various structures and advantages. Moreover, the challenges and future work of nanolasers in the development process are elaborated upon, and the broad applications of nanolasers are prospected.

To address the problem of the weak photoluminescence (PL) intensity of Au nanorods in optical detection, the PL intensity of Au rods is increased by more than two orders of magnitude via continuous wave laser irradiation based on the enhancement of localized surface plasma resonance, and the PL intensity is adjusted in real time. The variation in PL enhancement with the wavelength, power density of the irradiation laser, and the aspect ratio and surface-to-volume ratio (SVR) of Au nanorods is investigated. Experimental results indicate that Au nanorods with small SVR exhibit better improvement. For certain Au nanorods, this enhancement can be further improved by optimizing laser power density and wavelength that is resonant with the transverse plasma mode of Au nanorods. These results will guide the enhancement of the PL intensity of Au nanorods.

A magneto-optical surface plasmon resonance device (MOSPR) based on Au/Ce∶YIG/TiN structure is proposed. By constructing a three-layer structure which comprises the periodic Au nanodisk array, Ce∶YIG film, and TiN film, the coupling between the Au nanodisk's localized surface plasmon resonance (LSPR) and the TiN/Ce∶YIG interface propagation surface plasmon resonance can be realized, which can significantly reduce the scattering loss of LSPR and enhance the magneto-optical effect. The absolute value of the transverse magneto-optical Kerr effect (TMOKE) of MOSPR reaches 0.21. Using the MOSPR and the strong magneto-optical effect of the magneto-optical oxide to prepare the sensor can significantly improve the figure of merit(FoM)of the LSPR sensor. Based on the TMOKE spectrum for sensing, the sensor's FoM is up to 2192.4586 RIU -1. This research provides a new idea for the preparation of LSPR devices with high sensitivity and high FoM.

Surface-enhanced Raman scattering (SERS) technique can be applied to enhance the electric field intensity at some locations (hot spots) on the metal surface. In this paper, the feasibility for silver dimer to be a substrate for super-resolution SERS imaging is researched. According to the finite-difference time-domain (FDTD) method, the electric field distribution of silver dimer under excitation light of different wavelengths and polarization directions are calculated and studied. The results show that the electric field distribution of silver dimer is highly localized, and the electric field intensity of hot spots in silver dimer can be controlled by the polarization direction of excitation light, which make it an effective substrate to realize super-resolution Raman imaging.

Based on a dielectric loaded graphene plasmon waveguide (DLGPW), this study proposes and investigates a single dielectric loaded two-sheet graphene symmetric surface plasmon waveguide (DLTGSSPW). In the DLTGSSPW, the interaction between the surface plasmon polaritons (SPPs) in two graphene sheets induces the coupled SPP modes, i.e., the symmetric and anti-symmetric SPP modes. The effective index method and the finite element method are used to reveal that the effective mode refractive indexes, propagation losses, mode numbers, and electromagnetic fields of the coupled SPP modes are strongly dependent on the DLTGSSPW parameters, such as the incident wavelength and the width and height of a single dielectric strip. The coupled SPP modes are similar to the guided modes in a three-layer dielectric planar waveguide. In addition, when the single dielectric strip is sufficiently high, the symmetric and anti-symmetric SPPs degenerate into the uncouple SPP modes in the respective graphene sheets, and this structure can be considered as two independent DLGPWs. All the results about SPP waveguide may have some possible application in actively integrated optics.

Herein, based on the hydrodynamic Drude model and two size-corrective terms derived from the size-dependent dielectric function, a simplified dielectric theoretical model is proposed to describe the nonlocal and size-dependent effects of surface plasmons in metallic nanostructures. Different dielectric models are used to perform numerical simulation comparisons of the electron energy loss spectroscopy and optical responses for silver spherical nanoparticles with different radii of 1-100 nm. Results show that the proposed theoretical model can demonstrate great effectiveness in reflecting the effects of local, nonlocal, size-dependent effects, and even analogous quantum-size responses on the surface plasmon characteristics of metallic nanostructures, energy (1-5 eV), and size (2-200 nm) ranges. Simultaneously, these results are useful in understanding the resonance mode and energy distribution and dynamic evolution mechanisms of surface plasmons, and provide a reference for the development and design of plasmonic elements on the nanometer scale.

We establish a three-dimensional (3D) mathematical model based on the finite element method and calculate the effect of the Ag nanoparticle arrays that are periodically distributed on the surface of the silicon thin-film photodetector on its light absorption performance. The results denote that, for the spherical Ag particle arrays, the key parameter affecting the light absorption efficiency of the silicon film is the ratio of the period to particle diameter. When the top particles of the silicon substrate are densely packed (i.e., when the ratio P/d is small), the absorption efficiency of the plasmon photodetector is improved to different extents at different incident angles when compared with that of the bare silicon photodetector. The absorption efficiency increases from 5% to 65% at the wavelength of 700 nm with the incident angle ranging from 0° to 65°. Furthermore, the photoelectric conversion efficiency increases from 29% to 34% over the entire wavelength range.

In this paper, the abnormal optical absorption of subwavelength trapezoidal metal groove arrays illuminated by a plane wave was systematically studied by the rigorous coupled wave analysis method. The influences of structural parameters on the absorption efficiency of sub-wavelength metal trapezoidal groove arrays were simulated, and a semi-analytical Fabry-Perot model was introduced to analyze the calculation results. The results show that the absorption enhancement of the sub-wavelength metal trapezoidal groove arrays is mainly caused by the Fabry-Perot resonance effect of the in-groove mode and energy conduction coupling of surface plasmons between the arrays. The absorption peak value of the metal trapezoidal groove approaches 1 when the groove depth satisfies the Fabry-Perot resonance condition and the array period satisfies the surface plasmon excitation condition. By compared with the rectangular groove, the trapezoidal groove with an appropriate inclination angle can not only ensure the absorptivity but also relax the tolerance of the groove depth, which helps in reducing the difficulty of device processing and improves the feasibility of device design.

A tunable filter based on a metal-insulator-metal (MIM) nano-cavity waveguide is constructed by using side-coupled method, which consists of an arch-type resonator and a rectangular waveguide. The transmission characteristic spectra, resonance wavelength distribution and magnetic field distribution of the arch-type cavity waveguide MIM structure filter have been numerically simulated and analyzed by finite element method (FEM). The results show that the arch-cavity filter has smooth transmission spectra, flat passband with transmittance of 0.976, stopband with transmittance of 0.001 and wide bandwidth,which shows that this structure filter has good filtering characteristics. By optimizing the parameters of the type structure filter, the channel selection filtering function can be realized in three communication windows of the optical communication band. This structure filter has great application prospects in high-density optical integrated circuits and nano-optics.

In the simulation of cross-type terahertz bandpass filter by using the finite-difference time-domain method, the main peaks narrow as the thickness of the Al foil increases, and several abnormal transmission peaks appear at high frequencies. A terahertz filter with Al foil thickness of 150 μm is fabricated by femtosecond laser micro-machining; it is tested using a time-domain terahertz spectroscopy system. The results show that the experimental results are consistent with the finite-difference time-domain method simulation results. The anomalous transmission peaks result from the Fabry-Perot resonant coupling of the surface plasmon polariton waves on the sidewalls of the slits of the cross structure. This coupling effect may be useful in controlling surface plasmon polariton waves and fabricating new terahertz devices.

A single-layer dielectric matrix transmission model was developed to study the transmission characteristics of terahertz waves in high temperature plasma. The variation in the terahertz wave under the influences of plasma electron density, thickness, applied magnetic field strength, and temperature was studied. The numerical analysis results indicate that under different conditions, the high-temperature plasma exhibits different transmission characteristics for the incident wave. The reflectivity increases and transmittance decreases with increasing plasma-electron density and thickness; then, a magnetic field can be used to improve the attenuation. Therefore, the thickness decreases with decreasing electron density of the plasma, and the influence of the increasing temperature on electromagnetic waves decreases. Adjusting the magnitude of the applied magnetic field and avoiding the attenuation peak can prevent communication blackouts.

Multiple surface lattice resonances generated with noble metallic nanoparticle array can be used to suppress radiative losses around several spectral positions, enlarge the resonance quality factor, and enhance the localized near-field intensity. This study proposed a method to generate multiple surface lattice resonances with noble metallic split-ring resonator arrays. It shows that for the magnetic dipole resonance, the generated equivalent magnetic dipole is oriented perpendicular to the paper plane, and the scattering fields are propagating along x and y directions, which makes it possible to realize the coupling between the magnetic dipole mode and the Rayleigh anomaly along both directions. The calculation results indeed reveal that the coupling between the magnetic dipole mode and the Rayleigh anomaly leads to the formation of a sharp surface lattice resonance, and double surface lattice resonances are generated when the lattice spacing are different with each other. Furthermore, the similar optical response can be obtained with electric quadrupole resonance of the split-ring resonator. These properties make split-ring resonator arrays promise for the design of micro/nano photonic devices.

This paper uses terahertz time-domain spectroscopy (THz-TDS) to analyze the content of seed potato starch in kudzu qualitatively and quantitatively. The spectral data of kudzu powder mixed with seed potato starch was collected, and the qualitative model was established by partial least squares method (PLS) to determine whether the starch powder was mixed with potato powder. The total false positive rate of PLS is 0%, and the model correlation coefficient is 0.925. The results show that PLS can be used to determine whether the starch powder is qualitatively differentiated. PLS and least squares support vector machine (LS-SVM) were used to establish a quantitative prediction model for the content of seed potato starch in kudzu respectively; for PLS prediction model, the determination coefficient is 0.932, and the root mean square error (RMSE) of the predicted set is 2.6%; for LS-SVM prediction model, the determination coefficient is 0.957, and the RMSE of LS-SVM of the predicted set is 1.6%. The results show that the LS-SVM quantitative prediction model is excellent. The research shows that THz-TDS can be used to rapidly and effectively detect the content of seed potato starch in kudzu qualitatively and quantitatively.

This study develops a spectral analysis method to provide a convenient method for quantitatively analyzing flicker of electric light sources for mass basic quality inspectors. This method only requires the use of transient spectral data of electric light sources measured by a common spectrometer within a certain period of time, instead of using light source stroboscope and digital oscilloscope. By the means of high-quality fitting of the spectral luminous efficiency function of photopic vision, calculation of relative light flux, and eight-step Fourier fitting, the scintillation percentage, stroboscopic depth, and stroboscopic frequency of incandescent, LED filament, and iodine tungsten lamps are calculated and analyzed, and the test results are compared with data measured by an LFA-2000 light source stroboscope. The results show that the average relative errors of scintillation percentage, stroboscopic depth, and stroboscopic frequency for these three types of electric light sources calculated by this method are 4.93%, 4.89%, and 10.17%, respectively, and the corresponding maximum relative errors are 8.31%, 7.95%, and 14.22%, respectively. The method is proven to be correct, feasible and accurate when the stroboscopic frequency of the measured light source is less than 200 Hz. This method can provide references for the development of related instruments and equipment, as well as the research and quality inspection of artificial lighting equipment.