最新刊期
期 8 ， 2023
- 摘要：In order to realize multiple information encryption or storage of soft photonic crystal patterns， a stimuli-responsive cholesteric liquid crystal （CLC） soft photonic color film is designed and fabricated based on the thiol-acrylate Michael addition and photopolymerization reaction. First， the initial color of the reaction mixture is adjusted by changing the ratio of the doping chiral agent. Then small molecule liquid crystal is added into the mixture to adjust its viscosity. Finally， the temporal programming of the cross-linking density of the CLC soft photonic color film is carried out by ultraviolet （UV） exposure at different stages of the reaction， and the spatial programming is performed cooperatively with the help of photomasks. The experimental results indicate that the Bragg reflection wavelength of the CLC film only moves 19 nm during the reaction process of over 600 min. However， by locally modifying its color response via spatio-temporally dual-programming， the soft photonic film with invisible patterns can be made to gradually take on a colorful appearance from red to green with stretching， and reflected wavelength coverage over 100 nm. This stimuli-responsive soft photonic color film can be employed for the dynamic display of photonic crystal patterns， and is potentially useful for multiple anti-counterfeiting or information storage.关键词：stimulus responsiveness;cholesteric liquid crystal;soft photonic color film;michael addition reaction;Spatio-temporal dual-programming
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发布时间：2023-08-10 - 摘要：The curved liquid-crystal system has different characteristics from the planar liquid-crystal system. In this paper， the director of nematic liquid crystal in a cylindrical cavity is studied by applying a uniform electric field perpendicular to the axis of the cylinder under the strong axial anchoring boundary condition. Based on the elastic continuum theory of liquid crystal， the equilibrium equations and boundary conditions of the system are given. The analytical solution of the threshold electric field for the deformation of the director is obtained. It is found that different elastic constants will lead to the asymmetry of the change of the director on the cross section of the cylindrical cavity. It provides a more accurate theoretical analysis for the experimental research of photonic crystal fibers.关键词：cylindrical cavity;electric threshold;nematic liquid crystal;director
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发布时间：2023-08-10
Material Physics
- 摘要：Guest-host liquid crystal devices have attracted significant attention in see-through display due to their ability to control the transmittance of light without sacrificing the resolution of image. However， such complicated systems limite their contributions in practical applications. Herein， we propose a novel guest-host liquid crystal device for transparent display， with the coexistence of parallel and helical assembled microstructure fabricated by patterned polymer template. By applying an electrical field or rotating the linear polarization of incident light， the dynamic multi-grayscale patterns have been achieved owing to the distinct responses of different regions. The experimental results indicate that， under the driving voltage， the transmittance of parallel microstructure regions increases from 3.28% to 63.22%， and meanwhile the contrast ratio between the two regions increases from 0.41 to 5.12. By changing the linear polarization of incidence， the transmittance of parallel region increases from 3.28% to 65.45%， and the contrast ratio also increases from 0.41 to 4.54. The proposed guest-host liquid crystal device is capable for patterned display in various scenarios due to its simple configuration and convenient tunability， thus making further advances offer more brilliant liquid crystal devices in diversified fields.关键词：Guest-host liquid crystal;polymer template;Patterned assembly;dynamic display
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发布时间：2023-08-10 - 摘要：The contradiction between counterfeiting and forgery is deepening， and the development of counterfeiting technology with strong confidentiality， high security， and non-reproducibility has become an urgent need for social and economic development. In this context， liquid crystal anti-counterfeiting technology has become an area of great interest due to its excellent performance， high practicality， and wide market appreciation. However， the existing anti-counterfeiting technology is not rich enough in hierarchy， and the hidden graphic is only one color. Therefore， this study proposes a device structure with a dual information security layer consisting of a guest-host liquid crystal anti-counterfeiting film layer and a cholesteric liquid crystal anti-counterfeiting film layer， each layer containing different information content. Through different light patterns， different display contents can be obtained， thus achieving a multi-dimensional anti-counterfeiting effect. The design features polarization-related transmission-reflection differences and an asymmetric light response in the transmission direction compared to conventional single-layer guest-host liquid crystal anti-counterfeit film layers. The use of this easily prepared anti-counterfeit film layer overlay design not only improves the security level of the security code but also reduces the cost of application.关键词：Guest-host liquid crystal;Dichroic dyes;cholesteric liquid crystal;Anti-counterfeit;photoalignment
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发布时间：2023-08-10 - 摘要：With the development of display technology， the demand for high-performance and high-stability thin film transistors （TFTs） is increasing. The method of improving the performance of thin film transistors through crystallization has received a lot of attention. Currently， indium gallium zinc oxide （IGZO） materials are widely used in the channels of thin film transistors due to their advantages such as high mobility， flexibility， and high transparency. Improving the crystalline morphology of the IGZO channel layer has become a research hotspot. This article summarizes the research progress of crystalline IGZO thin film transistor devices， introduces in detail the crystal structure of IGZO compounds， and focuses on the structure of single crystalline， c-axis-aligned crystalline， hexagonal polycrystalline， spinel， nanocrystalline， and protocrystalline IGZO， as well as the preparation methods， device performance， and stability of various crystalline IGZO thin-film transistors. We also analyze the microstructure of crystalline IGZO， summarize the physical properties， describe the crystallization mechanism and establish the relationship between crystal structure and electrical properties. At last， the development of crystalline IGZO thin film transistor is prospected.关键词：Crystalline IGZO film;thin film transistor;crystal structure;Research progress
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发布时间：2023-08-10 - 摘要：For large size TFT-LCD displays， the black photo spacer （BPS） technology is adopted to replace the BM and PS （Photo Spacer） processes and shifted to the array substrate side in order to save the BM process and reduce panel costs. While the original BM process is the first production process， the new BPS process is located at the last process of the array. BPS exposure molding requires precise alignment using metal markers in the pre-array process to achieve fine patterns. Due to the low transmittance of BPS， it is very difficult to align the CCD by metal markers in the BPS pre-capture process. The principle of the exposure device to grasp the target is first analyzed， and then the BPS material with different transmittance is obtained by adjusting the composition of the BPS material. By exposure shaping of BPS materials with different transmittance， the minimum requirement of material transmittance during exposure alignment is studied to obtain the highest shading of BPS materials. The experimental results show that the wavelength of the NSK exposure machine alignment lamp source is located in the infrared region of 780~1 000 nm. When the transmittance of BPS material in this band is lower than 23%， the alignment fails. By using organic-inorganic mixed pigment components instead of organic black pigment components， nearly 90% transmittance can be obtained to meet the alignment requirements， and an optical density of 1.2/μm can be obtained after curing and molding to meet the shading needs of BPS products. The optical index of BPS board produced by this method is up to standard.关键词：TFT-LCD;BPS technology;Exposure process;Mark reading;transmittance
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发布时间：2023-08-10 - 摘要：In the gate etching process of thin film transistor （TFT）， there is a loading effect in the active area （AA area） and fanout area due to the difference in layout density. The etching time is difficult to determine because of the large difference in the etching degree between the two areas. It is urgent to suppress the loading effect in the Gate etching process for quality assurance. The wet etching microprocess was analyzed， and a scheme to increase the etchant spray flow rate to suppress the etch loading effect was proposed. The scheme of increasing flow rate was translated into the adjustment of the etching time ratio of the 3 etching chambers （Etch1~Etch3）. The verification of etching with different time ratios of the 3 chambers was performed with the total etching time unchanged， and the etching results were clustered and analyzed. Finally， the time ratio that suppresses the loading effect is preferably selected and the results are analyzed in conjunction with neural network. The results show that the loading effect can be suppressed by decreasing the Etch3 time ratio and increasing the Etch2 time ratio. The time ratio of Etch1~Etch3 is adjusted from 33.33%∶33.33%∶33.33% to 10%∶80%∶10%， and the difference of etching degree between AA and fanout area is decreased from 0.575 μm to 0.317 μm. By adjusting the time ratio among the three etching zones， the etching loading effect can be suppressed to alleviate the difference in etching degree in different areas to meet the TFT mass production requirements.关键词：Gate electrodes;wet etch;loading effect;cluster analysis;Neural networks
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发布时间：2023-08-10 - 摘要：This paper introduces the preparation of graphene material， the performance of graphene pressure sensor and its application prospect in wearable electronic devices. Firstly， the preparation method of graphene material is summarized， and the advantages of graphene pressure sensor in mechanical， conductive property and display are expounded. Then， the strategies of adding graphene， graphene derivatives or graphene composites to the structure of the pressure sensor to improve the performance of the sensor are investigated. Finally， it introduces the application of graphene pressure sensor in wearable electronic devices， including human behavior and health detection， human-computer interface， electronic skin and wearable display， excellent performance and prospect.关键词：graphene;pressure sensor;performance;applications;wearable electronics
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发布时间：2023-08-10
Device Physics and Device Preparation
- 摘要：In order to realize fast and high-quality image scaling on field programmable gate array （FPGA） hardware platform， this paper proposed a nine-point interpolation adaptive scaling algorithm. Firstly， in order to reduce the amount of logical resources， a basic algorithm of nine-point interpolation is proposed， the image scaling effect achieved is obviously better than the nearest neighbor interpolation algorithm but slightly worse than the bilinear interpolation algorithm， and the edge of the image is not clear. In order to optimize the scaling effect of the basic algorithm of nine-point interpolation on the edge of the image， an adaptive scaling algorithm combining nine-point interpolation and nearest neighbor domain interpolation is proposed. The algorithm software， hardware comparative analysis and experimental verification are carried out through MATLAB and FPGA. Experimental results indicate that the peak signal to noise ratio of the adaptive nine-point interpolation algorithm is 0.3~2.5 dB higher than that of the traditional scaling algorithm on average， and the hardware resource consumption is reduced by about 20% compared with bilinear interpolation. The nine-point interpolation algorithm alleviates the problems of image edge blur and severe image distortion of the traditional algorithms， and it occupies less FPGA resources and has higher application value.关键词：image scaling;field programmable gate array;linear interpolation;adaptive interpolation
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发布时间：2023-08-10 - 摘要：To address the problems of detail loss， color shift and visual quality degradation of images acquired under hazy weather， a fast dehazing algorithm is proposed for estimating atmospheric light veil based on segmental estimation of log-S type function. Firstly， the positive correlation between the atmospheric light veil and the minimum channel of the haze image is obtained by in-depth derivation on the atmospheric scattering model. Then， according to the different haze concentrations in different regions of the haze image， a segmented estimation model is constructed to estimate the atmospheric light veil of the haze image. Finally， the method of local atmospheric light estimation in the middle channel based on median filter optimization is proposed， and the haze-free image is recovered by the atmospheric scattering model. The experimental results show that the new visible edges， average gradient and information entropy of the restored image are increased respectively by 17.4%， 50.5% and 30%， the running time is 17.5% lower than that of the conventional fast dehazing algorithm. The algorithm is able to recover images with complete dehazing， natural colour and significant detail recovery.关键词：image dehazing;atmospheric light veil;log-S type function;segmentation estimation;mid-channel atmospheric light
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发布时间：2023-08-10 - 摘要：Aiming at the problems of low behavior discrimination ability and misjudgment caused by different change speeds of actors and action states and the lack of correlation research between actions in action recognition tasks， a temporal correlation attention mechanism model based on SlowFast architecture was proposed. Firstly， the optical flow was abandoned and the video data was directly used as the network input， so that the model could be trained end-to-end. Secondly， a temporal correlation attention mechanism composed of correlation attention and temporal attention was defined. The correlation attention mechanism was used to extract the correlation information between actions， and then the information was input into the temporal attention mechanism to suppress useless features. Finally， to solve the problem of the loss of correlation between features caused by the large step size of the convolution kernel in the path fusion process of SlowFast， a more effective continuous convolution operation was proposed. Experimental results on UCF101 and HMDB51 datasets show that the proposed method has advantages in accuracy and robustness compared with the existing methods.关键词：behavior recognition;SlowFast;time-dependent attention mechanism;end-to-end training;lateral connection
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发布时间：2023-08-10 - 摘要：For the problems of complex network structure design，large number of model parameters and low detection efficiency in the existing human pose estimation network pursues high-precision detection， this paper proposes a lightweight human pose estimation algorithm based on adaptive feature perception. Firstly， the lightweight Ghost module is used to reconstruct the feature extraction network of human pose estimation to reduce the computation amount of the network. Secondly， a lightweight adaptive feature sensing attention mechanism is designed to reduce the complexity of network model and enhance the effective communication between channels， which can improve the positioning effect of key points. Finally， Huber Loss（Exponential square loss function） is used to optimize the loss function training model to achieve better prediction of outliers and enhance the robustness of the model. Verified on the COCO dataset， the experimental results show that compared with the benchmark RMPE algorithm， the detection accuracy of the improved model is increased by about 0.5%， the number of parameters is reduced by 56.0%， the network calculation amount is reduced by 32.6%， the model volume is compressed by about 57.0%， and the model detection rate is increased by about 2.1 times. In this paper， the improved human pose estimation model improves the detection efficiency and enhances the robustness of the model while compressing the model volume.关键词：human pose estimation;lightweight;adaptive feature perception;ghost module;Huber Loss
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发布时间：2023-08-10 - 摘要：The tracking method based on correlation filtering has fast frame rate but is prone to tracking drift， resulting in target loss. Aimming to this problem， taking the correlation filtering method ECO-HC as the baseline， this paper proposes parameter
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发布时间：2023-08-10 - 摘要：The real-time multiple object tracking algorithms have achieved ideal tracking performance， but the tracking speed is slow，and tracking accuracy is also decreased with the increase of background complexity in most of the recent algorithms. In terms of these issues， a real-time multiple pedestrian tracking algorithm is proposed based on online data association. First of all， the dual prediction mechanism of kernelized correlation filter and Kalman filter is designed. This mechanism forms a prediction tracking calibration system with the cascade matching in DeepSORT， which makes the data correlation more reliable. In addition， the attention mechanism is introduced in the object detection part of tracking to enhance feature representation ability by strengthening position information of the object， so as to improve racking accuracy.The experiment is carried out on MOT16 dataset， the MOTA is up to 66.5%， IDF1 is up to 64.2， IDSW is 641. Compared with DeepSORT algorithm， MOTA and IDF1 increase 13% and 13.2% respectively， and IDSW decreases 410.Experimental results show that the proposed algorithm is helpful to solve the problem of object false detection， missing detection and other problems in multiple pedestrian real-time tracking. It still maintains high tracking accuracy for severe occlusion in tracking， which can achieve real-time and stable multiple pedestrian tracking in complex background.关键词：multiple object tracking;online tracking;YOLOv5;kernelized correlation filters;DeepSORT
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发布时间：2023-08-10 - 摘要：Wearing masks is an effective way for preventing COVID-19 and cooperating with the national epidemic prevention and control. An improved YOLOv7 algorithm is proposed to solve the problems such as whether masks are correctly worn， different shooting angles and being blocked. Based on YOLOv7， the convolutional attention mechanism is introduced into the Head region of the network to make the feature network more targeted in the processing of the mask region， thus enhancing the learning ability of the feature network to the mask region. The structure of Backbone area is optimized， the ConvNeXt network structure is improved， and partial convolution is introduced into the network instead， which improves the detection accuracy and robustness of the model and enhances the accuracy of prediction without introducing a large number of additional calculations. The space pyramid pool of the Head layer is improved to improve the training speed and accelerate the model convergence. Experiments show that in the case of complexity and occlusion， the loss function of the improved YOLOv7 decreases significantly， and the mAP on the test set is 93.8%， which is 3.6% higher than that of the original YOLOv7 algorithm.The accuracy of each category is improved， and the accuracy of no mask， correct mask and incorrect mask are increased by 6.8%， 2.1% and 1.7%， respectively. The cases of error detection are significantly reduced， and the generalization ability is significantly improved.关键词：image processing;object detection;YOLOv7 algorithm;convolutional attention mechanism;space pyramid pooling
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发布时间：2023-08-10
Image Processing
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