摘要:Cellulose nanocrystals (CNC) are prepared by hydrolysis of cellulose catalyzed by sulfuric acid. According to the source and hydrolysis conditions of cellulose, the diameter of the nanocrystals is about 5~15 nm and the length is about 100~300 nm.CNC organizes into chiral nematic liquid crystals in water. When dried into a thin solid film, the CNCs retain the helicoidal chiral nematic order and assemble into a layered structure. In the process of CNC self-assembly, it is possible to add sol-gel precursors, such as Si(OMe)4. With the evaporation of solvent, these precursors undergo hydrolysis and condensation, leading to a chiral nematic silica/CNC composite material.In addition, porous, rainbow colored organic silica or titanium dioxide films are also obtained using this methods. These thin films can be used as filters, reflectors, and membranes. The most important thing is that the synthesized chiral mesoporous silica can be used as a chiral chromatographic stationary phase material to separate chiral drugs. The results shows that the effect of chiral separation is remarkable, providing a new method for the development of chiral new materials based on CNC.
摘要:The modulation of azimuth and pretilt angle of liquid crystals (LCs) is widely used in the study of various liquid crystal photonic devices. Comparing to unstability and unreliability of small molecule LC devices fabricated by pretilt angle modulation, LC polymers have some prominent advantages like high phase transition temperature, heating and glaring resistance, stability of mechanical vibration, and so on. Since the LC monomer is affected by the anchoring energy at the interface between LC and air, the pretilt angle of LC polymers is related to the thickness of the LC layer, which makes it difficult to achieve a stable and controllable pretilt angle. In this study, a two-step exposure of azo-dye bright yellow (BY) film was used to guide the tilt of LC monomer RM257, and the effect of the anchoring force at the LC-air interface was reduced by using multilayer spin-coating process and the photopolymerization of LC monomer RM257. Through the controllable preparation of pretilt angle of the LC polymers, it shows that the range of pretilt angle can be continuously adjusted between 0° and 16° with the photo-thermal stability and the potential patterning capability for LC photonic devices. This study is expected to provide a new way for the preparation of LC photonic and display devices.
摘要:In this paper, a three-layer liquid crystal polarization grating is designed and implemented, and its diffraction characteristics and coupling in optical waveguide are studied. In theory, the transverse period of 424 nm is selected, and the corresponding three longitudinal periods is calculated according to the specific working wavelength of 450 nm, 532 nm and 633 nm to achieve the superposition of the thickness direction under the condition of Bragg diffraction. Secondly, the finite element method is used to simulate the device. Finally, the relationship between the incident angle and the diffraction angle coupled in the waveguide is simulated according to the red, green and blue light dispersion relationship. The liquid crystal polarization grating device is fabricated and its system performance is characterized. A preliminary optical waveguide coupling experiment is given to demonstrate its coupling effect. The results show that the diffraction efficiency of the prepared three-layer liquid crystal polarization grating device can reach more than 80% at 450 nm, 532 nm and 633 nm, and the angular bandwidth of the corresponding wavelength is 12°, 8° and 6°, respectively. The field of view of the device coupled in the waveguide can reach 27.81° by simulation, which is a good optical waveguide coupler.
摘要:Flexible display is an important research direction in the field of display, in which electronic paper is one of the ideal carriers for flexible display. Compared with other flexible e-paper display technologies, electrowetting display has the advantages of low energy consumption, comfortable outdoor viewing, fast response speed, wide color gamut and easy to realize flexibility, etc., so it is very promising for development. The display principle, preparation process and research status of flexible electrowetting display are systematically introduced. At the same time, the future development of the flexible electrowetting display is also prospected, and the development status and future direction are clarified. At last, the problems that still need to be solved for the flexibility of electrowetting e-paper are summarized, and the direction for the future development of flexible electrowetting e-paper display technology is pointed out.
关键词:flexible display;electronic paper display;reflective display;electrowetting display
摘要:Thin-film transistor (TFT) based on metal oxide semiconductor (MOS) has become a key technology to boost the development of the flat panel display or flexible display industry due to their high field-effect mobility (μFE), extremely low cut-off leakage current and good large-area electrical uniformity. After more than 30 years of research, amorphous indium gallium zinc oxide (a-IGZO) is the first to be popularized in TFT by replacing the amorphous silicon (a-Si). However, in order to simultaneously meet the multiple upgrade requirements of the display industry for higher productivity, better display performance (such as high resolution, high refresh rate, etc.) and lower power consumption, MOS TFTs technology with higher mobility is required. From the perspective of solid-state physics, this paper reviews the research progress of MOS TFTs to achieve high mobility characteristics through multi-component MOS materials, and discusses the relationship between mobility and device stability. Finally, the status quo and development trend of MOS TFTs are summarized and prospected.
摘要:Ultra-large IGZO (InGaZnO) products were prone to Abnormal Display (AD) during reliability evaluation at high temperature and humidity (50 ℃/80%). The main reason was that the key device’s (M2) transfer characteristic curve (IDS-VGS) of GOA (Gate Driver on Array) had a serious positive shift in the evaluation. In this paper, the real working environment of GOA’s key device(M2) was simulated by pulse experiment, and the bad phenomenon of serious positive shift of transfer characteristic curve was reproduced. By setting different pulse experiments, the main influencing factor was revealed. When the device(M2) was turned off, the VDS (pressure difference between Drain and Source) was too large, so that the oxygen vacancy in the IGZO layer migrated to the boundary of IGZO and GI (Gate Insulator) and to the Source at the same time under the electric field. Due to the electrons trapping effect of oxygen vacancy , the transfer characteristic curve would eventually shift positively. It was found that the migrated oxygen vacancy can be restored after heating. In addition, without changing the IGZO film forming conditions, by reducing the VDS pressure when the device(M2) was turned off, the ultra-large IGZO product did not occur AD defects during the reliability evaluation at high temperature and humidity for 2 000 h.
关键词:InGaZnO thin film transistor;gate driver on array;abnormal display;threshold voltage shift
摘要:A novel scanning strategy——centralized fusion (CF) scanning is proposed to address the visual perception issues encountered in OLED-on-silicon microdisplay driven digitally, especially the dynamic false contour(DFC) and flickering phenomena. This strategy incorporates the concepts of grayscale weight redistribution and the integration of subfields. It improves the quality of display images by reallocating the number and weights of integer subfields, and by positioning the integrated subfield at the midpoint of the modulation cycle. Experimental results indicate that the CF scanning approach achieves an approximate 13% increase in peak signal-to-noise ratio and a 10% reduction in mean square error compared to traditional scanning methods. Moreover, the structural similarity index score approaches 1, significantly surpassing existing scanning techniques. CF scanning outperforms the 19-subfield scanning method in JEITA flicker assessment, with a reduction in flicker quantification value by about 22%. The CF strategy offers an effective solution for enhancing the image display quality of digital-drive OLED-on-silicon microdisplay, paving the way for future research and innovation in display technology.
摘要:In the enhancement processing of real-time image, in addition to ensuring the high contrast of single frame image, the real-time performance of the processing algorithm and the coherence of the enhancement effect between image sequences should be considered.Gray-scale equispacing density equalization algorithm can effectively enhance image contrast by removing redundant gray level and rearranging effective gray level equispacing. In this paper, based on the gray-scale equispacing density equalization enhancement algorithm, the effective gray level effective threshold selection, excessive enhancement and other problems are improved accordingly, in order to meet the real-time enhancement processing requirements of continuous image sequences. Experimental results show that the improved algorithm can effectively avoid the influence of local changes on the overall enhancement effect. For 1 920×1 080 resolution images, the processing time of single frame is about 32 ms. The improved algorithm has good enhancement effect on continuous image sequence, and can better meet the processing requirements of real-time image enhancement for coherence, real-time performance and robustness.
关键词:real-time image enhancement;gray-scale equispacing density equalization;histogram
摘要:To investigate the feasibility of diffraction neural network to perform multi-task image classification recognition, a diffraction neural network system is designed and built. The system uses a spatial light modulator (SLM) to modulate the phase and amplitude weights of the diffraction neural network and the optical full connection of the network layers. A CMOS camera is adopted to realize the optical nonlinear activation of the output of each diffraction layer in the diffraction neural network and discriminate the output image recognition results. The designed system model achieves 94.1% and 92.1% accuracy in MNIST and Fashion-MNIST image classification recognition. Finally, by building optical path system, optical experiments have 91% and 81.7% accuracy respectively, which verifies that the designed diffraction neural network system can meet the requirements of various image classification and recognition applications, and provides a new idea for the design and construction of diffraction networks.
摘要:To address the difficulties of capturing the potential distinguishable features and subtle appearance differences in fine-grained image recognition tasks, dual-attention random selection global context fine-grained recognition network is proposed. Firstly, the ConvNeXt is taken as the backbone network, a dual-attention random selection module is proposed to perform channel random selection and spatial random selection on the features extracted at different stages, so that the network could focus on other potential subtle distinguishable features. Then, by using the global context attention module, the semantic information of top-level is applied to the middle-level to enhance the ability of the middle-level to locate potential subtle distinguishable features. Finally, the multi-branch loss is proposed, and classification loss is imposed on middle-level, top-level and concat-level characteristics. Combining the features extracted from different branches, the network is induced to obtain diverse distinguishable features. The network achieves the accuracies of 95.2%, 92.1%, 94.0% and 97.0% respectively on the three open datasets,Stanford-cars,CUB-200-2011,FGVC-Aircraft and dataset VMRURS in real scenes. The presented method in this paper greatly upgrades the comparison performance.
关键词:Fine-grained recognition;ConvNeXt;Dual-attention random selection;Global context attention;Multi-branch loss
摘要:At present, facial expression recognition methods have the problems of large number of parameters, large consumption of computing resources and low recognition accuracy. Aiming at the above problems, a lightweight human facial expression recognition method based on conditional coordinated attention mechanism is studied. First, the number of layers of MobileNet V3 network is reduced, while the numbers of intermediate channels and output channels of the inverse residual structure are increased to 1.5~3.2 times of the original number. Mish is used instead of Hardswish activation function to realize the nonlinearization after feature extraction. Secondly, an improved coordinated attention mechanism is introduced to encode the tensor information embedding along horizontal and vertical directions sequentially by maximum pooling and average pooling. And tensor information integration is used to generate features with global sensory field and precise location information to extract detailed information of facial expressions in space and channel location. Finally, experiments are conducted on the publicly available datasets FERPlus and RAF-DB, and the results show that the proposed method reduces the number of parameters by 15.91%, and the accuracy rates are 88.84% and 85.90%, respectively, which are 0.83% and 1.39% higher than the accuracy rates of the model before improvement. The method has good recognition performance and validate the effectiveness of the proposed method.
摘要:Object tracking for the unmanned aerial vehicle (UAV) in videos is an important part of the Anti-UAV task. The complex background during low-altitude flight and the small imaging size are two difficulties for UAV object tracking. A Siamese neural network object tracking algorithm (SiamAU) is proposed, which is based on SiamRPN++ in combination with an improved backbone and a feature rearrangement technique. Firstly, ECA-Net attention module is integrated into the backbone network, while the activation function is improved to enhance the representation ability of convolution features in complex background. Then, channel number of the last three convolution features is rearranged in order to make full use of low-level features that are conducive for small object tracking. The rearranged feathers are further fused to obtain the improved feature map. Finally, On the DUT Anti-UAV dataset, SiamAU algorithm achieves success and precession scores of 60.5% and 88.1%, an improvement of 5.6% and 8.1% in comparison with the baseline algorithm. Extensive experimental results on two public datasets validate that the proposed SiamAU achieves better UAV tracking performance and outperforms previous methods, especially in small object and complex background scenarios.
摘要:Aiming at the problem that the existing lane detection algorithms are difficult to balance the detection accuracy and speed in practical application, a new lane detection algorithm based on ARM embedded platform is proposed. Firstly, a lightweight semantic segmentation network is designed. When SegNet structure is optimized, skip connections are added to the first layer of the network, and channel attention mechanism modules are added after every two convolutional layers to ensure detection accuracy and improve detection speed. Secondly, Kalman filter lane tracking model is constructed to improve the robustness of detection in video streams. Then, the encoder is reconstructed and the model is lightweight. The deep separable convolution is used instead of the traditional convolution to reduce the calculation cost and improve the detection speed. Finally, the Trt model is generated by TensorRT accelerated reasoning to facilitate its deployment in ARM embedded platform for real-time lane detection. Experimental results on the self-produced Tusimeple extended data set show that the proposed algorithm can cope with various complex traffic scenarios, and its detection accuracy is 98.03%, which is superior to other algorithms. And its detection speed reaches 50 FSP, which meets the real-time detection requirements. This algorithm has high robustness and good real-time performance in complex traffic scenarios, and has certain theoretical and practical value.