最新刊期
期 9 ， 2021
- 摘要：In order to explore the sensitivity of the polymer film with one-dimensional periodic helical structure to the solution, a manner molded by cholesteric liquid crystal(CLC) is utilized for producing the chiral porous polymer film, and then the research is carried out through permeating the solution mixed by diverse proportions with nematic liquid crystal and different organic solvents into the film. The results indicate that the polymer film responds to the solution and exhibits selective reflection, which is attributed to the shape memory effect and the strong interface anchoring force of the polymer network. The reflection band shifts up to 140 nm owing to the difference in average refractive index of mixed solutions with different ratios of liquid crystal and solvent. In addition, it is also obvious that the type of solvent makes difference to the reflection band of the film when the solvent is mixed with the same proportion of liquid crystal. Specifically, the refractive index of the selected butyl acetate solvent is only 0.03 lower than that of butyl lactate, however, the central wavelength of the reflection band is approximately 20 nm larger than that of butyl lactate. Further experimental characterization and analysis manifest that the swelling degree of the polymer film varies with the discrepancy of solubility parameter between solvents and the polymer film, that is, the closer the solubility parameters are, the easier it is for the solvent to diffuse into the polymer and make its volume expand, resulting in the pitch elongation and consequent redshift of the reflection band. Therefore, the flexible reflective film is solution sensitive.关键词：cholesteric liquid crystal;helical structure;polymer film;solution sensitive
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发布时间：2021-09-10 - 摘要：In recent years, the research of liquid crystal in microwave communication devices has developed rapidly, and the dielectric loss of liquid crystal materials has become the main factor restricting its development. The isothiocyanate terphenyl compound is a low-viscosity, high-birefringence liquid crystal compound with stable structure, which is suitable as a component of liquid crystal material for microwave. In this paper, four fluorine-containing terphenyl isothiocyanate liquid crystal compounds nPGUS (n=2~5) were synthesized by coupling method, and the structure of the compounds was confirmed to be correct by IR, 1H NMR, 13C NMR, and 19F NMR. Differential thermal analysis (DSC) results show that they all have a wide-temperature nematic liquid crystal state and a relatively low melting point. The nematic temperature range of 5PGUS reaches 101.8 ℃, and the melting point is only 57.4 ℃. Their dielectric properties of LC in the microwave K bands were tested by the vector network analyzer, and they are mixed with the matrix liquid crystal, the dielectric constant value at 18 GHz (Δεr) is 0.95, the dielectric loss (tanδεr-max) 0.007 63, dieletric tunability coefficient (τ) 0.265, which can satisfy the performance requirements of nematic liquid crystal materials for microwave use.关键词：fluorinated terphenyl;isothiocyanate liquid crystal;high dielectric constant;low dielectric loss;synthesis
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发布时间：2021-09-10
Material Physics
- 摘要：Polymer stabilized liquid crystals (PSLCs) are a class of liquid crystal/polymer composite materials containing a small amount of polymer network. Due to their good optical properties and field responsive characteristics, they can be used as electronic paper, smart windows, sensors and other devices. In recent years, with the pressure of energy supply and the actual need of environment protecting, the importance of smart windows has gradually been highlighted. As the important of the branches, there is a variety of classification of PSLCs-based smart windows depending on the different response mode. In order to further improve their optical properties and enrich its field regulation styles, many researches have been carried out recently from the aspects of nano-particle doping, dye doping and polymer network structure improvement, etc. In this paper, the research progress of PSLCs-based smart windows in the past few years is reviewed and discussed, and the future development trend of PSLCs-based smart windows is forecasted.关键词：polymer stabilized liquid crystals;smart windows;external-field switching;energy saving
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发布时间：2021-09-10 - 摘要：To meet the requirement of low signal delay of the large-size printed display, it is necessary to develop low-resistance printed electrodes for oxide thin film transistors(TFTs). It is found that the interface contact between inkjet-printed Ag and the active layer is poor, which leads to the poor electrical performance of oxide TFT with the Ag electrode. By inserting inkjet-printed indium tin oxide (ITO) electrode between the Ag electrode and the active layer, the diffusion of Ag nanoparticles in the active layer can be blocked. In addition, the ITO electrode can form good contact characteristics with Ag and the active layer, greatly reducing the contact resistance. The performance of TFT based on Ag/ITO double-layer electrodes is significantly improved compared with that based on single-layer silver electrode: mobility of 16.0 cm2·V-1·s-1, switching ratio of 6.2×107, subthreshold swing of 174 mV/Decade, and threshold voltage of -2.0 V. The results demonstrate the application potential of printed Ag electrode in oxide TFT, and contribute to the establishment of a composite conductive film system of stacked structure of metallic conductive nanomaterials and conductive oxide film, realizing complementary advantages.关键词：TFTs;oxide semiconductors;inkjet printing;double-layer electrodes;Ag electrode
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发布时间：2021-09-10 - 摘要：The effect of the compatibility of monomer and liquid crystal on the surface composition of the polymer wall was explored, and the effect of the surface composition on the optoelectronic properties of polymer wall liquid crystal devices and its control method were investigated. Monomers with a large difference in compatibility with liquid crystals but similar surface energy are selected. Polymer films delaminated with liquid crystals are formed by surface initiation, and the polymer are etched to different depths by reactive ion etching after washing away the liquid crystals. The components of the polymer layer with different etching depths were characterized by Attenuated Total Reflection and X-ray photoelectron spectrometer. Polymer wall liquid crystal devices were prepared and the effect of polymer surface composition on their optoelectronic properties was investigated. The experimental results indicate that polymer components with high compatibility with liquid crystals are enriched at the polymer-liquid crystal interface, and the lower the polymerization light intensity, the more pronounced the bias effect of such components. When the polymerization light intensity is low, PTFEMA component in the polymer surface composition is 68.5%, which is 10.6% more than that at high light intensity. This resulted in a difference in the optoelectronic properties of the polymer wall liquid crystal devices prepared at different polymerization light intensities, with a threshold voltage of 0.879 V at a light intensity of 10 mW/cm2 and an increase to 1.172 V at 70 mW/cm2 light intensity. Polymer wall surface composition can be regulated by the compatibility difference between the monomer and the liquid crystal and the light intensity, which could influence the photoelectric performance of the liquid crystal device.关键词：surface composition;surface initiation;polymer wall;optoelectronic properties
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发布时间：2021-09-10 - 摘要：Traditional electrostatic measuring instruments have the disadvantages of high cost, low accuracy and complex operation. In this paper, a simple measurement based on the photoelectric effect of liquid crystal materials is proposed. The liquid crystal device has multiple layers of substrate. High and low pressure areas can be measured simultaneously. The device and system realizing this method are given in this paper. Then, the calibration of the liquid crystal device is realized by inputting the known variable voltage. Finally, the human body is used for the actual measurement and another set of voltage is applied to calculate the measurement error, which is calulated to be 9%. The measuring device mostly meets the requirements of convenience, stability and high precision of electrostatic measurement.关键词：liquid crystal device;electrostatic measurement;electro-optical effect
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发布时间：2021-09-10
Device Physicsand Device Preparation
- 摘要：Wide color gamut and low power TFT-LCD are prone to peripheral powdering during high temperature and high humidity operation test, which seriously affects the visual effect. In this paper, the transmittance deviation of the Mini Cell and the starting time of pink Mura of the TFT-LCD samples with different green color resin, active layer and flat layer during the high light, temperature and humidity environment are studied. Experimental results indicate that the root cause of pink Mura is Y pigment with non-metallic complex molecular structure in green color resin, and the Mura degree is also related to the TFT-LCD's frame and the water absorption of active layer and flat layer. Based on the no loss of material transmittance, the water vapor penetration into the effective display area of TFT-LCD is effectively reduced by using the green color resin with high hydrophobicity and high hardness and the flat layer with low water absorption, then improve the pink Mura of TFT-LCD to 1 000 h and 500 h for a-Si and a-IGZO TFT-LCD, respectively. Through the pink Mura improvement and mechanism analysis, the RGB color resin component management standard and the Fab./Lab. evaluation system of the pink Mura are established.关键词：TFT-LCD;pink Mura;green color resin;pigment;Förster resonance energy transfer
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发布时间：2021-09-10 - 摘要：With the operation of color filter production line for several years, the sublimation of pre-baking process brings serious equipment and glass substrate pollution, which can easily lead to the failure of exposure process and cost waste. In order to solve this problem, the composition analysis and improvement of sublimation in pre-baking process are carried out for red, green and blue production lines in 8.5 generation line. Sublimation is derived from photoresist. By replacing monomers and photoinitiators with small molecular structure with molecular weight between 190 and 300 into monomers and photoinitiators with macromolecular structure with molecular weight between 380 and 600, the improved photoresist is obtained, and the thermal sublimation of red, green and blue photoresist is successfully reduced by 91.8%, 98.5% and 93.1%, respectively. The optical properties and reliability of the improved photoresist are satisfied. After mass production, the exposure failure rate of glass substrate caused by pre-baked sublimation was reduced from 3 500×10-6 to 1 600×10-6. In the course of this study, a quantitative evaluation index of pre-baking sublimation of photoresist material is proposed, which can be applied to the development and selection of photoresist, and has reference significance for the long-term stable operation of production line.关键词：color filter;pre-bake;sublimation;photoresist
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发布时间：2021-09-10
Display Technologyand Applications
- 摘要：Image fusion is to fuse the complementary images under different acquisition conditions or sensors for improving the visual quality of images. For this task, this paper proposes an improved multi-scale fusion algorithm based on the combination of rolling guided filtering and neural network. Firstly, the siamese convolutional neural network is used to learn the image features and further obtain the weight map containing the significant features of the source image. Then, the image is decomposed by the improved rolling guide filter, and the weight parameters of the rolling guide filter are adaptive to achieve multi-scale adaptive decomposition by combining the information entropy, and the details of the image are enhanced by combining the nonlinear mapping. Finally, based on the local energy and weight map, an adaptive fusing strategy is designed to combine the multi-scale images adaptively. The experimental comparison shows that the proposed method can avoid the halo effect of image edge and better highlight the edge and detail texture features of image. In addition, compared with other algorithms, our algorithm can achieve a better performance according to the objective evaluation index items, such as average gradient, information entropy, visual information fidelity and spatial frequency.关键词：image processing;siamese convolution neural network;image fusion;rolling guided filtering;multiscale image
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发布时间：2021-09-10 - 摘要：Due to poor medical image quality, low contrast, large differences between patients, it is difficult for fully automatic segmentation methods to obtain sufficiently accurate and robust results. In order to solve the limitations of the automatic segmentation method, this paper proposes an improved region growing method based on neural network, and combined with the fully convolutional neural network to interactively segment liver CT images. Firstly, the image is preprocessed to highlight the liver area to be segmented. Then, the gradient value of the pixel under different edge detection operators is calculated as the feature of the pixel to form a pixel feature vector training network. The network takes a pair of pixel feature vectors as input and the correlation coefficient of two pixels as output. Then, the trained neural network model is used as the growth criterion of the region growing algorithm, and a point is manually selected interactively to generate the segmentation result. Finally, the segmentation result is connected as the interactive information of the original image and the gray channel of the original image and input into the full convolutional neural network. The experimental results show that the average Dice coefficient reaches 96.69%, the pixel accuracy rate reaches 99.62%, and the average intersection ratio reaches 96.65%. The results of liver segmentation in different abdominal CT image sequences show that this method can accurately extract liver regions and meet the needs of clinical applications.关键词：fully convolutional neural network;region growing method;interactive segmentation
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发布时间：2021-09-10 - 摘要：The current colorization algorithms generally suffer from color boring, color bleeding and detail loss. In order to address these problems, this paper proposes a adversarial colorization algorithm combined with global semantic optimization. The generator adopts the improved U-Net network. On the one hand, the improved U-Net gradually obtains multi-scale features and global feature by multiple convolution during the downsampling process. At the same time, the global feature and multi-scale features get adaptive fused in the skip connections, thus it can effectively enhance algorithm's ability to understand global semantic and ease the color bleeding. On the other hand, the improved U-Net network integrates the channel attention module in the upsampling process, which can effectively suppress the noise and reduce the feature redundancy when the convolutional features are extracted. The discriminator mainly adopts full convolution structure and achieves the purpose of optimizing the generator by reverse error transfer. In addition, the loss function combines the optimization idea of WGAN-GP with color loss to solve the gradient disappearance and mode collapse problems in the training of traditional GAN. The proposed algorithm is tested on Place365 test set, and the PSNR, SSIM and IE indexes are 24.455 dB, 0.943 and 7.489, respectively. The test results show that the proposed algorithm can alleviate color bleeding, and has certain advantages in detail retention and color saturation.关键词：global feature;channel attention module;WGAN-GP;image colorization
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发布时间：2021-09-10 - 摘要：In order to extract the texture features of finger-knuckle-print image and improve its recognition accuracy, a new method of finger-knuckle-print recognition based on improved Gabor wavelet and tetrolet is proposed. Firstly, the fused amplitude features of the neighboring pixels are used to represent the Gabor amplitude features of the point to enhance the local correlation between each pixel. Secondly, the filtered fingerprint feature image is transformed by tetrolet with high sparsity to obtain the optimal sparse representation of the image. Finally, band limited phase-only correlation is used to extract the cross power spectra of finger-knuckle-print image for matching. The correct recognition rate of PolyU-FK, PolyU-CFK and IITD database are 99.1300%, 98.8324% and 98.7937%, respectively. The lowest equal error rate is 1.4601%, and the shortest recognition time is 0.043 2 s. The method proposed in this paper can improve the performance of the recognition system, and is feasible and effective.关键词：pattern recognition;Finger-knuckle-print recognition;Fused Pixels;Gabor-Tetrolet;Band-Limited Phase-Only Correlation
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发布时间：2021-09-10 - 摘要：In view of the security and social problems caused by the unauthorized flying of civil UAV, a real-time detection system of UAV target based on a turntable and high-definition visible light camera is built firstly, and a sample database composed of 40 000 UAV images is constructed. Secondly, in order to find targets farther and earlier, a smaller scale of the feature map is added on the basis of YOLOv3 model to improve the detection effect of smaller targets. Finally, a model based on the combination of smaller feature scale for YOLOv3 and KCF model is proposed to detect and track UAV targets automatically, and the selection of the threshold corresponding to target loss in UAV tracking process is determined through field tests. Results demonstrate that the recognition rate of the modified model is 5% higher than that with YOLOv3 model on small targets in the test set composed of 8 000 UAV images including DJI Mavic pro, Phantom 3,etc. For 1 280×720 resolution video tests, the detection time of each frame is 0.025~0.030 s (33 fps), and according to the selected threshold, when the UAV target is lost, it can be detected automatically, with the tracking time of each frame 0.010~0.012 s (85 fps), which verifies the effectiveness of the proposed method, and meets the needs of real-time processing in engineering applications.关键词：counter-UAV;EO detection;deep learning;YOLOv3 model;KCF model
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发布时间：2021-09-10 - 摘要：In industrial production, there is a higher precision requirement for pin detection. In view of the burr phenomenon, holes, outliers and a large number of different types of noise in point cloud data, this paper proposes a method to extract the pin tip plane in three-dimensional space using structured light technology. First of all, rough extraction of point cloud is carried out by geometric characteristics and through filtering. It can locate the target point cloud quickly and remove a large number of non-target point clouds and outliers accurately. Then, the target point cloud is indexed by KD-tree, the Euclidean distance clustering segmentation algorithm is used to segment the number of point clouds. It can stably and effectively remove small-scale noise near the target point cloud. Finally, the angle is judged between the vector of the target point cloud and the normal vector of the reference plane. It can remove the uneven noise in the target point cloud effectively and accurately. The experimental results show that this method can not only remove the noise of the pin point cloud data accurately, but also extract the pin point coordinates accurately. The standard deviation of the pin height measurement in different directions is within 0.005 mm. The method proposed in this paper is generally applicable to the extraction of flat pin tip with high precision, high speed and good robustness.关键词：electronic connector;point cloud segmentation;euclidean cluster;normal vector estimation
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发布时间：2021-09-10
Image Processing
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