最新刊期
期 3 ， 2011
- 摘要：A series of 1,2-bisubstituted ethane's liquid crystals containing polyfluorophenyl group were synthesized from penta-fluorobromobenzene and aliphatic aldehydes.Their phase transition behaviours were studied by DSC and thermal polarizing microscopy.The results showed this series of compounds have high clearing point and wide temperature range of nematic phase.The phase transition temperature is lower when the alkyl chains of compounds become longer.
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发布时间：2020-08-12 - 摘要：Six asymmetric bent-core liquid crystals with different aromatic rings containing azo linkage were synthesized. Their chemical structures were confirmed by 1H NMR and HRMS spectra and the liquid crystalline property was studied with polarizing optical microscopy and differential scanning calorimeter. All of the synthesized compounds exhibit liquid crystalline phases and the compound containing three aromatic rings has nematic phase at low temperature. The absorption spectra of the azo-benzene groups display a high-intensity π-π* transition at about 330~360 nm and a low-intensity n-π* transition at around 430~450 nm. The result that the three ring compounds have longer π-π* transition absorption waves than those of the four and five ring compounds may be caused by the bent shape of the molecules.关键词：asymmetric;azo;bent-core liquid crystal;nematic phase;UV-Vis absorption
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发布时间：2020-08-12 - 摘要：Rod-shaped thiocyanic compounds based on a 4-benzoyloxy-biphenyl mesogen were prepared by nucleophilic substitution with a thiocyanic salt. The number of carbon atoms in one terminal alkyloxy chain was 6, 8 and 10. The mesomorphic properties of the synthesized compounds were characterized by means of polarized optical microscopy and differential scanning calorimeter. The results demonstrated that the thiocyanic compounds exhibited thermotropic smectic A and nematic phases. The isotropic point of the liquid crystals decreased with the increase in length of the terminal alkyloxy chain.关键词：thiocyanic compound;rod-shaped molecule;smectic A;nematic
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发布时间：2020-08-12 - 摘要：Under specific property of titanium dioxide and 4-vinylpyridine, titanium dioxide multi-core and poly(divinyl-benzene-styrene-4-vinyl pyridine) shell hybrid composite spherical and smooth particles were prepared in methanol by precipitation polymerization. DSC and TG had detected polymerizing effect, structure unit of polymer was confirmed by FT-IR, and SEM took photographs of composite microsphere. As a result, the stable spherical and smooth particles were obtained. The corresponding mechanism was confirmed by SEM photographs and changing some parameters of core/shell microspheres prepared in a series of methods. The dispersing order and amount of 4-vinylpyridine dominated the mechanism of forming composite spherical particle. Then, the electrophoretic property of the composite particle was verified with a quaternary ammonium salt combined with hydrocarbon bromide and pyridyl covered on the surface of microsphere prepared in methanol by precipitation polymerization.关键词：synthesis;core-shell polymers;crosslinking;pigments;interfaces
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发布时间：2020-08-12 - 摘要：Graphene, as a multifunctional two-dimensional nanomaterial, has inspired the considerable interests on its application in novel nanodevices. In this paper, the optoelectronic function of the complexes of typical semiconductors and graphene was reviewed based on the graphene's advantages of transmission, flexibility, turnable energy bandgap, and high electron mobility. It presented the representative application of graphene in inorganic and organic light-emitting diodes, solar cells, and nanogenerators. It is expected that graphene would play an important role for further nanometer sized electronic and photonic devices in the post-Mole era.关键词：graphene;light-emitting diode;solar cell;nanogenerator
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发布时间：2020-08-12 - 摘要：Based on the V-shaped molecule of biaxial nematic liquid crystal, a model of symmetric Y-shaped molecule is developed. In this model the Y-shaped molecule is abstracted to three linked rod-like arms. Using a simple biaxial molecular interaction model in nematic liquid crystal, the interaction energy between two molecules is obtained by the superposition of all rod-to-rod interactions. With the mean field approximation, the free energy of the system is derived and the result shows that the free energy is the function of order parameters. The relationship between the Y-shaped molecule and its ability to form a biaxial nematic phase is established. And phase transitions from isotropic to uniaxial nematic (NI phase transition) and from uniaxial to biaxial nematic(IB phase transition) are obtained.关键词：nematic liquid crystal;Y-shaped molecule;phase transition;mean field theory
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发布时间：2020-08-12
Material Physics & Chemistry
- 摘要：Polymer dispersed cholesteric liquid crystal (PDCLC) films are prepared by means of ultraviolet (UV) induced phase separation. The effects of UV cure power and UV cure temperature on morphology of PDCLC have been studied in detail, the relationship between morphology of PDCLC and reflectivity has also been studied. The results show that low UV cure power allows complete phase separation, large LC domains size and smooth interface between polymer and LC. Strong UV cure power results in a rough interface which also decreases the size of LC domains and reflectivity of PDCLC films. But the relationship of PDCLC morphology and UV cure temperature is complex. At low UV cure temperature, LC dispersed as circular droplets in polymer matrix. The size of LC domains become bigger which yield adjacent and uniform layers of LC and polymer when the UV cure temperature is up to 40 ℃. Higher UV cure temperature causes a type of three-dimensional polymer network structure in which LC is dispersed. Reflectivity of PDCLC films is up first and down later with UV cure temperature increasing. In this paper, the PDCLC films prepared with UV cure power 0.01 mW/cm2 and UV cure temperature 40 ℃ exhibit max reflectivity of 32.2%.关键词：polymer dispersed cholesteric liquid crystal;phase morphology;electro-optical property
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发布时间：2020-08-12 - 摘要：Mixed mode twisted nematic(MTN) characterized by excellent color dispersion effect and low driving voltage is used in liquid crystal on silicon(LCOS). Based on MTN mode, the influence of LCD parameters on LCOS display were simulated in this paper, such as the elastic constants, dielectric constant, pretilt angle and cell gap, et al. The simulation results can provide scientific basis for the research of LCOS.关键词：LCOS;MTN;simulation
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发布时间：2020-08-12 - 摘要：An electrode structure for local dimming was presented in this article with a newly developed co-planar type mercury free flat fluorescent lamp (FFL), which showed a large operating margin, high luminance and high luminous efficacy in the case of unipolar driving. Furthermore, the dimming circuit and method were presented and a 81 cm (32 in) FFL prototype was built and verified. The experiment results show that a local dimming can be implemented horizontally and vertically with the proposed electrode structure by pulse density modulation (PDM) method or frequency modulation method. It also demonstrates that the power consumption can be reduced since the light output of FFL can be controlled. The power varied with brightness from 100% of the max power consumption 256 W to 6% of the max power consumption, the luminous efficacy increased as the luminance decreased, a max system efficiency about 29 lm/W could be obtained when the luminance decreased to 400 cd/m2 and a dimming range about 100%~6% can be achieved by using the proposed method.关键词：flat fluorescent lamp;local dimming;luminance;luminous efficacy
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发布时间：2020-08-12 - 摘要：The temperature field of 119.4 cm(47 in) LED backlight unit was analyzed by finite element method. As a result, the efficiency of Al back cover is better than that of EGI one over 20%. Comparing the calculation result with the real temperature, the relative error is only 1.65%.The experimental results show that the temperature field analysis method for LED backlight unit is feasible.关键词：light-emitting diode;backlight unit;temperature field;thermal analysis
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发布时间：2020-08-12 - 摘要：The impact of the LC dropping amount on the LC leak and cold bubble in the ODF process was researched, and the safe scope of the LC dropping amount was found out. Then, a new method to realize the ODF and PS linkage was developed, which can effectively solve LC leak and cold bubble problem of PS production in the ODF process.关键词：LCD;ODF;PS;LC leak;cold bubble
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发布时间：2020-08-12 - 摘要：Laser projection display has advantages over traditional projection technologies, such as extended color gamut, greater colors saturation and low power consumption. It is regarded as a promising generation of full-color projection display technology. This paper investigated related patent documents from the State Intellectual Property Office of the People's Republic of China, United States Patent and Trademark Office and European Patent Office during the year of 2001~2010. The technology overview and future trend of laser display were discussed based on the analysis of 5 898 laser display patents.关键词：laser display;large color gamut;patent database;statistical analysis
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发布时间：2020-08-12
Device Technology & Physics
- 摘要：A image scaling and timing control scheme based on active matrix organic light emitting display(AMOLED) with RGB×640×480 resolution(VGA) is proposed in this letter. To achieve a high quality image and fewer hardware resources, the edge-based algorithm was adopted in horizontal interpolation and bilinear algorithm in vertical interpolation; Without off-chip memory, the time for writing panel was extended by 'horizontal black time’ which stems from image scaling down. Experiments based on FPGA effectively demonstrate that the scheme can realize the dynamic video display on VGA AMOLED with 64 gray scales.关键词：image scaling;AMOLED;FPGA
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发布时间：2020-08-12 - 摘要：According to the fact that portable instrument has more and more reliance on colo-rized LCD displaying devices, a TFT-LCD real-time display controller is designed in this paper. The controller adopts FPGA chips as its hardware core, which is a product XC3S400 of Xilinx Corporation, and embedded 8051 IP core is used as its time control kernel. Internal block RAM resource of FPGA is introduced to initially configure the memory modules needed by IP core. Asynchronous FIFO is applied to realize the speed matching between high speed data flow acquired by FPGA and the slow processing speed of IP core. The controller has a wide range of application, and it can be applied to a variety of LCD, so it has a broad space of usage.关键词：8051 IP core;asynchronous FIFO;FPGA;TFT-LCD controller
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发布时间：2020-08-12 - 摘要：This paper tries to exam the transmission bandwidth by establishing a scientific test-platform. The paper provides a test pattern formed by 10 bit raw image data which is generated by FPGA as transmitter. The receiver performs data conversion serial-to-parallel and then sends image data as well as clock and enable signals to the image grabber. The transmission reliability is estimated by checking the real-time received test pattern through the 3-wire LVDS serial port. From abundant experiments, the paper gets two results: when LVDS is implemented by imbedding modules in FPGA, transmission bandwidth is approx 152 Mbit/s; when LVDS is implemented by special LVDS devices, transmission bandwidth is approx 125.2 Mbit/s. In practical application cases, bandwidth derating is advised.关键词：LVDS;synchronous serial port;data bandwidth;test pattern
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发布时间：2020-08-12 - 摘要：LED dot-matrix display control system based on power line carrier has been designed. Power line carrier module based on STC7538 is used as the transmission tool of display information. Single chip microcomputer STC12C5A60S2 is used as control core. Dedicated LED 16 bit constant-current driver MBI5024 is used as dot-matrix control driver, in which raw address code is decoded and dot-matrix raw driver is controlled by the middle-power triode. LED dot-matrix is spliced by multiple 16×16 dot-matrix modules, which is made by high light LED.关键词：power line carrier;STC7538;LED dot-matrix display;STC12C5A32S2;constant-current driver;MBI5024
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发布时间：2020-08-12 - 摘要：This paper introduces the implementation of LCD real-time waveform dynamic display system based on the Flexible Static Memory Controller(FSMC) of chip STM32F-103ZET6 (ARM),presents the mapping relation between the collected data and the coordinates of the LCD screen,the characteristics and the specific set of FSMC.The optimization processes method for the waveform with the signals changing rapidly is introduced which makes the wave more lifelike. This technique is of highly practical value and has been applied to the AC-AC frequency conversion display system.关键词：ARM;STM32;FSMC;optimization processes
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发布时间：2020-08-12
Driving & Controlling
- 摘要：For the color inconsistencies between the projector and the monitor, this paper, advanced a method of Look-up table, proposed a color reproduction conversion from the display to the projector design, and exploited the hardware system which based on the FPGA technology. Making use of the characters of human visual, we matched several different colors displayed between projector and display, each frame is calculated the corresponding conversion of all the possible of the pixel based on the color reproduction theory, then transmitted the value through the USB interface to the color reproduction device and deposited it into the three Look-up tables within the FPGA. When it used, the output video signal from the PC is as the address to read the information of the Look-up table, then weighted sum of the final output and displayed it on the projector, which enabling the color reproduction from the display to the projector. The effectiveness of the program has been verified by the test.关键词：display;projector;color reproduction;FPGA;look-up table
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发布时间：2020-08-12 - 摘要：Because Super-resolution image reconstruction requires high precision and high speed of motion estimation of image,so it is proposed to make three improvements with the traditional Fourier-Mellin transform and Keren algorithm of motion estimation:to avoid the shortcoming of Fourier-Mellin transformation (bad registration accuracy of image with poor details), edge detection of the image in advance is made; as Fourier-Mellin transformation is used for coarse estimation,the number of sampling points is reduced during the log polar transform with the angle accuracy below 1°, which greatly reduced the size of matrix, and increased the rate of registration; with Fourier-Mellin transformation being used for coarse estimation firstly, do not need to use the pyramid of Keren algorithm, but only need one layer for motion estimation so that to reduce the registration time. The simulation in VC ++ shows that the method is effective in maintaining the advantages of Fourier-Mellin transform and Keren algorithm,at the same time improving the speed of motion estimation.Accordding to the experiment,with the traditional algorithm it needs 3.53 s to do motion estimation of image with 328 multiply 500 pixels,but needs 1.15 s with the improved algorithm which greatly improve the speed.关键词：super-resolution;Fourier-Mellin transformation;Keren algorithm;edge detection;sampling;motion estimation
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发布时间：2020-08-12 - 摘要：For the need of lager ground-based high resolution EO imaging telescope adaptive optics wave-front processing, thousands of units AO wave-front processing system is required to design. In this paper, an extendible adaptive optics wave-front processor has been presented. This system uses wave-front processing host board and wave-front processing sub board, and can realize expansion according to the scale of adaptive system. Each wave-front processing sub board can promote the output of 120 roads, with the maximum expansion capacity of 10, the system can reach 2 000 frames/s sampling and processing frequency and promote the momentum of the output of 1 200 roads. This article gives a detailed design, implementation and test results.关键词：adaptive optics;wave-front processor;extend
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发布时间：2020-08-12 - 摘要：Dark areas often exist in gray image as light and other reasons, hence, in these areas the image detail can not be directly identified. So an improved image enhancement algorithm based on local statistics and partially overlapped sub-block ideas is proposed in this paper. The proposed algorithm can achieve real-time enhancement of low gray image under dark background. Compared with traditional histogram equalization method,the new algorithm not only reserves the visual characteristics of bright region but also brings relatively weak noise enhancement. Experimental results tested on TMS320DM642 real-time image processing system show that the proposed algorithm obtains excellent display performance, and the processing time for each frame is around 8 ms, which satisfies the real-time requirement completely.关键词：real-time image enhancement;local statistics;partially overlapped subblock;TMS320DM642
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发布时间：2020-08-12 - 摘要：Several noises of TDI CCD were analyzed, and the effects of nonuniformity and fixed pattern noise to image quality were discussed. The nonuniformity was corrected by radiance retrieval method. The experimental results indicate that this method can eliminate the stripe and get clear image.关键词：radiance retrieval;nonuniformity correction;TDI CCD camera;radiation calibration
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发布时间：2020-08-12 - 摘要：Aiming at the problem that Kalman filter tracking algorithm is no longer accurate in non-Gauss and non-linear case and the Particle filter tracking algorithm costs huge computation, a improved targets tracking algorithm based on Kalman filter and Particle filter was proposed. Firstly, a candidate object was gotten by Kalman tracking algorithm.Then,the tracking result would be verified by Particle filter algorithm when the match threshold is lower than a certain. The improved algorithm used "template buffer" to updated object template to ensure the tracking process continuity, stability and accuracy.Experimental results show that this approach can maintain the efficiency of Kalman algorithm and the powerful ability of Particle filter algorithm, so it is of advanced property.关键词：Kalman filter;particle filter;object tracking;template updata
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发布时间：2020-08-12 -
Image Quality Assessment Method Based on Contrast Sensitivity Characteristics of Human Vision System
摘要：Combined the traditional gray image quality assessment method described by the mean square error and peak signal to noise ratio and color differences to describe color image difference, a color image quality assessment method described by the color difference MSE and color difference PSNR statistical parameters based on human vision system is proposed, which is validated by the experiments. Experimental results match the subjective image quality assessment provided by LIVE subjective image library,University of Texas at Austin very much, which shows that the method not only effectively reflects the difference among the local location or points from the statistical significance, and at the same time, which improves the consistency between the objective evaluation and subjective evaluation because the statistical method takes into account the human vision system characteristics.关键词：image quality assessment;human vision system characteristics;peak signal to noise ratio;color differences- 114
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发布时间：2020-08-12 - 摘要：In order to solve the problem that the data output of space optical remote sensing imaging system is multi-channel and high rate, a new design scheme for high-speed and multi-channel CCD (Charge Coupled Device) image data parallel processing and transmission system is proposed. The design uses field programmable gate arrays (FPGA) for the data processing and logic control. For high speed and multi-channel CCD image data processing, the paper adopts regional parallel processing based on FPGA. The FPGA inner block RAM is used to build high speed image data buffer and time-division multiplexing is put into operation to achieve high speed multi-channel image data integration and real-time processing. For high-speed multi-channel CCD image data transmission question involved, the paper analyzes in-depth low-voltage differential signal and high speed differential serial transmission technology, and put it in practice. Those technologies enhance the system high-speed transmission capacity, and lower power consumption, strengthen anti-interference ability. The result shows that the design has good stability, flexibility and versatility, which has already been successfully used in a 40-channels high-speed CCD imaging system with the data rate up to 7.68 Gbit/s.关键词：high-speed;multi-channel;CCD;parallel processing;LVDS
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发布时间：2020-08-12 - 摘要：In order to save the resource and improve the speed of wavelet transform's hardware realization, an effective 2-dimension wavelet transform hardware structure has been proposed. This structure used parallel pipeline architecture, each layer of wavelet transform processed by parallel while pixels processed by pipeline. And the structure can improve the speed of wavelet transform, save the on-chip and external memory resource. It had been tested on Xilinx SPARTEN-3 series FPGA by processing large image with size 1 024×2 048. Results showed the image processing speed could reach 80 Mpixel/s, meeting the real-time requirement.关键词：JPGA2000;wavelet transform;parallel architecture;lifting computation
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发布时间：2020-08-12 - 摘要：In order to acquire the clear and exact image of the ground object, the focus position of space camera should be adjusted according to the variety of the mechanism. If the focus of the camera can be adjusted continuously in the orbit, and the optimal focus can be exactly acquired from the photos transmitted to the ground, the quality and efficiency of the space camera will be greatly improved. In order to validate the continuous focus adjustment method, a simulation and detection method is proposed. A dynamic aim generator and a collimator are applied to simulating the ground object. The computer system is used to control the dynamic aim generator, accomplish the data processing, transmit and receive the data information. The command and parameter transmitted by the simulation devices are received by the space camera at the real time, then the photos are taken and the focus is adjusted continuously and simultaneously.The experiment results show that the optimal focus can be acquired and the detective method satisfies the test requirement.关键词：space camera;continuous focus adjustment;simulation and detection
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发布时间：2020-08-12
Imaging Technology & Image Processing
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