摘要 : In order to realize the driving of multi-channel passive liquid crystal optical devices, the driving circuit with low cost, low complexity and adjustable amplitude and frequency is designed and developed. Firstly, to facilitate the control of the liquid crystal device, the USB data transmission method is used to transmit the control signal between the PC and the driver board. Secondly, the driver board adopts the combination of the mother board and daughter board, and each daughter board can output 32 driving signals, which can flexibly select the number of daughter board according to actual needs, thereby reducing the cost. The mother board and the daughter board both use STM32 as the main control chip, and the daughter board communicates with the mother board through the SPI interface. Each daughter board distributes data packets to the DAC chip through 2 SPI interfaces, and each DAC chip can control 16 channels of digital-to-analog conversion, realize the output of 192 channels of analog signals eventually. Finally, the board is made and tested. The results show that the output analog voltage is in linear proportional relationship to the gray value, and its absolute error is about 0.010 V, which is in line with the modulation accuracy of 10 bit, 1 024-level voltage gray value. The driver board can realize the output of multi-channel driving signals and meet the requirements of driving control of multi-channel passive liquid crystal optical devices.

摘要 : Herein, we successfully prepared magnetic Co/Ni-based N-doped 3D carbon nanotubes and graphene nanocomposites (CoNi@NGC) using a simple high-temperature calcination method. The CoNi@NGC nanocomposites were used as adsorbents to study their adsorption performances and underlying kinetic mechanisms for six types of bisphenol compounds (BPs) in water. They were also used as extractants, and acid-base effervescent tablets were used to enhance extractant dispersion with the aid of vigorous CO2 bubbling. Thus, a novel pretreatment method was developed, denoted effervescent reaction-assisted dispersive solid-phase microextraction (ER-DSM), which was combined with high performance liquid chromatography-fluorescence detection (HPLC-FLD) to rapidly quantify trace-level BPs in several drinks. The morphology and structure of the CoNi@NGC adsorbent were characterized in detail using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption and desorption (BET-BJH), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM). The CoNi@NGC nanocomposites were successfully doped with N and exhibited large specific surface areas (109.42 m2/g), abundant pores, and strong magnetic properties (17.98 emu/g).Key parameters were rigorously optimized to maximize the adsorption performance of CoNi@NGC, including adsorbent dosage, solution pH, temperature, and time. Under the constant conditions of pH=7, 5 mg of CoNi@NGC, initial BP concentrations of 5 mg/L, and 5 min of shaking at 298 K, the adsorption percentages of bisphenol M (BPM) and bisphenol A (BPA) reached respective maxima of 99.01% and 98.21%. Remarkably, those of bisphenol Z (BPZ), BPA, and BPM reached almost 100% after 90 min. The adsorption between the BPs and CoNi@NGC was mainly governed by hydrogen bonds, electrostatic interactions, and π-π conjugation. The entire adsorption process was consistent with Freundlich adsorption and a quasi-second-order kinetic equation, representing spontaneous adsorption. Via integration with HPLC-FLD, ER-DSM was used to rapidly extract and analyze trace-level BPs in six types of boxed drinks. Critical factors were optimized individually, including the type of eluent and elution time and volume, which influenced the enrichment effect. Under the optimized extraction conditions (pH=7, 5 mg CoNi@NGC, elution with 2 mL acetone for 6 min), the limits of detection and quantification of the novel extraction method were 0.06-0.20 and 0.20-0.66 μg/L, respectively. The intra- and inter-day precisions spanned the ranges 1.44%-4.76% and 1.69%-5.36%, respectively, and the recoveries in the actual samples were in the range 82.4%-103.7%. Moreover, the respective residual levels of BPA and BPB in peach juice samples were 2.09 and 1.37 μg/L. Regeneration studies revealed that the CoNi@NGC adsorbent could be reused at least five times, which significantly reduced the cost of evaluation. In summary, compared to other methods, this method displays the advantages of a high sensitivity, rapid extraction, and environmental friendliness, thereby exhibiting considerable potential for use in conventional monitoring of trace-level BPs in food matrices.

摘要 : In this paper, the ultrafast transient nonlinear optical response and broadband dynamics mechanisms of carriers based on Fe defects in Fe-doped gallium nitride (GaN∶Fe) crystals were investigated with multi-dimensional pump-probe techniques. The results of the phase object (PO) pump-probe experiment show that the refraction dynamics curve of the carriers exhibits an obvious recovery compared with their absorption curve, and the recovery is due to the broadband absorption of Fe defect states according to the ultrafast transient absorption spectroscopy experiment. Furthermore, both the transient absorption response and the carrier trapping rate can be tuned over a wide range by the Fe content, and the absorption amplitude enlarges and the lifetime of trapped carriers shortens as the Fe content increases. On the basis of the transient optical nonlinearity results, this paper proposes an excitation and trapping model based on the different charge states of the Fe defects. The carrier trapping mechanisms in GaN∶Fe and the important parameters of Fe defect-related trapping rate and optical absorption cross-section are obtained by global analysis and rate equations. The tunable carrier lifetime and ultra-broadband absorption spectra in GaN∶Fe are of great significance for the design and development of optoelectronic devices, such as optical switches, optical limiters, and optoelectronic detectors.

摘要 : Dopamine plays a critical role in some fatal diseases including Parkinson's disease, schizophrenia, Tourette syndrome and HIV infection studies but its detection sensitivity demands further improvement. Aptamer-based biosensor has good selectivity to detect biologically active substances' however, it is very challenging to achieve high sensitivities for practical applications. Here an electrochemical biosensor is constructed by hollow carbon spheres, aptamer and methylene blue (MB) to monitor dopamine released from Parkinson's disease model (SH-SY5Y) cells with a low detection limit, wide detection range, high sensitivity and good selectivity for much better performance than reported aptamer sensors. Investigation discovers that MB intercalation in aptamers can offer two sites to absorb two dopamine through π-π interaction instead of one DA absorption on an aptamer alone, thereby doubling the detection sensitivity. The sensor was further used to monitor dopamine released from SH-SY5Y cells, clearly confirming the effect of 1-Methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine on dopamine synthesis in SH-SY5Y cells and demonstrating the great potential of the sensor in real-time detect dopamine released from living cells. This work renders a new avenue to amplify the detection sensitivity by intercalating redox small molecule to increase the aptamer reaction sites while bridging the interfacial electron transfer.

摘要 : Image engine optimizes the image signal through a variety of specific algorithms, which plays an extremely important role in the display system. The traditional color optimization algorithm of image engine is composed of various image optimization algorithms, which can not optimize images adaptively and easy to amplifies the noise. Therefore, a full convolution neural network based on dilated convolution is proposed to construct the optimization algorithm, which focuses on optimizing images from the perspective of subjective perception. At the same time, a large-scale dataset is constructed to improve the generalization ability of the algorithm and prevent overfitting. The experiment results show that the proposed algorithm can effectively enhance the color of original images. Compared with the traditional method, the average peak signal-to-noise ratio is improved by 4.01 dB and the average structural similarity is improved by 0.04. The subjective comparison experiment shows that the proposed algorithm has a significant impact on the subjective perception quality of the image, with an average improvement of 61%.

摘要 : To investigate the factors affecting the visual experience with the TV Ambilight system more deeply, this paper establishes a TV Ambilight simulation system based on the LED light distribution model. The measurement and comparison results show that the simulation system can simulate the light distribution and color fusion of real Ambilight accurately. Experiments designed and accomplished by the simulation system are employed to investigate the factors affecting the perception of Ambilight light effects. The visual perception experimental results indicate that the related factors of LED light intensity and distribution range exert a significant (p0.05). The proposed simulation model and preliminary research results can provide a theoretical reference for the design and manufacture of real TV Ambilight systems.

摘要 : Excessive levels of certain active substances in the water will cause a series of environmental problems and affect human health, among which, hydrogen peroxide (H 2 O 2 ) is a typical one. Therefore, it is of great significance to determine the content of H 2 O 2 in industrial wastewater. However, there are great challenges to monitoring H 2 O 2 due to the high redox overpotential of the traditional electrode and the poor measurement sensitivity. Herein, a g-C 3 N 4 /BiFeO 3 photoelectrochemical (PEC) sensor is prepared to effectively stimulate the reduction of H 2 O 2 . Under visible light irradiation, the H 2 O 2 detection limit of the g-C 3 N 4 /BiFeO 3 PEC sensor reaches 2.015 μM, which is 4.7 times that of traditional electrochemical method. Through UV-vis and Mott-Schottky characterizations, the mechanism concerning enhancement of sensor performance was studied. The results show that the band gap and energy band difference of g-C 3 N 4 and BiFeO 3 can effectively avoid the recombination of electrons and holes. The proposed photoelectrochemical sensor obtains a calibration curve range for H 2 O 2 from 2.99 μM to 0.03 M with high sensitivity and good selectivity. In addition, the sensor can detect H 2 O 2 in actual textile wastewater samples, providing a promosing method for the detection of active substances in the environment, and has broad prospects in environmental monitoring.

摘要 : Movement parallelism is one of the key parameters of motorized stages, and it can directly affect the performance of the stages. A spot image method for accurately measuring the movement parallelism is proposed. In addition, based on theoretical research and analysis, a measurement system with a precision better than 50 nm is set up. Utilizing this measurement system, movement parallelism of the motorized stage is measured, and the movement parallelism error is 11.66 μm. After optimizing the motorized stage according to the above results, the optimal movement parallelism error can reach 6.22 μm. In order to verify the feasibility of the proposed method, a displacement sensor is applied to re-measure the movement parallelism. The root-mean-square error between the measurement results of the displacement sensor and that of spot image method is lower than 248 nm. In other words, the two measurement results are basically the same.

摘要 : Aims: The study aims to improve the position control accuracy of a class of permanent magnet synchronous motors under friction. Background: Permanent magnet synchronous motor and servo system are important parts of modern industry, in which the friction effect is a typical nonlinear factor. To overcome the nonlinear friction effect, it is necessary to design a compound feedforward algorithm to improve the motion control accuracy. Objective: The objective of the study is to design a compound adaptive friction feedforward controller to overcome the nonlinear friction effect in the servo system while ensuring tracking accuracy. Methods: A compound algorithm combining velocity-acceleration double feedforward and adaptive friction feedforward is proposed to ensure the control accuracy, and then the backstepping control is used to ensure strict convergence. Finally, the friction parameter observer is used to estimate the parameters, and the performance of the control system is simulated in the Simulink module. Results: Compared to Pure Friction Feedforward Compensation (PFFC) and Adaptive Friction Compensation (AFC), Adaptive Backstepping Feedforward Friction Compensation (ABFFC) has a faster convergence speed, higher steady-state accuracy, and less friction nonlinear effect. Conclusion: The servo system with adaptive backstepping and feedforward friction compensation improves the accuracy and convergence of control performance. Moreover, the adaptive permanent magnet synchronous motor control system can effectively overcome the nonlinear friction effect.

摘要 : A hybrid neural network model based on 3D-2D convolution tandem is proposed as the spatial feature extractor to overcome the problem of low accuracy of conventional iteration reconstruction algorithm in the case of limited optical windows and projection views in practical flame reconstruction. In this model, 3D convolution is utilized to extract spatial features from multi-view projections simultaneously, and 2D convolution is used to further accelerate the training speed and reduce computational consumption. Compared with conventional iteration reconstruction algorithm and reconstruction algorithms based on residual networks, the proposed model has the advantages of high reconstruction accuracy and low time consumption. It shows potential in flame on-line monitoring and rapid reconstruction.