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The traditional calibration paradigms fail to give reliable and accurate results in case of low-quality 2D planar calibration plates. In this paper, an active method is proposed by employing an LCD panel for camera calibration. This method automatically generates a sequence of virtual patterns in different views by pre-defined transforms without manually manipulation or other equipment’s help to move the patterns. Then, the projections of virtual patterns are captured by a camera. The homography between projective patterns in virtual world coordinate and their images is calculated directly to obtain the camera parameters. Experimental results show that the calibration error is 0.018 pixel in terms of mean re-projection error by using 18 virtual patterns, which is significantly less than the state-of-the-art methods. The proposed scheme makes camera calibration flexible and easy to use.

It is challenging to align multi-exposed images due to large illumination variations, especially in presence of saturated regions. In this paper, a novel image alignment algorithm is proposed to cope with the multi-exposed images with saturated regions. Specifically, the multi-exposed images are first normalized by using intensity mapping functions (IMFs) in consideration of saturated pixels. Then, the normalized images are coded by using the local binary pattern (LBP). Finally, the coded images are aligned by formulating an optimization problem by using a differentiable Hamming distance. Experimental results show that the proposed algorithm outperforms state-of-the-art alignment methods for multi-exposed images in terms of alignment accuracy and robustness to exposure values.

The traditional estimation methods of space targets pose are based on artificial features to match the transformation relationship between the image and the object model. With the explosion of deep learning technology, the approach based on deep neural networks (DNN) has significantly improved the performance of pose estimation. However, the current methods still have problems such as complex calculation, low accuracy, and poor real-time performance. Therefore, a new pose estimation algorithm is proposed in this paper. Firstly, the mask image of the target is obtained by the instance segmentation algorithm, and its point cloud image is obtained based on a depth map combined with camera parameters. Finally, the correlation among points is established to realize the prediction of pose based on multi-modal feature fusion. Experimental results in the YCB-Video dataset show that the proposed algorithm can recognize complex images at a speed of about 24 images per second with an accuracy of more than 80%. In conclusion, the proposed algorithm can realize fast pose estimation for complex stacked objects and has strong stability for different objects.

Object detection and segmentation can improve the accuracy of image recognition, but traditional methods can only extract the shallow information of the target, so the performance of algorithms is subject to many limitations. With the development of neural network technology, semantic segmentation algorithms based on deep learning can obtain the category information of each pixel. However, the algorithm cannot effectively distinguish each object of the same category, so YOLOMask, an instance segmentation algorithm based on complementary fusion network, is proposed in this paper. Experimental results on public data sets COCO2017 show that the proposed fusion network can accurately obtain the category and location information of each instance and has good real-time performance.

A tunable terahertz (THz) narrowband absorber in view of bulk Dirac semimetal (BDS) is designed in this paper. The tunable terahertz absorber's basic unit comprises BDS, intermediate medium, and metal substrate. The BDS has good surface conductivity and the Fermi energy of that is flexible tunable, and the good surface conductivity might make controlled by Fermi energy. The absorption characteristics of the designed absorber are simulated by the finite integral time domain technique. The calculation results show that the designed absorber achieves ideal absorption in 139.97 μm, 163.52 μm, 247.76 μm bands, and the absorption rate is more than 0.96, which realizes ideal narrowband absorption and dynamic tuning. We find that the absorption peaks are flexible and adjustable by changing the Fermi energy of BDS, and the frequency adjustability of the absorber is analyzed. In addition, the effects of different structural parameters on the absorption efficiency and the absorption performance at different incident angles are studied. These results show that, compared with traditional metamaterials, Dirac semimetallic absorbing materials can tune the resonant frequency more effectively, even without reconstructing the structure, which has great application value in many fields, and provide a new reference for future research.

It is challenging to convert a hazy color image into a gray-scale image because the color contrast field of a hazy image is distorted. In this paper, a novel decolorization algorithm is proposed to transfer a hazy image into a distortion-recovered gray-scale image. To recover the color contrast field, the relationship between the restored color contrast and its distorted input is presented in CIELab color space. Based on this restoration, a nonlinear optimization problem is formulated to construct the resultant gray-scale image. A new differentiable approximation solution is introduced to solve this problem with an extension of the Huber loss function. Experimental results show that the proposed algorithm effectively preserves the global luminance consistency while represents the original color contrast in gray-scales, which is very close to the corresponding ground truth gray-scale one.

Droplet generation process can directly affect process regulation and output performance of electrohydrodynamic jet (E-jet) printing in fabricating micro-to-nano scale functional structures. This paper proposes a numerical simulation model for whole process of droplet generation of E-jet printing based on the Taylor-Melcher leaky-dielectric model. The whole process of droplet generation is successfully simulated in one whole cycle, including Taylor cone generation, jet onset, jet break, and jet retraction. The feasibility and accuracy of the numerical simulation model is validated by a 30G stainless nozzle with inner diameter ~160 &mu, m by E-jet printing experiments. Comparing numerical simulations and experimental results, period, velocity magnitude, four steps in an injection cycle, and shape of jet in each step are in good agreement. Further simulations are performed to reveal three design constraints against applied voltage, flow rate, and nozzle diameter, respectively. The established cone-jet numerical simulation model paves the way to investigate influences of process parameters and guide design of printheads for E-jet printing system with high performance in the future.

Carbon quantum dots (CQDs) have become an excellent candidate for light-converting phosphors. However, it is a challenge to develop white emission CQDs and overcome the agglomeration in the process of solid-state CQDs. Here, white fluorescence CQDs with graphite core structure were synthesized by a one-step hydrothermal method from 1,3-dihydroxynaphthalene and hydrochloric acid. The photoluminescence spectra and surface structure characterization along with UV-Vis absorption spectrum, photoluminescence excitation, and time-resolved photoluminescence spectra together reveal the luminescence of CQDs stems from carbon-oxygen-related surface fluorophores. The principle of solvent similarity compatibility is an effective thought to choose isolating matrix material for the sake of overcoming the agglomeration of CQDs in the process of forming solid film. Solid-state white light emitting device (WLED) was fabricated using the CQDs embedded in polymethyl methacrylate matrix as a single white-light converter excited by a 365 nm UV-LED chip. The fabricated WLED based on CQDs is cold white light source with CIE coordinates (0.3122, 0.3429) and with CCT of 6428 K.

Nanostructure and wettability present great potentials on high power electronics cooling. However, it is challenging to design optimal nanostructure for thermal management due to the mechanism of interaction between structure and wettability on boiling heat transfer which is not explicit. In this paper, a series of rough surfaces with different wettability were modeled to study the relationship between effects of nanostructure and wettability on rapid boiling. The simulation results showed that the increment of nanochannels height, which resulted in the enlargement of hydrophilic area, significantly promoted supply of liquid water and thermal energy transfer. What's more, potential energy and the density of water molecules on nanochannels zone were similar to that on hydrophobic zone, promoting nucleation points formation and evaporation. Based on those results, thermal design theory of optimized surface is established: big hydrophilic area, more nucleation points and potential energy difference of water molecules between hydrophilic zone and nucleation point are the key elements on surface designing. Thus, nanochannels with certain space and height were designed on a hydrophilic surface, which satisfied the optimization requirements, to enhance the nano heat transfer.

Screw press is a kind of dehydration machines of simple structure, low cost and reliable operation and is widely used in the food processing industry. Screw assembly is the core component of screw press, the force applies on its blade is very complex and prone to failure. This study analyzed the working principle of a type continuous screw press and established mathematical model of its screw mechanism. With the help of large-scale finite element software Patran/Nastran, the screw was analyzed and stress and deformation contour were obtained. It's found that the largest stress appears on the blade root near the discharging end. This study can provides a certain theoretical basis and basic methods to design the more stable screw press.

Automatic filling system is the main equipment in the food machinery industry. With the development of beverage industry and increasing demand of the filling system. The relay control method in traditional Filling machine has low automation and integration level and cannot satisfy the rapid development of automatic production. PLC control method has advantages of simple programming, strong anti-interference and high working reliability, has gradually replace the relay control method. In this study, hardware and software for the automatic filling system based on PLC control is designed, especially the injection section servo control system which adopts the servo motor driver metering pump is carefully analyzed and the filling precision is highly improved.

In this paper, we propose a novelradiometric response function estimationalgorithm for high dynamic range imaging. In this algorithm, imagesarecaptured in random time interval of asame scene. The camera response function (CRF)is estimated based on each image and obtained the average CRF. Then, the ratio of eachCRF and the average value is definedas acontrol factor tofinally determine the optimal imageCRF. Wepresent an image fusion method to fuse all the images to generate an optimal high dynamic range image. Results on a variety of benchmarked and real images demonstrate that the proposed approach improves image quality and can obtain the best high dynamic range (HDR) image.

In this paper, we propose a novel tone mapping method to obtain high visibility by boosting local luminance contrast with guided image filter. Specifically, the original images are decomposed into multi-scale layers by the weighted least square filter. A novel pixel-wise weighting map employing the guided image filter on each layer is presented. The key idea is to assign large weightings to the regions with large contrast such that lighting effects are highly reduced and halo artifacts merely occur. Moreover, color balancing correction is performed to suppress color distortion. Experiments on several testing sets demonstrate the proposed method preserves clearer details and more faithful color tone than the existing methods in terms of visual and objective evaluation.

Printhead with integrated electrodes plays an important role in electrohydrodynamic jet (E-jet) printing, which can remove the effect of substrate and may be potentially used in fabrication of microelectrodes for flexible electronics. In this paper, we propose a printhead with integrated electrodes to achieve E-jet printing on insulating substrate. Evaluation of the printhead is performed by E-jet printing tests of ethylene glycol in order to validate correctness of design and feasibility of printing on insulating substrate. The printing tests on silicon indicate that the design of proposed printhead with integrated electrodes is correct which can work normally. However, influence of repulsive force by remaining electric charges on substrate is the main cause for failure tests on PET substrate. This research can provide a lesson to implement E-jet printing on insulating substrate in future.

The poor operating conditions of fluid lubrication equipment during the start-up process are due to the resistance of the high-viscosity lubricating liquid. Moreover, the excessive reduction in fluid viscosity due to the elevated temperature resulting from power consumption during prolonged operation is not conducive to the generation of dynamic pressure. In this study, we examine the effect of energy accumulation and boundary slip on the laminar flow of a liquid between a pair of rotating plates. The experiments are conducted using a rotary rheometer, with polymethyl methacrylate (PMMA) as the thermal insulation material and polytetrafluoroethylene (PTFE) as the slip drag reduction material, and a three-dimensional simulation model is established. This model is derived by combining the energy equation including the slip length and the heat conduction equation. Thus, the temperature changes over time are predicted by this model, and the model accuracy is verified by experiments. The results reveal the following points: 1) boundary slips function as a drag reduction mechanism for short-time continuous operation; 2) under prolonged operation, the slip reduces the extent of the oil viscosity decrease and clear control of the elevated temperature by the boundary slip is observed.

We propose a novel robust method to accurately align large-photometric-variation and noisy images emerged from high dynamic range (HDR) imaging. First, the keypoints are detected from optimal multi-binary images to eliminate the noise and photometric effects. The feature descriptor, which is translation-, rotation- and scale-invariant and robust to noise and photometric changes, is then developed, and feature matching is implemented efficiently by use of the structure information of the keypoints. Finally, mutual information (MI) is employed in the RANSAC method for homography estimation and performance assessment, which makes the results accurate and stable. Experiments carried out on synthesized images demonstrate that the proposed method is much more robust to both photometric changes and noise than the SIFT method, the state-of-the-art alignment method.

The paper aims at piloted electro-hydraulic proportional pressure-reducing valve characteristics of uncertain parameters, immeasurable states and effect of load flow, designed an observer including load flow and it's feedback controller ,achieve robust output-feedback control to the output pressure .Based on linear matrix inequalities, theoretical analysis showed that the system was stable and had robust H-infinity performance , given the method to obtain the observer gain L and controller gain K. By simulating a certain proportional pressure reducing valve, verified the validity of the algorithm, eliminated the influence of load flow to output pressure and ensured it following the set pressure quickly.

A printhead that is compatible with Si-based processes and able to generate homogeneous micro- and nano-scale droplets plays an important role in electrohydrodynamic jet printing (E-jet printing) for the large-scale manufacturing. This paper proposes the design, fabrication and evaluation of a novel protruding Si-based printhead for E-jet printing. The protruding nozzle can concentrate the electrical field and restrain the lateral wetting so as to improve the jetting stability. However, it is a challenge to have both the protruding structure and a stable solution/voltage supply. Accordingly, a set of micro-manufacturing processes, as well as methods of adopting hydrophobic and insulation treatments, are also presented to stabilize the solution/voltage supply. The diameter and height of the protruding nozzle are 50 µm and 60 µm, respectively. Printing tests are performed using both quantum dots solution (CdSe/CdS/ZnS) and a mixed solution of glycerol, ethylene glycol and water. Feasibility of the protruding nozzle is proved by experiments that a stable meniscus with Taylor cone could form on the nozzle orifice, and fine dots (≤30 µm) could be printed successfully and continuously. The protruding design and micro-fabrication processes of the protruding Si-based printhead pave the way for the multi-nozzle E-jet printing with high efficiency and resolution.

The dynamic response test to the subgrade plays a very important role in railway construction and a new in-situ test system is proposed. This paper presents the application of non-dominated sorting genetic algorithm-II (NSGA-II) to analyze the stability of the supporting equipment for track subgrade dynamic response in-situ test device. Its stability is related with the extension length of the hydraulic cylinders and the backward condition of the supporting equipment - the hydraulic excavator. The problem is formulated as a multi-objective optimization problem with the objective of maximizing the supporting force for the test device. An 85 tons excavator is picked as the case to study. The first optimal results show the excavator may not support the test system successfully. After redesigning the boom and adding its weight and length as new parameters, the second optimize results indicate the test device can work normally. DOI: http://dx.doi.org/10.11591/telkomnika.v11i12.3986 Full Text: PDF

Subgrade bears both the weight of superstructures and the impacts of running trains. Its stability affects the line smoothness directly, but in situ testing method on it is inadequate. This paper presents a railway roadbed in situ testing device, the key component of which is an excitation hydraulic servo cylinder that can output the static pressure and dynamic pressure simultaneously to simulate the force of the trains to the subgrade. The principle of the excitation system is briefly introduced, and the transfer function of the closed-loop force control system is derived and simulated; that, it shows without control algorithm, the dynamic response is very low and the following performance is quite poor. So, the improvedadaptive model following control (AMFC) algorithm based on direct state method is adopted. Then, control block diagram is built and simulated with the input of different waveforms and frequencies. The simulation results show that the system has been greatly improved; the output waveform can follow the input signal much better except for a little distortion when the signal varies severely. And the following performance becomes even better as the load stiffness increases.