Publications by authors named "Lihao Xu"

In this paper, a dynamic quadrotor unmanned aircraft vehicle driven by bidirectional electronic speed controllers is proposed to enhance maneuverability and stability. Bidirectional electronic speed controllers are applied to achieve rapid deceleration of motors during flight. To match with bidirectional electronic speed controllers, fractional order Proportional-Integral-Derivative (PID) controllers are considered to attain better rapidity compared to PID controllers, and an innovative control allocation matrix with direction symbols is developed.

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  • A new fault-tolerant strategy using space vector pulse width modulation is proposed to enhance the reliability of two-level three-phase voltage source inverters during different leg faults.
  • The strategy addresses inconsistencies in the basic voltage vector phases of reconstructed inverter topologies by applying a coordinate transformation to unify calculations across these faulty systems.
  • Additionally, it introduces a transient compensation method for neutral point voltage offset to reduce current asymmetry without the complexity of traditional algorithms, and its effectiveness is confirmed through experimental testing.
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This paper describes the use of a weighted principal component analysis (PCA) method for camera spectral sensitivity estimation. A comprehensive set of spectral sensitivities of 111 cameras was collected from four publicly available databases. It was proposed to weight the spectral sensitivities in the database according to the similarities with those of the test camera.

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  • The article discusses the challenges in measuring perceptual color differences (CDs) in smartphone photography, as traditional methods are limited and may not apply well to complex contemporary images.
  • To address this, the authors compiled the largest dataset for perceptual CD assessment, featuring images from six flagship smartphones that have been altered in various ways, including editing and processing.
  • They developed a new, optimized formula using a lightweight neural network that significantly outperforms existing CD measures and provides useful local CD maps, with their resources available online for public access.
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This study developed a method to simulate the sensor responses and verify the effectiveness on spectral reconstruction by a spectrum tunable LED system. Studies have shown that the spectral reconstruction accuracy could be improved by including multiple channels in a digital camera. However, the real sensors with designed spectral sensitivities were hard to manufacture and validate.

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A new method was developed to evaluate the perceived gamut of a display. A multispectral image of a white gypsum sphere was projected onto various highly chromatic lights, producing a series of images with distinct hue perceptions at the gamut boundary of displays. These images were subsequently used in a psychophysical experiment to examine the perceived color gamut.

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  • The study introduces a new method for restoring reflectance information from organ samples using a commercial camera, consisting of three main stages.
  • The first stage employs a color clustering technique to identify the representative colors and corresponding spectral reflectance of the organ samples.
  • The proposed method was tested against six other common methods through physical experiments, showing superior performance in colorimetric and spectral metrics, suggesting it is an effective strategy for this type of restoration.
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  • High-performance pervaporation membranes face the challenge of balancing permeability and selectivity for effective industrial separation, particularly in alcohol-water separation.* -
  • Researchers developed flexible, superhydrophobic metal-organic framework nanosheet membranes on polymer substrates, enhancing separation efficiency by providing ultrafast transport channels.* -
  • The membranes exhibited a separation factor of 8.9 for 5% ethanol-water mixtures at 40°C, showing great potential for applications like biofuel recovery due to the combined benefits of MOF-NS and polydimethylsiloxane.*
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A personalized image enhancement method is proposed to improve color vision in hereditary color vision deficiency (CVD). It is divided into two stages: evaluation of CVD and gamut mapping for image enhancement. These two separate stages are connected via a psychophysical experiment, through which the deficiency test result expressed using the C-index can be further transformed into a physical parameter, namely the wavelength shift of the cone fundamental.

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  • A new gamut boundary descriptor (GBD) is introduced, which samples data in uniform color space (UCS) instead of the traditional RGB space, leading to simpler and smoother results.
  • The method consists of three steps: coarse sampling for a rough boundary estimate, dense sampling to refine this boundary, and identifying the cusp to finalize accuracy.
  • Experimental comparisons demonstrate that this new method outperforms two standard approaches (SMGBD and Mountain Range), providing the most accurate and smooth boundary, making it suitable for practical use.
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  • - The study introduces a method to improve color images specifically for people with color vision deficiencies (CVD) by evaluating the type and severity of their condition first.
  • - It uses a color deficiency simulation model to assess how these individuals perceive colors, and then modifies images originally designed for color normal observers to better fit color deficient observers’ perceptions.
  • - Validation through two experiments indicates that this approach is effective, emphasizing the importance of preserving perceived hues during color adjustment to enhance color discrimination for those with CVD.
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  • Determining the best RGB primaries for display design is complex, particularly due to the need to assess colorimetric performance.
  • The study introduced a systematic approach that involved nine testing metrics categorized into gamut metrics and color-related metrics to evaluate 52 displays with various RGB combinations.
  • Results confirmed the effectiveness of the proposed method, showing that some metrics yielded similar outcomes, suggesting that fewer metrics could still adequately reflect a display's overall performance.
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Carbon nanotubes (CNTs) are recognized as desirable candidates to fabricate electrochemical sensing interfaces owing to their high surface area and excellent electron conductivity. However, the poor catalytic properties of CNTs significantly hinder their further application in electrochemical detection. Herein, for the first time we combined defective CNTs with catalytically active cobalt nanoparticles (Co NPs) to give cobalt encapsulated in a bamboo-like N-doped carbon nanotube nanocomposite (Co/N-CNTs).

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A wide color gamut (WCG) display has great color rendering capability and offers the opportunity to achieve a pleasing and realistic appearance in terms of image quality. To take full advantage of the large display gamut, a new gamut extension algorithm (GEA) is proposed based on a new color appearance scale, vividness. The performance of the new GEA was investigated via a psychophysical experiment together with five commonly used GEAs.

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This paper describes an investigation into the performance of different gamut compression algorithms (GCAs) in different uniform colour spaces (UCSs) between small and large colour gamuts. Gamut mapping is a key component in a colour management system and has drawn much attention in the last two decades. Two new GCAs, i.

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Recent advances in bidirectional reflectance distribution function (BRDF) acquisitions have provided a novel approach for appearance measurement and analysis. In particular, since gloss appearance is dependent on the directional reflective properties of surfaces, it is reasonable to leverage the BRDF for gloss evaluation. In this paper, we investigate gloss appearance from both soft metrology and hard metrology.

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