A low-light colonoscopy video enhancement method is needed as poor illumination in colonoscopy can hinder accurate disease diagnosis and adversely affect surgical procedures. Existing low-light video enhancement methods usually apply a frame-by-frame enhancement strategy without considering the temporal correlation between them, which often causes a flickering problem. In addition, most methods are designed for endoscopic devices with fixed imaging styles and cannot be easily adapted to different devices. In this paper, we propose a Style-Guided Network (SGNet) for unpaired Low-Light Colonoscopy Video Enhancement (LLCVE). Given that collecting content-consistent paired videos is difficult, SGNet adopts a CycleGAN-based framework to convert low-light videos to normal-light videos, in which a Temporal Compensation (TC) module and a Style Guidance (SG) module are proposed to alleviate the flickering problem and achieve flexible style transfer, respectively. The TC module compensates for a low-light frame by learning the correlated feature of its adjacent frames, thereby improving the temporal smoothness of the enhanced video. The SG module encodes the text of the imaging style and adaptively explores its intrinsic relationships with video features to obtain style representations, which are then used to guide the subsequent enhancement process. Extensive experiments on a curated database show that SGNet achieves promising performance on the LLCVE task, outperforming state-of-the-art methods in both quantitative metrics and visual quality.

Captured retinal images usually have quality issues, manifested as containing multiple distortions (e.g., low light and blurring). Low-quality images bring a challenge to the screening and diagnosis of ophthalmic diseases. Existing image enhancement methods typically neglect the analysis of distortions and require high-quality reference images for model learning, making them unsuitable for clinical applications. In this paper, we propose a Distortion-Aware Network (DANet) for retinal image enhancement in a zero-reference way. DANet consists of three parallel branches by incorporating atmospheric scattering theory, which decomposes the low-quality image into a clean image, a transmission map, and an atmospheric light map. The upper branch utilizes a dark channel prior module to estimate the atmospheric light map, and the middle branch uses a transmission map generation module to estimate the transmission map. In contrast, the lower branch uses a deblurring module and a low-light enhancement module to obtain a deblurred image and an illumination-enhanced image and fuses these two images using a fusion block to generate the final enhanced image. Taking into account the limited publicly available datasets, we curate two datasets for the retinal image enhancement task. Experimental results show that our DANet can greatly improve the visual quality of the image with good interpretability, achieving superior performance over seven state-of-the-art methods.

With the increase in aircraft maintenance orders and heterogeneity of aircraft irregular shapes, outsourced aircraft maintenance companies urgently need a more efficient and tailored intelligent aircraft parking allocation method. However, existing methods could be improved in lightweight handling of non-overlapping constraints and effective use of problem-specific heuristics. To tackle these challenges and achieve a more rational allocation of parking stands, a bi-objective optimization model involving rotation angles is firstly constructed to maximize hangar utilization and safety margin, and is decomposed into two single-objective optimization problems via a lexicographic method. To efficiently solve this model, problem characteristics of “irregular contours matching” are analyzed. Furthermore, a series of mechanisms that fully utilize the problem characteristics are designed, thus integrating a two-stage metaheuristic framework based on irregular contours matching. These mechanisms include an aircraft parking strategy based on geometric fit for rationally locating aircraft parking positions and mitigating the dimensional explosion problem, a metaheuristic optimizer with similar insertion neighborhood operation for enhancing the hangar utilization, and a fast safety margin optimization algorithm based on binary searching iterator. Experimental studies conducted on 18 real-world instances show that the proposed framework outperforms several state-of-the-art algorithms, as well as the dynamic search algorithm automatically selected by the CPLEX optimizer. Note to Practitioners—This paper investigates an aircraft parking stand allocation problem that originated in outsourced aircraft maintenance companies. The goal of the problem is to maximize the hangar utilization and safety margin. Existing aircraft parking stand allocation methods ignore the lightweight handling of non-overlapping constraints, optimal configuration of rotation angles and safety margins, and effective utilization of problem-specific heuristics. Thus the allocation efficiency could be further improved when coping with large-scale order requirements. This paper constructs a mathematical optimization model with limited rotation angles, and introduces a concise geometric tool to address aircraft collision problem. Furthermore, a two-stage metaheuristic framework based on problem characteristics is proposed to solve the model efficiently. The superiority of the present method was verified on 18 real-instances with various hangar sizes and maintained aircraft. It is believed that this method effectively improves maintenance resource utilization, reducing labor and maintenance costs of outsourced aircraft maintenance companies.

In recent years, colorectal polyp segmentation has attracted increasing attention in academia and industry. Although most existing methods can achieve commendable outcomes, they often confront difficulty when localizing challenging polyps with complex background, variable shape/size, and ambiguous boundary, because of the limitations in modeling global context and in cross-layer feature interaction. To cope with these challenges, this paper proposes a novel Progressive Feature Enhancement Network (PFENet) for polyp segmentation. Specifically, PFENet follows an encoder-decoder structure and utilizes the pyramid vision transformer as the encoder to capture multi-scale long-term dependencies at different stages. A cross-stage feature enhancement (CFE) module is embedded in each stage. The CFE module enhances the feature representation ability from interaction among adjacent stages, which helps integrate scale information for recognizing polyps with complex background and variable shape/size. In addition, a foreground boundary co-enhancement (FBC) module is used at each decoder to simultaneously enhance the foreground and boundary information by incorporating the output of the adjacent high stage and the coarse segmentation map, which is generated by fusing features of all four stages via a coarse map generation module. Through top-down connections of FBC modules, PFENet can progressively refine the prediction in a coarse-to-fine manner. Extensive experiments show the effectiveness of our PFENet in the polyp segmentation task, with the mIoU and mDic values over 0.886 and 0.931 tested on two in-domain datasets and over 0.735 and 0.809 tested on three out-of-domain datasets.Note to Practitioners—Automated and accurate polyp segmentation in colonoscopy images is a critical prerequisite for subsequent detection, removal, and diagnosis of polyps in clinical practice. This paper proposes a novel deep neural network for polyp segmentation, termed PFENet, with a CFE module to enhance the feature representation ability for better capturing polyps with complex background and variable shape/size, and a FBC module to simultaneously enhance the foreground and boundary information on the feature representation provided by the CFE module. Qualitative and quantitative results on five public datasets show that our PFENet yields accurate predictions and is superior to 9 state-of-the-art polyp segmentation methods. The proposed PFENet will facilitate potential computer-aided diagnosis systems in clinical practice, in which it can better promote medical decision-making than competing methods in polyp detection and removal.

Colorectal polyp segmentation in endoscopic images is very important for the prevention and treatment of colorectal cancer. Because of the high similarity between polyps and their surrounding tissues, most deep neural network (DNN) based methods often struggle with blurry boundaries and result in inaccurate segmentation. In this paper, we propose a Boundary-guided Feature-aligned Network (BFNet) for polyp segmentation by taking a boundary prediction task as an auxiliary. Firstly, BFNet aggregates multi-layer features extracted from the backbone to mine boundary cues. Secondly, a flexible feature aggregation (FFA) module is used at each layer to adaptively fuse cross-layer features for coarse polyp localization. In the FFA module, considering the spatial misalignment between features at different layers, the feature of the high layer is aligned to and fused with that of the current layer using the deformable convolution and flexible merge block. After that, a boundary-guided feature enhancement (BFE) module is applied to refine the localization at boundary areas. In the BFE module, the boundary information is extracted and highlighted in both channel and spatial dimensions using the attention mechanisms with the assistance of boundary cues. By applying deep supervision to the BFE modules, BFNet can produce accurate polyp segmentation. Experimental results show that our BFNet outperforms 14 state-of-the-art DNN-based polyp segmentation methods on both in-domain and out-of-domain tests.

Although text-guided infrared-visible image fusion helps improve content understanding under extreme illumination, existing methods usually ignore semantic differences between textual and visual features, resulting in limited improvement. To address this challenge, we propose a Text-Guided Semantic Alignment Network, termed TSANet, for extreme-illumination infrared-visible image fusion. The network follows an encoder-decoder structure, with two image encoders, two text encoders, and one decoder. It uses a Semantic Alignment and Fusion (SAF) block to bridge the two image encoders in each layer. Specifically, the SAF block consists of two parallel Semantic Alignment (SA) modules, corresponding to the infrared and visible modalities, respectively, and a Spatial-Frequency Interaction (SFI) module. The SA module aligns the visual feature from the image encoder with its corresponding textual feature from the text encoder, to guide the network focus on key semantic regions of infrared and visible images. The SFI module aggregates the spatial and frequency information extracted from the modality-aligned features of two SA modules for complementary representation learning. The network progressively complements two image modalities by connecting the SAF blocks from top to down, and finally provides a visually pleasing fusion effect by feeding the output of the last block into the decoder. Recognizing that existing datasets lack illumination diversity, we contribute a new dataset specifically designed for extreme-illumination image fusion. Extensive experiments show the effectiveness and superiority of TSANet over seven state-of-the-art methods. The source code and dataset are available at https://github.com/WentaoLi-CV/TSANet.

In the context of contemporary artificial intelligence, increasing deep learning (DL) based segmentation methods have been recently proposed for brain tumor segmentation (BraTS) via analysis of multi-modal MRI. However, known DL-based works usually directly fuse the information of different modalities at multiple stages without considering the gap between modalities, leaving much room for performance improvement. In this paper, we introduce a novel deep neural network, termed ACFNet, for accurately segmenting brain tumor in multi-modal MRI. Specifically, ACFNet has a parallel structure with three encoder-decoder streams. The upper and lower streams generate coarse predictions from individual modality, while the middle stream integrates the complementary knowledge of different modalities and bridges the gap between them to yield fine prediction. To effectively integrate the complementary information, we propose an adaptive cross-feature fusion (ACF) module at the encoder that first explores the correlation information between the feature representations from upper and lower streams and then refines the fused correlation information. To bridge the gap between the information from multi-modal data, we propose a prediction inconsistency guidance (PIG) module at the decoder that helps the network focus more on error-prone regions through a guidance strategy when incorporating the features from the encoder. The guidance is obtained by calculating the prediction inconsistency between upper and lower streams and highlights the gap between multi-modal data. Extensive experiments on the BraTS 2020 dataset show that ACFNet is competent for the BraTS task with promising results and outperforms six mainstream competing methods.

Captured colonoscopy videos usually suffer from multiple real-world distortions, such as motion blur, low brightness, abnormal exposure, and object occlusion, which impede visual interpretation. However, existing works mainly investigate the impacts of synthesized distortions, which differ from real-world distortions greatly. This research aims to carry out an in-depth study for colonoscopy Video Quality Assessment (VQA). In this study, we advance this topic by establishing both subjective and objective solutions. Firstly, we collect 1,000 colonoscopy videos with typical visual quality degradation conditions in practice and construct a multi-attribute VQA database. The quality of each video is annotated by subjective experiments from five distortion attributes (i.e., temporal-spatial visibility, brightness, specular reflection, stability, and utility), as well as an overall perspective. Secondly, we propose a Distortion Attribute Reasoning Network (DARNet) for automatic VQA. DARNet includes two streams to extract features related to spatial and temporal distortions, respectively. It adaptively aggregates the attribute-related features through a multi-attribute association module to predict the quality score of each distortion attribute. Motivated by the observation that the rating behaviors for all attributes are different, a behavior guided reasoning module is further used to fuse the attribute-aware features, resulting in the overall quality. Experimental results on the constructed database show that our DARNet correlates well with subjective ratings and is superior to nine state-of-the-art methods.

Captured retinal images vary greatly in quality. Low-quality images increase the risk of misdiagnosis. This motivates to design effective retinal image quality assessment (RIQA) methods. Current deep learning-based methods usually classify the image into three levels of "Good", "Usable", and "Reject", while ignoring the quantitative feedback for more detailed quality scores. This study proposes a unified RIQA framework, named QAC-Net, that can evaluate the quality of retinal images in both qualitative and quantitative manners. To improve the prediction accuracy, QAC-Net focuses on extracting discriminative features by using two strategies. On the one hand, it adopts a pyramid network structure that simultaneously inputs the scaled images to learn quality-aware features at different scales and purify the feature representation through a consistency loss. On the other hand, to improve feature representation, it utilizes a quality-aware contrastive (QAC) loss that considers quality relationships between different images. The QAC losses for qualitative and quantitative evaluation tasks have different forms in view of the task differences. Considering the shortage of datasets for the quantitative evaluation task, we construct a dataset with 2,300 authentically distorted retinal images, each of which is annotated with a numerical quality score through subjective experiments. Experimental results on public and our constructed datasets show that our QAC-Net is competent for the RIQA tasks with considerable performance.

Camouflaged object detection (COD) aims to segment targeted objects that have similar colors, textures, or shapes to their background environment. Due to the limited ability in distinguishing highly similar patterns, existing COD methods usually produce inaccurate predictions, especially around the boundary areas, when coping with complex scenes. This paper proposes a Progressive Region-to-Boundary Exploration Network (PRBE-Net) to accurately detect camouflaged objects. PRBE-Net follows an encoder-decoder framework and includes three key modules. Specifically, firstly, both high-level and low-level features of the encoder are integrated by a region and boundary exploration module to explore their complementary information for extracting the object's coarse region and fine boundary cues simultaneously. Secondly, taking the region cues as the guidance information, a Region Enhancement (RE) module is used to adaptively localize and enhance the region information at each layer of the encoder. Subsequently, considering that camouflaged objects usually have blurry boundaries, a Boundary Refinement (BR) decoder is used after the RE module to better detect the boundary areas with the assistance of boundary cues. Through top-down deep supervision, PRBE-Net can progressively refine the prediction. Extensive experiments on four datasets indicate that our PRBE-Net achieves superior results over 21 state-of-the-art COD methods. Additionally, it also shows good results on polyp segmentation, a COD-related task in the medical field.

Thermal infrared images (TIIs) can be distorted by multiple factors, resulting in noise, low contrast, limited dynamic range, and fuzziness, which greatly impede their usefulness. It is crucial to evaluate the quality of TIIs. Unfortunately, there have been very few attempts to study this problem. In this study, we collected 1,000 authentically distorted TIIs using thermal infrared acquisition equipment and conducted strict subjective experiments to obtain a thermal infrared image quality assessment (IQA) database. Each image’s quality score was obtained under strict scoring rules. Finally, we investigated the feasibility of several no-reference (NR) IQA methods in quality assessment of TIIs. We found that existing NR-IQA methods achieve ordinary performance in such a task, and there is an urgent need to develop a specific IQA methods for TIIs. The findings together with the constructed database are expected to pave the way for the development of more advanced IQA methods for further development of this field.

AI-generated images (AGIs) are increasingly utilized across diverse domains due to their ability to quickly produce high-quality visuals. However, assessing the quality of AGIs re-mains challenging due to their inherent variability and distinctive distortions. To address these challenges, we propose a novel AGI quality assessment method named SIRQA, which enhances feature representation by integrating visual features with textual prompts, effectively measureing the alignment between the generated images and the described content to improve the precision of quality assessment. Specifically, SIRQA employs self-ranking and inter-ranking mechanisms to refine feature representation. The self-ranking mechanism maintains consistency between feature distances and sampling scales, making sure that features from similar sampling scales are positioned closer together. Addition-ally, inter-ranking mechanism sorts the weighted similarity scores between images and prompts to align with the ranking in the label space. Extensive experiments on the AGIQA3K and PKUI2IQA datasets show that our SIRQA outperforms eight state-of-the-art algorithms in terms of both Spearman’s rank correlation coefficient (SRCC) and Pearson linear correlation coefficient (PLCC).

To address the challenge of parameter adjustment in complex environments, this paper introduces a transfer learning-based parameter control framework via deep reinforcement learning for multiobjective evolutionary algorithms (MOEAs). To avoid the requirement for accurate Pareto front information, this framework is proposed with comprehensive global-state information, including basic problem features, the relative position of individuals, the distribution of fitness value, and the grid-IGD. Building on this framework, four reinforced multiobjective evolutionary algorithms (r-MOEAs) are proposed and tested on four DTLZ benchmarks and eight WFG benchmarks. The results of the comparative analyses reveal that compared with the original MOEAs, the four r-MOEAs exhibit faster convergence and stronger robustness. It is also confirmed that our proposed parameter control framework has the capability to learn knowledge from different experiences and improve the performance of MOEAs.

Precise polyp segmentation is vitally essential for detection and diagnosis of early colorectal cancer. Recent advances in artificial intelligence have brought infinite possibilities for this task. However, polyps usually vary greatly in shape and size and contain ambiguous boundary, bringing tough challenges to precise segmentation. In this letter, we introduce a novel Boundary Refinement Network (BRNet) for polyp segmentation. To be specific, we first introduce a boundary generation module (BGM) to generate boundary map by fusing both low-level spatial details and high-level concepts. Then, we utilize the boundary-guided refinement module to refine the polyp-aware features at each layer with the help of boundary cues from the BGM and the prediction from the adjacent high layer. Through top-down deep supervision, our BRNet can localize the polyp regions accurately with clear boundary. Extensive experiments are carried out on five datasets, and the results indicate the effectiveness of our BRNet over seven recently reported methods.

Endoscopic images captured under low-light enclosed intestinal environment usually have poor visibility (manifested as uneven illumination and noise), affecting the work efficiency of physicians and the accuracy of lesion detection. To improve the image quality, the literature has reported many low-light image enhancement (LIE) methods. However, most methods do not perform well in handling the low-light endoscopic image enhancement (LEIE) task, usually bringing additional artifacts or amplifying noise. In this paper, we propose a novel deep pyramid enhancement network (DPENet) to enhance endoscopic images from both global and local perspectives. Specifically, considering the uneven illumination of endoscopic images, DPENet utilizes an image pyramid framework with three parallel branches to explore and integrate both global and local features at different scales. To suppress noise, DPENet sets multiple scale-space feature extraction blocks (SFEBs) in each branch. SFEB consists of a contextual feature extraction module (CFEM) and a spatial residual attention module (SRAM). CFEM mines contextual information to help the network understand semantic information while suppress the isolated noise. SRAM leverages the spatial attention mechanism to help the network adaptively focus on dim regions. Experimental results on a public dataset and our collected dataset show that DPENet is competent for the LEIE task with promising results, and outperforms 9 state-of-the-art LIE methods in both qualitative and quantitative aspects.

Camouflaged object detection (COD) is an important yet challenging task, with great application values in industrial defect detection, medical care, etc. The challenges mainly come from the high intrinsic similarities between target objects and background. In this paper, inspired by the biological studies that object detection consists of two steps, i.e., search and identification, we propose a novel framework, named DCNet, for accurate COD. DCNet explores candidate objects and extra object-related edges through two constraints (object area and boundary) and detects camouflaged objects in a coarse-to-fine manner. Specifically, we first exploit an area-boundary decoder (ABD) to obtain initial region cues and boundary cues simultaneously by fusing multi-level features of the backbone. Then, an area search module (ASM) is embedded into each level of the backbone to adaptively search coarse regions of objects with the assistance of region cues from the ABD. After the ASM, an area refinement module (ARM) is utilized to identify fine regions of objects by fusing adjacent-level features with the guidance of boundary cues. Through the deep supervision strategy, DCNet can finally localize the camouflaged objects precisely. Extensive experiments on three benchmark COD datasets demonstrate that our DCNet is superior to 12 state-of-the-art COD methods. In addition, DCNet shows promising results on two COD-related tasks, i.e., industrial defect detection and polyp segmentation.

Blind image quality assessment (BIQA) targets predict the perceptual quality of an image without any reference information. However, known methods have considerable room for performance improvement due to limited efforts in distortion knowledge usage. This paper proposes a novel multitask learning based BIQA method termed KGANet, which takes image distortion classification as an auxiliary task and uses the knowledge learned from the auxiliary task to assist accurate quality prediction. Different from existing CNN-based methods, KGANet adopts a transformer as the backbone for feature extraction, which can learn more powerful and robust representations. Specifically, it comprises two essential components: a cross-layer information fusion (CIF) module and a knowledge-guided attention (KGA) module. Considering that both global and local distortions appear in an image, CIF fuses the features of the adjacent layers extracted by the backbone to obtain a multiscale feature representation. KGA incorporates the distortion probability estimated by the auxiliary task with the distortion embeddings, which are selected from subword unit embeddings based on a textual template, to form distortion knowledge. This knowledge further serves as guidance to enhance the features of each layer and strengthen the connection between the main and auxiliary task. We demonstrate the effectiveness of the proposed KGANet through extensive experiments on benchmark databases. Experimental results show that KGANet correlates well with subjective perceptual judgments and achieves superior performance over 12 state-of-the-art BIQA methods.

Recently, federated learning has become a powerful technique for medical image classification due to its ability to utilize datasets from multiple clinical clients while satisfying privacy constraints. However, there are still some obstacles in federated learning. Firstly, most existing methods directly average the model parameters collected by medical clients on the server, ignoring the specificities of the local models. Secondly, class imbalance is a common issue in medical datasets. In this article, to handle these two challenges, we propose a novel specificity-aware federated learning framework that benefits from an Adaptive Aggregation Mechanism (AdapAM) and a Dynamic Feature Fusion Strategy (DFFS). Considering the specificity of each local model, we set the AdapAM on the server. The AdapAM utilizes reinforcement learning to adaptively weight and aggregate the parameters of local models based on their data distribution and performance feedback for obtaining the global model parameters. For the class imbalance in local datasets, we propose the DFFS to dynamically fuse the features of majority classes based on the imbalance ratio in the min-batch and collaborate the rest of features. We conduct extensive experiments on a dermoscopic dataset and a fundus image dataset. Experimental results show that our method can achieve state-of-the-art results in these two real-world medical applications.

Nowadays, it is a common practice to retouch face images before sharing them on websites, social media, and even identification cards. In response, increased criticisms have appeared about taking photo retouching to an extreme. This naturally leads to the necessity of designing perceptual quality assessment methods that can measure how much a retouched face image has strayed from reality. However, such an issue has seldom been considered. In this paper, we conduct both subjective and objective studies to advance this field. Firstly, we construct a benchmark database (termed SZU-RFD) via subjective experiments. SZU-RFD consists of 200 high-quality images with Asian faces and 1,600 retouched images generated by three popular photo-editing tools under different settings. Secondly, considering that retouching usually distorts the image texture, we propose a novel no-reference (NR) quality assessment method, named TANet, for retouched face images by taking the textural artifact into account. Specifically, a texture enhancement module is embedded into the shallow layer to help the network focus on textural information, and a multi-task learning strategy is applied to improve the performance of the main task with the assistance of an auxiliary task, i.e., texture recognition. Extensive experiments on the constructed SZU-RFD show that our proposed TANet correlates well with subjective perceptual judgments and is superior to 19 mainstream NR image quality assessment methods in evaluating retouched face images.

Many retinal images sometimes suffer from uneven illumination, which influences the analysis and diagnosis of retinal diseases. To improve the image quality of those retinal images, one feasible solution is to utilize low-light image enhancement (LIE) algorithms. However, how to evaluate the perceptual quality of enhanced retinal images (ERIs) generated by different LIE algorithms remains a challenging problem. In this paper, we conduct subjective experiments to investigate the quality assessment of ERIs. First, we collect 250 retinal images with the authentic low-light distortion, and then adopt eight LIE algorithms to produce 2000 ERIs. Second, a subjective experiment is conducted, resulting in the proposed Enhanced Retinal Image Quality Assessment Database (ERIQAD). Finally, we test some well-known no reference image quality assessment (NR IQA) methods on our proposed ERIQAD. Experimental results demonstrate that existing mainstream NR IQA methods merely achieve ordinary performance to predict the perceptual quality of ERIs.

Abstract The information transfer mechanism within the population is an essential factor for population‐based multiobjective optimization algorithms. An efficient leader selection strategy can effectively help the population to approach the true Pareto front. However, traditional population‐based multiobjective optimization algorithms are restricted to a single global leader and cannot transfer information efficiently. To overcome those limitations, in this paper, a multiobjective bacterial colony optimization with dynamic multi‐leader co‐evolution (MBCO/DML) is proposed, and a novel information transfer mechanism is developed within the group for adaptive evolution. Specifically, to enhance convergence and diversity, a multi‐leaders learning mechanism is designed based on a dynamically evolving elite archive via direction‐based hierarchical clustering. Finally, adaptive bacterial elimination is proposed to enable bacteria to escape from the local Pareto front according to convergence status. The results of numerical experiments show the superiority of the proposed algorithm in comparison with related population‐based multiobjective optimization algorithms on 24 frequently used benchmarks. This paper demonstrates the effectiveness of our dynamic leader selection in information transfer for improving both convergence and diversity to solve multiobjective optimization problems, which plays a significant role in information transfer of population evolution. Furthermore, we confirm the validity of the co‐evolution framework to the bacterial‐based optimization algorithm, greatly enhancing the searching capability for bacterial colony.

Abstract Efficient management of aircraft and crew recovery system is crucial for cost savings and improving the satisfaction, which are related to the airline's reputation. However, most existing work considers only one objective of minimizing costs or maximizing satisfaction. In this study, we propose a new integrated multi‐objective recovery system that takes both cost and satisfaction into account simultaneously. To better capture crew satisfaction in the event of airport closure, a bidding mechanism for early off‐duty task is designed. To overcome the experience‐dependent and labour‐consuming problems associated with current manual or mathematical recoveries, we develop an intelligent optimizer based on multi‐swarm and MOPSO frameworks, termed adaptive seeking and tracking multi‐objective particle swarm optimization algorithm (ASTMOPSO). Specifically, during the evolutionary process, the sub‐swarm size undergoes adaptive internal transfer while executing more efficient evolutionary strategies to approach the global Pareto front. Additionally, five ad‐hoc repair procedures are designed to ensure feasibility for our aircraft and crew recovery system. The ASTMOPSO is applied to real‐world instances from Shenzhen Airlines with different sizes. Experimental results demonstrate the statistical superiority of our method over other popular peer algorithms. And the infeasible solution repair procedures significantly improve the feasibility rate by at least 40%, particularly for large‐scale instances.

Abstract Outsourcing maintenance service providers are vital to guarantee safe operation in airline industry. To reduce the workload and avoid incompatible arrangement schemes in traditional manual arrangement, this article constructs an intelligent system with a novelly designed model and algorithm for membership‐based aircraft parking stand allocation problem. This problem arises from outsourcing maintenance service providers. They need to first serve membership orders, while guaranteeing punctual delivery of other orders. In particular, mutual collision should be strictly avoided between aircrafts. To solve this problem, first, a mathematical model is constructed to optimize timetable and aircraft parking stand allocation scheme. Second, to quickly obtain feasible scheduling scheme, three kinds of mechanisms, including information guidance mechanism, boundary arrangement mechanisms and local optimal adjustment mechanism, are novelly proposed. Moreover, event‐based time–space separated heuristic algorithm is subtly designed based on time–space separation characteristics. In addition, coding schemes are proposed through problem analysis. Finally, three cases with different scales are utilized and six comparison algorithms are selected to illustrate the superiority of our proposed algorithm.

In colonoscopy, the captured images are usually with low-quality appearance, such as non-uniform illumination, low contrast, etc., due to the specialized imaging environment, which may provide poor visual feedback and bring challenges to subsequent disease analysis. Many low-light image enhancement (LIE) algorithms have recently proposed to improve the perceptual quality. However, how to fairly evaluate the quality of enhanced colonoscopy images (ECIs) generated by different LIE algorithms remains a rarely-mentioned and challenging problem. In this study, we carry out a pioneering investigation on perceptual quality assessment of ECIs. Firstly, considering the lack of specific datasets, we collect 300 low-light images with diverse contents during the real-world colonoscopy and conduct rigorous subjective studies to compare the performance of 8 popular LIE methods, resulting in a benchmark dataset (named ECIQAD) for ECIs. Secondly, in view of the distinctive distortion characteristics of ECIs, we propose an effective no-reference Enhanced Colonoscopy Image Quality (ECIQ) method to automatically evaluate the perceptual quality of ECIs via analysis of brightness, contrast, colorfulness, naturalness, and noise. Extensive experiments on ECIQAD demonstrate the superiority of our proposed ECIQ method over 14 mainstream no-reference image quality assessment methods.

In recent years, there has been significant progress in polyp segmentation in white-light imaging (WLI) colonoscopy images, particularly with methods based on deep learning (DL). However, little attention has been paid to the reliability of these methods in narrow-band imaging (NBI) data. NBI improves visibility of blood vessels and helps physicians observe complex polyps more easily than WLI, but NBI images often include polyps with small/flat appearances, background interference, and camouflage properties, making polyp segmentation a challenging task. This paper proposes a new polyp segmentation dataset (PS-NBI2K) consisting of 2,000 NBI colonoscopy images with pixel-wise annotations, and presents benchmarking results and analyses for 24 recently reported DL-based polyp segmentation methods on PS-NBI2K. The results show that existing methods struggle to locate polyps with smaller sizes and stronger interference, and that extracting both local and global features improves performance. There is also a trade-off between effectiveness and efficiency, and most methods cannot achieve the best results in both areas simultaneously. This work highlights potential directions for designing DL-based polyp segmentation methods in NBI colonoscopy images, and the release of PS-NBI2K aims to drive further development in this field.

Recently, deep neural network-based methods have shown promising advantages in accurately recognizing skin lesions from dermoscopic images. However, most existing works focus more on improving the network framework for better feature representation but ignore the data imbalance issue, limiting their flexibility and accuracy across multiple scenarios in multi-center clinics. Generally, different clinical centers have different data distributions, which presents challenging requirements for the network's flexibility and accuracy. In this paper, we divert the attention from framework improvement to the data imbalance issue and propose a new solution for multi-center skin lesion classification by introducing a novel adaptively weighted balance (AWB) loss to the conventional classification network. Benefiting from AWB, the proposed solution has the following advantages: 1) it is easy to satisfy different practical requirements by only changing the backbone; 2) it is user-friendly with no tuning on hyperparameters; and 3) it adaptively enables small intraclass compactness and pays more attention to the minority class. Extensive experiments demonstrate that, compared with solutions equipped with state-of-the-art loss functions, the proposed solution is more flexible and more competent for tackling the multi-center imbalanced skin lesion classification task with considerable performance on two benchmark datasets. In addition, the proposed solution is proved to be effective in handling the imbalanced gastrointestinal disease classification task and the imbalanced DR grading task. Code is available at https://github.com/Weipeishan2021.

Recently, convolutional neural networks (CNNs) have provided a favoured prospect for authentically distorted image quality assessment (IQA). For good performance, most existing CNN-based methods rely on a large amount of labeled data for training, which is time-consuming and cumbersome to collect. By simultaneously exploiting few labeled data and many unlabeled data, we make a pioneering attempt to propose a semi-supervised framework (termed SSLIQA) with consistency-preserving dual-branch CNN for authentically distorted IQA in this paper. The proposed SSLIQA introduces a consistency-preserving strategy and transfers two kinds of consistency knowledge from the teacher branch to the student branch. Concretely, SSLIQA utilizes the sample prediction consistency to train the student to mimic output activations of individual examples represented by the teacher. Considering that subjects often refer to previous analogous cases to make scoring decisions, SSLIQA computes the semantic relation among different samples in a batch and encourages the consistency of sample semantic relation between two branches to explore extra quality-related information. Benefiting from the consistency-preserving strategy, we can exploit numerous unlabeled data to improve network's effectiveness and generalization. Experimental results on three authentically distorted IQA databases show that the proposed SSLIQA is stably effective under different student-teacher combinations and different labeled-to-unlabeled data ratios. In addition, it points out a new way on how to achieve higher performance with a smaller network.

This study focuses on the challenges of aviation maintenance technician (AMT) scheduling and constructs a model based on personnel satisfaction and the parallel execution of aircraft maintenance tasks. To obtain the scheduling scheme from the constructed NP‐hard model, an interactive multi swarm bacterial foraging optimization (IMSBFO) algorithm is proposed using multi‐swarm coevolu tion, structural recombination, and three informa tion interactive mechanisms among individuals. Moreover, considering the distributed feature of the AMT scheduling problem, a specific mechanism is designed to convert continuous solution to a binary AMT scheduling scheme. Finally, a series of com parative experiments highlight the efficiency and superiority of our proposed IMSBFO algorithm, and the optimal scheduling scheme owns the delicate balance between the work and rest time.

Integrated berth and quay crane allocation problem (BQCAP) are two essential seaside operational problems in container terminal scheduling. Most existing works consider only one objective on operation and partition of quay into berths of the same lengths. In this study, BQCAP is modeled in a multiobjective setting that aims to minimize total equipment used and overall operational time and the quay is partitioned into berths of different lengths, to make the model practical in the real-world and complex quay layout setting. To solve the new BQCAP efficiently, a multiobjective hydrologic cycle optimization algorithm is devised considering problem characteristics and historical Pareto-optimal solutions. Specifically, the quay crane of the large vessel in all Pareto-optimal solutions is rearranged to increase the chance of finding a good solution. Besides, worse solutions are probabilistic retained to maintain diversity. The proposed algorithm is applied to a real-world terminal scheduling problem with different sizes from a container terminal company. Experimental results show that our algorithm generally outperforms the other well-known peer algorithms and its variants on solving BQCAP, especially in finding the Pareto-optimal solutions range.

Clinically, proper polyp localization in endoscopy images plays a vital role in the follow-up treatment (e.g., surgical planning). Deep convolutional neural networks (CNNs) provide a favoured prospect for automatic polyp segmentation and evade the limitations of visual inspection, e.g., subjectivity and overwork. However, most existing CNNs-based methods often provide unsatisfactory segmentation performance. In this paper, we propose a novel boundary constraint network, namely BCNet, for accurate polyp segmentation. The success of BCNet benefits from integrating cross-level context information and leveraging edge information. Specifically, to avoid the drawbacks caused by simple feature addition or concentration, BCNet applies a cross-layer feature integration strategy (CFIS) in fusing the features of the top-three highest layers, yielding a better performance. CFIS consists of three attention-driven cross-layer feature interaction modules (ACFIMs) and two global feature integration modules (GFIMs). ACFIM adaptively fuses the context information of the top-three highest layers via the self-attention mechanism instead of direct addition or concentration. GFIM integrates the fused information across layers with the guidance from global attention. To obtain accurate boundaries, BCNet introduces a bilateral boundary extraction module that explores the polyp and non-polyp information of the shallow layer collaboratively based on the high-level location information and boundary supervision. Through joint supervision of the polyp area and boundary, BCNet is able to get more accurate polyp masks. Experimental results on three public datasets show that the proposed BCNet outperforms seven state-of-the-art competing methods in terms of both effectiveness and generalization.

In this paper, a novel reference input and hysteresis quantizer-based active event-triggered control (RIHQAETC) scheme is proposed for nonlinear networked control systems with quantizer, networked induced delay, and packet dropout. Different from the traditional methods, such a design method is constructed involving the structure of the hysteresis quantizer. In view of the network induced delay and the potential packet dropout, our RIHQAETC method is designed to actively compensate the negative effects caused by these two issues. The corresponding coder and decoder are also excogitated on account of the potential packet dropout based on the proposed triggering mechanism. Furthermore, the transmission of the important triggering information can be ensured as well as the finite-gainL2stability performance. It is demonstrated by an example that our RIHQAETC method presents a more balanced updating frequency between the plant and the controller output sides and reduces the number of total triggering.

This article considers the synchronization problem of drive–response Lurie systems with sampled output error transmitted through a limited network channel with a one-step packet dropout. Two kinds of strategies, that is, quantizer-based triggered control (without packet dropout) and active quantizer and packet dropout-based triggered control (with one-step packet dropout), are put forward. By thoroughly exploring quantizer, sampling interval, and one-step packet dropout information and merging them together, the quantizer and packet dropout related triggering method is proposed to actively deal with the negative effects caused by packet dropout and sampling sensor. With the proposed method, it is demonstrated that synchronization can be ensured and the output error will always be bounded by the quantizer range. In addition, the relationship between the sensor sampling interval and the triggering parameter is provided to match up with our proposed methods. Lower transmission bit rate is also obtained to save more channel resources. Synchronization of two Chua’s circuits is given as an example to demonstrate the validity of our presented results.

Nowadays, the standard dynamic range (SDR) image acquired at a fixed exposure exposes weakness in portraying fine-grained details of real scenes. The high dynamic range (HDR) image and other types of SDR images generated by multiexposure fusion techniques provide us new choices for scene representation. To display on SDR screens, an HDR image must be tone-mapped to an SDR one. Since different tone-mapping/fusion algorithms produce images with varying visual quality levels, it naturally desires a quality evaluation model for comparison. This article proposes an effective model in the absence of the reference image. By analyzing the characteristics of tone-mapped HDR and multiexposure fused images, we first extract multiple quality-sensitive features from the following aspects: 1) colorfulness; 2) exposure; and 3) naturalness. Then, the model is built by bridging all extracted features and associated subjective ratings via support vector regression. Extensive experiments on publicly available databases prove the superiority of our model over the state-of-the-art referenceless quality evaluation ones.

This paper considers the observer-based event-triggered output control problem with quantization. Both plant-to-controller (measured output) channel and controller-to-plant (control input) channel have their own dynamic uniform quantizers and samplings. Therefore, the whole system has four asynchronous clocks, two quantizer updating clocks, and two sampling updating clocks. The main contribution of this paper is the proposed self-triggered and event-triggered control method based on these four clocks. The whole system is stabilized by two steps, i.e., system and controller synchronization, and controller stabilization. In the synchronization process, novel event-triggered and self-triggered samplings are proposed in terms of dynamic quantizer parameters. While in the stabilization process, event-triggered sampling is designed based on controller states and quantizer parameters. Moreover, it is proved that the Zeno behavior would not occur. The practicality and efficiency of the proposed method are illustrated by a numerical example borrowed from recent literature.

Depth-Image-Based-Rendering (DIBR) techniques are significant for three-dimensional (3D) video applications, e.g., 3D television and free viewpoint video (FVV). Unfortunately, the DIBR-synthesized image suffers from various distortions, which induce an annoying viewing experience for the entire FVV. Proposing a quality evaluator for DIBR-synthesized images is fundamental for the design of perceptual friendly FVV systems. Since the associated reference image is usually not accessible, full-reference (FR) methods cannot be directly applied for quality evaluation of the synthesized image. In addition, most traditional no-reference (NR) methods fail to effectively measure the specifically DIBR-related distortions. In this paper, we propose a novel NR quality evaluation method accounting for two categories of DIBR-related distortions, i.e., geometric distortions and sharpness. First, the disoccluded regions, as one of the most obvious geometric distortions, are captured by analyzing local similarity. Then, another typical geometric distortion (i.e., stretching) is detected and measured by calculating the similarity between it and its equal-size adjacent region. Second, considering the property of scale invariance, the global sharpness is measured as the distance between the distorted image and its downsampled version. Finally, the perceptual quality is estimated by linearly pooling the scores of two geometric distortions and sharpness together. Experimental results verify the superiority of the proposed method over the prevailing FR and NR metrics. More specifically, it is superior to all competing methods except APT in terms of effectiveness, but greatly outmatches APT in terms of implementation time.

In past years, various encrypted algorithms have been proposed to fully or partially protect the multimedia content in view of practical applications. In the context of digital TV broadcasting, transparent encryption only protects partial content and fulfills both security and quality requirements. To date, only a few reference-based works have been reported to evaluate the quality of transparently encrypted images. However, these works are incapable of reference-unavailable conditions. In this paper, we conduct the first attempt that proposes a novel quality evaluator in the absence of reference images. The key strategy of the proposed metric lies in extracting features by considering the motivation of transparently encrypted images. Specifically, given that encrypted images prevent content from being easily recognized, several features, including correlation coefficient, information entropy, and intensity statistic, are preliminarily extracted to estimate visual recognizability. Meanwhile, considering that encrypted images are avoided since they are of extremely low quality, we also capture many features to measure the distortions on multiple quality-sensitive image attributes, such as naturalness, structure, and texture. Finally, the quality evaluator is built by bridging all extracted features and corresponding quality scores via a regression module. Experimental results demonstrate that the proposed method is superior to the mainstream no-reference quality evaluation methods designed for synthetically distorted images and possesses a close approximation to state-of-the-art reference-based methods designed for encrypted images.

Subtitles, serving as a linguistic approximation of the visual content, are an essential element in stereoscopic advertisement and the film industry. Due to the vergence accommodation conflict, the stereoscopic 3D (S3D) subtitle inevitably causes visual discomfort. To meet the viewing experience, the subtitle region should be carefully arranged. Unfortunately, very few works have been dedicated to this area. In this article, we propose a method for S3D subtitle region selection in consideration of visual discomfort and viewing habit. First, we divide the disparity map into multiple depth layers according to the disparity value. The preferential processed depth layer is determined by considering the disparity value of the foremost object. Second, the optimal region and coarse disparity value for S3D subtitle insertion are chosen by convolving the selective depth layer with the mean filter. Specifically, the viewing habit is considered during the region selection. Finally, after region selection, the disparity value of the subtitle is further modified by using the just noticeable depth difference (JNDD) model. Given that there is no public database reported for the evaluation of S3D subtitle insertion, we collect 120 S3D images as the test platform. Both objective and subjective experiments are conducted to evaluate the comfort degree of the inserted subtitle. Experimental results demonstrate that the proposed method can obtain promising performance in improving the viewing experience of the inserted subtitle.

This paper mainly focuses on synchronization of controlled drive-response systems under Lurie form through a limited channel. The main contribution of this paper is the quantizer-based triggered methodology proposed based on three coders. By exploring coder structure information and fusing quantization and trigger errors together, this strategy can reduce transmission burden while increase synchronization speed concurrently. And the final synchronization error can be bounded within a predetermined fixed value. According to the initial output of drive system, different coders are purposely designed. With the proposed trigger schemes, traditional binary coder with memory cannot achieve desired performance. Meanwhile, it is found that the static coder leads to satisfactory performance when initial drive system output is within limited region. Combining the advantages of the above two coders, a mixed coder is designed to overcome the shortcomings. Moreover, synchronization error and transmission bit rate are thoroughly discussed and Zeno behavior is radically prevented. Finally, simulations for two Chua's circuits are given to illustrate the validity of the proposed method.