Aligning the decision-making process of deep learning models with that of experienced sonographers is essential for ultrasound-based reliable disease diagnosis. Although existing methods have made significant progress in this aspect, their alignments are primarily associational rather than causal, leading to pseudo-correlations between features and diagnostic results. Such a biased diagnosis blindly models the sonographer's diagnostic skills and attention to specific patterns, which we argue hardly produces an AI diagnoser that is comparable to human experts. To address this issue, we propose a causality-based diagnostic framework to align the model's diagnostic behaviors with those of experts. Specifically, by delving into both conspicuous and inconspicuous confounders within the ultrasound images, the back-door and front-door adjustment causal learning modules are proposed to promote unbiased learning by mitigating potential pseudo-correlations. In addition, we integrate causal inference into a well-designed dual-branch model with feature interaction bridges for compatibility with multimodal ultrasound inputs. To fully evaluate our method, we conduct comparative studies on different diseases and ultrasound modalities. In particular, we publish a carefully constructed multimodal ultrasound dataset for breast lesion diagnosis and segmentation. Sufficient comparative and ablation studies on this dataset emphasize that our method outperforms state-of-the-art methods.

Since a building's floorplan remains consistent over time and is inherently robust to changes in visual appearance, visual Floorplan Localization (FLoc) has received increasing attention from researchers. However, as a compact and minimalist representation of the building's layout, floorplans contain many repetitive structures (e.g., hallways and corners), thus easily result in ambiguous localization. Existing methods either pin their hopes on matching 2D structural cues in floorplans or rely on 3D geometry-constrained visual pre-trainings, ignoring the richer contextual information provided by visual images. In this paper, we suggest using broader visual scene context to empower FLoc algorithms with scene layout priors to eliminate localization uncertainty. In particular, we propose an unsupervised learning technique with clustering constraints to pre-train a room discriminator on self-collected unlabeled room images. Such a discriminator can empirically extract the hidden room type of the observed image and distinguish it from other room types. By injecting the scene context information summarized by the discriminator into an FLoc algorithm, the room style knowledge is effectively exploited to guide definite visual FLoc. We conducted sufficient comparative studies on two standard visual Floc benchmarks. Our experiments show that our approach outperforms state-of-the-art methods and achieves significant improvements in robustness and accuracy.

Object navigation (ObjcetNav), which enables an agent to seek any instance of an object category, has shown great advances. However, current agents are built upon occlusion-prone visual observations or compressed 2-D maps, which hinder their embodied perception of 3-D scene geometry. Furthermore, existing methods usually decouple ObjectNav into the exploration and exploitation subtasks, easily leading to ambiguous object localization and blind exploration. To address these issues, we first propose an embodied contrastive learning (ECL) method with geometric consistency (GC) and behavioral awareness (BA), which motivates agents to encode 3-D scene layouts and semantic cues actively. The BA is modeled by predicting navigational actions based on multiframe visual images, as behaviors causing differences between adjacent visual sensations are crucial for learning correlations among continuous visions. The GC is modeled by aligning the behavior-aware visual stimulus with 3-D semantic shapes through unsupervised contrastive learning. Then, based on the above ECL pretraining, a coarse-to-fine ObjectNav policy with explorer and discriminator cooperation is proposed, inspired by the treasure-hunting mindset. Concretely, the explorer is designed to adaptively switch the action spaces, thereby switching the global and local exploration thoughts according to the accumulated scene priors. The discriminator is designed to discriminate the target's authenticity using behavior-aware visual features and geometric invariance priors, which permits mimicking the human behavior of "approaching to confirm" when distinguishing objects from a distance. As expected, our ECL method performs well on object detection (ObjDet) and instance segmentation (InstSeg) tasks. Our ECL-enhanced ObjectNav strategy outperforms state-of-the-art (SOTA) methods on Matterport3D (MP3D), Gibson, and HM3D datasets.

In recent years, end-to-end congestion control algorithms or flow pausing mechanisms are proposed to achieve high throughput and low latency in datacenter networks. However, prior end-to-end congestion control works without complex signals fail to achieve fast convergence to a stable equilibrium state and effectively handle the transient congestion, while existing flow pausing mechanisms are decoupled from congestion control, which leads to long convergence time after transient states and incomplete queue elimination in equilibrium states. To address these issues, we present FAR, a rate control protocol that combines the advantages of flow pausing and congestion control. At its heart, FAR couples the bandwidth-estimation-based congestion control and the end-to-end flow pausing mechanisms. After flow pausing, FAR quickly explore the available bandwidth with a binary-search probe to achieve high throughput and low latency. Meanwhile, FAR employs a probe staggering mechanism to address the queue oscillation issue in high-concurrency scenarios. We implement the prototype of FAR using DPDK. Extensive evaluation results demonstrate that our protocol achieves accurate bandwidth estimation and reduces the tail flow completion time (FCT) by up to 67% compared with the state-of-the-art designs.

Object Target Search (OTS) tasks require robots to navigate to objects specified by semantic labels, (e.g., find a fire extinguisher). Many existing OTS methods strongly rely on semantic co-occurrence relations among objects to search and localize the object targets in a closed set. However, simplistic domestic or chaotic rescue scenes often fail to provide rich semantics, which in some cases even require the robot to find previously unseen object instances. In addition, most of the existing OTS methods adopt a fixed Field of View (FoV) setting relative to the robot base. When the limited FoV only allows the observation of incomplete objects, this can result in incorrect categorical information and lead to wrong navigation actions. To address the above issues, we propose an open-vocabulary object-seeking method named ChatSeek based on the Large Language Model (LLM)-informed Object Belief Field (OBF) and vehicle-arm cooperation. In particular, our method prompts LLM to generate target objects’ affordance and geometric-part attributes to enhance object localization. By projecting CLIP-based object recognition likelihoods into 3D reconstructions, the OBF is updated to maintain the robot’s cognition of the surrounding scene. During OTS, the robot achieves a flexible vision by moving the vehicle-mounted robotic arm intentionally to translate and rotate the robot’s FoV to look around or even inspect hidden corners. Sufficient comparative and ablation studies demonstrate that our method can significantly improve OTS performance. Furthermore, real-world experiments show that our approach can find novel objects without requiring semantic priors.

Active 3D reconstruction has a wide range of applications, including augmented/virtual reality and various robotics tasks such as navigation, object recognition and manipulation, and scene perception. Most existing approaches rely on offline images or online streams captured by human-operated cameras, requiring significant manual effort and depending on the operator’s expertise. Although some methods have explored using robots to assist data collection by planning the Next-Best-View and then moving the camera to cover these viewpoints, they are often constrained by fixed camera perspectives and suboptimal robot control strategies. These limitations result in inaccurate camera positioning and inaccessible viewpoints, leading to ineffective data collection. In this paper, we explore the feasibility of using a vehicle-arm collaborative robot to tackle the challenges of active 3D reconstruction. Specifically, we decompose this task into two mutually iterative subtasks: the object-centric planning task, which focuses solely on the objects to generate candidate viewpoints, and the agent-centric interaction task, where the robot moves the camera to cover these viewpoints. To achieve this, we propose a collaborative control framework that integrates the motions of the base and arm, enabling efficient recovery of the 3D shape of objects. Sufficient comparative and ablation studies validate that our approach achieves finer surface reconstruction with reduced reconstruction time.

In dynamic human crowds, robot navigation faces significant challenges due to uncertainty, which can negatively impact both navigation success and human safety. Although some approaches have attempted to address this issue, they often focus on modeling uncertainty at the individual pedestrian level, over-looking the complex interactions between pedestrians and robots. To tackle this gap, this paper introduces an adaptive, data-driven uncertainty interaction perception network that accounts for uncertainties in pedestrians, robots, and their mutual behaviors. By assigning adaptive weights to different attention heads, the network dynamically highlights key interaction features, enabling the robot to manage varying levels of uncertainty effectively. This dynamic adjustment enhances the robot’s ability to navigate unpredictable environments while maintaining a balance between safety and efficiency. Additionally, to better reflect the impact of uncertainty, our reward function incorporates the Mahalanobis distance, replacing the commonly used Euclidean distance. This provides a more accurate assessment of potential collision risks, enhancing both safety and social awareness. Through extensive experiments, we show that our approach outperforms state-of-the-art baselines in terms of safety, adherence to social norms, navigation efficiency, and robustness in extreme environments.

Since a building's floorplans are easily accessible, consistent over time, and inherently robust to changes in visual appearance, self-localization within the floorplan has attracted researchers' interest. However, since floorplans are minimalist representations of a building's structure, modal and geometric differences between visual perceptions and floorplans pose challenges to this task. While existing methods cleverly utilize 2D geometric features and pose filters to achieve promising performance, they fail to address the localization errors caused by frequent visual changes and view occlusions due to variously shaped 3D objects. To tackle these issues, this paper views the 2D Floorplan Localization (FLoc) problem from a higher dimension by injecting 3D geometric priors into the visual FLoc algorithm. For the 3D geometric prior modeling, we first model geometrically aware view invariance using multi-view constraints, i.e., leveraging imaging geometric principles to provide matching constraints between multiple images that see the same points. Then, we further model the view-scene aligned geometric priors, enhancing the cross-modal geometry-color correspondences by associating the scene's surface reconstruction with the RGB frames of the sequence. Both 3D priors are modeled through self-supervised contrastive learning, thus no additional geometric or semantic annotations are required. These 3D priors summarized in extensive realistic scenes bridge the modal gap while improving localization success without increasing the computational burden on the FLoc algorithm. Sufficient comparative studies demonstrate that our method significantly outperforms state-of-the-art methods and substantially boosts the FLoc accuracy.

LiDAR-camera extrinsic calibration (LCEC) is crucial for multi-modal data fusion in autonomous robotic systems. Existing methods, whether target-based or target-free, typically rely on customized calibration targets or fixed scene types, which limit their applicability in real-world scenarios. To address these challenges, we present EdO-LCEC, the first environment-driven online calibration approach. Unlike traditional target-free methods, EdO-LCEC employs a generalizable scene discriminator to estimate the feature density of the application environment. Guided by this feature density, EdO-LCEC extracts LiDAR intensity and depth features from varying perspectives to achieve higher calibration accuracy. To overcome the challenges of cross-modal feature matching between LiDAR and camera, we introduce dual-path correspondence matching (DPCM), which leverages both structural and textural consistency for reliable 3D-2D correspondences. Furthermore, we formulate the calibration process as a joint optimization problem that integrates global constraints across multiple views and scenes, thereby enhancing overall accuracy. Extensive experiments on real-world datasets demonstrate that EdO-LCEC outperforms state-of-the-art methods, particularly in scenarios involving sparse point clouds or partially overlapping sensor views.

Semantic segmentation and stereo matching, respectively analogous to the ventral and dorsal streams in our human brain, are two key components of autonomous driving perception systems. Addressing these two tasks with separate networks is no longer the mainstream direction in developing computer vision algorithms, particularly with the recent advances in large vision models and embodied artificial intelligence. The trend is shifting towards combining them within a joint learning framework, especially emphasizing feature sharing between the two tasks. The major contributions of this study lie in comprehensively tightening the coupling between semantic segmentation and stereo matching. Specifically, this study makes three key contributions: (1) a tightly coupled, gated feature fusion strategy, (2) a hierarchical deep supervision strategy, and (3) a coupling tightening loss function. The combined use of these technical contributions results in TiCoSS, a state-of-the-art joint learning framework that simultaneously tackles semantic segmentation and stereo matching. Through extensive experiments on the KITTI, vKITTI2, and Cityscapes datasets, along with both qualitative and quantitative analyses, we validate the effectiveness of our developed strategies and loss function. Our approach demonstrates superior performance compared to prior arts, with a notable increase in mean intersection over union by over 9%.

Object Goal Navigation (ObjectNav) in novel environments relies on comprehensive scene understanding, including precise visual perception and accurate modeling of spatial-semantic regularities. However, excessive attention to the hand-crafted scene representation in prevailing approaches leads to the neglect of the negative influence of the perception bias hidden in the visual observations. The hand-crafted semantic distribution in domestic environments causes the spurious association bias, while the semantic conflict bias arises due to the dynamic perspective changes. Biased visual perception significantly limits the generalization of the navigation strategy. In this article, we propose the U nbiased E mbodied V isual R epresentation ( UEVR ), which overcomes the perception biases using causal inference and cross-modality alignment. Specifically, we establish reasonable assumptions about confounders for multi-object features through our proposed Unbiased Causal R-CNN framework and eliminate the spurious associations bias through B ackdoor I ntervention C ausal A djustment ( BICA ) module during navigation. To overcome the dynamic-view bias hidden in 2D image features, we propose to employ the cross-modality alignment mechanism with the Geometric Consistency ( GeoCon ) to encode 3D geometry prior into the 2D representations. Finally, we design a modular ObjectNav framework integrated with UEVR named Causal-ObjectNav , which consists of the corner-based scene exploration module and target object discrimination module. Extensive experiments on the MP3D and HM3D datasets demonstrate the superiority of the unbiased navigation model over existing ObjectNav methods.

For the widely deployed on-chip shared buffer, efficient buffer management is the key to absorbing bursts and avoiding packet loss during transient congestion. However, as the buffer-per-port-per-Gbps in production data centers decreases, it becomes more challenging to provide efficient buffer management to meet the requirements of heterogeneous traffic. We observe that typical shared buffer management policies have two steps: first, they identify short flows arriving at ports and then allocate more buffer room for these ports. Unfortunately, the lack of isolation between long and short flows leads to increased queue buildup and even packet loss of short flows. To address this limitation, we propose D2T, which uses different queue length thresholds for long and short flows. Specifically, we first design a compact data structure to distinguish between long and short flows. Then when two kinds of flows coexist at the same port, the threshold of long flows will decrease to absorb the bursty short flows. What’s more, we introduce D2T${}^{*}$which combines D2T with advanced DRL techniques to move toward mastering buffer management for further improving performance across various scenarios. We implement D2T at a P4-programmable switch and large-scale simulations. The results demonstrate that D2T reduces both average and tail flow completion times (FCT) of short flows by up to 29% and 62% compared with the state-of-the-art policies, respectively.

Today, robots are finding more and more applications in areas such as industrial and agricultural production, environmental exploration, and disaster relief. To be effective in these roles, robots must be able to autonomously navigate complex and unstructured environments. Manipulative robotic arms can navigate through confined spaces and have the ability to explore diverse scenes. Therefore, the exploration of unknown environments, facilitated by the synergy between robotic arms and wheeled chassis, provides a more efficient and accurate approach. We have designed a comprehensive arm-chassis collaboration system that uses an information gain-based utility function to support exploration. By coordinating the motion of the robotic arm with the mobility of the chassis, this system efficiently performs complex exploration tasks. It enables autonomous exploration of unknown environments with reduced time and energy consumption. The code is published at: https://github.com/Southyang/Arm-Chassis.

State machine replication (SMR) uses consensus as its core component for reaching agreement among a group of processes, in order to provide fault-tolerant services. Most SMR protocols, such as Paxos and Raft, are designed in the partial synchrony model. Partially synchronous protocols rely on timing assumptions to elect a special role (such as the leader), which may become the performance bottleneck under a heavy workload. From an engineering perspective, partially synchronous protocols have to wait for a pre-defined period of time and implement a (complicated) failover mechanism in order to replace the faulty leader. In contrast, asynchronous protocols are immune to such problems.

Nowadays the data center switches employ the on-chip shared buffer to absorb bursts and avoid packet loss during transient congestion. However, as the buffer-per-port-per-Gbps in production data centers decreases, it becomes more challenging to provide efficient buffer management to meet the requirements of heterogeneous traffic. We observe that typical shared buffer management policies have two steps: first, they identify short flows arriving at ports and then allocate more buffer room for these ports. Unfortunately, the lack of isolation between long and short flows leads to increased queue buildup and even packet loss of short flows. To address this limitation, we propose D2T, which uses different queue length thresholds for long and short flows. Specifically, we first design a compact data structure to distinguish between long and short flows. Then when two kinds of flows coexist at the same port, the threshold of long flows will decrease to absorb the bursty short flows. We implement D2T at a P4- programmable switch and large-scale simulations. The results demonstrate that D2T reduces both average and tail flow completion times (FCT) of short flows by up to 29% and 62% compared with the state-of-the-art policies, respectively.

To achieve high throughput and low latency for data center applications, there are two broad lines of work: end-to-end congestion control algorithms and flow pausing mechanisms. It is challenging for end-to-end congestion control algorithms without complex signals to achieve fast convergence to a stable equilibrium state while effectively handling the transient congestion. Additionally, flow pausing mechanisms are decoupled from congestion control, which leads to long convergence time after transient state and incomplete queue elimination in equilibrium state. We propose a transport protocol that combines the advantages of flow pausing and congestion control, called FAR. The key idea is coupling the bandwidth-estimation based congestion control and the end-to-end flow pausing mechanisms. FAR quickly explores the available bandwidth with binary-search based packet train probe to achieve high throughput and low latency. Extensive evaluation results demonstrate that our protocol achieves accurate bandwidth estimation and reduces the tail flow completion time (FCT) by up to 67 <?TeX $\%$?> Math 1 compared with the state-of-the-art designs.

Visual Semantic Navigation (VSN) aims at navigating a robot to a given target object in a previously unseen scene. To tackle this task, the robot must learn a nimble navigation policy by utilizing spatial patterns and semantic co-occurrence relations among objects in the scene. Prevailing approaches extract scene priors from the instant visual observations and solidify them in neural episodic memory to achieve flexible navigation. However, due to the oblivion and underuse of the scene priors, these methods are plagued by repeated exploration, effective-knowledge sparsity, and wrong decisions. To alleviate these issues, we propose a novel VSN policy, HSPNav, based on Hierarchical Scene Priors (HSP) and Deep Reinforcement Learning (DRL). The HSP contains two components, i.e., the egocentric semantic map-based Local Scene Priors (LSP) and the commonsense relational graph-based Global Scene Priors (GSP). Then, efficient semantic navigation is achieved by employing an immediate LSP to retrieve conducive contextual memories from the GSP. By utilizing the MP3D dataset, the experimental results in the Habitat simulator demonstrate that our HSP brings a significant boost over the baselines. Furthermore, we take an essential step from simulation to reality by bridging the gap from Habitat to ROS. The migration evaluations show that HSPNav can generalize to realistic settings well and achieve promising performance.

Social navigation is a key consideration for integrating robots into human environments. Concurrently, it imposes heightened requisites: tasks must not only be executed succesfully without collisions, but also adhere to principles encompassing comprehensibility, courtesy, social compliance, comprehension, foresight, and scenario compliance. In this paper, we present the incorporation of social norms as a guiding framework for robot navigation within social contexts. We adopt field theory to provide a formal elucidation of the social norms, using Physical-Informed Neural Network (PINN) to predict pedestrian movement under the influence of social norms, respectively, and using Reinforcement Learning (RL) for navigation. We use supervised learning to train the pedestrian velocity field prediction model and reinforcement learning to train the navigation policy. We conduct three parts of experiments: (1) analyzing the spatiotemporal characteristics of the velocity field in the walking pedestrians dataset; (2) evaluating the accuracy of the vector field prediction in the pedestrian dataset; (3) using Gazebo simulation and the PEDSIM library to evaluate the improvement of navigation performance under constraints of social norms. Experiments have confirmed that the pedestrian motion data set indeed satisfies the Gaussian divergence theorem and can be described by the concept of field. The performance of navigation strategies incorporating social rules has been improved to a certain extent.

Object Navigation (ObjcetNav), which enables an agent to seek any instance of an object category specified by a semantic label, has shown great advances. However, current agents are built upon occlusion-prone visual observations or compressed 2D semantic maps, which hinder their embodied perception of 3D scene geometry and easily lead to ambiguous object localization and blind exploration. To address these limitations, we present an Embodied Contrastive Learning (ECL) method with Geometric Consistency (GC) and Behavioral Awareness (BA), which motivates agents to actively encode 3D scene layouts and semantic cues. Driven by our embodied exploration strategy, BA is modeled by predicting navigational actions based on multi-frame visual images, as behaviors that cause differences between adjacent visual sensations are crucial for learning correlations among continuous visions. The GC is modeled as the alignment of behavior-aware visual stimulus with 3D semantic shapes by employing unsupervised contrastive learning. The aligned behavior-aware visual features and geometric invariance priors are injected into a modular ObjectNav framework to enhance object recognition and exploration capabilities. As expected, our ECL method performs well on object detection and instance segmentation tasks. Our ObjectNav strategy outperforms state-of-the-art methods on MP3D and Gibson datasets, showing the potential of our ECL in embodied navigation.

In recent years, since edge computing has improved the performance of transportation systems, research on edge-computing-enabled transportation systems has received widespread attention. However, most previous studies overlooked that task requests in transportation systems are unevenly distributed in time and space, which easily causes the overloading of edge servers, resulting in high response latency. To this end, we present a novel task offloading scheme based on graph neural network (GNN) and deep reinforcement learning (DRL) in edge-computing-enabled transportation systems (TransEdge). Specifically, we first propose an adaptive node placement algorithm to assign Internet of Things sensors to appropriate edge servers, thereby minimizing transmission latency. Then, an improved DRL scheme based on GNN is designed to capture the spatial features between sensors, aiming to improve the accuracy of task offloading decisions. Finally, we introduce a task forwarding strategy based on the greedy algorithm to achieve collaborative task offloading between different edge servers and overcome the system instability caused by a sudden surge in task requests. We conduct extensive experiments on two real-world traffic data sets. The results show that TransEdge reduces the response latency by at least 3.7% compared to four baselines while achieving a success rate of 99%.

Recently, the Industrial Internet of Things (IIoT) has shown great application value in environmental monitoring. However, it suffers from serious bottlenecks in energy and computing capability. To address them, researchers have made lots of effort. Nevertheless, they neglect either the edge–end collaboration or the impact of task queue backlog, resulting in low system revenue. To this end, we design a queue-aware computation offloading method based on DRL (QDRL). Specifically, we represent the long-term system operation as a multistage stochastic mixed-integer optimization problem (M-SMIP), which is further converted into a deterministic problem using Lyapunov optimization. Given that the resource allocation and computation offloading in this deterministic problem are strongly coupled and difficult to solve, we decompose this problem into two subproblems. Subsequently, a reinforcement learning scheme with actor–critic architecture is designed to solve these subproblems. The Actor module is designed based on a deep learning model and quantization strategy for generating computation offloading actions. The mathematical reasoning and learning-based methods are integrated as the Critic module for achieving resource allocation. Extensive simulation results show that the performance of QDRL surpasses four baselines and approaches the approximate optimal algorithm in terms of average task queue length, normalized real computation rate, and computation time.

This paper presents URSAL, an HDD-only block storage system that achieves ultra-efficiency, reliability, scalability and availability at low cost. Compared to existing block stores such as URSA, Ceph, and Sheepdog, URSAL has the following distinctions. First, since parallelism is harmful to the random I/O performance on HDDs, we restrict URSAL storage servers to conservatively perform parallel I/O on HDDs for avoiding I/O contention and reducing tail latency. Second, URSAL designs a proxy-based storage architecture to separate the high-level and low-level I/O logic, where for each virtual machine (VM) there is one URSAL proxy process running at the client VM side to control (at a high level) the procedure of server-side low-level I/O. Third, to alleviate the problem of low random write performance of HDDs, URSAL selectively performs direct block writes on raw HDDs or indirect log appends to HDD journals (which are then asynchronously replayed to raw HDDs), depending on the characteristics of the workloads. Fourth, software failures are nontrivial in large-scale block storage systems of which the availability is vital to client VMs, and thus for high availability we design an efficient fault-tolerance mechanism by isolating the connection management module of URSAL proxy. We have implemented URSAL and deployed it at scale. Extensive evaluation results demonstrate that URSAL achieves much higher performance than the state-of-the-art solutions for underloaded scenarios.

The Object goal Navigation (ObjectNav) task requires an agent to navigate through a previously unknown domestic scenario using spatial and semantic contextual information, where the goal is specified by a semantic label (e.g., find a TV). Such a task is especially challenging as it requires formulating and understanding the complex co-occurrence relations among objects in diverse settings, which is critical for long-sequence navigational decision-making. Existing methods learn to either explicitly represent co-occurrence relationships as discrete semantic priors, or implicitly encode them from raw observations, thus can not benefit from the rich environmental semantics. In this work, we propose a novel Deep Reinforcement Learning (DRL) based ObjectNav strategy by actively imagining spatial and semantic clues outside the agent’s Field of View (FoV) and further mining Continuous Environmental Representations (CER) using self-supervised learning. Additionally, the illusion of spatial and semantic patterns allows the agent to perform Multi-Step Forward-Looking Planning (MSFLP) by considering the temporal evolution of egocentric local observations. Our approach is thoroughly evaluated and ablated in the visually realistic environments of the Matterport3D (MP3D) dataset. The experimental results reflect that our method combining CER and imagination-based MSFLP facilitates learning complicated semantic priors and navigation skills, thus achieving state-of-the-art performance on the ObjectNav task. In addition, adequate quantitative and qualitative analyses validate the excellent generalization ability and superiority of our method.

In tile-based 360° video streaming, the users employ the tile rate allocation algorithm to select appropriate bitrate to maximize the quality of experience (QoE). The preferences and viewports, however, can vary significantly across the different users. Since the users independently choose their bitrate according to their own preferences and viewports, it is hard to ensure QoE fairness for users under the constraint of available bandwidth. In this article, we propose a QoE-fairness aware bitrate allocation algorithm for multi-users (QBAM) to reduce difference of user QoE. According to the trajectory of the user viewpoint and user preferences for video quality, rebuffer time and quality switching, we leverage multi-agent reinforcement learning to train the bitrate allocation strategy. The experimental results show, compared with the current tile rate allocation algorithm, QBAM effectively improves the QoE fairness.

The autonomous exploration task we consider requires Unmanned Aerial Vehicles (UAVs) to actively navigate through unknown environments with the goal of fully perceiving and mapping the environments. Some existing exploration strategies suffer from rough cost budgets, ambiguous Information Gain (IG), and unnecessary backtracking exploration caused by Fragmented Regions (FRs). In our work, a hierarchical spatio-temporal-aware exploration framework is proposed to alleviate these problems. At the local exploration level, the Asymmetrical Traveling Salesman Problem (ATSP) is solved by comprehensively considering exploration time, IG, and heading consistency to avoid blindly exploring. Specifically, the exploration time is reasonably budgeted by fast marching in an artificial potential field. Meanwhile, a transformer-based map occupancy predictor is designed to assist in IG calculation by imagining spatial clues out of the Field of View (FoV), facilitating the prescient exploration. We verify that our local exploration is effective in alleviating the unnecessary back-and-forth movements caused by FRs and the interference of potential obstacle occlusion on the IG calculation. At the global exploration level, the classical Next Best View Points (NBVP) are generalized to Next Best Sub-Regions (NBSR) to choose informative sub-regions for further forward-looking exploration based on a well-designed utility function. Safe flight paths and dynamically feasible trajectories are reasonably generated throughout the exploration process by fast marching and B-spline curve optimization. Comparative simulations and benchmark tests demonstrate that our proposed exploration strategy is quite competitive in terms of exploration path length, total exploration time, and exploration ratio.

Multi-modal transportation recommendation plays an important role in navigation applications. It aims to recommend a travel plan with various transport modes, such as bus, metro, taxi, bicycle, and a hybrid. Analysis of real-world large-scale navigation data shows that the correlation between the data can be represented by a graph containing different types of nodes and edges. As an emerging technology, graph neural networks (GNN) have shown powerful capabilities in representing graph data. However, existing solutions based on GNN only consider converting heterogeneous graph data into homogeneous graph data, ignoring the effects of different types of nodes and edges. In addition, those methods usually face the over-smoothing problem, which reduces the accuracy of recommendation. To this end, we propose a multi-modalTransportation recommendation algorithm withHeterogeneous graphAttentionNetworks (THAN) based on carefully constructed heterogeneous graphs. We first design a novel graph embedding method to represent the correlation between the origin and the destination, as well as the correlation between origin-destination (OD) pairs and users. Next, a heterogeneous graph from large-scale data is built to describe the relationship between users, OD pairs, and transport modes. Then, we design a hierarchical attention mechanism with residual blocks to generate node embedding in terms of homogeneity and heterogeneity. Finally, a fusion neural layer is designed to fuse embeddings from different views and predict the proper transport mode for users. Extensive experimental results on a large-scale real-world dataset demonstrate that the performance of THAN outperforms five baselines.

The video streaming system employs adaptive bitrate (ABR) algorithms to optimize a user’s quality of experience. However, it is hard for ABR algorithms to choose the right bitrate consistently under highly dynamic bandwidth fluctuations in wild Internet. In this article, we propose a building block on the client side named Opportunistic Chunk Replacement Mechanism (OCRM) to help existing ABR algorithms make full use of the available bandwidth to improve the network utilization and viewing experience of users. Specifically, the servers take advantages of the spare bandwidth to opportunistically transmit high-quality chunks (called opportunistic chunks ) with low priority to the client, without incurring any extra delay. Then, the client player replaces the low-quality chunks with the opportunistic ones that have high quality. We compare OCRM with state-of-the-art ABR algorithms by using trace-driven experiments spanning a wide variety of quality of experience metrics and network conditions. The test results show that OCRM effectively achieves high network utilization and improves the user’s viewing experience by up to 35%.

Blockchain(e.g., Bitcoin) has widespread use in digital currency, which is entirely public to all participants, revealing users' privacy and transaction details. Anonymous blockchains without auditing capability can offer strong privacy guarantees, they could be used by illegal activities. However, anonymous blockchains with auditing capability suffer from two limitations: (i) inefficient auditing capability; (ii) lower degree of decentralization. To address these problems, this paper presents IAP, an instant auditing protocol based on anonymous blockchain with strong anonymity guarantees, which uses audit node cluster to implement decentralized instant auditing. The experimental results show that IAP only needs 60 milliseconds to complete an audit on average with 16 audit nodes, which accounts for one thousand of a complete transaction time. IAP can still complete efficient auditing when there are more than half of the nodes are honest in the audit node cluster. Moreover, its performance is virtually unaffected by increased number of transactions.

Integrity and privacy are two important secure matrices in cyber security. Due to the limited resources and computing capability of the sensor nodes, it is challenging to simultaneously satisfy these two matrices for top-k querying in two-tiered sensor networks. To solve this problem, this paper proposes a weight-bind-based secure top-k query processing scheme (WBB-TQ), which utilises both the order-preserving symmetric encryption scheme (OPES) and the pairwise-key encryption technique to ensure data privacy in top-k querying. Since OPES can keep the size orders of the sensed data items unchanged before and after they are encrypted, the upper-layer storage nodes in the network can process top-k queries without knowing the exact values of the sensed data items. To guarantee the completeness of query results, we propose a novel method to establish chaining relationship among all the data items generated by each sensor node. By checking whether the relationship holds on not, Sink can find out whether adversaries drop and/or tamper with part or all of the qualified top-k data items in the query results. Theoretical analyses show that WBB-TQ can preserve data integrity and privacy of the top-k query results. Extensive simulation results further demonstrate that, WBB-TQ incurs very low computational and communication cost in securing top-k querying.

Large-scale cloud block storage provides virtual disks for various applications and services like online booking, gaming, and offline data analytics. The state-of-the-art URSA [1] block store adopted a hybrid storage structure which placed primary data on solid-state drives (SSDs) and stored backup data on hard-disk drives (HDDs). URSA used small SSD journals to bridge the performance gap between SSDs and HDDs. Although URSA's SSD-HDD-hybrid storage structure achieves SSD-like I/O performance while using only one third of the SSDs required by the SSD-only storage pattern (storing both primary data and backup data on SSDs), we argue that the traditional HDDonly storage structure is still preferable for a large variety of relatively low-end customers and underloaded applications that are sensitive to the per-bit storage cost.To lower the storage cost, in this paper we design URSAL, an HDD-only block store which provides ultra efficiency, reliability, scalability and availability at low cost. Compared to existing block stores such as URSA, Ceph, and Sheepdog, URSAL has the following distinctions. First, URSAL designs the proxy-based storage architecture, where a proxy server process runs together with each virtual machine (VM) client mounting virtual disks and controls the procedure of all block-level I/O. Second, URSAL selectively performs direct block writes on raw HDDs or indirect log appends to HDD journals (which are then asynchronously replayed to raw HDDs), depending on the characteristics of the workloads. Third, URSAL runs one storage server process for each physical HDD, which conservatively has at most one active thread reading/writing the HDD to avoid I/O contention. We have implemented URSAL. Evaluation results show that URSAL significantly outperforms state-of-the-art HDD-only block stores (Ceph and Sheepdog) when providing virtual disks for underloaded applications.

Quantifying the associations between diseases is now playing an important role in modern biology and medicine. Actually discovering associations between diseases could help us gain deeper insights into pathogenic mechanisms of complex diseases, thus could lead to improvements in disease diagnosis, drug repositioning, and drug development. Due to the growing body of high-throughput biological data, a number of methods have been developed for computing similarity between diseases during the past decade. However, these methods rarely consider the interconnections of genes related to each disease in protein-protein interaction network (PPIN). Recently, the disease module theory has been proposed, which states that disease-related genes or proteins tend to interact with each other in the same neighborhood of a PPIN. In this study, we propose a new method called ModuleSim to measure associations between diseases by using disease-gene association data and PPIN data based on disease module theory. The experimental results show that by considering the interactions between disease modules and their modularity, the disease similarity calculated by ModuleSim has a significant correlation with disease classification of Disease Ontology (DO). Furthermore, ModuleSim outperforms other four popular methods which are all using disease-gene association data and PPIN data to measure disease-disease associations. In addition, the disease similarity network constructed by MoudleSim suggests that ModuleSim is capable of finding potential associations between diseases.

The blockchain uses a decentralized consensus mechanism to maintain the books in an immutable way, which ensures the blockchain smart contract system highly secure. In existing blockchain systems, all user information is disclosed in the blockchain. However, currently users begin to pay more and more attention to personal privacy, therefore the future blockchain smart contract system needs not only to keep immutability but also to protect user privacy. To achieve this goal, in this paper we propose a privacy-encrypted blockchain system, where all data is encrypted within a controllable period of time. Although the data is visible from a historical perspective, our design can effectively protect user privacy and against deceivers, making the system more secure and healthy.

Shared e-bikes are popular because of their green, eco-friendly and efficient features. Due to the limited battery capacity of the e-bikes, the energy problem has become one of the main factors limiting its further development. The energy problem can be solved by using static charging piles (SCP) to replenish the batteries of shared e-bike. The location of the shared e-bike is time-varying, resulting in the optimal deployment of SCP as a complex location problem. In this paper, we propose an optimal Deployment algorithm for Maximum Coverage combined the Dynamic Changes of nodes (max-DCDC) based on the known number of SCP. This method first quantitatively analyzes the dynamic change process of the shared e-bike to reduce the deployment scope of the SCP. Then, according to the geometric characteristics of the e-bike distribution within the deployment scope to optimizes the deployment location of the SCP. Simulation experiments show that max-DCDC has better performance in terms of deployment stability and e-bike coverage compared with the other algorithms.

Virtual machines (VMs) and processes are two important abstractions for cloud virtualization, where VMs usually install a complete operating system (OS) executing user processes. Although existing in different layers in the virtualization hierarchy, VMs and processes have overlapped functionalities. For example, they are both intended to provide execution abstraction (e.g., physical/virtual memory address space), and share similar objectives of isolation, cooperation and scheduling. However, neither of them could provide the benefits of the other: VMs provide higher isolation, security and portability, while processes are more efficient, flexible and easier to schedule and cooperate. Currently, this heavyweight architecture degrades both efficiency and security of cloud services. There are two trends for cloud virtualization: the first is to enhance processes to achieve VM-like security, and the second is to reduce VMs to achieve process-like flexibility. Based on these observations, our vision is that in the near future VMs and processes might be fused into one new abstraction for cloud virtualization that embraces the best of both, providing VM-level isolation and security while preserving process-level efficiency and flexibility. We describe a reference implementation, dubbed cKernel (customized kernel), for the new abstraction. Essentially, cKernel enhances the exokernel architecture by (i) adopting the LibOS paradigm to assemble isolated, smallest possible "execution environments", and (ii) following the the "core-shell" model to dynamically add traditional process features to the environments.

One of the important sources for big data is the datasets collected by wireless sensor networks. However, errors in sensor data could result in serious damages in industrial applications. Therefore, error detection plays a crucial role in industrial wireless sensor networks (IWSNs). Existing approaches of error detection are generally threshold-based, which rely on a predetermined threshold to judge whether a reading is erroneous. The threshold-based approaches, however, often fail to balance between detection accuracy and false alarm rate. It is thus difficult, if not impossible, to obtain a proper threshold for various errors in real-world applications. Motivated by this consideration, we propose a novel threshold-free error detection approach for IWSNs. By taking the advantage of the spatiotemporal correlations between sensor readings, we present the model to characterize the relationship between sensor pairs and, thus, construct a correlation graph for IWSN. In the correlation graph, the states of nodes, i.e., the states of sensor readings, are accurately exploited without requiring any threshold. Through the experiments on both real sensors and simulations, we demonstrate that the proposed approach is able to significantly improve the detection accuracy while largely reducing the false alarm rate.

RAM-based storage aggregates the RAM of servers in data center networks (DCN) to provide extremely high storage performance. For quick recovery of storage server failures, Mem-Cube [1] exploits the proximity of the BCube network to limit the recovery traffic to the recovery servers' 1-hop neighborhood. However, previous design is applicable only to BCube, and has suboptimal recovery performance due to congestion and contention. To address these problems, in this paper we propose CubeX, which generalizes the “1-hop” principle of MemCube for all cube-based networks, and improves the throughput and recovery performance of RAM-based key-value (KV) store via cross-layer optimizations. At the core of CubeX is to leverage the glocality (= globality + locality) of cube-based networks: it scatters backup data across a large number of disks globally distributed throughout the cube, and restricts all recovery traffic within the small local range of each server node. Our evaluation shows that CubeX efficiently supports RAM-based KV store for cube-based networks, and CubeX remarkably outperforms MemCube in both throughput and recovery time.

Summary The proliferation of Internet applications, cloud systems, and mobile social networks results in unprecedented data set scale and high data generation rate. For us to be able to extract any meaningful information, it is important to achieve real‐time online data analytics. Skyline queries are important in many online data applications such as real‐time Web mining, multipreference analysis, and decision making. Most existing studies mainly focus on centralized systems, and distributed skyline query processing is still an emerging and challenging topic. In this paper, we propose SkyStorm, a delay‐bounded parallel skyline computing approach for large‐scale real‐time data analytics by dividing the search into multiple rounds and limiting the search in each round within a budget‐restricted range. The effectiveness of our proposals is demonstrated through analysis and simulations.

The design of maintenance mechanisms ofdistributed hash tables (DHTs) is usually specific totheir initial graphs, and thus it is complicated anderror-prone. Zhang and Liu propose in [4] the "distributedline graphs" (DLG) mechanism, a universaltechnique for designing DHTs based on arbitraryregular graphs while preserving the main features ofthe initial graphs. However, two important propertiesof DLG, the expandability and fidelity, have notbeen studied with detailed explanations or analysis.In this paper, we study the above two properties ofDLG transformations, and prove that (i) the DLGtransformations are incrementally expandable, and(ii) the DLG transformations from Gi to Gi+1 keepfidelity.