Reviewerly/exHarmony huggingface dataset:
A global-energy-aware virtual machine placement strategy for cloud data centers

Virtual machine (VM) placement is a key technique for energy optimization in cloud data centers. Previous work generally focus on how to place the VMs efficiently in servers to optimize the physical resources used (e.g., memory, bandwidth, CPU, etc.), network resources used or cooling energy consumption. These work can optimize the energy consumption of cloud data centers according to one or two aspects (e.g. server, network or cooling), however, these methods may cause increased energy consumption in other aspects. To address this problem, we propose a global-energy-aware VMP (virtual machine placement) strategy to reduce, from multiple aspects, the total energy consumption of data centers. A two-step SAG algorithm is designed to lower the energy consumption of cloud data centers where multiple VMs are deployed. We conduct extensive experiments to evaluate the effectiveness of SAG. Two workloads from real-world data centers are utilized to quantitatively measure and compare the performance of our SAG with other typical algorithms. Experimental results indicate that, compared to other algorithms, our global-energy-aware VMP strategy can reduce the total energy consumption of the cloud data center by 8%–24.9%.
Trajectory Outlier Detection

This article introduces two new problems related to trajectory outlier detection: (1) group trajectory outlier (GTO) detection and (2) deviation point detection for both individual and group of trajectory outliers. Five algorithms are proposed for the first problem by adapting DBSCAN , k nearest neighbors (kNN) , and feature selection (FS) . DBSCAN-GTO first applies DBSCAN to derive the micro clusters , which are considered as potential candidates. A pruning strategy based on density computation measure is then suggested to find the group of trajectory outliers. kNN-GTO recursively derives the trajectory candidates from the individual trajectory outliers and prunes them based on their density. The overall process is repeated for all individual trajectory outliers. FS-GTO considers the set of individual trajectory outliers as the set of all features, while the FS process is used to retrieve the group of trajectory outliers. The proposed algorithms are improved by incorporating ensemble learning and high-performance computing during the detection process. Moreover, we propose a general two-phase-based algorithm for detecting the deviation points, as well as a version for graphic processing units implementation using sliding windows. Experiments on a real trajectory dataset have been carried out to demonstrate the performance of the proposed approaches. The results show that they can efficiently identify useful patterns represented by group of trajectory outliers, deviation points, and that they outperform the baseline group detection algorithms.
Medical Image Reconstruction Using Generative Adversarial Network for Alzheimer Disease Assessment with Class-Imbalance Problem

One of the most challenging problem faced with medical image analysis is the lack of some modality images. In this work, we propose an effective data augmentation method that uses the generative adversarial network to reconstruct the missing PET images. A densely connected convolutional network is developed as the classification model to make the binary classification. The experiments on ADNI class-imbalanced dataset demonstrate that add the reconstructed images can significantly improve the classification performance of the densely connected model and effectively deal with the class-imbalanced challenge. The influence of different noisy dimensions is also detailedly discussed in term of maximum mean discrepancy and structural similarity metric. The proposed method will make some contribution to other clinical class-imbalanced datasets.
Testing Graphical Causal Models Using the R Package “dagitty”

Causal diagrams such as directed acyclic graphs (DAGs) are used in several scientific fields to help design and analyze studies that aim to infer causal effects from observational data; for example, DAGs can help identify suitable strategies to reduce confounding bias. However, DAGs can be difficult to design, and the validity of any DAG-derived strategy hinges on the validity of the postulated DAG itself. Researchers should therefore check whether the assumptions encoded in the DAG are consistent with the data before proceeding with the analysis. Here, we explain how the R package 'dagitty', based on the web tool dagitty.net, can be used to test the statistical implications of the assumptions encoded in a given DAG. We hope that this will help researchers discover model specification errors, avoid erroneous conclusions, and build better models. © 2021 The Authors. Basic Protocol 1: Constructing and importing DAG models from the dagitty web interface Support Protocol 1: Installing R, RStudio, and the dagitty package Basic Protocol 2: Testing DAGs against categorical data Basic Protocol 3: Testing DAGs against continuous data Support Protocol 2: Testing DAGs against continuous data with non-linearities Basic Protocol 4: Testing DAGs against a combination of categorical and continuous data.
Efficient and Privacy-Preserving Similarity Range Query Over Encrypted Time Series Data

Similarity query over time series data plays a significant role in various applications, such as signal processing, speech recognition, and disease diagnosis. Meanwhile, driven by the reliable and flexible cloud services, encrypted time series data are often outsourced to the cloud, and as a result, the similarity query over encrypted time series data has recently attracted considerable attention. Nevertheless, existing solutions still have issues in supporting similarity queries over time series data with different lengths, query accuracy and query efficiency. To address these issues, in this article, we propose a new efficient and privacy-preserving similarity range query scheme, where the time warp edit distance (TWED) is used as the similarity metric. Specifically, we first organize time series data into a <inline-formula><tex-math notation="LaTeX">$k$</tex-math></inline-formula> d-tree by leveraging TWED’s triangle inequality, and design an efficient similarity range query algorithm for the <inline-formula><tex-math notation="LaTeX">$k$</tex-math></inline-formula> d-tree. Second, based on a symmetric homomorphic encryption technique, we carefully devise a suite of privacy-preserving protocols to provide a security guarantee for <inline-formula><tex-math notation="LaTeX">$k$</tex-math></inline-formula> d-tree based similarity range queries. After that, by using the similarity range query algorithm and these protocols, we propose our privacy-preserving similarity range query scheme, in which we elaborate on two strategies to make our scheme resist against the cloud inference attack. Finally, we analyze the security of our scheme and conduct extensive experiments to evaluate its performance, and the results indicate that our proposed scheme is indeed privacy-preserving and efficient.
Autonomous Exploration Under Uncertainty via Deep Reinforcement Learning on Graphs

We consider an autonomous exploration problem in which a range-sensing mobile robot is tasked with accurately mapping the landmarks in an a priori unknown environment efficiently in real-time; it must choose sensing actions that both curb localization uncertainty and achieve information gain. For this problem, belief space planning methods that forward- simulate robot sensing and estimation may often fail in real-time implementation, scaling poorly with increasing size of the state, belief and action spaces. We propose a novel approach that uses graph neural networks (GNNs) in conjunction with deep reinforcement learning (DRL), enabling decision-making over graphs containing exploration information to predict a robot's optimal sensing action in belief space. The policy, which is trained in different random environments without human intervention, offers a real-time, scalable decision-making process whose high-performance exploratory sensing actions yield accurate maps and high rates of information gain.
Cybercrime threat intelligence: A systematic multi-vocal literature review

Significant cybersecurity and threat intelligence analysts agree that online criminal activity is increasing exponentially. To offer an overview of the techniques and indicators to perform cyber crime detection by means of more complex machine- and deep-learning investigations as well as similar threat intelligence and engineering activities over multiple analysis levels (i.e., surface, deep, and darknets), we systematically analyze state of the art in such techniques. First, to aid the engineering and management of such intelligence solutions. We provide (i) a taxonomy of existing methods mapped to (ii) an overview of detectable criminal activities as well as (iii) an overview of the indicators and risk parameters that can be used for such detection. Second, to find the major engineering and management challenges and variables to be addressed. We apply a Topic Modelling Analysis to identify and analyze the most relevant threat concepts both in Surface and in Deep-, Dark-Web. Third, we identify gaps and challenges, defining a roadmap. Practitioners value and conclusions. The analysis mentioned above effectively provided a photograph of the scientific and practice gaps among the Surface Web and the Deep-, Dark-Web cybercrime and threat engineering and management. More specifically, our systematic literature review shows: (i) the dimensions of risk assessment techniques today available for the aforementioned areas—addressing these is vital for Law-enforcement agencies to combat cybercrime and cyber threats effectively; (ii) what website features should be used in order to identify a cyber threat or attack—researchers and non-governmental organizations in support of Law Enforcement Agencies (LEAs) should cover these features with appropriate technologies to aid in the investigative processes; (iii) what (limited) degree of anonymity is possible when crawling in Deep-, Dark-Web—researchers should strive to fill this gap with more and more advanced degrees of anonymity to grant protection to LEAs during their investigations.
Discovering hidden spatial patterns and their associations with controlling factors for potentially toxic elements in topsoil using hot spot analysis and K-means clustering analysis

The understanding of sources and controlling factors of potentially toxic elements (PTEs) in soils plays an important role in the improvement of environmental management. With the rapid growth of data volume, effective methods are required for data analytics for the large geochemical data sets. In recent years, spatial machine learning technologies have been proven to have the potential to reveal hidden spatial patterns in order to extract geochemical information. In this study, two spatial clustering techniques of Getis-Ord Gi* statistic and K-means clustering analysis were performed on 15 PTEs in 6,862 topsoil samples from the Tellus datasets of Northern Ireland to investigate the hidden spatial patterns and association with their controlling factors. The spatial clustering patterns of hot spots (high values) and cold spots (low values) for the 15 PTEs were revealed, showing clear association with geological features, especially peat and basalt. Peat was associated with high concentrations of Bi, Pb, Sb and Sn, while basalt was associated with high concentrations of Co, Cr, Cu, Mn, Ni, V and Zn. The high concentrations of As, Ba, Mo and U were associated with mixture of various lithologies, indicating the complicated influences on them. In addition, three hidden patterns in the 6,862 soil samples were revealed by K-means clustering analysis. The soil samples in the first and second clusters were overlaid on the peatland and basalt formation, respectively, while the samples in the third cluster were overlaid on the mixture of the other lithologies. These hidden patterns of soil samples were consistent with the spatial clustering patterns for PTEs, highlighting the dominant control of peat and basalt in the topsoil of Northern Ireland. This study demonstrates the power of spatial machine learning techniques in identifying hidden spatial patterns, providing evidences to extract geochemical knowledge in environmental studies.
Recovering Surface Normal and Arbitrary Images: A Dual Regression Network for Photometric Stereo

Photometric stereo recovers three-dimensional (3D) object surface normal from multiple images under different illumination directions. Traditional photometric stereo methods suffer from the problem of non-Lambertian surfaces with general reflectance. By leveraging deep neural networks, learning-based methods are capable of improving the surface normal estimation under general non-Lambertian surfaces. These state-of-the-art learning-based methods however do not associate surface normal with reconstructed images and, therefore, they cannot explore the beneficial effect of such association on the estimation of the surface normal. In this paper, we specifically exploit the positive impact of this association and propose a novel dual regression network for both fine surface normals and arbitrary reconstructed images in calibrated photometric stereo. Our work unifies the 3D reconstruction and rendering tasks in a deep learning framework, with the explorations including: 1. generating specified reconstructed images under arbitrary illumination directions, which provides more intuitive perception of the reflectance and is extremely useful for visual applications, such as virtual reality, and 2. our dual regression scheme introduces an additional constraint on observed images and reconstructed images, which forms a closed-loop to provide additional supervision. Experiments show that our proposed method achieves accurate reconstructed images under arbitrarily specified illumination directions and it significantly outperforms the state-of-the-art learning-based single regression methods in calibrated photometric stereo.
ResNet Autoencoders for Unsupervised Feature Learning From High-Dimensional Data: Deep Models Resistant to Performance Degradation

Efficient modeling of high-dimensional data requires extracting only relevant dimensions through feature learning. Unsupervised feature learning has gained tremendous attention due to its unbiased approach, no need for prior knowledge or expensive manual processing, and ability to handle exponential data growth. Deep Autoencoder (AE) is a state-of-the-art deep neural network for unsupervised feature learning, which learns embedded-representations using a series of stacked layers. However, as the AE network gets deeper, these learned embedded-representations can deteriorate due to vanishing gradient, leading to performance degradation. This article presents ResNet Autoencoder (RAE) and its convolutional version (C-RAE) for unsupervised feature learning. The advantage of RAE and C-RAE is that it enables the user to add residual connections for increased network capacity without incurring the cost of degradation for unsupervised feature learning compared to standard AEs. While RAE and C-RAE inherit all the advantages of AEs, such as automated non-linear feature extraction and unsupervised learning, they also allow users to design larger networks without adverse effects on feature learning performance. We performed classification on learned embedded-representation to evaluate RAE and C-RAE. RAE and C-RAE were compared against AEs on MNIST, Fashion MNIST, and CIFAR10 datasets. When increasing the number of layers, C-RAE outperformed AE by showing significantly lower performance degradation of classification accuracy (less than 3%) compared to AE (33% to 65%). Further, C-RAE exhibited higher mean accuracy and lower variance of accuracy than standard AE. When comparing RAE and C-RAE with widely used feature learning methods (Convolutional AE, PCA, ICA, LLE, Factor Analysis, and SVD), C-RAE showed the highest accuracy.
Tripool: Graph triplet pooling for 3D skeleton-based action recognition

Graph Convolutional Network (GCN) has already been successfully applied to skeleton-based action recognition. However, current GCNs in this task are lack of pooling operations such that the architectures are inherently flat, which not only increases the computational complexity but also requires larger memory space to keep the entire graph embedding. More seriously, a flat architecture forces the high-level semantic feature representations to have the same physical structure of the low-level input skeletons, which we argue is unreasonable and harmful for the final performance. To address these issues, we propose Tripool, a novel graph pooling method for 3D action recognition from skeleton data. Tripool provides to optimize a triplet pooling loss, in which both graph topology and global graph context are taken into consideration, to learn a hierarchical graph representation. The training process of graph pooling is efficient since it optimizes the graph topology by minimizing an upper bound of the pooling loss. Besides, Tripool also automatically generates an embedding matrix since the graph is changed after pooling. On one hand, Tripool reduces the computational cost by removing the redundant nodes. On the other hand it overcomes the limitation of the topology constrain for the high-level semantic representations, thus improves the final performance. Tripool can be combined with various graph neural networks in an end-to-end fashion. Comprehensive experiments on two current largest scale 3D datasets are conducted to evaluate our method. With our Tripool, we consistently get the best results in terms of various performance measures.
Conditions for professional digital competence: the teacher educators’ view

This study explores how Swedish teacher educators view individual, collegial, and organisational conditions framing the fulfilment of their dual didactical task, which is to use digital technology in a way that ensures student teachers graduate from teacher education (TE) with the professional digital competence (PDC) needed for their future working lives in a digitalised school. Using a purposive sampling approach, we used thematic coding to analyse 13 semistructured interviews with teacher educators representing 21 mandatory courses in educational science at one teacher education institution in Sweden. The findings cover aspects of the teacher educators’ PDC, how to act as a digital role model for the student teachers, support in educational policy and assignments, and the possibilities for participating in continuous professional development (CPD) in PDC. This study demonstrates an urgent need to improve conditions for successful fulfilment of teacher educators’ dual didactical task. For example, TE policy requires a strong focus on digital technology and PDC. CPD activities should be easy to access in order for teacher educators to develop their PDC. Moreover, leaders at the organisational level in TE institutions should acknowledge and place higher value on teacher educators’ work to digitalise educational practices.
Distributed attribute-based access control system using permissioned blockchain

Auditing provides essential security control in computer systems by keeping track of all access attempts, including both legitimate and illegal access attempts. This phase can be useful in the context of audits, where eventual misbehaving parties can be held accountable. Blockchain technology can provide the trusted auditability required for access control systems. In this paper, we propose a distributed Attribute-Based Access Control (ABAC) system based on blockchain to provide trusted auditing of access attempts. Besides auditability, our system presents a level of transparency that both access requesters and resource owners can benefit from it. We present a system architecture with an implementation based on Hyperledger Fabric, achieving high efficiency and low computational overhead. The proposed solution is validated through a use case of independent digital libraries. Detailed performance analysis of our implementation is presented, taking into account different consensus mechanisms and databases. The experimental evaluation shows that our presented system can effectively handle a transaction throughput of 270 transactions per second, with an average latency of 0.54 seconds per transaction.
A new structure-preserving quaternion QR decomposition method for color image blind watermarking

Most of the existing color image watermarking schemes are designed to mark each color channel individually, which ignores the correlation of different color channels and the synchronous embedding of watermarks. In this paper, we propose a robust blind watermarking scheme based on quaternion QR decomposition (QQRD) for color image copyright protection, while using algebraic structure-preserving method to release its computational complexity. In watermark embedding process, QQRD is applied to non-overlapping 4×4 image blocks in a whole manner, whereupon three strong correlation coefficient pairs determined by the Normalized Cross-Correlation (NC) method are modified to embed color watermark within factorized matrices. This avoids layered processing that causes abnormal sensitivity to attacks and less correlation that causes excessive modification of coefficient values. Numerical results show that the newly proposed watermarking scheme has strong ability to resist most image processing attacks and is error-free under no attack, brightness adjustment attack and Poisson noise attack. Its superiority over other state-of-the-art methods is also experimentally demonstrated.
Design and Analysis of MEC- and Proactive Caching-Based $360^{\circ }$ Mobile VR Video Streaming

Recently, 360-degree mobile virtual reality video (MVRV) has become increasingly popular because it can provide users with an immersive experience. However, MVRV is usually recorded in a high resolution and is sensitive to latency, which indicates that broadband, ultra-reliable, and low-latency communication is necessary to guarantee the users’ quality of experience. In this paper, we propose a mobile edge computing (MEC)-based 360-degree MVRV streaming scheme with field-of-view (FoV) prediction, which jointly considers video coding, proactive caching, computation offloading, and data transmission. To meet the requirement of stringent end-to-end (E2E) latency, the user’s viewpoint prediction is utilized to cache video data proactively, and computing tasks are partially offloaded to the MEC server. In addition, we propose an analytical model based on diffusion process to study the packet transmission process of 360-degree MVRV in multihop wired/wireless networks and analyze the performance of the MEC-enabled scheme. The simulation results verify the accuracy of the analysis and the effectiveness of the proposed MVRV streaming scheme in reducing the E2E delay. Furthermore, the analytical framework sheds some light on the impacts of system parameters, e.g., FoV prediction accuracy and transmission rate, on the balance between computation delay and communication delay.