Open AccessEditorial
Acknowledgement to Reviewers of Computers in 2017
Computers 2018, 7(1), 11; doi:10.3390/computers7010011 (registering DOI) -
Abstract
Peer review is an essential part in the publication process, ensuring that Computers maintains high quality standards for its published papers.[...] Full article
Open AccessArticle
High-Precision Control of a Piezo-Driven Nanopositioner Using Fuzzy Logic Controllers
Computers 2018, 7(1), 10; doi:10.3390/computers7010010 (registering DOI) -
Abstract
This paper presents single- and dual-loop fuzzy control schemes to precisely control the piezo-driven nanopositioner in the x- and y-axis directions. Various issues are associated with this control problem, such as low stability margin due to the sharp resonant peak, nonlinear
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This paper presents single- and dual-loop fuzzy control schemes to precisely control the piezo-driven nanopositioner in the x- and y-axis directions. Various issues are associated with this control problem, such as low stability margin due to the sharp resonant peak, nonlinear dynamics, parameter uncertainty, etc. As such, damping controllers are often utilised to damp the mechanical resonance of the nanopositioners. The Integral Resonant Controller (IRC) is used in this paper as a damping controller to damp the mechanical resonance. A further inherent problem is the hysteresis phenomenon (disturbance), which leads to degrading the positioning performance (accuracy) of the piezo-driven stage. The common approach to treat this disturbance is to invoke tracking controllers in a closed-loop feedback scheme in conjunction with the damping controllers. The traditional approach uses the Integral Controller (I) or Proportional Integral (PI) as a tracking controller, whereas this paper introduces the Proportional and Integral (PI)-like Fuzzy Logic Controller (FLC) as a tracking controller. The effectiveness of the proposed control schemes over conventional schemes is confirmed through comparative simulation studies, and results are presented. The stability boundaries of the proposed control schemes are determined in the same way as with a conventional controller. Robustness against variations in the resonant frequency of the proposed control schemes is verified. Full article
Open AccessArticle
An Improvement on Remote User Authentication Schemes Using Smart Cards
Computers 2018, 7(1), 9; doi:10.3390/computers7010009 -
Abstract
In 2010, Yeh et al. proposed two robust remote user authentication schemes using smart cards; their claims were such that their schemes defended against ID-theft attacks, reply attacks, undetectable on-line password guessing attacks, off-line password guessing attacks, user impersonation attack, server counterfeit attack
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In 2010, Yeh et al. proposed two robust remote user authentication schemes using smart cards; their claims were such that their schemes defended against ID-theft attacks, reply attacks, undetectable on-line password guessing attacks, off-line password guessing attacks, user impersonation attack, server counterfeit attack and man-in-the-middle attack. In this paper, we show that Yeh et al.’s schemes are still vulnerable to ID-theft attack, off-line password guessing attacks, undetectable on-line password guessing attacks and user impersonation attack. Notably, problems remain in situations where the user lost a smart card or the malicious legal user. To remedy these flaws, this paper proposes an improvement on Yeh et al.’s remote user authentication schemes using smart cards. Full article
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Open AccessArticle
Performance Evaluation of Discrete Event Systems with GPenSIM
Computers 2018, 7(1), 8; doi:10.3390/computers7010008 -
Abstract
Petri nets are a useful tool for the modeling and performance evaluation of discrete event systems. Literature reveals that the Petri Net models of real-world discrete event systems are most frequently event graphs (a subclass of Petri nets). Literature also reveals that there
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Petri nets are a useful tool for the modeling and performance evaluation of discrete event systems. Literature reveals that the Petri Net models of real-world discrete event systems are most frequently event graphs (a subclass of Petri nets). Literature also reveals that there are some simple methods for the performance evaluation of event graphs. The general-purpose Petri Net simulator (GPenSIM) is a new simulator that runs on the MATLAB platform. GPenSIM provides a Petri net language, with which Petri net classes and extensions can be developed. GPenSIM also provides functions for performance analysis. Since real-world discrete event systems usually possess a large number of resources, the Petri net models of these systems tend to become huge. Activity-Oriented Petri Nets (AOPN) is an approach that reduces the size of the Petri nets. In addition to the simulator functions, GPenSIM also realizes the AOPN approach on the MATLAB platform. Thus, AOPN is an integral part of GPenSIM. As a running example, a flexible manufacturing system is firstly modeled as an event graph, and then the size of the model is reduced with the AOPN approach. The advantages of GPenSIM and AOPN are discussed in this paper. Full article
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Open AccessArticle
Self-Monitoring of Emotions and Mood Using a Tangible Approach
Computers 2018, 7(1), 7; doi:10.3390/computers7010007 -
Abstract
Nowadays Personal Informatics (PI) devices are used for sensing and saving personal data, everywhere and at any time, helping people improve their lives by highlighting areas of good and bad performances and providing a general awareness of different levels of conduct. However, not
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Nowadays Personal Informatics (PI) devices are used for sensing and saving personal data, everywhere and at any time, helping people improve their lives by highlighting areas of good and bad performances and providing a general awareness of different levels of conduct. However, not all these data are suitable to be automatically collected. This is especially true for emotions and mood. Moreover, users without experience in self-tracking may have a misperception of PI applications’ limits and potentialities. We believe that current PI tools are not designed with enough understanding of such users’ needs, desires, and problems they may encounter in their everyday lives. We designed and prototype the Mood TUI (Tangible User Interface), a PI tool that supports the self-reporting of mood data using a tangible interface. The platform is able to gather six different mood states and it was tested through several participatory design sessions in a secondary/high school. The solution proposed allows gathering mood values in an amusing, simple, and appealing way. Users appreciated the prototypes, suggesting several possible improvements as well as ideas on how to use the prototype in similar or totally different contexts, and giving us hints for future research. Full article
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Open AccessFeature PaperArticle
6DoF Object Tracking based on 3D Scans for Augmented Reality Remote Live Support
Computers 2018, 7(1), 6; doi:10.3390/computers7010006 -
Abstract
Tracking the 6DoF pose of arbitrary 3D objects is a fundamental topic in Augmented Reality (AR) research, having received a large amount of interest in the last decades. The necessity of accurate and computationally efficient object tracking is evident for a broad base
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Tracking the 6DoF pose of arbitrary 3D objects is a fundamental topic in Augmented Reality (AR) research, having received a large amount of interest in the last decades. The necessity of accurate and computationally efficient object tracking is evident for a broad base of today’s AR applications. In this work we present a fully comprehensive pipeline for 6DoF Object Tracking based on 3D scans of objects, covering object registration, initialization and frame to frame tracking, implemented to optimize the user experience and to perform well in all typical challenging conditions such as fast motion, occlusions and illumination changes. Furthermore, we present the deployment of our tracking system in a Remote Live Support AR application with 3D object-aware registration of annotations and remote execution for delay and performance optimization. Experimental results demonstrate the tracking quality, real-time capability and the advantages of remote execution for computationally less powerful mobile devices. Full article
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Open AccessArticle
NEAT-Lamp and Talking Tree: Beyond Personal Informatics towards Active Workplaces
Computers 2018, 7(1), 4; doi:10.3390/computers7010004 -
Abstract
A growing number of personal informatics (PI) systems have been designed to break the habit of prolonged sitting and to encourage physical activity during workdays and leisure hours. Few studies, however, have investigated the nature of local movement and mobility in workspaces. Relatively
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A growing number of personal informatics (PI) systems have been designed to break the habit of prolonged sitting and to encourage physical activity during workdays and leisure hours. Few studies, however, have investigated the nature of local movement and mobility in workspaces. Relatively little is known about how such movement patterns are shaped and in what ways micro-mobility in workplaces could be increased. By undertaking a concept-driven design approach, and on the basis of our ethnographic prestudy, we introduce a conceptual framework. In this conceptual framework, we indicate the five main agencies that shape local movement and mobility among office workers. On the basis of this empirical and conceptual work, two prototypes, the non-exercise activity thermogenesis (NEAT)-Lamp and Talking Tree, have been designed, implemented and observed in an office environment. This paper describes this design project and articulates the role of discussions in socially established settings in work environments in order to increase daily movement. The paper concludes by highlighting not only technology, but also collective reflections to spark behavioral change in office environments as social settings. Full article
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Open AccessArticle
DARGS: Dynamic AR Guiding System for Indoor Environments
Computers 2018, 7(1), 5; doi:10.3390/computers7010005 -
Abstract
Complex public buildings, such as airports, use various systems to guide people to a certain destination. Such approaches are usually implemented by showing a floor plan that has guiding signs or color coded lines on the floor. With a technology that supports six
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Complex public buildings, such as airports, use various systems to guide people to a certain destination. Such approaches are usually implemented by showing a floor plan that has guiding signs or color coded lines on the floor. With a technology that supports six degrees of freedom (6DoF) tracking in indoor environments, it is possible to guide people individually, thereby considering obstacles, path lengths, or pathways for handicapped people. With an augmented reality (AR) device, such as a smart phone or AR glasses, the path can be presented on top of the real environment. In this paper, we present DARGS, an algorithm, which calculates a path through a complex building in real time. Usual path planning algorithms use either shortest paths or dynamic paths for robot interaction. The human factor in a real environment is not considered. The main advantage of DARGS is the incorporation of the current field of view (FOV) of the used device to visualize a more dynamic presentation. Rather than searching for the AR content with a small FOV, with the presented approach the user always gets a meaningful three-dimensional overlay of the path independent of the viewing direction. A detailed user study is performed to prove the applicability of the system. The results indicate that the presented system is especially helpful in the first few important seconds of the guiding process, when the user is still disoriented. Full article
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Open AccessFeature PaperArticle
Personalizing the Fitting of Hearing Aids by Learning Contextual Preferences From Internet of Things Data
Computers 2018, 7(1), 1; doi:10.3390/computers7010001 -
Abstract
The lack of individualized fitting of hearing aids results in many patients never getting the intended benefits, in turn causing the devices to be left unused in a drawer. However, living with an untreated hearing loss has been found to be one of
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The lack of individualized fitting of hearing aids results in many patients never getting the intended benefits, in turn causing the devices to be left unused in a drawer. However, living with an untreated hearing loss has been found to be one of the leading lifestyle related causes of dementia and cognitive decline. Taking a radically different approach to personalize the fitting process of hearing aids, by learning contextual preferences from user-generated data, we in this paper outline the results obtained through a 9-month pilot study. Empowering the user to select between several settings using Internet of things (IoT) connected hearing aids allows for modeling individual preferences and thereby identifying distinct coping strategies. These behavioral patterns indicate that users prefer to switch between highly contrasting aspects of omnidirectionality and noise reduction dependent on the context, rather than relying on the medium “one size fits all” program frequently provided by default in hearing health care. We argue that an IoT approach facilitated by the usage of smartphones may constitute a paradigm shift, enabling continuous personalization of settings dependent on the changing context. Furthermore, making the user an active part of the fitting solution based on self-tracking may increase engagement and awareness and thus improve the quality of life for hearing impaired users. Full article
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Open AccessFeature PaperArticle
Promises and Pitfalls of Computer-Supported Mindfulness: Exploring a Situated Mobile Approach
Computers 2018, 7(1), 2; doi:10.3390/computers7010002 -
Abstract
Computer-supported mindfulness (CSM) is a burgeoning area filled with varied approaches such as mobile apps and EEG headbands. However, many of the approaches focus on providing meditation guidance. The ubiquity of mobile devices may provide new opportunities to support mindfulness practices that are
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Computer-supported mindfulness (CSM) is a burgeoning area filled with varied approaches such as mobile apps and EEG headbands. However, many of the approaches focus on providing meditation guidance. The ubiquity of mobile devices may provide new opportunities to support mindfulness practices that are more situated in everyday life. In this paper, a new situated mindfulness approach is explored through a specific mobile app design. Through an experimental design, the approach is compared to traditional audio-based mindfulness meditation, and a mind wandering control, over a one-week period. The study demonstrates the viability for a situated mobile mindfulness approach to induce mindfulness states. However, phenomenological aspects of the situated mobile approach suggest both promises and pitfalls for computer-supported mindfulness using a situated approach. Full article
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Open AccessFeature PaperArticle
TaPT: Temperature-Aware Dynamic Cache Optimization for Embedded Systems
Computers 2018, 7(1), 3; doi:10.3390/computers7010003 -
Abstract
Embedded systems have stringent design constraints, which has necessitated much prior research focus on optimizing energy consumption and/or performance. Since embedded systems typically have fewer cooling options, rising temperature, and thus temperature optimization, is an emergent concern. Most embedded systems only dissipate heat
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Embedded systems have stringent design constraints, which has necessitated much prior research focus on optimizing energy consumption and/or performance. Since embedded systems typically have fewer cooling options, rising temperature, and thus temperature optimization, is an emergent concern. Most embedded systems only dissipate heat by passive convection, due to the absence of dedicated thermal management hardware mechanisms. The embedded system’s temperature not only affects the system’s reliability, but can also affect the performance, power, and cost. Thus, embedded systems require efficient thermal management techniques. However, thermal management can conflict with other optimization objectives, such as execution time and energy consumption. In this paper, we focus on managing the temperature using a synergy of cache optimization and dynamic frequency scaling, while also optimizing the execution time and energy consumption. This paper provides new insights on the impact of cache parameters on efficient temperature-aware cache tuning heuristics. In addition, we present temperature-aware phase-based tuning, TaPT, which determines Pareto optimal clock frequency and cache configurations for fine-grained execution time, energy, and temperature tradeoffs. TaPT enables autonomous system optimization and also allows designers to specify temperature constraints and optimization priorities. Experiments show that TaPT can effectively reduce execution time, energy, and temperature, while imposing minimal hardware overhead. Full article
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Open AccessArticle
On the Use of Voice Signals for Studying Sclerosis Disease
Computers 2017, 6(4), 30; doi:10.3390/computers6040030 -
Abstract
Multiple sclerosis (MS) is a chronic demyelinating autoimmune disease affecting the central nervous system. One of its manifestations concerns impaired speech, also known as dysarthria. In many cases, a proper speech evaluation can play an important role in the diagnosis of MS. The
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Multiple sclerosis (MS) is a chronic demyelinating autoimmune disease affecting the central nervous system. One of its manifestations concerns impaired speech, also known as dysarthria. In many cases, a proper speech evaluation can play an important role in the diagnosis of MS. The identification of abnormal voice patterns can provide valid support for a physician in the diagnosing and monitoring of this neurological disease. In this paper, we present a method for vocal signal analysis in patients affected by MS. The goal is to identify the dysarthria in MS patients to perform an early diagnosis of the disease and to monitor its progress. The proposed method provides the acquisition and analysis of vocal signals, aiming to perform feature extraction and to identify relevant patterns useful to impaired speech associated with MS. This method integrates two well-known methodologies, acoustic analysis and vowel metric methodology, to better define pathological compared to healthy voices. As a result, this method provides patterns that could be useful indicators for physicians in identifying patients affected by MS. Moreover, the proposed procedure could be a valid support in early diagnosis as well as in monitoring treatment success, thus improving a patient’s life quality. Full article
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Open AccessArticle
Application of Machine Learning Models in Error and Variant Detection in High-Variation Genomics Datasets
Computers 2017, 6(4), 29; doi:10.3390/computers6040029 -
Abstract
For metagenomics datasets, datasets of complex polyploid genomes, and other high-variation genomics datasets, there are difficulties with the analysis, error detection and variant calling, stemming from the challenges of discerning sequencing errors from biological variation. Confirming base candidates with high frequency of occurrence
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For metagenomics datasets, datasets of complex polyploid genomes, and other high-variation genomics datasets, there are difficulties with the analysis, error detection and variant calling, stemming from the challenges of discerning sequencing errors from biological variation. Confirming base candidates with high frequency of occurrence is no longer a reliable measure because of the natural variation and the presence of rare bases. The paper discusses an approach to the application of machine learning models to classify bases into erroneous and rare variations after preselecting potential error candidates with a weighted frequency measure, which aims to focus on unexpected variations by using the inter-sequence pairwise similarity. Different similarity measures are used to account for different types of datasets. Four machine learning models are implemented and tested. Full article
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Open AccessFeature PaperReview
3D NAND Flash Based on Planar Cells
Computers 2017, 6(4), 28; doi:10.3390/computers6040028 -
Abstract
In this article, the transition from 2D NAND to 3D NAND is first addressed, and the various 3D NAND architectures are compared. The article carries out a comparison of 3D NAND architectures that are based on a “punch-and-plug” process—with gate-all-around (GAA) cell devices—against
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In this article, the transition from 2D NAND to 3D NAND is first addressed, and the various 3D NAND architectures are compared. The article carries out a comparison of 3D NAND architectures that are based on a “punch-and-plug” process—with gate-all-around (GAA) cell devices—against architectures that are based on planar cell devices. The differences and similarities between the two classes of architectures are highlighted. The differences between architectures using floating-gate (FG) and charge-trap (CT) devices are also considered. Although the current production of 3D NAND is based on GAA cell devices, it is suggested that architectures with planar cell devices could also be viable for mass production. Full article
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Open AccessArticle
Promoting the Quality Level of Signaling in Railway Transportation System Taking Advantage from Wireless Sensor Networks Technology
Computers 2017, 6(3), 26; doi:10.3390/computers6030026 -
Abstract
Given the importance of using the railway networks for the reliable and safe transportation of goods and passengers, which plays an important role in the economy of rail transport of the country, it is necessary to use wireless sensor network techniques to raise
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Given the importance of using the railway networks for the reliable and safe transportation of goods and passengers, which plays an important role in the economy of rail transport of the country, it is necessary to use wireless sensor network techniques to raise the quality and quantity and also maintain the application of these facilities for better control and optimal use of relevant technologies in this regard. Regarding the development of wireless sensor networks for collecting and processing environmental information, we intended to employ them in order to maintain railways, and also prevent defects that might occur in mobile machines and parts, as well as to avoid probable events and reduce human errors. Considering the limited capacity of batteries for sensor nodes in a wireless sensor network, energy efficiency is an important issue; thus mobile sinks are presented as a possible solution. In this study, the proposed routing uses Ring Routing and an optimization gravitational search algorithm for the primary selection of the ring causes an increase in a sensor network’s lifespan. In this study, by applying the proposed method in the railway transportation system, it is improved to reduce the existing errors by creating a system with a higher safety factor and high quality and efficiency, together with maximum efficiency and good speed. Full article
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Open AccessReview
Architectural and Integration Options for 3D NAND Flash Memories
Computers 2017, 6(3), 27; doi:10.3390/computers6030027 -
Abstract
Nowadays, NAND Flash technology is everywhere, since it is the core of the code and data storage in mobile and embedded applications; moreover, its market share is exploding with Solid-State-Drives (SSDs), which are replacing Hard Disk Drives (HDDs) in consumer and enterprise scenarios.
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Nowadays, NAND Flash technology is everywhere, since it is the core of the code and data storage in mobile and embedded applications; moreover, its market share is exploding with Solid-State-Drives (SSDs), which are replacing Hard Disk Drives (HDDs) in consumer and enterprise scenarios. To keep the evolutionary pace of the technology, NAND Flash must scale aggressively in terms of bit cost. When approaching ultra-scaled technologies, planar NAND is hitting a wall: both academia researchers and industry worked to cope with this issue for several decades. Then, the 3D integration approach turned out to be the definitive alternative by eventually reaching mass production. This review paper exposes several 3D NAND Flash memory technologies, along with their related integration challenges, by showing their different layouts, scaling trends and performance/reliability features. Full article
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Open AccessArticle
Conceiving Human Interaction by Visualising Depth Data of Head Pose Changes and Emotion Recognition via Facial Expressions
Computers 2017, 6(3), 25; doi:10.3390/computers6030025 -
Abstract
Affective computing in general and human activity and intention analysis in particular comprise a rapidly-growing field of research. Head pose and emotion changes present serious challenges when applied to player’s training and ludology experience in serious games, or analysis of customer satisfaction regarding
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Affective computing in general and human activity and intention analysis in particular comprise a rapidly-growing field of research. Head pose and emotion changes present serious challenges when applied to player’s training and ludology experience in serious games, or analysis of customer satisfaction regarding broadcast and web services, or monitoring a driver’s attention. Given the increasing prominence and utility of depth sensors, it is now feasible to perform large-scale collection of three-dimensional (3D) data for subsequent analysis. Discriminative random regression forests were selected in order to rapidly and accurately estimate head pose changes in an unconstrained environment. In order to complete the secondary process of recognising four universal dominant facial expressions (happiness, anger, sadness and surprise), emotion recognition via facial expressions (ERFE) was adopted. After that, a lightweight data exchange format (JavaScript Object Notation (JSON)) is employed, in order to manipulate the data extracted from the two aforementioned settings. Motivated by the need to generate comprehensible visual representations from different sets of data, in this paper, we introduce a system capable of monitoring human activity through head pose and emotion changes, utilising an affordable 3D sensing technology (Microsoft Kinect sensor). Full article
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Open AccessArticle
BICM-ID with Physical Layer Network Coding in TWR Free Space Optical Communication Links
Computers 2017, 6(3), 24; doi:10.3390/computers6030024 -
Abstract
Physical layer network coding (PNC) is a promising technique to improve the network throughput in a two-way relay (TWR) channel for two users to exchange messages across a wireless network. The PNC technique incorporating a TWR channel is embraced by a free space
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Physical layer network coding (PNC) is a promising technique to improve the network throughput in a two-way relay (TWR) channel for two users to exchange messages across a wireless network. The PNC technique incorporating a TWR channel is embraced by a free space optical (FSO) communication link for full utilization of network resources, namely TWR-FSO PNC. In this paper, bit interleaved coded modulation with iterative decoding (BICM-ID) is adopted to combat the deleterious effect of the turbulence channel by saving the message being transmitted to increase the reliability of the system. Moreover, based on this technique, comparative studies between end-to-end BICM-ID code, non-iterative convolutional coded and uncoded systems are carried out. Furthermore, this paper presents the extrinsic information transfer (ExIT) charts to evaluate the performance of BICM-ID code combined with the TWR-FSO PNC system. The simulation results show that the proposed scheme can achieve a significant bit error rate (BER) performance improvement through the introduction of an iterative process between a soft demapper and decoder. Similarly, Monte Carlo simulation results are provided to support the findings. Subsequently, the ExIT functions of the two receiver components are thoroughly analysed for a variety of parameters under the influence of a turbulence-induced channel fading, demonstrating the convergence behaviour of BICM-ID to enable the TWR-FSO PNC system, effectively mitigating the impact of the fading turbulence channel. Full article
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Open AccessArticle
Data Partitioning Technique for Improved Video Prioritization
Computers 2017, 6(3), 23; doi:10.3390/computers6030023 -
Abstract
A compressed video bitstream can be partitioned according to the coding priority of the data, allowing prioritized wireless communication or selective dropping in a congested channel. Known as data partitioning in the H.264/Advanced Video Coding (AVC) codec, this paper introduces a further sub-partition
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A compressed video bitstream can be partitioned according to the coding priority of the data, allowing prioritized wireless communication or selective dropping in a congested channel. Known as data partitioning in the H.264/Advanced Video Coding (AVC) codec, this paper introduces a further sub-partition of one of the H.264/AVC codec’s three data-partitions. Results show a 5 dB improvement in Peak Signal-to-Noise Ratio (PSNR) through this innovation. In particular, the data partition containing intra-coded residuals is sub-divided into data from: those macroblocks (MBs) naturally intra-coded, and those MBs forcibly inserted for non-periodic intra-refresh. Interactive user-to-user video streaming can benefit, as then HTTP adaptive streaming is inappropriate and the High Efficiency Video Coding (HEVC) codec is too energy demanding. Full article
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Open AccessArticle
Towards Recognising Learning Evidence in Collaborative Virtual Environments: A Mixed Agents Approach
Computers 2017, 6(3), 22; doi:10.3390/computers6030022 -
Abstract
Three-dimensional (3D) virtual environments bring people together in real time irrespective of their geographical location to facilitate collaborative learning and working together in an engaging and fulfilling way. However, it can be difficult to amass suitable data to gauge how well students perform
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Three-dimensional (3D) virtual environments bring people together in real time irrespective of their geographical location to facilitate collaborative learning and working together in an engaging and fulfilling way. However, it can be difficult to amass suitable data to gauge how well students perform in these environments. With this in mind, the current study proposes a methodology for monitoring students’ learning experiences in 3D virtual worlds (VWs). It integrates a computer-based mechanism that mixes software agents with natural agents (users) in conjunction with a fuzzy logic model to reveal evidence of learning in collaborative pursuits to replicate the sort of observation that would normally be made in a conventional classroom setting. Software agents are used to infer the extent of interaction based on the number of clicks, the actions of users, and other events. Meanwhile, natural agents are employed in order to evaluate the students and the way in which they perform. This is beneficial because such an approach offers an effective method for assessing learning activities in 3D virtual environments. Full article
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