Showing items 141 - 160 of 17057

Machine learning for 5G security : architecture, recent advances, and challenges

- Afaq, Amir, Haider, Noman, Baig, Muhammad, Khan, Komal, Imran, Muhammad, Razzak, Imran

  • Authors: Afaq, Amir , Haider, Noman , Baig, Muhammad , Khan, Komal , Imran, Muhammad , Razzak, Imran
  • Date: 2021
  • Type: Text , Journal article
  • Relation: Ad Hoc Networks Vol. 123, no. (2021), p.
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  • Description: The granularization of crucial network functions implementation using software-centric, and virtualized approaches in 5G networks have brought forth unprecedented security challenges in general and privacy concerns. Moreover, these software components’ premature deployment and compromised supply chain put the individual network components at risk and have a ripple effect for the rest of the network. Some of the novel threats to 5G assets include tampering in identity and access management, supply-chain poisoning, masquerade and bot attacks, loop-holes in source codes. Machine learning (ML) in this context can help to provide heavily dynamic and robust security mechanisms for the software-centric architecture of 5G Networks. ML models’ development and implementation also rely on programmable environments; hence, they can play a vital role in designing, modelling, and automating efficient security protocols. This article presents the threat landscape across 5G networks and discusses the feasibility and architecture of different ML-based models to counter these threats. Also, we present the architecture for automated threat intelligence using cooperative and coordinated ML to secure 5G assets and infrastructure. We also present the summary of closely related existing works along with future research challenges. © 2021 Elsevier B.V.

Ethnobotany, rattan agroforestry, and conservation of ecosystem services in Central Kalimantan, Indonesia

- Afentina, McShane, Paul, Wright, Wendy

  • Authors: Afentina , McShane, Paul , Wright, Wendy
  • Date: 2020
  • Type: Text , Journal article
  • Relation: Agroforestry Systems Vol. 94, no. 2 (2020), p. 639-650
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  • Description: Rattan agroforestry is an important land use system in Central Kalimantan, Indonesia, providing a wide range of products for subsistence communities. The ethnobotanical importance of rattan includes heritage values reflecting traditional ecological knowledge. This traditional forestry practice is consistent with necessary conservation of biodiversity and ecosystem services currently threatened by expansion of oil palm plantations. We examined species composition and morphology (including life stages) of vegetation associated with rattan agroforests in the Katingan district, Central Kalimantan. An examination of harvested rattan plots revealed 101 species of vegetation of which 90% are considered to be useful (food, construction materials, medicines) and most (97%) were native species, typical of lowland tropical forest vegetation. Vegetation in the rattan agroforests was dominated by trees (in terms of species richness). There were 80 species of trees, representing 79% of the plants surveyed. Vitex pubescens (kaluan) had the highest importance value as it occupied more space, was represented by more individuals and was most frequently found in rattan gardens. These trees in general have a relatively open canopy with strong branches; properties considered ideal to support rattan. Canopy forming species are actively managed to provide for growth of useful understory vegetation (including rattan) important in the livelihoods of village communities. Rattan agroforests also provide cultural services reflecting traditional use (e.g. a sense of belonging and ancestral linkages for local forest-dependent communities). The importance of ethnobotanical approaches to rattan cultivation includes the socio-economic evaluation of land use and the promotion of sustainable land use policies in Indonesia. This is important in the context of oil palm expansion which has a demonstrably adverse impact on ecosystem services. © 2019, Springer Nature B.V.

Cultural ecosystem services of rattan garden : the hidden values

- Afentina, Afentina, McShane, Paul, Plahe, Jagjit, Wright, Wendy

  • Authors: Afentina, Afentina , McShane, Paul , Plahe, Jagjit , Wright, Wendy
  • Date: 2017
  • Type: Text , Journal article
  • Relation: European journal of sustainable development Vol. 6, no. 3 (2017), p.
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  • Description: Ecosystem Services (ES) are services provided to local communities by natural resources. Cultural Ecosystem Services (CES) are the nonmaterial benefits that people obtain from ecosystems. ES, and particularly CES are often omitted from cost-benefit analyses associated with development plans in favour of a focus on maximizing economic benefits. Consequently, economic development can lead to the disappearance of cultural values such as local knowledge, and cultural identity. This research attempts to understand and analyze CES and benefits provided by rattan gardens for local communities in Tumbang Runen village in Indonesia. Information about CES was obtained through in-depth interviews with key informants, focus group discussions with farmers, and observations of daily activities of local people. This research revealed that residents of Tumbang Runen village attach strong cultural importance to their rattan gardens, including spiritual, heritage and local knowledge values. The spiritual aspects of CES include the use of some plant species in rituals and healing ceremonies. Local people consider rattan to be historically important, intimately linking people with their ancestors and their belief system. Rattan gardens and rattan cultivation also serve as cultural symbols, facilitating the maintenance of practices, beliefs, and knowledge across generations. The importance of rattan gardens to the local community should be communicated to policy makers and included in sustainable development strategies

Improved switching scheme to reduce the junction temperature and power loss of CHB inverters

- Afrin, Sadia, Biswas, Suvra, Bin Islam, Md Sabbir, Islam, Md Rabiul, Shah, Rakibuzzaman

Efficient low bit-rate intra-frame coding using common information for 360-degree video

- Afsana, Fariha, Paul, Manoranjan, Murshed, Manzur, Taubman, David

  • Authors: Afsana, Fariha , Paul, Manoranjan , Murshed, Manzur , Taubman, David
  • Date: 2020
  • Type: Text , Conference paper
  • Relation: 22nd IEEE International Workshop on Multimedia Signal Processing, MMSP 2020
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  • Description: With the growth of video technologies, super-resolution videos, including 360-degree immersive video has become a reality due to exciting applications such as augmented/virtual/mixed reality for better interaction and a wide-angle user-view experience of a scene compared to traditional video with narrow-focused viewing angle. The new generation video contents are bandwidth-intensive in nature due to high resolution and demand high bit rate as well as low latency delivery requirements that pose challenges in solving the bottleneck of transmission and storage burdens. There is limited optimisation space in traditional video coding schemes for improving video coding efficiency in intra-frame due to the fixed size of processing block. This paper presents a new approach for improving intra-frame coding especially at low bit rate video transmission for 360-degree video for lossy mode of HEVC. Prior to using traditional HEVC intra-prediction, this approach exploits the global redundancy of entire frame by extracting common important information using multi-level discrete wavelet transformation. This paper demonstrates that the proposed method considering only low frequency information of a frame and encoding this can outperform the HEVC standard at low bit rates. The experimental results indicate that the proposed intra-frame coding strategy achieves an average of 54.07% BD-rate reduction and 2.84 dB BD-PSNR gain for low bit rate scenario compared to the HEVC. It also achieves a significant improvement in encoding time reduction of about 66.84% on an average. Moreover, this finding also demonstrates that the existing HEVC block partitioning can be applied in the transform domain for better exploitation of information concentration as we applied HEVC on wavelet frequency domain. © 2020 IEEE.

Efficient high-resolution video compression scheme using background and foreground layers

- Afsana, Fariha, Paul, Manoranjan, Murshed, Manzur, Taubman, David

  • Authors: Afsana, Fariha , Paul, Manoranjan , Murshed, Manzur , Taubman, David
  • Date: 2021
  • Type: Text , Journal article
  • Relation: IEEE Access Vol. 9, no. (2021), p. 157411-157421
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  • Description: Video coding using dynamic background frame achieves better compression compared to the traditional techniques by encoding background and foreground separately. This process reduces coding bits for the overall frame significantly; however, encoding background still requires many bits that can be compressed further for achieving better coding efficiency. The cuboid coding framework has been proven to be one of the most effective methods of image compression which exploits homogeneous pixel correlation within a frame and has better alignment with object boundary compared to traditional block-based coding. In a video sequence, the cuboid-based frame partitioning varies with the changes of the foreground. However, since the background remains static for a group of pictures, the cuboid coding exploits better spatial pixel homogeneity. In this work, the impact of cuboid coding on the background frame for high-resolution videos (Ultra-High-Definition (UHD) and 360-degree videos) is investigated using the multilayer framework of SHVC. After the cuboid partitioning, the method of coarse frame generation has been improved with a novel idea by keeping human-visual sensitive information. Unlike the traditional SHVC scheme, in the proposed method, cuboid coded background and the foreground are encoded in separate layers in an implicit manner. Simulation results show that the proposed video coding method achieves an average BD-Rate reduction of 26.69% and BD-PSNR gain of 1.51 dB against SHVC with significant encoding time reduction for both UHD and 360 videos. It also achieves an average of 13.88% BD-Rate reduction and 0.78 dB BD-PSNR gain compared to the existing relevant method proposed by X. Hoang Van. © 2013 IEEE.

Efficient scalable UHD/360-video coding by exploiting common information with cuboid-based partitioning

- Afsana, Fariha, Paul, Manoranjan, Murshed, Manzur, Taubman, David

  • Authors: Afsana, Fariha , Paul, Manoranjan , Murshed, Manzur , Taubman, David
  • Date: 2022
  • Type: Text , Journal article
  • Relation: IEEE Transactions on Circuits and Systems for Video Technology Vol. 32, no. 6 (2022), p. 3961-3977
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  • Description: The scalable extension of High Efficiency Video Coding, SHVC can code Ultra High-Definition (UHD) video, including 360-degree video for various devices to serve a single bitstream with different display resolutions and qualities. To improve the SHVC compression efficiency, this paper proposes a novel intra and inter-frame coding scheme by first separating the common/visually important information and then applying cuboid-based variable size block partitioning and coding process for the common/visually important information in the base layer. In cuboid-based partitioning a video frame is partitioned into arbitrary shaped rectangular regions, known as cuboids, based on the distribution of relatively homogeneous pixel values. As the cuboid adopts a variable block partitioning based on the homogeneity of the data value, the partitioned blocks have better alignment with the object boundary. Moreover, in the cuboid coding process, only the partitioning tree information and a single value for each block need to be coded which takes lower number of bits and computational time compared to the traditional SHVC base layer. To verify the performance of the proposed method we embedded the proposed scheme as a base layer into the standard SHVC reference software and used several popular UHD/360-degree videos. The experimental results indicate that the proposed scalable coding strategy achieves an average of 14.04% BD-Rate reduction and 0.61 dB BD-PSNR gain for UHD/360-video compared to the operation points provided by an SHVC conforming encoder. © 1991-2012 IEEE.

Efficient scalable 360-degree video compression scheme using 3d cuboid partitioning

- Afsana, Fariha, Paul, Manoranjan, Murshed, Manzur, Taubman, David

  • Authors: Afsana, Fariha , Paul, Manoranjan , Murshed, Manzur , Taubman, David
  • Date: 2022
  • Type: Text , Conference paper
  • Relation: 29th IEEE International Conference on Image Processing, ICIP 2022 p. 996-1000
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  • Description: Video coding techniques minimize spatial and temporal redundancies inherent in video sequences based on non-overlapping block-based image partitioning. Due to depending on the information from already encoded neighboring blocks, these algorithms lack efficient techniques to exploit the overall global redundancies. Compared to the traditional block-based coding, the cuboid coding (2D) framework has been proven to be a more effective method of image compression that exploits global redundancy by considering homogeneous pixel correlation within a frame. In this paper, we improved the idea of 2D cuboid coding to exploit both local and global redundancy from a video sequence by adopting a three-dimensional (3D) cuboid partitioning scheme for SHVC compression improvement of 360-degree videos. The proposed method considers a group of successive frames as a 3D cuboid and recursively partitions it into sub-3D cuboids where static information over a selected GOP share the same cuboid and moving regions share new cuboids with better-defined objects. All the 3D cuboids are then encoded to create a coarse representation of the video stream. Experiments indicate that the proposed framework significantly outperforms its relevant benchmarks, notably by 17.18% (average) in BD-Rate reduction and 0.82 dB in BD-PSNR gain with respect to the standard SHVC codec. © 2022 IEEE.

Shared value priorities in groups : The impact of the Bahá’i Faith on Values

- Afshar, Faezeh

  • Authors: Afshar, Faezeh
  • Date: 2012
  • Type: Text , Thesis , PhD
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  • Description: Values such as honesty, meaning in life, pleasure, justice and freedom are guiding principles in motivating the selection and evaluation of individual behaviour and goals. They are also important for understanding cultural norms, attitudes and practices. In previous studies individuals and groups have often been found to be willing to subordinate their values toward goals and behaviours that are aligned with their own group; their ‘in-group’. Studies of values within a group have not reported evidence for the subordination of their values toward universal goals and behaviours; their ‘out-groups’. This research is the first to examine widely the values held by adherents of the Bahá’i Faith; a world-wide religious community that envisions a united global society. The main aim of this thesis is to discover and explain the system of value priorities held by Bahá’is. Data was obtained from an online survey of over one thousand responses to the cross-culturally validated ‘Schwartz Value Survey’. Data relating to the degree of commitment to religion referred to as religiosity, was also collected in addition to demographic information.
  • Description: Doctor of Philosophy

A computer-mediated framework to facilitate group consensus based on a shared understanding ConSULT

- Afshar, Faezeh

  • Authors: Afshar, Faezeh
  • Date: 2004
  • Type: Text , Thesis , Masters , PhD
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  • Description: "Group decision-making usually involves a process of discussion and evaluation of alternatives. Important aspects of a group decision support system are: freedom to participate; the ability to explicitly present points of view; the ability to augment or oppose views by supporting evidence and reasoning; and the ability to use and consider other additional views .... The overall aim of this work is to develop an approach that can alleviate some of the problems associated with group commuication and consensus decision-making by effectively supporting group discussions towards consensus. Towards achieving this goal we have developed an approach called ConSULT (Consensus based on a Shared Understanding of a Leading Topic) as a computer-mediated framework to allow argumentation, collection and evaluation of discussion and group decision-making. This approach employs existing theories and techniques in computer-mediated communication, argumentation, Delphi and voting." -- Abstract.
  • Description: Master of Information Technology
  • Description: "Group decision-making usually involves a process of discussion and evaluation of alternatives. Important aspects of a group decision support system are: freedom to participate; the ability to explicitly present points of view; the ability to augment or oppose views by supporting evidence and reasoning; and the ability to use and consider other additional views .... The overall aim of this work is to develop an approach that can alleviate some of the problems associated with group commuication and consensus decision-making by effectively supporting group discussions towards consensus. Towards achieveing this goal we have developed an approach called ConSULT (Consensus based on a Shared Understanding of a Leading Topic) as a computer-mediated framework to allow argumentation, collection and evaluation of discussion and group decision-making. This approach employs existing theories and techniques in computer-mediated communication, argumentation, Delphi and voting." -- Abstract.

A Tool for Assisting Group Decision-Making for Consensus Outcomes in Organizations

- Afshar, Faye, Yearwood, John, Stranieri, Andrew

Formal modeling and verification of a blockchain-based crowdsourcing consensus protocol

- Afzaal, Hamra, Imran, Muhammad, Janjua, Muhammad, Gochhayat, Sarada

  • Authors: Afzaal, Hamra , Imran, Muhammad , Janjua, Muhammad , Gochhayat, Sarada
  • Date: 2022
  • Type: Text , Journal article
  • Relation: IEEE Access Vol. 10, no. (2022), p. 8163-8183
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  • Description: Crowdsourcing is an effective technique that allows humans to solve complex problems that are hard to accomplish by automated tools. Some significant challenges in crowdsourcing systems include avoiding security attacks, effective trust management, and ensuring the system's correctness. Blockchain is a promising technology that can be efficiently exploited to address security and trust issues. The consensus protocol is a core component of a blockchain network through which all the blockchain peers achieve an agreement about the state of the distributed ledger. Therefore, its security, trustworthiness, and correctness have vital importance. This work proposes a Secure and Trustworthy Blockchain-based Crowdsourcing (STBC) consensus protocol to address these challenges. Model checking is an effective and automatic technique based on formal methods that is utilized to ensure the correctness of STBC consensus protocol. The proposed consensus protocol's formal specification is described using Communicating Sequential Programs (CSP#). Safety, fault tolerance, leader trust, and validators' trust are important properties for a consensus protocol, which are formally specified through Linear Temporal Logic (LTL) to prevent several security attacks, such as blockchain fork, selfish mining, and invalid block insertion. Process Analysis Toolkit (PAT) is utilized for the formal verification of the proposed consensus protocol. © 2022 Institute of Electrical and Electronics Engineers Inc.. All rights reserved.

Formal verification of persistence and liveness in the trust-based blockchain crowdsourcing consensus protocol

- Afzaal, Hamra, Imran, Muhammad, Janjua, Muhammad

  • Authors: Afzaal, Hamra , Imran, Muhammad , Janjua, Muhammad
  • Date: 2022
  • Type: Text , Journal article
  • Relation: Computer Communications Vol. 192, no. (2022), p. 384-401
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  • Description: Crowdsourcing is a potential computing paradigm that exploits collective human intelligence to solve complex tasks, but it suffers from various safety and security problems. Blockchain has emerged as a promising technology to address most of the security issues, however, it is challenging to find an appropriate and trusted blockchain-based consensus protocol for crowdsourcing services. This work proposes a novel Trust-based Blockchain Crowdsourcing consensus protocol that selects a leader and validators based on various trust factors. The proposed protocol addresses a major issue of ensuring correctness associated with the safety and security-critical systems which has a vital importance because failure of such systems may lead to adverse consequences. Mainly it is focused on persistence and liveness properties preventing invalid block insertion and consensus delay attacks. Model checking technique is utilized because of its effectiveness and automatic nature to perform formal verification. The proposed protocol is specified using Communicating Sequential Programs, and the persistence and liveness properties are specified through Linear Temporal Logic. The model verification is performed by giving the formal model and the properties as input to the Process Analysis Toolkit which checks for the satisfaction or violation of the properties. © 2022 Elsevier B.V.

Formal verification of fraud-resilience in a crowdsourcing consensus protocol

- Afzaal, Hamra, Imran, Muhammad, Janjua, Muhammad

  • Authors: Afzaal, Hamra , Imran, Muhammad , Janjua, Muhammad
  • Date: 2023
  • Type: Text , Journal article
  • Relation: Computers & security Vol. 131, no. (2023), p. 103290
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  • Description: •A Trust and Transactions Chain consensus protocol is proposed for a blockchain-based crowdsourcing system.•Communicating Sequential Programs language is utilized for the formal modeling of the proposed consensus protocol.•The properties of no sybil attack, no eclipse attack, and fraud-resilience are defined through Linear Temporal Logic.•Model checking is employed to ensure the correctness of the proposed consensus protocol.•The formal verification is performed by giving the formal model and properties as input to the Process Analysis Toolkit. [Display omitted] Crowdsourcing has emerged as a promising computing paradigm that utilizes human intelligence to achieve complex tasks, but it encounters several security and trust issues. Blockchain is a potential technology that can resolve most of these issues, however, it is difficult to find an appropriate consensus protocol applicable to crowdsourcing systems. Therefore, this work presents a Trust and Transactions Chain (TTC) consensus protocol built upon blockchain technology. It selects a trusted leader and validators considering a trust model which depends on deposit ratio, block generation and validation rate, and waiting rate. The TTC protocol addresses the main challenge of ensuring correctness related to critical systems of crowdsourcing which has extreme significance as their failure can result in disastrous consequences. This work is primarily focused on fraud-resilience avoiding double-spending attack. It also deals with sybil and eclipse attacks. Model checking is exploited because it is effective and automatic to conduct formal verification. The TTC protocol is formally modeled utilizing Communicating Sequential Programs, and the fraud-resilience property is specified using Linear Temporal Logic. The verification of the model is done using Process Analysis Toolkit that takes the formal model and specified properties as input to inspect the properties’ satisfaction or violation. The results of the formal verification are analyzed with respect to the verification time and the number of visited states.

Facilitators to support the implementation of injury prevention training in youth handball : A concept mapping approach

- Ageberg, Eva, Bunke, Sofia, Lucander, Karolina, Nilsen, Per, Donaldson, Alex

  • Authors: Ageberg, Eva , Bunke, Sofia , Lucander, Karolina , Nilsen, Per , Donaldson, Alex
  • Date: 2019
  • Type: Text , Journal article
  • Relation: Scandinavian Journal of Medicine and Science in Sports Vol. 29, no. 2 (2019), p. 275-285
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  • Description: There is a need for research to identify effective implementation strategies for injury prevention training within real-world community sports. The aim of this ecological participatory study was to identify facilitators, among stakeholders at multiple levels, that could help injury prevention training become part of regular training routines in youth team handball. Concept mapping, a mixed-method approach for qualitative data collection and quantitative data analysis, was used. Stakeholders (n = 196) of two community team handball clubs (29% players, 13% coaches, 38% caregivers, 11% club, district and national handball administrators, 9% unknown) participated in a brainstorming process. After the research team synthesized the 235 generated statements, 50 stakeholders (34% players, 22% coaches, 24% caregivers, 20% administrators) sorted 89 unique facilitator statements into clusters and rated them for importance and feasibility. Multidimensional scaling and hierarchical cluster analysis yielded five clusters (stress value 0.231): “Understanding and applying knowledge,” “Education, knowledge, and consistency,” “Set-up and exercises,” “Inspiration, motivation, and routines,” and “Club policy and expert collaboration.” The cluster “Understanding and applying knowledge” had the highest mean importance (3.17 out of 4) and feasibility (2.93) ratings. The 32 statements rated as both highly important and feasible (Go-zone) indicate action is required at the individual (end-users) and organizational (policymakers) levels to implement injury prevention training. Results suggest that developing evidence-based context-specific injury prevention training, incorporating physiological, biomechanical and psychological components, and an associated context-specific implementation plan in partnership with all stakeholders should be a high priority to facilitate the implementation of injury prevention training in youth team handball.

A linearized energy hub operation model at the presence of uncertainties: An adaptive robust solution approach

- Aghamohamadi, Mehrdad, Amjady, Nima, Attarha, Ahmad

  • Authors: Aghamohamadi, Mehrdad , Amjady, Nima , Attarha, Ahmad
  • Date: 2020
  • Type: Text , Journal article
  • Relation: International transactions on electrical energy systems Vol. 30, no. 3 (2020), p. n/a
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  • Description: Summary This paper presents a new adaptive robust operation optimization approach for energy hub (EH) to identify the optimal decisions on purchased energy carriers, upstream network interactions, and storing/conversion of the energy resources considering uncertainties. In this regard, a linearized framework for EH operation is first introduced. The proposed model is used to develop an EH including electrical energy, natural gas, and direct heat as inputs and electricity and heat demands as outputs. The electrical input energy is provided considering both purchased energy from upstream market and a photovoltaic (PV) generation, operated by the EH operator (EHO). The proposed approach characterizes the uncertain nature of loads, energy prices, and PV generations through polyhedral uncertainty sets, while the robustness of the proposed model can be controlled using the budget of uncertainty. The proposed adaptive robust model is formulated as a min‐max‐min optimization problem, which cannot be solved directly through an off‐the‐shelf optimization package. Thus, a new method, consisting decomposition + primal cutting plane + duality theory + exact linearization + post‐optimization analysis, is introduced to determine the EH optimal solution. The performance of the proposed approach is evaluated through a comprehensive case study.

Improving voltage of remote connection using wind-solar farms equipped with new voltage control strategy based on virtual impedance monitoring enabled by IEC 61850 communication

- Aghanoori, Navid, Masoum, Mohammad, Islam, Syed, Abu-Siada, Ahmed, Nethery, Steven

  • Authors: Aghanoori, Navid , Masoum, Mohammad , Islam, Syed , Abu-Siada, Ahmed , Nethery, Steven
  • Date: 2019
  • Type: Text , Journal article
  • Relation: IET Generation, Transmission and Distribution Vol. 13, no. 11 (2019), p. 2112-2122
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  • Description: This study explores how the voltage control of a remote part of the utility gird can be improved using more sophisticated voltage control on wind-solar farms equipped with fast communication platforms. The idea is to make renewable plant the master voltage controller during large disturbance events in the grid. This is done by proposing an enhanced voltage droop control strategy based on instantaneous reactive power consumption by monitoring the virtual impedance of the point of connection using a new customised data class model of IEC 61850 communication protocol. The conventional centralised voltage droop control strategy and the proposed instantaneous direct voltage control method are both implemented on the White Rock Solar Wind Farm in NSW, Australia and their performances are compared using both MATLAB Simulink simulations under 5% voltage step disturbances, single-phase-to-ground and three-phase-to-ground faults as well as some tests conducted in the field.

Investigation of microgrid instability caused by time delay

- Aghanoori, Navid, Masoum, Mohammad, Islam, Syed, Nethery, Steven

  • Authors: Aghanoori, Navid , Masoum, Mohammad , Islam, Syed , Nethery, Steven
  • Date: 2017
  • Type: Text , Conference proceedings , Conference paper
  • Relation: 10th International Conference on Electrical and Electronics Engineering, ELECO 2017; Bursa, Turkey; 29th-2nd December 2017 Vol. 2018, p. 105-110
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  • Description: This paper investigates the impact of time delay in the control of a grid-connected microgrid with renewable energy resources. The considered microgrid has a critical load that needs to be powered and protected in the event of grid voltage disturbance while the microgrid maintains connection to the grid. Three case studies are performed considering three different time delays to indicate the advantages of fast communication system in the performance of renewable microgrids. Detailed simulation results illustrate that the proposed communication system using IEC 61850 substation automation standard provides better voltage and current quality to the critical local load with larger phase and gain margins while keeping the microgid connected to main grid.

Enhancement of microgrid operation by considering the cascaded impact of communication delay on system stability and power management

- Aghanoori, Navid, Masoum, Mohammad, Abu-Siada, Ahmed, Islam, Syed

  • Authors: Aghanoori, Navid , Masoum, Mohammad , Abu-Siada, Ahmed , Islam, Syed
  • Date: 2020
  • Type: Text , Journal article
  • Relation: International Journal of Electrical Power and Energy Systems Vol. 120, no. (2020), p.
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  • Description: Power management, system stability and communication structure are three key aspects of microgrids (MGs) that have been explored in many research studies. However, the cascaded effect of communication structure on system stability followed by the impact of stability on the power management has not been fully explored in the literature yet and needs more attention. This paper not only explores this cascaded impact, but also provides a comprehensive platform to optimally consider three layers of MG design and operation from this perspective. For generation cost minimization and stability assessment, the proposed platform uses an adaptive particle swarm optimization (PSO) while a new class of data exchange scheme based on IEC 61850 protocol is proposed to reduce the communication time delays among the inverters of distributed generations and the MG control center. This paper also considers the system stability using small-signal model of a MG in a real-time manner as an embedded function in the PSO. In this context investigations have been conducted by modeling an isolated MG with solar farm, fuel cell generator and micro-turbine in MATLAB Simulink. Detailed simulation results indicate the proposed power and stability management method effectively reduces the MG generation cost through maximizing the utilization of the available renewable generations while considering system stability. © 2020 Elsevier Ltd

Methicillin-resistant staphylococcus aureus in Melanesian children with haematogenous osteomyelitis from the Central Highlands of Papua New Guinea

- Aglua, Izzard, Jaworski, Jan, Drekore, Jimmy, Urakoko, Bohu, Poka, Harry, Michael, Audrey, Greenhill, Andrew

  • Authors: Aglua, Izzard , Jaworski, Jan , Drekore, Jimmy , Urakoko, Bohu , Poka, Harry , Michael, Audrey , Greenhill, Andrew
  • Date: 2018
  • Type: Text , Journal article
  • Relation: International Journal of Pediatrics Vol. 6, no. 10 (2018), p. 8361-8370
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  • Description: Background: Methicillin-Resistant Staphylococcus aureus (MRSA) has been an important cause of bone infection since the 1940s. Current guidelines recommend targeted antibiotic use for osteomyelitis treatment informed by microbial sensitivity patterns. However, in settings without microbiology facilities, empirical antibiotic use is common. Unrecognized antibiotic resistance potentiates persistence of MRSA with osteomyelitis progression to chronic forms with complications despite antibiotic treatment. Materials and Methods: A prospective observational study was done to identify common etiological agent (s) in bone infection in Melanesian children (that were admitted to the two surgical and one pediatric wards of the SJNM-KUGH in the Simbu province of Papua New Guinea in 2012 and 2017), observe for presence of antimicrobial resistance, and determine effective antibiotic regimes for treatment of bone pediatric osteomyelitis. Seventy pediatric patients presenting from the community with osteomyelitis were recruited, with bone and non-bone specimens sampled, cultured and isolates tested for resistance to common antibiotics. Results: Staphylococcus aureus (S. aureus) was isolated in 67% (47/70) of collected specimens. Of the 47 isolates, there was 91.5% resistance to penicillin, 85.1% resistance to methicillin, 89.4% resistance to oxacillin, 93.6% resistance to ampicillin and 80.9% resistance to ceftriaxone. S. aureus showed 91.5% sensitivity to gentamycin, 93.6% sensitivity to erythromycin, tetracycline and clindamycin, and 95.7% sensitivity to Co-trimoxazole. Conclusion: MRSA was the leading cause of haematogenous osteomyelitis in Melanesian children. S.aureus was isolated mainly from infected long bones of the lower limbs (79%) of children presenting from the community, suggesting a predominantly community-associated MRSA.