scholarly journals Link-Layer Retransmission-based Error-Control Protocols in FSO Communications: A Survey

2021 ◽  
Author(s):  
Hoang Le
Keyword(s):  
High Speed ◽  
Error Control ◽  
Design Guidelines ◽  
Lessons Learned ◽  
Future Research ◽  
Extensive Literature ◽  
Free Space Optical ◽  
Deep Space ◽  
Link Layer ◽  
Retransmission Protocols

Free-space optical (FSO) communications have gained significant interest over the last few years, thanks to the capability to transport extremely high-speed data over long distances without exhausting radio frequency (RF) resources. FSO communication is widely considered in various network scenarios, such as inter-satellite/deep-space links, ground-station/vehicles, satellite/aerial links, or terrestrial links. It is expected to be a key enabling technology for the next generation of 6G wireless networks. Nevertheless, despite the great potential of FSO communications, its performance suffers from various limitations and challenges: atmospheric turbulence, clouds, weather conditions, and pointing misalignment. The error-control solutions, including physical layer (PHY) and link-layer methods, aim to mitigate the transmission errors caused by such adverse issues. While the existing surveys on error-control solutions in FSO systems primarily focussed on the PHY methods, we instead provide a review of link-layer solutions. In particular, we conduct an extensive literature survey of state-of-the-art retransmission protocols, both automatic repeat request (ARQ) and hybrid ARQ (HARQ), for various FSO communication scenarios, including point-to-point terrestrial, cooperative, multi-hop relaying, hybrid FSO/RF, satellite/aerial, and deep-space systems. Furthermore, we provide a survey of recent literature and insightful discussion on the cross-layer design frameworks related to link-layer retransmission protocols in FSO communication networks. Finally, the lessons learned, design guidelines, related open issues, and future research directions are exposed.

scholarly journals Link-Layer Retransmission-based Error-Control Protocols in FSO Communications: A Survey

2021 ◽  
Author(s):  
Hoang Le
Keyword(s):  
High Speed ◽  
Error Control ◽  
Design Guidelines ◽  
Lessons Learned ◽  
Future Research ◽  
Extensive Literature ◽  
Free Space Optical ◽  
Deep Space ◽  
Link Layer ◽  
Retransmission Protocols

Free-space optical (FSO) communications have gained significant interest over the last few years, thanks to the capability to transport extremely high-speed data over long distances without exhausting radio frequency (RF) resources. FSO communication is widely considered in various network scenarios, such as inter-satellite/deep-space links, ground-station/vehicles, satellite/aerial links, or terrestrial links. It is expected to be a key enabling technology for the next generation of 6G wireless networks. Nevertheless, despite the great potential of FSO communications, its performance suffers from various limitations and challenges: atmospheric turbulence, clouds, weather conditions, and pointing misalignment. The error-control solutions, including physical layer (PHY) and link-layer methods, aim to mitigate the transmission errors caused by such adverse issues. While the existing surveys on error-control solutions in FSO systems primarily focussed on the PHY methods, we instead provide a review of link-layer solutions. In particular, we conduct an extensive literature survey of state-of-the-art retransmission protocols, both automatic repeat request (ARQ) and hybrid ARQ (HARQ), for various FSO communication scenarios, including point-to-point terrestrial, cooperative, multi-hop relaying, hybrid FSO/RF, satellite/aerial, and deep-space systems. Furthermore, we provide a survey of recent literature and insightful discussion on the cross-layer design frameworks related to link-layer retransmission protocols in FSO communication networks. Finally, the lessons learned, design guidelines, related open issues, and future research directions are exposed.

Agglomeration: Economic and Environmental Impacts

2019 ◽  
Vol 11 (1) ◽  
pp. 419-438
Author(s):  
JunJie Wu
Keyword(s):  
Emerging Economies ◽  
World Economy ◽  
Lessons Learned ◽  
Policy Implications ◽  
Future Research ◽  
Extensive Literature ◽  
Research Directions ◽  
Trade Offs ◽  
Future Research Directions ◽  
Different Levels

Urbanization is taking place at an unprecedented pace and scale in China, India, and many other emerging economies. This will have profound impacts on the world economy and environment. This review provides a critical assessment of the current understanding of the intertwined relationships between agglomeration, economic growth, and environmental quality. We start by providing a brief overview of the extensive literature on the drivers of agglomeration and its economic impact. We then discuss the opposing views on the environmental impact of agglomeration and illustrate the trade-offs involved when choosing among different levels and forms of agglomeration. Finally, we discuss challenges for environmental management in a rapidly urbanizing economy and some lessons learned from history and experiences of urban development and their policy implications. The review concludes with a discussion of key knowledge gaps and future research directions.

A Circular Business Model for Cloud Computing Services Providers

10.31355/33 ◽  
2018 ◽  
Vol 2 ◽  
pp. 105-120
Author(s):  
Hamed Motaghi ◽  
Saeed Nosratabadi ◽  
Thabit Qasem Atobishi
Keyword(s):  
Cloud Computing ◽  
Business Model ◽  
Circular Economy ◽  
Service Providers ◽  
Sustainable Consumption ◽  
Future Research ◽  
Extensive Literature ◽  
Computing Services ◽  
Proposed Model ◽  
Cloud Computing Service

NOTE: THIS ARTICLE WAS PUBLISHED WITH THE INFORMING SCIENCE INSTITUTE. Aim/Purpose................................................................................................................................................................................................. The main objective of the current study is to develop a business model for service providers of cloud computing which is designed based on circular economy principles and can ensure the sustainable consumption. Background Even though the demand for cloud computing technology is increasing day by day in all over the world, the current the linear economy principles are incapable to ensure society development needs. To consider the benefit of the society and the vendors at the same time, the principles of circular economy can address this issue. Methodology................................................................................................................................................................................................. An extensive literature review on consumption, sustainable consumption, circular economic, business model, and cloud computing were conducted. the proposed model of Osterwalder, Pigneur and Tucci (2005) is admitted designing the circular business model. Contribution................................................................................................................................................................................................. The proposed model of the study is the contribution of this study where provides the guidelines for the cloud computing service providers to achieve both their economic profits and the society’ needs. Findings Finding reveals that if the cloud computing service providers design their business model based on the “access” principle of circular economy, they can meet their economic profits and the society’ needs at a same time. Recommendations for Practitioners.............................................................................................................................................................. It is recommended to the startup and the existing businesses to utilize the proposed model of this study to reach a sustainable development. Recommendation for Researchers................................................................................................................................................................ It proposes a new circular business model and its linkages with community building. Impact on Society............................................................................................................................................................................................ The proposed model of the study provides guidelines to the cloud computing service providers to design a business model which is able not only to meet their economic profit, but also to meet the society’s and customers’ benefits. Future Research............................................................................................................................................................................................... Future researches can build on this research model which proposed in this study to examine the limitations of this model by using empirical researches.

Research on High-Speed Cutting of Cr12MoV Hardened Steel - A Review

2020 ◽  
Vol 15 ◽  
Author(s):  
Fei Sun ◽  
Guohe Li ◽  
Qi Zhang ◽  
Meng Liu
Keyword(s):  
High Speed ◽  
Cutting Temperature ◽  
High Hardness ◽  
High Strength ◽  
Hardened Steel ◽  
Parameters Optimization ◽  
Future Research ◽  
High Speed Machining ◽  
Machined Surface ◽  
Stamping Die

: Cr12MoV hardened steel is widely used in the manufacturing of stamping die because of its high strength, high hardness, and good wear resistance. As a kind of mainstream cutting technology, high-speed machining has been applied in the machining of Cr12MoV hardened steel. Based on the review of a large number of literature, the development of high-speed machining of Cr12MoV hardened steel was summarized, including the research status of the saw-tooth chip, cutting force, cutting temperature, tool wear, machined surface quality, and parameters optimization. The problems that exist in the current research were discussed and the directions of future research were pointed out. It can promote the development of high-speed machining of Cr12MoV hardened steel.

Review of Research on Hydrostatic Bearings

2020 ◽  
Vol 13 ◽  
Author(s):  
Xiaodong Yu ◽  
Yu Wang ◽  
Junfeng Wang ◽  
Wenkai Zhou ◽  
Hongwei Bi ◽  
...  
Keyword(s):  
High Speed ◽  
Static Pressure ◽  
Development Trend ◽  
Cnc Machining ◽  
Pressure Effects ◽  
Cnc Machine Tools ◽  
Future Research ◽  
Theoretical Formula ◽  
Hydrostatic Bearing ◽  
Hydrostatic Bearings

Background: Hydrostatic bearings have the advantages of strong bearing capacity, good stability, small friction coefficient and long life. The performance of liquid hydrostatic bearings directly affect the accuracy and efficiency of CNC machining equipment. The performance is conducive to the development of CNC machine tools towards high speed and heavy load, so it is necessary to sort out and summarize the existing research results. Objective: This study summarizes the current development status of hydrostatic bearings and explains the development trend of hydrostatic bearings. Methods: According to the recently published journal articles and patents, the recent experimental research on hydrostatic thrust bearings is summarized. This paper summarizes many factors that affect the performance of hydrostatic bearings, and discusses the causes of various factors on hydrostatic bearings. Finally, future research on hydrostatic bearings is presented. Results: The study discusses experimental methods, simulation processes, and experimental results. Conclusion: This study can produce dynamic and static pressure effects by changing the structure of the oil cavity of the hydrostatic bearing. This effect can make up for the static pressure loss. By improving the theoretical formula and mathematical model and proposing a new simulation method, the accuracy of the hydrostatic bearing simulation is satisfied; the future development trend of the hydrostatic bearing is proposed.

scholarly journals Wastewater Surveillance for SARS-CoV-2 on College Campuses: Initial Efforts, Lessons Learned, and Research Needs

2021 ◽  
Vol 18 (9) ◽  
pp. 4455
Author(s):  
Sasha Harris-Lovett ◽  
Kara L. Nelson ◽  
Paloma Beamer ◽  
Heather N. Bischel ◽  
Aaron Bivins ◽  
...  
Keyword(s):  
Information Needs ◽  
Community Dynamics ◽  
The United States ◽  
Lessons Learned ◽  
Future Research ◽  
Private Institutions ◽  
Community Members ◽  
Public And Private ◽  
College And University ◽  
University Systems

Wastewater surveillance for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an emerging approach to help identify the risk of a coronavirus disease (COVID-19) outbreak. This tool can contribute to public health surveillance at both community (wastewater treatment system) and institutional (e.g., colleges, prisons, and nursing homes) scales. This paper explores the successes, challenges, and lessons learned from initial wastewater surveillance efforts at colleges and university systems to inform future research, development and implementation. We present the experiences of 25 college and university systems in the United States that monitored campus wastewater for SARS-CoV-2 during the fall 2020 academic period. We describe the broad range of approaches, findings, resources, and impacts from these initial efforts. These institutions range in size, social and political geographies, and include both public and private institutions. Our analysis suggests that wastewater monitoring at colleges requires consideration of local information needs, sewage infrastructure, resources for sampling and analysis, college and community dynamics, approaches to interpretation and communication of results, and follow-up actions. Most colleges reported that a learning process of experimentation, evaluation, and adaptation was key to progress. This process requires ongoing collaboration among diverse stakeholders including decision-makers, researchers, faculty, facilities staff, students, and community members.

Staying the distance: Transforming Latin pedagogy at the Open University

2019 ◽  
Vol 18 (1-2) ◽  
pp. 101-128
Author(s):  
Mair E. Lloyd ◽  
James Robson
Keyword(s):  
Cultural Context ◽  
Learning Experience ◽  
New Technology ◽  
Significant Proportion ◽  
Lessons Learned ◽  
Future Research ◽  
Open University ◽  
Ancient Rome ◽  
Positive Effects ◽  
Pedagogical Changes

Abstract Between 2000 and 2013, over 8,000 students studied the module Reading Classical Latin at the Open University, the United Kingdom’s largest distance education provider. But while many learners attained high grades, a significant proportion withdrew from study or failed the module. In 2015, the original module was replaced with a completely new course, Classical Latin: The Language of Ancient Rome. This article details the innovative ways in which new technology and pedagogical theory from Modern Foreign Language (MFL) learning were drawn on by the team designing this new module, resulting in a learning experience which gives greater emphasis to elements such as spoken Latin, the intrinsic pleasure of reading, and cultural context. The (largely positive) effects of these pedagogical changes on student success and satisfaction are subsequently analysed using a rich mix of qualitative and quantitative data. Finally, the authors reflect on lessons learned and the possibilities for future research and enhancement.

Access Control Mechanisms in Named Data Networks

2021 ◽  
Vol 54 (3) ◽  
pp. 1-35
Author(s):  
Boubakr Nour ◽  
Hakima Khelifi ◽  
Rasheed Hussain ◽  
Spyridon Mastorakis ◽  
Hassine Moungla
Keyword(s):  
Access Control ◽  
Holistic Approach ◽  
Future Internet ◽  
Lessons Learned ◽  
Future Research ◽  
Communication Model ◽  
Control Mechanisms ◽  
Internet Communication ◽  
Future Internet Architecture ◽  
Comprehensive Survey

Information-Centric Networking (ICN) has recently emerged as a prominent candidate for the Future Internet Architecture (FIA) that addresses existing issues with the host-centric communication model of the current TCP/IP-based Internet. Named Data Networking (NDN) is one of the most recent and active ICN architectures that provides a clean-slate approach for Internet communication. NDN provides intrinsic content security where security is directly provided to the content instead of communication channel. Among other security aspects, Access Control (AC) rules specify the privileges for the entities that can access the content. In TCP/IP-based AC systems, due to the client-server communication model, the servers control which client can access a particular content. In contrast, ICN-based networks use content names to drive communication and decouple the content from its original location. This phenomenon leads to the loss of control over the content, causing different challenges for the realization of efficient AC mechanisms. To date, considerable efforts have been made to develop various AC mechanisms in NDN. In this article, we provide a detailed and comprehensive survey of the AC mechanisms in NDN. We follow a holistic approach towards AC in NDN where we first summarize the ICN paradigm, describe the changes from channel-based security to content-based security, and highlight different cryptographic algorithms and security protocols in NDN. We then classify the existing AC mechanisms into two main categories: Encryption-based AC and Encryption-independent AC . Each category has different classes based on the working principle of AC (e.g., Attribute-based AC, Name-based AC, Identity-based AC). Finally, we present the lessons learned from the existing AC mechanisms and identify the challenges of NDN-based AC at large, highlighting future research directions for the community.

scholarly journals Bridging Science and Practice-Importance of Stakeholders in the Development of Decision Support: Lessons Learned

2021 ◽  
Vol 13 (10) ◽  
pp. 5744
Author(s):  
Innocent K. Tumwebaze ◽  
Joan B. Rose ◽  
Nynke Hofstra ◽  
Matthew E. Verbyla ◽  
Daniel A. Okaali ◽  
...  
Keyword(s):  
Decision Support ◽  
Stakeholder Participation ◽  
Scientific Data ◽  
Lessons Learned ◽  
Future Research ◽  
Decision Support Tools ◽  
Local Data ◽  
Funding Sources ◽  
Sanitation And Hygiene ◽  
Support Tools

User-friendly, evidence-based scientific tools to support sanitation decisions are still limited in the water, sanitation and hygiene (WASH) sector. This commentary provides lessons learned from the development of two sanitation decision support tools developed in collaboration with stakeholders in Uganda. We engaged with stakeholders in a variety of ways to effectively obtain their input in the development of the decision support tools. Key lessons learned included: tailoring tools to stakeholder decision-making needs; simplifying the tools as much as possible for ease of application and use; creating an enabling environment that allows active stakeholder participation; having a dedicated and responsive team to plan and execute stakeholder engagement activities; involving stakeholders early in the process; having funding sources that are flexible and long-term; and including resources for the acquisition of local data. This reflection provides benchmarks for future research and the development of tools that utilize scientific data and emphasizes the importance of engaging with stakeholders in the development process.

scholarly journals Systematic Design and Evaluation of a Citation Function Classification Scheme in Indonesian Journals

Publications ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 27
Author(s):  
Yaniasih Yaniasih ◽  
Indra Budi
Keyword(s):  
Deep Learning ◽  
Short Term Memory ◽  
Scientific Evidence ◽  
Ease Of Use ◽  
Future Research ◽  
Extensive Literature ◽  
Journal Articles ◽  
Citation Function ◽  
Compilation Process ◽  
Long Short Term Memory

Classifying citations according to function has many benefits when it comes to information retrieval tasks, scholarly communication studies, and ranking metric developments. Many citation function classification schemes have been proposed, but most of them have not been systematically designed for an extensive literature-based compilation process. Many schemes were also not evaluated properly before being used for classification experiments utilizing large datasets. This paper aimed to build and evaluate new citation function categories based upon sufficient scientific evidence. A total of 2153 citation sentences were collected from Indonesian journal articles for our dataset. To identify the new categories, a literature survey was conducted, analyses and groupings of category meanings were carried out, and then categories were selected based on the dataset’s characteristics and the purpose of the classification. The evaluation used five criteria: coherence, ease, utility, balance, and coverage. Fleiss’ kappa and automatic classification metrics using machine learning and deep learning algorithms were used to assess the criteria. These methods resulted in five citation function categories. The scheme’s coherence and ease of use were quite good, as indicated by an inter-annotator agreement value of 0.659 and a Long Short-Term Memory (LSTM) F1-score of 0.93. According to the balance and coverage criteria, the scheme still needs to be improved. This research data was limited to journals in food science published in Indonesia. Future research will involve classifying the citation function using a massive dataset collected from various scientific fields and published from some representative countries, as well as applying improved annotation schemes and deep learning methods.

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