Academic literature on the topic 'Internet Engineering Task Force Case studies'
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Journal articles on the topic "Internet Engineering Task Force Case studies"
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Eklund, Peter, Jeff Thom, Tim Wray, and Edward Dou. "Location Based Context-Aware Services in a Digital Ecosystem with Location Privacy." Journal of Cases on Information Technology 13, no. 2 (April 2011): 49–68. http://dx.doi.org/10.4018/jcit.2011040104.
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This case discusses the architecture and application of privacy and trust issues in the Connected Mobility Digital Ecosystem (CMDE) for the University of Wollongong’s main campus community. The authors describe four mobile location-sensitive, context-aware applications (app(s)) that are designed for iPhones: a public transport passenger information app; a route-based private vehicle car-pooling app; an on-campus location-based social networking app; and a virtual art-gallery tour guide app. These apps are location-based and designed to augment user interactions within their physical environments. In addition, location data provided by the apps can be used to create value-added services and optimize overall system performance. The authors characterize this socio-technical system as a digital ecosystem and explain its salient features. Using the University of Wollongong’s campus and surrounds as the ecosystem’s community for the case studies, the authors present the architectures of these four applications (apps) and address issues concerning privacy, location-identity and uniform standards developed by the Internet Engineering Task Force (IETF).
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Mitchel, Christopher, Baraq Ghaleb, Safwan M. Ghaleb, Zakwan Jaroucheh, and Bander Ali Saleh Al-rimy. "The Impact of Mobile DIS and Rank-Decreased Attacks in Internet of Things Networks." International Journal of Engineering and Advanced Technology 10, no. 2 (December 30, 2020): 66–72. http://dx.doi.org/10.35940/ijeat.b1962.1210220.
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With a predicted 50 billion devices by the end of 2020, the Internet of things has grown exponentially in the last few years. This growth has seen an increasing demand for mobility support in low power and lossy sensor networks, a type of network characterized by several limitations in terms of their resources including CPU, memory and batter, causing manufactures to push products out to the market faster, without the necessary security features. IoT networks rely on the Routing Protocol for Low Power and Lossy Network (RPL) for communication, designed by the Internet Engineering Task Force (IETF). This protocol has been proven to be efficient in relation to the handling of routing in such constrained networks, However, research studies revealed that RPL was inherently designed for static networks, indicating poor handling of mobile or dynamic topologies which is worsen when introducing mobile attacker. In this paper, two IoT routing attacks are evaluated under a mobile attacker with the aim of providing a critical evaluation of the impact the attacks have on the network in comparison to the case with static attacker. The first attack is the Rank attack in which the attacker announces false routing information to its neighbour attracting them to forward their data via the attacker. The second attack is the DIS attack in which the attacker floods the network with DIS messages triggering them to reset their transmission timers and sending messages more frequently. The comparison were conducted in terms of average power consumption and also the packet delivery ratio (PDR). Based on the results collected from the simulations, it was established that when an attacking node is mobile, there’s an average increase of 36.6 in power consumption and a decrease of 14 for packet delivery ratios when compared to a static attacking node.
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Granata, Samuele, Marco Di Benedetto, Cristina Terlizzi, Riccardo Leuzzi, Stefano Bifaretti, and Pericle Zanchetta. "Power Electronics Converters for the Internet of Energy: A Review." Energies 15, no. 7 (April 2, 2022): 2604. http://dx.doi.org/10.3390/en15072604.
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This paper presents a comprehensive review of multi-port power electronics converters used for application in AC, DC, or hybrid distribution systems in an Internet of Energy scenario. In particular, multi-port solid-state transformer (SST) topologies have been addressed and classified according to their isolation capabilities and their conversion stages configurations. Non-conventional configurations have been considered. A comparison of the most relevant features and design specifications between popular topologies has been provided through a comprehensive and effective table. Potential benefits of SSTs in distribution applications have been highlighted even with reference to a network active nodes usage. This review also highlights standards and technical regulations in force for connecting SSTs to the electrical distribution system. Finally, two case studies of multi-port topologies have been presented and discussed. The first one is an isolated multi-port bidirectional dual active bridge DC-DC converter useful in fast-charging applications. The second case of study deals with a three-port AC-AC multi-level power converter in H-Bridge configuration able to replicate a network active node and capable of routing and controlling energy under different operating conditions.
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ELotmani, Fouad, Redouane Esbai, and Mohamed Atounti. "The Reverse Engineering of a Web Application Struts Based in the ADM Approach." International Journal of Online and Biomedical Engineering (iJOE) 16, no. 02 (February 12, 2020): 112. http://dx.doi.org/10.3991/ijoe.v16i02.11213.
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<p>Since web technologies are constantly evolving, the adaptation of legacy web applications to new paradigms such as rich internet applications (RIAs) is become a necessity. In such tendencies, we notice that several web leaders has already migrated their web applications to RIAs. However, it faces many challenges due to the variety of frameworks. Nevertheless, and in order to facilitate the process of migration, it would be ideal to use tools that could help automatically generate or ease the generation of UML (Unified Modeling Language) models from legacy web application. In this context, novel technical frameworks used for information integration and migration processes such as Architecture-Driven Modernization Task Force (ADMTF) were fashioned to describe specifications and promote industry accord on the modernization of existing applications. In this paper, we propose a process for migrating application from Struts to UML model using ADM standards and MoDisco. We then present a case study as an example illustrating the different steps of the proposed process. We then validated the proposition within Eclipse Modelling Framework since a number of its tools and run-time environments are indeed aligned with ADM standards.</p>
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Iqbal, Razib, Shervin Shirmohammadi, and Rasha Atwah. "A Dynamic Approach to Estimate Receiving Bandwidth for WebRTC." International Journal of Multimedia Data Engineering and Management 7, no. 3 (July 2016): 17–33. http://dx.doi.org/10.4018/ijmdem.2016070102.
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Web Real-Time Communication (WebRTC), drafted by the World Wide Web Consortium (W3C) and Internet Engineering Task Force (IETF), enables direct browser-to-browser real-time communication. As its congestion control mechanism, WebRTC uses the Google Congestion Control (GCC) algorithm. But using GCC will limit WebRTC's performance in cases of overusing due to using a fixed decreasing factor, known as alpha (a). In this paper, the authors propose a dynamic alpha model to reduce the receiving bandwidth estimate during overuse as indicated by the overuse detector. Using their proposed model, the receiver can more efficiently estimate its receiving rate in case of overuse. They implemented their model over both unconstrained and constrained networks. Experimental results show noticeable improvements in terms of higher incoming rate, lower Round-Trip Time, and lower packet loss compared to the fixed alpha model.
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Richard, Paul, Georges Birebent, Philippe Coiffet, Grigore Burdea, Daniel Gomez, and Noshir Langrana. "Effect of Frame Rate and Force Feedback on Virtual Object Manipulation." Presence: Teleoperators and Virtual Environments 5, no. 1 (January 1996): 95–108. http://dx.doi.org/10.1162/pres.1996.5.1.95.
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Research on virtual environments (VE) produced significant advances in computer hardware (graphics boards and i/o tools) and software (real-time distributed simulations). However, fundamental questions remain about how user performance is affected by such factors as graphics refresh rate, resolution, control latencies, and multimodal feedback. This article reports on two experiments performed to examine dextrous manipulation of virtual objects. The first experiment studies the effect of graphics frame rate and viewing mode (monoscopic vs. stereoscopic) on the time required to grasp a moving target. The second experiment studies the effect of direct force feedback, pseudoforce feedback, and redundant force feedback on grasping force regulation. The trials were performed using a partially-immersive environment (graphics workstation and LCD glasses), a DataGlove, and the Rutgers Master with force feedback. Results of the first experiment indicate that stereoscopic viewing is beneficial for low refresh rates (it reduced task completion time by about 50% vs. monoscopic graphics). Results of the second experiment indicate that haptic feedback increases performance and reduces error rates, as compared to the open loop case (with no force feedback). The best performance was obtained when both direct haptic and redundant auditory feedback were provided to the user. The large number of subjects participating in these experiments (over 160 male and female) indicates good statistical significance for the above results.
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Kim, Jiyoon, Daniel Gerbi Duguma, Sangmin Lee, Bonam Kim, JaeDeok Lim, and Ilsun You. "Scrutinizing the Vulnerability of Ephemeral Diffie–Hellman over COSE (EDHOC) for IoT Environment Using Formal Approaches." Mobile Information Systems 2021 (September 13, 2021): 1–18. http://dx.doi.org/10.1155/2021/7314508.
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Most existing conventional security mechanisms are insufficient, mainly attributable to their requirements for heavy processing capacity, large protocol message size, and longer round trips, for resource-intensive devices operating in an Internet of Things (IoT) context. These devices necessitate efficient communication and security protocols that are cognizant of the severe resource restrictions regarding energy, computation, communication, and storage. To realize this, the IETF (Internet Engineering Task Force) is currently working towards standardizing an ephemeral key-based lightweight and authenticated key exchange protocol called EDHOC (Ephemeral Diffie–Hellman over COSE). The protocol’s primary purpose is to build an OSCORE (Object Security for Constrained RESTful Environments) security environment by supplying crucial security properties such as secure key exchange, mutual authentication, perfect forward secrecy, and identity protection. EDHOC will most likely dominate IoT security once it becomes a standard. It is, therefore, imperative to inspect the protocol for any security flaw. In this regard, two previous studies have shown different security vulnerabilities of the protocol using formal security verification methods. Yet, both missed the vital security flaws we found in this paper: resource exhaustion and privacy attacks. In finding these vulnerabilities, we leveraged BAN-Logic and AVISPA to formally verify both EDHOC protocol variants. Consequently, we described these security flaws together with the results of the related studies and put forward recommended solutions as part of our future work.
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Zhang, Kuiyuan, Mingzhi Pang, Yuqing Yin, Shouwan Gao, and Pengpeng Chen. "ARS: Adaptive Robust Synchronization for Underground Coal Wireless Internet of Things." Sensors 20, no. 17 (September 2, 2020): 4981. http://dx.doi.org/10.3390/s20174981.
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Clock synchronization is still a vital and challenging task for underground coal wireless internet of things (IoT) due to the uncertainty of underground environment and unreliability of communication links. Instead of considering on-demand driven clock synchronization, this paper proposes a novel Adaptive Robust Synchronization (ARS) scheme with packets loss for mine wireless environment. A clock synchronization framework that is based on Kalman filtering is first proposed, which can adaptively adjust the sampling period of each clock and reduce the communication overhead in single-hop networks. The proposed scheme also solves the problem of outliers in data packets with time-stamps. In addition, this paper extends the ARS algorithm to multi-hop networks. Additionally, the upper and lower bounds of error covariance expectation are analyzed in the case of incomplete measurement. Extensive simulations are conducted in order to evaluate the performance. In the simulation environment, the clock accuracy of ARS algorithm is improved by 7.85% when compared with previous studies for single-hop networks. For multi-hop networks, the proposed scheme improves the accuracy by 12.56%. The results show that the proposed algorithm has high scalability, robustness, and accuracy, and can quickly adapt to different clock accuracy requirements.
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Sobral, José V. V., Joel J. P. C. Rodrigues, Ricardo A. L. Rabêlo, Jalal Al-Muhtadi, and Valery Korotaev. "Routing Protocols for Low Power and Lossy Networks in Internet of Things Applications." Sensors 19, no. 9 (May 9, 2019): 2144. http://dx.doi.org/10.3390/s19092144.
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The emergence of the Internet of Things (IoT) and its applications has taken the attention of several researchers. In an effort to provide interoperability and IPv6 support for the IoT devices, the Internet Engineering Task Force (IETF) proposed the 6LoWPAN stack. However, the particularities and hardware limitations of networks associated with IoT devices lead to several challenges, mainly for routing protocols. On its stack proposal, IETF standardizes the RPL (IPv6 Routing Protocol for Low-Power and Lossy Networks) as the routing protocol for Low-power and Lossy Networks (LLNs). RPL is a tree-based proactive routing protocol that creates acyclic graphs among the nodes to allow data exchange. Although widely considered and used by current applications, different recent studies have shown its limitations and drawbacks. Among these, it is possible to highlight the weak support of mobility and P2P traffic, restrictions for multicast transmissions, and lousy adaption for dynamic throughput. Motivated by the presented issues, several new solutions have emerged during recent years. The approaches range from the consideration of different routing metrics to an entirely new solution inspired by other routing protocols. In this context, this work aims to present an extensive survey study about routing solutions for IoT/LLN, not limited to RPL enhancements. In the course of the paper, the routing requirements of LLNs, the initial protocols, and the most recent approaches are presented. The IoT routing enhancements are divided according to its main objectives and then studied individually to point out its most important strengths and weaknesses. Furthermore, as the main contribution, this study presents a comprehensive discussion about the considered approaches, identifying the still remaining open issues and suggesting future directions to be recognized by new proposals.
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Alizadeh, Mojtaba, Mohammad Hesam Tadayon, Kouichi Sakurai, Hiroaki Anada, and Alireza Jolfaei. "A Secure Ticket-Based Authentication Mechanism for Proxy Mobile IPv6 Networks in Volunteer Computing." ACM Transactions on Internet Technology 21, no. 4 (July 22, 2021): 1–16. http://dx.doi.org/10.1145/3407189.
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Technology advances—such as improving processing power, battery life, and communication functionalities—contribute to making mobile devices an attractive research area. In 2008, in order to manage mobility, the Internet Engineering Task Force (IETF) developed Proxy Mobile IPv6, which is a network-based mobility management protocol to support seamless connectivity of mobile devices. This protocol can play a key role in volunteer computing paradigms as a user can seamlessly access computing resources. The procedure of user authentication is not defined in this standard; thus, many studies have been carried out to propose suitable authentication schemes. However, in the current authentication methods, with reduced latency and packet loss, some security and privacy considerations are neglected. In this study, we propose a secure and anonymous ticket-based authentication (SATA) method to protect mobile nodes against existing security and privacy issues. The proposed method reduces the overhead of handover authentication procedures using the ticket-based concept. We evaluated security and privacy strengths of the proposed method using security theorems and BAN logic.
Books on the topic "Internet Engineering Task Force Case studies"
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Powers, Shawn M., and Michael Jablonski. The Myth of Multistakeholder Governance. University of Illinois Press, 2017. http://dx.doi.org/10.5406/illinois/9780252039126.003.0006.
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This chapter examines how multistakeholder institutions reflect dominant political and/or economic interests, arguing that the discourse of multistakeholderism is used to legitimize arrangements benefiting powerful, established actors like the United States and its robust Information and Communication Technology (ICT) sector. After a brief discussion of what is actually at stake in debates over internet governance, the chapter provides an overview of the origins and theory of the multistakeholder process. It then considers how seemingly participatory, inclusive, and consensus-driven decision-making structures provide legitimacy for existing political and economic interests by using three case studies: ICANN, the Internet Society (ISOC), and the Internet Engineering Task Force (IETF). It shows that, by incentivizing inclusion and consensus, multistakeholder processes risk stifling legitimate dissent from external actors who have no interest in lending legitimacy to the facade of an apolitical negotiation.
Book chapters on the topic "Internet Engineering Task Force Case studies"
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Harcourt, Alison, George Christou, and Seamus Simpson. "Engineers and the Public Interest." In Global Standard Setting in Internet Governance, 175–88. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198841524.003.0010.
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Although tracking via social media platforms is widely recognized, as demonstrated by the Cambridge Analytica/Facebook scandal in 2018, other forms of tracking are less well known. Devices such as computers, cameras, and mobile phones can be identified by indicators such as screen size, software versions, and installed fonts. This is called ‘browser fingerprinting’. Commercial software can ‘fingerprint’ web browsers and analyse use without users’ knowledge, even when these users are aware enough to block browsing cookies and/or use virtual private networks (VPNs). This raised significant interest and concern from the engineering community which prompted a number of initiatives within standards-developing organizations (SDOs). This chapter covers case studies detailing work to mitigate the evasion of personal privacy in protocol development within the Internet Engineering Task Force (IETF) and the World Wide Web Consortium (W3C). It demonstrates how SDO work is flanked and supported externally by academics, digital rights groups, and wider civil society organizations.
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Eklund, Peter, Jeff Thom, Tim Wray, and Edward Dou. "Location Based Context-Aware Services in a Digital Ecosystem with Location Privacy." In Cases on Emerging Information Technology Research and Applications, 151–75. IGI Global, 2013. http://dx.doi.org/10.4018/978-1-4666-3619-4.ch008.
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This case discusses the architecture and application of privacy and trust issues in the Connected Mobility Digital Ecosystem (CMDE) for the University of Wollongong’s main campus community. The authors describe four mobile location-sensitive, context-aware applications (app(s)) that are designed for iPhones: a public transport passenger information app; a route-based private vehicle car-pooling app; an on-campus location-based social networking app; and a virtual art-gallery tour guide app. These apps are location-based and designed to augment user interactions within their physical environments. In addition, location data provided by the apps can be used to create value-added services and optimize overall system performance. The authors characterize this socio-technical system as a digital ecosystem and explain its salient features. Using the University of Wollongong’s campus and surrounds as the ecosystem’s community for the case studies, the authors present the architectures of these four applications (apps) and address issues concerning privacy, location-identity and uniform standards developed by the Internet Engineering Task Force (IETF).
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Tsai, Wei-Ho, and Cin-Hao Ma. "Overlapping Singer Identification in Music Recordings." In Advances in Web Technologies and Engineering, 23–43. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-7268-8.ch002.
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Singer identification (SID), which refers to the task of automatically identifying the singer(s) in a music recording, is of great help in handling the rapid proliferation of music data on the internet and digital media. Although a number of SID studies from acoustic features have been reported, most systems are designed to identify the singer in recordings of solo performances. Very little research has considered a more realistic case, which is to identify more than one singer in a music recording. The research presented in this chapter investigates the feasibility of identifying singers in music recordings that contain overlapping (simultaneous) singing voices (e.g., duet or trio singings). This problem is referred to as overlapping singer identification (OSID). Several approaches to OSID are discussed and evaluated in this chapter. In addition, a related issue on how to distinguish solo singings from overlapping singing recordings is also discussed.
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Pack, Sangheon, Sungmin Baek, Taekyoung Kwon, and Yanghee Choi. "Authentication, Authorization, and Accounting (AAA) Framework in Network Mobility (NEMO) Environments." In Handbook of Research on Wireless Security, 395–411. IGI Global, 2008. http://dx.doi.org/10.4018/978-1-59904-899-4.ch025.
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Network mobility (NEMO) enables seamless and ubiquitous Internet access while on-board vehicles. Even though the Internet Engineering Task Force (IETF) has standardized the NEMO basic support protocol as a network layer mobility solution, little studies have been conducted in the area of authentication, authorization, and accounting (AAA) framework that is a key technology for successful deployment. In this article, we first review the existing AAA protocols and analyze their suitability in NEMO environments. After that, we propose a localized AAA framework to retain the mobility transparency as the NEMO basic support protocol and to reduce the signaling cost incurred in the AAA procedures. The proposed AAA framework supports mutual authentication and prevents various threats such as replay attack, man-in-the-middle attack, and key exposure. Performance analysis on the AAA signaling cost is carried out. Numerical results demonstrate that the proposed AAA framework is efficient under different NEMO environments.
Conference papers on the topic "Internet Engineering Task Force Case studies"
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Hu, Daohang, and Xin Zhao. "Application of Damped Outriggers in Renovation of Super Tall Building Structures." In IABSE Symposium, Prague 2022: Challenges for Existing and Oncoming Structures. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2022. http://dx.doi.org/10.2749/prague.2022.1844.
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<p>The primary task of super tall buildings renovation is to reduce the engineering amount for existing structures. The additional viscous damping device can effectively increase the structural energy consumption of super tall buildings under earthquakes, thereby reducing the internal force and deformation response of the structure, and achieving the purpose that reduce the amount of renovation works. Assembling the deformation amplification device can effectively improve the energy consumption capacity of the viscous damping device. There are two damping types of deformation amplification for super tall buildings: toggle brace dampers and damped outriggers. Toggle brace dampers is suitable for high-rise building structures with shearing deformation, and damped outriggers is suitable for high-rise building structures with bending deformation. Based on the actual engineering case, this paper studies the viscous damper (damped outriggers) with outrigger deformation amplification device. Firstly, the sensitivity of installing damped outriggers on different equipment floors is analyzed, and the influence of different installation positions on the efficiency of damped outriggers is determined. Secondly, the reasonable number of damped outriggers is studied to effectively reduce the reconstruction work of the existing structure and control the number and parameters of viscous dampers in a reasonable range. Finally, the influence of the damped outrigger on the structural response of the unbuilt part is analyzed, and how to further optimize the structural members of the unbuilt part is studied.</p>
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Valentine, Daniel T. "Nonlinear Internal Waves: A Numerical Investigation of 2D Sloshing." In ASME 2004 23rd International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2004. http://dx.doi.org/10.1115/omae2004-51002.
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This paper examines internal sloshing motions in 2-D numerical wave tanks subjected to horizontal excitation. In all of the cases studied, the rectangular tank of liquid has a width-to-depth ratio of 2. The results presented are from simulations of internal waves induced by sloshing a density-stratified liquid. Non-linear, viscous flow equations of a Newtonian, Boussinesq liquid are solved. Some of the features of the evolution of sloshing in nearly two-layer and three-layer fluid systems are described. Initially, the middle of the two layers and the center of the middle layer of the three layers are horizontal and located at the center of the tank. The two-layer cases are forced at resonance. The evolution of sloshing from rest is examined. The maximum amplitude of sloshing occurs during the initial transient. If breaking occurs it is at the center of the container in the two-layer cases. The subharmonic forcing of a three-layer case induces a resonant response with the middle layer moving in such a way that motion is perpendicular to the isopycnals within this layer. These model problems provide some insights into the relatively complex sloshing that can occur in density-stratified liquids.
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Doué, Nicolas, Karim Loueslati, Dominique Alonso, Ghislain Genin, and Michel Molière. "Evaporation of Volatile Liquid Pools Under Forced Convection: Part 2—Integration of a Vaporization Model in a CFD Software." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68409.
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The transfer under dynamic conditions of volatile species from a liquid pool to the surrounding air is gaining interest in the engineering community. In particular, increasingly stringent regulations and standards apply to all types of flammable substances. This is especially the case in stationary gas turbine applications, where the vaporization of accidentally occurring pools of liquid fuels attracts increasing attention. Since the flame-to-explosion transition cases are insufficiently controlled, the current, only practicable approach to assess the explosion risks arising from a fuel pool in an enclosure consists in quantifying the amount of vapor that leaves the pool and minimizing, by means of a proper dilution strategy, the potential damages entailed by the ignition of the resulting cloud. This approach requires two steps: (1) The accurate assessment of vaporization rates under given ventilation conditions, a task that calls for skills in thermal and mass transfers. (2) The reliable prediction of the transport of the vapors in the ventilation stream, a task specifically focused on fluid dynamics. The three teams involved in this paper have joined their efforts to achieve this multidisciplinary objective. As a first task, the LRGP team (Laboratoire des Reactions et Génie des Procédés) and GE Energy have experimentally validated a vaporization model initially devised for water pools. This work has been reported in a recent paper. Concurrently, EURO/CFD and GE Energy have developed a CFD approach devoted to the mixing/dilution processes in defined enclosure geometries and under specified ventilation conditions. Finally both approaches havebeen coupled by EURO/CFD to produce predictive isopleth pictures of the vapor clouds generated under given temperature and velocity conditions. The present paper covers the integration of the liquid pool vaporization model in thecommercial CFD software ANSYS Fluent and sets out the results obtained. This dual, concerted approach is a first of the kind to the authors’ knowledge and proves fruitful for the prediction of the spatial distributions of the volatile species developed when a volatile pool vaporizes in a ventilated enclosure. It fills a gap in the analysis of safety scenarios arising from spillages of liquid fuels and provides a rational tool in zone classification studies.
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Sheng, Wanan, Anthony Lewis, and Raymond Alcorn. "Numerical Studies on Hydrodynamics of a Floating Oscillating Water Column." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49083.
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The oscillating water column (OWC) is one of the more successful wave energy converters so far due to its mechanical and structural simplicity; there are no components for power take-off in seawater. Though there are some successful practical developments in bottom-fixed OWCs, floating OWCs are still in different stages of development. A specific oscillating water column, the OE Buoy (i.e. backward-bent duct device, ‘B2D2’), developed by OceanEnergy (Ireland), has recently attracted much attention. A 1:2.5 scale device has finished a sea-trial in Galway Bay (Ireland) for a period over two years during which period the device has gone through a severe storm. Thus its survivability has been confirmed to some extent. In this research, numerical simulations to the floating wave energy device are performed using a boundary element method code WAMIT. To consider the motions of the internal water in the column for energy extraction, a “numerical lid” is placed on the free surface in the column. In WAMIT, the motions of the “numerical lid” can be calculated by introducing relevant generalized modes to the conventional 6-DOF motions of the floating structure. For wave energy extraction, the “piston effect” of the internal water must be considered. To include the effect of the mooring system to the motions of floating structure, the mooring forces have been linearised, and their equivalent spring coefficients have been input to WAMIT for analysis of the moored floating structure. For the numerical simulation, the first case is to tune the damping coefficients based on wave tank results since in WAMIT, only hydrodynamic damping is included in calculation. In reality, larger damping may be needed to limit the large responses in heave of floating structure and the motion of the internal water surface. The tuned damping coefficients are then applied to the modified OWCs of different duct length, in which it is hoping that the corresponding responses of the internal free surface structure are used to assess the performance of the floating OWC. The aim of the research is to explore the relation between the OWC size and its performance so that it may provide a reference for optimizing the design of a floating OWC in the future.
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Rueda, Guilherme E., Ma´rcio Michiharu Tsukamoto, Higor F. Medeiros, Cheng Liang Yee, and Kazuo Nishimoto. "Validation Study of MPS (Moving Particle Semi-Implicit Method) for Sloshing and Damage Stability Analysis." In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57460.
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The aim of this paper is to present validation studies of a CFD code based on MPS (Moving Particle Semi-implicit Method). In MPS method the fluid is represented by particles, and the particle interactions are governed by continuity and Navier-Stokes equations. It is a meshless method to simulate incompressible flow and it is able to simulate large surface distortion, fluid fragmentation and non-linear dynamics. For the validation studies, two cases with complex hydrodynamic phenomena were selected for experimental measurements in towing tank. The first one is the dynamics of a floating body in waves with an internal tank partial filled with water. In this way sloshing effects on the motion of the model can be evaluated. Usually, dynamics of the floating body and sloshing are calculated separately, by neglecting their coupling effects; the body’s motion is determined without sloshing and that motion is used to excite the liquid tank. Since the sloshing generates forces and moments, which may change the movement of the hull, sloshing forces and moments may act as a roll absorption device or can enlarger it. In MPS this coupled phenomena can be easily simulated, just by using particles representing water of the internal tank, water of the towing tank and structural particles representing the hull, the walls and the wave maker. The second phenomenon is the motions of a damaged hull from the moment soon after suffering damage until reaches the equilibrium position. This is an initial step of a validation study of the motion of a damage hull in waves, which will be compared with physical experiments. The comparisons between the numerical results obtained by the MPS with the experimental and theoretical ones show very good agreement, reinforcing the potential of MPS.
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Li, Xiang, Qing Xiao, Rodolfo T. Gonçalves, and Christophe Peyrard. "A Coupled Wave-Current-Structure Study for a Floating Offshore Wind Turbine Platform." In ASME 2022 41st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/omae2022-79016.
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Abstract In the present study, the influence of ocean conditions, in the combination of wave and current, on the dynamic response of the OC4 semi-submersible platform is numerically studied. The present work is inspired by the recent observations that the presence of current incidence usually induces the vortex-induced motions (VIM) phenomenon of multi-monocolumn platforms, while wave often leads to large inertia force on it. The integration of wave and current may further cause a more complex flow field around the structure than that only wave or current exists. Such VIM is not desirable considering its impact on the fatigue life of the riser, umbilical, and mooring system of the offshore structure due to the resonance behaviour of the VIM. A computational fluid dynamic (CFD) method is adopted to conduct a real-time simulation of the platform’s motion response. The tool is based on an open-source code library OpenFOAM. The results are validated against experiments with current-only conducted in the wave tank. The flow field around the platform and its impact on the structure motion and loading response are studied for a wide range of wave and current conditions. With the given incident waves, the VIM is mitigated for most cases, for a wide range of reduced velocity. This result is of practical interest for the design of FOWT, as VIM are not captured by industrial aero-hydro-mechanical models.
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Piovesan, Davide, and Felix C. Huang. "Control Mechanisms in Oscillatory Motor Behavior." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-63233.
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Studies on unimpaired humans have demonstrated that the central nervous system employs internal representations of limb dynamics and intended movement trajectories for planning muscle activation during pointing and reaching tasks. However, when performing rhythmic movements, it has been hypothesized that a control scheme employing an autonomous oscillator — a simple feedback circuit lacking exogenous input — can maintain stable control. Here we investigate whether such simple control architectures that can realize rhythmic movement that we observe in experimental data. We asked subjects to perform rhythmic movements of the forearm while a robotic interface simulated inertial loading. Our protocol included unexpected increases in loading (catch trials) as a probe to reveal any systematic changes in frequency and amplitude. Our primary findings were that increased inertial loading resulted in reduced frequency of oscillations, and in some cases multiple frequencies. These results exhibit some agreement with an autonomous oscillator model, though other features are more consistent with feedforward planning of force. This investigation provides a theoretical and experimental framework to reveal basic computational elements for how the human motor system achieves skilled rhythmic movement.
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Peric, Milovan, Tobias Zorn, Ould el Moctar, Thomas E. Schellin, and Yong-Soo Kim. "Simulation of Sloshing in LNG Tanks." In ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2007. http://dx.doi.org/10.1115/omae2007-29555.
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The aim of this paper is to demonstrate the prediction of internal loads on liquified natural gas (LNG) tanker ships and on offshore platforms. We use the moving grid approach and a finite volume solution method designed to allow for arbitrary ship motion. The motion of liquid is computed using an interface-capturing scheme which allows overturning and breaking waves. By performing a coupled simulation of the flow and vessel motion, it is possible to obtain a realistic response of the liquid in a tank to external excitation, e.g. by sea waves. Results are first presented for an LNG tanks whose motion is prescribed in accordance with planned laboratory experiments. Both two-dimensional (2D) and three-dimensional (3D) simulations are performed. The aim is to demonstrate that 1) realistic loads can be predicted using grids of moderate fineness, 2) the numerical method is able to accurately resolve the free surface even when severe fragmentation occurs, and 3) long-term simulations over many oscillation periods are possible without numerical mixing of liquid and gas. The plausibility of a coupled simulation of both vessel motion and the flow inside tanks and outside the vessel is then demonstrated for a full-size ship with partially-filled tanks exposed to head waves. In this simulation the forces and moments exerted by the sea cause the vessel to move, exciting the sloshing of liquid in tanks. For the computation of vessel motion, both sea-induced forces and forces due to sloshing in tanks are taken into account when determining the resultant forces and moments. While there are no experimental data for comparison at this time, the results look plausible and encourage further validation and application studies.
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Stieglitz, Ina, and Peter Ehrhard. "A Hybrid Model for the Simulation of Electroosmotic Flows in Microchannels, Induced by Internal Electrodes." In ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30750.
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In general, the modeling of electroosmotic flows can be approached in two fundamentally–different ways. (i) The thickness of electrical double layer (EDL) is ignored and the effect of the electrical forces within the EDL is imaged into a modified kinematic boundary condition, the so-called Helmholtz–Smoluchowski slip condition. This approach is numerically simple and inexpensive, but implies several restrictions. (ii) The EDL is fully resolved, using a first–principle approach based on differential conservation equations for mass, momentum, and charge. This approach is enormously elaborate and numerically expensive, but appears to be applicable for a much wider range of problems. As an example, the treatment of internal electrodes, adjacent to insulating walls at defined zeta potential, appears difficult with the simple approach (i), since any non–continuous potential distribution at the wall leads to a singularity of the electrical field strength. To avoid these difficulties, we develop a hybrid model which, on the one hand, electrically resolves the EDL to reveal a perfectly-continuous potential distribution in the complete microchannel. On the other hand, the flow equations are solved in the fluid bulk only, not comprising the EDL. Hence, the effect of the EDL is still incorporated by means of modified kinematic boundary conditions. The advantage of this hybrid model is, firstly, to avoid artificial singularities of the electrical field strength, where regions of different surface charge meet. These singularities are clearly artificial, since they result from neglecting the extend of the EDL. Secondly, the hybrid model, at each time step, needs to solve only once for the potential distribution, which makes it numerically inexpensive and simple. Hence, systematic parameter studies are within reach. We apply the hybrid model to investigate the influence of internal electrodes onto the flow field, driven by electroosmosis in a modular rectangular microchannel. As internal electrodes can be positioned at lower distances (if compared to external electrodes), they can be operated at lower voltages and still ensure strong electrical field strength. Systematic studies on the effect of different electrode positions and voltages are presented, leading to optimized settings for specific tasks as pumping or mixing. Further, a comparison to first-principle simulations using the approach (ii) is presented for selected cases. This demonstrates that the hybrid model perfectly captures the dominant physics.
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Genta, Giancarlo, and Marco Dolci. "Robotic Gripper for Payload Capture in Low Earth Orbit." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-65429.
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The consensus to a study phase for an IXV (Intermediate eXperimental Vehicle) successor, a preoperational vehicle called PRIDE (Programme for Reusable In-orbit Demonstrator in Europe), has been recently enlarged, as approved during last EU Ministerial Council. One of the main project task consists in developing PRIDE to conduct on orbit servicing activity with no docking. PRIDE would be provided with a robotic manipulator system (arm and gripper) able to transfer payloads, such as scientific payloads, from low Earth orbiting platforms to PRIDE payload bay. The platform is a part of a space tug designed to move small satellites and other payloads from Low Earth Orbits (LEO) to Geostationary orbit (GEO) and viceversa. A study on this robotic technology is here presented. This research is carried out by Politecnico di Torino and Thales Alenia Space Italy (Grasping Manipulator Design), and by Thales Alenia Space Italy and Amet (PRIDE Robotics System Design). The system configuration of the robotic manipulator is first described in terms of volumes and masses. The assumed housing payload bay requirements in terms of volume (<100 l) and mass (<50 kg) combined with the required overall arm dimensions (4 m length), as defined following the stated mission scenario, and mass of the payload (5–30 kg) force to developing an innovative robotic manipulator with the task-oriented end effector. It results in a 7 degree-of-freedom arm to ensure a high degree of dexterity and a dedicate end-effector designed to grasp the payload interface. The gripper concept here developed consists in a multi-finger hand able to lock both translational and rotational payload degrees of freedom through an innovative under actuation strategy to limit its mass and volume. While in the literature in usual actuation architectures, underactuated systems have been realized where the first (nearest) phalanx closure led afterwards to the closure of the second (distal) one using the loading of a torsional springs and mechanical linkages, this system presents a new underactuation strategy. In this case the distal phalanx closes before the nearest one, allowing to grasp the handle side and limiting the handle length and volume. This concept will allow the distal phalanx to move independently from the nearest one. A configuration study on the payload handle interface has also been performed. Moreover, trade-off studies, computer aided design models, multibody and structural analysis of the whole system are shown to prove its feasibility. Finally, the concept of system control architecture, organized in three main blocks is defined: the Control Overall System Block, the Control Arm Block and the Control Robotic Hand Block.