Academic literature on the topic 'Grid'
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Journal articles on the topic "Grid"
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Higashi, Tatsuichiro, Yuko Iwasaki, Yasuo Ohnishi, and Sueharu Horinouchi. "A-Factor and Phosphate Depletion Signals Are Transmitted to the Grixazone Biosynthesis Genes via the Pathway-Specific Transcriptional Activator GriR." Journal of Bacteriology 189, no. 9 (March 2, 2007): 3515–24. http://dx.doi.org/10.1128/jb.00055-07.
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ABSTRACT Grixazone (GX), which is a diffusible yellow pigment containing a phenoxazinone chromophore, is one of the secondary metabolites under the control of A-factor (2-isocapryloyl-3R-hydroxymethyl-γ-butyrolactone) in Streptomyces griseus. GX production is also induced by phosphate starvation. The whole biosynthesis gene cluster for GX was cloned and characterized. The gene cluster consisting of 13 genes contained six transcriptional units, griT, griSR, griR, griAB, griCDEFG, and griJIH. During cultivation in a phosphate-depleted medium, the six promoters were activated in the order (i) griR, (ii) griC and griJ, and (iii) griT, griS, and griA. Disruption of griR, which encodes a SARP family transcriptional regulator, abolished the transcriptional activation of all other genes in the cluster. In addition, ectopic expression of griR from a constitutively active promoter resulted in GX overproduction even in the absence of AdpA, a key transcriptional activator in the A-factor regulatory cascade, and in the presence of phosphate at a high concentration. GriR monomers bound direct repeat sequences in the griC and griJ promoters in a cooperative manner. Therefore, the early active genes (griCDEFG and griJIH), all of which, except for griG (which encodes a transporter-like protein), encode the GX biosynthesis enzymes, were directly activated by GriR. The transcription of griR was greatly reduced in the presence of phosphate at a high concentration and was hardly detected in the absence of AdpA. These findings showed that both A-factor and phosphate depletion signals were required for griR transcription and both signals were transmitted to the GX biosynthesis genes solely via the griR promoter.
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Evazi, M., and H. Mahani. "Unstructured-Coarse-Grid Generation Using Background-Grid Approach." SPE Journal 15, no. 02 (March 3, 2010): 326–40. http://dx.doi.org/10.2118/120170-pa.
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Summary Reservoir flow simulation involves subdivision of the physical domain into a number of gridblocks. This is best accomplished with optimized gridpoint density and a minimized number of gridblocks, especially for coarse-grid generation from a fine-grid geological model. In any coarse-grid generation, proper distribution of gridpoints, which form the basis of numerical gridblocks, is a challenging task. We show that this can be achieved effectively by a novel grid-generation approach based on a background grid that stores gridpoint spacing parameters. Spacing parameter (L) can be described by Poisson's equation (∇2L = G), where the local density of gridpoints is controlled by a variable source term (G); see Eq. 1. This source term can be based on different gridpoint density indicators, such as permeability variations, fluid velocity, or their combination (e.g., vorticity) where they can be extracted from the reference fine grid. Once a background grid is generated, advancing-front triangulation (AFT) and then Delaunay tessellation are invoked to form the final (coarse) gridblocks. The algorithm produces grids varying smoothly from high- to low-density gridpoints, thus minimizing use of grid-smoothing and -optimization techniques. This algorithm is quite flexible, allowing choice of the gridding indicator, hence providing the possibility of comparing the grids generated with different indicators and selecting the best. In this paper, the capabilities of approach in generation of unstructured coarse grids from fine geological models are illustrated using 2D highly heterogeneous test cases. Flexibility of algorithm to gridding indicator is demonstrated using vorticity, permeability variation, and velocity. Quality of the coarse grids is evaluated by comparing their two-phase-flow simulation results to those of fine grid and uniform coarse grid. Results demonstrate the robustness and attractiveness of the approach, as well as relative quality/performance of grids generated by using different indicators.
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Thormann, Bernd, and Thomas Kienberger. "Estimation of Grid Reinforcement Costs Triggered by Future Grid Customers: Influence of the Quantification Method (Scaling vs. Large-Scale Simulation) and Coincidence Factors (Single vs. Multiple Application)." Energies 15, no. 4 (February 14, 2022): 1383. http://dx.doi.org/10.3390/en15041383.
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The integration of future grid customers, e.g., electric vehicles, heat pumps, or photovoltaic modules, will challenge existing low-voltage power grids in the upcoming years. Hence, distribution system operators must quantify future grid reinforcement measures and resulting costs early. On this account, this work initially evaluates different methods to quantify future grid reinforcement needs, applied by the current state of research. Thereby, it indicates the significance of large-scale grid simulations, i.e., simulating several thousand low-voltage grids, to quantify grid reinforcements accurately. Otherwise, a selected area’s total grid reinforcement costs might be misjudged significantly. Due to its fast application, deterministic grid simulations based on coincidence factors are most commonly used in the current state of research to simulate several thousand grids. Hence, in the second step, recent studies’ approaches to applying grid customers’ coincidence factors are evaluated: While simplified approaches allow fast simulation of numerous grids, they underestimate potential grid congestion and grid reinforcement costs. Therefore, a fully automated large-scale grid simulation tool is developed in this work to allow the simulation of multiple grids applying grid customers’ coincidence factors appropriately. As a drawback, the applied deterministic framework only allows an estimation of future grid reinforcement costs. Detailed determination of each grid’s grid reinforcement costs requires time-resolved grid simulations.
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Bhandari, Khem Raj, and Narayan Prasad Adhikari. "Grid Integration of Solar and Solar/Wind Hybrid Mini-Grid Projects: A Case of Solar/Wind Hybrid Mini-Grid Project Implemented by AEPC." Journal of the Institute of Engineering 15, no. 3 (October 13, 2020): 42–48. http://dx.doi.org/10.3126/jie.v15i3.32004.
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Alternative Energy Promotion Center (AEPC) has been scaling up renewable energy technologies through Mini-grid power supply in Nepal’s off-grid areas in order to fulfill community electricity demands for both households and electricity-based enterprises. It is likely that, in some of the off-grid renewable energy (RE) mini-grid service areas, Nepal Electricity Authority (NEA) grid line might reach in near future. The objective of this study is to highlight success stories of solar and solar/wind mini-grids implemented by AEPC and for their longer-term sustainable operation grid integration policy of isolated mini-grid systems will require. Till the date AEPC has successfully electrified more than 20 rural communities through solar and solar/wind hybrid mini-grid systems. Some of these isolated mini-grid projects will seek grid interconnections in near future due to NEA distribution system expansion trend. When the isolated mini-grids will be connected to the national grid power network in future, the mini-grid can feed surplus electricity to the local utility grid line and will receive deficit electricity from the local utility grid system to serve the consumers connected to the local grid network. The methodology applied to this study is assessment of existing solar and solar/wind mini-grid projects, technological intervention required for grid integration, reviewing grid-connection policy of distributed renewable generations in the country and recommendation of relevant policy option for grid connection of rural mini-grids. Grid integration of isolated solar and solar/wind mini-grids will have positive impacts to the sustainability of the present isolated mini-grids, will help in retaining existing mini-grids end users, energy produced by mini-grid systems will be optimally utilized, the existing mini-grid power will contribute to stabilize weak national grid electrical parameters. The outcome of the study will recommend need of policy options as well as technological interventions in order to do grid integration of solar and solar/wind hybrid mini-grid systems in Nepal.
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Arad, Nur. "Grid-distortion on nonrectangular grids." Computer Aided Geometric Design 15, no. 5 (May 1998): 475–93. http://dx.doi.org/10.1016/s0167-8396(98)00003-x.
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Bernth, Henrik, and Chris Chapman. "A comparison of the dispersion relations for anisotropic elastodynamic finite-difference grids." GEOPHYSICS 76, no. 3 (May 2011): WA43—WA50. http://dx.doi.org/10.1190/1.3555530.
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Several staggered grid schemes have been suggested for performing finite-difference calculations for the elastic wave equations. In this paper, the dispersion relationships and related computational requirements for the Lebedev and rotated staggered grids for anisotropic, elastic, finite-difference calculations in smooth models are analyzed and compared. These grids are related to a popular staggered grid for the isotropic problem, the Virieux grid. The Lebedev grid decomposes into Virieux grids, two in two dimensions and four in three dimensions, which decouple in isotropic media. Therefore the Lebedev scheme will have twice or four times the computational requirements, memory, and CPU as the Virieux grid but can be used with general anisotropy. In two dimensions, the rotated staggered grid is exactly equivalent to the Lebedev grid, but in three dimensions it is fundamentally different. The numerical dispersion in finite-difference grids depends on the direction of propagation and the grid type and parameters. A joint numerical dispersion relation for the two grids types in the isotropic case is derived. In order to compare the computational requirements for the two grid types, the dispersion, averaged over propagation direction and medium velocity are calculated. Setting the parameters so the average dispersion is equal for the two grids, the computational requirements of the two grid types are compared. In three dimensions, the rotated staggered grid requires at least 20% more memory for the field data and at least twice as many number of floating point operations and memory accesses, so the Lebedev grid is more efficient and is to be preferred.
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M, Ponrekha, and Sujatha Balaraman. "A detailed study on Transient Stability Enhancement of Grid-Forming Inverters." Journal of Electrical Engineering and Automation 5, no. 2 (June 2023): 151–65. http://dx.doi.org/10.36548/jeea.2023.2.001.
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The integration of the weak grids along with the clean energy that comes from the natural resources requires stable interconnection of Voltage-Source Inverters (VSIs) with weak grids. During severe voltage sags, weak grid integrated VSIs may fail synchronization with the grid.These inverters' transient stability under severe grid disruptions is weak and significantly different from that of synchronous machines. To prevent the side band oscillations in the weak grids, the emerging inverters based on grid-forming are preferred over the grid following inverters in the weak grids. These inverters synchronise with the grid using a power-based synchronisation technique in order to prevent the instability brought on by a typical Phase Locked Loop in weak AC grids. This study presents a comprehensive review of the transient stability improvement of Grid-Forming VSIs.
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Coveney, Peter V. "Scientific Grid computing." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 363, no. 1833 (July 18, 2005): 1707–13. http://dx.doi.org/10.1098/rsta.2005.1632.
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We introduce a definition of Grid computing which is adhered to throughout this Theme Issue. We compare the evolution of the World Wide Web with current aspirations for Grid computing and indicate areas that need further research and development before a generally usable Grid infrastructure becomes available. We discuss work that has been done in order to make scientific Grid computing a viable proposition, including the building of Grids, middleware developments, computational steering and visualization. We review science that has been enabled by contemporary computational Grids, and associated progress made through the widening availability of high performance computing.
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Yan, Huang, Li Shanshan, Zhou Chuyuan, Li Xinxing, Lv Minghao, Fan Diao, Tan Xuli, and Wang Aoming. "Research and Construction of a Global Hexagonal Marine Gravity Gradient Reference Map for Navigation." Geofluids 2023 (March 23, 2023): 1–22. http://dx.doi.org/10.1155/2023/4141572.
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A high-precision marine gravity gradient reference map is key to enabling underwater gravity gradient matching navigation. At present, the construction of the reference maps is based on quadrilateral geographic grids. However, quadrilateral grids lead to detriangulation at high latitudes, which limits the global applicability of such maps to underwater gravity navigation. To circumvent the limitations of quadrilateral grids, a hexagonal grid is introduced for constructing the reference map. This paper analyzes the characteristics of the icosahedral Snyder equal area aperture 4 hexagon (ISEA4H) and H3 grid systems and selects an appropriate grid system. In addition, we calculate and analyze the grid model errors and matching positioning errors of hexagonal and quadrilateral grids at the same resolution. The experimental results show that the grid model and matching positioning errors of a hexagonal grid system are more than 14% and 15% less than those of a quadrilateral grid system, respectively, indicating the feasibility and effectiveness of applying hexagonal grids to gravity gradient matching navigation. Given the low construction efficiency of a marine hexagonal grid gravity gradient reference map, we propose an efficient CPU+GPU hybrid parallel scheme. A global total tensor marine hexagonal grid gravity gradient reference map model is then constructed.
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Tristan, A., A. Emde, M. Reisinger, M. Stauch, and A. Sauer. "Energieflexibilität im Industrial Smart Grid*/Energy Flexibility in Industrial Smart Grids – Methodical approach for incorporating energy flexibility measures in an Industrial Smart Grid." wt Werkstattstechnik online 109, no. 05 (2019): 301–6. http://dx.doi.org/10.37544/1436-4980-2019-05-3.
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Durch den Übergang in Smart Grids erhalten Stromnetze die notwendige Flexibilität, um auf die steigende Volatilität der Stromversorgung zu reagieren. Das standardisierte Smart-Grid-Architecture-Modell und die Use-Case-Methodik dienen dabei als Rahmen, um Smart Grids zu entwickeln. Ein methodischer Rahmen für den Aufbau von Industrial Smart Grids fehlt derzeit noch, ist aber besonders notwendig, um Energieflexibilitätsmaßnahmen für Industrieanlagen umzusetzen. Der hier vorgestellte methodische Ansatz liefert eine Blaupause für den Aufbau eines Industrial Smart Grid für Energieflexibilität. Mithilfe der Anpassung des Smart-Grid-Architecture-Modells und der Use-Case-Methodik wird ein Industrial-Smart-Grid-Architecture-Modell umgesetzt. Through their transition into Smart Grids, electrical power grids gain the neccesary flexibiltiy to respond to increasing electrical supply volatility. The standardized Smart Grid Architecture Model and Use Case Methodology serve as framework to develop Smart Grids. Currently, there is still a lack of such a methodical framework for setting up Industrial Smart Energy Grids and it is particularly necessary to implement energy flexibility measures in industrial plants. The methodical approach presented here provides a blueprint for building an Industrial Smart Grid for energy flexibility by adapting the Smart Grid Architecture Model and the use case methodology .
Dissertations / Theses on the topic "Grid"
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Wolter, Martin. "Grid state identification of distribution grids." Aachen Shaker, 2008. http://d-nb.info/990522008/04.
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Wolter, Martin [Verfasser]. "Grid State Identification of Distribution Grids / Martin Wolter." Aachen : Shaker, 2008. http://d-nb.info/1161303480/34.
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Liu, Qing. "Control of grid-tied inverters for nano-grids." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3422338.
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In recent times, with the development of renewables, the concept of micro-grid emerged, representing a novel bottom up power distribution organization. The micro-grid can integrate the nearby distributed, and mostly renewable, energy sources, the storage devices and the loads into the grid, with increased efficiency, flexibility and reliability, showing significant economical and environmental benefits. The micro-grid concept can be further scaled down to the range of a single house or small building, and differentiated by a new terminology, nano-grid. The proposal of the nano-grid concept is aimed at simplifying the application scenarios, so that a hierarchical bottom-up power distribution network can be established, where the nano-grid plays the lowest-end role. It can not only operate autonomously, feeding the typical household appliances from the available renewable sources; thanks to the modular smart grid architecture, it can also be conveniently interconnected to other similar units, operating in parallel and harmoniously energizing a larger region in a city, a small-island or a village. In addition, the nano-grid also has the possibility of self-integrating into the utility grid, exchanging power with the mains when needed, thanks to a specifically designed grid interface converter. Referring to the latter, a variety of requirements are defined by applicable standards, in terms of load power quality, grid support functionalities, abnormal condition ride-through and protection means.
The realization of the above functionalities is heavily dependent on the control of the grid interfacing inverter hosted within the nano-grid, about which numerous solutions have been proposed in the existing literature. However, few of them can realize all the functionalities simultaneously in a single controller. The target of this dissertation is therefore proposing, analyzing and testing a high-quality, multi-functional control scheme for grid-tied inverters.
This goal is reached in three steps: i) a deep literature review, ii) the identification, study and realization of the multi-functional inverter controller, and iii) the implementation of further, higher level functionalities, like the grid-supporting and parallel operation capabilities.
Accordingly, the study is initiated from step i), with an overview of existing control strategies and key functionalities of grid-tied inverters. The comprehensive review of a research topic is, in any case, very advantageous to define the state of the art solutions and to evaluate the margins for improvement in the existing technology. In this research case, it allowed to understand that a triple-loop controller structure is the most suitable to achieve high-performance control of the nano-grid electrical system and the most promising as to the capability of implementing multiple interface and protection functionalities jointly. In the second step ii), a large-bandwidth triple-loop controller is proposed, whose implementation is the first contribution of this dissertation. The peculiarity of the proposed controller is the large-bandwidth control of the injected grid current, which brings in many beneficial features. Leveraging on this controller organization, multiple functionalities are later implemented by means of a superimposed flexible mode-transition manager and an auto-tuner, altogether forming a high quality, multi-functional control scheme for grid-tied inverters. This represents the second contribution delivered by this dissertation. Finally, in step iii), the extended scenario of multiple parallel-connected grid-tied inverters is discussed, targeting the realization of distributed grid-supporting functionalities in grid-tied mode and the automatic balanced power sharing in parallel-islanded mode. The final implemented control scheme provides a feasible solution for the forthcoming smart nano-grids and represents the third contribution of this research activity.
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Hacker, Jonathan Bruce Rutledge David B. "Grid mixers and power grid oscillators /." Diss., Pasadena, Calif. : California Institute of Technology, 1994. http://resolver.caltech.edu/CaltechETD:etd-11302007-145419.
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Bertetti, Odilia. "Benchmarking of Smart Grid Conceptsin Low-Voltage Distribution Grids." Thesis, KTH, Kraft- och värmeteknologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-217979.
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Sirvent, Pardell Raül. "GRID superscalar: a programming model for the Grid." Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/6015.
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Durant els darrers anys el Grid ha sorgit com una nova plataforma per la computació distribuïda. La tecnologia Gris permet unir diferents recursos de diferents dominis administratius i formar un superordinador virtual amb tots ells. Molts grups de recerca han dedicat els seus esforços a desenvolupar un conjunt de serveis bàsics per oferir un middleware de Grid: una capa que permet l'ús del Grid. De tota manera, utilitzar aquests serveis no és una tasca fácil per molts usuaris finals, cosa que empitjora si l'expertesa d'aquests usuaris no està relacionada amb la informàtica.Això té una influència negativa a l'hora de que la comunitat científica adopti la tecnologia Grid. Es veu com una tecnologia potent però molt difícil de fer servir. Per facilitar l'ús del Grid és necessària una capa extra que amagui la complexitat d'aquest i permeti als usuaris programar o portar les seves aplicacions de manera senzilla.
Existeixen moltes propostes d'eines de programació pel Grid. En aquesta tesi fem un resum d'algunes d'elles, i podem veure que existeixen eines conscients i no-conscients del Grid (es programen especificant o no els detalls del Grid, respectivament). A més, molt poques d'aquestes eines poden explotar el paral·lelisme implícit de l'aplicació, i en la majoria d'elles, l'usuari ha de definir aquest paral·lelisme de manera explícita. Una altra característica que considerem important és si es basen en llenguatges de programació molt populars (com C++ o Java), cosa que facilita l'adopció per part dels usuaris finals.
En aquesta tesi, el nostre objectiu principal ha estat crear un model de programació pel Grid basat en la programació seqüencial i els llenguatges més coneguts de la programació imperativa, capaç d'explotar el paral·lelisme implícit de les aplicacions i d'accelerar-les fent servir els recursos del Grid de manera concurrent. A més, com el Grid és de naturalesa distribuïda, heterogènia i dinàmica i degut també a que el nombre de recursos que pot formar un Grid pot ser molt gran, la probabilitat de que es produeixi una errada durant l'execució d'una aplicació és elevada. Per tant, un altre dels nostres objectius ha estat tractar qualsevol tipus d'error que pugui sorgir durant l'execució d'una aplicació de manera automàtica (ja siguin errors relacionats amb l'aplicació o amb el Grid). GRID superscalar (GRIDSs), la principal contribució d'aquesta tesi, és un model de programació que assoleix els
objectius mencionats proporcionant una interfície molt petita i simple i un entorn d'execució que és capaç d'executar en paral·lel el codi proporcionat fent servir el Grid. La nostra interfície de programació permet a un usuari programar una aplicació no-conscient del Grid, amb llenguatges imperatius coneguts i populars (com C/C++, Java, Perl o Shell script) i de manera seqüencial, per tant dóna un pas important per ajudar als usuaris a adoptar la tecnologia Grid.
Hem aplicat el nostre coneixement de l'arquitectura de computadors i el disseny de microprocessadors a l'entorn d'execució de GRIDSs. Tal com es fa a un processador superescalar, l'entorn d'execució de GRIDSs és capaç de realitzar un anàlisi de dependències entre les tasques que formen l'aplicació, i d'aplicar tècniques de renombrament per incrementar el seu paral·lelisme. GRIDSs genera automàticament a partir del codi principal de l'usuari un graf que descriu les dependències de dades en l'aplicació. També presentem casos d'ús reals del model de programació en els camps de la química computacional i la bioinformàtica, que demostren que els nostres objectius han estat assolits.
Finalment, hem estudiat l'aplicació de diferents tècniques per detectar i tractar fallades: checkpoint, reintent i replicació de tasques. La nostra proposta és proporcionar un entorn capaç de tractar qualsevol tipus d'errors, de manera transparent a l'usuari sempre que sigui possible. El principal avantatge d'implementar aquests mecanismos al nivell del model de programació és que el coneixement a nivell de l'aplicació pot ser explotat per crear dinàmicament una estratègia de tolerància a fallades per cada aplicació, i evitar introduir sobrecàrrega en entorns lliures d'errors.
During last years, the Grid has emerged as a new platform for distributed computing. The Grid technology allows joining different resources from different administrative domains and forming a virtual supercomputer with all of them.
Many research groups have dedicated their efforts to develop a set of basic services to offer a Grid middleware: a layer that enables the use of the Grid. Anyway, using these services is not an easy task for many end users, even more if their expertise is not related to computer science. This has a negative influence in the adoption of the Grid technology by the scientific community. They see it as a powerful technology but very difficult to exploit. In order to ease the way the Grid must be used, there is a need for an extra layer which hides all the complexity of the Grid, and allows users to program or port their applications in an easy way.
There has been many proposals of programming tools for the Grid. In this thesis we give an overview on some of them, and we can see that there exist both Grid-aware and Grid-unaware environments (programmed with or without specifying details of the Grid respectively). Besides, very few existing tools can exploit the implicit parallelism of the application and in the majority of them, the user must define the parallelism explicitly. Another important feature we consider is if they are based in widely used programming languages (as C++ or Java), so the adoption is easier for end users.
In this thesis, our main objective has been to create a programming model for the Grid based on sequential programming and well-known imperative programming languages, able to exploit the implicit parallelism of applications and to speed them up by using the Grid resources concurrently. Moreover, because the Grid has a distributed, heterogeneous and dynamic nature and also because the number of resources that form a Grid can be very big, the probability that an error arises during an application's execution is big. Thus, another of our objectives has been to automatically deal with any type of errors which may arise during the execution of the application (application related or Grid related).
GRID superscalar (GRIDSs), the main contribution of this thesis, is a programming model that achieves these mentioned objectives by providing a very small and simple interface and a runtime that is able to execute in parallel the code provided using the Grid. Our programming interface allows a user to program a Grid-unaware application with already known and popular imperative languages (such as C/C++, Java, Perl or Shell script) and in a sequential fashion, therefore giving an important step to assist end users in the adoption of the Grid technology.
We have applied our knowledge from computer architecture and microprocessor design to the GRIDSs runtime. As it is done in a superscalar processor, the GRIDSs runtime system is able to perform a data dependence analysis between the tasks that form an application, and to apply renaming techniques in order to increase its parallelism. GRIDSs generates automatically from user's main code a graph describing the data dependencies in the application.
We present real use cases of the programming model in the fields of computational chemistry and bioinformatics, which demonstrate that our objectives have been achieved.
Finally, we have studied the application of several fault detection and treatment techniques: checkpointing, task retry and task replication. Our proposal is to provide an environment able to deal with all types of failures, transparently for the user whenever possible. The main advantage in implementing these mechanisms at the programming model level is that application-level knowledge can be exploited in order to dynamically create a fault tolerance strategy for each application, and avoiding to introduce overhead in error-free environments.
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Zabihi, Sheikhrajeh Nima. "Vehicle-to-grid (V2G) and grid conditioning systems." Doctoral thesis, Università degli studi di Padova, 2013. http://hdl.handle.net/11577/3426634.
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The term Vehicle-to-Grid (V2G) refers to the technology that enables a bidirectional power exchange between the electric grid and the batteries of plug-in electric vehicles (PEV). V2G technology can be a key element of the intelligent network, which may use the batteries of the vehicle as a system of local storage. The vehicle battery may contribute to the stability of the grid and to meeting the energy demand, especially in peak hours. A PEV needs a bidirectional charger to implement V2G, and, consequently, the studies regarding their design, functionality and efficiency are of the utmost interest.
This thesis describes the state of art of these chargers and discusses some aspects of a bi-directional converter and some case studies related to this topic. The main objective of this work is to develop the design and the control algorithms of a bidirectional battery charger with capability to charge the battery of a PEV and simultaneously to act as an active filter for the supply line.
After the first introductory chapter, the second chapter reports the terminology used in this field of research. Several smart strategies for charging, approaches for the implementation of the battery chargers for PEVs and the recharging standards are briefly described. The analysis of different types of charger is detailed in chapter three. The conventional battery chargers (CBC) with front-end formed by a diode rectifier, battery chargers with power factor correction (PFC), bi-directional battery chargers (BBC), and integral battery chargers (IBC) are considered. In chapter four, definitions are given of the electrical power in non-sinusoidal conditions, together with some examples of the inadequacies of the classical power theory in describing non-linear phenomena that occur during the operation of a power system. The fifth chapter presents the basic concepts of the theory of instantaneous active and reactive power (also known as p-q theory) applied to the compensation of non-sinusoidal systems. Definition of real, imaginary and zero sequence power are introduced and it is shown how this theory makes it easier to understand the phenomena caused by non-sinusoidal voltages or currents. The theory is particularly suitable for the design of a battery charger when it is seen as a power conditioner. Chapter six is devoted to the basic concepts of shunt active filters. They can perform different types of functions, such as the compensation of current harmonics generated by nonlinear loads to prevent their propagation in the network. The compensation algorithm based on powers defined in reference is very flexible and therefore the theory of instantaneous power has been considered as the basis for the development of the control system of active filters. Some examples of compensation described in the previous chapter were simulated and the results have been included. In chapter seven, sizing of the power devices that constitute the battery charger is considered in relation to the various auxiliary services that it can provide. The power electronic switches, the coupling inductors and the other passive components have been sized in voltage and current. In chapter eight it is considered a charger that supplies its load and simultaneously compensates for non-linear loads connected nearby. These additional features in terms of power conditioning were quantified in order to determine the capacity of a battery charger that is formed by given active and passive components to support the network acting as an active filter. In the ninth chapter the filter inductances of a battery charger are sized for a specific case study in which it is required the capability to recharge the battery and to inject active power in the network, both in the case of single-phase and three-phase connection. Evaluation of the ripple current is an important requirement for the design of inductors. Therefore a precise calculation was made of this magnitude both in the case of a battery charger connected to the single phase grid and operating according to the PWM technique, and, in the case of connection to the three-phase grid, operating according to the technique SVM. In chapter ten a case study is considered regarding the design of an LCL filter. Chapter eleven contains a theoretical study of resonant controllers. They solve the problem posed by the conventional PI controllers that, when used for the control of alternate quantities as it occurs for the currents of a DC/AC converter, are not able to cancel the steady state error due to the finite gain at the operating frequency. Instead, a resonant controller has a gain ideally infinite at the operating frequency and thus ensures a zero steady-state error. The effectiveness of the resonant regulators has been verified by means of simulations. Chapter twelve deals with the regulations regarding connectors, charging modes and ways of connecting the PEV chargers to the grid. They are intended to define a charging procedure common to all the PEVs and to all the charging infrastructures, whether public or private.Il termine Vehicle-to-Grid (V2G) si riferisce alla tecnologia che permette uno scambio di potenza bidirezionale tra la rete elettrica e le batterie dei veicoli elettrici di tipo plug-in (PEV). La tecnologia V2G può essere un elemento chiave della rete intelligente, che può utilizzare le batterie dei veicoli come un sistema di accumulo locale. Le batterie dei veicoli possono contribuire alla stabilità della rete e a soddisfare la domanda di energia soprattutto nelle ore di punta. Un PEV ha bisogno di un caricatore bidirezionale per implementare il V2G, e, di conseguenza, gli studi riguardo il loro progetto, la funzionalità e l'efficienza sono del massimo interesse. Questa tesi descrive lo stato dell’arte di questi caricabatteria e tratta alcuni aspetti di un convertitore bidirezionale e alcuni casi di studio relativi a questo argomento. L'obiettivo principale di questo lavoro è di sviluppare il progetto e gli algoritmi di controllo di un caricabatteria bidirezionale con capacità di caricare la batteria di un veicolo plug-in e contemporaneamente di agire come filtro attivo nei confronti della linea di alimentazione. Dopo il primo capitolo introduttivo, nel secondo capitolo viene riportata la terminologia usata in questo campo di ricerca. Vengono anche brevemente descritte diverse strategie intelligenti di ricarica, gli approcci per la realizzazione dei caricabatteria dei PEV e gli standard di ricarica. L’analisi dei vari tipi di caricabatteria viene approfondita nel terzo capitolo. Sono considerati il caricabatteria tradizionale (CBC) con front-end costituito da un raddrizzatore a diodi, il caricabatteria dotato di correttore del fattore di potenza (PFC), il caricabatteria bidirezionale (BBC), e il caricabatteria integrale (IBC). Nel capitolo quattro vengono date le definizioni della potenza elettrica in condizioni non sinusoidali assieme ad alcuni esempi delle inadeguatezze della teoria classica della potenza nel descrivere fenomeni non lineari che si verificano durante il funzionamento di un sistema di potenza. Nel quinto capitolo sono presentati i concetti di base della teoria potenza istantanea attiva e reattiva (nota anche come teoria pq) applicata alla compensazione di sistemi non sinusoidali. Vengono introdotte le definizioni della potenza reale, immaginaria e di sequenza zero e viene mostrato come questa teoria renda agevole la comprensione dei fenomeni causati da tensioni o correnti non sinusoidali. Essa è particolarmente adatta per il progetto di un caricabatteria quando esso viene visto come un condizionatore di potenza. Il capitolo sei è dedicato ai concetti di base dei filtri attivi di tipo shunt. Essi possono svolgere diversi tipi di funzioni, come la compensazione delle armoniche di corrente generate da carichi non lineari impedendo la loro propagazione nella rete. L’algoritmo di compensazione basato sulle potenze definite nel riferimento αβ è molto flessibile e quindi la teoria della potenza istantanea è stata considerata come la base per lo sviluppo del sistema di controllo dei filtri attivi. Alcuni esempi di compensazione descritti nel capitolo precedente sono stati simulati e sono stati riportati i risultati. Nel capitolo sette è considerato il dimensionamento dei dispositivi di potenza che costituiscono il caricabatteria in relazione ai diversi servizi ausiliari che esso può fornire. Sono stati dimensionati in tensione e corrente gli interruttori elettronici di potenza, gli induttori di accoppiamento con la rete e gli altri componenti passivi. Nel capitolo otto viene considerato un caricabatteria che alimenta il proprio carico e contemporaneamente compensa i carichi non lineari connessi nelle vicinanze, costituiti da raddrizzatori. Queste funzionalità aggiuntive in termini di condizionamento della potenza di rete sono state quantificate al fine di determinare la capacità di un caricabatteria costituito da determinati componenti attivi e passivi di supportare la rete svolgendo la funzione di filtro attivo. Nel nono capitolo sono state dimensionate le induttanze di filtro di un caricabatteria per uno specifico caso di studio in cui era richiesta la capacità sia di ricaricare la batteria che di iniettare potenza attiva in rete, sia nel caso di connessione monofase che trifase. La conoscenza dell’ampiezza dell’ondulazione di corrente è un requisito importante per il dimensionamento delle induttanze. Perciò è stato effettuato un calcolo preciso di questa grandezza sia nel caso di un caricabatteria connesso alla rete monofase e operante secondo la tecnica di PWM, sia nel caso di connessione alla rete trifase e adozione della tecnica SVM. Nel capitolo dieci viene considerato un caso di studio riguardo il dimensionamento di un filtro LCL. IL capitolo undici contiene uno studio teorico dei regolatori risonanti. Essi risolvono il problema posto dai convenzionali regolatori PI, che quando sono impiegati per il controllo di grandezze alternate, come accade nel caso delle correnti in un convertitore dc-ac, non sono in grado di annullare l’errore a regime a causa del guadagno finito alla frequenza di funzionamento. Un regolatore risonante presenta invece un guadagno idealmente infinito alla frequenza di funzionamento e quindi garantisce un errore a regime nullo. L’efficacia dei regolatori risonanti è stata verificata per mezzo di simulazioni. Nel capitolo dodici sono riportate le normative riguardanti i connettori, le modalità di ricarica e la connessione dei caricabatteria dei PEV alla rete elettrica. Esse mirano a definire una procedura di ricarica comune a tutti i PEV e tutte le infrastrutture di ricarica, siano esse pubbliche o private.
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Tysell, Lars. "Hybrid Grid Generation for Viscous Flow Computations Around Complex Geometries." Doctoral thesis, KTH, Mekanik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11934.
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A set of algorithms building a program package for the generation of twoandthree-dimensional unstructured/hybrid grids around complex geometrieshas been developed. The unstructured part of the grid generator is based on the advancing frontalgorithm. Tetrahedra of variable size, as well as directionally stretched tetrahedracan be generated by specification of a proper background grid, initiallygenerated by a Delaunay algorithm. A marching layer prismatic grid generation algorithm has been developedfor the generation of grids for viscous flows. The algorithm is able to handleregions of narrow gaps, as well as concave regions. The body surface is describedby a triangular unstructured surface grid. The subsequent grid layers in theprismatic grid are marched away from the body by an algebraic procedurecombined with an optimization procedure, resulting in a semi-structured gridof prismatic cells. Adaptive computations using remeshing have been done with use of a gradientsensor. Several key-variables can be monitored simultaneously. The sensorindicates that only the key-variables with the largest gradients give a substantialcontribution to the sensor. The sensor gives directionally stretched grids. An algorithm for the surface definition of curved surfaces using a biharmonicequation has been developed. This representation of the surface canbe used both for projection of the new surface nodes in h-refinement, and theinitial generation of the surface grid. For unsteady flows an algorithm has been developed for the deformationof hybrid grids, based on the solution of the biharmonic equation for the deformationfield. The main advantage of the grid deformation algorithm is that itcan handle large deformations. It also produces a smooth deformation distributionfor cells which are very skewed or stretched. This is necessary in orderto handle the very thin cells in the prismatic layers. The algorithms have been applied to complex three-dimensional geometries,and the influence of the grid quality on the accuracy for a finite volumeflow solver has been studied for some simpler generic geometries.QC 20100812
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Theisen, Matias Ebbe. "Offshore-Grid." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14477.
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This thesis has been conducted in cooperation with the Norwegian transmission system operator, Statnett, and their research on two new interconnectors linking Norway to England and Germany. The work presented in this thesis has considered one of these interconnectors, with a third terminal connected offshore to allow for integration of offshore wind power and oil platforms, as shown in fig.~ref{fig:theGrid}.Investigation of the voltage source converters (VSCs) control ability as well as operational aspects of multi-terminal DC-grids has been performed. Identified as the key control variable of a DC-grid is the DC-voltage serving as a measure of power balance, since an unbalance will affect the DC-voltage through charging or discharging of the DC-capacitances. Utilizing VSCs allowing a fast and accurate control of the DC-voltage can lead to a stable operation of a DC-grid.The three-terminal structure, fig.~ref{fig:theGrid}, was implemented in the simulation tool SIMPOW and connected to a 35-node AC-grid model representing the Nordic grid. The simulation model was used for analyzes of the DC-grid operation and its affect on the connected AC-grids. The converter station connected to the Nordic grid were applied with DC-voltage control, implying that it will act as the power balancing unit of the DC-grid. The simulations performed show that the control structure implemented could assure a stable DC-grid operation within 0.3s of a fault. It identified the need for a fast response to changes in the DC-voltage as the influence of the other connected AC-grids were directly linked to DC-voltage oscillations. Simulations were also conducted to study the advantage of applying AC-voltage control compared to reactive power for the converter connected to the Nordic grid. It was identified that an increased stability of the Nordic grid could be assured during faults in the grid itself. This also affected the DC-grid operation through an increased capability of power exchange with the Nordic grid.
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Rylander, Anton. "Smart Grid." Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-23430.
Full textBooks on the topic "Grid"
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Kim, Hyun Jin. Three dimensional adaptive grid generation on a composite structure. Mississippi State: Mississippi State University, 1987.
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V, Ushakova Olga, ed. Advances in grid generation. New York: Nova Science Publishers, 2004.
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Parashar, Manish, ed. Grid Computing — GRID 2002. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-36133-2.
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Lee, Craig A., ed. Grid Computing — GRID 2001. Berlin, Heidelberg: Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/3-540-45644-9.
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Buyya, Rajkumar, and Mark Baker, eds. Grid Computing — GRID 2000. Berlin, Heidelberg: Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/3-540-44444-0.
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Neuroth, Heike, Martina Kerzel, and Wolfgang Gentzsch, eds. German Grid Initiative D-Grid. Göttingen: Göttingen University Press, 2007. http://dx.doi.org/10.17875/gup2007-512.
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Grid. Regina, SK: Hagios Press, 2012.
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Grid. Volendam: LM Publishers, 2019.
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Center, Langley Research, ed. Wavelet-based grid generation. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1996.
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Alter, Stephen J. The Volume Grid Manipulator (VGM): A grid reusability tool. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1997.
Find full textBook chapters on the topic "Grid"
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Verbeke, Jerome, Neelakanth Nadgir, Greg Ruetsch, and Ilya Sharapov. "Framework for Peer-to-Peer Distributed Computing in a Heterogeneous, Decentralized Environment." In Grid Computing — GRID 2002, 1–12. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-36133-2_1.
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Mayer, Anthony, Stephen McGough, Murtaza Gulamali, Laurie Young, Jim Stanton, Steven Newhouse, and John Darlington. "Meaning and Behaviour in Grid Oriented Components." In Grid Computing — GRID 2002, 100–111. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-36133-2_10.
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Evan Chang, Bor-Yuh, Karl Crary, Margaret DeLap, Robert Harper, Jason Liszka, Tom Murphy VII, and Frank Pfenning. "Trustless Grid Computing in ConCert." In Grid Computing — GRID 2002, 112–25. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-36133-2_11.
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Hoschek, Wolfgang. "A Unified Peer-to-Peer Database Framework for Scalable Service and Resource Discovery." In Grid Computing — GRID 2002, 126–44. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-36133-2_12.
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Li, Wei, Zhiwei Xu, Fangpeng Dong, and Jun Zhang. "Grid Resource Discovery Based on a Routing-Transferring Model." In Grid Computing — GRID 2002, 145–56. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-36133-2_13.
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Faerman, Marcio, Adam Birnbaum, Henri Casanova, and Fran Berman. "Resource Allocation for Steerable Parallel Parameter Searches." In Grid Computing — GRID 2002, 157–68. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-36133-2_14.
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Ramakrishnan, Lavanya, Helen Rehn, Jay Alameda, Rachana Ananthakrishnan, Madhusudhan Govindaraju, Aleksander Slominski, Kay Connelly, et al. "An Authorization Framework for a Grid Based Component Architecture." In Grid Computing — GRID 2002, 169–80. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-36133-2_15.
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Lorch, Markus, and Dennis Kafura. "Supporting Secure Ad-hoc User Collaboration in Grid Environments." In Grid Computing — GRID 2002, 181–93. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-36133-2_16.
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Sundaram, Babu, and Barbara M. Chapman. "XML-Based Policy Engine Framework for Usage Policy Management in Grids." In Grid Computing — GRID 2002, 194–98. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-36133-2_17.
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Keahey, Kate, and Welch Von. "Fine-Grain Authorization for Resource Management in the Grid Environment." In Grid Computing — GRID 2002, 199–206. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-36133-2_18.
Full textConference papers on the topic "Grid"
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Mahjoub, O. Ben, A. Ouadoud, and J. M. Redondo. "The Decay of Turbulence Generated by Square Grid and Spaced Square Grid." In Topical Problems of Fluid Mechanics 2022. Institute of Thermomechanics of the Czech Academy of Sciences, 2022. http://dx.doi.org/10.14311/tpfm.2022.019.
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Fractal grids generate multi-scale turbulent flows which interact with each other and form new multi-scales with different properties compared with those generated by classical grids. The goal of this work was to study the influence of geometry multiscale fractal on the generation and decay of turbulence by comparing the turbulence produced by a traditional fractal square grid FSG for short to that produced by a spaced fractal square grid SFSG for short with similar physical properties. The velocity measurements were performed in an open circuit suction type wind tunnel using a constant temperature hot wire anemometer at various positions in the x direction along the tunnel’s center line and for three different Reynolds numbers ReL0 based on the inlet velocity U? and the length of the largest grid bar L0. It was found that the turbulence intensity decays with distance from the grid for SFSG. Whereas, for FSG at low Reynolds numbers the turbulence intensity shows the same behaviour as for SFSG but for higher Reynolds numbers the turbulence intensity increases to reach a peak at a distance xpeak from the grid and then decays. In the inhomogeneous region, for both types of grids, a scaling range spans over a decade with an exponent near, but not exactly, k?5/3. In contrast, the length of the scaling range larger for FSG than for SFSG.
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Mizusawa, Kiyoe. "Perception of computer-generated achromatic grid figures surrounded by chromatic grid background." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1987. http://dx.doi.org/10.1364/oam.1987.tur4.
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It is known that in Speillman's illusion, light regions are observed at the intersection of dark bars on a light background and dark regions are noted at the intersection of the light bars on a dark background. The illusion may disappear depending on the observation distance. The optimal visual angle of the distance is 6 and 18 min of arc. This indicates the excitatory region of human receptive fields. Although the process may not be the same as the illusion described above, the present research systematically investigates the perception of the computer-generated geometric figures consisting of fine black grids surrounded by high-frequency colored grids. Six different colors of surrounding grids figures with five different densities of grid were tested. The subjects perceived a black grid figure as various reflecting colors which were complementary to the surrounding grid colors. The perceived colors matched by the subjects and stimulus colors are further analyzed by a photodensitometer.
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Manzooor, Shahid, Michael G. Edwards, and Ali H. Dogru. "Acute PEBI Grid Generation for Reservoir Geometries." In SPE Reservoir Simulation Conference. SPE, 2021. http://dx.doi.org/10.2118/203908-ms.
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Abstract An unstructured grid generation method is presented that automates control-volume boundary alignment to geological objects and control point alignment to complex wells. The grid generation method is coupled with an iterative acute mesh reconstruction technique, to construct essentially acute triangulations, while satisfying quite general geometric constraints. For well aligned grids control points are constrained to the well trajectory and protection circles are used, whereas for boundary aligned grids halo construction is performed. Unstructured Delaunay triangulations (DT) have the desirable locally orthogonal perpendicular bisectional (PEBI) property, required by the industry standard two-point flux approximation for consistency for isotropic fields. The PEBI property can only be exploited if such grids are comprised of acute simplexes, with circumcentres located inside their respective elements. The method presented enables acute DT layered mesh generation while honoring internal boundaries and wells in a two dimensional space. A dual (Voronoi) grid derived from a feature honored simplicial mesh is then projected in the vertical direction generating 2.5D PEBI grids. Effectiveness of the method to construct acute PEBI grids honoring geological objects and complex wells is demonstrated by meshing representative reservoir geometries. Numerical results are presented that verify consistency of the two-point flux on the resulting boundary-aligned acute PEBI grids. Development of an unstructured grid generation method which 1) Automates interior boundary alignment, 2) Honors features with respect to control point and/or control volume, and 3) Generates acute PEBI grids for reservoir geometries is presented. A unique workflow is presented to generate boundary aligned acute PEBI grids for complex geometries. Development of boundary aligned grids that honor both geological objects and multilateral complex wells, together with mesh reconstruction to ensure circumcenter containment is presented. Further, 3D PEBI grid generation method which can limit refinement to well perforations and geological objects is also described.
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Yu, Shiwen, Shuaiang Rong, and Lina He. "Performance of Grid-forming Control of Grid-edge DERs in Distribution Grids." In 2022 IEEE Power & Energy Society General Meeting (PESGM). IEEE, 2022. http://dx.doi.org/10.1109/pesgm48719.2022.9916842.
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Mishev, Ilya, and Ruslan Rin. "Grid Quality Measures for PEBI Grids." In SPE Reservoir Simulation Conference. SPE, 2021. http://dx.doi.org/10.2118/203961-ms.
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Abstract Combining the Perpendicular Bisector (PEBI) grids with the Two Point Flux Approximation (TPFA) scheme demonstrates a potential to accurately model on unstructured grids, conforming to the geological and engineering features of real grids. However, with the increased complexity and resolution of the grids, the PEBI conditions will inevitably be violated in some cells and the approximation properties will be compromised. The objective is to develop accurate and practical grid quality measures that quantify such errors. We critically evaluated the existing grid quality measures and found them lacking predictive power in several areas. The available k-orthogonality measures predict error for flow along the strata, although TPFA provides an accurate approximation. The false-positive results are not only misleading but can overwhelm further analysis. We developed the so-called "truncation error" grid measure which is probably the most accurate measure for flow through a plane face and accurately measures the error along the strata. We also quantified the error due to the face curvature. Curved faces are bound to exist in any real grid. The impact of the quality of the 2-D Delaunay triangulation on TPFA approximation properties is usually not taken into account. We investigate the impact of the size of the smallest angles that can cause considerable increase of the condition number of the matrix and an eventual loss of accuracy, demonstrated with simple examples. Based on the analysis, we provide recommendations. We also show how the size of the largest angles impacts the approximation quality of TPFA. Furthermore, we discuss the impact of the change of the permeability on the TPFA approximation. Finally, we present simple tools that reservoir engineers can use to incorporate the above-mentioned grid quality measures into a workflow. The grid quality measures discussed up to now are static. We also sketch the further extension to dynamic measures, that is, how the static measures can be used to detect change in the flow behavior, potentially leading to increased error. We investigate a comprehensive set of methods, several of them new, to measure the static grid quality of TPFA on PEBI grids and possible extension to dynamic measures. All measures can be easily implemented in production reservoir simulators and examined using the suggested tools in a workflow.
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Bahrainian, Seyed Saied, and Zahra Mehrdoost. "A Novel Hybrid Approach for Unstructured Viscous Grid Generation." In ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2010. http://dx.doi.org/10.1115/esda2010-24325.
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Accurate solution of boundary layer and wake flow require generation of high aspect ratio grids in these regions. A hybrid approach for the efficient generation of inviscid and viscous unstructured grids has been introduced. A novel feature of the current work is its ability to produce boundary layer and wake grids that enables accurate flow solutions in viscous flow regions. The grid generation algorithm starts with a very coarse initial grid. In the inviscid region, isotropic cells of excellent quality are produced using a combination of point insertion and cell subdivision techniques. Simultaneously, a directional grid refinement strategy is used to construct highly stretched triangular cells in viscous regions. First, anisotropic unstructured grids are produced in the stream wise direction. Then, cells close to the solid surface are refined to highly stretched layer of triangles suitable for boundary layer region. Smooth transition between the boundary layer grid and the outer isotropic grid is easily obtained with a user specified cell size and stretch. The accuracy of the current grid generation approach is assessed by laminar and turbulent compressible flow solutions around NACA0012 and RAE2822 airfoils. The results of the numerical flow simulations are compared with published experimental and numerical data. Comparisons point to the ability of the proposed unstructured boundary layer and wake grid generation procedure.
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Cardew, George E. "A Composite Overlapping Grid Method in Solid Mechanics." In ASME 1995 15th International Computers in Engineering Conference and the ASME 1995 9th Annual Engineering Database Symposium collocated with the ASME 1995 Design Engineering Technical Conferences. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/cie1995-0771.
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Abstract A preliminary study of the effectiveness of composite overlapping, patched grid methods has been carried out using the finite element research code ‘TOMECH’ [1]. These methods could be of particular value in situations where a fully connected mesh model is difficult to achieve or where enhanced accuracy is needed in a small sub-region of a model. The methodology required to achieve the data communication between the sub-grids and the base grid is adapted from multi-grid methods. This is a ‘Global-Local’ style approach in which a multi-grid style iterative correction is applied following the updating of the displacements on the sub-grid boundaries. The approach provides a feedback mechanism within the global-local cycle, updating the base grid solution and enabling a subsequent improved estimate to the sub-grid boundaries. It is hoped that this study will ultimately facilitate very fine resolution, fully non-linear, damage predictions on adaptively created patched grids.
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Hellinckx, P., G. Stuer, W. Hendrickx, F. Arickx, and J. Broeckhove. "Grid-user driven grid research, the CoBRA grid." In Sixth IEEE International Symposium on Cluster Computing and the Grid. IEEE, 2006. http://dx.doi.org/10.1109/ccgrid.2006.1630941.
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Mokhtar, Jawad D., and James H. Oliver. "Parametric Volume Models for Interactive Three-Dimensional Grid Generation." In ASME 1994 Design Technical Conferences collocated with the ASME 1994 International Computers in Engineering Conference and Exhibition and the ASME 1994 8th Annual Database Symposium. American Society of Mechanical Engineers, 1994. http://dx.doi.org/10.1115/detc1994-0086.
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Abstract A method based on non-uniform rational B-spline (NURBS) curve, surface, and solid technology is presented for interactive grid generation of three-dimensional flow fields encountered in turbomachinery applications. The method allows construction of several types of multi-block grids including H-, O-, and C-grids for two-dimensional grids, and strict H-grids for three-dimensional grid generation. Automated two-dimensional block construction is facilitated via a traversal method that searches four-sided regions in the initial block structure. A NURBS surface is then constructed on each block by transfinite interpolation of the boundary curves themselves, and various point distribution options may be applied. Three-dimensional grid generation is an extension of the two-dimensional procedure. Tri-parametric hyperpatches (NURBS solids) are constructed from the two-dimensional block surfaces and grids may be generated via several point distribution functions. This method exploits existing geometric design data via Initial Graphics Exchange Specification (IGES) input of NURBS-based component geometry. It provides an efficient and robust method for complex grid generation to support a variety of analysis functions. Several example applications are presented to demonstrate the capabilities of the technique.
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Song, Kee-nam, Soo-bum Lee, Moon-Kyun Shin, Jae-Jun Lee, and Gyung-Jin Park. "Development of a New Spacer Grid Form to Enhance the Integrity of Fuel Rod Support and the Crush Strength of a Spacer Grid Assembly." In 17th International Conference on Nuclear Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/icone17-75008.
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A spacer grid is one of the most important structural components in a LWR fuel assembly. The spacer grid, which supports nuclear fuel rods laterally and vertically with a friction grip, is an interconnected array of slotted grid straps welded at the intersections to form an egg-crate structure. Dimples and springs are stamped into each grid strap to support the fuel rods. The form of grid straps and spring form is known to be closely related with the crush strength of spacer grid assembly and the integrity of fuel rod support, respectively. Zircaloy is prevailing as the material of the spacer grid because of its low neutron absorption characteristic and its successful extensive in-reactor use. The primary considerations are to provide a Zircaloy spacer grid with crush strength sufficient to resist design basis loads especially due to seismic accidents, without significantly increasing pressure drop across the reactor core. Generally, the thickness and height of the Zircaloy grid strap have been the main design variables in order to meet the above considerations. Recently, it was reported that a dimple location is also a design variable that affects the crush strength of a spacer grid assembly. In this study, a new spacer grid form was developed in order to enhance the integrity of the fuel rod support and the crush strength of the spacer grid assembly by using a systematic optimization technique. Finite element analysis and crush strength tests on the developed new spacer grid form were carried out to check the performance enhancement compared to commercial spacer grids. The enhancement of fuel rod support was confirmed by comparisons of contact area, peak stresses, plastic deformation and etc. According to the results, it is estimated that the actual critical load enhancement of the spacer grid assembly is approximately up to 30% and the actual contact area, when a fuel rod inserted into a spacer grid cell, is more than double for the developed new spacer grid form. And also, some design variables that effect the crush strength of a PWR spacer grid assembly were classified and their effects on the crush strength were investigated by a finite element analysis and a crush strength test.
Reports on the topic "Grid"
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Hager, John W., Larry L. Fry, Sandra S. Jacks, and David R. Hill. Datums, Ellipsoids, Grids, and Grid Reference Systems. Fort Belvoir, VA: Defense Technical Information Center, January 1992. http://dx.doi.org/10.21236/ada247651.
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Backhaus, Scott N., and Michael Chertkov. Getting a grip on the electrical grid. Office of Scientific and Technical Information (OSTI), April 2013. http://dx.doi.org/10.2172/1073732.
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Huang, C. Grid Data Crossing Platform (GriD-Xing). Office of Scientific and Technical Information (OSTI), May 2019. http://dx.doi.org/10.2172/1515345.
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Taft, Jeffrey D., and Angela S. Becker-Dippmann. Grid Architecture. Office of Scientific and Technical Information (OSTI), March 2015. http://dx.doi.org/10.2172/1176825.
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Rutledge, David. Grid Amplifiers. Fort Belvoir, VA: Defense Technical Information Center, July 1995. http://dx.doi.org/10.21236/ada300131.
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Venkata, Ramana G., Joseph Oliger, and Joel Ferziger. 3D Composite Grids for Flow Computations: the Grid Generation. Fort Belvoir, VA: Defense Technical Information Center, May 1991. http://dx.doi.org/10.21236/ada252105.
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Taft, Jeffrey. Electric Grid Resilience and Reliability for Grid Architecture. Office of Scientific and Technical Information (OSTI), March 2018. http://dx.doi.org/10.2172/1985267.
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