Littérature scientifique sur le sujet « Field’s elements and forces »
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Articles de revues sur le sujet "Field’s elements and forces"
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Potachits, Ya V. « A Study of the Occurrence of Resonance under the Influence of Dynamic Forces on the Structural Elements of Electrical Installations ». ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 64, no 3 (4 juin 2021) : 228–38. http://dx.doi.org/10.21122/1029-7448-2021-64-3-228-238.
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The increase in the levels of short-circuit currents in the power system of the Republic of Belarus requires the study of the parameters of the electrodynamic stability of the main structural elements of electrical installations with flexible conductors. In case of a short circuit in the network, currents tenfold exceeding the rated one hundreds of times can flow through the current-carrying part of the device. When the magnetic fields formed by these currents interact, significant electromagnetic forces arise, which have a destructive effect both on the current-carrying parts themselves and on the structural elements of electrical installations, viz. support insulators, switching devices, measuring equipment. The movement of the wires in a short-circuit mode leads to the appearance of significant dynamic loads in them, which, in turn, are transmitted to the portals, support insulators and electrical devices. A topical problem is the occurrence of unacceptable mechanical forces in the main structural elements that can cause their destruction. Thus, the analysis of the physical and mechanical parameters and geometric dimensions of the flexible busbar of switchgear shows that a violation of the condition of electrodynamic resistance to tension is unlikely due to the high mechanical strength of the large-section steel-aluminum wires used. At the same time, span-limiting portals, support insulators and other electrical devices have significantly lower permissible bending loads. When exposed to dynamic forces, the conductors bend and transfer the load to the structural elements which have certain elasticity. Thus, a reliable determination of dynamic loads, taking into account the current-carrying parts acting on the supporting structures, is possible only if a dynamic task is set. The article describes the methods of mathematical modeling and computational experiment for analyzing the parameters of the electro-dynamic stability of the main structural elements which are determined using coefficients that depend on the natural frequencies of oscillations and the nature of changes in dynamic forces over time. To solve these problems, mathematical models are compiled and boundary value problems are formulated for calculating the electrodynamic stability of structural elements, taking into account the possible coincidence of the frequencies of natural and forced oscillations of structural elements taking into account the probable coincidence of the frequencies of forced and natural vibrations of structural elements.
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Anischenko, Galyna, et Denys Lavinskyi. « Non-stationary phenomena in technological systems of electromagnetic processing of materials ». Bulletin of the National Technical University «KhPI» Series : Dynamics and Strength of Machines, no 2 (31 décembre 2022) : 39–42. http://dx.doi.org/10.20998/2078-9130.2022.2.270863.
Texte intégralRésumé :
A large number of technical and technological facilities work under the action of electromagnetic fields. In electroconductive bodies have significant largest electromagnetic forces that can cause movement or deformation of structural elements. The creation of effective methods of analysis of the distribution of the electromagnetic field and coupled nonstationary deformation of structural elements is topical at present time. The article contains a mathematical formulation of the problem of nonstationary deformation of structural elements under the action of electromagnetic fields. Coupling of electromagnetic field and mechanical field is carried out with the help of local electromagnetic forces. Further made the transition to a variational formulation on the basis of the task of finding the minimum of the total energy of the system, which includes the energy of the electromagnetic field. For the numerical solution the finite element method is used. Nodal unknowns in this case are the magnetic vector potential and displacements. The proposed method is applied to non-stationary deformation of the "inductor-billet" technological operation of magnetic-pulse processing of metals. Some results of the deformation are presented.
A large number of technical and technological facilities work under the action of electromagnetic fields. In electroconductive bodies have significant largest electromagnetic forces that can cause movement or deformation of structural elements. The creation of effective methods of analysis of the distribution of the electromagnetic field and coupled nonstationary deformation of structural elements is topical at present time. The article contains a mathematical formulation of the problem of nonstationary deformation of structural elements under the action of electromagnetic fields. Coupling of electromagnetic field and mechanical field is carried out with the help of local electromagnetic forces. Further made the transition to a variational formulation on the basis of the task of finding the minimum of the total energy of the system, which includes the energy of the electromagnetic field. For the numerical solution the finite element method is used. Nodal unknowns in this case are the magnetic vector potential and displacements. The proposed method is applied to non-stationary deformation of the "inductor-billet" technological operation of magnetic-pulse processing of metals. Some results of the deformation are presented.
A large number of technical and technological facilities work under the action of electromagnetic fields. In electroconductive bodies have significant largest electromagnetic forces that can cause movement or deformation of structural elements. The creation of effective methods of analysis of the distribution of the electromagnetic field and coupled nonstationary deformation of structural elements is topical at present time. The article contains a mathematical formulation of the problem of nonstationary deformation of structural elements under the action of electromagnetic fields. Coupling of electromagnetic field and mechanical field is carried out with the help of local electromagnetic forces. Further made the transition to a variational formulation on the basis of the task of finding the minimum of the total energy of the system, which includes the energy of the electromagnetic field. For the numerical solution the finite element method is used. Nodal unknowns in this case are the magnetic vector potential and displacements. The proposed method is applied to non-stationary deformation of the "inductor-billet" technological operation of magnetic-pulse processing of metals. Some results of the deformation are presented.
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Di Barba, P., A. Savini et I. Perugia. « Mixed finite elements for the simulation of fields and forces in electromagnetic devices ». IEEE Transactions on Magnetics 34, no 5 (1998) : 3572–75. http://dx.doi.org/10.1109/20.717843.
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Kupferman, Raz, Elihu Olami et Reuven Segev. « Stress theory for classical fields ». Mathematics and Mechanics of Solids 25, no 7 (8 août 2017) : 1472–503. http://dx.doi.org/10.1177/1081286517723697.
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Classical field theories, together with the Lagrangian and Eulerian approaches to continuum mechanics, are embraced under a geometric setting of a fiber bundle. The base manifold can be either the body manifold of continuum mechanics, the space manifold, or space–time. Differentiable sections of the fiber bundle represent configurations of the system and the configuration space containing them is given the structure of an infinite-dimensional manifold. Elements of the cotangent bundle of the configuration space are interpreted as generalized forces and a representation theorem implies that there exists a stress object representing forces, non-uniquely. The properties of stresses are studied, as well as the role of constitutive relations in this general setting.
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Metelkin, Sergey, et Vladimir Paramonov. « The effect of negative temperatures on the retaining walls of deep pits ». E3S Web of Conferences 371 (2023) : 02006. http://dx.doi.org/10.1051/e3sconf/202337102006.
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In countries with negative winter temperatures, pits and walls of underground structures are subjected to additional forces caused by frost heaving forces. In Russian construction practice, cases of the impact of such forces on the struts and anchors of construction walls are known, which led to the loss of stability of the struts and the failure of the anchors. Obviously, the design of retaining walls in winter should take into account the effect of additional forces caused by frost heaving and their evolution over time. The solution of test problems for an open pit shows that under certain conditions, the forces in the struts can exceed their values by an order of magnitude, determined when taking into account only the active pressure of the soil. Experimental studies were carried out to assess the processes of development of forces in the elements of the retaining walls in winter. The calculated assessment of the temperature fields and the stress-strain state in the excavation walls was performed using the Termoground program. The comparison of results of experimental and calculated data are shown in the article. The comparison of results of experimental and calculated data is shown in the article.
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Moyseychik, Е. А. « PASSIVE METHOD OF THERMAL NON-DESTRUCTIVE TESTING OF STEEL ELEMENTS AND PRODUCTS ON THE BASIS OF THE MECHANISM OF DEFORMATION HEAT GENERATION ». Kontrol'. Diagnostika, no 252 (2019) : 50–57. http://dx.doi.org/10.14489/td.2019.06.pp.050-057.
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The features of heat generation and the basic capabilities of the passive method of thermal non-destructive testing of steel elements and products are considered. The mechanism of heat generation in steel is presented and the structure of the formula for changing its temperature during deformation is substantiated. It is shown that the diagnosis of steel elements in the passive mode should be carried out with the operation of heat sources in them, resulting from the force effects on the structure. The features of determining the stress in steel elements by the passive thermal method are considered. It is shown that the passive method of thermal non-destructive testing of steel structures loaded with forces continuously changing in time, under the action of which internal deformation sources of heat and surface temperature fields operate in potentially dangerous areas of the elements, allows the kinetics and anomalies of temperature fields to exercise health -plastic stages of steel, with the birth and development of destruction.
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Darnell, I., R. Mousseau et G. Hulbert. « Analysis of Tire Force and Moment Response During Side Slip Using an Efficient Finite Element Model ». Tire Science and Technology 30, no 2 (1 avril 2002) : 66–82. http://dx.doi.org/10.2346/1.2135250.
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Abstract This paper describes the application of a new type of non-linear 3D finite element tire model for simulating tire spindle force and moment response during side slip. The simulation model, briefly described in the paper, is composed of shell elements, which model the tread deformation, coupled to special purpose finite elements that model the deformation of the sidewall and contact between the tread and the ground. The sidewall special purpose element uses a pre-computed look-up table to efficiently calculate the sidewall shape and the forces acting on the tread. The model is designed to predict the forces at the spindle and ground and the overall tire shape, as opposed to the internal stress fields. This paper considers the following deformation scenarios: 1) a vertically loaded tire deforming laterally on a flat surface and 2) a tire rolling straight ahead under a prescribed sideslip angle. Experimental data is also presented to verify the force predictions.
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Safarov, Q. A., G. Vagif gizi et S. V. Galkin. « Application of statistical dependencies to evaluate economic indicators of production efficiency by the example of oil fields in Azerbaijan ». IOP Conference Series : Earth and Environmental Science 1021, no 1 (1 mai 2022) : 012003. http://dx.doi.org/10.1088/1755-1315/1021/1/012003.
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Abstract Improving the use of basic funds and production capacity in oil and gas recovery is not only the introduction of new techniques and technology, but also the improvement of labor, management and organization of work. The process of renewal of the fixed capital and production forces is considered intensive at the time when the vast majority of the newly incorporated basic funds and forces are aimed at replacement of morally obsolete and physically worn out parts. This time, their compliance with the economically justified life expectancy is of interest. All these are elements of recycling. Oil and gas wells are important elements of the active part of the main production funds and they determine the future development of oil and gas recovery. Productive use of production wells for oil and gas recovery is considered as a source of improvement of production efficiency in terms of production-resource potential (PRP). In order to increase the efficient use of oil and gas wells as an active element of the main production funds, special attention is paid to both extensive and intensive factors at oil and gas production enterprises.
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Moffatt, H. K. « Helicity and celestial magnetism ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 472, no 2190 (juin 2016) : 20160183. http://dx.doi.org/10.1098/rspa.2016.0183.
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This informal article discusses the central role of magnetic and kinetic helicity in relation to the evolution of magnetic fields in geophysical and astrophysical contexts. It is argued that the very existence of magnetic fields of the intensity and scale observed is attributable in large part to the chirality of the background turbulence or random-wave field of flow, the simplest measure of this chirality being non-vanishing helicity. Such flows are responsible for the generation of large-scale magnetic fields which themselves exhibit magnetic helicity. In the geophysical context, the turbulence has a ‘magnetostrophic’ character in which the force balance is primarily that between buoyancy forces, Coriolis forces and Lorentz forces associated with the dynamo-generated magnetic field; the dominant nonlinearity here arises from the convective transport of buoyant elements erupting from the ‘mushy zone’ at the inner core boundary. At the opposite extreme, in a highly conducting low-density plasma, the near-invariance of magnetic field topology (and of associated helicity) presents the challenging problem of ‘magnetic relaxation under topological constraints’, of central importance both in astrophysical contexts and in controlled-fusion plasma dynamics. These problems are reviewed and open issues, particularly concerning saturation mechanisms, are reconsidered.
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Vaskovskiy, Yuriy, Alexandr Geraskin et Konstantin Tatarinov. « Research of dampher system damage physical processes of synchronous machines rotor ». Bulletin of NTU "KhPI". Series : Problems of Electrical Machines and Apparatus Perfection. The Theory and Practice, no 2 (6) (9 décembre 2021) : 19–24. http://dx.doi.org/10.20998/2079-3944.2021.2.04.
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The physical processes in the damper system of the rotor with the appearance of a static eccentricity of the rotor for two types of salient-pole synchronous machines - a capsule hydrogenator SGK 538/160-70M with a capacity of 22 MW and a synchronous generator with a capacity of 500 kW were investigated by means of mathematical modeling. A field mathematical model has been developed that takes into account the combined action of three physical fields of different nature: electromagnetic, temperature and field of thermomechanical stresses, and makes it possible to evaluate the heating and three-dimensional distribution of thermomechanical stresses in the structural elements of the rotor damper system of a salient-pole synchronous machine. These physical processes cause gradual destruction of the structure of the rotor damper system. It is proved that the primary cause of degradation and damage of the damping system of the rotor of an open-pole synchronous machine is the uneven distribution of induced currents in the rods at the poles of the rotor, which occurs when the machine works asynchronously or with the appearance of rotor static eccentricity. The largest induced currents and heat occur in the rods located at the edges of the pole pieces, while the central rods at the pole are heated significantly less. This asymmetric heating of the damping system of the rotor leads to significant thermomechanical stresses in the elements of the damping system of the rotor, which significantly depend on the magnitude of the eccentricity and slippery of the rotor in asynchronous mode. The magnitude of the total thermomechanical stresses in the rods is influenced not only by axially directed forces but also by transverse forces in the end short-circuiting elements. At considerable slippery and eccentricities there are inadmissibly big breaking forces which break cores and face short-circuiting elements of a damping system of a rotor. According to the results of the analysis, the heating and thermomechanical stresses of the structural elements were determined and recommendations for its structural improvement were given.
Thèses sur le sujet "Field’s elements and forces"
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BRAMBILLA, ROSSANA. « La differenza pedagogica. Consistenza e funzionamento del "campo" educativo ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2009. http://hdl.handle.net/10281/25187.
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Nonostante i suoi sforzi, il sapere pedagogico risulta ancora incapace di dire qualcosa di nuovo, rispetto agli altri saperi, circa l’educazione, la società e la cultura. Mentre la pedagogia si impegna soprattutto a produrre una sempre maggior quantità di finalità educative, la sua possibilità di dire qualcosa di nuovo circa l’educazione sembra invece legata a una inesplorata interpretazione di tre concetti importanti: quelli di scienza, epistemologia e critica. Assunti radicalmente, questi tre concetti potrebbero cambiare il rapporto tra la pedagogia e l’educazione, colmando anche la storica e riconosciuta spaccatura tra teoria pedagogica e prassi educativa. Nella seconda parte del lavoro, ho studiato e analizzato il pensiero pedagogico di Riccardo Massa, evidenziandone la capacità di rispondere proprio a quei criteri di scientificità e criticità. Massa propone di studiare l’educazione nei termini di uno specifico “campo” di esperienza . Seguendo per primo questa strada, il pedagogista arriva alla formulazione di una precisa teoria della consistenza e del funzionamento del campo educativo . L’educazione, secondo lui, funziona come un “dispositivo”, cioè come un meccanismo, fatto di specifici elementi e di specifici livelli di forza. Nel terzo passaggio del lavoro, al fine di mostrare la capacità trasformativa della teoria massiana – in termini di lettura e progettazione delle pratiche educative –, ho avanzato una proposta di strutturazione e gestione alternative per dei reparti ospedalieri di riabilitazione, e anche una nuova idea di progettazione e conduzione del lavoro educativo con le famiglie.Though its toils, pedagogy is still unable to say something new about education, society and culture. It continues only to produce all sort of teleologies, that is a large quantity of finalities for education. On the contrary, possibility to say something new about education seems linked to a new interpretation of three important concepts: science, epistemology and criticism. They could really let pedagogy to start a new connection with its object (education). In the second part of the work, I try to think of Riccardo Massa’s speech again. I consider his pedagogy as a new theory, able to think education as a particular “field” of experience. Education, in the opinion of Riccardo Massa, is a “device”, that is a mechanism made by specific elements and specific force levels. In the third part of the research, first, I try to use “device” theory to show a new possible way to structure and to run a rehabilitation ward. Finally, I try to use the same theory to show a new possible way to plan educational work with children families.
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Adams, Roy H. Jr. « Examining the forces, causes, and elements of practical drift| A case study ». Thesis, Capella University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3624518.
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When a crisis captures the attention of a nation and the world community, the questions are always Why did it happen and How did it happen. Such an event was revealed on April 28, 2004 with a report on CBS's 60 Minute II and in an article by Seymour Hersh posted online in the New Yorker magazine April 30, 2004. The event was the detainee abuse by U.S. Army soldiers at Abu Ghraib Prison in Iraq. The abuse occurred between late 2003 and early 2004, and the story shook the U.S. government and the coalition partners who helped the United States bring down the Saddam Hussein regime in Iraq. This case study examined how the detainee abuse occurred and why the detainee abuse occurred by applying the theory of practical drift to the events in Iraq. However, the study revealed that while the abuse was conducted in Iraq the forces and causes were not confined to Iraq. The forces that contributed to the breakdown in soldier discipline in Iraq were the result of leadership and doctrinal decisions made decades earlier and governmental decisions made to fight the War on Terror. The study also identified stages of practical drift that illustrate how practical drift occurs in organizations. The case study avoided dealing with the actual events of the detainee abuse but concentrated on the elements that contributed to setting the conditions for the abuse. Practical drift in the war fighting doctrine development of the U.S. Army and the policies adopted by the U.S. administration to fight the War on Terror were causes of the detainee abuse identified in the case study. Individual behavioral traits of dismissive responsibility and deflected responsibility also contributed to practical drift and ultimately the detainee abuse.
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Rouhani, Siamak. « Temperature analyses of Concrete Frame Bridges with Finite Elements ». Thesis, KTH, Bro- och stålbyggnad, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-145904.
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FE-modeling is a rapidly spreading method to analyze structures nowadays. With this theunderstanding of the outcome is of very high importance and potential inaccuracies areimportant to find so that faulty and over dimensioning of the structure does not occur whichleads to unnecessary costs. One of these inaccuracies is the unrealistic sectional forces that occurdue to thermal effects in the transversal direction for concrete frame bridges which leads to anexcessive amount much reinforcement in the structure than actually needed. This has beenstudied with several cases by using two approaches on how to apply the temperature in the framebridge, only in the superstructure and in the whole structure, but also by analyzing severalboundary conditions. By examining the results for the sectional forces and stresses one of thetemperature approaches could be disregarded because of the extreme values in the transitionbetween superstructure and support. But the other approach was much more useful because ofits better compliance with reality. With these results and by calculating the reinforcement neededfor the worst case, one model has been found to be the most favorable and can be used whenmodeling concrete frame bridges with acceptable outcome. The study resulted in a model whereone applies a varying temperature on the whole structure, with spring boundary conditions over asurface that represents the bottom slab.
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Bettess, Jacqueline Anne. « A software perspective on infinite elements for wave diffraction and wave forces on marine risers ». Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4289/.
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This thesis describes work on the problem of the scattering of water waves by fixed objects. The method used to solve this problem is that of finite and infinite elements. In particular the development of a new wave infinite element is described. Various aspects of the wave scattering problem are considered, but always from the perspective of the numerical methods, the algorithms and the computer implementations used. These deal not only with the modelling of the wave equations, but also the pre and post processing of the finite element algorithms. This encompasses the generation of suitable finite element meshes, in an accurate and economical way, and the presentation of the results, particularly as accurate contour plots of the wave surface. The first two chapters gives a brief introduction to water waves, and a summary of the basic concepts of finite and infinite elements. In the third chapter the new infinite element for waves, which is a development of an earlier infinite element, is described in detail, including the new mapping, the necessary shape functions and the integration of the element matrix. The earlier infinite element was restricted to the exterior of circular problems. For scattering objects of large aspect ratio this led to meshes with many finite elements, which performed no useful function, and which were computationally wasteful. The mapping in the new infinite element allows the mesh of infinite elements to be tailored to the shape of the diffracting body, without any observed loss of accuracy. It is therefore much more flexible and computationally efficient, because the infinite elements no longer need to be placed radially. The next three chapters, concentrate on the computer science aspects of the implementation of the finite and infinite elements dealing with the linked list data structures for storage of the element information, the special purpose mesh generation programs, which make it possible to analyse a large range of practical scattering problems and the plotting programs for the display of the results. The chief work in chapter six is the implementation of the Akin and Grey accurate predictor-corrector contour plotting algorithm, with colour fill. The advantage of an accurate contour plotting algorithm is that any discontinuities in the contours represent discontinuities in the results, rather than plotting deficiencies. Chapter seven shows results which validate the new infinite element, particularly on the problem of waves diffracted by an ellipse. In the remaining chapters eight to eleven, the emphasis is on a practical problem of the wave forces on groups of risers, which are the tubes which carry hydrocarbons from the sea-bed to the working areas of offshore platforms. The aim was to see if the forces on a group of risers were different from the sum of the forces on the individual risers, calculated on the assumption that the risers do not modify the wave field. The conclusion is that more detailed studies may well bring financial benefits to the companies operating offshore installations.
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El-Aouar, Walid Hassib. « Finite Element Analysis Based Modeling of Magneto Rheological Dampers ». Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/35165.
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A Finite Element model was built to analyze and examine a 2-D axisymmetric MR damper. This model has been validated with the experimental data. The results obtained in this thesis will help designers to create more efficient and reliable MR dampers. We can create some design analysis to change the shape of the piston in the damper or other parameters in the model. The main benefit of this research is to show a 2-D MR damper and generate the magnetic flux density along the MR Fluid gap. We can detect saturation by looking at the nodal solution for the magnetic flux density. Increasing the current in the model, results in an increase in magnetic induction.
We studied four different configurations of an MR damper piston in order to determine how changing the shape of the piston affects the maximum force that the damper can provide. In designing MR dampers, the designer always faces the challenge of providing the largest forces in the most compact and efficient envelope. Therefore, it is important to identify the configuration that gives more force in less space.
In chapter 4, shows the magnetic flux density contour before and after reaching the rheological saturation. By increasing the current, the color spectrum of the magnetic flux density will shift from the MR fluid gap to the piston centerline.
In chapter 5, we provided a reasonably good amount of force in model 4 at 1.4 Amps, but it reaches saturation before the other models. For cases with power constraint or heat build up limitations, this model could work the best among the four designs that we considered. For cases where higher electrical currents can be tolerated, model 3 would be the most advantageous design, since it provides the largest force among the four models.Master of Science
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Harrison, Stella, et Siri Nöjd. « Influence of Foundation Modelling on the Seismic Response of a Concrete Dam ». Thesis, KTH, Betongbyggnad, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-300448.
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It is of great importance to ensure the structural safety of dams during earthquakes since a failure may cause catastrophic consequences. Conventional computation of the structural response of dams is based on a simplified approach where the foundation is considered as massless. However, recent developments have produced several new analysis methods that consider the foundation mass, modelled with absorbing boundaries and free-field forces. These newer methods are intended to simulate the seismic structural response more accurately, optimize the design and minimise future unnecessary reparations. The aim of the thesis was to investigate the influence of foundation modelling in seismic time history analyses. This was done by comparing the established massless foundation approach to two approaches with foundation mass and free-field forces included; the analytical approach presented by Song et al. (2018) and the direct FE approach by Løkke (2018). Both the efficiency of the seismic wave propagation simulation and the structural response of the dam were of interest, and points on the dam and foundation were studied to accurately compare these modelling approaches. The time history analyses showed that the massless approach corresponded perfectly with the ideal theoretical velocity at the foundation surface when studying only the foundation block, as expected. The analytical and direct FE however, differed slightly from the theoretical value but still gave an accurate representation. Both methods using free-field forces obtained equivalent and realistic structural responses when studying the dam-reservoir-foundation model. The massless method however,strongly overestimated the dam response and was therefore found to not capture the actual behavior of the dam accurately, despite modifications such as increased material damping in the concrete. Additionally, another aim was to analyse the influence of modelling in 2D versus 3D for determining the dynamic characteristics of the dam such as natural frequencies and eigenmodes of the dam. These frequency analyses were made using models with and without foundation mass considered and was compared to experimental data.The massless 3D model was found to be the most effective modelling approach for deriving the dynamic characteristics of the dam since the use of a 3D model was necessary in order to study the behaviour of the whole dam and post-processing was simpler when using the massless model.Det är nödvändigt att säkerställa dammars säkerhet mot jordbävningar i design-processen eftersom ett dammbrott kan få katastrofala konsekvenser. Traditionellt används förenklade beräkningar där dammens strukturella respons beräknas med en berggrund där bergets massa är försummad. Den senaste tiden har flera nya analysmetoder tagits fram, som tar hänsyn till bergets massa och är modellerade med absorberande randvillkor och free-field forces. De nyare metoderna förväntas modellera de seismiska krafterna mer exakt för att optimera designen och minimera onödiga reparationer. Syftet med projektet var att undersöka inverkan från olika metoders sätt att beakta berggrunden vid seismiska analyser. Det utfördes genom att jämföra den etablerade masslösa metoden med två metoder som beaktar bergmassan och free-fieldforces; den analytiska metoden av Song et al. (2018) och Direct FE-metoden av Løkke (2018). Både effektiviteten i den seismiska vågutbredningssimuleringen och dammens strukturella respons var av intresse. Modelleringsmetoderna jämfördes genom att studera punkter på både dammen och berget. När enbart berggrunden studerades med den masslösa metoden så erhölls, som förväntat, god överenstämmelse med den ideala teoretiska hastigheten på bergsytan. De analytiska och Direct FE metoderna skiljde sig marginellt från det teoretiska värdet men gav fortfarande en korrekt hastighet på bergsytan. Vid analys av modeller med dam och reservoar inkluderade, gav metoderna som använde free-field forces ekvivalenta och realistiska strukturella responser. Den masslösa metoden däremot, överskattade kraftigt dammens respons och ansågs därför inte modelleradet verkliga beteendet hos dammen på ett korrekt sätt, trots modifieringar med ökad materialdämpning i betongen. Ett annat syfte var att analysera påverkan av modellering i 2D kontra 3D för att bestämma dammens dynamiska egenskaper, som egenfrekvenser och egenmoder. Dessa frekvensanalyser gjordes med hjälp av modeller som både beaktade och försummade bergets massa, och jämfördes med experimentella data. Den masslösa 3D-modellen visade sig vara den mest effektiva modelleringsmetoden för att erhållade dynamiska egenskaperna hos dammen. Det eftersom en 3D-modell var nödvändig för att studera hela dammens beteende och hantering av utdata var förenklad vid användning av den masslösa modellen.
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Michel, Kenan. « Distribution of Lateral Forces on Reinforced Masonry Bracing Elements Considering Inelastic Material Behavior - Deformation-Based Matrix Method - ». Technische Universität Dresden, 2021. https://tud.qucosa.de/id/qucosa%3A75156.
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The main goal of CIC-BREL project (Cracked and Inelastic Calculation of BRacing Elements) is to develop an analytical method to distribute horizontal forces on bracing elements, in this case reinforced masonry shear walls, of a building considering the cracked and inelastic state of material.
The moment curvature curve of the wall section is created first depending on the section geometry and material properties of both the masonry units and steel reinforcement. This curve will start with an elastic material behavior, then continue in inelastic material behavior where the masonry crushes and the steel start to yield, until the maximum bending moment M_p is reached. Due to reinforced masonry wall ductility, post maximum capacity is also considered assuming a maximum curvature of 0.1%. From the moment curvature curve, the force displacement curve could be extracted depending on the wall height and wall boundary conditions.
Matrix formulation has been developed for both elastic and damaged stiffness matrix, considering different boundary conditions. Fixed-fixed boundary condition which usually exists at the middle stories or last story with strong top diaphragm, fixed-pinned which is the case of the last story that has a relatively soft top diaphragm, and pinned-fixed in the first story case. Other boundary conditions could be considered depending on the degree of fixation on the wall both ends at the top and the bottom.
The matrix formulation combined with the force-displacement curve which considers different material stages (elastic, inelastic, ductile post peak force) is used to define forces in each bracing element even after elastic behavior. After elastic phase of each wall the stiffness of the element will degrade leading to a less portion of the total lateral force; other elastic walls, i.e., stronger walls, will receive more portion of the total force leading to a redistribution of the total force. This process will be iterated until the total force is distributed on each bracing element depending on the wall section state: elastic, inelastic and ductile post-peak capacity. Flowcharts clearly will show this process. Finally, a Fortran code is developed to show examples using this method.
The developed analytical method will be verified by the results of shake table tests held at the University of California in San Diego, USA. Last test performed in the year 2018 uses T-section reinforced masonry walls, subjected to shakings with increased intensity. The total applied force for each shaking could be defined depending on the structural weight and shaking intensity (acceleration). The damage and displacement at each intensity has been recorded and evaluated. Depending on these test results, the results of the analytically developed method will be compared and evaluated. Total system displacement at different lateral load values has been compared for analytical calculations and shake table tests; furthermore, each wall state at increased load has been compared, good agreement could be noticed.:Acknowledgement 5
1. Introduction 7
1.1. State of the Art 9
1.2. Elastic Formulae 9
1.3. Example, Elastic Calculation 12
1.3.1. Stiffnesses of the System 13
1.3.2. Torsion due to Eccentric Lateral Loading 14
1.3.3. Distribution of the Lateral Load on Wall “j” and Floor “i” 15
2. Force Displacement Curve of RM Shear Wall 19
2.1. Introduction 19
2.2. Cantilever Wall 19
2.2.1. Cantilever Elastic Wall 19
2.2.2. Cantilever Inelastic Wall 21
2.2.3. Cantilever Post-Peak Wall 22
2.3. Fixed-Fixed Wall 23
2.3.1. Fixed-Fixed Elastic Wall 23
2.3.2. Fixed-Fixed Inelastic Wall 24
2.3.3. Fixed-Fixed Post-Peak Wall 26
2.4. Moment – Curvature Analysis 26
2.5. Example, Rectangle Cross Section, Cantilever 29
a) Moment Curvature Curve 29
b) Force Displacement Curve 32
2.6. Example, Rectangle Cross Section, Fixed-Fixed 33
a) Moment Curvature Curve 33
b) Force Displacement Curve 33
2.7. Example, T Cross Section, Cantilever 35
a) Moment Curvature Curve 35
b) Force Displacement Curve 41
2.8. Example, T Cross Section, Fixed-Fixed 43
a) Moment Curvature Curve 43
b) Force Displacement Curve 43
3. Matrix Formulation 47
3.1. Procedure 47
3.2. Structure Discretization 47
3.3. Element, i.e.; Wall, Local Stiffness Matrix 48
3.4. Stiffness Matrix of Fixed-Pinned Beam 52
3.4.1. Elastic 52
3.4.2. Pre-Peak Inelastic 54
3.4.3. Post-Peak Inelastic 55
3.4.4. Normal Force Part in the Stiffness Matrix 56
3.5. Stiffness Matrix of Pinned-Fixed Beam 57
3.5.1. Elastic 57
3.5.2. Post-Peak Inelastic 57
3.6. Stiffness Matrix of Fixed-Fixed Beam 58
3.6.1. Elastic 58
3.6.2. Post-Peak Inelastic 60
3.7. Summary of Stiffness Matrices 61
3.7.1. Fixed-Fixed 61
3.7.2. Fixed-Pinned 62
3.7.3. Pinned-Fixed 63
3.8. Transformation Matrix 63
3.9. Assemble the Structure Stiffness Matrix 65
3.10. Assemble the Structure Nodal Vector 66
3.11. Solve, Get Nodal Displacements and Forces 66
4. Matrix Formulation and Deformation Based Method 69
4.1. Elastic Method in Distributing Lateral Force 69
4.2. Elastic and Inelastic Method in Distributing Lateral Force 70
5. Shake Table Tests 73
5.1. Introduction 73
5.2. Design of Test Structure 73
5.3. Material Properties 75
5.4. Tests and Observations 75
5.4.1. Tests up to Mul-90% 76
5.4.2. Tests with Mul-120% 76
5.4.3. Tests with Mul-133% 76
5.5. Deformations 77
6. Verification 81
6.1. T Cross Section, Dimensions, Reinforcement and Materials 81
6.2. Moment Curvature Curve 82
6.3. Force Displacement Curve 85
6.4. Force Displacement Curve of the Structure 88
7. Conclusions and Suggestions 91
8. References 93
Appendix 1, Timoshenko Beam 95
• Fixed-Fixed 95
• Fixed-Pinned 95
• Pinned-Fixed 96
Appendix 2, Bernoulli Beam 97
• Fixed-Fixed 97
• Fixed-Pinned 97
• Pinned-Fixed 98
8
Doolittle, John W. « Naval Special Warfare (NSW) enlisted manning concerns : key elements for succesful growth and retention of enlisted personnel / ». Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FDoolittle.pdf.
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Goby, Frédéric. « Utilisation d'une methode couplee : "elements finis-elements integrales de frontiere" pour le calcul des forces dans des dispositifs electromagnetiques : application au calcul du couple d'une machine a reluctance variable ». Paris 6, 1987. http://www.theses.fr/1987PA066401.
Texte intégralRésumé :
Le couplage de la methode des elements finis avec la methode des elements integrales de frontiere permet de resoudre plus facilement certains problemes d'electromagnetisme. On peut appliquer ce couplage au calcul des forces au sein de dispositifs electromagnetiques, en particulier pour determiner le couple d'une machine a reluctance variable
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Fan, Xijun. « Numerical study on some rheological problems of fibre suspensions ». Thesis, The University of Sydney, 2006. http://hdl.handle.net/2123/1096.
Texte intégralRésumé :
This thesis deals with numerical investigations on some rheological problems of fibre suspensions: the fibre level simulation of non-dilute fibre suspensions in shear flow; the numerical simulation of complex fibre suspension flows and simulating the particle motion in viscoelastic flows. These are challenging problems in rheology. Two numerical approaches were developed for simulating non-dilute fibre suspensions from the fibre level. The first is based on a model that accounts for full hydrodynamic interactions between fibres, which are approximately calculated as a superposition of the long-range and short-range hydrodynamic interactions. The long-range one is approximated by using slender body theory and includes infinite particle interactions. The short-range one is approximated in terms of the normal lubrication forces between close neighbouring fibres. The second is based on a model that accounts only for short-range interactions, which comprise the lubrication forces and normal contact and friction forces. These two methods were applied to simulate the microstructure evolution and rheological properties of non-dilute fibre suspensions. The Brownian configuration method was combined with the highly stable finite element method to simulate the complex flow of fibre suspensions. The method is stable and robust, and can provide both micro and macro information. It does not require any closure approximations in calculating the fibre stress tensor and is more efficient and variance reduction, compared to CONNFFESSITT, for example. The flow of fibre suspensions past a sphere in a tube and the shear induced fibre migration were successfully simulated using this method The completed double layer boundary element method was extended to viscoelastic flow cases. A point-wise solver was developed to solve the constitutive equation point by point and the fixed least square method was employed to interpolate and differentiate data locally. The method avoids volume meshing and only requires the boundary mesh on particle surfaces and data points in the flow domain. A sphere settling in the Oldroyd-B fluid and a prolate spheroid rotating in shear flow of the Oldroyd-B fluid were simulated. Based on the simulated orbit of a prolate spheroid in shear flow, a constitutive model for the weakly viscoelastic fibre suspensions was proposed and its predictions were compared with some available experimental results. All simulated results are in general agreement with experimental and other numerical results reported in literature. This indicates that these numerical methods are useful tools in rheological research.
Livres sur le sujet "Field’s elements and forces"
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Gifford, Clive. IScience : Elements, forces and explosive experiments ! London : Carlton Kids, 2015.
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Kříž, J. A. Elements of the nuclear binding energy. Brno, [Czech Republic] : J.A. Kriz, 1995.
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Cave, Jonathan A. K. Remarks on recent elements of drug policy. Santa Monica, CA : Rand, 1988.
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Fajans, Kasimir. Radioelements and isotopes : Chemical forces and optical properties of substances. Mineola, N.Y : Dover Publications, 2005.
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National Science Resources Center (U.S.). Experimenting with forces and motion : Student guide. Burlington, North Carolina : Carolina Biological Supply Company, 2012.
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Hix, William M. Elements of change in military medical force structure : A white paper. Santa Monica, CA (1700 Main St., Santa Monica 90406-2138) : Rand, 1992.
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United States. Dept. of Defense. Office of the Secretary of Defense., dir. Military compensation background papers : Compensation elements and related manpower cost items : their purposes and legislative backgrounds. 6e éd. [Washington, D.C.] : Dept. of Defense, Office of the Secretary of Defense, 2005.
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R, Morris Robert. Military compensation background papers : Compensation elements and related manpower cost items : their purposes and legislative backgrounds. 3e éd. [Washington] : Dept. of Defense, Office of the Secretary of Defense, 1987.
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R, Morris Robert. Military compensation background papers : Compensation elements and related manpower cost items : their purposes and legislative backgrounds. 5e éd. [Washington, D.C.] : Dept. of Defense, Office of the Secretary of Defense, 1996.
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R, Morris Robert. Military compensation background papers : Compensation elements and related manpower cost items : their purposes and legislative backgrounds. 4e éd. [Washington, D.C.?] : Dept. of Defense, Office of the Secretary of Defense, 1992.
Trouver le texte intégralChapitres de livres sur le sujet "Field’s elements and forces"
1
Schmitz, Wouter. « The Potential of a Field’s Elasticity ». Dans Particles, Fields and Forces, 37–43. Cham : Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-12878-4_5.
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Schmitz, Wouter. « The Potential of a Field’s Elasticity ». Dans Particles, Fields and Forces, 41–47. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-98753-4_5.
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Wellner, Marcel. « Magnetic Forces ». Dans Elements of Physics, 391–420. Boston, MA : Springer US, 1991. http://dx.doi.org/10.1007/978-1-4615-3860-8_18.
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Flores, Paulo. « Force Elements and Reaction Forces ». Dans Concepts and Formulations for Spatial Multibody Dynamics, 55–59. Cham : Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-16190-7_11.
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Maly, Ivan. « Forces that Shape the Cell ». Dans Quantitative Elements of General Biology, 99–142. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-79146-9_6.
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Dumont, N. A., et M. T. Monteiro de Carvalho. « The Hybrid Boundary Element Method for Problems Involving Body Forces ». Dans Boundary Elements XIII, 1015–26. Dordrecht : Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3696-9_81.
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Batty, Michael. « Defining Urban Science ». Dans Urban Informatics, 15–28. Singapore : Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-15-8983-6_3.
Texte intégralRésumé :
AbstractThis introductory chapter provides a brief overview of the theories and models that constitute what has come to be called urban science. Explaining and measuring the spatial structure of the city in terms of its form and function is one of the main goals of this science. It provides links between the way various theories about how the city is formed, in terms of its economy and social structure, and how these theories might be transformed into models that constitute the operational tools of urban informatics. First the idea of the city as a system is introduced, and then various models pertaining to the forces that determine what is located where in the city are presented. How these activities are linked to one another through flows and networks are then introduced. These models relate to formal models of spatial interaction, the distribution of the sizes of different cities, and the qualitative changes that take place as cities grow and evolve to different levels. Scaling is one of the major themes uniting these different elements grounding this science within the emerging field of complexity. We then illustrate how we might translate these ideas into operational models which are at the cutting edge of the new tools that are being developed in urban informatics, and which are elaborated in various chapters dealing with modeling and mobility throughout this book.
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Assis, André Koch Torres. « Forces of Ampère and Grassmann Between Current Elements ». Dans Weber’s Electrodynamics, 78–117. Dordrecht : Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-017-3670-1_4.
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Kaufmann, Walter. « Behaviour of Membrane Elements ». Dans Strength and Deformations of Structural Concrete Subjected to In-Plane Shear and Normal Forces, 65–94. Basel : Birkhäuser Basel, 1998. http://dx.doi.org/10.1007/978-3-0348-7612-4_5.
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Losev, A. « Hodge Strings and Elements of K. Saito’s Theory of Primitive Form ». Dans Topological Field Theory, Primitive Forms and Related Topics, 305–35. Boston, MA : Birkhäuser Boston, 1998. http://dx.doi.org/10.1007/978-1-4612-0705-4_11.
Texte intégralActes de conférences sur le sujet "Field’s elements and forces"
1
Matikainen, Marko K., et Aki M. Mikkola. « Improved Description of Elastic Forces for the Absolute Nodal Coordinate Based Plate Element ». Dans ASME 2005 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/detc2005-84592.
Texte intégralRésumé :
In this study, the improved description of elastic forces for the absolute nodal coordinate based plate element is introduced. The absolute nodal coordinate formulation, which utilizes global displacements and slope coordinates as nodal variables, can be used in large rotation and deformation dynamic analysis of beam and plate structures. The formulation avoids difficulties that arise when a rotation is interpolated in three-dimensional applications. In the absolute nodal coordinate formulation, a continuum mechanics approach has become the dominating procedure when elastic forces are defined. It has recently been perceived, however, that the continuum mechanics based absolute nodal coordinate elements suffer from serious shortcomings, including Poisson’s locking and poor convergence rate. These problems can be circumvented by modifying the displacement field of a finite element in the definition of elastic forces. This allows the use of the mixed type interpolation technique, leading to accurate and efficient finite element formulations. This approach has been previously applied to two- and three-dimensional absolute nodal coordinate based finite elements. In this study, the improved approach for elastic forces is extended to the absolute nodal coordinate plate element. The introduced plate element is compared in static examples to the continuum mechanics based absolute nodal coordinate plate element, as well as to commercial finite element software.
2
Huang, Yue, Kenneth E. Davis et Brent C. Houchens. « Flow Control Using Alternating Magnetic Fields During Crystal Growth From a Melt ». Dans ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-88373.
Texte intégralRésumé :
Flow control during bulk melt crystal growth is desirable for producing ternary alloy semiconductors with tunable lattice parameters and bandgap energy, providing custom materials for specific electro-optical applications. Segregation between constituent elements in the melt, be it through preferential rejection at the growth front or density variations, limits the growth rate and the uniformity in the crystal. External alternating magnetic fields are employed to stir the electrically conducting melt. While mixing is desired, turbulent flow is generally not. Precise control is required to maintain a laminar melt flow while providing sufficient mixing. Stirring via a rotating magnetic field (RMF) and a three-coil traveling magnetic field (TMF) is modeled and compared for a cylindrical melt confined in an ampule. The RMF imposes a body force in the azimuthal direction while the TMF induces primarily radial and axial body forces. The magnetic fields are effectively decoupled from the flow fields due to the small magnetic Reynolds number. Therefore, the magnetic fields are first determined using a finite element solver. The flows are then solved by a spectral element model of the Navier-Stokes equations including an electromagnetic body force term.
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Mavroidis, C., C. Pfeiffer, J. Celestino et Y. Bar-Cohen. « Design and Modeling of an Electro-Rheological Fluid Based Haptic Interface ». Dans ASME 2000 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/detc2000/mech-14121.
Texte intégralRésumé :
Abstract In this project, Rutgers University has teamed with the Jet Propulsion Laboratory (JPL) to pursue the development and demonstration of a novel haptic interfacing capability called MEMICA (remote MEchanical MIrroring using Controlled stiffness and Actuators). MEMICA is intended to provide human operators intuitive and interactive feeling of the stiffness and forces at remote or virtual sites in support of space, medical, underwater, virtual reality, military and field robots performing dexterous manipulation operations. The key aspect of the MEMICA system is a miniature Electrically Controlled Stiffness (ECS) element that mirrors the stiffness at remote/virtual sites. The ECS elements make use of Electro-Rheological Fluid (ERF), which is an Electro-Active Polymer (EAP), to achieve this feeling of stiffness. Forces applied at the robot end-effector due to a compliant environment will be reflected to the user by this ERF device where a change in the system viscosity will occur proportionally to the force to be transmitted. This paper describes the analytical modeling and experiments that are currently underway to develop an ERF based force feedback element.
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Schaarschmidt, David, et Holger Flederer. « Fatigue-resistant design of modular bridges made of precast concrete elements ». Dans 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.2022.1382.
Texte intégralRésumé :
<p>Modular construction with precast concrete has been becoming increasingly important for years. While the advantages of conventional precast construction have already been used for decades, modular structures go one step further due to the fact that no in-situ concrete or mortar is required. One way of transferring forces is to activate surface friction by post-tensioning. While shear bearing capacity is largely dependent on static friction, flexural capacity is linked to the decompression of dry joints. Two primary fields of application are bridge structures and wind turbines. Both groups of structures are stressed by non-static loads. In order to design them fatigue-resistant, an in-depth knowledge of this discontinuity zone is required. For this reason, experimental investigations, finite element analysis and probabilistic calculations were coupled in this study. The goal is a design proposal that allows the fatigue-proof design of dry joints.</p>
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El Wahed, Ali K., John L. Sproston et Graham K. Schleyer. « Electrorheological Fluids Applied to Impulsive Loads ». Dans ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0460.
Texte intégralRésumé :
Abstract This paper is concerned with an experimental determination of the dynamic performance of a prototype device employing an Electrorheological fluid for the rapid modification of the structural characteristics of fixing elements for use in offshore members subject to sudden explosive forces. The squeeze device has been built to incorporate an ER fluid sandwiched between two electrodes and which, upon sudden impact, is capable of absorbing the impulsive forces. The transient characteristics of the device were assessed under various mechanical force levels for DC excitation of the fluid in conjunction with a digital controller to provide a constant applied electrical field. Input and output force levels were monitored using a dedicated data acquisition system in conjunction with a PC enabling the dynamic response of the device to be determined using a combination of displacement, force, velocity and acceleration measurements.
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Gartrell, Jessica, et Deify Law. « Numerical Study on the Effect of Control Elements on Laminar Airflow Over a Flat Plate ». Dans ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-65767.
Texte intégralRésumé :
Boundary layer separation over a surface is an important phenomenon that has great implications on the aerodynamic performance of aircraft. The ability to control flow fields to improve performance and reduce drag is also important and driven by potential savings in fuel expenditures or expansion of the flight envelope. Drag reduction may be achieved by preventing or delaying laminar-to-turbulent transition from occurring over the surface or by inducing turbulence to create secondary flow motion that alters the flow field [1]. The present work is to perform CFD simulations in ANSYS FLUENT of flow velocity profiles with and without a single control element in laminar flow ranging from 2 cm/s to 8 cm/s on a 1 meter long flat plate in a two-dimensional (2D) space, respectively. The simulations without the control element on the flat plate were validated with the Blasius solution as well as compared with the flow velocity profiles produced by the control element on the flat plate. Additionally, the effects of multiple control elements on airflow over the flat plate were studied and compared with the cases with and without a control element on the flat plate. Furthermore, the effects of the flat plate’s angle of incidence at 3° on the drag forces of airflow on the flat plate with and without the control element at 2, 4, and 6 cm/s flow velocity will be investigated and compared numerically.
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Scott, Dan E., et Marc R. Skeem. « Diamond Enhanced Shear Cutting Elements on Roller Cone Bits ». Dans ASME 2001 Engineering Technology Conference on Energy. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/etce2001-17031.
Texte intégralRésumé :
Abstract Polycrystalline diamond (PCD) cutters and drag bit designs have been substantially improved since their 1972 introduction, and PCD drill bits now are approaching the rolling cone tungsten carbide insert (TCI) market is terms of revenue size and have surpassed it in terms of economic impact on the drilling industry.1,2 These performance improvements have lead to a significant encroachment into the drill bit market built upon the breakthrough invention of the rolling cone bit by Howard Hughes Sr. Material and design improvements in the last decade, however, have now led to the successful application of patented shear cutting PCD elements as well as conventional diamond enhanced crushing style inserts on rolling cone bits. Diamond enhanced rolling cone bits are also a growth market for diamond elements in drilling. Failing rock in shear is a more efficient process than by crushing, but most cutting materials can not stand up to the forces generated in the shearing process as rock strength increases. To take advantage of the unique ability of the PCD cutter to shear rock efficiently, a concerted R&D effort supported by laboratory and field-testing led to the application of diamond as a shear cutting element on roller cone bits. A variety of rolling cone shear cutting elements have been developed and successfully commercialized in the last decade. This paper will discuss laboratory results and increased field performance achieved relative to conventional crushing style diamond and tungsten carbide inserts. The authors will document through case studies increases in rate of penetration (ROP), footage, overall durability, and gauge holding ability in addition to bearing/seal effectiveness that have further reduced drilling costs and served to increase usage of polycrystalline diamond elements on roller cone bits. These applications range from such diverse markets as high cost offshore North Sea, to low cost North American land operations.
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Joo, Heon, et John P. Swensen. « Design and Experimentation of a Tunably-Compliant Robotic Finger Using Low Melting Point Metals ». Dans ASME 2016 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/smasis2016-9147.
Texte intégralRésumé :
In this paper, we describe the fabrication and testing of a tunably-compliant tendon-driven finger implemented through the geometric design of a skeleton made of the low-melting point Field’s metal encased in a silicone rubber. The initial prototype consists of a skeleton comprised of two rods of the metal, with heating elements in thermal contact with the metal at various points along its length, embedded in an elastomer. The inputs to the systems are both the force exerted on the tendon to bend the finger and the heat introduced to liquefy the metal locally or globally along the length of the finger. Selective localized heating allows multiple joints to be created along the length of the finger. Fabrication was accomplished via a multiple step process of elastomer casting and liquid metal casting. Heating elements such as power resistors or Ni-Cr wire with electric connections were added as an intermediate step before the final elastomer casting. The addition of a tradition tendon actuation was inserted after all casting steps had been completed. While preliminary, this combination of selective heating and engineered geometry of the low-melting point skeletal structure will allow for further investigation into the skeletal geometry and its effects on local and global changes in device stiffness.
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Kim, M. C., C. S. Lee et C. J. Kim. « Analysis of Volumetric Residence Time of Blood Elements in Stenosed Arteries ». Dans ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-42840.
Texte intégralRésumé :
Blood flow in arteries is known to be closely related to atherosclerosis. Presence of recirculation zones, and low, high, and oscillatory wall shear stresses have been suggested to be important fluid dynamic factors causing development and progress of atherosclerosis. Our study was motivated to develop fluid mechanical indices between residence time of blood particles in arteries and atherosclerosis. In rigid models of stenosed arteries with 75% area reduction, trajectories of blood particles were numerically computed and used to determine local volumetric residence time (VRT) of platelets. The motion of particles in the model artery was computed by considering viscous drag forces between blood particles and presolved transient flow field from computational fluid dynamics (CFD). Many cardiac cycles were considered in the computation to reflect temporally accumulative characteristics of VRT in the recirculation zones. Our results showed that VRT in the recirculation zone was relatively low in the first cardiac cycle. However it increased in the subsequent cycles as more particles were trapped in the same zone. The results suggested that VRT contour calculated in the present study would be an effective indicator of the presence of atherosclerosis.
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Sabir, A. B., et G. T. Davies. « Vibration and Buckling of Square Plates Containing Central Holes ». Dans ASME 1997 Turbo Asia Conference. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/97-aa-096.
Texte intégralRésumé :
The finite element method is used to determine the natural frequencies of flat square plates containing centrally located circular or square holes. The plates are subjected to either inplane uniaxial, biaxial or uniformly distributed shear along the four outer edges. These edges are either simply supported or clamped. To determine the stiffness and mass matrices, non conforming rectangular and triangular displacement elements are used to model the out of plane behaviour of the plate. The inplane stress distribution within the plates, which are required in the analysis are determined by using inplane finite elements having displacement fields based on assumed strains. These satisfy the exact requirements of strain free rigid body modes of displacements. The natural frequencies of simply supported and clamped plates are initially determined when no inplane loads are applied. This showed the influence of the size of the hole on the natural circular frequency. These plates were then subjected to inplane loads and the effect of these forces on the natural frequencies are given. The results show the natural frequencies of square plates with central circular holes decrease with increasing compressive forces, and that the frequencies become zero when the compressive forces are equal to the elastic buckling loads of the plates. By repeating this process for all boundary conditions and applied loads a comprehensive set of results is obtained for the buckling and vibrational properties of square plates containing centrally located holes.
Rapports d'organisations sur le sujet "Field’s elements and forces"
1
Call, Christopher D. US Army Special Forces Operational Interoperability with the US Army's Objective Force - The Future of Special Forces Liaison and Coordination Elements. Fort Belvoir, VA : Defense Technical Information Center, mai 2003. http://dx.doi.org/10.21236/ada415849.
Texte intégral
2
Kenan, Michel. Distribution of Lateral Forces on Reinforced Masonry Bracing Elements Considering Inelastic Material Behavior - Deformation-Based Matrix Method-. Technische Universität Dresden, juin 2021. http://dx.doi.org/10.25368/2021.2.
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Knight, R. D., et B. A. Kjarsgaard. Comparative pXRF and Lab ICP-ES/MS methods for mineral resource assessment, Northwest Territories. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/331239.
Texte intégralRésumé :
The Geological Survey of Canada undertook a mineral resource assessment for a proposed national park in northern Canada (~ 33,500 km2) spanning the transition from boreal forest to barren lands tundra. Bedrock geology of this region is complex and includes the Archean Slave Craton, the Archean and Paleoproterozoic Rae domain of the Churchill Province, the Paleoproterozoic Thelon and Taltson magmatic-tectonic zones, and the Paleoproterozoic East Arm sedimentary basin. The area has variable mineral potential for lode gold, kimberlite-hosted diamonds, VMS, vein uranium and copper, SEDEX, as well as other deposit types. A comparison of analytical methods was carried out after processing the field collected samples to acquire both the &lt; 2 mm and for the &lt; 0.063 mm size fractions for 241 surficial sediment (till) samples, collected using a 10 x 10 km grid. Analytical methods comprised: 1) aqua regia followed by ICP-MS analysis, 2) 4-acid hot dissolution followed by ICP-ES/MS analysis, 3) lithium metaborate/tetraborate fusion methods followed by ICP-ES for major elements and ICP-MS for trace elements and, 4) portable XRF on dried, non-sieved sediment samples subjected to a granular segregation processing technique (to produce a clay-silt proxy) for seventeen elements (Ba, Ca, Cr, Cu, Fe, K, Mn, Ni, Pb, Rb, Sr, Th, Ti, U, V, Zn, and Zr) Results indicate that pXRF data do not replicate exactly the laboratory 4-acid and fusion data (in terms of precision and accuracy), but the relationship between the datasets is systematic as displayed in x-y scattergrams. Interpolated single element plots indicate that till samples with anomalies of high and low pXRF concentration levels are synonymous with high and low laboratory-based analytical concentration levels, respectively. The pXRF interpolations thus illustrate the regional geochemical trends, and most importantly, the significant geochemical anomalies in the surficial samples. These results indicate that pXRF spectrometry for a subset of elements is comparable to traditional laboratory methods. pXRF spectrometry also provides the benefit of rapid analysis and data acquisition that has a direct influence on real time sampling designs. This information facilitates efficient and cost-effective field projects (i.e. where used to identify regions of interest for high density sampling), and to prioritize samples to be analyzed using traditional geochemical methods. These tactics should increase the efficiency and success of a mineral exploration and/or environmental sampling programs.
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Manor, M. J., et S. J. Piercey. Whole-rock lithogeochemistry, Nd-Hf isotopes, and in situ zircon geochemistry of VMS-related felsic rocks, Finlayson Lake VMS district, Yukon. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328992.
Texte intégralRésumé :
The Finlayson Lake district in southeastern Yukon is composed of a Late Paleozoic arc-backarc system that consists of metamorphosed volcanic, plutonic, and sedimentary rocks of the Yukon-Tanana and Slide Mountain terranes. These rocks host &gt;40 Mt of polymetallic resources in numerous occurrences and styles of volcanogenic massive sulphide (VMS) mineralization. Geochemical and isotopic data from these rocks support previous interpretations that volcanism and plutonism occurred in arc-marginal arc (e.g., Fire Lake formation) and continental back-arc basin environments (e.g., Kudz Ze Kayah formation, Wind Lake formation, and Wolverine Lake group) where felsic magmatism formed from varying mixtures of crust- and mantle-derived material. The rocks have elevated high field strength element (HFSE) and rare earth element (REE) concentrations, and evolved to chondritic isotopic signatures, in VMS-proximal stratigraphy relative to VMS-barren assemblages. These geochemical features reflect the petrogenetic conditions that generated felsic rocks and likely played a role in the localization of VMS mineralization in the district. Preliminary in situ zircon chemistry supports these arguments with Th/U and Hf isotopic fingerprinting, where it is interpreted that the VMS-bearing lithofacies formed via crustal melting and mixing with increased juvenile, mafic magmatism; rocks that were less prospective have predominantly crustal signatures. These observations are consistent with the formation of VMS-related felsic rocks by basaltic underplating, crustal melting, and basalt-crustal melt mixing within an extensional setting. This work offers a unique perspective on magmatic petrogenesis that underscores the importance of integrating whole-rock with mineral-scale geochemistry in the characterization of VMS-related stratigraphy.
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Roesler, Jeffery, Roberto Montemayor, John DeSantis et Prakhar Gupta. Evaluation of Premature Cracking in Urban Concrete Pavement. Illinois Center for Transportation, janvier 2021. http://dx.doi.org/10.36501/0197-9191/21-001.
Texte intégralRésumé :
This study investigated the causes for premature, transverse cracking on urban jointed plain concrete pavements in Illinois. A field survey of 67 sections throughout Illinois coupled with ultrasonic evaluation was completed to synthesize the extent of premature cracking on urban JPCP. The visual survey showed some transverse and longitudinal cracks were a result of improper slab geometry (excessive slab length and width). Ultrasonic tests over the contraction joints determined some notched joints had not activated and adjacent transverse cracks were likely formed as a result. Three-dimensional finite-element analyses confirmed that cracking would not develop as a result of normal environmental factors and slab-base frictional restraint. The concrete mixture also did not appear to be a contributing factor to the premature cracks. Finally, the lack of lubrication on dowel bars was determined to potentially be a primary mechanism that could restrain the transverse contraction joints, produce excessive tensile stresses in the slab, and cause premature transverse cracks to develop.
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Hunt, Charles T., et Shannon Zimmerman. Counter-Terrorism & ; Peace Operations : The Impacts of UN Security Council Approaches to Tackling Terror on the Pursuit of Peace. RESOLVE Network, juillet 2022. http://dx.doi.org/10.37805/sfi2022.2.
Texte intégralRésumé :
United Nations peace operations are generally considered a poor vehicle for counter-terrorism. Yet, UN peace operations are regularly deployed by the Security Council to settings affected by terrorism and violent extremism. The confluence of terrorism and conflict make this co-existence inevitable, but some missions have also engaged more directly in countering these elements. For example, the UNSC continues to support the mission in Somalia, which actively faces terrorist threats, and has also deployed a peacekeeping mission to Mali amid a jihadist insurgency. At the same time, in places like the Democratic Republic of Congo, peace operations have engaged in offensive military operations that target groups labelled as “terrorists” by their host government partners. Academics and peacekeeping experts have raised concerns and noted the initial impacts of counter-terrorism efforts on UN peace operations. Building on this work, this brief draws on illustrative examples from the field to examine how the UNSC’s counter-terrorism framework has impacted the mandates and practice of the UN’s peace operations, particularly the large stabilization operations deployed in Africa. It shows that counter-terrorism efforts at the level of the UNSC have blurred the normative distinctions between peace operations and counter-terrorism to the detriment of the former. This brief concludes by providing recommendations to ensure that UNSC responses to terrorism and violent extremism do not unintentionally undermine the effectiveness of UN peace operations.
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Wozniakowska, P., D. W. Eaton, C. Deblonde, A. Mort et O. H. Ardakani. Identification of regional structural corridors in the Montney play using trend surface analysis combined with geophysical imaging, British Columbia and Alberta. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328850.
Texte intégralRésumé :
The Western Canada Sedimentary Basin (WCSB) is a mature oil and gas basin with an extraordinary endowment of publicly accessible data. It contains structural elements of varying age, expressed as folding, faulting, and fracturing, which provide a record of tectonic activity during basin evolution. Knowledge of the structural architecture of the basin is crucial to understand its tectonic evolution; it also provides essential input for a range of geoscientific studies, including hydrogeology, geomechanics, and seismic risk analysis. This study focuses on an area defined by the subsurface extent of the Triassic Montney Formation, a region of the WCSB straddling the border between Alberta and British Columbia, and covering an area of approximately 130,000 km2. In terms of regional structural elements, this area is roughly bisected by the east-west trending Dawson Creek Graben Complex (DCGC), which initially formed in the Late Carboniferous, and is bordered to the southwest by the Late Cretaceous - Paleocene Rocky Mountain thrust and fold belt (TFB). The structural geology of this region has been extensively studied, but structural elements compiled from previous studies exhibit inconsistencies arising from distinct subregions of investigation in previous studies, differences in the interpreted locations of faults, and inconsistent terminology. Moreover, in cases where faults are mapped based on unpublished proprietary data, many existing interpretations suffer from a lack of reproducibility. In this study, publicly accessible data - formation tops derived from well logs, LITHOPROBE seismic profiles and regional potential-field grids, are used to delineate regional structural elements. Where seismic profiles cross key structural features, these features are generally expressed as multi-stranded or en echelon faults and structurally-linked folds, rather than discrete faults. Furthermore, even in areas of relatively tight well control, individual fault structures cannot be discerned in a robust manner, because the spatial sampling is insufficient to resolve fault strands. We have therefore adopted a structural-corridor approach, where structural corridors are defined as laterally continuous trends, identified using geological trend surface analysis supported by geophysical data, that contain co-genetic faults and folds. Such structural trends have been documented in laboratory models of basement-involved faults and some types of structural corridors have been described as flower structures. The distinction between discrete faults and structural corridors is particularly important for induced seismicity risk analysis, as the hazard posed by a single large structure differs from the hazard presented by a corridor of smaller pre-existing faults. We have implemented a workflow that uses trend surface analysis based on formation tops, with extensive quality control, combined with validation using available geophysical data. Seven formations are considered, from the Late Cretaceous Basal Fish Scale Zone (BFSZ) to the Wabamun Group. This approach helped to resolve the problem of limited spatial extent of available seismic data and provided a broader spatial coverage, enabling the investigation of structural trends throughout the entirety of the Montney play. In total, we identified 34 major structural corridors and number of smaller-scale structures, for which a GIS shapefile is included as a digital supplement to facilitate use of these features in other studies. Our study also outlines two buried regional foreland lobes of the Rocky Mountain TFB, both north and south of the DCGC.
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Pullammanappallil, Pratap, Haim Kalman et Jennifer Curtis. Investigation of particulate flow behavior in a continuous, high solids, leach-bed biogasification system. United States Department of Agriculture, janvier 2015. http://dx.doi.org/10.32747/2015.7600038.bard.
Texte intégralRésumé :
Recent concerns regarding global warming and energy security have accelerated research and developmental efforts to produce biofuels from agricultural and forestry residues, and energy crops. Anaerobic digestion is a promising process for producing biogas-biofuel from biomass feedstocks. However, there is a need for new reactor designs and operating considerations to process fibrous biomass feedstocks. In this research project, the multiphase flow behavior of biomass particles was investigated. The objective was accomplished through both simulation and experimentation. The simulations included both particle-level and bulk flow simulations. Successful computational fluid dynamics (CFD) simulation of multiphase flow in the digester is dependent on the accuracy of constitutive models which describe (1) the particle phase stress due to particle interactions, (2) the particle phase dissipation due to inelastic interactions between particles and (3) the drag force between the fibres and the digester fluid. Discrete Element Method (DEM) simulations of Homogeneous Cooling Systems (HCS) were used to develop a particle phase dissipation rate model for non-spherical particle systems that was incorporated in a two-fluid CFDmultiphase flow model framework. Two types of frictionless, elongated particle models were compared in the HCS simulations: glued-sphere and true cylinder. A new model for drag for elongated fibres was developed which depends on Reynolds number, solids fraction, and fibre aspect ratio. Schulze shear test results could be used to calibrate particle-particle friction for DEM simulations. Several experimental measurements were taken for biomass particles like olive pulp, orange peels, wheat straw, semolina, and wheat grains. Using a compression tester, the breakage force, breakage energy, yield force, elastic stiffness and Young’s modulus were measured. Measurements were made in a shear tester to determine unconfined yield stress, major principal stress, effective angle of internal friction and internal friction angle. A liquid fludized bed system was used to determine critical velocity of fluidization for these materials. Transport measurements for pneumatic conveying were also assessed. Anaerobic digestion experiments were conducted using orange peel waste, olive pulp and wheat straw. Orange peel waste and olive pulp could be anaerobically digested to produce high methane yields. Wheat straw was not digestible. In a packed bed reactor, anaerobic digestion was not initiated above bulk densities of 100 kg/m³ for peel waste and 75 kg/m³ for olive pulp. Interestingly, after the digestion has been initiated and balanced methanogenesis established, the decomposing biomass could be packed to higher densities and successfully digested. These observations provided useful insights for high throughput reactor designs. Another outcome from this project was the development of low cost devices to measure methane content of biogas for off-line (US$37), field (US$50), and online (US$107) applications.
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Megersa, Kelbesa. Effectiveness and Value for Money of Technical Assistance Approaches : In-house vs Contracting. Institute of Development Studies, juillet 2022. http://dx.doi.org/10.19088/k4d.2022.135.
Texte intégralRésumé :
In the development field, technical assistance (TA) broadly refers to support for a specific project or country programme in the form of technical advice, research and data sharing, and skills training, among other activities. As a result, TA may be more valuable as a development tool than the amount of funding received. The primary areas of focus for TA include developing a project pipeline, de-risking investments, and assisting TA beneficiaries in their efforts to improve business standards, as well as supporting policy reforms by developing country. Because TA recipients may face a variety of issues, effective TA programmes can take many forms. TA programmes must be established to address beneficiaries’ primary concerns. The goal for both TA recipients and donors should be to determine the main objective of the TA and to select from a variety of technical adviser, taking into account the limitations and enabling conditions for each approach (Nastase et al., 2020). Some useful principles (or good practices) when designing and implementing TA (through in-house or external contracting) include: • Importance of local ownership: • Partnerships and inclusivity: • Effectiveness: • Value-for-money (VFM): TA can be delivered in-house or by contracting out TA to other firms or suppliers. However, each approach has certain merits (VFM and other factors) and shortcomings. There is a very limited evidence base regarding an explicit discussion of the merits of in-house vs commissioned TA programming. Much of the available evidence simply describes TA programme elements – rather than the VFM behind business cases for in-house or contracted TA design and delivery.
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Barajas, Jesus, Lindsay Braun, Amanda Merck, Bob Dean, Paul Esling et Heidy Persaud. The State of Practice in Community Impact Assessment. Illinois Center for Transportation, août 2022. http://dx.doi.org/10.36501/0197-9191/22-011.
Texte intégralRésumé :
The objective of this research was to provide recommendations to the Illinois Department of Transportation for updating and revising the “Community Impact Assessment Manual” in accordance with the latest research and practice. The guide incorporated findings from a literature review, a scan of state department of transportation (DOT) community impact assessment (CIA) guidance and manuals, a survey of practitioners from state DOTs involved in CIA, and a series of interviews with those same practitioners to recommend process updates. According to the Federal Highway Administration, community impact assessment can be defined as “an iterative process to evaluate the effects of a transportation action on a community and its quality of life,” which includes elements of health, safety, air quality, connectivity and access, and equity. Six states had publicly available CIA guidance. While all manuals provided basic guidance, some were more detailed in prescribing analytical methods for different types of impacts or provided more structure for conducting the analysis, such as report templates, technical memos, interactive screening tools, field visit checklists, and community context audit forms. According to surveys and interviews with state DOT practitioners, DOTs varied in how or whether they conducted CIA, whether they screened for the need for CIA in advance of conducting it, and what factors they consider when conducting them. A few DOTs had innovative practices with respect to CIA, such as mapping tools, an equity and health assessment, and robust community engagement. The CIA guidance produced as a component to this project constitutes the state of the art in practice, including quantitative and qualitative analytical methods for screening and methods for conducting and documenting CIA. The guidance also emphasizes equity in the assessment process.