Letteratura scientifica selezionata sul tema "Force feasible set"
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Articoli di riviste sul tema "Force feasible set"
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Rezzoug, Nasser, Vincent Hernandez e Philippe Gorce. "Upper-Limb Isometric Force Feasible Set: Evaluation of Joint Torque-Based Models". Biomechanics 1, n. 1 (18 aprile 2021): 102–17. http://dx.doi.org/10.3390/biomechanics1010008.
Testo completoAbstract (sommario):
A force capacity evaluation for a given posture may provide better understanding of human motor abilities for applications in sport sciences, rehabilitation and ergonomics. From data on posture and maximum isometric joint torques, the upper-limb force feasible set of the hand was predicted by four models called force ellipsoid, scaled force ellipsoid, force polytope and scaled force polytope, which were compared with a measured force polytope. The volume, shape and force prediction errors were assessed. The scaled ellipsoid underestimated the maximal mean force, and the scaled polytope overestimated it. The scaled force ellipsoid underestimated the volume of the measured force distribution, whereas that of the scaled polytope was not significantly different from the measured distribution but exhibited larger variability. All the models characterized well the elongated shape of the measured force distribution. The angles between the main axes of the modelled ellipsoids and polytopes and that of the measured polytope were compared. The values ranged from 7.3° to 14.3°. Over the entire surface of the force ellipsoid, 39.7% of the points had prediction errors less than 50 N; 33.6% had errors between 50 and 100 N; and 26.8% had errors greater than 100 N. For the force polytope, the percentages were 56.2%, 28.3% and 15.4%, respectively.
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Rezzoug, Nasser, Xuguang Wang, Vincent Hernandez e Philippe Gorce. "Maximal isometric force exertion predicted by the force feasible set formalism: application to handbraking". Ergonomics 62, n. 12 (9 settembre 2019): 1551–62. http://dx.doi.org/10.1080/00140139.2019.1660418.
Testo completo
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Boumann, Roland, e Tobias Bruckmann. "Real-Time Cable Force Calculation beyond the Wrench-Feasible Workspace". Robotics 9, n. 2 (27 maggio 2020): 41. http://dx.doi.org/10.3390/robotics9020041.
Testo completoAbstract (sommario):
Under special circumstances, a cable-driven parallel robot (CDPR) may leave its wrench-feasible-workspace. Standard approaches for the computation of set-point cable forces are likely to fail in this case. The novel nearest corner method for calculating appropriate cable forces when the CDPR is outside of its wrench-feasible-workspace was introduced in former work of the authors. The obtained cable force distributions aim at continuity and generate wrenches close to the desired values. The method employs geometrical operations in the cable force space and promises real-time usability because of its non-iterative structure. In a simplified simulation, a cable break scenario was used to carry out more detailed testing of the method regarding different parameters, a higher number of cables, and the numerical efficiency. A brief discussion about the continuity of the method when entering the wrench-feasible-workspace is presented.
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Hernandez, Vincent, Nasser Rezzoug, Philippe Gorce e Gentiane Venture. "Force feasible set prediction with artificial neural network and musculoskeletal model". Computer Methods in Biomechanics and Biomedical Engineering 21, n. 14 (26 ottobre 2018): 740–49. http://dx.doi.org/10.1080/10255842.2018.1516763.
Testo completo
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Hernandez, Vincent, Gentiane Venture, Nasser Rezzoug e Philippe Gorce. "Improving the upper-limb force feasible set evaluation by muscles maximal isometric force identification and cocontraction factors". Journal of Biomechanics 57 (maggio 2017): 131–35. http://dx.doi.org/10.1016/j.jbiomech.2017.03.021.
Testo completo
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Hernandez, Vincent, Philippe Gorce e Nasser Rezzoug. "Evaluation and validation of musculoskeletal force feasible set indices: Application to manual wheelchair propulsion". Journal of Biomechanics 68 (febbraio 2018): 70–77. http://dx.doi.org/10.1016/j.jbiomech.2017.12.012.
Testo completo
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Hao, Jian Ming, e Kai Fa Zhou. "The Closure Scheme Optimization Analysis of Multiple Large-Span Prestressed Continuous Beam Bridges". Applied Mechanics and Materials 178-181 (maggio 2012): 2240–45. http://dx.doi.org/10.4028/www.scientific.net/amm.178-181.2240.
Testo completoAbstract (sommario):
It is critical to choose a reasonable closure scheme for the construction or post- construction state of multiple large-span prestressed continuous beam bridges. The feasible closure schemes were analyzed and evaluated. The optimum closure scheme analysis method was proposed. Take Wei river bridge for instance, by deformation, internal force and stress comparison, and construction roubustness analysis, the optimum closure scheme is set down to ensure the girder close smoothly with reasonable internal force.
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Carrión, Elena Ángela, Pedro Ignacio Saez, Juan Carlos Pomares e Antonio Gonzalez. "Average Force of Deployment and Maximum Arrest Force of Energy Absorbers Lanyards". International Journal of Environmental Research and Public Health 17, n. 20 (20 ottobre 2020): 7647. http://dx.doi.org/10.3390/ijerph17207647.
Testo completoAbstract (sommario):
Energy-absorbing lanyards (EAL) are part of fall arrest systems (FAS), their main mission is to dissipate the energy generated during the fall, ensuring that the arresting force does not cause injury to the user. For the design of FAS as set out in the American standard Z359.6 and the Canadian Z259.16 it is essential to know the deployment force or average arrest force (Fa). Fa is necessary to estimate the elongation that the absorber will suffer during the fall and therefore essential data to calculate the clearance distance. There is a lack of useful experimental data for the design of this personal protective equipment (PPE). This work provides empirical data required for the design of FAS with EAL in accordance with EN 355. This paper covers different types of EAL that are marketed internationally; different empirical data, average and maximum forces, required for improving safety design are researched. Six manufacturers, 10 models, and 2 samples of each model were selected, with total of 20 tests being performed. Dynamic performance tests were carried out, the free fall of a person was simulated using a 100 kg steel ballast from the maximum height allowed by the equipment, obtaining the maximum arrest force (Fm), average deployment force (Fa), and, by calculating the balance of forces, the maximum and average acceleration suffered by the ballast during its arrest. In light of the results, relevant conclusions for user safety are obtained. It is feasible to raise the safety requirements established by the different standards. The Fm can be established below 6 kN in the EAL, and the Fa can be estimated at 87.5% of the Fm. The categorization of the force–time curve in fall arrest with EAL has been obtained. Two EAL purchased on the market exceed the Fm permitted, therefore it is recommended to increase the quality controls of EAL.
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Toutoungi, D. E., A. B. Zavatsky e J. J. O'Connor. "Parameter sensitivity of a mathematical model of the anterior cruciate ligament". Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 211, n. 3 (1 marzo 1997): 235–46. http://dx.doi.org/10.1243/0954411971534340.
Testo completoAbstract (sommario):
This paper presents the results of an investigation into parameter sensitivity of a mathematical model of the human anterior cruciate ligament (ACL). The model ACL comprised a continuous array of fibres mapped between part-elliptical attachment areas on the femur and tibia. Relative motion of the two bones was controlled by a planar four-bar linkage. Parameter modifications were: (a) an alternative set of values for the coordinates of the four-bar linkage joints; (b) rotation of the attachment areas of the ligament by ±30°; and (c) variation of some mechanical properties. The alternative four-bar linkage parameter set produced extremely large changes in ACL force values, up to 130 per cent. Rotating the tibial attachment changed forces by less than 20 per cent, whereas rotating the femoral attachment changed forces by up to 100 per cent. Altering the mechanical parameters produced the smallest differences in force, under 15 per cent. These results highlight the importance, when using a theoretical model, of establishing the values of the parameters defining the model as accurately as possible and of carrying out a parameter sensitivity study. From a clinical viewpoint, they also suggest that, when reconstructing a ruptured ACL, one of the most important considerations must be to position the femoral attachment of the graft as accurately as is feasible.
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Kerk, Carter J., e Don B. Chaffin. "Evaluation of Limiting Strength Constraints in a Comprehensive Biomechanical Model". Proceedings of the Human Factors and Ergonomics Society Annual Meeting 37, n. 10 (ottobre 1993): 739–43. http://dx.doi.org/10.1177/154193129303701020.
Testo completoAbstract (sommario):
The strength constraints in a two-dimensional static human force exertion capability model (HFEC) have been evaluated using eight male and female subjects of varying anthropometry and strength capability. The model comprehensively estimates feasible exertion capability under symmetric conditions using a set of fifteen linear constraint equations from three constraint classes: strength, stability, and coefficient of friction (COF). This evaluation examines the nature of the limiting strength constraints. The computer model aided in designing tasks (combining posture with force exertion direction) that isolated upper extremity strength constraints and hip/torso strength constraints from stability and COF constraints. Subject performances of maximum exertions were recorded using force platforms and a multi-axis load cell to record external reaction forces at the hands and feet. Body posture was recorded with a 2D motion analysis system. The observed hand force exertions were compared to the exertions predicted by the model. The identity of the limiting constraints was well predicted by the model. The location of the constraints was logical and predictable. The results are discussed in the context of other modeling approaches as well as implications for future research. The HFEC approach shows excellent potential as an ergonomic engineering tool for teaching, evaluation, and design.
Tesi sul tema "Force feasible set"
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Riechel, Andrew T. "Force-Feasible Workspace Analysis and Motor Mount Disturbance Compensation for Point-Mass Cable Robots". Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5243.
Testo completoAbstract (sommario):
Cable-actuated manipulators (or 'cable robots') constitute a relatively new classification of robots which use motors, located at fixed remote locations, to manipulate an end-effector by extending or retracting cables. These manipulators possess a number of unique properties which make them proficient with tasks involving high payloads, large workspaces, and dangerous or contaminated environments. However, a number of challenges exist which have limited the mainstream emergence of cable robots. This thesis addresses two of the most important of these issues-- workspace analysis and disturbance compensation.
Workspace issues are particularly important, as many large-scale applications require the end-effector to operate in regions of a particular shape, and to exert certain minimum forces throughout those regions. The 'Force-Feasible Workspace' represents the set of end-effector positions, for a given robot design, for which the robot can exert a set of required forces on its environment. This can be considered as the robot's 'usable' workspace, and an analysis of this workspace shape for point-mass cable robots is therefore presented to facilitate optimal cable robot design. Numerical simulation results are also presented to validate the analytical results, and to aid visualization of certain complex workspace shapes.
Some cable robot applications may require mounting motors to moving bases (i.e. mobile robots) or other surfaces which are subject to disturbances (i.e. helicopters or crane arms). Such disturbances can propagate to the end-effector and cause undesired motion, so the rejection of motor mount disturbances is also of interest. This thesis presents a strategy for measuring these disturbances and compensating for them. General approaches and implementation issues are explored qualitatively with a simple one-degree-of-freedom prototype (including a strategy for mitigating accelerometer drift), and quantitative simulation results are presented as a proof of concept.
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Laisné, Gautier. "Capacités de force du membre supérieur : fondements théoriques et reconstruction de modèles musculosquelettiques". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0483.
Testo completoAbstract (sommario):
En interaction physique Humain-Robot, un robot et un individu effectuent une tâche de collaboration par le biais d'un contact physique, par exemple entre l'effecteur terminal du robot et la main de l'humain. Une attention nécessaire se porte alors sur la sécurité de cette collaboration. Afin que le robot puisse fournir une assistance adaptée, il est primordial de caractériser les limites d'un individu, notamment celles biomécaniques. Les capacités de force du membre supérieur humain correspondent à l'ensemble des efforts qu'il peut exercer au niveau de la main, dans une posture spécifique. La forme de ces ensembles reflète des propriétés individuelles, telles que l'anthropométrie et la force musculaire. De plus, leur surface caractérise les efforts maximaux possibles. Par conséquent, la connaissance des capacités de force d'un individu permet d'aiguiller l'assistance du robot afin de respecter les limites en force de l'humain.Expérimentalement, les capacités de force sont difficiles à mesurer directement. Néanmoins, en conditions isométriques, elles peuvent être décrites partiellement en mesurant des efforts maximaux dans des directions spécifiées. In silico, les modèles musculosquelettiques représentent mathématiquement le squelette, les articulations et les muscles. Ils permettent de simuler les capacités de force dans diverses postures, construites par le biais d'opérations géométriques (somme de Minkowski, projection, intersection) sur des ensembles convexes. Cependant, ces opérations sont coûteuses en temps de calcul. Cette thèse se concentre donc en premier lieu sur une nouvelle approche réduisant le temps de calcul de l'une de ces opérations.Par ailleurs, la modélisation des capacités de force nécessite de faire des hypothèses sur la façon dont les tensions musculaires contribuent aux couples articulaires. Ces hypothèses influencent la forme des capacités de force, notamment leur représentation sous forme de polytope ou d'ellipsoïde. Cette thèse propose donc une unification de ces représentations afin de considérer, de manière géométrique, diverses hypothèses biomécaniques sur les relations entre tensions musculaires. Bien que l'utilisation de modèles musculosquelettiques complexes et détaillés limite la simulation des capacités de force, ce cadre théorique met en évidence une forme universelle pour la représentation des capacités de force d'un individu.Également, une représentation précise des capacités de force d'un individu nécessite la connaissance d'un modèle musculosquelettique personnalisé. Compte tenu de l'approche ensembliste des capacités de force, cette thèse propose une analyse de sensibilité adaptée évaluant l'influence des paramètres musculaires sur les propriétés géométriques des capacités de force. Cette analyse met également en évidence les défis de la personnalisation en regard de l'inter-variabilité entre individus.Enfin, un protocole expérimental a été établi afin de confronter les méthodes de personnalisation in silico à des forces maximales isométriques mesurées dans différentes postures du membre supérieur. La représentation des capacités de force sous forme d'ellipsoïdes, moins coûteuse en temps de calcul, et l'ajout d'hypothèses biomécaniques sur le comportement musculaire amènent à la personnalisation des muscles d'un modèle musculosquelettique, validant in vivo les résultats théoriques proposés dans cette thèseIn physical Human-Robot Interaction, where robots and humans collaborate on shared tasks through physical contact, such as between the robot's end effector and the human's hand, human safety is a primary concern. This necessitates that the collaborative system inherently consider human characteristics to provide appropriate and safe robotic assistance. To achieve this, it is necessary to evaluate the capabilities of the human upper-limb. In biomechanics, these capabilities are defined through force feasible sets at the hand, which represent all the forces a human operator can exert in a given posture. These three-dimensional sets are influenced by individual factors such as anthropometry and muscle strength and the surface of these sets represents the maximum force capabilities of the human upper-limb in all directions. Therefore, force feasible sets are an invaluable tool for guiding robotic assistance, ensuring it respects biomechanical constraints by remaining within the human's exertable force limits.Force feasible sets are challenging to measure directly but can be partially represented in isometric conditions by measuring maximum exerted forces. Musculoskeletal models, which mathematically represent the human skeleton, joints, and muscles, allow for in silico representation of force feasible sets in various postures through geometric operations (Minkowski sum, projection, intersection) on convex sets. However, these operations are computationally expensive. This thesis first focuses on a novel approach to reduce the computational time of one of the most demanding tasks within this framework.Furthermore, existing in silico models often employ various geometric assumptions about how muscle tensions contribute to joint torques, leading to different characterizations of force feasible sets' shapes, including 3D polytopes and ellipsoids. This thesis proposes a unified framework to represent force feasible sets that explicitly incorporates these geometric assumptions. This framework addresses the limitations of current numerical simulations, which struggle to analyze complex scenarios involving more detailed representation of musculoskeletal models and inherently higher computational costs.In this regard, accurate representation of individual force capabilities requires precise parameterization of musculoskeletal model components. Given the set-theoretic nature of force feasible sets, this thesis introduces an adapted sensitivity analysis tailored to assess the influence of parameters on the geometric properties of force feasible sets. This analysis also highlights the challenges of personalizing musculoskeletal models due to biomechanical inter-variability.Finally, an experimental protocol was established to confront in silico personalization processes with experimentally measured maximal isometric force exertions collected across various postures. Through biomechanical assumptions leading to a computationally less expensive representation of force feasible sets as ellipsoids, muscle parameters personalization is achieved, validating in vivo the theoretically-driven results of this thesis
Libri sul tema "Force feasible set"
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Dilloway, James. From Cold War to Chaos? Praeger, 1999. http://dx.doi.org/10.5040/9798216968832.
Testo completoAbstract (sommario):
This challenging science-based book reviews today's global situation as well as our long evolution to humanness. It uncovers a crisis in policy and behavior impending since 1990—one stemming from earlier, but long-outmoded assumptions that now threaten future development in common. Feasible reforms, global and national, are outlined. Ranging widely through time, space, and subject-matter, and moving from earth and life history to economics and new vistas in brain science, Dilloway marshals analysis, ideas, and proposals to lay bare a climactic crisis that, since 1990 in particular, has been systematically concealed from view by the fresh force of a current conventional wisdom. Successive chapters review our global situation in its major demographic, environmental, economic, and human rights aspects. Our entire time perspective is then examined to throw new light on powerful human capacities and the way they are now being contradicted by assumptions—seemingly rational two centuries ago—that have become outmoded, yet still decisive, in the century now ending. Dilloway next looks at recent economic history to see how this now-obsolete philosophy has come to prevail and how massively it opposes the cooperative social basis of our entire human potential. After reviewing a many-sided United Nations push based on environmental conservation, development, and human rights, Dilloway arrives at feasible, yet far-reaching proposals for stronger international government and matching basic reforms at the level of the advanced nation-state.
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BERGUGNAT, Laurence, e Loic LEROUGE, a cura di. Revue Education, Santé, Sociétés, Vol. 7, No. 2. Editions des archives contemporaines, 2021. http://dx.doi.org/10.17184/eac.9782813003836.
Testo completoAbstract (sommario):
Présenter le titre de ce numéro dans une forme interrogative, c'est d'emblée questionner les paradigmes, théories et modèles qui sous-tendent la notion de santé au travail et plus encore de ses liens avec l'éducation et la formation, domaine à interroger aussi. Le projet est né des journées internationales et interdisciplinaires « Towards a Feasible New Economy of Innovative and Healthy Work » organisées à Bordeaux les 28-29 avril 2016 par Loïc Lerouge, Directeur de recherche au CNRS, spécialiste de droit de la santé au travail (CNRS, Bordeaux) et Robert Karasek, professeur émérite en psychosociologie de l'Université du Massachusetts Lowell et de l'Université de Copenhague. Cet événement a marqué un tournant dans la manière d'appréhender la santé au travail en mettant en discussion les développements de l'économie au regard de l'innovation et de la protection de la santé au travail. Le groupe d'experts scientifiques international et pluridisciplinaire qui a été réuni a dégagé neuf sujets et questions qui ont été ensuite confrontés aux acteurs du monde socio-économique (parties-prenantes). Le sujet de l'éducation à la santé au travail y figurait en bonne place et les conclusions finales ont notamment insisté sur la nécessité de développer l'approche éducative de la santé et de la sécurité au travail.
Capitoli di libri sul tema "Force feasible set"
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Richter, Michael, e Ariel Rubinstein. "1. Equilibrium in the Jungle". In No Prices No Games!, 13–36. Cambridge, UK: Open Book Publishers, 2024. http://dx.doi.org/10.11647/obp.0404.01.
Testo completoAbstract (sommario):
The standard economic approach treats economic activity as voluntary: all involved parties do whatever they do of their own free will. However, life is not just a series of voluntary actions. An agent might use power to seize assets from others or to force others to do things against their will. Economic Theory typically ignores the use of power as a driver of social activity. This chapter follows Piccione and Rubinstein (2007) which introduces a model of a society referred to as the jungle, in which economic transactions are governed only by coercion. The model consists of a set of agents with exogenous preferences over a set of assets and a power ordering of the agents. Power means that a stronger agent is able to take things away from a weaker agent without the weaker agent's consent. A jungle equilibrium is a feasible allocation of the assets such that no agent wishes to take assets from an agent (or agents) weaker than himself. We will apply versions of the concept to the housing economy (Shapley and Scarf (1974)) and to the division economy. Throughout, we will deal with standard issues, such as: existence, uniqueness and the fundamental theorems of welfare.
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Richter, Michael, e Ariel Rubinstein. "1. Equilibrium in the Jungle". In No Prices No Games!, 13–36. 2a ed. Cambridge, UK: Open Book Publishers, 2024. http://dx.doi.org/10.11647/obp.0438.01.
Testo completoAbstract (sommario):
The standard economic approach treats economic activity as voluntary: all involved parties do whatever they do of their own free will. However, life is not just a series of voluntary actions. An agent might use power to seize assets from others or to force others to do things against their will. Economic Theory typically ignores the use of power as a driver of social activity. This chapter follows Piccione and Rubinstein (2007) which introduces a model of a society referred to as the jungle, in which economic transactions are governed only by coercion. The model consists of a set of agents with exogenous preferences over a set of assets and a power ordering of the agents. Power means that a stronger agent is able to take things away from a weaker agent without the weaker agent's consent. A jungle equilibrium is a feasible allocation of the assets such that no agent wishes to take assets from an agent (or agents) weaker than himself. We will apply versions of the concept to the housing economy (Shapley and Scarf (1974)) and to the division economy. Throughout, we will deal with standard issues, such as: existence, uniqueness and the fundamental theorems of welfare.
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Richter, Michael, e Ariel Rubinstein. "2. The Permissible and the Forbidden". In No Prices No Games!, 37–64. Cambridge, UK: Open Book Publishers, 2024. http://dx.doi.org/10.11647/obp.0404.02.
Testo completoAbstract (sommario):
Following Richter and Rubinstein (2020), we analyze an equilibrium concept based upon social norms: the Y-equilibrium. A Y-equilibrium is a set of permissible alternatives and a profile of choices, one for each agent, such that: (i) each agent's choice is optimal from among the permissible alternatives; (ii) the profile of choices is feasible; and (iii) the set of permissible alternatives is maximal in the sense that there is no superset of permissible alternatives from which a profile satisfying (i) and (ii) can be found. By this definition, two forces make a permissible set unstable: The first modifies the permissible set in the case that the profile of (intended) choices is not feasible, while the second loosens restrictions on the permissible set as long as a new profile of optimal choices is feasible. We also consider a variant of this concept where we require that the permissible set is convex. We study the Y-equilibria of a variety of examples and prove existence theorems, “welfare” theorems and a structure theorem when the set of alternatives is Euclidean.
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Richter, Michael, e Ariel Rubinstein. "2. The Permissible and the Forbidden". In No Prices No Games!, 37–64. 2a ed. Cambridge, UK: Open Book Publishers, 2024. http://dx.doi.org/10.11647/obp.0438.02.
Testo completoAbstract (sommario):
Following Richter and Rubinstein (2020), we analyze an equilibrium concept based upon social norms: the Y-equilibrium. A Y-equilibrium is a set of permissible alternatives and a profile of choices, one for each agent, such that: (i) each agent's choice is optimal from among the permissible alternatives; (ii) the profile of choices is feasible; and (iii) the set of permissible alternatives is maximal in the sense that there is no superset of permissible alternatives from which a profile satisfying (i) and (ii) can be found. By this definition, two forces make a permissible set unstable: The first modifies the permissible set in the case that the profile of (intended) choices is not feasible, while the second loosens restrictions on the permissible set as long as a new profile of optimal choices is feasible. We also consider a variant of this concept where we require that the permissible set is convex. We study the Y-equilibria of a variety of examples and prove existence theorems, “welfare” theorems and a structure theorem when the set of alternatives is Euclidean.
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Peng, Chengming, Zhihui Peng, Jiaqi Li e Junzheng Zhang. "Key Construction and Control Technology of Long Span Self-anchored Suspension Bridge with Cable Before Beam". In Lecture Notes in Civil Engineering, 163–78. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-2532-2_14.
Testo completoAbstract (sommario):
AbstractShatian Bridge is a self-anchored suspension bridge with a main span of 320 m. It is constructed by the overall construction technology of “cable before the beam”. The main cable is temporarily fixed through the temporary anchorage system, and the main beam construction is based on the main cable. After the main beam is hoisted and welded, the main cable is temporarily fixed, and the tensile force of the main cable is transferred to the main beam to complete the system conversion. The bridge adopts permanent-temporary combined with temporary anchorage, effectively saving the cost. The lifting of the stiffening beam adopts inverted lifting technology. For the area of the short sling in the middle of the span, a non-full-length joist is designed to solve the problem of main beam lifting in the area of the short sling. During the construction, the steel beam of the anchorage section and the auxiliary pier are temporarily consolidated. The temporary cable actively balances the tension of the main cable with clear stress, which is convenient for construction control. Temperature welds are set at both ends of the closure beam section, which not only makes room for the hoisting of the closure beam section but also avoids the structural safety problems caused by the temperature deformation of the steel beam. The slip control method of cable strands based on water bag weight ensures that the main cable does not slip during steel beam hoisting. The length of the sling is increased through the extension rod, and the horn-shaped guide device is added to avoid sling damage caused by the sling colliding with the conduit mouth. Generally speaking, the construction scheme of “cable before beam” adopted by the bridge is reasonable and feasible, which enriches the construction technology of self-anchored suspension bridges and can provide a reference for similar bridge construction in the future.
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Xue, Zhi-Wu, e Qiang Guo. "Bridge Comparison of Erection Solutions for Steel Box Girders Spanning from Anchorage in the Sea on Shenzhen-Zhongshan Bridge". In Advances in Frontier Research on Engineering Structures, 365–77. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-8657-4_32.
Testo completoAbstract (sommario):
AbstractThe non-navigable hole bridge in the east and west flooding area of the Shenzhen-Zhongshan Bridge 110 m continuous steel box girder system, each with 2 holes of steel box girders spanning the Lingdingyang Bridge sea anchor, which is affected by the anchor and the subsidiary structure, and its installation is difficult. In view of the characteristics of the project, three installation solutions were proposed: large section lifting, small section incremental launching and large section incremental launching. Combined with the comparative analysis of construction efficiency, temporary structure usage, equipment input and construction risk, the large section incremental launching solution not only has less temporary structure input and controllable construction period, but also avoids the input of new equipment and has the best comprehensive economy, which is recommended as the preferred solution for this project. The finite element analysis of the incremental launching process shows that the structural forces meet the requirements after local reinforcement, and the scheme is safe and feasible.
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Lindsay, S. M. "Microscopy and manipulation tools". In Introduction to Nanoscience, 135–77. Oxford University PressOxford, 2009. http://dx.doi.org/10.1093/oso/9780199544202.003.0004.
Testo completoAbstract (sommario):
Abstract This chapter describes the important imaging and manipulation tools without which Nanoscience would be impossible. We begin with a description of the scanning tunneling microscope (STM; Section 4.1) because this was the first instrument that made the manipulation of single atoms feasible. Atomic scale imaging had been possible (using electron microscopes) for some time before the STM was invented, but the ease of operation and construction of STMs popularized Nanoscience and Nanotechnology. The STM has largely been superseded by its close relation, the atomic force microscope (AFM), because the AFM is capable of imaging insulating surfaces and therefore has a more general set of applications (Section 4.2). The AFM also enabled the measurement of the mechanical properties of individual molecules, and this application to single molecule force measurements is also reviewed here (Section 4.2.6). Despite these enormous advances in scanning probe microscopy, the electron microscope still offers the most accurate measurement of many nanoscale structures and we review some aspects of electron microscopy in Section 4.3. At around the same time that the AFM was becoming popular, the optics community began to develop techniques and dyes for fluorescent imaging of single molecules (Section 4.4). These methods broke the classical limits on optical resolution, allowing particles to be located with nanometer accuracy in optical images. The new optical methods also enabled new approaches to measuring motion at a single molecule level. The discovery that small particles could be manipulated with a light beam also occurred in this time frame (the mid-1980s), leading to the development of devices that manipulate single molecules attached to small particles (Section 4.5). Methods for the direct imaging of nanostructures and the measurement of their mechanical properties and their fluctuations have undergone a dramatic revolution in the past 20 years.
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Terrett, Nicholas K. "Library synthesis on resin beads". In Combinatorial Chemistry, 7–32. Oxford University PressOxford, 1998. http://dx.doi.org/10.1093/oso/9780198502203.003.0002.
Testo completoAbstract (sommario):
Abstract The synthesis of combinatorial libraries usually employs solid phase chemistry. The recent renaissance and growth of interest in solid supported chemistry stems from the opportunity to use filtration as a separation technique to purify both intermediates and final compounds. The ability to synthesize compounds on a resin bead for example, to force the reaction to completion by the addition of excess reagents and monomers, and then being able to remove all the unwanted materials by a simple filtration and wash is at the heart of many library syntheses (Fig. 2.1).This is not to say however, that solution methods are no longer suitable for combinatorial libraries. With appropriate chemistry, either that which is high yielding or that generates products which allow simple liquid-liquid extraction, solution phase library synthesis is highly feasible (see Chapter 4) and indeed has been chosen as a preferred strategy by many academic and industrial groups.
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Dickinson, Laura A. "The Future of Military and Security Privatization". In The Future Law of Armed Conflict, 239–64. Oxford University PressNew York, 2022. http://dx.doi.org/10.1093/oso/9780197626054.003.0014.
Testo completoAbstract (sommario):
Abstract The future of warfare is likely to see ongoing use of Private Military and Security Contractors (PMSCs) to expand State power not only in defensive and offensive battlefield contexts, but in clandestine cyber-related and AI-driven military initiatives as well. All of this privatization threatens “public law values” embedded in both the law of armed conflict (LOAC) and international human rights law. In the case of LOAC, core principles such as distinction, proportionality, feasible precautions, and avoidance of unnecessary suffering establish important limitations on the use of force. The challenge, however, is that these bodies of law—and the mechanisms of accountability and oversight that accompanied them—were designed by States in an era when the primary entities to be governed by this law were governmental actors that consisted primarily of large State militaries. This chapter surveys the present and likely future regarding States’ use of PMSCs. I argue that in the future although some categories of PMSCs will be increasingly regulated and professionalized, others will be deployed in secret and will tend to evade traditional oversight. Accordingly, those concerned about the survival of LOAC in the coming decades should explore alternative regulatory approaches that could go at least some distance toward mitigating the clear risks posed by the expansion of PMSCs.
Atti di convegni sul tema "Force feasible set"
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Wang, Jing, Qing Wei, Hongxu Ma, Honglei An, Pengming Zhu e Lin Lang. "Motion Planning for Legged Robots via the Feasible Force Set". In 2021 6th IEEE International Conference on Advanced Robotics and Mechatronics (ICARM). IEEE, 2021. http://dx.doi.org/10.1109/icarm52023.2021.9536194.
Testo completo
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SAIDA, MASAO, YASUHISA HIRATA e KAZUHIRO KOSUGE. "DEVELOPMENT OF PASSIVE TYPE DOUBLE WHEEL CASTER UNIT BASED ON FEASIBLE BRAKING FORCE AND MOMENT SET". In Proceedings of the Tohoku University Global Centre of Excellence Programme. IMPERIAL COLLEGE PRESS, 2012. http://dx.doi.org/10.1142/9781848169067_0057.
Testo completo
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Saida, M., Y. Hirata e K. Kosuge. "Development of passive type double wheel caster unit based on analysis of feasible braking force and moment set". In 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2011). IEEE, 2011. http://dx.doi.org/10.1109/iros.2011.6048373.
Testo completo
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Saida, M., Y. Hirata e K. Kosuge. "Development of passive type double wheel caster unit based on analysis of feasible braking force and moment set". In 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2011). IEEE, 2011. http://dx.doi.org/10.1109/iros.2011.6094765.
Testo completo
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Mikus, Oldrich, Nejat Olgac e Rifat Sipahi. "An Actively Controlled Harmonic Force Generator". In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-41410.
Testo completoAbstract (sommario):
The electromagnetic shakers (also known as voice coil actuators) are commonly utilized for computer controlled force applications. When the force trace becomes harmonic, however, the devices which use rotating eccentric masses are more feasible to operate. If, on the other hand, one wishes to vary three descriptors, the amplitude, frequency and the phase angle of these harmonics the design and the operation of the structure become more challenging. A novel design and control are presented in this paper to achieve this objective with a very favorable ratio between the peak force and the weight. The variation in the force amplitude is taken from zero to Fmax, while the frequency range varies about ±10% around the nominal operating frequency. Indefinite variations of relative phase angle (i.e., zero to 2π) with respect to a given harmonic signal can be achieved using this new device. The transition from a set of the tree descriptors to another set is achieved under an open loop control of the device. On a prototype experimental setting we demonstrate a successful deployment of the control. Such a structure can be used in some cases for generating desired harmonic force excitations, and in some mission critical application, for canceling vibration caused by quasi static harmonic forcing.
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Dassanayake, Darshana T., Alessandro Antonini e Alison Raby. "Efficacy of Analysis Techniques in Assessing Broken Wave Loading on a Cylinder Upon a Shoal". In ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-96262.
Testo completoAbstract (sommario):
Abstract Estimation of impulsive wave loading on a cylinder upon a shoal, such as an offshore rock lighthouse constructed on a partially emerged offshore rock with a steep foreshore, poses a unique challenge to marine structural engineers. Large and small scale experimental investigations are the most feasible methods to study this phenomena. However, any experimental investigation with impulsive loading faces challenges in the data analysis, when it is necessary to separate the total impact forces from the force response time series, and to separate the impulsive and quasi-static force components of the total force measurements. This paper is an attempt to re-visit several data analysis techniques with a unique experimental data set to study the advantages and limitations of those techniques, and also to learn how different techniques can be combined into a data analysis methodology to harness maximum information.
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Williams, Jeffrey C., e Santiago D. Solares. "3-Dimensional Force Curve and Dissipation Model Acquisition Using the Spectral Inversion Method in Tapping Mode AFM". In ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/detc2011-47112.
Testo completoAbstract (sommario):
Atomic force microscopy (AFM) has been a field driving at exploring nanoscale surfaces and measuring both topography as well as material properties. One of the phenomena that has attracted significant interest is tip-sample dissipation, which was initially investigated by Cleveland and coworkers [Appl. Phys. Lett. 72, 2613–2615 (1998)]. In this paper we expand on that work by developing a method to map the total conservative and non-conservative forces simultaneously in space and as a function of relative tip-sample velocity. This is accomplished through Fourier analysis performed on the response of a torsional harmonic cantilever (THC) probe, previously developed by Sahin and coworkers [Nature Nanotechnology 2, 507–514 (2007)]. The effect of a select group of AFM parameters (cantilever resonant frequency, force constant, quality factor, amplitude set point and excitation amplitude) is simulated in a feasible range of experimental conditions, which maximizes the spatial and velocity range of the oscillating tip, such that useful maps of the total force as a function of tip velocity and position can be acquired. We analyze the observed trends and propose an approach to acquire analytical models of the local tip-sample dissipative and conservative forces.
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Farmani, Mohammad Reza, e A. Jaamiolahmadi. "Optimization of Force and Moment Balance of a Four-Bar Linkage Using Multi-Objective Genetic Algorithm". In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12740.
Testo completoAbstract (sommario):
In this study, force and moment balance of a four-bar linkage is implemented by using a Multi-Objective Genetic Algorithm (MOGA). During the time that an unbalanced linkage moves, it transmits shaking forces and moments to its surroundings. These transmitted forces and moments may cause some serious and undesirable problems such as vibration, noise, wear, and fatigue. In the current problem, the concepts of inertia counterweights and physical pendulum are utilized to complete balance of all mass effects (both linear and rotary, but excluding external loads), independent of input angular velocity. In this paper, Non-Dominated Genetic Algorithm (NSGA-II) is applied to minimize two objective functions subject to some different design constraints. The applied algorithm produced a set of feasible solutions called Pareto optimal solutions for the design problem. Finally, a fuzzy decision maker is applied to select the best solution among the obtained Pareto solutions based on design criteria. The results show that obtained solutions minimize the weights of applied counterweights and eliminate both shaking forces and moments transmitted to the ground, simultaneously.
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Dang, Phuoc Vinh, Steven Chatterton, Paolo Pennacchi, Andrea Vania e Filippo Cangioli. "An Experimental Study of Nonlinear Oil-Film Forces in a Tilting-Pad Journal Bearing". In ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/detc2015-46601.
Testo completoAbstract (sommario):
Journal bearings have been widely used in high-speed rotating machinery. The dynamic coefficients of oil-film force affect the machine unbalance response and machine stability. The oil-film force of hydrodynamic bearing is often characterized by a set of linear stiffness and damping coefficients. However the linear oil-film coefficients with respect to an equilibrium position of the journal are inaccurate when the bearing system vibrates with large amplitudes due to a dynamic load. The study on nonlinear oil-film forces is still rare and most papers are confined to theoretical analyses. The purpose of this paper is to derive some new non-linear force models (28-co., 24-co. and 36-co. models) to identify these dynamic coefficients based on experimental data. The fundamental test model is obtained from a Taylor series expansion of bearing reaction force. Tests were performed with a nominal diameter of 100mm and a length–to–diameter ratio of 0.7 using a suitable test rig in which it is possible to apply the static load in any direction. The results show that these three models are feasible to identify the oil-film forces in which the second-order oil-film coefficients received from the 24-co. model are more stable compared to those of other two nonlinear models.
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Lee, Yong Hoon, R. E. Corman, Randy H. Ewoldt e James T. Allison. "A Multiobjective Adaptive Surrogate Modeling-Based Optimization (MO-ASMO) Framework Using Efficient Sampling Strategies". In ASME 2017 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/detc2017-67541.
Testo completoAbstract (sommario):
A novel multiobjective adaptive surrogate modeling-based optimization (MO-ASMO) framework is proposed to utilize a minimal number of training samples efficiently for sequential model updates. All the sample points are enforced to be feasible, and to provide coverage of sparsely explored sparse design regions using a new optimization subproblem. The MO-ASMO method only evaluates high-fidelity functions at feasible sample points. During an exploitation sample phase, samples are selected to enhance solution accuracy rather than the global exploration. Sampling tasks are especially challenging for multiobjective optimization; for an n-dimensional design space, a strategy is required for generating model update sample points near an (n − 1)-dimensional hypersurface corresponding to the Pareto set in the design space. This is addressed here using a force-directed layout algorithm, adapted from graph visualization strategies, to distribute feasible sample points evenly near the estimated Pareto set. Model validation samples are chosen uniformly on the Pareto set hypersurface, and surrogate model estimates at these points are compared to high-fidelity model responses. All high-fidelity model evaluations are stored for later use to train an updated surrogate model. The MO-ASMO algorithm, along with the set of new sampling strategies, are tested using two mathematical and one realistic engineering problems. The second mathematical test problems is specifically designed to test the limits of this algorithm to cope with very narrow, non-convex feasible domains. It involves oscillatory objective functions, giving rise to a discontinuous set of Pareto-optimal solutions. Also, the third test problem demonstrates that the MO-ASMO algorithm can handle a practical engineering problem with more than 10 design variables and black-box simulations. The efficiency of the MO-ASMO algorithm is demonstrated by comparing the result of two mathematical problems to the results of the NSGA-II algorithm in terms of the number of high fidelity function evaluations, and is shown to reduce total function evaluations by several orders of magnitude when converging to the same Pareto sets.
Rapporti di organizzazioni sul tema "Force feasible set"
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Ucak-Astarlioglu, Mine, Jedadiah Burroughs, Charles Weiss, Kyle Klaus, Stephen Murrell, Samuel Craig, Jameson Shannon, Robert Moser, Kevin Wyss e James Tour. Graphene in cementitious materials. Engineer Research and Development Center (U.S.), dicembre 2023. http://dx.doi.org/10.21079/11681/48033.
Testo completoAbstract (sommario):
This project aims to determine the influence of laboratory-generated graphene (LGG) and commercial-grade graphene (CGG) on the chemical structure and compressive strength of graphene-cement mixtures. Determining the graphene-cement structure/processing/property relationships provides the most useful information for attaining the highest compressive strength. Graphene dose and particle size, speed of mixing, and dispersant agent were found to have important roles in graphene dispersion by affecting the adhesion forces between calcium silicate hydrate (CSH) gels and graphene surfaces that result in the enhanced strength of cement-graphene mixtures. X-ray diffraction (XRD), Raman, and scanning electron microscope (SEM) analyses were used to determine chemical microstructure, and compression testing for mechanical properties characterization, respectively. Based on observed results both LGG and CGG graphene cement mixtures showed an increase in the compressive strength over 7-, 14-, and 28-day age curing periods. Preliminary dispersion studies were performed to determine the most effective surfactant for graphene dispersion. Future studies will continue to research graphene—cement mortar and graphene—concrete composites using the most feasible graphene materials. These studies will prove invaluable for military programs, warfighter support, climate change, and civil works.