Articoli di riviste: "STATIC CONSTRAINTS"

1

Eun, Hee-Chang, Eun-Taik Lee e Heon-Soo Chung. "On the static analysis of constrained structural systems". Canadian Journal of Civil Engineering 31, n. 6 (1 dicembre 2004): 1119–22. http://dx.doi.org/10.1139/l04-036.

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Complete structures might contain so many degrees of freedom that it would be infeasible to perform a structural analysis. The derivation of the equilibrium equations of an entire structure to utilize kinematical compatibility conditions at the interfaces of the substructures requires complicated intermediate processes or numerical schemes for determining multipliers. This study derives an explicit matrix form of the equilibrium equations of structural systems subjected to constraints like compatibility conditions or linear displacement relations. The equation is obtained by minimizing a quadratic form of the variation in unconstrained and constrained displacements with respect to all constrained displacements that satisfy the constraints. And the physical meaning of the constraint forces required to satisfy the constraints is investigated. The validity of the proposed method is illustrated by several applications.Key words: constraints, compatibility, equilibrium equation, generalized inverse.

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Mrzygłód, M. "Multi-constrained topology optimization using constant criterion surface algorithm". Bulletin of the Polish Academy of Sciences: Technical Sciences 60, n. 2 (1 ottobre 2012): 229–36. http://dx.doi.org/10.2478/v10175-012-0030-9.

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Abstract. This paper sets out to describe a multi-constrained approach to topology optimization of structures. In the optimization, a constant criterion surface algorithm and the multi-constraint procedure is used. The multi-constraint procedure consists of constraints normalization and equivalent design space assembling. The work is illustrated by an example of the L-shaped domain optimization with the horizontal line support and complex loads. The example takes into consideration stress, fatigue and compliance constraints. The separate and simultaneous application of constraints resulted in significant differences in structure topology layouts. The application of a fatigue constraint gave more conservative results when compared to static stress or compliance limitations. The multi-constrained approach allowed effectively lowering the mass of the structure while satisfying all constraints.

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Christopher Cruz, Arnold, e Ahmad Bani Younes. "Common Frame Dynamics for Conically-Constrained Spacecraft Attitude Control". Sensors 22, n. 24 (19 dicembre 2022): 10003. http://dx.doi.org/10.3390/s222410003.

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Attitude control subjected to pointing constraints is a requirement for most spacecraft missions carrying sensitive on-board equipment. Pointing constraints can be divided into two categories: exclusion zones that are defined for sensitive equipment such as telescopes or cameras that can be damaged from celestial objects, and inclusion zones that are defined for communication hardware and solar arrays. This work derives common frame dynamics that are fully derived for Modified Rodrigues Parameters and introduced to an existing novel technique for constrained spacecraft attitude control, which uses a kinematic steering law and servo sub-system. Lyapunov methods are used to redevelop the steering law and servo sub-system in the common frame for the tracking problem for both static and dynamic conic constraints. A numerical example and comparison between the original frame and the common frame for the static constrained tracking problem are presented under both unbounded and limited torque capabilities. Monte Carlo simulations are performed to validate the convergence of the constrained tracking problem for static conic constraints under small perturbations of the initial conditions. The performance of dynamic conic constraints in the tracking problem is addressed and a numerical example is presented. The result of using common frame dynamics in the constrained problem shows decreased control effort required to rotate the spacecraft.

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Gosain, Anjana, e Kavita Sachdeva. "Handling Constraints Using Penalty Functions in Materialized View Selection". International Journal of Natural Computing Research 8, n. 2 (aprile 2019): 1–17. http://dx.doi.org/10.4018/ijncr.2019040101.

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Materialized view selection (MVS) plays a vital role for efficiently making decisions in a data warehouse. This problem is NP-hard and constrained optimization problem. The authors have handled both the space and maintenance cost constraint using penalty functions. Three penalty function methods i.e. static, dynamic and adaptive penalty functions have been used for handling constraints and Backtracking Search Optimization algorithm (BSA) has been used for optimizing the total query processing cost. Experiments were conducted comparing the static, dynamic and adaptive penalty functions on varying the space constraint. The adaptive penalty function method yields the best results in terms of minimum query processing cost and achieves the optimality, scalability and feasibility of the problem on varying the lattice dimensions and on increasing the number of user queries. The authors proposed work has been compared with other evolutionary algorithms i.e. PSO and genetic algorithm and yields better results in terms of minimum total query processing cost of the materialized views.

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SCHIEX, THOMAS, e GÉRARD VERFAILLIE. "NOGOOD RECORDING FOR STATIC AND DYNAMIC CONSTRAINT SATISFACTION PROBLEMS". International Journal on Artificial Intelligence Tools 03, n. 02 (giugno 1994): 187–207. http://dx.doi.org/10.1142/s0218213094000108.

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Many AI synthesis problems such as planning, scheduling or design may be encoded in a constraint satisfaction problems (CSP). A CSP is typically defined as the problem of finding any consistent labeling for a fixed set of variables satisfying all given constraints between these variables. However, for many real tasks, the set of constraints to consider may evolve because of the environment or because of user interactions. The notion of dynamic CSP (DCSP) [DD88] has been proposed to represent such evolutions. The problem we consider here is the solution maintenance problem in a DCSP. Naively applying usual satisfaction algorithms to this problem results in redundant search and inefficiency. A general approach to suppress redundancies in case of both restrictions and relaxations is to concisely represent the frontier of the solution space and justifications of this frontier in terms of set of constraints. This paper proposes a new class of constraint recording algorithms called nogood recording that may be used for solving both dynamic CSPs and usual CSP (called static CSPs here). It offers an interesting compromise, polynomially bounded in space, between an ATMS-like (Assumption-based Truth Maintenance System) approach, that would give a precise and exhaustive description of the frontier, and the usual constraint satisfaction algorithms (that discover a new frontier at each execution). We first introduce the principles used for nogood generation and then examine various recording schemes, on top of different tree search algorithms, characterizing the tradeoffs between the amount of recorded constraints and the pruning achieved. We then present experimental results and comparisons with various existing techniques for solving static or dynamic CSP.

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Bernal, Dionisio, Martin D. Ulriksen e Esmaeil Memarzadeh. "Static constraints in direct model updating". Mechanical Systems and Signal Processing 163 (gennaio 2022): 108170. http://dx.doi.org/10.1016/j.ymssp.2021.108170.

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Olender, Kurt M., e Leon J. Osterweil. "Interprocedural static analysis of sequencing constraints". ACM Transactions on Software Engineering and Methodology (TOSEM) 1, n. 1 (2 gennaio 1992): 21–52. http://dx.doi.org/10.1145/125489.122822.

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8

Pan, Peng, Michael A. Peshkin, J. Edward Colgate e Kevin M. Lynch. "Static Single-Arm Force Generation With Kinematic Constraints". Journal of Neurophysiology 93, n. 5 (maggio 2005): 2752–65. http://dx.doi.org/10.1152/jn.00799.2004.

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Smooth, frictionless, kinematic constraints on the motion of a grasped object reduce the motion freedoms at the hand, but add force freedoms, that is, force directions that do not affect the motion of the object. We are studying how subjects make use of these force freedoms in static and dynamic manipulation tasks. In this study, subjects were asked to use their right hand to hold stationary a manipulandum being pulled with constant force along a low-friction linear rail. To accomplish this task, subjects had to apply an equal and opposite force along the rail, but subjects were free to apply a force against the constraint, orthogonal to the pulling force. Although constraint forces increase the magnitude of the total force vector at the hand and have no effect on the task, we found that subjects applied significant constraint forces in a consistent manner dependent on the arm and constraint configurations. We show that these results can be interpreted in terms of an objective function describing how subjects choose a particular hand force from an infinite set of hand forces that accomplish the task. Without assuming any particular form for the objective function, the data show that its level sets are convex and scale invariant (i.e., the level set shapes are independent of the hand-force magnitude). We derive the level sets, or “isocost” contours, of subjects' objective functions directly from the experimental data.

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Duan, Qingjuan, Quanli Zhao e Tianle Wang. "Consistent Solution Strategy for Static Equilibrium Workspace and Trajectory Planning of Under-Constrained Cable-Driven Parallel and Planar Hybrid Robots". Machines 10, n. 10 (10 ottobre 2022): 920. http://dx.doi.org/10.3390/machines10100920.

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This paper presents a consistent solution strategy for static equilibrium workspaces of different types of under-constrained robots. Considering the constraint conditions of cable force and taking the least squares error of the static equilibrium equation as the objective, the convex optimization solution is carried out, and the static equilibrium working space of the under-constrained system is obtained. A consistent solution strategy is applied to solve the static equilibrium workspaces of the cable-driven parallel and planar hybrid robots. The dynamic models are presented and introducing parameters that are applied to make the system stable for point-to-point movements. Based on this model, the traditional polynomial-based point-to-point trajectory planning algorithm is improved by adding unconstrained parameters to the kinematic law function. The constraints of the dynamics model are incorporated into the trajectory planning process to achieve point-to-point trajectory planning for the under-constrained cable-driven robots. Finally, under-constrained cable-driven parallel robots with three cables and planar hybrid robot with two cables are taken as examples to carry out numerical simulation. The final results show that the point-to-point trajectory planning algorithm introducing parameters is effective and feasible and can provide theoretical guidance for the design of subsequent under-constrained robots.

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Wang, Ren, Jingxiang Gao, Nanshan Zheng, Zengke Li, Yifei Yao, Long Zhao e Yifan Wang. "Research on Accelerating Single-Frequency Precise Point Positioning Convergence with Atmospheric Constraint". Applied Sciences 9, n. 24 (10 dicembre 2019): 5407. http://dx.doi.org/10.3390/app9245407.

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An increasing number of researchers have conducted in-depth research on the advantages of low-cost single-frequency (SF) receivers, which can effectively use ionospheric information when compared to dual-frequency ionospheric-free combination. However, SF observations are bound to increase the unknown parameters and prolong the convergence time. It is desirable if the convergence time can be reduced by external information constraints, for example atmospheric constraints, which include ionosphere- or troposphere constraints. In this study, ionospheric delay constraints, tropospheric delay constraints, and their dual constraints were considered. Additionally, a total of 18,720 test experiments were performed. First, the nearest-neighbor extrapolation (NENE), bilinear- (BILI), bicubic- (BICU), and Junkins weighted-interpolation (JUNK) method of Global Ionospheric Map (GIM) grid products were analyzed. The statistically verified BILI in the percentage of convergence time, average convergence time, and computation time consumption of them shows a good advantage. Next, the influences of global troposphere- and ionosphere-constrained on the convergence time of SF Precise Point Positioning (PPP) were analyzed. It is verified that the ionosphere-constrained (TIC2) has significant influence on the convergence time in the horizontal and vertical components, while the troposphere-constrained (TIC1) has better effect on the convergence time in the vertical components within some thresholds. Of course, the dual constraint (TIC3) has the shortest average convergence time, which is at least 46.5% shorter in static mode and 5.4% in kinematic mode than standard SF PPP (TIC0).

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Gess, Randall. "Reductive sound change and the perception/production interface". Canadian Journal of Linguistics/Revue canadienne de linguistique 54, n. 2 (luglio 2009): 229–53. http://dx.doi.org/10.1017/s0008413100001249.

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AbstractIn this article, I propose a phonetically-oriented constraint-based model of speech production that differs from recent approaches in assuming preservation constraints that refer directly to articulatory gestures rather than to perceptual cues. Articulatory gesture preservation constraints interact with a constraint that penalizes the expenditure of articulatory effort. Specific constraints and rankings are projected from a static perceptual knowledge source. Before exploring the model in detail, I address evidence that has been used to argue against precisely this type of “Articulatory Phonology-inspired” approach. The evidence, used to justify the claim that lenition cannot be modeled as gestural reduction alone, is shown to be problematic.

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Bich Quyen, Vu Thi, Dao Ngoc Tien, Tran Thi Thuy Van e Pham Van Dat. "Augmented Lagrangian method for imposing nonlinear multi freedom constraints in static analysis for frames using FEM". E3S Web of Conferences 281 (2021): 01010. http://dx.doi.org/10.1051/e3sconf/202128101010.

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This paper focuses on the treatment of nonlinear multi freedom constraints using an augmented Lagrangian method in finite element analysis of frames. The process of imposing boundary constraints is developed by changing the assembly stiffness equation to produce a modified system of equation considering nonlinear multi freedom constraints. For imposing the nonlinear constraints two better methods are the penalty augmentation method and Lagrange multiplier adjunction method. But there are not free of disadvantages. Using penalty method has a disadvantage in the choice appropriate weight values that balance solution accuracy with the violation of constraint conditions. Using the Lagrange multiplier adjunction method requires additional unknowns, and more complicated storage allocation procedures. This research proposes the connection between these methods using the augmented Lagrangian method for imposing the nonlinear multi freedom constraints in finite element analysis of frame. Based on the Newton Raphson method the incremental-iterative algorithm for solving the nonlinear balanced equations is established.

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Tran, Le Nhat Hoang, Laurent Gerbaud, Nicolas Retière e Hieu Nguyen Huu. "Use of SQP optimization algorithm to size a multiphysical system". COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 37, n. 2 (5 marzo 2018): 661–80. http://dx.doi.org/10.1108/compel-12-2016-0519.

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PurposeStatic converters generate current harmonics in power grids. For numerous studies, analytical frequency modeling is preferred to carry out their harmonic modeling in the context of sizing by optimization. However, a design by optimization has to consider other constraints, e.g. modeling constraints and operating constraints. In this way, this paper aims to focus on applying an analytical frequency modeling on the sizing by optimization of an aircraft electrical power channel. Design/methodology/approachThe paper aims to size a multiphysical system by optimization. In this way, the sizing of an aircraft electrical power channel by optimization has been carried out. The models of all the channel components are analytical. Specifically, the frequency model of the power electronics is based on Tran et al. (2016) and is made of equalities and inequalities. Due to this modeling choice, the optimization satisfies hundreds of constraints, such as modeling constraints and static converter operating constraints. Furthermore, transient constraints are only verified after optimization. FindingsThe difficulty is the modeling of the system by taking into account nonlinear implicit equations having several solutions. A solution is the addition of inequality constraints to the model to guide the implicit solving. Furthermore, this greatly helps the optimization algorithm to find the good operating mode of the static converter, at steady state. This aspect is indispensable to validate the sizing model. Research limitations/implicationsThe number of the configurations per operating period of the static converters is defined a priori and limited. Originality/valueThe analytical model for the sizing is formulated as a constrained optimization problem. Its solving and the sizing by optimization are carried out by the same optimization algorithm.

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Ilanko, Sinniah. "Asymptotic modelling theorems for the static analysis of linear elastic structures". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 461, n. 2063 (13 settembre 2005): 3525–42. http://dx.doi.org/10.1098/rspa.2005.1519.

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The work presented here justifies the use of restraints with large positive and negative stiffness values to asymptotically model geometric constraints of a structure in linear structural analysis. Replacing constraints by very stiff restraints improves the versatility of variational methods such as the Rayleigh–Ritz method as the limitation on the choice of functions is removed. Based on recently published theorems on the existence of natural frequencies of systems with artificial restraints of positive and negative stiffness and their convergence towards the frequencies of the corresponding constrained systems, a proof is given to show that the displacement of a constrained structure caused by any action along its direction is approached and bracketed by the displacement of systems with artificial restraints of positive and negative stiffness (positive and negative penalty functions) as the magnitude of stiffness is increased. A procedure for the practical use of positive and negative penalty functions in static analysis of linear structures is also proposed.

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Lin, Sheng, Chun Wang e Shi Jun Zhou. "Constraint Optimization of a Novel Flexure System with Two Rotation Freedom Degree". Applied Mechanics and Materials 268-270 (dicembre 2012): 1304–7. http://dx.doi.org/10.4028/www.scientific.net/amm.268-270.1304.

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A two freedom flexure system is presented. All the constraints are selected in Case 2, type 1 and Case 2, type 2 in FACT chart. The locations of the non-redundant constraints are optimizated by change laws of the three order natural frequency with the position of constraint. All the redundant constraints are selected to increase the add symmetry to the flexure system. Results of Simulation of static calibration dominates that the flexure system is decoupled. The synthesis process of the two freedom flexure system proposes important reference for design of the flexure system.

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Yang, Jian, Weiming Tang, Wei Xuan e Ruijie Xi. "Tight Integration of GNSS and Static Level for High Accuracy Dilapidated House Deformation Monitoring". Remote Sensing 14, n. 12 (20 giugno 2022): 2943. http://dx.doi.org/10.3390/rs14122943.

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Global Navigation Satellite System (GNSS) can provide high-precision three-dimensional real-time or quasi-real-time changes of monitoring points automatically in house monitoring applications. However, due to the signal sheltering problem, large observation noise and multipath effects in urban observing environment with dense buildings, ambiguity resolution would be hard, and GNSS accuracy cannot always achieve millimeter level to satisfy the requirement of house monitoring. Static level is a precision instrument for measuring elevation difference and its variations, with a precision up to sub-millimeter level. It could be integrated with GNSS to improve the positioning accuracy in height direction. However, the existing integration of GNSS and static level is mostly on a respective results level. In this study, we proposed a method of integrating GNSS and static level observations tightly to enhance the GNSS positioning performance. The hardware design and integration mathematic model in data processing were introduced, and a group of experiments were carried out to verify the performance in positioning with and without the static level observation constraints. It found that the vertical monitoring measurement results of static level can achieve less than 1 mm. The GNSS ambiguity resolution performance can be improved by incorporating the measurement of static level into GNSS positioning equation as external constraints, and the precision of GNSS float solutions was significantly improved. Finally, the static level constraint can further improve the accuracy of the fixed solution from about 2 cm to better than 2 mm in vertical direction, which is even better than the accuracy in horizontal directions with about 3–6 mm with the static level constraint. The tight combination data processing algorithm can significantly improve the working efficiency, accuracy, and reliability of the application of dangerous house monitoring.

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Song, Jun-Hyeok, Eun-Taik Lee e Hee-Chang Eun. "Optimal sensor placement through expansion of static strain measurements to static displacements". International Journal of Distributed Sensor Networks 17, n. 1 (gennaio 2021): 155014772199171. http://dx.doi.org/10.1177/1550147721991712.

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Optimal sensor placement is used to establish the optimal sensor quantity and layout. In this study, the minimum quantity and locations of measurement sensors were assumed to satisfy the constraint conditions of the optimal sensor placement. A set of strain data in a truss structure was expanded to another set of displacements corresponding to the entire degrees of freedom from the relationship between the strain and displacement. It indicates to reduce the number of sensors because the strain depends on the displacements in a finite element model. The damaged truss element was traced using the expanded data that satisfied the prescribed constraints. The proposed optimal sensor placement method has a merit to explicitly determine the optimal sensor locations without any numerical scheme and statistical methods. The method was applied to the damage detection of a single-damaged truss structure. It was shown that the optimal sensor placement method depended on the sensor layout irrespective of the same quantity of sensors. In addition, a numerical example was used to compare sensitivities to damage detection based on the sensor placement and the existence of external noise contained in the measurement data.

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Li, Chengbing, Chunxing Li e Yazhou Wang. "Compressive behavior and energy absorption capacity of unconstrained and constrained open-cell aluminum foams". Advanced Composites Letters 29 (1 gennaio 2020): 2633366X2092367. http://dx.doi.org/10.1177/2633366x20923671.

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In practical engineering applications, while the open-cell aluminum foam as crash absorber is filled to the hollow structures, its deformation occurs under constrained stress boundaries. The experimental work was conducted to examine the effect of radial constraints on the mechanical behavior of the open-cell aluminum foam under quasi-static and dynamic compression. Results show that the radial constraints induce significant strain hardening of the open-cell aluminum foam. The open-cell aluminum foams tested with and without radial constraints show a clear strain rate sensitivity. The densification of the foam occurs earlier (showing lower densification strain) under radial constraints. The radial constraints enhance the energy absorbed per unit volume of the open-cell aluminum foam.

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XU, Yining, Ittetsu TANIGUCHI e Hiroyuki TOMIYAMA. "Static Mapping of Parallelizable Tasks under Deadline Constraints". IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences E100.A, n. 7 (2017): 1500–1502. http://dx.doi.org/10.1587/transfun.e100.a.1500.

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PAPLIŃSKI, A. P., e M. J. GIBBARD. "On constraints in pole assignment by static feedback". International Journal of Control 42, n. 5 (novembre 1985): 1099–111. http://dx.doi.org/10.1080/00207178508933414.

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Bo, Yang, Chunhe Xia, Yang Luo e Qing Tang. "Static compliance checking beyond separation of duty constraints". International Journal of Embedded Systems 10, n. 5 (2018): 423. http://dx.doi.org/10.1504/ijes.2018.095019.

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Tang, Qing, Yang Luo, Yang Bo e Chunhe Xia. "Static compliance checking beyond separation of duty constraints". International Journal of Embedded Systems 10, n. 5 (2018): 423. http://dx.doi.org/10.1504/ijes.2018.10015744.

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23

Dems, K., e W. Gutkowski. "2D shape optimization with static and dynamic constraints". Structural Optimization 15, n. 3-4 (giugno 1998): 201–7. http://dx.doi.org/10.1007/bf01203532.

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Chen, T. Y. "Design optimization with static and dynamic displacement constraints". Structural Optimization 4, n. 3-4 (settembre 1992): 179–85. http://dx.doi.org/10.1007/bf01742742.

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Rubió-Massegú, J., J. M. Rossell, H. R. Karimi e F. Palacios-Quiñonero. "Static output-feedback control under information structure constraints". Automatica 49, n. 1 (gennaio 2013): 313–16. http://dx.doi.org/10.1016/j.automatica.2012.10.012.

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Blouin, Vincent Y., Michael M. Bernitsas e Denby Morrison. "Integrated Redesign of Large-Scale Structures by Large Admissible Perturbations". Journal of Offshore Mechanics and Arctic Engineering 125, n. 4 (1 ottobre 2003): 234–41. http://dx.doi.org/10.1115/1.1596236.

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In structural redesign (inverse design), selection of the number and type of performance constraints is a major challenge. This issue is directly related to the computational effort and, most importantly, to the success of the optimization solver in finding a solution. These issues are the focus of this paper, which provides and discusses techniques that can help designers formulate a well-posed integrated complex redesign problem. LargE Admissible Perturbations (LEAP) is a general methodology, which solves redesign problems of complex structures with, among others, free vibration, static deformation, and forced response amplitude constraints. The existing algorithm, referred to as the Incremental Method is improved in this paper for problems with static and forced response amplitude constraints. This new algorithm, referred to as the Direct Method, offers comparable level of accuracy for less computational time and provides robustness in solving large-scale redesign problems in the presence of damping, nonstructural mass, and fluid-structure interaction effects. Common redesign problems include several natural frequency constraints and forced response amplitude constraints at various frequencies of excitation. Several locations on the structure and degrees of freedom can be constrained simultaneously. The designer must exercise judgment and physical intuition to limit the number of constraints and consequently the computational time. Strategies and guidelines are discussed. Such techniques are presented and applied to a 2,694 degree of freedom offshore tower.

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Tsuboi, Masahito. "Exceptionally Steep Brain-Body Evolutionary Allometry Underlies the Unique Encephalization of Osteoglossiformes". Brain, Behavior and Evolution 96, n. 2 (2021): 49–63. http://dx.doi.org/10.1159/000519067.

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Brain-body static allometry, which is the relationship between brain size and body size within species, is thought to reflect developmental and genetic constraints. Existing evidence suggests that the evolution of large brain size without accompanying changes in body size (that is, encephalization) may occur when this constraint is relaxed. Teleost fish species are generally characterized by having close-fitting brain-body static allometries, leading to strong allometric constraints and small relative brain sizes. However, one order of teleost, Osteoglossiformes, underwent extreme encephalization, and its mechanistic bases are unknown. Here, I used a dataset and phylogeny encompassing 859 teleost species to demonstrate that the encephalization of Osteoglossiformes occurred through an increase in the slope of evolutionary (among-species) brain-body allometry. The slope is virtually isometric (1.03 ± 0.09 SE), making it one of the steepest evolutionary brain-body allometric slopes reported to date, and it deviates significantly from the evolutionary brain-body allometric slopes of other clades of teleost. Examination of the relationship between static allometric parameters (intercepts and slopes) and evolutionary allometry revealed that the dramatic steepening of the evolutionary allometric slope in Osteoglossiformes was a combined result of evolution in the slopes and intercepts of static allometry. These results suggest that the evolution of static allometry, which likely has been driven by evolutionary changes in the rate and timing of brain development, has facilitated the unique encephalization of Osteoglossiformes.

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Ke, Zhang, Zhang Huijie e Tang Zhiping. "Experimental study of thin-walled TiNi tubes under radial quasi-static compression". Journal of Intelligent Material Systems and Structures 22, n. 18 (19 ottobre 2011): 2113–26. http://dx.doi.org/10.1177/1045389x11426344.

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TiNi tubes with various sizes and boundary constraints subjected to radial quasi-static compression were systematically studied. The contour curves of the tubes were extracted from the real-time charge-coupled device (CCD) images, and the circumferential strain, bending moment, and phase composition distribution were calculated based on the contour curves and some assumptions. It was found that the load–displacement curves had hysteretic loops, and all specimens could recover to their initial shape after unloading, which was attributed to the effects of austenite–martensite phase transformation and phase transformation hinges (THs). For single-tube experiments, the numbers of TH were observed to be twice the numbers of constraints. For vertical double-tube experiments, the main deformation of each tube was concentrated on its upper half circle. The energy dissipation rate (EDR) and the dissipated specific energy (SE) in single-tube case increased with decrease of the diameter–wall thickness ratio (DTR; D/ t) or increase of the constraint number. With a four-directional constraint condition and same D/ t, the EDR and SE of vertical double tubes were greater than that of a single tube and close-packed seven tubes. The present results could give a reference for designing repeatedly used shock-resistant element with higher energy absorption capacity.

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Pralet, Cédric, e Gérard Verfaillie. "Dynamic Online Planning and Scheduling Using a Static Invariant-Based Evaluation Model". Proceedings of the International Conference on Automated Planning and Scheduling 23 (2 giugno 2013): 171–79. http://dx.doi.org/10.1609/icaps.v23i1.13561.

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Sequential decision-making under uncertainty often uses an approach in which a plan is built over a given horizon ahead using a deterministic model, the first decisions in this plan are applied, new information is acquired, the plan is adapted or rebuilt from scratch over a sliding horizon, and so on. This paper introduces a generic local search library that can be used in this context to quickly build and rebuild good quality plans. This library is built upon the notion of invariant used in constraint-based local search. Invariants allow temporal constraints, resource constraints, and criteria to be very quickly evaluated from a variable assignment and re-evaluated from a small change in this assignment. The paper also shows how the library can be used to reason on dynamic problem instances using a unique static problem model, without dynamic memory allocation. The approach is illustrated on a problem of data download under uncertainty about the volume of data, coming from the space domain.

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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.

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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.

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Li, Chi, Zuxing Gu, Min Zhou, Jiecheng Wu, Jiarui Zhang e Ming Gu. "API Misuse Detection in C Programs: Practice on SSL APIs". International Journal of Software Engineering and Knowledge Engineering 29, n. 11n12 (novembre 2019): 1761–79. http://dx.doi.org/10.1142/s0218194019400205.

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Libraries offer reusable functionality through Application Programming Interfaces (APIs) with usage constraints such as call conditions or orders. Constraint violations, i.e. API misuses, commonly lead to bugs and security issues. Although researchers have developed various API misuse detectors in the past few decades, recent studies show that API misuse is prevalent in real-world projects, especially for secure socket layer (SSL) certificate validation, which is completely broken in many security-critical applications and libraries. In this paper, we introduce SSLDoc to effectively detect API misuse bugs, specifically for SSL API libraries. The key insight behind SSLDoc is a constraint-directed static analysis technique powered by a domain-specific language (DSL) for specifying API usage constraints. Through studying real-world API misuse bugs, we propose ISpec DSL, which covers majority types of API usage constraints and enables simple but precise specification. Furthermore, we design and implement SSLDoc to automatically parse ISpec into checking targets and employ a static analysis engine to identify potential API misuses and prune false positives with rich semantics. We have instantiated SSLDoc for OpenSSL APIs and applied it to large-scale open-source programs. SSLDoc found 45 previously unknown security-sensitive bugs in OpenSSL implementation and applications in Ubuntu. Up to now, 35 have been confirmed by the corresponding development communities and 27 have been fixed in master branch.

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Shiromizu, T., e H. Yoshino. "Positive Energy Theorem Implies Constraints on Static Steller Models". Progress of Theoretical Physics 116, n. 6 (1 dicembre 2006): 1159–64. http://dx.doi.org/10.1143/ptp.116.1159.

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33

Cinar, Ahmet, e Mustafa Kiran. "The Performance of Penalty Methods on Tree-Seed Algorithm for Numerical Constrained Optimization Problems". International Arab Journal of Information Technology 17, n. 5 (1 settembre 2020): 799–807. http://dx.doi.org/10.34028/iajit/17/5/13.

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The constraints are the most important part of many optimization problems. The metaheuristic algorithms are designed for solving continuous unconstrained optimization problems initially. The constraint handling methods are integrated into these algorithms for solving constrained optimization problems. Penalty approaches are not only the simplest way but also as effective as other constraint handling techniques. In literature, there are many penalty approaches and these are grouped as static, dynamic and adaptive. In this study, we collect them and discuss the key benefits and drawbacks of these techniques. Tree-Seed Algorithm (TSA) is a recently developed metaheuristic algorithm, and in this study, nine different penalty approaches are integrated with the TSA. The performance of these approaches is analyzed on well-known thirteen constrained benchmark functions. The obtained results are compared with state-of-art algorithms like Differential Evolution (DE), Particle Swarm Optimization (PSO), Artificial Bee Colony (ABC), and Genetic Algorithm (GA). The experimental results and comparisons show that TSA outperformed all of them on these benchmark functions

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Peng, Zihan, Yang Gao, Chengfa Gao, Rui Shang e Lu Gan. "Improving Smartphone GNSS Positioning Accuracy Using Inequality Constraints". Remote Sensing 15, n. 8 (13 aprile 2023): 2062. http://dx.doi.org/10.3390/rs15082062.

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To improve smartphone GNSS positioning performance using extra inequality information, an inequality constraint method was introduced and verified in this study. Firstly, the positioning model was reviewed and three constraint applications were derived from it, namely, vertical velocity, direction, and distance constraints. Secondly, we introduced an estimator based on the density function truncation method to solve the inequality constraint problem. Finally, the performance of the method was investigated using datasets from three smartphones, including a Huawei P30, a Huawei P40, and a Xiaomi MI8. The results indicate that the position and velocity accuracy can be improved in the up component using a vertical velocity constraint. The horizontal positioning accuracy was increased using a heading direction constraint with dynamic datasets. Numerically, the root mean square error (RMSE) improvement percentages were 16.77%, 14.57%, and 31.09% for HP40, HP30, and XMI8, respectively. Using an inter-smartphone distance constraint could enhance the horizontal positioning of all participating smartphones, with improvement percentages of 34.27%, 75.58%, and 23.66% for HP40, HP30, and XMI8, respectively, in the static dataset. Additionally, the improvement percentages were 15.90%, 5.55%, and 0.17% in dynamic datasets. In summary, this study demonstrates that utilizing inequality constraints can significantly improve smartphone GNSS positioning.

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BOSTWICK, J. B., e P. H. STEEN. "Stability of constrained cylindrical interfaces and the torus lift of Plateau–Rayleigh". Journal of Fluid Mechanics 647 (18 marzo 2010): 201–19. http://dx.doi.org/10.1017/s0022112009993831.

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Surface tension acting at a cylindrical interface holds an underlying liquid in motionless equilibrium. This static base state is subject to dynamic capillary instability, including Plateau–Rayleigh breakup. If the interface is partially supported by a cylindrical cup-like solid, the extent of the wetting contact can significantly influence the dynamics and the stability of the configuration. The equation for the motion of small disturbances is formulated as an eigenvalue equation on linear operators. A solution is constructed on a constrained function space using a Rayleigh–Ritz procedure. The influence of the extent-of-constraint on the dispersion relation and on modal structures is reported. In the extreme, the support reduces to a wire, aligned axially, and just touching the interface. From prior work, this constraint is known to stabilize the Plateau–Rayleigh limit by some 13%. We report the wavenumber of maximum growth and estimate the time to breakup. The constraint is then bent in-plane to add a weak secondary curvature to the now nearly cylindrical base state. This is referred to as the torus lift of the cylinder. The static stability of these toroidal equilibria, calculated using a perturbation approach, shows that the position of constraint is crucial – constraint can stabilize (outside) or destabilize (inside). The combined influence of secondary curvature and wire constraint on the Plateau–Rayleigh limit is tracked. Finally, attention is restricted to constraints that yield a lens-like cylindrical meniscus. For these lenses, the torus lift is used as apparatus along with a symmetrization procedure to prove a large-amplitude static stability result. Our study is conveniently framed by a classic paper on rivulets by Davis (J. Fluid Mech., vol. 98, 1980, p. 225).

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Jochems, Jerome, Eddie Jones e Steven Ramsay. "Higher-Order MSL Horn Constraints". Proceedings of the ACM on Programming Languages 7, POPL (9 gennaio 2023): 2017–47. http://dx.doi.org/10.1145/3571262.

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The monadic shallow linear (MSL) class is a decidable fragment of first-order Horn clauses that was discovered and rediscovered around the turn of the century, with applications in static analysis and verification. We propose a new class of higher-order Horn constraints which extend MSL to higher-order logic and develop a resolution-based decision procedure. Higher-order MSL Horn constraints can quite naturally capture the complex patterns of call and return that are possible in higher-order programs, which make them well suited to higher-order program verification. In fact, we show that the higher-order MSL satisfiability problem and the HORS model checking problem are interreducible, so that higher-order MSL can be seen as a constraint-based approach to higher-order model checking. Finally, we describe an implementation of our decision procedure and its application to verified socket programming.

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Zhang, S. J., D. Howard e D. J. Sanger. "Workspaces of a walking machine and their graphical representation. Part II: static workspaces". Robotica 14, n. 2 (marzo 1996): 219–26. http://dx.doi.org/10.1017/s0263574700019135.

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SUMMARYPart I of this paper was concerned with kinematic workspaces of walking machines, while this paper addresses the static workspaces of a walking machine and their graphical representation. The results of static analysis are presented; the static workspace constraints are established; an algorithm for investigation of static workspaces is presented; and the position static workspaces are analysed and graphically represented for an example walking machine design.

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Chen, Shenyan, Ziqi Dai, Wenjing Shi, Yanjie Liu e Jianhongyu Li. "Local Modal Frequency Improvement with Optimal Stiffener by Constraints Transformation Method". Applied Sciences 11, n. 22 (22 novembre 2021): 11072. http://dx.doi.org/10.3390/app112211072.

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Local modal vibration could adversely affect the dynamical environment, which should be considered in the structural design. For the mode switching phenomena, the traditional structural optimization method for problems with specific order of modal frequency constraints could not be directly applied to solve problems with local frequency constraints. In the present work, a novel approximation technique without mode tracking is proposed. According to the structural character, three reasonable assumptions, unchanged mass matrix, accordant modal shape, and reversible stiffness matrix, have been used to transform the optimization problem with local frequency constraints into a problem with nodal displacement constraints in the local area. The static load case is created with the modal shape equilibrium forces, then the displacement constrained optimization is relatively easily solved to obtain the optimal design, which satisfies the local frequency constraints as well. A numerical example is used to verify the feasibility of the proposed approximation method. Then, the method is further applied in a satellite structure optimization problem.

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Zhou, Yang, e Xiaofu Ji. "Static Output Feedback Control for Nonlinear Time-Delay Semi-Markov Jump Systems Based on Incremental Quadratic Constraints". Mathematical and Computational Applications 28, n. 2 (24 febbraio 2023): 30. http://dx.doi.org/10.3390/mca28020030.

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This paper is concerned with the problem of static output feedback control for a class of continuous-time nonlinear time-delay semi-Markov jump systems with incremental quadratic constraints. For a class of time-delay semi-Markov jump systems satisfying incremental quadratic constrained nonlinearity, an appropriate mode-dependent Lyapunov–Krasovskii functional is constructed. Based on the matrix transformation, projection theorem and convex set principle, the mode-dependent static output feedback control laws are designed. The feedback control law is given in the form of a linear matrix inequality, which is convenient for a numerical solution. Finally, two practical examples are given to illustrate the effectiveness and superiority of the proposed method.

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Stoica, Adrian-Mihail, e Isaac Yaesh. "STATIC OUTPUT FEEDBACK DESIGN IN AN ANISOTROPIC NORM SETUP". Annals of the Academy of Romanian Scientists Series on Mathematics and Its Application 12, n. 1-2 (2020): 425–38. http://dx.doi.org/10.56082/annalsarscimath.2020.1-2.425.

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The design of static output feedback controllers in an anisotropic norm setup is considered. The aim is to determine a stabilizing static output feedback for a given four block system such that the resulting closed loop system has the a-anisotropic norm less than a given γ > 0. The solvability conditions are expressed in terms of the solution of a rank minimization problem with linear matrix inequalities constraints. Based on the specific form of these constraints it is shown that a solution of this problem may be obtained solving a semidefinite programming problem.

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Anderson, Neil, e Chris Button. "Development of Static Postural Control: An Overview and Summary of Entropy Analysis". Journal of Motor Learning and Development 5, n. 1 (giugno 2017): 126–47. http://dx.doi.org/10.1123/jmld.2016-0011.

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Control of static posture is constrained by multiple sensory inputs, motor ability, and task constraints. Development of static postural control across the lifespan can be analyzed effectively using nonlinear analyses of center of pressure (CoP) time series, including approximate and sample entropy. In this paper, the key findings from studies using nonlinear analysis tools are reviewed to describe the development of postural control. Preschool children learn to adopt relatively unstable postures (e.g., standing) in which the regularity of CoP initially increases as a consequence of restricting mechanical degrees of freedom. As children age, CoP regularity decreases as degrees of freedom are released, thus enabling a more functional, adaptable type of postural control. Changes to sensory inputs or task constraints also affect the regularity of CoP sway. For example, removing vision, adding vibration, or imposing dual-task conditions affect performer’s CoP regularity differently. One limitation of approximate and sample entropy analysis is the influence of different input parameters on the output and subsequent interpretation. Ongoing refinement to entropy analysis tools concern determining appropriate values for the length of sequence to be matched and the tolerance level used with CoP data.

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42

Hussain, Tahir, Khudija Shaheen e Faiza Saleem. "Homothetic matter collineations of static plane symmetric spacetimes". International Journal of Geometric Methods in Modern Physics 16, n. 12 (23 ottobre 2019): 1950182. http://dx.doi.org/10.1142/s0219887819501822.

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In this paper, we present a complete classification of static plane symmetric spacetimes via their homothetic symmetries of the energy–momentum tensor, known as homothetic matter collineations (HMCs). The HMC equations for these spacetimes are derived and then solved by considering the degeneracy and non-degeneracy of the energy–momentum tensor. In the former case, we have obtained 6, 11 and infinite number of HMCs, while in the latter case, the solution of HMC equations yields 6-, 7-, 8-, 10- and 11-dimensional algebra of HMCs. The obtained HMCs generate some differential constraints involving the components of the energy–momentum tensor. Some examples of static plane symmetric spacetime metrics satisfying these constraints are provided and the physical interpretations of these metrics are discussed.

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Goncharenko, Igor, Mikhail Svinin, Yutaka Kanou e Shigeyuki Hosoe. "Predictability of Rest-to-Rest Movements in Haptic Environments with 3D Constraints". Journal of Robotics and Mechatronics 18, n. 4 (20 agosto 2006): 458–66. http://dx.doi.org/10.20965/jrm.2006.p0458.

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We present a networked system with interchangeable constraints for studying skillful human movements via haptic (PHANToM-based) displays. The unified interface easily links different physical models with 2D and 3D static spatial constraints and graphical content related to the models. We analyzed motions based on data recorded by a history unit with a frequency of 100Hz. Theoretical and experimental kinematic profiles compared for several cases of basic reaching rest-to-rest tasks included curve-constrained motions with different curvatures, flexible object control, and cooperative two-arm movements. Experimental patterns exhibit the best agreement with optimal control models based on jerk and force-change minimization criteria.

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Karpel, M., B. Moulin e M. H. Love. "Modal-Based Structural Optimization with Static Aeroelastic and Stress Constraints". Journal of Aircraft 34, n. 3 (maggio 1997): 433–40. http://dx.doi.org/10.2514/2.2188.

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45

Bi, Kun, Guoping Luo, Shui Tian, Siqi Zhang, Xiaoxue Liu, Qiang Wang, Qing Lu e Zhijian Yao. "An enriched granger causal model allowing variable static anatomical constraints". NeuroImage: Clinical 21 (2019): 101592. http://dx.doi.org/10.1016/j.nicl.2018.11.002.

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46

Galrão Ramos, A., José F. Oliveira, José F. Gonçalves e Manuel P. Lopes. "A container loading algorithm with static mechanical equilibrium stability constraints". Transportation Research Part B: Methodological 91 (settembre 2016): 565–81. http://dx.doi.org/10.1016/j.trb.2016.06.003.

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47

Somayajula, Gopichand, e Jim Bernard. "Design optimization of structures subject to static and dynamic constraints". Finite Elements in Analysis and Design 5, n. 3 (ottobre 1989): 281–89. http://dx.doi.org/10.1016/0168-874x(89)90050-4.

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48

Park, Jaebum, You-Sin Kim e Jae Kun Shim. "Prehension synergy: Effects of static constraints on multi-finger prehension". Human Movement Science 29, n. 1 (febbraio 2010): 19–34. http://dx.doi.org/10.1016/j.humov.2009.11.001.

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49

Flake, Stephan, e Wolfgang Mueller. "Formal semantics of static and temporal state-oriented OCL constraints". Software & Systems Modeling 2, n. 3 (ottobre 2003): 164–86. http://dx.doi.org/10.1007/s10270-003-0026-x.

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50

Ferré, J. C., R. Legoux, J. L. Helary, F. Albugues, C. Floc'h, J. Bouteyre, J. P. Lumineau et al. "Study of the mandible under static constraints by holographic interferometry". Anatomia Clinica 7, n. 3 (settembre 1985): 193–201. http://dx.doi.org/10.1007/bf01654641.

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