An optimization-based strategy for peridynamic-FEM coupling and for the prescription of nonlocal boundary conditions
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We develop and analyze an optimization-based method for the coupling of a static peri-dynamic (PD) model and a static classical elasticity model. The approach formulates the coupling as a control problem in which the states are the solutions of the PD and classical equations, the objective is to minimize their mismatch on an overlap of the PD and classical domains, and the controls are virtual volume constraints and boundary conditions applied at the local-nonlocal interface. Our numerical tests performed on three-dimensional geometries illustrate the consistency and accuracy of our method, its numerical convergence, and its applicability to realistic engineering geometries. We demonstrate the coupling strategy as a means to reduce computational expense by confining the nonlocal model to a subdomain of interest, and as a means to transmit local (e.g., traction) boundary conditions applied at a surface to a nonlocal model in the bulk of the domain.Keywords:
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Many authors agree that preliminary traction prior to closed or open reduction for congenital dislocation of the hip is helpful. Different ways of traction have been used and each of them has its own advantages and disadvantages. One of the problems in the very young child is the difficulty in maintaining a suitable traction that is biomechanically effective. We found that using a rocker bed made the traction more "user friendly" for the child, the parent and the doctors.
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In this paper, we present a new stable and very dispersive boundary condition for the finite difference time domain (FD-TD) method. Compared with existing absorbing boundary conditions (ABC's), the new boundary condition has a similar computational complexity but much better absorbing performance. As well, the new boundary condition is more stable than presently existing ABC's.< >
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Aims Good submucosal exposure is a key factor for success during ESD, and can be achieved by different traction devices. Nevertheless, they all provide a fixed amount of traction force that tends to decrease as the dissection progresses. In contrast, the A-TRACT device, tightenable, offers the possibility of increasing traction during the procedure to improve exposure.
Endoscopic submucosal dissection
Tractive force
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To define the current application of preliminary traction for congenital dislocation of the hip (CDH), 335 members of the Pediatric Orthopaedic Society were surveyed, with an 87% response rate. Most respondents believe that traction reduces the incidence of avascular necrosis (AVN) and enables easier reduction. Only 5% of those surveyed do not use traction, but it is used more frequently in the Northeastern United States. Home traction, favored by 31% of the respondents, is used longer than hospital traction. Although traction is commonly used, a consensus to use preliminary traction has not been achieved. Practice patterns should not be used to determine effectiveness of a treatment.
Avascular Necrosis
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The paper discusses the correspondence between electromagnetic boundary conditions and interface conditions. In particular, the focus is on the synthetic approach where the interest is in finding material realizations for given boundary conditions. Material realizations are approximative but not unique because, especially if anisotropic and bianisotropic materials are allowed, there are different material classes with which any given boundary condition can be mimicked. As examples, the PEC, PMC, PEMC, and DB boundary conditions are discussed. By comparing the scattering characteristics, it is demonstrated how well certain extreme-parameter material realizations are able to simulate the boundary effect.
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Multipolar traction is a recent advance in colorectal endoscopic submucosal dissection (ESD) to expose the submucosal field [1] particularly for challenging lesions like residual lesions [2]. Nevertheless, two limitations exist with four-point traction. First, traction tends to reduce as ESD progresses, although new devices that can be stretched during the procedure to increase traction seem promising [3] [4]. Second, systematically placing four traction points is expensive (four clips), time-consuming, and not needed for lesions < 4 cm. For small lesions, two-point adaptive traction seems sufficient, but additional focal traction on the difficult area could help the physician.
Endoscopic submucosal dissection
CLIPS
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Weak consistency
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Tractive force
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