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On the Volume Conservation of the Immersed Boundary Method

Communications in Computational Physics 2012年第7期12卷 401-432页

作者： boyce e.griffith Leon H.Charney Division of Cardiology New York University School of Medicine550 First AvenueNew YorkNew York 10016USA

The immersed boundary(IB)method is an approach to problems of fluid-structure interaction in which an elastic structure is immersed in a viscous incompressible *** IB formulation of such problems uses a Lagrangian description of the structure and an eulerian description of the *** is well known that some versions of the IB method can suffer from poor volume *** have been introduced to improve the volume-conservation properties of the IB method,but they either have been fairly specialized,or have used complex,nonstandard eulerian finite-difference *** this paper,we use quasi-static and dynamic benchmark problems to investigate the effect of the choice of eulerian discretization on the volume-conservation properties of a formally second-order accurate IB *** consider both collocated and staggered-grid discretization *** the tests considered herein,the staggered-grid IB scheme generally yields at least a modest improvement in volume conservation when compared to cell-centered methods,and in many cases considered in this work,the spurious volume changes exhibited by the staggered-grid IB method are more than an order of magnitude smaller than those of the collocated *** also compare the performance of cell-centered schemes that use either exact or approximate projection *** find that the volumeconservation properties of approximate projection IB methods depend strongly on the formulation of the projection *** used with the IB method,we find that pressure-free approximate projection methods can yield extremely poor volume conservation,whereas pressure-increment approximate projection methods yield volume conservation that is nearly identical to that of a cell-centered exact projection method.

关键词： Immersed boundary method fluid-structure interaction collocated discretization staggered-grid discretization exact projection method approximate projection method volume conservation

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Simulating an elastic Ring with Bend and Twist by an Adaptive Generalized Immersed Boundary Method

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Communications in Computational Physics 2012年第7期12卷 433-461页

作者： boyce e.griffith Sookkyung Lim Leon H.Charney Division of Cardiology Department of MedicineNew York University School ofMedicine550 First AvenueNew YorkNew York 10016USA Department of Mathematical Sciences University of Cincinnati839 Old Chemistry BuildingCincinnatiOhio 45221USA

Many problems involving the interaction of an elastic structure and a viscous fluid can be solved by the immersed boundary(IB)*** the IB approach to such problems,the elastic forces generated by the immersed structure are applied to the surrounding fluid,and the motion of the immersed structure is determined by the local motion of the ***,the IB method has been extended to treatmore general elasticity models that include both positional and rotational degrees of *** such models,force and torque must both be applied to the *** positional degrees of freedomof the immersed structuremove according to the local linear velocity of the fluid,whereas the rotational degrees of freedom move according to the local angular *** paper introduces a spatially adaptive,formally second-order accurate version of this generalized immersed boundary *** use this adaptive scheme to simulate the dynamics of an elastic ring immersed in *** describe the elasticity of the ring,we use an unconstrained version of Kirchhoff rod *** demonstrate empirically that our numerical scheme yields essentially second-order convergence rates when applied to such *** also study dynamical instabilities of such fluid-structure systems,and we compare numerical results produced by our method to classical analytic results from elastic rod theory.

关键词： Immersed boundary method Kirchhoff rod theory adaptive mesh refinement

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efficient Variable-Coefficient Finite-Volume Stokes Solvers

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Communications in Computational Physics 2014年第10期16卷 1263-1297页

作者： Mingchao Cai Andy Nonaka John B.Bell boyce e.griffith Aleksandar Donev Courant Institute of Mathematical Sciences New York UniversityNew YorkNY 10012USA. Center for Computational Sciences and engineering Lawrence Berkeley National LaboratoryBerkeleyCA 94720USA. Leon H.Charney Division of Cardiology Department of MedicineNew York University School of MedicineNYUSA. Department of Mathematics University of North CarolinaChapel HillNC 27599USA

We investigate several robust preconditioners for solving the saddle-point linear systems that arise from spatial discretization of unsteady and steady variablecoefficient Stokes equations on a uniform staggered *** on the success of using the classical projection method as a preconditioner for the coupled velocitypressure system[***,***.,228(2009),pp.7565–7595],as well as established techniques for steady and unsteady Stokes flow in the finite-element literature,we construct preconditioners that employ independent generalized Helmholtz and Poisson solvers for the velocity and pressure *** demonstrate that only a single cycle of a standard geometric multigrid algorithm serves as an effective inexact solver for each of these *** to traditional wisdom,we find that the Stokes problem can be solved nearly as efficiently as the independent pressure and velocity subproblems,making the overall cost of solving the Stokes system comparable to the cost of classical projection or fractional step methods for incompressible flow,even for steady flow and in the presence of large density and viscosity *** of the five preconditioners considered here are found to be robust to GMReS restarts and to increasing problem size,making them suitable for large-scale *** work opens many possibilities for constructing novel unsplit temporal integrators for finite-volume spatial discretizations of the equations of low Mach and incompressible flow dynamics.

关键词： Stokes flow variable density variable viscosity saddle point problems projection method preconditioning GMReS.

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RANKL inhibition reduces lesional cellularity and Gαs variant expression and enables osteogenic maturation in fibrous dysplasia

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Bone Research 2024年第1期12卷 165-179页

作者： Luis F.de Castro Jarred M.Whitlock Zachary Michel Kristen Pan Jocelyn Taylor Vivian Szymczuk Brendan boyce Daniel Martin Vardit Kram Rebeca Galisteo Kamran Melikov Leonid V.Chernomordik Michael T.Collins Alison M.boyce Skeletal Disorders and Mineral Homeostasis Section National Institute of Dental and Craniofacial ResearchNational Institutes of HealthBethesdaMDUSA Section on Membrane Biology Eunice Kennedy Shriver National Institute of Child Health and Human DevelopmentNational Institutes of HealthBethesdaMDUSA Metabolic Bone Disorders Unit National Institute of Dental and Craniofacial ResearchNational Institutes of HealthBethesdaMDUSA Department of Plastic and Reconstructive Surgery The Johns Hopkins Medical InstitutionsBaltimoreMDUSA Department of Pathology and Laboratory Medicine University of Rochester Medical CenterRochesterNYUSA NIDCR Genomics and Computational Biology Core National Institute of Dental and Craniofacial ResearchNational Institutes of HealthBethesdaMDUSA

Fibrous dysplasia(FD)is a rare,disabling skeletal disease for which there are no established *** evidence supports inhibiting the osteoclastogenic factor receptor activator of nuclear kappa-B ligand(RANKL)as a potential treatment *** this study,we investigated the mechanisms underlying RANKL inhibition in FD tissue and its likely indirect effects on osteoprogenitors by evaluating human FD tissue pre-and post-treatment in a phase 2 clinical trial of denosumab(NCT03571191)and in murine in vivo and ex vivo preclinical *** analysis of human and mouse tissue demonstrated increased osteogenic maturation,reduced cellularity,and reduced expression of the pathogenic Gαs variant in FD lesions after RANKL *** sequencing of human and mouse tissue supported these *** interaction between osteoclasts and mutant osteoprogenitors was further assessed in an ex vivo lesion model,which indicated that the proliferation of abnormal FD osteoprogenitors was dependent on *** results from this study demonstrated that,in addition to its expected antiosteoclastic effect,denosumab reduces FD lesion activity by decreasing FD cell proliferation and increasing osteogenic maturation,leading to increased bone formation within *** findings highlight the unappreciated role of cellular crosstalk between osteoclasts and preosteoblasts/osteoblasts as a driver of FD pathology and demonstrate a novel mechanism of action of denosumab in the treatment of bone disease.

关键词： dysplasia treatment finding

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Colorectal resections for malignancy: A pilot study comparing conventional vs freehand robot-assisted laparoscopic colectomy

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World Journal of Clinical Cases 2024年第3期12卷 488-494页

作者： Shamir O Cawich Joseph Martin Plummer Sahle.griffith Vijay Naraynsingh Department of Surgery University of the West IndiesSt AugustineTrinidad and Tobago Department of General Surgery and Consultant General and Colorectal Surgeon Department of SurgeryUniversity of the West IndiesKingstonKIN7Jamaica Department of Surgery Queen Elizabeth HospitalBridgetownBarbados Department of Surgery Port of Spain General HospitalPort of SpainTrinidad and Tobago

BACKGROUND Laparoscopic colectomy is widely accepted as a safe operation for colorectal cancer,but we have experienced resistance to the introduction of the FreeHandffrobotic camera holder to augment laparoscopic colorectal *** To compare the initial results between conventional and FreeHandffrobot-assisted laparoscopic colectomy in Trinidad and *** This was a prospective study of outcomes from all laparoscopic colectomies per-formed for colorectal carcinoma from November 29,2021 to May 30,*** following data were recorded:Operating time,conversions,estimated blood loss,hospitalization,morbidity,surgical resection margins and number of nodes *** data were entered into an excel database and the data were analyzed using SPSS ver *** There were 23 patients undergoing colectomies for malignant disease:8(35%)FreeHandff-assisted and 15(65%)conventional laparoscopic *** were no *** time was significantly lower in patients under-going robot-assisted laparoscopic colectomy(95.13±9.22 vs 105.67±11.48 min;P=0.045).Otherwise,there was no difference in estimated blood loss,nodal harvest,hospitalization,morbidity or *** The FreeHandffrobot for colectomies is safe,provides some advantages over conventional laparoscopy and does not compromise oncologic standards in the resource-poor Caribbean setting.

关键词： Laparoscopic Colectomy Robot Surgery Minimally invasive

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Simplified seismic scenario analysis of existing masonry buildings accounting for local site effects

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Frontiers of Structural and Civil engineering 2024年第2期18卷 309-318页

作者： Ayşe e.ÖZSOYÖZBAY Işıl SANRI KARAPINAR Zehra N.KUTLU İsmail e.KILIÇ Department of Civil engineering Maltepe UniversityIstanbul 34857Turkey School of engineering and Construction Oryx Universal CollegeDoha 12253Qatar

This study discusses the effects of local sites and hazard amplification on the seismic vulnerability assessment of existing masonry *** this context,a rapid seismic evaluation procedure was implemented on an old masonry building stock in the historical center Galata,located inİstanbul,to determine the seismic risk priority of the built *** scenarios were generated for all soil classes,different moment magnitudes,and source-to-site distances to obtain more accurate results for the seismic vulnerability assessment of the studied building ***,damage distributions estimated under nine different scenarios with/without site effects were compared and illustrated in maps to discuss changes in vulnerability owing to amplification *** this study,by re-examining the rapid seismic evaluation procedure by including geo-hazard-based assessment,the importance of site effects on the vulnerability and risk assessment of built heritage was *** proposed framework integrating field data and local site effects is believed to advance the current applications for vulnerability assessment of masonry buildings and provide an improvement in the application of rapid seismic assessment procedures with more reliable results.

关键词： masonry buildings seismic vulnerability assessment cultural heritage local site effect

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CLASSIFICATIONS OF DUPIN HYPeRSURFACeS IN LIe SPHeRe GeOMeTRY

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Acta Mathematica Scientia 2024年第1期44卷 1-36页

作者： Thomas e.CeCIL Department of Mathematics and Computer Science College of the Holy CrossWorcesterMA01610USA

This is a survey of local and global classification results concerning Dupin hypersurfaces in S^(n)(or R^(n))that have been obtained in the context of Lie sphere *** emphasis is on results that relate Dupin hypersurfaces to isoparametric hypersurfaces in *** with these classification results,many important concepts from Lie sphere geometry,such as curvature spheres,Lie curvatures,and Legendre lifts of submanifolds of S^(n)(or R^(n)),are described in *** paper also contains several important constructions of Dupin hypersurfaces with certain special properties.

关键词： Dupin hypersurfaces isoparametric hypersurfaces Lie sphere geometry Lie sphere transformations Lie curvatures

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FSCIL-eACA: Few-Shot Class-Incremental Learning Network Based on embedding Augmentation and Classifier Adaptation for Image Classification

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Chinese Journal of electronics 2024年第1期33卷 139-152页

作者： Ruru ZHANG Haihong e Meina SONG School of Computer Science Beijing University of Posts and Telecommunications education Department Information Network engineering Research Center Beijing University of Posts and Telecommunications

The ability to learn incrementally is critical to the long-term operation of AI systems. Benefiting from the power of few-shot class-incremental learning(FSCIL), deep learning models can continuously recognize new classes with only a few samples. The difficulty is that limited instances of new classes will lead to overfitting and exacerbate the catastrophic forgetting of the old classes. Most previous works alleviate the above problems by imposing strong constraints on the model structure or parameters, but ignoring embedding network transferability and classifier adaptation(CA), failing to guarantee the efficient utilization of visual features and establishing relationships between old and new classes. In this paper, we propose a simple and novel approach from two perspectives: embedding bias and classifier bias. The method learns an embedding augmented(eA) network with cross-class transfer and class-specific discriminative abilities based on self-supervised learning and modulated attention to alleviate embedding bias. Based on the adaptive incremental classifier learning scheme to realize incremental learning capability,guiding the adaptive update of prototypes and feature embeddings to alleviate classifier bias. We conduct extensive experiments on two popular natural image datasets and two medical datasets. The experiments show that our method is significantly better than the baseline and achieves state-of-the-art results.

关键词： Training Adaptation models Visualization Image recognition Prototypes Self-supervised learning Power capacitors

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Investigating the impact of the universal function of the nuclear proximity potential in heavy-ion fusion cross sections

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Communications in Theoretical Physics 2024年第5期76卷 86-93页

作者： R Gharaei e Sarvari Department of Physics Sciences FacultyHakim Sabzevari UniversityPO Box 397SabzevarIran Department of Physics Faculty of ScienceFerdowsi University of MashhadPO Box 91775-1436MashhadIran Science Faculty Department of PhysicsTarbiat Modares UniversityTehranIran

The fusion barriers and cross sections of 15 colliding systems with 320≤Z_(1)Z_(2)≤1512 are investigated in detail to understand the influence of the universal function of proximity potential formalism in the heavy-ion fusion *** realize this goal,we select three versions of the phenomenological proximity potentials,including Prox.77,Zhang 2013,and Guo 2013,to calculate the nucleus-nucleus *** experimental fusion cross sections for the selected reactions are analyzed using the standard coupled-channel calculations,including couplings to the low-lying 2^(+)and 3^(-)states in the target and *** calculated results show that the universal functions of the Guo 2013 and Prox.77 models provide the lowest and highest fusion barriers,*** addition,it is found that the height of the fusion barriers is enhanced by increasing the mass number of the projectile from light to heavy *** highest sensitivity to the mass number of the projectile belongs to the results of Prox.77.A discussion is also presented on the influence of the universal function on the radial behavior of the interaction potential in the allowed region for overlapping *** results reveal that the best fit to the experimental data of the fusion cross sections for the reactions involving light and medium nuclei is obtained using the universal function of the Zhang 2013 *** the heavier systems,the results of the Guo 2013 model at sub-barrier energies provide a good description of the available data.

关键词： fusion reactions proximity-type potentials universal function coupled-channel calculations

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event-triggered H_(∞) consensus control for input-constrained multi-agent systems via reinforcement learning

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Control Theory and Technology 2024年第1期22卷 25-38页

作者： Jinxuan Zhang Chang-e Ren College of Information engineering Capital Normal UniversityBeijing100089China

This article presents an event-triggered H_(∞) consensus control scheme using reinforcement learning (RL) for nonlinear second-order multi-agent systems (MASs) with control constraints. First, considering control constraints, the constrained H_(∞) consensus problem is transformed into a multi-player zero-sum game with non-quadratic performance functions. Then, an event-triggered control method is presented to conserve communication resources and a new triggering condition is developed for each agent to make the triggering threshold independent of the disturbance attenuation level. To derive the optimal controller that can minimize the cost function in the case of worst disturbance, a constrained Hamilton–Jacobi–Bellman (HJB) equation is defined. Since it is difficult to solve analytically due to its strongly non-linearity, reinforcement learning (RL) is implemented to obtain the optimal controller. In specific, the optimal performance function and the worst-case disturbance are approximated by a time-triggered critic network;meanwhile, the optimal controller is approximated by event-triggered actor network. After that, Lyapunov analysis is utilized to prove the uniformly ultimately bounded (UUB) stability of the system and that the network weight errors are UUB. Finally, a simulation example is utilized to demonstrate the effectiveness of the control strategy provided.

关键词： H_(∞)optimal control Input constrains Multi-agent systems(MASs) Reinforcement learning(RL)

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