bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Mechanical Filter Concept to Suppress Crane Load Oscillations
Authors: Balachandran B. , Li Y.-Y. 
Published: February 2021

Abstract
In this article, preliminary results obtained in the exploration of a mechanical filter concept for suppressing crane-load oscillations on a ship vessel are presented. The pivot point about which the load oscillates is constrained to follow a circular track in the considered filter. The governing dynamical systems for the cases with and without the filter are presented, and the nonlinear dynamics of these systems is studied with respect to quasi-static variation of different scalar control parameters. It is shown that the presence of the filter helps in eliminating some of the sub-critical bifurcations that may arise in the crane-load response during periodic ship-roll excitations.
Magnetorheological Fluid Dampers for Seismic Control
Authors: Carlson J. David , Spencer B. F. 
Published: February 2021

Abstract
Magnetorheological (MR) fluid dampers have recently emerged as enabling technology for implementing semi-active control in a variety of applications. The successful use of a linear and rotary MR fluid damper in a variety of real-time control applications in the field has recently been demonstrated. Examples of several of these controllable MR fluid actuators, that are now either in commercial production or extended field test, are described herein. This technology is presently being extended to dampers for seismic control applications. Because of their mechanical simplicity, high dynamic range, low power requirements, large force capacity and robustness, magnetorheological (MR) fluid dampers mesh well with application demands and constraints to offer an attractive means of protecting civil infrastructure systems against severe earthquake and wind loading. Following an overview of the current status of MR fluid technology, this paper presents both laboratory and full-scale studies of the efficacy of MR dampers for seismic hazard mitigation.
Deconvolution by Wavelets for Extracting Impulse Response Functions
Authors: de Moraes Francisco José Vicente , Weber Hans Ingo 
Published: February 2021

Abstract
The extraction of Impulse Response Functions (Markov parameters) is a major feature on dynamic systems identification. The convolution integral is a most important input-output relationship for linear systems. Existing methods for calculating the IRFs from the convolution integral are carried out in time or frequency domains. The orthonormal wavelet transform consists on decomposing a given signal on mutually orthogonal local basis functions. It is possible to make use of the orthogonal properties of wavelets for calculating the convolution integral. The wavelet domain preserves the temporal nature of data and, simultaneously, different frequency bands are isolated by the multiresolution analysis, without loosing the orthogonality of the wavelet terms. Algorithm matrices are well conditioned and the method is not very sensitive to output noise. Simulated and experimental analysis are performed and results presented.
A Model Updating Method Based on the Concept of Frequency Shift Between Analytical and Experimental FRFs
Authors: Pascual Rodrigo , Golinval Jean-Claude , Razeto Mario 
Published: February 2021

Abstract
Up to now, model updating methods based on forced responses and local matrix sensitivities use both experimental and analytical quantities (FRFs and model impedance matrices) all evaluated at the same frequency(ies). However, this approach does not consider that between a reference system (the experimental model) and a perturbed one (the initial finite elements model), it exists a shift along the frequency axis that can be estimated using the Frequency Domain Assurance Criterion.
In this paper, a model updating method based on this observation is introduced. It can be interpreted as a generalisation of the existent techniques.
New Geometric Properties for Modelled Planar Vibration
Authors: Blanchet Pat , Lipkin Harvey 
Published: February 2021

Abstract
A novel analysis is used to identify new geometric properties for a seemingly well-known model — the linear vibration of an elastically suspended rigid body in planar motion. Vibration centers describe the modes shapes and are shown to be constrained to regions specified by the center-of-elasticity, center-ofmass, and stiffness principal directions. Responses are classified by the number of pure translational modes and conditions for existence are given. Vibration centers are also applied to forced vibration problems where there is a simple relation between an applied force and the resulting mode amplitudes. Numerical examples illustrate the results.
Reduction of Vibrations in Complex Structures With Viscoelastic Neutralizers: A Generalized Approach and a Physical Realization
Authors: de Espíndola J. J. , Bavastri C. A. 
Published: February 2021

Abstract
A general procedure for the optimization of the parameters of dynamic neutralizers is reviewed. It can be applied to the minimization of the vibration response and sound radiation of linear structures subjected to excitations in a specified frequency range.
Modal theory and generalized equivalent quantity concept for the neutralizers, introduced by Espíndola and Silva (1992), as applied to a non-linear optimization scheme, are also reviewed for clarity. That proposed procedure can be applied to relaxed and time invariant structures. It is not dependent on the structure complexity and the degree of discretization adopted.
In such conditions, a significant reduction in computing work is achieved, if compared with the more traditional methods.
Experimental results are compared with numerical ones.
Simulations of a Truck Driving on a Flexible Bridge
Authors: Friberg Olof , Möller Peter , Thorvald Boris 
Published: February 2021

Abstract
In this work, the main object was to perform simulations using a realistic model of a truck and trailer passing over a flexible bridge structure. Two driving cases were considered: straight forward driving with and without braking. In the latter case control logic was used to distribute the braking torques to the wheel axles.
A general multibody dynamics computer program, DADS, and its tire subroutines were interfaced with our FEM routines in order to create a vehicle/structure interaction computer program. A part of this process was to integrate different time stepping algorithms from the multibody dynamics and FEM disciplines into a “common” time integration procedure. Another part was to write code to search for finite elements where tire/structure interaction takes place.
Computational Schemes for Nonlinear Elastic Multi-Body Systems
Authors: Bauchau O. A. 
Published: February 2021

Abstract
This paper is concerned with the analysis of nonlinear elastic multi-body systems, i.e. a collection of bodies in arbitrary motion with respect to each other while each body is undergoing large displacements and rotations with respect to a body attached frame of reference. The focus is on problems where the strains within each elastic body remain small.
A New Numerical Method for the Dynamic Analysis of Impact Loads in Flexible Beams
Authors: Escalona José L. , Mayo Juana M. , Domínguez Jaime 
Published: February 2021

Abstract
The aim of this investigation is to compare the classical St. Venant’s solution of the axial impact on flexible rods with the numerical result from a finite element computational procedure involving component mode synthesis. A new technique developed to simulate impacts is used to this end. The impacts treated are those mainly governed by the propagation of elastic waves along the complete flexible body. Local effects at the vicinity of the contact surfaces are neglected. The phenomenon of succession of impacts is analytically proved, a second period of contact is found in a particular case. A numerical method is developed to solve the collision based on the theoretical solution. This technique is able to identify the elastic waves which travel along the rod and a force balance is continuously made to yield the contact stress and the velocity of the surfaces in contact. Numerical solution shows an excellent agreement between the numerically obtained displacements histories with the theoretical results. The capability of the eigenvectors to describe the wave propagation is analysed as well as the effect of the elements boundaries.
An Approach for the Dynamics of Robotic Manipulators With Structural Flexibility of Links and Joints
Authors: Kövecses J. , Fenton R. G. , Cleghorn W. L. 
Published: February 2021

Abstract
In this paper, an approach is presented for the dynamic modeling and analysis of robotic manipulators having structural flexibility in the links and joints. The formulation allows the user to include different types of flexibilities, as required. This approach includes the dynamic effects of joint driving systems by considering the mass and moments of inertia of their elements, the rotor-link interactions, and the gear reduction ratios; all of which can have significant influences on the behavior of the manipulator. Both distributed-discrete and discretized-discrete parameter models of a robot can be analysed. In the discretized-discrete case, dynamic equations of motion are developed for four model types: rigid link - rigid joint, rigid link - flexible joint, flexible link - rigid joint, and flexible link - flexible joint. An example of a two-link manipulator is considered. Simulation results are presented for different models (flexible joint - rigid link, rigid joint - flexible link, flexible joint - flexible link) of the manipulator. The computations show the influence of joint and link flexibilities on the manipulator performance.
Parallel O(log2N) Algorithm for the Motion Simulation of General Multi-Rigid-Body Mechanical Systems
Authors: Anderson Kurt S. 
Published: February 2021

Abstract
This paper presents a new highly efficient procedure for the determination of the dynamical equations of motion for complex multibody systems and their subsequent temporal integration using parallel computing. The method is applicable to general systems of rigid bodies which may contain arbitrary joint types, multiple branches, and/or close loops. The method is based on the explicit determination of constraint forces at key joint locations and the subsequent highly efficient determination of system state time derivatives. The algorithm uses a novel hybrid direct and iterative solution scheme which allows a substantially higher degree of parallelization than is generally obtainable using the more conventional recursive O(N) procedures. It is shown that at the coarsest level the parallelization obtainable easily exceeds that indicated by the topology of the system. The procedure can produce a theoretical and time optimal O(log2N) performance on computational throughput with a processor optimal O(N) processors on a MDMD distributed architecture processing system.
Fatigue Life Analysis Using Linear Transient Dynamics for Automotive Sheet Metal Structures
Authors: Huang Liping , Agrawal Hari 
Published: February 2021

Abstract
Since the environment of vehicle operation is dynamic in nature, dynamic method should be used in vehicle durability analysis. Due to the constraints in current computer resources, simulation of vehicle durability test and vehicle structural Me analysis need special approaches and efficient CAE tools. A methodology and an integrated analysis process is presented in this paper. Three examples of structural life analysis using transient dynamics are given. The examples show that dynamics analysis for vehicle life prediction is feasible by employing efficient methods and proper process. Results from the analysis demonstrate that dynamic stress levels are much higher than static stress at some locations and that dynamic methods give a significantly different structural life compared with static analysis.
Identifiability Issues for Parameter-Varying and Multidimensional Linear Systems
Authors: Lee Lawton H. , Poolla Kameshwar 
Published: February 2021

Abstract
This paper considers the identifiability of state space models for a system that is expressed as a linear fractional transformation (LFT): a constant matrix (containing identified parameters) in feedback with a finite-dimensional, block-diagonal (“structured”) linear operator. This model structure can represent linear time-invariant, linear parameter-varying, uncertain, and multidimensional systems. Families of input-output equivalent realizations are characterized as manifolds in the parameter space whose tangent spaces — and orthogonal complements — can be obtained via singular value decomposition. As illustrated by a numerical example, restricting iterative parameter estimation algorithms (e.g., maximum-likelihood with nonlinear programming) to the orthogonal directions offers significant computational advantages.
Benefits of Model Updating: A Case Study Using the Micro-Precision Interferometer Testbed
Authors: Joshi Sanjay S. , Melody James W. , Neat Gregory W. , Kissil Andrew 
Published: February 2021

Abstract
This paper presents a case study on the benefits of model updating using the Micro-Precision Interferometer (MPI) testbed, a full-scale model of a future spaceborne optical interferometer located at JPL. The MPI testbed is composed of several active and passive optical elements distributed across a 7 m × 7 m × 6.5 m truss structure. Successful operation of this complex optomechanical system requires positional stabilities of these optical elements down to the ten-nanometer level. Design of such systems for space requires a disturbance modeling capability that integrates optical modeling, structural modeling and control system design. An integrated model of MPI was built in parallel with the testbed, enabling a unique model updating and validation opportunity. Physical parameters of the structural finite element model were updated based on two separate modal tests: a comprehensive modal test of the base structure alone and an in situ component modal test. This paper quantifies the effect of these physical parameter updates on MPI integrated model prediction capability. Specifically, the paper compares three sets of disturbance-input to optical-output transfer functions: (1) measured data from the testbed, (2) predictions from a high-fidelity model without any parameter updates, and (3) similar predictions for the model with updated physical parameters. Results from this study indicate that physical parameter updating has provided little benefit for disturbance modeling on the MPI testbed. These results will have significant impact on the modeling strategy adopted for the Spaceborne Interferometer Mission (SIM).
Project Step: A Randomized Controlled Trial Investigating the Effects of Frequent Feedback and Contingent Incentives on Physical Activity
Authors: Kerrigan Stephanie G. , Forman Evan M. , Williams Dave , Patel Mitesh , Loyka Caitlin , Zhang Fengqing , Crosby Ross D. , Butryn Meghan L. 
Published: February 2021

Background: Financial incentives and feedback on behavior offer promise for promoting physical activity. However, evidence for the effect of each of these techniques is inadequate. The present study evaluated the effects of daily versus weekly feedback and incentives contingent on reaching a daily walking goal versus noncontingent incentives in a 2 × 2 trial. Methods: Participants (N = 57) had a body mass index >25 kg/m2 and were insufficiently active. Participants received a daily walking goal that adapted weekly. Results: Participants receiving daily feedback increased daily steps (P = .03) more than those receiving weekly feedback. Participants receiving contingent incentives did not significantly increase steps (P = .12) more than those receiving noncontingent incentives. A trend-level effect (P = .09) suggested that there may be an interaction such that the combination of daily feedback and contingent incentives is most effective. Conclusions: Results indicate that feedback is an important component of remotely delivered PA interventions and that evaluating each component of low-intensity interventions may help to improve efficacy. Moreover, results indicate that possible synergistic effects of feedback and rewards should be investigated further to help optimize interventions.
Covid-19 deaths in Africa: prospective systematic postmortem surveillance study
Authors: Mwananyanda Lawrence , Gill Christopher J , MacLeod William , Kwenda Geoffrey , Pieciak Rachel , Mupila Zachariah , Lapidot Rotem , Mupeta Francis , Forman Leah , Ziko Luunga , Etter Lauren , Thea Donald 
Published: February 2021

Abstract

Objective
To directly measure the fatal impact of coronavirus disease 2019 (covid-19) in an urban African population.

Design
Prospective systematic postmortem surveillance study.

Setting
Zambia’s largest tertiary care referral hospital.

Participants
Deceased people of all ages at the University Teaching Hospital morgue in Lusaka, Zambia, enrolled within 48 hours of death.

Main outcome measure
Postmortem nasopharyngeal swabs were tested via reverse transcriptase quantitative polymerase chain reaction (PCR) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Deaths were stratified by covis-19 status, location, age, sex, and underlying risk factors.

Results
372 participants were enrolled between June and September 2020; PCR results were available for 364 (97.8%). SARS-CoV-2 was detected in 58/364 (15.9%) according to the recommended cycle threshold value of <40 and in 70/364 (19.2%) when expanded to any level of PCR detection. The median age at death among people with a positive test for SARS-CoV-2 was 48 (interquartile range 36-72) years, and 69% (n=48) were male. Most deaths in people with covid-19 (51/70; 73%) occurred in the community; none had been tested for SARS-CoV-2 before death. Among the 19/70 people who died in hospital, six were tested before death. Among the 52/70 people with data on symptoms, 44/52 had typical symptoms of covid-19 (cough, fever, shortness of breath), of whom only five were tested before death. Covid-19 was identified in seven children, only one of whom had been tested before death. The proportion of deaths with covid-19 increased with age, but 76% (n=53) of people who died were aged under 60 years. The five most common comorbidities among people who died with covid-19 were tuberculosis (22; 31%), hypertension (19; 27%), HIV/AIDS (16; 23%), alcohol misuse (12; 17%), and diabetes (9; 13%).

Conclusions
Contrary to expectations, deaths with covid-19 were common in Lusaka. Most occurred in the community, where testing capacity is lacking. However, few people who died at facilities were tested, despite presenting with typical symptoms of covid-19. Therefore, cases of covid-19 were under-reported because testing was rarely done not because covid-19 was rare. If these data are generalizable, the impact of covid-19 in Africa has been vastly underestimated.
Laying the foundation for a Core Set of the International Classification of Functioning, Disability and Health for community-dwelling older adults in primary care: relevant categories of their functioning from the research perspective, a scoping review
Authors: Tomandl Johanna , Heinmüller Stefan , Selb Melissa , Graessel Elmar , Freiberger Ellen , Kühlein Thomas , Hueber Susann , Book Stephanie , Gotthardt Susann 
Published: February 2021

ObjectivesThe objective of this study was to find relevant concepts of functioning in community-dwelling older adults within frequently used assessment instruments published in the scientific literature. This was part of a larger project to develop an International Classification of Functioning, Disability and Health (ICF) Core Set for use in primary care.DesignA scoping review was conducted. Articles dealing with functioning in older adults were searched and assessed for eligibility. The study population included community-dwelling adults (≥75 years) without dementia, living in high-resource countries. Relevant concepts were extracted from assessment instruments and linked to the ICF using standardised linking rules. Finally, a frequency analysis was conducted.SettingHome, primary care.ParticipantsCommunity-dwelling adults aged 75 years and above.ResultsFrom 5060 identified publications, 68 were included and 30 assessment instruments extracted. Overall, 1182 concepts were retrieved. Most were linked to the ‘activities and participation’ component. The most frequently identified categories were ‘memory functions’, ‘dressing’ and ‘changing basic body position’.ConclusionsThis review provides a list of relevant ICF categories from the research perspective that will be used for developing an ICF Core Set for older primary care patients.Trial registration numbersPROSPERO (CRD42017067784), Versorgungsforschung Deutschland Datenbank (VfD_17_003833) and ClinicalTrials.gov (NCT03384732).
Cognitive measures during walking with and without lower-limb prosthesis: protocol for a scoping review
Authors: Yuan Jing , Cline Emily , Liu Ming , Huang He , Feng Jing 
Published: February 2021

IntroductionTuning of lower-limb (LL) robotic prosthesis control is necessary to provide personalised assistance to each human wearer during walking. Prostheses wearers’ adaptation processes are subjective and the efficiency largely depends on one’s mental processes. Therefore, beyond physical motor performance, prosthesis personalisation should consider the wearer’s preference and cognitive performance during walking. As a first step, it is necessary to examine the current measures of cognitive performance when a wearer walks with an LL prosthesis, identify the gaps and methodological considerations, and explore additional measures in a walking setting. In this protocol, we outlined a scoping review that will systematically summarise and evaluate the measures of cognitive performance during walking with and without LL prosthesis.Methods and analysisThe review process will be guided and documented by CADIMA, an open-access online data management portal for evidence synthesis. Keyword searches will be conducted in seven databases (Web of Science, MEDLINE, BIOSIS, SciELO Citation Index, ProQuest, CINAHL and PsycINFO) up to 2020 supplemented with grey literature searches. Retrieved records will be screened by at least two independent reviewers on the title-and-abstract level and then the full-text level. Selected studies will be evaluated for reporting bias. Data on sample characteristics, type of cognitive function, characteristics of cognitive measures, task prioritisation, experimental design and walking setting will be extracted.Ethics and disseminationThis scoping review will evaluate the measures used in previously published studies thus does not require ethical approval. The results will contribute to the advancement of prosthesis tuning processes by reviewing the application status of cognitive measures during walking with and without prosthesis and laying the foundation for developing needed measures for cognitive assessment during walking. The results will be disseminated through conferences and journals.