bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vasomotion analysis of speed resolved perfusion, oxygen saturation, red blood cell tissue fraction, and vessel diameter: Novel microvascular perspectives
Authors: Fredriksson Ingemar , Larsson Marcus , Strömberg Tomas , Iredahl Fredrik 
Published: November 2021

AbstractBackgroundVasomotion is the spontaneous oscillation in vascular tone in the microcirculation and is believed to be a physiological mechanism facilitating the transport of blood gases and nutrients to and from tissues. So far, Laser Doppler flowmetry has constituted the gold standard for in vivo vasomotion analysis.Materials and methodsWe applied vasomotion analysis to speed‐resolved perfusion, oxygen saturation, red blood cell tissue (RBC) tissue fraction, and average vessel diameter from five healthy individuals at rest measured by the newly developed Periflux 6000 EPOS system over 10 minutes. Magnitude scalogram and the time‐averaged wavelet spectra were divided into frequency intervals reflecting endothelial, neurogenic, myogenic, respiratory, and cardiac function.ResultsRecurrent high‐intensity periods of the myogenic, neurogenic, and endothelial frequency intervals were found. The neurogenic activity was considerably more pronounced for the oxygen saturation, RBC tissue fraction, and vessel diameter signals, than for the perfusion signals. In a correlation analysis we found that changes in perfusion in the myogenic, neurogenic, and endothelial frequency intervals precede changes in the other signals. Furthermore, changes in average vessel diameter were in general negatively correlated to the other signals in the same frequency intervals, indicating the importance of capillary recruitment.ConclusionWe conclude that vasomotion can be observed in signals reflecting speed resolved perfusion, oxygen saturation, RBC tissue fraction, and vessel diameter. The new parameters enable new aspects of the microcirculation to be observed.
Integrative taxonomy of Flatbill Flycatchers (Tyrannidae) reveals a new species from the Amazonian lowlands
Authors: Simões Carlynne C. , Cerqueira Pablo Vieira , Peloso Pedro , Aleixo Alexandre 
Published: November 2021

AbstractIntegrative taxonomic studies continue to reveal that many current polytypic species of birds are in fact constituted by two or more species and therefore have been central in uncovering ‘hidden’ or ‘cryptic’ biodiversity. The Olivaceous Flatbill (Aves: Tyrannidae: Rhynchocyclus olivaceus) currently has nine recognized subspecies distributed throughout the Neotropics, but so far, no complete phylogenetic hypothesis exists to test the validity and evolutionary relationships among them. To remedy this, we conducted a multi‐character integrative taxonomic revision of the genus Rhynchocyclus, focusing on the polytypic R. olivaceus. The combination of a taxonomically dense sampled multilocus phylogeny (including three mitochondrial and two nuclear genes) with phenotypic analyses including morphological and vocal characters pointed to several taxonomic inconsistencies within R. olivaceus. The analyses strongly support that R. olivaceus is paraphyletic, with an exclusively cis‐Andean clade (where the topotypic R. olivaceus is found) clustering as sister to Rhynchocyclus fulvipectus, to the exclusion of a clade grouping trans‐Andean and western Amazonian populations currently placed in R. olivaceus—one of which is unnamed and fully diagnosable based on vocal and genetic characters. Consistent with the phylogenetic results, our vocal analyses identified at least four morphologically cryptic lineages within R. olivaceus that can be mutually diagnosed from each other by different loudsongs and call parameters. Therefore, we provide evidence for splitting these four groups into separate species, two of which are sympatric but not syntopic in western Amazonia, including an unnamed species described herein—Rhynchocyclus cryptus, sp. nov. urn:lsid:zoobank.org:act:2DC17190‐2BDD‐49EC‐88E6‐4CF2FC2562A3.
Superposition Effect of the Leading Edge Film on the Downstream Film Cooling of a Turbine Vane Under Combustor Swirling Outflow
Authors: Wu Zhuang , Zhu Hui-ren , Liu Cun-liang , Li Lin , Wang Ming-rui 
Published: November 2021

Abstract
To investigate the superposition effect of the leading edge (LE) film on the downstream film cooling under swirling inflow, numerical simulations with three vane models (vane with films on the leading edge only, vane with films on the pressure side (PS), and suction side (SS) only, full-film cooling vane), two inlet conditions (axial inlet and swirling inlet) are conducted. The results indicate that the leading edge is the area where the film is most affected by the swirling inflow. For full-film cooling vane, the film on the leading edge does not always improve or even reduce the downstream film cooling. Flow mechanism analysis shows that the velocity direction near the downstream wall is governed by the interaction between the direction of swirling inflow and the direction of film hole incidence on the leading edge. A new type of leading-edge film proposed by the author is also investigated, with the dividing line of the counterinclined film-hole row coinciding with the twisted stagnant line to ensure that all films are incident at angles inverse to the direction of the swirling inflow. The new leading-edge film successfully changes the velocity direction near the downstream wall and suppresses the deflecting effect on the downstream film. The new leading-edge film can increase the overall area-averaged cooling effectiveness (η) of the full-film cooling vane by 10%, 15%, 18% and reduce the inhomogeneity by 13%, 19%, 27% over the traditional design, as the coolant mass flow increases.
Importance of Seismic SSI in 3-D Tunnels Assuming Inelastic Material Behavior
Authors: Hatzigeorgiou G. D. , Beskos D. E. 
Published: November 2021

Abstract
This paper investigates the importance of seismic soil-structure interaction in three-dimensional lined tunnels, assuming inelastic material behavior for both the concrete liner and the soft rock type of soil. The seismic response of the soil-structure system is obtained by the finite element method in the time domain. Viscous absorbing boundaries are used in conjunction with the discretization of the rock medium. Both the rock medium and the concrete liner are assumed to behave inelastically on the basis of the continuum damage mechanics theory. The seismic waves are assumed to have any arbitrary time variation and direction of propagation. The system is analysed with and without soil-structure interaction in order to assess its importance on the response of the system.
Compressive Instabilities in Braided Textile Composites
Authors: Quek Shu Ching , Waas Anthony M. , Agaram Venkatesh , Shahwan Khaled 
Published: November 2021

Abstract
This paper discusses the results of a finite element (FE) based study of the compressive instabilities of braided glass fiber composites. The micromodel was based on a 2-unitcell size 3-D FE model. Computational tests were carried out to first determine the elastic moduli of the system. Once the computational model was validated with experimental data for the elastic moduli, the compressive response of the micromodel was established using the RIKS method option available in the ABAQUS commercial FE code. The present approach is different from that reported in the literature where classical methods based on the technique of homogenization is used to model the elastic and inelastic response of braided composites. In the present work, explicit account of the braid microstructure (geometry and packing) and the inelastic properties of the matrix are accounted for via the use of the FE method. The macromechanical data pertaining to the braided composites were obtained through traditional means. Tensile tests were performed on the composites through the usage of ASTM D 3039 standard to obtain the macroscopic orthotropic moduli and response. For each test, 3 samples were used to ensure accuracy and the average data is reported in this paper. A separate test was conducted to obtain the in-situ matrix properties of the glass braided composites. The computational model provides a means to assess the compressive strength of braided composites and its dependence on various microstructural parameters. It also serves as a tool to assess the most significant parameter that affects compressive strength. Furthermore, the model is useful to understand the response of braided composites under multiaxial loads.
A New 3D Dynamic Tire/Road Friction Model for Vehicle Control and Simulation
Authors: Claeys Xavier , Yi Jingang , Alvarez Luis , Horowitz Roberto , de Wit Carlos Canudas 
Published: November 2021

Abstract
In this paper a 3D dynamic tire/road friction model is presented. This model is based on the LuGre dry friction model and tire dynamics. The longitudinal and lateral forces, and tire self-aligning torque are determined through several first-order dynamic systems. The main advantage of this model is that it can be easily used and identified for vehicle control and simulation. Furthermore, calibration of model parameters and comparison with “magic formula”, which is widely used in area, are presented to validate the model.
Co-Simulation of Algebraically Coupled Dynamic Subsystems
Authors: Gu Bei , Asada H. Harry 
Published: November 2021

Abstract
This paper analyzes the problem of Co-Simulation. The term Co-Simulation is used to describe a large dynamic system that is simulated by running a group of independently coded subsystem simulators. Very commonly, the Co-Simulation of subsystems faces incompatible boundary conditions, i.e., causal conflicts. These causal conflicts cannot be directly resolved, due to the nonlinearity and/or difficulties in modification of coded subsystem simulators. Causal conflicts result in algebraic constraints. Boundary Condition Coordinators (BCCs) are designed to calculate boundary conditions based on subsystem models and their algebraic constraints. The Co-Simulation, which is modeled as Differential Algebraic Equations, then relies on BCC to provide compatible boundary conditions for subsystem simulators. The high index constraint is reduced to index one by defining a sliding manifold. Different ways of enforcing the sliding manifold are discussed: A new Discrete-Time Sliding Mode (DTSM) controller is devised to serve as a BCC, enforcing sliding manifolds and providing boundary conditions. The multi-rate scheme can guarantee Co-Simulation stability at any given step size of all subsystem simulators, provided the subsystem simulators are tested stable at that step size. An example is given to demonstrate the DTSM method. Advantages and possible future improvements are discussed.
A Method for the Frequency Domain Design of PWM-Controlled Pneumatic Systems
Authors: Barth Eric J. , Zhang Jianlong , Goldfarb Michael 
Published: November 2021

Abstract
This paper presents a rigorous analysis and design method for PWM-based control of pneumatic systems. An equivalent analytical model incorporating the effects of a finite PWM switching period is formulated. This equivalent model was motivated by a lack of control design and analysis techniques needed to treat the inherently non-analytical switching models associated with PWM-based systems. The equivalent model enables the design of a loop compensator that rigorously addresses control design issues of stability robustness, disturbance rejection, insensitivity to sensor noise, performance bandwidth and actuator saturation. Simulation of this compensator with both the equivalent design model and a full nonlinear switching model for a particular pneumatic robot application is presented which demonstrates and validates the proposed method.
Delay-Dependent Induced L2Norm Analysis and Control for LPV Systems With State Delays
Authors: Wu Fen 
Published: November 2021

Abstract
In this paper, we address the analysis and state-feedback synthesis problems for linear parameter-varying (LPV) systems with parameter-varying time delays. It is assumed that the state-space data and the time delays depend on parameters that are measurable in real-time and vary in a compact set with bounded variation rates. We explore the delay-dependent stability and the induced L2 norm performance of these systems using parameter-dependent Lyapunov functions. In addition, the state-feedback control synthesis problem is examined when a variable state delay is present. Both analysis and synthesis conditions are formulated in terms of linear matrix inequalities (LMIs) that can be solved via efficient interior-point algorithms.
Adaptive Nonlinear Control for Spacecraft With Coupled Translational and Attitude Dynamics
Authors: Pan Haizhou , Kapila Vikram 
Published: November 2021

Abstract
In this paper, we address a tracking control problem for the coupled translational and attitude motion of a spacecraft. Specifically, a nonlinear adaptive control law is developed to ensure global asymptotic tracking of the desired translational and attitude trajectories in the presence of unknown mass and inertia parameters of spacecraft. Using the vectrix formalism the translational and attitude dynamics of spacecraft is modeled, where the mutual coupling in the translational and attitude motion induced by their gravitational interaction is duly accounted. The four-parameter quaternion representation is employed to describe the attitude kinematics of spacecraft in order to enable large orientation maneuvers. Based on the structure of the resulting system dynamics, the filtered translational and attitude tracking error dynamics are developed, which facilitate the transformation of second-order translational and attitude motion error dynamics as first-order equations, thus providing a considerable simplification in control law synthesis/analysis. With the aid of two linear operators, the open-loop filtered tracking error dynamics is parameterized such that the unknown mass and inertia parameters of spacecraft are isolated and can be estimated on-line. Using a Lyapunov framework, nonlinear control and adaptation laws are designed that ensure the global asymptotic convergence of the translational and attitude position tracking errors, despite the presence of unknown mass and inertia parameters of spacecraft. In addition, the form of the filtered tracking error reveals the convergence of translational and attitude velocity tracking errors of spacecraft. An illustrative numerical simulation is presented to demonstrate the effectiveness of the proposed control design methodology for the coupled translational and attitude motion control of spacecraft.
Adaptive AQM Routers Supporting TCP Flows
Authors: Chait Yossi , Oldak Salomon , Hollot C. V. , Misra Vishal 
Published: November 2021

Abstract
This paper describes the development of an adaptive algorithm for active queue management (AQM) routers supporting a dynamically varying number of long-lived TCP flows. We use a nonlinear dynamic model of TCP behavior which was recently developed from fluid-flow and stochastic differential equation analysis. We first show that the high-frequency gain of the linearized plant model is inversely proportional to the network load factor which can easily vary by an order of magnitude. The motivation for adaptation follows from the direct relation between the plant’s high-frequency gain and stability margins and speed of response. Our adaptive algorithm — the Externally Excited Adaptive Loop (EEAL) — is shown to achieve improved queue level management compared with that achieved using RED AQM and the recently proposed PI AQM.
Autonomous Decentralized Control
Authors: Šiljak Dragoslav D. , Stipanović Dušan M. 
Published: November 2021

Abstract
A decentralized control law is called autonomous if the resulting closed-loop interconnected system is connectively stable, that is, the system remains stable despite structural perturbations whereby subsystems are disconnected and again connected in an unpredictable way during operation. The objective of the paper is to propose an LMI scheme for design of autonomous decentralized controllers and observers for output control of complex systems. An interesting feature of the proposed observer-based controllers is that they do not impose any communication overhead since only the locally available output information is required.
A Method for the Study of Position in Highly Redundant Multibody Systems in Environments With Obstacles
Authors: Zelaia Josu Agirrebeitia , González Rafael Avilés , de Bustos Igor Fernandez , Martin Enrique Amezua San 
Published: November 2021

Abstract
The present article looks at a method of analysing the behaviour of highly redundant multibody systems (e.g. in the case of cellular adaptive structures of variable geometry) in environments with obstacles. It is sought to solve the inverse problem in successive positions of variable-geometry structures, avoiding the obstacles in its work environment; i.e. the computation of the increment that has to be assigned to the actuators throughout the movement of the multibody system so that it does not collide with obstacles, as one or more nodes perform a pre-established function (e.g. a certain path). The multibody systems are modelled via rod-type finite elements, both deformable and indeformable, and the coordinates of their nodes are chosen as variables. The obstacles are modelled via a mesh of points that exert repulsive forces on the nodes of the multibody, so that interference between the two is avoided. Such forces have been chosen inversely proportional to the Nth power of the distance between the corresponding points of the obstacle and of the multibody system. The method is based on a potential function and on its minimization using the Lagrange Multiplier Method. The solution of the resulting equations is undertaken iteratively with the Newton-Raphson Method. The 2D and 3D examples provided attest to the good performance of the algorithms and procedure here set forth.
Design of Haptic Interfaces to Assess the Driving Capabilities of People With Disabilities
Authors: Zekri S. , Pernalete N. , Dubey R. V. , Gage A. 
Published: November 2021

Abstract
Transportation is an area that needs to be studied from a disability perspective. Different types of barriers exist when it comes to enabling persons with disability to comfortably perform routine activities such as driving a vehicle.
Some of these barriers are due to lack of quantitative assessment techniques that will determine physical capabilities and ergonomic parameters related to the disabled person. The objective of this paper is to design an intelligent haptic interface for quantitative assessment of driving capabilities of persons with disabilities.
A twenty two year old subject with Muscular Dystrophy was introduced to the task of steering wheel control. This task tested the subject’s ability to control different steering wheel diameters, angles of orientation, and fatigue after an extended control period.
Robotic Assembly Based on Human Perception and Action
Authors: Chung Byunghoon , Lee Sooyong 
Published: November 2021

Abstract
Force guided assembly is a control scheme to guide a workpiece based on a stored map from forces to a correction of motion. Based on the geometry of the workpiece and its kinematic behavior in interacting with the environment, the functional map relating the correction of motion to force measurements is generated and stored as a control law. Central to the design of force guided control is how to synthesize this functional map. Although these explicit force-guided controls are a useful concept, particularly for the monitoring of assembly processes, there are inherent difficulties in applying it to real world problems.
In real assembly lines, pipe insertion task, for instance, has been performed only by human workers. Skilled workers insert pipes by perturbing the pipes in order to avoid jamming as well as to determine which way to correct the motion. According to them, the skilled workers monitor obstructing forces in response to the applied perturbation, and modify their motion accordingly. The proposed perturbation/correlation method was motivated by this human perception and action : perturbing the pipe, observing the reaction to the perturbation and correcting the trajectory.
In this paper, we propose a novel technique for acquiring effective force information despite sensor noise and friction. Instead of simply receiving force signals from the process, we give perturbation to the robot and measure the reaction forces to the perturbation. By taking the correlation between the perturbation signal and the reaction forces, reliable and useful information for guiding the robot would be extracted. It is expected that this perturbed force measurement provides much richer force information than that of stationary measurement. The perturbation/Correlation method presented in this paper is not only effective for reducing friction, but also effective for obtaining useful information for guiding the robot towards a desired direction. Preliminary experimental results with one directional perturbation are shown in this paper. Extensive mathematical analysis shows the potential application to assemblies in higher dimension.
Attitude Control of a String and Rigid Bodies System
Authors: Nohmi Masahiro , Terumichi Yoshiaki , Sogabe Kiyoshi 
Published: November 2021

Abstract
Applications of mechanical systems of a string with a rigid bodies subsystem have various possibilities for the engineering in extreme environment conditions, for example, in space or in ocean. This rigid bodies subsystem can be used as a robot subsystem. This paper discusses about attitude control of the rigid bodies subsystem, especially around an equilibrium point of the whole system. The control technique is consists of attitude control with reaction wheels and angular momentum control with manipulation of the rigid bodies subsystem. In order to confirm the effectiveness of the control approach, numerical simulations have been done, under condition that the shape of the string is described by the finite-element formulation, selecting a linear interpolation Also, from the view point of natural frequency analysis of the controlled system, characteristics of the control approach have been examined.
Direct Simulation of Electrorheological Suspensions
Authors: Wang Aijun , Singh Pushpendra , Aubry Nadine 
Published: November 2021

Abstract
A new distributed multiplier/fictitious (DLM) domain method is developed for direct simulation of electrorheological (ER) suspensions subjected to spatially uniform electrical fields. The method is implemented both in two and three dimensions. The fluid-particle system is treated implicitly using the combined weak formulation described in [1,2]. The governing Navier-Stokes equations for the fluid are solved everywhere, including the interior of the particles. The flow inside the particles is forced to be a rigid body motion by a distribution of Lagrange multipliers. The electrostatic force acting on the polarized spherical particles is modeled based on the point-dipole approximation. Using our code we have studied the time evolution of particle-scale structures of ER suspensions in channels subjected to the pressure driven flow. In our study, the flow direction is perpendicular to that of the electric field. Simulations show that when the hydrodynamic force is zero, or very small compared to the electrostatic force, the particles form chains that are aligned approximately parallel to the direction of electric field. But, when the magnitude of hydrodynamic force is comparable to that of the electrostatic force the particle chains orient at an angle with the direction of the electric field. The angle between the particle chain and the direction of the electric field depends on the relative strengths of the hydrodynamic and electrostatic forces.