bluuebunny/crossref_metadata_2025 huggingface dataset:
Relaxation Methods for Nonlinear Dynamics and Hysteresis Operators
Authors: Kurdila A. , Li J.
Published: February 2021

Previous research has demonstrated that rigorous modeling and identification theory can be derived for structural dynamical models that incorporate control influence operators that are static Krasnoselskii-Pokrovskii integral hysteresis operators. Experimental evidence likewise has shown that some dynamic hysteresis models provide more accurate representations of a class of structural systems actuated by some active materials including shape memory alloys and piezoceramics. In this paper, we show that the representation of control influence operators via static hysteresis operators can be interpreted in terms of a homogeneous Young’s measure. Within this framework, we subsequently derive dynamic hysteresis operators represented in terms of Young’s measures that are parameterized in time. We show that the resulting integrodifferential equations are similar to the class of relaxed controls discussed by Warga [10], Garnkrelidze [24], and Roubicek [25].

The formulation presented here differs from that studied in [10], [24] and [25] in that the kernel of the hysteresis operator is a history dependent functional, as opposed to Caratheodory integral satisfying a growth condition. The theory presented provides representations of dynamic hysteresis operators that have provided good agreement with experimental behavior in some active materials.
Influences of Coupler Consisting of Rotational Stiffness and Mass on Wave Propagation and Mode Localization in Simply Supported Multispan Beams
Authors: Kim Dong-Ok , Kim Jong-In , Lee In-Won
Published: February 2021

The influences of coupler on wave propagation and mode localization in simply supported multispan beams with couplers consisting of lumped rotational stiffness and mass on supports are studied. A transfer matrix equation governing the vibrational wave propagation in the simply supported multispan beams with couplers is newly derived and simplified. The eigenvalue of the simplified transfer matrix show that the larger stiffness or the larger mass of coupler makes the internal coupling between spans weaker and so it makes the system more sensitive to mode localization. As the wave frequency or the eigenvalues of the system increases, the mass effect is increased while the stiffness effect is decreased. In a case considering the large stiffness and mass at the same time, there is a region with relatively wider passbands and narrower stopbands having small attenuation rates and the normal modes in it become delocalized ones. As an example structure, simply supported two span beam with a coupler at the mid-span is considered.
An Advanced Damper Model for the Dynamics of Dry Friction Damped Systems
Authors: Guillen Jérôme , Pierre Christophe , Lagrange Thomas
Published: February 2021

In this work, a new, flexible friction damper model is introduced, for application to turbomachinery bladed-disk assemblies. The damper is modeled as a massless structure characterized by a stiffness matrix. It is connected to two (possibly more) structural systems at an arbitrary number of friction points where slip can occur. A new procedure is presented to calculate the force transmitted by the damper at each frictional interface. The multi-harmonic, hybrid, frequency/time method introduced previously by the authors, along with the Broyden resolution algorithm, are modified to handle this advanced damper model and to predict the steady-state periodic response of the system. The method is successfully applied to a four-degree of freedom friction damper connecting two beams at four frictional points. Several interesting features of the non-linear response are revealed, such as: situations where the damper slips at some frictional points and sticks at the other points; and complexity of the frequency response of the system, due to the existence of several modes of vibration that correspond to combinations of stick/slip motions at the various frictional interfaces.
An Experimental Investigation of Vortex-Induced Vibration of Drag-Cable
Authors: Fang Kai-xiang , Jiang Gue-he
Published: February 2021

In order to explore the vibration law of a cylindrical cable excited by wake vortices when a cable of a sonar is dragged underwater, an experimental research on the law of cable model vibration has been done. This paper introduces the model design, test conditions and measurement & analysis system in broad outline. The law of the model vibration and the mutual influence of some factors affecting vortices, such as Strouhal number, Reynold number, drag speed, dip angle and diversion patterns etc. have been discussed. These test data and research result afford us technological basis to further study this subject and design the sonar cable.
Using Genetic Algorithms for the Optimal Design of Fluid Journal Bearing
Authors: Lin Yun-Jeng , Noah Sherif T.
Published: February 2021

The current methods of designing journal bearings are achieved by trial and error and mathematical programming. A new method is used here to design the journal bearings, i.e., Genetic Algorithms (GA). GA is a very efficient method, providing relatively an easy way to find the optimum solution. For that purpose we need to construct the proper objective function for the design of the journal bearing. Then the rest exhaustive and repeated task could be left to the computer. GA can solve the linear or nonlinear, single parameter or multiparameter system.

Genetic Algorithms are very different from the traditional optimization techniques. It is a new generation of artificial intelligence and its principles mimic the behavior of the biologic genes in the natural world. It will search the best set of parameters of the objective function, reproduce them, eliminate unsuitable sets of parameters, cross-couple the survival sets of parameters, execute mutations and then return to plug the values of the new variables into objective function to repeat these procedures. Its execution is simple and could reach the solution in a very short time. According to these characteristics, it is a very powerful method for finding the minimum dissipation of energy in the journal bearing. This approach opens new paradigm for optimization. The GA’s procedure is robust and works even if the functions involve are not continuous and have no derivatives. The resulting set of optimal parameters was compared with the results of a recent paper addressing the same problem.
Transverse Vibrations of a Centrally Clamped Rotating Circular Disk
Authors: Nayfeh Ali H. , Jilani Adel , Manzione Piergiuseppe
Published: February 2021

The transverse vibrations of a circular disk of uniform thickness rotating about its axis with constant angular velocity are analyzed. The results specialized to the linear case of disks clamped at the center and free at the periphery are in good agreement with those reported in the literature. The natural frequencies of spinning hard and floppy disks are obtained for various nodal diameters and nodal circles. Primary resonance is shown to occur at the critical rotational speed at which, in the linear analysis, the spinning disk is unable to support arbitrary spatially fixed transverse loads. Using the method of multiple scales, we determine a set of four nonlinear ordinary-differential equations governing the modulation of the amplitudes and phases of two interacting modes. The symmetry of the system and the loading conditions are reflected in the symmetry of the modulation equations. They are reduced to an equivalent set of two first-order equations whose equilibrium solutions are determined analytically. The stability characteristics of these solutions is studied; the qualitative behavior of the response is independent of the mode being considered.
Dynamics of a Continuous System With Clearance and Motion Limiting Stops
Authors: Metallidis P. , Natsiavas S.
Published: February 2021

The present study generalises previous research work on the dynamics of discrete oscillators with piecewise linear characteristics and investigates the response of a continuous model system with clearance and motion-limiting constraints. More specifically, in the first part of this work, an analysis is presented for determining exact periodic response of a periodically excited deformable rod, whose motion is constrained by a flexible obstacle. This methodology is based on the exact solution form obtained within response intervals where the system parameters remain constant and its behavior is governed by a linear equation of motion. The unknowns of the problem are subsequently determined by imposing an appropriate set of periodicity and matching conditions. The analytical part is complemented by a suitable method for determining the stability properties of the located periodic motions. In the second part of the study, the analysis is applied to several cases in order to investigate the effect of the system parameters on its dynamics. Special emphasis is placed on comparing these results with results obtained for similar but rigid rods. Finally, direct integration of the equation of motion in selected areas reveals the existence of motions, which are more complicated than the periodic motions determined analytically.
A New Order-N Order-N3 Hybrid Parallelizable Algorithm for a Multi-Rigid-Body Mechanical System
Authors: Anderson Kurt S. , Duan Shanzhong
Published: February 2021

In this paper, a new hybrid parallelizable algorithm involving formulations of different computational orders is presented for chain systems. The parallel system model is constructed through the separation of certain system interbody joints so that largely independent multibody subchain systems are formed. These sub-chains in turn interact with one another through associated unknown constrain forces fc¯ at those separated joints. Within each of the floating subchains, equations of motion for the system of bodies are produced using a recursive state space O(n) formulation, while the equations associated specifically with the floating “composite” base body are formed using a more tradition O(n3) approach. Parallel strategies are used to form and solve constraint equations between subchains concurrently. 41% computational savings can be achieved for the floating base body motion description by using O(n3) approach relative to using sequential O(n) procedure.
A Vector Oriented Implementation Method for Efficient Dynamic Simulation of Multibody Vehicle Models
Authors: Bae D. S. , Kim H. W. , Yae H.
Published: February 2021

The most time taking processes in a dynamic analysis of multibody vehicle models are generation and LU-decomposition of various matrices. This research proposes a vector oriented implementation algorithm for explicit numerical integration methods so that relatively low cost computers can be used for the realtime simulation of the multibody vehicle dynamics models consisting of many bodies and joints, a powertrain model, antiroll bars, and tires. Newton chord method is employed to solve the equations of motion and constraints. The equations of motion and constraints are formulated such that the Jacobian matrix for Newton chord method is needed to be generated and LU-decomposed only once for a dynamic analysis. As a result, only computations which need to be carried out in runtime are residual vectors of the governing equations. Convergence analysis of Newton chord method with the proposed Jacobian generation method is carried out. The proposed algorithm yielded close solutions to exact solutions for a prototype vehicle multibody model in realtime on a 400 Mhz PC compatible.
Efficient Human Motion Planning Using Recursive Dynamics and Optimal Control Techniques
Authors: Lo Janzen , Metaxas Dimitris
Published: February 2021

We present an efficient optimal control based approach to simulate dynamically correct human movements. We model virtual humans as a kinematic chain consisting of serial, closed-loop, and tree-structures. To overcome the complexity limitations of the classical Lagrangian formulation and to include knowledge from biomechanical studies, we have developed a minimum-torque motion planning method. This new method is based on the use of optimal control theory within a recursive dynamics framework. Our dynamic motion planning methodology achieves high efficiency regardless of the figure topology. As opposed to a Lagrangian formulation, it obviates the need for the reformulation of the dynamic equations for different structured articulated figures.

We use a quasi-Newton method based nonlinear programming technique to solve our minimum torque-based human motion planning problem. This method achieves superlinear convergence. We use the screw theoretical method to compute analytically the necessary gradient of the motion and force. This provides a better conditioned optimization computation and allows the robust and efficient implementation of our method. Cubic spline functions have been used to make the search space for an optimal solution finite.

We demonstrate the efficacy of our proposed method based on a variety of human motion tasks involving open and closed loop kinematic chains. Our models are built using parameters chosen from an anthropomorphic database. The results demonstrate that our approach generates natural looking and physically correct human motions.
A New Design Methodology for Planar Vibration Absorbers
Authors: Blanchet Pat , Lipkin Harvey
Published: February 2021

A new methodology is presented for the design of planar vibration absorbers. For the most part, previous methods have dealt with systems constrained to a single degree-of-freedom and require the absorber to be along the line of the exciting force. The presented methodology is more versatile and allows the placement of the absorber as a design freedom. Three specific design techniques for force and couple excitations are detailed along with numerical examples illustrating the results.
On Some Intrinsic Features of the Dynamics of Mechanisms
Authors: Lerbet Jan
Published: February 2021

Using Lie group theory, we propose to analyse the dynamics of closed mechanisms without introducing frames or bases. After a brief presentation of the mathmatical tools, the kinematics of closed mechanisms is devolopped and the manifold of configurations described. It is then possible to obtain the dynamic equations by using the principle of virtual power. An intrinsic Lagrange’s multiplier A is introduced to take the closure equation into account. Explicit linear combinations for the elimination of A are given too. Last, some kinematic relations are given which are usefull for linearisation or for numerical integration.
Sliding Bearing Nonlinear Vibration Prediction
Authors: Jáuregui Juan Carlos , González Oscar M.
Published: February 2021

This study presents a method for analyzing and predicting the jump phenomena of a sliding bearing. The nonlinear behavior is caused by a discontinuity on the stiffness. These conditions are due to the number of rolling elements in contact and the backlash along the perpendicular direction of the motion.

It is shown here that the nonlinear stiffness of the sliding bearing presents jump phenomena. A detailed analysis of the nonlinear stiffness parameters and its effects on the jump conditions are included. In this paper only large displacements are considered.

Numerical results are compared to time domain measurements where the nonlinear behavior is clearly identified. This comparison shows under which condition the system behaves almost as a linear system, whereas under which conditions it behaves highly nonlinear.
Vibration of Moving Flexible Bodies (Formulation of Dynamics by Using Normal Modes and a Local Observer Frame)
Authors: Kawamoto Atsushi , Inagaki Mizuho , Aoyama Takayuki , Mori Nobuyuki , Yasuda Kimihiko
Published: February 2021

This paper deals with the formulation that can analyze vibration noise problems practically in the flexible multibody systems. Many kinds of formulations have been proposed on the flexible multibody systems so far. They are categorized into several groups according to their purposes and coordinate systems. The floating frame of reference formulation is at present the most popular method for general purpose simulations among them. The formulation uses Cartesian coordinates for the position of a body, Euler angles or Euler parameters for the orientations, and modal coordinates for the elastic degrees of freedom. The equations of motion with these different kinds of coordinates are complicated because of coupling between rigid body motion and elastic vibration. On the other hand, the linear theory of elasto-dynamics appears to be simple and could be practical for some limited uses. But it neglects the effect of the elastic deformation on the rigid body motion. In many cases, the effect is significant and essential. In this paper, we propose a new formulation with rigid body modes and a local observer frame (LOF) for large amplitude rigid body motion, and with elastic modes for small amplitude elastic vibration. The LOF is updated properly to compensate the gap between rigid body motion and the LOF motion. The new formulation makes the coupling terms as simple as possible without any loss of the effect of the elastic deformation on the rigid body motion and gives the uniform description in each modal coordinate.
Treatment of Lubrication in Long Bearings for Joint Clearances in Multibody Mechanical Systems
Authors: Ravn P. , Shivaswamy S. , Lankarani H. M.
Published: February 2021

Proper modeling of joint clearance is of great importance in the analysis of multibody mechanical systems. The clearance may be due to wear or imperfection in manufacturing. When there is no lubricant in the clearance, solid-to-solid contact occurs. The impulse due to contact between the links is transmitted throughout the system. The presence of a lubricant avoids such contact, as the hydrodynamic forces developed by the lubricant film supports the loads acting on the bodies and prevents the bodies from coming into contact. In this paper, an analysis of revolute joint clearances in multibody mechanical systems with and without lubricant is presented. Hydrodynamic theory of long bearing is utilized in this study. Unlike the traditional machine design approach, the instantaneous lubricant forces are the unknown and evaluated in terms of the known geometrical position and velocity of the journal and bearing. In the case of analysis of a joint clearance with no lubricant, a modified Hertzian relation is used to model the impact or contact between the journal and bearing, which includes a hysteresis damping term to account for the energy dissipation during impact. The methodology is applied for the analysis of a slider-crank mechanism having a clearance in the piston pin. The simulations are carried out with and without lubricant and the results are compared. It is shown that the lubricant results in a steady motion with fewer peaks in the required cranking moment for the system.
Analytical Reformulation of the Multibody Dynamics of a Satellite
Authors: Sanchez Nestor
Published: February 2021

The topic of dynamics has been somehow reshaped by computational power. The areas of computer algebra and symbolics now allow us to deal with a more involved analytical manipulation of equations. At the same time, the everyday increasing power of numerics put into our hands new tools to solve old problems. In this case, we reformulate the problem of the dynamics of a three body multibody system by using symbolic manipulation of the Newtonian equations, to produce a set of differential equations that can be solve with standard codes. This treatment should produce not only the same results as the numerical approach, but it allows us to use the analytical equations to expand the analysis into design, control and stability. The paper shows the process to build the symbolic code using Maple language, or any algebraic manipulator. The proper equations will be derived to solve for the unknowns angles {ψ,ϕ,θ}, in terms of the prescribed quantities {α(t),β(t),γ(t)t}, and initial conditions. This procedure gives a good idea about the nonlinear response of the satellite to the control parameters. The size of the equations obtained is large. However, considering the type of analysis that could be done with a set like this and the capacity of large computers, it will pay off the extra effort. The codes that could be used for further analysis would find folds, branch points, period doubling bifurcations, Hopf bifurcations, torus bifurcations, by changing the parameters of the governing equation. A large number of important applications will develop in this area in the near future.
The Integration of Structural and Fluid Film Dynamic Elements in Foil Bearings: Part I — Past Approaches to the Problem
Authors: Heshmat Hooshang
Published: February 2021

A review was conducted on work done in the past on the performance of foil bearings. The main aim of the survey was to see how the two-tiered construction of foil bearings, consisting as they do of two generically disparate elements, one hydrodynamic in nature and the other following the laws of elasticity, have been modeled in order to obtain integrated values of bearing stiffness and damping. A compilation was made of the parameters and processes inherent in the operation of foil bearings, including the kinematics of the bump foil and the accompanying Coulomb friction and damping. The main effort went into examining the results obtained from different dynamic models aimed at obtaining the values of the stiffness and damping coefficients. In Part II of this investigation it is shown that serious discrepancies exist between theory and experimental results and a new approach is offered for modeling the two-tiered domain of foil bearings to calculate the dynamic coefficients.
On the Vibration of Rotor With Rotor/Stopper Rubbing
Authors: Dai Xingjian , Zhang Xiaozhang , Jin Zhaoxiong
Published: February 2021

The vibration of a flywheel rotor with rotor/stopper rubbing is investigated by experimental methods. In the experiments, the large amplitude of the rotor vibration is excited by the electromagnetic harmonic excitation force and thus causes the rubbing between the rotor and the stopper. The stable rubbing rotor vibration shows that the stopper can limit the amplitude of low frequency precession effectively. The rotor to stopper collision and rub appears occasionally. The rubbing has little effect on the rotating speed of the rotor. The forced vibration becomes complex and nonlinear in the time and frequency domain when the collision and rubbing occurs. The observed high order harmonics are sub-synchronous but not subharmonic response. The second modal forward whirl of the rotor-bearing system is excited by the impact force and decays quickly.
Reduction of the 2F-Vibrations of Simple Flexible Rolls by Partial Machining
Authors: Wiese D. , Breitwieser M.
Published: February 2021

In paper and foil production plant, roll vibrations occurring at twice the rotational frequency often present serious problems. These are caused by anisotropy of roll stiffness — referred to below as stiffness anisotropy.

In the past the reduction of this stiffness anisotropy was impossible. When vibrations occurring at twice the frequency of rotation became too high, the entire roll had to be scrapped.

This paper deals with a method for the identification of the anisotropy of rotor stiffness on a balancing machine.

If the stiffness anisotropy is known, vibrations occurring at twice the frequency of rotation can be systematically reduced to a tolerable level by partial machining of the roll.
Application of the Mode-Acceleration Technique to the Solution of the Moving Oscillator Problem
Authors: Pesterev Alexander V. , Bergman Lawrence A.
Published: February 2021

The problem of calculating the dynamic response of a one-dimensional distributed parameter system excited by an oscillator traversing the system with an arbitrarily varying speed is investigated. An improved series representation for the solution is derived that takes into account the jump in the shear force at the point of the attachment of the oscillator, which makes it possible to efficiently calculate the distributed shear force and, where applicable, bending moment. The improvement is achieved through the introduction of the “quasi-static” solution, an approximation to the desired one, which makes it possible to apply to the moving oscillator problem the “mode-acceleration” technique conventionally used for acceleration of series in problems related to the steady-state vibration of distributed systems. Numerical results illustrating the efficiency of the method are presented.
Aerodynamic Flow Control Using Shape Adaptive Surfaces
Authors: Pern N. J. , Jacob J. D.
Published: February 2021

The present paper discusses results of experiments on flow control using an adaptive circular arc airfoil. A modified THUNDER actuator (piezoceramic bonded with a metallic substrate) serves as an adaptive airfoil that allows leading edge displacements of approximately 1 cm. The airfoil’s radius of curvature Rc is varied by altering the voltage applied across the upper and lower surfaces. The maximum input voltage varies Rc ±2% resulting in a variation in the lift coefficient Cl of approximately 7% at a frequency up to 25 Hz. Results of wake mitigation and flutter control tests are briefly discussed.
Use of Higher Order Spectra in Condition Monitoring: Simulation and Experiments
Authors: Rivola Alessandro , White Paul R.
Published: February 2021

In the field of machine condition monitoring one can observe that a link exists between machine vibrations and its health condition, that is, there is a change in the machine vibration signature when machine faults occur. Damages occurring in machine elements are often related to non-linear effects, which may lead to non-linearities in the machine vibration. This paper concerns the study of some systems by means of techniques based on Higher Order Spectra (HOS). These techniques are particularly useful in the situation where only a single measurement sensor is available. If a process is Gaussian then HOS provide no information that cannot be obtained from the second order statistics. On the contrary, HOS give information about a signal’s non-Gaussianity. Since a Gaussian input passing through a linear system leads to a Gaussian output, assuming the signal as an output of a system with a Gaussian input, then HOS make it possible to analyse the structure of the output signal and to provide information related to the non-linearity within the system. A simple model is presented with the aim of showing the effectiveness of the normalised version of polyspectra in detecting different kinds of system non-linearities. HOS are used to interpret the signal structure and the system’s physical characteristics. Moreover, two experimental cases are presented. The HOS are applied to detect the presence of a fatigue crack in a straight beam and to analyse the vibration signal measured on a test bench for rolling element bearings. Both third and fourth order spectra seem to provide a possibility of using HOS as a condition monitoring tool.
On the Planar Damped Linear Vibrations of a Rigid Body
Authors: Blanchet Pat , Lipkin Harvey
Published: February 2021

The planar motion associated with a damped mode of a vibrating rigid body is actually not well understood. This paper shows that a damped mode is a rotation about a point that is either translating along a straight line or is stationary, depending on how much damping is present. The transition between each type of damping is explained and an example illustrates the results.
Analysis of Motion of the Impact-Dry-Friction Pair of Bodies and its Application to the Investigation of the Impact Dampers Dynamics
Authors: Peterka František
Published: February 2021

The motion with impacts and dry friction forces appears in some mechanical systems as mechanisms with clearances, (e.g., in gearings, pins, slots, guides, valve gears etc.), impact dampers, relays, forming and mailing machines, power pics etc. Such mechanisms include one or more pairs of impacting bodies, which introduce the strong nonlinearity into the system motion. The motion of the general pair of bodies with the both-sides impacts and dry friction forces is assumed (Fig.1). It can be the part of a more complex chain of masses in the mechanical system. Dead zones in the relative motion of bodies can be caused by assumed nonlinearities. The mathematical conditions controlling the numerical simulations or analytical solution of the motion are introduced. The application of this method is explained by the study of the influence of dry friction force on amplitude-frequency characteristics of four types of dynamical and impact dampers with optimised parameters.
Modelling and Analysis of Dynamic Properties of Drive Systems With Gears
Authors: Kratochvíl Ctirad , Kotek Vladimír , Březina Tomáš , Krejsa Jiří
Published: February 2021

Contemporary trends show a marked tendency for solution of problems of dynamic analysis of drive systems as early as the design stage. It shows that during the modelling of complex drive systems it is necessary to respect its structural complexity and therefore it is necessary to make the models of particular drive subsystems first and then to combine it altogether. In the paper authors present some methods of creation of suitable mathematical models of complex drive systems respecting the drive structure. The methods are then applied onto real tasks. Examples are included.
Instant Chaos and Extreme Parametric Uncertainty in Nonlinearly Driven Continuum Mechanics
Authors: Schwartz Ira B. , Wood Yvette K. , Georgiou Ioannis T.
Published: February 2021

Bifurcation to high-dimensional hyperchaos is observed in a driven coupled pendulum-flexible rod system. When the rod is in resonance with the pendulum, the system changes from a low dimensional periodic attractor to a high dimensional chaotic attractor abruptly. It is shown that high dimensional chaotic dynamics is hysteretic, and exhibits extreme sensitivity with respect to small parameter changes. Such sensitivity poses a problem in obstructing predictability in mechanics.
Perceptual implications of different Ambisonics-based methods for binaural reverberation
Authors: Engel Isaac , Henry Craig , Amengual Garí Sebastià V. , Robinson Philip W. , Picinali Lorenzo
Published: February 2021

Reverberation is essential for the realistic auralisation of enclosed spaces. However, it can be computationally expensive to render with high fidelity and, in practice, simplified models are typically used to lower costs while preserving perceived quality. Ambisonics-based methods may be employed to this purpose as they allow us to render a reverberant sound field more efficiently by limiting its spatial resolution. The present study explores the perceptual impact of two simplifications of Ambisonics-based binaural reverberation that aim to improve efficiency. First, a “hybrid Ambisonics” approach is proposed in which the direct sound path is generated by convolution with a spatially dense head related impulse response set, separately from reverberation. Second, the reverberant virtual loudspeaker method (RVL) is presented as a computationally efficient approach to dynamically render binaural reverberation for multiple sources with the potential limitation of inaccurately simulating listener's head rotations. Numerical and perceptual evaluations suggest that the perceived quality of hybrid Ambisonics auralisations of two measured rooms ceased to improve beyond the third order, which is a lower threshold than what was found by previous studies in which the direct sound path was not processed separately. Additionally, RVL is shown to produce auralisations with comparable perceived quality to Ambisonics renderings.
The Influence of Biological Maturity on Sprint Speed, Standing Long Jump, and Vaulting Performance in Young Female Gymnasts
Authors: Moeskops Sylvia , Oliver Jon L. , Read Paul J. , Myer Gregory D. , Lloyd Rhodri S.
Published: February 2021

Purpose: To quantify speed, peak momentum, standing long jump (SLJ), and the ratio of vertical to horizontal take-off velocity (Ratiovert–hori TOV) in young female gymnasts of different maturity status and their influence on vaulting vertical TOV. Methods: One hundred twenty gymnasts age 5–14 years were subdivided into maturity groupings using percentage of predicted adult height. Participants performed three 20-m sprints, SLJ, and straight jump vaults that were recorded using 2-dimensional video and analyzed using digitizing software. Results: All speed intervals, peak speed, peak momentum, SLJ distance, vault height, and vertical TOV increased between the early prepubertal and late prepubertal (P < .001; d = 0.65–1.10) and early prepubertal and pubertal (P < .001; d = 0.75–1.00) groups. No differences between these metrics were observed between the 2 most mature groups (d = 0.01–0.55). Multiple regression analyses revealed peak speed had the strongest association with vertical TOV (R2 = 59%) and also identified the Ratiovert–hori as a secondary determinant (R2 = 12%). A separate regression model indicated that maturity status (percentage of predicted adult height) moderately influences vertical TOV during vaulting (R2 = 41%). Conclusion: Speed and SLJ performance increase between the early prepubertal and late prepubertal years in young female gymnasts. However, given that peak speed and Ratiovert–hori combined to explain 71% of the total variance in vaulting vertical TOV, in order to increase aerial time for more advanced vaulting, practitioners should attempt to enhance peak speed alongside takeoff technique to develop gymnasts’ ability to transfer linear speed to vertical TOV.
Demands of the Tour de France: A Case Study of a World-Class Sprinter (Part I)
Authors: van Erp Teun , Kittel Marcel , Lamberts Robert P.
Published: February 2021

Purpose: To describe the intensity, load, and performance characteristics of a world-class sprinter competing in the Tour de France (TdF). Method: Power output (PO) data were collected from 4 editions of the TdF (2013, 2014, 2016, and 2017) and analyzed. Load, intensity distribution in 5 PO zones, and the maximal mean PO for multiple durations were quantified. Stages were divided in accordance with the 4 different editions of the TdF, as well as the 4 different stage types, that is, flat (FLAT), semimountainous (SMT), mountain (MT), and (team) time trials. In addition, based on their location within the stage, mountain passes were further classified as BEGINNING, MIDDLE, or END of the stage. Results: No differences in load, intensity, and performance characteristics were found when the 4 editions of the TdF were compared. Time trials were associated with higher intensities but a lower load compared to the other stage types. MT showed higher load and intensity values compared to FLAT and SMT stages. FLAT stages were higher in short maximal mean PO (≤1 min), whereas MT stages showed higher longer endurance maximal mean PO values (≥20 min). In addition, mountain passes situated at the BEGINNING of the stage were completed with a higher PO, cadence, and speed compared with mountain passes situated at the END. Conclusions: A world-class sprinter sustains a higher load and spends more time in the high-intensity zones when competing in the TdF than previously reported values suggested. To finish the MT stages as efficiently as possible, sprinters adopt a reverse pacing strategy.
“He Leaned His Body Against Mine and Pushed Himself Against Me”: A Narrative of Sexual Harassment in Mental Performance Consulting
Authors: DeLisio Danielle C. , Lauer E. Earlynn , Shigeno Terilyn C. , Fisher Leslee A. , Zakrajsek Rebecca A.
Published: February 2021

Mental performance consultants in training need to be prepared to respond to the various ethical dilemmas they may encounter, including sexual misconduct. Sexual harassment (i.e., unwanted attention of a sexual nature that may create an uncomfortable environment) is a form of sexual misconduct that has increased dramatically in the general U.S. population. In this paper, the authors provide a composite narrative from the point of view of the “victim” of sexual harassment (i.e., a neophyte mental performance consultant) while consulting with a high school team. Then, the authors examine and interpret the narrative in light of four complicating factors: (a) gender identity and other demographics, (b) context, (c) training and experience, and (d) handling/reporting incidents of sexual harassment. Finally, the authors pose questions for readers related to each complication and present implications for sport psychology students and faculty.
Practitioners’ Use of Motivational Interviewing in Sport: A Qualitative Enquiry
Authors: Mack Rory , Breckon Jeff , Butt Joanne , Maynard Ian
Published: February 2021

This study explored the use of motivational interviewing (MI) in sport contexts by experts in that approach. Specifically, the purpose was to understand which aspects of the MI approach are deemed valuable for working in sport and to begin to understand how these aspects are best applied. Nine practitioners participated in semistructured interviews, and thematic analysis identified themes related to core and subcomponents of MI (e.g., relational spirit, technical microskills, applied tools, and the MI communication styles continuum). Additional themes relate to integrating MI with other interventions, the challenges of working with athletes (e.g., mandated attendance, ambivalence about change), and unique aspects of working in sport contexts (e.g., frequency, duration, and location of contact points). The participants also outlined essential ingredients for an MI training curriculum for practitioners in sport. This counseling approach appears to have valuable relational and technical components to facilitate the building of the therapeutic alliance, enhance athlete readiness for change, and support delivery of action-oriented interventions in applied sport psychology.
Quantum logic at a distance
Authors: Hunger David
Published: February 2021

A quantum gate is realized by optically coupling trapped atoms separated by 60 meters
Influence of Incubation Temperature and Total Dissolved Solids on Biofilm and Spore Formation by Dairy Isolates of Geobacillus stearothermophilus
Authors: Kumar Murali , Flint Steve , Palmer Jon , Chanapha Sawatdeenaruenat , Hall Chris
Published: February 2021

The thermophilic bacillus
Geobacillus stearothermophilus
is a predominant spoilage bacterium in milk powder manufacturing plants. If its numbers exceed the accepted levels, this may incur financial loses by lowering the price of the end product.
Mitochondria: Powering the Innate Immune Response to Mycobacterium tuberculosis Infection
Authors: Patrick Kristin L. , Watson Robert O.
Published: February 2021

Within the last decade, we have learned that damaged mitochondria activate many of the same innate immune pathways that evolved to sense and respond to intracellular pathogens. These shared responses include cytosolic nucleic acid-sensing and type I interferon (IFN) expression, inflammasome activation that leads to pyroptosis, and selective autophagy (called mitophagy when mitochondria are the cargo).
Mycobactericidal Effects of Different Regimens Measured by Molecular Bacterial Load Assay among People Treated for Multidrug-Resistant Tuberculosis in Tanzania
Authors: Mbelele Peter M. , Mpolya Emmanuel A. , Sauli Elingarami , Mtafya Bariki , Ntinginya Nyanda E. , Addo Kennedy K. , Kreppel Katharina , Mfinanga Sayoki , Phillips Patrick P. J. , Gillespie Stephen H. , Heysell Scott K. , Sabiiti Wilber , Mpagama Stellah G.
Published: February 2021

Rifampin or multidrug-resistant tuberculosis (RR/MDR-TB) treatment has largely transitioned to regimens free of the injectable aminoglycoside component, despite the drug class’ purported bactericidal activity early in treatment. We tested whether
Mycobacterium tuberculosis
Further evidence for the Matanuska megaflood hypothesis, Alaska
Authors: Wiedmer R. Michael , Gillespie Alan R. , Montgomery David R. , Greenberg Harvey M.
Published: February 2021

The Matanuska lowland north of Anchorage, Alaska, was episodically glaciated during the Pleistocene by the merged westward flow of the Matanuska and Knik glaciers. During the late Wisconsin glaciation, glacial Lake Atna filled the Copper River Basin, impounded by an ice dam blocking the Matanuska drainage divide at Tahneta Pass and the adjacent Squaw Creek headwaters and ice dams at other basin outlets, including the Susitna and Copper rivers. On the Matanuska lowland floor upvalley from the coalesced glacier’s late-Wisconsin terminus, a series of regularly spaced, symmetrical ridges with 0.9-km wavelengths and heights to 36 m are oriented normal to oblique to the valley and covered by smaller subparallel ridges with wavelengths typically ~80 m and amplitudes to 3 m. These and nearby drumlins, eskers, and moraines were previously interpreted to be glacial in origin. Borrow-pit exposures in the large ridges, however, show sorting and stratification, locally with foreset bedding. A decade ago we reinterpreted such observations as evidence of outburst flooding during glacial retreat, driven by water flushing from Lake Atna through breaches in the Tahneta Pass and Squaw Creek ice dam. In this view, the ridges once labeled Rogen and De Geer moraines were reinterpreted as two scales of fluvial dunes. New observations in the field and from meter-scale light detection and ranging (LiDAR) and interferometric synthetic aperture radar (IfSAR) digital elevation models, together with grain-size analyses and ground-penetrating radar profiles, provide further evidence that portions of the glacial landscape of the Matanuska lowlands were modified by megaflooding after the Last Glacial Maximum, and support the conclusion that the Knik Glacier was the last active glacier in the lowland.
Superficial peroneal nerve neuroma after syndesmotic stabilisation surgery
Authors: Baig Muhammad Nouman , Murphy Ben , Hurley Ciaran M , Kearns Stephen
Published: February 2021

The ankle is a region crowded with multiple neurovascular and musculotendinous structures. We describe a case of a rare neurological complication following ankle surgery.
Malignant triton tumour (MTT) of the lung with metastasis to the proximal femur
Authors: Elbardesy Hany , Gul Rehan , Bennett Michael , Power Derek G
Published: February 2021

A 65-year-old female patient has a history of malignant triton tumour of the right upper lobe of the lung. She underwent right upper lobectomy and lymphadenectomy in May 2018. She presented in November 2019 with pathological fracture of the left proximal femur. It was not associated with neurofibromatosis. We decided to do an excisional biopsy of the mass and proximal femoral replacement followed by radiotherapy. Four months later, she presented with local recurrence. We organised a multidisciplinary team between the orthopaedic, histopathology and oncology teams. Then, we decided to treat her with chemotherapy. After 2 months of follow-up, she responded well to the chemotherapy with no further deterioration of her condition.
Can cryptogenic multifocal ulcerous stenosing enteritis (CMUSE) be diagnosed in a patient with non-steroidal anti-inflammatory drug exposure?
Authors: Osman Karim T , Maselli Daniel B , Mounajjed Taofic M , Grotz Travis E
Published: February 2021

The differential diagnosis for ulcerating small bowel strictures is extensive and includes exposure to non-steroidal anti-inflammatory drugs (NSAIDs), Crohn’s disease, infections, gastrointestinal lymphoma and vasculopathy. It also encompasses the exceptionally rare and poorly understood diagnosis of cryptogenic multifocal ulcerative stenosing enterocolitis (CMUSE), often a diagnosis of exclusion and considerable difficulty. We present a case of persistent proximal jejunal ulcerating stenoses in a 75-year-old Caucasian man, which continued despite cessation of NSAIDs. After extensive clinical, radiographic, laboratory and ultimately surgical pathological appraisal—as well as failure to improve with both misoprostol and budesonide—he was diagnosed with CMUSE and managed with limited small bowel resection. In the presentation of this case, we aim to underscore the diagnostic challenges that clinicians face in differentiating CMUSE from other more common diagnoses, particularly NSAIDs-induced enteropathy.
Recurrent giant simple hepatic cyst: an unusual cause of dyspnoea in an elderly man
Authors: Bag Nerbadyswari Deep , Mohakud Sudipta , Naik Suprava , Shri Aishvarya
Published: February 2021

An 88-year-old man presented to the emergency department with exertional dyspnoea and orthopnoea. Clinical examination revealed mildly raised jugular venous pressure, increased respiratory rate, palpable non-tender hepatomegaly and reduced right basal breath sounds. Ultrasonography showed a large right simple hepatic cyst, multiple small left hepatic and renal cysts. A non-contrast CT scan revealed a large, right hepatic thin-walled cyst of volume 4.2 L, exhibiting few thin septae and tiny nodular mural calcifications. Pressure effects were elevated right haemidiaphragm, right atrial compression and adjacent atelectasis. He had a similar episode 2 years ago, treated by percutaneous needle aspiration. Giant simple hepatic cysts are rare and present when symptomatic due to pain, mass effect on adjacent organs, infection or rupture. These may unusually cause dyspnoea or orthopnoea by compressing cardiac chambers. Simple aspiration has a high recurrence rate. Percutaneous sclerosant injection, laparoscopic deroofing and cystectomy are better treatment modalities.
Isolated splenic abscess due to melioidosis in type 1 diabetes mellitus: laboratory diagnosis ofBurkholderia pseudomalleiin resource-restricted setting
Authors: Gupta Abhishek Prakash , Halder Ratan , Chakraborty Mandira , Chakraborty Partha Pratim
Published: February 2021

Diabetes mellitus, type 1 in particular, is a well-recognised risk factor for melioidosis, a disease caused byBurkholderia pseudomallei. Melioidosis is endemic in Southeast Asia and in northern Australia and has a variety of clinical presentation, isolated splenic abscess being one of them.B. pseudomallei, however, is an uncommon aetiology of splenic abscess. The diagnosis of melioidosis is often overlooked unless the clinician and the microbiologist are suspicious of the condition. Multiple splenic abscesses and perisplenic collection were noted in CT scan of the abdomen in a patient of type 1 diabetes, presenting with fever for preceding 4 weeks.B. pseudomalleiwas isolated from the splenic aspirate and the diagnosis was made based on gram stain and routine biochemical tests. He was successfully treated with antibiotics. We postulate that the likely route of infection was inoculation through skin, the integrity of which was compromised by multiple subcutaneous insulin injections.