bluuebunny/crossref_metadata_2025 huggingface dataset:
The Integration of Structural and Fluid Film Dynamic Elements in Foil Bearings: Part II — A New Approach to the Problem
Authors: Swanson Erik E. , Heshmat Hooshang
Published: February 2021

In Part I of this investigation a survey was made 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. Here a series of experiments is reported showing that serious discrepancies exist between results obtained from conventional dynamic models and test results. A new approach to the problem is here taken in modeling the two-tiered dynamic system of foil bearings. For this purpose a series of analytical solutions were obtained for different spring and dashpot arrangements. A basic approach was taken in considering the foil bearing as consisting of a two-degrees-of-freedom system. Differences in amplitude of vibration and phase angles were plotted for the different models. Similar data were obtained separately for the hydrodynamic and structural regimes. The solutions showed substantial differences in the amplitudes and phase angles between the two domains. It is concluded that treatment of foil bearing dynamics should be based on a two-degrees-of-freedom model. Suggestions are made for an analytical and experimental program to put the technology of foil bearings on a sounder basis than has been the case heretofore.
Vibrational Characteristics of Composite Shafts
Authors: Sekhar A. S. , Kumar N. Ravi
Published: February 2021

The present study aims in performing eigenvalue analysis and unbalance response for a rotor system having a composite shaft, modelled based on first order shear deformation theory using finite element method with shell elements. Different materials such as boron epoxy, carbon epoxy and graphite epoxy have been tried for various stacking sequences. From the study it is clear that the stacking sequence and material have great influence on the vibrational characteristics of composite shafts.
Compressibility Effects on the Static and Dynamic Characteristics in Stepped Thrust Gas Film Bearings
Authors: Hashimoto Hiromu , Ochiai Masayukl
Published: February 2021

Hydrodynamic gas film bearings are used for supporting high-speed, lightly loaded rotating machinery. Stepped type gas film bearings are often used for such machinery because of their simple structure, high stability and load carrying capacity. This paper describes the measurements of compressibility effects on the static and dynamic characteristics of stepped thrust gas film bearings. In the experiments, the minimum film thickness, friction torque on the bearing surface and stiffness and damping coefficients of gas films are measured for a range of rotational speed from 10,000 rpm to 20,000 rpm under a constant stator mass and a fixed step height. The measured data are compared with the theoretical results and the gas film compressibility effects on the static and dynamic characteristics of the bearings are discussed. The experimental results agree well with the predicted results based on the compressible lubrication theory.
Design and Testing of a Permanent Magnet Biased Active Magnetic Bearing
Authors: Overstreet Ross W. , Flowers George T. , Szasz Gyorgy
Published: February 2021

Magnetic bearings provide rotor support without direct contact. There is a great deal of current interest in using magnetic bearings for active vibration control. Conventional designs use electrical current to provide the bias flux, which is an integral feature of most magnetic bearing control strategies. Permanent magnet biased systems are a relatively recent innovation in the field of magnetic bearings. The bias flux is supplied by permanent magnets (rather than electrically) allowing for significant decreases in resistance related energy losses. The use of permanent magnet biasing in homopolar designs results in a complex flux flow path, unlike conventional radial designs which are much simpler in this regard. In the current work, a design is developed for a homopolar permanent magnet biased magnetic bearing system. Specific features of the design and results from experimental testing are presented and discussed. Of particular interest is the issue of reduction of flux leakage and more efficient use of the permanent magnets.
Damped Vibration Absorbers Applied to Lateral Modes of Rotating Machinery
Authors: Greenhill Lyn M. , Raven Linda F.
Published: February 2021

Damped vibration absorbers can significantly reduce the amplitude of resonant motion. Normally, these devices are used on machinery that is non-rotating (stationary). However, as this paper demonstrates both analytically and experimentally, a damped absorber can be successfully applied on rotating equipment, particularly on vertical machines, to attenuate lateral resonances. To illustrate this application, a detailed analysis of the damped absorber is presented, focusing on mass ratio, tuning frequency, amount of damping, and speed effects. It is shown that an optimum design can be obtained for use on a rotating machine that parametrically differs from a non-rotating application. Test data is also given illustrating the effectiveness of the concept and design methodology on an actual machine. Recommendations are provided to guide the application of this technology on other rotating machines.
Clearance and Dry Friction Study in a Nonlinear Torsional Vibration of a Rotating Machinery
Authors: Mizutani Kazuki , Md. Zahid Hossain
Published: February 2021

Clearance problem in coupling is often experienced in a rotary torsional vibration system. We tried to analyze the qualitative and quantitative characteristics of torsional vibration by modeling the bilinear spring stiffness with changing friction torque. Symmetric and asymmetric spring stiffness with friction models are developed to investigate the behavioral characteristics of the system for simulations and experiments. The frequency response curves and time response curves with external sinusoidal excitation are observed by several non-dimensional numerical simulations. The thoroughly experiments are done to understand the actual phenomena of torsional vibration, verification of models and adjustability of simulations. The frictional property considered as dry friction in coupling is found very significant parameter to reduce the vibration within a tolerable range in both of the simulations and experiments. The difference between the results getting from simulations and experiments are also demonstrated in this paper elaborately.
Surface Damping Treatment With an Active-Passive Hybrid Constraining Layer
Authors: Liu Yanning , Wang K. W.
Published: February 2021

A new surface-damping concept with an active-passive hybrid constraining layer (HCL) is proposed to improve the damping performance of traditional active constrained layer (ACL) systems. Instead of using a piezoelectric constraining layer, passive and active materials are used together to constrain the viscoelastic material layer. A generic model of the HCL treatment is presented. Non-dimensional equations of motion and boundary and connecting conditions are derived. The closed-form solutions to the equations are developed and analyzed. It is shown that by properly selecting a passive constraining material and assigning appropriate lengths for the active and passive constraining parts, HCL can outperform a system with pure active PZT coversheet, both in terms of its fail-safe ability and closed-loop damping performance.
Adaptive Vibration Isolation for Axially Moving Beams
Authors: Li Yugang , Rahn Christopher D.
Published: February 2021

Manufacture and use of metal bands, sheets, and cables often requires high-speed axial transport of the material. Disturbance forces can cause vibration to propagate through the process due to the bending stiffness coupling between adjacent roller-supported spans. This paper introduces an active pivoting roller that adaptively decouples adjacent spans, thereby isolating a controlled span from bounded disturbances in an adjacent span. The system includes a partial differential equation for the two spans and an ordinary differential equation for the actuator. Exact model knowledge and adaptive isolation controllers, based on Lyapunov theory, regulate the controlled span from bounded disturbances in the adjacent, uncontrolled span. Assuming distributed damping in the uncontrolled span, the exact model knowledge and adaptive controllers exponentially and asymptotically drive the controlled span displacement to zero, respectively, while ensuring bounded uncontrolled span displacement and control force.
Structural Vibration Control by Tuned Distributed Vibration Damper
Authors: Liu Xiaoping , Yang Bingen
Published: February 2021

In this paper a new structural vibration control technique, namely tuned distributed vibration damper (DVD) is studied. Through the analysis of damping amplification factor and the comparison of the frequency response under DVD, conventional damper, absorber, etc., the advantages of DVD in the vibration control are shown. This paper still presents the variable damping DVD, and sets forward the algorithm for selecting the damping coefficients of the variable damper. Numerical results indicate that the tuned DVD can significantly reduce the vibration responses of the structure system.
Characterization of Transient Effects in Rotordynamic Vibrations Using Harmonic Wavelets
Authors: Chancey Valeta Carol , Flowers George T.
Published: February 2021

Traditional vibration analysis methods for rotating machinery consider steady state or near steady state behavior. Perhaps a key to identifying the source of some complex behaviors may be the transients associated with such phenomena. In an effort to develop a means of identifying transients, the application of harmonic wavelets is explored. Simple vibratory models were studied using harmonic wavelet analysis. Several general observations were made with characteristics found in the harmonic wavelet coefficients associated with particular behavior. Specifically, a relationship with transient growth and the absolute value of the harmonic wavelet coefficients was identified. Example experimental data was collected and analyzed from a bench top test rig with a journal bearing exhibiting oil whirl to illustrate the proposed methods.
Wavelet Analysis of Strong Response Records of Building With Bilinear Restoring Force
Authors: Segawa Ryutaro , Yamamoto Shizuo , Sone Akira , Masuda Arata
Published: February 2021

It is very important to estimate the residual life of structures by analysing a strong response quantitatively, because it is necessary to judge whether they can be used or not in the future, after they are damaged by earthquakes. During a strong earthquake, the jerk response of a structure with bilinear restoring force has discontinuity, just when the restoring force changes rapidly from the elastic region to the plastic region. Authors have tried to detect the discontinuity in the jerk by using wavelet analysis and reported a successful paper (Sone, et al., 1994). The final goal of study is to estimate the low cycle fatigue of structure by analysing the observed records in a structure. For this object, the relationship between ductility factor; that is the ratio of peak relative displacement and yield relative displacement, and the number of discontinuity detection is needed. In this paper, the method is proposed to estimate the ductility factor of structure by the wavelet analysis of absolute acceleration response. Wavelet has the ability to detect discontinuity in acceleration response record; furthermore, it is found in this study that the wavelet coefficient is proportional to the velocity at the yield point. Besides, the ductility factor is estimated from the velocity at yield point by using the energy balance between kinetic energy at the yield point and strain energy from the yield point to the maximum relative displacement. Thus, using these relationships, the ductility factor is estimated from wavelet coefficient obtained by wavelet analysis of acceleration response. The applicability of this method is verified through some simulations.
Symbolic Bifurcation Boundaries and Time-Dependent Resonance Sets of Time-Periodic Nonlinear Systems
Authors: Butcher Eric A. , Sinha S. C.
Published: February 2021

A recent computational technique is utilized for symbolic computation of local stability boundaries and bifurcation surfaces for nonlinear multidimensional time-periodic dynamical systems as an explicit function of the system parameters. This is made possible by the recent development of a symbolic computational algorithm for approximating the parameter-dependent fundamental solution matrix of linear time-periodic systems. By evaluating this matrix at the end of the principal period, the parameter-dependent Floquet Transition Matrix (FTM), or the linear part of the Poincaré map, is obtained. The subsequent use of well-known criteria for the local stability and bifurcation conditions of equilibria and periodic solutions enables one to obtain the equations for the bifurcation surfaces in the parameter space as polynomials of the system parameters. Because this method is not based on expansion in terms of a small parameter, it can successfully be applied to periodic systems whose internal excitation is strong. In addition, the time-dependent normal forms and resonance sets for one and two degree-of-freedom time-periodic nonlinear systems are analyzed. For this purpose, the Liapunov-Floquet (L-F) transformation is employed which transforms the periodic variational equations into an equivalent form in which the linear system matrix is constant. Both quadratic and cubic nonlinearities are investigated, and all possible cases for the single degree-of-freedom case are studied. The above algorithm for computing stability boundaries may also be employed to compute the time-dependent resonance sets of zero measure in the parameter space. Two illustrative example problems, viz., a parametrically excited simple pendulum and a double inverted pendulum subjected to a periodic follower force, are included.
Time Varying Control of a Bladed Disk Assembly Using Shaft Based Actuation
Authors: Szász György , Flowers George T.
Published: February 2021

A study of bladed-disk vibration control using magnetic bearings is presented. A key issue is a method for achieving practical controllability for such a system. For a tuned or symmetrically mistuned bladed disk assembly, several vibration modes are coupled only to the axial dynamics. Magnetic thrust bearings generally lack sufficient bandwidth to control even moderately high frequency vibration. A simplified model is developed and used to identify controllable vibration modes. A control strategy based upon deliberately mistuning in a non-symmetric manner is developed. The method presented does not require a thrust bearing for complete controllability of a bladed disk assembly via hub based actuators. However, since the linearized model for such a system has time periodic coefficients, an advanced time period controller is required. Controlling time periodic systems is a significant engineering challenge. One innovative approach that seems to be especially promising involves application of the Lyapunov Floquet (LF) transformation to eliminate time periodic terms from the system state matrices. Traditional control design techniques are then applied and the resulting gains transformed back to the original domain. Some simulation results are presented and discussed to illustrate the method.
Modal Observability of a Cantilevered Beam Using an Array of Point Sensors
Authors: Solook M. , Oyadiji S. O.
Published: February 2021

This paper presents a class of modal sensors built with an array of point sensors. A modal sensor that is able to respond to only a particular vibrating mode of a structure has been designed and tested in this study. The theory of the design is based on orthogonality principle of the modal vectors with respect to the mass matrix. Seven the small piezoelectric sensors (PZT) are bonded on the surface of a cantilevered beam at arbitrary locations. The signals of the sensors are weighted and added together in such a way as to cancel the effect of all the vibrating modes but the mode of interest. The weighting coefficients play the main roll of minimising the response of unwanted modes and maximising the response of the mode of interest. The response of the modal sensors have been fed back separately into a PZT actuator to damp and control just that particular mode. Modal observability of modes 2 and 3 of a cantilevered beam have been investigated and tested experimentally. The experimental results indicate that a specific vibrating mode can be extracted and controlled without any spill over effects on the other modes.
Transient Resonance Oscillations of a Mechanical System With Regard to Non-Linear Damping Effects
Authors: Irretier Horst , Balashov Dmitri
Published: February 2021

Transient, forced vibrations of a mechanical system are considered. Dissipative effects such as material damping, aerodynamic damping and damping at interfaces are taken into account. For the modeling of these effects the set of isolated weakly non-linear single degree of freedom oscillators with damping dependent non-linearities is used. The superposition of their responses approximates the resulting response of the system. The justification of this assumption is discussed. The Krylov-Bogoljubov asymptotic method is applied for the investigation of the transient resonance response. Numerical calculations are provided to demonstrate the validity of the Krylov-Bogoljubov first approximation.
Impact of Flexible Bent Beam Using Component Mode Techniques
Authors: Diaconescu Cristian I. , Marghitu Dan B.
Published: February 2021

The Component Mode Synthesis technique is applied to the impact of a flexible curved bar. The mode functions are selected such that the method can be made computationally as simple as possible, without compromising accuracy. From this point of view, a simple power series is selected. Both transversal and axial elastic deflection are considered. To describe the impact between the elastic beam and the rigid surface the classical Hertzian contact theory and elastio-plastic indentation theory are used.
Impact Induced Internal Fatigue Cracks
Authors: Stépán Gábor , Szabó Zsolt
Published: February 2021

When cracks appear on the surface of a machine element, they can often be treated and the service operation of the machine can be prolonged. When cracks appear inside the material of the corresponding machine element, the internal fatigue crack grows during operation, and when it reaches the surface, the catastrophic failure is already unavoidable. One way to handle this problem is the precise prediction of the repeated tensile stresses in the material, and the results of this method are to be used already at the design stage. The paper deals with the explanation and numerical calculation of tensile stresses related to travelling waves induced by impacts in tups during forging.
Various Substructured Models of a 900 MW Pressurized Water Reactor Under Seismic Excitation
Authors: Rousseau G.
Published: February 2021

This paper describes the investigation made on a 3D Finite Element Model of a 900 MW Pressurized Water Reactor to simulate its response under seismic excitation. This model is used to compute the eigenmodes of this structure at first, then to simulate the transient response of the structure due to a seismic motion. The computation method used is a component mode synthesis method (substrucruring method), which was modified to take into account a method to evaluate the added mass induced by the primary coolant. Three different models of the core were considered. Finally, a non linear transient computation was led with the three different core models and the obtained acceleration spectra on upper and lower core plates are compared with each other and with those of a simplified beam model used for engineering design.
A Survey of the Present State of Friction Modelling in the Analytical and Numerical Investigation of Brake Noise Generation
Authors: Wallaschek Jörg , Hach Karl-Heinz , Stolz Ulrich , Mody Parimal
Published: February 2021

Noise and vibration have become key issues in the design of automotive braking systems. Efforts to improve present day braking systems must take noise and vibration behaviour into account. Good knowledge of the mechanisms involved in the generation of brake noise has thus become an important competitive factor in the design of automotive brake systems. The present paper summarizes some facts and hypotheses concerning the generation of brake noise.

First the different brake noise phenomena are classified. Then several approaches, including models of various levels of detail which have been suggested to explain the root causes of brake noise generation are discussed in detail.

It will be pointed out that friction and wear processes at the interface of brake pad and rotor play an important role in the understanding of brake noise generation. Unfortunately, our present day knowledge on these processes is quite limited. Further research of basic processes is still needed to improve the quality of analytical and numerical models of friction and wear processes, before reliable predictions of brake noise generation become possible. Based on a discussion of simple models frequently used in engineering practice, guidelines for further research in tribological modelling of the interface processes in pad/rotor interaction will be formulated.
Hidden Variable Tracking: Formulation and Analysis of a Mathematical Model
Authors: Chelidze David , Cusumano Joseph P. , Chatterjee Anindya
Published: February 2021

The hidden variable tracking method developed by Cusumano et al. (1998) is analyzed using a simple model of the mechanical oscillator with nonstationary two-well potential previously studied experimentally. Numerical experiments conducted using the model are in good agreement with the experimental study, and explicitly show how the tracking metric (or drift observer) is related to drift in system parameters caused by the slow evolution of a hidden variable. Using the idea of averaging, the slow flow equation governing hidden variable evolution is obtained. It is shown that solutions to the slow flow equation correspond to the drift trajectory obtained with the experimental tracking method.
Parametric Identification of an Experimental Two-Well Oscillator
Authors: Feeny B. F. , Yuan C.-M.
Published: February 2021

The identification of parameters in an experimental two-well chaotic system is presented. The method involves the extraction of periodic orbits from a chaotic set. The form of the differential-equation model is assumed, with unknown coefficients on the terms in the model. The harmonic-balance method is applied to these periodic orbits, resulting in a linear equation in the unknown parameters, which can then be solved in the least-squares sense. The identification process reveals the nonlinear force-displacement characteristic of the oscillator. The results are cross-checked with various sets of extracted periodic orbits. The model is validated by examining simulated responses.
Vibration Testing by Phase Shifted Electronic Holography for Damage Detection in a Car Door
Authors: Borza D. N.
Published: February 2021

The paper presents the use of phase-shifted electronic holography as a NDT tool, in particular using vibration stressing for detecting damage in a car door. After a short introductory description of this technique and of the most frequently used stressing methods used in testing, some of the criteria used in the localization and identification of defects are presented and illustrated with experimental results. Both material damage and assembling faults are detected by applying these criteria and by an adequate choice of the frequency range of excitation and of the optical setup parameters.
Parameter Identification of Beam Using Image Processing: 3rd Report, Experimental Verification
Authors: Kawai T. , Ito M.
Published: February 2021

We previously proposed new techniques to identify parameters of a finite element model, i.e. the density and the modulus of elasticity, of two types of cantilever beam, by using an image processing technique. One beam was a combined beam, the other a damaged beam with a small crack. To identify the parameters of a small segment of the combined beam, spline smoothing with symmetrization and the weighted Tikhonov regularization technique were used. In addition, to detect the size and the location of a small crack, a new type of Simulated Annealing method was proposed.

In this paper, we evaluate our technique experimentally in order to confirm its applicability with a high accuracy to an actual system. Both methods studied are shown to yield highly accurate estimations.
Damage Detection of Flexible Beams Using Transfer Function Correlation
Authors: Lew Jiann-Shiun , Hyde Carlo , Wade Montanez
Published: February 2021

In this paper, we use the change of the identified transfer function parameters of structural dynamics for damage detection of a flexible beam system. The technique used for damage detection is based on the correlation between the identified parameter change and the change of the analytical model, such as a finite element model, due to damage. A least-squares technique is developed to identify the transfer function parameters from the experimental data. In the damage detection process, first the location of damage is identified, then the intensity of damage is estimated. Applying the presented approach to a flexible beam, only one sensor is needed to successfully locate the damage position and accurately estimate the intensity of damage.
Variation in the Geometric Interpretation of the Eigenvalue Problem of a Structure Due to Damage
Authors: Just Agosto Frederick A. , Hendricks Scott L.
Published: February 2021

This paper studies the behavior of the geometric interpretation of the eigenvalue problem. An arbitrary two degree of freedom structure is modeled as a two mass, two spring system. The damage in the system is represented as a reduction in stiffness and the structure is assumed to be a natural conservative system. The geometric interpretation of the system is an ellipse which is examined under various damage conditions occurring on the structure. It is shown that this representation is a convex set and that damage produces a new set which is the convex hull of the existing condition. These results are graphed for several damage scenarios of the system.
Linearization and Optimal PID Control of an Electro-Magnetic Vibration Absorber With a Levitated Auxiliary Mass
Authors: Stephens Lyndon S. , Timmerman Marc A.
Published: February 2021

Electromagnetic vibration absorbers (EMA’s) act in analogy to timed bandstop filters by attenuating vibration modes of mechanical structures over a narrow bandwidth of frequencies. This paper presents the basic dynamic equations and a model of the nonlinear magnetic actuator force that includes the effects of magnetic flux leakage for the EMA. The model also includes the effects of gravity and the reluctance of the magnet iron. A method for linearizing the magnetic force about any desired operating point is presented. Equations are presented that give the optimal PID controller gains at any desired operating point in the air gap. Experimental actuator force measurements are also presented that are used to estimate flux leakage correction factors. Finally, PID controllers are synthesized and applied to an EMA test bed. Impulse response and harmonic response data verify the optimality of the controller gains, and show up to 19 dB attenuation of the main structure vibration when the EMA is tuned using the optimal control gains.
Surface wettability of silicon nanopillar array structures fabricated by biotemplate ultimate top-down processes
Authors: Takeuchi Sou , Ohori Daisuke , Sota Masahiro , Ishida Teruhisa , Li Yiming , Tarng Jenn-Hwan , Endo Kazuhiko , Samukawa Seiji
Published: February 2021

We fabricated high aspect ratio 10-nm Si nanopillar (NP) array structures with a few-tenths-nm-gap arranged by fusing biotemplate and neutral beam etching processes to investigate the wettability [e.g., contact angle (CA)] with and without surface silicon oxide film. The NP array with silicon native oxides in all gaps exhibited super-hydrophilicity due to the chemical liquid-solid interface interaction and larger surface area than the Si flat surface thanks to the NP structure. These phenomena can be explained by using the Wenzel model. In contrast, when we selectively removed the native oxide on Si NP surface with our radical treatment, a gap variation from 11 to 43 nm stably resulted in a CA of more than 96° (hydrophobicity) with a maximum of 115°. This can be explained by using the Cassie–Baxter model with a filling factor. Our findings demonstrate that controlled surface wettability can be achieved by combining our controllable gap silicon NP array structures and the surface with or without silicon native oxides. The gap of a Si NP fills with water due to the capillarity on a silicon native oxide, but on a pure stable silicon one with a defect-free surface, does not completely fill. We found that Si NP structures with controllable gaps exhibit a surface wettability ranging from super-hydrophilicity to high-hydrophobicity.
Atomic structure of CsBr thin films on Ag (111)
Authors: Varshney Shivani , Nogami Jun
Published: February 2021

Ultra-thin CsBr overlayers on the Ag (111) surface have been grown using physical vapor deposition and studied by scanning tunneling microscopy. Atomically resolved images of CsBr show the formation of the NaCl crystal structure rather than the bulk structure of CsBr, i.e., CsCl, in the first two atomic layers. The structure remains the same up to five monolayers, the maximum layer thickness being studied. Mobility of CsBr islands up to 1.1 nm thickness has been observed at room temperature. CsBr is one of the binary constituents for the growth of CsPbBr3 perovskites. Exploring the growth of CsBr on Ag (111) will provide reference information for the better understanding of the growth of CsPbBr3 perovskite thin films under similar growth conditions.
Multi-technique investigation of Ni-doped ZnO thin films on sapphire by metalorganic chemical vapor deposition
Authors: Chen Jiwei , Wang Jiabin , Saravade Vishal , Ferguson Ian T. , Hu Weiguo , Feng Zhe Chuan , Wan Lingyu
Published: February 2021

Optical and material properties of nickel-doped zinc oxide (ZnO-Ni) grown by metalorganic chemical vapor deposition with varying Ni source flow rates are investigated. ZnO-Ni showed a good crystal quality with (002) orientation but deteriorated at high Ni source flow rates. Photoluminescence responses show a reduction in the bandgap of ZnO-Ni with an increase in the Ni source flow and also with an increase in the temperature. Ni-doping can enhance luminescences at low concentrations (<25 SCCM and ∼2%) and suppress at high concentrations. Ni-related defects occur more toward the surface than bulk of the thin films. Longitudinal optical phonon replicas named 1LO and 2LO redshifts at low Ni source flow rates ≤100 SCCM with an increase in the temperature from 14 to 300 K, but exhibits an “S-shaped” red-blue-red shift with a dip at 50 K at higher Ni source flow rates (150 SCCM). Ni-doping also induces asymmetric crystal vibrations and rougher surfaces with the Ni incorporation. This study enhances the understanding of Ni-doped ZnO that is needed to apply transition-metal doped ZnO for various optoelectronic applications.
Effect of Acute Interset Foot Cooling on Lower Limb Strength Training Workout
Authors: Cai Zong-Yan , Wang Wen-Yi , Huang Yi-Ming , Wu Chih-Min
Published: February 2021

Purpose: The authors investigated the effect of foot cooling (FC) between sets in a leg press pyramid workout with resistance-trained participants. Methods: A total of 12 resistance-trained men (age = 21.8 [0.6] y; training experience = 1.7 [1] y) performed a pyramid workout, including 4 sets of 85% to 90% 1-repetition maximum leg press exercise to exhaustion with interset FC or noncooling in a repeated-measures crossover design separated by 5 days. The authors immersed the participants’ feet in 10°C water for 2.5 minutes between sets. Results: Two-way repeated-measures analysis of variance revealed that FC elicited significantly higher repetitions and electromyography (EMG) values of the vastus lateralis (simple main effect of condition) than did noncooling (P < .05) in the second (repetitions: 11 [3.5] vs 7.75 [3.2]; EMG: 63.4% [19.4%] vs 54.5% [18.4%]), third (repetitions: 8.9 [3.2] vs 6.4 [2.1]; EMG: 71.5% [17.4%] vs 60.6% [19.4%]), and fourth (repetitions: 7.5 [2.7] vs 5.1 [2.2]; EMG: 75.2% [19.6%] vs 59.3% [23.5%]) sets. The authors also detected a simple main effect of set in the FC and noncooling conditions on repetitions (P < .05) and in the FC condition on the vastus lateralis EMG values. Although the authors observed no time × trial interactions for the rating of perceived exertion, the authors observed main effects on the sets (7.7–9.6 vs 7.9–9.3, P < .05). Conclusions: Interset FC provides an ergogenic effect on a leg press pyramid workout and may offset fatigue, as indicated by higher repetitions and EMG response, without increasing perceived exertion.
Quantifying Training Demands of a 2-Week In-Season Squash Microcycle
Authors: James Carl , Dhawan Aishwar , Jones Timothy , Girard Olivier
Published: February 2021

Purpose: To quantify the demands of specific on- and off-court sessions, using internal and external training load metrics, in elite squash. Methods: A total of 15 professional squash players (11 males and 4 females) wore a 100-Hz triaxial accelerometer/global positioning system unit and heart rate monitor during on-court “Group,” “Feeding,” “Ghosting,” “Matchplay,” and off-court “Conditioning” sessions across a 2-week in-season microcycle. Comparisons of absolute training load (total values) and relative intensity (per minute) were made between sessions for internal (session rating of perceived exertion, differential rating of perceived exertion, TRIMP) and external (Playerload, very high–intensity movements [>3.5 m·s−2]) metrics. Results: The Group sessions were the longest (79 [12] min), followed by Feeding (55 [15] min), Matchplay (46 [17] min), Conditioning (37 [9] min), and Ghosting (35 [6] min). Time >90% maximum heart rate was the lowest during Feeding (vs all others P < .05) but other sessions were not different (all P > .05). Relative Playerload during Conditioning (14.3 [3.3] arbitrary unit [a.u.] per min, all P < .05) was higher than Ghosting (7.5 [1.2] a.u./min) and Matchplay (6.9 [1.5] a.u./min), with no difference between these 2 sessions (P ≥ .999). Conditioning produced the highest Playerloads (519 [153] a.u., all P < .001), with the highest on-court Playerloads from Group (450 [94] a.u., all P < .001). The highest session rating of perceived exertion (all P < .001), Edward’s TRIMP (all P < .001), and TEAM-TRIMP (all P < .019) occurred during the Group sessions. Conclusions: Squash Matchplay does not systematically produce the highest training intensities and loads. Group sessions provide the highest training loads for many internal and external parameters and, therefore, play a central role within the training process. These findings facilitate planning or adjustment of intensity, volume, and frequency of sessions to achieve desirable physical outcomes.
The Relationship Between Prescribed, Perceived, and Actual Delivery Intensity in Cricket Pace Bowling
Authors: Feros Simon A. , Bednarski Damon A. , Kremer Peter J.
Published: February 2021

Purpose: To investigate the relationship between prescribed (preDI), perceived (perDI), and actual delivery intensity (actDI) in cricket pace bowling. Methods: Fourteen male club-standard pace bowlers (mean [SD]: age 24.2 [3.2] y) completed 1 bowling session comprising 45 deliveries. The first 15 deliveries composed the warm-up, where participants bowled 3 deliveries each at a preDI of 60%, 70%, 80%, 90%, and 95%. Bowlers reported the perDI after each delivery. The fastest delivery in the session was used as a reference to calculate relative ball-release speed for the warm-up deliveries, with this measure representing the actDI. Ball-release speed was captured by a radar gun. Results: For perDI, there was a very large relationship with preDI (rs = .90, P < .001). Similarly, for actDI, there was a large relationship with preDI (rs = .52, P < .001). Higher concordance was observed between perDI and preDI from 60% to 80% preDI. A plateau was observed for actDI from 70% to 95% preDI. Conclusions: The relationship between perDI and actDI was very large and large with respect to preDI, indicating that both variables can be used to monitor delivery intensity against the planned intensity and thus ensure healthy training adaptation. The optimal preDI that allowed pace bowlers to operate at submaximal perDI but still achieve close to maximal ball-release speeds was 70%. Bowling at the optimal preDI may significantly reduce the psychophysiological load per delivery in exchange for a trivial loss in ball-release speed.
Results and lessons from a hospital-wide initiative incentivised by delivery system reform to improve infection prevention and sepsis care
Authors: Sreeramoju Pranavi , Voy-Hatter Karla , White Calvin , Ruggiero Rosechelle , Girod Carlos , Minei Joseph , Garvey Karen , Herrington Judith , Minhajuddin Abu , Madden Christopher , Haley Robert , Cerise Fred
Published: February 2021

Background

An academic safety-net hospital leveraged the federally funded state Delivery System Reform Incentive Payment programme to implement a hospital-wide initiative to reduce healthcare-associated infections (HAIs) and improve sepsis care.

Methods

The study period was from 2013 to 2017. The setting is a 770-bed urban hospital with six intensive care units and a large emergency department. Key interventions implemented were (1) awareness campaign and clinician engagement, (2) implementation of HAI and sepsis bundles, (3) education of clinical personnel using standardised curriculum on bundles, (4) training of key managers, leaders and personnel in quality improvement methods, and (5) electronic medical record-based clinical decision support. Throughout the 5-year period, staff received frequent, clear, visible and consistent messages from leadership regarding the importance of their participation in this initiative, performing hand hygiene and preventing potential regulatory failures. Several process measures including bundle compliance, hand hygiene and culture of safety were monitored. The primary outcomes were rates of central line-associated bloodstream infection (CLABSI), catheter-associated urinary tract infection (CAUTI), surgical site infection (SSI) and sepsis mortality.

Results

From 2013 to 2017, the hospital-wide rates of HAI reduced: CLABSI from 1.6 to 0.8 per 1000 catheter-days (Poisson regression estimate: −0.19; 95% CI −0.29 to −0.09; p=0.0002), CAUTI from 4.7 to 1.3 per 1000 catheter-days (−0.34; −0.43 to −0.26; p<0.0001) and SSI after 18 types of procedures from 3.4% to 1.3% (−0.29; −0.34 to −0.24; p<0.0001). Mortality of patients presenting to emergency department with sepsis reduced from 9.4% to 2.9% (−0.42; −0.49 to −0.36; p<0.0001). Adherence to bundles of care and hand hygiene and the hospital culture of patient safety improved. Results were sustained through 2019.

Conclusion

A hospital-wide initiative incentivised by the Delivery System Reform Incentive Payment programme succeeded in reducing HAI and sepsis mortality over 5 years in a sustainable manner.
Improving surgical quality in low-income and middle-income countries: why do some health facilities perform better than others?
Authors: Alidina Shehnaz , Chatterjee Pritha , Zanial Noor , Alreja Sakshie Sanjay , Balira Rebecca , Barash David , Ernest Edwin , Giiti Geofrey Charles , Maina Erastus , Mazhiqi Adelina , Mushi Rahma , Reynolds Cheri , Sydlowski Meaghan , Tinuga Florian , Maongezi Sarah , Meara John G , Kapologwe Ntuli A , Barringer Erin , Cainer Monica , Citron Isabelle , DiMeo Amanda , Fitzgerald Laura , Ghandour Hiba , Gruendl Magdalena , Hellar Augustino , Jumbam Desmond T , Katoto Adam , Kelly Lauren , Kisakye Steve , Kuchukhidze Salome , Lama Tenzing N , Menon Gopal , Mshana Stella , Reynolds Chase , Segirinya Hannington , Simba Dorcas , Smith Victoria , Staffa Steven J , Strader Christopher , Tibyehabwa Leopold , Troxel Alena , Varallo John , Wurdeman Taylor , Zurakowski David
Published: February 2021

Background

Evidence on heterogeneity in outcomes of surgical quality interventions in low-income and middle-income countries is limited. We explored factors driving performance in the Safe Surgery 2020 intervention in Tanzania’s Lake Zone to distil implementation lessons for low-resource settings.

Methods

We identified higher (n=3) and lower (n=3) performers from quantitative data on improvement from 14 safety and teamwork and communication indicators at 0 and 12 months from 10 intervention facilities, using a positive deviance framework. From 72 key informant interviews with surgical providers across facilities at 1, 6 and 12 months, we used a grounded theory approach to identify practices of higher and lower performers.

Results

Performance experiences of higher and lower performers differed on the following themes: (1) preintervention context, (2) engagement with Safe Surgery 2020 interventions, (3) teamwork and communication orientation, (4) collective learning orientation, (5) role of leadership, and (6) perceived impact of Safe Surgery 2020 and beyond. Higher performers had a culture of teamwork which helped them capitalise on Safe Surgery 2020 to improve surgical ecosystems holistically on safety practices, teamwork and communication. Lower performers prioritised overhauling safety practices and began considering organisational cultural changes much later. Thus, while also improving, lower performers prioritised different goals and trailed higher performers on the change continuum.

Conclusion

Future interventions should be tailored to facility context and invest in strengthening teamwork, communication and collective learning and facilitate leadership engagement to build a receptive climate for successful implementation of safe surgery interventions.
Screening and managing obesity: understanding paediatric residents' knowledge, attitudes and practice
Authors: Wu Vickie , Rosen Carolyn , Pan Stephanie , Mogilner Leora
Published: February 2021

Study purpose

Prior studies have identified paediatric attending physicians' screening and management patterns related to overweight/obesity, but less is known about resident physicians' behaviour. The objective was to understand paediatric resident physicians' knowledge, attitude and practice patterns of overweight/obesity screening and management.

Study design

We performed a retrospective chart review of preventive visits conducted by residents between August and October 2019. Charts of patients 2–18 years with body mass index ≥85th percentile at the visit were reviewed (85th–<95th for age and sex defined as overweight, ≥95th defined as obese). A survey was distributed to residents assessing knowledge, attitudes and barriers towards obesity management.

Results

Of 1250 visits reviewed, 405 (32%) patients met the criteria for overweight or obesity. 39% were identified correctly by the provider, 53% were not identified and 8% were identified incorrectly. 89% of patients had diet history, 31% had physical activity and 43% had family history documented. Patients with obesity received physical activity documentation/counselling, portion size counselling, at least one referral, laboratory tests and a diagnosis more often than overweight patients. 84% of residents completed the survey. Although the majority of residents felt ‘somewhat’ or ‘very’ well prepared to counsel families about overweight/obesity, the majority thought their counselling on overweight/obesity was ‘not at all’ or ‘slightly’ effective.

Conclusion

Despite residents feeling prepared and comfortable discussing overweight/obesity with patients, these diagnoses were often under-recognised or incorrectly made and appropriate counselling was lacking. Future work will focus on specific strategies to improve diagnosis, screening and management of overweight/obesity and include educational interventions and electronic medical record adaptations.
Combined lifestyle factors are associated with the risk of ischaemic stroke in a Chinese population
Authors: You Tao , Li Yi , Wu Xiaoguang , Wu Siyi , Zhang Yanlin , Zhou Xiang
Published: February 2021

Purpose

Lifestyle plays an important role in the development of ischaemic stroke (IS). The objective of this study was to evaluate the association between combined lifestyle factors and the risk of IS in an eastern Chinese population.

Methods

We collected lifestyle information from 191 patients with IS admitted to the second affiliated hospital of Soochow University and 575 control subjects from community clinics using a structured questionnaire. After division into training and test datasets, regularised stepwise logistic regression, least absolute shrinkage and selection operator regression and genetic algorithm models were used to identify lifestyle factors associated with IS. The improved discriminative ability by adding the lifestyle factors was determined by c-index and reclassification analysis. The final model was validated in the test dataset.

Results

After controlling for conventional cardiovascular disease (CVD) risk factors, preferences for fruits (OR (95% CI): 0.29 (0.18–0.46), p<0.001) and soy products (0.47 (0.29–0.75), p=0.002) were negatively associated with IS, while lower life satisfaction (mildly satisfied: 2.15 (1.27–3.63), p=0.004; not satisfied: 6.39 (1.76–25.44), p=0.006) was positively associated with IS. Adding these factors to a basic CVD risk model improved the c-index (0.825 vs 0.753, p<0.001) and reclassification for IS (net reclassification index (95% CI): 18.49% (7.90%–29.08%), integrated discrimination index (95% CI): 0.11% (0.08%–0.14%), p<0.001). The model with lifestyle factors achieved a c-index of 0.813 and good calibration in the test dataset.

Conclusions

Our results showed that combined lifestyle factors including dietary pattern and life satisfaction are independently associated with the risk of IS.
Migraines and keloids: a 15-year Taiwan claim database analysis
Authors: Lu Ying-Yi , Qin Hao , Lu Chun-Ching , Wu Ming-Kung , Zhang Cong-Liang , Wu Chieh-Hsin
Published: February 2021

Background

Fibroproliferative lesions with intractable pruritus, pain and hyperesthesia that cause uncontrolled scar growth are known as keloids. Migraines are common upsetting headache disorders characterised by frequent recurrence and attacks aggravated by physical activity. Both keloids and migraines can cause physical exhaustion and discomfort in patients; they have similar pathophysiological pathways, that is, the transforming growth factor-β1 gene and neurogenic inflammation.

Objective

To investigate subsequent development of migraines in patients with keloids.

Methods

Data were retrieved from the Taiwan National Health Insurance Research Database. The keloids group included patients aged 20 years and older with a recent diagnosis of keloids(n=9864). The non-keloids group included patients without keloids matched for gender and age at 1–4 ratio (n=39 456). Migraine risk between groups was measured by Cox proportional hazards regression models. Incidence rates and hazard ratios were calculated.

Results

During the study period, 103 keloids patients and 323 non-keloids patients developed migraines. The keloids patients had a 2.29-fold greater risk of developing migraines compared with the non-keloids group after adjustment for covariates (1.81 vs 0.55 per 1000 person-years, respectively). In the keloids group, female or patients younger than 50 years were prone to developing migraines.

Conclusion

The higher tendency to develop migraines in the keloids group in comparison with the non-keloids group suggests that keloids could be a predisposing risk factor for migraine development in adults. Keloids patients who complain of headaches should be examined for migraines.