bluuebunny/crossref_metadata_2025 huggingface dataset:
The welfare effects of free trade agreements in quantitative trade models: A comparison of studies about Transatlantic Trade and Investment Partnership
Authors: Bekkers Eddy , Rojas‐Romagosa Hugo
Published: July 2018

We compare different methodological approaches to predicting the welfare effects of trade policy experiments. We focus on studies that estimate the economic effects of the Transatlantic Trade and Investment Partnership (TTIP). Methodologically, the studies can be divided into those employing computable general equilibrium (CGE) models and structural gravity (SG) models. We compare and critically discuss differences in the estimated trade cost reductions and in the economic models employed, and how these can explain the relatively wide range of economic effects found in the different TTIP studies. We conclude that reasonable estimates of the welfare effects for the TTIP partners are between 0.5% and 2%.
An International Educational Training Course for Conducting Systematic Reviews in Health Care: The Joanna Briggs Institute's Comprehensive Systematic Review Training Program
Authors: Stern Cindy , Munn Zac , Porritt Kylie , Lockwood Craig , Peters Micah D. J. , Bellman Susan , Stephenson Matthew , Jordan Zoe
Published: July 2018

Background

The cornerstone of evidence‐based health care is the systematic review of international evidence. Systematic reviews follow a rigorous, standardized approach in their conduct and reporting, and as such, education and training are essential prior to commencement.

Aims

This study reports on the evolution of the Joanna Briggs Institute Comprehensive Systematic Review Training Program (JBICSRTP) as an exemplar approach for teaching systematic review methods.

Results

The Joanna Briggs Institute (JBI) is an international research and development center at the University of Adelaide, South Australia. Its mission is to promote and facilitate evidence‐based best practice globally, largely through the provision of education and training. JBI was one of the first to consider all forms of evidence in systematic reviews, and as such, implementation of standardized training was essential. Since 1999, JBI has offered a systematic review training program. The JBICSRTP is now delivered face to face over 5 days, with an optional online component; the content aligns to that proposed in the Sicily statement. Over the last 3 years, JBI and its Collaboration have trained over 3,300 people from over 30 countries. A ”train‐the‐trainer” (TtT) style program was established to cope with demand, and to date, hundreds of trainers have been licensed across the globe to deliver the JBICSRTP.

Linking Evidence to Action

Providing standardized training materials, ensuring open and ongoing communication, and adopting a TtT style program while still allowing for local adaptability are strategies that have led to the establishment of a highly skilled global training network and ensured the success and longevity of the JBICSRTP.
Reviewer Acknowledgements
Authors: Smith Robert
Published: July 2018

Journal of Education and Training Studies (JETS) would like to acknowledge the following reviewers for their assistance with peer review of manuscripts for this issue. Many authors, regardless of whether JETS publishes their work, appreciate the helpful feedback provided by the reviewers. Their comments and suggestions were of great help to the authors in improving the quality of their papers. Each of the reviewers listed below returned at least one review for this issue.Reviewers for Volume 6, Number 8Alkan Uğurlu, TurkeyAngel H. Y. Lai, Hong Kong Baptist University, Hong KongBegüm Yalçınkaya, Çanakkale Onsekiz Mart University, TurkeyCagla Atmaca, Pamukkale University, TurkeyCarmen Pérez-Sabater, Universitat Poltècnica de València, SpainCynthia M. Compton, Wingate University, USADamodar Khanal, The University of Manchester, UKEnisa Mede, Bahcesehir University, TurkeyErica D. Shifflet-Chila, Michigan State University, USAGüner Çiçek, University Of Hitit, TurkeyGunkut Mesci, Giresun University, TurkeyHasan Şahan, TurkeyHülya Uğur Tanriöver, Giresun University, Turkeyİbrahim Yaşar Kazu, Firat University, TurkeyIntakhab Khan, King Abdulaziz University, Saudi ArabiaIoannis Syrmpas, University of Thessaly, GreeceJohn Cowan, Edinburgh Napier University, UKJon S. Turner, Missouri State University, USALaura Bruno, The College of New Jersey, USALeila Youssef, Arab Open University, LebanonLorna T. Enerva, Polytechnic University of the Philippines, PhilippinesMahmut Gulle, Sirnak University, TurkeyMarcie Zaharee, The MITRE Corporation, USAMaurizio Sajeva, Pellervo Economic Research PTT, FinlandMehmet Inan, Marmara University, TurkeyMeral Seker, Alanya Alaaddin Keykubat University, TurkeyMichail Kalogiannakis, University of Crete, GreeceMustafa Çakır, Marmara Üniversity, TurkeyMustafa Güçlü, Erciyes University, TurkeyNurullah Şahin, Sinop University, TurkeyOktay Çoban, TurkeyOzgur Demirtas, Inonu University, TurkeyOzkan Guler, TurkeyPirkko Siklander, University of Lapland, FinlandSadia Batool, Preston University Islamabad, PakistanSandro Sehic, Oneida BOCES, USASayim Aktay, Mugla Sitki Kocman University, TurkeySelloane Pitikoe, University of Kwazulu-Natal, South AfricaStamatis Papadakis, University of Crete, GreeceYalçın Dilekli, Aksaray University, TurkeyZait Burak Aktuğ, Turkey Robert SmithEditorial AssistantOn behalf of,The Editorial Board of Journal of Education and Training StudiesRedfame Publishing9450 SW Gemini Dr. #99416Beaverton, OR 97008, USAURL: http://jets.redfame.com
Specific synaptic input strengths determine the computational properties of excitation–inhibition integration in a sound localization circuit
Authors: Gjoni Enida , Zenke Friedemann , Bouhours Brice , Schneggenburger Ralf
Published: July 2018

Key points

During the computation of sound localization, neurons of the lateral superior olive (LSO) integrate synaptic excitation arising from the ipsilateral ear with inhibition from the contralateral ear.

We characterized the functional connectivity of the inhibitory and excitatory inputs onto LSO neurons in terms of unitary synaptic strength and convergence.

Unitary IPSCs can generate large conductances, although their strength varies over a 10‐fold range in a given recording. By contrast, excitatory inputs are relatively weak.

The conductance associated with IPSPs needs to be at least 2‐fold stronger than the excitatory one to guarantee effective inhibition of action potential (AP) firing.

Computational modelling showed that strong unitary inhibition ensures an appropriate slope and midpoint of the tuning curve of LSO neurons. Conversely, weak but numerous excitatory inputs filter out spontaneous AP firing from upstream auditory neurons.

The lateral superior olive (LSO) is a binaural nucleus in the auditory brainstem in which excitation from the ipsilateral ear is integrated with inhibition from the contralateral ear. It is unknown whether the strength of the unitary inhibitory and excitatory inputs is adapted to allow for optimal tuning curves of LSO neuron action potential (AP) firing. Using electrical and optogenetic stimulation of afferent synapses, we found that the strength of unitary inhibitory inputs to a given LSO neuron can vary over a ∼10‐fold range, follows a roughly log‐normal distribution, and, on average, causes a large conductance (9 nS). Conversely, unitary excitatory inputs, stimulated optogenetically under the bushy‐cell specific promoter Math5, were numerous, and each caused a small conductance change (0.7 nS). Approximately five to seven bushy cell inputs had to be active simultaneously to bring an LSO neuron to fire. In double stimulation experiments, the effective inhibition window caused by IPSPs was short (1−3 ms) and its length depended on the inhibitory conductance; an ∼2‐fold stronger inhibition than excitation was needed to suppress AP firing. Computational modelling suggests that few, but strong, unitary IPSPs create a tuning curve of LSO neuron firing with an appropriate slope and midpoint. Furthermore, weak but numerous excitatory inputs reduce the spontaneous AP firing that LSO neurons would otherwise inherit from their upstream auditory neurons. Thus, the specific connectivity and strength of unitary excitatory and inhibitory inputs to LSO neurons is optimized for the computations performed by these binaural neurons.
Boundary Element Analysis of Bubble Oscillations in Elastic Tubes
Authors: Kitahara Tatsuya , Makihara Nariki , Ogasawara Toshiyuki , Takahira Hiroyuki
Published: July 2018

The interactions between a microbubble and ultrasound in an elastic tube are investigated to understand the bubble dynamics in a blood vessel. The tube wall is modeled with a spring-mass system. A simple bubble model for investigating bubble oscillations in the tube is introduced and is combined with the spring-mass system of the tube: the bubble is represented by a point source for the bubble volume oscillation and a dipole for the translational motion. The natural frequencies of the system are derived by linearizing the governing equations. The influences of an elastic tube on a bubble are mainly discussed by using eigenvalue analysis in the present work. It is shown that the resonance frequency of a bubble in the tube decreases with increasing the mass of the tube wall. The effects of the tube length and the initial location of a bubble are also investigated. The results show that although the resonance frequency decreases monotonically with increase in the tube length when the wall mass is large, it is not changed when the mass is sufficiently small. It is also shown that the resonance frequency is decreased with decreasing the distance between the bubble centroid and the tube wall when the mass is large. However, when the mass is small enough, it is increased with decreasing the distance. We also investigate the influence of the characteristics of an elastic tube on nonlinear oscillations of a bubble. The condition that the harmonic oscillation is enhanced is discussed.
Influence of Eccentric Vortex to Performance of Cross Flow Fan
Authors: Hayashi Hidechito , Okumura Tetsuya , Hamakawa Hiromitsu , Teraoka Hironobu
Published: July 2018

The flow in the cross flow fan is different from conventional turbo-machinery. The air passes the blades twice and the motion of the blades forms an eccentric vortex within the impeller. It is presented in this paper that the flow in the cross flow fan is divided to four parts; inflow, outflow, casing and tongue parts. The blade load is large in the outflow part and the circumferential variation of it is large. The pressure rise in the fan is higher at the short tongue than at the original tongue, but the efficiency is opposite to the pressure rise characteristics. The eccentric vortex emerges near the tongue in the impeller, and when the short tongue is used, the position of it moves to the outflow part. The energy increment in the impeller is different in circumferential position, that it is very large at the outflow part. The form of the eccentric vortex is closely relating to the fan performance, but the strength of it is not so large relating to it.
Turbulence Structure on the Surface of High Speed Liquid Jet
Authors: Gong Chen , Yang Minguan , Wang Yuli , Yan Longlong , Gao Bo
Published: July 2018

The structures on the surface of high-speed capillary liquid jet were captured with the help of high-speed camera and microscope. A power spectral density method is used to deal with the jet images. Based on captured jet image, the variation of surface structures near the exit of the nozzle is divided into three sections: laminar section, instability section and turbulence section. There is no clearly surface structures in the laminar section. The wave-like structures come out in the instability section with a sudden and are regularly increase with a small slope along the streamwise. The degree of order is rather weak in the turbulence section. The increase of the Reynolds numbers which based on the momentum thickness at the exit of the nozzle will accelerates the jet surface transition from the laminar section to turbulence section.
Influence Analysis of the Rounding Technique of Spiral Groove Root on the Performance of Upstream Pumping Mechanical Seal
Authors: Huilong Chen , Jie Fu , Shulin Li , Binjuan Zhao , Qiang Zou
Published: July 2018

In order to improve the performance of the upstream pumping mechanical seal, and considering one specific spiral groove upstream pumping mechanical seal, an improvement project about the groove structure on the seal surface is put forward. The slipping mesh technique was adopted to simulate the internal flow. After simulation, the pressure pulsation at different monitor points are compared and analyzed, and BVF (boundary vortex flow) diagnosis method is used to analyze the results, which is to explore the relationship between groove type and sealing performance. The results shows that the groove root with fillet compared to acute angle can improve the effect of dynamic pressure at the root of groove and increase static pressure in high pressure area. But overlarge round radius will weaken the pumping effect of spiral groove and increase vortex flow. It can also increase flow loss at groove root area, which will reduce of opening force of liquid film and increase the amplitude of pressure pulsation that affect the stability of the sealing performance. Hence, an optimum radius groove length ratio Rr exists, which can acquire the largest sealing performance and good stability, and this can provide reference to improve the upstream pumping mechanical seal performance.
Fluid-Structure Interaction Analysis for Resonance Investigation of Pump-Turbine Runner
Authors: Kurosawa Sadao , Matsumoto Kiyoshi , Miyagi Junpei , He Lingyan , Wang Zhengwei
Published: July 2018

In the development of high head pumped storage projects, one of the critical problems is the strength of pump-turbine runners. In this paper, the analysis method of forced response of the runner structure is presented and the prediction accuracy is validated by comparing with the results of the prototype head model test. And the application results for resonance of pump-turbine startup process are shown.

Basically it is necessary for the prediction of the runner dynamic stress to use a combined approach of fluid dynamics and structural dynamics. Due to the high complexity of the phenomena and the limitation of computer power, the numerical simulation for the fluid-structural interaction phenomena was in the past too expensive and not feasible. However, due to consideration that vibration displacement is very small, such complex analysis has been handled as one-way fluid-structural interaction problem. Namely the excitation force is calculated by whole passage flow analysis that is ignored the structural deformation and takes into account the rotor-stator interaction effect. And the dynamic stress of runner is calculated by the transient response analysis taken account into the added mass effect of surrounding water using an acoustic fluid formulation. Due to such a simplification, it has been possible to evaluate the runner dynamic stress in a short time.

As a result, it was confirmed that the dynamic behavior such as runner vibration and pressure fluctuation under turbine operating range and the runner stress can be analyzed with the sufficient accuracy and due to applying as standard procedure in TOSHIBA, it can be avoided a failure risk in an early design phase. Moreover the fluid-structure interaction analysis method in this paper can be easily adapted to apply for other type of turbines, such as Francis turbines and Kaplan turbines.
Diffusion Control in Circular Jet Using Coaxial Type DBD Plasma Actuator
Authors: Miyagi Norimasa , Ueki Hideo , Kimura Motoaki
Published: July 2018

This study investigated the use of a coaxial dielectric barrier discharge plasma actuator (DBD-PA) at a nozzle exit for jet diffusion control. In order to achieve enhanced mixing of the primary jet flow, the influence of the input voltage and frequency to the plasma actuator was examined. In the case of continuous operating, the secondary flow by the induced flow using coaxial plasma actuator is able to adjust the velocity gradient of the free shear layer near the jet nozzle. Intermittent control using the plasma actuator was also attempted by varying the intermittency frequency and the duty ratio. Based on the results of a PIV analysis, the optimum conditions for jet diffusion control were found to be an intermittency frequency that matched the preferred frequency and a duty ratio at 50%.
Electrical Capacitance Tomography Based Sorting Technique for Wasted Plastics
Authors: Hirose Yusuke , Hata Kazuaki , Achyut Sapkota , Takei Masahiro
Published: July 2018

This study has launched a concept to measure real time two-dimensional temperature distribution non-invasively by a combination of electrical capacitance tomography (ECT) technique and a permittivity-temperature equation for plastic pellets. The concept has two steps which are the relative permittivity calculation from the measured capacitance among the many electrodes by ECT technique, and the temperature distribution calculation from the relative permittivity distribution by permittivity-temperature equation. ECT sensor with 12-electrode is designed to measure and visualize the cross sectional temperature distribution during polymethyl methacrylate (PMMA) pellets cooling process. The images of the normalized relative permittivity distribution are successfully reconstructed at every time step during the process. The images indicate that the normalized relative permittivity of PMMA pellets is decreased as the temperature is decreased.
Coupled 6DoF Motion and Aerodynamics Simulation During Pass-By and Overtaken Motions
Authors: Ishioka Hirotaka , Ota Shoya , Nakasato Kosuke , Onishi Keiji , Tsubokura Makoto
Published: July 2018

Recently, unsteady aerodynamics has been drawing many attention because it is becoming clear that unsteady aerodynamics have a big effect on running stability, safety and ride comfort of vehicles. In order to estimate unsteady aerodynamics, it is necessary to reproduce the actual running condition including an atmospheric disturbance and vehicle motion. However, it is difficult to investigate the effect of unsteady aerodynamics in the road test because it has a lot of errors in measurement. In this study, a coupled simulation method between the 6DoF motion of a vehicle and aerodynamics was developed for these problems. Large Eddy Simulation (LES) was used to estimate the aerodynamics, and the motion equations of a vehicle was used to estimate vehicle motion. Vehicle motion in aerodynamic simulation was reproduced by using Arbitrary Lagrangian-Eulerian (ALE) method. In addition, sliding mesh method was used to reproduce overtaking and passing motions of two vehicles. By using the methods, aerodynamics and vehicle dynamics simulations are treated interactively (2-way) by exchanging each result at each time step. The 2-way results were compared with the 1-way coupled simulation estimating vehicle motion from aerodynamics results posteriori to investigate how vehicle’s motion itself further affects its aerodynamics during the pass-by and overtaking motions. Our main focus is, by using this method, to study the effect of unsteady aerodynamics on the running stability of a vehicle. The results of 1-way and 2-way coupling analysis showed difference with respect to behavior of a vehicle. It is believed that such differences result in the different aerodynamic forces and moments, which is caused by the vehicle’s posture changes in the 2-way coupling simulation.
Numerical Simulation of Flow Field Around a Circular-Bladed Butterfly Wind Turbine
Authors: Hara Yutaka , Sumi Takahiro , Matsubara Yuhei , Yasumoto Yoshiyuki
Published: July 2018

Three-dimensional computational fluid dynamics (3D-CFD) was performed to simulate the flow field around an aluminum circular-blade butterfly wind turbine, which is a vertical-axis-type turbine with four circular blades and a diameter of 2.06 m. Under the assumption of a loss factor of 0.8 due to a generator and an AC–DC converter, the CFD results agreed with the experimental results. Although tip vortices were observed at the top and bottom portions of the blades, the vorticity intensity was weaker than that of the straight-blade rotor case. In addition, the cross-sectional shape of the tip vortices seemed to be elliptical for circular blades rather than circular as for straight blades. As the tip speed ratio was less than 2, vortices arising from dynamic stall at maximum-radius portions of blades were observed at the downwind half-cycle as well as the upwind half-cycle. A feature of the vortices shed from a circular blade at the downwind half-cycle was the looped shape.
Turbulent Vorticity Diffusion in the Stronger Wall Jet Managed by a Flat Plate Wing in the Outer Layer
Authors: Katayama Takuma , Mochizuki Shinsuke
Published: July 2018

The present experiment focuses on the vorticity diffusion in a stronger wall jet managed by a three-dimensional flat plate wing in the outer layer. Measurement of the fluctuating velocities and vorticity correlation has been carried out with 4-wire vorticity probe. The turbulent vorticity diffusion due to the large scale eddies in the outer layer is quantitatively examined by using the 4-wire vorticity probe. Quantitative relationship between vortex structure and Reynolds shear stress is revealed by means of directly measured experimental evidence which explains vorticity diffusion process and influence of the manipulating wing. It is expected that the three-dimensional outer layer manipulator contributes to keep convex profile of the mean velocity, namely, suppression of the turbulent diffusion and entrainment.
Wireless Measurement of Fluid Force in Liquid-Solid Flow by Lagrangian Sensor Particle
Authors: Ikegai Tomoki , Yoshimori Wataru , Yasuda Shoichi , Harada Shusaku
Published: July 2018

We have developed a “sensor particle”, which is a Lagrangian sensor system for real-time measurement of the force acting on a particle moving freely in fluid flow. The sensor particle is composed of an acceleration sensor, magnetometer, microcomputer, wireless module and cells. The built-in acceleration sensor detects the acceleration of particle at each instant of time. However, the signals contain both dynamic and static (gravitational) accelerations. Therefore we applied the external magnetic field oriented in the gravitational direction in order to identify the attitude of the sensor particle and to remove the gravitational acceleration from the measured signals. Consequently, we can obtain the force acting on a particle moving in fluid at each time through the equation of the motion. We have applied our system to oscillatory liquid flow with particle assemblage to obtain the basic knowledge on unsteady fluid force in a multi-particle system.
Clarification of Performance Curve Instability Mechanism Using Large Eddy Simulation of Internal Flow of a Mixed-Flow Pump
Authors: Hagiya Isao , Kato Chisachi , Yamade Yoshinobu , Nagahara Takahide , Fukaya Masashi
Published: July 2018

We analyzed the internal flows of a test mixed-flow pump exhibiting performance curve instability at low flow rates by using LES to clarify the performance curve instability mechanism. The LES was conducted using the open source software FrontFlow/blue [1]. In particular, we investigated in detail the flows at the flow rates, where the head curve had a positive slope under low flow rate condition.

We clarified that Euler’s head drop caused by a stall near the tip of the rotor-blades is a dominant factor at the instability of the test pump. At the bottom point of the positive slope of the head curve, stall regions covered all the rotor-blade passages on the tip side. The drop of the angular momentum in the impeller caused by the stall on the leading edge side exceeds the increment caused by the decrease in the flow rate on the trailing edge at the bottom point of the positive slope.

At the middle point of the positive slope of the head curve we also found regions with low-velocities in some blade passages. Such regions, namely stall cells, rotated around the impeller for one revolution while the impeller rotated almost about 20 revolutions in the direction opposite to the impeller’s rotation. The region with low-velocity first appears at the trailing edge and expands toward the leading edge. The angle of attack of the neighbouring blade in the direction opposite to the rotation of the blade increases and that blade pitch begins to stall. When that blade pitch is fully stalled, it is no longer loaded and the positive pressure gradient in that blade pitch decreases. The blade pitch is most likely to accept the excess flow. It recovers from the stalled state.
The Effect of Tip Leakage Vortex on Cavitation Performance in Axial Hydro Turbine
Authors: Masuda Naoki , Austen Faris , Maeda Hideaki
Published: July 2018

From viewpoint of greenhouse gas emission reduction, recently utilization of renewable energy becomes the focus of attention. Among several renewable energy systems, hydro power generation can supply the most stable energy and Torishima has already supplied an axial micro hydro turbine [1].

In general, the low cost system is needed in the case of micro hydro turbine. And one solution is to apply a fixed blade and constant rotation speed type. However the operating range will be narrow because of a cavitation problem. As is well known, there are some kinds of cavitations in the hydro machinery and they cause adverse effects such as vibration, excessive noise, decreasing efficiency and affecting turbine life [2]. Furthermore, these effects are more serious at partial and/or overload condition, so that turbine allowable operating range is limited by them. Therefore, the purpose of this study is to improve the cavitation performance in wider range for satisfying this requirement.

In this paper, we focused on the influence of tip leakage vortex cavitation; one of the important phenomena for cavitation performance improvement as described in the references [3–5]. We tried to clarify the influence by both experimental and numerical investigation on the cavitation performance. In CFD (Computational Fluid Dynamics) analysis, tip clearance was applied for whole circumference model of runner and the full cavitation model [6] was used for the unsteady cavitation analysis. The calculation domain included guide vane was used to consider the effect of unsteady interference between runner and guide vane. In the CFD result, the tip leakage vortex cavitation was identified by void ratio and helicity [7] to analyze vortex structure with detail.
Linking Efficiency to Functional Performance by a Pump Test Standard for Wastewater Pumps
Authors: Pöhler Michael , Gerlach Stefan , Höchel Kristian , Mengdehl Tino , Thamsen Paul Uwe
Published: July 2018

Upcoming Energy related Products (ErP) regulations on wastewater pumps by the European Commission will affect all pump manufacturers and operators of wastewater systems. Hence, the preparation of efficiency standards for wastewater pumps is intensively accompanied by input from the affected stakeholders and experts of different fields [1]. The previous approaches of ErP regulations, as in lot 11 (Electric motors, Ventilation fans, Circulators in buildings, Electric pumps), focus only on efficiency. However, when applying the philosophy of Ecodesign directly to wastewater pumps, the complex flow structure and the transport behaviour of this inhomogeneous multi-phase fluid must be taken into account.

While efficiency is an important criterion, it is necessary to take the specifics of sewage transport into account when designing a new test standard, so as not to compromise on proven and “system-efficient” technologies. Therefore, the Berlin Institute of Technology is currently investigating wastewater compositions and limits for reliable pump operation in order to design a test standard for wastewater pumps comparable to the DIN EN ISO 9906 efficiency tests for clear water [2]. The test will assess the functional fulfilment level of the pump performance, differentiating between the wastewater classes.
Fully Parameterized Reduced Order Models Using Hyper-Dual Numbers and Component Mode Synthesis
Authors: Bonney Matthew S. , Kammer Daniel C. , Brake Matthew R. W.
Published: July 2018

The uncertainty of a system is usually quantified with the use of sampling methods such as Monte-Carlo or Latin hypercube sampling. These sampling methods require many computations of the model and may include re-meshing. The re-solving and re-meshing of the model is a very large computational burden. One way to greatly reduce this computational burden is to use a parameterized reduced order model. This is a model that contains the sensitivities of the desired results with respect to changing parameters such as Young’s modulus. The typical method of computing these sensitivities is the use of finite difference technique that gives an approximation that is subject to truncation error and subtractive cancellation due to the precision of the computer. One way of eliminating this error is to use hyperdual numbers, which are able to generate exact sensitivities that are not subject to the precision of the computer. This paper uses the concept of hyper-dual numbers to parameterize a system that is composed of two substructures in the form of Craig-Bampton substructure representations, and combine them using component mode synthesis. The synthesis transformations using other techniques require the use of a nominal transformation while this approach allows for exact transformations when a perturbation is applied. This paper presents this technique for a planar motion frame and compares the use and accuracy of the approach against the true full system. This work lays the groundwork for performing component mode synthesis using hyper-dual numbers.
A Discretized Optimization Strategy for Rest-to-Rest Maneuvers of Overhead Cranes Considering the Effect of Damping
Authors: Alghanim Khaled A. , Alhazza Khaled A. , Masoud Ziyad N.
Published: July 2018

An optimization strategy to reduce residual vibration of rest-to-rest maneuvers of overhead cranes is proposed. The proposed technique is based on generating shaped acceleration commands for a simple harmonic oscillator with damping included. Furthermore, the proposed technique solves the problem of discrete signal commands that result from using slow digital to analog convertors on real cranes. A discretized acceleration profile is derived analytically using finite step segments. These segments are integrated into a matrix, which is then coupled with a system response matrix through the system’s equations of motion. The resulting input acceleration matrix is then optimized to satisfy rest-to-rest maneuver conditions. The profile designer can control many parameters such as maneuver duration, discrete time step, hoisting speed, damping ratio, maximum velocity and acceleration. Unlike traditional command shapers, the proposed shaped profiles are independent of the natural period of the system, i.e., the acceleration profile duration is designer selectable. Through several examples, the performance of the proposed controller is validated numerically. Results show that the proposed shaping technique can effectively eliminate residual vibrations in rest-to-rest maneuvers of damped single-degree-of-freedom systems.
Behavior of a Tilting–Pad Journal Bearing With Different Load Directions
Authors: Dang Phuoc Vinh , Chatterton Steven , Pennacchi Paolo , Vania Andrea , Cangioli Filippo
Published: July 2018

Tilting–pad journal bearings (TPJBs) are widely used in rotating machinery to support the rotors efficiently at elevated speeds under light/heavy loadings. Because of the importance of this machine component, many authors have published several theoretical and experimental studies, to evaluate the influence of clearance, lubricant temperature, oil flow-rate and thermal effects on behavior of TPJB. However, the investigations of the influence of loading direction on properties of TPJB are very limited. In bearing models as well as in experimental tests, the load is often assumed along the vertical direction only and the geometry of the bearing is the same for each pad, which corresponds to an axial symmetry of the bearing. This paper presents first a theoretical analysis of the influence of the load direction on both the static and the dynamic behavior of a five-pad TPJB with a non-uniform clearance: that is, the different bearing configurations in the range between load-on-pad (LOP) and load-between-pads (LBP) are investigated. Then, the analytical results are compared with experimental measurements. The tests were performed with a nominal diameter of 100 mm and a length–to–diameter ratio of 0.7, using a suitable test-rig, in which it is possible to apply the static load in any direction. The procedure for the estimation of the bearing geometry from experimental measurement of the non-uniform clearance profile is also described. The results show that the load direction has considerable effects on both the static and the dynamic characteristics of the TPJB. Besides, the influence of load directions is stronger on the dynamic characteristics of tilting pad bearing than on the static ones.
An Experimental Study of Nonlinear Oil-Film Forces in a Tilting-Pad Journal Bearing
Authors: Dang Phuoc Vinh , Chatterton Steven , Pennacchi Paolo , Vania Andrea , Cangioli Filippo
Published: July 2018

Journal bearings have been widely used in high-speed rotating machinery. The dynamic coefficients of oil-film force affect the machine unbalance response and machine stability. The oil-film force of hydrodynamic bearing is often characterized by a set of linear stiffness and damping coefficients. However the linear oil-film coefficients with respect to an equilibrium position of the journal are inaccurate when the bearing system vibrates with large amplitudes due to a dynamic load. The study on nonlinear oil-film forces is still rare and most papers are confined to theoretical analyses. The purpose of this paper is to derive some new non-linear force models (28-co., 24-co. and 36-co. models) to identify these dynamic coefficients based on experimental data. The fundamental test model is obtained from a Taylor series expansion of bearing reaction force. Tests were performed with a nominal diameter of 100mm and a length–to–diameter ratio of 0.7 using a suitable test rig in which it is possible to apply the static load in any direction. The results show that these three models are feasible to identify the oil-film forces in which the second-order oil-film coefficients received from the 24-co. model are more stable compared to those of other two nonlinear models.
Diagnostics of Rolling Element Bearings by Means of the Higuchy Fractal Dimension
Authors: Chatterton Steven , Pennacchi Paolo , Vania Andrea , Dang Phuoc Vinh , Cangioli Filippo
Published: July 2018

In the field of rolling element bearing, the degradation of bearing health could be detected by means of suitable damage indexes. Band-Kurtosis index, that is the kurtosis value of the band-filtered signal, is often assumed. The critical point of this approach is the selection of a suitable filter band. In the paper, the use of a chaos metrics, namely the Higuchi fractal dimension as damage indicator is described. The trend of this index is compared with the common approach of band-kurtosis indicator for an experimental case of a rolling element bearing in which the defect developed until a permanent failure.
Elastodynamic Modeling and Simulation of an Axially Accelerating Beam
Authors: Ghaith Fadi A. , Ayub Ahmad
Published: July 2018

This paper aims to develop an accurate nonlinear mathematical model which may describe the coupled in-plane motion of an axially accelerating beam. The Extended Hamilton’s Principle was utilized to derive the partial differential equations governing the motion of a simply supported beam. The set of the ordinary differential equations were obtained by means of the assumed mode method. The derived elastodynamic model took into account the geometric non-linearity, the time-dependent axial velocity and the coupling between the transverse and longitudinal vibrations. The developed equations were solved numerically using the Runge-Kutta method and the obtained results were presented in terms of the vibrational response graphs and the system natural frequencies. The system dynamic characteristics were explored with a major focus on the influence of the velocity, acceleration and the excitation force frequency. The obtained results showed that the natural frequency decreased significantly at high axial velocities. Also it was found that the system may exhibit unstable behavior at high accelerations.
Layered Sheet-Steel Damping Estimation Using Optical Vibrometry
Authors: Nutakor Charles , Semken R. Scott , Heikkinen Janne E. , Sopanen Jussi , Mikkola Aki
Published: July 2018

A non-contact modal analysis method is implemented to estimate the structural damping ratios for four stacks of sheet-steel, each bound using a different method. The setup comprised the four subject stacks and, for comparison, two single homogeneous steel plates of the same length and width with thicknesses that approximated the layered stack heights. To carry out the modal analyses, each test item was hung to simulate a free-free boundary condition. A force and frequency adjustable impact hammer imparted transient vibration to each hanging test piece after which the local relative velocity for each one of an array of discrete target points across the entire length-to-width surface was measured using an optical transducer. Damping ratios were extracted from the frequency response curves using the half power bandwidth method. Comparing the results obtained for the layered sheet-steel stacks with those from the homogeneous steel plates showed that damping ratios and loss factors can be estimated using the proposed experimental technique. The consistent impacts and the elimination of test structure mass loading improves the accuracy of damping estimates. In comparison to the solid plates, the layered sheet-steel stacks were characterized by increased damping. The effect was most significant for the stack bound together by polymer rivets.
Concurrent Contact Planning and Trajectory Optimization in One Step Walking Motion
Authors: Mummolo Carlotta , Mangialardi Luigi , Kim Joo H.
Published: July 2018

Bipeds’ trajectories and control during walking are closely coupled with the contact force distribution in time and space as an indeterminate problem. Therefore, generating the motion of redundant bipeds in presence of unilateral contact is usually formulated as a nonlinear constrained optimization problem. The optimal walking motion must be solved in terms of trajectories, control, contact status (i.e., when, where, and whether a foot is in contact), and contact response (i.e., ground reaction forces). The solution for this problem requires predictive methods within the general optimal motion planning framework. However, there is a lack of fully predictive methods that can concurrently solve for all the above mentioned unknowns. This represents an important challenge in the simulation, design, analysis, and control of general robotic systems. A novel approach for the optimal motion planning of multibody systems with contacts is developed, based on a Sequential Quadratic Programming (SQP) algorithm for Nonlinear Programming (NLP). The complete formulation is presented and demonstrated with numerical experiments on a simple planar biped with the assigned task of one complete step motion in forward progression.
Experimentally Validated Nonlinear Electrohydroelastic Euler-Bernoulli-Morison Model for Macro-Fiber Composites With Different Aspect Ratios
Authors: Shahab Shima , Erturk Alper
Published: July 2018

Macro-fiber composite (MFC) piezoelectric structures with interdigitated electrodes can be used for effective hydrodynamic thrust generation by underwater actuation as well as low-power electricity production from underwater vibrations for powering wireless electronic components. In order to develop high-fidelity models to predict the electrohydroelastic dynamics of MFC structures, mixing rules based electroelastic mechanics modeling is coupled with the global electroelastic dynamics based on the Euler-Bernoulli kinematics and the nonlinear fluid loading based on Morison’s semi-empirical model. The focus is placed on the dynamic actuation problem for the first two bending vibration modes under geometrically, materially, and piezoelectrically linear, hydrodynamically nonlinear behavior. The electroelastic and dielectric properties of a representative volume element (piezoelectric fiber and epoxy matrix) between two subsequent interdigitated electrodes are correlated to physical parameters of MFC bimorphs and validated for different MFC types that have the same overhang length but different widths. Following the process of in-air electroelastic model development and validation, underwater experiments are conducted for different length-to-width aspect ratios (L/b), and empirical drag and inertia coefficients are extracted for Morison’s equation. The repeatability of these empirical coefficients is demonstrated for experiments conducted using aluminum cantilevers of different aspect ratios. Convergence of the nonlinear electrohydroelastic Euler-Bernoulli-Morison model to its hydrodynamically linear counterpart with increased L/b values is also reported. The proposed model, its harmonic balance analysis, and experimental results can be used for parameter identification as well as aspect ratio optimization for underwater piezoelectric actuation, sensing, and energy harvesting problems.
Flexoelectric Actuation and Vibration Control of Ring Shells
Authors: Deng Bolei , Li Huiyu , Tzou Hornsen
Published: July 2018

The converse flexoelectric effect that the gradient of polarization (or electric field) induces internal stress (or strain) can be utilized to control the vibration of flexible structures. This study focuses on the microscopic actuation behavior and effectiveness of a flexoelectric actuator patch on an elastic ring. An atomic force microscope (AFM) probe is placed on the upper surface of the patch to implement the inhomogeneous electric field inducing stresses inside the actuation patch. The flexoelectric membrane force and bending moment, in turn, actuate the ring vibration and its actuation effect is studied. Actuator’s influence in the transverse and circumferential directions is respectively evaluated. For the transverse direction, the gradient of the electric field decays quickly along the ring thickness, resulting in a nonuniform transverse distribution of the induced stress and such distribution is not influenced by the patch thickness. The flexoelectric induced circumferential membrane force and bending moment resembles the Dirac delta function at the AFM contact point. The influence of the actuator can be regarded as a drastic bending on the ring. To evaluate the actuation effect, dynamic response of controllable displacements of the elastic ring under flexoelectric actuation is analyzed by adjusting the geometric parameters, such as the thickness of flexoelectric patch, AFM probe radius, ring thickness and ring radius. This study represents a thorough understanding of the flexoelectric actuation behavior and serves as a foundation of the flexoelectricity based vibration control.
Soft Robotic Shoulder Assist Device: Towards Prevention of Shoulder Overuse Syndrome in Wheelchair Users
Authors: Sridar Saivimal , Narasimha Ripujit Gindam , Gadagi Amogh Maharudra , Taduru Vishwarath , Strzelczyk Courtney , Maruyama Trent , StClair Christopher , Polygerinos Panagiotis
Published: July 2018

Shoulder overuse syndrome (SOS) is a fatigue-related condition caused by repetitive motion or excessive practice, common amongst wheelchair users. Diagnostic treatment methods for SOS include physiotherapy sessions, kinesiology tapes and few other measures. Many commercial devices available in the market targeting rehabilitation and recovery of shoulder pathologies are expensive and inaccessible for in-home treatment. A detailed survey of the rehabilitative devices for upper limbs is given in [1]. Although, prognostic measures to avoid SOS in wheelchair users such as taking smoother strides and altering wheel stroke mechanics have been suggested [2], [3], there is a clear lack of assistive devices that augment the shoulder joint muscles during wheelchair propulsion.
A Novel Genioglossal Strengthening Device for Obstructive Sleep Apnea Treatment
Authors: Zavrel Erik A. , Ebben Matthew R.
Published: July 2018

Obstructive sleep apnea (OSA) is a condition characterized by temporary diminutions or cessations of breathing caused by repetitive collapse of the upper airway (UA) during sleep [1]. OSA is a common disorder — the American Academy of Sleep Medicine estimates the condition affects 29.4 million Americans — in which the muscles that hold the airway open weaken, resulting in partial or complete UA collapse during inspiration [2]. These pauses in breathing lead to blood oxygen desaturation and induce neurological arousal resulting in sleep disruption and fragmentation. The cycle of airway collapse and arousal can repeat hundreds of times per night.
Simulating Airway Collapse in Obstructive Sleep Apnea Using Fluid-Structure Interaction Methodologies
Authors: Le Trung Bao , Garcia Guilherme J. M.
Published: July 2018

Obstructive Sleep Apnea (OSA) is a prevalent disease among adults and children (Macey, Woo, Kumar, Cross, & Harper, 2010). Patients with OSA have recurrent episodes of airflow limitation during sleep, which lead to daytime sleepiness and several comorbidities, including cardiovascular diseases (Durán, Esnaola, Rubio, & Iztueta, 2001). During the episode of OSA, the airway is partially occluded (hypopnoeas) or totally blocked (apneas). Since the velopharynx is the narrowest segment of the pharyngeal airway, the local air velocity increases significantly leading to the large decrease in the intraluminal pressure. The relationship between the distribution of the minimum pressure and the anatomical geometry of the airway is thus very important. Hence, understanding the mechanical interaction between the soft palate and air flow is important in investigating OSA pathology.
Automatically Triggered FES Rowing Device for SCI Patients With Motorized Return
Authors: Kim Jinsoo , O’Neill Ciaran , Pathak Kavya , Rajagopal Sai Shanthanand , Moyne Martina , Picard Glen , Taylor J. Andrew , Walsh Conor
Published: July 2018

A quarter of a million people in the United States are affected by spinal cord injury (SCI), which causes loss of sensation and muscle function. Improvements in clinical care have resulted in a lower risk of mortality from initial complications like bedsores or urosepsis, though patients are more susceptible to long term conditions like coronary heart disease [1], which is a leading cause of death for SCI patients [2]. Patients with SCI have sedentary lifestyles, decreased aerobic fitness, and limited levels of oxygen uptake, which contribute to increased rates of cardiovascular complications [2]. To mitigate these factors, SCI patients must perform vigorous aerobic exercise, which can be done through functional electrical stimulation (FES) [3].