bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of Compact Heat Exchangers Operating in Self-Sustained Oscillatory Flows
Authors: Fullerton T. L. , Anand N. K. 
Published: November 2020

Abstract
Computer codes were developed to study the performance of compact heat exchangers (CHEs) operating in self-sustained oscillatory flow (SSOF) regimes. The methods were based on a control volume-based finite element (CVFEM) method for geometric discretization and the explicit first stage, single diagonal coefficient, diagonally implicit, Runge–Kutta (ESDIRK) method for temporal discretization. The developed codes were validated for both steady and unsteady cases. A study of nine geometrically related domains of flat tubes in staggered configurations was performed. Grid independence was established subject to double cyclic conditions—periodically fully developed flow and heat transfer in the stream-wise direction and cyclic or repeating flow and heat transfer in the cross-stream direction. The maximum Reynolds number was established at approximately 2000 for the cases studied to avoid the turbulent flow regime. Parameters of interest like Nusselt number, friction factor, and pumping power were calculated for steady and SSOF regimes. An approach was proposed to determine critical Reynolds number (Recrit) for the SSOFs such that for Reynolds number below Recrit the flow remains steady, and above Recrit, the flow exhibits the characteristics of SSOFs before finally transitioning to fully turbulent conditions. The results indicated a sensitivity of performance parameters to transverse spacing but not to longitudinal spacing.
Generating Structure-Borne Traveling Waves Favorable for Applications
Authors: Musgrave Patrick F. , Phoenix Austin A. , Albakri Mohammad I. , Tarazaga Pablo A. 
Published: November 2020

Abstract
Structure-Borne Traveling Waves (SBTWs) have significant promise as a means of underwater propulsion, drag reduction, and solid-state motion. However, there is poor understanding of how to tailor SBTWs favorable for these applications. This study establishes guidelines and a straight-forward method for generating favorable SBTWs on two-dimensional (2D) surfaces. SBTWs are a novel traveling wave generation method that take advantage of a surface’s inherent structural properties (i.e. mode shapes and natural frequencies). Due to this novel mechanism, SBTWs have significant advantages over other traveling wave methods. This includes active variability (propagation direction, frequency, wavelength), no reliance on complex control mechanisms, and a minimal actuation footprint (small size and weight). SBTWs utilize the two-mode excitation method, whereby a surface is harmonically excited at two locations with a phase offset between them. Due to the phase offset, participating mode shapes superimpose to yield steady-state traveling waves that do not reflect at the boundaries. A SBTW at a given frequency has an optimal phase offset that maximizes the quality; however, high quality does not ensure favorability for a specific application. For propulsion and solid-state motion applications, favorable SBTWs are those that have a uniform propagation direction and consistent amplitude. Using a previously validated electro-mechanical model of a 2D plate, this study demonstrates the generation of SBTWs favorable for such applications. It is shown that the frequency bandwidth can be divided into regions, and each region is classified as generating favorable or unfavorable SBTWs. The favorability of each region is defined by which mode shapes participate. Two guidelines are established that define which combinations of mode shapes yield favorable SBTWs. These guidelines are fundamental in nature, implying that they can be extended to generate favorable SBTWs on any thin-walled surface. This signifies that geometries with tailored SBTWs can be designed to target specific applications (e.g. underwater propulsion, drag reduction, and solid-state motion).
Simulation and Validation of Fully 3D Printed Soft Actuators
Authors: Torres Steffi , San Martin Julio , Newell Brittany , Garcia Jose 
Published: November 2020

Abstract
Flexible actuators are a growing class of devices implemented in soft robotic applications, medical devices and processes involving food and pharmaceutical products. Such actuators have traditionally been manufactured using casting processes or other conventional methods requiring more than one fabrication step. The arrival of flexible 3D printing materials and 3D printing techniques has facilitated the creation of these flexible actuators via additive manufacturing. The work presented in this article displays the analytical characterization and experimental validation of two materials and two actuator designs. The first case presents a finite element analysis (FEA) simulated model of a bellows actuator using a photocurable flexible resin (TangoPlus FLX930) and studies the effect of printing orientation on the simulation. The simulation used a 5 parameter Mooney-Rivlin model to predict the strain behavior of the actuator under hydrostatic pressure. A second case is presented where a Thermoplastic Polyurethane actuator was 3D printed and simulated using the same FEA model and a second calibration of the Mooney-Rivlin 5 parameter model. In both cases experimental data was used to calibrate and validate the simulation. The resulting simulated strain was consistent when the printing orientation of actuators was parallel (0 degrees) to the strain direction of the actuators. Results were less consistent when a print orientation of 45 degrees was applied.
Process Optimization of Local Annealing of SMA Wires for Plagiarism Detection
Authors: Langhoff Moritz , Roj Robin , Theiß Ralf , Dültgen Peter 
Published: November 2020

Abstract
The economic significance and damage caused by counterfeit products has been evident in industry and society for a long time. In addition to the loss in sales and image damage for the original manufacturers, plagiarism in security-relevant components can also have disastrous consequences for the customer. Manufacturers use technical features to identify their products. The aim of these features is to make them most difficult to copy or to find. None of these features are completely safe from being copied.
SMA-components can be treated to be used as a new kind of identification elements for products. In this paper a new method for coding information based on annealing of SMA-wires is presented. The focus is the development of a heat treatment that provides different annealing temperatures in small adjacent areas along the wire. As the annealing temperature has effects on the thermal resistance behavior of the SMA, a combined behavior of different annealing temperatures leads from a curved to a stepped resistance behavior when heated from martensite to austenite.
Adaptive Material Handling System Based on Shape Memory Alloy Actuators
Authors: Zimmer Lukas , Welsch Felix , Kirsch Susanne-Marie , Rizzello Gianluca , Seelecke Stefan , Motzki Paul 
Published: November 2020

Abstract
In this paper, a shape memory alloy (SMA) based handling system is presented. The gripping system consists of two different actuator systems based on SMA wires. The first one is a reconfigurable end-effector with four independent gripping arms. The second SMA actuator system is a bi-stable SMA actuated vacuum suction cup, of which one is mounted on each of the four arms of the end-effector. While the four independently adjustable gripping arms of the end-effector allow for an adaption to different workpiece geometries like a flat shaped workpiece or a round shaped, spherical workpiece, integrated SMA driven brake mechanisms enable an energy free position holding of the end-effector components. This means that an electric current is only required when the end-effector arms need to be rearranged. This results in a versatile, adaptive and energy-efficient handling system that can replace mostly pneumatically driven state-of-the-art systems in production and assembly industry. No manual adjustment of the gripping system or even exchanging is needed, if an assembly line switches between products with different work piece geometries as a result. The gripping unit is controlled using an external microcontroller and can be mounted on a robot for diverse handling purposes.
Interfacial Bond Strength of Various Rigid/Soft Multi-Materials Printed via Fused Filament Fabrication Process
Authors: Kalia Karun , Ameli Amir 
Published: November 2020

Abstract
Layered multi-materials of dissimilar polymers and their nanocomposites offer new opportunities as smart materials and structures. A critical aspect of such structures is the quality of interlayer adhesion between dissimilar polymer matrices. This work reports the development of asymmetric double cantilever beam (ADCB) specimens of dissimilar polymers and its use in the analysis and understanding of their interlayer adhesion in 3D-printed rigid/soft interfaces. Acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polylactic acid (PLA) were chosen as the rigid polymers and combined with thermoplastic polyurethane (TPU) as the soft component. 3D-printed ADCB specimens were loaded under opening mode, until fracture, to obtain the load-displacement data and the fracture surfaces were analyzed using optical microscopy. ABS/TPU/ABS and PC/TPU/PC material combinations resulted in a more stable crack growth with a high peak load indicating a relatively good interfacial adhesion. The high nozzle temperatures of ABS and PC and their amorphous nature contributed to a good layer-to-layer fusion during 3D printing. However, PLA/TPU/PLA specimens exhibited an unstable crack growth behavior with a pure adhesive failure mode and a significantly lower peak load. This poor interfacial bond strength was correlated to the relatively low nozzle temperature of PLA and its semi-crystalline structure. The maximum loads in ABS/TPU/ABS and PC/TPU/PC specimens were found to be ∼2.5 times greater than that of PLA/TPU/PLA ones. The method provides a valuable tool in quantifying interlayer adhesion quality in printed dissimilar polymers and their functional nanocomposites.
Mechanical Characterization of a Novel Concept of Adaptive Electrostatic Friction Damper
Authors: Testoni Oleg , Bodkhe Sampada , Ermanni Paolo , Bergamini Andrea 
Published: November 2020

Abstract
In this work, we present a novel concept of adaptive friction damper based on electrostatic adhesion and we characterize its performance under quasi-static conditions. The concept is based on a stack of circular electrodes structurally coupled to different ends of the damper, separated by a thin dielectric film and hinged around a common axle. When an electric potential is applied, the electrodes experience an attractive force, which is used to control the transfer of shear stress between electrodes and thus the resistive torque of the assembly and the amount of energy dissipated. However, imperfections on the contact surfaces and air gaps have a strong detrimental effect on the resistive torque.
A prototype of the damper was manufactured and the resistive torque was measured as a function of applied voltage. Theoretical and experimental results were compared to estimate the average thickness of the air gap. The surface roughness of the electrodes and of the dielectric was measured before and after the mechanical test. Moreover, the surface of an entire electrode was scanned to measure its planarity. Then, the results were compared with the value of the air gap previously estimated.
The maximum resistive torque measured was constant over five actuation cycles for constant values of the voltage applied and, as expected, increased quadratically with the voltage. The estimated value of the air gap amounted to 38 μm. Both the electrodes and the dielectric showed an increase in average surface roughness after the mechanical test; however, the surface roughness was lower than 1 μm in both cases and could not justify the estimated air gap. On the other hand, we observed a large inhomogeneity in the planarity of the electrode, which was comparable with the thickness of the air gap previously estimated.
The results obtained demonstrated the possibility to adapt the resistive torque of the damper using an electrical input and proved the feasibility of the concept. Further work has to focus on the design of the electrodes and on the operating life of the damper. We envisage that the concept could replace traditional, semi-active dampers in automotive or in aerospace applications.
True Presence Detection via Passive Infrared Sensor Network Using Liquid Crystal Infrared Shutters
Authors: Wu Libo , Wang Ya 
Published: November 2020

Abstract
Recently, smart home applications are increasing fast, including but not limited to occupancy-dependent control of lighting, heating and cooling. Passive infrared (PIR) sensors play an important role in these applications to perceive the presence and/or the motion of human. However, PIR sensors are not able to detect stationary occupants while stationary presence takes up most time of the day. And thus, the resulted false negative detection leads to uncomfortable light/temperature swings, shortened equipment’s lifespan, and/or energy waste, etc. To address this issue, our group has developed Synchronized Low-Energy Electronically-chopped PIR (SLEEPIR) sensors that integrate an electronic liquid crystal (LC) infrared shutter with an off-the-shelf PIR sensor. In this work, the infrared shutter made of polymer dispersed liquid crystal (PDLC) sandwiched by two germanium windows is proposed to periodically chop the long-wave infrared signal received by the PIR sensor so that stationary human presence can still be detected due to the electronical shuttering. A sensor module is fabricated, consisting of a wireless microcontroller, a SLEEPIR sensor and a traditional PIR sensor, with a field of view of 103° × 103°. Then, a sensor network consists of two sensor modules is developed. Three types of experiments are conducted in this paper: individual action-based, continuous activity-based, and daily routine-based. The detection logic is made by using the threshold value classification method, where the threshold values are determined from the action-based dataset and applied to the other two datasets. The results show that for activity-based dataset, the average accuracy reached 98.96%. For daily routine-based dataset, the average accuracy is 99.57%.
Prediction of the Behavior of Dynamically Actuated DE Roll-Actuators Using Equivalent Circuits
Authors: Bakardjiev Petko , Marschner Uwe , Franke Markus , Richter Andreas , Altinsoy Ercan M. 
Published: November 2020

Abstract
Dielectric elastomer actuators show suitable properties to be utilized for dynamic applications, e.g. speakers, shakers and pumps, with possible benefits to existing conventional systems. In this work a method to predict the performance of dynamically actuated dielectric-elastomer roll-actuators (DERA) depending on both, material and design parameters is presented. It incorporates in combination analytical computation, FEM, as well as electromechanical networks and considers a large variety of material configurations with a multitude of constructional degrees of freedom. DERA in push-configuration exhibit a distinct modal behavior in axial direction depending on the boundary conditions and loading at the actuators end terminals, which is described sufficiently by a one-dimensional longitudinal waveguide model. Several DERA were designed, manufactured and tested. The experimental studies were in good agreement with the made predictions. They allowed for further refinement regarding interface circuits and model updating, such as the estimation of inaccessible parameters (e. g. damping coefficients). The presented model allows for extensive parameter studies and the development of tailor-made actuators for given application in a very time efficient manner.
Enhanced Sound Energy Harvesting by Leveraging Gradient-Index Phononic Crystals
Authors: Allam Ahmed , Sabra Karim , Erturk Alper 
Published: November 2020

Abstract
We explore the harvesting of acoustic waves by leveraging a 3D-printed gradient-index phononic crystal (GRIN-PC) lens design. The concept is demonstrated numerically and experimentally for audio frequency range acoustic waves in air. Unit cell design procedure to achieve the required refractive index profile and numerical simulations of the band structure are executed using a high-fidelity finite-element model, followed by 3D simulations of the acoustic wave field for validation of the lens performance. Performance enhancement by focusing acoustic waves is quantified along with the level of anisotropy in the resulting 3D lens design. Additionally, a fully coupled multiphysics framework is developed to cover acoustic-structure interaction, piezoelectric coupling, as well as electrical load impedance. Finite-element simulations include the GRIN-PC lens and the harvester components along with basic electrical load to quantify the electrical power. In the full numerical simulations, design parameters such as the unit cell design, aperture of the lens, directional effects and anisotropy are explored in detail. Specifically, efforts are summarized on the unit cell design to minimize the directional sensitivity, toward making the lens close to omnidirectional.
Acute Impact of the Use of a Standing Desk on Appetite Sensations and Energy Intake
Authors: Josaphat Kapria-Jad , Labonté-Lemoyne Élise , Sénécal Sylvain , Léger Pierre-Majorique , Mathieu Marie-Eve 
Published: November 2020

Background: Sedentariness has been shown to increase energy intake and is associated with increased obesity prevalence. Active workstations are used to implement physical activity interventions in workplaces, but it is unclear if they can lead to reductions in body weight. This study aims to observe the acute impact of a standing desk on energy intake and appetite sensations.Methods: Participants came to the laboratory, where they were randomly assigned to a seated or a standing desk. They completed a work session (∼75 min) during which they performed cognitive tasks and reported their levels of stress. Following this, they had a 15-minute break during which buffet-type snacks were served. Subjects were asked to rate their appetite sensations on visual analog scales.Results: Thirty-six normal-weight men and women aged 24.3 (4.3) years participated in this study. Energy intake from snacks was similar (P = .472) between participants who sat (427.8 [286.9] kcal) and the ones who stood (461.2 [272.8] kcal) during the work session. There was no difference in satiety quotients around the snack and no significant interaction time × condition for appetite sensations.Conclusion: The use of a standing desk for 75 minutes did not increase food consumption following a meal.
An Interpretative Phenomenological Analysis of Coach Perceptions in the Practice Environment
Authors: Smith Steve M. , Cotterill Stewart T. , Brown Hazel 
Published: November 2020

The psychological environment where sporting activity is undertaken has been suggested to influence performance. The coach orchestrates practice activities and their perception of the psychological environment has been regularly evaluated in competition research but not in practice. The aim of this study was to explore coach perceptions of the psychological influencing factors present in the practice environment. Participants were six U.K. academy basketball coaches (mean age = 35 years). Data were collected through semi-structured interviews and analyzed using interpretative phenomenological analysis. Five superordinate themes were constructed from data analysis, which were player characteristics, team-first orientation, current performance perceptions, coach characteristics, and coaching structure. Results suggest that the coach has a unique insight into the psychological influencing factors of the practice environment. Combined with the practice environment framework offered by Smith, Cotterill, and Brown, a model is offered to aid practitioners in understanding the interrelatedness of psychological influencing factors in the practice environment.
Pliocene growth of the Dowlatabad syncline in Frontal Fars arc: Folding propagation across the Zagros Fold Belt, Iran
Authors: Najafi Mahdi , Beamud Elisabet , Ruh Jonas , Mouthereau Frédéric , Tahmasbi Alireza , Bernaola Gilen , Yassaghi Ali , Motamedi Hossein , Sherkati Shahram , Goodarzi Mohammad Ghasem Hassan , Vergés Jaume 
Published: November 2020

AbstractThe integration of biostratigraphy, strontium isotope stratigraphy, and magnetostratigraphy allowed for the precise dating of the &gt;3.0-km-thick marine to non-marine foreland sedimentary succession within the Dowlatabad growth syncline along the Frontal Fars arc in the Zagros Fold Belt that extends from eastern Turkey to southern Iran. This area was the missing link to complete the dating of syntectonic deposits in the Fars arc and quantify the migration of sedimentary belts as well as the propagation of folding across the entire Mesopotamian foreland basin. Both are essential for defining the interplay of basin evolution and sequence of folding.Deposition of the foreland marine marls in the Mishan Formation started at ca. 11.5 Ma. The transition to a non-marine basin infill occurred at 4.9 Ma by the progradation of thick fluvial deposits of the Aghajari Formation with a fast accumulation rate of 63 cm/k.y. The beginning of growth strata deposition and thus the onset of folding in the Dowlatabad syncline is dated at 4.65 Ma. The first appearance of carbonate conglomerates sourced from the Guri limestone at 2.8 Ma marked the progressive dismantling of the nearby growing anticlines. The tectonic deformation in the front of the Fars arc was active for at least 2.85 m.y. and ceased at 1.8 Ma before the deposition of the discordant and slightly folded Bakhtyari conglomerates characterized by a clast composition derived from the Zagros hinterland.The compilation of magnetostratigraphic ages reveals that both the migration of the Aghajari-Bakhtyari sedimentary belts and the propagation of the folding front was in-sequence toward the foreland at a rate close to 20 mm/yr in the Fars arc and 15 mm/yr in the Lurestan arc, in the last 20 m.y. These high rates of folding propagation are about one order of magnitude larger than age equivalent shortening rates (∼4 mm/yr in Fars arc and ∼2 mm/yr in Lurestan arc) and thus imply an efficient detachment level at the base of the deformed Arabian sedimentary cover.Numerical experiments on both the cover and basement sequences are designed to test the influence of inherited basement structures on the deformation propagation within the cover sequence, providing clues on the partly coeval in-sequence deformation of the Zagros Simply Folded Belt and the local out-of-sequence Mountain Frontal Fault system as illustrated by regional and local geology.