bluuebunny/crossref_metadata_2025 huggingface dataset:
Printed Graphene-Based Strain Sensors for Structural Health Monitoring
Authors: Wang Long , Loh Kenneth J. , Mousacohen Ramin , Chiang Wei-Hung
Published: November 2017

Strain sensors are one of the most widely used transducers for structural health monitoring, since strain can provide rich information regarding structural integrity. Recently, it has been shown that thin film sensors that incorporate nanomaterials can be engineered to possess unique properties, such as flexibility, high sensitivity, and distributed sensing capabilities, to name a few. To date, a plethora of different nanomaterials have been explored for fabricating strain sensors, such as by using conductive polymers, metal nanowires, and carbon nanotubes, among others. The aim of this work is to leverage the unique properties of graphene to fabricate next-generation thin film strain sensors. While graphene exhibits impressive mechanical and electrical properties, it remains challenging to harness these properties for sensing, primarily because of difficulties associated with high-quality synthesis and to incorporate them in a scalable fashion. In this study, few-layered graphene nano-sheets (GNS) were first synthesized using a low-cost, liquid-phase exfoliation technique. Second, GNS was dispersed in an aqueous solution with a low-concentration polymer acting as the dispersing agent. Third, the dispersion was printed onto flexible polymer substrates to form complex geometrical patterns, such as strain rosettes. Then, the electrical and electromechanical properties of the printed thin film sensors were characterized. It was found that the strain rosettes could resolve multi-axial strains applied during coupon tests. Overall, the GNS-based strain sensors showed excellent signal-to-noise ratio, stable sensing performance, high strain sensitivity, and remarkable reproducibility.
Dynamic Modeling of Triboelectric Generators Using Lagrange’s Equation
Authors: Gauntt Sean , Batt Gregory , Gibert James
Published: November 2017

Electret based energy scavenging devices utilize electro-static induction to convert mechanical energy into electrical energy. Uses for these devices include harvesting ambient energy in the environment and acting as sensors for a range of applications. These types of devices have been used in MEMS applications for over a decade. However, recently there is an interest in triboelectric generators/harvesters, i.e., electret based harvesters that utilize triboelectrification as well as electrostatic induction. The literature is filled with a variety of designs for the latter devices, constructed from materials ranging from paper and thin films; rendering the generators lightweight, flexible and inexpensive. However, most of the design of these devices is ad-hoc and not based on exploiting the underlying physics that govern their behavior; the few models that exist neglect the coupled electromechanical behavior of the devices. Motivated by the lack of a comprehensive dynamic model of these devices this manuscript presents a generalized framework based on a Lagrangian formulation to derive electromechanical equation for a lumped parameter dynamic model of an electret-based harvester. The framework is robust, capturing the effects of traditional MEMS devices as well as triboelectric generators. Exploiting numerical simulations the predictions are used to examine the behavior of electret based devices for a variety of loading conditions simulating real-world applications such as power scavengers under simple harmonic forcing and in pedestrian walking.
A Multi-Axial Electromechanically-Coupled Homogenized Energy Model for Ferroelectric Materials
Authors: Oates William S. , Smith Ralph C.
Published: November 2017

In this paper, we discuss the development and implementation of a 3-D electromechanically coupled homogenized energy model (HEM) for ferroelectric materials. A stochastic-based methodology is introduced and applied to problems involving large scale switching of ferroelectric and ferroelastic materials. Switching criteria for polarization variants are developed using density distributions in three dimensions to accommodate both electrical and mechanical loading and their coupled response. The theory accommodates non-proportional loading and major/minor loop hysteresis. Such formulations are known to accelerate computations for real-time control of nonlinear and hysteretic actuators. The proposed formulation maintains superior computational efficiency in the three dimensional case through the application of density formulations that are based on internal distributions of stress and electric field to produce a distribution of polarization switching events over a range of applied fields and stresses.
Shape Memory Alloy Actuation of a Metered-Dose Inhaler
Authors: Weaver Leslie , Utter Brent
Published: November 2017

Respiratory diseases such as asthma or chronic obstructive pulmonary disorder (COPD) affect millions of people around the world. The most common treatment approach is to take an inhaled corticosteroid as needed with a dry-powder inhaler or a metered-dose inhaler. Unfortunately, rates of inhaler mishandling and misuse are staggeringly high and as a result, the majority of those suffering from asthma and COPD are not receiving proper treatment. There are a myriad of ways inhalers are mishandled and misused, but one significant challenge results from the timing miscoordination of the medicine dispersion and inhalation breath. To address this, the current study successfully demonstrates the feasibility of automating the timing of the medicine dispersion by the addition of a Shape Memory Alloy (SMA) actuator and a differential pressure sensor into the casing of a traditional metered-dose inhaler. To meet actuation requirements and reliably depress the inhaler cartridge, the SMA wire was routed around a set of miniature bearings within the casing of the inhaler. By demonstrating that a metered-dose inhaler may be actuated by SMA without a significant increase of its weight or size, this study provides a practical technological approach to reducing the improper treatment of asthma and COPD due to inhaler misuse.
Dynamic Finite Element Modelling of a Hydrogel-Based Micro-Valve With 2-Way Fluid Structure Interactions
Authors: Mehner Philipp J. , Beck Anthony , Voigt Andreas , Marschner Uwe , Richter Andreas
Published: November 2017

We propose a finite element model which describes the dynamic behavior of hydrogels for step-responses and quasi-static regimes. The material properties are implemented in a fluid structure interaction (FSI) model which simulates the swelling behavior of hydrogels within a micro-valve. The resulting volume change effects the fluid domain describing the mass-flow behavior of the micro-valve. Furthermore, the concept is implemented in a high-level circuit and flow chart model to efficiently predict the response behavior of hydrogel-based micro-valves.

With these tools a foundation is set to efficiently simulate microfluidic systems with the aim to develop a fully computer-aided design process. The presented method will help to better understand, predict and visualize the behavior of hydrogels and support the development of highly integrated hydrogel-based microfluidic circuits.
Investigation of Vibration Energy Harvesting Using Two Cantilevers With Random Input
Authors: Yang Wei , Alevras Panagiotis , Towfighian Shahrzad
Published: November 2017

There is a growing interest to convert ambient mechanical energy to electrical energy by vibration energy harvesters. Realistic vibrations are random and spread over a large frequency range. Most energy harvesters are linear with narrow frequency bandwidth and show low performance, which led to creation of nonlinear harvesters that have larger bandwidth. This article presents a simulation study of a nonlinear energy harvester that contains two cantilever beams coupled by magnetic force. One of the cantilever beam is covered partially by piezoelectric material, while the other beam is normal to the first one and is used to create a variable potential energy function. The variable double-well potential function enables optimum conversion of the kinetic energy and thus larger output. The system is modeled by coupled Duffing oscillator equations. To represent the ambient vibrations, the response to Gaussian random input signal (generated by Shinozuka formula) is studied using power spectral density. The effects of different parameters on the system are also investigated. The results show that the double cantilever harvester has a threshold distance, where the harvester can perform optimally regardless of the excitation level. This observation is opposite to that of the conventional fixed magnet cantilever system where the optimal distance varies with the excitation level. Results of this study can be used to enhance energy efficiency of vibration energy harvesters.
A Comparative Study of Surface Cleaning Treatments for 3D Printed Medical Implants
Authors: Guo Lucy , Xie Zhiqiang , Yao Hong , Wang Ying
Published: November 2017

In the field of Additive Manufacturing (AM), one of the major applications of laser-based 3D metal printing is the creation of custom implants for medical purposes. However, a significant challenge in the manufacturing of implants using Selective Laser Melting (SLM) is the formation of partially melted particles on the surface of medical implants. These particles result in a multitude of issues including plurality of structurally weak points on the designed implants, obstruction of important design features, and possibility of dislodgement over the service life span, thereby posing a threat to the recipient. To address the above challenges, it is imperative to develop a simple but effective surface cleaning method to remove partially melted particles from the surface without damage to the designed medical implants.

In this work, a comparative study was conducted to investigate the effect of both chemical and electro-plasma based cleaning processes on the removal of partially melted particles from the surfaces of 3D printed Ti-6Al-4V medical screw implants. These techniques include chemically polishing implants with HF-HNO3 acid solutions and using an electro-plasma based cleaning process. With the field of additive manufacturing rapidly expanding, this work offers valuable insight on proper post-process treatment of 3D printed parts for future medical purposes in biomedical fields.
Constitutive Modeling of Patterned Liquid Crystal Elastomer for Active Flow Control
Authors: Beblo Richard , Settle Michael , Guin Tyler , White Timothy , Reich Gregory
Published: November 2017

Patterned liquid crystal elastomer (LCE) has been shown to have significant promise in surface topography control. Large and diverse shapes and surface adaptive responses have been shown using LCE materials with patterned director profiles. Using various techniques, crystal orientation across the surface of the material as well as through the thickness can be achieved yielding the capability to design out-of-plane deformation. These topological features can be used as active flow effectors manipulating, among other things, drag on an object in cross-flow.

It is well known that surface topography can have a large effect on skin friction drag by effecting the boundary layer transition, separation, and interfering with the shedding of vortices. In regards to a cylinder in a cross-flow, spatially manipulating surface topography, and thus drag, in this way gives rise to forces exerted by the fluid on the body. An imbalance of forces due to non-uniform surface topography can then be used to control the cylinder.

Designing such a system requires optimization of the surface topography via optimization of the crystal orientation pattern over a wide range of environments. Key to this optimization, described in detail in the presented work, is an accurate material model validated against experimental data. By representing the strain energy of the material as a combination of contributions of the elastomer backbone and the liquid crystals separately, unique material properties can be properly modeled. This is achieved by combining a traditional isotropic 3 chain Arruda-Boyce hyperelastic equation modeling the elastomer backbone with an anisotropic extension modeling the patterned liquid crystals, resulting in an anisotropic hyperelastic material model. The model can then be used to predict the material response of various patterns and investigate the design space of possible surface topographies.
One Way Sound Propagation in a Smart Fluid
Authors: Nanda Aditya , Karami M. Amin
Published: November 2017

This manuscript investigates one way sound propagation in Magnetorheological fluids (MRF) using spatio-temporal modulation of the applied magnetic field. One-way propagation of waves in a structure can have potential technological applications such as sound isolation, filtering and echo suppression. Several experimental works in the literature have shown that elastic properties of MRF’s (local speed of sound, in particular) are dependent on the applied magnetic field. Therefore, several fascinating possibilities regarding the manipulation of sound waves in MRF, by tailoring the applied magnetic field, exist.

A effective medium approximation (previously used in literature) is used to analyze sound propagation in a MRF composed of hydrogen-reduced Iron particles suspended in pure glycerine. Floquet-Bloch theory is used to obtain a quadratic eigenvalue problem that gives the band structure as a function of the material and modulation parameters. When the applied magnetic field is allowed to vary only in space, regular bandgaps are obtained as a result of Bragg scattering. In contrast, the temporal variation of the magnetic field to induce a traveling wave like variation of the modulated parameters, breaks the symmetry of the Brilloouin zones and we obtain directional bandgaps. The theoretical band structure is validated by numerical band diagrams obtained using a Finite Element code. This research has important applications in active sound manipulation.
Parameter Optimization Algorithm of a Discrete Energy-Averaged Model for Galfenol Alloys
Authors: Nas Ismail , Deng Zhangxian , Chakrabarti Suryarghya , Dapino Marcelo J.
Published: November 2017

An optimization algorithm is proposed to determine the parameters of a discrete energy-averaged (DEA) model for Galfenol alloys. A new numerical approximation approach for partial derivative expressions is developed, which improves computational speed of the DEA model by 61% relative to existing partial derivative expressions. Initial estimation of model parameters and a two-step optimization procedure, including an-hysteresis and hysteresis steps, are performed to improve accuracy and efficiency of the algorithm. Initial estimation of certain material properties such as saturation magnetization, saturation magnetostriction, Young’s modulus, and anisotropy energies can improve the convergence and enhance efficiency by 41% compared to the case where these parameters are not estimated. The two-step optimization improves efficiency by 28% while preserving accuracy compared to one-step optimization. Proposed algorithm is employed to find the material properties of Galfenol samples with different compositions and heat treatments. The trends obtained from these optimizations can guide future Galfenol modeling studies.
Improving High-Speed Nanomaterials Printing With Sub-Process-Decoupled Gravure Printer Design
Authors: Scheideler William , Subramanian Vivek
Published: November 2017

Printing technologies are attractive methods for high-throughput additive manufacturing of nanomaterials-based thin film electronics. Roll-to-roll (R2R) compatible techniques such as gravure printing can operate at high-speed (1–10 m/s) and high-resolution (< 10 μm) to drive down manufacturing costs and produce higher quality flexible electronic devices. However, large-scale deployment of printed wireless sensors, flexible displays, and wearable electronics, will require greater understanding of the printing physics of nanomaterial-based inks in order to improve the resolution, reliability, and uniformity of printed systems.

In this study, we designed and constructed a custom sheet-fed gravure printer which features registered multilayer printing for nanomaterial exploration and thin film device development. The design allows precise, independent control of the speeds and forces of each of the subprocesses of gravure (ink filling, wiping, and transfer), enabling novel experimental controls for dissecting the printing process fluid mechanics. We use these new capabilities to investigate the primary artifacts which distort printed nanomaterial patterns, such as dragout tails, edge roughness, and pinholes. These artifacts are studied as a function of print parameters such as contact pressure, wiping speed, and transfer speed, by printing silver nanoparticle ink to form continuous features with dimensions in the range of 100 μm to 10 mm. We found that the contact mechanics of the ink transfer process have a strong influence on the formation of dragout artifacts, indicating the presence of a transfer-driven squeezing flow which distorts the trailing edges of features. By engineering the transfer contact mechanics with varying rubber substrate backing stiffness, we found it is also possible to suppress this artifact formation for a particular nanomaterial ink. The improved areal uniformity and print quality achieved using these methods highlight the potential for gravure printing to be a versatile nano-manufacturing tool for patterning a variety of thin film smart materials. We also hope that the open-source printer designs presented here can serve to accelerate the development of high-speed nanomaterial printing.
Temperature Influence on Electrical Properties of Carbon Nanotubes Modified Solid Electrolyte-Based Structural Supercapacitor
Authors: Liao G. Y. , Geier S. , Mahrholz T. , Wierach P. , Wiedemann M.
Published: November 2017

In the present work, we report on structural supercapacitors which are based on NASICON-type solid electrolyte Li1.4Al0.4Ti1.6(PO4)3 (LATP). The nanostructured electrodes incorporate single-wall carbon nanotubes (SWCNTs) mixed with the LATP electrolyte. The complete energy storage devices are manufactured in a sandwich structure consisting of two nanostructured electrode layers which are separated by a pure LATP layer. The as-prepared specimens are embedded in composite materials with Airstone 880/886H epoxy resin as matrix. Their electrical properties are characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). At ambient temperature, the addition of 6.5 wt. % SWCNTs results in a distinct improvement by reducing the total resistance of the embedded devices and enhances the capacitance from 0.025 mF g−1 to 3.160 mF g−1 at a scan rate of 5 mV s−1. Electrical measurements of two types of specimens are then applied under different temperatures from ambient temperature to 80 °C. It is observed that the equivalent series resistance (ESR) of device with SWCNTs decreases greatly and capacitance increases comparing with the device without SWCNTs. As a conclusion, the structural supercapacitors acquire excellent performance through high efficient double layer effects realized by nanostructured electrode/electrolyte interphase (large surface electrode areas).
Study of Bioinspired Surgery Needle Advancing in Soft Tissues
Authors: Sahlabadi Mohammad , Khodaei Seyedvahid , Jezler Kyle , Hutapea Parsaoran
Published: November 2017

Although needle-based surgeries are considered as minimally invasive surgeries, the damage caused by the needle insertion in soft tissues, namely brain needs to be reduced. Any minor damage, swelling or bleeding in the brain tissue can lead to a long-lasting traumatic brain injury. Our approach to this challenge is to search for a proper solution in nature such as honeybees. In our previous studies, some new bioinspired needles (passive/active) mimicking honeybee stingers have been proposed and tested by conducting needle insertion tests in tissue gel phantoms. The main feature of the bioinspired needles is specially-design barbs on the needle structures. It was discovered that the insertion forces of the bioinspired needles are decreased by as much as 35%, which means that there is a decrease in tissue gel phantom damages. It was also observed that the needle path deflection in the tissue was greatly affected by the reduction in needle bending stiffness and the insertion force. The reduction in the bending stiffness would require lower forces of Nitinol actuators to navigate our smart/active needle inside the tissues. This work specifically aims to investigate the mechanics of the bioinspired needles in bovine brain tissues. The needle insertion tests in real tissues are designed and performed. The insertion mechanics of the bioinspired needles in bovine brain is studied and presented.
Thermodynamic Analysis of a Direct Mechanical to Electrical Energy Harvesting Cycle in Ferroelectric Crystals
Authors: Gallagher John A.
Published: November 2017

Field induced phase transformations in ferroelectric crystals occur when the applied electrical or mechanical load exceeds a certain threshold. Mechanical cycling about these transformation field thresholds under varying open and closed circuit conditions has been shown to yield a near ideal mechanical to electrical energy harvesting technique. Numerical integration of experimentally measured stress – strain and electric field – electric displacement data has shown mechanical to electrical energy conversion efficiency near 60% for 0.24PIN-0.44PMN-0.32PT. In this work, the total irreversible energy is determined by the offset between the forward and reverse loading paths, equivalent to the hysteresis in the phase transformation behavior. This is equal to the available mechanical energy for conversion to electrical energy for harvesting. Following the ideal mechanical to electrical energy harvesting procedure, the total possible energy harvested is a direct function of the hysteresis area in the phase transformation and the electromechanical coupling factor. Efficiency is predicted to be equal to the electromechanical coupling factor, 0.596 (59.6%). Predicted results agree with experimental data from numerical integration. Energy densities are calculated up to 5 kJ/m3 with potential power densities of 102–103 kW/m3.
A Maximum Entropy Approach for Uncertainty Quantification and Analysis of Multifunctional Materials
Authors: Gao Wei , Oates William S. , Smith Ralph C.
Published: November 2017

The Maximum Entropy (ME) method is shown to provide a new approach for quantifying model uncertainty in the presence of complex, heterogeneous data. This is important in model validation of a variety of multifunctional constitutive relations. For example, multifunctional materials contain field-coupled material parameters that should be self-consistent regardless of the measurement. A classical example is piezoelectricity which may be quantified from charge induced by stress or strain induced by an electric field. The proposed tools provide new statistical information to address measurement discrepancies, guide model development, and catalyze materials discovery for data fusion problems. The error between the model outputs and heterogeneous data is quantified and used to formulate a second moment constraint within the entropy functional. This leads to an augmented likelihood function that weights each individual set of data by its respective variance and covariance between each data set. As a first step, the method is evaluated on a piezoelectric ceramic to illustrate how the covariance matrix influences piezoelectric parameter estimation from heterogeneous electric displacement and strain data.
Redox Transistor Battery: An Emerging Architecture for Electrochemical Energy Storage
Authors: Marino Chris , Hery Travis M. , Sundaresan Vishnu-Baba
Published: November 2017

In this article, it is proposed that a membrane with tunable ionic conductivity can be used as a separator between the electrodes of a supercapacitor to both allow normal charge/discharge operation and minimize self-discharge when not in use. It is shown that the redox active conducting polymer PPy(DBS), when polymerized on a porous substrate, will span across the pores of the membrane. PPy(DBS) is also shown to function as an ionic redox transistor, in which the transmembrane ionic conductivity of the polymer membrane is a function of its redox state. The PPy(DBS) ionic redox transistor is applied between the electrodes in a supercapacitor as a smart membrane separator. It is demonstrated that the maximum tunable ionic conductivity of the smart membrane separator is comparable in operation to an industry standard separator at maximum ionic conductivity, with a self-discharge leakage current of ∼0.12mA/cm2 at 1V. The minimum tunable ionic conductivity of the smart membrane separator is shown to decrease the supercapacitor self-discharge when not in use by a factor of 10, with a leakage current of 0.012mA/cm2 at 1V. This range of tunable ionic conductivity could lead to the emergence of redox transistor batteries with high energy density and low self-discharge for short and long-term storage applications.
Damage Identification Using Piezoelectric Impedance Measurement With Compressed Sensing Technique
Authors: Cao Pei , Shuai Qi , Tang Jiong
Published: November 2017

During the last decades, extensive research has been conducted on structural health monitoring (SHM) techniques based on the changes of coupled structure properties, e.g. piezoelectric impedance, which enjoys high detection sensitivity due to high-frequency actuation/sensing nature. However, the actual identification of fault locations and severities remains to be challenging owing to underdetermined underling mathematics. Recently, compressed sensing, a signal processing technique originally developed to recover signals from the compressed measurements, has shown its potential to address some of the mathematical challenges encountered in SHM practices. In this research, we morph the impedance-based SHM problem into a compressed sensing scheme such that the impedance change are used as measured data to reconstruct the damage locations and severities through convex optimization, e.g. l1 optimization. The proposed approach offers practical attractions of only requiring a small number of measurements and a short amount of computational time, and the results are promising if certain properties are fulfilled. Finally, the proposed approach is applied to and validated by several test problems.
Preliminary Experimental Study of the Effect of Shape Setting on Knitted SMA Structures
Authors: Yi Shiping , Weinberg Charles , Eschen Kevin , Abel Julianna
Published: November 2017

Smart materials can be integrated into textile structures to produce active textiles with tailored mechanical properties and large, complex actuation motions. Active textiles have the potential to enable a wide range of applications including wearable technologies, soft robots, medical devices, and aerospace structures. One type of active textile is the shape memory alloy (SMA) knitted structure. SMA knitted structures produce a range of kinematic actuation motions as a result of the bending, torsion, extension, and buckling of the SMA wire during the loop-based knitting manufacturing process. The kinematic motions of several different patterns of SMA knitted actuators have been cataloged, and the mechanical performance of basic knitted patterns have been characterized. However, the effect of shape-setting of knitted SMA structures has not been explored. This paper investigates the effect of post-manufacturing shape-setting on the kinematic and kinetic performance of basic SMA knitted structures. A design of experiment methodology was employed to isolate the impact of knitted pattern, SMA wire diameter, and shape-set curvature on mechanical performance. The introduction of a large curvature shape-set in the SMA wire resulted in a very stiff textile structure with a minimal change in length between the austenite and martensite states, thus, minimal capacity for large actuation deformations. Meanwhile, the introduction of a small curvature in the SMA wire resulted in a nearly constant force plateau and a larger change in length between the austenite and martensite state for the same applied load, and the potential for enhanced structural actuation deformations. Shape-setting is an additional design parameter that can be employed to enhance and tune the mechanical performance of knitted SMA structures.
Multifunctional Energy Harvesting Locally Resonant Metastructures
Authors: Sugino Christopher , Guillot Vinciane , Erturk Alper
Published: November 2017

Vibration-based energy harvesting is a growing field for generating low-power electricity to use in wireless electronic devices, such as the sensor networks used in structural health monitoring applications. Locally resonant metastructures, which are structures that comprise locally resonant metamaterial components, enable bandgap formation at wavelengths much longer than the lattice size, for critical applications such as low-frequency vibration attenuation in flexible structures. This work aims to bridge the domains of energy harvesting and locally resonant metamaterials to form multifunctional structures that exhibit both low-power electricity generation and vibration attenuation capabilities. A fully coupled electromechanical modeling framework is developed for two characteristic systems and their modal analysis is presented. Simulations are performed to explore the vibration and electrical power frequency response maps for varying electrical load resistance, and optimal loading conditions are presented. Case studies are presented to understand the interaction of bandgap formation and energy harvesting capabilities of this new class of multifunctional energy-harvesting locally resonant metastructures. It is shown that useful energy can be harvested from the locally resonant metastructure without significantly diminishing their dramatic vibration attenuation in the locally resonant bandgap. Thus, by integrating energy harvesters into a locally resonant metastructure, there is new potential for multifunctional self-powering or self-sensing locally resonant metastructures.
Elastomer Health Monitoring Utilizing Elastico-Mechanoluminescence From Impregnated ZnS:Cu
Authors: Krishnan Srivatsava , Sundaresan Vishnubaba
Published: November 2017

Mechanically induced light emission, termed mechanoluminescence (ML) has been a potential candidate for stress sensing, stress visualization, damage detection and crack propagation applications. In this work, we demonstrate utilizing ML from elastic loading, termed elastico-mechanoluminescence (EML), for structural health monitoring and failure prediction applications. EML from ZnS:Cu phosphors impregnated in elastomeric matrix is shown to correlate with the structural health of the matrix as well as indicate impending failure of the matrix. Indicators for real-time monitoring to predict impeding failure are also identified. EML based SHM system can be implemented to monitor health of several existing engineering devices that depend on functional elastomeric components for reliable operation.
Multifunctional Mechano-Luminescent-Optoelectronic Composites for Self-Powered Strain Sensing
Authors: Pulliam Elias , Hoover George , Ryu Donghyeon
Published: November 2017

Aerospace mechanical structures encounter various forms of damage throughout their operation due to mechanical stimuli. Structural health monitoring (SHM) is suggested as a way to actively check the integrity of a component by using a system of sensors. However, these conventional sensors can often require external power that is not always readily available in aerospace, thus the development of self-powered sensors could prove beneficial for SHM applications. In this study, the design of multifunctional mechano-luminescent-optoelectronic (MLO) composites strain sensor is suggested. The MLO composites sensor is composed of two transformative materials: 1) mechano-luminescent (ML) copper-doped zinc sulfide (ZnS:Cu) and 2) mechano-optoelectronic (MO) poly(3-hexylthiophene) (P3HT). ML ZnS:Cu emits light in response to mechanical stimuli. MO P3HT showed self-sensing capability by generating direct current (DC) sensor signal under light. First, ZnS:Cu ML crystals will be embedded in polydimethylsiloxane (PDMS) matrix to fabricate ZnS:Cu/PDMS elastomeric composites. ML light emission characteristics of ZnS:Cu/PDMS will be studied by subjecting the ZnS:Cu/PDMS to cyclic tensile strain loadings while videos are recorded of the light emission. The data are analyzed using a statistical factorial methodology so that a regression model to predict light emission based on loading strain and frequency can be calculated. Second, MO P3HT-based self-sensing thin films will be fabricated on glass slides using a spin-coating technique. Last, self-powered sensing capability of the MLO composites strain sensor will be validated by measuring DC voltage (DCV) in close proximity of the ZnS:Cu/PDMS subjected to cyclic tensile loadings.
Two-Speed Transmission Based on MRF Coupling Elements
Authors: Hegger Christian , Maas Jürgen
Published: November 2017

In this contribution the conceptual development of a two-speed transmission utilizing coupling elements based on magnetorheological fluids (MRF) will be presented. The transmission concept is based on a mechanical power split. The transmission ratios are optimized for an appropriate utilization of MRF coupling elements. This transmission concept can be applied in several applications, like vehicles or industrial use. Besides, the electrical feeding power of the coupling elements will be investigated for certain scenarios considering the proposed transmission concept. MRF coupling elements provide a highly dynamical and continuously adjustable torque transmission. In combination with the MR fluid movement control to avoid viscous losses, a very energy efficient operation in contrast to conventional coupling elements can be achieved. For a reduction of the weight, space and feeding energy also a novel design with serpentine flux guidance will be introduced. Due to this design, combined arrangements of MRF coupling elements can be achieved, to create a very compact dual coupling element for the proposed transmission concept.
Using the trapped energy ratio for source depth discrimination with a horizontal line array: Theory and experimental results
Authors: Conan Ewen , Bonnel Julien , Nicolas Barbara , Chonavel Thierry
Published: November 2017

The problem of acoustic source depth discrimination was introduced as a way to get basic information on source depth in configurations where accurate depth estimation is not feasible. It is a binary classification problem, aiming to evaluate whether the source is near the surface or submerged. Herein, the classification relies on a signal measured with a horizontal line array in shallow water. Knowing the source-array distance is not required but the source bearing has to be close to the array endfire. Signal processing relies on a normal-mode propagation model, and thus requires prior knowledge of the mode characteristics. The decision relies on an estimation of the trapped energy ratio in mode space. The performance is predicted with simulations and Monte Carlo methods, allowing one to compare several estimators based on different mode filters, and to choose an appropriate decision threshold. The impact on performance of frequency, noise level, horizontal aperture, and environmental mismatch is numerically studied. Finally, the approach is validated on experimental data acquired with a horizontal line array deployed off the coast of New Jersey, and the impact of errors in the environmental model is illustrated. The investigated approach successfully identifies a surface ship and a submerged towed source.
North Atlantic right whale faces extinction
Authors: Pennisi Elizabeth
Published: November 2017

Entanglements and ship strikes are taking a grave toll, reversing past population
gains
A neural algorithm for a fundamental computing problem
Authors: Dasgupta Sanjoy , Stevens Charles F. , Navlakha Saket
Published: November 2017

Fly brain inspires computing algorithm

Flies use an algorithmic neuronal strategy to sense and categorize odors. Dasgupta
et al.
applied insights from the fly system to come up with a solution to a computer science problem. On the basis of the algorithm that flies use to tag an odor and categorize similar ones, the authors generated a new solution to the nearest-neighbor search problem that underlies tasks such as searching for similar images on the web.

Science
, this issue p.
793
Comment on “The extent of forest in dryland biomes”
Authors: de la Cruz Marcelino , Quintana-Ascencio Pedro F. , Cayuela Luis , Espinosa Carlos I. , Escudero Adrián
Published: November 2017

The study by Bastin
et al
. (Reports, 12 May 2017, p. 635) is based on an incomplete delimitation of dry forest distribution and on an old and incorrect definition of drylands. Its sampling design includes many plots located in humid ecosystems and ignores critical areas for the conservation of dry forests. Therefore, its results and conclusions may be unreliable.
Integrated view of
Vibrio cholerae
in the Americas
Authors: Domman Daryl , Quilici Marie-Laure , Dorman Matthew J. , Njamkepo Elisabeth , Mutreja Ankur , Mather Alison E. , Delgado Gabriella , Morales-Espinosa Rosario , Grimont Patrick A. D. , Lizárraga-Partida Marcial Leonardo , Bouchier Christiane , Aanensen David M. , Kuri-Morales Pablo , Tarr Cheryl L. , Dougan Gordon , Parkhill Julian , Campos Josefina , Cravioto Alejandro , Weill François-Xavier , Thomson Nicholas R.
Published: November 2017

Wave upon wave of disease

The cholera pathogen,
Vibrio cholerae
, is considered to be ubiquitous in water systems, making the design of eradication measures apparently fruitless. Nevertheless, local and global
Vibrio
populations remain distinct. Now, Weill
et al.
and Domman
et al.
show that a surprising diversity between continents has been established. Latin America and Africa bear different variants of cholera toxin with different transmission dynamics and ecological niches. The data are not consistent with the establishment of long-term reservoirs of pandemic cholera or with a relationship to climate events.

Science
, this issue p.
785
, p.
789
Plant invasions in the Anthropocene
Authors: Kueffer Christoph
Published: November 2017

Human activities not only facilitate plant invasions, but also shape invasion mechanisms
Science for global understanding
Authors: Schlegel Flavia
Published: November 2017

Since its founding in 1945, the United Nations Educational, Scientific, and Cultural Organization (UNESCO) has been a leading convener and advocate for the natural and social sciences and the humanities. Every year since 2001, on 10 November, UNESCO's World Science Day reminds us of the importance of science for sustainable development and peace. This year's theme, “Science for Global Understanding,” also underpins the debates of scientists and policy-makers from around the world who are convening in Jordan this week at the UNESCO World Science Forum. One of their key concerns is the growing criticism of scientific integrity and denial of scientific findings. Building trust in science and fostering scientific excellence is central to all of UNESCO's work.
Ruthenium-106 brachytherapy for iris and iridociliary melanomas
Authors: Marinkovic Marina , Horeweg Nanda , Laman Mirjam S , Bleeker Jaco C , Ketelaars Martijn , Peters Femke P , Luyten Gre P M , Creutzberg Carien L
Published: November 2017

Background and purpose

To evaluate ruthenium-106 (Ru106) brachytherapy as eye-conserving treatment of iris melanomas (IMs) and iridociliary melanomas (ICMs).

Materials and methods

Eighty-eight patients received Ru106 brachytherapy between 2006 and 2016. Primary outcome was local control, and secondary outcomes were metastasis, survival, eye preservation, complications and visual acuity (VA).

Results

Overall median follow-up was 36 months. Of 88 patients, 58 (65.9%) had IM and 30 (34.1%) had ICM. ICM were on average larger and more advanced than IM. Local failure-free survival at 3years was 98.9% (SE 1.2%). Metastasis-free survival was 98.2% (SE 1.8%) at 3years; no deaths due to melanoma occurred during follow-up. Eye preservation rate was 97.7%. Treatment-related toxicities were mostly mild and observed in 80.7% of the patients. Common toxicities were worsening of pre-existing or new cataract (51.1%), dry eyes (29.5%) and glaucoma (20.5%). VA was not affected by Ru106 brachytherapy, with only 2.3% having VA <0.33 (low vision) at follow-up.

Conclusions

Ru106 for IM and ICM yielded excellent local control (98.9%) and eye preservation (97.7%). Toxicities were common, but mostly mild and transient. Moreover, Ru106 did not affect visual acuity.
Clinical characteristics and prognosis of drug-associated acute respiratory distress syndrome compared with non-drug-associated acute respiratory distress syndrome: a single-centre retrospective study in Japan
Authors: Anan Keisuke , Ichikado Kazuya , Kawamura Kodai , Johkoh Takeshi , Fujimoto Kiminori , Suga Moritaka
Published: November 2017

Objectives

To report the clinical features and prognosis of drug-associatedacute respiratory distress syndrome (ARDS).

Design

A retrospective analysis of data collected during a prospective cohort study.

Setting

Intensive care unit in a teaching hospital.

Participants

A total of 197 Japanese patients with ARDS diagnosed by the Berlin definition who were admitted to the Division of Respiratory Medicine from October 2004 to December 2015 were enrolled in the study and were classified as two groups according to their causes: a drug-associated ARDS group (n=27) and a non-drug-associated ARDS group (n=170). Primary outcome measure is 28-day mortality, and the secondaryoutcome measure is ventilator-free days.

Results

The Acute Physiology and Chronic Health Evaluation II scores were significantly lower in the drug-associated ARDS group than in the non-drug-associated ARDS group (median (IQR): 18.0 (16.5–21.0) vs 23.0 (18.0–26.0), p<0.001), and the arterial oxygen tension/fractional inspired oxygen ratio was higher (148.0 (114.1–177.5) vs 101.0 (71.5–134.0), p=0.003). In the drug-associated ARDS group, although high-resolution CT scores indicative of the extent of fibroproliferation (301.6 (244.1–339.8) vs 208.3 (183.4–271.6), p<0.001), serum lactate dehydrogenase levels (477 (365–585) vs 322 (246–434), p=0.003) and the McCabe scores (score 1/2/3, n (%): 20 (74)/4 (15)/3 (11)vs154 (91)/7 (4)/9 (5), p=0.04) were significantly higher, ventilator weaning was earlier (p<0.001) and 28-day mortality was better (p=0.043). After adjusting for potentially confounding covariates, drug-associated ARDS group was associated with lower 28-day mortality (adjusted HR (HR) 0.275; 95% CI 0.106 to 0.711; p=0.008).

Conclusions

Although more severe lung damage with fibroproliferation was observed in patients with drug-associated ARDS, ventilator weaning was earlier, and their prognosis was better than the others. Further well-designed prospective studies are needed.
Impact of heterogeneity and effect size on the estimation of the optimal information size: analysis of recently published meta-analyses
Authors: Garcia-Alamino Josep M , Bankhead Clare , Heneghan Carl , Pidduck Nicola , Perera Rafael
Published: November 2017

Objective

To estimate the proportion of systematic reviews that meet the optimal information size (OIS) and assess the impact heterogeneity and effect size have on the OIS estimate by type of outcome (eg, mortality, semiobjective or subjective).

Methods

We carried out searches of Medline and Cochrane to retrieve meta-analyses published in systematic reviews from 2010 to 2012. We estimated the OIS usingTrial Sequential Analysissoftware (TSA V.0.9) and based on several heterogeneity and effect size scenarios, stratifying by type of outcome (mortality/semiobjective/subjective) and by Cochrane/non-Cochrane reviews.

Results

We included 137 meta-analyses out of 218 (63%) potential systematic reviews (one meta-analysis from each systematic review). Of these reviews, 83 (61%) were Cochrane and 54 (39%) non-Cochrane. The Cochrane reviews included a mean of 6.5 (SD 6.1) studies and the non-Cochrane included a mean of 13.2 (SD 10.2) studies. The mean number of patients was 2619.1 (SD 6245.8 or median 586.0) for the Cochrane and 19 888.5 (SD 32 925.7 or median 6566.5) patients for the non-Cochrane reviews. The percentage of systematic reviews that achieved the OIS for all-cause mortality outcome were 0% Cochrane and 25% for non-Cochrane reviews; for semiobjective outcome 17% for Cochrane and 46% for non-Cochrane reviews and for subjective outcome 45% for Cochrane and 72% for non-Cochrane reviews.

Conclusions

The number of systematic reviews that meet an optimal information size is low and varies depending on the type of outcome and the type of publication. Less than half of primary outcomes synthesised in systematic reviews achieve the OIS, and therefore the conclusions are subject to substantial uncertainty.
A nationwide population-based cohort study of peripartum hysterectomy and arterial embolisation in Belgium: results from the Belgian Obstetric Surveillance System
Authors: Vandenberghe Griet , Guisset Marine , Janssens Iris , Leeuw Virginie Van , Roelens Kristien , Hanssens Myriam , Russo Erika , Van Keirsbilck Joachim , Englert Yvon , Verstraelen Hans
Published: November 2017

Objectives

To assess the prevalence of major obstetric haemorrhage managed with peripartum hysterectomy and/or interventional radiology (IR) in Belgium. To describe women characteristics, the circumstances in which the interventions took place, the management of the obstetric haemorrhage, the outcome and additional morbidity of these women.

Design

Nationwide population-based prospective cohort study.

Setting

Emergency obstetric care. Participation of 97% of maternities covering 98.6% of deliveries in Belgium.

Participants

All women who underwent peripartum hysterectomy and/or IR procedures in Belgium between January 2012 and December 2013.

Results

We obtained data on 166 women who underwent peripartum hysterectomy (n=84) and/or IR procedures (n=102), corresponding to 1 in 3030 women undergoing a peripartum hysterectomy and another 1 in 3030 women being managed by IR, thereby preserving the uterus. Seventeen women underwent hysterectomy following IR and three women needed further IR despite hysterectomy. Abnormal placentation and/or uterine atony were the reported causes of haemorrhage in 83.7%. Abnormally invasive placenta was not detected antenatally in 34% of cases. The interventions were planned in 15 women. Three women were transferred antenatally and 17 women postnatally to a hospital with emergency IR service. Urgent peripartum hysterectomy was averted in 72% of the women who were transferred, with no significant difference in need for transfusion. IR procedures were able to stop the bleeding in 87.8% of the attempts. Disseminated intravascular coagulation secondary to major haemorrhage was reported in 32 women (19%).

Conclusion

The prevalence in Belgium of major obstetric haemorrhage requiring peripartum hysterectomy and/or IR is estimated at 6.6 (95% CI 5.7 to 7.7) per 10 000 deliveries. Increased clinician awareness of the risk factors of abnormal placentation could further improve the management and outcome of major obstetric haemorrhage. A case-by-case in-depth analysis is necessary to reveal whether the hysterectomies and arterial embolisations performed in this study were appropriate or preventable.