bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seed enhancing treatments: comparative analysis of germination characteristics of 23 key herbaceous species used in European restoration programmes
Authors: Lopez del Egido L. , Toorop P. E. , Lanfermeijer F. C. 
Published: November 2018

Abstract

The response of seeds from 23 wild plant species to a range of seed enhancing treatments was studied. We tested the hypothesis that sensitivity of the 23 species to these compounds is related to their ecological niche. The three ecological niches considered were open land, open‐pioneer and woodland. Hence, the germination of a species is likely adapted to different light conditions and other environmental signals related to the niche.

As representatives of environmental signals, the effects of smoke‐related compounds (karrikinolide, KAR1), nitrate and plant growth regulator (gibberellic acid, GA3) on germination were studied. Seeds were exposed to these additives in the imbibition medium; all described as germination cues. We also investigated the effect of light regimes and additives on germination parameters, which included final germination, germination rate and uniformity of germination. Seeds were placed to germinate under three light conditions: constant red light, constant darkness and 12 h white light photoperiod.

We observed inhibition by KAR under light in some species, which may have ecological implications. The results showed that no single treatment increased the germination of all the tested species, rather a wide variation of responsiveness of the different species to the three compounds was found. Additionally, no interaction was found between responsiveness to compounds and ecological niche. However, species in the same ecological niche and dormancy class showed a similar responsiveness to light.

Species that share a similar environment have similar light requirements for germination, while differences exist among species in their responsiveness to other germination cues.
Evaluating Potential Distribution of High‐Risk Aquatic Invasive Species in the Water Garden and Aquarium Trade at a Global Scale Based on Current Established Populations
Authors: West Amanda M. , Jarnevich Catherine S. , Young Nicholas E. , Fuller Pam L. 
Published: November 2018

AbstractAquatic non‐native invasive species are commonly traded in the worldwide water garden and aquarium markets, and some of these species pose major threats to the economy, the environment, and human health. Understanding the potential suitable habitat for these species at a global scale and at regional scales can inform risk assessments and predict future potential establishment. Typically, global habitat suitability models are fit for freshwater species with only climate variables, which provides little information about suitable terrestrial conditions for aquatic species. Remotely sensed data including topography and land cover data have the potential to improve our understanding of suitable habitat for aquatic species. In this study, we fit species distribution models using five different model algorithms for three non‐native aquatic invasive species with bioclimatic, topographic, and remotely sensed covariates to evaluate potential suitable habitat beyond simple climate matches. The species examined included a frog (Xenopus laevis), toad (Bombina orientalis), and snail (Pomacea spp.). Using a unique modeling approach for each species including background point selection based on known established populations resulted in robust ensemble habitat suitability models. All models for all species had test area under the receiver operating characteristic curve values greater than 0.70 and percent correctly classified values greater than 0.65. Importantly, we employed multivariate environmental similarity surface maps to evaluate potential extrapolation beyond observed conditions when applying models globally. These global models provide necessary forecasts of where these aquatic invasive species have the potential for establishment outside their native range, a key component in risk analyses.
Positive versus negative incentives for loan repayment in microfinance: A game theory approach
Authors: Brihaye Thomas , Pril Julie De , Labie Marc , Périlleux Anaïs 
Published: November 2018

AbstractIn most of the methodologies used so far by microfinance institutions, negative incentives are predominant, which can contrast with these institutions’ social mission. This paper investigates whether the microfinance industry could benefit from using more positive incentives. The main results of our game model are twofold. First, (positive or negative) incentives increase “on‐time” repayments. Second, the client is more likely to repay her loan with the encouragement of a bonus scheme rather than under the pressure of a sanction, regardless of the amount. This paper therefore argues for the increased use of positive incentives in the industry.
Effect of PVP Addition in the Preparation of Polyethersulfone (PES)–AgNO3 Antibacterial Membrane
Authors: Basri H. , Ismail A. F. , Aziz M. 
Published: November 2018

Association of antibacterial agent into polymer–based material is an interesting, recent extension in membrane technologies research area. Asymmetric polyethersulfone–silver nitrate (PES–AgNO3) nanocomposite membranes were synthesized by wet phase inversion with polyvinylpyrrolidone (PVP) as additive. Three different molecular weights (MW) of PVP in the range of 10 K to 360 K were tested for their ability to stabilize and disperse silver in the polymer solution. Results showed that PVP 360 K plays a significant role in altering silver particle size with better dispersion compared to the membranes prepared without addition of PVP and with the addition of lower MW of PVP. Results agreed with the leaching detected by ICP–MS where silver loss during membrane fabrication for PES–Ag–P360 is only 0.4636 ppm (0.0093%). The antibacterial activity for the resultant membranes was tested using inhibition zone method. Results indicated that PES–AgNO3 and PES–AgNO3–PVP (loaded with only 0.5 wt% silver) were antibacterial to Escherichia coli and Staphylococcus aureus. The improvement of antibacterial properties of the prepared membranes could be primarily attributed to the PVP addition as well as the surface morphology and permeation properties.
The Effect of Silica Loading on the Performance and Morphology of Polyimide–Silica Hybrid Membrane
Authors: Bakar N. S. A. , Hashemifard S. A. , Mustafa A. 
Published: November 2018

The performance of silica-polyimide hybrid membranes has been investigated for gas separation processes. The dope solution consisted of polyimide resin dissolved in NMP and silica sols at various weight percentages. The silica sols were prepared using a sol–gel process and the flat–sheet silica–polyimide hybrid membranes were cast using an immersion precipitation technique. The effects of silica sols loading on the gas transport properties of polyimide hybrid membranes and the correlation of morphology changes in the membrane structure and molecular orientation were studied. Polyimide hybrid membranes with silica sols loading ranging from 0 to 50 wt% were tested on gas permeation performance with single gas of O2, N2, CH4 and CO2. The gas permeation results showed that the hybrid membranes with 20 wt% to 25 wt% silica loading exhibited higher selectivity than the pure polyimide membrane. Morphological properties and molecular orientations of the silica–polyimide hybrid membranes were also studied using SEM and FTIR, respectively. The SEM and FTIR results confirmed that the 20 and 25 wt% of silica loading was the ideal composition of polyimide–silica hybrid membrane for gas separation.
Carbon Molecular Sieve Membranes from Polyetherimide: Effect of Pyrolysis Temperature on O2/N2 Selectivity
Authors: Ahmad M. A. , Rashid N. K. A. , Hameed B. H. 
Published: November 2018

Carbon molecular sieve (CMS) membranes with excellent separation performance and stability appear to be promising candidate for gas separation. In this work, CMS membranes were formed by a thin carbon layer obtained by pyrolysis of a coated polyetherimide solution onto porous disk support. The pyrolysis temperatures were varied under inert condition. Results showed that the pyrolysis temperature played an important role in determining the gas permeability of CMS membranes. The CMS membrane prepared at pyrolysis temperature of 700°C shows high surface area and narrow PSD with well developed microporous carbon structures. The development of large pore occurs at higher pyrolysis temperature. The O2/N2 permselectivities of 2.86, 2.61 and 2.22, respectively were attained by CMS membranes prepared at pyrolyzed temperature of 700, 800 and 900°C.
Magnetic-Assisted Alignment of Reinforcing Functionalized-Fibers in a Composite for Lightweight Structures
Authors: Torres-Sánchez C. , Haghihi-Abayneh M. , Conway P. P. 
Published: November 2018

Localized reinforcement of composites employed to manufacture parts for the transport industries is making possible the lightweighting of components that have a much sought-after effect in the reduction of CO2 and NOx emissions. However, its realization, through the removing of mass where it is not required and reinforcement added to areas more prone to stress from working loads, relies on the development of novel manufacturing processes that can create structures whose performance is on a par with their solid counterparts, but at a fraction of the weight and at an affordable production cost.
In this work we exploit the use of a very weak and safe magnetic field to control the location and orientation of functionalized discontinuous carbon fibers within a polymeric structural (polyurethane) foam to create performance-optimized composites.
Two wet-chemistry methods (i.e. in-situ precipitation-deposition and amine-co-adjuvated electrodeposition of magnetite) to transform commercial carbon fiber into a magnetically active form were explored. The resulting fibers were analyzed and characterized through a set of physico-chemical tests. The functionalized fibers were then embedded at 3 different %vol contents in the polymeric matrix at given locations and with a desired alignment. Their mechanical performance (incl. compression, tension) was assessed and benchmarked against both a similar %volumetric content but non-functionalized-reinforcement (i.e. randomly distributed) composites and to non-reinforced matrices. In the two sets of reinforced composites (random and aligned) there is a positive correlation between stiffness, yield strength and strain with increasing %vol content. Both sets outperformed the non-reinforced matrix, demonstrating good fiber adhesion within the matrix and successful load transfer from matrix to fiber. The magnetically aligned composites generally outperformed the non-functionalized ones in terms of stiffness and strength at yield.
Design of an Adaptive Twist Trailing Edge for Large Commercial Aircraft Applications
Authors: Rea Francesco , Amoroso Francesco , Pecora Rosario , Kintscher Markus 
Published: November 2018

Researchers and engineers design modern aircraft wings to reach high levels of efficiency with the main outcome of weight saving and airplane lift-to-drag ratio increasing. Future commercial aircraft need to be mission-adaptive to improve their operational efficiency. Twistable trailing edge could be used to improve aircraft performances during climb and off-design cruise conditions in response to variations in speed, altitude, air temperature, and other flight parameters. Indeed, “continuous” span-wise twist of the wing trailing edge could provide significant reduction of the wing root bending moment through redistribution of the aerodynamic load leading to an increase of the payload/structural weight ratio. Within the framework of the Clean Sky 2 (CS2) European research project, the authors focused on the preliminary design of a full-scale composite multifunctional tab retrofitting the outboard morphing Fowler flap of a turboprop regional aircraft. The investigation domain of the novel device is equal to 5.15 meters in span-wise direction and 10% of the local wing chord.
The structural and kinematic design process of the actuation system is completely addressed: two rotary electromechanical motors, placed in the root and tip flap sections, are required to activate the inner mechanisms enabling delta twist angles up to 10 degrees along the outboard region when the flap is stowed in the wing. The structural layout of the thin-walled closed-section composite tab represents a promising concept to balance the conflicting requirements between load-carrying capability and shape adaptivity in morphing lightweight structures. The main design parameters are optimized to minimize actuation torque required for twisting while providing proper flexural rigidity to withstand limit aerodynamic pressure distributions for large airplanes. Finally, the embedded system functionality of the actuation system coupled with the composite wing trailing edge is fully investigated by means of detailed finite element simulations. Results of actuation system performances, and aeroelastic deformations considering operative aerodynamic loads demonstrate the potential of the proposed structural concept to be energy efficient, and lightweight for real aircraft implementation.
The Duffing-Holmes Oscillator With Hybrid Position Feedback Controller: Stability and Response Analysis
Authors: Simsek Mehmet R. , Bilgen Onur 
Published: November 2018

The dynamic behavior of a Duffing-Holmes oscillator subjected to a Hybrid Position Feedback (HPF) controller is investigated. The so-called hybrid controller is a combination of two controllers, namely, the Negative Position Feedback (NPF), and Positive Position Feedback (PPF) controllers. The controller uses the inertial properties of the structure around its stable positions to achieve large displacements by effectively destabilizing the system using an NPF controller. Once the unstable equilibrium is reached, the system is stabilized to the target stable equilibrium using the PPF controller. This dynamic switch of controllers creates the HPF control concept, which specifically enables the monotonic and controlled transition between the states of bistable systems such as the Duffing-Holmes oscillator. This concept can be implemented to morphing structures such as bistable wings, wind turbine blades, and deployable structures.
In this paper, a detailed response type and stability analyses of a Duffing-Holmes oscillator controlled by the HPF controller are presented. First, the response types for the components of the HPF, NPF and PPF controllers are analyzed individually. For the NPF controller, three response types are defined. These are intra-well, single cross-well, and multiple cross-well response types describing the possible responses. For the PPF controller, only two response types are defined. These are stabilized and not-stabilized, since the role of the PPF controller is to generate an attractor to the desired stable equilibrium. Finally, the complete HPF controller is analyzed in terms of response type. In this case, three response types are defined: intra-well, single cross-well and multiple cross-well. The paper summarizes all the response types with detailed analyses, and recommends controller parameters for best control performance.
Vacuum Gripper System Based on Bistable SMA Actuation
Authors: Welsch Felix , Kirsch Susanne-Marie , Motzki Paul , Schmidt Marvin , Seelecke Stefan 
Published: November 2018

This paper presents the design and the realization of an innovative SMA actuated bistable vacuum suction cup. The sealed, compact and fully integrated design enables the positioning and transport of inherent stable components in mobile and stationary applications. The bistable actuator mechanism based on SMA wires combined with a bistable spring represent an energy-efficient, noiseless gripping system without the need for compressed air. Additionally, the self-sensing effect of the SMA enables a sensorless condition-monitoring and energy-efficient control.
The mechanics consists of antagonistic SMA wires, which are laterally arranged and connected to the bistable spring via levers. The membrane is directly connected to the bistable spring. The actuation of the wires leads to a rotational movement of the levers thus changes the state of the bistable spring, which directly deforms the membrane. When the membrane is sealed connected to the workpiece, the deformation of the membrane generates a vacuum.
The integrated microcontroller electronics manages the joule heating of the wires by measuring the transmitted electrical energy. By applying an electrical energy to the pre-strained SMA wire, the wire heats up and contracts due to the phase transformation from martensite to austenite. The contraction of the wire is accompanied by a significant change in electrical resistance, which enables a resistance based strain feedback. The integrated electronics is able to correlate this resistance change to the actual state of the bistable spring, which leads to a position feedback of the membrane. This allows an adequate electrical energy deposition in the SMA wire by turning-off the heating directly after the position toggle of the membrane. Thereby, a successful position toggle is ensured independent from the ambient temperature and the real supply voltage. The new position of the membrane is then held by the bistable spring without the use of additional energy. This concept leads to a reliable gripping system with fast actuation times.
Reduction of Low-Frequency Sound Transmission Using an Array of 3D-Printed Resonant Structures
Authors: Algermissen Stephan , Monner Hans P. 
Published: November 2018

The reduction of low-frequency noise transmission through thin-walled structures is a topic of research for many years now. Due to large wavelengths and the mass law, passive solutions usually gain low performance in the frequency range below 500 Hz. Active systems promised to fill the gap and to achieve significant reductions of transmitted sound. Nevertheless, experiments showed the outstanding performance of such specialized systems, but also demonstrated the computational and hardware effort of such solutions. The upcoming additive manufacturing technology enabled new multi-material designs of complex structures. Based on this technology, acoustic metamaterials emerged in the laboratories and in literature. Arrays of miniaturized locally resonant structures are able to change the noise transmission of thin walled structures beyond the limits of the given mass law in certain frequency bands.
For future aircraft contra-rotating open rotor (CROR) engines are a promising technology to reduce their CO2 footprint. Since the contribution of CROR engines to the cabin noise is higher than for jet engines, new strategies for the reduction of noise transmissions for frequency bands below 200 Hz are necessary. For the tonal noise of the CROR engines, acoustic metamaterials seem to be an appropriate solution. In this paper a 110 × 110 × 1 mm3 thin-walled sample plate is presented. It is covered with a 5 × 5 array of multi-material resonant structures, which are printed as mass on a beam. The rubber-like beam material combines a low Young’s modulus with a high material damping, leading to a low eigenfrequency of the resonators. The design of the resonators using simulations and experimental data is shown. To explore the potential of the design, an acoustic test box is manufactured. Starting with all resonators unblocked the emitted sound intensity of the plate is measured. Sequential blocking of selected resonators proves the concept. Additional laser scanning vibrometer measurements give insights into the vibration behavior of single resonators.
Modeling Hydrogel-Controlled Micro-Reactors for Enzyme Assays With Finite Elements for Improved Flow and Filling Distribution
Authors: Mehner Philipp J. , Obst Franziska , Simon David , Tang Jing , Beck Anthony , Gruner Denise , Busek Mathias , Appelhans Dietmar , Marschner Uwe , Voit Brigitte , Richter Andreas 
Published: November 2018

We propose an improved micro reactor design for a scalable microfluidic device, in which enzymes are immobilized in a hydrogel matrix. Furthermore, fluid flow is controlled by means of hydrogel-based micro-valves. In this work, computational flow simulations will be compared to experimental results to highlight new design ideas and to improve wetting and concentration distribution through the entire chamber volume, even for high aspect ratios. Additionally, modelling concepts will be introduced to efficiently describe multi-domain problems like enzyme reactions.
With the help of a computer-aided design process which is capable to simulate hydrogel-based microfluidic systems it is possible to better understand, predict and visualize the behavior of micro-reactors and support the development of highly integrated hydrogel-based microfluidic circuits.
Melt Processed Conductive Polycarbonate Composites With Ternary Fillers Towards Bipolar Plate Applications
Authors: Naji Ahmed , Pötschke Petra , Ameli Amir 
Published: November 2018

The demand for clean and sustainable energy sources continuously increases. One of the promising ways to provide electrical power is using fuel cells. Polymer electrolyte membrane fuel cell (PEMFC) represents the most common type of fuel cells. However, PEMFCs have not yet been fully commercialized because of the high cost and low performance. A main part of PEMFC, which significantly contributes to the cost and weight is the bipolar plate (BPP). The US Department of Energy (DOE) has recommended some physical properties for BPP for sustainable commercialization of PEMFC. Those set properties have yet to be met. Conductive polymer composites (CPCs) use conductive fillers such as carbon nanotube (CNT), carbon fiber (CF), and graphite (Gr) to impart electrical and thermal conductivities and can potentially provide an optimum combination of weight, cost, mechanical properties and conductivity characteristics for BPPs.
In the current work, CPCs of polycarbonate (PC) filled with singular filler of CNT, binary fillers of CNT and CF and ternary fillers of CNT, CF and Gr were fabricated using melt mixing method followed by compression molding. The through-plane and in-plane electrical conductivities of the CPCs were investigated. The results showed that the electrical percolation thresholds for the PC-CNT is ∼1 wt. % CNT in both the through-plane and in-plane directions. Addition of 3 wt. % CNT to PC composites with 10 - 30 wt. % CF improved the conductivity performance. It was noticed increasing CF content from 20 to 30 wt. % did not yield a big change in conductivity, so that at 20 wt. % CF, the through-plane and in-plane electrical conductivities are 0.11 S.cm−1 and 6.4 S.cm−1 respectively. Moreover, using 20 wt. % CF will allow for higher loading of graphite. To further enhance the conductivities towards the DOE recommendations, 30 wt. % Gr was introduced to the PC composite with binary filler (i.e., 3 wt. % CNT and 20 wt. % CF). The results showed that the through-plane and in-plane electrical conductivities were increased to 1.5 S.cm−1 and 13.5 S.cm−1, respectively. These properties recommend a potential application of polycarbonate based CPCs for BPP manufacturing.