bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of soil aggregate size and dicyandiamide on N2O emissions and ammonia oxidizer abundance in a grazed pasture soil
Authors: Robinson A. , Di H. J. , Cameron K. C. , Podolyan A. 
Published: February 2014

AbstractNitrous oxide (N2O) is a potent greenhouse gas, which is mainly produced from agricultural soils. Ammonia oxidation is the rate‐determining step in N2O production, and the process is carried out by ammonia oxidizers, bacteria and archaea. Soil aggregate size has been shown to alter soil properties, which affect N2O emissions and bacterial communities. However, the effect of aggregate size on temporal and total N2O emissions and ammonia‐oxidizing bacteria (AOB) and archaea (AOA) is not fully understood. This incubation study investigated the effect of three different soil aggregate sizes on N2O emissions and ammonia oxidizer abundance under high urine‐N concentrations and the effectiveness of a nitrification inhibitor, dicyandiamide (DCD), at reducing N2O emissions in different aggregate soils. It was found that temporal patterns of N2O emissions were affected by aggregate size with higher peak emissions in the large and medium aggregates. However, the total emissions were the same due to a ‘switch’ in emissions at day 66, after which smaller aggregates produced higher N2O emissions. It is suggested that the switch was caused by an increase in aggregate disruption in the small aggregates, following the urine application, due to their higher surface area to volume ratio. AOB and AOA abundances were not significantly affected by aggregate size. DCD was effective in reducing N2O emissions in all aggregate sizes by an average of 79%. These results suggest that similar ammonia oxidizer abundance is found in soils of different aggregate sizes, and the efficacy of DCD in reducing N2O emissions was not affected by aggregate size of the soil.
The Arabidopsis thaliana tandem zinc finger 1 (AtTZF1) protein in RNA binding and decay
Authors: Qu Jie , Kang Shin Gene , Wang Wei , Musier‐Forsyth Karin , Jang Jyan‐Chyun 
Published: February 2014

SummaryThe Arabidopsis thaliana tandem zinc finger 1 (AtTZF1) protein is characterized by two tandem‐arrayed CCCH‐type zinc fingers. We have previously found that AtTZF1 affects hormone‐mediated growth, stress and gene expression responses. While much has been learned at the genetic and physiological level, the molecular mechanisms underlying the effects of AtTZF1 on gene expression remain obscure. A human TZF protein, hTTP, is known to bind and trigger the degradation of mRNAs containing AU‐rich elements (AREs) at the 3′ untranslated regions. However, while the TZF motif of hTTP is characterized by CX8CX5CX3H‐X18‐CX8CX5CX3H, AtTZF1 contains an atypical motif of CX7CX5CX3H‐X16‐CX5CX4CX3H. Moreover, the TZF motif of AtTZF1 is preceded by an arginine‐rich (RR) region that is unique to plants. Using fluorescence anisotropy and electrophoretic mobility shift binding assays, we have demonstrated that AtTZF1 binds to RNA molecules with specificity and the interaction is dependent on the presence of zinc. Compared with hTTP, in which TZF is solely responsible for RNA binding, both TZF and RR regions of AtTZF1 are required to achieve high‐affinity RNA binding. Moreover, zinc finger integrity is vital for RNA binding. Using a plant protoplast transient expression analysis we have further revealed that AtTZF1 can trigger the decay of ARE‐containing mRNAs in vivo. Taken together, our results support the notion that AtTZF1 is involved in RNA turnover.
Fundamental Understanding of Wave Propagation in a Beam Using PZT Actuators and Sensors
Authors: Venugopal Vishnu Prasad , Wang Gang 
Published: February 2014

Embedded smart actuators/sensors, such as piezoelectric types, have been used to conduct wave transmission and reception, pulse-echo, pitch-catch, and phased array functions in order to achieve in-situ nondestructive evaluation for different structures. By comparing to baseline signatures, the damage location, amount, and type can be determined. Typically, this methodology does not require analytical structural models and interrogation algorithm is carefully designed with little wave propagation knowledge of the structure. However, the wave excitation frequency, waveform, and other signal characteristics must be comprehensively considered to effectively conduct diagnosis of incipient forms of damage. Accurate prediction of high frequency wave response requires a prohibitively large number of conventional finite elements in the structural model. A new high fidelity approach is needed to capture high frequency wave propagations in a structure.
In this paper, a spectral finite element method (SFEM) is proposed to characterize wave propagations in a beam structure under piezoelectric material (i.e., PZT) actuation/sensing. Mathematical models are developed to account for both Uni-morph and bi-morph configurations, in which PZT layers are modeled as either an actuator or a sensor. The Timoshenko beam theory is adopted to accommodate high frequency wave propagations, i.e., 20–200 KHz. The PZT layer is modeled as a Timoshenko beam as well. Corresponding displacement compatibility conditions are applied at interfaces. Finally, a set of fully coupled governing equations and associated boundary conditions are obtained when applying the Hamilton’s principle. These electro-mechanical coupled equations are solved in the frequency domain. Then, analytical solutions are used to formulate the spectral finite element model. Very few spectral finite elements are required to accurately capture the wave propagation in the beam because the shape functions are duplicated from exact solutions. Both symmetric and antisymmetric mode of lamb waves can be generated using bimorph or uni-morph actuation. Comprehensive simulations are conducted to determine the beam wave propagation responses. It is shown that the PZT sensor can pick up the reflected waves from beam boundaries and damages. Parametric studies are conducted as well to determine the optimal actuation frequency and sensor sensitivity. Such information helps us to fundamentally understand wave propagations in a beam structure under PZT actuation and sensing. Our SFEM predictions are validated by the results in the literature.
Nonlinear Dynamics of the Hybrid Rotary-Translational Energy Harvester
Authors: Karami M. Amin , Inman Daniel J. 
Published: February 2014

The analytical modeling and experimental investigation of a nonlinear electromagnetic rotational energy harvester, which can harvest power from rotary and translational excitations, are presented. Some application of energy harvesting such as energy harvesting for tire pressure sensing require an energy harvester which is efficient in generating power from rotational ambient vibrations. The majority of literature on vibration energy harvesting assumes that the ambient excitations are along a single axis. The vibrations from human motion or rotary machines have two components of translational motion as well as a strong rotary motion. The energy harvesting device studied in this paper is a pendulum like device. The base excitations result in rotations of a pendulum. The pendulum is connected to a direct current micro generator. The rotational vibrations of the pendulum generates electricity through the DC generator. Since the energy harvester is responsive to both translational and rotational base excitations, it is called Hybrid Rotary-Translational (HRT) generator.
In this paper a small size HRT harvester is introduced and modeled. The model is used to investigate the relation between the frequency and the amplitude of base vibrations on the vibrations and power generation characteristics of the HRT system. For each frequency and amplitude of vibrations the coexistence of multiple solutions and their basin of attractions are investigated. Three types of ambient excitations are studied: rotational, translational along the direction of gravity, and translational normal to the direction of the gravity.
Analysis of the Experimental Torque Characteristic of a Magnetorheological Clutch Using Neural Networks
Authors: Bucchi Francesco , Forte Paola , Frendo Francesco 
Published: February 2014

In this paper the dependence of the torque characteristic of a magnetorheological clutch on several working parameters is analysed by means of a feedforward neural network. The clutch was envisaged to have the possibility to disengage the vacuum pump in diesel engine vehicles, in order to increase the overall vehicle efficiency.
A large set of test was carried out following different protocols in order to obtain a detailed characterization of the clutch. Results showed how, due to the characteristics of MR fluids and to the complex mechanism of torque transmission, the torque characteristics (both the yield torque and the torque-slip behaviour) is function of the relative speed between the primary and secondary clutch groups and also function of the dissipated energy during the clutch slip and of the rest time between consecutive slippages. The data acquired during all tests were used to train a neural network with five input elements and one output element.
The developed neural network was proved to satisfactorily reproduce the actual clutch properties and can be used in the future in an engine-vehicle simulator in order to model the torque characteristic of the clutch subjected to different operating cycles.
A Systematic Approach to Corrosion-Powered Sensor Network Design
Authors: Ouellette Scott , Todd Michael 
Published: February 2014

Energy harvesting systems for structural health monitoring applications may be described by three stages: ambient energy transduction, electrical power conditioning, and data acquisition and transmission. Recent developments in low-power CMOS devices have allowed for expanded energy harvesting techniques by reducing the total power demand of sensor nodes.
This paper investigates the system-level interaction between a corrosion-based energy harvester and the low-power sensor node to which it is supplying power. An equivalent circuit model of the energy harvester is developed and the matched parameters (source voltage and equivalent series resistance) are used in the design of the power conditioning and wireless transmitter circuitry. Analysis of the power demand from the sensor node is used to determine the optimum data sampling parameters in terms of available supplied power for long-term in-situ sensing operations on a marine structure.
Control of Snap-Through Transitions in the Response of Mechanically-Equivalent Frequency Modulators
Authors: Borchani Wassim , Lajnef Nizar , Burgueño Rigoberto 
Published: February 2014

Converted energy from ambient loading in civil and mechanical structures is typically used as a viable alternative. Although, piezoelectric vibration harvesters have been widely used given their energy conversion ability, these elements exhibit a narrow natural frequency response range, thus considerably limiting the levels of harvestable power.
Recently our group has introduced the concept of using mechanically-equivalent frequency modulators that can transform the low-amplitude and low-rate service and ambient deformations into an amplified input to the piezoelectric transducer. The introduced methods allow energy generation and conversion within the unexplored quasi-static frequency range (≪ 1 Hz). The post-buckling behavior of bilaterally constrained columns was used for frequency up-conversion, and piezoelectric cantilever beams, attached to the columns, were used for energy conversion.
The introduced concept was experimentally validated and finite element simulations were developed to evaluate the effect of system parameters (stiffness, thickness, and walls gap) on the position of the snap-through transition events and the levels of force-displacement at the multiple-equilibrium configurations. It was shown that the considered system parameters can determine the absolute levels of force and displacement, but they offer limited control on the number and the relative spacing between the energy-drop events. This paper shows that the combination of multiple slender elastic columns modulators, in parallel configurations, allows for the tailoring of the number and magnitude of the mode branch switching during the postbuckling response of the complete system. Experimental and numerical results are presented to validate the proposed concept.
Folding Actuation and Locomotion of Novel Magneto-Active Elastomer (MAE) Composites
Authors: von Lockette Paris , Sheridan Robert 
Published: February 2014

Magneto-active elastomers (also called magnetorheological elastomers) are most often used in vibration attenuation application due to their ability to increase in shear modulus under a magnetic field. These shear-stiffening materials are generally comprised of soft-magnetic iron particles embedded in a rubbery elastomer matrix. More recently researchers have begun fabricating MAEs using hard-magnetic particles such as barium ferrite. Under the influence of uniform magnetic fields these hard-magnetic MAEs have shown large deformation bending behaviors resulting from magnetic torques acting on the distributed particles and consequently highlight their ability for use as remotely powered actuators.
Using the magnetic-torque-driven hard-magnetic MAE materials and an unfilled silicone elastomer, this work develops novel composite geometries for actuation and locomotion. MAE materials are fabricated using 30% v/v 325 mesh barium ferrite particles in Dow Corning HS II silicone elastomers. MAE materials are cured in a 2T magnetic field to create magnetically aligned (anisotropic) materials as confirmed by vibrating sample magnetometry (VSM). Gelest optical encapsulant is used as the uniflled elastomer material.
Mechanical actuation tests of cantilevers in bending and of accordion folding structures highlight the ability of the material to perform work in moderate, uniform fields of μ0H = 150 mT. Computational simulations are developed for comparison. Folding structures are also investigated as a means to produce untethered locomotion across a flat surface when subjected to an alternating field similar to scratch drive actuators; geometries investigated show promising results.
Non-Contact Torque Measurement Using Magnetostrictive Galfenol
Authors: Raghunath Ganesh , Flatau Alison B. , Purekar Ashish , Yoo Jin-Hyeong 
Published: February 2014

This work deals with the development of a non-contact torque sensor system prototype made from rolled and textured Galfenol, a magnetostrictive alloy of Iron and Gallium. It is already known that this smart material exhibits a linear response to strain in the presence of appropriate biasing magnets. The response of a sensor system built from it follows commercially available strain gages. In this research, the magnetic change in Galfenol due to shear strain experienced by the shaft in torque will be monitored using Hall effect sensors to derive the torque information. Factors affecting the performance of this Wireless Magneto-Elastic Torque Sensor System (WIMETs) such as annealing, rolling process and strain transfer of adhesives shall be explored.
The ability to provide real-time measurements with minimal signal conditioning requirements make a well-designed torque system attractive for applications such as condition based maintenance. Factors such as being non-contact and passive to the shaft, compact and easy to install, accurate, sensitive and cost effective are highly desired for any torque measurement system. A rate-of-change torque sensor that demonstrates both a sensitivity and time resolution high enough to not only recognize failing machinery, but to specifically identify the failing part is also a critical feature. These characteristics have been incorporated in the current design of WIMETs.
A mathematical model for the magneto-elastic coupling along with simulations from COMSOL shall be presented. Results from static tests for various torques and dynamic tests for various torques at different RPMs will be discussed. It will be shown that the WiMET sensor system setup in a clamshell is reliable and exhibits sensitivity of up to 10mV/in-lb. over a wide range of torque (0–150 lb.-in). Its performance will be compared with a commercial torque sensor and results for detection of eccentric loads on the shaft will also be furnished.
Damage Detection in Composite Structures With Wavenumber Array Data Processing
Authors: Tian Zhenhua , Leckey Cara , Yu Lingyu 
Published: February 2014

Guided ultrasonic waves (GUW) have the potential to be an efficient and cost-effective method for rapid damage detection and quantification of large structures. Attractive features include sensitivity to a variety of damage types and the capability of traveling relatively long distances. They have proven to be an efficient approach for crack detection and localization in isotropic materials. However, techniques must be pushed beyond isotropic materials in order to be valid for composite aircraft components.
This paper presents our study on GUW propagation and interaction with delamination damage in composite structures using wavenumber array data processing, together with advanced wave propagation simulations. Parallel elastodynamic finite integration technique (EFIT) is used for the example simulations. Multi-dimensional Fourier transform is used to convert time-space wavefield data into frequency-wavenumber domain. Wave propagation in the wavenumber-frequency domain shows clear distinction among the guided wave modes that are present. This allows for extracting a guided wave mode through filtering and reconstruction techniques. Presence of delamination causes spectral change accordingly. Results from 3D CFRP guided wave simulations with delamination damage in flat-plate specimens are used for wave interaction with structural defect study.
Impact of Length Mismatch on the Fatigue Life of Parallel Shape Memory Alloy Wires
Authors: Churchill Christopher B. , Bedegi Anthony , Gao Xiujie 
Published: February 2014

Shape memory alloy (SMA) actuator wires promise substantial size, weight, and potential cost advantages over their solenoid and electric motor counterparts. Designing actuators which fully realize these advantages is hampered by a limited understanding of how interactions between wires and their environment affect cyclic lifetime. For example, many devices use two SMA wires mechanically in parallel but electrically in series. This has practical advantages in simplified electrical routing and thermal lag. However, it complicates modeling in that wires interact both electrically and mechanically.
Here we study the effect of a mismatch in length between two SMA wires in parallel. We perform a series of fatigue experiments to show that mismatch of up to 0.75%, at the chosen set of conditions, has no measurable effect on cycle life. We also perform a series of simulations to show how the mechanical interaction between the two parallel wires tends to suppress, rather than amplify, any impact of length mismatch.
Vibration Analysis of Shrouded Turbine Blades for a 30 MW Gas Turbine
Authors: Tamai Ryoji , Tanaka Ryozo , Sato Yoshichika , Kusterer Karsten , Lin Gang , Kemper Martin , Panning-von Scheidt Lars 
Published: February 2014

Turbine blades are subjected to high static and dynamic loads. In order to reduce the vibration amplitude means of friction damping devices have been developed, e.g. damping wires, interblade friction dampers and shrouds. This paper presents both numerical and experimental results for investigating the dynamical behavior of shrouded turbine blades. The studies are focused on the lowest family of the bladed disk.
The aspect of experimental studies, the effect of the shroud contact force on the resonance frequency of the blade was examined by using the simplified blade test stand. Based on the result of the simplified blade studies, the shroud contact force of the real blade was determined in order to stabilize the resonance frequencies of the bladed disk system. The resonance frequencies and mode shapes of the real bladed disk assembly were measured in no rotation and room temperature condition. Finally, the dynamic strains were measured in the actual engine operations by using a telemetry system.
The aspect of analytical studies, a non-linear vibration analysis code named DATES was applied to predict vibration behavior of a shrouded blade model which includes contact friction surfaces. The DATES code is a forced response analysis code that employs a 3-dimensional friction contact model. The Harmonic Balance Method (HBM) is applied to solve resulting nonlinear equations of motion in frequency domain. The simulated results show a good agreement with the experimental results.
Advanced Coating Systems for Future Shroudless Turbines
Authors: Gebhard Susanne , Wobst Tanja , Roth-Fagaraseanu Dan , Hancock Matthew 
Published: February 2014

Shroudless turbine designs offer the advantages of weight reduction and lower mechanical loads on the one hand but bear challenges as high gap sensitivity and high temperatures of the static parts on the other hand. In the last years, a lot of work was carried out in order to develop a sealing system for a shroudless design consisting of an abrasive blade tip coating and an abradable segment coating addressing all the requirements defined. Aside from being abradable, the segment coatings have to be mechanically stable, withstand high thermo-mechanical loadings and have to work for thicknesses larger than 1 mm.
Due to the limited temperature capability of the currently used segment coating material yttria-stabilised zirconia, which combines advantageously a suitable thermal conductivity with a high thermal expansion coefficient, new ceramic materials for the segment coating had to be developed.
A very promising sealing system combines an abrasive blade tip coating with an yttria-stabilised zirconia / magnesia alumina spinel double-layer abradable coating system with a 3D interface structure between the bond coat and the ceramic coatings. The present work gives an overview of the development and the performance of this sealing system.
Impact of Wall Temperature on Turbine Blade Tip Aero-Thermal Performance
Authors: Zhang Q. , He L. 
Published: February 2014

Currently, the aerodynamics and heat transfer over a turbine blade tip tend to be analyzed separately with the assumption that the wall thermal boundary conditions do not affect the Over-Tip-Leakage (OTL) flow field. There are some existing correlations for correcting the wall temperature effect on heat transfer. But they were mainly developed to account for the temperature dependence on fluid properties, and are inherently limited by the empirical nature. The questions arise with regard to: is the OTL aerodynamics significantly affected by the wall thermal condition? And if it is, how can we count this effect consistently in turbine blade tip design and analysis using modern CFD methods?
In the present study, the problem has been examined for typical HP turbine blade tip configurations. An extensively developed RANS code (HYDRA) is employed and validated against the experimental data from a high speed linear cascade testing rig. The numerical analysis reveals that the wall-gas temperature ratio could greatly affect the transonic OTL flow field and there is a strong two-way coupling between aerodynamics and heat transfer. The feedbacks of the thermal boundary condition to aerodynamics behave differently at different flow regimes over the tip, clearly indicating a highly localized dependence of the convective heat transfer coefficient (HTC) upon wall temperatures. This implies that to use HTC for blade metal temperature predictions without resorting a fully conjugate solution, the temperature dependence needs to be corrected locally. A nonlinear correction approach has been adopted in the present work, and the results demonstrate its effectiveness for the transonic turbine tip configurations studied.