bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Cyclic Loading and Temperature on Integrity of Piezoceramic Patch Transducers
Authors: Gall Monika , Thielicke Ba¨rbel
Published: July 2009

In this study the loading limits, damage behavior and long-term integrity of piezoceramic patch transducers, based on monolithic PZT wafers (PIC 255) were investigated. The presented results involve quasi-static and long-term cyclic testing under tensile as well as compressive mechanical loading of the patches, under varied temperatures. Also long-term cyclic electric activation was investigated. A strain-cycle life-span diagram was established for tensile loading at room temperature (RT), +60 °C, +100 °C and −40 °C. In all cases cracking in the PZT ceramic was found to be the relevant failure mechanism which could be correlated to the observed degradation of the patches’ sensor performance. Preliminary investigations with fracture mechanics methods were carried out on the specimen with fractured PZT wafers. No mechanical damage was found under compressive loading at strain levels of up to −0.6%. Finite element analyses were performed using 3D material modeling with electromechanical coupling behavior, achieving very good predictability of the sensor and actuator performance. Analytical calculations and numerical simulation were used to interpret experimental findings and also allow the transfer of results to various applications.
Multi-Objective Optimization of Piezoelectric Actuator Placement for Shape Control of Plate Using Genetic Algorithms
Authors: Kudikala Rajesh , Kalyanmoy Deb , Bhattacharya Bishakh
Published: July 2009

Shape control of adaptive structures using piezoelectric actuators has found a wide range of applications in recent years. In this paper, the problem of finding optimal distribution of piezoelectric actuators and corresponding actuation voltages for static shape control of a plate is formulated as a multi objective optimization problem. Two conflicting objectives: minimization of input control energy and minimization of mean square deviation between the desired and actuated shapes are considered with constraints on maximum number of actuators and maximum induced stresses. A shear lag model of the smart plate structure is created and the optimization problem is solved using an evolutionary multi-objective optimization (EMO) algorithm NSGA-II. Pareto-optimal solutions are obtained for different case studies. Further, the obtained solutions are verified by comparing with single-objective optimization solutions.
Embedded Optical Sensor for Oil Film Pressure Measurements in Journal Bearings
Authors: Ronkainen Helena , Valkonen Antti , Kapulainen Markku , Simo Varjus , Hokkanen Ari , Stuns Ingmar , Virtanen Juha , Martikainen Juhani
Published: July 2009

The oil film pressure is one of the essential functional parameters in journal bearings. Until now, the oil film pressure has been estimated by theoretical calculations, since the measurement of oil film pressure has been a demanding or even unfeasible task in journal bearings, especially in bearings carrying dynamic loads. In this study a new approach has been developed for experimental determination of the oil film pressure. The sensor design utilizes the optical fibre technique and the sensor is integrated in the sliding surface of the bearing thus providing the possibility to measure the actual oil film pressure under load. The finite element method (FEM) calculations have been used for optimizing the design of the sensor and for ensuring the appropriate mechanical performance of the sensor design. The optical sensor was integrated in a hydrodynamic journal bearing made of bronze. A versatile bearing test rig was used for testing the journal bearing with integrated optical sensor. The tests were carried out with both static and dynamic loading. The oil film pressure was measured with different loads and speeds and the data was compared with simulated one. The results showed that the optical sensor was capable to measure the oil film pressure in journal bearing at real operating conditions and the sensitivity of the sensor was good enough to verify the speed and load effects on pressure. According to this work, it is possible to increase the knowledge of true operating conditions of journal bearings by using the optical sensor for oil film pressure measurement. The knowledge can be utilized in the development work of safer and more efficient machines and engines with journal bearings carrying high and dynamic loads. The optical sensor can be used also in other applications for smart control of pressure.
A Multiphysics Micromechanics Model of Smart Materials Using the Variational Asymptotic Method
Authors: Tang Tian , Yu Wenbin
Published: July 2009

The primary objective of the present paper is to develop a micromechanics model for the prediction of the effective properties and the distribution of local fields of smart materials which are responsive to fully coupled electric, magnetic, thermal and mechanical fields. This work is based on the framework of the variational asymptotic method for unit cell homogenization (VAMUCH), a recently developed micromechanics modeling scheme. For practicle use of this theory, we implement this new model using the finite element method into the computer program VAMUCH. For validation, several examples will be presented in the full paper to compare with existing models and demonstrate the application and advantages of the new model.
Morphing Laminar Wing With Flexible Extrados Powered by Shape Memory Alloy Actuators
Authors: Brailovski Vladimir , Terriault Patrick , Coutu Daniel , Georges Thomas , Morellon Emeric , Fischer Charles , Be´rube´ Se´bastien
Published: July 2009

An active structure of a morphing wing designed for subsonic cruise flight conditions combines three principal subsystems: (1) flexible extrados, (2) rigid intrados and (3) an actuator group located inside the wing box. A structural model of the flexible extrados built with ANSYS finite element software is coupled with X’Foil fluid dynamics software to evaluate mechanical and aerodynamic performances of the morphing wing in different flight conditions. Using the multicriteria optimization technique, an active structure consisting of the 4-ply laminated composite flexible extrados powered by two individually controlled actuators is selected. Shape memory alloy (SMA) actuators are designed as power elements for the morphing wing. To meet the functional requirements of the application, the geometry of the SMA elements is calculated using the results of the constrained recovery testing of the selected material.
Analyzing Carbohydrate-Based Regenerative Fuel Cells as a Power Source for Unmanned Aerial Vehicles
Authors: Wojnar Olek , Swenson Eric D. , Reich Gregory W.
Published: July 2009

Based on current capabilities, we examine the feasibility of creating a carbohydrate-based regenerative fuel cell (CRFC) as the primary power source for unmanned aerial vehicles (UAV) for long endurance missions where station keeping is required. The CRFC power system evaluated in this research is based on a closed-loop construct where carbohydrates are generated from zooxanthellae, algae which create excess carbohydrates during photosynthesis. The carbohydrates are then fed to a carbohydrate fuel cell where electric power is generated for the UAV’s propulsion, flight control, payload, and accessory systems. The waste products from the fuel cell, carbon dioxide and water, are used by the zooxanthellae to create more carbohydrates, therefore mass is conserved in the process of power generation. The overall goal of this research is to examine the potential of CRFCs as a viable power source for UAV systems, to look at scaling issues related to different vehicle sizes and missions, and to identify sensitivities in the CRFC system to different system parameters, indicating the areas where technology improvements may make CRFCs a viable technology. Through simulations, a UAV is sized to determine if greater than 24 hour endurance flight is possible and these results are compared to UAVs using more traditional photo-cell based power systems. The initial results suggest that CRFCs have potential as a power system for long endurance UAVs, and could offer significant improvements to the overall system performance. The final outcome of this research is to identify the most important areas for more detailed follow-on work in designing a production-ready CRFC power system for long endurance UAVs.
On Phase Field Modeling of Ferroelectrics: Parameter Identification and Verification
Authors: Schrade David , Xu Bai-Xiang , Mu¨ller Ralf , Gross Dietmar
Published: July 2009

This contribution introduces a thermodynamically consistent, fully electro-mechanically coupled micro-mechanical model for ferroelectric materials. Adopting a phase field concept, in which the spontaneous polarization is used as order parameter, a Ginzburg-Landau type theory is formulated for the evolution of the order parameter. The equations are discretized within the scope of the Finite Element Method, and implicit time integration is used to solve the non-linear evolution equation. Examples illustrate the physical meaning of phase field parameters and give an application to multi-axial switching in which experimental results are used for comparison.
Towards Functionally Graded Cellular Microstructures
Authors: Corney J. R. , Torres-Sanchez C.
Published: July 2009

Many materials require functionally graded cellular microstructures whose porosity (i.e. ratio of the void to solid volume of a material) is engineered to meet specific requirements. Indeed numerous applications have demonstrated the engineering potential of porous materials (e.g. polymeric foams) in areas ranging from biomaterial science through to structural engineering. Although a huge variety of foams can be manufactured with homogenous porosity, for heterogeneous foams there are no generic processes for controlling the distribution of porosity throughout the resulting matrix. Motivated by the desire to create a flexible process for engineering heterogeneous foams, this paper reports how ultrasound, applied during some of the foaming stages of a polyurethane (PU) melt, affects both the cellular structure and distribution of the pore size. The experimental results allowed an empirical understanding of how the parameters of ultrasound exposure (i.e. frequency and acoustic pressure) influenced the volume and distribution of pores within the final polyurethane matrix: the data demonstrates that porosity (i.e. volume fraction) varies in direct proportion to the acoustic pressure magnitude of the ultrasound signal. The effects of ultrasound on porosity demonstrated by this work offer the prospect of a manufacturing process that can adjust the cellular geometry of foam and hence ensure that the resulting characteristics match the functional requirements.
Self-Assembled Highly Tunable Magnetoelectric
Authors: Ren Shenqiang , Wuttig Manfred
Published: July 2009

A magnetoelectric (ME) composite with controlled nanostructures is synthesized using co-assembly of two inorganic precursors with a block copolymer. This solution processed material consists of hexagonally arranged ferromagnetic cobalt ferrite [CoFe2O4, CFO] nano-cylinders within a matrix of ferroelectric lead zirconium titanate [Pb1.1(Zr0.53Ti0.47)O3, PZT] when thin films were prepared by spin coating. The initial magnetic permeability of the self-assembled CFO/PZT nano-composite changes by a factor of five through the application of 2.5 V.
Active Vibration Control and Isolation for Micro-Machined Devices
Authors: Kim Seong Jin , Chen Chen , Flowers George , Dean Robert
Published: July 2009

Some harsh environments contain high frequency, high amplitude mechanical vibrations. Unfortunately some very useful components, such as MEMS gyroscopes, can be very sensitive to these high frequency mechanical vibrations. Passive micromachined silicon lowpass filter structures (spring-mass-damper) have been demonstrated in recent years. However, the performance of these filter structures is typically limited by low damping. This is especially true if operated in low pressure environments, which is often the optimal operating environment for the attached device that requires vibration isolation. An active micromachined vibration isolator can be realized by combining a state sensor, and electrostatic actuator and feedback electronics with the passive isolator. Using this approach, a prototype active micromachined vibration isolator is realized and used to decrease the filter Q from approximately 135 to approximately 60, when evaluated in a low pressure environment. The physical size of these active isolators is suitable for use in or as packaging for sensitive electronic and MEMS devices, such as MEMS vibratory gyros.
Synthesis and Electromechanical Characterization of Polypyrrole Bi-Layer Thin Porous Films
Authors: Chan Christine , Wu Alan , Naguib Hani
Published: July 2009

This paper investigated the physical and electromechanical properties of polypyrrole thin films that were prepared using electrochemical synthesis techniques. The morphology, mass, and thickness of the as-made films were examined when the processing parameters were varied in terms of synthesis voltage, deposition time, and polarization time. Upon actuation of the polypyrrole bi-layer, there were similar trends for both morphology and bending displacement with varying deposition and polarization times as well as actuation voltages. A general relationship between morphology and bending displacement was observed when the processing parameters were varied.
Acoustic Sensor With PVDF Micro-Pillars and Patterned Electrodes
Authors: Xu Jian , Dapino Marcelo J. , Gallego Perez Daniel , Hansford Derek
Published: July 2009

This paper addresses the design and theoretical analysis of a new type of millimeter-size acoustic sensor that uses Polyvinylidene Fluoride (PVDF) micro-pillars and patterned electrodes. The sensor has the potential to achieve 100x the sensitivity of existing commercial sensors in combination with a dynamic range of 181dB and a frequency bandwidth of at least 100 kHz. A constrained optimization algorithm has been developed as a function of geometric parameters (sensor footprint, diameter and height of the micro-pillars, gap between pillar edges, number of pillars) and electrical parameters of the sensor and conditioning amplifier.
A New Fabrication Method for a Curved Shape Piezoelectric Unimorph Actuator
Authors: Kang Lae-Hyong , Lee Jong-Won , Han Jae-Hung , Chung Sang-Joon , Ko Han-Young
Published: July 2009

This paper proposes a new fabrication method for a curved shape piezoelectric actuator. Instead of using thermal coefficient mismatch, which has been used for conventional processes for curved shape actuators, we used pre-stressed substrates and the room temperature adhesion process. First, a substrate material is strained in the longitudinal direction, and then a piezoelectric material is attached on the substrate. A difference of the mechanical strains between the substrate and the piezoelectric layer makes the final manufactured actuator get curved. Using this method, the curved shape actuator can be easily fabricated at room temperature. Several performance tests of the proposed unimorph actuators were accomplished and the test results showed the proposed actuator got comparable actuation capability compared with conventional curved shape actuators.
Measurement of the Thermal Expansion for Space Structures Using Fiber Bragg Grating Sensors and Displacement Measuring Interferometers
Authors: Kim Hong-Il , Kang Lae-Hyong , Han Jae-Hung
Published: July 2009

Dimensional stability of the space structures, such as large telescope mirrors or metering substructures, is very important because even extremely small deformations of these structures might degrade the optical performances. Therefore, precise deformation data of the space structures according to environment change are required to design these structures correctly. Also, real-time deformation monitoring of these structures in space environment is demanded to verify whether these structures are properly designed or manufactured. FBG (fiber Bragg grating) sensors are applicable to real time monitoring of the space structure because they can be embedded onto the structures with minimal weight penalty. In this research, therefore, thermal deformation measurement system for the space structures, composed of FBG sensors for real time strain measurement and DMI (displacement measuring interferometers) for accurate specimen expansion data acquisition, is developed. Thermal strains measured by distributed FBG sensors are evaluated by the comparison with the strains obtained by highly accurate DMI.
Novel Phase-Field Simulation of Microstructure in Martensitic Materials
Authors: Shu Y. C. , Yen J. H.
Published: July 2009

A novel phase-field model of martensite suitable for microstructure simulation is developed here. It is motivated by the hierarchical structure of multirank laminates for establishing the rule of mixtures. As a result, a different choice of field variables, local volume fraction of laminates, is introduced to represent each martensitic variant. It provides an advantage of expressing the energy-well structure of martensitic variants in a unified fashion, instead of choosing the special polynomial expansions of conventional order parameters for a particular transformation. In addition, only two parameters are needed for microsturcture simulation. One is related to the energetic cost due to formation of the interface, and the other is the cost due to the deviation from the ground state energy. The framework is applied to the investigation of optimal microstructures for achieving large actuation strains for dome-shaped and tunnel-shaped microactuators. Finally, the framework is extended to ferroelectric domain simulation. Two cases are discussed: one is for the constrained modeling which restricts polarization remaining on the ground state, and the other is for the unconstrained modeling which allows polarization deviating from the ground state.
A Semi-Active Magnetorheological Fluid Snubber Lag Damper for a Hingeless/Bearingless Helicopter
Authors: Ngatu Grum T. , Hu Wei , Kothera Curt S. , Wereley Norman M.
Published: July 2009

A magnetorheolocial fluid elastomeric (snubber) lag damper is developed to provide adaptive lead-lag damping augmentation for a hingeless helicopter rotor. The MR fluid elastomeric (MRFE) lag damper consists of a flow valve, a flexible snubber body, and a flexible center wall separating the body into two fluid chambers. MR fluid enclosed in the snubber body can flow through the valve and be activated by a magnetic field in the valve. Consistent with the loading conditions for a helicopter lag damper, the MRFE damper is tested under single frequency (lag/rev) sinusoidal excitation. The complex modulus method was used to compare the MRFE damper damping characteristics with a baseline passive snubber type Fluidlastic® damper. The field-off damping of MRFE damper is smaller than the baseline damper. A significant controllable damping range is also observed as current was applied to a magnetic valve in the MRFE damper. Furthermore, the non-linear behavior of the MRFE damper is not sufficiently modeled using the complex modulus method. Thus, to account for the hysteresis behavior of the MRFE damper and estimate the damping force, a hydro-mechanical model is formulated based on lumped parameters. Parameters for the model are established using experimental data and a least-mean-square error minimization technique. The model is then applied to reconstruct the force time history under lag/rev excitation frequency. The average error between the predicted and measured damping forces is also evaluated to assess model accuracy.
Technology Integration for Active Poly-Morphing Winglets Development
Authors: Ursache Narcis M. , Melin Tomas , Isikveren Askin T. , Friswell Michael I.
Published: July 2009

This article presents the preparation of a working physical mock-up wingtip device with morphing functionality. The objective of the mechanical demonstrator is to achieve a technology readiness level to establish confidence that one would proceed to an in-service R&D initiative. To establish the feasibility of scalable technology integration for product development, a tier schedule is employed to demonstrate material compliance, mechanism kinematics and perform bandwidth experimentation. Potential composite materials for design of flexible skins (i.e., Hexweb®, Kevlar® 49 and HexPly®) were assessed using a spectrum of experimental verification procedures. These results are embodied to benchmark qualitatively and quantitatively the mechanical performance of the potential materials to use in a preliminary optimized morphing schedule.
Design and Testing of a Piezoelectrically Driven Airspike System on a .40 Cal Supersonic Projectile
Authors: Long Robert W.
Published: July 2009

This paper investigates the feasibility of using a piezoelectrically driven airspike system as a method of flight control on .40 caliber supersonic projectiles. The paper begins with a description of airspikes and a summary of their history in missiles and munitions. The paper then describes the piezoelectric actuation system and models its unloaded characteristics using bending beam theory. When the airspike is deflected, the axial force acting upon the airspike is shifted so that it no longer goes through the center of gravity and creates a pitching moment. This allows the bullet to create a pitching moment which can control the projectile. A basic aerodynamic analysis was done on the projectile, and subsequent wind tunnel tests through Mach 2.5 were done to prove this data. Bench top tests were also done on the system to determine the relationship of voltage to deflection of the airspike. The paper also includes considerations for setback, setforward and balloting. The paper includes a finite element analysis for the setback acceleration. The paper concludes with a system design of a beam rider projectile and simulates the trajectory of the projectile.
Development of Two Part Porous Shape Memory Polymer Nanocomposites
Authors: Simkevitz S. , Naguib H. E.
Published: July 2009

The porous structure and shape memory effect (SME) were studied for shape memory polymer (SMP) and SMP nanocomposites. In order to alter the density of the SMP, a batch processing technique was utilized on the creation of porous structure, where the saturation pressure and foaming time were varied and saturation time and foaming temperature were kept constant. The change in density on the time response of the SME was investigated. Also the effects of the change in density and thickness or the addition of organoclay on the recovery force of the SMP were elucidated. With the objective of designing an SMP to be used as an actuator, response time, recovery force and weight savings were found to be critical parameters.
Continuous Carbon Nanotube-PDMS Composites
Authors: Suhr Jonghwan , Ci Lijie , Jang Jae-Soon , Pushparaj Victor , Ajayan Pulickel M.
Published: July 2009

Carbon nanotubes are considered short fibers and the nanotube reinforced composites are always analogues of randomly distributed short fiber composites. In contrast, the real structural fibrous composites often contain fiber reinforcements where fibers run continuously through the matrix material. With the recent advance in nanotube growth, vertical arrays of nanotubes in macroscopic lengths have become available and this allows the fabrication of continuous nano-composites that are similar to the continuous fiber composites utilizing the nanotube arrays as the continuous reinforcement in the composites. This provides a chance to take full advantage of the extreme high modulus and strength for the nanotubes in structural composites. Here, this study fabricates continuous nanotube reinforced polydimethylsiloxane (PDMS) composites and shows that under compressive loadings such continuous nanotube composites can generate dramatic increase in the longitudinal modulus and also significantly enhanced damping capability.
Low-Power Switching Control Schemes for Piezoelectric Micro-Robotic Actuators
Authors: Oldham Kenn , Hahn Bongsu , Edamana Biju , Polcawich Ronald , Pulskamp Jeffrey
Published: July 2009

This article describes the development of piezoelectric micro-actuators for use in micro-robotic systems, and surveys controllers and power electronics for such actuators to meet power limitations of terrestrial micro-robots with high mobility. A thin-film lead-zirconate-titanate lateral actuator design with one micron stroke and several millinewtons of actuation force is described, and sample experimental results provided. A method for integrating these actuators with flexible silicon micro-structures, and implications for micro-robotic pay-load capacity are presented. On-off control is proposed as a method to minimize energy usage by piezoelectric actuators and driving circuitry when moving a micro-robotic appendage based on these designs. Low efficiency of voltage converters and large power consumption of sensing circuitry are identified as barriers to further enhancing servo capabilities of bio-inspired terrestrial micro-robots.
Ionomer Design for Augmented Charge Transport in Novel Ionic Polymer Transducers
Authors: Duncan Andrew J. , Leo Donald J. , Long Timothy E. , Akle Barbar J. , Sarles Stephen A.
Published: July 2009

Ionic polymer transducers (IPT) are devices that display electromechanical transduction and have been applied extensively both as actuators and sensors. This study employs novel, highly-branched sulfonated polysulfones to investigate the contribution of polymer topology to electromechanical transduction. We assess two methods for ionic liquid uptake in the central ionomeric membrane. The effects of casting membranes in the presence of ionic liquid and swelling cast membranes in ionic liquid on film stability and ionic conductivity are examined. Casting in the presence of ionic liquid appears to cause macrophase separation of the ionic liquid from the polymer, causing limited charge transport. Overall, swelling appears to be a more stable method and achieves higher conductivity at lower uptake levels.
Optimal Design of Piezoelectric Energy Harvesters Based on Multilayer Plates and Shells
Authors: Rupp Cory J. , Evgrafov Anton , Maute K. , Dunn Martin L.
Published: July 2009

We describe and demonstrate a computational approach to analyze and design piezoelectric energy harvesting systems composed of layered plate and shell-like structures with an external harvesting circuit. We model the coupled dynamic electromechanics of a piezoelectric harvester as well as the dynamics of an electrical circuit that is connected to the harvester with the finite element method. We assume the harvester is subjected to a prescribed harmonic excitation that may have broadband frequency content. Our design approach uses topology optimization to optimally design a piezoelectric harvester by tailoring the layout of a multilayer structure consisting of structural layers, piezoelectric layers, electrodes, as well as the electrical circuit parameters. We admit the spatially tailoring of these items both in the plane and through the thickness of the multilayer plate and shell. After a description of our analysis and design approaches, we present a number of examples that demonstrate some of the capabilities of our approach and show how it can be used to explore general behavior and develop overarching principles through the study of a suite of particular problems.
Photomechanics of Light-Activated Shape Memory Polymers
Authors: Long Kevin N. , Scott Timothy F. , Qi H. Jerry , Dunn Martin L.
Published: July 2009

Photomechanical shape memory polymers are an exciting class of materials that are able to store a temporary shape and recover their original shape when stimulated by light. In this work we develop a model to simulate the photomechanical behavior of light-activated shape memory polymers. To the best of our knowledge this is the first theoretical model developed to describe this exciting class of active materials. Our model incorporates the interplay among four aspects of the underlying physical phenomena: light propagation, photo-chemistry, chemical-mechanical coupling, and mechanical response. The model framework is applied to a recently developed photo-induced shape memory polymer system [1, 2]. We describe a suite of experiments used to guide the modeling efforts, calibrate the model parameters, and then validate model predictions. Regarding the latter, we measure and then simulate the photo-induced bending behavior of shape memory polymer samples; model predictions are in good agreement with measurements. We use the model to then explore the effect of important photomechanical parameters (applied strain magnitude, irradiation time and intensity, and photoabsorber concentration) on material response with a view toward the design of novel actuator materials and structures.
Electrical Properties of Magneto-Rheological Elastomers
Authors: Wang Xiaojie , Gordaninejad Faramarz , Calgar Mert , Liu Yanming , Sutrisno Joko , Fuchs Alan
Published: July 2009

A magnetorheological elastomer (MRE) is comprised of ferromagnetic particles aligned in a polymer medium by exposure to a magnetic field. The structures of the magnetic particles within elastomers are very sensitive to the external stimulus of either mechanical force or magnetic field, which result in multi-response behaviors in MRE. In this study, sensing properties of MREs through experimentally characterizing the electrical properties of materials and theirs interfaces with external stimulus (magnetic field or stress/strain) are investigated. A phenomenological model is proposed to model the impedance response of MREs. Results show that MRE samples exhibit significant changes in measured values of impedance and resistance in response to compressive deformation, as well as applied magnetic field.
Rotary MR Actuators for Automotive Comfort Functionalities
Authors: Wiehe A. , Aust M. , Maas J.
Published: July 2009

Improvement of comfort functionalities is an important distinguishing mark for competitiveness of automotive manufactures. The utilization of rotary MR actuators offers several new comfort functionalities. As an example an entry assist function is described in the following, where a rotary MR actuator is used for motion control of vehicle doors. Another possible application is force feedback generation for a steer-by-wire system. Furthermore a modeling method for eddy current phenomena is proposed, which can be used for optimizing the response time of MR actuators.
High Temperature Thermoelectric Auxiliary Power Unit for Automotive Applications
Authors: Headings Leon M. , Midlam-Mohler Shawn , Washington Gregory N. , Heremans Joseph P.
Published: July 2009

While the thermoelectric effects have been known for over 100 years, their traditionally low conversion efficiency for power generation has limited their use to highly specialized applications. With the rapid advancement of thermoelectric materials in recent years, their inherent reliability and power density is being augmented by improvements in efficiency. Recent increases in the figure of merit of materials suitable for operation around 500 °C make them candidates for waste heat recovery, as well as primary power using combustion heaters. The characteristic scalability of thermoelectric generators makes them best suited for low power applications where alternative generators become impractical. However, with the development of thermoelectric device technology in parallel with materials advancements, it may become viable to design thermoelectric generators for auxiliary power in automotive applications. The research presented here represents the initial stages of the development of a thermoelectric power unit (TEPU). While thermoelectric generator technology can be applied to any fuel, this research targets the use of diesel fuel which is readily available for both military and consumer applications and is more easily and safely transported than many alternatives. The use of diesel fuel for a TEPU is enabled by the use of an atomizer technology developed at The Ohio State University Center for Automotive Research. A baseline prototype incorporating this novel diesel fuel atomizer/combustor with conventional thermoelectric materials and heat exchange designs has been constructed and tested. Preliminary data highlights the viability of diesel fuel for thermoelectric power generation as well as the areas which demand further development. This prototype will serve as the baseline for evaluating future designs incorporating advanced materials and novel system designs.
Characterization and Modeling of Dynamic Sensing Behavior in Ferromagnetic Shape Memory Alloys
Authors: Sarawate Neelesh , Dapino Marcelo
Published: July 2009

This paper is focused on the characterization and modeling of a commercial Ni-Mn-Ga alloy for use as a dynamic deformation sensor. The flux density is experimentally determined as a function of cyclic strain loading at frequencies from 0.2 Hz to 160 Hz. With increasing frequency, the stress-strain response remains almost unchanged whereas the flux density-strain response shows increasing hysteresis. This behavior indicates that twin-variant reorientation occurs in concert with the mechanical loading, whereas the rotation of magnetization vectors occurs with a delay as the loading frequency increases. The increasing hysteresis in magnetization must be considered when utilizing the material in dynamic sensing applications. A modeling strategy is developed which incorporates magnetic diffusion and a linear constitutive equation.
Pre-Target Axon Sorting Establishes the Neural Map Topography
Authors: Imai Takeshi , Yamazaki Takahiro , Kobayakawa Reiko , Kobayakawa Ko , Abe Takaya , Suzuki Misao , Sakano Hitoshi
Published: July 2009

Mapping the Neuronal Map

In vertebrates, sensory information is topographically represented as a neural map in the brain. How is the neural map formed in the brain? Nearly a half-century ago, Roger Sperry proposed the “chemoaffinity” model, in which the positional cues on the target determine the axonal projection site, thereby establishing the topographic neural map. However, molecular mechanisms of topographic map formation remain controversial.

Imai
et al.

(p.
585
, published online 9 July; see the Perspective by

Miyamichi and Luo

) now report that the topographic map is formed by axon-axon interactions before the axons reach the target. In the mouse olfactory system, the topography of the map is determined by the relative expression levels of a guidance receptor, Neuropilin-1, and its repulsive ligand, Semaphorin-3A, expressed in axons. Topographic organization occurs even in the absence of the target, the olfactory bulb. These findings require that Sperry's model, which suggests that only the targets determine the topography of neural maps, needs to be reconsidered.
Addition of lithiated methoxyallene to aziridines – a novel access to enantiopure piperidine and β-amino acid derivatives
Authors: Prisyazhnyuk Vladimir , Jachan Matthias , Brüdgam Irene , Zimmer Reinhold , Reissig Hans-Ulrich
Published: July 2009

Addition of lithiated methoxyallene to aziridine derivatives provided the expected primary addition products. The less substituted carbon of the aziridine ring was attacked selectively. The primary adducts could be converted to enantiopure piperidine derivatives or β-amino acid derivatives. The unexpected reactions lead to a tricyclic sulfonamide and to alkynyl-substituted aminoethers. The efficient two-step conversion of a piperidone derivative to a benzomorphan demonstrates the potential of this approach to biologically active compounds.
WELL-POSEDNESS FOR THE EULER–NORDSTRÖM SYSTEM WITH COSMOLOGICAL CONSTANT
Authors: SPECK JARED
Published: July 2009

In this paper, the author considers the motion of a relativistic perfect fluid with self-interaction mediated by Nordström's scalar theory of gravity. The evolution of the fluid is determined by a quasilinear hyperbolic system of PDEs, and a cosmological constant is introduced in order to ensure the existence of nonzero constant solutions. Accordingly, the initial value problem for a compact perturbation of an infinitely extended quiet fluid is studied. Although the system is neither symmetric hyperbolic nor strictly hyperbolic, Christodoulou's constructive results on the existence of energy currents for equations derivable from a Lagrangian can be adapted to provide energy currents that can be used in place of the standard energy principle available for first-order symmetric hyperbolic systems. After providing such energy currents, the author uses them to prove that the Euler–Nordström system with a cosmological constant is well-posed in a suitable Sobolev space.
Sediment-hosted gas hydrates: new insights on natural and synthetic systems
Authors: Long D. , Lovell M. A. , Rees J. G. , Rochelle C. A.
Published: July 2009

In the public's imagination, hydrates are seen as either a potential new source of energy to be exploited as the world uses up its reserves of oil and gas or as a major environmental hazard. Scientists, however, have expressed great uncertainty as to the global volume of hydrates and have reached little agreement on how they might be exploited. Both of these uncertainties can be reduced by a better understanding of how hydrates are held within sediments. There are conflicting ideas as to whether hydrates are disseminated within selected lithologies or trapped within fractures comparable to mineral lodes. To resolve this, hydrates have to be examined at all scales ranging from using seismics to microscopic studies. Their position within sediments also influences the stability of methane hydrate in responding to pressure and temperature and how the released gas might transfer to the ocean, atmosphere, or to a transport mechanism for recovery. These results also run parallel with the studies of carbon dioxide hydrate, which is being considered as a potential sequestion medium.
Gas hydrate crystallite size investigations with high-energy synchrotron radiation
Authors: Klapp S. A. , Klein H. , Kuhs W. F.
Published: July 2009

The grain sizes of gas hydrate crystallites are largely unknown in natural samples. Single grains are hardly detectable with electron or optical microscopy. For the first time, we have used high-energy synchrotron diffraction to determine grain sizes of six natural gas hydrates retrieved from the Bush Hill region in the Gulf of Mexico and from ODP Leg 204 at the Hydrate Ridge offshore Oregon from varying depth between 1 and 101 metres below seafloor. High-energy synchrotron radiation provides high photon fluxes as well as high penetration depth and thus allows for investigation of bulk sediment samples. Gas hydrate grain sizes were measured at the Beam Line BW 5 at the HASYLAB/Hamburg. A ‘moving area detector method’, originally developed for material science applications, was used to obtain both spatial and orientation information about gas hydrate grains within the sample. The gas hydrate crystal sizes appeared to be (log-)normally distributed in the natural samples. All mean grain sizes lay in the range from 300 to 600 µm with a tendency for bigger grains to occur in greater depth. Laboratory-produced methane hydrate, aged for 3 weeks, showed half a log-normal curve with a mean grain size value of
c
. 40 µm. The grains appeared to be globular shaped.
Exploration strategy for economically significant accumulations of marine gas hydrate
Authors: Kleinberg R. L.
Published: July 2009

There are at present no validated methods for reliably finding economically significant accumulations of natural gas hydrate in marine environments. The seismic bottom simulating reflector (BSR) has been regarded as a primary indicator of hydrate presence in marine environments, but the presence of a BSR conveys no information about the abundance of hydrate in the sediments above it. Seafloor features such as gas seeps, pockmarks or hydrate outcrops may be qualitative markers of deeper hydrate presence, but cannot be interpreted quantitatively. Another approach to exploration geophysics is required to find exploitable gas hydrate reservoirs with high reliability. It is known that in many cases gas is supplied to the gas hydrate stability zone primarily through faults or fractures. In a certain range of gas flux, these fissures should become mineralized with gas hydrate and form vertical or subvertical dykes. The dip and strike of these dykes are controlled by the principal stress directions, which can be predetermined. Thus multiple hydrate dykes are expected to be parallel. Even if the greatest volume of gas hydrate is to be found in sub-horizontal permeable beds, the steeply dipping mineralized conduits that fed gas to them may be the most reliable marker of substantial subsurface hydrate presence. Geological and geophysical survey methods sensitive to parallel arrays of vertical and subvertical hydrate dykes are presented.
Gas hydrate forming fluids on the NE Sakhalin slope, Sea of Okhotsk
Authors: Mazurenko L. L. , Matveeva T. V. , Prasolov E. M. , Shoji H. , Obzhirov A. I. , Jin Y. K. , Poort J. , Logvina E. A. , Minami H. , Sakagami H. , Hachikubo A. , Salomatin A. S. , Salyuk A. N. , Prilepskiy E. B. ,   CHAOS 2003 Scientific Team
Published: July 2009

An area of focused fluid venting off NE Sakhalin, Sea of Okhotsk, was investigated in 2003 during the 31st and 32nd international expeditions of R/V
Akademik M. A. Lavrentyev
within the framework of the CHAOS Project. More than 40 structures related to seafloor gas venting were discovered and gas hydrates were sampled from three of these: CHAOS, Hieroglyph and Kitami. Geochemical analyses were used to define the mechanisms of gas hydrate accumulation and the sources of fluids involved. Chemical and isotopic analyses of the interstitial and hydrate waters suggest that hydrates were formed from seawater (or
in-situ
pore water) and an ascending fluid enriched in salts. Hydrate formation occurs at locations of the most intensive saline water upflow, and this is probably a function of the gas solubility in water in equilibrium with hydrate. The water involved in gas hydrate formation consists of about 70% pore water derived from the host sediment and 30% from the ascending fluid. The overall isotopic composition of the ‘fluid’ taking part in hydrate formation was calculated as
δ
2
H≈−11‰ and δ
18
O≈−1.5‰.
Mapping hydrate stability zones offshore Scotland
Authors: Camps A. P. , Long D. , Rochelle C. A. , Lovell M. A.
Published: July 2009

One practical method to reduce environmentally damaging greenhouse gas emissions is through the geological storage of carbon dioxide. Deep, warm storage of carbon dioxide is currently taking place at Sleipner, North Sea and Weyburn, Canada. It is, however, also possible to store carbon dioxide as a liquid and hydrate in cool, sub-seabed sediments. Offshore north and west of Scotland seafloor pressures and temperatures are suitable for hydrate formation. In addition to the possibility of natural methane hydrate being present in this region, conditions may also be favourable for carbon dioxide storage as a liquid and hydrate. A computer program has been developed to calculate the depth to the base of the carbon dioxide and methane hydrate stability zones in two offshore regions: the Faeroe–Shetland Channel and the northern Rockall Trough. Results predict that methane hydrate remains stable to a maximum depth of 650 m below the seabed in the Faeroe–Shetland Channel, and 600 m below the seabed in the northern Rockall Trough; the carbon dioxide hydrate stability zone extends below the seabed to a depth of 345 and 280 m, respectively. No physical evidence for the existence of natural hydrate in these regions has been confirmed. Suitable conditions for carbon dioxide storage as a liquid and hydrate exist, and should this storage method be developed further, a more refined program and greater offshore investigations to improve data sets would be necessary to scope the full potential.
Regional versus detailed velocity analysis to quantify hydrate and free gas in marine sediments: the South Shetland Margin case study
Authors: Tinivella Umberta , Loreto Maria Filomena , Accaino Flavio
Published: July 2009

The presence of gas hydrate and free gas within marine sediments deposited along the South Shetland margin, offshore the Antarctic Peninsula, was confirmed by low and high resolution geophysical data, acquired during three research cruises. Seismic data analysis has revealed the presence of a bottom-simulating reflector that is very strong and continuous in the eastern part of the margin. This area can be considered as a useful site to study the seismic characteristics of sediments containing gas hydrate, with a particular focus on the estimation of gas hydrate and free gas amounts in the pore space. Pre-stack depth migration and tomographic inversion were performed to produce a regional velocity field of gas-phase bearing sediments and to obtain information about the average thickness of gas hydrate and free gas layers. Using these data and theoretical models, the gas hydrate and free gas concentrations can be estimated. Moreover, the common image gather semblance analysis revealed the presence of detailed features, such as layers with small thickness characterized by low velocity alternating with high velocity layers, below and above the bottom-simulating reflector. These layers are associated with free gas trapped within the hydrate stability zone and deeper sediments. Thus, the use of the detailed and the regional velocity field analysis is important to give a more reliable estimate of gas content in the marine sediments.
Hypothermia Therapy for Brain Injury
Authors: Diller Kenneth R. , Zhu Liang
Published: July 2009

Induced hypothermia is an acknowledged useful therapy for treating conditions that lead to cell and tissue damage caused by ischemia, including traumatic brain injury, stroke, and cardiac arrest. An accumulating body of clinical evidence, together with several decades of research, has documented that the efficacy of hypothermia is dependent on achieving a reduced temperature in the target tissue before or soon following the ischemia-precipitating event. The temperature must be lowered to within a rather small range of values to effect therapeutic benefit without introducing collateral problems. Rewarming must be much slower than cooling. Many different methods and devices have been used for cooling, with mixed results. There are existing opportunities for bioengineers to improve our understanding of the mechanisms of hypothermia and to develop more effective methods of cooling the brain following trauma.
Fluorescent Probes for Live-Cell RNA Detection
Authors: Bao Gang , Rhee Won Jong , Tsourkas Andrew
Published: July 2009

Commonly used techniques for analyzing gene expression, such as polymerase chain reaction (PCR), microarrays, and in situ hybridization, have proven invaluable in understanding RNA processing and regulation. However, these techniques rely on the use of lysed and/or fixed cells and are therefore limited in their ability to provide important spatial-temporal information. This has led to the development of numerous techniques for imaging RNA in living cells, some of which have already provided important insight into the dynamic role RNA plays in dictating cell behavior. Here we review the fluorescent probes that have allowed for RNA imaging in living cells and discuss their utility and limitations. Common challenges faced by fluorescent probes, such as probe design, delivery, and target accessibility, are also discussed. It is expected that continued advancements in live cell imaging of RNA will open new and exciting opportunities in a wide range of biological and medical applications.