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Sample records for giant magnetostrictive materials

  1. Giant magnetostrictive composites

    NASA Astrophysics Data System (ADS)

    Duenas, Terrisa Ann

    The limitation of magnetostrictive composites has been in their low magnetostrictive response when compared to their monolithic counterparts. In this dissertation research is presented describing the methods and analysis used to create a giant magnetostrictive composite (GMC) producing giant strains at low fields, exhibiting magnetization ``jumping'' and the ΔE effect. This composite combines the giant magnetostrictive material, Terfenol-D (Tb0.3Dy0.7Fe2) in particle form, with a nonmetallic binder and is capable of producing strains (at room temperature) exceeding 1000 ppm at a nominal field of 1.5 kOe mechanically unloaded and 1200 ppm at 8 MPa preload (2.5 kOe). Several studies leading to the high response of this composite are presented. A connectivity study shows that a [1-3] connected composite produces 50% more strain than a [0-3] composite. A resin study indicates that the lower the viscosity of the resin, the greater the magnetostrictive response; this is attributed to the removal of voids during degassing. A void study correlates the increase in voids to the decrease in strain response. A model is used to correlate analysis with experimental results within 10% accuracy and shows that an optimal volume fraction exists based on the properties of the binder. Using a Polyscience Spurr low- viscosity (60 cps) binder this volume fraction is nominally 20%; this optimum is attributed to the balance of epoxy contracting on the particle (built-in preload) and the actuation delivered by the magnetostrictive material. In addition to the connectivity, resin, void, and volume-fraction study, particle size and gradation studies are presented. Widely dispersed (<106, <212, <300 μm), narrowly dispersed (<45, (90-106), (275-300) μm), and an optimized bimodal (18.7% of (45-90) μm with 81.3% of (250-300) μm) particle distributions are studied. Results show that the larger the particle size, the higher the magnetostrictive response; this is attributed to the reduction of

  2. Development of vibratory stress relief actuators based on giant magnetostrictive materials

    NASA Astrophysics Data System (ADS)

    He, Wen

    2005-12-01

    A kind of actuator, which is used in the high frequency Vibratory Stress Relief (VSR), was researched. The actuator is based on the technology of giant magnetostrictive materials. The design principle of the actuator was firstly analyzed, which consists of the analysis of giant magnetostrictive materials and a force generator. Then the design criterion of magnetostrictive actuators was deeply discussed, which includes the dimension design of magnetostrictive materials, the design of magnetic field and the design of elimination of heat. Finally, a real actuator was developed, which has been used in the high frequency VSR. The experimental results show that the developed actuator works very well. Large exciting force but small vibration amplitude will make it widely used in the VSR.

  3. On the use of giant magnetostrictive materials in sonic transducers for liquid atomizers

    NASA Astrophysics Data System (ADS)

    Sheykholeslami, M.; Ghodsi, M.; Hojjat, Y.; Sadeghian, H.; Cinquemani, S.

    2016-04-01

    Liquid atomization has many applications such as car fuel injector, heat dissipation, coating, medical use, etc. The most common way in atomization is to exploit high frequency and high vibration amplitudes of piezoelectric devices. This paper investigates the effectiveness of a giant magnetostrictive transducer for atomizing liquids. Effect of vibration amplitudes on output parameters such as atomization size and output Dubai have been investigated so as the frequency response of the transducer when plunged into the water. Droplet size particles have been measured through high speed camera. Results show that using giant magnetostrictive transducer leads to uniformity that is considered a key factor in many applications. Results demonstrates that sonic transducers based on giant magnetostrictive material can be profitably used as liquid atomizers.

  4. An analytical and explicit multi-field coupled nonlinear constitutive model for Terfenol-D giant magnetostrictive material

    NASA Astrophysics Data System (ADS)

    Zhou, Hao-Miao; Li, Meng-Han; Li, Xiao-Hong; Zhang, Da-Guang

    2016-08-01

    For a giant magnetostrictive rod under the action of multiple physical loads, such as an external magnetic field, temperature and axial pre-stress, this paper proposes a general one-dimensional nonlinear magneto-thermo-mechanical coupled constitutive model. This model is based on the Taylor expansion of the elastic Gibbs free energy of giant magnetostrictive material and thermodynamic relations from the perspective of macro continuum mechanics. Predictions made using this model are in good agreement with experimental data for magnetization and the magnetostrictive strain curve under the collective effect of pre-stress and temperature. Additionally, the model overcomes the drawback of the existing magneto-thermo-mechanical constitutive model that cannot accurately predict the magnetization and magnetostrictive strain curve for different temperatures and pre-stresses. Furthermore, the constitutive model does not contain an implicit function and is compact, and can thus be applied in both situations of tensile and compressive stress and to both positive and negative magnetostrictive materials, and it is thus appropriate for engineering applications. Comprehensive analysis shows that the model fully describes the nonlinear coupling properties of a magnetic field, magnetostrictive strain and elasticity of a magnetostrictive material subjected to stress, a magnetic field and heat.

  5. Study on the dynamic characteristics of a high frequency brake based on giant magnetostrictive material

    NASA Astrophysics Data System (ADS)

    Xu, Ai Qun

    2016-06-01

    In order to meet the requirements of rapid and smooth braking, high-frequency braking using a giant magnetostrictive actuator is proposed, which can solve the problems in hydraulic braking, such as, it leaks easily, catches fire easily, is difficult to find failures, high cost on maintenance and repairing, etc. The main factors affecting the force of a high-frequency braking actuator are emphatically analyzed, the brakes dynamic model is established and a performance testing device for high frequency braking is constructed based on LabVIEW. The output force of the actuator increases with the excitation current of the driving coil increasing, and the increased multiple of the output force is greater than that of the excitation current; the range of the actuator force amplitude is 121.63 N ∼ 158.14 N, which changes little, while excitation frequency changes between 200 Hz ∼ 1000 Hz. In a minor range of pre-stress, the output force decreases with an increase in the axial pre-stress of the giant magnetostrictive rod, but is not obvious. It is known by finite element simulation analysis that high-frequency braking shortens the braking displacement and time effectively, which proves the feasibility and effectiveness of high frequency braking. Theoretical analysis and experimental results indicate that the output force of the actuator changes at the same frequency with excitation current; it is controllable and its mechanical properties meet the requirements of high frequency braking.

  6. Giant self-biased converse magnetoelectric effect in multiferroic heterostructure with single-phase magnetostrictive materials

    NASA Astrophysics Data System (ADS)

    Zhang, Jitao; Li, Ping; Wen, Yumei; He, Wei; Yang, Aichao; Wang, Decai; Yang, Chao; Lu, Caijiang

    2014-10-01

    Giant self-biased converse magnetoelectric (CME) effects with obvious hysteretic behaviors are systematically investigated in two-phase SmFe2/PZT [Pb(Zr1-x, Tix)O3] multiferroic laminates at room temperature. Taking advantage of the huge anisotropic field of SmFe2 plate, large remnant CME coupling is provoked by this field instead of permanent magnets to bias the laminate. Consequently, bitable magnetization status switching is realized through a smaller ac voltage far below the electric coercive field in the absence of magnetic bias field. Experiments demonstrate that a large remnant CME coefficient (αCME) of 0.007 mG/V is achieved, exhibiting ˜50 times higher CME coefficient than the previous laminate composite multi-phase magnetostrictive plates. These results provide promising applications for realization of high-density magnetoelectric random access memories (MERAMs) devices with lower energy consumption.

  7. Design and experimental study of a novel giant magnetostrictive actuator

    NASA Astrophysics Data System (ADS)

    Xue, Guangming; Zhang, Peilin; He, Zhongbo; Li, Dongwei; Huang, Yingjie; Xie, Wenqiang

    2016-12-01

    Giant magnetostrictive actuator has been widely used in precise driving occasions for its excellent performance. However, in driving a switching valve, especially the ball-valve in an electronic controlled injector, the actuator can't exhibit its good performance for limits in output displacement and responding speed. A novel giant magnetostrictive actuator, which can reach its maximum displacement for being exerted with no bias magnetic field, is designed in this paper. Simultaneously, elongating of the giant magetostrictive material is converted to shortening of the actuator's axial dimension with the help of an output rod in "T" type. Furthermore, to save responding time, the driving voltage with high opening voltage while low holding voltage is designed. Responding time and output displacement are studied experimentally with the help of a measuring system. From measured results, designed driving voltage can improve the responding speed of actuator displacement quite effectively. And, giant magnetostrictive actuator can output various steady-state displacements to reach more driving effects.

  8. Magnetization and magnetostriction in highly magnetostrictive materials

    SciTech Connect

    Thoelke, J.B.

    1993-05-26

    The majority of this research has been in developing a model to describe the magnetostrictive properties of Terfenol-D, Tb{sub 1{minus}x}Dy{sub x}Fe{sub y} (x = 0.7-0.75 and y = 1.8--2.0), a rare earth-iron alloy which displays much promise for use in device applications. In the first chapter an introduction is given to the phenomena of magnetization and magnetostriction. The magnetic processes responsible for the observed magnetic properties of materials are explained. An overview is presented of the magnetic properties of rare earths, and more specifically the magnetic properties of Terfenol-D. In the second chapter, experimental results are presented on three composition of Tb{sub 1{minus}x}Dy{sub x}Fe{sub y} with x = 0.7, y= 1.9, 1.95, and x= 0.73, y= 1.95. The data were taken for various levels of prestress to show the effects of composition and microstructure on the magnetic and magnetostrictive properties of Terfenol-D. In the third chapter, a theoretical model is developed based on the rotation of magnetic domains. The model is used to explain the magnetic and magnetostrictive properties of Terfenol-D, including the observed negative strictions and large change in strain. The fourth chapter goes on to examine the magnetic properties of Terfenol-D along different crystallographic orientations. In the fifth chapter initial data are presented on the time dependence of magnetization in nickel.

  9. Part Design of Giant Magnetostrictive Actuator

    NASA Astrophysics Data System (ADS)

    Sun, Zhonglei; Zhao, Meiying; Yin, Zidong

    The key parts of giant magnetostrictive actuator, flexure hinge and pre-stress disc spring, were designed and analyzed. Rotation stiffness and strength characteristics of flexure hinge were analyzed, calculation equations for rotation stiffness and strength were established as well. Fatigue characteristic was also analyzed as flexure hinge usually worked under high frequency situation. In order to improve output efficiency of the giant magnetostrictive actuator and reduce energy loss, an ideal spring force-deformation curve, whose shape was bilinear broken line, of the pre- stress disc spring was put forward, and a disc spring was designed by configuring its geometric parameters to make its spring force-deformation curve was approximate to the ideal spring force-deformation curve.

  10. Cryogenic Magnetostrictive Materials and Devices

    NASA Astrophysics Data System (ADS)

    Joshi, C. H.; Mavanur, A.; Tai, C.-Y.; Han, Z.-X.; Rodenbush, A. J.; Wong, Y.

    2004-06-01

    Energen has patented KelvinAll™, the first material, to exhibit magnetostrictive properties from elevated temperatures to near absolute zero, opening up a new range of applications for magnetostrictive devices. Magnetostrictive materials change their shape in the presence of a magnetic field. This elongation is precise, predictable, reversible and repeatable thereby enabling practical electromechanical devices. KelvinAll has magnetostriction comparable to Terfenol-D at room temperature and its magnetostriction increases at cryogenic temperatures. Energen has developed and prototyped practical electromechanical devices using KelvinAll. These devices include tuners for superconducting radio frequency (SRF) cavities, components for magnetic refrigerators, flow control valves and precision translation stages some of which will be discussed in greater detail. Energen's KelvinAll products enhance performance, increase reliability and reduce development costs.

  11. Method of making active magnetic refrigerant, colossal magnetostriction and giant magnetoresistive materials based on Gd-Si-Ge alloys

    DOEpatents

    Gschneidner, Jr., Karl A.; Pecharsky, Alexandra O.; Pecharsky, Vitalij K.

    2003-07-08

    Method of making an active magnetic refrigerant represented by Gd.sub.5 (Si.sub.x Ge.sub.1-x).sub.4 alloy for 0.ltoreq.x.ltoreq.1.0 comprising placing amounts of the commercially pure Gd, Si, and Ge charge components in a crucible, heating the charge contents under subambient pressure to a melting temperature of the alloy for a time sufficient to homogenize the alloy and oxidize carbon with oxygen present in the Gd charge component to reduce carbon, rapidly solidifying the alloy in the crucible, and heat treating the solidified alloy at a temperature below the melting temperature for a time effective to homogenize a microstructure of the solidified material, and then cooling sufficiently fast to prevent the eutectoid decomposition and improve magnetocaloric and/or the magnetostrictive and/or the magnetoresistive properties thereof.

  12. Development of thin-slice fiber Bragg grating-giant magnetostrictive material sensors used for measuring magnetic field of magnetic bearings

    NASA Astrophysics Data System (ADS)

    Ding, Guoping; Wang, Huaqiang; Liu, Jiayi; Gao, Bin; Zhang, Biyun

    2015-10-01

    The magnetic field is a physical medium used to realize the levitation and motion control of magnetic bearings. It is necessary to conduct the air-gap flux density measurement so as to validate theoretical analyses and provide instructions for practical design. A thin-slice fiber Bragg grating-giant magnetostrictive material (FBG-GMM) sensor, in which the FBG was stuck perpendicular to the principal magnetostriction orientation of a thin GMM slice, was proposed to measure magnetic-flux density in the small air gap. The configuration of FBG-GMM sensor was the same with that of a sensor of 1.5 mm×14 mm×7 mm TbDyFe slice stuck with a 1300 nm-wavelength FBG on the side of the slice. The FBG-GMM magnetic field sensor was tested on an U-shape electromagnet test setup under static conditions. The sensor had a linear region of 0.121 to 0.261 T with the sensitivity of 1089.056 pm/T. The FBG-GMM magnetic field sensor was introduced to measure the air-gap flux density of radial magnetic bearings. Measurement of static flux density was conducted with 2 FBG-GMM sensors compensated with a temperature FBG; and the measured data showed that the FBG-GMM sensor had feasible linear region and sensitivity to measure the air-gap flux density of magnetic bearings.

  13. Analytical model of a giant magnetostrictive resonance transducer

    NASA Astrophysics Data System (ADS)

    Sheykholeslami, M.; Hojjat, Y.; Ansari, S.; Cinquemani, S.; Ghodsi, M.

    2016-04-01

    Resonance transducers have been widely developed and studied, as they can be profitably used in many application such as liquid atomizing and sonar technology. The active element of these devices can be a giant magnetostrictive material (GMM) that is known to have significant energy density and good performance at high frequencies. The paper introduces an analytical model of GMM transducers to describe their dynamics in different working conditions and to predict any change in their performance. The knowledge of the transducer behavior, especially in operating conditions different from the ideal ones, is helpful in the design and fabrication of highly efficient devices. This transducer is design to properly work in its second mode of vibration and its working frequency is around 8000 Hz. Most interesting parameters of the device, such as quality factor, bandwidth and output strain are obtained from theoretical analysis.

  14. Design, analysis, and modeling of giant magnetostrictive transducers

    NASA Astrophysics Data System (ADS)

    Calkins, Frederick Theodore

    The increased use of giant magnetostrictive, Terfenol-D transducers in a wide variety of applications has led to a need for greater understanding of the materials performance. This dissertation attempts to add to the Terfenol-D transducer body of knowledge by providing an in-depth analysis and modeling of an experimental transducer. A description of the magnetostriction process related to Terfenol-D includes a discussion of material properties, production methods, and the effect of mechanical stress, magnetization, and temperature on the material performance. The understanding of the Terfenol-D material performance provides the basis for an analysis of the performance of a Terfenol-D transducer. Issues related to the design and utilization of the Terfenol-D material in the transducers are considered, including the magnetic circuit, application of mechanical prestress, and tuning of the mechanical resonance. Experimental results from two broadband, Tonpilz design transducers show the effects of operating conditions (prestress, magnetic bias, AC magnetization amplitude, and frequency) on performance. In an effort to understand and utlilize the rich performance space described by the experimental results a variety of models are considered. An overview of models applicable to Terfenol-D and Terfenol-D transducers is provided, including a discussion of modeling criteria. The Jiles-Atherton model of ferromagnetic hysteresis is employed to describe the quasi-static transducer performance. This model requires the estimation of only six physically-based parameters to accurately simulate performance. The model is shown to be robust with respect to model parameters over a range of mechanical prestress, magnetic biases, and AC magnetic field amplitudes, allowing predictive capability within these ranges. An additional model, based on electroacoustics theory, explains trends in the frequency domain and facilitates an analysis of efficiency based on impedance and admittance

  15. A critical analysis of the feasibility of pure strain-actuated giant magnetostrictive nanoscale memories

    NASA Astrophysics Data System (ADS)

    Gowtham, P. G.; Rowlands, G. E.; Buhrman, R. A.

    2015-11-01

    Concepts for memories based on the manipulation of giant magnetostrictive nanomagnets by stress pulses have garnered recent attention due to their potential for ultra-low energy operation in the high storage density limit. Here, we discuss the feasibility of making such memories in light of the fact that the Gilbert damping of such materials is typically quite high. We report the results of numerical simulations for several classes of toggle precessional and non-toggle dissipative magnetoelastic switching modes. Material candidates for each of the several classes are analyzed and forms for the anisotropy energy density and ranges of material parameters appropriate for each material class are employed. Our study indicates that the Gilbert damping as well as the anisotropy and demagnetization energies are all crucial for determining the feasibility of magnetoelastic toggle-mode precessional switching schemes. The roles of thermal stability and thermal fluctuations for stress-pulse switching of giant magnetostrictive nanomagnets are also discussed in detail and are shown to be important in the viability, design, and footprint of magnetostrictive switching schemes.

  16. Characteristics of vibration energy harvesting using giant magnetostrictive cantilevers with resonant tuning

    NASA Astrophysics Data System (ADS)

    Mori, Kotaro; Horibe, Tadashi; Ishikawa, Shigekazu; Shindo, Yasuhide; Narita, Fumio

    2015-12-01

    This work deals with the dynamic bending and energy harvesting characteristics of giant magnetostrictive cantilevers with resonant tuning both numerically and experimentally. The giant magnetostrictive cantilever is fabricated using a thin Terfenol-D layer, SUS layer, movable proof mass, etc, and, is designed to automatically adjust its own resonant frequency to match the external vibration frequency in real time. Three-dimensional finite element analysis was conducted, and the resonant frequency, induced voltage and stress in the magnetostrictive cantilevers were predicted. The resonant frequency and induced voltage were also measured, and comparison was made between simulation and experiment. The time-varying behavior and self-tuning ability are discussed in detail.

  17. Giant volume magnetostriction in the Y2Fe17 single crystal at room temperature

    NASA Astrophysics Data System (ADS)

    Nikitin, S. A.; Pankratov, N. Yu.; Smarzhevskaya, A. I.; Politova, G. A.; Pastushenkov, Yu. G.; Skokov, K. P.; del Moral, A.

    2015-05-01

    An investigation of the Y2Fe17 compound belonging to the class of intermetallic alloys of rare-earth and 3d-transition metals is presented. The magnetization, magnetostriction, and thermal expansion of the Y2Fe17 single crystal were studied. The forced magnetostriction and magnetostriction constants were investigated in the temperature range of the magnetic ordering close to the room temperature. The giant field induced volume magnetostriction was discovered in the room temperature region in the magnetic field up to 1.2 T. The contributions of both anisotropic single-ion and isotropic pair exchange interactions to the volume magnetostriction and magnetostriction constants were determined. The experimental results were interpreted within the framework of the Standard Theory of Magnetostriction and the Landau thermodynamic theory. It was found out that the giant values of the volume magnetostriction were caused by the strong dependence of the 3d-electron Coulomb charge repulsion on the deformations and width of the 3d-electron energy band.

  18. Design of a uniform bias magnetic field for giant magnetostrictive actuators applying triple-ring magnets

    NASA Astrophysics Data System (ADS)

    Zhang, Heng; Zhang, Tianli; Jiang, Chengbao

    2013-11-01

    Uniform bias magnetic field is very important for giant magnetostrictive actuators (GMA) to fully utilize the performance of giant magnetostrictive materials (GMM). However, it is difficult to keep it uniform when the length to diameter ratio (α) of the GMM is larger than 3.5, though the shapes of the applied GMM are different with α usually larger than 3.5. In this paper, a design method with triple-ring permanent magnets is established to provide an even bias magnetic field for GMM with varying α. Firstly, the magnetic circuit model is set up. According to the analysis of the field distribution along the GMM rod, the main factor causing unevenness of the bias magnetic field is confirmed to be the inner leakage flux. A design of triple-ring topology for the magnets is developed to control the inner leakage flux to reduce the unevenness. Then, finite element analysis is adopted to optimize a design which can ensure an unevenness of the bias magnetic field of less than 3% while the α of a GMM rod is up to 20. Finally, an actual GMA is fabricated with the GMM dimension of ∅10 mm × 50 mm (α = 5), and the testing results show that the unevenness of the bias field along the GMM is 1.38%. The bias magnetic system design is practicable, simple and efficient for offering an even bias magnetic field when α lies in a wide range.

  19. Hysteresis Modeling in Magnetostrictive Materials Via Preisach Operators

    NASA Technical Reports Server (NTRS)

    Smith, R. C.

    1997-01-01

    A phenomenological characterization of hysteresis in magnetostrictive materials is presented. Such hysteresis is due to both the driving magnetic fields and stress relations within the material and is significant throughout, most of the drive range of magnetostrictive transducers. An accurate characterization of the hysteresis and material nonlinearities is necessary, to fully utilize the actuator/sensor capabilities of the magnetostrictive materials. Such a characterization is made here in the context of generalized Preisach operators. This yields a framework amenable to proving the well-posedness of structural models that incorporate the magnetostrictive transducers. It also provides a natural setting in which to develop practical approximation techniques. An example illustrating this framework in the context of a Timoshenko beam model is presented.

  20. Giant magnetostriction in Tb-doped Fe{sub 83}Ga{sub 17} melt-spun ribbons

    SciTech Connect

    Wu, Wei; Liu, Jinghua; Jiang, Chengbao; Xu, Huibin

    2013-12-23

    Giant magnetostriction is achieved in lightly Tb-doped Fe{sub 83}Ga{sub 17} melt-spun ribbons. The average perpendicular magnetostriction λ{sub ⊥} is −886 ppm along the melt-spun ribbon direction in the Fe{sub 82.89}Ga{sub 16.88}Tb{sub 0.23} alloy and the calculated parallel magnetostriction λ{sub ‖‖} is 1772 ppm. These values are more than four times as large as those found in binary Fe{sub 83}Ga{sub 17}. The enhanced magnetostriction is attributed to a small amount of Tb entering solution in the A2 matrix phase during rapid solidification. The strong localized magnetocrystalline anisotropy of terbium is thought to cause the giant magnetostriction.

  1. Nonlinear behavior of coupled magnetostrictive material systems analytical/experimental

    NASA Astrophysics Data System (ADS)

    Roberts, Mark M.; Mitrovic, Milan; Carman, Gregory P.

    1995-05-01

    In this paper, we present a nonlinear constitutive relation for magnetostrictive materials that includes coupling between temperature/preload and magnetic field strengths. The nonlinear constitutive relations are also integrated into a 1-dimensional nonlinear finite element model for studying structural components or composite materials containing magnetostrictive materials. The accuracy of the nonlinear constitutive relation is evaluated by comparing experimental results obtained on a Terfenol-D rod operating under both magnetic field and stress biases with theoretical values present in the literature. Results indicate that the model adequately predicts the nonlinear strain/field relations in specific regimes. Experimental tests, conducted on monolithic samples of different geometry, suggests that size effects may be important. A manufacturing process and preliminary experimental tests are also presented for a 1 - 3 magnetostrictive composite sample.

  2. Giant volume magnetostriction in the Y{sub 2}Fe{sub 17} single crystal at room temperature

    SciTech Connect

    Nikitin, S. A. Pankratov, N. Yu.; Smarzhevskaya, A. I.; Politova, G. A.; Pastushenkov, Yu. G. Skokov, K. P.; Moral, A. del

    2015-05-21

    An investigation of the Y{sub 2}Fe{sub 17} compound belonging to the class of intermetallic alloys of rare-earth and 3d-transition metals is presented. The magnetization, magnetostriction, and thermal expansion of the Y{sub 2}Fe{sub 17} single crystal were studied. The forced magnetostriction and magnetostriction constants were investigated in the temperature range of the magnetic ordering close to the room temperature. The giant field induced volume magnetostriction was discovered in the room temperature region in the magnetic field up to 1.2 T. The contributions of both anisotropic single-ion and isotropic pair exchange interactions to the volume magnetostriction and magnetostriction constants were determined. The experimental results were interpreted within the framework of the Standard Theory of Magnetostriction and the Landau thermodynamic theory. It was found out that the giant values of the volume magnetostriction were caused by the strong dependence of the 3d-electron Coulomb charge repulsion on the deformations and width of the 3d-electron energy band.

  3. The principle and physical models of novel jetting dispenser with giant magnetostrictive and a magnifier

    PubMed Central

    Zhou, C.; Li, J.H.; Duan, J.A.; Deng, G.L.

    2015-01-01

    In order to develop jetting technologies of glue in LED and microelectronics packaging, giant-magnetostrictive-material (GMM) is firstly applied to increase jetting response, and a new magnifying device including a lever and a flexible hinge is designed to improve jetting characteristics. Physical models of the jetting system are derived from the magnifying structure and working principle, which involves circuit model, electro-magneto-displacement model, dynamic model and fluid-solid coupling model. The system model is established by combining mathematical models with Matlab-Simulink. The effectiveness of the GMM-based dispenser is confirmed by simulation and experiments. The jetting frequency significantly increases to 250 Hz, and dynamic behaviors jetting needle are evaluated that the velocity and displacement of the jetting needle reaches to 320 mm•s-1 and 0.11 mm respectively. With the increasing of the filling pressure or the amplitude of the current, the dot size will become larger. The dot size and working frequency can be easily adjusted. PMID:26670008

  4. The principle and physical models of novel jetting dispenser with giant magnetostrictive and a magnifier.

    PubMed

    Zhou, C; Li, J H; Duan, J A; Deng, G L

    2015-01-01

    In order to develop jetting technologies of glue in LED and microelectronics packaging, giant-magnetostrictive-material (GMM) is firstly applied to increase jetting response, and a new magnifying device including a lever and a flexible hinge is designed to improve jetting characteristics. Physical models of the jetting system are derived from the magnifying structure and working principle, which involves circuit model, electro-magneto-displacement model, dynamic model and fluid-solid coupling model. The system model is established by combining mathematical models with Matlab-Simulink. The effectiveness of the GMM-based dispenser is confirmed by simulation and experiments. The jetting frequency significantly increases to 250 Hz, and dynamic behaviors jetting needle are evaluated that the velocity and displacement of the jetting needle reaches to 320 mm•s-1 and 0.11 mm respectively. With the increasing of the filling pressure or the amplitude of the current, the dot size will become larger. The dot size and working frequency can be easily adjusted.

  5. The principle and physical models of novel jetting dispenser with giant magnetostrictive and a magnifier

    NASA Astrophysics Data System (ADS)

    Zhou, C.; Li, J. H.; Duan, J. A.; Deng, G. L.

    2015-12-01

    In order to develop jetting technologies of glue in LED and microelectronics packaging, giant-magnetostrictive-material (GMM) is firstly applied to increase jetting response, and a new magnifying device including a lever and a flexible hinge is designed to improve jetting characteristics. Physical models of the jetting system are derived from the magnifying structure and working principle, which involves circuit model, electro-magneto-displacement model, dynamic model and fluid-solid coupling model. The system model is established by combining mathematical models with Matlab-Simulink. The effectiveness of the GMM-based dispenser is confirmed by simulation and experiments. The jetting frequency significantly increases to 250 Hz, and dynamic behaviors jetting needle are evaluated that the velocity and displacement of the jetting needle reaches to 320 mm•s-1 and 0.11 mm respectively. With the increasing of the filling pressure or the amplitude of the current, the dot size will become larger. The dot size and working frequency can be easily adjusted.

  6. The principle and physical models of novel jetting dispenser with giant magnetostrictive and a magnifier.

    PubMed

    Zhou, C; Li, J H; Duan, J A; Deng, G L

    2015-01-01

    In order to develop jetting technologies of glue in LED and microelectronics packaging, giant-magnetostrictive-material (GMM) is firstly applied to increase jetting response, and a new magnifying device including a lever and a flexible hinge is designed to improve jetting characteristics. Physical models of the jetting system are derived from the magnifying structure and working principle, which involves circuit model, electro-magneto-displacement model, dynamic model and fluid-solid coupling model. The system model is established by combining mathematical models with Matlab-Simulink. The effectiveness of the GMM-based dispenser is confirmed by simulation and experiments. The jetting frequency significantly increases to 250 Hz, and dynamic behaviors jetting needle are evaluated that the velocity and displacement of the jetting needle reaches to 320 mm•s-1 and 0.11 mm respectively. With the increasing of the filling pressure or the amplitude of the current, the dot size will become larger. The dot size and working frequency can be easily adjusted. PMID:26670008

  7. Research on hysteresis loop considering the prestress effect and electrical input dynamics for a giant magnetostrictive actuator

    NASA Astrophysics Data System (ADS)

    Zhu, Yuchuan; Yang, Xulei; Wereley, Norman M.

    2016-08-01

    In this paper, focusing on the application-oriented giant magnetostrictive material (GMM)-based electro-hydrostatic actuator, which features an applied magnetic field at high frequency and high amplitude, and concentrating on the static and dynamic characteristics of a giant magnetostrictive actuator (GMA) considering the prestress effect on the GMM rod and the electrical input dynamics involving the power amplifier and the inductive coil, a methodology for studying the static and dynamic characteristics of a GMA using the hysteresis loop as a tool is developed. A GMA that can display the preforce on the GMM rod in real-time is designed, and a magnetostrictive model dependent on the prestress on a GMM rod instead of the existing quadratic domain rotation model is proposed. Additionally, an electrical input dynamics model to excite GMA is developed according to the simplified circuit diagram, and the corresponding parameters are identified by the experimental data. A dynamic magnetization model with the eddy current effect is deduced according to the Jiles–Atherton model and the Maxwell equations. Next, all of the parameters, including the electrical input characteristics, the dynamic magnetization and the mechanical structure of GMA, are identified by the experimental data from the current response, magnetization response and displacement response, respectively. Finally, a comprehensive comparison between the model results and experimental data is performed, and the results show that the test data agree well with the presented model results. An analysis on the relation between the GMA displacement response and the parameters from the electrical input dynamics, magnetization dynamics and mechanical structural dynamics is performed.

  8. Research on hysteresis loop considering the prestress effect and electrical input dynamics for a giant magnetostrictive actuator

    NASA Astrophysics Data System (ADS)

    Zhu, Yuchuan; Yang, Xulei; Wereley, Norman M.

    2016-08-01

    In this paper, focusing on the application-oriented giant magnetostrictive material (GMM)-based electro-hydrostatic actuator, which features an applied magnetic field at high frequency and high amplitude, and concentrating on the static and dynamic characteristics of a giant magnetostrictive actuator (GMA) considering the prestress effect on the GMM rod and the electrical input dynamics involving the power amplifier and the inductive coil, a methodology for studying the static and dynamic characteristics of a GMA using the hysteresis loop as a tool is developed. A GMA that can display the preforce on the GMM rod in real-time is designed, and a magnetostrictive model dependent on the prestress on a GMM rod instead of the existing quadratic domain rotation model is proposed. Additionally, an electrical input dynamics model to excite GMA is developed according to the simplified circuit diagram, and the corresponding parameters are identified by the experimental data. A dynamic magnetization model with the eddy current effect is deduced according to the Jiles-Atherton model and the Maxwell equations. Next, all of the parameters, including the electrical input characteristics, the dynamic magnetization and the mechanical structure of GMA, are identified by the experimental data from the current response, magnetization response and displacement response, respectively. Finally, a comprehensive comparison between the model results and experimental data is performed, and the results show that the test data agree well with the presented model results. An analysis on the relation between the GMA displacement response and the parameters from the electrical input dynamics, magnetization dynamics and mechanical structural dynamics is performed.

  9. The Giant Magnetostriction of [Fe/Tb/Fe/Dy]n Multilayer Films Under Different Annealing Temperature

    NASA Astrophysics Data System (ADS)

    Li, X. D.; Zhao, Z. J.; Feng, T.; Pan, L. K.; Huang, S. M.; Chen, Y. W.; Sun, Z.

    The effect of annealing temperature on the magnetic and giant magnetostriction (GMS) of [Fe/Tb/Fe/Dy]n multilayer films were investigated. X-ray diffraction showed that the multilayer films' microstructures were still in amorphous at annealing temperature 300°C. The multilayer films began to crystalline at annealing temperature 400°C. The saturation magnetization of multilayer films increased by the increasing annealed temperature. The coercivity first decreased at annealing temperature 300°C and then increased when the annealing temperature was higher than 400°C. The multilayer films had good low-field GMS, and the magnetostriction of the multilayer films increased by the increasing annealing temperature.

  10. Modeling magnetostrictive material for high-speed tracking

    NASA Astrophysics Data System (ADS)

    Bottauscio, Oriano; Roccato, Paolo E.; Zucca, Mauro

    2011-04-01

    This work proposes a simplified model applicable to devices based on magnetostrictive materials conceived to be implemented in the control of a micropositioner. The 1D magnetomechanical dynamic model of the active material is based on the Preisach hysteresis model and includes classical eddy currents. The model has been used in a digital signal processing procedure for the determination of the supply current tracking position. Comparisons with experiments, obtained by controlling the actual micropositioner in an open loop chain, are satisfactory.

  11. Deformation of rectangular thin glass plate coated with magnetostrictive material

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoli; Yao, Youwei; Liu, Tianchen; Liu, Chian; Ulmer, M. P.; Cao, Jian

    2016-08-01

    As magnetic smart materials (MSMs), magnetostrictive materials have great potential to be selected as coating materials for lightweight x-ray telescope mirrors due to their capability to tune the mirror profile to the desired shape under a magnetic field. To realize this potential, it is necessary to study the deformation of the mirror substrate with the MSM coating subjected to a localized magnetic field. In this paper, an analytical model is developed to calculate the deformation of rectangular coated samples locally affected by magnetostrictive strains driven by an external magnetic field. As a specific case to validate the model, a square glass sample coated with MSMs is prepared, and its deformation is measured in a designed experimental setup by applying a magnetic field. The measured deformation of the sample is compared with the results calculated from the analytical model. The comparison results demonstrate that the analytical model is effective in calculating the deformation of a coated sample with the localized mismatch strains between the film and the substrate. In the experiments, different shape patterns of surface profile changes are achieved by varying the direction of the magnetic field. The analytical model and the experimental method proposed in this paper can be utilized to further guide the application of magnetostrictive coating to deformable lightweight x-ray mirrors in the future.

  12. Magnetic sensor for high temperature using a laminate composite of magnetostrictive material and piezoelectric material

    NASA Astrophysics Data System (ADS)

    Ueno, Toshiyuki; Higuchi, Toshiro

    2005-05-01

    A high sensitive and heat-resistive magnetic sensor using a magnetostrictive/piezoelectric laminate composite is investigated. The sensing principle is based on the magnetostrictive- and piezoelectric effect, whereby a detected yoke displacement is transduced into a voltage on the piezoelectric materials. The sensor is intended to detect the displacement of a ferromagnetic object in a high temperature environment, where conventional magnetic sensors are not useful. Such applications include sensors in engine of automobile and machinery used in material processing. The sensor features combination of a laminate composite of magnetostrictive/piezoelectric materials with high Curie temperatures and an appropriate magnetic circuit to convert mechanical displacement to sensor voltages and suppress temperature fluctuation. This paper describes the sensing principle and shows experimental results using a composite of Terfenol-D and Lithium Niobate to assure high sensitivity of 50V/mm at bias gap of 0.1mm and a temperature operating range over 200 °C.

  13. Non-Joulian magnetostriction.

    PubMed

    Chopra, Harsh Deep; Wuttig, Manfred

    2015-05-21

    All magnets elongate and contract anisotropically when placed in a magnetic field, an effect referred to as Joule magnetostriction. The hallmark of Joulian magnetostriction is volume conservation, which is a broader definition applicable to self-accommodation of ferromagnetic, ferroelectric or ferroelastic domains in all functional materials. Here we report the discovery of 'giant' non-volume-conserving or non-Joulian magnetostriction (NJM). Whereas Joulian strain is caused by magnetization rotation, NJM is caused by facile (low-field) reorientation of magnetoelastically and magnetostatically autarkic (self-sufficient) rigid micro-'cells', which define the adaptive structure, the origin of which is proposed to be elastic gradients ultimately caused by charge/spin density waves. The equilibrium adaptive cellular structure is responsible for long-sought non-dissipative (hysteresis-free), linearly reversible and isotropic magnetization curves along all directions within a single crystal. Recently discovered Fe-based high magnetostriction alloys with special thermal history are identified as the first members of this newly discovered magnetic class. The NJM paradigm provides consistent interpretations of seemingly confounding properties of Fe-based alloys, offers recipes to develop new highly magnetostrictive materials, and permits simultaneously large actuation in longitudinal and transverse directions without the need for stacked composites. PMID:25993965

  14. Rare earth-iron magnetostrictive materials and devices using these materials

    DOEpatents

    Savage, Howard T.; Clark, Arthur E.; McMasters, O. Dale

    1981-12-29

    Grain-oriented polycrystalline or single crystal magnetostrictive materials n the general formula Tb.sub.x Dy.sub.1-x Fe.sub.2-w, Tb.sub.x Ho.sub.1-x Fe.sub.2-w, Sm.sub.x Dy.sub.1-x Fe.sub.x-w, Sm.sub.x Ho.sub.1-x Fe.sub.2-w, Tb.sub.x Ho.sub.y Dy.sub.z Fe.sub.2-w, or Sm.sub.x Ho.sub.y Dy.sub.z Fe.sub.2-w, wherein O.ltoreq.w.ltoreq.0.20, and x+y+z=1. X, y, and z are selected to maximize the magnetostrictive effect and the magnetomechanical coupling coefficient K.sub.33. These material may be used in magnetostrictive transducers, delay lines, variable frequency resonators, and filters.

  15. Magnetostrictive Pressure Regulating System

    NASA Technical Reports Server (NTRS)

    Richard, James A. (Inventor); Pickens, Herman L. (Inventor)

    2013-01-01

    A magnetostrictive pressure regulating system includes a magnetostrictive valve that incorporates a magnetostrictive actuator with at least one current-carrying coil disposed thereabout. A pressure force sensor, in fluid communication with the fluid exiting the valve, includes (i) a magnetostrictive material, (ii) a magnetic field generator in proximity to the magnetostrictive material for inducing a magnetic field in and surrounding the magnetostrictive material wherein lines of magnetic flux passing through the magnetostrictive material are defined, and (iii) a sensor positioned adjacent to the magnetostrictive material and in the magnetic field for measuring changes in at least one of flux angle and flux density when the magnetostrictive material experiences an applied force that is aligned with the lines of magnetic flux. The pressure of the fluid exiting the valve causes the applied force. A controller coupled to the sensor and to the current-carrying coil adjusts a current supplied to the current-carrying coil based on the changes so-measured.

  16. Analysis of the giant magnetostrictive actuator with strong bias magnetic field

    NASA Astrophysics Data System (ADS)

    Xue, Guangming; He, Zhongbo; Li, Dongwei; Yang, Zhaoshu; Zhao, Zhenglong

    2015-11-01

    Giant magnetostrictive actuator with strong bias magnetic field is designed to control the injector bullet valve opening and closing. The relationship between actuator displacement amplitude and input signal direction is analyzed. And based on the approximate linearity of strain-magnetic field, second-order system model of the actuator displacement is established. Experimental system suitable for the actuator is designed. The experimental results show that, the square voltage amplitude being 12 V, the actuator displacement amplitude is about 17 μm with backward direction signal input while being 1.5 μm under forward direction signal. From the results, the suitable input direction is confirmed to be backward. With exciting frequncy lower than 200 Hz, the error between the model and experimental result is less than 1.7 μm. So the model is validated under the low-frequency signal input. The testing displacement-voltage curves are approximately straight lines. But due to the biased position, the line slope and the displacement-voltage linearity change as the input voltage changes.

  17. Material for magnetostrictive sensors and other applications based on ferrite materials

    DOEpatents

    McCallum, R. William; Snyder, John E.; Dennis, Kevin W.; Schwichtenberg, Carl R.; Jiles, David C.

    2000-07-25

    The present invention provides magnetostrictive compositions that include an oxide ferrite which provides mechanical properties that make the magnetostrictive compositions effective for use as sensors and actuators.

  18. Magnetostrictive materials and method for improving AC characteristics in same

    DOEpatents

    Pulvirenti, Patricia P.; Jiles, David C.

    2001-08-14

    The present invention provides Terfenol-D alloys ("doped" Terfenol) having optimized performances under the condition of time-dependent magnetic fields. In one embodiment, performance is optimized by lowering the conductivity of Terfenol, thereby improving the frequency response. This can be achieved through addition of Group III or IV elements, such as Si and Al. Addition of these types of elements provides scattering sites for conduction electrons, thereby increasing resistivity by 125% which leads to an average increase in penetration depth of 80% at 1 kHz and an increase in energy conversion efficiency of 55%. The permeability of doped Terfenol remains constant over a wider frequency range as compared with undoped Terfenol. These results demonstrate that adding impurities, such as Si and Al, are effective in improving the ac characteristics of Terfenol. A magnetoelastic Gruneisen parameter, .gamma..sub.me, has also been derived from the thermodynamic equations of state, and provides another means by which to characterize the coupling efficiency in magnetostrictive materials on a more fundamental basis.

  19. Magnetostrictive Alternator

    NASA Technical Reports Server (NTRS)

    Dyson, Rodger; Bruder, Geoffrey

    2013-01-01

    This innovation replaces the linear alternator presently used in Stirling engines with a continuous-gradient, impedance-matched, oscillating magnetostrictive transducer that eliminates all moving parts via compression, maintains high efficiency, costs less to manufacture, reduces mass, and eliminates the need for a bearing system. The key components of this new technology are the use of stacked magnetostrictive materials, such as Terfenol-D, under a biased magnetic and stress-induced compression, continuous-gradient impedance-matching material, coils, force-focusing metallic structure, and supports. The acoustic energy from the engine travels through an impedancematching layer that is physically connected to the magnetostrictive mass. Compression bolts keep the structure under compressive strain, allowing for the micron-scale compression of the magnetostrictive material and eliminating the need for bearings. The relatively large millimeter displacement of the pressure side of the impedance-matching material is reduced to micron motion, and undergoes stress amplification at the magnetostrictive interface. The alternating compression and expansion of the magnetostrictive material creates an alternating magnetic field that then induces an electric current in a coil that is wound around the stack. This produces electrical power from the acoustic pressure wave and, if the resonant frequency is tuned to match the engine, can replace the linear alternator that is commonly used.

  20. Determination of Terfenol-D magnetostriction characteristics for sensor application using fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    de Morais Sousa, Kleiton; Zandonay, Ricardo; Vagner da Silva, Erlon; Martelli, Cicero; Cardozo da Silva, Jean Carlos

    2014-08-01

    Electric current sensor based on magnetostriction phenomenon has been reported in several papers. In common these previous papers used a fiber Bragg grating (FBG) to determine the strain of the magnetostrictive material. However, magnetostriction sensors present few disadvantages often neglected, such as the temperature dependence of magnetostriction. In this paper a Terfenol-D rod (a giant magnetostrictive material-GMM) is used for tests. For simultaneous measurement of temperature and strain two multiplexed FBGs are used. The first test presents unipolar characteristics of Terfenol-D magnetostriction. Other test determines the Terfenol-D response for different temperatures. The Terfenol-D sensitivity increase when the temperature increases, however the saturation of the material occurs in small field values. The characteristics presented in this paper must be taken into account in the development of magnetostrictive sensors and its limitations.

  1. Cobalt ferrite based magnetostrictive materials for magnetic stress sensor and actuator applications

    NASA Technical Reports Server (NTRS)

    Jiles, David C. (Inventor); Paulsen, Jason A. (Inventor); Snyder, John E. (Inventor); Lo, Chester C. H. (Inventor); Ring, Andrew P. (Inventor); Bormann, Keith A. (Inventor)

    2008-01-01

    Magnetostrictive material based on cobalt ferrite is described. The cobalt ferrite is substituted with transition metals (such manganese (Mn), chromium (Cr), zinc (Zn) and copper (Cu) or mixtures thereof) by substituting the transition metals for iron or cobalt to form substituted cobalt ferrite that provides mechanical properties that make the substituted cobalt ferrite material effective for use as sensors and actuators. The substitution of transition metals lowers the Curie temperature of the material (as compared to cobalt ferrite) while maintaining a suitable magnetostriction for stress sensing applications.

  2. Frequency spectra of magnetostrictive and Lorentz forces generated in ferromagnetic materials by a CW excited EMAT

    NASA Astrophysics Data System (ADS)

    Rouge, C.; Lhémery, A.; Aristégui, C.

    2014-04-01

    Magnetostriction arises in ferromagnetic materials subjected to magnetization, e.g., when an EMAT (Electro-Magnetic Acoustic Transducer) is used to generate ultrasonic waves. In such a case, the magnetostriction force must be taken into account as a transduction process that adds up to the Lorentz force. When the static magnetic field is high compared to the dynamic field, both forces are driven by the excitation frequency. For lower static relative values of the magnetic fields, the Lorentz force comprises both the excitation frequency and its first harmonic. In this work, a model is derived to predict the frequency content of the magnetostrictive force that comprises several harmonics. The discrete frequency spectrum strongly depends on both the static field and the relative amplitude of the dynamic field. The only material input data needed to predict it is the curve of macroscopic magnetostrictive strain that can be measured in the direction of an imposed magnetic field. Then, the various frequency-dependent distributions of Lorentz and magnetostriction body forces can be transformed into equivalent surface stresses. Examples of computation are given for different static and dynamic magnetic fields to study their influence on the frequency content of waves generated in ferromagnetic materials.

  3. A general one-dimension nonlinear magneto-elastic coupled constitutive model for magnetostrictive materials

    SciTech Connect

    Zhang, Da-Guang; Li, Meng-Han; Zhou, Hao-Miao

    2015-10-15

    For magnetostrictive rods under combined axial pre-stress and magnetic field, a general one-dimension nonlinear magneto-elastic coupled constitutive model was built in this paper. First, the elastic Gibbs free energy was expanded into polynomial, and the relationship between stress and strain and the relationship between magnetization and magnetic field with the polynomial form were obtained with the help of thermodynamic relations. Then according to microscopic magneto-elastic coupling mechanism and some physical facts of magnetostrictive materials, a nonlinear magneto-elastic constitutive with concise form was obtained when the relations of nonlinear strain and magnetization in the polynomial constitutive were instead with transcendental functions. The comparisons between the prediction and the experimental data of different magnetostrictive materials, such as Terfenol-D, Metglas and Ni showed that the predicted magnetostrictive strain and magnetization curves were consistent with experimental results under different pre-stresses whether in the region of low and moderate field or high field. Moreover, the model can fully reflect the nonlinear magneto-mechanical coupling characteristics between magnetic, magnetostriction and elasticity, and it can effectively predict the changes of material parameters with pre-stress and bias field, which is useful in practical applications.

  4. Applications of magnetostrictive materials in the real-time monitoring of vehicle suspension components

    NASA Astrophysics Data System (ADS)

    Estrada, Raul

    The purpose of this project is to explore applications of magnetostrictive materials for real-time monitoring of railroad suspension components, in particular bearings. Monitoring of such components typically requires the tracking of temperature vibration and load. In addition, real-time, long-term monitoring can be greatly facilitated through the use of wireless, self-powered sensors. Magnetostrictive materials, such as Terfenol-D, have the potential to address both requirements. Currently, piezoelectrics are used for many load and energy harvesting applications; however, they are fragile and are difficult to use for static load measurements. Magnetostrictive metals are tougher, and their property of variable permeability when stressed can be utilized to measure static loads. A prototype load sensor was successfully fabricated and characterized yielding less than 10% error under normal operating conditions. Energy harvesting experiments generated a little over 80 mW of power, which is sufficient to run low-power condition monitoring systems.

  5. Directional solidification and heat treatment of terfenol-D magnetostrictive materials

    NASA Astrophysics Data System (ADS)

    Verhoeven, J. D.; Gibson, E. D.; McMasters, O. D.; Ostenson, J. E.

    1990-08-01

    Directional solidification techniques have been developed to produce grain-aligned rods of the highly magnetostrictive material Terfenol-D, TbxDy1-xFey The magnetostrictive properties have been compared to those of single-crystal, bicrystal, and polycrystal rod prepared by a float zone melting (ZM) technique. It was found that the properties of the grain-aligned material were comparable to three-and four-grain ZM material and the magnetostriction for both materials was less than the ZM single crystal and the better bicrystal rods by around 20 pct. It was demonstrated that a heat treatment consisting of a 1-hour hold at 950 °C was very effective at improving the magnetostrictive properties of all of the materials. Experiments have demonstrated that, to be effective, the heat-treatment temperature must be above somewhere between 850 °C and 900 °C. It is postulated that the mechanism for the improved properties involves a relief or redistribution of residual stresses produced by localized melting near second-phase particles at the predicted eutectic temperature of around 875 °C in the Terfenol-D material.

  6. Material for magnetostrictive sensors and other applications based on ferrite materials

    DOEpatents

    McCallum, R. William; Snyder, John E.; Dennis, Kevin W.; Schwichtenberg, Carl R.; Jiles, David C.

    2002-03-05

    The present invention provides magnetostrictive composites that include an oxide ferrite and metallic binders which provides mechanical properties that make the magnetostrictive compositions effective for use as sensors and actuators.

  7. Magnetostrictive resonance excitation

    DOEpatents

    Schwarz, Ricardo B.; Kuokkala, Veli-Tapani

    1992-01-01

    The resonance frequency spectrum of a magnetostrictive sample is remotely determined by exciting the magnetostrictive property with an oscillating magnetic field. The permeability of a magnetostrictive material and concomitant coupling with a detection coil varies with the strain in the material whereby resonance responses of the sample can be readily detected. A suitable sample may be a magnetostrictive material or some other material having at least one side coated with a magnetostrictive material. When the sample is a suitable shape, i.e., a cube, rectangular parallelepiped, solid sphere or spherical shell, the elastic moduli or the material can be analytically determined from the measured resonance frequency spectrum. No mechanical transducers are required and the sample excitation is obtained without contact with the sample, leading to highly reproducible results and a measurement capability over a wide temperature range, e.g. from liquid nitrogen temperature to the Curie temperature of the magnetostrictive material.

  8. Non-linear dynamic characteristics and optimal control of giant magnetostrictive film subjected to in-plane stochastic excitation

    SciTech Connect

    Zhu, Z. W.; Zhang, W. D. Xu, J.

    2014-03-15

    The non-linear dynamic characteristics and optimal control of a giant magnetostrictive film (GMF) subjected to in-plane stochastic excitation were studied. Non-linear differential items were introduced to interpret the hysteretic phenomena of the GMF, and the non-linear dynamic model of the GMF subjected to in-plane stochastic excitation was developed. The stochastic stability was analysed, and the probability density function was obtained. The condition of stochastic Hopf bifurcation and noise-induced chaotic response were determined, and the fractal boundary of the system's safe basin was provided. The reliability function was solved from the backward Kolmogorov equation, and an optimal control strategy was proposed in the stochastic dynamic programming method. Numerical simulation shows that the system stability varies with the parameters, and stochastic Hopf bifurcation and chaos appear in the process; the area of the safe basin decreases when the noise intensifies, and the boundary of the safe basin becomes fractal; the system reliability improved through stochastic optimal control. Finally, the theoretical and numerical results were proved by experiments. The results are helpful in the engineering applications of GMF.

  9. Positioning devices based on submicro-textured magnetostrictive alloys (Fe85Ga15)

    NASA Astrophysics Data System (ADS)

    Dannangoda, Gamage; Martirosyan, Karen

    2011-10-01

    Magnetostrictive materials can convert magnetic energy into kinetic energy. Under the influence of an external magnetic field, the rotation of small magnetic domains causes a change in a magnetostrictive materials shape in the direction of the magnetic field. Applying stronger magnetic field will tend to rotate more domains and makes the material to stretch even more until it reaches its saturation. This property has been used in many applications such as micro acoustic sensors, generators, marine sonar, devices, linear motors, robust actuators, automotive accessories, positioning devices etc. There is increasing interest in magnetostrictive applications after discovering the giant magnetostrictive alloys such as Galfenol and Terfenol-D which is capable of generating strains 100 times greater than traditional magnetostrictive materials at high temperatures. Even though Galfenol doesn't produce as much as magnetostriction as Terfenol-D, it can be constructed mechanically strong with tensile strengths up to 500 MPa and can be rolled, extruded, and welded. The magnetostrictive positioning devices based on submicro-textured magnetostrictive alloys (Fe85Ga15) and their advantages will be discussed.

  10. The design, construction and testing of a scour monitoring system using magnetostrictive materials

    NASA Astrophysics Data System (ADS)

    Day, Steven Richard

    A system for the continuous monitoring of scour has been designed, constructed and implemented. The system detects the level of scour by attaching flow to a buried post at known depths, and detecting when individual sensors become unearthed. Two bio-inspired flow sensors were designed and constructed for use on the post. The first, resembling a seal whisker, utilized the magnetostrictive materials Alfenol and Galfenol and was optimized for >0.15m/s flow. The second, resembling seaweed, used a conventional permanent magnet and was optimized for <0.15m/s flow. A small, low powered data acquisition system was designed and constructed to monitor and record the data from the sensors. A total of four scour posts were installed at two different sites; two vertically to monitor conventional scour and two horizontally to monitor lateral riverbed migration. Data from the posts was analyzed and presented and lessons learned were documented.

  11. Note: high sensitivity self-bias magnetoelectric sensor with two different magnetostrictive materials.

    PubMed

    Chen, Lei; Li, Ping; Wen, Yumei; Zhu, Yong

    2013-06-01

    The self-bias magnetoelectric (ME) sensor is designed, fabricated, and characterized for detecting weak ac magnetic-field. The two different magnetostrictive materials produce the gradient of magnetization, resulting in an internal magnetic field and a strong ME response. At zero-biased dc magnetic field, a low-frequency ME voltage coefficient (dVME∕dHac) of 22.11 mV∕Oe is achieved, which is 17.69 times higher than that of the previous magnets∕0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) sensor. Furthermore, the ME voltage coefficient reaches 2.73 V∕Oe at resonance. The induced ME voltage shows an excellent linear relationship to ac magnetic field when field amplitude varies from ~10(-7) Oe to 1 Oe. PMID:23822388

  12. Evaluation of magnetostrictive composite coated fabric as a fragment barrier material

    NASA Astrophysics Data System (ADS)

    Son, Kwon Joong; Fahrenthold, Eric P.

    2012-10-01

    Over the last decade a surge in fragment barrier research has led to investigation of numerous materials and material augmentations in the attempt to improve the ballistic performance of systems designed to protect personnel, vehicles or infrastructure from impact and blast loads. One widely studied material augmentation approach is the use of coatings, often polymers, to enhance the performance of protection systems constructed from metal, concrete, composite and fabric materials. In recent research the authors have conducted the first experimental study of the ballistic performance of fabrics coated with a magnetically responsive polymer. Zero field impact experiments on coated fabric targets showed a 61% increase in impact energy dissipation, although the coated targets were not competitive with neat fabrics on a protection per unit mass basis. Under an applied field of 110 kA m-1, the ballistic performance of the coated fabric was reduced. The reduction in performance may be attributed to a reduction in material damping and an increase in material modulus for the magnetostrictive component of the coating. Analysis of the coated fabric response to magnetic preloads suggests that coating tensile stresses and coating-fabric interface stresses induced by the applied field may also adversely affect ballistic performance.

  13. Characterization of the Dynamic Material Properties of Magnetostrictive Terfenol-D

    NASA Technical Reports Server (NTRS)

    Calkins, Frederick T.; Flatau, Alison B.; Hall, David L.

    1996-01-01

    A major limitation in use of electromagnetic and/or magnetomechanical models for design of Terfenol-D actuators is the lack of reliable material property data for Terfenol-D. In particular data on the performance of Terfenol-D as employed in a transducer, operating under real world dynamic conditions is needed. To provide this information, Terfenol-D rod properties need to be measured under as run prestressed and magnetically biased states. Using a Terfenol-D actuator, the following properties can be measured and/or calculated: mechanical quality factor, speed of sound in the material, the resonant frequency, the anti-resonant frequency, two magnetic permeabilities (one at constant stress and one at constant strain), two Young's moduli (one at constant amplitude applied magnetic field and one at constant amplitude magnetic flux density in the material), the magnetomechanical coupling, and the axial strain coefficient. The development of the material properties measurements and calculations is based on the model of low signal, linear, magnetostriction from Clark, the linear transduction equations for a transducer from Hunt, and a one degree of freedom mechanical model of the transducer. The electrical impedance and admittance mobility loops are used to determine the resonant, anti-resonant, and half power point frequencies. The rest of the material properties indicated above can then be calculated using these frequencies, acceleration from an accelerometer mounted on the actuator arm, and readily measurable transducer and Terfenol-D rod parameters.

  14. Magnetostrictive actuators compared to piezoelectric actuators

    NASA Astrophysics Data System (ADS)

    Claeyssen, Frank; Lhermet, Nicolas; Maillard, T.

    2003-03-01

    Magnetostriction occurs in the most ferromagnetic materials and leads to many effect. The most useful one to refer to is the Joule effect. It is responsible for the expansion or the contraction of a rod subjected to a longitudinal static magnetic field. In a given material, this magnetostrian is quadratic and occurs always in the same direction whatever is the field direction. Giant Magnetostrictive Materials (GMM), especially Rare erath-iron discovered by AE Clark, feature magnetostrains which are two orders of magntitude larger than Nickel. Among them, bulk Tb0.3Dy0.7Fe1.9, called Terfenol-D, presents the best compromise between a large magnetostrain and a low magnetic field, at room temperature. Positive magnetostrains of 1000 to 2000 ppm obtained with fields of 50 to 200 kA/m are reported for bulk materials. In the 90s, bulk magnetostrictive composite materials have been developed for high frequency ultrasonic applications. More recently, high magnetostrains have also been obtained in rare earth-iron thin films.

  15. Stress-induced variation in magnetization and the dynamic magnetostrictive characteristic of soft magnetic materials

    NASA Astrophysics Data System (ADS)

    Gonda, P.

    1980-04-01

    The low-field magnetostrictive properties of amorphous ribbons are examined. From the measured hysteresis loops of as-prepared samples of Fe 35Co 32B 20Si 10Al 3, (FeNi) 80B 17.5Al 2Si 0.5 the stress-induced variation of the magnetization is used for the calculation of the dynamic magnetostrictive characteristic Δλ( H) and λ( H). The resulting hysteresis loops may be attributed to the curling magnetization mode.

  16. An optimal design of magnetostrictive material (MsM) based energy harvester

    NASA Astrophysics Data System (ADS)

    Hu, Jingzhen; Yuan, Fuh-Gwo; Xu, Fujun; Huang, Alex Q.

    2010-04-01

    In this study, an optimal vibration-based energy harvesting system using magnetostrictive material (MsM) has been designed to power the Wireless Intelligent Sensor Platform (WISP), developed at North Carolina State University. A linear MsM energy harvesting device has been modeled and optimized to maximize the power output. The effects of number of MsM layers and glue layers, and load matching on the output power of the MsM energy harvester have been analyzed. From the measurement, the open circuit voltage can reach 1.5 V when the MsM cantilever beam operates at the 2nd natural frequency 324 Hz. The AC output power is 0.97 mW, giving power density 279 μW/cm3. Since the MsM device has low open circuit output voltage characteristics, a full-wave quadrupler has been designed to boost the rectified output voltage. To deliver the maximum output power to the load, a complex conjugate impedance matching between the load and the MsM device has been implemented using a discontinuous conduction mode (DCM) buck-boost converter. The maximum output power after the voltage quadrupler is now 705 μW and power density reduces to 202.4 μW/cm3, which is comparable to the piezoelectric energy harvesters given in the literature. The output power delivered to a lithium rechargeable battery is around 630 μW, independent of the load resistance.

  17. Self-contained hybrid electro-hydraulic actuators using magnetostrictive and electrostrictive materials

    NASA Astrophysics Data System (ADS)

    Chaudhuri, Anirban

    Hybrid electro-hydraulic actuators using smart materials along with flow rectification have been widely reported in recent years. The basic operation of these actuators involves high frequency bidirectional operation of an active material that is converted into unidirectional fluid motion by a set of valves. While theoretically attractive, practical constraints limit the efficacy of the solid-fluid hybrid actuation approach. In particular, inertial loads, fluid viscosity and compressibility combine with loss mechanisms inherent in the active material to limit the effective bandwidth of the driving actuator and the total output power. A hybrid actuator was developed by using magnetostrictive TerFeNOL-D as the active driving element and hydraulic oil as the working fluid. Tests, both with and without an external load, were carried out to measure the unidirectional performance of the actuator at different pumping frequencies and operating conditions. The maximum no-load output velocity was 84 mm/s with a 51 mm long rod and 88 mm/s with a 102 mm long rod, both noted around 325 Hz pumping frequency, while the blocked force was close to 89 N. Dynamic tests were performed to analyze the axial vibration characteristics of the Terfenol-D rods and frequency responses of the magnetic circuits. A second prototype actuator employing the same actuation principle was then designed by using the electrostrictive material PMN-32%PT as the driving element. Tests were conducted to measure the actuator performance for varying electrical input conditions and fluid bias pressures. The peak output velocity obtained was 330 mm/s while the blocked force was 63 N. The maximum volume flow rate obtained with the PMN-based actuator was more than double that obtained from the Terfenol-D--based actuator. Theoretical modeling of the dynamics of the coupled structural-hydraulic system is extremely complex and several models have been proposed earlier. At high pumping frequencies, the fluid inertia

  18. Optimal design of a vibration-based energy harvester using magnetostrictive material (MsM)

    NASA Astrophysics Data System (ADS)

    Hu, J.; Xu, F.; Huang, A. Q.; Yuan, F. G.

    2011-01-01

    In this study, an optimal vibration-based energy harvesting system using magnetostrictive material (MsM) was designed and tested to enable the powering of a wireless sensor. In particular, the conversion efficiency, converting from magnetic to electric energy, is approximately modeled from the magnetic field induced by the beam vibration. A number of factors that affect the output power such as the number of MsM layers, coil design and load matching are analyzed and explored in the design optimization. From the measurements, the open-circuit voltage can reach 1.5 V when the MsM cantilever beam operates at the second natural frequency 324 Hz. The AC output power is 970 µW, giving a power density of 279 µW cm - 3. The attempt to use electrical reactive components (either inductors or capacitors) to resonate the system at any frequency has also been analyzed and tested experimentally. The results showed that this approach is not feasible to optimize the power. Since the MsM device has low output voltage characteristics, a full-wave quadrupler has been designed to boost the rectified output voltage. To deliver the maximum output power to the load, a complex conjugate impedance matching between the load and the MsM device is implemented using a discontinuous conduction mode (DCM) buck-boost converter. The DC output power after the voltage quadrupler reaches 705 µW and the corresponding power density is 202 µW cm - 3. The output power delivered to a lithium rechargeable battery is around 630 µW, independent of the load resistance.

  19. Stochastic bifurcation and fractal and chaos control of a giant magnetostrictive film-shape memory alloy composite cantilever plate subjected to in-plane harmonic and stochastic excitation

    SciTech Connect

    Zhu, Zhiwen; Zhang, Qingxin Xu, Jia

    2014-05-07

    Stochastic bifurcation and fractal and chaos control of a giant magnetostrictive film–shape memory alloy (GMF–SMA) composite cantilever plate subjected to in-plane harmonic and stochastic excitation were studied. Van der Pol items were improved to interpret the hysteretic phenomena of both GMF and SMA, and the nonlinear dynamic model of a GMF–SMA composite cantilever plate subjected to in-plane harmonic and stochastic excitation was developed. The probability density function of the dynamic response of the system was obtained, and the conditions of stochastic Hopf bifurcation were analyzed. The conditions of noise-induced chaotic response were obtained in the stochastic Melnikov integral method, and the fractal boundary of the safe basin of the system was provided. Finally, the chaos control strategy was proposed in the stochastic dynamic programming method. Numerical simulation shows that stochastic Hopf bifurcation and chaos appear in the parameter variation process. The boundary of the safe basin of the system has fractal characteristics, and its area decreases when the noise intensifies. The system reliability was improved through stochastic optimal control, and the safe basin area of the system increased.

  20. Magnetostriction in glass-coated magnetic microwires

    NASA Astrophysics Data System (ADS)

    Zhukov, A.; Zhukova, V.; Blanco, J. M.; Cobeño, A. F.; Vazquez, M.; Gonzalez, J.

    2003-03-01

    The hysteretic magnetic properties of glass coated magnetic microwires depend on the magnetostriction constant: Co-rich microwires with negative magnetostriction constant present an almost non-hysteretic loop with relatively high magnetic anisotropy field up to around 8 kA/m. In contrast, Fe-rich microwires with positive magnetostriction show rectangular hysteresis loops with switching field depending on diameter of the metallic nucleus and the thickness of the glass coating. The softest magnetic properties, such as large magnetic permeability, are observed in nearly zero magnetostrictive alloys. It is then obvious that the experimental determination of the saturation magnetostriction λs of glass-coated microwires is very important to predict their magnetic behaviour. Different methods for the determination of the saturation magnetostriction λs of tiny glass coated microwires have been reviewed and compared in this manuscript. Small angle magnetization rotation (SAMR) method and change of the giant magneto-impedance spectrum under applied stress have been employed in nearly zero magnetostrictive in as-prepared and current annealed glass-covered microwires. The conditions of applicability of these methods to the microwires have been analysed, taking into account the domain structure expected for vanishing magnetostriction constant of the metallic nucleus. These different techniques give similar saturation magnetostriction constant values. Heat treatment results in a significant change of λs.

  1. Remote control of magnetostriction-based nanocontacts at room temperature

    PubMed Central

    Jammalamadaka, S. Narayana; Kuntz, Sebastian; Berg, Oliver; Kittler, Wolfram; Kannan, U. Mohanan; Chelvane, J. Arout; Sürgers, Christoph

    2015-01-01

    The remote control of the electrical conductance through nanosized junctions at room temperature will play an important role in future nano-electromechanical systems and electronic devices. This can be achieved by exploiting the magnetostriction effects of ferromagnetic materials. Here we report on the electrical conductance of magnetic nanocontacts obtained from wires of the giant magnetostrictive compound Tb0.3Dy0.7Fe1.95 as an active element in a mechanically controlled break-junction device. The nanocontacts are reproducibly switched at room temperature between “open” (zero conductance) and “closed” (nonzero conductance) states by variation of a magnetic field applied perpendicularly to the long wire axis. Conductance measurements in a magnetic field oriented parallel to the long wire axis exhibit a different behaviour where the conductance switches between both states only in a limited field range close to the coercive field. Investigating the conductance in the regime of electron tunneling by mechanical or magnetostrictive control of the electrode separation enables an estimation of the magnetostriction. The present results pave the way to utilize the material in devices based on nano-electromechanical systems operating at room temperature. PMID:26323326

  2. Remote control of magnetostriction-based nanocontacts at room temperature

    NASA Astrophysics Data System (ADS)

    Jammalamadaka, S. Narayana; Kuntz, Sebastian; Berg, Oliver; Kittler, Wolfram; Kannan, U. Mohanan; Chelvane, J. Arout; Sürgers, Christoph

    2015-09-01

    The remote control of the electrical conductance through nanosized junctions at room temperature will play an important role in future nano-electromechanical systems and electronic devices. This can be achieved by exploiting the magnetostriction effects of ferromagnetic materials. Here we report on the electrical conductance of magnetic nanocontacts obtained from wires of the giant magnetostrictive compound Tb0.3Dy0.7Fe1.95 as an active element in a mechanically controlled break-junction device. The nanocontacts are reproducibly switched at room temperature between “open” (zero conductance) and “closed” (nonzero conductance) states by variation of a magnetic field applied perpendicularly to the long wire axis. Conductance measurements in a magnetic field oriented parallel to the long wire axis exhibit a different behaviour where the conductance switches between both states only in a limited field range close to the coercive field. Investigating the conductance in the regime of electron tunneling by mechanical or magnetostrictive control of the electrode separation enables an estimation of the magnetostriction. The present results pave the way to utilize the material in devices based on nano-electromechanical systems operating at room temperature.

  3. Remote control of magnetostriction-based nanocontacts at room temperature.

    PubMed

    Jammalamadaka, S Narayana; Kuntz, Sebastian; Berg, Oliver; Kittler, Wolfram; Kannan, U Mohanan; Chelvane, J Arout; Sürgers, Christoph

    2015-01-01

    The remote control of the electrical conductance through nanosized junctions at room temperature will play an important role in future nano-electromechanical systems and electronic devices. This can be achieved by exploiting the magnetostriction effects of ferromagnetic materials. Here we report on the electrical conductance of magnetic nanocontacts obtained from wires of the giant magnetostrictive compound Tb0.3Dy0.7Fe1.95 as an active element in a mechanically controlled break-junction device. The nanocontacts are reproducibly switched at room temperature between "open" (zero conductance) and "closed" (nonzero conductance) states by variation of a magnetic field applied perpendicularly to the long wire axis. Conductance measurements in a magnetic field oriented parallel to the long wire axis exhibit a different behaviour where the conductance switches between both states only in a limited field range close to the coercive field. Investigating the conductance in the regime of electron tunneling by mechanical or magnetostrictive control of the electrode separation enables an estimation of the magnetostriction. The present results pave the way to utilize the material in devices based on nano-electromechanical systems operating at room temperature. PMID:26323326

  4. Design and modeling of a single-crystal iron-gallium large magnetostrictive dynamic research transducer

    NASA Astrophysics Data System (ADS)

    Twarek, Luke M.; Haack, Sarah J.; Flatau, Alison B.

    2004-07-01

    Alloys of iron and non-magnetic gallium (of the form Fe1-xGax where x ranges from 13 to 30) exhibit large magnetostrictions of over 300 ppm at room temperature that are produced by saturation magnetic fields of approximately 600 Oe. While not producing magnetostrictions of the degree achievable with giant magnetostrictives, large magnetostrictive alloys of iron and gallium, called Galfenol, have much more desirable mechanical characteristics, such as non-brittleness and in-plane auxetic behavior. Additionally, Galfenol requires a much smaller saturation magnetic field than the giant magnetostrictives Terfenol and Terfenol-D (alloys of Iron and non-metallic Terbium and Dysprosium). Beginning from the body of knowledge gained from Terfenol and Terfenol-D dynamic research transducer designs is a good starting point for designing a Galfenol dynamic research transducer. However, several modifications are being made to adapt the transducer to some of Galfenol's unique properties. Any measured value uncertainty will quickly propagate through the calculated material properties. While not completely successful at addressing all the unique aspects Galfenol in this transducer design, the data presented will assist in future design attempts.

  5. Modeling of resonant magneto-electric effect in a magnetostrictive and piezoelectric laminate composite structure coupled by a bonding material

    NASA Astrophysics Data System (ADS)

    Hasanyan, D.; Wang, Y.; Gao, J.; Li, M.; Shen, Y.; Li, J.; Viehland, D.

    2012-09-01

    The harmonic magneto-electro-elastic vibration of a thin laminated composite was considered. A theoretical model, including shear lag and vibration effects was developed for predicting the magneto-electric (ME) effect in a laminate composite consisting of magnetostrictive and piezoelectric layers. To avoid bending, we assumed that the composite was geometrically symmetric. For finite length symmetrically fabricated laminates, we derived the dynamic strain-stress field and ME coefficients, including shear lag and vibration effects for several boundary conditions. Parametric studies are presented to evaluate the influences of material properties and geometries on the strain distribution and the ME coefficient. Analytical expressions indicate that the shear lag and the vibration frequency strongly influence the strain distribution in the laminates and these effects strongly influence the ME coefficients.

  6. A continuum three-dimensional, fully coupled, dynamic, non-linear finite element formulation for magnetostrictive materials

    NASA Astrophysics Data System (ADS)

    Pérez-Aparicio, José L.; Sosa, Horacio

    2004-06-01

    Magnetostriction is a phenomenon observed in all ferromagnetic materials. It couples elastic, electric, magnetic and in some situations also thermal fields and is of great industrial interest for use in sensors, actuators, adaptive or functional structures, robotics, transducers and MEMS. In this work, the governing equations of the three-field problem (i.e., the interactions of elastic, electric and magnetic effects) are formulated in three dimensions, accounting for non-linear (through magnetic body forces represented by the Maxwell tensor) and dynamic effects, and with constitutive equations resembling those of piezoelectricity. Through manipulation of Maxwell equations it is possible to find suitable expressions for developing the numerical weak, Galerkin and matrix forms in a natural way, including seven residuals (one for each nodal degree of freedom) and non-symmetric tangent, 'capacity' and mass consistent matrices. Simple backward Euler and central difference schemes can be used for the time domain integration. The only assumption made in this work for simplification is that the time variation of electric induction is negligible. This is justified by the relatively low frequencies ({\\ll }1 GHz) under which magnetostrictive materials usually work. The principal feature of the equations is the use of a magnetic potential (without much physical meaning) that allows a complete 'displacement' finite element formulation: all elastic, electric and magnetic nodal unknowns are zero derivatives. This allows the algorithm to be treated in a standard way, and important effects such as eddy currents can be obtained naturally. The formulation is implemented in the research finite element code FEAP. Although seven degrees of freedom per node is computer expensive to solve (especially for 3D problems), the current trend in the performance of computers, even personal ones, makes it worthwhile to build complete finite elements following the well-established (in mechanics

  7. Optimal orientation field to manufacture magnetostrictive composites with high magnetostrictive performance

    NASA Astrophysics Data System (ADS)

    Dong, Xufeng; Ou, Jinping; Guan, Xinchun; Qi, Min

    2010-11-01

    Magnetostrictive properties have relationship with the applied orientation field during the preparation of giant magnetostrictive composites. To understand the dependence of the optimal orientation field on particle volume fraction, composites with 20%, 30% and 50% particles by volume were fabricated by distributing Terfenol-D particles in an unsaturated polyester resin under various orientation fields. Their magnetostrictive properties were tested without pre-stress at room temperature. The results indicate that as the particle volume fraction increases, the optimal orientation field increases. The main reason for this phenomenon is the packing density for the composites with higher particle volume fraction is larger than that for those with lower particle content.

  8. The possibility of giant dielectric materials for multilayer ceramic capacitors

    PubMed Central

    Ishii, Tatsuya; Endo, Makoto; Masuda, Kenichiro; Ishida, Keisuke

    2013-01-01

    There have been numerous reports on discovery of giant dielectric permittivity materials called internal barrier layer capacitor in the recent years. We took particular note of one of such materials, i.e., BaTiO3 with SiO2 coating. It shows expressions of giant electric permittivity when processed by spark plasma sintering. So we evaluated various electrical characteristics of this material to find out whether it is applicable to multilayer ceramic capacitors. Our evaluation revealed that the isolated surface structure is the sole cause of expressions of giant dielectric permittivity. PMID:23479496

  9. Large Scale Magnetostrictive Valve Actuator

    NASA Technical Reports Server (NTRS)

    Richard, James A.; Holleman, Elizabeth; Eddleman, David

    2008-01-01

    Marshall Space Flight Center's Valves, Actuators and Ducts Design and Development Branch developed a large scale magnetostrictive valve actuator. The potential advantages of this technology are faster, more efficient valve actuators that consume less power and provide precise position control and deliver higher flow rates than conventional solenoid valves. Magnetostrictive materials change dimensions when a magnetic field is applied; this property is referred to as magnetostriction. Magnetostriction is caused by the alignment of the magnetic domains in the material s crystalline structure and the applied magnetic field lines. Typically, the material changes shape by elongating in the axial direction and constricting in the radial direction, resulting in no net change in volume. All hardware and testing is complete. This paper will discuss: the potential applications of the technology; overview of the as built actuator design; discuss problems that were uncovered during the development testing; review test data and evaluate weaknesses of the design; and discuss areas for improvement for future work. This actuator holds promises of a low power, high load, proportionally controlled actuator for valves requiring 440 to 1500 newtons load.

  10. Magnetostrictive direct drive motor

    NASA Technical Reports Server (NTRS)

    Naik, Dipak; Dehoff, P. H.

    1991-01-01

    Highly magnetostrictive materials such as Tb.3Dy.7Fe2, commercially known as TERFENOL-D, have been used to date in a variety of devices such as high power actuators and linear motors. The larger magnetostriction available in twinned single crystal TERFENOL-D, approx. 2000 ppm at moderate magnetic field strengths, makes possible a new generation of magnetomechanical devices. NASA researchers are studying the potential of this material as the basis for a direct microstepping rotary motor with torque densities on the order of industrial hydraulics and five times greater than that of the most efficient, high power electric motors. Such a motor would be a micro-radian stepper, capable of precision movements and self-braking in the power-off state. Innovative mechanical engineering techniques are juxtaposed on proper magnetic circuit design to reduce losses in structural flexures, inertias, thermal expansions, eddy currents, and magneto-mechanical coupling, thus optimizing motor performance and efficiency. Mathematical models are presented, including magnetic, structural, and both linear and nonlinear dynamic calculations and simulations. In addition, test results on prototypes are presented.

  11. Terbium-Aluminum (TbAl2) Binary Alloy as High Magnetostrictive Material

    NASA Astrophysics Data System (ADS)

    Boghosian, Mary; Sanchez, Carlos; Bernal, Oscar; Kocharian, Armen; Cal State LA Team

    2015-03-01

    Magnetic phase diagram for the cubic intermetallic terbium-aluminum (Tb-Al) binary alloy is being investigated for the purpose of developing material with high magnetostrain properties that can be used for energy harvesting. Low temperature magnetizations, specific heat, combined with structural examinations are few of the techniques that are being used for this purpose. Preliminary DC magnetization results on as-cast material show magnetic ordering of around 109 K in zero applied fields that varies in magnitude and direction with the increase of applied magnetic field. The preliminary results will be discussed. Supported by Grant # NS-DMR1105380.

  12. Dirac State in Giant Magnetoresistive Materials

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Jo, N. H.; Ochi, M.; Huang, L.; Mou, D.; Kong, T.; Mun, E.; Wang, L.; Lee, Y.; Bud'Ko, S. L.; Canfield, P. C.; Trivedi, N.; Arito, R.; Kaminski, A.

    We use ultrahigh resolution, tunable, vacuum ultraviolet laser-based angle-resolved photoemission spectroscopy (ARPES) to study the electronic properties of materials that recently were discovered to display titanic magnetoresistance. We find that that several of these materials have Dirac-like features in their band structure. In some materials those features are ``ordinary'' Dirac cones, while in others the linear Dirac dispersion of two crossing bands forms a linear object in 3D momentum space. Our observation poses an important question about the role of Dirac dispersion in the unusually high, non-saturating magnetoresistance of these materials. Research was supported by the US DOE, Office of Basic Energy Sciences under Contract No. DE-AC02-07CH11358; Gordon and Betty Moore Foundation EPiQS Initiative (Grant No. GBMF4411); CEM, a NSF MRSEC, under Grant No. DMR-1420451.

  13. Magnetostrictive direct drive motors

    NASA Technical Reports Server (NTRS)

    Naik, Dipak; Dehoff, P. H.

    1992-01-01

    A new rare earth alloy, Terfenol-D, combines low frequency operation and extremely high energy density with high magnetostriction. Its material properties make it suitable as a drive element for actuators requiring high output torque. The high strains, the high forces and the high controllability of Terfenol alloys provide a powerful and challenging basis for new ways to generate motion in actuators. Two prototypes of motors using Terfenol-D rods were developed at NASA Goddard. The basic principles of operation are provided of the motor along with other relevant details. A conceptual design of a torque limiting safety clutch/brake under development is illustrated. Also, preliminary design drawings of a linear actuator using Terfenol-D is shown.

  14. Giant magnetoresistance materials for magnetic recording technology

    SciTech Connect

    Heffner, R.H.; Adams, C.D.; Brosha, E.L.

    1997-12-01

    This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). This work focused on a class of transition-metal-oxide (TMO) materials (LaMnO{sub 3} doped with Ca, Ba, or Sr) that exhibits an insulator-to-metal transition near a ferromagnetic phase transition temperature. This yields a very large magnetoresistance; thus these materials may have important uses as magnetic sensors in a variety of applications, ranging from automobiles to read heads for magnetic storage. In addition, the transport current in the ferromagnetic state is likely to be very highly polarized, which means that additional device applications using the phenomena of spin-polarized tunneling can be envisioned. Use of these materials as magnetic sensors depends upon learning to control the synthesis parameters (principally temperature, pressure and composition) to achieve a specific carrier concentration and/or mobility. A second challenge is the high magnetic fields ({ge}1 Tesla) currently required to achieve a large change in resistance. The authors began an investigation of two novel approaches to this field-sensitivity problem, involving the development of multilayer structures of the TMO materials. Finally, they began to explore the use of epitaxial strain as a means of changing the transport properties in thin-film multilayers.

  15. Development of Magnetostrictive Sensors

    NASA Astrophysics Data System (ADS)

    Kleinke, Darrell Kenneth

    1995-11-01

    The behavior of Magnetostrictive sensors was investigated through experimentation and mathematical modeling. Two prototype sensors were designed, built and tested. A generalized design procedure is proposed and applied. The experimental data shows the viability of the magnetostrictive sensor as an alternative to conventional sensors. The experimental data was used to uncover the limitations of existing mathematical models, and to validate a new model. The prototype sensors demonstrate the ruggedness and cost effectiveness of the magnetostrictive sensor. The mathematical model accurately predicted the behavior of two different sensor configurations, thus illustrating the model's flexibility. The design procedure can be used by sensor designers as a general guideline. The application of the design procedure is a unique application of magnetostrictive sensors, illustrating the viability, practicality and flexibility of magnetostrictive sensor technology.

  16. A constitutive model for magnetostriction based on thermodynamic framework

    NASA Astrophysics Data System (ADS)

    Ho, Kwangsoo

    2016-08-01

    This work presents a general framework for the continuum-based formulation of dissipative materials with magneto-mechanical coupling in the viewpoint of irreversible thermodynamics. The thermodynamically consistent model developed for the magnetic hysteresis is extended to include the magnetostrictive effect. The dissipative and hysteretic response of magnetostrictive materials is captured through the introduction of internal state variables. The evolution rate of magnetostrictive strain as well as magnetization is derived from thermodynamic and dissipative potentials in accordance with the general principles of thermodynamics. It is then demonstrated that the constitutive model is competent to describe the magneto-mechanical behavior by comparing simulation results with the experimental data reported in the literature.

  17. Magnetostriction and hysteresis of lang1 1 0rang oriented Tb0.29Dy0.48Ho0.23Fe2 single crystal

    NASA Astrophysics Data System (ADS)

    Jiang, Chengbao; Zhang, Hongbo; Wang, Zhibin; Xu, Huibin

    2008-08-01

    Magnetostriction behaviour and magnetostriction hysteresis of the single crystal alloy Tb0.29Dy0.48Ho0.23Fe2 are investigated experimentally and theoretically. The oriented lang1 1 0rang single crystals of the magnetostrictive alloy Tb0.29Dy0.48Ho0.23Fe2 are successfully prepared by the optical floating zone melting method. The single crystals are characterized by optical metallography, x-ray diffraction and x-ray Laue back-reflection measurement. The giant magnetostrictive properties are achieved in a wide operating temperature range from -60 to 80 °C. The calculated magnetostriction of the present alloy is reduced by only 6%, but the magnetostriction hysteresis (Wh) is reduced by more than 30%, compared with the traditional Terfenol-D giant magnetostrictive alloy. The magnetostriction behaviour is modelled using phenomenological theory. The rotation paths of magnetic domain moments are mathematically calculated and hence the resultant magnetostriction is obtained. The theoretical model of magnetostriction hysteresis Wh is proposed and the intrinsic factors of Wh are determined, which can well explain the pre-stress and temperature dependence of magnetostriction hysteresis.

  18. Giant Mechanocaloric Effects in Fluorite-Structured Superionic Materials.

    PubMed

    Cazorla, Claudio; Errandonea, Daniel

    2016-05-11

    Mechanocaloric materials experience a change in temperature when a mechanical stress is applied on them adiabatically. Thus, far, only ferroelectrics and superelastic metallic alloys have been considered as potential mechanocaloric compounds to be exploited in solid-state cooling applications. Here we show that giant mechanocaloric effects occur in hitherto overlooked fast ion conductors (FIC), a class of multicomponent materials in which above a critical temperature, Ts, a constituent ionic species undergoes a sudden increase in mobility. Using first-principles and molecular dynamics simulations, we found that the superionic transition in fluorite-structured FIC, which is characterized by a large entropy increase of the order of 10(2) JK(-1) kg(-1), can be externally tuned with hydrostatic, biaxial, or uniaxial stresses. In particular, Ts can be reduced several hundreds of degrees through the application of moderate tensile stresses due to the concomitant drop in the formation energy of Frenkel pair defects. We predict that the adiabatic temperature change in CaF2 and PbF2, two archetypal fluorite-structured FIC, close to their critical points are of the order of 10(2) and 10(1) K, respectively. This work advocates that FIC constitute a new family of mechanocaloric materials showing great promise for prospective solid-state refrigeration applications. PMID:27070506

  19. Calculation of magnetostriction constants

    NASA Astrophysics Data System (ADS)

    Tatebayashi, T.; Ohtsuka, S.; Ukai, T.; Mori, N.

    1986-02-01

    The magnetostriction constants h1 and h2 for Ni and Fe metals and the anisotropy constants K1 and K2 for Fe metal are calculated on the basis of the approximate d bands obtained by Deegan's prescription, by using Gilat-Raubenheimer's method. The obtained results are compared with the experimental ones.

  20. Galerkin finite element scheme for magnetostrictive structures and composites

    NASA Astrophysics Data System (ADS)

    Kannan, Kidambi Srinivasan

    The ever increasing-role of magnetostrictives in actuation and sensing applications is an indication of their importance in the emerging field of smart structures technology. As newer, and more complex, applications are developed, there is a growing need for a reliable computational tool that can effectively address the magneto-mechanical interactions and other nonlinearities in these materials and in structures incorporating them. This thesis presents a continuum level quasi-static, three-dimensional finite element computational scheme for modeling the nonlinear behavior of bulk magnetostrictive materials and particulate magnetostrictive composites. Models for magnetostriction must deal with two sources of nonlinearities-nonlinear body forces/moments in equilibrium equations governing magneto-mechanical interactions in deformable and magnetized bodies; and nonlinear coupled magneto-mechanical constitutive models for the material of interest. In the present work, classical differential formulations for nonlinear magneto-mechanical interactions are recast in integral form using the weighted-residual method. A discretized finite element form is obtained by applying the Galerkin technique. The finite element formulation is based upon three dimensional eight-noded (isoparametric) brick element interpolation functions and magnetostatic infinite elements at the boundary. Two alternative possibilities are explored for establishing the nonlinear incremental constitutive model-characterization in terms of magnetic field or in terms of magnetization. The former methodology is the one most commonly used in the literature. In this work, a detailed comparative study of both methodologies is carried out. The computational scheme is validated, qualitatively and quantitatively, against experimental measurements published in the literature on structures incorporating the magnetostrictive material Terfenol-D. The influence of nonlinear body forces and body moments of magnetic origin

  1. Improved magnetostrictive transducer drive elements achieved by reduction of crystalline defects and improved crystalline orientation

    NASA Astrophysics Data System (ADS)

    McMasters, Dale

    1993-10-01

    The discovery of the 'giant' magnetostrictive rare earth-iron alloys in the 1970's was a direct result of the efforts initiated at DOD's Naval Surface Warfare Center (NSWC), Silver Spring, MD in conjunction with DOE's Ames Laboratory (AL), Ames, IA. This research into these new materials was specifically targeted for the development of low frequency, high power transducers for underwater sonar systems. The most technologically advanced of these materials is TERFENOL-D, Tb(3)Dy(7)Fe(1.9-1.95) an intermetallic compound consisting of iron (Fe) and the rare earth metals terbium (Tb), and dysprosium (Dy). Because of the advantages over existing transducer materials, the use of TERFENOL-D as a transducer drive element is expanding into a broad range of commercial applications and advanced defense systems. One of the disadvantages is the cost of these drivers, primarily due to the terbium and dysprosium raw materials.

  2. Magnetostrictive thin films for microwave spintronics

    PubMed Central

    Parkes, D. E.; Shelford, L. R.; Wadley, P.; Holý, V.; Wang, M.; Hindmarch, A. T.; van der Laan, G.; Campion, R. P.; Edmonds, K. W.; Cavill, S. A.; Rushforth, A. W.

    2013-01-01

    Multiferroic composite materials, consisting of coupled ferromagnetic and piezoelectric phases, are of great importance in the drive towards creating faster, smaller and more energy efficient devices for information and communications technologies. Such devices require thin ferromagnetic films with large magnetostriction and narrow microwave resonance linewidths. Both properties are often degraded, compared to bulk materials, due to structural imperfections and interface effects in the thin films. We report the development of epitaxial thin films of Galfenol (Fe81Ga19) with magnetostriction as large as the best reported values for bulk material. This allows the magnetic anisotropy and microwave resonant frequency to be tuned by voltage-induced strain, with a larger magnetoelectric response and a narrower linewidth than any previously reported Galfenol thin films. The combination of these properties make epitaxial thin films excellent candidates for developing tunable devices for magnetic information storage, processing and microwave communications. PMID:23860685

  3. Nonlinearities in Magnetostrictive Transducer Dynamic Output

    NASA Astrophysics Data System (ADS)

    Flatau, Alison; Faidley, L. E.; Calkins, F. T.; Dapino, M. J.

    1997-03-01

    We have designed a magnetostrictive transducer for use in characterizing material properties of 11.5 cm long by 1.27 cm diameter cylindrical samples of the magnetostrictive material Terfenol-D. The material studied is a commercially available Terfenol-D, made using a modified Brigman manufacturing process. Output displacements in the stiffness controlled portion of the transducer's dynamic range (as loaded, up to 1000 Hz) were measured using a LVDT. Trends in output were observed as controlled changes in operating conditions were made. Excitation frequency, amplitude of magnetic excitation, and prestress were varied independently as other operating conditions (including temperature, mass load, and magnetic bias) were held fixed. Data are presented demonstrating distinct nonlinearities associated with a monotonic decrease in output with increased excitation frequency, a monotonic increase in output with increased excitation amplitude, and an initial increase followed by a decrease in output with increased prestress.

  4. Magnetostrictive thin films for microwave spintronics.

    PubMed

    Parkes, D E; Shelford, L R; Wadley, P; Holý, V; Wang, M; Hindmarch, A T; van der Laan, G; Campion, R P; Edmonds, K W; Cavill, S A; Rushforth, A W

    2013-01-01

    Multiferroic composite materials, consisting of coupled ferromagnetic and piezoelectric phases, are of great importance in the drive towards creating faster, smaller and more energy efficient devices for information and communications technologies. Such devices require thin ferromagnetic films with large magnetostriction and narrow microwave resonance linewidths. Both properties are often degraded, compared to bulk materials, due to structural imperfections and interface effects in the thin films. We report the development of epitaxial thin films of Galfenol (Fe81Ga19) with magnetostriction as large as the best reported values for bulk material. This allows the magnetic anisotropy and microwave resonant frequency to be tuned by voltage-induced strain, with a larger magnetoelectric response and a narrower linewidth than any previously reported Galfenol thin films. The combination of these properties make epitaxial thin films excellent candidates for developing tunable devices for magnetic information storage, processing and microwave communications.

  5. Design of an innovative magnetostrictive patch actuator

    NASA Astrophysics Data System (ADS)

    Cinquemani, S.; Giberti, H.

    2015-04-01

    Magnetostrictive actuators can be profitably used to reduce vibration in structures. However, this technology has been exploited only to develop inertial actuators, while patches actuators have not been ever used in practice. Patches actuators consist on a layer of magnetostrictive material, which has to be stuck to the surface of the vibrating structure, and on a coil surrounding the layer itself. However, the presence of the winding severely limits the use of such devices. As a matter of fact, the scientific literature reports only theoretical uses of such actuators, but, in practice it does not seem they were ever used. This paper presents an innovative solution to improve the structure of the actuator patches, allowing their use in several practical applications. The principle of operation of these devices is rather simple. The actuator patch is able to generate a local deformation of the surface of the vibrating structure so as to introduce an equivalent damping that dissipates the kinetic energy associated to the vibration. This deformation is related to the behavior of the magnetostrictive material immersed in a variable magnetic field generated by the a variable current flowing in the winding. Contrary to what suggested in the theoretical literature, the designed device has the advantage of generating the variable magnetic field no longer in close proximity of the material, but in a different area, thus allowing a better coupling. The magnetic field is then conveyed through a suitable ferromagnetic structure to the magnetostrictive material. The device has been designed and simulated through FEA. Results confirm that the new configuration can easily overcome all the limits of traditional devices.

  6. Modeling of Magnetostriction of Soft Elastomer

    NASA Astrophysics Data System (ADS)

    Petr, Andriushchenko; Leonid, Afremov; Mariya, Chernova

    2014-03-01

    Small magnetic particles placed in a relatively soft polymer (with elastic modulus E ~ 10 ÷ 100 kPa) are magnetically soft elastomers. The external magnetic field acts on each particle which leads to microscopic deformation of the material and consequently to changing of its shape - magnetostriction. For purposes of studying of magnetostriction the model of movable cellular automata (MCA), in which a real heterogeneous material is an ensemble of interacting elements of finite size - automata, is used. It's supposed to be that the motion of each automata can be described by Newton's Second law. The force acting on the i-th automata consists of the following components: volume-dependent force acting on the automata i which is caused by pressure from the surrounding automata; force of an external magnetic field acting on the i-th automata with some magnetic moment; and normal and tangential interaction force between a pair of i and j automata. This approach was used for modeling of magnetostriction elastomer.

  7. Rhombohedral magnetostriction in dilute iron (Co) alloys

    SciTech Connect

    Jones, Nicholas J. Wun-Fogle, Marilyn; Restorff, J. B.; Petculescu, Gabriela; Clark, Arthur E.; Hathaway, Kristl B.; Schlagel, Deborah; Lograsso, Thomas A.

    2015-05-07

    Iron is a well-utilized material in structural and magnetic applications. This does not mean, however, that it is well understood, especially in the field of magnetostriction. In particular, the rhombohedral magnetostriction of iron, λ{sub 111}, is anomalous in two respects: it is negative in sign, in disagreement with the prediction of first principles theory, and its magnitude decreases with increasing temperature much too rapidly to be explained by a power law dependence on magnetization. These behaviors could arise from the location of the Fermi level, which leaves a small region of the majority 3d t{sub 2g} states unfilled, possibly favoring small internal displacements that split these states. If this view is correct, adding small amounts of Co to Fe fills some of these states, and the value of λ{sub 111} should increase toward a positive value, as predicted for perfect bcc Fe. We have measured the magnetostriction coefficients (λ{sub 111} and λ{sub 100}) of pure Fe, Fe{sub 97}Co{sub 3}, and Fe{sub 94}Co{sub 6} single crystals from 77 K to 450 K. Resonant ultrasound spectroscopy has been used to check for anomalies in the associated elastic constants, c{sub 44} and c′. The additional electrons provided by the cobalt atoms indeed produced positive contributions to both magnetostriction constants, λ{sub 111} and λ{sub 100}, exhibiting an increase of 2.8 × 10{sup −6} per at. % Co for λ{sub 111} and 3.8 × 10{sup −6} per at. % Co for λ{sub 100}.

  8. Improved magnetostrictive transducer drive elements achieved by reduction of crystalline defects and improved crystalline orientation. Final report

    SciTech Connect

    McMasters, D.

    1993-10-29

    The discovery of the giant magnetostrictive rare earth-iron alloys in the 1970's was a direct result of the efforts initiated at DOD's Naval Surface Warfare Center (NSWC), Silver Spring, MD in conjunction with DOE's Ames Laboratory (AL), Ames, IA. This research into these new materials was specifically targeted for the development of low frequency, high power transducers for underwater sonar systems. The most technologically advanced of these materials in TERFENOL-D, Tb(3)Dy(7)Fe(1.9-1.95) an intermetallic compound consisting of iron (Fe) and the rare earth metals terbium (Tb) and dysprosium (Dy). Because of the advantages over existing transducer materials, the use of TERFENOL-D as a transducer drive element is expanding into a broad range of commercial applications and advanced defense systems. One of the disadvantages is the cost of these drivers, primarily the terbium and dysprosium raw materials.

  9. Improvement in indirect magnetostriction measurements

    NASA Astrophysics Data System (ADS)

    Németh, S.; Kopasz, C.; Hargitai, C.

    1992-07-01

    The SAMR and AtS methods are simultaneously applied for determination magnetostriction constants to reduce the uncertainties in the interpretation of the quantities directly measured and to improve the accuracy in λ values determined.

  10. Development of magnetostrictive active members for control of space structures

    NASA Technical Reports Server (NTRS)

    Johnson, Bruce G.; Avakian, Kevin M.; Fenn, Ralph C.; Gaffney, Monique S.; Gerver, Michael J.; Hawkey, Timothy J.; Boudreau, Donald J.

    1992-01-01

    The goal of this Phase 2 Small Business Innovative Research (SBIR) project was to determine the technical feasibility of developing magnetostrictive active members for use as truss elements in space structures. Active members control elastic vibrations of truss-based space structures and integrate the functions of truss structure element, actively controlled actuator, and sensor. The active members must control structural motion to the sub-micron level and, for many proposed space applications, work at cryogenic temperatures. Under this program both room temperature and cryogenic temperature magnetostrictive active members were designed, fabricated, and tested. The results of these performance tests indicated that room temperature magnetostrictive actuators feature higher strain, stiffness, and force capability with lower amplifier requirements than similarly sized piezoelectric or electrostrictive active members, at the cost of higher mass. Two different cryogenic temperature magnetostrictive materials were tested at liquid nitrogen temperatures, both with larger strain capability than the room temperature magnetostrictive materials. The cryogenic active member development included the design and fabrication of a cryostat that allows operation of the cryogenic active member in a space structure testbed.

  11. Giant and universal magnetoelectric coupling in soft materials and concomitant ramifications for materials science and biology.

    PubMed

    Liu, Liping; Sharma, Pradeep

    2013-10-01

    Magnetoelectric coupling-the ability of a material to magnetize upon application of an electric field and, conversely, to polarize under the action of a magnetic field-is rare and restricted to a rather small set of exotic hard crystalline materials. Intense research activity has recently ensued on materials development, fundamental scientific issues, and applications related to this phenomenon. This tantalizing property, if present in adequate strength at room temperature, can be used to pave the way for next-generation memory devices such as miniature magnetic random access memories and multiple state memory bits, sensors, energy harvesting, spintronics, among others. In this Rapid Communication, we prove the existence of an overlooked strain mediated nonlinear mechanism that can be used to universally induce the giant magnetoelectric effect in all (sufficiently) soft dielectric materials. For soft polymer foams-which, for instance, may be used in stretchable electronics-we predict room-temperature magnetoelectric coefficients that are comparable to the best known (hard) composite materials created. We also argue, based on a simple quantitative model, that magnetoreception in some biological contexts (e.g., birds) most likely utilizes this very mechanism.

  12. Giant and universal magnetoelectric coupling in soft materials and concomitant ramifications for materials science and biology

    NASA Astrophysics Data System (ADS)

    Liu, Liping; Sharma, Pradeep

    2013-10-01

    Magnetoelectric coupling—the ability of a material to magnetize upon application of an electric field and, conversely, to polarize under the action of a magnetic field—is rare and restricted to a rather small set of exotic hard crystalline materials. Intense research activity has recently ensued on materials development, fundamental scientific issues, and applications related to this phenomenon. This tantalizing property, if present in adequate strength at room temperature, can be used to pave the way for next-generation memory devices such as miniature magnetic random access memories and multiple state memory bits, sensors, energy harvesting, spintronics, among others. In this Rapid Communication, we prove the existence of an overlooked strain mediated nonlinear mechanism that can be used to universally induce the giant magnetoelectric effect in all (sufficiently) soft dielectric materials. For soft polymer foams—which, for instance, may be used in stretchable electronics—we predict room-temperature magnetoelectric coefficients that are comparable to the best known (hard) composite materials created. We also argue, based on a simple quantitative model, that magnetoreception in some biological contexts (e.g., birds) most likely utilizes this very mechanism.

  13. Magnetostrictive microelectromechanical loudspeaker.

    PubMed

    Albach, Thorsten S; Lerch, Reinhard

    2013-12-01

    A microelectromechnical-loudspeaker based on the magnetostrictive effect is presented. The membrane consists of a comb structure of monomorph bending cantilevers with an area of about 16 mm(2). Prototypes generate a sound pressure level (SPL) of up to 102 dB at 450 Hz with a total harmonic distortion of 2% inside a 2 cm(3) measurement volume. The fabrication process of the device as well as a coupled simulation model to calculate its sound pressure is introduced. The model reproduces the measurements and is employed to further optimize the loudspeaker membrane. As a result, a computed maximum SPL of 106 dB has been achieved with a -6 dB frequency range extending from 100 Hz to 2.6 kHz.

  14. Laser ablation of a Terfenol-D microparticle aerosol and subsequent supersonic nanoparticle impaction for magnetostrictive thick films

    NASA Astrophysics Data System (ADS)

    O'Brien, Daniel Thomas

    This dissertation describes using microparticles of the (giant) magnetostrictive material Terfenol-D (Tb0.3Dy0.7Fe1.92) in the Laser Ablation of Microparticle (LAM) aerosols process for the generation of nanoparticles and their subsequent supersonic impaction to form nanostructured magnetostrictive thick films. Solid Terfenol-D was ground to a powder having diameters from 0.3 to 3 mum. This microparticle powder was then aerosolized and ablated by a KrF ultraviolet, pulsed laser in a continuously flowing aerosol process. The nanoparticles formed from the ablation were then accelerated through a supersonic nozzle into vacuum where they impacted onto a substrate at room temperature forming a film. The nanoparticles were amorphous, as shown by x-ray diffraction analysis of the deposited films and by Transmission Electron Microscopy of individual particles, and had a size distribution typical of the LAM process: 3 to 20 nm in diameter with a mean size less than 10 nm. The deposited films were characterized using the cantilever method to determine magnetostriction and elastic modulus. Values of magnetostriction were on the order of 15 ppm for LAM deposited films. The films were porous, due to their granular nature, reducing the elastic modulus to about 15 GPa. The reduced magnetostriction (1/30 that of comparable thin films) was due to oxidation. Spectroscopic analysis of the ablation plasma provided data in determining the source of the oxidation. Calculations showed that the extent of oxidation in the films was dependent on the microparticle feedstock size. For typical aerosol densities used in the LAM process, calculations showed that material made from microparticles having a diameter larger than 3 mum was not significantly affected by background gas impurities or by an oxide shell on the microparticles, whereas 0.3 mum diameter microparticles resulted in completely oxidized nanoparticles and hence films that were completely oxidized. From the behavior of the

  15. Recent advances in magnetostrictive particulate composite technology

    NASA Astrophysics Data System (ADS)

    Pulliam, Wade J.; McKnight, Geoffrey P.; Carman, Gregory P.

    2002-07-01

    Recently, there have been significant advances in using magnetostrictive particles in a polymer matrix; finding uses in many applications, both as an active transducer and a passive damper. Termed magnetostrictive particulate composites (MPC), the material provides capabilities identical or superior to the monolithic material. Fortis Technologies has been pursuing improvements in the application and fabrication of this innovative material. The MPC technology provides a passive, broadband, large temperature range, high stiffness, dampling material to be used where current technologies fall short. Damping applications of this technology include sporting goods, power/hand tools, space launch and satellite design, noise abatement and vibration isolation. Energy absorption of the composites has been measured and is approaching that of the monolithic material. The material can also be actively controlled by a magnetic field, producing a transducer that can be used for sonar applications. The advantage of this technology over those currently in use is the large power density at relatively low frequencies and the ease of fabrication, allowing less expensive and more effective conformal arrays. Effective strain output and piezomagnetic coefficients have been measured, as have its dynamic properties. The results show significant improvement of the strain output and piezomagnetic coefficients, approaching the monolithic material.

  16. Vibration Control via Stiffness Switching of Magnetostrictive Transducers

    NASA Technical Reports Server (NTRS)

    Scheidler, Justin J.; Asnani, Vivake M.; Dapino, Marcelo J.

    2016-01-01

    This paper presents a computational study of structural vibration control that is realized by switching a magnetostrictive transducer between high and low stiffness states. Switching is accomplished by either changing the applied magnetic field with a voltage excitation or changing the shunt impedance on the transducer's coil (i.e., the magnetostrictive material's magnetic boundary condition). Switched-stiffness vibration control is simulated using a lumped mass supported by a damper and the magnetostrictive transducer (mount), which is represented by a nonlinear, electromechanical model. Free vibration of the mass is calculated while varying the mount's stiffness according to a reference switched-stiffness vibration control law. The results reveal that switching the magnetic field produces the desired change in stiffness, but also an undesired actuation force that can significantly degrade the vibration control. Hence, a modified switched-stiffness control law that accounts for the actuation force is proposed and implemented for voltage-controlled stiffness switching. The influence of the magnetomechanical bias condition is also discussed. Voltage-controlled stiffness switching is found to introduce damping equivalent to a viscous damping factor up to about 0.25; this is shown to primarily result from active vibration reduction caused by the actuation force. The merit of magnetostrictive switched-stiffness vibration control is then quantified by comparing the results of voltage- and shunt-controlled stiffness switching to the performance of optimal magnetostrictive shunt damping.

  17. Vibration analysis of magnetostrictive thin-film composite cantilever actuator

    NASA Astrophysics Data System (ADS)

    Xu, Yan; Shang, Xinchun

    2016-09-01

    The transverse vibration of a composed cantilever beam with magnetostrictive layer is analyzed, which is employed to simulate dynamic response of an actuator. The high-order shear deformation theory of beam and the coupling magnetoelastic constitutive relationship are introduced to construct the governing equations, all interface conditions between magnetostrictive film and elastic substrate as well as the free stress condition on the top and bottom surfaces of the beam can be satisfied. In order to demonstrate validity of the presented mathematical modeling, the verification examples are also given. Furthermore, the effect of geometry and material parameters on dynamic characteristics of magnetostrictive cantilever beam, such as the nature frequency and amplitude, is discussed. Moreover, through computing the magneto-mechanical coupling factor of the beam structure, the variation tendency curves of the factor along with different parameters and frequencies of magnetostrictive cantilever beam actuator have been presented. These numerical results should be useful for the design of beam-type with magnetostrictive thin-film actuators.

  18. An Energy-Based Hysteresis Model for Magnetostrictive Transducers

    NASA Technical Reports Server (NTRS)

    Calkins, F. T.; Smith, R. C.; Flatau, A. B.

    1997-01-01

    This paper addresses the modeling of hysteresis in magnetostrictive transducers. This is considered in the context of control applications which require an accurate characterization of the relation between input currents and strains output by the transducer. This relation typically exhibits significant nonlinearities and hysteresis due to inherent properties of magnetostrictive materials. The characterization considered here is based upon the Jiles-Atherton mean field model for ferromagnetic hysteresis in combination with a quadratic moment rotation model for magnetostriction. As demonstrated through comparison with experimental data, the magnetization model very adequately quantifies both major and minor loops under various operating conditions. The combined model can then be used to accurately characterize output strains at moderate drive levels. The advantages to this model lie in the small number (six) of required parameters and the flexibility it exhibits in a variety of operating conditions.

  19. Temperature dependence of the magnetostriction and the induced anisotropy in nanocrystalline FeCuNbSiB alloys, and their fluxgate properties

    SciTech Connect

    Nielsen, O.V.; Petersen, J.R.; Herzer, G.

    1994-03-01

    Making use of the stress induced magnetic anisotropy in some iron-rich FeCuNbSiD nanocrystalline materials the authors studied the thermal dependence of their magnetostriction which becomes zero below the Curie temperature. The choice of a suitable composition and annealing temperature results in materials with zero magnetostriction at room temperature. Due to the low magnetostriction these materials have very promising fluxgate properties which were studied as well.

  20. Magnetostriction of field-structured magnetoelastomers.

    SciTech Connect

    Gulley, Gerald L. (Dominican University, River Forest, IL); Read, Douglas H.; Martin, James Ellis; Huber, Dale L.; Anderson, Robert Alan; Frankamp, Benjamin L.

    2005-12-01

    Field-structured magnetic particle composites are an important new class of materials that have great potential as both sensors and actuators. These materials are synthesized by suspending magnetic particles in a polymeric resin and subjecting these to magnetic fields while the resin polymerizes. If a simple uniaxial magnetic field is used, the particles will form chains, yielding composites whose magnetic susceptibility is enhanced along a single direction. A biaxial magnetic field, comprised of two orthogonal ac fields, forms particle sheets, yielding composites whose magnetic susceptibility is enhanced along two principal directions. A balanced triaxial magnetic field can be used to enhance the susceptibility in all directions, and biased heterodyned triaxial magnetic fields are especially effective for producing composites with a greatly enhanced susceptibility along a single axis. Magnetostriction is quadratic in the susceptibility, so increasing the composite susceptibility is important to developing actuators that function well at modest fields. To investigate magnetostriction in these field-structured composites we have constructed a sensitive, constant-stress apparatus capable of 1 ppm strain resolution. The sample geometry is designed to minimize demagnetizing field effects. With this apparatus we have demonstrated field-structured composites with nearly 10,000 ppm strain.

  1. Composition and crystallinity in electrochemically deposited magnetostrictive galfenol (FeGa)

    SciTech Connect

    Estrine, Eliot C. Hein, Matt; Robbins, William P.; Stadler, Bethanie J. H.

    2014-05-07

    Here, we report the first measurements of magnetostriction as a function of composition for electrodeposited iron-gallium alloys, also known as galfenol. Galfenol is an exciting material due to its large magnetostriction constant (up to 400 ppm) and robust mechanical properties. A wide range of sensors, actuators, and other transducers can be fabricated by taking advantage of galfenol's unique mix of magnetic and mechanical properties. Electrodeposition allows galfenol to be easily integrated into a variety of applications, such as toque sensors with conformal, monolithic active layers. In this work, we examine the underlying factors that influence magnetostriction in electrodeposited galfenol, including crystallinity and composition. Here, we have controlled the film composition, as measured by energy dispersive x-ray spectroscopy, over the range of 5–25% gallium using a single plating bath by varying deposition parameters. This composition range corresponds to the region of largest expected magnetostriction for iron gallium alloys. However, our measured magnetostriction values were significantly lower than the values for single crystal galfenol from literature. The electrodeposited films in this work appeared polycrystalline when measured using x-ray diffraction. When the texture of the film is taken into account, the magnetostriction results closely matched the predicted values. These results show that it is possible to achieve magnetostrictive galfenol thin films over a wide range of compositions using electrodeposition.

  2. Taming the first-order transition in giant magnetocaloric materials.

    PubMed

    Guillou, François; Porcari, Giacomo; Yibole, Hargen; van Dijk, Niels; Brück, Ekkes

    2014-05-01

    Large magnetically driven temperature changes are observed in MnFe(P,Si,B) materials simultaneously with large entropy changes, limited (thermal or magnetic) hysteresis, and good mechanical stability. The partial substitution of B for P in MnFe(P,Si) compounds is found to be an ideal parameter to control the latent heat observed at the Curie point without deteriorating the magnetic properties, which results in promising magnetocaloric properties suitable for magnetic refrigeration. PMID:24677518

  3. Magnetostriction measurements of amorphous ribbons and thin films

    NASA Astrophysics Data System (ADS)

    Ouyang, Chien

    The theme of the present work is to measure the saturation magnetostriction constants of amorphous ribbons and thin films. The saturation magnetostriction constants of amorphous ribbons, and thin films of Cosb{39}Nisb{31}Fesb8Sisb8Bsb{14}, CoZrY, and CoZrTb have been measured either by the Small Angle Magnetization Rotation (SAMR) method or by the initial susceptibility method. The SAMR method is used for the soft materials. It is found that the amorphous Cosb{39}Nisb{31}Fesb8Sisb8Bsb{14} prepared by ion beam deposition from an alloy target shows very soft magnetic properties and has a very small negative saturation magnetostriction, lambdasb{s}, of about {-}1×10sp{-7}. Sputtered films of CoZrTb show a strong perpendicular anisotropy when the Tb content is high. We have found that the SAMR method can be applied to CoZrTb films when the Tb content is low. The saturation magnetostriction constant of a sputtered film of Cosb{78.4}Zrsb{20.8}Tbsb{0.8} is 2×10sp{-6}. When the material is not magnetically soft or has a strong perpendicular anisotropy, the initial susceptibility method is used. The saturation magnetostriction constants of amorphous Cosb{77.2}Zrsb{20.4}Tbsb{2.4} and Cosb{72.2}Zrsb{14.6}Ysb{13.2} thin films are 6×10sp{-6}, and (2{˜}6)×10sp{-7}, respectively. The two methods, the SAMR and the initial susceptibility, utilize the same measurement setup making it a very convenient technique which is applicable for a range of materials.

  4. Understanding strong magnetostriction in Fe100−xGax alloys

    PubMed Central

    Wang, Hui; Zhang, Y. N.; Wu, R. Q.; Sun, L. Z.; Xu, D. S.; Zhang, Z. D.

    2013-01-01

    Magnetostriction of ferromagnetic materials describes the change of their shape or dimension in response to the reorientation of magnetization under the influence of external magnetic field. Fe100−xGax binary alloys (Galfenol) have large magnetostriction and excellent ductility; and they are very promising rare-earth free materials for applications in sensors, actuators, energy-harvesters and spintronic devices. Here we report results of large-scale ab initio molecular dynamics (AIMD) simulations for Galfenol, especially regarding the mechanism that leads to the sudden drop of tetragonal magnetostriction at x ~ 19, a long-standing puzzle for the community. Based on rigid band analysis, we propose possible ways to further optimize the performance of Galfenol for device applications. For example, we found that the substitution of a small amount of Cu for Ga (1.6%) in certain configuration may double the magnetostriction of Galfenol. PMID:24343479

  5. Anisotropic perpendicular axis magnetostriction in twinned TbxDy1 - xFe1.95

    NASA Astrophysics Data System (ADS)

    Teter, J. P.; Wun-Fogle, M.; Clark, A. E.; Mahoney, K.

    1990-05-01

    The longitudinal magnetostriction (Δl/l) for twinned TbxDy1-xFe1.95 material, prepared by the free-standing float-zone method, has been previously measured and found to be very large (2000×10-6) at room temperature. The magnetostrictions for the [111] and [11¯0] crystallographic axes perpendicular to the applied stress and magnetic-field [112¯] direction are presented as functions of temperature, applied stress, and applied magnetic field. The temperature range is ±60 °C centered about the anisotropy compensation temperature of Terfenol-D (+10 °C). The stress ranges from 2 to 32 MPa and the magnetic field to ±2000 Oe. The temperature dependence of the perpendicular axes magnetostriction is similar to that of the conventional magnetostriction measured parallel to the [112¯] growth axis. Relative values for the saturation magnetostriction exhibit a large anisotropy in the perpendicular direction, ranging from -117% for the [111] to +19% for the [11¯0] direction. This ratio stays constant as a function of temperature above the compensation temperature for a given prestress above 8 MPa. The largest absolute value of magnetostriction (2260×10-6) occurs in the [111] direction at 10 °C at a prestress pressure of 12 MPa. Above this temperature the magnetostriction falls at a rate of -8.5×10-6/°C. The volume magnetostriction is shown to be small and highly sample dependent. All data is consistent with the parent-twin magnetization model and also the magnetostriction values along nonprincipal axes.

  6. Magnetostrictive wire-bonding clamp for semiconductor packaging: initial prototype design, modeling, and experiments

    NASA Astrophysics Data System (ADS)

    Dozor, David M.

    1998-06-01

    A magnetostrictive wire-bonding clamp for use in semiconductor packaging applications has been developed by Mechatronic Technology Co. Semiconductor industry trends, requiring high process throughput on increasing lead count packaging, make the magnetostrictive material Terfenol-D a candidate for this application. To construct this small, lightweight device, small samples of Terfenol-D were prepared by ETREMA Products, Inc. This paper reports the initial design, mathematical modeling, and experiments related to this initial prototype.

  7. Vibration control via stiffness switching of magnetostrictive transducers

    NASA Astrophysics Data System (ADS)

    Scheidler, Justin J.; Asnani, Vivake M.; Dapino, Marcelo J.

    2016-04-01

    In this paper, a computational study is presented of structural vibration control that is realized by switching a magneto-strictive transducer between high and low stiffness states. Switching is accomplished by either changing the applied magnetic field with a voltage excitation or changing the shunt impedance on the transducer's coil (i.e., the magneto-strictive material's magnetic boundary condition). Switched-stiffness vibration control is simulated using a lumped mass supported by a damper and the magneto-strictive transducer (mount), which is represented by a nonlinear, electromechanical model. Free vibration of the mass is calculated while varying the mount's stiffness according to a reference switched-stiffness vibration control law. The results reveal that switching the magnetic field produces the desired change in stiffness, but also an undesired actuation force that can significantly degrade the vibration control. Hence, a modified switched-stiffness control law that accounts for the actuation force is proposed and implemented for voltage-controlled stiffness switching. The influence of the magneto-mechanical bias condition is also discussed. Voltage-controlled stiffness switching is found to introduce damping equivalent to a viscous damping factor up to about 0.13; this is shown to primarily result from active vibration reduction caused by the actuation force. The merit of magneto-strictive switched-stiffness vibration control is then quantified by comparing the results of voltage- and shunt-controlled stiffness switching to the performance of optimal magneto-strictive shunt damping. For the cases considered, optimal resistive shunt damping performed considerably better than both voltage- and shunt-controlled stiffness switching.

  8. Vibration Control via Stiffness Switching of Magnetostrictive Transducers

    NASA Technical Reports Server (NTRS)

    Scheidler, Justin J.; Asnani, Vivake M.; Dapino, Marcelo J.

    2016-01-01

    In this paper, a computational study is presented of structural vibration control that is realized by switching a magnetostrictive transducer between high and low stiffness states. Switching is accomplished by either changing the applied magnetic field with a voltage excitation or changing the shunt impedance on the transducer's coil (i.e., the magnetostrictive material's magnetic boundary condition). Switched-stiffness vibration control is simulated using a lumped mass supported by a damper and the magnetostrictive transducer (mount), which is represented by a nonlinear, electromechanical model. Free vibration of the mass is calculated while varying the mount's stiffness according to a reference switched-stiffness vibration control law. The results reveal that switching the magnetic field produces the desired change in stiffness, but also an undesired actuation force that can significantly degrade the vibration control. Hence, a modified switched-stiffness control law that accounts for the actuation force is proposed and implemented for voltage-controlled stiffness switching. The influence of the magneto-mechanical bias condition is also discussed. Voltage-controlled stiffness switching is found to introduce damping equivalent to a viscous damping factor up to about 0.13; this is shown to primarily result from active vibration reduction caused by the actuation force. The merit of magnetostrictive switched-stiffness vibration control is then quantified by comparing the results of voltage- and shunt-controlled stiffness switching to the performance of optimal magnetostrictive shunt damping. For the cases considered, optimal resistive shunt damping performed considerably better than both voltage- and shunt-controlled stiffness switching.

  9. Magnetostrictive Actuators For Cryogenic Applications

    NASA Technical Reports Server (NTRS)

    Dolgin, Benjamin P.

    1996-01-01

    Linear-translation motors containing magnetostrictive actuator elements proposed for use in making fine position adjustments on scientific instruments at temperatures from near absolute zero to room temperature. Actuators produce small increments of linear motion and operate in "set-and-forget" mode in sense they automatically lock themselves against motion when power not applied. Do not consume or dissipate power when stationary. Proposed linear-translation motors also made to produce large maximum displacements.

  10. Nebular and Interstellar Materials in a Giant Cluster IDP of Probable Cometary Origin

    NASA Technical Reports Server (NTRS)

    Messenger, S.; Brownlee, D. E.; Joswiak, D. J.; Nguyen, A. N.

    2015-01-01

    Comets contain a complex mixture of materials with presolar and Solar System origins. Chondritic porous interplanetary dust particles (CP-IDPs) are associated with comets by their fragile nature, unequilibrated anhydrous mineralogy and high abundances of circumstellar grains and isotopically anomalous organic materials. Comet 81P/Wild 2 samples returned by the Stardust spacecraft contain presolar materials as well as refractory 16O-rich Ca-Al-rich inclusion- (CAI), chondrule-, and AOA-like materials. We are conducting coordinated chemical, mineralogical, and isotopic studies of a giant cluster CP-IDP (U2-20-GCA) to determine the proportions of inner Solar System and interstellar materials. We previously found that this IDP contains abundant presolar silicates (approx. 1,800 ppm) and 15N-rich hotspots [6].

  11. Including Magnetostriction in Micromagnetic Models

    NASA Astrophysics Data System (ADS)

    Conbhuí, Pádraig Ó.; Williams, Wyn; Fabian, Karl; Nagy, Lesleis

    2016-04-01

    The magnetic anomalies that identify crustal spreading are predominantly recorded by basalts formed at the mid-ocean ridges, whose magnetic signals are dominated by iron-titanium-oxides (Fe3-xTixO4), so called "titanomagnetites", of which the Fe2.4Ti0.6O4 (TM60) phase is the most common. With sufficient quantities of titanium present, these minerals exhibit strong magnetostriction. To date, models of these grains in the pseudo-single domain (PSD) range have failed to accurately account for this effect. In particular, a popular analytic treatment provided by Kittel (1949) for describing the magnetostrictive energy as an effective increase of the anisotropy constant can produce unphysical strains for non-uniform magnetizations. I will present a rigorous approach based on work by Brown (1966) and by Kroner (1958) for including magnetostriction in micromagnetic codes which is suitable for modelling hysteresis loops and finding remanent states in the PSD regime. Preliminary results suggest the more rigorously defined micromagnetic models exhibit higher coercivities and extended single domain ranges when compared to more simplistic approaches.

  12. Micromotors using magnetostrictive thin films

    NASA Astrophysics Data System (ADS)

    Claeyssen, Frank; Le Letty, Ronan; Barillot, Francois; Betz, Jochen; MacKay, Ken; Givord, Dominique; Bouchilloux, Philippe

    1998-07-01

    This study deals with a micromotor based on the use of magnetostrictive thin films. This motor belongs to the category of the Standing Wave Ultrasonic Motors. The active part of the motor is the rotor, which is a 100 micrometers thick ring vibrating in a flexural mode. Teeth (300 micrometers high) are placed on special positions of the rotor and produce an oblique motion which can induce the relative motion of any object in contact with them. The magnetic excitation field is radial and uses the transverse coupling of the 4 micrometers thick magnetostrictive film. The film, deposited by sputtering on the ring, consists of layers of different rare-earth/iron alloys and was developed during a European Brite-Euram project. The finite element technique was used in order to design a prototype of the motor and to optimize the active rotor and the energizer coil. The prototype we built delivered a speed of 30 turns per minute with a torque of 2 (mu) N.m (without prestress applied on the rotor). Our experimental results show that the performance of this motor could easily be increased by a factor of 5. The main advantage of this motor is the fact that it is remotely powered and controlled. The excitation coil, which provides both power and control, can be placed away from the active rotor. Moreover, the rotor is completely wireless and is not connected to its support or to any other part. It is interesting to note that it would not be possible to build this type of motor using piezoelectric technology. Medical applications of magnetostrictive micromotors could be found for internal microdistributors of medication (the coil staying outside the body). Other applications include remote control micropositioning, micropositioning of optical components, and for the actuation of systems such as valves, electrical switches, and relays.

  13. Magnetostrictive Vibration Damper and Energy Harvester for Rotating Machinery

    NASA Technical Reports Server (NTRS)

    Deng, Zhangxian; Asnani, Vivake M.; Dapino, Marcelo J.

    2015-01-01

    Vibrations generated by machine driveline components can cause excessive noise and structural damage. Magnetostrictive materials, including Galfenol (iron-gallium alloys) and Terfenol-D (terbium-iron-dysprosium alloys), are able to convert mechanical energy to magnetic energy. A magnetostrictive vibration ring is proposed, which generates electrical energy and dampens vibration, when installed in a machine driveline. A 2D axisymmetric finite element (FE) model incorporating magnetic, mechanical, and electrical dynamics is constructed in COMSOL Multiphysics. Based on the model, a parametric study considering magnetostrictive material geometry, pickup coil size, bias magnet strength, flux path design, and electrical load is conducted to maximize loss factor and average electrical output power. By connecting various resistive loads to the pickup coil, the maximum loss factors for Galfenol and Terfenol-D due to electrical energy loss are identified as 0.14 and 0.34, respectively. The maximum average electrical output power for Galfenol and Terfenol-D is 0.21 W and 0.58 W, respectively. The loss factors for Galfenol and Terfenol-D are increased to 0.59 and 1.83, respectively, by using an L-C resonant circuit.

  14. Detection of Salmonella typhimurium using phage-based magnetostrictive sensor

    NASA Astrophysics Data System (ADS)

    Lakshmanan, Ramji S.; Hu, Jing; Guntupalli, Rajesh; Wan, Jiehui; Huang, Shichu; Yang, Hong; Petrenko, Valery A.; Barbaree, James M.; Chin, Bryan A.

    2006-05-01

    This article presents a contactless, remote sensing Salmonella typhimurium sensor based on the principle of magnetostriction. Magnetostrictive materials have been used widely for various types of sensor systems. In this work, the use of a magnetostrictive material for the detection of Salmonella typhimurium has been established. The mass of the bacteria attached to the sensor causes changes in the resonance frequency of the sensor. Filamentous bacteriophage was used as a probe order to ensure specific and selective binding of the bacteria onto the sensor surface. Thus changes in response of the sensor due to the mass added onto the sensor caused by specific attachment of bacteria can be monitored in absence of any contact to the sensor. The response of the sensor due to increasing concentrations (from 5x101 to 5x10 8 cfu/ml) of the bacteria was studied. A reduction in the physical dimensions enhances the sensitivity of these sensors and hence different dimensions of the sensor ribbons were studied. For a 2mm x 0.1mm x 0.02mm the detection limit was observed to be of the order of 10 4 cfu/mL and for a sensor of 1mm x 0.2mm x 0.02mm a reduced detection limit of 10 3 cfu/mL was achieved.

  15. Magnetostrictive vibration damper and energy harvester for rotating machinery

    NASA Astrophysics Data System (ADS)

    Deng, Zhangxian; Asnani, Vivake M.; Dapino, Marcelo J.

    2015-04-01

    Vibrations generated by machine driveline components can cause excessive noise and structural dam- age. Magnetostrictive materials, including Galfenol (iron-gallium alloys) and Terfenol-D (terbium-iron- dysprosium alloys), are able to convert mechanical energy to magnetic energy. A magnetostrictive vibration ring is proposed, which generates electrical energy and dampens vibration, when installed in a machine driveline. A 2D axisymmetric finite element (FE) model incorporating magnetic, mechanical, and electrical dynamics is constructed in COMSOL Multiphysics. Based on the model, a parametric study considering magnetostrictive material geometry, pickup coil size, bias magnet strength, flux path design, and electrical load is conducted to maximize loss factor and average electrical output power. By connecting various resistive loads to the pickup coil, the maximum loss factors for Galfenol and Terfenol-D due to electrical energy loss are identified as 0.14 and 0.34, respectively. The maximum av- erage electrical output power for Galfenol and Terfenol-D is 0.21 W and 0.58 W, respectively. The loss factors for Galfenol and Terfenol-D are increased to 0.59 and 1.83, respectively, by using an L-C resonant circuit.

  16. Investigation of the influence of magnetostriction and magnetic forces on transformer core noise and vibration

    NASA Astrophysics Data System (ADS)

    Phophongviwat, Teeraphon

    Transformer noise is of increasing environmental concern so continued efforts are being made by electrical steel and transformer producers to satisfy users by reducing the noise. Magnetostriction and magnetic forces are the main causes of transformer core noise and vibration. Understanding of the relationship from the core material to core structure and core vibration to core noise can help the design of low noise transformer cores. The most appropriate parameter for investigating the relationship between noise and vibration is sound pressure (in the unit of Pascals) in the frequency domain because it is not A-weighted. In this study, the side surfaces of transformer cores were found to emit higher noise than front and top surfaces at low magnetic induction. When the magnetic induction was increased, the effect of magnetic force increased and caused the front surfaces to emit higher noise. For three phase three limb transformer cores, the front surface of the middle limb generated higher noise than the outer limbs due to the effect of T-joint. However this does not translate higher noise level because of the phase difference of the vibration between the limbs. Due to this A-weighted sound power level of three phase, three limb transformer cores were shown to be lower than single phase transformer cores, although at the same cross sectional area and core window size the three phase cores has larger size.. A model, developed to separate the effects of magnetostriction and magnetic forces on transformer core vibration, showed that at low induction, magnetostriction is more significant than magnetic forces. The magnetic forces become more significant than magnetostriction when the induction is increased. Magnetostriction primarily depends on material and stress but magnetic forces principally depend on core building. Louder noise can be generated from a core built with low magnetostriction material than higher magnetostriction if the building tolerances are worse. The

  17. Broadband giant-refractive-index material based on mesoscopic space-filling curves.

    PubMed

    Chang, Taeyong; Kim, Jong Uk; Kang, Seung Kyu; Kim, Hyowook; Kim, Do Kyung; Lee, Yong-Hee; Shin, Jonghwa

    2016-01-01

    The refractive index is the fundamental property of all optical materials and dictates Snell's law, propagation speed, wavelength, diffraction, energy density, absorption and emission of light in materials. Experimentally realized broadband refractive indices remain <40, even with intricately designed artificial media. Herein, we demonstrate a measured index >1,800 resulting from a mesoscopic crystal with a dielectric constant greater than three million. This gigantic enhancement effect originates from the space-filling curve concept from mathematics. The principle is inherently very broad band, the enhancement being nearly constant from zero up to the frequency of interest. This broadband giant-refractive-index medium promises not only enhanced resolution in imaging and raised fundamental absorption limits in solar energy devices, but also compact, power-efficient components for optical communication and increased performance in many other applications. PMID:27573337

  18. Broadband giant-refractive-index material based on mesoscopic space-filling curves.

    PubMed

    Chang, Taeyong; Kim, Jong Uk; Kang, Seung Kyu; Kim, Hyowook; Kim, Do Kyung; Lee, Yong-Hee; Shin, Jonghwa

    2016-08-30

    The refractive index is the fundamental property of all optical materials and dictates Snell's law, propagation speed, wavelength, diffraction, energy density, absorption and emission of light in materials. Experimentally realized broadband refractive indices remain <40, even with intricately designed artificial media. Herein, we demonstrate a measured index >1,800 resulting from a mesoscopic crystal with a dielectric constant greater than three million. This gigantic enhancement effect originates from the space-filling curve concept from mathematics. The principle is inherently very broad band, the enhancement being nearly constant from zero up to the frequency of interest. This broadband giant-refractive-index medium promises not only enhanced resolution in imaging and raised fundamental absorption limits in solar energy devices, but also compact, power-efficient components for optical communication and increased performance in many other applications.

  19. Broadband giant-refractive-index material based on mesoscopic space-filling curves

    NASA Astrophysics Data System (ADS)

    Chang, Taeyong; Kim, Jong Uk; Kang, Seung Kyu; Kim, Hyowook; Kim, Do Kyung; Lee, Yong-Hee; Shin, Jonghwa

    2016-08-01

    The refractive index is the fundamental property of all optical materials and dictates Snell's law, propagation speed, wavelength, diffraction, energy density, absorption and emission of light in materials. Experimentally realized broadband refractive indices remain <40, even with intricately designed artificial media. Herein, we demonstrate a measured index >1,800 resulting from a mesoscopic crystal with a dielectric constant greater than three million. This gigantic enhancement effect originates from the space-filling curve concept from mathematics. The principle is inherently very broad band, the enhancement being nearly constant from zero up to the frequency of interest. This broadband giant-refractive-index medium promises not only enhanced resolution in imaging and raised fundamental absorption limits in solar energy devices, but also compact, power-efficient components for optical communication and increased performance in many other applications.

  20. Broadband giant-refractive-index material based on mesoscopic space-filling curves

    PubMed Central

    Chang, Taeyong; Kim, Jong Uk; Kang, Seung Kyu; Kim, Hyowook; Kim, Do Kyung; Lee, Yong-Hee; Shin, Jonghwa

    2016-01-01

    The refractive index is the fundamental property of all optical materials and dictates Snell's law, propagation speed, wavelength, diffraction, energy density, absorption and emission of light in materials. Experimentally realized broadband refractive indices remain <40, even with intricately designed artificial media. Herein, we demonstrate a measured index >1,800 resulting from a mesoscopic crystal with a dielectric constant greater than three million. This gigantic enhancement effect originates from the space-filling curve concept from mathematics. The principle is inherently very broad band, the enhancement being nearly constant from zero up to the frequency of interest. This broadband giant-refractive-index medium promises not only enhanced resolution in imaging and raised fundamental absorption limits in solar energy devices, but also compact, power-efficient components for optical communication and increased performance in many other applications. PMID:27573337

  1. Design of a Magnetostrictive-Hydraulic Actuator Considering Nonlinear System Dynamics and Fluid-Structure Coupling

    NASA Astrophysics Data System (ADS)

    Larson, John Philip

    Smart material electro-hydraulic actuators (EHAs) utilize fluid rectification via one-way check valves to amplify the small, high-frequency vibrations of certain smart materials into large motions of a hydraulic cylinder. Although the concept has been demonstrated in previously, the operating frequency of smart material EHA systems has been limited to a small fraction of the available bandwidth of the driver materials. The focus of this work is to characterize and model the mechanical performance of a magnetostrictive EHA considering key system components: rectification valves, smart material driver, and fluid-system components, leading to an improved actuator design relative to prior work. The one-way valves were modeled using 3-D finite element analysis, and their behavior was characterized experimentally by static and dynamic experimental measurement. Taking into account the effect of the fluid and mechanical conditions applied to the valves within the pump, the dynamic response of the valve was quantified and applied to determine rectification bandwidth of different valve configurations. A novel miniature reed valve, designed for a frequency response above 10~kHz, was fabricated and tested within a magnetostrictive EHA. The nonlinear response of the magnetostrictive driver, including saturation and hysteresis effects, was modeled using the Jiles-Atherton approach to calculate the magnetization and the resulting magnetostriction based on the applied field calculated within the rod from Maxwell's equations. The dynamic pressure response of the fluid system components (pumping chamber, hydraulic cylinder, and connecting passages) was measured over a range of input frequencies. For the magnetostrictive EHA tested, the peak performance frequency was found to be limited by the fluid resonances within the system. A lumped-parameter modeling approach was applied to model the overall behavior of a magnetostrictive EHA, incorporating models for the reed valve response

  2. Torsional dependence of the magnetostriction of a Co-rich non-magnetostrictive amorphous wire

    NASA Astrophysics Data System (ADS)

    Aragoneses, P.; Blanco, J. M.; Domínguez, L.; González, J.; Kulakowski, K.

    The influence of the torsion strain on the coefficients λ(0) and A of the linear dependence of the magnetostriction constant on the applied stress, λ = λ(0) + Aσ, has been investigated in a non-magnetostrictive Co-Fe (Co-rich) amorphous wire. The measurements of the magnetostriction were carried out by means of the small-angle magnetization rotation (SAMR) method on the as-quenched and Joule heated wire. The current annealing was carried out at 550 mA (˜ 450° C) for 2 min. For the as-quenched samples, the magnetostriction is negative and increases with torsion, despite the negative sign of its strain derivative.

  3. Hysteresis of the resonance frequency of magnetostrictive bending cantilevers

    NASA Astrophysics Data System (ADS)

    Löffler, Michael; Kremer, Ramona; Sutor, Alexander; Lerch, Reinhard

    2015-05-01

    Magnetostrictive bending cantilevers are applicable for wirelessly measuring physical quantities such as pressure and strain. Exploiting the ΔE-effect, the resonance frequency of the cantilevers is shifted because of a change in the magnetic biasing field. The biasing field, in turn, depends on the applied pressure or strain, respectively. With a view to the application as a reliable sensor, maximum sensitivity but minimum hysteresis in the biasing field/resonance frequency dependence is preferred. In this contribution, monomorph bending cantilevers fabricated using magnetostrictive Fe49Co49V2 and Metglas 2605SA1 are investigated regarding their applicability for future sensors. For this purpose, the biasing field-dependent polarization of the magnetostrictive materials and bending of the cantilevers are determined. Furthermore, a setup to magnetically bias the cantilevers and determine the bending resonance frequency is presented. Here, the resonance frequency is identified by measuring the impulse response employing a laser Doppler vibrometer. The measurement results reveal that cantilevers made of Fe49Co49V2 possess a distinct hysteretic behaviour at low magnetic biasing field magnitudes. This is ascribed to the polarization and bending hysteresis. Cantilevers fabricated using Metglas 2605SA1 feature a lower resonance frequency shift compared to cantilevers with Fe49Co49V2, which would result in a lower sensitivity of the sensor. However, their resonance frequency hysteresis is almost negligible.

  4. Donor-site giant cell reaction following backfill with synthetic bone material during osteochondral plug transfer.

    PubMed

    Fowler, Donald E; Hart, Joseph M; Hart, Jennifer A; Miller, Mark D

    2009-10-01

    Osteochondral defects are common in younger, active patients. Multiple strategies have been used to treat these lesions, including microfracture and osteochondral plug transfer. We describe a patient experiencing chronic knee pain and a full-thickness cartilage defect on the lateral femoral condyle. After failing conservative management and microfracture surgery, the patient underwent osteochondral autograft plug transfer, with backfilling of the donor sites using synthetic bone graft substitute. Initial recovery was uncomplicated until the patient experienced pain following a twist of the knee. Magnetic resonance imaging for the subsequent knee injury revealed poor healing at the donor sites. The donor sites were debrided, and specimens revealed a foreign body giant cell reaction. Donor-site morbidity is of primary concern during osteochondral plug transfer; however, insufficient data exist to support the use of synthetic bone graft material. Our results indicate that off-label use of synthetic bone graft substitute during a primary procedure requires further investigation.

  5. A comparison of and the compensation for magnetostrictive core inductances in magnetic transducer systems

    NASA Astrophysics Data System (ADS)

    Bartlett, P. A.; Meydan, T.; Lea, S. C.; Moses, A. J.; Williams, P. I.; Landini, G.; Walmsley, A. D.

    Magnetostrictive materials have been utilized for the production of ultrasonic frequency vibrations for a number of years. This has particularly been the case in laminated nickel-based ultrasonic dental-scaler cleaning systems. In this study, a comparison has been made between the impedances of a number of magnetostrictive stacks of 50 mm×4 mmט0.3 mm strips at frequencies in the range of 10-50 kHz in a coil used for the excitation of a stack in a dental-scaler system. The magnetostrictive stacks tested comprised of potential replacement materials for standard nickel ones. The study showed that it was possible to compensate for the inductive 'imaginary' components of the impedance through the use of a tuned, series capacitance so that only the 'real' resistive component of the impedance remained. This reduced the electrical losses associated with the excitation of the magnetostrictive stacks as a result of the frequency-dependent inductance of the coil system. Consequently, the maximum power transfer from an amplifier to the transducer was increased. Also, the investigation showed how the 'real' component of impedance of the different stacks varied with frequency. In a tuned resonant electrical circuit, the resistive component of the impedance, if considered as a loss, would be the lowest that could be achieved with such a magnetic circuit. Consequently, the losses associated with resonant magnetostrictive devices, like dental scalers, can be reduced.

  6. Evaluation of material microstructure changes in high speed tool steel by the non-collinear wave mixing technique with MST(magnetostrictive transducer)

    NASA Astrophysics Data System (ADS)

    Choi, Jeongseok; Lee, Dong Jin; Cho, Younho

    2015-03-01

    Evaluation of material microstructure changes plays an important role in predicting material failure. Both destructive and nondestructive testings can be used to evaluate the variation of material microstructure. Destructive methods are used to directly verify the changes of material via microstructure picture in a vigorous manner while nonlinear ultrasonic NDE can render a promising tool for the cases. In this study, the MST driven non-collinear wave mixing technique is implemented to evaluate the material microstructure changes in high speed tool steel. The resonant wave is used to analyze the acoustic nonlinearity which is influenced by microstructure changes with various austenitizing temperature effects. Correlation microstructure change between the acoustic nonlinearity and material microstructure is accomplished to explore the feasibility of the non-collinear mixing technique.

  7. Application of high-temperature superconducting wires to magnetostrictive transducers for underwater sonar

    SciTech Connect

    Voccio, J.P.; Joshi, C.H.; Lindberg, J.F.

    1994-07-01

    Recently discovered cryogenic magnetostrictive materials show maximum strains greater than any room temperature materials. These cryogenic magnetostrictors can be combined with high-temperature superconducting (HTS) coils to create a sonar transducer with high efficiency and high acoustic power density. A prototype low-frequency (< 1,000 Hz) magnetostrictive transducer is described. This transducer uses a terbium-dysprosium (TbDy) magnetostrictor rod with HTS coils cooled to 50--80 K using a single-stage cryocooler. The device is designed for operation at water depths of 100 m and is believed to be the first fully integrated prototype demonstration of HTS.

  8. Energy harvesting with coupled magnetostrictive resonators

    NASA Astrophysics Data System (ADS)

    Naik, Suketu; Phipps, Alex; In, Visarath; Cavaroc, Peyton; Matus-Vargas, Antonio; Palacios, Antonio; Gonzalez-Hernandez, H. G.

    2014-03-01

    We report the investigation of an energy harvesting system composed of coupled resonators with the magnetostrictive material Galfenol (FeGa). A coupled system of meso-scale (1-10 cm) cantilever beams for harvesting vibration energy is described for powering and aiding the performance of low-power wireless sensor nodes. Galfenol is chosen in this work for its durability, compared to the brittleness often encountered with piezoelectric materials, and high magnetomechanical coupling. A lumped model, which captures both the mechanical and electrical behavior of the individual transducers, is first developed. The values of the lumped element parameters are then derived empirically from fabricated beams in order to compare the model to experimental measurements. The governing equations of the coupled system lead to a system of differential equations with all-to-all coupling between transducers. An analysis of the system equations reveals different patterns of collective oscillations. Among the many different patterns, a synchronous state appears to yield the maximum energy that can be harvested by the system. Experiments on coupled system shows that the coupled system exhibits synchronization and an increment in the output power. Discussion of the required power converters is also included.

  9. Giant piezoelectric voltage coefficient in grain-oriented modified PbTiO3 material

    NASA Astrophysics Data System (ADS)

    Yan, Yongke; Zhou, Jie E.; Maurya, Deepam; Wang, Yu U.; Priya, Shashank

    2016-10-01

    A rapid surge in the research on piezoelectric sensors is occurring with the arrival of the Internet of Things. Single-phase oxide piezoelectric materials with giant piezoelectric voltage coefficient (g, induced voltage under applied stress) and high Curie temperature (Tc) are crucial towards providing desired performance for sensing, especially under harsh environmental conditions. Here, we report a grain-oriented (with 95% <001> texture) modified PbTiO3 ceramic that has a high Tc (364 °C) and an extremely large g33 (115 × 10-3 Vm N-1) in comparison with other known single-phase oxide materials. Our results reveal that self-polarization due to grain orientation along the spontaneous polarization direction plays an important role in achieving large piezoelectric response in a domain motion-confined material. The phase field simulations confirm that the large piezoelectric voltage coefficient g33 originates from maximized piezoelectric strain coefficient d33 and minimized dielectric permittivity ε33 in [001]-textured PbTiO3 ceramics where domain wall motions are absent.

  10. Giant piezoelectric voltage coefficient in grain-oriented modified PbTiO3 material

    PubMed Central

    Yan, Yongke; Zhou, Jie E.; Maurya, Deepam; Wang, Yu U.; Priya, Shashank

    2016-01-01

    A rapid surge in the research on piezoelectric sensors is occurring with the arrival of the Internet of Things. Single-phase oxide piezoelectric materials with giant piezoelectric voltage coefficient (g, induced voltage under applied stress) and high Curie temperature (Tc) are crucial towards providing desired performance for sensing, especially under harsh environmental conditions. Here, we report a grain-oriented (with 95% <001> texture) modified PbTiO3 ceramic that has a high Tc (364 °C) and an extremely large g33 (115 × 10−3 Vm N−1) in comparison with other known single-phase oxide materials. Our results reveal that self-polarization due to grain orientation along the spontaneous polarization direction plays an important role in achieving large piezoelectric response in a domain motion-confined material. The phase field simulations confirm that the large piezoelectric voltage coefficient g33 originates from maximized piezoelectric strain coefficient d33 and minimized dielectric permittivity ɛ33 in [001]-textured PbTiO3 ceramics where domain wall motions are absent. PMID:27725634

  11. Giant Negative Area Compressibility Tunable in a Soft Porous Framework Material.

    PubMed

    Cai, Weizhao; Gładysiak, Andrzej; Anioła, Michalina; Smith, Vincent J; Barbour, Leonard J; Katrusiak, Andrzej

    2015-07-29

    A soft porous material [Zn(L)2(OH)2]n·Guest (where L is 4-(1H-naphtho[2,3-d]imidazol-1-yl)benzoate, and Guest is water or methanol) exhibits the strongest ever observed negative area compressibility (NAC), an extremely rare property, as at hydrostatic pressure most materials shrink in all directions and few expand in one direction. This is the first NAC reported in metal-organic frameworks (MOFs), and its magnitude, clearly visible and by far the highest of all known materials, can be reversibly tuned by exchanging guests adsorbed from hydrostatic fluids. This counterintuitive strong NAC of [Zn(L)2(OH)2]n·Guest arises from the interplay of flexible [-Zn-O(H)-]n helices with layers of [-Zn-L-]4 quadrangular puckered rings comprising large channel voids. The compression of helices and flattening of puckered rings combine to give a giant piezo-mechanical response, applicable in ultrasensitive sensors and actuators. The extrinsic NAC response to different hydrostatic fluids is due to varied host-guest interactions affecting the mechanical strain within the range permitted by exceptionally high flexibility of the framework.

  12. Temperature-dependent magnetostriction as the key factor for martensite reorientation in magnetic field

    NASA Astrophysics Data System (ADS)

    L’vov, Victor A.; Kosogor, Anna

    2016-09-01

    The magnetic field application leads to spatially inhomogeneous magnetostriction of twinned ferromagnetic martensite. When the increasing field and magnetostrictive strain reach certain threshold values, the motion of twin boundaries and magnetically induced reorientation (MIR) of twinned martensite start. The MIR leads to giant magnetically induced deformation of twinned martensite. In the present article, the threshold field (TF) and temperature range of observability of MIR were calculated for the Ni–Mn–Ga martensite assuming that the threshold strain (TS) is temperature-independent. The calculations show that if the TS is of the order of 10‑4, the TF strongly depends on temperature and MIR can be observed only above the limiting temperature (~220 K). If the TS is of the order of 10‑6, the TF weakly depends on temperature and MIR can be observed at extremely low temperatures. The obtained theoretical results are in agreement with available experimental data.

  13. Temperature-dependent magnetostriction as the key factor for martensite reorientation in magnetic field

    NASA Astrophysics Data System (ADS)

    L'vov, Victor A.; Kosogor, Anna

    2016-09-01

    The magnetic field application leads to spatially inhomogeneous magnetostriction of twinned ferromagnetic martensite. When the increasing field and magnetostrictive strain reach certain threshold values, the motion of twin boundaries and magnetically induced reorientation (MIR) of twinned martensite start. The MIR leads to giant magnetically induced deformation of twinned martensite. In the present article, the threshold field (TF) and temperature range of observability of MIR were calculated for the Ni-Mn-Ga martensite assuming that the threshold strain (TS) is temperature-independent. The calculations show that if the TS is of the order of 10-4, the TF strongly depends on temperature and MIR can be observed only above the limiting temperature (~220 K). If the TS is of the order of 10-6, the TF weakly depends on temperature and MIR can be observed at extremely low temperatures. The obtained theoretical results are in agreement with available experimental data.

  14. An Anisotropic Model for Magnetostriction and Magnetization Computing for Noise Generation in Electric Devices

    PubMed Central

    Mbengue, Serigne Saliou; Buiron, Nicolas; Lanfranchi, Vincent

    2016-01-01

    During the manufacturing process and use of ferromagnetic sheets, operations such as rolling, cutting, and tightening induce anisotropy that changes the material’s behavior. Consequently for more accuracy in magnetization and magnetostriction calculations in electric devices such as transformers, anisotropic effects should be considered. In the following sections, we give an overview of a macroscopic model which takes into account the magnetic and magnetoelastic anisotropy of the material for both magnetization and magnetostriction computing. Firstly, a comparison between the model results and measurements from a Single Sheet Tester (SST) and values will be shown. Secondly, the model is integrated in a finite elements code to predict magnetostrictive deformation of an in-house test bench which is a stack of 40 sheets glued together by the Vacuum-Pressure Impregnation (VPI) method. Measurements on the test bench and Finite Elements results are presented. PMID:27092513

  15. The resonance frequency shift characteristic of Terfenol-D rods for magnetostrictive actuators

    NASA Astrophysics Data System (ADS)

    Jin, Ke; Kou, Yong; Zheng, Xiaojing

    2012-04-01

    This paper focuses on the resonance frequency shift characteristic of Terfenol-D rods for magnetostrictive actuators. A 3D nonlinear dynamic model to describe the magneto-thermo-elastic coupling behavior of actuators is proposed based on a nonlinear constitutive model. The coupled interactions among stress- and magnetic-field-dependent variables for actuators are solved iteratively using the finite element method. The model simulations show a good correlation with the experimental data, which demonstrates that this model can capture the coupled resonance frequency shift features for magnetostrictive actuators well. Moreover, a comprehensive description for temperature, pre-stress and bias field dependences of resonance frequency is discussed in detail. These essential and important investigations will be of significant benefit to both theoretical research and the applications of magnetostrictive materials in smart or intelligent structures and systems.

  16. Magnetoelectric Properties in Piezoelectric and Magnetostrictive Laminate Composites

    NASA Astrophysics Data System (ADS)

    Ryu, Jungho; Carazo, Alfredo Vázquez; Uchino, Kenji; Kim, Hyoun-Ee

    2001-08-01

    Magnetoelectric laminate composites of piezoelectric-magnetostrictive materials were investigated. The composites were prepared by stacking and bonding Pb(Zr, Ti)O3 (PZT) and Terfenol-D disks. Experimental results indicated that the magnetoelectric voltage coefficient, dE/dH, increased with decreasing thickness and increasing piezoelectric voltage constant (g31) of the PZT layer. We obtained the highest magnetoelectric voltage coefficient of 4.68 V/cm\\cdotOe at room temperature for the sample with high g33 PZT of 0.5 mm in thickness. This value is about 36 times higher than the best reported value.

  17. Development of highly magnetostrictive composites for applications in magnetomechanical torque sensors

    NASA Astrophysics Data System (ADS)

    Chen, Yonghua

    1999-07-01

    The objective of this work was to investigate and develop a new type of magnetomechanical material with high magnetomechanical response and low hysteresis. This material will be used in electronic torque sensors. A major appreciation could be for advanced steering systems in automobiles which will replace the fuel inefficient hydraulic steering systems currently in use. The effect of the matrix material on the magnetostriction of composites containing highly magnetostrictive particles was studied. Both experimental and modeled results showed that the elastic modulus of the matrix is an important factor determining the magnetostriction of the composite. For a series of composites with the same volume fraction of Terfenol-D particles but different matrix materials, the saturation magnetostriction was found to increase systematically with decreasing modulus of the matrix. A magnetic torque sensor test bed was developed as part of the present investigation. This instrumentation was used to make the magnetomechanical measurements under torsional stress. After investigating both of the H- σ processes and σ-H processes of metal rods (Fe, Co, Ni), it was shown that a high piezomagnetic coefficient, together with a high saturation magnetostriction are two ``figures of merit'' for choosing materials for magnetomechanical sensors. A new class of materials, metal-bonded (Ag/Ni/Co) Co- ferrite composites, has been found to be better than the traditional magnetostrictive materials for this application. These materials exhibited magnetostriction in excess of 200 ppm and a d33 Coefficient, 1.3 × 10-9 A-1m. A prototype of torque sensor was constructed from this material. The sensitivity of surface magnetic field to applied torque as high as 65 AN-1m-2 in the torque range of +/-10N.m was observed. The temperature dependence of the magnetomechanical sensitivity and hysteresis were measured over the range -37 to 90°C. Both decreased as the temperature increased throughout the

  18. Role of extrinsic factors in utilizing the giant magnetocaloric effect on materials: Frequency and time dependence

    NASA Astrophysics Data System (ADS)

    Madireddi, Sesha

    Magnetic refrigeration (MR) is potentially a high efficiency, low cost, and greenhouse gas-free refrigeration technology, and with the looming phase out of HCFC and HFC fluorocarbons refrigerants is drawing more attention as an alternative to the existing vapor compression refrigeration. MR is based on the magnetocaloric effect (MCE), which occurs due to the coupling of a magnetic sublattice with an external magnetic field. With the magnetic spin system aligned by magnetic field, the magnetic entropy changes by Delta SM as a result of isothermal magnetization of a material. On the other hand, the sum of the lattice and electronic entropies of a solid must be changed by -DeltaSM as a result of adiabatically magnetizing the material, thus resulting in an increase of the lattice vibrations and the adiabatic temperature change, DeltaTad. Both the isothermal entropy change DeltaSM and adiabatic temperature change DeltaTad are important parameters in quantifying the MCE and performance of magnetocaloric materials (MCM). In general, DeltaSM and Delta Tad are obtained using magnetization and heat capacity data and the Maxwell equations. Although Maxwell equations can be used to calculate MCE for first order magnetic transition (FOMT) materials due to the fact that the transition is not truly discontinuous, there can be some errors depending on the numerical integration method used. Thus, direct measurements of DeltaTad are both useful and required to better understand the nature of the giant magnetocaloric effect (GMCE). Moreover, the direct measurements of DeltaTad allow investigation of dynamic performance of FOMT materials experiencing repeated magnetization/demagnetization cycles. This research utilized a special test facility to directly measure MCE of Gd5Si2Ge2, Gd5Si2.7 Ge1.3, MnFePAs, LaFeSiH, Ni55.2M 18.6Ga26.2, Dy, Tb, DyCo2, (Hf0.83 Ta0.17)Fe1.98, GdAl2 and Nd2Fe 17, MCMs, both FOMT and second order magnetic transition (SOMT) materials, at different magnetizing

  19. Influence of Tb on easy magnetization direction and magnetostriction of ferromagnetic Laves phase GdFe2 compounds

    NASA Astrophysics Data System (ADS)

    Murtaza, Adil; Yang, Sen; Zhou, Chao; Song, Xiaoping

    2016-09-01

    The crystal structure, magnetization, and spontaneous magnetostriction of ferromagnetic Laves phase GdFe2 compound have been investigated. High resolution synchrotron x-ray diffraction (XRD) analysis shows that GdFe2 has a lower cubic symmetry with easy magnetization direction (EMD) along [100] below Curie temperature TC. The replacement of Gd with a small amount of Tb changes the EMD to [111]. The Curie temperature decreases while the field dependence of the saturation magnetization (Ms) measured in temperature range 5–300 K varies with increasing Tb concentration. Coercivity Hc increases with increasing Tb concentration and decays exponentially as temperature increases. The anisotropy in GdFe2 is so weak that some of the rare-earth substitution plays an important role in determining the easy direction of magnetization in GdFe2. The calculated magnetostrictive constant λ100 shows a small value of 37×10‑6. This value agrees well with experimental data 30×10‑6. Under a relatively small magnetic field, GdFe2 exhibits a V-shaped positive magnetostriction curve. When the field is further increased, the crystal exhibits a negative magnetostriction curve. This phenomenon has been discussed in term of magnetic domain switching. Furthermore, magnetostriction increases with increasing Tb concentration. Our work leads to a simple and unified mesoscopic explanation for magnetostriction in ferromagnets. It may also provide insight for developing novel functional materials. Project supported by the National Basic Research Program of China (Grant No. 2012CB619401).

  20. Hysteresis and magnetostriction of TbxDyyHo1-x-yFe1.95 [112] dendritic rods

    NASA Astrophysics Data System (ADS)

    Wun-Fogle, M.; Restorff, J. B.; Clark, A. E.

    1999-04-01

    The magnetization and magnetostriction of a variety of 3/16-in.-diam Laves phase rods of TbxDyyHo1-x-yFe1.95 grown in the form of [112] oriented dendritic compounds were measured as a function of applied magnetic field -3000magnetostrictive material, Ho containing alloys can have substantially lower hysteresis with only slightly lower magnetostriction. The Ho concentration was kept relatively small (⩽0.3) to avoid a substantial decrease in the magnetostriction, while the ratio of x and y was chosen to examine alloys spanning the line of minimum magnetic anisotropy. Most of the compositions have twice the Ho content of the previous study. As expected, alloys with higher Ho concentrations showed narrower hysteresis curves. The data shows that at 22 MPa, the Tb0.28Dy0.57Ho0.15Fe1.95 composition has a minimal (3%) loss of magnetostriction, while the hysteresis width decreased by 15%. Between 15% and 20% Ho content, the magnetostriction drops abruptly. For alloys with a fixed Ho concentration, the strain showed a peak near the expected anisotropy minimum, but the hysteresis width always increased with increasing Tb content.

  1. Influence of Tb on easy magnetization direction and magnetostriction of ferromagnetic Laves phase GdFe2 compounds

    NASA Astrophysics Data System (ADS)

    Murtaza, Adil; Yang, Sen; Zhou, Chao; Song, Xiaoping

    2016-09-01

    The crystal structure, magnetization, and spontaneous magnetostriction of ferromagnetic Laves phase GdFe2 compound have been investigated. High resolution synchrotron x-ray diffraction (XRD) analysis shows that GdFe2 has a lower cubic symmetry with easy magnetization direction (EMD) along [100] below Curie temperature TC. The replacement of Gd with a small amount of Tb changes the EMD to [111]. The Curie temperature decreases while the field dependence of the saturation magnetization (Ms) measured in temperature range 5-300 K varies with increasing Tb concentration. Coercivity Hc increases with increasing Tb concentration and decays exponentially as temperature increases. The anisotropy in GdFe2 is so weak that some of the rare-earth substitution plays an important role in determining the easy direction of magnetization in GdFe2. The calculated magnetostrictive constant λ100 shows a small value of 37×10-6. This value agrees well with experimental data 30×10-6. Under a relatively small magnetic field, GdFe2 exhibits a V-shaped positive magnetostriction curve. When the field is further increased, the crystal exhibits a negative magnetostriction curve. This phenomenon has been discussed in term of magnetic domain switching. Furthermore, magnetostriction increases with increasing Tb concentration. Our work leads to a simple and unified mesoscopic explanation for magnetostriction in ferromagnets. It may also provide insight for developing novel functional materials. Project supported by the National Basic Research Program of China (Grant No. 2012CB619401).

  2. Bill Armstrong memorial symposium: free energy model for magnetization and magnetostriction in stressed Galfenol alloys

    NASA Astrophysics Data System (ADS)

    Evans, Phillip G.; Dapino, Marcelo J.; Restorff, James B.

    2007-04-01

    We present a thermodynamic framework to quantify the magnetization and magnetostriction of Galfenol alloys in response to magnetic fields, mechanical stress, and/or stress-annealing. The framework utilizes only physical parameters and thus provides useful information for material characterization. Furthermore, we formulate the model in state-space form, thus facilitating the computational implementation for design and control of dynamic Galfenol devices.

  3. Giant intracranial aneurysm embolization with a yield stress fluid material: insights from CFD analysis.

    PubMed

    Wang, Weixiong; Graziano, Francesca; Russo, Vittorio; Ulm, Arthur J; De Kee, Daniel; Khismatullin, Damir B

    2013-01-01

    The endovascular treatment of intracranial aneurysms remains a challenge, especially when the aneurysm is large in size and has irregular, non-spherical geometry. In this paper, we use computational fluid dynamics to simulate blood flow in a vertebro-basilar junction giant aneurysm for the following three cases: (1) an empty aneurysm, (2) an aneurysm filled with platinum coils, and (3) an aneurysm filled with a yield stress fluid material. In the computational model, blood and the coil-filled region are treated as a non-Newtonian fluid and an isotropic porous medium, respectively. The results show that yield stress fluids can be used for aneurysm embolization provided the yield stress value is 20 Pa or higher. Specifically, flow recirculation in the aneurysm and the size of the inflow jet impingement zone on the aneurysm wall are substantially reduced by yield stress fluid treatment. Overall, this study opens up the possibility of using yield stress fluids for effective embolization of large-volume intracranial aneurysms. PMID:23863277

  4. Processing of magnetostrictive thin film devices

    NASA Astrophysics Data System (ADS)

    Loveless, Michael Ray

    (Tb,Dy)Fesb2 intermetallic alloys exhibit very large magnetostrictive strains. Alloys with composition near Tbsb{0.3}Dysb{0.7}Fesb2, known as Terfenol-D, are of particular interest because this is the composition where room temperature anisotropy compensation occurs and the moment can be easily rotated. Terfenol-D has a cubic Laves phase structure and exhibits maximum magnetostrictive strain along $ directions at room temperature. Bulk Terfenol-D tends to grow as twinned dendritic sheets with $ orientation. Recently, there has been increased interest in Terfenol-D thin film devices. Crystallographic texture can change the magnetostrictive properties of thin films. It is the purpose of this research to study the effect of postdeposition annealing and magnetic annealing treatments on the microstructure of Terfenol-D thin films. It is predicted that textured films can be obtained by exploiting increased magnetocrystalline anisotropy at elevated temperatures. This would improve the low field magnetostrictive strains attainable for device applications. Also of recent interest is the fabrication of magnetostrictive composites. Increased toughness and durability are attainable at the cost of reduced magnetostrictive performance. Terfenol-D composites have been made with polymers. Composites with metals would be stronger and tougher but conventional high temperature processing routes cause unwanted reactions. Temperatures high enough to allow appreciable diffusion for sintering would also allow the metal binder phase to interdiffuse with Terfenol-D. This work also examines the feasibility of explosive compaction of Terfenol-D-metal composites. The short duration, on the order of microseconds, of the pressure and temperature pulse experienced by the powder leads to compaction at near room temperature. This is expected to prevent unwanted reactions between Terfenol-D and the metal binder.

  5. Magnetostrictive Roller-Drive Stepping Motor

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1993-01-01

    Proposed motor based on magnetostrictive effect provides stepped angular motion with angular increments of order of 100 microradians. Driven to repeat stepping cycle rapidly enough to achieve maximum speed of about 20 rpm, provides torque an order of magnitude greater than electric motors, and brakes itself when power turned off. Magnetostrictive rods in electromagnet coils push against drive plate, causing it to rotate slightly. This slight rotation jams conical rollers between cam surfaces on outer drive ring and split drum, so rollers transmit rotation to drum. Suitable for precise, high-torque, fail-safe-braking, direct drive of robot joint, without bulk and weight of additional brake mechanism and gear train.

  6. Magneto-thermo-mechanical characterization of magnetostrictive composites

    NASA Astrophysics Data System (ADS)

    Nersessian, Nersesse; Carman, Gregory P.

    2001-07-01

    This paper describes magneto-thermo-mechanical characterization of magnetostrictive composites. The purpose of this study is to evaluate the behavior of magnetostrictive composites under combined magnetic, thermal and mechanical loading, and to determine fundamental properties used for design of actuator and sensor systems that incorporate these materials. Currently the composites are being used in sonar transducers. The magnetostrictive composite contains Terfenol-D (Tb0.3Dy0.7Fe2) particulate embedded into an epoxy binder. Composite form is used due to the relative brittleness and limited operational frequencies of monolithic Terfenol-D. Two different tests were performed both at room temperature and under thermal loading: 1) constant magnetic field with cyclically varying load around a bias load and 2) constant pre-load with varying magnetic field. Testing was performed on five different volume fraction composites, namely, 10%, 20%, 30%, 40% and 50%. Parameters that were evaluated include strain output, magnetic field, magnetization and elastic modulus. Results for the constant magnetic field tests indicate that modulus generally increases with increasing volume fraction and increasing magnetic field. However, for low fields, an initial dip is noticed in modulus (i.e. (Delta) E effect) attributed to domains becoming more mobile at lower magnetic field levels. Results also indicate an increase in modulus with decrease in temperature. Results for the constant load test indicate a strong dependence of strain output on applied pre-stress. Results indicate that max strain peaks at a certain value of the pre-stress and then decreases for increasing pre-stress. Results also indicate that strain output peaks between 0 degree(s)C and +10 degree(s)C and that strain generally increases with increasing volume fraction.

  7. Magnetic and Magnetostrictive Characterization and Modeling of High Strength Steel

    NASA Astrophysics Data System (ADS)

    Burgy, Christopher Donald

    High strength steels exhibit small amounts of magnetostriction, which is a useful property for non-destructive testing amongst other things. This property cannot currently be fully utilized due to a lack of adequate measurements and models. This thesis reports measurements of these material parameters, and derives a model using these parameters to predict magnetization changes due to the application of compressive stresses and magnetic fields. The resulting Preisach model, coupled with COMSOL MultiphysicsRTM finite element modeling, accurately predicts the magnetization change seen in a separate high strength steel sample previously measured by the National Institute of Standards and Technology. Three sets of measurements on low-carbon, low-alloy high strength steel are introduced in this research. The first experiment measured magnetostriction in steel rods under uniaxial compressive stresses and magnetic fields. The second experiment consisted of magnetostriction and magnetization measurements of the same steel rods under the influence of bi-axially applied magnetic fields. The final experiment quantified the small effect that temperature has on magnetization of steels. The experiments demonstrated that the widely used approximation of stress as an "effective field" is inadequate, and that temperatures between -50 and 100 °C cause minimal changes in magnetization. Preisach model parameters for the prediction of the magnetomechanical effect were derived from the experiments. The resulting model accurately predicts experimentally derived major and minor loops for a high strength steel sample, including the bulging and coincident points attributed to compressive stresses. A framework is presented which couples the uniaxial magnetomechanical model with a finite element package, and was used successfully to predict experimentally measured magnetization changes on a complex sample. These results show that a 1-D magnetomechanical model can be applied to predict 3-D

  8. Bioprospecting Finds the Toughest Biological Material: Extraordinary Silk from a Giant Riverine Orb Spider

    PubMed Central

    Agnarsson, Ingi; Kuntner, Matjaž; Blackledge, Todd A.

    2010-01-01

    Background Combining high strength and elasticity, spider silks are exceptionally tough, i.e., able to absorb massive kinetic energy before breaking. Spider silk is therefore a model polymer for development of high performance biomimetic fibers. There are over 41.000 described species of spiders, most spinning multiple types of silk. Thus we have available some 200.000+ unique silks that may cover an amazing breadth of material properties. To date, however, silks from only a few tens of species have been characterized, most chosen haphazardly as model organisms (Nephila) or simply from researchers' backyards. Are we limited to ‘blindly fishing’ in efforts to discover extraordinary silks? Or, could scientists use ecology to predict which species are likely to spin silks exhibiting exceptional performance properties? Methodology We examined the biomechanical properties of silk produced by the remarkable Malagasy ‘Darwin's bark spider’ (Caerostris darwini), which we predicted would produce exceptional silk based upon its amazing web. The spider constructs its giant orb web (up to 2.8 m2) suspended above streams, rivers, and lakes. It attaches the web to substrates on each riverbank by anchor threads as long as 25 meters. Dragline silk from both Caerostris webs and forcibly pulled silk, exhibits an extraordinary combination of high tensile strength and elasticity previously unknown for spider silk. The toughness of forcibly silked fibers averages 350 MJ/m3, with some samples reaching 520 MJ/m3. Thus, C. darwini silk is more than twice tougher than any previously described silk, and over 10 times better than Kevlar®. Caerostris capture spiral silk is similarly exceptionally tough. Conclusions Caerostris darwini produces the toughest known biomaterial. We hypothesize that this extraordinary toughness coevolved with the unusual ecology and web architecture of these spiders, decreasing the likelihood of bridgelines breaking and collapsing the web into the river

  9. Tailoring magnetostriction sign of ferromagnetic composite by increasing magnetic field strength

    NASA Astrophysics Data System (ADS)

    Gou, Junming; Liu, Xiaolian; Wu, Kaiyun; Wang, Yue; Hu, Shanshan; Zhao, Hui; Xiao, Andong; Ma, Tianyu; Yan, Mi

    2016-08-01

    The unitary deformation of single-phase ferromagnets by a magnetic field, i.e., either positive or negative linear magnetostriction, allows only monotonous control. Here we report a proof-of-principle ferromagnetic composite Fe73Ga27, for which the magnetostriction sign changes from positive to negative by increasing the magnetic field strength. Based on the transformation from body-centered-cubic (BCC) to face-centered-cubic (FCC) phases in this binary system, Fe73Ga27 composite is prepared by aging the BCC averaged precursor for 3 days at 803 K. Magnetic measurements indicate that the BCC phase exhibits smaller magnetocrystalline anisotropy constant than the FCC phase. The offset effect between BCC and FCC phases produces positive net magnetostriction at low magnetic fields but negative net magnetostriction at high magnetic fields. By tuning the field strength, such composites can mediate compressive and tensile strains to other functional materials, e.g., piezoelectric material or optic-fibers, which is beneficial to design multifunctional devices.

  10. Passive damping and velocity sensing using magnetostrictive transduction

    NASA Astrophysics Data System (ADS)

    Fenn, Ralph C.; Gerver, Michael J.

    1994-05-01

    Magnetostrictive Terfenol-D transducers are an attractive alternative to viscoelastic dampers, and electrodynamic and piezoelectric actuators for damping and self-sensing. These advantages include high stiffness and primary load carrying capability, high power density, low voltages, and low temperature sensitivity. Terfenol-D converts 50 percent of the transducer strain energy into magnetic field energy. Because the Terfenol-D transducer is a primary load carrying member, large amounts of structural energy are converted into magnetic field energy. This magnetic field energy is converted into electric energy by a surrounding coil and dissipated in a resistor to provide damping. The voltage developed in the surrounding coil is proportional to the strain rate of the magnetostrictive material, thus producing a velocity signal. This velocity signal can be used for colocated active damping by controlling coil current based on coil voltage induced by transducer velocity. Experiments using a Terfenol-D actuator capable of 65 microns motion and 1,000 N force showed modal loss factors to 0.22 (relative damping to 0.11) and velocity sensing scale factors to 183 volts/(meter/sec). Room temperature tests of a transducer designed for 77 degree(s)K use showed only 20 percent reductions in damping and velocity signals. Magnetic modeling supports the damping and sensing observations.

  11. Optimization of sputter deposition parameters for magnetostrictive Fe62Co19Ga19/Si(100) films

    NASA Astrophysics Data System (ADS)

    Jen, S. U.; Tsai, T. L.

    2012-04-01

    A good magnetostrictive material should have large saturation magnetostriction (λS) and low saturation (or anisotropy) field (HS), such that its magnetostriction susceptibility (SH) can be as large as possible. In this study, we have made Fe62Co19Ga19/Si(100) nano-crystalline films by using the dc magnetron sputtering technique under various deposition conditions: Ar working gas pressure (pAr) was varied from 1 to 15 mTorr; sputtering power (Pw) was from 10 to 120 W; deposition temperature (TS) was from room temperature (RT) to 300 °C, The film thickness (tf) was fixed at 175 nm. Each magnetic domain looked like a long leaf, with a long-axis of about 12-15 μm and a short-axis of about 1.5 μm. The optimal magnetic and electrical properties were found from the Fe62Co19Ga19 film made with the sputter deposition parameters of pAr = 5 mTorr, Pw = 80 W, and TS = RT. Those optimal properties include λS = 80 ppm, HS = 19.8 Oe, SH = 6.1 ppm/Oe, and electrical resistivity ρ = 57.0 μΩ cm. Note that SH for the conventional magnetostrictive Terfenol-D film is, in general, equal to 1.5 ppm/Oe only.

  12. Effects of intrinsic magnetostriction on tube-topology magnetoelectric sensors with high magnetic field sensitivity

    SciTech Connect

    Gillette, Scott M.; Fitchorov, Trifon; Obi, Ogheneyunume; Chen, Yajie Harris, Vincent G.; Jiang, Liping; Hao, Hongbo; Wu, Shuangxia

    2014-05-07

    Three quasi-one-dimensional magnetoelectric (ME) magnetic field sensors, each with a different magnetostrictive wire material, were investigated in terms of sensitivity and noise floor. Magnetostrictive Galfenol, iron-cobalt-vanadium, and iron-nickel wires were examined. Sensitivity profiles, hysteresis effects, and noise floor measurements for both optimally biased and zero-biased conditions are presented. The FeNi wire (FN) exhibits high sensitivity (5.36 mV/Oe) at bias fields below 22 Oe and an optimal bias of 10 Oe, whereas FeGa wire (FG) exhibits higher sensitivity (6.89 mW/Oe) at bias fields >22 Oe. The sensor of FeCoV wire (FC) presents relatively low sensitivity (2.12 mV/Oe), due to low magnetostrictive coefficient. Each ME tube-topology sensor demonstrates relatively high sensitivity at zero bias field, which results from a magnetic shape anisotropy and internal strain of the thin magnetostrictive wire.

  13. Development of highly magnetostrictive composites for applications in magnetomechanical torque sensors

    SciTech Connect

    Chen, Yonghua

    1999-12-01

    The objective of this work was to investigate and develop a magnetomechanical material with high magnetomechanical response and low hysteresis. This material will be used in electronic torque sensors for advanced steering systems in automobiles which will replace the costly and fuel inefficient hydraulic steering systems currently in use. Magnetostruction and the magnetomechanical effect under torsional stress of magnetostrictive composites have been investigated in the present study.

  14. Exchange-Coupling in Magnetic Nanoparticles to Enhance Magnetostrictive Properties

    SciTech Connect

    Radousky, H; McElfresh, M; Berkowitz, A; Carman, G P

    2002-01-31

    Spark erosion is a versatile and economical method for producing particles of virtually any type of material that has a nominal conductivity: particles can be prepared in sizes ranging from a few nm to tens of {micro}m. The purpose of this feasibility study was to demonstrate the capability of making spherical particles of specific magnetic materials. We chose (Tb Dy)Fe{sub 2} (Terfenol-D) due to its potential use as the magnetostrictive component in magneto-elastomer composites. We also chose to work with pure Ni as a model system. Improvements in the properties of magneto-elastomer composites have broad applications in the areas of sensor development, enhanced actuators and damping systems.

  15. Optical fiber magnetic field sensors with ceramic magnetostrictive jackets.

    PubMed

    Sedlar, M; Paulicka, I; Sayer, M

    1996-09-20

    Optical fibers coated by magnetostrictive ceramic films were tested with a Mach-Zehnder interferometer in an open-loop mode. The sensors exhibited excellent linearity and good sensitivity. The response of ceramic-jacketed fibers was not affected by small dc fluctuations that are due to the linear behavior of tested ceramic coatings in low magnetic fields. Tested ceramic materials included magnetite, γ-Fe(2) O(3), nickel ferrite, and cobalt-doped nickel ferrite (NCF2) jackets. The latter showed the best performance. A minimum detectable field of 3.2 × 10(-3) A/m for optical fiber jacketed with 2-μm-thick and 1-m-long NCF2 material has been achieved. The capability of detecting magnetic fields as low as 2.6 × 10(-7) A/m with a 10-μm-thick cobalt-doped nickel ferrite jacket is proposed.

  16. Magnetostriction behavior of Co-Fe-Si-B amorphous alloys

    SciTech Connect

    Gomez-Polo, C.; Pulido, E. ); Rivero, G.; Hernando, A. )

    1990-05-01

    It is well known that the saturation magnetostriction constant of nearly-zero-magnetostriction amorphous alloys exhibits a dependence on both magnetic field and applied stress. Therefore the anisotropy field induced by the applied stress does not depend linearly on the stress strength. Experiments carried out on Co-rich amorphous alloys show a stress dependence of the anisotropy field as that expected by assuming long-range fluctuations of the magnetoelastic anisotropy. In this report the existence of local fluctuations of saturation magnetostriction is shown to be a reasonable cause of the stress dependence of magnetostriction.

  17. Progress towards developing neutron tolerant magnetostrictive and piezoelectric transducers

    SciTech Connect

    Reinhardt, Brian; Tittmann, Bernhard; Rempe, Joy; Daw, Joshua; Kohse, Gordon; Carpenter, David; Ames, Micheal; Ostrovsky, Yakov; Ramuhalli, Pradeep; Montgomery, Robert; Chien, Hualte; Wernsman, Bernard

    2014-07-01

    Current generation light water reactors (LWRs), sodium cooled fast reactors (SFRs), small modular reactors (SMRs), and next generation nuclear plants (NGNPs) provide harsh environments in and near the core that can severely test material performance and limit their operational life. To address this issue, several Department of Energy Office of Nuclear Energy (DOE-NE) research programs are evaluating the long duration radiation performance of fuels and materials. In To reduce the amount of Material and Test Reactor (MTR) irradiations required, DOE is also funding development of enhanced instrumentation that will be able to obtain data, with unprecedented accuracy and resolution, that are required to validate new multi-scale multiphysics modeling tools . It is not feasible to obtain such data with the current state of instrumentation technology. To address this need, PSU and collaborators have started an experiment to test the potential for utilizing ultrasonic instruments in-pile. Ultrasonic sensors must be resistant to high neutron flux, high gamma radiation, and high temperature. PSU and collaborators have designed, fabricated, and started to irradiate piezoelectric and magnetostrictive transducers designed to perform in such harsh environments. Three piezoelectric transducers were fabricated with aluminum nitride, zinc oxide, and bismuth titanate as the active element. The transducers are coupled kovar and aluminum waveguides of which pulse-echo ultrasonic measurements are made in-situ. Two magnetostrictive transducers were fabricated with Remendur and Arnokrome as the active elements. These devices will be pulsed and monitored in-situ. (1) Selection of candidate sensor materials as well as optimization of test assembly parameters (2) High temperature benchmark testing and (3) initial data from the irradiation will be reported.

  18. A Cryogenic Magnetostrictive Actuator Using a Persistent High Temperature Superconducting Magnet. Part 1; Concept and Design

    NASA Technical Reports Server (NTRS)

    Horner, Garnett; Bromberg, Leslie; Teter, J. P.

    2000-01-01

    Cryogenic magnetostrictive materials, such as rare earth zinc crystals, offer high strains and high forces with minimally applied magnetic fields, making the material ideally suited for deformable optics applications. For cryogenic temperature applications the use of superconducting magnets offer the possibility of a persistent mode of operation, i.e., the magnetostrictive material will maintain a strain field without power. High temperature superconductors (HTS) are attractive options if the temperature of operation is higher than 10 degrees Kelvin (K) and below 77 K. However, HTS wires have constraints that limit the minimum radius of winding, and even if good wires can be produced, the technology for joining superconducting wires does not exist. In this paper, the design and capabilities of a rare earth zinc magnetostrictive actuator using bulk HTS is described. Bulk superconductors can be fabricated in the sizes required with excellent superconducting properties. Equivalent permanent magnets, made with this inexpensive material, are persistent, do not require a persistent switch as in HTS wires, and can be made very small. These devices are charged using a technique which is similar to the one used for charging permanent magnets, e.g., by driving them into saturation. A small normal conducting coil can be used for charging or discharging. Because of the magnetic field capability of the superconductor material, a very small amount of superconducting magnet material is needed to actuate the rare earth zinc. In this paper, several designs of actuators using YBCO and BSCCO 2212 superconducting materials are presented. Designs that include magnetic shielding to prevent interaction between adjacent actuators will also be described. Preliminary experimental results and comparison with theory for BSCCO 2212 with a magnetostrictive element will be discussed.

  19. Giant electric-field-induced strain in lead-free piezoelectric materials.

    PubMed

    Chen, Lan; Yang, Yurong; Meng, X K

    2016-05-03

    First-principles calculations are performed to investigate the structures, electrical, and magnetic properties of compressive BiFeO3 films under electric-field and pressure perpendicular to the films. A reversible electric-field-induced strain up 10% is achieved in the compressive BiFeO3 films. The giant strain originates from rhombohedral-tetragonal (R-T) phase transition under electric-filed, and is recoverable from tetragonal-rhombohedral (T-R) phase transition by compressive stress. Additionally, the weak ferromagnetism in BiFeO3 films is largely changed in R-T phase transition under electric-filed and T-R phase transition under pressure - reminiscent of magnetoelectric effect and magnetoelastic effect. These results suggest exciting device opportunities arising from the giant filed-induced strain, large magnetoelectric effect and magnetoelastic effect.

  20. Giant electric-field-induced strain in lead-free piezoelectric materials

    PubMed Central

    Chen, Lan; Yang, Yurong; Meng, X. K.

    2016-01-01

    First-principles calculations are performed to investigate the structures, electrical, and magnetic properties of compressive BiFeO3 films under electric-field and pressure perpendicular to the films. A reversible electric-field-induced strain up 10% is achieved in the compressive BiFeO3 films. The giant strain originates from rhombohedral-tetragonal (R-T) phase transition under electric-filed, and is recoverable from tetragonal-rhombohedral (T-R) phase transition by compressive stress. Additionally, the weak ferromagnetism in BiFeO3 films is largely changed in R-T phase transition under electric-filed and T-R phase transition under pressure – reminiscent of magnetoelectric effect and magnetoelastic effect. These results suggest exciting device opportunities arising from the giant filed-induced strain, large magnetoelectric effect and magnetoelastic effect. PMID:27139526

  1. Giant electric-field-induced strain in lead-free piezoelectric materials.

    PubMed

    Chen, Lan; Yang, Yurong; Meng, X K

    2016-01-01

    First-principles calculations are performed to investigate the structures, electrical, and magnetic properties of compressive BiFeO3 films under electric-field and pressure perpendicular to the films. A reversible electric-field-induced strain up 10% is achieved in the compressive BiFeO3 films. The giant strain originates from rhombohedral-tetragonal (R-T) phase transition under electric-filed, and is recoverable from tetragonal-rhombohedral (T-R) phase transition by compressive stress. Additionally, the weak ferromagnetism in BiFeO3 films is largely changed in R-T phase transition under electric-filed and T-R phase transition under pressure - reminiscent of magnetoelectric effect and magnetoelastic effect. These results suggest exciting device opportunities arising from the giant filed-induced strain, large magnetoelectric effect and magnetoelastic effect. PMID:27139526

  2. Magnetostrictively actuated control flaps for vibration reduction in helicopter rotors

    SciTech Connect

    Millott, T.; Friedmann, P.P.

    1994-12-31

    High vibration levels can impose constraints on helicopter operations and hinder passenger acceptance. Vibration reduction using blade root pitch control introduces a significant power penalty and may adversely affect the airworthiness of the flight control system. Comparable levels of vibration reduction can be achieved using considerably less power through an actively controlled trailing edge flap mounted on the blade. Such a device would have no effect on helicopter airworthiness since it is controlled by a loop separate from the primary flight control system which utilizes the swashplate. Control flap actuation using the magnetostrictive material Terfenol-D is studied in this paper by designing a minimum weight actuator, subject to a set of actuation and stress constraints. The resulting device is capable of producing vibration reduction in excess of 90% at cruise conditions.

  3. Testing Results of Magnetostrictive Ultrasonic Sensor Cables for Signal Loss

    SciTech Connect

    JT Evans

    2005-05-01

    The purpose of this test was to determine the signal strength and resolution losses of a magnetostrictive ultrasonic system with an extended signal cable. The cable of interest carries electrical signals between the pulse generator/receiver and the magnetostrictive transducer. It was desired to determine the loss introduced by different lengths of the signal cable (6', 100', and 200').

  4. A versatile platform for magnetostriction measurements in thin films

    NASA Astrophysics Data System (ADS)

    Pernpeintner, M.; Holländer, R. B.; Seitner, M. J.; Weig, E. M.; Gross, R.; Goennenwein, S. T. B.; Huebl, H.

    2016-03-01

    We present a versatile nanomechanical sensing platform for the investigation of magnetostriction in thin films. It is based on a doubly clamped silicon nitride nanobeam resonator covered with a thin magnetostrictive film. Changing the magnetization direction within the film plane by an applied magnetic field generates a magnetoelastic stress and thus changes the resonance frequency of the nanobeam. A measurement of the resulting resonance frequency shift, e.g., by optical interferometry, allows to quantitatively determine the magnetostriction constants of the thin film. In a proof-of-principle experiment, we determine the magnetostriction constants of a 10 nm thick polycrystalline cobalt film, showing very good agreement with literature values. The presented technique aims, in particular, for the precise measurement of magnetostriction in a variety of (conducting and insulating) thin films, which can be deposited by, e.g., electron beam deposition, thermal evaporation, or sputtering.

  5. Analysis of an operator-differential model for magnetostrictive energy harvesting

    NASA Astrophysics Data System (ADS)

    Davino, D.; Krejčí, P.; Pimenov, A.; Rachinskii, D.; Visone, C.

    2016-10-01

    We present a model of, and analysis of an optimization problem for, a magnetostrictive harvesting device which converts mechanical energy of the repetitive process such as vibrations of the smart material to electrical energy that is then supplied to an electric load. The model combines a lumped differential equation for a simple electronic circuit with an operator model for the complex constitutive law of the magnetostrictive material. The operator based on the formalism of the phenomenological Preisach model describes nonlinear saturation effects and hysteresis losses typical of magnetostrictive materials in a thermodynamically consistent fashion. We prove well-posedness of the full operator-differential system and establish global asymptotic stability of the periodic regime under periodic mechanical forcing that represents mechanical vibrations due to varying environmental conditions. Then we show the existence of an optimal solution for the problem of maximization of the output power with respect to a set of controllable parameters (for the periodically forced system). Analytical results are illustrated with numerical examples of an optimal solution.

  6. Magnetostrictive properties of amorphous and partially crystalline TbDyFe thin films

    SciTech Connect

    Speliotis, A.; Kalogirou, O.; Niarchos, D.

    1997-04-01

    A series of amorphous and partially crystalline giant magnetostrictive thin films of the composition (Tb{sub 0.3}Dy{sub 0.7}){sub 39}Fe{sub 61} has been prepared by dc magnetron sputtering. The sputtering conditions were the same for all samples apart from the substrate temperature T{sub S}, which varied between 330 and 510{degree}C. The crystalline state and the magnetic properties of the samples were investigated in relation to the substrate temperature. Films deposited at T{sub S}=330{endash}400{degree}C were amorphous. Crystallization started at T{sub S}=425{degree}C. The magnetostrictive coefficient {lambda}, at 4 kOe and at room temperature, increased with increasing T{sub S} from 185 to 750 ppm at H{sub max}. This was related also to an increase of the Curie temperature T{sub C} from 35 to 315{degree}C. The hysteresis loops of the amorphous samples showed coercivities lower than 10 Oe. These samples presented {lambda}{approx}300 ppm in a field of 1000 Oe. The direction of the magnetic moments in the amorphous films changed gradually from perpendicular to parallel to the film plane with increasing T{sub S}. The samples deposited at T{sub S}{ge}425{degree}C showed {lambda}{sub max}{approx}350{endash}750 ppm, but the magnetostrictive curve was much broader and shifted to the value of H{sub c}. {copyright} {ital 1997 American Institute of Physics.}

  7. Evaluation of concrete reinforcements using magnetostrictive sensors

    NASA Astrophysics Data System (ADS)

    Bartels, Keith A.; Dynes, Chris P.; Lu, Yichi; Kwun, Hegeon

    1999-02-01

    In this paper, a review is presented of various applications of the magnetostrictive sensor (MsS) technology to the nondestructive evaluation of steel reinforcing bars and seven-wire strands. MsSs have been applied to the detection of corrosion in and out of concrete, the quantification of corrosion, the detection of debonding, the measurement of tensile stress, the monitoring of concrete curing, the monitoring of wire breakage, and the location of broken or fractured wires. A review of the MsS technology is given along with an assessment of the utility of the technology in the above-mentioned applications.

  8. Optimisation Of a Magnetostrictive Wave Energy Converter

    NASA Astrophysics Data System (ADS)

    Mundon, T. R.; Nair, B.

    2014-12-01

    Oscilla Power, Inc. (OPI) is developing a patented magnetostrictive wave energy converter aimed at reducing the cost of grid-scale electricity from ocean waves. Designed to operate cost-effectively across a wide range of wave conditions, this will be the first use of reverse magnetostriction for large-scale energy production. The device architecture is a straightforward two-body, point absorbing system that has been studied at length by various researchers. A large surface float is anchored to a submerged heave (reaction) plate by multiple taut tethers that are largely made up of discrete, robust power takeoff modules that house the magnetostrictive generators. The unique generators developed by OPI utilize the phenomenon of reverse magnetostriction, which through the application of load to a specific low cost alloy, can generate significant magnetic flux changes, and thus create power through electromagnetic induction. Unlike traditional generators, the mode of operation is low-displacement, high-force, high damping which in combination with the specific multi-tether configuration creates some unique effects and interesting optimization challenges. Using an empirical approach with a combination of numerical tools, such as ORCAFLEX, and physical models, we investigated the properties and sensitivities of this system arrangement, including various heave plate geometries, with the overall goal of identifying the mass and hydrodynamic parameters required for optimum performance. Furthermore, through a detailed physical model test program at the University of New Hampshire, we were able to study in more detail how the heave plate geometry affects the drag and added mass coefficients. In presenting this work we will discuss how alternate geometries could be used to optimize the hydrodynamic parameters of the heave plate, allowing maximum inertial forces in operational conditions, while simultaneously minimizing the forces generated in extreme waves. This presentation

  9. Exchange-striction induced giant ferroelectric polarization in copper-based multiferroic material α -Cu2V2O7

    NASA Astrophysics Data System (ADS)

    Sannigrahi, J.; Bhowal, S.; Giri, S.; Majumdar, S.; Dasgupta, I.

    2015-06-01

    We report α -Cu2V2O7 to be an improper multiferroic with the simultaneous development of electric polarization and magnetization below TC=35 K . The observed spontaneous polarization of 0.55 μ C cm-2 magnitude is highest among copper-based improper multiferroic materials. Our study demonstrates a sizable amount of magnetoelectric coupling below TC, even with a low magnetic field. The theoretical calculations based on density functional theory indicate magnetism in α -Cu2V2O7 is a consequence of ferro-orbital ordering driven by a polar lattice distortion due to the unique pyramidal (CuO5) environment of Cu. Spin-orbit coupling further stabilizes orbital ordering and is crucial for magnetism. The calculations indicate that the origin of the giant ferroelectric polarization is primarily due to the symmetric exchange-striction mechanism and is corroborated by temperature-dependent x-ray studies.

  10. Measurement of the magnetostriction constants of amorphous thin films on kapton substrates

    NASA Astrophysics Data System (ADS)

    Ouyang, C.; Kim, T. W.; Gambino, R. J.; Jahnes, C.

    1998-06-01

    The saturation magnetostriction constants of thin films of amorphous Co39Ni31Fe8Si8B14 and CoZrTb have been measured either by the small angle magnetization rotation (SAMR) method or by the initial susceptibility method. The SAMR method is used for the soft materials. When the material is magnetically hard or has a strong perpendicular anisotropy, the initial susceptibility method is used. It is found that the amorphous Co39Ni31Fe8Si8B14 prepared by ion beam deposition from an alloy target shows very soft magnetic properties and has a very small negative saturation magnetostriction, λs, of -1×10-7. Sputtered films of CoZrTb show a strong perpendicular anisotropy when the concentration of Tb is high. We have found that the SAMR method can be applied to CoZrTb films when the Tb content is low. The saturation magnetostricition constant of a sputtered film of Co78.4Zr20.8Tb0.8 is 2×106. When the Tb content is high, however, the initial susceptibility method is used to measure magnetostriction.

  11. The effect of the condensation of ice materials in the atmosphere on the thermal evolution of ice giants

    NASA Astrophysics Data System (ADS)

    Kurosaki, Kenji; Ikoma, Masahiro

    2015-12-01

    Though Uranus and Neptune are similar in mass and radius, the former is significantly fainter than the latter. As previous theoretical studies of thermal evolution of the ice giants demonstrated, the faintness of Uranus is not explained by simple three-layer models that are composed of a H/He-dominated envelope, an ice mantle and a rocky core. Namely, the observed effective temperature of Uranus is lower than theoretically predicted (e.g., Fortney et al., 2011; Nettelmann et al., 2013). Since the speed of the thermal evolution is determined by how efficiently the planetary atmosphere radiates energy, the atmospheric structure is important. If the atmosphere contains ice materials such as water, ammonia and methane, those materials have been condensed and removed from the atmosphere during the cooling. In this study, we quantify the impact of the condensation of ice components in the atmosphere on the thermal evolution, which previous studies ignore, to explain the current luminosity of Uranus. To do so, we simulate the thermal cooling of ice giants, based on three layer models with a relatively ice-component-rich, H/He-dominated atmosphere on top of a water mantle that surrounds a rocky core. We demonstrate that the effect of the condensation makes the timescale of the thermal cooling of the planet shorter by an order of magnitude than in the case without condensation. Such accelerated cooling is shown to be fast enough to explain the current faintness of Uranus. We also discuss what caused the difference in current luminosity between Uranus and Neptune.

  12. Magnetostriction of some rare earth-aluminum Laves phase compounds

    NASA Technical Reports Server (NTRS)

    Pourarian, F.; Wallace, W. E.

    1979-01-01

    Measurements of the linear and volume magnetostriction of RAl2 cubic Laves compounds in which R is one of the rare earth elements Gd, Dy, Ho or Er, at temperatures between 4.2 K and the Curie temperature of each compound, are reported. Magnetic fields up to 2.5 Tesla were applied, and magnetostriction was measured using standard strain gage techniques. Saturation magnetostrictions of 17 x 10 to the -6th, -1420 x 10 to the -6th, 60 x 10 to the -6th and -920 x 10 to the -6th are determined at 4.2 K for GdAl2, DyAl2, HoAl2 and ErAl2, respectively. Large forced magnetostriction is observed in GdAl2 above the saturation field and the strain temperature dependence shows a decrease in magnitude below 40 K. A linear dependence of magnetostriction on magnetic field was observed for DyAl2 above 40 K, and the observed temperature dependence is interpreted in terms of the lowest order single-ion magnetoelastic theory. An observed decrease in the magnitude of the strain of HoAl2 below 15 K is associated with a change of the easy direction of magnetization, while in the case of ErAl2, magnetostriction is observed to occur normally up to the Curie temperature. Large volume magnetostriction is obtained for all the compounds with the exception of GdAl2.

  13. Magnetostrictive GMR spin valves with composite FeGa/FeCo free layers

    NASA Astrophysics Data System (ADS)

    Liu, Luping; Zhan, Qingfeng; Yang, Huali; Li, Huihui; Zhang, Shuanglan; Liu, Yiwei; Wang, Baomin; Tan, Xiaohua; Li, Run-Wei

    2016-03-01

    We have fabricated strain-sensitive spin valves on flexible substrates by utilizing the large magnetostrictive FeGa alloy to promote the strain sensitivity and the composite free layer of FeGa/FeCo to avoid the drastic reduction of giant magnetoresistance (GMR) ratio. This kind of spin valve (SV-FeGa/FeCo) displays a MR ratio about 5.9%, which is comparable to that of the conventional spin valve (SV-FeCo) with a single FeCo free layer. Different from the previously reported works on magnetostrictive spin valves, the SV-FeGa/FeCo displays an asymmetric strain dependent GMR behavior. Upon increasing the lateral strain, the MR ratio for the ascending branch decreases more quickly than that for the descending branch, which is ascribed to the formation of a spiraling spin structure around the FeGa/FeCo interface under the combined influences of both magnetic field and mechanical strain. A strain sensitivity of GF = 7.2 was achieved at a magnetic bias field of -30 Oe in flexible SV-FeGa/FeCo, which is significantly larger than that of SV-FeCo.

  14. Progress towards developing neutron tolerant magnetostrictive and piezoelectric transducers

    NASA Astrophysics Data System (ADS)

    Reinhardt, Brian; Tittmann, Bernhard; Rempe, Joy; Daw, Joshua; Kohse, Gordon; Carpenter, David; Ames, Michael; Ostrovsky, Yakov; Ramuhalli, Pradeep; Montgomery, Robert; Chien, Hualte; Wernsman, Bernard

    2015-03-01

    Current generation light water reactors (LWRs), sodium cooled fast reactors (SFRs), small modular reactors (SMRs), and next generation nuclear plants (NGNPs) produce harsh environments in and near the reactor core that can severely tax material performance and limit component operational life. To address this issue, several Department of Energy Office of Nuclear Energy (DOE-NE) research programs are evaluating the long duration irradiation performance of fuel and structural materials used in existing and new reactors. In order to maximize the amount of information obtained from Material Testing Reactor (MTR) irradiations, DOE is also funding development of enhanced instrumentation that will be able to obtain in-situ, real-time data on key material characteristics and properties, with unprecedented accuracy and resolution. Such data are required to validate new multi-scale, multi-physics modeling tools under development as part of a science-based, engineering driven approach to reactor development. It is not feasible to obtain high resolution/microscale data with the current state of instrumentation technology. However, ultrasound-based sensors offer the ability to obtain such data if it is demonstrated that these sensors and their associated transducers are resistant to high neutron flux, high gamma radiation, and high temperature. To address this need, the Advanced Test Reactor National Scientific User Facility (ATR-NSUF) is funding an irradiation, led by PSU, at the Massachusetts Institute of Technology Research Reactor to test the survivability of ultrasound transducers. As part of this effort, PSU and collaborators have designed, fabricated, and provided piezoelectric and magnetostrictive transducers that are optimized to perform in harsh, high flux, environments. Four piezoelectric transducers were fabricated with either aluminum nitride, zinc oxide, or bismuth titanate as the active element that were coupled to either Kovar or aluminum waveguides and two

  15. Progress towards developing neutron tolerant magnetostrictive and piezoelectric transducers

    SciTech Connect

    Reinhardt, Brian; Tittmann, Bernhard; Rempe, Joy; Daw, Joshua; Kohse, Gordon; Carpenter, David; Ames, Michael; Ostrovsky, Yakov; Ramuhalli, Pradeep; Montgomery, Robert; Chien, Hualte; Wernsman, Bernard

    2015-03-31

    Current generation light water reactors (LWRs), sodium cooled fast reactors (SFRs), small modular reactors (SMRs), and next generation nuclear plants (NGNPs) produce harsh environments in and near the reactor core that can severely tax material performance and limit component operational life. To address this issue, several Department of Energy Office of Nuclear Energy (DOE-NE) research programs are evaluating the long duration irradiation performance of fuel and structural materials used in existing and new reactors. In order to maximize the amount of information obtained from Material Testing Reactor (MTR) irradiations, DOE is also funding development of enhanced instrumentation that will be able to obtain in-situ, real-time data on key material characteristics and properties, with unprecedented accuracy and resolution. Such data are required to validate new multi-scale, multi-physics modeling tools under development as part of a science-based, engineering driven approach to reactor development. It is not feasible to obtain high resolution/microscale data with the current state of instrumentation technology. However, ultrasound-based sensors offer the ability to obtain such data if it is demonstrated that these sensors and their associated transducers are resistant to high neutron flux, high gamma radiation, and high temperature. To address this need, the Advanced Test Reactor National Scientific User Facility (ATR-NSUF) is funding an irradiation, led by PSU, at the Massachusetts Institute of Technology Research Reactor to test the survivability of ultrasound transducers. As part of this effort, PSU and collaborators have designed, fabricated, and provided piezoelectric and magnetostrictive transducers that are optimized to perform in harsh, high flux, environments. Four piezoelectric transducers were fabricated with either aluminum nitride, zinc oxide, or bismuth titanate as the active element that were coupled to either Kovar or aluminum waveguides and two

  16. Application of the SAMR method to high magnetostrictive samples

    NASA Astrophysics Data System (ADS)

    Sanchez, P.; Lopez, E.; Trujillo, M. C. Sanchez; Aroca, C.

    1988-12-01

    Magnetostriction measurement by using the small angle magnetization rotation method (SAMR) has been performed in high magnetostrictive amorphous samples. To apply the SAMR method to these samples, a theoritical model about the influence of the internal stresses and magnetization distribution has been proposed. The dependence of the magnetostriction, λ s, with the temperature and applied stress was measured in as-cast and in different annealed samples. In the as-cast samples the existence of a stray field and a dependence of λ s with the applied stress has been observed.

  17. Optimization of magnetostriction, coercive field and magnetic transition temperature in nanocrystalline TbDyFe+Zr/Nb multilayers

    NASA Astrophysics Data System (ADS)

    Fischer, S. F.; Kelsch, M.; Kronmüller, H.

    1999-06-01

    The magnetostrictive properties of TbDyFe/Nb multilayers containing 2 at% Zr as an additive have been investigated after different annealing treatments for the (Terfenol-D near) composition of [Tb 0.27Dy 0.73] 0.27Fe 0.73. The multilayer structure has been produced by ion-beam sputtering on a sapphire substrate. After 10 min annealing of the multilayers at temperatures from 873 to 973 K the parallel magnetostriction increased from λ‖(0.8 T)=265 to 520 ppm accompanied by an increase of the magnetic phase transition temperature from TC=333 to 592 K, while the increase of the coercive fields from μ0Hc<5 to 75 mT lies distinctively below 100 mT. These properties are suitable for applications of giant magnetostrictive films in microsystems where values of λ>500 ppm, TC>500 K and μ0Hc≪100 mT are required. Establishing a nanocrystalline microstructure with grain sizes d< dc˜15 nm ( dc is the critical grain diameter) smaller than the exchange length is essential for the combination of intrinsic magnetic properties (increased λ and TC) with soft magnetic properties ( μ0Hc of a few mT) as typical for an amorphous microstructure. It is shown by microstructural XRD and TEM investigations that such a nanocrystalline microstructure can be realized by a suitable heat treatment of TbDyFe+Zr/Nb multilayers. Introducing Nb spacer layers effectively reduces grain growth for certain annealing temperatures while Zr is assumed to play a dominant role in forming nucleation centers of nanograins. In combination, both effects can be well used to optimize the magnetostrictive layer properties.

  18. Performance of improved magnetostrictive vibrational power generator, simple and high power output for practical applications

    SciTech Connect

    Ueno, Toshiyuki

    2015-05-07

    Vibration based power generation technology is utilized effectively in various fields. Author has invented novel vibrational power generation device using magnetostrictive material. The device is based on parallel beam structure consisting of a rod of iron-gallium alloy wound with coil and yoke accompanied with permanent magnet. When bending force is applied on the tip of the device, the magnetization inside the rod varies with induced stress due to the inverse magnetostrictive effect. In vibration, the time variation of the magnetization generates voltage on the wound coil. The magnetostrictive type is advantageous over conventional such using piezoelectric or moving magnet types in high efficiency and high robustness, and low electrical impedance. Here, author has established device configuration, simple, rigid, and high power output endurable for practical applications. In addition, the improved device is lower cost using less volume of Fe-Ga and permanent magnet compared to our conventional, and its assembly by soldering is easy and fast suitable for mass production. Average power of 3 mW/cm{sup 3} under resonant vibration of 212 Hz and 1.2 G was obtained in miniature prototype using Fe-Ga rod of 2 × 0.5× 7 mm{sup 3}. Furthermore, the damping effect was observed, which demonstrates high energy conversion of the generator.

  19. Vertical positioning surveillance by magnetostrictive transducer

    NASA Astrophysics Data System (ADS)

    Carvalho, A. S.; Lopes, C.; Pinto, O. O.; Nunes, C. D.; Borges, M. F.; Strohaecker, T. R.

    2015-10-01

    This work purpose is to create a positioning automated system of a tailstock to perform impact resistance tests on silicone mammary implants. This system is capable to measure and oversight the positioning through interrelation between three main components: programmable logic controller, human-machine interface and magnetostrictive transducer. Together, these components form an operational closed loop that ensures an appropriate positioning for the impact device. The paper describes how the closed loop works and also the algorithm implemented in the programmable logic controller which surveys the positioning. As a last topic, the paper presents the operator work on the machine's operation in conjunction with human-machine interface. The results were satisfactory and in accordance with the limits determined on ABNT NBR ISO 14607 for this method of tests.

  20. Development of a magnetostrictive borehole seismic source

    SciTech Connect

    Cutler, R.P.; Sleefe, G.E.; Keefe, R.G.

    1997-04-01

    A magnetostrictive borehole seismic source was developed for use in high resolution crosswell surveys in environmental applications. The source is a clamped, vertical-shear, swept frequency, reaction-mass shaker design consisting of a spring pre-loaded magnetostrictive rod with permanent magnet bias, drive coils to induce an alternating magnetic field, and an integral tungsten reaction mass. The actuator was tested extensively in the laboratory. It was then incorporated into an easily deployable clamped downhole tool capable of operating on a standard 7 conductor wireline in borehole environments to 10,000{degrees} deep and 100{degrees}C. It can be used in either PVC or steel cased wells and the wells can be dry or fluid filled. It has a usable frequency spectrum of {approx} 150 to 2000 Hz. The finished tool was successfully demonstrated in a crosswell test at a shallow environmental site at Hanford, Washington. The source transmitted signals with a S/N ratio of 10-15 dB from 150-720 Hz between wells spaced 239 feet apart in unconsolidated gravel. The source was also tested successfully in rock at an oil field test site, transmitting signals with a S/N ratio of 5-15 dB over the full sweep spectrum from 150-2000 Hz between wells spaced 282 feet apart. And it was used successfully on an 11,000{degrees} wireline at a depth of 4550{degrees}. Recommendations for follow-on work include improvements to the clamp, incorporation of a higher sample rate force feedback controller, and increases in the force output of the tool.

  1. Presolar Materials in a Giant Cluster IDP of Probable Cometary Origin

    NASA Technical Reports Server (NTRS)

    Messenger, S.; Brownlee, D. E.; Joswiak, D. J.; Nguyen, A. N.

    2015-01-01

    Chondritic porous interplanetary dust particles (CP-IDPs) have been linked to comets by their fragile structure, primitive mineralogy, dynamics, and abundant interstellar materials. But differences have emerged between 'cometary' CP-IDPs and comet 81P/Wild 2 Stardust Mission samples. Particles resembling Ca-Al-rich inclusions (CAIs), chondrules, and amoeboid olivine aggregates (AOAs) in Wild 2 samples are rare in CP-IDPs. Unlike IDPs, presolar materials are scarce in Wild 2 samples. These differences may be due to selection effects, such as destruction of fine grained (presolar) components during the 6 km/s aerogel impact collection of Wild 2 samples. Large refractory grains observed in Wild 2 samples are also unlikely to be found in most (less than 30 micrometers) IDPs. Presolar materials provide a measure of primitive-ness of meteorites and IDPs. Organic matter in IDPs and chondrites shows H and N isotopic anomalies attributed to low-T interstellar or protosolar disk chemistry, where the largest anomalies occur in the most primitive samples. Presolar silicates are abundant in meteorites with low levels of aqueous alteration (Acfer 094 approximately 200 ppm) and scarce in altered chondrites (e.g. Semarkona approximately 20 ppm). Presolar silicates in minimally altered CP-IDPs range from approximately 400 ppm to 15,000 ppm, possibly reflecting variable levels of destruction in the solar nebula or statistical variations due to small sample sizes. Here we present preliminary isotopic and mineralogical studies of a very large CP-IDP. The goals of this study are to more accurately determine the abundances of presolar components of CP-IDP material for comparison with comet Wild 2 samples and meteorites. The large mass of this IDP presents a unique opportunity to accurately determine the abundance of pre-solar grains in a likely cometary sample.

  2. Nonlinear Modeling and Characterization of the Villari Effect and Model-guided Development of Magnetostrictive Energy Harvesters and Dampers

    NASA Astrophysics Data System (ADS)

    Deng, Zhangxian

    The Villari effect, through which mechanical energy is transferred to magnetic energy in magnetostrictive materials can be utilized in energy harvester and damper designs. Significant research has been conducted on two magnetostrictive materials, Terfenol-D (TbxDy1-xFe2.0, x ≈ 0.3) and Galfenol (Fe1-xGax, 0.15 ≤ x ≤ 0.3), due to their high magnetomechanical coupling. Both materials have strengths and weaknesses. Terfenol-D exhibits low eddy current loss, but it is brittle and difficult to machine. Terfenol-D also provides higher magnetostriction while requiring a large magnetic field. On the other hand, Galfenol is mechanically robust, and thus can be machined, welded, and formed into complex geometries. However, due to its severe eddy current effect, lamination is necessary in high frequency applications. This work first characterized the Villari effect of Galfenol in terms of the piezo-magnetic constant d33* and hysteresis loss. The stress-flux density loops of oriented, polycrystalline Fe18.4Ga81.6 Galfenol were measured at quasi-static and dynamic regimes (up to 800 Hz). Advanced modeling tools are necessary for magnetostrictive device development. On the material level, this work proposed a dynamic, discrete energy-averaged (DEA) model incorporating time-dependent volume fractions into the static DEA framework. This dynamic DEA model took eddy current loss, mechanical loss, and pinning site loss into account and accurately simulated the measured Villari effect up to 600 Hz. On the system level, this work integrated a hysteresis static DEA model with a 3D finite element (FE) framework, and accurately modeled stress-flux density minor loops in a quasi-static state. Based on the assumption that the magnetostriction and magnetization are uniaxial, this work also proposed an efficient 2D FE framework describing nonlinear magnetostrictive responses via interpolation functions. This enhanced knowledge of the Villari effect facilitates magnetostrictive vibration

  3. Progress Report 2011: Understanding compound phase transitions in Heusler alloy giant magnetocaloric materials

    SciTech Connect

    Stadler, Shane

    2011-12-13

    Our goal is to gain insight into the fundamental physics that is responsible for magnetocaloric effects (MCE) and related properties at the atomic level. We are currently conducting a systematic study on the effects of atomic substitutions in Ni2MnGa-based alloys, and also exploring related full- and half-Heusler alloys, for example Ni-Mn-X (X=In, Sn, Sb), that exhibit a wide variety of interesting and potentially useful physical phenomena. It is already known that the magnetocaloric effect in the Heusler alloys is fundamentally connected to other interesting phenomena such as shape-memory properties. And the large magnetic entropy change in Ni2Mn0.75Cu0.25Ga has been attributed to the coupling of the first-order, martensitic transition with the second-order ferromagnetic paramagnetic (FM-PM) transition. Our research to this point has focused on understanding the fundamental physics at the origin of these complex, compound phase transitions, and the novel properties that emerge. We synthesize the materials using a variety of techniques, and explore their material properties through structural, magnetic, transport, and thermo-magnetic measurements.

  4. Substituting Al for Fe in Pr(AlxFe1-x)1.9 alloys: Effects on magnetic and magnetostrictive properties

    NASA Astrophysics Data System (ADS)

    Tang, Yan-Mei; Chen, Le-Yi; Wei, Jun; Tang, Shao-Long; Du, You-Wei

    2014-07-01

    The magnetostrictive effects of substituting Al for Fe in Pr(AlxFe1-x)1.9 (x = 0.0, 0.02, 0.05, 0.10) alloys between 5 K and 300 K were investigated. The substitution decreases the Curie temperature and the value of λ111. Fortunately, the substitution slightly increases the magnetostriction in a low magnetic field, which imbues these materials with potential advantages for applications. Rotation of the easy magnetization direction (EMD) from [111] to [100] in the Pr(Al0.02Fe0.98)1.9 alloy as temperature decreases was detected by step scanned XRD reflections.

  5. Magnetostriction measurements on the multidirectional magnetization performance of SiFe steel

    NASA Astrophysics Data System (ADS)

    Yamaguchi, H.; Pfüzner, H.; Hasenzagl, A.

    By means of a 3-phase excited rotational single sheet tester in combination with three sets of strain gauges, multi-directional magnetostriction (MS) was studied for highly grain oriented (HGO) SiFe. Emphasis was put on a new type of material with hyper-stress coating based on titanium nitride. Experiments were performed for elliptical, Lozenge-type and circular magnetization. In all states that are relevant for practice, the new type showed lowest levels of MS, especially for the rolling direction and the normal direction. By means of a domain model, which is based on the results of MS, the superior behavior is explained by a suppression of oblique domains.

  6. Feasibility of Magnetostrictive Sensor Inspection of Containments

    SciTech Connect

    Kwun, H.

    1999-03-01

    This report describes the results of a study on the feasibility of using guided waves for long-range global inspection of containment metallic pressure boundaries (i.e., steel containments and liners of reinforced concrete containments) in nuclear power plants. Of particular concern in this study was the potential of the guided-wave approach for remotely inspecting the regions that are inaccessible; for example, regions where the metallic pressure boundary is backed by concrete on one or both sides. The study includes a literature review on long-range guided-wave inspection techniques, a modeling study of the behavior of guided waves in plates with different boundary conditions (e.g., freestanding and backed by concrete on one or both sides), and an experimental investigation of the feasibility of a guided-wave technique called ''magnetostrictive sensor (MsS)'' for (1) generating and detecting guided waves in plates and (2) detecting a defect over a long range. Results of the study showed (1) that it is feasible to achieve long-range global inspection of plates, including regions that are inaccessible, using low-frequency guided waves and (2) that the MsS technique is well suited for this application. Recommendations are made to further test and develop the MsS technique for practical implementation for containment inspection in nuclear power plants.

  7. The nature of photoinduced changes in the magnetostriction of yttrium-iron garnet single crystals

    SciTech Connect

    Vorob'eva, N. V.

    2011-05-15

    A model of the occurrence of photoinduced changes in linear magnetostriction is proposed based on a complex experimental study of magnetostrictive strains in yttrium-iron garnets Y{sub 3}Fe{sub 5}O{sub 12} with low contents of different impurities. Analytical expressions for calculating the magnetostriction in yttrium-iron garnet single crystals with different types of doping are presented. The correlation of the photoinduced change in the magnetostriction with the crystallographic features of the samples is demonstrated. The changes in the magnetostriction constants are analyzed quantitatively for samples prepared in different ways.

  8. Continuous method for manufacturing grain-oriented magnetostrictive bodies

    DOEpatents

    Gibson, Edwin D.; Verhoeven, John D.; Schmidt, Frederick A.; McMasters, O. Dale

    1988-01-01

    The invention comprises a continuous casting and crystallization method for manufacturing grain-oriented magnetostrictive bodies. A magnetostrictive alloy is melted in a crucible having a bottom outlet. The melt is discharged through the bottom of the crucible and deposited in an elongated mold. Heat is removed from the deposited melt through the lower end portion of the mold to progressively solidify the melt. The solid-liquid interface of the melt moves directionally upwardly from the bottom to the top of the mold, to produce the axial grain orientation.

  9. Magnetostriction and palæomagnetism of igneous rocks

    USGS Publications Warehouse

    Graham, John W.; Buddington, A.F.; Balsley, J.R.

    1959-01-01

    IN a recent communication, Stott and Stacey1 report on a “crucial experiment” from which they conclude: “This excellent agreement between the dip and the directions of artificial thermoremanent magnetization of the stressed and unstressed rocks indicates that large systematic errors due to magnetostriction are most improbable in igneous rocks of types normally used for palæomagnetic work”. This experiment was intended to test the proposals2 and measurements3 bearing on the role of magnetostriction in rock magnetism. We present here our reasons for believing that the experiment was not crucial and that the conclusion is not justified.

  10. Design, test and model of a hybrid magnetostrictive hydraulic actuator

    NASA Astrophysics Data System (ADS)

    Chaudhuri, Anirban; Yoo, Jin-Hyeong; Wereley, Norman M.

    2009-08-01

    The basic operation of hybrid hydraulic actuators involves high frequency bi-directional operation of an active material that is converted to uni-directional motion of hydraulic fluid using valves. A hybrid actuator was developed using magnetostrictive material Terfenol-D as the driving element and hydraulic oil as the working fluid. Two different lengths of Terfenol-D rod, 51 and 102 mm, with the same diameter, 12.7 mm, were used. Tests with no load and with load were carried out to measure the performance for uni-directional motion of the output piston at different pumping frequencies. The maximum no-load flow rates were 24.8 cm3 s-1 and 22.7 cm3 s-1 with the 51 mm and 102 mm long rods respectively, and the peaks were noted around 325 Hz pumping frequency. The blocked force of the actuator was close to 89 N in both cases. A key observation was that, at these high pumping frequencies, the inertial effects of the fluid mass dominate over the viscous effects and the problem becomes unsteady in nature. In this study, we also develop a mathematical model of the hydraulic hybrid actuator in the time domain to show the basic operational principle under varying conditions and to capture phenomena affecting system performance. Governing equations for the pumping piston and output shaft were obtained from force equilibrium considerations, while compressibility of the working fluid was taken into account by incorporating the bulk modulus. Fluid inertia was represented by a lumped parameter approach to the transmission line model, giving rise to strongly coupled ordinary differential equations. The model was then used to calculate the no-load velocities of the actuator at different pumping frequencies and simulation results were compared with experimental data for model validation.

  11. Magnetostriction and susceptibilities of twinned single crystals of Terfenol-D

    NASA Astrophysics Data System (ADS)

    Zhao, X. G.; Lord, D. G.

    1998-06-01

    Measurements are presented of the dc magnetostriction, and both the ac and dc susceptibility along the three orthogonal axes of [112¯], [111], and [11¯0] from twinned single crystals of Terfenol-D as a function of varying compressive stress and magnetic field mutually applied along the [112¯] rod axis. The data are used in an attempt to analyze the magnetization processes occurring in such a specimen. The experimental results show clearly the two characteristics of the magnetization process corresponding to (i) the magnetostrictive "jump" effect, and (ii) the slow changes of magnetostriction occurring above the "jump." It is estimated that in stage (i) of the magnetization process, the domains aligned along the [111] axis by the applied stress rapidly and massively redistribute their moments both to the [111¯] direction closest to the applied field as well as to the [1¯11¯] and [11¯1¯] directions; and during stage (ii), the domains occupying the [1¯11¯] and [11¯1¯] directions redistribute to the [111¯] successively by non-180° domain-wall motion. However, two fine magnetization processes are found in the field range of the jump effect indicating that some domains must redistribute from the [111] to the [1¯11¯] and [11¯1¯] initially, then to the [111¯] even when the field is only increased in the initial stage (i). The nonzero susceptibilities measured along the [111] and [11¯0] suggest that both the volumes of parent and twin material as well as the probabilities for domain redistribution from one easy direction to the [1¯11¯] and [11¯1¯] might be different.

  12. High pressure study of gadolinium (silicon-germanium) giant magnetocaloric materials using x-ray magnetic circular dichroism

    NASA Astrophysics Data System (ADS)

    Tseng, Yuan-Chieh

    The role of Si-doping in enhancing the magnetic ordering temperature (Tc) of Gd5(SixGe1--x )4 giant magnetocaloric compounds was investigated using x-ray magnetic circular dichroism (XMCD) and diamond anvil cell (DAC) techniques. The purpose of the study is to understand the mechanism of doping-induced ferromagnetic order in these compounds that may advance the magnetic refrigeration technology. The results demonstrate that hydrostatic pressure leads to similar effects as Si-doping for x ≥ 0.125 because the P-T phase diagram reproduces the most notable features of the x-T phase diagram, indicating that the magnetic properties of these compounds are volume-driven. The low-x (0 < x ≤ 0.75) region exhibits an inhomogeneous magneto-structural ground state featured by a mixed antiferromagnetic (orthorhombic (II))--ferromagnetic (orthorhombic (I)) phase at low temperature. Pressure was found to remove this magneto-structural inhomogeneity by fully restoring the magnetization that is obtained for x ≥ 0.125. However, unlike the nearly constant dTc/dP obtained for 0.125 ≤ x < 0.5, dTc/dP of the low-x samples is strongly x-dependent. This suggests that the emergence of the ferromagnetic order from within the antiferromagnetic phase of Gd 5Ge4 parent compound cannot be simply described as a volume-effect due to the existence of the magneto-structural inhomogeneity. Finally, the quantitative correspondence between Si-doping and hydrostatic pressure was examined in order to know if the properties of these materials are monotonically volume-dependent. It was found that Si-doping increases Tc much more effectively than pressure, by a factor of ˜ 11 for a given volume reduction. A local lattice contraction was found around Si atoms as a result of the substitution of Ge by the smaller Si atoms resulting in a remarkably high local chemical pressure. This local contraction results in a stronger Si 3p-Gd 5d orbital hybridization benefiting the indirect ferromagnetic exchange

  13. Magnetostriction of rare-earth random magnetic anisotropy spin glasses

    SciTech Connect

    del Moral, A.; Arnaudas, J.I.

    1989-05-01

    A model of magnetostriction for single-ion random magnetic anisotropy (RMA) spin glasses (SG) is developed, the calculation being based on the replica technique. An overall uniform strain is assumed and coupled to the local easy axis (or easy plane) by an adequate projection. The obtained bulk magnetostriction becomes proportional to the average quadrupolar moment, which depends upon the assumed ferromagnetic uniform exchange, J/sub 0/, and the RMA crystal field (CEF), D/sub 0/, strengths. Magnetostriction measurements parallel (lambda/sub X/) and perpendicular (lambda/sub perpendicular/) to the applied magnetic field (up to 7 T) have been performed between 4.2 and 150 K (much larger than the SG temperature, T/sub SG/) for the amorphous spin glasses R/sub 40/Y/sub 23/Cu/sub 37/ (R = Tb, Dy, Ho, and Er). Anisotropic magnetostriction is a forced effect, with no sign of saturation, and is quite large well above T/sub SG/. The developed model fits quantitatively and remarkably well the temperature variation of the anisotropic magnetostriction, lambda/sub t/ = lambda/sub X/-lambda/sub perpendicular/, in the case of Tb, Dy, and Ho alloys. The values obtained from the fit for D/sub 0/, respectively, are +3.0, +1.25, and +0.6 K. For Er, D/sub 0/ becomes -0.37 K. The signs of D/sub 0/ are in agreement with having local axial anisotropy for the Tb, Dy, and Ho compounds, and planar for the Er one, in good agreement with the signs of the ..cap alpha../sub J/ Stevens quadrupolar parameter.

  14. Unique magnetostriction of Fe68.8Pd31.2 attributable to twinning

    PubMed Central

    Steiner, Jake; Lisfi, Abdellah; Kakeshita, Tomoyuki; Fukuda, Takashi; Wuttig, Manfred

    2016-01-01

    Fe68.8Pd31.2 exhibits an anomalously large magnetostriction of ~400 ppm at room temperature as well as linear, isotropic, and hysteresis free magnetization behavior. This near perfectly reversible magnetic response is attributable to the presence of a large number of premartensitic magnetoelastic twin clusters present in the system made possible through the elastic softening that occurs near a martensitic transformation temperature of 252 K. It is proposed that the twin clusters in the material reduce both internal elastic and magnetic energy, causing the elastic and magnetic behavior of the material to be intimately linked. In such a framework, the anisotropy energy becomes extremely low causing the material to bear no crystalline dependence on magnetization, and application of a magnetic field causes simultaneous magnetic and twin domain movement which relaxes the system. PMID:27688053

  15. Effect of the large magnetostriction of Terfenol-D on microwave transmission and reflection

    NASA Astrophysics Data System (ADS)

    Sourivong, Phoumyphon

    The purpose of this dissertation is to study certain physical properties of Terfenol-D, a magnetic material which is extremely magnetostrictive. Of particular interest is the magnetoelastic behavior of Terfenol-D when interacting with the microwave radiation in the presence of a static magnetic field. A microwave transmission spectrometer was used to measure transmission and I modified the spectrometer to perform reflection measurements. Experiments were done over a small temperature interval near room temperature using static magnetic fields from 0 kOe to 13 kOe and with microwaves of frequency 16.95 GHz. The results of this study followed from observing at what magnetic field ferromagnetic resonance (FMR) occurs. The enormous anisotropy of Terfenol-D should shift the field for ferromagnetic resonance; the experimental results confirm this effect and give an experimental value for the anisotropy constant of K1 = (-2.00 +/- 0.025) x 106 erg/cm3 at room temperature. Observation of the microwave transmission through Terfenol-D should confirm the predicted role magnetostriction plays in its response to microwaves.

  16. Giant Planets

    NASA Astrophysics Data System (ADS)

    Lunine, J. I.

    Beyond the inner solar system's terrestrial planets, with their compact orbits and rock -metal compositions, lies the realm of the outer solar system and the giant planets. Here the distance between planets jumps by an order of magnitude relative to the spacing of the terrestrial planets, and the masses of the giants are one to two orders of magnitude greater than Venus and Earth - the largest terrestrial bodies. Composition changes as well, since the giant planets are largely gaseous, with inferred admixtures of ice, rock, and metal, while the terrestrial planets are essentially pure rock and metal. The giant planets have many more moons than do the terrestrial planets, and the range of magnetic field strengths is larger in the outer solar system. It is the giant planets that sport rings, ranging from the magnificent ones around Saturn to the variable ring arcs of Neptune. Were it not for the fact that only Earth supports abundant life (with life possibly existing, but not proved to exist, in the martian crust and liquid water regions underneath the ice of Jupiter's moon Europa), the terrestrial planets would pale in interest next to the giant planets for any extraterrestrial visitor.

  17. Magnetostrictive properties of titanate coupling agent treated Terfenol-D composites

    NASA Astrophysics Data System (ADS)

    Dong, Xufeng; Qi, Min; Guan, Xinchun; Li, Jinhai; Ou, Jinping

    2012-03-01

    As a kind of composites, the bond strength between the polymer matrix and the Terfenol-D particles affects the performance of magnetostrictive composites. By observing the fracture morphologies, the bond strength of the magnetostrictive composites prepared with untreated Terfenol-D was proved weak. Titanate coupling agent was used for particles to improve the bond strength. Contact angle analysis indicates the work of adhesion of the epoxy resin to the treated Terfenol-D is larger than that to the untreated Terfenol-D. Different magnetostrictive composites with 20%, 35% and 50% particle volume fractions were prepared with treated and untreated Terfenol-D particles. Their static and dynamic magnetostriction was tested without pre-stress at room temperature. The results indicate titanate coupling agent treating increases the magnetostrictive properties of magnetostrictive composites, that is probably because the bond strength improves due to the particle treating.

  18. Experimental Exploration of the Origin of Magnetostriction in Single Crystal Iron

    SciTech Connect

    Xing, Q.; Lograsso, T.A.; Ruffoni, M.P.; Azimonte, C.; Pascarelli, S.; Miller, D.J.

    2010-08-19

    The magnetostrictive atomic strain in a pure Fe single crystal was measured by differential x-ray absorption spectroscopy. The obtained tetragonal magnetostriction constant, (3/2){lambda}{sub 100}, was determined to be 45 ppm, consistent with the previously reported theoretical value calculated from a spin-orbit coupling theory. These results provide a foundation for understanding the origin of magnetostriction in pure Fe as well as Fe-based binary alloys.

  19. Sintered rare earth-iron Laves phase magnetostrictive alloy product and preparation thereof

    DOEpatents

    Malekzadeh, Manoochehr; Pickus, Milton R.

    1979-01-01

    A sintered rare earth-iron Laves phase magnetostrictive alloy product characterized by a grain oriented morphology. The grain oriented morphology is obtained by magnetically aligning powder particles of the magnetostrictive alloy prior to sintering. Specifically disclosed are grain oriented sintered compacts of Tb.sub.x Dy.sub.1-x Fe.sub.2 and their method of preparation. The present sintered products have enhanced magnetostrictive properties.

  20. U-shape magnetostrictive vibration based power generator for universal use

    NASA Astrophysics Data System (ADS)

    Ueno, T.

    2016-04-01

    Vibrational power generator extracts electrical energy from ambient vibration. Author invented novel configuration using magnetostrictive material. The device is based on parallel beams of iron-gallium alloy and magnetic material, and features high efficiency, high robustness, and low electrical impedance. In this paper, author proposes U-shape generator for universal use. It consists of the parallel beams and fixed and free end beams forming U-shape frame flexibly modified for variety of mechanical input. Miniature U-shape prototype using Fe-Ga rod 6 by 0.5 by 13 mm3 exhibited average power of 3.7 mW under vibration of 166 Hz and 2.5 G. L-shape type was demonstrated to generate electromotive force by two directional vibrations. In switch type, maximum energy of 0.7 mJ was retrieved by one pushing force. The performances are sufficient to drive wireless module for heath monitoring and remote control.

  1. Giant magnetoimpedance effect in ultrasoft FeAlSiBCuNb nanocomposites for sensor applications

    SciTech Connect

    Phan, M.-H.; Peng, H.-X.; Wisnom, Michael R.; Yu, S.-C.

    2005-07-01

    Fe{sub 73-x}Al{sub x}Si{sub 14}B{sub 8.5}Cu{sub 1}Nb{sub 3.5} (x=0,2) nanocomposite materials consisting of a nanocrystalline phase in an amorphous matrix were obtained by annealing their precursor amorphous ribbons, which were prepared by the melt-spinning technique, at different temperatures ranging between 350 and 650 deg. C for 45 min in vacuum. Investigation on their magnetic and magnetoimpedance properties indicates that the Al-containing sample (x=2) possesses superior magnetic softness and giant magnetoimpedance (GMI) effect over the Al-free counterpart. This can be likely ascribed to the increased magnetic permeability, decreased coercive force, and decreased resistivity. The increased magnetic permeability results from a reduction in magnetocrystalline anisotropy and saturation magnetostriction. The correlations between magnetic softness, electrical properties, and GMI behavior are discussed in the light of the skin effect model. These results indicate that the Al-containing Fe-based nanocomposite material can be ideally used for high-performance GMI sensor applications.

  2. A Cryogenic Magnetostrictive Actuator using a Persistent High Temperature Superconducting Magnet, Part 1: Concept and Design. Part 1; Concept and Design

    NASA Technical Reports Server (NTRS)

    Horner, Garnett C.; Bromberg, Leslie; Teter, J. P.

    2001-01-01

    Cryogenic magnetostrictive materials, such as rare earth zinc crystals, offer high strains and high forces with minimally applied magnetic fields, making the material ideally suited for deformable optics applications. For cryogenic temperature applications, such as Next Generation Space Telescope (NGST), the use of superconducting magnets offer the possibility of a persistent mode of operation, i.e., the magnetostrictive material will maintain a strain field without power. High temperature superconductors (HTS) are attractive options if the temperature of operation is higher than 10 degrees Kelvin (K) and below 77 K. However, HTS wires have constraints that limit the minimum radius of winding, and even if good wires can be produced, the technology for joining superconducting wires does not exist. In this paper, the design and capabilities of a rare earth zinc magnetostrictive actuator using bulk HTS is described. Bulk superconductors can be fabricated in the sizes required with excellent superconducting properties. Equivalent permanent magnets, made with this inexpensive material, are persistent, do not require a persistent switch as in HTS wires, and can be made very small. These devices are charged using a technique which is similar to the one used for charging permanent magnets, e.g., by driving them into saturation. A small normal conducting coil can be used for charging or discharging. Very fast charging and discharging of HTS tubes, as short as 100 microseconds, has been demonstrated. Because of the magnetic field capability of the superconductor material, a very small amount of superconducting magnet material is needed to actuate the rare earth zinc. In this paper, several designs of actuators using YBCO and BSCCO 2212 superconducting materials are presented. Designs that include magnetic shielding to prevent interaction between adjacent actuators will also be described. Preliminary experimental results and comparison with theory for BSSCO 2212 with a

  3. A Magnetostrictive Composite-Fiber Bragg Grating Sensor

    PubMed Central

    Quintero, Sully M. M.; Braga, Arthur M. B.; Weber, Hans I.; Bruno, Antonio C.; Araújo, Jefferson F. D. F.

    2010-01-01

    This paper presents a light and compact optical fiber Bragg Grating sensor for DC and AC magnetic field measurements. The fiber is coated by a thick layer of a magnetostrictive composite consisting of particles of Terfenol-D dispersed in a polymeric matrix. Among the different compositions for the coating that were tested, the best magnetostrictive response was obtained using an epoxy resin as binder and a 30% volume fraction of Terfenol-D particles with sizes ranging from 212 to 300 μm. The effect of a compressive preload in the sensor was also investigated. The achieved resolution was 0.4 mT without a preload or 0.3 mT with a compressive pre-stress of 8.6 MPa. The sensor was tested at magnetic fields of up to 750 mT under static conditions. Dynamic measurements were conducted with a magnetic unbalanced four-pole rotor. PMID:22163644

  4. Quasi-static characterization and modeling of the bending behavior of single crystal galfenol for magnetostrictive sensors and actuators

    NASA Astrophysics Data System (ADS)

    Datta, Supratik

    2009-12-01

    Iron-gallium alloys (Galfenol) are structural magnetostrictive materials that exhibit high free-strain at low magnetic fields, high stress-sensitivity and useful thermo-mechanical properties. Galfenol, like smart materials in general, is attractive for use as a dynamic actuator and/or sensor material and can hence find use in active shape and vibration control, real-time structural health monitoring and energy harvesting applications. Galfenol possesses significantly higher yield strength and greater ductility than most smart materials, which are generally limited to use under compressive loads. The unique structural attributes of Galfenol introduce opportunities for use of a smart material in applications that involve tension, bending, shear or torsion. A principal motivation for the research presented in this dissertation is that bending and shear loads lead to development of non-uniform stress and magnetic fields in Galfenol which introduce significantly more complexity to the considerations to be modeled, compared to modeling of purely axial loads. This dissertation investigates the magnetostrictive response of Galfenol under different stress and magnetic field conditions which is essential for understanding and modeling Galfenol's behavior under bending, shear or torsion. Experimental data are used to calculate actuator and sensor figures of merit which can aid in design of adaptive structures. The research focuses on the bending behavior of Galfenol alloys as well as of laminated composites having Galfenol attached to other structural materials. A four-point bending test under magnetic field is designed, built and conducted on a Galfenol beam to understand its performance as a bending sensor. An extensive experimental study is conducted on Galfenol-Aluminum laminated composites to evaluate the effect of magnetic field, bending moment and Galfenol-Aluminum thickness ratio on actuation and sensing performance. A generalized recursive algorithm is presented for

  5. Magnetic and magnetostrictive properties of Cu substituted Co-ferrites

    NASA Astrophysics Data System (ADS)

    Chandra Sekhar, B.; Rao, G. S. N.; Caltun, O. F.; Dhana Lakshmi, B.; Parvatheeswara Rao, B.; Subba Rao, P. S. V.

    2016-01-01

    Copper substituted cobalt ferrite, Co1-xCuxFe2O4 (x=0.00-0.25), nanoparticles were synthesized by sol-gel autocombustion method. X-ray diffraction analysis on the samples was done to confirm the cubic spinel structures and Scherrer equation was used to estimate the mean crystallite size as 40 nm. Using the obtained nanoparticles, fabrication of the sintered pellets was done by standard ceramic technique. Magnetic and magnetostrictive measurements on the samples were made by strain gauge and vibrating sample magnetometer techniques, respectively. Maximum magnetostriction and strain derivative values were deduced from the field dependent magnetostriction curves while the magnetic parameters such as saturation magnetization (51.7-61.9 emu/g) and coercivity (1045-1629 Oe) on the samples were estimated from the obtained magnetic hysteresis loops. Curie temperature values (457-315 °C) were measured by a built in laboratory set-up. Copper substituted cobalt ferrites have shown improved strain derivative values as compared to the pure cobalt ferrite and thus making them suitable for stress sensing applications. The results have been explained on the basis of cationic distributions, strength of exchange interactions and net decreased anisotropic contributions due to the increased presence of Co2+ ions in B-sites as a result of Cu substitutions.

  6. Asymptotic models in magnetostriction with application to design of sensors

    NASA Astrophysics Data System (ADS)

    Krishnan, Shankar Narayan

    Magnetostrictive wires of diameter in the nanometer scale have been proposed for application as acoustic sensors [Downey et al., 2008], [Yang et al., 2006]. The sensing mechanism is expected to operate in the bending regime. In the first part of this work, we derive a variational theory for the bending of magnetostrictive nanowires starting from a full 3-dimensional continuum theory of magnetostriction. We recover a theory which looks like a typical Euler-Bernoulli bending model but includes an extra term contributed by the magnetic part of the energy. The solution of this variational theory for an important, newly developed magnetostricitve alloy called Galfenol cf. [Clark et al., 2000] is compared with the result of experiments on actual nanowires cf. [Downey, 2008] which shows agreement. In the next part of this thesis, Multilayered wires of diameter in the nanometer scale with periodic layering of non-magnetic copper and ferromagnetic galfenol segments are studied. The numerical computation of the physics of magnetization for such geometries is very costly computationally. We use the theory of periodic homogenization to understand the overall behavior of such structures. We first determine a "homogenized theory" after which this "homogenized model" is used to study the nucleation and stability of staturated states. Thus we get a broad generalization of what is known in the magnetic literature as the "fanning model" first introduced in [Jacobs and Bean, 1955] for a chain of spheres geometry. Some further numerical work on computing M vs H curves for such geometries is also presented.

  7. Detection of Salmonella typhimurium using polyclonal antibody immobilized magnetostrictive biosensors

    NASA Astrophysics Data System (ADS)

    Guntupalli, R.; Hu, Jing; Lakshmanan, Ramji S.; Wan, Jiehui; Huang, Shichu; Yang, Hong; Barbaree, James M.; Huang, T. S.; Chin, Bryan A.

    2006-05-01

    Novel mass-sensitive, magnetostrictive sensors have a characteristic resonant frequency that can be determined by monitoring the magnetic flux emitted by the sensor in response to an applied, time varying, magnetic field. This magnetostrictive platform has a unique advantage over conventional sensor platforms in that measurement is wireless or remote. These biosensors can thus be used in-situ for detecting pathogens and biological threat agents. In this work, we have used a magnetostrictive platform immobilized with a polyclonal antibody (the bio-molecular recognition element) to form a biosensor for the detection of Salmonella typhimurium. Upon exposure to solutions containing Salmonella typhimurium bacteria, the bacteria were bound to the sensor and the additional mass of the bound bacteria caused a shift in the sensor's resonant frequency. Responses of the sensors to different concentrations of S. typhimurium were recorded and the results correlated with those obtained from scanning electron microscopy (SEM) images of samples. Good agreement between the measured number of bound bacterial cells (attached mass) and frequency shifts were obtained. The longevity and specificity of the selected polyclonal antibody were also investigated and are reported.

  8. A uniaxial stress capacitive dilatometer for high-resolution thermal expansion and magnetostriction under multiextreme conditions.

    PubMed

    Küchler, R; Stingl, C; Gegenwart, P

    2016-07-01

    Thermal expansion and magnetostriction are directional dependent thermodynamic quantities. For the characterization of novel quantum phases of matter, it is required to study materials under multi-extreme conditions, in particular, down to very low temperatures, in very high magnetic fields or under high pressure. We developed a miniaturized capacitive dilatometer suitable for temperatures down to 20 mK and usage in high magnetic fields, which exerts a large spring force between 40 to 75 N on the sample. This corresponds to a uniaxial stress up to 3 kbar for a sample with cross section of (0.5 mm)(2). We describe design and performance test of the dilatometer which resolves length changes with high resolution of 0.02 Å at low temperatures. The miniaturized device can be utilized in any standard cryostat, including dilution refrigerators or the commercial physical property measurement system. PMID:27475567

  9. Method of forming magnetostrictive rods from rare earth-iron alloys

    DOEpatents

    McMasters, O.D.

    1986-09-02

    Rods of magnetostrictive alloys of iron with rare earth elements are formed by flowing a body of rare earth-iron alloy in a crucible enclosed in a chamber maintained under an inert gas atmosphere, forcing such molten rare-earth-iron alloy into a hollow mold tube of refractory material positioned with its lower end portion within the molten body by means of a pressure differential between the chamber and mold tube and maintaining a portion of the molten alloy in the crucible extending to a level above the lower end of the mold tube so that solid particles of higher melting impurities present in the alloy collect at the surface of the molten body and remain within the crucible as the rod is formed in the mold tube. 5 figs.

  10. A uniaxial stress capacitive dilatometer for high-resolution thermal expansion and magnetostriction under multiextreme conditions

    NASA Astrophysics Data System (ADS)

    Küchler, R.; Stingl, C.; Gegenwart, P.

    2016-07-01

    Thermal expansion and magnetostriction are directional dependent thermodynamic quantities. For the characterization of novel quantum phases of matter, it is required to study materials under multi-extreme conditions, in particular, down to very low temperatures, in very high magnetic fields or under high pressure. We developed a miniaturized capacitive dilatometer suitable for temperatures down to 20 mK and usage in high magnetic fields, which exerts a large spring force between 40 to 75 N on the sample. This corresponds to a uniaxial stress up to 3 kbar for a sample with cross section of (0.5 mm)2. We describe design and performance test of the dilatometer which resolves length changes with high resolution of 0.02 Å at low temperatures. The miniaturized device can be utilized in any standard cryostat, including dilution refrigerators or the commercial physical property measurement system.

  11. Volume magnetostriction of rare-earth metals with unstable 4f shells

    NASA Astrophysics Data System (ADS)

    Zieglowski, J.; Hafner, H. U.; Wohlleben, D.

    1986-01-01

    The volume magnetostriction is reported for a series of well-known intermediate-valence and heavy-fermion systems with Ce, Eu, and Yb. An expression is derived which reproduces the volume magnetostriction of all these systems quantitatively with the aid of independently measured microscopic parameters. A very large difference is found between superconducting and nonsuperconducting CeCu2Si2. .AE

  12. Thermal treatment for increasing magnetostrictive response of rare earth-iron alloy rods

    DOEpatents

    Verhoeven, J.D.; McMasters, O.D.

    1989-07-18

    Magnetostrictive rods formed from rare earth-iron alloys are subjected to a short time heat treatment to increase their magnetostrictive response under compression. The heat treatment is preferably carried out at a temperature of from 900 to 1,000 C for 20 minutes to six hours.

  13. Thermal treatment for increasing magnetostrictive response of rare earth-iron alloy rods

    DOEpatents

    Verhoeven, John D.; McMasters, O. D.

    1989-07-18

    Magnetostrictive rods formed from rare earth-iron alloys are subjected to a short time heat treatment to increase their Magnetostrictive response under compression. The heat treatment is preferably carried out at a temperature of from 900.degree. to 1000.degree. C. for 20 minutes to six hours.

  14. Influence of the anisotropy on the ``SAMR'' method for measuring magnetostriction in amorphous ribbons

    NASA Astrophysics Data System (ADS)

    Hernando, A.; Vázquez, M.; Madurga, V.; Ascasibar, E.; Liniers, M.

    1986-09-01

    The small angle magnetization rotation (SAMR) method has been found to be quite convinient for measuring magnetostriction in metallic glasses with low magnetostriction. Nevertheless the method fails in some sense when applied to high magnetostrictive samples. The origin of such failure has been analysed. The method becomes reliable when the sample saturates under the action of the axial field H z. On the other hand the sensitivity decreases with H2z. Since the internal str esses are the main source of anisotropy, via magnetoelastic coupling, the higher magnetostriction is, the stronger H z, required for saturating, becomes. Therefore the sensitivity of the method drops with the square of the magnetostriction of the sample. Some experiments confirming this explanation are shown.

  15. Giant self-biased magnetoelectric coupling in co-fired textured layered composites

    NASA Astrophysics Data System (ADS)

    Yan, Yongke; Zhou, Yuan; Priya, Shashank

    2013-02-01

    Co-fired magnetostrictive/piezoelectric/magnetostrictive laminate structure with silver inner electrode was synthesized and characterized. We demonstrate integration of textured piezoelectric microstructure with the cost-effective low-temperature co-fired layered structure to achieve strong magnetoelectric coupling. Using the co-fired composite, a strategy was developed based upon the hysteretic response of nickel-copper-zinc ferrite magnetostrictive materials to achieve peak magnetoelectric response at zero DC bias, referred as self-biased magnetoelectric response. Fundamental understanding of self-bias phenomenon in composites with single phase magnetic material was investigated by quantifying the magnetization and piezomagnetic changes with applied DC field. We delineate the contribution arising from the interfacial strain and inherent magnetic hysteretic behavior of copper modified nickel-zinc ferrite towards self-bias response.

  16. Design and Testing of a Dynamically-Tuned Magnetostrictive Spring with Electrically-Controlled Stiffness

    NASA Technical Reports Server (NTRS)

    Scheidler, Justin; Asnani, Vivake M.; Dapino, Marcelo J.

    2015-01-01

    This paper details the development of an electrically-controlled, variable-stiffness spring based on magnetostrictive materials. The device, termed a magnetostrictive Varispring, can be applied as a semi-active vibration isolator or switched stiffness vibration controller for reducing transmitted vibrations. The Varispring is designed using 1D linear models that consider the coupled electrical response, mechanically-induced magnetic diffusion, and the effect of internal mass on dynamic stiffness. Modeling results illustrate that a Terfenol-D-based Varispring has a rise time almost an order of magnitude smaller and a magnetic diffusion cut-off frequency over two orders of magnitude greater than a Galfenol-based Varispring. The results motivate the use of laminated Terfenol-D rods for a greater stiffness tuning range and increased bandwidth. The behavior of a prototype Varispring is examined under vibratory excitation up to 6 MPa and 25 Hz using a dynamic load frame. For this prototype, stiffness is indirectly varied by controlling the excitation current. Preliminary measurements of continuous stiffness tuning via sinusoidal currents up to 1 kHz are presented. The measurements demonstrate that the Young's modulus of the Terfenol-D rod inside the Varispring can be continuously varied by up to 21.9 GPa. The observed stiffness tuning range is relatively constant up to 500 Hz, but significantly decreases thereafter. The stiffness tuning range can be greatly increased by improving the current and force control such that a more consistent current can be applied and the Varispring can be accurately tested at a more optimal bias stress.

  17. Giant Axonal Neuropathy

    MedlinePlus

    ... Diversity Find People About NINDS NINDS Giant Axonal Neuropathy Information Page Table of Contents (click to jump ... done? Clinical Trials Organizations What is Giant Axonal Neuropathy? Giant axonal neuropathy (GAN) is a rare inherited ...

  18. Shape anisotropy in zero-magnetostrictive rapidly solidified amorphous nanowires

    NASA Astrophysics Data System (ADS)

    Rotărescu, C.; Atitoaie, A.; Stoleriu, L.; Óvári, T.-A.; Lupu, N.; Chiriac, H.

    2016-04-01

    The magnetic behavior of zero-magnetostrictive rapidly solidified amorphous nanowires has been investigated in order to understand their magnetic bistability. The study has been performed both experimentally - based on inductive hysteresis loop measurements - and theoretically, by means of micromagnetic simulations. Experimental hysteresis loops have shown that the amorphous nanowires display an axial magnetic bistability, characterized by a single-step magnetization reversal when the applied field reaches a critical value called switching field. The simulated loops allowed us to understand the effect of shape anisotropy on coercivity. The results are key for understanding and controlling the magnetization processes in these novel nanowires, with important application possibilities in new miniaturized sensing devices.

  19. Dynamics, Bifurcations and Normal Forms in Arrays of Magnetostrictive Energy Harvesters with All-to-All Coupling

    NASA Astrophysics Data System (ADS)

    Matus-Vargas, Antonio; González-Hernandez, Hugo G.; Chan, Bernard S.; Palacios, Antonio; Buono, Pietro-Luciano; in, Visarath; Naik, Suketu; Phipps, Alex; Longhini, Patrick

    Modeling and bifurcation analysis of an energy harvesting system composed of coupled resonators using the Galfenol-based magnetostrictive material are presented. The analysis in this work should be broad enough to be applicable to a large class of vibratory-based energy harvesting systems since various types of vibratory harvesters share the same normal forms, e.g. magnetostrictive and piezoelectric materials. A combined model of the mechanical and electrical domains of a single energy harvester is discussed first. Building on this model, the governing equations of the coupled system are derived, leading to a system of differential equations with an all-to-all coupling between the resonators. A bifurcation analysis of the system equations reveals different patterns of collective oscillations. Among the many different patterns, a synchronous state exists and it is stable over a broad region of parameter space. This pattern has the potential to yield significant increases in power output and it will be used as a starting point to guide future experimental work. A Hamiltonian approach is employed to study analytically the nature of the bifurcations and to calculate an expression for the onset of synchronization valid for any number of harvesters.

  20. Temperature dependence of the magnetostriction in polycrystalline PrFe{sub 1.9} and TbFe{sub 2} alloys: Experiment and theory

    SciTech Connect

    Tang, Y. M.; Chen, L. Y.; Huang, H. F.; Xia, W. B.; Zhang, S. Y.; Wei, J.; Tang, S. L. Du, Y. W.; Zhang, L.

    2014-05-07

    A remarkable magnetostriction λ{sub 111} as large as 6700 ppm was found at 70 K in PrFe{sub 1.9} alloy. This value is even larger than the theoretical maximum of 5600 ppm estimated by the Steven's equivalent operator method. The temperature dependence of λ{sub 111} for PrFe{sub 1.9} and TbFe{sub 2} alloys follows well with the single-ion theory rule, which yields giant estimated λ{sub 111} values of about 8000 and 4200 ppm for PrFe{sub 1.9} and TbFe{sub 2} alloys, respectively, at 0 K. The easy magnetization direction of PrFe{sub 1.9} changes from [111] to [100] as temperature decreases, which leads to the abnormal decrease of the magnetostriction λ. The rare earth sublattice moment increases sharply in PrFe{sub 1.9} alloy with decreasing temperature, resulting in the remarkably largest estimated value of λ{sub 111} at 0 K according to the single-ion theory.

  1. Dynamically tuned magnetostrictive spring with electrically controlled stiffness

    NASA Astrophysics Data System (ADS)

    Scheidler, Justin J.; Asnani, Vivake M.; Dapino, Marcelo J.

    2016-03-01

    This paper presents the design and testing of an electrically controllable magnetostrictive spring that has a dynamically tunable stiffness (i.e., a magnetostrictive Varispring). The device enables in situ stiffness tuning or stiffness switching for vibration control applications. Using a nonlinear electromechanical transducer model and an analytical solution of linear, mechanically induced magnetic diffusion, Terfenol-D is shown to have a faster rise time to stepped voltage inputs and a significantly higher magnetic diffusion cut-off frequency relative to Galfenol. A Varispring is manufactured using a laminated Terfenol-D rod. Further rise time reductions are achieved by minimizing the rod’s diameter and winding the electromagnet with larger wire. Dynamic tuning of the Varispring’s stiffness is investigated by measuring the Terfenol-D rod’s strain response to dynamic, compressive, axial forces in the presence of sinusoidal or square wave control currents. The Varispring’s rise time is \\lt 1 ms for 1 A current switches. Continuous modulus changes up to 21.9 GPa and 500 Hz and square wave modulus changes (dynamic {{Δ }}E effect) up to 12.3 GPa and 100 Hz are observed. Stiffness tunability and tuning bandwidth can be considerably increased by operating about a more optimal bias stress and improving the control of the electrical input.

  2. Theory of electromechanical resonance in magnetostrictive - piezoelectric multilayer composites

    NASA Astrophysics Data System (ADS)

    Filippov, D. A.; Nan, C. W.; Srinivasan, G.

    2005-03-01

    The theory of electromechanical resonance in multilayer magnetostrictive - piezoelectric composites is developed. The theory is based on the use of initial (not effective) parameters of magnetostrictive and piezoelectric phases. Equations of motion were used to obtain an expression for the frequency-dependence of magnetoelectric response in a multilayer composite [1,2]. The enhanced magnetoelectric response at the electromechanical resonance is dependent on the interface coupling. The calculations predict a peak in the magnetoelectric voltage coefficient at electromechanical resonance, with a two-order of magnitude increase relative to low-frequency values. These predictions are in agreement with data for ferrite-lead zirconante titanate (PZT) bilayers and metal-PZT-metal trilayers. 1. M. I. Bichurin, D.A. Filippov, V. M. Petrov, V. M. Laletin, N. Paddubnaya, and G. Srinivasan, Phys. Rev., B 68, 132408 (2003). 2. D. A. Fillipov, M. I. Bichurin, V. M. Petrov, V. M. Laletsin, N. N. Puddubnaya, and G. Srinivasan, Magnetoelectric Interaction Phenomena in Crystals-NATO Science Series II. Vol. 164, Eds. M. Fiebig, V. V. Eremenko, and I. E. Chupis (Kluwer Academic Publishers, London, 2004), p.71-80. - supported by grants from the Russian Ministry of Education (Å02-3.4-278), the Universities of Russia Foundation (UNR 01.01.026) and the National Science Foundation (DMR-0302254).

  3. Torsional wave experiments with a new magnetostrictive transducer configuration

    NASA Astrophysics Data System (ADS)

    Kim, Yoon Young; Park, Chan Il; Cho, Seung Hyun; Han, Soon Woo

    2005-06-01

    For the efficient long-range nondestructive structural health inspection of pipes, guided waves have become widely used. Among the various guided wave modes, the torsional wave is most preferred since its first branch is nondispersive. Our objective in this work is to develop a new magnetostrictive transducer configuration to transmit and receive torsional waves in cylindrical waveguides. The conventional magnetostrictive transducer for the generation and measurement of torsional waves consists of solenoid coils and a nickel strip bonded circumferentially to test pipes. The strip must be premagnetized by a permanent magnet before actual measurements. Because of the premagnetization, the transducer is not suitable for the long-term on-line monitoring of pipes buried underground. To avoid the cumbersome premagnetization and to improve the transduction efficiency, we propose a new transducer configuration using several pieces of nickel strips installed at 45° with respect to the pipe axis. If a static bias magnetic field is also applied, the transducer output can be substantially increased. Several experiments were conducted to study the performance of the proposed transducer configuration. The proposed transducer configuration was also applied for damage detection in an aluminum pipe. .

  4. Nano-magnetism of magnetostriction in Fe{sub 35}Co{sub 65}

    SciTech Connect

    Lisfi, A.; Ren, T.; Wuttig, M.; Khachaturyan, A.

    2014-03-03

    The nature of the large magnetostriction in body-centered Fe-based solid solutions has been widely discussed in the literature. Here, we use a combination of magnetostriction, magnetization, torque, and transmission electron microscopy measurements of specially annealed Co{sub 65}Fe{sub 35} to show that the magnetostriction is caused by coherent uniaxial nano-precipitates. We show further that these nano-precipitates lower the magnetocrystalline anisotropy in these alloys to K{sub 1} = −2.16 × 10{sup 4} J/m{sup 3}.

  5. Magnetostriction and magnetism of rare earth intermetallic compounds: First principle study

    NASA Astrophysics Data System (ADS)

    Gavrilenko, V. I.; Wu, R. Q.

    2001-06-01

    Magnetism and magnetostriction of rare earth intermetallic compounds, GdCo2, GdFe2, NdCo2, SmCo2, and ErCo2, have been studied by using the first principles full-potential linearized augmented plane-wave method with the generalized gradient approximation. The calculated magnetostriction coefficients agree well with experiment. The itinerant electrons of transition metal elements are found to play a significant role in magnetoelastic coupling. The strong anisotropy of magnetostriction in GdCo2 is explained. Contributions due to spatial anisotropic charge distribution of the incomplete 4f shells are calculated and discussed.

  6. Real-time integrity monitoring of composite laminates with magnetostrictive sensory layer

    NASA Astrophysics Data System (ADS)

    Kumar, Anand; Bhattacharya, Bishakh

    2008-12-01

    Fundamental research and development in smart materials and structures have shown great potential for enhancing the functionality, serviceability and increased life span of civil and mechanical infrastructure systems. Researchers from diverse disciplines have been drawn into vigorous efforts to develop smart and intelligent structures that can monitor their own conditions, detect impending failure, control damage and adapt to changing environments. Smart structures are generally created through synthesis by combining sensing, processing and actuating elements integrated with conventional structural materials. The conventional non-destructive evaluation techniques are not very effective in monitoring the structural integrity of composite structures due to their micro-mechanical complexities. With the commercial availability of the magnetostrictive (MS) material Terfenol-D in particulate form, it is now feasible to develop particulate sensors to detect damage with minimum effect on structural integrity. In present investigation, the electromagnetic response in the MS layer at the onset of delamination in one of the weakest ply of the composite laminate has been analyzed. For the numerical analysis symmetric and asymmetric carbon epoxy laminates with one of its layers embedded with Terfenol-D particles have been taken. Terfenol-D layer experiences a change in stress due to onset of delamination causing a change in its magnetic state, which can be sensed as induced open circuit voltage in the sensing coil enclosing the laminate beam. The effect of material properties, lamination schemes and placement of MS layer on the sensing capabilities has been analyzed.

  7. Atmosphere expansion and mass loss of close-orbit giant exoplanets heated by stellar XUV. I. Modeling of hydrodynamic escape of upper atmospheric material

    SciTech Connect

    Shaikhislamov, I. F.; Khodachenko, M. L.; Sasunov, Yu. L.; Lammer, H.; Kislyakova, K. G.; Erkaev, N. V.

    2014-11-10

    In the present series of papers we propose a consistent description of the mass loss process. To study in a comprehensive way the effects of the intrinsic magnetic field of a close-orbit giant exoplanet (a so-called hot Jupiter) on atmospheric material escape and the formation of a planetary inner magnetosphere, we start with a hydrodynamic model of an upper atmosphere expansion in this paper. While considering a simple hydrogen atmosphere model, we focus on the self-consistent inclusion of the effects of radiative heating and ionization of the atmospheric gas with its consequent expansion in the outer space. Primary attention is paid to an investigation of the role of the specific conditions at the inner and outer boundaries of the simulation domain, under which different regimes of material escape (free and restricted flow) are formed. A comparative study is performed of different processes, such as X-ray and ultraviolet (XUV) heating, material ionization and recombination, H{sub 3}{sup +} cooling, adiabatic and Lyα cooling, and Lyα reabsorption. We confirm the basic consistency of the outcomes of our modeling with the results of other hydrodynamic models of expanding planetary atmospheres. In particular, we determine that, under the typical conditions of an orbital distance of 0.05 AU around a Sun-type star, a hot Jupiter plasma envelope may reach maximum temperatures up to ∼9000 K with a hydrodynamic escape speed of ∼9 km s{sup –1}, resulting in mass loss rates of ∼(4-7) · 10{sup 10} g s{sup –1}. In the range of the considered stellar-planetary parameters and XUV fluxes, that is close to the mass loss in the energy-limited case. The inclusion of planetary intrinsic magnetic fields in the model is a subject of the follow-up paper (Paper II).

  8. Atmosphere Expansion and Mass Loss of Close-orbit Giant Exoplanets Heated by Stellar XUV. I. Modeling of Hydrodynamic Escape of Upper Atmospheric Material

    NASA Astrophysics Data System (ADS)

    Shaikhislamov, I. F.; Khodachenko, M. L.; Sasunov, Yu. L.; Lammer, H.; Kislyakova, K. G.; Erkaev, N. V.

    2014-11-01

    In the present series of papers we propose a consistent description of the mass loss process. To study in a comprehensive way the effects of the intrinsic magnetic field of a close-orbit giant exoplanet (a so-called hot Jupiter) on atmospheric material escape and the formation of a planetary inner magnetosphere, we start with a hydrodynamic model of an upper atmosphere expansion in this paper. While considering a simple hydrogen atmosphere model, we focus on the self-consistent inclusion of the effects of radiative heating and ionization of the atmospheric gas with its consequent expansion in the outer space. Primary attention is paid to an investigation of the role of the specific conditions at the inner and outer boundaries of the simulation domain, under which different regimes of material escape (free and restricted flow) are formed. A comparative study is performed of different processes, such as X-ray and ultraviolet (XUV) heating, material ionization and recombination, H_3^ + cooling, adiabatic and Lyα cooling, and Lyα reabsorption. We confirm the basic consistency of the outcomes of our modeling with the results of other hydrodynamic models of expanding planetary atmospheres. In particular, we determine that, under the typical conditions of an orbital distance of 0.05 AU around a Sun-type star, a hot Jupiter plasma envelope may reach maximum temperatures up to ~9000 K with a hydrodynamic escape speed of ~9 km s-1, resulting in mass loss rates of ~(4-7) · 1010 g s-1. In the range of the considered stellar-planetary parameters and XUV fluxes, that is close to the mass loss in the energy-limited case. The inclusion of planetary intrinsic magnetic fields in the model is a subject of the follow-up paper (Paper II).

  9. Phenotypic expression in human monocyte-derived interleukin-4-induced foreign body giant cells and macrophages in vitro: dependence on material surface properties.

    PubMed

    McNally, Amy K; Anderson, James M

    2015-04-01

    The effects of different material surfaces on phenotypic expression in macrophages and foreign body giant cells (FBGC) were addressed using our in vitro system of interleukin (IL)-4-induced macrophage fusion and FBGC formation. Arginine-glycine-aspartate (RGD)-, vitronectin (VN)-, and chitosan (CH)-adsorbed cell culture polystyrene, carboxylated (C, negatively charged) polystyrene, and unmodified (PS, non-cell culture treated) polystyrene were compared for their abilities to support monocyte/macrophage adhesion and IL-4-induced macrophage fusion. Pooled whole cell lysates from four different donors were evaluated by immunoblotting for expression of selected components in monocytes, macrophages, and FBGC. In addition to RGD and VN as previously shown, we find that CH supports macrophage adhesion and FBGC formation, whereas C or PS support macrophage adhesion but do not permit macrophage fusion under otherwise identical conditions of IL-4 stimulation. Likewise, components related to macrophage fusion (CD206, CD98, CD147, CD13) are strongly expressed on RGD-, VN-, and CH-adsorbed surfaces but are greatly diminished or not detected on C or PS. Importantly, material surfaces also influence the FBGC phenotype itself, as demonstrated by strong differences in patterns of expression of HLA-DR, B7-2, B7-H1, and toll-like receptor (TLR)-2 on RGD, VN, and CH despite morphologic similarities between FBGC on these surfaces. Likewise, we observe differences in the expression of B7-2, α2-macroglobulin, TLR-2, and fascin-1 between mononuclear macrophages on C and PS. Collectively, these findings reveal the extent to which material surface chemistry influences macrophage/FBGC phenotype beyond evident morphological similarities or differences and identify CH as an FBGC-supportive substrate.

  10. Variable temperature study of the crystal and magnetic structures of the giant magnetoresistant materials LMnAsO(L = La, Nd)

    NASA Astrophysics Data System (ADS)

    Emery, N.; Wildman, E. J.; Skakle, J. M. S.; McLaughlin, A. C.; Smith, R. I.; Fitch, A. N.

    2011-04-01

    A variable temperature neutron and synchrotron diffraction study has been performed on the giant magnetoresistant oxypnictides LMnAsO (L = La, Nd). The low-temperature magnetic structures have been studied, and results show a spin reorientation of the Mn2+ spins below TN (Nd) for NdMnAsO. The Mn2+ spins rotate from alignment along c to alignment into the basal plane, and the Mn2+ and Nd3+ moments refine to 3.54(4) μB and 1.93(4) μB, respectively, at 2 K. In contrast, there is no change in magnetic structure with temperature for LaMnAsO. There is no evidence of a structural transition down to 2 K; however, discontinuities in the cell volume and L-O and Mn-As bond lengths are detected at ˜150 K for both materials. This temperature coincides with the electronic transition previously reported and suggests a coupling between electronic and lattice degrees of freedom.

  11. Experimental study and analytical model of deformation of magnetostrictive films as applied to mirrors for x-ray space telescopes.

    PubMed

    Wang, Xiaoli; Knapp, Peter; Vaynman, S; Graham, M E; Cao, Jian; Ulmer, M P

    2014-09-20

    The desire for continuously gaining new knowledge in astronomy has pushed the frontier of engineering methods to deliver lighter, thinner, higher quality mirrors at an affordable cost for use in an x-ray observatory. To address these needs, we have been investigating the application of magnetic smart materials (MSMs) deposited as a thin film on mirror substrates. MSMs have some interesting properties that make the application of MSMs to mirror substrates a promising solution for making the next generation of x-ray telescopes. Due to the ability to hold a shape with an impressed permanent magnetic field, MSMs have the potential to be the method used to make light weight, affordable x-ray telescope mirrors. This paper presents the experimental setup for measuring the deformation of the magnetostrictive bimorph specimens under an applied magnetic field, and the analytical and numerical analysis of the deformation. As a first step in the development of tools to predict deflections, we deposited Terfenol-D on the glass substrates. We then made measurements that were compared with the results from the analytical and numerical analysis. The surface profiles of thin-film specimens were measured under an external magnetic field with white light interferometry (WLI). The analytical model provides good predictions of film deformation behavior under various magnetic field strengths. This work establishes a solid foundation for further research to analyze the full three-dimensional deformation behavior of magnetostrictive thin films. PMID:25322105

  12. Experimental study and analytical model of deformation of magnetostrictive films as applied to mirrors for x-ray space telescopes.

    PubMed

    Wang, Xiaoli; Knapp, Peter; Vaynman, S; Graham, M E; Cao, Jian; Ulmer, M P

    2014-09-20

    The desire for continuously gaining new knowledge in astronomy has pushed the frontier of engineering methods to deliver lighter, thinner, higher quality mirrors at an affordable cost for use in an x-ray observatory. To address these needs, we have been investigating the application of magnetic smart materials (MSMs) deposited as a thin film on mirror substrates. MSMs have some interesting properties that make the application of MSMs to mirror substrates a promising solution for making the next generation of x-ray telescopes. Due to the ability to hold a shape with an impressed permanent magnetic field, MSMs have the potential to be the method used to make light weight, affordable x-ray telescope mirrors. This paper presents the experimental setup for measuring the deformation of the magnetostrictive bimorph specimens under an applied magnetic field, and the analytical and numerical analysis of the deformation. As a first step in the development of tools to predict deflections, we deposited Terfenol-D on the glass substrates. We then made measurements that were compared with the results from the analytical and numerical analysis. The surface profiles of thin-film specimens were measured under an external magnetic field with white light interferometry (WLI). The analytical model provides good predictions of film deformation behavior under various magnetic field strengths. This work establishes a solid foundation for further research to analyze the full three-dimensional deformation behavior of magnetostrictive thin films.

  13. Q-switched all-fiber laser based on magnetostriction modulation of a Bragg grating.

    PubMed

    Pérez-Millán, P; Díez, A; Andrés, M; Zalvidea, D; Duchowicz, R

    2005-06-27

    We report an actively Q-switched all-fiber laser based on magnetostriction modulation of a Bragg grating. The laser employs a pair of Bragg gratings as reflective mirrors, one of which is bonded to a magnetostrictive element. Lengthening of the magnetostrictive element when a magnetic field is applied shifts the Bragg wavelength of the grating, allowing control of the Q-factor of the cavity and, thus, performing active Q-switching. The magnetostrictive modulator is small, compact and requires less than 300 mW electrical drive power. Using erbium-doped fiber and a maximum pump power of 120 mW, Q-switch pulses of more than 1 W peak power were obtained, with a pulse repetition rate that can be continuously varied from 1 Hz to 125 kHz. PMID:19498492

  14. Development of phage/antibody immobilized magnetostrictive biosensors

    NASA Astrophysics Data System (ADS)

    Fu, Liling

    There is an urgent need for biosensors that are able to detect and quantify the presence of a small amount of pathogens in a real-time manner accurately and quickly to guide prevention efforts and assay food and water quality. Acoustic wave (AW) devices, whose performance is defined by mass sensitivity (Sm) and quality factor (Q value), have been extensively studied as high performance biosensor platforms. However, current AW devices still face some challenges such as the difficulty to be employed in liquid and low Q value in practical applications. The objective of this research is to develop magnetostrictive sensors which include milli/microcantilever type (MSMC) and particle type (MSP). Compared to other AW devices, MSMC exhibits the following advantages: (1) wireless/remote driving and sensing; (2) easy to fabricate; (3) works well in liquid; (4) exhibits a high Q value (> 500 in air). The fundamental study of the damping effect on MSMCs from the surrounding media including air and liquids were conducted to improve the Q value of MSMCs. The experiment results show that the Q value is dependent on the properties of surrounding media (e.g. viscosity, density), the geometry of the MSMCs, and the harmonic mode on the resonance behavior of MSMCs, etc. The phage-coated MSMC has high specificity and sensitivity even while used in water with a low concentration of targeted bacteria. Two currently developed phages, JRB7 and E2, respectively respond to Bacillus anthracis spores and Salmonella typhimurium, were employed as bio-recognition elements in this research. The phage-immobilized MSMC biosensors exhibited high performance and detection of limit was 5 x 104 cfu/ml for the MSMC in size of 1.4 x 0.8 x 0.035 mm. The MSMC-based biosensors were indicated as a very potential method for in-situ monitoring of the biological quality in water. The MSP combine antibody was used to detect Staphylococcus aureus in this experiment. The interface between MSPs and antibody was

  15. Relevance of multidirectional magnetostriction for the noise generation of transformer cores

    NASA Astrophysics Data System (ADS)

    Krell, C.; Baumgartinger, N.; Krismanic, G.; Leiss, E.; Pfützner, H.

    2000-06-01

    As well known, T-joint regions of three-phase transformer cores tend to show rotational magnetisation (RM) patterns which yield distinct increases of magnetostriction. The present work was focused on the question whether these local phenomena exhibit practical relevance for the core's global magnetostriction-caused strain. A main effect was found for the yoke's horizontal direction, RM causing about 80% increase of total strain in the T-joint region and 40% for the total yoke.

  16. Method of increasing magnetostrictive response of rare earth-iron alloy rods

    DOEpatents

    Verhoeven, J.D.; McMasters, O.D.; Gibson, E.D.; Ostenson, J.E.; Finnemore, D.K.

    1989-04-04

    This invention comprises a method of increasing the magnetostrictive response of rare earth-iron (RFe) magnetostrictive alloy rods by a thermal-magnetic treatment. The rod is heated to a temperature above its Curie temperature, viz. from 400 to 600 C; and, while the rod is at that temperature, a magnetic field is directionally applied and maintained while the rod is cooled, at least below its Curie temperature. 2 figs.

  17. Method of increasing magnetostrictive response of rare earth-iron alloy rods

    DOEpatents

    Verhoeven, John D.; McMasters, O. Dale; Gibson, Edwin D.; Ostenson, Jerome E.; Finnemore, Douglas K.

    1989-04-04

    This invention comprises a method of increasing the magnetostrictive response of rare earth-iron (RFe) magnetostrictive alloy rods by a thermal-magnetic treatment. The rod is heated to a temperature above its Curie temperature, viz. from 400.degree. to 600.degree. C.; and, while the rod is at that temperature, a magnetic field is directionally applied and maintained while the rod is cooled, at least below its Curie temperature.

  18. Measuring system for magnetostriction of silicon steel sheet under ac excitation using optical methods

    SciTech Connect

    Nakase, Tomoya; Nakano, Masanori; Fujiwara, Koji; Takahashi, Norio

    1998-07-01

    A measuring system for magnetostriction of silicon steel sheet using optical methods and a single sheet tester has been developed to establish a standard test method for IEC and JIS. Various factors affecting measurement accuracy and reproducibility of the developed system are examined.s Two optical instruments, such as a laser Doppler vibrometer and a heterodyne displacement meter, are compared. 3-D characteristics of magnetostriction under ac excitation in the rolling direction are measured up to 2.0 T.

  19. Correlation of magnetostriction variation on magnetic loss and noise for power transformer

    NASA Astrophysics Data System (ADS)

    Cheng, Shan-Jen; Liu, Jui-Jung; Chang, Yeong-Hwa; Fu, Chao-Ming; Hsu, Chang-Hung; Lee, Chun-Yao; Chang, Chia-Wen

    2015-05-01

    Magnetostriction (MS)-caused strain in single-phase three-legged cores with different core cutting forms, which suffer from induced magnetic loss and noise, was studied. It is found that adopting each different core form types induces magnetostriction ɛ variation in a transformer core operating with a high-frequency AC signal. The results are compared with finite element analysis simulations. It is also indicated that magnetostriction ɛ variations are significant in the rolling direction and along limbs and yokes. In this paper, it is proposed that core corner sides and T-joint parts without cutting structure, the core exhibits lower core loss and lower heat dissipation due to the fact that the magnetic flux that passes through corner sides shows lower magnetostriction variation. The magnetic properties resulting from magnetostriction variation in core loss and heat dissipation phenomena are significantly different from other core forms because of stronger contributions from magnetostatic forces. The main contribution for reducing core loss and noise, making them much less in corner numbers and cutting-fabricated forms, can be expected to come from lower magnetic flux and magnetostriction variation.

  20. Magnetostrictive behaviors of Fe-Si(001) single-crystal films under rotating magnetic fields

    NASA Astrophysics Data System (ADS)

    Kawai, Tetsuroh; Aida, Takuya; Ohtake, Mitsuru; Futamoto, Masaaki

    2015-05-01

    Magnetostrictive behaviors under rotating magnetic fields are investigated for bcc(001) single-crystal films of Fe100-x-Six(x = 0, 6, 10 at. %). The magnetostriction observation directions are along bcc[100] and bcc[110] of the films. The magnetostriction waveform varies greatly depending on the observation direction. For the observation along [100], the magnetostriction waveform of all the films is bathtub-like and the amplitude stays at almost constant even when the magnetic field is increased up to the anisotropy field. On the other hand, the waveform along [110] is triangular and the amplitude increases with increasing magnetic field up to the anisotropy field and then saturates. In addition, the waveform of Fe90Si10 film is distorted triangular when the applied magnetic fields are less than its anisotropy field. These magnetostrictive behaviors under rotating magnetic fields are well explained by employing a proposed modified coherent rotation model where the anisotropy field and the magnetization reversal field are determined by using measured magnetization curves. The results show that magnetocrystalline anisotropy plays important role on magnetostrictive behavior under rotating magnetic fields.

  1. Image analysis of the microstructure of pseudo-1-3 magnetostrictive composites

    NASA Astrophysics Data System (ADS)

    Dong, Xufeng; Qi, Min; Guan, Xinchun; Ou, Jinping

    2010-04-01

    Previous studies did by some scholars proved applying a magnetic field during the manufacture process of polymer-bonded Terfenol-D could orient the magnetic easy direction of the particles along the field direction and form a pseudo-1-3 structure. Compared to the 0-3 composites composed of Terfenol-D particles dispersed randomly in a polymer matrix, pseudo-1-3 magnetostrictive composites present much larger magnetostrictive performance. In this paper, magnetostrictive composites based on Terfenol-D particles in an unsaturated polyester resin matrix were fabricated under different magnetic fields. Magentostriction was tested and compared to get the detail effects of orientation fields on magnetostrictive properties of magnetostrictive composites. Scanning electron microscopy was used to observe their microstructures. Image analysis was applied to describe the microstructures. The distribution of the angles between the major axis of the particles and the magnetic field direction was used to evaluate the arrangement of particles in the matrix quantitatively. The results confirm particle chain-like structures in composites prepared under larger magnetic field, and show that particle arrangement changes with the strength of the orientation field, which is result in the changes of magnetostrictive performance.

  2. Large magnetostrictive susceptibility in Tb{endash}FeCo/FeCo multilayers

    SciTech Connect

    Duc, N. H.; Danh, T. M.; Tuan, N. A.; Teillet, J.

    2001-06-04

    [Tb(Fe{sub 0.55}Co{sub 0.45}){sub 1.5}/Fe]{sub n} and [Tb(Fe{sub 0.55}Co{sub 0.45}){sub 1.5}/(Fe{sub 0.5}Co{sub 0.5})]{sub n} multilayers were fabricated by rf-magnetron sputtering from composite targets. Magnetostriction was measured using an optical deflectometer. The as-deposited films showed a soft magnetic and magnetostrictive character, with a coercive field {mu}{sub 0}H{sub c}=5 mT and a parallel magnetostrictive susceptibility {chi}{sub {lambda}{parallel}}=d{lambda}{sub {parallel}}/d({mu}{sub 0}H)=1.4{times}10{sup {minus}2} T{sup {minus}1}. This magnetostrictive softness was strongly improved by heat treatments: the magnetostrictive susceptibility attains the huge value of 5{times}10{sup {minus}2} T{sup {minus}1} in applied field of 6 mT. The low-field dependence of the magnetostrictive susceptibility and their technical characters are described in detail. {copyright} 2001 American Institute of Physics.

  3. Giant Magnons Meet Giant Gravitons

    SciTech Connect

    Hofman, Diego M.

    2008-07-28

    We study the worldsheet reflection matrix of a string attached to a D-brane in AdS{sub 5}xS{sup 5}. The D-brane corresponds to a maximal giant graviton that wraps an S{sup 3} inside S{sup 5}. In the gauge theory, the open string is described by a spin chain with boundaries. We focus on open strings with a large SO(6) charge and define an asymptotic boundary reflection matrix. Using the symmetries of the problem, we review the computation of the boundary reflection matrix, up to a phase. We also discuss weak and strong coupling computations where we obtain the overall phase factor and test our exact results.

  4. Landauer limit of energy dissipation in a magnetostrictive particle

    NASA Astrophysics Data System (ADS)

    Roy, Kuntal

    2014-12-01

    According to Landauer's principle, a minimum amount of energy proportional to temperature must be dissipated during the erasure of a classical bit of information compensating the entropy loss, thereby linking the information and thermodynamics. Here, we show that the Landauer limit of energy dissipation is achievable in a shape-anisotropic single-domain magnetostrictive nanomagnet having two mutually anti-parallel degenerate magnetization states that store a bit of information. We model the magnetization dynamics using the stochastic Landau-Lifshitz-Gilbert equation in the presence of thermal fluctuations and show that on average the Landauer bound is satisfied, i.e. it is in accordance with the generalized Landauer's principle for small systems with stochastic fluctuations.

  5. Numerical computation for a new way to reduce vibration and noise due to magnetostriction and magnetic forces of transformer cores

    NASA Astrophysics Data System (ADS)

    Zhu, Lihua; Yang, Qingxin; Yan, Rongge; Li, Yongjian; Zhang, Xian; Yan, Weili; Zhu, Jianguo

    2013-05-01

    Magnetostriction (MS) caused by the global magnetization of limbs and yokes and magnetic forces are the undisputed causes of the vibration and noise in power transformer cores. This paper presents a novel way to reduce the vibration and noise, in which nanocrystalline soft magnetic composite (NSMC) material with high permeability is used to fill the step-lap joint gaps of the power transformer magnetic cores. In order to numerically predict the effectiveness of the proposed method, a 3-D magneto-mechanical strong coupled model including MS and magnetic anisotropy of steel sheet was founded. Then, the numerical model was applied to analyze the step-lap joint region of the corner of magnetic cores. The analysis results illustrated that the deformation and noise of core with NSMC are lower than with the traditional epoxy damping material. Moreover, the validity of the proposed new way was verified by the simplified step-lap joint cores, which were achieved based on Epstein Frames.

  6. Fully coupled, dynamic model of a magnetostrictive amorphous ribbon and its validation

    SciTech Connect

    Bergmair, Bernhard Huber, Thomas; Bruckner, Florian; Vogler, Christoph; Fuger, Markus; Suess, Dieter

    2014-01-14

    Magnetostrictive amorphous ribbons are widely used in electronic article surveillance as well as for magnetoelastic sensors. Both applications utilize the fact that the ribbons' resonant frequency can be read out remotely by applying external magnetic AC fields. This paper proposes a magnetomechanical model to simulate the dynamics of such ribbons. The goal was to only use general material properties as input parameters, which are usually denoted in the data sheet of amorphous metals. Thus, only the magnetization curve at zero stress has to be gained via measurement. The magnetization under stress is calculated thereof. The equation of motion for a longitudinally oscillating ribbon is derived and coupled to Maxwell's equations for magnetostatics. The fully coupled initial value problem is solved simultaneously by a finite difference approach. The model is validated by comparing calculated and measured resonant frequencies of various amorphous ribbons, which turned out to be in good agreement. When slightly adapting single material properties from the data sheet, the match is almost perfect. The model is then used to calculate the local magnetic and mechanical properties inside static and vibrating ribbons. These local distributions can be directly linked to the field dependence of the resonant frequency and its higher harmonics.

  7. SHM of pipes using torsional waves generated by in situ magnetostrictive tapes

    NASA Astrophysics Data System (ADS)

    Kannan, E.; Maxfield, B. W.; Balasubramaniam, Krishnan

    2007-12-01

    Long-range, torsional guided waves generated in pipes using magnetostrictive sensors (MsSs) have great potential for applications to the structural health monitoring (SHM) of hard-to-inspect pipes. This paper reports an improved MsS technique (when compared to related techniques currently used for the NDT of pipes) that uses polymeric magnetic tape material that is suitable for use in a variety of industries as an SHM tool for pipes. Improvements include increased efficiency, reduced cost and increased long-term survivability of the sensor system. Transduction efficiency was increased by reducing the sensor eddy current losses and by using a field concentrator strip. For long-term monitoring, a low-cost magnetic oxide based MsS material (video recording tape) having the required magnetic properties was used. The MsS strips were oriented to generate non-dispersive torsional guided ultrasonic waves that propagate long distances with minimal mode conversion. Further, considering both safety and long-term survivability of the sensor, low-power ultrasonic instrumentation was developed and tested. Measurements reported here demonstrate the sensitivity of this sensor to both radial notches (saw cuts) and drilled holes. Results also show that magnetic anisotropy of the strip plays a role in generating torsional waves. It is envisioned that results obtained from the present study will significantly enhance the ability to monitor the long-term structural health of piping systems.

  8. Optimization on magnetic anisotropy and magnetostriction in TbxHo0.8-xPr0.2(Fe0.8Co0.2)1.93 compounds

    NASA Astrophysics Data System (ADS)

    Liu, X. Y.; Liu, J. J.; Pan, Z. B.; Song, X. H.; Zhang, Z. R.; Du, J.; Ren, W. J.

    2015-10-01

    The structure, magnetocrystalline anisotropy compensation, magnetic properties, and magnetostriction of TbxHo0.8-xPr0.2(Fe0.8Co0.2)1.93 (0≤x≤0.30) polycrystalline alloys have been investigated. X-ray diffraction (XRD) analysis shows that all the alloys stabilize in the single Laves phase with a MgCu2-type cubic structure. The lattice parameter, Curie temperature and saturation magnetization monotonically increase with increasing Tb content. The easy magnetization direction (EMD) at room temperature is detected rotating from the <100> axis (x≤0.10) to the <111> axis (x≥0.15), accompanied by a rhombohedral distortion with large spontaneous magnetostriction coefficients λ111. The analysis of XRD, EMD and magnetostriction shows that TbxHo0.8-xPr0.2(Fe0.8Co0.2)1.93 is an anisotropy compensation system, and the critical compensation point is realized around x=0.15, which shifts to the Tb-poor side compared with the Pr-free counterpart. An optimized effect on magnetostriction especially at a relatively low field (λS~445 ppm, λa~510 ppm/3 kOe) was obtained in Tb0.15Ho0.65Pr0.2(Fe0.8Co0.2)1.93 compound, which is much larger than that of the Pr-free counterpart Tb0.15Ho0.85(Fe0.8Co0.2)1.93 (λS~300 ppm) and the Tb0.15Ho0.85Fe2 (λS~325 ppm), due to the 20 at% Pr introduction. Low content of heavy rare earth Tb, low anisotropy, high saturation magnetostriction and large low-field magnetostriction are obtained in Tb0.15Ho0.65Pr0.2(Fe0.8Co0.2)1.93 compound, which may make it a promising magnetostrictive material.

  9. Effect of thermal deformation on giant magnetoresistance of flexible spin valves grown on polyvinylidene fluoride membranes

    NASA Astrophysics Data System (ADS)

    Luping, Liu; Qingfeng, Zhan; Xin, Rong; Huali, Yang; Yali, Xie; Xiaohua, Tan; Run-wei, Li

    2016-07-01

    We fabricated flexible spin valves on polyvinylidene fluoride (PVDF) membranes and investigated the influence of thermal deformation of substrates on the giant magnetoresistance (GMR) behaviors. The large magnetostrictive Fe81Ga19 (FeGa) alloy and the low magnetostrictive Fe19Ni81 (FeNi) alloy were selected as the free and pinned ferromagnetic layers. In addition, the exchange bias (EB) of the pinned layer was set along the different thermal deformation axes α 31 or α 32 of PVDF. The GMR ratio of the reference spin valves grown on Si intrinsically increases with lowering temperature due to an enhancement of spontaneous magnetization. For flexible spin valves, when decreasing temperature, the anisotropic thermal deformation of PVDF produces a uniaxial anisotropy along the α 32 direction, which changes the distribution of magnetic domains. As a result, the GMR ratio at low temperature for spin valves with EB∥ α 32 becomes close to that on Si, but for spin valves with EB∥ α 31 is far away from that on Si. This thermal effect on GMR behaviors is more significant when using magnetostrictive FeGa as the free layer. Project supported by the National Natural Science Foundation of China (Grant Nos. 11374312, 51401230, 51522105, and 51471101) and the Ningbo Science and Technology Innovation Team, China (Grant No. 2015B11001).

  10. Transforming giants.

    PubMed

    Kanter, Rosabeth Moss

    2008-01-01

    Large corporations have long been seen as lumbering, inflexible, bureaucratic--and clueless about global developments. But recently some multinationals seem to be transforming themselves: They're engaging employees, moving quickly, and introducing innovations that show true connection with the world. Harvard Business School's Kanter ventured with a research team inside a dozen global giants--including IBM, Procter & Gamble, Omron, CEMEX, Cisco, and Banco Real--to discover what has been driving the change. After conducting more than 350 interviews on five continents, she and her colleagues came away with a strong sense that we are witnessing the dawn of a new model of corporate power: The coordination of actions and decisions on the front lines now appears to stem from widely shared values and a sturdy platform of common processes and technology, not from top-down decrees. In particular, the values that engage the passions of far-flung workforces stress openness, inclusion, and making the world a better place. Through this shift in what might be called their guidance systems, the companies have become as creative and nimble as much smaller ones, even while taking on social and environmental challenges of a scale that only large enterprises could attempt. IBM, for instance, has created a nonprofit partnership, World Community Grid, through which any organization or individual can donate unused computing power to research projects and see what is being done with the donation in real time. IBM has gained an inspiring showcase for its new technology, helped business partners connect with the company in a positive way, and offered individuals all over the globe the chance to contribute to something big.

  11. Giant congenital nevus

    MedlinePlus

    ... pigmented nevus; Giant hairy nevus; Giant pigmented nevus; Bathing trunk nevus; Congenital melanocytic nevus - large ... baby grows in the womb. In some families bathing trunk nevi may be inherited. The condition may ...

  12. Giant Cell Arteritis

    MedlinePlus

    Giant cell arteritis is a disorder that causes inflammation of your arteries, usually in the scalp, neck, and arms. ... arteries, which keeps blood from flowing well. Giant cell arteritis often occurs with another disorder called polymyalgia ...

  13. Magnetostrictive gradient in Tb0.27Dy0.73Fe1.95 induced by high magnetic field gradient applied during solidification

    NASA Astrophysics Data System (ADS)

    Gao, Pengfei; Liu, Tie; Dong, Meng; Yuan, Yi; Wang, Kai; Wang, Qiang

    2016-09-01

    We investigated how high magnetic field gradients affected the magnetostrictive performance of Tb0.27Dy0.73Fe1.95 during solidification. At high applied magnetic field gradients, the magnetostriction exhibited a gradient distribution throughout the alloy. Increasing the magnetic field gradient also increased the magnetostriction gradient. We attributed the graded magnetostrictive performance to the gradient distribution of (Tb, Dy)Fe2 phase in the alloy and its orientation.

  14. Magnetic tunnel junction on a magnetostrictive substrate: An ultrasensitive magnetic-field sensor

    NASA Astrophysics Data System (ADS)

    Pertsev, N. A.

    2016-09-01

    The concept of a magnetic tunnel junction (MTJ) fabricated on an active substrate made of a highly magnetostrictive ferromagnetic material is described theoretically. It is shown that, under certain conditions, such hybrid device exhibits strongly enhanced sensitivity of the tunnel current to the external magnetic field. This feature results from the field-induced substrate deformations, which create lattice strains in the MTJ due to the interfacial mechanical interaction. If the free electrode of MTJ is made of a cubic ferromagnet like Co40Fe60 having strong magnetoelastic coupling between the magnetization and strains, the field-induced magnetization reorientation here may be enhanced by the strain effect drastically. This reorientation should lead to a change in the junction's electrical conductance because the magnetization of the reference electrode may be pinned by adjacent antiferromagnetic layer to keep its initial direction. Taking into account additional strain effects on the height and width of the tunnel barrier and the effective mass of tunneling electrons, we performed numerical calculations of the conductance magnetosensitivity for the CoFe/MgO/CoFeB junctions mechanically coupled to the FeGaB film grown on Si and found that such hybrid device is promising as an ultrasensitive room-temperature magnetic-field sensor.

  15. Wide operation frequency band magnetostrictive vibration power generator using nonlinear spring constant by permanent magnet

    NASA Astrophysics Data System (ADS)

    Furumachi, S.; Ueno, T.

    2016-04-01

    We study magnetostrictive vibration based power generator using iron-gallium alloy (Galfenol). The generator is advantages over conventional, such as piezoelectric material in the point of high efficiency highly robust and low electrical impedance. Generally, the generator exhibits maximum power when its resonant frequency matches the frequency of ambient vibration. In other words, the mismatch of these frequencies results in significant decrease of the output. One solution is making the spring characteristics nonlinear using magnetic force, which distorts the resonant peak toward higher or lower frequency side. In this paper, vibrational generator consisting of Galfenol plate of 6 by 0.5 by 13 mm wound with coil and U shape-frame accompanied with plates and pair of permanent magnets was investigated. The experimental results show that lean of resonant peak appears attributed on the non-linear spring characteristics, and half bandwidth with magnets is 1.2 times larger than that without. It was also demonstrated that the addition of proof mass is effective to increase the sensitivity but also the bandwidth. The generator with generating power of sub mW order is useful for power source of wireless heath monitoring for bridge and factory machine.

  16. Giant impacts on giant planets

    NASA Astrophysics Data System (ADS)

    de Pater, Imke

    2014-10-01

    The 2009 impact and recent superbolides on Jupiter caught the world by surprise and cast doubt on impactor flux estimates for the outer solar system. Enhanced amateur planetary imaging techniques yield both high spatial resolution (enabling the 2009 impact debris field detection) and rapid frame rates (enabling the 2010/2012 impact flash detections and lightcurve measurements).We propose a ToO program to image future impacts on Jupiter and Saturn. To remove the possibility of impact cloud non-detections, the program will be triggered only if an existing impact debris field is seen, an object on a collision course with Jupiter or Saturn is discovered, or an impact light curve is measured with an estimated total energy large enough to generate an impact cloud in a giant planet atmosphere (10^20 J).HST provides the only way to image these events in the ultraviolet, providing information on aerosol altitudes and on smaller particles that are less visible to ground-based infrared observations. High-resolution imaging with proper timing (not achievable from the ground) is required to measure precisely both the velocity fields of impact sites and the optical spectrum of impact debris. HST observations of past impacts on Jupiter have also served both as cornerstones of science investigations at other wavelengths and as vehicles for effective public outreach.Large outer solar system impacts are governed by the same physics as in the terrestrial events that dominate the impact threat to humans. Studying the behavior of impactors of various sizes and compositions, as they enter the atmosphere at varying angles and speeds, will better quantify terrestrial impact hazards.

  17. Giant impacts on giant planets

    NASA Astrophysics Data System (ADS)

    de Pater, Imke

    2013-10-01

    The 2009 impact and recent superbolides on Jupiter caught the world by surprise and cast doubt on impactor flux estimates for the outer solar system. Enhanced amateur planetary imaging techniques yield both high spatial resolution {enabling the 2009 impact debris field detection} and rapid frame rates {enabling the 2010/2012 impact flash detections and lightcurve measurements}.We propose a ToO program to image future impacts on Jupiter and Saturn. To remove the possibility of impact cloud non-detections, the program will be triggered only if an existing impact debris field is seen, an object on a collision course with Jupiter or Saturn is discovered, or an impact light curve is measured with an estimated total energy large enough to generate an impact cloud in a giant planet atmosphere {10^20 J}.HST provides the only way to image these events in the ultraviolet, providing information on aerosol altitudes and on smaller particles that are less visible to ground-based infrared observations. High-resolution imaging with proper timing {not achievable from the ground} is required to measure precisely both the velocity fields of impact sites and the optical spectrum of impact debris. HST observations of past impacts on Jupiter have also served both as cornerstones of science investigations at other wavelengths and as vehicles for effective public outreach.Large outer solar system impacts are governed by the same physics as in the terrestrial events that dominate the impact threat to humans. Studying the behavior of impactors of various sizes and compositions, as they enter the atmosphere at varying angles and speeds, will better quantify terrestrial impact hazards.

  18. Critical Behavior of Thermal Expansion and Magnetostriction in the Vicinity of the First order transition at the Curie Point of Gd5(SixGe1-x)4

    SciTech Connect

    Han, Mangui

    2004-01-01

    Thermal expansion (TE) and magnetostriction (MS) measurements have been conducted for Gd5(SixGe1-x)4 with a series of x values to study its critical behavior in the vicinity of transition temperatures. It was found that the Curie temperature of Gd5(SixGe1-x)4 for x 0 ~ 0.5 is dependent on magnetic field, direction of change of temperature (Tc on cooling was lower than Tc on heating), purity of Gd starting material, compositions, material preparation methods, and also can be triggered by the external magnetic field with a different dT/dB rate for different x values. For Gd5(Si1.95Ge2.05), Gd5(Si2Ge2), Gd5(Si2.09Ge1.91), it was also found that the transition is a first order magneto-structural transition, which means the magnetic transition and crystalline structure transition occur simultaneously, and completely reversible. Temperature hysteresis and phase coexistence have been found to confirm that it is a first order transformation. While for Gd5(Si0.15Ge3.85), it is partially reversible at some temperature range between the antiferromagnetic and the ferromagnetic state. For Gd5(Si2.3Ge1.7) and Gd5(Si3Ge1), it was a second order transformation between the paramagnetic and ferromagnetic state, because no ΔT have been found. Giant magnetostriction was only found on Gd5(Si1.95Ge2.05), Gd5(Si2Ge2), Gd5(Si2.09Ge1.91) in their vicinity of first order transformation. MFM images have also been taken on polycrystal sample Gd5(Si2.09Ge1.91) to investigate the transformation process. The results also indicates that the Curie temperature was lower and the thermally

  19. Green Giants.

    ERIC Educational Resources Information Center

    Wright, Michaella; Maine, Bruce

    2001-01-01

    Explains how designing and constructing sustainable, environmentally friendly school buildings does not have to be a costly venture. Provides advice for selecting building materials, developing energy efficiency, and minimizing toxins. Reviews the status of national sustainable design standards. (GR)

  20. Spin-phonon and magnetostriction phenomena in CaMn{sub 7}O{sub 12} helimagnet probed by Raman spectroscopy

    SciTech Connect

    Nonato, A.; Araujo, B. S.; Ayala, A. P.; Maciel, A. P.; Yanez-Vilar, S.; Sanchez-Andujar, M.; Senaris-Rodriguez, M. A.; Paschoal, C. W. A.

    2014-12-01

    In this letter, we investigated the temperature-dependent Raman spectra of CaMn{sub 7}O{sub 12} helimagnet from room temperature down to 10 K. The temperature dependence of the Raman mode parameters shows remarkable anomalies for both antiferromagnetic and incommensurate transitions that this compound undergoes at low temperatures. The anomalies observed at the magnetic ordering transition indicate a spin-phonon coupling at higher-temperature magnetic transition in this material, while a magnetostriction effect at the lower-temperature magnetic transition.

  1. Inverse effect of morphotropic phase boundary on the magnetostriction of ferromagnetic Tb1-xGdxCo2

    NASA Astrophysics Data System (ADS)

    Zhou, Chao; Ren, Shuai; Bao, Huixin; Yang, Sen; Yao, Yonggang; Ji, Yuanchao; Ren, Xiaobing; Matsushita, Yoshitaka; Katsuya, Yoshio; Tanaka, Masahiko; Kobayashi, Keisuke

    2014-03-01

    The morphotropic phase boundary (MPB) has been utilized extensively in ferroelectrics and recently has attracted interest in ferromagnets [S. Yang, H. Bao, C. Zhou, Y. Wang, X. Ren, Y. Matsushita, Y. Katsuya, M. Tanaka, K. Kobayashi, X. Song, and J. Gao, Phys. Rev. Lett. 104, 197201 (2010), 10.1103/PhysRevLett.104.197201; R. Bergstrom, M. Wuttig, J. Cullen, P. Zavalij, R. Briber, C. Dennis, V. O. Garlea, and M. Laver, Phys. Rev. Lett. 111, 017203 (2013), 10.1103/PhysRevLett.111.017203] for obtaining enhanced large field-induced strain. Here we report that the MPB can also lead to weakening (the inverse effect as compared to the known MPB materials) of field-induced strain, as exhibited in the Tb1-xGdxCo2 system. With synchrotron x-ray diffractometry, the structure symmetry of TbCo2-rich compositions is detected to be rhombohedral below TC and that of GdCo2-rich compositions is tetragonal. The MPB composition Tb0.1Gd0.9Co2, corresponding to the two phases (rhombohedral and tetragonal) of coexistence, shows the exotic minimum (near zero) magnetostriction as well as the largest magnetic susceptibility among all samples. Further analysis suggests that whether MPB can enhance or weaken magnetostriction is determined by the degree of magnetic ordering of two end members that form ferromagnetic MPBs, which was not considered previously. Our work not only reveals a new type of ferromagnetic MPB, but also provides a new recipe for designing functional high-susceptibility and low-strain magnetic materials.

  2. Magnetostrictive Fe73Ga27 nanocontacts for low-field conductance switching

    NASA Astrophysics Data System (ADS)

    Kannan, U. M.; Kuntz, S.; Berg, O.; Kittler, W.; Basumatary, H.; Arout Chelvane, J.; Sürgers, C.; Narayana Jammalamadaka, S.

    2016-06-01

    The electrical conductance G of magnetostrictive nanocontacts made from Galfenol (Fe73Ga27) can be reproducibly switched between "on" and "off" states in a low magnetic field of ˜20-30 mT at 10 K. The switching behavior is in agreement with the magnetic field dependence of the magnetostriction inferred from the magnetization behavior, causing a positive magnetostrictive strain along the magnetic field. The repeated magnetic-field cycling leads to a stable contact geometry and to a robust contact configuration with a very low hysteresis of ˜1 mT between opening and closing the contact due to a training effect. Non-integral multiples of the conductance quantum G0 observed for G > G0 are attributed to electron backscattering at defect sites in the electrodes near the contact interface. When the contact is closed either mechanically or by magnetic field, the conductance shows an exponential behavior below G0 due to electron tunneling. This allows to estimate the magnetostriction λ = 4 × 10-5 at 10 K. The results demonstrate that such magnetostrictive devices are suitable for the remote control of the conductance by low magnetic fields in future nanotechnology applications.

  3. Magnetostriction ``jumps'' in twinned Tb0.3Dy0.7Fe1.9

    NASA Astrophysics Data System (ADS)

    Clark, A. E.; Teter, J. P.; McMasters, O. D.

    1988-04-01

    Large ``jumps'' in the magnetostriction have been observed in twinned single crystals of Tb0.3Dy0.7Fe1.9 (Terfenol-D) for magnetic fields parallel to the crystalline [112¯] direction. The interpretation of these large magnetostriction discontinuities is based upon a model of twinned dendritic Terfenol-D in which the magnetization of one twin jumps between two [111] directions while the magnetization of the remaining twin undergoes a continuous rotation of the magnetization. The field dependence of the magnetization and magnetostriction of cubic single crystals with λ111≫λ100 was calculated using an expression which included the anisotropy constants K1 and K2 and compressive loads along [112¯]. With K1=-0.6 J/m3 and K2=-2.0 J/m3 (values appropriate for Terfenol-D near room temperature), magnetization ``jumping'' is predicted. For the twinned crystal, the jump in the magnetostriction was calculated to be greater than 1000 ppm. Because of this large magnetostriction, it is possible to configure a device to perform a substantial amount of work by the application of only a triggering magnetic field centered about an optimum bias field.

  4. Studies of magnetostriction and spin polarized band structures of rare earth intermetallics

    NASA Technical Reports Server (NTRS)

    Wallace, W. E.

    1979-01-01

    Anisotropic magnetostriction measurements of R6Fe23, R = (Tb, Dy, Ho, and Er) were carried out from 77 K to room temperature. Magnetic fields up to 2.1 Tesla were applied. All the compounds exhibited large magnetostrictions at 77 K, the largest effect being obtained for Tb6Fe23. Saturation magnetostriction values for the compounds were also determined for 77 K and room temperature. Results of the temperature dependence of magnetostriction for Er6Fe23 are in good agreement with Callen and Callen's single ion theory. Therefore, the main sources of magnetostriction in this compound is the Er ion. The spin-up and spin-down electronic energy bands, the density of states and the magnetic moments of YCo5, SmCo5, and GdCo5 were calculated by the spin polarized augmented plane wave technique. The calculations obtained show the origin of the moment, provide good estimates of its magnitude and variation, and the reasons for those variations. They also show the important role of partial charge transfer and of d-d electronic coupling. Calculations for LaNi5 and GdNi5 systems are discussed.

  5. Magnetostrictive Effect Type Force (Strain) Sensor Using Mutual Induction of Planar Coils

    NASA Astrophysics Data System (ADS)

    Koga, Fumitaka; Sasada, Ichiro

    A new structure is proposed for the magnetostrictive effect type force sensors using a pickup head layered with magnetostrictive foil and a pair of planar coils. Mutual coupling between two planar coils is used as a measure of force applied to the magnetostrictive foil glued to a mechanical component. The mutual coupling is governed by force-induced anisotropic permeability at the magnetostrictive foil. In this type of the force sensor, the output voltage is zero when force is zero, and the planar coils with electric wires can be put on and taken off easily because the magnetostrictive foil does not need a current contact. Basic characteristics of the force sensors are examined using Metglas2605SC amorphous foil glued to the side of an aluminum square bar of 15mm×15mm in cross-section area and a pair of 16-turn planar coils. Sensitivity was 38.4 mV/Nm (1.57 mV/με(ε= δl/l)) at the coil excitation condition of 1 MHz, 60 mA.

  6. Saturation magnetostriction dependence on torsion in amorphous wire as measured by modified small angle magnetization rotation method

    NASA Astrophysics Data System (ADS)

    Chubykalo, O. A.; González, J.; Aragoneses, P.; Blanco, J. M.; Domínguez, L.; González, J. M.

    1997-05-01

    The small angle magnetization rotation (SAMR) method has been applied to the measurement of the torsional dependence of the saturation magnetostriction in a low-magnetostrictive amorphous Co-rich wire. The behaviour of the electric signal picked up from the sense coil has been investigated using experimental and numerical methods. The torsion introduces the first harmonic into the signal but the general formula for the measurement of the saturation magnetostriction remains valid. The conditions for the application of the method are discussed. The measurements of the saturation magnetostriction in the presence of an applied torsion have been carried out for as-quenched and annealed samples using different intensities of the annealing current. The magnetostriction coefficient, λs, depends linearly on the applied stress σ: λs = λs(0) + Aσ. The experimental dependence of the parameters λs(0) and A on the applied torsion and for different thermal treatments of the samples are also presented.

  7. Voltage induced magnetostrictive switching of nanomagnets: Strain assisted strain transfer torque random access memory

    SciTech Connect

    Khan, Asif Nikonov, Dmitri E.; Manipatruni, Sasikanth; Ghani, Tahir; Young, Ian A.

    2014-06-30

    A spintronic device, called the “strain assisted spin transfer torque (STT) random access memory (RAM),” is proposed by combining the magnetostriction effect and the spin transfer torque effect which can result in a dramatic improvement in the energy dissipation relative to a conventional STT-RAM. Magnetization switching in the device which is a piezoelectric-ferromagnetic heterostructure via the combined magnetostriction and STT effect is simulated by solving the Landau-Lifshitz-Gilbert equation incorporating the influence of thermal noise. The simulations show that, in such a device, each of these two mechanisms (magnetostriction and spin transfer torque) provides in a 90° rotation of the magnetization leading a deterministic 180° switching with a critical current significantly smaller than that required for spin torque alone. Such a scheme is an attractive option for writing magnetic RAM cells.

  8. Voltage induced magnetostrictive switching of nanomagnets: Strain assisted strain transfer torque random access memory

    NASA Astrophysics Data System (ADS)

    Khan, Asif; Nikonov, Dmitri E.; Manipatruni, Sasikanth; Ghani, Tahir; Young, Ian A.

    2014-06-01

    A spintronic device, called the "strain assisted spin transfer torque (STT) random access memory (RAM)," is proposed by combining the magnetostriction effect and the spin transfer torque effect which can result in a dramatic improvement in the energy dissipation relative to a conventional STT-RAM. Magnetization switching in the device which is a piezoelectric-ferromagnetic heterostructure via the combined magnetostriction and STT effect is simulated by solving the Landau-Lifshitz-Gilbert equation incorporating the influence of thermal noise. The simulations show that, in such a device, each of these two mechanisms (magnetostriction and spin transfer torque) provides in a 90° rotation of the magnetization leading a deterministic 180° switching with a critical current significantly smaller than that required for spin torque alone. Such a scheme is an attractive option for writing magnetic RAM cells.

  9. Asymptotic behavior of a low-dimensional model for magnetostriction for periodic input

    NASA Astrophysics Data System (ADS)

    Ekanayake, D. B.; Iyer, R. V.

    2008-02-01

    Models for magnetostrictive actuators need to include rate-independent hysteresis phenomena, magneto-elastic coupling, and eddy current losses that vary nonlinearly with the frequency of the input. In this paper, we study a low-dimensional model for magnetostrictive rod actuators that describes the physical phenomena which are most prominent in the frequency range 0-800 Hz. We show that the solution of the system is asymptotically periodic for bounded, continuous and periodic voltage inputs and with general conditions on a Preisach operator modeling rate-independent hysteresis. The results of this paper are crucial for developing a parameter identification methodology for the model that is addressed in [D.B. Ekanayake, R.V. Iyer, W.P. Dayawansa, Wide band modeling and parameter identification in magnetostrictive actuators, in: Proceedings of IEEE American Control Conference, New York, NY (2007) 4321-4326].

  10. Low Temperature Magnetostrictive Strain Of Terfenol-D and Terbium Dysprosium

    NASA Astrophysics Data System (ADS)

    Graetz, Jason

    1998-03-01

    The goal of this project is to measure the magnetostrictive strain of Terfenol-D and Terbium Dysprosium at 300K and 77K. This involves the observation of the strain difference over a metamagnetic transition in Terfenol-D and a para- ferro-magnetic transition in Terbium Dysprosium. The experimental data is in agreement with general magnetostriction theory. This data is used in the construction of a prototype of a high-resolution magnetostrictive actuator. This device has been successfully tested at 300K with a minimum step size of 10nm. Low temperature devices of this nature have applicability to electron microscopy, Infrared cameras, and mirror positioning on low temperature space telescopes.

  11. On the Origin of the "Giant" Electroclinic Effect in a "De Vries"-Type Ferroelectric Liquid Crystal Material for Chirality Sensing Applications

    SciTech Connect

    Kapernaum, N.; Walba, D; Korblova, E; Zhu, C; Jones, C; Shen, Y; Clark, N; Giesselmann, F

    2009-01-01

    W415 is a chiral smectic compound with a remarkably weak temperature dependence of its giant electroclinic effect in the liquid crystalline smectic A* phase. Furthermore it possesses a high spontaneous polarization in the smectic C* phase. The origin of this striking electroclinic effect is the co-occurrence of a de Vries-type ordering with a weak first-order tilting transition (see the synchroton X-ray scattering profiles).

  12. Domain observation and magnetostriction in Tb0.3Dy0.7Fe2 twinned single crystals

    NASA Astrophysics Data System (ADS)

    Teter, J. P.; Mahoney, K.; Al-Jiboory, M.; Lord, D. G.; McMasters, O. D.

    1991-04-01

    The ternary alloy Tb0.3Dy0.7Fe2 (Terfenol-D) exhibits the largest known magnetostriction to anisotropy ratio near room temperature. To better determine the interaction between the elastic and magnetic properties of this material, a stoichiometric twinned single crystal was grown by a free-standing float-zone technique. Observations using Scanning electron microscopy and energy dispersive spectroscopy confirmed that the sample was free of the normally present rare-earth (RE) eutectic phase and simultaneously free of Widmanstatten precipitate (RE Fe3). A bar with (111) and (11¯0) faces perpendicular to the [112¯] growth direction was examined. Also, a [111¯] slab was cut from the boule. This slab was studied along the [111¯] and [11¯0] directions with prestress applied along the [111¯]. This is the first report of the effects of applying prestress and magnetic fields in a direction not collinear with the [112¯] growth direction. From magnetization (M) and magnetostriction (λ) measurements as a function of field, prestress, and temperature, we determined the hysteresis and saturation parameters. These measurements do not indicate the [11¯0] λ and M behaviors found previously for RE-rich Terfenol-D. Domain observations with differential phase contrast and x-ray topography have shown different orientations in the twin and parent sections of the [111¯] specimen. The observed structures can be interpreted as arising from domains with magnetization components normal to the surface. The domain observations on the (111) and (11¯0) bar faces and on the [111¯] slab correlate with each other with respect to orientations and domain interpretations.

  13. Sharp Goss texture and magnetostriction in binary Fe81Ga19 sheets

    NASA Astrophysics Data System (ADS)

    He, Zhenghua; Sha, Yuhui; Fu, Quan; Lei, Fan; Jin, Bokai; Zhang, Fang; Zuo, Liang

    2016-11-01

    Goss ({110}<001>) texture development and magnetostriction in binary Fe81Ga19 sheet were investigated. Millimeters-sized Goss grains, covering 80% area of the annealed sheet surface, are produced by secondary recrystallization without effects of inhibitor and surface energy. The micro-texture analysis demonstrates that primarily recrystallized Goss grains have an evident advantage in size and number to be potential secondary nuclei. The grain size distribution of primary Goss grains can induce the continuable abnormal growth until the completion of secondary recrystallization. The obtained magnetostriction coefficient is close to those with the help of inhibitor or surface energy.

  14. Coagulation sensors based on magnetostrictive delay lines for biomedical and chemical engineering applications

    NASA Astrophysics Data System (ADS)

    Maliaritsi, E.; Zoumpoulakis, L.; Simitzis, J.; Vassiliou, P.; Hristoforou, E.

    2006-04-01

    Coagulation sensors based on the magnetostrictive delay line technique are presented in this paper. They are based on magnetostrictive ribbons and are used for measuring the coagulation, curing or solidification time of different liquids. Experimental results indicate that the presented sensing elements can determine the blood coagulation with remarkable repeatability, thus allowing their use as blood coagulation sensors. Additionally, results indicate that they can also measure curing time of resins, solidification of fluids and coagulation of chemical substances, therefore allowing their implementation in chemical engineering applications.

  15. Combining large magnetostriction and large magnetostrictive susceptibility in TbFeCo/Y{sub x}Fe{sub 1-x} exchange-spring-type multilayers

    SciTech Connect

    Huong Giang, D.T.; Duc, N.H.; Thuc, V.N.; Vu, L.V.; Chau, N.

    2004-08-30

    An approach to obtain both large magnetostriction and large magnetostrictive susceptibility is developed. It is applied to sputtered {l_brace}Tb(Fe{sub 0.55}Co{sub 0.45}){sub 1.5}/(Y{sub x}Fe{sub 1-x}){r_brace} (x=0, 0.1 and 0.2) multilayers. In the as-deposited samples, the TbFeCo layers are in the amorphous state, but the microstructure of the Y{sub x}Fe{sub 1-x} layers is not the same: A crystalline state is observed in pure Fe layers (x=0), whereas body-centered-cubic-Fe nanocrystals coexist within an YFe amorphous matrix in Y{sub 0.1}Fe{sub 0.9} layers. A parallel magnetostrictive susceptibility {chi}{sub {lambda}}{sub parallel} as large as 29.4x10{sup -2} T{sup -1}, which is almost half of that (79.6x10{sup -2} T{sup -1}) of the Metglas 2605SC was obtained for x=0.1. This is attributed to the exchange coupling between sandwiched TbFeCo layers and nanostructured YFe layers.

  16. Giant strain with ultra-low hysteresis and high temperature stability in grain oriented lead-free K₀̣₅Bi₀̣₅TiO₃-BaTiO₃-Na₀̣₅Bi₀̣₅TiO₃ piezoelectric materials

    DOE PAGES

    Maurya, Deepam; Zhou, Yuan; Wang, Yaojin; Yan, Yongke; Li, Jiefang; Viehland, Dwight; Priya, Shashank

    2015-02-26

    We synthesized grain-oriented lead-free piezoelectric materials in (K₀̣₅Bi₀̣₅TiO₃-BaTiO₃-xNa₀̣₅Bi₀̣₅TiO₃ (KBT-BT-NBT) system with high degree of texturing along the [001]c (c-cubic) crystallographic orientation. We demonstrate giant field induced strain (~0.48%) with an ultra-low hysteresis along with enhanced piezoelectric response (d₃₃ ~ 190pC/N) and high temperature stability (~160°C). Transmission electron microscopy (TEM) and piezoresponse force microscopy (PFM) results demonstrate smaller size highly ordered domain structure in grain-oriented specimen relative to the conventional polycrystalline ceramics. The grain oriented specimens exhibited a high degree of non-180° domain switching, in comparison to the randomly axed ones. These results indicate the effective solution to the lead-free piezoelectricmore » materials.« less

  17. Direct method for magnetostriction coefficient measurement based on atomic force microscope, illustrated by the example of Tb-Co film

    NASA Astrophysics Data System (ADS)

    Lima, B. L. S.; Maximino, F. L.; Santos, J. C.; Santos, A. D.

    2015-12-01

    This paper presents a method based on the Atomic Force Microscopy technique for direct measurement of magnetostriction coefficient of amorphous Tb-Co films deposited on Si(100) substrate. The magnetostriction coefficient of the film is determined by AFM measuring the deflection of the sample when applying a magnetic field. In order to maximize the deflection of the sample, in-plane magnetic anisotropy was induced by heat treatment under a magnetic field of 5 kOe. The value obtained for the saturation magnetostriction is 204×10-6 for the Tb23Co77 film.

  18. Magnetostriction Measured by Holographic Interferometry with the Simple and Inexpensive "Arrowhead" Setup

    ERIC Educational Resources Information Center

    Ladera, Celso L.; Donoso, Guillermo; Contreras, Johnny H.

    2012-01-01

    Double-exposure holographic interferometry is applied to measure the "linear" or "longitudinal" magnetostriction constant of a soft-ferrite rod. This high-accuracy measurement is done indirectly, by measuring the small rotations of a lever in contact with the rod using double-exposure holographic interferometry implemented with a robust…

  19. Magnetostrictive behaviors of Fe-Al(001) single-crystal films under rotating magnetic fields

    NASA Astrophysics Data System (ADS)

    Kawai, Tetsuroh; Abe, Tatsuya; Ohtake, Mitsuru; Futamoto, Masaaki

    2016-05-01

    Magnetostrictive behaviors of Fe100-x - Alx(x = 0 - 30 at.%)(001) single-crystal films under rotating magnetic fields are investigated along the two different crystallographic orientations, [100] and [110]. The behaviors of Fe and Fe90Al10 films show bath-tub like waveform along [100], easy magnetization axis, and triangular waveform along [110], hard magnetization axis, with respect to their four-fold magnetic anisotropy. On the other hand, the behaviors of Fe80Al20 film are different from those of Fe or Fe90Al10 film. The output of the film along [100] shows a strong magnetic field dependence. The Fe70Al30 film shows similar magnetostrictive behaviors along both [100] and [110] reflecting its magnetic properties, which are almost same for the both directions. The growth of ordered phase (B2) in Fe80Al20 and Fe70Al30 films is considered to have affected their magnetostrictive behaviors. The Al content dependence on λ100 and λ111 values shows similar tendency to that reported for the bulk samples but the values are slightly different. The Fe90Al10(001) single-crystal film shows a large magnetostriction along [100] under a very small magnetic field of 0.02 kOe, which is comparable to the saturated one, and changes the value abruptly in relation to the angle of applied magnetic field.

  20. Circumferential phased array of shear-horizontal wave magnetostrictive patch transducers for pipe inspection.

    PubMed

    Kim, Hoe Woong; Lee, Joo Kyung; Kim, Yoon Young

    2013-02-01

    Several investigations report effective uses of magnetostrictive patch transducers to generate and measure longitudinal and torsional guided waves in a pipe. They can be used to form a phased array for the circumferential inspection of pipes. Although there are circumferential phased arrays employing piezoelectric transducers or EMAT's, no magnetostrictive patch transducer based array system has been attempted. In this investigation, we aim to develop a circumferential phased magnetostrictive patch transducer (PMPT) array that can focus shear-horizontal waves at any target point on a cylindrical surface of a pipe. For the development, a specific configuration of a PMPT array employing six magnetostrictive patch transducers is proposed. A wave simulation model is also developed to determine time delays and amplitudes of signals generated by the transducers of the array. This model should be able to predict accurately the angular profiles of shear-horizontal waves generated by the transducers. For wave focusing, the time reversal idea will be utilized. The wave focusing ability of the developed PMPT array is tested with multiple-crack detection experiments. Imaging of localized surface inspection regions is also attempted by using wave signals measured by the developed PMPT array system.

  1. Exotic Earths: forming habitable worlds with giant planet migration.

    PubMed

    Raymond, Sean N; Mandell, Avi M; Sigurdsson, Steinn

    2006-09-01

    Close-in giant planets (e.g., "hot Jupiters") are thought to form far from their host stars and migrate inward, through the terrestrial planet zone, via torques with a massive gaseous disk. Here we simulate terrestrial planet growth during and after giant planet migration. Several-Earth-mass planets also form interior to the migrating jovian planet, analogous to recently discovered "hot Earths." Very-water-rich, Earth-mass planets form from surviving material outside the giant planet's orbit, often in the habitable zone and with low orbital eccentricities. More than a third of the known systems of giant planets may harbor Earth-like planets.

  2. Exotic Earths: forming habitable worlds with giant planet migration.

    PubMed

    Raymond, Sean N; Mandell, Avi M; Sigurdsson, Steinn

    2006-09-01

    Close-in giant planets (e.g., "hot Jupiters") are thought to form far from their host stars and migrate inward, through the terrestrial planet zone, via torques with a massive gaseous disk. Here we simulate terrestrial planet growth during and after giant planet migration. Several-Earth-mass planets also form interior to the migrating jovian planet, analogous to recently discovered "hot Earths." Very-water-rich, Earth-mass planets form from surviving material outside the giant planet's orbit, often in the habitable zone and with low orbital eccentricities. More than a third of the known systems of giant planets may harbor Earth-like planets. PMID:16960000

  3. Formation of Giant Planets and Brown Dwarves

    NASA Technical Reports Server (NTRS)

    Lissauer, Jack J.

    2003-01-01

    According to the prevailing core instability model, giant planets begin their growth by the accumulation of small solid bodies, as do terrestrial planets. However, unlike terrestrial planets, the growing giant planet cores become massive enough that they are able to accumulate substantial amounts of gas before the protoplanetary disk dissipates. Models predict that rocky planets should form in orbit about most stars. It is uncertain whether or not gas giant planet formation is common, because most protoplanetary disks may dissipate before solid planetary cores can grow large enough to gravitationally trap substantial quantities of gas. Ongoing theoretical modeling of accretion of giant planet atmospheres, as well as observations of protoplanetary disks, will help decide this issue. Observations of extrasolar planets around main sequence stars can only provide a lower limit on giant planet formation frequency . This is because after giant planets form, gravitational interactions with material within the protoplanetary disk may cause them to migrat inwards and be lost to the central star. The core instability model can only produce planets greater than a few jovian masses within protoplanetary disks that are more viscous than most such disks are believed to be. Thus, few brown dwarves (objects massive enough to undergo substantial deuterium fusion, estimated to occur above approximately 13 jovian masses) are likely to be formed in this manner. Most brown dwarves, as well as an unknown number of free-floating objects of planetary mass, are probably formed as are stars, by the collapse of extended gas/dust clouds into more compact objects.

  4. Ultra sensitive magnetic sensors integrating the giant magnetoelectric effect with advanced microelectronics

    NASA Astrophysics Data System (ADS)

    Fang, Zhao

    This dissertation investigates approaches to enhance the performance, especially the sensitivity and signal to noise ratio of magnetoelectric sensors, which exploits the magnetoelectric coupling in magnetostrictive and piezoelectric laminate composites. A magnetic sensor is a system or device that can measure the magnitude of a magnetic field or each of its vector components. Usually the techniques encompass many aspects of physics and electronics. The common technologies used for magnetic field sensing include induction coil sensors, fluxgate, SQUID (superconducting quantum interference device), Hall effect, giant magnetoresistance, magnetostrictive/piezoelectric composites, and MEMS (microelectromechanical systems)-based magnetic sensors. Magnetic sensors have found a broad range of applications for many decades. For example, ultra sensitive magnetic sensors are able to detect tiny magnetic fields produced outside the brain by the neuronal currents which can be used for diagnostic application. Measuring the brain's magnetic field is extremely challenging because they are so weak, have strengths of 0.1--1 pT and thus requiring magnetic sensors with sub-picotesla sensitivity. In fact, to date, these measurements can only performed with the most sensitive magnetic sensors, i.e., SQUID. However, such detectors need expensive and cumbersome cryogenics to operate. Additionally, the thermal insulation of the sensors prevents them from being placed very closed to the tissues under study, thereby preventing high-resolution measurement capability. All of these severely limit their broad usage and proliferation for biomedical imaging, diagnosis, and research. A novel ultra-sensitive magnetic sensor capable of operating at room temperature is investigated in this thesis. Magnetoelectric effect is a material phenomenon featuring the interchange between the magnetic and electric energies or signals. The large ME effect observed in ME composites, especially the ME laminates

  5. Strong anisotropy and magnetostriction in the two-dimensional Stoner ferromagnet Fe3GeTe2

    DOE PAGES

    Zhuang, Houlong L.; Kent, P. R. C.; Hennig, Richard G.

    2016-04-06

    Comore » mputationally characterizing magnetic properies of novel two-dimensional (2D) materials serves as an important first step of exploring possible applications. Using density-functional theory, we show that single-layer Fe3GeTe2 is a potential 2D material with sufficiently low formation energy to be synthesized by mechanical exfoliation from the bulk phase with a van der Waals layered structure. In addition, we calculated the phonon dispersion demonstrating that single-layer Fe3GeTe2is dynamically stable. Furthermore, we find that similar to the bulk phase, 2D Fe3GeTe2 exhibits amagnetic moment that originates from a Stoner instability. In contrast to other 2D materials, we find that single-layer Fe3GeTe2 exhibits a significant uniaxial magnetocrystalline anisotropy energy of 920μ eV per Fe atom originating from spin-orbit coupling. In conclusion, we show that applying biaxial tensile strains enhances the anisotropy energy, which reveals strong magnetostriction in single-layer Fe3GeTe2 with a sizable magneostrictive coefficient. Our results indicate that single-layer Fe3GeTe2 is potentially useful for magnetic storage applications.« less

  6. Mechanics of Magnetostrictive Thin Film Deformation and its Application in Active X-ray Optics

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoli

    High quality imaging system of telescopes in astronomy requires innovations to remove or correct the mid-spatial frequency (MSF) ripples on the mirror surface of lightweight optics. When the telescope is sent to the space, its launch mass is the key point to limit its collecting area. Therefore, the lightweight optics (100-150 mum thick electroplated nickel/cobalt, or 200-400 mum thick glass) is considered to be employed. However, the surface profile of the thin optical surface can't be polished to extremely high accuracy. Instead, the profile is expected to be corrected by applying voltage or magnetic field to drive the coating of smart materials (piezo or magnetostrictive materials) on the back side of the mirrors. During the process, the surface profile correction by the local stress on the 2-d surface is challenging. Both the measurements and the theoretical prediction of the surface profiles after correction are investigated. As a first step in the development of tools to predict the deformation of the coated glass strip samples (20x5x0.1 mm), one commercial magnetically smart material (MSM) was deposited on the samples by the magnetron sputtering method. One experimental setup was established to measure the deflections of these coated samples under an external magnetic field by Zygo NewView white light interferometry (WLI). These deflections agreed well with the results from the developed analytical and numerical analysis under various magnetic field strengths. In the further research, more efforts were made to analyze the full three-dimensional deformation behavior of MSM thin films on a square glass sample (50x50x0.2 mm). With the magnetic field applied, the 2-d surface profile of the coated glass sample was measured by WLI. To better study the deformation of the sample coated with MSMs, a finite element method (FEM) and a theoretical model were developed to predict the deformation of the sample with local misfit strains. The results calculated form the FEM

  7. Unstable giant gravitons

    SciTech Connect

    Mello Koch, Robert de; Ives, Norman; Smolic, Jelena; Smolic, Milena

    2006-03-15

    We find giant graviton solutions in Frolov's three parameter generalization of the Lunin-Maldacena background. The background we study has {gamma}-tilde{sub 1}=0 and {gamma}-tilde{sub 2}={gamma}-tilde{sub 3}={gamma}-tilde. This class of backgrounds provides a nonsupersymmetric example of the gauge theory/gravity correspondence that can be tested quantitatively, as recently shown by Frolov, Roiban, and Tseytlin. The giant graviton solutions we find have a greater energy than the point gravitons, making them unstable states. Despite this, we find striking quantitative agreement between the gauge theory and gravity descriptions of open strings attached to the giant.

  8. Evolution of Chromospheric Activity: M67 Red Giants

    NASA Astrophysics Data System (ADS)

    Dupree, A. K.; Whitney, B. A.; Pasquini, L.

    1999-08-01

    Echelle spectra of the Ca II H- and K-line region (λ3950) of 15 red giant stars in the open cluster M67 reveal atmospheric dynamics and determine chromospheric radiative losses in order to assess chromospheric heating requirements and to follow the evolution of chromospheric activity. M67 red giants in conjunction with giants in younger clusters create a continuous group of red giants in the color-magnitude diagram, with 0.1<=(B-V)<=1.65 along the red giant branch. M67 contains the more evolved clump giants as well. Asymmetric line emission cores, indicative of outflowing material, are found in a majority of the M67 giants on the red giant branch and occur over the complete sample, from MV=-0.8 to MV=1.9, suggesting that outward mass motions are well established at these luminosities. Radiative losses, as measured by emission strengths from Ca II, decrease smoothly with decreasing stellar effective temperature in M67 and connect well to a combined sample of warmer cluster giants (NGC 2477, IC 4756, and the Hyades) with M<=3 Msolar studied by Beasley & Cram. Stellar effective temperature predominantly determines the level of chromospheric Ca II losses for giants with M<=3 Msolar. No evidence is found for a sharp decline in the flux of Ca II predicted by the Rutten & Pylyser magnetic model for chromospheric heating. However, emission in field giants (which tend to be younger) suggests that sharp declines in surface flux with decreasing effective temperature characteristic of pure magnetic activity occur for ion species more highly excited than Ca II. Although acoustic models for chromospheric heating apparently agree with the measured Ca II flux levels for the coolest giants, additional heating processes must be present in warmer giants and clump stars. Clump giants exhibit Ca II fluxes consistent with stars of similar colors on the red giant branch, suggesting a renaissance in chromospheric heating occurs after evolution beyond the red giant branch. Chromospheric

  9. Magnetostriction and texture development in binary and ternary iron-gallium-based alloys

    NASA Astrophysics Data System (ADS)

    Mungsantisuk, Pinai

    2005-07-01

    The rare earth-free bcc FeGa-based alloys have an excellent combination of large low-field magnetostriction at room temperature, good mechanical properties, low hysteresis, and relatively low cost. These alloys are attractive for use in numerous sensor and actuator devices. The first part of this dissertation examines the influence of partial substitutions of Ga with Al, Be, Si, Ge, and Sn and partial substitutions of Fe with Co and Ni. The work involved directional growth of [001] textured rods of these ternary alloys using a Vertical Bridgman process, X-ray diffraction analysis, magnetic property measurements using vibrating sample magnetometry, and magnetostriction measurements. It is shown that substitution of Ga with Al can be made in FeGa alloys in certain composition ranges without a reduction in magnetostriction, and the additions of Si, Ge, and Sn results in a sharp decrease of magnetostriction. The addition or substitute of Be, due to its smaller size than Fe, resulted in only a slight decrease of magnetostriction. Substitution of Fe with Ni and Co results in a significant decrease of the magnetostriction. The work also evaluated the elastic properties of Fe-x at. % Ga and Fe-(20-y) at. % Ga-y at. % Al polycrystalline alloys using resonant ultrasound spectroscopy. Young's modulus obtained for FeGa and FeGaAl alloys were in the range of 110 to 170 GPa which are several times that for Terfenol-D alloys. Thus, large-force delivery is possible from FeGa alloy based actuators even though saturation strain values are smaller than that of Terfenol-D. The second part of this work examined the development of an inexpensive thermomechanical processing method to obtain [001] textured polycrystalline Fe-15 at. % Ga alloys. The processing involved a sequence of controlled hot rolling, two-stage warm rolling with intermediate anneal, and texture anneal. Roll forces measured and the extent of reductions feasible indicated an excellent processability. Texture evolution

  10. A Cascaded Magnetostrictive Vibration Source System for Underground Construction Applications

    NASA Astrophysics Data System (ADS)

    Hock, S.; Polom, U.; Mikulla, S.; Krüger, K.; Giese, R.; Lüth, S.

    2009-04-01

    For underground construction seismic measurements can contribute knowledge to geology and relevant geotechnical parameters. Within the cooperative project OnSITE - Online Seismic Imaging System for Tunnel Excavation - a new seismic source is in development. The design of the seismic source takes into account the special requirements for such an application: high signal frequency (up to several kHz) to obtain resolution in the order of few meters (1-2 m), generation of repeatable signals at short time intervals to implement a large measuring point density, and a high signal/noise ratio. In the first step, two magnetostrictive actuators in similar fashion - custom-made by ETREMA Products, Inc. (USA) - were used for a cascaded seismic vibration source system. The bandwidth of the pilot signal for this vibration source system covers the range from 300 Hz up to 6 kHz. After principally testing the source system in the research and teaching mine Reiche Zeche in Freiberg (Germany), further field measurements at this test site showed a high-grade signal repeatability for frequencies above 600 Hz for the head signal and good signal repeatability in the near field (Hock et al. 2008). To avoid 1) feedback effects between vibrator and medium - causing resonance at certain frequencies, e.g. around 3000 Hz and around 5500 Hz - and 2) unwanted phase shifts between the two vibrator signals at frequencies above 3000 Hz, an signal excitation with an open loop control for amplitude and phase is necessary in combination with only one real-time processor for controlling both actuators. In a second step, a source system was constructed consisting of 2 nearly identical (90%) actuators - again custom-made by ETREMA Products, Inc. (USA) - which are approximately one third lighter than the actuators in the first prototype. This new prototype was applied for the first time during a seismic survey in the Piora adit (above the Gotthard base tunnel near Faido, CH) in November 2008 with success

  11. EDITORIAL: Materially speaking!

    NASA Astrophysics Data System (ADS)

    Cornwall, Malcolm G.

    1997-05-01

    areas of physics-based science and technology. Can materials science be made intellectually more exciting and mind-stretching for our students? In this special issue we present several articles by researchers in less-than-familiar but important areas of materials science and technology. Following a review by Mathew Philip of some of the basic atomic theory which underlies materials science, Jose Silva looks at how artificial diamonds can be made and at how we can apply this exotic material (other than on fingers and around necks). Alan Piercy reviews the field of giant magnetostrictive materials, which, when magnetized, change dimensions hundreds or even thousands of times more than traditional ferromagnetics. David Pettifor provides a nicely interdisciplinary overview of how computer simulations, from the subatomic to the macroscopic level, can be used to help in the design of new materials for such things as turbine blades. Adrian Rennie offers a much-requested written version of the entertaining 1995/6 IOP Schools Lecture on the physics of polymers. (We had hoped to include an article by Professor Colin Gough of Birmingham University on High Temperatue Superconductors, but for technical reasons this has had to be postponed until a future issue.) Finally, there are two articles describing an initiative which will have a direct practical impact on the teaching and learning of `Materials' in the UK. Karen Davies describes the exciting new Materials Gallery due to be opened at the Science Museum as this issue goes to press in May 1997 (no coincidence!), and David Sang provides details of how the new gallery has been linked directly with the GNVQ curriculum, and can certainly be exploited more widely in our physics and technology teaching. Perhaps this can help provide the missing 'zing' that materials science at present seems to lack.

  12. The Giant Cell.

    ERIC Educational Resources Information Center

    Stockdale, Dennis

    1998-01-01

    Provides directions for the construction of giant plastic cells, including details for building and installing the organelles. Also contains instructions for preparing the ribosomes, nucleolus, nucleus, and mitochondria. (DDR)

  13. The Next Giant Step

    NASA Video Gallery

    Artist Robert McCall painted "The Next Giant Step" in 1979 to commemorate the heroism and courage of spaceflight pioneers. Located in the lobby of Johnson's building 2, the mural depicts America's ...

  14. Spontaneous symmetry breaking of magnetostriction in metals with multivalley band structure

    NASA Astrophysics Data System (ADS)

    Mikitik, G. P.; Sharlai, Yu. V.

    2015-02-01

    We show that a first-order phase transition can take place in a metal in a strong magnetic field if an electron Landau level approaches the Fermi energy of the metal. This transition is due to the electron-phonon interaction and is characterized by a jump in magnetostriction of the metal. If there are several equivalent groups of charge carriers in the metal, a spontaneous symmetry breaking of the magnetostriction can occur when the Landau level crosses the Fermi energy, and this breaking manifests itself as a series of the structural phase transitions that change a crystal symmetry of the metal. With these results, we discuss unusual findings recently discovered in bismuth.

  15. Magnetic, magnetostrictive and structural properties of iron-cobalt/silver multilayers

    NASA Astrophysics Data System (ADS)

    Lafford, T. A.; Gibbs, M. R. J.; Shearwood, C.

    1994-04-01

    Magnetic and magnetostrictive measurements have been carried out on FeCo/Ag multilayers using a dc magnetometer and the SAMR method, respectively. The samples were deposited by rf magnetron sputtering onto 26 μm polyimide substrates, half of each multilayer being deposited on each side. The Ag thickness was maintained at 2 nm while tFeCo was varied between 2 and 12 nm. The coercivity of the multilayers was much reduced by the presence of Ag from that observed in a homogeneous FeCo film. Magnetostriction values were also altered from those expected from bulk polycrystalline FeCo alloy. X-ray diffraction analysis indicates that the FeCo layers form a bcc structure with no strong crystallographic orientation. It is likely that the Ag layers are not continuous.

  16. Thermal expansion and magnetostriction measurements using a high sensitive capacitive dilatometer at millikelvin temperatures

    NASA Astrophysics Data System (ADS)

    Inoue, Daiki; Kaido, Daisuke; Yoshikawa, Yuta; Minegishi, Mitsuyuki; Matsumoto, Koichi; Abe, Satoshi

    2014-12-01

    We have developed a dilatometric measuring system for thermal expansion and magnetostriction, those are more singular than specific heat in approaching to a quantum critical point. With decreasing temperature, thermal expansion becomes small in proportional to the square of temperature, thus, high sensitivity and reproducibility are necessary for the dilatometric measurements in millikelvin temperatures. Our dilatometer composed of the sample and the reference capacitor provides the extremely high resolution of ΔL/L ~ 10-10 using the ratio-transformer-based capacitance bridge. The dilatometer was installed on the 3He-4He dilution refrigerator with the 9 T superconducting magnet, and temperature was measured by the 3He melting curve thermometer. We have measured thermal expansion and magnetostriction of the typical heavy fermion compound CeRu2Si2 along a-axis at temperature down to 10 mK in magnetic fields up to 9 T.

  17. Temperature and stress dependences of the magnetostriction in ternary and quaternary Terfenol alloys

    NASA Astrophysics Data System (ADS)

    Restorff, J. B.; Wun-Fogle, M.; Clark, A. E.

    2000-05-01

    The magnetization and magnetostriction of a variety of Laves phase rods of TbxDyyHo1-x-yFe1.95 grown in the form of [112] oriented dendritic platelets were measured as a function of magnetic field H(-2200magnetostriction. Sample compositions were chosen both along a line of minimum near room-temperature anisotropy (Tb0.3Dy0.7Fe1.95-Tb0.20Dy0.22Ho0.58Fe1.95) and at Ho0.15 and Ho0.30 across the line.

  18. Passive compensation of the thermal drift of magnetostriction based Q-switched fiber lasers

    NASA Astrophysics Data System (ADS)

    Pérez-Millán, P.; Díez, A.; Cruz, J. L.; Andrés, M. V.

    2009-02-01

    The authors propose and demonstrate a method to compensate the thermal drift of magnetostriction based Q-switched fiber lasers, which is caused by the eddy currents induced in the Terfenol-D magnetostrictive actuators. The consequent wavelength detuning between the fiber gratings of the laser is passively compensated by the use of Monel 400 as thermal actuator of the non-modulated grating. A highly stable pulsed signal is achieved in the range of 1 Hz-5 kHz, with a wavelength detuning between gratings maintained below 10 pm. Furthermore, an optimization of the use of the pump power is proposed, utilizing part of it for simultaneously pumping a fiber optic based amplification stage.

  19. Phage-based magnetostrictive-acoustic microbiosensors for detecting bacillus anthracis spores

    NASA Astrophysics Data System (ADS)

    Wan, J.; Yang, H.; Lakshmanan, R. S.; Guntupalli, R.; Huang, S.; Hu, J.; Petrenko, V. A.; Chin, B. A.

    2006-05-01

    Magnetostrictive particles (MSPs) as biosensor platform have been developed recently. The principle of MSPs as sensor platform is the same as that of other acoustic wave devices, such as quartz crystal microbalance. In this paper, the fabrication, characterization and performance of phage-based MSP biosensors for detecting Bacillus anthracis spores are reported. A commercially available magnetostrictive alloy was utilized to fabricate the sensor platform. The phage was immobilized onto the MSPs using physical adsorption technology. The following performance of the phage-based MSP sensors will be presented: sensitivity, response time, longevity, specificity and binding efficacy. The performance of the sensors at static and dynamic conditions was characterized. The experimental results are confirmed by microscopy photographs. The excellent performance including high sensitivity and rapid response is demonstrated. More importantly, it is experimentally found that the phage-based MSP sensors have a much better longevity than antibody-based sensors.

  20. Giant eruptions of very massive stars

    NASA Astrophysics Data System (ADS)

    Davidson, Kris

    2016-07-01

    Giant eruptions or supernova-impostor events are far more mysterious than true supernovae. An extreme example can release as much radiative energy as a SN, ejecting several Mʘ of material. These events involve continuous radiation-driven outflows rather than blast waves. They constitute one of the main unsolved problems in stellar astrophysics, but have received little theoretical attention. The most notorious giant-eruption survivor, ƞ Carinae, is amazingly close to us for such a rare event. It offers a wealth of observational clues, many of them quite unexpected in terms of simple theory.

  1. Finite element model-simulation-based characterization of a magnetostrictive gyrosensor

    SciTech Connect

    Marschner, U.; Graham, F.; Yoo, J.-H.; Flatau, A. B.; Mudivarthi, C.; Neubert, H.

    2010-05-15

    This paper analyzes a prototype microgyrosensor that employs the magnetostrictive alloy Galfenol for transduction of Coriolis-induced forces into an electrical output for quantifying a given angular velocity. The magnetic induction distribution in the Galfenol sensor patch depends on its bending shape and magnetoelastic properties and is investigated using a finite element model. Fluctuations in magnetic induction caused by a sinusoidal rotation of the sensor produce an amplitude modulated voltage in a surrounding coil which is simulated and measured.

  2. Magnetostrictive and piezomagnetic properties of Tb1-xDyxZn at low temperatures

    NASA Astrophysics Data System (ADS)

    Wun-Fogle, Marilyn; Restorff, James B.; Clark, Arthur E.; Cullen, James B.; Lograsso, Thomas A.

    2001-07-01

    Tb1-xDyxZn(0magnetostrictive alloys based up on the anisotropic 4f electron shell of rare elements, such as Tb, Dy, and Sm. The interaction of the oblate 4f electron distribution of Tb and Dy with nearest neighbor ions in these alloys is the source of a huge magnetic anisotropy and high ( 1%) positive magnetostriction. (Alternatively, the prolate shape of the Sm 4f shell gives rise to very large negative magnetostrictions.) Surprisingly, in all measurements to date, the high magnetic anisotropies are independent of crystal structure. Notably, Tb1-xDyx alloys exist in the hexagonal phase, with the c-axis extremely hard, whereas for Tb1-xDyxFe2, a cubic Laves phase alloy, very hard <111> axes can be changed to very hard <100> axes by increasing x from 0 to 1. (In fact, the existence of a near zero magnetic anisotropy by the proper choice of x is the origin of the well-known Terfenol-D alloys, Tb1-xDyxFe2). The Tb$1-x)DyxZn system discussed here is particularly attractive because of the simplicity of its crystal structure (CsCl), its relatively high Curie temperatures (for rare earth alloys), and the existence of a large (uv0) phase for T < 50K. A summary of some of the important properties of these three alloy systems is given in Table I. In all these systems, at least one of the magnetostriction constraints is very large.

  3. A Magnetic Flux Leakage and Magnetostrictive Guided Wave Hybrid Transducer for Detecting Bridge Cables

    PubMed Central

    Xu, Jiang; Wu, Xinjun; Cheng, Cheng; Ben, Anran

    2012-01-01

    Condition assessment of cables has gained considerable attention for the bridge safety. A magnetic flux leakage and magnetostrictive guided wave hybrid transducer is provided to inspect bridge cables. The similarities and differences between the two methods are investigated. The hybrid transducer for bridge cables consists of an aluminum framework, climbing modules, embedded magnetizers and a ribbon coil. The static axial magnetic field provided by the magnetizers meets the needs of the magnetic flux leakage testing and the magnetostrictive guided wave testing. The magnetizers also provide the attraction for the climbing modules. In the magnetic flux leakage testing for the free length of cable, the coil induces the axial leakage magnetic field. In the magnetostrictive guided wave testing for the anchorage zone, the coil provides a pulse high power variational magnetic field for generating guided waves; the coil induces the magnetic field variation for receiving guided waves. The experimental results show that the transducer with the corresponding inspection system could be applied to detect the broken wires in the free length and in the anchorage zone of bridge cables. PMID:22368483

  4. A magnetic flux leakage and magnetostrictive guided wave hybrid transducer for detecting bridge cables.

    PubMed

    Xu, Jiang; Wu, Xinjun; Cheng, Cheng; Ben, Anran

    2012-01-01

    Condition assessment of cables has gained considerable attention for the bridge safety. A magnetic flux leakage and magnetostrictive guided wave hybrid transducer is provided to inspect bridge cables. The similarities and differences between the two methods are investigated. The hybrid transducer for bridge cables consists of an aluminum framework, climbing modules, embedded magnetizers and a ribbon coil. The static axial magnetic field provided by the magnetizers meets the needs of the magnetic flux leakage testing and the magnetostrictive guided wave testing. The magnetizers also provide the attraction for the climbing modules. In the magnetic flux leakage testing for the free length of cable, the coil induces the axial leakage magnetic field. In the magnetostrictive guided wave testing for the anchorage zone, the coil provides a pulse high power variational magnetic field for generating guided waves; the coil induces the magnetic field variation for receiving guided waves. The experimental results show that the transducer with the corresponding inspection system could be applied to detect the broken wires in the free length and in the anchorage zone of bridge cables. PMID:22368483

  5. Global Goss grain growth and grain boundary characteristics in magnetostrictive Galfenol sheets

    NASA Astrophysics Data System (ADS)

    Na, S. M.; Flatau, A. B.

    2013-12-01

    Single Goss grains were globally grown in magnetostrictive Galfenol thin sheets via an abnormal grain growth (AGG) process. The sample behaves like single crystal Galfenol, exhibiting large magnetostriction along the <100> axes. Small variations in surface energy conditions, which were governed by different flow rates of 0.5% H2S gas in argon during annealing, had a significant impact of the development of AGG. AGG with a fully developed Goss (011) grain over 95% of the sample surface is very reproducible and feasible for a broad range of annealing conditions. In addition, the <100> orientation of the single-crystal-like Galfenol sheet aligns exactly with the rolling direction, and produces magnetostriction values of ˜300 ppm. AGG often produces isolated grains inside Goss grains due to anisotropic properties of grain boundaries. To better understand island formation mechanisms, grain orientation and grain boundary characteristics of island grains in Goss-oriented Galfenol thin sheets were also investigated. We examined samples annealed either under an argon atmosphere or under a sulfur atmosphere, and characterized the observed island grain boundaries in terms of grain misorientation angles. Trends in measured and simulated data on misorientation angles indicate that the presence of (001) island grain boundaries with angles higher than 45° can be explained by the high energy grain boundary (HEGB) model, whereas (111) boundaries with intermediate angles (20°-45°) cannot. The role of low energy coincident site lattice (CSL) boundaries on AGG in both annealing cases was found to be negligible.

  6. Electrodeposition of high magnetostrictive cobalt-iron alloy films for smart tags and sensor applications

    SciTech Connect

    Pillars, Jamin Ryan

    2015-12-01

    Magnetostrictive CoFe films were investigated for use as magnetoelastic tags or sensors. The ability to electrodeposit these films enables batch fabrication processes to pattern a variety of geometries while controlling the film stoichiometry and crystallography. In current research looking at CoFe, improved magnetostriction was achieved using a co-sputtering, annealing, and quenching method1. Other current research has reported electrodeposited CoFe films using a sulfate based chemistry resulting in film compositions that are Fe rich in the range of Co0.3-0.4Fe0.7-0.6 and have problems of codeposition of undesirables that can have a negative impact on magnetic properties. The research presented here focused on maximizing magnetostriction at the optimal stoichiometry range of Co0.7-0.75Fe0.3-0.25, targeting the (fcc+bcc)/bcc phase boundary, and using a novel chemistry and plating parameters to deposit films without being limited to “line of sight” deposition.

  7. Enhanced off-resonance magnetoelectric response in laser annealed PZT thick film grown on magnetostrictive amorphous metal substrate

    NASA Astrophysics Data System (ADS)

    Palneedi, Haribabu; Maurya, Deepam; Kim, Gi-Yeop; Priya, Shashank; Kang, Suk-Joong L.; Kim, Kwang-Ho; Choi, Si-Young; Ryu, Jungho

    2015-07-01

    A highly dense, 4 μm-thick Pb(Zr,Ti)O3 (PZT) film is deposited on amorphous magnetostrictive Metglas foil (FeBSi) by granule spray in vacuum process at room temperature, followed by its localized annealing with a continuous-wave 560 nm ytterbium fiber laser radiation. This longer-wavelength laser radiation is able to anneal the whole of thick PZT film layer without any deteriorative effects, such as chemical reaction and/or atomic diffusion, at the interface and crystallization of amorphous Metglas substrate. Greatly enhanced dielectric and ferroelectric properties of the annealed PZT are attributed to its better crystallinity and grain growth induced by laser irradiation. As a result, a colossal off-resonance magnetoelectric (ME) voltage coefficient that is two orders of magnitude larger than previously reported output from PZT/Metglas film-composites is achieved. The present work addresses the problems involved in the fabrication of PZT/Metglas film-composites and opens up emerging possibilities in employing piezoelectric materials with low thermal budget substrates (suitable for integrated electronics) and designing laminate composites for ME based devices.

  8. Enhanced off-resonance magnetoelectric response in laser annealed PZT thick film grown on magnetostrictive amorphous metal substrate

    SciTech Connect

    Palneedi, Haribabu; Maurya, Deepam; Priya, Shashank; Kim, Gi-Yeop; Choi, Si-Young; Kang, Suk-Joong L.; Kim, Kwang-Ho; Ryu, Jungho

    2015-07-06

    A highly dense, 4 μm-thick Pb(Zr,Ti)O{sub 3} (PZT) film is deposited on amorphous magnetostrictive Metglas foil (FeBSi) by granule spray in vacuum process at room temperature, followed by its localized annealing with a continuous-wave 560 nm ytterbium fiber laser radiation. This longer-wavelength laser radiation is able to anneal the whole of thick PZT film layer without any deteriorative effects, such as chemical reaction and/or atomic diffusion, at the interface and crystallization of amorphous Metglas substrate. Greatly enhanced dielectric and ferroelectric properties of the annealed PZT are attributed to its better crystallinity and grain growth induced by laser irradiation. As a result, a colossal off-resonance magnetoelectric (ME) voltage coefficient that is two orders of magnitude larger than previously reported output from PZT/Metglas film-composites is achieved. The present work addresses the problems involved in the fabrication of PZT/Metglas film-composites and opens up emerging possibilities in employing piezoelectric materials with low thermal budget substrates (suitable for integrated electronics) and designing laminate composites for ME based devices.

  9. Giant congenital melanocytic nevus.

    PubMed

    Viana, Ana Carolina Leite; Gontijo, Bernardo; Bittencourt, Flávia Vasques

    2013-01-01

    Giant congenital melanocytic nevus is usually defined as a melanocytic lesion present at birth that will reach a diameter ≥ 20 cm in adulthood. Its incidence is estimated in <1:20,000 newborns. Despite its rarity, this lesion is important because it may associate with severe complications such as malignant melanoma, affect the central nervous system (neurocutaneous melanosis), and have major psychosocial impact on the patient and his family due to its unsightly appearance. Giant congenital melanocytic nevus generally presents as a brown lesion, with flat or mammilated surface, well-demarcated borders and hypertrichosis. Congenital melanocytic nevus is primarily a clinical diagnosis. However, congenital nevi are histologically distinguished from acquired nevi mainly by their larger size, the spread of the nevus cells to the deep layers of the skin and by their more varied architecture and morphology. Although giant congenital melanocytic nevus is recognized as a risk factor for the development of melanoma, the precise magnitude of this risk is still controversial. The estimated lifetime risk of developing melanoma varies from 5 to 10%. On account of these uncertainties and the size of the lesions, the management of giant congenital melanocytic nevus needs individualization. Treatment may include surgical and non-surgical procedures, psychological intervention and/or clinical follow-up, with special attention to changes in color, texture or on the surface of the lesion. The only absolute indication for surgery in giant congenital melanocytic nevus is the development of a malignant neoplasm on the lesion.

  10. Giant pop-ins and amorphization in germanium during indentation

    NASA Astrophysics Data System (ADS)

    Oliver, David J.; Bradby, Jodie E.; Williams, Jim S.; Swain, Michael V.; Munroe, Paul

    2007-02-01

    Sudden excursions of unusually large magnitude (>1 μm), "giant pop-ins," have been observed in the force-displacement curve for high load indentation of crystalline germanium (Ge). A range of techniques including Raman microspectroscopy, focused ion-beam cross sectioning, and transmission electron microscopy, are applied to study this phenomenon. Amorphous material is observed in residual indents following the giant pop-in. The giant pop-in is shown to be a material removal event, triggered by the development of shallow lateral cracks adjacent to the indent. Enhanced depth recovery, or "elbowing," observed in the force-displacement curve following the giant pop-in is explained in terms of a compliant response of plates of material around the indent detached by lateral cracking. The possible causes of amorphization are discussed, and the implications in light of earlier indentation studies of Ge are considered.

  11. Magnetostriction and thermal expansion of the Kondo semiconductor Ce{sub 3}Bi{sub 4}Pt{sub 3}

    SciTech Connect

    Hundley, M.F.; Neumeier, J.J.; Thompson, J.D.; Lacerda, A.; Canfield, P.C.

    1995-05-01

    We report dilatometric thermal expansion ({alpha}) and magnetostriction ({lambda}) measurements on the Kondo semiconductor Ce{sub 3}Bi{sub 4}Pt{sub 3} and its non-magnetic analog La{sub 3}Bi{sub 4}Pt{sub 3} in fields to 100 kOe. The magnetic contribution to the thermal expansion of Ce{sub 3}Bi{sub 4}Pt{sub 3} displays a broad maximum centered at 50 K, close to the temperature where the 4f specific heat is a maximum. The linear magnetostriction is anomalously large in Ce{sub 3}Bi{sub 4}Pt{sub 3}, with values that are characteristic of mixed-valent compounds ({lambda}{sub {perpendicular}} = 3.26x10{sup {minus}5}, {lambda}{sub {parallel}} = -6.24x10{sup {minus}5} in 100 kOe at 4 K). The volume magnetostriction is positive and a factor of ten smaller than the linear coefficients ({lambda}{sub V} = 2.75x10{sup {minus}6} in 100 kOe at 4 K). The volume magnetostriction is temperature-dependent, and peaks at 50 K. The data are considered in terms of a Grueneisen analysis that links the temperature-dependent magnetic susceptibility, thermal expansion, magnetostriction, bulk modulus, and specific heat of Ce{sub 3}Bi{sub 4}Pt{sub 3} via temperature-dependent electronic and magnetic scaling parameters.

  12. CrAlN coating to enhance the power loss and magnetostriction in grain oriented electrical steel

    NASA Astrophysics Data System (ADS)

    Goel, Vishu; Anderson, Philip; Hall, Jeremy; Robinson, Fiona; Bohm, Siva

    2016-05-01

    Grain oriented electrical steels (GOES) are coated with aluminium orthophosphate on top of a forsterite (Mg2SiO4) layer to provide stress and insulation resistance to reduce the power loss and magnetostriction. In this work Chromium Aluminium Nitride (CrAlN) was coated on GOES samples with electron beam physical vapour deposition and was tested in the single strip and magnetostriction tester to measure the power loss and magnetostriction before and after coating. Power loss was reduced by 2% after coating and 6 % post annealing at 800 °C. For applied compressive stress of 6 MPa, the magnetostrictive strain was zero with the CrAlN coating as compared to 22 and 24 μɛ for fully finished GOES and GOES without phosphate coating. The thickness of the coating was found to be 1.9 ± 0.2 μm estimated with Glow Discharge Optical Emission Spectroscopy (GDOES). The magnetic domain imaging showed domain narrowing after coating. The reduction in power loss and magnetostriction was due to the large residual compressive stress and Young's modulus (270 GPa) of the coating.

  13. Anisotropic magnetostriction in a <110> oriented crystal Tb0.36Dy0.64(Fe0.85Co0.15)2 after coaxial field annealing

    NASA Astrophysics Data System (ADS)

    Zhang, Changsheng; Ma, Tianyu; Qi, Ruilei; Yan, Mi

    2010-08-01

    Axial magnetostriction of Terfenol-D oriented crystals is highly anisotropic when changing the magnetization direction. Magnetostrictions of a ⟨110⟩ oriented crystal Tb0.36Dy0.64(Fe0.85Co0.15)2 were investigated under magnetic fields with a series of angles θ to its axis. Totally different anisotropic magnetostrictive behaviors are observed after annealing under a coaxial field of 240 kA/m. The magnetostriction for the field annealed specimen seems unsaturated even under 640 kA/m for angles θ in the range from 0° to 55°. At these angles, magnetostriction "ascending" is observed during the final magnetization process, while magnetostriction "dropping" occurs at angles above 35° for the untreated crystal. With the increase in angle θ, the corresponding field where magnetostriction starts dropping decreases for the untreated crystal, while the field at which magnetostriction starts ascending increases for the field annealed one. A simplified model based on moment "jump" and "rotation" is proposed to explain such anisotropic behaviors.

  14. Stress-anneal-induced magnetic anisotropy in highly textured Fe-Ga and Fe-Al magnetostrictive strips for bending-mode vibrational energy harvesters

    NASA Astrophysics Data System (ADS)

    Park, Jung Jin; Na, Suok-Min; Raghunath, Ganesh; Flatau, Alison B.

    2016-05-01

    Magnetostrictive Fe-Ga and Fe-Al alloys are promising materials for use in bending-mode vibrational energy harvesters. For this study, 50.8 mm × 5.0 mm × 0.5 mm strips of Fe-Ga and Fe-Al were cut from 0.50-mm thick rolled sheet. An atmospheric anneal was used to develop a Goss texture through an abnormal grain growth process. The anneal lead to large (011) grains that covered over 90% of sample surface area. The resulting highly-textured Fe-Ga and Fe-Al strips exhibited saturation magnetostriction values (λsat = λ∥ - λ⊥) of ˜280 ppm and ˜130 ppm, respectively. To maximize 90° rotation of magnetic moments during bending of the strips, we employed compressive stress annealing (SA). Samples were heated to 500°C, and a 100-150 MPa compressive stress was applied while at 500°C for 30 minutes and while being cooled. The effectiveness of the SA on magnetic moment rotation was inferred by comparing post-SA magnetostriction with the maximum possible yield of rotated magnetic moments, which is achieved when λ∥ = λsat and λ⊥ = 0. The uniformity of the SA along the sample length and the impact of the SA on sensing/energy harvesting performance were then assessed by comparing pre- and post-SA bending-stress-induced changes in magnetization at five different locations along the samples. The SA process with a 150 MPa compressive load improved Fe-Ga actuation along the sample length from 170 to 225 ppm (from ˜60% to within ˜80% of λsat). The corresponding sensing/energy harvesting performance improved by as much as a factor of eight in the best sample, however the improvement was not at all uniform along the sample length. The SA process with a 100 MPa compressive load improved Fe-Al actuation along the sample length from 60 to 73 ppm (from ˜46% to ˜56% of λsat, indicating only a marginally effective SA and suggesting the need for modification of the SA protocol. In spite of this, the SA was effective at improving the sensing/energy harvesting

  15. Giant colon diverticulum.

    PubMed

    Chater, C; Saudemont, A; Zerbib, P

    2015-11-01

    Giant colonic diverticulum is defined by a diverticulum whose diameter is greater than 4 cm. This is a rare entity, arising mainly in the sigmoid colon. The diagnosis is based on abdominal computed tomography that shows a gas-filled structure communicating with the adjacent colon, with a smooth, thin diverticular wall that does not enhance after injection of contrast. Surgical treatment is recommended even in asymptomatic diverticula, due to the high prevalence and severity of complications. The gold standard treatment is segmental colectomy. Some authors propose a diverticulectomy when the giant diverticulum is unique.

  16. Electronic origin of the negligible magnetostriction of an electric steel Fe1-xSix alloy: A density-functional study

    NASA Astrophysics Data System (ADS)

    Odkhuu, Dorj; Seok Yun, Won; Cheol Hong, Soon

    2012-03-01

    To understand the negligible magnetostriction of Fe-Si alloys used as cores in electric transformers or motors, density-functional calculations were performed on the tetragonal magnetostriction coefficient, λ001, of Fe1-xSix (x ≤ 0.25) alloys as a function of x using the highly precise all-electron full-potential linearized augmented plane-wave method. It was found that the calculated magnetostriction coefficients closely reproduced experimental trends and the negligible magnetostriction near x = 0.111 originated from the mixed phases of A2, B2, and D03; each different atomic type of Fe of Fe0.889Si0.111 has a small and opposite contribution to the magnetostriction.

  17. Warm Disks from Giant Impacts

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-10-01

    In the process of searching for exoplanetary systems, weve discovered tens of debris disks close around distant stars that are especially bright in infrared wavelengths. New research suggests that we might be looking at the late stages of terrestrial planet formation in these systems.Forming Terrestrial PlanetsAccording to the widely-accepted formation model for our solar-system, protoplanets the size of Mars formed within a protoplanetary disk around our Sun. Eventually, the depletion of the gas in the disk led the orbits of these protoplanets to become chaotically unstable. Finally, in the giant impact stage, many of the protoplanets collided with each other ultimately leading to the formation of the terrestrial planets and their moons as we know them today.If giant impact stages occur in exoplanetary systems, too leading to the formation of terrestrial exoplanets how would we detect this process? According to a study led by Hidenori Genda of the Tokyo Institute of Technology, we might be already be witnessing this stage in observations of warm debris disks around other stars. To test this, Genda and collaborators model giant impact stages and determine what we would expect to see from a system undergoing this violent evolution.Modeling CollisionsSnapshots of a giant impact in one of the authors simulations. The collision causes roughly 0.05 Earth masses of protoplanetary material to be ejected from the system. Click for a closer look! [Genda et al. 2015]The collaborators run a series of simulations evolving protoplanetary bodies in a solar system. The simulations begin 10 Myr into the lifetime of the solar system, i.e., after the gas from the protoplanetary disk has had time to be cleared and the protoplanetary orbits begin to destabilize. The simulations end when the protoplanets are done smashing into each other and have again settled into stable orbits, typically after ~100 Myr.The authors find that, over an average giant impact stage, the total amount of

  18. Influence of aging and thermomechanical cycling on the magnetostriction and magnetic shape memory effect in martensitic alloy

    NASA Astrophysics Data System (ADS)

    L'vov, Victor A.; Kosogor, Anna; Barandiaran, Jose M.; Chernenko, Volodymyr A.

    2015-10-01

    An influence of internal stress created by the crystal defects on the magnetically induced reorientation (MIR) of martensite variants in the ferromagnetic shape memory alloy (FSMA) has been analyzed. Using the internal stress conception, a noticeable influence of the spatial reconfiguration of crystal defects on the ordinary magnetostriction of FSMA and magnetic shape memory (MSM) effect has been predicted. It has been shown that the defect reconfiguration, which stabilizes the martensitic phase during martensite aging, increases the shear elastic modulus. The increase of shear modulus reduces the magnetostriction value and in this way suppresses the MSM effect. The magneto-thermo-mechanical training of aged alloys destabilizes the martensitic phase, restores the initial magnetostriction value, and promotes the MSM effect.

  19. Spontaneous volume magnetostriction and non-Stoner behavior of the valence band in pure hcp Gd

    NASA Astrophysics Data System (ADS)

    Khmelevskyi, S.; Turek, I.; Mohn, P.

    2004-10-01

    Employing the disordered local moment formalism in combination with first-principles band-structure calculations, we study the behavior of the valence band in pure hcp Gd upon disorder of the local 4f GD moments. We show that the large value of the spontaneous volume magnetostriction in Gd is entirely due to changes in the magnetic state of the valence band at Tc and can be calculated in good agreement with experiment. The local exchange splitting of the valence band persists above Tc , which is in strong disagreement with the conventional Stoner picture. The analysis of our results provides a theoretical background for the discussion of recent photoemission experiments.

  20. High resolution magnetostriction measurements in pulsed magnetic fields using fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Daou, Ramzy; Weickert, Franziska; Nicklas, Michael; Steglich, Frank; Haase, Ariane; Doerr, Mathias

    2010-03-01

    We report on a new high resolution apparatus for measuring magnetostriction suitable for use at cryogenic temperatures in pulsed high magnetic fields which we have developed at the Hochfeld-Magnetlabor Dresden. Optical fiber strain gauges based on fiber Bragg gratings are used to measure the strain in small (˜1 mm) samples. We describe the implementation of a fast measurement system capable of resolving strains in the order of 10-7 with a full bandwidth of 47 kHz, and demonstrate its use on single crystal samples of GdSb and GdSi.

  1. Synchrotron Diffraction Studies of Spontaneous Magnetostriction in Rare Earth Transition Metal Compounds

    SciTech Connect

    Ning Yang

    2004-12-19

    Thermal expansion anomalies of R{sub 2}Fe{sub 14}B and R{sub 2}Fe{sub 17}C{sub x} (x = 0,2) (R = Y, Nd, Gd, Tb, Er) stoichiometric compounds are studied with high-energy synchrotron X-ray powder diffraction using Debye-Schemer geometry in temperature range 10K to 1000K. Large spontaneous magnetostriction up to their Curie temperatures (T{sub c}) is observed. The a-axes show relatively larger invar effects than c-axes in the R{sub 2}Fe{sub 14}B compounds whereas the R{sub 2}Fe{sub 17}C{sub x} show the contrary anisotropies. The iron sub-lattice is shown to dominate the spontaneous magnetostriction of the compounds. The contribution of the rare earth sublattice is roughly proportional to the spin magnetic moment of the rare earth in the R{sub 2}Fe{sub 14}B compounds but in R{sub 2}Fe{sub 17}C{sub x}, the rare earth sub-lattice contribution appears more likely to be dominated by the local bonding. The calculation of spontaneous magnetostrain of bonds shows that the bonds associated with Fe(j2) sites in R{sub 2}Fe{sub 14}B and the dumbbell sites in R{sub 2}Fe{sub 17}C{sub x} have larger values, which is strongly related to their largest magnetic moment and Wigner-Seitz atomic cell volume. The roles of the carbon atoms in increasing the Curie temperatures of the R{sub 2}Fe{sub 17} compounds are attributed to the increased separation of Fe hexagons. The R{sub 2}Fe{sub 17} and R{sub 2}Fe{sub 14}B phases with magnetic rare earth ions also show anisotropies of thermal expansion above T{sub c}. For R{sub 2}Fe{sub 17} and R{sub 2}Fe{sub 14}B the a{sub a}/a{sub c} > 1 whereas the anisotropy is reversed with the interstitial carbon in R{sub 2}Fe{sub 17}. The average bond magnetostrain is shown to be a possible predictor of the magnetic moment of Fe sites in the compounds. Both of the theoretical and phenomenological models on spontaneous magnetostriction are discussed and a Landau model on the spontaneous magnetostriction is proposed.

  2. Giant intrathyroidal parathyroid adenoma

    PubMed Central

    Vilallonga, Ramon; Zafón, Carlos; Migone, Raul; Baena, Juan Antonio

    2012-01-01

    Primary hyperparathyroidism (PHPT) is not an uncommon endocrine disorder. However, acute primary hyperparathyroidism, or parathyroid crisis (PC), is a rare clinical entity characterized by life-threatening hypercalcemia of a sudden onset in patients with PHPT. We describe a patient with PC who presented with acute worsening of depressive symptoms, nausea and vomiting, and required emergency surgery. Serum calcium, alkaline phosphatase, and parathyroid hormone were elevated and serum phosphorus was low. An emergency hemithyroidectomy was performed because of none medical control of hypercalcemia. A giant intrathyroidal parathyroid adenoma was diagnosed. PHTP can be a life-threatening situation for patients, requiring immediate surgical treatment. A giant intrathyroidal parathyroid adenoma is an uncommon cause of PC. PMID:22787355

  3. Giant cell arteritis

    PubMed Central

    Calvo-Romero, J

    2003-01-01

    Giant cell arteritis (GCA), temporal arteritis or Horton's arteritis, is a systemic vasculitis which involves large and medium sized vessels, especially the extracranial branches of the carotid arteries, in persons usually older than 50 years. Permanent visual loss, ischaemic strokes, and thoracic and abdominal aortic aneurysms are feared complications of GCA. The treatment consists of high dose steroids. Mortality, with a correct treatment, in patients with GCA seems to be similar that of controls. PMID:13679546

  4. Giant thymic carcinoid.

    PubMed

    John, L C; Hornick, P; Lang, S; Wallis, J; Edmondson, S J

    1991-05-01

    Thymic carcinoid is a rare tumour. It may present with ectopic endocrine secretion or with symptoms of compression as a result of its size. A case is reported which presented with symptoms of compression where the size of the tumour was uniquely large such as to warrant the term giant thymic carcinoid. The typical histological features are described, together with its possible origin and its likely prognosis.

  5. Ice Giant Exploration

    NASA Astrophysics Data System (ADS)

    Rymer, A. M.; Arridge, C. S.; Masters, A.; Turtle, E. P.; Simon, A. A.; Hofstadter, M. D.; Turrini, D.; Politi, R.

    2015-12-01

    The Ice Giants in our solar system, Uranus and Neptune, are fundamentally different from their Gas Giant siblings Jupiter and Saturn, from the different proportions of rock and ice to the configuration of their planetary magnetic fields. Kepler space telescope discoveries of exo-planets indicate that planets of this type are among the most ubiquitous universally and therefore a future mission to explore the nature of the Ice Giants in our own solar system will provide insights into the nature of extra-solar system objects in general. Uranus has the smallest self- luminosity of all the planets, potentially related to catastrophic events early in the planet's history, which also may explain Uranus' large obliquity. Uranus' atmosphere is subject to extreme seasonal forcing making it unique in the Solar System. Neptune is also unique in a number of ways, notably its large moon Triton which is likely a captured Kuiper Belt Object and one of only two moons in the solar system with a robustly collisional atmosphere. Similar to Uranus, the angle between the solar wind and the magnetic dipole axis is subject to large-amplitude variations on both diurnal and seasonal timescales, but peculiarly it has one of the quietest magnetospheres of the solar system, at least according to Voyager 2, the only spacecraft to encounter Neptune to date. A comprehensive mission, as advocated in the Decadal Survey, would provide enormous science return but is also challenging and expensive. In this presentation we will discuss mission scenarios and suggest how collaboration between disciplines and internationally can help us to pursue a mission that includes Ice Giant exploration.

  6. Optical properties of the giant dielectric material CaCu_3Ti_4O_12 and CdCu_3Ti_4O_12 \\unboldmath

    NASA Astrophysics Data System (ADS)

    Homes, Christopher

    2002-03-01

    The cubic perovskite-related oxide CaCu_3Ti_4O_12 has one of the largest dielectric constants at room temperature ever measured, ɛ_0~= 80 000, [ɛ_0≈ ɛ_1(ω arrow 0)]; ɛ0 drops by a factor of 1000 below about 100 K to ɛ_0~= 100, but curiously no change in the crystallographic structure is observed. The substitution of Cd for Ca results in a much lower value for the dielectric constant of ɛ_0~= 500, but the same general temperature dependence. The temperature-dependent reflectance of CaCu_3Ti_4O_12 and CdCu_3Ti_4O_12 has been measured over a wide frequency range, and the real and imaginary parts of the complex dielectric function were calculated from a Kramers-Kronig analysis. The optical properties are dominated by the unscreened lattice modes. There are a total of 11 infrared-active Tu modes expected; all 11 modes are observed in the CdCu_3Ti_4O_12 material, but only 10 are found in CaCu_3Ti_4O_12; the mode at ≈ 480 cm-1 is absent. The low frequency mode at ≈ 120 cm-1 in CaCu_3Ti_4O_12 shows an anomalous increase in oscillator strength at low temperature, in violation of the f-sum rule.(C.C. Homes et al.), Science 293, 673 (2001). The same behavior is found, although to a lesser extent, in the Cd material. A normal coordinate analysis of the vibrational modes indicates that the low-frequency mode involves primarily the Ca(Cd) atoms, as well as the Cu-O sublattice. The increase in strength of this mode is an indication that this bonding is becoming more ionic, implying that there is a redistribution of charge on this sublattice at low temperature. This suggests that the electric fields responsible for the large value of ɛ0 may originate not from the TiO6 octahedra, as is often seen in ferroelectrics, but from the Ca/Cu-O sublattice. A possible mechanism for the reduction of ɛ0 at low temperature will be discussed in light of recent high-resolution structural studies.

  7. Influence of volume magnetostriction on the thermodynamic properties of Ni-Mn-Ga shape memory alloys

    NASA Astrophysics Data System (ADS)

    Kosogor, Anna; L'vov, Victor A.; Cesari, Eduard

    2015-10-01

    In the present article, the thermodynamic properties of Ni-Mn-Ga ferromagnetic shape memory alloys exhibiting the martensitic transformations (MTs) above and below Curie temperature are compared. It is shown that when MT goes below Curie temperature, the elastic and thermal properties of alloy noticeably depend on magnetization value due to spontaneous volume magnetostriction. However, the separation of magnetic parts from the basic characteristics of MT is a difficult task, because the volume magnetostriction does not qualitatively change the transformational behaviour of alloy. This problem is solved for several Ni-Mn-Ga alloys by means of the quantitative theoretical analysis of experimental data obtained in the course of stress-strain tests. For each alloy, the entropy change and the transformation heat evolved in the course of MT are evaluated, first, from the results of stress-strain tests and, second, from differential scanning calorimetry data. For all alloys, a quantitative agreement between the values obtained in two different ways is observed. It is shown that the magnetic part of transformation heat exceeds the non-magnetic one for the Ni-Mn-Ga alloys undergoing MTs in ferromagnetic state, while the elevated values of transformation heat measured for the alloys undergoing MTs in paramagnetic state are caused by large MT strains.

  8. Influence of volume magnetostriction on the thermodynamic properties of Ni-Mn-Ga shape memory alloys

    SciTech Connect

    Kosogor, Anna; L'vov, Victor A.; Cesari, Eduard

    2015-10-07

    In the present article, the thermodynamic properties of Ni-Mn-Ga ferromagnetic shape memory alloys exhibiting the martensitic transformations (MTs) above and below Curie temperature are compared. It is shown that when MT goes below Curie temperature, the elastic and thermal properties of alloy noticeably depend on magnetization value due to spontaneous volume magnetostriction. However, the separation of magnetic parts from the basic characteristics of MT is a difficult task, because the volume magnetostriction does not qualitatively change the transformational behaviour of alloy. This problem is solved for several Ni-Mn-Ga alloys by means of the quantitative theoretical analysis of experimental data obtained in the course of stress-strain tests. For each alloy, the entropy change and the transformation heat evolved in the course of MT are evaluated, first, from the results of stress-strain tests and, second, from differential scanning calorimetry data. For all alloys, a quantitative agreement between the values obtained in two different ways is observed. It is shown that the magnetic part of transformation heat exceeds the non-magnetic one for the Ni-Mn-Ga alloys undergoing MTs in ferromagnetic state, while the elevated values of transformation heat measured for the alloys undergoing MTs in paramagnetic state are caused by large MT strains.

  9. High-pressure magnetostrictive pump development: a comparison of prototype and modeled performance

    NASA Astrophysics Data System (ADS)

    Bridger, Keith; Sewell, John M.; Cooke, Arthur V.; Lutian, Joseph L.; Kohlhafer, Dennis; Small, George E.; Kuhn, Philip M.

    2004-07-01

    Current efforts to extend the mission profile of Unmanned Aerial Vehicles (UAVs) have highlighted the need for scalable linear actuators. Typically, electrical power and control are specified for their high specific performance and ease of maintenance and replacement. Electro-Hydraulic Actuators (EHAs) provide the advantages of electrical power and control along with the proven reliability, robustness and graceful failure modes of hydraulic actuation. Current EHA technology, however, is not scalable to the degree required for projected UAVs and extension to other markets and applications. This paper will describe the measured and theoretical performance of a magnetostrictive hydraulic pump developed for one such EHA as part of the DARPA Compact Hybrid Actuator Program (CHAP). This work will focus on prototype pump designs utilizing a resonant magnetostrictive piston driver. The numerous design and operational parameters that have been tested and studied in an effort to produce an optimized pump design will be discussed. In particular, the measured and predicted performance of the resonant structure and fluidics will be compared and contrasted for several pump designs. The paper will also examine the interdependence of pump parameters and the balance required to produce a viable design with the required performance characteristics.

  10. Forced Volume Magnetostriction in Composite Gd5Si2Ge2

    SciTech Connect

    Choe, W; McCall, S K; Radousky, H B; Nersessian, N; Or, S W; Carman, G P; Pecharsky, V K; Pecharsky, A O

    2004-04-01

    A -1200 ppm forced volume magnetostriction has been obtained in a [0-3], resin binder, Gd{sub 5}Si{sub 2}Ge{sub 2} particulate composite. The strain is a result of a magnetically induced phase transformation from a high volume (high temperature, low magnetic field) monoclinic phase to a low volume (low temperature, high magnetic field) orthorhombic phase. The particles used in the composite were ball-milled from a bulk sample and were sieved to obtain a size distribution of {approx}> 600 {micro}m. Bulk Gd{sub 5}Si{sub 2}Ge{sub 2} was manufactured via arc melting and subsequently annealed at 1300 C for 1 hour to produce a textured, polycrystalline sample. The transformation temperatures of the bulk sample, as measured using a Differential Scanning Calorimeter (DSC), were M{sub s}= -9.3 C, M{sub f}=-14.6 C, A{sub s}=-4.4 C, and A{sub f}=-1.2 C. The composite and the bulk samples were magnetically characterized using a SQUID magnetometer, and found to undergo a paramagnetic to ferromagnetic transition during the phase transformation, consistent with published results. The bulk sample was also found to possess a maximum linear magnetostriction -2500 ppm.

  11. Technique for measurement of magnetostriction in an individual nanowire using atomic force microscopy

    SciTech Connect

    Jin Park, Jung Flatau, Alison B.; Estrine, Eliot C.; Madhukar Reddy, Sai; Stadler, Bethanie J. H.

    2014-05-07

    We have investigated a method for measuring the dimensions of an individual multilayered Fe-Ga/Cu nanowire (NW) as it changes with induced magnetization. In this study, we demonstrate the proposed approach and establish this as a viable method for measuring the magnetostrictive behavior of an individual Fe-Ga/Cu NW using atomic force microscopy (AFM). When an external magnetic field (∼300 Oe) was applied perpendicular to the NW axis, the NW length appeared minimized. When a field (∼1000 Oe) was applied parallel to the NW axis, the height profile of the NW was found to be higher than in the case with no parallel external field. Since both ends of the NW were welded to the substrate, the magnetic field induced dimensional change of the NW caused deflection of the NW in the upward direction, which was significant enough to be detected by AFM. An average height difference of 15 nm was measured with and without an applied field which was then used to calculate the magnetostriction of the multilayered NW.

  12. Shear-horizontal wave-based pipe damage inspection by arrays of segmented magnetostrictive patches.

    PubMed

    Kim, Hoe Woong; Kwon, Young Eui; Cho, Seung Hyun; Kim, Yoon Young

    2011-12-01

    The lowest-branch torsional guided wave is very effective in pipe damage inspection because of its non-dispersive characteristics, but it cannot be used for the simultaneous identification of axial and circumferential locations of a defect in a pipe. Motivated by recent developments in magnetostrictive transducer technology, which is especially efficient in torsional and shear wave generation, the goal of this investigation is to extend this technology for simultaneous identification of the axial and circumferential locations of cracks by using shear horizontal (SH) waves. Unlike the conventional magnetostrictive patch method using a single complete patch wound around the pipe's circumference, the proposed method segments the patch into several pieces to generate SH waves propagating over the pipe surface. Accordingly, SH waves in a pipe are generated and sensed individually by a meander coil placed separately on each segment. By using two sets of segmented-patch arrays separated by some distance, the cylindrical surface of a pipe can be inspected both axially and circumferentially. After the underlying angular profile of the patch segment is investigated, experiments identifying the axial and circumferential locations of multiple cracks in a pipe are carried out to demonstrate the potential of the proposed methodology.

  13. Spin-lattice coupling in uranium dioxide probed by magnetostriction measurements at high magnetic fields (P08358-E001-PF)

    SciTech Connect

    Gofryk, K.; Jaime, M.

    2014-12-01

    Our preliminary magnetostriction measurements have already shown a strong interplay of lattice dynamic and magnetism in both antiferromagnetic and paramagnetic states, and give unambiguous evidence of strong spin- phonon coupling in uranium dioxide. Further studies are planned to address the puzzling behavior of UO2 in magnetic and paramagnetic states and details of the spin-phonon coupling.

  14. Giant viruses in the environment: their origins and evolution.

    PubMed

    Yamada, Takashi

    2011-07-01

    The recent identification of giant viruses has raised important questions, not only regarding their origin and evolution, but also regarding the differentiation between viruses and living organisms. These viruses possess large genomes encoding genes potentially involved in various metabolic processes and even protein synthesis, indicating their putative autonomy. Giant viruses of the Phycodnaviridae and Mimiviridae families appear to share a common evolutionary ancestor with members of the nucleo-cytoplasmic large DNA viruses. Many giant viruses are associated with protists in aquatic environments and might have evolved in protist cells. They may therefore play important roles in material cycling in natural ecosystems. With the advent of environmental metagenomic projects, there will be more chances to encounter novel giant viruses in the future.

  15. Structure and magnetic properties of mechanically alloyed Tb{sub 0.7}Pr{sub 0.3}(Fe{sub 0.9}B{sub 0.1}){sub 1.93} and the magnetostriction of its epoxy composites

    SciTech Connect

    Liu, J.J.; Ren, W.J.; Zhao, X.G.; Liu, W.; Zhang, Z.D.

    2005-05-15

    The C15 Laves phase with composition Tb{sub 0.7}Pr{sub 0.3}(Fe{sub 0.9}B{sub 0.1}){sub 1.93} has been synthesized by mechanical alloying and subsequent annealing process. The structure and magnetic properties of Tb{sub 0.7}Pr{sub 0.3}(Fe{sub 0.9}B{sub 0.1}){sub 1.93} have been investigated. The effect of the annealing on the magnetic properties has been studied. The samples annealed at 773 K are found to have a coercivity of 6.66 kOe at room temperature. The coercivity decreases monotonically with increase in the annealing temperature. The epoxy/Tb{sub 0.7}Pr{sub 0.3}(Fe{sub 0.9}B{sub 0.1}){sub 1.93} composites have been produced by a cold compression-molding technique. The magnetostriction of the epoxy/Tb{sub 0.7}Pr{sub 0.3}(Fe{sub 0.9}B{sub 0.1}){sub 1.93} composites with different weight ratios of epoxy resin to powder is measured by a standard strain technique. The Tb{sub 0.7}Pr{sub 0.3}(Fe{sub 0.9}B{sub 0.1}){sub 1.93} composites, with a weight ratio of epoxy resin to powder of 5:100, have a high magnetostriction of 810 ppm, at an applied magnetic field of 12 kOe. The Tb{sub 0.7}Pr{sub 0.3}(Fe{sub 0.9}B{sub 0.1}){sub 1.93} alloy combines a high magnetostriction with a low coercivity, which is a promising magnetostrictive material.

  16. Giant nonlocal lossless permittivity at optical frequencies.

    PubMed

    Goncharenko, A V; Nazarov, V U

    2015-08-10

    We show how to achieve a giant permittivity combined with negligible losses in both the visible and the near-IR for composites made of alternating layers of plasmonic and gain materials as the electric field is directed normally to the layers. The effects of nonlocality are taken into account that makes the method quite realistic. Solving the dispersion equation for eigenmodes of an infinite layered composite, we show that both propagating and nonpropagating modes can be excited, that leads to the realization of a giant nonlocal permittivity. Both phase and group velocities for the propagating eigenmode have been calculated showing that slow light can be achieved in the system under study. The results obtained open new possibilities for designing nanolaser, slow-light, superresolution imaging devices, etc. PMID:26367898

  17. Effects of a giant impact on Uranus

    NASA Technical Reports Server (NTRS)

    Slattery, W. L.; Benz, W.; Cameron, A. G. W.

    1991-01-01

    The effects of a giant impact on Uranus with respect to the axis tilt of Uranus and its satellites are discussed. The simulations of possible giant impacts were carried out using Cray supercomputers. The technique used is called smooth particle hydrodynamics (SPH). In this technique, the material in the proto-Uranus planet and in the impactor is divided into a large number of particles which can overlap one another so that local averages over these particles determine density and pressure in the problem, and the particles themselves have their own temperatures and internal energies. During the course of the simulation, these particles move around under the influence of the forces acting on them: gravity and pressure gradients. The results of model simulations are presented.

  18. Giant magnetoelectric effect at low frequencies in polymer-based thin film composites

    SciTech Connect

    Kulkarni, A.; Meurisch, K.; Strunskus, T.; Faupel, F.; Teliban, I.; Jahns, R.; Knöchel, R.; Piorra, A.

    2014-01-13

    A polymer-based magnetoelectric 2-2 composite was fabricated in a thin film approach by direct spin coating of polyvinylidenefluoride-co-trifluoroethylene onto a Metglas substrate without the usage of an adhesive for the mechanical coupling between the piezoelectric and magnetostrictive materials. For a prototype single-sided clamped cantilever, a magnetoelectric coefficient as high as 850 V cm{sup −1} Oe{sup −1} is observed at its fundamental bending mode resonance frequency at 27.8 Hz and a detection limit of 10 pTHz{sup −1/2} at its second bending mode resonance frequency at 169.5 Hz.

  19. Imaging Extrasolar Giant Planets

    NASA Astrophysics Data System (ADS)

    Bowler, Brendan P.

    2016-10-01

    High-contrast adaptive optics (AO) imaging is a powerful technique to probe the architectures of planetary systems from the outside-in and survey the atmospheres of self-luminous giant planets. Direct imaging has rapidly matured over the past decade and especially the last few years with the advent of high-order AO systems, dedicated planet-finding instruments with specialized coronagraphs, and innovative observing and post-processing strategies to suppress speckle noise. This review summarizes recent progress in high-contrast imaging with particular emphasis on observational results, discoveries near and below the deuterium-burning limit, and a practical overview of large-scale surveys and dedicated instruments. I conclude with a statistical meta-analysis of deep imaging surveys in the literature. Based on observations of 384 unique and single young (≈5-300 Myr) stars spanning stellar masses between 0.1 and 3.0 M ⊙, the overall occurrence rate of 5-13 M Jup companions at orbital distances of 30-300 au is {0.6}-0.5+0.7 % assuming hot-start evolutionary models. The most massive giant planets regularly accessible to direct imaging are about as rare as hot Jupiters are around Sun-like stars. Dividing this sample into individual stellar mass bins does not reveal any statistically significant trend in planet frequency with host mass: giant planets are found around {2.8}-2.3+3.7 % of BA stars, <4.1% of FGK stars, and <3.9% of M dwarfs. Looking forward, extreme AO systems and the next generation of ground- and space-based telescopes with smaller inner working angles and deeper detection limits will increase the pace of discovery to ultimately map the demographics, composition, evolution, and origin of planets spanning a broad range of masses and ages.

  20. GIANT INTRACANALICULAR FIBROADENOMA

    PubMed Central

    Smith, Clyn; Parsons, Robert J.; Bogart, William M.

    1951-01-01

    Five cases of giant intracanalicular fibroadenoma (“cystosarcoma phylloides”) were observed at one hospital in a period of three years. In a search of the literature, additional reports of breast tumors of this kind, not included in previous reviews, were noted. As there is record of 229 cases, it would appear that this rapidly growing benign tumor should be kept in mind in the diagnosis of masses in the breast. If removal is incomplete, there may be recurrence. Simple mastectomy is the treatment of choice. Radical mastectomy should be avoided. ImagesFigure 1Figure 2.Figure 3Figure 4Figure 5 PMID:14848732

  1. Gas Giants Form Quickly

    NASA Technical Reports Server (NTRS)

    2007-01-01

    This is an artist's concept of a hypothetical 10-million-year-old star system. The bright blur at the center is a star much like our sun. The other orb in the image is a gas-giant planet like Jupiter. Wisps of white throughout the image represent traces of gas.

    Astronomers using NASA's Spitzer Space Telescope have found evidence showing that gas-giant planets either form within the first 10 million years of a sun-like star's life, or not at all. The lifespan for sun-like stars is about 10 billion years.

    The scientists came to this conclusion after searching for traces of gas around 15 different sun-like stars, most with ages ranging from 3 million to 30 million years. With the help of Spitzer's Infrared Spectrometer instrument, they were able to search for relatively warm gas in the inner regions of these star systems, an area comparable to the zone between Earth and Jupiter in our own solar system. They also used ground-based radio telescopes to search for cooler gas in the outer regions of these systems, an area comparable to the zone around Saturn and beyond.

  2. Giant solitary trichoepithelioma

    PubMed Central

    Teli, Bhavuray; Thrishuli, P. B.; Santhosh, R.; Amar, D. N.; Rajpurohit, Shravan

    2015-01-01

    Adnexal tumors like giant solitary trichoepitheliomas are uncommon to most of us to permit a ready familiarity with them. Information regarding the genesis, clinical profile, behavior, and management options for this tumor is limited. There are 18 cases reported in the world literature till date. This review attempts to provide insight to this rare tumor. Our search included indexed literature from Pubmed, Directory of Open Access Journals, Health Inter Network Access to Research Initiative and Google databases in addition to standard dermatology texts. Giant solitary trichoepithelioma is a rare trichogenic tumor with potential for local recurrence. It has predilection for the older age, but may present at any age including at birth. It has close resemblance to basal cell carcinoma and other skin adnexal tumors - clinically, cytologically, and histologically. CD10, CD 34, PHLDA1 but not p75NTR are useful adjunct markers. Surgical excision is the standard treatment. Recurrence and possible transformation into BCC cautions follow up at regular intervals. PMID:25839021

  3. Giant papillary conjunctivitis.

    PubMed Central

    Donshik, P C

    1994-01-01

    Giant papillary conjunctivitis is a syndrome found frequently as a complication of contact lenses. Many variables can affect the onset and severity of the presenting signs and symptoms. Rigid gas permeable contact lenses appear to result in less severe signs and symptoms, with a longer time before the development of giant papillary conjunctivitis. Nonionic, low-water-content soft contact lenses tend to produce less severe signs and symptoms than ionic, low-water-content soft contact lenses. Enzymatic treatment appears to lessen the severity of signs and symptoms. The association of an allergy appears to play a role in the onset of the severity of the signs and symptoms but does not appear to affect the final ability of the individual to wear contact lenses. Using multiple treatment options, such as changing the polymer to a glyceryl methyl methacrylate or a rigid lens, or utilizing a soft lens on a frequent-replacement basis, can result in a success rate of over 90%. In individuals who still have a return of symptoms, the use of topical mast cell stabilizers or a nonsteroidal anti-inflammatory drug as an adjunctive therapy offers the added possibility of keeping these patients in contact lenses. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 11 A FIGURE 11 B FIGURE 11 C FIGURE 11 D PMID:7886881

  4. Rheology of giant micelles

    NASA Astrophysics Data System (ADS)

    Cates, M. E.; Fielding, S. M.

    2006-12-01

    Giant micelles are elongated, polymer-like objects created by the self-assembly of amphiphilic molecules (such as detergents) in solution. Giant micelles are typically flexible, and can become highly entangled even at modest concentrations. The resulting viscoelastic solutions show fascinating flow behaviour (rheology) which we address theoretically in this article at two levels. First, we summarize advances in understanding linear viscoelastic spectra and steady-state nonlinear flows, based on microscopic constitutive models that combine the physics of polymer entanglement with the reversible kinetics of self-assembly. Such models were first introduced two decades ago, and since then have been shown to explain robustly several distinctive features of the rheology in the strongly entangled regime, including extreme shear thinning. We then turn to more complex rheological phenomena, particularly involving spatial heterogeneity, spontaneous oscillation, instability and chaos. Recent understanding of these complex flows is based largely on grossly simplified models which capture in outline just a few pertinent microscopic features, such as coupling between stresses and other order parameters such as concentration. The role of ‘structural memory’ (the dependence of structural parameters such as the micellar length distribution on the flow history) in explaining these highly nonlinear phenomena is addressed. Structural memory also plays an intriguing role in the little-understood shear thickening regime, which occurs in a concentration regime close to but below the onset of strong entanglement, and which is marked by a shear-induced transformation from an inviscid to a gelatinous state.

  5. Magnetostriction of polycrystalline strong-textured Fe-17at%Ga alloy fabricated by combining rapid-solidification and sintering processes

    NASA Astrophysics Data System (ADS)

    Saito, Chihiro; Furuya, Yasubumi; Okazaki, Teiko; Omori, Mamori

    2006-03-01

    Melt-spun, rapid solidified Galfenol (Fe-Ga) ribbon sample showed large magnetostriction and good ductility as compared with conventional bulk sample because the ribbon has fine columnar grain which was formed during melt-spinning process. The large magnetostriction is caused by the release of considerable large internal stresses in as-spun ribbon as well as the remained [100] oriented strong textures after annealing. In order to obtain larger magnetostrictive force than ribbon sample, in this study, magnetostrictive bulky Fe-Ga alloy was fabricated by combining laminate of rapid-solidified ribbons (80 μm in thickness) and spark plasma sintering/joining (SPSJ). SPSJ is characterized by short time and low temperature heating and sintering process. The laminated sample made by SPSJ maintained the unique metallurgical microstructure of polycrystalline texture of columnar grains as well as almost non-equilibrium metastable phase with little existence of ordered precipitations in as-spun ribbons. The excellent sintered sample having large magnetostoriction was obtained under a condition of the compressive stress of 100 MPa at the temperature of 973 K. The magnetostriction depended on compressive pre-stress level for specimen and reached about 100 ppm which was a half of value obtained for the ribbon sample. Furthermore, by following short annealing for this specimen, the magnetostriction increased to 170-190 ppm comparable to the ribbon's value.

  6. Large magneto-chemical-elastic coupling in highly magnetostrictive Fe-Ga alloys

    SciTech Connect

    Narsu, B.; Wang, Gui-Sheng; Johansson, B.; Vitos, L.

    2013-12-02

    The strong softening of the tetragonal shear elastic constant (C{sup ′}) is the main reason for the second magnetostriction peak observed in Fe{sub 100–x}Ga{sub x} alloys. Here, we study the coupling between chemical order and magnetism with the aim to understand the origin of the elastic softening. We demonstrate that C{sup ′} strongly depends on the degree of order of Ga atoms in α-Fe. The B{sub 2} type ordering proves to have an important role on the elastic softening for x<19%, whereas the extreme shear lattice softening and the anomalous temperature dependence of C{sup ′} are found to be due to the strong magnetochemical coupling in the DO{sub 3} phase.

  7. Liquid pressure wireless sensor based on magnetostrictive microwires for applications in cardiovascular localized diagnostic

    NASA Astrophysics Data System (ADS)

    Aragón, A. M.; Hernando-Rydings, M.; Hernando, A.; Marín, P.

    2015-08-01

    In this letter, we report a method to measure changes in a fluid pressure, flowing through a flexible pipeline, by means of a ring of magnetic microwire concentric to the pipeline. The detection is based on the modulated scattering of electromagnetic waves by the magnetoelastic ring. This modulation is driven by applying a low frequency bias magnetic field able to tune the magnetic permeability of the ferromagnetic microwire. Pressure detection, by means of magnetic permeability changes, is possible due to the magnetostrictive character of the sample. The experimental work developed has, also, allowed fluid pressure detection in a hydraulic circuit connected to ventricular assist system where a fluid with a viscosity close to blood flows.

  8. On the correlation between magnetoacoustic emission and magnetostriction dependence on the applied magnetic field

    NASA Astrophysics Data System (ADS)

    Piotrowski, Leszek; Chmielewski, Marek; Augustyniak, Bolesław

    2016-07-01

    The correlation between magnetoacoustic emission signal envelopes and magnetostriction curves is investigated. Two sets of samples are being considered: tempered martensitic steel and plastically deformed ferritic steel. It is shown that even though some general relations may be observed, as was demonstrated in the literature, the correlation is not always present. One may not expect to change both quantities in the same way if a serious modification of microstructure takes place, as for instance in the case of plastically deformed samples for which the dislocation cell structure is formed once a certain level (1.5-2%) of deformation is reached. Being so, any relation not taking into account statistical properties of domain structure and pinning sites distribution may not yield a general solution of the problem.

  9. Crystallization behaviour and magnetic properties of highly magnetostrictive Fe-Tb-Dy thin films

    NASA Astrophysics Data System (ADS)

    Farber, P.; Kronmüller, H.

    2000-06-01

    Thin films of the Fe-Tb-Dy alloy with compositions near to the Terfenol-D alloy (Fe 67Tb 9Dy 24) have been produced by ion-beam sputtering on sapphire substrates at room temperature. Mosaic and sintered targets have been used to vary the chemical composition of Fe, Tb and Dy. Additionally, 2 at% of the additive Zr has been used for some films. Polycrystalline films consisting mainly of the Fe 2RE (RE=Tb, Dy) Laves phase could be obtained by subsequent heat treatment for all compositions investigated here. Measurements of the magnetostriction, the magnetic polarization and the Curie temperature combined with wide-angle X-ray diffraction (XRD) and wavelength dispersive X-ray analysis (WDX) allowed an interpretation of the crystallization behaviour. It has been found that Fe excess increases and rare earth excess decreases the crystallization temperature, whereas the addition of Zr leaves the crystallization temperature unaffected.

  10. A system for magnetostrictive transduction of guided waves in fluid-filled pipes of small diameter.

    PubMed

    Challis, Richard E; Phang, Albert P Y; Lowe, Michael J S; Mather, Melissa L

    2008-09-01

    This paper is concerned with the design of magnetostrictive transducers for the excitation and detection of guided waves in metal pipes of small diameter (mm) and their application to the study of wave propagation in pipes filled with water or supercritical CO(2). Optimized system design is based on a simulation of the overall signal pathway which includes the electric circuit conditions at the transducers, mode excitability, and the wavenumber filtering effect of the spatial distribution of the exciting alternating magnetic field. A prototype system was built, and experimental observations on small diameter pipes indicated good agreement with expected results from simulations. The reassigned spectrogram has been used to compare expectation on the basis of guided wave dispersion curves for fluid-filled pipes with experimental data. PMID:18986895

  11. Magnetostrictive hypersound generation by spiral magnets in the vicinity of magnetic field induced phase transition

    NASA Astrophysics Data System (ADS)

    Bychkov, Igor V.; Kuzmin, Dmitry A.; Kamantsev, Alexander P.; Koledov, Victor V.; Shavrov, Vladimir G.

    2016-11-01

    In present work we have investigated magnetostrictive ultrasound generation by spiral magnets in the vicinity of magnetic field induced phase transition from spiral to collinear state. We found that such magnets may generate transverse sound waves with the wavelength equal to the spiral period. We have examined two types of spiral magnetic structures: with inhomogeneous exchange and Dzyaloshinskii-Moriya interactions. Frequency of the waves from exchange-caused spiral magnetic structure may reach some THz, while in case of Dzyaloshinskii-Moriya interaction-caused spiral it may reach some GHz. These waves will be emitted like a sound pulses. Amplitude of the waves is strictly depends on the phase transition speed. Some aspects of microwaves to hypersound transformation by spiral magnets in the vicinity of phase transition have been investigated as well. Results of the work may be interesting for investigation of phase transition kinetics as well, as for various hypersound applications.

  12. A Nonlinear Physics-Based Optimal Control Method for Magnetostrictive Actuators

    NASA Technical Reports Server (NTRS)

    Smith, Ralph C.

    1998-01-01

    This paper addresses the development of a nonlinear optimal control methodology for magnetostrictive actuators. At moderate to high drive levels, the output from these actuators is highly nonlinear and contains significant magnetic and magnetomechanical hysteresis. These dynamics must be accommodated by models and control laws to utilize the full capabilities of the actuators. A characterization based upon ferromagnetic mean field theory provides a model which accurately quantifies both transient and steady state actuator dynamics under a variety of operating conditions. The control method consists of a linear perturbation feedback law used in combination with an optimal open loop nonlinear control. The nonlinear control incorporates the hysteresis and nonlinearities inherent to the transducer and can be computed offline. The feedback control is constructed through linearization of the perturbed system about the optimal system and is efficient for online implementation. As demonstrated through numerical examples, the combined hybrid control is robust and can be readily implemented in linear PDE-based structural models.

  13. Allometry indicates giant eyes of giant squid are not exceptional

    PubMed Central

    2013-01-01

    Background The eyes of giant and colossal squid are among the largest eyes in the history of life. It was recently proposed that sperm whale predation is the main driver of eye size evolution in giant squid, on the basis of an optical model that suggested optimal performance in detecting large luminous visual targets such as whales in the deep sea. However, it is poorly understood how the eye size of giant and colossal squid compares to that of other aquatic organisms when scaling effects are considered. Results We performed a large-scale comparative study that included 87 squid species and 237 species of acanthomorph fish. While squid have larger eyes than most acanthomorphs, a comparison of relative eye size among squid suggests that giant and colossal squid do not have unusually large eyes. After revising constants used in a previous model we found that large eyes perform equally well in detecting point targets and large luminous targets in the deep sea. Conclusions The eyes of giant and colossal squid do not appear exceptionally large when allometric effects are considered. It is probable that the giant eyes of giant squid result from a phylogenetically conserved developmental pattern manifested in very large animals. Whatever the cause of large eyes, they appear to have several advantages for vision in the reduced light of the deep mesopelagic zone. PMID:23418818

  14. Theory-based development of high-performance magnostrictive particulate actuated polymer composite transducer materials with strongly improved cyclic strain endurance

    NASA Astrophysics Data System (ADS)

    Armstrong, William D.

    2001-07-01

    The present experimental effort characterizes the development of damage in two different forms of experimental magnetostrictive composite material. This effort is intended to identify the various forms of damage mechanisms operating in the two very different materials, and to identify how the development of fine scale damage influences the overall magnetostrictive behavior and performance. Optical examination of as-magneto-strain cycled Terfenol-D particle actuated epoxy matrix composite material strongly suggests the following primary damage processes, particle fracture under cyclic internal stress, severe degradation of the particle to epoxy matrix interfacial bond, and ultimate sample failure by matrix crack coalescence leading to complete granulation.

  15. Influence of the deposition-induced stress on the magnetic properties of magnetostrictive amorphous (Fe{sub 80}Co{sub 20}){sub 80}B{sub 20} multilayers with orthogonal anisotropy

    SciTech Connect

    Gonzalez-Guerrero, Miguel; Prieto, Jose Luis; Sanchez, Pedro; Aroca, Claudio

    2007-12-15

    In this work, we experimentally justify that the control of the mechanical stress induced during the deposition of sputtered amorphous magnetostrictive (Fe{sub 80}Co{sub 20}){sub 80}B{sub 20} allows a custom design of its magnetic properties. FeCoB multilayers have been sputtered on thermal oxide Si substrates with different buffer materials. The crystalline quality and the thermomechanical properties of the buffer layer influence both the coercive and the anisotropy field. Those buffer layers with both high rigidity and poor thermal conductivity do not allow the dissipation of energy of the incoming sputtered material. Therefore, the mechanical stresses related to the deposition process cannot be released, leading to magnetic layers with high easy-axis coercive field and low anisotropy field. This shows that the mechanical stresses accumulated during deposition are a key parameter for the control of coercivity.

  16. Giant photoluminescence emission in crystalline faceted Si grains

    PubMed Central

    Faraci, Giuseppe; Pennisi, Agata R.; Alberti, Alessandra; Ruggeri, Rosa; Mannino, Giovanni

    2013-01-01

    Empowering an indirect band-gap material like Si with optical functionalities, firstly light emission, represents a huge advancement constantly pursued in the realization of any integrated photonic device. We report the demonstration of giant photoluminescence (PL) emission by a newly synthesized material consisting of crystalline faceted Si grains (fg-Si), a hundred nanometer in size, assembled in a porous and columnar configuration, without any post processing. A laser beam with wavelength 632.8 nm locally produce such a high temperature, determined on layers of a given thickness by Raman spectra, to induce giant PL radiation emission. The optical gain reaches the highest value ever, 0.14 cm/W, representing an increase of 3 orders of magnitude with respect to comparable data recently obtained in nanocrystals. Giant emission has been obtained from fg-Si deposited either on glass or on flexible, low cost, polymeric substrate opening the possibility to fabricate new devices. PMID:24056300

  17. Juno and Cassini Proximal: Giant Steps Towards Understanding Giant Planets

    NASA Astrophysics Data System (ADS)

    Stevenson, D. J.

    2014-12-01

    In 2016-17, Juno and Cassini Proximal will provide comparable large advances in our understanding of the interiors of Jupiter and Saturn. Both will provide high accuracy gravity and magnetic field data, while Juno will in addition determine the water abundance deep in the Jovian atmosphere, essential for understanding of giant planet formation and the density of the outer envelope (needed to construct interior models). Although Jupiter and Saturn are both gas giants, they differ in important ways (magnetic field, strength of zonal flows, enrichment in heavy elements, and probably the distribution of helium within). The opportunity to contrast and compare will be invaluable. Juno and Cassini are expected to determine the gravity field to about a part in 109 though with different spatial coverage and with less accurate determination near the poles. The determination of Jupiter's likely central concentration of heavy elements is particularly challenging because it is only a few percent at most of the total mass and yet important for understanding Jupiter's formation, which in turn likely determined the architecture of our solar system. This determination will be done from gravity, water determination and magnetic field and also aided by advances in our understanding of material properties. The corresponding determination for Saturn may prove easier (because the heavy element enrichment is a larger fraction of the mass) though complicated by lack of knowledge of water abundance and the need to identify a more precise value for the deep rotation of the planet (difficult for Saturn because of the lack of a measurable magnetic dipole tilt thus far). For both planets, the higher harmonics of gravity will likely be controlled by differential rotation (the zonal flows) and this will tell us their depth, an issue of major interest in the dynamics of these bodies. The magnetic field structure for Jupiter will be determined to higher accuracy than the Earth's core field (since

  18. Giant vesicles: preparations and applications.

    PubMed

    Walde, Peter; Cosentino, Katia; Engel, Helen; Stano, Pasquale

    2010-05-01

    There is considerable interest in preparing cell-sized giant unilamellar vesicles from natural or nonnatural amphiphiles because a giant vesicle membrane resembles the self-closed lipid matrix of the plasma membrane of all biological cells. Currently, giant vesicles are applied to investigate certain aspects of biomembranes. Examples include lateral lipid heterogeneities, membrane budding and fission, activities of reconstituted membrane proteins, or membrane permeabilization caused by added chemical compounds. One of the challenging applications of giant vesicles include gene expressions inside the vesicles with the ultimate goal of constructing a dynamic artificial cell-like system that is endowed with all those essential features of living cells that distinguish them from the nonliving form of matter. Although this goal still seems to be far away and currently difficult to reach, it is expected that progress in this and other fields of giant vesicle research strongly depend on whether reliable methods for the reproducible preparation of giant vesicles are available. The key concepts of currently known methods for preparing giant unilamellar vesicles are summarized, and advantages and disadvantages of the main methods are compared and critically discussed. PMID:20336703

  19. [Giant adrenal myelolipoma].

    PubMed

    El Mejjad, Amine; Fekak, Hamid; Dakir, Mohamed; Sarf, Ismail; Manni, Ahmed; Meziane, Fethi

    2004-02-01

    Adrenal myelolipoma is a rare, benign, non-secreting tumour composed of adipose and haematopoietic tissue. The authors report a rare case of giant adrenal myelolipoma in a 53-year-old patient presenting with low back pain and a palpable flank mass on examination. CT scan suggested the diagnosis and surgical resection was indicated in view of the size and symptomatic nature of this mass. Histological examination confirmed the diagnosis. The outcome was favourable without recurrence after a follow-up of one year. The diagnosis of adrenal myelolipoma is based on radiology. Conservative management is generally sufficient for small asymptomatic tumours, but resection is required for large (> 5 cm) and/or symptomatic tumours.

  20. Two giant stellar complexes

    NASA Astrophysics Data System (ADS)

    Efremov, Yu. N.; Efremov, E. Yu.

    Common star complexes are huge (0.3-1 kpc in diameter) groups of relatively young stars, associations and clusters. The complexes usually form regular chains along spiral arms of grand design galaxies, being evidently formed and supported by magneto- gravitational instability developing along an arm. Special attention is given to a few large complexes which have signatures of gravitational boundness, such as round shape and high central density. Concentrations of stars and clusters in such a complex in M51 galaxy were found in this paper; we concluded it is possible to suggest that the complex is gravitationally bound. It is also stressed that some properties of the giant complex in NGC 6946 (such as its semicircular and sharp Western edge) are still enigmatic.

  1. Enhanced magnetocaloric effect material

    DOEpatents

    Lewis, Laura J. H.

    2006-07-18

    A magnetocaloric effect heterostructure having a core layer of a magnetostructural material with a giant magnetocaloric effect having a magnetic transition temperature equal to or greater than 150 K, and a constricting material layer coated on at least one surface of the magnetocaloric material core layer. The constricting material layer may enhance the magnetocaloric effect by restriction of volume changes of the core layer during application of a magnetic field to the heterostructure. A magnetocaloric effect heterostructure powder comprising a plurality of core particles of a magnetostructural material with a giant magnetocaloric effect having a magnetic transition temperature equal to or greater than 150 K, wherein each of the core particles is encapsulated within a coating of a constricting material is also disclosed. A method for enhancing the magnetocaloric effect within a giant magnetocaloric material including the step of coating a surface of the magnetocaloric material with a constricting material is disclosed.

  2. A Comparative Study of Cathepsin D Expression in Peripheral and Central Giant Cell Granuloma of the Jaws by Immunohistochemistry Technique

    PubMed Central

    Zargaran, Massoumeh; Moghimbeigi, Abbas; Afsharmoghadam, Noushin; Nasr Isfahani, Mohsen; Hashemi, Atefeh

    2016-01-01

    Statement of the Problem Peripheral and central giant cell granuloma are two common benign lesions of the oral cavity. In spite of histopathological similarities, they have different clinical behaviors. Cathepsin D is a lysosomal enzyme which has different functions on the basis of protein and applied peptide cleavage. Purpose This research aimed to evaluate and compare the expression level of Cathepsin D in these two lesions to find the reasons for the differences in clinical and biologic characteristics. Materials and Method The expression of Cathepsin D was investigated by using the immunohistochemistry method in 20 samples of peripheral giant cell granuloma and 20 samples of central giant cell granuloma. The percentage of stained giant cells (labeling index), the intensity of staining of giant cells, and staining-intensity-distribution in both groups were calculated and compared. Results The labeling indices of Cathepsin D in peripheral giant cell granuloma and central giant cell granuloma were 95.9±4.03 and 95.6±2.34, respectively. There was no significant difference in the percentages of stained giant cells between the two groups (p= 0.586). The intensity of staining of giant cells in central giant cell granuloma was stronger than that of peripheral giant cell granuloma (p> 0.001). Staining- intensity- distribution of giant cells in central giant cell granuloma was significantly greater than that of the peripheral type of lesion (p= 0.001). Conclusion The higher expression level of Cathepsin D in central giant cell granuloma compared to peripheral type of lesion can explain more aggressive behavior of central giant cell granuloma. PMID:27284554

  3. Analysis of internal wave reflection within a magnetostrictive patch transducer for high-frequency guided torsional waves.

    PubMed

    Kim, Hoe Woong; Cho, Seung Hyun; Kim, Yoon Young

    2011-08-01

    Recently, megahertz-range torsional waves have been successfully generated and measured by a magnetostrictive patch transducer employing a meander coil. But the waveform of a high-frequency torsional wave generated by magnetostrictive patch transducers becomes greatly distorted with multiple trailing pulses. The hypothesis explaining the cause of the waveform distortion is that the distortion results mainly from the internal wave reflection within the magnetostrictive patch, which is in turn caused by the impedance mismatch between the bare and patch-bonded parts of the pipe. Based on the hypothesis, we developed an analytic model for internal reflection simulation and conducted several experiments using a patch transducer to verify the hypothesis. The comparison of the analytical and experimental results showed that the internal reflection at the edge of the patch was responsible for the distortion of the measured waveform. The present study also confirmed that the standard acoustic impedance matching to avoid sudden discontinuities at the patch edges can effectively reduce the internal reflection and alleviate the waveform distortion problem. PMID:21420708

  4. Analysis of internal wave reflection within a magnetostrictive patch transducer for high-frequency guided torsional waves.

    PubMed

    Kim, Hoe Woong; Cho, Seung Hyun; Kim, Yoon Young

    2011-08-01

    Recently, megahertz-range torsional waves have been successfully generated and measured by a magnetostrictive patch transducer employing a meander coil. But the waveform of a high-frequency torsional wave generated by magnetostrictive patch transducers becomes greatly distorted with multiple trailing pulses. The hypothesis explaining the cause of the waveform distortion is that the distortion results mainly from the internal wave reflection within the magnetostrictive patch, which is in turn caused by the impedance mismatch between the bare and patch-bonded parts of the pipe. Based on the hypothesis, we developed an analytic model for internal reflection simulation and conducted several experiments using a patch transducer to verify the hypothesis. The comparison of the analytical and experimental results showed that the internal reflection at the edge of the patch was responsible for the distortion of the measured waveform. The present study also confirmed that the standard acoustic impedance matching to avoid sudden discontinuities at the patch edges can effectively reduce the internal reflection and alleviate the waveform distortion problem.

  5. Atmospheres of Extrasolar Giant Planets

    NASA Technical Reports Server (NTRS)

    Marley, Mark

    2006-01-01

    The next decade will almost certainly see the direct imaging of extrasolar giant planets around nearby stars. Unlike purely radial velocity detections, direct imaging will open the door to characterizing the atmosphere and interiors of extrasola planets and ultimately provide clues on their formation and evolution through time. This process has already begun for the transiting planets, placing new constraints on their atmospheric structure, composition, and evolution. Indeed the key to understanding giant planet detectability, interpreting spectra, and constraining effective temperature and hence evolution-is the atmosphere. I will review the universe of extrasolar giant planet models, focusing on what we have already learned from modeling and what we will likely be able to learn from the first generation of direct detection data. In addition to these theoretical considerations, I will review the observations and interpretation of the - transiting hot Jupiters. These objects provide a test of our ability to model exotic atmospheres and challenge our current understanding of giant planet evolution.

  6. Landscape of the lost giants

    NASA Astrophysics Data System (ADS)

    2013-09-01

    The Pleistocene megafauna extinction erased a group of remarkable animals. Whether humans had a prominent role in the extinction remains controversial, but it is emerging that the disappearance of the giants has markedly affected the environment.

  7. Pharma giants swap research programs.

    PubMed

    2014-07-01

    Pharmaceutical giants Novartis and GlaxoSmithKline (GSK) agreed in late April to swap some assets, with Novartis handing off its vaccine business to GSK and getting most of the British company's cancer portfolio in return.

  8. Giant Magnetoresistance: Basic Concepts, Microstructure, Magnetic Interactions and Applications

    PubMed Central

    Ennen, Inga; Kappe, Daniel; Rempel, Thomas; Glenske, Claudia; Hütten, Andreas

    2016-01-01

    The giant magnetoresistance (GMR) effect is a very basic phenomenon that occurs in magnetic materials ranging from nanoparticles over multilayered thin films to permanent magnets. In this contribution, we first focus on the links between effect characteristic and underlying microstructure. Thereafter, we discuss design criteria for GMR-sensor applications covering automotive, biosensors as well as nanoparticular sensors. PMID:27322277

  9. Giant Magnetoresistance: Basic Concepts, Microstructure, Magnetic Interactions and Applications.

    PubMed

    Ennen, Inga; Kappe, Daniel; Rempel, Thomas; Glenske, Claudia; Hütten, Andreas

    2016-01-01

    The giant magnetoresistance (GMR) effect is a very basic phenomenon that occurs in magnetic materials ranging from nanoparticles over multilayered thin films to permanent magnets. In this contribution, we first focus on the links between effect characteristic and underlying microstructure. Thereafter, we discuss design criteria for GMR-sensor applications covering automotive, biosensors as well as nanoparticular sensors. PMID:27322277

  10. Giant Magnetoresistance: Basic Concepts, Microstructure, Magnetic Interactions and Applications.

    PubMed

    Ennen, Inga; Kappe, Daniel; Rempel, Thomas; Glenske, Claudia; Hütten, Andreas

    2016-01-01

    The giant magnetoresistance (GMR) effect is a very basic phenomenon that occurs in magnetic materials ranging from nanoparticles over multilayered thin films to permanent magnets. In this contribution, we first focus on the links between effect characteristic and underlying microstructure. Thereafter, we discuss design criteria for GMR-sensor applications covering automotive, biosensors as well as nanoparticular sensors.

  11. Enhancement of the Excitation Efficiency of the Non-Contact Magnetostrictive Sensor for Pipe Inspection by Adjusting the Alternating Magnetic Field Axial Length

    PubMed Central

    Sun, Pengfei; Wu, Xinjun; Xu, Jiang; Li, Jian

    2014-01-01

    The non-contact magnetostrictive sensor (MsS) has been widely used in the guided wave testing of pipes, cables, and so on. However, it has a disadvantage of low excitation efficiency. A new method for enhancing the excitation efficiency of the non-contact MsS for pipe inspection using guided waves, by adjusting the axial length of the excitation magnetic field, is proposed. A special transmitter structure, in which two copper rings are added beside the transmitter coil, is used to adjust the axial length at the expense of weakening the excitation magnetic field. An equivalent vibration model is presented to analyze the influence of the axial length variation. The final result is investigated by experiments. Results show that the excitation efficiency of the non-contact MsS is enhanced in the whole inspection frequency range of the L(0,2) mode if the axial length is adjusted to a certain value. Moreover that certain axial length is the same for pipes of different sizes but made of the same material. PMID:24441769

  12. An in-situ study of magnetic domain structures in undercooled Fe-29.5 at. %Pd magnetostrictive alloys by Lorentz microscopy and electron holography

    SciTech Connect

    Sun, Wen; Xu, Xianhui; Liu, Jian E-mail: xiawxing@nimte.ac.cn; Xia, Weixing E-mail: xiawxing@nimte.ac.cn; Yan, Aru

    2015-04-28

    Understanding of correlation between magnetic domain structure and functional properties is of importance for the magnetic field driven phase transition (e.g., martensitic transformation) or microstructure variation (e.g., twin boundary motion) materials. In this work, we report a Fe-29.5 at. %Pd shape memory alloy treated by undercooling processing upon a degree of 320 K below the liquid temperature. The effect of high undercooling on the solidified microstructure and martensitic transformation temperatures was investigated. By in-situ Lorentz transmission electron microscopy and electron holography, magnetic domain structure and the field-induced domain wall motion behavior in as-cast and undercooled samples have been schematically studied. The irregular domain structure can be observed in these alloys. On the application of a field up to 300 Oe, the domain walls for both samples are able to move along the direction of the external magnetic field, but structural transition and rearrangement of variants are not observed in the undercooled alloy. The large magnetostriction of Fe-29.5 at. %Pd undercooled alloy originates from the irregular domain walls motion instead of the rearrangement of martensitic twin variants.

  13. Enhancement of the excitation efficiency of the non-contact magnetostrictive sensor for pipe inspection by adjusting the alternating magnetic field axial length.

    PubMed

    Sun, Pengfei; Wu, Xinjun; Xu, Jiang; Li, Jian

    2014-01-16

    The non-contact magnetostrictive sensor (MsS) has been widely used in the guided wave testing of pipes, cables, and so on. However, it has a disadvantage of low excitation efficiency. A new method for enhancing the excitation efficiency of the non-contact MsS for pipe inspection using guided waves, by adjusting the axial length of the excitation magnetic field, is proposed. A special transmitter structure, in which two copper rings are added beside the transmitter coil, is used to adjust the axial length at the expense of weakening the excitation magnetic field. An equivalent vibration model is presented to analyze the influence of the axial length variation. The final result is investigated by experiments. Results show that the excitation efficiency of the non-contact MsS is enhanced in the whole inspection frequency range of the L(0,2) mode if the axial length is adjusted to a certain value. Moreover that certain axial length is the same for pipes of different sizes but made of the same material.

  14. Coordinated observations of interacting peculiar red giant binaries, 1

    NASA Technical Reports Server (NTRS)

    Ake, T.

    1995-01-01

    IUE Observations were begun for a two-year program to monitor the UV variability of three interacting peculiar red giant (PRG) binaries, HD 59643 (C6,s) HD 35155 (S3/2), and HR 1105 (S3.5/2.5). All of these systems were suspected to involve accretion of material from the PRG to a white-dwarf secondary, based mainly on previous IUE investigations. From our earlier surveys of PRG's, they were primary candidates to test the hypothesis that Tc-poor PRG's are formed as a result of mass transfer from a secondary component rather than from internal thermal pulsing while on the asymptotic red giant branch.

  15. A presynaptic complex in the giant synapse of the squid.

    PubMed

    Martin, R; Miledi, R

    1975-04-01

    A presynaptic complex consisting of thin lamellae associated with vesicles was found frequently in presynaptic terminals of the squid giant synapse. The lamellae, made of osmiophilic material, had an average length and width of about 10 mum and a thickness of 30 nm; they were of rectangular shape. While most frequent in the axoplasm of the most distal, and largest, terminal of the presynaptic giant axon, the lamellae were found also in smaller terminal branches of this fibre; They have not been observed in the proximal parts of the presynaptic or postsynaptic giant axons. Vesicles the size of synaptic vesicles surrounded the sides of the lamellae. The presynaptic complex resembles the synaptic ribbons in sensory cells.

  16. Recurrent renal giant leiomyosarcoma.

    PubMed

    Öziş, Salih Erpulat; Gülpınar, Kamil; Şahlı, Zafer; Konak, Baha Burak; Keskin, Mete; Özdemir, Süleyman; Ataoğlu, Ömür

    2016-01-01

    Primary renal leiomyosarcomas are rare, aggressive tumors. They constitute 1-2% of adult malignant renal tumors. Although leiomyosarcomas are the most common histological type (50-60%) of renal sarcomas, information on renal leiomyosarcoma is limited. Local or systemic recurrences are common. The radiological appearance of renal leiomyosarcomas is not specific, therefore renal leiomyosarcoma cannot be distinguished from renal cell carcinoma by imaging methods in all patients. A 74-year-old female patient presented to our clinic complaining of a palpable mass on the right side of her abdomen in November 2012. The abdominal magnetic resonance imaging revealed a mass, 25 × 24 × 23 cm in size. Her past medical history revealed that she has undergone right radical nephrectomy in 2007, due to a 11 × 12 × 13 cm renal mass that was then reported as renal cell carcinoma on abdominal magnetic resonance imaging, but the pathological diagnosis was low-grade renal leiomyosarcoma. The most recent follow-up of the patient was in 2011, with no signs of local recurrence or distant metastases within this four-year period. The patient underwent laparotomy on November 2012, and a 35 cm retroperitoneal mass was excised. The pathological examination of the mass was reported as high-grade leiomyosarcoma. The formation of this giant retroperitoneal mass in 1 year can be explained by the transformation of the lesion's pathology from low-grade to a high-grade tumor. PMID:27436926

  17. A unique advantage for giant eyes in giant squid.

    PubMed

    Nilsson, Dan-Eric; Warrant, Eric J; Johnsen, Sönke; Hanlon, Roger; Shashar, Nadav

    2012-04-24

    Giant and colossal deep-sea squid (Architeuthis and Mesonychoteuthis) have the largest eyes in the animal kingdom [1, 2], but there is no explanation for why they would need eyes that are nearly three times the diameter of those of any other extant animal. Here we develop a theory for visual detection in pelagic habitats, which predicts that such giant eyes are unlikely to evolve for detecting mates or prey at long distance but are instead uniquely suited for detecting very large predators, such as sperm whales. We also provide photographic documentation of an eyeball of about 27 cm with a 9 cm pupil in a giant squid, and we predict that, below 600 m depth, it would allow detection of sperm whales at distances exceeding 120 m. With this long range of vision, giant squid get an early warning of approaching sperm whales. Because the sonar range of sperm whales exceeds 120 m [3-5], we hypothesize that a well-prepared and powerful evasive response to hunting sperm whales may have driven the evolution of huge dimensions in both eyes and bodies of giant and colossal squid. Our theory also provides insights into the vision of Mesozoic ichthyosaurs with unusually large eyes.

  18. Magnetic properties and magnetostriction of PrxNd1-xFe1.9 (0 <= x <= 1.0) alloys at low temperature

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Tang, Shao-Long; Li, Yu-Long; Xie, Ren; Du, You-Wei

    2013-03-01

    The crystal structure, magnetic and magnetostrictive properties of high-pressure synthesized PrxNd1-xFe1.9 (0 <= x <= 1.0) alloys were studied. The alloys exhibit single cubic Laves phase with MgCu2-type structure. The initial magnetization curve reveals that Pr0.2Nd0.8Fe1.9 has a minimum magnetocrystalline anisotropy at 5 K. The magnetostriction curve at 5 K shows that Pr0.2Nd0.8Fe1.9 has a very good low-field magnetostrictive property, and the magnetostriction of the PrxNd1-xFe1.9 alloy in high magnetic field is attributable mainly to Pr. The temperature dependence of the magnetostriction (λ‖) at the field of 5 kOe shows that the substitution of Nd reduces the K1 remarkably, and the values of λ‖ of Pr0.2Nd0.8Fe1.9 and Pr0.8Nd0.2Fe1.9 alloys are nearly five times larger than that of the PrFe1.9 alloy below 50 K; the λ‖ of Pr0.8Nd0.2Fe1.9 reaches up to 1082 ppm at 100 K, which makes it a potential candidate for application in this temperature range.

  19. Giant magnetoimpedance effect in Fe75.5Cu1Nb3Si13.5B7 ribbon/FeGa film composite

    NASA Astrophysics Data System (ADS)

    Zhang, Yi; Gan, Tao; Wang, Tao; Wang, Feifei; Shi, Wangzhou

    2016-11-01

    Optimized giant magnetoimpedance effect of Fe75.5Cu1Nb3Si13.5B7 amorphous ribbon/Fe80Ga20 film composites has been investigated. FeCuNbSiB amorphous ribbons as the substrates are commercially available, magnetostrictive FeGa films are deposited on one or both sides of the ribbons by ion-beam sputtering. Compared with the GMI curves without FeGa layer, the GMI effect of FeCuNbSiB amorphous ribbon has been obviously improved with FeGa film covered (from 4% to 16%). Moreover, the details exhibit an interesting phenomenon: at a certain frequency, when the FeGa film covered on one side of the ribbon, the GMI ratio decreases with the thickness of the FeGa film; however, when the FeGa films covered on both sides of the ribbon, the GMI ratio increases with the thickness of the FeGa film. We mainly attribute the reason to strain-induced anisotropy, which is induced by magnetostrictive effect under a longitudinal applied magnetic field.

  20. Giant magnetoresistance in organic spin-valves.

    PubMed

    Xiong, Z H; Wu, Di; Vardeny, Z Valy; Shi, Jing

    2004-02-26

    A spin valve is a layered structure of magnetic and non-magnetic (spacer) materials whose electrical resistance depends on the spin state of electrons passing through the device and so can be controlled by an external magnetic field. The discoveries of giant magnetoresistance and tunnelling magnetoresistance in metallic spin valves have revolutionized applications such as magnetic recording and memory, and launched the new field of spin electronics--'spintronics'. Intense research efforts are now devoted to extending these spin-dependent effects to semiconductor materials. But while there have been noteworthy advances in spin injection and detection using inorganic semiconductors, spin-valve devices with semiconducting spacers have not yet been demonstrated. pi-conjugated organic semiconductors may offer a promising alternative approach to semiconductor spintronics, by virtue of their relatively strong electron-phonon coupling and large spin coherence. Here we report the injection, transport and detection of spin-polarized carriers using an organic semiconductor as the spacer layer in a spin-valve structure, yielding low-temperature giant magnetoresistance effects as large as 40 per cent. PMID:14985756

  1. HST images of ubiquitous dark giants as dark matter in the galactic discs

    NASA Astrophysics Data System (ADS)

    Celis, L. S.

    2003-07-01

    A revision of the Bubble Nebula Region (NGC 7635) and the Trifid Nebula Region (NGC 6514) whose images were taken by the Hubble Space Telescope HST gives clues of the ubiquitous character of the dark giants, which were found for the first time in the Carina Nebula Region (NGC 3324) [1]. The formation of dark giants, due to the extreme ageing of red giant cocoon stars, can explain the enormous quantity of dark giants pointing out their presence of dark matter as a residual material from successive generations of stars. The dark giants might be as many as 98.9% of dark matter needed to represent the gravitational support of the optical stars in the galactic discs.

  2. Giant strain with ultra-low hysteresis and high temperature stability in grain oriented lead-free K0.5Bi0.5TiO3-BaTiO3-Na0.5Bi0.5TiO3 piezoelectric materials.

    PubMed

    Maurya, Deepam; Zhou, Yuan; Wang, Yaojin; Yan, Yongke; Li, Jiefang; Viehland, Dwight; Priya, Shashank

    2015-02-26

    We synthesized grain-oriented lead-free piezoelectric materials in (K0.5Bi0.5TiO3-BaTiO3-xNa0.5Bi0.5TiO3 (KBT-BT-NBT) system with high degree of texturing along the [001]c (c-cubic) crystallographic orientation. We demonstrate giant field induced strain (~0.48%) with an ultra-low hysteresis along with enhanced piezoelectric response (d33 ~ 190pC/N) and high temperature stability (~160°C). Transmission electron microscopy (TEM) and piezoresponse force microscopy (PFM) results demonstrate smaller size highly ordered domain structure in grain-oriented specimen relative to the conventional polycrystalline ceramics. The grain oriented specimens exhibited a high degree of non-180° domain switching, in comparison to the randomly axed ones. These results indicate the effective solution to the lead-free piezoelectric materials.

  3. Giant strain with ultra-low hysteresis and high temperature stability in grain oriented lead-free K₀̣₅Bi₀̣₅TiO₃-BaTiO₃-Na₀̣₅Bi₀̣₅TiO₃ piezoelectric materials

    SciTech Connect

    Maurya, Deepam; Zhou, Yuan; Wang, Yaojin; Yan, Yongke; Li, Jiefang; Viehland, Dwight; Priya, Shashank

    2015-02-26

    We synthesized grain-oriented lead-free piezoelectric materials in (K₀̣₅Bi₀̣₅TiO₃-BaTiO₃-xNa₀̣₅Bi₀̣₅TiO₃ (KBT-BT-NBT) system with high degree of texturing along the [001]c (c-cubic) crystallographic orientation. We demonstrate giant field induced strain (~0.48%) with an ultra-low hysteresis along with enhanced piezoelectric response (d₃₃ ~ 190pC/N) and high temperature stability (~160°C). Transmission electron microscopy (TEM) and piezoresponse force microscopy (PFM) results demonstrate smaller size highly ordered domain structure in grain-oriented specimen relative to the conventional polycrystalline ceramics. The grain oriented specimens exhibited a high degree of non-180° domain switching, in comparison to the randomly axed ones. These results indicate the effective solution to the lead-free piezoelectric materials.

  4. Giant strain with ultra-low hysteresis and high temperature stability in grain oriented lead-free K0.5Bi0.5TiO3-BaTiO3-Na0.5Bi0.5TiO3 piezoelectric materials

    PubMed Central

    Maurya, Deepam; Zhou, Yuan; Wang, Yaojin; Yan, Yongke; Li, Jiefang; Viehland, Dwight; Priya, Shashank

    2015-01-01

    We synthesized grain-oriented lead-free piezoelectric materials in (K0.5Bi0.5TiO3-BaTiO3-xNa0.5Bi0.5TiO3 (KBT-BT-NBT) system with high degree of texturing along the [001]c (c-cubic) crystallographic orientation. We demonstrate giant field induced strain (~0.48%) with an ultra-low hysteresis along with enhanced piezoelectric response (d33 ~ 190pC/N) and high temperature stability (~160°C). Transmission electron microscopy (TEM) and piezoresponse force microscopy (PFM) results demonstrate smaller size highly ordered domain structure in grain-oriented specimen relative to the conventional polycrystalline ceramics. The grain oriented specimens exhibited a high degree of non-180° domain switching, in comparison to the randomly axed ones. These results indicate the effective solution to the lead-free piezoelectric materials. PMID:25716551

  5. Enhanced bending-resonance magnetoelectric response in end-bonding magnetostrictive/piezoelectric heterostructure

    NASA Astrophysics Data System (ADS)

    Peng, Jinshuan; Lu, Caijiang; Xu, Changbao; Gao, Jipu; Gui, Junguo; Lin, Chenhui

    2015-05-01

    In this paper, we present a magnetoelectric (ME) heterostructure made by attaching two magnetostrictive Nickel (Ni) plates at the two free ends of a piezoelectric Pb(Zr1-xTix)O3 (PZT) plate. With this configuration, the Ni and the PZT plates vibrate more freely due to the absence of an interfacial epoxy layer, which results in a larger bending deformation of the PZT plate. The Ni and the PZT plates couple to each other by mechanical magnetic forces, instead of shear forces. In addition, the two Ni plates act as proof masses for the PZT plate, which can reduce the bending resonant frequency ( f r) the of PZT plate. The experimental results demonstrate that the bendingresonance ME voltage coefficient ( aME,r) is 2.82 times larger than that of the traditional bilayer laminate Ni/PZT. As the length of the Ni plates (L) increases, the fr decreases and can be shifted in a range of 34.6 kHz ≤ fr ≤ 61.02 kHz. The maximum aME,r of 49.84 V/cm Oe is observed at dc bias magnetic field H dc = 158 Oe when L = 18 mm. This heterostructure is of interest for high-sensitive dc magnetic-field sensors, ME transducers.

  6. Magnetostriction and magnetoelastic quantum oscillations in P-type lead telluride

    NASA Technical Reports Server (NTRS)

    Thompson, T. E.; Aron, P. R.; Chandrasekhar, B. S.; Langenberg, D. N.

    1972-01-01

    A detailed experimental and theoretical study of quantum oscillations in the magnetostriction and Young's modulus of p-PbTe is presented. The valance band of PbTe is approximated by a spheroidal, nonparabolic model in which the effects of strain on the valance band parameters are described by a deformation potential model. Using appropriate thermodynamic derivatives of the modified Lifshitz-Kosevich expression for the oscillatory parts of the electronic free energy, it is shown that both types of oscillations arise mainly from relative shifts of the valance band maxima due to shear strains, accompanied by intervalley charge transfer. Band parameters derived from the periods, phases, and spin splitting of the oscillations are in generally good agreement with values reported by other workers. A detailed comparison is made of the experimentally observed oscillation amplitudes with those predicted by theory, and satisfactory agreement is found. The ratio of the amplitudes of the two effects yields a value of the valance band deformation potential in good agreement with a value found from piezoresistance experiments by Burke.

  7. Experimental manipulation of magnetic states of magnetostrictive nanomagnets using surface acoustic waves

    NASA Astrophysics Data System (ADS)

    Sampath, Vimal; Bhattacharya, Dhritiman; D'Souza, Noel; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha

    The use of Surface Acoustic Waves (SAW) to assist magnetization switching in magnetostrictive nanomagnets has been theoretically studied and SAW-induced magnetization rotation in micron size magnets has been experimentally demonstrated. We report recent experiments on manipulation of magnetic states of Co nanoscale magnets shaped like elliptical disks (~300 nm major axis, 240 nm minor axis and 10 nm thickness) delineated on bulk 128 Y-cut lithium niobate using SAW. Specifically, isolated nanomagnets that are initially in single domain states with magnetization pointing along the major axis of the ellipse are driven into a vortex state by SAW waves. However, SAW waves can trigger complete magnetization reversal in nanomagnets of moderate shape anisotropy that are dipole coupled to a highly shape anisotropic neighboring nanomagnet. The authors acknowledge the use of high voltage and high frequency pulse generator from Prof. Umit Ozgur's lab and the help of Prof. Gary Atkinson in fabrication of the IDTs for generating the SAW. We acknowledge SHF-Small CCF-1216614 and CAREER CCF-1253370 grants; and use of CNST Nanofab facility at NIST, Gaithersburg.

  8. A compact and miniaturized high resolution capacitance dilatometer for measuring thermal expansion and magnetostriction

    SciTech Connect

    Kuechler, R.; Bauer, T.; Brando, M.; Steglich, F.

    2012-09-15

    We describe the design, construction, calibration, and two different applications of a miniature capacitance dilatometer. The device is suitable for thermal expansion and magnetostriction measurements from 300 K down to about 25 mK, with a resolution of 0.02 A at low temperatures. The main body of the dilatometer is fabricated from a single block of a Be-Cu alloy by electrical discharge milling. This creates an extremely compact high-resolution measuring cell. We have successfully tested and operated dilatometers of this new type with the commonly used physical property measurement system by quantum design, as well as with several other cryogenic refrigeration systems down to 25 mK and in magnetic fields up to 20 T. Here, the capacitance is measured with a commercially available capacitance bridge. Using a piezoelectric rotator from Attocube Systems, the cell can be rotated at T= 25 mK inside of an inner vacuum chamber of 40 mm diameter. The miniaturized design for the one-axis rotation setup allows a rotation of 360 Degree-Sign .

  9. WARM DEBRIS DISKS PRODUCED BY GIANT IMPACTS DURING TERRESTRIAL PLANET FORMATION

    SciTech Connect

    Genda, H.; Kobayashi, H.; Kokubo, E.

    2015-09-10

    In our solar system, Mars-sized protoplanets frequently collided with each other during the last stage of terrestrial planet formation, called the giant impact stage. Giant impacts eject a large amount of material from the colliding protoplanets into the terrestrial planet region, which may form debris disks with observable infrared excesses. Indeed, tens of warm debris disks around young solar-type stars have been observed. Here we quantitatively estimate the total mass of ejected materials during the giant impact stages. We found that ∼0.4 times the Earth’s mass is ejected in total throughout the giant impact stage. Ejected materials are ground down by collisional cascade until micron-sized grains are blown out by radiation pressure. The depletion timescale of these ejected materials is determined primarily by the mass of the largest body among them. We conducted high-resolution simulations of giant impacts to accurately obtain the mass of the largest ejected body. We then calculated the evolution of the debris disks produced by a series of giant impacts and depleted by collisional cascades to obtain the infrared excess evolution of the debris disks. We found that the infrared excess is almost always higher than the stellar infrared flux throughout the giant impact stage (∼100 Myr) and is sometimes ∼10 times higher immediately after a giant impact. Therefore, giant impact stages would explain the infrared excess from most observed warm debris disks. The observed fraction of stars with warm debris disks indicates that the formation probability of our solar-system-like terrestrial planets is approximately 10%.

  10. Formation of giant planets

    NASA Astrophysics Data System (ADS)

    Magni, G.; Coradini, A.

    2003-04-01

    In this presentation we address the problem of the formation of giant planets and their regular satellites. We study in particular the problem of formation of the Jupiter System comparing the results of the model with the present characteristics of the system, in order to identify what are those better represented by our approach. In fact here, using a 3-D hydro-dynamical code, we study the modalities of gas accretion onto a solid core, believed to be the seed from which Jupiter started. To do that we have modelled three main regions: the central planet, a turbulent accretion disk surrounding it and an extended region from which the gas is collected. In the extended region we treat the gas as a frictionless fluid. Our main goal is to identify what are the characteristics of the planet during its growth and the physical parameters affecting its growth at the expenses of the nebular gas present in the feeding zone. Moreover we want to understand what are the thermodynamical parameters characterizing the gas captured by the planet and swirling around it. Finally, we check if a disk can be formed in prograde rotation around the planet and if this disk can survive the final phases of the planet formation. Due to the interaction between the accreting planet and the disk it has been necessary to develop a complete model of the Jupiter’s structure. In fact the radiation emitted by the growing planet heats up the surrounding gas. In turn the planet’s thermodynamic structure depend on the mass accretion rate onto it. When the accretion is rapid, shock waves in the gas are formed close to the planet. This region cannot be safely treated by a numerical code; for this reason we have developed a semi-analytically model of a a turbulent accretion disk to be considered as transition between the planet and the surrounding disk.

  11. Giant Magellan Telescope: overview

    NASA Astrophysics Data System (ADS)

    Johns, Matt; McCarthy, Patrick; Raybould, Keith; Bouchez, Antonin; Farahani, Arash; Filgueira, Jose; Jacoby, George; Shectman, Steve; Sheehan, Michael

    2012-09-01

    The Giant Magellan Telescope (GMT) is a 25-meter optical/infrared extremely large telescope that is being built by an international consortium of universities and research institutions. It will be located at the Las Campanas Observatory, Chile. The GMT primary mirror consists of seven 8.4-m borosilicate honeycomb mirror segments made at the Steward Observatory Mirror Lab (SOML). Six identical off-axis segments and one on-axis segment are arranged on a single nearly-paraboloidal parent surface having an overall focal ratio of f/0.7. The fabrication, testing and verification procedures required to produce the closely-matched off-axis mirror segments were developed during the production of the first mirror. Production of the second and third off-axis segments is underway. GMT incorporates a seven-segment Gregorian adaptive secondary to implement three modes of adaptive-optics operation: natural-guide star AO, laser-tomography AO, and ground-layer AO. A wide-field corrector/ADC is available for use in seeing-limited mode over a 20-arcmin diameter field of view. Up to seven instruments can be mounted simultaneously on the telescope in a large Gregorian Instrument Rotator. Conceptual design studies were completed for six AO and seeing-limited instruments, plus a multi-object fiber feed, and a roadmap for phased deployment of the GMT instrument suite is being developed. The partner institutions have made firm commitments for approximately 45% of the funds required to build the telescope. Project Office efforts are currently focused on advancing the telescope and enclosure design in preparation for subsystem- and system-level preliminary design reviews which are scheduled to be completed in the first half of 2013.

  12. Rotation of Giant Stars

    NASA Astrophysics Data System (ADS)

    Kissin, Yevgeni; Thompson, Christopher

    2015-07-01

    The internal rotation of post-main sequence stars is investigated, in response to the convective pumping of angular momentum toward the stellar core, combined with a tight magnetic coupling between core and envelope. The spin evolution is calculated using model stars of initial mass 1, 1.5, and 5 {M}ȯ , taking into account mass loss on the giant branches. We also include the deposition of orbital angular momentum from a sub-stellar companion, as influenced by tidal drag along with the excitation of orbital eccentricity by a fluctuating gravitational quadrupole moment. A range of angular velocity profiles {{Ω }}(r) is considered in the envelope, extending from solid rotation to constant specific angular momentum. We focus on the backreaction of the Coriolis force, and the threshold for dynamo action in the inner envelope. Quantitative agreement with measurements of core rotation in subgiants and post-He core flash stars by Kepler is obtained with a two-layer angular velocity profile: uniform specific angular momentum where the Coriolis parameter {Co}\\equiv {{Ω }}{τ }{con}≲ 1 (here {τ }{con} is the convective time), and {{Ω }}(r)\\propto {r}-1 where {Co}≳ 1. The inner profile is interpreted in terms of a balance between the Coriolis force and angular pressure gradients driven by radially extended convective plumes. Inward angular momentum pumping reduces the surface rotation of subgiants, and the need for a rejuvenated magnetic wind torque. The co-evolution of internal magnetic fields and rotation is considered in Kissin & Thompson, along with the breaking of the rotational coupling between core and envelope due to heavy mass loss.

  13. Giant Mitochondria as Possible Bioindicators of Environmental Injuries in Fish Liver.

    PubMed

    Benedeczky, István; Nemcsók, János

    1997-01-01

    The effect of hypoxia (80 pHg) and simultaneously applied paraquat (1,1'-dimethyl-4,4-bipyridynum dichloride) was investigated on carp liver using electron microscopic methods. The appearance of giant mitochondria was the most conspicuous alteration in the liver cells. Most of the giant mitochondria were elongated and rod-shaped, often arranged side by side forming clusters beside the nucleus. Crook-like and irregular forms also occured among giant mitochondria. The lenght of the giant mitochondria often was greater than the diameter of nucleus: namely 5-10 µm. The outer membrane of the giant mitochondria was well preserved, but inner membranes (cristae) were usually absent, and a high density matrix filled in the inner space of mitochondria. High power magnification often revealed a regular, filamentous paracristal arrangement in the dense material of the matrix. Swollen giant mitochondria with light matrix and tubular elements also occured in low number. Although fine structural characteristics of carp liver giant mitochondria are not specific for inducing agents (hypoxia + paraquat treatment) the appearance of altered giant mitochondria may be a useful signal for monitoring cell damaging enviromental xenobiotics. PMID:11173631

  14. Meibomian gland function and giant papillary conjunctivitis.

    PubMed

    Mathers, W D; Billborough, M

    1992-08-15

    We examined 42 contact lens-wearing patients for clinical evidence of giant papillary conjunctivitis and for meibomian gland dysfunction with gland dropout. Fifteen patients were free of clinical signs and symptoms of giant papillary conjunctivitis, whereas 27 had clinical symptoms and evidence of giant papillary conjunctivitis. Patients with giant papillary conjunctivitis had significantly more gland dropout with an average of 0.6 +/- 1.2 gland absent in both lower eyelids compared with 0.2 +/- 0.4 gland absent in patients without giant papillary conjunctivitis. Additionally, the viscosity of meibomian gland excreta was greater in the giant papillary conjunctivitis group. There was no difference in tear osmolarity or in the Schirmer test results between the two groups. These results indicated patients with giant papillary conjunctivitis were more likely to have meibomian gland dysfunction with gland dropout than patients without giant papillary conjunctivitis.

  15. Giant myoma and erythrocytosis syndrome.

    PubMed

    Ozsaran, A A; Itil, I M; Terek, C; Kazandi, M; Dikmen, Y

    1999-08-01

    The objective of this study is to discuss the myomatous erythrocytosis syndrome in a patient with a giant subserous uterine myoma. She presented with plethora and an abdominal mass. After venesection of 4 units of blood, the preoperative haematocrit value of 53.3% and haemoglobin value of 17.5 g/dL had decreased to 48.6% and 16.8 g/dL levels, respectively. After the operative extraction of the giant subserous myoma with attached uterus weighing 14.2 kg, the haematocrit and the haemoglobin values had regressed to 40.3% and 14.3 g/dL levels, respectively. The findings indicated that the giant subserous myoma was the cause of the myomatous erythrocytosis syndrome in this patient. PMID:10554963

  16. Structure of giant muscle proteins

    PubMed Central

    Meyer, Logan C.; Wright, Nathan T.

    2013-01-01

    Giant muscle proteins (e.g., titin, nebulin, and obscurin) play a seminal role in muscle elasticity, stretch response, and sarcomeric organization. Each giant protein consists of multiple tandem structural domains, usually arranged in a modular fashion spanning 500 kDa to 4 MDa. Although many of the domains are similar in structure, subtle differences create a unique function of each domain. Recent high and low resolution structural and dynamic studies now suggest more nuanced overall protein structures than previously realized. These findings show that atomic structure, interactions between tandem domains, and intrasarcomeric environment all influence the shape, motion, and therefore function of giant proteins. In this article we will review the current understanding of titin, obscurin, and nebulin structure, from the atomic level through the molecular level. PMID:24376425

  17. "The joy in believing": the Cardiff giant, commercial deceptions, and styles of observation in Gilded Age America.

    PubMed

    Pettit, Michael

    2006-12-01

    This essay presents a historical epistemology of the nineteenth-century controversy concerning a scientific hoax, the Cardiff giant. My focus is on the shifting meanings given to the giant, which were based on epistemologies derived from scientific authority, religious belief, and market relations. In 1869 a farmer in Cardiff, New York, claimed to have discovered the fossilized remains of a prehistoric, perhaps biblical, giant on his property. While some scientists stressed the need to cooperate with commercial showmen, enthusiasm for the giant incited the ire of others, who sought to debunk it and the culture that sustained it. Drawing on local newspaper reports, memoirs, nineteenth-century exposés, and publicity materials associated with the giant's display, I link the episode to the history of popular and scientific observation. The giant was a particularly troubling spectacle because as an object of inquiry it blurred the modern boundaries separating nature, society, and religion. PMID:17367004

  18. Review of Giant cell arteritis

    PubMed Central

    Chacko, Joseph G.; Chacko, J. Anthony; Salter, Michael W.

    2014-01-01

    Giant-cell arteritis (GCA) is a systemic autoimmune disease affecting primarily the elderly. Giant cell arteritis can cause sudden and potentially bilateral sequential vision loss in the elderly. Therefore, it is considered a medical emergency in ophthalmology and a significant cause of morbidity in an increasingly aging population. Ophthalmologists need to be able to recognize the classic symptoms and signs of this disease, and then be able to work-up and treat these patients in an efficient manner. An in-depth review of GCA from the literature as well as personal clinical experience follows. PMID:25859139

  19. Chemical Abundances of Symbiotic Giants

    NASA Astrophysics Data System (ADS)

    Gałan, C.; Mikołajewska, J.; Hinkle, K. H.; Joyce, R. R.

    2015-12-01

    High resolution (R ˜ 50000), near-IR spectra were used to measure photospheric abundances of CNO and elements around the iron peak for 24 symbiotic giants. Spectrum synthesis was employed using local thermal equilibrium and hydrostatic model atmospheres. The metallicities are distributed in a wide range with maximum around [Fe/H] ˜-0.4 - - 0.3 dex. Enrichment in 14N indicates that all the sample giants have experienced the first dredge-up. The relative abundance of [Ti/Fe] is generally large in red symbiotic systems.

  20. Charting the Giants

    NASA Astrophysics Data System (ADS)

    2004-06-01

    zero expansion asymptotically after an infinite time and has a flat geometry). All three observational tests by means of supernovae (green), the cosmic microwave background (blue) and galaxy clusters converge at a Universe around Ωm ~ 0.3 and ΩΛ ~ 0.7. The dark red region for the galaxy cluster determination corresponds to 95% certainty (2-sigma statistical deviation) when assuming good knowledge of all other cosmological parameters, and the light red region assumes a minimum knowledge. For the supernovae and WMAP results, the inner and outer regions corespond to 68% (1-sigma) and 95% certainty, respectively. References: Schuecker et al. 2003, A&A, 398, 867 (REFLEX); Tonry et al. 2003, ApJ, 594, 1 (supernovae); Riess et al. 2004, ApJ, 607, 665 (supernovae) Galaxy clusters are far from being evenly distributed in the Universe. Instead, they tend to conglomerate into even larger structures, "super-clusters". Thus, from stars which gather in galaxies, galaxies which congregate in clusters and clusters tying together in super-clusters, the Universe shows structuring on all scales, from the smallest to the largest ones. This is a relict of the very early (formation) epoch of the Universe, the so-called "inflationary" period. At that time, only a minuscule fraction of one second after the Big Bang, the tiny density fluctuations were amplified and over the eons, they gave birth to the much larger structures. Because of the link between the first fluctuations and the giant structures now observed, the unique REFLEX catalogue - the largest of its kind - allows astronomers to put considerable constraints on the content of the Universe, and in particular on the amount of dark matter that is believed to pervade it. Rather interestingly, these constraints are totally independent from all other methods so far used to assert the existence of dark matter, such as the study of very distant supernovae (see e.g. ESO PR 21/98) or the analysis of the Cosmic Microwave background (e

  1. Positive magnetoresistance and large magnetostriction at first-order antiferro ferromagnetic phase transitions in RMn2Si2 compounds

    NASA Astrophysics Data System (ADS)

    Gerasimov, E. G.; Mushnikov, N. V.; Koyama, K.; Kanomata, T.; Watanabe, K.

    2008-11-01

    The magnetostriction and magnetoresistance associated with the field-induced and spontaneous first-order antiferro-ferromagnetic (AF-F) phase transitions have been studied for quasi-single-crystalline samples of La0.25Sm0.75Mn2Si2, La0.25Y0.75Mn2Si2 and La0.27Y0.73Mn2Si2 compounds with natural layered ThCr2Si2-type structure. It was found that both the spontaneous and field-induced AF-F transitions are accompanied by a large volume magnetostriction ΔV/V≈2 × 10-3 and anisotropic linear changes of the lattice parameters Δa/a≈1.6 × 10-3, Δc/c≈-0.75 × 10-3. The field-induced AF-F magnetic phase transition has been observed in magnetic fields applied both along the c-axis and in the basal plane, and the magnetostriction value is virtually independent of the direction of applied field. It has been found also that the magnetoresistance is positive in these compounds (the value of the electrical resistance in the ferromagnetic state is higher than that in the antiferromagnetic state) for the fields applied both along the c-axis and in the basal plane. The value of the magnetoresistance observed along the c-axis is 30 times as high as that in the basal plane. The obtained results indicate that the electronic band structure changes are likely responsible for the AF-F magnetic phase transitions observed in the RMn2X2 compounds.

  2. Giant magnetoresistance through a single molecule.

    PubMed

    Schmaus, Stefan; Bagrets, Alexei; Nahas, Yasmine; Yamada, Toyo K; Bork, Annika; Bowen, Martin; Beaurepaire, Eric; Evers, Ferdinand; Wulfhekel, Wulf

    2011-03-01

    Magnetoresistance is a change in the resistance of a material system caused by an applied magnetic field. Giant magnetoresistance occurs in structures containing ferromagnetic contacts separated by a metallic non-magnetic spacer, and is now the basis of read heads for hard drives and for new forms of random access memory. Using an insulator (for example, a molecular thin film) rather than a metal as the spacer gives rise to tunnelling magnetoresistance, which typically produces a larger change in resistance for a given magnetic field strength, but also yields higher resistances, which are a disadvantage for real device operation. Here, we demonstrate giant magnetoresistance across a single, non-magnetic hydrogen phthalocyanine molecule contacted by the ferromagnetic tip of a scanning tunnelling microscope. We measure the magnetoresistance to be 60% and the conductance to be 0.26G(0), where G(0) is the quantum of conductance. Theoretical analysis identifies spin-dependent hybridization of molecular and electrode orbitals as the cause of the large magnetoresistance. PMID:21336269

  3. Measurement of magnetostriction and induced magnetic anisotropy by SAMR method in Co-rich stress + field annealed amorphous ribbons

    NASA Astrophysics Data System (ADS)

    Blanco, J. M.; González, J.; Vázquez, M.; Barandiarán, J. M.; Hernando, A.

    1991-10-01

    The saturation magnetostriction (λ s) and induced magnetic anisotropy ( Kind) in (Co 0.95Fe 0.05) 80Si 10B 10 annealed amorphous alloy ribbons have been measured at room temperature with the SAMR (small-angle magnetization rotation) method. The ribbons were annealed under simulataneous action of a stress and/or magnetic field. The variations of λ s and Kind show parallel trends in the cases of stress and stress+field annealings but not for single field annealing. These variations are connected with microstructural changes originated during the treatments.

  4. The giant panda gut microbiome.

    PubMed

    Wei, Fuwen; Wang, Xiao; Wu, Qi

    2015-08-01

    Giant pandas (Ailuropoda melanoleuca) are bamboo specialists that evolved from carnivores. Their gut microbiota probably aids in the digestion of cellulose and this is considered an example of gut microbiota adaptation to a bamboo diet. However, this issue remains unresolved and further functional and compositional studies are needed.

  5. Giant Serpentine Aneurysms: Multidisciplinary Management

    PubMed Central

    Anshun, W.; Feng, L.; Daming, W.

    2000-01-01

    Summary Sixty-five cases of intracranial giant serpentine aneurysms (GSΛs), including 61 cases reported in the literature and four additional cases presented in this study were reviewed. The clinical presentation, possible causes, natural history, and especially management of GSAs are discussed with emphasis on the need for aggressive intervention and multidisciplinary management. PMID:20667180

  6. The giant panda gut microbiome.

    PubMed

    Wei, Fuwen; Wang, Xiao; Wu, Qi

    2015-08-01

    Giant pandas (Ailuropoda melanoleuca) are bamboo specialists that evolved from carnivores. Their gut microbiota probably aids in the digestion of cellulose and this is considered an example of gut microbiota adaptation to a bamboo diet. However, this issue remains unresolved and further functional and compositional studies are needed. PMID:26143242

  7. Pressure tuning of the magnetic transition in Gd{sub5}(Si{sub 0.375} Ge{sub 0.625}){sub 4}giant magnetocaloric effect material.

    SciTech Connect

    Tseng, Y. C.; Haskel, D.; Lang, J. C.; Mudryk, Ya.; Pecharsky, V. K.; Gschneidner, K. A.; Northwestern Univ.; Iowa State Univ.

    2008-04-01

    The effect of hydrostatic pressure on the ferromagnetic ordering transition of the monoclinic Gd{sub 5}(Si{sub 0.375}Ge{sub 0.625}){sub 4} giant magnetocaloric effect compound was investigated using x-ray magnetic circular dichroism measurements in a diamond anvil cell. The Curie temperature T{sub C} increases linearly with applied pressure up to {approx}7.2 GPa, at which point a discontinuity in dT{sub c}/dP occurs. This discontinuity, which appears when T{sub C} reaches {approx}277 K, is also observed when the unit cell volume is reduced by Si doping and is associated with the volume-driven monoclinic (M) to orthorhombic [O(I)] structural transition.

  8. Improvement of force factor of magnetostrictive vibration power generator for high efficiency

    SciTech Connect

    Kita, Shota Ueno, Toshiyuki; Yamada, Sotoshi

    2015-05-07

    We develop high power magnetostrictive vibration power generator for battery-free wireless electronics. The generator is based on a cantilever of parallel beam structure consisting of coil-wound Galfenol and stainless plates with permanent magnet for bias. Oscillating force exerted on the tip bends the cantilever in vibration yields stress variation of Galfenol plate, which causes flux variation and generates voltage on coil due to the law of induction. This generator has advantages over conventional, such as piezoelectric or moving magnet types, in the point of high efficiency, highly robust, and low electrical impedance. Our concern is the improvement of energy conversion efficiency dependent on the dimension. Especially, force factor, the conversion ratio of the electromotive force (voltage) on the tip velocity in vibration, has an important role in energy conversion process. First, the theoretical value of the force factor is formulated and then the validity was verified by experiments, where we compare four types of prototype with parameters of the dimension using 7.0 × 1.5 × 50 mm beams of Galfenol with 1606-turn wound coil. In addition, the energy conversion efficiency of the prototypes depending on load resistance was measured. The most efficient prototype exhibits the maximum instantaneous power of 0.73 W and energy of 4.7 mJ at a free vibration of frequency of 202 Hz in the case of applied force is 25 N. Further, it was found that energy conversion efficiency depends not only on the force factor but also on the damping (mechanical loss) of the vibration.

  9. Improvement of force factor of magnetostrictive vibration power generator for high efficiency

    NASA Astrophysics Data System (ADS)

    Kita, Shota; Ueno, Toshiyuki; Yamada, Sotoshi

    2015-05-01

    We develop high power magnetostrictive vibration power generator for battery-free wireless electronics. The generator is based on a cantilever of parallel beam structure consisting of coil-wound Galfenol and stainless plates with permanent magnet for bias. Oscillating force exerted on the tip bends the cantilever in vibration yields stress variation of Galfenol plate, which causes flux variation and generates voltage on coil due to the law of induction. This generator has advantages over conventional, such as piezoelectric or moving magnet types, in the point of high efficiency, highly robust, and low electrical impedance. Our concern is the improvement of energy conversion efficiency dependent on the dimension. Especially, force factor, the conversion ratio of the electromotive force (voltage) on the tip velocity in vibration, has an important role in energy conversion process. First, the theoretical value of the force factor is formulated and then the validity was verified by experiments, where we compare four types of prototype with parameters of the dimension using 7.0 × 1.5 × 50 mm beams of Galfenol with 1606-turn wound coil. In addition, the energy conversion efficiency of the prototypes depending on load resistance was measured. The most efficient prototype exhibits the maximum instantaneous power of 0.73 W and energy of 4.7 mJ at a free vibration of frequency of 202 Hz in the case of applied force is 25 N. Further, it was found that energy conversion efficiency depends not only on the force factor but also on the damping (mechanical loss) of the vibration.

  10. Ab initio search for a high permeability material based on bcc iron

    NASA Astrophysics Data System (ADS)

    Ostanin, S.; Staunton, J. B.; Razee, S. S.; Demangeat, C.; Ginatempo, B.; Bruno, Ezio

    2004-02-01

    Using the fully relativistic spin-polarized Korringa-Kohn-Rostoker method, we study the prototypical soft magnet, bcc iron. We investigate how its magnetic anisotropy (MAE) varies as a function of volume, band filling, and tetragonal distortions of the crystal lattice. We follow the trends of the linear magnetostriction and magnetic permeability. We find that a slight reduction in band filling and modest lattice expansion produces a significant magnetic softening of this model system. We explore whether this situation can be realized by doping bcc Fe with vanadium. Treating the compositional disorder with the coherent potential approximation, we calculate the magnetic anisotropy and magnetostriction trends of iron-rich Fe1-cVc disordered alloys and find the behavior to accord with the predictions from the bcc Fe model. In particular we find that for c≈0.1 the MAE is very small and the linear magnetostriction is zero. We propose Fe0.9V0.1 as a high permeability material. Fair agreement with experimental values for the MAE and magnetostriction of both Fe and FeV is found.

  11. Atmospheric models for post- giant impact planets

    NASA Astrophysics Data System (ADS)

    Lupu, R.; Zahnle, K. J.; Marley, M. S.; Schaefer, L. K.; Fegley, B.; Morley, C.; Cahoy, K.; Freedman, R. S.; Fortney, J. J.

    2013-12-01

    The final assembly of terrestrial planets is now universally thought to have occurred through a series of giant impacts, such as Earth's own Moon-forming impact. These collisions take place over a time interval of about 100 million years, during which time it takes at least 10 collisions between planets to make a Venus or an Earth. In the aftermath of one of these collisions the surviving planet is hot, and can remain hot for millions of years. During this phase of accretion, the proto-terrestrial planet may have a dense steam atmosphere, that will affect both the cooling of the planet and our ability to detect it. Here we explore the atmospheric chemistry, photochemistry, and spectral signatures of post-giant-impact terrestrial planets enveloped by thick atmospheres consisting of vaporized rock material. The atmospheric chemistry is computed self-consistently for atmospheres in equilibrium with hot surfaces, with compositions reflecting either the bulk silicate Earth (BSE, which includes the crust, mantle, atmosphere and oceans) or Earth's continental crust (CC). These two cases allow us to examine differences in atmospheres formed by outgassing of silica-rich (felsic) rocks - like the Earth's continental crust - and MgO- and FeO-rich (mafic) rocks - like the BSE. Studies of detrital zircons from Jack Hills, Australia, show that the continental crust existed 164 million years after the formation of the solar system, in which case the material vaporized in a giant impact should likely reflect the CC composition. However, if at the time of impact the surface of the planet does not yet exhibit the formation of continents, then the BSE case becomes relevant. We compute atmospheric profiles for surface temperatures ranging from 1000 to 2200 K, surface pressures of 10 and 100 bar, and surface gravities of 10 and 30 m/s^2. We account for all major molecular and atomic opacity sources, including collision-induced absorption, to derive the atmospheric structure and compute

  12. Exploring How Giant Planet Formation Affected the Asteroid Belt

    NASA Astrophysics Data System (ADS)

    Kretke, Katherine A.; Levison, Harold F.; Bottke, William

    2016-10-01

    The asteroid belt is observed to be a mixture of objects with different compositions, with volatile-poor asteroids (mostly S-complex) dominant in the inner asteroid belt while volatile-rich (mostly C-complex) asteroids dominate the outer asteroid belt. While this general compositional stratification was originally thought to be an indicator of the primordial temperature gradient in the protoplanetary disk, the very distinct properties of these populations suggest that they must represent two completely decoupled reservoirs, not a simple gradient (e.g., Warren 2011). It is possible to create this general stratification (as well as the observed mixing) as the implantation of outer Solar System material into the asteroid belt by the early migration of the giant planets (e.g. the Grand Tack, Walsh et al. 2011). However, this presupposes that the inner and outer Solar System materials were still sorted in their primordial locations prior to any migration of the planets. The lack of a fully dynamically self-consistent model of giant planet core formation has prevented the study of how the core formation process itself may result in dynamical mixing in the early Solar System's history. Recently, pebble accretion, the process by which planetesimals can grow to giant planet cores via the accretion of small, rapidly drifting sub-meter-sized bodies known as ``pebbles,'' (Lambrechts & Johansen 2012, Levison, Kretke & Duncan 2015) finally offers such a model. Here we show how the process of giant planet formation will impact the surrounding planetesimal population, possibly resulting in the observed compositional mixture of the asteroid belt, without requiring a dramatic migration of the giant planets. For example, preliminary runs suggest planetesimals from the Jupiter-formation zone can be implanted in the outer main belt via interactions with scattered Jupiter-zone protoplanets. This could potentially provide an alternative non-Grand Tack solution to the origin of many C

  13. The giant dipole vortex

    NASA Astrophysics Data System (ADS)

    Arnoldus, Henk F.; Li, Xin; Xu, Zhangjin

    2016-06-01

    The field lines of energy flow of radiation emitted by an oscillating electric dipole in free space are either straight lines (linear dipole) or they form a vortex (rotating dipole). When the dipole is embedded in a material, the properties of the medium affect the direction of energy flow. Damping due to the imaginary part of the relative permittivity ? makes the field lines curve for the case of a linear dipole, and for a rotating dipole, the shape of the vortex is altered. In addition, a negative value of the real part of ? has the effect that the rotation direction of the vortex reverses for the case of a rotating dipole. The value of the relative permeability ? has in general not much effect on the redistribution of the direction of energy propagation. We show that a dramatic effect occurs when the embedding material is near-single-negative (both ? and ? approximately real, and the real parts of opposite sign). The curving of field lines is in general a sub-wavelength phenomenon. For near-single-negative materials, however, this curving extends over large distances from the dipole. In particular, the small free-space vortex of a rotating dipole becomes a vortex of enormous dimensions when the radiation is emitted into a near-single-negative material.

  14. Bio-assembled nanocomposites in conch shells exhibit giant electret hysteresis.

    PubMed

    Yao, Yingbang; Wang, QingXiao; Wang, Hongtao; Zhang, Bei; Zhao, Chao; Wang, Zhihong; Xu, Zhengkui; Wu, Ying; Huang, Wei; Qian, Pei-Yuan; Zhang, Xi Xiang

    2013-02-01

    Giant electric polarization (2000-4000 μC cm(-2)) is observed in natural conch shells. The nanolaminas and biopolymer layers of their unique hierarchical microstructures exhibit ferroelectret behavior and account for the observed polarization. Such huge polarization leads to extremely high pyroelectric coefficients, 2-3 orders of magnitude larger than those of conventional ferroelectric materials. The possibility of tailoring the giant polarization for various applications is considered.

  15. Bio-assembled nanocomposites in conch shells exhibit giant electret hysteresis.

    PubMed

    Yao, Yingbang; Wang, QingXiao; Wang, Hongtao; Zhang, Bei; Zhao, Chao; Wang, Zhihong; Xu, Zhengkui; Wu, Ying; Huang, Wei; Qian, Pei-Yuan; Zhang, Xi Xiang

    2013-02-01

    Giant electric polarization (2000-4000 μC cm(-2)) is observed in natural conch shells. The nanolaminas and biopolymer layers of their unique hierarchical microstructures exhibit ferroelectret behavior and account for the observed polarization. Such huge polarization leads to extremely high pyroelectric coefficients, 2-3 orders of magnitude larger than those of conventional ferroelectric materials. The possibility of tailoring the giant polarization for various applications is considered. PMID:23090938

  16. Spectroscopic Determination of Masses (and Implied Ages) for Red Giants

    NASA Astrophysics Data System (ADS)

    Ness, M.; Hogg, David W.; Rix, H.-W.; Martig, M.; Pinsonneault, Marc H.; Ho, A. Y. Q.

    2016-06-01

    The mass of a star is arguably its most fundamental parameter. For red giant stars, tracers luminous enough to be observed across the Galaxy, mass implies a stellar evolution age. It has proven to be extremely difficult to infer ages and masses directly from red giant spectra using existing methods. From the Kepler and apogee surveys, samples of several thousand stars exist with high-quality spectra and asteroseismic masses. Here we show that from these data we can build a data-driven spectral model using The Cannon, which can determine stellar masses to ˜0.07 dex from apogee dr12 spectra of red giants; these imply age estimates accurate to ˜0.2 dex (40%). We show that The Cannon constrains these ages foremost from spectral regions with CN absorption lines, elements whose surface abundances reflect mass-dependent dredge-up. We deliver an unprecedented catalog of 70,000 giants (including 20,000 red clump stars) with mass and age estimates, spanning the entire disk (from the Galactic center to R˜ 20 kpc). We show that the age information in the spectra is not simply a corollary of the birth-material abundances {{[Fe/H]}} and [α /{Fe}], and that, even within a monoabundance population of stars, there are age variations that vary sensibly with Galactic position. Such stellar age constraints across the Milky Way open up new avenues in Galactic archeology.

  17. Giant Piezoelectricity on Si for Hyperactive MEMS

    NASA Astrophysics Data System (ADS)

    Baek, S. H.; Park, J.; Kim, D. M.; Aksyuk, V. A.; Das, R. R.; Bu, S. D.; Felker, D. A.; Lettieri, J.; Vaithyanathan, V.; Bharadwaja, S. S. N.; Bassiri-Gharb, N.; Chen, Y. B.; Sun, H. P.; Folkman, C. M.; Jang, H. W.; Kreft, D. J.; Streiffer, S. K.; Ramesh, R.; Pan, X. Q.; Trolier-McKinstry, S.; Schlom, D. G.; Rzchowski, M. S.; Blick, R. H.; Eom, C. B.

    2011-11-01

    Microelectromechanical systems (MEMS) incorporating active piezoelectric layers offer integrated actuation, sensing, and transduction. The broad implementation of such active MEMS has long been constrained by the inability to integrate materials with giant piezoelectric response, such as Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT). We synthesized high-quality PMN-PT epitaxial thin films on vicinal (001) Si wafers with the use of an epitaxial (001) SrTiO3 template layer with superior piezoelectric coefficients (e31,f = -27 ± 3 coulombs per square meter) and figures of merit for piezoelectric energy-harvesting systems. We have incorporated these heterostructures into microcantilevers that are actuated with extremely low drive voltage due to thin-film piezoelectric properties that rival bulk PMN-PT single crystals. These epitaxial heterostructures exhibit very large electromechanical coupling for ultrasound medical imaging, microfluidic control, mechanical sensing, and energy harvesting.

  18. Giant impacts on a primitive Uranus

    NASA Technical Reports Server (NTRS)

    Slattery, Wayne L.; Benz, Willy; Cameron, A. G. W.

    1992-01-01

    Simulations of collisions are conducted between a model of the primitive Uranus and 1-3 earth-mass impactors, using smooth-particle hydrodynamics. A series of collisions was simulated for each impactor while varying the total angular momentum of the system. Most of the simulation runs left ices in orbit; a subset of the runs also left rock or iron (from the impactor). It is concluded on the basis of these results that there is a wide range of giant impacts which could have produced the current period and inclination of the spin axis relative to the plane of the ecliptic. A subset of these could have deposited the material in orbit from which the regular satellites of Uranus were assembled.

  19. Giant intracranial aneurysms: rapid sequential computed tomography

    SciTech Connect

    Pinto, R.S.; Cohen, W.A.; Kricheff, I.I.; Redington, R.W.; Berninger, W.H.

    1982-11-01

    Giant intracranial aneurysms often present as mass lesions rather than with subarachnoid hemorrhage. Routine computed tomographic (CT) scans with contrast material will generally detect them, but erroneous diagnosis of basal meningioma is possible. Rapid sequential scanning (dynamic CT) after bolus injection of 40 ml of Renografin-76 can conclusively demonstrate an intracranial aneurysm, differentiating it from other lesions by transit-time analysis of the passage of contrast medium. In five patients, the dynamics of contrast bolus transit in aneurysms were consistently different from the dynamics in pituitary tumors, craniopharyngiomas, and meningiomas, thereby allowing a specific diagnosis. Dynamic CT was also useful after treatment of the aneurysms by carotid artery ligation and may be used as an alternative to angiographic evaluation in determining luminal patency or thrombosis.

  20. Giant barocaloric effects at low pressure in ferrielectric ammonium sulphate.

    PubMed

    Lloveras, P; Stern-Taulats, E; Barrio, M; Tamarit, J-Ll; Crossley, S; Li, W; Pomjakushin, V; Planes, A; Mañosa, Ll; Mathur, N D; Moya, X

    2015-11-26

    Caloric effects are currently under intense study due to the prospect of environment-friendly cooling applications. Most of the research is centred on large magnetocaloric effects and large electrocaloric effects, but the former require large magnetic fields that are challenging to generate economically and the latter require large electric fields that can only be applied without breakdown in thin samples. Here we use small changes in hydrostatic pressure to drive giant inverse barocaloric effects near the ferrielectric phase transition in ammonium sulphate. We find barocaloric effects and strengths that exceed those previously observed near magnetostructural phase transitions in magnetic materials. Our findings should therefore inspire the discovery of giant barocaloric effects in a wide range of unexplored ferroelectric materials, ultimately leading to barocaloric cooling devices.

  1. Giant barocaloric effects at low pressure in ferrielectric ammonium sulphate.

    PubMed

    Lloveras, P; Stern-Taulats, E; Barrio, M; Tamarit, J-Ll; Crossley, S; Li, W; Pomjakushin, V; Planes, A; Mañosa, Ll; Mathur, N D; Moya, X

    2015-01-01

    Caloric effects are currently under intense study due to the prospect of environment-friendly cooling applications. Most of the research is centred on large magnetocaloric effects and large electrocaloric effects, but the former require large magnetic fields that are challenging to generate economically and the latter require large electric fields that can only be applied without breakdown in thin samples. Here we use small changes in hydrostatic pressure to drive giant inverse barocaloric effects near the ferrielectric phase transition in ammonium sulphate. We find barocaloric effects and strengths that exceed those previously observed near magnetostructural phase transitions in magnetic materials. Our findings should therefore inspire the discovery of giant barocaloric effects in a wide range of unexplored ferroelectric materials, ultimately leading to barocaloric cooling devices. PMID:26607989

  2. Giant barocaloric effects at low pressure in ferrielectric ammonium sulphate

    PubMed Central

    Lloveras, P.; Stern-Taulats, E.; Barrio, M.; Tamarit, J.-Ll.; Crossley, S.; Li, W.; Pomjakushin, V.; Planes, A.; Mañosa, Ll.; Mathur, N. D.; Moya, X.

    2015-01-01

    Caloric effects are currently under intense study due to the prospect of environment-friendly cooling applications. Most of the research is centred on large magnetocaloric effects and large electrocaloric effects, but the former require large magnetic fields that are challenging to generate economically and the latter require large electric fields that can only be applied without breakdown in thin samples. Here we use small changes in hydrostatic pressure to drive giant inverse barocaloric effects near the ferrielectric phase transition in ammonium sulphate. We find barocaloric effects and strengths that exceed those previously observed near magnetostructural phase transitions in magnetic materials. Our findings should therefore inspire the discovery of giant barocaloric effects in a wide range of unexplored ferroelectric materials, ultimately leading to barocaloric cooling devices. PMID:26607989

  3. Giant barocaloric effects at low pressure in ferrielectric ammonium sulphate

    NASA Astrophysics Data System (ADS)

    Lloveras, P.; Stern-Taulats, E.; Barrio, M.; Tamarit, J.-Ll.; Crossley, S.; Li, W.; Pomjakushin, V.; Planes, A.; Mañosa, Ll.; Mathur, N. D.; Moya, X.

    2015-11-01

    Caloric effects are currently under intense study due to the prospect of environment-friendly cooling applications. Most of the research is centred on large magnetocaloric effects and large electrocaloric effects, but the former require large magnetic fields that are challenging to generate economically and the latter require large electric fields that can only be applied without breakdown in thin samples. Here we use small changes in hydrostatic pressure to drive giant inverse barocaloric effects near the ferrielectric phase transition in ammonium sulphate. We find barocaloric effects and strengths that exceed those previously observed near magnetostructural phase transitions in magnetic materials. Our findings should therefore inspire the discovery of giant barocaloric effects in a wide range of unexplored ferroelectric materials, ultimately leading to barocaloric cooling devices.

  4. Influence of composition and heat treatment on damping and magnetostrictive properties of Fe–18%(Ga + Al) alloys

    SciTech Connect

    Golovin, I. S.; Palacheva, V. V.; Zadorozhnyy, V. Yu.; Zhu, J.; Jiang, H.; Cifre, J.; Lograsso, T. A.

    2014-07-16

    The structure, magnetostriction and damping properties of Fe82Ga(18–x)Alx (x = 0, 5, 8, 12) alloys were analyzed. The anelastic response of Fe–18(Ga + Al) alloys was studied as a function of temperature (from 0 to 600 °C), frequency (from 0.01 to 200 Hz) and amplitude (from 0.0004% to 0.2%) of forced vibrations. The origin of the relatively high damping capacity of Fe–Ga–Al alloy at room temperature was determined by applying a magnetic field and different heat treatment regimes. The substitution of Ga by Al in Fe–18% Ga alloys was found to decrease magnetostriction and damping. The heat treatment of alloys influences the damping capacity of alloys more than variations of their chemical compositions. Thermally activated frequency and temperature-dependent anelastic effects in Fe–Ga–Al alloys were analyzed and the corresponding activation parameters for relaxation processes were evaluated. Internal friction effects caused by structural transformations were recorded and were found to be consistent with the A2 → D03 → L12 reaction. Thus, the physical mechanisms for all anelastic effects are discussed.

  5. Influence of composition and heat treatment on damping and magnetostrictive properties of Fe–18%(Ga + Al) alloys

    DOE PAGES

    Golovin, I. S.; Palacheva, V. V.; Zadorozhnyy, V. Yu.; Zhu, J.; Jiang, H.; Cifre, J.; Lograsso, T. A.

    2014-07-16

    The structure, magnetostriction and damping properties of Fe82Ga(18–x)Alx (x = 0, 5, 8, 12) alloys were analyzed. The anelastic response of Fe–18(Ga + Al) alloys was studied as a function of temperature (from 0 to 600 °C), frequency (from 0.01 to 200 Hz) and amplitude (from 0.0004% to 0.2%) of forced vibrations. The origin of the relatively high damping capacity of Fe–Ga–Al alloy at room temperature was determined by applying a magnetic field and different heat treatment regimes. The substitution of Ga by Al in Fe–18% Ga alloys was found to decrease magnetostriction and damping. The heat treatment of alloysmore » influences the damping capacity of alloys more than variations of their chemical compositions. Thermally activated frequency and temperature-dependent anelastic effects in Fe–Ga–Al alloys were analyzed and the corresponding activation parameters for relaxation processes were evaluated. Internal friction effects caused by structural transformations were recorded and were found to be consistent with the A2 → D03 → L12 reaction. Thus, the physical mechanisms for all anelastic effects are discussed.« less

  6. A Guided Wave Sensor Based on the Inverse Magnetostrictive Effect for Distinguishing Symmetric from Asymmetric Features in Pipes

    PubMed Central

    Xu, Jiang; Wu, Xinjun; Kong, Dongying; Sun, Pengfei

    2015-01-01

    The magnetostrictive guided wave sensor with a single induced winding cannot distinguish axially symmetric from non-axially symmetric features in a pipe, because it is impossible for the sensor to detect the non-axially symmetric mode waves. When we study the effect of the change of the magnetic field in the air zone for receiving the longitudinal guided wave mode, we find that the change of the magnetic flux in the air zone is almost equivalent to the change of the flux in the pipe wall, but in opposite directions. Based on this phenomenon, we present a sensor that can detect the flexural-mode waves in pipes based on the inverse magnetostrictive effect. The sensor is composed of several coils that are arranged evenly on the outside of pipes. The coils induce a change in magnetic flux in the air to detect the flexural-mode waves. The waves can be determined by adding a phase delay to the induced signals. The symmetric and asymmetric features of a pipe can be distinguished using the sensor. A prototype sensor that can detect F(1,3) and F(2,3) mode waves is presented. The function of the sensor is verified by experiments. PMID:25738769

  7. Influence of composition and heat treatment on damping and magnetostrictive properties of Fe-18%(Ga+Al) alloys

    SciTech Connect

    Golovin, I S; Palacheva, V V; Zadorozhnyy, V Yu; Zhu, J; Jiang, H; Cifre, J; Lograsso, Thomas A

    2014-10-01

    The structure, magnetostriction and damping properties of Fe82Ga(18?x)Alx(x = 0, 5, 8, 12) alloys were analyzed. The anelastic response of Fe–18(Ga + Al) alloys was studied as a function of temperature (from 0 to 600 ?C), frequency (from 0.01 to 200 Hz) and amplitude (from 0.0004% to 0.2%) of forced vibrations. The origin of the relatively high damping capacity of Fe–Ga–Al alloy at room temperature was determined by applying a magnetic field and different heat treatment regimes. The substitution of Ga by Al in Fe–18% Ga alloys was found to decrease magnetostriction and damping. The heat treatment of alloys influences the damping capacity of alloys more than variations of their chemical compositions. Thermally activated frequency and temperature-dependent anelastic effects in Fe– Ga–Al alloys were analyzed and the corresponding activation parameters for relaxation processes were evaluated. Internal friction effects caused by structural transformations were recorded and were found to be consistent with the A2 ! D03! L12reaction. The physical mechanisms for all anelastic effects are discussed

  8. Self-vibration cancellation of a novel bi-directional magnetized NdFeB/magnetostrictive/piezoelectric laminate.

    PubMed

    Leung, Chung Ming; Wang, Feifei; Wang, Ya

    2016-06-01

    A novel magnetoelectric (ME) laminated composite structure is proposed in this work, aiming to provide a good self-vibration cancellation performance under the magnetic field detection environment. The proposed structure consists of two Terfenol-D magnetostrictive alloy plates which are revised and length-magnetized by two NdFeB magnets bonded on the top surface of a thickness-polarized Pb(Zr, Ti)O3 (PZT) ceramic plate with separate electrodes. Experiments have shown that great vibration suppression up to 44 dB under harmonic disturbance was observed. The ME coefficient of the proposed structure also reaches up to ∼29 mV/Oe at non-resonance frequency and 758 mV/Oe at resonance frequency of 79 kHz which is ∼2 times larger than the traditional L-T Terfenol-D/PZT bilayer configuration of the same scale. Such performance improvement is achieved based on the bi-directional magnetic field bias (HBias) of two NdFeB magnets in magnetostrictive layer, internal in-series electrical wire connection in piezoelectric layer. The proposed design has great potential to be used for industrial applications associated with heavy environmental vibration noise. PMID:27370467

  9. Self-vibration cancellation of a novel bi-directional magnetized NdFeB/magnetostrictive/piezoelectric laminate

    NASA Astrophysics Data System (ADS)

    Leung, Chung Ming; Wang, Feifei; Wang, Ya

    2016-06-01

    A novel magnetoelectric (ME) laminated composite structure is proposed in this work, aiming to provide a good self-vibration cancellation performance under the magnetic field detection environment. The proposed structure consists of two Terfenol-D magnetostrictive alloy plates which are revised and length-magnetized by two NdFeB magnets bonded on the top surface of a thickness-polarized Pb(Zr, Ti)O3 (PZT) ceramic plate with separate electrodes. Experiments have shown that great vibration suppression up to 44 dB under harmonic disturbance was observed. The ME coefficient of the proposed structure also reaches up to ˜29 mV/Oe at non-resonance frequency and 758 mV/Oe at resonance frequency of 79 kHz which is ˜2 times larger than the traditional L-T Terfenol-D/PZT bilayer configuration of the same scale. Such performance improvement is achieved based on the bi-directional magnetic field bias (HBias) of two NdFeB magnets in magnetostrictive layer, internal in-series electrical wire connection in piezoelectric layer. The proposed design has great potential to be used for industrial applications associated with heavy environmental vibration noise.

  10. Mechanism of spin crossover in LaCoO3 resolved by shape magnetostriction in pulsed magnetic fields

    NASA Astrophysics Data System (ADS)

    Rotter, M.; Wang, Z.-S.; Boothroyd, A. T.; Prabhakaran, D.; Tanaka, A.; Doerr, M.

    2014-11-01

    In the scientific description of unconventional transport properties of oxides (spin-dependent transport, superconductivity etc.), the spin-state degree of freedom plays a fundamental role. Because of this, temperature- or magnetic field-induced spin-state transitions are in the focus of solid-state physics. Cobaltites, e.g. LaCoO3, are prominent examples showing these spin transitions. However, the microscopic nature of the spontaneous spin crossover in LaCoO3 is still controversial. Here we report magnetostriction measurements on LaCoO3 in magnetic fields up to 70 T to study the sharp, field-induced transition at Hc ~ 60 T. Measurements of both longitudinal and transversal magnetostriction allow us to separate magnetovolume and magnetodistortive changes. We find a large increase in volume, but only a very small increase in tetragonal distortion at Hc. The results, supported by electronic energy calculations by the configuration interaction cluster method, provide compelling evidence that above Hc LaCoO3 adopts a correlated low spin/high spin state.

  11. Mechanism of spin crossover in LaCoO3 resolved by shape magnetostriction in pulsed magnetic fields.

    PubMed

    Rotter, M; Wang, Z-S; Boothroyd, A T; Prabhakaran, D; Tanaka, A; Doerr, M

    2014-01-01

    In the scientific description of unconventional transport properties of oxides (spin-dependent transport, superconductivity etc.), the spin-state degree of freedom plays a fundamental role. Because of this, temperature- or magnetic field-induced spin-state transitions are in the focus of solid-state physics. Cobaltites, e.g. LaCoO3, are prominent examples showing these spin transitions. However, the microscopic nature of the spontaneous spin crossover in LaCoO3 is still controversial. Here we report magnetostriction measurements on LaCoO3 in magnetic fields up to 70 T to study the sharp, field-induced transition at Hc ≈ 60 T. Measurements of both longitudinal and transversal magnetostriction allow us to separate magnetovolume and magnetodistortive changes. We find a large increase in volume, but only a very small increase in tetragonal distortion at Hc. The results, supported by electronic energy calculations by the configuration interaction cluster method, provide compelling evidence that above Hc LaCoO3 adopts a correlated low spin/high spin state. PMID:25384532

  12. Interpretation of a Mode Converted Guided Wave Signal from a Piping Mockup by a Magnetostrictive Strip Transducer

    NASA Astrophysics Data System (ADS)

    Cheong, YongMoo; Kim, Shin

    2009-03-01

    A torsional guided wave by a magnetostrictive strip transducer technique has a advantage that the wave patterns are relatively clear and simple when compared to a conventional piezoelectric ultrasonic transducer. If we can characterize the evolution of those defect signals, it could be a promising tool for a structural health monitoring of pipes for a long period of time as well as an identification of flaws. However, an examiner need to be careful when evaluating a signal during a realistic field examination because of some spurious signals or false indications, such as signals due to a directionality, multiple reflections, mode conversion, geometrical reflections etc. In this paper, mode converted signals from a realistic piping mockup are analysed. We found mode conversions between a torsional guided wave T(0,1) mode and a flexural F(1,3) or longitudinal L(0,2) mode generated by a magnetostrictive strip transducer. Based on the experimental observations, an interpretation of the source of the mode conversion is discussed.

  13. Giant magnetoresistive sensor

    DOEpatents

    Stearns, Daniel G.; Vernon, Stephen P.; Ceglio, Natale M.; Hawryluk, Andrew M.

    1999-01-01

    A magnetoresistive sensor element with a three-dimensional micro-architecture is capable of significantly improved sensitivity and highly localized measurement of magnetic fields. The sensor is formed of a multilayer film of alternately magnetic and nonmagnetic materials. The sensor is optimally operated in a current perpendicular to plane mode. The sensor is useful in magnetic read/write heads, for high density magnetic information storage and retrieval.

  14. Temperature, stress, and structural-relaxation dependence of the magnetostriction in (Co0.94/BFe0.06)75/BSi15B10 glasses

    NASA Astrophysics Data System (ADS)

    Barandiarán, J. M.; Hernando, A.; Madurga, V.; Nielsen, O. V.; Vázquez, M.; Vázquez-López, M.

    1987-04-01

    High-sensitivity measurements of the magnetostriction constant λs have been performed in the nearly zero magnetostriction (Co0.94Fe0.06)75Si15B10 metallic glass as a function of the stress and temperature after pulse-annealing treatments. A stress dependence of λs in this amorphous alloy is reported for the first time. At room temperature a slope of about -2×10-7 GPa-1 has been determined leading to a change in the sign of the magnetostriction constant in some circumstances. For determination of the thermal variation of λs, the temperature was changed by means of the alternating current flowing through the sample during the measurement, which was done by the small-angle magnetization-rotation (SAMR) method. The compensation temperatures, i.e., those temperatures at which the value of λs vanishes in going from negative to positive, were determined after isochronal annealing. In this way, the evolution of the single-ion and two-ion contributions to the magneto- striction was monitored during the structural relaxation. The ratio between the two contributions follows a chemical short-range-order kinetics. The stress dependence of the single-ion and two-ion contributions was deduced from measurements of the stress dependence of the magnetostriction at different temperatures.

  15. Establishment and cryopreservation of a giant panda skeletal muscle-derived cell line.

    PubMed

    Yu, Fang-Jian; Zeng, Chang-Jun; Zhang, Yan; Wang, Cheng-Dong; Xiong, Tie-Yi; Fang, Sheng-Guo; Zhang, He-Min

    2015-06-01

    The giant panda Ailuropoda melanoleuca is an endangered species and is a symbol for wildlife conservation. Although efforts have been made to protect this rare and endangered species through breeding and conservative biology, the long-term preservation of giant panda genome resources (gametes, tissues, organs, genomic libraries, etc.) is still a practical option. In this study, the giant panda skeletal muscle-derived cell line was successfully established via primary explants culture and cryopreservation techniques. The population doubling time of giant panda skeletal cells was approximately 33.8 h, and this population maintained a high cell viability before and after cryopreservation (95.6% and 90.7%, respectively). The two skeletal muscle-specific genes SMYD1 and MYF6 were expressed and detected by RT-PCR in the giant panda skeletal muscle-derived cell line. Karyotyping analysis revealed that the frequencies of giant panda skeletal muscle cells showing a chromosome number of 2n=42 ranged from 90.6∼94.2%. Thus, the giant panda skeletal muscle-derived cell line provides a vital resource and material platform for further studies and is likely to be useful for the protection of this rare and endangered species.

  16. Establishment and cryopreservation of a giant panda skeletal muscle-derived cell line.

    PubMed

    Yu, Fang-Jian; Zeng, Chang-Jun; Zhang, Yan; Wang, Cheng-Dong; Xiong, Tie-Yi; Fang, Sheng-Guo; Zhang, He-Min

    2015-06-01

    The giant panda Ailuropoda melanoleuca is an endangered species and is a symbol for wildlife conservation. Although efforts have been made to protect this rare and endangered species through breeding and conservative biology, the long-term preservation of giant panda genome resources (gametes, tissues, organs, genomic libraries, etc.) is still a practical option. In this study, the giant panda skeletal muscle-derived cell line was successfully established via primary explants culture and cryopreservation techniques. The population doubling time of giant panda skeletal cells was approximately 33.8 h, and this population maintained a high cell viability before and after cryopreservation (95.6% and 90.7%, respectively). The two skeletal muscle-specific genes SMYD1 and MYF6 were expressed and detected by RT-PCR in the giant panda skeletal muscle-derived cell line. Karyotyping analysis revealed that the frequencies of giant panda skeletal muscle cells showing a chromosome number of 2n=42 ranged from 90.6∼94.2%. Thus, the giant panda skeletal muscle-derived cell line provides a vital resource and material platform for further studies and is likely to be useful for the protection of this rare and endangered species. PMID:26035009

  17. Digestive physiology of captive giant anteaters (Myrmecophaga tridactyla): determinants of faecal dry matter content.

    PubMed

    Gull, J M; Stahl, M; Osmann, C; Ortmann, S; Kreuzer, M; Hatt, J-M; Clauss, M

    2015-06-01

    Giant anteaters (Myrmecophaga tridactyla) are specialized insectivores and consume mainly ants and termites in the wild. In captivity, giant anteaters are either fed a complete diet, or a combination of a domestic carnivore diet with leaf eater pellets, or a traditional gruel-type diet. Soft faeces are a frequently encountered problem with this type of feeding. In the present study, we analysed diet and faeces composition, calculated digestibility and measured mean retention time on various diets in eight giant anteaters (total of n = 64 experiments). The results suggest that the digestive physiology of giant anteaters is similar to that of domestic dogs and cats in terms of nutrient digestibility and digesta retention. When testing correlations between faecal dry matter content and other variables, no relationship with dietary crude fibre content or mean digesta retention time could be detected. However, acid insoluble ash intake was significantly and positively correlated with faecal dry matter content. The amount of acid insoluble ash excreted with the faeces was higher than that ingested with the diet offered, indicating that the giant anteaters ingested soil from their enclosure of up to 93 g per day. This finding is consistent with observation of faeces of wild giant anteaters that contain soil or sand most likely due to indiscriminate feeding. It also corresponds to reports that indigestible materials such as peat, soil, chitin or cellulose contribute to a firmer faecal consistency in various carnivore species. Therefore, offering giant anteaters the opportunity to voluntarily ingest soil from their enclosure might be beneficial. PMID:25041215

  18. Digestive physiology of captive giant anteaters (Myrmecophaga tridactyla): determinants of faecal dry matter content.

    PubMed

    Gull, J M; Stahl, M; Osmann, C; Ortmann, S; Kreuzer, M; Hatt, J-M; Clauss, M

    2015-06-01

    Giant anteaters (Myrmecophaga tridactyla) are specialized insectivores and consume mainly ants and termites in the wild. In captivity, giant anteaters are either fed a complete diet, or a combination of a domestic carnivore diet with leaf eater pellets, or a traditional gruel-type diet. Soft faeces are a frequently encountered problem with this type of feeding. In the present study, we analysed diet and faeces composition, calculated digestibility and measured mean retention time on various diets in eight giant anteaters (total of n = 64 experiments). The results suggest that the digestive physiology of giant anteaters is similar to that of domestic dogs and cats in terms of nutrient digestibility and digesta retention. When testing correlations between faecal dry matter content and other variables, no relationship with dietary crude fibre content or mean digesta retention time could be detected. However, acid insoluble ash intake was significantly and positively correlated with faecal dry matter content. The amount of acid insoluble ash excreted with the faeces was higher than that ingested with the diet offered, indicating that the giant anteaters ingested soil from their enclosure of up to 93 g per day. This finding is consistent with observation of faeces of wild giant anteaters that contain soil or sand most likely due to indiscriminate feeding. It also corresponds to reports that indigestible materials such as peat, soil, chitin or cellulose contribute to a firmer faecal consistency in various carnivore species. Therefore, offering giant anteaters the opportunity to voluntarily ingest soil from their enclosure might be beneficial.

  19. Method for deriving information regarding stress from a stressed ferromagnetic material

    DOEpatents

    Jiles, D.C.

    1991-04-30

    A nondestructive evaluation technique is disclosed for deriving stress in ferromagnetic materials including deriving anhysteretic and hysteresis magnetization curves for the material in both unstressed and stressed states. The anhysteretic curve is expressed as a Langevin function. The stress is expressed as an equivalent magnetic field dependent on stress and change of magnetostriction with magnetization. By measurement of these bulk magnetic properties, stress can be derived.

  20. Method for deriving information regarding stress from a stressed ferromagnetic material

    DOEpatents

    Jiles, David C.

    1991-04-30

    A non-destructive evaluation technique for deriving stress in ferromagnetic materials including deriving anhysteretic and hysteresis magnetization curves for the material in both unstressed and stressed states. The anhysteretic curve is expressed as a Langevin function. The stress is expressed as an equivalent magnetic field dependent on stress and change of magnetostriction with magnetization. By measurement of these bulk magnetic properties, stress can be derived.

  1. Materials

    NASA Technical Reports Server (NTRS)

    Glaessgen, Edward H.; Schoeppner, Gregory A.

    2006-01-01

    NASA Langley Research Center has successfully developed an electron beam freeform fabrication (EBF3) process, a rapid metal deposition process that works efficiently with a variety of weldable alloys. The EBF3 process can be used to build a complex, unitized part in a layer-additive fashion, although the more immediate payoff is for use as a manufacturing process for adding details to components fabricated from simplified castings and forgings or plate products. The EBF3 process produces structural metallic parts with strengths comparable to that of wrought product forms and has been demonstrated on aluminum, titanium, and nickel-based alloys to date. The EBF3 process introduces metal wire feedstock into a molten pool that is created and sustained using a focused electron beam in a vacuum environment. Operation in a vacuum ensures a clean process environment and eliminates the need for a consumable shield gas. Advanced metal manufacturing methods such as EBF3 are being explored for fabrication and repair of aerospace structures, offering potential for improvements in cost, weight, and performance to enhance mission success for aircraft, launch vehicles, and spacecraft. Near-term applications of the EBF3 process are most likely to be implemented for cost reduction and lead time reduction through addition of details onto simplified preforms (casting or forging). This is particularly attractive for components with protruding details that would require a significantly large volume of material to be machined away from an oversized forging, offering significant reductions to the buy-to-fly ratio. Future far-term applications promise improved structural efficiency through reduced weight and improved performance by exploiting the layer-additive nature of the EBF3 process to fabricate tailored unitized structures with functionally graded microstructures and compositions.

  2. Asteroseismology of Red Giant stars

    NASA Astrophysics Data System (ADS)

    Tarrant, N. J.; Chaplin, W. J.; Elsworth, Y. P.; Spreckley, S. A.; Stevens, I. R.

    2008-12-01

    Sun-like oscillations, that is p-modes excited stochastically by convective noise, have now been observed in a number of Red Giant stars. Compared to those seen in the Sun, these modes are of large amplitude and long period, making the oscillations attractive prospects for observation. However, the low Q-factor of these modes, and issues relating to the rising background at low frequencies, present some interesting challenges for identifying modes and determining the related asteroseismic parameters. We report on the analysis procedure adopted for peak-bagging by our group at Birming- ham, and the techniques used to robustly ensure these are not a product of noise. I also show results from a number of giants extracted from multi-year observations with the SMEI instrument

  3. Proteorhodopsin genes in giant viruses.

    PubMed

    Yutin, Natalya; Koonin, Eugene V

    2012-01-01

    Viruses with large genomes encode numerous proteins that do not directly participate in virus biogenesis but rather modify key functional systems of infected cells. We report that a distinct group of giant viruses infecting unicellular eukaryotes that includes Organic Lake Phycodnaviruses and Phaeocystis globosa virus encode predicted proteorhodopsins that have not been previously detected in viruses. Search of metagenomic sequence data shows that putative viral proteorhodopsins are extremely abundant in marine environments. Phylogenetic analysis suggests that giant viruses acquired proteorhodopsins via horizontal gene transfer from proteorhodopsin-encoding protists although the actual donor(s) could not be presently identified. The pattern of conservation of the predicted functionally important amino acid residues suggests that viral proteorhodopsin homologs function as sensory rhodopsins. We hypothesize that viral rhodopsins modulate light-dependent signaling, in particular phototaxis, in infected protists.

  4. Effects of phase transformation on the microstructures and magnetostriction of Fe-Ga and Fe-Ga-Zn ferromagnetic shape memory alloys

    NASA Astrophysics Data System (ADS)

    Lin, Yin-Chih; Lin, Chien-Feng

    2015-05-01

    The phase transformation and magnetostriction of bulk Fe73Ga27 and Fe73Ga18Zn9 (at. %) ferromagnetic shape memory alloys (FSMs) were investigated by transmission electron microscopy (TEM), x-ray diffraction (XRD), and a magnetostrictive-meter setup. For the Fe73Ga27 FSM alloy solution treated at 1100 °C for 4 h and quenched in ice brine, the antiphase boundary segments of the D03 domain were observed in the A2 (disordered) matrix, and the Fe73Ga27 FSM alloy had an optimal magnetostriction (λ‖s = 71 × 10-6 and λ⊥s = -31 × 10-6). In Fe73Ga27 FSM alloy as-quenched, aged at 700 °C for 24 h, and furnace cooled, D03 nanoclusters underwent phase transformation to an intermediate tetragonal phase (i.e., L10-like martensite) via Bain distortion, and finally L12 (Fe3Ga) structures precipitated, as observed by TEM and XRD. The L10-like martensite and L12 phases in the aged Fe73Ga27 FSM alloy drastically decreased the magnetostriction from positive to negative (λ‖s = -20 × 10-6 and λ⊥s = -8 × 10-6). However, in Fe73Ga18Zn9 FSM alloy as-quenched and aged, the phase transformation of D03 to an intermediate tetragonal martensite phase and precipitation of L12 structures were not found. The results indicate that the aged Fe73Ga18Zn9 FSM alloy maintained stable magnetostriction (λ‖s = 36 × 10-6 and λ⊥s = -31 × 10-6). Adding Zn can improve the ferromagnetic shape memory effect of aged Fe73Ga18Zn9 alloy, which may be useful in application of the alloy in high temperature environments.

  5. Giant dielectric and magnetoelectric responses in insulating nanogranular films at room temperature

    PubMed Central

    Kobayashi, Nobukiyo; Masumoto, Hiroshi; Takahashi, Saburo; Maekawa, Sadamichi

    2014-01-01

    The electric and magnetic properties of matter are of great interest for materials science and their use in electronic applications. Large dielectric and magnetoelectric responses of materials at room temperature are a great advantage for electromagnetic device applications. Here we present a study of FeCo-MgF nanogranular films exhibiting giant dielectric and magnetoelectric responses at room temperature; with dielectric constant ε′=490 and magnetoelectric response Δε′/ε′0=3%. In these films, Fe-Co alloy-based nanometer-sized magnetic granules are dispersed in a Mg-fluoride-based insulator matrix. Insulating nanogranular films are a new class of multifunctional materials. The giant responses are caused by spin-dependent charge oscillation between magnetic granules via quantum-mechanical tunnelling. A possible application of such insulating nanogranular materials with giant response is in the construction of a tunable device, in which impedance components such as capacitance and inductance are tunable at room temperature. PMID:25048805

  6. Giant South Brae platform installed

    SciTech Connect

    Cranfield, J.

    1982-12-01

    During the summer 1982 another giant production platform was installed in the North Sea in Marathon's South Brae field. The complex structure of that field necessitated careful planning of the offshore producing structure design and placement. The platform has 46 well slots; 19 will be used as producing wells, 3 for gas injection, and 14 for water injection. The remainder of the well slots are reserved for future development. The platform structure design is examined.

  7. Giant magnetoresistance in silicene nanoribbons.

    PubMed

    Xu, Chengyong; Luo, Guangfu; Liu, Qihang; Zheng, Jiaxin; Zhang, Zhimeng; Nagase, Shigeru; Gao, Zhengxiang; Lu, Jing

    2012-05-21

    By performing first-principle quantum transport calculations, we predict a giant magnetoresistance in zigzag silicene nanoribbons (ZSiNRs) connecting two semi-infinite silicene electrodes through switch of the edge spin direction of ZSiNRs. Spin-filter efficiency of both the antiferromagnetic and ferromagnetic ZSiNRs is sign-changeable with the bias voltage. Therefore, potential application of silicene in spintronics devices is suggested.

  8. A giant juvenile nasopharyngeal angiofibroma.

    PubMed

    Yüce, Salim; Uysal, Ismail Önder; Doğan, Mansur; Polat, Kerem; Salk, Ismail; Müderris, Suphi

    2013-05-01

    Juvenile nasopharyngeal angiofibromas are locally growing and highly vascular tumors. They are primarily treated through surgical excision ranging from an open approach to an endoscopic approach. We presented a 20-year-old man with a giant juvenile nasopharyngeal angiofibroma that bilaterally obliterated the pterygopalatine fossa, invaded the sphenoid bone, and extended to the left nasal passage. His complaints were epistaxis and nasal obstruction. After embolization, the patient was treated surgically using the endoscopic approach and declared cured and discharged without any complications.

  9. A Giant Juvenile Nasopharyngeal Angiofibroma

    PubMed Central

    Yüce, Salim; Uysal, İsmail Önder; Doğan, Mansur; Polat, Kerem; Şalk, İsmail; Müderris, Suphi

    2012-01-01

    Juvenile nasopharyngeal angiofibroma (JNA) are locally growing highly vascular tumours. They are treated primarily by surgical excision ranging from open approach to endoscopic approach. We presented a 20-year-old male with a giant nasopharyngeal juvenile angiofibroma obliterating the pterygopalatine fossa bilaterally, invasing the sphenoid bone and extending to the left nasal passage. His complaints were epistaxis and nasal obstruction. After embolization, the patient was treated surgically with endoscopic approach and discharged as cured without any complication. PMID:23714961

  10. Ferrite phase shifters using stress insensitive materials. Final report, July 1991-July 1993

    SciTech Connect

    Vaughn, T.; Cox, P.; Harrison, G.; Rodrigue, P.

    1993-10-01

    This RD program sponsored by the Naval Research Laboratory and being conducted by EMS Technologies, Inc., Norcross, Georgia, is focused toward achieving improved performance in microwave switching components via use of stress insensitive' microwave ferrite materials for applications where stable hysteresis characteristics of the materials are critical to the RF performance. The program, therefore, primarily addresses how to relieve or improve the magnetostrictive characteristics of the materials with emphasis on the specific application and demonstration of these materials in microwave switching components, particularly ferrite toroidal phase shifters. Material investigations were focused on Mn+3 substitutions in Yttrium-gadolinium iron garnet. These compounds were evaluated in dual toroid waveguide phase shifter structures with temperature, pressure Rf power as variables Manganese substitution per formula unit for Fe+3 of 0.11 to 0.13 (2.2 to 2.6%) produced compounds which exhibited stable performance from magnetostrictive stresses in phaser structures. Ferrite phase shifters, Stress insensitive materials Manganese substitution in garnets, Magnetostrictive, Stresses in ferrite phasers.

  11. KEPLER RAPIDLY ROTATING GIANT STARS

    SciTech Connect

    Costa, A. D.; Martins, B. L. Canto; Bravo, J. P.; Paz-Chinchón, F.; Chagas, M. L. das; Leão, I. C.; Oliveira, G. Pereira de; Silva, R. Rodrigues da; Roque, S.; Oliveira, L. L. A. de; Silva, D. Freire da; De Medeiros, J. R.

    2015-07-10

    Rapidly rotating giant stars are relatively rare and may represent important stages of stellar evolution, resulting from stellar coalescence of close binary systems or accretion of substellar companions by their hosting stars. In the present Letter, we report 17 giant stars observed in the scope of the Kepler space mission exhibiting rapid rotation behavior. For the first time, the abnormal rotational behavior for this puzzling family of stars is revealed by direct measurements of rotation, namely from photometric rotation period, exhibiting a very short rotation period with values ranging from 13 to 55 days. This finding points to remarkable surface rotation rates, up to 18 times the rotation of the Sun. These giants are combined with six others recently listed in the literature for mid-infrared (IR) diagnostics based on Wide-field Infrared Survey Explorer information, from which a trend for an IR excess is revealed for at least one-half of the stars, but at a level far lower than the dust excess emission shown by planet-bearing main-sequence stars.

  12. Hairpin Furans and Giant Biaryls.

    PubMed

    Geng, Xin; Mague, Joel T; Donahue, James P; Pascal, Robert A

    2016-05-01

    The thermal reaction of two cyclopentadienones with 5,5'-binaphthoquinone or 6,6'-dimethoxy-5,5'-binaphthoquinone in refluxing nitrobenzene (210 °C) gives, in a single synthetic step that includes two Diels-Alder additions, two decarbonylations, and two dehydrogenations, giant biaryl bisquinones (compounds 13, 14, 15, 18, and 21). However, when two cyclopentadienones react with 6,6'-dimethoxy-5,5'-binaphthoquinone in nitrobenzene at higher temperatures (250-260 °C), the resulting products are molecular ribbons composed of two twisted aromatic systems fused to a heteropentahelicene (19, 20, and 22). These molecules are representatives of a new class of chiral polycyclic aromatic compounds, the "hairpin furans". Interestingly, reheating a dimethoxy-substituted giant biaryl (e.g., 21) in nitrobenzene at 260 °C does not yield the corresponding hairpin furan (22), and mechanistic studies indicate that some intermediate or byproduct of the synthesis of the giant biaryls is a reagent or catalyst necessary for the conversion of the dimethoxybiaryl to the furan.

  13. Observed Properties of Giant Cells

    NASA Technical Reports Server (NTRS)

    Hathaway, David H.; Upton, Lisa; Colegrove, Owen

    2014-01-01

    The existence of Giant Cells has been suggested by both theory and observation for over 45 years. We have tracked the motions of supergranules in SDO/HMI Doppler velocity data and find larger (Giant Cell) flows that persist for months. The flows in these cells are clockwise around centers of divergence in the north and counter-clockwise in the south. Equatorward flows are correlated with prograde flows - giving the transport of angular momentum toward the equator that is needed to maintain the Sun's rapid equatorial rotation. The cells are most pronounced at mid- and high-latitudes where they exhibit the rotation rates representative of those latitudes. These are clearly large, long-lived, cellular features, with the dynamical characteristics expected from the effects of the Sun's rotation, but the shapes of the cells are not well represented in numerical models. While the Giant Cell flow velocities are small (<10 m/s), their long lifetimes should nonetheless substantially impact the transport of magnetic flux in the Sun's near surface layers.

  14. Red Giants and Solar Sails

    NASA Astrophysics Data System (ADS)

    Matloff, G. L.

    Our Sun will eventually leave the main sequence and expand in size and luminosity to become a giant star. For much of its ~108 year career as a giant, the Sun will reside on the horizontal branch of the Hertzsprung-Russell diagram, with a surface temperature of ~5000 K, a radius about 10x its present-day radius, and about 50x its current luminosity. A space-manufactured beryllium solar-photon sail could be used for emigration from the solar system during this solar phase. Space environmental effects limit the closest approach distance to the giant star to around 0.5 AU, assuming the quiet phase of the stellar activity cycle. Beryllium spectral reflectivity values are used to calculate a wavelength averaged sail spectral reflectivity. This parameter and a reasonable value of spacecraft areal mass thickness (8.87 x 10-5 kg/m2) are used to estimate the interstellar cruise velocity for a sail fully unfurled at a 0.5-1 AU perihelion from an initially parabolic orbit that is always oriented normal to the star. These will be 2-3x greater than those possible for the same craft launched from today's Sun.

  15. Straintronics-based magnetic tunneling junction: Dynamic and static behavior analysis and material investigation

    NASA Astrophysics Data System (ADS)

    Barangi, Mahmood; Mazumder, Pinaki

    2014-04-01

    We theoretically study the dynamic and static effects of mechanical stress on a straintronics device that includes a piezoelectric film combined with a magnetic tunneling junction. The inverse magnetostriction effect is studied in detail by realizing the varying magnetic susceptibility of the nanomagnet under stress. A dynamic model is developed based on the Landau-Lifshitz-Gilbert (LLG) equation, which provides a platform to simulate the magnetization vector's behavior, critical flipping voltage, and delay properties. Furthermore, by converting the LLG equation into a 2nd order damping differential equation, we develop a proximate approach. This approach predicts the dynamic behavior of the magnetization vector and its dependency on material properties and applied voltage across the device without using sophisticated numerical calculations of the LLG model. Different dynamic and static material properties are observed by simulating five common magnetostrictive materials, including a newly discovered alloy, Galfenol.

  16. Effectiveness of Lichtenstein repairs in planned treatment of giant inguinal hernia – own experience

    PubMed Central

    Kosim, Anna; Kołodziejczak, Małgorzata; Zmora, Jan; Kultys, Ewa

    2012-01-01

    Introduction Occurrence of giant inguinal hernias is not frequent because of growing medical awareness in the community as well as progress in surgical treatment in this field. Aim To evaluate the effectiveness of repairs using the Lichtenstein technique in scheduled treatment of giant inguinal hernias. Material and methods Between 2006 and 2010 in the Department of Surgery with the Subdepartment of Proctology, Hospital at Solec in Warsaw, 909 repairs of inguinal hernia were performed, including 15 patients (1.65%) with the diagnosis of giant hernia. In 3 cases it was direct inguinal hernia and in 12 cases indirect inguinal hernia. All giant hernias occurred in male patients between 33 and 87 years of age (mean age 65 years old) and developed for many years, median of 14.2 years. All patients underwent scheduled repairs using the tension-free Lichtenstein technique. A non-absorbable polypropylene mesh was used for hernioplasty. Exact Fisher's test (p < 0.01) was used for statistical analysis. Results In all cases contents of the hernial sac consisted of loops of small intestine, colon and omentum. Early complications occurred in 11 patients (73%) in the group of patients with giant hernias, whereas in the remaining group of patients early complications occurred in 53 patients (5.9%). The difference was statistically significant. In the group of patients with giant hernias no recurrence was observed over the observation period ranging from 6 months to 4.5 years. In the remaining group of patients recurrences occurred in 23 patients (2.6%). Conclusions The Lichtenstein technique of repair is effective in management of giant inguinal hernias. A statistically significantly higher percentage of complications was observed in the group of patients with giant hernias as compared to the remaining group of patients with inguinal hernias. Patients with giant hernias require proper preparation for surgery, especially in relation to their respiratory efficiency. PMID:23630552

  17. Supplying the Giant

    NASA Technical Reports Server (NTRS)

    Lawson, Larry

    2003-01-01

    It was critical for our team to find a radically different way of doing business. Deciding to build the airframe out of composites was the first step, refining processes from the boat building industry was second, and the final step was choosing a supplier. Lockheed Martin built the first prototypes at our Skunk Works facility in Palmdale, California. These units were hand-built and used early prototypical tooling. They looked great but were not affordable. We had to focus on minimizing touch labor and cycle time and reducing material costs. We needed a company to produce the composite quilts we would use to avoid hand lay-ups. The company we found surprised a lot of people. We partnered with a small company outside of Boston whose primary business was making baseball bats and golf club shafts.

  18. Guiding the Giant

    NASA Astrophysics Data System (ADS)

    1998-08-01

    New ESO Survey Provides Targets for the VLT Giant astronomical telescopes like the ESO Very Large Telescope (VLT) must be used efficiently. Observing time is expensive and there are long waiting lines of excellent research programmes. Thus the work at the telescope must be very well prepared and optimized as much as possible - mistakes should be avoided and no time lost! Astronomers working with the new 8-m class optical/infrared telescopes must base their observations on detailed lists of suitable target objects if they want to perform cutting-edge science. This is particularly true for research programmes that depend on observations of large samples of comparatively rare, distant objects. This type of work requires that extensive catalogues of such objects must be prepared in advance. One such major catalogue - that will serve as a very useful basis for future VLT observations - has just become available from the new ESO Imaging Survey (EIS). The Need for Sky Surveys Astronomers have since long recognized the need to carry out preparatory observations with other telescopes in order to "guide" large telescopes. To this end, surveys of smaller or larger parts of the sky have been performed by wide-field telescopes, paving the way for subsequent work at the limits of the largest available ground-based telescopes. For instance, a complete photographic survey of the sourthern sky (declination < -17.5°) was carried out in the 1970's with the ESO 1-metre Schmidt Telescope in support of the work at the 3.6-m telescope at the ESO La Silla observatory. However, while until recently most observational programmes could rely on samples of objects found on photographic plates, this is no longer possible. New image surveys must match the fainter limiting magnitudes reached by the new and larger telescopes. Modern digital, multi-colour, deep imaging surveys have thus become an indispensable complement to the 8-m telescopes. The new generation of imaging surveys will, without

  19. Red giants: then and now

    NASA Astrophysics Data System (ADS)

    Faulkner, John

    Fred Hoyle's work on the structure and evolution of red giants, particularly his pathbreaking contribution with Martin Schwarzschild (Hoyle and Schwarzschild 1955), is both lauded and critically assessed. In his later lectures and work with students in the early 1960s, Hoyle presented more physical ways of understanding some of the approximations used, and results obtained, in that seminal paper. Although later ideas by other investigators will be touched upon, Hoyle's viewpoint - that low-mass red giants are essentially white dwarfs with a serious mass-storage problem - is still extremely fruitful. Over the years, I have further developed his method of attack. Relatively recently, I have been able to deepen and broaden the approach, finally extending the theory to provide a unifying treatment of the structure of low-mass stars from the main sequence though both the red-giant and horizontal-branch phases of evolution. Many aspects of these stars that had remained puzzling, even mysterious, for decades have now fallen into place, and some questions have been answered that were not even posed before. With low-mass red giants as the simplest example, this recent work emphasizes that stars, in general, may have at least two distinct but very important centres: (I) a geometrical centre, and (II) a separate nuclear centre, residing in a shell outside a zero-luminosity dense core for example. This two-centre perspective leads to an explicit, analytical, asymptotic theory of low-mass red-giant structure. It enables one to appreciate that the problem of understanding why such stars become red giants is one of anticipating a remarkable yet natural structural bifurcation that occurs in them. This bifurcation occurs because of a combination of known and understandable facts just summarized namely that, following central hydrogen exhaustion, a thin nuclear-burning shell does develop outside a more-or-less dense core. In the resulting theory, both ρsh/ρolinec and

  20. Spontaneous thrombosis in giant intracranial aneurysms.

    PubMed Central

    Whittle, I R; Dorsch, N W; Besser, M

    1982-01-01

    Twelve patients in a series of 22 with giant intracranial aneurysms demonstrated neuroradiological features of partial or total spontaneous intra-aneurysmal thrombosis. The presence of this intra-aneurysmal clot significantly altered the computed tomographic appearance of the giant aneurysm. Massive intra-aneurysmal thrombosis did not protect against subarachnoid haemorrhage and the likelihood of rupture of a clot containing giant aneurysm was not significantly different from that of a non-thrombosed giant aneurysm. Although parent artery occlusion from a thrombosed giant aneurysm, and massive aneurysmal thrombosis leading to the formation of giant serpentine aneurysm were documented, these are rare epiphenomena. The risk of embolisation from a partially thrombosed giant aneurysm, which was documented in one case, would appear to be greater than that from a non-thrombosed giant aneurysm. The findings in this series, and a review of literature, suggest that the presence of intra-aneurysmal clot in giant intracranial aneurysms has little prognostic significance and does not alter the management or outcome after treatment. Images PMID:7175528

  1. Speciation and phylogeography of giant petrels Macronectes.

    PubMed

    Techow, N M S M; O'Ryan, C; Phillips, R A; Gales, R; Marin, M; Patterson-Fraser, D; Quintana, F; Ritz, M S; Thompson, D R; Wanless, R M; Weimerskirch, H; Ryan, P G

    2010-02-01

    We examine global phylogeography of the two forms of giant petrel Macronectes spp. Although previously considered to be a single taxon, and despite debate over the status of some populations and the existence of minimal genetic data (one mitochondrial cytochrome b sequence per form), the current consensus based on morphology is that there are two species, Northern Giant Petrel M. halli and Southern Giant Petrel M. giganteus. This study examined genetic variation at cytochrome b as well as six microsatellite loci in giant petrels from 22 islands, representing most island groups at which the two species breed. Both markers support separate species status, although sequence divergence in cytochrome b was only 0.42% (corrected). Divergence was estimated to have occurred approximately 0.2mya, but with some colonies apparently separated for longer (up to 0.5 my). Three clades were found within giant petrels, which separated approximately 0.7mya, with the Southern Giant Petrel paraphyletic to a monophyletic Northern Giant Petrel. There was evidence of past fragmentation during the Pleistocene, with subsequent secondary contact within Southern Giant Petrels. The analysis also suggested a period of past population expansion that corresponded roughly to the timing of speciation and the separation of an ancestral giant petrel population from the fulmar Fulmarus clade. PMID:19755164

  2. Selective assemblies of giant tetrahedra via precisely controlled positional interactions

    NASA Astrophysics Data System (ADS)

    Huang, Mingjun; Hsu, Chih-Hao; Wang, Jing; Mei, Shan; Dong, Xuehui; Li, Yiwen; Li, Mingxuan; Liu, Hao; Zhang, Wei; Aida, Takuzo; Zhang, Wen-Bin; Yue, Kan; Cheng, Stephen Z. D.

    2015-04-01

    Self-assembly of rigid building blocks with explicit shape and symmetry is substantially influenced by the geometric factors and remains largely unexplored. We report the selective assembly behaviors of a class of precisely defined, nanosized giant tetrahedra constructed by placing different polyhedral oligomeric silsesquioxane (POSS) molecular nanoparticles at the vertices of a rigid tetrahedral framework. Designed symmetry breaking of these giant tetrahedra introduces precise positional interactions and results in diverse selectively assembled, highly ordered supramolecular lattices including a Frank-Kasper A15 phase, which resembles the essential structural features of certain metal alloys but at a larger length scale. These results demonstrate the power of persistent molecular geometry with balanced enthalpy and entropy in creating thermodynamically stable supramolecular lattices with properties distinct from those of other self-assembling soft materials.

  3. Coordinated observations of interacting peculiar red giant binaries, 2

    NASA Technical Reports Server (NTRS)

    Ake, T.

    1995-01-01

    IUE and H alpha observations continued on a two-year program to monitor the UV variability of three interacting peculiar red giant (PRG) binaries, HD 59643 (C6,s), HD 35155 (S3/2), and HR 1105 (S3.5/2.5). All of these systems were suspected to involve accretion of material from the PRG to a white-dwarf secondary, based mainly on previous IUE investigations. They were primary candidates from earlier surveys of PRG's to test the hypothesis that the Tc-poor PRG's are formed as a result of mass transfer from a secondary component rather than from internal thermal pulsing while on the asymptotic red giant branch.

  4. Giant electrocaloric effect in ferroelectric nanotubes near room temperature.

    PubMed

    Liu, Man; Wang, Jie

    2015-01-12

    Ferroelectric perovskite oxides possess large electrocaloric effect, but only at high temperature, which limits their potential as next generation solid state cooling devices. Here, we demonstrate from phase field simulations that a giant adiabatic temperature change exhibits near room temperature in the strained ferroelectric PbTiO₃ nanotubes, which is several times in magnitude larger than that of PbTiO₃ thin films. Such giant adiabatic temperature change is attributed to the extrinsic contribution of unusual domain transition, which involves a dedicated interplay among the electric field, strain, temperature and polarization. Careful selection of external strain allows one to harness the extrinsic contribution to obtain large adiabatic temperature change in ferroelectric nanotubes near room temperature. Our finding provides a novel insight into the electrocaloric response of ferroelectric nanostructures and leads to a new strategy to tailor and improve the electrocaloric properties of ferroelectric materials through domain engineering.

  5. Transport of cytoskeletal elements in the squid giant axon.

    PubMed Central

    Terasaki, M; Schmidek, A; Galbraith, J A; Gallant, P E; Reese, T S

    1995-01-01

    In order to explore how cytoskeletal proteins are moved by axonal transport, we injected fluorescent microtubules and actin filaments as well as exogenous particulates into squid giant axons and observed their movements by confocal microscopy. The squid giant axon is large enough to allow even cytoskeletal assemblies to be injected without damaging the axon or its transport mechanisms. Negatively charged, 10- to 500-nm beads and large dextrans moved down the axon, whereas small (70 kDa) dextrans diffused in all directions and 1000-nm beads did not move. Only particles with negative charge were transported. Microtubules and actin filaments, which have net negative charges, made saltatory movements down the axon, resulting in a net rate approximating that previously shown for slow transport of cytoskeletal elements. The present observations suggest that particle size and charge determine which materials are transported down the axon. Images Fig. 1 Fig. 2 Fig. 3 PMID:8524791

  6. Transport of cytoskeletal elements in the squid giant axon.

    PubMed

    Terasaki, M; Schmidek, A; Galbraith, J A; Gallant, P E; Reese, T S

    1995-12-01

    In order to explore how cytoskeletal proteins are moved by axonal transport, we injected fluorescent microtubules and actin filaments as well as exogenous particulates into squid giant axons and observed their movements by confocal microscopy. The squid giant axon is large enough to allow even cytoskeletal assemblies to be injected without damaging the axon or its transport mechanisms. Negatively charged, 10- to 500-nm beads and large dextrans moved down the axon, whereas small (70 kDa) dextrans diffused in all directions and 1000-nm beads did not move. Only particles with negative charge were transported. Microtubules and actin filaments, which have net negative charges, made saltatory movements down the axon, resulting in a net rate approximating that previously shown for slow transport of cytoskeletal elements. The present observations suggest that particle size and charge determine which materials are transported down the axon.

  7. Chirality induced tilted-hill giant Nernst signal.

    PubMed

    Kotetes, P; Varelogiannis, G

    2010-03-12

    We reveal a novel source of a giant Nernst response exhibiting strong nonlinear temperature and magnetic field dependence, including the mysterious tilted-hill temperature profile observed in a pleiad of materials. The phenomenon results directly from the formation of a chiral ground state, e.g., a chiral d-density wave, which is compatible with the eventual observation of diamagnetism and is distinctly different from the usual quasiparticle and vortex Nernst mechanisms. Our picture provides a unified understanding of the anomalous thermoelectricity observed in materials as diverse as the hole-doped cuprates and heavy-fermion compounds like URu(2)Si(2). PMID:20366442

  8. Rocky core solubility in Jupiter and giant exoplanets.

    PubMed

    Wilson, Hugh F; Militzer, Burkhard

    2012-03-16

    Gas giants are believed to form by the accretion of hydrogen-helium gas around an initial protocore of rock and ice. The question of whether the rocky parts of the core dissolve into the fluid H-He layers following formation has significant implications for planetary structure and evolution. Here we use ab initio calculations to study rock solubility in fluid hydrogen, choosing MgO as a representative example of planetary rocky materials, and find MgO to be highly soluble in H for temperatures in excess of approximately 10,000 K, implying the potential for significant redistribution of rocky core material in Jupiter and larger exoplanets.

  9. Acoustic-Wave-Induced Magnetization Switching of Magnetostrictive Nanomagnets from Single-Domain to Nonvolatile Vortex States.

    PubMed

    Sampath, Vimal; D'Souza, Noel; Bhattacharya, Dhritiman; Atkinson, Gary M; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha

    2016-09-14

    We report experimental manipulation of the magnetic states of elliptical cobalt magnetostrictive nanomagnets (with nominal dimensions of ∼340 nm × 270 nm × 12 nm) delineated on bulk 128° Y-cut lithium niobate with acoustic waves (AWs) launched from interdigitated electrodes. Isolated nanomagnets (no dipole interaction with any other nanomagnet) that are initially magnetized with a magnetic field to a single-domain state with the magnetization aligned along the major axis of the ellipse are driven into a vortex state by acoustic waves that modulate the stress anisotropy of these nanomagnets. The nanomagnets remain in the vortex state until they are reset by a strong magnetic field to the initial single-domain state, making the vortex state nonvolatile. This phenomenon is modeled and explained using a micromagnetic framework and could lead to the development of extremely energy efficient magnetization switching methodologies for low-power computing applications.

  10. The effects of interface misfit strain and surface tension on magnetoelectric effects in layered magnetostrictive-piezoelectric composites

    NASA Astrophysics Data System (ADS)

    Hao, Feng; Pei, Yongmao; Fang, Daining

    2013-07-01

    A nonlinear model is proposed to study low-frequency magnetoelectric (ME) effects in layered magnetostrictive-piezoelectric composites, taking into account the effects of interface misfit strain and surface stress. As a specific case, L-T mode of Terfenol-D/lead zirconate titanate (PZT) composites is investigated. The results show that flexural deformation can suppress the ME voltage coefficient, especially for elevated Terfenol-D volume fraction. Interface misfit strain demonstrates a notable impact on the ME voltage coefficient, and this strain-mediated ME effect is intensified with increasing interface misfit strain. Owing to residual surface tension, the ME voltage coefficient is found to be size-dependent when the thickness of Terfenol-D/PZT layered composite reduces to the nanoscale. In addition, substrate effect on ME voltage coefficients is evaluated.

  11. Acoustic-Wave-Induced Magnetization Switching of Magnetostrictive Nanomagnets from Single-Domain to Nonvolatile Vortex States.

    PubMed

    Sampath, Vimal; D'Souza, Noel; Bhattacharya, Dhritiman; Atkinson, Gary M; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha

    2016-09-14

    We report experimental manipulation of the magnetic states of elliptical cobalt magnetostrictive nanomagnets (with nominal dimensions of ∼340 nm × 270 nm × 12 nm) delineated on bulk 128° Y-cut lithium niobate with acoustic waves (AWs) launched from interdigitated electrodes. Isolated nanomagnets (no dipole interaction with any other nanomagnet) that are initially magnetized with a magnetic field to a single-domain state with the magnetization aligned along the major axis of the ellipse are driven into a vortex state by acoustic waves that modulate the stress anisotropy of these nanomagnets. The nanomagnets remain in the vortex state until they are reset by a strong magnetic field to the initial single-domain state, making the vortex state nonvolatile. This phenomenon is modeled and explained using a micromagnetic framework and could lead to the development of extremely energy efficient magnetization switching methodologies for low-power computing applications. PMID:27564572

  12. Pressure dependencies of magnetostrictive strain and d coefficient in Terfenol-D after thermal or magnetic annealing

    NASA Astrophysics Data System (ADS)

    Galloway, N.; Greenough, R. D.; Jenner, A. G. I.; Schulze, M. P.

    1994-11-01

    The pressure dependence of the magnetostrictive strain coefficient, d(sub 33), and maximum strains in applied fields of 120 kA/m have been measured in samples of Terfenol-D before and after thermal or magnetic annealing. Application of an annealing field, H(sub a), parallel to the (111) axes which are normal to grains oriented along the (11-2) axis, leads to an increase in d(sub 33) of as much as 81%, with applied uniaxial prestresses as low as 3 MPa. The variation of optimum d(sub 33) values as a function of stress applied along the (11-2) axis shows anomalous oscillations after magnetic annealing. The thermal and magnetic effects of the annealing are discussed and a mechanism to explain magnetic annealing is proposed.

  13. Vibration modes of giant gravitons

    SciTech Connect

    Das, Sumit R.; Jevicki, Antal; Mathur, Samir D.

    2001-01-15

    We examine the spectrum of small vibrations of giant gravitons when the gravitons expand in anti--de Sitter space and when they expand on the sphere. For any given angular harmonic, the modes are found to have frequencies related to the curvature length scale of the background; these frequencies are independent of radius (and hence angular momentum) of the brane itself. This implies that the holographic dual theory must have, in a given R charge sector, low-lying non-BPS excitations with level spacings independent of the R charge.

  14. Giant Sigmoid Diverticula: A Review

    PubMed Central

    Kempczinski, Richard F.; Ferrucci, Joseph T.

    1974-01-01

    Two patients with giant sigmoid diverticula are added to 13 cases reported in the literature and the clinical features of this rare complication of diverticulosis are reviewed. These lesions probably arise as pseudodiverticula of the sigmoid colon with herniation of the mucosa through the muscle wall. They become progressively inflated by colonic gas via a ball-valve type mechanism. They are best treated by resection of the diverticulum, in continuity with the involved sigmoid, and primary anastomosis. ImagesFig. 1.Fig. 2.Fig. 3. PMID:4433171

  15. High Curie temperature drive layer materials for ion-implanted magnetic bubble devices

    NASA Technical Reports Server (NTRS)

    Fratello, V. J.; Wolfe, R.; Blank, S. L.; Nelson, T. J.

    1984-01-01

    Ion implantation of bubble garnets can lower the Curie temperature by 70 C or more, thus limiting high temperature operation of devices with ion-implanted propagation patterns. Therefore, double-layer materials were made with a conventional 2-micron bubble storage layer capped by an ion-implantable drive layer of high Curie temperature, high magnetostriction material. Contiguous disk test patterns were implanted with varying doses of a typical triple implant. Quality of propagation was judged by quasistatic tests on 8-micron period major and minor loops. Variations of magnetization, uniaxial anisotropy, implant dose, and magnetostriction were investigated to ensure optimum flux matching, good charged wall coupling, and wide operating margins. The most successful drive layer compositions were in the systems (SmDyLuCa)3(FeSi)5O12 and (BiGdTmCa)3(FeSi)5O12 and had Curie temperatures 25-44 C higher than the storage layers.

  16. Sodium in weak G-band giants

    NASA Technical Reports Server (NTRS)

    Drake, Jeremy J.; Lambert, David L.

    1994-01-01

    Sodium abundances have been determined for eight weak G-band giants whose atmospheres are greatly enriched with products of the CN-cycling H-burning reactions. Systematic errors are minimized by comparing the weak G-band giants to a sample of similar but normal giants. If, further, Ca is selected as a reference element, model atmosphere-related errors should largely be removed. For the weak-G-band stars (Na/Ca) = 0.16 +/- 0.01, which is just possibly greater than the result (Na/Ca) = 0.10 /- 0.03 from the normal giants. This result demonstrates that the atmospheres of the weak G-band giants are not seriously contaminated with products of ON cycling.

  17. Giant Planets in Open Clusters

    NASA Astrophysics Data System (ADS)

    Quinn, S. N.; White, R. J.; Latham, D. W.

    2015-10-01

    Two decades after the discovery of 51 Peg b, more than 200 hot Jupiters have now been confirmed, but the details of their inward migration remain uncertain. While it is widely accepted that short period giant planets could not have formed in situ, several different mechanisms (e.g., Type II migration, planet-planet scattering, Kozai-Lidov cycles) may contribute to shrinking planetary orbits, and the relative importance of each is not well-constrained. Migration through the gas disk is expected to preserve circular, coplanar orbits and must occur quickly (within ˜ 10 Myr), whereas multi-body processes should initially excite eccentricities and inclinations and may take hundreds of millions of years. Subsequent evolution of the system (e.g., orbital circularization and inclination damping via tidal interaction with the host star) may obscure these differences, so observing hot Jupiters soon after migration occurs can constrain the importance of each mechanism. Fortunately, the well-characterized stars in young and adolescent open clusters (with known ages and compositions) provide natural laboratories for such studies, and recent surveys have begun to take advantage of this opportunity. We present a review of the discoveries in this emerging realm of exoplanet science, discuss the constraints they provide for giant planet formation and migration, and reflect on the future direction of the field.

  18. Giant magnetoresistance in silicene nanoribbons

    NASA Astrophysics Data System (ADS)

    Xu, Chengyong; Luo, Guangfu; Liu, Qihang; Zheng, Jiaxin; Zhang, Zhimeng; Nagase, Shigeru; Gao, Zhengxiang; Lu, Jing

    2012-05-01

    By performing first-principle quantum transport calculations, we predict a giant magnetoresistance in zigzag silicene nanoribbons (ZSiNRs) connecting two semi-infinite silicene electrodes through switch of the edge spin direction of ZSiNRs. Spin-filter efficiency of both the antiferromagnetic and ferromagnetic ZSiNRs is sign-changeable with the bias voltage. Therefore, potential application of silicene in spintronics devices is suggested.By performing first-principle quantum transport calculations, we predict a giant magnetoresistance in zigzag silicene nanoribbons (ZSiNRs) connecting two semi-infinite silicene electrodes through switch of the edge spin direction of ZSiNRs. Spin-filter efficiency of both the antiferromagnetic and ferromagnetic ZSiNRs is sign-changeable with the bias voltage. Therefore, potential application of silicene in spintronics devices is suggested. Electronic supplementary information (ESI) available: The total current contrasts between the AFM and FM configurations and the spin-resolved I-Vbias characteristics in the AFM and FM configurations of all the checked ZSiNRs as a function of bias voltage; the spin-resolved I-Vbias characteristics and SFEs of different-length 5-ZSiNR in the AFM and FM configurations as a function of bias voltage. See DOI: 10.1039/c2nr00037g

  19. Ultrasonic measurement of the moduli of elasticity of refractory materials at high temperatures

    NASA Astrophysics Data System (ADS)

    Fargeot, D.; Gault, C.; Platon, F.

    1980-02-01

    A method of ultrasonic measurement of moduli of elasticity of refractory materials up to temperatures of the order of 2000 K is described. The use of magnetostrictive transducers allows operation in the 150-350 kHz frequency range of filamentary test samples with a diameter of about 2 mm and a length of 40-50 mm. Two practical examples are considered, for alpha alumina and for gamma alumina obtained by plasma torch projection.

  20. THE ORBITAL EVOLUTION OF GAS GIANT PLANETS AROUND GIANT STARS

    SciTech Connect

    Villaver, Eva; Livio, Mario E-mail: mlivio@stsci.ed

    2009-11-01

    Recent surveys have revealed a lack of close-in planets around evolved stars more massive than 1.2 M{sub sun}. Such planets are common around solar-mass stars. We have calculated the orbital evolution of planets around stars with a range of initial masses, and have shown how planetary orbits are affected by the evolution of the stars all the way to the tip of the red giant branch. We find that tidal interaction can lead to the engulfment of close-in planets by evolved stars. The engulfment is more efficient for more-massive planets and less-massive stars. These results may explain the observed semimajor axis distribution of planets around evolved stars with masses larger than 1.5 M{sub sun}. Our results also suggest that massive planets may form more efficiently around intermediate-mass stars.

  1. Magnetostriction and anisotropy of twin-free single-crystals Tb0.5Dy0.5(Fe0.9Mn0.1)2

    NASA Astrophysics Data System (ADS)

    Wang, Jinghua; Wu, Guangheng; Zhao, Xuegen; Jia, Kechang; Zhan, Wenshan

    1996-04-01

    A study of the effects of substituting a small amount of Mn for Fe in the Terfenol-D system is presented. The twin-free and <111>-oriented single-crystal rods of Tb0.5Dy0.5(Fe0.9Mn0.1)2 were prepared by Czochralski method. The magnetization, lattice constant, Curie temperature, and magnetostriction were examined. From the experimental results, it is possible to determine the effect of Mn substitution on magnetic anisotropy and magnetostriction. Because of Mn substituting for Fe, magnetic moment values of Tb0.5Dy0.5(Fe0.9Mn0.1)2 show two inflections and the easy magnetization directions also show changes from 1.5 to 300 K at an applied field of 1000 Oe. It strongly suggests that Mn substitution remarkably influences magnetocrystalline anisotropy of Tb0.5Dy0.5(Fe0.9Mn0.1)2. Its saturation magnetostrictions are 1.48×10-3 and 1.67×10-3, maximum d33 values are 1 and 1.5 under compressive stress of 0 and 12 MPa, respectively. These magnetostrictive properties are clearly better than those measured from the <112>-oriented twinned samples. This is the first time that the experimental data measured from the single-crystalline samples on the magnetic properties of Tb0.5Dy0.5(Fe0.9Mn0.1)2 are reported.

  2. Nano-eutectic growth in Co-17.8 wt%Gd alloy ribbons and the magnetostrictive properties at different wheel speeds.

    PubMed

    Yao, Wen-Jing; Sun, Wen; Wang, Nan; Han, Seung Zeon; Lee, Je-Hyun

    2014-11-01

    Under near-equilibrium solidification conditions, the Co-17.8 wt%Gd eutectic alloy forms rod-like eutectic microstructure of (αCo) solid solution and Co17Gd2 compound. When the solidification condition is far from the equilibrium, the rapid growth of nano-eutectic in Co-17.8 wt%Gd alloy ribbons is realized by the single-roller techniques. The average granular size (d) of nano-eutectic in the center of ribbons varies with the increase of wheel speed (V), d = 510.36-25.51 V+0.44 V2. XRD results of ribbons at different wheel speeds indicate that, with the rise of wheel speed, the main peak of Co17Gd2 compound becomes more and more notable, whereas the main peak of (αCo) solid solution tends to reduce. Along the length direction, the Co-17.8 wt%Gd alloy ribbons have the negative magnetostrictive strain. The magnetostrictive strain enhances with the increase of wheel speed. At the wheel speed of 40 m/s, the magnetostrictive coefficient of ribbons is measured to be - 733 ppm at the magnetic field of 6 kOe. The influence of the wheel speed and the magnetic field on the maanetostrictive coefficient is discussed.

  3. Giant magnetoresistive heterogeneous alloys and method of making same

    DOEpatents

    Bernardi, J.J.; Thomas, G.; Huetten, A.R.

    1999-03-16

    The inventive material exhibits giant magnetoresistance upon application of an external magnetic field at room temperature. The hysteresis is minimal. The inventive material has a magnetic phase formed by eutectic decomposition. The bulk material comprises a plurality of regions characterized by (a) the presence of magnetic lamellae wherein the lamellae are separated by a distance smaller than the mean free path of the conduction electrons, and (b) a matrix composition having nonmagnetic properties that is interposed between the lamellae within the regions. The inventive, rapidly quenched, eutectic alloys form microstructure lamellae having antiparallel antiferromagnetic coupling and give rise to GMR properties. The inventive materials made according to the inventive process yielded commercially acceptable quantities and timeframes. Annealing destroyed the microstructure lamellae and the GMR effect. Noneutectic alloys did not exhibit the antiparallel microstructure lamellae and did not possess GMR properties. 7 figs.

  4. Giant magnetoresistive heterogeneous alloys and method of making same

    DOEpatents

    Bernardi, J.J.; Thomas, G.; Huetten, A.R.

    1998-10-20

    The inventive material exhibits giant magnetoresistance upon application of an external magnetic field at room temperature. The hysteresis is minimal. The inventive material has a magnetic phase formed by eutectic decomposition. The bulk material comprises a plurality of regions characterized by (a) the presence of magnetic lamellae wherein the lamellae are separated by a distance smaller than the mean free path of the conduction electrons, and (b) a matrix composition having nonmagnetic properties that is interposed between the lamellae within the regions. The inventive, rapidly quenched, eutectic alloys form microstructure lamellae having antiparallel antiferromagnetic coupling and give rise to GMR properties. The inventive materials made according to the inventive process yielded commercially acceptable quantities and timeframes. Annealing destroyed the microstructure lamellae and the GMR effect. Noneutectic alloys did not exhibit the antiparallel microstructure lamellae and did not possess GMR properties. 7 figs.

  5. Giant magnetoresistive heterogeneous alloys and method of making same

    DOEpatents

    Bernardi, Johannes J.; Thomas, Gareth; Huetten, Andreas R.

    1998-01-01

    The inventive material exhibits giant magnetoresistance upon application of an external magnetic field at room temperature. The hysteresis is minimal. The inventive material has a magnetic phase formed by eutectic decomposition. The bulk material comprises a plurality of regions characterized by a) the presence of magnetic lamellae wherein the lamellae are separated by a distance smaller than the mean free path of the conduction electrons, and b) a matrix composition having nonmagnetic properties that is interposed between the lamellae within the regions. The inventive, rapidly quenched, eutectic alloys form microstructure lamellae having antiparallel antiferromagnetic coupling and give rise to GMR properties. The inventive materials made according to the inventive process yielded commercially acceptable quantities and timeframes. Annealing destroyed the microstructure lamellae and the GMR effect. Noneutectic alloys did not exhibit the antiparallel microstructure lamellae and did not possess GMR properties.

  6. Giant magnetoresistive heterogeneous alloys and method of making same

    DOEpatents

    Bernardi, Johannes J.; Thomas, Gareth; Huetten, Andreas R.

    1999-01-01

    The inventive material exhibits giant magnetoresistance upon application of an external magnetic field at room temperature. The hysteresis is minimal. The inventive material has a magnetic phase formed by eutectic decomposition. The bulk material comprises a plurality of regions characterized by a) the presence of magnetic lamellae wherein the lamellae are separated by a distance smaller than the mean free path of the conduction electrons, and b) a matrix composition having nonmagnetic properties that is interposed between the lamellae within the regions. The inventive, rapidly quenched, eutectic alloys form microstructure lamellae having antiparallel antiferromagnetic coupling and give rise to GMR properties. The inventive materials made according to the inventive process yielded commercially acceptable quantities and timeframes. Annealing destroyed the microstructure lamellae and the GMR effect. Noneutectic alloys did not exhibit the antiparallel microstructure lamellae and did not possess GMR properties.

  7. Giant photostriction in organic-inorganic lead halide perovskites

    NASA Astrophysics Data System (ADS)

    Zhou, Yang; You, Lu; Wang, Shiwei; Ku, Zhiliang; Fan, Hongjin; Schmidt, Daniel; Rusydi, Andrivo; Chang, Lei; Wang, Le; Ren, Peng; Chen, Liufang; Yuan, Guoliang; Chen, Lang; Wang, Junling

    2016-04-01

    Among the many materials investigated for next-generation photovoltaic cells, organic-inorganic lead halide perovskites have demonstrated great potential thanks to their high power conversion efficiency and solution processability. Within a short period of about 5 years, the efficiency of solar cells based on these materials has increased dramatically from 3.8 to over 20%. Despite the tremendous progress in device performance, much less is known about the underlying photophysics involving charge-orbital-lattice interactions and the role of the organic molecules in this hybrid material remains poorly understood. Here, we report a giant photostrictive response, that is, light-induced lattice change, of >1,200 p.p.m. in methylammonium lead iodide, which could be the key to understand its superior optical properties. The strong photon-lattice coupling also opens up the possibility of employing these materials in wireless opto-mechanical devices.

  8. Giant photostriction in organic–inorganic lead halide perovskites

    PubMed Central

    Zhou, Yang; You, Lu; Wang, Shiwei; Ku, Zhiliang; Fan, Hongjin; Schmidt, Daniel; Rusydi, Andrivo; Chang, Lei; Wang, Le; Ren, Peng; Chen, Liufang; Yuan, Guoliang; Chen, Lang; Wang, Junling

    2016-01-01

    Among the many materials investigated for next-generation photovoltaic cells, organic–inorganic lead halide perovskites have demonstrated great potential thanks to their high power conversion efficiency and solution processability. Within a short period of about 5 years, the efficiency of solar cells based on these materials has increased dramatically from 3.8 to over 20%. Despite the tremendous progress in device performance, much less is known about the underlying photophysics involving charge–orbital–lattice interactions and the role of the organic molecules in this hybrid material remains poorly understood. Here, we report a giant photostrictive response, that is, light-induced lattice change, of >1,200 p.p.m. in methylammonium lead iodide, which could be the key to understand its superior optical properties. The strong photon-lattice coupling also opens up the possibility of employing these materials in wireless opto-mechanical devices. PMID:27044485

  9. Water/Icy Super-Earths: Giant Impacts and Maximum Water Content

    NASA Astrophysics Data System (ADS)

    Marcus, Robert A.; Sasselov, Dimitar; Stewart, Sarah T.; Hernquist, Lars

    2010-08-01

    Water-rich super-Earth exoplanets are expected to be common. We explore the effect of late giant impacts on the final bulk abundance of water in such planets. We present the results from smoothed particle hydrodynamics simulations of impacts between differentiated water(ice)-rock planets with masses between 0.5 and 5 M ⊕ and projectile to target mass ratios from 1:1 to 1:4. We find that giant impacts between bodies of similar composition never decrease the bulk density of the target planet. If the commonly assumed maximum water fraction of 75 wt% for bodies forming beyond the snow line is correct, giant impacts between similar composition bodies cannot serve as a mechanism for increasing the water fraction. Target planets either accrete materials in the same proportion, leaving the water fraction unchanged, or lose material from the water mantle, decreasing the water fraction. The criteria for catastrophic disruption of water-rock planets are similar to those found in previous work on super-Earths of terrestrial composition. Changes in bulk composition for giant impacts onto differentiated bodies of any composition (water rock or rock iron) are described by the same equations. These general laws can be incorporated into future N-body calculations of planet formation to track changes in composition from giant impacts.

  10. WATER/ICY SUPER-EARTHS: GIANT IMPACTS AND MAXIMUM WATER CONTENT

    SciTech Connect

    Marcus, Robert A.; Sasselov, Dimitar; Hernquist, Lars; Stewart, Sarah T.

    2010-08-10

    Water-rich super-Earth exoplanets are expected to be common. We explore the effect of late giant impacts on the final bulk abundance of water in such planets. We present the results from smoothed particle hydrodynamics simulations of impacts between differentiated water(ice)-rock planets with masses between 0.5 and 5 M{sub +} and projectile to target mass ratios from 1:1 to 1:4. We find that giant impacts between bodies of similar composition never decrease the bulk density of the target planet. If the commonly assumed maximum water fraction of 75 wt% for bodies forming beyond the snow line is correct, giant impacts between similar composition bodies cannot serve as a mechanism for increasing the water fraction. Target planets either accrete materials in the same proportion, leaving the water fraction unchanged, or lose material from the water mantle, decreasing the water fraction. The criteria for catastrophic disruption of water-rock planets are similar to those found in previous work on super-Earths of terrestrial composition. Changes in bulk composition for giant impacts onto differentiated bodies of any composition (water rock or rock iron) are described by the same equations. These general laws can be incorporated into future N-body calculations of planet formation to track changes in composition from giant impacts.

  11. Giant polygons and circular graben in western Utopia basin, Mars: Exploring possible formation mechanisms

    NASA Astrophysics Data System (ADS)

    Buczkowski, Debra L.; Seelos, Kim D.; Cooke, Michele L.

    2012-08-01

    Large-scale fracture systems surrounding the Utopia basin include giant polygons and circular graben. Data covering the northern Utopia basin now allow high-resolution mapping of these features in all regions of the basin. Giant polygons to the north and south of the basin are different in both size and morphology, leading to the polygon classifications (1) S-style, (2) subdued S-style, (3) northern S-style and (4) N-style. Also, ten circular graben have been identified to the north of the Utopia basin. These have generally larger diameters than southern circular graben, and their fracture morphology is similar to N-style giant polygons. As with southern circular graben, the surface relief of the depression inside the northern circular graben scales directly with diameter. However, northern circular graben have less steep trend slopes, larger average diameters and greater ring spacing compared to southern circular graben of the same diameter and similar distance to the center of the Utopia basin. Both the giant polygons and circular graben of Utopia Planitia are consistent with formation by volumetric compaction of a fine-grained sedimentary material covering an uneven buried surface. Giant polygon size variations can be explained by the material being wet to the south but frozen or partially frozen to the north, while differences between northern and southern circular graben may be attributed to changes in cover thickness. Differences in fracture morphology can be explained by subsequent alteration of the northern troughs due to polar processes.

  12. Giant Impacts on Terrestrial Planets: A High-Resolution 3D Study of Magma Ocean Formation and Atmospheric Blowoff

    NASA Astrophysics Data System (ADS)

    Stewart-Mukhopadhyay, Sarah

    The end stages of terrestrial planet formation are dominated by giant impact events, which may significantly affect the final composition of a planet. The physical changes from giant impacts include formation of magma oceans and atmospheric blowoff. We propose to conduct unique numerical experiments to investigate the physics of giant impacts in order to determine their effect on the thermal state and volatile budget of terrestrial planets (0.1 to 10 Earth masses). Proposed work: High-resolution 3D giant impacts between differentiated silicate-iron and ice-silicate planets will be modeled with both the widely-used CTH shock physics code and a new second-order Godunov finite-volume hydrocode called AREPO. AREPO's powerful arbitrary Lagrangian-Eulerian grid and computational efficiency allows for unprecedented resolution of planetary structure (e.g., crust and ocean). Expected results: (1) We will calculate the amount of melt generated and fraction of atmosphere lost during different classes of giant impacts (merging, graze and merge, hit and run, and erosion/disruption). (2) We will derive general scaling laws to describe these complicated phenomena. (3) We will consider the effect of re-accretion of ejected material at late times on the total thermal input of giant impact events. (4) And we will test the giant impact hypothesis for the high bulk density of Mercury by conducting orbital integrations of ejected debris to determine the amount of re-accreted mantle material for different impact orientations. The science team has an established collaborative body of work in giant impact simulations and hydrocode development. As in previous studies, the simulation results will be generalized into sets of simple equations describing collision outcomes that are suitable for N-body planet formation models. The proposed work supports the goals of the Origins of Solar Systems program by conducting a fundamental theoretical investigation of a key stage of planet formation

  13. Giant barrier layer capacitance effects in the lithium ion conducting material La0.67Li0.25Ti0.75Al0.25O3

    NASA Astrophysics Data System (ADS)

    García-Martín, Susana; Morata-Orrantia, Ainhoa; Aguirre, Myriam H.; Alario-Franco, Miguel Á.

    2005-01-01

    High dielectric permittivity (ɛ'˜500000) has been observed in polycrystalline samples of La0.67Li0.25Ti0.75Al0.25O3 over a large frequency range (˜10material.

  14. The Giant Metrewave Radio Telescope

    NASA Astrophysics Data System (ADS)

    Nityananda, R.

    2003-05-01

    The Giant Metrewave Radio Telescope (GMRT) of the National Centre of Radio Astrophysics (NCRA) of the Tata Institute of Fundamental Research (TIFR) at Khodad, India, has been operational in the band 0.2 to 2 metres for the last two and a half years. The system characteristics and performance and recent results from the group will be presented. Details of use over the last six months by scientists from other observatories under the GMRT Time Allocation Committee (GTAC) and future plans will be also be reviewed in this paper. Areas which have been studied include observations made in the GMRT band of neutral hydrogen, nearby galaxies, supernova remnants, the Galactic Centre, pulsars, the Sun and others.

  15. Giant tunneling magnetoresistance in silicene

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Lou, Yiyi

    2013-11-01

    We have theoretically studied ballistic electron transport in silicene under the manipulation of a pair of ferromagnetic gate. Transport properties like transmission and conductance have been calculated by the standard transfer matrix method for parallel and antiparallel magnetization configurations. It is demonstrated here that, due to the stray field-induced wave-vector filtering effect, remarkable difference in configuration-dependent transport gives rise to a giant tunneling magnetoresistance. In combination with the peculiar buckled structure of silicene and its electric tunable energy gap, the receiving magnetoresistance can be efficiently modulated by the externally-tunable stray field, electrostatic potential, and staggered sublattice potential, providing some flexible strategies to construct silicene-based nanoelectronic device.

  16. Giant tunneling magnetoresistance in silicene

    SciTech Connect

    Wang, Yu; Lou, Yiyi

    2013-11-14

    We have theoretically studied ballistic electron transport in silicene under the manipulation of a pair of ferromagnetic gate. Transport properties like transmission and conductance have been calculated by the standard transfer matrix method for parallel and antiparallel magnetization configurations. It is demonstrated here that, due to the stray field-induced wave-vector filtering effect, remarkable difference in configuration-dependent transport gives rise to a giant tunneling magnetoresistance. In combination with the peculiar buckled structure of silicene and its electric tunable energy gap, the receiving magnetoresistance can be efficiently modulated by the externally-tunable stray field, electrostatic potential, and staggered sublattice potential, providing some flexible strategies to construct silicene-based nanoelectronic device.

  17. Giant Raman gain in silicon nanocrystals

    PubMed Central

    Sirleto, Luigi; Antonietta Ferrara, Maria; Nikitin, Timur; Novikov, Sergei; Khriachtchev, Leonid

    2012-01-01

    Nanostructured silicon has generated a lot of interest in the past decades as a key material for silicon-based photonics. The low absorption coefficient makes silicon nanocrystals attractive as an active medium in waveguide structures, and their third-order nonlinear optical properties are crucial for the development of next generation nonlinear photonic devices. Here we report the first observation of stimulated Raman scattering in silicon nanocrystals embedded in a silica matrix under non-resonant excitation at infrared wavelengths (~1.5 μm). Raman gain is directly measured as a function of the silicon content. A giant Raman gain from the silicon nanocrystals is obtained that is up to four orders of magnitude greater than in crystalline silicon. These results demonstrate the first Raman amplifier based on silicon nanocrystals in a silica matrix, thus opening new perspectives for the realization of more efficient Raman lasers with ultra-small sizes, which would increase the synergy between electronic and photonic devices. PMID:23187620

  18. Giant landslide deposits in northwest Argentina

    SciTech Connect

    Fauque, L.; Strecker, M.R.; Bloom, A.L.

    1985-01-01

    Giant Quaternary landslide deposits occur along mountain fronts in the structural transition zone between the high-angle reverse-fault-bounded Sierras Pampeanas and the low-angle thrust belt of the Sierras Subandinas. There are two modes of occurrence: (1) chaotic masses without distinct geometry, and (2) masses with distinct lobate geometry similar to glacial moraines. Type (1) deposits occur where the moving rock mass followed a narrow valley and blocked the drainage. Many of these caused subsequent formation of lakes and changed the sedimentation processes on pediments at the mountain fronts. In type (2) deposits, lateral and frontal ridges are up to 10 m higher than the interior parts; in some places pressure ridges within the lobes are well preserved. Type (2) deposits show reverse grading and were deposited on relatively smooth pediments or alluvial fans. The lobate geometry strongly suggests that type (2) deposits are a product of flowage and are debris stream or sturzstrom deposits (sense of Heim, 1932 and Hsu, 1975). All investigated deposits occur in areas of demonstrated Quaternary faulting and are interpreted as the result of tectonic movements, although structural inhomogeneities in the source area may have been a significant factor for some of the landslides. No datable materials have yet been found associated with the deposits.

  19. Type II Migration and Giant Planet Survival

    NASA Technical Reports Server (NTRS)

    Ward, William R.

    2003-01-01

    Type II migration, in which a newly formed large planet opens a gap in its precursor circumstellar nebula and subsequently evolves with it, has been implicated as a delivery mechanism responsible for close stellar companions. Large scale migration is possible in a viscously spreading disk of surface density sigma (r,t) when most of it is sacrificed to the primary in order to promote a small portion of the disk to much higher angular momentum orbits. Embedded planets generally follow its evolution unless their own angular momentum is comparable to that of the disk. The fraction of the starting disk mass, M (sub d) = 2pi integral rsigma(r,0)dr, that is consumed by the star depends on the distance at which material escapes the disk's outer boundary. If the disk is allowed to expand indefinitely, virtually all of the disk will fall into the primary in order to send a vanishingly small portion to infinity. For such a case, it is difficult to explain the survival of any giant planets, including Jupiter and Saturn. Realistically, however, there are processes that could truncate a disk at a finite distance, r(sub d). Recent numerical modeling has illustrated that planets can survive in this case. We show here that much of these results can be understood by simple conservation arguments.

  20. Early Asymptotic Giant Branch: Theory and Observations

    NASA Astrophysics Data System (ADS)

    Frantsman, Ju.

    1995-08-01

    While on the asymptotic giant branch (AGB), a star passes through two evolutionary phases: an early stage (E-AGB), and thermally pulsing AGB (TP-AGB). The theory of two AGB stages was developed more than a decade ago but till now some authors do not take into account the E-AGB phase in spite of the fact that E-AGB phase lasts for some stars considerably longer than the TP-AGB phase. The typical outcomes of such ignoration are shown in the report (wrong conclusions about the evolution of Large Magellanic Cloud, the mistakes in the determination of the ages of Magellanic Cloud clusters). The results are obtained using the "population simultaion" technique. The origin of some types of chemically peculiar stars is investigated (S-stars, faint carbon stars, carbon stars bluer and somewhat brighter than in the mean N-Type stars in the Magellanic Clouds). A suggestion is proposed that these stars are on the E-AGB evolutionary stage. They develop chemical peculiarities in the process of mass transfer in close binaries. It was assumed that during the TP-AGB phase, the primary (more massive) component, when being the carbon star, transfered the carbon enriched material by Roche-lobe overflow to the secondary component, which becomes the star with carbon overabundance. During the subsequent evolution the former secondary (and now after mass transfer carbon enriched) component reaches the E-AGB phase. The results of calculations are discussed and compared with observations.