WorldWideScience

Sample records for high coercive forces

  1. Magnetic properties of cementite and the coercive force of carbon steels after plastic deformation and annealing

    Science.gov (United States)

    Ul'Yanov, A. I.; Chulkina, A. A.

    2009-05-01

    Magnetic hysteresis properties of cementite obtained by the method of mechanical alloying have been studied. It is shown that the strongly deformed cementite is in a low-coercivity state, and the cementite annealed at 500°C is in a high-coercivity state. The need to allow for the contribution of the coercivity of cementite to the coercive force of high-carbon steel is shown. Taking into account this point of view, the behavior of the coercive force depending on the degree of cold plastic deformation by drawing is explained for a number of carbon steels with a structure of fine platelike and globular cementite.

  2. Force transducers based on the stress dependence of coercive force

    Science.gov (United States)

    Garshelis, I. J.

    1993-05-01

    An alternative measurement regime for magnetoelastic force transducers, based on variations in coercive field, is described. Hc is shown to be more directly related to the primary magnetic influence of stress, namely, the orientation of effective anisotropy, than conventionally used magnetization related parameters. The stress dependence of Hc is shown to generally reflect opposing factors associated with rotational and wall displacement magnetization reversal processes. In materials wherein Hc≪K/Ms wall motion dominates and if the product of λs/K and yield stress is high enough, large monotonic reductions of Hc with positive (tensile) stress are shown to be possible. A more complex variation of Hc with increasing compression is similarly expected. Experimental results from a transducer having an 18% Ni maraging steel core support these expectations.

  3. Iron in the Fire: Searching for Fire's Magnetic Fingerprint using Controlled Heating Experiments, High-Resolution FORCs, IRM Coercivity Spectra, and Low-Temperature Remanence Experiments

    Science.gov (United States)

    Lippert, P. C.; Reiners, P. W.

    2014-12-01

    Evidence for recent climate-wildfire linkages underscores the need for better understanding of relationships between wildfire and major climate shifts in Earth history, which in turn offers the potential for prognoses for wildfire and human adaptations to it. In particular, what are the links between seasonality and wildfire frequency and severity, and what are the feedbacks between wildfire, landscape evolution, and biogeochemical cycles, particularly the carbon and iron cycles? A key first step in addressing these questions is recovering well-described wildfire records from a variety of paleolandscapes and paleoclimate regimes. Although charcoal and organic biomarkers are commonly used indicators of fire, taphonomic processes and time-consuming analytical preparations often preclude their routine use in some environments and in high-stratigraphic resolution paleowildfire surveying. The phenomenological relationship between fire and magnetic susceptibility can make it a useful surveying tool, but increased magnetic susceptibility in sediments is not unique to fire, and thus limits its diagnostic power. Here we utilize component-specific rock magnetic methods and analytical techniques to identify the rock magnetic fingerprint of wildfire. We use a custom-designed air furnace, a series of iron-free laboratory soils, natural saprolites and soils, and fuels from Arizona Ponderosa pine forests and grasslands to simulate wildfire in a controlled and monitored environment. Soil-ash residues and soil and fuel controls were then characterized using First Order Reversal Curve (FORC) patterns, DC backfield IRM coercivity spectra, low-temperature SIRM demagnetization behavior, and low-temperature cycling of room-temperature SIRM behavior. We will complement these magnetic analyses with high-resolution TEM of magnetic extracts. Here we summarize the systematic changes to sediment magnetism as pyrolitized organic matter is incorporated into artificial and natural soils. These

  4. Magnetic microstructure and coercivity mechanism of high performance Nd-Fe-B magnets

    Institute of Scientific and Technical Information of China (English)

    ZHU Minggang; LIU Xingmin; FANG Yikun; LI Zhengbang; LI Wei

    2006-01-01

    Magnetic microstructure of high performance Nd-Fe-B magnets was investigated by using magnetic force microscopy. The correlation between magnetic microstructure and coercivity for high performance Nd-Fe-B magnets was studied. It is found that the magnets with different coercivity mechanism take on different microstructures and magnetism. Moreover, the magnetic microstructures of high performance permanent magnets can be explained by the starting field theory model.

  5. Tuning coercive force by adjusting electric potential in solution processed Co/Pt(111) and the mechanism involved

    Science.gov (United States)

    Chang, Cheng-Hsun-Tony; Kuo, Wei-Hsu; Chang, Yu-Chieh; Tsay, Jyh-Shen; Yau, Shueh-Lin

    2017-03-01

    A combination of a solution process and the control of the electric potential for magnetism represents a new approach to operating spintronic devices with a highly controlled efficiency and lower power consumption with reduced production cost. As a paradigmatic example, we investigated Co/Pt(111) in the Bloch-wall regime. The depression in coercive force was detected by applying a negative electric potential in an electrolytic solution. The reversible control of coercive force by varying the electric potential within few hundred millivolts is demonstrated. By changing the electric potential in ferromagnetic layers with smaller thicknesses, the efficiency for controlling the tunable coercive force becomes higher. Assuming that the pinning domains are independent of the applied electric potential, an electric potential tuning-magnetic anisotropy energy model was derived and provided insights into our knowledge of the relation between the electric potential tuning coercive force and the thickness of the ferromagnetic layer. Based on the fact that the coercive force can be tuned by changing the electric potential using a solution process, we developed a novel concept of electric-potential-tuned magnetic recording, resulting in a stable recording media with a high degree of writing ability.

  6. High coercivity in nanostructured Co-ferrite thin films

    Indian Academy of Sciences (India)

    J H Yin; B H Liu; J Ding; Y C Wang

    2006-11-01

    Three methods including sol–gel, rf sputtering and pulsed laser deposition (PLD) have been used for the fabrication of high coercivity Co-ferrite thin films with a nanocrystalline structure. The PLD method is demonstrated to be a possible tool to achieve Co-ferrite films with high coercivity and small grain size at low deposition temperature. High coercivity, over 10 kOe, has been successfully achieved in Co-ferrite films with a thickness of ∼ 100 nm deposited using PLD with a substrate temperature at 550°C. The Co-ferrite films prepared by PLD at over 300°C on different substrates including amorphous glass, quartz and silicon exhibits an obvious (111) textured structure and possesses perpendicular anisotropy. Our study has also shown that the high coercivity is related with a large residual strain, which may induce an additional magnetic anisotropy (stress anisotropy) and at the same time serve as pinning centres, which can restrict the domain wall movement and therefore, increase the coercivity.

  7. High coercivity remanence in baked clay materials used in archeomagnetism

    Science.gov (United States)

    McIntosh, Gregg; Kovacheva, Mary; Catanzariti, Gianluca; Donadini, Fabio; Lopez, Maria Luisa Osete

    2011-02-01

    A study of the high coercivity remanence in archeological baked clays has been carried out. More than 150 specimens from 46 sites across Europe have been analyzed, selected on the basis of the presence of a fraction of their natural remanence that was resistant to alternating field demagnetization to 100 mT. The study was based on the stability of isothermal remanence to alternating field and thermal demagnetization and its variation on cooling to liquid nitrogen temperature. Results indicate that the high coercivity remanence may be carried by magnetite, hematite, and in isolated cases partially oxidized magnetite and goethite. In addition, a high coercivity, thermally stable, low unblocking temperature phase has been identified. The unblocking temperatures of both the isothermal remanence and the alternating field resistant natural remanence exhibit similar unblocking temperatures, suggesting that the same phases carry both signals. The high coercivity, low unblocking temperature phase contributes to the natural remanence, sometimes carrying a stable direction and behaving ideally during palaeointensity experiments and sometimes not. An unambiguous mineralogical identification of this phase is lacking, although likely candidates include hemoilmentite, related to clay source lithology, and substituted hematite or magnetic ferri-cristabolite, both possible products of thermal transformation of iron-bearing clays.

  8. Formation of FePt Nanoparticles Having High Coercivity

    Energy Technology Data Exchange (ETDEWEB)

    Rutledge, R.D. [Vanderbilt University; MorrisIII, William H [Vanderbilt University; Wellons, M.S. [Vanderbilt University; Gai, Zheng [ORNL; Shen, Jian [ORNL; Bentley, James [ORNL; Wittig, J. E. [Vanderbilt University; Lukehart, C.M. [Vanderbilt University

    2006-01-01

    Ultrasonication of toluene solutions of the heteropolynuclear cluster complex, Pt{sub 3}Fe{sub 3}(CO){sub 15}, in the presence of oleic acid and oleylamine affords surface-capped fcc FePt nanoparticles having an average diameter of ca. 2 nm. Self-assembled arrays of these nanoparticles on oxidized Si wafers undergo a fcc-to-fct phase transition at 775 C to form ferromagnetic FePt nanocrystals ca. 5.8 nm in diameter well dispersed on the Si wafer surface. Room-temperature coercivity measurements of these annealed FePt nanoparticles confirm a high coercivity of ca. 22.3 kOe. Such high coercivity for fct FePt nanoparticles might result from use of a heterpolynuclear complex as a single-source precursor of Fe and Pt neutral atoms or from use of ultrasonication to form fcc FePt nanoparticles under conditions of exceptionally rapid heating. Experiments to determine the critical experimental conditions required to achieve such high room-temperature coercivities in ferromagnetic nanoparticles are underway.

  9. Variable substrate temperature deposition of CoFeB film on Ta for manipulating the perpendicular coercive forces

    Science.gov (United States)

    Lakshmanan, Saravanan; Rao, Subha Krishna; Muthuvel, Manivel Raja; Chandrasekaran, Gopalakrishnan; Therese, Helen Annal

    2017-08-01

    Magnetization of Ta/CoFeB/Ta trilayer films with thick layer of CoFeB deposited under different substrate temperatures (Ts) via ultra-high vacuum DC sputtering technique has been measured with the applied magnetic field parallel and perpendicular to the plane of the film respectively to study the perpendicular coercive forces of the film. The samples were further analyzed for its structural, topological, morphological, and electrical transport properties. The core chemical states for the elements present in the CoFeB thin film were analyzed by XPS studies. Magnetization studies reveal the existence of perpendicular coercive forces in CoFeB films deposited only at certain temperatures such as RT, 450 °C, 475 °C and 500 °C. CoFeB film deposited at 475 °C exhibited a maximum coercivity of 315 Oe and a very low saturation magnetization (Ms) of 169 emu/cc in perpendicular direction. This pronounced effect in perpendicular coercive forces observed for CoFeB475 could be attributed to the effect of temperature in enhancing the crystallization of the film at the Ta/CoFeB interfaces. However at temperatures higher than 475 °C the destruction of the Ta/CoFeB interface due to intermixing of Ta and CoFeB results in the disappearance of magnetic anisotropy.

  10. Relation between Nd{sub 2}Fe{sub 14}B grain alignment and coercive force decrease ratio in NdFeB sintered magnets

    Energy Technology Data Exchange (ETDEWEB)

    Matsuura, Yutaka, E-mail: Yutaka_Matsuura@hitachi-metals.co.jp [Hitachi Metals Ltd., NEOMAX Division, 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka 618-0013 (Japan); Hoshijima, Jun; Ishii, Rintaro [Hitachi Metals Ltd., NEOMAX Division, 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka 618-0013 (Japan)

    2013-06-15

    It was found that the coercive force of NdFeB sintered magnets decreases as the Nd{sub 2}Fe{sub 14}B grain alignment improves. Because of this phenomenon, studies looked at the relation between this alignment and the coercive force decrease ratio. In experiments, it was expected that the coercive force of perfectly aligned magnet reached 0.7 of coercive force in istotropically aligned magnet. When it is postulated that the coercive force is determined by the Stoner–Wohlfarth model, coercive force increases as the alignment improves and it becomes difficult to explain our experimental data. On the other hand, when the coercive force is determined by magnetic domain wall motion, the coercive force decreases as the alignment improves and the coercive force of the perfectly aligned magnet reaches 1/√(2) of the isotropically aligned magnet. This tendency and value was very close to our data. It strongly suggests that the coercive force of NdFeB sintered magnets is determined by the domain wall motion. - Highlights: ► Coercive force of NdFeB sintered magnets decreases as grains alignment improves. ► Coercive force decrease ratio reaches −30% at the perfect aligned magnet. ►These experimental results are different from the Stoner–Wohlfarth model. ► The magnetic domain wall motion could explain this coercive force decrease ratio.

  11. Growth, structural and magnetic properties of high coercivity Co/Pt multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Weller, D.; Folks, L.; Best, M.; Fullerton, E.EwqTerris, B.D.; Kusinski, G.J.; Krishnan, K.M.; Thomas, G.

    2000-11-01

    Co/Pt multilayer films ([Co (tCo nm)/Pt(1 nm)]10, 0.2 < tCo < 2 nm) with perpendicular magnetic anisotropy and room temperature coercivity Hc = 12-15 kOe are fabricated using electron beam evaporation at elevated growth temperatures onto Si(001)/SiNx(40nm)/Pt(20nm) substrate/seed structures. Hysteresis and magnetic force microscopy (MFM) studies indicate changes in the magnetization reversal mechanism along with a sharp increase in coercivity for growth temperatures higher TG {approx} 230 - 250 degrees C. Films grown at TG < 230 degrees C (tCo = 0.2 - 0.4 nm) show large micrometer size magnetic domains and rectangular hysteresis loops indicating magnetization reversal dominated by rapid domain wall motion throughout the film following nucleation at Hn {approx} Hc. Films grown at TG > 250 degrees C show fine-grained MFM features on the sub-100 nm length scale and hysteresis studies indicate reversal dominated by localized switching of small clusters. The hysteresis curves for the highest coercivity films are sheared with a hysteresis slope alpha=4(pi)dM/dH|Hc approximately equal 1.5, which is close to the ideal value for completely decoupled grains of alpha =1. High resolution cross-sectional TEM with elemental analysis shows columnar grains extending throughout the multilayer stack. Sharp Co/Pt interfaces are found from TEM and grazing incidence X-ray diffraction. At higher TG, Co depletion and structural defects at the grain boundaries provide a mechanism for exchange decoupling of adjacent grains, which may result in the high coercivities observed. Anisotropy and magnetization values are estimated as Ku {approx} 8x106 erg/cc and MS {approx} 450 emu/cc (per total volume), hence Hk = 2Ku/MS {approx} 17.5 kOe for the highest coercivity Hc {approx} 15 kOe films.

  12. Coercive diplomacy

    DEFF Research Database (Denmark)

    Jakobsen, Peter Viggo

    2016-01-01

    Coercive diplomacy (CD) involves the use of military threats and/or limited force in support of diplomatic negotiations relying on persuasion, rewards and assurances. This combination of coercion (sticks) and diplomacy (carrots) is as old as the practice of diplomacy, and it is typically employed...... separate strategic eras with distinct challenges and theoretical developments are identified since the field’s emergence in the 1960s: the Cold War, the humanitarian 1990s, the war on terror and the hybrid future. The record clearly shows that skilful use of coercive diplomacy can resolve crises...... that coercive diplomacy does hold....

  13. Very high coercivity magnetic stripes produced by particle rotation

    Energy Technology Data Exchange (ETDEWEB)

    Naylor, R.B.

    1992-12-01

    This paper describes a current research program at Sandia National Laboratories whereby magnetic stripes are produced through the use of a new particle rotation technology. This new process allows the stripes to be produced in bulk and then held in a latent state so that they may be encoded at a later date. Since particle rotation is less dependent on the type of magnetic particle used, very high coercivity particles could provide a way to increase both magnetic tamper-resistance and accidental erasure protection. This research was initially funded by the Department of Energy, Office of Safeguard and Security as a portion of their Science and Technology Base Development, Advanced Security Concepts program. Current program funding is being provided by Sandia National Laboratories as part of their Laboratory Directed Research and Development program.

  14. Temperature stability and microstructure of ultra-high intrinsic coercivity Nd-Fe-B magnets

    Institute of Scientific and Technical Information of China (English)

    HU Zhihua; CHENG Xinghua; ZHU Minggang; LI Wei; LIAN Fazeng

    2008-01-01

    The variations of intrinsic coercivity and remanence of sintered Nd-Fe-B magnets with ultra-high intrinsic coercivity were investigated.The results showed that the intrinsic coercivity and remanence declined simultaneously with increasing temperature,but the squareness of the magnets has hardly been changed.The temperature coefficients of remanence (α) and coercivity (β) for the magnets were calculated by two different methods,and the variations of the temperature coefficients and the microstructure of sintered Nd-Fe-B magnets were analyzed.The temperature coefficients of remanence (α) and coercivity (β) for the sintered magnets are very small,and the existence of free microstructure is necessary to obtain sintered Nd-Fe-B magnets with ultra-high intrinsic coercivity.

  15. Iridate compound produces extraordinarily high coercive magnetic field

    Science.gov (United States)

    Zapf, Vivien; Topping, Craig; Kim, Jae-Wook; Mun, Eun-Deok; Goddard, Paul; Ghannadzadeh, Saman; Luo, Xuan; Cheong, Sang-Wook; Singleton, John

    2014-03-01

    We present a data on an iridate compound that shows an extraordinarily large magnetic hysteresis loop. The coercive magnetic field exceeds 40 Tesla in single-crystal samples. The hysteresis coexists with a linear background, and the total remanent magnetization is about half a Bohr magneton. We will discuss the emergence of these properties from the interplay of spin-orbit coupling, magnetic exchange and possible frustration. The single crystalline material exhibits a magnetic hysteresis loop for one orientation of the magnetic field and a smooth linear increase in the magnetization with field for the other. Measurements were conducted in 65 T short-pulse magnets and the 60 Tesla shaped-pulse magnet at the National High Magnetic Field Lab in Los Alamos. We do not observe any dependence of the magnetic hysteresis on magnetic field sweep rate. Compounds containing Ir4 + have attracted attention recently due to strong spin-orbit coupling that competes with crystal-electric field and exchange interactions. This competition can result in non-Hund's-rule ground states with unusual properties.

  16. τ-MnAl with high coercivity and saturation magnetization

    Directory of Open Access Journals (Sweden)

    J. Z. Wei

    2014-12-01

    Full Text Available In this paper, high purity τ-Mn54Al46 and Mn54−xAl46Cxalloys were successfully prepared using conventional arc-melting, melt-spinning, and heat treatment process. The magnetic and the structural properties were examined using x-ray diffraction (XRD, powder neutron diffraction and magnetic measurements. A room temperature saturation magnetization of 650.5 kAm-1, coercivity of 0.5 T, and a maximum energy product of (BHmax = 24.7 kJm-3 were achieved for the pure Mn54Al46 powders without carbon doping. The carbon substituted Mn54−xAl46Cx, however, reveals a lower Curie temperature but similar saturation magnetization as compared to the carbon-free sample. The electronic structure of MnAl shows that the Mn atom possesses a magnetic moment of 2.454 μB which results from strong hybridization between Mn-Al and Mn-Mn. We also investigated the volume and c/a ratio dependence of the magnetic moments of Mn and Al. The results indicate that an increase in the intra-atomic exchange splitting due to the cell volume expansion, leads to a large magnetic moment for the Mn atom. The Mn magnetic moment can reach a value of 2.9 μB at a volume expansion rate of ΔV/V ≈ 20%.

  17. Effect of the residual stresses on surface coercive force in amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tejedor, M.; Garcia, J.A.; Carrizo, J.; Elbaile, L. E-mail: elbaile@pinon.ccu.uniovi.es; Santos, J.D

    2000-06-02

    The dependence of the coercivity H{sub c} on the applied stress {sigma} in the surfaces of various amorphous ribbons with positive magnetostriction is studied. The results obtained show that the behaviour of H{sub c}({sigma}) in the surfaces is the same as in the bulk and the minimum of H{sub c}({sigma}) does not depend on the residual stresses. The residual stresses affect the value of the coercive field but not its stress dependence.

  18. SiO{sub 2} modified Co-ferrite with high coercivity

    Energy Technology Data Exchange (ETDEWEB)

    Ding, J. E-mail: masdingj@nus.edu.sg; Gong, H.; Melaka, R.; Wang, S.; Shi, Y.; Chen, Y.J.; Phuc, N.X

    2001-05-01

    Magnetic and Moessbauer measurements have shown that 1-2 wt% of SiO{sub 2} were solved in the CoFe{sub 2}O{sub 4} structure after mechanical milling and subsequent heat treatment. Coercivity values up to 3.5 kOe were measured for CoFe{sub 2}O{sub 4}/SiO{sub 2} powders. High coercivities were also achieved in SiO{sub 2} doped Co-ferrite thin films prepared by sputtering technique. The Co-ferrite thin film deposited on silicon wafer using a 5 wt%-SiO{sub 2}/Co-ferrite target possessed a coercivity of 7.4 kOe, which is the highest value in Co-ferrite and spinel materials according to our knowledge.

  19. Mechanochemical synthesis of Nd2Fe14B alloy with high coercivity

    Energy Technology Data Exchange (ETDEWEB)

    Pal, A; Gabay, A; Hadjipanayis, GC

    2012-12-05

    High coercivity nanocrystalline Nd2Fe14B particles were synthesized by mechanochemical processing involving the reduction of Nd2O3 with Ca in presence of Fe-B and Fe. The as-milled powder shows amorphous structure and subsequent heat treatment results in formation of nanocrystalline Nd2Fe14B. The resulting powder does not only consist of Nd2Fe14B but also some Nd-rich phase. The optimally heat treated sample exhibits coercivity of more than 12 kOe. (C) 2012 Elsevier B.V. All rights reserved.

  20. High coercivity through texture formation in SmCo5/Co multilayers

    Science.gov (United States)

    Sastry, P. U.; Mishra, P. K.; Krishnan, M.; Chowdhury, P.; Ravikumar, G.

    2013-02-01

    We have shown that high coercivity in SmCo5/Co multilayer exchange spring magnet can be obtained on silicon substrates as well. This is achieved by annealing the as-grown sample at an optimum temperature that favors texture formation. This compares well with multilayers grown on MgO substrates and post-annealed at the same temperature.

  1. On the use of temperature dependences of the coercive force for an analysis of structural and phase changes that occur upon tempering of alloy carbon steels

    Science.gov (United States)

    Ul'yanov, A. I.; Baranova, I. A.; Chulkina, A. A.; Zagainov, A. V.; Volkov, V. A.

    2014-05-01

    The effect of alloying elements Mn, Cr, and Si on the magnetic hysteresis properties of cementite and model steels with a carbon concentration of 0.6 wt % has been studied. It has been shown that alloying with carbide-forming elements (Mn, Cr) reduces the coercive force and the Curie temperature of cementite. Measurements of the temperature dependences of the coercive force of the model steels with carbon content of 0.6 wt % alloyed with manganese, chromium, or silicon have been performed in the temperature range of -196 to +300°C. It has been established that the local maximum of the coercive force of these steels in this temperature range coincides with the Curie point of the precipitates of the carbide phases. Based on an analysis of the temperature dependences of the coercive force, the content of the alloying element in the precipitates of cementite of steels tempered at different temperatures has been estimated. It has been shown that the character of the dependence of the coercive force of alloy steels on the temperature of tempering in the temperature range of 250-700°C is mainly determined by the coercivity and by the kinetics of the formation of cementite precipitates.

  2. Perspectives for high-performance permanent magnets: applications, coercivity, and new materials

    Science.gov (United States)

    Hirosawa, Satoshi; Nishino, Masamichi; Miyashita, Seiji

    2017-03-01

    High-performance permanent magnets are indispensable in the production of high-efficiency motors and generators and ultimately for sustaining the green earth. The central issue of modern permanent magnetism is to realize high coercivity near and above room temperature on marginally hard magnetic materials without relying upon the critical elements such as heavy rare earths by means of nanostructure engineering. Recent investigations based on advanced nanostructure analysis and large-scale first principles calculations have led to significant paradigm shifts in the understandings of coercivity mechanism in Nd–Fe–B permanent magnets, which includes the discovery of the ferromagnetism of the thin (2 nm) intergranular phase surrounding the Nd2Fe14B grains, the occurrence of negative (in-plane) magnetocrystalline anisotropy of Nd ions and some Fe atoms at the interface which degrades coercivity, and visualization of the stochastic behaviors of magnetization in the magnetization reversal process at high temperatures. A major change may occur also in the motor topologies, which is currently overwhelmed by the magnetic flux weakening interior permanent magnet motor type, to other types with variable flux permanent magnet type in some applications to open up a niche for new permanent magnet materials. Keynote talk at 8th International Workshop on Advanced Materials Science and Nanotechnology (IWAMSN2016), 8–12 November 2016, Ha Long City, Vietnam.

  3. Isotropic, high coercive field in melt-spun tetragonal Heusler Mn3Ge

    Directory of Open Access Journals (Sweden)

    Adel Kalache

    2016-08-01

    Full Text Available Nanostructured Mn3Ge ribbons with a composition ranging from 77 to 74 at.% Mn were prepared using induction melting, melt-spinning, and subsequent heat treatment. The hard magnetic properties of the ribbons originate from the highly anisotropic tetragonal D022 structure of Mn3Ge. Depending on the composition and the amount of ferrimagnetic Mn5Ge2 as a secondary phase, a coercivity of up to μ0HC = 2.62 T was obtained for the Mn3Ge ribbons. Microstructure investigations by transmission electron microscopy confirmed the formation of the secondary phase. All samples show isotropic coercive fields, i.e., independent of the direction of the applied magnetic field in contrast to already known epitaxial thin films. The Curie temperature was found to be higher than 800 K, which is the temperature of the phase transition from the tetragonal D022 structure to the hexagonal D019 structure.

  4. Isotropic, high coercive field in melt-spun tetragonal Heusler Mn3Ge

    Science.gov (United States)

    Kalache, Adel; Kreiner, Guido; Ouardi, Siham; Selle, Susanne; Patzig, Christian; Höche, Thomas; Felser, Claudia

    2016-08-01

    Nanostructured Mn3Ge ribbons with a composition ranging from 77 to 74 at.% Mn were prepared using induction melting, melt-spinning, and subsequent heat treatment. The hard magnetic properties of the ribbons originate from the highly anisotropic tetragonal D022 structure of Mn3Ge. Depending on the composition and the amount of ferrimagnetic Mn5Ge2 as a secondary phase, a coercivity of up to μ0HC = 2.62 T was obtained for the Mn3Ge ribbons. Microstructure investigations by transmission electron microscopy confirmed the formation of the secondary phase. All samples show isotropic coercive fields, i.e., independent of the direction of the applied magnetic field in contrast to already known epitaxial thin films. The Curie temperature was found to be higher than 800 K, which is the temperature of the phase transition from the tetragonal D022 structure to the hexagonal D019 structure.

  5. High-Coercivity Iron Oxide Based Nanocomposites - Particle Shape and Magnetic Structure by Synchrotron and Neutron Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Vejpravova, Jana Poltierova; Prokleska, Jan; Vales, Vaclav; Danis, Stanislav; Mantlikova, Alice; Holy, Vaclav [Charles University Prague, Faculty of Mathematics and Physics, Department of Condensed Matter Physics, Ke Karlovu 5, 121 16 - Prague 2 (Czech Republic); Brazda, Petr [Institute of Inorganic Chemistry, Academy of Sciences of the CR, 250 68 - Rez (Czech Republic); Doyle, Stephen [Synchrotron Light Source ANKA, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany); Ritter, Clemens [Institute Laue Langevin, 6 rue Jules Horowitz, F-38042 - Grenoble Cedex 9 (France); Kitazawa, H [National Institute for Materials Science, Quantum Beam Center, Neutron Scattering Group, 1-2-2 Sengen, Tsukuba-shi, Ibaraki 305-0047 (Japan); Niznansky, D, E-mail: vejpravova@seznam.cz [Charles University Prague, Faculty of Science, Department of Inorganic Chemistry, Hlavova 2, 121 16 - Prague 2 (Czech Republic)

    2011-03-15

    We report on advanced investigation of structure and magnetism of high-coercivity Fe{sub 2-x}Al{sub x}O{sub 3}/SiO{sub 2} (x = 0 - 0.75) nanocrystals obtained by a smart sol-gel route. The substitution of Fe by Al originates suppression of the high-to-low coercivity crossover at 120 K typical for the {epsilon}-Fe{sub 2}O{sub 3} phase. Our neutron scattering experiment revealed, that the high-coercivity collinear magnetic structure of the {epsilon}-Fe{sub 2}O{sub 3} persists in the Al-doped nanocrystals down to low temperatures, while an incommensurate magnetic structure develops in the low-coercivity phase in the undoped {epsilon}-Fe{sub 2}O{sub 3} only. The size and shape of the nanocrystals was obtained by advanced profile analysis of the high-quality S-PXRD data.

  6. High perpendicular coercive field of CoFe{sub 2}O{sub 4} thin films deposited by PLD

    Energy Technology Data Exchange (ETDEWEB)

    Terzzoli, M.C.; Duhalde, S.; Jacobo, S.; Steren, L.; Moina, C

    2004-04-28

    Thin films of CoFe{sub 2}O{sub 4} were deposited on (1 0 0) Si and (1 0 0) MgO substrates by pulsed laser deposition (PLD). The X-ray analysis shows the existence of single-phase spinel structure. Thin films deposited on (1 0 0) MgO substrates are epitaxial and completely oriented in-plane and out of plane due to the small lattice mismatch between Co ferrite and MgO. The surface microstructure was probed by atomic force microscopy and we can describe it like a tidy mosaic of monocrystals. Surprisingly, the films grew on (1 0 0) Si using 355 nm, reveal a complete (1 1 1) orientation in spite of the native oxide of the substrate when deposited. The films deposited with 266 nm also were textured in the (1 1 1) but with less particulate on the surface. (1 0 0) films show at 35 K a perpendicular coercive field H{sub c} as high as 12.9 kOe, meanwhile for the (1 1 1) films H{sub c} was around 9 kOe. However, at room temperature, the (1 1 1) films deposited with 266 nm show a perpendicular coercive field of 5.1 kOe and a squareness of 0.86 which make them attractive for magneto-optic recording applications.

  7. High coercivity in mechanically milled ThMn12-type Nd-Fe-Mo nitrides

    Science.gov (United States)

    Zhang, Xiao-dong; Cheng, Ben-pei; Yang, Ying-chang

    2000-12-01

    Starting from carefully homogenized Nd10Fe90-yMoy (y=12, 10, 7) alloys and by appropriate mechanical milling, the as-milled microstructure consisting of a nanoscale mixture of severely distorted 1:12 phase and substitutional α-Fe-based solid solution was obtained. This kind of as-milled microstructure was thought to have a critical effect on the formation of iron-free nanocrystalline 1:12 phase during subsequent annealing. Upon nitrogenation, the sample of Nd10Fe78Mo12Nx exhibited a record-high coercivity of 13.1 kOe at 293 K. Measurements of initial magnetization curve and a family of demagnetization curves engendered under different maximum applied fields Hm were carried out, and the results revealed the domain-wall pinning at grain boundaries as the coercivity mechanism. A low Mo-content sample of Nd10Fe83Mo7Nx with iHc˜5.8 kOe, Br˜6.8 kG, and (BH)max˜7.0 MG Oe was made by optimizing the preparation conditions.

  8. Thermal effect on magnetic parameters of high-coercivity cobalt ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Chagas, E. F., E-mail: efchagas@fisica.ufmt.br; Ponce, A. S.; Prado, R. J.; Silva, G. M. [Instituto de Física, Universidade Federal de Mato Grosso, 78060-900 Cuiabá-MT (Brazil); Bettini, J. [Laboratório Nacional de Nanotecnologia, Centro Nacional de Pesquisa em Energia e Materiais, 13083-970 Campinas (Brazil); Baggio-Saitovitch, E. [Centro Brasileiro de Pesquisas Físicas, Rua Xavier Sigaud 150 Urca. Rio de Janeiro (Brazil)

    2014-07-21

    We prepared very high-coercivity cobalt ferrite nanoparticles synthesized by a combustion method and using short-time high-energy mechanical milling to increase strain and the structural defects density. The coercivity (H{sub C}) of the milled sample reached 3.75 kOe—a value almost five times higher than that obtained for the non-milled material (0.76 kOe). To investigate the effect of the temperature on the magnetic behavior of the milled sample, we performed a thermal treatment on the milled sample at 300, 400, and 600 °C for 30 and 180 min. We analyzed the changes in the magnetic behavior of the nanoparticles due to the thermal treatment using the hysteresis curves, Williamson-Hall analysis, and transmission electron microscopy. The thermal treatment at 600 °C causes decreases in the microstructural strain and density of structural defects resulting in a significant decrease in H{sub C}. Furthermore, this thermal treatment increases the size of the nanoparticles and, as a consequence, there is a substantial increase in the saturation magnetization (M{sub S}). The H{sub C} of the samples treated at 600 °C for 30 and 180 min were 2.24 and 1.93 kOe, respectively, and the M{sub S} of these same samples increased from 57 emu/g to 66 and 70 emu/g, respectively. The H{sub C} and the M{sub S} are less affected by the thermal treatment at 300 and 400 °C.

  9. Observation of high coercive fields in chemically synthesized coated Fe-Pt nanostructures

    Science.gov (United States)

    Dalavi, Shankar B.; Panda, Rabi N.

    2017-04-01

    Nanocrystalline Fe-Pt alloys have been synthesized via chemical reduction route using various capping agents; such as: oleic acid/oleylamine (route-1) and oleic acid/CTAB (route-2). We could able to synthesize Fe50Pt and Fe54Pt alloys via route 1 and 2, respectively. As-prepared Fe-Pt alloys crystallize in disordered fcc phase with crystallite sizes of 2.3 nm and 6 nm for route-1 and route-2, respectively. Disordered Fe-Pt alloys were transformed to ordered fct phase after annealing at 600 °C. SEM studies confirm the spherical shape morphologies of annealed Fe-Pt nanoparticles with SEM particle sizes of 24.4 nm and 21.2 nm for route-1 and route-2, respectively. TEM study confirms the presence of 4.6 nm particles for annealed Fe50Pt alloys with several agglomerating clusters of bigger size and appropriately agrees well with the XRD study. Room temperature magnetization studies of as-prepared Fe-Pt alloys (fcc) show ferromagnetism with negligible coercivities. Average magnetic moments per particle for as-prepared Fe-Pt alloys were estimated to be 753 μB and 814 μB, for route 1 and 2, respectively. Ordered fct Fe-Pt alloys show high values of coercivities of 10,000 Oe and 10,792 Oe for route-1 and route-2, respectively. Observed magnetic properties of the fct Fe-Pt alloys nps were interpreted with the basis of order parameters, size, surface, and composition effects.

  10. Highly coercive cobalt ferrite nanoparticles-CuTl-1223 superconductor composites

    Energy Technology Data Exchange (ETDEWEB)

    Jabbar, Abdul; Qasim, Irfan; Khan, Shahid A.; Nadeem, K.; Waqee-ur-Rehman, M.; Mumtaz, M., E-mail: mmumtaz75@yahoo.com; Zeb, F.

    2015-03-01

    We explored the effects of highly coercive cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles addition on structural, morphological, and superconducting properties of Cu{sub 0.5}Tl{sub 0.5}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10-δ} (CuTl-1223) matrix. Series of (CoFe{sub 2}O{sub 4}){sub x}/CuTl-1223 (x=0 ∼2.0 wt%) composites samples were synthesized and were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) absorption spectroscopy, and dc-resistivity versus temperature measurements. The magnetic behavior of CoFe{sub 2}O{sub 4} nanoparticles was determined by MH-loops with the help of superconducting quantum interference device (SQUID). MH-loops analysis showed that these nanoparticles exhibit high saturation magnetization (86 emu/g) and high coercivity (3350 Oe) at 50 K. The tetragonal structure of host CuTl-1223 superconducting matrix was not altered after the addition of CoFe{sub 2}O{sub 4} nanoparticles, which gave us a clue that these nanoparticles had occupied the inter-granular sites (grain-boundaries) and had filled the pores. The increase of mass density with increasing content of these nanoparticles in composites can also be an evidence of filling up the voids in the matrix. The resistivity versus temperature measurements showed an increase in zero resistivity critical {T_c(0)}, which could be most probably due to improvement of weak-links by the addition of these nanoparticles. But the addition of these nanoparticles beyond an optimum level caused the agglomeration and produced additional stresses in material and suppressed the superconductivity. - Highlights: • T{sub c}(0) increased with increasing CoFe{sub 2}O{sub 4} nanoparticles up to x=1.5. • CoFe{sub 2}O{sub 4} nanoparticles addition has not affected the structure of CuTl-1223. • Addition of CoFe{sub 2}O{sub 4} nanoparticles has improved inter-grains weak links. • Non-monotonic variation of ρ{sub (300} {sub K)} (Ω-cm) is due to

  11. High-coercivity CoFe2O4 thin films on Si substrates by sol-gel

    Science.gov (United States)

    Tang, Xianwu; Jin, Linghua; Wei, Renhuai; Zhu, Xiaoguang; Yang, Jie; Dai, Jianming; Song, Wenhai; Zhu, Xuebin; Sun, Yuping

    2017-01-01

    CoFe2O4 (CFO) thin films with high coercivity HC are desirable in applications. The difficulty in achieving large-area CFO thin films with high coercivity by sol-gel has hindered the development of CFO thin films. Herein, polycrystalline CFO thin films with the room temperature out-of-plane and in-plane coercivity HC respectively reached ~5.9 and 3.6 kOe has been achieved on the silicon substrate by sol-gel. The room-temperature maximum magnetic energy product (BH)max and remanence ratio Mr/Ms are of 1.66 MG Oe and 0.58 respectively, which are also the largest values amongst the CFO thin films prepared by solution methods. At the same time, annealing temperature and thickness effects on the HC, (BH)max and Mr/Ms of the derived CFO thin films have been investigated. It is observed that grain size and residual tensile strain in the derived films play an important role in the variations of HC and Mr/Ms. These results will provide an effective route for fabricating larger-area high-coercivity CFO thin films with low-cost by sol-gel on silicon wafers.

  12. Effect of the oxidation in the surface coercive force of nanocrystalline Fe{sub 73.5}Cu{sub 1}Nb{sub 3}Si{sub 13.5}B{sub 9}alloy

    Energy Technology Data Exchange (ETDEWEB)

    Elbaile, Laura [Departamento de Fisica. Universidad de Oviedo, c/ Calvo Sotelo s/n, 33007 Oviedo (Spain); Pierna, Angel R. [Departamento de Ingenieria Quimica y Medio Ambiente. Universidad del Pais Vasco, PO Box 1379, 20080 San Sebastian (Spain); Garcia, Jose A. [Departamento de Fisica. Universidad de Oviedo, c/ Calvo Sotelo s/n, 33007 Oviedo (Spain)]. E-mail: joseagd@uniovi.es; Crespo, Rosario D. [Departamento de Fisica. Universidad de Oviedo, c/ Calvo Sotelo s/n, 33007 Oviedo (Spain); Vara, Gemma [Departamento de Ingenieria Quimica y Medio Ambiente. Universidad del Pais Vasco, PO Box 1379, 20080 San Sebastian (Spain); Angeles Cerdeira, M. [Departamento de Fisica. Universidad de Oviedo, c/ Calvo Sotelo s/n, 33007 Oviedo (Spain); Tejedor, Marcos [Departamento de Fisica. Universidad de Oviedo, c/ Calvo Sotelo s/n, 33007 Oviedo (Spain)

    2006-09-15

    Influence of electrochemical corrosion on the surface coercive force of Fe{sub 73.5}Cu{sub 1}Nb{sub 3}Si{sub 13.5}B{sub 9}in the amorphous and nanocrystalline states is investigated. The results show that, in both amorphous and nanocrystalline states, when the oxidized layer increases the surface coercivity decreases.

  13. High coercivity in Fe-Nb-B-Dy bulk nanocrystalline magnets

    Energy Technology Data Exchange (ETDEWEB)

    Ziolkowski, Grzegorz; Chrobak, Artur; Klimontko, Joanna [Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007, Katowice (Poland); Chrobak, Dariusz; Rak, Jan [Institute of Materials Science, University of Silesia, 75 Pulku Piechoty 1, 41-500, Chorzow (Poland); Zivotsky, Ondrej; Hendrych, Ales [Department of Physics, VSB-TU Ostrava, Ostrava (Czech Republic)

    2016-11-15

    The paper refers to structural and magnetic properties of the (Fe{sub 80}Nb{sub 6}B{sub 14}){sub 1-x}Dy{sub x} (x = 0.08, 0.10, 0.12, 0.16) bulk nanocrystalline alloys prepared by making use of the vacuum suction casting technique. The samples are in a form of rods with different diameters d = 1.5, 1, and 0.5 mm. The phase structure was investigated by XRD technique and reveals an occurrence of magnetically hard Dy{sub 2}Fe{sub 14}B as well as other relatively soft Dy-Fe, Fe-B, and Fe phases dependently on the Dy content. The alloys show hard magnetic properties with high coercive field up to 5.5 T (for x = 0.12 and d = 0.5 mm). The observed magnetic hardening effect with the increase of cooling rate (decrease of sample diameter d) can be attributed to a formation of ultra-hard magnetic objects as well as increasing role of low dimensional microstructure. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Mechanisms of High Coercivity in Ni/NiO Composite Films by Post Annealing

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A coercivity as large as 2.4 kOe has been achieved in the Ni/NiO composite film after an annealing under a magnetic field of 10 kOe and an O2 partial pressure of 0.001 torr. The coercivity was attributed to the strong exchange coupling of Ni and NiO. Small grain size of Ni and NiO was observed after the post-annealing. The enhanced coercivity is probably associated with the domain wall pinning by local energy minima, the distribution of Ni and NiO, and the domain structure in the interface of Ni/NiO generated under the presence of the magnetic field during the post-annealing.

  15. Synthesis of High Coercivity Core–Shell Nanorods Based on Nickel and Cobalt and Their Magnetic Properties

    Directory of Open Access Journals (Sweden)

    Shaijumon MM

    2009-01-01

    Full Text Available Abstract Hybrid magnetic nanostructures with high coercivity have immense application potential in various fields. Nickel (Ni electrodeposited inside Cobalt (Co nanotubes (a new system named Ni @ Co nanorods were fabricated using a two-step potentiostatic electrodeposition method. Ni @ Co nanorods were crystalline, and they have an average diameter of 150 nm and length of ~15 μm. The X-ray diffraction studies revealed the existence of two separate phases corresponding to Ni and Co. Ni @ Co nanorods exhibited a very high longitudinal coercivity. The general mobility-assisted growth mechanism proposed for the growth of one-dimensional nanostructures inside nano porous alumina during potentiostatic electrodeposition is found to be valid in this case too.

  16. High coercivity microcrystalline Nd-rich Nd-Fe-Co-Al-B bulk magnets prepared by direct copper mold casting

    Science.gov (United States)

    Zhao, L. Z.; Hong, Y.; Fang, X. G.; Qiu, Z. G.; Zhong, X. C.; Gao, X. S.; Liu, Z. W.

    2016-06-01

    High coercivity Nd25Fe40Co20Al15-xBx (x=7-15) hard magnets were prepared by a simple process of injection casting. Different from many previous investigations on nanocomposite compositions, the magnets in this work contain hard magnetic Nd2(FeCoAl)14B, Nd-rich, and Nd1+ε(FeCo)4B4 phases. The magnetic properties, phase evolution, and microstructure of the as-cast and annealed magnets were investigated. As the boron content increased from 7 to 11 at%, the intrinsic coercivity Hcj of the as-cast magnet increased from 816 to 1140 kA/m. The magnets annealed at 750 °C have shown more regular and smaller grains than the as-cast alloys, especially for the x=11 alloy. The high intrinsic coercivities for the annealed alloys with x=8~11 result from the presence of small-sized grains in the microstructure. The highest Hcj of 1427 kA/m was obtained for the heat treated alloy with x=10. This work provides an alternative approach for preparing fully dense Nd-rich bulk hard magnets with relatively good properties.

  17. MnxGa1-x nanodots with high coercivity and perpendicular magnetic anisotropy

    Science.gov (United States)

    Karel, J.; Casoli, F.; Lupo, P.; Celegato, F.; Sahoo, R.; Ernst, B.; Tiberto, P.; Albertini, F.; Felser, C.

    2016-11-01

    A MnxGa1-x (x = 0.70) epitaxial thin film with perpendicular magnetic anisotropy and a large coercivity (μ0Hc = 1 T) was patterned into nanodots using a combined self-assembly nanolithography and plasma etching procedure. Nanostructuring is achieved by self-assembly of polystyrene nanospheres acting as a mask on the magnetic film. This procedure allows easy patterning of a large area although introduced some chemical disorder, which resulted in a soft magnetic component in the magnetic hysteresis loops. However, chemical order was recovered after vacuum annealing at low temperature. The resulting nanodots retain the properties of the original film, i.e. magnetization oriented perpendicular to the particle and large coercivity. Our results suggest this lithography procedure could be a promising direction for nanostructuring tetragonal Heusler alloys.

  18. Thickness dependence of the magnetic properties of high-coercive Pr-Fe-B thin films with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Yang, F. [Shenyang National Laboratory for Materials Science, Institute of Metal Research and International Centre for Materials Physics, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang Liaoning 110016 (China); Liu, W. [Shenyang National Laboratory for Materials Science, Institute of Metal Research and International Centre for Materials Physics, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang Liaoning 110016 (China)], E-mail: wliu@imr.ac.cn; Cui, W.B.; Feng, J.N.; Zhang, Y.Q.; Zhang, Z.D [Shenyang National Laboratory for Materials Science, Institute of Metal Research and International Centre for Materials Physics, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang Liaoning 110016 (China)

    2008-10-01

    The magnetic properties of Pr-Fe-B films with perpendicular magnetic anisotropy have been studied as a function of thickness varying from 10 to 1200 nm. The crucial thickness for forming the Pr{sub 2}Fe{sub 14}B phase is estimated to be about 25 nm in our study, and the perpendicular anisotropy shows a trend to vanish for thick films. The coercivity of the films initially increases with increasing film thickness, gradually reaching a value which is near the value for bulk material. The magnetic domain size increases with increasing thickness. The surface morphology, the roughness and the domain structure of the films have been investigated by means of atomic-force microscopy and magnetic-force microscopy.

  19. High coercivity sized controlled cobalt–gold core–shell nano-crystals prepared by reverse microemulsion

    Energy Technology Data Exchange (ETDEWEB)

    Bahmanrokh, Ghazaleh, E-mail: ghazalehbahmanrokh@yahoo.com [Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Hashim, Mansor [Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Soltani, Nayereh [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Ismail, Ismayadi [Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Vaziri, Parisa [Department of Medical Physics and Biomedical Engineering, Shahid Beheshti University of Medical Sciences, Tehran (Iran, Islamic Republic of); Navaseri, Manizheh; Erfani, Maryam [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Kanagesan, Samikannu [Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia)

    2013-10-15

    Graphical abstract: - Highlights: • Calculating the crystallinity percentage and percentage of phases presented in Co–Au core–shell nanoparticles. • Magnetic properties of four groups nanogarin: 5, 10, 15, 20 nm. • Single domain ferromagnetic materials with high coercivity at room temperature. • Intrinsic blocking temperature measured in zero field cooled-warmed (ZFC-W). - Abstract: Size-controlled cobalt–gold core–shell nanoparticles were synthesized via the reverse-micelle microemulsion method. In order to control the size of the nanoparticles, the nucleation and growth process were performed within a confined space by adjusting the water to surfactant ratio of reverse micelles solution during synthesis. The crystallinity percentage and percentage of phases presented in Co–Au core–shell nanoparticles were calculated using X-ray diffraction data. The results from transmission electron microscopy provide direct evidence for core–shell structure nanomaterials. Magnetic properties of the samples were investigated using a vibrating sample magnetometer. The as-prepared samples showed significant coercivity at room temperature. The intrinsic blocking temperature was experimentally deduced from zero-field-cooled warmed (ZFC-W) curves by a simple method without employing an external magnetic field. The B-field dependence temperature data of Co–Au nanoparticles exhibited an intrinsic blocking temperature at 45 K. Annealing these samples at 400 °C caused an increase in particle size, crystallinity percentage and further enhanced their magnetic properties.

  20. A link between the coercivity and microstructure of high moment Fe films and their use in magnetic tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Georgieva, M.T. [Institute for Materials Research, Maxwell Building, The University of Salford, Salford M5 4WT (United Kingdom)]. E-mail: milena.georgieva@mdm.infm.it; Telling, N.D. [Institute for Materials Research, Maxwell Building, The University of Salford, Salford M5 4WT (United Kingdom); Magnetic Spectroscopy Group, CCLRC Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Grundy, P.J. [Institute for Materials Research, Maxwell Building, The University of Salford, Salford M5 4WT (United Kingdom)

    2006-01-25

    Magnetron sputtered single Fe films have been 'softened' magnetically by controlled N-doping during the sputter deposition. This technique allows a reduction in grain size and coercivity of the Fe films, without decreasing the saturation magnetization and without the formation of any crystalline FeN phases. We describe this effect through a modification of the random magnetocrystalline anisotropy model, by taking the film thickness into account. The coercivities calculated in this way are in good agreement with those obtained experimentally. It is demonstrated that N-doping can be samples increased as to control the switching field of the 'free' layer in magnetic trilayer films of the MTJ type. It is thus possible to construct an all Fe-electrode magnetic tunnel junction (MTJ) that displays the tunneling magnetoresistance (TMR) effect by altering the switching field of one Fe layer using N-doping. The ability to control the magnetic softness of high magnetic moment materials is important in regard to their incorporation into TMR devices.

  1. Is a diagnostic category for paraphilic coercive disorder defensible?

    Science.gov (United States)

    Knight, Raymond A

    2010-04-01

    There is a proposal to establish a paraphilic coercive disorder as a new paraphilia in the DSM-V. The empirical data do not, however, support the hypothesis that a distinct syndrome exists that comprises males who are sexually aroused by the coercive elements of rape per se. Purported evidence for this syndrome has centered on the results of phallometric studies. Higher plethysmographic responses of rapists to coercive rape scenarios may, however, be better explained by the failure of coercive elements to inhibit arousal to sexual aspects of the stimuli rather than by arousal specifically to the coercive elements. In addition, sexual fantasies about forcing sex and about struggling victims are highly correlated with sadistic fantasies and have not been shown to identify a syndrome that can be discriminated from sadism. Finally, taxometric evidence strongly supports the hypothesis that the underlying components of rape are distributed as dimensions and do not constitute a separate taxon. Consequently, the criteria purported to categorize rapists into the proposed syndrome would have to be arbitrarily determined. Not only does there seem to be little empirical justification for the creation of this new syndrome, the inclusion of this disorder among the paraphilias would have serious potential for misuse. It would imply endorsement of Paraphilia, NOS, nonconsent, which is currently inappropriately employed in civil commitment proceedings to justify commitment.

  2. Rethinking Coercive Control.

    Science.gov (United States)

    Stark, Evan

    2009-12-01

    The critical appraisals of Coercive Control focus largely on what my analysis implies for intervention, a matter to which the book devotes only limited space. In this reply, I reiterate core concepts in the book and acknowledge that much more work is needed to translate the realities of coercive control into practical legal and advocacy strategies. I review how coercive control differs from partner assaults and so why it merits a distinct response; the extent to which coercive control targets gender identity; the wisdom of complementing the focus on violence with an emphasis on male domination, sexual inequality and personal liberty; what this implies for shelters and the law; why sexual inequality differentiates coercive control from female partner abuse of men; how sexual equality can be both cause and antidote for coercive control; why I think an affirmative concept of freedom is essential to grasp the human rights violations inflicted by coercive control; and what it means to "story" coercive control by integrating women into the larger liberty narrative on which our national identity rests.

  3. Synthesis of Fe–Si–B–Mn-based nanocrystalline magnetic alloys with large coercivity by high energy ball milling

    Indian Academy of Sciences (India)

    P D Reddi; N K Mukhopadhyay; B Majumdar; A K Singh; S S Meena; S M Yusuf; N K Prasad

    2014-06-01

    Alloys of Fe–Si–B with varying compositions of Mn were prepared using high energy planetary ball mill for maximum duration of 120 h. X-ray diffraction (XRD) analysis suggests that Si gets mostly dissolved into Fe after 80 h of milling for all compositions. The residual Si was found to form an intermetallic Fe3Si. The dissolution was further confirmed from the field emission scanning electron microscopy/energy dispersive X-ray analysis (FE-SEM/EDX). With increased milling time, the lattice parameter and lattice strain are found to increase. However, the crystallite size decreases from micrometer (75–95 m) to nanometer (10–20 nm). Mössbauer spectra analysis suggests the presence of essentially ferromagnetic phases with small percentage of super paramagnetic phase in the system. The saturation magnetization (s), remanance (r) and coercivity (c) values for Fe–0Mn sample after 120 h of milling were 96.4 Am2/kg, 11.5 Am2/kg and 12.42 k Am-1, respectively. However, for Fe–10Mn–5Cu sample the s, c and r values were found to be 101.9 Am2/kg, 10.98 kA/m and 12.4 Am2/kg, respectively. The higher value of magnetization could be attributed to the favourable coupling between Mn and Cu.

  4. Atomic structure of high-coercivity cobalt-carbide nanoparticles ensembles

    Science.gov (United States)

    Arena, D. A.; Sterbinsky, G.; Stephens, P. W.; Carroll, K. J.; Yoon, H.; Meng, S.; Huba, Z.; Carpenter, E. E.

    2013-03-01

    Permanent magnets are increasingly important in numerous applications, including the quickly expanding area of green technologies (e . g . high efficiency electric car motors and wind turbine power systems). We present studies of novel permanent magnet materials based on cobalt carbide nanoparticles (NPs), where the energy product (BHmax) exceeds 20 kJ / m3. The NPs are synthesized via a polyol process, which offers a flexible approach to modify the Co-carbide phase (Co2C and Co3C), and NP morphology, size and size dispersion. The Co2C and Co3C phases have unique magnetic properties, and the combination exhibits the high BHmax . We present a detailed assessment of the structure of mixtures of Co2C and Co3 NPs, measured by high-resolution, synchrotron based powder x-ray diffraction (p-XRD). Both the Co2C and Co3 phases exhibit an orthorhombic structure (Pnnm and Pnma space groups, respectively). The high-resolution p-XRD facilitates identification of mixed phase samples, enabling detailed comparisons of the atomic structure with the magnetic properties, measured by both lab-based magnetometry and x-ray spectroscopy (soft x-ray XAS & XMCD).

  5. Anisotropy and Microstructure of High Coercivity Rare Earth Iron Permanent Magnets, List of Papers Published

    Science.gov (United States)

    1989-01-01

    aublattice anisotropy. 1. Introduction The compound Nd2Fe14B is the basic material for the production of high quality Permanent magniets [1, 21. It...the in-plane anisotropy is in disagreement with the observed different magnetiza- tion curves for Nd2Fe14B in the [1001 and [1101 directions [101... Nd2Fe14B based permanent magnets so far. The grain size of the magnets also strongly der ds on the processing technique. The electron micrographs of Fig

  6. High Coercivity Sr-ferrite Magnetic Thin Films Induced by Various Underlayers

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Three kinds of oxide underlayers, namely SiO2, ZnO and Al2O3, were deposited prior to the sputtering of Sr-ferrite films, respectively, in order to induce the optimum grain morphology and the texture of the films. A Sr-ferrite film with an easy axis in-plane orientation was induced by SiO2 underlayer. In contrast, it prefers to be perpendicular to film plane for the cases of ZnO and Al2O3 underlayers. The optimum magnetic properties of the former film along film plane are: 4πMr=1.7 kG, iHc=5.35 kOe, and Sq=0.59, which are mainly dominated by the exchange coupling effect, determined by Wohlfarth's remanence analysis, among grains. While those for the films with an easy axis perpendicular to film plane can be as high as 4πMr=3.72 kG, iHc=6.42 kOe, and Sq=0.82, which are mainly dominated by the magnetostatic interaction among grains.

  7. Ultrathin SmCo5 nanoflakes with high-coercivity prepared by solid particle (NaCl) and surfactant co-assisted ball milling

    Science.gov (United States)

    Zuo, Wen-Liang; Zhao, Xin; Zhao, Tong-Yun; Hu, Feng-Xia; Sun, Ji-Rong; Shen, Bao-Gen

    2016-05-01

    The ultrathin SmCo5 nanoflakes with average thickness smaller than 50 nm are prepared by a novel method of solid particle (NaCl) and surfactant co-assisted ball milling. The as-prepared nanoflakes exhibit a narrower thickness distribution of 10–50 nm and high coercivity of 23 kOe. The possible formation mechanism of nanoflakes are proposed. Temperature dependence of demagnetization curves indicate that the magnetization reversal may be controlled by both nucleation and pinning. The results of X-ray powder diffraction and magnetic measurement for aligned SmCo5 nanoflakes resin composite indicate that the nanoflakes have a high texture degree. The ultrathin thickness and high coercivity are beneficial for preparing the high performance soft/hard coupling magnets and nanocomposite magnets.

  8. High coercivity, anisotropic, heavy rare earth-free Nd-Fe-B by Flash Spark Plasma Sintering.

    Science.gov (United States)

    Castle, Elinor; Sheridan, Richard; Zhou, Wei; Grasso, Salvatore; Walton, Allan; Reece, Michael J

    2017-09-11

    In the drive to reduce the critical Heavy Rare Earth (HRE) content of magnets for green technologies, HRE-free Nd-Fe-B has become an attractive option. HRE is added to Nd-Fe-B to enhance the high temperature performance of the magnets. To produce similar high temperature properties without HRE, a crystallographically textured nanoscale grain structure is ideal; and this conventionally requires expensive "die upset" processing routes. Here, a Flash Spark Plasma Sintering (FSPS) process has been applied to a Dy-free Nd30.0Fe61.8Co5.8Ga0.6Al0.1B0.9 melt spun powder (MQU-F, neo Magnequench). Rapid sinter-forging of a green compact to near theoretical density was achieved during the 10 s process, and therefore represents a quick and efficient means of producing die-upset Nd-Fe-B material. The microstructure of the FSPS samples was investigated by SEM and TEM imaging, and the observations were used to guide the optimisation of the process. The most optimal sample is compared directly to commercially die-upset forged (MQIII-F) material made from the same MQU-F powder. It is shown that the grain size of the FSPS material is halved in comparison to the MQIII-F material, leading to a 14% increase in coercivity (1438 kA m(-1)) and matched remanence (1.16 T) giving a BHmax of 230 kJ m(-3).

  9. Influence of dysprosium substitution on magnetic and mechanical properties of high intrinsic coercivity Nd-Fe-B magnets prepared by double-alloy powder mixed method

    Institute of Scientific and Technical Information of China (English)

    胡志华; 瞿海锦; 马冬威; 罗成; 王会杰

    2016-01-01

    The double-alloy powder mixed method is very proper for developing new small-mass products by changing the composi-tion of sintered Nd-Fe-B magnets, and there is little research on this aspect. The variation on magnetic and mechanical properties of high intrinsic coercivity Nd-Fe-B magnets prepared by double-alloy powder mixed method was discussed, which is a method blend-ing two-type main phase alloy powders with different components. The results showed that the intrinsic coercivity and density of sin-tered Nd-Fe-B magnets increased gradually with the increase in Dy content, and the double-alloy powder mixed method could obtain high intrinsic coercivity Nd-Fe-B magnets with good crystallographic alignment and microstructure. The bending strength of sintered Nd-Fe-B magnets declined, and the Rockwell hardness of sintered Nd-Fe-B magnets first declined, and then increased with the in-crease in Dy content. The microstructure showed that there existed the phenomenon that the Dy element diffused into main phase dur-ing sintering process, and the distribution of Dy content in main phase had some variation in homogeneity as a result of incomplete reaction between the double-alloy powder types.

  10. Preparation of YCo{sub 5}, PrCo{sub 5} and SmCo{sub 5} anisotropic high-coercivity powders via mechanochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Gabay, A.M., E-mail: gabay@udel.edu [Department of Physics and Astronomy, University of Delaware, 217 Sharp Lab, Newark, DE 19716 (United States); Hu, X.C. [Department of Materials Science and Engineering, University of Delaware, Newark, DE 19716 (United States); Hadjipanayis, G.C. [Department of Physics and Astronomy, University of Delaware, 217 Sharp Lab, Newark, DE 19716 (United States)

    2014-11-15

    Polydispersed RCo{sub 5} powders consisting mostly of single crystal particles with an average size ranging from 280 nm to 400 nm have been prepared mechanochemically for R=Y, Pr, Pr–Sm and Sm. The synthesis included (i) mechanical activation of a mixture of rare earth oxides, Co, Ca and CaO, (ii) short annealing and (iii) separation of the RCo{sub 5} particles through a multi-step washing process. The highest room-temperature coercivities of the oriented YCo{sub 5}, PrCo{sub 5} and SmCo{sub 5} powders were 20.6, 19.1 and 41.5 kOe, respectively. This improvement compared to traditionally ground powders is attributed to a lower density of crystalline defects. An investigation of a broad, 1050–1320 K, range of the synthesis temperatures revealed nearly universal evolution of crystalline anisotropy of the particles and their remanent magnetization, significant variations in the particle growth rate—with growth of the YCo{sub 5} particles being the most sluggish—and, surprisingly, no correlation between the average size of the particles and their coercivity. These findings extend the practical limits associated with hard magnetic materials and demonstrate that the hard magnetic properties of the mechanochemically synthesized YCo{sub 5} and PrCo{sub 5} powders are similar to those of traditionally prepared SmCo{sub 5}. - Highlights: • Mechanochemistry yields RCo{sub 5} single crystals few hundred nanometers in size. • Coercivity of powders is 2–5 times larger than the one attainable through milling. • The high coercivity is attributed to a lower density of crystalline defects.

  11. Synthesis, morphology and microstructure of pomegranate-like hematite ({alpha}-Fe{sub 2}O{sub 3}) superstructure with high coercivity

    Energy Technology Data Exchange (ETDEWEB)

    Tadic, Marin, E-mail: marint@vinca.rs [Condensed Matter Physics Laboratory, Vinca Institute, University of Belgrade, P.O. Box 522, 11001 Belgrade (Serbia); Citakovic, Nada [Military Academy, Generala Pavla Jurisica Sturma 33, University of Belgrade, 11000 Belgrade (Serbia); Panjan, Matjaz [Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Stanojevic, Boban [Vinca Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, University of Belgrade (Serbia); Markovic, Dragana [Condensed Matter Physics Laboratory, Vinca Institute, University of Belgrade, P.O. Box 522, 11001 Belgrade (Serbia); Jovanovic, Dorde [Center for Solid State Physics and New Materials, Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Spasojevic, Vojislav [Condensed Matter Physics Laboratory, Vinca Institute, University of Belgrade, P.O. Box 522, 11001 Belgrade (Serbia)

    2012-12-05

    Highlights: Black-Right-Pointing-Pointer We found superior magnetic properties of the hematite ({alpha}-Fe{sub 2}O{sub 3}). Black-Right-Pointing-Pointer TEM and HRTEM images show a pomegranate-like superstructure. Black-Right-Pointing-Pointer Magnetic measurements display high coercivity H{sub C} = 4350 Oe at the room temperature. - Abstract: We found novel and superior magnetic properties of the hematite ({alpha}-Fe{sub 2}O{sub 3}) that originate from an internal microstructure of particles and strong inter-particle interactions between nanocrystal sub-units. The hematite particles were synthesized by thermal decomposition of iron (III) nitrate without any template or surfactant. The purity, size, crystallinity, morphology, microstructure and magnetic features of the as-prepared particles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS) and SQUID magnetometry. An XRD study reveals a pure phase of {alpha}-Fe{sub 2}O{sub 3} whereas TEM shows {alpha}-Fe{sub 2}O{sub 3} spheres with a diameter of about 150 nm. RS also shows high quality and purity of the sample. Moreover, TEM and HRTEM images show a pomegranate-like superstructure and evidence that the spherical particles are composed of individual well-crystallized nanoparticle sub-units (self-assembled nanoparticles) with a size of about 20 nm. Magnetic measurements display hysteretic behavior at the room temperature with remanent magnetization M{sub r} = 0.731 emu/g, saturation magnetization M{sub S} = 6.83 emu/g and coercivity H{sub C} = 4350 Oe, as well as the Morin transition at T{sub M} = 261 K. These results and comparison with those in the literature reveal that the sample has extremely high coercivity. The magnetic properties of the sample are discussed in relation to morphology, internal microstructure, surface

  12. Attachment and coercive sexual behavior.

    Science.gov (United States)

    Smallbone, S W; Dadds, M R

    2000-01-01

    This study examined the relationships between childhood attachment and coercive sexual behavior. One hundred sixty-two male undergraduate students completed self-report measures of childhood maternal attachment, childhood paternal attachment, adult attachment, antisociality, aggression, and coercive sexual behavior. As predicted, insecure childhood attachment, especially insecure paternal attachment, was associated with antisociality, aggression, and coercive sexual behavior. Moreover, childhood attachment independently predicted coercive sexual behavior after antisociality and aggression were statistically controlled. The hypothesis that paternal avoidant attachment would predict coercive sexual behavior independently of its relationship with aggression and antisociality was also supported. Posthoc analysis indicated that maternal anxious attachment was associated with antisociality and that paternal avoidant attachment was associated with both antisociality and coercive sexual behavior. These results are consistent with criminological and psychological research linking adverse early family experiences with offending and lend support to an attachment-theoretical framework for understanding offending behavior in general and sexual offending behavior in particular.

  13. Environmental control on the occurrence of high-coercivity magnetic minerals and formation of iron sulfides in a 640 ka sediment sequence from Lake Ohrid (Balkans)

    Science.gov (United States)

    Just, Janna; Nowaczyk, Norbert R.; Sagnotti, Leonardo; Francke, Alexander; Vogel, Hendrik; Lacey, Jack H.; Wagner, Bernd

    2016-04-01

    The bulk magnetic mineral record from Lake Ohrid, spanning the past 637 kyr, reflects large-scale shifts in hydrological conditions, and, superimposed, a strong signal of environmental conditions on glacial-interglacial and millennial timescales. A shift in the formation of early diagenetic ferrimagnetic iron sulfides to siderites is observed around 320 ka. This change is probably associated with variable availability of sulfide in the pore water. We propose that sulfate concentrations were significantly higher before ˜ 320 ka, due to either a higher sulfate flux or lower dilution of lake sulfate due to a smaller water volume. Diagenetic iron minerals appear more abundant during glacials, which are generally characterized by higher Fe / Ca ratios in the sediments. While in the lower part of the core the ferrimagnetic sulfide signal overprints the primary detrital magnetic signal, the upper part of the core is dominated by variable proportions of high- to low-coercivity iron oxides. Glacial sediments are characterized by high concentration of high-coercivity magnetic minerals (hematite, goethite), which relate to enhanced erosion of soils that had formed during preceding interglacials. Superimposed on the glacial-interglacial behavior are millennial-scale oscillations in the magnetic mineral composition that parallel variations in summer insolation. Like the processes on glacial-interglacial timescales, low summer insolation and a retreat in vegetation resulted in enhanced erosion of soil material. Our study highlights that rock-magnetic studies, in concert with geochemical and sedimentological investigations, provide a multi-level contribution to environmental reconstructions, since the magnetic properties can mirror both environmental conditions on land and intra-lake processes.

  14. Coercive Force and Antimagnetizing Mechanism Relating to Size of Ferromagnetic Microcrystal--A Consummating to Result of Stoner-Wohlforth Theory

    Institute of Scientific and Technical Information of China (English)

    Yu Ning; Ji Jingwen

    2004-01-01

    The expression of critical size of ferromagnetic microcrystal in an external magnetic field with an intensity of H is derived by means of comparing energies of domain structure states.The ferromagnetic microcrystal here means an ferromagnetic single crystal with the size which is smaller than L0, and L0 is the critical value of the size of single-domain particles at the external magnetic field intensity H =0.Also, the coercive strength H(Ls) relating to the size of microcrystal Ls is given and quantitatively evaluated with the material SmCo5 as an instance.It is thus concluded that if L0 > Ls > LC, the antimagnetization of microcrystal will be subjected to a multi-domain process just like the particles of a size greater than L0, only if Ls < LC, the anti-magnetizaton will be carried on in accordance with the Stoner-Wohlforth mechanism( LC is the maximum size of microcrystal with MHcth ).It is suggested that the material RECo5 is available to make an advanced magnet with MHC = 2 K/Mc.

  15. Discriminating Coercive from Sadomasochistic Sexuality.

    Science.gov (United States)

    Martin, Shannon M; Smith, Felix; Quirk, Stuart W

    2016-07-01

    Sadomasochistic (SM) sexual interest is reported by a wide range of individuals. Within the sex offender literature, the presence of SM interest is often viewed as a herald of criminal sexual behavior; however, research indicates that SM interests are not predictive of coercive sexual behavior. In the current study, we measured a range of sexual fantasies and behaviors, and then applied cluster analyses to determine (1) if individuals endorsed elevated SM interests also endorsed coercive fantasies and, (2) to explore cluster membership correlates using measures of sensation seeking, externalizing and antisocial behaviors, attitudes toward rape, and empathic capacity. A total of 550 participants were recruited through a variety of on-line discussion areas. A four cluster solution best fit the data with distinct clusters observed for those endorsing SM behaviors and those reporting coercive sexual behavior. Additional analyses revealed greater endorsement of victim blaming attitudes and lower empathic concern among members of the coercive sexual behavior cluster. Elevated sensation seeking and externalizing behaviors were reported by members of clusters marked by SM and coercive sexual behavior. Results provide further support for the differentiation between SM and coercive sexual behaviors as representative of individuals with divergent attitudes, traits, and behaviors.

  16. Coercive Diplomacy: Countering War-Threatening Crises and Armed Conflicts

    DEFF Research Database (Denmark)

    Jakobsen, Peter Viggo

    2015-01-01

    Nowadays states rarely resort to war to defeat each other or to address war-threatening crises and armed conflicts. Instead, coercive diplomacy has emerged as their strategy of choice when persuasion and other non-military instruments fall short. Coercive diplomacy involves the use of military...... threats and/or limited force (sticks) coupled with inducements and assurances (carrots) in order to influence the opponent to do something it would prefer not to. States use coercive diplomacy in the hope of achieving their objectives without having to resort to full-scale war. This chapter presents...... the strategy of coercive diplomacy and its requirements for success and shows how states have employed it to manage crises and conflicts during the three strategic eras that the world has passed through since the end of the Cold War....

  17. Formation of submicron-sized SrFe{sub 12-x}Al{sub x}O{sub 19} with very high coercivity

    Energy Technology Data Exchange (ETDEWEB)

    Kazin, P.E. [Chemistry Department, Moscow State University, 119991 Moscow (Russian Federation); Trusov, L.A. [Department of Materials Science, Moscow State University, 119991 Moscow (Russian Federation)], E-mail: doz.trusov@gmail.com; Zaitsev, D.D. [Department of Materials Science, Moscow State University, 119991 Moscow (Russian Federation); Tretyakov, Yu.D. [Chemistry Department, Moscow State University, 119991 Moscow (Russian Federation); Department of Materials Science, Moscow State University, 119991 Moscow (Russian Federation); Jansen, M. [Max-Planck-Institut fuer Festkoerperforschung, D-70569 Stuttgart (Germany)

    2008-03-15

    Submicron-sized SrFe{sub 12-x}Al{sub x}O{sub 19} (x=1.3) was formed in glass-ceramic matrix using controlled thermocrystallization of the SrO-Fe{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3} glass and the hexaferrite powder was obtained by removing the matrix phases. The samples were characterized by X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray (EDX) analysis and magnetization measurements. The glass-ceramic material exhibits very high coercivity value up to 10.18 kOe which approaches a theoretically estimated maximum value for the compound. The hexaferrite powder consists of well faceted single crystals, which adopt the shape of a truncated hexagonal bipyramid. The powder saturation magnetization value is close to the theoretically estimated one for bulk material. Crystal structure of the powder was refined by Rietveld method and distribution of Al atoms on Fe sites was determined. Al atoms occupy 41% of 2a sites, 14% of 12k sites and 5% of 4e(1/2) sites, while 4f sites are not affected.

  18. Magnetic properties and large coercivity of Mn{sub x}Ga nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Jamer, M.E., E-mail: m.jamer@neu.edu [Department of Physics, Northeastern University, Boston, MA 02115 (United States); Assaf, B.A. [Department of Physics, Northeastern University, Boston, MA 02115 (United States); Bennett, S.P. [Department of Electrical Engineering, Northeastern University, Boston, MA 02115 (United States); Lewis, L.H. [Department of Chemical Engineering, Northeastern University, Boston, MA 02115 (United States); Heiman, D. [Department of Physics, Northeastern University, Boston, MA 02115 (United States)

    2014-05-01

    To investigate structure–property correlations, high-coercivity Mn{sub x}Ga nanoparticles were synthesized by the method of sequential deposition of Ga and Mn fluxes using molecular beam epitaxy. Spontaneous nanostructuring was assisted by the use of an Au precursor and thermal annealing, and the growth properties, structure and magnetic properties were characterized. Atomic force microscopy revealed average particle dimensions of 100 nm and X-ray diffraction revealed a dominant tetragonal D0{sub 22} crystal structure. Magnetic characterization at room temperature identified the presence of two magnetic phases, dominated by a high-coercivity (2.3 T) component in addition to a low-coercivity component. - Highlights: • Mn{sub x}Ga nanoparticles were synthesized using Molecular Beam Epitaxy. • The tetragonal D0{sub 22} structure of Mn{sub x}Ga (x=2.3–2.6) was found to be the dominant phase. • The D0{sub 22} phase of the Mn{sub x}Ga nanoparticles exhibited a large coercivity µ{sub o}H=2.3 T. • MFM showed that multiple nanoparticles contributed to a single domain.

  19. Simultaneous effects of surface spins: rarely large coercivity, high remanence magnetization and jumps in the hysteresis loops observed in CoFe2O4 nanoparticles

    Science.gov (United States)

    Xu, S. T.; Ma, Y. Q.; Zheng, G. H.; Dai, Z. X.

    2015-04-01

    Well-dispersed uniform cobalt ferrite nanoparticles were synthesized by thermal decomposition of a metal-organic salt in organic solvent with a high boiling point. Some of the nanoparticles were diluted in a SiO2 matrix and then the undiluted and diluted samples were characterized and their magnetic behavior explored. The undiluted and diluted samples exhibited maximum coercivity Hc of 23 817 and 15 056 Oe at 10 K, respectively, which are the highest values reported to date, and the corresponding ratios of remanence (Mr) to saturation (Ms) magnetization (Mr/Ms) were as high as 0.85 and 0.76, respectively. Interestingly, the magnetic properties of the samples changed at 200 K, which was observed in magnetic hysteresis M(H) loops and zero-field cooling curves as well as the temperature dependence of Hc, Mr/Ms, anisotropy, dipolar field, and the magnetic grain size. Below 200 K, both samples have large effective anisotropy, which arises from the surface spins, resulting in large Hc and Mr/Ms. Above 200 K, the effective anisotropy decreases because there is no contribution from surface spins, while the dipolar interaction increases, resulting in small Hc and Mr/Ms. Our results indicate that strong anisotropy and weak dipolar interaction tend to increase Hc and Mr/Ms, and also clarify that the jumps around H = 0 in M(H) loops can be attributed to the reorientation of surface spins. This work exposes the underlying mechanism in nanoscale magnetic systems, which should lead to improved magnetic performance.

  20. Dynamic coercivity of Mo-doped FINEMETs

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Srimoy; Mandal, Kalyan; Sakar, Debashis [S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India); Cremaschi, Victoria J. [Lab. de Solidos Amorfos, INTECIN, Facultad de Ingenieria, Universidad de Buenos Aires-CONICET, Paseo Colon 850, C1063ACV Buenos Aires (Argentina); Member of CONICET (Argentina); Silveyra, Josefina M., E-mail: jsilveyra@fi.uba.a [Lab. de Solidos Amorfos, INTECIN, Facultad de Ingenieria, Universidad de Buenos Aires-CONICET, Paseo Colon 850, C1063ACV Buenos Aires (Argentina)

    2011-05-01

    The structure and the dc magnetic behavior of FINEMET-type alloys doped with molybdenum have been recently reported. Most commercial applications of these materials are, however, not at dc but at high magnetizing frequencies. Therefore, we report a study of the frequency dependence of coercivity, H{sub c}(f), in amorphous and nanocrystalline ribbons of composition Fe{sub 73.5}Si{sub 13.5}Nb{sub 3-x}Mo{sub x}B{sub 9}Cu{sub 1} (x=0, 1.5 and 3) in the frequency range from 0.5 to 1.3 kHz. The nature of H{sub c}(f) measurements revealed the influence of eddy currents in the magnetization of samples. The frequency dependence of coercivity did not vary with the molybdenum content in the amorphous samples. All the alloys exhibited a systematic improvement in the coercivity after nanocrystallization and it was found that this improvement was better as more Nb was replaced by Mo.

  1. Coercivity and the critical switching field

    Energy Technology Data Exchange (ETDEWEB)

    Kahler, G.R. [George Washington University, Washington, DC 20052 (United States)]. E-mail: grkahler@aol.com; Bennett, L.H. [George Washington University, Washington, DC 20052 (United States); Della Torre, E. [George Washington University, Washington, DC 20052 (United States)

    2006-02-01

    The critical switching field and the coercivity of a material are not necessarily the same; these field values depend upon the magnetization process. Several field-related parameters are used to identify the major hysteresis loop of a material: the saturation field, remanent coercivity, critical field, average critical field, coercivity, median coercivity, and intrinsic coercivity. The parameters vary with changes in the magnetization process, which usually is assumed to be quasi-static. If the process is not quasi-static; i.e., it is faster or slower, the results of the process will change, and the field parameters will be differen000.

  2. Strong coercivity reduction and high initial permeability in NiCoP coated BaFe12O19-polystyrene bilayer composite

    Science.gov (United States)

    Hamad, Mahmoud A.; El-Sayed, Adly H.; Hemeda, O. M.; Tawfik, A.

    2016-03-01

    Soft-magnetic NiCoP coated hard-magnetic M-type ferrite BaFe12O19 (BaM)-polystyrene (PS) bilayer composite film was successfully synthesized. X-ray diffraction peaks exhibited no change in the structure of BaM after coating with PS. The NiCoP coated BaM-PS composite exhibited a wasp-waisted magnetic hysteretic loop with remarkable reduction in the coercivity, remanence and squareness with respect to BaM-PS, which is useful for the core of a magnetic switching device to control currents so large that they are unmanageable. Moreover, the initial permeability measurement exhibits initial permeability of around 100 000 and thermal stability up to 558 K, which is good for flux-amplifying components of smaller inductors.

  3. High-speed atomic force microscopy: imaging and force spectroscopy.

    Science.gov (United States)

    Eghiaian, Frédéric; Rico, Felix; Colom, Adai; Casuso, Ignacio; Scheuring, Simon

    2014-10-01

    Atomic force microscopy (AFM) is the type of scanning probe microscopy that is probably best adapted for imaging biological samples in physiological conditions with submolecular lateral and vertical resolution. In addition, AFM is a method of choice to study the mechanical unfolding of proteins or for cellular force spectroscopy. In spite of 28 years of successful use in biological sciences, AFM is far from enjoying the same popularity as electron and fluorescence microscopy. The advent of high-speed atomic force microscopy (HS-AFM), about 10 years ago, has provided unprecedented insights into the dynamics of membrane proteins and molecular machines from the single-molecule to the cellular level. HS-AFM imaging at nanometer-resolution and sub-second frame rate may open novel research fields depicting dynamic events at the single bio-molecule level. As such, HS-AFM is complementary to other structural and cellular biology techniques, and hopefully will gain acceptance from researchers from various fields. In this review we describe some of the most recent reports of dynamic bio-molecular imaging by HS-AFM, as well as the advent of high-speed force spectroscopy (HS-FS) for single protein unfolding.

  4. The modified procedures in coercivity scaling*

    Directory of Open Access Journals (Sweden)

    Najgebauer Mariusz

    2015-09-01

    Full Text Available The paper presents a scaling approach to the analysis of coercivity. The Widom-based procedure of coercivity scaling has been tested for non-oriented electrical steel. Due to insufficient results, the scaling procedure was improved relating to the method proposed by Van den Bossche. The modified procedure of coercivity scaling gave better results, in comparison to the original approach. The influence of particular parameters and a range of measurement data used in the estimations on the final effect of the coercivity scaling were discussed.

  5. High-resolution traction force microscopy.

    Science.gov (United States)

    Plotnikov, Sergey V; Sabass, Benedikt; Schwarz, Ulrich S; Waterman, Clare M

    2014-01-01

    Cellular forces generated by the actomyosin cytoskeleton and transmitted to the extracellular matrix (ECM) through discrete, integrin-based protein assemblies, that is, focal adhesions, are critical to developmental morphogenesis and tissue homeostasis, as well as disease progression in cancer. However, quantitative mapping of these forces has been difficult since there has been no experimental technique to visualize nanonewton forces at submicrometer spatial resolution. Here, we provide detailed protocols for measuring cellular forces exerted on two-dimensional elastic substrates with a high-resolution traction force microscopy (TFM) method. We describe fabrication of polyacrylamide substrates labeled with multiple colors of fiducial markers, functionalization of the substrates with ECM proteins, setting up the experiment, and imaging procedures. In addition, we provide the theoretical background of traction reconstruction and experimental considerations important to design a high-resolution TFM experiment. We describe the implementation of a new algorithm for processing of images of fiducial markers that are taken below the surface of the substrate, which significantly improves data quality. We demonstrate the application of the algorithm and explain how to choose a regularization parameter for suppression of the measurement error. A brief discussion of different ways to visualize and analyze the results serves to illustrate possible uses of high-resolution TFM in biomedical research. © 2014 Elsevier Inc. All rights reserved.

  6. Coercivity enhancement in (Co/CoO)n superlattices

    Science.gov (United States)

    Polisetty, Srinivas; Binek, Christian

    2009-03-01

    The temperature dependence of the coercivity is studied in (Co/CoO)n periodic multilayer thin film superstructures below and above the exchange bias blocking temperature. The ferromagnetic Co thin films are grown with the help of MBE at a base pressure of 10E-10 m.bar whereas antiferromagnetic CoO thin films are grown from in-situ oxidized Co. The thicknesses of these films are monitored by reflection high energy electron diffraction (RHEED). A mean-field theory^1 is outlined which provides an analytic and intuitive expression for the enhancement of the coercivity of the ferromagnet which experiences the exchange coupling with a neighboring antiferromagnet. An experimental approach is developed allowing to determine the interface susceptibility of an individual antiferromagnetic pinning layer by systematic change in the thickness of the antiferromagnet thin films in various sets of superlattice samples measured at different temperatures, respectively. The experiment enables us to separate out the intrinsic coercivity from the contribution induced by exchange coupling at the interface. It is the goal of our study to evidence or disprove if it is simply this susceptibility of the reversible interface magnetization creating the spin drag effect and by that the coercivity enhancement. Financial support by NSF through CAREER DMR-0547887, NRI and Nebraska MRSEC. ^1G. Scholten, K. D. Usadel, and U. Nowak, Phys. Rev B. 71, 064413 (2005).

  7. Rock Magnetic Detection of Two Coercivity Components of Magnetosomes in Lake Ely Sediments

    Science.gov (United States)

    Kodama, K. P.; Chen, A.; Egli, R.; Vavrek, J.

    2007-12-01

    The modeling of IRM acquisition curves has become an important tool used by environmental magnetists to characterize a sample's magnetic mineralogy. We have applied IRM modeling to lake sediments from Lake Ely, a small, post-glacial lake located in northeastern Pennsylvania. The lake is unique in having a strong sedimentary magnetization dominated by the magnetosomes produced by magnetotactic bacteria. Measurements of Fe, S, and O2 at different depths in the lake's water column, as well as the magnetization of material filtered from the water, indicate that magnetotactic bacteria live in the water column at the oxic-anoxic interface. Magnetic measurements and TEM observations of lake sediments and material caught in a sediment trap indicate that magnetosomes are the major constituent of the magnetic minerals in the lake sediments. IRM modeling shows two separate coercivity components at about 30 mT and 60 mT that are consistent with Egli's (2004) observations of BS (biogenic soft) and BH (biogenic hard) coercivity components for magnetosomes in lake sediments. However, the peaks are poorly determined because only 6-7 data points constrain the 0-100 mT part of the IRM coercivity spectrum. We used pARMs (97 μT DC field) applied in 5 mT alternating field steps between 0 and 100 mT to better resolve the BH and BS coercivity peaks. pARM spectra collected from lake sediment samples reveal one strong coercivity peak at approximately 30 mT in the 0-100 mT range. A second higher coercivity peak at about 80 mT is weakly evident in some samples. Alternating field demagnetization in 104 steps of an ARM applied to one sample also suggests the presence of two coercivity peaks but at 20 and 40 mT. First order reversal curves (FORCs) measured at the Institute for Rock Magnetism show that the magnetic grains behave as non-interacting single domain grains, implying that the magnetosome chains are relatively far apart and probably still intact. The FORC diagrams also show a large

  8. HDDR法制备NdFeB永磁体的高矫顽力研究%Study on the Mechanism of the High Coercivity of NdFeB Magnets Prepared by HDDR Method

    Institute of Scientific and Technical Information of China (English)

    张朋越; 泮敏翔; 朱津津; 葛洪良; 孙浩; 金一彪

    2011-01-01

    , especially for the coercivity which is reduced by 1496 kA/m from 295 to 448 K.The coercivity mechanism of the NdFeB magnets prepared by HDDR method was analyzed by studying the behavior of Hc(T)/Ms(T) versus HminN (T)/Ms(T) (Kronmilller-plot).The results of Kronmiiller-plot sbow that nucleation is the dominating mechanism for the magnetization reversal in these samples.Micromagnetic parameters ak of 1.39 and Neff of 1.75 are responsible for the high coercivity of magnetic alloys.

  9. Remote Robot Control With High Force-Feedback Gain

    Science.gov (United States)

    Kim, Won S.

    1993-01-01

    Improved scheme for force-reflecting hand control of remote robotic manipulator provides unprecedently high force-reflection gain, even when dissimilar master and slave arms used. Three feedback loops contained in remote robot control system exerting position-error-based force feedback and compliance control. Outputs of force and torque sensors on robot not used directly for force reflection, but for compliance control, while errors in position used to generate reflected forces.

  10. High-resolution noncontact atomic force microscopy.

    Science.gov (United States)

    Pérez, Rubén; García, Ricardo; Schwarz, Udo

    2009-07-01

    original papers authored by many of the leading groups in the field with the goal of providing a well-balanced overview on the state-of-the-art in this rapidly evolving field. These papers, many of which are based on notable presentations given during the Madrid conference, feature highlights such as (1) the development of sophisticated force spectroscopy procedures that are able to map the complete 3D tip-sample force field on different surfaces; (2) the considerable resolution improvement of Kelvin probe force microscopy (reaching, in some cases, the atomic scale), which is accompanied by a thorough, quantitative understanding of the contrast observed; (3) the perfecting of atomic resolution imaging on insulating substrates, which helps reshape our microscopic understanding of surface properties and chemical activity of these surfaces; (4) the description of instrumental and methodological developments that pave the way to the atomic-scale characterization of magnetic and electronic properties of nanostructures, and last but not least (5) the extension of dynamic imaging modes to high-resolution operation in liquids, ultimately achieving atomic resolution. The latter developments are already having a significant impact in the highly competitive field of biological imaging under physiological conditions. This special issue of Nanotechnology would not have been possible without the highly professional support from Nina Couzin, Amy Harvey, Alex Wotherspoon and the entire Nanotechnology team at IOP Publishing. We are thankful for their help in pushing this project forward. We also thank the authors who have contributed their excellent original articles to this issue, the referees whose comments have helped make the issue an accurate portrait of this rapidly moving field, and the entire NC-AFM community that continues to drive NC-AFM to new horizons.

  11. Coercivity in SmCo hard magnetic films for MEMS applications

    Energy Technology Data Exchange (ETDEWEB)

    Pina, E. [Instituto de Magnetismo Aplicado, RENFE-UCM, Universidad Complutense de Madrid, P.O. Box 155, 28230 Las Rozas, Madrid (Spain)]. E-mail: epina@renfe.es; Palomares, F.J. [Instituto de Ciencia de Materiales de Madrid-CSIC, c/ Sor Juana Ines de la Cruz s/n, 28049 Madrid (Spain); Garcia, M.A. [Instituto de Magnetismo Aplicado, RENFE-UCM, Universidad Complutense de Madrid, P.O. Box 155, 28230 Las Rozas, Madrid (Spain); Cebollada, F. [Departamento de Fisica Aplicada a las Telecomunicaciones, EUITT-UPM, Crtra. De Valencia km 7, 28031 Madrid (Spain); Hoyos, A. de [Instituto de Magnetismo Aplicado, RENFE-UCM, Universidad Complutense de Madrid, P.O. Box 155, 28230 Las Rozas, Madrid (Spain); Romero, J.J. [Instituto de Magnetismo Aplicado, RENFE-UCM, Universidad Complutense de Madrid, P.O. Box 155, 28230 Las Rozas, Madrid (Spain); Hernando, A. [Instituto de Magnetismo Aplicado, RENFE-UCM, Universidad Complutense de Madrid, P.O. Box 155, 28230 Las Rozas, Madrid (Spain); Unidad asociada ICMM-IMA. P.O. Box 155, 28230 Las Rozas Madrid (Spain); Gonzalez, J.M. [Unidad asociada ICMM-IMA. P.O. Box 155, 28230 Las Rozas Madrid (Spain)

    2005-04-15

    In this work we have investigated the thermal dependence of coercivity in 1.5 {mu}m thick SmCo{sub 5} films fabricated by sputtering technique. Samples were deposited onto Si substrates kept at different temperatures. Samples grown below 450 deg. C are amorphous, present low coercivity and require further crystallization processes in order to obtain the 1:5 SmCo hard phase. Samples grown at 450 deg. C are nanocrystalline in the as-deposited state and exhibit high room temperature in-plane coercivity. Correlation between the thermal dependence of coercivity and the nanostructure has been analyzed in the frame of the so-called micromagnetic model.

  12. Differentiating between Confrontive and Coercive Kinds of Parental Power-Assertive Disciplinary Practices

    Science.gov (United States)

    Baumrind, Diana

    2012-01-01

    In this essay, I differentiate between coercive and confrontive kinds of power assertion to elucidate the significantly different effects on children's well-being of authoritarian and authoritative styles of parental authority. Although both parenting styles (in contrast to the permissive style) are equally demanding, forceful, and…

  13. Differentiating between Confrontive and Coercive Kinds of Parental Power-Assertive Disciplinary Practices

    Science.gov (United States)

    Baumrind, Diana

    2012-01-01

    In this essay, I differentiate between coercive and confrontive kinds of power assertion to elucidate the significantly different effects on children's well-being of authoritarian and authoritative styles of parental authority. Although both parenting styles (in contrast to the permissive style) are equally demanding, forceful, and…

  14. High-frequency multimodal atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Adrian P. Nievergelt

    2014-12-01

    Full Text Available Multifrequency atomic force microscopy imaging has been recently demonstrated as a powerful technique for quickly obtaining information about the mechanical properties of a sample. Combining this development with recent gains in imaging speed through small cantilevers holds the promise of a convenient, high-speed method for obtaining nanoscale topography as well as mechanical properties. Nevertheless, instrument bandwidth limitations on cantilever excitation and readout have restricted the ability of multifrequency techniques to fully benefit from small cantilevers. We present an approach for cantilever excitation and deflection readout with a bandwidth of 20 MHz, enabling multifrequency techniques extended beyond 2 MHz for obtaining materials contrast in liquid and air, as well as soft imaging of delicate biological samples.

  15. Protein high-force pulling simulations yield low-force results.

    Directory of Open Access Journals (Sweden)

    Seth Lichter

    Full Text Available All-atom explicit-solvent molecular dynamics simulations are used to pull with extremely large constant force (750-3000 pN on three small proteins. The introduction of a nondimensional timescale permits direct comparison of unfolding across all forces. A crossover force of approximately 1100 pN divides unfolding dynamics into two regimes. At higher forces, residues sequentially unfold from the pulling end while maintaining the remainder of the protein force-free. Measurements of hydrodynamic viscous stresses are made easy by the high speeds of unfolding. Using an exact low-Reynolds-number scaling, these measurements can be extrapolated to provide, for the first time, an estimate of the hydrodynamic force on low-force unfolding. Below 1100 pN, but surprisingly still at extremely large applied force, intermediate states and cooperative unfoldings as seen at much lower forces are observed. The force-insensitive persistence of these structures indicates that decomposition into unfolded fragments requires a large fluctuation. This finding suggests how proteins are constructed to resist transient high force. The progression of [Formula: see text] helix and [Formula: see text] sheet unfolding is also found to be insensitive to force. The force-insensitivity of key aspects of unfolding opens the possibility that numerical simulations can be accelerated by high applied force while still maintaining critical features of unfolding.

  16. Hollow Threats: Why Coercive Diplomacy Fails

    Science.gov (United States)

    2015-06-01

    Most likely, Argentina invaded the Falkland Islands in an attempt to achieve that unity and overcome its affliction of domestic discord. The...benefit during British coercion of Argentina was this hoped-for internal unity. 26. George, “Coercive Diplomacy,” 77. 27. Barry R. Posen, “Military...recognized government has taken refuge in Eastern Libya.90 In December 2014, one of the larger militias, Fajr Libya, fought to control oil export

  17. Enhanced coercivity thermal stability realized in Nd-Fe-B thin films diffusion-processed by Nd-Co alloys

    Science.gov (United States)

    Zhong, Hui; Fu, Yanqing; Li, Guojian; Liu, Tie; Cui, Weibin; Liu, Wei; Zhang, Zhidong; Wang, Qiang

    2017-03-01

    A proposed Nd2Fe14B-core/Nd2(Fe, Co)14B-shell microstructure was realized by diffusion-processing textured Nd14Fe77B9 single-layer film with Nd100-xCox (x=10, 20 and 40) alloys to improve the coercivity thermal stability. The ambient coercivity was increased from around 1 T in single-layer film to nearly 2 T in diffusion-processed films, which was due to the Nd-rich grain boundaries as seen from transmission electron microscopy (TEM) images. The coercivity thermal stability was improved by the core/shell microstructure because Nd-rich grain boundaries provided the high ambient coercivity and Co-rich shell provided the improved coercivity stability.

  18. High-Multipolar Effects on Dispersive Forces

    CERN Document Server

    Noguez, C; Esquivel-Sirvent, R; Villarreal, C; Noguez, Cecilia; Roman-Velazquez, Carlos E.

    2003-01-01

    We show that the dispersive force between a spherical nanoparticle (with a radius $\\le$ 100 nm) and a substrate is enhanced by several orders of magnitude when the sphere is near to the substrate. We calculate exactly the dispersive force in the non-retarded limit by incorporating the contributions to the interaction from of all the multipolar electromagnetic modes. We show that as the sphere approaches the substrate, the fluctuations of the electromagnetic field, induced by the vacuum and the presence of the substrate, the dispersive force is enhanced by orders of magnitude. We discuss this effect as a function of the size of the sphere.

  19. The coercivity mechanism of Pr–Fe–B nanoflakes prepared by surfactant-assisted ball milling

    Energy Technology Data Exchange (ETDEWEB)

    Zuo, Wen-Liang, E-mail: wlzuo@iphy.ac.cn; Zhang, Ming; Niu, E.; Shao, Xiao-Ping; Hu, Feng-Xia; Sun, Ji-Rong; Shen, Bao-Gen, E-mail: shenbg@aphy.iphy.ac.cn

    2015-09-15

    The strong (00l) textured Pr{sub 12+x}Fe{sub 82−x}B{sub 6} (x=0, 1, 2, 3, 4) nanoflakes with high coercivity were prepared by surfactant-assisted ball milling (SABM). The thickness and length of the flakes are mainly in the range of 50−200 nm and 0.5−2 μm, respectively. A coercivity of 4.16 kOe for Pr{sub 15}Fe{sub 79}B{sub 6} nanoflakes was obtained, which is the maximum coercivity of R{sub 2}Fe{sub 14}B (R=Pr, Nd) nanoflakes or nanoparticles reported up to now. The results of XRD and SEM for the aligned Pr{sub 15}Fe{sub 79}B{sub 6} nanoflakes indicate that a strong (00l) texture is obtained and the easy magnetization direction is parallel to the surface of the flakes. The angular dependence of coercivity for aligned sample indicates that the coercivity mechanism of the as-milled nanoflakes is mainly dominated by domain wall pinning. Meanwhile, the field dependence of coercivity, isothermal (IRM) and dc demagnetizing (DCD) remanence curves also indicate that the coercivity is mainly determined by domain wall pinning, and nucleation also has an important effect. In addition, the mainly interaction of flakes is dipolar coupling. The research of coercivity mechanism for Pr{sub 15}Fe{sub 79}B{sub 6} nanoflakes is important for guidance the further increase its value, and is useful for the future development of the high performance nanocomposite magnets and soft/hard exchange spring magnets. - Highlights: • A coercivity of 4.16 kOe for Pr{sub 15}Fe{sub 79}B{sub 6} nanoflakes was obtained. • The strong (00l) textured is obtained for Pr{sub 15}Fe{sub 79}B{sub 6} nanoflakes. • The interaction of nanoflakes is mainly dipolar coupling. • Domain wall pinning is the mainly coercivity mechanism.

  20. Development of uniaxial magnetocrystalline anisotropy in SrFe{sub 12−x}(DyGd){sub x}O{sub 19} thin film synthesized by incorporation of high coercivity nanoparticles in sol–gel method

    Energy Technology Data Exchange (ETDEWEB)

    Ghasemi, Ali, E-mail: ali13912001@yahoo.com

    2014-06-01

    SrFe{sub 12−x}(DyGd){sub x}O{sub 19} thin films with x=0–2.5 were synthesized by a sol–gel method on thermally oxidized silicon wafer (Si/SiO{sub 2}). XRD patterns and FE-SEM micrographs demonstrated that single phase c-axis hexagonal ferrite films with rather narrow grain size distribution were obtained. It was found that the grain size is decreased from about 110 nm (for the film with no substitution) to 35 nm (for the film with the highest amount of substitution cations). AFM micrographs exhibited that the surface roughness decreases with an increase in substitution content. It was found from the VSM graphs that with an increase in substitution contents coercivity and saturation of magnetization increase. The maximum saturation of magnetization and coercivity at perpendicular direction were 250 emu/g and 5.5 kOe, respectively. - Highlights: • SrFe{sub 12−x}(DyGd){sub x}O{sub 19} ferrite thin films were successfully synthesized by a sol–gel method. • With an increase in Dy-Gd substitution coercivity and saturation of magnetization increase. • The existence of perpendicular magnetic anisotropy was confirmed by plotting magnetization curve.

  1. Proliferation Persuasion. Coercive Bargaining with Nuclear Technology

    Energy Technology Data Exchange (ETDEWEB)

    Volpe, Tristan A. [George Washington Univ., Washington, DC (United States)

    2015-08-31

    Why do states wait for prolonged periods of time with the technical capacity to produce nuclear weapons? Only a handful of countries have ever acquired the sensitive nuclear fuel cycle technology needed to produce fissile material for nuclear weapons. Yet the enduring trend over the last five decades is for these states to delay or forgo exercising the nuclear weapons option provided by uranium enrichment or plutonium reprocessing capabilities. I show that states pause at this threshold stage because they use nuclear technology to bargain for concessions from both allies and adversaries. But when does nuclear latency offer bargaining benefits? My central argument is that challengers must surmount a dilemma to make coercive diplomacy work: the more they threaten to proliferate, the harder it becomes to reassure others that compliance will be rewarded with nuclear restraint. I identify a range of mechanisms able to solve this credibility problem, from arms control over breakout capacity to third party mediation and confidence building measures. Since each step towards the bomb raises the costs of implementing these policies, a state hits a sweet spot when it first acquires enrichment and/or reprocessing (ENR) technology. Subsequent increases in proliferation capability generate diminishing returns at the bargaining table for two reasons: the state must go to greater lengths to make a credible nonproliferation promise, and nuclear programs exhibit considerable path dependency as they mature over time. Contrary to the conventional wisdom about power in world politics, less nuclear latency thereby yields more coercive threat advantages. I marshal new primary source evidence from archives and interviews to identify episodes in the historical record when states made clear decisions to use ENR technology as a bargaining chip, and employ this theory of proliferation persuasion to explain how Japan, North Korea, and Iran succeeded and failed to barter concessions from the

  2. 脉冲磁场技术在高矫顽力稀土永磁测量领域的应用%Application of pulsed field technique to magnetic property measurements of rare earth based hard magnetic materials with high coercivity

    Institute of Scientific and Technical Information of China (English)

    林安利; 贺建; 张跃; John Dudding

    2009-01-01

    An inherent problem was introduced when measuring the magnetic properties of high coercivity hard magnetic materials with an existent static BH tracer (hysteresisograph) and the reason why the problem happens was discussed. To deal with the problem a pulsed field magnetometer (PFM) system based on the f-2f method, which could generates 8756kA·m~(-1) magnetic field, was designed and applied to measure the whole hysteresis loop of high coercivity hard magnetic materials. The technical advantages, structure and eddy current effect correction of the system were also introduced. It can be approved, from a large quantity of measurement results, that the long term repeatability of the system is very good. The deviation of magnetic properties, i.e. remanence B_r, intrinsic coercivity H_(cJ), magnetic flux density coercivity H_(cB), and maximum energy product (BH)_(max), measured with a PFM compared with that measured with a national standard static BH tracer is within 1% for low coercivity hard magnets. For high coercivity hard magnets the system could measure the whole hysteresis loop and solve the high coercivity problem that a static BH tracer could not avoid.%简述了超高矫顽力永磁体测量现状,分析了静态磁滞回线仪在测量高矫顽力永磁体时存在的问题及其原因.为解决此问题,采用"f-2f"原理建立了基于脉冲磁场技术的高矫顽力永磁测量装置,该装置能产生最高8756kA·m~(-1)的测量磁场,能够测量高矫顽力永磁体的整个磁滞回线.阐述了该脉冲磁场测量装置的优势、组成结构以及涡流修正方法.经过实验验证,该系统具有良好的测量重复性.与国家永磁标准测量装置的对比结果显示:在低矫顽力范围内两者剩磁Br、内禀矫顽力H_(cJ)、磁感应强度矫顽力H_(cB)和最大磁能积(BH)_(max)四个参数的测量偏差在1%以内;在高矫顽力范围,该装置解决了静态磁滞回线仪测量曲线变形的问题.

  3. Imaging stability in force-feedback high-speed atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Byung I., E-mail: ByungKim@boisestate.edu [Department of Physics, Boise State University, 1910 University Drive Boise, ID 83725-1570, United States of America (United States); Boehm, Ryan D. [Department of Physics, Boise State University, 1910 University Drive Boise, ID 83725-1570, United States of America (United States)

    2013-02-15

    We studied the stability of force-feedback high-speed atomic force microscopy (HSAFM) by imaging soft, hard, and biological sample surfaces at various applied forces. The HSAFM images showed sudden topographic variations of streaky fringes with a negative applied force when collected on a soft hydrocarbon film grown on a grating sample, whereas they showed stable topographic features with positive applied forces. The instability of HSAFM images with the negative applied force was explained by the transition between contact and noncontact regimes in the force–distance curve. When the grating surface was cleaned, and thus hydrophilic by removing the hydrocarbon film, enhanced imaging stability was observed at both positive and negative applied forces. The higher adhesive interaction between the tip and the surface explains the improved imaging stability. The effects of imaging rate on the imaging stability were tested on an even softer adhesive Escherichia coli biofilm deposited onto the grating structure. The biofilm and planktonic cell structures in HSAFM images were reproducible within the force deviation less than ∼0.5 nN at the imaging rate up to 0.2 s per frame, suggesting that the force-feedback HSAFM was stable for various imaging speeds in imaging softer adhesive biological samples. - Highlights: ► We investigated the imaging stability of force-feedback HSAFM. ► Stable–unstable imaging transitions rely on applied force and sample hydrophilicity. ► The stable–unstable transitions are found to be independent of imaging rate.

  4. Random magnetic anisotropy: Switching and coercivity behavior

    Science.gov (United States)

    Creswell, A.; Paul, D. I.

    1990-05-01

    Starting from a Hamiltonian based on the random magnetic anisotropy model to describe the magnetic characteristics of amorphous materials such as TbFe2, we determine the low-temperature dependence of the coercivity as well as the magnetization dynamics of these materials. Our model features clusters, each characterized by its anisotropy direction. The exchange energy term entering the Hamiltonian is represented by an effective exchange interaction acting in the intercluster regions. Our Hamiltonian has a minimum in each of the two opposite hemispheres defined by the applied field. We derive the temperature-dependent coercivity by calculating the field necessary to have the one metastable minimum disappear. Our results agree well with experimental data for reasonable values of the parameters. We study the dynamics of the magnetization at 0 K by performing a numerical integration of the equations of motion derived from our Hamiltonian augmented by a Gilbert and Kelly damping term. The average magnetization of the material is reevaluated at each integration step in order for the mean-field approximation for exchange to remain physically meaningful. We obtain the time dependence of the magnetization, determine the switching fields and switching times, and study the influence of the exchange on the results.

  5. Low coercivity giant magnetoresistance with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jeong-Seop; Yoon, Jungbum; Kang, Mool-Bit; You, Chun-Yeol, E-mail: cyyou@inha.ac.kr

    2014-05-01

    We find the perpendicular magnetic anisotropy giant magnetoresistance structure, whose coercivity is less than 10 Oe. We reveal that the coercivity of free layer can be smaller than 5 Oe in Co/Pd/Cu/[Co/Pd]{sub 4} multilayer structure with a TiO{sub 2} seed layer. The TiO{sub 2} seed layer plays a critical role in the small coercivity of free layer. The GMR ratio is around 1–1.8% for the out-of-plane magnetic fields, and the maximum MR sensitivity of 0.12%/Oe is achieved. - Highlights: • We find an extremely small coercivity giant magnetoresistance (GMR) structure for the out-of-plane magnetic field. • The key ingredient of small coercivity is a TiO{sub 2} seed layer. • Such a small coercivity GMR structure will be useful for automotive applications such as wheel speed, rotation, and position sensors.

  6. The use of Coercive Interventions in Mental Health Care in Germany and the Netherlands. A comparison of the developments in two neighbouring countries

    Directory of Open Access Journals (Sweden)

    Tilman eSteinert

    2014-09-01

    Full Text Available In this review we compare the use of coercion in mental health care in Germany and in the Netherlands. Legal frameworks and published data on involuntary commitment, involuntary medication, seclusion, and restraint are highlighted as well as the role of guidelines, training and attitudes held by psychiatrists and the public. Legal procedures regulating involuntary admission and commitment are rather similar, and so is the percentage of involuntary admissions and the rate per 100.000 inhabitants. However, opposing trends can be observed in the use of coercive interventions during treatment which in both countries are considered as a last resort after all other alternative approaches have failed. In the Netherlands, for a long time seclusion has been considered as preferred intervention while the use of medication by force was widely disapproved as being unnecessarily invasive. However, after increasing evidence showed that number and duration of seclusions as well as the number of aggressive incidents per admission were considerably higher than in other European countries, attitudes changed within recent years. A national programme with spending of 15 million € was launched to reduce the use of seclusion, while the use of medication was facilitated. A legislation is scheduled which will allow also outpatient coercive treatment. In Germany, the latter was never legalized. While coercive treatment in Germany was rather common for involuntarily committed patients and mechanical restraint was preferred to seclusion in most hospital as a containment measure, the decisions of the Constitutional Court in 2011 had a high impact on legislation, attitudes and clinical practice. Though since 2013 coercive medication is approvable again under strict conditions, it is now widely perceived as very invasive and last resort. There is evidence that this change of attitudes lead to a considerable increase of the use of seclusion and restraint for some patients.

  7. Ultrahigh coercivity and core-shell microstructure achieved in oriented Nd-Fe-B thin films diffusion-processed with Dy-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Tongbo; Zhou, Xiaoqian; Yu, Dedong; Fu, Yanqing; Cui, Weibin [Northeastern University, Key Laboratory of Electromagnetic Processing of Materials (EPM), Ministry of Education, Shenyang (China); Northeastern University, Department of Physics and Chemistry of Materials, School of Materials Science and Engineering, Shenyang (China); Li, Guojian; Wang, Qiang [Northeastern University, Key Laboratory of Electromagnetic Processing of Materials (EPM), Ministry of Education, Shenyang (China)

    2017-01-15

    Ultrahigh ambient coercivities of ∝4 T were achieved in Nd-Fe-B benchmark thin film with coercivity of 1.06 T by diffusion-processing with Dy, Dy{sub 70}Cu{sub 30} and Dy{sub 80}Ag{sub 20} alloy layer. High texture and good squareness were obtained. In triple-junction regions, Dy element was found to be immiscible with Nd element. Microstructure observation indicated the typical gradient elementary distribution. Unambiguous core/shell microstructure was characterized by transition electron microscopy. Due to the enhanced ambient coercivity, the coercivity temperature stability was also substantially increased. (orig.)

  8. Ultrahigh coercivity and core-shell microstructure achieved in oriented Nd-Fe-B thin films diffusion-processed with Dy-based alloys

    Science.gov (United States)

    Zhang, Tongbo; Zhou, Xiaoqian; Yu, Dedong; Fu, Yanqing; Li, Guojian; Cui, Weibin; Wang, Qiang

    2017-01-01

    Ultrahigh ambient coercivities of 4 T were achieved in Nd-Fe-B benchmark thin film with coercivity of 1.06 T by diffusion-processing with Dy, Dy70Cu30 and Dy80Ag20 alloy layer. High texture and good squareness were obtained. In triple-junction regions, Dy element was found to be immiscible with Nd element. Microstructure observation indicated the typical gradient elementary distribution. Unambiguous core/shell microstructure was characterized by transition electron microscopy. Due to the enhanced ambient coercivity, the coercivity temperature stability was also substantially increased.

  9. Study of coercive measures in prisons and secure psychiatric hospitals: the views of inmates and caregivers

    Directory of Open Access Journals (Sweden)

    A. Runte-Geidel

    2014-06-01

    Full Text Available Aim: The aim of the study was to ascertain the opinions of both inmates and staff of prison establishments about the use of coercive measures justified for clinical reasons for people with mental health problems and about the need to create protocols to regulate the application of these measures. Method: These opinions were gathered in a Qualitative Study with Focus Groups (prison inmates and prison staff from the Granada Penitentiary Centre and the Alicante Penitentiary Psychiatric Hospital, both in Spain. Results: The results showed that forced medication is the most commonly used coercive measure in these institutions. The inmates did not understand and rejected the use of this measure, above all because they were poorly informed about their illness and the medication required to treat it. The staff however defended the benefits of psychiatric medicine, even when administered without the patient's consent. Conclusions: Both inmates and staff agreed that it would be useful to have a protocol regulating the use of coercive measures. The study has also identified a number of important factors that could help to reduce the need for coercive measures or make their use unnecessary.

  10. Formation and characterization of magnetic barium ferrite hollow fibers with low coercivity via co-electrospun

    Science.gov (United States)

    Liu, Gui-fang; Zhang, Zi-dong; Dang, Feng; Cheng, Chuan-bing; Hou, Chuan-xin; Liu, Si-da

    2016-08-01

    BaFe12O19 fibers and hollow fibers were successfully prepared by electrospun and co-electrospun. A very interesting result appeared in this study that hollow fibers made by co-electrospun showed low coercivity values of a few hundred oersteds, compared with the coercivity values of more than thousand oersteds for the fibers made by electrospun. So the hollow fibers with high saturation magnetization (Ms) and while comparatively low coercivity (Hc) exhibited strong magnetism and basically showed soft character. And this character for hollow fibers will lead to increase of the permeability for the samples which is favorable for impedance matching in microwave absorption. So these hollow fibers are promised to have use in a number of applications, such as switching and sensing applications, electromagnetic materials, microwave absorber.

  11. Effective anisotropy and coercivity in nanocrystalline single-phase NdFeB permanent magnetic material

    Institute of Scientific and Technical Information of China (English)

    韩广兵; 高汝伟; 冯维存; 刘汉强; 王标; 张鹏; 陈伟; 李卫; 郭永权

    2003-01-01

    The effect of exchange-coupling interaction on the effective anisotropy and its varying tendency in nanocrystalline single-phase NdFeB permanent magnetic material have been investigated. The results show that the exchange-coupling interaction between grains makes the effective anisotropy of material, Keff, decrease with the reduction of grain size. The variation of Keff is basically the same as that of coercivity. The decrease in effective anisotropy is the main reason of the reduction of coercivity for nanocrystalline single-phase NdFeB permanent magnetic material. In order to get high anisotropy and coercivity in nanocrystalline single-phase NdFeB permanent material, the grain size should be larger than 35 nm.

  12. Task force for integral test of High Energy nuclear data

    Energy Technology Data Exchange (ETDEWEB)

    Oyama, Yukio [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-11-01

    According to completion of the JENDL-High Energy file for neutron nuclear cross sections up to 50 MeV, a task force for integral test of high energy nuclear data was organized to discuss a guide line for integral test activities. A status of existing differential and integral experiments and how to perform such a test were discussed in the task force. Here the purpose and outline of the task force is explained with some future problems raised in discussion among the task member. (author)

  13. Textured Nd2Fe14B flakes with enhanced coercivity

    Energy Technology Data Exchange (ETDEWEB)

    Cui, BZ; Zheng, LY; Marinescu, M; Liu, JF; Hadjipanayis, GC

    2012-04-01

    Morphology, structure, and magnetic properties of the [001] textured Nd2Fe14B nanocrystalline flakes prepared by surfactant-assisted high energy ball milling (HEBM) and subsequent annealing were studied. These flakes have a thickness of 80-200 nm, a length of 0.5-10 mu m, and an average grain size of 10-14nm. The addition of some amount of Dy, Nd70Cu30 alloy, and an appropriate post annealing increased the coercivity H-i(c) of the Nd2Fe14B flakes. iHc was 3.7, 4.3, and 5.7 kOe for the Nd15.5Fe78.5B6, Nd14Dy1.5Fe78.5B6 and 83.3wt.% Nd14Dy1.5Fe78.5B6+16.7 wt.% Nd70Cu30 flakes prepared by HEBM for 5 h in heptane with 20 wt.% oleylamine, respectively. After annealing at 450 degrees C for 0.5h, their iHc increased to 5.1, 6.2, and 7.0 kOe, respectively. Anisotropic magnetic behavior was found in all of the as-milled and annealed flakes. Both, the thickening of Nd-rich phase at grain boundaries via diffusion of Nd70Cu30 and the surface modification of the Nd2Fe14B flake could be the main reasons for the coercivity enhancement in the as-milled and annealed Nd70Cu30-added Nd2Fe14B flakes. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3679425

  14. High-throughput screening for modulators of cellular contractile force

    CERN Document Server

    Park, Chan Young; Tambe, Dhananjay; Chen, Bohao; Lavoie, Tera; Dowell, Maria; Simeonov, Anton; Maloney, David J; Marinkovic, Aleksandar; Tschumperlin, Daniel J; Burger, Stephanie; Frykenberg, Matthew; Butler, James P; Stamer, W Daniel; Johnson, Mark; Solway, Julian; Fredberg, Jeffrey J; Krishnan, Ramaswamy

    2014-01-01

    When cellular contractile forces are central to pathophysiology, these forces comprise a logical target of therapy. Nevertheless, existing high-throughput screens are limited to upstream signaling intermediates with poorly defined relationship to such a physiological endpoint. Using cellular force as the target, here we screened libraries to identify novel drug candidates in the case of human airway smooth muscle cells in the context of asthma, and also in the case of Schlemm's canal endothelial cells in the context of glaucoma. This approach identified several drug candidates for both asthma and glaucoma. We attained rates of 1000 compounds per screening day, thus establishing a force-based cellular platform for high-throughput drug discovery.

  15. The FORCE: A highly portable parallel programming language

    Science.gov (United States)

    Jordan, Harry F.; Benten, Muhammad S.; Alaghband, Gita; Jakob, Ruediger

    1989-01-01

    Here, it is explained why the FORCE parallel programming language is easily portable among six different shared-memory microprocessors, and how a two-level macro preprocessor makes it possible to hide low level machine dependencies and to build machine-independent high level constructs on top of them. These FORCE constructs make it possible to write portable parallel programs largely independent of the number of processes and the specific shared memory multiprocessor executing them.

  16. The FORCE - A highly portable parallel programming language

    Science.gov (United States)

    Jordan, Harry F.; Benten, Muhammad S.; Alaghband, Gita; Jakob, Ruediger

    1989-01-01

    This paper explains why the FORCE parallel programming language is easily portable among six different shared-memory multiprocessors, and how a two-level macro preprocessor makes it possible to hide low-level machine dependencies and to build machine-independent high-level constructs on top of them. These FORCE constructs make it possible to write portable parallel programs largely independent of the number of processes and the specific shared-memory multiprocessor executing them.

  17. Coercivity of the Nd–Fe–B hot-deformed magnets diffusion-processed with low melting temperature glass forming alloys

    Energy Technology Data Exchange (ETDEWEB)

    Seelam, U.M.R. [Elements Strategy Initiative Center for Magnetic Materials (ESICMM), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Liu, Lihua [Elements Strategy Initiative Center for Magnetic Materials (ESICMM), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan); Akiya, T.; Sepehri-Amin, H.; Ohkubo, T. [Elements Strategy Initiative Center for Magnetic Materials (ESICMM), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Sakuma, N.; Yano, M.; Kato, A. [Advanced Material Engineering Division, Toyota Motor Corporation, Susono 410-1193 (Japan); Hono, K., E-mail: kazuhiro.hono@nims.go.jp [Elements Strategy Initiative Center for Magnetic Materials (ESICMM), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan)

    2016-08-15

    Nd- and Pr-based alloys with bulk glass forming ability and low melting temperatures, Nd{sub 60}Al{sub 10}Ni{sub 10}Cu{sub 20} and Pr{sub 60}Al{sub 10}Ni{sub 10}Cu{sub 20}, were used for grain boundary diffusion process to enhance the coercivity of hot-deformed magnets. The coercivity increment was proportional to the weight gain after the diffusion process. For the sample with 64% weight gain, the coercivity increased up to 2.8 T, which is the highest value for bulk Nd–Fe–B magnets that do not contain heavy rare-earth elements, Dy or Tb. Approximately half of the intergranular regions were amorphous and the remaining regions were crystalline. Magnetic isolation of the Nd{sub 2}Fe{sub 14}B grains by the Nd-rich amorphous/crystalline intergranular phases is attributed to the large coercivity enhancement. The coercivity does not change after the crystallization of the intergranular phase, indicating that the coercivity is not influenced by the strain at the interface with the crystalline intergranular phase. - Highlights: • Bulk-glass forming alloys were infiltrated into hot-deformed Nd–Fe–B magnets. • Very high coercivity of 2.8 T was attained without heavy rare-earth elements. • Approximately half of the inter-granular regions were amorphous. • Crystallization of amorphous intergranular phase does not change coercivity.

  18. Performance of Halbach magnet arrays with finite coercivity

    DEFF Research Database (Denmark)

    Insinga, Andrea Roberto; Bahl, C.R.H.; Bjørk, Rasmus;

    2016-01-01

    A numerical method to study the effect of finite coercivity on the Halbach cylinder geometry is presented. Despite the fact that the analytical solution available for this geometry does not set any limit to the maximum air gap flux density achievable, in real life the non-linear response...... based on a numerical approach, the presented method can be employed to analyze the demagnetization effects due to coercivity for any geometry, even when the analytical solution is not available....... of the magnetic material and the fact that the coercivity is not infinite will limit the attainable field. The presented method is able to predict when and where demagnetization will occur, and these predictions are compared with the analytical solution for the case of infinite coercivity. However, the approach...

  19. INTERPARTICLE FORCES IN HIGH TEMPERATURE FLUIDIZATION OF GELDART A PARTICLES

    Institute of Scientific and Technical Information of China (English)

    Heping Cui; Jamal Chaouki

    2004-01-01

    Previous reports and current studies show that fluidization of some Geldart A particles is enhanced by increasing bed temperature. Both the averaged local particle concentration and the particle concentration in the dense phase decrease with increasing bed temperature, at constant superficial gas velocities. However, conventional models fail to predict these changes, because the role of interparticle forces is usually neglected at different bed temperatures.Here, the interparticle forces are analyzed to explore the mechanism of gas-solid fluidization at high temperatures. Indeed, as the temperature increases, the interparticle attractive forces decrease while the interparticle repulsive forces increase. Consequently, fluidization behaviors of some Geldart A particles seem to increasingly shift from typical Geldart A towards B with increasing temperature.

  20. Force

    CERN Document Server

    Graybill, George

    2007-01-01

    Forces are at work all around us. Discover what a force is, and different kinds of forces that work on contact and at a distance. We use simple language and vocabulary to make this invisible world easy for students to ""see"" and understand. Examine how forces ""add up"" to create the total force on an object, and reinforce concepts and extend learning with sample problems.

  1. Acceleration of objects to high velocity by electromagnetic forces

    Energy Technology Data Exchange (ETDEWEB)

    Post, Richard F

    2017-02-28

    Two exemplary approaches to the acceleration of projectiles are provided. Both approaches can utilize concepts associated with the Inductrack maglev system. Either of them provides an effective means of accelerating multi-kilogram projectiles to velocities of several kilometers per second, using launchers of order 10 meters in length, thus enabling the acceleration of projectiles to high velocities by electromagnetic forces.

  2. Period Prevalence of Acute Neck Injury in US Air Force Pilots Exposed to High G Forces

    Science.gov (United States)

    1986-06-01

    unquantified clinical and epidemiological problem in exposed pilots. There has been a paucity of research in this area. This proposal is a beginning, with a...larg-e majority of pilots. Thus neck injury and its sequelae are unquantified clinical and epidemiological problems in pilots exposed to high G forces...Basal Impression 19. Cervical Ribs 20. Scoliosis , 21. Intraspongy Nuclear Hernitation 22. Significant Compression or Loss of Height of Any Vertebral

  3. High-Resolution Force Balance Analyses of Tidewater Glacier Dynamics

    Science.gov (United States)

    Enderlin, E. M.; Hamilton, G. S.; O'Neel, S.

    2015-12-01

    Changes in glacier velocity, thickness, and terminus position have been used to infer the dynamic response of tidewater glaciers to environmental perturbations, yet few analyses have attempted to quantify the associated variations in the glacier force balance. Where repeat high-resolution ice thickness and velocity estimates are available, force balance time series can be constructed to investigate the redistribution of driving and resistive forces associated with changes in terminus position. Comparative force balance analyses may, therefore, help us understand the variable dynamic response observed for glaciers in close proximity to each other. Here we construct force balance time series for Helheim Glacier, SE Greenland, and Columbia Glacier, SE Alaska, to investigate differences in dynamic sensitivity to terminus position change. The analysis relies on in situ and remotely sensed observations of ice thickness, velocity, and terminus position. Ice thickness time series are obtained from stereo satellite image-derived surface elevation and continuity-derived bed elevations that are constrained by airborne radar observations. Surface velocity time series are obtained from interferometric synthetic aperture radar (InSAR) observations. Approximately daily terminus positions are from a combination of satellite images and terrestrial time-lapse photographs. Helheim and Columbia glaciers are two of the best-studied Arctic tidewater glaciers with comprehensive high-resolution observational time series, yet we find that bed elevation uncertainties and poorly-constrained stress-coupling length estimates still hinder the analysis of spatial and temporal force balance variations. Here we use a new observationally-based method to estimate the stress-coupling length which successfully reduces noise in the derived force balance but preserves spatial variations that can be over-smoothed when estimating the stress-coupling length as a scalar function of the ice thickness

  4. High-resolution friction force microscopy under electrochemical control

    Science.gov (United States)

    Labuda, Aleksander; Paul, William; Pietrobon, Brendan; Lennox, R. Bruce; Grütter, Peter H.; Bennewitz, Roland

    2010-08-01

    We report the design and development of a friction force microscope for high-resolution studies in electrochemical environments. The design choices are motivated by the experimental requirements of atomic-scale friction measurements in liquids. The noise of the system is analyzed based on a methodology for the quantification of all the noise sources. The quantitative contribution of each noise source is analyzed in a series of lateral force measurements. Normal force detection is demonstrated in a study of the solvation potential in a confined liquid, octamethylcyclotetrasiloxane. The limitations of the timing resolution of the instrument are discussed in the context of an atomic stick-slip measurement. The instrument is capable of studying the atomic friction contrast between a bare Au(111) surface and a copper monolayer deposited at underpotential conditions in perchloric acid.

  5. High-Force Dielectric Electroactive Polymer (DEAP) membrane actuator

    Science.gov (United States)

    Hau, Steffen; York, Alexander; Seelecke, Stefan

    2016-04-01

    Energy efficiency, lightweight and scalability are key features for actuators in applications such as valves, pumps or any portable system. Dielectric electroactive Polymer (DEAP) technology is able to fulfill these requirements1 better than commonly used technology e.g. solenoids, but has limitations concerning force and stroke. However, the circular DEAP membrane actuator shows a potential increase in stroke in the mm range, when combined with an appropriate biasing mechanism2. Although, thus far, their force range is limited to the single-digit Newton range, or less3,4. This work describes how this force limit of DEAP membrane actuators can be pushed to the high double-digit Newton range and beyond. The concept for such an actuator consists of a stack of double-layered DEAPs membrane actuator combined with a biasing mechanism. These two components are combined in a novel way, which allows a compact design by integrating the biasing mechanism into the DEAP membrane actuator stack. Subsequently, the single components are manufactured, tested, and their force-displacement characteristic is documented. Utilizing this data allows assembling them into actuator systems for different applications. Two different actuators are assembled and tested (dimensions: 85x85x30mm3 (LxWxH)). The first one is able to lift 7.5kg. The second one can generate a force of 66N while acting against a spring load.

  6. Coercive and precocious sexuality as a fundamental aspect of psychopathy.

    Science.gov (United States)

    Harris, Grant T; Rice, Marnie E; Hilton, N Zoe; Lalumiére, Martin L; Quinsey, Vernon L

    2007-02-01

    Sexual behavior is closely associated with delinquency and crime. Although psychopaths, by definition, have many short-term sexual relationships, it has not been shown that sexuality is a core aspect of psychopathy. A Darwinian view of psychopathy led to the hypothesis that psychopaths have a unique sexuality involving early, frequent, and coercive sex. Our subjects were 512 sex offenders assessed on the Hare Psychopathy Checklist (PCL-R). Five variables reflecting early, frequent, and coercive sex loaded on the same principal component in exploratory factor analysis on a subset of the sample, whereas PCL-R items pertaining to adult sexual behavior did not. Confirmatory factor analysis of the remaining subjects yielded a measurement model containing three inter-correlated factors - the traditional two PCL-R factors, and coercive and precocious sexuality. Taxometric analyses gave evidence of a natural discontinuity underlying coercive and precocious sexuality. Coercive and precocious sexuality yielded statistically significant associations with other study variables predicted by the Darwinian hypothesis. The present findings are consistent with prior empirical findings and support the hypothesis that psychopathy has been a nonpathological, reproductively viable, alternate life history strategy.

  7. Strong textured SmCo5 nanoflakes with ultrahigh coercivity prepared by multistep (three steps) surfactant-assisted ball milling

    Science.gov (United States)

    Zuo, Wen-Liang; Zhao, Xin; Xiong, Jie-Fu; Zhang, Ming; Zhao, Tong-Yun; Hu, Feng-Xia; Sun, Ji-Rong; Shen, Bao-Gen

    2015-08-01

    The high coercivity of 26.2 kOe for SmCo5 nanoflakes are obtained by multistep (three steps) surfactant-assisted ball milling. The magnetic properties, phase structure and morphology are studied by VSM, XRD and SEM, respectively. The results demonstrate that the three step ball-milling can keep more complete crystallinity (relatively less defects) during the process of milling compared with one step high energy ball-milling, which enhances the texture degree and coercivity. In addition, the mechanism of coercivity are also studied by the temperature dependence of demagnetization curves for aligned SmCo5 nanoflakes/resin composite, the result indicates that the magnetization reversal could be controlled by co-existed mechanisms of pinning and nucleation.

  8. Evidences of Persuasion Coercive for Indoctrination of Jihadists Terrorists: Towards Violent Radicalization

    OpenAIRE

    Humberto M. Trujillo; Juan J. Ramírez; Ferran Alonso

    2009-01-01

    This work analyzes two processes of psychological manipulation for indoctrination and violent radicalization of jihadist terrorists in Spain: coercive persuasion and psychological group abuse. This research is based on the trustworthy information used in findings of the Spanish “Audiencia Nacional”(the Spanish High Court charged with terrorist trials) about the affidavits NOVA Operation I, II, and III. This research facilitates a reliable analysis of the possible processes of psychological ma...

  9. High-speed adaptive contact-mode atomic force microscopy imaging with near-minimum-force.

    Science.gov (United States)

    Ren, Juan; Zou, Qingze

    2014-07-01

    In this paper, an adaptive contact-mode imaging approach is proposed to replace the traditional contact-mode imaging by addressing the major concerns in both the speed and the force exerted to the sample. The speed of the traditional contact-mode imaging is largely limited by the need to maintain precision tracking of the sample topography over the entire imaged sample surface, while large image distortion and excessive probe-sample interaction force occur during high-speed imaging. In this work, first, the image distortion caused by the topography tracking error is accounted for in the topography quantification. Second, the quantified sample topography is utilized in a gradient-based optimization method to adjust the cantilever deflection set-point for each scanline closely around the minimal level needed for maintaining stable probe-sample contact, and a data-driven iterative feedforward control that utilizes a prediction of the next-line topography is integrated to the topography feeedback loop to enhance the sample topography tracking. The proposed approach is demonstrated and evaluated through imaging a calibration sample of square pitches at both high speeds (e.g., scan rate of 75 Hz and 130 Hz) and large sizes (e.g., scan size of 30 μm and 80 μm). The experimental results show that compared to the traditional constant-force contact-mode imaging, the imaging speed can be increased by over 30 folds (with the scanning speed at 13 mm/s), and the probe-sample interaction force can be reduced by more than 15% while maintaining the same image quality.

  10. Coercive agency in mission education at Lovedale Missionary Institution

    Directory of Open Access Journals (Sweden)

    Graham A. Duncan

    2004-11-01

    Full Text Available Any society and its institutions are coercive. While acknowledging the invaluable contribution made by mission education towards the development of black South Africans, Lovedale Missionary Institution exemplifies the concept of a “total institution” susceptible to the problems of power relations. Those who studied there internalized its ethos. Coercive agency encouraged adaptation to missionary ideology. However, many Lovedale students rejected the mores of the religion and education they received as they challenged and resisted the effects of the coercive agency of internalization. Institutionalisation is, by nature, resistant to change as can be seen in the policies of the respective Principals of the Institution. Consequently, black people were alienated by a process of “exclusion”. The values of justice, love and peace are appropriate tools for a new model of education in South Africa.

  11. High resolution atomic force microscopy of double-stranded RNA

    Science.gov (United States)

    Ares, Pablo; Fuentes-Perez, Maria Eugenia; Herrero-Galán, Elías; Valpuesta, José M.; Gil, Adriana; Gomez-Herrero, Julio; Moreno-Herrero, Fernando

    2016-06-01

    Double-stranded (ds) RNA mediates the suppression of specific gene expression, it is the genetic material of a number of viruses, and a key activator of the innate immune response against viral infections. The ever increasing list of roles played by dsRNA in the cell and its potential biotechnological applications over the last decade has raised an interest for the characterization of its mechanical properties and structure, and that includes approaches using Atomic Force Microscopy (AFM) and other single-molecule techniques. Recent reports have resolved the structure of dsDNA with AFM at unprecedented resolution. However, an equivalent study with dsRNA is still lacking. Here, we have visualized the double helix of dsRNA under near-physiological conditions and at sufficient resolution to resolve the A-form sub-helical pitch periodicity. We have employed different high-sensitive force-detection methods and obtained images with similar spatial resolution. Therefore, we show here that the limiting factors for high-resolution AFM imaging of soft materials in liquid medium are, rather than the imaging mode, the force between the tip and the sample and the sharpness of the tip apex.Double-stranded (ds) RNA mediates the suppression of specific gene expression, it is the genetic material of a number of viruses, and a key activator of the innate immune response against viral infections. The ever increasing list of roles played by dsRNA in the cell and its potential biotechnological applications over the last decade has raised an interest for the characterization of its mechanical properties and structure, and that includes approaches using Atomic Force Microscopy (AFM) and other single-molecule techniques. Recent reports have resolved the structure of dsDNA with AFM at unprecedented resolution. However, an equivalent study with dsRNA is still lacking. Here, we have visualized the double helix of dsRNA under near-physiological conditions and at sufficient resolution to

  12. Nuclear Forces and High-Performance Computing: The Perfect Match

    Energy Technology Data Exchange (ETDEWEB)

    Luu, T; Walker-Loud, A

    2009-06-12

    High-performance computing is now enabling the calculation of certain nuclear interaction parameters directly from Quantum Chromodynamics, the quantum field theory that governs the behavior of quarks and gluons and is ultimately responsible for the nuclear strong force. We briefly describe the state of the field and describe how progress in this field will impact the greater nuclear physics community. We give estimates of computational requirements needed to obtain certain milestones and describe the scientific and computational challenges of this field.

  13. Temperature Dependence of Exchange Bias and Coercivity in Ferromagnetic Layer Coupled with Polycrystalline Antiferromagnetic Layer

    Institute of Scientific and Technical Information of China (English)

    ZHAO Jin-Wei; HU Jing-Guo; CHEN Guang

    2004-01-01

    The temperature dependence of exchange bias and coercivity in a ferromagnetic layer coupled with an antiferromagnetic layer is discussed.In this model,the temperature dependence comes from the thermal instability of the system states and the temperature modulated relative magnetic parameters.Morever,the thermal fluctuation of orientations of easy axes of antiferromagnetic grains at preparing has been considered.From the present model,the experimental results can be illustrated qualitatively for available magnetic parameters.Based on our discussion,we can conclude that soft ferromagnetic layer coupled by hard antiferromagnetic layer may be very applicable to design magnetic devices.In special exchange coupling,we can get high exchange bias and low coercivity almost independent of temperature for proper temperature ranges.

  14. Casimir force between δ -δ' mirrors transparent at high frequencies

    Science.gov (United States)

    Braga, Alessandra N.; Silva, Jeferson Danilo L.; Alves, Danilo T.

    2016-12-01

    We investigate, in the context of a real massless scalar field in 1 +1 dimensions, models of partially reflecting mirrors simulated by Dirac δ -δ' point interactions. In the literature, these models do not exhibit full transparency at high frequencies. In order to provide a more realistic feature for these models, we propose a modified δ -δ' point interaction that enables full transparency in the limit of high frequencies. Taking this modified δ -δ' model into account, we investigate the Casimir force, comparing our results with those found in the literature.

  15. Self-organization and FORC-based magnetic characterization of ultra-high aspect ratio epitaxial Co nanostrips produced by oblique deposition on an ordered step-bunched silicon surface

    Science.gov (United States)

    Ognev, A. V.; Ermakov, K. S.; Samardak, A. Yu; Kozlov, A. G.; Sukovatitsina, E. V.; Davydenko, A. V.; Chebotkevich, L. A.; Stancu, A.; Samardak, A. S.

    2017-03-01

    Further development of microelectronics requires novel or improved technological approaches for device nanofabrication and functional properties characterization. In this paper, we studied the crystal structure and magnetic properties of epitaxial Co nanostrips with the average width of 32.6, 45.3, and 62.6 nm grown on a step-bunched Si(111)5.55 × 5.55-Cu/Cu surface. Technological conditions, under which the ultra-high aspect ratio (˜104) structurally solid, straight nanostrips of hcp-Co with crystallographic axis [0001] oriented along their long side can be grown, were determined. The dependence of the coercive force on the width of the nanostrips was demonstrated. Magnetization reversal through the transverse domain-wall nucleation and propagation in a Co nanostrip was defined with an analytical approach based on the Stoner-Wohlfarth model. Using the first-order reversal curve method, we analyzed the effect of nanostrip uniformity degree on magnetic behavior and the influence of the magnetostatic interactions on the coercive force of individual nanostrips.

  16. Nonlinear geometric scaling of coercivity in a three-dimensional nanoscale analog of spin ice

    Science.gov (United States)

    Shishkin, I. S.; Mistonov, A. A.; Dubitskiy, I. S.; Grigoryeva, N. A.; Menzel, D.; Grigoriev, S. V.

    2016-08-01

    Magnetization hysteresis loops of a three-dimensional nanoscale analog of spin ice based on the nickel inverse opal-like structure (IOLS) have been studied at room temperature. The samples are produced by filling nickel into the voids of artificial opal-like films. The spin ice behavior is induced by tetrahedral elements within the IOLS, which have the same arrangement of magnetic moments as a spin ice. The thickness of the films vary from a two-dimensional, i.e., single-layered, antidot array to a three-dimensional, i.e., multilayered, structure. The coercive force, the saturation, and the irreversibility field have been measured in dependence of the thickness of the IOLS for in-plane and out-of-plane applied fields. The irreversibility and saturation fields change abruptly from the antidot array to the three-dimensional IOLS and remain constant upon further increase of the number of layers n . The coercive force Hc seems to increase logarithmically with increasing n as Hc=Hc 0+α ln(n +1 ) . The logarithmic law implies the avalanchelike remagnetization of anisotropic structural elements connecting tetrahedral and cubic nodes in the IOLS. We conclude that the "ice rule" is the base of mechanism regulating this process.

  17. 5 CFR 950.108 - Preventing coercive activity.

    Science.gov (United States)

    2010-01-01

    ... giving is fundamental to Federal fundraising activities. Actions that do not allow free choices or create... or to keep them confidential, are contrary to Federal fundraising policy. Activities contrary to the non-coercive intent of Federal fundraising policy are not permitted in campaigns. They include,...

  18. High resolution, large deformation 3D traction force microscopy.

    Science.gov (United States)

    Toyjanova, Jennet; Bar-Kochba, Eyal; López-Fagundo, Cristina; Reichner, Jonathan; Hoffman-Kim, Diane; Franck, Christian

    2014-01-01

    Traction Force Microscopy (TFM) is a powerful approach for quantifying cell-material interactions that over the last two decades has contributed significantly to our understanding of cellular mechanosensing and mechanotransduction. In addition, recent advances in three-dimensional (3D) imaging and traction force analysis (3D TFM) have highlighted the significance of the third dimension in influencing various cellular processes. Yet irrespective of dimensionality, almost all TFM approaches have relied on a linear elastic theory framework to calculate cell surface tractions. Here we present a new high resolution 3D TFM algorithm which utilizes a large deformation formulation to quantify cellular displacement fields with unprecedented resolution. The results feature some of the first experimental evidence that cells are indeed capable of exerting large material deformations, which require the formulation of a new theoretical TFM framework to accurately calculate the traction forces. Based on our previous 3D TFM technique, we reformulate our approach to accurately account for large material deformation and quantitatively contrast and compare both linear and large deformation frameworks as a function of the applied cell deformation. Particular attention is paid in estimating the accuracy penalty associated with utilizing a traditional linear elastic approach in the presence of large deformation gradients.

  19. High resolution, large deformation 3D traction force microscopy.

    Directory of Open Access Journals (Sweden)

    Jennet Toyjanova

    Full Text Available Traction Force Microscopy (TFM is a powerful approach for quantifying cell-material interactions that over the last two decades has contributed significantly to our understanding of cellular mechanosensing and mechanotransduction. In addition, recent advances in three-dimensional (3D imaging and traction force analysis (3D TFM have highlighted the significance of the third dimension in influencing various cellular processes. Yet irrespective of dimensionality, almost all TFM approaches have relied on a linear elastic theory framework to calculate cell surface tractions. Here we present a new high resolution 3D TFM algorithm which utilizes a large deformation formulation to quantify cellular displacement fields with unprecedented resolution. The results feature some of the first experimental evidence that cells are indeed capable of exerting large material deformations, which require the formulation of a new theoretical TFM framework to accurately calculate the traction forces. Based on our previous 3D TFM technique, we reformulate our approach to accurately account for large material deformation and quantitatively contrast and compare both linear and large deformation frameworks as a function of the applied cell deformation. Particular attention is paid in estimating the accuracy penalty associated with utilizing a traditional linear elastic approach in the presence of large deformation gradients.

  20. "Coercion Experience Scale" (CES - validation of a questionnaire on coercive measures

    Directory of Open Access Journals (Sweden)

    Flammer Erich

    2010-01-01

    Full Text Available Abstract Background Although the authors of a Cochrane Review on seclusion and mechanical restraint concluded that "there is a surprising and shocking lack of published trials" on coercive interventions in psychiatry, there are only few instruments that can be applied in trials. Furthermore, as main outcome variable safety, psychopathological symptoms, and duration of an intervention cannot meet the demand to indicate subjective suffering and impact relevant to posttraumatic stress syndromes. An instrument used in controlled trials should assess the patients' subjective experiences, needs to be applicable to more than one intervention in order to compare different coercive measures and has to account for the specific psychiatric context. Methods The primary version of the questionnaire comprised 44 items, nine items on restrictions to human rights, developed on a clinical basis, and 35 items on stressors, derived from patients' comments during the pilot phase of the study. An exploratory factor analysis (EFA using principal axis factoring (PAF was carried out. The resulting factors were orthogonally rotated via VARIMAX procedure. Items with factor loadings less than .50 were eliminated. The reliability of the subscales was assessed by calculating Cronbach. Results Data of 102 patients was analysed. The analysis yielded six factors which were entitled "Humiliation", "Physical adverse effects", "Separation", "Negative environment", "Fear" and "Coercion". These six factors explained 54.5% of the total variance. Cronbach alpha ranged from .67 to .93, which can be interpreted as a high internal consistency. Convergent and discriminant validity yielded both highly significant results (r = .79, p Conclusions The "Coercion Experience Scale" is an instrument to measure the psychological impact during psychiatric coercive interventions. Its psychometric properties showed satisfying reliability and validity. For purposes of research it can be used to

  1. Soft Pneumatic Actuator Fascicles for High Force and Reliability

    Science.gov (United States)

    Robertson, Matthew A.; Sadeghi, Hamed; Florez, Juan Manuel

    2017-01-01

    Abstract Soft pneumatic actuators (SPAs) are found in mobile robots, assistive wearable devices, and rehabilitative technologies. While soft actuators have been one of the most crucial elements of technology leading the development of the soft robotics field, they fall short of force output and bandwidth requirements for many tasks. In addition, other general problems remain open, including robustness, controllability, and repeatability. The SPA-pack architecture presented here aims to satisfy these standards of reliability crucial to the field of soft robotics, while also improving the basic performance capabilities of SPAs by borrowing advantages leveraged ubiquitously in biology; namely, the structured parallel arrangement of lower power actuators to form the basis of a larger and more powerful actuator module. An SPA-pack module consisting of a number of smaller SPAs will be studied using an analytical model and physical prototype. Experimental measurements show an SPA pack to generate over 112 N linear force, while the model indicates the benefit of parallel actuator grouping over a geometrically equivalent single SPA scale as an increasing function of the number of individual actuators in the group. For a module of four actuators, a 23% increase in force production over a volumetrically equivalent single SPA is predicted and validated, while further gains appear possible up to 50%. These findings affirm the advantage of utilizing a fascicle structure for high-performance soft robotic applications over existing monolithic SPA designs. An example of high-performance soft robotic platform will be presented to demonstrate the capability of SPA-pack modules in a complete and functional system. PMID:28289573

  2. High resolution magnetic imaging: MicroSQUID Force Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hasselbach, K; Ladam, C; Dolocan, V O; Hykel, D; Crozes, T [Institut Neel, CNRS et Universite Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9 (France); Schuster, K [Institut de RadioAstronomie Millimetrique 300 rue de la Piscine, Domaine Universitaire F-38406 Saint Martin d' Heres (France); Mailly, D [Laboratoire de Photonique et de Nanostructures, CNRS, Site Alcatel de Marcoussis Route de Nozay F-91460 Marcoussis (France)], E-mail: klaus.hasselbach@grenoble.cnrs.fr

    2008-02-01

    Magnetic imaging at the micrometer scale with high sensitivity is a challenge difficult to be met. Magnetic force microscopy has a very high spatial resolution but is limited in magnetic resolution. Hall probe microscopy is very powerful but sensor fabrication at the one micron scale is difficult and effects due to discreteness of charge appear in the form of significant 1/f noise. SQUID microscopy is very powerful, having high magnetic resolution, but spatial resolution is usually of the order of 10 {mu}m. The difficulties lay mostly in an efficient way to couple flux to the sensor. The only way to improve spatial resolution is to place the probe close to the very edge of the support, thus maximising coupling and spatial resolution. If there has been found a way to bring close the tip, there must be also found a reliable a way to maintain distance during scanning. We want to present recent improvements on scanning microsquid microscopy: Namely the improved fabrication of microSQUID tips using silicon micro machining and the precise positioning of the micrometer diameter microSQUID loop by electron beam lithography. The microSQUID is a microbridge DC SQUID, with two opposite microbridges. The constrictions are patterned by high-resolution e-beam lithography and have a width of 20 nm and a length of about 100 nm. The distance control during scanning is obtained by integrating the microSQUID sensor with a piezoelectric tuning fork acting as a force sensor allowing to control height and even topographic imaging. The detector is placed in a custom built near field microscope and the sample temperature can be varied between 0.1 Kelvin and 10 K. The microscope is used to study magnetic flux structures in unconventional superconductors and will be used to observe thermal domains in superconducting detectors in the voltage state.

  3. Measurement of Metal Cutting Forces at High Speeds

    Science.gov (United States)

    Princehouse, David W.

    1996-03-01

    Proposed numerically-controlled milling machines will cut aluminum alloys with cutter tip speeds of up to 130 m/s (300 MPH). There are a variety of challenging technical problems to be solved--high power density motors, inverters, cutter/machine dynamics, servo control systems--and compelling reasons to do so. We measured time-varying cutting forces at these tip speeds with a 25.4-cm (10-in) diameter cutter turning at rates up to 167 Hz (10,000 RPM.) We took special care to measure and compensate for the dynamic response of the force transducer (a three-axis quartz-crystal milling dynamometer), extending the useful bandwidth of the measurements well into the mechanical resonances of the dynamometer. We instrumented a production milling machine on the factory floor and processed megabytes of data, obtaining results minutes after a cut was made. This case study shows how a physicist's background in mechanics, instrumentation, signal processing, and computing hardware and software can help advance the state of the art in aerospace manufacturing.

  4. Scientific and conceptual flaws of coercive treatment models in addiction.

    Science.gov (United States)

    Uusitalo, Susanne; van der Eijk, Yvette

    2016-01-01

    In conceptual debates on addiction, neurobiological research has been used to support the idea that addicted drug users lack control over their addiction-related actions. In some interpretations, this has led to coercive treatment models, in which, the purpose is to 'restore' control. However, neurobiological studies that go beyond what is typically presented in conceptual debates paint a different story. In particular, they indicate that though addiction has neurobiological manifestations that make the addictive behaviour difficult to control, it is possible for individuals to reverse these manifestations through their own efforts. Thus, addicted individuals should not be considered incapable of making choices voluntarily, simply on the basis that addiction has neurobiological manifestations, and coercive treatment models of addiction should be reconsidered in this respect.

  5. Ultrafast Coercivity Dynamics in GaMnAs

    Science.gov (United States)

    Hall, Kimberley; Zahn, Jeremy; March, Samuel; Liu, Xinyu; Furdyna, Jacek

    2008-03-01

    The hole-mediated ferromagnetism in III-Mn-V diluted magnetic semiconductors opens up a whole host of possibilities for future multifunctional devices. Control over the ferromagnetic properties in these materials through hole density modulation has been demonstrated using electrical gates [1] and CW optical excitation [2], and more recently using femtosecond optical excitation [3,4]. Using time-resolved magneto-optical Kerr Effect spectroscopy, we have measured the magnetization and coercivity dynamics in GaMnAs. Our experiments reveal a subpicosecond ferromagnetic to paramagnetic phase transition followed by coercivity enhancement on longer time scales. Our findings are promising for possible applications in ultrafast, nonthermal magneto-optical recording using diluted magnetic semiconductors. [1] H. Ohno et al., Nature 408, 944 (2000). [2] S. Koshihara et al., Phys. Rev. Lett. 78, 4617 (1997). [3] J. Wang et al., Phys. Rev. Lett. 95, 167401 (2005). [4] J. Wang et al., Phys. Rev. Lett. 98, 217401 (2007).

  6. Coercive Disarmament, Demobilization and Reintegration (DDR): Can It Be Successful

    Science.gov (United States)

    2008-03-01

    DEMOBLIZATION AND REINTEGRATION (DDR): CAN IT BE SUCCESSFUL ? by Shane R. Doolan March 2008 Thesis Co-Advisors: Jeanne Giraldo...DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE Coercive Disarmament Demobilization and Reintegration (DDR): Can it be Successful ? 6. AUTHOR(S...DISARMAMENT DEMOBILIZATION AND REINTEGRATION (DDR): CAN IT BE SUCCESSFUL ? Shane R. Doolan Captain, United States Army B.S., Police Studies, John Jay

  7. Quadrature phase interferometer for high resolution force spectroscopy

    CERN Document Server

    Paolino, Pierdomenico; Bellon, Ludovic

    2013-01-01

    In this article, we present a deflection measurement setup for Atomic Force Microscopy (AFM). It is based on a quadrature phase differential interferometer: we measure the optical path difference between a laser beam reflecting above the cantilever tip and a reference beam reflecting on the static base of the sensor. A design with very low environmental susceptibility and another allowing calibrated measurements on a wide spectral range are described. Both enable a very high resolution (down to $2.5E-15 m/sqrt{Hz}$), illustrated by a thermal noise measurement on an AFM cantilever. A quick review shows that our precision is equaling or outperforming the best results reported in the literature, but for a much larger deflection range, up to a few microns.

  8. Miniature High-Force, Long-Stroke SMA Linear Actuators

    Science.gov (United States)

    Cummin, Mark A.; Donakowski, William; Cohen, Howard

    2008-01-01

    Improved long-stroke shape-memory-alloy (SMA) linear actuators are being developed to exert significantly higher forces and operate at higher activation temperatures than do prior SMA actuators. In these actuators, long linear strokes are achieved through the principle of displacement multiplication, according to which there are multiple stages, each intermediate stage being connected by straight SMA wire segments to the next stage so that relative motions of stages are additive toward the final stage, which is the output stage. Prior SMA actuators typically include polymer housings or shells, steel or aluminum stages, and polymer pads between successive stages of displacement-multiplication assemblies. Typical output forces of prior SMA actuators range from 10 to 20 N, and typical strokes range from 0.5 to 1.5 cm. An important disadvantage of prior SMA wire actuators is relatively low cycle speed, which is related to actuation temperature as follows: The SMA wires in prior SMA actuators are typically made of a durable nickel/titanium alloy that has a shape-memory activation temperature of 80 C. An SMA wire can be heated quickly from below to above its activation temperature to obtain a stroke in one direction, but must then be allowed to cool to somewhat below its activation temperature (typically, less than or equal to 60 C in the case of an activation temperature of 80 C) to obtain a stroke in the opposite direction (return stroke). At typical ambient temperatures, cooling times are of the order of several seconds. Cooling times thus limit cycle speeds. Wires made of SMA alloys having significantly higher activation temperatures [denoted ultra-high-temperature (UHT) SMA alloys] cool to the required lower return-stroke temperatures more rapidly, making it possible to increase cycle speeds. The present development is motivated by a need, in some applications (especially aeronautical and space-flight applications) for SMA actuators that exert higher forces, operate

  9. A harsh parenting team? Maternal reports of coparenting and coercive parenting interact in association with children's disruptive behaviour.

    Science.gov (United States)

    Latham, Rachel M; Mark, Katharine M; Oliver, Bonamy R

    2017-05-01

    Parenting and coparenting are both important for children's adjustment, but their interaction has been little explored. Using a longitudinal design and considering two children per family, we investigated mothers' and fathers' perceptions of coparenting as moderators of associations between their coercive parenting and children's disruptive behaviour. Mothers and fathers from 106 'intact' families were included from the Twins, Family and Behaviour study. At Time 1 (Mchild age  = 3 years 11 months, SDchild age  = 4.44 months) parents reported on their coercive parenting and children's disruptive behaviour via questionnaire; at Time 2 (Mchild age  = 4 years 8 months, SDchild age  = 4.44 months) perceptions of coparenting and the marital relationship were collected by telephone interview. Questionnaire-based reports of children's disruptive behaviour were collected at follow-up (Mchild age  = 5 years 11 months, SDchild age  = 5.52 months). Multilevel modelling was used to examine child-specific and family-wide effects. Conservative multilevel models including both maternal and paternal perceptions demonstrated that maternal perceptions of coparenting and overall coercive parenting interacted in their prediction of parent-reported child disruptive behaviour. Specifically, accounting for perceived marital quality, behavioural stability, and fathers' perceptions, only in the context of perceived higher quality coparenting was there a positive association between mother-reported overall coercive parenting and children's disruptive behaviour at follow-up. When combined with highly coercive parenting, maternal perceptions of high quality coparenting may be detrimental for children's adjustment. © 2016 Association for Child and Adolescent Mental Health.

  10. The Properties of Light Pressure Force with High Order in Laser Fields

    Institute of Scientific and Technical Information of China (English)

    陈险峰; 方建兴; 朱士群

    2002-01-01

    In this paper, the light pressure force in low and high intensity laser fields is derived. The exact numerical results of forces Fn∥(n=0,1,2,3,4,5,6…) through the matrix continued fraction method are presented. At low intensity field (G=1), the spatially averaged force F0∥ gives a cooling effect at the negative detuning. At high intensity (G=64), the effects of the forces with higher order (n≥2) appear and the contributes of the forces with odd or even order are opposite. It is great different from no high order force at low intensity.

  11. [Architectural modernization of psychiatric hospitals influences the use of coercive measures].

    Science.gov (United States)

    Rohe, T; Dresler, T; Stuhlinger, M; Weber, M; Strittmatter, T; Fallgatter, A J

    2017-01-01

    Coercive measures are widely applied in psychiatric hospitals as a last resort to prevent patients seriously harming themselves or others, with negative psychological and somatic consequences for those affected. In a naturalistic observational study it was investigated whether relocation of the structural milieu of a psychiatric hospital to an architectonically improved new building influenced the application of coercive measures. The frequency and duration of coercive measures (e.g. fixation, coercive medication and preventive restraints) were routinely documented and compared in the periods before and after the relocation. After the relocation the utilization of coercive measures was significantly reduced by 48-84 %. Despite the limitations of the study design the results suggest that the architectural improvements reduced the application of coercive measures. It is speculated that the positive structural milieu enhanced the well-being of patients and staff and their social relations, which in turn prevented coercive measures.

  12. Response of thermosphere density to high-latitude forcing

    Science.gov (United States)

    Yamazaki, Y.; Kosch, M. J.; Vickers, H.; Sutton, E. K.; Ogawa, Y.

    2014-12-01

    Solar wind-magnetospheric disturbances cause enhancements in the energy input to the high-latitude upper atmosphere through particle precipitation and Joule heating. As the upper atmosphere is heated and expanded during geomagnetically disturbed periods, the neutral density in the thermosphere increases at a fixed altitude. Conversely, the thermosphere contracts during the recovery phase of the disturbance, resulting in a decrease of the density. The main objectives of this study are (1) to determine the morphology of the global thermospheric density response to high-latitude forcing, and (2) to determine the recovery speed of the thermosphere density after geomagnetic disturbances. For (1), we use thermospheric density data measured by the Challenging Minisatellite Payload (CHAMP) satellite during 2000-2010. It is demonstrated that the density enhancement during disturbed periods occurs first in the dayside cusp region, and the density at other regions slowly follows it. The reverse process is observed when geomagnetic activity ceases; the density enhancement in the cusp region fades away first, then the global density slowly goes back to the quiet level. For (2), we analyze EISCAT Svalbard radar and Tromso UHF radar data to estimate thermospheric densities during the recovery phase of geomagnetic disturbances. We attempt to determine the time constant for the density recovery both inside and outside the cusp region.

  13. Cryogenic Impinging Jets Subjected to High Frequency Transverse Acoustic Forcing in a High Pressure Environment

    Science.gov (United States)

    2016-07-27

    Forcing in a High Pressure Environment 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Mario Roa, S. Alex Schumaker...disclose the work. PA Clearance Number: 16308 Clearance Date: 6/17/2016 13. SUPPLEMENTARY NOTES For presentation at AIAA Propulsion and Energy; Salt...the coupling between the impact waves created by impinging jets and high frequency acoustic pressure perturbations. High speed, backlit imaging was

  14. Grain structure dependence of coercivity in thin films

    CERN Document Server

    Bachleitner-Hofmann, Anton; Satz, Armin; Suess, Dieter

    2016-01-01

    We investigated coercive fields of 200nm x 1200nm x 5nm rectangular nanocrystalline thin films as a function of grain size D using finite elements simulations. To this end, we created granular finite element models with grain sizes ranging from 5nm to 60nm, and performed micromagnetic hysteresis calculations along the y-axis (easy direction) as well as along the x-axis (hard direction). We then used an extended Random Anisotropy model to interpret the results and to illustrate the interplay of random and uniform anisotropy in thin films.

  15. Coercive Region-level Registration for Multi-modal Images

    CERN Document Server

    Chen, Yu-Hui; Newstadt, Gregory; Simmons, Jeffrey; hero, Alfred

    2015-01-01

    We propose a coercive approach to simultaneously register and segment multi-modal images which share similar spatial structure. Registration is done at the region level to facilitate data fusion while avoiding the need for interpolation. The algorithm performs alternating minimization of an objective function informed by statistical models for pixel values in different modalities. Hypothesis tests are developed to determine whether to refine segmentations by splitting regions. We demonstrate that our approach has significantly better performance than the state-of-the-art registration and segmentation methods on microscopy images.

  16. The differential effect of metabolic alkalosis on maximum force and rate of force development during repeated, high-intensity cycling.

    Science.gov (United States)

    Siegler, Jason C; Marshall, Paul W M; Raftry, Sean; Brooks, Cristy; Dowswell, Ben; Romero, Rick; Green, Simon

    2013-12-01

    The purpose of this investigation was to assess the influence of sodium bicarbonate supplementation on maximal force production, rate of force development (RFD), and muscle recruitment during repeated bouts of high-intensity cycling. Ten male and female (n = 10) subjects completed two fixed-cadence, high-intensity cycling trials. Each trial consisted of a series of 30-s efforts at 120% peak power output (maximum graded test) that were interspersed with 30-s recovery periods until task failure. Prior to each trial, subjects consumed 0.3 g/kg sodium bicarbonate (ALK) or placebo (PLA). Maximal voluntary contractions were performed immediately after each 30-s effort. Maximal force (F max) was calculated as the greatest force recorded over a 25-ms period throughout the entire contraction duration while maximal RFD (RFD max) was calculated as the greatest 10-ms average slope throughout that same contraction. F max declined similarly in both the ALK and PLA conditions, with baseline values (ALK: 1,226 ± 393 N; PLA: 1,222 ± 369 N) declining nearly 295 ± 54 N [95% confidence interval (CI) = 84-508 N; P force vs. maximum rate of force development during a whole body fatiguing task.

  17. Ion drag force in plasmas at high electronegativity.

    Science.gov (United States)

    Denysenko, I; Yu, M Y; Stenflo, L; Xu, S

    2005-07-01

    The electric as well as the positive- and negative-ion drag forces on an isolated dust grain in an electronegative plasma are studied for large negative-ion densities, when the negative ions are not Boltzmann distributed. The investigation is carried out for submicrometer dust particles, so that the theory of Coulomb scattering is applicable for describing ion-dust interaction. Among the forces acting on the dust grain, the negative-ion drag force is found to be important. The effects of the negative-ion density, neutral-gas pressure, and dust-grain size on the forces are also considered. It is shown that by increasing the density of the negative ions one can effectively manipulate the dust grains. Our results imply that both dust voids and balls can be formed.

  18. Precipitation-Strengthened, High-Temperature, High-Force Shape Memory Alloys

    Science.gov (United States)

    Noebe, Ronald D.; Draper, Susan L.; Nathal, Michael V.; Crombie, Edwin A.

    2008-01-01

    Shape memory alloys (SMAs) are an enabling component in the development of compact, lightweight, durable, high-force actuation systems particularly for use where hydraulics or electrical motors are not practical. However, commercial shape memory alloys based on NiTi are only suitable for applications near room temperature, due to their relatively low transformation temperatures, while many potential applications require higher temperature capability. Consequently, a family of (Ni,Pt)(sub 1-x)Ti(sub x) shape memory alloys with Ti concentrations ranging from about 15 to 25 at.% have been developed for applications in which there are requirements for SMA actuators to exert high forces at operating temperatures higher than those of conventional binary NiTi SMAs. These alloys can be heat treated in the range of 500 C to produce a series of fine precipitate phases that increase the strength of alloy while maintaining a high transformation temperature, even in Ti-lean compositions.

  19. Fundamental High-Speed Limits in Single-Molecule, Single-Cell, and Nanoscale Force Spectroscopies

    Science.gov (United States)

    2016-01-01

    Force spectroscopy is enhancing our understanding of single-biomolecule, single-cell, and nanoscale mechanics. Force spectroscopy postulates the proportionality between the interaction force and the instantaneous probe deflection. By studying the probe dynamics, we demonstrate that the total force acting on the probe has three different components: the interaction, the hydrodynamic, and the inertial. The amplitudes of those components depend on the ratio between the resonant frequency and the frequency at which the data are measured. A force–distance curve provides a faithful measurement of the interaction force between two molecules when the inertial and hydrodynamic components are negligible. Otherwise, force spectroscopy measurements will underestimate the value of unbinding forces. Neglecting the above force components requires the use of frequency ratios in the 50–500 range. These ratios will limit the use of high-speed methods in force spectroscopy. The theory is supported by numerical simulations. PMID:27359243

  20. A battered women's movement perspective of Coercive Control.

    Science.gov (United States)

    Arnold, Gretchen

    2009-12-01

    In Coercive Control, Evan Stark calls on battered women's activists to reorient their understanding of abusive relationships. Rather than being primarily about physical violence, he maintains, domestic violence is better conceptualized as men's attempts to destroy women's autonomy and reinstate patriarchy in intimate relationships. His analysis suggests important changes to defending battered women in court, modifications to the kinds of support services the movement provides for battered women, and changes in the laws and law enforcement regarding battering. Stark also maintains that, to end coercive control, the battered women's movement must renew its commitment not only to ensuring the safety of individual women but also to attaining the feminist goal of substantive freedom and equality for women in both public and private life. I contend that Stark's reframing of woman abuse is useful for battered women's advocates and may, in some cases but not in others, lead to more effective practices in battered women's programs. At the same time, it is likely to complicate activists' efforts to mobilize public opinion, resources, and public policy to address the problem of woman abuse.

  1. Scaling of coercivity in a 3d random anisotropy model

    Energy Technology Data Exchange (ETDEWEB)

    Proctor, T.C., E-mail: proctortc@gmail.com; Chudnovsky, E.M., E-mail: EUGENE.CHUDNOVSKY@lehman.cuny.edu; Garanin, D.A.

    2015-06-15

    The random-anisotropy Heisenberg model is numerically studied on lattices containing over ten million spins. The study is focused on hysteresis and metastability due to topological defects, and is relevant to magnetic properties of amorphous and sintered magnets. We are interested in the limit when ferromagnetic correlations extend beyond the size of the grain inside which the magnetic anisotropy axes are correlated. In that limit the coercive field computed numerically roughly scales as the fourth power of the random anisotropy strength and as the sixth power of the grain size. Theoretical arguments are presented that provide an explanation of numerical results. Our findings should be helpful for designing amorphous and nanosintered materials with desired magnetic properties. - Highlights: • We study the random-anisotropy model on lattices containing up to ten million spins. • Irreversible behavior due to topological defects (hedgehogs) is elucidated. • Hysteresis loop area scales as the fourth power of the random anisotropy strength. • In nanosintered magnets the coercivity scales as the six power of the grain size.

  2. CONTEMPORARY U.S. FEDERALISM: COERCIVE CHANGE WITH COOPERATIVE CONTINUITY

    Directory of Open Access Journals (Sweden)

    John Kincaid

    2008-04-01

    Full Text Available Contemporary U.S. federalism is a complex mixture of coercive, cooperative,and dual elements. Constitutionally and politically, the federal system hasbecome coercive because there has been a vast expansion of federal-governmentpower over the states since the 1960s. This coercion involves, amongother things, increased regulations attached to federal grants-in-aid, mandatesimposed on the states, and federal preemptions of state powers. Neitherthe U.S. Senate nor the Supreme Court or the president serves as a protectorof state powers today. Administratively, however, intergovernmentalrelations between the federal, state, and local governments remain highlycooperative. State and local officials implement and comply with federalgovernmentpolicies and occasionally obtain concessions and adjustmentsin implementation from federal officials. At the same time, the states stillretain considerable residual powers, which, along with their substantial fiscalcapacities, allow them to engage in independent and innovative policymakingin a large number of policy fields. State policy activism in suchfields as consumer protection, criminal justice, environmental protection,health care, and worker rights has, in part, been a reaction against coercivefederalism and, in turn, has often highlighted weaknesses in comparablefederal-government policies.

  3. Toward a Standard Approach to Operationalizing Coercive Control and Classifying Violence Types.

    Science.gov (United States)

    Hardesty, Jennifer L; Crossman, Kimberly A; Haselschwerdt, Megan L; Raffaelli, Marcela; Ogolsky, Brian G; Johnson, Michael P

    2015-08-01

    Coercive control is central to distinguishing between Johnson's (2008) 2 main types of intimate partner violence: (a) coercive controlling violence and (b) situational couple violence. Approaches to assessing coercive control, however, have been inconsistent. Using data from 2 projects involving divorcing mothers (N = 190), the authors compared common analytic strategies for operationalizing coercive control and classifying types of violence. The results establish advantages to measuring coercive control in terms of frequency versus number of tactics, illustrate the use of both hierarchical and k-means clustering methods to identify patterns of coercive control and evaluate clustering solutions, and offer a suggested cutoff for classifying violence types in general samples of separated women using the Dominance-Isolation subscale of the widely used Psychological Maltreatment of Women Inventory (Tolman, 1992). Finally, the authors demonstrate associations between types of violence and theoretically relevant variables, including frequency and severity of violence, harassment and violence after separation, fear, and perceived threat.

  4. New linear piezomotors for high-force precise positioning applications

    Science.gov (United States)

    Le Letty, Ronan; Claeyssen, Frank; Barillot, Francois; Six, Marc F.; Bouchilloux, Philippe

    1998-07-01

    Piezomotors are an increasingly competitive alternative to electromagnetic stepper motors, especially in applications where large bandwidths and/or precise positioning control are desired. Piezomotors use a combination of electromechanical and frictional forces and, compared to conventional electromagnetic motors, have the advantages that no power supply is required to maintain the motor in position and no lubrication is necessary in the device. The operating principle of these motors relies on the use of an ultrasonic vibration, which is created via the piezoelectric effect (at resonance in most cases), in order to generate vibration forces at the `stator/rotor' contact interface. A mechanical preload is also applied at this contact interface and is responsible for the motor's holding force at rest. To meet the specifications of an aerospace application, we developed a new design of Linear PiezoMotors (LPMs). The first prototype we built shows very promising results, and makes the LPM a serious candidate to replace conventional stepper motors. The LPM features the following characteristics: a standing force of 100 N, a blocked force of 37 N, a maximum actuation speed of 23 mm/s, a maximum run of 10 mm, a mass of 500 g, an electrical power of 2.2 W, and a position accuracy superior to 1 micrometers . To our knowledge, the driving force delivered by the LPM has never before been achieved in resonant devices. This paper describes the physical operating principles of the LPM, as well as the modeling tools and experimental techniques we used for its development. Several implementation schemes are also presented and show the wide range of possible applications offered by the linear piezomotor.

  5. Structure and coercivity of nanocrystalline Fe–Si–B–Nb–Cu alloys

    Indian Academy of Sciences (India)

    B Majumdar; D Akhtar

    2005-08-01

    Crystallization behaviour and magnetic properties of melt-spun Fe–Si–B–Nb–Cu alloys have been investigated. It is found that the primary phase changes from -Fe(Si) to Fe3Si (DO3) on increasing the Si content. The coercivity of the alloys containing the Fe3Si phase is significantly lower as compared to the alloy containing -Fe(Si) phase. A heat treatment temperature–time–coercivity map has been obtained for optimization of the coercivity.

  6. Correlation between coercive field and radiation attenuation in Ni and Mg ferrite doped with Mn and Co

    Energy Technology Data Exchange (ETDEWEB)

    Silva, José Eves M., E-mail: evesquimica@yahoo.com.br [Chemistry Institute, UFRN, Cep. 59078-970, Natal, do Norte (Brazil); Nasar, Ricardo S., E-mail: nasar@terra.com.br [Chemistry Institute, UFRN, Cep. 59078-970, Natal, do Norte (Brazil); Nasar, Marinalva C., E-mail: mari.nat@terra.com.br [Chemistry Institute, UFRN, Cep. 59078-970, Natal, do Norte (Brazil); Firme, Caio L. [Chemistry Institute, UFRN, Cep. 59078-970, Natal, do Norte (Brazil); Araújo, José H., E-mail: humberto@dfte.ufrn.br [Department of Theoretical and Experimental Physics, UFRN, Cep. 59078-970, Natal, Grande do Norte (Brazil)

    2015-11-15

    It was investigated NiMg{sub 0.1}M{sub x}Fe{sub 2}O{sub 4} ferrite where M stands for Mn, Co or simultaneously Mn and Co dopants. The concentration of M is 0.1 and it was divided by two in the sample with addition of Mn and Co. It was used the method of citrate precursors with 1100 °C calcination. The materials were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and reflectivity measures by waveguide method. The X-ray diffraction measures, with Rietveld refinement, present average crystallite sizes between 0.576 and 0.626 µm. The SEM analysis shows clustered particles smaller than 1 µm at 1100 °C, in agreement with Rietveld refinement. The compositions with Mn reach magnetization between 42.09 and 53.20 Am{sup 2}/kg, which does not generate high microwave absorption. The 0.1 Co addition reached greater coercivity (2.96×10{sup −2} T), with up to 84% reflectivity at 10.17 GHz frequency. The Co material has high magnetocrystalline anisotropy, which is associated with the increase of coercive field, H{sub c}. The higher coercivity optimizes the reflectivity results. - Highlights: • Manganese diffusion occurs in octahedral sites. • Analysis by SEM and by Rietved shows agreement. • The structure is the inverse spinel type. • Low loss leads to obtain low radiation absorption. • The Co addition gets high reflectivity and coincides with high coercivity.

  7. Switching fields of high-resolution magnetic force microscope tips coated with Co, Co75Pt10Cr15, Co75Pt25, and Co50Pt50 films

    Directory of Open Access Journals (Sweden)

    Ishihara Shinji

    2014-07-01

    Full Text Available Magnetic force microscope (MFM tips are prepared by coating Si tips of 4 nm radius with Co, Co75Pt10Cr15, Co75Pt25, and Co50Pt50 (at. % films of 20 nm thickness at 300 °C. The effects of coating film material on the spatial resolution and the switching field are investigated. Higher resolutions are observed in the order of Co75Pt10Cr15 < (Co50Pt50, Co75Pt25 < Co. The Co-coated tip shows the highest resolution of 7.3 nm, which seems to be depending on a high detection sensitivity related with the magnetic moment of Co material. The saturation magnetization increases in the order of Co75Pt10Cr15 < Co50Pt50 < Co75Pt25 < Co. Higher switching fields are observed in the order of Co < Co75Pt10Cr15 < Co75Pt25 < Co50Pt50. The Co50Pt50-coated tip shows the highest switching field of 1.675±0.025 kOe, which is due to a high coercive field of the magnetic film involving L11 ordered phase with high magnetocrystalline anisotropy energy. The coercive field is recognized in the order of Co < Co75Pt10Cr15 < Co75Pt25 < Co50Pt50. A tip prepared by coating Co50Pt50 film which has high resolution and high switching field is useful for MFM observations of high-density recording media and permanent magnets.

  8. Cryogenic Impinging Jets Subjected to High Frequency Transverse Acoustic Forcing in a High Pressure Environment

    Science.gov (United States)

    2016-07-27

    other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a ...Transverse Acoustic Forcing in a High Pressure Environment 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Mario...Briefing Charts 15. SUBJECT TERMS N/ A 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF RESPONSIBLE

  9. Investigation of energy losses in low-coercivity resin-bonded magnets in alternating magnetic fields

    Science.gov (United States)

    Milov, E. V.; Sipin, I. A.; Milov, V. N.; Andreenko, A. S.; Balan, I. A.

    2017-01-01

    Energy losses during alternating remagnetization of low-coercitivity resin-bonded magnets and commercially produced electrical steels were studied experimentally. The studies were conducted on several samples of resin-bonded magnets with different manufacturing technologies and samples of electrical steel sheets of various thicknesses. The static and dynamic magnetic properties of the samples were measured on a vibration magnetometer and a specially designed apparatus, respectively. It was found that the studied samples of bonded magnets have a relatively high level of hysteresis losses associated with high coercivity, which reaches a value of 4-5 Oe. At the same time, the remagnetization losses due to the Foucault currents in the bonded magnets are considerably lower than in electrical steels. The measurement results show that bonded magnets at high frequencies of remagnetization, especially in high-rpm motors, can be competitive in comparison with electrical steels.

  10. Irreversible evolution of angular-dependent coercivity in Fe80Ni20 nanowire arrays: Detection of a single vortex state

    Science.gov (United States)

    Alikhani, M.; Ramazani, A.; Almasi Kashi, M.; Samanifar, S.; Montazer, A. H.

    2016-09-01

    The irreversible evolution of magnetic coercivity in arrays of 75 nm diameter Fe80Ni20 nanowires (NWs) has been explored by means of first-order reversal curve (FORC) analysis as a function of the angle between the magnetic field and the NW axis (0°≤θ≤90°). The Fe80Ni20 NWs with lengths up to 60 μm were fabricated using a pulsed electrodeposition method into hard-anodic aluminum oxide templates with an interpore distance of 275 nm. Investigating the interwire and intrawire magnetostatic interactions, the angular FORC (AFORC) diagrams indicated enhanced intrawire interactions with increasing length and θ (magnetization reversal through vortex domain wall (VDW) propagation. Intriguingly, in addition to the VDW mode, a single vortex state with broad irreversible switching of nucleation and annihilation fields was detected at θ=83° for 60 μm long NWs. At θ=90°, the NWs reversed magnetization through transverse domain wall, involving a reversible component by a fraction of 95%. Furthermore, the transition angle between the reversal modes was found to decrease with increasing aspect ratio from 200 to 800. The irreversible angular-dependent coercivity (HcIrrev(θ)) of Fe80Ni20 NWs was extracted from the AFORC measurements and compared with the major angular dependence of coercivity (HcMajor(θ)) obtained from the conventional hysteresis loop measurements. While HcMajor(θ) showed a non-monotonic behavior, HcIrrev(θ) constantly increased with increasing θ (<90°). On the other hand, using analytical models, a 93% agreement was obtained between the theoretical angular-dependent nucleation field and experimental HcIrrev(θ) for irreversible switching of VDW when 0°≤θ≤86°.

  11. Application of a novel flash-milling procedure for coercivity development in nanocrystalline MnAl permanent magnet powders

    Science.gov (United States)

    Rial, J.; Villanueva, M.; Céspedes, E.; López, N.; Camarero, J.; Marshall, L. G.; Lewis, L. H.; Bollero, A.

    2017-03-01

    This study shows the possibility of dramatically tuning microstructure and magnetic properties of gas-atomized Mn54Al46 particles by milling for an unprecedented duration of 30 s. This flash-milling procedure avoids the high temperatures typically achieved in lengthy conventional ball milling experiments, and is efficient to reduce the crystallite size to the nanometer scale, induce microstructural strain and ease phase transformations. This leads to the creation of the τ-MnAl phase providing magnetization, and the β-Mn phase operating in the mechanism for coercivity development. Post-annealing at 355 °C for 10 min results in a coercivity about three times larger than that of the annealed starting material, and thus reduces the optimum processing temperature in 75 °C by comparison with that needed for the latter to achieve the best combination of magnetic properties. A maximum obtained coercivity exceeding 5 kOe compares to the highest values reported to date for isotropic MnAl powders attained after milling for times above 20 h. This high coercivity is of additional relevance for further consideration of this material as a hard magnetic phase in the preparation of nanocomposite permanent magnets. The combination of the cost-efficient synthesis technique (gas-atomization) and novel processing route (flash-milling) for the production of low-cost isotropic nanocrystalline MnAl powders, opens new paths to the possible mass production of these materials as an alternative to permanent magnets containing critical raw materials.

  12. Enhanced coercivity of HCP Co–Pt alloy thin films on a glass substrate at room temperature for patterned media

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y.S. [Department of Chemical Engineering and Materials Science, Yuan-Ze University, Chung-Li 32003, Taiwan (China); Sun, An-Cheng, E-mail: acsun@saturn.yzu.edu.tw [Department of Chemical Engineering and Materials Science, Yuan-Ze University, Chung-Li 32003, Taiwan (China); Lee, H.Y. [National Synchrotron Radiation Research Center (NSRRC), Hsinchu 300, Taiwan (China); Department of Applied Science, National Hsinchu University of Education, Hsinchu 300, Taiwan (China); Lu, Hsi-Chuan; Wang, Sea-Fue [Department of Materials and Mineral Resources Engineering, National Taipei University of Technology, Taipei 106, Taiwan (China); Sharma, Puneet [School of Physics and Materials Science, Thapar University, Patiala (India)

    2015-10-01

    High coercivity (H{sub c}) Co-rich type Co–Pt alloy thin films with a columnar grain structure were deposited at room temperature (RT) by magnetron sputtering. Films with a thickness (t) of up to 10 nm had a FCC structure and exhibited soft magnetic properties. When t>25 nm, the magnetic anisotropy changed from in-plane to isotropic. H{sub c} was also enhanced with increasing t and found to be maximum at t=50 nm. The in-plane and out-of-plane H{sub c} of the film was 2.2 and 2.7 kOe, respectively. Further increasing t led to a slight decrease in H{sub c}. Microstructure and phase structure studies revealed columnar Co–Pt grains with a uniform lateral size grown on a 7 nm initial layer. Films with t>25 nm showed a HCP phase, due to the internal stress and volume effect. The microstructural details responsible for the enhanced RT magnetic properties of the HCP Co–Pt alloy thin films were investigated by TEM. - Highlights: • Deposited Co–Pt alloy thin films on glass substrate at room temperature. • High out-of-plane coercivity of Co-rich type Co–Pt thin film at thinner thickness. • Columnar structure contributed out-of-plane coercivity.

  13. Nike Court Force High Lux 奢华外衣

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Nike这次将使用在Air Force1中惯用的Lux的处理手法重新包装经典的Court Force High,这两双球鞋分别采用了黑色和灰色的单色顶级绒面革物料制作鞋面。而Lux系列的标志则印制在球鞋的后跟处。这是一款设计简洁的球鞋,与时下流行的色彩潮流截然不同.也许反潮流而行之也是体现纯粹经典的好办法。

  14. Angular dependence of the coercivity in arrays of ferromagnetic nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Holanda, J. [Departamento de Física, Universidade Federal de Pernambuco, Recife 50670-901, PE (Brazil); Silva, D.B.O. [Pós-Graduação em Ciência de Materiais, Universidade Federal de Pernambuco, Recife 50670-901, PE (Brazil); Padrón-Hernández, E., E-mail: padron@df.ufpe.br [Departamento de Física, Universidade Federal de Pernambuco, Recife 50670-901, PE (Brazil); Pós-Graduação em Ciência de Materiais, Universidade Federal de Pernambuco, Recife 50670-901, PE (Brazil)

    2015-03-15

    We present a new magnetic model for polycrystalline nanowires arrays in porous anodic aluminum oxide. The principal consideration here is the crystalline structure and the morphology of the wires and them the dipolar interactions between the crystals into the wire. Other aspect here is the direct calculation of the dipolar energy for the interaction of one wire with the others in the array. The free energy density was formulated for polycrystalline nanowires arrays in order to determinate the anisotropy effective field. It was using the microstructure study by scanning and transmission electron microscopy for the estimation of the real structure of the wires. After the structural analysis we used the angular dependences for the coercivity field and for the remnant magnetization to determine the properties of the wires. All analysis were made by the theory treatment proposed by Stoner and Wohlfarth.

  15. Magnetically extracted microstructural development along the length of Co nanowire arrays: The interplay between deposition frequency and magnetic coercivity

    Science.gov (United States)

    Montazer, A. H.; Ramazani, A.; Almasi Kashi, M.

    2016-09-01

    Providing practical implications for developing the design and optimizing the performance of hard magnets based on nanowires (NWs) requires an in-depth understanding of the processes in fabrication and magnetic parameters. Here, an electrochemical deposition technique with different frequencies is used to fabricate 50 nm diameter Co NW arrays into the nanopores of anodic aluminum oxide templates. The resulting NWs with dendrites at the base are subsequently exposed to a chemical etching with which to prepare cylindrical Co NWs with an aspect ratio of 200. In this way, the coercivity at room temperature increases up to 20% for different deposition frequencies, indicating the occurrence of a magnetic hardening along the NW length. Decreasing the length of the cylindrical NWs in ascending order whilst also using a successive magnetometry, the deposition frequency is found to be an important parameter in further enhancing the initial coercivity up to 65% in the length range of 10 to 3 μm. The first-order reversal curve diagrams evaluated along the NW length evidence the elimination of a soft magnetic phase and the formation of harder magnetic domains when reducing the length. Alternatively, X-ray diffraction patterns show improvements in the crystallinity along the [002] direction, pertaining to the alignment of the hexagonal close-packed c-axis of cobalt and long axis of NWs when reducing the length. These results may address the growing need for the creative design and low cost fabrication of rare-earth-free permanent magnets with high coercivity and availability.

  16. Parental Perceptions of the Use of Coercive Measures on Children with Developmental Disabilities

    Science.gov (United States)

    Saloviita, Timo; Pirttimaa, Raija; Kontu, Elina

    2016-01-01

    Background: Children with developmental disabilities who exhibit challenging behaviour are potentially subject to the use of coercive interventions. The aim of the study was to investigate the prevalence of the use of coercive measures by authorities, according to parents' reports. Materials and Methods: A postal survey was distributed, as a total…

  17. Attonewton force detection using microspheres in a dual-beam optical trap in high vacuum

    CERN Document Server

    Ranjit, Gambhir; Stutz, Jordan H; Cunningham, Mark; Geraci, Andrew A

    2015-01-01

    We describe the implementation of laser-cooled silica microspheres as force sensors in a dual-beam optical dipole trap in high vacuum. Using this system we have demonstrated trap lifetimes exceeding several days, attonewton force detection capability, and wide tunability in trapping and cooling parameters. Measurements have been performed with charged and neutral beads to calibrate the sensitivity of the detector. This work establishes the suitability of dual beam optical dipole traps for precision force measurement in high vacuum with long averaging times, and enables future applications including the study of gravitational inverse square law violations at short range, Casimir forces, acceleration sensing, and quantum opto-mechanics.

  18. Central fatigue of the first dorsal interosseous muscle during low-force and high-force sustained submaximal contractions.

    Science.gov (United States)

    Eichelberger, Tamara D; Bilodeau, Martin

    2007-09-01

    The aim of this study was to compare the extent of central fatigue in the first dorsal interosseous (FDI) muscle of healthy adults in low, moderate and high-force submaximal contractions. Nine healthy adults completed four experimental sessions where index finger abduction force was recorded during voluntary contractions and in response to brief trains (five pulses at 100 Hz) of electrical stimulation. The ability to maximally activate FDI under volition, or voluntary activation, and its change with sustained activity (central fatigue) was assessed using the twitch interpolation technique. The fatigue tasks consisted of continuous isometric index finger abduction contractions held until exhaustion at four target force levels: 30%, 45%, 60% and 75% of the maximal voluntary contraction. The main finding was the presence of central fatigue for the 30% task, but not for the three other fatigue tasks. The extent of central fatigue was also associated with changes in a measure reflecting the status of peripheral structures/mechanisms. It appears that central fatigue contributed to task failure for the lowest force fatigue task (30%), but not for the other (higher) contraction intensities.

  19. High-Throughput Atomic Force Microscopes Operating in Parallel

    CERN Document Server

    Sadeghian, H; Dekker, B; Winters, J; Bijnagte, T; Rijnbeek, R

    2016-01-01

    Atomic force microscopy (AFM) is an essential nanoinstrument technique for several applications such as cell biology and nanoelectronics metrology and inspection. The need for statistically significant sample sizes means that data collection can be an extremely lengthy process in AFM. The use of a single AFM instrument is known for its very low speed and not being suitable for scanning large areas, resulting in very-low-throughput measurement. We address this challenge by parallelizing AFM instruments. The parallelization is achieved by miniaturizing the AFM instrument and operating many of them simultaneously. This nanoinstrument has the advantages that each miniaturized AFM can be operated independently and that the advances in the field of AFM, both in terms of speed and imaging modalities, can be implemented more easily. Moreover, a parallel AFM instrument also allows one to measure several physical parameters simultaneously; while one instrument measures nano-scale topography, another instrument can meas...

  20. One-step solution combustion synthesis of pure Ni nanopowders with enhanced coercivity: The fuel effect

    Science.gov (United States)

    Khort, Alexander; Podbolotov, Kirill; Serrano-García, Raquel; Gun'ko, Yurii K.

    2017-09-01

    In this paper, we report a new modified one-step combustion synthesis technique for production of Ni metal nanoparticles. The main unique feature of our approach is the use of microwave assisted foam preparation. Also, the effect of different types of fuels (urea, citric acid, glycine and hexamethylenetetramine) on the combustion process and characteristics of resultant solid products were investigated. It is observed that the combination of microwave assisted foam preparation and using of hexamethylenetetramine as a fuel allows producing pure ferromagnetic Ni metal nanoparticles with enhanced coercivity (78 Oe) and high value of saturation magnetization (52 emu/g) by one-step solution combustion synthesis under normal air atmosphere without any post-reduction processing.

  1. High resolution magnetic force microscopy using focused ion beam modified tips

    NARCIS (Netherlands)

    Phillips, G.N.; Siekman, M.H.; Abelmann, L.; Lodder, J.C.

    2002-01-01

    Atomic force microscope tips coated by the thermal evaporation of a magnetic 30 nm thick Co film have been modified by focused ion beam milling with Ga+ ions to produce tips suitable for magnetic force microscopy. Such tips possess a planar magnetic element with high magnetic shape anisotropy, an ex

  2. Calculating levitation forces in the magnet-high-temperature superconductor systems

    NARCIS (Netherlands)

    Ermolaev, YS; Rudnev, IA

    2005-01-01

    A new method of calculation of the magnetic levitation force in the permanent magnet-high-temperature superconductor systems is proposed based on the Maxwell equations and the Bean model. The dependences of the levitation force on the gap width calculated for various regimes of superconductor coolin

  3. Calculating levitation forces in the magnet-high-temperature superconductor systems

    NARCIS (Netherlands)

    Ermolaev, YS; Rudnev, IA

    2005-01-01

    A new method of calculation of the magnetic levitation force in the permanent magnet-high-temperature superconductor systems is proposed based on the Maxwell equations and the Bean model. The dependences of the levitation force on the gap width calculated for various regimes of superconductor coolin

  4. High-throughput atomic force microscopes operating in parallel

    Science.gov (United States)

    Sadeghian, Hamed; Herfst, Rodolf; Dekker, Bert; Winters, Jasper; Bijnagte, Tom; Rijnbeek, Ramon

    2017-03-01

    Atomic force microscopy (AFM) is an essential nanoinstrument technique for several applications such as cell biology and nanoelectronics metrology and inspection. The need for statistically significant sample sizes means that data collection can be an extremely lengthy process in AFM. The use of a single AFM instrument is known for its very low speed and not being suitable for scanning large areas, resulting in a very-low-throughput measurement. We address this challenge by parallelizing AFM instruments. The parallelization is achieved by miniaturizing the AFM instrument and operating many of them simultaneously. This instrument has the advantages that each miniaturized AFM can be operated independently and that the advances in the field of AFM, both in terms of speed and imaging modalities, can be implemented more easily. Moreover, a parallel AFM instrument also allows one to measure several physical parameters simultaneously; while one instrument measures nano-scale topography, another instrument can measure mechanical, electrical, or thermal properties, making it a lab-on-an-instrument. In this paper, a proof of principle of such a parallel AFM instrument has been demonstrated by analyzing the topography of large samples such as semiconductor wafers. This nanoinstrument provides new research opportunities in the nanometrology of wafers and nanolithography masks by enabling real die-to-die and wafer-level measurements and in cell biology by measuring the nano-scale properties of a large number of cells.

  5. Effects of orientation and interaction of grains on coercivity for sintered NdFeB magnets

    Institute of Scientific and Technical Information of China (English)

    高汝伟; 李卫; 张建成; 吴良学; 喻晓军

    1999-01-01

    The coercivity of NdFeB magnets is determined by the coercivity of individual grains and the interaction between the grains composed of the magnets. The coercivity of individual grains and the intergrain interaction depend on the degree of the grain alignment. "tanθ type" Ganssian function is applied to describing the degree of the grain alignment. According to different coercivity mechanisms, there are different formula on the coercivity and the angular dependence of coercivity. The interaction between grains can be classified as the long-range magnetostatic interaction and the exchange-coupling interaction of neighboring grains. For the sintered magnet, the grain size is large and the grain boundaries are mostly separated by the non-magnetic phase. So, the long-range magnetostatic interaction is much stronger than the exchange coupling interaction and it makes the coercivity of the magnet composed of misaligned grains be bigger than that of the magnet composed of ideally aligned grains. The effects o

  6. Coercivity enhancement in Ce-Fe-B based magnets by core-shell grain structuring

    Directory of Open Access Journals (Sweden)

    M. Ito

    2016-05-01

    Full Text Available Ce-based R2Fe14B (R= rare-earth nano-structured permanent magnets consisting of (Ce,Nd2Fe14B core-shell grains separated by a non-magnetic grain boundary phase, in which the relative amount of Nd to Ce is higher in the shell of the magnetic grain than in its core, were fabricated by Nd-Cu infiltration into (Ce,Nd2Fe14B hot-deformed magnets. The coercivity values of infiltrated core-shell structured magnets are superior to those of as-hot-deformed magnets with the same overall Nd content. This is attributed to the higher value of magnetocrystalline anisotropy of the shell phase in the core-shell structured infiltrated magnets compared to the homogeneous R2Fe14B grains of the as-hot-deformed magnets, and to magnetic isolation of R2Fe14B grains by the infiltrated grain boundary phase. First order reversal curve (FORC diagrams suggest that the higher anisotropy shell suppresses initial magnetization reversal at the edges and corners of the R2Fe14B grains.

  7. Structure, coercive control, and autonomy promotion: A comparison of fathers' and mothers' food parenting strategies.

    Science.gov (United States)

    Pratt, Mercedes; Hoffmann, Debra; Taylor, Maija; Musher-Eizenman, Dara

    2017-05-01

    This study explored differences in mothers' and fathers' food parenting strategies, specifically coercive control, structure, and autonomy promotion, and whether parenting style and parental responsibility for food parenting related to the use of these strategies. Parents of children aged 2.5-7.5 years ( N = 497) reported about their parenting practices and food parenting strategies. Parenting style accounted for the majority of the variance in food parenting. Fathers were more authoritarian than mothers. Authoritarian and permissive parenting practices were related to more coercive strategies. Mothers reported more food parenting responsibility. Responsibility was related to less coercive practices and more autonomy promotion and structure.

  8. Single phase forced convection cooling of high power leds

    NARCIS (Netherlands)

    Ozdemir, M.Z.; Chestakov, D.; Frijns, A.J.H.

    2011-01-01

    LEDs are strong candidates for future illumination applications dueto their much lower consumption of energy compared to conventional lighting options. One of key problems in development of LEDs is successful thermal management during illumination. Therefore, current research ongoing related to high

  9. Does the sole description of a tax authority affect tax evasion?--the impact of described coercive and legitimate power.

    Directory of Open Access Journals (Sweden)

    Barbara Hartl

    Full Text Available Following the classic economic model of tax evasion, taxpayers base their tax decisions on economic determinants, like fine rate and audit probability. Empirical findings on the relationship between economic key determinants and tax evasion are inconsistent and suggest that taxpayers may rather rely on their beliefs about tax authority's power. Descriptions of the tax authority's power may affect taxpayers' beliefs and as such tax evasion. Experiment 1 investigates the impact of fines and beliefs regarding tax authority's power on tax evasion. Experiments 2-4 are conducted to examine the effect of varying descriptions about a tax authority's power on participants' beliefs and respective tax evasion. It is investigated whether tax evasion is influenced by the description of an authority wielding coercive power (Experiment 2, legitimate power (Experiment 3, and coercive and legitimate power combined (Experiment 4. Further, it is examined whether a contrast of the description of power (low to high power; high to low power impacts tax evasion (Experiments 2-4. Results show that the amount of fine does not impact tax payments, whereas participants' beliefs regarding tax authority's power significantly shape compliance decisions. Descriptions of high coercive power as well as high legitimate power affect beliefs about tax authority's power and positively impact tax honesty. This effect still holds if both qualities of power are applied simultaneously. The contrast of descriptions has little impact on tax evasion. The current study indicates that descriptions of the tax authority, e.g., in information brochures and media reports, have more influence on beliefs and tax payments than information on fine rates. Methodically, these considerations become particularly important when descriptions or vignettes are used besides objective information.

  10. Does the sole description of a tax authority affect tax evasion?--the impact of described coercive and legitimate power.

    Science.gov (United States)

    Hartl, Barbara; Hofmann, Eva; Gangl, Katharina; Hartner-Tiefenthaler, Martina; Kirchler, Erich

    2015-01-01

    Following the classic economic model of tax evasion, taxpayers base their tax decisions on economic determinants, like fine rate and audit probability. Empirical findings on the relationship between economic key determinants and tax evasion are inconsistent and suggest that taxpayers may rather rely on their beliefs about tax authority's power. Descriptions of the tax authority's power may affect taxpayers' beliefs and as such tax evasion. Experiment 1 investigates the impact of fines and beliefs regarding tax authority's power on tax evasion. Experiments 2-4 are conducted to examine the effect of varying descriptions about a tax authority's power on participants' beliefs and respective tax evasion. It is investigated whether tax evasion is influenced by the description of an authority wielding coercive power (Experiment 2), legitimate power (Experiment 3), and coercive and legitimate power combined (Experiment 4). Further, it is examined whether a contrast of the description of power (low to high power; high to low power) impacts tax evasion (Experiments 2-4). Results show that the amount of fine does not impact tax payments, whereas participants' beliefs regarding tax authority's power significantly shape compliance decisions. Descriptions of high coercive power as well as high legitimate power affect beliefs about tax authority's power and positively impact tax honesty. This effect still holds if both qualities of power are applied simultaneously. The contrast of descriptions has little impact on tax evasion. The current study indicates that descriptions of the tax authority, e.g., in information brochures and media reports, have more influence on beliefs and tax payments than information on fine rates. Methodically, these considerations become particularly important when descriptions or vignettes are used besides objective information.

  11. Does the Sole Description of a Tax Authority Affect Tax Evasion? - The Impact of Described Coercive and Legitimate Power

    Science.gov (United States)

    Hartl, Barbara; Hofmann, Eva; Gangl, Katharina; Hartner-Tiefenthaler, Martina; Kirchler, Erich

    2015-01-01

    Following the classic economic model of tax evasion, taxpayers base their tax decisions on economic determinants, like fine rate and audit probability. Empirical findings on the relationship between economic key determinants and tax evasion are inconsistent and suggest that taxpayers may rather rely on their beliefs about tax authority’s power. Descriptions of the tax authority’s power may affect taxpayers’ beliefs and as such tax evasion. Experiment 1 investigates the impact of fines and beliefs regarding tax authority’s power on tax evasion. Experiments 2-4 are conducted to examine the effect of varying descriptions about a tax authority’s power on participants’ beliefs and respective tax evasion. It is investigated whether tax evasion is influenced by the description of an authority wielding coercive power (Experiment 2), legitimate power (Experiment 3), and coercive and legitimate power combined (Experiment 4). Further, it is examined whether a contrast of the description of power (low to high power; high to low power) impacts tax evasion (Experiments 2-4). Results show that the amount of fine does not impact tax payments, whereas participants’ beliefs regarding tax authority’s power significantly shape compliance decisions. Descriptions of high coercive power as well as high legitimate power affect beliefs about tax authority’s power and positively impact tax honesty. This effect still holds if both qualities of power are applied simultaneously. The contrast of descriptions has little impact on tax evasion. The current study indicates that descriptions of the tax authority, e.g., in information brochures and media reports, have more influence on beliefs and tax payments than information on fine rates. Methodically, these considerations become particularly important when descriptions or vignettes are used besides objective information. PMID:25923770

  12. Successful interventions on an organisational level to reduce violence and coercive interventions in in-patients with adjustment disorders and personality disorders

    Directory of Open Access Journals (Sweden)

    Goeser Ulla

    2008-11-01

    Full Text Available Abstract Background Self-directed and other violence as well as subsequent coercive interventions occur in a substantial proportion of patients with personality disorders during in-patient treatment. Different strategies may be required to reduce coercive interventions for patients of different diagnostic groups. Methods We specialised one of our acute admission wards in the treatment of personality disorders and adjustment disorders (ICD-10 F4 and F6. Patients are not transferred to other acute wards in case of suicidal or violent behaviour. Violent behaviour and coercive interventions such as seclusion or restraint were recorded in the same way as in the rest of the hospital. We recorded the percentage of subjects affected by diagnostic group and average length of an intervention in the year before and after the change in organisational structure. Results The total number of coercive interventions decreased by 85% both among patients with an F4 and those with an F6 primary diagnosis. Violent behaviours decreased by about 50%, the proportion of involuntary committed patients decreased by 70%. Conclusion The organisational change turned out to be highly effective without any additional cost of personnel or other resources.

  13. Enhanced coercivity in Co-doped α-Fe2O3 cubic nanocrystal assemblies prepared via a magnetic field-assisted hydrothermal synthesis

    Directory of Open Access Journals (Sweden)

    Kinjal Gandha

    2017-05-01

    Full Text Available Ferromagnetic Co-doped α-Fe2O3 cubic shaped nanocrystal assemblies (NAs with a high coercivity of 5.5 kOe have been synthesized via a magnetic field (2 kOe assisted hydrothermal process. The X-ray diffraction pattern and Raman spectra of α-Fe2O3 and Co-doped α-Fe2O3 NAs confirms the formation of single-phase α-Fe2O3 with a rhombohedral crystal structure. Electron microscopy analysis depict that the Co-doped α-Fe2O3 NAs synthesized under the influence of the magnetic field are consist of aggregated nanocrystals (∼30 nm and of average assembly size 2 μm. In contrast to the NAs synthesized with no magnetic field, the average NAs size and coercivity of the Co-doped α-Fe2O3 NAs prepared with magnetic field is increased by 1 μm and 1.4 kOe, respectively. The enhanced coercivity could be related to the well-known spin–orbit coupling strength of Co2+ cations and the redistribution of the cations. The size increment indicates that the small ferromagnetic nanocrystals assemble into cubic NAs with increased size in the magnetic field that also lead to the enhanced coercivity.

  14. Dispersion and optical gradient force from high-order mode coupling between two hyperbolic metamaterial waveguides

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Guanghui, E-mail: gsnuwgh@163.com; Zhang, Weifeng; Lu, Jiahui; Zhao, Huijun

    2016-08-12

    We analytically study dispersion properties and optical gradient forces of different-order transverse magnetic (TM) modes in two coupled hyperbolic metamaterial waveguides (HMMWs). According to Maxwell's equations, we obtain the dispersion relation of symmetric and antisymmetric modes, and calculate optical gradient forces of different-order modes by using Maxwell stress tensor. Numerical results show that the dispersion properties are dependent on the filling ratio, and the optical gradient forces of high-order TM modes are larger than the fundamental mode when the gap between two HMMWs is very narrow, but they weaken much faster than the case of low-order TM modes with the gap width increasing. In addition, the effects of the dielectric surrounding of waveguides on the coupling effect and optical gradient force are clarified. These properties offer an avenue for various optomechanical applications in optical sensors and actuators. - Highlights: • The dependence of dispersion properties in hyperbolic metamaterials on the filling ratio is analyzed. • It is possible that the optical gradient forces of high-order modes are larger than the fundamental mode. • Optical gradient forces of high-order modes weaken much faster than the case of low-order modes. • The influence of the dielectric surrounding on the coupling effect and optical gradient force are clarified.

  15. Prying Force Calculation and Design Method for T-shaped Tensile Connector with High Strength Bolt

    Institute of Scientific and Technical Information of China (English)

    Zhaoxin Hou; Guohong Huang; Chao Gong

    2015-01-01

    In order to establish the design method for T⁃shaped tensile connector with high strength bolt, the theoretical analysis is carried out. Firstly, it analyzes the performance of the connector and establishes prying force calculation model. Based on the model, prying force equation and function between bolt prying force and flange thickness is derived, and the min and max thickness requirement of flange plate under a certain tension load is then obtained. Finally, two simplified design methods of the connector are proposed, which are bolt pulling capacity method and flange plate bending capacity method.

  16. Flange joint system for SRF cavities utilizing high force spring clamps for low particle generation

    Energy Technology Data Exchange (ETDEWEB)

    None

    2017-09-05

    A flange joint system for SRF cavities. The flange joint system includes a set of high force spring clamps that produce high force on the simple flanges of Superconducting Radio Frequency (SRF) cavities to squeeze conventional metallic seals. The system establishes the required vacuum and RF-tight seal with minimum particle contamination to the inside of the cavity assembly. The spring clamps are designed to stay within their elastic range while being forced open enough to mount over the flange pair. Upon release, the clamps have enough force to plastically deform metallic seal surfaces and continue to a new equilibrium sprung dimension where the flanges remain held against one another with enough preload such that normal handling will not break the seal.

  17. A high performance sensor for triaxial cutting force measurement in turning.

    Science.gov (United States)

    Zhao, You; Zhao, Yulong; Liang, Songbo; Zhou, Guanwu

    2015-04-03

    This paper presents a high performance triaxial cutting force sensor with excellent accuracy, favorable natural frequency and acceptable cross-interference for high speed turning process. Octagonal ring is selected as sensitive element of the designed sensor, which is drawn inspiration from ring theory. A novel structure of two mutual-perpendicular octagonal rings is proposed and three Wheatstone full bridge circuits are specially organized in order to obtain triaxial cutting force components and restrain cross-interference. Firstly, the newly developed sensor is tested in static calibration; test results indicate that the sensor possesses outstanding accuracy in the range of 0.38%-0.83%. Secondly, impacting modal tests are conducted to identify the natural frequencies of the sensor in triaxial directions (i.e., 1147 Hz, 1122 Hz and 2035 Hz), which implies that the devised sensor can be used for cutting force measurement in a high speed lathe when the spindle speed does not exceed 17,205 rev/min in continuous cutting condition. Finally, an application of the sensor in turning process is operated to show its performance for real-time cutting force measurement; the measured cutting forces demonstrate a good accordance with the variation of cutting parameters. Thus, the developed sensor possesses perfect properties and it gains great potential for real-time cutting force measurement in turning.

  18. A High Performance Sensor for Triaxial Cutting Force Measurement in Turning

    Directory of Open Access Journals (Sweden)

    You Zhao

    2015-04-01

    Full Text Available This paper presents a high performance triaxial cutting force sensor with excellent accuracy, favorable natural frequency and acceptable cross-interference for high speed turning process. Octagonal ring is selected as sensitive element of the designed sensor, which is drawn inspiration from ring theory. A novel structure of two mutual-perpendicular octagonal rings is proposed and three Wheatstone full bridge circuits are specially organized in order to obtain triaxial cutting force components and restrain cross-interference. Firstly, the newly developed sensor is tested in static calibration; test results indicate that the sensor possesses outstanding accuracy in the range of 0.38%–0.83%. Secondly, impacting modal tests are conducted to identify the natural frequencies of the sensor in triaxial directions (i.e., 1147 Hz, 1122 Hz and 2035 Hz, which implies that the devised sensor can be used for cutting force measurement in a high speed lathe when the spindle speed does not exceed 17,205 rev/min in continuous cutting condition. Finally, an application of the sensor in turning process is operated to show its performance for real-time cutting force measurement; the measured cutting forces demonstrate a good accordance with the variation of cutting parameters. Thus, the developed sensor possesses perfect properties and it gains great potential for real-time cutting force measurement in turning.

  19. Superhydrophobic gecko feet with high adhesive forces towards water and their bio-inspired materials

    Science.gov (United States)

    Liu, Kesong; Du, Jiexing; Wu, Juntao; Jiang, Lei

    2012-01-01

    Functional integration is an inherent characteristic for multiscale structures of biological materials. In this contribution, we first investigate the liquid-solid adhesive forces between water droplets and superhydrophobic gecko feet using a high-sensitivity micro-electromechanical balance system. It was found, in addition to the well-known solid-solid adhesion, the gecko foot, with a multiscale structure, possesses both superhydrophobic functionality and a high adhesive force towards water. The origin of the high adhesive forces of gecko feet to water could be attributed to the high density nanopillars that contact the water. Inspired by this, polyimide films with gecko-like multiscale structures were constructed by using anodic aluminum oxide templates, exhibiting superhydrophobicity and a strong adhesive force towards water. The static water contact angle is larger than 150° and the adhesive force to water is about 66 μN. The resultant gecko-inspired polyimide film can be used as a ``mechanical hand'' to snatch micro-liter liquids. We expect this work will provide the inspiration to reveal the mechanism of the high-adhesive superhydrophobic of geckos and extend the practical applications of polyimide materials.

  20. Enhancing Tax Compliance through Coercive and Legitimate Power of Tax Authorities by Concurrently Diminishing or Facilitating Trust in Tax Authorities.

    Science.gov (United States)

    Hofmann, Eva; Gangl, Katharina; Kirchler, Erich; Stark, Jennifer

    2014-07-01

    Both coercion, such as strict auditing and the use of fines, and legitimate procedures, such as assistance by tax authorities, are often discussed as means of enhancing tax compliance. However, the psychological mechanisms that determine the effectiveness of each strategy are not clear. Although highly relevant, there is rare empirical literature examining the effects of both strategies applied in combination. It is assumed that coercion decreases implicit trust in tax authorities, leading to the perception of a hostile antagonistic tax climate and enforced tax compliance. Conversely, it is suggested that legitimate power increases reason-based trust in the tax authorities, leading to the perception of a service climate and eventually to voluntary cooperation. The combination of both strategies is assumed to cause greater levels of intended compliance than each strategy alone. We conducted two experimental studies with convenience samples of 261 taxpayers overall. The studies describe tax authorities as having low or high coercive power (e.g., imposing lenient or severe sanctions) and/or low or high legitimate power (e.g., having nontransparent or transparent procedures). Data analyses provide supportive evidence for the assumptions regarding the impact on intended tax compliance. Coercive power did not reduce implicit trust in tax authorities; however, it had an effect on reason-based trust, interaction climate, and intended tax compliance if applied solely. When wielded in combination with legitimate power, it had no effect.

  1. Dispersion and optical gradient force from high-order mode coupling between two hyperbolic metamaterial waveguides

    Science.gov (United States)

    Wang, Guanghui; Zhang, Weifeng; Lu, Jiahui; Zhao, Huijun

    2016-08-01

    We analytically study dispersion properties and optical gradient forces of different-order transverse magnetic (TM) modes in two coupled hyperbolic metamaterial waveguides (HMMWs). According to Maxwell's equations, we obtain the dispersion relation of symmetric and antisymmetric modes, and calculate optical gradient forces of different-order modes by using Maxwell stress tensor. Numerical results show that the dispersion properties are dependent on the filling ratio, and the optical gradient forces of high-order TM modes are larger than the fundamental mode when the gap between two HMMWs is very narrow, but they weaken much faster than the case of low-order TM modes with the gap width increasing. In addition, the effects of the dielectric surrounding of waveguides on the coupling effect and optical gradient force are clarified. These properties offer an avenue for various optomechanical applications in optical sensors and actuators.

  2. Impact-force sparse reconstruction from highly incomplete and inaccurate measurements

    Science.gov (United States)

    Qiao, Baijie; Zhang, Xingwu; Gao, Jiawei; Chen, Xuefeng

    2016-08-01

    The classical l2-norm-based regularization methods applied for force reconstruction inverse problem require that the number of measurements should not be less than the number of unknown sources. Taking into account the sparse nature of impact-force in time domain, we develop a general sparse methodology based on minimizing l1-norm for solving the highly underdetermined model of impact-force reconstruction. A monotonic two-step iterative shrinkage/thresholding (MTWIST) algorithm is proposed to find the sparse solution to such an underdetermined model from highly incomplete and inaccurate measurements, which can be problematic with Tikhonov regularization. MTWIST is highly efficient for large-scale ill-posed problems since it mainly involves matrix-vector multiplies without matrix factorization. In sparsity frame, the proposed sparse regularization method can not only determine the actual impact location from many candidate sources but also simultaneously reconstruct the time history of impact-force. Simulation and experiment including single-source and two-source impact-force reconstruction are conducted on a simply supported rectangular plate and a shell structure to illustrate the effectiveness and applicability of MTWIST, respectively. Both the locations and force time histories of the single-source and two-source cases are accurately reconstructed from a single accelerometer, where the high noise level is considered in simulation and the primary noise in experiment is supposed to be colored noise. Meanwhile, the consecutive impact-forces reconstruction in a large-scale (greater than 104) sparse frame illustrates that MTWIST has advantages of computational efficiency and identification accuracy over Tikhonov regularization.

  3. Experimental study of forced convection heat transfer during upward and downward flow of helium at high pressure and high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Francisco Valentin; Narbeh Artoun; Masahiro Kawaji; Donald M. McEligot

    2015-08-01

    Fundamental high pressure/high temperature forced convection experiments have been conducted in support of the development of a Very High Temperature Reactor (VHTR) with a prismatic core. The experiments utilize a high temperature/high pressure gas flow test facility constructed for forced convection and natural circulation experiments. The test section has a single 16.8 mm ID flow channel in a 2.7 m long, 108 mm OD graphite column with four 2.3kW electric heater rods placed symmetrically around the flow channel. This experimental study presents the role of buoyancy forces in enhancing or reducing convection heat transfer for helium at high pressures up to 70 bar and high temperatures up to 873 degrees K. Wall temperatures have been compared among 10 cases covering the inlet Re numbers ranging from 500 to 3,000. Downward flows display higher and lower wall temperatures in the upstream and downstream regions, respectively, than the upward flow cases due to the influence of buoyancy forces. In the entrance region, convection heat transfer is reduced due to buoyancy leading to higher wall temperatures, while in the downstream region, buoyancyinduced mixing causes higher convection heat transfer and lower wall temperatures. However, their influences are reduced as the Reynolds number increases. This experimental study is of specific interest to VHTR design and validation of safety analysis codes.

  4. "He Could Scare Me Without Laying a Hand on Me": Mothers' Experiences of Nonviolent Coercive Control During Marriage and After Separation.

    Science.gov (United States)

    Crossman, Kimberly A; Hardesty, Jennifer L; Raffaelli, Marcela

    2016-03-01

    Studies demonstrate the negative effects of violent coercive control but few examine coercive control without violence. This study describes the characteristics of nonviolent coercive control among 8 divorcing mothers and compares them with 47 mothers who experienced violent coercive control or no violence/no control. Mothers with nonviolent coercive control reported more coping strategies, risk, harassment, and perceived threat than mothers with no violence/no control; similar levels of fear and control during marriage as mothers with violent coercive control; and more postseparation fear than both groups. Findings highlight the need to include nonviolent coercive control in screening methods and research measures.

  5. Creating social policy to support women's agency in coercive settings: A case study from Uganda.

    Science.gov (United States)

    Burgess, Rochelle; Campbell, Catherine

    2016-01-01

    Many emphasise the need for policies that support women's agency in highly coercive settings, and the importance of involving target women in public deliberation to inform policy design. The Ugandan Marriage and Divorce Bill seeks to strengthen women's agency in marriage, but has faced many obstacles, including objections from many women themselves in public consultations. We explore key stakeholders' accounts of the difficulties facing the Bill's progress to date, through focus groups with 24 rural and urban men and women, interviews with 14 gender champions in government, non-governmental organisations and legal sectors, and 25 relevant media and radio reports. Thematic analysis revealed an array of representations of the way the Bill's progress was shaped by the public consultation process, the nature of the Ugandan public sphere, the understanding and manipulation of concepts such as 'culture' and 'custom' in public discourse, the impact of economic inequalities on women's understandings of their gendered interests and low women's trust in the law and the political process. We discuss the complexities of involving highly marginalised women in public debates about gender issues and highlight possible implications for conceptualising agency, gender and social change as tools for gender policy and activism in extreme inequality.

  6. High Precision Prediction of Rolling Force Based on Fuzzy and Nerve Method for Cold Tandem Mill

    Institute of Scientific and Technical Information of China (English)

    JIA Chun-yu; SHAN Xiu-ying; NIU Zhao-ping

    2008-01-01

    The rolling force model for cold tandem mill was put forward by using the Elman dynamic recursive network method, based on the actual measured data. Furthermore, a good assumption is put forward, which brings a full universe of discourse self-adjusting factor fuzzy control, closed-loop adjusting, based on error feedback and expertise into a rolling force prediction model, to modify prediction outputs and improve prediction precision and robustness. The simulated results indicate that the method is highly effective and the prediction precision is better than that of the traditional method. Predicted relative error is less than ±4%, so the prediction is high precise for the cold tandem mill.

  7. A review of Air Force high efficiency cascaded multiple bandgap solar cell research and development

    Science.gov (United States)

    Rahilly, W. P.

    1979-01-01

    At the time of their conception, the cell stack systems to be discussed represent the best semiconductor materials combinations to achieve Air Force program goals. These systems are investigated thoroughly and the most promising systems, from the standpoint of high efficiency, are taken for further development with large area emphasized (at least 4 sq cm). The emphasis in the Air Force cascaded cell program is placed on eventual nonconcentrator application. This use of the final cell design considerably relieves the low resistance requirements for the tunnel junction. In a high concentration application the voltage drop across the tunnel junction can be a very serious problem.

  8. Reduction of magnetic damping and isotropic coercivity and increase of saturation magnetization in Rh-incorporated CoIr system

    Science.gov (United States)

    Wong, H. S.; He, S. K.; Chung, H. J.; Zhang, M. S.; Cher, Kelvin; Low, Melvin; Zhou, T. J.; Yang, Y.; Wong, S. K.

    2016-11-01

    Replacing Ir with Rh in a CoIr system possessing negative uniaxial magnetocrystalline anisotropy (K u ) substantially reduces its magnetic damping and coercivity by more than half while retaining its high negative K u . Moreover, a higher saturation magnetization (M s ) and more isotropic coercivity are achieved. Such material development makes it particularly suitable for use as the soft underlayer (SUL) of magnetic recording media for reducing noise, and as the oscillation layer of a spin-torque oscillator (STO) for achieving higher oscillation frequency, larger AC magnetic field and lower driving current, which can be readily integrated with the current recording head for microwave-assisted magnetic recording. Finally, we recommend a composite free layer by coupling CoIr with a spin polarizer (Co or Co/Cu/Co) for the enhancement of the spin-polarization rate and, therefore, the improvement of STO efficiency. These could pave the way for CoIr-based materials to be implemented in devices requiring a negative Ku with low damping and high ‘softness’, such as oscillators.

  9. Acoustic radiation force of high-order Bessel beam standing wave tweezers on a rigid sphere.

    Science.gov (United States)

    Mitri, F G

    2009-12-01

    Particle manipulation using the acoustic radiation force of Bessel beams is an active field of research. In a previous investigation, [F.G. Mitri, Acoustic radiation force on a sphere in standing and quasi-standing zero-order Bessel beam tweezers, Annals of Physics 323 (2008) 1604-1620] an expression for the radiation force of a zero-order Bessel beam standing wave experienced by a sphere was derived. The present work extends the analysis of the radiation force to the case of a high-order Bessel beam (HOBB) of positive order m having an angular dependence on the phase phi. The derivation for the general expression of the force is based on the formulation for the total acoustic scattering field of a HOBB by a sphere [F.G. Mitri, Acoustic scattering of a high-order Bessel beam by an elastic sphere, Annals of Physics 323 (2008) 2840-2850; F.G. Mitri, Equivalence of expressions for the acoustic scattering of a progressive high order Bessel beam by an elastic sphere, IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 56 (2009) 1100-1103] to derive the general expression for the radiation force function YJm,st(ka,beta,m)Bessel beam standing wave incident upon a rigid sphere immersed in non-viscous water are computed. The rigid sphere calculations for YJm,st(ka,beta,m)Bessel beam standing wave (m=0). The proposed theory is of particular interest essentially due to its inherent value as a canonical problem in particle manipulation using the acoustic radiation force of a HOBB standing wave on a sphere. It may also serve as the benchmark for comparison to other solutions obtained by strictly numerical or asymptotic approaches.

  10. Design principles for high-pressure force fields: Aqueous TMAO solutions from ambient to kilobar pressures

    Science.gov (United States)

    Hölzl, Christoph; Kibies, Patrick; Imoto, Sho; Frach, Roland; Suladze, Saba; Winter, Roland; Marx, Dominik; Horinek, Dominik; Kast, Stefan M.

    2016-04-01

    Accurate force fields are one of the major pillars on which successful molecular dynamics simulations of complex biomolecular processes rest. They have been optimized for ambient conditions, whereas high-pressure simulations become increasingly important in pressure perturbation studies, using pressure as an independent thermodynamic variable. Here, we explore the design of non-polarizable force fields tailored to work well in the realm of kilobar pressures - while avoiding complete reparameterization. Our key is to first compute the pressure-induced electronic and structural response of a solute by combining an integral equation approach to include pressure effects on solvent structure with a quantum-chemical treatment of the solute within the embedded cluster reference interaction site model (EC-RISM) framework. Next, the solute's response to compression is taken into account by introducing pressure-dependence into selected parameters of a well-established force field. In our proof-of-principle study, the full machinery is applied to N,N,N-trimethylamine-N-oxide (TMAO) in water being a potent osmolyte that counteracts pressure denaturation. EC-RISM theory is shown to describe well the charge redistribution upon compression of TMAO(aq) to 10 kbar, which is then embodied in force field molecular dynamics by pressure-dependent partial charges. The performance of the high pressure force field is assessed by comparing to experimental and ab initio molecular dynamics data. Beyond its broad usefulness for designing non-polarizable force fields for extreme thermodynamic conditions, a good description of the pressure-response of solutions is highly recommended when constructing and validating polarizable force fields.

  11. The RSC chromatin remodelling ATPase translocates DNA with high force and small step size.

    Science.gov (United States)

    Sirinakis, George; Clapier, Cedric R; Gao, Ying; Viswanathan, Ramya; Cairns, Bradley R; Zhang, Yongli

    2011-06-15

    ATP-dependent chromatin remodelling complexes use the energy of ATP hydrolysis to reposition and reconfigure nucleosomes. Despite their diverse functions, all remodellers share highly conserved ATPase domains, many shown to translocate DNA. Understanding remodelling requires biophysical knowledge of the DNA translocation process: how the ATPase moves DNA and generates force, and how translocation and force generation are coupled on nucleosomes. Here, we characterize the real-time activity of a minimal RSC translocase 'motor' on bare DNA, using high-resolution optical tweezers and a 'tethered' translocase system. We observe on dsDNA a processivity of ∼35 bp, a speed of ∼25 bp/s, and a step size of 2.0 (±0.4, s.e.m.) bp. Surprisingly, the motor is capable of moving against high force, up to 30 pN, making it one of the most force-resistant motors known. We also provide evidence for DNA 'buckling' at initiation. These observations reveal the ATPase as a powerful DNA translocating motor capable of disrupting DNA-histone interactions by mechanical force.

  12. Multimode laser cooling and ultra-high sensitivity force sensing with nanowires

    CERN Document Server

    Hosseini, Mahdi; Slatyer, Harri J; Buchler, Ben C; Lam, Ping Koy

    2015-01-01

    Photo-induced forces can be used to manipulate and cool the mechanical motion of oscillators. When the oscillator is used as a force sensor, such as in atomic force microscopy, active feedback is an enticing route to enhancing measurement performance. Here, we show broadband multimode cooling of $-23$ dB down to a temperature of $8 \\pm 1$~K in the stationary regime. Through the use of periodic quiescence feedback cooling, we show improved signal-to-noise ratios for the measurement of transient signals. We compare the performance of real feedback to numerical post-processing of data and show that both methods produce similar improvements to the signal-to-noise ratio of force measurements. We achieved a room temperature force measurement sensitivity of $< 2\\times10^{-16}$ N with integration time of less than $0.1$ ms. The high precision and fast force microscopy results presented will potentially benefit applications in biosensing, molecular metrology, subsurface imaging and accelerometry.

  13. Radiation forces on a three-level atom in the high-order Bessel beams

    Institute of Scientific and Technical Information of China (English)

    Wang Zheng-Ling; Yin Jian-Ping

    2008-01-01

    The general expressions of the average dissipative and dipole forces acting on a A-configuration three-level atom in an arbitrary light field are derived by means of the optical Bloch equations based on the atomic density matrix elements, and the general properties of the average dissipative and dipole forces on a three-level atom in the linearly-polarized high-order Bessel beams (HBBs) are analysed. We find a resonant property (with two resonant peaks) of the dissipative force and a non-resonant property (with two pairs of non-resonant peaks) of the dipole force on the three-level atom, which are completely different from those on the two-level atom. Meanwhile we find a saturation effect of the average dissipative force in the HBB, which comes from the saturation of the upper-level population. Our study shows that the general expressions of the average dissipative and dipole forces on the three-level atom will be simplified to those of the two-level atom under the approximation of large detuning. Finally, we study the axial and azimuthal Doppler cooling of atoms in 1D optical molasses composed of two counter-propagating HBBs and discuss the azimuthal influence of the HBB on the Doppler cooling limit. We also find that the Doppler limit of atoms in the molasses HBB is slightly below the conventional Doppler limit of hг/(2кB) due to the orbital angular momentum lh of the HBB.

  14. Radiation force on absorbing targets and power measurements of a high intensity focused ultrasound (HIFU) source

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Based on the analytic expressions for the radiated field of a circular concave piston given by Hasegawa et al.,an integral for calculation of the radiation force on a plane absorbing target in a spherically focused field is derived.A general relation between acoustic power P and normal radiation force Fn is obtained under the condition of kr 1.Numerical computation is carried out by using the symbolic computation program for practically focused sources and absorbing circular targets.The results show that,for a given source,there is a range of target positions where the radiation force is independent of the target’s position under the assumption that the contribution of the acoustic field behind the target to the radiation force can be neglected.The experiments are carried out and confirm that there is a range of target positions where the measured radiation force is basically independent of the target’s position even at high acoustic power (up to 700 W).It is believed that when the radiation force method is used to measure the acoustic power radiated from a focused source,the size of the target must be selected in such a way that no observable sound can be found in the region behind the target.

  15. Ferroelectric Domain Imaging Mechanism in High-Vacuum Scanning Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    ZENG Hua-Rong; YU Han-Feng; CHU Rui-Qing; LI Guo-Rong; YIN Qing-Rui

    2005-01-01

    @@ High-vacuum scanning force microscopy of the domain structures in PMN-PT single crystals is investigated. It has been shown that under high vacuum conditions, the polarization charges are not effectively compensated for by intrinsic screening charges from the ferroelectrics. This result suggests that the electrostatic tip-sample interaction plays a great contribution to the domain imaging mechanism in PMN-PT ferroelectric single crystals under high vacuum conditions.

  16. Effect of various loads on the force-time characteristics of the hang high pull.

    Science.gov (United States)

    Suchomel, Timothy J; Beckham, George K; Wright, Glenn A

    2015-05-01

    The purpose of this study was to investigate the effect of various loads on the force-time characteristics associated with peak power during the hang high pull (HHP). Fourteen athletic men (age: 21.6 ± 1.3 years; height: 179.3 ± 5.6 cm; body mass: 81.5 ± 8.7 kg; 1 repetition maximum [1RM] hang power clean [HPC]: 104.9 ± 15.1 kg) performed sets of the HHP at 30, 45, 65, and 80% of their 1RM HPC. Peak force, peak velocity, peak power, force at peak power, and velocity at peak power were compared between loads. Statistical differences in peak force (p = 0.001), peak velocity (p < 0.001), peak power (p = 0.015), force at peak power (p < 0.001), and velocity at peak power (p < 0.001) existed, with the greatest values for each variable occurring at 80, 30, 45, 80, and 30% 1RM HPC, respectively. Effect sizes between loads indicated that larger differences in velocity at peak power existed as compared with those displayed by force at peak power. It seems that differences in velocity may contribute to a greater extent to differences in peak power production as compared with force during the HHP. Further investigation of both force and velocity at peak power during weightlifting variations is necessary to provide insight on the contributing factors of power production. Specific load ranges should be prescribed to optimally train the variables associated with power development during the HHP.

  17. Opposing Shear-Induced Forces Dominate Inertial Focusing in Curved Channels and High Reynolds Numbers

    CERN Document Server

    Keinan, Eliezer; Nahmias, Yaakov

    2015-01-01

    Inertial focusing is the migration of particles in fluid toward equilibrium, where current theory predicts that shear-induced and wall-induced lift forces are balanced. First reported in 1961, this Segre-Silberberg effect is particularly useful for microfluidic isolation of cells and particles. Interestingly, recent work demonstrated particle focusing at high Reynolds numbers that cannot be explained by current theory. In this work, we show that non-monotonous velocity profiles, such as those developed in curved channels, create peripheral velocity maxima around which opposing shear-induced forces dominate over wall effects. Similarly, entry effects amplified in high Reynolds flow produce an equivalent trapping mechanism in short, straight channels. This new focusing mechanism in the developing flow regime enables a 10-fold miniaturization of inertial focusing devices, while our model corrects long-standing misconceptions about the nature of mechanical forces governing inertial focusing in curved channels.

  18. Relative Contributions of Heating and Momentum Forcing to High-Latitude Lower Thermospheric Winds

    Science.gov (United States)

    Kwak, Y. S.; Richmond, A. D.

    2015-12-01

    At high latitudes the thermospheric dynamics are gov­erned by various heat and momentum sources. Recently several modeling studies have been attempt­ed to understand the physical process that control the high-latitude lower thermospheric dynamics. Kwak and Richmond [2007] and Kwak et al. [2007] studied the momentum forcing bal­ance that are mainly responsible for maintaining the high-latitude lower thermospheric wind system by using the National Center for Atmospheric Research Thermo­sphere Ionosphere Electrodynamics General Circulation Model (NCAR TIE-GCM). Kwak and Richmond [2014] analyzed the divergence and vorticity of the high-latitude neutral wind field in the lower thermosphere during the south­ern summertime. In this study, we extend previous works by Kwak and Rich­mond [2007, 2014] and Kwak et al. [2007], which helped to better understand the physical processes maintaining thermospheric dynamics at high latitudes, and here perform a "term analysis of the potential vorticity equation" for the high-latitude neu­tral wind field in the lower thermosphere, on the basis of numerical simulations using the NCAR TIE-GCM. These analyses can provide insight into the relative strength of the heating and the momentum forcing responsible for driving rotational winds at the high-latitude lower thermosphere. The heating is the net heat including the heat transfer by downward molecular and eddy heat conduction, the absorption of solar ultraviolet (UV) and extreme ultraviolet (EUV) ra­diation, auroral heating by particles, Joule dissipation of ionospheric currents, release of chemical energy by the atomic oxygen recombination, and radiative CO2, NO and O infrared emissions. The momentum forcing is associated with the viscous force and the frictional drag force from convecting ions.

  19. Highly eccentric inspirals into a Schwarzschild black hole using self-force calculations

    Science.gov (United States)

    Osburn, Thomas; Warburton, Niels; Evans, Charles

    2016-03-01

    Eccentric-orbit inspirals into a massive black hole are calculated using the gravitational self-force. Both extreme-mass-ratio inspirals (EMRIs) and intermediate-mass-ratio inspirals (IMRIs) are modeled. These calculations include all dissipative and conservative first-order-in-the-mass-ratio effects for inspirals into a Schwarzschild black hole. We compute systems with initial eccentricities as high as e = 0.8 and initial separations as large as 100 M. In the case of EMRIs, the calculations follow the decay through many thousands of orbits up to the onset of the plunge. Inspirals are computed using an osculating-orbits scheme that is driven by self-force data from a hybridized self-force code. A Lorenz gauge self-force code is combined with highly accurate flux data from a Regge-Wheeler-Zerilli code, allowing the hybrid self-force model to track orbital phase in the inspirals to within 0.1 radians or better. Extensions of the method to include other physical effects are considered.

  20. Bullet Retarding Forces in Ballistic Gelatin by Analysis of High Speed Video

    CERN Document Server

    Gaylord, Steven; Courtney, Michael; Courtney, Amy

    2013-01-01

    Though three distinct wounding mechanisms (permanent cavity, temporary cavity, and ballistic pressure wave) are described in the wound ballistics literature, they all have their physical origin in the retarding force between bullet and tissue as the bullet penetrates. If the bullet path is the same, larger retarding forces produce larger wounding effects and a greater probability of rapid incapacitation. By Newton's third law, the force of the bullet on the tissue is equal in magnitude and opposite in direction to the force of the tissue on the bullet. For bullets penetrating with constant mass, the retarding force on the bullet can be determined by frame by frame analysis of high speed video of the bullet penetrating a suitable tissue simulant such as calibrated 10% ballistic gelatin. Here the technique is demonstrated with 9mm NATO bullets, 32 cm long blocks of gelatin, and a high speed video camera operating at 20,000 frames per second. It is found that different 9mm NATO bullets have a wide variety of pot...

  1. Nanomagnets with high shape anisotropy and strong crystalline anisotropy: perspectives on magnetic force microscopy.

    Science.gov (United States)

    Campanella, H; Jaafar, M; Llobet, J; Esteve, J; Vázquez, M; Asenjo, A; del Real, R P; Plaza, J A

    2011-12-16

    We report on a new approach for magnetic imaging, highly sensitive even in the presence of external, strong magnetic fields. Based on FIB-assisted fabricated high-aspect-ratio rare-earth nanomagnets, we produce groundbreaking magnetic force tips with hard magnetic character where we combine a high aspect ratio (shape anisotropy) together with strong crystalline anisotropy (rare-earth-based alloys). Rare-earth hard nanomagnets are then FIB-integrated to silicon microcantilevers as highly sharpened tips for high-field magnetic imaging applications. Force resolution and domain reversing and recovery capabilities are at least one order of magnitude better than for conventional magnetic tips. This work opens new, pioneering research fields on the surface magnetization process of nanostructures based either on relatively hard magnetic materials-used in magnetic storage media-or on materials like superparamagnetic particles, ferro/antiferromagnetic structures or paramagnetic materials.

  2. On the evolutionary stability of male harassment in a coercive mating game

    Directory of Open Access Journals (Sweden)

    Oyita Udiani

    2016-03-01

    Full Text Available In many animals, males employ coercive mating strategies to help them maximize their expected number of offspring. In such systems, selection will favor behavioral adaptations in females that help them mitigate harassment costs and maximize their reproductive fitness. Previously, Bokides et al. [1] presented a model showing how male harassment strategies can co-evolve with female habitat preferences in a mating game. Their results indicated that if females dispersed freely between habitats where males were present and where males were excluded, selection could favor males who strategically harassed at high (or low levels, depending on the proximity of their phenotype to a threshold level $h^*$. This article is a continuation of that work addressing the questions of stability at equilibria where males harass at the threshold level (i.e., $h^*$. We show these states are both locally and globally asymptotically stable. Further, we argue based on these results that $h^*$ is an evolutionary stable male harassment level at which females will be ideally distributed to match the resource quality and social environments of their alternative habitats.

  3. Measurement of Levitation Forces of High-"T[subscript c] Superconductors

    Science.gov (United States)

    Becker, M.; Koblischka, M. R.; Hartmann, U.

    2010-01-01

    We show the construction of a so-called levitation balance which is capable of measuring the levitation forces between a permanent magnet and a superconducting high-T[subscript c] thin film sample. The underlying theoretical basis is discussed in detail. The experiment is performed as an introductory physics experiment for school students as well…

  4. Measurement of Levitation Forces of High-"T[subscript c] Superconductors

    Science.gov (United States)

    Becker, M.; Koblischka, M. R.; Hartmann, U.

    2010-01-01

    We show the construction of a so-called levitation balance which is capable of measuring the levitation forces between a permanent magnet and a superconducting high-T[subscript c] thin film sample. The underlying theoretical basis is discussed in detail. The experiment is performed as an introductory physics experiment for school students as well…

  5. Monsoonal response to mid-holocene orbital forcing in a high resolution GCM

    NARCIS (Netherlands)

    Bosmans, J.H.C.; Drijfhout, S.S.; Tuenter, E.; Lourens, L.J.; Hilgen, F.J.; Weber, S.L.

    2012-01-01

    In this study, we use a sophisticated high-resolution atmosphere-ocean coupled climate model, EC-Earth, to investigate the effect of Mid-Holocene orbital forcing on summer monsoons on both hemispheres. During the Mid-Holocene (6 ka), there was more summer insolation on the Northern Hemisphere than

  6. Monsoonal response to mid-holocene orbital forcing in a high resolution GCM

    NARCIS (Netherlands)

    Bosmans, J.H.C.; Drijfhout, S.S.; Tuenter, E.; Lourens, L.J.; Hilgen, F.J.; Weber, S.L.

    2012-01-01

    In this study, we use a sophisticated high-resolution atmosphere-ocean coupled climate model, EC-Earth, to investigate the effect of Mid-Holocene orbital forcing on summer monsoons on both hemispheres. During the Mid-Holocene (6 ka), there was more summer insolation on the Northern Hemisphere than t

  7. Levitation force and magnetization in bulk and thin film high T{sub c} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Riise, A.B

    1998-04-01

    The authors present high-resolution measurements of the repulsive vertical force and its associated stiffness between a Nd-B-Fe magnet and a YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconductor in cylindrical geometry. The results are compared with theoretical predictions. The calculations are based on a model in which the superconductor is assumed to be either a sintered granular material or consisting of grains embedded in a nonactive matrix so that only intragranular currents are important. The critical state model is applied to each grain individually and closed form expressions for both vertical force F{sub z} and stiffness are obtained in a configuration with cylindrical symmetry. The model explains all features of the experimental results in a consistent way. A good quantitative agreement has been obtained using only three adjustable parameters. Several central aspects of the phenomenon of magnetic levitation with high-T{sub c} superconductors are presented. High-resolution measurements are made of the repulsive vertical force and its associated stiffness as well as the horizontal stabilizing force and the stiffness governing lateral vibrations. The results obtained at 77 K using a granular YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} sample and Nd-Fe-B magnet in a rectangular levitation configuration are compared with theoretical predictions. The calculations, which are based on the critical state model with the assumption that it applies to the grins individually, give closed-form expressions for all the measured quantities. It is concluded that the present model explains all features of the observations in a consistent way. Using only three adjustable parameters a good agreement exists also at a quantitative level. Experimental studies and theoretical modelling of the levitation force on a permanent magnet placed above a superconducting thin film are offered. It is shown that measurements of the levitation force is a simple and precise method to determine the

  8. Improvement of force factor of magnetostrictive vibration power generator for high efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Kita, Shota, E-mail: happiest3.7@gmail.com; Ueno, Toshiyuki; Yamada, Sotoshi [Kanazawa University, Kakuma-machi, Kanazawa-city, Ishikawa 920-1164 (Japan)

    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. Reforming Military Resources and the Authority of the United Nations Security Council in implementing coercive military measures

    Directory of Open Access Journals (Sweden)

    Sofia Santos

    2013-05-01

    Full Text Available The lack of a de facto military component is rather significant in normative and operational terms within the UN system. The differences among the permanent members of the Security Council, which exist since its beginning, have stopped provisions from being enforced which were included in the United Nations Charter, as well as the design of credible and effective alternatives. Considering that what is at stake are coercive military measures decided by the Security Council under Chapter VII, this becomes a decisive issue, as these measures were decided ultima ratio to maintain or restore international peace and security. Without an operational Military Staff Committee, without armed forces and without power of authority in the enforcement process, the Council is limited to approving decisions and held hostage to the options of Member-States, namely its permanent members. To ignore the urgency of a reform implies perpetuating a double paradox: on the one hand, the Security Council is required to take increasingly wider responsibility, laid down in article 24 and, in this context, in art. 42, and this body still lacks adequate military instruments; on the other hand, by correlating the reinforcement of efficiency, legitimacy and enforcement of Council decisions exclusively with the reform of its composition and work methodology, we are neglecting the fact that this change requires a reform of military instruments and of its authority within the scope of the body's multidimensional reform process. This paper begins by analyzing the enforcement mechanism established in the Charter and then addresses the issue underlying the delegation of implementing coercive military measures. Finally, the paper discusses the reform proposals, their guidelines and puts forward possible solutions.

  10. Magnetic properties and coercivity mechanism of precipitation-hardened Gd-Co based ribbons

    Institute of Scientific and Technical Information of China (English)

    Rong Chuan-Bing; Zhang Jian; Du Xiao-Bo; Zhang Hong-Wei; Zhang Shao-Ying; Shen Bao-Gen

    2004-01-01

    Gd(Co0.88-xCuxFe0.09Zr0.03)z ribbons with x = 0.075 - 0.200 and z=6.4-7.7 have been prepared by a meltspinning technique. A cellular microstructure consisting of 2:17 cells surrounded by the 1:5 cell boundary phase is obtained after precipitation hardening. The dependence of room temperature coercivity on the heat treatment process suggests that the long-time isothermal aging is not helpful for the development of magnetic properties. Positive temperature coefficient of remanence from room temperature to about 673K is typical for all samples, while positive temperature coefficient of coercivity is obtained only in ribbons with low Cu content. The coercivity mechanism of the precipitation-hardened ribbons at different temperatures is also discussed.

  11. Voltage control of the magnetic coercive field: Multiferroic coupling or artifact?

    Science.gov (United States)

    Vopsaroiu, M.; Cain, M. G.; Woolliams, P. D.; Weaver, P. M.; Stewart, M.; Wright, C. D.; Tran, Y.

    2011-03-01

    The ability to dynamically tune the coercive field of magnetic thin films is a powerful tool for applications, including in magnetic recording disk technologies. Recently, a number of papers have reported the electrical voltage control of the coercive field of various magnetic thin films in multiferroic composites. Theoretically, this is possible in magneto-electric (ME) multiferroics due to the piezoferroelectric component that can be electrically activated to dynamically modify the properties of the magnetic component of the composite via a direct or strain mediated ME coupling. In this paper we fabricated and examined such structures and we determined that the magnetic coercive field reduction is most likely due to a heating effect. We concluded that this effect is probably an artifact that cannot be attributed to a multiferroic coupling.

  12. Excess use of coercive measures in psychiatry among migrants compared with native Danes

    DEFF Research Database (Denmark)

    Nørredam, Marie Louise; Garcia-Lopez, A; Keiding, N;

    2010-01-01

    Norredam M, Garcia-Lopez A, Keiding N, Krasnik A. Excess use of coercive measures in psychiatry among migrants compared with native Danes.Objective: To investigate differences in risk of compulsory admission and other coercive measures in psychiatric emergencies among refugees and immigrants...... compared with that among native Danes. Method: A register-based retrospective cohort design. All refugees (n = 29 174) and immigrants (n = 33 287) who received residence permission in Denmark from 1.1.1993 to 31.12.1999 were included and matched 1 : 4 on age and sex with native Danes. Civil registration...... numbers were cross-linked to the Danish Psychiatric Central Register and the Registry of Coercive Measures in Psychiatric Treatment. Results: Refugees (RR = 1.82; 95%CI: 1.45; 2.29) and immigrants (RR = 1.14; 95%CI: 0.83; 1.56) experienced higher rates of compulsory admissions than did native Danes...

  13. Excitation Forces on Point Absorbers Exposed to High Order Non-linear Waves

    DEFF Research Database (Denmark)

    Viuff, Thomas Hansen; Andersen, Morten Thøtt; Kramer, Morten

    2013-01-01

    of proper methods to calculate design pressure distributions has led to structural failures such as buckling in the shells in wave energy prototypes. As a step towards understanding the complex loading from high order non-linear waves, this paper presents a practical approach to estimate wave excitation...... forces accounting for both non-linearity and diffraction effects. The method is validated by laboratory experiments using a hemispherical point absorber with a 6-axis force transducer, but the technique is believed to be applicable for most types of submerged or semi-submerged floating devices...

  14. Highly asymmetric interaction forces induced by acoustic waves in coupled plate structures

    CERN Document Server

    Fan, Xiying; Zhang, Shenwei; Ke, Manzhu; Liu, Zhengyou

    2015-01-01

    Mutual forces can be induced between coupled structures when illuminated by external acoustic waves. In this Letter, we propose a concept of asymmetric interaction between two coupled plate-like structures, which is generated by oppositely incident plane waves. Besides the striking contrast in magnitude, the mutual force induced by one of the incidences can be tuned extremely strong due to the resonant excitation of the flexural plate modes. The highly asymmetric interaction with enhanced strength in single side should be potentially useful, such as in designing ultrasound instruments and sensors.

  15. Prediction of forces and moments on finned bodies at high angle of attack in transonic flow

    Energy Technology Data Exchange (ETDEWEB)

    Oberkampf, W. L.

    1981-04-01

    This report describes a theoretical method for the prediction of fin forces and moments on bodies at high angle of attack in subsonic and transonic flow. The body is assumed to be a circular cylinder with cruciform fins (or wings) of arbitrary planform. The body can have an arbitrary roll (or bank) angle, and each fin can have individual control deflection. The method combines a body vortex flow model and lifting surface theory to predict the normal force distribution over each fin surface. Extensive comparisons are made between theory and experiment for various planform fins. A description of the use of the computer program that implements the method is given.

  16. Kink topology control by high-frequency external forces in nonlinear Klein-Gordon models

    Science.gov (United States)

    Alvarez-Nodarse, R.; Quintero, N. R.; Mertens, F. G.

    2014-10-01

    A method of averaging is applied to study the dynamics of a kink in the damped double sine-Gordon equation driven by both external (nonparametric) and parametric periodic forces at high frequencies. This theoretical approach leads to the study of a double sine-Gordon equation with an effective potential and an effective additive force. Direct numerical simulations show how the appearance of two connected π kinks and of an individual π kink can be controlled via the frequency. An anomalous negative mobility phenomenon is also predicted by theory and confirmed by simulations of the original equation.

  17. Kink topology control by high-frequency external forces in nonlinear Klein-Gordon models.

    Science.gov (United States)

    Alvarez-Nodarse, R; Quintero, N R; Mertens, F G

    2014-10-01

    A method of averaging is applied to study the dynamics of a kink in the damped double sine-Gordon equation driven by both external (nonparametric) and parametric periodic forces at high frequencies. This theoretical approach leads to the study of a double sine-Gordon equation with an effective potential and an effective additive force. Direct numerical simulations show how the appearance of two connected π kinks and of an individual π kink can be controlled via the frequency. An anomalous negative mobility phenomenon is also predicted by theory and confirmed by simulations of the original equation.

  18. Experimental Contribution to High-Precision Characterization of Magnetic Forces in Active Magnetic Bearings

    DEFF Research Database (Denmark)

    Kjølhede, Klaus; Santos, Ilmar

    2007-01-01

    Parameter identification procedures and model validation are major steps toward intelligent machines supported by active magnetic bearings (AMB). The ability of measuring the electromagnetic bearing forces, or deriving them from measuring the magnetic flux, strongly contributes to the model...... of the magnetic forces is conducted using different experimental tests: (i) by using hall sensors mounted directly on the poles (precise measurements of the magnetic flux) and by an auxiliary system, composed of strain gages and flexible beams attached to the rotor (ii) by measuring the input current and bearing...... gap variations, monitoring the bearing input signals. Advantages and drawbacks of the different methodologies are critically discussed. The linearity ranges are experimentally determined and the characterization of magnetic forces with a high accuracy of

  19. Experimental Contribution to High Precision Characterization of Magnetic Forces in Active Magnetic Bearings

    DEFF Research Database (Denmark)

    Kjølhede, Klaus; Santos, Ilmar

    2006-01-01

    Parameter identification procedures and model validation are major steps towards intelligent machines supported by active magnetic bearings (AMB). The ability of measuring the electromagnetic bearing forces, or deriving them from measuring the magnetic flux, strongly contributes to the model...... of the magnetic forces is conducted using different experimental tests: (a) by using hall sensors mounted directly on the poles (precise measurements of the magnetic flux) and by an auxiliary system, composed of strain gages and flexible beams attached to the rotor, (b) by measuring the input current and bearing...... gap variations, monitoring the bearing input signals. Advantages and drawbacks of the different methodologies are critically discussed. The linearity ranges are experimentally determined and the characterization of magnetic forces with a high accuracy of less than 1% is achieved. (%error is normalized...

  20. Force measurement and design of a torquing high-pull headgear.

    Science.gov (United States)

    Tabash, J W; Sandrik, J L; Bowman, D; Lang, R L; Klapper, L

    1984-07-01

    The dynamic extraoral force analyzer (DEFA) was found to be capable of measuring linear deflection as a function of force created by a headgear. Ten standard nontorqued face-bows with a cervical and a high-pull direction were tested to determine the reliability of the DEFA. Statistical analysis showed the DEFA to be reliable and accurate in differentiating various directions and deflections of maxillary molars. Doubled-over distal ends of the inner bow with 0 degree of torque and a parietal direction of pull were used as controls. The same face-bows with 9 degrees of buccal root torque were tested on the DEFA. These face-bows were tested to determine whether transverse translation without buccal crown tipping of the maxillary first molar will occur. Statistical analysis showed that transverse translation occurred at a force of 200 to 347 gm.

  1. Depolarization corrections to the coercive field in thin-film ferroelectrics

    CERN Document Server

    Dawber, M; Littlewood, P B; Scott, J F

    2003-01-01

    Empirically, the coercive field needed to reverse the polarization in a ferroelectric increases with decreasing film thickness. For ferroelectric films of 100 mu m to 100 nm in thickness the coercive field has been successfully described by a semi-empirical scaling law. Accounting for depolarization corrections, we show that this scaling behaviour is consistent with field measurements of ultrathin ferroelectric capacitors down to one nanometre in film thickness. Our results also indicate that the minimum film thickness, determined by a polarization instability, can be tuned by the choice of electrodes, and recommendations for next-generation ferroelectric devices are discussed. (letter to the editor)

  2. Low coercive field of polymer ferroelectric via x-ray induced phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyeon Jun; Kim, Jihong; Lee, Hye Jeong; Kwak, Jeong Hun; Kim, Jae Myung; Lee, Sung Su; Kim, Dong-Yu; Jo, Ji Young, E-mail: jyjo@gist.ac.kr [School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Oryong-Dong, Buk-Gu, Gwangju 61005 (Korea, Republic of); Kwon, Owoong; Kim, Yunseok [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 400-746 (Korea, Republic of)

    2015-12-28

    We present an experimental strategy via X-ray irradiation combined with time-resolved X-ray diffraction to reduce a coercive field of ferroelectric thin films. We found in real-time that X-ray irradiation enables the irreversible phase transition from a polar to non-polar phase in ferroelectric poly(vinylidene fluoride-trifluoroethylene) thin films. The non-polar regions act as initial nucleation sites for opposite domains thus reducing the coercive field, directly related to the switching of domains, by 48%.

  3. Assessment of coercive and noncoercive pressures to enter drug abuse treatment.

    Science.gov (United States)

    Marlowe, D B; Kirby, K C; Bonieskie, L M; Glass, D J; Dodds, L D; Husband, S D; Platt, J J; Festinger, D S

    1996-10-01

    This paper reports preliminary data derived from a standardized interview scoring procedure for detecting and characterizing coercive and noncoercive pressures to enter substance abuse treatment. Coercive and noncoercive pressures stemming from multiple psychosocial domains are operationalized through recourse to established behavioral principles. Inter-rater reliability for the scoring procedure was exceptional over numerous rater trials. Substantive analyses indicate that, among clients in outpatient cocaine treatment, 'coercion' is operative in multiple psychosocial domains, and that subjects perceive legal pressures as exerting substantially less influence over their decisions to enter treatment than informal psychosocial pressures. Implications for drug treatment planning, legal and ethical issues, and directions for future research are proposed.

  4. Angular dependence of the exchange bias and coercivity of IrMn/Co bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Nicolodi, S. [Instituto de Fisica-UFRGS, CP 15051, 91501-970 Porto Alegre, RS (Brazil)]. E-mail: nicolodi@if.ufrgs.br; Pereira, L.G. [Instituto de Fisica-UFRGS, CP 15051, 91501-970 Porto Alegre, RS (Brazil); Schmidt, J.E. [Instituto de Fisica-UFRGS, CP 15051, 91501-970 Porto Alegre, RS (Brazil); Nagamine, L.C.C.M. [Instituto de Fisica-UFRGS, CP 15051, 91501-970 Porto Alegre, RS (Brazil); Viegas, A.D.C. [Departamento de Fisica, CCNE, UFSM, 97105-900, Santa Maria, RS (Brazil); Deranlot, C. [Unite Mixte de Physique CNRS/Thales, 91767 Palaiseau and Universite Paris-Sud, 91405 Orsay (France); Petroff, F. [Unite Mixte de Physique CNRS/Thales, 91767 Palaiseau and Universite Paris-Sud, 91405 Orsay (France); Geshev, J. [Instituto de Fisica-UFRGS, CP 15051, 91501-970 Porto Alegre, RS (Brazil)

    2006-10-01

    In this study we present the in-plane angular dependences of the exchange-bias and coercive fields of magnetron-sputtered IrMn/Co exchange-coupled system before and after magnetic field annealing. Two experimental techniques were employed for the magnetic characterization of the samples, i.e., alternate gradient field magnetometry and anisotropic magnetoresistance measurements, which gave practically the same value for the exchange-bias field shift. An increase of the exchange-bias field and a substantial decrease of the coercivity are observed after the annealing. A phenomenological model was also used to adjust the data and to derive the anisotropy characteristics.

  5. A new class of high force, low-voltage, compliant actuation system

    Energy Technology Data Exchange (ETDEWEB)

    RODGERS,M. STEVEN; KOTA,SRIDHAR; HETRICK,JOEL; LI,ZHE; JENSEN,BRIAN D.; KRYGOWSKI,THOMAS W.; MILLER,SAMUEL L.; BARNES,STEPHEN MATTHEW; BURG,MICHAEL STANLEY

    2000-04-10

    Although many actuators employing electrostatic comb drives have been demonstrated in a laboratory environment, widespread acceptance in mass produced microelectromechanical systems (MEMS) may be limited due to issues associated with low drive force, large real estate demands, high operating voltages, and reliability concerns due to stiction. On the other hand, comb drives require very low drive currents, offer predictable response, and are highly compatible with the fabrication technology. The expand the application space and facilitate the widespread deployment of self-actuated MEMS, a new class of advanced actuation systems has been developed that maintains the highly desirable aspects of existing components, while significantly diminishing the issues that could impede large scale acceptance. In this paper, the authors will present low-voltage electrostatic actuators that offer a dramatic increase in force over conventional comb drive designs. In addition, these actuators consume only a small fraction of the chip area previously used, yielding significant gains in power density. To increase the stroke length of these novel electrostatic actuators, the authors have developed highly efficient compliant stroke amplifiers. The coupling of compact, high-force actuators with fully compliant displacement multipliers sets a new paradigm for highly integrated microelectromechanical systems.

  6. Percent voluntary inactivation and peak force predictions with the interpolated twitch technique in individuals with high ability of voluntary activation.

    Science.gov (United States)

    Herda, Trent J; Walter, Ashley A; Costa, Pablo B; Ryan, Eric D; Hoge, Katherine M; Stout, Jeffrey R; Cramer, Joel T

    2011-10-01

    The purpose of this study was to examine the sensitivity and peak force prediction capability of the interpolated twitch technique (ITT) performed during submaximal and maximal voluntary contractions (MVCs) in subjects with the ability to maximally activate their plantar flexors. Twelve subjects performed two MVCs and nine submaximal contractions with the ITT method to calculate percent voluntary inactivation (%VI). Additionally, two MVCs were performed without the ITT. Polynomial models (linear, quadratic and cubic) were applied to the 10-90% VI and 40-90% VI versus force relationships to predict force. Peak force from the ITT MVC was 6.7% less than peak force from the MVC without the ITT. Fifty-eight percent of the 10-90% VI versus force relationships were best fit with nonlinear models; however, all 40-90% VI versus force relationships were best fit with linear models. Regardless of the polynomial model or the contraction intensities used to predict force, all models underestimated the actual force from 22% to 28%. There was low sensitivity of the ITT method at high contraction intensities and the predicted force from polynomial models significantly underestimated the actual force. Caution is warranted when interpreting the % VI at high contraction intensities and predicted peak force from submaximal contractions.

  7. LIFT FORCE ON ROTATING SPHERE AT LOW REYNOLDS NUMBERS AND HIGH ROTATIONAL SPEEDS

    Institute of Scientific and Technical Information of China (English)

    由长福; 祁海鹰; 徐旭常

    2003-01-01

    The lift force on an isolated rotating sphere in a uniform flow was investigated by means of a three-dimensional numerical simulation for low Reynolds numbers (based on the sphere diameter) (Re < 68.4) and high dimensionless rotational speeds (Γ< 5). The Navier-Stokes equations in Cartesian coordinate system were solved using a finite volume formulation based on SIMPLE procedure. The accuracy of the numerical simulation was tested through a comparison with available theoretical, numerical and experimental results at low Reynolds numbers, and it was found that they were in close agreement under the above mentioned ranges of the Reynolds number and rotational speed. From a detailed computation of the flow field around a rotational sphere in extended ranges of the Reynolds number and rotational speed, the results show that, with increasing the rotational speed or decreasing the Reynolds number, the lift coefficient increases. An empirical equation more accurate than those obtained by previous studies was obtained to describe both effects of the rotational speed and Reynolds number on the lift force on a sphere. It was found in calculations that the drag coefficient is not significantly affected by the rotation of the sphere. The ratio of the lift force to the drag force, both of which act on a sphere in a uniform flow at the same time, was investigated. For a small spherical particle such as one of about 100μm in diameter, even if the rotational speed reaches about 106 revolutions per minute, the lift force can be neglected as compared with the drag force.

  8. HIGHLY QUALIFIED WORKING FORCE – KEY ELEMENT OF INNOVATIVE DEVELOPMENT MODEL

    Directory of Open Access Journals (Sweden)

    M. Avksientiev

    2014-12-01

    Full Text Available Highly qualified working force is a central element of intensive development model in modern society. The article surveys the experience of countries that managed to transform their economy to the innovative one. Ukrainian economy cannot stand aside processes that dominate the world economy trends, thus we are to use this experience to succeed in future. Today any government of the world is facing challenges that occur due to transformation of the economy into informational one. This type of economy causes its transformation form extensive to intensive one. The main reasons under that is limitation of nature resources, material factors of production. Thus this approach depends much on the quality of working force. Unfortunately in Ukraine there is a misbalance in specialist preparation. This puts additional pressure on the educational sphere also. In order to avoid this pressure we are to conduct reforms in education sphere. Nowadays, in the world views and concepts of governmental role in the social development are changing. This why, even at times of economic recession educational costs are not reduced under the new economical doctrine in the EU. Highly qualified specialists, while creating new products and services play role of engineers in XXI century. They are to lead their industries to world leading positions. From economic point of view, highly qualified specialists benefit society with higher income rates, taxation and thus, increasing the living standards in society. Thus, the majority if modern scientists prove the importance of highly trained working force for more effective economic development.

  9. A fast high-order method to calculate wakefield forces in an electron beam

    CERN Document Server

    Qiang, Ji; Ryne, Robert D

    2012-01-01

    In this paper we report on a high-order fast method to numerically calculate wakefield forces in an electron beam given a wake function model. This method is based on a Newton-Cotes quadrature rule for integral approximation and an FFT method for discrete summation that results in an $O(Nlog(N))$ computational cost, where $N$ is the number of grid points. Using the Simpson quadrature rule with an accuracy of $O(h^4)$, where $h$ is the grid size, we present numerical calculation of the wakefields from a resonator wake function model and from a one-dimensional coherent synchrotron radiation (CSR) wake model. Besides the fast speed and high numerical accuracy, the calculation using the direct line density instead of the first derivative of the line density avoids numerical filtering of the electron density function for computing the CSR wakefield force.

  10. Reply to "Comment on 'Performance of Halbach magnet with finite coercivity'"

    DEFF Research Database (Denmark)

    Insinga, Andrea Roberto; Bahl, Christian; Bjørk, Rasmus

    2017-01-01

    We reply to Dr. Xu's comment on our paper 'Performance of Halbach magnet arrays with finite coercivity' (JMMM 407 (2016), 369-376). Contrary to Dr. Xu's objections we show that the procedure employed by us correctly accounts for the shape effects of the magnet elements. We show that the partial d...

  11. Effect of microstructure on the coercivity of HDDR Nd-Fe-B permanent magnetic alloy

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The effect of the grain boundary microstructure on the anisotropy and coercivity was investigated in an HDDR Nd-Fe-B permanent magnetic alloy. Considering the special microstructure of its magnetic powder grain, an anisotropic theoretical model influenced simultaneously by the structure defect at the grain boundary and the exchange coupling interaction was put forward. The variations of the structure defect factors based on the nucleation and pinning mechanism with 2r0/lex (where r0 and lex are the defect thickness and the length of exchange coupling, respec-tively) were calculated. The results show that the coercivity mechanism of an HDDR Nd-Fe-B permanent magnetic alloy is greatly related to its microstructure defect at the grain boundary. For a fixed lex, when 2r0/lex < 1.67, the coercivity is controlled by the pinning mechanism; when 2r0/lex > 1.67, it is determined by the nucleation mechanism. The coercivity reaches the maximum when 2r0/lex = 1.67. The calcula-tion result is consistent well with the experimental result given by Morimoto et al.

  12. Coercive and Supportive Teacher Behaviour: Within- and across-Lesson Associations with the Classroom Social Climate

    Science.gov (United States)

    Mainhard, M. Tim; Brekelmans, Mieke; Wubbels, Theo

    2011-01-01

    The present study investigated whether the classroom social climate varies between lessons. Specifically, the within- and across-lesson associations of coercive and supportive teacher behaviour incidents with the classroom social climate were studied. Participants in the study were 48 Dutch secondary school teachers and their classes, that is,…

  13. Sex-Symmetric Effects of Coercive Behaviors on Mental Health? Not Exactly

    Science.gov (United States)

    Prospero, Moises

    2009-01-01

    The present study tested a section of the model of coercion in intimate partner violence (IPV) by investigating the relationships among coercion, IPV and mental health symptoms. The study's sample consisted of 573 culturally diverse university students (age M = 21.4) who completed a survey that measured past IPV victimization, coercive behaviors,…

  14. Predicting commitment in young adults' physically aggressive and sexually coercive dating relationships.

    Science.gov (United States)

    Young, Brennan J; Furman, Wyndol

    2013-11-01

    Intimate partner violence often begins during the courtship stage of romantic relationships. Although some relationships dissolve as a result of aggression, other relationships remain intact, increasing the risk for escalated violence. The present study identified factors predictive of individual differences in emerging adults' commitment to physically aggressive or sexually coercive dating relationships. Specifically, Rusbult's Investment Model of romantic relationships (e.g., investment, satisfaction, quality of alternatives, and commitment) was applied to a longitudinal sample of 148 young adult women who reported experiencing aggression or coercion from their current partners. To further explain commitment within aggressive or coercive dating relationships, rejection sensitivity and anxious and avoidant romantic relational styles were included as predictors of the Investment Model variables. A more avoidant romantic style indirectly predicted commitment through relationship satisfaction and investment. Both commitment and rejection sensitivity significantly predicted continuing an aggressive or coercive relationship 6 months later. The present study improves our understanding of the processes involved in relationship commitment. Continuing to understand these processes will inform interventions that seek to help women who have decided to end aggressive or coercive dating relationships.

  15. Authorities' Coercive and Legitimate Power: The Impact on Cognitions Underlying Cooperation

    Science.gov (United States)

    Hofmann, Eva; Hartl, Barbara; Gangl, Katharina; Hartner-Tiefenthaler, Martina; Kirchler, Erich

    2017-01-01

    The execution of coercive and legitimate power by an authority assures cooperation and prohibits free-riding. While coercive power can be comprised of severe punishment and strict monitoring, legitimate power covers expert, and informative procedures. The perception of these powers wielded by authorities stimulates specific cognitions: trust, relational climates, and motives. With four experiments, the single and combined impact of coercive and legitimate power on these processes and on intended cooperation of n1 = 120, n2 = 130, n3 = 368, and n4 = 102 student participants is investigated within two exemplary contexts (tax contributions, insurance claims). Findings reveal that coercive power increases an antagonistic climate and enforced compliance, whereas legitimate power increases reason-based trust, a service climate, and voluntary cooperation. Unexpectedly, legitimate power is additionally having a negative effect on an antagonistic climate and a positive effect on enforced compliance; these findings lead to a modification of theoretical assumptions. However, solely reason-based trust, but not climate perceptions and motives, mediates the relationship between power and intended cooperation. Implications for theory and practice are discussed. PMID:28149286

  16. Measuring the interaction force between a high temperature superconductor and a permanent magnet

    OpenAIRE

    Valenzuela, S. O.; Jorge, G. A.; Rodriguez, E.

    1999-01-01

    Repulsive and attractive forces are both possible between a superconducting sample and a permanent magnet, and they can give place to magnetic levitation or free-suspension phenomena, respectively. We show experiments to quantify this magnetic interaction which represents a promising field regarding to short-term technological applications of high temperature superconductors. The measuring technique employs an electronic balance and a rare-earth magnet that induces a magnetic moment in a melt...

  17. High-throughput single-molecule force spectroscopy for membrane proteins

    Energy Technology Data Exchange (ETDEWEB)

    Bosshart, Patrick D; Casagrande, Fabio; Frederix, Patrick L T M; Engel, Andreas; Fotiadis, Dimitrios [M E Mueller Institute for Structural Biology, Biozentrum of the University of Basel, CH-4056 Basel (Switzerland); Ratera, Merce; Palacin, Manuel [Institute for Research in Biomedicine, Barcelona Science Park, Department of Biochemistry and Molecular Biology, Faculty of Biology, University of Barcelona and Centro de Investigacion Biomedica en Red de Enfermedades Raras, E-08028 Barcelona (Spain); Bippes, Christian A; Mueller, Daniel J [BioTechnology Center, Technical University, Tatzberg 47, D-01307 Dresden (Germany)], E-mail: andreas.engel@unibas.ch, E-mail: dimitrios.fotiadis@mci.unibe.ch

    2008-09-24

    Atomic force microscopy-based single-molecule force spectroscopy (SMFS) is a powerful tool for studying the mechanical properties, intermolecular and intramolecular interactions, unfolding pathways, and energy landscapes of membrane proteins. One limiting factor for the large-scale applicability of SMFS on membrane proteins is its low efficiency in data acquisition. We have developed a semi-automated high-throughput SMFS (HT-SMFS) procedure for efficient data acquisition. In addition, we present a coarse filter to efficiently extract protein unfolding events from large data sets. The HT-SMFS procedure and the coarse filter were validated using the proton pump bacteriorhodopsin (BR) from Halobacterium salinarum and the L-arginine/agmatine antiporter AdiC from the bacterium Escherichia coli. To screen for molecular interactions between AdiC and its substrates, we recorded data sets in the absence and in the presence of L-arginine, D-arginine, and agmatine. Altogether {approx}400 000 force-distance curves were recorded. Application of coarse filtering to this wealth of data yielded six data sets with {approx}200 (AdiC) and {approx}400 (BR) force-distance spectra in each. Importantly, the raw data for most of these data sets were acquired in one to two days, opening new perspectives for HT-SMFS applications.

  18. The response of a high-speed train wheel to a harmonic wheel-rail force

    Science.gov (United States)

    Sheng, Xiaozhen; Liu, Yuxia; Zhou, Xin

    2016-09-01

    The maximum speed of China's high-speed trains currently is 300km/h and expected to increase to 350-400km/h. As a wheel travels along the rail at such a high speed, it is subject to a force rotating at the same speed along its periphery. This fast moving force contains not only the axle load component, but also many components of high frequencies generated from wheel-rail interactions. Rotation of the wheel also introduces centrifugal and gyroscopic effects. How the wheel responds is fundamental to many issues, including wheel-rail contact, traction, wear and noise. In this paper, by making use of its axial symmetry, a special finite element scheme is developed for responses of a train wheel subject to a vertical and harmonic wheel-rail force. This FE scheme only requires a 2D mesh over a cross-section containing the wheel axis but includes all the effects induced by wheel rotation. Nodal displacements, as a periodic function of the cross-section angle 6, can be decomposed, using Fourier series, into a number of components at different circumferential orders. The derived FE equation is solved for each circumferential order. The sum of responses at all circumferential orders gives the actual response of the wheel.

  19. Casimir force between $\\delta-\\delta^{\\prime}$ mirrors transparent at high frequencies

    CERN Document Server

    Braga, Alessandra N; Alves, Danilo T

    2016-01-01

    We investigate, in the context of a real massless scalar field in $1+1$ dimensions, models of partially reflecting mirrors simulated by Dirac $\\delta-\\delta^{\\prime}$ point interactions. In the literature, these models do not exhibit full transparency at high frequencies. In order to provide a more realistic feature for these models, we propose a modified $\\delta-\\delta^{\\prime}$ point interaction that enables to achieve full transparency in the limit of high frequencies. Taking this modified $\\delta-\\delta^{\\prime}$ model into account, we investigate the Casimir force, comparing our results with those found in the literature.

  20. High resolution miniature dilatometer based on an atomic force microscope piezocantilever

    Energy Technology Data Exchange (ETDEWEB)

    Park, J.-H.; Graf, D.; Murphy, T. P.; Tozer, S. W. [National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310 (United States); Schmiedeshoff, G. M. [Department of Physics, Occidental College, Los Angeles, California 90041 (United States)

    2009-11-15

    Thermal expansion, or dilation, is closely related to the specific heat, and provides useful information regarding material properties. The accurate measurement of dilation in confined spaces coupled with other limiting experimental environments such as low temperatures and rapidly changing high magnetic fields requires a new sensitive millimeter size dilatometer that has little or no temperature and field dependence. We have designed an ultracompact dilatometer using an atomic force microscope piezoresistive cantilever as the sensing element and demonstrated its versatility by studying the charge density waves in alpha uranium to high magnetic fields (up to 31 T). The performance of this piezoresistive dilatometer was comparable to that of a titanium capacitive dilatometer.

  1. Radiation forces on a Rayleigh dielectric sphere produced by highly focused parabolic scaling Bessel beams.

    Science.gov (United States)

    Guo, Mengwen; Zhao, Daomu

    2017-02-20

    The radiation forces on a Rayleigh dielectric particle induced by a highly focused parabolic scaling Bessel beam (PSBB) are investigated. Numerical results show that the zero-order PSBB can be used to trap a high-index particle at the focus and near the focus by the first-order PSBB. For the low-index particle, it can be guided or confined in the dark core of the nonzero-order PSBB but cannot be stably trapped in this single-beam trap. Further, we analyze the condition of trapping stability. It is found that the lower limit in the particle radius for stable trapping is different for different orders.

  2. High-speed atomic force microscope based on an astigmatic detection system

    Energy Technology Data Exchange (ETDEWEB)

    Liao, H.-S.; Chen, Y.-H.; Hwu, E.-T.; Chang, C.-S.; Hwang, I.-S., E-mail: ishwang@phys.sinica.edu.tw [Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan (China); Ding, R.-F.; Huang, H.-F.; Wang, W.-M. [Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan (China); Department of Mechanical Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Huang, K.-Y. [Department of Mechanical Engineering, National Taiwan University, Taipei 10617, Taiwan (China)

    2014-10-15

    High-speed atomic force microscopy (HS-AFM) enables visualizing dynamic behaviors of biological molecules under physiological conditions at a temporal resolution of 1s or shorter. A small cantilever with a high resonance frequency is crucial in increasing the scan speed. However, detecting mechanical resonances of small cantilevers is technically challenging. In this study, we constructed an atomic force microscope using a digital versatile disc (DVD) pickup head to detect cantilever deflections. In addition, a flexure-guided scanner and a sinusoidal scan method were implemented. In this work, we imaged a grating sample in air by using a regular cantilever and a small cantilever with a resonance frequency of 5.5 MHz. Poor tracking was seen at the scan rate of 50 line/s when a cantilever for regular AFM imaging was used. Using a small cantilever at the scan rate of 100 line/s revealed no significant degradation in the topographic images. The results indicate that a smaller cantilever can achieve a higher scan rate and superior force sensitivity. This work shows the potential for using a DVD pickup head in future HS-AFM technology.

  3. Magnetic Signals of High-Temperature Superconductor Bulk During the Levitation Force Measurement Process

    Science.gov (United States)

    Huang, Huan; Zheng, Jun; Qian, Nan; Che, Tong; Zheng, Botian; Jin, Liwei; Deng, Zigang

    2017-05-01

    In order to study the commonly neglected magnetic field information in the course of levitation force measurement process in a superconducting maglev system, a multipoint magnetic field measurement platform was employed to acquire magnetic signals of a bulk high-Tc superconductor on both the top and the bottom surface. Working conditions including field cooling (FC) and zero field cooling were investigated for these vertical down and up motions above a permanent magnet guideway performed on a HTS maglev measurement system. We have discussed the magnetic flux variation process based on the Bean model. A magnetic hysteresis effect similar to the levitation force hysteresis loop of the bulk superconductor was displayed and analyzed in this paper. What is more valuable, there exists some available magnetic flux on the top surface of the bulk superconductor, and the proportion is as high as 62.42% in the FC condition, which provides an experimental hint to design the superconductor bulk and the applied field for practical use in a more efficient way. In particular, this work reveals real-time magnetic flux variation of the bulk superconductor in the levitation application, which is the other important information in contrast to the macroscopic levitation and guidance force investigations in previous studies, and it enriches the existing research methods. The results are significant for understanding the magnetic characteristic of superconductors, and they can contribute to optimize the present HTS maglev system design.

  4. Magnetic Signals of High-Temperature Superconductor Bulk During the Levitation Force Measurement Process

    Science.gov (United States)

    Huang, Huan; Zheng, Jun; Qian, Nan; Che, Tong; Zheng, Botian; Jin, Liwei; Deng, Zigang

    2017-02-01

    In order to study the commonly neglected magnetic field information in the course of levitation force measurement process in a superconducting maglev system, a multipoint magnetic field measurement platform was employed to acquire magnetic signals of a bulk high-Tc superconductor on both the top and the bottom surface. Working conditions including field cooling (FC) and zero field cooling were investigated for these vertical down and up motions above a permanent magnet guideway performed on a HTS maglev measurement system. We have discussed the magnetic flux variation process based on the Bean model. A magnetic hysteresis effect similar to the levitation force hysteresis loop of the bulk superconductor was displayed and analyzed in this paper. What is more valuable, there exists some available magnetic flux on the top surface of the bulk superconductor, and the proportion is as high as 62.42% in the FC condition, which provides an experimental hint to design the superconductor bulk and the applied field for practical use in a more efficient way. In particular, this work reveals real-time magnetic flux variation of the bulk superconductor in the levitation application, which is the other important information in contrast to the macroscopic levitation and guidance force investigations in previous studies, and it enriches the existing research methods. The results are significant for understanding the magnetic characteristic of superconductors, and they can contribute to optimize the present HTS maglev system design.

  5. Experimental and numerical investigation of nanoparticle releasing in AFM nanomanipulation using high voltage electrostatic forces

    Science.gov (United States)

    Ghattan Kashani, H.; Shokrolahi, S.; Akbari Moayyer, H.; Shariat Panahi, M.; Shahmoradi Zavareh, A.

    2017-07-01

    Atomic Force Microscopes (AFMs) have been widely used as nanomanipulators due to their versatility to work with a broad range of materials and their controllable interaction force, among other features. While AFMs can effectively grasp, move, and position nanoscale objects in 2D environments through basic pull/push operations, they often lack the high precision required in many 3D pick and place applications, especially in non-vacuum environments. In this study, a novel method to resolve the adhesion problem between nanoscale objects and the AFM tip has been developed and tested. The method is based on the application of a high electrostatic voltage to the tip to produce the repulsive force required for the release of the nanoobject. The method is proposed for conductive nanoparticles and tips used in many nanomanipulation applications, and can be easily implemented on typical AFMs with minimal alterations. The applicability of the proposed method is investigated through a series of combined Molecular Dynamics/Finite Element simulations.

  6. High-resolution dynamic atomic force microscopy in liquids with different feedback architectures

    Directory of Open Access Journals (Sweden)

    John Melcher

    2013-02-01

    Full Text Available The recent achievement of atomic resolution with dynamic atomic force microscopy (dAFM [Fukuma et al., Appl. Phys. Lett. 2005, 87, 034101], where quality factors of the oscillating probe are inherently low, challenges some accepted beliefs concerning sensitivity and resolution in dAFM imaging modes. Through analysis and experiment we study the performance metrics for high-resolution imaging with dAFM in liquid media with amplitude modulation (AM, frequency modulation (FM and drive-amplitude modulation (DAM imaging modes. We find that while the quality factors of dAFM probes may deviate by several orders of magnitude between vacuum and liquid media, their sensitivity to tip–sample forces can be remarkable similar. Furthermore, the reduction in noncontact forces and quality factors in liquids diminishes the role of feedback control in achieving high-resolution images. The theoretical findings are supported by atomic-resolution images of mica in water acquired with AM, FM and DAM under similar operating conditions.

  7. Forced and natural gradient tracer tests in a highly heterogeneous porous aquifer: instrumentation and measurements

    Science.gov (United States)

    Ptak, T.; Teutsch, G.

    1994-07-01

    At the Horkheimer Insel experimental field site, several short to intermediate distance forced and natural gradient tracer tests with depth-integrated and multilevel sampling were conducted to characterize the aquifer transport properties. Compared with other test sites, the aquifer at the Horkheimer Insel is highly heterogeneous and highly conductive. Hence, new tracer measurement techniques had to be developed. This paper presents some of the instrumentation developed together with measurements and their initial interpretation. The results demonstrate that for contaminant transport predictions in highly heterogeneous and highly conductive aquifers, investigation techniques with a high resolution in time and space are needed. The aquifer heterogeneity is evident from the spatial variability of peak concentration, transport velocity and longitudinal macrodispersivity values obtained from the tracer tests. Furthermore, the tracer test results indicate that at the observation scale investigated, a complex numerical flow and transport model is needed to describe adequately mass transport within the heterogeneous aquifer.

  8. High sensitivity piezomagnetic force microscopy for quantitative probing of magnetic materials at the nanoscale.

    Science.gov (United States)

    Chen, Qian Nataly; Ma, Feiyue; Xie, Shuhong; Liu, Yuanming; Proksch, Roger; Li, Jiangyu

    2013-07-01

    Accurate scanning probing of magnetic materials at the nanoscale is essential for developing and characterizing magnetic nanostructures, yet quantitative analysis is difficult using the state of the art magnetic force microscopy, and has limited spatial resolution and sensitivity. In this communication, we develop a novel piezomagnetic force microscopy (PmFM) technique, with the imaging principle based on the detection of magnetostrictive response excited by an external magnetic field. In combination with the dual AC resonance tracking (DART) technique, the contact stiffness and energy dissipation of the samples can be simultaneously mapped along with the PmFM phase and amplitude, enabling quantitative probing of magnetic materials and structures at the nanoscale with high sensitivity and spatial resolution. PmFM has been applied to probe magnetic soft discs and cobalt ferrite thin films, demonstrating it as a powerful tool for a wide range of magnetic materials.

  9. Schlieren High Speed Imaging on Fluid Flow in Liquid Induced by Plasma-driven Interfacial Forces

    Science.gov (United States)

    Lai, Janis; Foster, John

    2016-10-01

    Effective plasma-based water purification depends heavily on the transport of plasma-derived reactive species from the plasma into the liquid. Plasma interactions at the liquid-gas boundary are known to drive circulation in the bulk liquid. This forced circulation is not well understood. A 2-D plasma- in-liquid water apparatus is currently being investigated as a means to study the plasma-liquid interface to understand not only reactive species flows but to also understand plasma- driven fluid dynamic effects in the bulk fluid. Using Schlieren high speed imaging, plasma-induced density gradients near the interfacial region and into the bulk solution are measured to investigate the nature of these interfacial forces. Plasma-induced flow was also measured using particle imaging velocimetry. NSF CBET 1336375 and DOE DE-SC0001939.

  10. Analysis of Electromagnetics Forces on Magnetically Suspended High-Speed Trains

    Directory of Open Access Journals (Sweden)

    Daniel Mayer

    2004-01-01

    Full Text Available High-speed superexpresses (HSST developed by Japanese airlines (JAL are based on the electrodynamics principle of magnetic suspension. The track contains short-circuited coils and interaction between them and superconductive coils in the vehicle produces its suspension. The paper includes a mathematical model for traction electrodynamics suspension device HSST represented by a system of linear differential equations with coefficients varying in time. Numerical analysis of this model fields the velocity-dependent lift and drag forces acting on the system. The time distribution of the lift force exhibits certain oscillations that may be suppressed by suitable placement of several superconductive levitation wings in the vehicle. The results obtained are in a good agreement with the knowledge found by various authors on prototype vehicles.

  11. Tip radius preservation for high resolution imaging in amplitude modulation atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, Jorge R., E-mail: jorge.rr@cea.cu [Instituto de Ciencia de Materiales de Madrid, Sor Juana Inés de la Cruz 3, Canto Blanco, 28049 Madrid, España (Spain)

    2014-07-28

    The acquisition of high resolution images in atomic force microscopy (AFM) is correlated to the cantilever's tip shape, size, and imaging conditions. In this work, relative tip wear is quantified based on the evolution of a direct experimental observable in amplitude modulation atomic force microscopy, i.e., the critical amplitude. We further show that the scanning parameters required to guarantee a maximum compressive stress that is lower than the yield/fracture stress of the tip can be estimated via experimental observables. In both counts, the optimized parameters to acquire AFM images while preserving the tip are discussed. The results are validated experimentally by employing IgG antibodies as a model system.

  12. Measuring the interaction force between a high temperature superconductor and a permanent magnet

    Science.gov (United States)

    Valenzuela, S. O.; Jorge, G. A.; Rodríguez, E.

    1999-11-01

    Repulsive and attractive forces are both possible between a superconducting sample and a permanent magnet, and they can give rise to magnetic levitation or free-suspension phenomena, respectively. We show experiments to quantify this magnetic interaction, which represents a promising field with regard to short-term technological applications of high temperature superconductors. The measuring technique employs an electronic balance and a rare-earth magnet that induces a magnetic moment in a melt-textured YBa2Cu3O7 superconductor immersed in liquid nitrogen. The simple design of the experiments allows a fast and easy implementation in the advanced physics laboratory with a minimum cost. Actual levitation and suspension demonstrations can be done simultaneously as a help to interpret magnetic force measurements.

  13. Large coercivity FePt nanoparticles prepared via a one-step method without post-annealing

    Science.gov (United States)

    Zhang, Xinwei; Xiong, Fang; Jiang, Xiaohong; Hua, Zhenghe; Wang, Chunlei; Yang, Shaoguang

    2016-12-01

    L10 FePt nanoparticles were synthesized by a one-step sol-gel autocombustion method, using nontoxic ferric nitrate, hexachloroplatinic acid, and glycine as starting materials. In contrast to common syntheses, high-temperature post-annealing was not required to form the L10 FePt phase. The entire ignition and combustion process lasted no more than one minute. The L10 FePt phase could form in the presence of the high temperature caused by the exothermic combustion reaction. Adjusting the glycine-to-metal ion molar ratio from 0.5 to 6.0 allowed its effects on the phase transformation and magnetic properties of the products to be investigated. X-ray diffraction indicated that pure phase L10 FePt was obtained at a glycine-to-metal ion molar ratio of 1.5. Transmission electron microscopy indicated that the monodisperse L10 FePt nanoparticles had an average particle size of about 20 nm. The reasons why the as-synthesized L10 FePt nanoparticles were not aggregated and sintered could be attributed to the large amount, a gas is being released and the short duration of heat treatment during this combustion. This finding constituted a significant improvement in the synthesis of L10 FePt nanoparticles. Magnetic measurements showed that the L10 FePt nanoparticles had a coercivity of 15.8 kOe at 300 K, and 23.2 kOe at 5 K. Thus, the L10 FePt nanoparticles had a very large coercivity.

  14. Development of nanomanipulator using a high-speed atomic force microscope coupled with a haptic device

    Energy Technology Data Exchange (ETDEWEB)

    Iwata, F., E-mail: tmfiwat@ipc.shizuoka.ac.jp [Faculty of Engineering, Shizuoka University, Johoku, Naka-ku, Hamamatsu 432-8561 (Japan); Research Institute of Electronics, Shizuoka University, Johoku, Naka-ku, Hamamatsu 432-8011 (Japan); Ohashi, Y.; Ishisaki, I. [Faculty of Engineering, Shizuoka University, Johoku, Naka-ku, Hamamatsu 432-8561 (Japan); Picco, L.M. [H Will Physics Laboratory and IRC in Nanotechnology, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Ushiki, T. [Graduate School of Medical and Dental Sciences, Niigata University, Asahimachidori, Niigata, 951-8122 (Japan)

    2013-10-15

    The atomic force microscope (AFM) has been widely used for surface fabrication and manipulation. However, nanomanipulation using a conventional AFM is inefficient because of the sequential nature of the scan-manipulation scan cycle, which makes it difficult for the operator to observe the region of interest and perform the manipulation simultaneously. In this paper, a nanomanipulation technique using a high-speed atomic force microscope (HS-AFM) is described. During manipulation using the AFM probe, the operation is periodically interrupted for a fraction of a second for high-speed imaging that allows the topographical image of the manipulated surface to be periodically updated. With the use of high-speed imaging, the interrupting time for imaging can be greatly reduced, and as a result, the operator almost does not notice the blink time of the interruption for imaging during the manipulation. This creates a more intuitive interface with greater feedback and finesse to the operator. Nanofabrication under real-time monitoring was performed to demonstrate the utility of this arrangement for real-time nanomanipulation of sample surfaces under ambient conditions. Furthermore, the HS-AFM is coupled with a haptic device for the human interface, enabling the operator to move the HS-AFM probe to any position on the surface while feeling the response from the surface during the manipulation. - Highlights: • A nanomanipulater based on a high-speed atomic force microscope was developped. • High-speed imaging provides a valuable feedback during the manipulation operation. • Operator can feel the response from the surface via a haptic device during manipulation. • Nanofabrications under real-time monitoring were successfully performed.

  15. Fabrication and magnetic properties of Co7oCu3o alloy nanowire arrays with high coercivity%高矫顽力的C0(70)Cu(30)合金纳米线阵列的制备及磁性研究

    Institute of Scientific and Technical Information of China (English)

    刘晓旭; 赵兴涛; 张颖; 朱岩; 吴光恒

    2012-01-01

    利用直流电化学沉积法,在多孔阳极氧化铝模板中首次制备出了具有[220]取向的单晶面心立方结构的CoCu固溶体合金纳米线阵列,其Co含量高达70%.透射电子显微镜显示纳米线均匀连续,具有较高的长径比,约为300.磁性测量表明所制备的Co(70)Cu(30)合金纳米线具有超高的矫顽力Hc//=2438 Oe(1 Oe=79.5775 A/m)和较高的矩形比S//=0.76,远高于以往报道的CoCu合金纳米线的磁性,分析表明磁性好的主要原因是由于较高Co含量和高形状各向异性.通过磁性测量和模型计算,得到Co(70)Cu(30)合金纳米线阵列在反磁化过程中遵从对称扇型转动的球链模型,并从结构的角度分析了Co(70)Cu(30)合金纳米线阵列的反磁化行为.%CoCu solid solution alloy nanowire arrays which exhibit the face-centered cubic structure with strong [220] orientation along the nanowire axes are fabricated for first time in the anodic aluminum oxide template by electrodeposition. The proportion of Co ingredient in CoCu alloy nanowire arrays is up to 70%. Transmission electron microscopy revealts that the nanowire arrays are uniform and continuous and have a large aspect ratio of about 300. The magnetic hysteresis loop demonstrates that the Cor0Cua0 alloy nanowire arrays have a large coercivity of about 2438 Oe and relatively large squareness of about 0.76 parallel to nanowire arrays which greatly exceeds the value previousely reported. Good magnetic properties are achieved due mainly to the larger proportion of Co ingredient than that in the normal CoCu alloy nanowire arrays and the large shape anisotropy. The results of magnetic measurement and the calculations from formula demonstrate that the symmetric fanning mechanism of sphere chains model could be employed to explain the magnetization reversal process which is related to the structure of the Co70Cu3o nanowire arrays.

  16. Vertical and lateral forces between a permanent magnet and a high-temperature superconductor

    Science.gov (United States)

    Hull, John R.; Cansiz, Ahmet

    1999-12-01

    The vertical and horizontal forces and associated stiffnesses on a permanent magnet (PM) above a high-temperature superconductor (HTS) were measured during vertical and horizontal traverses in zero-field cooling (ZFC) and in field cooling (FC). In ZFC, the vertical stiffness was greater in the first descent than in the first ascent and second descent, and the stiffness in the second descent was between those of the first descent and the first ascent. At the FC position, the vertical stiffness was two times greater than the lateral stiffness at each height, to within 1% of the vertical stiffness value. The cross stiffness of vertical force with respect to lateral position was positive for FC, but negative for ZFC. Free-spin-down experiments of a PM levitated above a HTS were also performed. These results showed that the coefficient of friction is double valued at frequencies just below the rotor resonance, a result attributed to cross stiffness in the PM/HTS interaction. A frozen-image model was used to calculate the vertical and horizontal forces and stiffnesses, and reasonable agreement with the data occurred for vertical or horizontal movements of the PM less than several mm from the FC position.

  17. A broadband x-ray imaging spectroscopy with high-angular resolution: the FORCE mission

    Science.gov (United States)

    Mori, Koji; Tsuru, Takeshi Go; Nakazawa, Kazuhiro; Ueda, Yoshihiro; Okajima, Takashi; Murakami, Hiroshi; Awaki, Hisamitsu; Matsumoto, Hironori; Fukazawa, Yasushi; Tsunemi, Hiroshi; Takahashi, Tadayuki; Zhang, William W.

    2016-07-01

    We are proposing FORCE (Focusing On Relativistic universe and Cosmic Evolution) as a future Japan-lead Xray observatory to be launched in the mid 2020s. Hitomi (ASTRO-H) possesses a suite of sensitive instruments enabling the highest energy-resolution spectroscopy in soft X-ray band, a broadband X-ray imaging spectroscopy in soft and hard X-ray bands, and further high energy coverage up to soft gamma-ray band. FORCE is the direct successor to the broadband X-ray imaging spectroscopy aspect of Hitomi (ASTRO-H) with significantly higher angular resolution. The current design of FORCE defines energy band pass of 1-80 keV with angular resolution of black holes" in various mass-scales: "buried supermassive black holes (SMBHs)" (> 104 M⊙) residing in the center of galaxies in a cosmological distance, "intermediate-mass black holes" (102-104 M⊙) acting as the possible seeds from which SMBHs grow, and "orphan stellar-mass black holes" (mirror and wide-band X-ray detector. The focal length is currently planned to be 10 m. The silicon mirror with multi-layer coating is our primary choice to achieve lightweight, good angular optics. The detector is a descendant of hard X-ray imager onboard Hitomi (ASTRO-H) replacing its silicon strip detector with SOI-CMOS silicon pixel detector, allowing an extension of the low energy threshold down to 1 keV or even less.

  18. Atomic force microscopy with nanoelectrode tips for high resolution electrochemical, nanoadhesion and nanoelectrical imaging

    Science.gov (United States)

    Nellist, Michael R.; Chen, Yikai; Mark, Andreas; Gödrich, Sebastian; Stelling, Christian; Jiang, Jingjing; Poddar, Rakesh; Li, Chunzeng; Kumar, Ravi; Papastavrou, Georg; Retsch, Markus; Brunschwig, Bruce S.; Huang, Zhuangqun; Xiang, Chengxiang; Boettcher, Shannon W.

    2017-03-01

    Multimodal nano-imaging in electrochemical environments is important across many areas of science and technology. Here, scanning electrochemical microscopy (SECM) using an atomic force microscope (AFM) platform with a nanoelectrode probe is reported. In combination with PeakForce tapping AFM mode, the simultaneous characterization of surface topography, quantitative nanomechanics, nanoelectronic properties, and electrochemical activity is demonstrated. The nanoelectrode probe is coated with dielectric materials and has an exposed conical Pt tip apex of ∼200 nm in height and of ∼25 nm in end-tip radius. These characteristic dimensions permit sub-100 nm spatial resolution for electrochemical imaging. With this nanoelectrode probe we have extended AFM-based nanoelectrical measurements to liquid environments. Experimental data and numerical simulations are used to understand the response of the nanoelectrode probe. With PeakForce SECM, we successfully characterized a surface defect on a highly-oriented pyrolytic graphite electrode showing correlated topographical, electrochemical and nanomechanical information at the highest AFM-SECM resolution. The SECM nanoelectrode also enabled the measurement of heterogeneous electrical conductivity of electrode surfaces in liquid. These studies extend the basic understanding of heterogeneity on graphite/graphene surfaces for electrochemical applications.

  19. Coercivity enhancement of hot-deformed Nd-Fe-B magnets by the eutectic grain boundary diffusion process

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Lihua [Elements Strategy Initiative Center for Magnetic Materials, National Institute of Materials Science, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Science, University of Tsukuba, Tsukuba 305-8577 (Japan); Sepehri-Amin, H.; Ohkubo, T. [Elements Strategy Initiative Center for Magnetic Materials, National Institute of Materials Science, Tsukuba 305-0047 (Japan); Yano, M.; Kato, A.; Shoji, T. [Toyota Motor Corporation, Advanced Material Engineering Div., Susono 410-1193 (Japan); Hono, K., E-mail: kazuhiro.hono@nims.go.jp [Elements Strategy Initiative Center for Magnetic Materials, National Institute of Materials Science, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Science, University of Tsukuba, Tsukuba 305-8577 (Japan)

    2016-05-05

    Nd-M (M = Al, Cu, Ga, Zn, Mn) alloys with compositions close to eutectic points were investigated as diffusion sources for the grain boundary diffusion process to hot-deformed Nd-Fe-B magnets. Coercivity enhancement was observed for most of the alloys. Among them, the sample processed with Nd{sub 90}Al{sub 10} exhibited the highest coercivity of 2.5 T at room temperature. However, the sample processed with Nd{sub 70}Cu{sub 30} exhibited the highest coercivity of 0.7 T at 200 {sup °}C. Microstructural observations using scanning transmission electron microscope (STEM) showed that nonferromagnetic Nd-rich intergranular phase envelops the Nd{sub 2}Fe{sub 14}B grains after the diffusion process. Abnormal grain growth and the dissolution of Al into the Nd{sub 2}Fe{sub 14}B grains were observed in the sample processed with Nd{sub 90}Al{sub 10}, which explains its inferior thermal stability of coercivity compared to the sample processed with Nd{sub 70}Cu{sub 30}. The coercivity enhancement and poor thermal stability of the coercivity of the Nd{sub 90}Al{sub 10} diffusion-processed sample are discussed based on microstructure studies by transmission electron microscopy. - Highlights: • Coercivity of hot-deformed Nd-Fe-B magnets is enhanced by the infiltration of various R-TM eutectic alloys. • The sample infiltrated with Nd{sub 90}Al{sub 10} shows the highest coercivity of 2.5 T at room temperature. • At 200 °C, Nd{sub 70}Cu{sub 30} diffusion-processed sample possesses the highest coercivity of 0.7 T.

  20. Facile preparation of superhydrophobic surface with high adhesive forces based carbon/silica composite films

    Indian Academy of Sciences (India)

    Ruanbing Hu; Guohua Jiang; Xiaohong Wang; Xiaoguang Xi; Rijing Wang

    2013-11-01

    Glass substrates modified by carbon/silica composites are fabricated through a two-step process for the preparation of a superhydrophobic surface (water contact angle ≥ 150°). Carbon nanoparticles were first prepared through a deposition process on glass using a hydrothermal synthesis route, then the glass was modified by SiO2 using the hydrolysis reaction of tetraethylorthosilicate at room temperature. It is not only a facile method to create a superhydrophobic surface, but also helps to form a multi-functional surface with high adhesive forces.

  1. Joining Forces: Collaborating Internationally to Deliver High-Quality, Online Postgraduate Education in Pain Management

    Directory of Open Access Journals (Sweden)

    Elizabeth Devonshire

    2011-01-01

    Full Text Available The effective management of pain is a complex and costly global issue, requiring a range of innovative educational strategies to enable culturally appropriate and high-quality health care provision. In response to this issue, the Pain Management Research Institute at the University of Sydney (Sydney, Australia has established several strategic alliances with other overseas universities to deliver online postgraduate education in pain management. The present article discusses the rationale for joining forces, and the approach adopted in creating and maintaining these alliances. It also provides insights into the benefits, challenges and opportunities associated with collaborative educational initiatives of this nature, from institutional, academic and student perspectives.

  2. Wide-area scanner for high-speed atomic force microscopy

    OpenAIRE

    Watanabe, Hiroki; Uchihashi, Takayuki; Kobashi, Toshihide; Shibata, Mikihiro; Nishiyama, Jun; Yasuda, Ryohei; Ando, Toshio

    2013-01-01

    High-speed atomic force microscopy (HS-AFM) has recently been established. The dynamic processes and structural dynamics of protein molecules in action have been successfully visualized using HS-AFM. However, its maximum scan ranges in the X- and Y-directions have been limited to ∼1 μm and ∼4 μm, respectively, making it infeasible to observe the dynamics of much larger samples, including live cells. Here, we develop a wide-area scanner with a maximum XY scan range of ∼46 × 46 μm2 by magnifyin...

  3. Influence of the lateral movement on the levitation and guidance force in the high-temperature superconductor maglev system

    Science.gov (United States)

    Song, Honghai; de Haas, Oliver; Beyer, Christoph; Krabbes, Gernot; Verges, Peter; Schultz, Ludwig

    2005-05-01

    After the levitation force relaxation was studied for different field-cooling height and working-levitation height, the high-temperature superconductor (HTS) bulk was horizontally moved in the lateral direction above the permanent magnet guideway. Both levitation and guidance force were collected by the measurement system at the same time. It was found that the decay of levitation force is dependent on both the maximum lateral displacement and the movement cycle times, while the guidance force hysteresis curve does not change after the first cycle. This work provided scientific analysis for the HTS maglev system design.

  4. Recommendations for a National High Blood Pressure Community Education Plan. Report of Task Force III--Community Education.

    Science.gov (United States)

    National Institutes of Health (DHEW), Bethesda, MD. High Blood Pressure Information Center.

    Hypertensive disease being one of the most important medical problems now facing American medicine brought about the formation of the Federally sponsored National High Blood Pressure Education Program, which included four Task Forces. Task Force 3 reviews in this study information and experience useful for the development of guidelines for…

  5. Forced canonical thermalization in a hadronic transport approach at high density

    Science.gov (United States)

    Oliinychenko, Dmytro; Petersen, Hannah

    2017-03-01

    Hadronic transport approaches based on an effective solution of the relativistic Boltzmann equation are widely applied for the dynamical description of heavy ion reactions at low beam energies. At high densities, the assumption of binary interactions often used in hadronic transport approaches may not be applicable anymore. Therefore, we effectively simulate the high-density regime using the local forced canonical thermalization. This framework provides the opportunity to interpolate in a dynamical way between two different limits of kinetic theory: the dilute gas approximation and the ideal fluid case. This approach will be important for studies of the dynamical evolution of heavy ion collisions at low and intermediate energies as experimentally investigated at the beam energy scan program at RHIC, and in the future at FAIR and NICA. On the other hand, this new way of modeling hot and dense strongly interacting matter might be relevant for small systems at high energies (LHC and RHIC) as well.

  6. Enhancement of perpendicular magnetic anisotropy and coercivity in ultrathin Ru/Co/Ru films through the buffer layer engineering

    Science.gov (United States)

    Kolesnikov, Alexander G.; Stebliy, Maxim E.; Ognev, Alexey V.; Samardak, Alexander S.; Fedorets, Aleksandr N.; Plotnikov, Vladimir S.; Han, Xiufeng; Chebotkevich, Ludmila A.

    2016-10-01

    We present results on a study of the interplay between microstructure and the magnetic properties of ultrathin Ru/Co/Ru films with perpendicular magnetic anisotropy (PMA). To induce PMA in the Co layer, we experimentally determined thicknesses of the buffer and capping layers of Ru. The maximum value of PMA was observed for the Co thickness of 0.9 nm with the 3 nm thick capping layer. The effective anisotropy field (H eff) and coercive force (H c) of the Co layer are very sensitive to the Ru buffer layer thickness (t b). The values of H eff and H c increase approximately by two and ten times, correspondingly, when t b changes from 6 to 20 nm, owing to an increase in volume fraction of the crystalline phase as a result of the grains’ growth. PMA is found to be mainly enhanced by elastic strains induced by the lattice mismatch on the Ru/Co and Co/Ru interfaces, leading to the deformation of the Co lattice. The surface impact is determined to be less than 10% of the magneto-elastic contribution to the effective anisotropy. Observation of the magnetic domain structure by means of polar Kerr microscopy reveals that out-of-plane magnetization reversal occurs through the nucleation, growth, and annihilation of domains, where the average size drastically rises with the increasing t b.

  7. Large magnetocaloric effect, moment, and coercivity enhancement after coating Ni nanoparticles with Ag.

    Science.gov (United States)

    Srinath, Sanyadanam; Poddar, Pankaj; Das, Raja; Sidhaye, Deepti; Prasad, Bhagavatula Lakshmi Vara; Gass, James; Srikanth, Hariharan

    2014-06-06

    We observe a large magnetocaloric effect in monodisperse Ni and Ni(core)Ag(shell) nanoparticles in the superparamagnetic region. The organically passivated Ni nanospheres show a large magnetic entropy change of 0.9 J kg(-1)  K for a 3 T magnetic field change. In comparison to the surfactant-coated Ni nanoparticles, the Ni(core)Ag(shell) nanoparticles show an enhanced coercivity, magnetization, and magnetocaloric effect (1.3 kg K for a 3 T magnetic field change). The coercivity at 10 K increases from 360 Oe for Ni nanoparticles to nearly 610 Oe for Ni(core)Ag(shell) particles. This large enhancement is attributed to the enhanced inter-particle interaction, which is mediated by the metallic shell, over the relatively weaker dipolar interaction in the surfactant-coated Ni nanoparticles, and to modification of the surface spin structure.

  8. Angular dependence of coercivity with temperature in Co-based nanowires

    Science.gov (United States)

    Bran, C.; Espejo, A. P.; Palmero, E. M.; Escrig, J.; Vázquez, M.

    2015-12-01

    The magnetic behavior of arrays of Co and CoFe nanowire arrays has been measured in the temperature range between 100 and 300 K. We have paid particular attention to the angular dependence of magnetic properties on the applied magnetic field orientation. The experimental angular dependence of coercivity has been modeled according to micromagnetic analytical calculations, and we found that the propagation of a transversal domain wall mode gives the best fitting with experimental observations. That reversal mode holds in the whole measuring temperature range, for nanowires with different diameters and crystalline structure. Moreover, the quantitative strength of the magnetocrystalline anisotropy and its magnetization easy axis are determined to depend on the crystalline structure and nanowires diameter. The evolution of the magnetocrystalline anisotropy with temperature for nanowires with different composition gives rise to an opposite evolution of coercivity with increasing temperature: it decreases for CoFe while it increases for Co nanowire arrays.

  9. Magnetic Relaxation and Coercivity of Finite-size Single Chain Magnets

    Science.gov (United States)

    Gredig, Thomas; Byrne, Matthew; Vindigni, Alessandro

    2015-03-01

    The magnetic coercivity of hysteresis loops for iron phthalocyanine thin films depends on the iron chain length and the measurement sweep speed below 5 K. The average one-dimensional (1D) iron chain length in samples is controlled during deposition. These 1D iron chains can be tuned over one order of magnitude with the shortest chain having 100 elements. We show that the coercivity strongly increases with the average length of the iron chains, which self-assemble parallel to the substrate surface. Magnetic relaxation and sweep speed data suggest spin dynamics play an important role. Implementing Glauber dynamics with a finite-sized 1D Ising model provides qualitative agreement with experimental data. This suggests that iron phthalocyanine thin films act as single chain magnets and provide a solid test system for tunable finite-sized magnetic chains. This research has been supported with the NSF-DMR 0847552 grant.

  10. Angular dependence of coercivity with temperature in Co-based nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Bran, C., E-mail: cristina.bran@icmm.csic.es [Institute of Materials Science of Madrid, CSIC, 28049 Madrid (Spain); Espejo, A.P. [Departamento de Física, Universidad de Santiago de Chile (USACH) and Center for the Development of Nanoscience and Nanotechnology (CEDENNA), Avenida Ecuador 3493, 9170124 Santiago (Chile); Palmero, E.M. [Institute of Materials Science of Madrid, CSIC, 28049 Madrid (Spain); Escrig, J. [Departamento de Física, Universidad de Santiago de Chile (USACH) and Center for the Development of Nanoscience and Nanotechnology (CEDENNA), Avenida Ecuador 3493, 9170124 Santiago (Chile); Vázquez, M. [Institute of Materials Science of Madrid, CSIC, 28049 Madrid (Spain)

    2015-12-15

    The magnetic behavior of arrays of Co and CoFe nanowire arrays has been measured in the temperature range between 100 and 300 K. We have paid particular attention to the angular dependence of magnetic properties on the applied magnetic field orientation. The experimental angular dependence of coercivity has been modeled according to micromagnetic analytical calculations, and we found that the propagation of a transversal domain wall mode gives the best fitting with experimental observations. That reversal mode holds in the whole measuring temperature range, for nanowires with different diameters and crystalline structure. Moreover, the quantitative strength of the magnetocrystalline anisotropy and its magnetization easy axis are determined to depend on the crystalline structure and nanowires diameter. The evolution of the magnetocrystalline anisotropy with temperature for nanowires with different composition gives rise to an opposite evolution of coercivity with increasing temperature: it decreases for CoFe while it increases for Co nanowire arrays.

  11. Enhancement of magnetic coercivity and macroscopic quantum tunneling in monodispersed Co/CoO cluster assemblies

    OpenAIRE

    Peng, D. L.; Sumiyama, Kenji; Hihara, Takehiko; Yamamuro, S.; ヒハラ, タケヒコ; スミヤマ, ケンジ; 日原, 岳彦; 隅山, 兼治; Hihara, T.; Sumiyama, K.

    1999-01-01

    Magnetic properties have been measured for monodisperse-sized Co/CoO cluster assemblies prepared by a plasma-gas-condensation-type cluster beam deposition technique. The clear correlation obtained between exchange bias field and coercivity suggests the enhancement of uniaxial anisotropy owing to the exchange coupling between the ferromagnetic Co core and antiferromagnetic CoO shell, and magnetic disorder at the core-shell interface. A nonthermal magnetic relaxation observed below 8 K, being r...

  12. Cognitive Targeting: A Coercive Air Power Theory for Conventional Escalation Control Against Nuclear Armed Adversaries

    Science.gov (United States)

    2016-06-01

    COGNITIVE TARGETING: A COERCIVE AIR POWER THEORY FOR CONVENTIONAL ESCALATION CONTROL AGAINST NUCLEAR- ARMED ADVERSARIES BY PAUL A. GOOSSEN, MAJ...process with both critical analysis and with encouragement. Most importantly, I want to express my most sincere appreciation to my family. Their love...regional powers such as North Korea, the post-Cold War geo-political environment characterized by U.S. hegemony is fading away. In the emerging

  13. Covert Coercion: A Formal Analysis of Unconventional Warfare as an Interstate Coercive Policy Option

    Science.gov (United States)

    2013-06-01

    coercive effect, then proxy armies may be used to preserve the military resources of the coercing state.36 Nutter explicates further, “The reasons...food. Consider a large slice of pizza for dinner when an individual has not eaten since breakfast. Hungry, the individual’s desire for the pizza is...at a considerable level. After the first bite, the individual’s desire for the pizza is still great, but marginally less than it was before the first

  14. Childhood Sexual Abuse, Attachments in Childhood and Adulthood, and Coercive Sexual Behaviors in Community Males.

    Science.gov (United States)

    Langton, Calvin M; Murad, Zuwaina; Humbert, Bianca

    2017-04-01

    Associations between self-reported coercive sexual behavior against adult females, childhood sexual abuse (CSA), and child-parent attachment styles, as well as attachment with adult romantic partners, were examined among 176 adult community males. Attachment style with each parent and with romantic partners was also investigated as a potential moderator. Using hierarchical multiple regression analysis, avoidant attachment with mothers in childhood (and also with fathers, in a second model) accounted for a significant amount of the variance in coercive sexual behavior controlling for scores on anxious ambivalent and disorganized/disoriented attachment scales, as predicted. Similarly, in a third model, avoidance attachment in adulthood was a significant predictor of coercive sexual behavior controlling for scores on the anxiety attachment in adulthood scale. These main effects for avoidant and avoidance attachment were not statistically significant when CSA and control variables (other types of childhood adversity, aggression, antisociality, and response bias) were added in each of the models. But the interaction between scales for CSA and avoidance attachment in adulthood was significant, demonstrating incremental validity in a final step, consistent with a hypothesized moderating function for attachment in adulthood. The correlation between CSA and coercive sexual behavior was .60 for those with the highest third of avoidance attachment scores (i.e., the most insecurely attached on this scale), .24 for those with scores in the middle range on the scale, and .01 for those with the lowest third of avoidance attachment scores (i.e., the most securely attached). Implications for study design and theory were discussed.

  15. High g-Force Rollercoaster Rides Induce Sinus Tachycardia but No Cardiac Arrhythmias in Healthy Children.

    Science.gov (United States)

    Pieles, Guido E; Husk, Victoria; Blackwell, Teresa; Wilson, Deirdre; Collin, Simon M; Williams, Craig A; Stuart, A Graham

    2017-01-01

    Theme park operators and medical professionals advise children with heart conditions against using rollercoaster rides, but these recommendations are not evidence-based. The underlying assumption is that the combination of adrenergic stimulation through stress and acceleration might trigger arrhythmias in susceptible individuals. We conducted a cross-sectional observational study to assess heart rate and rhythm in healthy children during commercial rollercoaster rides. Twenty healthy children (9 male) aged 11-15 (mean 13.3 ± 1.4) years underwent continuous heart rate and rhythm monitoring (2-lead ECG) from 5 min before until 10 min after each of 4 high speed (>50 km h(-1)), high g-force (>4) commercial rollercoaster rides. Total recording time was 13 h 20 min. No arrhythmic events were detected. Resting heart rate was 81 ± 10 b min(-1) and increased to 158 ± 20 b·min(-1) during rides. The highest mean HR (165 ± 23 b min(-1)) was observed on the ride with the lowest g-force (4.5 g), but one of the highest speeds (100 km h(-1)). Anticipatory tachycardia (126 ± 15 b min(-1)) within 5 min was frequently observed. A 10 min recovery HR (124 ± 17 b min(-1)) was 56 % greater than resting HR. The speed and g-force experienced on roller coasters induce sinus tachycardia but do not elicit pathological arrhythmias in healthy children.

  16. Microstructure and coercivity in La-coated Nd2Fe14B thin films

    Directory of Open Access Journals (Sweden)

    M. Itakura

    2017-03-01

    Full Text Available We investigated La-coated Nd2Fe14B thin film magnets by scanning/transmission electron microscopy to clarify the coercivity enhancement mechanism in Nd-Fe-B permanent magnets. The coercivity of La-coated film magnets was increased from 8.5 to 15 kOe by post-annealing. The fcc-LaOx layer was epitaxially grown on [001]-oriented Nd2Fe14B fine grains with a crystallographic orientation relation of Nd2Fe14B (001[110] || LaOx (111[112¯], both in the as-deposited and post-annealed films. STEM-EDS elemental analysis revealed that the only difference caused by post-annealing was the O content in the LaOx layer, which increased from 15 to 35 at.%. These results suggest that the magnetocrystalline anisotropy of the Nd ions, which were reduced at the surface of Nd2Fe14B, would be recovered by the presence of O, leading to a remarkable increase in the coercivity.

  17. Influence of dipolar interactions on the angular-dependent coercivity of nickel nanocylinders

    Science.gov (United States)

    Bender, P.; Krämer, F.; Tschöpe, A.; Birringer, R.

    2015-04-01

    In this study the influence of dipolar interactions on the orientation-dependent magnetization behavior of an ensemble of single-domain nickel nanorods was investigated. The rods were synthesized by electrodeposition of nickel into porous alumina templates. Some of the rods were released from the oxide and embedded in gelatine hydrogels (ferrogel) at a sufficiently large average interparticle distance to suppress dipolar interactions. By comparing the orientation-dependent hystereses of the two ensembles in the template and the gel-matrix it could be shown that the dipolar interactions in the template considerably alter the functional form of the angular-dependent coercivity. Analysis of the magnetization curves for an angle of 60° between the rod-axes and the field revealed a significantly reduced coercivity of the template compared to the ferrogel, which could be directly attributed to a stray field induced magnetization reversal of a steadily increasing number of rods with increasing field strength. The magnetization curve of the template could be approximated by a weighted linear superposition of the hysteresis branches of the ferrogel. The magnetization reversal process of the rods was investigated by analyzing the angular-dependent coercivity of the non-interacting nanorods. Comparison of the functional form with analytical models and micromagnetic simulations emphasized the assumption of a localized magnetization reversal. Additionally, it could be shown that the nucleation field of rods with diameters in the range 18-29 nm tends to increase with increasing diameter.

  18. Temperature dependent coercivity and magnetization of light rare-earth Nd doped permalloy thin films

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Chen [Physics Department, Southeast University, Nanjing 211189 (China); Fu, Yu [Physics Department, Southeast University, Nanjing 211189 (China); Institut Nanosciences et Cryogénie, CEA, 38054 Grenoble (France); Zhang, Dong [Physics Department, Southeast University, Nanjing 211189 (China); School of Physics Science and Information Engineering, Liaocheng University, Liaocheng 252059 (China); Yuan, Shijun [Physics Department, Southeast University, Nanjing 211189 (China); Zhai, Ya, E-mail: yazhai@seu.edu.cn [Physics Department, Southeast University, Nanjing 211189 (China); Dong, Shuai [Physics Department, Southeast University, Nanjing 211189 (China); Zhai, Hongru [National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-01-15

    The temperature dependence of the magnetic properties of Ni{sub 80}Fe{sub 20} thin films with dilute Nd dopants has been studied. The effect of Nd dopants on the hysteresis loops of Nd-doped Ni{sub 80}Fe{sub 20} thin films is small at room temperature but large at low temperature. The measurements show an interesting temperature dependence of the coercivity with different concentrations of Nd impurities, which might be related to the film structure. The temperature dependence of the saturation magnetization for Nd-doped Ni{sub 80}Fe{sub 20} thin films is fitted by a theoretical expression of spin-wave excitation plus Stoner-type-like contribution, in which the spin-wave excitation plays a main role at low temperature. The spin-wave stiffness constant D evaluated from the fitting shows a strong doping concentration dependence. - Highlights: • The abnormal coercivity behavior of Nd-doped Permalloy thin films is studied. • The mechanism of temperature dependence of coercivity is discussed. • The effect of Nd dopants on temperature dependence of Ms is studied. • Spin-wave excitations and Stoner-type excitations are discussed quantitatively.

  19. Receptivity and Forced Response to Acoustic Disturbances in High-Speed Boundary Layers

    Science.gov (United States)

    Balakumar, P.; King, Rudolph A.; Chou, Amanda; Owens, Lewis R.; Kegerise, Michael A.

    2016-01-01

    Supersonic boundary-layer receptivity to freestream acoustic disturbances is investigated by solving the Navier-Stokes equations for Mach 3.5 flow over a sharp flat plate and a 7-deg half-angle cone. The freestream disturbances are generated from a wavy wall placed at the nozzle wall. The freestream acoustic disturbances radiated by the wavy wall are obtained by solving the linearized Euler equations. The results for the flat plate show that instability modes are generated at all the incident angles ranging from zero to highly oblique. However, the receptivity coefficient decreases by about 20 times when the incident angle increases from zero to a highly oblique angle of 68 degrees. The results for the cone show that no instability modes are generated when the acoustic disturbances impinge the cone obliquely. The results show that the perturbations generated inside the boundary layer by the acoustic disturbances are the response of the boundary layer to the external forcing. The amplitude of the forced disturbances inside the boundary layer are about 2.5 times larger than the incoming field for zero azimuthal wavenumber and they are about 1.5 times for large azimuthal wavenumbers.

  20. LLW disposal wasteform preparation in the UK: the role of high force compaction

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, L. F.; Fearnley, I. G. [British Nuclear Fuels Ltd., Sellafield (United Kingdom)

    1991-07-01

    British Nuclear Fuels plc (BNFL) owns and operates the principal UK solid low level radioactive waste (LLW) disposal site. The site is located at Drigg in West Cumbria some 6 km to the south east of BNFL's Sellafield reprocessing complex. Sellafield is the major UK generator of LLW, accounting for about 85% of estimated future arisings of raw (untreated, unpackaged) waste. Non-Sellafield consignors to the Drigg site include other BNFL production establishments, nuclear power stations, sites of UKAEA, Ministry of Defence facilities, hospitals, universities, radioisotope production sites and various other industrial organisations. In September 1987, BNFL announced a major upgrade of operations at the Drigg site aimed at improving management practices, the efficiency of space utilisation and enhancing the visual impact of disposal operations. During 1989 a review of plans for compaction and containerisation of Sellafield waste identified that residual voidage in ISO freight containers could be significant even after the introduction of compaction. Subsequent studies which examined a range of compaction and packaging options concluded that the preferred scheme centred on the use of high force compaction (HFC) of compactable waste, and grouting to take up readily accessible voidage in the wasteform. The paper describes the emergence of high force compaction as the preferred scheme for wasteform preparation and subsequent benefits against the background of the overall development of Low Level Waste disposal operations at Drigg.

  1. Cutting force and its frequency spectrum characteristics in high speed milling of titanium alloy with a polycrystalline diamond tool

    Institute of Scientific and Technical Information of China (English)

    Peng LIU; Jiu-hua XU; Yu-can FU

    2011-01-01

    In this paper, a series of experiments were performed by high speed milling of Ti-6.5Al-2Zr-1Mo-1V(TA15)by use of polycrystalline diamond(PCD)tools. The characteristics of high speed machining(HSM)dynamic milling forces were investigated. The effects of the parameters of the process, I.e., cutting speed, feed per tooth, and depth of axial cut, on cutting forces were studied. The cutting force signals under different cutting speed conditions and different cutting tool wear stages were analyzed by frequency spectrum analysis. The trend and frequency domain aspects of the dynamic forces were evaluated and discussed. The results indicate that a characteristic frequency in cutting force power spectrum does in fact exist. The amplitudes increase with the increase of cutting speed and tool wear level, which could be applied to the monitoring of the cutting process.

  2. Synthesis of one-molecule-thick single-crystalline nanosheets of energetic material for high-sensitive force sensor.

    Science.gov (United States)

    Yang, Guangcheng; Hu, Hailong; Zhou, Yong; Hu, Yingjie; Huang, Hui; Nie, Fude; Shi, Weimei

    2012-01-01

    Energetic material is a reactive substance that contains a great amount of potential energy, which is extremely sensitive to external stimuli like force. In this work, one-molecule-thick single-crystalline nanosheets of energetic material were synthesized. Very small force applied on the nanosheet proves to lead to the rotation of the tilted nitro groups, and subsequently change of current of the nanosheet. We apply this principle to design high-sensitive force sensor. A theoretical model of force-current dependence was established based on the nanosheets' molecular packing structure model that was well supported with the high resolution XPS, AFM analysis results. An ultra-low-force with range of several picoNewton to several nanoNewton can be measured by determination of corresponding current value.

  3. Evaluation and optimization of quartz resonant-frequency retuned fork force sensors with high Q factors, and the associated electric circuits, for non-contact atomic force microscopy.

    Science.gov (United States)

    Ooe, Hiroaki; Fujii, Mikihiro; Tomitori, Masahiko; Arai, Toyoko

    2016-02-01

    High-Q factor retuned fork (RTF) force sensors made from quartz tuning forks, and the electric circuits for the sensors, were evaluated and optimized to improve the performance of non-contact atomic force microscopy (nc-AFM) performed under ultrahigh vacuum (UHV) conditions. To exploit the high Q factor of the RTF sensor, the oscillation of the RTF sensor was excited at its resonant frequency, using a stray capacitance compensation circuit to cancel the excitation signal leaked through the stray capacitor of the sensor. To improve the signal-to-noise (S/N) ratio in the detected signal, a small capacitor was inserted before the input of an operational (OP) amplifier placed in an UHV chamber, which reduced the output noise from the amplifier. A low-noise, wideband OP amplifier produced a superior S/N ratio, compared with a precision OP amplifier. The thermal vibrational density spectra of the RTF sensors were evaluated using the circuit. The RTF sensor with an effective spring constant value as low as 1000 N/m provided a lower minimum detection limit for force differentiation. A nc-AFM image of a Si(111)-7 × 7 surface was produced with atomic resolution using the RTF sensor in a constant frequency shift mode; tunneling current and energy dissipation images with atomic resolution were also simultaneously produced. The high-Q factor RTF sensor showed potential for the high sensitivity of energy dissipation as small as 1 meV/cycle and the high-resolution analysis of non-conservative force interactions.

  4. High Speed Photography, Videography, And Photonic Instrumentation Development At The Air Force Armament Laboratory

    Science.gov (United States)

    Snyder, Donald R.; Powell, Rodney M.

    1989-02-01

    The Instrumentation Technology Branch of the Air Force Armament Laboratory is currently involved in the development of several high speed photographic, videographic, and photonic instrumentation systems to support the testing and analysis of developmental weapons and test items under dynamic conditions. These projects include development of a large format (14 inch by 17 inch) laser illuminated Cranz-Schardin shadowgraph system for materials research, development of a solid state imager based shadowgraph system for aeroballistic studies, experiments with gated imagers for a variety of test applications, and experiments with high speed video imagers and illuminators for airborne and range tracking instrumentation. An additional issue discussed is the development of a timing and annotation standard for video imaging instrumentation systems operating at higher than NTSC standard rates.

  5. Dynamics of highly-flexible solar sail subjected to various forces

    Science.gov (United States)

    Liu, Jiafu; Cui, Naigang; Shen, Fan; Rong, Siyuan

    2014-10-01

    Solar sail is a novel spacecraft and has the potential applications in the near future. The large amplitude vibration should be considered because it is characterized by its huge and lightweight structure. In this paper, the supporting beam of solar sail is regarded as the most important structure and used to model the sailcraft as it accounts for most of the mechanical energies when it is in deformed configuration, also as the Euler beam can model the bending motion dominant sailcraft when it experiences attitude motions. The structural dynamics of solar sail supporting beam with geometric nonlinearity undergoing the forces generated by solar radiation pressure, sliding masses and control vanes are presented. The axial and transverse vibration equations with the properties of strong coupling, nonlinearity and time-varying coefficient matrices are obtained by using Lagrange equation method after calculating the related energies and works. The vibration equations are transformed into nonlinear algebraic equations utilizing implicit unconditionally stable Newmark-β algorithm for each time step. The nonlinear algebraic equations are solved by Newton-iterative algorithm. We compute and analyze the linear and nonlinear vibration responses affected by the mass and velocity of the sliding mass, the angular velocity of the force generated by control vane in detail. The computational results indicate that the mass and velocity of sliding mass affect the vibration responses (including the vibration frequency), but the angular velocity of the force generated by control vane hardly affects the vibration responses. Moreover, the linear and nonlinear vibrations are distinct obviously by comparing the linear and nonlinear responses. It is demonstrated that the geometric nonlinearity of the highly-flexible structure should be considered for performing vibration analysis exactly, and the vibration responses excited by the prescribed motion of the attitude control actuators should

  6. Effect of high-intensity interval training on cardiovascular function, VO2max, and muscular force.

    Science.gov (United States)

    Astorino, Todd A; Allen, Ryan P; Roberson, Daniel W; Jurancich, Matt

    2012-01-01

    The purpose of this study was to examine the effects of short-term high-intensity interval training (HIIT) on cardiovascular function, cardiorespiratory fitness, and muscular force. Active, young (age and body fat = 25.3 ± 4.5 years and 14.3 ± 6.4%) men and women (N = 20) of a similar age, physical activity, and maximal oxygen uptake (VO2max) completed 6 sessions of HIIT consisting of repeated Wingate tests over a 2- to 3-week period. Subjects completed 4 Wingate tests on days 1 and 2, 5 on days 3 and 4, and 6 on days 5 and 6. A control group of 9 men and women (age and body fat = 22.8 ± 2.8 years and 15.2 ± 6.9%) completed all testing but did not perform HIIT. Changes in resting blood pressure (BP) and heart rate (HR), VO2max, body composition, oxygen (O2) pulse, peak, mean, and minimum power output, fatigue index, and voluntary force production of the knee flexors and extensors were examined pretraining and posttraining. Results showed significant (p VO2max, O2 pulse, and Wingate-derived power output with HIIT. The magnitude of improvement in VO2max was related to baseline VO2max (r = -0.44, p = 0.05) and fatigue index (r = 0.50, p 0.05) in resting BP, HR, or force production was revealed. Data show that HIIT significantly enhanced VO2max and O2 pulse and power output in active men and women.

  7. SIMULATION STUDY OF AERODYNAMIC FORCE FOR HIGH-SPEED MAGNETICALLY-LEVITATED TRAINS

    Institute of Scientific and Technical Information of China (English)

    LI Renxian; LIU Yingqing; ZHAI Wanming

    2006-01-01

    Based on Reynolds average Navier-Storkes equations of viscous incompressible fluid and k-ε two equations turbulent model, the aerodynamic forces of high-speed magnetically-levitated(maglev) trains in transverse and longitudinal wind are investigated by finite volume method. Near 80 calculation cases for 2D transverse wind fields and 20 cases for 3D longitudinal wind fields are and lyzed. The aerodynamic side force, yawing, drag, lift and pitching moment for different types of maglev trains and a wheel/rail train are compared under the different wind speeds. The types of maglev train models for 2D transverse wind analysis included electromagnetic suspension (EMS) type train,electrodynamic suspension (EDS) type train, EMS type train with shelter wind wall in one side or two sides of guideway and the walls, which are in different height or/and different distances from train body. The situation of maglev train running on viaduct is also analyzed. For 3D longitudinal wind field analysis, the model with different sizes of air clearances beneath maglev train is examined for the different speeds. Calculation result shows that: ① Different transverse effects are shown in different types of maglev trains. ② The shelter wind wall can fairly decrease the transverse effect on the maglev train. ③ When the shelter wall height is 2 m, there is minimum side force on the train.When the shelter wall height is 2.5 m, there is minimum yawing moment on the train. ④ When the distance between inside surfaces of the walls and center of guideway is 4.0 m, there is minimum transverse influence on the train. ⑤ The size of air clearance beneath train body has a small influence on aerodynamic drag of the train, but has a fairly large effect on aerodynamic lift and pitching moment of the train. ⑥ The calculating lift and pitching moment for maglev train models are minus values.

  8. Dependence of coercivity on phase distribution and grain size in nanocomposite Nd2Fe14B/α-Fe magnets

    Institute of Scientific and Technical Information of China (English)

    Feng Wei-Cun; Gao Ru-Wei; Li Wei; Han Guang-Bing; Sun Yan

    2005-01-01

    The dependence of coercivity on the grain size in nanocomposite Nd2Fe14B/α-Fe magnets with different distributions of magnetically soft and hard phases is investigated by means of statistical mean. The calculations show that when there exists no soft phase, the coercivity of magnets decreases monotonically with hard grain size reducing. For a given volume fraction of hard phase, the coercivity of nanocomposite Nd2Fe14B/α-Fe magnets with a random distribution of soft and hard grains shows a peak value as a function of hard grain size. When the hard grain size is larger than an optimum value of soft grain size (15nm), the nanocomposite Nd2Fe14B/α-Fe magnets with the multilayer structure of soft and hard grains can possess a higher coercivity than that with the random distribution of soft and hard grains.

  9. Investigation of the coercivity mechanism for Nd-Fe-B based magnets prepared by a new technique of strip casting

    Institute of Scientific and Technical Information of China (English)

    LI Bo; HU Jifan; WANG Dongling; GUO Binglin; WANG Xinlin

    2004-01-01

    The coercivity mechanism of Nd-Fe-B based magnets prepared by a new technique of strip casting was investigated. Different from the traditional magnets, α-Fe phases are difficult to be found in Nd-Fe-B magnets prepared by strip casting. Meanwhile, the rich-Nd phases occur not only near the grain boundaries of main phases, but also within the main-phase grains. Investigation on the magnetizing field dependence of the coercivity for the (Nd0.935Dy0.065)14.5Fe79.4B6.1magnet and the temperature dependence of the coercivity for the Nd14.5Fe79.4B6.1magnet have been done. Results show that coercivities for strip casting magnets are controlled by the nucleation mechanism.

  10. High intensity interior aircraft noise increases the risk of high diastolic blood pressure in Indonesian Air Force pilots

    Directory of Open Access Journals (Sweden)

    Minarma Siagian

    2009-12-01

    Full Text Available Aim: To analyze the effects of aircraft noise, resting pulse rate, and other factors on the risk of high diastolic blood pressure (DBP in Indonesian Air Force pilots.Methods: A nested case-control study was conducted using data extracted from annual medical check-ups indoctrination aerophysiologic training records at the Saryanto Aviation and Aerospace Health Institute (LAKESPRA in Jakarta from January 2003 – September 2008. For analysis of DBP: the case group with DBP ≥ 90 mmHg were compared with contral group with DBP < 79 mmHG. One case matched to 12 controls.Results: Out of 567 pilots, 544 (95.9% had complete medical records. For this analysis there were 40 cases of high DBP and 480 controls for DBP. Pilots exposed to aircraft noise 90-95 dB rather than 70-80 dB had a 2.7-fold increase for high DBP [adjusted odds ratio (ORa = 2.70; 95% confi dence interval (CI = 1.05-6.97]. Pilots with resting pulse rates of ≥ 81/minute rather than ≤ 80/minute had a 2.7-fold increase for high DBP (ORa = 2.66; 95% CI = 1.26-5.61. In terms of total fl ight hours, pilots who had 1401-11125 hours rather than 147-1400 hours had a 3.2-fold increase for high DBP (ORa = 3.18; 95% CI = 1.01-10.03.Conclusion: High interior aircraft noise, high total flight hours,  and high resting pulse rate, increased risk for high DBP. Self assessment of resting pulse rate can be used to control the risk of high DBP. (Med J Indones 2009; 276: 276-82Keywords: diastolic blood pressure, aircraft noise, resting pulse rate, military pilots

  11. Independent component analysis of high-density electromyography in muscle force estimation.

    NARCIS (Netherlands)

    Staudenmann, D.; Daffertshofer, A.; Kingma, I.; Stegeman, D.F.; Dieen, J.H. van

    2007-01-01

    Accurate force prediction from surface electromyography (EMG) forms an important methodological challenge in biomechanics and kinesiology. In a previous study (Staudenmann et al., 2006), we illustrated force estimates based on analyses lent from multivariate statistics. In particular, we showed the

  12. Large surface radiative forcing from topographic blowing snow residuals measured in the High Arctic at Eureka

    Directory of Open Access Journals (Sweden)

    G. Lesins

    2009-03-01

    Full Text Available Ice crystals, also known as diamond dust, are suspended in the boundary layer air under clear sky conditions during most of the Arctic winter in Northern Canada. Occasionally ice crystal events can produce significantly thick layers with optical depths in excess of 2.0 even in the absence of liquid water clouds. Four case studies of high optical depth ice crystal events at Eureka in the Nunavut Territory of Canada during the winter of 2006/07 are presented. They show that the measured ice crystal surface infrared downward radiative forcing ranged from 8 to 36 W m−2 in the wavelength band from 5.6 to 20 μm for 532 nm optical depths ranging from 0.2 to 1.7. MODIS infrared and visible images and the operational radiosonde wind profile were used to show that these high optical depth events were caused by surface snow being blown off 600 to 800 m high mountain ridges about 20 to 30 km North-West of Eureka and advected by the winds towards Eureka as they settled towards the ground within the highly stable boundary layer. This work presents the first study that demonstrates the important role that surrounding topography plays in determining the occurrence of high optical depth ice crystal events from residual blowing snow that becomes a source of boundary layer ice crystals distinct from the classical diamond dust phenomenon.

  13. Modeling of stochastic dynamics of time-dependent flows under high-dimensional random forcing

    Science.gov (United States)

    Babaee, Hessam; Karniadakis, George

    2016-11-01

    In this numerical study the effect of high-dimensional stochastic forcing in time-dependent flows is investigated. To efficiently quantify the evolution of stochasticity in such a system, the dynamically orthogonal method is used. In this methodology, the solution is approximated by a generalized Karhunen-Loeve (KL) expansion in the form of u (x , t ω) = u ̲ (x , t) + ∑ i = 1 N yi (t ω)ui (x , t) , in which u ̲ (x , t) is the stochastic mean, the set of ui (x , t) 's is a deterministic orthogonal basis and yi (t ω) 's are the stochastic coefficients. Explicit evolution equations for u ̲ , ui and yi are formulated. The elements of the basis ui (x , t) 's remain orthogonal for all times and they evolve according to the system dynamics to capture the energetically dominant stochastic subspace. We consider two classical fluid dynamics problems: (1) flow over a cylinder, and (2) flow over an airfoil under up to one-hundred dimensional random forcing. We explore the interaction of intrinsic with extrinsic stochasticity in these flows. DARPA N66001-15-2-4055, Office of Naval Research N00014-14-1-0166.

  14. Characterization of the surface charge distribution on kaolinite particles using high resolution atomic force microscopy

    Science.gov (United States)

    Kumar, Naveen; Zhao, Cunlu; Klaassen, Aram; van den Ende, Dirk; Mugele, Frieder; Siretanu, Igor

    2016-02-01

    Most solid surfaces, in particular clay minerals and rock surfaces, acquire a surface charge upon exposure to an aqueous environment due to adsorption and/or desorption of ionic species. Macroscopic techniques such as titration and electrokinetic measurements are commonly used to determine the surface charge and ζ -potential of these surfaces. However, because of the macroscopic averaging character these techniques cannot do justice to the role of local heterogeneities on the surfaces. In this work, we use dynamic atomic force microscopy (AFM) to determine the distribution of surface charge on the two (gibbsite-like and silica-like) basal planes of kaolinite nanoparticles immersed in aqueous electrolyte with a lateral resolution of approximately 30 nm. The surface charge density is extracted from force-distance curves using DLVO theory in combination with surface complexation modeling. While the gibbsite-like and the silica-like facet display on average positive and negative surface charge values as expected, our measurements reveal lateral variations of more than a factor of two on seemingly atomically smooth terraces, even if high resolution AFM images clearly reveal the atomic lattice on the surface. These results suggest that simple surface complexation models of clays that attribute a unique surface chemistry and hence homogeneous surface charge densities to basal planes may miss important aspects of real clay surfaces.

  15. High harmonic interferometry of the Lorentz force in strong mid-infrared laser fields

    CERN Document Server

    Pisanty, Emilio; Galloway, Benjamin R; Durfee, Charles G; Kapteyn, Henry C; Murnane, Margaret M; Ivanov, Misha

    2016-01-01

    The interaction of intense mid-infrared laser fields with atoms and molecules leads to a range of new opportunities, from the production of bright, coherent radiation in the soft x-ray range to imaging molecular structures and dynamics with attosecond temporal and sub-angstrom spatial resolution. However, all these effects, which rely on laser-driven recollision of an electron removed by the strong laser field and the parent ion, suffer from the rapidly increasing role of the magnetic field component of the driving pulse: the associated Lorentz force pushes the electrons off course in their excursion and suppresses all recollision-based processes, including high harmonic generation, elastic and inelastic scattering. Here we show how the use of two non-collinear beams with opposite circular polarizations produces a forwards ellipticity which can be used to monitor, control, and cancel the effect of the Lorentz force. This arrangement can thus be used to re-enable recollision-based phenomena in regimes beyond t...

  16. Design and Analysis of a High Force, Low Voltage and High Flow Rate Electro-Thermal Micropump

    Directory of Open Access Journals (Sweden)

    Ghader Yosefi

    2014-12-01

    Full Text Available This paper presents the design and simulation of an improved electro-thermal micromachined pump for drug delivery applications. Thermal actuators, which are a type of Micro Electro Mechanical system (MEMS device, are highly useful because of their ability to deliver with great force and displacement. Thus, our structure is based on a thermal actuator that exploits the Joule heating effect and has been improved using the springy length properties of MEMS chevron beams. The Joule heating effect results in a difference in temperature and therefore displacement in the beams (actuators. Simulation results show that a maximum force of 4.4 mN and a maximum flow rate of 16 μL/min can be obtained by applying an AC voltage as low as 8 V at different frequencies ranging from 1 to 32 Hz. The maximum temperature was a problem at the chevron beams and the center shaft. Thus, to locally increase the temperature of the chevron beams alone and not that of the pumping diaphragm: (1 The air gaps 2 μm underneath and above the device layer were optimized for heat transfer. (2 Release holes and providing fins were created at the center shaft and actuator, respectively, to decrease the temperature by approximately 10 °C. (3 We inserted and used a polymer tube to serve as an insulator and eliminate leakage problems in the fluidic channel.

  17. The Effects of Drag and Tidal Forces on the Orbits of High-Velocity Clouds

    Science.gov (United States)

    Fernandes, Alexandre; Benjamin, R. A.

    2013-06-01

    Over the past several years, orbital constraints have been obtained for several high velocity cloud complexes surrounding the Milky Way: Complex GCP (Smith Cloud), Complex A, Complex H, Complex GCN, and the Magellanic Stream. We summarize what is known about the orbits of these clouds and and discuss how well each of these complexes fits a balistic trajectory, and discuss how the length of a complex across the sky is related to the inital "fragmentation" and velocity dispersion of the clouds. We then introduce gas drag into the simulation of the orbits of these complexes. We present analytical tests of our numerical method and characterize the departure of the clouds from the ballistic trajectory as a function of drag parameters (ambient gas density and velocity and cloud column density). Using the results of these simulations we comment on the survivability and ultimate fate of HVC in the context of the different models of drag forces.

  18. Trial of "Force and Motion Conceptual Evaluation" Tests in Japanese High Schools

    Science.gov (United States)

    Ryu, Junpei; Iwama, Toru; Yamazaki, Toshiaki; Ogawa, Masashi; Sakatani, Takafumi; Uchimura, Hiroshi; Taniguchi, Kazunari; Murata, Takatoshi

    A tentative version of Japanese translation of "Force and Motion Conceptual Evaluation" was used in a preliminary research to investigate high school students' conceptual understanding of Newtonian dynamics after the students attended formal courses on the topic in 2006-07. The results obtained were generally similar to those of post-tests after traditional lectures in universities in U.S.A.. It was also used as pre- and post-test at two extramural classes on dynamics based on the active learning materials. The results of those uses suggested a well validated version of the translated test and more systematic large scale research can contribute well to physics education research in Japan.

  19. High-speed atomic force microscopy reveals rotary catalysis of rotorless F₁-ATPase.

    Science.gov (United States)

    Uchihashi, Takayuki; Iino, Ryota; Ando, Toshio; Noji, Hiroyuki

    2011-08-05

    F(1) is an adenosine triphosphate (ATP)-driven motor in which three torque-generating β subunits in the α(3)β(3) stator ring sequentially undergo conformational changes upon ATP hydrolysis to rotate the central shaft γ unidirectionally. Although extensive experimental and theoretical work has been done, the structural basis of cooperative torque generation to realize the unidirectional rotation remains elusive. We used high-speed atomic force microscopy to show that the rotorless F(1) still "rotates"; in the isolated α(3)β(3) stator ring, the three β subunits cyclically propagate conformational states in the counterclockwise direction, similar to the rotary shaft rotation in F(1). The structural basis of unidirectionality is programmed in the stator ring. These findings have implications for cooperative interplay between subunits in other hexameric ATPases.

  20. Atomic force microscopy study of anion intercalation into highly oriented pyrolytic graphite

    Energy Technology Data Exchange (ETDEWEB)

    Alliata, D.; Haering, P.; Haas, O.; Koetz, R. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Siegenthaler, H. [University of Berne (Switzerland)

    1999-08-01

    In the context of ion transfer batteries, we studied highly oriented pyrolytic graphite (HOPG) in perchloric acid, as a model to elucidate the mechanism of electrochemical intercalation in graphite. Aim of the work is the local and time dependent investigation of dimensional changes of the host material during electrochemical intercalation processes on the nanometer scale. We used atomic force microscopy (AFM), combined with cyclic voltammetry, as in-situ tool of analysis during intercalation and expulsion of perchloric anions into the HOPG electrodes. According to the AFM measurements, the HOPG interlayer spacing increases by 32% when perchloric anions intercalate, in agreement with the formation of stage IV of graphite intercalation compounds. (author) 3 figs., 3 refs.

  1. Serum induced degradation of 3D DNA box origami observed by high speed atomic force microscope

    DEFF Research Database (Denmark)

    Jiang, Zaixing; Zhang, Shuai; Yang, Chuanxu;

    2015-01-01

    3D DNA origami holds tremendous potential to encapsulate and selectively release therapeutic drugs. Observations of real-time performance of 3D DNA origami structures in physiological environment will contribute much to its further applications. Here, we investigate the degradation kinetics of 3D...... DNA box origami in serum using high-speed atomic force microscope optimized for imaging 3D DNA origami in real time. The time resolution allows characterizing the stages of serum effects on individual 3D DNA box origami with nanometer resolution. Our results indicate that the whole digest process...... is a combination of a rapid collapse phase and a slow degradation phase. The damages of box origami mainly happen in the collapse phase. Thus, the structure stability of 3D DNA box origami should be further improved, especially in the collapse phase, before clinical applications...

  2. A serial-kinematic nanopositioner for high-speed atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wadikhaye, Sachin P., E-mail: sachin.wadikhaye@uon.edu.au; Yong, Yuen Kuan; Reza Moheimani, S. O. [School of Electrical Engineering and Computer Science, The University of Newcastle, Callaghan, NSW (Australia)

    2014-10-15

    A flexure-guided serial-kinematic XYZ nanopositioner for high-speed Atomic Force Microscopy is presented in this paper. Two aspects influencing the performance of serial-kinematic nanopositioners are studied in this work. First, mass reduction by using tapered flexures is proposed to increased the natural frequency of the nanopositioner. 25% increase in the natural frequency is achieved due to reduced mass with tapered flexures. Second, a study of possible sensor positioning in a serial-kinematic nanopositioner is presented. An arrangement of sensors for exact estimation of cross-coupling is incorporated in the proposed design. A feedforward control strategy based on phaser approach is presented to mitigate the dynamics and nonlinearity in the system. Limitations in design approach and control strategy are discussed in the Conclusion.

  3. Recombination and selectional forces in cyanopeptolin NRPS operons from highly similar, but geographically remote Planktothrix strains

    Directory of Open Access Journals (Sweden)

    Kristensen Tom

    2008-08-01

    Full Text Available Abstract Background Cyanopeptolins are nonribosomally produced heptapetides showing a highly variable composition. The cyanopeptolin synthetase operon has previously been investigated in three strains from the genera Microcystis, Planktothrix and Anabaena. Cyanopeptolins are displaying protease inhibitor activity, but the biological function(s is (are unknown. Cyanopeptolin gene cluster variability and biological functions of the peptide variants are likely to be interconnected. Results We have investigated two cyanopeptolin gene clusters from highly similar, but geographically remote strains of the same genus. Sequencing of a nonribosomal peptide synthetase (NRPS cyanopeptolin gene cluster from the Japanese strain Planktothrix NIES 205 (205-oci, showed the 30 kb gene cluster to be highly similar to the oci gene cluster previously described in Planktothrix NIVA CYA 116, isolated in Norway. Both operons contained seven NRPS modules, a sulfotransferase (S and a glyceric acid loading (GA-domain. Sequence analyses showed a high degree of conservation, except for the presence of an epimerase domain in NIES 205 and the regions around the epimerase, showing high substitution rates and Ka/Ks values above 1. The two strains produce almost identical cyanopeptolins, cyanopeptolin-1138 and oscillapeptin E respectively, but with slight differences regarding the production of minor cyanopeptolin variants. These variants may be the result of relaxed adenylation (A-domain specificity in the nonribosomal enzyme complex. Other genetic markers (16S rRNA, ntcA and the phycocyanin cpcBA spacer were identical, supporting that these geographically separated Planktothrix strains are closely related. Conclusion A horizontal gene transfer event resulting in exchange of a whole module-encoding region was observed. Nucleotide statistics indicate that both purifying selection and positive selection forces are operating on the gene cluster. The positive selection forces are

  4. Measurement of repulsive force of high Tc materials due to Meissner effect and its two dimensional distribution

    Science.gov (United States)

    Ishigaki, H.; Itoh, M.; Hida, A.; Endo, H.; Oya, T.

    1991-03-01

    As a basic study for magnetic bearings using high-Tc superconductors, evaluations of the materials were conducted. These evaluations included measurements of the repulsive force and lateral restoring force of various kinds of YBCO pellets. Pure air, which was supplied in the process of fabrication, and the presence of Ag in YBCO showed evidence of the effects of increasing the repulsive force. The lateral restoring force which was observed in the lateral displacement of a levitated permanent magnet over YBCO pellets was also affected by pure air and the presence of Ag. A new measuring instrument for magnetic fields was developed by using a highly sensitive force sensor. Because this instrument has the capability of measuring the repulsive force due to the Meissner effect, it was used for evaluating the two-dimensional distribution of superconducting properties. Results show that the pellets had nonuniform superconducting properties. The two-dimensional distribution of residual flux density on the pellets which had been cooled in a magnetic field (field cooling) was also observed by means of the instrument. The mechanism for generating lateral force is discussed in relation to the distribution.

  5. High-density force myography: A possible alternative for upper-limb prosthetic control

    Directory of Open Access Journals (Sweden)

    Ashkan Radmand, PhD

    2016-07-01

    Full Text Available Several multiple degree-of-freedom upper-limb prostheses that have the promise of highly dexterous control have recently been developed. Inadequate controllability, however, has limited adoption of these devices. Introducing more robust control methods will likely result in higher acceptance rates. This work investigates the suitability of using high-density force myography (HD-FMG for prosthetic control. HD-FMG uses a high-density array of pressure sensors to detect changes in the pressure patterns between the residual limb and socket caused by the contraction of the forearm muscles. In this work, HD-FMG outperforms the standard electromyography (EMG-based system in detecting different wrist and hand gestures. With the arm in a fixed, static position, eight hand and wrist motions were classified with 0.33% error using the HD-FMG technique. Comparatively, classification errors in the range of 2.2%–11.3% have been reported in the literature for multichannel EMG-based approaches. As with EMG, position variation in HD-FMG can introduce classification error, but incorporating position variation into the training protocol reduces this effect. Channel reduction was also applied to the HD-FMG technique to decrease the dimensionality of the problem as well as the size of the sensorized area. We found that with informed, symmetric channel reduction, classification error could be decreased to 0.02%.

  6. Evaluation of cutting force and surface roughness in high-speed milling of compacted graphite iron

    Directory of Open Access Journals (Sweden)

    Azlan Suhaimi Mohd

    2017-01-01

    Full Text Available Compacted Graphite Iron, (CGI is known to have outstanding mechanical strength and weight-to-strength ratio as compared to conventional grey cast iron, (CI. The outstanding characteristics of CGI is due to its graphite particle shape, which is presented as compacted vermicular particle. The graphite is interconnected with random orientation and round edges, which results in higher mechanical strength. Whereas, graphite in the CI consists of a smooth-surfaced flakes that easily propagates cracks which results in weaker and brittle properties as compared to CGI. Owing to its improved properties, CGI is considered as the best candidate material in substituting grey cast iron that has been used in engine block applications for years. However, the smooth implementation of replacing CI with CGI has been hindered due to the poor machinability of CGI especially at high cutting speed. The tool life is decreased by 20 times when comparing CGI with CI under the same cutting condition. This study investigates the effect of using cryogenic cooling and minimum quantity lubrication (MQL during high-speed milling of CGI (grade 450. Results showed that, the combination of internal cryogenic cooling and enhanced MQL improved the tool life, cutting force and surface quality as compared to the conventional flood coolant strategy during high-speed milling of CGI.

  7. A miniaturized, high frequency mechanical scanner for high speed atomic force microscope using suspension on dynamically determined points

    Energy Technology Data Exchange (ETDEWEB)

    Herfst, Rodolf; Dekker, Bert; Witvoet, Gert; Crowcombe, Will; Lange, Dorus de [Department of Optomechatronics, Netherlands Organization for Applied Scientific Research, TNO, Delft (Netherlands); Sadeghian, Hamed, E-mail: hamed.sadeghianmarnani@tno.nl, E-mail: h.sadeghianmarnani@tudelft.nl [Department of Optomechatronics, Netherlands Organization for Applied Scientific Research, TNO, Delft (Netherlands); Department of Precision and Microsystems Engineering, Delft University of Technology, Delft (Netherlands)

    2015-11-15

    One of the major limitations in the speed of the atomic force microscope (AFM) is the bandwidth of the mechanical scanning stage, especially in the vertical (z) direction. According to the design principles of “light and stiff” and “static determinacy,” the bandwidth of the mechanical scanner is limited by the first eigenfrequency of the AFM head in case of tip scanning and by the sample stage in terms of sample scanning. Due to stringent requirements of the system, simply pushing the first eigenfrequency to an ever higher value has reached its limitation. We have developed a miniaturized, high speed AFM scanner in which the dynamics of the z-scanning stage are made insensitive to its surrounding dynamics via suspension of it on specific dynamically determined points. This resulted in a mechanical bandwidth as high as that of the z-actuator (50 kHz) while remaining insensitive to the dynamics of its base and surroundings. The scanner allows a practical z scan range of 2.1 μm. We have demonstrated the applicability of the scanner to the high speed scanning of nanostructures.

  8. A miniaturized, high frequency mechanical scanner for high speed atomic force microscope using suspension on dynamically determined points.

    Science.gov (United States)

    Herfst, Rodolf; Dekker, Bert; Witvoet, Gert; Crowcombe, Will; de Lange, Dorus; Sadeghian, Hamed

    2015-11-01

    One of the major limitations in the speed of the atomic force microscope (AFM) is the bandwidth of the mechanical scanning stage, especially in the vertical (z) direction. According to the design principles of "light and stiff" and "static determinacy," the bandwidth of the mechanical scanner is limited by the first eigenfrequency of the AFM head in case of tip scanning and by the sample stage in terms of sample scanning. Due to stringent requirements of the system, simply pushing the first eigenfrequency to an ever higher value has reached its limitation. We have developed a miniaturized, high speed AFM scanner in which the dynamics of the z-scanning stage are made insensitive to its surrounding dynamics via suspension of it on specific dynamically determined points. This resulted in a mechanical bandwidth as high as that of the z-actuator (50 kHz) while remaining insensitive to the dynamics of its base and surroundings. The scanner allows a practical z scan range of 2.1 μm. We have demonstrated the applicability of the scanner to the high speed scanning of nanostructures.

  9. Gold-decorated highly ordered self-organized grating-like nanostructures on Ge surface: Kelvin probe force microscopy and conductive atomic force microscopy studies

    Science.gov (United States)

    Alam Mollick, Safiul; Kumar, Mohit; Singh, Ranveer; Satpati, Biswarup; Ghose, Debabrata; Som, Tapobrata

    2016-10-01

    Nanoarchitecture by atomic manipulation is considered to be one of the emerging trends in advanced functional materials. It has a gamut of applications to offer in nanoelectronics, chemical sensing, and nanobiological science. In particular, highly ordered one-dimensional semiconductor nanostructures fabricated by self-organization methods are in high demand for their high aspect ratios and large number of applications. An efficient way of fabricating semiconductor nanostructures is by molecular beam epitaxy, where atoms are added to a crystalline surface at an elevated temperature during growth, yielding the desired structures in a self-assembled manner. In this article, we offer a room temperature process, in which atoms are sputtered away by ion impacts. Using gold ion implantation, the present study reports on the formation of highly ordered self-organized long grating-like nanostructures, with grooves between them, on a germanium surface. The ridges of the patterns are shown to have flower-like protruding nanostructures, which are mostly decorated by gold atoms. By employing local probe microscopic techniques like Kelvin probe force microscopy and conductive atomic force microscopy, we observe a spatial variation in the work function and different nanoscale electrical conductivity on the ridges of the patterns and the grooves between them, which can be attributed to gold atom decorated ridges. Thus, the architecture presented offers the advantage of using the patterned germanium substrates as periodic arrays of conducting ridges and poorly conducting grooves between them.

  10. Task III: Development of an Effective Computational Methodology for Body Force Representation of High-speed Rotor 37

    Science.gov (United States)

    Tan, Choon-Sooi; Suder, Kenneth (Technical Monitor)

    2003-01-01

    A framework for an effective computational methodology for characterizing the stability and the impact of distortion in high-speed multi-stage compressor is being developed. The methodology consists of using a few isolated-blade row Navier-Stokes solutions for each blade row to construct a body force database. The purpose of the body force database is to replace each blade row in a multi-stage compressor by a body force distribution to produce same pressure rise and flow turning. To do this, each body force database is generated in such a way that it can respond to the changes in local flow conditions. Once the database is generated, no hrther Navier-Stokes computations are necessary. The process is repeated for every blade row in the multi-stage compressor. The body forces are then embedded as source terms in an Euler solver. The method is developed to have the capability to compute the performance in a flow that has radial as well as circumferential non-uniformity with a length scale larger than a blade pitch; thus it can potentially be used to characterize the stability of a compressor under design. It is these two latter features as well as the accompanying procedure to obtain the body force representation that distinguish the present methodology from the streamline curvature method. The overall computational procedures have been developed. A dimensional analysis was carried out to determine the local flow conditions for parameterizing the magnitudes of the local body force representation of blade rows. An Euler solver was modified to embed the body forces as source terms. The results from the dimensional analysis show that the body forces can be parameterized in terms of the two relative flow angles, the relative Mach number, and the Reynolds number. For flow in a high-speed transonic blade row, they can be parameterized in terms of the local relative Mach number alone.

  11. Effect of temperature-dependent shape anisotropy on coercivity with aligned Stoner-Wohlfarth soft ferromagnets

    OpenAIRE

    He, Lin; Chen, Chinping

    2007-01-01

    The temperature variation effect of shape anisotropy on the coercivity, HC(T), for the aligned Stoner-Wohlfarth (SW) soft ferromagnets, such as fcc Ni, fcc Co and bcc Fe, are investigated within the framework of Neel-Brown (N-B) analysis. An extended N-B equation is thus proposed,by introducing a single dimensionless correction function, the reduced magnetization, m(\\tao) = MS(T)/MS(0), in which \\tao = T/TC is the reduced temperature, MS(T) is the saturation magnetization, and TC is the Curie...

  12. Coercive control and abused women's decisions about their pets when seeking shelter.

    Science.gov (United States)

    Hardesty, Jennifer L; Khaw, Lyndal; Ridgway, Marcella D; Weber, Cheryl; Miles, Teresa

    2013-09-01

    The importance of pets in families, especially during major life stressors, is well documented. Research suggests links between pet ownership and intimate partner violence (IPV). This study explored abused women's decisions about pets when seeking help from a shelter. Interviews were conducted with 19 women who were pet owners. Using grounded theory methods, two patterns emerged surrounding abusers' treatment of pets, bonds to pets, women's decisions about pets upon seeking shelter, and future plans for pets. The presence of coercive control was central to these patterns. Women also discussed their experiences with and needs from shelter professionals and veterinarians with implications for practice.

  13. High-multipolar effects on the Casimir force: the non-retarded limit

    CERN Document Server

    Noguez, C; Esquivel-Sirvent, R; Villarreal, C; Noguez, Cecilia; Roman-Velazquez, Carlos E.; Esquivel-Sirvent, Raul; Villarreal, Carlos

    2003-01-01

    We calculate exactly the Casimir force or dispersive force, in the non-retarded limit, between a spherical nanoparticle and a substrate beyond the London's or dipolar approximation. We find that the force is a non-monotonic function of the distance between the sphere and the substrate, such that, it is enhanced by several orders of magnitude as the sphere approaches the substrate. Our results do not agree with previous predictions like the Proximity theorem approach.

  14. Control Parametric Analysis on Improving Park Restoring Force Model and Damage Evaluation of High-Strength Structure

    Directory of Open Access Journals (Sweden)

    Huang-bin Lin

    2016-01-01

    Full Text Available In the dynamic time-history analysis of structural elastoplasticity, it is important to develop a universal mathematical model that can describe the force-displacement characteristics for restoring force. By defining three control parameters (stiffness degradation, slip closure γ, energy degradation β, the Park restoring force mathematical model can simulate various components. In this study, the Park restoring force has been improved by adding two control parameters (energy-based strength degradation βe and ductility-based strength degradation βd. Based on the testing data, the constitutive model is input and 55 numerical models are developed to analyze the effects of various parameters on structural behavior. Conclusion. (1 β has determinative effect on structural behavior; the effect of βe is basically consistent with that of β; α has significant effect on shear forces and bending moments; γ has significant effect on displacements and accelerations; βd has significant effect on shearing forces, acceleration, and total energy consumptions. (2 Based on the classification of four types of damage level, the recommended values for α, γ, β, βe, and βd are presented. (3 Based on the testing data of high-strength columns, the recommended values for the five control parameters of the improved Park restoring force model are presented.

  15. High-speed atomic force microscopy for large scan sizes using small cantilevers

    Science.gov (United States)

    Braunsmann, Christoph; Schäffer, Tilman E.

    2010-06-01

    We present a high-speed atomic force microscope that exhibits a number of practical advantages over previous designs. Its central component is a high-speed scanner with a maximum scan size of 23 µm × 23 µm and a conveniently large sample stage area (6.5 mm × 6.5 mm). In combination with small cantilevers, image rates of up to 46 images s - 1 in air and 13 images s - 1 in liquid are reached under z-feedback control. By large scan size imaging of collagen fibrils in air, sample velocities of 8.8 mm s - 1 in the xy-direction and 11 mm s - 1 in the z-direction are reached. To provide optimized imaging conditions for both large and small scan sizes, a modular scanner design allows easily exchanging the x- and y-piezos. The scanner is therefore also suited for investigations on the molecular and atomic scale, which is demonstrated by imaging the step dynamics of a calcite surface during dissolution and the hexagonal lattice of a mica surface in liquid.

  16. Study on a high thrust force bi-double-sided permanent magnet linear synchronous motor

    Directory of Open Access Journals (Sweden)

    Liang Tong

    2016-03-01

    Full Text Available A high thrust force bi-double-sided permanent magnet linear synchronous motor used in gantry-type five-axis machining center is designed and its performance was tested in this article. This motor is the subproject of Chinese National Science and Technology Major Project named as “development of domestic large thrust linear motor used in high-speed gantry-type five-axis machining center project” jointly participated by enterprises and universities. According to the requirement of the application environment and motor performance parameters, the linear motor’s basic dimensions, form of windings, and magnet arrangement are preliminarily specified through theoretical analysis and calculation. To verify the correctness of the result of the calculation, the finite element model of the motor is established. The static and dynamic characteristics of the motor are studied and analyzed through the finite element method, and the initial scheme is revised. The prototype of the motor is manufactured based on the final revised structure parameters, and the performance of the motor is fully tested using the evaluation platform for direct-drive motor component. Experimental test results meet the design requirements and show the effectiveness of design method and process.

  17. High-speed atomic force microscopy reveals structural dynamics of amyloid β1-42 aggregates.

    Science.gov (United States)

    Watanabe-Nakayama, Takahiro; Ono, Kenjiro; Itami, Masahiro; Takahashi, Ryoichi; Teplow, David B; Yamada, Masahito

    2016-05-24

    Aggregation of amyloidogenic proteins into insoluble amyloid fibrils is implicated in various neurodegenerative diseases. This process involves protein assembly into oligomeric intermediates and fibrils with highly polymorphic molecular structures. These structural differences may be responsible for different disease presentations. For this reason, elucidation of the structural features and assembly kinetics of amyloidogenic proteins has been an area of intense study. We report here the results of high-speed atomic force microscopy (HS-AFM) studies of fibril formation and elongation by the 42-residue form of the amyloid β-protein (Aβ1-42), a key pathogenetic agent of Alzheimer's disease. Our data demonstrate two different growth modes of Aβ1-42, one producing straight fibrils and the other producing spiral fibrils. Each mode depends on initial fibril nucleus structure, but switching from one growth mode to another was occasionally observed, suggesting that fibril end structure fluctuated between the two growth modes. This switching phenomenon was affected by buffer salt composition. Our findings indicate that polymorphism in fibril structure can occur after fibril nucleation and is affected by relatively modest changes in environmental conditions.

  18. Cantilevered bimorph-based scanner for high speed atomic force microscopy with large scanning range.

    Science.gov (United States)

    Zhou, Yusheng; Shang, Guangyi; Cai, Wei; Yao, Jun-en

    2010-05-01

    A cantilevered bimorph-based resonance-mode scanner for high speed atomic force microscope (AFM) imaging is presented. The free end of the bimorph is used for mounting a sample stage and the other one of that is fixed on the top of a conventional single tube scanner. High speed scanning is realized with the bimorph-based scanner vibrating at resonant frequency driven by a sine wave voltage applied to one piezolayer of the bimorph, while slow scanning is performed by the tube scanner. The other piezolayer provides information on vibration amplitude and phase of the bimorph itself simultaneously, which is used for real-time data processing and image calibration. By adjusting the free length of the bimorph, the line scan rate can be preset ranging from several hundred hertz to several kilohertz, which would be beneficial for the observation of samples with different properties. Combined with a home-made AFM system and a commercially available data acquisition card, AFM images of various samples have been obtained, and as an example, images of the silicon grating taken at a line rate of 1.5 kHz with the scan size of 20 microm are given. By manually moving the sample of polished Al foil surface while scanning, the capability of dynamic imaging is demonstrated.

  19. High-speed Lissajous-scan atomic force microscopy: scan pattern planning and control design issues.

    Science.gov (United States)

    Bazaei, A; Yong, Yuen K; Moheimani, S O Reza

    2012-06-01

    Tracking of triangular or sawtooth waveforms is a major difficulty for achieving high-speed operation in many scanning applications such as scanning probe microscopy. Such non-smooth waveforms contain high order harmonics of the scan frequency that can excite mechanical resonant modes of the positioning system, limiting the scan range and bandwidth. Hence, fast raster scanning often leads to image distortion. This paper proposes analysis and design methodologies for a nonlinear and smooth closed curve, known as Lissajous pattern, which allows much faster operations compared to the ordinary scan patterns. A simple closed-form measure is formulated for the image resolution of the Lissajous pattern. This enables us to systematically determine the scan parameters. Using internal model controllers (IMC), this non-raster scan method is implemented on a commercial atomic force microscope driven by a low resonance frequency positioning stage. To reduce the tracking errors due to actuator nonlinearities, higher order harmonic oscillators are included in the IMC controllers. This results in significant improvement compared to the traditional IMC method. It is shown that the proposed IMC controller achieves much better tracking performances compared to integral controllers when the noise rejection performances is a concern.

  20. Acoustic radiation force impulse (ARFI) imaging of zebrafish embryo by high-frequency coded excitation sequence.

    Science.gov (United States)

    Park, Jinhyoung; Lee, Jungwoo; Lau, Sien Ting; Lee, Changyang; Huang, Ying; Lien, Ching-Ling; Kirk Shung, K

    2012-04-01

    Acoustic radiation force impulse (ARFI) imaging has been developed as a non-invasive method for quantitative illustration of tissue stiffness or displacement. Conventional ARFI imaging (2-10 MHz) has been implemented in commercial scanners for illustrating elastic properties of several organs. The image resolution, however, is too coarse to study mechanical properties of micro-sized objects such as cells. This article thus presents a high-frequency coded excitation ARFI technique, with the ultimate goal of displaying elastic characteristics of cellular structures. Tissue mimicking phantoms and zebrafish embryos are imaged with a 100-MHz lithium niobate (LiNbO₃) transducer, by cross-correlating tracked RF echoes with the reference. The phantom results show that the contrast of ARFI image (14 dB) with coded excitation is better than that of the conventional ARFI image (9 dB). The depths of penetration are 2.6 and 2.2 mm, respectively. The stiffness data of the zebrafish demonstrate that the envelope is harder than the embryo region. The temporal displacement change at the embryo and the chorion is as large as 36 and 3.6 μm. Consequently, this high-frequency ARFI approach may serve as a remote palpation imaging tool that reveals viscoelastic properties of small biological samples.

  1. Investigation of polymer derived ceramics cantilevers for application of high speed atomic force microscopy

    Science.gov (United States)

    Wu, Chia-Yun

    High speed Atomic Force Microscopy (AFM) has a wide variety of applications ranging from nanomanufacturing to biophysics. In order to have higher scanning speed of certain AFM modes, high resonant frequency cantilevers are needed; therefore, the goal of this research is to investigate using polymer derived ceramics for possible applications in making high resonant frequency AFM cantilevers using complex cross sections. The polymer derived ceramic that will be studied, is silicon carbide. Polymer derived ceramics offer a potentially more economic fabrication approach for MEMS due to their relatively low processing temperatures and ease of complex shape design. Photolithography was used to make the desired cantilever shapes with micron scale size followed by a wet etching process to release the cantilevers from the substrates. The whole manufacturing process we use borrow well-developed techniques from the semiconducting industry, and as such this project also could offer the opportunity to reduce the fabrication cost of AFM cantilevers and MEMS in general. The characteristics of silicon carbide made from the precursor polymer, SMP-10 (Starfire Systems), were studied. In order to produce high qualities of silicon carbide cantilevers, where the major concern is defects, proper process parameters needed to be determined. Films of polymer derived ceramics often have defects due to shrinkage during the conversion process. Thus control of defects was a central issue in this study. A second, related concern was preventing oxidation; the polymer derived ceramics we chose is easily oxidized during processing. Establishing an environment without oxygen in the whole process was a significant challenge in the project. The optimization of the parameters for using photolithography and wet etching process was the final and central goal of the project; well established techniques used in microfabrication were modified for use in making the cantilever in the project. The techniques

  2. Synchronous fire activity in the tropical high Andes: an indication of regional climate forcing.

    Science.gov (United States)

    Román-Cuesta, R M; Carmona-Moreno, C; Lizcano, G; New, M; Silman, M; Knoke, T; Malhi, Y; Oliveras, I; Asbjornsen, H; Vuille, M

    2014-06-01

    Global climate models suggest enhanced warming of the tropical mid and upper troposphere, with larger temperature rise rates at higher elevations. Changes in fire activity are amongst the most significant ecological consequences of rising temperatures and changing hydrological properties in mountainous ecosystems, and there is a global evidence of increased fire activity with elevation. Whilst fire research has become popular in the tropical lowlands, much less is known of the tropical high Andean region (>2000 masl, from Colombia to Bolivia). This study examines fire trends in the high Andes for three ecosystems, the Puna, the Paramo and the Yungas, for the period 1982-2006. We pose three questions: (i) is there an increased fire response with elevation? (ii) does the El Niño- Southern Oscillation control fire activity in this region? (iii) are the observed fire trends human driven (e.g., human practices and their effects on fuel build-up) or climate driven? We did not find evidence of increased fire activity with elevation but, instead, a quasicyclic and synchronous fire response in Ecuador, Peru and Bolivia, suggesting the influence of high-frequency climate forcing on fire responses on a subcontinental scale, in the high Andes. ENSO variability did not show a significant relation to fire activity for these three countries, partly because ENSO variability did not significantly relate to precipitation extremes, although it strongly did to temperature extremes. Whilst ENSO did not individually lead the observed regional fire trends, our results suggest a climate influence on fire activity, mainly through a sawtooth pattern of precipitation (increased rainfall before fire-peak seasons (t-1) followed by drought spells and unusual low temperatures (t0), which is particularly common where fire is carried by low fuel loads (e.g., grasslands and fine fuel). This climatic sawtooth appeared as the main driver of fire trends, above local human influences and fuel build

  3. Ultra-low coercive field of improper ferroelectric Ca3Ti2O7 epitaxial thin films

    Science.gov (United States)

    Li, X.; Yang, L.; Li, C. F.; Liu, M. F.; Fan, Z.; Xie, Y. L.; Lu, C. L.; Lin, L.; Yan, Z. B.; Zhang, Z.; Dai, J. Y.; Liu, J.-M.; Cheong, S. W.

    2017-01-01

    Hybrid improper ferroelectrics have their electric polarization generated by two or more combined non-ferroelectric structural distortions, such as the rotation and tilting of Ti-O octahedral in the Ca3Ti2O7 (CTO) family. In this work, we prepare the high quality (010)-oriented CTO thin films on (110) SrTiO3 (STO) substrates by pulsed laser deposition. The good epitaxial growth of the CTO thin films on the substrates with the interfacial epitaxial relationship of [001]CTO//[001]STO and [100]CTO//[-110]STO is revealed. The in-plane ferroelectric hysteresis unveils an ultralow coercive field of ˜5 kV/cm even at low temperature, nearly two orders of magnitude lower than that of bulk CTO single crystals. The huge difference between the epitaxial thin films and bulk crystals is most likely due to the lattice imperfections in the thin films rather than substrate induced lattice strains, suggesting high sensitivity of the ferroelectric properties to lattice defects.

  4. Nuclear forces and the properties of matter at high temperature and density

    Energy Technology Data Exchange (ETDEWEB)

    Rayet, M.; Arnould, M.; Paulus, G.; Tondeur, F.

    1982-12-01

    We present two Skyrme-type forces which are particularly well suited for the description of presupernova core or matter in nascent neutron star. They are compared to other forces currently used in this field, with regard to finite nuclei and infinite matter properties, and to the coexistence of nuclei in a hot and dense nucleon gas.

  5. A method to calculate and counterbalance the inertia force of slider-crank mechanisms in high-speed presses

    Institute of Scientific and Technical Information of China (English)

    Jim Wang; Sheng-dun Zhao; Hu-shan Shi; Chun-jian Hua

    2009-01-01

    A new method to calculate and counterbalance the inertia force of slider-crank mechanisms in high-speed mechanical presses was put forward. By analyzing the kinematic characteristics of a center-located slider-crank mechanism whose crank rotates at a constant angular velocity, the kinematic parameters of the slide, connecting rod and crank were formulated approximately. On the basis of the results above, three inertia forces and the input moment in the mechanism during its idle running were investigated and formulated by dynamic analysis. A verification experiment was performed on a slider-crank mechanism at a high-speed press machine. The forces derived from the established formulas were compared respectively with those obtained by the ADAMS software and the classical method of connecting rod mass substitution. It was experimentally found that the proposed formulas have an improved performance over related earlier techniques. By use of these results, a 1000 kN 1250 rpm four-point high-speed press machine was designed and manufactured. The slide of this press is driven by four sets of slider-crank mechanisms with symmetrical layout and opposite rotation directions to counterbalance the horizontal inertia forces. Four eccentric counterbalance blocks were designed to counterbalance the vertical force after their mass and equivalent eccentric radius were formulated. The high-speed press machine designed by the proposed counterbalance method has worked with satisfactory performance and good dynamic balance for more than four years in practical production.

  6. A comparison of low- and high-impact forced exercise: Effects of training paradigm on learning and memory

    Science.gov (United States)

    Kennard, John A.; Woodruff-Pak, Diana S.

    2012-01-01

    In this study we compared two types of forced exercise—a low impact paradigm to minimize stress, which included speeds up to 10 m/min and a stressful high impact paradigm, with speeds up to 21 m/min. 150 male C57BL/6J mice were randomly assigned to the low impact, high impact, or sedentary control conditions and were tested on the rotorod and Morris water maze (MWM) as indices of motor learning and spatial memory. We found that five weeks of stressful high speed forced exercise led to significant improvement in rotorod performance, as high impact runners outperformed both low impact runners and controls at 15 and 25 RPM speeds. These differences were the result of improved physical fitness due to exercise and likely do not reflect enhanced learning in these mice. In the MWM, five weeks of stressful high impact exercise led to significant impairment in spatial memory acquisition compared to low impact runners and controls. Low impact exercise for 10 weeks significantly improved retention of spatial memory compared to high impact exercise. Results suggested that these two paradigms produced different effects of forced exercise on learning and memory. The low impact paradigm led to some improvements, whereas the stressful high impact program caused significant impairment. Comparison of these two paradigms begins to address the window between the beneficial and detrimental effects of forced exercise, and have suggested a boundary of exercise intensity that leads to impairment in learning. PMID:22402029

  7. A comparison of low- and high-impact forced exercise: effects of training paradigm on learning and memory.

    Science.gov (United States)

    Kennard, John A; Woodruff-Pak, Diana S

    2012-06-25

    In this study we compared two types of forced exercise-a low impact paradigm to minimize stress, which included speeds up to 10 m/min and a stressful high impact paradigm, with speeds up to 21 m/min. 150 male C57BL/6J mice were randomly assigned to the low impact, high impact, or sedentary control conditions and were tested on the rotorod and Morris water maze (MWM) as indices of motor learning and spatial memory. We found that 5 weeks of stressful high speed forced exercise led to significant improvement in rotorod performance, as high impact runners outperformed both low impact runners and controls at 15 and 25 rpm speeds. These differences were the result of improved physical fitness due to exercise and likely do not reflect enhanced learning in these mice. In the MWM, 5 weeks of stressful high impact exercise led to significant impairment in spatial memory acquisition compared to low impact runners and controls. Low impact exercise for 10 weeks significantly improved retention of spatial memory compared to high impact exercise. Results suggested that these two paradigms produced different effects of forced exercise on learning and memory. The low impact paradigm led to some improvements, whereas the stressful high impact program caused significant impairment. Comparison of these two paradigms begins to address the window between the beneficial and detrimental effects of forced exercise, and have suggested a boundary of exercise intensity that leads to impairment in learning.

  8. Micromagnetic simulation and the angular dependence of coercivity and remanence for array of polycrystalline nickel nanowires

    Science.gov (United States)

    Fuentes, G. P.; Holanda, J.; Guerra, Y.; Silva, D. B. O.; Farias, B. V. M.; Padrón-Hernández, E.

    2017-02-01

    We present here our experimental results for the preparation and characterization of nanowires of nickel and the analysis of the angular dependence of coercivity and remanence using experimental data and micromagnetic simulation. The fabrication was made by using aluminum oxide membranes as templates and deposited nickel by an electrochemical route. The magnetic measurements showed that coercivity and remanence are dependent of the angle of application of the external magnetic field. Our results are different than that expected for the coherent, vortex and transversal modes of the reversion for the magnetic moments. According to the transmission electron microscopy analysis we can see that our nanowires have not a perfect cylindrical format. That is why we have used the ellipsoids chain model for better understanding the real structure of wires and its relation with the magnetic behavior. In order to generate theoretical results for this configuration we have made micromagnetic simulation using Nmag code. Our numerical results for the realistic distances are in correspondence with the magnetic measurements and we can see that there are contradictions if we assume the transverse reversal mode. Then, we can conclude that structure of nanowires should be taken into account to understand the discrepancies reported in the literature for the reversion mechanism in arrays of nickel nanowires.

  9. Paraphilic Coercive Disorder in the DSM: the right diagnosis for the right reasons.

    Science.gov (United States)

    Stern, Paul

    2010-12-01

    The recommendation to include a Paraphilic Coercive Disorder (PCD) diagnosis in the DSM-5 represents an improvement over current options and would lead to the shrinking of the pool of individuals considered for detention as Sexually Violent Predators. A precise description of the diagnostic criteria for PCD would permit psychologists and psychiatrists to use more specific and narrow criteria for those who seek sexual gratification by coercing others to engage in unwanted sexual behavior. This might permit mental health professionals to abandon the Paraphilia NOS designation in favor of the more defined PCD in appropriate cases. Various critics have attacked the proposal on what appears to be misplaced ideological grounds. Not only should ideological concerns not play a part in a scientific debate, but the critics' predictions of how the PCD diagnosis would play out in the legal arena are likely wrong. Paraphilic Coercive Disorder would give the judicial system the best opportunity to most accurately identify the small group of men who have previously committed, and are likely in the future to commit, this type of predatory sexual violence.

  10. Tailoring coercivity of unbiased exchange-coupled ferromagnet/antiferromagnet bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Sossmeier, K. D.; Schafer, D.; Bastos, A. P. O.; Schmidt, J. E.; Geshev, J. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, 91501-970 Rio Grande do Sul (Brazil)

    2012-07-01

    This paper reports experimental results obtained on unconventional exchange-coupled ferromagnet/antiferromagnet (FM/AF) system showing zero net bias. The Curie temperature of the FM (NiCu) is lower than the blocking temperature of the AF (IrMn). Samples were either annealed or irradiated with He, Ar, or Ge ions at 40 keV. Due to the exchange coupling at the FM/AF interface, the coercivity (H{sub C}) of the as-deposited FM/AF bilayer is rather higher than that of the corresponding FM single layer. We found that by choosing a proper ion fluence or annealing temperature, it is possible to controllably vary H{sub C}. Ion irradiation of the FM single layer has lead to only a decrease of H{sub C} and annealing or He ion irradiation has not caused important changes at the FM/AF interface; nevertheless, a twofold increase of H{sub C} was obtained after these treatments. Even more significant enhancement of H{sub C} was attained after Ge ion irradiation and attributed to ion-implantation-induced modification of only the FM layer; damages of the FM/AF interface, on the other hand, decrease the coercivity.

  11. New Features of the Coercivity in Exchange-Coupled Ni81Fe19/CoO Bilayers

    Institute of Scientific and Technical Information of China (English)

    蔡建旺; 赖武彦

    2001-01-01

    The coercivity behaviour of the Nis1Fe19 film exchange-coupled with an antiferromagnetic CoO underlayer has been investigated systematically. It has been found that the coercivity is greatly enhanced not only in the easy axis direction but also in the hard axis direction when the temperature is below the Néel temperature of CoO. Also, the thickness dependence of coercivity at low temperature follows the scaling relation as 1/tNiFe with α = 2.5 at the hard axis, which is quite in contrast with the case of the easy axis, i.e. α = 1.5, predicted theoretically and verified experimentally previously. The increase of the temperature leads to the decrease of the coercivity at both the easy and hard axes, but the scaling relations are held except the narrow region just below the Néel temperature of CoO, at which the coercivity varies as 1/t NiFe with α = 1.0 for both the easy and hard axes. Based upon Hoffmann's ripple theory and Malozemoff's random field model, a simple interpretation of the experiment findings is presented.

  12. Extensive wet episodes in Late Glacial Australia resulting from high-latitude forcings

    Science.gov (United States)

    Bayon, Germain; De Deckker, Patrick; Magee, John W.; Germain, Yoan; Bermell, Sylvain; Tachikawa, Kazuyo; Norman, Marc D.

    2017-01-01

    Millennial-scale cooling events termed Heinrich Stadials punctuated Northern Hemisphere climate during the last glacial period. Latitudinal shifts of the intertropical convergence zone (ITCZ) are thought to have rapidly propagated these abrupt climatic signals southward, influencing the evolution of Southern Hemisphere climates and contributing to major reorganisation of the global ocean-atmosphere system. Here, we use neodymium isotopes from a marine sediment core to reconstruct the hydroclimatic evolution of subtropical Australia between 90 to 20 thousand years ago. We find a strong correlation between our sediment provenance proxy data and records for western Pacific tropical precipitations and Australian palaeolakes, which indicates that Northern Hemisphere cooling phases were accompanied by pronounced excursions of the ITCZ and associated rainfall as far south as about 32°S. Comparatively, however, each of these humid periods lasted substantially longer than the mean duration of Heinrich Stadials, overlapping with subsequent warming phases of the southern high-latitudes recorded in Antarctic ice cores. In addition to ITCZ-driven hydroclimate forcing, we infer that changes in Southern Ocean climate also played an important role in regulating late glacial atmospheric patterns of the Southern Hemisphere subtropical regions.

  13. A high-pressure atomic force microscope for imaging in supercritical carbon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Lea, A. S.; Higgins, S. R.; Knauss, K. G.; Rosso, K. M.

    2011-01-01

    A high-pressure atomic force microscope(AFM) that enables in situ, atomic scale measurements of topography of solid surfaces in contact with supercritical CO2 (scCO2) fluids has been developed. This apparatus overcomes the pressure limitations of the hydrothermal AFM and is designed to handle pressures up to 100 atm at temperatures up to ~350 K. A standard optically-based cantilever deflection detection system was chosen. When imaging in compressible supercritical fluids such as scCO2, precise control of pressure and temperature in the fluid cell is the primary technical challenge. Noise levels and imaging resolution depend on minimization of fluid density fluctuations that change the fluidrefractive index and hence the laser path. We demonstrate with our apparatus in situ atomic scale imaging of a calcite (CaCO3) mineral surface in scCO2; both single, monatomic steps and dynamic processes occurring on the (101¯4) surface are presented. Finally, this new AFM provides unprecedented in situ access to interfacial phenomena at solid–fluid interfaces under pressure.

  14. High-speed atomic force microscopy shows that annexin V stabilizes membranes on the second timescale

    Science.gov (United States)

    Miyagi, Atsushi; Chipot, Christophe; Rangl, Martina; Scheuring, Simon

    2016-09-01

    Annexins are abundant cytoplasmic proteins that can bind to negatively charged phospholipids in a Ca2+-dependent manner, and are known to play a role in the storage of Ca2+ and membrane healing. Little is known, however, about the dynamic processes of protein-Ca2+-membrane assembly and disassembly. Here we show that high-speed atomic force microscopy (HS-AFM) can be used to repeatedly induce and disrupt annexin assemblies and study their structure, dynamics and interactions. Our HS-AFM set-up is adapted for such biological applications through the integration of a pumping system for buffer exchange and a pulsed laser system for uncaging caged compounds. We find that biochemically identical annexins (annexin V) display different effective Ca2+ and membrane affinities depending on the assembly location, providing a wide Ca2+ buffering regime while maintaining membrane stabilization. We also show that annexin is membrane-recruited and forms stable supramolecular assemblies within ˜5 s in conditions that are comparable to a membrane lesion in a cell. Molecular dynamics simulations provide atomic detail of the role played by Ca2+ in the reversible binding of annexin to the membrane surface.

  15. Wide-area scanner for high-speed atomic force microscopy.

    Science.gov (United States)

    Watanabe, Hiroki; Uchihashi, Takayuki; Kobashi, Toshihide; Shibata, Mikihiro; Nishiyama, Jun; Yasuda, Ryohei; Ando, Toshio

    2013-05-01

    High-speed atomic force microscopy (HS-AFM) has recently been established. The dynamic processes and structural dynamics of protein molecules in action have been successfully visualized using HS-AFM. However, its maximum scan ranges in the X- and Y-directions have been limited to ~1 μm and ~4 μm, respectively, making it infeasible to observe the dynamics of much larger samples, including live cells. Here, we develop a wide-area scanner with a maximum XY scan range of ~46 × 46 μm(2) by magnifying the displacements of stack piezoelectric actuators using a leverage mechanism. Mechanical vibrations produced by fast displacement of the X-scanner are suppressed by a combination of feed-forward inverse compensation and the use of triangular scan signals with rounded vertices. As a result, the scan speed in the X-direction reaches 6.3 mm/s even for a scan size as large as ~40 μm. The nonlinearity of the X- and Y-piezoelectric actuators' displacements that arises from their hysteresis is eliminated by polynomial-approximation-based open-loop control. The interference between the X- and Y-scanners is also eliminated by the same technique. The usefulness of this wide-area scanner is demonstrated by video imaging of dynamic processes in live bacterial and eukaryotic cells.

  16. Enhanced coercivity of HCP Co-Pt alloy thin films on a glass substrate at room temperature for patterned media

    Science.gov (United States)

    Chen, Y. S.; Sun, An-Cheng; Lee, H. Y.; Lu, Hsi-Chuan; Wang, Sea-Fue; Sharma, Puneet

    2015-10-01

    High coercivity (Hc) Co-rich type Co-Pt alloy thin films with a columnar grain structure were deposited at room temperature (RT) by magnetron sputtering. Films with a thickness (t) of up to 10 nm had a FCC structure and exhibited soft magnetic properties. When t>25 nm, the magnetic anisotropy changed from in-plane to isotropic. Hc was also enhanced with increasing t and found to be maximum at t=50 nm. The in-plane and out-of-plane Hc of the film was 2.2 and 2.7 kOe, respectively. Further increasing t led to a slight decrease in Hc. Microstructure and phase structure studies revealed columnar Co-Pt grains with a uniform lateral size grown on a 7 nm initial layer. Films with t>25 nm showed a HCP phase, due to the internal stress and volume effect. The microstructural details responsible for the enhanced RT magnetic properties of the HCP Co-Pt alloy thin films were investigated by TEM.

  17. Modeling the effect of intercalators on the high-force stretching behavior of DNA

    CERN Document Server

    Schakenraad, Koen; Biebricher, Andreas; Wuite, Gijs; Storm, Cornelis; van der Schoot, Paul

    2015-01-01

    DNA is structurally and mechanically altered by the binding of intercalator molecules. Intercalation strongly affects the force-extension behavior of DNA, in particular the overstretching transition. We present a statistical model that captures all relevant findings of recent force-extension experiments. Two predictions from our model are presented. The first suggests the existence of a novel hyper-stretching regime in the presence of intercalators and the second, a linear dependence of the overstretching force on intercalator concentration, is verified by re-analyzing available experimental data. Our model pins down the physical principles that govern intercalated DNA mechanics, providing a predictive understanding of its limitations and possibilities.

  18. Propagation and Breaking at High Altitudes of Gravity Waves Excited by Tropospheric Forcing

    Science.gov (United States)

    Prusa, Joseph M.; Smolarkiewicz, Piotr K.; Garcia, Rolando R.

    1996-01-01

    An anelastic approximation is used with a time-variable coordinate transformation to formulate a two-dimensional numerical model that describes the evolution of gravity waves. The model is solved using a semi-Lagrangian method with monotone (nonoscillatory) interpolation of all advected fields. The time-variable transformation is used to generate disturbances at the lower boundary that approximate the effect of a traveling line of thunderstorms (a squall line) or of flow over a broad topographic obstacle. The vertical propagation and breaking of the gravity wave field (under conditions typical of summer solstice) is illustrated for each of these cases. It is shown that the wave field at high altitudes is dominated by a single horizontal wavelength; which is not always related simply to the horizontal dimension of the source. The morphology of wave breaking depends on the horizontal wavelength; for sufficiently short waves, breaking involves roughly one half of the wavelength. In common with other studies, it is found that the breaking waves undergo "self-acceleration," such that the zonal-mean intrinsic frequency remains approximately constant in spite of large changes in the background wind. It is also shown that many of the features obtained in the calculations can be understood in terms of linear wave theory. In particular, linear theory provides insights into the wavelength of the waves that break at high altitudes, the onset and evolution of breaking. the horizontal extent of the breaking region and its position relative to the forcing, and the minimum and maximum altitudes where breaking occurs. Wave breaking ceases at the altitude where the background dissipation rate (which in our model is a proxy for molecular diffusion) becomes greater than the rate of dissipation due to wave breaking, This altitude, in effect, the model turbopause, is shown to depend on a relatively small number of parameters that characterize the waves and the background state.

  19. Control of fingertip forces in young and older adults pressing against fixed low- and high-friction surfaces.

    Directory of Open Access Journals (Sweden)

    Kevin G Keenan

    Full Text Available Mobile computing devices (e.g., smartphones and tablets that have low-friction surfaces require well-directed fingertip forces of sufficient and precise magnitudes for proper use. Although general impairments in manual dexterity are well-documented in older adults, it is unclear how these sensorimotor impairments influence the ability of older adults to dexterously manipulate fixed, low-friction surfaces in particular. 21 young and 18 older (65+ yrs adults produced maximal voluntary contractions (MVCs and steady submaximal forces (2.5 and 10% MVC with the fingertip of the index finger. A Teflon covered custom-molded splint was placed on the fingertip. A three-axis force sensor was covered with either Teflon or sandpaper to create low- and high-friction surfaces, respectively. Maximal downward forces (F(z were similar (p = .135 for young and older adults, and decreased by 15% (p<.001 while pressing on Teflon compared to sandpaper. Fluctuations in F(z during the submaximal force-matching tasks were 2.45× greater (p<.001 for older adults than in young adults, and reached a maximum when older adults pressed against the Teflon surface while receiving visual feedback. These age-associated changes in motor performance are explained, in part, by altered muscle activity from three hand muscles and out-of-plane forces. Quantifying the ability to produce steady fingertip forces against low-friction surfaces may be a better indicator of impairment and disability than the current practice of evaluating maximal forces with pinch meters. These age-associated impairments in dexterity while interacting with low-friction surfaces may limit the use of the current generation of computing interfaces by older adults.

  20. Force measurements on natural membrane nanovesicles reveal a composition-independent, high Young's modulus

    Science.gov (United States)

    Calò, Annalisa; Reguera, David; Oncins, Gerard; Persuy, Marie-Annick; Sanz, Guenhaël; Lobasso, Simona; Corcelli, Angela; Pajot-Augy, Edith; Gomila, Gabriel

    2014-01-01

    Mechanical properties of nano-sized vesicles made up of natural membranes are crucial to the development of stable, biocompatible nanocontainers with enhanced functional, recognition and sensing capabilities. Here we measure and compare the mechanical properties of plasma and inner membrane nanovesicles ~80 nm in diameter obtained from disrupted yeast Saccharomyces cerevisiae cells. We provide evidence of a highly deformable behaviour for these vesicles, able to support repeated wall-to-wall compressions without irreversible deformations, accompanied by a noticeably high Young's modulus (~300 MPa) compared to that obtained for reconstituted artificial liposomes of similar size and approaching that of some virus particles. Surprisingly enough, the results are approximately similar for plasma and inner membrane nanovesicles, in spite of their different lipid compositions, especially on what concerns the ergosterol content. These results point towards an important structural role of membrane proteins in the mechanical response of natural membrane vesicles and open the perspective to their potential use as robust nanocontainers for bioapplications.Mechanical properties of nano-sized vesicles made up of natural membranes are crucial to the development of stable, biocompatible nanocontainers with enhanced functional, recognition and sensing capabilities. Here we measure and compare the mechanical properties of plasma and inner membrane nanovesicles ~80 nm in diameter obtained from disrupted yeast Saccharomyces cerevisiae cells. We provide evidence of a highly deformable behaviour for these vesicles, able to support repeated wall-to-wall compressions without irreversible deformations, accompanied by a noticeably high Young's modulus (~300 MPa) compared to that obtained for reconstituted artificial liposomes of similar size and approaching that of some virus particles. Surprisingly enough, the results are approximately similar for plasma and inner membrane nanovesicles, in

  1. Origins of the Exchange-Bias Phenomenology, Coercivity Enhancement, and Asymmetric Hysteretic Shearing in Core-Surface Smart Nanoparticles

    Directory of Open Access Journals (Sweden)

    Rıza Erdem

    2016-01-01

    Full Text Available We have used a spin-1 Ising model Hamiltonian with dipolar (bilinear, J, quadrupolar (biquadratic, K, and dipolar-quadrupolar (odd, L interactions in pair approximation to investigate the exchange-bias (EB, coercive field, and asymmetric hysteretic shearing properties peculiar to core/surface (C/S composite nanoparticles (NPs. Shifted hysteresis loops with an asymmetry and coercivity enhancement are observed only in the presence of the odd interaction term in the Hamiltonian expression and their magnitudes show strong dependence on the value of L. The observed coercivity and EB in C/S NPs originated from nonzero odd coupling energies and their dependence on temperature (T and particle size (R are also discussed in relation to experimental findings.

  2. Micromagnetic simulation of the orientation dependence of grain boundary properties on the coercivity of Nd-Fe-B sintered magnets

    Science.gov (United States)

    Fujisaki, Jun; Furuya, Atsushi; Uehara, Yuji; Shimizu, Koichi; Ataka, Tadashi; Tanaka, Tomohiro; Oshima, Hirotaka; Ohkubo, Tadakatsu; Hirosawa, Satoshi; Hono, Kazuhiro

    2016-05-01

    This paper is focused on the micromagnetic simulation study about the orientation dependence of grain boundary properties on the coercivity of polycrystalline Nd-Fe-B sintered magnets. A multigrain object with a large number of meshes is introduced to analyze such anisotropic grain boundaries and the simulation is performed by combining the finite element method and the parallel computing. When the grain boundary phase parallel to the c-plane is less ferromagnetic the process of the magnetization reversal changes and the coercivity of the multigrain object increases. The simulations with various magnetic properties of the grain boundary phases are executed to search for the way to enhance the coercivity of polycrystalline Nd-Fe-B sintered magnets.

  3. REMARKABLE IMPROVEMENT OF THE COERCIVITY OF TbMn6Sn6 COMPOUND BY MELT-SPINNING PROCESS

    Institute of Scientific and Technical Information of China (English)

    赵鹏; 张绍英; 张宏伟; 阎阿儒; 沈保根

    2001-01-01

    The melt-spinning process has been carried out to improve the hard-magnetic properties of the TbMn6Sn6 compound. For the TbMn6Sn6 ribbons quenched at a rate of 40m/s and annealed at 545K for 30min, the highest coercivity of about 0.6T is achieved at room temperature, which is much higher than that of the TbMn6Sn6 ingot. Both the ingot and the ribbon coercivities will increase with decreasing temperature. For ribbons, a greater improvement of coercivity has been made at lower temperatures. Microstructural studies show the uniform nanocrystalline distribution in the TbMn6Sn6 ribbons and a small amount of Tb-rich phase in grain boundaries. The observed remarkable improvement of magnetic hardening in ribbons is believed to arise from the uniform nanoscale microstructure and the domain-wall pinning at the grain boundaries.

  4. Levitation force from high-Tc superconducting thin-film disks

    Science.gov (United States)

    Riise, Anjali B.; Johansen, T. H.; Bratsberg, H.; Koblischka, M. R.; Shen, Y. Q.

    1999-10-01

    Experimental studies and theoretical modeling of the levitation force between a permanent magnet and superconducting thin film are reported. Measurements of the force Fz and magnetic stiffness κz=\\|δFz/δz\\| as functions of the magnet-superconductor separation z, show several features contrasting all previous levitation force data for bulk superconductors. In particular, the Fz(z) curves measured for decreasing and increasing separation form hysteresis loops of nearly symmetrical shape, also displaying a peak in the repulsive force branch. Recent theories for flux penetration in thin type-II superconductors in transverse magnetic fields are invoked to explain the results, which were obtained using a cylindrical Nd-Fe-B magnet and a YBa2Cu3O7-δ circular disk made by laser ablation. We derive explicit formulas for both Fz and κz, reproducing quantitatively all the features seen experimentally.

  5. Nursing Education in High Blood Pressure Control. Report of the Task Force on the Role of Nursing in High Blood Pressure Control.

    Science.gov (United States)

    National Institutes of Health (DHEW), Bethesda, MD. High Blood Pressure Information Center.

    This curriculum guide on high blood pressure (hypertension) for nursing educators has five sections: (1) Introduction and Objectives provides information regarding the establishment and objectives of the National Task Force on the Role of Nursing in High Blood Pressure Control and briefly discusses nursing's role in hypertension control; (2) Goals…

  6. An isometric muscle force estimation framework based on a high-density surface EMG array and an NMF algorithm

    Science.gov (United States)

    Huang, Chengjun; Chen, Xiang; Cao, Shuai; Qiu, Bensheng; Zhang, Xu

    2017-08-01

    Objective. To realize accurate muscle force estimation, a novel framework is proposed in this paper which can extract the input of the prediction model from the appropriate activation area of the skeletal muscle. Approach. Surface electromyographic (sEMG) signals from the biceps brachii muscle during isometric elbow flexion were collected with a high-density (HD) electrode grid (128 channels) and the external force at three contraction levels was measured at the wrist synchronously. The sEMG envelope matrix was factorized into a matrix of basis vectors with each column representing an activation pattern and a matrix of time-varying coefficients by a nonnegative matrix factorization (NMF) algorithm. The activation pattern with the highest activation intensity, which was defined as the sum of the absolute values of the time-varying coefficient curve, was considered as the major activation pattern, and its channels with high weighting factors were selected to extract the input activation signal of a force estimation model based on the polynomial fitting technique. Main results. Compared with conventional methods using the whole channels of the grid, the proposed method could significantly improve the quality of force estimation and reduce the electrode number. Significance. The proposed method provides a way to find proper electrode placement for force estimation, which can be further employed in muscle heterogeneity analysis, myoelectric prostheses and the control of exoskeleton devices.

  7. Analysis of adhesive binding forces between laminin-1 and C2C12 muscle cell membranes measured via high resolution force spectroscopy

    Science.gov (United States)

    Gluck, George; Gilbert, Richard; Ortiz, Christine

    2002-03-01

    Laminins are a family of glycoproteins that regulate cell differentiation, shape, and motility through interactions with various cell surface receptors. Here, we have directly measured the biomolecular adhesive binding forces between a cantilever / probe tip that was covalently attached with laminin-1 and membrane receptors on C2C12 muscle cells using the technique of high-resolution force spectroscopy (HRFS). On retraction of the probe tip away from the membrane surface, discrete, long-range adhesive unbinding events were always observed. Statistical analysis of the data revealed an initial broad distribution of heterogeneous unbinding events (occurring at separation distances, D=0-2µm from the point of maximum compression) of magnitude 92.23±37.87pN followed by a narrow distribution of homogeneous unbinding events (occurring at D > 2µm) of magnitude 38.16±9.10pN, which is suggestive of an individual biomolecular adhesive interaction. On-going studies include loading rate dependence and effect of dystroglycan mutation.

  8. Exploring Variations Within Situational Couple Violence and Comparisons With Coercive Controlling Violence and No Violence/No Control.

    Science.gov (United States)

    Nielsen, Samantha K; Hardesty, Jennifer L; Raffaelli, Marcela

    2016-02-01

    We examined variations within situational couple violence among 23 divorcing mothers and compared them with mothers with coercive controlling violence and no violence/no control. Situational couple violence had great variability in frequency and severity of violence, fear, harassment, and protective strategies. In some cases, situational couple violence was frequent and severe and resembled coercive controlling violence in its consequences. The dynamics of fear and harassment in situational couple violence and in the divorce process in general warrant attention. Finally, mothers reported mental health symptoms that did not differ by group, which is likely due to the stresses of divorce.

  9. Final Report of the National Black Health Providers Task Force on High Blood Pressure Education and Control.

    Science.gov (United States)

    Public Health Service (DHHS), Rockville, MD.

    This is the final report of National Black Health Providers Task Force (NBHPTF) on High Blood Pressure Education and Control. The first chapter of the report recounts the history of the NBHPTF and its objectives. In the second chapter epidemiological evidence is presented to demonstrate the need for a suggested 20 year plan aimed at controlling…

  10. Monsoonal response to mid-holocene orbital forcing in a high resolution GCM

    Directory of Open Access Journals (Sweden)

    J. H. C. Bosmans

    2012-04-01

    Full Text Available In this study, we use a sophisticated high-resolution atmosphere-ocean coupled climate model, EC-Earth, to investigate the effect of Mid-Holocene orbital forcing on summer monsoons on both hemispheres. During the Mid-Holocene (6 ka, there was more summer insolation on the Northern Hemisphere than today, which intensified the meridional temperature and pressure gradients. Over North Africa, monsoonal precipitation is intensified through increased landward monsoon winds and moisture advection as well as decreased moisture convergence over the oceans and more convergence over land compared to the pre-industrial simulation. Precipitation also extends further north as the ITCZ shifts northward in response to the stronger poleward gradient of insolation. This increase and poleward extent is stronger than in most previous ocean-atmosphere GCM simulations. In north-westernmost Africa, precipitation extends up to 35° N. Over tropical Africa, internal feedbacks completely overcome the direct warming effect of increased insolation. We also find a weakened African Easterly Jet. Over Asia, monsoonal precipitation during the Mid-Holocene is increased as well, but the response is different than over North-Africa. There is more convection over land at the expense of convection over the ocean, but precipitation does not extend further northward, monsoon winds over the ocean are weaker and the surrounding ocean does not provide more moisture. On the Southern Hemisphere, summer insolation and the poleward insolation gradient were weaker during the Mid-Holocene, resulting in a reduced South American monsoon through decreased monsoon winds and less convection, as well as an equatorward shift in the ITCZ. This study corroborates the findings of paleodata research as well as previous model studies, while giving a more detailed account of Mid-Holocene monsoons.

  11. A nanocrystalline Sm-Co compound for high-temperature permanent magnets.

    Science.gov (United States)

    Zhang, Zhexu; Song, Xiaoyan; Qiao, Yinkai; Xu, Wenwu; Zhang, Jiuxing; Seyring, Martin; Rettenmayr, Markus

    2013-03-21

    The inherently high magnetic anisotropy and nanoscale grain size in a Sm5Co19 compound result in an intrinsic coercivity far higher than those of known Sm-Co compounds prior to orientation treatment. The combination of ultrahigh intrinsic coercivity, high Curie temperature and low coercivity temperature coefficient of nanocrystalline Sm5Co19 as a single phase material shows it to be a very promising compound to develop outstanding high-temperature permanent magnets.

  12. A method to calculate and counterbalance the inertia force of slider-crank mechanisms in high-speed presses

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A new method to calculate and counterbalance the inertia force of slider-crank mechanisms in high-speed mechanical presses was put forward. By analyzing the kinematic characteristics of a center-located slider-crank mechanism whose crank rotates at a constant angular velocity,the kinematic parameters of the slide,connecting rod and crank were formulated approximately. On the basis of the results above,three inertia forces and the input moment in the mechanism during its idle running were investigated and fo...

  13. Increased rate of force development and neuromuscular activity after high-load resistance training in patients undergoing dialysis

    DEFF Research Database (Denmark)

    Molsted, Stig; Andersen, Jesper L.; Eidemak, Inge

    2013-01-01

    AimThe aim of this study was to investigate the effects of high-load resistance training on the rate of force development and neuromuscular function in patients undergoing dialysis. MethodsTwenty-nine patients were tested before and after 16 weeks of resistance training. The rate of force...... development was tested using the Good Strength dynamometer chair. Muscle strength and neuromuscular function in the m. Vastus lateralis was estimated using electromyography in a one repetition maximum test during dynamic knee extension and during a 20s isometric knee extension with 50% of the one repetition...

  14. Interrogating biology with force: single molecule high-resolution measurements with optical tweezers.

    Science.gov (United States)

    Capitanio, Marco; Pavone, Francesco S

    2013-09-17

    Single molecule force spectroscopy methods, such as optical and magnetic tweezers and atomic force microscopy, have opened up the possibility to study biological processes regulated by force, dynamics of structural conformations of proteins and nucleic acids, and load-dependent kinetics of molecular interactions. Among the various tools available today, optical tweezers have recently seen great progress in terms of spatial resolution, which now allows the measurement of atomic-scale conformational changes, and temporal resolution, which has reached the limit of the microsecond-scale relaxation times of biological molecules bound to a force probe. Here, we review different strategies and experimental configurations recently developed to apply and measure force using optical tweezers. We present the latest progress that has pushed optical tweezers' spatial and temporal resolution down to today's values, discussing the experimental variables and constraints that are influencing measurement resolution and how these can be optimized depending on the biological molecule under study. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  15. The validation of the Checklist of Controlling Behaviors (CCB): assessing coercive control in abusive relationships.

    Science.gov (United States)

    Lehmann, Peter; Simmons, Catherine A; Pillai, Vijayan K

    2012-08-01

    The current study addresses the validation of the Checklist of Controlling Behaviors (CCB), an 84-item domestic violence assessment instrument that can be used to address multiple levels of violence and coercive control in violent relationships. Derived from clinical observation and current theories, the CCB makes use of intimate partner violence survivor reports to identify the intensity and frequency of relationship violence. The instrument is divided into 10 subscales including (1) physical abuse, (2) sexual abuse, (3) male privilege, (4) isolation, (5) minimizing and denying, (6) blaming, (7) intimidation, (8) threats, (9) emotional abuse, and (10) economic abuse. To assess validity and reliability of the CCB, 2,135 female volunteers taking refuge at a domestic violence shelter were administered the instrument. Results of principal component analysis of the individual subscales revealed 10 factors having goodness-of-fit values above the desired normative level of .90.

  16. MAX UnMix: A web application for unmixing magnetic coercivity distributions

    Science.gov (United States)

    Maxbauer, Daniel P.; Feinberg, Joshua M.; Fox, David L.

    2016-10-01

    It is common in the fields of rock and environmental magnetism to unmix magnetic mineral components using statistical methods that decompose various types of magnetization curves (e.g., acquisition, demagnetization, or backfield). A number of programs have been developed over the past decade that are frequently used by the rock magnetic community, however many of these programs are either outdated or have obstacles inhibiting their usability. MAX UnMix is a web application (available online at http://www.irm.umn.edu/maxunmix), built using the shiny package for R studio, that can be used for unmixing coercivity distributions derived from magnetization curves. Here, we describe in detail the statistical model underpinning the MAX UnMix web application and discuss the programs functionality. MAX UnMix is an improvement over previous unmixing programs in that it is designed to be user friendly, runs as an independent website, and is platform independent.

  17. Perpendicular coercivity enhancement of CoPt/TiN films by nitrogen incorporation during deposition

    Science.gov (United States)

    An, Hongyu; Wang, Jian; Szivos, Janos; Harumoto, Takashi; Sannomiya, Takumi; Muraishi, Shinji; Safran, Gyorgy; Nakamura, Yoshio; Shi, Ji

    2015-11-01

    The effect of N incorporation on the structure and magnetic properties of CoPt thin films deposited on glass substrates with TiN seed layers has been investigated. During the deposition of CoPt, introducing 20% N2 into Ar atmosphere promotes the (001) texture and enhances the perpendicular coercivity of CoPt film compared with the film deposited in pure Ar and post-annealed under the same conditions. From the in situ x-ray diffraction results, it is confirmed that N incorporation expands the lattice parameter of CoPt, which favors the epitaxial growth of CoPt on TiN. During the post-annealing process, N releases from CoPt film and promotes the L10 ordering transformation of CoPt.

  18. Lipschitz regularity for integro-differential equations with coercive Hamiltonians and application to large time behavior

    Science.gov (United States)

    Barles, Guy; Ley, Olivier; Topp, Erwin

    2017-02-01

    In this paper, we provide suitable adaptations of the ‘weak version of Bernstein method’ introduced by the first author in 1991, in order to obtain Lipschitz regularity results and Lipschitz estimates for nonlinear integro-differential elliptic and parabolic equations set in the whole space. Our interest is to obtain such Lipschitz results to possibly degenerate equations, or to equations which are indeed ‘uniformly elliptic’ (maybe in the nonlocal sense) but which do not satisfy the usual ‘growth condition’ on the gradient term allowing to use (for example) the Ishii-Lions’ method. We treat the case of a model equation with a superlinear coercivity on the gradient term which has a leading role in the equation. This regularity result together with comparison principle provided for the problem allow to obtain the ergodic large time behavior of the evolution problem in the periodic setting.

  19. Relationship between harmonic spectra and coercive field of immobilized magnetic nanoparticles

    Science.gov (United States)

    Sasayama, Teruyoshi; Yoshida, Takashi; Enpuku, Keiji

    2017-02-01

    We studied the AC hysteresis loop and the harmonic spectra of samples containing immobilized magnetic nanoparticles (MNPs) at different values of the excitation field frequency f and amplitude H 0. First, we measured the dependences of the coercive field on f and H 0. The measured dependences agreed qualitatively with the numerically predicted values. Next, we studied the relationship between and the harmonic spectra, and found strong correlation between and the attenuation rate of these harmonic spectra. We obtained an empirical expression for the harmonic spectra using and a static magnetization curve for the immobilized MNPs. The expression obtained explained the experimental data well. Finally, the harmonic spectra were measured for two MNP samples with different distributions of the magnetic moment m. The MNP sample with the lower m distribution produces richer harmonic spectra for use in magnetic particle imaging.

  20. Evidence regarding the need for a diagnostic category for a coercive paraphilia.

    Science.gov (United States)

    Thornton, David

    2010-04-01

    Evidence relevant to a potential diagnosis of Paraphilic Coercive Disorder is reviewed. Salient cues indicating that their partner is feeling coerced normally at least partially inhibit male sexual arousal while cues indicating mutual interest heighten arousal. However, for a minority of males, this pattern reverses with salient coercion cues leading to heightened arousal. This unusual pattern of arousal and fantasy is associated with a self-reported willingness to rape among non-convicted samples and is more common among convicted rapists than in other offender groups. It is inconsistently associated with Sadism as defined by the DSM-IV-TR and only weakly associated with psychopathy or general criminality. Evidence for it as an abnormal and persistent sexual interest comes from behavioral patterns, self-reported sexual fantasy, and laboratory tests. Two possible ways of incorporating it into a future version of the DSM are outlined.

  1. Perpendicular coercivity enhancement of CoPt/TiN films by nitrogen incorporation during deposition

    Energy Technology Data Exchange (ETDEWEB)

    An, Hongyu; Harumoto, Takashi; Sannomiya, Takumi; Muraishi, Shinji; Nakamura, Yoshio; Shi, Ji, E-mail: Shi.j.aa@m.titech.ac.jp [Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8552 (Japan); Wang, Jian [National Institute for Materials Science (NIMS), Sengen 1-2-1, Tsukuba, Ibaraki 305-0047 (Japan); Szivos, Janos; Safran, Gyorgy [Hungarian Academy of Sciences, Research Institute for Technical Physics and Materials Science, H-1121 Budapest, Konkoly-Thege ut 29-33 (Hungary)

    2015-11-28

    The effect of N incorporation on the structure and magnetic properties of CoPt thin films deposited on glass substrates with TiN seed layers has been investigated. During the deposition of CoPt, introducing 20% N{sub 2} into Ar atmosphere promotes the (001) texture and enhances the perpendicular coercivity of CoPt film compared with the film deposited in pure Ar and post-annealed under the same conditions. From the in situ x-ray diffraction results, it is confirmed that N incorporation expands the lattice parameter of CoPt, which favors the epitaxial growth of CoPt on TiN. During the post-annealing process, N releases from CoPt film and promotes the L1{sub 0} ordering transformation of CoPt.

  2. Electric field induced changes in the coercivity of a thin-film ferromagnet

    Energy Technology Data Exchange (ETDEWEB)

    Fowley, C; Rode, K; Oguz, K; Kurt, H; Coey, J M D [CRANN and School of Physics, Trinity College Dublin (Ireland)

    2011-08-03

    Data are presented which indicate a modification of magnetic anisotropy in the MgO/CoFeB/Pd and MgO/CoFeB/Pt systems, using electric fields of order 500 MV m{sup -1} (0.5 V nm{sup -1}) applied across a thermally grown SiO{sub 2} as a gate dielectric. The effect is most prominent at low temperature (12 K) and is manifested as a small change in coercivity. The sign of the effect depends on the choice of both capping layer and annealing temperature. The results suggest that both interfaces play a role in the appearance of perpendicular magnetic anisotropy in these thin-film stacks, and not just the interface with MgO.

  3. Switchable voltage control of the magnetic coercive field via magnetoelectric effect

    Science.gov (United States)

    Wang, Jing; Ma, Jing; Li, Zheng; Shen, Yang; Lin, Yuanhua; Nan, C. W.

    2011-08-01

    Switchable voltage modulation of the magnetic properties is reported in different multiferroic bilayers with magnetic films grown on pre-poled ferroelectric substrates, based on the magneto-optical Kerr effect observations. The dynamic voltage control of the magnetic coercive field (Hc) is dependent not only on the materials properties of each ferroic layer, but also on the bias voltage history. The Hc versus electric field behaviors essentially track the dependence of the piezostrains of the substrates on the bias voltage. The observations demonstrate that Hc in such multiferroic bilayers can be controlled by voltage via strain-mediated magnetoelectric coupling and that the Hc change is not an artifact due to a heating effect.

  4. The manipulation of magnetic coercive field and orientation of magnetic anisotropy via electric fields

    Science.gov (United States)

    Xiang, Jun-Sen; Ye, Jun; Yang, Yun-Long; Xie, Yong; Li, Wei; Chen, Zi-Yu

    2016-08-01

    We report the effects of the electric field on the magnetic coercive field (H c) and uniaxial magnetic anisotropy (UMA) orientation of polycrystalline Ni film grown on an unpoled (0 1 1) [Pb(Mg1/3Nb2/3)O3](1-x)-[PbTiO3] x (PMN-PT) single crystal substrate. Under various electric fields, normalized magnetic hysteresis loops of Ni films change in width; this represents the change of coercive field (ΔH c). Loop shapes are found to depend on the angle between the magnetic field and the sample, where changes in the shape reveal a small rotation of UMA. All these changes show that the magnetic properties vary periodically with a periodic electric field, by strain-mediated magnetoelectric coupling in the Ni/Ag/PMN-PT/Ag heterostructure. The poled PMN-PT produces strains under electric fields in the range of  -4.2 kV cm-1  ⩽  E  ⩽  4.2 kV cm-1, then transfers it to Ni films resulting in changes to its H c and UMA. The curves of the in-plane H c and strain, at two mutually orthogonal directions, represent butterfly patterns versus the applied electric field. In addition, the changes observed in both the H c and strain show asymmetric features in two orthogonal directions, which results in a small rotation angle of the UMA of Ni as the electric field decreases. The effective manipulation of magnitude and orientation of magnetic anisotropy via electric fields in ferromagnetic/ferroelectric (FM/FE) heterostructures is an important step towards controlling the magnetic tunnel junctions.

  5. Coercivity and nanostructure of melt-spun Ti-Fe-Co-B-based alloys

    Directory of Open Access Journals (Sweden)

    W. Y. Zhang

    2016-05-01

    Full Text Available Nanocrystalline Ti-Fe-Co-B-based alloys, prepared by melt spinning and subsequent annealing, have been characterized structurally and magnetically. X-ray diffraction and thermomagnetic measurements show that the ribbons consist of tetragonal Ti3(Fe,Co5B2, FeCo-rich bcc, and NiAl-rich L21 phases; Ti3(Fe,Co5B2, is a new substitutional alloy series whose end members Ti3Co5B2 and Ti3Fe5B2 have never been investigated magnetically and may not even exist, respectively. Two compositions are considered, namely Ti11+xFe37.5-0.5xCo37.5−0.5xB14 (x = 0, 4 and alnico-like Ti11Fe26Co26Ni10Al11Cu2B14, the latter also containing an L21-type alloy. The volume fraction of the Ti3(Fe,Co5B2 phase increases with x, which leads to a coercivity increase from 221 Oe for x = 0 to 452 Oe for x = 4. Since the grains are nearly equiaxed, there is little or no shape anisotropy, and the coercivity is largely due to the magnetocrystalline anisotropy of the tetragonal Ti3(Fe,Co5B2 phase. The alloy containing Ni, Al, and Cu exhibits a magnetization of 10.6 kG and a remanence ratio of 0.59. Our results indicate that magnetocrystalline anisotropy can be introduced in alnico-like magnets, adding to shape anisotropy that may be induced by field annealing.

  6. Variation of Surface Charge along the Surface of Wool Fibers Assessed by High-Resolution Force Spectroscopy

    Science.gov (United States)

    Zimmerman, Bonnie; Chow, James; Abbott, Albert G.; Ellison, Michael S.; Kennedy, Marian S.; Dean, Delphine

    2011-01-01

    In this study, we have mapped the surface charge of wool fibers using chemically specific high-resolution force spectroscopy in order to better understand the dispersion of amino acids in relation to fiber morphology. The inter-surface forces between standard atomic force microscopy (AFM) probe tips (tip radius ~ 50 nm) functionalized with COOH and NH3 terminated alkanethiol self assembling monolayers and the wool surface were used to estimate the surface charge per unit area using linear Poisson-Boltzmann-based electrostatic double layer theory. The positional measurement of nano-scale surface charge showed a correlation between the surface charge and fiber morphology, indicated that basic amino acids are located near the scale edges. PMID:21866220

  7. Effects of a sweptback hydrofoil on the force and longitudinal stability characteristics of a typical high-speed airplane

    Science.gov (United States)

    Wood, Raymond B

    1948-01-01

    An investigation was conducted in the Langley 8-foot high-speed tunnel to determine the effects of a sweptback hydrofoil on the force and longitudinal stability characteristics of a typical high-speed airplane. The Mach number range for this investigation was from 0.60 to 0.95 and at M = 1.20. The effects of the hydrofoil on the lift, drag, and pitching-moment characteristics are presented.

  8. Optimal design of high damping force engine mount featuring MR valve structure with both annular and radial flow paths

    Science.gov (United States)

    Nguyen, Q. H.; Choi, S. B.; Lee, Y. S.; Han, M. S.

    2013-11-01

    This paper focuses on the optimal design of a compact and high damping force engine mount featuring magnetorheological fluid (MRF). In the mount, a MR valve structure with both annular and radial flows is employed to generate a high damping force. First, the configuration and working principle of the proposed MR mount is introduced. The MRF flows in the mount are then analyzed and the governing equations of the MR mount are derived based on the Bingham plastic behavior of the MRF. An optimal design of the MR mount is then performed to find the optimal structure of the MR valve to generate a maximum damping force with certain design constraints. In addition, the gap size of MRF ducts is empirically chosen considering the ‘lockup’ problem of the mount at high frequency. Performance of the optimized MR mount is then evaluated based on finite element analysis and discussions on performance results of the optimized MR mount are given. The effectiveness of the proposed MR engine mount is demonstrated via computer simulation by presenting damping force and power consumption.

  9. Research on Key Factors and Their Interaction Effects of Electromagnetic Force of High-Speed Solenoid Valve

    Science.gov (United States)

    Fan, Liyun; Xu, De; Ma, Xiuzhen; Song, Enzhe

    2014-01-01

    Analysis consisting of numerical simulations along with lab experiments of interaction effects between key parameters on the electromagnetic force based on response surface methodology (RSM) has been also proposed to optimize the design of high-speed solenoid valve (HSV) and improve its performance. Numerical simulation model of HSV has been developed in Ansoft Maxwell environment and its accuracy has been validated through lab experiments. Effect of change of core structure, coil structure, armature structure, working air gap, and drive current on the electromagnetic force of HSV has been analyzed through simulation model and influence rules of various parameters on the electromagnetic force have been established. The response surface model of the electromagnetic force has been utilized to analyze the interaction effect between major parameters. It has been concluded that six interaction factors including working air gap with armature radius, drive current with armature thickness, coil turns with side pole radius, armature thickness with its radius, armature thickness with side pole radius, and armature radius with side pole radius have significant influence on the electromagnetic force. Optimal match values between coil turns and side pole radius; armature thickness and side pole radius; and armature radius and side pole radius have also been determined. PMID:25243217

  10. Analysis and Environmental Fate of Air Force Distillate and High Density Fuels

    Science.gov (United States)

    1981-10-01

    the program, D. Thomas and C. Beeman for obtaining and interpreting the GC-MS data, and D. L. Haynes for his technical assistance throughout the program...practical. 6 About two-thirds of the way through this project, data were received from Major Donald Potter, U.S. Air Force, Wright-Patterson AFB. lajor...identifications were confirmed by compating the Kovats indexes with those compiled by Major Donald D. Potter, U.S. Air Force. Tables 5 through 7 list the major

  11. Design of a superconducting insert to obtain a high and quasi-uniform magnetic force field

    Energy Technology Data Exchange (ETDEWEB)

    Leveque, Jean [GREEN, University of Nancy BP 239, 54506 Vandoeuvre (France); Netter, Denis [GREEN, University of Nancy BP 239, 54506 Vandoeuvre (France); Quettier, Lionel [DAPNIA, CEA Saclay (France); Mailfert, Alain [INPL, 2 av de la foret de Haye, 54516 Vandoeuvre (France)

    2005-10-01

    In this paper, we study the magnetic force generated by the combination of a solenoid and a superconducting ring insert. We have focused our study on the uniformity of the magnetic force. We use a genetic algorithm to determine the optimal shape of the superconducting ring. We are able to obtain uniformity of 0.5% variance. We also study the influence of several factors on uniformity, such as the critical current of the coil, the ring, and the size of the working area.

  12. Highly sensitive force sensor based on optical microfiber asymmetrical Fabry-Perot interferometer.

    Science.gov (United States)

    Gong, Yuan; Yu, Cai-Bin; Wang, Ting-Ting; Liu, Xiu-Ping; Wu, Yu; Rao, Yun-Jiang; Zhang, Ming-Lei; Wu, Hui-Juan; Chen, Xiao-Xiao; Peng, Gang-Ding

    2014-02-10

    An asymmetrical Fabry-Perot interferometric (AFPI) force sensor is fabricated based on a narrowband reflection of low-reflectivity fiber Bragg grating (LR-FBG) and a broadband Fresnel reflection of the cleaved fiber end. The AFPI sensor includes a section of microfiber made by tapering and it achieves a force sensitivity of 0.221 pm/μN with a tapered microfiber of 40 mm length and 6.1 μm waist diameter. Compared with similar AFPI structure in 125 μm-diameter single mode fiber, the force sensitivity of the microfiber AFPI structure is greatly enhanced due to its smaller diameter and can be optimized for different force scales by controlling the diameter. The fabrication process of the AFPI sensor is simple and cost-effective. The AFPI sensor has better multiplexing capacity than conventional extrinsic fiber-optic Fabry-Perot sensors, while it also release the requirement on the wavelength matching of the FBG-pair-based FPI.

  13. Forces from highly focused laser beams: modeling, measurement and application to refractive index measurements

    CERN Document Server

    Knoener, G; Nieminen, T A; Heckenberg, N R; Rubinsztein-Dunlop, H

    2007-01-01

    The optical forces in optical tweezers can be robustly modeled over a broad range of parameters using generalsed Lorenz-Mie theory. We describe the procedure, and show how the combination of experimental measurement of properties of the trap coupled with computational modeling, can allow unknown parameters of the particle - in this case, the refractive index - to be determined.

  14. Electron beam fabrication and characterization of high- resolution magnetic force microscopy tips

    NARCIS (Netherlands)

    Rührig, M.; Porthun, S.; Lodder, J.C.; McVitie, S.; Heyderman, L.J.; Johnston, A.B.; Chapman, J.N.

    1996-01-01

    The stray field, magnetic microstructure, and switching behavior of high‐resolution electron beam fabricated thin film tips for magnetic force microscopy (MFM) are investigated with different imaging modes in a transmission electron microscope (TEM). As the tiny smooth carbon needles covered with a

  15. High resolution magnetic force microscopy: instrumentation and application for recording media

    NARCIS (Netherlands)

    Porthun, Steffen

    1996-01-01

    This thesis describes aspects of the use of magnetic force microscopy for the study of magnetic recording media. The maximum achievable storage density in magnetic recording is limited by the magnetic reversal behaviour of the medium and by the stability of the written information. The shape and siz

  16. High resolution magnetic force microscopy: instrumentation and application for recording media

    NARCIS (Netherlands)

    Porthun, Steffen; Porthun, S.

    1996-01-01

    This thesis describes aspects of the use of magnetic force microscopy for the study of magnetic recording media. The maximum achievable storage density in magnetic recording is limited by the magnetic reversal behaviour of the medium and by the stability of the written information. The shape and siz

  17. High-refractive index particles in counter-propagating optical tweezers - manipulation and forces

    NARCIS (Netherlands)

    Horst, Astrid van der

    2006-01-01

    With a tightly focused single laser beam, also called optical tweezers, particles of a few nanometers up to several micrometers in size can be trapped and manipulated in 3D. The size, shape and refractive index of such colloidal particles are of influence on the optical forces exerted on them in the

  18. Self-Centering Seismic Lateral Force Resisting Systems: High Performance Structures for the City of Tomorrow

    Directory of Open Access Journals (Sweden)

    Nathan Brent Chancellor

    2014-09-01

    Full Text Available Structures designed in accordance with even the most modern buildings codes are expected to sustain damage during a severe earthquake; however; these structures are expected to protect the lives of the occupants. Damage to the structure can require expensive repairs; significant business downtime; and in some cases building demolition. If damage occurs to many structures within a city or region; the regional and national economy may be severely disrupted. To address these shortcomings with current seismic lateral force resisting systems and to work towards more resilient; sustainable cities; a new class of seismic lateral force resisting systems that sustains little or no damage under severe earthquakes has been developed. These new seismic lateral force resisting systems reduce or prevent structural damage to nonreplaceable structural elements by softening the structural response elastically through gap opening mechanisms. To dissipate seismic energy; friction elements or replaceable yielding energy dissipation elements are also included. Post-tensioning is often used as a part of these systems to return the structure to a plumb; upright position (self-center after the earthquake has passed. This paper summarizes the state-of-the art for self-centering seismic lateral force resisting systems and outlines current research challenges for these systems.

  19. Magnetic properties and coercivity mechanism of Sm{sub 1-x}Pr{sub x}Co{sub 5} (x=0-0.6) nanoflakes prepared by surfactant-assisted ball milling

    Energy Technology Data Exchange (ETDEWEB)

    Xu, M. L.; Yue, M., E-mail: yueming@bjut.edu.cn; Wu, Q.; Li, Y. Q.; Lu, Q. M. [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China)

    2016-05-15

    Sm{sub 1-x}Pr{sub x}Co{sub 5} (x=0-0.6) nanoflakes with CaCu{sub 5} structure were successfully prepared by surfactant-assisted high-energy ball milling (SAHEBM). The crystal structure and magnetic properties of Sm{sub 1-x}Pr{sub x}Co{sub 5} (x=0-0.6) nanoflakes were studied by X-ray diffraction and vibrating sample magnetometer. Effects of Pr addition on the structure, magnetic properties and coercivity mechanism of Sm{sub 1-x}Pr{sub x}Co{sub 5} nanoflakes were systematically investigated. XRD results show that all the nanoflakes have a hexagonal CaCu{sub 5}-type (Sm, Pr){sub 1}Co{sub 5} main phase and the (Sm, Pr){sub 2}Co{sub 7} impurity phase, and all of the samples exhibit a strong (00l) texture after magnetic alignment. As the Pr content increases, remanence firstly increases, then slightly reduced, while anisotropy field (H{sub A}) and H{sub ci} of decrease monotonically. Maximum energy product [(BH){sub max}] of the flakes increases first, peaks at 24.4 MGOe with Pr content of x = 0.4, then drops again. Magnetization behavior analysis indicate that the coercivity mechanism is mainly controlled by inhomogeneous domain wall pinning, and the pinning strength weakens with the increased Pr content, suggesting the great influence of H{sub A} on the coercivity of flakes.

  20. COERCIVITY AND VECTOR MAGNETIZATION ANALYSIS OF OBSIDIAN SAMPLES FROM THE TRANS-MEXICAN VOLCANIC BELT (Coercitividad y análisis de magnetización vectorial de muestras de obsidianas de la faja volcánica transmexicana

    Directory of Open Access Journals (Sweden)

    Jaime Urrutia-Fucugauchi

    2017-09-01

    Full Text Available This note presents initial results of a paleomagnetic study of obsidian from twenty localities in the eastern, central and western sectors of the Trans-Mexican volcanic belt in central Mexico. We focus on the coercivity and vector composition of the remanent magnetization, which are critical for paleodirectional and paleointensity studies. Alternating field demagnetization shows that obsidians carry single and two-component magnetizations residing in low- and high-coercivity magnetic minerals, with discrete and overlapping coercivity spectra. Magnetic minerals are likely iron-titanium oxides with fine-grain sizes characterized by pseudo-single domain states. ESPAÑOL: Se presentan los resultados preliminares del estudio de obsidianas de veinte localidades en los sectores este, central y oeste de la faja volcánica transmexicana. Los análisis se concentran en la coercitividad y la composición vectorial de la magnetización remanente, que son propiedades claves para evaluar los registros de direcciones e intensidades. La desmagnetización por campos alternos revela la presencia de magnetizaciones de una y dos componentes, que residen en minerales con baja y alta coercitividad con espectros que traslapan y discretos. Los minerales magnéticos son óxidos de hierro-titanio con grano fino y estados de dominio seudosencillo.

  1. A miniaturized, high frequency mechanical scanner for high speed atomic force microscope using suspension on dynamically determined points

    NARCIS (Netherlands)

    Herfst, R.W.; Dekker, A.; Witvoet, G.; Crowcombe, W.E.; Lange, T.J. de; Sadeghian Marnani, H.

    2015-01-01

    One of the major limitations in the speed of the atomic force microscope (AFM) is the bandwidth of the mechanical scanning stage, especially in the vertical (z) direction. According to the design principles of “light and stiff” and “static determinacy,” the bandwidth of the mechanical scanner is

  2. A miniaturized, high frequency mechanical scanner for high speed atomic force microscope using suspension on dynamically determined points

    NARCIS (Netherlands)

    Herfst, R.W.; Dekker, A.; Witvoet, G.; Crowcombe, W.E.; Lange, T.J. de; Sadeghian Marnani, H.

    2015-01-01

    One of the major limitations in the speed of the atomic force microscope (AFM) is the bandwidth of the mechanical scanning stage, especially in the vertical (z) direction. According to the design principles of “light and stiff” and “static determinacy,” the bandwidth of the mechanical scanner is lim

  3. From Antisocial Behavior to Violence: A Model for the Amplifying Role of Coercive Joining in Adolescent Friendships

    Science.gov (United States)

    Van Ryzin, Mark J.; Dishion, Thomas J.

    2013-01-01

    Background: Aggression is one of the more stable characteristics of child and adolescent development, and violent behavior in early adulthood is often foreshadowed by aggressive behavior in childhood and early adolescence. Considerable evidence has linked coercive family interactions to aggressive behavior in childhood, but less research has been…

  4. Predicting sexual coercion in early adulthood: The transaction among maltreatment, gang affiliation, and adolescent socialization of coercive relationship norms.

    Science.gov (United States)

    Ha, Thao; Kim, Hanjoe; Christopher, Caroline; Caruthers, Allison; Dishion, Thomas J

    2016-08-01

    This study tested a transactional hypothesis predicting early adult sexual coercion from family maltreatment, early adolescent gang affiliation, and socialization of adolescent friendships that support coercive relationship norms. The longitudinal study of a community sample of 998 11-year-olds was intensively assessed in early and middle adolescence and followed to 23-24 years of age. At age 16-17 youth were videotaped with a friend, and their interactions were coded for coercive relationship talk. Structural equation modeling revealed that maltreatment predicted gang affiliation during early adolescence. Both maltreatment and gang affiliation strongly predicted adolescent sexual promiscuity and coercive relationship norms with friends at age 16-17 years. Adolescent sexual promiscuity, however, did not predict sexual coercion in early adulthood. In contrast, higher levels of observed coercive relationship talk with a friend predicted sexual coercion in early adulthood for both males and females. These findings suggest that peers have a socialization function in the development of norms prognostic of sexual coercion, and the need to consider peers in the promotion of healthy relationships.

  5. Sex Differences in Intimate Partner Violence and the Use of Coercive Control as a Motivational Factor for Intimate Partner Violence

    Science.gov (United States)

    Tanha, Marieh; Beck, Connie J. A.; Figueredo, Aurelio Jose; Raghavan, Chitra

    2010-01-01

    Research argues that coercive control (CC) is a special case of intimate partner violence (IPV). The present study hypothesized that instead CC is the "motivator" for other types of IPV, with control of the victim as the goal. When CC fails, physical types of IPV are used. This hypothesized relationship was tested using a large matched sample of…

  6. Breaking down the coercive cycle: How parent and child risk factors influence real-time variability in parental responses to child misbehavior

    NARCIS (Netherlands)

    Lunkenheimer, E.S.; Lichtwarck-Aschoff, A.; Hollenstein, T.P.; Kemp, C.J.; Granic, I.

    2016-01-01

    Objective. Parent-child coercive cycles have been associated with both rigidity and inconsistency in parenting behavior. To explain these mixed findings, we examined real-time variability in maternal responses to children’s off-task behavior to determine whether this common trigger of the coercive c

  7. High quality NMR structures: a new force field with implicit water and membrane solvation for Xplor-NIH.

    Science.gov (United States)

    Tian, Ye; Schwieters, Charles D; Opella, Stanley J; Marassi, Francesca M

    2017-01-01

    Structure determination of proteins by NMR is unique in its ability to measure restraints, very accurately, in environments and under conditions that closely mimic those encountered in vivo. For example, advances in solid-state NMR methods enable structure determination of membrane proteins in detergent-free lipid bilayers, and of large soluble proteins prepared by sedimentation, while parallel advances in solution NMR methods and optimization of detergent-free lipid nanodiscs are rapidly pushing the envelope of the size limit for both soluble and membrane proteins. These experimental advantages, however, are partially squandered during structure calculation, because the commonly used force fields are purely repulsive and neglect solvation, Van der Waals forces and electrostatic energy. Here we describe a new force field, and updated energy functions, for protein structure calculations with EEFx implicit solvation, electrostatics, and Van der Waals Lennard-Jones forces, in the widely used program Xplor-NIH. The new force field is based primarily on CHARMM22, facilitating calculations with a wider range of biomolecules. The new EEFx energy function has been rewritten to enable OpenMP parallelism, and optimized to enhance computation efficiency. It implements solvation, electrostatics, and Van der Waals energy terms together, thus ensuring more consistent and efficient computation of the complete nonbonded energy lists. Updates in the related python module allow detailed analysis of the interaction energies and associated parameters. The new force field and energy function work with both soluble proteins and membrane proteins, including those with cofactors or engineered tags, and are very effective in situations where there are sparse experimental restraints. Results obtained for NMR-restrained calculations with a set of five soluble proteins and five membrane proteins show that structures calculated with EEFx have significant improvements in accuracy, precision

  8. LightForce Photon-Pressure Collision Avoidance: Updated Efficiency Analysis Utilizing a Highly Parallel Simulation Approach

    Science.gov (United States)

    Stupl, J.; Faber, N.; Foster, C.; Yang, F.; Nelson, B.; Aziz, J.; Nuttall, A.; Henze, C.; Levit, C.

    2014-09-01

    This paper provides an updated efficiency analysis of the LightForce space debris collision avoidance scheme. LightForce aims to prevent collisions on warning by utilizing photon pressure from ground based, commercial off the shelf lasers. Past research has proven that a few ground-based systems consisting of 10 kW class lasers directed by 1.5 m telescopes with adaptive optics could lower the expected number of collisions in Low Earth Orbit (LEO) by an order of magnitude. Our simulation approach utilizes the entire Two Line Element (TLE) catalogue in LEO for a given day as initial input. Least-squares fitting of a TLE time series is used for an improved orbit estimate. We then calculate the probability of collision for all LEO objects in the catalogue for a time step of the simulation. The conjunctions that exceed a threshold probability of collision are then engaged by a simulated network of laser ground stations. After those engagements, the perturbed orbits are used to re-assess the probability of collision and evaluate the efficiency. This paper describes new simulations with three updated aspects: 1) By utilizing a highly parallel simulation approach employing hundreds of processors, we have extended our analysis to a much broader dataset. The simulation time is extended to one year. 2) We analyze not only the efficiency of LightForce on conjunctions that naturally occur, but also take into account conjunctions caused by orbit perturbations due to LightForce engagements. 3) We use a new simulation approach that is regularly updating the LightForce engagement strategy, as it would be during actual operations. In this paper we present both our simulation approach to parallelize the efficiency analysis, its computational performance and the resulting expected efficiency of the LightForce collision avoidance system.

  9. Plasticity of the mate choice mind: courtship evokes choice-like brain responses in females from a coercive mating system.

    Science.gov (United States)

    Wang, S M T; Ramsey, M E; Cummings, M E

    2014-04-01

    Female mate choice is fundamental to sexual selection, and determining molecular underpinnings of female preference variation is important for understanding mating character evolution. Previously it was shown that whole-brain expression of a synaptic plasticity marker, neuroserpin, positively correlates with mating bias in the female choice poeciliid, Xiphophorus nigrensis, when exposed to conspecific courting males, whereas this relationship is reversed in Gambusia affinis, a mate coercive poeciliid with no courting males. Here we explore whether species-level differences in female behavioral and brain molecular responses represent 'canalized' or 'plastic' traits. We expose female G. affinis to conspecific males and females, as well as coercive and courting male Poecilia latipinna, for preference assays followed by whole-brain gene expression analyses of neuroserpin, egr-1 and early B. We find positive correlations between gene expression and female preference strength during exposure to courting heterospecific males, but a reversed pattern following exposure to coercive heterospecific males. This suggests that the neuromolecular processes associated with female preference behavior are plastic and responsive to different male phenotypes (courting or coercive) rather than a canalized response linked to mating system. Further, we propose that female behavioral plasticity may involve learning because female association patterns shifted with experience. Compared to younger females, we found larger, more experienced females spend less time near coercive males but associate more with males in the presence of courters. We thus suggest a conserved learning-based neuromolecular process underlying the diversity of female mate preference across the mate choice and coercion-driven mating systems.

  10. High Performance Polymer Film Dielectrics for Air Force Wide-Temperature Power Electronics Applications (Preprint)

    Science.gov (United States)

    2009-02-01

    perform, display, or disclose the work. 14. ABSTRACT Air Force currently has a strong need for the development of compact capacitors which are... capacitors typically use polycarbonate (PC) dielectric films in wound capacitors for operation from -55 ºC to 125 ºC, future power electronic systems would...such as fluorinated polybenzoxazoles (6F-PBO) and fluorenyl polyesters incorporating diamond-like hydrocarbon units (FDAPE). The discussion will be

  11. High Flight: History of the U.S. Air Force Academy

    Science.gov (United States)

    2009-09-01

    of Sunshine , Colorado Springs, Colorado. Colorado Springs, CO: Chamber of Commerce. (F 784 .C7 C68 Spec Coll) Curtin, Dave and Rob Lynde. Colorado...1984. (R 154 .W2995 C57 1984) Colorado Springs Chamber of Commerce. City of Sunshine , Colorado Springs, Colorado. Colorado Springs, CO: Chamber...Zielinski, Constantine. " Eternal Faith in a World of Change." Air Force Magazine 42.6 (1959): 91-92.     XXIX. RESEARCH AND TECHNOLOGY AT

  12. Controlling police (excessive force: The American case

    Directory of Open Access Journals (Sweden)

    Zakir Gül

    2013-09-01

    Full Text Available This article addresses the issue of police abuse of power, particularly police use of excessive force. Since the misuse of force by police is considered a problem, some entity must discover a way to control and prevent the illegal use of coercive power. Unlike most of the previous studies on the use of excessive force, this study uses a path analysis. However, not all the findings are consistent with the prior studies and hypotheses. In general, findings indicate that training may be a useful tool in terms of decreasing the use of excessive force, thereby reducing civilians’ injuries and citizens’ complaints. The results show that ethics training in the academy is significantly related to the use of excessive force. Further, it was found that community-oriented policing training in the academy was associated with the citizens’ complaints. A national (secondary data, collected from the law enforcement agencies in the United States are used to explore the research questions.

  13. Design of the magnetorheological mount with high damping force for medium speed diesel generators

    Science.gov (United States)

    Kang, O.-H.; Kim, W.-H.; Joo, W. H.; Park, J.-H.

    2013-04-01

    This paper investigates the controllable magnetorheological (MR) mount for the marine diesel-generator (D/G) sets. Sometimes, significant vibrations over the allowable limit are observed on the D/G sets due to their huge excitation forces. Because the severe vibration can lead to structural damages to the D/G sets, it should be reduced to below the limit. Although passive mounts with rubber isolators are usually used, the vibration reduction performance is not always sufficient. In addition, expecting that the vibration levels required by customers will get more severe, semi-active vibration isolation system needs to be developed. To the aim, the valve (flow) mode type of MR mount has been designed. Especially, the annular-radial configuration was adopted to enhance the damping force within the restricted space. The geometry of the mount has been optimized to obtain the required damping force and the magnetic field analysis has been carried out using ANSYS APDL. To verify the performance of the developed MR mount, excitation test was conducted and the dynamic characteristics were identified. Since damping property of the MR fluid is changed by the applied magnetic field strength and excitation frequency, responses to changing applied currents and frequencies were obtained. From the results, damping performance of the MR mount was evaluated.

  14. High-order accurate finite-volume formulations for the pressure gradient force in layered ocean models

    CERN Document Server

    Engwirda, Darren; Marshall, John

    2016-01-01

    The development of a set of high-order accurate finite-volume formulations for evaluation of the pressure gradient force in layered ocean models is described. A pair of new schemes are presented, both based on an integration of the contact pressure force about the perimeter of an associated momentum control-volume. The two proposed methods differ in their choice of control-volume geometries. High-order accurate numerical integration techniques are employed in both schemes to account for non-linearities in the underlying equation-of-state definitions and thermodynamic profiles, and details of an associated vertical interpolation and quadrature scheme are discussed in detail. Numerical experiments are used to confirm the consistency of the two formulations, and it is demonstrated that the new methods maintain hydrostatic and thermobaric equilibrium in the presence of strongly-sloping layer-wise geometry, non-linear equation-of-state definitions and non-uniform vertical stratification profiles. Additionally, one...

  15. Forced sex, rape and sexual exploitation: attitudes and experiences of high school students in South Kivu, Democratic Republic of Congo.

    Science.gov (United States)

    Mulumeoderhwa, Maroyi; Harris, Geoff

    2015-01-01

    This paper reports on fieldwork carried out in 2011 with the aim of investigating the attitudes and reported behaviour of Congolese high school students concerning sexual relationships. A total of 56 boys and girls aged 16-20 from two urban and two rural high schools in South Kivu Province took part in focus groups, and 40 of these were subsequently interviewed individually. The majority of boys felt that they were entitled to sex from their girlfriends and that if persuasion was unsuccessful, the use of force was legitimate; this, in their minds, did not constitute rape. Girls, on the other hand, were clear that such forced sex was rape. However it may be understood, rape was perceived as having increased in recent years and was explained by weak legal systems, pornography and provocative dressing by girls. Boys were angry at the competition from older, often married, men who were able to provide monetary and other incentives to the girls.

  16. Research on Ultrafine WC-10Co Cemented Carbide with High Properties

    Institute of Scientific and Technical Information of China (English)

    SHI Xiaoliang; YANG Hua; SHAO Gangqin; DUAN Xinglong; XIONG Zhen; ZHANG Weifeng

    2006-01-01

    WC- 10Co nanocomposite powder produced by spray pyrolysis-continuous reduction and carbonization technology was used, and the vacuum sintering plus sinterhip process was adopted to prepare ultrafine WCCo cemented carbide. The microstructure, grain size, porosity, density, Rockwell A hardness ( HRA ), transverse rupture strength (TRS), saturated magnetization and coercivity force were studied. The experimental results show that average grain size of the sample prepared by vacuum sintering plus sinterhip technology was about 420 nm, transverse rupture strength was more than 3460 MPa, and Rockwell A hardness of sintered specimen was more than 92.5. Ultrafine WC- 10Co cemented carbide with high strength and high hardness is obtained.

  17. Unexpected weak seasonal climate in the western Mediterranean region during MIS 31, a high-insolation forced interglacial

    Science.gov (United States)

    Oliveira, Dulce; Sánchez Goñi, Maria Fernanda; Naughton, Filipa; Polanco-Martínez, J. M.; Jimenez-Espejo, Francisco J.; Grimalt, Joan O.; Martrat, Belen; Voelker, Antje H. L.; Trigo, Ricardo; Hodell, David; Abrantes, Fátima; Desprat, Stéphanie

    2017-04-01

    Marine Isotope Stage 31 (MIS 31) is an important analogue for ongoing and projected global warming, yet key questions remain about the regional signature of its extreme orbital forcing and intra-interglacial variability. Based on a new direct land-sea comparison in SW Iberian margin IODP Site U1385 we examine the climatic variability between 1100 and 1050 ka including the ;super interglacial; MIS 31, a period dominated by the 41-ky obliquity periodicity. Pollen and biomarker analyses at centennial-scale-resolution provide new insights into the regional vegetation, precipitation regime and atmospheric and oceanic temperature variability on orbital and suborbital timescales. Our study reveals that atmospheric and SST warmth during MIS 31 was not exceptional in this region highly sensitive to precession. Unexpectedly, this warm stage stands out as a prolonged interval of a temperate and humid climate regime with reduced seasonality, despite the high insolation (precession minima values) forcing. We find that the dominant forcing on the long-term temperate forest development was obliquity, which may have induced a decrease in summer dryness and associated reduction in seasonal precipitation contrast. Moreover, this study provides the first evidence for persistent atmospheric millennial-scale variability during this interval with multiple forest decline events reflecting repeated cooling and drying episodes in SW Iberia. Our direct land-sea comparison shows that the expression of the suborbital cooling events on SW Iberian ecosystems is modulated by the predominance of high or low-latitude forcing depending on the glacial/interglacial baseline climate states. Severe dryness and air-sea cooling is detected under the larger ice volume during glacial MIS 32 and MIS 30. The extreme episodes, which in their climatic imprint are similar to the Heinrich events, are likely related to northern latitude ice-sheet instability and a disruption of the Atlantic Meridional Overturning

  18. Amplified Late Pliocene terrestrial warmth in northern high latitudes from greater radiative forcing and closed Arctic Ocean gateways

    Science.gov (United States)

    Feng, Ran; Otto-Bliesner, Bette L.; Fletcher, Tamara L.; Tabor, Clay R.; Ballantyne, Ashley P.; Brady, Esther C.

    2017-05-01

    Proxy reconstructions of the mid-Piacenzian warm period (mPWP, between 3.264 and 3.025 Ma) suggest terrestrial temperatures were much warmer in the northern high latitudes (55°-90°N, referred to as NHL) than present-day. Climate models participating in the Pliocene Model Intercomparison Project Phase 1 (PlioMIP1) tend to underestimate this warmth. For instance, the underestimate is ∼10 °C on average across NHL and up to 17 °C in the Canadian Arctic region in the Community Climate System Model version 4 (CCSM4). Here, we explore potential mPWP climate forcings that might contribute to this mPWP mismatch. We carry out seven experiments to assess terrestrial temperature responses to Pliocene Arctic gateway closure, variations in CO2 level, and orbital forcing at millennial time scale. To better compare the full range of simulated terrestrial temperatures with sparse proxy data, we introduce a pattern recognition technique that simplifies the model surface temperatures to a few representative patterns that can be validate with the limited terrestrial proxy data. The pattern recognition technique reveals two prominent features of simulated Pliocene surface temperature responses. First, distinctive patterns of amplified warming occur in the NHL, which can be explained by lowered surface elevation of Greenland, pattern and amount of Arctic sea ice loss, and changing strength of Atlantic meridional overturning circulation. Second, patterns of surface temperature response are similar among experiments with different forcing mechanisms. This similarity is due to strong feedbacks from responses in surface albedo and troposphere water vapor content to sea ice changes, which overwhelm distinctions in forcings from changes in insolation, CO2 forcing, and Arctic gateway closure. By comparing CCSM4 simulations with proxy records, we demonstrate that both model and proxy records show similar patterns of mPWP NHL terrestrial warmth, but the model underestimates the magnitude

  19. Terminal Performance of Lead Free Pistol Bullets in Ballistic Gelatin Using Retarding Force Analysis from High Speed Video

    Science.gov (United States)

    2016-04-04

    2013) and Keys et al. (2015) were applied on a number of different lead- free bullet loads. Rounds in 9mm NATO, .357 SIG, and .40 S&W were fired...encountered shot angles . This bullet also fails to meet the FBI recommended minimum penetration depth of 12 inches for duty use. Figure 4: Retarding...Terminal Performance of Lead- Free Pistol Bullets in Ballistic Gelatin Using Retarding Force Analysis from High Speed Video ELIJAH COURTNEY, AMY

  20. Effects of Extremely High ’G’ Acceleration Forces on NASA’s Control and Space Exposed Tomato Seeds

    Science.gov (United States)

    1991-12-01

    as solid brown discolored tomatoes and then became wrinkled like prunes . The non-ripened portion remained solid green tomato. While the abnormal...die-back, initial production of vine -ripened red tomatoes, etc could not be directly related to ultra-high gravity force treatment. Abnormal Off-plant...The result of further ripening/aging produced tomatoes that looked like prune s with badly wrinkled surfaces over most of the tomato. These areas

  1. High refractive index silicone gels for simultaneous total internal reflection fluorescence and traction force microscopy of adherent cells.

    Directory of Open Access Journals (Sweden)

    Edgar Gutierrez

    Full Text Available Substrate rigidity profoundly impacts cellular behaviors such as migration, gene expression, and cell fate. Total Internal Reflection Fluorescence (TIRF microscopy enables selective visualization of the dynamics of substrate adhesions, vesicle trafficking, and biochemical signaling at the cell-substrate interface. Here we apply high-refractive-index silicone gels to perform TIRF microscopy on substrates with a wide range of physiological elastic moduli and simultaneously measure traction forces exerted by cells on the substrate.

  2. A novel two-axis parallel-kinematic high-speed piezoelectric scanner for atomic force microscopy

    Science.gov (United States)

    Alunda, Bernard Ouma; Lee, Yong Joong; Park, Soyeun

    2016-09-01

    High-speed atomic force microscopy permits the capture of static, as well as the dynamic, processes present in various physical phenomena. Unlike visualizing static processes, capture of dynamic processes requires high-speed scanning in all three dimensions. Despite the recent increased interest in high-speed atomic force microscopy, relatively few reports concerning piezoelectric actuator-driven scanners for high-speed scanning have been published. In this paper, we propose a novel design for a high-speed two-dimensional piezoelectric scanner unit by combining the positive features developed from works published in the literature. The proposed design ensures high vertical stiffness by utilizing compliant double-hinged flexure that minimizes cross-coupling and parasitic motions. Any high-speed scanner design requires a compromise between the two main competing parameters: maximum scan size and speed. The performance of the proposed scanner was evaluated by using numerical simulations with finite element analyses in terms of the mechanical resonance frequencies and the scan range. Finally, the results from the numerical simulations are compared with the experimental measurements.

  3. Force of tuberculosis infection among adolescents in a high HIV and TB prevalence community: a cross-sectional observation study

    Directory of Open Access Journals (Sweden)

    Sebastian Elaine

    2011-06-01

    Full Text Available Abstract Background Understanding of the transmission dynamics of tuberculosis (TB in high TB and HIV prevalent settings is required in order to develop effective intervention strategies for TB control. However, there are little data assessing incidence of TB infection in adolescents in these settings. Methods We performed a tuberculin skin test (TST and HIV survey among secondary school learners in a high HIV and TB prevalence community. TST responses to purified protein derivative RT23 were read after 3 days. HIV-infection was assessed using Orasure® collection device and ELISA testing. The results of the HIV-uninfected participants were combined with those from previous surveys among primary school learners in the same community, and force of TB infection was calculated by age. Results The age of 820 secondary school participants ranged from 13 to 22 years. 159 participants had participated in the primary school surveys. At a 10 mm cut-off, prevalence of TB infection among HIV-uninfected and first time participants, was 54% (n = 334/620. HIV prevalence was 5% (n = 40/816. HIV infection was not significantly associated with TST positivity (p = 0.07. In the combined survey dataset, TB prevalence was 45% (n = 645/1451, and was associated with increasing age and male gender. Force of infection increased with age, from 3% to 7.3% in adolescents ≥20 years of age. Conclusions We show a high force of infection among adolescents, positively associated with increasing age. We postulate this is due to increased social contact with infectious TB cases. Control of the TB epidemic in this setting will require reducing the force of infection.

  4. Force balance and deformation characteristics of anisotropic Arctic sea ice (a high resolution study)

    Science.gov (United States)

    Feltham, D. L.; Heorton, H. D.; Tsamados, M.

    2016-12-01

    The spatial distribution of Arctic sea ice arises from its deformation, driven by external momentum forcing, thermodynamic growth and melt. The deformation of Arctic sea ice is observed to have structural alignment on a broad range of length scales. By considering the alignment of diamond-shaped sea ice floes, an anisotropic rheology (known as the Elastic Anisotropic Plastic, EAP, rheology) has been developed for use in a climate sea ice model. Here we present investigations into the role of anisotropy in determining the internal ice stress gradient and the complete force balance of Arctic sea ice using a state-of-the-art climate sea ice model. Our investigations are focused on the link between external imposed dynamical forcing, predominantly the wind stress, and the emergent properties of sea ice, including its drift speed and thickness distribution. We analyse the characteristics of deformation events for different sea ice states and anisotropic alignment over different regions of the Arctic Ocean. We present the full seasonal stress balance and sea ice state over the Arctic ocean. We have performed 10 km basin-scale simulations over a 30-year time scale, and 2 km and 500 m resolution simulations in an idealised configuration. The anisotropic EAP sea ice rheology gives higher shear stresses than the more customary isotropic EVP rheology, and these reduce ice drift speed and mechanical thickening, particularly important in the Archipelago. In the central Arctic the circulation of sea ice is reduced allowing it to grow thicker thermodynamically. The emergent stress-strain rate correlations from the EAP model suggest that it is possible to characterise the internal ice stresses of Arctic sea ice from observable basin-wide deformation and drift patterns.

  5. High Fidelity Non-Gravitational Force Models for Precise and Accurate Orbit Determination of TerraSAR-X

    Science.gov (United States)

    Hackel, Stefan; Montenbruck, Oliver; Steigenberger, -Peter; Eineder, Michael; Gisinger, Christoph

    Remote sensing satellites support a broad range of scientific and commercial applications. The two radar imaging satellites TerraSAR-X and TanDEM-X provide spaceborne Synthetic Aperture Radar (SAR) and interferometric SAR data with a very high accuracy. The increasing demand for precise radar products relies on sophisticated validation methods, which require precise and accurate orbit products. Basically, the precise reconstruction of the satellite’s trajectory is based on the Global Positioning System (GPS) measurements from a geodetic-grade dual-frequency receiver onboard the spacecraft. The Reduced Dynamic Orbit Determination (RDOD) approach utilizes models for the gravitational and non-gravitational forces. Following a proper analysis of the orbit quality, systematics in the orbit products have been identified, which reflect deficits in the non-gravitational force models. A detailed satellite macro model is introduced to describe the geometry and the optical surface properties of the satellite. Two major non-gravitational forces are the direct and the indirect Solar Radiation Pressure (SRP). Due to the dusk-dawn orbit configuration of TerraSAR-X, the satellite is almost constantly illuminated by the Sun. Therefore, the direct SRP has an effect on the lateral stability of the determined orbit. The indirect effect of the solar radiation principally contributes to the Earth Radiation Pressure (ERP). The resulting force depends on the sunlight, which is reflected by the illuminated Earth surface in the visible, and the emission of the Earth body in the infrared spectra. Both components of ERP require Earth models to describe the optical properties of the Earth surface. Therefore, the influence of different Earth models on the orbit quality is assessed within the presentation. The presentation highlights the influence of non-gravitational force and satellite macro models on the orbit quality of TerraSAR-X.

  6. Elastic-properties measurement at high temperatures through contact resonance atomic force microscopy

    DEFF Research Database (Denmark)

    Marinello, Francesco; Pezzuolo, Andrea; Carmignato, Simone;

    2015-01-01

    Miniaturization of products and need for further improvement of machines performance introduce new serious challenges in materials characterization. In particular non-destructive mechanical testing in the sub-micrometer scale is needed to better understand and improve micro-manufacturing operations...... fast direct and non-destructive measurement of Young's modulus and related surface parameters.In this work an instrument set up for Contact Resonance Atomic Force Microscopy is proposed, where the sample with is coupled to a heating stage and a piezoelectric transducer directly vibrate the cantilever...

  7. Techniques for determining propulsion system forces for accurate high speed vehicle drag measurements in flight

    Science.gov (United States)

    Arnaiz, H. H.

    1975-01-01

    As part of a NASA program to evaluate current methods of predicting the performance of large, supersonic airplanes, the drag of the XB-70 airplane was measured accurately in flight at Mach numbers from 0.75 to 2.5. This paper describes the techniques used to determine engine net thrust and the drag forces charged to the propulsion system that were required for the in-flight drag measurements. The accuracy of the measurements and the application of the measurement techniques to aircraft with different propulsion systems are discussed. Examples of results obtained for the XB-70 airplane are presented.

  8. LightForce Photon-Pressure Collision Avoidance: Updated Efficiency Analysis Utilizing a Highly Parallel Simulation Approach

    Science.gov (United States)

    Stupl, Jan; Faber, Nicolas; Foster, Cyrus; Yang, Fan Yang; Nelson, Bron; Aziz, Jonathan; Nuttall, Andrew; Henze, Chris; Levit, Creon

    2014-01-01

    This paper provides an updated efficiency analysis of the LightForce space debris collision avoidance scheme. LightForce aims to prevent collisions on warning by utilizing photon pressure from ground based, commercial off the shelf lasers. Past research has shown that a few ground-based systems consisting of 10 kilowatt class lasers directed by 1.5 meter telescopes with adaptive optics could lower the expected number of collisions in Low Earth Orbit (LEO) by an order of magnitude. Our simulation approach utilizes the entire Two Line Element (TLE) catalogue in LEO for a given day as initial input. Least-squares fitting of a TLE time series is used for an improved orbit estimate. We then calculate the probability of collision for all LEO objects in the catalogue for a time step of the simulation. The conjunctions that exceed a threshold probability of collision are then engaged by a simulated network of laser ground stations. After those engagements, the perturbed orbits are used to re-assess the probability of collision and evaluate the efficiency of the system. This paper describes new simulations with three updated aspects: 1) By utilizing a highly parallel simulation approach employing hundreds of processors, we have extended our analysis to a much broader dataset. The simulation time is extended to one year. 2) We analyze not only the efficiency of LightForce on conjunctions that naturally occur, but also take into account conjunctions caused by orbit perturbations due to LightForce engagements. 3) We use a new simulation approach that is regularly updating the LightForce engagement strategy, as it would be during actual operations. In this paper we present our simulation approach to parallelize the efficiency analysis, its computational performance and the resulting expected efficiency of the LightForce collision avoidance system. Results indicate that utilizing a network of four LightForce stations with 20 kilowatt lasers, 85% of all conjunctions with a

  9. Maximal voluntary contraction force, SR function and glycogen resynthesis during the first 72 h after a high-level competitive soccer game

    DEFF Research Database (Denmark)

    Krustrup, Peter; Ortenblad, Niels; Nielsen, Joachim

    2011-01-01

    The aim of this study was to examine maximal voluntary knee-extensor contraction force (MVC force), sarcoplasmic reticulum (SR) function and muscle glycogen levels in the days after a high-level soccer game when players ingested an optimised diet. Seven high-level male soccer players had a vastus...... lateralis muscle biopsy and a blood sample collected in a control situation and at 0, 24, 48 and 72 h after a competitive soccer game. MVC force, SR function, muscle glycogen, muscle soreness and plasma myoglobin were measured. MVC force sustained over 1 s was 11 and 10% lower (P ...

  10. Design and microfabrication of a high-aspect-ratio PDMS microbeam array for parallel nanonewton force measurement and protein printing

    Science.gov (United States)

    Sasoglu, F. M.; Bohl, A. J.; Layton, B. E.

    2007-03-01

    Cell and protein mechanics has applications ranging from cellular development to tissue engineering. Techniques such as magnetic tweezers, optic tweezers and atomic force microscopy have been used to measure cell deformation forces of the order of piconewtons to nanonewtons. In this study, an array of polymeric polydimethylsiloxane (PDMS) microbeams with diameters of 10-40 µm and lengths of 118 µm was fabricated from Sylgard® with curing agent concentrations ranging from 5% to 20%. The resulting spring constants were 100-300 nN µm-1. The elastic modulus of PDMS was determined experimentally at different curing agent concentrations and found to be 346 kPa to 704 kPa in a millimeter-scale array and ~1 MPa in a microbeam array. Additionally, the microbeam array was used to print laminin for the purpose of cell adhesion. Linear and nonlinear finite element analyses are presented and compared to the closed-from solution. The highly compliant, transparent, biocompatible PDMS may offer a method for more rapid throughput in cell and protein mechanics force measurement experiments with sensitivities necessary for highly compliant structures such as axons.

  11. Measurement and characterization of force dynamics in high T(sub c) superconductors

    Science.gov (United States)

    Higuchi, Toshiro; Kelley, Allan J.; Tsutsui, Yukio

    1994-01-01

    Magnetic bearing implementations using more exotic superconducting phenomena have been proliferating in recent years because they have important advantages over conventional implementations. For example, the stable suspension of a six degrees-of-freedom object by superconducting means can be achieved without a control system and with the use of only a single superconductor. It follows that the construction becomes much simpler with decreased need for position sensors and stabilizers. However, it is recognized that the design of superconducting systems can be difficult because important characteristics relating to the 6 degree-of-freedom dynamics of an object suspended magnetically are not readily available and the underlying principles of superconducting phenomena are not yet completely understood. To eliminate some of the guesswork in the design process, this paper proposes a system which can resolve the mechanical properties of suspension by superconductivity and provide position and orientation dependent data about the system's damping, stiffness, and frequency response characteristics. This system employs an actively-controlled magnetically-suspended fine-motion device that can also be used as a six degree-of-freedom force sensor. By attaching the force sensor to a permanent magnet that is being levitated above a superconducting magnet, mechanical characteristics of the superconductor levitation can be extracted. Such information would prove useful for checking the validity of theoretical models and may even give insights into superconducting phenomena.

  12. Scalar self-force for highly eccentric equatorial orbits in Kerr spacetime

    CERN Document Server

    Thornburg, Jonathan

    2016-01-01

    If a small "particle" of mass $\\mu M$ (with $\\mu \\ll 1$) orbits a black hole of mass $M$, the leading-order radiation-reaction effect is an $\\mathcal{O}(\\mu^2)$ "self-force" acting on the particle, with a corresponding $\\mathcal{O}(\\mu)$ "self-acceleration" of the particle away from a geodesic. Such "extreme--mass-ratio inspiral" systems are likely to be important gravitational-wave sources for future space-based gravitational-wave detectors. Here we consider the "toy model" problem of computing the self-force for a scalar-field particle on a bound eccentric orbit in Kerr spacetime. We use the Barack-Golbourn-Vega-Detweiler effective-source regularization with a 4th order puncture field, followed by an $e^{im\\phi}$ ("m-mode") Fourier decomposition and a separate time-domain numerical evolution in $2+1$ dimensions for each $m$. We introduce a finite worldtube that surrounds the particle worldline and define our evolution equations in a piecewise manner so that the effective source is only used within the world...

  13. Development of a low cost, high resolution position detection system for photonic force microscopy

    CERN Document Server

    Pal, Sambit Bikas; Roy, Basudev; Banerjee, Ayan

    2011-01-01

    A photonic force microscope comprises of an optically trapped micro-probe and a position detection system to track the motion of the probe. In this paper, we report the use of the optical pick-up head of a compact disc player as an extremely low cost yet accurate position sensor for photonic force microscopy. The size of the quadrant photo-IC in the pick-up head makes it ideal to work with a 1:1 image of a micron-sized probe in the microscope back-focal plane after the standard magnification by the trapping objective lens. This is an advantage over most commercial quadrant photodiodes or position sensitive detectors where it is difficult to image only the probe since such detectors require larger beams. This warrants external magnification optics leading to losses that may be significant in back-focal plane detection where the signal level directly off the probe is already very weak. Using a commercially available spare pick-up head, we demonstrate that the detector could measure absolute displacements with a...

  14. Reduction of Coercivity of Fe-N Soft Magnetic Film by Heat Treatment

    Institute of Scientific and Technical Information of China (English)

    Dan LI; Yousong GU; Xiangrong CHANG; Fushen LI; Lijie QIAO; Zhongzhuo TIAN

    2003-01-01

    200 nm thick Fe-N magnetic thin films were deposited on glass substrates by RF sputtering. The as-deposited films havehigh saturation magnetization but their coercivity is also higher than what is needed Therefore it is very important to reducecoercivity. The samples were vacuum annealed at 250℃ under 12000 A/m magnetic field. When the N content was in therange of 5~7 at. pct, the thin films consisted of α′ + α″ after heat treatment and had excellent soft magnetic properties of4rMs=2.4 T, HC <80 A/m. However, the thickness of a recording head was 2μm, andHc increased as thickness increased.In order to reduce the Hc, the sputtering power was raised from 200 W to 1000 W to reduce the grain size. 2μm Fe-N thinfilms were vacuum annealed under the same condition, when the N content was in the range of 5.9~8.5 at. pct, the thin filmskept its excellent magnetic properties of 4πMs=2.2 T, HC <80 A/m. The properties of the films meet the need of a recordinghead material used in the dual-element GMR/inductive heads.

  15. Neem leaves mediated preparation of NiO nanoparticles and its magnetization, coercivity and antibacterial analysis

    Science.gov (United States)

    Helan, V.; Prince, J. Joseph; Al-Dhabi, Naif Abdullah; Arasu, Mariadhas Valan; Ayeshamariam, A.; Madhumitha, G.; Roopan, Selvaraj Mohana; Jayachandran, M.

    Nickel oxides nanoparticles (NiO NPs) were synthesized by biosynthesis method with the help of phytoconstituents present in the neem leaf. Further the synthesized NiO NPs were subjected for structural, optical, morphological and magnetic properties. The XRD patterns clearly infer the presence of polycrystalline nature of samples (0 1 0), (0 1 1) and (0 1 2) with hexagonal crystal phase. Morphological studies using Transmission Electron Microscope (TEM) reveals that the biosynthesized NiO NPs were in shape of oblong with 12 nm in size. Elemental analysis (EDAX) confirms the quantity of Ni is present at 51% and remaining O as 49% as well as the mass magnetization values of 61 emu/g are also recorded for NiO NPs and its coercivity values in the range of 0.2-0.4 of nanoparticles respectively. Finally the NiO NPs was studied for bacterial activity against Staphylococcus aureus (MTCC 1430) and followed by Escherichia coli (MTCC 739) by agar diffusion assay.

  16. Giant magnetic coercivity in orthorhombic YNi4Si-type SmNi4Si compound

    Science.gov (United States)

    Yao, Jinlei; Morozkin, A. V.

    2015-10-01

    Magnetic properties, magnetocaloric effect and heat capacity of the YNi4Si-type SmNi4Si compound have been investigated. SmNi4Si exhibits ferromagnetic transition at 17 K. Below ~9 K, the magnetic isotherms of SmNi4Si show metamagnetic-like behavior with critical field of 20 kOe at 5 K. Heat capacity measurements of SmNi4Si show the electronic heat capacity coefficient γ=94 mJ/(mol K2), phonon coefficient β=0.35 mJ/(mol K4) and Debye temperature TD=310 K. The magnetocaloric effect of SmNi4Si is calculated in terms of isothermal magnetic entropy change which is obtained by the isothermal magnetization (ΔSmmagn) and heat capacity measurements (ΔSmheat). Both ΔSmmagn and ΔSmheat reach a maximum of -1.0 J/kg K at 17 K for a field change of 50 kOe and they show positive values for a field change of 20 kOe at ~9 K. Below 15 K, SmNi4Si shows large magnetic hysteresis with considerable remanence. At 5 K it exhibits giant coercive field of 58 kOe in an applied field of 90 kOe.

  17. Beyond "Witnessing": Children's Experiences of Coercive Control in Domestic Violence and Abuse.

    Science.gov (United States)

    Callaghan, Jane E M; Alexander, Joanne H; Sixsmith, Judith; Fellin, Lisa Chiara

    2015-12-10

    Children's experiences and voices are underrepresented in academic literature and professional practice around domestic violence and abuse. The project "Understanding Agency and Resistance Strategies" (UNARS) addresses this absence, through direct engagement with children. We present an analysis from interviews with 21 children in the United Kingdom (12 girls and 9 boys, aged 8-18 years), about their experiences of domestic violence and abuse, and their responses to this violence. These interviews were analyzed using interpretive interactionism. Three themes from this analysis are presented: (a) "Children's experiences of abusive control," which explores children's awareness of controlling behavior by the adult perpetrator, their experience of that control, and its impact on them; (b) "Constraint," which explores how children experience the constraint associated with coercive control in situations of domestic violence; and (c) "Children as agents," which explores children's strategies for managing controlling behavior in their home and in family relationships. The article argues that, in situations where violence and abuse occur between adult intimate partners, children are significantly affected, and can be reasonably described as victims of abusive control. Recognizing children as direct victims of domestic violence and abuse would produce significant changes in the way professionals respond to them, by (a) recognizing children's experience of the impact of domestic violence and abuse; (b) recognizing children's agency, undermining the perception of them as passive "witnesses" or "collateral damage" in adult abusive encounters; and (c) strengthening professional responses to them as direct victims, not as passive witnesses to violence.

  18. [Female victims of sexual abuse: coercive methods and non-genital injuries].

    Science.gov (United States)

    Reis, Jair Naves dos; Martin, Carmen Cinira Santos; Ferriani, Maria das Graças Carvalho

    2004-01-01

    This study aims to analyze the coercive methods used by sex offenders and the occurrence of non-genital injuries in female children, adolescent, and adult victims of sexual abuse reported to the Women's Police Precinct and examined at the Department of Forensic Medicine in Ribeirão Preto, São Paulo State, Brazil, from 1996 to 2000. Age distribution followed the criteria established by Brazil's Statute for Children and Adolescents (the prevailing legislation on issues pertaining to minors). Physical violence was the most frequently used form of coercion against adults (44.1%) and adolescents (25.0%), followed by serious threat in 36.5% and 17.0% of the cases, respectively. Presumed violence by innocentia consilii occurred in 94.1% of the children and 42.8% of the adolescents. Minor non-genital injuries were found in 7.8% of the cases, involving children (3.0%), adolescents (7.2%), and adults (14.4%), with no weapons involved in 75.0% of these cases. A decrease in the number of cases with injuries was observed in relation to knives (14.3%) and handguns (10.7%) used against adult and adolescent victims.

  19. Nitriding-induced texture, ordering and coercivity enhancement in FePtAgB nanocomposite magnets

    Science.gov (United States)

    Crisan, O.; Vasiliu, F.; Palade, P.; Mercioniu, I.

    2016-03-01

    FePt system attracts currently a great deal of interest for applications as future RE free permanent magnets. Among the key issues to be solved one may count the decreasing of the ordering temperature and improvement of magnetic behavior. For that purpose we have studied the effect of a nitriding post-synthesis procedure on the FePtAgB melt spun ribbons, aimed at refining the microstructure and enhancing the magnetic performances. Deep structural characterization by transmission electron microscopy, electron diffraction, energy dispersive X-ray spectroscopy and X-ray diffraction allowed us to observe the morphology and to correctly assign and identify the nature of the main granular phases observed. Nitriding procedure is shown to strongly enhance the (001) texturing and the degree of ordering of the L10 FePt phase, as well as largely increase of coercivity, compared to the as-cast state. These changes are interpreted in terms of Ag segregation towards intergranular region associated to N diffusion and creation of vacancies that favor consistently the process of ordering the FePt grains into the L10 tetragonal phase.

  20. Reframing violence against women as a human rights violation: Evan Stark's Coercive Control.

    Science.gov (United States)

    Libal, Kathryn; Parekh, Serena

    2009-12-01

    Evan Stark claims that partner-perpetrated physical abuse and other forms of violence against women ought to be understood as a human rights violation. The authors engage Stark's rhetorically powerful political and analytical innovation by outlining one theoretical and one practical challenge to shifting the paradigm that researchers, advocates, and policy makers use to describe, explain, and remedy the harms of coercive control from misdemeanor assault to human rights violation. The theoretical challenge involves overcoming the public/ private dichotomy that underpins liberal conceptions of human rights.The practical challenge involves using the human rights framework in the United States, given public indifference to human rights rhetoric or law, reluctance of U.S. policy makers to submit to scrutiny or justice-oriented processes under international law on issues of human rights and especially war crimes, and the consequent U.S. legacy of refusal to participate meaningfully in the international human rights process. The authors conclude that employing a human rights framework holds potential in the United States, but the paradigm shift Stark advocates will not materialize without widespread mobilization of interest in and understanding of human rights among domestic violence advocates and the society in general.

  1. The exponentiated Hencky-logarithmic strain energy. Part II: Coercivity, planar polyconvexity and existence of minimizers

    Science.gov (United States)

    Neff, Patrizio; Lankeit, Johannes; Ghiba, Ionel-Dumitrel; Martin, Robert; Steigmann, David

    2015-08-01

    We consider a family of isotropic volumetric-isochoric decoupled strain energies based on the Hencky-logarithmic (true, natural) strain tensor log U, where μ > 0 is the infinitesimal shear modulus, is the infinitesimal bulk modulus with the first Lamé constant, are dimensionless parameters, is the gradient of deformation, is the right stretch tensor and is the deviatoric part (the projection onto the traceless tensors) of the strain tensor log U. For small elastic strains, the energies reduce to first order to the classical quadratic Hencky energy which is known to be not rank-one convex. The main result in this paper is that in plane elastostatics the energies of the family are polyconvex for , extending a previous finding on its rank-one convexity. Our method uses a judicious application of Steigmann's polyconvexity criteria based on the representation of the energy in terms of the principal invariants of the stretch tensor U. These energies also satisfy suitable growth and coercivity conditions. We formulate the equilibrium equations, and we prove the existence of minimizers by the direct methods of the calculus of variations.

  2. Coercivity enhancement in exchange biased CoO/Co{sub 3}Pt bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Kosub, T; Schubert, C; Schletter, H; Daniel, M; Hietschold, M; Makarov, D; Albrecht, M [Institute of Physics, Chemnitz University of Technology, D-09107 Chemnitz (Germany); Neu, V [Institute for Metallic Materials, IFW Dresden, D-01069 Dresden (Germany); Maret, M, E-mail: d.makarov@ifw-dresden.de [SIMAP, INP Grenoble-CNRS-UJF, BP75, F-38402 Saint Martin d' Heres (France)

    2011-01-12

    A study on the exchange bias (EB) effect in an hcp (0 0 0 2)-textured Co{sub 3}Pt alloy film biased by a thin CoO film is presented. The Co{sub 3}Pt film reveals an out-of-plane easy axis of magnetization although it was grown on an amorphous silica substrate at room temperature. Similar EB fields measured in in-plane and out-of-plane directions of the CoO/Co{sub 3}Pt bilayer system were observed for maximum cooling field. Whereas a pronounced cooling field dependence of the EB field is observed in the in-plane geometry, it remains constant in the out-of-plane direction. The temperature evolution of the coercivity and the shift of the hysteresis loop caused by the EB effect are discussed in terms of thermal activation accounting for the temperature dependent competition between the interfacial exchange energy and the anisotropy energy of antiferromagnetic grains.

  3. High-resolution nanomechanical analysis of suspended electrospun silk fibers with the torsional harmonic atomic force microscope

    Directory of Open Access Journals (Sweden)

    Mark Cronin-Golomb

    2013-04-01

    Full Text Available Atomic force microscopes have become indispensable tools for mechanical characterization of nanoscale and submicron structures. However, materials with complex geometries, such as electrospun fiber networks used for tissue scaffolds, still pose challenges due to the influence of tension and bending modulus on the response of the suspended structures. Here we report mechanical measurements on electrospun silk fibers with various treatments that allow discriminating among the different mechanisms that determine the mechanical behavior of these complex structures. In particular we were able to identify the role of tension and boundary conditions (pinned versus clamped in determining the mechanical response of electrospun silk fibers. Our findings show that high-resolution mechanical imaging with torsional harmonic atomic force microscopy provides a reliable method to investigate the mechanics of materials with complex geometries.

  4. Application of a high-throughput process analytical technology metabolomics pipeline to Port wine forced ageing process.

    Science.gov (United States)

    Castro, Cristiana C; Martins, R C; Teixeira, José A; Silva Ferreira, António C

    2014-01-15

    Metabolomics aims at gathering the maximum amount of metabolic information for a total interpretation of biological systems. A process analytical technology pipeline, combining gas chromatography-mass spectrometry data preprocessing with multivariate analysis, was applied to a Port wine "forced ageing" process under different oxygen saturation regimes at 60°C. It was found that extreme "forced ageing" conditions promote the occurrence of undesirable chemical reactions by production of dioxane and dioxolane isomers, furfural and 5-hydroxymethylfurfural, which affect the quality of the final product through the degradation of the wine aromatic profile, colour and taste. Also, were found high kinetical correlations between these key metabolites with benzaldehyde, sotolon, and many other metabolites that contribute for the final aromatic profile of the Port wine. The use of the kinetical correlations in time-dependent processes as wine ageing can further contribute to biological or chemical systems monitoring, new biomarkers discovery and metabolic network investigations.

  5. Magnetic Microstructures of 2:17 Type Sm(Co,Fe,Cu,Zr)z Magnets Detected by Magnetic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    Xia Ailin; Guo Zhaohui; Li Wei; Han Baoshan

    2006-01-01

    The magnetic microstructures of 2:17 type Sm(Co,Fe,Cu,Zr)z magnets were detected by magnetic force microscopy.Comparing the microstructures of the specimens coated with and without Ta thin film before and after heat-treatment, it is found that: (a) as a protection layer, Ta coating layer about 20 nm thick can effectively restrain Sm volatilization under high temperature;(b) the stress built in the 2:17 type Sm-Co magnets during specimen preparation only affects some local parts of the domain structures;(c) the magnetic microstructures vary largely for specimens heat-treated at high temperature without Ta film coating due to Sm volatilization.In addition, by comparing with high coercivity Fe-Pt point tips, it is found that the Co-Cr thin-film tips are not suitable for detecting the magnetic microstructures of strong permanent magnets.

  6. Control of mean and fluctuating forces on a circular cylinder at high Reynolds numbers

    Institute of Scientific and Technical Information of China (English)

    Chuanping Shao; Jianming Wang

    2007-01-01

    A narrow strip is used to control mean and fluctuating forces on a circular cylinder at Reynolds numbers from 2.0 x 104 to 1.0 x 105. The axes of the strip and cylinder are parallel. The control parameters are strip width ratio and strip position characterized by angle of attack and distance from the cylinder. Wind tunnel tests show that the vortex shedding from both sides of the cylinder can be suppressed, and mean drag and fluctuating lift on the cylinder can be reduced if the strip is installed in an effective zone downstream of the cylinder. A phenomenon of mono-side vortex shedding is found. The strip-induced local changes of velocity profiles in the near wake of the cylinder are measured, and the relation between base suction and peak value in the power spectrum of fluctuating lift is studied. The control mechanism is then discussed from different points of view.

  7. Automated cantilever exchange and optical alignment for High-throughput, parallel atomic force microscopy

    CERN Document Server

    Bijnagte, Tom; Kramer, Lukas; Dekker, Bert; Herfst, Rodolf; Sadeghian, Hamed

    2016-01-01

    In atomic force microscopy (AFM), the exchange and alignment of the AFM cantilever with respect to the optical beam and position-sensitive detector (PSD) are often performed manually. This process is tedious and time-consuming and sometimes damages the cantilever or tip. To increase the throughput of AFM in industrial applications, the ability to automatically exchange and align the cantilever in a very short time with sufficient accuracy is required. In this paper, we present the development of an automated cantilever exchange and optical alignment instrument. We present an experimental proof of principle by exchanging various types of AFM cantilevers in 6 seconds with an accuracy better than 2 um. The exchange and alignment unit is miniaturized to allow for integration in a parallel AFM. The reliability of the demonstrator has also been evaluated. Ten thousand continuous exchange and alignment cycles were performed without failure. The automated exchange and alignment of the AFM cantilever overcome a large ...

  8. Probing weak force induced parity violation by high resolution mid-infrared molecular spectroscopy

    CERN Document Server

    Tokunaga, Sean K; Auguste, Frédéric; Shelkovnikov, Alexander; Daussy, Christophe; Amy-Klein, Anne; Chardonnet, Christian; Darquié, Benoît

    2013-01-01

    To date no experiment has reached the level of sensitivity required to observe weak nuclear force induced parity violation (PV) energy differences in chiral molecules. In this paper, we present the approach, adopted at Laboratoire de Physique des Lasers (LPL), to measure frequency differences in the vibrational spectrum of enantiomers. We review different spectroscopic methods developed at LPL leading to the highest resolutions, as well as 20 years of CO2 laser stabilization work enabling such precise measurements. After a first attempt to observe PV vibrational frequency shifts using sub-Doppler saturated absorption spectroscopy in a cell, we are currently aiming at an experiment based on Doppler-free two-photon Ramsey interferometry on a supersonic beam. We report on our latest progress towards observing PV with chiral organo-metallic complexes containing a heavy rhenium atom.

  9. Electrothermally driven high-frequency piezoresistive SiC cantilevers for dynamic atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Boubekri, R.; Cambril, E.; Couraud, L.; Bernardi, L.; Madouri, A. [LPN, CNRS-UPR20, route de Nozay, 91460 Marcoussis (France); Portail, M. [Centre de Recherche sur l' Hetero-Epitaxie et ses Applications CNRS, Rue Bernard Gregory, 06560 Valhonne (France); Chassagne, T.; Moisson, C.; Zielinski, M. [NOVASiC, Savoie Technolac, Arche bât 4, BP 267, 73375 Le Bourget du Lac Cedex (France); Jiao, S.; Michaud, J.-F.; Alquier, D. [Université François Rabelais, Tours, GREMAN, CNRS-UMR7347, 16 rue Pierre et Marie Curie, BP 7155, 37071 Tours Cedex 2 (France); Bouloc, J.; Nony, L.; Bocquet, F.; Loppacher, C. [IM2NP-CNRS/Aix-Marseille University, 38 rue Frédéric Joliot-Curie, 13451 Marseille (France); Martrou, D.; Gauthier, S., E-mail: gauthier@cemes.fr [CEMES, CNRS UPR 8011 et Université de Toulouse, 29 rue Jeanne Marvig, 31055 Toulouse (France)

    2014-08-07

    Cantilevers with resonance frequency ranging from 1 MHz to 100 MHz have been developed for dynamic atomic force microscopy. These sensors are fabricated from 3C-SiC epilayers grown on Si(100) substrates by low pressure chemical vapor deposition. They use an on-chip method both for driving and sensing the displacement of the cantilever. A first gold metallic loop deposited on top of the cantilever is used to drive its oscillation by electrothermal actuation. The sensing of this oscillation is performed by monitoring the resistance of a second Au loop. This metallic piezoresistive detection method has distinct advantages relative to more common semiconductor-based schemes. The optimization, design, fabrication, and characteristics of these cantilevers are discussed.

  10. Coercivity and morphology in Fe/NiO films deposited on nano porous Al {sub 2}O{sub 3} membranes

    Energy Technology Data Exchange (ETDEWEB)

    Navarro, E.; Palomares, F. J.; Alonso, M.; Cebollada, F.; Dominguez-Canizares, G.; Gutierrez, A.; Soriano, L.; Gonzalez, J. M.

    2015-07-01

    The occurrence of ferro-antiferromagnetic (F/AF) interfaces in Fe/NiO bilayers brings about the possibility of controlling the Fe layer hysteretic properties through the unidirectional anisotropy induced by the presence of unbalanced, antiferromagnetic phase moments at that interface. In this work, we report on the Fe thickness and temperature dependencies of the hysteretic parameters measured in Fe/NiO bilayers deposited on Al{sub 2}O{sub 3} nano porous membranes. The Fe/NiO bilayers grew in a six-fold columnar way around each one of the membrane nano pores. The in-plane hysteresis loops measured by field cooling the samples down to different temperatures below 300 K, evidenced the occurrence of coercive forces larger than that associated to the Fe anisotropy field and also of significant loop shifts, both of them clearly linked to the occurrence of exchange bias at the Fe/NiO interfaces. The magnetization reversal mechanism active in the Fe/NiO bilayers essentially differs from that responsible for the reversal occurring in continuous films incorporating lithographed antidots, due to the fact that in our samples it does not involve either domain wall propagation or pinning, and the reversal events are spatially restricted to the Fe-covered, hexagonally closely packed dot-like tops of the NiO columns. (Author)

  11. Tailoring the coercivity in ferromagnetic ZnO thin films by 3d and 4f elements codoping

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J. J.; Xing, G. Z., E-mail: guozhong.xing@unsw.edu.au; Yi, J. B.; Li, S. [School of Materials Science and Engineering, The University of New South Wales, Sydney, New South Wales 2052 (Australia); Chen, T. [Department of Physics, The Chinese University of Hong Kong, Shatin (Hong Kong); Ionescu, M. [Australian Nuclear Science and Technology Organization, Sydney, New South Wales 2234 (Australia)

    2014-01-06

    Cluster free, Co (3d) and Eu (4f) doped ZnO thin films were prepared using ion implantation technique accompanied by post annealing treatments. Compared with the mono-doped ZnO thin films, the samples codoped with Co and Eu exhibit a stronger magnetization with a giant coercivity of 1200 Oe at ambient temperature. This was further verified through x-ray magnetic circular dichroism analysis, revealing the exchange interaction between the Co 3d electrons and the localized carriers induced by Eu{sup 3+} ions codoping. The insight gained with modulating coercivity in magnetic oxides opens up an avenue for applications requiring non-volatility in spintronic devices.

  12. First-Principles Study of the Role of Cu in Improving the Coercivity of Nd-Fe-B Permanent Magnets

    Science.gov (United States)

    Tatetsu, Y.; Tsuneyuki, S.; Gohda, Y.

    2016-12-01

    We study the magnetic and electronic properties of Cu-doped Nd2 Fe14 B /NdOx systems with first-principles calculations in order to understand the roles of Cu in improving the coercivity of Nd-Fe-B permanent magnets. By analyzing the formation energies of several model systems, we find that Cu prefers to be at the interface. We conclude that the Cu addition to Nd-Fe-B magnets is a practical way of not only increasing the anisotropy of Nd atoms at the interface but also of lessening the magnetic coupling between the Nd and Fe atoms. Particularly, substituting Fe at the interface of the main phase with Cu works effectively in terms of improving the magnetic anisotropy in Nd atoms. This may explain the coercivity improvements reported recently.

  13. Exchange biased FeNi/FeMn bilayers with coercivity and switching field enhanced by FeMn surface oxidation

    Directory of Open Access Journals (Sweden)

    A. V. Svalov

    2013-09-01

    Full Text Available FeNi/FeMn bilayers were grown in a magnetic field and subjected to heat treatments at temperatures of 50 to 350 °C in vacuum or in a gas mixture containing oxygen. In the as-deposited state, the hysteresis loop of 30 nm FeNi layer was shifted. Low temperature annealing leads to a decrease of the exchange bias field. Heat treatments at higher temperatures in gas mixture result in partial oxidation of 20 nm thick FeMn layer leading to a nonlinear dependence of coercivity and a switching field of FeNi layer on annealing temperature. The maximum of coercivity and switching field were observed after annealing at 300 °C.

  14. Design and investigation of high-speed, large-force and longlifetime electromagnetic actuators by finite element modelling

    Energy Technology Data Exchange (ETDEWEB)

    Khan, S H [Measurement and Instrumentation Centre, School of Engineering and Mathematical Sciences, City University, Northampton Square, London EC1V 0HB (United Kingdom); Cai, M [Measurement and Instrumentation Centre, School of Engineering and Mathematical Sciences, City University, Northampton Square, London EC1V 0HB (United Kingdom); Grattan, K T V [Measurement and Instrumentation Centre, School of Engineering and Mathematical Sciences, City University, Northampton Square, London EC1V 0HB (United Kingdom); Kajan, K [Measurement and Instrumentation Centre, School of Engineering and Mathematical Sciences, City University, Northampton Square, London EC1V 0HB (United Kingdom); Honeywood, M [Sortex Limited, Pudding Mill Lane, London E15 2PJ (United Kingdom); Mills, S [Sortex Limited, Pudding Mill Lane, London E15 2PJ (United Kingdom)

    2005-01-01

    Electromagnetic (EM) solenoid actuators are widely used in many applications such as the automobile, aerospace, printing and food industries where repetitive, often high-speed linear or rotating motions are required. In some of these applications they are used as highspeed 'switching' valves for switching pneumatic channels. This paper describes the finite element (FE) modelling and design of high-speed solenoid actuators. Operating at frequencies between 150-300 Hz, these actuators are unique in terms of the large force they produce (8-15 N) and the requirement for very long lifetime (2-5 billion cycles). The complex nature of electromagnetic, motional and thermal problems is discussed. The methodologies for FE modelling of such high-performance actuators are developed and discussed. These are used for modelling, design, performance evaluation and prediction of the above high-speed actuators. Modelling results showing some of the key design features of the actuators are presented in terms of force produced as a function of various design parameters.

  15. Multi-actuation and PI control: A simple recipe for high-speed and large-range atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Soltani Bozchalooi, I., E-mail: isoltani@mit.edu; Youcef-Toumi, K.

    2014-11-15

    High speed atomic force microscopy enables observation of dynamic nano-scale processes. However, maintaining a minimal interaction force between the sample and the probe is challenging at high speed specially when using conventional piezo-tubes. While rigid AFM scanners are operational at high speeds with the drawback of reduced tracking range, multi-actuation schemes have shown potential for high-speed and large-range imaging. Here we present a method to seamlessly incorporate additional actuators into conventional AFMs. The equivalent behavior of the resulting multi-actuated setup resembles that of a single high-speed and large-range actuator with maximally flat frequency response. To achieve this, the dynamics of the individual actuators and their couplings are treated through a simple control scheme. Upon the implementation of the proposed technique, commonly used PI controllers are able to meet the requirements of high-speed imaging. This forms an ideal platform for retroactive enhancement of existing AFMs with minimal cost and without compromise on the tracking range. A conventional AFM with tube scanner is retroactively enhanced through the proposed method and shows an order of magnitude improvement in closed loop bandwidth performance while maintaining large range. The effectiveness of the method is demonstrated on various types of samples imaged in contact and tapping modes, in air and in liquid. - Highlights: • We present a novel method to incorporate extra actuators into conventional AFMs. • A maximally flat frequency response is achieved for the out of plane piezo-motion. • Commonly used PI or PID control is enabled to handle high speed AFM imaging. • An order of magnitude improvement in closed loop bandwidth performance is obtained. • High speed imaging is achieved on a large range piezo-tube.

  16. Measurement of the adhesion force between particles for high gradient magnetic separation of pneumatic conveyed powder products

    Energy Technology Data Exchange (ETDEWEB)

    Senkawa, K., E-mail: senkawa@qb.see.eng.osaka-u.ac.jp [Osaka University, A1 Bldg, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Nakai, Y.; Mishima, F.; Akiyama, Y.; Nishijima, S. [Osaka University, A1 Bldg, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan)

    2011-11-15

    In the industrial plants such as foods, medicines or industrial materials, there are big amount of issues on contamination by metallic wear debris originated from pipes of manufacturing lines. In this study, we developed a high gradient magnetic separation system (HGMS) under the dry process by using superconducting magnet to remove the ferromagnetic particles. One of the major problems of dry HGMS systems is, however, the blockage of magnetic filter caused by particle coagulation or deposition. In order to actualize the magnetic separation without blockage, we introduced pneumatic conveyance system as a new method to feed the powder. It is important to increase the drag force acting on the sufficiently dispersed particles, which require strong magnetic fields. To generate the strong magnetic fields, HGMS technique was examined which consists of a magnetic filter and a superconducting solenoid magnet. As a result of the magnetic separation experiment, it was shown that the separation efficiency changes due to the difference of the cohesive property of the particles. On the basis of the result, the adhesion force which acts between the ferromagnetic particles and the medium particles used for the magnetic separation was measured by Atomic Force Microscope (AFM), and cohesion of particles was studied from the aspect of interparticle interaction. We assessed a suitable flow velocity for magnetic separation according to the cohesive property of each particle based on the result.

  17. Highly accurate and efficient self-force computations using time-domain methods: Error estimates, validation, and optimization

    CERN Document Server

    Thornburg, Jonathan

    2010-01-01

    If a small "particle" of mass $\\mu M$ (with $\\mu \\ll 1$) orbits a Schwarzschild or Kerr black hole of mass $M$, the particle is subject to an $\\O(\\mu)$ radiation-reaction "self-force". Here I argue that it's valuable to compute this self-force highly accurately (relative error of $\\ltsim 10^{-6}$) and efficiently, and I describe techniques for doing this and for obtaining and validating error estimates for the computation. I use an adaptive-mesh-refinement (AMR) time-domain numerical integration of the perturbation equations in the Barack-Ori mode-sum regularization formalism; this is efficient, yet allows easy generalization to arbitrary particle orbits. I focus on the model problem of a scalar particle in a circular geodesic orbit in Schwarzschild spacetime. The mode-sum formalism gives the self-force as an infinite sum of regularized spherical-harmonic modes $\\sum_{\\ell=0}^\\infty F_{\\ell,\\reg}$, with $F_{\\ell,\\reg}$ (and an "internal" error estimate) computed numerically for $\\ell \\ltsim 30$ and estimated ...

  18. THE IMPACT OF REWARD AND COERCIVE POWERS ON COMPLIANCE AND CONFLICT: TAKING KAZAKHSTAN TOBACCO INDUSTRY AS AN EXAMPLE

    Directory of Open Access Journals (Sweden)

    Pletenaya, Y.

    2016-05-01

    Full Text Available This paper tests the effects of reward and punishment powers exercised by power holder on weak partner’s compliance and channel conflict in the context of  marketing channel in Kazakhstan in the setting of tobacco company and their retailers. In this study we found that usage of both reward and coercive powers by power holder have negative impact on compliance and on channel conflict.

  19. Effects of grain size distribution on remanence and coercivity of Pr2Fe14B nanocrystalline magnet

    Institute of Scientific and Technical Information of China (English)

    He Shu-Li; Zhang Hong-Wei; Rong Chuan-Bing; Chen Ren-Jie; Shen Bao-Gen

    2005-01-01

    The demagnetization curves of Pr2Fe14B nanocrystalline magnets are calculated using micromagnetic finiteelement method. Samples with three different distributions of grain size are simulated. We find that the remanence enhancement does not depend on grain size distribution but on the mean diameter of grains, and the influence of grain size distribution on coercivity is affected by the strength of intergrain exchange coupling.

  20. Growth and giant coercive field of spinel-structured Co3- x Mn x O4 thin films

    Science.gov (United States)

    Kwak, Yongsu; Song, Jonghyun; Koo, Taeyeong

    2016-08-01

    We grew epitaxial thin films of CoMn2O4 and Co2MnO4 on Nb-doped SrTiO3(011) and SrTiO3(001) single crystal substrates using pulsed laser deposition. The magnetic Curie temperature ( T c ) of the Co2MnO4 thin films was ~176 K, which is higher than that of the bulk whereas CoMn2O4 thin films exhibited a value of T c (~151 K) lower than that of the bulk. For the Co2MnO4 thin films, the M - H loop showed a coercive field of ~0.7 T at 10 K, similar to the value for the bulk. However, the M -H loop of the CoMn2O4(0 ll) thin film grown on a Nb-doped SrTiO3(011) substrate exhibited a coercive field of ~4.5 T at 30 K, which is significantly higher than those of the Co2MnO4 thin film and bulk. This giant coercive field, only observed for the CoMn2O4(0 ll) thin film, can be attributed to the shape anisotropy and strong spin-orbit coupling.

  1. Serial forced displacement in American cities, 1916-2010.

    Science.gov (United States)

    Fullilove, Mindy Thompson; Wallace, Rodrick

    2011-06-01

    Serial forced displacement has been defined as the repetitive, coercive upheaval of groups. In this essay, we examine the history of serial forced displacement in American cities due to federal, state, and local government policies. We propose that serial forced displacement sets up a dynamic process that includes an increase in interpersonal and structural violence, an inability to react in a timely fashion to patterns of threat or opportunity, and a cycle of fragmentation as a result of the first two. We present the history of the policies as they affected one urban neighborhood, Pittsburgh's Hill District. We conclude by examining ways in which this problematic process might be addressed.

  2. Reversal mechanisms and interactions in magnetic systems: coercivity versus switching field and thermally assisted demagnetization

    Directory of Open Access Journals (Sweden)

    Cebollada, F.

    2005-06-01

    Full Text Available In this paper we present a comparative analysis of the magnetic interactions and reversal mechanisms of two different systems: NdFeB-type alloys with grain sizes in the single domain range and Fe-SiO2 nanocomposites with Fe concentrations above and below the percolation threshold. We evidence that the use of the coercivity as the main parameter to analyse them might be misleading due to the convolution of both reversible and irreversible magnetization variations. We show that the switching field and thermally assisted demagnetization allow a better understanding of these mechanisms since they involve just irreversible magnetization changes. Specifically, the experimental analysis of the coercivity adquisition process for the NdFeB-type system suggests that the magnetization reversal is nucleated at the spin misalignments present due to intergranular exchange interactions. On the other hand, the study of the magnetic viscosity and of the isothermal remanent magnetization (IRM and direct field demagnetization (DCD remanence curves indicates that the dipolar interactions are responsible for the propagation of the switching started at individual particles.

    En este artículo presentamos un análisis comparativo de la influencia de la microestructura a través de las interacciones magnéticas en los mecanismos de inversión de la magnetización en dos sistemas diferentes: aleaciones tipo NdFeB con tamaños de grano en el rango de monodominio y nanocompuestos de Fe-SiO2 con concentraciones de Fe tanto por encima como por debajo del umbral de percolación. Ponemos de manifiesto que el uso del campo coercitivo como parámetro de análisis puede llevar a equívocos debido a la coexistencia de variaciones reversibles e irreversibles de la magnetización. También mostramos que el campo de conmutación y la desimanación térmicamente asistida permiten una mejor comprensión de dichos mecanismos ya que reflejan exclusivamente cambios irreversibles de

  3. GeoFORCE Alaska: Four-Year Field Program Brings Rural Alaskan High School Students into the STEM Pipeline

    Science.gov (United States)

    Fowell, S. J.; Rittgers, A.; Stephens, L.; Hutchinson, S.; Peters, H.; Snow, E.; Wartes, D.

    2016-12-01

    GeoFORCE Alaska is a four-year, field-based, summer geoscience program designed to raise graduation rates in rural Alaskan high schools, encourage participants to pursue college degrees, and increase the diversity of Alaska's technical workforce. Residents of predominantly Alaska Native villages holding degrees in science, technology, engineering, or math (STEM) bring valuable perspectives to decisions regarding management of cultural and natural resources. However, between 2010 and 2015 the average dropout rate for students in grades 7-12 was 8.5% per year in the North Slope School District and 7% per year in the Northwest Arctic School District. 2015 graduation rates were 70% and 75%, respectively. Statewide statistics highlight the challenge for Alaska Native students. During the 2014-2015 school year alone 37.6% of Alaska Native students dropped out of Alaskan public schools. At the college level, Alaska Native students are underrepresented in University of Alaska Fairbanks (UAF) science departments. Launched in 2012 by UAF in partnership with the longstanding University of Texas at Austin program, GeoFORCE applies the cohort model, leading the same group of high school students on geological field academies during four consecutive summers. Through a combination of active learning, teamwork, and hands-on projects at spectacular geological locations, students gain academic skills and confidence that facilitate high school and college success. To date, GeoFORCE Alaska has recruited two cohorts. 78% of these students identify as Alaska Native, reflecting community demographics. The inaugural cohort of 18 students from the North Slope Borough completed the Fourth-Year Academy in summer 2015. 94% of these students graduated from high school, at least 72% plan to attend college, and 33% will major in geoscience. A second cohort of 34 rising 9th and 10th graders entered the program in 2016. At the request of corporate sponsors, this cohort was recruited from both the

  4. High-order comparisons between post-Newtonian and perturbative self forces

    CERN Document Server

    Blanchet, Luc; Whiting, Bernard F

    2015-01-01

    Recent numerical and analytic computations based on the self-force (SF) formalism in general relativity showed that half-integral post-Newtonian (PN) terms, i.e. terms involving odd powers of 1/c, arise in the redshift factor of small mass-ratio black-hole binaries on exact circular orbits. Although those contributions might seem puzzling at first sight for conservative systems that are invariant under time-reversal, they are in fact associated with the so-called non-linear tail-of-tail effect. We shall describe here how the next-to-next-to-leading order contributions beyond the first half-integral 5.5PN conservative effect (i.e. up to order 7.5PN included) have been obtained by means of the standard PN formalism applied to binary systems of point-like objects. The resulting redshift factor in the small mass-ratio limit fully agrees with that of the SF approach.

  5. Experimental evidence for strong stabilizing forces at high functional diversity of aquatic microbial communities.

    Science.gov (United States)

    Carrara, Francesco; Giometto, Andrea; Seymour, Mathew; Rinaldo, Andrea; Altermatt, Florian

    2015-05-01

    Unveiling the mechanisms that promote coexistence in biological communities is a fundamental problem in ecology. Stable coexistence of many species is commonly observed in natural communities. Most of these natural communities, however, are composed of species from multiple trophic and functional groups, while theory and experiments on coexistence have been focusing on functionally similar species. Here, we investigated how functional diversity affects the stability of species coexistence and productivity in multispecies communities by characterizing experimentally all pairwise species interactions in a pool of 11 species of eukaryotes (10 protists and one rotifer) belonging to three different functional groups. Species within the same functional group showed stronger competitive interactions compared to among-functional group interactions. This often led to competitive exclusion between species that had higher functional relatedness, but only at low levels of species richness. Communities with higher functional diversity resulted in increased species coexistence and community biomass production. Our experimental findings and the results of a stochastic model tailored to the experimental interaction matrix suggest the emergence of strong stabilizing forces when species from different functional groups interact in a homogeneous environment. By combining theoretical analysis with experiments we could also disentangle the relationship between species richness and functional diversity, showing that functional diversity per se is a crucial driver of productivity and stability in multispecies community.

  6. High-bandwidth multimode self-sensing in bimodal atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Michael G. Ruppert

    2016-02-01

    Full Text Available Using standard microelectromechanical system (MEMS processes to coat a microcantilever with a piezoelectric layer results in a versatile transducer with inherent self-sensing capabilities. For applications in multifrequency atomic force microscopy (MF-AFM, we illustrate that a single piezoelectric layer can be simultaneously used for multimode excitation and detection of the cantilever deflection. This is achieved by a charge sensor with a bandwidth of 10 MHz and dual feedthrough cancellation to recover the resonant modes that are heavily buried in feedthrough originating from the piezoelectric capacitance. The setup enables the omission of the commonly used piezoelectric stack actuator and optical beam deflection sensor, alleviating limitations due to distorted frequency responses and instrumentation cost, respectively. The proposed method benefits from a more than two orders of magnitude increase in deflection to strain sensitivity on the fifth eigenmode leading to a remarkable signal-to-noise ratio. Experimental results using bimodal AFM imaging on a two component polymer sample validate that the self-sensing scheme can therefore be used to provide both the feedback signal, for topography imaging on the fundamental mode, and phase imaging on the higher eigenmode.

  7. The mate choice brain: comparing gene profiles between female choice and male coercive poeciliids.

    Science.gov (United States)

    Lynch, K S; Ramsey, M E; Cummings, M E

    2012-03-01

    Genes that mediate mate preferences potentially play a key role in promoting and maintaining biological diversity. In this study, we compare mate preference behavior in two related poeciliid fishes with contrasting behavioral phenotypes and relate these behavioral differences to gene profiles in the brain. Results reveal that one poeciliid fish, the Northern swordtail, exhibits robust mate preference as compared to the Western mosquitofish, which utilizes a coercive mating system. Female swordtails display no significant difference in association time between male- and female-exposure trials, whereas female mosquitofish spend significantly less time associating with males relative to females. Furthermore, the preference strength for large males is significantly lower in female mosquitofish relative to swordtails. We then examine expression of three candidate genes previously shown to be associated with mate preference behavior in female swordtails and linked to neural plasticity in other vertebrates: neuroserpin (NS), neuroligin-3 (NLG-3) and N-methyl-d-aspartate receptor (NMDA-R). Whole brain gene expression patterns reveal that two genes (NS and NLG-3) are positively associated with mate preference behavior in female swordtails, a pattern opposing that of the mosquitofish. In mosquitofish females, these genes are downregulated when females express biases toward males yet are elevated in association with total motor activity patterns under asocial conditions, suggesting that the presence of males in mosquitofish species may inhibit expression of these genes. Both gene expression and female behavioral responses to males exhibit opposing patterns between these species, suggesting that this genetic pathway may potentially act as a substrate for the evolution of mate preference behavior.

  8. Abnormal temperature dependence of the coercive field in FePt thin films

    Energy Technology Data Exchange (ETDEWEB)

    Guzmán, J.M. [Facultad de Ciencias Químicas – Universidad Nacional de Córdoba – 5000 Córdoba (Argentina); Álvarez, N.; Salva, H.R.; Vásquez Mansilla, M.; Gómez, J. [Centro Atómico Bariloche (CNEA), Instituto Balseiro (U. N. Cuyo) and Conicet, 8400 Bariloche, Río Negro (Argentina); Butera, A., E-mail: butera@cab.cnea.gov.ar [Centro Atómico Bariloche (CNEA), Instituto Balseiro (U. N. Cuyo) and Conicet, 8400 Bariloche, Río Negro (Argentina)

    2013-12-15

    We have observed notable changes in the magnetic response of FePt thin films that we have attributed to a transition in the magnetic domain structure when the film thickness or the temperature is varied. The critical thickness for this transition depends on the Q-factor, Q=K{sub ⊥}/2πM{sub s}{sup 2}, so that a change in the domain structure is expected when changes in the perpendicular anisotropy, K{sub ⊥}, or the saturation magnetization, M{sub s}, occur. At room temperature these samples have Q∼0.3, and a transition between planar to stripe-like domains occurs for a film thickness d∼30nm. Due to the different thermal expansion of the FePt alloy and the Si substrate a reduction in Q is predicted when the temperature is lowered. From magnetization vs. field loops measured at different temperatures below T=300 K, we have effectively observed a change in the coercive field which can be associated to a transition from stripe-like to in-plane domains. The transition temperature range is broad, indicating a gradual variation between the two magnetic configurations, but changes systematically with film thickness, consistent with an interfacial induced stress. A model that includes the temperature dependence of the strain and the magnetization, predicts correctly the observation of a larger critical thickness at lower temperatures. - Highlights: • The magnetic domain configuration of disordered FePt films can be thermally switched between in-plane domains and stripe domains. • Results are explained by considering the full temperature dependence of the induced stress which produces an out-of-plane anisotropy axis. • The transition temperature changes systematically with film thickness, consistent with an interfacial induced stress.

  9. Thermal noise limit for ultra-high vacuum noncontact atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Jannis Lübbe

    2013-01-01

    Full Text Available The noise of the frequency-shift signal Δf in noncontact atomic force microscopy (NC-AFM consists of cantilever thermal noise, tip–surface-interaction noise and instrumental noise from the detection and signal processing systems. We investigate how the displacement-noise spectral density dz at the input of the frequency demodulator propagates to the frequency-shift-noise spectral density dΔf at the demodulator output in dependence of cantilever properties and settings of the signal processing electronics in the limit of a negligible tip–surface interaction and a measurement under ultrahigh-vacuum conditions. For a quantification of the noise figures, we calibrate the cantilever displacement signal and determine the transfer function of the signal-processing electronics. From the transfer function and the measured dz, we predict dΔf for specific filter settings, a given level of detection-system noise spectral density dzds and the cantilever-thermal-noise spectral density dzth. We find an excellent agreement between the calculated and measured values for dΔf. Furthermore, we demonstrate that thermal noise in dΔf, defining the ultimate limit in NC-AFM signal detection, can be kept low by a proper choice of the cantilever whereby its Q-factor should be given most attention. A system with a low-noise signal detection and a suitable cantilever, operated with appropriate filter and feedback-loop settings allows room temperature NC-AFM measurements at a low thermal-noise limit with a significant bandwidth.

  10. The effect of Nd-Cu diffusion during hot pressing and hot deformation on the coercivity and the deformation ability of Nd-Fe-B HDDR magnets

    Science.gov (United States)

    Wang, Haihang; Chen, Renjie; Yin, Wenzong; Zhu, Mingyuan; Tang, Xu; Wang, Zexuan; Jin, Chaoxiang; Ju, Jinyun; Lee, Don; Yan, Aru

    2017-09-01

    HDDR processed Nd-Fe-B powders blended with Nd-Cu powders were hot-pressed and then hot-deformed to obtain fully dense, anisotropic magnets. The microstructure evolution in hot-pressed and hot-deformed HDDR magnets was studied to illustrate the impact of Nd-Cu diffusion on coercivity and deformation ability. It was found that the coercivity and the deformation ability were improved significantly by Nd-Cu addition. The coercivity of hot-deformed magnets was increased from 3.81 kOe to 13.01 kOe after 2 wt% Nd-Cu additions and the annealing at 900 °C for 2 h. Scanning electron microscopy and transmission electron microscopy observations revealed that the variation in coercivity was attributed to the diffusion of Nd-Cu along the grain boundaries during hot pressing and hot deformation.

  11. Interaction of Parametric and Forced Vibrations in High Speed Rotor-Bearing-Systems

    National Research Council Canada - National Science Library

    Weyh, Bernhardt

    1997-01-01

    ... and the manifold of inhomogeneous solutions are discussed. The application to a realisation of a high speed twin-disc rotor-bearing-system of a textile spinning turbine illustrates the resonance effects...

  12. Report of the Interagency Task Force on High Energy Density Physics

    Energy Technology Data Exchange (ETDEWEB)

    None

    2007-08-01

    Identifies the needs for improving Federal stewardship of specific aspects of high energy density physics, particularly the study of high energy density plasmas in the laboratory, and strengthening university activities in this latter discipline. The report articulates how HEDP fits into the portfolio of federally funded missions and includes agency actions to be taken that are necessary to further this area of study consistent with Federal priorities and plans, while being responsive to the needs of the scientific community.

  13. Federal Plan for High-End Computing. Report of the High-End Computing Revitalization Task Force (HECRTF)

    Science.gov (United States)

    2004-07-01

    and other energy feedstock more efficiently. Signal Transduction Pathways Develop atomic-level computational models and simulations of complex...biomolecules to explain and predict cell signal pathways and their disrupters. Yield understanding of initiation of cancer and other diseases and their...calculations also introduces a requirement for a high degree of internodal connectivity (high bisection bandwidth). These needs cannot be met simply by

  14. High-speed broadband nanomechanical property quantification and imaging of life science materials using atomic force microscope

    Science.gov (United States)

    Ren, Juan

    Nanoscale morphological characterization and mechanical properties quantification of soft and biological materials play an important role in areas ranging from nano-composite material synthesis and characterization, cellular mechanics to drug design. Frontier studies in these areas demand the coordination between nanoscale morphological evolution and mechanical behavior variations through simultaneous measurement of these two aspects of properties. Atomic force microscope (AFM) is very promising in achieving such simultaneous measurements at high-speed and broadband owing to its unique capability in applying force stimuli and then, measuring the response at specific locations in a physiologically friendly environment with pico-newton force and nanometer spatial resolution. Challenges, however, arise as current AFM systems are unable to account for the complex and coupled dynamics of the measurement system and probe-sample interaction during high-speed imaging and broadband measurements. In this dissertation, the creation of a set of dynamics and control tools to probe-based high-speed imaging and rapid broadband nanomechanical spectroscopy of soft and biological materials are presented. Firstly, advanced control-based approaches are presented to improve the imaging performance of AFM imaging both in air and in liquid. An adaptive contact mode (ACM) imaging scheme is proposed to replace the traditional contact mode (CM) imaging by addressing the major concerns in both the speed and the force exerted to the sample. In this work, the image distortion caused by the topography tracking error is accounted for in the topography quantification and the quantified sample topography is utilized in a gradient-based optimization method to adjust the cantilever deflection set-point for each scanline closely around the minimal level needed for maintaining a stable probe-sample contact, and a data-driven iterative feedforward control that utilizes a prediction of the next

  15. Consideration of nonlinear wheel-rail contact forces for dynamic vehicle-bridge interaction in high-speed railways

    Science.gov (United States)

    Antolín, Pablo; Zhang, Nan; Goicolea, José M.; Xia, He; Astiz, Miguel Á.; Oliva, Javier

    2013-03-01

    In this work models with nonlinear wheel-rail contact forces are considered for analysing the dynamic interaction between high speed trains and bridges, in order to study dynamic effects both in the bridge and in the vehicles resulting from the coupling. Nonlinear contact models may be necessary for evaluating the stability and the safety of running traffic in situations such as vehicle overturn when the train is crossing a bridge under strong lateral winds or when an earthquake occurs. For studying the coupled dynamic response of trains and bridges, models of multibody dynamics are used for vehicles and the finite element method for structures. Special relevance is given here to the consideration of contact interaction forces between railway vehicles and the track. Four different interaction models are compared in this work: (1) a model where the vehicle wheelset is considered to be rigidly coupled to the track; (2) a staggered uncoupled method in which vehicle and structure are analysed separately; (3) a linear contact model in which lateral relative displacements between rails and train wheels are allowed, assuming biconic wheel and rail profiles and linear Kalker theory for tangential contact; (4) a nonlinear model in which realistic wheel and rail profiles, Hertz's nonlinear theory for normal contact and Kalker's nonlinear theory for tangential contact are used. The different models are applied and compared to experimental measurements for a test case of a high-speed train in China.

  16. High-order accurate finite-volume formulations for the pressure gradient force in layered ocean models

    Science.gov (United States)

    Engwirda, Darren; Kelley, Maxwell; Marshall, John

    2017-08-01

    Discretisation of the horizontal pressure gradient force in layered ocean models is a challenging task, with non-trivial interactions between the thermodynamics of the fluid and the geometry of the layers often leading to numerical difficulties. We present two new finite-volume schemes for the pressure gradient operator designed to address these issues. In each case, the horizontal acceleration is computed as an integration of the contact pressure force that acts along the perimeter of an associated momentum control-volume. A pair of new schemes are developed by exploring different control-volume geometries. Non-linearities in the underlying equation-of-state definitions and thermodynamic profiles are treated using a high-order accurate numerical integration framework, designed to preserve hydrostatic balance in a non-linear manner. Numerical experiments show that the new methods achieve high levels of consistency, maintaining hydrostatic and thermobaric equilibrium in the presence of strongly-sloping layer geometries, non-linear equations-of-state and non-uniform vertical stratification profiles. These results suggest that the new pressure gradient formulations may be appropriate for general circulation models that employ hybrid vertical coordinates and/or terrain-following representations.

  17. Multifunctional shape memory electrodes for dielectric elastomer actuators enabling high holding force and low-voltage multisegment addressing

    Science.gov (United States)

    McCoul, David; Rosset, Samuel; Besse, Nadine; Shea, Herbert

    2017-02-01

    Dielectric elastomer actuators (DEAs) are an attractive form of electromechanical transducer, possessing high energy densities, an efficient design, mechanical flexibility, high speed, and noiseless operation. They have been incorporated into a variety of elegant devices, such as microfluidic devices, tunable optics, haptic displays, and minimum-energy grippers. Dielectric elastomer minimum energy structures (DEMESs) take advantage of the prestretch of the DEA to bend a non-stretchable but flexible component to perform mechanical work. The gripper is perhaps the most intuitive type of DEMES, capable of grasping objects but with only small to moderate forces. We present a novel configuration of a DEA using electrodes made of a conductive shape-memory polymer (SMP), incorporated into the design of a gripper. The SMP electrodes allow the DEA to be rigid in the cold state, offering greater holding force than a conventional gripper. Joule heating applied to the SMP electrodes softens them, allowing for electrostatic actuation. Cooling then locks in the actuated position without the need for continued power to be supplied. Additionally, the Joule heating voltage is at least one order of magnitude less than electrostatic actuation voltages, allowing for addressing of multiple actuator elements using commercially available transistors. The shape memory gripper incorporates this addressing into its design, enabling the three segments of each finger to be controlled independently.

  18. Study of coercive fields and Kβ/Kα X-ray intensity ratios of nickel films in the thickness range of 5-2000 nm

    Science.gov (United States)

    Prajapat, C. L.; Singh, M. R.; Ravikumar, G.; Gupta, S. K.; Joseph, D.; Nayak, B. K.; Saxena, A.

    2012-06-01

    Coercive fields and X-Ray intensity ratios of the K-series lines of Ni films in the thickness range of 5-2000 nm deposited onto Si (111) substrate have been studied. The Coercive field is observed to increase with thickness and follows power law for the thickness range ≥ 50 nm. For lower thickness, there is a deviation from power law. A correlated change is also observed in the Kβ/Kα X-ray intensity ratios.

  19. The Influence of Tropical Forcing on Westerly Disturbances: Implications for Extreme Precipitation in High Asia

    Science.gov (United States)

    Cannon, F.; Carvalho, L. V.; Jones, C.; Norris, J.; Kiladis, G. N.; Hoell, A.

    2015-12-01

    Extratropical cyclones, including winter westerly disturbances (WD) over central Asia, are fundamental features of the atmosphere that redistribute energy, momentum, and moisture from global to regional scales. Within the Karakoram and western Himalaya (KH), snowfall from only a few WD each winter maintains the region's snowpack and its vast network of glaciers, which seasonally melt to sustain water resources for downstream populations across Asia. WD activity and subsequent precipitation in the mountains are influenced by global atmospheric variability and tropical-extratropical interactions. This research explores the independent influences of the Madden Julian Oscillation (MJO) and El Niño Southern Oscillation on WD and extreme precipitation events in the KH. On interannual time-scales, El Niño suppresses convection in the Indian Ocean and induces a Rossby wave response over Southwest Asia that is linked with enhanced dynamical forcing of WD and available moisture content. Consequently, extreme orographic precipitation events are more frequent during El Niño than La Niña or neutral conditions. A similar spatial pattern of tropical diabatic heating anomalies is produced by the MJO at intraseasonal scales. In comparison to El Niño, the Rossby wave response to MJO activity is less spatially uniform over southwest Asia and exists on a much shorter time-scale. Consequently, this mode's relationship with WD behavior and KH precipitation is more complex. Phases of the MJO propagation cycle that favor the dynamical enhancement of WD simultaneously suppress available moisture over southwest Asia, and vice versa. As a result, extreme precipitation events in the KH occur with similar frequency in most phases of the MJO, however, the relative importance of the dynamic and thermodynamic components of WD to orographic precipitation in the KH transitions as the MJO propagates. These findings give insight into the dynamics and predictability of extreme precipitation

  20. Implosion lessons from national security, high reliability spacecraft, electronics, and the forces which changed them

    CERN Document Server

    Temple, L Parker

    2012-01-01

    Implosion is a focused study of the history and uses of high-reliability, solid-state electronics, military standards, and space systems that support our national security and defense. This book is unique in combining the interdependent evolution of and interrelationships among military standards, solid-state electronics, and very high-reliability space systems. Starting with a brief description of the physics that enabled the development of the first transistor, Implosion covers the need for standardizing military electronics, which began during World War II and continu

  1. United States Air Force High School Apprenticeship Program: 1989 Program Management Report. Volume 3

    Science.gov (United States)

    1988-12-01

    with Biotinylated Probes to Heat Shock Protein and Tumor Necrosis Factor 1 01 The Influence of Broad Spectrum Lori Olenick Illumination on Circadian...Systems, Inc 4 3,3 ui g* samis’ ITOG AGENCY MAMA ($) ANM AONuMI4S) 16.SP03m O~saT w 0113 AFOSR/XOT NWapyj" Bid 410 F49620-88-C-0053 Boiling AFB D.C...PROBES TO HEAT SHOCK PROTEIN AND TUMOR NECROSIS FACTOR Prepared by: BRIAN G. McBURNETT Academic Rank: HIGH SCHOOL SENIOR School: SAMUEL CLEMENS HIGH

  2. The High-Energy Laser: Tomorrow’s Weapon to Improve Force Protection

    Science.gov (United States)

    2012-01-01

    State or non-State entity.” 6 For the physics , see R.P. Feynman , R.B. Leighton, and M.L. Sands, The Feynman Lectures on Physics (Reading, MA: Addison...New York: Plenum Publish- ing, 1992), 93. 4 J. Thomas Schriempf and Brian Hankla, “Navy HEL Lethality Program,” lecture given at the High Energy...96. 9 Dan Marker, “Hi-power Phased Array Trans- ceiver (HiPAT),” lecture given at the High Energy Laser Joint Technology Office Directed Energy

  3. Comparison of Combined Aerobic and High-Force Eccentric Resistance Exercise With Aerobic Exercise Only for People With Type 2 Diabetes Mellitus

    OpenAIRE

    Marcus, Robin L.; Smith, Sheldon; Morrell, Glen; Addison, Odessa; Dibble, Leland E.; Wahoff-Stice, Donna; LaStayo, Paul C.

    2008-01-01

    Background and Purpose: The purpose of this study was to compare the outcomes between a diabetes exercise training program using combined aerobic and high-force eccentric resistance exercise and a program of aerobic exercise only.

  4. The effect of high pass filtering and non-linear normalization on the EMG-force relationship during sub-maximal finger exertions.

    Science.gov (United States)

    McDonald, Alison C; Sanei, Kia; Keir, Peter J

    2013-06-01

    Muscle force estimates are important for full understanding of the musculoskeletal system and EMG is a modeling method used to estimate muscle force. The purpose of this investigation was to examine the effect of high pass filtering and non-linear normalization on the EMG-force relationship of sub-maximal finger exertions. Sub-maximal isometric ramp exertions were performed under three conditions (i) extension with restraint at the mid-proximal phalanx, (ii) flexion at the proximal phalanx and (iii) flexion at the distal phalanx. Thirty high pass filter designs were compared to a standardized processing procedure and an exponential fit equation was used for non-linear normalization. High pass filtering significantly reduced the %RMS error and increased the peak cross correlation between EMG and force in the distal flexion condition and in the other two conditions there was a trend towards improving force predictions with high pass filtering. The degree of linearity differed between the three contraction conditions and high pass filtering improved the linearity in all conditions. Non-linear normalization had greater impact on the EMG-force relationship than high pass filtering. The difference in optimal processing parameters suggests that high pass filtering and linearity are dependent on contraction mode as well as the muscle analyzed.

  5. Bullet Retarding Forces in Ballistic Gelatin by Analysis of High Speed Video

    Science.gov (United States)

    2012-12-28

    ADA291697&Location=U2&doc=GetTRDoc.pdf . Accessed July 15, 2012. Bruchey WJ Jr., Sturdivan LM. An Instrumented Range Meeting the Requirements of a Wound...318. Selman YS, et al., Medico -legal Study of Shockwave Damage by High Velocity Missiles in Firearm Injuries, Fac Med Baghdad 2011; Vol. 53

  6. A High Performance Piezoelectric Sensor for Dynamic Force Monitoring of Landslide

    Directory of Open Access Journals (Sweden)

    Ming Li

    2017-02-01

    Full Text Available Due to the increasing influence of human engineering activities, it is important to monitor the transient disturbance during the evolution process of landslide. For this purpose, a high-performance piezoelectric sensor is presented in this paper. To adapt the high static and dynamic stress environment in slope engineering, two key techniques, namely, the self-structure pressure distribution method (SSPDM and the capacitive circuit voltage distribution method (CCVDM are employed in the design of the sensor. The SSPDM can greatly improve the compressive capacity and the CCVDM can quantitatively decrease the high direct response voltage. Then, the calibration experiments are conducted via the independently invented static and transient mechanism since the conventional testing machines cannot match the calibration requirements. The sensitivity coefficient is obtained and the results reveal that the sensor has the characteristics of high compressive capacity, stable sensitivities under different static preload levels and wide-range dynamic measuring linearity. Finally, to reduce the measuring error caused by charge leakage of the piezoelectric element, a low-frequency correction method is proposed and experimental verified. Therefore, with the satisfactory static and dynamic properties and the improving low-frequency measuring reliability, the sensor can complement dynamic monitoring capability of the existing landslide monitoring and forecasting system.

  7. The Making of Masculinities: Fighting the Forces of Hierarchy and Hegemony in the High School Setting

    Science.gov (United States)

    Heinrich, Jill

    2013-01-01

    This study stems from a yearlong qualitative inquiry examining the influence that gender ideologies exercised in the lives of four young men in the high school setting. Utilizing a feminist, post-structuralist perspective (Davies, 1997, 1989; Connell, 1996, 1997, 1989; Martino, 1995), it analyzes how masculinity constructs itself through…

  8. Elastic-properties measurement at high temperatures through contact resonance atomic force microscopy

    DEFF Research Database (Denmark)

    Marinello, Francesco; Pezzuolo, Andrea; Carmignato, Simone;

    2015-01-01

    . To this regard, some open issues are of particular interest: low depth of penetration, high lateral resolution and measurements at elevated temperatures. An interesting solution is given by acoustic microscopy techniques, which can be successfully implemented for advanced research in surface elasticity, allowing...

  9. High-latitude forcing of diatom productivity in the southern Agulhas Plateauduring the past 350kyr

    NARCIS (Netherlands)

    Romero, O.E.; Kim, J.-H.; Bárcena, M.A.; Hall, I.R.; Zahn, R.; Schneider, R.

    2015-01-01

    The hydrography of the Indian-Atlantic Ocean gateway has been connected to high-latitude climate dynamics by oceanic and atmospheric teleconnections on orbital and suborbital timescales. A wealth of sedimentary records aiming at reconstructing the late Pleistocene paleoceanography around the souther

  10. High-Performing Primary Care Teams: Creating The Air Force Medical Home Advantage

    Science.gov (United States)

    2015-02-17

    teams demonstrate a high level of cohesion. Underpinning this cohesion is a foundation of “mutual trust…defined as the shared perception …that individuals...disadvantage is the potential for decreased cohesion. 19 The beauty of multidisciplinary teams is that each member brings a perspective unique to his/her

  11. The Making of Masculinities: Fighting the Forces of Hierarchy and Hegemony in the High School Setting

    Science.gov (United States)

    Heinrich, Jill

    2013-01-01

    This study stems from a yearlong qualitative inquiry examining the influence that gender ideologies exercised in the lives of four young men in the high school setting. Utilizing a feminist, post-structuralist perspective (Davies, 1997, 1989; Connell, 1996, 1997, 1989; Martino, 1995), it analyzes how masculinity constructs itself through…

  12. A High Performance Piezoelectric Sensor for Dynamic Force Monitoring of Landslide.

    Science.gov (United States)

    Li, Ming; Cheng, Wei; Chen, Jiangpan; Xie, Ruili; Li, Xiongfei

    2017-02-17

    Due to the increasing influence of human engineering activities, it is important to monitor the transient disturbance during the evolution process of landslide. For this purpose, a high-performance piezoelectric sensor is presented in this paper. To adapt the high static and dynamic stress environment in slope engineering, two key techniques, namely, the self-structure pressure distribution method (SSPDM) and the capacitive circuit voltage distribution method (CCVDM) are employed in the design of the sensor. The SSPDM can greatly improve the compressive capacity and the CCVDM can quantitatively decrease the high direct response voltage. Then, the calibration experiments are conducted via the independently invented static and transient mechanism since the conventional testing machines cannot match the calibration requirements. The sensitivity coefficient is obtained and the results reveal that the sensor has the characteristics of high compressive capacity, stable sensitivities under different static preload levels and wide-range dynamic measuring linearity. Finally, to reduce the measuring error caused by charge leakage of the piezoelectric element, a low-frequency correction method is proposed and experimental verified. Therefore, with the satisfactory static and dynamic properties and the improving low-frequency measuring reliability, the sensor can complement dynamic monitoring capability of the existing landslide monitoring and forecasting system.

  13. Seismic Behavior and Force-Displacement Characterization of Neotype Column-Slab High Piers

    Directory of Open Access Journals (Sweden)

    YanQun Zhou

    2014-01-01

    Full Text Available The seismic behavior and plasticity spreading of a neotype column-slab high pier are researched in this paper. Four scale model tests of a web slab with two boundary columns are carried out under cyclic inelastic lateral displacements simulating seismic response. The test results show that the neotype column-slab high pier has strong and stable bearing capacity, good ductility, and energy dissipation capacity. The experimental values pertaining to the spread of plasticity are derived. An approach for deriving the spread of plasticity analytically is deduced and applied to the four tests. This method accurately assesses a pier’s spread of plasticity for most ductility levels. At nearly all ductility levels, the mean difference between analytical assessments of the spread of plasticity and results from 4 large-scale tests is 12% with a 9% coefficient of variation.

  14. Study on High-Performance Computing for Simulation of End Milling Force

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Milling Process Simulation is one of the important re search areas in manufacturing science. For the purpose of improving the prec ision of simulation and extending its usability, numerical algorithm is more and more used in the milling modeling areas. But simulative efficiency is decreasin g with increase of its complexity. As a result, application of the method is lim ited. Aimed at above question, high-efficient algorithm for milling process sim ulation is studied. It is important for milling process...

  15. Search and Rescue in the High North: An Air Force Mission?

    Science.gov (United States)

    2013-12-01

    at the strange new things in the land of the midnight sun. What wouldn’t surprise him are the things that never change: six months of darkness ... motivations include untapped oil and natural gas deposits, un- precedented (to known history) melting of Arctic ice, a quest for terri- torial rights, the...8-98) Prescribed by ANSI Std Z39-18 November–December 2013 Air & Space Power Journal | 5 Conway Search and Rescue in the High North Feature tourism

  16. New Types of Artificial Muscles for Large Stroke and High Force Applications

    Science.gov (United States)

    2012-10-10

    coated Si substrate while in un-actuated (1) and actuated (2) states and subsequently densified on the substrate by absorption and evaporation of...micrometer-thick freestanding carbon nanotube (CNT) polarizers. Simple winding of nanotube sheets on a U-shaped polyethylene reel (Figure 2) enabled rapid...Fermat yarns (J). The realized tensile strokes and power densities for contraction are so high for coiled wax hybrid yarns that practical

  17. Tailoring interlayer coupling and coercivity in Co/Mn/Co trilayers by controlling the interface roughness

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Bin; Wu, Chii-Bin; Kuch, Wolfgang, E-mail: kuch@physik.fu-berlin.de [Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin (Germany)

    2014-06-21

    Epitaxial Co/Mn/Co trilayers with a wedged Mn layer were grown on Cu(001) and studied by magneto-optical Kerr effect measurements. The bottom Co film as well as the Mn film exhibits a layer-by-layer growth mode, which allows to modify both interface roughnesses on the atomic scale by tuning the thicknesses of the films to achieve a certain filling of their topmost atomic layers. The onset of antiferromagnetic order in the Mn layer at room temperature was found at thicknesses of 4.1 (4.8) and 3.4 (4.0) atomic monolayers (ML) for a filled (half-filled) topmost atomic layer of the bottom Co film in Mn/Co bilayers and Co/Mn/Co trilayers, respectively. Magnetization loops with only one step were found for a trilayer with half-filled topmost atomic layer of the bottom Co film, while loops with two separate steps have been observed in trilayers with an integer number of atomic layers in the bottom Co film. The coercivity of the top Co film shows an oscillation with 1 ML period as a function of the Mn thickness above 10 ML, which is interpreted as the influence of the atomic-scale control of the interface roughness on the interface exchange coupling between the antiferromagnetic Mn and the top ferromagnetic (FM) Co layer. The strength of the magnetic interlayer coupling between the top and bottom Co layers through the Mn layer for an integer number of atomic layers in the bottom Co layer, deduced from minor-loop measurements, exhibits an oscillation with a period of 2 ML Mn thickness, indicative of direct exchange coupling through the antiferromagnetic Mn layer. In addition, a long-period interlayer coupling of the two FM layers with antiparallel coupling maxima at Mn thicknesses of 2.5, 8.2, and 13.7 ML is observed and attributed to indirect exchange coupling of the Rudermann-Kittel-Kasuya-Yosida type.

  18. Large surface radiative forcing from surface-based ice crystal events measured in the High Arctic at Eureka

    Directory of Open Access Journals (Sweden)

    G. Lesins

    2008-09-01

    Full Text Available Ice crystals, also known as diamond dust, are suspended in the boundary layer air under clear sky conditions during most of the Arctic winter in Northern Canada. Occasionally ice crystal events can produce significantly thick layers with optical depths in excess of 2.0 even in the absence of liquid water clouds. Four case studies of high optical depth ice crystal events at Eureka in the Nunavut Territory of Canada during the winter of 2006–2007 are presented. They show that the measured ice crystal surface infrared downward radiative forcing ranged from 8 to 36 W m−2 in the wavelength band from 5.6 to 20 μm for visible optical depths ranging from 0.2 to 1.7. MODIS infrared and visible images and the operational radiosonde wind profile were used to show that these high optical depth events were caused by surface snow being blown off 600 to 800 m high mountain ridges about 20 to 30 km North-West of Eureka and advected by the winds towards Eureka as they settled towards the ground within the highly stable boundary layer. This work presents the first study that demonstrates the important role that surrounding topography plays in determining the occurrence of high optical depth ice crystal events and points to a new source of boundary layer ice crystal events distinct from the classical diamond dust phenomenon.

  19. The hydrodynamic and ultrasound-induced forces on microbubbles under high Reynolds number flow representative of the human systemic circulation

    Science.gov (United States)

    Clark, Alicia; Aliseda, Alberto

    2016-11-01

    Ultrasound contrast agents (UCAs) are micron-sized bubbles that are used in conjunction with ultrasound (US) in medical applications such as thrombolysis and targeted intravenous drug delivery. Previous work has shown that the Bjerknes force, due to the phase difference between the incoming US pressure wave and the bubble volume oscillations, can be used to manipulate the trajectories of microbubbles. Our work explores the behavior of microbubbles in medium sized blood vessels under both uniform and pulsatile flows at a range of physiologically relevant Reynolds and Womersley numbers. High speed images were taken of the microbubbles in an in-vitro flow loop that replicates physiological flow conditions. During the imaging, the microbubbles were insonified at different diagnostic ultrasound settings (varying center frequency, PRF, etc.). An in-house Lagrangian particle tracking code was then used to determine the trajectories of the microbubbles and, thus, a dynamic model for the microbubbles including the Bjerknes forces acting on them, as well as drag, lift, and added mass. Preliminary work has also explored the behavior of the microbubbles in a patient-specific model of a carotid artery bifurcation to demonstrate the feasibility of preferential steering of microbubbles towards the intracranial circulation with US.

  20. High-resolution noncontact AFM and Kelvin probe force microscopy investigations of self-assembled photovoltaic donor–acceptor dyads

    Directory of Open Access Journals (Sweden)

    Benjamin Grévin

    2016-06-01

    Full Text Available Self-assembled donor–acceptor dyads are used as model nanostructured heterojunctions for local investigations by noncontact atomic force microscopy (nc-AFM and Kelvin probe force microscopy (KPFM. With the aim to probe the photo-induced charge carrier generation, thin films deposited on transparent indium tin oxide substrates are investigated in dark conditions and upon illumination. The topographic and contact potential difference (CPD images taken under dark conditions are analysed in view of the results of complementary transmission electron microscopy (TEM experiments. After in situ annealing, it is shown that the dyads with longer donor blocks essentially lead to standing acceptor–donor lamellae, where the acceptor and donor groups are π-stacked in an edge-on configuration. The existence of strong CPD and surface photo-voltage (SPV contrasts shows that structural variations occur within the bulk of the edge-on stacks. SPV images with a very high lateral resolution are achieved, which allows for the resolution of local photo-charging contrasts at the scale of single edge-on lamella. This work paves the way for local investigations of the optoelectronic properties of donor–acceptor supramolecular architectures down to the elementary building block level.

  1. Flexible Helicoids, Atomic Force Microscopy (AFM Cantilevers in High Mode Vibration, and Concave Notch Hinges in Precision Measurements and Research

    Directory of Open Access Journals (Sweden)

    Yakov Tseytlin

    2012-05-01

    Full Text Available Flexible structures are the main components in many precision measuring and research systems. They provide miniaturization, repeatability, minimal damping, low measuring forces, and very high resolution. This article focuses on the modeling, development, and comparison of three typical flexible micro- nano-structures: flexible helicoids, atomic force microscopy (AFM cantilevers, and concave notch hinges. Our theory yields results which allow us to increase the accuracy and functionality of these structures in new fields of application such as the modeling of helicoidal DNA molecules’ mechanics, the definition of instantaneous center of rotation in concave flexure notch hinges, and the estimation of the increase of spring constants and resolution at higher mode vibration in AFM cantilevers with an additional concentrated and end extended mass. We developed the original kinetostatic, reverse conformal mapping of approximating contours, and non-linear thermomechanical fluctuation methods for calculation, comparison, and research of the micromechanical structures. These methods simplify complicated solutions in micro elasticity but provide them with necessary accuracy. All our calculation results in this article and in all corresponding referenced author’s publications are in a good agreement with experimental and finite element modeling data within 10% or less.

  2. Childhood motocross truncal injuries: high-velocity, focal force to the chest and abdomen.

    Science.gov (United States)

    Kennedy, Raelene D; Potter, D Dean; Osborn, John B; Zietlow, Scott; Zarroug, Abdalla E; Moir, Christopher R; Ishitani, Michael B; McIntosh, Amy

    2012-01-01

    To review the need for operative intervention and critical care services for motocross truncal injuries in children. DESIGN COHORT: Retrospective review of patients identified via the hospital trauma registry. Our Level 1 Pediatric Trauma Center serves five motocross tracks. These patients require frequent medical care for injuries. All patients ≤17 years of age with truncal injuries sustained during motocross activities, between 2000 and 2011, were identified through the trauma registry. Operative intervention, intensive care unit (ICU) admission, length of stay, morbidity and demographics were reviewed. Motocross injured 162 children. Thirty (18.5%) were thoracic or abdominal injuries. Operative intervention was required in eight (27%) patients. Mean injury severity score (ISS) was 11.8. ICU admission was required in 50% and average hospital length of stay was 4.1 days. The most common injuries include pulmonary contusion, pneumothorax, spleen and liver lacerations. 13% of subjects suffered truncal injury from motocross on more than one occasion. Paediatric motocross-related truncal injuries are significant. Surgical intervention is required in 27% of patients. The lower ISS incurred from motocross combined with high surgical and ICU admission rates suggests focal high-impact injuries to the chest and abdomen. Despite significant injury, 13% of motocross patients suffer recurrent injuries. Parents and children need injury prevention education.

  3. Iron Oxide Nanoparticles: Tunable Size Synthesis and Analysis in Terms of the Core-Shell Structure and Mixed Coercive Model

    Science.gov (United States)

    Phong, P. T.; Oanh, V. T. K.; Lam, T. D.; Phuc, N. X.; Tung, L. D.; Thanh, Nguyen T. K.; Manh, D. H.

    2017-04-01

    Iron oxide nanoparticles (NPs) are currently a very active research field. To date, a comprehensive study of iron oxide NPs is still lacking not only on the size dependence of structural phases but also in the use of an appropriate model. Herein, we report on a systematic study of the structural and magnetic properties of iron oxide NPs prepared by a co-precipitation method followed by hydrothermal treatment. X-ray diffraction and transmission electron microscopy reveal that the NPs have an inverse spinel structure of iron oxide phase (Fe3O4) with average crystallite sizes ( D XRD) of 6-19 nm, while grain sizes ( D TEM) are of 7-23 nm. In addition, the larger the particle size, the closer the experimental lattice constant value is to that of the magnetite structure. Magnetic field-dependent magnetization data and analysis show that the effective anisotropy constants of the Fe3O4 NPs are about five times larger than that of their bulk counterpart. Particle size ( D) dependence of the magnetization and the non-saturating behavior observed in applied fields up to 50 kOe are discussed using the core-shell structure model. We find that with decreasing D, while the calculated thickness of the shell of disordered spins ( t ˜ 0.3 nm) remains almost unchanged, the specific surface areas S a increases significantly, thus reducing the magnetization of the NPs. We also probe the coercivity of the NPs by using the mixed coercive Kneller and Luborsky model. The calculated results indicate that the coercivity rises monotonously with the particle size, and are well matched with the experimental ones.

  4. Terminal Performance of Lead-Free Pistol Bullets in Ballistic Gelatin Using Retarding Force Analysis from High Speed Video

    CERN Document Server

    Courtney, Elijah; Andrusiv, Lubov; Courtney, Michael

    2016-01-01

    Due to concerns about environmental and industrial hazards of lead, a number of military, law enforcement, and wildlife management agencies are giving careful consideration to lead-free ammunition. The goal of lead-free bullets is to gain the advantages of reduced lead use in the environment while maintaining equal or better terminal performance. Accepting reduced terminal performance would foolishly risk the lives of military and law enforcement personnel. This paper uses the established technique of studying bullet impacts in ballistic gelatin to characterize the terminal performance of eight commercial off-the- shelf lead-free handgun bullets for comparison with earlier analysis of jacketed lead bullets. Peak retarding force and energy deposit in calibrated ballistic gelatin are quantified using high speed video. The temporary stretch cavities and permanent wound cavities are also characterized. Two factors tend to reduce the terminal performance of these lead-free projectiles compared to similar jacketed ...

  5. Systematic study of the dolomite (104) surface by bimodal dynamic force microscopy in ultra-high vacuum.

    Science.gov (United States)

    Kawai, Shigeki; Pina, Carlos M; Bubendorf, Alexander; Fessler, Gregor; Glatzel, Thilo; Gnecco, Enrico; Meyer, Ernst

    2013-02-08

    We have investigated the morphology and structure of dolomite MgCa(CO(3))(2)(104) surfaces by bimodal dynamic force microscopy with flexural and torsional resonance modes in ultra-high vacuum at room temperature. We found that the surface slowly decomposes by degassing CO(2) in a vacuum and becomes covered by amorphous clusters, presumably MgO and CaO. By choosing an optimal sample preparation procedure (i.e. cleaving in a vacuum and mild annealing for stabilizing clusters for a short time), atomically clean surfaces were obtained. The complex tip-sample interaction, arising from carbonate groups and Mg and Ca atoms of the surface, induces a large variety of atomic-scale imaging features.

  6. Large-scale analysis of high-speed atomic force microscopy data sets using adaptive image processing

    Directory of Open Access Journals (Sweden)

    Blake W. Erickson

    2012-11-01

    Full Text Available Modern high-speed atomic force microscopes generate significant quantities of data in a short amount of time. Each image in the sequence has to be processed quickly and accurately in order to obtain a true representation of the sample and its changes over time. This paper presents an automated, adaptive algorithm for the required processing of AFM images. The algorithm adaptively corrects for both common one-dimensional distortions as well as the most common two-dimensional distortions. This method uses an iterative thresholded processing algorithm for rapid and accurate separation of background and surface topography. This separation prevents artificial bias from topographic features and ensures the best possible coherence between the different images in a sequence. This method is equally applicable to all channels of AFM data, and can process images in seconds.

  7. Atomic force microscopic study of the structure of high-density polyethylene deformed in liquid medium by crazing mechanism.

    Science.gov (United States)

    Bagrov, D V; Yarysheva, A Y; Rukhlya, E G; Yarysheva, L M; Volynskii, A L; Bakeev, N F

    2014-02-01

    A procedure has been developed for the direct atomic force microscopic (AFM) examination of the native structure of high-density polyethylene (HDPE) deformed in an adsorption-active liquid medium (AALM) by the crazing mechanism. The AFM investigation has been carried out in the presence of a liquid medium under conditions preventing deformed films from shrinkage. Deformation of HDPE in AALM has been shown to proceed through the delocalized crazing mechanism and result in the development of a fibrillar-porous structure. The structural parameters of the crazed polymer have been determined. The obtained AFM images demonstrate a nanosized nonuniformity of the deformation and enable one to observe the structural rearrangements that take place in the deformed polymer after removal of the liquid medium and stress relaxation. A structural similarity has been revealed between HDPE deformed in the AALM and hard elastic polymers.

  8. High-resolution African population projections from radiative forcing and socio-economic models, 2000 to 2100

    Science.gov (United States)

    Boke-Olén, Niklas; Abdi, Abdulhakim M.; Hall, Ola; Lehsten, Veiko

    2017-01-01

    For its fifth assessment report, the Intergovernmental Panel on Climate Change divided future scenario projections (2005-2100) into two groups: Socio-Economic Pathways (SSPs) and Representative Concentration Pathways (RCPs). Each SSP has country-level urban and rural population projections, while the RCPs are based on radiative forcing caused by greenhouse gases, aerosols and associated land-use change. In order for these projections to be applicable in earth system models, SSP and RCP population projections must be at the same spatial scale. Thus, a gridded population dataset that takes into account both RCP-based urban fractions and SSP-based population projection is needed. To support this need, an annual (2000-2100) high resolution (approximately 1km at the equator) gridded population dataset conforming to both RCPs (urban land use) and SSPs (population) country level scenario data were created.

  9. Serum-induced degradation of 3D DNA box origami observed with high-speed atomic force microscopy

    Institute of Scientific and Technical Information of China (English)

    Zaixing Jiang[1,2,3; Shuai Zhang[2,3; Chuanxu Yang[2; Jorgen Kjems[2; Yudong Huang[1; Flemming Besenbacher[2; Mingdong Dong[2

    2015-01-01

    3D DNA origami holds tremendous potential for the encapsulation and selective release of therapeutic drugs. Observations of the real-time performance of these structures in physiological environments will contribute to the development of future applications. We investigated the degradation kinetics of 3D DNA box origami in serum by using high-speed atomic force microscope optimized for imaging 3D DNA origami in real time. The time resolution allowed to characterize the stages of serum effects on individual 3D DNA boxes origami with nanometer resolution. Our results indicate that the digestion process is a combination of rapid collapse and slow degradation phases. Damage to box origami occurs mainly in the collapse phase. Thus, the structural stability of 3D DNA box origami should be improved, especially in the collapse phase, before these structures are used in clinical applications.

  10. High-resolution terrestrial record of orbital climate forcing in coal

    Energy Technology Data Exchange (ETDEWEB)

    Large, D.J.; Jones, T.F.; Somerfield, C.; Gorringe, M.C.; Spiro, B.; Macquaker, J.H.S.; Atkin, B.P. [University of Nottingham, Nottingham (United Kingdom). School of Chemical Environmental & Mining Engineering

    2003-04-01

    Pre-Quaternary terrestrial climate records in which time has been calibrated using astronomical cycles are, with the exception of lacustrine proxies, poorly represented in the geological record. This omission is a significant gap in our knowledge of ancient climate systems. Here the authors present new evidence of orbital periodicities in an 18.3-m-thick late Paleocene coal and conclude that coal has the potential to provide continuous time-calibrated terrestrial climate data. Spectral analysis of changes in the relative proportions of vitrinite to inertinite, two environmentally sensitive coal macerals, reveals several characteristic frequencies, some of which display evidence of amplitude modulation every five to six cycles. Combining this observation with depositional time limitations derived from present-day rates of carbon accumulation in mires, the characteristic frequencies as resulting from precession and obliquity and their influence on oxidation and decay are interpreted. Using the inferred precession component of the data to derive an internal time scale, it is estimated that the Wyodak coal was deposited over a period of similar to 414 k.y. with a long-term carbon sequestration rate of 29 g m{sup -2} yr{sup -1}. The identification of an internal astronomical time scale in coal is an important step toward realizing the potential for coal to extend our high-resolution knowledge of Earth's terrestrial climate back to the formation of the first peat deposits at 360 Ma.

  11. Aerosol Characteristics at a High Altitude Location in Central Himalayas: Optical Properties and Radiative Forcing

    CERN Document Server

    Pant, P; Dumka, U C; Sagar, R; Satheesh, S K; Moorthy, K K; Sagar, Ram

    2006-01-01

    Collocated measurements of the mass concentrations of aerosol black carbon (BC) and composite aerosols near the surface were carried out along with spectral aerosol optical depths (AODs) from a high altitude station, Manora Peak in Central Himalayas, during a comprehensive aerosol field campaign in December 2004. Despite being a pristine location in the Shivalik Ranges of Central Himalayas, and having a monthly mean AOD (at 500 nm) of 0.059 $\\pm$ 0.033 (typical to this site), total suspended particulate (TSP) concentration was in the range 15 - 40 micro g m^(-3) (mean value 27.1 $\\pm$ 8.3 micro g m^(-3)). Interestingly, aerosol BC had a mean concentration of 1.36 $\\pm$ 0.99 micro g m^(-3), contributed to ~5.0 $\\pm$ 1.3 % to the composite aerosol mass. This large abundance of BC is found to have linkages to the human activities in the adjoining valley and to the boundary layer dynamics. Consequently, the inferred single scattering albedo lies in the range of 0.87 to 0.94 (mean value 0.90 $\\pm$ 0.03), indicatin...

  12. Exposure of mouse to high gravitation forces induces long-term potentiation in the hippocampus.

    Directory of Open Access Journals (Sweden)

    Ishii M

    2004-06-01

    Full Text Available The central nervous system is highly plastic and has been shown to undergo both transient and chronic adaptive changes in response to environmental influences. The purpose of this study was to investigate the effect of hypergravic field on long-term potentiation (LTP in the mouse hippocampus. Exposure of mice to 4G fields for 48 h had no effect on input-output coupling during extracellular stimulation of Schaffer collaterals and paired pulse facilitation, suggesting that the hypergravic exposure had no detrimental effect on basal neurotransmission in the hippocampus. However, the exposure to 4G fields for 48 h significantly induced LTP compared with the control mouse hippocampus. In contrast, no significant changes of late-phase LTP (L-LTP were found in the hippocampi of mice exposed to the hypergravic field. Exposure of mice to 4G fields for 48 h enhanced AMPA receptor phosphorylation but not cyclic AMP-responsive element binding protein (CREB phosphorylation. These results suggest that exposure to hyperdynamic fields influences the synaptic plasticity in the hippocampus.

  13. High-resolution high-speed dynamic mechanical spectroscopy of cells and other soft materials with the help of atomic force microscopy

    Science.gov (United States)

    Dokukin, M.; Sokolov, I.

    2015-01-01

    Dynamic mechanical spectroscopy (DMS), which allows measuring frequency-dependent viscoelastic properties, is important to study soft materials, tissues, biomaterials, polymers. However, the existing DMS techniques (nanoindentation) have limited resolution when used on soft materials, preventing them from being used to study mechanics at the nanoscale. The nanoindenters are not capable of measuring cells, nanointerfaces of composite materials. Here we present a highly accurate DMS modality, which is a combination of three different methods: quantitative nanoindentation (nanoDMA), gentle force and fast response of atomic force microscopy (AFM), and Fourier transform (FT) spectroscopy. This new spectroscopy (which we suggest to call FT-nanoDMA) is fast and sensitive enough to allow DMS imaging of nanointerfaces, single cells, while attaining about 100x improvements on polymers in both spatial (to 10–70 nm) and temporal resolution (to 0.7s/pixel) compared to the current art. Multiple frequencies are measured simultaneously. The use of 10 frequencies are demonstrated here (up to 300 Hz which is a rather relevant range for biological materials and polymers, in both ambient conditions and liquid). The method is quantitatively verified on known polymers and demonstrated on cells and polymers blends. Analysis shows that FT-nanoDMA is highly quantitative. The FT-nanoDMA spectroscopy can easily be implemented in the existing AFMs. PMID:26218346

  14. High-resolution high-speed dynamic mechanical spectroscopy of cells and other soft materials with the help of atomic force microscopy.

    Science.gov (United States)

    Dokukin, M; Sokolov, I

    2015-07-28

    Dynamic mechanical spectroscopy (DMS), which allows measuring frequency-dependent viscoelastic properties, is important to study soft materials, tissues, biomaterials, polymers. However, the existing DMS techniques (nanoindentation) have limited resolution when used on soft materials, preventing them from being used to study mechanics at the nanoscale. The nanoindenters are not capable of measuring cells, nanointerfaces of composite materials. Here we present a highly accurate DMS modality, which is a combination of three different methods: quantitative nanoindentation (nanoDMA), gentle force and fast response of atomic force microscopy (AFM), and Fourier transform (FT) spectroscopy. This new spectroscopy (which we suggest to call FT-nanoDMA) is fast and sensitive enough to allow DMS imaging of nanointerfaces, single cells, while attaining about 100x improvements on polymers in both spatial (to 10-70 nm) and temporal resolution (to 0.7 s/pixel) compared to the current art. Multiple frequencies are measured simultaneously. The use of 10 frequencies are demonstrated here (up to 300 Hz which is a rather relevant range for biological materials and polymers, in both ambient conditions and liquid). The method is quantitatively verified on known polymers and demonstrated on cells and polymers blends. Analysis shows that FT-nanoDMA is highly quantitative. The FT-nanoDMA spectroscopy can easily be implemented in the existing AFMs.

  15. Effect of external shearing force on exfoliation structure and properties of high-performance epoxy/clay nanocomposites

    Institute of Scientific and Technical Information of China (English)

    LU Hai-jun; ZHANG Bao-yan; CHEN Xiang-bao

    2005-01-01

    To further investigate the influence of organic modifiers (primary amine with catalytic hydrogen and quaternary alkylammonium salt) on exfoliation behavior of clay tactoids, high-speed emulsifying and homogeneous mixing(HEHM) and ball milling were used to exert external shearing force on two organic clay tactoids (termed as MMTDDA and MMTDBDA, respectively), which were organically modified with DoDecyl Amine(DDA) and Dodecyl Benzyl Dimethyl Ammonium chloride(DBDA) ,respectively. The effects of external shearing force on microstructure and properties of both resultant nanocomposites were investigated by X-ray diffractometry(XRD), transmission electron microscopy(TEM) and thermogravimetric analysis(TGA). The results show that whether the clay tactoids are organically modified with catalytic primary amine or quaternary alkylammonium salt, the large agglomerates will not be finely dispersed or exfoliated by conventional mixing (magnetic stirring). After being vigorously sheared by HEHM or ball milling, the dispersion and exfoliation of clay tactoids are increasingly promoted for both MMTDDA and MMTDBDA, and the mechanical properties of the high-performance epoxy/clay nanocomposites are enhanced. For epoxy/MMTDDA nanocomposites, impact strength can be increased up to 44.5 kJ/m2 from 32.1 kJ/m2 , which is about 39% higher than that of pristine matrix, and the flexural strength is enhanced by about 4%. A similar enhancement for epoxy/MMTDBDA nanocomposites has also been achieved. Improvement on thermal stability of epoxy/clay nanocomposites is dependent on the exfoliation of clay layers and molecular structure of the modifiers. The onset temperature is increased with the clay loading decreasing from 5% or higher content to 3% (mass fraction), and the DBDA modifier with the heat-resistant benzyl may also improve the stability of epoxy/MMTDBDA nanocomposites.

  16. Influence of high-latitude geomagnetic pulsations on recordings of broadband force-balanced seismic sensors

    Directory of Open Access Journals (Sweden)

    E. Kozlovskaya

    2012-08-01

    Full Text Available Seismic broadband sensors with electromagnetic feedback are sensitive to variations of surrounding magnetic field, including variations of geomagnetic field. Usually, the influence of the geomagnetic field on recordings of such seismometers is ignored. It might be justified for seismic observations at middle and low latitudes. The problem is of high importance, however, for observations in Polar Regions (above 60° geomagnetic latitude, where magnitudes of natural magnetic disturbances may be two or even three orders larger. In our study we investigate the effect of ultra-low frequency (ULF magnetic disturbances, known as geomagnetic pulsations, on the STS-2 seismic broadband sensors. The pulsations have their sources and, respectively, maximal amplitudes in the region of the auroral ovals, which surround the magnetic poles in both hemispheres at geomagnetic latitude (GMLAT between 60° and 80°. To investigate sensitivity of the STS-2 seismometer to geomagnetic pulsations, we compared the recordings of permanent seismic stations in northern Finland to the data of the magnetometers of the IMAGE network located in the same area. Our results show that temporary variations of magnetic field with periods of 40–150 s corresponding to regular Pc4 and irregular Pi2 pulsations are seen very well in recordings of the STS-2 seismometers. Therefore, these pulsations may create a serious problem for interpretation of seismic observations in the vicinity of the auroral oval. Moreover, the shape of Pi2 magnetic disturbances and their periods resemble the waveforms of glacial seismic events reported originally by Ekström (2003. The problem may be treated, however, if combined analysis of recordings of co-located seismic and magnetic instruments is used.

  17. Highly Accurate Quartic Force Fields, Vibrational Frequencies, and Spectroscopic Constants for Cyclic and Linear C3H3(+)

    Science.gov (United States)

    Huang, Xinchuan; Taylor, Peter R.; Lee, Timothy J.

    2011-01-01

    High levels of theory have been used to compute quartic force fields (QFFs) for the cyclic and linear forms of the C H + molecular cation, referred to as c-C H + and I-C H +. Specifically the 33 3333 singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations, CCSD(T), has been used in conjunction with extrapolation to the one-particle basis set limit and corrections for scalar relativity and core correlation have been included. The QFFs have been used to compute highly accurate fundamental vibrational frequencies and other spectroscopic constants using both vibrational 2nd-order perturbation theory and variational methods to solve the nuclear Schroedinger equation. Agreement between our best computed fundamental vibrational frequencies and recent infrared photodissociation experiments is reasonable for most bands, but there are a few exceptions. Possible sources for the discrepancies are discussed. We determine the energy difference between the cyclic and linear forms of C H +, 33 obtaining 27.9 kcal/mol at 0 K, which should be the most reliable available. It is expected that the fundamental vibrational frequencies and spectroscopic constants presented here for c-C H + 33 and I-C H + are the most reliable available for the free gas-phase species and it is hoped that 33 these will be useful in the assignment of future high-resolution laboratory experiments or astronomical observations.

  18. Facile fabrication of functional PDMS surfaces with tunable wettablity and high adhesive force via femtosecond laser textured templating

    Directory of Open Access Journals (Sweden)

    Yanlei Hu

    2014-12-01

    Full Text Available Femtosecond laser processing is emerged as a promising tool to functionalize surfaces of various materials, including metals, semiconductors, and polymers. However, the productivity of this technique is limited by the low efficiency of laser raster scanning. Here we report a facile approach for efficiently producing large-area functional polymer surfaces, by which metal is firstly textured by a femtosecond laser, and the as-prepared hierarchical structures are subsequently transferred onto polydimethylsiloxane (PDMS surfaces. Aluminum pieces covered by laser induced micro/nano-structures act as template masters and their performance of displaying diverse colors are investigated. Polymer replicas are endowed with tunable wetting properties, which are mainly attributed to the multi-scale surface structures. Furthermore, the surfaces are found to have extremely high adhesive force for water drops because of the high water penetration depth and the resultant high contact angle hysteresis. This characteristic facilitates many potential applications like loss-free tiny water droplets transportation. The reusability of metal master and easiness of soft lithography make it to be a very simple, fast and cost-efficient way for mass production of functional polymeric surfaces.

  19. Destruction of Landscape by the Forces of Commercial Industrialism in Maxwell Anderson’s play, High Tor

    Directory of Open Access Journals (Sweden)

    Gholamreza Samigorganroodi

    2015-01-01

    Full Text Available This study examines Maxwell Anderson’s play High Tor that is an aesthetic engagement with nature and dramatizes Anderson’s environmental sensibilities. The play is a satirical fantasy in verse loaded with allusions, symbolism and philosophical meditation, dramatizing the end of America’s pioneering tradition. High Tor refers to a mountain overlooking the Hudson River, only a few miles away from Anderson’s home in New City in the district of New York. The name derives from Celtic lore and means a sacred and holy place where people commune with the gods. The area where High Tor stands is steeped in history, legend and the supernatural. There are many accounts of ghosts haunting this historical mountain and the surrounding areas. In this play, Anderson makes use of the aura of mystery surrounding this region to dramatize the story of the protagonist, Van Dorn, and his struggle against the advancing forces of industrialism and materialism that threaten his independence and the pioneering values, pastoral tradition and the Arcadian beauty of the American wilderness. Keywords: American drama, the Great Depression, environment, American pastoral tradition, individualism

  20. Spatiotemporal dynamics of the nuclear pore complex transport barrier resolved by high-speed atomic force microscopy

    Science.gov (United States)

    Sakiyama, Yusuke; Mazur, Adam; Kapinos, Larisa E.; Lim, Roderick Y. H.

    2016-08-01

    Nuclear pore complexes (NPCs) are biological nanomachines that mediate the bidirectional traffic of macromolecules between the cytoplasm and nucleus in eukaryotic cells. This process involves numerous intrinsically disordered, barrier-forming proteins known as phenylalanine-glycine nucleoporins (FG Nups) that are tethered inside each pore. The selective barrier mechanism has so far remained unresolved because the FG Nups have eluded direct structural analysis within NPCs. Here, high-speed atomic force microscopy is used to visualize the nanoscopic spatiotemporal dynamics of FG Nups inside Xenopus laevis oocyte NPCs at timescales of ∼100 ms. Our results show that the cytoplasmic orifice is circumscribed by highly flexible, dynamically fluctuating FG Nups that rapidly elongate and retract, consistent with the diffusive motion of tethered polypeptide chains. On this basis, intermingling FG Nups exhibit transient entanglements in the central channel, but do not cohere into a tightly crosslinked meshwork. Therefore, the basic functional form of the NPC barrier is comprised of highly dynamic FG Nups that manifest as a central plug or transporter when averaged in space and time.