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1

Inverted Linear Halbach Array for Separation of Magnetic Nanoparticles  

PubMed Central

A linear array of Nd-Fe-B magnets has been designed and constructed in an inverted Halbach configuration for use in separating magnetic nanoparticles. The array provides a large region of relatively low magnetic field, yet high magnetic field gradient in agreement with finite element modeling calculations. The magnet assembly has been combined with a flow channel for magnetic nanoparticle suspensions, such that for an appropriate distance away from the assembly, nanoparticles of higher moment aggregate and accumulate against the channel wall, with lower moment nanoparticles flowing unaffected. The device is demonstrated for iron oxide nanoparticles with diameters of ~ 5 and 20 nm. In comparison to other approaches, the inverted Halbach array is more amenable to modeling and to scaling up to preparative quantities of particles.

Ijiri, Y.; Poudel, C.; Williams, P.S.; Moore, L.R.; Orita, T.; Zborowski, M.

2014-01-01

2

Analysis and comparison of two two-dimensional Halbach permanent magnet arrays for magnetically levitated planar motor  

NASA Astrophysics Data System (ADS)

A novel 2-D Halbach permanent magnet array which can be used in magnetically levitated planar motor is proposed in this paper. The air-gap flux density distribution of the novel 2-D Halbach permanent magnet array is solved by the scalar magnetic potential equation. In order to compare with the well-known Halbach magnet array that was used by Jansen et al. [IEEE Trans. Ind. Appl. 44(4), 1108 (2008)], harmonic analysis of the x- and z- component of the air-gap flux density are carried out by Fourier decomposition. Comparison of Bx and Bz between the two 2-D Halbach magnet arrays are made. And it is verified that the performance of the new Halbach magnet array is superior to the existing Halbach magnet arrays, its higher magnetic flux density and lower high-order harmonics will help to improve the performance of the magnetically levitated planar motor.

Zhang, Lu; Kou, Baoquan; Xing, Feng; Zhang, He

2014-05-01

3

Modeling maglev passenger compartment static magnetic fields from linear Halbach permanent-magnet arrays  

Microsoft Academic Search

Passenger compartment magnetic field levels in a low-speed magnetic levitation (maglev) vehicle that uses linear Halbach permanent-magnet arrays for both levitation and propulsion are computed through superposition of fields due to patches of magnetization charge at surfaces where the magnetization is discontinuous. End effects due to the finite lengths of the arrays lead to fields that decay much less rapidly

James F. Hoburg

2004-01-01

4

Permanent Magnet Type Eddy Current Heater Based on Cylindrical Halbach Array for Reducing Oil's Viscosity  

Microsoft Academic Search

The eddy current, Joule heat and input electrical power of a permanent magnet type eddy current heater based on cylindrical Halbach arrays to reduce the viscosity of crude oil in oil wells were analysed and studied by means of a three-dimensional finite-element method. The results show that when Halbach arrays generate a 0.9 T sinusoidal static field and the annulus

L. Z. Zhao; Y. Peng; C. W. Sha; R. Li; Y. Y. Xu

2010-01-01

5

Dynamics of magnetic particles in cylindrical Halbach array: implications for magnetic cell separation and drug targeting.  

PubMed

Magnetic nanoparticles for therapy and diagnosis are at the leading edge of the rapidly developing field of bionanotechnology. In this study, we have theoretically studied motion of magnetic nano- as well as micro-particles in the field of cylindrical Halbach array of permanent magnets. Magnetic flux density was modeled as magnetostatic problem by finite element method and particle motion was described using system of ordinary differential equations--Newton law. Computations were done for nanoparticles Nanomag-D with radius 65 nm, which are often used in magnetic drug targeting, as well as microparticles DynaBeads-M280 with radius 1.4 microm, which can be used for magnetic separation. Analyzing snapshots of trajectories of hundred magnetite particles of each size in the water as well as in the air, we have found that optimally designed magnetic circuits of permanent magnets in quadrupolar Halbach array have substantially shorter capture time than simple blocks of permanent magnets commonly used in experiments, therefore, such a Halbach array may be useful as a potential source of magnetic field for magnetic separation and targeting of magnetic nanoparticles as well as microparticles for delivery of drugs, genes, and cells in various biomedical applications. PMID:20517710

Babinec, Peter; Krafcík, Andrej; Babincová, Melánia; Rosenecker, Joseph

2010-08-01

6

Halbach arrays in precision motion control  

SciTech Connect

The Halbach array was developed for use as an optical element in particle accelerators. Following up on a suggestion from Klaus Halbach, the authors have investigated the utility of such arrays as the permanent magnet structure for synchronous machines in cartesian, polar, and cylindrical geometries. Their work has focused on the design of a novel Halbach array linear motor for use in a magnetic suspension stage for photolithography. This paper presents the details of the motor design and its force and power characteristics.

Trumper, D.L.; Williams, M.E. [Massachusetts Institute of Technology, Cambridge, MA (United States)

1995-02-01

7

Halbach Magnetic Rotor Development  

NASA Technical Reports Server (NTRS)

The NASA John H. Glenn Research Center has a wealth of experience in Halbach array technology through the Fundamental Aeronautics Program. The goals of the program include improving aircraft efficiency, reliability, and safety. The concept of a Halbach magnetically levitated electric aircraft motor will help reduce harmful emissions, reduce the Nation s dependence on fossil fuels, increase efficiency and reliability, reduce maintenance and decrease operating noise levels. Experimental hardware systems were developed in the GRC Engineering Development Division to validate the basic principles described herein and the theoretical work that was performed. A number of Halbach Magnetic rotors have been developed and tested under this program. A separate test hardware setup was developed to characterize each of the rotors. A second hardware setup was developed to test the levitation characteristics of the rotors. Each system focused around a unique Halbach array rotor. Each rotor required original design and fabrication techniques. A 4 in. diameter rotor was developed to test the radial levitation effects for use as a magnetic bearing. To show scalability from the 4 in. rotor, a 1 in. rotor was developed to also test radial levitation effects. The next rotor to be developed was 20 in. in diameter again to show scalability from the 4 in. rotor. An axial rotor was developed to determine the force that could be generated to position the rotor axially while it is rotating. With both radial and axial magnetic bearings, the rotor would be completely suspended magnetically. The purpose of this report is to document the development of a series of Halbach magnetic rotors to be used in testing. The design, fabrication and assembly of the rotors will be discussed as well as the hardware developed to test the rotors.

Gallo, Christopher A.

2008-01-01

8

A low-field, low-cost Halbach magnet array for open-access NMR  

NASA Astrophysics Data System (ADS)

A working prototype of a novel low-cost Halbach-array-based NMR system is described. The new design provides open access to the sample relative to conventional NMR magnet designs and this facilitates the simultaneous use of multi-sensor techniques on the same sample, in which NMR/MRI can potentially be combined with other spectroscopies such as impedance spectroscopy, laser scattering and rheological experiments.

Hills, B. P.; Wright, K. M.; Gillies, D. G.

2005-08-01

9

Axial Halbach Magnetic Bearings  

NASA Technical Reports Server (NTRS)

Axial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control.

Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

2008-01-01

10

Analysis of eddy current losses in cylindrical linear oscillatory actuator with Halbach permanent magnet array mover  

NASA Astrophysics Data System (ADS)

This paper describes calculations and comparisons of eddy current losses in a cylindrical linear oscillatory actuator with a Halbach array permanent magnet mover for different voltage source waveforms. Using the magnetic vector potential and a two-dimensional cylindrical coordinate system, the paper presents an analytical procedure and obtains solutions for the eddy current losses using the Poynting theorem. To verify the proposed method, the eddy current losses obtained from the analytical solutions are compared with the results of a non-linear finite element method. Moreover, this paper shows that the eddy current losses are more significant when the actuator is driven by a square voltage waveform than when it is driven by a sinusoidal voltage waveform.

Ko, Kyoung-Jin; Choi, Ji-Hwan; Jang, Seok-Myeong; Choi, Jang-Young

2012-04-01

11

Design of Feedforward Controller to Reduce Force Ripple for Linear Motor using Halbach Magnet Array with T Shape Magnet  

NASA Astrophysics Data System (ADS)

Recently, in micro/nano fabrication equipments, linear motors are widely used as an actuator to position workpiece, machining tool and measurement head. To control them faster and more precise, the motor should have high actuating force and small force ripple. High actuating force enable us to more workpiece with high acceleration. Eventually, it may provide higher throughput. Force ripple gives detrimental effect on the precision and tracking performance of the equipments. In order to accomplish more precise motion, it is important to make lower the force ripple. Force ripple is categorized into cogging and mutual ripple. First is dependent on the shape of magnets and/or core. The second is not dependent on them but dependent on current commutation. In this work, coreless mover i.e. coil winding is applied to the linear motor to avoid the cogging ripple. Therefore, the mutual ripple is only considered to be minimized. Ideal Halbach magnet array has continuously varying magnetization. The THMA (Halbach magnet array with T shape magnets) is proposed to approximate the ideal one. The THMA can not produce ideal sinusoidal flux, therefore, the linear motor with THMA and sinusoidal commutation of current generates the mutual force ripple. In this paper, in order to compensate mutual force ripple by feedforward(FF) controller, we calculate the optimized commutation of input current. The ripple is lower than 1.17% of actuating force if the commutation current agree with the magnetic flux from THMA. The performance of feedforward(FF) controller is verified by experiment.

Kim, Moojong; Kim, Jinyoung; Lee, Moon G.

12

A Comparison of Two Magnetic Ultra-Cold Neutron Trapping Concepts Using a Halbach-Octupole Array  

NASA Astrophysics Data System (ADS)

This paper describes a new magnetic trap for ultra-cold neutrons (UCNs) made from a 1.2m long Halbach-octupole array of permanent magnets with an inner bore radius of 47mm combined with an assembly of superconducting end coils and bias field solenoid. The use of the trap in a vertical, magneto-gravitational and a horizontal setup are compared in terms of the effective volume and ability to control key systematic effects that need to be addressed in high precision neutron lifetime measurements.

Leung, K.; Ivanov, S.; Martin, F.; Rosenau, F.; Simson, M.; Zimmer, O.

2014-03-01

13

The use of a linear Halbach array combined with a step-SPLITT channel for continuous sorting of magnetic species  

NASA Astrophysics Data System (ADS)

The Quadrupole Magnetic Sorter (QMS), employing an annular flow channel concentric with the aperture of a quadrupole magnet, is well established for cell and particle separations. Here we propose a magnetic particle separator comprising a linear array of cylindrical magnets, analogous to the array proposed by Klaus Halbach, mated to a substantially improved form of a parallel plate SPLITT channel, known as the step-SPLITT channel. While the magnetic force and throughput are generally lower than for the QMS, the new separator has advantages in ease of fabrication and the ability to vary the magnetic force to suit the separands. Preliminary experiments yield results consistent with prediction and show promise regarding future separations of cells of biomedical interest.

Hoyos, Mauricio; Moore, Lee; Williams, P. Stephen; Zborowski, Maciej

2011-05-01

14

Halbach array motor/generators: A novel generalized electric machine  

SciTech Connect

In August 1979, Halbach submitted a paper entitled ``Design of Permanent Multipole Magnets with Oriented Rare Earth Cobalt Material.`` In this paper, he presented a novel method of generating multipole magnetic fields using non-intuitive geometrical arrangements of permanent magnets. In subsequent publications, he further defined these concepts. Of particular interest to one of the authors (RFP) was the special magnet array that generated a uniform dipole field. In 1990 Post proposed the construction of an electric machine (a motor/generator) using a dipole field based on Klaus Halbach`s array of permanent magnets. He further proposed that such a system should be employed as an integral part of ``an electromechanical battery`` (EMB), i.e., a modular flywheel system to be used as a device for storing electrical energy, as an alternative to the electrochemical storage battery. This paper reviews Halbach`s theory for the generation of a dipole field using an array of permanent magnet bars, presents a simple analysis of a family of novel ``ironless`` electric machines designed using the dipole Halbach array, and describes the results obtained when they were tested in the laboratory.

Merritt, B.T.; Post, R.F.; Dreifuerst, G.R.; Bender, D.A.

1994-10-28

15

Halbach array DC motor/generator  

DOEpatents

A new configuration of DC motor/generator is based on a Halbach array of permanent magnets. This motor does not use ferrous materials so that the only losses are winding losses and losses due to bearings and windage. An ``inside-out`` design is used as compared to a conventional motor/generator design. The rotating portion, i.e., the rotor, is on the outside of the machine. The stationary portion, i.e., the stator, is formed by the inside of the machine. The rotor contains an array of permanent magnets that provide a uniform field. The windings of the motor are placed in or on the stator. The stator windings are then ``switched`` or ``commutated`` to provide a DC motor/generator much the same as in a conventional DC motor. The commutation can be performed by mechanical means using brushes or by electronic means using switching circuits. The invention is useful in electric vehicles and adjustable speed DC drives. 17 figs.

Merritt, B.T.; Dreifuerst, G.R.; Post, R.F.

1998-01-06

16

Energy harvesting from electric power lines employing the Halbach arrays  

NASA Astrophysics Data System (ADS)

This paper proposes non-invasive energy harvesters to scavenge alternating magnetic field energy from electric power lines. The core body of a non-invasive energy harvester is a linear Halbach array, which is mounted on the free end of a piezoelectric cantilever beam. The Halbach array augments the magnetic flux density on the side of the array where the power line is placed and significantly lowers the magnetic field on the other side. Consequently, the magnetic coupling strength is enhanced and more alternating magnetic field energy from the current-carrying power line is converted into electrical energy. An analytical model is developed and the theoretical results verify the experimental results. A power of 566 ?W across a 196 k? resistor is generated from a single wire, and a power of 897 ?W across a 212 k? resistor is produced from a two-wire power cord carrying opposite currents at 10 A. The harvesters employing Halbach arrays for a single wire and a two-wire power cord, respectively, exhibit 3.9 and 3.2 times higher power densities than those of the harvesters employing conventional layouts of magnets. The proposed devices with strong response to the alternating currents are promising to be applied to electricity end-use environment in electric power systems.

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

2013-10-01

17

A two-pole Halbach permanent magnet guideway for high temperature superconducting Maglev vehicle  

Microsoft Academic Search

In order to improve the levitation performance of the high temperature superconducting (HTS) magnetic levitation (Maglev) vehicle, a two-pole Halbach array’s permanent magnet guideway (PMG) is proposed, which is called as Halbach PMG. The finite element method (FEM) calculations indicate that Halbach PMG has a wider high-field region than the present PMG of equal PM’s transverse section. The levitation force

H. Jing; J. Wang; S. Wang; L. Wang; L. Liu; J. Zheng; Z. Deng; G. Ma; Y. Zhang; J. Li

2007-01-01

18

Development and Testing of an Axial Halbach Magnetic Bearing  

NASA Technical Reports Server (NTRS)

The NASA Glenn Research Center has developed and tested a revolutionary Axial Halbach Magnetic Bearing. The objective of this work is to develop a viable non-contact magnetic thrust bearing utilizing Halbach arrays for all-electric flight, and many other applications. This concept will help to reduce harmful emissions, reduce the Nation s dependence on fossil fuels and mitigate many of the concerns and limitations encountered in conventional axial bearings such as bearing wear, leaks, seals and friction loss. The Axial Halbach Magnetic Bearing is inherently stable and requires no active feedback control system or superconductivity as required in many magnetic bearing designs. The Axial Halbach Magnetic Bearing is useful for very high speed applications including turbines, instrumentation, medical systems, computer memory systems, and space power systems such as flywheels. Magnetic fields suspend and support a rotor assembly within a stator. Advanced technologies developed for particle accelerators, and currently under development for maglev trains and rocket launchers, served as the basis for this application. Experimental hardware was successfully designed and developed to validate the basic principles and analyses. The report concludes that the implementation of Axial Halbach Magnetic Bearings can provide significant improvements in rotational system performance and reliability.

Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

2006-01-01

19

Development and Testing of a Radial Halbach Magnetic Bearing  

NASA Technical Reports Server (NTRS)

The NASA John H. Glenn Research Center has developed and tested a revolutionary Radial Halbach Magnetic Bearing. The objective of this work is to develop a viable non-contact magnetic bearing utilizing Halbach arrays for all-electric flight, and many other applications. This concept will help reduce harmful emissions, reduce the Nation s dependence on fossil fuels and mitigate many of the concerns and limitations encountered in conventional axial bearings such as bearing wear, leaks, seals and friction loss. The Radial Halbach Magnetic Bearing is inherently stable and requires no active feedback control system or superconductivity as required in many magnetic bearing designs. The Radial Halbach Magnetic Bearing is useful for very high speed applications including turbines, instrumentation, medical applications, manufacturing equipment, and space power systems such as flywheels. Magnetic fields suspend and support a rotor assembly within a stator. Advanced technologies developed for particle accelerators, and currently under development for maglev trains and rocket launchers, served as the basis for this application. Experimental hardware was successfully designed and developed to validate the basic principles and analyses. The report concludes that the implementation of Radial Halbach Magnetic Bearings can provide significant improvements in rotational system performance and reliability.

Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

2006-01-01

20

Halbach array motor/generators: A novel generalized electric machine.  

National Technical Information Service (NTIS)

In August 1979, Halbach submitted a paper entitled ''Design of Permanent Multipole Magnets with Oriented Rare Earth Cobalt Material.'' In this paper, he presented a novel method of generating multipole magnetic fields using non-intuitive geometrical arran...

B. T. Merritt, R. F. Post, G. R. Dreifuerst, D. A. Bender

1994-01-01

21

Optimal Halbach permanent magnet designs for maximally pulling and pushing nanoparticles  

Microsoft Academic Search

Optimization methods are presented to design Halbach arrays to maximize the forces applied on magnetic nanoparticles at deep tissue locations. In magnetic drug targeting, where magnets are used to focus therapeutic nanoparticles to disease locations, the sharp fall off of magnetic fields and forces with distances from magnets has limited the depth of targeting. Creating stronger forces at a depth

A. Sarwar; A. Nemirovski; B. Shapiro

22

Magnet Guideways for Superconducting Maglevs: Comparison Between Halbach-Type and Conventional Arrangements of Permanent Magnets  

NASA Astrophysics Data System (ADS)

The characteristics of the permanent magnets composing the guideway in superconducting magnetic levitation devices are very important for their performance in terms of levitation force and stability. From a model based on minimizing the magnetic energy in the superconductor and considering realistic parameters of actual maglev devices, we calculate the levitation and guidance forces and stability arising from both conventional arrangements and recently proposed Halbach-like arrangements. When a comparison is carefully made under similar conditions, we conclude that not always complicated arrangements based on Halbach arrays bring significant improvements with respect to some simpler arrangements that also provide large force. These results may help improving the design of actual maglev devices.

Del-Valle, Nuria; Sanchez, Alvaro; Navau, Carles; Chen, Du-Xing

2011-01-01

23

Magnet arrays for synchronous machines  

Microsoft Academic Search

The authors demonstrate that the Halbach array is highly applicable for magnetic excitation in synchronous machines. To this end, they present the geometry of Halbach arrays in Cartesian, polar, and cylindrical coordinates. They also present the design of a Cartesian linear motor which has been optimized for use in conjunction with a class of high-precision magnetic suspension stages for photolithography.

David L. Trumper; Mark E. Williams; Tiep H. Nguyen

1993-01-01

24

Inductional Effects in a Halbach Magnet Motion Above Distributed Inductance  

NASA Astrophysics Data System (ADS)

We experimented with attempts to levitate a linear (bar) Halbach array of five 1" Nd magnets above a linear inductive track. Next, in order to achieve a control over the relative velocity, we designed a different experiment. In it a large wheel with circumferentially positioned along its rim inducting coils rotates, while the magnet is suspended directly above the rim of the wheel on a force sensor. Faraday’s Law with the Lenz's Rule is responsible for the lifting and drag forces on the magnet; the horizontal drag force is measured by another force sensor. Approximating the magnet's linear relative motion over inductors with a motion along a large circle, we may use formulas derived earlier in the literature for linear inductive levitation. We measured lift and drag forces as functions of relative velocity of the Halbach magnet and the inductive ``track,'' in an approximate agreement with the existing theory. We then vary the inductance and shape of the inductive elements to find the most beneficial choice for the lift/drag ratio at the lowest relative speed.

Tchatchoua, Yves; Conrow, Ary; Kim, Dong; Morgan, Daniel; Majewski, Walerian; Zafar, Zaeema

2013-03-01

25

Halbach array type focusing actuator for small and thin optical data storage device  

NASA Astrophysics Data System (ADS)

The small form factor optical data storage devices are developing rapidly nowadays. Since it is designed for portable and compatibility with flesh memory, its components such as disk, head, focusing actuator, and spindle motor should be assembled within 5 mm. The thickness of focusing actuator is within 2 mm and the total working range is +/-100um, with the resolution of less than 1?m. Since the thickness is limited tightly, it is hard to place the yoke that closes the magnetic circuit and hard to make strong flux density without yoke. Therefore, Halbach array is adopted to increase the magnetic flux of one side without yoke. The proposed Halbach array type focusing actuator has the advantage of thin actuation structure with sacrificing less flex density than conventional magnetic array. The optical head unit is moved on the swing arm type tracking actuator. Focusing coil is attached to swing arm, and Halbach magnet array is positioned at the bottom of deck along the tracking line, and focusing actuator exerts force by the Fleming's left hand rule. The dynamics, working range, control resolution of focusing actuator are analyzed and performed.

Lee, Sung Q.; Park, Kang-Ho; Paek, Mun Chul

2004-09-01

26

Magnetomechanics of internal-dipole, Halbach-array motor\\/generators  

Microsoft Academic Search

The magnetomechanical behavior of internal-dipole, Halbach-type magnet arrays is analyzed for application as a motor\\/generator (M\\/G) with an energy-storage flywheel that is suspended by low-stiffness bearings. Scaling laws for the maximization of torque are derived as a function of geometry. The optimal geometry is relatively insensitive to gap and stator design and occurs approximately at a ratio of inner to

John R. Hull; Larry R. Turner

2000-01-01

27

Magnetomechanics of internal-dipole, Halbach-array motor/generators.  

SciTech Connect

The magnetomechanical behavior of internal-dipole, Halbach-type magnet arrays is analyzed for application as a motor/generator (M/G) with an energy-storage flywheel that is suspended by low-stiffness bearings. Scaling laws for the maximization of torque are derived as a function of geometry. The optimal geometry is relatively insensitive to gap and stator design and occurs approximately at a ratio of inner to outer diameter of the array of 0.8. Values are found for the angular extent of each phase of the stator coil that minimize the stiffness. The negative stiffness of the internal-dipole array is calculated for several manufacturable configurations and is shown to provide an upper limit on the available torque of the M/G according to the positive stiffness of the bearings. Experimental results are reported for an internal-dipole array used as a M/G for a flywheel suspended by a bearing consisting of a permanent-magnet assembly levitated over an array of high-temperature superconductors. Results show that the system is stable and that idling losses are low.

Hull, J. R.; Turner, L. R.; Energy Technology

2000-07-01

28

The art and science of magnet design: Selected notes of Klaus Halbach. Volume 2  

SciTech Connect

This volume contains a compilation of 57 notes written by Dr. Klaus Halbach selected from his collection of over 1650 such documents. It provides an historic snapshot of the evolution of magnet technology and related fields as the notes range from as early as 1965 to the present, and is intended to show the breadth of Dr. Halbach`s interest and ability that have long been an inspiration to his many friends and colleagues. As Halbach is an experimental physicist whose scientific interests span many areas, and who does his most innovative work with pencil and paper rather than at the workbench or with a computer, the vast majority of the notes in this volume were handwritten and their content varies greatly--some reflect original work or work for a specific project, while others are mere clarifications of mathematical calculations or design specifications. As the authors converted the notes to electronic form, some were superficially edited and corrected, while others were extensively re-written to reflect current knowledge and notation. The notes are organized under five categories which reflect their primary content: Beam Position Monitors, (bpm), Current Sheet Electron Magnets (csem), Magnet Theory, (thry), Undulators and Wigglers (u-w), and Miscellaneous (misc). Within the category, they are presented chronologically starting from the most recent note and working backwards in time.

NONE

1995-02-01

29

A portable Halbach magnet that can be opened and closed without force: The NMR-CUFF  

NASA Astrophysics Data System (ADS)

Portable equipment for nuclear magnetic resonance (NMR) is becoming increasingly attractive for use in a variety of applications. One of the main scientific challenges in making NMR portable is the design of light-weight magnets that possess a strong and homogeneous field. Existing NMR magnets can provide such magnetic fields, but only for small samples or in small regions, or are rather heavy. Here we show a simple yet elegant concept for a Halbach-type permanent magnet ring, which can be opened and closed with minimal mechanical force. An analytical solution for an ideal Halbach magnet shows that the magnetic forces cancel if the structure is opened at an angle of 35.3° relative to its poles. A first prototype weighed only 3.1 kg, and provided a flux density of 0.57 T with a homogeneity better than 200 ppm over a spherical volume of 5 mm in diameter without shimming. The force needed to close it was found to be about 20 N. As a demonstration, intact plants were imaged and water (xylem) flow measured. Magnets of this type (NMR-CUFF = Cut-open, Uniform, Force Free) are ideal for portable use and are eminently suited to investigate small or slender objects that are part of a larger or immobile whole, such as branches on a tree, growing fruit on a plant, or non-metallic tubing in industrial installations. This new concept in permanent-magnet design enables the construction of openable, yet strong and homogeneous magnets, which aside from use in NMR or MRI could also be of interest for applications in accelerators, motors, or magnetic bearings.

Windt, Carel W.; Soltner, Helmut; Dusschoten, Dagmar van; Blümler, Peter

2011-01-01

30

Demonstration of Halbach-like magnets for improving microwave window power capacity  

NASA Astrophysics Data System (ADS)

The application of a resonant magnetic field to suppress the multipactor at the vacuum/dielectric interface of a high-power microwave window was theoretically proposed by Chang et al. [Appl. Phys. Lett. 96, 111502 (2010)] and the proof-of-principle was experimentally demonstrated by Chang et al. [Appl. Phys. Lett. 97, 141501 (2010)]. However, for transmitting gigawatt power, conventional large-scale magnets have the significant drawback of a nonuniform and heterogeneous B-field, which enhances the multipactor rather than suppresses it. The Halbach-like magnets for generating the transverse homogeneous B-field in a large scale are studied for suppressing the multipactor; the underlying physics in the particle-in-cell simulation was simulated, and the window breakdown threshold was significantly enhanced at multi-gigawatt.

Chang, Chao; Liu, Yansheng; Ouyang, Xiaoping; Guo, Letian; Wu, Xiaolong; Sun, Xu; Wang, Limin

2014-09-01

31

Magnetic arrays  

DOEpatents

Electromagnet arrays which can provide selected field patterns in either two or three dimensions, and in particular, which can provide single-sided field patterns in two or three dimensions. These features are achieved by providing arrays which have current densities that vary in the windings both parallel to the array and in the direction of array thickness.

Trumper, David L. (Plaistow, NH); Kim, Won-jong (Cambridge, MA); Williams, Mark E. (Pelham, NH)

1997-05-20

32

Magnetic arrays  

DOEpatents

Electromagnet arrays are disclosed which can provide selected field patterns in either two or three dimensions, and in particular, which can provide single-sided field patterns in two or three dimensions. These features are achieved by providing arrays which have current densities that vary in the windings both parallel to the array and in the direction of array thickness. 12 figs.

Trumper, D.L.; Kim, W.; Williams, M.E.

1997-05-20

33

Relaxation-relaxation exchange experiments in porous media with portable Halbach-Magnets.  

NASA Astrophysics Data System (ADS)

Mobile NMR became a powerful tool following the development of portable NMR sensors for well logging. By now there are numerous applications of mobile NMR in materials analysis and chemical engineering where, for example, unique information about the structure, morphology and dynamics of polymers is obtained, and new opportunities are provided for geo-physical investigations [1]. In particular, dynamic information can be retrieved by two-dimensional Laplace exchange NMR, where the initial NMR relaxation environment is correlated with the final relaxation environment of molecules migrating from one environment to the other within a so-called NMR mixing time tm [2]. Relaxation-relaxation exchange experiments of water in inorganic porous media were performed at low and moderately inhomogeneous magnetic field with a simple, portable Halbach-Magnet. By conducting NMR transverse relaxation exchange experiments for several mixing times and converting the results to 2D T2 distributions (joint probability densities of transverse relaxation times T2) with the help of the inverse 2D Laplace Transformation (ILT), we obtained characteristic exchange times for different pore sizes. The results of first experiments on soil samples are reported, which reveal information about the complex pore structure of soil and the moisture content. References: 1. B. Blümich, J. Mauler, A. Haber, J. Perlo, E. Danieli, F. Casanova, Mobile NMR for Geo-Physical Analysis and Material Testing, Petroleum Science, xx (2009) xxx - xxx. 2. K. E. Washburn, P.T. Callaghan, Tracking pore to pore exchange using relaxation exchange spectroscopy, Phys. Rev. Lett. 97 (2006) 175502.

Haber, A.; Haber-Pohlmeier, S.; Casanova, F.; Blümich, B.

2009-04-01

34

Two dimensional exchange NMR experiments of natural porous media with portable Halbach-Magnets  

NASA Astrophysics Data System (ADS)

The characterization of pore space and connectivity in soils of different textures is one topic within Cluster A, Partial Project A1. For this purpose low field mobile NMR became a powerful tool following the development of portable NMR sensors for well logging. By now there are numerous applications of mobile NMR in materials analysis and chemical engineering where, for example, unique information about the structure, morphology and dynamics of polymers is obtained, and new opportunities are provided for geophysical investigations [1]. In particular, dynamic information can be retrieved by two-dimensional Laplace exchange NMR, where the initial NMR relaxation environment is correlated with the final relaxation environment of molecules migrating from one environment to the other within a so-called NMR mixing time tm [2]. Relaxation-relaxation exchange experiments were performed with saturated and un-saturated soil samples at low and moderately inhomogeneous magnetic field with a simple, portable Halbach-Magnet. By conducting NMR transverse relaxation exchange experiments for several mixing times and inverting the results to 2D T2 distributions (similar to joint probability densities of transverse relaxation times T2) with the help of inverse 2D Laplace Transformation (ILT), we observed characteristic exchange processes: Soils consisting mainly of silt and clay components show predominantly exchange between the smaller pores at mixing times of some milliseconds. In addition, there exists also weaker exchange with the larger pores observable for longer mixing time. In contrast to that fine sand exhibits 2D T2 distributions with no exchange processes which can be interpreted that water molecules move within pores of the same size class. These results will be compared to the exchange behaviour under unsaturated conditions. References: 1. B. Blümich, J. Mauler, A. Haber, J. Perlo, E. Danieli, F. Casanova, Mobile NMR for geophysical analysis and material testing, Petroleum Science 6 (2009) 1-7. 2. K. E. Washburn, P.T. Callaghan, Tracking pore to pore exchange using relaxation exchange spectroscopy, Phys. Rev. Lett. 97 (2006) 175502.

Haber, Agnes; Haber-Pohlmeier, Sabina; Casanova, Federico; Blümich, Bernhard

2010-05-01

35

The application of Halbach cylinders to brushless ac servo motors  

SciTech Connect

Halbach cylinders are applied to brushless ac servo motors. It is shown that a sinusoidal back-emf waveform and a low cogging torque can be achieved without recourse to conventional design features such as distributed windings and/or stator/rotor skew. A technique for imparting a multipole Halbach magnetization distribution on an isotropic permanent magnet cylinder is described, and it is shown that the torque capability of a Halbach ac servo motor can be up to 33% higher than conventional brushless permanent magnet ac motors.

Atallah, K.; Howe, D. [Univ. of Sheffield (United Kingdom). Dept. of Electronic and Electrical Engineering] [Univ. of Sheffield (United Kingdom). Dept. of Electronic and Electrical Engineering

1998-07-01

36

Structural parameter optimization design for Halbach permanent maglev rail  

NASA Astrophysics Data System (ADS)

Maglev rail is an important part of the magnetic levitation launch system. Reducing the manufacturing cost of magnetic levitation rail is the key problem for the development of magnetic levitation launch system. The Halbach permanent array has an advantage that the fundamental spatial field is cancelled on one side of the array while the field on the other side is enhanced. So this array used in the design of high temperature superconducting permanent maglev rail could improve the surface magnetic field and the levitation force. In order to make the best use of Nd-Fe-B (NdFeB) material and reduce the cost of maglev rail, the effect of the rail’s structural parameters on levitation force and the utilization rate of NdFeB material are analyzed. The optimal ranges of these structural parameters are obtained. The mutual impact of these parameters is also discussed. The optimization method of these structure parameters is proposed at the end of this paper.

Guo, F.; Tang, Y.; Ren, L.; Li, J.

2010-11-01

37

Magnetic field-assisted hydrothermal synthesis of magnetic microwire arrays  

NASA Astrophysics Data System (ADS)

Using magnetic force lines as invisible template, cobalt microwire arrays, which are formed by cobalt nanoparticles and array along the direction of magnetic force lines, have been successfully obtained. It was confirmed that strong interaction between the synthetic magnetic material and the magnet template has a key effect on the formation of the arrays while weak interaction leads to the formation of individual microwires. This result provides us a new idea that the magnetic force lines could be an ideal template for magnetic material arrays and by controlling the arraying manner of magnet templates, different magnetic patterns could be obtained.

Pang, Huan; Gao, Feng; Guan, Lina; Huang, Yiming; Lu, Qingyi

2009-11-01

38

Magnetic Activated Cell Sorting using Microfabricated Arrays  

Microsoft Academic Search

Magnetic Activated Cell Sorting (MACS) isolates rare cells from whole blood by binding the cells to anti-body labeled paramagnetic beads. The blood is passed through a column with a high magnetic field gradient that traps the paramagnetic beads. We are interested in introducing the isolated cells into microfabricated arrays for further analysis. For this purpose, it is necessary to work

Judith Castelino; Robert Austin

2000-01-01

39

Magnetic force microscopy studies of submicron and nanoscale magnet arrays  

NASA Astrophysics Data System (ADS)

Magnetic structure and magnetization reversal of lithographically patterned submicron and nanometer scaled magnets with elliptical, disk, ring shapes, and pseudo spin valve structures, were studied by magnetic force microscopy. Magnetic measurements were performed with a custom built vacuum magnetic force microscopy with in-situ in plane magnetic fields. The MFM has been optimized with a force gradient sensitivity as high as 1 x 10-6 N/m. By using various magnetic tips, operating in different modes, and studying different samples, the effect of the magnetic tip stray field induced distortion of the magnetic state of a submicron sized magnet is presented. Through the systematic study, a method of how to detect and to avoid these irreversible distortions is also presented. A local 'hysteresis loop' technique has been invented to study the abrupt switching behavior of individual elements. In arrays of elongated magnetic particle array, the aspect ratio dependence of the switching indicates that the vortex state can be trapped inside the elements and form an energetic stable state, leading to a broad switching field distribution. In an array of 70 nm wide pseudo spin valve elements, parallel and antiparallel single domain configurations are found. Major and minor hysteresis loops as well as inter-layer coupling are investigated. We found that interlayer coupling leads to switching field variations. In a Permalloy disk array, the vortex state with vortex core singularity is found. The switching mechanism through the nucleation and annihilation processes is demonstrated by the local hysteresis loop. An interdot coupling-induced anisotropic switching is observed. In Permalloy ring structures, a vortex state and an 'onion' state are found. The onion state in permalloy rings with diameters of 5mum is found to be a flux closure state with a head to head domain wall. The switching behavior of these ring elements is found to be domain wall propagation.

Zhu, Xiaobin

40

Magnetic flux array for spontaneous magnetic reconnection experiments A. Kesich, J. Bonde, J. Egedal,a  

E-print Network

Magnetic flux array for spontaneous magnetic reconnection experiments A. Kesich, J. Bonde, J; published online 24 June 2008 Experimental investigation of reconnection in magnetized plasmas relies on accurate characterization of the evolving magnetic fields. In experimental configurations where the plasma

Egedal, Jan

41

The Inductrack Approach to Magnetic Levitation  

SciTech Connect

Concepts developed during research on passive magnetic bearing systems at the Lawrence Livermore National Laboratory gave rise to a new approach to magnetic levitation, the Inductrack. A passive induced-current system employing permanent magnets on the moving vehicle, the Inductrack maximizes levitation forces by a combination of two elements. First, the permanent magnets on the vehicle are arranged in a ''Halbach array,'' a magnet configuration that optimally produces a periodic magnetic field below the array, while canceling the field above the array. Second, the track is made up of close-packed shorted electrical circuits. These circuits couple optimally to the magnetic field of the Halbach array. As a result, levitating forces of order 40 metric tonnes per square meter of Halbach array can be generated, using NdFeB magnets whose weight is a few percent of the levitated weight. Being an induced-current system, the levitation requires motion of the vehicle above a low transition speed. For maglev applications this speed is a few kilometers per hour, walking speed. At rest or in the station auxiliary wheels are needed. The Inductrack is thus fail-safe, that is, drive system failure would only result in the vehicle slowing down and finally settling on its auxiliary wheels. On the basis of theoretical analyses a small model vehicle and a 20-meter-long track was built and tested at speeds of order 12 meters per second. A second model, designed to achieve 10-g acceleration levels and much higher speeds, is under construction under NASA sponsorship, en route to the design of maglev-based launchers for rockets. Some of the presently perceived practical problems of implementing full-scale maglev systems based on the Inductrack concept will be discussed.

Post, R.F.; Ryutov, D.D.

2000-04-19

42

Model Based Commutation Containing Edge Coils for a Moving Magnet Planar Actuator  

NASA Astrophysics Data System (ADS)

An extension of a special analytical commutation method for long-stroke magnetically levitated moving magnet type planar actuators is presented. It enables the use of coils that are influenced by the end-effect of the Halbach magnet array. They are located near the edge of the magnet array and are referred to as edge coils. The method adds those coils to the commutation correcting for the end-effect by modeling it as a multiplicative error in the commutation. As a result thermal losses are decreased while the error in the commutation is kept in the same order of magnitude. Experiments support the results.

Achterberg, J.; Rovers, J. M. M.; Lierop, C. M. M. Van; Jansen, J. W.; Bosch, P. P. J. Van Den; Lomonova, E. A.

43

A Novel Method of Arraying Permanent Magnets Circumferentially to Generate a Rotation Magnetic Field  

Microsoft Academic Search

An outer magnetic field is extensively applied to drive the movement of a clinic micro-robot. However, how to produce a suitable magnetic field is a complicated problem. Commonly, the drive magnetic field is generated by a combination of power coils. This paper presents a novel method that circumferentially arrays identical permanent magnets to generate a rotational magnetic field in the

Wei Zhang; Yonggang Meng; Ping Huang

2008-01-01

44

Micro eddy current testing by micro magnetic sensor array  

Microsoft Academic Search

A micro Eddy Current Testing (ECT) system for planar thin specimens made of INCONEL 600 with flaws was proposed and developed. A micro ECT probe used here consists of a conventional pancake-type coil as an exciting coil and a micro magnetic sensor array as a set of pickup coils. Magnetic field perturbation due to a flaw was measured with high

Mitsuru Uesaka; Takahiro Nakanishi; Kenzo Miya; Hidenobu Komatsu; Kazuhiko Aoki; Kazuo Kasai

1995-01-01

45

Effect of magnetic yoke on magnetic field distribution and intercepting effect of multi-channel cascading magnet arrays  

NASA Astrophysics Data System (ADS)

`Magnetic-Sieve' possesses a potential use in oxygen separation. The effect of a magnetic yoke on magnetic field distribution and intercepting effect of multi-channel cascading magnet arrays in a `Magnetic-Sieve' configuration is studied by ANSYS finite element software. The multi-channel cascading magnet arrays consist of cuboid neodymium-iron-boron permanent magnets. The size of the magnets is W×H = 38 mm×5 mm, and the clearance between two adjacent magnets is 1 mm. The results show that the intercepting effect tends to decrease from the central channel to the most lateral channels in multi-channel cascading magnet arrays. Compared with the simulation result of two magnets, the central magnetic inductions of the center channel and the most lateral channels in the multi-channel cascading magnet array including 14 magnets decrease respectively 10% and 31%, and the intercepting effects of the center channel and the most lateral channels decrease 19% and 60%, respectively. When the magnetic yoke is added on the multi-channel cascading magnet array, the above-mentioned four values are increased by 28%, 29%, 63% and 65%, respectively. The simulation study shows that the introducing of magnetic yokes can enhance the central magnetic induction and the intercepting effect of the gradient magnetic field, and moreover, reduce the disparities of intercepting effect among the channels.

Zhang, S. P.; Wu, P.; Wang, L.; Li, F. C.; Chen, S.; Sun, S. F.

2010-03-01

46

Fabrication, characterization and applications of magnetic nanowire arrays  

NASA Astrophysics Data System (ADS)

Fe-Co-Ni ternary alloy nanowire arrays 32--106 nm in diameter are fabricated within nanoporous alumina membranes using 15 Vrms alternating current electrodeposition at frequencies of 50, 250, 500, 750, and 1000 Hz. The alumina membranes, 10--15 microns thick, are synthesized by anodization of aluminum foil using a two-step technique to increase pore uniformity. The alumina membrane structure is tailored with the end aim being uniform magnetic nanowire electrodeposition. Using an electrodeposition frequency of 1000 Hz, 15 Vrms, consistently and repeatably yield nanowire arrays over membranes several cm2 in extent. Electrochemical Impedance Spectroscopy (EIS) is used to explain the effects of AC electrodeposition frequency. The impedance of the residual alumina barrier layer, separating the underlying aluminum metal and the nanoporous membrane, decreases drastically with electrodeposition frequency facilitating uniform pore-filling of samples several cm2 in area. The magnetic coercivity and hysteresis loop squareness-ratio (Mr/Ms) were studied as functions of electrolyte composition, nanowire diameter, and nanowire aspect ratio. Anodic polarization studies on thin films having alloy compositions identical to the nanowires display excellent corrosion resistance properties. Two potential applications of the nanowire arrays are investigated. Iron nanowire arrays, oriented perpendicular to the substrate, are fabricated by electrodeposition of iron in nanoporous alumina membranes, followed by precise wet etching of the alumina membrane to partially expose the nanowire array. It is shown that oxidation of standing iron nanowire arrays, at 600°C in an oxygen ambient leads to standing alpha-Fe2O3 (hematite) nanowire arrays. These hematite nanowire arrays show a distinct photocurrent response and can be used as photocatalysts. Second, protein adsorption studies on standing Fe-Co-Ni nanowire arrays and flat Fe-Co-Ni thin films show that nanowire array morphology leads to attenuation of protein adsorption. Since protein adsorption is the first step in the biofouling process magnetic nanowire arrays can potentially find applications as non-biofouling surfaces. Placing magnetic nanowire arrays in a sinusoidally varying magnetic field leads to their oscillation that further reduces protein adsorption in comparison to stationary nanowire arrays.

Sharma, Gaurav

47

Multilayer phased microcoil array for magnetic resonance imaging  

Microsoft Academic Search

We present for the first time wirebonded microcoils arranged in a planar phased-array configuration for large field of view (FOV) microscale magnetic resonance imaging (MRI) of 2D samples. The phased array consists of seven microcoils providing a sensitive area of 18.3 mm 2 . We demonstrate successful high-resolution imaging of a water phantom with 16 x 16 ?? m 2

O. G. Gruschke; L. Clad; N. Baxan; K. Kratt; M. Mohmmadzadeh; D. von Elverfeldt; A. Peter; J. Hennig; V. Badilita; U. Wallrabe; J. G. Korvink

2011-01-01

48

Single magnet levitation by repulsion using a planar coil array  

Microsoft Academic Search

This paper describes the controlled levitation of a single disk magnet above an array of cylindrical coils, using electromagnetic repulsion to generate actuation forces and torques from coil currents, and an optical motion tracking system to provide realtime position and orientation measurements for feedback control. Our method is to measure the electromagnetic forces and torques generated from a single cylindrical

Peter Berkelman; Michael Dzadovsky

2008-01-01

49

Array combination for parallel imaging in Magnetic Resonance Imaging  

E-print Network

In Magnetic Resonance Imaging, the time required to generate an image is proportional to the number of steps used to encode the spatial information. In rapid imaging, an array of coil elements and receivers are used to reduce the number of encoding...

Spence, Dan Kenrick

2007-09-17

50

Emerging magnetic stability in atomically assembled spin arrays  

NASA Astrophysics Data System (ADS)

Magnetic stability is usually created by the interaction of a large ensemble of atomically small magnetic moments that are themselves unstable. We make use of the Scanning Tunneling Microscope's ability to move individual atoms and construct arrays of interacting spins. Owed to their smallness, the magnetic states of these spin arrays are quantized and we probe their energies by inelastic electron tunneling spectroscopy [1]. To gain access to the equally important dynamical properties we employ an all-electronic pump-probe measurement scheme with which we follow the evolution between the spin states at nanosecond speed [2]. The combination of energetic and dynamical information allows identification of the relevant spin interaction and spin relaxation mechanisms at the atomic level. We design arrangements of atoms that suppress quantum tunneling of magnetization and drastically stabilize different spin configurations. Tracing the emergence of magnetic stability in the progression from individual atoms to arrays of spins points to new avenues for spintronic applications at atomic dimensions. [4pt] [1] A. J. Heinrich, J. A. Gupta, C. P. Lutz, D. M. Eigler, Science 306 466 (2004).[0pt] [2] S. Loth, M. Etzkorn, C. P. Lutz, D. M. Eigler, A. J. Heinrich, Science 329 1628 (2010).

Loth, Sebastian; Baumann, Susanne; Lutz, Christopher P.; Eigler, D. M.; Heinrich, Andreas J.

2012-02-01

51

Superconducting arrays in a magnetic field: Quantum effects  

SciTech Connect

We consider a Josephson-coupled superconducting array with finite quantum fluctuations, arising from a nonzero capacitive charging energy, placed in a transverse magnetic field. To estimate the superconducting transition temperature as a function of magnetic field, we introduce a Hartree-type mean-field approximation. With no applied magnetic field, this approximation is very similar to that of Simanek, but unlike the latter, it does not lead to a reentrant normal phase transition. Reentrance is absent because we include no 4..pi..-periodic eigenstates of Mathieu's equation in calculating quantum-statistical expectation values. We argue that these 4..pi..-periodic functions are properly omitted because the original Hamiltonian does not include pair-breaking terms. With charging energies included, we find the transition temperature to be highly nonmonotonic in magnetic field, just as in the zero-capacitance limit. For every field B, there exists an upper critical charging energy U/sub c/(B) above which the array is normal even at T = 0; this charging energy is highly nonmonotonic in field. A brief comparison is made between our results and other recent calculations involving superconducting arrays in the presence of charging energies.

Fishman, R.S.; Stroud, D.

1987-02-01

52

Life on Magnets: Stem Cell Networking on Micro-Magnet Arrays  

PubMed Central

Interactions between a micro-magnet array and living cells may guide the establishment of cell networks due to the cellular response to a magnetic field. To manipulate mesenchymal stem cells free of magnetic nanoparticles by a high magnetic field gradient, we used high quality micro-patterned NdFeB films around which the stray field’s value and direction drastically change across the cell body. Such micro-magnet arrays coated with parylene produce high magnetic field gradients that affect the cells in two main ways: i) causing cell migration and adherence to a covered magnetic surface and ii) elongating the cells in the directions parallel to the edges of the micro-magnet. To explain these effects, three putative mechanisms that incorporate both physical and biological factors influencing the cells are suggested. It is shown that the static high magnetic field gradient generated by the micro-magnet arrays are capable of assisting cell migration to those areas with the strongest magnetic field gradient, thereby allowing the build up of tunable interconnected stem cell networks, which is an elegant route for tissue engineering and regenerative medicine. PMID:23936425

Zablotskii, Vitalii; Dejneka, Alexandr; Kubinova, Sarka; Le-Roy, Damien; Dumas-Bouchiat, Frederic; Givord, Dominique; Dempsey, Nora M.; Sykova, Eva

2013-01-01

53

The Square Kilometre Array: A new probe of cosmic magnetism  

E-print Network

Magnetic fields are a fundamental part of many astrophysical phenomena, but the evolution, structure and origin of magnetic fields are still unresolved problems in physics and astrophysics. When and how were the first fields generated? Are present-day magnetic fields the result of standard dynamo action, or do they represent rapid or recent field amplification through other processes? What role do magnetic fields play in turbulence, cosmic ray acceleration and structure formation? I explain how the Square Kilometre Array (SKA), a next-generation radio telescope, can deliver stunning new data-sets that will address these currently unanswered issues. The foundation for these experiments will be an all-sky survey of rotation measures, in which Faraday rotation toward >10^7 background sources will provide a dense grid for probing magnetism in the Milky Way, nearby galaxies, and in distant galaxies, clusters and protogalaxies. Using these data, we can map out the evolution of magnetized structures from redshifts z > 3 to the present, can distinguish between different origins for seed magnetic fields in galaxies, and can develop a detailed model of the magnetic field geometry of the intergalactic medium and of the overall Universe. In addition, the SKA will certainly discover new magnetic phenomena beyond what we can currently predict or imagine.

Bryan M. Gaensler

2006-03-02

54

Micro Eddy Current Testing by micro magnetic sensor array  

SciTech Connect

A micro Eddy Current Testing (ECT) system for planar thin specimens made of INCONEL 600 with flaws was proposed and developed. A micro ECT probe used here consists of a conventional pancake-type coil as an exciting coil and a micro magnetic sensor array as a set of pickup coils. Magnetic field perturbation due to a flaw was measured with high spatial resolution and signal-to-noise (S/N) ratio. The measured signals from the array were compared with numerical results obtained by a three-dimensional A-[phi] code. It was confirmed that the Micro ECT system has the potential to evaluate the length and depth of a flaw with better accuracy than that of a conventional pancake-type ECT in the stream generator tubings in a pressurized water nuclear reactor.

Uesaka, Mitsuru; Nakanishi, Takahiro; Miya, Kenzo (Univ. of Tokyo, Ibaraki (Japan). Nuclear Engineering Research Lab.); Komatsu, Hidenobu; Aoki, Kazuhiko (Nuclear Fuel Industries, Ltd., Osaka (Japan)); Kasai, Kazuo (Sumitomo Precision Co. Ltd., Hyogo (Japan))

1995-01-01

55

Rogowski Coil Array for Collisionless Magnetic Reconnection Experiments at VTF  

NASA Astrophysics Data System (ADS)

Recent experiments on magnetic reconnection at the Versatile Toroidal Facility (VTF) indicate that the electron current may become filamented during spontaneous reconnection events [1]. A new array of Rogowski coils, which has centimeter-scale resolution, will measure the parallel currents driven by fast reconnection in the presence of a guide magnetic field. The diagnostic should confirm the filamentary structure of the current profile, determine the distribution of filaments around the X-line, and reveal when the filaments are generated with respect to the onset of reconnection. In addition, multi-shot scans performed by moving the Rogowski coil array across a poloidal section and to several different toroidal angles will yield high-resolution measurements of the reproducible features of the current profile that develops during three-dimensional reconnection at VTF. Preliminary data will be presented if available.[1ex] [1] J. Egedal et al., Phys. Rev. Lett., 98, 015003 (2007)

Le, A.; Egedal, J.; Fox, W.; Katz, N.; Vrublevskis, A.; Porkolab, M.

2009-11-01

56

Magnetic properties of lithographically defined rectangular antidot permalloy arrays  

NASA Astrophysics Data System (ADS)

We have investigated the magnetic properties of rectangular antidot (2×10?m2) arrays embedded into 80nm thick continuous permalloy films with the inter-hole spacing of 2 and 6?m. We observed that the presence of the rectangular hole structures strongly modifies the shape of M-H loops, when compared with the reference continuous film. Specifically, the coercivity increases drastically as the inter-hole spacing is reduced. This is in agreement with our magnetic force microscopy images. Marked changes in both the shape and sign of the magnetoresistance curve were also observed.

Wang, C. C.; Adeyeye, A. O.; Lin, C. C.

2004-05-01

57

Magnetic properties of lithographically defined rectangular antidot permalloy arrays  

NASA Astrophysics Data System (ADS)

We have investigated the magnetic properties of rectangular antidot (2×10 ?m2) arrays embedded into 80 nm thick continuous permalloy films with the inter-hole spacing of 2 and 6 ?m. We observed that the presence of the rectangular hole structures strongly modifies the shape of M- H loops, when compared with the reference continuous film. Specifically, the coercivity increases drastically as the inter-hole spacing is reduced. This is in agreement with our magnetic force microscopy images. Marked changes in both the shape and sign of the magnetoresistance curve were also observed.

Wang, C. C.; Adeyeye, A. O.; Lin, C. C.

58

Domain configuration and magnetization switching in arrays of permalloy nanostripes  

NASA Astrophysics Data System (ADS)

The proximity effect in the collective behavior of arrays of magnetic nanostripes is currently a subject of intensive research. The imperative of reducing the size and distances between elements in order to achieve higher storage capacity, faster access to the information as well as low energy consumption, brings consequences about the isolated behavior of the elements and devices. Parallel to each other permalloy nanostripes with high aspect ratio have been prepared by the nanolithography technique. The evolution of the closure domains and the magnetization direction in individual nanostructures has been imaged under applied magnetic fields using Variable Field Magnetic Force Microscopy. Moreover, the magnetostatic interactions between neighboring elements and the proximity effects in arrays of such nanostructures have been quantitatively analyzed by Magnetic Force Microscopy and micromagnetic simulations. The agreement between simulations and the experimental results allows us to conclude the relevance of those interactions depending on the geometry characteristics. In particular, results suggest that the magnetostatic coupling between adjacent nanostripes vanishes for separation distances higher than 500 nm.

Iglesias-Freire, Ó.; Jaafar, M.; Pérez, L.; de Abril, O.; Vázquez, M.; Asenjo, A.

2014-04-01

59

Self-Assembled Growth and Magnetism of Ordered Cluster Arrays  

NASA Astrophysics Data System (ADS)

It is generally recognized that the fabrication of magnetic storage media with bit densities of Gigabytes per square inch and more is out of reach of currently available thin film technologies. Patterned media may therefore set off to challenge thin film media as they allow in principle for bit densities several orders of magnitude larger than what is currently feasible. In this talk I will show how nanoclusters can be fabricated on substrates directly by self-assembled growth, and how their magnetism and their lateral arrangement on the substrate can be controlled. Buffer layer assisted growth is used to form clusters of controlled density and size, in the range between a few atoms to several nanometers diameter. The clusters are randomly distributed over the bare substrate surface. The cluster nucleation on the buffer layer and their growth after making contact with the substrate was studied with variable temperature scanning tunneling microscopy, and will be discussed in the talk. The investigation of the cluster magnetism with X-ray magnetic circular dichroism revealed size and strain effects as well as mutual dipolar and cluster-substrate interactions. We found a pronounced dependence of the magnetic anisotropy on the substrate material. On Pt, for instance, the preferential magnetization direction is out-of-plane, while it is in-plane on Ag. The application of self-assembled clusters as individually addressable magnetic units requires their controlled arrangement into well-defined ordered arrays. We are therefore guiding the clusters with energetic sinks provided by periodic network structures prefabricated on the substrate. We use mechanically extremely stable, electronically insulating boron nitride nanomesh monolayers as template surfaces. Repeated cluster deposition cycles increase the cluster density on the nanomesh, eventually resulting in an densely packed, ordered cluster array with a cluster-cluster distance corresponding to the BN nanomesh periodicity of 3.2 nm. These cluster layers offer densities of magnetic elements as high as 80 x 10^12 clusters per square inch.

Enders, Axel

2008-03-01

60

Controlling the flux dynamics in superconductors by nanostructured magnetic arrays  

NASA Astrophysics Data System (ADS)

In this thesis we investigate theoretically how the critical current jc of nano-engineered mesoscopic superconducting film can be improved and how one can control the dynamics of the magnetic flux, e.g., the transition from flux-pinned to flux-flow regime, using arrays of magnetic nanostructures. In particularly we investigate: (1) Vortex transport phenomena in superconductors with deposited ferromagnetic structures on top, and the influence of the sample geometry on the critical parameters and on the vortex configurations. Changing geometry of the magnetic bars and magnetization of the bars will affect the critical current jc of the superconducting film. Such nanostructured ferromagnets strongly alter the vortex structure in its neighborhood. The influence of geometry, position and magnetization of the ferromagnet (single bar or regular lattice of the bars) on the critical parameters of the superconductor is investigated. (2) Effect of flux confinement in narrow superconducting channels with zigzag-shaped banks: the flux motion is confined in the transverse (perpendicular) direction of a diamond-cell-shape channel. The matching effect for the magnetic flux is found in the system relevantless of boundary condition. We discuss the dynamics of vortices in the samples and vortex pattern formation in the channel. We show how the inclusion of higher-Tc superconductor into the sample can lead to enhanced properties of the system. By adding an external driving force, we study the vortex dynamics. The different dynamic regimes are discussed. They allowed an effective control of magnetic flux in superconductors.

Kapra, Andrey

61

Dependence of magnetization process on thickness of Permalloy antidot arrays  

SciTech Connect

Nanohole films or antidot arrays of Permalloy have been prepared by the sputtering of Ni{sub 80}Fe{sub 20} onto anodic alumina membrane templates. The film thickness varies from 5 to 47 nm and the antidot diameters go from 42 to 61 nm, for a hexagonal lattice parameter of 105 nm. For the thinner antidot films (5 and 10 nm thick), magnetic moments locally distribute in a complex manner to reduce the magnetostatic energy, and their mostly reversible magnetization process is ascribed to spin rotations. In the case of the thicker (20 and 47 nm) antidot films, pseudodomain walls appear and the magnetization process is mostly irreversible where hysteresis denotes the effect of nanoholes pinning to wall motion.

Merazzo, K. J.; Real, R. P. del; Asenjo, A.; Vazquez, M. [Instituto de Ciencia de Materiales de Madrid, Campus de Cantoblanco, 28049 Madrid (Spain)

2011-04-01

62

Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient  

PubMed Central

Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direct measure of phenomenological parameter ? that describes non-adiabaticity in the current induced magnetization dynamics. This spinmotive force opens a door for new types of spintronic devices that exploit the field-gradient. PMID:25365971

Yamane, Yuta; Hemmatiyan, Shayan; Ieda, Jun'ichi; Maekawa, Sadamichi; Sinova, Jairo

2014-01-01

63

Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient.  

PubMed

Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direct measure of phenomenological parameter ? that describes non-adiabaticity in the current induced magnetization dynamics. This spinmotive force opens a door for new types of spintronic devices that exploit the field-gradient. PMID:25365971

Yamane, Yuta; Hemmatiyan, Shayan; Ieda, Jun'ichi; Maekawa, Sadamichi; Sinova, Jairo

2014-01-01

64

Probing arrays of circular magnetic microdots by ferromagnetic resonance.  

SciTech Connect

X-band ferromagnetic resonance (FMR) was used to characterize in-plane magnetic anisotropies in rectangular and square arrays of circular nickel and Permalloy microdots. In the case of a rectangular lattice, as interdot distances in one direction decrease, the in-plane uniaxial anisotropy field increases, in good agreement with a simple theory of magnetostatically interacting uniformly magnetized dots. In the case of a square lattice a four-fold anisotropy of the in-plane FMR field H(r) was found when the interdot distance a gets comparable to the dot diameter D. This anisotropy, not expected in the case of uniformly magnetized dots, was explained by a non-uniform magnetization m(r) in a dot in response to dipolar forces in the patterned magnetic structure. It is well described by an iterative solution of a continuous variation procedure. In the case of perpendicular magnetization multiple sharp resonance peaks were observed below the main FMR peak in all the samples, and the relative positions of these peaks were independent of the interdot separations. Quantitative description of the observed multiresonance FMR spectra was given using the dipole-exchange spin wave dispersion equation for a perpendicularly magnetized film where in-plane wave vector is quantized due to the finite dot radius, and the inhomogenetiy of the intradot static demagnetization field in the nonellipsoidal dot is taken into account. It was demonstrated that ferromagnetic resonance force microscopy (FMRFM) can be used to determine both local and global properties of patterned submicron ferromagnetic samples. Local spectroscopy together with the possibility to vary the tip-sample spacing enables the separation of those two contributions to a FMRFM spectrum. The global FMR properties of circular submicron dots determined using magnetic resonance force microscopy are in a good agreement with results obtained using conventional FMR and with theoretical descriptions.

Kakazei, G. N.; Mewes, T.; Wigen, P. E.; Hammel, P. C.; Slavin, A. N.; Pogorelov, Y. G.; Costa, M. D.; Golub, V. O.; Guslienko, K. Y.; Novosad, V. (Materials Science Division); (Univ. of Porto); (National Academy of Sciences Ukraine); (Univ. of Alabama); (Ohio State Univ.); (Oakland Univ.)

2008-06-01

65

How finite sample dimensions affect the reversal process of magnetic dot arrays  

NASA Astrophysics Data System (ADS)

We investigate the magnetization reversal of a magnetic dot array by means of magneto-optical Kerr effect and magnetic force microscopy measurements as well as micromagnetic simulations. We find that the finite dimensions of the dot array introduce a global configurational anisotropy that promotes state transitions first in dots near the sample boundaries. From there, the reversal process expands towards the sample body by means of collective magnetization processes originating in the magnetostatic coupling between the dots. These processes are characterized by transition avalanches and the formation of magnetization chains. These findings are important in the development of applications that rely on a robust control of dot magnetization states in dot arrays.

Van de Wiele, Ben; Fin, Samuele; Sarella, Anandakumar; Vavassori, Paolo; Bisero, Diego

2014-10-01

66

SQUID array for magnetic inspection of prestressed concrete bridges  

NASA Astrophysics Data System (ADS)

For detection of tendon ruptures in prestressed members of bridges, a four-channel SQUID system was developed. The tendons are magnetized by scanning a yoke electromagnet over the concrete surface along the hidden member. Four HTS dc-SQUID magnetometers with ramp-type junctions, optimized for high-field performance, are mounted in an orientation-independent liquid nitrogen cryostat. The SQUIDs are integrated as a linear array within the yoke and operated in magnetic fields up to 15 mT, recording the stray field during magnetization as well as the remanent field after switching off the excitation. Unwanted signals from stirrups of the mild steel reinforcement are suppressed with two types of techniques: either the comparison of remanent field signals after changing the magnetization direction of the stirrups, or a best fit of typical stirrup signals to the stray field signal and their subtraction. Subsequent correlation analysis with the dipolar signal of a typical void yields rupture signal amplitudes. A finite element program was written to simulate stray field and remanent field traces of typical steel configurations. Excellent agreement with measured data was found. Results of measurements on a prestressed highway bridge are presented. Signal amplitudes above the threshold values were verified as originating from ruptures of the steel tendon by opening the bridge deck.

Krause, H.-J.; Wolf, W.; Glaas, W.; Zimmermann, E.; Faley, M. I.; Sawade, G.; Mattheus, R.; Neudert, G.; Gampe, U.; Krieger, J.

2002-03-01

67

Vibrational Properties of High- Superconductors Levitated Above a Bipolar Permanent Magnetic Guideway  

NASA Astrophysics Data System (ADS)

A bipolar permanent magnetic guideway (PMG) has a unique magnetic field distribution profile which may introduce a better levitation performance and stability to the high- superconducting (HTS) maglev system. The dynamic vibration properties of multiple YBCO bulks arranged into different arrays positioned above a bipolar PMG and free to levitate were investigated. The acceleration and resonance frequencies were experimentally measured, and the stiffness and damping coefficients were evaluated for dynamic stability. Results indicate that the levitation stiffness is closely related to the field-cooling-height and sample positioning. The damping ratio was found to be low and nonlinear for the Halbach bipolar HTS-PMG system.

Liu, Lu; Wang, Jiasu

2014-05-01

68

Levitation Force Investigation of Bulk HTSC Above Halbach PMG with Different Cross-Section Physical Dimensions by 3D-Modeling Numerical Method  

NASA Astrophysics Data System (ADS)

The levitation force of a bulk high temperature superconductor (HTSC) over Halbach permanent magnet guideways (PMG) with different cross-section configuration is studied by numerical method. The Halbach PMG is composed of three host permanent magnets (HPMs) and two slave permanent magnets (SPMs). One cylindrical bulk HTSC with a diameter of 30 mm and height of 15 mm is used. The 3D-modeling is formulated by the H-method. The numerical resolving codes are practiced using finite element method (FEM). The E-J power law is used to describe the electric current nonlinear characteristics of bulk HTSC. By the method, the influence of the cross-section physical dimensions of Halbach PMG on the levitation forces of bulk HTSC levitated above the PMG is studied. The simulation results show that increasing the width of SPM ( can enhance the bulk HTSC levitation performance immediately under the condition of keeping the ratio of ( : the width of HPM) to between 1.6 and 1.8, the ratio of td (the height of the PMG) to between 1.2 and 1.4. By the method, the bulk HTSC better levitation performance can be expected.

Lu, Yiyun; Liu, Guoliang; Qin, Yujie

2014-10-01

69

Magnetic wire trap arrays for biomarker-based molecular detection  

NASA Astrophysics Data System (ADS)

Submicrometer-scale magnetic devices built on chip-based platforms have recently been shown to present opportunities for new particle trapping and manipulation technologies. Meanwhile, advances in nanoparticle fabrication allow for the building of custom-made particles with precise control of their size, composition, and other properties such as magnetism, fluorescence, and surface biomarker characteristics. In particular, carefully tailored surface biomarkers facilitate precise binding to targeted molecules, self-actuated construction of hybrid structures, and fluorescence-based detection schemes. Based on these progresses, we present an on-chip detection mechanism for molecules with known surface markers. Hybrid nanostructures consisting of micelle nanoparticles, fluorescent quantum dots, and superparamagnetic iron oxide nanoparticles are used to detect proteins or DNA molecules. The target is detected by the magnetic and fluorescent functionalities of the composite nanostructure, whereas in the absence of the target these signals are not present. Underlying this approach is the simultaneous manipulation via ferromagnetic zigzag nanowire arrays and imaging via quantum dot excitation. This chip-based detection technique could provide a powerful, low cost tool for ultrasensitive molecule detection with ramifications in healthcare diagnostics and small-scale chemical synthesis.

Vieira, Gregory; Mahajan, Kalpesh; Ruan, Gang; Winter, Jessica; Sooryakumar, R.

2012-02-01

70

A Mobile Ferromagnetic Shape Detection Sensor Using a Hall Sensor Array and Magnetic Imaging  

PubMed Central

This paper presents a Mobile Hall Sensor Array system for the shape detection of ferromagnetic materials that are embedded in walls or floors. The operation of the Mobile Hall Sensor Array system is based on the principle of magnetic flux leakage to describe the shape of the ferromagnetic material. Two permanent magnets are used to generate the magnetic flux flow. The distribution of magnetic flux is perturbed as the ferromagnetic material is brought near the permanent magnets and the changes in magnetic flux distribution are detected by the 1-D array of the Hall sensor array setup. The process for magnetic imaging of the magnetic flux distribution is done by a signal processing unit before it displays the real time images using a netbook. A signal processing application software is developed for the 1-D Hall sensor array signal acquisition and processing to construct a 2-D array matrix. The processed 1-D Hall sensor array signals are later used to construct the magnetic image of ferromagnetic material based on the voltage signal and the magnetic flux distribution. The experimental results illustrate how the shape of specimens such as square, round and triangle shapes is determined through magnetic images based on the voltage signal and magnetic flux distribution of the specimen. In addition, the magnetic images of actual ferromagnetic objects are also illustrated to prove the functionality of Mobile Hall Sensor Array system for actual shape detection. The results prove that the Mobile Hall Sensor Array system is able to perform magnetic imaging in identifying various ferromagnetic materials. PMID:22346653

Misron, Norhisam; Shin, Ng Wei; Shafie, Suhaidi; Marhaban, Mohd Hamiruce; Mailah, Nashiren Farzilah

2011-01-01

71

Magnetic properties of (Fe, Co)-Pd nanowire arrays.  

PubMed

Ordered arrays of ferromagnetic nanowires with (Fe, Co)-Pd compositions have been fabricated from chloride based electrochemical baths by means of template-assisted electrodeposition into self-assembled nanopores of anodic alumina membranes. The nanowires have a diameter and inter-spacing distance of 72 nm and 105 nm, respectively, and around 0.6-1.6 microm in length. Their microstructure and basic magnetic properties are reported. Coercivity, remanence and respective angular dependences on the applied field up to +/- 3 T have been determined from room temperature hysteresis loops measured in a VSM. The study has been performed paying particular attention to the influence of increasing from about 27 up to 63 percent the Pd content in the nanowire alloy. PMID:23035504

Vega, V; Garcia, J; Rosa, W O; Vivas, L G; Prida, V M; Hernando, B; Vázquez, M

2012-09-01

72

Self-organized magnetic nanowire arrays based on alumina and titania templates.  

PubMed

Densely packed arrays of magnetic nanowires have been synthesized by electrodeposition filling of nanopores in alumina and titania membranes formed by self-assembling during anodization process. Emphasis is made on the control of the production parameters leading to ordering degree and lattice parameter of the array as well as nanowires diameter and length. Structural, morphological and magnetic properties exhibited by nanowire arrays have been studied for several nanowire compositions, different ordering degree and for different nanowire aspect ratios. The magnetic behaviour of nanowires array is governed by the balance between different energy contributions: shape anisotropy of individual nanowires, the magnetostatic interaction of dipolar origin among nanowires, and magnetocrystalline and magnetoelastic anisotropies induced by the pattern templates. These novel nanocomposites, based on ferromagnetic nanowires embedded in anodic nanoporous templates, are becoming promising candidates for technological applications such as functionalised arrays for magnetic sensing, ultrahigh density magnetic storage media or spin-based electronic devices. PMID:17455492

Prida, V M; Pirota, K R; Navas, D; Asenjo, A; Hernández-Vélez, M; Vázquez, M

2007-01-01

73

Planar microcoils array applied to magnetic beads based lab-on-chip for high throughput applications  

Microsoft Academic Search

In some magnetic beads based lab-on-chip (LoC) applications, such as purification and fast cell detection, high throughput capacity is required. In this paper, we propose an optimization method for the implementation of in-channel planar microcoils array. By generating more dispersed trapping centers and exploiting the array scanning scheme, the problem of interaction among magnetic beads is controlled and both power

Yushan Zheng; Sara Bekhiche; Mohamad Sawan

2011-01-01

74

Addition spectra of arrays of interacting quantum dots: Dependence on array geometry and magnetic field  

Microsoft Academic Search

We use the extended Hubbard model to calculate the addition spectra of linear chains and ring-shaped arrays of three, four, and five quantum dots. We find that for linear arrays, the addition spectra obtained with the pure Hubbard model and the pure charging model show no qualitative differences. For rings of quantum dots, however, the Hubbard model always produces doubly

Zhiming Yu; A. T. Johnson; Thomas Heinzel

1998-01-01

75

TOPICAL REVIEW: Magnetism of Fe, Co and Ni nanowires in self-assembled arrays  

NASA Astrophysics Data System (ADS)

Recent work on magnetic properties of transition-metal nanowire arrays produced by electro-deposition is reviewed. The wires, which are electro-deposited into self-assembled porous anodic alumina, form nearly hexagonal arrays characterized by wire diameters down to less than 10 nm, wire lengths up to about 1 µm, and variable centre-to-centre spacings of the order of 50 nm. The fabrication and structural characterization of the arrays is summarized, magnetic data are presented and theoretical explanations of the behaviour of the wires are given. Emphasis is on extrinsic phenomena such as coercivity, magnetization reversal and interactions of the magnetic nanowires. In particular, we analyse how wire imperfections give rise to magnetic localization and dominate the hysteresis behaviour of the wires. Potential applications are outlined in the last section.

Sellmyer, D. J.; Zheng, M.; Skomski, R.

2001-06-01

76

Measurements of the Azimuthal Magnetic Field within Imploding Multiwire Arrays in the Angara-5-1 Facility  

SciTech Connect

Results are presented from measurements of the azimuthal magnetic fields within imploding multiwire tungsten arrays in the Angara-5-1 facility at currents of 2.5-4 MA. It is shown that the penetration of the magnetic field into the axial region of the wire array lags behind the discharge current pulse. The current of a precursor produced at the array axis prior to the implosion of the bulk array mass is measured. It is found that the magnetic field in the initial stage of implosion is azimuthally nonuniform. The mass distribution inside the array is calculated from the measured magnetic field.

Zukakishvili, G.G.; Mitrofanov, K.N.; Aleksandrov, V.V.; Grabovskii, E.V.; Oleinik, G.M.; Porofeev, I.Yu.; Frolov, I.N. [Troitsk Institute for Innovation and Fusion Research, Troitsk, Moscow oblast, 142190 (Russian Federation); Sasorov, P.V. [Institute of Theoretical and Experimental Physics, Bol'shaya Cheremushkinskaya ul. 25, Moscow, 117218 (Russian Federation)

2005-11-15

77

Calibration of a fluxgate magnetometer array and its application in magnetic object localization  

NASA Astrophysics Data System (ADS)

The magnetometer array is effective for magnetic object detection and localization. Calibration is important to improve the accuracy of the magnetometer array. A magnetic sensor array built with four three-axis DM-050 fluxgate magnetometers is designed, which is connected by a cross aluminum frame. In order to improve the accuracy of the magnetometer array, a calibration process is presented. The calibration process includes magnetometer calibration, coordinate transformation and misalignment calibration. The calibration system consists of a magnetic sensor array, a GSM-19T proton magnetometer, a two-dimensional nonmagnetic rotation platform, a 12 V-dc portable power device and two portable computers. After magnetometer calibration, the RMS error has been decreased from an original value of 125.559 nT to a final value of 1.711 nT (a factor of 74). After alignment, the RMS error of misalignment has been decreased from 1322.3 to 6.0 nT (a factor of 220). Then, the calibrated array deployed on the nonmagnetic rotation platform is used for ferromagnetic object localization. Experimental results show that the estimated errors of X, Y and Z axes are -0.049 m, 0.008 m and 0.025 m, respectively. Thus, the magnetometer array is effective for magnetic object detection and localization in three dimensions.

Pang, Hongfeng; Luo, Shitu; Zhang, Qi; Li, Ji; Chen, Dixiang; Pan, Mengchun; Luo, Feilu

2013-07-01

78

Universal temperature behavior of remanent magnetization observed in low- Tc and high- Tc Josephson junction arrays  

NASA Astrophysics Data System (ADS)

A comparative study of the magnetic remanence exhibited by tridimensional Josephson junction arrays in response to an excitation with an AC magnetic field is presented. The observed temperature behavior of the remanence curves for disordered arrays fabricated from three different materials (Nb, YBa 2Cu 3O 7- ? and La 1.85Sr 0.15CuO 4- ?) is found to follow the same universal law (based on the explicit temperature expressions for the activation energy and the inductance-dominated contribution to the magnetization of the array within the framework of the phase-slip model) regardless of the origin of the superconducting electrodes of the junctions which form the array.

Sergeenkov, S.; Passos, W. A. C.; Lisboa-Filho, P. N.; Ortiz, W. A.

2001-12-01

79

Nonlinear excitations in a magnetic quantum dot array with biquadratic interaction  

Microsoft Academic Search

Magnetic quantum dots are promising candidates for applications like quantum computers and data storage devices. We investigate the nonlinear excitations in a coupled magnetic quantum dot array with biquadratic interaction. Starting from the Heisenberg Hamiltonian, which gives the interactive energy, we derive the equations of motion in the semiclassical limit using Glauber's coherent state ansatz combined with the Holstein Primakoff

R. Amuda

2006-01-01

80

Optimization of magnetic sensor arrays for current measurement based on swarm intelligence and D-optimality  

Microsoft Academic Search

Purpose – The purpose of this paper is to improve the accuracy of innovative current transducers based on magnetic sensor arrays. Design\\/methodology\\/approach – The positions and the orientations of the magnetic sensors are optimized. The objective function is defined according to D-optimality theory and the optimization problem solved using particle swarm optimization (PSO). Findings – PSO is shown to be

Z. Zhang; L. Di Rienzo

2009-01-01

81

A decoupled control approach for magnetic suspension systems using electromagnets mounted in a planar array  

NASA Technical Reports Server (NTRS)

A decoupled control approach for a Large Gap Magnetic Suspension System (LGMSS) is presented. The control approach is developed for an LGMSS which provides five degree-of-freedom control of a cylindrical suspended element that contains a core composed of permanent magnet material. The suspended element is levitated above five electromagnets mounted in a planar array. Numerical results are obtained by using the parameters of the Large Angle Magnetic Suspension Test Fixture (LAMSTF) which is a small scale laboratory model LGMSS.

Groom, Nelson J.

1993-01-01

82

Nonlithographic fabrication of 25 nm magnetic nanodot arrays with perpendicular anisotropy over a large area  

SciTech Connect

A simple method is demonstrated to fabricate 25 nm magnetic nanodot arrays with perpendicular anisotropy over 10 cm{sup 2} coverage area. The nanodot arrays are fabricated by depositing Co/Pt multilayers (MLs) onto the SiO{sub 2} dot arrays formed on a Si wafer. At first, arrays of the SiO{sub 2} dots are fabricated on a Si wafer by anodizing a thin Al film deposited on it. The SiO{sub 2} dots are formed at the base of the anodized alumina (AAO) pores due to the selective oxidation of the Si through the AAO pores during over anodization of the Al film. The average diameter, periodicity, and height of the SiO{sub 2} dots are about 24, 43, and 17 nm, respectively. Then (Co(0.4 nm)/Pt(0.08 nm)){sub 8} MLs with a 3 nm Pt buffer layer is deposited onto the SiO{sub 2} dot arrays by sputtering. The average diameter and periodicity of the Co/Pt nanodot arrays are 25.4 and 43 nm, respectively, with narrow distribution. The nanodot arrays exhibit strong perpendicular anisotropy with a squareness ratio of unity and negative nucleation fields. The coercivity of the nanodot arrays is about one order higher than that of the continuous film, i.e., the same structure deposited on the SiO{sub 2} substrate. The magnetization reversal of the continuous film is governed by domain-wall motion, while the magnetization reversal of the nanodot arrays is dominated by the Stoner-Wohlfarth-like rotation. These results indicate that the fabricated structure can be considered as an isolated nanodot array.

Rahman, M. Tofizur; Shams, Nazmun N.; Lai, C.-H. [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

2009-04-01

83

Fabrication and magnetic properties of Fe 3O 4 nanowire arrays in different diameters  

NASA Astrophysics Data System (ADS)

Fe 3O 4 nanowire arrays with different diameters of D=50, 100, 150 and 200 nm were prepared in anodic aluminum oxide (AAO) templates by an electrodeposition method followed by heat-treating processes. A vibrating sample magnetometer (VSM) and a Quantum Design SQUID MPMS magnetometer were used to investigate the magnetic properties. At room temperature the nanowire arrays change from superparamagnetism to ferromagnetism as the diameter increases from 50 to 200 nm. The zero-field-cooled (ZFC) and field-cooled (FC) magnetization measurements show that the blocking temperature TB increases with the diameter of nanowire. The ZFC curves of D=50 nm nanowire arrays under different applied fields ( H) were measured and a power relationship between TB and H were found. The temperature dependence of coercivity below TB was also investigated. Mössbauer spectra and micromagnetic simulation were used to study the micro-magnetic structure of nanowire arrays and the static distribution of magnetic moments of D=200 nm nanowire arrays was investigated. The unique magnetic behaviors were interpreted by the competition of the demagnetization energy of quasi-one-dimensional nanostructures and the magnetocrystalline anisotropy energy of particles in nanowires.

Zhang, Liying; Zhang, Yafei

2009-03-01

84

Two-Slotted Surface Coil Array for Magnetic Resonance Imaging at 4 Tesla  

SciTech Connect

Arrays of antennas have been widely accepted for magnetic resonance imaging applications due to their high signal-to-noise ratio (SNR) over large volumes of interest. A new surface coil based on the magnetron tube and called slotted surface coil, has been recently introduced by our group. This coil design experimentally demonstrated a significant improvement over the circular-shaped coil when used in the receive-only mode. The slotted coils formed a two-sheet structure with a 90 deg. separation and each coil had 6 circular slots. Numerical simulations were performed using the finite element method for this coil design to study the behaviour of the array magnetic field. Then, we developed a two-coil array for brain magnetic resonance imaging to be operated at the resonant frequency of 170 MHz in the transceiver mode. Phantom images were acquired with our coil array and standard pulse sequences on a research-dedicated 4 Tesla scanner. Numerical simulations demonstrated that electromagnetic interaction between the coil elements is negligible, and that the magnetic field showed a good uniformity. In vitro images showed the feasibility of this coil array for standard pulses for high field magnetic resonance imaging.

Solis, S. E. [Medical Department, Brookhaven National Laboratory, Upton, N.Y. 11973 (United States); Centro de Investigacion e Instrumentacion e Imagenologia Medica, Universidad Autonoma Metropolitana Iztapalapa, Mexico, DF 09340 (Mexico); Hernandez, J. A.; Rodriguez, A. O. [Centro de Investigacion e Instrumentacion e Imagenologia Medica, Universidad Autonoma Metropolitana Iztapalapa, Mexico, DF 09340 (Mexico); Tomasi, D. [Medical Department, Brookhaven National Laboratory, Upton, N.Y. 11973 (United States)

2008-08-11

85

Stabilizing a magnetic vortex/antivortex array in single crystalline Fe/Ag(001) microstructures  

NASA Astrophysics Data System (ADS)

While a magnetic antivortex state can be created in ring structures, much effort has been devoted to stabilizing a magnetic antivortex as the ground state in a single island. Among many proposals, less attention has been paid to the role of magnetocrystalline anisotropy because most magnetic microstructures are made of polycrystalline materials. By patterning epitaxial Fe/Ag(001) films along different in-plane directions, we show that the Fe magnetocrystalline anisotropy plays a very important role in stabilizing different types of vortex/antivortex states. In particular, we find that an Fe island in the shape of an elongated hexagon favors vortex array formation when the long edge is parallel to the Fe easy magnetization axis, and favors the vortex-antivortex array formation when the long edge is parallel to the Fe hard magnetization axis.

Li, J.; Tan, A.; Moon, K. W.; Doran, A.; Marcus, M. A.; Young, A. T.; Arenholz, E.; Ma, S.; Yang, R. F.; Hwang, C.; Qiu, Z. Q.

2014-06-01

86

Magnetic wall decoupling method for monopole coil array in ultrahigh field MRI: a feasibility test.  

PubMed

Ultrahigh field (UHF) MR imaging of deeply located target in high dielectric biological samples faces challenges due to the reduced penetration depth at the corresponding high frequencies. Radiative coils, e.g., dipole and monopole coils, have recently been applied for UHF MRI applications to obtain better signal-noise-ratio (SNR) in the area deep inside the human head and body. However, due to the unique structure of radiative coil elements, electromagnetic (EM) coupling between elements in radiative coil arrays cannot be readily addressed by using traditional decoupling methods such as element overlapping and L/C decoupling network. A new decoupling method based on induced current elimination (ICE) or magnetic wall technique has recently been proposed and has demonstrated feasibility in designing microstrip transmission line (MTL) arrays and L/C loop arrays. In this study, an array of two monopole elements decoupled using magnetic wall decoupling technique was designed, constructed and analyzed numerically and experimentally to investigate the feasibility of the decoupling technique in radiative coil array designs for MR imaging at 7 T. An L-shaped capacitive network was employed as the matching circuit and the reflection coefficients (S11) of the monopole element achieved -30 dB or better. Isolation between the two monopole elements was improved from about -10 dB (without decoupling treatment) to better than -30 dB with the ICE/magnetic wall decoupling method. B1 maps and MR images of the phantom were acquired and SNR maps were measured and calculated to evaluate the performance of the ICE/magnetic wall decoupling method. Compared with the monopole elements without decoupling methods, the ICE-decoupled array demonstrated more independent image profiles from each element and had a higher SNR in the peripheral area of the imaging subject. The experimental and simulation results indicate that the ICE/magnetic wall decoupling technique might be a promising solution to reducing the EM coupling of monopole arrays for UHF MRI. PMID:24834419

Yan, Xinqiang; Zhang, Xiaoliang; Wei, Long; Xue, Rong

2014-04-01

87

Synthesis, Magnetic Anisotropy and Optical Properties of Preferred Oriented Zinc Ferrite Nanowire Arrays  

PubMed Central

Preferred oriented ZnFe2O4 nanowire arrays with an average diameter of 16 nm were fabricated by post-annealing of ZnFe2 nanowires within anodic aluminum oxide templates in atmosphere. Selected area electron diffraction and X-ray diffraction exhibit that the nanowires are in cubic spinel-type structure with a [110] preferred crystallite orientation. Magnetic measurement indicates that the as-prepared ZnFe2O4 nanowire arrays reveal uniaxial magnetic anisotropy, and the easy magnetization direction is parallel to the axis of nanowire. The optical properties show the ZnFe2O4 nanowire arrays give out 370–520 nm blue-violet light, and their UV absorption edge is around 700 nm. The estimated values of direct and indirect band gaps for the nanowires are 2.23 and 1.73 eV, respectively. PMID:20676211

2010-01-01

88

Template-assisted CoPd nanowire arrays: magnetic properties and FORC analysis.  

PubMed

Highly hexagonally ordered CoPd alloy nanowire arrays were synthesized through electrochemical deposition techniques into the nanopores of anodic alumina membranes used as templates. Two different electrolytes were used for this purpose, one with pH = 4.1 and the other with pH = 7. Under applying different electrodeposition parameters and by adjusting both, the current density and the electrolyte composition, it could be possible make to vary the composition of CoPd alloy nanowires in a wide range. Their composition and morphology were investigated by SEM and EDX. The magnetic properties of the nanowires array have been measured with a VSM as a function of the temperature, ranging from RT down to 50 K, for different CoPd alloy nanowires composition. Also, the temperature influence on the reversible-irreversible magnetization processes related with the magnetization reversal of the CoPd nanowires array has been analyzed by first order reversal curve (FORC) method. PMID:22905524

Vega, V; Rosa, W O; García, J; Sánchez, T; Santos, J D; Béron, F; Pirota, K R; Prida, V M; Hernando, B

2012-06-01

89

Development of flexible array eddy current probes for complex geometries and inspection of magnetic parts using magnetic sensors  

NASA Astrophysics Data System (ADS)

Eddy Current Technique is a powerful method of inspection of metal parts. When size of flaws decreases, inspection areas become hardly accessible or material is magnetic, traditional winding coil probes are less efficient. Thanks to new CIVA simulation tools, we have designed and optimized advanced EC probes: flexible EC probe based on micro-coil arrays and EC probe with magnetic sensors, including specific electronics.

Marchand, B.; Decitre, J.-M.; Sergeeva-Chollet, N.; Skarlatos, A.

2013-01-01

90

Mid-Range Coil Array for Magnetic Resonance Imaging of Small Animals  

SciTech Connect

The vast majority of articles on MRI RF coils over the past two decades have focused on large coils, where sample losses dominate, or on micro-coils, where sample and capacitor losses are negligible. Few have addressed the mid-range coils, seen in the majority of small-animal applications, where all the sources of loss are important, for example, mouse brain and body coils from 125 to 750 MHz. We developed a four-saddle coil array for magnetic resonance imaging of small animals. The saddle coil elements in the array were evenly distributed to cover the rat's head. The coil array was tuned to the resonant frequency of 170 MHz. Due to the close proximity of the coil elements, it was necessary to decouple the coil array using nonmagnetic trimmers and, it was operated in the transceiver mode and quadrature-driven. To test the coil array performance at high field, phantom images were acquired with our saddle coil array and standard pulse sequences on a research-dedicated 4 Tesla scanner. Ex vivo brain images of a rat were also acquired, and proved the feasibility of the scaled version of a saddle coil array and, its compatibility with standard pulse sequences when used in a high field magnetic resonance imager.

Solis, S. E. [Centro de Investigacion e Instrumentacion e Imagenologia Medica, Universidad Autonoma Metropolitana Iztapalapa, Mexico, DF 09340 (Mexico); Medical Department, Brookhaven National Laboratory, Upton, NY, 11973 (United States); Tomasi, D.; Rodriguez, A. O. [Medical Department, Brookhaven National Laboratory, Upton, NY, 11973 (United States)

2008-08-11

91

Circular sensor array and nonlinear analysis of homopolar magnetic bearings  

E-print Network

Magnetic bearings use variable attractive forces generated by electromagnetic control coils to support rotating shafts with low friction and no material wear while providing variable stiffness and damping. Rotor deflections are stabilized...

Wiesenborn, Robert Kyle

2007-04-25

92

Fast magnetic resonance spectroscopic imaging using RF coil arrays  

E-print Network

Conventional Magnetic Resonance Spectroscopic Imaging (MRSI) suffers from both low signal-to-noise (SNR), as well as long acquisition times. The development of high-fidelity gradient coils has opened opportunities for fast ...

Gagoski, Borjan Aleksandar

2006-01-01

93

Nanoparticle arrays: From magnetic response to coupled plasmon resonances  

NASA Astrophysics Data System (ADS)

We study optical properties of optomagnetic metamaterials consisting of regular arrays of single and double Au nanodots (nanopillars). Using a combination of data from variable angle spectroscopic ellipsometry, transmission, and reflection measurements, we identify localized plasmon resonances of gold nanodots and measure their dependence on dot size and substrate type. We demonstrate that arrays of Au nanopillars can support narrow collective plasmon resonances coupled to in-plane and out-of-plane localized plasmon resonances. The spectral positions of these plasmon modes are extracted from the angular dependence of the transmission and reflection spectra for two beam polarizations. We show that nanoarrays exhibit dramatically different optical response on conductive and nonconductive substrates and study its angular dependence. The optical response of nanoarrays is described well by coupled dipole approximation. The procedure for extracting optical constants of metamaterials based on ellipsometry is discussed and applied to our samples resulting in a calculated negative index of refraction for double-dot arrays at green light.

Kravets, V. G.; Schedin, F.; Pisano, G.; Thackray, B.; Thomas, P. A.; Grigorenko, A. N.

2014-09-01

94

Study of plasma dynamics affected by a global magnetic field in linear wire array Z pinches  

NASA Astrophysics Data System (ADS)

In the experiments described in this paper a linear wire array composed of several wires (e.g., four wires) was viewed as a small portion of a large cylindrical array. Comparing to cylindrical arrays, linear wire arrays have relatively simple geometry and therefore are much easier to diagnose. To simulate the global magnetic field present in a cylindrical array, a return current conductor was positioned near the linear wire array. A global magnetic field in the tens of Tesla was produced by the return current in the vicinity of the linear array. The plasma dynamics affected by the global magnetic field was studied using shearing interferometry and x-ray backlighting techniques. Experimental results on tungsten wire arrays (four wires, 1.4cm long, 12.7?m diameter, 1mm interwire gaps) are discussed. Current transfer from wire cores to the surrounding corona plasmas appeared to happen at around 10ns relative to the start of the current pulse. After that, some of the wire plasma was swept away from the wire cores by the J ×B force and formed a localized, high-density peak (precursor plasma). The motion of the precursor plasma was observed to accelerate for about 20ns, indicating that current was present inside the precursor plasma during this time range. Using an x-ray backlighter and a laser interferometer, the resumption of wire core expansion, major mass ablation, and the termination of precursor plasma acceleration were observed to occur at 32-34ns. These effects can be interpreted as evidence of the transfer of the current back to the wire cores from the precursor plasma.

Hu, Min; Kusse, Bruce R.

2005-10-01

95

Highly Stable and Finely Tuned Magnetic Fields Generated by Permanent Magnet Assemblies  

NASA Astrophysics Data System (ADS)

Permanent magnetic materials are the only magnetic source that can be used to generate magnetic fields without power consumption or maintenance. Such stand-alone magnets are very attractive for many scientific and engineering areas, but they suffer from poor temporal field stability, which arises from the strong sensitivity of the magnetic materials and mechanical support to temperature variation. In this work, we describe a highly efficient method useful to cancel the temperature coefficient of permanent magnet assemblies in a passive and accurate way. It is based on the combination of at least two units made of magnetic materials with different temperature coefficients arranged in such a way that the ratio of the fields generated by each unit matches the ratio of their effective temperature coefficients defined by both the magnetic and mechanical contributions. Although typically available magnetic materials have negative temperature coefficients, the cancellation is achieved by aligning the fields generated by each unit in the opposite direction. We demonstrate the performance of this approach by stabilizing the field generated by a dipolar Halbach magnet, recently proposed to achieve high field homogeneity. Both the field drift and the homogeneity are monitored via nuclear magnetic resonance spectroscopy experiments. The results demonstrate the compatibility of the thermal compensation approach with existing strategies useful to fine-tune the spatial dependence of the field generated by permanent magnet arrays.

Danieli, E.; Perlo, J.; Blümich, B.; Casanova, F.

2013-05-01

96

High frequency umbilical magnetic probe array for SSX wind tunnel  

NASA Astrophysics Data System (ADS)

The Swarthmore Spheromak Experiment (SSX) wind tunnel consists of a high velocity plume of magnetized plasma injected into a copper flux conserver with dimensions L = 1 m and R = 0.08 m (aspect ratio 10:1). The plasma spheromaks in this wind tunnel typically have densities on the order of 1 - 5 x10^15 cm-3 and flow speeds of 50 km/s. In the past, fluctuations and turbulence in the SSX plasma wind tunnel during magnetic reconnection have been examined by means of two high resolution (16 position at 0.46 cm spacing) radial magnetic probes. Results from the radial probes show high frequency magnetic fluctuations at the site of reconnection. Four more probes have been design to help detect magnetic fluctuations and reconnection activity along the axial direction of the wind tunnel. The four new probes have 8 positions at 0.95 cm spacing and have a flexible bellow in vacuum and a quartz jacket. The bellows act as an umbilical giving the probe excellent flexibility and versatility. The flexibility allows the probe to be bent so it lies along the axis of the flux conserver.

Werth, A. M.; Gray, T.; Brown, M. R.

2012-10-01

97

Non-liftoff block copolymer nanolithography of magnetic nanodot arrays  

NASA Astrophysics Data System (ADS)

Nanolithographic techniques based on self-assembled block copolymer templates offer exceptional potential for fabrication of large-area nanostructure arrays from a wide variety of functional materials. Despite significant progress with control of the template ordering, and development of pattern transfer schemes, significant issues exist with common techniques such as lift-off and etching. Here, we demonstrate successful execution of a nanolithographic process based on climate-controlled solvent annealing of easily degradable cylinder-forming poly(styrene-b-lactide) block copolymer films that avoids both lift-off and the most challenging aspects of etching. Essentially, we use an overfill/planarize/etch-back "Damascene-type" process, exploiting the large Ar ion beam etch rate contrast between polystyrene and typical metals. The process is demonstrated via formation of a large-area array of 12 nm thick, 25 ± 3 nm diameter Ni80Fe20 nanodots (˜0.4 x 10^12 dots/in^2) with hexagonally-close-packed local order. Extensive microscopy, magnetometry, and electrical measurements provide detailed characterization of the pattern formation and fidelity. We argue that this generic approach can be applied to a wide variety of materials and is scalable to even smaller feature sizes. Funded by NSF MRSEC.

Baruth, A.; Rodwogin, M. D.; Shankar, A.; Torija, M. A.; Erickson, M. J.; Hillmyer, M. A.; Leighton, C.

2011-03-01

98

A DNA array sensor utilizing magnetic microbeads and magnetoelectronic detection  

Microsoft Academic Search

We describe a multi-analyte biosensor that uses magnetic microbeads as labels to detect DNA hybridization on a micro-fabricated chip. The beads are detected by giant magnetoresistance (GMR) magnetoelectronic sensors embedded in the chip. The prototype device is a tabletop unit containing electronics, a chip carrier with a microfluidic flow cell, and a compact electromagnet and is capable of simultaneous detection

M. M. Miller; P. E. Sheehan; R. L. Edelstein; C. R. Tamanaha; L. Zhong; S. Bounnak; L. J. Whitman; R. J. Colton

2001-01-01

99

Arrays of Ni nanowires in alumina membranes: magnetic properties and spatial ordering  

NASA Astrophysics Data System (ADS)

Magnetic characteristics of arrays of Ni nanowires embedded in porous alumina are reviewed as a function of their spatial ordering. The different steps for the controlled production of highly-ordered nanowires is firstly described. Nanopores are formed into an hexagonal symmetry arrangement by self-organized process during anodization of pure Al. Parameters of the anodization allow us to control their diameter, hexagonal lattice parameter and size of crystalline domains. Subsequently, Ni nanowires are grown inside the pores by electrodeposition. Control of the pores filling and of geometrical ordering characteristics has been performed by SEM, HRSEM, RBS and AFM techniques. The magnetic characterisation of the arrays has been achieved by SQUID and VSM magnetometers, while information on the magnetic state of individual nanowires is obtained by MFM. Experimental studies are presented, particularly coercivity and remanence, for arrays with different degree of ordering (crystalline domains up to around 1 ?m), and for ratio diameter to lattice parameter (diameter ranging between 20 and 180 nm, and distance between 35 and 500 nm). FMR studies have allows us to obtain complementary information of the anisotropy and magnetic characteristics. A modelling of multipolar interacting nanowires is introduced to account for the influence of short and long range ordering degree of the arrays.

Vázquez, M.; Hernández-Vélez, M.; Pirota, K.; Asenjo, A.; Navas, D.; Velázquez, J.; Vargas, P.; Ramos, C.

2004-08-01

100

Magnetic and magnetothermal tunabilities of subwavelength-hole arrays in a  

E-print Network

of the semiconductor, then, instead of surface plasmons, we have surface magnetoplasmons. In lieu of a dc magnetic 4 Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering); published April 30, 2009 In the low-terahertz regime, the resonance frequency of an array of subwavelength

Oklahoma State University

101

Least Squares Magnetic-Field Optimization for Portable Nuclear Magnetic Resonance Magnet Design  

SciTech Connect

Single-sided and mobile nuclear magnetic resonance (NMR) sensors have the advantages of portability, low cost, and low power consumption compared to conventional high-field NMR and magnetic resonance imaging (MRI) systems. We present fast, flexible, and easy-to-implement target field algorithms for mobile NMR and MRI magnet design. The optimization finds a global optimum ina cost function that minimizes the error in the target magnetic field in the sense of least squares. When the technique is tested on a ring array of permanent-magnet elements, the solution matches the classical dipole Halbach solution. For a single-sided handheld NMR sensor, the algorithm yields a 640 G field homogeneous to 16 100 ppm across a 1.9 cc volume located 1.5 cm above the top of the magnets and homogeneous to 32 200 ppm over a 7.6 cc volume. This regime is adequate for MRI applications. We demonstrate that the homogeneous region can be continuously moved away from the sensor by rotating magnet rod elements, opening the way for NMR sensors with adjustable"sensitive volumes."

Paulsen, Jeffrey L; Franck, John; Demas, Vasiliki; Bouchard, Louis-S.

2008-03-27

102

Open-loop characteristics of magnetic suspension systems using electromagnets mounted in a planar array  

NASA Technical Reports Server (NTRS)

The open-loop characteristics of a Large-Gap Magnetic Suspension System (LGMSS) were studied and numerical results are presented. The LGMSS considered provides five-degree-of-freedom control. The suspended element is a cylinder that contains a core composed of permanent magnet material. The magnetic actuators are air core electromagnets mounted in a planar array. Configurations utilizing five, six, seven, and eight electromagnets were investigated and all configurations were found to be controllable from coil currents and observable from suspended element positions. Results indicate that increasing the number of coils has an insignificant effect on mode shapes and frequencies.

Groom, Nelson J.; Britcher, Colin P.

1992-01-01

103

The Magnetic Spectrometer PRISMA Combined With Large Gamma Arrays  

SciTech Connect

The large solid angle magnetic spectrometer for heavy ions PRISMA was operated at LNL in conjunction with the highly efficient CLARA set-up up to the end of March 2008. The AGATA Demonstrator is being mounted around the target area of PRISMA replacing the CLARA set-up. It will allow to carry out nuclear structure and reaction mechanism studies with better resolution and higher statistics. New detectors for light ions and slow moving heavy ions have been designed for the focal plane of the spectrometer.

Fioretto, E.; Corradi, L.; Stefanini, A. M.; De Angelis, G.; Gadea, A.; Napoli, D. R.; Recchia, F.; Silvestri, R.; Valiente-Dobon, J. J. [INFN-Laboratori Nazionali di Legnaro, Viale dell'Universita 2, Legnaro (PD), 35020 (Italy); Beghini, S.; Bazzacco, D.; Farnea, E.; Mason, P.; Menegazzo, R.; Ur, C. A. [INFN Sez. di Padova, Via Marzolo 4, Padova, 35131 (Italy); Montagnoli, G.; Scarlassara, F.; Guiot, B.; Lenzi, S. M.; Lunardi, S. [Dipartimento di Fisica dell'Universita di Padova, Via Marzolo 4, Padova, 35131 (Italy); INFN Sez. di Padova, Via Marzolo 4, Padova, 35131 (Italy)] (and others)

2009-03-04

104

Zero magnetization states in electrodeposited Co0.45Fe0.55 nanowire arrays  

NASA Astrophysics Data System (ADS)

Co0.45Fe0.55 alloy nanowires with 12 to 35 nm diameter and 12 ?m length were fabricated by electrodeposition in porous anodic alumina templates. The initial magnetization curves reveal that the zero magnetization state is not unique and is determined by the field history (ac demagnetization process) leading to the zero average moment state. For ac demagnetization processes with the field applied parallel to the nanowire axis, the subsequent magnetization curves suggest that an individual nanowire behaves as a single domain with neighboring nanowires being antiparallel to each other in the zero magnetization state. However, for a demagnetization process with the field applied perpendicular to the nanowires, a different zero magnetization state is created in which the individual nanowires consist of multidomains having opposite axial orientations. These results are consistent with the asymmetric (symmetric) behavior found in the minor hysteresis loops measured after perpendicular (parallel) ac demagnetization on these nanowire arrays.

Fodor, P. S.; Tsoi, G. M.; Wenger, L. E.

2003-05-01

105

Investigation of energy harvesting for magnetic sensor arrays on Mars by wireless power transmission  

NASA Astrophysics Data System (ADS)

This paper proposes the energy harvesting for magnetic sensor arrays on Mars, which can receive the power from Mars Rover by wireless power transmission (WPT). The schematic idea is presented with the energy receiver as the magnetic sensor and the energy transmitter as the transducer on Mars Rover. The key is to adopt the resonant inductive power transmission (IPT) topology between the magnetic sensor and Mars Rover. The basic topology and its operating principle are discussed. By using the magnetic frequency analysis with the finite element method, the output power and efficiency of the WPT system are calculated. The results show that Mars Rover could flexibly transmit its power to different types of small-size magnetic sensors based on their energy on demand using different resonant frequencies and distances.

Liu, Chunhua; Chau, K. T.; Qiu, Chun; Lin, Fei

2014-05-01

106

An Orientation Measurement Method Based on Hall-effect Sensors for Permanent Magnet Spherical Actuators with 3D Magnet Array.  

PubMed

An orientation measurement method based on Hall-effect sensors is proposed for permanent magnet (PM) spherical actuators with three-dimensional (3D) magnet array. As there is no contact between the measurement system and the rotor, this method could effectively avoid friction torque and additional inertial moment existing in conventional approaches. Curved surface fitting method based on exponential approximation is proposed to formulate the magnetic field distribution in 3D space. The comparison with conventional modeling method shows that it helps to improve the model accuracy. The Hall-effect sensors are distributed around the rotor with PM poles to detect the flux density at different points, and thus the rotor orientation can be computed from the measured results and analytical models. Experiments have been conducted on the developed research prototype of the spherical actuator to validate the accuracy of the analytical equations relating the rotor orientation and the value of magnetic flux density. The experimental results show that the proposed method can measure the rotor orientation precisely, and the measurement accuracy could be improved by the novel 3D magnet array. The study result could be used for real-time motion control of PM spherical actuators. PMID:25342000

Yan, Liang; Zhu, Bo; Jiao, Zongxia; Chen, Chin-Yin; Chen, I-Ming

2014-01-01

107

An Orientation Measurement Method Based on Hall-effect Sensors for Permanent Magnet Spherical Actuators with 3D Magnet Array  

PubMed Central

An orientation measurement method based on Hall-effect sensors is proposed for permanent magnet (PM) spherical actuators with three-dimensional (3D) magnet array. As there is no contact between the measurement system and the rotor, this method could effectively avoid friction torque and additional inertial moment existing in conventional approaches. Curved surface fitting method based on exponential approximation is proposed to formulate the magnetic field distribution in 3D space. The comparison with conventional modeling method shows that it helps to improve the model accuracy. The Hall-effect sensors are distributed around the rotor with PM poles to detect the flux density at different points, and thus the rotor orientation can be computed from the measured results and analytical models. Experiments have been conducted on the developed research prototype of the spherical actuator to validate the accuracy of the analytical equations relating the rotor orientation and the value of magnetic flux density. The experimental results show that the proposed method can measure the rotor orientation precisely, and the measurement accuracy could be improved by the novel 3D magnet array. The study result could be used for real-time motion control of PM spherical actuators. PMID:25342000

Yan, Liang; Zhu, Bo; Jiao, Zongxia; Chen, Chin-Yin; Chen, I-Ming

2014-01-01

108

An Orientation Measurement Method Based on Hall-effect Sensors for Permanent Magnet Spherical Actuators with 3D Magnet Array  

NASA Astrophysics Data System (ADS)

An orientation measurement method based on Hall-effect sensors is proposed for permanent magnet (PM) spherical actuators with three-dimensional (3D) magnet array. As there is no contact between the measurement system and the rotor, this method could effectively avoid friction torque and additional inertial moment existing in conventional approaches. Curved surface fitting method based on exponential approximation is proposed to formulate the magnetic field distribution in 3D space. The comparison with conventional modeling method shows that it helps to improve the model accuracy. The Hall-effect sensors are distributed around the rotor with PM poles to detect the flux density at different points, and thus the rotor orientation can be computed from the measured results and analytical models. Experiments have been conducted on the developed research prototype of the spherical actuator to validate the accuracy of the analytical equations relating the rotor orientation and the value of magnetic flux density. The experimental results show that the proposed method can measure the rotor orientation precisely, and the measurement accuracy could be improved by the novel 3D magnet array. The study result could be used for real-time motion control of PM spherical actuators.

Yan, Liang; Zhu, Bo; Jiao, Zongxia; Chen, Chin-Yin; Chen, I.-Ming

2014-10-01

109

Crystallographically driven magnetic behaviour of arrays of monocrystalline Co nanowires.  

PubMed

Cobalt nanowires, 40 nm in diameter and several micrometers long, have been grown by controlled electrodeposition into ordered anodic alumina templates. The hcp crystal symmetry is tuned by a suitable choice of the electrolyte pH (between 3.5 and 6.0) during growth. Systematic high resolution transmission electron microscopy imaging and analysis of the electron diffraction patterns reveals a dependence of crystal orientation from electrolyte pH. The tailored modification of the crystalline signature results in the reorientation of the magnetocrystalline anisotropy and increasing experimental coercivity and squareness with decreasing polar angle of the 'c' growth axis. Micromagnetic modeling of the demagnetization process and its angular dependence is in agreement with the experiment and allows us to establish the change in the character of the magnetization reversal: from quasi-curling to vortex domain wall propagation modes when the crystal 'c' axis tilts more than 75° in respect to the nanowire axis. PMID:25380279

Ivanov, Yu P; Trabada, D G; Chuvilin, A; Kosel, J; Chubykalo-Fesenko, O; Vázquez, M

2014-11-28

110

Study of the termination phase of plasma production and the formation of magnetic flux breakthroughs during wire array implosion  

NASA Astrophysics Data System (ADS)

The phenomenon of magnetic flux breakthrough into a wire array during its implosion was studied experimentally at the Angara-5-1 facility. It is shown that breakthroughs develop in the final stage of plasma production from the wire material and occur near the initial wire position. The spatial distributions of the azimuthal magnetic field within tungsten, molybdenum, copper, and aluminum wire arrays were studied using magnetic probes. The distributions of the azimuthal magnetic field B ?( z, t) along the array height in different stages of implosion were measured, and the characteristic dimensions of regions with a nonuniform magnetic field that appear during magnetic flux breakthroughs at the outer boundary of the wire array plasma were determined. The dimensions of these regions are compared with those of the regions with depressed plasma radiation observed in frame and time-integrated X-ray images. The dynamics of the distribution B ?( z, t) in regions with a nonuniform magnetic field during breakthroughs of the azimuthal magnetic flux is compared with that of the spatial distribution of pinch radiation in the frame X-ray images in different stages of implosion. The experimental data on the characteristics of spatially nonuniform breakthroughs of the magnetic flux into the wire array are analyzed using the plasma rainstorm model proposed by V.V. Aleksandrov et al. (JETP 97, 745 (2003)). The plasma density in the region of magnetic flux breakthrough is estimated.

Mitrofanov, K. N.; Aleksandrov, V. V.; Grabovski, E. V.; Ptichkina, E. A.; Gritsuk, A. N.; Frolov, I. N.; Laukhin, Ya. N.

2014-09-01

111

High-resolution imaging of remanent state and magnetization reversal of superdomain structures in high-density cobalt antidot arrays  

NASA Astrophysics Data System (ADS)

Remanent state and magnetization reversal processes of a series of cobalt antidot arrays with a fixed hole diameter (d ? 55 nm) and an array periodicity (p) ranging between 95 and 524 nm were studied by in situ Lorentz microscopy (LM) as a function of the magnetic field. At remanence, defocused LM images showed the periodicity dependence of the magnetic states inside the lattice. A remarkable transition was observed in the type of domain structures as a function of p: for the large periodicities (p > 300 nm), conventional 90° and 180° domain walls were formed, whereas in small-period antidot arrays (p ? 160 nm) magnetic superdomain walls (SDWs) were nucleated to separate regions with different average magnetization direction, the so-called magnetic superdomains. In the SDW regime, a low-frequency Fourier filtering method was implemented to allow a quantitative analysis of the LM images by the transport of intensity equation method. In situ LM experiments under applied magnetic fields were performed to study the reversal magnetization process in a particular array (p = 160 nm), and clear differences were observed as a function of the magnetic field orientation. The switching process under magnetic fields parallel to the horizontal antidot rows occurs in two stages: the system first nucleates and propagates horizontal SDWs, parallel to the field. Then, at higher magnetic fields, vertical SDWs, perpendicular to the field, appear before saturation. When the magnetic field is applied at 45° with respect to the antidot rows, both horizontal and vertical SDWs are nucleated and propagated simultaneously. All the experiments were successfully correlated with micromagnetic simulations. The current study sheds new light on the magnetization reversal processes of antidot arrays and opens new possibilities of exploiting the potential of high-resolution in situ LM and new data analysis procedures to probe magnetization processes in nanomagnetism, particularly in periodic arrays of nanomagnets.

Rodríguez, L. A.; Magén, C.; Snoeck, E.; Gatel, C.; Castán-Guerrero, C.; Sesé, J.; García, L. M.; Herrero-Albillos, J.; Bartolomé, J.; Bartolomé, F.; Ibarra, M. R.

2014-09-01

112

SQUID (superconducting quantum interference device) arrays for simultaneous magnetic measurements: Calibration and source localization performance  

NASA Astrophysics Data System (ADS)

Recently developed small arrays of SQUID-based magnetic sensors can, if appropriately placed, locate the position of a confined biomagnetic source without moving the array. The authors present a technique with a relative accuracy of about 2 percent for calibrating such sensors having detection coils with the geometry of a second-order gradiometer. The effects of calibration error and magnetic noise on the accuracy of locating an equivalent current dipole source in the human brain are investigated for 5- and 7-sensor probes and for a pair of 7-sensor probes. With a noise level of 5 percent of peak signal, uncertainties of about 20 percent in source strength and depth for a 5-sensor probe are reduced to 8 percent for a pair of 7-sensor probes, and uncertainties of about 15 mm in lateral position are reduced to 1 mm, for the configuration considered.

Kaufman, Lloyd; Williamson, Samuel J.; Costaribeiro, P.

1988-02-01

113

Designing shielded radio-frequency phased-array coils for magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

In this paper, an approach to the design of shielded radio-frequency (RF) phased-array coils for magnetic resonance imaging (MRI) is proposed. The target field method is used to find current densities distributed on primary and shield coils. The stream function technique is used to discretize current densities and to obtain the winding patterns of the coils. The corresponding highly ill-conditioned integral equation is solved by the Tikhonov regularization with a penalty function related to the minimum curvature. To balance the simplicity and smoothness with the homogeneity of the magnetic field of the coil's winding pattern, the selection of a penalty factor is discussed in detail.

Xu, Wen-Long; Zhang, Ju-Cheng; Li, Xia; Xu, Bing-Qiao; Tao, Gui-Sheng

2013-01-01

114

Magnetic alignment of high-aspect ratio microwires into vertical arrays  

NASA Astrophysics Data System (ADS)

Fundamental studies of magnetic alignment of highly anisotropic mesostructures can enable the clean-room-free fabrication of flexible, array-based solar and electronic devices, in which preferential orientation of nano- or microwire-type objects is desired. In this study, ensembles of 100 micron long Si microwires with ferromagnetic Ni and Co coatings are oriented vertically in the presence of magnetic fields. The degree of vertical alignment and threshold field strength depend on geometric factors, such as microwire length and ferromagnetic coating thickness, as well as interfacial interactions, which are modulated by varying solvent and substrate surface chemistry. Microwire ensembles with vertical alignment over 97% within 10 degrees of normal, as measured by X-ray diffraction, are achieved over square cm scale areas and set into flexible polymer films. A force balance model has been developed as a predictive tool for magnetic alignment, incorporating magnetic torque and empirically derived surface adhesion parameters. As supported by these calculations, microwires are shown to detach from the surface and align vertically in the presence of magnetic fields on the order of 100 gauss. Microwires aligned in this manner are set into a polydimethylsiloxane film where they retain their vertical alignment after the field has been removed and can subsequently be used as a flexible solar absorber layer. Finally, these microwires arrays can be protected for use in electrochemical cells by the conformal deposition of a graphene layer.

Beardslee, Joseph

115

Self-organisation, orientation and magnetic properties of FePt nanoparticle arrays  

NASA Astrophysics Data System (ADS)

Self-organised magnetic arrays (SOMA) of high anisotropy particles are a promising candidate for ultra-high-density recording media. In principle SOMA media have the capability of storing 1 bit per particle, leading to possible reecording densities in excess of 10 Tbit/sq in. In this paper we consider two major aspects of SOMA media, namely the self-organisation process itself and the physics of the particle orientation process.

Verdes, C.; Chantrell, R. W.; Satoh, A.; Harrell, J. W.; Nikles, D.

2006-09-01

116

High spatial resolution Hall sensor array for edge plasma magnetic field measurements  

SciTech Connect

A one-dimensional, high-spatial resolution, 20-element Hall sensor array has been developed to directly measure the edge plasma perpendicular magnetic field and its fluctuations as a function of radius with 4-mm resolution. The array employs new small-area, high-sensitivity indium antimonide (InSb) Hall probes in combination with a high-density seven-layer printed circuit board to provide for connections to supply Hall current, record the measured Hall voltage output signals, and mitigate inductive pickup. A combination of bench and in situ measurements is described that provides absolute calibration of the diagnostic array in the presence of a strong transverse magnetic field component that is approximately 1000 times greater than the perpendicular fluctuating field needed to be resolved by the diagnostic. The Hall probes calibrated using this method are capable of magnetic field measurements with a sensitivity of 7 V/T over the frequency band from 0 to 20 kHz.

Liu Yuhong; Maurer, David A.; Navratil, Gerald A.; Rivera, Nicholas [Department of Applied Physics and Applied Mathematics, Columbia University in the City of New York, New York, New York 10027 (United States)

2005-09-15

117

Anisotropic magnetization of epitaxial Ni nanogroove-arrays prepared by reduction of self-organized oxides  

NASA Astrophysics Data System (ADS)

A straight and periodic nanogroove-array pattern was formed on the surface of epitaxial Ni (1 1 1) thin films via a unique process, which included self-organization and reduction of oxides. In the formation of the Ni nanopattern, the epitaxial NiO (1 1 1) thin film grown on an ?-Al2O3 (0 0 0 1) substrate by laser molecular-beam epitaxy (LaserMBE) was used as a starting material. The NiO (1 1 1) films were subsequently subjected to thermal treatment at 700 °C in air for the formation of self-organized nanopatterns, and then at 500 °C in a hydrogen atmosphere for reducing NiO to Ni. The epitaxy and morphology of the Ni (1 1 1) nanogroove array were proved by exsitu X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. Anisotropic magnetization behavior of the Ni (1 1 1) nanogroove-array pattern was examined by a M-H measurement using a superconducting quantum interference device (SQUID) magnetometer. The M-H squareness ratios for the directions parallel and perpendicular to the nanogrooves were about 0.83 and 0.52, respectively. The coercivity along the parallel line was ?0.5 kOe, which was approximately 200% of the value for the other direction. From the magnetization results, the parallel direction was considered as the magnetic easy axis in the in-plane orientation, probably due to the shape effect.

Matsuda, Akifumi; Yamauchi, Ryosuke; Tan, Geng; Nakai, Hirokazu; Koyama, Koji; Sunakawa, Kazuhiko; Kaneko, Satoru; Yoshimoto, Mamoru

2012-10-01

118

MAGNETIC INDUCTION MAPPING IN TEM OF MICRO AND NANO PATTERNED CO/NI ARRAYS.  

SciTech Connect

Understanding magnetic structures and properties of patterned magnetic films at nanometer length-scale is the area of immense technological and fundamental scientific importance. The patterned magnetic films can be used for magnetic sensing . applications, magnetic recording, magnetoelectronics, microactuators and hybrid magneto-superconducting devices. The optimization of film properties is crucially dependent on the understanding of their magnetic properties, which in turn, become sensitive to the specific geometry and, hence, magnetic configurations of a given system when the elements diminish in size. Recent progress in the field of noninterferometric phase retrieval brings the ordinary Fresnel microscopy to a new quantitative level, capable of recovering both the amplitude and phase of the object from the experimental images [1,2], and thus induction mapping of small magnetic elements with known geometry ranging from micro- to few nanometers in size. The key concept behind this approach is the improvement of phase recovery algorithm derived from the transport-of-intensity (TIE) equation with a fast-solution via Fourier transform. A number of quantitative in-situ TEM magnetization experiments can be realized now with the help of magnetic-field calibrated microscope (see, for example [3]). To demonstrate the practical use of the new approach in TEM magnetic imaging with nanoscale resolution we have prepared several films directly on 3mm TEM-grids: (a) square-patterned magnetic films of Co islands with size of 6 pm (Fig. 1), and (b) nano-patterned arrays of Ni-nanodots (Fig.2) with lateral size about 40nm. The Co-films were prepared in UHV system by electron-beam evaporation of Co through an appropriate mask onto 30-nm-thick Si{sub 3}N{sub 4} membrane. The thickness of magnetic elements was approximately 40 nm as determined by EELS. The array of Ni-nanodots on a carbon membrane was prepared by electron-beam TEM-nanolithography followed by oblique angle deposition. Both types of the patterned arrays for Co and Ni films have been characterized by the TEM/ED methods. They were found to have a polycrystalline microstructure with the average crystallite size {approx}10 and 7 nm respectively. The Co films consisted of mixture of cubic and hcp phases. To experimentally check the sensitivity of TIE-recovered phase information to local magnetic configurations a set of in-focus and out-of-focus images was recorded on CCD (llarlk) during the in-situ magnetizing experiments in JEOL3000F microscope at different magnifications using the Gatan Imaging Filter (GIF) as function of applied field (H) and/or specimen tilt angle ({var_phi}) under constant external field. The results of the image processing (Figs.1-2), strongly suggest that TIE-phase retrieval method is a powerful tool suitable for local induction mapping B(x,y) of in-plane magnetization of magnetic elements down to few nanometers scale. The method is fast, robust, insensitive to noise, does not require the holographic equipment, and can be applied to a wide class of objects. The quantitative results can be obtained for films of known or uniform thickness.

VOLKOV,V.V.; ZHU,Y.; MALAC,M.; LAU,J.W.; SCHOFIELD,M.A.

2002-08-04

119

FAST TRACK COMMUNICATION: Gyration mode splitting in magnetostatically coupled magnetic vortices in an array  

NASA Astrophysics Data System (ADS)

We present the experimental observation of gyration mode splitting by the time-resolved magneto-optical Kerr effect in an array consisting of magnetostatically coupled Ni81Fe19 discs of 1 µm diameter, 50 nm thickness and inter-disc separations varying between 150 and 270 nm. A splitting of the vortex core gyration mode is observed when the inter-disc separation is 200 nm or less and the splitting is controllable by a bias magnetic field. The observed mode splitting is interpreted by micromagnetic simulations as the normal modes of the vortex cores analogous to the coupled classical oscillators. The splitting depends upon the strength of the inter-disc magnetostatic coupling mediated by magnetic side charges, which depends strongly on the magnetic ground states of the samples.

Barman, Anjan; Barman, Saswati; Kimura, T.; Fukuma, Y.; Otani, Y.

2010-10-01

120

Magnetic Field Measurements in Wire-Array Z-Pinches and X Pinches  

SciTech Connect

We are investigating several techniques to obtain time-dependent magnetic field measurements in wire-array Z-pinches and X-pinches. One general approach is to use 'remote sensing' methods whereby a very small sensor material is placed in the plasma and then is investigated to extract useful information. Faraday rotation of polarized laser light traversing a small area through thin film waveguides coupled to a fine optical fiber is a possibility. While these films may not survive for long in a dense Z-pinch, they may provide useful information for a significant fraction of the current pulse. We also discuss results of experiments conducted using magnetic CoPt thin films to obtain the maximum magnetic field seen by the film near the end of the load current pulse.

Syed, W. [School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853 (United States); Laboratory of Plasma Studies, Cornell University, Ithaca, NY 14853 (United States); Hammer, D.A. [Laboratory of Plasma Studies, Cornell University, Ithaca, NY 14853 (United States); School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853 (United States); Lipson, M. [School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853 (United States); Van Dover, R.B. [Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853 (United States)

2006-01-05

121

Effects of annealing on the structure and magnetic properties of Fe27Co23Pb50 nanowire arrays  

NASA Astrophysics Data System (ADS)

Ferromagnetic-nonmagnetic heterogeneous Fe27Co23Pb50 ternary metal nanowire arrays were successfully fabricated by alternating current electrodeposition into anodic alumina oxide (AAO) template. The effects of the different annealing temperatures (100, 200, 300, 400, 500, 600°C) on the structure and magnetic properties have been discussed. X-ray diffraction observations indicated that FeCo and Pb phases coexist for the as-deposited and annealed samples. Magnetic measurements indicate that the nanowire arrays have high perpendicular magnetic anisotropy with their easy axis parallel to the nanowire arrays. The coercivity and remanence ratio increases as the annealing temperature rises, reaches their maximum at 400°C, and then decreases as the annealing temperature rises further. The mechanism of the magnetic properties and magnetic variety should be attributed to the special structure of the nanowires/AAO.

Wang, R. L.; Tang, S. L.; Shi, Y. G.; Fei, X. L.; Nie, B.; Du, Y. W.

2008-04-01

122

A Novel SNPs Detection Method Based on Gold Magnetic Nanoparticles Array and Single Base Extension  

PubMed Central

To fulfill the increasing need for large-scale genetic research, a high-throughput and automated SNPs genotyping method based on gold magnetic nanoparticles (GMNPs) array and dual-color single base extension has been designed. After amplification of DNA templates, biotinylated extension primers were captured by streptavidin coated gold magnetic nanoparticle (SA-GMNPs). Next a solid-phase, dual-color single base extension (SBE) reaction with the specific biotinylated primer was performed directly on the surface of the GMNPs. Finally, a “bead array” was fabricated by spotting GMNPs with fluorophore on a clean glass slide, and the genotype of each sample was discriminated by scanning the “bead array”. MTHFR gene C677T polymorphism of 320 individual samples were interrogated using this method, the signal/noise ratio for homozygous samples were over 12.33, while the signal/noise ratio for heterozygous samples was near 1. Compared with other dual-color hybridization based genotyping methods, the method described here gives a higher signal/noise ratio and SNP loci can be identified with a high level of confidence. This assay has the advantage of eliminating the need for background subtraction and direct analysis of the fluorescence values of the GMNPs to determine their genotypes without the necessary procedures for purification and complex reduction of PCR products. The application of this strategy to large-scale SNP studies simplifies the process, and reduces the labor required to produce highly sensitive results while improving the potential for automation. PMID:23139724

Li, Song; Liu, Hongna; Jia, Yingying; Deng, Yan; Zhang, Liming; Lu, Zhuoxuan; He, Nongyue

2012-01-01

123

Application of an array processor to the analysis of magnetic data for the Doublet III tokamak  

SciTech Connect

Discussed herein is a fast computational technique employing the Floating Point Systems AP-190L array processor to analyze magnetic data for the Doublet III tokamak, a fusion research device. Interpretation of the experimental data requires the repeated solution of a free-boundary nonlinear partial differential equation, which describes the magnetohydrodynamic (MHD) equilibrium of the plasma. For this particular application, we have found that the array processor is only 1.4 and 3.5 times slower than the CDC-7600 and CRAY computers, respectively. The overhead on the host DEC-10 computer was kept to a minimum by chaining the complete Poisson solver and free-boundary algorithm into one single-load module using the vector function chainer (VFC). A simple time-sharing scheme for using the MHD code is also discussed.

Wang, T.S.; Saito, M.T.

1980-08-01

124

Magnetic field annealing dependent magnetic properties of Co90Pt10 nanowire arrays  

NASA Astrophysics Data System (ADS)

Co90Pt10 alloy and elemental Co nanowires (NWs) are fabricated by electrodeposition in the self-assembled anodic alumina templates. The fabricated NWs are subjected to magnetic field (MF) annealing under 1000 Oe applied magnetic field in a direction parallel to the nanowire axis at 265 °C. The corresponding changes in the saturation magnetization, coercivity, remanent squareness, the shape of hysteresis loops and crystal structure of NWs before and after MF annealing have been investigated. The enhanced magnetic anisotropy has been observed in Co90Pt10 alloy NWs by MF annealing. The elemental Co NWs have not been affected by MF annealing. The stress relief between the domains and diffusional pair ordering of unlike atoms along the direction of external applied field are thought to be the causes of enhanced anisotropy. Re-annealing of the samples in the absence of magnetic field at 600 °C does not completely remove the enhanced anisotropy. The shape of the NWs is concluded to play major role in persistence of enhanced magnetic anisotropy after high temperature reannealing.

Shamaila, S.; Sharif, R.; Chen, J. Y.; Liu, H. R.; Han, X. F.

2009-12-01

125

An investigation of the applicability of permanent magnet quadrupole arrays for high-power microwave tubes  

SciTech Connect

Magnetic quadrupoles have long been used in accelerator research for focusing high-energy particle beams. The advent of high-field, rare-earth permanent magnet materials has also spurred interest in permanent magnet quadrupoles (PMQ`s) since they are more lightweight and compact than their electromagnet counterparts and do not require power supplies or extraneous cooling. Here the authors study the potential use of closely-packed periodic permanent magnet quadrupoles for use in microwave tubes. In the most basic configuration, PMQ`s require four separate magnets in any given transverse plane, hence they are more expensive and complicated to assemble than conventional PPM stacks. Despite this fact, the stronger focusing available from PMQ`s may make them attractive for high-perveance beams, even at the low beam voltages generally of interest for compact slow-wave devices. Being iron-free systems, PMQ arrays may also lead to reductions in tube weight. The authors will compare and contrast PMQ and PPM stacks in terms of the beam focusing and beam quality that each provide and in terms of the comparative cost and difficulty of assembly. Results from two-dimensional beam envelope calculations and particle-in-cell simulations is discussed.

Booske, J.H.; Basten, M.A.; Louis, L.J.; Joe, J.; Scharer, J.E. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Electrical and Computer Engineering

1996-12-31

126

Standing-wave excited soft x-ray photoemission microscopy: application to Co microdot magnetic arrays  

SciTech Connect

We demonstrate the addition of depth resolution to the usual two-dimensional images in photoelectron emission microscopy (PEEM), with application to a square array of circular magnetic Co microdots. The method is based on excitation with soft x-ray standing-waves generated by Bragg reflection from a multilayer mirror substrate. Standing wave is moved vertically through sample simply by varying the photon energy around the Bragg condition. Depth-resolved PEEM images were obtained for all of the observed elements. Photoemission intensities as functions of photon energy were compared to x-ray optical calculations in order to quantitatively derive the depth-resolved film structure of the sample.

Gray, Alexander; Kronast, Florian; Papp, Christian; Yang, See-Hun; Cramm, Stefan; Krug, Ingo P.; Salmassi, Farhad; Gullikson, Eric M.; Hilken, Dawn L.; Anderson, Erik H.; Fischer, Peter; Durr, Hermann A.; Schneider, Claus M.; Fadley, Charles S.

2010-10-29

127

Implementation of a decoupled controller for a magnetic suspension system using electromagnets mounted in a planar array  

NASA Technical Reports Server (NTRS)

An implementation of a decoupled, single-input/single-output control approach for a large angle magnetic suspension test fixture is described. Numerical and experimental results are presented. The experimental system is a laboratory model large gap magnetic suspension system which provides five degree-of-freedom control of a cylindrical suspended element. The suspended element contains a core composed of permanent magnet material and is levitated above five electromagnets mounted in a planar array.

Cox, D. E.; Groom, N. J.

1994-01-01

128

Template-based synthesis and magnetic properties of Mn-Zn ferrite nanotube and nanowire arrays  

NASA Astrophysics Data System (ADS)

Template-based electrophoretic deposition of Mn-Zn ferrite nanotubes (NTs) and nanowires (NWs) were achieved using anodic alumina oxide (AAO) membranes. The effect of electrophoretic current and deposition time on the morphology of the tubes was investigated. The samples show cubic spinel structure with no preferred orientation. Room-temperature magnetic properties of the Mn-Zn ferrite NT/NW arrays were studied. The magnetic easy axis parallels the NT/NW's channel axis attributing to the large shape anisotropy in this direction, especially for the NTs with a small wall thickness. Magnetocrystalline anisotropy and magnetostatic interactions were found dominant in the samples when applied field was perpendicular to the channel axis.

Guo, Limin; Wang, Xiaohui; Zhong, Caifu; Li, Longtu

2012-01-01

129

Dynamical localization effect in a coupled quantum dot array driven by an AC magnetic field  

NASA Astrophysics Data System (ADS)

We have studied the transport properties of a ring-coupled quantum dot array driven by an AC magnetic field, which is connected to two leads, and we give the response of the transport current to the dynamical localization. We found that when the ratio of the magnetic flux to the total quantum dots number is a root of the zeroth order Bessel function, dynamical localization and collapse of quasi-energy occurs and importantly, the transport current displays a dip which is the signal of dynamical localization. The dynamical localization effect is strengthened as a result of the increase of the quantum dot number, and it is weakened on account of the increase of the dots-lead hopping rate.

Xia, Jun-Jie; Nie, Yi-Hang

2011-09-01

130

The ENIGMA project: a ground-based magnetic array for space research  

NASA Astrophysics Data System (ADS)

National Observatory of Athens (NOA) currently operates ENIGMA (HellENIc GeoMagnetic Array), an array of 4 ground-based magnetometer stations in the area of south-eastern Europe (central and southern Greece). The current stations are latitudinally equi-spaced between 30° and 33° corrected geomagnetic latitude. In the near future another station will be installed in Macedonia or Thrace, and there are plans for the installation of an additional station in Crete by mid-2010. One of the primary research objectives assigned to ENIGMA is the study of geomagnetic field line resonances (FLRs). The latter is a well-established phenomenon taking place in the Earth's magnetosphere. It can be pictured as the formation of standing magnetohydrodynamic waves on magnetic field lines with fixed ends at the conjugate ionospheres. An interesting option in this field of research would be to compare ultra-low-frequency (ULF) wave observations in space made by ESA's Cluster mission and on the ground acquired by these mid-to-low-latitude ground-based observation sites of the Earth's magnetic field. Cluster has a high inclination orbit; insofar studies at high latitudes are more justified for direct interactions along the magnetic field lines. So, for a Cluster-ENIGMA study one has to expect some indirect, somehow related reactions with propagations perpendicular to the B-field. The Cluster-ENIGMA study can serve as a pilot-study for the upcoming Swarm mission of ESA. The Swarm constellation of spacecraft will allow, for the first time, the unique determination of the near-Earth field aligned currents, which connect various regions of the magnetosphere with the ionosphere and can be regarded as a complement to the Cluster mission.

Daglis, I. A.; Balasis, G.; Anastasiadis, A.; Ganas, A.; Melis, N.; Baumjohann, W.; Magnes, W.; Mandea, M.; Lesur, V.; Korte, M.

2010-05-01

131

Transport measurements on a thin Nb film with square array of nanoscale magnetic dots.  

NASA Astrophysics Data System (ADS)

Transport measurements (R vs. T, R vs. B, and V-I characteristics) were made on a thin Nb film deposited on top of a square array of nanoscale magnetic dots [1]. These measurements established that in many ways this system behaved like a Josephson junction array (JJA). We hypothesized that the stray magnetic field of the dots reduced the superconductivity in the Nb film in such a way as to make the film a superconductor-weaker superconductor-superconductor (S-S-S) JJA. Studies of the VIs in the presence of a radio frequency (rf) signal revealed the appearance of Shapiro steps in the VI's. The voltage location at which the steps occurred follow the Josephson relation Vn=n*N*(h/2)*?, where n=1,2,3, etc, N is the number of junctions along the current direction, and ? is the frequency of the rf signal. Sample provided by Dr. Axel Hoffmann from Argonne National Laboratory and Dr. Ivan K. Schuller from UCSD. [1] J. I. Martin, Y. Jaccard, A. Hoffmann, J. Nogues, J. M. George, J. I. Vicent, and I. K. Schuller, J. Appl. Physics. 84, 411 (1998)

Gómez, Luis B.; Mast, David B.

2002-03-01

132

Cryogenic Characterization and Testing of Magnetically-Actuated Microshutter Arrays for the James Webb Space Telescope  

NASA Technical Reports Server (NTRS)

Two-dimensional MEMS microshutter arrays (MSA) have been fabricated at the NASA Goddard Space Flight Center (GSFC) for the James Webb Space Telescope (JWST) to enable cryogenic (approximately 35 K) spectrographic astronomy measurements in the near-infrared region. Functioning as a focal plane object selection device, the MSA is a 2-D programmable aperture mask with fine resolution, high efficiency and high contrast. The MSA are close- packed silicon nitride shutters (cell size of 100 x 200 microns) patterned with a torsion flexure to allow opening to 90 degrees. A layer of magnetic material is deposited onto each shutter to permit magnetic actuation. Two electrodes are deposited, one onto each shutter and another onto the support structure side-wall, permitting electrostatic latching and 2-D addressing. New techniques were developed to test MSA under mission-similar conditions (8 K less than or equal to T less than 300K). The magnetic rotisserie has proven to be an excellent tool for rapid characterization of MSA. Tests conducted with the magnetic rotisserie method include accelerated cryogenic lifetesting of unpackaged 128 x 64 MSA and parallel measurement of the magneto-mechanical stiffness of shutters in pathfinder test samples containing multiple MSA designs. Lifetest results indicate a logarithmic failure rate out to approximately 10(exp 6) shutter actuations. These results have increased our understanding of failure mechanisms and provide a means to predict the overall reliability of MSA devices.

King, T. T.; Kletetschka, G.; Jah, M. A.; Li, M. J.; Jhabvala, M. D.; Wang, L. L.; Beamesderfer, M. A.; Kutyrev, A. S.; Silverberg, R. F.; Rapchun, D.; Schwinger, D. S.

2004-01-01

133

Magnetic behavior of NiCu nanowire arrays: Compositional, geometry and temperature dependence  

NASA Astrophysics Data System (ADS)

Arrays of Ni100-xCux nanowires ranging in composition 0 ? x ? 75, diameter from 35 to 80 nm, and length from 150 nm to 28 ?m have been fabricated by electrochemical co-deposition of Ni and Cu into self-ordered anodic aluminum oxide membranes. As determined by X-ray diffraction and Transmission Electron Microscopy, the crystalline structure shows fcc cubic symmetry with [111] preferred texture and preferential Ni or Cu lattice depending on the composition. Their magnetic properties such as coercivity and squareness have been determined as a function of composition and geometry in a Vibrating Sample Magnetometer in the temperature range from 10 to 290 K for applied magnetic fields parallel and perpendicular to the nanowires axis. Addition of Cu into the NiCu alloy up to 50% enhances both parallel coercivity and squareness. For the higher Cu content, these properties decrease and the magnetization easy axis becomes oriented perpendicular to the wires. In addition, coercivity and squareness increase by decreasing the diameter of nanowires which is ascribed to the increase of shape anisotropy. The temperature dependent measurements reflect a complex behavior of the magnetic anisotropy as a result of energy contributions with different evolution with temperature.

Palmero, E. M.; Bran, C.; del Real, R. P.; Magén, C.; Vázquez, M.

2014-07-01

134

Development of 3-D magnetic nano-arrays by electrodeposition into mesoporous silica.  

SciTech Connect

The development of periodic nanostructures fabricated by self-assembly of surfactants and block co-polymers has opened up the possibility of generating periodic magnetic nanostructures of types not accessible by self-assembly of nano-particles. The fabrication of mesoporous silica thin films around self-assembled block co-polymers is well established. Common structures for such films are SBA-15 which consists of hexagonal arrays of cylindrical pores and SBA-16 which has face centered arrays of spherical voids. These pores are connected by 1-2 nm thick flaws in the continuous silica phase producing an effectively continuous porous phase. After removal of the block co-polymer template, electrodeposition into the mesoporous silica thin films produces arrays of 5-10 nm diameter nano-wires and nano-particles. We have demonstrated that such materials can be fabricated on a wide range of metal substrates. Characterization by Scanning Electron Microscopies shows that the mesoporous silica is well ordered over micron scale areas. Grazing Incidence Small Angle X-ray Scattering (GISAXS) studies shows diffraction spots, consistent with the entire film being well ordered. GISAXS also shows that the mesoporous silica films survive removal of the template and electrodeposition of nickel and cobalt into the mesoporous silica films. Such films are of interest for their magnetic properties, as the nanophase and scale can be independently varied. Further, the presence of nanowires inside an insulator suggests that these films might also be of interest as the current confining element for Confined Current Path-Current Perpendicular to Plane GMR sensors.

Campbell, R.; Manning, J.; Bakker, M.G.; Li, X.; Lee, D.R.; Wang, J.; X-Ray Science Division; Univ. of Alabama

2006-01-01

135

Measurements of the Axial Magnetic Field during the Implosion of Wire Arrays in the Angara-5-1 Facility  

SciTech Connect

Results are presented from measurements of the axial magnetic field during the implosion of tungsten wire arrays in the Angara-5-1 facility at currents of 2.5-4.5 MA. The azimuthal structure of the plasma produced from the wires is examined using the effect of the compression of the axial magnetic flux by this plasma. It is shown that the plasma starts to penetrate into the axial region of the wire array at the very beginning of implosion. A mechanism other than the formation of a closed current-carrying shell is proposed for describing the transfer of the external axial magnetic field to the central region of the array.

Zukakishvili, G.G.; Mitrofanov, K.N.; Grabovskii, E.V.; Oleinik, G.M. [Troitsk Institute for Innovation and Fusion Research, Troitsk, Moscow oblast, 142190 (Russian Federation)

2005-08-15

136

Development of novel techniques to study the magnetic field evolution in wire array Z-pinches and X pinches  

NASA Astrophysics Data System (ADS)

Understanding the magnetic field topology in wire-array Z-pinches is of great significance for their ultimate application to stockpile stewardship and inertial confinement fusion. We have developed and tested several novel techniques involving material-based sensors to measure magnetic fields as a function of space and time in high energy density plasmas on pulsed power machines. We first briefly introduce a technique that was used to measure a lower limit of the maximum magnetic field of a sub-microsecond duration pulse using magnetic reversal in CoPt thin films. The time-varying magnetic field was generated by an exploding wire array plasma called an X pinch produced on the 0.5 MA, 100 ns pulse duration, XP pulsed power generator. We then introduce a technique based on Faraday rotation that was used to measure magnetic fields in wire-array Z-pinches produced on the 1 MA, 100 ns rise time, COBRA pulsed power generator as well as on the XP generator. This technique measures magnetic fields as a function of space and time using Faraday rotation of a single longitudinal mode (SLM) laser through a magneto-optically active bulk waveguide, multicomponent terbium borate glass, placed adjacent to, or within, the wire array. We have measured fields > 10 T with 100 ns rise times outside of a wire-array Z-pinch for the entire duration (˜250 ns) of the current pulse and as much as ˜2 T inside a wire-array for ˜40 ns from the start of current. This is the first time that such rapidly varying and large fields have been measured using the terbium borate glass. The third method, also based on Faraday rotation of SLM laser light utilized an integrated optical fiber sensor (a fiber-sensor-fiber assembly) on the XP pulsed power generator that also yielded a measurement of the magnetic field of a wire-array Z-pinch for part of the current pulse. Finally, we repeated the third method by fabricating a "thin film waveguide" of terbium borate glass to increase the spatial resolution of the measurement. The thin film waveguide was then coupled to an optical fiber system. Although we successfully fabricated thin film nanowaveguides of terbium borate glass, the first time such waveguides have been made, due to poor coupling efficiency of light between components, preliminary Faraday rotation measurements were unsuccessful. The technique developed in this dissertation is potentially viable for magnetic field measurements in high current pulsed power systems if the device is protected from intimate interaction with the high energy density plasma during the time that a magnetic field measurement is to be made.

Syed, Wasif

137

Correlations among magnetic, electrical and magneto-transport properties of NiFe nanohole arrays.  

PubMed

In this work, we use anodic aluminum oxide (AAO) templates to build NiFe magnetic nanohole arrays. We perform a thorough study of their magnetic, electrical and magneto-transport properties (including the resistance R(T), and magnetoresistance MR(T)), enabling us to infer the nanohole film morphology, and the evolution from granular to continuous film with increasing thickness. In fact, different physical behaviors were observed to occur in the thickness range of the study (2 nm < t < 100 nm). For t < 10 nm, an insulator-to-metallic crossover was visible in R(T), pointing to a granular film morphology, and thus being consistent with the presence of electron tunneling mechanisms in the magnetoresistance. Then, for 10 nm < t < 50 nm a metallic R(T) allied with a larger anisotropic magnetoresistance suggests the onset of morphological percolation of the granular film. Finally, for t > 50 nm, a metallic R(T) and only anisotropic magnetoresistance behavior were obtained, characteristic of a continuous thin film. Therefore, by combining simple low-cost bottom-up (templates) and top-down (sputtering deposition) techniques, we are able to obtain customized magnetic nanostructures with well-controlled physical properties, showing nanohole diameters smaller than 35 nm. PMID:23315433

Leitao, D C; Ventura, J; Teixeira, J M; Sousa, C T; Pinto, S; Sousa, J B; Michalik, J M; De Teresa, J M; Vazquez, M; Araujo, J P

2013-02-13

138

Degradation of phosphate ester hydraulic fluid in power station turbines investigated by a three-magnet unilateral magnet array.  

PubMed

A three-magnet array unilateral NMR sensor with a homogeneous sensitive spot was employed for assessing aging of the turbine oils used in two different power stations. The Carr-Purcell-Meiboom-Gill (CPMG) sequence and Inversion Recovery-prepared CPMG were employed for measuring the ¹H-NMR transverse and longitudinal relaxation times of turbine oils with different service status. Two signal components with different lifetimes were obtained by processing the transverse relaxation curves with a numeric program based on the Inverse Laplace Transformation. The long lifetime components of the transverse relaxation time T?eff and longitudinal relaxation time T? were chosen to monitor the hydraulic fluid aging. The results demonstrate that an increase of the service time of the turbine oils clearly results in a decrease of T?eff,long and T?,long. This indicates that the T?eff,long and T?,long relaxation times, obtained from the unilateral magnetic resonance measurements, can be applied as indices for degradation of the hydraulic fluid in power station turbines. PMID:24736132

Guo, Pan; He, Wei; García-Naranjo, Juan C

2014-01-01

139

Tailoring the magnetic properties of cobalt antidot arrays by varying the pore size and degree of disorder  

NASA Astrophysics Data System (ADS)

Magnetic properties of Co antidot arrays with different hole sizes fabricated by a template-assisted method have been studied by means of first-order reversal curves (FORCs) and micromagnetic simulations. Hysteresis curves show a significant increase of the coercivity of the antidot arrays, as compared with their parent continuous film, which depends on the hole size introduced in the Co thin film. This effect is related to the reversibility of the magnetic domains during magnetization reversal, since due to the appearance of pores, domains may become trapped between them. On the other hand, micromagnetic simulations performed on a perfect hexagonal lattice, when compared with those made on our disordered system taken from the scanning microscope images, reveal that the presence of defects in the antidot lattice affects its magnetic properties. Finally, FORCs show that there is greater interaction attributed to domain-domain interaction.

Michea, S.; Palma, J. L.; Lavín, R.; Briones, J.; Escrig, J.; Denardin, J. C.; Rodríguez-Suárez, R. L.

2014-08-01

140

Magneto-optical characteristics of magnetic nanowire arrays in anodic aluminum oxide templates  

NASA Astrophysics Data System (ADS)

Nanocomposite films consisting of regularly ordered iron nanowires embedded in anodic aluminum oxide templates have been fabricated and their magneto-optical properties studied by determining the four Stokes parameters of the transmitted laser beam (?=670 nm), originally linearly polarized and at normal incidence to the film surfaces. The results of the nanowire arrays are found to be considerably different from that of bulk iron. While an increase in diameter of the nanowire leads to a substantial increase in the values of the Faraday rotation angles per unit length at a fixed value of the magnetic fields, they are substantially less than that of bulk iron, indicating that the effective media theory may not be directly applicable.

Peng, Yong; Shen, T.-H.; Ashworth, Brian; Zhao, Xue-Gen; Faunce, Chester A.; Liu, Yan-Wei

2003-07-01

141

Development of novel techniques to study the magnetic field evolution in wire array Z-pinches and X pinches  

Microsoft Academic Search

Understanding the magnetic field topology in wire-array Z-pinches is of great significance for their ultimate application to stockpile stewardship and inertial confinement fusion. We have developed and tested several novel techniques involving material-based sensors to measure magnetic fields as a function of space and time in high energy density plasmas on pulsed power machines. We first briefly introduce a technique

Wasif Syed

2010-01-01

142

Geometrical Design of a Scalable Overlapping Planar Spiral Coil Array to Generate a Homogeneous Magnetic Field  

PubMed Central

We present a design methodology for an overlapping hexagonal planar spiral coil (hex-PSC) array, optimized for creation of a homogenous magnetic field for wireless power transmission to randomly moving objects. The modular hex-PSC array has been implemented in the form of three parallel conductive layers, for which an iterative optimization procedure defines the PSC geometries. Since the overlapping hex-PSCs in different layers have different characteristics, the worst case coil-coupling condition should be designed to provide the maximum power transfer efficiency (PTE) in order to minimize the spatial received power fluctuations. In the worst case, the transmitter (Tx) hex-PSC is overlapped by six PSCs and surrounded by six other adjacent PSCs. Using a receiver (Rx) coil, 20 mm in radius, at the coupling distance of 78 mm and maximum lateral misalignment of 49.1 mm (1/?3 of the PSC radius) we can receive power at a PTE of 19.6% from the worst case PSC. Furthermore, we have studied the effects of Rx coil tilting and concluded that the PTE degrades significantly when ? > 60°. Solutions are: 1) activating two adjacent overlapping hex-PSCs simultaneously with out-of-phase excitations to create horizontal magnetic flux and 2) inclusion of a small energy storage element in the Rx module to maintain power in the worst case scenarios. In order to verify the proposed design methodology, we have developed the EnerCage system, which aims to power up biological instruments attached to or implanted in freely behaving small animal subjects’ bodies in long-term electrophysiology experiments within large experimental arenas. PMID:24782576

Jow, Uei-Ming; Ghovanloo, Maysam

2014-01-01

143

Anion controlled 2D assembly of a LaCu cation array and its unusual magnetic properties  

E-print Network

series.2,3 On the other hand, geometrically frustrated two-dimensional systems with triangular or kagomeAnion controlled 2D assembly of a La­Cu cation array and its unusual magnetic properties Qin-De Liu Laboratory of Rare Earth Materials Chemistry and Applications & PKU-HKU Joint Laboratory on Rare Earth

Gao, Song

144

A digital magnetic resonance imaging spectrometer using digital signal processor and field programmable gate array.  

PubMed

A digital spectrometer for low-field magnetic resonance imaging is described. A digital signal processor (DSP) is utilized as the pulse programmer on which a pulse sequence is executed as a subroutine. Field programmable gate array (FPGA) devices that are logically mapped into the external addressing space of the DSP work as auxiliary controllers of gradient control, radio frequency (rf) generation, and rf receiving separately. The pulse programmer triggers an event by setting the 32-bit control register of the corresponding FPGA, and then the FPGA automatically carries out the event function according to preset configurations in cooperation with other devices; accordingly, event control of the spectrometer is flexible and efficient. Digital techniques are in widespread use: gradient control is implemented in real-time by a FPGA; rf source is constructed using direct digital synthesis technique, and rf receiver is constructed using digital quadrature detection technique. Well-designed performance is achieved, including 1 ?s time resolution of the gradient waveform, 1 ?s time resolution of the soft pulse, and 2 MHz signal receiving bandwidth. Both rf synthesis and rf digitalization operate at the same 60 MHz clock, therefore, the frequency range of transmitting and receiving is from DC to ~27 MHz. A majority of pulse sequences have been developed, and the imaging performance of the spectrometer has been validated through a large number of experiments. Furthermore, the spectrometer is also suitable for relaxation measurement in nuclear magnetic resonance field. PMID:23742570

Liang, Xiao; Binghe, Sun; Yueping, Ma; Ruyan, Zhao

2013-05-01

145

Directed Fluid Flow Produced by Arrays of Magnetically Actuated Core-Shell Biomimetic Cilia  

NASA Astrophysics Data System (ADS)

We have developed a novel core-shell microstructure that we use to fabricate arrays of flexible, magnetically actuated biomimetic cilia. Our biomimetic cilia mimic the size and beat shape of biological cilia in order to replicate the transport of fluid driven by cilia in many biological systems including the determination of left-right asymmetry in the vertebrate embryonic nodal plate and mucociliary clearance in the lung. Our core-shell structures consist of a flexible poly(dimethylsiloxane) (PDMS) core surrounded by a shell of nickel approximately forty nanometers thick; by using a core-shell structure, we can tune the mechanical and magnetic properties independently. We present the fabrication process and the long-range transport that occurs above the beating biomimetic cilia tips and will report on progress toward biomimetic cilia induced flow in viscoelastic fluids similar to mucus in the human airway. These flows may have applications in photonics and microfluidics, and our structures may be further useful as sensors or actuators in microelectromechanical systems.

Fiser, B. L.; Shields, A. R.; Evans, B. A.; Superfine, R.

2010-03-01

146

A digital magnetic resonance imaging spectrometer using digital signal processor and field programmable gate array  

NASA Astrophysics Data System (ADS)

A digital spectrometer for low-field magnetic resonance imaging is described. A digital signal processor (DSP) is utilized as the pulse programmer on which a pulse sequence is executed as a subroutine. Field programmable gate array (FPGA) devices that are logically mapped into the external addressing space of the DSP work as auxiliary controllers of gradient control, radio frequency (rf) generation, and rf receiving separately. The pulse programmer triggers an event by setting the 32-bit control register of the corresponding FPGA, and then the FPGA automatically carries out the event function according to preset configurations in cooperation with other devices; accordingly, event control of the spectrometer is flexible and efficient. Digital techniques are in widespread use: gradient control is implemented in real-time by a FPGA; rf source is constructed using direct digital synthesis technique, and rf receiver is constructed using digital quadrature detection technique. Well-designed performance is achieved, including 1 ?s time resolution of the gradient waveform, 1 ?s time resolution of the soft pulse, and 2 MHz signal receiving bandwidth. Both rf synthesis and rf digitalization operate at the same 60 MHz clock, therefore, the frequency range of transmitting and receiving is from DC to ˜27 MHz. A majority of pulse sequences have been developed, and the imaging performance of the spectrometer has been validated through a large number of experiments. Furthermore, the spectrometer is also suitable for relaxation measurement in nuclear magnetic resonance field.

Liang, Xiao; Binghe, Sun; Yueping, Ma; Ruyan, Zhao

2013-05-01

147

Nonlinear effects in magnetic garnet films and nonreciprocal optical Bloch oscillations in waveguide arrays  

NASA Astrophysics Data System (ADS)

This dissertation presents detailed experimental and theoretical investigations of nonlinear and nonreciprocal effects in magnetic garnet films. The dissertation thus comprises two major sections. The first section concentrates on the study of a new class of nonlinear magneto-optic thin film materials possessing strong higher order magnetic susceptibility for nonlinear optical applications. The focus was on enlarging the nonlinear performance of ferrite garnet films by strain generation and compositional gradients in the sputter-deposition growth of these films. Under this project several bismuth-substituted yttrium iron garnet (Bi,Y)3(Fe,Ga)5O12 (acronym as Bi:YIG) films have been sputter-deposited over gadolinium gallium garnet (Gd 3Ga5O12) substrates and characterized for their nonlinear optical response. One of the important findings of this work is that lattice mismatch strain drives the second harmonic (SH) signal in the Bi:YIG films, in agreement with theoretical predictions; whereas micro-strain was found not to correlate significantly with SH signal at the micro-strain levels present in these films. This study also elaborates on the role of the film's constitutive elements and their concentration gradients in nonlinear response of the films. Ultrahigh sensitivity delivered by second harmonic generation provides a new exciting tool for studying magnetized surfaces and buried interfaces, making this work important from both a fundamental and application point of view. The second part of the dissertation addresses an important technological need; namely the development of an on-chip optical isolator for use in photonic integrated circuits. It is based on two related novel effects, nonreciprocal and unidirectional optical Bloch oscillations (BOs), recently proposed and developed by Professor Miguel Levy and myself. This dissertation work has established a comprehensive theoretical background for the implementation of these effects in magneto-optic waveguide arrays. The model systems we developed consist of photonic lattices in the form of one-dimensional waveguide arrays where an optical force is introduced into the array through geometrical design turning the beam sideways. Laterally displaced photons are periodically returned to a central guide by photonic crystal action. The effect leads to a novel oscillatory optical phenomenon that can be magnetically controlled and rendered unidirectional. An on-chip optical isolator was designed based on the unidirectionality of the magneto-opticBloch oscillatory motion. The proposed device delivers an isolation ratio as high as 36 dB that remains above 30 dB in a 0.7 nm wavelength bandwidth, at the telecommunication wavelength 1.55 mum. Slight modifications in isolator design allow one to achieve an even more impressive isolation ratio ~ 55 dB, but at the expense of smaller bandwidth. Moreover, the device allows multifunctionality, such as optical switching with a simultaneous isolation function, well suited for photonic integrated circuits.

Kumar, Pradeep

148

Autonomous low-power magnetic data collection platform to enable remote high latitude array deployment  

NASA Astrophysics Data System (ADS)

A major driver in the advancement of geophysical sciences is improvement in the quality and resolution of data for use in scientific analysis, discovery, and for assimilation into or validation of empirical and physical models. The need for more and better measurements together with improvements in technical capabilities is driving the ambition to deploy arrays of autonomous geophysical instrument platforms in remote regions. This is particularly true in the southern polar regions where measurements are presently sparse due to the remoteness, lack of infrastructure, and harshness of the environment. The need for the acquisition of continuous long-term data from remote polar locations exists across geophysical disciplines and is a generic infrastructure problem. The infrastructure, however, to support autonomous instrument platforms in polar environments is still in the early stages of development. We report here the development of an autonomous low-power magnetic variation data collection system. Following 2 years of field testing at the south pole station, the system is being reproduced to establish a dense chain of stations on the Antarctic plateau along the 40° magnetic meridian. The system is designed to operate for at least 5 years unattended and to provide data access via satellite communication. The system will store 1 s measurements of the magnetic field variation (<0.2 nT resolution) in three vector components plus a variety of engineering status and environment parameters. We believe that the data collection platform can be utilized by a variety of low-power instruments designed for low-temperature operation. The design, technical characteristics, and operation results are presented here.

Musko, Stephen B.; Clauer, C. Robert; Ridley, Aaron J.; Arnett, Kennneth L.

2009-04-01

149

Precision formed micro magnets: LDRD project summary report  

SciTech Connect

A microfabrication process is described that provides for the batch realization of miniature rare earth based permanent magnets. Prismatic geometry with features as small as 5 microns, thicknesses up through several hundred microns and with submicron tolerances may be accommodated. The processing is based on a molding technique using deep x-ray lithography as a means to generate high aspect-ratio precision molds from PMMA (poly methyl methacrylate) used as an x-ray photoresist. Subsequent molding of rare-earth permanent magnet (REPM) powder combined with a thermosetting plastic binder may take place directly in the PMMA mold. Further approaches generate an alumina form replicated from the PMMA mold that becomes an intermediate mold for pressing higher density REPM material and allows for higher process temperatures. Maximum energy products of 3--8 MGOe (Mega Gauss Oersted, 1 MGOe = 100/4{pi} kJ/m{sup 3}) are obtained for bonded isotropic forms of REPM with dimensions on the scale of 100 microns and up to 23 MGOe for more dense anisotropic REPM material using higher temperature processing. The utility of miniature precision REPMs is revealed by the demonstration of a miniature multipole brushless DC motor that possesses a pole-anisotropic rotor with dimensions that would otherwise prohibit multipole magnetization using a multipole magnetizing fixture at this scale. Subsequent multipole assembly also leads to miniaturized Halbach arrays, efficient magnetic microactuators, and mechanical spring-like elements which can offset miniaturized mechanical scaling behavior.

CHRISTENSON,TODD R.; GARINO,TERRY J.; VENTURINI,EUGENE L.

2000-02-01

150

Robotic apparatuses, systems and methods  

NASA Technical Reports Server (NTRS)

A mobile device for traversing a ferromagnetic surface. The device includes a frame and at least one surface contacting device attached to the frame. The device also includes a Halbach magnet array attached to the frame, wherein the Halbach magnet array provides a magnetic force to maintain the surface contacting device substantially into contact with the ferromagnetic surface.

Ross, William P. (Inventor); Hoburg, James F. (Inventor); Fromme, Christopher (Inventor); Bares, John (Inventor); DeLouis, Mark (Inventor)

2004-01-01

151

Fault tolerant control of homopolar magnetic bearings and circular sensor arrays  

E-print Network

magnetic suspension system. The homopolar magnetic bearings are biased by permanent magnets to reduce the energy consumption. One control scheme is to adjust system parameters by swapping current distribution matrices for magnetic bearings and weighting...

Li, Ming-Hsiu

2006-04-12

152

Magnetic property of a staggered-array undulator using a bulk high-temperature superconductor  

NASA Astrophysics Data System (ADS)

The magnetic field of a staggered-array undulator using a bulk high-temperature superconductor is calculated by analytical and numerical methods. Analytical formulas for the undulator field and the solenoid field required to generate the undulator field are derived from a simple two-dimensional model. The analytical calculation shows the degree of dependence of these fields on the undulator parameters, the generation of a high undulator field proportional to the critical current density of the bulk superconductor, and the good tunability of the undulator field over a wide range of values. The numerical calculation is performed in a three-dimensional geometry by two methods: the center field and energy minimization methods. The latter treats the current distribution inside the bulk, whereas the former neglects it as a natural extension of the analytical model. The calculation also reveals the dependence of the fields on the undulator parameters arising from the current distribution. From the comparison with experimental results, we find that the latter method reproduces the experimental results well, which indicates the importance of the current distribution inside the bulk. Therefore, we derive a semiempirical formula for the required solenoid field by modifying the analytical formula using the numerical results so as to include the effect of the current distribution. The semiempirical formula reproduces the numerical result with an error of 3%. Finally, we estimate the magnetic performance of the undulator as an example of using the formulas and values presented in this paper. The estimation shows that an undulator field twice as large as that of the present in-vacuum undulator but with an equal period and gap can be obtained at a temperature of approximately 20-40 K, and that deflection parameters (K values) of 1 and 2 can be achieved with periods of 5 and 10 mm at approximately 4-20 K.

Kinjo, Ryota; Mishima, Kenta; Choi, Yong-Woon; Omer, Mohamed; Yoshida, Kyohei; Negm, Hani; Torgasin, Konstantin; Shibata, Marie; Shimahashi, Kyohei; Imon, Hidekazu; Okumura, Kensuke; Inukai, Motoharu; Zen, Heishun; Kii, Toshiteru; Masuda, Kai; Nagasaki, Kazunobu; Ohgaki, Hideaki

2014-02-01

153

Enhanced synchronization in an array of spin torque nano oscillators in the presence of oscillating external magnetic field  

E-print Network

We demonstrate that the synchronization of an array of electrically coupled spin torque nano-oscillators (STNO) modelled by Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation can be enhanced appreciably in the presence of a common external microwave magnetic field. The applied microwave magnetic field stabilizes and enhances the regions of synchronization in the parameter space of our analysis, where the oscillators are exhibiting synchronized oscillations thereby emitting improved microwave power. To characterize the synchronized oscillations we have calculated the locking range in the domain of external source frequency.

B. Subash; V. K. Chandrasekar; M. Lakshmanan

2014-09-15

154

Influence of asynchronous actuation of the Angara-5-1 facility modules on the penetration of the magnetic field inside a wire array  

NASA Astrophysics Data System (ADS)

The influence of asynchronous actuation of the Angara-5-1 facility modules on the implosion symmetry of the wire array plasma in the Z-pinch mode is studied. It is shown that an increase in the r.m.s. jitter in the start times of the modules leads to an appreciable azimuthal asymmetry of magnetic field penetration inside the wire array and, as a consequence, to an increase in the duration of the soft X-ray pulse, a decrease in its power, and a shift of the Z-pinch with respect to the array axis. Necessary conditions for axisymmetric pinch implosion are determined. Experimental data on the magnitude and azimuthal distribution of the current (magnetic field) inside the wire array were obtained from magnetic probe measurements. The position of the Z-pinch with respect to the wire array axis was determined from two-dimensional X-ray images and radial optical streak images.

Mitrofanov, K. N.; Aleksandrov, V. V.; Grabovski, E. V.; Gritsuk, A. N.; Oleinik, G. M.; Frolov, I. N.; Laukhin, Ya. N.; Samokhin, A. A.

2014-05-01

155

The influence on magnetic property of nickel nanoparticles deposited on the silicon nanowires arrays at low temperature  

NASA Astrophysics Data System (ADS)

There are a large number of paramagnetic defects on the surface of as-grown silicon nanowires (SiNWs) in contrast to H-terminated silicon (Si). Herein, SiNWs arrays were fabricated by chemical etching, Nickel nanoparticles (Ni NPs) were deposited on the surface of SiNWs arrays by the electroless plating. The influence of paramagnetic defects on the magnetic property of Ni/SiNWs was investigated and compared to Ni/Si. The paramagnetic defects of as-grown SiNWs and H-terminated Si were studied by ESR and FTIR spectra. The diameter distribution of Ni NPs on the surface of SiNWs arrays and Si was probed by SEM and fitted by the lognormal probability density function. The results reveal that the diameters of Ni NPs are 35.09 ± 0.53 and 34.92 ± 0.72 nm respectively. The magnetic properties of M-H hysteresis loops for Ni/SiNWs and Ni/Si were measured from 5 to 400 K. With the temperature increasing, the saturation magnetization of Ni/SiNWs and Ni/Si decreases gradually due to the thermal activation effect. Overall temperature range (5-400 K), the saturation magnetization of Ni/Si follows the modified Bloch's law. However, the data of Ni/SiNWs are only valid for high temperature range (50-400 K). At low temperature (5 K), there is an abrupt increase and the experimental data deviated from the modified Bloch model. This deviation at low temperature is associated with surface paramagnetic defects of SiNWs.

Wang, Zhiliang; Yin, Haihong; Chen, Yonghong; Guo, Xinglong; Zhang, Xuefeng; Song, Changqing; Zhang, Jian

2014-09-01

156

Effect of deposition voltage and Co 2+ concentration on the texture and magnetic properties of Co nanowire arrays  

NASA Astrophysics Data System (ADS)

Highly ordered Co nanowire arrays were grown using a direct current (DC) electrodeposition method based on an anodic aluminum oxide (AAO) template. The electrolyte consists of CoSO 4·7H 2O and H 3BO 3 in distilled water. Co nanowires fabricated by electrodeposition are cylindrical monocrystals with a packed surface, and behave as hcp dominant structures. The nanowires are preferentially oriented along the [1 0 0] direction. The effective demagnetizing factors parallel and perpendicular to the plane of the film are Neff(?)=0.65 and Neff(?)=0.175, respectively. The magnetic property of the Co nanowire arrays depends on the concentration of the deposition electrolyte and the deposition voltage.

Cui, C. X.; Wang, B. L.; Yang, W.; Sun, J. B.

2011-06-01

157

Controlled Assembly of Magnetic Nanoparticles from Magnetotactic Bacteria Using Microelectromagnets Arrays  

Microsoft Academic Search

Controlled assembly of magnetic nanoparticles was demonstrated by manipulating magnetotactic bacteria in a fluid with microelectromagnets. Magnetotactic bacteria synthesize a chain of magnetic nanoparticles inside their bodies. Microelectromagnets, consisting of multiple layers of lithographically patterned conductors, generate versatile magnetic fields on micrometer length scales, allowing sophisticated control of magnetotactic bacteria inside a microfluidic chamber. A single bacterium was stably trapped

Hakho Lee; Alfreda M. Purdon; Vincent Chu; Robert M. Westervelt

2004-01-01

158

Bi-directional-bi-dimensionality alignment of self-supporting Mn3O4 nanorod and nanotube arrays with different bacteriostasis and magnetism.  

PubMed

Self-supported Mn3O4 patterns of aligned nanorods and nanotubes were synthesized through a bi-directional-bi-dimensionality growth model by using sodium gluconate and urea as additives under mild hydrothermal conditions without the use of any substrates. In one direction, Mn3O4 grows to form one-dimensional nanorods or nanotubes, while in the other direction Mn3O4 grows into two-dimensional nanoplates to support the nanorods or nanotubes to align into arrays. These two kinds of new nanostructures, a nanotube pattern and a nanorod pattern, show similar and good bacteriostasis for Gram positive bacteria, but for Gram negative bacteria the nanotube pattern shows much better bacterial restraint than the nanorod pattern. Magnetic studies show that the nanorod arrays display similar magnetic properties to the commercial Mn3O4, while the nanotube arrays show different ferromagnetic behaviors with enhanced remnant magnetization and saturation magnetization (Ms) at low temperature. PMID:24136592

Chen, Qun; Wei, Chengzhen; Gao, Feng; Pang, Huan; Lu, Qingyi

2013-12-21

159

Bi-directional-bi-dimensionality alignment of self-supporting Mn3O4 nanorod and nanotube arrays with different bacteriostasis and magnetism  

NASA Astrophysics Data System (ADS)

Self-supported Mn3O4 patterns of aligned nanorods and nanotubes were synthesized through a bi-directional-bi-dimensionality growth model by using sodium gluconate and urea as additives under mild hydrothermal conditions without the use of any substrates. In one direction, Mn3O4 grows to form one-dimensional nanorods or nanotubes, while in the other direction Mn3O4 grows into two-dimensional nanoplates to support the nanorods or nanotubes to align into arrays. These two kinds of new nanostructures, a nanotube pattern and a nanorod pattern, show similar and good bacteriostasis for Gram positive bacteria, but for Gram negative bacteria the nanotube pattern shows much better bacterial restraint than the nanorod pattern. Magnetic studies show that the nanorod arrays display similar magnetic properties to the commercial Mn3O4, while the nanotube arrays show different ferromagnetic behaviors with enhanced remnant magnetization and saturation magnetization (Ms) at low temperature.Self-supported Mn3O4 patterns of aligned nanorods and nanotubes were synthesized through a bi-directional-bi-dimensionality growth model by using sodium gluconate and urea as additives under mild hydrothermal conditions without the use of any substrates. In one direction, Mn3O4 grows to form one-dimensional nanorods or nanotubes, while in the other direction Mn3O4 grows into two-dimensional nanoplates to support the nanorods or nanotubes to align into arrays. These two kinds of new nanostructures, a nanotube pattern and a nanorod pattern, show similar and good bacteriostasis for Gram positive bacteria, but for Gram negative bacteria the nanotube pattern shows much better bacterial restraint than the nanorod pattern. Magnetic studies show that the nanorod arrays display similar magnetic properties to the commercial Mn3O4, while the nanotube arrays show different ferromagnetic behaviors with enhanced remnant magnetization and saturation magnetization (Ms) at low temperature. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03453d

Chen, Qun; Wei, Chengzhen; Gao, Feng; Pang, Huan; Lu, Qingyi

2013-11-01

160

A radio-frequency source using direct digital synthesis and field programmable gate array for nuclear magnetic resonance  

NASA Astrophysics Data System (ADS)

A radio-frequency (rf) source for nuclear magnetic resonance (NMR) is described. With the application of direct digital synthesis (DDS), the rf source has the ability to yield rf pulses with short switching time and high resolution in frequency and phase. To facilitate the generation of a soft pulse, a field programmable gate array (FPGA) cooperating with a pulse programmer is used as the auxiliary controller of the DDS chip. Triggered by the pulse programmer, the FPGA automatically controls the DDS to generate soft pulse according to predefined parameters, and the operation mode of the pulse programmer is optimized. The rf source is suitable for being used as transmitter in low-field (<1 T) NMR applications, for example, magnetic resonance imaging and relaxation measurement. As a compact and low-cost module, the rf source is of general use for constructing low-field NMR spectrometer.

Liang, Xiao; Weimin, Wang

2009-12-01

161

Investigation of high-resolution functional magnetic resonance imaging by means of surface and array radiofrequency coils at 7 T.  

PubMed

In this investigation, high-resolution, 1x1x1-mm(3) functional magnetic resonance imaging (fMRI) at 7 T is performed using a multichannel array head coil and a surface coil approach. Scan geometry was optimized for each coil separately to exploit the strengths of both coils. Acquisitions with the surface coil focused on partial brain coverage, while whole-brain coverage fMRI experiments were performed with the array head coil. BOLD sensitivity in the occipital lobe was found to be higher with the surface coil than with the head array, suggesting that restriction of signal detection to the area of interest may be beneficial for localized activation studies. Performing independent component analysis (ICA) decomposition of the fMRI data, we consistently detected BOLD signal changes and resting state networks. In the surface coil data, a small negative BOLD response could be detected in these resting state network areas. Also in the data acquired with the surface coil, two distinct components of the positive BOLD signal were consistently observed. These two components were tentatively assigned to tissue and venous signal changes. PMID:19261421

van der Zwaag, Wietske; Marques, José P; Hergt, Martin; Gruetter, Rolf

2009-10-01

162

Magnetic properties of ordered bi-layer nanowire arrays with different Co crystallographic structures  

NASA Astrophysics Data System (ADS)

Cobalt nanowire arrays with varying length were grown by pulse electrochemical route into the pores of alumina template. The structural investigation reveals that at the bottom of the nanowire, it grows with hcp (002) structure up to few hundred nanometer in length and then changes its crystal orientation to hcp (100) phase as it further grows along the wire axis. The variation of measured coercivity and the remanent ratio as a function of nanowire length indicate that each nanowire in array grows with three different segments. The micromagnetic simulations carried out on these structures are then correlated with experimental observations.

Sellarajan, B.; Kulkarni, P. D.; Krishnan, M.; Barshilia, Harish C.; Chowdhury, P.

2013-03-01

163

Complete numerical description of nonlocal quantum diffusion in an array of magnetic-flux vortices  

Microsoft Academic Search

A hybrid experimental system in which the inhomogeneous magnetic-field distribution near a superconducting gate layer is projected down onto the two-dimensional electron gas beneath it has been the subject of a large number of recent investigations. Studies have focused on both the transport of carriers in such a ``magnetic'' mesoscopic system as well as the dynamics of vortices in the

S. J. Bending

1994-01-01

164

Physical realization of magnetic walls using finite-thickness 3D printed arrays  

Microsoft Academic Search

Perfect magnetic conductors (PMC) have been useful in electromagnetics for many years as subsidiary hypothetical surfaces in conjunction with formal dualities between dielectric and magnetic currents and vector potentials. This in turn helped formulating equivalence theorems and solving many scattering problems involving either a single scatterer in a solvable background (aperture in waveguiding structures) or many scatterers in highly symmetrical

H. Contopanagos; C. Kyriazidou; W. Merrill; N. G. Alexopoulos

1999-01-01

165

MAGNET LEVITATION AND TRAJECTORY FOLLOWING MOTION CONTROL USING A PLANAR ARRAY OF CYLINDRICAL COILS  

Microsoft Academic Search

We have formulated and implemented a control system for levitation and motion control of a disk magnet using a planar ar- ray of electromagnetic coils and an optical localizer to provide real time position feedback. The significance of this work is that this is the first magnetic levitation system which controls the ori- entation and position of a levitated body

Peter Berkelman; Michael Dzadovsky

2008-01-01

166

Study of the magnetic interaction of a 4-coil array and copper shielding with a PET/MRI using the finite-element method.  

PubMed

The effect of the shielding in a PET-MRI system was numerically estimated by calculating the RF magnetic field, B1, produced by a coil array of 4 independent elements at the resonant frequency of 171 MHz (4T for protons). The array coil is located inside a ?PET camera to simultaneously acquire PET and MR images of a rat brain. Profiles showed a good uniformity despite the shielding that is interacting between the coil array and the ?PET camera. These limitations are currently being dealt with the fabrication of a birdcage coil design. PMID:21097202

Solis, S E; Rodriguez, A O; Tomasi, D

2010-01-01

167

Study of the radial distribution of the magnetic field in the wire array plasma at the Angara-5-1 facility  

NASA Astrophysics Data System (ADS)

Results are presented from experimental studies of the implosion of wire (tungsten, aluminum, and molybdenum) and fiber (kapron) arrays at the Angara 5-1 facility at currents of up to 4 MA. The radial distributions of the azimuthal magnetic field in the stage of plasma production in such arrays are measured in detail for the first time, and the radial profiles of the current density are evaluated. The data obtained using an optical streak camera are compared with the results of measurements of the current and voltage. Using the obtained experimental results, the rate of plasma production in the arrays made of different materials is estimated.

Mitrofanov, K. N.; Grabovski, E. V.; Oleinik, G. M.; Aleksandrov, V. V.; Gritsuk, A. N.; Frolov, I. N.; Laukhin, Ya. N.; Sasorov, P. V.; Samokhin, A. A.

2012-10-01

168

Amplification of electromagnetic waves excited by a chain of propagating magnetic vortices in YBa2Cu3O7-? Josephson-junction arrays at 77 K and above  

NASA Astrophysics Data System (ADS)

When a soliton propagates in a discrete lattice it excites small-amplitude linear waves in its wake. In a dc current-biased Josephson-junction (JJ) array these manifest as electromagnetic (EM) waves excited by a (magnetic field induced) chain of propagating magnetic vortices. When the vortex velocity and the phase velocity of one of the excited EM waves match, phase-locking occurs. This produces resonant steps in the current-voltage characteristics where amplification of EM radiation occurs. We report the first observation of phase-locking-induced amplification of EM radiation at 77 K and above in JJ arrays made of high temperature superconductors.

Chesca, Boris; John, Daniel; Mellor, Christopher J.

2014-08-01

169

Gas-assisted growth of boron-doped nickel nanotube arrays: rapid synthesis, growth mechanisms, tunable magnetic properties, and super-efficient reduction of 4-nitrophenol  

NASA Astrophysics Data System (ADS)

Highly ordered noncrystalline boron-doped nickel nanotube arrays are rapidly synthesized within 150 s by template-based electroless deposition. The as-prepared nanotubes have tunable magnetic properties and exhibit super efficient catalytic activity (~70 s) for the reduction of 4-nitrophenol.Highly ordered noncrystalline boron-doped nickel nanotube arrays are rapidly synthesized within 150 s by template-based electroless deposition. The as-prepared nanotubes have tunable magnetic properties and exhibit super efficient catalytic activity (~70 s) for the reduction of 4-nitrophenol. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00411b

Li, Xiang-Zi; Wu, Kong-Lin; Ye, Yin; Wei, Xian-Wen

2013-04-01

170

Planar array of self-assembled GaxFe4-xN nanocrystals in GaN: magnetic anisotropy determined via ferromagnetic resonance.  

PubMed

The magnetic anisotropy of a planar array of GaxFe(4 - x)N nanocrystals (NCs) embedded in a GaN host is studied by ferromagnetic resonance. X-ray diffraction and transmission electron microscopy are employed to determine the phase and distribution of the nanocrystals. The magnetic anisotropy is found to be primarily uniaxial with the hard axis normal to the NCs plane and to have a comparably weak in-plane hexagonal symmetry. The origin of the magnetic anisotropy is discussed taking into consideration the morphology of the nanocrystals, the epitaxial relations, strain effects and magnetic coupling between the NCs. PMID:25201242

Grois, A; Devillers, T; Li, Tian; Bonanni, A

2014-10-01

171

Planar array of self-assembled GaxFe4-xN nanocrystals in GaN: magnetic anisotropy determined via ferromagnetic resonance  

NASA Astrophysics Data System (ADS)

The magnetic anisotropy of a planar array of GaxFe4 - xN nanocrystals (NCs) embedded in a GaN host is studied by ferromagnetic resonance. X-ray diffraction and transmission electron microscopy are employed to determine the phase and distribution of the nanocrystals. The magnetic anisotropy is found to be primarily uniaxial with the hard axis normal to the NCs plane and to have a comparably weak in-plane hexagonal symmetry. The origin of the magnetic anisotropy is discussed taking into consideration the morphology of the nanocrystals, the epitaxial relations, strain effects and magnetic coupling between the NCs.

Grois, A.; Devillers, T.; Li, Tian; Bonanni, A.

2014-09-01

172

Electronic spectrum of a two-dimensional quantum dot array in the presence of electric and magnetic fields in the Hall configuration  

NASA Astrophysics Data System (ADS)

We report calculations of the electronic spectrum of a two-dimensional lattice of coupled quantum dots, subject to external electric and magnetic fields in the Hall configuration. The quantum dots array was modeled by a periodic superposition of truncated, parabolic potential wells. By adopting the Landau gauge, a single-particle Hamiltonian was formulated, and its eigenfunctions were obtained as appropriately symmetrized, magnetic field-dependent Bloch functions. The magnetic field was consistently included in the corresponding Wannier functions, which were approximated by the eigenvectors of an isolated quantum dot in the presence of the external magnetic field, and multiplied by the Peierls’s phase.

Muñoz, Enrique; Barticevic, Zdenka; Pacheco, Monica

2005-04-01

173

Magnetic and magnetotransport properties of arrays of nanostructured antidots obtained by self-assembling polystyrene nanosphere lithography  

SciTech Connect

A well-ordered nanopatterned structure has been obtained in sputtered magnetic thin films by self-assembling of polystyrene nanospheres. Arrays of holes in Co, Ni, and Ni{sub 80}Fe{sub 20} films having a mean size ranging in the interval of 200-400 nm depending on the experimental condition have been prepared. Sample microstructure has been studied by scanning electron microscopy and atomic force microscopy. Room-temperature hysteresis loops have been measured in the parallel and perpendicular configuration (H{sub max}=20 kOe). Magnetoresistance (MR) measurements have been performed by means of a standard four-contact technique at several angles between the current and the magnetic field (H{sub max}=70 kOe) in the temperature interval of 4-200 K. An anisotropic MR effect has been observed in all compositions independent on the hole mean dimension. The role on magnetic and magnetotransport properties of either sample microstructure or composition has been studied in such patterned structures.

Tiberto, Paola; Boarino, Luca; Celegato, Federica; Coiesson, Marco; De Leo, Natascia; Vinai, Franco [INRIM, Strada delle Cacce 91, Torino I-10135 (Italy); Allia, Paolo [DISMIC, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino, 1-10129 (Italy)

2010-05-15

174

Force measurements of a magnetic micro actuator proposed for a microvalve array  

NASA Astrophysics Data System (ADS)

Low-cost, easily-fabricated and power-efficient microvalves are necessary for many microfluidic lab-on-a-chip applications. In this study, we present a simple, low-power, scalable, CMOS-compatible magnetic actuator for microvalve applications composed of a paramagnetic bead as the ball valve over a picoliter reaction well etched into a silicon substrate. The paramagnetic bead, composed of either pure FeSi or magnetite in a SiO2 matrix, is actuated by the local magnetic field gradient generated by a microcoil in an aqueous environment, and the reaction well is situated at the microcoil center. A permanent magnet beneath the microvalve device provides an external magnetic biasing field that magnetizes the bead, enabling bidirectional actuation and reducing the current required to actuate the bead to a level below 10 mA. The vertical and radial magnetic forces exerted on the bead by the microcoil were measured for both pure FeSi and composite beads and agree well with the predictions of 2D axisymmetric finite element method models. Vertical forces were within a range of 13-80 nN, and radial forces were 11-60 nN depending on the bead type. The threshold current required to initiate bead actuation was measured as a function of bead diameter and is found to scale inversely with volume for small beads, as expected based on the magnetic force model. To provide an estimate of the stiction force acting between the bead and the passivation layer on the substrate, repeated actuation trials were used to study the bead throw distance for substrates coated with silicon dioxide, Parylene-C, and photoresist. The stiction observed was lowest for a photoresist-coated substrate, while silicon dioxide and Parylene-C coated substrates exhibited similar levels of stiction.

Chang, Pauline J.; Chang, Frank W.; Yuen, Michelle C.; Otillar, Robert; Horsley, David A.

2014-03-01

175

Experimental investigations on a permanent magnet brushless DC motor fed by PV array for water pumping system  

SciTech Connect

This paper describes the experimental study carried out on a Permanent Magnet Brushless DC (PMBLDC) Motor drive coupled to a pump load powered by photovoltaic (PV) array for water pumping system. A simple low cost prototype controller has been designed and developed without current and position sensors which reduces drastically the overall cost of the drive system. This controller is used to test the dynamic behavior of the PMBLDC motor drive system. The mathematical model of the system is developed with a view to carrying out a comparison between experimental and simulated response of the drive system. The necessary computer algorithm is developed to analyze the performance under different conditions of varying solar insolation for a pump load. The developed state space equations are simulated to obtain the performance characteristics which are also verified by conducting suitable experiments on the development system.

Putta Swamy, C.L.; Singh, B.; Singh, B.P.; Murthy, S.S. [IIT Delhi, New Delhi (India). Dept. of Electrical Engineering

1996-12-31

176

Comment on ``Magnetization of two-dimensional square arrays of nanomagnets''  

NASA Astrophysics Data System (ADS)

Recently, Takagaki and Ploog [Phys. Rev. B 71, 184439 (2005)] used a fourth-order Runge-Kutta technique to integrate the Landau-Lifschitz-Gilbert equations for square lattices of N×N magnetic nanodots with dipolar interdot interactions. Some of their results appeared to differ qualitatively from the second-order Runge-Kutta results obtained for the same systems by Kayali and Saslow [Phys. Rev. B 70, 174404 (2004)], both in the hysteresis area AN and in the number of steps of the magnetization hysteresis loops. We show that these differences are not due to inaccuracies in either calculation or to the potentially different magnetic induction sweep rates used, but can be attributed entirely to different choices of the dipolar interaction strength hdip?a-3 , where a is the two-dimensional lattice constant.

Alcántara Ortigoza, Marisol; Klemm, Richard A.; Rahman, Talat S.

2006-12-01

177

Preparation and magnetic properties of cylindrical NiFe films and antidot arrays.  

PubMed

Continuous NiFe (Permalloy) cylindrical films and arrays of cylindrical NiFe antidots 7 nm thick have been prepared by sputtering onto cylindrical aluminum wires and onto wires anodized to form a porous anodic alumina layer. The antidots are arranged in a close-packed pattern determined by the hexagonal pore arrangement in the porous alumina, with period 103 nm and diameter 42 nm. Hysteresis loops were measured at different angles with respect to the cylinder axis and indicate an easy plane normal to the radius of the wire. The antidots enhance the coercivity compared to the continuous cylindrical film. PMID:21137795

Sanz, R; Navas, D; Vazquez, M; Hernández-Vélez, M; Ross, C A

2010-10-01

178

Subwavelength terahertz spin-flip laser based on a magnetic point-contact array.  

PubMed

We present a theoretical design for a single-mode, truly subwavelength terahertz disk laser based on a nanocomposite gain medium comprising an array of normal-metal/ferromagnetic (FM) point contacts embedded in a thin dielectric layer. Stimulated emission of light occurs due to spin-flip relaxation of spin-polarized electrons injected from the FM side of the contacts. Ultrahigh electrical current densities in the contacts and a dielectric material with a large refractive index, neither condition being achievable in conventional semiconductor media, enables the thresholds of lasing to be overcome for the lowest-order modes of the disk, making single-mode operation possible. PMID:21686027

Shekhter, Robert I; Kadigrobov, Anatoliy M; Jonson, Mats; Smotrova, Elena I; Nosich, Alexander I; Korenivski, Vladislav

2011-06-15

179

Onset temperature of the collective magnetic response of a tridimensional disordered Josephson junction array  

NASA Astrophysics Data System (ADS)

In this work, measurements of AC-susceptibility, magnetic remanence and resistivity, carried out on a superconducting sample of YBa 2Cu 3O 7- ? are presented. The sample was produced by a two-steps solid state reaction, a variation of the conventional method. AC-susceptibility and magnetic remanence measurements, carried out at different excitation fields, and resistivity measurements, conducted for a variety of values of current, reveal a unique temperature at which the weak-links cease to respond. Present results are consistent with those obtained for other systems.

Rodriguez-Aliaga, L. C.; Caparroz, R.; Lisboa-Filho, P. N.; Passos, W. A. C.; Ortiz, W. A.

2004-08-01

180

Controllable step motors and rectifiers of magnetic flux quanta using periodic arrays of asymmetric pinning defects  

NASA Astrophysics Data System (ADS)

We study the transport of vortices in superconductors with regular arrays of asymmetric pinning wells when applying an alternating electrical current. The asymmetric traps are modelled by the superposition of two interpenetrating square lattices of weak and strong pinning centers with separation smaller than the lattice constant. We show that this system can induce a net rectifying or diode effect for the vortex motion, including collective step-motor-type dynamics, where many vortices move forward a controlled and exact number of pin-lattice spacings at each cycle of the ac driving force. This system exhibits a remarkable net dc response with striking sawtooth-type oscillations. The net dc voltage response Vdc of the ac-driven vortices versus both the half period P and the amplitude FL of the “square wave” ac drive has been detailed in the present work. The influence of the equilibrium thermal noise, the shift between the two pinning sublattices, the degree of translational and orientational disorder, and the size of the simulation system on the Vdc response of the vortex motion at ac drive has also been addressed. Devil staircase and Arnold’s tongue structures are revealed. We also analytically derive all the key features of our numerical results. This system provides a very controllable stepmotor for the control of collective motion. Our results apply mutatis mutandis to arrays of Josephson junctions, colloidal systems with optical traps, Wigner crystals, and any system with repelling movable objects that can be pinned by a lattice of traps.

Zhu, B. Y.; Marchesoni, F.; Moshchalkov, V. V.; Nori, Franco

2003-07-01

181

Fabrication and magnetic properties of amorphous Co 0.71Pt 0.29 nanowire arrays  

NASA Astrophysics Data System (ADS)

Highly ordered Co 0.71Pt 0.29 alloy nanowire arrays have been fabricated successfully by direct current electro-deposition into the pores of a porous anodic aluminum oxide (AAO) template. SEM and TEM images reveal that the nanowires of array are uniform, well isolated, and parallel to one another. The aspect ratio of nanowires is over 200. XRD and EDS pattern indicates that amorphous Co 0.71Pt 0.29 structure was formed during electro-deposition. In amorphous sample, magnetocrystal anisotropy is very small, therefore, shape anisotropy plays a dominant role which leads to strong perpendicular anisotropy. High coercivity (Hc=1.7 kOe) and squareness (Mr/Ms) around 0.7 were obtained in the samples when the field was applied parallel to the axis of the nanowires. However, when it changed to polycrystalline structure after annealing, due to the competition of magnetocrystal anisotropy and shape anisotropy, the sample did not display perpendicular anisotropy.

Li, Hua; Xu, Cailing; Zhao, Guangyu; Su, Yikun; Xu, Tao; Li, Hulin

2004-11-01

182

Stability considerations for magnetic suspension systems using electromagnets mounted in a planar array  

NASA Technical Reports Server (NTRS)

Mathematical models of a 5, 6, 7, and 8 coil large gap magnetic suspension system (MSDS) are presented. Some of the topics covered include: force and torque equations, reduction of state-space form, natural modes, origins of modes, effect of rotation in azimuth (yaw), future work, and n-coil ring conclusions.

Groom, Nelson J.; Britcher, Colin P.

1991-01-01

183

An Ultrasensitive CMOS Magnetic Biosensor Array with Correlated Double Counting Noise Suppression  

E-print Network

, Pasadena, California, 91125, USA Abstract -- This paper presents a scalable and ultrasensitive frequency magnetic particles with an SNR of 14.6dB for a single bead and an effective dynamic range of at least 74.5d integrated circuits, integrated circuit noise. I. INTRODUCTION Portable microarrays are promising for Point-of-Care

Hajimiri, Ali

184

Spectral gap of shear Alfvn waves in a periodic array of magnetic mirrors Yang Zhang, W. W. Heidbrink, H. Boehmer, and R. McWilliams  

E-print Network

Spectral gap of shear Alfvén waves in a periodic array of magnetic mirrors Yang Zhang, W. W-dot probes at many axial locations. Alfvén wave spectral gaps and continua are formed similar to wave propagation in other periodic media due to the Bragg effect. The measured width of the propagation gap

Heidbrink, William W.

185

Ambient-Temperature Passive Magnetic Bearings for Flywheel Energy Storage Systems  

SciTech Connect

Based on prior work at the Lawrence Livermore National Laboratory ambient-temperature passive magnetic bearings are being adapted for use in high-power flywheel energy storage systems developed at the Trinity Flywheel Power company. En route to this goal specialized test stands have been built and computer codes have been written to aid in the development of the component parts of these bearing systems. The Livermore passive magnetic bearing system involves three types of elements, as follows: (1) Axially symmetric levitation elements, energized by permanent magnets., (2) electrodynamic ''stabilizers'' employing axially symmetric arrays of permanent magnet bars (''Halbach arrays'') on the rotating system, interacting with specially wound electrically shorted stator circuits, and, (3) eddy-current-type vibration dampers, employing axially symmetric rotating pole assemblies interacting with stationary metallic discs. The theory of the Livermore passive magnetic bearing concept describes specific quantitative stability criteria. The satisfaction of these criteria will insure that, when rotating above a low critical speed, a bearing system made up of the three elements described above will be dynamically stable. That is, it will not only be stable for small displacements from equilibrium (''Earnshaw-stable''), but will also be stable against whirl-type instabilities of the types that can arise from displacement-dependent drag forces, or from mechanical-hysteritic losses that may occur in the rotor. Our design problem thus becomes one of calculating and/or measuring the relevant stiffnesses and drag coefficients of the various elements and comparing our results with the theory so as to assure that the cited stability criteria are satisfied.

Bender, D.; Post, R.

2000-05-26

186

Atomic ordering and magnetic properties of polycrystalline L1 0-FePd dot arrays  

NASA Astrophysics Data System (ADS)

The polycrystalline L1 0-FePd (0 0 1) films considering a highly ordered dot array with various sizes have been successfully prepared by using a microfabrication process. The lateral size of square dots was changed in between 1 and 10 ?m. The coercivity ( Hc) of patterned L1 0-ordered FePd films was found to be slightly reduced compared to that of continuous film. Furthermore, Hc was slightly decreased after annealing at 500 °C. In the pinning mechanism, Hc can be determined by strong pinning sites for domain walls, which are the grain boundary regions in L1 0-ordered polycrystalline FePd films. These results indicate that the dot size dependence of Hc before and after annealing may be related to the pinning mechanism. The long-range ordering parameter ( S) was increased after annealing. This demonstrates that post-annealing accelerates L1 0-FePd ordering, but there is no clear correlation between S and Hc.

Kang, J.-G.; Ha, J.-G.; Koh, J.-H.; Koo, S.-M.; Kamiko, M.; Mitani, S.; Sakuraba, Y.; Takanashi, K.; Bae, S.-T.; Yeom, H.-J.

2010-08-01

187

Magnetic measurements using array of integrated Hall sensors on the CASTOR tokamak  

SciTech Connect

We have performed the first tests of 'integrated' Hall sensors (IHSs) in a tokamak in-vessel environment. IHS combines the sensing element together with the complex electronic circuitry on a single small chip. The on-chip integrated circuits provide stabilization of the supply voltage, output amplification, noise suppression, and elimination of temperature dependencies. Eight IHSs of A1322LUA type produced by Allegro MicroSystems, Inc. were mounted on a stainless steel ring symmetrically encircling the CASTOR plasmas in poloidal direction 10 mm outside the limiter radius. IHSs were oriented such that they measure the horizontal and vertical magnetic fields. We found out that these sensors qualify for in-vessel use of small to middle sized fusion devices where the radiation is not an issue and the temperature below 150 deg. C can be guaranteed. The main advantages over the traditional pickup coils are the smaller size and more straightforward interpretation of output without the need of rather cumbersome integration and drift removal procedure associated with the use of inductive loops. We successfully exploited the sensors for determination of vertical plasma displacement on CASTOR. This new diagnostic helped us to shed more light into long term observed discrepancy on CASTOR between vertical plasma displacement as deduced by standard magnetic and by nonmagnetic diagnostics (Langmuir probes, bolometers)

Duran, Ivan; Hronova, Olena; Stoeckel, Jan [Association EURATOM/IPP.CR, Institute of Plasma Physics AS CR, v. v. i., Za Slovankou 3, 182 00 Praha 8 (Czech Republic); Sentkerestiova, Jana [Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Brehova 7, 115 19 Praha 1 (Czech Republic); Havlicek, Josef [Association EURATOM/IPP.CR, Institute of Plasma Physics AS CR, v. v. i., Za Slovankou 3, 182 00 Praha 8 (Czech Republic); Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Praha 2 (Czech Republic)

2008-10-15

188

Electro-magnetic Sensing and Actuation Array on Silicon Substrate Faisal T. Abu-Nimeh and Fathi M. Salem  

E-print Network

-Nimeh and Fathi M. Salem Abstract-- Electromagnetic arrays can be precisely con- structed on silicon CMOS1815,salem}@egr.msu.edu Fig. 1. Silicon-die of an integrated 16x16 array of coil actuators with support

Salem, Fathi M.

189

Confinement Scaling of Magnetically-Channeled SIEC Array (MCSA) Fusion Device  

NASA Astrophysics Data System (ADS)

A spherical inertia electrostatic confinement (SIEC) is one of the most attractive fusion concepts because of its simple structure. It requires only a spherical meshed grid in a vacuum chamber and yields 108 neutrons/s from deuterium plasma in small laboratory devices. However, detailed studies such as stability analysis and development of special ion beam sources are required for improving the performance of SIEC. After certain improvements to avoid instabilities and to integrate sharp-focusing ion sources, an improved SIEC might first be utilized for various ion beam or neutron beam applications. However, a proof of principle experiment to demonstrate the basic physics (recirculation type stable cusp confinement and end cone loss re-trapping in multiple units) of this concept is required to demonstrate the feasibility of this approach for development as a fusion power reactor. Such a POP experiment is the objective of this proposal. High-temperature plasma (SIEC in low-field region) is confined by stable magnetic configuration while radial losses are minimized by channeling flow is into neighboring IEC regions. Confinement time can be very long due to an extremely large effective mirror ratio resulting in higher efficiency than a single SIEC. Fusion-product heating and ignition is also possible using collimating properties of the confinement field. Predicted scaling is linear with radius of device, possibly allowing break-even machine at a few meter radius with a several Tesla field.

Miley, George; Stubbers, Robert; Webber, Jason; Momota, Hiromu

2003-10-01

190

Development of a magnetic electrochemical bar code array for point mutation detection in the H5N1 neuraminidase gene.  

PubMed

Since its first official detection in the Guangdong province of China in 1996, the highly pathogenic avian influenza virus of H5N1 subtype (HPAI H5N1) has reportedly been the cause of outbreaks in birds in more than 60 countries, 24 of which were European. The main issue is still to develop effective antiviral drugs. In this case, single point mutation in the neuraminidase gene, which causes resistance to antiviral drug and is, therefore, subjected to many studies including ours, was observed. In this study, we developed magnetic electrochemical bar code array for detection of single point mutations (mismatches in up to four nucleotides) in H5N1 neuraminidase gene. Paramagnetic particles Dynabeads® with covalently bound oligo (dT)?? were used as a tool for isolation of complementary H5N1 chains (H5N1 Zhejin, China and Aichi). For detection of H5N1 chains, oligonucleotide chains of lengths of 12 (+5 adenine) or 28 (+5 adenine) bp labeled with quantum dots (CdS, ZnS and/or PbS) were used. Individual probes hybridized to target molecules specifically with efficiency higher than 60%. The obtained signals identified mutations present in the sequence. Suggested experimental procedure allows obtaining further information from the redox signals of nucleic acids. Moreover, the used biosensor exhibits sequence specificity and low limits of detection of subnanogram quantities of target nucleic acids. PMID:23860384

Krejcova, Ludmila; Hynek, David; Kopel, Pavel; Rodrigo, Miguel Angel Merlos; Adam, Vojtech; Hubalek, Jaromir; Babula, Petr; Trnkova, Libuse; Kizek, Rene

2013-07-01

191

Critical current of tridimensional La 1.85Sr 0.15CuO 4- ? disordered Josephson junction arrays - dependence with the magnetic field  

NASA Astrophysics Data System (ADS)

This paper deals with the magnetic field ( H) dependence of the critical current of a tridimensional disordered Josephson junction array. The average critical current of an array of La 1.85Sr 0.15CuO 4- ? is determined through the AC-susceptibility measured with an excitation field of amplitude h. The critical field Hc, necessary to switch off supercurrents through the weak-links at the working temperature is also obtained. This configuration relies on ???( h) - instead of ??( H) - to determine the critical currents, what proved to be particularly useful for experimental setups with excitation and applied fields parallel to each other, a case in which the static flux imposed to the array affects ?? much more severely than ???.

Caparroz, R.; Lisboa-Filho, P. N.; Passos, W. A. C.; Ortiz, W. A.

2001-05-01

192

Submillimeter Array Observations of Magnetic Fields in G240.31+0.07: An Hourglass in a Massive Cluster-forming Core  

NASA Astrophysics Data System (ADS)

We report the first detection of an hourglass magnetic field aligned with a well-defined outflow rotation system in a high-mass, star-forming region. The observations were performed with the Submillimeter Array toward G240.31+0.07, which harbors a massive, flattened, and fragmenting molecular cloud core and a wide-angle bipolar outflow. The polarized dust emission at 0.88 mm reveals a clear hourglass-shaped magnetic field aligned within 20° of the outflow axis. Maps of high-density tracing spectral lines, e.g., H13CO+ (4-3), show that the core is rotating about its minor axis, which is also aligned with the magnetic field axis. Therefore, both the magnetic field and kinematic properties observed in this region are surprisingly consistent with the theoretical predictions of the classic paradigm of isolated low-mass star formation. The strength of the magnetic field in the plane of sky is estimated to be ~1.1 mG, resulting in a mass-to-magnetic flux ratio of 1.4 times the critical value and a turbulent-to-ordered magnetic energy ratio of 0.4. We also find that the specific angular momentum almost linearly decreases from r ~ 0.6 pc to 0.03 pc scales, which is most likely attributed to magnetic braking.

Qiu, Keping; Zhang, Qizhou; Menten, Karl M.; Liu, Hauyu B.; Tang, Ya-Wen; Girart, Josep M.

2014-10-01

193

Array of Hall Effect Sensors for Linear Positioning of a Magnet Independently of Its Strength Variation. A Case Study: Monitoring Milk Yield during Milking in Goats  

PubMed Central

In this study we propose an electronic system for linear positioning of a magnet independent of its modulus, which could vary because of aging, different fabrication process, etc. The system comprises a linear array of 24 Hall Effect sensors of proportional response. The data from all sensors are subject to a pretreatment (normalization) by row (position) making them independent on the temporary variation of its magnetic field strength. We analyze the particular case of the individual flow in milking of goats. The multiple regression analysis allowed us to calibrate the electronic system with a percentage of explanation R2 = 99.96%. In our case, the uncertainty in the linear position of the magnet is 0.51 mm that represents 0.019 L of goat milk. The test in farm compared the results obtained by direct reading of the volume with those obtained by the proposed electronic calibrated system, achieving a percentage of explanation of 99.05%. PMID:23793020

Garcia-Diego, Fernando-Juan; Sanchez-Quinche, Angel; Merello, Paloma; Beltran, Pedro; Peris, Cristofol

2013-01-01

194

Submillimeter Array Observations of Magnetic Fields in G240.31+0.07: an Hourglass in a Massive Cluster-forming Core  

E-print Network

We report the first detection of an hourglass magnetic field aligned with a well-defined outflow-rotation system in a high-mass star-forming region. The observations were performed with Submillimeter Array toward G240.31+0.07, which harbors a massive, flattened, and fragmenting molecular cloud core and a wide-angle bipolar outflow. The polarized dust emission at 0.88 mm reveals a clear hourglass-shaped magnetic field aligned within 20 degree of the outflow axis. Maps of high-density tracing spectral lines, e.g., H13CO+ (4-3), show that the core is rotating about its minor axis, which is also aligned with the magnetic field axis. Therefore, both the magnetic field and kinematic properties observed in this region are surprisingly consistent with the theoretical predictions of the classic paradigm of isolated low-mass star formation. The strength of the magnetic field in the plane of sky is estimated to be about 1.1 mG, resulting in a mass-to-magnetic flux ratio of 1.4 times the critical value and a turbulent to...

Qiu, Keping; Menten, Karl M; Liu, Hauyu B; Tang, Ya-Wen; Girart, Josep M

2014-01-01

195

The reliability of the seismo-magnetic method derived from ULF/ELF observations by the South European Geomagnetic Array (SEGMA)  

NASA Astrophysics Data System (ADS)

In the frame of the South European GeoMagnetic Array (SEGMA) project magnetic field variations are studied in the frequency range from several milli-Hz to several Hz. The fluxgate and induction coil magnetometers are located in Italy, Bulgaria and Hungary. The scientific objectives comprises field-line resonances, space weather phenomena and seismo-magnetic (SM) studies. In our present study on the reliability of the seismo-magnetic method we emphasize on the influence of external non-seismic sources on the quality of seismo-magnetic studies. External magnetic sources include lightning, power lines, railway and traffic as well as geomagnetic variations of magnetospheric origin. We observe anomalies of the ratio of the vertical to horizontal magnetic field component in the ultra/extreme-low-frequency (ULF/ELF) frequency range up to several Hz [2]. These signals can be produced in the lithosphere near a seismic active region and are interpreted as earthquake precursors. In order to differentiate geomagnetic from seismo-magnetic fluctuations, we use mainly observations around midnight because the night time geomagnetic fluctuations are much smaller than during day time. The SEGMA network provides the unique opportunity to use multipoint observations, which are also useful to distinguish local from global phenomena. In order to get undisturbed magnetic field observations, the stations are located outside populated areas [2]. The electrical conductivity of the soil in the vicinity of magnetometers on the terrestrial surface is a further source for interferences. This type of disturbances caused by induced electrical currents can be minimized either by a careful selection of the magnetometer site ans/or by the measurement of the conductivity profile in the vicinity of the instrument site. In the frame of the investigation of the April 6, 2009 L'Aquila earthquake magneto-telluric methods have been used to measure the conductivity profile near the epicenter of the earthquake and thus correct the observed magnetic field fluctuations [1]. A further interference source which can reduce the sensitivity of the seismo-magnetic methods (SM) is the mechanical vibration of the magnetometer sensors. We present a SM reliability number taking into account all above mentioned interference sources. The SM number can be used to improve the sensitivity of the seismo-magnetic method. References [1] G. Prattes, et al.: Ultra Low Frequency (ULF) European multi station magnetic field analysis before and during the 2009 earthquake at L'Aquila regarding regional geotechnical information, Nat. Hazards Earth Syst. Sci., 11, 1959-1968, 2011 [2] K. Schwingenschuh, et al.: 'Clean' observations of magnetic field fluctuations on planetary surfaces, Aerospace EMC, 2012 Proceedings ESA Workshop on 21-23 May 2012, 4 p., 2012.

Schwingenschuh, Konrad; Prattes, Gustav; Eichelberger, Hans Ulrich; Magnes, Werner; Berghofer, Gerhard; Aydogar, Özer; Besser, Bruno P.; Boudjada, Mohammed; Stangl, Günter; Zhang, Tie Long; Wolbang, Daniel; Vellante, Massimo; Villante, Umberto; Rozhnoi, Alexander; Solovieva, Maria; Nenovski, Petko; Veztergom, Victor; Szendr?i, Judith

2013-04-01

196

Novel magnetite-silica nanocomposite (Fe3O4-SBA-15) particles for DNA binding and gene delivery aided by a magnet array.  

PubMed

Novel magnetite-silica nanocomposite particles were prepared using SBA-15 nanoporous silica as template. Magnetite nanoparticles were impregnated into the nanopore array of the silica template through thermal decomposition of iron(III) acetylacetonate, Fe(AcAc)3 at 200 degrees C. These composite particles were characterized using TEM, XRD and SQUID magnetometry. The TEM images showed that the size of composite particles was around 500 nm and the particles retained the nanoporous array of SBA-15. The formation of magnetite nanoparticles was confirmed by the powder XRD study. These composite particles also exhibited ferrimagnetic properties. By coating with short chain polyethyleneimine (PEI), these particles are capable of binding DNA molecules for gene delivery and transfection. With an external magnetic field, the transfection efficiency was shown to have an increase of around 15%. The results indicated that these composite nanoparticles may be further developed as a new tool for nanomagnetic gene transfection. PMID:21776740

Yiu, Humphrey H P; McBain, Stuart C; Lethbridge, Zoe A D; Lees, Martin R; Palona, Iryna; Olariu, Cristina I; Dobson, Jon

2011-04-01

197

Development of the axial instability and magnetic field topology in low wire number wire array Z-pinches  

Microsoft Academic Search

Summary form only given. We are investigating the development of the axial instability that occurs on each exploding wire in wire-array Z-pinches. The axial instability is a growing modulation of the size of the coronal plasma around individual wires of the array that results in non-uniform ablation of material from the cold wire core. It has long been known that

P. F. Knapp; K. S. Bell; I. C. Blesener; D. A. Chalenski; J. B. Greenly; C. L. Hoyt; M. R. Martin; R. D. McBride; S. Pikuz; T. A. Shelkovenko; D. A. Hammer; B. R. Kusse

2009-01-01

198

Nonuniform radiation damage in permanent magnet quadrupoles  

NASA Astrophysics Data System (ADS)

We present data that indicate nonuniform magnetization loss due to radiation damage in neodymium-iron-boron Halbach-style permanent magnet quadrupoles. The proton radiography (pRad) facility at Los Alamos uses permanent-magnet quadrupoles for magnifying lenses, and a system recently commissioned at GSI-Darmsdadt uses permanent magnets for its primary lenses. Large fluences of spallation neutrons can be produced in close proximity to these magnets when the proton beam is, intentionally or unintentionally, directed into the tungsten beam collimators; imaging experiments at LANL's pRad have shown image degradation with these magnetic lenses at proton beam doses lower than those expected to cause damage through radiation-induced reduction of the quadrupole strength alone. We have observed preferential degradation in portions of the permanent magnet quadrupole where the field intensity is highest, resulting in increased high-order multipole components.

Danly, C. R.; Merrill, F. E.; Barlow, D.; Mariam, F. G.

2014-08-01

199

Micromanipulation using a microcoil array  

Microsoft Academic Search

A method of micromanipulation using a microcoil array is proposed. Active coils drive permanent magnets on a work platform. The magnets can push mechanical parts to perform 2-dimensional assembly. Three-dimensional operation may be achieved from 2D magnet motion when the permanent magnets are part of a closed loop spatial linkage. Manipulation on a 4 cm×4 cm coil array was tested.

Tadanobu Inoue; Yukio Hamasaki; Isao Shimoyama; Hirofumi Miura

1996-01-01

200

A Multi-axis Compact Positioner with a 6-coil Platen Moving Over a Superimposed Halbach Magnet Matrix  

E-print Network

diagram ............................................................... 71 5.2 DSP board Pentek 4284 and data acquisition board Pentek 6102 ............. 72 5.3 Hall-effect sensors...-2 A picture of (a) the DSP board Pentek 4284 and (b) the data I/O board Pentek 6102 ............................................................................................... 73 5-3 A drawing of 2SA-10 with its sensitive sensing...

Nguyen, Vu Huy

2012-07-16

201

Dynamic templating: A new pathway for the assembly of large-area arrays of plasmonic, magnetic and semiconductor nanomaterials  

NASA Astrophysics Data System (ADS)

Substrate-based nanostructures are of great importance due to their applications in microelectronic devices, chemical sensors, catalysis and photovoltaics. This dissertation describes a novel fabrication technique for the formation of periodic arrays of substrate-based nanoparticles. The prescribed route, referred to as dynamic templating, requires modest levels of instrumentation consisting of a sputter coater, micrometer-scale shadow masks and a tube furnace. The route has broad applicability, having already produced periodic arrays of gold, silver, copper, platinum, nickel, cobalt, germanium and Au--Ag alloys on substrates as diverse as silicon, sapphire, silicon--carbide, and glass. The newly devised method offers large-area, high-throughput capabilities for the fabrication of periodic arrays of sub-micrometer and nanometer-scale structures and overcomes a significant technological barrier to the widespread use of substrate-based templated assembly by eliminating the need for periodic templates having nanoscale features. Because this technique only requires modest levels of instrumentation, researchers are now able to fabricate periodic arrays of nanostructures that would otherwise require advanced fabrication facilities.

Farzinpour, Pouyan

202

Determining the minimum mass and cost of a magnetic refrigerator  

E-print Network

An expression is determined for the mass of the magnet and magnetocaloric material needed for a magnetic refrigerator and these are determined using numerical modeling for both parallel plate and packed sphere bed regenerators as function of temperature span and cooling power. As magnetocaloric material Gd or a model material with a constant adiabatic temperature change, representing a infinitely linearly graded refrigeration device, is used. For the magnet a maximum figure of merit magnet or a Halbach cylinder is used. For a cost of \\$40 and \\$20 per kg for the magnet and magnetocaloric material, respectively, the cheapest 100 W parallel plate refrigerator with a temperature span of 20 K using Gd and a Halbach magnet has 0.8 kg of magnet, 0.3 kg of Gd and a cost of \\$35. Using the constant material reduces this cost to \\$25. A packed sphere bed refrigerator with the constant material costs \\$7. It is also shown that increasing the operation frequency reduces the cost. Finally, the lowest cost is also found a...

Bjørk, R; Bahl, C R H; Pryds, N

2014-01-01

203

OH MASER SOURCES IN W49N: PROBING MAGNETIC FIELD AND DIFFERENTIAL ANISOTROPIC SCATTERING WITH ZEEMAN PAIRS USING THE VERY LONG BASELINE ARRAY  

SciTech Connect

Our analysis of a Very Long Baseline Array 12 hr synthesis observation of the OH masers in the well-known star-forming region W49N has yielded valuable data that enable us to probe distributions of magnetic fields in both the maser columns and the intervening interstellar medium (ISM). The data, consisting of detailed high angular resolution images (with beam width ?20 mas) of several dozen OH maser sources, or spots, at 1612, 1665, and 1667 MHz, reveal anisotropic scatter broadening with typical sizes of a few tens of milliarcseconds and axial ratios between 1.5 and 3. Such anisotropies have been reported previously by Desai et al. and have been interpreted as being induced by the local magnetic field parallel to the Galactic plane. However, we find (1) apparent angular sizes of, on average, a factor of about 2.5 less than those reported by Desai et al., indicating significantly less scattering than inferred previously, and (2) a significant deviation in the average orientation of the scatter-broadened images (by ?10°) from that implied by the magnetic field in the Galactic plane. More intriguingly, for a few Zeeman pairs in our set, significant differences (up to 6?) are apparent in the scatter-broadened images for the two hands of circular polarization, even when the apparent velocity separation is less than 0.1 km s{sup –1}. This may possibly be the first example of a Faraday rotation contribution to the diffractive effects in the ISM. Using the Zeeman pairs, we also study the distribution of the magnetic field in the W49N complex, finding no significant trend in the spatial structure function. In this paper, we present the details of our observations and analysis leading to these findings, discuss implications of our results for the intervening anisotropic magneto-ionic medium, and suggest possible implications for the structure of magnetic fields within this star-forming region.

Deshpande, Avinash A. [Raman Research Institute, Sadashivanagar, Bangalore 560080 (India); Goss, W. M. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Mendoza-Torres, J. E., E-mail: desh@rri.res.in, E-mail: mgoss@aoc.nrao.edu, E-mail: mend@inaoep.mx [Instituto Nacional de Astrofísica Optica y Electrónica, Tonantzintla, Puebla 72840 (Mexico)

2013-09-20

204

Structural and magnetic characterization of as-prepared and annealed FeCoCu nanowire arrays in ordered anodic aluminum oxide templates  

NASA Astrophysics Data System (ADS)

Herein, we report on the preparation, structure, and magnetic characterization of FeCoCu nanowire arrays grown by DC electrodeposition inside self-assembled ordered nanopores of anodic aluminum oxide templates. A systematic study of their structure has been performed both in as-prepared samples and after annealing in the temperature range up to 800 °C, although particular attention has been paid to annealing at 700 °C after which maximum magnetic hardening is achieved. The obtained nanowires have a diameter of 40 nm and their Fe0.28Co0.67Cu0.05 composition was confirmed by energy dispersive X-ray spectroscopy (EDS). Focused ion-beam lamellas of two samples (as-prepared and annealed at 700 °C) were prepared for their imaging in the high-resolution transmission electron microscopy (HRTEM) perpendicularly to the electron beam, where the obtained EDS compositional mappings show a homogeneous distribution of the elements. X-ray diffraction analysis, and selected area electron diffraction (SAED) patterns confirm that nanowires exhibit a bcc cubic structure (space group Im-3m). In addition, bright-dark field images show that the nanowires have a polycrystalline structure that remains essentially the same after annealing, but some modifications were observed: (i) an overall increase and sharpening of recrystallized grains, and (ii) an apparent shrinkage of the nanowires diameter. Obtained SAED patterns also show strong textured components with determined ?111? and ?112? crystalline directions parallel to the wires growth direction. The presence of both directions was also confirmed in the HRTEM images doing Fourier transform analyses. Magnetic measurements show strong magnetic anisotropy with magnetization easy axis parallel to the nanowires in as-prepared and annealed samples. The magnetic properties are tuned by suitable thermal treatments so that, maximum enhanced coercivity (˜2.7 kOe) and normalized remanence (˜0.91 Ms) values are achieved after annealing at temperature of 700 °C. The contribution of the changes in the crystalline structure, induced by the heat treatment, to the magnetic hardening of the FeCoCu nanowires is discussed.

Rodríguez-González, B.; Bran, C.; Warnatz, T.; Rivas, J.; Vazquez, M.

2014-04-01

205

Array Games  

NSDL National Science Digital Library

Arrays are very important in Computer Programming. An array is a way to store similar items in computer memory. The items may be numbers, words, pictures, or even sounds. Many games use an array because it is an easy way to keep track of the objects used to play the game. The Arrow Game uses an array to store arrow ...

Watts, Mrs.

2007-10-05

206

Fabrication and magnetic properties of La-X (X = Co, Ni, and Fe) nanotube arrays prepared by electrodeposition methods  

NASA Astrophysics Data System (ADS)

Well-ordered La-X (X = Co, Ni and Fe) nanotubes, with the average diameter of ˜200 nm, wall thicknesses of ˜40 nm, have been fabricated into anodized aluminum oxide template by potentiostatic electrodeposition method. Various composition of La-X nanotubes were obtained by tuning the applied deposition potential. Magnetization measurements reveal that doped La could enhance the coercivity (Hc) of La-X nanotubes and their easy axis is perpendicular to the nanotube axis. There is a transition from the curling to transverse mode with increase of angle. Temperature dependent magnetization indicates the existence of superparamagnetic nanoparticles and that the surface effect results in the increase of saturation magnetization (Ms) at low temperature. Abnormal behavior of temperature dependent Hc may result from thermal excitation, magnetoelastic anisotropy, as well as oxide layer of nanotube inner surface induced coupling. These one-dimensional rare-earth transition metal nanostructures could have potential applications in novel spintronics device, ultra-small magnetic media, drug delivery, or other nanodevice.

Chen, J. Y.; Shi, D. W.; Ahmad, N.; Liu, D. P.; Zhou, W. P.; Han, X. F.

2013-08-01

207

Standing Microcoil Actuator Array  

NASA Astrophysics Data System (ADS)

A standing microcoil actuator array fabricated for driving three-dimensional out-of-plane structures is proposed. Since the microcoil structures have a magnetic thin-film layer, they can be erected on the substrate when a vertical magnetic field is applied to them. Additionally they can be actuated when a current is applied to the coil structure. In this paper, we have demonstrated the driving of a microslit on the standing microcoil actuator array. It could achieve parallel motion to the substrate at the frequency from DC to 1 kHz.

Takeuchi, Shoji; Shimoyama, Isao

2003-06-01

208

Influence of Y-doped induced defects on the optical and magnetic properties of ZnO nanorod arrays prepared by low-temperature hydrothermal process  

PubMed Central

One-dimensional pure zinc oxide (ZnO) and Y-doped ZnO nanorod arrays have been successfully fabricated on the silicon substrate for comparison by a simple hydrothermal process at the low temperature of 90°C. The Y-doped nanorods exhibit the same c-axis-oriented wurtzite hexagonal structure as pure ZnO nanorods. Based on the results of photoluminescence, an enhancement of defect-induced green-yellow visible emission is observed for the Y-doped ZnO nanorods. The decrease of E2(H) mode intensity and increase of E1(LO) mode intensity examined by the Raman spectrum also indicate the increase of defects for the Y-doped ZnO nanorods. As compared to pure ZnO nanorods, Y-doped ZnO nanorods show a remarked increase of saturation magnetization. The combination of visible photoluminescence and ferromagnetism measurement results indicates the increase of oxygen defects due to the Y doping which plays a crucial role in the optical and magnetic performances of the ZnO nanorods. PMID:22768847

2012-01-01

209

An improved permanent magnet quadrupole design with larger good field region for high intensity proton linacs  

NASA Astrophysics Data System (ADS)

The Low Energy High Intensity Proton Accelerator (LEHIPA), being developed at the Bhabha Atomic Research Centre (BARC) will produce a 20 MeV, 30 mA, continuous wave (CW) proton beam. At these low velocities, space-charge forces dominate, and could lead to larger beam sizes and beam halos. Hence in the design of the focusing lattice of the LEHIPA drift tube linac (DTL) using permanent magnet quadrupoles (PMQs), a larger good field region is preferred. Here we study, using the two dimensional (2D) and three dimensional (3D) simulation codes PANDIRA and RADIA, four different types of cylindrical PMQ designs: 16-segment trapezoidal Halbach configuration, bullet-nosed geometry and 8- and 16-segment rectangular geometries. The trapezoidal Halbach geometry is used in a variety of accelerators since it provides very high field gradients in small bores, while the bullet-nosed geometry, which is a combination of the trapezoidal and rectangular designs, is used in some DTLs. This study shows that a larger good field region is possible in the 16-segment rectangular design as compared to the Halbach and bullet-nosed designs, making it more attractive for high-intensity proton linacs. An improvement in good-field region by ˜16% over the Halbach design is obtained in the optimized 16-segment rectangular design, although the field gradient is lower by ˜20%. Tolerance studies show that the rectangular segment PMQ design is substantially less sensitive to the easy axis orientation errors and hence will be a better choice for DTLs.

Mathew, Jose V.; Rao, S. V. L. S.; Krishnagopal, S.; Singh, P.

2013-11-01

210

Amazing Arrays  

NSDL National Science Digital Library

This is a hands-on lesson for introducing and practicing building arrays to create models that represent the distributive property of multiplication, and then using those arrays to draw models of the equations they represent.

Edit, Format

2012-04-18

211

Nanocylinder arrays  

DOEpatents

Pathways to rapid and reliable fabrication of nanocylinder arrays are provided. Simple methods are described for the production of well-ordered arrays of nanopores, nanowires, and other materials. This is accomplished by orienting copolymer films and removing a component from the film to produce nanopores, that in turn, can be filled with materials to produce the arrays. The resulting arrays can be used to produce nanoscale media, devices, and systems.

Tuominen, Mark (Shutesbury, MA); Schotter, Joerg (Bielefeld, DE); Thurn-Albrecht, Thomas (Freiburg, DE); Russell, Thomas P. (Amherst, MA)

2009-08-11

212

Method and apparatus for control of a magnetic structure  

DOEpatents

A method and apparatus for independently adjusting the spacing between opposing magnet arrays in charged particle based light sources. Adjustment mechanisms between each of the magnet arrays and the supporting structure allow the gap between the two magnet arrays to be independently adjusted. In addition, spherical bearings in the linkages to the magnet arrays permit the transverse angular orientation of the magnet arrays to also be adjusted. The opposing magnet arrays can be supported above the ground by the structural support.

Challenger, Michael P. (Bothell, WA); Valla, Arthur S. (Bothell, WA)

1996-06-18

213

Hybrid photomultiplier tube and photodiode parallel detection array for wideband optical spectroscopy of the breast guided by magnetic resonance imaging  

PubMed Central

Abstract. A new optical parallel detection system of hybrid frequency and continuous-wave domains was developed to improve the data quality and accuracy in recovery of all breast optical properties. This new system was deployed in a previously existing system for magnetic resonance imaging (MRI)-guided spectroscopy, and allows incorporation of additional near-infrared wavelengths beyond 850 nm, with interlaced channels of photomultiplier tubes (PMTs) and silicon photodiodes (PDs). The acquisition time for obtaining frequency-domain data at six wavelengths (660, 735, 785, 808, 826, and 849 nm) and continuous-wave data at three wavelengths (903, 912, and 948 nm) is 12 min. The dynamic ranges of the detected signal are 105 and 106 for PMT and PD detectors, respectively. Compared to the previous detection system, the SNR ratio of frequency-domain detection was improved by nearly 103 through the addition of an RF amplifier and the utilization of programmable gain. The current system is being utilized in a clinical trial imaging suspected breast cancer tumors as detected by contrast MRI scans. PMID:23979460

El-Ghussein, Fadi; Mastanduno, Michael A.; Jiang, Shudong; Pogue, Brian W.; Paulsen, Keith D.

2013-01-01

214

Hybrid photomultiplier tube and photodiode parallel detection array for wideband optical spectroscopy of the breast guided by magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

A new optical parallel detection system of hybrid frequency and continuous-wave domains was developed to improve the data quality and accuracy in recovery of all breast optical properties. This new system was deployed in a previously existing system for magnetic resonance imaging (MRI)-guided spectroscopy, and allows incorporation of additional near-infrared wavelengths beyond 850 nm, with interlaced channels of photomultiplier tubes (PMTs) and silicon photodiodes (PDs). The acquisition time for obtaining frequency-domain data at six wavelengths (660, 735, 785, 808, 826, and 849 nm) and continuous-wave data at three wavelengths (903, 912, and 948 nm) is 12 min. The dynamic ranges of the detected signal are 105 and 106 for PMT and PD detectors, respectively. Compared to the previous detection system, the SNR ratio of frequency-domain detection was improved by nearly 103 through the addition of an RF amplifier and the utilization of programmable gain. The current system is being utilized in a clinical trial imaging suspected breast cancer tumors as detected by contrast MRI scans.

El-Ghussein, Fadi; Mastanduno, Michael A.; Jiang, Shudong; Pogue, Brian W.; Paulsen, Keith D.

2014-01-01

215

Hybrid photomultiplier tube and photodiode parallel detection array for wideband optical spectroscopy of the breast guided by magnetic resonance imaging.  

PubMed

A new optical parallel detection system of hybrid frequency and continuous-wave domains was developed to improve the data quality and accuracy in recovery of all breast optical properties. This new system was deployed in a previously existing system for magnetic resonance imaging (MRI)-guided spectroscopy, and allows incorporation of additional near-infrared wavelengths beyond 850 nm, with interlaced channels of photomultiplier tubes (PMTs) and silicon photodiodes (PDs). The acquisition time for obtaining frequency-domain data at six wavelengths (660, 735, 785, 808, 826, and 849 nm) and continuous-wave data at three wavelengths (903, 912, and 948 nm) is 12 min. The dynamic ranges of the detected signal are 105 and 106 for PMT and PD detectors, respectively. Compared to the previous detection system, the SNR ratio of frequency-domain detection was improved by nearly 103 through the addition of an RF amplifier and the utilization of programmable gain. The current system is being utilized in a clinical trial imaging suspected breast cancer tumors as detected by contrast MRI scans. PMID:23979460

El-Ghussein, Fadi; Mastanduno, Michael A; Jiang, Shudong; Pogue, Brian W; Paulsen, Keith D

2014-01-01

216

Magnetism  

NSDL National Science Digital Library

This webpage is part of the University Corporation for Atmospheric Research (UCAR) Windows to the Universe program. It describes the nature and configuration of magnetic fields, which are the result of moving electric charges, including how they cause magnetic objects to orient themselves along the direction of the magnetic force points, which are illustrated as lines. Magnetic field lines by convention point outwards at the north magnetic pole and inward at the south magnetic pole. The site features text, scientific illustrations and an animation. Text and vocabulary are selectable for the beginning, intermediate, or advanced reader.

Team, University C.

2007-12-12

217

Striped tertiary storage arrays  

NASA Technical Reports Server (NTRS)

Data stripping is a technique for increasing the throughput and reducing the response time of large access to a storage system. In striped magnetic or optical disk arrays, a single file is striped or interleaved across several disks; in a striped tape system, files are interleaved across tape cartridges. Because a striped file can be accessed by several disk drives or tape recorders in parallel, the sustained bandwidth to the file is greater than in non-striped systems, where access to the file are restricted to a single device. It is argued that applying striping to tertiary storage systems will provide needed performance and reliability benefits. The performance benefits of striping for applications using large tertiary storage systems is discussed. It will introduce commonly available tape drives and libraries, and discuss their performance limitations, especially focusing on the long latency of tape accesses. This section will also describe an event-driven tertiary storage array simulator that is being used to understand the best ways of configuring these storage arrays. The reliability problems of magnetic tape devices are discussed, and plans for modeling the overall reliability of striped tertiary storage arrays to identify the amount of error correction required are described. Finally, work being done by other members of the Sequoia group to address latency of accesses, optimizing tertiary storage arrays that perform mostly writes, and compression is discussed.

Drapeau, Ann L.

1993-01-01

218

Magnetism  

NSDL National Science Digital Library

This radio broadcast discusses the history of magnetism from the time of its discovery by an apocryphal Greek sheperd until the late 16th century and the work of William Gilbert. There is also discussion of who pioneered the study of magnetism, what theories they constructed from its curious abilities, and how the power of the magnet was brought out of the realm of magic and into the service of science. The broadcast concludes with a discussion of why magnetism is still mysterious and how the modern search for the single magnetic pole, or magnetic monopole, could provide a fundamental unit of magnetism, essential for ultimate explanation. The broadcast is 41 minutes and 45 seconds in length.

2010-10-27

219

DNA Arrays  

NSDL National Science Digital Library

This animation from Cold Spring Harbor Laboratory's Dolan DNA Learning Center presents DNA arrays. The animation contains information on Pat Brown's discovery and the purpose of DNA arrays to study gene expression as well as its role in the development of pharmacogenomic treatment for diseases such as cancer.

2012-04-10

220

Rapid magnetic cell delivery for large tubular bioengineered constructs  

PubMed Central

Delivery of cells into tubular tissue constructs with large diameters poses significant spatial and temporal challenges. This study describes preliminary findings for a novel process for rapid and uniform seeding of cells onto the luminal surface of large tubular constructs. Fibroblasts, tagged with superparamagnetic iron oxide nanoparticles (SPION), were directed onto the luminal surface of tubular constructs by a magnetic field generated by a k4-type Halbach cylinder device. The spatial distribution of attached cells, as measured by the mean number of cells, was compared with a conventional, dynamic, rotational cell-delivery technique. Cell loading onto the constructs was measured by microscopy and magnetic resonance imaging. The different seeding techniques employed had a significant effect on the spatial distribution of the cells (p < 0.0001). The number of attached cells at defined positions within the same construct was significantly different for the dynamic rotation technique (p < 0.05). In contrast, no significant differences in the number of cells attached to the luminal surface were found between the defined positions on the construct loaded with the Halbach cylinder. The technique described overcomes limitations associated with existing cell-delivery techniques and is amenable to a variety of tubular organs where rapid loading and uniform distribution of cells for therapeutic applications are required. PMID:22696487

Gonzalez-Molina, J.; Riegler, J.; Southern, P.; Ortega, D.; Frangos, C. C.; Angelopoulos, Y.; Husain, S.; Lythgoe, M. F.; Pankhurst, Q. A.; Day, R. M.

2012-01-01

221

Magnetism  

NSDL National Science Digital Library

This overview of magnetism provides a brief history prior to 1600 and continues with the work of William Gilbert, Hans Christian Oersted, and Andre-Marie Ampere in describing and exploring the magnetosphere and learning the role that electric current plays in producing magnetism. Magnetic field lines are then discussed, citing the work of Michael Faraday. The work of James Clerk Maxwell and Heinrich Hertz is mentioned in a discussion of the relationship of light waves and radio waves as part of the electromagnetic spectrum.

Stern, David

222

Geophysical Institute Magnetometer Array  

NASA Astrophysics Data System (ADS)

The Geophysical Institute Magnetometer Array (GIMA) consists of twelve magnetometer stations distributed across Alaska cutting the auroral oval. Each station is equipped with a ring-core, fluxgate magnetometer, GPS clock and data logger. Data are returned from each station to the Geophysical Institute, University of Alaska where it is verified, archived, and made available to the space science community. The GIMA web page, at http://magnet.gi.alaska.edu/, provides the data from eight stations online in real-time. The GIMA web page also provides limited data access from five Russian magnetometer stations. The GIMA data set available online spans the time period 1995 to the present. This presentation describes the current operation of the array, its capabilities (data collection parameters), the web site, and methods for acessing the data set. Current efforts to improve data access and integrate the data set with online virtual observatories is described.

Wilkinson, D.; Heavner, M. J.

2006-12-01

223

Very Large Array and Green Bank Telescope Observations of Orion B (NGC 2024, W12): Photodissociation Region Properties and Magnetic Field  

NASA Astrophysics Data System (ADS)

We present images of C110? and H110? radio recombination line (RRL) emission at 4.8 GHz and images of H166?, C166?, and X166? RRL emission at 1.4 GHz, observed toward the star-forming region NGC 2024. The 1.4 GHz image with angular resolution ~70'' is obtained using Very Large Array (VLA) data. The 4.8 GHz image with angular resolution ~17'' is obtained by combining VLA and Green Bank Telescope data in order to add the short and zero spacing data in the uv plane. These images reveal that the spatial distributions of C110? line emission is confined to the southern rim of the H II region close to the ionization front whereas the C166? line emission is extended in the north-south direction across the H II region. The LSR velocity of the C110? line is 10.3 km s–1 similar to that of lines observed from molecular material located at the far side of the H II region. This similarity suggests that the photodissociation region (PDR) responsible for C110? line emission is at the far side of the H II region. The LSR velocity of C166? is 8.8 km s–1. This velocity is comparable with the velocity of molecular absorption lines observed from the foreground gas, suggesting that the PDR is at the near side of the H II region. Non-LTE models for carbon line-forming regions are presented. Typical properties of the foreground PDR are T PDR ~ 100 K, n_e^{PDR} \\sim 5 cm–3, n H ~ 1.7 × 104 cm–3, and path length l ~ 0.06 pc, and those of the far side PDR are T PDR ~ 200 K, n_e^{PDR} \\sim 50 cm–3, n H ~ 1.7 × 105 cm–3, and l ~ 0.03 pc. Our modeling indicates that the far side PDR is located within the H II region. We estimate the magnetic field strength in the foreground PDR to be 60 ?G and that in the far side PDR to be 220 ?G. Our field estimates compare well with the values obtained from OH Zeeman observations toward NGC 2024. The H166? spectrum shows narrow (1.7 km s–1) and broad (33 km s–1) line features. The narrow line has spatial distribution and central velocity (~9 km s–1) similar to that of the foreground carbon line emission, suggesting that they are associated. Modeling the narrow H166? emission provides physical properties T PDR ~ 50 K, n_e^{PDR} \\sim 4 cm–3, and l ~ 0.01 pc and implies an ionization fraction of ~10–4. The broad H166? line originates from the H II region. The X166? line has a different spatial distribution compared to other RRLs observed toward NGC 2024 and is probably associated with cold dust clouds. Based on the expected low depletion of sulfur in such clouds and the –8.1 km s–1 velocity separation between the X166? and C166? lines, we interpret that the X166? transition arises from sulfur.

Anish Roshi, D.; Goss, W. M.; Jeyakumar, S.

2014-10-01

224

Very Large Array and Green Bank Telescope Observations of Orion B (NGC 2024, W12): Photodissociation Region Properties and Magnetic Field  

NASA Astrophysics Data System (ADS)

We present images of C110? and H110? radio recombination line (RRL) emission at 4.8 GHz and images of H166?, C166?, and X166? RRL emission at 1.4 GHz, observed toward the star-forming region NGC 2024. The 1.4 GHz image with angular resolution ~70'' is obtained using Very Large Array (VLA) data. The 4.8 GHz image with angular resolution ~17'' is obtained by combining VLA and Green Bank Telescope data in order to add the short and zero spacing data in the uv plane. These images reveal that the spatial distributions of C110? line emission is confined to the southern rim of the H II region close to the ionization front whereas the C166? line emission is extended in the north-south direction across the H II region. The LSR velocity of the C110? line is 10.3 km s-1 similar to that of lines observed from molecular material located at the far side of the H II region. This similarity suggests that the photodissociation region (PDR) responsible for C110? line emission is at the far side of the H II region. The LSR velocity of C166? is 8.8 km s-1. This velocity is comparable with the velocity of molecular absorption lines observed from the foreground gas, suggesting that the PDR is at the near side of the H II region. Non-LTE models for carbon line-forming regions are presented. Typical properties of the foreground PDR are T PDR ~ 100 K, n_e^{PDR} \\sim 5 cm-3, n H ~ 1.7 × 104 cm-3, and path length l ~ 0.06 pc, and those of the far side PDR are T PDR ~ 200 K, n_e^{PDR} \\sim 50 cm-3, n H ~ 1.7 × 105 cm-3, and l ~ 0.03 pc. Our modeling indicates that the far side PDR is located within the H II region. We estimate the magnetic field strength in the foreground PDR to be 60 ?G and that in the far side PDR to be 220 ?G. Our field estimates compare well with the values obtained from OH Zeeman observations toward NGC 2024. The H166? spectrum shows narrow (1.7 km s-1) and broad (33 km s-1) line features. The narrow line has spatial distribution and central velocity (~9 km s-1) similar to that of the foreground carbon line emission, suggesting that they are associated. Modeling the narrow H166? emission provides physical properties T PDR ~ 50 K, n_e^{PDR} \\sim 4 cm-3, and l ~ 0.01 pc and implies an ionization fraction of ~10-4. The broad H166? line originates from the H II region. The X166? line has a different spatial distribution compared to other RRLs observed toward NGC 2024 and is probably associated with cold dust clouds. Based on the expected low depletion of sulfur in such clouds and the -8.1 km s-1 velocity separation between the X166? and C166? lines, we interpret that the X166? transition arises from sulfur.

Roshi, D. Anish; Goss, W. M.; Jeyakumar, S.

2014-10-01

225

An Electrodynamic Wheel with a Split-Guideway Capable of Simultaneously Creating Suspension, Thrust and  

E-print Network

-Madison, USA jbird@wisc.edu, lipo@engr.wisc.edu Abstract When a radially positioned permanent magnet Halbach array is rotated above a flat aluminium guideway a travelling time-varying magnetic field is created and propulsion force. With a suitably designed guideway the `Electrodynamic Wheel' (EDW) can also create guidance

Lipo, Thomas

226

Advanced superconducting gradiometer\\/Magnetometer arrays and a novel signal processing technique  

Microsoft Academic Search

Recent developments in superconducting magnetic gradiometer technology have led to the construction of advanced ultrasensitive gradiometer\\/magnetometer arrays. Details of construction techniques and data showing operational capabilities are presented. The most recent of the gradiometer\\/magnetometer arrays simultaneously measures five independent spatial gradients of the magnetic field and three vector components of the magnetic field. The measured signals from this array are

W. Wynn; C. Frahm; P. Carroll; R. Clark; J. Wellhoner; M. Wynn

1975-01-01

227

Optimizing wire parameters in exploding wire arrays  

Microsoft Academic Search

Exploding wire arrays as fast switches are of interest for explosive pulsed power applications utilizing magnetic flux compression. This type of opening switch has proven effective in producing pulses of several hundred kilovolts into vacuum diode loads. The research presented here discusses an exploding wire array capable of producing single digit kilo- joules, 100 nanosecond pulses when driven by a

C. Davis; A. Neuber; J. Stephens; A. Young; J. Dickens; M. Kristiansen

2010-01-01

228

Electromagnetically Clean Solar Arrays  

NASA Technical Reports Server (NTRS)

The term 'electromagnetically clean solar array' ('EMCSA') refers to a panel that contains a planar array of solar photovoltaic cells and that, in comparison with a functionally equivalent solar-array panel of a type heretofore used on spacecraft, (1) exhibits less electromagnetic interferences to and from other nearby electrical and electronic equipment and (2) can be manufactured at lower cost. The reduction of electromagnetic interferences is effected through a combination of (1) electrically conductive, electrically grounded shielding and (2) reduction of areas of current loops (in order to reduce magnetic moments). The reduction of cost is effected by designing the array to be fabricated as a more nearly unitary structure, using fewer components and fewer process steps. Although EMCSAs were conceived primarily for use on spacecraft they are also potentially advantageous for terrestrial applications in which there are requirements to limit electromagnetic interference. In a conventional solar panel of the type meant to be supplanted by an EMCSA panel, the wiring is normally located on the back side, separated from the cells, thereby giving rise to current loops having significant areas and, consequently, significant magnetic moments. Current-loop geometries are chosen in an effort to balance opposing magnetic moments to limit far-0field magnetic interactions, but the relatively large distances separating current loops makes full cancellation of magnetic fields problematic. The panel is assembled from bare photovoltaic cells by means of multiple sensitive process steps that contribute significantly to cost, especially if electomagnetic cleanliness is desired. The steps include applying a cover glass and electrical-interconnect-cell (CIC) sub-assemble, connecting the CIC subassemblies into strings of series-connected cells, laying down and adhesively bonding the strings onto a panel structure that has been made in a separate multi-step process, and mounting the wiring on the back of the panel. Each step increases the potential for occurrence of latent defects, loss of process control, and attrition of components. An EMCSA panel includes an integral cover made from a transparent material. The silicone cover supplants the individual cover glasses on the cells and serves as an additional unitary structural support that offers the advantage, relative to glass, of the robust, forgiving nature of the silcone material. The cover contains pockets that hold the solar cells in place during the lamination process. The cover is coated with indium tin oxide to make its surface electrically conductive, so that it serves as a contiguous, electrically grounded shield over the entire panel surface. The cells are mounted in proximity to metallic printed wiring. The painted-wiring layer comprises metal-film traces on a sheet of Kapton (or equivalent) polyimide. The traces include contact pads on one side of the sheet for interconnecting the cells. Return leads are on the opposite side of the sheet, positioned to form the return currents substantially as mirror images of, and in proximity to, the cell sheet currents, thereby minimizing magnetic moments. The printed-wiring arrangement mimics the back-wiring arrangement of conventional solar arrays, but the current-loop areas and the resulting magnetic moments are much smaller because the return-current paths are much closer to the solar-cell sheet currents. The contact pads are prepared with solder fo electrical and mechanical bonding to the cells. The pocketed cover/shield, the solar cells, the printed-wiring layer, an electrical bonding agent, a mechanical-bonding agent, a composite structural front-side face sheet, an aluminum honeycomb core, and a composite back-side face sheet are all assembled, then contact pads are soldered to the cells and the agents are cured in a single lamination process.

Stem, Theodore G.; Kenniston, Anthony E.

2008-01-01

229

Genotyping Arrays  

NASA Astrophysics Data System (ADS)

Although the most common use of DNA microarrays is gene expression profiling, microarrays are also used for many other applications, including genotyping, resequencing, SNP analysis, and DNA methylation assays. Here we describe genotyping arrays for Influenza A subtype identification and for upper respiratory pathogen diagnostics using standard hybridization techniques and we also describe resequencing, SNP, and methylation assays using an enzyme-based strategy [25, 26].

Lodes, Michael J.; Suciu, Dominic; Danley, David; McShea, Andrew

230

Magnetometer array for cusp and cleft studies observations of the spatial extent of broadband ULF magnetic pulsations at cusp\\/cleft latitudes  

Microsoft Academic Search

The authors have used magnetometer data from 10 locations in Arctic Canada and Greenland, covering over 5 hours in magnetic local time at magnetic latitudes from 75° to 79°, to characterize the dayside patterns of enhanced long-period ULF (10- to 600-s period) wave power at cusp\\/cleft latitudes. They conclude the following: (1) In agreement with earlier single-station studies, the authors

M. J. Engebretson; J. L. Alford; W. J. Hughes; E. Zesta; L. J. Cahill; R. L. Arnoldy; G. D. Reeves

1995-01-01

231

Analysis of similar behaviors of planar and linear arrays  

Microsoft Academic Search

In this paper, the method of moments is employed to analyze both planar and linear finite phased arrays of radiating slots fed by rectangular waeguides.The equi alent magnetic currents and actie patterns due to these elements of phased arrays are discussed in detail. The relationship between linear and planar arrays is analyzed, and some similar behaiors are realized. 2001 John

Jian-Ying Li; Le-Wei Li; Ban-Leong Ooi; Pang-Shyan Kooi; Mook-Seng Leong

2001-01-01

232

Coupling Between Waveguide-Fed Slot Arrays  

NASA Technical Reports Server (NTRS)

Coupling between two waveguide-fed planar slot arrays has been investigated using full-wave analysis. The analysis employs the method-of-moments solution to the pertinent coupled integral equations for the aperture electric field of all slots. In order to compute coupling between two arrays, the input port of the first array is excited with a TE(sub 10) mode wave while the second one is match-terminated. After solving the moment method matrix equations, the aperture fields of all slots are obtained and thereby the TE(sub 10) mode wave received at the input port of the second array is determined. Coupling between two arrays is the ratio of the wave amplitude arriving in the second array port to the incident wave amplitude at the first array port. The coupling mechanism has been studied as a function of spacing between arrays in different directions, e.g. the electric field plane, the magnetic field plane, and the diagonal plane. Computed coupling values are presented for different array geometries. This work is novel since it provides a good understanding of coupling between waveguide-fed slot arrays as a function of spacing and orientation for different aperture distributions and array architectures. This serves as a useful tool for antenna design engineers and system engineers.

Rengarajan, Sembiam

2011-01-01

233

Nonvolatile Power-Gating Field-Programmable Gate Array Using Nonvolatile Static Random Access Memory and Nonvolatile Flip-Flops Based on Pseudo-Spin-Transistor Architecture with Spin-Transfer-Torque Magnetic Tunnel Junctions  

NASA Astrophysics Data System (ADS)

We proposed and computationally analyzed a nonvolatile power-gating field-programmable gate array (NVPG-FPGA) based on pseudo-spin-transistor architecture with spin-transfer-torque magnetic tunnel junctions (STT-MTJs). The circuit employs nonvolatile static random memory (NV-SRAM) cells and nonvolatile flip-flops (NV-FFs) as the storage circuits of the NVPG-FPGA. The circuit configuration and microarchitecture are compatible with SRAM-based FPGAs, and the additional nonvolatile memory functionality makes it possible to execute efficient power gating (PG). The break-even time (BET) for the nonvolatile configuration logic block (NV-CLB) of the NVPG-FPGA was also analyzed, and reduction techniques of the BET, which allows highly efficient PG operations with fine granularity, were proposed.

Yamamoto, Shuu'ichirou; Shuto, Yusuke; Sugahara, Satoshi

2012-11-01

234

Radiation Yield and Dynamics of Planar Wire-Array Plasma  

SciTech Connect

In our experiments, we compared planar wire arrays, to which little energy could be coupled via the conventional magnetic-to-kinetic conversion mechanism, to cylindrical wire arrays of comparable dimensions and mass. The planar wire arrays were shown to radiate much higher peak power and more energy in sub-keV and keV spectral ranges, than cylindrical wire arrays. We tested the theoretical conjecture that enhanced resistivity due to the small-scale inhomogeneity of wire-array plasmas has a major effect on dynamics, energy coupling to and radiation performance of wire-array Z-pinches.

Kantsyrev, Victor; Safronova, Alla; Fedin, Dmitry; Ivanov, Vladimir; Esaulov, Andrey; Nalajala, Vidya; Shrestha, Ishor; Pokala, Shivaji; Ouart, Nicholas; Yilmaz, Fatih; Batie, Steven; Astanovitsky, Alexey; Laca, Paul; Le Galloudec, Bruno; Cowan, Thomas [Physics Department/220, University of Nevada, Reno, NV 89557 (United States); Rudakov, Leonid [Icarus Research, Inc., P. O. Box 30780, Bethesda, MD 20824-0780 (United States); Velikovich, Alexander [Plasma Physics Division, Naval Research Laboratory, Code 6720, Washington D.C. 20375 (United States); Chuvatin, Alexander [Laboratoire de Physique et Technologie des Plasmas, Ecole Polytechnique, 91128 Palaiseau (France); Gradel, Joshua [Ktech Corp. Albuquerque, New Mexico (United States)

2006-01-05

235

Microshutter arrays for JWST - programmable field masks.  

NASA Astrophysics Data System (ADS)

Two-dimensional microshutter arrays are being developed at NASA Goddard Space Flight Center for the James Webb Space Telescope (JWST, formerly NGST) for use as a programmable aperture mask for object selection for the Near Infrared Multiobject Spectrograph (NIRSpec). We employ a hybrid actuation and addressing of the shutters. The shutters are actuated magnetically and then held open and addressed electrostatically. A tripole magnet for microshutter actuation has been designed and recently fabricated. Our first tests of the magnet demonstrated that the magnetic field is stronger compared to previously used bipolar magnets. As a result, the actuation was possible at larger distances from the microshutter array. The transport stage for for 512x256 shutter array has been designed and built. It is going to be used for cryogenic tests of the 512x256 arrays, including actuation, addressing and electronics operation, as well as optical testing. We continue our study of the effects of the shutter structure on the optical performance of the spectrometer. Issues of the diffraction, vignetting and sampling are considered. The efforts are directed toward finding the optimal slit size and observing strategy that would maximize the instrument performance over its whole spectral range. We are in the process of fabricating 2D addressable 128x128 shutter arrays (100 microns pitch). These arrays will be first fully functional large format 2D addressable microshutter arrays. It is an important step on the way to full size 512x256 arrays. We plan to have fully qualified demonstration devices by the end of 2003. This project is supported by JWST.

Moseley, S. H.; Blumenstock, K. A.; Ewin, A.; Franz, D. E.; Hein, J.; Hu, R.; Kotecki, C.; Kutyrev, A. S.; Laughlin, J.; Li, M. J.; Lynch, B.; Miles, A.; Mott, D. B.; Rapchun, D. A.; Schwinger, D. S.; Silverberg, R.; Smith, W.; Wesenberg, R. P.; Zincke, C.; Zheng, Y.

2002-12-01

236

Tunable magnetic properties of arrays of Fe(1 1 0) nanowires grown on kinetically grooved W(1 1 0) self-organized templates  

Microsoft Academic Search

We report a detailed magnetic study of a new type of self-organized nanowires discussed briefly previously [B. Borca et al., Appl. Phys. Lett. 90 (2007) 142507]. The templates, prepared on sapphire wafers in a kinetically limited regime, consist of uniaxially grooved W(110) surfaces, with a lateral period here tuned to 15nm. Fe deposition leads to the formation of (110) 7nm-wide

Bogdana Borca; Olivier Fruchart; Evaggelos Kritsikis; Fabien Cheynis; Anthony Rousseau; Philippe David; Claire Meyer; Jean-Christophe Toussaint

2010-01-01

237

Tunable magnetic properties of arrays of Fe(1 1 0) nanowires grown on kinetically grooved W(1 1 0) self-organized templates  

NASA Astrophysics Data System (ADS)

We report a detailed magnetic study of a new type of self-organized nanowires discussed briefly previously [B. Borca et al., Appl. Phys. Lett. 90 (2007) 142507]. The templates, prepared on sapphire wafers in a kinetically limited regime, consist of uniaxially grooved W(1 1 0) surfaces, with a lateral period here tuned to 15 nm. Fe deposition leads to the formation of (1 1 0) 7 nm-wide wires located at the bottom of the grooves. The effect of capping layers (Mo, Pd, Au, Al) and underlayers (Mo, W) on the magnetic anisotropy of the wires was studied. Significant discrepancies with figures known for thin flat films are evidenced and discussed in terms of step anisotropy and strain-dependent surface anisotropy. Demagnetizing coefficients of cylinders with a triangular isosceles cross-section have also been calculated, to estimate the contribution of dipolar anisotropy. Finally, the dependence of magnetic anisotropy with the interface element was used to tune the blocking temperature of the wires, here from 50 to 200 K.

Borca, B.; Fruchart, O.; Kritsikis, E.; Cheynis, F.; Rousseau, A.; David, Ph.; Meyer, C.; Toussaint, J. C.

2010-01-01

238

nanotube arrays  

NASA Astrophysics Data System (ADS)

We reported Ce and its oxide-modified TiO2 nanotube arrays (TNTs) and their semiconductor properties. The TNTs were prepared by anodic oxidation on pure Ti and investigated by electrochemical photocurrent response analysis. Then, the TNT electrodes were deposited of Ce by cathodic reduction of Ce(NO3)3 6H2O. After deposition, the TNT electrodes were fabricated by anodic oxidation at E = 1.0 V(SCE) for various electricity as Ce-Ce2O3-CeO2 modification. The Ce-deposited TNTs (band gap energy E g = 2.92 eV) exhibited enhanced photocurrent responses under visible light region and indicated more negative flat band potential ( E fb) compared with the TNTs without deposition. After anodic oxidation, the mixed Ce and its oxide (Ce2O3-CeO2)-modified TNT photoelectrodes exhibited higher photocurrent responses under both visible and UV light regions than the TNTs without deposition. The photocurrent responses and E fb were found to be strongly dependent on the contents of Ce2O3 and CeO2 deposited on TNTs. A new characteristic of E g = 2.1 ± 0.1 eV was investigated in the Ce2O3- and CeO2-modified photoelectrodes. X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were also employed to characterize various modified TNTs photoelectrodes.

Tan, Yu; Zhang, Shenghan; Liang, Kexin

2014-02-01

239

caArray - Array Data Management System  

Cancer.gov

Skip to Page Content Build 2.5.3_RC1 | Node: NCICB Welcome to caArray Browse Login Register About caArray What is caArray? Release Notes User Guide Global Quick Links National Cancer Institute (NCI) NCI Center for Biomedical Informatics and Information

240

The Mileura Widefield Array Demonstrator  

NASA Astrophysics Data System (ADS)

The Mileura Widefield Array is a low-frequency radio array planned for construction in the outback of Western Australia. In the next 3 years, we plan to build a demonstration array operating in the 80-300 MHz range, comprising 500 antenna systems, and capable of a variety of frontier scientific investigations. The instrument will feature a number of innovations that exploit modern digital signal processing capabilities, and implement functionality that has not hitherto been possible. Among the science goals of the demonstration array is the first detection and characterization of the redshifted 21cm signal from neutral hydrogen during the period of reheating and reionization at redshifts from 6 to 16. The array will also enable a search for transient radio phenomena with a sensitivity that is 6 orders of magnitude better than current limits. The measurement of scintillation and Faraday rotation due to plasma in the heliosphere will be used to diagnose density and magnetic field parameters of coronal mass ejections, with application to space weather studies. The project is a collaboration between MIT, CfA, the Australia Telescope National Facility, and multiple Australian universities.

Lonsdale, C. J.; Salah, J. E.; Hewitt, J. N.; Greenhill, L. J.; Cappallo, R. J.; Morales, M. F.

2004-12-01

241

Effects of Cu diffusion-doping on structural, optical, and magnetic properties of ZnO nanorod arrays grown by vapor phase transport method  

NASA Astrophysics Data System (ADS)

Well-aligned ZnO nanorods were prepared by the vapor phase transport method on Si covered with a ZnO buffer layer. After the nanostructure growth, Cu was doped into the ZnO nanorods by diffusion at three different temperatures and for different times. Undoped and Cu diffusion-doped ZnO samples are highly textured, with the c axis of the wurtzite structure along the growth direction. The incorporation of Cu caused some slight changes in the nanorod alignment, although the wurtzite crystal structure was maintained. X-ray photoelectron spectroscopy measurements revealed that Cu ions were in a divalent state and substituted for the Zn2+ ions of the ZnO matrix. Photoluminescence results at 10 K indicate that the incorporation of copper leads to a relative increase of Cu-related structured green band deep level intensity. Magnetic measurements revealed that both undoped and Cu diffusion-doped ZnO samples exhibited room temperature ferromagnetism. It was also found that bound magnetic polarons play an important role in the appearance of room temperature ferromagnetism in Cu diffusion-doped ZnO nanorods.

Y?lmaz, S.; McGlynn, E.; Bacaks?z, E.; Özcan, ?.; Byrne, D.; Henry, M. O.; Chellappan, R. K.

2012-01-01

242

Analysis on operational power and eddy current losses for applying coreless double-sided permanent magnet synchronous motor/generator to high-power flywheel energy storage system  

NASA Astrophysics Data System (ADS)

This paper deals with analytical approach of operational power defined as load power and rotor loss represented as eddy current loss for applying a permanent magnet (PM) synchronous motor/generator to the high-power flywheel energy storage system. The used model is composed of a double-sided Halbach magnetized PM rotor and coreless three-phase winding stator. For one such motor/generator structure, we provide the magnetic field and eddy current with space and time harmonics via magnetic vector potential in two-dimensional (2D) polar coordinate system. From these, the operational power is estimated by backelectromotive force according to the PM rotor speed, and the rotor loss is also calculated from Poynting theorem.

Jang, Seok-Myeong; Park, Ji-Hoon; You, Dae-Joon; Choi, Sang-Ho

2009-04-01

243

Integrated infrared array technology  

NASA Technical Reports Server (NTRS)

An overview of integrated infrared (IR) array technology is presented. Although the array pixel formats are smaller, and the readout noise of IR arrays is larger than the corresponding values achieved with optical charge-coupled-device silicon technology, substantial progress is being made in IR technology. Both existing IR arrays and those being developed are described. Examples of astronomical images are given which illustrate the potential of integrated IR arrays for scientific investigations.

Goebel, J. H.; Mccreight, C. R.

1987-01-01

244

Integrated infrared array technology  

NASA Technical Reports Server (NTRS)

An overview of integrated infrared (IR) array technology is presented. Although the array pixel formats are smaller, and the readout noise of IR arrays is larger, than the corresponding values achieved with optical charge-coupled-device silicon technology, substantial progress is being made in IR technology. Both existing IR arrays and those being developed are described. Examples of astronomical images are given which illustrate the potential of integrated IR arrays for scientific investigations.

Goebel, J. H.; Mccreight, C. R.

1986-01-01

245

Investigation of ablation and implosion dynamics in linear wire arrays  

SciTech Connect

Ablation and implosion dynamics were investigated by optical probing in linear wire arrays of different geometry. Formation of ablation jets begins on the outermost wires. In the beginning of implosion plasma bubbles arise in breaks on the outer wires. Implosion bubbles move to the next wire in the array and hit the plasma column with the speed >250 km/s. Imploding plasma moves to the center of the array cascading from wire to wire. Configuration of magnetic fields in the linear array can be changed by variation of wire spacing. The regimes of ablation and implosion in the wire arrays are found to differ with different wire spacing.

Ivanov, V. V.; Sotnikov, V. I.; Haboub, A.; Sarkisov, G. E.; Presura, R.; Cowan, T. E. [University of Nevada, Reno, 5625 Fox Avenue, Reno, Nevada 89506 (United States); Ktech Corporation, Albuquerque, New Mexico 87123 (United States); University of Nevada, Reno, 5625 Fox Avenue, Reno, Nevada 89506 (United States)

2007-03-15

246

Implosion Dynamics in Conical Wire Array Z-pinches  

SciTech Connect

We present initial results from imploding conical wire array experiments performed on both the MAGPIE generator (1MA, 240ns) at Imperial College London and the Nevada Terawatt Facility's Zebra generator (1MA, 100ns) at University of Nevada, Reno. This paper will discuss the implosion dynamics of conical wire arrays, including initial implosion of the cathode end of the array and the formation of a magnetic bubble.

Ampleford, D.J.; Lebedev, S.V.; Chittenden, J.P.; Bland, S.N.; Bott, S.C.; Hall, G.N.; Palmer, J.B.A.; Rapley, J. [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom); Kantsyrev, V.L.; Safronova, A.S.; Ivanov, V.V.; Fedin, D.A.; Laca, P.J.; Sotnikov, V.I.; Yilmaz, F.; Ouart, N.; Nalajala, V.; Shrestha, I.; Pokala, S. [Physics Department, University of Nevada, Reno, NV 89557 (United States); Jones, B. [Sandia National Laboratories, Albuquerque, NM 87185 (United States)] (and others)

2006-01-05

247

Array to Multiply  

NSDL National Science Digital Library

In this lesson, students will understand the concept of arrays and will be able to create/draw an array for multiplication sentences. Engaging center game is used to help student with concrete visual representation of multiplication sentences.

2013-01-28

248

Adaptive dome antenna array  

NASA Astrophysics Data System (ADS)

The class of antenna arrays examined consists of a plane multielement array emitting through a hemispherical dome which acts as a lens. Computer simulation studies were conducted for such an adaptive dome array having 21 isotropic elements. The studies simulated the effects of one and two narrow-band interference signals as well as white noise. The adaptation criterion corresponded to a generalized SNR.

Samoilenko, V. I.; Grubrin, I. V.

1981-02-01

249

Thermophotovoltaic Array Optimization  

SciTech Connect

A systematic approach to thermophotovoltaic (TPV) array design and fabrication was used to optimize the performance of a 192-cell TPV array. The systematic approach began with cell selection criteria that ranked cells and then matched cell characteristics to maximize power output. Following cell selection, optimization continued with an array packaging design and fabrication techniques that introduced negligible electrical interconnect resistance and minimal parasitic losses while maintaining original cell electrical performance. This paper describes the cell selection and packaging aspects of array optimization as applied to fabrication of a 192-cell array.

SBurger; E Brown; K Rahner; L Danielson; J Openlander; J Vell; D Siganporia

2004-07-29

250

Building of tridimensional Josephson junction arrays with controlled anisotropy  

NASA Astrophysics Data System (ADS)

This work depicts optimized preparation routes employed to produce and characterize tridimensional disordered Josephson junction arrays. The arrays were fabricated from granular superconductors, using Nb powder. All relevant signatures of a Josephson junction array are exhibited by the samples, including the typical Fraunhofer dependence of the critical current with the applied magnetic field, a magnetic remanence presented in a certain temperature interval, and the paramagnetic Meissner effect. Our results show that the anisotropy of the samples can be controlled by the pressure applied in the preparation process.

Passos, Wagner de A. C.; Lima, Emerson de; Ortiz, Wilson A.

2004-08-01

251

High Linearity Voltage Response Parallel-Array Cell  

NASA Astrophysics Data System (ADS)

We studied in detail a cell consisting of two parallel SQUID arrays or two parallel superconducting interference filters (SQIFs) connected differentially with the goal of achieving highly linear voltage response to magnetic signal. In these different cell designs, we accounted for realistic values of coupling inductances in contrast to limiting case of vanishing inductances considered earlier. We found that a cell based on regular parallel SQUID arrays produces higher linearity as compared to the cell based on SQIFs. This high-linearity cell can be used for realizing Superconducting Quantum Arrays (SQA) capable of providing a broadband, highly-linear magnetic field-to-voltage transfer function and high dynamic range.

Kornev, V.; Kolotinskiy, N.; Skripka, V.; Sharafiev, A.; Soloviev, I.; Mukhanov, O.

2014-05-01

252

Microshutter Arrays for James Webb Space Telescope  

NASA Technical Reports Server (NTRS)

Two-dimensional MEMS microshutter arrays are being developed at NASA Goddard Space Flight Center for use in the near-infrared region on the James Webb Space Telescope (JWST). The microshutter arrays are designed for the selective transmission of light with high efficiency and high contrast. The JWST environment requires cryogenic operation at 35K. Microshutter arrays are fabricated out of silicon-oxide-insulated (SOI) silicon wafers. Arrays are close-packed silicon nitride membranes with a pixel size of 100x200 p. Individual shutters are patterned with a torsion flexure permitting shutters to open 90 degrees with a minimized mechanical stress concentration. The mechanical shutter arrays are fabricated using MEMS technologies. The processing includes a multi- layer metal deposition and patterning of shutter electrodes and magnetic pads, reactive ion etching (NE) of the front side to form shutters out of the nitride membrane, an anisotropic back-etch for wafer thinning, followed by a deep RIE (DRIE) back-etch down to the nitride shutter membrane to form W e s and relieve shutters from the silicon substrate. An additional metal deposition and patterning is used to form back electrodes. Shutters are actuated using a magnetic force and latched using an electrostatic force. . . . KEYWORDS: microshutter, MEMS, RIE, DRIE, micro-optics, near inbred, space telescope

Li, Mary J.; Acuna, Nadine; Beamesderfer, Michael; Ewin, Audrey; Fettig, Rainer; Franz, Dave; Hess, Larry; Hu, Ron; Kelly, Dan; King, Todd

2004-01-01

253

Viking magnetic properties investigation - Preliminary results  

NASA Technical Reports Server (NTRS)

Three permanent-magnet arrays are aboard the Viking lander. By sol 35, one array, fixed on a photometric reference test chart on top of the lander, has clearly attracted magnetic particles from airborne dust; two other magnet arrays, one strong and one weak, incorporated in the backhoe of the surface sampler, have both extracted considerable magnetic mineral from the surface as a result of nine insertions associated with sample acquisition. The loose Martian surface material around the landing site is judged to contain 3 to 7 per cent highly magnetic mineral which, pending spectrophotometric study, is thought to be mainly magnetite.

Hargraves, R. B.; Collinson, D. W.; Spitzer, C. R.

1976-01-01

254

Eigenvalues imbedded in the band spectrum for the periodic array of quantum dots  

E-print Network

Eigenvalues imbedded in the band spectrum for the periodic array of quantum dots V. A. Geyler a.­Petersburg, 197101, Russia Abstract Solvable model of a periodic array of quantum dots in a uniform magnetic field. II. Model We consider an array of quantum dots displaced in the nodes of a plane lattice \\Gamma which

255

Electronic Switch Arrays for Managing Microbattery Arrays  

NASA Technical Reports Server (NTRS)

Integrated circuits have been invented for managing the charging and discharging of such advanced miniature energy-storage devices as planar arrays of microscopic energy-storage elements [typically, microscopic electrochemical cells (microbatteries) or microcapacitors]. The architecture of these circuits enables implementation of the following energy-management options: dynamic configuration of the elements of an array into a series or parallel combination of banks (subarrarys), each array comprising a series of parallel combination of elements; direct addressing of individual banks for charging/or discharging; and, disconnection of defective elements and corresponding reconfiguration of the rest of the array to utilize the remaining functional elements to obtain the desited voltage and current performance. An integrated circuit according to the invention consists partly of a planar array of field-effect transistors that function as switches for routing electric power among the energy-storage elements, the power source, and the load. To connect the energy-storage elements to the power source for charging, a specific subset of switches is closed; to connect the energy-storage elements to the load for discharging, a different specific set of switches is closed. Also included in the integrated circuit is circuitry for monitoring and controlling charging and discharging. The control and monitoring circuitry, the switching transistors, and interconnecting metal lines are laid out on the integrated-circuit chip in a pattern that registers with the array of energy-storage elements. There is a design option to either (1) fabricate the energy-storage elements in the corresponding locations on, and as an integral part of, this integrated circuit; or (2) following a flip-chip approach, fabricate the array of energy-storage elements on a separate integrated-circuit chip and then align and bond the two chips together.

Mojarradi, Mohammad; Alahmad, Mahmoud; Sukumar, Vinesh; Zghoul, Fadi; Buck, Kevin; Hess, Herbert; Li, Harry; Cox, David

2008-01-01

256

Soft-edged magnet models for higher-order beam-optics map codes  

SciTech Connect

Continuously varying surface and volume source-density distributions are used to model magnetic fields inside of cylindrical volumes. From these distributions, a package of subroutines computes on-axis generalized gradients and their derivatives at arbitrary points on the magnet axis for input to the numerical map-generating subroutines of the Lie-algebraic map code Marylie. In the present version of the package, the magnet menu includes: 1. cylindrical current-sheet or radially thick current distributions with either open boundaries or with a surrounding cylindrical boundary with normal field lines (which models high-permeability iron), 2. Halbach-type permanent mutipole magnets, either as sheet magnets or as radially thick magnets, 3. modeling of arbitrary fields inside a cylinder by use of a fictitious current sheet. The subroutines provide on-axis gradients and their z derivatives to essentially arbitrary order, although in the present 3rd and 5th order Marylie only the 0th through 6th derivatives are needed. The formalism is especially useful in beam-optics applications, such as magnetic lenses, where realistic treatment of fringefield effects is needed.

Walstrom, P. L. (Peter L.)

2002-01-01

257

Phased-array radars  

NASA Astrophysics Data System (ADS)

The operating principles, technology, and applications of phased-array radars are reviewed and illustrated with diagrams and photographs. Consideration is given to the antenna elements, circuitry for time delays, phase shifters, pulse coding and compression, and hybrid radars combining phased arrays with lenses to alter the beam characteristics. The capabilities and typical hardware of phased arrays are shown using the US military systems COBRA DANE and PAVE PAWS as examples.

Brookner, E.

1985-02-01

258

Sorting white blood cells in microfabricated arrays  

NASA Astrophysics Data System (ADS)

Fractionating white cells in microfabricated arrays presents the potential for detecting cells with abnormal adhesive or deformation properties. A possible application is separating nucleated fetal red blood cells from maternal blood. Since fetal cells are nucleated, it is possible to extract genetic information about the fetus from them. Separating fetal cells from maternal blood would provide a low cost noninvasive prenatal diagnosis for genetic defects, which is not currently available. We present results showing that fetal cells penetrate further into our microfabricated arrays than adult cells, and that it is possible to enrich the fetal cell fraction using the arrays. We discuss modifications to the array which would result in further enrichment. Fetal cells are less adhesive and more deformable than adult white cells. To determine which properties limit penetration, we compared the penetration of granulocytes and lymphocytes in arrays with different etch depths, constriction size, constriction frequency, and with different amounts of metabolic activity. The penetration of lymphocytes and granulocytes into constrained and unconstrained arrays differed qualitatively. In constrained arrays, the cells were activated by repeated shearing, and the number of cells stuck as a function of distance fell superexponentially. In unconstrained arrays the number of cells stuck fell slower than an exponential. We attribute this result to different subpopulations of cells with different sticking parameters. We determined that penetration in unconstrained arrays was limited by metabolic processes, and that when metabolic activity was reduced penetration was limited by deformability. Fetal cells also contain a different form of hemoglobin with a higher oxygen affinity than adult hemoglobin. Deoxygenated cells are paramagnetic and are attracted to high magnetic field gradients. We describe a device which can separate cells using 10 ?m magnetic wires to deflect the paramagnetic cells. We present preliminary results from a test system that separates paramagnetic beads from latex beads. The separation is limited by our ability to produce the high field gradients which are necessary to separate cells according to their hemoglobin content, and we present estimates of the magnetic gradients we achieved.

Castelino, Judith Andrea Rose

259

Galfenol tactile sensor array and visual mapping system  

Microsoft Academic Search

The smart material, Galfenol, is being explored for its uses as a magnetostrictive material. This project seeks to determine if Galfenol can be used as a tactile sensor in a 2-D grid array, magnetic circuit system. When used within a magnetic circuit, Galfenol indicates induced stress and force as a change in flux, due to a change in permeability of

Kathleen Hale; Alison Flatau

2006-01-01

260

Permutations of cubical arrays  

NASA Astrophysics Data System (ADS)

The structure constants of an algebra determine a cube called the cubical array associated with the algebra. The permuted indices of the cubical array associated with a finite semifield generate new division algebras. We do not not require that the algebra be finite and ask "Is it possible to choose a basis for the algebra such any permutation of the indices of the structure constants leaves the algebra unchanged?" What are the associated algebras? Author shows that the property "weakly quadratic" is invariant under all permutations of the indices of the corresponding cubical array and presents two algebras for which the cubical array is invariant under all permutations of the indices.

Wene, G. P.

2014-09-01

261

Algorithms for Sorting Arrays  

NSDL National Science Digital Library

It is often necessary to have elements of an array sorted into ascending or descending order. There are several approaches or algorithms available for sorting unordered arrays. Choosing an appropriate algorithm may depend upon the situation, however, some well-known algorithms are just more efficient than others. Exercise 1 To move an element in an array, an algorithm must make sure that each element being moved is inserted into an empty location or it will overwrite the current element. Therefore, to swap two items in an array, one of the items must be moved to an empty location ...

Watts, Mrs.

2007-09-26

262

Testing Microshutter Arrays Using Commercial FPGA Hardware  

NASA Technical Reports Server (NTRS)

NASA is developing micro-shutter arrays for the Near Infrared Spectrometer (NIRSpec) instrument on the James Webb Space Telescope (JWST). These micro-shutter arrays allow NIRspec to do Multi Object Spectroscopy, a key part of the mission. Each array consists of 62414 individual 100 x 200 micron shutters. These shutters are magnetically opened and held electrostatically. Individual shutters are then programmatically closed using a simple row/column addressing technique. A common approach to provide these data/clock patterns is to use a Field Programmable Gate Array (FPGA). Such devices require complex VHSIC Hardware Description Language (VHDL) programming and custom electronic hardware. Due to JWST's rapid schedule on the development of the micro-shutters, rapid changes were required to the FPGA code to facilitate new approaches being discovered to optimize the array performance. Such rapid changes simply could not be made using conventional VHDL programming. Subsequently, National Instruments introduced an FPGA product that could be programmed through a Labview interface. Because Labview programming is considerably easier than VHDL programming, this method was adopted and brought success. The software/hardware allowed the rapid change the FPGA code and timely results of new micro-shutter array performance data. As a result, numerous labor hours and money to the project were conserved.

Rapchun, David

2008-01-01

263

SOUTH AFRICA'S MEERKAT ARRAY  

E-print Network

SOUTH AFRICA'S MEERKAT ARRAY THE MEERKAT ARRAY, currently taking shape in South Africa's Karoo) is completed around 2024. Via MeerKAT, South Africa is playing a key role in design and technology developments at the engineering office in Cape Town, and at universities and technology companies across South Africa and Africa

Jarrett, Thomas H.

264

Solar array cost reduction  

NASA Technical Reports Server (NTRS)

A brief description is given of the cost of solar power systems over the last decade and means by which cost reductions may be achieved in the future. Costs were broken down into nonrecurring and recurring costs for solar array, battery, and power conditioning. Correlation of costs with power were poor; however, costs correlated reasonably well with the array area.

Bernatowicz, D. T.

1972-01-01

265

ISS Solar Array Management  

NASA Technical Reports Server (NTRS)

The International Space Station (ISS) Solar Array Management (SAM) software toolset provides the capabilities necessary to operate a spacecraft with complex solar array constraints. It monitors spacecraft telemetry and provides interpretations of solar array constraint data in an intuitive manner. The toolset provides extensive situational awareness to ensure mission success by analyzing power generation needs, array motion constraints, and structural loading situations. The software suite consists of several components including samCS (constraint set selector), samShadyTimers (array shadowing timers), samWin (visualization GUI), samLock (array motion constraint computation), and samJet (attitude control system configuration selector). It provides high availability and uptime for extended and continuous mission support. It is able to support two-degrees-of-freedom (DOF) array positioning and supports up to ten simultaneous constraints with intuitive 1D and 2D decision support visualizations of constraint data. Display synchronization is enabled across a networked control center and multiple methods for constraint data interpolation are supported. Use of this software toolset increases flight safety, reduces mission support effort, optimizes solar array operation for achieving mission goals, and has run for weeks at a time without issues. The SAM toolset is currently used in ISS real-time mission operations.

Williams, James P.; Martin, Keith D.; Thomas, Justin R.; Caro, Samuel

2010-01-01

266

Modifying Wire Array Z-pinch Ablation Structure and Implosion Dynamics Using Coiled Arrays  

SciTech Connect

Coiled arrays, a cylindrical array in which each wire is formed into a helix, suppress the modulation of ablation at the fundamental wavelength. Outside the vicinity of the wire cores, ablation flow from coiled arrays is modulated at the coil wavelength and has a 2-stream structure in the r,{theta} plane. Within the vicinity of the helical wires, ablation is concentrated at positions with the greatest azimuthal displacement and plasma is axially transported from these positions such that the streams become aligned with sections of the coil furthest from the array axis. The GORGON MHD code accurately reproduces this observed ablation structure, which can be understood in terms of JxB forces that result from the interaction of the global magnetic field with a helical current path as well as additional current paths suggested by the simulations. With this ability to control where ablation streamers occur, large wavelength coils were constructed such that the breaks that form in the wires had sufficient axial separation to prevent perturbations in the implosion sheath from merging. This produces a new mode of implosion in which the global instability can be controlled and perturbations correlated between all wires in an array. For large wavelength 8-wire coiled arrays, this produced a dramatic increase in x-ray power, equalling that of a 32-wire straight array. These experiments were carried out on the MAGPIE generator (1 MA, 240 ns) at Imperial College, and the COBRA generator (1 MA, 100 ns) at Cornell University.

Hall, Gareth N.; Bland, Simon N.; Lebedev, Sergey V.; Chittenden, Jeremy P.; Palmer, James B. A.; Suzuki-Vidal, Francisco A.; Swadling, George F.; Niasse, Nicolas [Blackett Laboratory, Imperial College, London, SW7 2BW (United Kingdom); Knapp, P. F.; Blesener, I. C.; McBride, R. D.; Chalenski, D. A.; Bell, K. S.; Greenly, J. B.; Blanchard, T.; Wilhelm, H.; Hammer, D. A.; Kusse, B. R. [Laboratory of Plasma Studies, Cornell University, Ithaca, US (United States); Bott, Simon C. [University of California, San Diego, US (United States)

2009-01-21

267

Micromachined electrode array  

DOEpatents

An electrode array is disclosed which has applications for neural stimulation and sensing. The electrode array, in certain embodiments, can include a plurality of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. In other embodiments of the electrode array, the electrodes can be fixed to the substrate. The electrode array can be formed from a combination of bulk and surface micromachining, and can include electrode tips having an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis.

Okandan, Murat (Edgewood, NM); Wessendorf, Kurt O. (Albuquerque, NM)

2007-12-11

268

Nonplanar switchable arrays  

SciTech Connect

On-line signal-processing and automatic-control applications give rise to numerous examples of computationally intense algorithms. Architectures that are algorithmically specialized and provide massive parallelism are necessary to cope with such computational requirements. Systolic arrays, which feature parallelism, local communications, and VLSI compatibility appear to match up well with these computational requirements. This paper summarizes recent research on a general class of nonplanar systolic arrays. These arrays feature closed-loop data flow. The arrays may be switched dynamically to facilitate I/O simplicity and to accommodate iterative calculations without intermediate I/O interdiction. The closed-loop data flows also facilitate restructuring of the array to accommodate specific algorithmic requirements. The potential for multiuser, multialgorithm operation is also enhanced. Matrix operations are used as examples in the development. Algorithms as diversified as the Riccati equation, LU factorization, the Faddeev algorithm, FFT calculation, and controllabilty Grammians can be implemented on the nonplanar architectures.

Aravena, J.L.; Porter, W.A.

1988-01-01

269

Multibeam Phased Array Antennas  

NASA Technical Reports Server (NTRS)

In this study, a new architecture for Ka-band multi-beam arrays was developed and demonstrated experimentally. The goal of the investigation was to demonstrate a new architecture that has the potential of reducing the cost as compared to standard expensive phased array technology. The goals of this specific part of the project, as stated in the yearly statement of work in the original proposal are: 1. Investigate bounds on performance of multi-beam lens arrays in terms of beamwidths, volume (size), isolation between beams, number of simultaneous beams, etc. 2. Design a small-scale array to demonstrate the principle. The array will be designed for operation around 3OGHz (Ka-band), with two 10-degree beamwidth beams. 3. Investigate most appropriate way to accomplish fine-tuning of the beam pointing within 5 degrees around the main beam pointing angle.

Popovic, Zoya; Romisch, Stefania; Rondineau, Sebastien

2004-01-01

270

High density pixel array  

NASA Technical Reports Server (NTRS)

A pixel array device is fabricated by a laser micro-milling method under strict process control conditions. The device has an array of pixels bonded together with an adhesive filling the grooves between adjacent pixels. The array is fabricated by moving a substrate relative to a laser beam of predetermined intensity at a controlled, constant velocity along a predetermined path defining a set of grooves between adjacent pixels so that a predetermined laser flux per unit area is applied to the material, and repeating the movement for a plurality of passes of the laser beam until the grooves are ablated to a desired depth. The substrate is of an ultrasonic transducer material in one example for fabrication of a 2D ultrasonic phase array transducer. A substrate of phosphor material is used to fabricate an X-ray focal plane array detector.

Wiener-Avnear, Eliezer (Inventor); McFall, James Earl (Inventor)

2004-01-01

271

Dipolar interactions in periodic arrays of rectangular ferromagnetic islands  

NASA Astrophysics Data System (ADS)

The increasing number of technological applications of micro- and nanomagnetism triggered the interest in the magnetic reversal behavior and the remanent states of laterally structured sub-micron sized magnetic elements. We have studied periodic arrays of dipolar coupled, rectangular permalloy stripes arranged on a square lattice. For distances below 1 ?m the dipolar interaction lead to ordered, symmetric remanent states. At larger distances the magnetic orientation was found to be disordered. The structures were defined by conventional e-beam lithography, the magnetic characterization was performed by magnetic force microscopy.

Remhof, A.; Schumann, A.; Westphalen, A.; Last, T.; Kunze, U.; Zabel, H.

272

Optical Magnetometer Array for Fetal Magnetocardiography  

E-print Network

We describe an array of spin-exchange relaxation free optical magnetometers designed for detection of fetal magnetocardiography (fMCG) signals. The individual magnetometers are configured with a small volume with intense optical pumping, surrounded by a large pump-free region. Spin-polarized atoms that diffuse out of the optical pumping region precess in the ambient magnetic field and are detected by a probe laser. Four such magnetometers, at the corners of a 7 cm square, are configured for gradiometry by feeding back the output of one magnetometer to a field coil to null uniform magnetic field noise at frequencies up to 200 Hz. Using this array, we present the first measurements of fMCG signals using an atomic magnetometer.

Wyllie, Robert; Wakai, Ronald T; Walker, Thad G

2012-01-01

273

Magneto-Electric Dipole Antenna Arrays  

E-print Network

A planar magneto-electric (ME) dipole antenna array is proposed and demonstrated by both full-wave analysis and experiments. The proposed structure leverages the infinite wavelength propagation characteristic of composite right/left-handed (CRLH) transmission lines to form high-gain magnetic radiators combined with radial conventional electric radiators, where the overall structure is excited by a single differential feed. The traveling-wave type nature of the proposed ME-dipole antenna enables the formation of directive arrays with high-gain characteristics and scanning capability. Peak gains of 10.84 dB and 5.73 dB are demonstrated for the electric dipole and magnetic-dipole radiation components, respectively.

Gupta, Shulabh; Caloz, Christophe

2014-01-01

274

Compound semiconductor SPAD arrays  

NASA Astrophysics Data System (ADS)

Single photon avalanche diodes (SPADs) are revolutionizing ultra-sensitive photodetection applications, providing single photon sensitivity, high quantum efficiency and low dark noise at or near room temperature. When aggregated into arrays, these devices have demonstrated the ability to operate as photon number resolving detectors with wide dynamic range, or as single-photon imaging detectors. SPAD array performance has reached a point where replacing vacuum tube based MCP and PMT photodetectors for most applications is inevitable. Compound semiconductor SPAD arrays offer the unique proposition to tailor performance to match application specific wavelength, speed and radiation hardness requirements. We present a theoretical framework describing performance limits to compound semiconductor SPAD arrays and our latest experimental results detailing the performance of GaAs SPAD arrays. These devices achieve nanosecond rise and fall times, excellent photon number resolving capability, and low dark count rates. Single photon number resolving is demonstrated with 4% single photon detection efficiency at room temperature with dark count rates below 7 Mcps/mm2. Compound semiconductor SPAD arrays have the opportunity to provide orders of magnitude improvement in dark count rate and radiation hardness over silicon SPAD arrays, as well as the ability to detect wavelengths where silicon is blind.

Harmon, Eric S.; Naydenkov, Mikhail; Hyland, James T.

2013-06-01

275

The Relationship of Magnetic Stiffness Between Single and Multiple YBCO Superconductors over Permanent Magnet Guideway  

NASA Astrophysics Data System (ADS)

For YBCO bulk levitating over a permanent magnet guideway (PMG), the magnetic stiffness is connected directly with the pinning properties of the measured sample. An experimental setup has been built to investigate the vertical and lateral magnetic stiffness of five high-temperature superconducting (HTS) bulk arrays over a PMG by two methods: the additive method, i.e., calculating the summation of the measured magnetic stiffness values of each HTS bulk in the array; the direct method, i.e., measuring directly the magnetic stiffness of the HTS bulk array. From the experimental results, it is found that the resultant magnetic stiffness of the HTS bulk array composing of multiple YBCO bulk is related with the magnetic stiffness of each individual single bulk, but the additive method does not predict the magnetic stiffness of the array very well because of the interaction between adjacent HTS bulk. The resultant magnetic stiffness of the HTS bulk array is less than the summation magnetic stiffness of each single HTS bulk. One numerical method is used to calculate the magnetic stiffness for comparing with experimental results. The results may be helpful to the design and optimization of the superconducting magnetic levitation system.

Lu, Yiyun; Lu, Bingjuan; Wang, Suyu

2011-09-01

276

Ultralightweight solar array technology  

NASA Astrophysics Data System (ADS)

Flat fold array technology is described, and performance for a range of missions and power levels is predicted. The array employs large area flat panel flexible substrates. The solar cells are adhesively bonded to a thin Kapton substrate to form individual panel assemblies. Any number of these panel assemblies may be joined together to make a blanket assembly. A container assembly protects each blanket assembly when stowed, and a tension guide wire assembly controls the flexible blanket shape when fully extended. Blanket extension and retraction are achieved through a motor powered lightweight trilongeron coilable lattice mast assembly. Ground and zero gravity flight tests on prototype array assemblies are successful.

Goldsmith, P.; Kurland, R.

1982-06-01

277

Arrays vs. single telescopes  

NASA Astrophysics Data System (ADS)

The question of the relative efficiencies of telescope arrays versus an equivalent mirror-area very large telescope is re-examined and summarized. Four separate investigations by Bowen, Johnson and Richards, Code, and Disney all came to the same conclusion: that an array of telescopes is superior, both scientifically and economically, to a single very large telescope. The costs of recently completed telescopes are compared. The costs of arrays of telescopes are shown to be significantly lower than that of a single, very large telescope, with the further advantage that because existing, proven, designs can be used, no engineering 'break-throughs' are needed.

Johnson, H. L.

278

The Geophysical Institute Magnetometer Array  

NASA Astrophysics Data System (ADS)

The Geophysical Institute Magnetometer Array (GIMA) consists of eight magnetometer stations distributed across Alaska spanning the auroral oval. Each station is equipped with a ring-core, fluxgate magnetometer, GPS clock and data logger. Data are returned from each station to the Geophysical Insitute, University of Alaska where it is verified, archived, and made available to the space science community. The GIMA web page, at http://magnet.gi.alaska.edu/, provides the data from five stations online in real-time. The GIMA web page also provides realtime data from four Russian magnetometer stations (NOK, Norilsk; PBK, Pebek; TIK, Tixie Bay; CCS, Cape Chelynskin). In addition, three other stations (operated by the USGS) in Alaska have online data available. The data set online spans the time period 1995 to the present. This presentation includes a review of the array, its capabilities (data collection parameters), the web site, and methods for acessing the data set. Interesting examples of the data will be used to illustrate the performance and capability of GIMA.

Heavner, M.

2005-12-01

279

Earthscope US Array: Array Network Facility  

NSDL National Science Digital Library

This is the homepage of the Array Network Facility (ANF), a component of the EarthScope USArray and Plate Boundary Observatory (PBO) programs. The ANF, established by the Anza Group (a realtime seismic array located in Anza, California), is charged with ensuring all seismic data collected from the arrays are transmitted, checked for quality, archived, and accessible online for researchers and the general public. A set of links provides access to other components of Earthscope such as USArray, a continental-scale seismic observatory; the Plate Boundary Observatory, a geodetic observatory designed to study strain fields resulting from deformation across the active boundary between the North American and Pacific plates; and Earthscope, an initiative to explore the structure and evolution of the North American continent. There are links to public information, including publications about ANF and USArray; maps and information on the active seismic stations in USArray; maps and information on recent earthquakes recorded by USArray stations; and a selection of online tools that can be used to observe the data from USArray. There is also a link to the Incorporated Research Institutions for Seismology (IRIS) Data Management Center, which houses data collected by USArray.

Vernon, Frank

280

Final Progress Report for the NASA Inductrack Model Rocket Launcher at the Lawrence Livermore National Laboratory  

SciTech Connect

The Inductrack magnetic levitation system, developed at the Lawrence Livermore National Laboratory, was studied for its possible use for launching rockets. Under NASA sponsorship, a small model system was constructed at the Laboratory to pursue key technical aspects of this proposed application. The Inductrack is a passive magnetic levitation system employing special arrays of high-field permanent magnets (Halbach arrays) on the levitating cradle, moving above a ''track'' consisting of a close-packed array of shorted coils with which are interleaved with special drive coils. Halbach arrays produce a strong spatially periodic magnetic field on the front surface of the arrays, while canceling the field on their back surface. Relative motion between the Halbach arrays and the track coils induces currents in those coils. These currents levitate the cradle by interacting with the horizontal component of the magnetic field. Pulsed currents in the drive coils, synchronized with the motion of the carrier, interact with the vertical component of the magnetic field to provide acceleration forces. Motional stability, including resistance to both vertical and lateral aerodynamic forces, is provided by having Halbach arrays that interact with both the upper and the lower sides of the track coils. At present, a 7.8 meter track composed of drive and levitation coils has been built and the electronic drive circuitry performs as designed. A 9 kg cradle that carries the Halbach array of permanent magnets has been built. A mechanical launcher is nearly complete which will provide an initial cradle velocity of 9 m/s into the electronic drive section. We have found that the drag forces from the levitation coils were higher than in our original design. However, measurements of drag force at velocities less than 1 m/s are exactly as predicted by theory. Provided here are recommended design changes to improve the track's performance so that a final velocity of 40 m/s can be achieved with the existing track. This project was designed and built as part of a Phase II contract that started in Feb. 1999 and ended in Sep. 2000 at a cost of $600K. A detailed budget on how this funding was spent is also included here.

Tung, L S; Post, R F; Martinez-Frias, J

2001-06-27

281

SERS based immuno-microwell arrays for multiplexed detection of foodborne pathogenic bacteria  

NASA Astrophysics Data System (ADS)

A novel surface enhanced Raman scattering (SERS)-based immuno-microwell array has been developed for multiplexed detection of foodborne pathogenic bacteria. The immuno-microwell array was prepared by immobilizing the optical addressable immunomagnetic beads (IMB) into the microwell array on one end of a fiber optic bundle. The IMBs, magnetic beads coated with specific antibody to specific bacteria, were used for immunomagnetic separation (IMS) of corresponding bacteria. The magnetic separation by the homemade magnetic separation system was evaluated in terms of the influences of several important parameters including the beads concentration, the sample volume and the separation time. IMS separation efficiency of the model bacteria E.coli O157:H7 was 63% in 3 minutes. The microwell array was fabricated on hydrofluoric acid etched end of a fiber optic bundle containing 30,000 fiber elements. After being coated with silver, the microwell array was used as a uniform SERS substrate with the relative standard deviation of the SERS enhancement across the microwell array < 2% and the enhancement factor as high as 2.18 x 107. The antibody modified microwell array was prepared for bacteria immobilization into the microwell array, which was characterized by a sandwich immunoassay. To demonstrate the potential of multiplexed SERS detection with the immuno-microwell array, the SERS spectra of different Raman dye labeled magnetic beads as well as mixtures were measured on the mircrowell array. In bead mixture, different beads were identified by the characteristic SERS bands of the corresponding Raman label.

Sun, Jian; Hankus, Mikella E.; Cullum, Brian M.

2009-05-01

282

Cherenkov Telescope Array Technologies  

NASA Astrophysics Data System (ADS)

The Cherenkov Telescope Array (CTA) will feature innovative technologies to achieve an order of magnitude greater sensitivity than the current generation of ground-based imaging atmospheric Cherenkov telescope (IACT) arrays. Several telescope designs of various sizes are currently in the prototyping stage. In addition to the traditional single-mirror Davies-Cotton design used for IACTs to date, a dual-mirror Schwarzschild-Couder design is being prototyped for both the small (4 m diameter) and medium (9.5 m diameter) telescopes. The dual-mirror designs feature compact focal planes that enable Cherenkov photon detection with innovative photo-detectors including silicon photomultipliers. The prototype telescopes are also testing several designs for readout electronics to capture the fast 10 ns) Cherenkov light pulses from hundreds of thousands of channels across the array. Finally, the CTA prototype telescopes are testing technologies for telescope mounts and mirrors that meet the unique needs of a large array of IACTs.

Vandenbroucke, Justin

2014-08-01

283

Glory Solar Array Deployment  

NASA Video Gallery

The Glory spacecraft uses Orbital Sciences Corporation Space Systems Group's LEOStar-1 bus design, with deployable, four-panel solar arrays. This conceptual animation reveals Glory's unique solar a...

284

Flexible retinal electrode array  

DOEpatents

An electrode array which has applications for neural stimulation and sensing. The electrode array can include a large number of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. The electrode array can be formed from a combination of bulk and surface micromachining, with electrode tips that can include an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis where the electrodes can be tailored to provide a uniform gentle contact pressure with optional sensing of this contact pressure at one or more of the electrodes.

Okandan, Murat (Albuquerque, NM); Wessendorf, Kurt O. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

2006-10-24

285

Intelligent field emission arrays  

E-print Network

Field emission arrays (FEAs) have been studied extensively as potential electron sources for a number of vacuum microelectronic device applications. For most applications, temporal current stability and spatial current ...

Hong, Ching-yin, 1973-

2003-01-01

286

OncoArray Network  

Cancer.gov

The overall goal of the OncoArray Network is to gain new insight into the genetic architecture and mechanisms underlying breast, ovarian, prostate, colorectal, and lung cancers. The Network's major aim is to discover new cancer susceptibility variants.

287

Computing Array Shapes in MATLAB  

Microsoft Academic Search

This paper deals with the problem of statically inferring the shape of an array in languages such as MATLAB. Inferring an array's shape is desirable because it empowers better compilation and interpre- tation; specifically, knowing an array's shape could permit reductions in the number of run-time array conformability checks, enable memory preallocation optimizations, and facilitate the in-lining of \\

Pramod G. Joisha; U. Nagaraj Shenoy; Prithviraj Banerjee

2001-01-01

288

The Atacama Compact Array (ACA)  

NASA Astrophysics Data System (ADS)

For realizing high fidelity of imaging with mosaicing observations, the Atacama Large Millimeter/submillimeter Array (ALMA) consists of a homogeneous array of 12 m antennas (12 m Array) and the Atacama Compact Array (ACA) in order to cover all spatial frequency Fourier components of the brightness distribution of observed sources. The array is located at an altitude site of about 5000m with an operating wavelength range of 0.3 to 3mm. ACA is an array composed of four 12 m dishes [TP (Total Power) Array] and twelve 7 m dishes (7 m Array). The 7 m Array has a very compact configuration to take short-baseline data corresponding to the low spatial frequency Fourier components. The 7 m Array has two configurations extended over 30--50m to avoid shadowing at low elevation. The scientific importances and operation concepts of ACA, and the system design of ACA and its performance are presented in this paper.

Iguchi, Satoru; Morita, Koh-Ichiro; Sugimoto, Masahiro; Vila Vilaró, Baltasar; Saito, Masao; Hasegawa, Tetsuo; Kawabe, Ryohei; Tatematsu, Ken'ichi; Seiichi, Seiichi; Kiuchi, Hitoshi; Okumura, Sachiko K.; Kosugi, George; Inatani, Junji; Takakuwa, Shigehisa; Iono, Daisuke; Kamazaki, Takeshi; Ogasawara, Ryusuke; Ishiguro, Masato

2009-02-01

289

Optimizing Chemical Sensor Array Sizes  

SciTech Connect

Optimal selection of array sensors for a chemical sensing application is a nontrivial task. It is commonly believed that "more is better" when choosing the number of sensors required to achieve good chemical selectivity. However, cost and system complexity issues point towards the choice of small arrays. A quantitative array optimization is carried out to explore the selectivity of arrays of partially-selective chemical sensors as a function of array size. It is shown that modest numbers (dozens) of target analytes are completely distinguished with a range of arrays sizes. However, the array selectivity and the robustness against sensor sensitivity variability are significantly degraded if the array size is increased above a certain number of sensors, so that relatively small arrays provide the best performance. The results also suggest that data analyses for very large arrays of partially-selective sensors will be optimized by separately anal yzing small sensor subsets.

Bartholomew, J.W.; Martinez, R.F.; Osbourn, G.C.; Ricco, A.J.; Yelton, W.G.

1999-05-05

290

For publication in the Terrestrial, Atmospheric, and Oceanic Sciences, 1999 On two methods using magnetometer-array data for studying  

E-print Network

magnetometer-array data for studying magnetic pulsations P. J. Chi and C. T. Russell Institute of Geophysics-phase spectrum, ionospheric Hall currents, geomagnetic induction. Abstract Ground magnetometer data have been arrays of magnetometer stations have been established. However, the usage of magnetometer arrays

Chi, Pi-Jen "Peter"

291

Contactless diamagnetic trapping of living cells onto a micromagnet array.  

PubMed

This paper focuses on the application of magnetophoresis to a new cell patterning method. The principle was demonstrated by using a CoPt micromagnet array, producing regularly spaced magnetic traps where cells were confined without any contact under the effect of negative magnetophoresis. To obtain this effect, yeast cells (Saccharomyces cerevisiae), which are diamagnetic, were placed in an aqueous solution enriched in paramagnetic ions. Unlabeled (non-magnetic) cell manipulation by magnetophoresis requires the production of high magnetic field gradients, ensuring significant forces. Therefore, micromagnets are particularly interesting for our application, since the field gradient increases as magnet dimensions are reduced. PMID:19163429

Frenea-Robin, M; Chetouani, H; Haddour, N; Rostaing, H; Laforet, J; Reyne, G

2008-01-01

292

Microbial Cell Arrays  

NASA Astrophysics Data System (ADS)

The coming of age of whole-cell biosensors, combined with the continuing advances in array technologies, has prepared the ground for the next step in the evolution of both disciplines - the whole cell array. In the present chapter, we highlight the state-of-the-art in the different disciplines essential for a functional bacterial array. These include the genetic engineering of the biological components, their immobilization in different polymers, technologies for live cell deposition and patterning on different types of solid surfaces, and cellular viability maintenance. Also reviewed are the types of signals emitted by the reporter cell arrays, some of the transduction methodologies for reading these signals, and the mathematical approaches proposed for their analysis. Finally, we review some of the potential applications for bacterial cell arrays, and list the future needs for their maturation: a richer arsenal of high-performance reporter strains, better methodologies for their incorporation into hardware platforms, design of appropriate detection circuits, the continuing development of dedicated algorithms for multiplex signal analysis, and - most importantly - enhanced long term maintenance of viability and activity on the fabricated biochips.

Elad, Tal; Lee, Jin Hyung; Gu, Man Bock; Belkin, Shimshon

293

Solar array flight experiment  

NASA Technical Reports Server (NTRS)

Emerging satellite designs require increasing amounts of electrical power to operate spacecraft instruments and to provide environments suitable for human habitation. In the past, electrical power was generated by covering rigid honeycomb panels with solar cells. This technology results in unacceptable weight and volume penalties when large amounts of power are required. To fill the need for large-area, lightweight solar arrays, a fabrication technique in which solar cells are attached to a copper printed circuit laminated to a plastic sheet was developed. The result is a flexible solar array with one-tenth the stowed volume and one-third the weight of comparably sized rigid arrays. An automated welding process developed to attack the cells to the printed circuit guarantees repeatable welds that are more tolerant of severe environments than conventional soldered connections. To demonstrate the flight readiness of this technology, the Solar Array Flight Experiment (SAFE) was developed and flown on the space shuttle Discovery in September 1984. The tests showed the modes and frequencies of the array to be very close to preflight predictions. Structural damping, however, was higher than anticipated. Electrical performance of the active solar panel was also tested. The flight performance and postflight data evaluation are described.

1986-01-01

294

Composite arrays of superconducting microstrip line resonators  

NASA Astrophysics Data System (ADS)

A novel design of an array of half-wave superconductive microstrip resonators is described. The resonator is intended to be useful for electron spin resonance studies of thin film samples at cryogenic temperatures. It achieves a high quality factor, has a small mode-volume, and creates a uniform magnetic field in a plane above the resonator. The device is made of thin film Niobium on sapphire wafer and is tested with a static magnetic field. Variation of Q-factor versus the magnetic field's strength at different temperatures is reported and is in a good agreement with simulation when the loss due to the vortices is included. Also, the power-dependence response of the resonator is shown in experiments and is verified by capturing the nonlinearity associated with the surface impedance of the superconducting film into the circuit model of the device.

Mohebbi, H. R.; Benningshof, O. W. B.; Taminiau, I. A. J.; Miao, G. X.; Cory, D. G.

2014-03-01

295

Red microchip VECSEL array  

NASA Astrophysics Data System (ADS)

We report an InGaP/AlInGaP/GaAs microchip vertical-external-cavity surface emitting laser operating directly at red wavelengths and demonstrate its potential for array-format operation. Optical pumping with up to 3.3W at 532nm produced a maximum output power of 330mW at 675nm, in a single circularly-symmetric beam with M2<2. Simultaneous pumping with three separate input beams, generated using a diffractive optical element, achieved lasing from three discrete areas of the same chip. Output power of ~95mW per beam was obtained from this 3x1 array, each beam having a Gaussian intensity profile with M2<1.2. In a further development, a spatial light modulator allowed computer control over the orientation and separation of the pump beams, and hence dynamic control over the configuration of the VECSEL array.

Hastie, Jennifer E.; Morton, Lynne G.; Calvez, Stephane; Dawson, Martin D.; Leinonen, Tomi; Pessa, Markus; Gibson, Graham; Padgett, Miles J.

2005-09-01

296

Red microchip VECSEL array.  

PubMed

We report an InGaP/AlInGaP/GaAs microchip vertical-external-cavity surface emitting laser operating directly at red wavelengths and demonstrate its potential for array-format operation. Optical pumping with up to 3.3W at 532nm produced a maximum output power of 330mW at 675nm, in a single circularly-symmetric beam with M2<2. Simultaneous pumping with three separate input beams, generated using a diffractive optical element, achieved lasing from three discrete areas of the same chip. Output power of ~95mW per beam was obtained from this 3x1 array, each beam having a Gaussian intensity profile with M2<1.2. In a further development, a spatial light modulator allowed computer control over the orientation and separation of the pump beams, and hence dynamic control over the configuration of the VECSEL array. PMID:19498743

Hastie, Jennifer; Morton, Lynne; Calvez, Stephane; Dawson, Martin; Leinonen, Tomi; Pessa, Markus; Gibson, Graham; Padgett, Miles

2005-09-01

297

Pyroelectric detector arrays  

NASA Technical Reports Server (NTRS)

A pryoelectric detector array and the method for making it are described. A series of holes formed through a silicon dioxide layer on the surface of a silicon substrate forms the mounting fixture for the pyroelectric detector array. A series of nontouching strips of indium are formed around the holes to make contact with the backside electrodes and form the output terminals for individual detectors. A pyroelectric detector strip with front and back electrodes, respectively, is mounted over the strip. Biasing resistors are formed on the surface of the silicon dioxide layer and connected to the strips. A metallized pad formed on the surface of the layer is connected to each of the biasing resistors and to the film to provide the ground for the pyroelectric detector array.

Fripp, A. L.; Robertson, J. B.; Breckenridge, R. A. (inventors)

1982-01-01

298

Pyroelectric detector arrays  

NASA Technical Reports Server (NTRS)

A pyroelectric detector array and the method for using it are described. A series of holes formed through a silicon dioxide layer on the surface of a silicon substrate forms the mounting fixture for the pyroelectric detector array. A series of nontouching strips of indium are formed around the holes to make contact with the backside electrodes and form the output terminals for individual detectors. A pyroelectric detector strip with front and back electrodes, respectively, is mounted over the strips. Biasing resistors are formed on the surface of the silicon dioxide layer and connected to the strips. A metallized pad formed on the surface of layer is connected to each of the biasing resistors and to the film to provide the ground for the pyroelectric detector array.

Fripp, A. L.; Robertson, J. B.; Breckenridge, R. (inventors)

1982-01-01

299

Fabrication and characterization of nanostructured magnetic particles for applications in data storage  

E-print Network

Arrays of nanostructured magnetic particles ('nanomagnets') have potential applications in ultra-high-density data storage devices and dynamic magnetic memories, and are model systems for the study of magnetic phenomena ...

Farhoud, Maya S. (Maya Sami)

2001-01-01

300

GMR biosensor arrays: a system perspective.  

PubMed

Giant magnetoresistive biosensors are becoming more prevalent for sensitive, quantifiable biomolecular detection. However, in order for magnetic biosensing to become competitive with current optical protein microarray technology, there is a need to increase the number of sensors while maintaining the high sensitivity and fast readout time characteristic of smaller arrays (1-8 sensors). In this paper, we present a circuit architecture scalable for larger sensor arrays (64 individually addressable sensors) while maintaining a high readout rate (scanning the entire array in less than 4s). The system utilizes both time domain multiplexing and frequency domain multiplexing in order to achieve this scan rate. For the implementation, we propose a new circuit architecture that does not use a classical Wheatstone bridge to measure the small change in resistance of the sensor. Instead, an architecture designed around a transimpedance amplifier is employed. A detailed analysis of this architecture including the noise, distortion, and potential sources of errors is presented, followed by a global optimization strategy for the entire system comprising the magnetic tags, sensors, and interface electronics. To demonstrate the sensitivity, quantifiable detection of two blindly spiked samples of unknown concentrations has been performed at concentrations below the limit of detection for the enzyme-linked immunosorbent assay. Lastly, the multiplexing capability and reproducibility of the system was demonstrated by simultaneously monitoring sensors functionalized with three unique proteins at different concentrations in real-time. PMID:20207130

Hall, D A; Gaster, R S; Lin, T; Osterfeld, S J; Han, S; Murmann, B; Wang, S X

2010-05-15

301

Incipient magnetic rotation? A magnetic dipole band in 104Cd  

E-print Network

High spin states of the nucleus 104Cd have been studied using the Gammapshere array. The level scheme for 104Cd has been revised and evidence for a structure consisting of magnetic dipole transitions is presented. Shell model calculations, published previously, are invoked to support an interpretation of this structure as an incpient case of magnetic rotation where the transversal magnetic dipole moment is not strong enough to break the signature symmetry.

D. G. Jenkins; R. Wadsworth; J. A. Cameron; M. P. Carpenter; C. J. Chiara; R. M. Clark M. Devlin; P. Fallon; D. B. Fossan; I. M. Hibbert; R. V. F. Janssens; V. P. Janzen; R. Kruecken; D. R. LaFosse; G. J. Lane; T. Lauritsen; I. Y. Lee; A. O. Macchiavelli; C. M. Parry; D. G. Sarsantities; J. M. Sears; D. Seweryniak; J. F. Smith; K. Starosta; D. Ward; I. Wiedenhoever; A. N. Wilson; J. N. Wilson; S. Frauendorf

2000-07-05

302

Solar array subsystems study  

NASA Technical Reports Server (NTRS)

The effects on life cycle costs of a number of technology areas are examined for a LEO, 500 kW solar array. A baseline system conceptual design is developed and the life cycle costs estimated in detail. The baseline system requirements and design technologies are then varied and their relationships to life cycle costs quantified. For example, the thermal characteristics of the baseline design are determined by the array materials and masses. The thermal characteristics in turn determine configuration, performance and hence life cycle cost.

Richardson, P. W.; Miller, F. Q.; Badgley, M. B.

1980-01-01

303

Wire Array Photovoltaics  

NASA Astrophysics Data System (ADS)

Over the past five years, the cost of solar panels has dropped drastically and, in concert, the number of installed modules has risen exponentially. However, solar electricity is still more than twice as expensive as electricity from a natural gas plant. Fortunately, wire array solar cells have emerged as a promising technology for further lowering the cost of solar. Si wire array solar cells are formed with a unique, low cost growth method and use 100 times less material than conventional Si cells. The wires can be embedded in a transparent, flexible polymer to create a free-standing array that can be rolled up for easy installation in a variety of form factors. Furthermore, by incorporating multijunctions into the wire morphology, higher efficiencies can be achieved while taking advantage of the unique defect relaxation pathways afforded by the 3D wire geometry. The work in this thesis shepherded Si wires from undoped arrays to flexible, functional large area devices and laid the groundwork for multijunction wire array cells. Fabrication techniques were developed to turn intrinsic Si wires into full p-n junctions and the wires were passivated with a-Si:H and a-SiNx:H. Single wire devices yielded open circuit voltages of 600 mV and efficiencies of 9%. The arrays were then embedded in a polymer and contacted with a transparent, flexible, Ni nanoparticle and Ag nanowire top contact. The contact connected >99% of the wires in parallel and yielded flexible, substrate free solar cells featuring hundreds of thousands of wires. Building on the success of the Si wire arrays, GaP was epitaxially grown on the material to create heterostructures for photoelectrochemistry. These cells were limited by low absorption in the GaP due to its indirect bandgap, and poor current collection due to a diffusion length of only 80 nm. However, GaAsP on SiGe offers a superior combination of materials, and wire architectures based on these semiconductors were investigated for multijunction arrays. These devices offer potential efficiencies of 34%, as demonstrated through an analytical model and optoelectronic simulations. SiGe and Ge wires were fabricated via chemical-vapor deposition and reactive ion etching. GaAs was then grown on these substrates at the National Renewable Energy Lab and yielded ns lifetime components, as required for achieving high efficiency devices.

Turner-Evans, Dan

304

A review of array radars  

NASA Astrophysics Data System (ADS)

Achievements in the area of array radars are illustrated by such activities as the operational deployment of the large high-power, high-range-resolution Cobra Dane; the operational deployment of two all-solid-state high-power, large UHF Pave Paws radars; and the development of the SAM multifunction Patriot radar. This paper reviews the following topics: array radars steered in azimuth and elevation by phase shifting (phase-phase steered arrays); arrays steered + or - 60 deg, limited scan arrays, hemispherical coverage, and omnidirectional coverage arrays; array radars steering electronically in only one dimension, either by frequency or by phase steering; and array radar antennas which use no electronic scanning but instead use array antennas for achieving low antenna sidelobes.

Brookner, E.

1981-10-01

305

Periodic nanowire array at the crystal interface.  

PubMed

A dislocation in a crystalline material has dangling bonds at its core and a strong strain field in its vicinity. Consequently, the dislocation attracts solute atoms and forms a so-called Cottrell atmosphere along the dislocation. A crystalline dislocation can be used as a template to produce nanowires by selectively doping foreign atoms along the dislocation. However, control of the configuration, spacing, and density of the formed periodic nanowire array has heretofore been extremely difficult. Here we show a method for fabricating ordered, electrically conductive nanowire arrays using periodic dislocations at crystal interfaces. As a demonstration, we fabricated arrays of titanium nanowires arranged at intervals of either 13 or 90 nm and then confirmed by scanning probe microscopy that they exhibit electrical conductivity inside an insulating aluminum oxide. Significantly, we were able to precisely control nanowire periodicity by the choice of crystal orientation and/or crystal planes at the crystal interface. This simple method for the fabrication of periodic nanowire arrays of highly controlled density should be widely applicable to electrical, magnetic, and optical devices. PMID:23876048

Nakamura, Atsutomo; Mizoguchi, Teruyasu; Matsunaga, Katsuyuki; Yamamoto, Takahisa; Shibata, Naoya; Ikuhara, Yuichi

2013-07-23

306

Stability of discrete breathers in magnetic metamaterials  

E-print Network

Stability of discrete breathers in magnetic metamaterials Dmitry Pelinovsky1 and Vassilis Rothos2 1 describing magnetic metamaterials which consist of periodic arrays of split- ring resonators [4, 7]: ¨qn + V criterion to the multi-site breathers in magnetic metamaterials. 2 Formalism In what follows, we shall use

Pelinovsky, Dmitry

307

Data Allocation and Scheduling in Disks and Disk Arrays  

Microsoft Academic Search

\\u000a Magnetic disks, which together with disk arrays constitute a multibillion dollar industry, were developed in 1950s. Disks\\u000a were an advance over magnetic drums, which had a dedicated read\\/write head per track, since much higher amounts of data could\\u000a be accessed in a cost effective manner due to the sharability of the movable read\\/write heads. DRAM memories, which are volatile, were

Alexander Thomasian

2003-01-01

308

The Askaryan Radio Array  

NASA Astrophysics Data System (ADS)

Ultra high energy cosmogenic neutrinos could be most efficiently detected in dense, radio frequency (RF) transparent media via the Askaryan effect. Building on the expertise gained by RICE, ANITA and IceCube's radio extension in the use of the Askaryan effect in cold Antarctic ice, we are currently developing an antenna array known as ARA (The Askaryan Radio Array) to be installed in boreholes extending 200 m below the surface of the ice near the geographic South Pole. The unprecedented scale of ARA, which will cover a fiducial area of ~ 100 square kilometers, was chosen to ensure the detection of the flux of neutrinos suggested by the observation of a drop in high energy cosmic ray flux consistent with the GZK cutoff by HiRes and the Pierre Auger Observatory. Funding to develop the instrumentation and install the first prototypes has been granted, and the first components of ARA were installed during the austral summer of 2010-2011. Within 3 years of commencing operation, the full ARA will exceed the sensitivity of any other instrument in the 0.1-10 EeV energy range by an order of magnitude. The primary goal of the ARA array is to establish the absolute cosmogenic neutrino flux through a modest number of events. This information would frame the performance requirements needed to expand the array in the future to measure a larger number of neutrinos with greater angular precision in order to study their spectrum and origins.

Hoffman, Kara D.

2013-01-01

309

Uniformly redundant arrays  

Microsoft Academic Search

A recent development in coded aperture imaging removed the basic limitation on the quality of the reconstructed images when a correlation analysis is used. A pattern of holes for the aperture was designed that has an autocorrelation that is perfectly flat. The pattern is referred to as a uniformly redundant array (URA) and combines the high-transmission characteristics of the random

E. E. Fenimore; T. M. Cannon

1977-01-01

310

TRMM Solar Array Panels  

NASA Technical Reports Server (NTRS)

This final report presents conclusions/recommendations concerning the TRMM Solar Array; deliverable list and schedule summary; waivers and deviations; as-shipped performance data, including flight panel verification matrix, panel output detail, shadow test summary, humidity test summary, reverse bias test panel; and finally, quality assurance summary.

1998-01-01

311

Array processors in chemistry  

SciTech Connect

The field of attached scientific processors (''array processors'') is surveyed, and an attempt is made to indicate their present and possible future use in computational chemistry. The current commercial products from Floating Point Systems, Inc., Datawest Corporation, and CSP, Inc. are discussed.

Ostlund, N.S.

1980-01-01

312

Log periodic dipole arrays  

Microsoft Academic Search

A new class of coplanar dipole arrays is introduced. The antennas described provide unidirectional radiation patterns of constant beamwidth and nearly constant input impedances over any desired bandwidth. The broad-band properties are achieved by making use of the principles of log periodic antenna design. Models are discussed which are capable of providing 8- to 9-db directive gain with an associated

D. Isbell

1960-01-01

313

Analysis de arrays Introduction  

E-print Network

estadístico de arrays de expresión y de CGH (II) Ramón Díaz-Uriarte http://ligarto.org/rdiaz BM-13: 2009 y copyright This work is Copyright, ©, 2011, Ramón Díaz-Uriarte, and is licensed under the Creative

Díaz-Uriarte, Ramón

314

Near Field Accelerometer Array.  

National Technical Information Service (NTIS)

The report outlines the accomplishments during the two and one half years of the Grant. A portable near-field accelerometer array consisting of 9 stations was developed and installed in the Stone Canyon-Bear Valley region of central California. A detailed...

T. V. McEvilly, L. R. Johnson

1975-01-01

315

Countermeasure Flexible Line Array.  

National Technical Information Service (NTIS)

A countermeasure buoy for use in an underwater environment includes a main body portion, a propulsion portion, a hull section, and an acoustical array. The main body portion includes a first end and a second end longitudinally opposed from the first end. ...

1998-01-01

316

Arrays for space applications  

NASA Technical Reports Server (NTRS)

Concepts that were studied for application in space based radar (SBR) systems are presented. These antenna systems were for low earth orbit and require large fields of view (FOV). The systems included both space-fed and corporate-fed arrays.

Schuman, Harvey K.; Antonik, Paul; Malagisi, Carmen

1989-01-01

317

Basic Photovoltaic Array Sizing  

NSDL National Science Digital Library

This learning activity from the Advanced Technology Environmental and Energy Center (ATEEC) allows students to conduct a photovoltaic array sizing assessment. Users must download this resource for viewing, which requires a free log-in. There is no cost to download the item.

2013-01-10

318

Automated array assembly  

NASA Technical Reports Server (NTRS)

A general technology assessment and manufacturing cost analysis was presented. A near-term (1982) factory design is described, and the results of an experimental production study for the large-scale production of flat-panel silicon and solar-cell arrays are detailed.

Daiello, R. V.

1977-01-01

319

Science with the Square Kilometre Array  

NASA Technical Reports Server (NTRS)

The Square Kilometre Array (SKA) is the centimeter- and meter-wavelength telescope for the 21st Century. Its Key Science Projects are (a) The end of the Dark Ages, involving searches for an H i signature and the first metalrich systems; (b) Testing theories of gravitation using an array of pulsars to search for gravitational waves and relativistic binaries to probe the strong-field regime; (c) Observations of H i to a redshift z 2 from which to study the evolution of galaxies and dark energy. (d) Astrobiology including planetary formation within protoplanetary disks; and (c) The origin and evolution of cosmic magnetism, both within the Galaxy and in intergalactic space. The SKA will operate over the wavelength range of at least 1.2 cm to 4 m (70 MHz to 25 GHz), providing milliarcsecond resolution at the shortest wavelengths.

Lazio, Joseph; Huynh, Minh

2010-01-01

320

Detail of array structural elements through axis of array, looking ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Detail of array structural elements through axis of array, looking north-northeast - Over-the-Horizon Backscatter Radar Network, Columbia Falls Radar Site Receive Sector Two Antenna Array, At the end of Shadagee Ridge Road, Columbia Falls, Washington County, ME

321

Dynamics of conical wire array Z-pinch implosions  

NASA Astrophysics Data System (ADS)

A modification of the wire array Z pinch, the conical wire array, has applications to the understanding of wire array implosions and potentially to pulse shaping relevant to inertial confinement fusion. Results are presented from imploding conical wire array experiments performed on university scale 1 MA generators—the MAGPIE generator (1 MA, 240 ns) at Imperial College London [I. H. Mitchell et al., Rev. Sci Instrum. 67, 1533 (1996)] and the Nevada Terawatt Facility's Zebra generator (1 MA, 100 ns) at the University of Nevada, Reno [B. Bauer et al., in Dense Z-Pinches, edited by N. Pereira, J. Davis, and P. Pulsifer (AIP, New York, 1997), Vol. 409, p. 153]. This paper will discuss the implosion dynamics of conical wire arrays. Data indicate that mass ablation from the wires in this complex system can be reproduced with a rocket model with fixed ablation velocity. Modulations in the ablated plasma are present, the wavelength of which is invariant to a threefold variation in magnetic field strength. The axial variation in the array leads to a zippered precursor column formation. An initial implosion of a magnetic bubble near the cathode is followed by the implosion zippering upwards. Spectroscopic data demonstrating a variation of plasma parameters (e.g., electron temperature) along the Z-pinch axis is discussed, and experimental data are compared to magnetohydrodynamic simulations.

Ampleford, D. J.; Lebedev, S. V.; Bland, S. N.; Bott, S. C.; Chittenden, J. P.; Jennings, C. A.; Kantsyrev, V. L.; Safronova, A. S.; Ivanov, V. V.; Fedin, D. A.; Laca, P. J.; Yilmaz, M. F.; Nalajala, V.; Shrestha, I.; Williamson, K.; Osborne, G.; Haboub, A.; Ciardi, A.

2007-10-01

322

Superconducting bulk magnets for magnetic levitation systems  

NASA Astrophysics Data System (ADS)

The major applications of high-temperature superconductors have mostly been confined to products in the form of wires and thin films. However, recent developments show that rare-earth REBa 2Cu 3O 7- x and light rare-earth LREBa 2Cu 3O 7- x superconductors prepared by melt processes have a high critical-current density at 77 K and high magnetic fields. These superconductors will promote the application of bulk high-temperature superconductors in high magnetic fields; the superconducting bulk magnet for the Maglev train is one possible application. We investigated the possibility of using bulk magnets in the Maglev system, and examined flux-trapping characteristics of multi-superconducting bulks arranged in array.

Fujimoto, H.; Kamijo, H.

2000-06-01

323

Wave modes of collective vortex gyration in dipolar-coupled-dot-array magnonic crystals  

PubMed Central

Lattice vibration modes are collective excitations in periodic arrays of atoms or molecules. These modes determine novel transport properties in solid crystals. Analogously, in periodical arrangements of magnetic vortex-state disks, collective vortex motions have been predicted. Here, we experimentally observe wave modes of collective vortex gyration in one-dimensional (1D) periodic arrays of magnetic disks using time-resolved scanning transmission x-ray microscopy. The observed modes are interpreted based on micromagnetic simulation and numerical calculation of coupled Thiele equations. Dispersion of the modes is found to be strongly affected by both vortex polarization and chirality ordering, as revealed by the explicit analytical form of 1D infinite arrays. A thorough understanding thereof is fundamental both for lattice vibrations and vortex dynamics, which we demonstrate for 1D magnonic crystals. Such magnetic disk arrays with vortex-state ordering, referred to as magnetic metastructure, offer potential implementation into information processing devices. PMID:23877284

Han, Dong-Soo; Vogel, Andreas; Jung, Hyunsung; Lee, Ki-Suk; Weigand, Markus; Stoll, Hermann; Schutz, Gisela; Fischer, Peter; Meier, Guido; Kim, Sang-Koog

2013-01-01

324

Multi-array borehole resistivity and induced polarization method with mathematical inversion of redundant data  

DOEpatents

Multiple arrays of electric or magnetic transmitters and receivers are used in a borehole geophysical procedure to obtain a multiplicity of redundant data suitable for processing into a resistivity or induced polarization model of a subsurface region of the earth.

Ward, Stanley H. (Salt Lake City, UT)

1989-01-01

325

NEMS fabrication of metal coated sub-wavelength size aperture array and its optical characterization  

E-print Network

oxide aperture array with sub-wavelength size was revealed after the water-diluted HF acid etching fabricated the sub-wavelength size silicon oxide aperture array as a near-field optical probe in order to examine the possible light resonance-tunneling phenomenon. Initially, using a magnetic enhanced reactive

Boo, Jin-Hyo

326

Crystals of Crystals: Fabrication of Encapsulated and Ordered Two-Dimensional Arrays of Microcrystals  

E-print Network

Crystals of Crystals: Fabrication of Encapsulated and Ordered Two-Dimensional Arrays demonstrates a method of making ordered arrays of encapsulated microcrystals: "crystals of crystals". Single crystals may have properties useful for optical, magnetic and electronic applications.1-3 Large single

Prentiss, Mara

327

A case for redundant arrays of inexpensive disks (RAID)  

Microsoft Academic Search

Increasing performance of CPUs and memories will be squandered if not matched by a similar performance increase in I\\/O. While the capacity of Single Large Expensive Disks (SLED) has grown rapidly, the performance improvement of SLED has been modest. Redundant Arrays of Inexpensive Disks (RAID), based on the magnetic disk technology developed for personal computers, offers an attractive alternative to

David A. Patterson; Garth A. Gibson; Randy H. Katz

1988-01-01

328

Photon detection with high gain avalanche photodiode arrays  

Microsoft Academic Search

The detection of light emitted in fast scintillating fibers and Cerenkov radiators used for fiber calorimetry and tracking applications in high energy colliders, requires fast detector arrays with high sensitivity to short wavelength photons. Photomultiplier tubes, the traditional imaging detectors for short wavelength optical radiation, have limited spatial resolution and require expensive anti-magnetic shielding. We report on short wavelength sensitivity

S. Vasile; P. Gothoskar; R. Farrell; D. Sdrulla

1998-01-01

329

Permanent Magnet Ecr Plasma Source With Magnetic Field Optimization  

DOEpatents

In a plasma-producing device, an optimized magnet field for electron cyclotron resonance plasma generation is provided by a shaped pole piece. The shaped pole piece adjusts spacing between the magnet and the resonance zone, creates a convex or concave resonance zone, and decreases stray fields between the resonance zone and the workpiece. For a cylindrical permanent magnet, the pole piece includes a disk adjacent the magnet together with an annular cylindrical sidewall structure axially aligned with the magnet and extending from the base around the permanent magnet. The pole piece directs magnetic field lines into the resonance zone, moving the resonance zone further from the face of the magnet. Additional permanent magnets or magnet arrays may be utilized to control field contours on a local scale. Rather than a permeable material, the sidewall structure may be composed of an annular cylindrical magnetic material having a polarity opposite that of the permanent magnet, creating convex regions in the resonance zone. An annular disk-shaped recurve section at the end of the sidewall structure forms magnetic mirrors keeping the plasma off the pole piece. A recurve section composed of magnetic material having a radial polarity forms convex regions and/or magnetic mirrors within the resonance zone.

Doughty, Frank C. (Plano, TX); Spencer, John E. (Plano, TX)

2000-12-19

330

Reduction of magnetostatic interactions in self-organized arrays of nickel nanowires using atomic layer deposition  

NASA Astrophysics Data System (ADS)

Ordered arrays of magnetic nanowires are commonly synthesized by electrodeposition in nanoporous alumina templates. Due to their dense packing, strong magnetostatic interactions prevent the manipulation of wires individually. Using atomic layer deposition we reduce the diameter of the pores prior to electrodeposition. This reduces magnetostatic interactions, yielding fully remanent hysteresis loops. This is a first step toward the use of such arrays for magnetic racetrack memories.

Da, S., Col; Darques, M.; Fruchart, O.; Cagnon, L.

2011-03-01

331

Large scale two-dimensional arrays of magnesium diboride superconducting quantum interference devices  

NASA Astrophysics Data System (ADS)

Magnetic field sensors based on two-dimensional arrays of superconducting quantum interference devices were constructed from magnesium diboride thin films. Each array contained over 30 000 Josephson junctions fabricated by ion damage of 30 nm weak links through an implant mask defined by nano-lithography. Current-biased devices exhibited very large voltage modulation as a function of magnetic field, with amplitudes as high as 8 mV.

Cybart, Shane A.; Wong, T. J.; Cho, E. Y.; Beeman, J. W.; Yung, C. S.; Moeckly, B. H.; Dynes, R. C.

2014-05-01

332

Angle sensing with ferromagnetic nanowire arrays  

NASA Astrophysics Data System (ADS)

Hysteresis loops and Ferromagnetic Resonance (FMR) linewidths of Nickel ferromagnetic nanowire arrays are measured versus angle ?H between the applied magnetic field angle and the common nanowire axis. Using Preisach analysis, we extract from the hysteresis loop an interaction parameter ?i that strongly depends on ?H. Extending the analysis to FMR lineshapes, we deduce a strong dependence of the FMR field linewidth ?H on ?H through the interaction parameter ?i. Existence of a link between static (hysteresis) and dynamic (FMR) cases through ?H might be exploited in contactless absolute angle sensing devices that could compete with inductive, Hall, and magnetoresistive devices.

Tannous, C.; Gieraltowski, J.

2014-01-01

333

Spatially resolved single photon detection with a quantum sensor array  

PubMed Central

We propose a method of resolving a spatially coherent signal, which contains on average just a single photon, against the background of local noise at the same frequency. The method is based on detecting the signal simultaneously in several points more than a wavelength apart through the entangling interaction of the incoming photon with the quantum metamaterial sensor array. The interaction produces the spatially correlated quantum state of the sensor array, characterised by a collective observable (e.g., total magnetic moment), which is read out using a quantum nondemolition measurement. We show that the effects of local noise (e.g., fluctuations affecting the elements of the array) are suppressed relative to the signal from the spatially coherent field of the incoming photon as , where N is the number of array elements. The realisation of this approach in the microwave range would be especially useful and is within the reach of current experimental techniques. PMID:24322568

Zagoskin, A. M.; Wilson, R. D.; Everitt, M.; Savel'ev, S.; Gulevich, D. R.; Allen, J.; Dubrovich, V. K.; Il'ichev, E.

2013-01-01

334

Forces on a magnet moving past figure-eight coils  

SciTech Connect

For the first time, the lift, drag, and guidance forces acting on a permanent magnet are measured as the magnet passes over different arrays of figure-eight (null-flux) coils. The experimental results are in good agreement with the predictions of dynamic circuit theory, which is used to explain more optimal coil arrays.

Mulcahy, T.H.; He, Jianliang; Rote, D.M. [Argonne National Lab., IL (United States); Rossing, T.D. [Northern Illinois Univ., De Kalb, IL (United States). Dept. of Physics

1993-03-01

335

Forces on a magnet moving past figure-eight coils  

SciTech Connect

For the first time, the lift, drag, and guidance forces acting on a permanent magnet are measured as the magnet passes over different arrays of figure-eight (null-flux) coils. The experimental results are in good agreement with the predictions of dynamic circuit theory, which is used to explain more optimal coil arrays.

Mulcahy, T.H.; He, Jianliang; Rote, D.M. (Argonne National Lab., IL (United States)); Rossing, T.D. (Northern Illinois Univ., De Kalb, IL (United States). Dept. of Physics)

1993-01-01

336

Holographic telescope arrays.  

PubMed

A typical job in optical computing is to illuminate an array of small nonlinear optical components, separated by wide gaps to avoid crosstalk. We do this by letting a wide uniform beam fall onto a densely packed array of minifying telescopes. Each telescope produces a narrow bundle of parallel rays which illuminates one of the nonlinear optical components. The holographic telescopes can do more than change the width of the bundles of parallel rays. Their image forming capability allows the transmission of many pixels per channel in parallel. The pair of lenslets of a single holographic telescope (Kepler or Galilean) is produced in rigid coupling. The monolithic production avoids adjusting the two lenslets later on. PMID:20531877

Lohmann, A W; Sauer, F

1988-07-15

337

Optically interconnected phased arrays  

NASA Technical Reports Server (NTRS)

Phased-array antennas are required for many future NASA missions. They will provide agile electronic beam forming for communications and tracking in the range of 1 to 100 GHz. Such phased arrays are expected to use several hundred GaAs monolithic integrated circuits (MMICs) as transmitting and receiving elements. However, the interconnections of these elements by conventional coaxial cables and waveguides add weight, reduce flexibility, and increase electrical interference. Alternative interconnections based on optical fibers, optical processing, and holography are under evaluation as possible solutions. In this paper, the current status of these techniques is described. Since high-frequency optical components such as photodetectors, lasers, and modulators are key elements in these interconnections, their performance and limitations are discussed.

Bhasin, Kul B.; Kunath, Richard R.

1988-01-01

338

Fluorescence Based Sensor Arrays  

Microsoft Academic Search

\\u000a Fluorescence-based cross reactive sensor arrays have experienced significant development in the last decade because of the\\u000a advantages that they can offer with respect to other transduction mechanisms, in terms of the usual performance parameters\\u000a such as sensitivity, selectivity and so on. From this point of view, a great impulse to this development has been due to the\\u000a realization of novel

Roberto Paolesse; Donato Monti; Francesca Dini; Corrado Di Natale

339

Photovoltaic cell array  

NASA Technical Reports Server (NTRS)

A photovoltaic cell array consisting of parallel columns of silicon filaments is described. Each fiber is doped to produce an inner region of one polarity type and an outer region of an opposite polarity type to thereby form a continuous radial semi conductor junction. Spaced rows of electrical contacts alternately connect to the inner and outer regions to provide a plurality of electrical outputs which may be combined in parallel or in series.

Eliason, J. T. (inventor)

1976-01-01

340

Array Transposition in SSD  

NASA Technical Reports Server (NTRS)

One obstacle to running very large two- and three-dimensional codes on the Cray X-MP and Y-MP systems is to efficiently perform array transpositions using SSD storage. This article discusses how such transpositions can be performed by means of algorithms that feature exclusively unit stride, long vector transfers between main memory and SSD, and which only require a single pass through the data (provided sufficient main memory buffers are available).

Bailey, David H.; Kutler, Paul (Technical Monitor)

1998-01-01

341

Array processor architecture  

NASA Technical Reports Server (NTRS)

A high speed parallel array data processing architecture fashioned under a computational envelope approach includes a data base memory for secondary storage of programs and data, and a plurality of memory modules interconnected to a plurality of processing modules by a connection network of the Omega gender. Programs and data are fed from the data base memory to the plurality of memory modules and from hence the programs are fed through the connection network to the array of processors (one copy of each program for each processor). Execution of the programs occur with the processors operating normally quite independently of each other in a multiprocessing fashion. For data dependent operations and other suitable operations, all processors are instructed to finish one given task or program branch before all are instructed to proceed in parallel processing fashion on the next instruction. Even when functioning in the parallel processing mode however, the processors are not locked-step but execute their own copy of the program individually unless or until another overall processor array synchronization instruction is issued.

Barnes, George H. (Inventor); Lundstrom, Stephen F. (Inventor); Shafer, Philip E. (Inventor)

1983-01-01

342

Spaceborne Processor Array  

NASA Technical Reports Server (NTRS)

A Spaceborne Processor Array in Multifunctional Structure (SPAMS) can lower the total mass of the electronic and structural overhead of spacecraft, resulting in reduced launch costs, while increasing the science return through dynamic onboard computing. SPAMS integrates the multifunctional structure (MFS) and the Gilgamesh Memory, Intelligence, and Network Device (MIND) multi-core in-memory computer architecture into a single-system super-architecture. This transforms every inch of a spacecraft into a sharable, interconnected, smart computing element to increase computing performance while simultaneously reducing mass. The MIND in-memory architecture provides a foundation for high-performance, low-power, and fault-tolerant computing. The MIND chip has an internal structure that includes memory, processing, and communication functionality. The Gilgamesh is a scalable system comprising multiple MIND chips interconnected to operate as a single, tightly coupled, parallel computer. The array of MIND components shares a global, virtual name space for program variables and tasks that are allocated at run time to the distributed physical memory and processing resources. Individual processor- memory nodes can be activated or powered down at run time to provide active power management and to configure around faults. A SPAMS system is comprised of a distributed Gilgamesh array built into MFS, interfaces into instrument and communication subsystems, a mass storage interface, and a radiation-hardened flight computer.

Chow, Edward T.; Schatzel, Donald V.; Whitaker, William D.; Sterling, Thomas

2008-01-01

343

NOBA (NObeyama Bolometer Array)  

NASA Astrophysics Data System (ADS)

NOBA is seven element bolometer array developed for the 45-m telescope at Nobeyama Radio Observatory (NRO) using AC bridge readout method (Kuno et al. 1993). Although NOBA was developed for 150 GHz observations, it can be used at higher frequency by changing band pass filters. We purchased the filters for 230 GHz observations and have started test observations. The sensitivity at 150 GHz and 230 GHz are about 45 mJy ?{s} and about 200 mJy ?{s}, respectively, under good sky condition. The beam size and beam separation are 12 arcsec and 16 arcsec, respectively, at both 150 GHz and 230 GHz. Therefore, we can get two band images with the same angular resolution, although we can not get them simultaneously because we have to change the filters. Furthermore, BEARS (SIS 25-BEam Array Receiver System) which can be used at the frequency range of 84-116 GHz are being developed at NRO. These array systems mounted on the NRO 45-m telescope are useful to get multi-band images with high angular resolution. We present the first results of 230GHz observations with NOBA.

Kuno, N.; Matsuo, H.; Sakamoto, A.

344

Mir Cooperative Solar Array  

NASA Technical Reports Server (NTRS)

The Mir Cooperative Solar Array (MCSA), produced jointly by the United States and Russia, was deployed on the Mir Russian space station on May 25, 1996. The MCSA is a photovoltaic electrical power system that can generate up to 6 kW. The power from the MCSA is needed to extend Mir's lifetime and to support experiments conducted there by visiting U.S. astronauts. The MCSA was brought to Mir via the Space Shuttle Atlantis on the STS-74 mission, launched November 12, 1995. This cooperative venture combined the best technology of both countries: the United States provided high-efficiency, lightweight photovoltaic panel modules, whereas Russia provided the array structure and deployment mechanism. Technology developed in the Space Station Freedom Program, and now being used in the International Space Station, was used to develop MCSA's photovoltaic panel. Performance data obtained from MCSA operation on Mir will help engineers better understand the performance of the photovoltaic panel modules in orbit. This information will be used to more accurately predict the performance of the International Space Station solar arrays. Managed by the NASA Lewis Research Center for NASA's International Space Station Program Office in Houston, Texas, the MCSA Project was completed on time and under budget despite a very aggressive schedule.

Skor, Mike; Hoffman, Dave J.

1997-01-01

345

Solar array construction  

DOEpatents

An interconnect tab on each cell of a first set of circular solar cells connects that cell in series with an adjacent cell in the set. This set of cells is arranged in alternate columns and rows of an array and a second set of similar cells is arranged in the remaining alternate columns and rows of the array. Three interconnect tabs on each solar cell of the said second set are employed to connect the cells of the second set to one another, in series and to connect the cells of the second set to those of the first set in parallel. Some tabs (making parallel connections) connect the same surface regions of adjacent cells to one another and others (making series connections) connect a surface region of one cell to the opposite surface region of an adjacent cell; however, the tabs are so positioned that the array may be easily assembled by depositing the cells in a certain sequence and in proper orientation.

Crouthamel, Marvin S. (Pennsauken, NJ); Coyle, Peter J. (Oaklyn, NJ)

1982-01-01

346

Tutorial: Performance and reliability in redundant disk arrays  

NASA Technical Reports Server (NTRS)

A disk array is a collection of physically small magnetic disks that is packaged as a single unit but operates in parallel. Disk arrays capitalize on the availability of small-diameter disks from a price-competitive market to provide the cost, volume, and capacity of current disk systems but many times their performance. Unfortunately, relative to current disk systems, the larger number of components in disk arrays leads to higher rates of failure. To tolerate failures, redundant disk arrays devote a fraction of their capacity to an encoding of their information. This redundant information enables the contents of a failed disk to be recovered from the contents of non-failed disks. The simplest and least expensive encoding for this redundancy, known as N+1 parity is highlighted. In addition to compensating for the higher failure rates of disk arrays, redundancy allows highly reliable secondary storage systems to be built much more cost-effectively than is now achieved in conventional duplicated disks. Disk arrays that combine redundancy with the parallelism of many small-diameter disks are often called Redundant Arrays of Inexpensive Disks (RAID). This combination promises improvements to both the performance and the reliability of secondary storage. For example, IBM's premier disk product, the IBM 3390, is compared to a redundant disk array constructed of 84 IBM 0661 3 1/2-inch disks. The redundant disk array has comparable or superior values for each of the metrics given and appears likely to cost less. In the first section of this tutorial, I explain how disk arrays exploit the emergence of high performance, small magnetic disks to provide cost-effective disk parallelism that combats the access and transfer gap problems. The flexibility of disk-array configurations benefits manufacturer and consumer alike. In contrast, I describe in this tutorial's second half how parallelism, achieved through increasing numbers of components, causes overall failure rates to rise. Redundant disk arrays overcome this threat to data reliability by ensuring that data remains available during and after component failures.

Gibson, Garth A.

1993-01-01

347

Technique to measure sub-microsecond magnetic field pulses using magnetic (CoPt) thin films  

Microsoft Academic Search

We introduce a technique to measure the maximum magnetic field of a submicrosecond duration pulse using magnetic CoPt thin films. In the present experiment, this technique yields a lower limit for the field intensity and reveals the sense of that peak field. The time-varying magnetic field was generated by an exploding wire array plasma called an X pinch. Using a

W. Syed; R. B. van Dover; J. R. Petrie; M. D. Mitchell; D. A. Hammer

2005-01-01

348

Solid state neutron detector array  

DOEpatents

A neutron detector array is capable of measuring a wide range of neutron fluxes. The array includes multiple semiconductor neutron detectors. Each detector has a semiconductor active region that is resistant to radiation damage. In one embodiment, the array preferably has a relatively small size, making it possible to place the array in confined locations. The ability of the array to detect a wide range of neutron fluxes is highly advantageous for many applications such as detecting neutron flux during start up, ramp up and full power of nuclear reactors. 7 figs.

Seidel, J.G.; Ruddy, F.H.; Brandt, C.D.; Dulloo, A.R.; Lott, R.G.; Sirianni, E.; Wilson, R.O.

1999-08-17

349

Solid state neutron detector array  

DOEpatents

A neutron detector array is capable of measuring a wide range of neutron fluxes. The array includes multiple semiconductor neutron detectors. Each detector has a semiconductor active region that is resistant to radiation damage. In one embodiment, the array preferably has a relatively small size, making it possible to place the array in confined locations. The ability of the array to detect a wide range of neutron fluxes is highly advantageous for many applications such as detecting neutron flux during start up, ramp up and full power of nuclear reactors.

Seidel, John G. (Pittsburgh, PA); Ruddy, Frank H. (Monroeville, PA); Brandt, Charles D. (Mount Lebanon, PA); Dulloo, Abdul R. (Pittsburgh, PA); Lott, Randy G. (Pittsburgh, PA); Sirianni, Ernest (Monroeville, PA); Wilson, Randall O. (Greensburg, PA)

1999-01-01

350

Optical magnetometer array for fetal magnetocardiography  

PubMed Central

We describe an array of spin-exchange-relaxation-free optical magnetometers designed for detection of fetal magnetocardiography (fMCG). The individual magnetometers are configured with a small volume with intense optical pumping, surrounded by a large pump-free region. Spin-polarized atoms that diffuse out of the optical pumping region precess in the ambient magnetic field and are detected by a probe laser. Four such magnetometers, at the corners of a 7 cm square, are configured for gradiometry by feeding back the output of one magnetometer to a field coil to null uniform magnetic field noise at frequencies up to 200 Hz. We present the first measurements of fMCG signals using an atomic magnetometer. PMID:22739870

Wyllie, Robert; Kauer, Matthew; Wakai, Ronald T.; Walker, Thad G.

2012-01-01

351

Highly Parallel Magnetic Resonance Imaging with a Fourth Gradient Channel for Compensation of RF Phase Patterns  

E-print Network

A fourth gradient channel was implemented to provide slice dependent RF coil phase compensation for arrays in dual-sided or "sandwich" configurations. The use of highly parallel arrays for single echo acquisition magnetic resonance imaging allows...

Bosshard, John 1983-

2012-08-20

352

Symmetric aluminum-wire arrays generate high-quality Z pinches at large array radii  

SciTech Connect

A Saturn-accelerator study of annular, aluminum-wire array, Z-pinch implosions, in the calculated high-wire-number plasma-shell regime [Phys. Rev. Lett. {bold 77}, 5063 (1996)], shows that the radiated x-ray pulse width increases from about 4 nsec to about 7 nsec, when the radius of the array is increased from 8.75 to 20 mm at a fixed array mass of 0.6 mg. Eulerian radiation- magnetohydrodynamic code (E-RMHC) simulations in the r-z plane suggest that this pulse-width increase with radius is due to the faster growth of the shell thickness (that arises from a two-stage development in the magnetic Rayleigh{endash}Taylor instability) relative to the increase in the shell implosion velocity. Over the array radii explored, the measured peak total x-ray power of {approximately}40 TW and energy of {approximately}325 kJ show little change outside of a {plus_minus}15{percent} shot-to-shot fluctuation and are consistent with the E-RMHC simulations. Similarly, the measured peak {ital K}-shell (lines plus continuum) power of {approximately}8 TW and energy of {approximately}70 kJ show little change with radius. The minimal change in {ital K}-shell yield is in agreement with simple {ital K}-shell radiation scaling models that assume a fixed radial compression for all initial array radii. These results suggest that the improved uniformity provided by the large number of wires in the initial array reduces the disruptive effects of the Rayleigh{endash}Taylor instability observed in small-wire-number imploding loads. {copyright} {ital 1998 American Institute of Physics.}

Sanford, T.W.; Mock, R.C.; Spielman, R.B. [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185 (United States); Peterson, D.L. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545-0010 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545-0010 (United States); Mosher, D. [Naval Research Laboratory, Pulsed Power Physics Branch, Washington, DC 20375 (United States)] [Naval Research Laboratory, Pulsed Power Physics Branch, Washington, DC 20375 (United States); Roderick, N.F. [University of New Mexico, Albuquerque, New Mexico 87131 (United States)] [University of New Mexico, Albuquerque, New Mexico 87131 (United States)

1998-10-01

353

Weld quality evaluation using a high temperature SQUID array  

SciTech Connect

This paper presents preliminary data for evaluating weld quality using high temperature SQUIDS. The SQUIDS are integrated into an instrument known as the SQUID Array Microscope, or SAMi. The array consists of ll SQUIDs evenly distributed over an 8.25 mm baseline. Welds are detected using SAMi by using an on board coil to induce eddy currents in a conducting sample and measuring the resulting magnetic fields. The concept is that the induced magnetic fields will differ in parts of varying weld quality. The data presented here was collected from three stainless steel parts using SAMi. Each part was either solid, included a good weld, or included a bad weld. The induced magnetic field's magnitude and phase relative to the induction signal were measured. For each sample considered, both the magnitude and phase data were measurably different than the other two samples. These results indicate that it is possible to use SAMi to evaluate weld quality.

Clark, D. D. (David D.); Espy, M. A. (Michelle A.); Kraus, Robert H., Jr.; Matlachov, A. N. (Andrei N.); Lamb, J. S. (Jessica S.)

2002-01-01

354

A full optically operated magnetometer array: An experimental study  

NASA Astrophysics Data System (ADS)

We show the operation of an optically pumped magnetometer array in a 50 ?T magnetic field. The various components for a fully optical and non-magnetic detector unit were constructed and evaluated, from which a prototype unit was assembled with fiber coupled electronics. In this unit the magnetometers were operated using the intensity modulated method and heated with an off-resonant laser. Calculations on the temperature distribution were used to design the magnetometer array. Different magnetometers in such a detector unit were characterized and showed identical performance. Without applying noise reduction schemes, the obtained magnetic field resolution is a factor 2.5 above the shot noise level down to frequencies of about 7 Hz.

IJsselsteijn, R.; Kielpinski, M.; Woetzel, S.; Scholtes, T.; Kessler, E.; Stolz, R.; Schultze, V.; Meyer, H.-G.

2012-11-01

355

Magnetocardiography with a modular spin-exchange relaxation free atomic magnetometer array  

PubMed Central

We present a portable four-channel atomic magnetometer array operating in the spin exchange relaxation-free regime. The magnetometer array has several design features intended to maximize its suitability for biomagnetic measurement, specifically foetal magnetocardiography, such as a compact modular design and fibre coupled lasers. The modular design allows the independent positioning and orientation of each magnetometer. Using this array in a magnetically shielded room, we acquire adult magnetocadiograms. These measurements were taken with a 6–11 fT Hz?1/2 single-channel baseline sensitivity that is consistent with the independently measured noise level of the magnetically shielded room. PMID:22504066

Wyllie, R; Kauer, M; Smetana, G S; Wakai, R T; Walker, T G

2012-01-01

356

UAVSAR Phased Array Aperture  

NASA Technical Reports Server (NTRS)

This paper describes the development of a patch antenna array for an L-band repeat-pass interferometric synthetic aperture radar (InSAR) instrument that is to be flown on an unmanned aerial vehicle (UAV). The antenna operates at a center frequency of 1.2575 GHz and with a bandwidth of 80 MHz, consistent with a number of radar instruments that JPL has previously flown. The antenna is designed to radiate orthogonal linear polarizations in order to facilitate fully-polarimetric measurements. Beam-pointing requirements for repeat-pass SAR interferometry necessitate electronic scanning in azimuth over a range of -20degrees in order to compensate for aircraft yaw. Beam-steering is accomplished by transmit/receive (T/R) modules and a beamforming network implemented in a stripline circuit board. This paper, while providing an overview of phased array architecture, focuses on the electromagnetic design of the antenna tiles and associated interconnects. An important aspect of the design of this antenna is that it has an amplitude taper of 10dB in the elevation direction. This is to reduce multipath reflections from the wing that would otherwise be detrimental to interferometric radar measurements. This taper is provided by coupling networks in the interconnect circuits as opposed to attenuating the output of the T/R modules. Details are given of material choices and fabrication techniques that meet the demanding environmental conditions that the antenna must operate in. Predicted array performance is reported in terms of co-polarized and crosspolarized far-field antenna patterns, and also in terms of active reflection coefficient.

Chamberlain, Neil; Zawadzki, Mark; Sadowy, Greg; Oakes, Eric; Brown, Kyle; Hodges, Richard

2009-01-01

357

Bit-array alignment effect of perpendicular SOMA media  

NASA Astrophysics Data System (ADS)

One effective way to overcome the superparamagnetic limit of magnetic recording system is to reduce the grain number per bit at given signal-to-noise ratio (SNR) level by using uniformed media grains. The self organized magnetic array (SOMA) is designed to have uniform grains with perfect grain array structure. It is believed that high enough SNR with small number of grains per bit can be acheived. But in the engineering application, the recorded bit on SOMA media may align with the regular array at different locations and angles due to non-grain synchronized writing, skew angle, and circular track. This induces the bit-array alignment effect and degrades system performance of SOMA media. In this paper, the micromagnetic simulation results show that the bit array alignment effect causes large level SNR fluctuation on the same media. The SOMA media is not preferred to be used in the conventional recording configuration. It is only suitable for the configuration of patterned media.

Xiao, Peiying; Yuan, Zhimin; Kuan Lee, Hwee; Guo, Guoxiao

2006-08-01

358

Modeling high gradient magnetic separation from biological fluids.  

SciTech Connect

A proposed portable magnetic separator consists of an array of biocompatible capillary tubing and magnetizable wires immersed in an externally applied homogeneous magnetic field. While subject to the homogeneous magnetic field, the wires create high magnetic field gradients, which aid in the collection of blood-borne magnetic nanospheres from blood flow. In this study, a 3-D numerical model was created using COMSOL Multiphysics 3.2 software to determine the configuration of the wire-tubing array from two possible configurations, one being an array with rows alternating between wires and tubing, and the other being an array where wire and tubing alternate in two directions. The results demonstrated that the second configuration would actually capture more of the magnetic spheres. Experimental data obtained by our group support this numerical result.

Bockenfeld, D.; Chen, H.; Rempfer, D.; Kaminski, M. D.; Rosengart, A. J.; Chemical Engineering; Illinois Inst. of Tech.; Univ. of Chicago, Pritzker School of Medicine

2006-01-01

359

Magnetism and Magnetic Properties  

NSDL National Science Digital Library

Students will identify properties of magnetism and begin to develop understanding of their practical applications. Students will also begin to develop understanding of the essential nature of Earth's magnetic fields.

Schneck, Roberta

2011-10-13

360

Magnetic force microscopy investigation of the magnetization reversal of permalloy particles at high temperatures  

NASA Astrophysics Data System (ADS)

The magnetization reversal of an array of permalloy particles formed by scanning probe lithography on the silicon dioxide surface has been investigated in the temperature range from room temperature to 800 K. Using scanning magnetic force microscopy and numerical calculations of the magnetic anisotropy field of a particle at different temperatures, it has been shown that an increase in the temperature leads to a decrease in the external magnetic field required to reverse the magnetization direction of the particle. From the obtained results, it has been concluded that the magnetization reversal of the studied particles is accompanied by the formation of an intermediate state with an inhomogeneous magnetization structure.

Nurgazizov, N. I.; Khanipov, T. F.; Bizyaev, D. A.; Bukharaev, A. A.; Chuklanov, A. P.

2014-09-01

361

Target localization techniques for vehicle-based electromagnetic induction array applications  

NASA Astrophysics Data System (ADS)

State-of-the-art electromagnetic induction (EMI) arrays provide significant capability enhancement to landmine, unexploded ordnance (UXO), and buried explosives detection applications. Arrays that are easily configured for integration with a variety of mobile platforms offer improved safety and efficiency to personnel conducting detection operations including site remediation, explosive ordnance disposal, and humanitarian demining missions. We present results from an evaluation of two vehicle-based frequency domain EMI arrays. Our research includes implementation of a simple circuit model to estimate target location from sensor measurements of the scattered vertical magnetic field component. Specifically, we characterize any conductive or magnetic target using a set of parameters that describe the eddy current and magnetic polarizations induced about a set of orthogonal axes. Parameter estimations are based on the fundamental resonance mode of a series inductance and resistance circuit. This technique can be adapted to a variety of EMI array configurations, and thus offers target localization capabilities to a number of applications.

Miller, Jonathan S.; Schultz, Gregory M.; Shubitidze, Fridon; Marble, Jay A.

2010-04-01

362

IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 11, 2012 663 Monopole Antenna With Inkjet-Printed EBG Array  

E-print Network

. The printed EBG array is placed above a copper sheet, forming an artificial magnetic conductor (AMC) reflector they are considered for wearable applications. Index Terms--Artificial magnetic conductor (AMC), electro- magnetic, TX 75039 USA (e-mail: yjren03@gmail.com). S. Nikolaou is with the Electrical Engineering Department

Tentzeris, Manos

363

The kilopixel array pathfinder project (KAPPa), a 16-pixel integrated heterodyne focal plane array: characterization of the single pixel prototype  

NASA Astrophysics Data System (ADS)

We report on the laboratory testing of KAPPa, a 16-pixel proof-of-concept array to enable the creation THz imaging spectrometer with ~1000 pixels. Creating an array an order of magnitude larger than the existing state of the art of 64 pixels requires a simple and robust design as well as improvements to mixer selection, testing, and assembly. Our testing employs a single pixel test bench where a novel 2D array architecture is tested. The minimum size of the footprint is dictated by the diameter of the drilled feedhorn aperture. In the adjoining detector block, a 6mm × 6mm footprint houses the SIS mixer, LNA, matching and bias networks, and permanent magnet. We present an initial characterization of the single pixel prototype using a computer controlled test bench to determine Y-factors for a parameter space of LO power, LO frequency, IF bandwidth, magnet field strength, and SIS bias voltage. To reduce the need to replace poorly preforming pixels that are already mounted in a large format array, we show techniques to improve SIS mixer selection prior to mounting in the detector block. The 2D integrated 16-pixel array design has been evolved as we investigate the properties of the single pixel prototype. Carful design of the prototype has allowed for rapid translation of single pixel design improvements to be easily incorporated into the 16-pixel model.

Wheeler, Caleb H.; Groppi, Christopher E.; Mani, Hamdi; McGarey, Patrick; Kuenzi, Linda; Weinreb, Sander; Russell, Damon S.; Kooi, Jacob W.; Lichtenberger, Arthur W.; Walker, Christopher K.; Kulesa, Craig

2014-07-01

364

Beamforming with collocated microphone arrays  

NASA Astrophysics Data System (ADS)

A collocated microphone array, including three gradient microphones with different orientations and one omnidirectional microphone, was used to acquire data in a sound-treated room and in an outdoor environment. This arrangement of gradient microphones represents an acoustic vector sensor used in air. Beamforming techniques traditionally associated with much larger uniformly spaced arrays of omnidirectional sensors are extended to this compact array (1 cm3) with encouraging results. A frequency-domain minimum-variance beamformer was developed to work with this array. After a calibration of the array, the recovery of sources from any direction is achieved with high fidelity, even in the presence of multiple interferers. SNR gains of 5-12 dB with up to four speech sources were obtained with both indoor and outdoor recordings. This algorithm has been developed for new MEMS-type microphones that further reduce the size of the sensor array.

Lockwood, Michael E.; Jones, Douglas L.; Su, Quang; Miles, Ronald N.

2003-10-01

365

Active membrane phased array radar  

NASA Technical Reports Server (NTRS)

We have developed the first membrane-based active phased array in L-band (1.26GHz). The array uses membrane compatible Transmit/Receive (T/R) modules (membrane T/R) for each antenna element. We use phase shifters within each T/R module for electronic beam steering. We will discuss the T/R module design and integration with the membrane, We will also present transmit and receive beam-steering results for the array.

Moussessian, Alina; Del Castillo, Linda; Huang, John; Sadowy, Greg; Hoffman, James; Smith, Phil; Hatake, Toshiro; Derksen, Chuck; Lopez, Bernardo; Caro, Ed

2005-01-01

366

Correlated magnetic reversal in periodic stripe patterns  

SciTech Connect

The magnetization reversal in a periodic magnetic stripe array has been studied with a combination of direct and reciprocal space methods: Kerr microscopy and polarized neutron scattering. Kerr images show that during magnetization reversal over a considerable magnetic-field range a ripple domain state occurs in the stripes with magnetization components perpendicular to the stripes. Quantitative analysis of polarized neutron specular reflection, Bragg diffraction, and off-specular diffuse scattering provides a detailed picture of the mean magnetization direction in the ripple domains as well as longitudinal and transverse fluctuations, and reveals a strong correlation of those components over a number of stripes.

Theis-Broehl, Katharina; Toperverg, Boris P.; Leiner, Vincent; Westphalen, Andreas; Zabel, Hartmut; McCord, Jeffrey; Rott, Karsten; Brueckl, Hubert [Department of Physics, Ruhr-University Bochum, 44780 Bochum (Germany); Leibniz Institute for Solid State and Materials Research Dresden, Institute for Metallic Materials, Helmholtzstr. 20, D-01169 Dresden (Germany); Department of Physics, University Bielefeld, Universitaetsstr. 25, 33615 Bielefeld (Germany)

2005-01-01

367

The Earth's Magnetic Field  

NSDL National Science Digital Library

This section of the Windows to the Universe website provides information and images about Earth's magnetic field (the magnetosphere), including detailed information about the aurora borealis, magnets, and solar wind. Windows to the Universe is a user-friendly learning system pertaining to the Earth and Space sciences. The objective of this project is to develop an innovative and engaging website that includes a rich array of documents, including images, movies, animations, and data sets that explore the Earth and Space sciences and the historical and cultural ties between science, exploration and the human experience. Links at the top of each page allow users to navigate between beginner, intermediate and advanced levels.

Johnson, Roberta

2000-07-01

368

Modeling and analysis of a magnetically levitated synchronous permanent magnet planar motor  

NASA Astrophysics Data System (ADS)

In this paper, a new magnetically levitated synchronous permanent magnet planar motor (MLSPMPM) driven by composite-current is proposed, of which the mover is made of a copper coil array and the stator are magnets and magnetic conductor. The coil pitch ?t and permanent magnet pole pitch ?p satisfy the following relationship 3n?t = (3n ± 1)?p. Firstly, an analytical model of the planar motor is established, flux density distribution of the two-dimensional magnet array is obtained by solving the equations of the scalar magnetic potential. Secondly, the expressions of the electromagnetic forces induced by magnetic field and composite current are derived. To verify the analytical model and the electromagnetic forces, finite element method (FEM) is used for calculating the flux density and electromagnetic forces of the MLSPMPM. And the results from FEM are in good agreement with the results from the analytical equations. This indicates that the analytical model is reasonable.

Kou, Baoquan; Zhang, Lu; Li, Liyi; Zhang, Hailin

2012-04-01

369

Peculiarities of Wire Array Implosion  

SciTech Connect

The results of the experiments on Z-pinch produced from wire arrays performed on the facility Angara-5-1 are presented. The models of liner implosion, i.e. prolonged plasma production have found their confirmation. Estimation based on our experimental data show that W wire cores are heterogeneous. The velocity of core expansion is determined by energy deposited at the first nanoseconds after current start. The effect of the inner array on the current distribution in the region between the arrays has been revealed. The ?lost mass ? was measured at initial radius of array at the moment of X-ray pulse maximum.

Aleksandrov, V.V.; Volkov, G.S.; Grabovski, E.V.; Zaitsev, V.I.; Zukakishvili, G.G.; Medovschikov, S.F.; Mitrofanov, K.N.; Nedoseev, S.L.; Oleinik, G.M.; Porofeev, I.Yu.; Samokhin, A.A.; Smirnov, V.P.; Frolov, I.N.; Fedulov, M. V. [SRC RF TRINITI, Troitsk, Moscow Reg., 142190 (Russian Federation); Sasorov, P.V. [Institute of Theoretical and Experimental Physics, Moscow, 142190 (Russian Federation)

2006-01-05

370

Thickness dependence of the levitation performance of double-layer high-temperature superconductor bulks above a magnetic rail  

NASA Astrophysics Data System (ADS)

A double-layer high-temperature superconductor (HTSC) arrangement was proposed and proved to be able to bring improvements to both levitation force and guidance force compared with present single-layer HTSC arrangement. To fully exploit the applied magnetic field by a magnetic rail, the thickness dependence of a double-layer HTSC arrangement on the levitation performance was further investigated in the paper. In this study, the lower-layer bulk was polished step by step to different thicknesses, and the upper-layer bulk with constant thickness was directly superimposed on the lower-layer one. The levitation force and the force relaxation of the double-layer HTSC arrangement were measured above a Halbach magnetic rail. Experimental result shows that a bigger levitation force and a less levitation force decay could be achieved by optimizing the thickness of the lower-layer bulk HTSC. This thickness optimization method could be applied together with former reported double-layer HTSC arrangement method with aligned growth sector boundaries pattern. This series of study on the optimized combination method do bring a significant improvement on the levitation performance of present HTS maglev systems.

Sun, R. X.; Zheng, J.; Liao, X. L.; Che, T.; Gou, Y. F.; He, D. B.; Deng, Z. G.

2014-10-01

371

Chapter 4: Homogeneous Array Processing Page 39 Homogeneous Array Processing  

E-print Network

Chapter 4: Homogeneous Array Processing Page 39 Chapter 4 Homogeneous Array Processing Since most of individual sensors operating under identical conditions. Homogeneous processing converts the outputs from variations. For example, a simple homogeneous process- ing step might involve the averaging of a cluster

Wilson, Denise

372

Scripps Orbit and Permanent Array Center: Permanent GPS Array Sites  

NSDL National Science Digital Library

This portal provides access to an extensive selection of Global Positioning Systems (GPS) arrays worldwide, totaling hundreds of sites. Each array link contains a listing of sites, a dynamic map, and contact information (when available). Data from the stations can be downloaded from an anonymous ftp site, and there are also links for data processing.

373

Finite size effect on spread of resonance frequencies in arrays of coupled vortices  

SciTech Connect

Dynamical properties of magnetic vortices in arrays of magnetostatically coupled ferromagnetic disks are studied by means of a broadband ferromagnetic-resonance (FMR) setup. Magnetic force microscopy and magnetic transmission soft X-ray microscopy are used to image the core polarizations and the chiralities which are both found to be randomly distributed. The resonance frequency of vortex-core motion strongly depends on the magnetostatic coupling between the disks. The parameter describing the relative broadening of the absorption peak observed in the FMR transmission spectra for a given normalized center-to-center distance between the elements is shown to depend on the size of the array.

Vogel, Andreas; Drews, André; Im, Mi-Young; Fischer, Peter; Meier, Guido

2011-01-25

374

Superconducting vortex dynamics on arrays with bicrystal-like structures: matching and rectifier effects  

NASA Astrophysics Data System (ADS)

Hybrid nanostructures of magnetic Ni dots embedded in superconducting Nb films have been fabricated. The dot arrays show bicrystal-like structures with an interface which separates two different dot arrangements in the same array. Vortex lattice dynamics is studied on these particular bi-arrays using magnetotransport measurements. Commensurability and rectifier (ratchet) effects have been observed. Matching between the vortex lattice and the pinning bi-array is only governed by the interplay between the densities of vortices and pinning centers. In bi-arrays with dissimilar pinning densities, for vortex flow parallel to the boundary, the highest pinning center density governs the matching effects. Hybrid samples with only half of the array with asymmetric potentials show a ratchet effect; that is input ac currents yield a net flow of vortices.

Gomez, A.; Gonzalez, E. M.; Vicent, J. L.

2012-12-01

375

Array biosensor: recent developments  

NASA Astrophysics Data System (ADS)

A fluorescence-based immunosensor has been developed for simultaneous analyses of multiple samples for 1 to 6 different antigens. A patterned array of recognition antibodies immobilized on the surface of a planar waveguide is used to 'capture' analyte present in samples. Bound analyte is then quantified by means of fluorescent detector molecules. Upon excitation of the fluorescent label by a small diode laser, a CCD camera detects the pattern of fluorescent antigen:antibody complexes on the sensor surface. Image analysis software correlates the position of fluorescent signals with the identity of the analyte. A new design for a fluidics distribution system is shown, as well as results from assays for physiologically relevant concentrations of staphylococcal enterotoxin B (SEB), F1 antigen from Yersinia pestis, and D- dimer, a marker of sepsis and thrombotic disorders.

Golden, Joel P.; Rowe-Taitt, Chris A.; Feldstein, Mark J.; Ligler, Frances S.

1999-05-01

376

Atacama compact array antennas  

NASA Astrophysics Data System (ADS)

The ACA (Atacama Compact Array) system is an important element of ALMA and consists of four ACA 12-m antennas and twelve ACA 7-m antennas. The ACA system aims to acquire the total power data with four 12-m antennas and the short baseline interferometer data with 7-m antennas. The ACA system also increases reliability of the interferometer maps of astronomical sources larger than the field view of the 12-m antenna. The science performance of these antennas has been extensively verified at OSF (operation support facility) at an elevation of 2900 m in Atacama desert in northern Chile since 2007. The pointing performance has been verified with a dedicated optical pointing telescope, the servo performance is tested with angle encoders, and the surface accuracy has been measured with a radio holography method. Both ACA 12-m antennas and 7-m antennas have been successfully demonstrated to meet the very stringent ALMA specifications.

Saito, M.; Inatani, J.; Nakanishi, K.; Saito, H.; Iguchi, S.

2012-09-01

377

Light harvesting arrays  

DOEpatents

A light harvesting array useful for the manufacture of devices such as solar cells comprises: (a) a first substrate comprising a first electrode; and (b) a layer of light harvesting rods electrically coupled to the first electrode, each of the light harvesting rods comprising a polymer of Formula I: X.sup.1.paren open-st.X.sup.m+1).sub.m (I) wherein m is at least 1, and may be from two, three or four to 20 or more; X.sup.1 is a charge separation group (and preferably a porphyrinic macrocycle, which may be one ligand of a double-decker sandwich compound) having an excited-state of energy equal to or lower than that of X.sup.2, and X.sup.2 through X.sup.m+1 are chromophores (and again are preferably porphyrinic macrocycles).

Lindsey, Jonathan S. (Raleigh, NC)

2002-01-01

378

TRMM Solar Array  

NASA Technical Reports Server (NTRS)

Basic requirement of 978.59 watts per Panel output @ 58.9 volts B.O.L. was met on an average basis per agreement with NASA. Lower grade Cells were used on the shadowed Panel (Boom shadow) to maximize available power to the Spacecraft. The average output @ 58.9 volts was 991 watts. The outputs of the four t4) Panels ranged from 960 to 1,022 watts. The Panels successfully passed environmental testing at TRW to the contract specification and subsequent testing at NASA which involved output measurements at elevated temperatures. As this type of Array had never previously been built by TRW (aluminum Substrate with 4 cm x 4.4 cm GaAs Cells), the TRMM Program was a development effort combined with a Qual and Flight production effort. The most significant technical problem was Cell cracking during Qual thermal cycling. The cracking problem was determined to be generic within our Solar Array factory in the application of GaAs Cells to our designs. As a result, a TRW funded manufacturing process verification panel (known as the Manufacturing Verification Panel) was built to demonstrate our ability to properly apply GaAs Cells. The original Qual Panel comprised three (3) design variations with respect to Coverglass-to-Cell and Cell-to-Substrate adhesives. The intent was to qualify multiple designs in case one or more failed. When two of the three combinations failed due to excessive Cell breakage during thermal cycling, NASA was reluctant to allow Flight production based on the one remaining good Qual Panel Quadrant. This issue was pivotal for continuing the contract. Facts and recommendations are as follows: (1) The cause of the excessive cracking was never determined. and (2) The areas where the excessive cracking occurred utilized DC93-500 glassing adhesive which was NASA approved, and had been widely used by TRW on a multitude of projects.

1996-01-01

379

Networked Sensor Arrays  

SciTech Connect

A set of independent radiation sensors, coupled with real-time data telemetry, offers the opportunity to run correlation algorithms for the sensor array as well as to incorporate non-radiological data into the system. This may enhance the overall sensitivity of the sensors and provide an opportunity to project the location of a source within the array. In collaboration with Lawrence Livermore National Laboratory (LLNL) and Sandia National Laboratories (SNL), we have conducted field experiments to test a prototype system. Combining the outputs of a set of distributed sensors permits the correlation that the independent sensor outputs. Combined with additional information such as traffic patterns and velocities, this can reduce random/false detections and enhance detection capability. The principle components of such a system include: (1) A set of radiation sensors. These may be of varying type and complexity, including gamma and/or neutron detectors, gross count and spectral-capable sensors, and low to high energy-resolution sensors. (2) A set of non-radiation sensors. These may include sensors such as vehicle presence and imaging sensors. (3) A communications architecture for near real-time telemetry. Depending upon existing infrastructure and bandwidth requirements, this may be a radio or hard-wire based system. (4) A central command console to pole the sensors, correlate their output, and display the data in a meaningful form to the system operator. Both sensitivity and selectivity are important considerations when evaluating the performance of a detection system. Depending on the application, the optimization of sensitivity as well as the rejection of ''nuisance'' radioactive sources may or may not be critical.

R. J. Tighe

2002-10-01

380

ULTIMA: Array of ground-based magnetometer arrays for monitoring magnetospheric and ionospheric perturbations on a global scale  

NASA Astrophysics Data System (ADS)

ULTIMA (Ultra Large Terrestrial International Magnetic Array) is an international consortium that aims at promoting collaborative research on the magnetosphere, ionosphere, and upper atmosphere through the use of ground-based magnetic field observatories. ULTIMA is joined by individual magnetometer arrays in different countries/regions, and the current regular-member arrays are Australian, AUTUMN, CARISMA, DTU Space, Falcon, IGPP-LANL, IMAGE, MACCS, MAGDAS, McMAC, MEASURE, THEMIS, and SAMBA. The Chair of ULTIMA has been K. Yumoto (MAGDAS), and its Secretary has been P. Chi (McMAC, Falcon). In this paper we perform case studies in which we estimate the global patterns of (1) near-Earth currents and (2) magnetic pulsations; these phenomena are observed over wide areas on the ground, thus suitable for the aims of ULTIMA. We analyze these two phenomena during (a) quiet period and (b) magnetic storm period. We compare the differences between these two periods by drawing the global maps of the ionospheric equivalent currents (which include the effects of all the near-Earth currents) and pulsation amplitudes. For ionospheric Sq currents at low latitudes during quiet periods, MAGDAS data covering an entire solar cycle has yielded a detailed statistical model, and we can use it as a reference for the aforementioned comparison. We also estimate the azimuthal wave numbers of pulsations and compare the amplitude distribution of pulsations with the distribution of highly energetic (in MeV range) particles simultaneously observed at geosynchronous satellites.

Yumoto, K.; Chi, P. J.; Angelopoulos, V.; Connors, M. G.; Engebretson, M. J.; Fraser, B. J.; Mann, I. R.; Milling, D. K.; Moldwin, M. B.; Russell, C. T.; Stolle, C.; Tanskanen, E.; Vallante, M.; Yizengaw, E.; Zesta, E.

2012-12-01

381

Students' Structuring of Rectangular Arrays  

ERIC Educational Resources Information Center

This paper presents the results of a study of the structural development of young students' drawings of arrays, and in particular, the significance of using lines instead of drawing individual squares. Students' array drawings were classified on basis of numerical properties, and perceived structural similarities that reflected the spatial…

Outhred, Lynne; Mitchelmore, Michael

2004-01-01

382

High Voltage Space Solar Arrays  

NASA Technical Reports Server (NTRS)

Recent tests performed at the NASA Glenn Research Center and elsewhere have shown promise in the design and construction of high voltage (300-1000 V) solar arrays for space applications. Preliminary results and implications for solar array design will be discussed, with application to direct-drive electric propulsion and space solar power.

Ferguson, D. C.; Hillard, G. B.; Vayner, B. V.; Galofaro, J. T.; Lyons, Valerie (Technical Monitor)

2002-01-01

383

A Language for Manipulating Arrays  

Microsoft Academic Search

This paper describes the Array Manipulation Language (AML), an algebra for multidimen- sional array data. AML is generic, in the sense that it can be customized to support a wide variety of domain-specific operations on ar- rays. AML expressions can be treated declara- tively and subjected to rewrite optimizations. To illustrate this, several rewrite rules that exploit the structural properties

Arunprasad P. Marathe; Kenneth Salem

1997-01-01

384

Hubble Space Telescope Solar Array  

NASA Technical Reports Server (NTRS)

This is a view of a solar cell blanket deployed on a water table during the Solar Array deployment test. The Hubble Space Telescope (HST) Solar Arrays provide power to the spacecraft. The arrays are mounted on opposite sides of the HST, on the forward shell of the Support Systems Module. Each array stands on a 4-foot mast that supports a retractable wing of solar panels 40-feet (12.1-meters) long and 8.2-feet (2.5-meters) wide, in full extension. The arrays rotate so that the solar cells face the Sun as much as possible to harness the Sun's energy. The Space Telescope Operations Control Center at the Goddard Space Center operates the array, extending the panels and maneuvering the spacecraft to focus maximum sunlight on the arrays. The purpose of the HST, the most complex and sensitive optical telescope ever made, is to study the cosmos from a low-Earth orbit. By placing the telescope in space, astronomers are able to collect data that is free of the Earth's atmosphere. The HST Solar Array was designed by the European Space Agency and built by British Aerospace. The Marshall Space Flight Center had overall responsibility for design, development, and construction of the HST.

1985-01-01

385

Microjet fabrication of microlens arrays  

Microsoft Academic Search

Microjet, or inkjet, technology is used to fabricate lenslet arrays with packing densities greater than 15000\\/cm2. Typical lens diameters range between 70 and 150 ?m, and focal lengths are between 50 and 150 ?m. Individual lenslets are characterized in the Fraunhofer plane. The full array is characterized in its far field

D. L. MacFarlane; V. Narayan; J. A. Tatum; W. R. Cox; T. Chen; D. J. Hayes

1994-01-01

386

Massively Parallel MRI Detector Arrays  

PubMed Central

Originally proposed as a method to increase sensitivity by extending the locally high-sensitivity of small surface coil elements to larger areas, the term parallel imaging now includes the use of array coils to perform image encoding. This methodology has impacted clinical imaging to the point where many examinations are performed with an array comprising multiple smaller surface coil elements as the detector of the MR signal. This article reviews the theoretical and experimental basis for the trend towards higher channel counts relying on insights gained from modeling and experimental studies as well as the theoretical analysis of the so-called “ultimate” SNR and g-factor. We also review the methods for optimally combining array data and changes in RF methodology needed to construct massively parallel MRI detector arrays and show some examples of state-of-the-art for highly accelerated imaging with the resulting highly parallel arrays. PMID:23453758

Keil, Boris; Wald, Lawrence L

2013-01-01

387

ALMA array element astronomical verification  

NASA Astrophysics Data System (ADS)

The Atacama Large Millimeter/submillimeter Array (ALMA) will consist of at least 54 twelve-meter antennas and 12 seven-meter antennas operating as an aperture synthesis array in the (sub)millimeter wavelength range. The ALMA System Integration Science Team (SIST) is a group of scientists and data analysts whose primary task is to verify and characterize the astronomical performance of array elements as single dish and interferometric systems. The full set of tasks is required for the initial construction phase verification of every array element, and these can be divided roughly into fundamental antenna performance tests (verification of antenna surface accuracy, basic tracking, switching, and on-the-fly rastering) and astronomical radio verification tasks (radio pointing, focus, basic interferometry, and end-to-end spectroscopic verification). These activities occur both at the Operations Support Facility (just below 3000 m elevation) and at the Array Operations Site at 5000 m.

Asayama, S.; Knee, L. B. G.; Calisse, P. G.; Cortés, P. C.; Jager, R.; López, B.; López, C.; Nakos, T.; Phillips, N.; Radiszcz, M.; Simon, R.; Toledo, I.; Whyborn, N.; Yatagai, H.; McMullin, J. P.; Planesas, P.

2012-09-01

388

Chunking of Large Multidimensional Arrays  

SciTech Connect

Data intensive scientific computations as well on-lineanalytical processing applications as are done on very large datasetsthat are modeled as k-dimensional arrays. The storage organization ofsuch arrays on disks is done by partitioning the large global array intofixed size hyper-rectangular sub-arrays called chunks or tiles that formthe units of data transfer between disk and memory. Typical queriesinvolve the retrieval of sub-arrays in a manner that accesses all chunksthat overlap the query results. An important metric of the storageefficiency is the expected number of chunks retrieved over all suchqueries. The question that immediately arises is "what shapes of arraychunks give the minimum expected number of chunks over a query workload?"In this paper we develop two probabilistic mathematical models of theproblem and provide exact solutions using steepest descent and geometricprogramming methods. Experimental results, using synthetic workloads onreal life data sets, show that our chunking is much more efficient thanthe existing approximate solutions.

Rotem, Doron; Otoo, Ekow J.; Seshadri, Sridhar

2007-02-28

389

PEP solar array definition study  

NASA Technical Reports Server (NTRS)

The conceptual design of a large, flexible, lightweight solar array is presented focusing on a solar array overview assessment, solar array blanket definition, structural-mechanical systems definition, and launch/reentry blanket protection features. The overview assessment includes a requirements and constraints review, the thermal environment assessment on the design selection, an evaluation of blanket integration sequence, a conceptual blanket/harness design, and a hot spot analysis considering the effects of shadowing and cell failures on overall array reliability. The solar array blanket definition includes the substrate design, hinge designs and blanket/harness flexibility assessment. The structural/mechanical systems definition includes an overall loads and deflection assessment, a frequency analysis of the deployed assembly, a components weights estimate, design of the blanket housing and tensioning mechanism. The launch/reentry blanket protection task includes assessment of solar cell/cover glass cushioning concepts during ascent and reentry flight condition.

1979-01-01

390

A Stratospheric Balloon Array for Radiation Belt Studies  

NASA Astrophysics Data System (ADS)

The Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) is an Antarctic balloon investigation designed to study electron losses from Earth's radiation belts. Two BARREL balloon campaigns were carried out from Antarctic Research Stations SANAE IV and Halley VI in January-February 2013 and 2014. During each campaign, a total of 20 small (~20 kg) balloon payloads were hand-launched on 300,000 cubic foot balloons to an altitude of 38 km to maintain an array of 5-8 payloads distributed in magnetic latitude and local time. Each balloon carried a NaI scintillator to measure the bremsstrahlung X-rays produced by precipitating relativistic electrons as they collide with neutrals in Earth’s atmosphere, and a DC magnetometer. We present a summary of BARREL build-up and operations. BARREL successfully demonstrated the feasibility of maintaining a stratospheric balloon array as an observing platform.

Millan, Robyn

391

Ordered arrays of multiferroic epitaxial nanostructures  

PubMed Central

Epitaxial heterostructures combining ferroelectric (FE) and ferromagnetic (FiM) oxides are a possible route to explore coupling mechanisms between the two independent order parameters, polarization and magnetization of the component phases. We report on the fabrication and properties of arrays of hybrid epitaxial nanostructures of FiM NiFe2O4 (NFO) and FE PbZr0.52Ti0.48O3 or PbZr0.2Ti0.8O3, with large range order and lateral dimensions from 200 nm to 1 micron. Methods The structures were fabricated by pulsed-laser deposition. High resolution transmission electron microscopy and high angle annular dark-field scanning transmission electron microscopy were employed to investigate the microstructure and the epitaxial growth of the structures. Room temperature ferroelectric and ferrimagnetic domains of the heterostructures were imaged by piezoresponse force microscopy (PFM) and magnetic force microscopy (MFM), respectively. Results PFM and MFM investigations proved that the hybrid epitaxial nanostructures show ferroelectric and magnetic order at room temperature. Dielectric effects occurring after repeated switching of the polarization in large planar capacitors, comprising ferrimagnetic NiFe2O4 dots embedded in ferroelectric PbZr0.52Ti0.48O3 matrix, were studied. Conclusion These hybrid multiferroic structures with clean and well defined epitaxial interfaces hold promise for reliable investigations of magnetoelectric coupling between the ferrimagnetic / magnetostrictive and ferroelectric / piezoelectric phases. PMID:22132299

Vrejoiu, Ionela; Morelli, Alessio; Biggemann, Daniel; Pippel, Eckhard

2011-01-01

392

Study of the precursor and non-precursor implosion regimes in wire array Z-pinches  

NASA Astrophysics Data System (ADS)

Star-like and closely spaced nested wire array configurations were investigated in precursor and non-precursor implosions. Closely spaced nested cylindrical arrays have inner and outer arrays with equal wire numbers, and inner and outer wires aligned to each other. The gap between the outer and inner wires is not more than 1 mm. Calculation of magnetic fields shows that the small gap results in a reversed, outward j × B force on the inner wires. Closely spaced arrays of 6-16 wires with outer diameter of 16 mm and with gaps of ?R = 0.25-1 mm were tested. 6-8-wire arrays with a gap of ?R = 0.4-1 mm imploded without precursor, but precursor was present in loads with 12-16 wires and ?R = 0.25-1 mm. Implosion dynamics of closely spaced arrays was similar to that of star-like arrays. Implosion time was found to decrease with decreased wire numbers. Star array configurations were designed with a numerical scheme to implode with or without precursor. The lack of precursor resulted in a marginal improvement in total x-ray yield and power, and up to 20% increase in Al K-shell yield. The Al K-shell radiated energy was found to increase with decreasing the number of arrays in closely spaced and star-like wire arrays.

Papp, D.; Ivanov, V. V.; Jones, B.; Haboub, A.; Anderson, A. A.; Altemara, S. D.; Talbot, B. R.

2012-09-01

393

Study of the precursor and non-precursor implosion regimes in wire array Z-pinches  

SciTech Connect

Star-like and closely spaced nested wire array configurations were investigated in precursor and non-precursor implosions. Closely spaced nested cylindrical arrays have inner and outer arrays with equal wire numbers, and inner and outer wires aligned to each other. The gap between the outer and inner wires is not more than 1 mm. Calculation of magnetic fields shows that the small gap results in a reversed, outward j Multiplication-Sign B force on the inner wires. Closely spaced arrays of 6-16 wires with outer diameter of 16 mm and with gaps of {Delta}R = 0.25-1 mm were tested. 6-8-wire arrays with a gap of {Delta}R = 0.4-1 mm imploded without precursor, but precursor was present in loads with 12-16 wires and {Delta}R = 0.25-1 mm. Implosion dynamics of closely spaced arrays was similar to that of star-like arrays. Implosion time was found to decrease with decreased wire numbers. Star array configurations were designed with a numerical scheme to implode with or without precursor. The lack of precursor resulted in a marginal improvement in total x-ray yield and power, and up to 20% increase in Al K-shell yield. The Al K-shell radiated energy was found to increase with decreasing the number of arrays in closely spaced and star-like wire arrays.

Papp, D.; Ivanov, V. V.; Anderson, A. A.; Altemara, S. D.; Talbot, B. R. [University of Nevada, Reno, Reno, Nevada 89507 (United States); Jones, B. [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185 (United States); Haboub, A. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2012-09-15

394

Array gain for a cylindrical array with baffle scatter effects.  

PubMed

Cylindrical arrays used in sonar for passive underwater surveillance often have sensors surrounding a cylindrical metal baffle. In some operational sonars, the phones in each stave (i.e., each line of phones aligned with the cylinder axis) are hardwired together so that the array is equivalent to a baffled circular array of directional elements, where each element corresponds to a line array of omnidirectional phones steered to broadside. In this paper a model is introduced for computing the array gain of such an array at high frequencies, which incorporates baffle scatter using infinite, rigid cylinder scattering theory, and with ambient noise described by an angular spectral density function. In practice the phones are often offset from the baffle surface, and the acoustic field sampled by the staves is distorted at high frequencies due to interference between the incident and scattered fields. Examples are given to illustrate the resulting array gain degradation, using three noise distributions that are frequently used in sonar performance modeling: three-dimensional isotropic, two-dimensional isotropic, and surface dipole noise. PMID:18189560

Bertilone, Derek C; Killeen, Damien S; Bao, Chaoying

2007-11-01

395

Planning a Global Array of Broadband Seismic Arrays  

NASA Astrophysics Data System (ADS)

A diverse group of more than 70 seismologists met for 2 days in Raleigh, N.C., to report on recent innovations in seismic array methods and to discuss the future of seismic arrays in global seismology. The workshop was sponsored by the Incorporated Research Institutions for Seismology (IRIS), with U.S. National Science Foundation funding. Participants included representatives of existing array research groups in Australia, Canada, Germany, Japan, Norway, and the United States, with individuals from academia, government, and industry. The workshop was organized by the authors of this meeting report, Pablo Ampeuro (California Institute of Technology), and Colleen Dalton (Boston University), along with IRIS staff support.

Koper, Keith D.; Ammon, Charles J.

2013-08-01

396

Micromagnetism of permalloy antidot arrays prepared from alumina templates.  

PubMed

Magnetic hysteresis processes of hexagonal arrays of permalloy antidots have been studied by means of micromagnetic simulations as a function of geometrical parameters. The ideal system shows a maximum of the coercive field as a function of the antidot diameter. The simulated magnetic behavior has been compared with experimental values for antidot arrays of permalloy prepared from alumina templates with thicknesses between 2 and 60 nm, showing a monotonic increase of the coercive field as a function of the antidot diameter. We show that the introduction into simulations of the combination of variable antidot diameters from bottom to top due to the fabrication process and, more importantly, large geometrical domains, which break the sample symmetry, solves the discrepancy between the simulations and the experiment. PMID:25380329

Gawronski, P; Merazzo, K J; Chubykalo-Fesenko, O; Del Real, R P; Vázquez, M

2014-11-28

397

Plasma dynamics in an inverse wire array z-pinch  

NASA Astrophysics Data System (ADS)

We describe experiments on the MAGPIE facility (1MA, 250ns) with inverse wire array z-pinches, in which the wires act as a return current cage placed around a central current conductor. In this configuration the plasma ablated from the wires is pushed by the JxB force in the radially outward direction and expands into the region free of the magnetic field. The parameters of the coronal plasma were measured using laser interferometry, X-ray and XUV imaging. The experimental set-up also allows addition of axial and radial magnetic fields, and we study the effects of these fields on the plasma dynamics and the ablation rate. The complete ablation of the wires triggers radial ``explosion'' of the plasma which proceeds through formation of gaps in the wire cores, similar to the dynamics of standard wire arrays. The opening of the current path in the final stages could potentially be used as a plasma opening switch.

Lebedev, Sergey; Bland, S. N.; Bott, S. C.; Chittenden, J. P.; Hall, G. N.; Suzuki, F. A.; Ciardi, A.; Palmer, J. B. A.

2006-10-01

398

Apparatus and method for reducing inductive coupling between levitation and drive coils within a magnetic propulsion system  

Microsoft Academic Search

An apparatus and method is disclosed for reducing inductive coupling between levitation and drive coils within a magnetic levitation system. A pole array has a magnetic field. A levitation coil is positioned so that in response to motion of the magnetic field of the pole array a current is induced in the levitation coil. A first drive coil having a

Post; Richard F

2001-01-01

399

Pinning, ordering, and dynamics of vortices in conformal crystal and gradient pinning arrays  

NASA Astrophysics Data System (ADS)

We numerically investigate magnetization, pinning, ordering, and dynamics of vortices interacting with pinning arrangements which have a density gradient. We focus on conformal crystal structures obtained by conformally transforming a spatially uniform periodic array, as well as nonconformal gradient structures and structures with quasiperiodic order. The conformal structures feature a density gradient and local ordering. Using magnetization simulations we find that conformal pinning arrays exhibit enhanced pinning compared to nonconformal gradient arrays as well as compared to random, periodic, and quasiperiodic arrays, for a broad range of fields. The effectiveness of conformal arrays arises from the continuum of length scales introduced into the arrays by the conformal transformation, allowing for a broad range of local commensuration effects. At higher vortex fillings above the range of conformal effectiveness, we show that a nonconformal rectangular gradient array exhibits strong pinning due to a novel commensuration effect and vortex ordering. Using transport simulations where vortices are driven along the gradient and at an angle to the gradient, we confirm the effectiveness of conformal pinning at increasing the critical current. For a rotated drive, the gradient arrays produce a strong vortex guidance effect in the direction perpendicular to the gradient.

Ray, D.; Reichhardt, C.; Reichhardt, C. J. Olson

2014-09-01

400

Sequential vortex hopping in an array of artificial pinning centers  

SciTech Connect

We use low-temperature magnetic force microscopy (MFM) to study the hopping motion of vortices in an array of artificial pinning centers (APCs). The array consists of nanoscale holes etched in a niobium thin film by Ar-ion sputtering through an anodic aluminum-oxide template. Variable-temperature magnetometry shows a transition temperature of 7.1 K and an enhancement of the magnetization up to the third matching field at 5 K. Using MFM with attractive and repulsive tip-vortex interaction, we measure the vortex-pinning strength and investigate the motion of individual vortices in the APC array. The depinning force for individual vortices at low field ranged from 0.7 to 1.2 pN. The motion of individual vortices was found to be reproducible and consistent with movement between adjacent holes in the film. The movements are repeatable but the sequence of hops depends on the scan direction. This asymmetry in the motion indicates nonuniform local pinning, a consequence of array disorder and hole-size variation.

Keay, J. C.

2010-02-24

401

A novel electron gun with an independently addressable cathode array.  

SciTech Connect

The design of a novel electron gun with an array of independently addressable cathode elements is presented. Issues relating to operation in a 6.5 Tesla axial magnetic field are discussed. Simulations with the TriComp [1] electromagnetic field code that were used to determine the space charge limited tube characteristic and to model focusing of the electron beam in the magnetic field are reviewed. Foil heating and stress calculations are discussed. The results of CYLTRAN [2] simulations yielding the energy spectrum of the electron beam and the current transmitted through the foil window are presented.

Rudys, Joseph Matthew; Reed, Kim Warren; Peña, Gary Edward; Schneider, Larry X.

2006-08-01

402

Large array VLSI filter  

NASA Technical Reports Server (NTRS)

A 35 by 35 element pipelined convolutional kernel is being fabricated using VLSI chips, each containing a 5 by 1 segment of the kernel. Three levels of printed circuitry are used: the first level is used for the VLSI chips, the second level connects seven chips together on one platform, and the third level connects seven platforms with associated delay lines, all fitting on one board. Therefore, on each board there are seven rows of the kernel containing 245 multipliers and adders, and five such boards complete the kernel array. Each multiplier accepts an 8 bit picture element which is multiplied by a 16 bit weight. A truncated 22 bit product is added to a previously stored product sum and the results are shifted to the following multiplier as the next picture element is read in. The multiplier uses a modified Booth algorithm to reduce the number of shift add operations nearly in half. The filter box is presently configured as an ancillary box to a VAX 11/780, but can be connected to essentially any CPU. The I/O bandwidth is easily compatible with most CPU devices.

Nathan, R.

1983-01-01

403

Offering an Array of Improvements  

NASA Technical Reports Server (NTRS)

Sensors Unlimited, Inc., with SBIR funding from NASA's Langley Research Center, Goddard Space Flight Center, Marshall Space Flight Center, and the Jet Propulsion Laboratory, developed a monolithic focal plane array for near-infrared imaging. The company developed one- (1- D) and two-dimensional (2-D) imaging arrays consisting of a highly reliable InGaAs p-I-n diode as a photodetector for monitoring a variety of applications, including single element device applications in receivers. The InGaAs 1-D and 2-D arrays have many applications. For example, they monitor the performance of dense wavelength division multiplexing (DWDM) systems- the process of packaging many channels into a single fiber-optic cable. Sensors Unlimited commercially offers its LXTM and LYTM Series InGaAs linear arrays for reliable DWDM performance monitoring. The LX and LY arrays enable instrument module designs with no moving parts, which provides for superior uniformity, and fast, linear outputs that remain stable over a wide temperature range. Innovative technologies derived from the monolithic focal plane array have enabled telecommunication companies to optimize existing bandwidth in their fiber-optic networks in order to support a high volume of network traffic. At the same time, the technologies obtained from the array have the potential for reducing costs, while increasing performance from Sensors Unlimited's current product lines.

2001-01-01

404

Three-dimensional Dammann array.  

PubMed

We demonstrate a scheme that can produce a three-dimensional (3D) focus spot array in a 3D lattice structure, called a 3D Dammann array, in focal region of an objective. This 3D Dammann array is generated by using two separate micro-optical elements, a Dammann zone plate (DZP) that produces a series of coaxial focus spots and a conventional two-dimensional (2D) Dammann grating (DG). A simple, fast, and clear method is presented to design this binary pure-phase (0,?) DZP in vectorial Debye theory regime. Based on this kind of DZP, one can always obtain a 3D Dammann array both for low and high numerical aperture (NA) focusing objectives. For experimental demonstration, an arrangement combining a DZP, a 2D DG, and a pair of opposing lenses is proposed to generate a 5×5×5 Dammann array in focal region of an objective with NA=0.127 and another 6×6×7 Dammann array for an objective of NA=0.66. It is shown that this arrangement makes it possible to achieve 3D Dammann arrays with micrometer-sized focus spots and focus spacings of tens of micrometers for various practical applications, such as 3D parallel micro- and nanomachining, 3D simultaneous optical manipulation, 3D optical data storage, and multifocal fluorescence microscope, etc. PMID:22505083

Yu, Junjie; Zhou, Changhe; Jia, Wei; Cao, Wugang; Wang, Shaoqing; Ma, Jianyong; Cao, Hongchao

2012-04-01

405

Storage of photovoltaic arrays on a ship  

SciTech Connect

A system is described for installing and storing photovoltaic arrays on a ship, comprising: solar photovoltaic cell arrays laying substantially horizontal, means for framing said photovoltaic arrays, means for rolling and unrolling said arrays connected to said arrays by ropes located along at least one side of said arrays, rigging means connected to said means for rolling and unrolling, guide means for said rigging means and for said rolling and unrolling means to facilitate installing and storing operations.

Newman, E.

1993-08-17

406

Permanent magnet edge-field quadrupole  

DOEpatents

Planar permanent magnet edge-field quadrupoles for use in particle accelerating machines and in insertion devices designed to generate spontaneous or coherent radiation from moving charged particles are disclosed. The invention comprises four magnetized rectangular pieces of permanent magnet material with substantially similar dimensions arranged into two planar arrays situated to generate a field with a substantially dominant quadrupole component in regions close to the device axis. 10 figs.

Tatchyn, R.O.

1997-01-21

407

Permanent magnet edge-field quadrupole  

DOEpatents

Planar permanent magnet edge-field quadrupoles for use in particle accelerating machines and in insertion devices designed to generate spontaneous or coherent radiation from moving charged particles are disclosed. The invention comprises four magnetized rectangular pieces of permanent magnet material with substantially similar dimensions arranged into two planar arrays situated to generate a field with a substantially dominant quadrupole component in regions close to the device axis.

Tatchyn, Roman O. (Mountain View, CA)

1997-01-01

408

ESPRIT And Uniform Linear Arrays  

NASA Astrophysics Data System (ADS)

Abstract ¬â€?ESPRIT is a recently developed and patented technique for high-resolution estimation of signal parameters. It exploits an invariance structure designed into the sensor array to achieve a reduction in computational requirements of many orders of magnitude over previous techniques such as MUSIC, Burg's MEM, and Capon's ML, and in addition achieves performance improvement as measured by parameter estimate error variance. It is also manifestly more robust with respect to sensor errors (e.g. gain, phase, and location errors) than other methods as well. Whereas ESPRIT only requires that the sensor array possess a single invariance best visualized by considering two identical but other-wise arbitrary arrays of sensors displaced (but not rotated) with respect to each other, many arrays currently in use in various applications are uniform linear arrays of identical sensor elements. Phased array radars are commonplace in high-resolution direction finding systems, and uniform tapped delay lines (i.e., constant rate A/D converters) are the rule rather than the exception in digital signal processing systems. Such arrays possess many invariances, and are amenable to other types of analysis, which is one of the main reasons such structures are so prevalent. Recent developments in high-resolution algorithms of the signal/noise subspace genre including total least squares (TLS) ESPRIT applied to uniform linear arrays are summarized. ESPRIT is also shown to be a generalization of the root-MUSIC algorithm (applicable only to the case of uniform linear arrays of omni-directional sensors and unimodular cisoids). Comparisons with various estimator bounds, including CramerRao bounds, are presented.

Roy, R. H.; Goldburg, M.; Ottersten, B. E.; Swindlehurst, A. L.; Viberg, M.; Kailath, T.

1989-11-01

409

CLAES focal plane array. [Cryogenic Limb Array Etalon Spectrometer  

NASA Technical Reports Server (NTRS)

The Cryogenic Limb Array Etalon Spectrometer for the NASA Upper Atmospheric Research Satellite uses solid-state focal plane arrays to detect emission from the earth's atmosphere over the IR wavelength range 3.5 to 13 microns. This paper discusses the design of the focal plane detector assembly and compares calculated performance with measurements. Measurements were made of focal plane noise and responsivity as functions of frequency (2 to 500 Hz) and temperature (12 to 19 K), pixel-to-pixel and across-array crosstalk, and linearity over a dynamic range of 100,000. The measurements demonstrate that the arrays satisfy the science requirements, and that, in general, there is reasonable agreement between the measurements and the analytical model.

Roche, A. E.; Sterritt, L. W.; Kumer, J. B.; Callary, P. C.; Nielsen, R. L.

1989-01-01

410

Terahertz superconducting plasmonic hole array  

E-print Network

We demonstrate thermally tunable superconductor hole array with active control over their resonant transmission induced by surface plasmon polaritons . The array was lithographically fabricated on high temperature YBCO superconductor and characterized by terahertz-time domain spectroscopy. We observe a clear transition from the virtual excitation of the surface plasmon mode to the real surface plasmon mode. The highly tunable superconducting plasmonic hole arrays may have promising applications in the design of low-loss, large dynamic range amplitude modulation, and surface plasmon based terahertz devices.

Tian, Zhen; Han, Jiaguang; Gu, Jianqiang; Xing, Qirong; Zhang, Weili

2010-01-01

411

Spontaneous vortex nanodomain arrays at ferroelectric heterointerfaces.  

PubMed

The polarization of the ferroelectric BiFeO(3) sub-jected to different electrical boundary conditions by heterointerfaces is imaged with atomic resolution using a spherical aberration-corrected transmission electron microscope. Unusual triangular-shaped nanodomains are seen, and their role in providing polarization closure is understood through phase-field simulations. Heterointerfaces are key to the performance of ferroelectric devices, and this first observation of spontaneous vortex nanodomain arrays at ferroelectric heterointerfaces reveals properties unlike the surrounding film including mixed Ising-Ne?el domain walls, which will affect switching behavior, and a drastic increase of in-plane polarization. The importance of magnetization closure has long been appreciated in multidomain ferromagnetic systems; imaging this analogous effect with atomic resolution at ferroelectric heterointerfaces provides the ability to see device-relevant interface issues. Extension of this technique to visualize domain dynamics is envisioned. PMID:21247184

Nelson, Christopher T; Winchester, Benjamin; Zhang, Yi; Kim, Sung-Joo; Melville, Alexander; Adamo, Carolina; Folkman, Chad M; Baek, Seung-Hyub; Eom, Chang-Beom; Schlom, Darrell G; Chen, Long-Qing; Pan, Xiaoqing

2011-02-01

412

Kink and displacement instabilities in imploding wire arrays  

SciTech Connect

Cylindrical arrays of parallel wires can be imploded by the magnetic forces generated by currents through the wires to form hot, dense Z-pinch plasmas. Analytic growth rates of displacements and deformations of wires in imploding wire arrays are calculated. Arrays of six or more wires are reasonably stable against asymmetric displacements. The growth rate of the kink instability on a single wire of linear mass density m, radius a, and carrying current I peaks at l/sub max/ = 0.7I/m/sup 1/2/ca at a kink wavelength of about 4a. The most unstable kink modes of n-wire arrays are the symmetric (l = 0) radial modes and antisymmetric (l = n/2) tangential modes. The effect of a center wire is to tend to destabilize radial kink modes and stabilize tangential modes. In the experimental parameter range of the largest current generators, the number of kink growth times before collision is insensitive to values of maximum current and current pulse width. In general, the kink instability will grow nonlinearly if the initial array radius is more than a few plasma wire radii. In the limit of long wavelengths, the kink instability is shown to be equivalent to the displacement instability.

Felber, F.S.; Rostoker, N.

1981-06-01

413

DC and RF Measurements of Serial Bi-SQUID Arrays  

E-print Network

SQUID arrays are promising candidates for low profile antennas and low noise amplifier applications. We present the integrated circuit designs and results of DC and RF measurements of the wideband serial arrays based on integration of linear bi-SQUID cells forming a Superconducting Quantum Interference Filter (bi-SQUID SQIF). Various configurations of serial arrays designs are described. The measured linearity, power gain, and noise temperature are analyzed and compared. The experimental results are matched to results of mathematical modeling. A serial bi-SQUID SQIF arrays are mounted into a coplanar waveguide (CPW) and symmetrically grounded to corresponding sides of CPW. The RF output comes out from the central common line, which is also used for DC biasing and forms a symmetrical balanced output. The signal and DC flux biasing line is designed as coplanar lines passed in parallel over each bi-SQUID cell in a bidirectional fashion concentrating magnetic flux inside of each cell. Serial bi-SQUID SQIF arrays ...

Prokopenko, G V; de Escobar, A Leese; Taylor, B; de Andrade, M C; Berggren, S; Longhini, P; Palacios, A; Nisenoff, M; Fagaly, R L

2012-01-01

414

Areal array jetting device for ball grid arrays  

SciTech Connect

Package designs for microelectronics devices have moved from through-hole to surface mount technology in order to increase the printed wiring board real estate available by utilizing both sides of the board. The traditional geometry for surface mount devices is peripheral arrays where the leads are on the edges of the device. As the technology drives towards high input/output (I/O) count (increasing number of leads) and smaller packages with finer pitch (less distance between peripheral leads), limitations on peripheral surface mount devices arise. A solution to the peripheral surface mount issue is to shift the leads to the area under the device. This scheme is called areal array packaging and is exemplified by the ball grid array (BGA) package. In a BGA package, the leads are on the bottom surface of the package in the form of an array of solder balls. The current practice of joining BGA packages to printed wiring boards involves a hierarchy of solder alloy compositions. A high melting temperature ball is typically used for standoff. A promising alternative to current methods is the use of jetting technology to perform monolithic solder ball attachment. This paper describes an areal array jetter that was designed and built to simultaneously jet arrays of solder balls directly onto BGA substrates.

Frear, D.R.; Yost, F.G.; Schmale, D.T.; Essien, M.

1997-08-01

415

Silicon Heat Pipe Array  

NASA Technical Reports Server (NTRS)

Improved methods of heat dissipation are required for modern, high-power density electronic systems. As increased functionality is progressively compacted into decreasing volumes, this need will be exacerbated. High-performance chip power is predicted to increase monotonically and rapidly with time. Systems utilizing these chips are currently reliant upon decades of old cooling technology. Heat pipes offer a solution to this problem. Heat pipes are passive, self-contained, two-phase heat dissipation devices. Heat conducted into the device through a wick structure converts the working fluid into a vapor, which then releases the heat via condensation after being transported away from the heat source. Heat pipes have high thermal conductivities, are inexpensive, and have been utilized in previous space missions. However, the cylindrical geometry of commercial heat pipes is a poor fit to the planar geometries of microelectronic assemblies, the copper that commercial heat pipes are typically constructed of is a poor CTE (coefficient of thermal expansion) match to the semiconductor die utilized in these assemblies, and the functionality and reliability of heat pipes in general is strongly dependent on the orientation of the assembly with respect to the gravity vector. What is needed is a planar, semiconductor-based heat pipe array that can be used for cooling of generic MCM (multichip module) assemblies that can also function in all orientations. Such a structure would not only have applications in the cooling of space electronics, but would have commercial applications as well (e.g. cooling of microprocessors and high-power laser diodes). This technology is an improvement over existing heat pipe designs due to the finer porosity of the wick, which enhances capillary pumping pressure, resulting in greater effective thermal conductivity and performance in any orientation with respect to the gravity vector. In addition, it is constructed of silicon, and thus is better suited for the cooling of semiconductor devices.

Yee, Karl Y.; Ganapathi, Gani B.; Sunada, Eric T.; Bae, Youngsam; Miller, Jennifer R.; Beinsford, Daniel F.

2013-01-01

416

Dynamically Reconfigurable Systolic Array Accelerator  

NASA Technical Reports Server (NTRS)

A polymorphic systolic array framework has been developed that works in conjunction with an embedded microprocessor on a field-programmable gate array (FPGA), which allows for dynamic and complimentary scaling of acceleration levels of two algorithms active concurrently on the FPGA. Use is made of systolic arrays and a hardware-software co-design to obtain an efficient multi-application acceleration system. The flexible and simple framework allows hosting of a broader range of algorithms, and is extendable to more complex applications in the area of aerospace embedded systems. FPGA chips can be responsive to realtime demands for changing applications needs, but only if the electronic fabric can respond fast enough. This systolic array framework allows for rapid partial and dynamic reconfiguration of the chip in response to the real-time needs of scalability, and adaptability of executables.

Dasu, Aravind; Barnes, Robert

2012-01-01

417

RF coil arrays in MRI  

SciTech Connect

Because it plays such an important role in determining the signal-to-noise ratio (SNR) in MR imaging and because it is one of the few elements of the imaging system that is easily modifiable by engineers and physicists, the radio-frequency (RF) detector coil has been the subject of significant research. More recently, investigators have begun using arrays of RF coils. RF coil arrays have already found widespread use in MRI, and should become more widely used as applications increase. Presently the most important use of RF coil arrays are to increase the SNR per unit time, increase the available field-of-view, or some combination of the two. Dynamic imaging appears to be another important potential application. An introduction to the theory and application of RF coil arrays is provided in this paper, and examples of several applications are shown.

Wright, Steven M. [Magnetic Resonance Systems Laboratory, Department of Electrical Engineering, Texas A and M University, College Station, Texas 77843-3128 (United States)

1998-08-28

418

Glycan arrays for functional glycomics  

Microsoft Academic Search

Interactions between carbohydrates and proteins mediate intracellular traffic, cell adhesion, cell recognition and immune system function. Two recent papers describe how arrays of oligosaccharide and polysaccharide molecules can be used to investigate these interactions more fully.

Kurt Drickamer; Maureen E Taylor

2002-01-01

419

High density synthetic oligonucleotide arrays  

Microsoft Academic Search

Experimental genomics involves taking advantage of sequence information to investigate and understand the workings of genes, cells and organisms. We have developed an approach in which sequence information is used directly to design high–density, two–dimensional arrays of synthetic oligonucleotides. The GeneChip® probe arrays are made using spatially patterned, light–directed combinatorial chemical synthesis, and contain up to hundreds of thousands of

Robert J. Lipshutz; Stephen P. A. Fodor; Thomas R. Gingeras; David J. Lockhart

1999-01-01

420

Carbon Nanotube Array Immunosensor Development  

Microsoft Academic Search

This paper describes the development of a label-free immunosensor using carbon nanotube array electrodes. Highly aligned multi-walled carbon nanotubes were grown by chemical vapor deposition using a metallic catalyst, Fe\\/Al2O3\\/SiO2, On Si wafers. Harvested towers were cast in epoxy and polished on both ends; one end being for electrical connection and the other being the electrode array surface. The nanotubes

A. Bange; H. B. Halsall; W. R. Heineman; YeoHeung Yun; M. J. Schulz; V. Shanov

2006-01-01

421

Sensor arrays for detecting microorganisms  

NASA Technical Reports Server (NTRS)

A sensor array for detecting a microorganism comprising first and second sensors electrically connected to an electrical measuring apparatus, wherein the sensors comprise a region of nonconducting organic material and a region of conducting material compositionally that is different than the nonconducting organic material and an electrical path through the regions of nonconducting organic material and the conducting material. A system for identifying microorganisms using the sensor array, a computer and a pattern recognition algorithm, such as a neural net are also disclosed.

Lewis, Nathan S. (Inventor); Freund, Michael S. (Inventor)

2000-01-01

422

Integrated residential photovoltaic array development  

NASA Technical Reports Server (NTRS)

Sixteen conceptual designs of residential photovoltaic arrays are described. Each design concept was evaluated by an industry advisory panel using a comprehensive set of technical, economic and institutional criteria. Key electrical and mechanical concerns that effect further array subsystem development are also discussed. Three integrated array design concepts were selected by the advisory panel for further optimization and development. From these concepts a single one will be selected for detailed analysis and prototype fabrication. The three concepts selected are: (1) An array of frameless panels/modules sealed in a T shaped zipper locking neoprene gasket grid pressure fitted into an extruded aluminum channel grid fastened across the rafters. (2) An array of frameless modules pressure fitted in a series of zipper locking EPDM rubber extrusions adhesively bonded to the roof. Series string voltage is developed using a set of integral tongue connectors and positioning blocks. (3) An array of frameless modules sealed by a silicone adhesive in a prefabricated grid of rigid tape and sheet metal attached to the roof.

Royal, G. C., III

1981-01-01