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Applied Superconductivity, IEEE Transactions on

Issue 1  Part 2 • Date March 2001

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Displaying Results 1 - 25 of 298
  • Conference Author Index

    Page(s): 2638 - 2655
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    Freely Available from IEEE
  • A new flywheel energy storage system using hybrid superconducting magnetic bearings

    Page(s): 1657 - 1660
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    The high temperature superconductor (HTS) YBaCuO coupled with permanent magnets has been applied to construct the superconducting magnetic bearings (SMB) which can be utilized in some engineering fields such as the flywheel energy storage system (FESS). However, there are many problems needed to be resolved, such as low stiffness and damping, the uncertainty of working displacement, flux creep and flux flow. In this paper, a new FESS using hybrid SMB system which consists of SMB, active magnetic bearings (AMB), and permanent magnetic bearings (PMB) is presented. In this design, the authors constructed an experimental device for the FESS with hybrid SMB. An axial PMB is joined to provide a levitation force so as to suspend a heavier flywheel; in addition, two AMB are added in radial degrees to improve the stiffness by two orders of magnitude from 104 N/m to 106 N/m and the damping of FESS View full abstract»

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  • Quenching behaviour of superconductors in an inductive fault current limiter

    Page(s): 2495 - 2498
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    Earlier papers introduced a new form of inductive superconducting fault current limiter (FCL) in which the primary and secondary windings were interleaved symmetrically, producing current sharing in the multiplicity of secondary coils. A new FCL which employs similar structure but in a higher rating has been designed and constructed. The new FCL, has eight series connected primary coils interleaving with at least eight isolated secondary superconductor rings around a toroidal iron core. Investigation of this FCL when carrying a different number of superconductor rings has showed the ability to reduce the leakage fields around the windings hence improving the current rating of the FCL by increasing the number of superconductor rings in the FCL. However, being isolated, each superconductor ring has a different switching profile as a result of the development of normal regime resistance at different current values. A new way of characterising this nonuniform quenching behaviour of the superconductors in the FCL as the fault occurs is reported View full abstract»

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  • Performance of the 1-m model of the 70 mm bore twin-aperture superconducting quadrupole for the LHC insertions

    Page(s): 1641 - 1644
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    Individually powered twin-aperture superconducting quadrupoles with a coil bore of 70 mm will be installed in certain areas of the LHC insertions where increased geometrical acceptance is required. A 1-m twin-aperture model of the quadrupole, featuring a four-layer coil with a nominal gradient of 160 T/m at 4.5 K, has been built and tested. In this report we present the quench performance of the magnet, and discuss the results of the quench protection studies and magnetic field measurements View full abstract»

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  • Drag torque in high Tc superconducting magnetic bearings with multi-piece superconductors in low speed high load applications

    Page(s): 1661 - 1664
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    The design of superconductor magnet bearings for high load applications such as flywheel kinetic energy storage necessitates the use of large pieces of high quality high temperature superconductors. Limitations on the size of one continuous block of HTS materials that can be produced make it very attractive to use contiguous pieces of high quality HTS materials to provide the same large amount of HTS surface that can interact with magnets to give as high a levitation force. More often than not, the shape of such a composite piece is not symmetric about any axis of rotation. Variations in the drag torque are observed within each rotation cycle of the magnet above the composite HTS piece. The authors show that part of this drag torque variation originates from the nonaxisymmetric shape of the composite HTS piece. Implications of this drag torque variation on the power loss of superconductor magnet bearings made with composite HTS pieces are discussed View full abstract»

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  • Optimization of high-temperature superconducting power transformers

    Page(s): 1574 - 1577
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    The discovery of high-temperature superconductors in 1987 opened new opportunities in the design of power supply equipment. The advantages of a transformer with high-temperature superconducting windings have been discussed and presented in several papers in the past. The design of transformers depends on the operation requirements and the installed position in the power network. In this paper the fundamental equations for the design of transformers are discussed and modified in such a way that an optimization of HTS transformers can be successfully studied. The best design in terms of low load losses or low no-load losses is calculated for different power transformers considering the volume of the transformer and the impedance voltage. The resulting “growth laws” are discussed and analyzed View full abstract»

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  • Field demonstration of a 24-kV warm dielectric HTS cable

    Page(s): 2461 - 2466
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    Prototype HTS cable systems have been installed in laboratories and tested successfully around the world, proving the technical feasibility of the HTS cable system. Commercial cable systems, however, must not only be feasible, but meet practical requirements as well. To facilitate the transition of HTS cable technology from the laboratory to the field, a project has been initiated to install the world's first HTS power cable to deliver electricity in a utility network. This program will demonstrate a retrofit upgrade application of the warm dielectric HTS cable design in the Detroit Edison utility network, and involve the design, engineering, installation, test and routine operation of a 24-kV, 100 MVA, 3-phase cable system. Each HTS cable will carry 2400 A RMS, a level triples the ampacity of original cables powering this circuit. This paper addresses the field application of HTS cables in the context of the demonstration program. Customer perception will play a crucial role in the adoption of HTS cable systems by the utility industry. An updated perspective provided by the utility industry team members is included View full abstract»

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  • The background magnets of the Samsung Superconductor Test Facility (SSTF)

    Page(s): 2082 - 2085
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    The background magnet system of SSTF (Samsung Superconductor Test Facility) for KSTAR (Korea Superconducting Tokamak Advanced Research) is now under design. The main coil (MC) is split solenoids and the gap can be changed from 0 to 750 mm. The ID of MC is 750 mm. It will be wound using a CICC (cable-in-conduit conductor) designed for the central solenoid of KSTAR. The central field is 8 T at 22.5 kA when the gap is 250 mm. The ramp rate of MC is 3 T/s. A pair of blip coils will simulate (during the discharge) 1 T amplitude and 20 T/s rate electromagnetic disturbances expected from the KSTAR operation. To compensate the inductive interaction between MC and blip coils during the discharge of the blip coils, a pair of cancellation coils is foreseen. Both blip and cancellation coils (BCC) are fed in series and generate 1 T central field at 7 kA and 250 mm gap. The BCC are wound with CICC and cooled internally and externally View full abstract»

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  • Performance of the single and twin-aperture models of the 6 kA superconducting quadrupole for the LHC insertions

    Page(s): 1645 - 1648
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    The LHC dispersion suppressors and matching sections will be equipped with individually powered superconducting quadrupoles with an aperture of 56 mm. In order to optimise the parameters and cost of the magnets and of their powering, the quadrupole has been designed on the basis of an 8.2 mm wide Rutherford-type cable for a nominal current of 5300 A, corresponding to a gradient of 200 T/m at 1.9 K. In order to validate the design two 1-m single-aperture quadrupoles and one twin-aperture quadrupole have been built and tested. In this report we describe the construction features of the magnets and present the results of the magnet tests View full abstract»

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  • AC losses of HTS power transmission cables using Bi-2223 tapes with twisted filaments

    Page(s): 2192 - 2195
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    TEPCO and Furukawa have been developing compact 66 kV HTS power cables that can fit into 150 mm ducts. To realize these compact and highly efficient cables, decreasing AC losses in the cables is important. An effective method for reducing the AC losses is to suppress the electromagnetic coupling between layers and between filaments: equalizing the impedance of each layer suppresses the electromagnetic coupling between layers; and using twisted filaments in Bi-2223 tape suppresses the electromagnetic coupling between filaments. An HTS conductor was fabricated using Ag-Mg sheathed tapes that had twisted filaments, and the AC losses in the conductor were measured. The AC losses were lower than that of nontwisted filamentary conductors. Furthermore, the AC losses in an HTS cable were measured at temperatures ranging from 67 K to 77 K, using a device that can cool liquid nitrogen to less than 77 K. As a result of twisting the filaments in the tape and uniform current distribution for the conductor, the AC losses were reduced to the lowest levels ever achieved View full abstract»

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  • The B00 model coil in the ATLAS Magnet Test Facility

    Page(s): 1582 - 1585
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    A 1-m size model coil has been developed to investigate the transport properties of the three aluminum-stabilized superconductors used in the ATLAS magnets. The coil, named B00, is also used for debugging the cryogenic, power and control systems of the ATLAS Magnet Test Facility. The coil comprises two double pancakes made of the barrel toroid and end-cap toroid conductors and a single pancake made of the central solenoid conductor. The pancakes are placed inside an aluminum coil casing. The coil construction and cooling conditions are quite similar to the final design of the ATLAS magnets. The B00 coil is well equipped with various sensors to measure thermal and electrodynamic properties of the conductor inside the coils. Special attention has been paid to the study of the current diffusion process and the normal zone propagation in the ATLAS conductors and windings. Special pick-up coils have been made to measure the diffusion at different currents and magnetic field values View full abstract»

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  • Initial quench development in uniform Au/Y-Ba-Cu-O thin films [superconducting fault current limiters]

    Page(s): 2414 - 2417
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    The authors investigated the initial quench development process in resistive superconducting fault current limiters based on YBa2Cu3O7-δ thin films of uniform quench current. The film was coated insitu with a gold layer and patterned into pairs of 1 mm wide and 26 cm long meander lines by photolithography. Voltage taps were mounted along the meander lines to detect quench development. Fabricated limiters were tested with simulated AC fault currents. Upon fault current passing quench current, all sections of the meander line made transitions into the pull flow regime simultaneously with similar flux flow resistivity. Transfer of the generated Joule heat, however, soon changed its distribution. At lower source voltages the center area of the meander line always had the highest resistivity and the edge area the lowest. At higher voltages quench started first and propagated fastest in the area close to the center electrode. But, once quench was completed, the resistivity became the highest in the central area of the meander line. This phenomenon was observed in all uniform samples on which measurements were taken and should be considered in design of fault current limiters made from uniform YBa2Cu3O7-δ thin films. The heat transfer from limiter meander lines to surroundings explains the results View full abstract»

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  • Thermal and magnetic characteristics of bulk superconductor and performance analysis of magnetic shielding type of superconducting fault current limiter

    Page(s): 2402 - 2405
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    Superconducting fault current limiter (SCFCL) is expected to be the first application of a high-temperature superconductor (HTS) to electric power systems. The authors have been developing a magnetic shielding type of SCFCL that uses a cylindrical Bi-2223 HTS bulk. Short-circuit fault tests in a small SCFCL model were performed experimentally. A computer program based on the finite element method (FEM) taking the voltage-current (E-J) characteristics of the bulk material into account was developed to analyze the performance in the short-circuit fault tests and to investigate the dynamic electromagnetic behavior within a bulk superconductor. Because the E-J characteristic of HTS bulk depends on temperature and magnetic field, they investigated experimentally the E-J characteristics of a bulk superconductor in various operating temperatures and magnetic fields. The computer program considering the measured E-J characteristics simulated the electromagnetic behaviors in an SCFCL test model successfully (BiPb)2Sr2Ca2Cu3O10 View full abstract»

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  • Helium and current feeder systems of KSTAR

    Page(s): 2062 - 2065
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    We have estimated the heat load due to an operating sequence and designed a cooling scheme for the coil, structure, and bus-line of the Korea Superconducting Tokamak Advanced Research (KSTAR) device cooled by supercritical helium. We have also estimated the heat load of the current lead cooled by liquid helium. Since KSTAR will be operated in a pulse mode, the AC loss is dominant in the heat load. The cooling scheme of the magnet system is presented. Discussion is given for the cooling parameters that consist of temperature, pressure, mass flow rate, etc View full abstract»

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  • Study on recovery time of a superconducting fault current limiter with adjustable trigger current level

    Page(s): 2086 - 2089
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    The recovery time of a transformer type SCFCL (superconducting fault current limiter) with adjustable trigger current level, is studied experimentally The recovery time is defined as the required time of zero current period of SCFCL for recovery from its current limiting mode to its waiting mode. A trial SCFCL, which was designed and made, is tested to measure the recovery time with various fault time. The experimental results show that the recovery time depends on the fault time. When the fault time is longer than 200 ms, the recovery time becomes shorter and approaches a certain value (a few ten ms) as the fault time is longer View full abstract»

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  • Feasibility of Nb3Sn in a μ-SMES concept

    Page(s): 1757 - 1760
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    Today's SMES related efforts are mainly concentrating on a number of small-scale devices for high value applications such as improving power quality and providing frequency control or dynamic response. The commercialised SMES units utilise NbTi at 4.2 K as a coil material. In addition some demonstration concepts have been tested with HTS materials operating at 20-30 K or even at 77 K. One approach is to utilise Nb3Sn in the vicinity of 10 K. This kind of system has been constructed. The designed SMES coil is compared to a NbTi coil cooled with liquid helium and a conduction cooled BSCCO coil operating at 20 K. The starting point is a 200 kJ magnet where the coil volume has been optimised under electromagnetic and mechanical constraints. The comparison of these three coil concepts is mainly concentrated on the questions of stability and coil protection. The benefits and disadvantages of adopting Nb3Sn as a coil material are emphasized View full abstract»

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  • Stability analysis of a power system with superconducting fault current limiter installed

    Page(s): 2098 - 2101
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    As a process of developing high temperature superconducting fault current limiter (SFCL), the stability of a power system in which SFCLs were installed was analyzed. For the investigation into the effect of SFCLs to a power system, we have proposed a simple model power system that had SFCL circuits. The modeling parameters of SFCL are obtained by experiment of a prototype SFCL, which is 440 V class and a shielding type model. This electric circuit was solved for transient performance by numerical methods. In case the SFCLs are installed in a power system, it can effectively protect synchronization both in a symmetrical three-phase fault and a single-phase line to ground fault by maintaining synchronism of the synchronous machines for a long time. By this analysis, we found a quantitative effect of SFCLs to a power system. Limiting fault currents means not only an improvement of circuit breaker abilities but also a protection of synchronism. So its synchronism protection property must be considered for a design of superconducting fault current limiters View full abstract»

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  • Study on high temperature superconducting magnetic bearing for 10 kWh flywheel energy storage system

    Page(s): 1649 - 1652
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    Flywheel energy storage systems with high temperature superconducting magnetic bearings are expected for load leveling use. A 1 kWh flywheel of 600 mm diameter was developed and the maximum energy storage of 1.4 kWh at 20,000 RPM was attained. For the development of a large capacity flywheel system, it is necessary to sophisticate the cooling system and improve the performance of the HTS magnetic bearing. So, an advanced cooling system of the bearing with a cryogenic refrigerator has been developed, and also the bearing characteristics in several cooling conditions have been investigated. It has been confirmed that the repulsive force of the bearing at 50 K was 1.5 times of its value at 80 K, and the rotating loss of the bearing at 50 K was one third of its value at 80 K, but the lateral magnetic stiffness at 50 K became small in comparison to that of 80 K. On the basis of the above results, an HTS magnetic bearing for 12.5 kWh flywheel system is under development View full abstract»

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  • Application of resistor based superconducting fault current limiter to enhancement of power system transient stability

    Page(s): 2122 - 2125
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    This paper presents an application of a superconducting fault current limiter (SFCL) to enhance the power system transient stability. Resistance as the current limiting devices is used for damping the generator accelerating power. A method to evaluate an appropriate resistance is proposed. The SFCL is combined with the superconducting magnetic energy storage (SMES) for power system stabilization. As a result the capacity of SMES is significantly reduced View full abstract»

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  • Progress of LHC low-β quadrupole magnets at KEK

    Page(s): 1562 - 1565
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    Development of the LHC low-β insertion quadrupole magnet has been in progress at KEK since 1995 as a cooperative program between CERN and KEK. Five 1-m short model magnets have been fabricated and three of them have been tested. From the various test results of the first two models, the coil configuration was further optimized to reduce the higher magnetic field harmonic coefficients. The cold test of the third model showed satisfactory performances of the field harmonics. After this R&D work, the authors are at a stage for the fabrication of two prototype magnets which have the same scale as the production magnets. The status of the R&D for the LHC low-beta insertion quadrupole magnet at KEK is described View full abstract»

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  • Design and characteristic analysis of a rod type high-Tc superconducting fault current limiter through electromagnetic analysis

    Page(s): 2102 - 2105
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    The existence of large air gaps, between a high-Tc superconducting (HTS) tube and an iron core, or between a primary winding and a HTS tube, possibly causes some undesirable voltage drops under the condition of normal operation. It makes the power system unstable. For this reason, the optimization of air gaps is essential in designing a high-Tc superconducting fault current limiter (SFCL). In this paper, the optimal values of air gaps are determined through electromagnetic analysis, and the comparison between computational and experimental results is provided View full abstract»

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  • Evaluation of the magnetic field within a BPSCCO cylinder superimposed by multi-layered soft-iron cylinders by use of an HTS DC-SQUID

    Page(s): 2387 - 2390
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    The evaluation of the maximum shielded magnetic flux density Bs of a high-critical temperature superconducting (HTS) cylinder acting as a magnetic shielding vessel, is required to improve the value of Bs for practical use. The authors have improved the value of Bs by the superposition of multi-layered soft-iron cylinders over a Bi-Pb-Sr-Ca-Cu-O cylinder which is termed the superimposed cylinder. Little is known, however, of the characteristics and evaluation procedures for the magnetic flux density Bia within the innermost of the superimposed cylinders when the value of the external magnetic flux density Bex is less than that of Bs. The present research has evaluated the shielding effect for the superimposed cylinder with the use of an HTS DC-SQUID magnetometer and spectrum analyzer. The present paper examines the magnetic step response of Bin to the applied Bex, the characteristics of Bin when exposed to a Bex having a value less than that of Bs, and the magnetic noise power spectra within the superimposed cylinder. In addition, a discussion is conducted on the relationship between the number of layers of the multi-layered soft-iron cylinder and the value of Bin View full abstract»

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  • Superconducting magnetic system of the fast cycling intermediate energy ion synchrotron

    Page(s): 1514 - 1517
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    A superconducting magnetic system for the 250 to 500 MeV/Amu booster synchrotron of the Nuclotron is discussed. The repetition rate of the booster is 1 Hz and the circumference 84 m. There are 32 dipole and 24 quadrupole magnets with a “cold” iron yoke and a hollow superconductor winding (NbTi) in the accelerator ring. Basic parameters of the magnets, superconducting cable construction, cryogenic system and cryomagnetic assembly design are presented View full abstract»

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  • Test results of a demonstration HTS magnet for minesweeping

    Page(s): 2527 - 2530
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    American Superconductor completed building a demonstration HTS minesweeping magnet for airborne superconducting mine countermeasure system in December 1999, The demonstration magnet consisted of a single-layer HTS coil wound on a 457-mm G-10 mandrel, and housed in a 560 mm diameter by 1.5-m long stainless steel vacuum vessel. It is conduction cooled with a two-stage cryocooler. It has a magnetic moment of 15 kAm2. The magnet was successfully ramped up to 400 A at ~35 K. The magnet current was kept at 400 A for six hours without any voltage run-away. The magnet was also successfully tested for 50% AC modulation (200 A to 400 A) with a trapezoidal current waveform. Experimental data from these tests are presented View full abstract»

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  • Development of a 22 kV/6.9 kV single-phase model for a 3 MVA HTS power transformer

    Page(s): 1578 - 1581
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    We have developed a 22 kV/6.9 kV HTS single-phase transformer cooled by liquid nitrogen for field test, which is a practical model for the single-phase part of a 3 MVA HTS power transformer. First, we numerically simulated electromagnetic, mechanical and thermal conditions of the windings in accidental cases of short-circuit and lightning impulse, and considered the winding structure withstanding the severe loads. We constructed a small-sized model coil of Bi-2223 Ag/Mn-sheathed tapes and confirmed applicability of the design concept for the overcurrent and high-withstand-voltage tests. We designed and constructed a single-phase HTS transformer on the basis of the model-coil-test results. The primary and secondary windings are transposed parallel conductors of two and six Bi-2223 Ag/Mn tapes, respectively. The same tests for the HTS transformer as for usual oil-filled ones indicated the reliable operation and high performance. The field test in a distribution grid of Kyushu Electric Power Co. included in-rush-current test and long-term operation of the transformer cooled by a continuous supply system of subcooled liquid nitrogen with cryocoolers View full abstract»

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IEEE Transactions on Applied Superconductivity contains articles on the applications of superconductivity and other relevant technology.

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Meet Our Editors

Editor-in-Chief
Britton L. T. Plourde
Syracuse University
bplourde@syr.edu
http://www.phy.syr.edu/~bplourde