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This paper presents a methodology for feature extraction of a new fault indicator focused on detecting demagnetization faults in a surface-mounted permanent-magnet synchronous motors operating under nonstationary conditions. Preprocessing of transient-current signals is performed by applying Choi–Williams distribution to highlight the salient features of this demagnetization fault. In this paper, fractal dimension calculation based on the computation of the box-counting method is performed to extract the optimal features for diagnosis purposes. It must be noted that the applied feature-extraction process is autotuned, so it does not depend on the severity of the fault and is applicable to a wide range of operating conditions of the motor. The performance of the proposed system is validated experimentally. According to the obtained results, the proposed methodology is reliable and feasible for diagnosing demagnetization faults in industrial applications. [ABSTRACT FROM AUTHOR]

The production of a stochastic background of relic gravitational waves is well known in various works in the literature, where, by using the so called adiabatically-amplified zero-point fluctuations process, it has been shown how the standard inflationary scenario for the early universe can in principle provide a distinctive spectrum of relic gravitational waves. In this paper, it is shown that, in general, f( R) theories of gravity produce a third massive polarization of gravitational waves and the primordial production of this polarization is analyzed adapting the adiabatically-amplified zero-point fluctuations process at this case. In this way, previous results, where only particular cases of f( R) theories have been analyzed, will be generalized. The presence of the mass could also have important applications in cosmology, because the fact that gravitational waves can have mass could give a contribution to the dark matter of the Universe. An upper bound for these relic gravitational waves, which arises from the WMAP constrains, is also mentioned. At the end of the paper, the potential detection of such massive gravitational waves using interferometers like Virgo and LIGO is discussed. [ABSTRACT FROM AUTHOR]

This paper discusses the role of media damping for a perpendicular recording system that uses a realistic head field and media parameters in a micromagnetic model based on the Landau-Lifshitz-Gilbert formulation for the magnetization dynamics. The modeling approach uses pulsed write fields of varying pulse duration to record footprints of the head on the media. Using a criterion that 95% of the grains are reversed in the footprints, we calculate the field needed to record as a function of pulse duration, i.e., the dynamic coercivity. As shown in a previous paper, we find two distinct regions in the dynamic coercivity plots. The thermally dominated (long time) region can be described by appropriately including the demagnetization effects in the thermal stability factor Ku V/kBT. The short time (dynamic) behavior shows a precipitous increase in the required recording field accompanied by an increase in the erase width. The latter effect causes the recording performance to degrade, especially in the short time dynamic regime. The onset of dynamic effects strongly depends on the media damping. In order to achieve high data and high areal density, we need to optimize damping in the recording heads and media. [ABSTRACT FROM AUTHOR]

Although interior permanent magnet synchronous machines and their cooling are designed to match the rated power, power demands other than rated may arise. One may keep the same machine dimensions and basic electromagnetic design, but increase the cooling for different operating conditions. Modifications of the cooling system can compensate for the increase in machine losses in the windings, magnets, or iron. Increasing the allowed stator current affects the machine performance in other ways as well. These include demagnetization of the magnets, and hence, shrinking of the speed range to avoid this. In this paper, these effects are studied for a baseline machine, as well as for machines with the same stator but modified rotor design. A cross-saturated model is developed and shown to be more accurate than the classic one. To account for higher stator current with higher temperatures, the effects on efficiency, torque, and speed range by changing the magnet material from the more commonly used NdFeB to SmCo are also studied and discussed. [ABSTRACT FROM AUTHOR]

Flux-reversal machine (FRM) is a new doubly salient stator-permanent magnet (PM) machine with flux linkage reversal in the stator concentrated windings. It can operate in both motoring and generating modes. Its simple structure makes it cost effective and suitable for mass production. However, there is notable permanent magnet flux leakage which deteriorates the torque ability of the FRM. In this paper, a novel design to improve the performance of an FRM is proposed. The proposed FRM has permanent magnets parallel to the stator magnet flux lines and thus is much more difficult to demagnetize. To analyze the characteristics of the proposed FRM, a two-dimensional finite-element method (2-D FEM) is used. The prototype FRM is also built to prove the advantage of the new design method. From the analysis and experimental results, it is shown that the proposed FRM has an improved performance. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present a new model for the demagnetization problem in a permanent magnet machine having a reversed structure. The permeance network approach and superposition theorem have been used to check out the semi-analytical model. In order to validate the model, a two-dimensional finite element method analysis has been carried out. The obtained results are encouraging to continue the modeling process and this will open several prospects particularly in the diagnostics areas of the permanent magnet machines. [ABSTRACT FROM AUTHOR]

Titanium alloys (Ti6Al4V) have been widely applied in modern aerospace industry as structural components due to their excellent mechanical and physical properties. Meanwhile, the drilling process is essential for machining the assembly holes of Ti6Al4V. However, Ti6Al4V is also a difficult-to-cut material owing to their low thermal conductivity and high chemical reactivity with many tool materials during machining, which easily lead to rapid tool wear, premature tool failure, and poor machining quality. This has attracted wide attention of researchers. In recent years, the rotary ultrasonic-assisted drilling (RUAD) technology, as a novel machining method, has been found to be very effective in the machining of difficult-to-cut materials like nickel alloys and titanium alloys. This paper first introduced an 8-facet drill tool and combined the advantages of RUAD to carry out a study on the drilling of Ti6Al4V under no cooling condition. The experimental results indicated that compared with the common drilling (CD) of Ti6Al4V, in RUAD process with the vibration amplitude of 10 μm, the thrust force, torque, cutting temperature near the drilled hole exit, surface roughness of drilled hole, expansion increment of hole diameter, and burr height of drilled hole exit decreased by 16.79 to 20.2 %, 31.5 to 33.6 %, 18.54 to 21.68 %, 24.87 to 25.36 %, 46.75 to 57.63 %, and 82.27 to 89.18 %, respectively; the excellent chip breakability and removal effect of chip evacuation, superior surface integrity of drilled hole, enhanced tool cutting ability, and prolonged tool life were obtained in RUAD. Furthermore, the experimental results also proved that the drilling technology of RUAD of Ti6Al4V using the 8-facet drill was feasible and the cutting effects were superior. [ABSTRACT FROM AUTHOR]

This paper proposes an automatic test bench, based on a rigorous and repeatable measurement procedure, for the analysis of a position sensor linear variable differential transformer (LVDT). The test bench allows complete characterization of an LVDT sensor working in an interfering magnetic field by evaluating the uncertainty and nonlinearity of the sensor. This issue is addressed in neither the sensor datasheet nor the scientific literature. The potential of the method and the performance of the automated test bench are proven by measuring the main sensor characteristics such as nonlinearity and uncertainty, and the error of a position reading due to external magnetic interference on two commercial LVDTs. The sensors are based on two different reading techniques, and both are analyzed using current and voltage excitations. In fact, the test bench permits to study the robustness of the sensor with respect to external magnetic fields by comparing position drifts due to interference at varying source excitations and reading techniques. [ABSTRACT FROM AUTHOR]

A two-dimensional quench simulation model was developed for the Superconducting Electromagnetic Iron Separator (SEIS) system, which is designed to separate small pieces of ferromagnetic materials, such as detonators, from coal to achieve high purity and good yield. The SEIS coil adopted passive quench protection system with four-sectioned arrangement, each shunted with four diodes. The aluminum slices, with 99.99% purity and 0.5 mm x 12 mm cross section dimension, working as quench propagator, were clothed on the inner and the outer surfaces of the coil. The minimum quench energy, the temporal variations of current, voltage and hot spot temperature rise of the coil were analysed. Furthermore, the coil stress during winding, cool-down, charging and quench process was also included in this paper. The simulation results demonstrated that the existing protection system could guarantee the SEIS magnet experience no fatal damage during quench. [ABSTRACT FROM AUTHOR]

For a permanent magnet dipole to produce fields higher than the remnant induction of the magnetic materials, Halbach and Stelter array are commonly used structures. This paper presents a novel design for strong field permanent magnet dipole. We analyzed the structure using current sheet method. We then used BEA software to simulate the structure. A prototype dipole was built. The field from the prototype dipole was measured and compared to the analytical and BEA results. The actual field matches the calculation very well. There is no visible demagnetizing effect. [ABSTRACT FROM AUTHOR]

Gd5Si2Ge2 is known for its giant magnetocaloric effect (GMCE), but also for its associated large hysteretic losses. These losses result in a significant reduction in the net cooling capacity of this material when it is used for magnetic cooling. Attempts have been made to reduce these losses by adding other elements, like iron. Individual Ge and Si substitutions have been reported, but in this paper we focus on the system where both elements were substituted simultaneously with different amounts of Fe, with an additional interest in the new Gd5 (Si,Ge)3 phase that appears after the substitution. We found that when substituting iron in small quantities the MCE and the hysteresis losses remain high, with a small decrease in the Curie temperature, and the low-temperature XRD revealed that the structural transformation is still present. However, with an increasing amount of Fe the MCE was drastically reduced because of the newly formed Gd5 (Si,Ge)3 phase. The magnetic transition temperature of this newly formed phase was investigated in all three substituted systems: Si, Ge and Si and Ge. This transition temperature was strongly affected by the type and the amount of substitution; however, the changes could not be directly related to the composition of the phases. [ABSTRACT FROM AUTHOR]

In the stably stratified interior of the ocean, mesoscale eddies transport materials by quasi-adiabatic isopycnal stirring. Resolving or parameterizing these effects is important for modeling the oceanic general circulation and climate. Near the bottom and near the surface, however, microscale boundary layer turbulence overcomes the adiabatic, isopycnal constraints for the mesoscale transport. In this paper a formalism is presented for representing this transition from adiabatic, isopycnally oriented mesoscale fluxes in the interior to the diabatic, along-boundary mesoscale fluxes near the boundaries. A simple parameterization form is proposed that illustrates its consequences in an idealized flow. The transition is not confined to the turbulent boundary layers, but extends into the partially diabatic transition layers on their interiorward edge. A transition layer occurs because of the mesoscale variability in the boundary layer and the associated mesoscale–microscale dynamical coupling. [ABSTRACT FROM AUTHOR]

Abstract-The MICE focusing solenoids have three 4 K coolers (two for the superconducting magnet and one for the liquid absorber) and four HTS leads that feed the current to the focusing coils. The focusing solenoids produce large radial external fields when they operate with the polarity of the two coils in opposition (the gradient or flip mode). When the MICE focusing coils operate at the same polarity (the solenoid or non-flip mode), the fields are much smaller and parallel to the axis of the solenoid. The worst-case magnetic field affects the selection of the cooler and the HTS leads. This magnetic field can also determine the height of the service towers that house the three coolers and the four HTS leads. This paper shows the criteria used for Cooler selection, HTS lead selection, and the position of both the cooler and leads with respect to the solenoid axis of rotation. [ABSTRACT FROM AUTHOR]

This paper presents the results of work, experimental and simulation, performed on an YBCO pancake coil to develop a detect-and-activate-the-heater (DAH) protection technique. In this DAH protection technique a "protection heater" (PH) is activated, upon the detection of a quench zone in a coil, to create an additional normal zone to absorb the stored magnetic energy sufficient to keep the initially quenched zone (hot spot) from overheating. It is computed that a protection heater for most coils needs to cover only a fraction of the winding to keep the quenched zone from overheating. The pancake coil used in the experiment, 100-mm i.d., 190-mm 04., and 4.3-mm height, is dry-wound with copper plated YBCO tape, 4.3-mm wide, 96.3-μm thick, 100-m long, and is turn-to-turn insulated with 38-μm thick Nomex spacer. The pancake stores a magnetic energy of 30 J at an operating current of 80 A at 65 K. Because the smaller the magnet size, the less applicable the assumption of adiabatic conditions is and also the more beneficial NZP becomes that would otherwise be negligible in "large" magnets, the hot spot temperature observed in the experiment with this "small" test coil was much less than that computed based on the assumptions of adiabatic conditions and no NZP. To validate the basic concept and consequences of DAH protection technique either a test coil has to be large or if the same coil is to be used, it should be tested at the temperature range close to 20-30 K so that the coil can carry a large current and thus store a large magnetic energy. [ABSTRACT FROM AUTHOR]

This paper presents the mathematical analysis of a single stage absorption cycle using heat rejected from thermoelectric modules to drive the cycle. The absorption cycle uses LiBr/H2 O solution as the working pair with thermoelectric modules sandwiched between the generator and absorber. The results of the analysis show that thermoelectric modules would provide the heat required to drive the absorption cycle and the overall coefficient of performance (COP) of the integrated system could be higher than unity. [ABSTRACT FROM AUTHOR]

The ATLAS B0 model coil has been extensively tested, reproducing the operational conditions of the final ATLAS Barrel Toroid coils [1]. Two test campaigns have taken place on B0, at the CERN facility where the individual BT coils are about to be tested. The first campaign aimed to test the cool-down, warm-up phases and to commission the coil up to its nominal current of 20.5 kA, reproducing Lorentz forces similar to the ones on the BT coil. The second campaign aimed to evaluate the margins above the nominal conditions. The B0 was tested up to 24 kA and specific tests were performed to assess: the coil temperature margin with respect to the design value, the performance of the double pancake internal joints, static and dynamic heat loads, behavior of the coil under quench conditions. The paper reviews the overall test program with emphasis on second campaign results not covered before. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a new type of reciprocating magnetic refrigerator working with high remanence permanent magnets as the source of the magnetic field is presented. The simulated and measured magnetic field at the machine air gap is about 1.45T. Initially, gadolinium metal (Gd) was used as the magnetocaloric refrigerant. Its magnetocaloric performances and its quality were checked experimentally in a developed test bench. To attain high values of temperature difference between the hot and the cold sources (temperature span), a new design of the Active Magnetic Refrigeration (AMR) cycle was implemented. However, in order to reduce the energy consumption and then increase the thermodynamic performances of the magnetic system, a special configuration of the magnetocaloric materials is developed. The numerical results of the applied magnetic forces on the new configuration are given and analysed. The developed machine is designed to produce a cooling power between 80 and 100W with a temperature span larger than 20K. The obtained results demonstrate that magnetic cooling is a promising alternative to replace traditional systems. [Copyright &y& Elsevier]

Abstract: This paper presents a numerical study of natural convection cooling of two heat sources vertically attached to horizontal walls of a cavity. The right opening boundary is subjected to the copper–water nanofluid at constant low temperature and pressure, while the other boundaries are assumed to be adiabatic. The governing equations have been solved using the finite volume approach, using SIMPLE algorithm on the collocated arrangement. The study has been carried out for the Rayleigh number in the range 104 ≤Ra≤107, and for solid volume fraction 0≤φ≤0.05. In order to investigate the effect of heat source location, three different placement configurations of heat sources are considered. The effects of both Rayleigh numbers and heat source locations on the streamlines, isotherms, Nusselt number are investigated. The results indicate that the flow field and temperature distributions inside the cavity are strongly dependent on the Rayleigh numbers and the position of the heat sources. The results also indicate that the Nusselt number is an increasing function of the Rayleigh number, the distance between two heat sources, and distance from the wall. In addition it is observed that the average Nusselt number increases linearly with the increase in the solid volume fraction of nanoparticles. [Copyright &y& Elsevier]

Sixteen months of observations from a surface-to-bottom mooring in the central Gulf of Mexico show that acoustic Doppler current profilers (ADCPs) are useful for directly measuring the vertical velocity within mesoscale anticyclonic eddies, such as those shed from the Loop Current; and combining simultaneous temperature measurements, vertical heat flux can also be estimated (as a covariance of both variables). There is evidence of significant and coherent signals of vertical velocity ∼2–3 mm s-1 and vertical heat (temperature) transport ∼10-3 °C m s-1 during the presence of three anticyclones. A simple analysis shows downward flow near the eddies’ centers above 350 m and essentially upward flow in the peripheries, but below 700-m depth the pattern is indeed the opposite; however, further study is necessary to determine the eddies’ interior structures. The observations also suggest the existence of a vertical convergence of heat somewhere around 600-m depth, and estimations of adiabatic heat flux suggest that part of the converged heat, which is not recirculated within the eddy, must escape from the eddy and flow upward along the isopycnals up to the surface layers. This is in good agreement with previous results that have suggested that an excess heat gained by the Gulf in the intermediate levels through exchanges with the Caribbean Sea must be exported to the upper layers by an upward mean heat flux. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, syngas (hydrogen and carbon monoxide) production was investigated by a numerical model of an adiabatic monolithic reformer (e.g. for a micro fuel cell system). The study includes the thermal and diffusive properties of a washcoat of finite thickness that is modeled as a porous layer composed of a ceramic support containing catalytic active rhodium sites. It was combined with a two-dimensional radially symmetric model of a single tubular mini-channel, considering both the thermal and the diffusive transport phenomena in all domains. It was found that both the methane conversion and the hydrogen yield depended markedly on the washcoat thickness. An interesting result was obtained by implementing the common experimental conditions into the numerical model: if the inlet volume flow and the amount of catalyst per washcoat volume are constant, an optimum washcoat thickness of was found, where the hydrogen yield is maximal. For a thinner washcoat, the smaller amount of catalyst is limiting, leading to a low methane conversion. For a thicker washcoat, the limiting effect is the reduced residence time, which stems inherently from the constraint of constant volume flow, rather than the increased diffusive resistance. The demonstration of the existence of an optimum washcoat thickness is important, because it can have economic effects due to saving of the precious catalyst rhodium. [Copyright &y& Elsevier]

As it is well known, a quantum system depending on parameters exhibits the (geometric) Berry phase when parameters are varying in the adiabatic limit. A generalization of the Berry phase is given in the present paper for a nonadiabatic change of parameters, which leads to quantum transitions in the system. This generalization is applied to noninertial motions and it is shown that such motions may induce quantum transitions for a system in an external field governed by Schrodinger's equation. [ABSTRACT FROM AUTHOR]

This research presents a topology optimization for manipulating the main heat flow in coupled magnetothermal systems. The heat generated by eddy currents is considered in the design domain assuming an adiabatic boundary. For a practical optimization, the convection condition is considered in the topological process of the thermal field. Topology design sensitivity is derived employing the discrete system equations combined with the adjoint variable method. As numerical examples, a simple iron and a C-core design heated-up by eddy currents demonstrate the strength of the proposed approach to solve the coupled problem. [ABSTRACT FROM AUTHOR]

The magnetization of various design internal-Sn type Nb3Sn strands was analyzed in terms of effective filament diameter, deff. Assuming circular geometry and ignoring demagnetization, values of deff have been calculated numerically for various configurations including unsplit subelement and split subelement cases with 2, 3, 4 and 6 splits. In the numerical calculation, the magnetization was treated as the summation of the magnetization of sections aligned perpendicular to the applied field. The angle-averaged deff value was calculated for every degree over the split regions. The deff of single restacked strands using subelements with various numbers of splits has been calculated and the results show the influence of the split design of strands on the magnetization in high fields. Furthermore, the numerical results were compared with the reported simplified analytical results, about 20% difference indicates the approximation of the simplification. [ABSTRACT FROM AUTHOR]

This paper presents a new theoretical approach for the description of quasiadiabatic evolution of thermodynamic observables. The new method extends the projection operator technique by considering time-dependent projectors. A master equation is derived in the limit of a slow or adiabatic evolution and is applied to calculate the rate of saturation of dipolar order in a slowly rotating sample. To cite this article: T. Charpentier et al., C. R. Physique 5 (2004). [Copyright &y& Elsevier]

Reports the invention of the adiabatic anti-jitter circuit (AAJC), giving the anti-jitter circuit (AJC) improved power consumption, frequency range and maximum frequency of operation. Information on the AJC and AAJC principle; Description of AJC; Advantages of the AAJC invention.

Magnetic and magnetocaloric properties of a spin-1 Heisenberg diamond cluster with two different coupling constants are investigated with the help of an exact diagonalization based on the Kambe's method, which employs a local conservation of composite spins formed by spin-1 entities located in opposite corners of a diamond spin cluster. It is shown that the spin-1 Heisenberg diamond cluster exhibits several intriguing quantum ground states, which are manifested in low-temperature magnetization curves as intermediate plateaus at 1/4, 1/2, and 3/4 of the saturation magnetization. In addition, the spin-1 Heisenberg diamond cluster may also exhibit an enhanced magnetocaloric effect, which may be relevant for a low-temperature refrigeration achieved through the adiabatic demagnetization. It is evidenced that the spin-1 Heisenberg diamond cluster with the antiferromagnetic coupling constants J¹/kB = 41.4 K and J2/kB = 9.2 K satisfactorily reproduces a low-temperature magnetization curve recorded for the tetranuclear nickel complex [Ni4(μ-CO3)2(aetpy)8](ClO4)4 (aetpy = 2-aminoethyl-pyridine) including a size and position of intermediate plateaus detected at 1/2 and 3/4 of the saturation magnetization. A microscopic nature of fractional magnetization plateaus observed experimentally is clarified and interpreted in terms of valence-bond crystal with either a single or double valence bond. It is suggested that this frustrated magnetic molecule can provide a prospective cryogenic coolant with the maximal isothermal entropy change -ΔSM=10.6 J·K-1·kg-1 in a temperature range below 2.3 K. [ABSTRACT FROM AUTHOR]

The spin-1/2 Ising octahedron and dodecahedron with a unique antiferromagnetic interaction display an outstanding magnetization jump at zero magnetic field, which consequently leads to a giant magnetocaloric effect during the adiabatic demagnetization. In the present work we report temperature dependences of two basic magnetocaloric response functions: the isothermal entropy change and the adiabatic change of temperature. It is shown that the Ising octahedron and dodecahedron generally exhibit a large negative isothermal entropy change upon increase of the magnetic field, which serves in evidence of their cooling performance. [ABSTRACT FROM AUTHOR]

We report experimental demonstration of the feasibility of reaching temperatures below 1 mK using cryogen-free technology. Our prototype system comprises an adiabatic nuclear demagnetization stage, based on hyperfine-enhanced nuclear magnetic cooling, integrated with a commercial cryogen-free dilution refrigerator and 8 T superconducting magnet. Thermometry was provided by a current-sensing noise thermometer. The minimum temperature achieved at the experimental platform was 600 μK. The platform remained below 1 mK for over 24 h, indicating a total residual heat-leak into the experimental stage of 5 nW. We discuss straightforward improvements to the design of the current prototype that are expected to lead to enhanced performance. This opens the way to widening the accessibility of temperatures in the microkelvin regime, of potential importance in the application of strongly correlated electron states in nanodevices to quantum computing. [ABSTRACT FROM AUTHOR]

We are dealing with the influence of Hopkinson effect on magnetocaloric effect in glass-coated Ni-Mn-In-Co microwires in the given contribution. We have shown that although the entropy change is smaller in low fields, the refrigerant capacity per unit of applied field is three times higher for low field (300 Oe) comparing to that of 30 kOe. This points to the fact that Hopkinson effect can be employed to increase the efficiency of magnetocaloric effect. [ABSTRACT FROM AUTHOR]

A process for permanent magnet (PM) demagnetization control for optimal and reliable flux weakening control in permanent magnet synchronous machines (PMSM) is presented. A physics-based model was developed to estimate the magnetic flux operating point of the PM poles during the operation of PMSM. The model is enabled to dynamically estimate the average and the partial PM demagnetization due to reverse armature field as well as the PM temperature rise. The model is a function of physical geometry and material of the PMSM, physics of demagnetization, and the ambient temperature. The demagnetization assessment and control is verified on a V-type PMSM using the modified FE-based coupled thermal-field-circuit phase variable model and the time step FE analysis. [ABSTRACT FROM AUTHOR]

The conditions for determination of the parameters of the saw-toothed transition under the action of an external magnetic field (process of recording) and under no external field (process of demagnetization) were presented with the use of the effective fields. Examples of calculating the parameters of the saw-toothed transitions for various values of the coercitive force of the magnetic medium at recording under the action of the magnetic field of the thin-film head and during the progress of demagnetization were given. [ABSTRACT FROM AUTHOR]

A generalization of the previously-described positive-feedback theory of first- and second-order reversal curves permits modeling of minor loops of arbitrarily high order n. The validity of the theory is tested by using it to model various types of high-order phenomena (n \geq 3), including symmetrical and asymmetrical spirals as well as closed minor loops, in a variety of different hard and soft ferromagnetic materials that exhibit the return-point memory property. [ABSTRACT FROM PUBLISHER]

Interaction-free measurement (IFM) is a surprising consequence of quantum interference, where the presence of objects can be sensed without any disturbance of the object being measured. Here, we show an extension of IFM using techniques from spatial adiabatic passage, specifically multiple recipient adiabatic passage. Due to subtle properties of the adiabatic passage, it is possible to image an object without interaction between the imaging photons and the sample. The technique can be used on multiple objects in parallel and is entirely deterministic in the adiabatic limit. Unlike more conventional IFM schemes, this adiabatic process is driven by the symmetry of the system, and not by more usual interference effects. As such it provides an interesting alternative quantum protocol that may be applicable to photonic implementations of spatial adiabatic passage.We also show that this scheme can be used to implement a collision-free quantum routing protocol. [ABSTRACT FROM AUTHOR]

Irradiating a ferromagnetic material with an ultrashort laser pulse leads to demagnetization on the femtosecond timescale. We implement Elliott-Yafet-type spin-flip scattering, mediated by electron-electron and electron-phonon collisions, in the framework of a spin-resolved Boltzmann equation. Considering three mutually coupled reservoirs, (i) spin-up electrons, (ii) spin-down electrons and (iii) phonons, we trace non-equilibrium electron distributions during and after laser excitation. We identified the driving force for ultrafast magnetization dynamics as the equilibration of temperatures and chemical potentials between electronic subsystems. This principle can be used to easily predict the maximum quenching of magnetization upon ultrashort laser irradiation in any material, as we show for the case of 3d-ferromagnetic nickel. [ABSTRACT FROM AUTHOR]

The first commissioning of a magnet system for the neutrino beam line in the J-PARC has been performed from January to March, 2009. The magnet system could be cooled down successfully in 9 days. RRRs of all the magnets and joint resistances in the magnet string were measured to be reasonable values. The magnet string composed of 28 superconducting combined function magnets could be excited up to 5000 A after several shutdown tests without a spontaneous quench. A quench protection scheme with a magnet safety system developed by CEA/SACLAY were verified to work properly. As for beam commissioning, the proton beams could pass through the arc section including the superconducting magnet string on the first attempt, and the magnet protection system were verified to work quite well even in a beam induced quench test. [ABSTRACT FROM AUTHOR]

Demagnetization occurring with time in a constant temperature is often assumed to be negligible, provided that the operating point of the magnet is above the knee of the B-H curve. However, because it is important to ensure that no permanent flux losses occur in permanent magnets during their use in industrial applications, there is a clear need to quantify these time-dependent losses. We measured losses over time for four commercial sintered Nd-Fe-B magnet grades at five different temperatures (23 °C-150 °C). We tested samples with three different permeance coefficient (Pc) values for each material. The time-dependent losses measured fitted the logarithmic law of magnetic viscosity well. We demonstrated that the total flux loss in a lifetime of 30 years can be estimated according to the temperature, coercivity of the material, and the permeance coefficient of the magnet. With proper selection of the magnet material, in accordance with the designed Pc of the application, the total flux loss in 30 years can be minimized almost to zero even at 150 °C. [ABSTRACT FROM AUTHOR]

Extremes of precipitation are examined in a wide range of climates simulated with an idealized aquaplanet GCM. The high percentiles of daily precipitation increase as the climate warms. Their fractional rate of increase with global-mean surface temperature is generally similar to or greater than that of mean precipitation, but it is less than that of atmospheric (column) water vapor content. A simple scaling is introduced for precipitation extremes that accounts for their behavior by including the effects of changes in the moist-adiabatic lapse rate, the circulation strength, and the temperature when the extreme events occur. The effects of changes in the moist-adiabatic lapse rate and circulation strength on precipitation extremes are important globally, whereas the difference in the mean temperature and the temperature at which precipitation extremes occur is important only at middle to high latitudes. [ABSTRACT FROM AUTHOR]

The variation characteristics of flux density and field intensity of trapezoidal permanent magnets (PM) in the variable-flux memory motor (VFMM) under different demagnetizing magnetomotive forces are analyzed using the finite element method. A prototype machine is fabricated and tested. Good agreement between the calculated and experimental results is achieved. It confirms the easy controllability of air gap flux of the developed VFMM with trapezoidal PMs. [ABSTRACT FROM AUTHOR]

Nanofabricated islands in bit patterned media (BPM) for magnetic data storage tend to vary in shape, size, and material properties which leads to variations in switching fields, causing write errors. In a working system, write errors will be rare, and therefore, an efficient analytic model is preferable to a micromagnetic model. An analytic model has been developed that calculates magnetometric (volume averaged) demagnetizing factors and predicts switching fields for different island shapes, particularly islands that can be described as truncated elliptic cones, since variants of this geometry can represent real islands. The model has been shown to agree well with micro-magnetic simulations for various island shapes with fields at various angles to the perpendicular. Switching field calculations reveal that 4: 1 aspect ratio islands may be more prone to adjacent track erasure compared to those with lower aspect ratios and that islands with slanted side walls were easier to reverse compared to cylindrical ones. [ABSTRACT FROM AUTHOR]

Extensive applications of YBCO tapes claim for a comprehensive knowledge of their behavior in every possible operating condition. In particular, one of the main topics to explore is the tape stability against heat and current disturbances, in terms of minimum quench energy and normal zone propagation velocity (NZPV). In this work we present the results of NZPV measured in a 35 cm long YBCO coated conductors manufactured by SuperPower Inc. The tape is cooled by means of a cryocooler and kept under vacuum in order to achieve near-adiabatic conditions. Two independent heaters are positioned on the tape: one on the YBCO side and the other on the substrate side. The quench is monitored by recording the voltage and the temperature evolution along the tape. The NZPV, at 77 K, reaches a value larger than 2.5 cm/s for a bias current I = 50 A which represents the 56% of the critical current value. The quench dynamics of the tape are discussed with the help of a simulation program based on the finite difference discretization of the tape with the Fourier's heat equation: the model is able to reproduce the experimental behavior. [ABSTRACT FROM AUTHOR]

Micro-X is a sounding-rocket experiment that will combine a transition edge sensor (TES) microcalorimeter array with an imaging mirror to obtain high-spectral-resolution images of astronomical X-ray sources. The instrument's resolution across the 0.3-2.5 keV band will be 2 eV. The first flight will target the region of the Bright Eastern Knot of the Puppis A supernova remnant and is slated for January 2011. The obtained high-resolution X-ray spectra will be used to ascertain the temperature and ionization state of the X-ray-emitting gas and to determine its velocity structure. The TES array is read out bya time-division superconducting quantum interference device (SQUID) multiplexing system. The detector front end assembly and the SQUID multiplexing circuit are cooled to the operating temperature of 50 mK with an adiabatic demagnetization refrigerator (ADR). The design of this refrigerator is tailored to the requirements of rocket flight. Stable operation of the TES array close to the ADR magnet will be achieved with a magnetic shielding system, which will be based on a combination of a bucking coil and high-permeability and superconducting shield materials to cancel out residual fields. We describe our progress in developing the Micro-X instrument. [ABSTRACT FROM AUTHOR]

Continuous thermal demagnetization, in which measurements of magnetization are made at high temperature T during heating, is considerably faster than the conventional palaeomagnetic method of stepwise demagnetization, in which measurements are made at room temperature T0 in a series of cooling-reheating cycles. In the case of single-domain (SD) grains, the two methods give equivalent results after the continuous measurements are converted to equivalent room-temperature values by correcting for the reversible decrease of spontaneous magnetization MS between T0 and T. To test for equivalence of the two methods in larger pseudo-SD and multidomain grains, three different samples containing magnetite of different grain sizes and origins were heated in zero magnetic field and measurements taken either continuously at T during heating or at T0 after a set of cooling steps from T. Two samples contained 100–125 μm (mean 110 μm) and 125–150 μm (mean 135 μm) sieve fractions from a crushed natural crystal of magnetite, while the third sample is a natural diabase core sample containing coarse magnetite in the dark minerals and groundmass and fine magnetite in the plagioclase. Two different vibrating-sample magnetometers were used for continuous demagnetization and a mini-furnace and SQUID magnetometer were used for stepwise measurements. Both total thermoremanent magnetization (TRM) and partial TRMs with non-overlapping blocking temperatures ( TC, TI) and ( TI, T0) were demagnetized. The Thellier laws of partial TRMs are approximately although not exactly obeyed. In MS( T)-corrected continuous data, there is little overlap of unblocking temperatures: pTRM ( TC, TI) demagnetizes almost entirely above TI and pTRM ( TI, T0) almost entirely below TI, demonstrating reciprocity and independence. The stepwise measurements decrease more rapidly in intensity with increasing T than the corrected continuous results, some of which increase slightly with heating up to T≈ TI. Some additional decay of magnetization must occur during cooling from T, where the continuous measurement is made, to T0, where the stepwise result is measured. There are no high-temperature measurements of subsidiary cooling-heating cycles to confirm this deduction, but continuously recorded heating-cooling cycles below room temperature in inverse thermal demagnetization (or low-temperature demagnetization) show both reversible and irreversible features, depending on the remanence tested. The most important conclusion of this study is that MS( T)-corrected continuous demagnetization results do not exactly reproduce measured stepwise demagnetization results except for very fine grains, of SD size or close to it. Continuous thermal demagnetization cannot be used in general as a time-saving alternative to stepwise demagnetization if exact equivalence is required. [ABSTRACT FROM AUTHOR]

The tangent linear and adjoint of an adiabatic version of the Weather Research and Forecasting (WRF) Model with its Advanced Research WRF (ARW) dynamic core have been developed. The source-to-source automatic differentiation tool [i.e., the Transformation of Algorithm (TAF) in FORTRAN] was used in the development. Tangent linear and adjoint checks of the developed adiabatic WRF adjoint modeling system (WAMS) were conducted, and all necessary correctness verification procedures were passed. As the first application, the adiabatic WAMS was used to study the adjoint sensitivity of a severe windstorm in Antarctica. Linearity tests indicated that an adjoint-based sensitivity study with the Antarctic Mesoscale Prediction System (AMPS) 90-km domain configuration for the windstorm is valid up to 24 h. The adjoint-based sensitivity calculation with adiabatic WAMS identified sensitive regions for the improvement of the 24-h forecast of the windstorm. It is indicated that the windstorm forecast largely relies on the model initial conditions in the area from the south part of the Trans-Antarctic Mountains to West Antarctica and between the Ross Ice Shelf and the South Pole. Based on the sensitivity analysis, the southerly or southeasterly wind at lower levels in the sensitivity region should be larger, the cyclone should be stronger, and the atmospheric stratification should be more stable over the north slope of the Trans-Antarctic Mountain to the Ross Ice Shelf, than the AMPS analyses. By constructing pseudo-observations in the sensitivity region using the gradient information of forecast windstorm intensity around McMurdo, the model initial conditions are revised with the WRF three-dimensional variational data assimilation, which leads to significant improvement in the prediction of the windstorm. An adjoint sensitivity study is an efficient way to identify sensitivity regions in order to collect more observations in the region for better forecasts in a specific aspect of interest. [ABSTRACT FROM AUTHOR]

We describe an analytical technique for assessing the risk of partial demagnetization in tubular permanent-magnet (PM) machines. The technique establishes analytical expressions for the open-circuit and armature reaction fields in the cylindrical coordinate system and superposes the fields in the permanent-magnet regions to determine the extent to which the magnets may be partially irreversibly demagnetized. We have applied the technique to a quasi-Halbach magnetized tubular PM machine equipped with a modular stator winding, and have validated the predictions by finite-element analysis. We found that partial demagnetization may occur even under an open-circuit operating condition when the machine is operating at high temperature. We propose alternative Halbach magnetization distributions that improve the demagnetization withstand capability. The analytical technique provides a computationally efficient tool for identifying regions that are prone to partial demagnetization and for assessing the consequences. It enables the risk of demagnetization to be fully assessed at the design stage so as to achieve a robust machine, particularly when operating in harsh environments. [ABSTRACT FROM AUTHOR]

A Landau-Lifshitz-Gilbert (LLG) micromagnetic analysis using a parallelized program on a PC cluster is investigated. In the analysis, the whole magnetic material is treated micromagnetically using the LLG equation. The fast Fourier transform (FFT) algorithm is incorporated in the head region in addition to the medium region to derive the demagnetization field and the program is parallelized using the message passing interface (MPI). The PC cluster system with 8 CPU has achieved a calculation speed 4800 times faster than our original program on a single 64-bit processor system. Quasistatic field distributions for a single-pole type (SPT) are derived and the accuracy is validated by comparison with the finite-element method (FEM). Finally, dynamic responses are derived for various head structures and materials. [ABSTRACT FROM AUTHOR]

Abstract  The present work investigates the characteristics of adiabatic two-phase flow, and compares the flow distribution in two different multi-channel configurations. One is a standard straight channel design, and the second is similar, except that it has two cross-linked paths located at one-third and two-thirds of the channel length. Each test section consists of 45 rectangular channels with a hydraulic diameter of 1.59 mm and is fabricated out of acrylic to enable flow visualization. The test facility operates with water and air as the working fluids. Gas and water superficial velocities range from 0.03 to 9.93 and 0.04 to 0.83 m/s, respectively, corresponding to a flow quality between 0 and 0.25, whereby the mass flux range is from 41 to 834 kg/m2s. Four channels were selected for flow distribution tracking, and the results showed that the straight and cross-linked designs both have unequal flow distributions. Flow patterns are presented in terms of a fractional time function to gain insight into the flow characteristics. Compared to a single channel flow regime map, the intermittent flow regime was observed 65 to 85% of the times expected, whereas the dispersed flow regime only occurred ∼40% of the times expected for both designs. Further discussion on flow distribution and flow patterns are also documented. [ABSTRACT FROM AUTHOR]