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This paper is a study on the application position of skew in order to reduce the cogging torque of a magnetic geared synchronous motor (MGM). The cogging torque affects the noise and vibration of the motor, so it should be reduced as much as possible. To solve this problem, a conventional permanent magnet (PM) synchronous motor is skewed to a PM. However, unlike other synchronous motors, the MGM has pole pieces (PPs), and a larger cogging torque is generated due to a larger reluctance difference. There have been few studies on the reduction of cogging torque of MGM, so it is essential to study the skew structure of MGM. Therefore, this paper has derived the optimum skew method by comparing and analyzing three models of MGM skewed to PM, PP, and PM and PP simultaneously. [ABSTRACT FROM AUTHOR]

This paper presents the reduction of noise and vibration concerning the magnetostriction effects for a single-phase power transformer with a large capacity of 200 MVA. Two magnetic core shapes are investigated: 1) D-yoked core and 2) square-yoked core. The D-yoked core is used for the construction of the transformer prototype in this paper. The magnetostriction and the hysteresis loop of the core material are measured for the simulation and analysis of noise and vibration. The transformer prototype is assembled with an external clamping force applied on the core, and the core vibration and sound-level are observed. The transformer operates with a periodic excitation that may induce resonance in the core. To avoid this, a finite-element analysis is used for modal analysis to identify the natural frequencies of the core. A tank is also designed with a sufficiently rigid structure to avoid resonances. The sound-level of the fully assembled transformer prototype is measured, and it is found to have a low-noise level below 65 dB. [ABSTRACT FROM AUTHOR]

In some situations, only a limited number of measurements under a limited number of conditions may be available for analysis. This paper describes an approach for creating additional interpolated measurements in which both measurement noise as well as signal have appropriate values. This is important, for example, when evaluating the behavior of advanced readback channels where quantities, such as sector failure rate (SFR), change very abruptly from 0% to 100% in response to relatively small parameter changes. This means that a smooth interpolation of SFR between coarse measurement points is little help in determining the actual boundary of good performance. If, instead, interpolated waveforms are fed into the channel, the boundary of the region of good performance can be clearly identified. This paper formulates a solution for the general problem of noisy measurement (waveform) interpolation and then applies this approach specifically to the situation, where a series of spin-stand waveforms were captured at various reader positions and with various written track squeeze positions (i.e., a set of “747s”). Using this approach, realistic waveforms can now be created and the SFR evaluated at any arbitrary intermediate reader and writer positions. [ABSTRACT FROM AUTHOR]

This paper examines the improvement in performance of rotated and normally oriented heads by using the quasi-cyclic low-density parity-check (QC-LDPC) code in a two-dimensional magnetic recording (TDMR) system. This paper indicates that the significant improvement in performance in the rotated head compared to the normally oriented head can be attributed to the larger amplitude of its dibit response and the reduced overlap between conditional probability density functions. Simulation also indicates that maximum areal densities of 9.85 T/in ^2 and 6.64 T/in ^2 can be reached by the rotated head array (RHA) and normally oriented head array (NHA) at optimum bit aspect ratios of 0.67 and 3.5 for 5.5 nm Voronoi grains, respectively. After decoding, the performance of the NHA is about 8.5 dB worse than the RHA. With an oversampled signal, 2-D linear minimum mean-squared error (LMMSE) equalizer and LDPC codes, a user bit density near 10 Tbits/in ^2 is feasible for a rotated head array. [ABSTRACT FROM AUTHOR]

This paper focuses on the development of an algorithm for the prediction of transformer core deformation, using a fully coupled magneto-mechanical approach. An imposed magnetic flux method coupled with finite-element modeling is employed for the magnetic resolution. The constitutive law of the material is considered with a simplified multi-scale model describing both magnetic and magnetostrictive anisotropies. Magnetostriction is introduced as an input free strain of a mechanical problem to get the deformation and displacement fields. A 3-D estimation of acoustic power is carried out to evaluate the global core deformation and acoustic noise level. The numerical process is applied to a three-phase transformer made of grain-oriented FeSi core, leading to a set of noise estimation for different flux excitations and core geometries. [ABSTRACT FROM PUBLISHER]

Cobalt-rich amorphous wires have been extensively used as a core of many types of magnetic field sensors, notably of a fundamental model orthogonal fluxgates, because they allow us to manufacture sensors with very low noise. However, commercial wires are available only in one diameter, namely, $125~\mu \text{m}$ ; therefore, most of the literature is always referred to this diameter. In this paper, we investigated the effects of different diameters versus the noise of the sensor. Our purpose is to understand that if there is a room for improvement of noise by producing amorphous wires with different diameters. We casted wires with (Co0.94Fe0.06)72.5Si12.5B15 composition and a diameter spanning from 80 to $220~\mu \text{m}$ , and we discovered that the wires show crystalline structure starting from $200~\mu \text{m}$. This means we can increase the diameter to values higher than $125~\mu \text{m}$ and still achieve an amorphous structure, considering the upper limit of $200~\mu \text{m}$. Then, we studied the noise of the sensors based on wires with three different diameters, namely, 80, 120, and $175~\mu \text{m}$. Because the diameter affects the demagnetizing factor, we also changed the length of the wire in the range from 40 to 120 mm. We discovered that increasing the diameter of the wire always decreases the noise, regardless of the demagnetizing effect, which indicates larger cross section of the wire is a predominant factor. [ABSTRACT FROM AUTHOR]

The total noise level of transformers is mainly influenced by harmonics in load current. The reasons are the interaction of harmonics with large load current at power frequency and the rising sound radiation efficiency with frequency. It is noted that the dynamic vibration behaviors under load harmonics operation are important to decrease the equipment noise. This paper mainly studies the vibration noise effects of three-phase three-leg transformer with the load of wireless power transfer (WPT) system, which would bring harmonics in the load current. Accelerometer sensors were arranged on the surface of the cores and windings of the transformer. Then, the vibration was measured in different positions of a transformer under the power of WPT system from 0 to 20 kW. The spectral distribution of vibration was obtained through the fast-Fourier transform analysis of the acquisition signals. The experimental results with and without PWT load imply that the harmonics in load-current have great effect on the vibration noise. It is to conclude that the main several harmonics of load current should be eliminated to reduce the vibration noise level. [ABSTRACT FROM AUTHOR]

Barkhausen noise emissions occur in ferromagnetic materials on application of an externally varying magnetic field. These emissions primarily occur due to the presence of pinning sites or discontinuities within a material which act as inhibitors to domain wall motion. Overall, Barkhausen noise emissions can capture variations in microstructure, chemical composition, lattice strain, and grain size, and can detect the presence of residual stresses in materials. In this paper, the Barkhausen noise response for a Jominy end-quench test steel sample is examined. Microstructural variations in the form of constituent phases, such as martensite, bainite, pearlite, or ferrite, can be detected via changes in Barkhausen noise signatures. Through Barkhausen noise measurements, it is observed that characteristic peaks corresponding to different phases appear in the spectrum. The characteristic peaks become distinct when the contribution to Barkhausen noise from individual phases becomes significant. This analysis method may be further used to monitor microstructural evolution, and thus understand the contributions of constituent phases to material properties. The technique may be used as a potential tool for the nondestructive evaluation of ferromagnetic materials employed in industrial applications. [ABSTRACT FROM AUTHOR]

Noise in tunneling magnetoresistive (TMR) read heads play an important role in magnetic recording. Extensive studies were carried out in understanding thermal magnetic noise in the TMR heads. The thermal noise is mostly attributed to the synthetic antiferromagnet in the TMR sensor. In this paper, we have studied the noise generated in the TMR sensor due to instabilities in the free layer using the magnetic field generated from the media dc-pattern of different polarities, and propose a test to study the read sensor instability caused by defects in the free layer. The influence of write noise from the written tracks created by the single-pole writer on the TMR sensor reader is also studied. [ABSTRACT FROM AUTHOR]

The shingled magnetic recording (SMR) system is influenced by not only jitter-like medium noise from adjacent bits in the down-track direction but also intertrack interference (ITI) from the adjacent tracks. In this paper, we investigate the relationship between the recording pattern and the decoding reliability by classifying the log-likelihood ratio at the a posteriori probability decoder output according to the recording patterns under an SMR R–W channel specification of 4 Tb/in2 by computer simulation. The result shows that the decoding reliability for the recording pattern “010” heavily affected by transition jitter is the lowest and little improved even if the influence of ITI is mitigated by a 2-D finite-impulse response filter. [ABSTRACT FROM AUTHOR]

In this paper, we propose a general write channel model for bit-patterned media recording by adding physically justifiable noise and feedback to the previously studied model. First, we study the noisy writing process by discussing several sources of errors causing some extra disturbances during the write process, in addition to data-dependent write synchronization errors that were studied before. Then, for this generalized model with various input and state distributions, we obtain information rate lower and upper bounds including the previous bounds as special cases. Second, a simplified feedback in the proposed channel is considered which stems from the special features of writing, and the behavior of this channel is analyzed in response to the feedback and compared mathematically and numerically with the situation, at which the feedback is ignored. [ABSTRACT FROM AUTHOR]

Two-dimensional magnetic recording (TDMR) was proposed in 2008 as a means of pushing beyond 1 Tbit/in ^2 areal-density yet staying with relatively conventional magnetic components. A density of approximately 1 Tbit/in ^2 is considered to be the limit for conventional perpendicular magnetic recording. The original concept for TDMR has evolved greatly since it was originally proposed. This evolution has occurred as more information has become available about the characteristics of shingled tracks and 2-D read-back signals and as constraints have become apparent in the implementation of recording components and electronics. With today’s technology, the projected gains are smaller than originally envisioned. As a very practical first step that introduces TDMR and provides modest gains without incurring undue complexity or cost, this paper focuses on the idea of a stacked two-element reader operating on shingled magnetic recording tracks and a two-input equalizer feeding a standard data detector. The dual-reader gains are assessed based on combining waveforms captured from a single reader at many off-track positions, track-pitches, and radii. [ABSTRACT FROM AUTHOR]

This paper presents the results of a comprehensive study of the shingled writing process and various signal processing and data detection approaches applied to the readback waveforms. The recording simulations include realistic head fields, a random granular media, magnetostatic and exchange interactions, and a READ head sensitivity function. Readback waveforms are examined in both one and two dimensions in terms of signal characteristics (linear and nonlinear), noise behavior (stationary and signal-dependent), and intertrack interference. Different equalization and detection approaches are compared and about a 10% density gain is reported for such 2-D magnetic recording compared with traditional single-track recording. These gains depend strongly on the number of readers, the reader positioning, and the reader width. [ABSTRACT FROM AUTHOR]

Phase change memory (PCM) is a new solid-state memory technology that promises disruptive changes in the way servers and enterprise storage systems are built. Multilevel-cell (MLC) storage is highly desirable for increasing capacity and thus lowering cost-per-bit in memory technologies. In PCM, MLC storage is hampered by noise and resistance drift. In this paper, the issue of reliability in MLC PCM is addressed. A statistical model is developed that captures the main impairments in MLC PCM cell-arrays. A signal processing and coding framework is then introduced that provides robustness to drift and noise, improving reliability and prolonging data retention. Several examples of codes are provided and practical detection schemes are described. [ABSTRACT FROM AUTHOR]

Shingled magnetic recording (SMR) with 2-D magnetic recording has recently emerged as a promising technology to sustain the growth of magnetic storage areal density. However, with the reduction of track pitch, the intertrack interference (ITI) becomes a major impairment. Furthermore, in SMR, the ITI is non-uniform among the top and lower tracks. A 2-D read channel which makes use of an array of read heads can effectively detect and compensate the severe ITI. In this paper, based on a read-array SMR channel model with non-uniform ITI, a shuffled multi-track detection (SMTD) detector, which shuffles and propagates the most reliable extrinsic information among the upper, lower, and middle detectors, is proposed to mitigate ITI more effectively. With the optimized non-binary low-density parity-check code, the performance of the proposed SMTD over the read-array SMR channel is evaluated. [ABSTRACT FROM AUTHOR]

In a perpendicular recording environment, when reading at an offtrack position, the head can experience a local field in the longitudinal direction from the written track. This field can change head sensitivity depending on the polarity of the written magnet and the offtrack direction. This effect is particularly strong when reading null servo position error signal (PES) pattern, where two adjacent servo tracks are written with opposite polarity. This paper studies the effect of this longitudinal field on the PES signal using a spin stand, which permits multiple PES patterns to be evaluated side-by-side. The result shows that the effect can distort the PES linearity. The extent of its impact depends on the servo PES transition density and head design. As a result, design compromise must be made. [ABSTRACT FROM AUTHOR]

In this paper, we present a new material stack for planar Hall effect bridge (PHEB) sensors and a detailed investigation of the sensitivity and noise properties of PHEB sensors made from these. The sputter deposited material stack was based on a ferromagnetic (FM) NiFe sensing layer surrounded by two layers of anti-FM IrMn. This material stack enables implementation of a thick NiFe layer without loss of sensitivity. We present an improvement in detectivity in the PHEB by changing the shape and the materials of the corners between the sensors in a meander shape. A significant reduction of noise also comes from the thick NiFe layer, due to the reduced resistance of the sensor. [ABSTRACT FROM AUTHOR]

This paper presents an inductance derivative estimation method of linear switched reluctance actuator (LSRA) employing tracking-differentiating technology. The inductance of LSRA is highly nonlinear and varies with phase current and translator position. To achieve direct force control, the derivative of inductance must be estimated to generate required phase currents. The inductance profile of LSRA is obtained from finite element analysis calculation. Tracking differentiator is introduced to track the inductance and its derivative for further control purpose. A simple Proportional-Integral control with compensation unit using the estimated inductance derivative is used to examine the effectiveness of the estimation of inductance derivative. [ABSTRACT FROM AUTHOR]

This paper investigates acoustic noise when an electric motor is fed with three-phase pulsewidth-modulated (PWM) currents with varying modulation indices. The procedure involves using a data-driven process to create a design space for different geometries of an interior permanent magnet synchronous motor. The motor structures are then analyzed using a finite-element analysis package to extract knowledge related to the sound pressure levels from the PWM excitation. It is demonstrated that sampling the air-gap space at a single time instant, which is a routine procedure in acoustic noise calculations, can result in an inaccurate estimation of the sound pressure levels, especially when the noise source is PWM motivated. Multiple-time sampling over the electrical period is proposed as a better approach for analyzing the sound pressure levels, irrespective of the type of supply current quality. [ABSTRACT FROM AUTHOR]

In this paper, we present a technique of noise analysis for perpendicular and shingled magnetic recording that is variance centric, i.e., with analysis focused on noise power. Measured noise from a home track viewpoint is decomposed into electronic noise, transition noise, nontransition noise, and inter-track interference components. The separation of media noise into transition and nontransition noise components is accomplished by a variance deconvolution technique. Experimental noise analysis is shown for cases of track squeeze, adjacent track erasure, and read head offset. Potential capacity gains are also assessed for the case of electronic noise improvement. [ABSTRACT FROM PUBLISHER]

A flux-reversal permanent magnet (FRPM) machine typically suffers from unfavorably large cogging torque due to its special doubly salient structure and high air-gap flux density, resulting in undesired torque and speed ripples, as well as acoustic noise and vibration, especially at low speeds. Therefore, an improved configuration of FRPM machines by introducing a small space-gap between the two adjacent magnets belonging to the same stator tooth is proposed in this paper. The analytical expression of cogging torque taking this small space gap into consideration is derived, and furthermore, the optimal dimensions of the space gap are obtained analytically for cogging torque minimization. In addition, the influences of the space-gap-based configuration on key electromagnetic performances, including cogging torque, back electromotive force, and electromagnetic torque, are investigated by both 2-D finite-element analysis and experimental results. It turns out to be that by employing this configuration, not only the cogging torque, and hence, torque ripples can be suppressed, but also the electromagnetic torque can be improved. [ABSTRACT FROM AUTHOR]

Signal processing in TDMR encounters several challenges such as read channel modeling and detection in the presence of severe two-dimensional intersymbol interference (2-D ISI). The contribution of this paper is twofold. 1) In this paper, we introduce a novel 2-D read channel model which we call the 2-D Microcell model. In this model, we use generalized 2-D microtracks called microcells to captures the properties of irregular grain boundaries of the medium in a relatively simple yet accurate manner. The data dependent noise (DDN) distributions are analytically derived for this model. The derivation of the DDN distributions makes the 2-D Microcell suitable for detector design purposes. 2) We propose a new framework for designing truly two-dimensional detectors for the Microcell model based on near-optimal generalized belief propagation (GBP). The GBP algorithm is purposefully applied for detection in this model in order to handle the data dependent media noise which is caused by irregular bit transitions in both dimensions. Results are provided to show that the incorporation of the DDN distributions into the GBP detection helps improving the detection performance. [ABSTRACT FROM AUTHOR]

It has been shown that annealing of amorphous magnetic wire used as a core for orthogonal fluxgates in the fundamental mode can significantly decrease the noise of the sensors in the $1/f$ region. This is due to an increase in the circumferential anisotropy due to the dc current flowing through the wire during annealing. This method, however, presents some drawbacks: first, it requires an infrared furnace and precise compensation of the magnetic field inside it. Second, it is very slow, because it requires the cooling of the whole furnace before removing the wire. Most importantly, while the $1/f$ noise decreases, the noise floor increases. In this paper, we present a method that allows the simultaneous reduction of $1/f$ noise and noise floor. This method is based on Joule annealing by means of a very large current in the wire. The current is periodically flipped with 0.25 Hz frequency in order to avoid an excessive increase in the offset. The annealing is performed in a four-layer shielding to avoid the presence of an external dc field. Annealing for 1 min, 1 wire-based sensor returned a considerable noise reduction both in the $1/f$ regions from 2.5 to 1.5 $\text {pT}/\sqrt {\mathrm{ Hz}}$) while the noise floor was unchanged at $650~\text {fT}/\sqrt {\mathrm{ Hz}}$. For larger annealing time, however, the noise floor rose. We tried to compensate this problem by increasing the number of wires to four, but also in this case, we achieved the best noise reduction (from 1.7 to $0.75~\text {pT}/\sqrt {\mathrm{ Hz}}$ at 1 Hz and from 470 to $350~\text {fT}/\sqrt {\mathrm{ Hz}}$ noise floor) with 1 min annealing. By the use of thermocamera, we discovered that the problem of long-time annealing was that the sensor head support was warming up too much. Therefore, we repeated the experiment by annealing 21 min as a series of 1 min annealing followed by 3 min of no current for 21 times to let the sensor head totally cool to room temperature after every annealing period. In this way, we achieved the lowest noise of 630 $\text {fT}/\sqrt {\mathrm{ Hz}}$ at 1 Hz and $400~\text {fT}/\sqrt {\mathrm{ Hz}}$ noise floor. [ABSTRACT FROM AUTHOR]

The noise generated by rotating machines and electrical transformers is harmful and its reduction has been the subject of several studies. Such systems are likely to come into resonance and become noisier. This resonance may come from mechanical or magnetic forces. The phenomenon of resonance is usually studied only if the frequency and the known spatial distribution of the excitation force are consistent with the natural frequency and the shape of the corresponding mode of the structure. We demonstrate in this paper that magnetostriction can induce resonance without, however, knowing its spatial distribution. A ferromagnetic frame made of a stack of non-oriented electrical steel (e.g., low-power transformers for railway applications) is used to confirm that mechanical resonance can be induced by magnetostrictive strain at a very low magnitude in in-plane and out-of-plane directions. Finite-element calculations are performed with laminated model and vibratory measurements are presented. A numerical model based on homogenization technique is also detailed. Then, experimental and computation results are analyzed and compared. Finally, results of resonance under magnetization when double the magnetizing frequency matches the resonance frequency of the ferromagnetic frame are described as well as the corresponding spectrum. [ABSTRACT FROM AUTHOR]

Optimal design techniques, which consist of numerical analysis and optimization technique, are commonly used for enhancing the efficiency and for reducing the noise of electromagnetic device. In the optimal design techniques, it is required that the exact solution of the analysis and the precise characteristic of the electromagnetic devices should be obtained. However, usually it is impossible to make the exact mod!! of an electromagnetic device and to remove the numerical error of the numerical analysis. This is one of the reasons why the optimal design techniques has not been more widely utilized. In this paper, a new concept for optimal design considering the accuracy of the analysis is proposed. The proposed optimal design method considers the accuracy of the analysis and indicates multiple solutions. To verify its usefulness, in this paper, an example using the proposed method is shown. [ABSTRACT FROM AUTHOR]

Some classes of bone fractures are routinely stabilized and aligned by the use of intramedullary nails. The identification of the pose, i.e., the position and the orientation of the drill holes hidden by a bone and the tissue is currently obtained by X-ray with all the well-known disadvantages of this technology. The idea of substituting this methodology with an eddy-current-based one has been explored in the previous work, but, in spite of interesting features, the developed technique suffered from some shortcomings. In this paper, we propose a novel technique that is very computationally efficient and provides real-time identification performance. [ABSTRACT FROM AUTHOR]

This paper proposes Ag–Fe3O4 films as a novel noise absorption material for the microstrip transmission line to replace current magnetic materials. The effect of the Ag–Fe3O4 films on a microstrip transmission line for high-frequency noise absorption is discussed. Ag–Fe3O4 films were prepared using the spin-coating technique and deposited on FR4 substrates. The film thickness was approximately 25–75 \mu \textm and sheet resistance was controlled in the range of 450–150 $\Omega $ . Crystal structures of Ag–Fe3O4 films were conducted using the X-ray diffraction technique. The radio frequency properties of these films were measured using an Agilent Technologies E8364A vector network analyzer in the frequency range of 1–20 GHz. The experimental results show that the composite sheet in the broadband frequency region effectively absorbs the electromagnetic noise, exhibiting a power loss greater than 70% in the frequency range of 6–20 GHz. [ABSTRACT FROM AUTHOR]

In low- to medium-power-rated brushless machines, noise of electromagnetic origin is generally prevailing over mechanical and aerodynamic sources. The appropriate combination of pole and slot of a permanent magnet synchronous motor is one of the keys to its performances among which stands noise reduction. This paper investigates configurations regarding this aspect for distributed overlapping and single-layer concentrated nonoverlapping winding configurations. Chosen combinations are 8 poles 48 slots (8p48s), 8p72s, 46p48s and 50p48s. The air-gap flux density is obtained by 2-D finite element analysis (FEA), allowing to compute the electromagnetic pressure. It then serves as input of mechanical and acoustical 3-D FEA models of the stator with carter. [ABSTRACT FROM PUBLISHER]

This paper presents an enhancement of high spacial resolution magnetic probe for the applications of measuring magnetic fields emitted from cryptography micro-electronic devices. The on-chip sensing system includes a magnetic pick-up coil, three-stage low-noise amplifier, mixer, and low-pass filter. Noise problems are reduced by the proposal of using the down-conversion mixer. A two-step removal of Si-substrate (Si-SUBS) areas is also proposed by applying a focused-ion-beam process to avoid eddy currents that reduces the coil sensitivity. Four probe chips are fabricated in a 0.18 \mu m CMOS five-metal layer process with different coil sizes and with/without Si-SUBS removals. Experimental results on a thin wire and micro-strip line show the proposed system achieves high spacial resolution and sensitivity for near-field magnetic scanning. [ABSTRACT FROM AUTHOR]

This paper investigates dynamical behavior of magnetic Barkhausen noise (BN). The measurements were performed for a soft mild steel at controllable magnetizing conditions: 1) the fixed sinusoidal/triangular waveforms of the magnetic induction or 2) the surface magnetic field. Two vertically mounted Hall sensors were used for direct determination of the sample magnetic field. The BN was detected locally by a surface-mounted coil. A typical two-peak shape of the BN envelope was found to reduce to a usual single-peak profile at the constant field rate. These two peaks were shown to correspond to the regions of the magnetic domain reconfiguration preceding and following the rapid magnetization reversal at the coercive field. In ac magnetizing frequency range of 0.2–30 Hz, the BN parameters followed a nearly square root dependence on the frequency. A low-frequency component of the BN signal, approximately up to 25 kHz, was revealed to contain an important part of the micromagnetic information. [ABSTRACT FROM AUTHOR]

This paper presents a new algorithm for the onboard calibration of three-axis magnetometers under noisy environment. The ordinary least squares (OLS) estimator is inconsistent for ellipsoid fitting problem. Proper corrections of the OLS estimator are derived, which can provide a consistent solution to the magnetometer’s calibration parameters without noise preknown. Simulation and experimental results are presented and discussed, supporting the application of the algorithm in the noisy platform. [ABSTRACT FROM AUTHOR]

Shingled writing eliminates the writer width limitation and enables further bit aspect ratio reduction to extend the areal density growth of current perpendicular magnetic recording. The achievable track density of shingled magnetic recording (SMR) is determined by the reader width rather than the writer width. However, continuously scaling of reader width increases the reader resistance and results in higher reader noise. It would be an issue to maintain enough signal-to-noise ratio of reader. The 2-D magnetic recording (TDMR) was proposed to extend the density growth by advanced signal processing technique. In TDMR configuration, there are multiple readers to read multiple tracks simultaneously. Recently, the TDMR reader was proposed as a solution of intertrack interference cancelation, which allows to use wider reader to reproduce signals from narrow tracks. In this paper, an additional reader noise is observed when the reader was positioned to read two tracks at the same time. The formation of the reader sensor appears to be closely related to the current reader structure with hard bias magnet. This issue highlights that a solution is required to enable TDMR, probably a reader structure without hard-biased. [ABSTRACT FROM AUTHOR]

The standard of Japan Electronics and Information Technology Industries Association EM-4502, in which the shielding factor (SF \(_{o}\) ) of magnetically shielded rooms (MSRs) for the uniform magnetic field can be estimated using coils within 10% error for the extremely low-frequency region of <1 Hz without eddy current effects, has been already published. In this paper, to establish standard methods for evaluating SF for low-frequency region using coils, the effects of the setting method, size, and distance from MSR of the coils on SF are investigated by a linear eddy current analysis of an actual MSR made of copper and permalloy plates. It is shown that the coil should be placed in front of the door, and a much larger estimation error than 10% should be permitted for practical use in a standardization to estimate SF \(_{o}\) for low frequency. Moreover, a method of estimating not only SF \(_{o}\) but SFs as well when the noise source is close to MSR should be added in a standardization. [ABSTRACT FROM AUTHOR]

In a permanent magnet brushless (PMBL) motor, any special structural design in the stator lamination may induce asymmetry in the magnetic circuit to result in intrinsic imbalanced force. Likewise, an asymmetrical phase winding arrangement may also induce imbalanced force in the motor when the armature currents are flowing. This paper presents the analysis of the imbalanced forces of two PMBL motors in an electric coolant pump system with magnetic and/or electric asymmetries using both numerical simulation and prototyping test. The results confirm the validity of force calculation method and illustrate the contributions of magnetic and electric asymmetries to the imbalanced forces in PMBL motors. [ABSTRACT FROM AUTHOR]

One of the sources of fluxgate noise is the noise originating in the magnetic core. Several parameters, such as anisotropy and shape, are traditionally studied and optimized to reduce the noise. In this paper, we show how the magnetostriction influences the noise of the fluxgate. We electroplated NiFe thin-film over a copper layer using different current density. By energy-dispersive X-ray spectroscopy we show that the mutual percentage of Fe and Ni in the film depends on the current density. As a result the magnetostriction is changed from negative to positive values, with minimum magnetostriction found at around Fe19Ni81 composition. When we used these ring cores as base for a fluxgate we observed that the noise rapidly rises as the absolute value of magnetostriction increases, while the minimum noise is achieved at lowest value of magnetostriction. An increase of one order of magnitude of the magnetostriction causes and increment of almost two orders of magnitude in the noise. Therefore, we conclude that it is vital to employ alloys with the lowest possible magnetostriction as core for fluxgates. [ABSTRACT FROM AUTHOR]

In this paper, we study the possibility to exploit the noise correlation in a fundamental mode orthogonal fluxgate used as a gradiometer in order to maximize the noise suppression. We study the correlation of the noise along a single core fluxgate using two short coils at a variable distance, and we derive how it drops as the distance increases. Furthermore, we observed this phenomenon with the central point of the coils located at different parts of the wire, obtaining a similar behavior. This implies that the noise propagates in the core in a similar fashion, and—most important—that any mechanism taking advantage of the noise correlation to suppress noise can be replicated along the whole length of the core. We have also investigated the dependence of the noise correlation on the ac component of the excitation current, finding out that in the range where the 1/f noise of the magnetometer does not significantly change larger excitation current increases the correlation thus must be preferred as it allows better noise suppression when used as a gradiometer. Next, we verified that the noise suppression mechanism based on correlation does in fact return lower noise at higher correlation verifying that it matches with the expected values. Finally, we proposed a new configuration of the gradiometer where instead of two long coils we use multiple short coils at close distance calculating that the maximum length of such coils in order to take advantage of this configuration. We also explain that the response of such configuration of the gradiometer to the homogeneous field is zero even if the single coils are not symmetric with the respect of the center of the core if the pairs of coils are all symmetric. [ABSTRACT FROM PUBLISHER]

In this paper, we analyze the vibration and noise characteristics of the basic and skewed models of permanent brushless direct current (BLDC) motor. The electromagnetic characteristics of the basic model are analyzed by the finite-element method. We analyzed the electromagnetic characteristics for skew angles from 15° to 25°. The skew angle was selected based on the analytical results of the electromagnetic characteristics. We analyzed the characteristics of radial force density for the basic model and the skewed model. The vibration and noise characteristics were analyzed through the mechanical harmonic analysis of the radial force and tangential force generated in the motor. We developed the basic and skewed models, and performed vibration and noise tests. The validity of this analysis is verified by comparing the simulation results with the actual test results of the model. Finally, for the optimal design of the BLDC motor considering vibration, the design variables such as teeth shoe length, yoke thickness, and teeth thickness were used. Based on the results of vibration analysis, the final model is derived and its performance is described. [ABSTRACT FROM AUTHOR]

In this paper, we study the effect of the signal-to-noise ratio of magnetization measurements on the determination of the Curie temperature from the analysis of the magnetocaloric response. The procedure has been compared with the method of the inflection point of the magnetization versus temperature curves. Magnetization data have been simulated using the Arrott–Noakes equation of state, with the addition of different noise levels (either 1% of the measured signal or 0.3% of the measurement range). It is shown that the obtained values of the Curie temperature are more accurate in the case of the magnetocaloric procedure, although this method requires more data analysis than the inflection point method. Moreover, the field independence of the Curie temperature obtained from the magnetocaloric procedure allows us to perform a statistical analysis of the obtained values, reducing the associated error in the Curie temperature determination. [ABSTRACT FROM AUTHOR]

The noise of electrical machines has drawn more attention in recent years due to their harm to people and the environment. Normal skewed slot has proven to be an effective method to reduce vibration and noise of squirrel-cage induction motor. Double skewed slot is superior to normal skewed slot on reducing vibration and noise. However, it is still difficult to meet the requirements of noise standards in some occasions. In this paper, based on double skewed slot, a new skewed slot type is proposed, which can offer a better effect on reducing vibration and noise. 2-D fast Fourier transform and 3-D finite-element method are adopted to analyze and compare the performance of the three types of skewed slots. [ABSTRACT FROM AUTHOR]

Vibration and acoustic noises are viewed as a drawback in switched reluctance machines (SRMs), which prohibit their widespread use in noise sensitive applications. Double-stator SRMs (DSSRMs) can be considered as a solution to this problem by incorporating an improved magnetic configuration, which reduces the radial forces in the machine. This paper compares structural behavior of a DSSRM and a conventional SRM using a multi-physic analysis. An electromagnetic finite-element (FE) method is used to calculate force density at various parts of the stator surface in both machines. These force densities are then used in a structural FE analysis to compute acceleration, deformation, and velocity of the vibrating surface at selected point on the outer surface of the machine. [ABSTRACT FROM AUTHOR]

In this paper, we present an orthogonal fluxgate in fundamental mode with extremely stable offset and low noise. The typical solution to stabilizing the offset in this type of sensor is to flip the dc bias of its excitation current and subtract the output obtained with opposite polarities. In this case, on the contrary, we flip both the ac and dc components of the excitation current and sum the output voltages. This is performed using fast solid-state switches with low on-resistance. In this way, we achieved a large suppression of the dependence of the offset on temperature, obtaining an average offset drift of 0.012 nT/K, making this sensor on the top class for offset stability. We digitally sampled and numerically demodulated the output voltage of the sensor to extract the first harmonic. The value of the first harmonic shows noise right after switching of the current. Therefore, we numerically erased those few noisy values of the first harmonic before integrating it. In this way, we managed to limit the noise growth given by switching of the current. Finally, we strongly improved the offset stability with minor increment of noise. [ABSTRACT FROM PUBLISHER]

The jump-noise is a phenomenological stochastic process used to model the thermal fluctuation of magnetization in nanomagnets. In this paper, the large nucleation regime of jump-noise dynamics is studied, and its reversal time is characterized from Monte Carlo simulations and analysis. Results show that the reversal time of jump-noise dynamics for large nucleation is asymptotically equal to the time constant associated with a single jump-noise scattering event from the energy minimum in the energy landscape of the magnetization. The reversal time for large nucleation depends linearly on the height of the energy barrier for large barriers. The significance of the large nucleation regime of jump-noise dynamics to phenomenologically explain the magnetoelectric switching of antiferromagnetic order parameter is also prospected. [ABSTRACT FROM AUTHOR]

This paper presents a simple code to combat the two-dimensional inter-symbol interference (2D-ISI) effect that is present in data storage on magnetic bit patterned media. Whether the ISI effect is constructive or destructive depends on the surrounding bits. Therefore, we propose a simple 2D coding scheme to mitigate the ISI effect. With this 2D coding scheme in square patterned media, every 2-by-3 array has one redundant bit which has the opposite or same value of one of its adjacent bits. Compared to the 2D coding scheme in refid="ref1"/ under the condition of the same areal density, the proposed 2D coding scheme increases the allowable bit-position jitter in square patterned media by 1% at a BER of 10^-4; while it allows the effective storage capacity to be increased by around 5.5%. [ABSTRACT FROM AUTHOR]

In this paper, sensitivity analysis and Taguchi's method are applied to the design of dual band patch antenna using gap coupling. The proposed structure uses T-slotted aperture coupling between patch and feed line of ground plane. Using sensitivity analysis, optimum dimensions of patch and coplanar waveguide (CPW) feed line are first sought. Then the optimized values are modified by Taguchi's method in order to obtain robustness against the change of material constant and gap between patch and feed line. Moreover, the validity of the robust design has been tested with two antennas manufactured according to the final design. From the numerical and experimental results, it is confirmed that the final design is insensitive to noise factors. [ABSTRACT FROM PUBLISHER]

This paper applies artificial neural networks (ANNs) trained with a multiobjective algorithm to preprocess the ground penetrating radar data obtained from a finite-difference time-domain (FDTD) model. This preprocessing aims at improving the target's reflected wave signal-to-noise ratio (SNR). Once trained, the NN behaves as an adaptive filter which minimizes the cross-validation error. Results considering both White and colored Gaussian noise, with many different SNR, are presented and they show the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

By comparing the analyses of magnetic recording media noise and shot noise, this paper shows that a very close analogy exists between the two. It demonstrates that all the well-known results for both kinds of noise are caused by random processes that have equal probabilities in equal volumes. [ABSTRACT FROM AUTHOR]

Saccharin is a common additive used in Watts-type baths for electroplating of NiFe alloys (especially in the Permalloy composition). The reason is that saccharin is helpful in reducing the internal stress of the resulting ferromagnetic film, which is most often unwanted in many applications of NiFe electroplated alloys. In this paper, we consider fluxgate sensors based on Permalloy rings. The rings were electroplates using the same bath composition except for saccharin concentration, which varied from 1.5 to 17 g/L being 6 g/L the almost universally used concentration. The pH was corrected to 2.8 for every bath by adding different quantities of KOH according to the different values of pH obtained with a different saccharin concentration. We did so to assure that for the same electroplating current density, we obtain the same potential and finally the same composition ratio of nickel and iron. The rings show a noise spectral density when used as a core of fluxgates, which dropped from 180 pT/ $\surd $ Hz at 1 Hz for 1.5 g/L saccharin concentration to 60 pT/ $\surd $ Hz when saccharin was increased to at least 15 g/L. This shows that the most common saccharin concentration (6 g/L) in fact is not the most best concentration when it comes to minimize the noise of the fluxgate, but larger concentration is required. [ABSTRACT FROM AUTHOR]

Random number generators are well known for their ubiquitous use in cryptography, statistical sampling, and computer simulations. In order to establish secure data transfers in cryptographic applications, these number generators need to reliably produce unpredictable numbers at a high rate. In this paper, by exploiting the metastability of the stressed straintronics (STR) device, we theoretically propose a proof-of-concept nanomagnetic-based scheme to generate random numbers at very high rates with low-energy overhead. The dynamic modeling of the device, including the Langevin thermal noise field, is discussed, and the effect of process variation on the energy barrier and reliability is analyzed. The device is interfaced with CMOS circuitry and simulated in the 65 nm technology. At 1 V supply level, the system can generate random numbers as fast as 510 MHz. The entire circuit, including the CMOS peripherals, consumes 12.5 uW at 100 MHz random number generation rate while dissipating merely 0.125 pJ/bit. By reducing the supply level to 0.5 V, the energy per bit can be reduced further to 19 fJ. Since the STR device can be placed on the top of the CMOS circuitry, the total area of the design is estimated to be 0.001 mm2. [ABSTRACT FROM PUBLISHER]

This paper investigates 2-D media noise in shingled magnetic recording (SMR) systems. The media noises caused by the overwriting of the next track and the residual information from the previous track are asymmetric in the cross-track (CT) direction and are found to vary with the linear density. The media noise after equalization is found to be 2-D data dependent, with its mean and variance affected by the nonlinear transition shift in the CT and down-track directions, respectively. Also the effect of media noise on the bit error rate (BER) is studied for increased track densities during the writing process. The effect of jitter on the BER is always significant with increased track density in SMR systems, while the effect of overwriting and inter-track interference on the BER performance are quite different for readback with rotated and normally oriented readers, even though the same writer is used during the writing process. [ABSTRACT FROM AUTHOR]

Two-dimensional magnetic recording (2-D TDMR) is an emerging technology that aims to achieve areal densities as high as 10 Tb/in2 using sophisticated 2-D signal-processing algorithms. High areal densities are achieved by reducing the size of a bit to the order of the size of magnetic grains, resulting in severe 2-D intersymbol interference (ISI). Jitter noise due to irregular grain positions on the magnetic medium is more pronounced at these areal densities. Therefore, a viable read-channel architecture for TDMR requires 2-D signal-detection algorithms that can mitigate 2-D ISI and combat noise comprising jitter and electronic components. Partial response maximum likelihood (PRML) detection scheme allows controlled ISI as seen by the detector. With the controlled and reduced span of 2-D ISI, the PRML scheme overcomes practical difficulties such as Nyquist rate signaling required for full response 2-D equalization. As in the case of 1-D magnetic recording, jitter noise can be handled using a data-dependent noise-prediction (DDNP) filter bank within a 2-D signal-detection engine. The contributions of this paper are threefold: 1) we empirically study the jitter noise characteristics in TDMR as a function of grain density using a Voronoi-based granular media model; 2) we develop a 2-D DDNP algorithm to handle the media noise seen in TDMR; and 3) we also develop techniques to design 2-D separable and nonseparable targets for generalized partial response equalization for TDMR. This can be used along with a 2-D signal-detection algorithm. The DDNP algorithm is observed to give a 2.5 dB gain in SNR over uncoded data compared with the noise predictive maximum likelihood detection for the same choice of channel model parameters to achieve a channel bit density of 1.3 Tb/in2 with media grain center-to-center distance of 10 nm. The DDNP algorithm is observed to give $\sim$ 10% gain in areal density near 5 grains/bit. The proposed signal-processing framework can broadly scale to various TDMR realizations and areal density points. [ABSTRACT FROM AUTHOR]