다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Non-destructive techniques are used widely in the metal industry in order to control the quality of materials. Eddy current testing is one of the most extensively used non-destructive techniques for inspecting electrically conductive materials at very high speeds that does not require any contact between the test piece and the sensor. This paper includes an overview of the fundamentals and main variables of eddy current testing. It also describes the state-of-the-art sensors and modern techniques such as multi-frequency and pulsed systems. Recent advances in complex models towards solving crack-sensor interaction, developments in instrumentation due to advances in electronic devices, and the evolution of data processing suggest that eddy current testing systems will be increasingly used in the future.

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Non-Destructive Techniques Based on Eddy Current Testing

The most important milestone in the field of magnetic sensors was when AMR sensors started to replace Hall sensors in many applications where the greater sensitivity of AMRs was an advantage. GMR and SDT sensors finally found applications. We also review the development of miniaturization of fluxgate sensors and refer briefly to SQUIDs, resonant sensors, GMIs, and magnetomechanical sensors.

Advances in Magnetic Field Sensors

MEMS-based oscillators are an emerging class of highly miniaturized, batch manufacturable timing devices that can rival the electrical performance of well-established quartz-based oscillators. In this review, a description is given of the key properties of a MEMS resonator that determine the overall performance of a MEMS oscillator. Piezoelectric, capacitive and active resonator transduction methods are compared and their impact on oscillator noise and power dissipation is explained. An overview is given of the performance of MEMS resonators and MEMS-based oscillators that have been demonstrated to date. Mechanisms that affect the frequency stability of the resonator, such as temperature-induced frequency drift, are explained and an overview is given of methods that have been demonstrated to improve the frequency stability. The aforementioned performance indicators of MEMS-based oscillators are benchmarked against established quartz and CMOS technologies.

https://iopscience.iop.org/article/10.1088/0960-1317/22/1/013001/pdf

A review of MEMS oscillators for frequency reference and timing applications

In recent decades, several detector technologies have been developed with the quest to directly detect dark matter interactions and to test one of the most important unsolved questions in modern physics. The sensitivity of these experiments has improved with a tremendous speed due to a constant development of the detectors and analysis methods, proving uniquely suited devices to solve the dark matter puzzle, as all other discovery strategies can only indirectly infer its existence. Despite the overwhelming evidence for dark matter from cosmological indications at small and large scales, clear evidence for a particle explaining these observations remains absent. This review summarises the status of direct dark matter searches, focusing on the detector technologies used to directly detect a dark matter particle producing recoil energies in the keV energy scale. The phenomenological signal expectations, main background sources, statistical treatment of data and calibration strategies are discussed.

https://iopscience.iop.org/article/10.1088/0954-3899/43/1/013001/pdf

Dark matter direct-detection experiments

Detecting theorientationofdeeporientedcracksisamajorchallengeinthedevelopmentofEddy- Current (EC)Non-DestructiveTesting(NDT).Infact,thedetectionsensitivityofEC-NDTdependsonthe interactionbetweenthecracklengthdirectionandtheEC flowinginthematerials.Inconventional EC-NDT systems,theinducedcurrentsareprimarilygeneratedalongasingledirectioninthetested sample. Thispaperpresentsanewexcitationmethodforgeneratingapseudo-rotatingacmagnetic field and, consequently,pseudo-rotatingeddycurrents.Thismethodsignificantly improvesthedetectionof deep cracksofanyorientation.ThedetectedsignalduetothecrackismeasuredbyanImprovedGiant Magneto-ResistanceMagnetometer(IGMRM).Themagnetic flux densitysignatureofthecrackisstudied using a3D finite elementmodel.Numericalandexperimentalresultsdemonstratethepotentialandthe efficiency ofthismethod.

https://hal.archives-ouvertes.fr/hal-00987058/document

Eddy-current non-destructive testing system for the determination of crack orientation

The performance of magnetic field sensors based upon the giant magnetoimpedance (GMI) effect in soft magnetic wires is investigated in the MHz frequency range The performance of the sensor is based on its sensitivity, voltage noise level and (voltage) noise-to-sensitivity ratio, or intrinsic magnetic noise level Optimization of the sensitivity and noise response of the sensor through variation of the sample anisotropy direction and external applied axial field and dc bias current suggest an intrinsic noise level in the fT/Hz level Qualitative agreement is obtained between theory and experiment on a CoFeSiB microwire, for the maximum sensitivity and the corresponding noise, as a function of the external field and dc bias current

Optimization of the magnetic noise and sensitivity of giant magnetoimpedance sensors

Two versions of an operational giant magnetoimpedance (GMI)-based magnetometer, one of which is capable of working in an unshielded geomagnetic field, has been design, built and benchmarked against a commercial fluxgate magnetometer. The sensing element consists of a detection coil, strongly coupled to the GMI wire, in a two-port configuration. Its optimization is based on the surface impedance tensor of the sensing element, in which we include parasitic capacitance and geometric parameters of the coil. Conditions for optimizing the electronic noise level are deduced from the model recently published in (IEEE Sensors Journal, vol. 11, no. 6, pp. 1317-1324, 2011.). The optimized sensor and its conditioning electronics are operated in a field-locked loop, using an external coil or the detection coil for feedback. Experimental noise performance correlates well with that expected from the sensitivity and noise models and are comparable to those of a commercial Flux-Gate magnetometer, offering a low-cost solution for high sensitivity magnetometry. However, the proposed GMI magnetometers still exhibit significant 1/f noise.

https://hal.archives-ouvertes.fr/hal-00831475/document

Development of a High Sensitivity Giant Magneto-Impedance Magnetometer: Comparison With a Commercial Flux-Gate

We present a noise analysis of a giant magnetoimpedance (GMI) sensor using a peak detector at the optimal magnetic field working bias point of a sensor wire, by considering internal noise sources (intrinsic GMI device associated noise sources and conditioning electronic noise sources). An expression is obtained for the theoretical expected noise for known electronic design parameters and physical characteristics of the GMI wire. The most significant contributions to noise in a GMI measurement, using two basic oscillators (either a simple discrete RC oscillator or quartz oscillator) along with a peak detector, are presented. We discuss the expected extrinsic equivalent magnetic noise limit.

Equivalent Magnetic Noise Limit of Low-Cost GMI Magnetometer

An optimized giant magneto-impedance effect magnetometer has been developed, based on an overall analysis of the measurement chain, including physical material properties, associated detection coil parameters, and equivalent magnetic noise performances. The field response model for the sensing element and the noise model yield good agreement with experimental results. The noise performance of the magnetometer, approximately 1.7 pT/√{Hz} in the white noise region, with a band-pass of about 70 kHz, is competitive with that of other technologies. Present limitations are clearly established, leaving room for further improvements.

https://hal.archives-ouvertes.fr/hal-00824131/document

Christophe Dolabdjian

Papers

Eddy-current non-destructive testing system for the determination of crack orientation

Optimization of the magnetic noise and sensitivity of giant magnetoimpedance sensors

Development of a High Sensitivity Giant Magneto-Impedance Magnetometer: Comparison With a Commercial Flux-Gate

Equivalent Magnetic Noise Limit of Low-Cost GMI Magnetometer

Characterization of an Optimized Off-Diagonal GMI-Based Magnetometer