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  • AIP Publishing  (241)
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  • 11
    Online Resource
    Online Resource
    Magnetic gradient full-tensor fingerprints for metallic objects detection of a security system based on anisotropic magnetoresistance sensor arrays
    AIP Publishing ; 2020
    In:  AIP Advances Vol. 10, No. 1 ( 2020-01-01)
    Details
    In: AIP Advances, AIP Publishing, Vol. 10, No. 1 ( 2020-01-01)
    Abstract: Concealed metallic object detection is one of the critical tasks for any security system. It has been proved that different objects have their own magnetic fingerprints, which are a series of magnetic anomalies determined by shape, size, physical composition, etc. This study addresses the design of a low-cost power security system for the detection of metallic objects according to their response to the magnetic field. The system consists of three anisotropic magnetoresistance (AMR) sensor arrays, detection circuits, and a microcontroller. A magnetic gradient full-tensor configuration, utilizing four AMR sensors arranged on a planar cross structure, was employed to construct a two-dimensional image from the obtained data, which can further suppress the background noise and reduce the orientation and orthogonality errors. The performance of the system is validated by data validation and multiple object feature segmentation. Numerous magnetic fingerprinting results demonstrate that the system can configure metallic objects more than 50cm clearly and identify multiple objects separated by less than 20 cm, which indicates the feasibility of using this magnetic gradient tensor fingerprint method for metallic object detection.
    Type of Medium: Online Resource
    ISSN: 2158-3226
    URL: Article
    DOI: 10.1063/1.5133857
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 2583909-3
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  • 12
    Online Resource
    Online Resource
    Transversal and longitudinal mode selections in double-corrugation coaxial slow-wave devices
    AIP Publishing ; 2009
    In:  Physics of Plasmas Vol. 16, No. 6 ( 2009-06-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 16, No. 6 ( 2009-06-01)
    Abstract: To reduce the dimensions of relativistic backward wave oscillators (RBWOs) operating in the low frequency regime of less than 2 GHz, the theory of transversal and longitudinal mode selections are introduced in this paper. The transversal mode selection is achieved using the property of “surface wave” of the coaxial slow-wave structure (SWS) to excite the quasi transverse electromagnetic (quasi-TEM) mode without the higher transverse magnetic (TM) modes and it is proved that the coaxial SWS may decrease the transversal dimension of the SWS sections. In addition, the S-parameter method is employed to investigate the longitudinal resonant characteristic of the finite-length SWS, and the scheme of longitudinal mode selection is put forward. It is proposed that the introduction of a well-designed coaxial extractor to slow-wave devices can help to achieve the longitudinal mode selection and reduce the period number of the SWS, which not only can make the devices more compact, but also can avoid the destructive competition between various longitudinal modes, therefore can enhance the efficiency and stabilize the frequency. To sum up, the physical mechanisms of transversal and longitudinal mode selections ensure that the microwave is produced with a single mode and a narrow band. Based on the above discussion, a compact L-band coaxial RBWO is investigated and optimized in detail with the particle-in-cell KARAT code (V. P. Tarakanov, Berkeley Research Associates, Inc., 1992). In simulation, the L-band coaxial RBWO, driven by a 700 kV, 11 kA electron beam, comes to a nonlinear steady state in 20 ns. High-power microwave of quasi-TEM mode is generated with an average power of 2.66 GW, a frequency of 1.6 GHz, and power conversion efficiency of 34.5% in durations of 30–60 ns.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.3158573
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2009
    detail.hit.zdb_id: 1472746-8
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  • 13
    Online Resource
    Online Resource
    Anomaly detection of complex magnetic measurements using structured Hankel low-rank modeling and singular value decomposition
    AIP Publishing ; 2022
    In:  Review of Scientific Instruments Vol. 93, No. 4 ( 2022-04-01)
    Details
    In: Review of Scientific Instruments, AIP Publishing, Vol. 93, No. 4 ( 2022-04-01)
    Abstract: The magnetic anomalies generated by the ferromagnetic targets are usually buried within uncontrollable interference sources, such as the power frequency and random noises. In particular, the variability of the geomagnetic field and the low signal-to-noise ratio (SNR) of the magnetic anomalies cannot be avoided. In this paper, to improve the performance of magnetic anomaly detection (MAD) with a low SNR, we propose a novel structured low-rank (SLR) decomposition-based MAD method. In addition, a new framework based on the SLR and singular value decomposition (SVD) is constructed, dubbed SLR-SVD, and the corresponding working principle and implemented strategy are elaborated. Through comparing the SLR-SVD with two state-of-the-art methods, including principal component analysis and SVD, the results demonstrate that the proposed SLR-SVD can not only suppress the noise sufficiently, i.e., improving 55.26% approximately of the SNR, but also retain more boundary information of magnetic anomalies, i.e., decreasing approximately 68.05% of the mean squared error and improving approximately 28.47% of the structural similarity index.
    Type of Medium: Online Resource
    ISSN: 0034-6748 , 1089-7623
    URL: Article
    DOI: 10.1063/5.0088254
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 209865-9
    detail.hit.zdb_id: 1472905-2
    SSG: 11
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  • 14
    Online Resource
    Online Resource
    Adaptive pre-whiten filtering for the free induction decay transversal signal in weak magnetic detection
    AIP Publishing ; 2019
    In:  Review of Scientific Instruments Vol. 90, No. 10 ( 2019-10-01)
    Details
    In: Review of Scientific Instruments, AIP Publishing, Vol. 90, No. 10 ( 2019-10-01)
    Abstract: The free induction decay (FID) transversal signal is always employed by a proton precession magnetometer (PPM) to evaluate the time-domain geomagnetic field. Nevertheless, the signal-to-noise ratio (SNR) is an important factor that severely affects the detection accuracy of the magnetic field due to uncontrollable interference sources, including random noise and power frequency noise. In this study, aiming to boost the SNR of the FID transversal signal, a novel filtering algorithm based on a prewhiten (PW) strategy is proposed and the PW filtering was combined with singular value decomposition (SVD) for further noise reduction. This method aims to generate adaptive PW input data before filtering, further decorrelating the noise to reduce the impact of varying noise levels in the received FID signals. The efficiency of the proposed joint filtering framework, dubbed PW-SVD, was evaluated by comparing with two state-of-the-art methods, i.e., SVD and principal component analysis and decomposition, using the same data. The results demonstrated that the proposed PW-SVD method obtained the smallest root mean square error and the highest signal-to-noise ratio improvement among all the compared methods, especially for the strong-noisy scenario, which enhances the environmental adaptability of a PPM.
    Type of Medium: Online Resource
    ISSN: 0034-6748 , 1089-7623
    URL: Article
    DOI: 10.1063/1.5119387
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2019
    detail.hit.zdb_id: 209865-9
    detail.hit.zdb_id: 1472905-2
    SSG: 11
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    Online Resource
  • 15
    Online Resource
    Online Resource
    Tuning the metamagnetism in a metallic helical antiferromagnet
    AIP Publishing ; 2017
    In:  Applied Physics Letters Vol. 111, No. 23 ( 2017-12-04)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 111, No. 23 ( 2017-12-04)
    Abstract: The antiferromagnetic (AFM)-ferromagnetic (FM) conversion in martensite was observed in Mn/Ni-substitution upon FM elements, such as Fe or Co, in MnNiGe helical antiferromagnets. Here, we report an AFM-FM conversion and consequently a sharp magnetic-field-driven metamagnetic martensitic transformation from paramagnetic (PM) austenite to FM martensite in the Ni- and Mn-substituted MnNiGe alloys with indium, a non-magnetic and large-sized main group element. Accordingly, a giant magnetocaloric effect such that a twofold increase of the magnetic entropy change in MnNi0.92GeIn0.08 and even a nearly threefold increase in the Mn0.92NiGeIn0.08 alloy is obtained with respect to the MnNiGe0.95In0.05 alloy. The origin of AFM-FM conversion and resultantly sharp magnetic-field-induced PM-FM metamagnetic transformation is discussed based on the first-principles calculations and X-ray absorption spectroscopic results.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.5004667
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2017
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 16
    Online Resource
    Online Resource
    Apparatus and method for efficient sampling of critical parameters demonstrated by monitoring an Overhauser geomagnetic sensor
    AIP Publishing ; 2018
    In:  Review of Scientific Instruments Vol. 89, No. 12 ( 2018-12-01)
    Details
    In: Review of Scientific Instruments, AIP Publishing, Vol. 89, No. 12 ( 2018-12-01)
    Abstract: The polarization frequency of free radical solution in Overhauser geomagnetic sensor determines the quality of the Larmor precession signal generated by the sensor. To obtain the polarization frequency accurately, a test apparatus was designed in this paper, which can overcome existing problems in the presently used apparatuses, such as lower resolution, complex operation, etc. The proposed apparatus adopts a high-resolution direct digital synthesis as the controllable radio frequency (RF) signal source. Meanwhile, an analog-to-digital converter synchronization acquisition technology combined with a normalization approach is proposed, which effectively solves the problem of the uneven amplitude-frequency characteristic in the range of 50 MHz–100 MHz. Moreover, the apparatus is integrated by adopting the RF power and applying the weak signal amplifier as an auxiliary measurement channel. The equivalent circuit of the sensors resonant cavity was simulated, and the efficiency curve of the adjustable capacitors to the resonant frequency and the quality factor were obtained. The simulated results were further verified by testing the resonance cavity characteristics of a commercial Overhauser geomagnetic sensor under different conditions. Furthermore, the relationship between the polarization degree of the free radical solution and RF excitation power and time were also obtained. The testing methods and results were given, and the experimental data were analyzed. Finally, the experimental results demonstrate that the proposed apparatus can measure the polarization frequency of the free radical solution, the bandwidth, and the quality factor, accurately. Furthermore, it can be used for the determination of the polarization power and time during the design process for an Overhauser magnetometer.
    Type of Medium: Online Resource
    ISSN: 0034-6748 , 1089-7623
    URL: Article
    DOI: 10.1063/1.5054749
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2018
    detail.hit.zdb_id: 209865-9
    detail.hit.zdb_id: 1472905-2
    SSG: 11
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  • 17
    Online Resource
    Online Resource
    Novel silicon waveguide switch based on total internal reflection
    AIP Publishing ; 1994
    In:  Applied Physics Letters Vol. 64, No. 16 ( 1994-04-18), p. 2079-2080
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 64, No. 16 ( 1994-04-18), p. 2079-2080
    Abstract: Novel silicon asymmetric optical switches with transverse injection structure have been proposed and fabricated which are based on total internal reflection and free-carrier effect. The switches have a quite short operation length of about 200 μm. The device performance was measured at the wavelength of 1.3 μm. It shows that the crosstalk is less than −11.4 dB at an injection current of 85 mA. Response time is 100 ns. They are very suitable for silicon monolithic optoelectronic integration
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.111689
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1994
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 18
    Online Resource
    Online Resource
    Long-time measurements of line-integrated plasma electron density using a two-color homodyne optical fiber interferometer
    AIP Publishing ; 2021
    In:  Review of Scientific Instruments Vol. 92, No. 9 ( 2021-09-01)
    Details
    In: Review of Scientific Instruments, AIP Publishing, Vol. 92, No. 9 ( 2021-09-01)
    Abstract: A two-color homodyne Mach–Zehnder (M–Z) optical fiber interferometer with wavelengths of 1.55 and 1.31 µm was developed for long-time measurement of line-integrated plasma electron density. A novel phase difference demodulation algorithm based on a single 3 × 3 optical coupler was implemented in a two-color optical fiber interferometer scheme for the first time. Our laboratory tests showed that this new optical fiber interferometer could determine the phase shift due to the low-frequency ambient vibration and could maintain high phase resolution measurement. The resolution of the new interferometer was less than 0.04 rad in 1000 s, corresponding to a line-averaged electron density of less than 1.0 × 1019 m−2. Actual plasma discharge experiments performed on KTX-CTI, which is a new compact torus injector (CTI) constructed at the Keda Torus eXperiment (KTX), showed that this interferometer has excellent several-second stability.
    Type of Medium: Online Resource
    ISSN: 0034-6748 , 1089-7623
    URL: Article
    DOI: 10.1063/5.0055570
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 209865-9
    detail.hit.zdb_id: 1472905-2
    SSG: 11
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  • 19
    Online Resource
    Online Resource
    A modular magneto-inductive sensor for low vector magnetic field measurements
    AIP Publishing ; 2021
    In:  Review of Scientific Instruments Vol. 92, No. 8 ( 2021-08-01)
    Details
    In: Review of Scientific Instruments, AIP Publishing, Vol. 92, No. 8 ( 2021-08-01)
    Abstract: The low magnetic field measurement has been utilized since ancient times in order to find economic resources, to detect magnetic anomalies, etc. In this case, the vector magnetic survey can simultaneously obtain the modulus and direction information of the magnetic field, which can contribute to obtaining more precise information and characteristics of magnetic field resources. This paper is concerned with the potential to exploit the signals of vector magnetic field measurement with a magneto-inductive (MI) sensor. To evaluate the capability of the MI sensor, a test platform is set up and its performance, including the noise floor, the resolution, and the sensitivity, is comprehensively characterized. Furthermore, a comparative geomagnetic observation and magnetic anomaly detection among the proposed MI sensor, a high-precision Overhauser sensor, and a commonly used and accepted commercial MI sensor are conducted. The experimental results identify the capability of the proposed MI sensor in weak magnetic detection.
    Type of Medium: Online Resource
    ISSN: 0034-6748 , 1089-7623
    URL: Article
    DOI: 10.1063/5.0063450
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 209865-9
    detail.hit.zdb_id: 1472905-2
    SSG: 11
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  • 20
    Online Resource
    Online Resource
    Forming desired polymer patterns through spatial-modulated ionic wind
    AIP Publishing ; 2018
    In:  Applied Physics Letters Vol. 113, No. 8 ( 2018-08-20)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 113, No. 8 ( 2018-08-20)
    Abstract: Patterning polymer films is of significant interest for a broad range of applications. In this paper, a method of patterning polymer films is proposed, which is based on the liquid polymer film flow actuated by ionic wind. We placed the mask in ionic wind which can be modulated spatially. Under such conditions of spatial-modulated ionic winds, the liquid polymer presents different flow regimes, the morphologies of which duplicate the masks of different shapes. The patterning mechanism was investigated through numerical simulations. Different masks, such as line strips, serpentine-shaped stripes, and nuts, were adopted to manipulate the polymer-patterns with the presented method. The different polymer patterns were solidified and characterized, which verifies the feasibility of the methods for the formation of different complex polymer patterns.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.5048649
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2018
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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