Browsing by Author "Lin, Wen-Chin"

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Quantification of Cable Deformation with Time Domain Reflectometry-Implications to Landslide Monitoring
(2009-01-01)
Lin, Chih-Ping
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Tang, Shr-Hong
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Lin, Wen-Chin
;
Chung, Chih-Chung
;
交大名義發表
Time domain reflectometry (TDR) technology has become a valuable tool for detecting displacements and locating shear planes in rock or soil slopes. It is based on transmitting an electromagnetic pulse into a coaxial cable grouted in rock or soil mass and watching for reflections of this transmission due to cable deformity induced by the ground deformation. Early detection of localized shear deformation in soft soils and quantifying the shear displacement using TDR remains a challenging work. The TDR response due to localized shear deformation is affected by cable resistance, soil-grout-cable interaction, and shear bandwidth. A comprehensive TDR wave propagation model considering cable resistance is introduced to model TDR response to cable deformity. Effects of the influencing factors on the relationship between the reflection spike and the shear displacement are investigated through laboratory tests and numerical simulations. The implications to enhancing TDR response and quantifying shear displacement are stressed. Practical suggestions are made, including procedure for correcting resistance effect, selection of cable and grout, and how to quantify shear displacement using TDR.
Realization of an H-2/CO dual-gas sensor using CoPd magnetic structures
(2018-10-29)
Liang, Jaw-Yeu
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Chou, Yu-Jun
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Yin, Chiao-Wen
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Lin, Wen-Chin
;
Lin, Hong-Ji
We demonstrated the application of CoPd magnetic devices in single (H-2) and dual (H-2 and CO) gas detection by varying the thin-film structure. The anomalous Hall effect provided the read-out signal of the devices. The dual-gas sensor was particularly useful for examining whether methane reformation by steam was completed during H-2 production where CO is a byproduct. Through in situ Fourier transform infrared and X-ray absorption spectroscopy, we discovered that H-2 detection involved a charge-transfer effect between Co and Pd in addition to a surface-adsorption process, for both multilayer and alloy structures; however, CO detection was solely associated with a surface-adsorption process, which only occurred in the alloy structure. The proposed devices demonstrated performances exceeding those of current commercial models (solid-state based) regarding power consumption (<5 mW) because they were not required to undergo a heating process. An Arduino prototype platform was employed to test the modularization of the device, and adequate feasibility was demonstrated. Published by AIP Publishing.
Superparamagnetic ground state of CoFeB/MgO magnetic tunnel junction with dual-barrier
(2018-11-01)
Thanh-Nga Tran
;
Tu-Ngoc Lam
;
Yang, Chao-Yao
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Lin, Wen-Chin
;
Chen, Po-Wen
CoFeB/MgO-based magnetic tunnel junctions (MTJs) have considerable potential in magnetic random access memory (MRAM), thanks to their tunable perpendicular magnetic anisotropy (PMA). We found significant reduction of dead-layer by inserting additional MgO into the MTJ structure. Interface, electronic and transport characterizations were utilized to approach the modified magnetic properties driven by the dual-MgO structure in this work. The dual-MgO structure appeared to hinder boron (B) diffusion into the metallic layer and prevent capping-layer (Ta) penetration across the interface. This suppressed the dead-layer effect and promoted overall magnetization despite PMA degradation. A robust BOx phase that formed within the dual-MgO structure presented a superparamagnetic ground state. In the single-MgO structure, any reduction in the thickness of the CoFeB promoted PMA, albeit at the cost of spin-polarization. The dual-MgO structure could restore spin-polarization by preferentially populating spin electrons into Fe/Co minority states. X-ray magnetic spectroscopy and anomalous Hall effect suggest that, the dual-MgO differs from the single-MgO with a favorable longitudinal polarized spin-channel. This makes the dual-MgO structure applicable to applications requiring in-plane rather than out-of-plane sensing.
Using magnetic structure of Co40Pd60/Cu for the sensing of hydrogen
(2017-07-10)
Lang, Jaw-Yeu
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Pai, Yun-Chieh
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Lam, Tu-Ngoc
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Lin, Wen-Chin
;
Chan, Ting-Shan
This paper reports on a magnetic device with a [Co40Pd60/Cu](10)/Fe structure for use in the detection of H-2. In a magneto-optical, transport, and gas-detection system, the proposed device presented sharp, reproducible H-2-dependent magnetic/electrical properties. The device's saturation magnetization (induced resistance change) dropped (increased) by a factor of similar to 5 when a H-2 pressure of 75 kPa is given. Besides, the electrical signal-to-noise ratio of the device can be restored similar to 50% by exposing it to a magnetic field of 1000 Oe, even when the sensitivity of the device dropped at a low H-2 pressure (0.7 KPa). This demonstrates the applicability of the device for use as a low-pressure H-2 detector. Operando x-ray spectroscopy revealed that changes in H-2-induced magnetism arose from a Co-Pd charge transfer effect coupled to changes in the local-structure symmetry. Published by AIP Publishing.
Voltage-induced Interface Reconstruction and Electrical Instability of the Ferromagnet-Semiconductor Device
(2017-03-23)
Chang, Shu-Jui
;
Chang, Po-Chun
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Lin, Wen-Chin
;
Lo, Shao-Hua
;
Chang, Liang-Chun
Using x-ray magnetic spectroscopy with in-situ electrical characterizations, we investigated the effects of external voltage on the spin-electronic and transport properties at the interface of a Fe/ZnO device. Layer-, element-, and spin-resolved information of the device was obtained by cross-tuning of the x-ray mode and photon energy, when voltage was applied. At the early stage of the operation, the device exhibited a low-resistance state featuring robust Fe-O bonds. However, the Fe-O bonds were broken with increasing voltage. Breaking of the Fe-O bonds caused the formation of oxygen vacancies and resulted in a high-resistance state. Such interface reconstruction was coupled to a charge-transfer effect via Fe-O hybridization, which suppressed/enhanced the magnetization/coercivity of Fe electronically. Nevertheless, the interface became stabilized with the metallic phase if the device was continuously polarized. During this stage, the spin-polarization of Fe was enhanced whereas the coercivity was lowered by voltage, but changes of both characteristics were reversible. This stage is desirable for spintronic device applications, owing to a different voltage-induced electronic transition compared to the first stage. The study enabled a straightforward detection of the spin-electronic state at the ferromagnet-semiconductor interface in relation to the transport and reversal properties during operation process of the device.