• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2006년도 하계학술대회
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• pp.91-94
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• 2006

In this paper, we deployed the tunnel inspection and monitoring system by wireless sensor network. It is shown that the wireless sensor network which is composed of sensor, wireless communication module, and gateway system can be applied to tunnel monitoring system. Sensors included herein are acceleration transducers, fire-alarm sensors, water-level sensors, and magnetic contact sensors. It is also found that the wireless sensor network can deliver sensing data reliably by ad-hoc networking technology. The gateway system that can send the sensing data to server by CDMA (code division multiple access) is developed. Finally, monitoring system is constructed by web service technology, and it is observed that this system can monitor the present state of tunnel without difficulties. Furthermore, the above system provides an alternative to inspect and monitor the tunnel efficiently where the conventional wired system cannot be applied.

• 전기학회논문지
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• 제60권3호
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• pp.600-605
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• 2011

This paper shows field test and evaluation results for a wireless vehicle detector with anisotropic magneto-resistive (AMR) sensors. The detector consists of two AMR sensors and mechanical and electronic apparatuses. The AMR sensor senses disturbance of the earth magnetic field caused by a vehicle moving over the sensor and then produces an output indicative of the moving vehicle. In this paper, vehicle speeds are calculated by using two AMR sensors fixed on a board, with constant distance. To test and evaluate the accuracy of the detector in real traffic situations, the detector was installed on a local highway and vehicle speeds and volumes were measured both in a free running and a highly congested traffic. The measurements from the detector are compared with the reference measurements obtained from a traffic camera with the Mean Absolute Percentage Errors (MAPE), which has proved the usefulness of the detector in the field.

• Smart Structures and Systems
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• 제2권2호
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• pp.155-169
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• 2006

In this paper, the application of magnetoelasticity in static tension monitoring for large steel cables is discussed. Magnetoelastic (EM) stress sensors make contact-free tension monitoring possible for hanger cables and post-tensioned cables on suspension and cable-stayed bridges. By quantifying the correlation of magnetic relative permeability with tension and temperature, the EM sensors inspect the load levels in the steel cables. Cable tension monitoring on Qiangjiang (QJ) 4th Bridge demonstrates the reliability of the EM sensors.

• 한국전기전자재료학회논문지
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• 제31권5호
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• pp.351-356
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• 2018

Commonly, a live-line alarm can be used to measure the electric field strength of a high-voltage system to calculate its current, but it is hard to detect the electric field of shielded cables or concealed structures, such as underground distribution cables. Current sensors can detect the magnetic field in a single core wire, but they cannot determine the magnetic field about a double-core wire because the currents flow in opposite directions. Therefore, it is very difficult to detect certain current problems, such as a fault current in an extension line comprised of a double line. In this paper, to ultimately develop a sensor that can detect the current regardless of line conditions, we used a simulation to determine the concentration of the magnetic field dependent on the distribution of the external magnetic field and the path of each line's core.

• 센서학회지
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• 제15권3호
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• pp.158-163
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• 2006

This paper reports a novel immunoassay method using superparamagnetic nanoparticles and an enhanced magnetic field gradient for the detection of protein in a microfluidic device. We use superparamagnetic nanoparticles as a label and fluorescent polystyrene beads as a solid support. Based on this platform, magnetic force-based microfluidic immunoassay is successfully applied to analyze the concentration of IgG as model analytes. In addition, we present ferromagnetic microstructure connected with a permanent magnet to increase magnetic flux density gradient (dB/dx, ${\sim}10^{4}$ T/m), which makes limit of detection reduced. The detection limit is reduced to about 1 pg/mL.

• 전기학회논문지
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• 제59권3호
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• pp.562-568
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• 2010

In this paper, a low cost magnetic position sensor for linear position detection is proposed. The proposed magnetic sensor can be applied to the linear motor which has stator with periodical teeth, such as transverse flux linear motor(TFLM). Sine and cosine waves can be generated from the unit sensor module as the linear motor moves, and the outputs can be converted to the position data by interpolation IC. To reduce the speed ripple caused by the position error, the Luenberg observer is introduced. The validity of the proposed magnetic position sensor is verified by experiment with a 750N three-phase TFLM.

• 동력기계공학회지
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• 제11권2호
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• pp.72-76
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• 2007

Since the magnetic bearing system has unstability inherently it is necessary to measure the displacement for stable operation. Normally the displacement measurement is implemented by using sensors. The sensor for the displacement measurement is selected by precision, installation space, effect of magnetic field and response speed. And the cost of displacement measurement sensor also is considered. At the cost the hall effect sensor has a large advantage comparing with the others. Therefore this study concern about the basis experimental test for the displacement measurement of the magnetic bearing system that uses the hall effect sensor coupled with a tiny permanent magnet. The experimental results confirm the validity and practicability for this displacement measurement sensor.

• 한국자기공명학회논문지
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• 제20권4호
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• pp.114-120
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• 2016

Nitrogen vacancy-centered diamond has recently emerged as a promising material for various applications due to its special optical and magnetic properties. In particular, its applications as a fluorescent biomarker with small toxicity, magnetic field and electric field sensors have been a topic of great interest. Recent review (R. Schirhagl et al 2014) introduced those applications using single NV-center in nanodiamond. In this minireview, I introduce the rapidly emerging DNP (Dynamic Nuclear Polarization) field using optically-pumped NV center in diamonds. Additionally, the possibility of exploiting the optically-pumped NV center for polarization transfer source, which will produce a profound impact on room temperature DNP, will be discussed.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.151-154
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• 2000

We have developed a YBCO SQUID gradiometer system for the measurement of a very weak magnetic field in an unshielded environment. The system consists of a SQUID gradiometer sensor, low noise pre-amp, and FLL(fluxlocked loop) control electronics. The gradiometer sensors have been fabricated on STO bicrystal substrates, and exhibit a magnetic noise of 300 fT/${\surd}$ Hz/cm at 100 Hz. The overall magnetic field noise of the SQUID gradiometer system was about 10 pT/${\surd}$ Hz/cm at 10 Hz without any magnetic shield. The system demonstrated a high stability for a long time, and real-time measurement resolution ${\le}$ 100 pT/cm in the unshielded environments.

• 한국전기전자재료학회논문지
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• 제16권12S호
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• pp.1305-1309
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• 2003

To utilize FeCoSiB amorphous films for magnetoelastic sensors, the temperature dependency of magnetization (M-T curve) and the magnetization properties of the amorphous films were investigated in this study. As the amount of cobalt In the films increased, the Curie temperature decreased but the crystallization temperature increased. In addition to this, the crystallization temperature was lower than the Curie temperature in the film containing 20 at% cobalt. The optimized annealing condition was set up by analyzing the H-T curve. And then, the amorphous film that has excellent magnetic properties and uni-axal anisotropy could be prepared for construction of the magnetoelastic sensor devices. The coercive force of the film was below 0.5 Oe and the anisotripic field was about 5 Oe.