• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.2
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• pp.361-366
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• 2017

The abnormal state of the main equipment across the industry is accompanied by abnormal rise of temperature, change in the vibration and noise. In this study, we developed a smart sensing module equipped with BLE, and developed a smart sensing device that can detect abnormal vibration due to its own flaws of the equipment by interfacing with an MEMS-based acceleration sensor. The smart sensing device developed in this study can be easily installed in a small space and can monitor the vibration status of the equipment in real time, and can easily inform the user of the steady state and the problem occurrence status with array LED display.

• Journal of Sensor Science and Technology
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• v.7 no.2
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• pp.103-110
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• 1998

Pyroelectric infrared detectors based on La-modified $PbTiO_{3}$ (PLT) thin films have been fabricated by RF magnetron sputtering and rnicrornachining technology. The detectors form $Pb_{l-x}La_{x}Ti_{1-x/4}O_{3}$ (x=0.05) thin film ferroelectric capacitors epitaxially grown by RF magnetron sputtering on Pt/MgO (100) substrate. The sputtered PLT thin film exhibits highly c-axis oriented crystal structure that no poling treatment for sensing applications is required. This is an essential factor to increase the yield for realization of an infrared image sensor. Micromachining technology is used to lower the thermal mass of the detector by giving maximum sensor efficiency. Polymide is coated on top of the sensing elements to support the fragile structure and the backside of the MgO substrate is selectively etched to reduce the heat loss. The sensing element exhibited a very high detectivity D* of $8.5{\times}10^{8}cm{\cdot}\sqrt{Hz}/W$ at room temperature and it is about 100 times higher than the case of micromachining technology is not used. A sensing system that detects the position as well as the existence of a human body is realized using the array sensor.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.156-156
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• 2017

Most crop damages have been occurred by vermin(e.g., wild birds and herbivores) during the period between seeding and the cotyledon level. In this study, to minimize the damage by vermin and acquire the benefits such as protection against weeds and maintenance of water content in soil, immediately vinyl mulching after seeding was devised. Vinyl mulching has been generally covered with black color vinyl, that crop seeding locations cannot be detected by visible light range. Before punching vinyl, non-contact and non-destructive methods that can continuously determine the locations are necessary. In this study, a crop position detection method was studied that uses infrared thermal image sensor to determine the cotyledon position under vinyl mulch. The moving system for acquiring image arrays has been developed for continuously detecting crop locations under plastic mulching on the field. A sliding mechanical device was developed to move the sensor, which were arranged in the form of a linear array, perpendicular to the array using a micro-controller integrated with a stepping motor. The experiments were conducted while moving 4.00 cm/s speed of the IR sensor by the rotational speed of the stepping motor based on a digital pulse width modulation signal from the micro-controller. The acquired images were calibrated with the spatial image correlation. The collected data were processed using moving averaging on interpolation to determine the frame where the variance was the smallest in resolution units of 1.02 cm. For this study, the spline method was relatively faster than the other polynomial interpolation methods, because it has a lower maximum order of formulation when using a system such as the tridiagonal linear equation system which provided the capability of real-time processing. The temperature distribution corresponding to the distance between the crops was 10 cm, and the more clearly the leaf pattern of the crop was visually confirmed. The frequency difference was decreased, as the number of overlapped pixels was increased. Also the wave pattern of points where the crops were recognized were reduced.

• Journal of Sensor Science and Technology
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• v.18 no.4
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• pp.301-306
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• 2009

This paper describes the design and fabrication of 16$\times$16 microbolometer infrared focal plane arrays based on iMEMS technology. Amorphous silicon was used for infrared-sensitive material, and it showed the resistance of 18 Mohm and the temperature coefficient of resistivity of -2.4 %. The fabricated sensors exhibited responsivity of 78 kV/W and thermal time constant of 8.0 msec at a bias voltage of 0.5 V. The array performances had satisfactory uniformity less than 5 % within one-sigma. Also, 1/f noise of pixel was measured and the noise factor of $6\times10^{-11}$ was extracted. Finally, we obtained detectivity of $1.27\times10^9cmHz^{0.5}/W$ and noise equivalent temperature difference of 200 mK at a frame rate of 30 Hz.

• Journal of Sensor Science and Technology
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• v.18 no.5
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• pp.377-384
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• 2009

The ultrasonic hyperthermia for oncology has been developed and studied. The HIFU(high intensity focused ultrasound) is the most recent method to treat the tumor by using ultrasound. In this study, an insertion-type transducer for treating a prostate cancer, which can focus the ultrasonic beam mechanically and electrically, was designed and developed. The developed transducer was composed of three arrays, and each array has 32 elements. For the purpose of the mechanical focusing, both side arrays are slanted to the center array by $15^{\circ}$. With this structure, NFL(near field length) was set up as 30 mm. The PZT-4 and two matching layers were used, and the backing layer was excepted to prevent energy losses. The acoustic field analysis and the heating test were performed to evaluate the performance of developed transducer. The shape of an acoustic field, peak pressure, and acoustic pressure distribution were compared with numerical simulation. The NFL was 32 mm, the beam width was 5 mm, focal area was $40\;mm^2$, and peak pressure was 5.5 MPa. With heating by using developed transducer, the temperature increased up to $33^{\circ}C$ at focal zone. As a result of this study, the usefulness of suggested transducer for prostate cancer hyperthermia was confirmed by the acoustic field analysis and the heating test with TMM(tissue mimicking) phantom.

• Journal of Sensor Science and Technology
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• v.5 no.6
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• pp.51-59
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• 1996

A flow sensor has been fabricated by preparing thin film Pt-heater and Bi-Sb thermocouples array on 150 nm-$Si_{3}N_{4}$/300 nm-$SiO_{2}$/150 nm-$Si_{3}N_{4}$ dielectric diaphragm which has low thermal conductivity and balanced stress with silicon substrate for the purpose of improving the thermal isolation between heater and silicon substrate. Pt-heater showed nonlinear I-V characteristics due to the thermal isolation effect of the diaphragm. Its temperature coefficient of resistance was about $0.00378\;/^{\circ}C$ and Seebeck coefficient of Bi-Sb thermocouple was about $97\;{\mu}V/K$. The sensor showed that thermoelectric voltage decreased as thermal conductivity of gas increased, and flow sensitivity increased as heater voltage increased or as the distance between heater and thermocouple decreased. When heater voltage was about 2.5 V, $N_{2}$-flow sensitivity and thermal response time of the sensor were about $1.27\;mV{\cdot}(sccm)^{-1/2}$ and 0.13 sec., respectively.

• Journal of Sensor Science and Technology
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• v.16 no.6
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• pp.475-483
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• 2007

This paper proposes a readout integrated circuit (ROIC) for $32{\times}32$ infrared focal plane array (IRFPA) detector, which consist of reference resistor, detector resistor, reset switch, integrated capacitor and operational amplifier. Proposed ROIC is designed using $0.35{\;}{\mu}m$ 2P-4M (double poly four metal) n-well CMOS process parameters. Low noise folded cascode operational amplifier which is a key element in the ROIC showed 12.8 MHz unity-gain bandwidth and open-gain 89 dB, phase margin $67^{\circ}$, SNR 82 dB. From proposed circuit, we gained output voltage variation ${\Delta}17{\};mV/^{\circ}C$ when the detector resistor varied according to the temperature.

• International Journal of Advanced Culture Technology
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• v.7 no.4
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• pp.236-241
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• 2019

This paper will read about a multichannel frequency-modulated continuous wave (FMCW) radar sensor with switching transmit (TX) antennas is developed at W-band. To achieve a high angular resolution, a uniform linear array consisting of 5 switching-TX and 12 receive (RX) antennas is employed with the digital beamforming technique. The overall radar front-end module comprises a W-band transceiver and TX/RX antennas. A multichannel transceiver module consists of 5 up-conversion and 12 down-conversion channels, where one of the TX channels is sequentially switched ON. For developing transmitter, we developed an HPA (high power amplified) MMIC chip for W-band radar system and fabricated a transmitter module using this chip. In order to develop the W-band transmitter, we analyzed the important antenna transition structure from HPA MMIC line to W/G (Waveguide)antenna via M/S(microstrip) and fabricated it with 5 transmission channels. As a result, the output power of the transmitter was within 1 dB of the error range after analysis and measurement under normal temperature and environmental conditions.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.6
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• pp.907-915
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• 2013

Tire Pressure Monitoring System (TPMS) is an auxiliary safety system for recognizing the condition of tires based on the pressure and temperature data transmitted from the sensor unit installed on a tire of the vehicle. Using TPMS, a driver can frequently check the state of tires and it aids to maintain the optimum running condition of the vehicle. Since TPMS must utilize the wireless communication technique to transmit data from a sensor unit to a signal processing unit installed in the vehicle, it suffers from interference signals caused by various external electrical or electronic devices. In order to suppress high-power interference signals, we employ beamforming techniques based on the uniform linear antenna array. As the number of the antennas is increased, the performance of the interference suppression is improved. However, there is the limit of the number of antennas, installed in the center of a vehicle, because of its size. In this paper, we compare and analyze the performance of the beamformer, when reducing the interelement spacing of antennas, to increase the number of the receiving antennas. For the performance analysis of the beamformers, we consider the switching beamformer and minimum-variance distortionless-response (MVDR) beamformer for TPMS, recently proposed.

• Korean Journal of Materials Research
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• v.28 no.1
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• pp.32-37
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• 2018

We report on the efficient detection of NO gas by an all-oxide semiconductor p-n heterojunction diode structure comprised of n-type zinc oxide (ZnO) nanorods embedded in p-type copper oxide (CuO) thin film. The CuO thin film/ZnO nanorod heterostructure was fabricated by directly sputtering CuO thin film onto a vertically aligned ZnO nanorod array synthesized via a hydrothemal method. The transport behavior and NO gas sensing properties of the fabricated CuO thin film/ZnO nanorod heterostructure were charcterized and revealed that the oxide semiconductor heterojunction exhibited a definite rectifying diode-like behavior at various temperatures ranging from room temperature to $250^{\circ}C$. The NO gas sensing experiment indicated that the CuO thin film/ZnO nanorod heterostructure had a good sensing performance for the efficient detection of NO gas in the range of 2-14 ppm under the conditions of an applied bias of 2 V and a comparatively low operating temperature of $150^{\circ}C$. The NO gas sensing process in the CuO/ZnO p-n heterostructure is discussed in terms of the electronic band structure.