• Current Optics and Photonics
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• v.3 no.6
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• pp.583-589
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• 2019

We report experimental results on 940-nm 350-mW AlGaAs/InGaAs transverse single-mode laser diodes (LDs) adopting graded-index separate confinement heterostructures (GRIN-SCH) and p,n-clad asymmetric structures, with improved temperature and small-divergence beam characteristics under high-output-power operation, for a three-dimensional (3D) motion-recognition sensor. The GRIN-SCH design provides good carrier confinement and prevents current leakage by adding a grading layer between cladding and waveguide layers. The asymmetric design, which differs in refractive-index distribution of p-n cladding layers, reduces the divergence angle at high-power operation and widens the transverse mode distribution to decrease the power density around emission facets. At an optical power of 350 mW under continuous-wave (CW) operation, Gaussian narrow far-field patterns (FFP) are measured with the full width at half maximum vertical divergence angle to be 18 degrees. A threshold current (I_th) of 65 mA, slope efficiency (SE) of 0.98 mW/mA, and operating current (I_op) of 400 mA are obtained at room temperature. Also, we could achieve catastrophic optical damage (COD) of 850 mW and long-term reliability of 60℃ with a TO-56 package.

• Journal of the Korean Magnetics Society
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• v.23 no.6
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• pp.200-204
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• 2013

In this study, we have fabricated magnetoresistive sensors of $50{\mu}m{\times}50{\mu}m$ cross type by trilayer structure of antiferromagnetic/nonmagnetic/ferromagnetic. The magnetic signal and magnetic domain of this sensor is measured. The sensor hysteresis loop is not in symmetrical at 0 Oe. This is may be due to the exchange coupling between ferromagnetic layer and anti ferromagnetic layer. This exchange bias value is 20 Oe. The sensor signal is measured at between the applied magnetic field and current. The sensor signal is measured between the applied magnetic field and current at $20^{\circ}$ and $90^{\circ}$ angles. The sensitivity of sensor signals is $20{\mu}V/Oe$ and $7{\mu}V/Oe$ at $20^{\circ}$ and $90^{\circ}$ angles, respectively. In addition, this sensor is also applied for the detection of magnetic bacteria at $20^{\circ}$ angle. From these results, we calculate the stray field of single bacteria is to be $5{\times}10^{-5}$Oe.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.31-32
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• 2006

A signal conditioning circuit for capacitive sensors was developed using a commercial single chip solution. Since capacitive displacement sensors can achieve high resolution and linearity, they have been widely used as precision sensors within the range of several hundred micrometers. However, they inherently have a limitation in low frequency range and some nonlinearity characteristics and so a specially designed signal conditioning circuit is needed to handle these properties. Up to now, several companies already have succeeded in the development of the capacitive sensors system and they are commercially available in the market. In this research, to construct the signal processing circuits more easily and simply, we used a universal LVDT signal conditioner (AD698). Since the AD698 provides one chip solution for a basic signal processing including modulation and demodulation using various internal components, we can build the processing circuits successfully with minimal additional circuits: a compensation circuits for the drift caused by the bias current of OP amplifiers and a fine adjustment circuit for the elimination of nonlinearity. The signal processing circuits shows nonlinearity less than 0.05% in the comparison with a laser interferometer.

• The Research Journal of the Costume Culture
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• v.26 no.4
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• pp.632-648
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• 2018

This study aims to contribute to the development of sports wearables. It was conducted by a convergence team of professionals in the fashion industry, kinesiology and sports studies, and computer science and engineering. The purpose of the current study was to design and develop a fabric-type fitness band for a sensor to measure acceleration during jump rope exercises. Computer science and engineering professionals developed the Arduino board and sensor, kinesiology and sports studies provided the necessary exercise protocol, and the fashion industry professionals developed the band. First, a fitness band preference survey was completed by men and women between the ages of 20 and 50. Typical uses of the band included tracking exercise amount as measured by the number of steps taken and calories burned. Strap watch closure, a single color and achromatic color, and soft and smooth touch materials were preferred as band design. Second, two fabric-type fitness bands were designed and developed. Design 1 had a 3-dimensional pocket for the sensor, bright blue color, and stretch binding around the edges and for a loop. Design 2 had a flat pocket for the sensor, achromatic color, mesh binding around the edges and two metal loops. Both designs had Velcro as a closure. Third, wear testing of both bands with the sensor were conducted of 15 women in their 20s. They wore the bands during jump rope exercises. Both bands generally satisfied the participants. The Design 2 band was slightly more satisfying than the Design 1 band.

• Progress in Medical Physics
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• v.13 no.1
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• pp.44-50
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• 2002

CsI(T1) single crystal was grown in a Bridgman growing apparatus, which has the diameter of 11 mm and the mole ratio of 0.001 mol%. Radiation sensors were made with CsITl)crystal and two photodiodes, and measured spectroscopic characteristics and linearity for gamma-ray and X-ray. The energy resolution of CsI(T1) radiation sensor has been measured with $^{22}$ Na, $^{137}$ Cs and $^{60}$ Co gamma standard sources. Also output linearity of CsITl) sensor was measured for diagnostic radiation region. The energy resolutions of CsI(T1) radiation sensor for 0.511MeV gamma-ray from Na-22 source, 0.662MeV from Cs-137 source, and 1.17MeV and 1.332MeV from Co-60 source were 13.2%, 8.3%, 6.7%, and 5.1% respectively. Also the output linearity up to 80mAs current for 60kVp, 80kvp, 100kVp, 120kVp tube voltages has been studied.

• Journal of IKEEE
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• v.22 no.3
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• pp.786-792
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• 2018

A third-order sigma-delta modulator with the architecture of cascade of integrator feedback (CIFB) is proposed for an analog-digital converter used in low-power sensor interfaces. It consists of three switched-capacitor integrators using a gain-enhanced current-mirror-based amplifier, a single-bit comparator, and a non-overlapped clock generator. The proposed sigma-delta analog modulator with over-sampling ratio of 160 and maximum SNR of 90.45 dB is implemented using $0.11-{\mu}m$ CMOS process with 1.2-V supply voltage. The area and power consumption of the sigma-delta analog modulator are $0.145mm^2$ and $341{\mu}W$, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.624-629
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• 2018

The current study was conducted to develop a portable composite gas detector allowing the detection of both $CO_2$ and $CH_4$ gases by means of the Non Dispersive Infra-Red (NDIR) method. The gas detector is configured to radiate infrared waves using infrared lamps, where the wavelength of the infrared light is reduced due to absorption throughout the chamber, and this reduction (absorption) is detected by the absorption detector, before being converted and amplified to a 3.5V~6V electrical signal, providing as accurate a measurement as possible. The conventional singe sensor method measures the relative measurement by absorbing only specified wavelengths of infrared radiation, which in the case of gas detection leads to problems with accuracy due to the lack of a reference sensor when detecting light with a wavelength of only $4.26{\mu}m$. The dual sensor employed in this study provides a comparative measurement between the reference value derived from the wavelength of $3.91{\mu}m$, which is not influenced by other gas sources, and the measurement value derived from the wavelength of $4.26{\mu}m$, in order to reduce the errors and enhance the reliability, thereby allowing low power consumption for portable devices and multi-gas detection for both $CO_2$ and $CH_4$ gases. The portable composite gas detector developed herein provides a measurement rage of 0ppm~5,000ppm for $CO_2$ gas, and 0.5%vol for $CH_4$, which allows the determination of whether the $CO_2$ and $CH_4$ contents in indoor air are less than 1,000ppm or not. The current study established that the composite gas detector can be interlinked with firefighting appliances through portable devices or home automation, and is anticipated to be very effective in fire prevention.

• Journal of the Korean Vacuum Society
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• v.18 no.4
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• pp.259-265
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• 2009

We fabricated the field effect transistor using single crystalline ZnO nanowires synthesized by a conventional thermal evaporation method and investigated their basic properties under the various conditions such as ultraviolet irradiation, reducing gas and electrolyte. The typical carrier concentration and mobility of the single crystalline ZnO nanowire with a diameter of 100 nm and length of 5 um were $1.30{\times}10^{18}cm^{-3}$ and $15.6cm^2V^{-1}s^{-1}$, respectively. The current of ZnO nanowire under ultraviolet irradiation significantly increased about 400 times higher as compared to in the darkness. In addition, the ZnO nanowire showed typical sensing characteristics for $H_2$ and CO due to well-known surface reactions and typical current-voltage characteristics under the 0.1 M NaCl electrolyte.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.492-498
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• 2016

It is well known that since abrupt faults in induction motors tend to lead to subsequent faults and deterioration of the drive apparatus, motor faults may lead to several operating restrictions, such as security problems and economic loss. A lot of research has been done in the area of diagnosis to detect machine faults and to prevent catastrophic hazards in the motor drive system. This paper presents a new method of motor current signature analysis in which the DC-link current of the inverter-driven induction motor system, where a single current sensor is employed instead of three AC current sensors, is measured, and fast Fourier transform analysis is performed. This proposed method makes it possible to easily discern and clearly separate the motor fault current signature from the normal operation current flowing through the stator and rotor windings.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.2
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• pp.119-127
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• 2008

In this paper, the modular line-connected photovoltaic PCS (photovoltaic power conditioning system) is proposed. A step-up DC-DC converter using a active-clamp circuit and a dual series-resonant rectifier is proposed to achieve a high efficiency and a high input-output voltage ratio efficiently. An IncCond (incremental conductance) MPPT (maximum power point tracking) algorithm that improves MPPT characteristic is used. The PV module current is estimated without using a DC current sensor. By control a inverter using a linearized output current controller, a unity power factor is achieved. All algorithms and controllers are implemented on a single-chip microcontroller and the superiority of the proposed DC-DC converter and controllers is proved by experiments.