• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.72-72
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• 2011

Recently, Zinc oxide (ZnO) nano-structures have been received attractive attention because of their outstanding optical and electrical properties. It might be a promising material considered for applications to photonic and electronic devices such as ultraviolet light emitting diode, thin film transistor, and gas sensors. ZnO nano-structures can be typically synthesized by the VLS growth mode and self-assembly. In the VLS growth mode using various growth techniques, the noble metal catalysts such as Au and Sn were used. However, the growth of ZnO nano-structures on nano-crystalline Au seeds using radio frequency (RF) magnetron sputtering might be explained by the profile coating, i.e. the ZnO nano-structures were a morphological replica of Au seeds. Ga doped ZnO (ZnO:Ga) nano-structures using this concept were synthesized and characterized by XRD, AFM, SEM, and TEM. We found that surface morphology is drastically changed from initial islands to later sun-flower typed nano-structures. We will present the structural evolution of ZnO:Ga nano-structures with increasing the film thickness.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권1호
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• pp.46-63
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• 2024

One of the biggest dangers in the globe is water contamination. Water is a necessity for human survival. In most cities, the digging of borewells is restricted. In some cities, the borewell is allowed for only drinking water. Hence, the scarcity of drinking water is a vital issue for industries and villas. Most of the water sources in and around the cities are also polluted, and it will cause significant health issues. Real-time quality observation is necessary to guarantee a secure supply of drinking water. We offer a model of a low-cost system of monitoring real-time water quality using IoT to address this issue. The potential for supporting the real world has expanded with the introduction of IoT and other sensors. Multiple sensors make up the suggested system, which is utilized to identify the physical and chemical features of the water. Various sensors can measure the parameters such as temperature, pH, and turbidity. The core controller can process the values measured by sensors. An Arduino model is implemented in the core controller. The sensor data is forwarded to the cloud database using a WI-FI setup. The observed data will be transferred and stored in a cloud-based database for further processing. It wasn't easy to analyze the water quality every time. Hence, an Optimized Neural Network-based automation system identifies water quality from remote locations. The performance of the feed-forward neural network classifier is further enhanced with a hybrid GA- PSO algorithm. The optimized neural network outperforms water quality prediction applications and yields 91% accuracy. The accuracy of the developed model is increased by 20% because of optimizing network parameters compared to the traditional feed-forward neural network. Significant improvement in precision and recall is also evidenced in the proposed work.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1694-1697
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• 2002

KEPCO is planing to adopt a preventive diagnostic system to obtain the reliability of transformer and GIS in 765kV substation. KEPRI has developed the preventive diagnostic system for 765kV substation since 1997. We used various sensors and fault detecting devices such as a dissolved gas analyzer in oil, a ultrasonic detector and LA leakage current detector, etc., and carried out adaptation tests at the both a laboratory and a site. We developed a data acquisition system, a communication control unit and a server system as well. Furthermore, monitoring program and diagnostic expert system were also developed. This paper describes the preventive diagnostic system for 765kV Sin-Ga-Pyong and Sin-Tae-Baek substations which will be operated from 2004.

• Journal of information and communication convergence engineering
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• 제16권1호
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• pp.12-16
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• 2018

In this work, a voltage controlled oscillator (VCO) monolithic microwave integrated circuit (MMIC) was demonstrated for 10-GHz band motion detecting sensors. The VCO MMIC was fabricated using a $2-{\mu}m$ InGap/GaAs HBT process, and the tuning of the oscillation frequency is achieved by changing the internal capacitance in the HBT, instead of using extra varactor diodes. The implemented VCO MMIC has a micro size of $500{\mu}m{\times}500{\mu}m$, and demonstrates the value of inserting the VCO into a single chip transceiver. The experimental results showed that the frequency tuning characteristic was above 30 MHz, with the excellent output flatness characteristic of ${\pm}0.2dBm$ over the tuning bandwidth. And, the VCO MMIC exhibited a phase noise characteristic of -92.64 dBc/Hz and -118.28 dBc/Hz at the 100 kHz and 1 MHz offset frequencies from the carrier, respectively. The measured values were consistent with the design values, and exhibited good performance.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.99-99
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• 2014

Transparent oxide semiconductors (TOSs) are. currently attracting attention for application to transparent electrodes in optoelectronic devices and active channel layers in thin-film transistors. One of the key issues for the realization of next generation transparent electronic devices such as transparent complementary metal-oxide-semiconductor thin-film transistors (CMOS TFTs), transparent wall light, sensors, and transparent solar cell is to develop p-type TOSs. In this talks, I will introduce issues and status related to p-type TOSs such as LnCuOQ (Ln=lanthanide, Q=S, Se), $SrCu_2O_2$, $CuMO_2$ (M=Al, Ga, Cr, In), ZnO, $Cu_2O$ and SnO. The growth and properties of SnO and Cu-based oxides and their application to electronic devices will be discussed.

• 센서학회지
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• 제17권6호
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• pp.437-446
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• 2008

Single crystalline ${ZnIn_2}{Se_4}$ layers were grown on thoroughly etched semi-insulating GaAs (100) substrate at $400^{\circ}C$ with hot wall epitaxy (HWE) system by evaporating ${ZnIn_2}{Se_4}$ source at $630^{\circ}C$. The crystalline structure of the single crystalline thick films was investigated by the photoluminescence (PL) and Double crystalline X-ray rocking curve (DCRC). The carrier density and mobility of ${ZnIn_2}{Se_4}$ single crystalline thick films measured from Hall effect by van der Pauw method are $9.41{\times}10^{16}cm^{-3}$ and $292cm^2/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the ${ZnIn_2}{Se_4}$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)$=1.8622 eV-$(5.23{\times}10^{-4}eV/K)T^2$/(T+775.5 K). After the as-grown ${ZnIn_2}{Se_4}$ single crystalline thick films was annealed in Zn-, Se-, and In-atmospheres, the origin of point defects of ${ZnIn_2}{Se_4}$ single crystalline thick films has been investigated by the photoluminescence (PL) at 10 K. The native defects of $V_{Zn}$, $V_{Se}$, $Zn_{int}$, and $Se_{int}$ obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the Se-atmosphere converted ${ZnIn_2}{Se_4}$ single crystalline thick films to an optical p-type. Also, we confirmed that In in ${ZnIn_2}{Se_4}$/GaAs did not form the native defects because In in ${ZnIn_2}{Se_4}$ single crystalline thick films existed in the form of stable bonds.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.69-70
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• 2008

Micro resonators have been actively investigated for bio/chemical sensors and RF M/NEMS devices. Among various materials, SiC is a very promising material for micro/nano resonators since the ratio of its Young's modulus, E, to mass density, $\rho$, is significantly higher than other semiconductor materials, such as, Si and GaAs. Polycrystalline 3C-SiC cantilever with different lengths were fabricated using a surface micromachining technique. Polycrystalline 3C-SiC micro resonators were actuated by piezoelectric element and its fundamental resonance was measured by a laser vibrometer in air and vacuum at room temperature, respectively. For the cantilever with $100{\mu}m$ length, $10{\mu}m$width and $1.3{\mu}m$ thickness, the fundamental frequency appeared at 147.2 kHz.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.386-391
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• 1998

Parameter estimation method of induction motor for vector control is presented in this paper. It can be easily implemented and applied to inverters in the industrial field, because it needs no additional hardware such as voltage sensors and measuring equipment. The proposed algorithm in this paper is so straightforward and practical that it can be easily implemented on the built-in controllers with little overhead. The proposed estimation algorithm has good accuracy and repeatability for parameters due to the sensitivity of estimation errors. This enables its total consuming time to be made shorter. Experimental results and applications in the industrial fields verify the validity and usefulness of the proposed method.

• ETRI Journal
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• 제32권5호
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• pp.827-830
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• 2010

For an adaptive cruise control (ACC) stop-and-go system in automotive applications, three radar sensors are needed because two 24 GHz short range radars are used for object detection in an adjacent lane, and one 77 GHz long-range radar is used for object detection in the center lane. In this letter, we propose a single sensor-based 24 GHz radar with a detection capability of up to 150 m and ${\pm}30^{\circ}$ for an ACC stop-and-go system. The developed radar is highly integrated with a high gain patch antenna, four channel receivers with GaAs RF ICs, and back-end processing board with subspace based digital beam forming algorithm.

• 센서학회지
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• 제31권1호
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• pp.36-40
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• 2022

High-power devices, such as LEDs and radars, inevitably generate a large amount of heat, which is the main cause of shortening lifespan, deterioration in performance, and failure of electronic devices. The embedded IC process can be a solution; however, when applied to large-area substrates (larger than 8 in), there is a limit owing to the difficulty in the process after wafer thinning. In this study, an 8-in wafer-level high-power electronic package based on the embedded IC process was implemented with temporary bonding and debonding technology using double-sided thermal release tape. Good heat-dissipation characteristics were demonstrated both theoretically and experimentally. These findings will advance the commercialization of high-power electronic packaging.