• Journal of Sensor Science and Technology
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• v.25 no.6
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• pp.440-446
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• 2016

This study introduces the characteristics of current-voltage (I-V) and impedance variance for $ZnO-Zn_2BiVO_6-Co_3O_4$ (ZZCo), which is sintered at $900^{\circ}C$, according to temperature changes. ZZCo varistor demonstrates dramatic improvement of non-linear coefficient, ${\alpha}=66$, with lower leakage current and higher insulating resistivity than those of ZZ ($ZnO-Zn_2BiVO_6$) from the aspect of I-V curves. While both systems are thermally stable up to $125^{\circ}C$, ZZCo represents a higher grain boundary activation energy with 1.05 eV and 0.94 eV of J-E-T and from IS & MS, respectively, than that of ZZ with 0.73 eV and 0.82 eV of J-E-T and from IS & MS, respectively, in the region above $180^{\circ}C$. It could be attributed to the formation of $V^*_o$(0.41~0.47 eV) as dominant defect in two systems, as well as the defect-induced capacitance increase from 781 pF to 1 nF in accordance with increasing temperature. On the other hand, both the grain boundary capacitances of ZZ and ZZCo are shown to decrease to 357 pF and 349 pF, respectively, while the resistances systems decreased exponentially, in accordance with increasing temperature. So, this paper suggests that the application of newly formed liquid phases as sintering additives in both $Zn_2BiVO_6$ and the ZZCo-based varistors would be helpful in developing commercialized devices such as chips, disk-type ZnO varistors in the future.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.260-260
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• 2013

Multiferroic materials have attracted much attention due to their fascinating fundamental physical properties and technological applications in magnetic/ferroelectric data-storage systems, quantum electromagnets, spintronics, and sensor devices. Among single-phase multiferroic materials, $BiFeO_3 $ is a typical multiferroic material with a room temperature magnetoelectric coupling in view of high magnetic-and ferroelectric-ordering temperatures (Neel temperature $T_N$~647 K and Curie temperature $T_C$~1,103 K). Rare-earth ion substitution at the Bi sties is very interesting, which induces suppressed volatility of Bi ion and improved ferroelectric properties. At the same time, Fe-site substitution with magnetic ions is also attracting, and the enhanced ferromagnetism was reported. In this study, $Bi_{1-x}Dy_xFe_{0.95}Co_{0.05}O_3$ (x=0, 0.05 and 0.1) bulk ceramic compounds were prepared by solid-state reaction and rapid sintering. High-purity $Bi_2O_3$, $Dy_2O_3$, $Fe_2O_3$ and $Co_3O_4$ powders with the stoichiometric proportions were mixed, and calcined at $500^{\circ}C$ or 24 h to produce $Bi_{1-x}Dy_xFe_{0.95}Co_{0.05}O_3$. The samples were immediately put into an oven, which was heated up to $800^{\circ}C$ nd sintered in air for 30 min. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The field-dependent magnetization measurements were performed with a vibrating-sample magnetometer. The electric polarization was measured at room temperature by using a standard ferroelectric tester (RT66B, Radiant Technologies).

• 한국연소학회:학술대회논문집
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• 2003.05a
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• pp.75-83
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• 2003

Diode laser absorption system is advantageous of their non-invasive nature, fast response time, high sensitivity and real-time measurement capability. Furthermore, recent advances in room-temperature, near-IR and visible diode laser sources for telecommunication, optical data storage applications are enabling combustion diagnostics system based on diode laser absorption spectroscopy. So, combined with fiber-optics and high sensitive detection strategies, compact and portable sensor system are now appearing for a variety of applications. The objective of this research is to take advantage of distributed feed-back diode laser and develope new gas sensing system. It experimentally found out that the wavelength, power characteristics as a function of injection current and temperature. In addition to direct absorption and wavelength modulation spectroscopy have been demonstrated in these experiments and have a bright prospect to this diode laser system.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1114-1116
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• 1995

P/N(CuO/ZnO) Heterojunction gas sensors were made by 2-step sintering methods and its gas sensing property was measured by varying the injected gases and the operating temperatures. As the applied voltage was increased in air ambients, the current-voltage characteristics shown the ohmic properties. However, when the CO gas ambients, 500 ppm at $200^{\circ}C$, the current-voltage characteristics behaves like a rectifying diode s after 3 mins later and its conduction mechanism is discussed qualitatively for the first times.

• Journal of Welding and Joining
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• v.14 no.5
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• pp.113-121
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• 1996

The arc sensor has been most widely used for weld seam tracking through welding current or voltage variation. In this work, the relation between the arc light intensity and welding condition is investigated using heat balance in the Plasma for its possible application to seam tracking in the GMAW process. The arc light intensity is derived to be the function of the arc length and welding current Experiments are carried out to verify the proposed heat balance model. Performances of least square and integration methods to process the signals for seam tracking are compared experimentally. Predicted arc light intensity shows reasonably good agreement with experimental results. The weld seam is successfully tracked through the arc light intensity. The least square and integration methods demonstrate almost same performance of seam tracking with $CO_2$gas shielding.

• Journal of Energy Engineering
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• v.24 no.3
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• pp.34-39
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• 2015

Recently, Air pollution is gradually increasing which are coming from the exhaust of the ICE vehicles in the world. ICE vehicle exhaust gas and $CO_2$ are widely suspected of contributing to the called greenhouse effect, fueling fears of global warming. Therefore, many countries are striving to decrease the vehicle exhaust gas and have developed a variety of policies as air pollution regulation plans. To comply with the regulations, automotive industry has developed hybrid vehicles, which have features of both ICE vehicles and electric vehicles. Hybrid car is eco-friendly and has lowered exhausting gases and improved fuel efficiency. This research has been written to show that break down cases with EGR valve in hybrid cars, steadily increasing in use, and to help with on-site maintenance.

• Proceedings of the Korean Society of Computer Information Conference
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• 2013.07a
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• pp.345-347
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• 2013

최근 환경문제의 심각성이 고조됨에 따라 Co2 배출량 감소계획에 따른 세계 각국의 정부주도로 민간 및 지방자치단체에서도 그린에너지, 저탄소 녹색성장 프로젝트, 승용차요일제 등 다양한 정책을 시행하고 있다. 따라서 탄소저감의 효율적인 방안으로서 승용차 운행을 줄이고 자전거 활용의 활성화에 대한 관심이 증대되고 있다. 본 논문에서는 자전거활용의 활성화를 위하여 자전거 도난방지와 관리를 위한 저비용의 무선 네트워크를 활용한 임베디드 제어 모듈과 모바일 서비스 기반의 자전거 관리시스템을 설계하고 구현 기법을 제안하였다.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.832-834
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• 1999

This paper is a study on the real-position measurements of mobile object using n network. 2-D PSD sensor is used to measure th position of moving object with light source. Position Sensitive Detector(PSD) is an useful which can be used to measure the position o incidence light in accuracy and in real-time. T the position of light source of moving target, neural network technique are proposed and applied. Real-time position measurements of the mobile robot with light source is examined to validate the proposed method. It is shown that the proposed technique provides accurate position estimation of the moving object.

• Annual Conference of KIPS
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• 2005.05a
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• pp.1593-1596
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• 2005

홈 네트워크 기술에서 무선 통신의 중요성이 날로 커져가고 있다. 본 논문에서는 무선 통신 방식으로 구현함에 있어서 중요한 것을 저전력 특성을 가져야 한다는 것이다. 저전력 특성 구현을 위하여 센서, CPU, RF 모듈의 선택에 대해 알아보고, 저전력 무선 보드 센서 설계 및 실제 구현 방식을 제시한다. 저전력 방식으로 설계된 센서는 AA 배터리 2 개로 1 년 이상의 성능을 낼 것으로 판단된다.

• Design & Manufacturing
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• v.12 no.2
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• pp.11-15
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• 2018

In this study, we proposed three analysis methods to calculate the flatness of torque-angle sensors (TAS). We introduced two statistical and one geometrical methods in evaluating the precision of the flat plane in the axis direction for TAS. To verified the results, we fabricated TAS and a reference sample using a injection molding machine, mold, polyester as a raw material. We measured ($x_i$, $y_i$) position using 3D contact automated system and applied three analysis methods developed for TAS and a reference sample to see the feasibility. While each analysis method has its own pros and cons, the analysis using the shortest optimal distance was the most precise technique for the flatness evaluation of TAS components.