• 센서학회지
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• 제9권3호
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• pp.153-162
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• 2000

평형수소 삼중점 (13.8033 K)부터 물의 삼중점 (273.16 K) 온도영역에서 표준온도계로 사용되는 캡슐형 백금저항온도계를 일차 교정하려면 고순도 물질의 삼중점이 사용된다. 국제온도눈금-1990 (ITS-90)을 확립하기 위해 평형수소, 네온, 산소, 아르곤, 수은 및 물의 삼중점 중에서 평형수소의 삼중점을 제외한 5 개의 삼중점을 실현하였다. 각각의 삼중점에서 국제비교용으로 채택된 캡슐형 백금저항온도계 2대의 저항을 2회 반복하여 측정하였다. 측정된 삼중점에서의 합성표준불확도는 A형 불확도와 B형 불확도 평가방법을 고려하여 산출하였다. 한국표준과학연구원에서 ITS-90에 정의된 네온, 산소, 아르곤, 수은 및 물의 삼중점에서의 합성표준불확도 추정결과는 각각 0.18 mK, 0.14 mK, 0.14 mK, 0.24 mK 및 0.11 mK 이었다.

• 센서학회지
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• 제16권2호
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• pp.159-164
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• 2007

Thin films of platinum were deposited on a $Al_{2}O_{3}/ONO(SiO_{2}-Si_{3}N_{4}-SiO_{2})/Si$-substrate with an 2-inch Pt(99.99 %) target at room temperature for 20, 30 and 60 min by DC magnetron sputtering, respectively X-ray diffract meter (XRD) was used to analyze the crystallanity of the thin films and field emission scanning electron microscopy (FE-SEM) was employed for the investigation on crystal growth. The densification and the grain growth of the sputtered films have a considerable effect on sputtering time and annealing temperatures. The resistance of the Pt thin films was decreased with increasing deposition time and sintering temperature. Pt micro heater thin film deposited for 60 min by DC magnetron sputtering on an $Al_{2}O_{3}$/ONO-Si substrate and annealed at $600^{\circ}C$ for 1 h in air is found to be a most suitable micro heater with a generation capacity of $350^{\circ}C$ temperature and 645 mW power at 5.0 V input voltage. Adherence of Pt thin film and $Al_{2}O_{3}$ substrate was also found excellent. This characteristic is in good agreement with the uniform densification and good crystallanity of the Pt film. Efforts are on progress to find the parameters further reduce the power consumption and the results will be presented as soon as possible.

• 한국재료학회지
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• 제18권11호
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• pp.628-633
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• 2008

ZnO nanopowders were synthesized by the sol-gel method using hydrazine reduction, and their gas responses to 6 gases (200 ppm of $C_2H_5OH$, $CH_3COCH_3$, $H_2$, $C_3H_8$, 100 ppm of CO, and 5 ppm of $NO_2$) were measured at $300\;{\sim}\;400^{\circ}C$. The prepared ZnO nanopowders showed high gas responses to $C_2H_5OH$ and $CH_3COCH_3$ at $400^{\circ}C$. The sensing materials prepared at the compositions of [$ZnCl_2$]:[$N_2H_4$]:[NaOH] = 1:1:1 and 1:2:2 showed particularly high gas responses ($S\;=\;R_a/R_g,\;R_a$ : resistance in air, $R_g$ : resistance in gas) to 200 ppm of $C_2H_5OH$($S\;=\;102.8{\sim}160.7$) and 200 ppm of $CH_3COCH_3$($S\;= 72.6{\sim}166.2$), while they showed low gas responses to $H_2$, $C_3H_8$, CO, and $NO_2$. The reason for high sensitivity to these 2 gases was discussed in relation to the reaction mechanism, oxidation state, surface area, and particle morphology of the sensing materials.

• Journal of Multimedia Information System
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• 제7권2호
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• pp.189-196
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• 2020

We have developed a device for recording biological data by inserting three electrodes and a needle with an angular velocity sensor into the moth for the purpose of measuring the electromyogram of the flapping and the corresponding lift force. With this measurement, it is possible to evaluate the moth-physiological function of moths, and the amount of pesticides that insects are exposed to (currently LD50-based standards), especially the amount of chronic low-concentration exposure, can be reduced the dose. We measured and recorded 2-channel electromyography (EMG) and angular velocity corresponding to pitch angle (pitch-like angle) associated with wing flapping for 100 sweet potato hawkmoths (50 females and 50 males) with the animals suspended and constrained in air. Overall, the angular velocity and amplitude of EMG signals demonstrated high correlation, with a correlation coefficient of R = 0.792. In contrast, the results of analysis performed on the peak-to-peak (PP) EMG intervals, which correspond to the RR intervals of ECG signals, indicated a correlation between ΔF fluctuation and angular velocity of R = 0.379. Thus, the accuracy of the regression curve was relatively poor. Using a DC amplification circuit without capacitive coupling as the EMG amplification circuit, we confirmed that the baseline changes at the gear change point of wing flapping. The following formula gives the lift provided by the wing: angular velocity × thoracic weight - air resistance - (eddy resistance due to turbulence). In future studies, we plan to attach a micro radio transmitter to the moths to gather data on potential energy, kinetic energy, and displacement during free flight for analysis. Such physiological functional evaluations of moths may alleviate damage to insect health due to repeated exposure to multiple agrochemicals and may lead to significant changes in the toxicity standards, which are currently based on LD50 values.

• Journal of Electrical Engineering and Technology
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• 제2권4호
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• pp.468-477
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• 2007

The DTC of voltage source inverter-fed PMSMs is based on hysteresis controllers of torque and flux. It has several advantages, namely, elimination of the mandatory rotor position sensor, less computation time, and rapid torque response. In addition, the stator resistance is the only parameter, which should be known, and no reference frame transformation is required. The DTC theory has achieved great success in the control of induction motors. However, for the control of PMSM drives proposed a few years ago, there are many basic theoretical problems that must be clarified. This paper describes an investigation into the effect of the zero voltage space vectors in the DTC system and points out that if using it rationally, not only can the DTC of the PMSM drive be driven successfully, but torque and flux ripples are reduced and overall performance of the system is improved. The implementation of DTC in PMSM drives is described and the switching tables specific for an interior PMSM are derived. The conventional eight voltage-vector switching table, which is namely used in the DTC of induction motors does not seem to regulate the torque and stator flux in a PMSM well when the motor operates at low speed. Modelling and simulation studies have both revealed that a six voltage-vector switching table is more appropriate for PMSM drives at low speed. In addition, the sources of difficulties, namely, the error in the detection of the initial rotor position, the variation of stator resistance, and the offsets in measurements are analysed and discussed.

• 센서학회지
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• 제28권6호
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• pp.366-370
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• 2019

In this study, we have successfully fabricated a highly conductive transparent electrode using Ag nanowires, based on piezoelectric polyvinylidene difluoride (PVDF) film, that can be applied as transparent and flexible speakers. The structural morphology of the Ag nanowires was confirmed by a detailed scanning electron microscopy. Ultraviolet-visible spectroscopy demonstrated that the transparent electrode fabricated by the Ag nanowires exhibited a transmittance of above 70%. The transparent electrode also showed very low sheet resistance with high flexibility. We have further developed an anti-oxidation coating layer by using a tetraethyl orthosilicate-poly trimethyloxyphenylsilane (TEOS-PTMS) slurry technique. It was confirmed that the transmittance and sheet resistance of the antioxidant film depends critically on the humidity of the film surface. We believe such Ag nanowire electrodes are a very promising next-generation transparent electrode technology that can be used in future flexible and transparent devices.

• 한국세라믹학회지
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• 제22권4호
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• pp.54-60
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• 1985

Gas sensing materials for detecting flammable gases such as $CH_4$, $C_3H_8$ and n-$C_4H_{10}$ were developed by util-izing $In_2O_3$ as the principal sensing material. The sensing materials were formulated by mixing $In_2O_3$ powder with one or two other chemicals such as $SnO_2$, $Y_2O_3$ and $Al_2O_3$ with a small addition of $PdCl_2$ as a catalyst. Sample of sensor were fabricated by coating each of the mixtures on a ceramic tube impregnating ethylsili-cate and firing at 75$0^{\circ}C$ Each material mixture was evaluated by measuring and comparing gas sensitivity(resistance in air/resistance with gas) to flammable gases such as $CH_4$, $C_3H-8$ and n-$C_4H_{10}$. It was found that among fifteen compositions tested three compositions as follows show the highest gas sensitivity and thus are very feasible for commercialization as the gas sensors ; o49.5 $In_2O_3$+50 Al2O3_0.5 PdCl2(wt%) o $20In_2O_3+29$ $SnO_2+50$ $Al_2O_3+1$ $PdCl_2$(wt%) o40 $In_2O_3$+9 $Y_2O_3+50$ $Al_2O_3+1$ $PdCl_2$(wt%)

• 한국세라믹학회지
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• 제56권2호
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• pp.197-204
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• 2019

An electrochemical oxygen permeating membrane (OPM) is fabricated using Zr_0.895Sc_0.095Ce_0.005Gd_0.005O_2-δ (ScCeGdZ) as the solid electrolyte and aLa_0.7Sr_0.3MnO₃-bScCeGdZ composite (LZab, electrode) as the electrode. The crystal phase of the electrode and the microstructure of the membrane is investigated with X-ray diffraction and scanning electron microscopy. The electrochemical resistance of the membrane is examined using 2-p ac impedance spectroscopy, and LZ55 shows the lowest electrode resistance among LZ82, LZ55 and LZ37. The oxygen permeation is studied with an oxygen permeation cell with a zirconia oxygen sensor. The oxygen flux of the OPM with LZ55 is nearly consistent with the theoretical value calculated from Faraday's Law below a critical current. However, it becomes saturated above the critical current due to the limit of the oxygen ionic conduction of the OPM. The OPM with LZ55 has a very high oxygen permeation flux of ~ 3.5 × 10^-6 mol/㎠s in I = 1.4 A/㎠.

• 센서학회지
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• 제5권4호
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• pp.71-79
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• 1996

Indium tin oxide(ITO) 전극을 스파터링 법으로 피막시킨 9 MHz 수정진동자를 작용전극으로 사용하여 피롤을 전기화학적으로 중합시키면서, 수정진동자의 공진주파수 변화로 부터 중합량을 분석하고 공진저항의 변화로부터 막의 점탄성 변화를 분석함으로써 중합막의 유변학적 변화를 해석하였다. 본 실험에서 피롤막이 중합될 때 초기에는 탄성막을 형성하다가 점차 점탄성막으로 변화하지만 어느 순간에 다시 탄성막 점탄성막의 변화를 반복함을 확인하였다. 본 연구결과, 수정진동자를 이용하여 전기화학적 중합막의 유변학적 동특성을 중합과정에서 해석할 수 있음을 확인하였다.

• 한국재료학회지
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• 제8권3호
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• pp.263-267
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• 1998

본 연구에서는 금속 칼날 마스크와 펄스형 레이저 증착장치를 이용하여 $YBa_2Cu_3O_{7-\delta}$/$SrTiO_{3}$/$YBa_2Cu_3O_{7-\delta}$ 다층박막 형태의 In-situ SIS ramp dege 형태의 접합을 제작하였으며, 이의 특성을 조사하였다. 접합은 RSJ 형태의 전류-전압 특성ㅇ르 나타내고 있으며, 온도 변화에 따른 접합의 normal resistance는 약 $18 \omega$으로 온도에 무관하게 일정한 값을 나타내었다. 접합형태를 이용하여 감도(transfer function, dV/$d\Phi$)가 약 $22\mu$V/$\Phi_{0}$인 dc-SQUID센서를 제작하였으며, in-situ SIS ramp edge 형태의 접합이 센서로의 응용가능성을 충분히 가지고 있음을 보여 주었다.