• 한국재료학회지
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• 제18권12호
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• pp.655-659
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• 2008

The NO gas sensing properties of ZnO-carbon nanotube (ZnO-CNT) composites fabricated by the coaxial coating of single-walled CNTs with ZnO were investigated using pulsed laser deposition. Upon examination, the morphology and crystallinity of the ZnO-CNT composites showed that CNTs were uniformly coated with polycrystalline ZnO with a grain size as small as 5-10 nm. Gas sensing measurements clearly indicated a remarkable enhancement of the sensitivity of ZnO-CNT composites for NO gas compared to that of ZnO films while maintaining the strong sensing stability of the composites, properties that CNT-based sensing materials do not have. The enhanced gas sensing properties of the ZnO-CNT composites are attributed to an increase in the surface adsorption area of the ZnO layer via the coating by CNTs of a high surface-to-volume ratio structure. These results suggest that the ZnO-CNT composite is a promising template for novel solid-state semiconducting gas sensors.

• 전기화학회지
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• 제11권2호
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• pp.105-108
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• 2008

최근, 증폭되는 관심은 창조적인 방법에 따른 CNTs의 합리적인 기능화에 집중하고 있다. 하지만 CNTs의 적지 않은 독성은 아직 논쟁의 이슈가 되어 그 생물학적 응용이 제한되어왔다. CNT의 생체 적합성을 개선하기 위해 본 연구에서는 CNT와 유기적인 티타늄을 시작 물질로 나노 혼성의 CNT-$TiO_2$를 제조하여 전기화학적 거동을 고찰하였다. 본 연구는 개질 된 접촉면이 이질의 전자 전송율을 가속하고, 그 결과, 관련 검출감도를 강화할 수 있었음을 확인하였다. 또한 암의 초기 진단을 위한 생물학적 적합성으로 멀티신호의 민감한 바이오센서의 개발에 새로운 전략으로서 그 잠재력의 응용을 제안하고자 한다.

• 대한기계학회논문집B
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• 제37권8호
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• pp.789-798
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• 2013

형식인증시험을 통해 획득된 풍력발전기의 기계적 하중 데이터를 분석하기 위한 관련 프로그램 개발과 절차가 수행되었다. IEC 61400-13 규격을 기반으로 하는 측정 데이터에 대한 검증, 하중유형에 따른 분류, 시계열 및 통계 데이터 분석, 파워 스펙트럼 밀도함수 및 피로하중 스펙트럼 계산, 등가하중 계산 등의 절차가 본 프로그램을 통해 수행되었다. 수집된 데이터들이 피로하중을 산정하기에 충분한가를 판단하기 위해 정상전력생산의 경우에 대한 수집행렬을 구성하였다. 50 개의 하중 범위 분할 개수를 사용하는 우수집계법을 통해 피로하중 스펙트럼이 얻어지며, 사용된 재료에 따라 다르게 S-N 선도의 기울기를 적용하여 최종적으로 등가하중을 산출하였다. 모노파일 하부구조를 가지는 NREL 5MW 풍력발전기의 공탄성 시뮬레이션 데이터에 이용하여 위의 전반적인 절차를 수행하였다.

• 한국식품과학회지
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• 제48권2호
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• pp.117-121
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• 2016

시판 증류주 13종을 선정하여 전자코, 전자혀를 이용한 향기패턴과 맛패턴을 분석하였다. 전자코 분석 결과, 원재료에 따라 증류주의 향기성분이 구분됨을 확인하였다. 원재료가 좁쌀인 증류주가 향기 성분이 가장 많으며 쌀의 함량이 적고 보리가 함유된 증류주가 향기성분이 가장 적었다. 또한 오크통에서 숙성시킨 원액을 100% 사용한 경우 향기성분이 뚜렷하게 구분됨을 보였다. 따라서 숙성재에 의해 증류주의 향기성분이 구분될 것으로 예측된다. 시판 증류주를 전자혀로 분석한 결과, 증류주는 단맛과 쓴맛 보다는 신맛, 감칠맛, 짠맛으로 시료간의 차이가 구분되었다. 본 연구를 통하여 전자코와 전자혀가 증류주 모니터링에 활용이 가능한지 여부를 확인하고 분석한 시판 증류주의 향미특성 결과를 추후 증류주 개발 및 품질관리에 이용하고자 한다.

• Molecules and Cells
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• 제39권11호
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• pp.807-813
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• 2016

Escherichia coli are important indicator organisms, used routinely for the monitoring of water and food safety. For quick, sensitive and real-time detection of E. coli we developed a 2'F modified RNA aptamer Ec3, by Cell-SELEX. The 31 nucleotide truncated Ec3 demonstrated improved binding and low nano-molar affinity to E. coli. The aptamer developed by us out-performs the commercial antibody and aptamer used for E. coli detection. Ec3(31) aptamer based E. coli detection was done using three different detection formats and the assay sensitivities were determined. Conventional Ec3(31)-biotin-streptavidin magnetic separation could detect E. coli with a limit of detection of $1.3{\times}10^6CFU/ml$. Although, optical analytic technique, biolayer interferometry, did not improve the sensitivity of detection for whole cells, a very significant improvement in the detection was seen with the E. coli cell lysate ($5{\times}10^4CFU/ml$). Finally we developed Electrochemical Impedance Spectroscopy (EIS) gap capacitance biosensor that has detection limits of $2{\times}10^4CFU/mL$ of E. coli cells, without any labeling and signal amplification techniques. We believe that our developed method can step towards more complex and real sample application.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.361.1-361.1
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• 2016

Due to their high sensitivity, fast response, small energy consumption and ease of integration, nanoelectromechanical systems (NEMS) have attracted much interest in various applications such as high speed memory devices, energy harvesting devices, frequency tunable RF receivers, and ultra sensitive mass sensors. Since the device performance of NEMS is closely related with the mechanical and flexural properties of the material in NEMS, analysis of the mechanical and flexural properties such as intrinsic tensile stress and Young's modulus is a crucial factor for designing the NEMS structures. In the present work, the intrinsic mechanical properties of highly stressed silicon nitride (SiN) beams are investigated as a function of the beam length using two different techniques: (i) dynamic flexural measurement using optical interferometry and (ii) quasi-static flexural measurement using atomic force microscopy. The reliability of the results is analysed by comparing the results from the two different measurement techniques. In addition, the mass density, Young's modulus and internal stress of the SiN beams are estimated by combining the techniques, and the prospect of SiN based NEMS for application in high sensitive mass sensors is discussed.

• 센서학회지
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• 제26권1호
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• pp.7-14
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• 2017

A threshold-based fall recognition algorithm using a tri-axial accelerometer and a bi-axial gyroscope mounted on the skin above the upper sternum was proposed to recognize fall-like activities of daily living (ADL) events. The output signals from the tri-axial accelerometer and bi-axial gyroscope were obtained during eight falls and eleven ADL action sequences. The thresholds of signal vector magnitude (SVM_Acc), angular velocity (${\omega}_{res}$), and angular variation (${\theta}_{res}$) were calculated using MATLAB. When the measured values of SVM_Acc, ${\omega}_{res}$, and ${\theta}_{res}$ were compared to the threshold values (TH1, TH2, and TH3), fall-like ADL events could be distinguished from a fall. When SVM_Acc was larger than 2.5 g (TH1), ${\omega}_{res}$ was larger than 1.75 rad/s (TH2), and ${\theta}_{res}$ was larger than 0.385 rad (TH3), eight falls and eleven ADL action sequences were recognized as falls. When at least one of these three conditions was not satisfied, the action sequences were recognized as ADL. Fall-like ADL events such as jogging and jumping up (or down) have posed a problem in distinguishing ADL events from an actual fall. When the measured values of SVM_Acc, ${\omega}_{res}$, and ${\theta}_{res}$ were applied to the sequential processing algorithm proposed in this study, the sensitivity was determined to be 100% for the eight fall action sequences and the specificity was determined to be 100% for the eleven ADL action sequences.

• 한국재료학회지
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• 제19권11호
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• pp.631-636
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• 2009

We investigated the NO gas sensing characteristics of ZnO-carbon nanotube (ZnO-CNT) layered composites fabricated by coaxial coating of single-walled CNTs with a thin layer of 1 wt% Al-doped ZnO using rf magnetron sputtering deposition. Morphological studies clearly revealed that the ZnO appeared to form beadshaped crystalline nanoparticles with an average diameter as small as 30 nm, attaching to the surface of the nanotubes. It was found that the NO gas sensing properties of the ZnO-CNT layered composites were dramatically improved over Al-doped ZnO thin films. It is reasoned from these observations that an increase in the surface-to-volume ratio associated with the numerous ZnO “nanobeads” on the surface of the CNTs results in the enhancement of the NO gas sensing properties. The ZnO-CNT layered composite sensors exhibited a maximum sensitivity of 13.7 to 2 ppm NO gas at a temperature of 200${^{\circ}C}$ and a low NO gas detection limit of 0.2 ppm in dry air.

• Imaging Science in Dentistry
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• 제47권1호
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• pp.25-31
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• 2017

Purpose: The aim of this study was to compare the diagnostic accuracy of previously trained endodontists in the detection of artificially created periapical lesions using cone-beam computed tomography (CBCT) and digital periapical radiography (DPR). Materials and Methods: An ex vivo model using dry skulls was used, in which simulated apical lesions were created and then progressively enlarged using #1/2, #2, #4, and #6 round burs. A total of 11 teeth were included in the study, and 110 images were obtained with CBCT and with an intraoral digital periapical radiographic sensor (Instrumentarium dental, Tuusula, Finland) initially and after each bur was used. Specificity and sensitivity were calculated. All images were evaluated by 10 previously trained, certified endodontists. Agreement was calculated using the kappa coefficient. The accuracy of each method in detecting apical lesions was calculated using the chisquare test. Results: The kappa coefficient between examiners showed low agreement (range, 0.17-0.64). No statistical difference was found between CBCT and DPR in teeth without apical lesions (P=.15). The accuracy for CBCT was significantly higher than for DPR in all corresponding simulated lesions(P<.001). The correct diagnostic rate for CBCT ranged between 56.9% and 73.6%. The greatest difference between CBCT and DPR was seen in the maxillary teeth (CBCT, 71.4%; DPR, 28.6%; P<.01) and multi-rooted teeth (CBCT, 83.3%; DPR, 33.3%; P<.01). Conclusion: CBCT allowed higher accuracy than DPR in detecting simulated lesions for all simulated lesions tested. Endodontists need to be properly trained in interpreting CBCT scans to achieve higher diagnostic accuracy.

• 센서학회지
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• 제3권2호
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• pp.11-15
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• 1994

LiF(Mg,Cu,Na,Si)형광체의 ${\gamma}$ 선과 ${\beta}$ 선에 대한 TSEE 특성을 조사하였다. 이 형광체의 TSEE glow 곡선은 $20^{\circ}C$에서 $400^{\circ}C$사이에서 5개의 피크를 나타내었으며 주피크는 $240^{\circ}C$였다. $^{60}Co$ ${\gamma}$ 선에 대한 형광체의 감도는 약 450 counts/mR 이었다. ${\beta}$ 선에 대한 TSEE 에너지의존성은 ${\beta}$ 입자의 평균에너지 0.02MeV에서 0.8MeV 사이에서 ${\pm}10%$이었다. 그리고 이 형광체의 ${\beta}$ 선에 대한 TSEE 효율은 $(2{\sim}15){\times}10^{-3}$ 이었다.