• Structural Monitoring and Maintenance
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• 제4권4호
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• pp.301-329
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• 2017

Impedance-based damage detection method has been known as an innovative tool with various successful implementations for structural health monitoring of civil structures. To monitor the local critical area of a structure, the impedance-based method utilizes the high-frequency impedance responses sensed by piezoelectric sensors as the local dynamic features. In this paper, current advances and future challenges of the impedance-based structural health monitoring are presented. Firstly, theoretical background of the impedance-based method is outlined. Next, an overview is given to recent advances in the wireless impedance sensor nodes, the interfacial impedance sensing devices, and the temperature-effect compensation algorithms. Various research works on these topics are reviewed to share up-to-date information on research activities and implementations of the impedance-based technique. Finally, future research challenges of the technique are discussed including the applicability of wireless sensing technology, the predetermination of effective frequency bands, the sensing region of impedance responses, the robust compensation of noise and temperature effects, the quantification of damage severity, and long-term durability of sensors.

• 한국멀티미디어학회논문지
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• 제20권8호
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• pp.1430-1438
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• 2017

Recently, interest that intra-abdominal pressure has been increased as change of pathophysiology to critical patients. The intra-abdominal pressure is measured by cystometry what can be available for non-inclusively. However, conventional methods have some problems such as low SNR, weakness of environment temperature, and unsuitable size of sensor. In this paper, a new subminiature pressure sensor module and sensing system are proposed using a sensor of semiconductor type and FPCB. The module is more stable, flexible, and smaller than the conventional catheter. The performance of the developed module is evaluated by various quantitative analysis indexes. The proposed sensor has the high sensitivity and suitable size for measurement of cystometry more than the conventional method. In order to prove efficiency between conventional and proposed method, proposed method compared for sensitivity, fixable, and size. The proposed method will be help measurement of intra-abdominal pressure of patients due to high accuracy and comfortableness.

• 한국초전도ㆍ저온공학회논문지
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• 제10권4호
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• pp.38-42
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• 2008

Miniature J-T cryocooler using nitrogen or argon has been widely adopted in cooling infrared sensor for space/military application and cryosurgery. Argon or nitrogen, however, has relatively low specific cooling power compared to nitrous oxide, but the ultimate operating temperature is much lower than nitrous oxide. On the other hand, nitrous oxide has large specific cooling power, but the operating temperature is limited to its boiling point (>183K). To compromise the different characteristics of these gases, the performance of miniature J-T cryocooler using argon and nitrous oxide mixture is investigated in this paper. Three different compositions of mixture (25/75, 50/50, and 75/25 molar fraction) are blended and tested. The results are compared with the experiments of pure argon and pure nitrous oxide. The experimental results show some encouraging potentiality of mixed refrigerant J-T cryocooler. The critical clogging problem, however, was observed with argon and nitrous oxide mixture, and the lowest achievable temperature with this mixture was limited to the freezing point of nitrous oxide. The paper discusses detailed clogging process of the mixture and suggests an alternative.

• JSTS:Journal of Semiconductor Technology and Science
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• 제7권1호
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• pp.1-10
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• 2007

In recent few years, low-power electronics has been a leading drive for technology developments nourished by rapidly growing market share. Mobile DRAM, as a fundamental block of hand-held devices, is now becoming a product developed by limitless competition. To support application specific mobile features, various new power-reduction schemes have been proposed and adopted by standardization. Tightened power budget in battery-operated systems makes conventional schemes not acceptable and increases difficulty of the circuit design. The mobile DRAM has successfully moved down to 1.5V era, and now it is about to move to 1.2V. Further voltage scaling, however, presents critical problems which must be overcome. This paper reviews critical issues in mobile DRAM design and various circuit schemes to solve the problems. Focused on analog circuits, bitline sensing, IO line sensing, refresh-related schemes, DC bias generation, and schemes for higher data rate are covered.

• 센서학회지
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• 제26권3호
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• pp.149-154
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• 2017

Detection of rain is one of the essential weather factors that are monitored by automatic weather stations in Korea. In this work, we studied the operation standards required for impedance-based rain detectors in terms of surface temperature and sensitivity, in an effort to establish a qualification procedure for rain detectors. The surface temperature of rain detectors was measured at varying air temperatures from $-30^{\circ}C$ to $20^{\circ}C$, considering the hypothetical presence and absence of rain/snow. In addition, the sensitivity of rain detectors was studied generating artificial raindrops of regular size. The sensitivity was evaluated in terms of the critical number of droplets that triggers the activation of the rain detector. We found that the sensitivity is affected by stationary, horizontal, and vertical droplet deposition methods. The critical number of droplets for the stationary deposition is higher than that for both horizontal and vertical depositions, which provides the maximum limit of droplets required to activate the detector. Based on our experiments considering surface temperature measurements and sensitivity tests, we suggest a revised version of surface temperature and sensitivity requirements for the qualification of impedance-based rain detectors.

• 대한기계학회논문집A
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• 제39권1호
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• pp.37-43
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• 2015

압전소자(Piezoelectric transducer, PZT)는 구조물의 안정성 평가를 목적으로 하는 구조 건전성 모니터링 기법(Structural Health Monitoring, SHM)의 센서(sensor) 및 구동기(actuator)로 많이 활용되고 있다. 사용되는 센서 및 구동기의 성능을 사전에 파악하고, 잔존수명 및 결함을 탐지하는 센서 자가 진단법은 안정적인 SHM의 결과를 얻기 위해 매우 중요한 절차이다. 본 연구에서는 Admittance 값을 기반으로 한 센서 자가 진단절차를 통하여 압전체 센서의 결함을 탐지하였으며, 센서 진단과정에 영향을 줄 수 있는 접합층 및 온도 등의 영향인자에 대해 실험적 분석을 실시하였다. 분석 결과 Admittance와 온도 및 접착제의 상관관계를 파악할 수 있었으며, admittance를 기반으로 한 센서 자가 진단 절차를 통해 센서의 접착상태와 접착제의 성능평가가 가능함을 검증하였다.

• International journal of advanced smart convergence
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• 제6권1호
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• pp.76-81
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• 2017

This paper presents a low cost and flexible IoT enabled smart LED controller using Arduino that is used for emergency exit signs. The Internet of Things (IoT) is become a global network that put together physical objects using network communications for the purpose of inter-communication of devices, access information on internet, interaction with users as well as permanent connected environment. A crucial point in this paper, is underlined on the potential key points of applying the Arduino platform as low cost, easy to use microcontroller with combination of various sensors applied in IoT technology to facilitate and establishment of intelligent products. To demonstrate the feasibility and effectiveness of the system, devices such as LED strip, combination of various sensors, Arduino, power plug and ZigBee module have been integrated to setup smart emergency exit sign system. The general concept of the proposed system design discussed in this paper is all about the combination of various sensor such as smoke detector sensor, humidity, temperature sensor, glass break sensors as well as camera sensor that are connected to the main controller (Arduino) for the purpose of communicating with LED exit signs displayer and dedicated PC monitors from integrated system monitoring (controller room) through gateway devices using Zig bee module. A critical appraisal of the approach in the area concludes the paper.

• 전자공학회논문지CI
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• 제44권5호
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• pp.28-37
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• 2007

IEEE 1451 standard는 네트워크와 transducer간에 표준 interface를 정의한다. 본 논문에서는 IEEE 1451 Standard 기반의 data acquisition system과 무선 smart sensor node를 구성하기 위한 구조적인 모델을 제안한다. 제안 된 Network Capable Application Processor(NCAP)은 data acquisition의 역할과 smart sensor node와 네트워크 사이에 가교 역할을 한다. 또한 무선 sensor node에게 영향을 주지 않으면서 재구성이 가능하고 DB를 이용하여 transducer의 정확한 정보를 얻는다. Smart sensor node는 그 자신에 관한 기본적인 정보를 디지털 형식으로 제공하는 능력을 가지고 있다. 이 디지털 형식은 Transducer Electronic Data Sheet(TEDS)라 하며 sensor node의 plug-and-play 기능을 가능하게 한다. IEEE 1451.4에서 정의하고 있는 TEDS와 Template를 무선 환경에서 적용하기 위해 형식을 간략화 하였으며 ad-hoc routing을 통해 전송이 이루어진다. 본 연구 시스템은 의료정보 서비스를 제공하기 위한 목적으로 체온과 ECG(Electrocardiogram) 센서를 사용하였다. Template 형식은 센서들의 data sheet를 통해 결정하였으며 센서의 특징을 정확히 표현하기 위해 재구성하였다. NCA의 DB는 다양한 센서 개발에 따라 새로운 Template 및 하부 항목의 등록이 가능하도록 구현하였다.

• 센서학회지
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• 제18권4호
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• pp.263-268
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• 2009

With the increasing number of automobiles, the problem of air pollution from the exhaust gases of automobiles has become a critical issue. The principal gases that cause air pollution are nitrogen oxide or NO$_x$(NO and NO$_2$), and CO. Because NO$_x$ gases cause acid rain and global warming and produce ozone(O$_3$) that leads to serious metropolitan smog from photochemical reaction, they must be detected and reduced. Mixtures of WO$_3$ and $In_2O_3$(WO$_3$:$In_2O_3$=10:0, 7:3, 5:5, 3:7, and 0:10 in wt.%), which are NO$_x$ gas-sensing materials, were prepared, and thick-film gas sensors that included a heater and a temperature sensor were fabricated. Their sensitivity to NO$_x$ was measured at 250$\sim$400$^{\circ}C$ for NO$_x$ concentrations of 1$\sim$5 ppm. The $In_2O_3$ thick-film sensor showed excellent sensitivity($R_{gas}/R_{air}$=10.22) at 300$^{\circ}C$ to 5-ppm NO. The response time for 70 % saturated sensitivity was about 3 seconds, and the sensors exhibited very fast reactivity to NO$_x$.

• 대한원격탐사학회지
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• 제39권6_1호
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• pp.1477-1482
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• 2023

본 연구는 2012년부터 2021년까지 동북아시아 해역에서 발생한 해수고온현상을 Communication, Ocean, and Meteorological Satellite (COMS)/Meteorological Imager sensor (MI)와 GEO-KOMPSAT-2A (GK-2A)/Advanced Meteorological Imager sensor (AMI) 정지궤도 위성 해수면온도 자료를 통해 탐지하였다. 특히 2018년 이후 및 2020년에 해수고온현상의 빈도와 강도가 눈에 띄게 증가하였음을 발견하였다. Optimal Interpolation Sea Surface Temperature (OISST) 자료와 천리안위성 자료를 활용한 T-test 통계적 검증은 해수면 온도가 통계학적으로 유의미하게 상승했다는 것을 확인시켜 주었으며, 이는 기후 변화의 직접적 영향이라는 결론을 뒷받침한다. 이 연구 결과는 해수고온현상의 지속적인 모니터링과 정밀한 분석의 중요성을 강조한다. 복잡한 지형과 다양한 기후 조건을 가진 동북아시아에서 이루어진 연구는 글로벌 기후 변화가 지역 환경에 미치는 영향을 이해하는 데 있어 중요한 통찰을 제공한다.