• Smart Structures and Systems
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• 제29권4호
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• pp.589-598
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• 2022

Timber structures are susceptible to structural damages caused by variations in moisture content (MC), inducing severe durability deterioration and safety issues. Therefore, it is of great significance to detect MC levels in timber structures. Compared to current methods for timber MC detection, which are time-consuming and require bulky equipment deployment, Lead Zirconate Titanate (PZT)-enabled stress wave sensing combined with statistic machine learning classification proposed in this paper show the advantage of the portable device and ease of operation. First, stress wave signals from different MC cases are excited and received by PZT sensors through active sensing. Subsequently, two non-baseline features are extracted from these stress wave signals. Finally, these features are fed to a statistic machine learning classifier (i.e., naïve Bayesian classification) to achieve MC detection of timber structures. Numerical simulations validate the feasibility of PZT-enabled sensing to perceive MC variations. Tests referring to five MC cases are conducted to verify the effectiveness of the proposed method. Results present high accuracy for timber MC detection, showing a great potential to conduct rapid and long-term monitoring of the MC level of timber structures in future field applications.

• Smart Structures and Systems
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• 제8권1호
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• pp.139-155
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• 2011

Polymeric thin-film assemblies whose bulk electrical conductivity and mechanical performance have been enhanced by single-walled carbon nanotubes are proposed for measuring strain and corrosion activity in metallic structural systems. Similar to the dermatological system found in animals, the proposed self-sensing thin-film assembly supports spatial strain and pH sensing via localized changes in electrical conductivity. Specifically, electrical impedance tomography (EIT) is used to create detailed mappings of film conductivity over its complete surface area using electrical measurements taken at the film boundary. While EIT is a powerful means of mapping the sensing skin's spatial response, it requires a data acquisition system capable of taking electrical impedance measurements on a large number of electrodes. A low-cost wireless impedance analyzer is proposed to fully automate EIT data acquisition. The key attribute of the device is a flexible sinusoidal waveform generator capable of generating regulated current signals with frequencies from near-DC to 20 MHz. Furthermore, a multiplexed sensing interface offers 32 addressable channels from which voltage measurements can be made. A wireless interface is included to eliminate the cumbersome wiring often required for data acquisition in a structure. The functionality of the wireless impedance analyzer is illustrated on an experimental setup with the system used for automated acquisition of electrical impedance measurements taken on the boundary of a bio-inspired sensing skin recently proposed for structural health monitoring.

• 한국정보과학회논문지:정보통신
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• 제31권3호
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• pp.327-334
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• 2004

본 논문에서는 다중 홉 무선 애드 혹 망의 성능향상을 위한 MAC 프로토콜의 개선 안을 제시한다. 무선 애드 흑 망의 노드는 매체가 가능할 때만 패킷을 전송할 수 있으며, 패킷이 전송되고 있는 중에 송신 노드의 전송파 감지 범위(carrier sensing range)에 속하는 노드들은 패킷을 전송할 수 없다. 전송파 감지 범위는 전송 범위(transmission range)와 전송파 감지 영역(carrier sensing zone)으로 나뉠 수 가 있으며(9), 본 논문에서는 노드가 전송파 감지 영역에 속해있을 때 프로토콜 동작의 중요성에 초점을 맞추고 있다. 전송파 감지 영역에 속하는 노드는 현재 진행되고 있는 전송 세션의 종료 시점이나 매체가 가능해지는 시점을 알 수 없다는 특징이 있다. 현재의 MAC 프로토콜은 노드가 전송 범위에 속해 있을 때와 전송파 감지 영역에 속해 있을 때의 동작이 크게 다르지 않다. 성능 개선을 위해 다양한 시뮬레이션을 수행하였으며, 시뮬레이션의 결과를 통해 충돌이 반 이상 감소하여, 손실되는 패킷의 수가 줄고 성능이 향상되었음을 확인하였다.

• 대한원격탐사학회지
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• 제26권2호
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• pp.209-220
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• 2010

해양현상을 이해하기 위한 관측분야의 노력 중에서 해류 정보의 생산은 가장 어려운 작업 중의 하나이다. 이를 극복하기 위한 대안으로서 연속 화상 자료로부터 해류벡터를 추정하려는 많은 연구들이 진행 되고 있다. 본 연구에서는 한반도 주변의 SeaWiFS (Sea-viewing Wide Field-of-view Sensor) chlorophyll-a 해색 자료와 AVHRR/SST 를 이용하여 연속 화상 사이의 유사한 형태를 추적하는 최대상 관계수법을 사용한 표층 유속 벡터의 추정을 시도하였다. 한국의 남해역에서 적용한 유속 벡터 결과는 해면 고도계를 이용한 지형류, ADCP 관측 결과와 비교하여 유속은 약 15% 정도 작고, 유향은 약 $36^{\circ}$의 차이로 근접하여 기존 연구 결과에 비해 양호하게 나타났다. 이는 향후 GOCI 자료의 응용적 측면에서 매우 고무적이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 심포지엄 논문집 정보 및 제어부문
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• pp.236-238
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• 2005

In this paper, we propose a new discrete-time predictive current controller for a PMLSM(permanent magnet linear synchronous motor). The main objectives of the current controllers are that the measured stator current is tracked the command current value accurately and the transient interval is shorten as much as possible, in order to obtain high-performance of ac drive system. The conventional predictive current controller is hard to implement in full digital current controller since a finite calculation time causes a delay between the current sensing time and the time that take to apply the voltage to motor. A new control strategy is the schema that gets the fast adaptation of transient current change, the fast transient response tracking. Moreover, the simulation results will be verified the improvements of Predictive controller and accuracy of the current controller.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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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.

• 통합자연과학논문집
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• 제5권4호
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• pp.253-256
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• 2012

The rugate porous silicons containing multiple photonic band gaps have been generated by applying a composite waveform summed three computer-generated pseudo-sinusoidal current waveforms and exhibit three sharp photonic band gaps in the optical reflectivity spectrum. Generated multiple rugate porous silicons display three rugate peaks corresponding to the each of the sine components varied from 0.42, 0.36, and 0.30 Hz, with a spacing of 0.06 Hz between each sine component. The resulting rugate PSi films have been removed from the silicon substrate by applying an lift-off current and are then made into particles by ultrasono-method in a organic solution. The sensing experiments using these particles for organic solvents such as toluene, hexane, acetone, and methanol have been achieved. Condensing of organic vapors in the pores increases the refractive indices of entire particle which results a red shift in the photonic peaks.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 춘계학술대회 논문집 전자세라믹스 센서 및 박막재료 반도체재료 일렉트렛트 및 응용기술
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• pp.14-17
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• 2000

The rise throughput and the stability in fabrication of device can be obtained by applying of CMP process to STI structure in 0.18um semiconductor device. To employ in STI CMP, the reverse moat process has been added thus the process became complex and the defects were seriously increased. Removal rates of each thin films in STi CMP was not equal hence the devices must to be effected, that is, the damage was occured in the device dimension in the case of excessive CMP process and the nitride film was remained on the device dimension in the case of insufficient CMP process than these defects affect the device characteristics. We studied the current sensing method in STI-CMP with the reverse moat pattern.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.45-48
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• 2007

COMS satellite is a multipurpose satellite in the geostationary orbit, which accommodates multiple payloads of Meteorological Imager, Geostationary Ocean Color Imager and Ka band Satellite Communication Payload in a single spacecraft platform. In this paper, current status of Korea's first geostationary Communication, Ocean and Meteorological Satellte(COMS) program development is introduced. The satellite platform is based on the Astrium EUROSTAR 3000 communication satellite, but creatively combined with MARS Express satellite platform to accommodate three different payloads efficiently for COMS. The system design difficulties are in the different kinds of payload mission requirements of communication and remote sensing purposes and how to combine them into a single satellite to meet the overall satellite requirements. The COMS satellite critical design has been accomplished successfully to meet three different mission payloads. The platform is in Korea, KARI facility for the system integration and test. The expected launch target of COMS satellite is scheduled in June 2009.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.326-328
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• 2005

High speed rotational arc sensing is an important method to detect the torch deviation during automatic seam tracking of arc welding. In this paper, a mathematic model of high speed rotational arc sensing is analyzed. The simulation results are consistent with the experimental results. The current waveforms at the beginning of the welding are different from those at middle of the welding because of the formation of the weld bead profile. The signal patterns for seam tracking and end-point detection are proposed. A phase shift between the rotation and the current variation is also discovered in the experiments.