• 한국정밀공학회지
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• 제26권1호
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• pp.89-96
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• 2009

This paper describes the intelligent robot's hand with three finger sensors for a humanoid robot. In order to grasp an unknown object safely, the intelligent robot's hand should measure the mass of the object, and determine the grasping force using the mass, finally control the grasping force using the finger sensors and the controller. In this paper, the intelligent robot's hand for a humanoid robot was developed. First, the six-axis force/moment sensor was manufactured. second, three finger force sensors were designed and fabricated, third, the high-speed controller was manufactured using DSP(digital signal processor), finally, the characteristic test for determining a grasping force and for grasping an unknown object safely It is confirmed that the hand could grasp an unknown object safely.

• Smart Structures and Systems
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• 제5권4호
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• pp.381-395
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• 2009

The paper presents a case study in which the structural condition assessment of the East Bay bridge in Gibsonton, Florida is evaluated with the help of remote health monitoring techniques. The bridge is a four-span, continuous, deck-type reinforced concrete structure supported on prestressed pile bents, and is instrumented with smart Fiber Optic Sensors. The sensors used for remote health monitoring are the newly emerged Fabry-Perot (FP), and are both surface-mounted and embedded in the deck. The sensing system can be accessed remotely through fast Digital Subscriber Lines (DSL), which permits the evaluation of the bridge behavior under live traffic loads. The bridge was open to traffic since March 2005, and the collected structural data have been continuously analyzed since. The data revealed an increase in strain readings, which suggests a progression in damage. Recent visual observations also indicated the presence of longitudinal cracks along the bridge length. After the formation of these cracks, the sensors readings were analyzed and used to extrapolate the values of the maximum stresses at the crack location. The data obtained were also compared to initial design values of the bridge under factored gravity and live loads. The study showed that the proposed structural health monitoring technique proved to provide an efficient mean for condition assessment of bridge structures providing it is implemented and analyzed with care.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.330-337
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• 2002

The HANARO seismic monitoring system is classified as non-nuclear safety(NNS), seismic category I, and quality class T The seismic monitoring system installed at the instrument room consists of five field sensors and one monitoring cabinet. The field sensors are composed of three triaxial accelerometers which installed at base slab, free field and overhead crane support respectively, a seismic trigger and a seismic switch at base slab. The most parts of analog system except field sensors are not produced any more, the improvement of the system is to be needed. The analog system with magnetic tape recorder is not only out-of-date model but dependent upon foreign technology. So it is difficult to get the spare parts and the cost to buy them is increased. Therefore we have improved the analog seismic monitoring system into a new digital seismic monitoring analysis system(SMAS) except five field sensors. After the installation of the new SMAS, we have carried out the site acceptance test(SAT) to confirm the field functions. The results of SAT satisfy the requirements of the fabrication technical specification. This new SMAS is operating at HANARO instrument room to acquire and analyse the signal of earthquake.

• 상하수도학회지
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• 제30권5호
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• pp.491-500
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• 2016

Pressure monitoring is expected to be expanded in a water distribution system according to accelerated development of smart water network management technologies caused by appearances of affordable digital infrastructures like computing, storage and bandwidth. However, the placement of pressure sensors has been determined by engineer's technical decisions since there is no well-defined criteria for deciding a suitable location of pressure sensor. This study presents a placement method of pressure sensors based on the consideration of allowable error in calibrating water network analysis modeling. The proposed method is to find a minimum set of pressure sensors for achieving a reliable management of water transmissions main and increasing the efficiency of their real-time operation. In the case study in Y area's transmission main, the proposed method shows equally distributed pressure sensors in terms of hydraulics. It is expected that the proposed method can be used to manage transmission mains stably and construct a robust real-time network analysis system as a minimal criteria.

• Imaging Science in Dentistry
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• 제35권4호
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• pp.203-205
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• 2005

Purpose: This study was aimed to compare skin entrance dose of digital radiography with that of film radiography and to show the dose reduction achievement with digital systems at 11 dental schools in Korea. Materials and Methods: Forty six intraoral radiographic systems in 11 dental schools were included in this study. Digital sensors were used in 33 systems and film was used in 13 systems. Researchers and the volunteer visited 11 dental schools in Korea. Researchers asked the radiologic technician (s) at each school to set the exposure parameters and aiming the x-ray tube for the periapical view of the mandibular molar of the volunteer. The skin entrance doses were measured at the same exposure parameters and distance by the technician for each system with a dosimeter (Multi-O-Meter : Unfors instruments, Billdal, Sweden). Results: The median dose was $491.2{\mu}Gy$ for digital radiography and $1,205.0{\mu}Gy$ for film radiography. The skin entrance dose in digital radiography was significantly lower than that of film radiography (p<0.05). Conclusion: Fifty-nine percent skin entrance dose reduction with digital periapical radiography was achieved over the film radiography in Korean dental schools.

• 한국BIM학회 논문집
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• 제9권3호
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• pp.1-7
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• 2019

Digital twin technology has been actively developed to monitor and assess the current state of actual structures. The digital twin changes the traditional observation method performed in the field to the real-time observation and detection system using virtual online model. Thus, this study designed a digital twin model for a beam and examined the feasibility of the digital twin for bridges. To reflect the current state of the bridge, model updating was performed according to the field test data to construct an analysis model. Based on the constructed bridge analysis model, the relationship between strain and displacement was used to represent a virtual model that behaves in the same way as the actual structure. The strain and displacement relationship was expressed as a matrix derived using an approximate analytical theory. Then, displacements can be obtained using the measured data obtained from strain sensors installed on the bridge. The coordinates of the obtained displacements are used to construct a virtual digital model for the bridge. For verification, a beam was fabricated and tested to evaluate the digital twin model constructed in this study. The displacements obtained from the strain and displacement relationship agrees well with the actual displacements of the beam. In addition, the displacements obtained from the virtual model was visualized at the locations of the strain sensor.

• Smart Structures and Systems
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• 제33권5호
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• pp.375-383
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• 2024

Infrastructure facilities contain various pipe systems, which can be considerably damaged by external loads such as earthquakes. Therefore, structural health monitoring (SHM) and safety assessment of pipes are crucial. Digital twin technology for SHM of pipes is important in the industry. This study proposes a digital twin system that estimates the behavior, stress, and external load of real-scale pipes in real time under simultaneous seismic and external loads using a minimum number of sensors. Vibration tests were performed to construct the digital twin system, and a numerical model was developed that considered the dynamic characteristics of a target pipe. Moreover, a reduced-order modeling technique of a numerical model was applied to enhance its real-time performance. The digital twin system successfully estimated the response of the pipe at all points. Verification of the digital twin system was performed by comparing it with the experimental parameters of a real-scale pipe. The proposed digital twin system can help enhance SHM and system's maintenance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.802-804
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• 2002

An analysis of the skeleton type BLDC motor is presented. The single phase skeleton type BLDC motor consists of the stator, rotor with the permanent magnet, and drive circuit with hall sensors that detect the rotor position. The major factors for the initial starting, efficiency, and torque ripples of the skeleton type BLDC motor are the detent groove of the stator and the lead angle of the phase voltage. The performance characteristics according to the angle and height of the detent groove is analyzed. The optimum lead angles of the phase voltage with the torque ripple and motor efficiency is described using the finite element method.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2006년도 춘계학술발표회 논문집
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• pp.319-326
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• 2006

All around tile world there has been great human and economical damage continuously by disasters like the earthquakes and storms(Tsunami) in eastern asia which recently occurred, and like the New Orleams hurricane in USA. The situation is our countries damage from natural disasters due to heavy snow, storms, forest fires have been increasing In this research we obtained GSIS data of the 05' Yang-yang forest fire disaster area using multi-sensors like airborne laser data, GPS/INS, aerial photograph surveying. In result we produced digital topographical maps, digital elevation models, digital external models, digital images, infrared images. By, analyzing and comparing with past aerial photography we obtained the exact damage area, amount of damage, estimated tile areas where a landslide might occur, and we analyzed vegetations amount of damage and possibility of recovery.

• 대한전자공학회논문지SP
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• 제47권6호
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• pp.137-145
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• 2010

디지털 선박에서는 선박 내의 각종 센서로부터 측정된 디지털 데이터에 대한 정확하고 에너지 효율적인 관리가 필요하다. 그러나, 센서 네트워크에서 대용량 스트림 데이터를 제한된 네트워크, 전력, 프로세서를 이용하여 모든 센서 데이터를 전송하고 분석하는 것은 어렵고 효율적이지 못하다. 그러므로, 연속적으로 입력되는 데이터를 사전에 분류하여 특성에 따라 선택적으로 데이터를 처리하는 데이터 분류 기법이 요구된다. 본 논문에서는 디지털 선박 내에 다수 개의 센서(온도, 습도, 조도, 음성 센서)를 배치하고 효율적인 입력 스트림 처리를 위해서 슬라이딩 윈도우 기반으로 다중 Support Vector Machine(SVM) 알고리즘을 이용하여 사전 분류(pre-clustering)한 후 요약된 정보를 해쉬 테이블로 관리하는 효율적인 처리 기법을 제안한다. 해쉬테이블을 이용하여 다차원 스트림 데이터의 저장될 레코드 순서를 빠르게 찾아 저장 및 검색함으로서 처리 속도가 향상되고 메모리에 해쉬 테이블 만을 유지하면 되므로 메모리 사용량이 감소한다. 35,912개의 데이터 집합을 사용하여 실험한 결과 제안 기법의 정확도와 처리 성능이 향상되었다.