• Smart Structures and Systems
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• 제21권6호
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• pp.761-776
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• 2018

Guided wave testing is a reliable and safe method for pipeline inspection. In general, guided wave testing employs a circumferential array of piezoelectric transducers to clamp on the pipe circumference. The sensitivity of the operation depends on many factors, including transducer distribution across the circumferential array. This paper presents the sensitivity analysis of transducer array for the circumferential characteristics of guided waves in a pipe using finite element modelling and experimental studies. Various cases are investigated for the outputs of guided waves in the numerical simulations, including the number of transducers per array, transducer excitation variability and variations in transducer spacing. The effect of the dimensions of simulated notches in the pipe is also investigated for different arrangements of the transducer array. The results from the finite element numerical simulations are then compared with the related experimental results. Results show that the numerical outputs agree well with the experimental data, and the guided wave mode T(0,1) presents high sensitivity to the notch size in the circumferential direction, but low sensitivity to the notch size in the axial direction.

• Smart Structures and Systems
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• 제30권2호
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• pp.173-181
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• 2022

The current paper presents a technique to detect crack in non-uniform cantilever-type pipe beams, that have step changes in the properties of their cross sections, restrained by a translational and rotational spring with a tip mass at the free end. An equation for estimating the natural frequencies for the non-uniform beams is derived using the boundary and continuity conditions, and an equivalent bending stiffness for cracked beam is applied to calculate the natural frequencies of the cracked beam. An experimental study for a step-changed non-uniform cantilever-type pipe beam restrained by bolts with a tip mass is carried out to verify the proposed method. The translational and rotational spring constants are updated using the neural network technique to the results of the experiment for intact case in order to establish a baseline model for the subsequent crack detection. Then, several numerical simulations for the specimen are carried out using the derived equation for estimating the natural frequencies of the cracked beam to construct a set of training patterns of a neural network. The crack locations and sizes are identified using the trained neural network for the 5 damage cases. It is found that the crack locations and sizes are reasonably well estimated from a practical point of view. And it is considered that the usefulness of the proposed method for structural health monitoring of the step-changed non-uniform cantilever-type pipe beam-like structures elastically restrained in the ground and have a tip mass at the free end could be verified.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.416-421
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• 2005

Concrete are brittle materials and they are which come to brittle fracture rapidly by progress of cracks. Therefore, what the time for repairing the damage portion is understands importantly by such cracks. When they happened the glass pipe similar to concrete was used. Such a glass pipe can insert repair material in an inside, or can use it by switch. They are interested in the crack monitoring of structure using FM radio sensor and PZT sensor. In this study, the monitoring to a crack was studied using FM radio sensor and PZT sensor. Therefore, the purpose of this study is the fundamental research which detects damages of main members using the compound sensor which consisted of the radio sensors of resistance, PZT, and FM system.

• Smart Structures and Systems
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• 제3권3호
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• pp.357-372
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• 2007

Parametric density concept is proposed for a long-range pipeline health monitoring. This concept is designed to obtain the attenuation of ultrasonic guided waves propagating in underwater pipelines without complicated calculation of attenuation dispersion curves. For the study, three different pipe materials such as aluminum, cast iron, and steel are considered, ten different transporting fluids are assumed, and four different geometric pipe dimensions are adopted. It is shown that the attenuation values based on the parametric density concept reasonably match with the attenuation values obtained from dispersion curves; hence, its efficiency is proved. With this concept, field engineers or inspectors associated with long-range pipeline health monitoring would take the advantage of easier capturing wave attenuation value, which is a critical variable to decide sensor location or sensors interval.

• Smart Structures and Systems
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• 제19권5호
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• pp.473-485
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• 2017

Ratcheting behavior of $90^{\circ}$ elbow piping subject to internal pressure 20 MPa and reversed bending 20 kN was investigated using experimental method. The maximum ratcheting strain was found in the circumferential direction of intrados. Ratcheting strain at flanks was also very large. Moreover, the effect of temperature on ratcheting strain of $90^{\circ}$ elbow piping was studied through finite element analysis, and the results were compared with room condition ($25^{\circ}$). The results revealed that ratcheting strain of $90^{\circ}$ elbow piping increased with increasing temperature. Ratcheting boundary of $90^{\circ}$ elbow piping was determined by Chaboche model combined with C-TDF method. The results revealed that there was no relationship between the dimensionless form of ratcheting boundary and temperature.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2015년도 제52차 하계학술대회논문집 23권2호
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• pp.327-328
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• 2015

본 논문은 지하공동구에서의 출입자의 통제를 위해 스마트폰을 이용한 출입관리시스템을 제안한다. 제안하는 시스템은 지하공동구 자동개폐기의 MCU를 통해 온습도, 개폐기의 상태, 출입자의 기록 등 다양한 정보를 취득하여 관리한다. 이때 취득한 정보는 블루투스4.0 모듈을 통해 ECB 암호화 방식을 사용하여 스마트폰에 전송한다. 본 논문에서 제안하는 출입관리시스템은 기존 물리적인 키에 의존하던 출입 방식을 대체하여 신뢰성 있는 보안 및 체계적인 관리가 가능할 것으로 기대한다.

• International journal of advanced smart convergence
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• 제10권2호
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• pp.15-20
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• 2021

We constructed an air-lifted seawater propulsion system for decreasing fuel consumption of the ships. The system has a form of pipes which can be easily installed on the sides of the ship. Seawater mixed with air, will rise along within the pipe, and will be discharged downward. If the directions of inlet / outlet of the pipe are designed properly, a propulsive energy can be obtained. We tested the system with a model ship in Jangsa port at Sokcho-city with a water depth of 2.5 meters. The system was supplied regulated air at 6 bars during the 3 tests. The model ship was moving forward at a rate of 0.18 meters per second. In case of large ships equipped zfrom clean energy.

• 한국콘텐츠학회논문지
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• 제9권12호
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• pp.477-484
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• 2009

스마트 의류가 고객 중심으로 다변화 되어가는 생활환경 속에서 날씨정보를 제공하는 것은 서비스 전략의 중요한 성공요소가 되고 있다. 최근에는 스마트 의류의 다양한 어플리케이션이 연구자와 개발자에 의해 제시되고 있다. 그 중 센서 기반의 스마트 의류는 시장에서 가장 수요가 높을 것으로 기대된다. 본 논문에서는 웨어러블 기반의 스마트 모자를 이용한 생활기상지수 모니터링 시스템을 제안하였다. 제안된 스마트 모자를 착용하여, 기상상태를 수집하고 신호를 UMPC로 무선 전송되어 이를 실시간으로 모니터링 할 수 있도록 고안하였다. 센서에 따른 생활기상지수를 제공하기 위해서, 기상지수를 6가지 요소(열지수, 식중독지수, 불쾌지수, 자외선지수, 체감온도지수, 동파가능지수)에 따라 분석하였다. 생활기상지수 모니터링 시스템을 개발하여 논리적 타당성과 유효성을 검증하기 위해 실험적인 적용을 시도하고자 한다. 따라서 스마트 의류에서 서비스의 만족도와 질을 향상시켰다.

• 융합정보논문지
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• 제9권7호
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• pp.78-84
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• 2019

본 연구의 목적은 스마트 하수도의 개념을 소개하고, 2021년부터 2040년까지 우리나라 전역에 스마트 하수도가 구축되는 경우 그 경제적 파급효과를 분석하는 것에 있다. 연구방법으로는 산업연관분석 모형을 이용한다. 분석 결과, 스마트 하수도 투자 사업을 통한 생산유발효과는 343조 7,330억원, 부가가치유발효과는 155조 8,675억원, 취업유발효과는 251만 8,470명 증가하는 것으로 추정되어 스마트 하수도 사업의 국민경제적 파급효과는 상당히 큰 것으로 나타났다. 또한 스마트 하수도에 의한 사회후생의 증가는 환경개선과 국민건강 개선을 통하여 실현될 것으로 예상되므로 빠른 시일 안에 스마트 하수도 사업에 대한 구체적인 Road map을 수립, 확정하고 예산을 투입하여 적극 추진할 필요가 있다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제23회 추계학술대회 논문집
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• pp.5-8
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• 2004

본 논문에서는 현재 개발 중인 스마트 무인기 연료 시스템의 기본설계 결과를 제시하였다. 시스템 요구를 바탕으로 연료 시스템을 구성한 후, 이에 필요한 부스트 펌프, 제트펌프, 도관, 벤트 시스템등 각 구성품에 대한 설계를 수행하였고 연료 시스템의 중량예측을 수행하였다.