• Structural Engineering and Mechanics
• /
• 제89권3호
• /
• pp.309-321
• /
• 2024

In this paper, the effect of semi-rigid connections on the stability bearing capacity of cross-bracings in steel tubular transmission towers is investigated. Herein, a prediction method based on the hybrid model which is a combination of particle swarm optimization (PSO) and backpropagation neural network (BPNN) is proposed to accurately predict the stability bearing capacity of cross-bracings with semi-rigid connections and to efficiently conduct its probabilistic assessment. Firstly, the establishment of the finite element (FE) model of cross-bracings with semi-rigid connections is developed on the basis of the development of the mechanical model. Then, a dataset of 7425 samples generated by the FE model is used to train and test the PSO-BPNN model, and the accuracy of the proposed method is evaluated. Finally, the probabilistic assessment for the stability bearing capacity of cross-bracings with semi-rigid connections is conducted based on the proposed method and the Monte Carlo simulation, in which the geometric and material properties including the outer diameter and thickness of cross-sections and the yield strength of steel are considered as random variables. The results indicate that the proposed method based on the PSO-BPNN model has high accuracy in predicting the stability bearing capacity of cross-bracings with semi-rigid connections. Meanwhile, the semi-rigid connections could enhance the stability bearing capacity of cross-bracings and the reliability of cross-bracings would significantly increase after considering semi-rigid connections.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제49권8호
• /
• pp.509-513
• /
• 2000

This paper deals with the parallel operation of space vector PWM for large capacity inverter system. To enlarge the capacity of inverter system and to reduce the current ripples on inverter output side, two or more inverters are operated in parallel. In this paper, a new parallel operation strategy which minimizes the harmonic distortion of the output stage is described. The proposed method is developed on the basis of the space-vector PWM in order to increase the linearly controllable voltage range. With the help of the proposed voltage synthesis method, the total harmonic distortion of the output stage can be greatly reduced in compared with that of conventional method with sinusoidal PWM or that of the single inverter operation case. The experimental results with reduced scale test show the feasibility of the proposed voltage synthesis method.

• Journal of Information Processing Systems
• /
• 제10권2호
• /
• pp.256-270
• /
• 2014

A new morphed steganographic algorithm is proposed in this paper. Image security is a challenging problem these days. Steganography is a method of hiding secret data in cover media. The Least Significant Bit is a standard Steganographic method that has some limitations. The limitations are less capacity to hide data, poor stego image quality, and imperceptibility. The proposed algorithm focuses on these limitations. The morphing concept is being used for image steganography to overcome these limitations. The PSNR and standard deviation are considered as a measure to improve stego image quality and morphed image selection, respectively. The stego keys are generated during the morphed steganographic embedding and extracting process. Stego keys are used to embed and extract the secret image. The experimental results, which are based on hiding capacity and PSNR, are presented in this paper. Our research contributes towards creating an improved steganographic method using image morphing. The experimental result indicates that the proposed algorithm achieves an increase in hiding capacity, stego image quality, and imperceptibility. The experimental results were compared with state of the art steganographic methods.

• 한국지반공학회논문집
• /
• 제16권1호
• /
• pp.235-241
• /
• 2000

기존의 장대강관말뚝 공법들은 말뚝의 용접이음이나 관내토의 제거 작업으로 인하여 공비와 공기가 증가하고 이들 작업이 진행되는 동안 시간효과에 의하여 말뚝의 관입 저항이 증가하여 타입이 어려워지는 등 각종 비경제적인 문제점들을 갖고 있다. 이러한 문제들을 해결하기 위하여 본 연구에서는 새로운 장대강관말뚝 공법을 제안하였으며, 제안된 공법의 시공성과 경제성을 분석하기 위하여 모형말뚝시험을 행하였다. 시험결과 새로 제안된 장대말뚝공법은 기존 공법에 비해 공기와 공비는 절감되고 지지력은 증가시키는 것으로 나타났다.

• 한국구조물진단유지관리공학회 논문집
• /
• 제13권4호통권56호
• /
• pp.159-169
• /
• 2009

본 연구는 다단계 온도프리스트레싱 공법으로 보강된 합성보의 하중재하 실험 및 구조해석을 통하여 온도프리스트레싱 공법의 프리스트레스 도입효과와 단면증가효과를 평가하였다. 연구결과 온도프리스트레싱을 이용한 합성보의 보강공법은 온도프리스트레싱에 의한 프리스트레스 도입 뿐 아니라 커버플레이트의 설치에 의한 단면증가로 합성보의 처짐 또한 감소시킬 수 있으므로 합성보의 효율적인 보강공법으로 적용이 가능할 것이다.

• 산업기술연구
• /
• 제20권A호
• /
• pp.101-111
• /
• 2000

This research is results of experimental and numerical works on characteristic of strength increase and bearing capacity in dredged and reclaimed soil due to desiccation shrinkage. For a soil sampled from southern coastal area in Korea, basic soil property tests and standard consolidation test with falling head permeability tests were carried out to obtain consolidational characteristics of soil. Double cone penetration test, laboratory vane test and unconfined compression test were also performed to investigate the change of shear strength with degree of desiccation. Model tests were performed in 1G environment and 30G level artificially accelerated condition by using the centrifuge model test facilities to investigate the bearing capacity of desiccated ground. Test results were analyzed by using the theoretical and load-settlement characteristics method proposed by Meyehof & Hanna(1978). On the other hands, the numerical technique, using the finite strain consolidation theory considering the effect of desiccation was used to estimate the appropriate time of using heavy construction equipments in field with respect to strength increase due to desiccation.

• 한국치위생학회지
• /
• 제24권2호
• /
• pp.99-108
• /
• 2024

연구목적: 본 연구는 캡스톤 디자인 설계 지역사회 치위생학 수업 후 학생들의 역량과 자기주도력 증가에 미치는 효과를 검증하고자 하였다. 연구방법: 연구 참여자는 C시에 소재한 4년제 대학에서 지역사회 치위생학 수업을 이수한는 치위생 전공 34명이었다. 설문도구는 치과위생사 역량 52문항과 자기주도력 20문항으로 구성되었다. 연구결과: 캡스톤 디자인 수업 후 전반적인 치과위생사의 역량이 증가하였고(p<0.05), 임상치위생 및 지역사회 건강증진 역량도 높은 증가를 보였다(p<0.001). 자기주도력에 따른 치과위생사의 역량 증가를 분석한 결과, 자기주도력이 낮은 집단일수록 임상 치위생 역량과 지역사회 건강증진 역량이 높은 향상을 보였다. 결론: 본 연구를 통해 캡스톤 디자인 설계지역사회 치위생학 수업이 학생들의 치과위생사 역량과 자기주도력을 향상시켰음을 확인하였고, 캡스톤 디자인 수업법은 미래사회에서 요구되는 역량을 배양하는데 탁월한 교수법임을 시사하였다.

• 한국지반환경공학회 논문집
• /
• 제21권12호
• /
• pp.23-28
• /
• 2020

사질토지반에서 적용할 수 있는 합리적인 침투능 산정기법을 제시하기 위하여 실내실험결과를 분석한 결과, 단위중량이 감소함에 따라 침투속도는 증가하는 경향을 보였으며, 강우강도가 증가함에 따라 침투속도 또한 증가하는 것으로 나타났다. 또한 본 논문에서 제안한 초기침투능 감소상수(α계수)를 적용한 침투능 변화 곡선에 대하여 비교·분석한 결과 시간에 따른 침투능 변화가 거의 일치하는 것으로 나타났다. 본 연구에서는 침투능 및 침투량 산정 시 널리 사용되고 있는 Horton 경험식이 사질토지반에서는 적용이 어려운 점을 개선하여 침투능 산정 모형을 제안하였다.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2007년도 정기 학술대회 논문집
• /
• pp.217-222
• /
• 2007

An Emergency Diesel Generator (EDG) is one of the safety related equipments of a Nuclear Power Plant. The seismic capacity of an EDG in nuclear power plants influences the seismic safety of the plants significantly. A recent study showed that the increase of the seismic capacity of the EDG could reduce the core damage frequency (CDF) remarkably. It is known that the major failure mode of the EDG is a concrete coning failure due to a pulling out of the anchor bolts. The use of base isolators instead of anchor bolts can increase the seismic capacity of the EDG without any major problems. This study introduces a seismic risk analysis method and presents sample results about the seismically isolated and conventional EDG system.

• Earthquakes and Structures
• /
• 제22권1호
• /
• pp.39-51
• /
• 2022

The axial compression behavior of nine self-compacting concrete columns confined with CFRP-PVC spirals was studied. Three parameters of spiral reinforcement spacing, spiral reinforcement diameter and height diameter ratio were studied. The test results show that the CFRP strip and PVC tube are destroyed first, and the spiral reinforcement and longitudinal reinforcement yield. The results show that with the increase of spiral reinforcement spacing, the peak bearing capacity decreases, but the ductility increases; with the increase of spiral reinforcement diameter, the peak bearing capacity increases, but has little effect on ductility, and the specimen with the ratio of height to diameter of 7.5 has the best mechanical properties. According to the reasonable constitutive relation of material, the finite element model of axial compression is established. Based on the verified finite element model, the stress mechanism is revealed. Finally, the composite constraint model and bearing capacity calculation method are proposed.