• 한국해양공학회지
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• 제4권1호
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• pp.87-87
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• 1990

Fatigue crack closure levels based on the behavior of residual displacements on crack surfaces, are determined analytically according to the microscopic crack closure mechanisms, i.e., whether the first contact of crack surfaces takes place at the very crack tip or on the surfaces near the tip. The comparative analysis on the two models is carried out empirically by the constant amplitude fatigue tests on 2024-T3 aluminum alloy plate, and it shows that under negative stress ratio, the case of the first contact at crack tip gives better agreement with the experimental results than the other.

• 한국세라믹학회지
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• 제40권7호
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• pp.667-671
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• 2003

테이프 캐스팅법을 이용하여 알루미나/지르콘(반응결합 뮬라이트/지르코니아 유도)을 내부층으로 하고 알루미나/지르코니아 혹은 뮬라이트/지르코니아를 외부층으로 하는 산화물 층상 복합체를 고온가압소결법으로 제조하였다. 나노압입시험법을 이용하여 층상 산화물 복합체의 기계적 성질(경도 및 탄성계수)을 측정하고, SEM을 통하여 복합체의 미세구조를 관찰하였다. 산화물 층상 복합체의 제조를 위한 가열·냉각시 유도된 구성 산화물간의 열팽창 계수의 차이로 인하여 생성된 잔류응력을 하중-변위곡선을 이용하여 확인할 수 있었다.

• Steel and Composite Structures
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• 제19권1호
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• pp.173-190
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• 2015

This study presents an analytical investigation on the seismic response of a medium-rise buckling-restrained braced frame (BRBF) under the near-fault ground motions. A seven-story BRBF is designed as per the current code provisions for five different combinations of brace configurations and beam-column connections. Two types of brace configurations (i.e., Chevron and Double-X) are considered along with a combination of the moment-resisting and the non-moment-resisting beam-to-column connections for the study frame. Nonlinear dynamic analyses are carried out for all study frames for an ensemble of forty SAC near-fault ground motions. The main parameters evaluated are the interstory and residual drift response, brace displacement ductility, and plastic hinge mechanisms. Fragility curves are developed using log-normal probability density functions for all study frames considering the interstory drift ratio and residual drift ratio as the damage parameters. The average interstory drift response of BRBFs with Double-X brace configurations significantly exceeded the allowable drift limit of 2%. The maximum displacement ductility characteristics of BRBs is efficiently utilized under the seismic loading if these braces are arranged in the Double-X configurations instead of Chevron configurations in BRBFs located in the near-fault regions. However, BRBFs with the Double-X brace configurations exhibit the higher interstory drift and residual drift response under near-fault ground motions due to the formation of plastic hinges in the columns and beams at the intermediate story levels.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.454-459
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• 2013

For the purpose of rapid development and superior design quality assurance, sophisticated finite element model for SOM(Spatial Optical Modulator) piezo actuator of MOEMS device has been developed and evaluated for the accuracy of dynamics and residual stress analysis. Parametric finite element model is constructed using ANSYS APDL language to increase the design and analysis performance. Geometric dimensions, mechanical material properties for each thin film layer are input parameters of FE model and residual stresses in all thin film layers are simulated by thermal expansion method with psedu process temperature. $6^{th}$ mask design samples are manufactured and $1^{st}$ natural frequency and 10V PZT driving displacement are measured with LDV. The results of experiment are compared with those of the simulation and validate the good agreement in $1^{st}$ natural frequency within 5% error. But large error over 30% occurred in 10V PZT driving displacement because of insufficient PZT constant $d_{31}$ measurement technology.

• Steel and Composite Structures
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• 제45권5호
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• pp.683-695
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• 2022

Conventional braces are often used to provide stiffness to structures; however due to buckling they cannot be used as seismic energy dissipating elements. In this study, a seismic energy dissipation device is proposed which is comprised of a bracing member and a steel hysteretic damper made of steel hexagonal plates. The hexagonal shaped designated fuse causes formation of plastic hinges under axial deformation of the brace. The main advantages of this damper compared to conventional metallic dampers and buckling-restrained braces are the stable and controlled energy dissipation capability with ease of manufacture. The mechanical behavior of the damper is formulated first and a design procedure is provided. Next, the theoretical formulation and the efficiency of the damper are verified using finite element (FE) analyses. An analytical model of the damper is established and its efficiency is further investigated by applying it to seismic retrofit of a case study structure. The seismic performance of the structure is evaluated before and after retrofit in terms of maximum interstory drift ratio, top story displacement, residual displacement, and energy dissipation of dampers. Overall, the median of maximum interstory drift ratios is reduced from 3.8% to 1.6% and the residual displacement decreased in the x-direction which corresponds to the predominant mode shape of the structure. The analysis results show that the developed damper can provide cost-effective seismic protection of structures.

• 치과방사선
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• 제19권1호
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• pp.163-169
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• 1989

The purpose of this study is to investigate on the clinical and radiographic patterns of residual cyst of the jaw for early diagnosis and treatment. The auther studied 87 cases of residual cyst with regard to age, sex distribution, the site of the lesion and several radiographic features. The results were as follows: 1. The average age was found to be 42.6 years, with a range of 15 to 84 years. The incidence was highest in the third and fourth decades(50.6%) and total 87 cases consist of 47 males and 38 females. 2. The common clinical symptoms were pus discharge, swelling, pain and no symptoms was presented in 5 cases(12.5%). 3. Residual cysts were found to be 46.0% maxillary anterior region, 18.4% maxillary molar region, 17.2% mandibular molar region and to be more common in the maxilla(70.1%) than in the mandible(29.9%) 4. Most of residual cysts were unilocular type(86 cases, 98.8%), showing distinct border(62 cases, 71.3%) with smooth margin(78 cases, 89.7%). 5. The adjacent teeth showed root resorption in 13 cases(14.9%), and root divergence in 16 cases(18.4%). 6. The residual cysts extended to the nasal fossa(22 cases, 22.5%), the maxillary sinus(19 cases, 19.4%) and caused the displacement of the mandibular canal wall (11 cases, 11.2%)

• Advances in concrete construction
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• 제6권5호
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• pp.485-507
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• 2018

Concrete-Filled Steel Tube (CFST) columns are an increasingly popular means to support great compressive loads in buildings. The residual strength capacity of CFST stub columns may be utilized to assess the potential damage caused by fire and calculate the structural fire protection for least post-fire repair. Ten specimens under room conditions and 10 specimens under fire exposure to the Eurocode smouldering slow-growth fire were tested to examine the effects of diameter to thickness D/t ratio and reinforcing bars on residual strength capacity, ductility and stiffness of CFST stub columns. On the other hand, in sixteen among the twenty specimens, three or six reinforcing bars were welded inside the steel tube. The longitudinal strains in the steel tube and load-displacement relationships were recorded throughout the subsequent compressive tests. Corresponding values of residual strength capacity calculated using AISC 360-10 and EC4 standards are presented for comparison purposes with the experimental results of this study. The test results showed that after exposure to $750^{\circ}C$, the residual strength capacity increased for all specimens, while the ductility and stiffness were slightly decreased. The comparison results showed that the predicted residual strength using EC4 were close to those obtained experimentally in this research.

• 한국항행학회논문지
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• 제14권5호
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• pp.668-676
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• 2010

광 위상 공액기 (OPC; optical phase conjugator)가 단일 모드 광섬유 (SMF; single mode fiber)로 이루어진 전체 전송 거리 1000 km의 50 km 간격으로 250 km부터 750 km까지 존재하는 광전송 랭크에 inline 분산제어 (DM; dispersion management)를 통해 $24{\times}40$ Gbps WDM 채널의 신호 왜곡을 보상하기 위한 최적의 전체 잉여 분산 (NRD; net residual dispersion)을 OPC 위치별로 도출하였고, 최적 NRD가 적용된 경우의 WDM 채널의 성능 개선 정도를 NRD = 0 ps/nm로 고정된 전송 링크에서의 수신 성능과 비교하였다. 최적 NRD는 OPC가 전체 전송 거리의 중간인 500km로부터 이동된 정도에 따라 결정되어야 하고, 최적 NRD의 결정과 적용에 있어 OPC가 500km로부터 수신부쪽으로 이동되는 경우보다 송신부쪽으로 이동되는 경우가 더욱 안정적이고 효과적임을 확인하였다. 또한 0 ps/nm로 NRD가 고정된 전송 랭크에 비해 최적 NRD로 셜계된 전 송 랭크에서의 WDM 채널의 눈 열림 패널티 (EOP; eye opening penalty)가 OPC 위치에 따라 1.5 dB부터 3dB까지 개선되는 것을 확인하였다.

• 한국기계가공학회지
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• 제2권1호
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• pp.22-31
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• 2003

The compressive residual stress, which is induced by shot peening process, seems to be an Important factor in increasing the fatigue strength. And then it was showed that residual stress was disappearenced at the high temperature. The fatigue charateristic investigation of a SUP9 spring steel processed shot peening is performed by considering the high temperature service conditions in the range of room temperature through $180^{\circ}C$ in the range of stress ratio of 0.3 by means of opening mode displacement. The fatigue resistance characteristics and fracture strength at high temperature is considerable lower than that of room temperature in the early stage and stable of fatigue crack growth region.

• 한국자동차공학회논문집
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• 제12권4호
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• pp.58-64
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• 2004

The purpose of this study is to predict the behavior of fatigue crack propagation as one of fracture mechanics on the compressive residual stress. We got the following characteristics from fatigue crack growth test carried out in the environment of room temperature and low temperature at $25^{\circ}C$, -6$0^{\circ}C$, -8$0^{\circ}C$, and -10$0^{\circ}C$ in the range of stress ratio of 0.3 by means of opening mode displacement. There is a difference between shot peened specimen and unpeened specimen. Fatigue crack growth rate of shot peened specimen was lower than that of unpeened specimen. Shot peening is improve the resistance of crack growth by fatigue that make a compressive residual stress on surface. That is the constrained force about plasticity deformation was strengthened by resultant stress, which resulted from plasticity deformation and compressive residual stress in the process of fatigue crack propagation. Temperature goes down, fatigue crack growth rate decreased.