• Bulletin of the Korean Chemical Society
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• 제14권2호
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• pp.234-238
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• 1993

The method of study describes the determination of the nanogram amounts of mono-, di-, and tri-butyltin compounds in sea water. The procedure is based on 1) the conversion of tin compounds to non-ionic species by sodium tetraethyl borate as an alkylation reagent, 2) one-step ethylation and 3) extraction. No further purification or concentration of the extract was required before GC-FPD (Flame Photometric Detector). The detection limits for mono-, di- and tri-butyltin were 12.50, 6.02, and 4.19 ng/L. The linear range (0-120 ng/L) was solely dependent on the detector response height. Sea water samples (n=24) were obtained from Masan Bay, Busan, Ullsan, Gunsan, Sockcho, Yeasu, Donghae, Inchun, Kanghwa, and Ahsan in Korea. The samples were collected between June, 1992 to July, 1992 and the distribution of monobutyltintrichloride (MBTC), dibutyltindichloride (DBTC), and tributyltinchloride (TBTC) in sea water was recorded. The concentrations of butyltin compounds in seawater were found to be in the range of N.D. (not detected)-61.93 ng/L for MBTC, N.D.-32.16 ng/L for DBTC, and N.D.-55.76 ng/L for TBTC.

• 시스템엔지니어링학술지
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• 제16권2호
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• pp.67-77
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• 2020

Traditionally nuclear thermal hydraulic and nuclear safety has relied on numerical simulations to predict the system response of a nuclear power plant either under normal operation or accident condition. However, this approach may sometimes be rather time consuming particularly for design and optimization problems. To expedite the decision-making process data-driven models can be used to deduce the statistical relationships between inputs and outputs rather than solving physics-based models. Compared to the traditional approach, data driven models can provide a fast and cost-effective framework to predict the behavior of highly complex and non-linear systems where otherwise great computational efforts would be required. The objective of this work is to develop an AI algorithm to predict the peak fuel cladding temperature as a metric for the successful implementation of FLEX strategies under extended station black out. To achieve this, the model requires to be conditioned using pre-existing database created using the thermal-hydraulic analysis code, MARS-KS. In the development stage, the model hyper-parameters are tuned and optimized using the talos tool.

• Advances in aircraft and spacecraft science
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• 제10권1호
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• pp.19-49
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• 2023

The present study proposes a theoretical and numerical investigation on the dynamic response behaviour of a functional graded (FG) ceramic-metal tapered rotor shaft system, by the differential quadrature finite elements method (DQFEM) to identify the natural frequencies for modelling and analysis of the structure with suitable validations. The purpose of this paper is to explore the influence of heat gradients on the natural frequency of rotation of FG shafts via three-dimensional solid elements, as well as a theoretical examination using the Timoshenko beam mode, which took into account the gyroscopic effect and rotational inertia. The functionally graded material's distribution is described by two distribution laws: the power law and the exponential law. To simulate varied thermal conditions, radial temperature distributions are obtained using the nonlinear temperature distribution (NLTD) and exponential temperature distribution (ETD) approaches. This work deals with the results of the effect on the fundamental frequencies of different material's laws gradation and temperature gradients distributions. Attempts are conducted to identify adequate explanations for the behaviours based on material characteristics. The effect of taper angle and material distribution on the dynamic behaviour of the FG conical rotor system is discussed.

• 한국지반공학회논문집
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• 제25권7호
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• pp.47-54
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• 2009

도로하부에 대한 현장에서의 역학적인 거동에 대한 이해는 교통기반시스템의 장기공용성을 예측하는데 매우 중요하다. 이러한 현장거동에서 지반재료에 대한 회복변형 거동 정량화는 교통하중과 환경조건을 고려한 역학적인 해석이 필수적이다. 따라서 본 논문에서는 한국도로공사 시험도로에서 현장자료의 계측과 분석을 통하여 선택된 도로하부 입상재료에 대한 구성방정식을 활용한 비선형 재료거동과 응력을 예측 분석하고 이를 현장자료와 비교하고 검증하였다.

• Steel and Composite Structures
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• 제48권2호
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• pp.131-143
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• 2023

The CFRP bar was used to achieve more ductile and durable headed-stud shear connectors in composite components. Three series of push-out tests were firstly conducted, including specimens reinforced with pure steel fibers, steel and CFRP bars. The distributed stress was measured by the commercial PPP-BOTDA (Pre-Pump-Pulse Brillouin optical time domain analysis) optical fiber sensor with high spatial resolution. A series of numerical analyses using non-linear FE models were also made to study the shear force transfer mechanism and crack response based on the test results. Test results show that the CFRP bar increases the shear strength and stiffness of the large diameter headed-stud shear connection, and it has equivalent reinforcing effects on the stud shear capacity as the commonly used steel bar. The embedded CFRP bar can also largely improve the shear force transfer mechanism and decrease the tensile stress in the transverse direction. The parametric study shows that low content steel fibers could delay the crack initiation of slab around the large diameter stud, and the CFRP bar with normal elastic modulus and the standard reinforcement ratio has good resistance to splitting crack growth in headed stud shear connectors.

• Computers and Concrete
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• 제33권2호
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• pp.163-173
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• 2024

Fiber-reinforced polymers (FRP) have a proven strength enhancement capability when installed into Reinforced Concrete (RC) beams. The brittle failure of traditional FRP strengthening systems has attracted researchers to develop novel materials with improved strength and ductility properties. One such material is that known as polyethylene terephthalate (PET). This study presents a numerical investigation of the flexural behavior of reinforced concrete beams externally strengthened with PET-FRP systems. This material is distinguished by its large rupture strain, leading to an improvement in the ductility of the strengthened structural members compared to conventional FRPs. A three-dimensional (3-D) finite element (FE) model is developed in this study to predict the load-deflection response of a series of experimentally tested beams published in the literature. The numerical model incorporates constitutive material laws and bond-slip behavior between concrete and the strengthening system. Moreover, the validated model was applied in a parametric study to inspect the effect of concrete compressive strength, PET-FRP sheet length, and reinforcing steel bar diameter on the overall performance of concrete beams externally strengthened with PET-FRP.

• Geomechanics and Engineering
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• 제36권3호
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• pp.277-293
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• 2024

Shored Mechanically Stabilized Earth (SMSE) walls are types of soil retaining structures that increase soil stability under static and dynamic loads. The damage caused by an earthquake can be determined by evaluating the probabilistic seismic response of SMSE walls. This study aimed to assess the seismic performance of SMSE walls and provide fragility curves for evaluating failure levels. The generated fragility curves can help to improve the seismic performance of these walls through assessing and controlling variables like backfill surface settlement, lateral deformation of facing, and permanent relocation of the wall. A parametric study was performed based on a non-linear elastoplastic constitutive model known as the hardening soil model with small-strain stiffness, HSsmall. The analyses were conducted using PLAXIS 2D, a Finite Element Method (FEM) program, under plane-strain conditions to study the effect of the number of geogrid layers and the axial stiffness of geogrids on the performance of SMSE walls. In this study, three areas of damage (minor, moderate, and severe) were observed and, in all cases, the wall has not completely entered the stage of destruction. For the base model (Model A), at the highest ground acceleration coefficient (1 g), in the moderate damage state, the fragility probability was 76%. These values were 62%, and 54%, respectively, by increasing the number of geogrids (Model B) and increasing the geogrid stiffness (Model C). Meanwhile, the fragility values were 99%, 98%, and 97%, respectively in the case of minor damage. Notably, the probability of complete destruction was zero percent in all models.

• 디지털융복합연구
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• 제12권4호
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• pp.103-113
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• 2014

공급망 내에서의 교섭지위와 신뢰는 전략적으로 매우 중요한 이슈임에도 불구하고 교섭지위가 신뢰에 미치는 영향에 대해서는 논란이 많다. 본 연구는 교섭지위 및 신뢰에 관한 이론적 배경을 토대로 연구가설을 설정하고 공급망 참여기업에 대한 설문조사를 통해 타당성을 평가하는데 목적이 있다. 특히 교섭지위의 다양한 위상이 신뢰에 미치는 영향을 비선형함수로 설정하고 이를 반응곡선모형을 통해 분석해 본다는 데에 방법론적 차별성이 있다. 127개 기업의 설문조사 데이터를 통계적으로 분석한 결과, 구매기업이 인식하는 교섭지위는 공급자에 대한 신뢰요인에 대해 비선형적 영향을 미친다는 결과를 도출할 수 있었다. 본 연구는 공급망 내에서의 신뢰와 거래관계에 대한 통합적 시각을 제시했다는 측면에서 의의가 있을 것이다.

• Structural Engineering and Mechanics
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• 제65권5호
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• pp.621-631
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• 2018

In this paper, an exact analytical solution is developed for the analysis of the post-buckling non-linear response of simply supported deformable symmetric composite beams. For this, a new theory of higher order shear deformation is used for the analysis of composite beams in post-buckling. Unlike any other shear deformation beam theories, the number of functions unknown in the present theory is only two as the Euler-Bernoulli beam theory, while three unknowns are needed in the case of the other beam theories. The theory presents a parabolic distribution of transverse shear stresses, which satisfies the nullity conditions on both sides of the beam without a shear correction factor. The shear effect has a significant contribution to buckling and post-buckling behaviour. The results of this analysis show that classical and first-order theories underestimate the amplitude of the buckling whereas all the theories considered in this study give results very close to the static response of post-buckling. The numerical results obtained with the novel theory are not only much more accurate than those obtained using the Euler-Bernoulli theory but are almost comparable to those obtained using higher order theories, Accuracy and effectiveness of the current theory.

• Structural Engineering and Mechanics
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• 제74권6호
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• pp.789-807
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• 2020

Multiple earthquakes that occur during short seismic intervals affect the inelastic behavior of the structures. Sequential ground motions against the single earthquake event cause the building structure to face loss in stiffness and its strength. Although, numerous research studies had been conducted in this research area but still significant limitations exist such as: 1) use of traditional design procedure which usually considers single seismic excitation; 2) selecting a seismic excitation data based on earthquake events occurred at another place and time. Therefore, it is important to study the effects of successive ground motions on the framed structures. The objective of this study is to overcome the aforementioned limitations through testing a two storey RC building structural model scaled down to 1/10 ratio through a similitude relation. The scaled model is examined using a shaking table. Thereafter, the experimental model results are validated with simulated results using ETABS software. The test framed specimen is subjected to sequential five artificial and four real-time earthquake motions. Dynamic response history analysis has been conducted to investigate the i) observed response and crack pattern; ii) maximum displacement; iii) residual displacement; iv) Interstorey drift ratio and damage limitation. The results of the study conclude that the low-rise building model has ability to resist successive artificial ground motion from its strength. Sequential artificial ground motions cause the framed structure to displace each storey twice in correlation with vary first artificial seismic vibration. The displacement parameters showed that real-time successive ground motions have a limited impact on the low-rise reinforced concrete model. The finding shows that traditional seismic design EC8 requires to reconsider the traditional design procedure.