• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.845-850
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• 2007

The empirical AISC panel zone thickness provision$(t_z\geq(d_z+w_z)$/90) to prevent the cyclic shear buckling of the panel zone was proposed based on the test data of Krawinkler et al. (1971) and Bertero et al. (1973) However, no published records of the equation development or any other background information appear to be available. The calibrated finite element analysis results of this study indicated that the AISC provision was not reasonable. In this study, through including the effects of the column axial force and the aspect ratio of the panel zone, a new equation for the relative strength between the beam and the panel zone was proposed such that the proposed equation can prevent the panel zone shear buckling and reduce the potential fracture associated with the kinking of the column flanges.

• Korean Journal of Crystallography
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• v.6 no.2
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• pp.134-140
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• 1995

SAW properties of SiNx/ZnO bilayer thin film structure were analyzed. ZnO thin films were deposited by rf magnetron sputter using O2 gas as an oxidizer. Structure of ZnO thin films was affected by Ar/O2 ratio. At the gas ratio of Ar/O2=67/33, the standard deviation of X-ray rocking curve of (002) preferred ZnO thin film was 2.17 degree. This value is sufficient to use ZnO thin films as an acoustic element. SAW velocity of glass/SiNx(7000Å)/Al/ZnO(5μm) structure was max. 2.2% faster than that of ZnO/glass.

• Steel and Composite Structures
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• v.39 no.2
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• pp.149-158
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• 2021

In this research paper, the free vibrational response of laminated composite plates is investigated using a non-polynomial refined shear deformation theory (NP-RSDT). The most interesting feature of this theory is the parabolic distribution of transverse shear deformations while ensuring the conditions of nullity of shear stresses at the free surfaces of the plate without requiring the Shear correction factor "Ks". A fourth-nodded isoparametric element with four degrees of freedom per node is employed for laminated composite plates. The numerical analysis of simply supported square anti-symmetric cross-ply and angle-ply laminated plate is carried out using a special discretization based on four-node finite element method which four degrees of freedom per node. Several numerical results are presented to show the effect of the coupling parameters of the plate such as the modulus ratios, the thickness ratio and the plate layers number on adimensional eigen frequencies. All numerical results presented using the current finite element method (FEM) is presented in 3D curve form.

• Journal of Soil and Groundwater Environment
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• v.13 no.1
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• pp.92-100
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• 2008

Experimental studies were conducted to identify the active agents for reductive dechlorination of TCE in cement/Fe(II) systems focusing on cement components such as CaO, $Fe_2O_3$, and $Al_2O_3$. A hematite that was used to simulate an $Fe_2O_3$ component in cement was found to have degradation efficiencies (k = 0.641 $day^{-1}$) equivalent to that of cement/Fe(II) systems in the presence of CaO/Fe(II), only when it contained an aluminum impurity$(Al_2O_3)$. When the effect of $Al_2O_3$ content of hematite/CaO/$Al_2O_3$/Fe(II) system was tested, the mole ratio of $Al_2O_3$ to CaO affected the rate of TCE degradation with an optimum ratio around 1 : 10 that resulted in a rate constant of 0.895 $day^{-1}$. In the SEM images of hematite/CaO/$Al_2O_3$/Fe(II) systems, acicular crystals were also found that were also observed in cement/Fe(II) systems. Thus it was suspected that these crystals were reactive reductants and that they might be goethite or ettringite that are known to have acicular structures. An EDS element map analysis revealed that these crystals were not goethite crystals. A subsequent experiment that tested reactivities of compounds formed during the ettringite synthesis showed that ettringite and minerals associated with ettringite formation are not reactive reductants. These observations conclude that a mineral containing CaO and $Al_2O_3$ with a acicular structure could be a major reactive reductant of cement/Fe(II) systems.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.519-524
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• 2004

This study is concerned with the braking distance estimation using frictional energy rate. First, steady state rolling analysis is performed, and using this result, the braking distance is estimated. Dynamic rolling analysis during entire braking time period is impratical, so that this study divides the vehicle velocity by 10km/h to reduce the analysis time. The multiplication of the slip rate and the shear stress provides the frictional energy rate. Using frictional energy rate, total braking distance is estimated, In addition, ABS(Anti-lock Brake System) is considered, and two type of slip ratios are compared, One is 15% slip ratio for the ABS condition, and the other is 100% slip ratio which leads lo the almost same braking distance as the elementary kinematic theory. A slip ratio is controlled by angular velocity in ABAQUS/Explicit, A 15% slip ratio gives the real vehicle's braking distance when the frictional energy occurred al disk pad is included. Disk pad's frictional energy rate is calculated by the theoretical approach.

• Smart Structures and Systems
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• v.25 no.6
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• pp.669-678
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• 2020

This paper focuses on the free vibration analysis of axially functionally graded (FG) Euler-Bernoulli beams. The material properties of the beams are assumed to obey the linear law distribution. The complexities in solving differential equation of transverse vibration of composite beams which limit the analytical solution to some special cases are overcome using the Differential Transformation Method (DTM). Natural frequencies and corresponding normalized mode shapes are calculated. Validation targets are experimental data or finite element results. Different parameters such as reinforcement distribution, ratio of the reinforcement Young's modulus to the matrix Young's modulus and ratio of the reinforcement density to the matrix density are taken into investigation. The delivered results prove the capability and the robustness of the applied method. The studied parameters are demonstrated to be very crucial for the normalized natural frequencies and mode shapes.

• Journal of the Korean institute of surface engineering
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• v.33 no.5
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• pp.309-318
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• 2000

The 6063 Aluminium alloy were electrocolored and anodized at the same time in addition of $CoSO_4$, $FeSO_4$, in the electrolyte and investigated by AES/SAM. It was found that the thickness of anodic oxide film is increased linearly in DC type, and DC combined AC type, the more ratio of anodic Portion in AC, the more increased of anodic film thickness. The color of anodic film was changed from silver to yellow when the increase of the ratio of cathodic portion in AC. Also the increase of $CoSO_4$, $FeSO_4$ in the electrolyte, the coloring time is decreased. From the AES/SAM results, the element of anodic oxide film are Al,O and S. The result of depth profile, the most of the S distributed on the surface and the more S is in DC combined AC type than only DC type.

• Journal of Korea Foundry Society
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• v.35 no.5
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• pp.120-127
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• 2015

The effects of Ti, B and Zr on grain refinement and castability were investigated in Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe alloy. Measurement of cooling curve and micro-structure observation were performed to analyze the effects of the addition of minor elements Ti, B and Zr during solidification. The prominence of effect on grain refinement was in increasing order for Ti, Zr and B element. Fine grain size and an increase of the crystallization temperature for ${\alpha}$-Al solution were evident as the amount of addition elements increased in this study. Addition of 0.15wt% Ti was most effective for grain refinement, and the resulting grain size of ${\alpha}$-Al solution for shell mold and steel mold were $72.3{\mu}m$ and $23.5{\mu}m$, respectively. Fluidity and shrinkage tests were perform to evaluate the castability of the alloy. Maximum fluidity length and minimum ratio of micro shrinkage were recorded for 0.15wt% Ti addition due to the effect of the finest grain size.

• The Journal of the Petrological Society of Korea
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• v.14 no.3 s.41
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• pp.127-140
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• 2005

The Samyuri area of Jeoksang-myeon, Muju-gun at the Middle Yeongnam Massif consists of granitic gneiss, porphyroblastic gneiss and leucocratic gneiss, which correspond to Precambrian Wonnam Series. Here we discuss a geochemical implication of the data based on major element composition, trace element, rare earth element (REE), Sm-Nd and Rb-Sr isotope systematics of the boring cores in the granite gneiss area. The boring cores are granitic gneiss (including biotite gneiss) and amphibolite. The major and trace element compositions of granitic gneiss and amphibolite suggest that the protolith belongs to TTG (Tonalite-Trondhjemite-Granodiorite) and tholeiitic series, respectively. Chondrte-normalized REE patterns vary in LREE, HREE and Eu anomalies. The granitic gneiss and amphibolite have Sm-Nd whole rock age of $2,026{\pm}230(2{\sigma})$ Ma with an initial Nd isotopic ratio of $0.50979{\pm}0.00028(2{\sigma})$ (initial ${\epsilon}_{Nd}=-4.4$), which suggests that the source material was derived from old crustal material. Particularly, this initial ${\epsilon}$ Nd value belongs to the range of the geochemical evolution of Archean basement in North-China Craton, and also corresponds to the initial Nd isotope evolution line by Lee et al. (2005). In addition, chondrite-normalized REE pattern and initial Nd value of amphibolite are very similar to those of juvenile magma in crustal formation process.

• Computers and Concrete
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• v.24 no.1
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• pp.37-49
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• 2019

In this study, the shear behaviour of reinforced concrete (RC) beams that were retrofitted using precast panels of ultra-high performance fiber reinforced concrete (UHPFRC) is presented. The precast UHPFRC panels were glued to the side surfaces of RC beams using epoxy adhesive in two different configurations: (i) retrofitting two sides, and (ii) retrofitting three sides. Experimental tests on the adhesive bond were conducted to estimate the bond capacity between the UHPFRC and normal concrete. All the specimens were tested in shear under varying levels of shear span-to-depth ratio (a/d=1.0; 1.5). For both types of configuration, the retrofitted specimens exhibited a significant improvement in terms of stiffness, load carrying capacity and failure mode. In addition, the UHPFRC retrofitting panels glued in three-sides shifted the failure from brittle shear to a more ductile flexural failure with enhancing the shear capacity up to 70%. This was more noticeable in beams that were tested with a/d=1.5. An approach for the approximation of the failure capacity of the retrofitted RC beams was evolved using a multi-level regression of the data obtained from the experimental work. The predicted values of strength have been validated by comparing them with the available test data. In addition, a 3-D finite element model (FEM) was developed to estimate the failure load and overall behaviour of the retrofitted beams. The FEM of the retrofitted beams was conducted using the non-linear finite element software ABAQUS.