• Smart Structures and Systems
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• v.22 no.3
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• pp.315-326
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• 2018

This paper presents a novel time-domain method for the identification of plastic rotations and stiffness parameters of single-bay frames with nonlinear plastic hinges. Each plastic hinge is modelled as a pseudo-semi-rigid connection with nonlinear hysteretic moment-curvature characteristics at an element end. Through the comparison of the identified end rotations of members that are connected together, the plastic rotation that furnishes information of the locations and plasticity degrees of plastic hinges can be identified. The force consideration of the frame members may be used to relate the stiffness parameters to the elastic rotations and the excitation. The damped-least-squares method and damped-and-weighted-least-squares method are adopted to estimate the stiffness parameters of frames. A noise-removal strategy employing a de-noising technique based on wavelet packets with a smoothing process is used to filter out the noise for the parameter estimation. The numerical examples show that the proposed method can identify the plastic rotations and the stiffness parameters using measurements with reasonable level of noise. The unknown excitation can also be estimated with acceptable accuracy. The advantages and disadvantages of both parameter estimation methods are discussed.

• Steel and Composite Structures
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• v.33 no.6
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• pp.865-875
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• 2019

The current article proposed to develop a geometrical model for the analysis and modelling of the uniaxial functionally graded structure using the higher-order displacement kinematics with and without the presence of porosity including the distribution. Additionally, the formulation is capable of modelling three different kinds of grading patterns i.e., Power-law, sigmoid and exponential distribution of the individual constituents through the thickness direction. Also, the model includes the distribution of porosity (even and uneven kind) through the panel thickness. The structural governing equation of the porous graded structure is obtained (Hamilton's principle) and solved mathematically by means of the isoparametric finite element technique. Initially, the linear frequency parameters are obtained for different geometrical configuration via own computer code. The comparison and the corresponding convergence studies are performed for the unidirectional FG structure for the validation purpose. Finally, the impact of different influencing parameters like aspect ratio (O), thickness ratio (S), curvature ratio (R/h), porosity index (λ), type of porosity (even or uneven), power-law exponent (n), boundary condition on the free vibration characteristics are obtained for the FG panel and discussed in details.

• Computers and Concrete
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• v.8 no.4
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• pp.445-463
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• 2011

In the design of reinforced concrete (RC) beams, apart from providing adequate strength, it is also necessary to provide a minimum deformability even for beams not located in seismic regions. In most RC design codes, this is achieved by restricting the maximum tension steel ratio or neutral axis depth. However, this empirical deemed-to-satisfy method, which was developed based on beams made of normal-strength concrete (NSC) and normal-strength steel (NSS), would not provide a consistent deformability to beams made of high-strength concrete (HSC) and/or high-strength steel (HSS). More critically, HSC beams would have much lower deformability than that provided previously to NSC beams. To ensure that a consistent deformability is provided to all RC beams, it is proposed herein to set an absolute minimum rotation capacity to all RC beams in the design. Based on this requirement, the respective maximum limits of tension steel ratio and neutral axis depth for different concrete and steel yield strengths are derived based on a formula developed by the authors. Finally for incorporation into design codes, simplified guidelines for designing RC beams having the proposed minimum deformability are developed.

• Restorative Dentistry and Endodontics
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• v.38 no.3
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• pp.167-171
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• 2013

Biomechanical preparation of root canals with accentuated curvature is challenging. New rotatory systems, such as Reciproc, require a shorter period of time to prepare curved canals, and became a viable alternative for endodontic treatment of teeth with root dilaceration. Thus, this study aimed to report a clinical case of endodontic therapy of root with accentuated dilaceration using Reciproc single-file system. Mandibular right second molar was diagnosed as asymptomatic irreversible pulpitis. Pulp chamber access was performed, and glide path was created with #10 K-file (Dentsply Maillefer) and PathFile #13, #16 and #19 (Dentsply Maillefer) up to the temporary working length. The working length measured corresponded to 20 mm in the mesio-buccal and mesio-lingual canals, and 22 mm in the distal canal. The R25 file (VDW GmbH) was used in all the canals for instrumentation and final preparation, followed by filling with Reciproc gutta-percha cones (VDW GmbH) and AH Plus sealer (Dentsply Maillefer), using thermal compaction technique. The case has been receiving follow-up for 6 mon and no painful symptomatology or periapical lesions have been found. Despite the difficulties, the treatment could be performed in a shorter period of time than the conventional methods.

• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.443-454
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• 2013

Various metal ions (transition and base metals) incorporated MCM-41 catalysts can be synthesized using colloidal and soluble silica with non-sodium involved process. Transition metal ion-typically $V^{5+}$, $Co^{2+}$, and $Ni^{2+}$-incorporated MCM-41 catalysts were synthesized by isomorphous substitution of Si ions in the framework. Each incorporated metal ion created a single species in the silica framework, single-site solid catalyst, showing a substantial stability in reduction and catalytic activity. Radius of pore curvature effect was investigated with Co-MCM-41 by temperature programmed reduction (TPR). The size of metallic Co clusters, sub-nanometer, could be controlled by a proper reduction treatment of Co-MCM-41 having different pore size and the initial pH adjustment of the Co-MCM-41 synthesis solution. These small metallic clusters showed a high stability under a harsh reaction condition without serious migration, resulting from a direct anchoring of small metallic clusters to the partially or unreduced metal ions on the surface. After a complete reduction, partial occlusion of the metallic cluster surface by amorphous silica stabilized the particles against aggregations. As a probe reaction of particle size sensitivity, carbon single wall nanotubes (SWNT) were synthesized using Co-MCM-41. A metallic cluster stability test was performed by CO methanation using Co- and Ni-MCM-41. Methanol and methane partial oxidations were carried out with V-MCM-41, and the radius of pore curvature effect on the catalytic activity was investigated.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.511-514
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• 1997

The objective of this study is to propose a finite element based design of the dental implant replacing unction and shape of natural teeth. For this, geometric actors were varied to investigate stress distribution of the alveolar bone around dental implant. In this study, the results were obtained based on the theory of linear elastic, with geometrically axisymmetric assumption. Geometric actors determining implant shape are ranged as 0.2mm-0.6mm, 0.04mm-0.1mm, 0.46mm-0.84mm or height of thread, radius of curvature of thread, and pitch, respectively. The stresses in the alveolar bone caused by biting force playa major role in determining implant stability. Especially, the stress concentration in the cortical bone causes bone resorption and finally makes the implant unstable. Therefore, the stress distributions were investigated on the side of the alveolar bone focusing on the area of cortical bone. The maximum von Mises stress was found to increase up to 6% as the height of thread increases, while its value was to decrease to 19% when the radius of curvature increase within the assigned ranges. For the variation of pitch, the larger size of pitch results in greater maximum von Mises stress when the length of the implant under consideration is fixed. The existence of the neck below the shoulder did not affect the stress distribution in the region of alveolar bone. However, the stresses on the side of the implant near the neck were found to be different by 20% approximately. Therefore, the neck can provide the stability of the implant against continuing biting movement. As a conclusion, the finite element based study shows a potential in designing the dental implant systematically.

• Journal of Korean Society on Water Environment
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• v.20 no.3
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• pp.197-205
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• 2004

Batch test methods have developed for a long time to measure kinetic and stoichiometric parameters which are required to perform steady state design and mathematical modelling of activated sludge processes. However, at various So/Xo ratios, abnormal behaviors of ordinary heterotrophic organism in batch tests have been reported in many researches. Thus, in this research, abnormal behaviors of heterotrophs in batch tests were investigated at various So/Xo conditions by measuring and interpreting oxygen utilization rate. As So/Xo ratio increased, the calculated values of maximum specific growth rates, ${\mu}_{H,max}$ and $K_{MP,max}$, increased. However, at a certain point of So/Xo (around 10mgCOD/mgMLAVSS), ${\mu}_{H,max}$ and $K_{MP,max}$ values started to decrease. According to this observation, three prominent behaviours of heterotrophs were identified at various So/Xo conditions. (1) At low So/Xo region (below 5 mgCOD/mgMLAVSS), the oxygen utilization rate of heterotrophs in batch tests were almost stable and consequently yielded lower maximum specific growth rate. (2) At high So/Xo region (up to 5~10 mgCOD/mgMLAVSS), oxygen utilization rate incresed sharply with time and indicated more upward curvature than the predicted OUR with conventional activated sludge model, which consists of single hetetrotrophs group. Thus, in this region, competition model of two organisms, fast-grower and slow-grower, seemed to be appropriate. (3) At extremely high So/Xo region (over 10mgCOD/mgMLAVSS), significant oxygen utilization rate was still observed even after depletion of readily biodegradable COD. This might be caused by retarded utilization of intermediates which were generated by self inhibition mechanism in the process of RBCOD uptake.

• Journal of the Korean Statistical Society
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• v.36 no.2
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• pp.201-208
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• 2007

Evolutionary operation (EVOP) proposed by Box (1957) is a method for continuous monitoring and improvement of a full-scale manufacturing process with the objective of moving the operating conditions toward the better ones. EVOP consists of systematically making small changes in the levels of the two or three process variables under consideration. Data are collected on the response variable at each point of two level factorial design with the center point and a cycle is said to have been completed. The cycles are replicated sequentially until the decision is made on whether further cycle of experiments is needed to conclude the significance of any of main effects or interaction effects or the curvature. In this paper, an improved flow chart of EVOP is proposed and how to determine the number of cycles is studied based on the size of type II error. In order to reject the alternative hypothesis of interests with more confidence and conclude that we believe in the null hypothesis of no effects, we propose a counter measure $p^*-value$ corresponding to the p-value. The relationship of $p^*-value$ to the probability of type II error ${\beta}$ under the alternative hypothesis of interests is analogous to that of p-value to the probability of type I error ${\alpha}$. Also the implementation of EVOP with a mixture experiment is discussed.

• Bulletin of the Korean Chemical Society
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• v.32 no.4
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• pp.1187-1194
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• 2011

The hydrogen abstraction reaction of $CF_3CH_2CHO$ + OH has been studied theoretically by dual-level direct dynamics method. Two stable conformers, trans- and cis-$CF_3CH_2CHO$, have been located, and there are four distinct OH hydrogen-abstraction channels from t-$CF_3CH_2CHO$ and two channels from c-$CF_3CH_2CHO$. The required potential energy surface information for the kinetic calculation was obtained at the MCG3-MPWB//M06-2X/aug-cc-pVDZ level. The rate constants, which were calculated using improved canonical transitionstate theory with small-curvature tunneling correction (ICVT/SCT) were fitted by a four-parameter Arrhenius equation. It is shown that the reaction proceeds predominantly via the H-abstraction from the -CHO group over the temperature range 200-2000 K. The calculated rate constants were in good agreement with the experimental data between 263 and 358 K.

• Journal of Energy Engineering
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• v.24 no.3
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• pp.135-141
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• 2015

The core melts stratifies into lower mixture layer and upper metal layer by density in a severe accident condition. The decay heat generated from the mixture layer threatens the integrity of the reactor vessel. This study simulated the natural convection heat transfer of the mixture layer with volumetric heat source using the mass transfer system. $H_2SO_4-CuSO_4$ electroplating system was used as the mass transfer system. With the modified Rayleigh number of $3{\times}10^{14}$, the Nusselt number showed minimum at the bottom and increased along curvature to the top of the experimental apparatus.