• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.2
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• pp.467-474
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• 2017

Each river confluence has the inherent hydraulic and mixing characteristics coming from its bathymetry and topography. It is necessary to make the measurement covering the spatial extent of studying area in order to catch these 2-dimensional intrinsic characteristics. This study focuses to investigate the hydraulic and mixing characteristics at the confluence of Nakdong and Geumho River, from field measurement of flow, water quality, and suspended particle distribution with ADCP (Riversurveyor M9), multi-parameter water quality sonde (YSI6600V2), and submersible system for in-situ observations of particle size distribution and volume concentration (LISST : Laser In-Situ Scattering & Transmissometry), respectively. From the results, it can be found that the field measurement of suspended particle and water quality distribution can be the useful approach to catch the hydraulic and mixing characteristics at a river confluence.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.1
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• pp.11-19
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• 2015

We present the results of a multi-material numerical investigation of the propagation of a combustible gas mixture detonation in narrow metal tubes. We use an experimentally tuned one step Arrhenius chemical reaction and ideal gas equation of state (EOS) to describe stoichiometric $H_2-O_2$ and $C_2H_4-O_2$ detonations. The purely plastic deformations of copper and steel tubes are modeled using the Mie-Gruneisen EOS and Johnson-Cook strength model. To precisely track the interface motion between the detonating gas and the deforming wall, we use the hybrid particle level-sets within the ghost fluid framework. The calculated results are validated against the experimental data because the results explain the process of the generation and subsequent interaction of the expansion wave with the high-strain-rate deformation of the walls.

• Journal of Korean Society of Steel Construction
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• v.20 no.3
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• pp.409-419
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• 2008

A co-rotational quasi-conforming formulation of four- node stress resultant shell elements using Ivanov-Ilyushin yield criteria are presented for the nonlinear analysis of plate and shell structure. The formulation of the geometrical stiffness is defined by the full definition of the Green strain tensor and it is efficient for analyzing stability problems of moderately thick plates and shells as it incorporates the bending moment and transverse shear resultant force. As a result of the explicit integration of the tangent stiffness matrix, this formulation is computationally very efficient in incremental nonlinear analysis. This formulation also integrates the elasto-plastic material behaviour using Ivanov Ilyushin yield condition with isotropic strain hardening and its asocia ted flow rules. The Ivanov Ilyushin plasticity, which avoids multi-layer integration, is computationally efficient in large-scale modeling of elasto-plastic shell structures. The numerical examples herein illustrate a satisfactory concordance with test ed and published references.

• Tribology and Lubricants
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• v.33 no.1
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• pp.23-30
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• 2017

The electric controlled marine diesel engine has fuel pump generating the high pressurized fuel for fuel injection to combustion chamber via a common rail. Fuel pump consists of a cam-roller system. Journal bearing installed between a roller and a cam-roller pin is subjected to fluctuating heavy and instant loads by cam lift. First, Kinematic analysis is carried out to predict bearing loads during one cycle acting on the journal bearing. Second, flexible multi-body dynamic analysis and transient elasto-hydrodynamic(EHD) lubrication analysis for journal bearing considering elastic deformation of cam-roller pin, roller and bearing are conducted using AVL EXCITE/PU software to predict lubrication performance. The clearance ratio and journal groove shape providing lubrication oil are important parameter in bearing design having good performance and can be changed easier than other design parameters such as diameter, width, oil supply pressure and bearing material grade. Generally, journal bearing performance is represented by the minimum oil film thickness(MOFT) and peak oil film pressure(POFP). As well as the traditional design parameters(MOFT, POFP), in this study, temperature rise of lubrication oil is also evaluated through the side leakage flow of supplied oil. By the evaluating MOFT, POFP and temperature rise, the optimum bearing clearance ratio is decided.

• Transactions of Materials Processing
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• v.29 no.5
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• pp.257-264
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• 2020

This paper is concerned with the influence of the plastic property of the rivet on the numerical prediction of the Self-Piercing Rivet (SPR) Joining. In order to predict the plastic property of the rivet, a ring compression specimen was directly fabricated from the rivet used for the mechanical joining of dissimilar materials, and the FE analysis together with the ring compression test was iteratively carried out by changing the plastic property of the rivet. For reliable FE analysis, a friction coefficient was estimated based on a friction calibration curve, measuring the reductions in inner diameter and height of the ring specimen after the compression test. From each simulation result, the force-displacement curves were then compared from each other so as to obtain the rivet plastic property that shows good agreement with the experimental result. The SPR joining between GA590 1.0t and Al5052 2.0t was conducted, and the numerical prediction was performed with the use of the plastic property evaluated based on the inverse analysis and the one referred from Mori et al. [11]. Comparison of the experiment and the numerical predictions in terms of the interlock and bottom thickness revealed that the reliable evaluation of the plastic property of the rivet is necessary for the trustworthy numerical prediction of the SPR joining.

• Applied Chemistry for Engineering
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• v.18 no.5
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• pp.506-510
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• 2007

Vacuum deposited 4,4',4''-tris(N-(1-naphthyl)-N-phenylamino)-triphenylamine (1-TNATA), a widely-used semiconductor material, is placed as a thin interlayer between indium tin oxide (ITO) electrode and a hole transporting layer (HTL) in OLEDs and a well-stacked 1-TNATA layer leads to stable and high efficiency devices by reducing the carrier injection barrier at the interface between the ITO anode and hole transport layers. According to Raman spectra, thermal annealing after deposition as well as electromagnetic field treatment during deposition lead to closer stacking of 1-TNATA molecules and resulted in molecular ordering. By thermal annealing at about $110^{\circ}C$, an increase in current flow through the film by over 25% was observed. Molecularly-ordered 1-TNATA films played an important role in achieving higher luminance efficiency as well as higher power efficiency of the multi-layered organic EL devices in the present work. Electromagnetic field treatment during deposition was less effective compared to thermal annealing

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.157-163
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• 2018

This study is aimed at controlling the fiber orientation and improve the fiber distribution in fiber-reinforced cement composites using blades that can be placed inside the existing nozzles. To optimize the blade parameters, multi-physics finite element analysis was performed that could account for the flow of the cementitious matrix material, the movement of the entrained fibers, and the interactions with the nozzle. As a result, this study defined the blade distance, length, and position as a function of the fiber length to be used in the field. The blades with a distance from 1.2 to 2.4 times the fiber length and length from 4 to 8 times the fiber length, as well as located at below 14 times the fzfiber length from the nozzle exit maintained the fiber orientation angle less than $5^{\circ}$. In addition, the blade-type nozzle proposed in the study can be attachable and detachable to the conventional casting equipment, and thus it can provide the usability and convenience in practical applications.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.9
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• pp.799-804
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• 2016

Broadband powerline communication (BPLC) uses distribution lines as a medium for achieving effective bidirectional data communication along with electric current flow. As the material characteristics of power lines are not good at the communication channel, the development of power line communication (PLC) systems for internet, voice, and data services requires measurement-based models of the transfer characteristics of the network suitable for performance analysis by simulation. In this paper, an analytic model describing a complex transfer function is presented to obtain the attenuation and path parameters for a multipath power line model. The calculated results demonstrated frequency-selective fading in multipath channels and signal attenuation with frequency, and were in good agreement with the experimental results. Inductive coupling units are used as couplers for coupling the signal to the power line to avoid physical connections to the distribution line. The inductance of the ferrite core, which depends on the frequency, determines the cut-off frequency of the inductive coupler. Coupling loss can be minimized by increasing the number of windings around the coupler. Coupling efficiency was improved by more than 6 dB with three windings compared to the results obtained with one winding.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.2
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• pp.238-244
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• 2003

With the purpose of evaluating the effect of ailing amount of pit and assure sealants on the microleakage, 6 groups of specimens with different filling amount, filling materials and surface pretreatment were investigated. Sixty permanent third molars were divided into three groups. The occlusal surface of each tooth was divided into two parts; the filing width of one part was below 1mm (group1, 3, 5), and in the other part more than 2mm (group 2, 4, 6) Group 1 and 2: Helioseal F was applied directly to etched enamel; Group 3 and 4: Helioseal F was applied to etched and scotchbond Multi-purpose plus pre-treated enamel; Group 5 and 6: Tetric Flow was applied. After 500 times thermocycling and dye infiltration, we evaulated the microleakage. The results were as follows; 1. The mean microleakage score at each width were increased in the following order;group 5<3<1, and group 6<4<2. 2. In comparing the groups with same material and surface pretreatment but with different filling width (group 1 versus 2, 3 versus 4, 5 versus 6), the microleakage scores were significantly different. 3 The microleage was affected by filling amount of pit and assure sealants than Oiling materials and dentin bonding agent pretreatment.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.518-529
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• 2022

In Task C of the DECOVALEX-2023 project, nine institutes from six nations are developing their numerical codes to simulate thermo-hydro-mechanical coupled behavior for the FE experiment performed at Mont Terri underground rock laboratory, Switzerland. Currently, Step 1 for comparing the simulation results to field data is the ongoing stage, and we used the OGS-FLAC simulator for a series of numerical simulations. As a result, temperature increase depending on the heating hysteresis was well simulated, and saturation variation in the bentonite depending on phase change was observed. However, due to the suction overestimation, relative humidity and temperature change in the bentonite and the pressure variation in the Opalinus clay showed a difference compared to the field data. From the observation, it is confirmed that the effect of the bentonite capillary pressure is dominant to the flow analysis in the disposal system. We further plan to draw improved results considering tunnel support material and accurate initial water pressure distribution. Additionally, the thermal, hydrological, and mechanical anisotropy of the Opalinus clay was well simulated. From the simulation results, we confirmed the applicability of the OGS-FLAC simulator in the disposal system analysis.