• Special Issue of the Society of Naval Architects of Korea
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• 2008.09a
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• pp.106-111
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• 2008

A hull form is 181K DWT Bulk Carrier, of which new design and hull form have been developed using CFD tools and model tests. The basic concept design of hull form has been carried out with considering the factors, which are a lot of influence of the wave and viscosity resistance. The considered factors of particular are LCB, DLWL shape, tern and stem profile, Cp-curve shape, etc. Numerical calculations are carried out in the initial design stage and experimental model tests are also carried out in towing tank of MOERI. The variation of the significantly effective characteristics is carried out to achieve optimized hull form. The results from numerical calculations and model test as well as the design procedures to obtain an optimized hull form resent in this paper.

• Geomechanics and Engineering
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• v.9 no.3
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• pp.313-328
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• 2015

In the present study, a CPT-based p-y analysis method was proposed for offshore mono-piles embedded in sands. Static and cyclic loading conditions were both taken into account for the proposed method. The continuous soil profiling capability of CPT was an important consideration for the proposed method, where detailed soil profile condition with depth can be readily incorporated into the analysis. The hyperbolic function was adopted to describe the non-linear p-y curves. For the proposed hyperbolic p-y relationship, the ultimate lateral soil resistance $p_u$ was given as a function of the cone resistance, which is directly introduced into the analysis as an input data. For cyclic loading condition, two different cyclic modification factors were considered and compared. Case examples were selected to check the validity of the proposed CPT-based method. Calculated lateral displacements and bending moments from the proposed method were in good agreement with measured results for lateral displacement and bending moment profiles. It was observed the accuracy of calculated results for the conventional approach was largely dependent on the selection of friction angle that is to be adopted into the analysis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.3
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• pp.225-230
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• 2006

The overall performance and local flow fields of the fan, heat sink, and fan-sink were experimentally and numerically studied to investigate the flow characteristics of a fan-sink. The flow resistance of the heat sink was measured by small fan tester based on AMCA standards and compared with the CFD results to select available cooling fan for the fan-sink. The nonuniform velocity profile behind the fan outlet was shown by the flow visualization. The effects of nonuniform velocities on the performance of heat sink were discussed. To validate the commercial CFD code CFX-5.6, the predicted performance curve was compared with that of fan testing. The local flow fields of the fan-sink were analyzed by CFD results. MFR (multiple frame of reference) was used as a computational model combining rotating fan and stationary heat sink. Through the CFD results of the fan-sink, the flow patterns behind the fan outlet influenced the flow resistance and overall performance of the heat sink.

• Korean Journal of Food Science and Technology
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• v.17 no.5
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• pp.345-349
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• 1985

The textural properties of acorn flour gels were investigated with the variations in the concentraction, storage time and storage temperature by the use of Instron Universal Testing Machine. The experimental design was $3^3$ factorial experiment. TPA curves of acorn flour gels showed two sharp peaks in the first bite and no negative peak. The hardness and brittleness of acorn flour gels were very significantly affected by concentration, storage time and storage temperature. For the height difference between first peak and second peals, the main effects for concentration and storage temperature were very significant and the main effect for storage time was not negligible. For bend, the effect of concentration was more significant than the effect of storage temperature, and storage time effect was negligible. Springiness was affected only by the concentration.

• The Korean Journal of Physiology and Pharmacology
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• v.8 no.1
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• pp.65-67
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• 2004

Dehydroevodiamine (DHED) is one of the bioactive components of the Chinese herbal medicine Wu-chu-yu-tang that has been shown to produce various pharmacological effects. In the present study, we investigated the pharmacokinetics of DHED after intravenous administration of two doses (2.5 and 5 mg/kg) in anesthetized rats. The plasma concentration of DHED was measured by reverse-phase high-performance liquid chromatography with UV detection. The mean area under the curve of the time-concentration profile was $21.9\;and\;53.9\;{\mu}g{\cdot}min/ml$ after the 2.5- and 5-mg/kg doses, respectively, and the volume of distribution was 1584.9 and 1580.6 ml following 2.5- and 5-mg/kg doses, respectively. Plasma concentration profiles versus time were compatible with a two-compartment model and first-order kinetics. The terminal elimination half-life was $91.8{\pm}16.6\;min$ and $78.7{\pm}11.9\;min$ in the dose of 2.5 and 5 mg/kg, respectively. This is the first report to study the pharmacokinetics of DHED in animals.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.8
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• pp.113-119
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• 2000

There are two major factors which affect the cam design : the pressure angle and the radius of curvature, Cam shape will have an instantaneous radius of curvature at every point. Even though the design constraint of the pressure angle has been satisfied the follower may still not complete the desired contact motion. If the radius of the follower roller is larger than the concave(negative) radius on the cam it occurs the gap between the cam and the follower roller at the contact point. And also if the curvature of the pitch curve of the cam is too sharp the cam profile may be undercut. This paper proposes a new approach which uses the relative velocity of the follower roller parallel to the tangent line at the contact point on the cam surface for determining the pressure angle and the relative acceeration for determining the radius of curvature.

• Geomechanics and Engineering
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• v.13 no.5
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• pp.775-791
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• 2017

Surface wave techniques are widely used as non-invasive method for geotechnical site characterization. Field surface wave data are collected and analyzed using different processing techniques to generate the dispersion curves, which are further used to extract the shear wave velocity profile by inverse problem solution. Characteristics of a dispersion curve depend on the subsurface layering information of a vertically heterogeneous medium. Sometimes soft layer can be found between two stiff layers in the vertically heterogeneous media, and it can affect the wave propagation dramatically. Now most of the surface wave techniques use the fundamental mode Rayleigh wave propagation during the inversion, but this may not be the actual scenario when a soft layer is present in a vertically layered medium. This paper presents a detailed and comprehensive study using finite element method to examine the effect of soft layers which sometimes get trapped between two high velocity layers. Determination of the presence of a soft layer is quite important for proper mechanical characterization of a soil deposit. Present analysis shows that the thickness and position of the trapped soft layer highly influence the dispersion of Rayleigh waves while the higher modes also contribute in the resulting wave propagation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.213-217
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• 2008

This paper describes an application of centrifugal compressor optimization system, in which the blade profile of impeller is represented with NURBS(Non-Uniform Rational B-Spline) curve. A commercial CFD(Computational Fluid Dynamics) program named NUMECA fine/turbo was used to evaluate the performance of the whole centrifugal compressor flow passage including impeller and diffuser. The whole optimization design system was integrated based on iSIGHT, a commercial integration and optimization software, which provides a direct application of some optimization algorithms. To insure the practicability of optimization, the performance of centrifugal compressor under all condition was concerned during the optimizing process. That means a compositive object function considering the aerodynamic efficiency, pressure ratio and mass flow rate under different work condition was applied by using different weight number for different conditions. Using the optimization method described in this paper, an optimized design of the impeller blade of centrifugal compressor was obtained. Comparing to the original design, optimized design has a better performance not only under the design work condition, but also the off-design work condition including near stall and near choke condition.

• Nuclear Engineering and Technology
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• v.51 no.2
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• pp.607-617
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• 2019

Global warming and climate change are increasing the intensity of typhoons and hurricanes and thus increasing the risk effects of typhoon and hurricane hazards on nuclear power plants (NPPs). To reflect these changes, a new NPP should be designed to endure design-basis hurricane wind speeds corresponding to an exceedance frequency of $10^{-7}/yr$. However, the short typhoon and hurricane observation records and uncertainties included in the inputs for an estimation cause significant uncertainty in the estimated wind speeds for return periods of longer than 100,000 years. A logic-tree framework is introduced to handle the epistemic uncertainty when estimating wind speeds. Three key parameters of a typhoon wind field model, i.e., the central pressure difference, pressure profile parameter, and radius to maximum wind, are used for constructing logic tree branches. The wind speeds of the simulated typhoons and the probable maximum wind speeds are estimated using Monte Carlo simulations, and wind hazard curves are derived as a function of the annual exceedance probability or return period. A logic tree decreases the epistemic uncertainty included in the wind intensity models and provides reasonably acceptable wind speeds.

• Geomechanics and Engineering
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• v.24 no.4
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• pp.359-370
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• 2021

Joint roughness is combination of primary and secondary roughness. Ordinarily primary roughness is a geostatistical part of a joint surface that has a periodic nature but secondary roughness or unevenness is a statistical part of that which have a random nature. Using roughness generating algorithms is a useful method for evaluation of joint roughness. In this paper after determining geostatistical parameters of the joint profile, were presented two roughness generating algorithms using Mount-Carlo method for evaluation of primary (GJRGAP) and secondary (GJRGAS) roughness. These based on geostatistical parameters (range and sill) and statistical parameters (standard deviation of asperities height, SDH, and standard deviation of asperities angle, SDA) for generation two-dimensional joint roughness profiles. In this study different geostatistical regions were defined depending on the range and SDH. As SDH increases, the height of the generated asperities increases and asperities become sharper and at a specific range (a specific curve) relation between SDH and SDA is linear. As the range in GJRGAP becomes larger (the base of the asperities) the shape of asperities becomes flatter. The results illustrate that joint profiles have larger SDA with increase of SDH and decrease of range. Consequencely increase of SDA leads to joint roughness parameters such Z2, Z3 and RP increases. The results showed that secondary roughness or unevenness has a great influence on roughness values. In general, it can be concluded that the shape and size of asperities are appropriate parameters to approach the field scale from the laboratory scale.