• Elastomers and Composites
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• v.44 no.4
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• pp.373-377
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• 2009

Most of the plastics products are being manufactured by injection molding. Warpage in injection molded affects the product dimension and it causes assembling problem. In this study, warpages in the injection molded part been studied. Specimens are rectangular flat shapes with and without ribs. Amorphous polymers (PC and ABS) and crystalline polymers (PP and PA66) were used for material. Flat shape with ribs showed higher warpage than flat shape without ribs by 6 to 9%. The specimens with ribs that are located parallel to the flow direction has higher warpage than specimens with ribs that are located perpendicular to the flow direction by 25 to 39%. Crystalline polymers have higher warpage than amorphous polymers by 23 to 67%. Warpage decreases as packing time increases and it increases as injection temperature increases.

• Journal of Korean Society on Water Environment
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• v.34 no.4
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• pp.399-408
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• 2018

This research investigated the effects of weir (Ipobo) construction on the dynamics and the related spatial distributions of pollutants inflowing from tributaries (Yanghwacheon and Bokhacheon). Conductivity measurements and water sampling were conducted longitudinally, horizontally, and vertically in the waterbody upstream of the area located in Ipobo. Additionally, collected water samples were used for the dissolved organic carbon (DOC) analysis and fluorescence analysis which results in the SUVA, HIX, BIX, and FI calculation and parallel factor analysis (PARAFAC). Consequently, the results of the Conductivity, DOC, SUVA, and HIX showed that high concentration of pollutants that were flowing from the area of Bokhacheon which was mixed along the flow of the main river. The results of the BIX and FI did not show significant difference along the river flow which represented that allochthonous and terrestrial DOM, and for this reason was dominated in the whole waterbody rather than just the autochthonous DOM. The PARAFAC results showed that the two fluorescence components, humic-like and protein-like, constituted the fluorescence matrices of the water samples. The prevailing discipline notes that the two components were inflowing from the tributaries, however, a refractory component, humic-like substances, was relatively accumulated near the weir. From the results, the dynamics and spatial distributions of the DOM are dependent on the DOM characteristics, which induces the application of a specialized DOM analysis method to investigate the effects of a subsequent weir construction on the dynamics and spatial distributions of pollutants inflowing from the tributaries.

• Journal of Biomedical Engineering Research
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• v.19 no.2
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• pp.143-152
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• 1998

In this paper, we present the performances of a Doppler system using single channel RF(Radio Frequency) sampling. This technique consists of undersampling the ultrasonic blood backscattered RF signal on a single channel. Conventional undersampling method in Doppler imaging system have to use a minimum of two identical parallel demodulation channels to reconstruct the multigate analytic Doppler signal. However, this system suffers from hardware complexity and problem of unbalance(gain and phase) between the channels. In order to reduce these problems, we have realized a multigate pulsed Doppler system using undersampling on a single channel, It requires sampling frequency at $4f_o$(where $f_o$ is the center frequency of the transducer) and 12bits A/D converter. The proposed " single-Channel RF Sampling" method aims to decrease the required sampling frequency proportionally to $4f_o$/(2k+1). To show the influence of the factor k on the measurements, we have compared the velocity profiles obtained in vitro and in vivo for different intersequence delays time (k=0 to 10). We have used a 4MHz center frequency transducer and a Phantom Doppler system with a laminar stationary flow. The axial and volumetric velocity profiles in the vessel have been computed according to factor k and have been compared. The influence of the angle between the ultrasonic beam and the flow axis direction, and the fluid viscosity on the velocity profiles obtained for different values of k factor is presented. For experiment in vivo on the carotid, we have used a data acquisition system with a sampling frequency of 20MHz and a dynamic range of 12bits. We have compared the axial velocity profiles in systole and diastole phase obtained for single channel RF sampling factor.ng factor.

• Nuclear Engineering and Technology
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• v.51 no.7
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• pp.1738-1748
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• 2019

Previous research has shown that the inclined condition has an impact on the natural circulation (natural circulation) mode operation of Floating Nuclear Power Plant (FNPP) mounted on the movable marine platform. Due to its compact structure, small volume, strong maneuverability, the Integral Pressurized Water Reactor (IPWR) is adopted as marine reactor in general. The OTSGs of IPWR are symmetrically arranged in the annular region between the reactor vessel and core support barrel in this paper. Therefore, many parallel natural circulation loops are built between the core and the OTSGs primary side when the main pump is stopped. and the inclined condition would lead to discrepancies of the natural circulation drive head among the OTSGs in different locations. In addition, the flow rate and temperature nonuniform distribution of the core caused by inclined condition are coupled with the thermal hydraulics parameters maldistribution caused by OTSG group operating mode on low power operation. By means of the RELAP5 codes were modified by adding module calculating the effect of inclined, heaving and rolling condition, the simulation model of IPWR in inclined condition was built. Using the models developed, the influences on natural circulation operation by inclined angle and OTSG position, the transitions between forced circulation (forced circulation) and natural circulation and the effect on natural circulation operation by different OTSG grouping situations in inclined condition were analyzed. It was observed that a larger inclined angle results the temperature of the core outlet is too high and the OTSG superheat steam is insufficient in natural circulation mode operation. In general, the inclined angle is smaller unless the hull is destroyed seriously or the platform overturn in the ocean. In consequence, the results indicated that the IPWR in the movable marine platform in natural circulation mode operation is safety. Selecting an appropriate average temperature setting value or operating the uplifted OTSG group individually is able to reduce the influence on natural circulation flow of IPWR by inclined condition.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.4 no.3
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• pp.161-167
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• 1992

We consider the preparation of long finite amplitude nondispersive waves over a step bottom between two regions of finite different depths. Two dimensional motion is assumed. with the wave crests parallel to the step, and irrotational flow in the inviscid fluid is considered. To describe the transformation of finite amplitude waves we use the finite-amplitude shallow-water equations, the conditions of mass flow conservation and pressure continuity at the cut above the step in Riemann's variables. The equations define four families of curves-characteristics on which the values of the Riemann's invariants remain constant and a system of two nonlinear equations that relates the amplitudes of incident reflected and transmitted waves. The system obtained is difficult to analyze in common form. Thus we consider some special cases having practical usage for tsunami waves. The results obtained are compared with the long wave theory and significant nonlinear effects are found even for quite small amplitude waves.

• Economic and Environmental Geology
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• v.57 no.1
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• pp.41-50
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• 2024

This study reports the structural geometry and folding mechanism of a regional-scale overturned fold in the Daecheong Island, central-western part of the Korean Peninsula. Based on low-hemisphere stereographic and down-plunge projections using data from a detailed field survey, we classify the regional-scale fold as an open overturned fold shallowly plunging toward NE. The asymmetric and symmetric parasitic folds in the limb and hinge zones indicate layer-parallel shortening prior to flexural-flow folding. Fold dating must be required to decipher the orogenic process causing the regional-scale overturned fold in the Daecheong Island.

• Journal of Venture Innovation
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• v.5 no.1
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• pp.59-73
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• 2022

Untact marketing is being activated due to COVID-19. As a result, live commerce, an untact seller, is also active in the e-commerce market. Therefore, in this study, we tried to find out what factors influence consumers when they purchase through live commerce. In particular, since consumers' trust and flow in live commerce platforms and products is important, their mediating effects were analyzed. The research model was established by deriving common variables among the characteristics of live commerce based on previous studies. An online survey was conducted for empirical analysis. 200 users who made at least one purchase in live commerce were analyzed. The study results are as follows. Among the characteristics of live commerce, entertainment, economics, professionality were found to have a positive (+) effect on purchase intention. On the other hand, ease of use did not significantly affect purchase intention. The influence was shown in the order of entertainment, professionality and economics. The mediating effect of trust was found to play a mediating role in that entertainment, economics, and professionality affect purchase intention. On the other hand, a significant mediating effect was not tested between ease of use and purchase intention. As for the mediating effect of flow, it was found that flow plays a mediating role in that entertainment and economics affect purchase intention. On the other hand, the mediating effect of flow in terms of ease of use and economics affecting purchase intention was not tested. As for the multiple mediating effect of flow and trust, the mediating effect of flow was stronger than the mediating effect of trust when entertainment had an effect on purchase intention. In terms of professionality affecting purchase intention, the mediating effect of flow was also stronger than the mediating effect of trust. On the other hand, it was analyzed that only trust had a mediating effect when economics had an effect on purchase intention. The results of this study empirically tested that entertainment, which is a fun and interesting factor of live commerce content, is the most important factor when consumers use live commerce. In addition, various results were derived, such as cases where trust and flow act as mediators at the same time or not at all. Practical implications can be found in that it provided a clue about what to prioritize in order to reach consumers for live commerce platform.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6D
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• pp.785-791
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• 2011

Two-lane and two-way traffic flow shows various dynamic relationships according to the behaviors of low-speed vehicle and overtaking. And it is essential to develop a vehicle model which simultaneously explains the behaviors of low-speed vehicle and overtaking using opposite lane in order to microscopically analyze various two-lane and two-way traffic flows by traffic flow simulation. In Korea, some studies for car-following and lane-changing models for freeway or signalized road have been reported, but few researches for the development of vehicle model for two-lane and two-way highway have been done. Hence, a microscopic two-lane and two-way vehicle model was, in this study, developed with the consideration of overtaking process and is based on CA (Cellular Automata) which is one of discrete time-space models. The developed model is parallel combined with an adjusted CA car-following model and an overtaking model. The results of experimental simulation showed that the car-following model explained the various macroscopic relationships of traffic flow and overtaking model reasonably generated the various behaviors of macroscopic traffic flows under the conditions of both opposite traffic flow and stochastic parameter to consider overtaking. The vehicle model presented in this study is expected to be used for the simulation of more various two-lane, two-way traffic flows.

• Journal of Soil and Groundwater Environment
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• v.6 no.2
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• pp.69-81
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• 2001

The constitutive relation among capillary pressure, saturation and relative permeability should be predetermined in order to simulate immiscible water-gas flow in porous media. The relation between saturation and relative permeability becomes more important when the capillary force can be disregarded and viscous friction force governs the flow. In this study, a 2-dimensional finite difference numerical model was developed, in which the variation of viscosity with pressure and that of relative permeability with water saturation can be treated. Seven cases of parallel plate tests were performed in order to obtain the characteristic equation of relative permeability which would be used in. the developed numerical model. It was not possible, however, to match the curves of relative permeability from the plate tests with the existing emperical models. Consequently a logistic equation was proposed as a new emperical model. As this model was composed of the parameter involving aperture size, any aperture size of fracture can be applied to the model. For the purpose of verification, the characteristic equation of relative permeability was applied to the developed numerical model and the computed results were compared with those of plate test. As a result of application of numerical model, in order to check the field applicability, to single fracture surrounding an underground storage cavern, the simultaneous flow of water and propane gas was able to be simulated properly by the model.

• Ocean and Polar Research
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• v.26 no.2
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• pp.273-286
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• 2004

The effects of environmental forcing on autotrophic picoplankton distributional patterns were investigated for convergence ($5^{\circ}N$), divergence ($9^{\circ}N-10^{\circ}30'N$) and oligotrophic ($17^{\circ}N$) sites in the tropical eastern Pacific during 2001 and 2003 KODOS (Korea Deep Ocean Study) cruises. The distributions of picoplankton populations - Prochlorococcus, Synechococcus and picoeukaryotes algae - were determined by flow cytometric analyses. Latitudinal variations in abundance maxima, vertical profiles, integrated abundance (0-150 m), and estimated carbon biomass were contrasted for each site according to three hydrological conditions. Prochlorococcus showed consistently high abundance in the surface mixed layers of all sites at $1\;{\times}\;10^5{\sim}3\;{\times}\;10^5\;cells\;ml^{-1}$ and showed declining abundance below these layers. However, these decreasing rates were not particularly sharp showing considerably high abundance at $1\;{\times}\;10^4\;cells\;ml^{-1}$ or higher even at 100 m depth. Vertical profiles of Synechococcus and picoeukaryotes were generally parallel to each other in all sites. A clear abundance maximum was observed at divergence site at or slightly above the pycnocline depth. Higher abundance was observed at the surface mixed layer for convergence site but a sharp decrease was observed below the pycnocline. However, there was no significant abundance fluctuation with depth at more oligotrophic site ($17^{\circ}N$). Integrated cell abundance of Prochlorococcus was high in the oligotrophic site at $2.17\;{\times}\;10^{13}\;m^{-2}$, and low in the convergence site at $0.88\;{\times}\;10^{13}\;m^{-2}$. However, opposite pattern was observed for Synechococcus and picoeukaryotes where relatively high integrated cell abundance was shown in the convergence site. Estimated carbon biomass of Prochlorococcus contributed 30.4-80.3% of total autotrophic picoplankton carbon showing the highest contribution in the oligotrophic site and the lowest contribution in the convergence site. Synechococcus contribution of total autotrophic picoplantkon carbon biomass was lower than 5.8% for most of sites except the convergence site where Synechococcus contributed 23.2% of picoplankton carbon biomass. Carbon biomass of picoeukaryotes was 18.8-46.4% showing the highest carbon biomass at the convergence site. Overall, Prochlorococcus showed higher cell abundance and carbon biomass and exhibited different reaction to hydrological conditions when compare with the other two major autotrophic picoplankton groups.