• Journal of Navigation and Port Research
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• v.27 no.4
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• pp.455-463
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• 2003

Time series of suspended sediment concentration, surface elevation and velocity were measured and analysed to investigate the role of waves and the predominance of infra-gravity wave component for sediment suspension phenomena in the surf zone. For the investigation in detail, we adopted the cross spectral analysis method between suspended sediment concentration and the characteristic values of wave, and ensemble average analysis method about long-period wave component, which is dominant to sediment suspension in the measurement point. The obtained results are summarized as follows: 1)The relationship between suspended sediment concentration and the characteristic values of wave is stronger for the long-period standing wave components(about 60s and 30s where the nodal point of the first mode and the anti-nodal point of the second mode are located at the measurement point, respectively) than the long wave components(about 100s), which have the most energetic power, 2) and also, it is cleared that suspended sediment concentration is increased in the case of the phase, the velocity components of the first mode long-period standing wave(60sec) were accelerated toward on-shore direction, that is, the water surface in offshore side is higher than on-shore side.

• The Journal of Internal Korean Medicine
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• v.30 no.1
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• pp.107-118
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• 2009

Objectives : This study was aimed to investigated the effect of Yijin-tang on gastric motility and its mechanism of action in normal intact and partial pyloric obstructed rats. Methods : Gastric emptying was measured by the number of glass beads expelled from the stomach (containing one hundred of glass beads. ${\phi}1mm$) in 1 hour or 2 hours after glass beads and test drugs (normal saline. Yijin-tang 90mg/kg. Yijin-tang 270mg/kg) administration in normal intact and partial pyloric obstructed rats. In another series of experiments to evaluate the mechanism of Yijin-tang 270mg/kg under delayed conditions, normal intact rats were treated with atropine sulfate (1mg/kg,s.c.), cisplatin (10mg/kg,i.p.), quinpirole HCI (0.3mg/kg,i.p.) and NAME (NG-nitro-L-arginine methyl ester. 75mg/ kg,s.c.), respectively. Partial pyloric obstructed rats were modified by wrapping the nonabsorbable rubber ring (D :6mm, W:4mm, T: 1mm) around the 1st portion of the duodenum for 8 weeks. The myoelectrical activity of the gastric smooth muscle was recorded by a bipolar electrode placed at the abdominal surface in normal intact and partial pyloric obstructed rats. The gastric myoelectrical activity was measured for 30 minutes before and after orogastric administration of each solution (normal saline, Yijin-tang 270mg/kg) and expressed as dominant frequency, percent of normogastria and power ratio. Results : Yijin-tang improved gastric emptying more than normal saline in normal intact(p<0.001) and partial pyloric obstructed rats(p=0.002). Under the delayed gastric emptying induced by atropine sulfate, cisplatin, quinpirole HCI and NAME. Yijin-tang enhanced gastric emptying significantly in the cisplatin treated group(p<0.001). but didn't in other treated groups. Administration of Yijin-tang 270mg/kg has no significant effect on the myoelectrical activity of the gastric smooth muscle in both normal intact rats and partial pyloric obstructed rats. Conclusions : Yijin-tang seems to stimulate the gastric motility through suppressing the 5HT3 receptor and promoting the antroduodenal flow. We expect that Yijin-tang would be effective especially in dysmotility-like functional dyspepsia with partial pyloric obstruction or the side effects of cisplatin such as nausea, vomiting, abdominal discomfort, and delay of gastric emptying.

• Asia pacific journal of information systems
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• v.23 no.4
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• pp.29-51
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• 2013

In line with network technology development and smart device penetration, the social network service (SNS) has expanded its influence. The SNS which is a service based on communication and sharing among people, has grown based on users' voluntary engagement and participation and its influence has appeared beyond the cyberspace into the overall areas of domestic and foreign culture and society. In particular, SNS-based real-time communication during diverse disasters, can help prevent further damage. By sharing information on social donation activities and environmental campaigns, people have used SNS as a tool to change the society in a more positive way. Such series of activities functioning as a power to change the society have been made much faster and wider through the help of a new media called SNS. To better understand such trends, we are required to study about the SNS and its user relationships first. In this context, this study sought to identify the effects of people's desire to build friendships through SNS on the voluntary and society-friendly activities of people. This study considers online pro-social behavior and proposes online citizenship behavior. Citizenship behavior has been examined in organization context. That is, organizational citizenship behavior explains an employee's pro-social behavior in an organization context. Organizational citizenship behavior is characterized by the individual's helping others and promoting the functioning of the organization. By applying organizational citizenship behavior to an online context, we propose online citizenship behavior, an individual's pro-social behavior in an online context. An individual's pro-social behavior, i.e., online citizenship behavior, could be considered as a way for the better management of online community and society. It also needs to examine the development of online citizenship behavior. This study examined online citizenship behavior from the friendship desire. Because online society or community is characterized by online relationships between members, the friendship between members would lead to pro-social behavior, i.e., helping others and promoting the functioning of the online society, in such online context. This study further examines the antecedents of friendship desire in terms of SNS interactivity with its four factors. The findings based on the survey from real SNS users explain that the three factors of SNS interactivity (connectivity, enjoyment, and synchronicity) increases online friendship desire which then increases online citizenship behavior significantly. This study contributes to the literature by examining the key role of online friendship desire in leading to online citizenship behavior and identifying its antecedents in terms of SNS characteristics. The findings in this study also provide guidance on how to manage online society and how to promote the effective functioning of SNS.

• Journal of the Korean Institute of Gas
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• v.7 no.4 s.21
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• pp.44-52
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• 2003

In this work dynamic heat transfer in a CPFS (cable penetration fire stop) system built in the firewall of nuclear power plants is three-dimensionally investigated to develop a test-simulator that can be used to verify effectiveness of the sealant. Dynamic heat transfer in the fire stop system is formulated in a parabolic PDE (partial differential equation) subjected to a set of initial and boundary conditions. First, the PDE model is divided into two parts; one corresponding to heat transfer in the axial direction and the other corresponding to heat transfer on the vertical planes. The first PDE is converted to a series of ODEs (ordinary differential equations) at finite discrete axial points for applying the numerical method of SOR (successive over-relaxation) to the problem. The ODEs are solved by using an ODE solver In such manner, the axial heat flux can be calculated at least at the finite discrete points. After that, all the planes are separated into finite elements, where the time and spatial functions are assumed to be of orthogonal collocation state at each element. The initial condition of each finite element can be obtained from the above solution. The heat fluxes on the vertical planes are calculated by the Galerkin FEM (finite element method). The CPFS system was modeled, simulated, and analyzed here. The simulation results were illustrated in three-dimensional graphics. Through simulation, it was shown clearly that the temperature distribution was influenced very much by the number, position, and temperature of the cable stream, and that dynamic heat transfer through the cable stream was one of the most dominant factors, and that the feature of heat conduction could be understood as an unsteady-state process.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.4
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• pp.80-87
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• 2015

Memristor is a new kind of memory device whose resistance varies depending upon applied charge and whose previous resistance state is preserved even when its power is off. Ordinary memristor has a nonlinear programming characteristics about time when a constant voltage is applied. For the easiness of programming, it is desirable that resistance is programmed linearly about time. We had proposed previously a memristor bridge configuration with which weight can be programmed nicely in positive, negative or zero. In memristor bridge circuit, two memristors are connected in series with different polarity. Memristors are complementary each other and it follows that the memristance variation is linear with respect to time. In this paper, the linearization effect of weight programming of memristor bridge synapse is investigated and verified about both $TiO_2$ memristor from HP and a nonlinear memristor with a window function. Memristor bridge circuit would be helpful to conduct synaptic weight programming.

• Journal of Energy Engineering
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• v.28 no.3
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• pp.1-9
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• 2019

A major stress determining the remaining life of the tube in feedwater heater of fossil fuel power plant is hoop stress by the internal pressure. However, thermal stress due to temperature difference across the wall thickness also contributed to reduce the remaining life of the tube. Therefore, thermal loading must be considered even though the contribution of internal pressure loading to the stresses of the tube was known to be much higher than that of the thermal loading. In this study, thermal stress of the tubes in the de-superheating zone was estimated, which was generated due to the temperature difference across the tube thickness. Analytic equations were shown for determining the hoop stress and the radial stress of the tube with uniform thinning and for the temperature across the tube thickness. Accuracy and effectiveness of the analytic equations for the stresses were verified by comparing the results obtained by the analytic equations with those obtained from finite element analysis. Using finite element analysis, the stresses for eccentric thinning were also determined. The effect of heat transfer coefficient on thermal stress was investigated using series of finite element analyses with various values of heat transfer coefficient for both inner and outer surface of the tube. It was shown that the effect of heat transfer coefficient at outer surface was larger than that of heat transfer coefficient at inner surface on the thermal stress of the tube. Also, the hoop stress was larger than the radial stress for both cases of uniformly and eccentrically thinned tubes when the thermal loading was only considered without internal pressure loading.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.74-79
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• 2019

The military vehicle produces electric power through an engine-integrated serial hybrid generator that is connected to the engine and does not have a separate generator installation space. However, depending on the mechanical characteristics of the connection between the generator and the engine, iron oxide for internal rusting and lubrication grew scattered. The iron oxide is adhered to the starter to deteriorate the starting performance, and there is a problem that the noise of the leg due to wear of the gear is increased. To solve this problem, the connection spline material and the surface treatment of the engine were improved and the shape was changed to a grease sealing type to prevent the generation of iron oxide inside. As the shape of the generator connector composing the shafting system was changed, the integrity of the structure was confirmed through the torsional endurance test. In addition, through the actual vehicle load test, it was verified that no corrosion occurred during the target life span without internal corrosion. It was confirmed that the anti-scattering structure of the grease effectively suppresses the generation of iron oxide, thereby reducing the noise generated from the generator. In this paper, we propose a fundamental solution to the degradation of the starter and the noise generation by preventing the back corrosion caused by the serial hybrid generator installed between the engine and the transmission.

• Korean Journal of Cognitive Science
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• v.29 no.3
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• pp.161-192
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• 2018

Retrieving temporal information of encoded events is one of the core control processes in episodic memory. Despite much prior neuroimaging research on episodic retrieval, little is known about how large-scale connectivity patterns are involved in the retrieval of sequentially organized episodes. Task-related functional connectivity multivariate pattern analysis was used to distinguish the different sequential retrieval. In this study, participants performed temporal episodic memory tasks in which they were required to retrieve the encoded items in either the forward or backward direction. While separately parsed local networks did not yield substantial efficiency in classification performance, the large-scale patterns of interactivity across the cortical and sub-cortical brain regions implicated in both the cognitive control of memory and goal-directed cognitive processes encompassing lateral and medial prefrontal regions, inferior parietal lobules, middle temporal gyrus, and caudate yielded high discriminative power in classification of temporal retrieval processes. These findings demonstrate that mnemonic control processes across cortical and subcortical regions are recruited to re-experience temporally-linked series of memoranda in episodic memory and are mirrored in the qualitatively distinct global network patterns of functional connectivity.

• Journal of Korean Society on Water Environment
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• v.35 no.1
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• pp.64-71
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• 2019

In recent years, carbon dioxide ($CO_2$) bubbles emerged as the most widely applied material with the recycling of sequestrated storage to decrease global warming. Flotation using $CO_2$ as an alternative to air could be effective in overcoming the high power consumption in the dissolved air flotation (DAF) process. The comparison of DAF and DCF system indicated that, the carbon dioxide flotation (DCF) system with pressurized $CO_2$ only requires 1.5 ~ 2.0 atm, while the DAF system requires 3.0 ~ 6.0 atm. In a bid to understand the characteristics of particle separation, the single collector collision (SCC) model was used and a series of simulations were conducted to compare the differences of collision and flotation between $CO_2$ bubbles and air bubbles. In addition, laboratory experiments were sequentially done to verify the simulation results of the SCC model. Based on the simulation results, surfactant injection, which is known to decrease bubble size, cloud improved the collision efficiency of $CO_2$ bubbles similar to that of air bubbles. Furthermore, the results of the flotation experiments showed similar results with the simulation of the SCC model under anionic surfactant injection. The findings led us to conclude that $CO_2$ bubbles can be an alternative to air bubbles and a promising material as a collector to separate particles in the water and wastewater.

• Journal of Korea Water Resources Association
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• v.54 no.5
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• pp.301-309
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• 2021

In this study, we tried to improve the performance of the existing U-net-based deep learning rainfall prediction model, which can weaken the meaning of time series order. For this, ConvLSTM2D U-Net structure model considering temporal consistency of data was applied, and we evaluated accuracy of the ConvLSTM2D U-Net model using a RainNet model and an extrapolation-based advection model. In addition, we tried to improve the uncertainty in the model training process by performing learning not only with a single model but also with 10 ensemble models. The trained neural network rainfall prediction model was optimized to generate 10-minute advance prediction data using four consecutive data of the past 30 minutes from the present. The results of deep learning rainfall prediction models are difficult to identify schematically distinct differences, but with ConvLSTM2D U-Net, the magnitude of the prediction error is the smallest and the location of rainfall is relatively accurate. In particular, the ensemble ConvLSTM2D U-Net showed high CSI, low MAE, and a narrow error range, and predicted rainfall more accurately and stable prediction performance than other models. However, the prediction performance for a specific point was very low compared to the prediction performance for the entire area, and the deep learning rainfall prediction model also had limitations. Through this study, it was confirmed that the ConvLSTM2D U-Net neural network structure to account for the change of time could increase the prediction accuracy, but there is still a limitation of the convolution deep neural network model due to spatial smoothing in the strong rainfall region or detailed rainfall prediction.