• Journal of Korean Society of Transportation
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• v.21 no.3
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• pp.59-69
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• 2003

Signalized intersections are widely used in urban street network. However, it was reported that a roundabout is better than a signalized intersection in terms of delay when the approaching traffic volume for each bound is low. The objective of this study is to develop entry capacity models of roundabout and establish the warrant for signalized intersection based on the delay. The entry capacity of a roundabout is determined by the circulating traffic volume and the geometric design of the roundabout such as the diameter of central island, entry lane widths, and the circulating roadway width. The traffic and geometric characteristics of four roundabouts were collected and analyzed. The study reveals that; i)among the geometric features, the diameter of central island and the circulating roadway width influence the entry capacity, and ii)even though it is difficult to compare the models of each country due to different geometric features considered in the models, the models developed in this study show higher capacity than the models from Israel or Germany. These seem to be attributed to the facts that; i)the outside diameters of the roundabouts selected in this study are larger than in the other studies, and ii)the acceptable gap in Korea is smaller than that in the other countries. In order to compare the performances of round- about and signalized intersection, the performance of roundabouts was evaluated with the SIDRA. The simulation was conducted only for the roundabouts composed of single lane. According to the result of the analysis, it may be concluded that when the approaching traffic volume for each bound is lower than 600pcph, a roundabout is better than a signalized intersection in terms of its operational performance.

• Journal of Korean Society on Water Environment
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• v.23 no.4
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• pp.474-481
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• 2007

With population growth, industrialization, and urbanization within the watershed, the hydrologic response changed dramatically, resulting in increases in peak flow with lesser time to peak and total runoff with shortened time of concentration. Infiltration is directly affected by initial soil moisture condition, which is a key element to determine runoff. Influence of the initial soil moisture condition on hydrograph analysis should be evaluated to assess land use change impacts on runoff and non-point source pollution characteristics. The Long-Term Hydrologic Impact Assessment (L-THIA) model has been widely used for the estimation of the direct runoff worldwide. The L-THIA model was applied to the Little Eagle Creek (LEC) watershed and Its estimated direct runoff values were compared with the BFLOW filtered direct runoff values by other researchers. The $R^2$ value Was 0.68 and the Nash-Sutcliffe coefficient value was 0.64. Also, the L-THIA estimates were compared with those separated using optimized $BFI_{max}$ value for the Eckhardt filter. The $R^2$ value and the Nash-Sutcliffe coefficient value were 0.66 and 0.63, respectively. Although these higher statistics could indicate that the L-THIA model is good in estimating the direct runoff reasonably well, the Antecedent Moisture Condition (AMC) was not adjusted in that study, which might be responsible for mismatches in peak flow between the L-THIA estimated and the measured peak values. In this study, the L-THIA model was run with AMC adjustment for direct runoff estimation. The $R^2$ value was 0.80 and the Nash-Sutcliffe coefficient value was 0.78 for the comparison of L-THIA simulated direct runoff with the filtered direct runoff. However there was 42.44% differences in the L-THIA estimated direct runoff and filtered direct runoff. This can be explained in that about 80% of the simulation period is classified as 'AMC I' condition, which caused lower CN values and lower direct runoff estimation. Thus, the coefficients of the equation to adjust CN II to CN I and CN III depending on AMC condition were modified to minimize adjustments impacts on runoff estimation. The $R^2$ and the Nash-Sutcliffe coefficient values increase, 0.80 and 0.80 respectively. The difference in the estimated and filtered direct runoff decreased from 42.44% to 7.99%. The results obtained in this study indicate the AMC needs to be considered for accurate direct runoff estimation using the L-THIA model. Also, more researches are needed for realistic adjustment of the AMC in the L-THIA model.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.7
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• pp.645-653
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• 2013

Seoul National University flap(SNUF) blade is a small-scale rotor blade incorporating a small trailing-edge flap control surface driven by piezoelectric actuators at higher harmonics for vibration attenuation. Initially, the blade was designed using two-dimensional cross-section analysis and geometrically exact one-dimensional beam analysis, and its material configuration was finalized. A flap-deflection angle of ${\pm}4^{\circ}$ was established as the criterion for enhanced vibration reduction based on an earlier simulation. The flap-linkage mechanism was designed and static bench tests were conducted for verifying the performance of the flap-actuation mechanism. Different versions of test beds were developed and tested with the designed flap and the selected APA 200M piezoelectric actuators. Through significant improvements, a maximum deflection of ${\pm}3.7^{\circ}$ was achieved. High-frequency experiments were conducted for evaluating the performance, and the transfer function of the test bed was determined experimentally. With the static tests almost complete, the rotor power required for testing the blade in a whirl tower (centrifugal environment) was calculated, and further preparations are underway.

• Korean Journal of Organic Agriculture
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• v.26 no.1
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• pp.57-72
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• 2018

Organic agriculture seeks sustainable agriculture. Organic agriculture is based on circulating agriculture of a family farm unit. However, as of the end of 2016, only 33 out of the total organic farming farms were implementing Crop-Livestock cycling organic farming. The reason seems to be a matter of income after all. The optimal size combination refers to the scale by which family farms can maintain their quality of life while engaging in farming activities. In other words. it is a farm scale that maintains optimal income through stable labor costs. In the meantime, there has been no previous study on the optimal economical combination of Crop-Livestock cycling farming. Choi (2016) analyzed whether the economies of scope (EOS) were realized in the combined production by using the management data of the farmers who practiced Crop-Livestock cycling organic farming for four years. As a result, it has been revealed that the EOS measurement value is 0 or more so the economies of scope are being realized. Therefore, the purpose of this empirical analysis is to identify farm incomes under this circumstance. It is assumed that the optimum production is achieved by balancing the total income curve and the total cost curve in the optimal scale production range. The results of the analysis are as follows. First, the income after the conversion to Crop-Livestock cycling farming was 44,789,280 won, the sum of the seedling-livestock sector, which was 17,873,120 won higher when the non-Crop-Livestock cycling farming was assumed. The same is true for 2014 and 2015. The reason for this is that pig droppings were composted from organic seedlings, and the cost of selling pork was 150,000 won/per pig more expensive even though the manufacturing cost of organic feeds was higher than the purchasing cost. Secondly, this study simulated the result that the economic index varies when the farm size combination is changed by the farm size of 100% standard (S100) as of 2014. S130 is the increase in size from 100% of 2014, whereas S30 is the result of 3ha crop and 66 livestock (pigs). As a result of this simulation, Crop-Livestock cycling farming income decreased more than non-Crop-Livestock cycling farming as the farm size decreased, whereas the income decreased as the farm size increased. When the size was reduced below S50, the income tended to decrease. In this situation, EOS changed in the same direction. The results showed that when the farming size was reorganized and reduced to 50% compared to 2014, the income and income difference was the highest. At the same time, economies of scope (EOS) were the highest at 0.12985. In other words, it was found that the income of farm houses in a family farm unit sector was the best in the combination of 1.5ha crop agriculture and 110 livestock (pigs).

• Journal of Internet Computing and Services
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• v.17 no.6
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• pp.33-39
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• 2016

With recent advances in sensor technology, CMOS-based semiconductor devices and networking protocol, the areas for application of wireless sensor networks greatly expanded and diversified. Such diversification of uses for wireless sensor networks creates a multitude of beneficial possibilities for several industries. In the application of wireless sensor networks for monitoring systems' data transmission process from the sensor node to the sink node, transmission through multi-hop paths have been used. Also mobile sink techniques have been applied. However, high energy costs, unbalanced energy consumption of nodes and time gaps between the measured data values and the actual value have created a need for advancement. Therefore, this thesis proposes a new model which alleviates these problems. To reduce the communication costs due to frequent data exchange, a State Prediction Model has been developed to predict the situation of the peripheral node using a geographic autocorrelation of sensor nodes constituting the wireless sensor networks. Also, a Risk Analysis Model has developed to quickly alert the monitoring system of any fatal abnormalities when they occur. Simulation results have shown, in the case of applying the State Prediction Model, errors were smaller than otherwise. When the Risk Analysis Model is applied, the data transfer latency was reduced. The results of this study are expected to be utilized in any efficient communication method for wireless sensor network monitoring systems where all nodes are able to identify their geographic location.

• Fire Science and Engineering
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• v.18 no.1
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• pp.24-30
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• 2004

In this work the dynamic heat transfer occurring in a 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 sealants. Here was carried out an experiment to observe the heat transfer in the cable penetration fire stop system made of DOW CORNING products. The dynamic heat transfer occurring in the fire stop system is formulated in a parabolic partial differential equation subjected to a set of initial and boundary conditions. And it was modeled, simulated, and analyzed. The simulation results were illustrated in three-dimensional graphics and were compared with experimental data. Through the simulations, it was shown clearly that the temperature distribution was influenced very much by the number, position, and temperature of the cable streams. It also was found that the dynamic heat transfer through the cable streams was one of the most dominant factors, and the feature of heat conduction could be understood as an unsteady-state process. It is certain that these numerical results are useful for making a performance-based design for the cable penetration fire stop system.

• Journal of Biomedical Engineering Research
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• v.24 no.6 s.81
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• pp.533-541
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• 2003

In the paper. the health card system to integrate several cards into one card for protecting patient's privacy and security problems is proposed. Firstly, it is defined the minimal data set for integrating several patient cards into one card using IC card, and developed the issuing system to issue the integrated patient IC card. In order to secure and certificate a patient's personal information. the integrated patient IC card has applied 3-DES and the PKI certificate authority based Windows 2000 is established. The receipt and reservation system for taking care of a healthcare has developed to cooperate with the existing hospital computer system. The integrating patient IC card system proposed in this paper is implemented to 11 hospitals and used for 1.000 patients. On the result of the simulation. the proposed system can receive or reserve for a patient to take care of healthcare in the simulated hospitals and also establish the basis of the mechanism to share a medical information.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.696-701
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• 2016

Multi-stage deep drawing is a widely used industrial manufacturing process, and its applications are gradually expanding to both small products and large metallic products. The USB C-type socket used in smart phones, for example, is manufactured using oval multi-stage deep drawing. The socket is very small and slender and it requires precise manufacturing. The thickness distribution of the final product is guaranteed only if it is uniform throughout the overall process. Therefore, minimizing the height difference between long and short sidewalls after the first operation is important for this goal. An initial blank optimization was performed for an oval-type drawing process based on finite element simulations. The goal was to determine an initial blank geometry that can maintain uniform height and thickness after the first draw operation. The initial blank shape of the sheet metal was optimized, and the results show that it satisfied the conditions of minimal thickness reduction and even thickness distribution. The geometry from the optimized simulation was compared with experimental results, which showed good agreement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.724-731
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• 2016

As the structural damage caused by earthquakes has been gradually increasing, estimating the seismic fragility of structures has become essential for earthquake preparation. Seismic fragility curves are widely used as a probabilistic indicator of structural safety against earthquakes, and many researchers have made efforts to develop them in a more accurate and effective manner. However, most of the previous research studies used simplified 2D analytical models when deriving fragility curves, mainly to reduce the numerical simulation time; however, in many cases 2D models are inadequate to accurately evaluate the seismic behavior of a structure and its seismic vulnerability. Thus, this study provides a way to derive more accurate, but still effective, seismic fragility curves by using 3D analytical models. In this method, the reliability analysis software, FERUM, is integrated with the structural analysis software, ZEUS-NL, enabling the automatic exchange of data between these two software packages, and the first order reliability method (FORM), which is not a sampling-based method, is utilized to calculate the structural failure probabilities. These tools make it possible to conduct structural reliability analyses effectively even with 3D models. By using the proposed method, this study conducted a seismic vulnerability assessment of RC frame structures with their 3D analytical models.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.39-45
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• 2016

This study analyses the macroeconomic effects of the direct payment system (DPS) for environment-friendly agriculture in Korea. We utilized the applied general equilibrium model (AGE model) for the general agricultural sector as well as the environmentally-friendly agricultural sector. We considered several scenarios based on various direct payment amounts to measure and analyze economic impacts. Scenario 1 considers the current direct payment system. Scenario 2 examines an additional 5% increase from the direct payment amount in scenario 1. Scenario 3 reviews an increase of 10% in direct payment amount while Scenario 4 considers an additional increase of 15% compared with Scenario 1. Lastly, scenario 5 examines a 20% increase in direct payment amounts compared with scenario 1. In addition, the baseline considers conditions prior to the introduction of the direct payment system. The simulation analysis results show that capital formation, production volume, and labor productivity increased in the environment-friendly agricultural sector. In contrast, employment in the environment-friendly agricultural sector decreased. The price of environment-friendly agricultural products following the introduction of the DPS remain consistent with the price of environment-friendly agricultural product before introducing the DPS. This results from price elasticity of supply and demand are inelastic, and there is no change in the income of consumers during the analysis period. However, additional research is necessary for improvement of the model using complementary statistical data for the environmental-friendly agriculture sector.