• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.3
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• pp.93-100
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• 2021

Since the IB (Immersed Boundary) method, which can perform coupling analysis with objects and fluids having an impermeable boundary of arbitrary shape on a fixed grid system, has been developed, the IB method in various CFD models is increasing. The representative IB methods are the directing-forcing method and the ghost cell method. The directing-forcing type method numerically satisfies the boundary condition from the fluid force calculated at the boundary surface of the structure, and the ghost-cell type method is a computational method that satisfies the boundary condition through interpolation by placing a virtual cell inside the obstacle. These IB methods have a disadvantage in that the computational algorithm is complex. In this study, the simplified immersed boundary (SIB) method enables the analysis of temporary structures on a fixed grid system and is easy to expand to three proposed dimensions. The SIB method proposed in this study is based on a one-field model for immiscible two-phase fluid that assumes that the density function of each phase moves with the center of local mass. In addition, the volume-weighted average method using the density function of the solid was applied to handle moving solid structures, and the CIP method was applied to the advection calculation to prevent numerical diffusion. To examine the analysis performance of the proposed SIB method, a numerical simulation was performed on an object falling to the free water surface. The numerical analysis result reproduced the object falling to the free water surface well.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.5
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• pp.320-325
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• 2015

This paper dealt with a defect identification algorithm which is based on single partial discharge (PD) pulse analysis in gas insulated structure. Four types of electrode systems such as a needle-plane, a plane-needle, a free particle and a crack inside spacer were fabricated to simulate defects in gas insulated switchgear (GIS). We measured single PD pulse by an oscilloscope with a sampling rate of 5 GS/s and a frequency bandwidth of 1 GHz. Data aquisition and signal processing were controlled by a LabVIEW program. Physical shapes of PD pulses were compared with kurtosis, skewness and time-based parameters as rising time, falling time and pulse-width. These parameters were analysed by an algorithm with a back propagation algorithm (BPA). By applying the algorithm, the identification rate was 97% for the needle-plane electrode, 96% for the plane-needle electrode, 91% for the free particle and 93% for the crack inside spacer. The results verified that the algorithm could identify the type of defects in GIS.

• The Journal of the Korea Contents Association
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• v.20 no.4
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• pp.315-330
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• 2020

Although tariffs are falling due to the establishment of WTO and the increase of FTA agreements, Non-tariff measures such as trade remedies, trade technology barriers (TBT), sanitary quarantine (SPS) and customs regulations have become trade barriers, limiting free trade. Korea, which has achieved export-led economic growth, should present countermeasures. As Non-tariff measures are complex and are applied in different countries, Customized countermeasures by type, industry and country should be presented. To this end, non-tariff DB should be established. In order to collect, analyze, and present measures for non-tariff measures, a dedicated organization dedicated to the government is essential. And consultation among the other parties on non-tariff measures is important, and activities are important at the WTO committee. In addition, it is necessary to foster expertise and expertise in non-tariff organizations. Existing research shows non-tariff measures in each country. As existing studies have been analyzed through studies based on the non-tariff measures of each country or reports of international organizations, there are limitations in the identification of regulations and comparative analysis between countries. Therefore, this paper analyzes on the basis of non-tariff measures DB of WTO I-TIP.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.10
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• pp.798-805
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• 2018

This study introduces an adaptive design of experiment (DoE) approach for the hypersonic shock-tunnel testing. A series of experiments are conducted to model the pitch moment coefficient of a cone as the function of the angle of attack and the pitch rate. An algorithm to construct the trajectory of the test model from the images obtained by the high-speed camera is developed to effectively analyze multiple time series experimental data. An adaptive DoE procedure to determine the experimental point based on the analysis results of the past experiments using the algorithm is proposed.

• Journal of Korean Society of Transportation
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• v.18 no.4
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• pp.31-39
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• 2000

Cellular Phone use while driving is one of the critical causes of traffic accident by falling the driver into the improper lookout and inattention situations by disturbing the driving behaviors and by increasing the driver's mental workloads. These days, therefore, governments in many countries are trying to Prohibit the cellular Phone use while driving by the law focused on the hand-held type of cellular phone. This Paper investigated the impacts on the hands-free cellular Phone use while driving to the drivers Performance among normal and two different level of secondary task driving conditions in the urban of Japan. As the results, quantitative differences of drivers eye movement, subjective mental workload, steering wheel angle entropy, and cognitive Performance of secondary tasks were compared between straight and curve (right turn) section for each driving condition.

• Journal of the Korean Institute of Landscape Architecture
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• v.34 no.5 s.118
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• pp.84-99
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• 2006

The traditional temples located in national parks have various functions, such as religious practice, tourist destination, and conservation for cultural and natural resources. One functions have implicit monetary values in terms of public benefits. The purpose of this study was to estimate both use and non-use conservation values for two traditional temples, Sinheungsa and Haeinsa, using the contingent valuation method. In the study, both single-bounded and double-bounded dichotomous choice methods were used in an application of Turnbull distribution-free model. A total of 659 visitors were interviewed, 350 in Sinheungsa and 309 in Haeinsa. The mean WTP (willingness to pay) for Sinheungsa using single-bounded method was 4,040 Won for the use value, 6,157 Won for the cultural conservation value, and 5,624 Won for the natural conservation value. The mean WTP for Haeinsa using single-bounded method was 6,463 Won for the use value, 8,769 Won for the cultural conservation value, and 8,013 Won for the natural conservation value. The total economic value of each temple accounted for 50% (Sinheungsa) and 80% (Haeinsa) of the total economic value of the associated national park. It was also found that the single-bounded method was more conservative than the double-bounded method in terms of value estimation. The WTP was highest for the cultural conservation value and lowest for the use values in both temples, with natural conservation values falling in the middle, which showed that people perceived traditional temples as the cultural heritage. Based on these results, it was suggested that traditional temples should be designated as an 'multiple heritage area' so that conservation can be used as the main criteria for various use programs.

• Physical Therapy Korea
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• v.28 no.2
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• pp.123-131
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• 2021

Background: Only 2% of falls in older adults result in serious injuries (i.e., hip fracture). Therefore, it is important to differentiate injurious versus non-injurious falls, which is critical to develop effective interventions for injury prevention. Objects: The purpose of this study was to a. extract the best features of surface electromyography (sEMG) for classification of injurious falls, and b. find a best model provided by data mining techniques using the extracted features. Methods: Twenty young adults self-initiated falls and landed sideways. Falling trials were consisted of three initial fall directions (forward, sideways, or backward) and three knee positions at the time of hip impact (the impacting-side knee contacted the other knee ("knee together") or the mat ("knee on mat"), or neither the other knee nor the mat was contacted by the impacting-side knee ("free knee"). Falls involved "backward initial fall direction" or "free knee" were defined as "injurious falls" as suggested from previous studies. Nine features were extracted from sEMG signals of four hip muscles during a fall, including integral of absolute value (IAV), Wilson amplitude (WAMP), zero crossing (ZC), number of turns (NT), mean of amplitude (MA), root mean square (RMS), average amplitude change (AAC), difference absolute standard deviation value (DASDV). The decision tree and support vector machine (SVM) were used to classify the injurious falls. Results: For the initial fall direction, accuracy of the best model (SVM with a DASDV) was 48%. For the knee position, accuracy of the best model (SVM with an AAC) was 49%. Furthermore, there was no model that has sensitivity and specificity of 80% or greater. Conclusion: Our results suggest that the classification model built upon the sEMG features of the four hip muscles are not effective to classify injurious falls. Future studies should consider other data mining techniques with different muscles.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.11
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• pp.1035-1042
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• 2005

In the present study, the principle of minimum energy is employed to configure the shape of rivulet flowing down an inclined surface. The profile of laminar rivulet is determined by numerical integration. The maximum center thickness, which corresponds to the minimum thickness of falling film, is found to exist regardless of liquid flow rate and is compared with the analytical and experimental data. At small liquid flow rate the center thickness of rivulet and its width increase almost linearly with flow rate. Once the center thickness of rivulet becomes very close to its maximum value, its growth rate retards abruptly. However the width of rivulet increases proportionally to the liquid flow rate and most part of its free surface is as flat as that of stable film. The growth rate of rivulet thickness with respect to liquid flow rate becomes larger at bigger contact angle. The width of rivulet increases rapidly with its flow rate especially at small contact angle, As the liquid-vapor interfacial shear stress increases, the center thickness of rivulet decreases with its flow rate, which is remarkable at small contact angle. However the effect of interfacial shear stress on the width of rivulet is almost negligible.

• International Journal of Highway Engineering
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• v.17 no.4
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• pp.25-31
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• 2015

PURPOSES: Implementation and verification of the simple linear cohesive viscoelastic contact model that can be used to simulate dynamic behavior of sticky aggregates. METHODS: The differential equations were derived and the initial conditions were determined to simulate a free falling ball with a sticky surface from a ground. To describe this behavior, a combination of linear contact model and a cohesive contact model was used. The general solution for the differential equation was used to verify the implemented linear cohesive viscoelastic API model in the DEM. Sensitivity analysis was also performed using the derived analytical solutions for several combinations of damping coefficients and cohesive coefficients. RESULTS : The numerical solution obtained using the DEM showed good agreement with the analytical solution for two extreme conditions. It was observed that the linear cohesive model can be successfully implemented with a linear spring in the DEM API for dynamic analysis of the aggregates. CONCLUSIONS: It can be concluded that the derived closed form solutions are applicable for the analysis of the rebounding behavior of sticky particles, and for verification of the implemented API model in the DEM. The assumption of underdamped condition for the viscous behavior of the particles seems to be reasonable. Several factors have to be additionally identified in order to develop an enhanced contact model for an asphalt mixture.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.163-170
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• 2010

Today, In-Situ testing for measureing geotechnical characterization are divided by Cone Penetration Test, Standard Penetration Test and Dilatometer Test, and will vary depending on soil conditions have been applied (Korea Geotechnical Engineering, 2006). However, these methods can be applied on sand or soft clay soil. Now, many studies are progressing for evaluating the stiffness characteristic of rocks and IGM. and Nam moon suk(2006) did Texas Cone Penetrometer Test for designing field penetration pile intruded at rocks and IGM. but, reliability of Texas Cone Penetration Test has confidence limits because TCPT is testing in Texas centrally, and energy dose not measure Woojin Lee, etc. (1998) did calculate Standard Penetration Test Hammer's dynamic energy efficiency by using dongjaeha analyzer. this research, we installed strain gage and accelerometer for supply existing equipment, and develop MCP that can use variety soils. this thesis, we measured energy at head and tip of Rod for evaluating energy that transport at free falling. As a result, Energy differences are occurred at head and tip of Rod.