• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.7
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• pp.2925-2930
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• 2011

A vehicle fuel economy is very important issue in the view of fuel cost and environmental regulation. The fuel economy is much improved according to the development of electric, electronic and mechanical technology, but up to now the measurement of it tests the given mode(LA-4, FTP-75, etc) within computer simulation program and engine dynamometer. This fuel economy is different with it of real road. The one of main reason is not considered the gradient of the road. To estimate the effects of fuel economy at highway with gradient in this paper, we measure the amount of fuel consumption and calculate the fuel economy of it with running the Youngdong highway with high gradient. Also this paper analysis and compares the fuel economy with gradient and without gradient when the vehicle runs the same driveway. Then we calculate the total energy created the difference of fuel consumption amount of the two cases and calculate the consumpted energy by tire driving force from the torque and power of engine in the simulation. This paper verifies the relation of the driving force and the total energy by creating the difference of fuel consumption amount. This paper also proposes the method of fuel economy improvement despite of gradient at the result.

• Journal of the Korean earth science society
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• v.36 no.6
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• pp.553-566
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• 2015

The effects of vertical resolutions and planetary boundary layer (PBL) physics schemes in a numerical simulation with a very high resolution over the metropolitan area were investigated. The numerical experiments using the Weather Research and Forecast model were conducted from 0000 UTC 25 October to 0000 UTC 26 October 2013. We verified the numerical results against with six hourly observation data from the radiosonde at Seolleung, which was located in southern part of Seoul, and forty three auto weather systems in Seoul. In the experiments of vertical resolutions in low level atmosphere with 44, 50, and 60 layers, which are set to be subdivided particularly under 2 km height. The experiment in 60 layers, which has the highest vertical resolution in this study, showed relatively a clear diurnal variation of PBL heights. Especially, the difference of PBL heights and 10-meter wind fields were mainly seen in the area of high altitude lands for the experiments of vertical resolution. In the sensitivity experiment of PBL schemes such as asymmetric convective model-version 2 (ACM2), Yonsei University (YSU), and Mellow-Yamada-Janjic (MYJ) to the temperature, all three PBL schemes revealed lower temperature than observed profile from the radiosonde in the entire period. The experiments with YSU PBL and ACM2 PBL schemes show relatively less biased in comparison with the experiment of the MYJ PBL scheme.

• Journal of the Korean earth science society
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• v.29 no.3
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• pp.263-279
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• 2008

This study is concerned with the optimization of models using MM5 and WRF mesoscale numerical models to simulate strong sea surface winds, such as that of typhoon Shanshan on 17 September 2006, and the Siberian high event on 16 December 2006, which were selected for displaying the two highest mean wind speeds. The model optimizations for the lowest level altitude, physical parameters and horizontal resolution were all examined. The sea surface wind values obtained using a logarithmic function which takes into account low-level stability and surface roughness were more accurate than those obtained by adjusting the lowest-level of the model to 10 m linearly. To find the optimal parameters for simulating strong sea surface winds various physical parameters were combined and applied to the model. Model grid resolutions of 3-km produced better results than those of 9-km in terms of displaying accurately regions of strong wind, low pressure intensities and low pressure mesoscale structures.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.12
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• pp.1846-1854
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• 2022

The sophistication and diversification of mission equipment for surveillance and reconnaissance is leading to a demand for large-capacity public data links. Overseas, a T4 class(274Mbps) common data link was applied to the Global hwak, a high-altitude unmanned aerial vehicle, and various research and development are being conducted in Korea. In this paper, we propose a structure in which pilot is additionally applied to improve SNR performance while minimizing data transmission rate loss in the DVB-S2 frame structure, which is a european satellite broadcasting standard, for high-capacity transmission of T4 class or higher in the common data link. For the performance evaluation of the proposed structure, the performance of the DVB-S2 was compared and analyzed by simulating the UAV data link channel environment. As a result of simulation, 0.15% of transmission rate loss occurred at T4 class transmission rate compared to DVB-S2 in the proposed structure, but improved SNR reception performance of 0.2~0.3dB was confirmed in the UAV channel environment.

• Journal of the Korean Association of Geographic Information Studies
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• v.22 no.2
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• pp.152-171
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• 2019

In this study, we analyzed the characteristics of the cold air generated in Hannamgeumbuk and Geumbuk-Jeongmaek and proposed their management strategies. We also suggested management strategies after analyzing detailed cold airflows for Cheongju located Hannamgeumbuk-Jeongmaek and we compared the degree of nighttime temperature reduction of the Jeongmaek by using data obtained from observatories located on Cheongju. We used KALM(Kaltluftabflussmodell), a cold air simulation model developed in Germanay and identified both cold airflows and altitude of cold air layers generated during 360minutes at night. As a result, the cold airflow generated in the Jeongmaek became strong and the cold air was appeared clearly in the western part of the Hannamgeumbuk-Jeongamek and in the northern part of the Geumbuk-Jeongmaek. The average velocity of cold airflow was recorded at 0.45m/s, and the maximum speed of cold airflow was recorded at 2.70m/s. The average height of the cold air layer was 104.27m/s and the maximum thickness was 255.0m. The average velocity of cold airflows in Cheongju was 0.51m/s and the average height of cold air layer was 48.87m high. The highest degree of nighttime temperature reduction appeared in the Cheongnamdae observatory($-3.8^{\circ}C$), where the altitude of the cold air layer is high. The results showed that cooling effect of Jeongmaek actually affected the temperature reduction during nighttime. Based on the results, we designated the main mountain area of the Jeongmaek with active cold air generation as "cold air conservation areas" and proposed the current forest and topography conservation. We also proposed to designate areas that facilitate the cold airflows as "cold air management areas" and to complement the function of Jeongmaek. This study could support the establishment of systematic management plans of the Jeongmaek. In addition, it is expected that the results can be applied as basic data for ventilation paths of Cheongju.

• Journal of the Korean Institute of Landscape Architecture
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• v.50 no.2
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• pp.1-22
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• 2022

The modification effects of street trees on outdoor thermal comfort in summertime according to tree planting types and road direction were analyzed using a computer simulation program, ENVI-met. With trees, the air temperature and wind speed decreased, and the relative humidity increased. In the case of mean radiant temperature (T_mrt) and human thermal sensation, physiological equivalent temperature (PET) and universal thermal climate index (UTCI), there was a decrease during the daytime. The greatest change among the meteorological factors by trees happened in Tmrt, and PET and UTCI showed similar patterns with T_mrt·The most effective tree planting type on thermal comfort modification was low tree height, wide tree crown, high leaf area index, and narrow planting interval (LWDN). T_mrt, PET and UTCI showed a large difference depending on shadow patterns of buildings and trees according to solar altitude and azimuth angles, and building locations. When the building shade areas increased, the thermal modification effect by trees decreased. In particular, results on the east and west sidewalks showed a large deviation over time. When applying the LWDN, the northwest, west and southwest sidewalks showed a significant reduction of 8.6-12.3℃ PET and 4.2-4.5℃ UTCI at 10:00, and the northeast, east and southeast sidewalks showed 8.1-11.8℃ PET and 4.4-5.0℃ UTCI at 16:00. On the other hand, when the least effective type (high tree height, narrow tree crown, low leaf area index, and wide planting interval) was applied, the maximum reduction was up to 1.8℃ PET and 0.9℃ UTCI on the eastern sidewalks, and up to 3.0℃ PET and 0.9℃ UTCI on the western ones. In addition, the difference in modification effects on T_mrt, PET and UTCI between the tree planting types was not significant when the tree effects were reduced by the effects of buildings. These results can be used as basic data to make the most appropriate street tree planting model for thermal comfort improvement in urban areas in summer.

• Journal of Environmental Impact Assessment
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• v.23 no.5
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• pp.379-392
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• 2014

This study was performed to predict the future climate envelope of Pinus pumila, a subalpine plant and a Climate-sensitive Biological Indicator Species (CBIS) of Korea. P. pumila is distributed at Mt. seorak in South Korea. Suitable habitat were predicted under two alternative RCPscenarios (IPCC AR5). The SDM used for future prediction was a Maxent model, and the total number of environmental variables for Maxent was 8. It was found that the distribution range of P. pumila in the South Korean was $38^{\circ}7^{\prime}8^{{\prime}{\prime}}N{\sim}38^{\circ}7^{\prime}14^{{\prime}{\prime}}N$ and $128^{\circ}28^{\prime}2^{{\prime}{\prime}}E{\sim}128^{\circ}27^{\prime}38^{{\prime}{\prime}}E$ and 1,586m~1,688m in altitude. The variables that contribute the most to define the climate envelope are altitude. Climate envelope simulation accuracy was evaluated using the ROC's AUC. The P. pumila model's 5-cv AUC was found to be 0.99966. which showed that model accuracy was very high. Under both the RCP4.5 and RCP8.5 scenarios, the climate envelope for P. pumila is predicted to decrease in South Korea. According to the results of the maxent model has been applied in the current climate, suitable habitat is $790.78km^2$. The suitable habitats, are distributed in the region of over 1,400m. Further, in comparison with the suitable habitat of applying RCP4.5 and RCP8.5 suitable habitat current, reduction of area RCP8.5 was greater than RCP4.5. Thus, climate change will affect the distribution of P. pumila. Therefore, governmental measures to conserve this species will be necessary. Additionally, for CBIS vulnerability analysis and studies using sampling techniques to monitor areas based on the outcomes of this study, future study designs should incorporate the use of climatic predictions derived from multiple GCMs, especially GCMs that were not the one used in this study. Furthermore, if environmental variables directly relevant to CBIS distribution other than climate variables, such as the Bioclim parameters, are ever identified, more accurate prediction than in this study will be possible.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.6
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• pp.501-506
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• 2017

An infrared seeking missile does not emit any signal by itself as it is guided by passive heat signature from an aircraft. Therefore, it is difficult for the target aircraft to notice the existence of incoming missile, making it a serious threat. The usage of MAW(missile approach warning) that can notify the approaching infrared seeking missile is currently limited due to its high cost. Furthermore, effectiveness of MAW against infrared seeking missile is not available in open literature. Therefore, effect of evasive maneuver by MAW on the survivability of the aircraft is simulated to evaluate the benefit of the MAW in this research. The lethal range is used as a measure of aircraft survivability. An aircraft flying at an altitude of 5km with Mach 0.9 being tracked by air-launched AIM-9 infrared seeking missile is considered in this research. As a variable for the evasive maneuver, the MAW recognition distance of 5~7km and the G-force of 3~7G that limits maximum directional change of the aircraft are considered. Simulation results showed that the recognition of incoming missile by MAW and following evasive maneuver can reduce the lethal range considerably. Maximum reduction in lethal range is found to be 29.4%. Also, the MAW recognition distance have a greater importance than the aircraft maneuverability that is limited by structural limit of the aircraft.

• Journal of Korea Water Resources Association
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• v.57 no.6
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• pp.421-435
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• 2024

In April 2023, a wildfire broke out in Gangneung located in the east coast region due to the influence of the Yanggang-local wind. In this study, GIS-based RUSLE(Revised Universal Soil Loss Equation) and SEMMA (Soil Erosion Model for Mountain Areas) were used to evaluate the erosion rate due to vegetation recovery in a small watershed of the Gangneung WUI(Wildland-Urban Interface) fire. The small watershed of WUI fire has a low altitude range of 10-30 m and the average slope of 10.0±7.4° which corresponds to a gentle slope. The soil texture was loamy sand with a high organic content and the deep soil depth. As herbaceous layer regenerated profusely in the gully after the wildfire, the NDVI (Normalized Difference Vegetation Index) reached a maximum of 0.55. Simulation results of erosion rates showed that RUSLE ranged from 0.07-94.9 t/ha/storm and SEMMA ranged from 0.24-83.6 t/ha/storm. RUSLE overestimated the average erosion rate by 1.19-1.48 times compared to SEMMA. The erosion rates were estimated to be high in the middle slope where burned pine trees were widely distributed and the slope was steep and to be relatively low in the hollow below the gully where herbaceous layer recovers rapidly. SEMMA showed a rapid increase in erosion sensitivity under at certain vegetation covers with NDVI below 0.25 (Ic = 0.35) on post-fire hillslopes. Gentle slopes with high organic content and rapid recovery of natural vegetation had relatively low erosion rate compared to steep slopes. As subsequent infrastructure and human damages due to sediment disaster by heavy rain is anticipated in WUI fire areas, the research results may be used as basic data for targeted management and decision making on the implementation of emergency treatment after the wildfire.

• Journal of the Korean Association of Geographic Information Studies
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• v.26 no.3
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• pp.52-64
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• 2023

As cities continue to develop rapidly, overcrowding, pollution, and urban sanitation problems arise, and the need to separate conflicting uses is emerging. From this perspective, there is no disagreement that urban land use should be planned. Therefore, all activities in land space must be predicted in advance and planned so that land use can be rationally established. This study used the constructed data to compare and analyze the use distribution characteristics of residential, commercial, and industrial areas in Busan Metropolitan City to identify the building area status, total floor area, and floor area ratio by use zone in districts and counties in Busan Metropolitan City. As a result, it was found that the residential area accounted for the largest proportion of the area by use zone at 51%, and that the residential area accounted for the largest proportion at 63% of the total floor area by use zone. And the analysis was conducted using a specialization coefficient that can identify regional characteristics based on land use composition ratio. Because it is difficult to determine the trend of the entire region just by counting the absolute value of the area, the area composition ratio was calculated and compared. Looking at the residential facilities among the specialization coefficients by use area, it is above 1.0 except for Gijang-gun, Sasang-gu, Saha-gu, and Jung-gu. Commercial facilities are over 1.0 except for Gijang-gun, Gangseo-gu, Nam-gu, Sasang-gu, and Saha-gu. Looking at industrial facilities, you can see that the industrial complex distribution area is Gangseo-gu (2.5), Gijang-gun (1.22), Sasang-gu (2.06), and Saha-gu (1.64). In addition, it was found that business facilities and educational welfare facilities were evenly distributed. Land use analysis was conducted through simulation of the current status of building heights according to each elevation in each use area and the height of buildings in each use area. In general, areas over 80m account for more than 43% of Busan City, showing that the distribution of use areas is designated in areas with high altitude due to the influence of topographical conditions.