• Journal of The Korean Society of Agricultural Engineers
• /
• v.57 no.5
• /
• pp.1-12
• /
• 2015

The study aimed to project inflows and demmands for the agricultural reservoir watersheds in South Korea considering a variety of regional characteristics and the uncertainty of future climate information. The study bias-corrected and spatially downscaled retrospective daily Global Climate Model (GCM) outputs under Representative Concentration Pathways (RCP) 4.5 and 8.5 emission scenarios using non-parametric quantile mapping method to force Soil and Water Assessment Tool (SWAT) model. Using the historical simulation, the skills of un-calibrated SWAT model (without calibration process) was evaluated for 5 reservoir watersheds (selected as well-monitored representatives). The study then, evaluated the performance of 9 GCMs in reproducing historical upstream inflow and irrigation demand at the five representative reservoirs. Finally future inflows and demands for 58 watersheds were projected using 9 GCMs projections under the two RCP scenarios. We demonstrated that (1) un-calibrated SWAT model is likely applicable to agricultural watershed, (2) the uncertainty of future climate information from different GCMs is significant, (3) multi-model ensemble (MME) shows comparatively resonable skills in reproducing water balances over the study area. The results of projection under the RCP 4.5 and RCP 8.5 scenario generally showed the increase of inflow by 9.4% and 10.8% and demand by 1.4% and 1.7%, respectively. More importantly, the results for different seasons and reservoirs varied considerably in the impacts of climate change.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.41 no.6
• /
• pp.543-551
• /
• 2017

A campus guide robot was developed that can autonomously guide people through a university campus. The robot is able to evaluate its location using Differential Global Positioning System (DGPS) and Dead-Reckoning using the encoders mounted on its wheels. The robot can navigate autonomously along a guide route that is set in advance. A new position-based guidance approach was suggested. Unlike the conventional method of setting the guide sequence in advance, the robot acquires guidance by judging whether there is guide information corresponding to its current position. The robot searches guide information from the guide database while it moves along the guide path autonomously. If there is any guide information available around the location of the robot, then it performs guide functions. We also suggested an effective guide scenario that can maximize the interest of people. The performance of the robot was tested through sets of experiments in a true campus environment.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.56 no.2
• /
• pp.47-57
• /
• 2014

This study was conducted to predict greenhouse gas (GHG) emission from paddy by future climate change scenario in Korea. Chuncheon city in Kangwon province were selected as study area. A1B Special Report on Emission Scenario (SRES) of the IPCC (Intergovernmental panel on climate change) was used to assess the future potential climate change. The rainfall and temperature was projected to increase by 8.4 % and 1.9 % (2040s), 35.9 % and 27.0 % (2060s), 19.2 % and 30.8 % (2090s), respectively, compare to the 2010s value. Under the climate change, Denitrification-Decomposition (DNDC) predicted an increase in $N_2O$, $CO_2$ and $CH_4$ emissions from paddy. The simulations resulted in annual net emissions of 0.4~2.4, 500.5~734.5 and 29.4~160.4 kg/ha/year of $N_2O-N$, $CH_4-C$ and $CO_2-C$, respectively, with a cumulated global warming potential (GWP) of $14.5{\sim}21.7t{\cdot}CO_2/ha/year$ were affected by rainfall, temperature, manure amendment and fertilizer amount. The simulation results suggested that implementation of manure amendment or reduction of water consumption instead of increased fertilizer application rates would more efficiently mitigate GHG emissions.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.59 no.1
• /
• pp.31-43
• /
• 2017

Recent studies about irrigation water use have focused on agricultural reservoir operation in irrigation period. At the same time, it is significant to store water resource in reservoir during non-irrigation period in order to secure sufficient water in early growing season. In this study, Representative Concentration Pathways (RCP) 4.5, 8.5 scenarios with the Global Climate Model (GCM) of The Second Generation Earth System Model (CanESM2) were downscaled with bias correlation method. Cumulative precipitation during non-irrigation season, October to March, was analyzed. Interaction between cumulative precipitation and carry-over storage was analyzed with linear regression model for ten study reservoirs. Using the regression model, reservoir drought response ability was evaluated with expression of excess and deficiency. The results showed that future droughts will be more severe than past droughts. Especially in case of non-exceedance probability of 10%, drought in southern region seemed to be serious. Nine study reservoirs showed deficiency range from 10% to 55%, which turned out to be vulnerable for future drought. Only Jang-Chan reservoir was secure for early growing season in spite of drought with deficiency of 8% and -2%. The results of this study represents current agricultural reservoirs have vulnerability for the upcoming drought.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.62 no.4
• /
• pp.99-110
• /
• 2020

The objective of this study is to analyze the trend of changes in the water circulation rates under climate change by adopting the concept of WCR defined by the Ministry of Environment. With the need for sound water circulation recovery, the MOE proposed the idea of WCR as (1-direct flow/precipitation). The guideline for calculating WCR suggests the SCS method, which is only suitable for short term rainfall events. However, climate change, which affects WCR significantly, is a global phenomenon and happens gradually over a long period. Therefore, long-term trends in WCRs should also be considered when analyzing changes in WCR due to climate change. RCP (Representative Concentration Pathway) 4.5 and 8.5 scenarios were used to simulate future runoff. SWAT (Soil and Water Assessment Tool) was run under the future daily data from GCMs (General Circulation Models) after the calibration. In 2085s, monthly WCR decreased by 4.2-9.9% and 3.3-8.7% in April and October. However, the WCR in the winter increased as the precipitation during the winter decreased compared to the baseline. In the aspect of yearly WCR, the value showed a decrease in most GCMs in the mid-long future. In particular, in the case of the RCP 8.5 scenario, the WCR reduced 2-3 times rapidly than the RCP 4.5 scenario. The WCR of 2055s did not significantly differ from the 2025s, but the value declined by 0.6-2.8% at 2085s.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.60 no.5
• /
• pp.149-162
• /
• 2018

It is necessary to select the appropriate global climate model (GCM) to take into account the impacts of climate change on integrated water management. The objective of this study was to develop the selection technique of representative GCMs for uncertainty in climate change scenario. The selection technique which set priorities of GCMs consisted of two steps. First step was evaluating original GCMs by comparing with grid-based observational data for the past period. Second step was evaluating whether the statistical downscaled data reflect characteristics for the historical period. Spatial Disaggregation Quantile Delta Mapping (SDQDM), one of the statistical downscaling methods, was used for the downscaled data. The way of evaluating was using explanatory power, the stepwise ratio of the entire GCMs by Expert Team on Climate Change Detection and Indices (ETCCDI) basis. We used 26 GCMs based on CMIP5 data. The Representative Concentration Pathways (RCP) 4.5 and 8.5 scenarios were selected for this study. The period for evaluating reproducibility of historical period was 30 years from 1976 to 2005. Precipitation, maximum temperature, and minimum temperature were used as collected climate variables. As a result, we suggested representative 13 GCMs among 26 GCMs by using the selection technique developed in this research. Furthermore, this result can be utilized as a basic data for integrated water management.

• Journal of Climate Change Research
• /
• v.9 no.3
• /
• pp.235-243
• /
• 2018

Loss of favorable habitats for species due to temperature increase is one of the main concerns of climate change on the ecosystem, and endangered species might be much more sensitive to such unfavorable changes. This study aimed to analyze the impact of future climate change on endangered wild animals in South Korea by investigating thermal sensitivity and vulnerability to temperature increase. We determined thermal sensitivity by testing normality in species distribution according to temperature. Then, we defined the vulnerability when the future temperature range of South Korea completely deviate from the current temperature range of species distribution. We identified 13 species with higher thermal sensitivity. Based on IPCC future scenarios RCP 4.5 and RCP 8.5, the number of species vulnerable to future warming doubled from 3 under RCP4.5 to 7 under the RCP8.5 scenario. The species anticipated to be at risk under RCP 8.5 are flying squirrel (Pteromys volans aluco), ural owl (Pteromys volans aluco), black woodpecker (Dryocopus martius), tawny owl (Strix aluco), watercock (Gallicrex cinerea), schrenck?s bittern (Ixobrychus eurhythmus), and fairy pitta (Pitta nympha). The other 10 species showing very narrow temperature ranges even without normal distributions and out of the future temperature range may also need to be treated as vulnerable species, considering the inevitable observation scarcity of such endangered species.

• Journal of Climate Change Research
• /
• v.9 no.2
• /
• pp.143-156
• /
• 2018

Evapotranspiration is a key element in designing and operating agricultural hydraulic structures. The profound effect of climate change to local agro-hydrological systems makes it inevitable to study the potential variability in evapotranspiration rate in order to develop policies on future agricultural water management as well as to evaluate changes in agricultural environment. The APEX-Paddy model was used to simulate local evapotranspiration responses to climate change scenarios. Nine Global Climate Models(GCMs) downscaled using a non-parametric quantile mapping method and a Multi?Model Ensemble method(MME) were used for an uncertainty analysis in the climate scenarios. Results indicate that APEX-Paddy and the downscaled 9 GCMs reproduce evapotranspiration accurately for historical period(1976~2005). For future periods, simulated evapotranspiration rate under the RCP 4.5 scenario showed increasing trends by -1.31%, 2.21% and 4.32% for 2025s(2011~2040), 2055s(2041~2070) and 2085s(2071~2100), respectively, compared with historical(441.6 mm). Similar trends were found under the RCP 8.5 scenario with the rates of increase by 0.00%, 4.67%, and 7.41% for the near?term, mid?term, and long?term periods. Monthly evapotranspiration was predicted to be the highest in August, July was the month having a strong upward trend while. September and October were the months showing downward trends in evapotranspiration are mainly resulted from the shortening of the growth period of paddy rice due to temperature increase and stomatal closer as ambient $CO_2$ concentration increases in the future.

• International Journal of High-Rise Buildings
• /
• v.7 no.4
• /
• pp.375-387
• /
• 2018

This paper presents a review on progressive collapse mechanism of steel framed buildings exposed to fire. The influence of load ratios, strength of structural members (beam, column, slab, connection), fire scenarios, bracing systems, fire protections on the collapse mode and collapse time of structures is comprehensively reviewed. It is found that the key influencing factors include load ratio, fire scenario, bracing layout and fire protection. The application of strong beams, high load ratios, multi-compartment fires will lead to global downward collapse which is undesirable. The catenary action in beams and tensile membrane action in slabs contribute to the enhancement of structural collapse resistance, leading to a ductile collapse mechanism. It is recommended to increase the reinforcement ratio in the sagging and hogging region of slabs to not only enhance the tensile membrane action in the slab, but to prevent the failure of beam-to-column connections. It is also found that a frame may collapse in the cooling phase of compartment fires or under travelling fires. This is because that the steel members may experience maximum temperatures and maximum displacements under these two fire scenarios. An edge bay fire is more prone to induce the collapse of structures than a central bay fire. The progressive collapse of buildings can be effectively prevented by using bracing systems and fire protections. A combination of horizontal and vertical bracing systems as well as increasing the strength and stiffness of bracing members is recommended to enhance the collapse resistance. A protected frame dose not collapse immediately after the local failure but experiences a relatively long withstanding period of at least 60 mins. It is suggested to use three-dimensional models for accurate predictions of whether, when and how a structure collapses under various fire scenarios.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.16 no.4
• /
• pp.1392-1413
• /
• 2022

In order to meet the rapid development of the unmanned aerial vehicle (UAV) communication needs, cooperative spectrum sensing (CSS) helps to identify unused spectrum for the primary users (PU). However, multi-UAV mode (MUM) requires the large communication resource in a cognitive UAV network, resulting in a severe decline of spectrum efficiency (SE) and energy efficiency (EE) and increase of energy consumption (EC). On this account, we extend the traditional 2D spectrum space to 3D spectrum space for the UAV network scenario and enable UAVs to proceed with spectrum sensing behaviors in this paper, and propose a novel multi-slot mode (MSM), in which the sensing slot is divided into multiple mini-slots within a UAV. Then, the CSS process is developed into a composite hypothesis testing problem. Furthermore, to improve SE and EE and reduce EC, we use the sequential detection to make a global decision about the PU channel status. Based on this, we also consider a truncation scenario of the sequential detection under the sensing delay constraint, and further derive a closed-form performance expression, in terms of the CSS performance and cooperative efficiency. At last, the simulation results verify that the performance and cooperative efficiency of MSM outperforms that of the traditional MUM in a low EC.