• Water Engineering Research
• /
• v.6 no.2
• /
• pp.73-89
• /
• 2005

Two kinds of high resolution GCMs with the same spatial resolutions but with different schemes run by domestic and foreign agencies are used to clarify the usefulness and sensitivity of GCM for water resources applications for Korea. One is AMIP-II (Atmospheric Model Intercomparison Project-II) type GCM simulation results done by ECMWF (European Centre for Medium-Range Weather Forecasts) and the other one is AMIP-I type GCM simulation results done by METRI (Korean Meteorological Research Institute). Observed mean areal precipitation, temperature, and discharge values on 7 major river basins were used for target variables. Monte Carlo simulation was used to establish the significance of the estimator values. Sensitivity analyses were done in accordance with the proposed ways. Through the various tests, discrimination condition is sensitive for the distribution of the data. Window size is sensitive for the data variation and the area of the basins. Discrimination abilities of each nodal value affects on the correct association. In addition to theses sensitivity analyses results, we also noticed some characteristics of each GCM. For Korean water resources, monthly and small window setting analyses are recommended using GCMs.

• Journal of Environmental Impact Assessment
• /
• v.22 no.1
• /
• pp.1-17
• /
• 2013

Carbon sequestration on soil is one of the counter measurements against climate change in agricultural sector. Increasing incorporation of organic fertilizer would increase soil organic carbon (SOC) but it could bring high potential of nutrient losses which would result in water quality degradation. In this paper, literature review on soil organic carbon behavior according to agricultural management is presented. The results of field experiment to identify the effect of organic and commercial fertilizer applications on SOC and runoff water quality were also presented. Field experiment confirmed increased SOC and nutrient concentrations in runoff water as application rate of organic fertilizer increase. The potential use of simulation model to develop best agricultural management practice considering carbon sequestration and water quality conservation at the same time is discussed and monitoring and modeling strategies are also suggested to achieve the goal.

• Nuclear Engineering and Technology
• /
• v.41 no.4
• /
• pp.413-426
• /
• 2009

Nuclear energy plays an important role in world energy production by supplying 6% of the world's current total electricity production. However, 86% of the energy consumed worldwide to produce industrial process heat, to generate electricity and to power the transportation sector still originates in fossil fuels. To cope with dwindling fossil fuels and climate change, it is clear that a clean alternative energy that can replace fossil fuels in these sectors is urgently required. Clean hydrogen energy is one such alternative. Clean hydrogen can play an important role not only in synthetic fuel production but also through powering fuel cells in the anticipated hydrogen economy. With the introduction of the high temperature gas-cooled reactor (HTGR) that can produce nuclear heat up to $950^{\circ}C$ without greenhouse gas emissions, nuclear power is poised to broaden its mission beyond electricity generation to the provision of nuclear process heat and the massive production of hydrogen. In this paper, the features and potential of the HTGR as the energy source of the future are addressed. Perspectives on nuclear heat and hydrogen applications using the HTGR are discussed.

• Ocean and Polar Research
• /
• v.29 no.4
• /
• pp.319-326
• /
• 2007

Coastal marine ecosystems continue to suffer unrelenting pressures from human population growth, increased development, and climate change. Moreover, these systems' capacity for self-repair is declining with such increases in anthropogenic production of various pollutants. What is the present health status or condition of the coastal ecosystem? If our coastal areas are unhealthy, which conditions are considered serious? To answer such questions, the United States, Canada, and Australia are currently assessing coastal ecosystem health using systematic monitoring programs as well as identifying and implementing management plans to improve the health of degraded coastal ecosystems. To evaluate marine environments, Korea is currently using a limited number of factors to estimate water quality. In fact, we are ill-prepared for assessing coastal ecosystem health because no biologically specific criteria are in place to measure the responses to various pollutants. We should select ecosystem-specific indicators from physicochemical stressors and evaluate the subsequent biological responses within each ecosystem. Furthermore, a set of practical indicators should be generated by considering the characteristics and uses of a local coastal area and the key issues at hand. The values of indicators should be presented as indices that allow understanding by the general public as well as by practitioners, policy makers, environmental managers and other stakeholders.

• Proceedings of the KIEE Conference
• /
• 2005.04a
• /
• pp.277-279
• /
• 2005

The imbalance of energy demand and supply caused by rapid industrialization around the world and the associated environmental issues require and alternative energy source with possible renewable fuels. Political instability and depletion of cruel oils are other factors that cause fluctuation of oil price. Securing a new alternative energy source for the next century became an urgent issue that our nation is confronting with. As a matter of fact, the fuel cell technology can be widely used as next generation energy regardless of regions and climate. Specially, the ability of expansion and quick installation enable one to apply it for distributed power, where the technology is already gaining remarkable attentions for the application. Particularly, leading industrialized nations are focusing on the PEM fuel dell with anticipation that this technology will find their place of applications in the vehicles and homes. In this study, demonstrate the multi physics modeling of a proton exchange membrane(PEM) fuel cell with interdigitated flow field design. The model uses current balances, mass balance(Maxwell-Stefan diffusion for reactant, water and nitrogen gas) and momentum balance(gas flow) to simulate the PEM fuel cell behavior.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.26 no.6
• /
• pp.287-293
• /
• 2014

Internal combustion engines release 30~40% of the energy from fossil fuels into the atmosphere in the form of exhaust gases. By utilizing this waste heat, plenty of energy can be conserved in the auto industry. Thermoelectric generation is one way of transforming the energy from engine's exhaust gases into electricity in a vehicle. The thermoelectric generators located on the exhaust pipe have been developed for vehicle applications. Different experiments with thermoelectric generators have been conducted under various test conditions as following examples: hot gas temperature, hot gas mass flow rate, coolant temperature, and coolant mass flow rate. The experimental results have shown that the generated electrical power increases significantly with the temperature difference between the hot and the cold side of the thermoelectric generator and the gas flow rate of the hot-side heat exchanger. In addition, the gas temperature of the hot-side heat exchanger decreases with the length of the thermoelectric generator, especially at a low gas flow rate.

• Journal of Korea Water Resources Association
• /
• v.39 no.5 s.166
• /
• pp.417-430
• /
• 2006

In this study, the probability density functions (PDFs) of the rainfall generated by PRPM(Poisson Rectangular Pulse Model) and the runoff simulated by SLRM(Single Linear Reservoir Model) and Nash model, were compared to find out the changes of runoff characteristics due to the change of rainfall characteristics. Effect of rainfall frequency, Intensity, and duration on runoff were evaluated using the PDFs derived. Two basin, small and midium-sized ones, were also selected to find out the effect of basin size. As the results, we found that the arrival time, the intensity, and the duration of rainfall differently influence the runoff characteristics, which could be applied to evaluate the effect of climate change.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.10 no.3
• /
• pp.107-112
• /
• 2008

"Jeung-Bo-San-Lim-Gyeong-Je" (meaning "Revised Forest Management") has been well recognized as the informative document that introduces scientific knowledge and experiences of Korean ancestors regarding weather and climate. The tradition of Gwan-Cheon-Mang-Gi(i.e., empirical forecasting of short-term weather phenomena based on the status of cloud or sky) has been continuously utilized as a civilian weather forecasting method and even for very short-term weather prediction by operational forecasters these days. This agricultural technology textbook, published during the Great King Youngjo in Chosun-Dynasty, may be regarded as a poorly written document from the modern standpoint. Nonetheless, this study demonstrates that by and large the empirical knowledge contained in the book is indeed science based although their applications are limited to several hours for local forecasts in agricultural practices and daily living. For example, the wisdom of keeping water at an optimum level in a paddy field after sowing to prevent young seedlings from late frost damages was not at all different from the present technique of vinyl covered seedling nursery.

• Korean Journal of Remote Sensing
• /
• v.25 no.6
• /
• pp.507-515
• /
• 2009

Land surface temperature (LST) is a key environmental variable in a wide range of applications, such as weather, climate, hydrology, and ecology. However, LST is one of the most difficult surface variables to observe regularly due to the strong spatio-temporal variations. So, we have developed the LST retrieval algorithm from COMS (Communication, Ocean and Meteorological Satellite) data through the radiative transfer simulations under various atmospheric profiles (TIGR data), satellite zenith angle (SZA), spectral emissivity, and surface lapse rate conditions using MODTRAN 4. However, the LST retrieval algorithm has a tendency to overestimate and underestimate the LST for surface inversion and superadiabatic conditions, respectively. To minimize the overestimation and underestimation of LST, we also developed day/night LST algorithms separately based on the surface lapse rate (local time) and recalculated the final LST by using the weighted sum of day/night LST. The analysis results showed that the quality of weighted LST of day/night algorithms is greatly improved compared to that of LST estimated by original algorithm regardless of the surface lapse rate, spectral emissivity difference (${\Delta}{\varepsilon}$) SZA, and atmospheric conditions. In general, the improvements are greatest when the surface lapse rate and ${\Delta}{\varepsilon}$ are negatively large (strong inversion conditions and less vegetated surface).

• Proceedings of the Korea Water Resources Association Conference
• /
• 2018.05a
• /
• pp.147-147
• /
• 2018

In this article, we use an open source software library: TensorFlow, developed for the purposes of conducting very complex machine learning and deep neural network applications. However, the system is general enough to be applicable in a wide variety of other domains as well. The proposed model based on a deep neural network model, LSTM (Long Short-Term Memory) to predict the river water level at Okcheon Station of the Guem River without utilization of rainfall - forecast information. For LSTM modeling, the input data is hourly water level data for 15 years from 2002 to 2016 at 4 stations includes 3 upstream stations (Sutong, Hotan, and Songcheon) and the forecasting-target station (Okcheon). The data are subdivided into three purposes: a training data set, a testing data set and a validation data set. The model was formulated to predict Okcheon Station water level for many cases from 3 hours to 12 hours of lead time. Although the model does not require many input data such as climate, geography, land-use for rainfall-runoff simulation, the prediction is very stable and reliable up to 9 hours of lead time with the Nash - Sutcliffe efficiency (NSE) is higher than 0.90 and the root mean square error (RMSE) is lower than 12cm. The result indicated that the method is able to produce the river water level time series and be applicable to the practical flood forecasting instead of hydrologic modeling approaches.