• Korean Journal of Agricultural and Forest Meteorology
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• v.18 no.1
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• pp.30-41
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• 2016

The temporal variation of soil water storage is important in hydrological modeling. In order to evaluate an antecedent wetness state, the antecedent precipitation index (API) has been used. The aim of this article is to compare observed soil water storage with APIs calculated by widely used four equations, to configure the relationship between soil water storage and API by a regression model for one-year(2009), and to predict the soil water storage for the next two years(2010~2011). The soil water storage was evaluated from the observed soil moisture dataset in soil depths of 10, 30, 60cm at 21 locations by TDR measurement system for 3 years. As a result, API with the exponential function among the four equations can describe the variation of the observed soil water storage. Monthly optimized parameters of the API's equations seemed to be roughly related with the (potential) evapotranspiration (PET). Using revised monthly optimized parameters of APIs considering the seasonal pattern of PET, we characterize the relationship between API and the observed soil water storage for one year, which looks better than those of other researches.

• Journal of Korean Association for Spatial Structures
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• v.7 no.5
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• pp.75-82
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• 2007

The present work measured and analyzed changes in the acoustics of a sound field which has a retractable ceiling. An 1/20 scale model of an openable space was built and measurement was carried out by varying the opened area of a ceiling. The most widely used room acoustic and design parameters, RT, EDT, and D50 were investigated. The results suggest that the use of RT as an acoustic design parameter may not be proper in an openable space and further it is likely to mislead the initial acoustic design of such spaces. It is mainly due to the characteristics of RT in which non-exponential decay processes are linearly fitted. Early decay times were found to be decreased in proportion to increaing the ratio of opened area. D50, an index of speech intelligibility, was effectively shows the influence of openings on the acoustics. It is also found that EDT and D50 at the seats, not directly exposed to the opened part of a ceiling, were almost linearly decreased in proportion to the ratio of opened area, while little influence was found for the opening ratio larger than 40% at the directly exposed seats to the opened part of a ceiling.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.1
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• pp.44-49
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• 2013

Hydrogen penetration into a metal leads to damages and mechanical degradations and its content measurement is of importance. For a precise measurement, a sample preparation procedure must be optimized through a series of studies on sample washing and drying. In this study, two-step washing with organic solvents and thermal soaking in inert gas were tried with a rod-shaped, API X65 steel sample. The samples were machined from a steel plate and then washed in acetone and etyl-alcohol for 5 minute each and dried with compressed air. After then, the samples were thermally soaked in a home-made nitrogen gas chamber during 10 minute at different heat gun temperatures from 100 to $400^{\circ}C$ and corresponding temperature range in the soaking chamber was from 77 to $266^{\circ}C$ according to the temperature calibration. Hydrogen residue in the samples was measured with a hot extraction system after each soaking step; hydrogen residue of $0.70{\pm}0.12$ wppm after the thermal soaking at $77^{\circ}C$ decayed with increase of the soaking temperature. By adopting the heat transfer model, decay behavior of the hydrogen residue was fitted into an exponential decay function of the soaking temperature. Saturated value or lower bound of the hydrogen residue was 0.36 wppm and chamber temperature required to lower the hydrogen residue about 95% of the lower bound was $360^{\circ}C$. Furthermore, a thermal desorption spectroscopy was done for the fully soaked samples at $360^{\circ}C$. Weak hydrogen peak was observed for whole temperature range and it means that hydrogen-related contaminants of the sample surface are steadily removed by heating. In addition, a broad peak found around $400^{\circ}C$ means that parts of the hydrogen residue are irreversibly trapped in the steel microstructure.

• Journal of KIISE:Databases
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• v.31 no.4
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• pp.395-408
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• 2004

A conjunctive Boolean text query refers to a query that searches for tort documents containing all of the specified keywords, and is the most frequently used query form in information retrieval systems. Typically, the query specifies a long list of keywords for better precision, and in this case, the order of keyword processing has a significant impact on the query speed. Currently known approaches to this ordering are based on heuristics and, therefore, cannot guarantee an optimal ordering. We can use a systematic approach by leveraging a database query processing algorithm like the dynamic programming, but it is not suitable for a text query with a typically long list of keywords because of the algorithm's exponential run-time (Ο(n2$^{n-1}$)) for n keywords. Considering these problems, we propose a new approach based on a property called the join sequence separability. This property states that the optimal join sequence is separable into two subsequences of different join methods under a certain condition on the joined relations, and this property enables us to find a globally optimal join sequence in Ο(n2$^{n-1}$). In this paper we describe the property formally, present an optimization algorithm based on the property, prove that the algorithm finds an optimal join sequence, and validate our approach through simulation using an analytic cost model. Comparison with the heuristic text query optimization approaches shows a maximum of 100 times faster query processing, and comparison with the dynamic programming approach shows exponentially faster query optimization (e.g., 600 times for a 10-keyword query).

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.4
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• pp.527-533
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• 2011

Decomposition of compost applied to soils is affected basically by its biological stability; but, many other chemical properties of the compost may also influence compost organic-C mineralization. This study was conducted to investigate the principal substrate quality factors of composts that determine C mineralization of compost with similar stability degree (SD). Three composts samples with similar SD but different chemical properties such as pH, C/N, $K_2SO_4$-extractable C, and molar ratio of $NH_4^+$ to $NO_3^-$ were mixed with an acid loamy soil and $CO_2$ emission was monitored during the laboratory incubation for 100 days. Temporal pattern of cumulative compost organic-C mineralization expressed as % of total organic C ($C_{%\;TOC}$) followed double exponential first order kinetics model and the $C_{%\;TOC}$ ranged from 4.8 to 11.8% at the end of incubation. The pattern of C%TOC among the composts was not coincident with the SD pattern (40.1 to 58.6%) of the composts; e.g. compost with the lowest SD resulted in the least $C_{%\;TOC}$ and vice versa. This result indicates that SD of compost can not serve as a concrete predictor of compost mineralization as SD is subject not only to maturity of compost but also to characteristics of co-composting materials such as rice hull (low SD) and sawdust (high SD). Meanwhile, such pattern of $C_{%\;TOC}$ collaborated with pH, C/N, $K_2SO_4$-extractable C, and molar ratio of $NH_4^+$ to $NO_3^-$ of the composts that are regarded as chemical indices of the progress of composting. Therefore, for better prediction of compost mineralization in soils, it is necessary to consider both SD and other chemical indices (pH, C/N, and molar ratio of $NH_4^+$ to $NO_3^-$).

• Journal of agriculture & life science
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• v.46 no.6
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• pp.147-156
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• 2012

This study evaluated the effects of presoaking apple slices in 2 or 5% brine solution prior to air-drying at $50^{\circ}C$. Several quality factors of the dried apples were measured including moisture content (MC), water activity ($a_w$), shear force, color values, appearance and consumer likability. Except at time 0, the $a_w$ of presoaked samples was lower than those of control during and after drying. The relationship between MC and water activity during drying was well-fit by an exponential model. During drying, the moisture contents of presoaked samples were slightly higher than control samples with no presoaking. However, the $a_w$ of presoaked slices were lower than control at a given drying time. At a given $a_w$, presoaked slices had higher moisture content. The shear force was lower for samples presoaked in brine solution, particularly at shorter drying times. Presoaked apple slices also were lighter in color after drying than controls. Sensory evaluations suggest that presoaking of apple slices before drying may help enhance palatability. Samples presoaked in 2% brine solution had the highest scores for taste, texture and overallacceptability, while those presoaked in 5% brine solution had the highest scores for appearance.

• Journal of Korean Society of Forest Science
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• v.112 no.3
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• pp.340-351
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• 2023

Landslides are major natural geological hazards that cause enormous property damage and human casualties annually. The vulnerability of mountainous areas to landslides is further exacerbated by the impacts of climate change. Soil depth is a crucial parameter in landslide and debris flow analysis, and plays an important role in the evaluation of watershed hydrological processes that affect slope stability. An accurate method of estimating soil depth is to directly investigate the soil strata in the field. However, this requires significant amounts of time and money; thus, numerous models for predicting soil depth have been proposed. However, they still have limitations in terms of practicality and accuracy. In this study, 71 seismic survey results were collected from domestic mountainous areas to estimate soil depth on hill slopes. Soil depth was estimated on the basis of a shear wave velocity of 700 m/s, and a database was established for slope angle, elevation, and soil depth. Consequently, the statistical characteristics of soil depth were analyzed, and the correlations between slope angle and soil depth, and between elevation and soil depth were investigated. Moreover, various soil depth prediction models based on slope angle were investigated, and corrected linear and exponential soil depth prediction models were proposed.

• Journal of Korean Port Research
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• v.5 no.2
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• pp.19-37
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• 1991

This work aims to : establish a model of the container physical distribution system of Pusan port comprising 4 sub-systems of a navigational system, on-dock cargo handling/transfer/storage system, off-dock CY system and an in-land transport system : examine the system regarding the cargo handling capability of the port and analyse the cost of the physical distribution system. The overall findings are as follows : Firstly in the navigational system, average tonnage of the ships visiting the Busan container terminal was 33,055 GRT in 1990. The distribution of the arrival intervals of the ships' arriving at BCTOC was exponential distribution of $Y=e^{-x/5.52}$ with 95% confidence, whereas that of the ships service time was Erlangian distribution(K=4) with 95% confidence, Ships' arrival and service pattern at the terminal, therefore, was Poisson Input Erlangian Service, and ships' average waiting times was 28.55 hours In this case 8berths were required for the arriving ships to wait less than one hour. Secondly an annual container through put that can be handled by the 9cranes at the terminal was found to be 683,000 TEU in case ships waiting time is one hour and 806,000 TEU in case ships waiting is 2 hours in-port transfer capability was 913,000 TEU when berth occupancy rate(9) was 0.5. This means that there was heavy congestion in the port when considering the fact that a total amount of 1,300,000 TEU was handled in the terminal in 1990. Thirdly when the cost of port congestion was not considered optimum cargo volume to be handled by a ship at a time was 235.7 VAN. When the ships' waiting time was set at 1 hour, optimum annual cargo handling capacity at the terminal was calculated to be 386,070 VAN(609,990 TEU), whereas when the ships' waiting time was set at 2 hours, it was calculated to be 467,738 VAN(739,027 TEU). Fourthly, when the cost of port congestion was considered optimum cargo volume to be handled by a ship at a time was 314.5 VAN. When the ships' waiting time was set at I hour optimum annual cargo handling capacity at the terminal was calculated to be 388.416(613.697 TEU), whereas when the ships' waiting time was set 2 hours, it was calculated to be 462,381 VAN(730,562 TEU).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4A
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• pp.373-384
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• 2009

For the first step on the quantitative evaluation of shrinkage reduction and differential shrinkage analysis of lightweight aggregate concrete, this study sets the moisture transport model of concrete by pre-absorbed water of porous lightweight aggregates and measured effective moisture diffusion coefficient, moisture capacity, degree of humidity supply and degree of humidity consumption by water binder ratio and aggregate type. The effective moisture diffusion coefficient in steady state caused by humidity difference between inside and outside of concrete had low value as low water-binder ratio. And in case of same water-binder ratio, effective moisture diffusion of mixtures used normal aggregates were lower than those used lightweight aggregates. To determine moisture store capability of concrete - moisture capacity, moisture contents were measured in 9 humidity conditions. As a result moisture contents of mixtures used lightweight aggregates was higher than mixtures used normal aggregates in all humidity conditions. This study measured lightweight aggregates' degree of humidity supply that applicable to normal atmospheric environment (above RH 50%) and made it quantitatively. Also amount of moisture release was set as a exponential function that represents a clear trend proportion to time and inverse proportion to humidity of the surroundings. As the result of measurement about degree of moisture consumption inside concrete following the internal consumption caused by cement hydration self-drying, it was showed that rapid decrease of humidity, around 10%, at early ages (7~10 days) when water-binder ratio is 0.3 and slow decrease around 5% and 1% when water-binder ratio is 0.4 and 0.5.

• Journal of Soil and Groundwater Environment
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• v.12 no.5
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• pp.19-32
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• 2007

In Korea, there have been various methods of estimating groundwater recharge which generally can be subdivided into three types: baseflow separation method by means of groundwater recession curve, water budget analysis based on lumped conceptual model in watershed, and water table fluctuation method (WTF) by using the data from groundwater monitoring wells. However, groundwater recharge rate shows the spatial-temporal variability due to climatic condition, land use and hydrogeological heterogeneity, so these methods have various limits to deal with these characteristics. To overcome these limitations, we present a new method of estimating recharge based on water balance components from the SWAT-MODFLOW which is an integrated surface-ground water model. Groundwater levels in the interest area close to the stream have dynamics similar to stream flow, whereas levels further upslope respond to precipitation with a delay. As these behaviours are related to the physical process of recharge, it is needed to account for the time delay in aquifer recharge once the water exits the soil profile to represent these features. In SWAT, a single linear reservoir storage module with an exponential decay weighting function is used to compute the recharge from soil to aquifer on a given day. However, this module has some limitations expressing recharge variation when the delay time is too long and transient recharge trend does not match to the groundwater table time series, the multi-reservoir storage routing module which represents more realistic time delay through vadose zone is newly suggested in this study. In this module, the parameter related to the delay time should be optimized by checking the correlation between simulated recharge and observed groundwater levels. The final step of this procedure is to compare simulated groundwater table with observed one as well as to compare simulated watershed runoff with observed one. This method is applied to Mihocheon watershed in Korea for the purpose of testing the procedure of proper estimation of spatio-temporal groundwater recharge distribution. As the newly suggested method of estimating recharge has the advantages of effectiveness of watershed model as well as the accuracy of WTF method, the estimated daily recharge rate would be an advanced quantity reflecting the heterogeneity of hydrogeology, climatic condition, land use as well as physical behaviour of water in soil layers and aquifers.