• Bulletin of the Korean Chemical Society
• /
• v.24 no.1
• /
• pp.55-59
• /
• 2003

This work is focused on analyzing ion-pair interactions and showing the effect of solvent induced inter-atomic attractions in various dielectric environments. To estimate the stability of ion-pairs, SCI-PCM ab initio MO calculations were carried out. We show that the solvent-induced attraction or ‘cavitation' energy of the ion-pair interactions in solution that arises mainly from the stabilization of the water molecules by the generation of an electrostatic field. In fact, even the strong electrostatic interaction characteristic of ion-pair interactions in the gas phase cannot overcome the destabilization or reorganization of the water molecules around solute cavities that arise from cancellation of the electrostatic field. The solvent environment, possibly supplemented by some specific solvent molecules, may help place the solute molecule in a cavity whose surroundings are characterized by an infinite polarizable dielectric medium. This behavior suggests that hydrophobic residues at a protein surface could easily contact the side chains of other nearby residues through the solvent environment, instead of by direct intra-molecular interactions.

• Environmental Engineering Research
• /
• v.18 no.1
• /
• pp.37-43
• /
• 2013

Water distribution pipes installed underground have potential risks of pipe failure and burst. After years of use, pipe walls tend to be corroded due to aggressive soil environments where they are located. The present study aims to assess the degree of external corrosion of a distribution pipe network. In situ data obtained through test pit excavation and direct sampling are carefully collated and assessed. A statistical approach is useful to predict severity of pipe corrosion at present and in future. First, criteria functions defined by discriminant function analysis are formulated to judge whether the pipes are seriously corroded. Data utilized in the analyses are those related to soil property, i.e., soil resistivity, pH, water content, and chloride ion. Secondly, corrosion factors that significantly affect pipe wall pitting (vertical) and spread (horizontal) on the pipe surface are identified with a view to quantifying a degree of the pipe corrosion. Finally, a most reliable model represented in the form of a multiple regression equation is developed for this purpose. From these analyses, it can be concluded that our proposed model is effective to predict the severity and rate of pipe corrosion utilizing selected factors that reflect the fuzzy soil environment.

• Bulletin of the Korean Chemical Society
• /
• v.21 no.12
• /
• pp.1239-1244
• /
• 2000

A study of K addition to the catalyst of CoMo/ ${\gamma}-Al_2O_3$ was studied. The catalyst with 10 at% of K to Mo atoms in 3C10M, the catalyst added 3 wt% CoO to 10 wt% $MoO_3/{\gamma}-Al_2O_3$, showed the highest activity for water gas shift reaction. The addition of K retarded the reducibility of cobalt-molybdenum catalysts. It gave, however, good dispersion and large BET surface area to the catalysts which were attributed to the disappearance of polymolybdate clustyer such as $Mo_7O_{24}^{6-}$ and the formation of small Mo$O_4^{2-}$ cluster. It was confirmed by the analyses of pore size distribution, activation energy, Raman spectroscopy, and electron diffraction. The activation energies and the frequency factors of the catalysts 3C10M and 5KC10M (the catalyst added 5 at% K for Mo to the catalyst 3C10M) were 43.1 and 47.8 kJ/mole, and 4,297 and 13,505 $sec^{-1}$, respectively. These values were also well correlated with our suggestion. These phenomena were attributed to the direct interaction between K and CoMo oxides irrelevant to the support.

• Journal of ILASS-Korea
• /
• v.27 no.2
• /
• pp.77-83
• /
• 2022

In this study, the thickness of the liquid sheet formed by a low speed impinging jet onto a flat plate was measured by the direct contact method. The spatial distribution characteristics of the sheet thickness in the radial and circumferential directions, and the effects of jet velocity and liquid viscosity were analyzed. The measurement results were compared with the theoretical predictions. The wavy surface was observed in the case of low viscosity water, but not in the high viscosity aqueous glycerol solutions. The sheet thickness increased as the circumferential angle increased or the distance from the impinging point increased, but the thickness decreased as the circumferential angle increased around the impinging point. As the jet speed increased, the sheet thickness decreased, and the sheet thickness increased as the liquid viscosity increased. Comparison with the theoretical predictions showed that the measurement results agreed well in the case of low viscosity water or high viscosity liquids around the impinging point. The distribution characteristics of the sheet thickness can provide useful means for prediction of spray characteristics in splash plate injectors.

• Korean Journal of Materials Research
• /
• v.33 no.5
• /
• pp.222-228
• /
• 2023

Transition metal oxides formed by a single or heterogeneous combination of transition metal ions and oxygen ions have various types of crystal structures, which can be classified as layered structures and non-layered structures. With non-layered structures, it is difficult to realize a two-dimensional structure using conventional synthesis methods. In this study, we report the synthesis of cobalt oxide into wafer-scale nanosheets using a surfactant-assisted method. A monolayer of ionized surfactant at the water-air interface acts as a flexible template for direct cobalt oxide crystallization below. The nanosheets synthesized on the water surface can be easily transferred to an arbitrary substrate. In addition, the synthesizing morphological and crystal structures of the nanosheets were analyzed according to the reaction temperatures. The electrochemical properties of the synthesized nanosheets were also measured at each temperature. The nanosheets synthesized at 70 ℃ exhibited higher catalytic properties for the oxygen evolution reaction than those synthesized at other temperatures. This work suggests the possibility of changing material performance by adjusting synthesis temperature when synthesizing 2D nanomaterials using a wide range of functional oxides, resulting in improved physical properties.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2022.05a
• /
• pp.151-151
• /
• 2022

The impact of raindrops on the soil surface causes soil detachment, which may be estimated by measuring the kinetic energy (KE) of the raindrops. Since direct measurements of rainfall force on ground surfaces are not generally available, empirical equations are an alternative option to estimate KE from rainfall intensity (I), which has the greatest influence over soil erosion and is easily accessible. Establishing the optimal formulation for the relationship between kinetic energy and rainfall intensity has proven to be difficult. Thus, this research considered thirty-seven rainfall events observed from June 2020 to December 2021 using a laster optical disdrometer erected in Kyungpook National University to examine the characteristics of KE-I relationships. We concentrated our discussion on the formation of two different expressions of the KE, including KE expenditure (KE_exp) and KE content (KE_con). The following conclusions were drawn: (1) We employed statistical analysis to demonstrate that the KE_exp is more suitable expression for establishing an empirical rule between KE and I than the KE_con. (2) A power-law model was used to find the best correlation between KE_exp-I relationship, whereas the best match between KE_con and I were found using an exponential equation.

• Journal of Korean Society of Rural Planning
• /
• v.30 no.2
• /
• pp.69-77
• /
• 2024

As impervious area increases due to urbanization, rainfall on the impervious area does not infiltrate into the ground, and stormwater drains quickly. Low impact development (LID) practices have been suggested as alternatives to infiltrate and store water in soil layers. The practices in South Korea is applied to urban development projects, urban renewal projects, urban regeneration projects, etc., it is required to perform literature research, watershed survey, soil quality, etc. for the LID practices implementation. Prior to the LID implementation at fields, there is a need to simulate its' effect on watershed hydrology, and Storm Water Management Model (SWMM) provides an opportunity to simulate LID practices. The LIDs applied in South Korea are infiltration-based practices, vegetation-based practices, rainwater-harvesting practices, etc. Vegetation-based practices includes bio-retention cell and rain garden, bio-retention cells are mostly employed in the model, adjusting the model parameters to simulate various practices. The bio-retention cell requires inputs regarding surface layer, soil layer, and drain layer, but the inputs for the drain layer are applied without sufficient examination, while the model parameters or inputs are somewhat influential to the practice effects. Thus, the approach to simulate vegetation-based LID practices in SWMM uses was explored and suggested for better LID simulation in South Korea.

• The Journal of the Acoustical Society of Korea
• /
• v.32 no.2
• /
• pp.95-103
• /
• 2013

An underwater acoustic (UWA) communication in shallow water is strongly affected by the water surface and the seabed acoustical properties. Every reflected signal to receiver experiences a time-variant scattering in sea surface roughness and a grazing-angle-dependent reflection loss in bottom. Consequently, the performance of UWA communication systems is degraded, and high-speed digital communication is disrupted. If there is a dominant signal path such as a direct path, the received signal is modeled statistically as Rice fading but if not, it is modeled as Rayleigh fading. However, it has been known to be very difficult to reproduce the statistical estimation by real experimental evaluation in the sea. To give an insight for this scattering and grazing-angle-dependent bottom reflection loss effect in UWA communication, authors conduct experiments to quantify these effects. The image is transmitted using binary frequency shift keying (BFSK) modulation. The quality of the received image is shown to be affected by water surface scattering and grazing-angle-dependent bottom reflection loss. The analysis is based on the transmitter to receiver range and the receiver depth dependent image quality and bit error rate (BER). The results show that the received image quality is highly dependent on the transmitter-receiver range and receiver depth which characterizes the channel coherence bandwidth.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.21 no.2
• /
• pp.81-103
• /
• 1979

The weathered granite soil involves problems in its stability in soil structures depending upon the reduction of soil strength due to the water absorption, crushability, and content of colored mineral and feldspar. As an attemt to solve the problems associated with soil stability, the crushability of weathered granite soil was investigated by conducting tests such as compaction test, CBR test, unconfined compression test, direct shear test, triaxial compression test, and permeability test on the five soil samples different in weathering and mineral compositions. The experimental results are summarized as follows: The ratio of increasing dry density in the weathered granite soil was high as the compaction energy was low, while it was low as the compaction energy was increased. The unconfined compressive strength. and CBR value were highest in the dry side rather than in the soil with the optimum moisture content, when the soil was compacted by adjusting water content. However, the unconfined compressive strength of smples, which were compacted and oven dried, were highest in the wet side rather than in soil with the optimum moisture content. As the soil becomes coarse grain, the ratio of specific surface area increased due to increased crushability, and the increasing ratio of the specific surface area decreased as the compaction energy was increased. The highest ratio of grain crushability was attained in the wet side rather than in the soil with the optimum moisture content. Such tendency was transforming to the dry side as the compaction energy was increased. The effect of water on the grain crushability of soil was high in the coarse grained soil. The specific surface area of WK soil sample, when compacted under the condition of air dried and under the optimum moisture content, was constant regardless of the compaction energy. When the weathered granite soil and river sand with the same grain size were compacted with low compaction energy, the weathered granite soil with crushability had higher dry density than river sand. However, when the compaction energy reached to certain point over limitation, the river sand had higher dry density than the weathered granite soil. The coefficient of permeability was lowest in the wet side rather than in the optimum moisture content, when the soil was compacted by adjusting soil water content. The reduction of permeability of soil due to the compaction was more apparent in the weathered granite soil than in the river sand. The highly significant correlation coefficient was obtained between the amount of particle breakage and dry density of the compacted soil.

• Journal of Multimedia Information System
• /
• v.4 no.4
• /
• pp.195-204
• /
• 2017

Mobile robots are used for years as a valuable research and educational tool in form of available open-platform designs and Do-It-Yourself kits. Rapid development and costs reduction of Unmanned Air Vehicles (UAV) and ground based mobile robots in recent years allowed researchers to utilize them as an affordable research platform. Despite of recent developments in the area of ground and airborne robotics, only few examples of Unmanned Surface Vehicle (USV) platforms targeted for research purposes can be found. Aim of this paper is to present the development of open-design USV drone with integrated multi-level control hardware architecture. Proposed catamaran - type water surface drone enables direct control over wireless radio link, separate development of algorithms for optimal propulsion control, navigation and communication with the ground-based control station. Whole design is highly modular, where each component can be replaced or modified according to desired task, payload or environmental conditions. Developed USV is planned to be utilized as a part of the system for detection and identification of marine and lake waste. Cameras mounted to the USV would record sea or lake surfaces, and recorded video sequences and images would be processed by state-of-the-art computer vision and machine learning algorithms in order to identify and classify marine and lake waste.