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        검색결과 6

        1.
        2021.01 KCI 등재 서비스 종료(열람 제한)
        To reduce pollution, decrease the production of carbon dioxide, and to maintain a secure supply of energy, interest continues to grow in the area of renewable energy especially since there is a finite supply of cheap oil. Wind energy is one of the most viable options to consider and supply part of the energy needed to reduce dependence on foreign oil. However, it is difficult to predict the wind speed in an environment with many obstacles such as buildings and trees and getting accurate dimensions of those obstacles is difficult particularly on sloped mountainous terrain. In this study a drone was used to create a 3-D map of the campus of the Catholic University of Pusan. The dimensions and elevations for the 3-D map were used to make a model of the school campus in the CFD program Envi-met. Simulations were run for five different wind directions and 4 different elevations to find the location that would give the highest electrical output for a wind turbine. When considering all of these variables it was found that the optimal location was above the Student Union which had a 40% higher wind speed and could produce 274% more electrical power than the original wind speed.
        2.
        2018.10 KCI 등재 서비스 종료(열람 제한)
        Water and oxygen are two of the most essential molecules for many species on earth. Their unique properties have been studied in many areas of science. In this study, the interaction of water and oxygen molecules was observed at the nano-scale. Using molecular dynamics, a water droplet with 30,968 water molecules was simulated. Then, 501 oxygen molecules were introduced into the domain. A few oxygen molecules were attracted to the surface of the water droplet due to van der Waals forces, and some oxygen molecules actually entered the water droplet. These interactions were visualized and quantified at four temperatures ranging from 280 to 370 K. It was found that at high temperatures, there was a higher possibility of the oxygen molecules penetrating the water droplet than that at lower temperatures. However, at lower temperatures, oxygen molecules were more likely to be found interacting at the surface of the water droplet than at high temperatures.
        3.
        2016.07 KCI 등재 서비스 종료(열람 제한)
        Dissolved oxygen is necessary for many biological processes as well as many industrial practices. Dissolved oxygen released from water in dissolved air flotation (DAF) systems can be have many different applications. However, DAF systems are very costly to operate. To develop more efficient DAF systems, a deeper understanding of the process of oxygen being released from water is required. In this study, molecular dynamics (MD) simulations were used to simulate 100 oxygen molecules surrounded by 31002 water molecules at temperatures ranging from 0℃ to 100℃. Simulations were carried out for 10 ns, during which, in most cases, all the oxygen molecules were released from the water droplet. With MD simulations, visualization of the molecules escaping the water droplet was possible, which aided the understanding of the interactions between molecules at the nano-scale. The results showed that as the oxygen molecules moved near the edge of the water droplet that the oxygen molecules hesitated before escaping the water droplet or returned to the interior of the water droplet. This was because of the attractive forces between the water and oxygen molecules. Moreover, after most of the oxygen molecules were released from the droplet, some were found to return to the droplet's edge or even the interior of the droplet. It was also confirmed that oxygen molecules were released at a faster rate at higher temperatures.
        4.
        2016.06 KCI 등재 서비스 종료(열람 제한)
        The mechanism of micro-bubble generation with a pump is not clarified yet, so the design of water treatment systems with a micro-bubble generating pump is based on trial and error methods. This study tried to explain clearly quantitative relationships of experimental micro-bubble concentration (Cair) of continuous operation tests with a micro-bubble generating pump and theoretical air solubility. Operation parameters for the tests were discharge pressure (Pg), water (Qw0) and air (q0) flow rates, orifice diameter (DO), and retention time (t). The experimental micro-bubble concentrations (Cair) at 4.8 atm of discharge pressure (Pg) were in the range of 21.04 to 25.29 mL/L. When the retention time (t) by changing the pipe line length (LP) increased from 1.22 to 6.77s, the experimental micro-bubble concentrations (Cair) increased from 25.86 to 30.78 mL air/L water linearly. The dissolved and dispersed micro-bubble concentrations (Cair) are approximately 4 times more than the theoretical air solubility.
        5.
        2013.10 KCI 등재 서비스 종료(열람 제한)
        Na-A zeolite (Z-Cl) was synthesized from coal fly ash, which is a byproduct of coal combustion for the generation of electricity. The adsorption of Cu2+ and Zn2+ions onto Z-C1 was investigated via batch tests over a range of temperatures (303.15 to 323.15 K). The resultant experimental equilibrium data were compared to theoretical values calculated using model equations. With these results, the kinetics and equilibrium parameters of adsorption were calculated using Lagergren and Langmuir-Freundlich models. The adsorption kinetics revealed that the pseudo second-order kinetic mechanism is predominant. The maximum adsorption capacity (qmax) values were 139.0-197.9 mg Zn2+/g and 75.0-105.1 mg Cu2+/g. Calculation of the thermodynamic properties revealed that the absorption reactions for both Cu2+and Zn2+ were spontaneous and endothermic. Collectively, these results suggest that the synthesized zeolite, Z-C1, can potentially be used as an adsorbent for metal ion recovery during the treatment of industrial wastewater at high temperatures.
        6.
        2013.04 KCI 등재 서비스 종료(열람 제한)
        The flow of sewage has been studied for hundreds of years. Reducing drag in pipes can allow sewer to be removed easily and quickly. Drag reduction is not only a macroscale issue. Physical and chemical properties of the nano-scale can affect flow at the macroscopic scale. In this paper the predictability of hydrophobicity at the nano-scale is studied. Molecular dynamics simulations were used to calculate the range of contact angles of water droplets in equilibrium on a pillared graphite surface. It was found that at a pillar height of two graphite layers there was the largest range of contact angles. It is observed that at this height the droplet begins to transition from the Wenzel state to the Cassie-Baxter state. Surfaces with larger pillar heights have much larger contact angles corresponding to a more hydrophobic surface. Silicon dioxide was also simulated in the water droplet. The contaminant slight decreased the contact angle of the water droplet.