• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.247-250
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• 2005

Underwater acoustic transducers are widely used for SONAR application, whose important design parameters are shapes, materials, dimensions and supporting structures. Practical design method of transducers consists of manufacturing, experiments and modifications so that It requires much time and expenses. In this study, an analytical method was developed for the Tonpilz type transducers using the commercial finite element analysis code ATILA which can solve the electro-mechanical coupling Problems. A finite element model was established including the transducer elements such as ceramic stack, head mass, tall mass, tensile bolt, and molding layers. The proposed model was verified and modified by comparing the in-air and in-water test results of prototypes. The developed analysis method will be effectively used for the sensitivity analysis of design parameters in transducer design process.

• Bulletin of the Society of Naval Architects of Korea
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• v.23 no.2
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• pp.21-26
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• 1986

An analysis is made of hydrodynamic forces acting horizontally on a two-dimensional cylinder, when it is exposed to incident waves and consequently undergoes a swaying motion in shallow water. Applying the method of matched asymptotic expansions the added mass, wave damping and the wave exciting force are obtained in terms of the difference in potential across the cylinder in a simple manner. The potential jump is related to the so-called blockage coefficient which is determined purely from geometry. It is found that the wave damping coefficient can not exceed the blockage coefficient.

• Proceedings of the PSK Conference
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• 2000.04a
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• pp.133.2-133.2
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• 2000

• Journal of Korean Society of Environmental Engineers
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• v.37 no.11
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• pp.649-655
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• 2015

As a novel water treatment membrane, concept of ceramic-based graphene membrane (CbGM) was suggested, and its mass transport behavior was investigated. The selectivity of CbGM was given by graphene material which is consisting of active layer, only transmitting water, but rejecting salts. Filtration-assisted assembly methods was employed as a facile method to fabricate CbGM. Surface morphology and characteristics of CbGM were analyzed by scanning electron microscopy (SEM) and contact angle. In addition, three different kinds of solutes (i.e., NaCl, $MgCl_2$, $Na_2SO_4$) were tested in batch forward osmosis system to confirm the mass transport behavior. Through surface morphology analysis and mass transport behavior, it was revealed that interlocking between graphene layers is very important, rather than thickness of laminated graphene layers, in terms of selectivity to CbGM. All the anions in each solute showed faster transport than those of cations. In addition, solutes which have high ion valence charge ratio of anion to cation ($Z^-/Z^+$) was easier to be passed through CbGM. It indirectly implied that the surface charge of CbGM appear to be positive. In addition, It showed that surface charge of CbGM has a great role on mass transport, in particular, transport of matter having charges, generally ions.

• Mass Spectrometry Letters
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• v.13 no.4
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• pp.166-176
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• 2022

Banana peels are also widely used as bio-adsorbent in the removal of chemicals contaminants and heavy metals from water and soil. GC-MS plays an essential role in the phytochemical analysis and chemo taxonomic studies of medicinal plants containing biologically active components. Intrinsically, with the use of the flame ionization detector and the electron capture detector which have very high sensitivities, Gas chromatography can quantitatively determine materials present at very low concentrations and most important application is in pollution studies. In the present study banana peels were used as bio-adsorbent to remediate the heavy metal contaminated water taken from three different stations located around the industrial belts of Ranipet, Tamilnadu, India. The AAS analysis of the samples shows a decrement of chromium concentration of 98.93%, 96.16% and 96.5% in Station 1, 2 and 3 respectively which proves the efficiency of the powdered peels of Musa paradisiaca. The GC-MS analysis of the control and treated peels of Musa paradisiaca reveals the presence of phytochemicals like Acetic Acid, 1-Methylethyl Ester, DL-Glyceraldehyde Dimer, N-Hexadecanoic Acid, 3-Decyn-2-Ol, 26-Hydroxy, Cholesterol, Ergost-25-Ene-3,5,6,12-Tetrol, (3.Beta.,5.Alpha.,6.Beta.,12.Beta.)-, 1-Methylene-2b-Hydroxymethyl-3, and 3-Dimethyl-4b-(3-Methylbut-2-Enyl)-Cyclohexane in the control banana peels. The banana peels which were used for the treatment reveals the changes and alteration of the phytochemicals. It is concluded that the alteration in phytochemicals of the experimental banana peels were due to adsorption of chromium heavy metal from the sample.

• Journal of Korean Society on Water Environment
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• v.29 no.4
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• pp.489-496
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• 2013

Ground water underlying soil is vulnerable to pollution by organic chemicals through their percolation through the soil system. This study was conducted to provide information on the seepage behavior of organic chemical contaminants in clay, silty and sandy soils. Chloroform, 1,1,1-trichloroethane and trichloroethylene are readily transported through the soil; their percolated mass were 4.6-19.2 percent of the total mass applied. Tetrachloroethylene, 1,2-dichlorobenzene and 1,3-dichlorobenzene were retarded by soils due to sorption. Between 0.6 and 4.8 percent of the material applied to the surface percolated within the experimental period. Carbon tetrachloride was attenuated considerably by passage through soils. Only 0.1-0.4 percent of the mass reached the groundwater. Significant degradation of bromoform was observed. Apparent breakdown of intermediates of the brominated compounds were detected. Transformations of the brominated compounds appear to be the result of both biological and chemical processes. The effect of soil type on the mobility of organic chemical contaminants was considerable. The organic contaminants moved faster in sandy soil than in either clay or silty soils.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.7
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• pp.373-384
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• 2017

The objective of this study was to determine the effect of refrigerant heat exchanger on the performance of type II absorption heat pump performance using numerical analysis. Two heat exchange installation methods were used: solution to refrigerant and waste hot water to refrigerant. These methods were compared to the standard model of hot water flow without using refrigerant heat exchanger. When waste hot waters were bypassed to refrigerant heat exchanger, COP was not affected. However, steam mass generation rates were increased compared to those of the standard model. When solutions were bypassed to the refrigerant heat exchanger, results were different depending on the place where the solution rejoined. COP and steam mass generation rates were lower compared to those when waste heat water was passed to refrigerant heat exchanger. Thus, it is possible to obtain higher steam mass generation rates by using waste water and installing refrigerant heat exchanger.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.4
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• pp.461-472
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• 2014

The tap water plays a critical role in our daily life by providing clean water for drinking as well as for residential use. Its importance, however, is often hidden and criticized in mass media because drinking the unprocessed tap water as a primary source of drinking water is very low comparing to other countries. This is because survey tool in Korea is often different from those in other countries so their results on the tap water cannot be directly compared without analysis on survey questionnaire. Therefore, we examplified cases showing the difference of questions of each country and discussed the reason why results of tap water intake should not be compared without analysis on the questions. Also, distrust on Arisu without rational reason is known as the first reason of distrust on the tap water. However, it was not the ultimate reason of distrust on the tap water. To verify, we designed survey questions in a tricky way that the same question was asked twice with different choices in the survey questionnaire. Most of the people who distrust Arisu without rational reason at the first question were selected different choices and significantly reduced in the second question. This proved that the ratio of distrust on the tap water is not actually the right reason and that by providing more choices, people's distrust on the tap water without rational reason can turn into more specific reasons.

• Journal of Navigation and Port Research
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• v.32 no.9
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• pp.705-709
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• 2008

In the sea various methods have been conducted to capture wave energy which include the use of pendulums, pneumatic devices, etc. Floating devices, such as a cavity resonance device take advantages of both the water motion and the wave induced motions of the floating body itself. The wave energy converter is known commercially as the WAGB(Wave Activated Generator Buoy) and is used in some commercially available buoys to power navigation aids such as lights and horns. This wave energy converter consists of a circular flotation body which contains a vertical water column that has free communication with the sea. A theoretical analysis of this power generated by a pneumatic type wave energy converter is performed and the results obtained from the analysis are used for a real wave energy converter buoy. This paper is shown to have an optimum value for which maximum power is obtained at a given resonant wave period Also, the length of the internal water column corresponds to that of the water mass in the water column. If designed properly, wave energy converter can take advantage not only of the cavity resonance, but also qf the heaving motion of the buoy. Finally, simulation is performed with a LabVIEW program and the simulation results are applied to a wave energy simulator for modifying design data for a wave energy converter.

• 연구논문집
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• s.29
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• pp.5-15
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• 1999

Present study deals with performance analysis of an inert gas generator (IGG) which is to be used as an effective mean to suppress the fire. The IGG uses a turbo jet cycle gas turbine engine to generate inert gas for fire extinguishing. It is generally known that a lesser degree of oxygen content in the product of combustion will increase the effectiveness of fire suppressing. An inert gas generator system with water injection will bring advantages of suffocating and cooling effects which are considered as vital factors for fire extinguishing. As the inert gas is injected to the burning site, it lowers the oxygen content of the air surrounding the flame as well as reduces the temperature around the fire as the vapour in the inert gas evaporates during the time of spreading. Some important aspects of influencing parameters, such as, air excess coefficient. $\alpha$, compressor pressure ratio, $ pi_c$, air temperature before combustion chamber, $T_2$, gas temperature after combustion chamber, $T_3$, mass flow rate of water injection, $M_w$, etc., on the performance of IGG system are investigated. Calculations of total amount of water needed to reduce the turbine exit temperature to pre-set nozzle exit temperature employing a heat exchanger were made to compare the economics of the system. A heat exchanger with two step cooling by water and steam is considered to be better than water cooling only. Computer programs were developed to perform the cycle analysis of the IGG system and heat exchanger considered in the present study.