• Journal of Korean Society of Water and Wastewater
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• v.30 no.2
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• pp.131-137
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• 2016

The development of alternative water resources has emerged as an effective method for solving drought of water resources due to extreme weather and increase in water consumption. Recently, in Korea, there has been active research on reverse osmosis desalination technology, wastewater reuse using forward osmosis membranes, and the forward osmosis(FO)-reverse osmosis(RO) hybrid process combining these two technologies. In this study, the basic performance of FO membranes manufactured by three domestic and international manufactures such as Microfilter Co., Ltd., Toray Chemical Korea Inc., and Hydration Technologies Inc., were investigated for wastewater reuse. In addition, as an experiment to select feed solution, the selected membranes were operated 48 consecutive hours using three secondary effluents pretreated by the UF membrane with a pore size of $0.1{\mu}m$ and auto strainer with pore sizes of $1{\mu}m$ and $100{\mu}m$ as feed solution. Although there was not much difference in the operating performance. Thus, the treated water using the $100{\mu}m$ auto strainer was selected as feed solution applied to the assessment.

• Membrane and Water Treatment
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• v.13 no.2
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• pp.63-72
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• 2022

Choline chloride-glycerol (1:2 mol), a natural deep eutectic solvent (NADES) is examined as a draw solution in forward osmosis (FO) for dewatering application. The NADES is easy to prepare, low in toxicity and environmentally benign. A polyamide thin film composite membrane was used. Characterization of the membrane confirmed porous membrane structure with good hydrophilicity and a low structural parameter (722 ㎛) suitable for FO application. A dilute solution of 20% (v/v) NADES was enough to generate moderate water flux (14.98 L m^-2h^-1) with relatively low reverse solute flux (0.125 g m^-2h^-1) with deionized water feed. Application in dewatering industrial wastewater feed showed reasonably good water flux (11.9 L m^-2h^-1) which could be maintained by controlling the external concentration polarization and fouling/scaling mitigation via simple periodic deionized water wash. In another application, clarified sugarcane juice could be successfully concentrated. Recovery of the draw solute was accomplished easily by chilling utilizing thermo responsive phase transition property of NADES. This study established that low concentration NADES can be a viable alternative as a draw solute for dewatering of wastewater and other heat sensitive applications along with a simple recovery process.

• Membrane Journal
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• v.26 no.3
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• pp.187-196
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• 2016

Pressure-assisted forward osmosis (PAFO) process has recently been under spotlight for its potential to improve forward osmosis (FO) process performance by applying low hydraulic pressure on the feed side. Structure parameter, one of the governing factors in estimating water flux and solute flux across FO membranes in the solution-diffusion model (S-D model), determines solute resistivity in FO and PAFO processes. This study aims to estimate the trend of structure parameter change with respect to varying additional hydraulic pressure condition in PAFO.

• Membrane Journal
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• v.28 no.3
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• pp.196-204
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• 2018

The anaerobic fluidized bed bioreactor (AFBR) treating synthetic wastewater to simulate domestic sewage was operated under GAC fluidization to provide high surface area for biofilm formation. Although the AFBR achieves excellent COD removal efficiency due to biological activities, concerns are still made with nutrient such as nitrogen remaining in the effluent produced by AFBR. In this study, forward osmosis membrane was applied to treat the effluent produced by AFBR to investigate removal efficiency of total nitrogen (TN) with respect to the draw solution (DS) such as NaCl and glucose. Permeability of FO membrane increased with increasing DS concentration. About 55% of TN removal efficiency was observed with the FO membrane using 1 M of NaCl of draw solution, but almost complete TN removal efficiency was achieved with 1 M of glucose of draw solution. During 24 h of filtration, there was no permeate flux decline with the FO membrane regardless of draw solution applied.

• Journal of the Korean Chemical Society
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• v.23 no.1
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• pp.7-14
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• 1979

Changes in CD, ORD and uv-spectra during the mutarotation of poly(trans-5-methyl-L-proline) (PTMP) were studied. The forward mutarotion of PTMP occurred in strong organic acids and trifluoroethanol, while the reverse mutarotation was observed by dilution of the trifluoroethanol solution with excess aliphatic alcohols. The changes in CD, ORD and uv-spectra during the forward and reverse mutarotation proceeded paralell to those found for the mutarotation of polyproline. The chemical shift of the ${\alpha}CH-$proton was shifted downfield about 0.3 ppm during the forward mutarotation. The reduced viscosity for the forward mutarotation increased from 0.15 to 0.26 (dl/g) during 5 days. The equilibrium between form I and form II was estabilished in an appropriate solvent mixture. All changes in solution properties mentioned above are similar to those found for polypoline. These results support that the two forms of PTMP are the same conformations as polyproline form I and form II, i. e., a right-handed helix with all cis amide bonds and a lefthanded helix with all trans amide bonds.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1309_1310
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• 2009

The topology of active clamp forward converter provides ZVS characteristic and also the stress of voltage and current is smaller than that of the conventional forward converters. The benefits of this technique include a higher efficiency at a high switching frequency, lower EMI/RFI. In this paper, the active clamp forward converter is designed for operation in wide range voltage and has 19.5V/120W ratings with efficiency more than 90%.

• Journal of Digital Contents Society
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• v.8 no.3
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• pp.393-401
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• 2007

P2P systems have gained a lot of research interests and popularity over the years and have the capability to unleash and distribute awesome amounts of computing power, storage and bandwidths currently languishing - often underutilized - within corporate enterprises and every Internet connected home in the world. Since there is no central control over resources or devices and no before hand information about the resources or devices, device discovery remains a substantial problem in P2P environment. In this paper, we cover some of the current solutions to this problem and then propose our feed forward neural network (FFNN) based solution for device discovery in mobile P2P environment. We implements feed forward neural network (FFNN) trained with back propagation (BP) algorithm for device discovery and show, how large computation task can be distributed among such devices using agent technology. It also shows the possibility to use our architecture in home networking where devices have less storage capacity.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.1
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• pp.93-100
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• 2021

Forward osmosis (FO) process is a chemical potential driven process, where highly concentrated draw solution (DS) is used to take water through semi-permeable membrane from feed solution (FS) with lower concentration. Recently, commercial FO membrane modules have been developed so that full-scale FO process can be applied to seawater desalination or water reuse. In order to design a real-scale FO plant, the performance prediction of FO membrane modules installed in the plant is essential. Especially, the flux prediction is the most important task because the amount of diluted draw solution and concentrate solution flowing out of FO modules can be expected from the flux. Through a previous study, a theoretical based FO module model to predict flux was developed. However it needs an intensive numerical calculation work and a fitting process to reflect a complex module geometry. The idea of this work is to introduce deep learning to predict flux of FO membrane modules using 116 experimental data set, which include six input variables (flow rate, pressure, and ion concentration of DS and FS) and one output variable (flux). The procedure of optimizing a deep learning model to minimize prediction error and overfitting problem was developed and tested. The optimized deep learning model (error of 3.87%) was found to predict flux better than the theoretical based FO module model (error of 10.13%) in the data set which were not used in machine learning.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1624-1627
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• 1997

The 6-DOF parallel manipulator is a closed-kindmatic chain robot manipulator that is capable of providing high structural rigidity and positional accuracy. Because of its advantage, the parallel manipulator have been widely used in many engineering applications such as vehicle/flight driving simulators, rogot maniplators, attachment tool of machining centers, etc. However, the kinematic analysis for the implementation of a real-time controller has some problem because of the lack of an efficient lagorithm for solving its highly nonliner forward kinematic equation, which provides the translational and orientational attitudes of the moveable upper platform from the lenght of manipulator linkages. Generally, Newton-Raphson method has been widely sued to solve the forward kinematic problem but the effectiveness of this methodology depend on how to set initial values. This paper proposes a hybrid method using genetic algorithm(GA) and Newton-Raphson method to solve forward kinematics. That is, the initial values of forward kinematics solution are determined by adopting genetic algorithm which can search grobally optimal solutions. Since determining this values, the determined values are used in Newton-Raphson method for real time calcuation.

• Membrane Journal
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• v.24 no.5
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• pp.400-408
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• 2014

This study is to evaluate the performance of draw solutions in forward osmosis desalination using fertilizer as draw solution. Considering osmotic pressure, solubility, and pH, $NH_4NO_3$, $NH_4H_2PO_4$, $(NH_4)_2HPO_4$, KCl, $KNO_3$, and $KHCO_3$ were screened from a comprehensive lists of fertilizer. Their performance were evaluated in terms of pure water permeate flux, reverse solute flux, and specific reverse solute flux for nitrogen and phosphorus. KCl showed the highest pure water permeate flux among the selected fertilizers while $(NH_4)_2HPO_4$ draw solution had the lowest flux. $NH_4H_2PO_4$ showed the lowest reverse solute flux and specific reverse solute flux for nitrogen followed by $(NH_4)_2HPO_4$, $KNO_3$, and $NH_4NO_3$. Although the pure water permeate flux of $NH_4H_2PO_4$ is lower than the other draw solutions, because it contains both nitrogen and phosphorus, and have the lowest reverse solute flux and specific reverse solute flux, it is a promising candidate as draw solution for forward osmosis desalination.