• Membrane Journal
• /
• v.33 no.6
• /
• pp.377-382
• /
• 2023

In this study, a PEBAX/PVDF composite membrane was fabricated, and its pervaporation performance was tested in an ethanol/water mixture. In addition, we attempted to improve the pervaporation performance of the composite membrane by forming a ZIF-8 layer on the surface of the PVDF substrate. The thickness of selective layer was optimized by comparing the pervaporation performance depending on the PEBAX thickness. A pervaporation test was performed on the Ethanol/Water mixture. As a result, the composite membrane using PVDF substrate with ZIF-8 layer had a flux of 1.98 kg/m²h and separation factor of 3.88, showing higher values of both permeation flux and selectivity than the composite membrane using bare PVDF substrate.

• Journal of Aerospace System Engineering
• /
• v.17 no.4
• /
• pp.118-125
• /
• 2023

The wind tunnel test is one of the essential processes in the development of guided missile systems, and various wind tunnel facilities exist depending on the test requirements, various conditions, and their purposes. The Ludwieg tube is very useful in the development of guided missile systems, and we have necessitated the upgrade of the Ludwieg tube in ADD to acquire various test requirements, such as high angle of attack, repeatability, and stability. In this paper, upgrading the nozzle, vacuum tank, and model support is suggested to improve the Ludwieg tube performance, and we demonstrate a result of the solution through pressure measurement.

• Journal of Korean Society of Steel Construction
• /
• v.16 no.3 s.70
• /
• pp.377-385
• /
• 2004

An experimental and analytical study on the behavior of the wall-support joint in SC(steel plate-concrete) structure was performed. Nine full-scale specimens were tested with a horizontal monotonic load, all acting in the same plane, causing a uni-axial moment on the SC structure's wall-support beam joint. The main focus is to examine thenonlinear behavior and ultimate strength of the SC wall-support joint. The effects of parameters, such aslocation of support, thickness of the steel plate, and size of support, were studied. The yield strength and ultimate strength of the plate-concrete wall was defined by examining the load-deflection relationship, showing the tension membrane action.

• The KIPS Transactions:PartB
• /
• v.17B no.3
• /
• pp.249-254
• /
• 2010

We propose an automatic spam filter for e-mail data using Support Vector Machines(SVM). We use a lexical form of a word and its part of speech(POS) tags as features and select features by chi square statistics. We represent each feature by TF(text frequency), TF-IDF, and binary weight for experiments. After training SVM with the selected features, SVM classifies each e-mail as spam or not. In experiment, the selected features improve the performance of our system and we acquired overall 98.9% of accuracy with TREC05-p1 spam corpus.

• Korean Chemical Engineering Research
• /
• v.54 no.4
• /
• pp.510-518
• /
• 2016

Ethyl cellulose-g-poly(ethylene glycol) (EP) was synthesized by esterification of carboxylic acid functionalized methoxy polyethylene glycol (MPEG-COOH) with ethyl cellulose (EC) in order to develop a hydrophilic substrate for thin-film composite (TFC) membrane in a forward osmosis (FO) system. A porous EP substrate, fabricated by a non-solvent induced phase separation method, was found to be more hydrophilic than the EC substrate due to the presence of polyethylene glycol (PEG) side chains in the EP. Since the EP substrate exhibits smaller water contact angles and higher porosity, the structural parameter (S) of TFC-EP is smaller than that of TFC-EC, indicating that internal concentration polarization (ICP) within porous substrates can occur less when TFC-EP is used as a membrane. For example, the water flux value of the TFC-EP is 15.7 LMH, whereas the water flux value of the TFC-EC is only 6.6 LMH. Therefore, we strongly believe that the TFC-EP could be a promising candidate with good FO performances.

• Membrane Journal
• /
• v.11 no.2
• /
• pp.83-88
• /
• 2001

A methodology for enhancing the bond strength of a coating layer with a support has been established in preparing low-pressure reverse osmosis mO) hollow fiber which would experience shear badly in flowing feed un it. Prior to coating process, the support membrane, ultrafiltratiun polysulfone(PS) hollow fibers was pretreated with a reaction solution containing glutaraldehyde (GAl which has a good affinity to the suppurt membrane material as well as a reactivity to some of the cunstituents of cuating layer subsequently formed on the support by interfacial polymerization. Therefore, the reactant GA distributed unifonnly over the support layer through the pretreatment could provide a strong adhesive bond between the coating layer and the support, sticking fast to the support membrane through physical bond and, at the same time, connecting its functional group with the coating laycr by chemical bonding. Due to the strong adhesive bond, the resulting hollow fiber membrane showed an excellent long-tcnn stability in pcnneation.

• Journal of the Korean Geosynthetics Society
• /
• v.15 no.1
• /
• pp.37-46
• /
• 2016

Rotary pile consists a single or multiple helix plate and it is installed into the ground using the rotation of the helix plate. Rotary pile in soft ground is able to be supported by pile shaft and helix plate. When the pile is installed into hard layer relatively, the end bearing capacity is possible to be increased by the lower helix plate. In this paper, small-size rotary piles were manufactured with using steel pipe which is reduced to 1/5 size of the rotary pile on the construction field. Pile load test was carried out on the foundation soil which was formed by weathered soft soil. The bearing capacity of small-scale piles depends on the number of helix plate, the length of plate diameter, and an interval of plates, respectively. The bearing capacity of pile increases about 40% with 3 helix plate and it is also confirmed that the bearing capacity is improved about 10% as the increment of plate interval.

• Journal of the Korean GEO-environmental Society
• /
• v.24 no.1
• /
• pp.37-44
• /
• 2023

In this study, the performance of the support modular system, as substructure of the proposed sustainable-perpetual modular road system to reduce road construction time and maintenance costs was evaluated. A modular road system consisting of 4 support modular cross-beams with a lower curved surface was constructed on the test-bed. Six load cells and eight LVDTs were installed in the center part of two cross-beam support modular systems. Two loads, 50kN and 100kN, were applied to 15 points on the pavement slab to measure the load and displacement occurring in the modular road system. The measured displacements were less than 1 mm, so it is considered that there was no problem in the stability of the actual road. When comparing the two applied loads and the measured loads in the field test, it was considered that the load transmitted to the ground under the support modular system is very small. It is considered that the modular road system with the support modular system is applicable to the actual road site.

• Korean Chemical Engineering Research
• /
• v.50 no.4
• /
• pp.749-753
• /
• 2012

In present work, anode support for micro-tubular SOFC was fabricated with outer diameter of 3 mm and characterized with microstructure, mechanical properties and gas permeability. The microstructure of surface and cross section of a porous anode support were analyzed by using SEM (Scanning Electron Microscope) image. The gas permeability and the mechanical strength of anode support was measured and analysed by using differential pressure at the flow rates of 50, 100, 150 cc/min. and using universal testing machine respectively. The unit cell composed of NiO-YSZ, YSZ, YSZ-LSM/LSM/LSCF was fabricated and operated with reaction temperature and fuel flow rate and showed maximum power density of $1095mW/cm^2$ on the condition of $800^{\circ}C$. The performance of single cell for micro-tubular SOFC increased with the increasing the reaction temperature due to the decrement of ohmic resistance of cell by the increment of the ionic conductivity of electrolyte through the evaluation of electrochemical impedance analysis for single cell with reaction temperature.

• Korean Chemical Engineering Research
• /
• v.61 no.3
• /
• pp.341-347
• /
• 2023

In PEMFC, PtCo/C alloy catalysts are widely used because of good performance and durability. However, few studies have been reported on the durability of carbon supports of PtCo/C evaluated at high voltages (1.0~1.5 V). In this study, the durability of PtCo/C catalysts and Pt/C catalysts were compared after applying the accelerated degradation protocol of catalyst support. After repeating the 1.0↔1.5V voltage change cycles, the mass activity, electrochemical surface area (ECSA), electric double layer capacitance (DLC), Pt dissolution and the particle growth were analyzed. After 2,000 cycles of voltage change, the current density per catalyst mass at 0.9V decreased by more than 1.5 times compared to the Pt/C catalyst. This result was because the degradation rate of the carbon support of the PtCo/C catalyst was higher than that of the Pt/C catalyst. The Pt/C catalyst showed more than 1.5 times higher ECSA reduction than the PtCo/C catalyst, but the corrosion of the carbon support of the Pt/C catalyst was small, resulting in a small decrease in I-V performance. In order to improve the high voltage durability of the PtCo/C catalyst, it was shown that improving the durability of the carbon support is essential.