Jo Apr 8, 2024
Short bed ion exchange technology utilizes fine mesh resin beads, a fully packed resin bed, and counter-current regeneration. These unique features help to improve exchange kinetics, reduce regenerant consumption and increase the concentration of strip solutions. Commercially, this technology has been extensively used in the following areas: separation and purification of strong mineral acids, removal and recycle of dissolved metals in the surface finishing industries, and production of high purity water.
The most frequent questions concerning short-bed ion exchange relate to flow distribution, because the column is only a few centimeters tall and it has to treat tremendous amount of solution in a short time.
There have been a lot of introductions of the advantages of a short-bed ion exchange column, but no articles on its detailed geometric size and design have been published yet. What is more, no information has been found on the influence of the structure and geometric size of a flow distribution plate on the flow distribution characteristics of the short-bed ion exchange column and on the optimal design based on the influence.
Kim Yong Min, a section head at the Faculty of Chemical Engineering, has discussed the influences of several parameters on flow distribution in Recoflo by using CFD program and consequently done some research to design a reasonable flow distribution plate for optimization of ion exchange processes and enhancement of separation efficiency.
The simulation results showed that 60 radial flow channels and 3 circumferential flow channels were the reasonable parameters for ensuring even flow distribution through the bed in the short-bed ion exchange column.
...
Jo Apr 5, 2024
Plastic products have high productivity for their high corrosion resistance and large-quantity injection molding. When they are coated with metal decoration, they have higher durability and shock-resistance. It means they have longer life time.
Extrinsic decoration methods include evaporation, plating and electrophoresis, of which plating is most widely used. The most suitable plastic for plating is acrylonitrile-butadiene-styrene (ABS).
Decorative nickel plating of acrylonitrile-butadiene-styrene (ABS) plastics has depended on pretreatment of precious metals including Cr and Pd, but it is subject to restriction due to both environmental pollution by chromium oxides and increasing prices of precious metals.
Kim Kyong Chol, a researcher at the Faculty of Chemical Engineering, has found a reasonable method of etching and forming a conducting layer in the pretreatment process of plastic products, and investigated the influences of some factors.
Permanganate was used for etching and the conducting layer was formed by complexing agent of tartaric acid and lactic acid. First, he investigated the etching characteristics in terms of amounts of potassium permanganate, phosphoric acid and sulfuric acid, and then, he assessed the characteristics of the conducting layer with respect to the amounts of metal ion, mixed ligand and temperature.
The scanning electron microscope (SEM) images, X-ray diffraction (XRD) patterns and electric resistances confirmed that the current etching is environmentally friendly and the electric resistance of formed Cu2S is below 50Ω/cm2.
...
Jo Mar 29, 2024
In recent decades, temperature/pH dual responsive amphiphilic polymers have attracted the interest of researchers because they can perform certain functions by changing the hydrophilic hydrophobic balance in conformity with changes in the external environment. Therefore, these types of amphiphilic polymers are very useful, especially for drug delivery, tissue engineering, biotechnology, and related fields.
However, most of the temperature/pH dual responsive polymers are prepared using petroleum chemical monomers as the main raw material and their use has biocompatibility and toxicity problems. In recent years, many researchers have focused on biomass derivatives to improve the temperature/pH dual responsiveness of polymers.
Jong Kwang Hyok, a section head at the Faculty of Chemical Engineering, has synthesized a novel type of temperature-pH dual responsive amphiphilic hydrogel, PD(Hydroxyethyl starch(HES)-propynyl glycidylether(PGE)-2-dimethylamino ethanethiol (DMAET)- Triethoxyvinylsilane(TEVS)) and studied its characteristics.
First, HES, a hydrophilic polysaccharide, underwent etherification of hydroxyl groups in its glucose units with PGE and then click reaction between carbon-carbon triple bonds in PGE and thiol groups in DMAET, thereby possessing a hydrophilic-hydrophobic structure to be used for the preparation of PD, a temperature-pH dual responsive material, with pH-responsive tertiary amine groups. Next, it further became a dual responsive hydrogel through the formation of its internal network by TEVS.
He found that during the test experiments to use it as a drug carrier for oral delivery, the doxorubicin(DOX) release was ≤15% in acidic conditions in the stomach (pH < 2.0) and ≤94% in basic conditions in the small intestine, which ensures that it exhibits relatively good protective and release properties of drugs.
You can find the details in his paper “ Preparation of temperature-pH dual responsive hydrogel from hydroxyethyl starch for drug delivery” in “Colloid and Polymer Science” (SCI).
...
Jo Mar 28, 2024
Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier modulation technique widely used in different wireless communication systems such as Digital Video Broadcasting (DVB), Digital Radio Mondiale (DRM), Wireless Local Area Network (WLAN), Long Term Evolution (LTE), etc.
But OFDM signals are prone to suffer from spectral spreading and in-band distortion due to the large envelope fluctuations.
As solutions to this problem, several methods have been presented. For reducing the signal envelope fluctuations without any in-band distortion, some methods such as Partial Transmit Sequence (PTS), Selected Mapping (SLM) and their hybrid techniques have been investigated, but they are in high computational complexity and need side information. Tone Reservation (TR) can reduce the signal envelope fluctuations significantly, but it does not use some subcarriers and depends on computationally intensive optimization. Systematic coding techniques are distortion-less methods, which can bound signal fluctuations but they require data rate compensation. As the simplest method, Amplitude Clipping could reduce the out-of-band radiation, but these non-linear techniques cause in-band distortion and the additional clipping noise compensation requires high computational complexity.
Among the presented methods, constellation extension based ACE would be one of the promising methods because ACE maintains the minimum Euclidean distance between symbols in a constellation and causes no reduction of BER performance and, especially, it does not require any side information. However, because the reduction performance of signal envelope fluctuations of ACE depends on the number of iterative computations, its computational complexity is usually very high. So, it is necessary to find an approach to maintain high reduction performance of signal envelope fluctuations and low computational complexity.
Jon Ji Hyon, a researcher at the Faculty of Communications, has proposed a novel ACE-DE approach to deal with this issue, where the anti-peak signal decomposition based double extension is applied to improving reduction performance of signal envelop fluctuations.
By using Fourier transform properties, an anti-peak signal is decomposed into 4 sub-signals in the time domain, and then recomposed via Second Order Cone Programming optimization. To realize the low computational complexity of ACE-DE, MPT algorithm is also proposed.
The simulation results show that ACE-DE with MPT outperforms other approaches in terms of CCDF, BER and OOB radiation.
For more information, please refer to his paper “Reduction of Signal Envelope Fluctuations in OFDM Systems Using ACE with Double Extension” in “Wireless Personal communications” (SCI).
...
Jo Mar 26, 2024
Induction channel furnace (ICF) is widely used for melting, holding and casting metals and alloys in many processing industries because it has high overall efficiency, low electric power consumption and operation costs, better degassing and homogenization of melt and low oxide and slag formation. However, thermal stresses in the refractory lining caused by high temperature and flow of molten metal may cause premature erosion of the lining and failure of the inductor, and so it is difficult to repair the furnace. In addition, the furnace for steel melting often experiences shortened operating life and quicker needs for a repair cycle due to high temperature of molten metal and severe erosion of lining, so it is rarely used.
In order to solve these problems and make easy operation, it is important to improve the structure and to numerically simulate Joule heat generation and molten metal flow in the channel.
Song Hak Myong, a lecturer at the Mechanical Engineering Department, has designed a new type of channel of three-phase ICF for steel melting and investigated temperature distribution of the channel by a coupled simulation on the electromagnetism-heat-fluid using COMSOL Multiphysics 5.4.
ICF consists of molten metal bath and induction unit that is made up of iron core, inductor and channel. If one three-phase induction unit is fixed to the furnace body, it will lead to decrease in electrical unbalance and ease of furnace repair.
According to his simulation results, the optimal design parameters (with maximum S/N ratio) for three-phase ICF are as follows:
• Type of channel: Elliptic
• Dimensions of channel: 85×90 mm2
• Existence of protruding part: Yes
• Setting angle of channel: 30°
The local superheating temperature is relatively low (20.8–22.9K) and the maximum local superheating temperature is similar to the maximum local superheating temperature 33K in the channel of the twin channel induction furnaces.
It is one of the ways to prevent early erosion and expansion of refractory lining by local superheating in the channel and to increase its repair cycle.
The proposed method could be used for reducing manufacturing cost and regularizing operation through optimizing the parameters of induction furnace needed for aimed melting and flow.
If further information is needed, please refer to his paper “ Simulation on Temperature in Channel of Three-phase Induction Channel Furnace for Steel Melting Using COMSOL Multiphysics and Taguchi Method” in “International Journal of Metalcasting” (SCI).
...
Jo Mar 23, 2024
As modern industrial processes become more complex with the development of technology, more advanced monitoring methodologies are required to keep high efficiency and safe operation. In order to improve monitoring performance, it is important to identify the operational phase of a process by evaluating all measurable variables comprehensively. Multiple operational characteristic that occurs in most industrial processes like chemical processes by their physical and chemical properties, variations in market requirement and product specification, catalyst degradation, etc. has become an important factor to be considered in process monitoring.
Since most multimode monitoring approaches with the mode-identification are only based on the similarity of process mean, the identification of transitions and faults is possible only after the cluster of process data should be formed or neighbour modes could be analyzed. Furthermore, mode-identification based approach seems to be inappropriate to monitoring of process with lots of modes not only because it requires a large amount of off-line data but also because its capability of adapting to unexpected states may not be acceptable.
Song Kwang Rim, a researcher at the Faculty of Automation Engineering, has proposed an online transition-identification based monitoring procedure for industrial process with multiple operational modes using process variability.
Firstly, he detected the change point in the dynamical behavior of multimode process by the log determinant of covariance matrix.
Second, based upon the analysis of the change behavior of process variability during transition and fault state, he developed new statistics to identify the transition.
Finally, he adopted an adaptive monitoring strategy to monitor multimode processes by the single model using the transition-identification.
Then, he conducted three case studies through TE benchmark to verify the usefulness and effectiveness of the proposed approach.
The result showed that the proposed approach has high ability to identify transitions and faults and to cope with the occurrence of new modes.
The details of this are found in his paper “Monitoring Industrial Processes with Multiple Operation Modes: a Transition-Identi¦cation Approach Based on Process Variability” in “Industrial & Engineering Chemistry Research” (SCI).
...
