• Macromolecular Research
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• v.15 no.2
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• pp.134-141
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• 2007

The direct chromatographic separation of enantiomers by chiral stationary phases (CSPs) has been extensively developed over the past two decades, and has now become the most popular method for the analytical and preparative separations of enantiomers. Polysaccharide derivatives coated onto silica gel, as CSPs, playa significantly important role in the enantioseparations of a wide range of chiral compounds using high-performance liquid chromatography (HPLC). Unfortunately, the strict solvent limitation of the mobile phases is the main defect in the method developments of these types of coated CSPs. Therefore, the immobilization of polysaccharide derivatives onto silica gel, via chemical bonding, to obtain a new generation of CSPs compatible with the universal solvents used in HPLC is increasingly important. In this article, our recent studies on the immobilization of polysaccharide derivatives onto the silica gel, as CSPs, through radical copolymerization with various vinyl monomers are reported. Polysaccharide derivatives, with low vinyl content, can be efficiently fixed onto silica gel with high chiral recognition.

• Journal of the Korean Chemical Society
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• v.57 no.1
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• pp.73-80
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• 2013

An efficient synthesis of quinoxalines derivatives is described using magnetic material separated from coal fly ash. Coal fly ash is a waste material generated in huge amount by burning of coal for the generation of electricity in thermal power station. It contains $SiO_2$, $Al_2O_3$ and magnetic material in significant amounts, from which magnetic material was separated by using magnetic separation method. These separated magnetic material further characterized by XPS, XRD, EDS, FTIR, SEM, TEM and BET techniques. The merits of present method are mild reaction conditions, and also excellent yields and short reaction times.

• Clinical and Experimental Reproductive Medicine
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• v.36 no.4
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• pp.311-319
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• 2009

Objective: Human embryonic stem cells (hESCs) have the capacity to differentiate into all of the cell types and therefore hold promise for cell therapeutic applications. In order to utilize this important potential of hESCs, enhancement of currently used technologies for handling and manipulating the cells is required. The cryopreservation of hESC colonies was successfully performed using the vitrification and slow freezing-rapid thawing method. However, most of the hESC colonies were showed extremely spontaneous differentiation after freezing and thawing. In this study, we were performed to rapidly collect of early passage hESCs, which was thawed and had high rate of spontaneously differentiation of SNUhES11 cell line. Methods: Four days after plating, partially spontaneously differentiated parts of hESC colony were cut off using finely drawn-out dissecting pipette, which is mechanical separation method. Results: After separating of spontaneously differentiated cells, we observed that removed parts were recovered by undifferentiated cells. Furthermore, mechanical separation method was more efficient for hESCs expansion after thawing when we repeated this method. The recovery rate after removing differentiated parts of hESC colonies were 55.0%, 74.5%, and 71.1% when we have applied this method to three passages. Conclusion: Mechanical separation method is highly effective for rapidly collecting and large volumes of undifferentiated cells after thawing of cryopreserved early passage hESCs.

• Clean Technology
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• v.29 no.1
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• pp.31-38
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• 2023

Due to water shortages caused by water pollution and climate change, total organic carbon (TOC) standards have been implemented for wastewater discharged from public sewage treatment facilities. Furthermore, there is a growing interest and body of research pertaining to the reuse of sewage treatment water as a secure alternative water resource. The membrane bio-reactor (MBR) method is commonly used for advanced wastewater treatment because it can remove organic and inorganic ions and it does not require or emit any chemicals. However, the MBR process uses a separation membrane (MF), which requires frequent film cleaning due to fouling caused by a high concentration of mixed liquor suspended solid (MLSS). In this study, process improvement and microbubble cleaning efficiency were evaluated to improve the differential pressure, water flow, and MF fouling, which are the biggest disadvantages of operating the MF. The existing MBR method was improved by installing a precipitation tank between the air tank and the MBR tank in which raw water was introduced. Microbubbles were injected into a separation membrane tank into which the supernatant water from the precipitation tank was introduced. The microbubble generator was operated with a 15 day on, 15 day off cycle for 5 months to collect discharged water samples (4L) and measure TOC. As the supernatant water from the precipitation tank flowed into the separation membrane tank, about 95% of the supernatant water MLSS was removed so the MF fouling from biological contamination was prevented. Due to the application of microbubbles to supernatant water from the precipitation tank, the differential pressure of the separation membrane tank decreased by 1.6 to 2.3 times and the water flow increased by 1.4 times. Applying microbubbles increased the TOC removal rate by more than 58%. This study showed that separately operating the air tank and the separation membrane tank can reduce fouling, and suggested that applying additional microbubbles could improve the differential pressure, water flow, and fouling to provide a more efficient advanced treatment method.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.10
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• pp.4814-4834
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• 2018

This paper presents an architecture for wireless sensor networks (WSNs) with blind source separation (BSS) applied to retrieve the received mixing signals of the sink nodes first. The little-to-no need of prior knowledge about the source signals of the sink nodes in the BSS method is obviously advantageous for WSNs. The optimization problem of the BSS of multiple independent source signals with complex and noncircular distributions from observed sensor nodes is considered and addressed. This paper applies Castella's reference-based scheme to Novey's negentropy-based algorithms, and then proposes a novel fast fixed-point (FastICA) algorithm, defined as the reference-signal negentropy complex FastICA (RSNT-cFastICA) for complex-valued noncircular-distribution source signals. The proposed method for the sink nodes is substantially more efficient than Novey's quasi-Newton algorithm in terms of computational speed under large numbers of samples, can effectively improve the power consumption effeciency of the sink nodes, and is significantly beneficial for WSNs and wireless communication networks (WCNs). The effectiveness and performance of the proposed method are validated and compared with three related BSS algorithms through theoretical analysis and simulations.

• The Korean Journal of Applied Statistics
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• v.28 no.2
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• pp.159-174
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• 2015

Dragomiretskiy and Zosso (2014) developed a new decomposition method, termed variational mode decomposition (VMD), which is efficient for handling the tone detection and separation of signals. However, VMD may be inefficient in the presence of missing data since it is based on a fast Fourier transform (FFT) algorithm. To overcome this problem, we propose a new approach based on a novel combination of VMD and hierarchical (or h)-likelihood method. The h-likelihood provides an effective imputation methodology for missing data when VMD decomposes the signal into several meaningful modes. A simulation study and real data analysis demonstrates that the proposed method can produce substantially effective results.

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.636-639
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• 2004

In present, there are many methods such as DCT, Wavelet Transform, or Quantization -to the image compression field, but the basic image compression method have based on DCT. The representative thing of the efficient techniques for information compression is DCT method. It is more superior than other information conversion method. It is widely applied in digital signal processing field and MPEG and JPEG which are selected as basis algorithm for an image compression by the international standardization group. It is general that DCT is consisted of using multiplier with main arithmetic blocks having many arithmetic amounts. But, the use of multiplier requires many areas when hardware is embodied, and there is fault that the processing speed is low. In this paper, we designed the hardware module that could run high-speed operation using row-column separation calculation method and Chen algorithm by distributed arithmetic method using ROM table instead of multiplier for design DCT module of high speed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.21-27
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• 2018

FRN (Full range Naphtha) is distilled from crude oil in a Naphtha Splitter Unit and is separated into the Light Straight Naphtha, Heavy Naphtha, and kerosene according to the boiling point in sequence. This separation is conducted using a series of binary-like columns. In this separation method, the energy consumed in the reboiler is used to separate the heaviest components and most of this energy is discarded as vapor condensation in the overhead cooler. In this study, the first two columns of the separation process are replaced with the Petlyuk column. A structural design was exercised by a stage to stage computation with an ideal tray efficiency in the equilibrium condition. Compared to the performance of a conventional system of 3-column model, the design outcome indicates that the procedure is simple and efficient because the composition of the liquid component in the column tray was designed to be similar to the equilibrium distillation curve. An analysis of the performance of the new process indicated an energy saving of 12.3% under same total number of trays and with a saving of the initial investment cost.

• The Journal of the Acoustical Society of Korea
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• v.35 no.4
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• pp.303-309
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• 2016

This paper proposes a novel approach to the problem of audio signal clustering using a stacked autoencoder. The proposed stacked autoencoder learns an efficient representation for the input signal, enables clustering constituent signals with similar characteristics, and therefore the original sources can be separated based on the clustering results. STFT (Short-Time Fourier Transform) is performed to extract time-frequency spectrum, and rectangular windows at all the possible locations are used as input values to the autoencoder. The outputs at the middle, encoding layer, are used to cluster the rectangular windows and the original sources are separated by the Wiener filters derived from the clustering results. Source separation experiments were carried out in comparison to the conventional NMF (Non-negative Matrix Factorization), and the estimated sources by the proposed method well represent the characteristics of the orignal sources as shown in the time-frequency representation.

• Resources Recycling
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• v.18 no.3
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• pp.27-35
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• 2009

To solve resource exhaustion and waste management problems caused by mass consumption, there are many efforts to change from resource consumption system to recycling system. Specially, interests about management of construction waste have increased, but efficient recycling system of waste concrete is not established yet. In this study, high quality recycled aggregate processing circuit was developed to recycle waste concrete. From the waste concrete which is a hydrated compound with coarse aggregate, fine aggregate, and cement material, high quality recycled coarse aggregate for concrete making was produced by autogenous milling and heat pretreatment method. After then, refinement process was performed to separate fine aggregate and cement material from waste concrete fines by sink float separation and hindered-settling separation. As a result, high quality recycled aggregate was produced from waste concrete by developed processing circuit.