• Journal of Microbiology and Biotechnology
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• 제24권1호
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• pp.80-86
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• 2014

Tannase (Tan410) from a soil metagenomic library was immobilized on different supports, including mesoporous silica SBA-15, chitosan, calcium alginate, and amberlite IRC 50. Entrapment in calcium alginate beads was comparatively found to be the best method and was further characterized. The optimum pH of the immobilized Tan410 was shifted toward neutrality compared with the free enzyme (from pH 6.4 to pH 7.0). The optimum temperature was determined to be $45^{\circ}C$ for the immobilized enzyme and $30^{\circ}C$ for the free enzyme, respectively. The immobilized enzyme had no loss of activity after 10 cycles, and retained more than 90% of its original activity after storage for 30 days. After immobilization, the enzyme activity was only slightly affected by $Hg^{2+}$, which completely inhibited the activity of the free enzyme. The immobilized tannase was used to remove 80% of tannins from a green tea infusion on the first treatment. The beads were used for six successive runs resulting in overall hydrolysis of 56% of the tannins.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제15권5호
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• pp.352-359
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• 2003

The present study has been conducted for manufacturing MPCM (microencapsulated phase change material) slurry with in-situ polymerization and proving their applicabilities for tooling system. The surface of MPCM is composed of melamine, while tetradecane, paraffin wax, is centered in the MPCM. The produced capsules are observed by the optical microscope and SEM for superficial shapes. Their thermal properties are measured by DSC. Their size distributions are observed by FA particle analyzer. A narrow size distribution from 1 to 10 ${\mu}{\textrm}{m}$ with 5 ${\mu}{\textrm}{m}$ of average diameter was observed. Melting temperature was 6.7$^{\circ}C$. The durability of MPCM was tested with various types of pump such as centrifugal, peristaltic, and mono pumps. During 10000 cycles the fraction of broken capsules was smaller than 6% for the centrifugal and peristaltic pumps, while bigger value of 8% for the mono pump. A cooling system, which adopted MPCM slurry as a media for transporting cold thermal energy, was designed to investigate the performance of the MPCM. The discharging times of 10 and 20 wt% MPCM slurry were lasted up to 105 and 285 minutes longer, respectively, than the water cooling system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제23권4호
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• pp.281-286
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• 2011

The objective of this study is to optimize the four-bed six-step pressure swing adsorption(PSA) process for high purity $CH_4$ recovery from the biogas. The effects of P/F(purge to feed) ratio and cycle time on the process performance were evaluated. The cyclic steady-states of PSA process were reached after 12 cycles. The purity and recovery rate of product gas, pressure and temperature changes were constant as the cycle repeated. It was shown that the P/F ratio gave significant effect on the product recovery rate by increasing the amount of purge gas in purge and regeneration step. The optimal P/F ratio was found to be 0.08. As the cycle time increased, the product purity decreased by increasing the feed gas flow rate. It was found that the optimal operating conditions were P/F ratio of 0.08 and total cycle time of 1,440 seconds with the purity of 97%.

• YAKHAK HOEJI
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• 제33권6호
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• pp.365-371
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• 1989

Microbiological conversion of sterols to 17-ketosteroids has been recognized as a source for commercial preparation of steroidal drugs. In order to develop bacterial strains and process with Brevibacterium lipolyticum IAM 1398 capable of converting cholesterol to 1,4-Androstadiene-3,17-dione (ADD) at about 27% yield, we studied on strain improvement, fermentation condition and whole cell immobilization. By using UV and/or NTG as mutagens, a mutant to convert cholesterol to ADD with higher yield than 60% was selected. Better production of ADD was manifested in the case of maltose used as a supplemental carbon source, and yeast extract or soytone as a nitrogen source. Addition of tween 80 (0.05%) as a surfactant beneficial for increasing the productivity. The optimal initial pH of the medium was 6.5 and optimal culture temperature was $30^{\circ}C$. Whole cell immobilization by using carrageenan, agar, alginate and acrylamide was carried out and the activity of conversion was tested. In the case of carrageenan and agar, immobilized cells were active for at least two cycles of fermentation.

• Journal of Welding and Joining
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• 제35권3호
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• pp.15-20
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• 2017

In this paper, two types of assemblies using CNT-filled SACAs (with 0.03 wt% CNTs and without CNT) were prepared to investigate the influence of carbon nanotubes (CNTs) on the reliability properties of solderable anisotropic conductive adhesives (SACAs) with a low-melting-point alloy (LMPA). Two types of reliability test including thermal shock (TS: -55 to $125^{\circ}C$, 1000 cycles) and high-temperature and high-humidity (HTHH: $85^{\circ}C$, 85% RH, 1000 h) tests were conducted. The SACA assemblies with and without CNTs showed stable electrical reliability properties due to the formation of wide and stable metallurgical interconnection between corresponding metallizations by the molten LMPA fillers. Although the mechanical pull strength of CNT-filled SACA assemblies was decreased after thermal aging (because of the excessive layer growth and planarization of the IMCs), the CNT-filled SACA with 0.03wt% CNTs showed enhanced mechanical reliability properties compared with the SACA assemblies no CNTs. This enhancement in mechanical performance was due to the reinforcement effect of the CNTs. These results demonstrate that CNTs within the CNT-filled SACAs can improve the reliability properties of CNT-filled SACAs joints due to their superior physical properties.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제27권2호
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• pp.81-84
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• 2014

The bipolar resistive switching characteristics of resistive random access memory (ReRAM) based on $HfO_2$ thin films have been demonstrated by using Ag/$HfO_2$/Pt structured ReRAM device. MIcrowave irradiation (MWI) treatment at low temperature was employed in device fabrication with $HfO_2$ thin films as a transition layer. Compared to the as-deposited Ag/$HfO_2$/Pt device, highly improved uniformity characteristics of resistance values and operating voltages were obtained from the MWI treatment Ag/$HfO_2$/Pt ReRAM device. In addition, a stable DC endurance (> 100 cycles) and a high data retention (> $10^4$ sec) were achieved.

• KSBB Journal
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• 제8권4호
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• pp.307-312
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• 1993

A fructosyltransferase from Aureobasidium pullulans was immobilized onto a polystyrene-type anionic ion-exchange resin and the production of fructo-oligosaccharides was Investigated by the immobilized enzyme. The optimum pH and the temperature of immobilized enzyme were found to be pH 5.0, $55^{\circ}C$ respectively. The thermal stability of the enzyme was greatly enhanced after immobilization. The reaction profiles of the immobilized enzyme was almost identical to those of the free cells and the soluble enzyme. The immobilized enzymes were stable up to 20 cycles without loss of initial activity in a repeated-batch operation $50^{\circ}C$.

• Steel and Composite Structures
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• 제34권1호
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• pp.35-51
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• 2020

Integral abutment bridges (IABs) are those bridges without expansion joints. A single row of steel H-piles (SHPs) is commonly used at the thin and stub abutments of IABs to form a flexible support system at the bridge ends to accommodate thermal-induced displacement of the bridge. Consequently, as the IAB expands and contracts due to temperature variations, the SHPs supporting the abutments are subjected to cyclic lateral (longitudinal) displacements, which may eventually lead to low-cycle fatigue (LCF) failure of the piles. In this paper, the potential of using finite element (FE) modeling techniques to estimate the LCF life of SHPs commonly used in IABs is investigated. For this purpose, first, experimental tests are conducted on several SHP specimens to determine their LCF life under thermal-induced cyclic flexural strains. In the experimental tests, the specimens are subjected to longitudinal displacements (or flexural strain cycles) with various amplitudes in the absence and presence of a typical axial load. Next, nonlinear FE models of the tested SHP specimens are developed using the computer program ANSYS to investigate the possibility of using such numerical models to predict the LCF life of SHPs commonly used in IABs. The comparison of FE analysis results with the experimental test results revealed that the FE analysis results are in close agreement with the experimental test results. Thus, FE modeling techniques similar to that used in this research study may be used to predict the LCF life of SHP commonly used in IABs.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• 제19권3호
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• pp.359-364
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• 2010

The objective of this study is to propose an effective method for measurement and analysis of fatigue crack. A technique that can measure the statue of fatigue crack propagation fast and correctly for enhancing safety of constructions and securing reliability is necessary. Moreover, the crack propagation behavior characteristics evaluation technique has to be developed using this technique. In this paper, fatigue crack was caused via the fatigue experiment with repeated load on the CT specimen that is made up of STS304. Fatigue crack propagation was measured by tracing the position of the maximum temperature according to the cycles using infrared thermography. The crack growth characteristics was evaluated by applying the moment values on the measuring area to the measured value. As a result of this study, the possibility that the infrared thermography could be applied to measure the fatigue crack was identified. Moreover, it was identified that fatigue crack propagation have a relationship with the moment value of construction.

• Proceedings of the SAREK Conference
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.198-202
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• 2008

Refrigeration plants using absorption principles have been around for many years with initial development taking place over 100 years ago. Although the majority of absorption cycles are based on water-LiBr cycle, many applications exist where ammonia-water can be used, especially where lower temperatures are desirable. In both systems water is used as working fluid, but in quite different ways: as a solvent for the ammonia system, and as refrigerant for the lithium bromide system. This explains that the lithium bromide absorption system is strictly limited to evaporation temperatures above $0^{\circ}C$. The main industrial applications for refrigeration are in the temperature range below $0^{\circ}C$, the field for the binary system ammonia-water.