• Applied Chemistry for Engineering
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• v.27 no.2
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• pp.165-170
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• 2016

In this study, we investigated the cause of the decrease in activities of $VO_x/TiO_2$ SCR catalyst used for the burner reactor at a scale of $150000Nm^3/hr$ using X-ray diffraction (XRD), brunauer-emmett-teller (BET), atomic emission spectroscopy inductively coupled plasma (AES ICP), $H_2$ temperature programmed reduction ($H_2$-TPR), and $NH_3$ temperature programmed desorption ($NH_3$-TPD) analysis. Since the crystallization of the $VO_x$ and phase transition of $TiO_2$ did not occur, it was concluded that the catalyst was not deactivated by the thermal effect. In addition, from the elemental analysis showing that a large quantity of calcium was detected but not sulfur, the deactivation process of the $VO_x/TiO_2$ SCR catalyst was mainly caused by Ca but not by $SO_2$. The calcium was also found to decrease the catalytic activity by means of reducing $NH_3$ adsorption.

• Progress in Medical Physics
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• v.30 no.1
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• pp.22-31
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• 2019

Purpose: To develop a new diffusion-based functional MRI (fMRI) sequence to generate apparent diffusion coefficient (ADC) maps in single excitation and evaluate the contribution of b0 signal on neuronal changes. Materials and Methods: A diffusion-based fMRI sequence was designed with single measurement that can acquire images of three directions at a time, obtaining $b=0s/mm^2$ during the first baseline condition (b0_b), followed by 107 diffusion-weighted imaging (DWI) with $b=600s/mm^2$ during the baseline and visual stimulation conditions, and another $b=0s/mm^2$ during the last activation condition (b0_a). ADC was mapped in three different ways: 1) using b0_b (ADC_b) for all time points, 2) using b0_a (ADC_a) for all time points, and 3) using b0_b and b0_a (ADC_ba) for baseline and stimulation scans, respectively. The fMRI studies were conducted on the brains of 16 young healthy volunteers using visual stimulations in a 3T MRI system. In addition, the blood oxygen level dependent (BOLD) fMRI was also acquired to compare it with diffusion-based fMRI. A sample t-test was used to investigate the voxel-wise average between the subjects. Results: The BOLD data consisted of only activated voxels. However, ADC_ba data was observed in both deactivated and activated voxels. There were no statistically significant activated or deactivated voxels for DWI, ADC_b, and ADC_a. Conclusions: With the new sequence, neuronal activations can be mapped with visual stimulation as compared to the baseline condition in several areas in the brain. We showed that ADC should be mapped using both DWI and b0 images acquired with the same conditions.

• Clean Technology
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• v.16 no.4
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• pp.265-271
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• 2010

The deactivated diesel oxidation catalyst(DOC) was remanufactured by ultrasonic wave treatment with various solutions, followed by active component re-impregnation. The catalytic performance and surface properties of remanufactured DOC were studied at various remanufacturing conditions. The proper ultrasonic-wave cleaning time at various solutions and optimal re-impregnation amounts of active component for the best catalytic performance were investigated. The catalytic performance tests on the conversions of CO and THC(total hydrocarbon) were also carried out at various temperatures by catalytic reaction test unit using bypass gas from the diesel engine dynamo system. It was found that the catalytic performance of DOC remanufactured with the high-temperature air washing, ultrasonic wave cleaning at acidic/basic solutions and active component re-impregnation method was recovered to 90% level of its activity compared to that of the fresh DOC, which was caused by removing the deactivating materials from the surface of the DOC through the analyses of catalyst performance test and their characterization by Optical microscope, EDX, ICP, TGA, and porosimeter.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.609-617
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• 2000

This study is aimed at investigating an effect of HCl gas on selective reduction of NOx over a CuHM and $V_2O_5-WO_3/TiO_2$ catalyst. SCR process is the most effective method to remove NOx, but catalyst can be deactivated by the acidic gas such as HCl gas which is also included in flue gas from the incinerator. In dry condition of flue gas, the CuHM catalyst treated by HCl gas has shown higher NO removal activity than the fresh catalyst. The activity of the catalyst can be restored by treating at $500^{\circ}C$. On the contrary. $V_2O_5-WO_3/TiO_2$ catalyst is obviously deactivated by HCl and the deactivation increases in proportion to the concentration of HCl gas. The deactivated catalyst is not restored to it's original activity by heat treatment for regeneration. In wet flue gas stream, the CuHM catalyst has shown lower activity than fresh catalyst and $V_2O_5-WO_3/TiO_2$ catalyst was severely deactivated by HCl treatment. The activity loss of catalysts are mainly due to the decrease of Br$\ddot{o}$nsted acid site on the catalyst surface by $NH_3$ TPD. The change of BET surface area of CuHM catalyst after the reaction isn't observed but $V_2O_5-WO_3/TiO_2$ catalyst is observed. The amount of $Cu^{{+}{+}}$ and $V_2O_5$ is decreased after the reaction. From these results, it is expected that CuHM catalyst should be better than $V_2O_5-WO_3/TiO_2$ catalyst for its application to the incineration of flue gas.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.9-16
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• 2004

Close-coupled catalyst (CCC) can reduce the engine cold-start emissions by utilizing the energy in the exhaust gas. However, in case the engine is operated at high engine speed and load condition, the catalytic converter may be damaged and eventually deactivated by thermal aging. Excess fuel is sometimes supplied intentionally to lower the exhaust gas temperature avoiding the thermal aging. This sacrifices the fuel economy and exhaust emissions. This paper describes the results of an exhaust heat exchanger to lower the exhaust gas temperature mainly under high load conditions. The heat exchanger was installed between the exhaust manifold and the inlet of close-coupled catalytic converter. The exhaust heat exchanger successfully decreased the exhaust gas temperature, which eliminated the requirement of fuel enrichment under high load conditions. However, the cooling of the exhaust gas through the heat exchanger may cause the deterioration of exhaust emissions at cold start due to the increment of catalyst light-off time.

• ETRI Journal
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• v.31 no.5
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• pp.598-600
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• 2009

A highly efficient and compactly integrated balanced power amplifier (PA) for W-CDMA handset applications is presented. To overcome the size limit of a typical balanced PA, a bulky input divider is integrated into a PA MMIC, and a complex output network is replaced with simple lumped-element networks. For efficiency improvement at the low output power level, one of the two amplifiers in parallel is deactivated and the other is partially operated with corresponding load impedance optimization. The implemented PA shows excellent average current consumption of 34.5 mA in urban and 56.3 mA in suburban environments, while exhibiting very good load-insensitivity under condition of VSWR=4:1.

• Bulletin of the Korean Chemical Society
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• v.27 no.9
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• pp.1429-1432
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• 2006

Polyaromatic hydrocarbons were separated by a capillary supercritical fluid chromatographic (SFC) column and detected by a UV detector at the wavelength of 280 $\mu$m. The temperature-controlled restrictor was designed for UV detection. The temperature-controlled restrictor is a 20 cm length of deactivated fused silica of 7 mm i.d. which is held right after UV detector of the capillary SFC. The temperature of the restrictor will control the flow rate of the supercritical carbon dioxide mobile phase through the capillary column in SFC. Thus as the pressure in the column is increased from 1500 psi to 4000 psi during a pressure program, the temperature of 7 $\mu$m fused-silica tube can be varied from 100 to 350 ${^{\circ}C}$ to maintain a constant flow rate.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.541-544
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• 2001

One of the most promising TCE treatment systems is trickling biofilter (TBF), in which monooxygenase, the corresponding enzyme for initiating growth substrate oxidation, fortuitously transforms TCE via cometabolism. TCE. however. is not easily treated by simple cometabolic biotransformation. This is mainly due to the toxicity of TCE to microbial cell and monooxygenase. In this study, we cleveloped and operated a two-stage CSTR/TBF system for the long-term continuous treatment of TCE. In the two-stage biotransfon11ation system, CSTR with cell recycle from TBR was coupled to the TBR for the reactivation of the cells deactivated during TCE degradation.

• Bulletin of the Korean Chemical Society
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• v.23 no.5
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• pp.669-673
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• 2002

Ni catalyst (Ni: 15 wt%) supported on precalcined SiO2 has been investigated in reforming reactions of methane to synthesis gas. The catalyst exhibited fairly good activity and stability in partial oxidation of methane (POM), whereas it deactivated in steam reforming of methane (SRM). Pulse reaction results of CH4, O2, and CH4/O2 revealed that Ni/SiO2 has high capability to dissociate methane. The results also revealed that both CH4 and O2 are activated on the surface of metallic Ni, and then surface carbon species react with adsorbed oxygen to produce CO and CO2 depending on the bond strength of the oxygen species on the catalyst surface.

• Journal of KIISE:Software and Applications
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• v.31 no.6
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• pp.840-848
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• 2004

Garbage collecting objects in Java makes memory management easier for the programmer, but it is time consuming. Stack allocation may be an alternative which identifies stack-allocatable objects before the execution, without performance degradation. We suggest an escaping analysis recording the interprocedural movement of the method, to detect an object the method of whose creation may have been already deactivated during the access. Our approach is different from prior works, enables us to handle some cases that are missed in the previous variable - oriented approach.