• Journal of Environmental Health Sciences
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• v.37 no.3
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• pp.218-225
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• 2011

Objectives: In this paper, a dielectric barrier discharge (DBD) plasma reactor was investigated for degrading the dye Rhodamine B (RhB) in aqueous solutions. Methods: The DBD plasma reactor system in this study consisted of a plasma component [titanium discharge (inner), ground (outer) electrode and quartz dielectric tube], power source, and gas supply. The effects of various parameters such as first voltage (input power), gas flow rate, second voltage (output power), conductivity and pH were investigated. Results: Experimental results showed that a 99% aqueous solution of 20 mg/l Rhodamine B is decolorized following an eleven minute plasma treatment. When comparing the performance of electrolysis and plasma treatment, the RhB degradation of the plasma process was higher that of the electrolysis. The optimum first voltage and air flow rate were 160 V (voltage of trans is 15 kV) and 3 l/min, respectively. With increased second voltage (4 kV to 15 kV), RhB degradation was increased. The higher the pH and the lower conductivity, the more Rhodamine B degradation was observed. Conclusions: OH radical generation of dielectric plasma process was identified by degradation of N, N-dimethyl-4-nitrosoaniline (RNO, indicator of OH radical generation). It was observed that the effect of UV light, which was generated as streamer discharge, on Rhodamine B degradation was not high. Rhodamine B removal was influenced by real second voltage regardless of initial first and second voltage. The effects of pH and conductivity were not high on the Rhodamine B degradation.

• Environmental Engineering Research
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• v.25 no.2
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• pp.178-185
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• 2020

The aim of this study is to investigate the degradation of ciprofloxacin (CIP) from its aqueous solutions via different advanced oxidation processes (AOP). The effects of persulfate (PS) concentration, pH, zinc oxide nanoparticles (ZnO-NPs) dose, initial CIP concentration, and reaction time on the degradation of CIP were studied. It was found that the sonochemical (US) degradation is a less efficient process (with removal efficiency of 36%) compared to the sono-nano-chemical (US/ZnO) process which resulted in removal efficiency of 70%. Maximum removal of 99% was obtained using the sono-nano-chemical/PS (US/ZnO/PS) process at a frequency of 60 kHz, time of 10 min, pH of 7, initial CIP concentration of 25 mg/L, and PS concentration of 476.06 mg/L. The addition of PS and ZnO-NPs to the process enhanced the rate of US degradation of CIP. In addition, the kinetic parameters for the US/ZnO/PS process were obtained by fitting the kinetic data into the pseudo-first-order and pseudo-second-order kinetic models. The kinetic data was found to fit into the pseudo-first-order kinetic model than the pseudo-second-order model. The results showed that the AOP using US/ZnO/PS is a promising technique for the treatment of ciprofloxacin containing solutions.

• Journal of the Korean Wood Science and Technology
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• v.39 no.2
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• pp.179-186
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• 2011

In an effort to understand the hydrolytic degradation process of cured urea-formaldehyde (UF) resins responsible for the formaldehyde emission of wood-based composite panels, this study analyzed the influence of acid hydrolysis on the morphology of cured UF resins with different formaldehyde/urea (F/U) mole ratios such as 1.6, 1.4, 1.2 and 1.0. Field emission-scanning electron microscopy (FE-SEM) was employed to observe both exterior and fracture surfaces on thin films of cured UF resins before and after the etching with hydrochloric acid as a simulation of the hydrolytic degradation process. FE-SEM images showed that the exterior surface of cured UF resin with the F/U mole ratio of 1.0 had spherical structures after the acid hydrolysis while the other cured UF resins were not the case. However, the fracture surface observation showed that all the samples possessed spherical structures in the cured state of UF resins although their occurrence and size decreased as the F/U mole ratio increased. For the first time, we found the spherical structures in cured UF resins of higher F/U mole ratio of 1.4. After the acid hydrolysis, the spherical structures became a much predominant at the fracture surface. These results indicated that the spherical structures in cured UF resinswere much more resistant to the hydrolytic degradation by the acid than amorphous region.

• Journal of Industrial Technology
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• v.22 no.B
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• pp.117-124
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• 2002

We prepared the nano-sized $TiO_2$ particles by the diffusion flame reactor and investigated the effects of several process variables on the generation and transport properties of $TiO_2$ particle. As the length from the tip of diffusion flame reactor increases, the size of $TiO_2$ particle increases by the coagulation between particles. The structure of $TiO_2$ particles prepared is almost found to be anatase. It was found that the $TiO_2$ particle size depends more largely on the change of reactor temperature than on the change of inlet $TiCl_4$ concentration. By the photo-degradation experiment of phenol and toluene with the prepared $TiO_2$ particles, we found that the photo-degradation efficiencies of phenol and toluene change, depending on the process variables such as size of $TiO_2$ photocatlysts, concentration of phenol or toluene. Degradation efficiencies of phenol and toluene was above 90% in our experiments in 60 minutes.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.6
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• pp.46-52
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• 2018

Nondestructive evaluation for mechanical degradation of ultrasuper-critical (USC) heat-resistance steel, which is attractive to the next generation of power plants is studied by magnetic reversible permeability. The interrelationship between reversible permeability and high-temperature mechanical degradation has been investigated by precise measurement of permeability nondestructively. Also, the effects of microstructural variation on reversible permeability are discussed. Isothermal aging was observed to coarsen the tempered carbides ($Cr_{23}C_6$), generated the intermetallic phases ($Fe_2W$), and grow rapidly during aging. The dislocation density also decreases steeply within lath interior. The peak to peak interval (PPI) of reversible permeability profile decreased drastically during the initial 500 h aging period, and was thereafter observed to decrease only slightly. The variation in PPI is closely related to the decrease in the number of pinning sites and the degradation in tensile strength.

• Journal of Environmental Science International
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• v.13 no.3
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• pp.313-318
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• 2004

We studied a storage of waste-brown seaweed at room temperature and degradation of alginate in seaweed by microorganism DS-02. The seaweeds, mixed with 5.0 wt% DS-02 and sealed in vinyl package without any other treatment, could be stored longer than 1 year without spoilage at room temperature. During the storage process, the alginate of seaweed was decomposed by enzyme of DS-02 and the molecular weight of alginate decreased to about 1/10 of initial quantity. DS-02 growed as fast as it had maximum weight after 24 hour culture and it's enzyme had a maximum activity of alginate degradation at $40^{\circ}C.$ The seaweed sample became particles in DS-02 culture solution and the M. W of alginate decreased to about 1/10 of initial value after 24 hour decomposition. The effect of alginate degradation with DS-02 was similar to that of degradation with 3.0 M HCI solution for 24 hour.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.10
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• pp.902-908
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• 2005

Various stresses (such as electrical stress, mechanical stress, environmental and electrochemical stress, and defects of structure) result in insulation degradation of epoxy mold type insulators. Since the insulation degradation of BCT(Bushing Current Transformer) and bushing proceeds during fabrication process or operation time due to these causes, various methods to reduce the degradation in their insulation ability have been suggested. In this paper, we investigated surface temperature increment of these insulators due to PD(partial discharge). After the voltage applied into the insulator to generate the artificial PD, the surface temperature of the insulator was measured with non-contact thermometer using infrared rays. It was confirmed through the analysis based on PD experiments that the procession in the insulation degradation of the insulator could be estimated through the measurement of the surface temperature in the insulator.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.863-864
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• 2008

To predict the iris matching performance and guarantee its reliability, image quality measure prior to matching is desired. An analysis on iris image degradation factors which deteriorate matching performance is a basic step for iris image quality measure. We considered five degradation factors-white-out, black-out, noise, blur, and occlusion by specular reflection-which happen generally during the iris image acquisition process. Experimental results show that noise and white-out degraded the EER most significantly, while others on EER were either insignificant or degradation images resulted in even better performance in some cases of blur. This means that degradation factors that affect the performance can be different from those based on human perception or image degradation evaluation.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.43-47
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• 2002

Weight loss experiments have been performed for unidirectional carbon fiber/epoxy laminates under both isothermal and cyclic thermal conditions. It was found that weight losses were the result of both specimen-geometry dependent oxidative degradation and volumetric geometry dependent thermal degradation. Thermal degradation was found to play a major role in the overall weight loss process, and photomicrographs of cross-sectioned, aged specimens confirmed this fact. A method to predict the effect of isothermal environment on the weight loss was introduced and found to be in good agreement with experimental data at temperatures near Tg (glass transition temperature).

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.286-291
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• 2001

As part of fundamental studies on the degradation of the organic compounds in industrial waste water, the photocatalytic degradation properties of the organic compound by means of the UV/TiO$_2$degradation process have been investigated. The test organic compound of acetic acid was chosen in this study. The testing of photo catalytic degradation were performed under various operation conditions such as TiO$_2$dosages, initial concentration of the organic, the aqueous pH's, etc. The effects of various parameters on the short time activity of the present acetic acid-UV/TiO$_2$system could be demonstrated from this investigation.