• Proceedings of the KAIS Fall Conference
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• 2007.05a
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• pp.287-290
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• 2007

We investigated the effect of ultrasound on the dewaterability of sewage sludge. Because, dewatering and disposal of waste sludge is a major economical factor in the operation of wastewater treatment plants. Capillary Suction Time(CST) and Specific Resistance to Filtration (SRF) were used to evaluate the sludge dewatering behaviors. From the results of the experiment, it was found that ultrasonic treatment can improve the dewaterability. We discovered that CST and SRF were highly related, according to the correlation coefficient($R^{2}$).

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.6
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• pp.576-579
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• 2014

Rails are continuously exposed to severe environments due to increases in train service frequency, passing tonnage, and speed. Wear is one of the most common types of damage observed on rails. The surface of railsis heat treated to secure safety at critical sites, such as curved tracks or turnouts. Ultrasonic nanocrystal surface modification (UNSM), a new approach for rails, was examined to strengthen the rail surface. The effect of UNSM on the wear resistance of rail specimens was compared with that of heat treatment. Wear resistance was improved after UNSM treatment due to increased hardness and surface compressive residual stress.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2630-2634
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• 2014

The surface of natural graphite was modified by the use of hydrogen peroxide and evaluated as an anode material for lithium ion capacitors (LICs). The surface treatment was carried out under various ultrasonic conditions of 200, 300, and 400W, which were applied to a mixture of natural graphite and hydrogen peroxide solution for 1 h. While the bulk structure was maintained, the hexagonal symmetry and physical properties of natural graphite, such as BET surface area, tap density, and particle size, were affected by the surface treatment. FT-IR and XPS measurements confirmed the signature of C=O on the surface of graphite samples after treatment. Both the pristine and surface-treated graphites showed a similar reversible capacity of $370mAhg^{-1}$, and the coulombic efficiency of surface-treated graphite decreased with higher ultrasonic energies (89.1%, 89.0%, and 88.0% for 200, 300, and 400 W) comparing with pristine graphite (89.4%). The capacity retention of LICs was greatly improved with the treated natural graphite. The graphite treated under the ultrasonic energy of 300 W and pristine natural graphite showed capacity retention of 77.5% and 42.9%, implying that the surface treatment was an effective method for the improvement of natural graphite as an anode material for LICs.

• Advanced Composite Materials
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• v.18 no.3
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• pp.221-232
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• 2009

The allylamine plasma treatment is used to modify the surface properties of vapor grown carbon fibers (VGCF). It is to improve the interfacial bonding between the VGCF and epoxy matrix. The allylamine plasma process was performed by batch process in a vacuum chamber, using gas injection followed by plasma discharge for the durations of 20, 40 and 60 min. The interdependence of mechanical properties on the VGCF contents, treatment time and interfacial bonding between VGCF/ep was investigated. The interfacial bonding between VGCF and epoxy matrix was observed by scanning electron microscopy (SEM) micrographs of nanocomposites fracture surfaces. The changes in the mechanical properties of VGCF/ep, such as the tensile modulus and strength were discussed. The mechanical properties of allylamine plasma treated (AAPT) VGCF/ep were compared with those of raw VGCF/ep. The tensile strength and modulus of allyamine plasma treated VGCF40 (40 min treatment)/ep demonstrated a higher value than those of other samples. The mechanical properties were increased with the allyamine plasma treatment due to the improved adhesion at VGCF/ep interface. The modification of the carbon nanofibers surface was observed by transmission electron microscopy (TEM). SEM micrographs showed an excellent dispersion of VGCF in epoxy matrix by ultrasonic method.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.12
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• pp.1310-1315
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• 2006

This study examines algae removal and reduction using ultrasonic. Experiments were carried out on frequency: 28 kHz single-wave, 40 kHz multi-wave; intensity: 10, 15, 20, 25, 30 W/L; algae concentration: 500, 1000, 1700/ml; exposure time: 1, 3, 5, 7, 10, 15, 20 min. Also, We investigated algae removal and reduction in single cistern where raw water including algae was directly exposed to ultrasonic and in the double cisterns located in 4 cm from ultrasonic vibrator. The algae type used in this study was Melosira genus of Bacillariophceae. The Bacillariophceae is the representative algae which causes blockage of filter basin. Because of its resistance against oxidizers, it flows into the filter basin after sterilization. As a result of this study, the form of Bacillariophceae was completely destroyed and dissolved after the application of ultrasonic waves unlike the sterilization using oxidizers. Removal efficiency of algae using ultrasonic waves increased in proportion to intensity and exposure time of ultrasonic waves, and in double cisterns is better than single cistern.

• Journal of Periodontal and Implant Science
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• v.31 no.3
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• pp.531-542
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• 2001

Periodontal debridement is most important procedure in periodontal treatment, because periodontal disease is the biofilm infection. The use of ultrasonic instrument has many clinical advantages compared to classical hand instrument. The introduction of newly developed ultrasonic scaler tips made the use of ultrasonic scaler popular. However the study of tooth substance removal according to the working parameters of ultrasonic scaler with newly developed tips is not sufficient. The purpose of this study is to evaluate the effects of working parameters of piezoelectric ultrasonic scaler with curette tip on casting gold removal. The working parameters was standardized by the sledge device which controls lateral force(0.5 N, 1.0 N, 2.0 N) and power setting was adjusted 2, 4, 8 in P mode and S mode and instrumentation time was 5 seconds. The defect depth and width were measured with profile meter and defect surface was examined by SME. The depth of defect was significantly large in S mode( $39.58{\pm}19.35{\mu}m$) compared to P mode( $8.37{\pm}6.98{\mu}m$). There was significant decrease of depth of defect between 1.0N($32.87{\pm}27.18{\mu}m$) and 2.0N( $14.86{\pm}15.04{\mu}m$). The area of defect was also significantly large in S mode($4482.42{\pm}3551.71{\mu}m^2$) compared to P mode( $922.06{\pm}960.32{\mu}m^2$). There was significant decrease of area of defect between 1.0N($3889.12{\pm}3936.00{\mu}m$) and 2.0N( $974.66{\pm}986.01{\mu}m$). The change of mode did not effect on the width of the defect. The change of power setting did not effect on the depth, width, and area of defect. In spite of limitation of this study it could be concluded that the use of piezoelectric ultrasonic scaler with curette tip on S mode could make significant tooth substance loss.

• Journal of Periodontal and Implant Science
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• v.31 no.1
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• pp.257-269
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• 2001

Removal of subgingival calculus is essential for the success in periodontal treatment. Subgingival instrumentation is used for the removal of all bacterial plaque and calculus. In this study, Gracey curet and Ultrasonic curet were used on single rooted teeth to conduct subgingval scaling and root planning. The remaining amount of calculus was evaluated according to type of instrument, depth of pocket, and tooth surface. 24 teeth were extracted from 14 patients being treated at department Periodontology Seoul Advantist dental hospital were used. Total 96 area(4 surface per teeth) were evaluated. 12 teeth treated with Gracey curet were used as the control group and the other 12 teeth treated with Ultrasonic curet were examined for experimental group. The 4 surface of the teeth(buccal, mesial, lingual or palatal, distal) were observed through the stereomicroscope and the images of the surface were captured and saved in CCD. The images were displayed on the monitor and the amount of calculus remained was evaluated by overlapping $10{\times}10$ grid pixel screen produced by Microsoft power point. The results evaluated were as follows 1. There was no statistically significant difference in residual calculus and tooth position following scaling and root planning of all group, but statistically significant correlation with residual calculus, probing depth, instruments and tooth surface. 2. There was statistically significant correlation between residual calculus and probing depth, but no statistically significant difference in residual calculus, tooth surface and tooth position on experimental(Ultrasonic curet) group. 3. There was no statistically significant difference in residual calculus according to the pre-treatment pocket depth and tooth position, but statistically significant correlation with tooth surface. The amount of residual calculus increase with mesial, distal, buccal and lingual(or palatal) surface on control(Gracey curet) group. 4. The Gracey showed better results than ultrasonic curet in mesial and distal surface, and there is significant difference. The results demonstrate that ultrasonic curet alone is inadequate for thorough subgingival debridement and suggest that Ultrasonic curet with Gracey curet should be more effective.

• Journal of Ocean Engineering and Technology
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• v.22 no.6
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• pp.27-34
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• 2008

The temperature distribution in the weldment is not uniform because a weldment is locally heated. Thermal plastic deformation results from the local expansion and shrinkage by the heating and cooling of metal. Therefore, residual stresses and distortion occur in the weldment. In this study, we had conducted on the weld thermal cycle simulation that is supposed as the HAZ on SS400 steel and STS304 steel. The residual stresses that were obtained from the drawing and the weld thermal cycle simulation were estimated by X-ray diffraction. We also carried out ultrasonic test for the weld thermal cycle simulated specimens, and then conducted on nondestructive evaluation by the ultrasonic parameters obtained ultrasonic test. From the results, residual stresses of weld thermal cycle simulated specimens after the residual stress removal heat treatment are lower than that of the drawing.

• Journal of Korean Society of Water and Wastewater
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• v.16 no.6
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• pp.733-740
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• 2002

The effects on dewaterability and settlability of wastewater sludge according to acid and ultrasonic pretreatment which was expected to change ECP (exocellular polymers) compounds in the sludge and bulk solution was investigated. Though ECP which attached to the sludge could stimulate coagulation of sludge particles by bridging effect, but ECP in the bulk solution deteriorated dewaterability and settlability of the sludge on the contrary. That is as the pH of the solution was decreased to 3 gradually by acid treatment, proportionally ECP in the bulk solution was attached to the sludge flocs and resulted in improvement of dewaterability and settlability of the sludge. In case of ultrasonic pretreatment, with proportional to the intensity and duration of ultrasonic application, ECP was detached and extracted from sludge flocs and these phenomena deteriorated dewaterability and settlability. Also because of the increasement of minute sludge particles according to ultrasonic, dewaterability became so much the worse.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.4
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• pp.449-458
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• 2023

As an adsorption technology for dissolved organic matter, the adsorption capacity of granular activated carbon, GAC, can be applied, but activated carbon whose adsorption capacity is significantly reduced by use is inevitably replaced or regenerated. However, due to the economics of replacement cost, thermal regeneration method is used commercially, but high energy cost and loss of activated carbon occur under high temperature conditions above 800℃. In this study, the Sono-Fenton method, a multi-oxidation technology that combines Fenton oxidation and ultrasonic oxidation, was applied to improve the regeneration efficiency of spent GAC used to treat dissolved organic matter in combined sewer overflows (CSOs), and the regeneration efficiency of spent GAC by oxidant and ultrasonic frequency was investigated. In the applied Sono-Fenton treatment, the highest regeneration efficiency of 68.5% was obtained under the regeneration conditions of Fe²⁺ 10 mmol/L, H₂O₂ concentration 1,000 mmol/L, ultrasonic treatment time of 120 min, and ultrasonic frequency of 40 kHz. And similar efficiency was also obtained at 750 kHz, while ultrasonic waves of other frequencies had poor regeneration efficiency, and the magnitude of frequency and GAC regeneration efficiency did not show a linear relationship. In the case of continuous operation of the GAC adsorption tower with CSOs prepared by diluting raw sewage, about 700 hours of operation without regeneration was possible, and as a result of applying one Sono-Fenton treatment, 40-70% COD_cr removal efficiency was obtained during a total of 1,000 hours of GAC adsorption operation.