• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1512-1517
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• 2003

Augmentation of CHF by ultrasonic is experimentally studied under subcooling pool boiling condition. Experiment is carried out for downward-facing plate with and without the ultrasonic. The working fluid is distilled water. Experimental apparatus is composed of a bath, power supply, test section, ultrasonic generator, DAQ system. Experiment is performed with the subcooling temperature of $5^{\circ}C$, $20^{\circ}C$, $40^{\circ}C$ and the inclined angle of $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $45^{\circ}$, 90. From the experimental results, it is found that ultrasonic effect enhances CHF of the downward-facing plate. As increasing the degree of subcooling, the rate of CHF increase is enhanced. As increasing the inclined angle, the rate of CHF increase decreases. Also, we can see that the heat transfer mechanism of CHF augmentation is closely connected with the dynamic behavior of bubble generation and departure.

• Applied Chemistry for Engineering
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• v.20 no.3
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• pp.322-328
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• 2009

Emulsion polymerization of octamethylcyclotetrasiloxane (OMCTS) was conducted under ultrasonic irradiation. Two sources of ultrasound with different intensities and frequencies of 20 KHz and 40 KHz were used for horn and bath type reactor, respectively. A combined process of horn and bath was also investigated. The effectiveness of the reaction systems was investigated by measuring conversion as well as intrinsic viscosity of the products. The influence of reaction temperature and sonication time on the progress of sonochemical polymerization was examined. It was found that conversion of greater than 80% and high viscosity were achieved within a few minutes of sonication in a horn type reactor, however, conversion and viscosity showed maximum values depending upon the sonication time. In a bath type reactor where a relatively weak intensity was maintained, longer duration time of more than one hour of sonication was required to reach a high level of conversion and viscosity. Compared with the horn type system, the conversion and viscosity in the bath type reactor were increased along with the sonication time. When the polymerization was carried out in a combined system of horn and bath, the evolution of conversion and molecular weight was quite different from the other cases. For the given geometry of reaction system, acoustic analysis using a commercial software was carried out and the results were correlated with experimental observation.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.4 s.33
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• pp.55-59
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• 2004

We fabricates the $TiO_2$ thin film from anatase phase $TiO_2$ powder having good photocatalytic property using aerosol deposition method at room temperature. Aerosol deposition method, which sprays an aerosol powder with ultrasonic velocity and deposits a thin film on substrate at low temperature, has the advantages of low thermal stress and low cost. To fabricate the $TiO_2$ thin film, the aerosol bath pressure and chamber pressure were 500 torr and 0.4 torr, respectively. The difference of aerosol bath pressure and chamber pressure accelerated the $TiO_2$ nano powder to ultrasonic velocity through the nozzle of $0.4 mm{\times}10 mm$ and $TiO_2$ thin film was finally formed. SS mesh with diameter of 50 mm was used as a substrate to apply the $TiO_2$ thin film to water quality purification. The raw powder was dehydrated for the good dispersion of $TiO_2$ powder. To suppress the formation of second particle, the powder was dispersed for 90 min in alcohol bath by ultrasonic treatment and desiccated. The grain size of $1 {\mu}m$ was observed in $TiO_2$ thin film deposited on SUS mesh by scanning electron microscopy (SEM). The anatase phase of $TiO_2$ thin film was also observed by X-ray diffraction (XRD) and the anatase phase of raw powder was nicely maintained after aerosol deposition. The results are applicable to water treatment filter having photocatalytic reaction.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.278-281
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• 2003

A new type of ultrasonic spray nozzle was fabricated with piezoelectric devices. The spray nozzle was designed for the chemicals dispersion in the water purification bath. The piezoelectric properties in ultrasonic spray nozzles were optimized for the better dispersion of chemicals for purification process. Ultrasonic spray nozzle was packaged in metal case with silicone resin for the water proof application.

• Analytical Science and Technology
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• v.36 no.4
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• pp.152-160
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• 2023

Adenosine and cordycepin are bioactive compounds with health benefits. Therefore, both substances are often used to assess the quality of Cordyceps products. Optimization and validation of the HPLC/DAD method for determining two nucleosides were studied. The samples were prepared using an ultrasound-assisted extraction (ultrasonic bath). The result was optimal conditions for aqueous extraction, an extraction time of 35 min, and an extraction temperature of 40 ℃. The Chromatographic separation was achieved using a reverse phase column (InfinityLab Poroshell 120 EC-C18, 4.6 × 250 mm, 2.7 ㎛) at 30 ℃ with a mobile phase gradient elution of water and methanol at a flow rate of 0.7 mL/min. The eluents were monitored via a diode array detector at 260 nm. Two nucleosides were separated by less than 12 min after injection. The developed method was found to be excellent linear (r² > 0.9999), accurate (% recovery 95.34-98.51), and precise (% relative standard deviation < 2.0). The limit of detection (LOD) and quantification (LOQ) were 0.45 and 1.38 mg/mL for adenosine and 0.47 and 1.43 mg/mL for cordycepin, respectively. This method was satisfactory for simultaneously quantitating two nucleoside contents, which were used to evaluate Cordyceps products.

• Journal of Energy Engineering
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• v.12 no.2
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• pp.139-144
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• 2003

Augmentation of CHF by ultrasonic vibration in water pool is experimentally investigated under pool boiling condition. The experiments are carried out using copper coated plates and distilled water. Measurements of CHF on flat plate heated surface were made with and without ultrasonic wave and with variations in inclined angle of the surface and water subcooling. Experimental apparatus consists of a bath, power supply, test section, ultrasonic generator, and data acquisition system. The measurements show that ultrasonic wave enhances CHF and its extent is dependent upon inclination angle as well as water subcooling. The rate of increase in CHF increases with an increase in water subcooling while it decreases with an increase in inclination angle. Visual observation shows that the cause of CHF augmentation is closely related with the dynamic behavior of bubble generation and departure in acoustic field.

• Journal of the Korean institute of surface engineering
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• v.20 no.1
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• pp.4-14
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• 1987

The nickel-zinc alloy depositions have been studied in nickel chloride added chloride baths, to find out the effects of ultrasonic irradiation for the electrodeposition processes. The compositions of deposited alloys, the current efficiencies and the metallographic appearances in various conditions of Electrodeposition were investigated, in the range of ultrasonic irradiation of 50,500 and 1,000 Kc/s respectively. The results obtained are as follows; 1. Generally the nickel deposition process is more preferably activated than that of zinc by the ultrasonic irradiation. 2. The radios of nickel to zinc in the deposit are higher according to increase of nickel ion concentration and bath temperatures in irradiated baths. 3. The current efficiencies are also higher in the irradiated baths, so that the depolarization effect is noticeable. 4. The brightness and leveling effect of the deposits are appreciably better in the irradiated baths than in non-irradiated in 0.3M and 0.6M of nickel chloride and zinc chloride solutions and the current density of 3A/$dm^2$. 5. The mechanism of alloy deposition has been tentatively suggested in the case of ultrasonic irradiation.

• Corrosion Science and Technology
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• v.12 no.4
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• pp.185-190
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• 2013

In the present study, $Ni-TiO_2$ composite coatings were electrodeposited in a sulfamate bath containing $TiO_2$ particles. The influence of the ultrasonic treatment on the co-deposition of $TiO_2$ particles in the coating and the hardness of the electrodeposited $Ni-TiO_2$ composite has been investigated. Three different ultrasonic treatments (pretreatment before the electrodeposition (pre-UT), pretreatment + applied during the electrodeposition (UT), and the electrodeposition without the ultrasonic treatment (w/o UT)) were performed. The $Ni-TiO_2$ composite coatings are characterized using scanning electron microscopy (SEM), image analyzer, and hardness tester. Comparison of results indicates that the volume fraction is more important factor than the agglomerated particle size in terms of the strength improvement, and the strength of the electrodeposited $Ni-TiO_2$ composite coatings is enhanced with pre-UT condition.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.101-106
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• 1999

Pb$(Zr_{0.5},Ti_{0.5})O_3$ thin films were prepared on $Pt/Ti/SiO_2/Si$substrates by spin-coating. The sol was sonicated in an ultrasonic bath to promoto homogenization and the results were compared with untreated case. In the case of PZT thin films prepared from sonicated sol, only perovskite phase was obtained at $550^{\circ}C$ and "rosette" structures in the films disappeared. Dieletric constants (10kHz), remnant polarization, and coercive field of the films prepared from untreated and sonicated sol were 335 and 443, 12.3 and17.7$\mu$C/$\textrm{cm}^2$, 168.4 and 153.5 kV/cm. Electrical properties were improved by introduction of the sonication processon process

• Journal of Soil and Groundwater Environment
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• v.17 no.1
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• pp.42-46
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• 2012

The ISO document of ISO/TC/190/SC3/WG11/N11 is a working draft of international standard (WD) dealing with analytical method for the determination of explosives and related compounds using high performance liquid chromatography. The scope of this WD covers the storage of samples, preparing test portion, extraction and instrumentation. The main purpose of this study was to improve the extraction conditions which were already adopted in the WD. For this purpose, mechanical shaking method could be corresponded up to 18 hours of ultrasonic bath extraction in the WD was tested. Methanol was also tested with the intention of being added as an extracting solvent other than acetonitrile in the WD. According to the results, 16 hours of mechanical shaking method showed statistically the same effectiveness as that of 18 hours of ultrasonic bath extraction. In case of extracting solvent, methanol also showed statistically the same extraction capability as acetonitrile for DNB, TNT, 2-A-DNT and 2,4-DNT. However, the recovery rate of TNB with methanol extraction was 40% higher than that of acetonitrile extraction. Through adding mechanical shaking method into committee draft (cf. the next stage draft of the WD during the process for making international standard), ISO standard of analyzing explosives and related compounds in soil would become more useful in dealing with huge number of field samples in the laboratory. In other aspect, adopting methanol as an alternative extracting solvent would be very effective in the terms of exchangeability with GC-ECD/MS method which is being developed by German experts.