• Journal of the Korean Society of Visualization
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• v.20 no.3
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• pp.19-26
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• 2022

In droplet microfluidics, precise droplet manipulation is required in numerous applications. This study presents ultrasonic surface acoustic wave (USAW)-based microfluidic device for label-free droplet separation based on size. The proposed device is composed of a slanted-finger interdigital transducer on a piezoelectric substrate and a polydimethylsiloxane microchannel placed on the substrate. The microchannel is aligned in the cross-type configuration where the USAWs propagate in a perpendicular direction to the flow in the microchannel. When droplets are exposed to an acoustic field, they experience the USAW-induced acoustic radiation force (ARF), whose magnitude varies depending on the droplet size. We modeled the USAW-induced ARF based on ray acoustics and conducted a series of experiments to separate different-sized droplets. We found that the experimental results were in good agreement with the theoretical estimation. We believe that the proposed method will serve as a promising tool for size-based droplet separation in a label-free manner.

• Advances in nano research
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• v.12 no.1
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• pp.1-23
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• 2022

To date, nondestructive tests (NDT) applications and advances in detecting the dispersion and defections of the nano concrete (NC) materials fields are very limited. The current paper provides a review of the dispersion efficiency of nanomaterials in cement-based materials and how NDT can be efficiently used in detecting and visualizing the defections and dispersions of NC. The review identifies the characteristics of different types of nanoparticles used in NC. Nanomaterials influences on concrete characteristics and their dispersion degree are presented and discussed. The main aim of this article is to present and compare the common NDT that can be used for detecting and visualizing the defections and dispersions of different kinds of nanomaterials utilized in NC. The different microscopy and X-ray methods are explicitly reviewed and compared. Based on the collected data, it can be concluded that the fully detecting and visualizing of NC defections and dispersions have not been fully discovered and that needs further investigations. So, the distinction of this paper lies in defining NDT that can be employed for detecting and/or visualizing NC defections and dispersions.

• Journal of Sensor Science and Technology
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• v.33 no.5
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• pp.242-247
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• 2024

Pure and 0.3 wt% Au-doped In₂O₃ hollow spheres were synthesized via ultrasonic spray pyrolysis of droplets containing an In-source and sucrose in air and their gas sensing characteristics to 1 ppm ethanol, 1 ppm toluene, 1 ppm xylene, 2 ppm nitrogen dioxide (NO₂), and 30 ppm carbon monoxide (CO) were measured at 400 - 450℃. The pure In₂O₃ hollow spheres exhibited relatively low gas responses and sluggish recovery kinetics. In contrast, the doping of Au into In₂O₃ hollow spheres significantly increased the gas response (S= resistance ratio) to 1 ppm ethanol (S= 20.6) at 400℃ with low cross-responses (S = 1.3-8.8) to other interference gases. Furthermore, the hollow spherical morphology of In₂O₃ provides a large surface area and facilitates rapid gas diffusion, resulting in fast response and recovery times. The sensor exhibited excellent performance with a low detection limit of 1.6 ppb. These findings indicate that the Au-In₂O₃ hollow spheres are promising candidates for advanced ethanol-sensing applications, particularly in breath-alcohol monitoring for ignition interlock devices.

• Korean Journal of Acupuncture
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• v.40 no.4
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• pp.156-168
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• 2023

Objectives : This study aimed to determine the status of thermal stimulation devices approved in Korea for medical applications over the past 10 years, and based on this, to obtain insight for future thermal treatment in Korean medical institutions. Methods : We searched the item classification list entitled "Regulations on Medical Device Items and Rating by Item" from the Ministry of Food and Drug Safety Notice No. 2021-24, 2021 (Enforced March 19, 2021; www.mfds.go.kr) for individually licensed heaters using the terms "heat" and "heating". Results : We identified 17 items of thermal stimulation product group, of which 1,308 devices were licensed by February 4, 2022, and 53.2% of them (n=696) were devices with valid permits for distribution in Korea. Among the licensed devices, heating pad systems under/overlay (electric, home use) were approved the most, but combinational stimulator (for medical use, home use; Grade 2) accounted for the highest percentage among the current valid permission. Moxibustion apparatuses were licensed separately for electrical use and non-electrical use, and occupied a low percentage of the total devices. We analyzed 307 devices that were accompanied by technical documents and found that the heat sources were wires in 145 (47.2%), infrared rays in 44 (14.3%) and ultrasonic waves in 42 (13.7%) devices. Most (83.1%) devices were used for pain relief, while other applications included beauty, cancer treatment, maintenance of infant body temperature, and healing fractures. Conclusions : Thermal stimulation devices accounted for about 0.9% of all medical devices, and among them, combinational stimulators and heating pad systems under/overlay had the most valid permits. Thermal stimulation devices using heating wires and infrared rays were the most prevalent, and most were used to relieve pain. In order to develop a range of thermal stimulation devices that can be utilized in Korean medical institutions, it is imperative that they have potential applications beyond pain management, addressing various medical purposes. To achieve this, foundational research is necessary to effectively apply diverse heat sources based on medical objectives.

• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.782-788
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• 2002

Several non-destructive test methods have been developed to estimate compressive strength of concrete in other countries. However, their applications are limited in domestic concrete due to their inaccuracies. The purpose of this study is to propose an aging coefficient of compressive strength of structural concrete in rebound number method and ultrasonic pulse velocity method for domestic concrete. The test variables include type of aggregate, curing condition, and compressive strength. Two approaches are used to estimate aging coefficient. One is evaluated by uniform linear regression equation for all ages and shows uniform strength reduction coefficient regardless of material properties and the other is evaluated by individual regression equation for each ages and shows nonuniform strength reduction and rebound increasing coefficients which decrease with increasing of rebound number and compressive strength. The latter result which can include the effect of rebound number and compressive strength is more resonable than the former.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.297.2-297.2
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• 2016

Photoacoustic generation of ultrasound is an effective approach for development of high-frequency and high-amplitude ultrasound transmitters. This requires an efficient energy converter from optical input to acoustic output. For such photoacoustic conversion, various light-absorbing materials have been used such as metallic coating, dye-doped polymer composite, and nanostructure composite. These transmitters absorb laser pulses with 5-10 ns widths for generation of tens-of-MHz frequency ultrasound. The short optical pulse leads to rapid heating of the irradiated region and therefore fast thermal expansion before significant heat diffusion occurs to the surrounding. In this purpose, nanocomposite thin films containing gold nanoparticles, carbon nanotubes (CNTs), or carbon nanofibers have been recently proposed for high optical absorption, efficient thermoacosutic transfer, and mechanical robustness. These properties are necessary to produce a high-amplitude ultrasonic output under a low-energy optical input. Here, we investigate carbon nanotube (CNT)-polydimethylsiloxane (PDMS) composite transmitters and their nanostructure-originated characteristics enabling extraordinary energy conversion. We explain a thermoelastic energy conversion mechanism within the nanocomposite and examine nanostructures by using a scanning electron microscopy. Then, we measure laser-induced damage threshold of the transmitters against pulsed laser ablation. Particularly, laser-induced damage threshold has been largely overlooked so far in the development of photoacoustic transmitters. Higher damage threshold means that transmitters can withstand optical irradiation with higher laser energy and produce higher pressure output proportional to such optical input. We discuss an optimal design of CNT-PDMS composite transmitter for high-amplitude pressure generation (e.g. focused ultrasound transmitter) useful for therapeutic applications. It is fabricated using a focal structure (spherically concave substrate) that is coated with a CNT-PDMS composite layer. We also introduce some application examples of the high-amplitude focused transmitter based on the CNT-PDMS composite film.

• Journal of Sensor Science and Technology
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• v.25 no.4
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• pp.271-274
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• 2016

The reliability and reproducibility of gas sensors are very important for real applications. The influence of nanofiber length and sensing film thickness on the reliability and response of gas sensing characteristics was investigated. For this, the length of $SnO_2$ nanofibers was controlled by tuning ultrasonic treatment and the different thicknesses of sensing films were prepared by manipulating the amount of slurry deposition. The sensor prepared from long nanofibers (length: ${\sim}3.6{\mu}m$) showed the significant fluctuation of gas sensing characteristics when the film becomes thinner than $18{\mu}m$, while that prepared from short nanofibers (length: ${\sim}0.9{\mu}m$) showed reproducible sensor response and resistance regardless of film thickness. Moreover, the shortening of nanofibers enhanced the gas response ~2 times, which can be explained by the increase of chemiresistive fiber-to-fiber contacts. The reproducibility, gas response, and selectivity of $SnO_2$ nanofiber gas sensor could be controlled by tuning nanofiber length, film thickness, and catalyst loading.

• Journal of KIISE:Software and Applications
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• v.36 no.11
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• pp.920-927
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• 2009

In this paper, we developed a system that could assist appropriate activities for medication compliancy of the elderly. It employs a proactive knowledge which is represented as XML templates predefined for their medication activities. The knowledge-based assistance depends on the contexts considerably, which the system can recognize by continuously monitoring the current position and the time-schedule for their medications. The monitoring can be performed with ultrasonic sensors and infrared sensors mounted in a display and a pillbox respectively. According to the recognized contexts, the medication activities required by the elderly can be serviced through user-friendly multimedia display. In special, our experiment evaluates that the developed system is able to enhance the medication compliancy of chronic disease patients.

• Proceedings of the Korea Contents Association Conference
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• 2007.11a
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• pp.201-205
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• 2007

This thesis aims to realize an intelligent home service robot that alerts the user to dangerous situations such as fires and gas leaks by utilizing wireless internet platforms in a cellular phone. The intelligent home service robot is composed of the following parts: The robot part consists of a gas sensor, a fire detector, a smoke sensor, ultrasonic sensors, motors, a camera and a Blue-tooth module and perceives various danger circumstances; The middleware part connects the robot part with the mobile part through the middleware applications, monitors the robot and notifies an emergency situation using SMS modules; The mobile part communicates with the middleware using TCP/IP protocol and controls the robot through various commands; The proposed scheme is to control the sensors of the robot part through and Atmega128 processor, and the mobile part was developed based on the WIPI platform. The robot and middleware parts will be installed in the household, and will be controled by mobile part from the outside.

• Journal of ILASS-Korea
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• v.11 no.4
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• pp.251-265
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• 2006

To prevent the ozonosphere from being destroyed by Halon, it is an urgent task to find out Halon replacement. As one of the replacements water mist have showed broad applications by its advantages: little pollution to environment (not destroying the ozone layer or bring green house effect), extinguishing fire quickly, consuming a small quantity of water and having little damage to the protected objects. The methods of generating water mist strongly influence fire suppression effectiveness, which determine the cone angle, drop size distribution, flux uniformity, and momentum of the generating spray. The traditional water mist nozzle included pressure jet nozzles, impingement nozzles and twin-fluid nozzles. All of them have more or less disadvantages for fire suppression. Therefore, many research institutes and corporations are taking up with innovations in mist generation. This article provided some recent studies in State Key Laboratory of Fire Science (SKLFS) of University of Science and Technology of China. SKLFS have investigated new methods of generating water mist (i.e. effervescent atomization and ultrasonic atomization). and self developed a series of nozzles and developed advanced DPIVS (Digital Particle Image Velocimetry and Sizing) technique. Characteristics of water mist (the distribution of droplet sizes, flux density, spray dynamics and cone angle) produced by these nozzles were measured under different conditions (work pressure, nozzle geometry, etc.) using LDV/APV and DPTVS systems. A series of experiments were performed to study the fire suppression effectiveness in different fire scenario (different kindsof the fuel, fire size and ventilation conditions). The fire extinguishing mechanisms of water mist was also discussed.