• Ecology and Resilient Infrastructure
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• v.9 no.3
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• pp.183-193
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• 2022

The growth inhibitory effect of Microcystis aeruginosa according to the ultrasonic irradiation time was evaluated using a large algae sample volume (10 L) for various ultrasonic irradiation times (0.5, 1, 1.5, 2, 2.5 and 3 hr) at a laboratory scale. Based on the analysis of Chl-a and cell number of M. aerginosa, algae growth inhibition was observed with the decrease in Chl-a and cell number in all experimental groups after the ultrasonic irradiation. For the experimental group (T_B, T_C, T_D) with an ultrasonic irradiation time of less than 2 hours, rapid regrowth of algae was observed after growth inhibition, but the experimental group (T_E, T_F, T_G) with an irradiation time of more than 2 hours successfully inhibited algal growth lasting one or two more days. Based on the comparison of the recovery time to initial cell number the experimental group (T_B, T_C, T_D) took less than 20 days whereas the experimental group (T_E, T_F, T_G) took about 30 days. Correspondingly, the experimental group showed a high first order decay rate (𝜅) in proportion to the ultrasonic irradiation time during the growth inhibition period. Additionally, the specific growth rates (𝜇) during regrowth in the experimental group with irradiation time of more than 2 hours were relatively low compared to those in the experimental group with less than 2 hours. Therefore, ultrasonic irradiation for more than 2 hours is required for long-term (30 days) inhibition of algal growth in stagnant waters. However, the appropriate ultrasonic irradiation time for algae growth inhibition should be determined according to various field conditions such as the volume of stagnant water, water depth, flow rate, algae concentration, etc. Finally, damages to the algal cell surface and cell membrane were clearly observed, and both destruction and disturbance of gas vesicles of M. aeruginosa in the experimental group were discovered, indicating the growth inhibitory effect of Microcystis aeruginosa according to the ultrasonic irradiation time was confirmed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.5
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• pp.432-438
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• 2004

Acoustic levitation induced by ultrasonic flexural vibration at 28.4 KHz with a vibration amplitude of 10 micrometers is presented. Levitation of multiple objects along the length of the beam in a gap of 8.3 mm which is the half of acoustic wavelength is experimentally demonstrated. Analytical analysis predicts that levitated objects for the gap of half-the wavelength converges to the center of the gap, which is experimentally verified. It is observed that levitated objects with well-balanced mass distribution are set into rotation due to acoustic streaming. For cylinder-shaped Styrofoam with a diameter of 1.8 mm and a length of 3 mm, measured rotational velocity is 2400 revolution per minute. Applications of standing wave field levitation (SWFL) include manipulation of biological cells and blood constituents in biotechnology, and fine powder in material engineering.

• Wind and Structures
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• v.12 no.6
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• pp.553-574
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• 2009

This paper presents statistical analysis results of wind speed and atmospheric turbulence data measured from more than 30 anemometers installed at 15 different height levels on 325 m high Beijing Meteorological Tower and is primarily intended to provide useful information on boundary layer wind characteristics for wind-resistant design of tall buildings and high-rise structures. Profiles of mean wind speed are presented based on the field measurements and are compared with empirical models' predictions. Relevant parameters of atmospheric boundary layer at urban terrain are determined from the measured wind speed profiles. Furthermore, wind velocity data in longitudinal, lateral and vertical directions, which were recorded from an ultrasonic anemometer during windstorms, are analyzed and discussed. Atmospheric turbulence information such as turbulence intensity, gust factor, turbulence integral length scale and power spectral densities of the three-dimensional fluctuating wind velocity are presented and used to evaluate the adequacy of existing theoretical and empirical models. The objective of this study is to investigate the profiles of mean wind speed and atmospheric turbulence characteristics over a typical urban area.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.3
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• pp.395-400
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• 2013

In this paper, we introduce the implementation of high accurate level sensor system using the pulse wave type magnetostriction sensor. When a current pulse flows along the waveguide, the magnetic field also propagates towards the end of waveguide. When this magnetic field just passes the position of the magnet for level detection, the resultant magnetic field by these two magnetic fields makes a torsional reflected signal. This is used to calculate the time difference between a interrogation pulse wave and this torsional reflected signal. The key elements and characteristics were investigated to implement level sensor system based on this principle. We introduce a method to calculate the speed of ultrasonic reflected signal and how to make a model of sensing coil. In particular, we experiment with the characteristics of the torsional reflected signal according to the changes of the interrogation voltage and displacement. To make high accurate level sensor system, two methods were compared. One is to use the comparator and time counter, the other is STFT(Short Time FFT) which is capable of the time-frequency analysis.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.1
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• pp.27-33
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• 1997

A neural network approach has been developed to determine the depth of a surface breaking crack in a steel plate from ultrasonic backscattering data. The network is trained by the use of feedforward three-layered network together with a back-scattering algorithm for error correction. The signal used for crack insonification is a mode converted 70$^{\circ}$transverse wave. A numerical analysis of back scattered field is carried out based on elastic wave theory, by the use of the boundary element method. The numerical data are calibrated by comparison with experimental data. The numerical analysis provides synthetic data for the training of the network. The training data have been calculated for cracks with specified increments of the crack depth. The performance of the network has been tested on other synthetic data and experimental data which are different from the training data.

• The Journal of Engineering Geology
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• v.29 no.3
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• pp.315-327
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• 2019

Back analysis has been used to evaluate the factor of safety and circular failure plane at the landfill failure site. However, the estimated circular failure plane by back analysis is quite different from what is observed in the field. Thus, this study was conducted to estimate an actual shear failure plane inside the ground which gives a more accurate failure plane. Cone penetration test (CPT), boring test, soft X-ray image scan, density logging, and ultrasonic logging were conducted at the field and laboratory. The result of CPT showed significantly lower cone resistance, pore pressure, and undrained shear strength at a particular part. This part is a possible shear failure plane inside the ground. To validate, the soft X-ray scan images were analyzed and found the disturbed (inclined) bedding plane induced by shear activity at the estimated shear failure plane. Density and ultrasonic logging tests also found a similar result. Thus, the method in this study is possible to estimate the shear failure plane inside the ground.

• Journal of Korean Society of Transportation
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• v.14 no.3
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• pp.91-125
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• 1996

The purpose of this paper is comparatively to evaluate the confidence of Vehicle-Detector informations for various detectors in order to test to be possible the application of these to real time traffic signal control. The detectors which are tested for this study are Circle-Shaped Loop, Ultrasonic, Microwave and Image detector. The tested items for each detectors are traffic volume, degree of saturation for through and left turn movement, speed and queue length, etc. These items for each are tested at the field according to several situations, such as dry day, raining day, night and daytime. The result of these tests are performed comparative analysis and statistical examination in order to increase the confidence of the experiments.

• Journal of the Korean Graphic Arts Communication Society
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• v.15 no.1
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• pp.57-69
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• 1997

The field of printing to use pressurized ink using screen gossamer that is called screen printing. Existing cleaning solvents for the screen printing are the organic solvents containing aromatic compounds and stench. Also, Cleaning method of screen printing are for the most part mixed cleaning method of dipping and polish. In this study, we measured the cleaning efficiency by gravimetric analysis and the property change of gossamer by image analyzer using existing cleaning solvent. Also, we investigated a new cleaning process showing excellent cleaning efficiency using the ultrasonic and vibration cleaning method instead of the exsiting mixed cleaning method.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.4
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• pp.417-423
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• 2008

For the evaluation in the safety of outdoor insulator, there are various methods such as: visual observation; voltage measurement; use of ultrasonic wave due to partial discharge; electric field measurement; use of infrared/ultraviolet sensor-type camera. However, many problems have been issued regrading the reliability of the evaluation test and safety of testing operation. Accordingly, the present study has investigated and analyzed the characteristics and mechanisms of the insulator deterioration, in order to obtain an optimal method for detecting poor insulator so that the reliability of power facilities can be enhanced. Besides, based on theoretical analysis of domestic and international detection methods for poor insulator, the reliability has been compared and evaluated quantitatively. As a result, it was shown that the corona camera would be the best choice for domestic workplace application in detecting poor insulator for enhancing the reliability of power transmission line.

• Plant Journal
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• v.13 no.4
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• pp.38-40
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• 2017

This study is for stabilization of the water balance of the closed cooling water system. The pipe network analysis program is used for the water balance review, and the resistance factor correction is performed through the field measurement with the ultrasonic flowmeter to improve the reliability of the pipe network software. Based on this, it is aimed to derive optimal driving method through various case simulations.