• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.05a
• /
• pp.841-846
• /
• 2002

Development on non-destructive testing methods were performed to evaluate the effectiveness of crack repair for test beams induced a crack. Cracked beams are repaired with expoxy and microcement, and then they are tested by two methods, the ultrasonic pulse velocity method and the transfer function method. It is proved that the ultrasonic pulse velocity method is very valid for the evaluation of the effectiveness on expoxy repair, and the transfer function method is very applicable to evaluate the effectiveness on microcement repair.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.11 no.1
• /
• pp.34-42
• /
• 2007

Ultrasonic inspection method is more profitable than X-ray radiographic inspection in cost and effect of defect detection such as debond, damage, and it doesn't need special constructions. The method can also be a possible real time inspection with safety. This report explains 1)the experiment and analysis of ultrasonic property of solid propellant, 2)the inspection methods of propellant/liner debond by inside or outside inspection, and 3)the inspection methods of propellant microcrack by damage. From the results, it is possible to detect the defect of propellant/liner debond by inside or outside inspection. Futhermore, it can be possible to detect the propellant microcrack caused by damage using the ultrasonic attenuation.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.16 no.2
• /
• pp.66-73
• /
• 2008

In this paper, ultrasonic range system which detects parking lot in parking area is studied. The important part for detecting parking lot accurately is to detect the first and second corners of possible parking lot, and for that, new method using multiple echo function is introduced in this paper. Many probabilistic methods have been used to reduce uncertainties of ultrasonic sensor for distance and location of objects. Method using multiple echo, however, gives accurates results as well as simple algorithm. For experiments in parking space, ultrasonic range system was attached to a Pioneer AT-2 and final parking space map was created in a fusion with position information from wheels of a Pioneer AT-2. We will show the results are compared with error of another methods.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07b
• /
• pp.705-709
• /
• 2004

In this study, the foot-spa driving circuit using ultrasonic vibrator was manufactured The used ultrasonic vibrator was PSN-PMN-PZT ceramic with the radius of $25{\Phi}$ and the thickness of 2, 2.5, 3, 3.5 and 4mm, respectively. Resonent frequency for driving ultrasonic vibrator at the fabricated circuit was generated using the self exciting and the external exciting methods. Fabricated foot-spa showed the best condition at the resonent frequency of 1.130MHz and the ceramic thickness of 2.0mm. That is, when the foot-spa was operated for 360 min. at $0.5\ell$ water, temperature increase of water was $14^{\circ}C$ at the self exciting method and $16^{\circ}C$ at the external exciting methods, respectively.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.19 no.5
• /
• pp.363-368
• /
• 1999

Ultrasonic pulse-echo methods measuring the transit time through specimens have been widely used in determination of ultrasonic velocity and thickness of specimens. Usually, to determine the velocity of the ultrasonic. the transit time of the ultrasonic pulse through specimen is measured by using the ultrasonic measuring equipment such as the oscilloscope including ultrasonic pulser/receiver and the thickness of the specimen is measured by using the length measuring instrument such as micrometer or vernier calipers etc., i. e. each parameter is measured by using each measuring method. In the case of the measuring the thickness of a specimen by using the ultrasonics. the ultrasonic equipments, which measure the thickness, such as the ultrasonic thickness gauge must be calibrated by using the reference block of which the ultrasonic velocity is known beforehand. In the present work, we proposed a new method for simultaneous measurement of ultrasonic velocity and thickness without reference blocks. Experimental results for several specimens show that proposed method have good agreements with those by traditional ultrasonic method.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.7 no.2
• /
• pp.231-233
• /
• 2003

To understand the physical method for induction of anti-bacterial substances from the silkworm larvae, Bombyx mori, three physical methods, i.e., infrared radiation, ultraviolet radiation and ultrasonic wave, have been used in this study. The results have shown that ultrasonic wave can induce anti-bacterial sub-stances effectively than radiations in the B. mori larva. The induction of anti-bacterial substances was different from silkworm race to race. Summer-autumn silkworm race (Qiufeng${\times}$Baiyu) was easy to induce antibacterial substances. It is suggested that the ultrasonic wave is a simple and easy method for induction.

• 유체기계공업학회:학술대회논문집
• /
• 2005.12a
• /
• pp.287-294
• /
• 2005

Flow rate measurement uncertainties of the ultrasonic flow meter are generally influenced by many different factors, such as Reynolds number, flow distortion, turbulence intensity, wall surface roughness, velocity integration method along the acoustic paths, and transducer installation method, etc. Of these influencing factors, one of the most important uncertainties comes from the velocity integration method. In the present study, a optimization weighting factor method for 5-chord, which is given by a function of the chord locations of acoustic paths, is employed to obtain the mean velocity in the flow through a pipe. The power law profile is assumed to model the axi-symmetric pipe flow and its results are compared with the present weighting factor concept. For an asymmetric pipe flow, the Salami flow model is applied to obtain the velocity profiles. These theoretical methods are also compared with the previous Gaussian, Chebyshev, and Tailor methods. The results obtained show that for the fully developed turbulent pipe flows with surface roughness effects, the present weighting factor method is much less sensitive than Chebyshev and Tailor methods, leading to a better reliability in flow rate measurement using the ultrasonic flow meters.

• Restorative Dentistry and Endodontics
• /
• v.18 no.2
• /
• pp.377-386
• /
• 1993

The purpose of this study was to evaluate the disinfection efficacy of root canal irrigation method and irrigation solution in infected root canals. Access cavity were prepared in single-rooted extracted human teeth and each canals were prepared with step-back method and sterilized with ethylene oxide gas. Prepared teeth were experimentally inoculated in the canals for 30 minutes with four aerobes(Streptococcus mutans, Stapylococcus aures, Streptococcus sanguis, and E. coli) and two anaerobes(Streptoccus intermedius, and Clostrium perfringens). Normal saline, 3% $H_2O_2$, and 3% NaOCl were used as irrgation solutions. And root canals were irrigated with each irrigation solutions manually with disposible syringe or ultrasonic instument. (Apoza Uitrasonc, Taiwan). The irrigation effect on the eradication of S. aures and S. intermedius with normal saline was not similar between manual method and ultrasonic method. No significant differences were observed in the eradication of E. coli and C. perfringens among the irrigation solution and irrespective of the irrigation methods. In S. aurues and S. mutans, there was somewhat different eradication effect according to irrigation solutions, but there was no significant difference between manual method and ultrasonic methods. These results suggest that ultrasonic irrigation method with saline is more effective in some strains than manual irrigation.

• Journal of IKEEE
• /
• v.26 no.2
• /
• pp.169-175
• /
• 2022

This paper introduces an interference elimination method using k-nearest neighbor (KNN) algorithm for precise distance estimation by reducing interference between ultrasonic sensors. Conventional methods compare current distance measurement result with previous distance measurement results. If the difference exceeds some thresholds, conventional methods recognize them as interference and exclude them, but they often suffer from imprecise distance prediction. KNN algorithm classifies input values measured by multiple ultrasonic sensors and predicts high accuracy outputs. Experiments of distance measurements are conducted where interference frequently occurs by multiple ultrasound sensors of same type, and the results show that KNN algorithm significantly reduce distance prediction errors. Also the results show that the prediction performance of KNN algorithm is superior to conventional voting methods.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.2
• /
• pp.116-129
• /
• 2000

Due to the great complexity of the physical phenomena involved in most ultrasonic nondestructive testing, the numerical method is effective in many cases of their theoretical modeling. A brief overview is provided in this paper of the numerical methods used in modeling ultrasonic nondestructive testing, with an emphasis on the finite difference and the finite element methods. The procedures of execution, special considerations required, and some previous research results of the finite difference and the finite element methods are presented, with a rather extensive list of work reported in the literature. These numerical modeling techniques for ultrasonic nondestructive testing are expected to be more reliable and more convenient, as a result of the continuing technological development of computers.