• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.42-47
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• 1996

Due to high increase of labor charge and necessarity of better quality control on concrete, various studies have been carried out to improve a flowability of concrete without the use of mechanical vibrator. As a result of enthusiastic study, one can closely access to the development of high flowable concrete in a laboratorial view. Application to practical field, however, is still far as long as a regulation for construction is not properly specified. Based on the idea that lateral pressure measured from high flowable concrete will be larger than those from general typed concrete, we read a series of lateral pressure from mechanical pressure plate and compared those with the values calculated form specified formula.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.113-116
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• 2002

In this paper, we propose the sound-mapping algorithm of the detected obstacle by ultrasonic sensors. We apply this algorithm to a Obstacle alarm for the visually impaired. In our system, we acquire obstacles information using ultrasonic sensors, and transform two-dimensional and distance information into sound-imaging information and vibrator with azimuth (direction) and distance. We implement this system with ultrasonic sensors to more effective expression of the obstacle information. The distance of an obstacle can be expressed by sound pressure level, and azimuth of the obstacles can be expressed by inter-aural time difference (ITD) and inter-aural level difference (ILD) that are two important cues in a binaural system. These are the principal cues for sound localization, to detect sound source. In this system, the obstacle is substituted with a sound source. The visually impaired receive sound information of obstacles by headphone.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.525-528
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• 2000

Piezoelectric ceramics can provide electro-mechanical transduction with high stresses but low displacement. To obtain larger displacements, several mechanical amplifying structures have been used. High alternating displacements can be obtained using resonant structure. In this paper, we designed three kinds of the bolt-tightened Langevin type ultrasonic vibrators whose resonant frequencies are 30[kHz], 40[kHz]. FEM(Finite Element Methode) was employed to calculated the resonant frequencies and maximum displacements of designed vibrators. The designed resonant frequencies and computer calculated frequencies were coincided. When input voltages were increased, maximum displacements were also raised. ANSYS was used to find resonant frequencies and calculate displacements of vibrators.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.754-758
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• 2000

Milli-structure components are classified as component group whose size is between macro and micro scale. that is, about less than 20mm and larger than 1mm. The forming of these components has a typical phenomenon of bulk deformation with thin sheets because of the forming size. In order to conventional metal forming, where numerical process simulation is already fully applied, the micro-forming process is characterized by some scale effects which have to be considered in an advanced process simulation. milli-structure rectangular cup drawing is analyzed and designed using the finite element method and experiment. The result of the finite element analysis is confirmed by a series of experiments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.8 no.1
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• pp.38-42
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• 1983

The characteristic of a Tunnel Diode(TD) is approximated by the summation of two exponential terms, obtained from the haracteristic curves displayed on the curve tracer. Using this result, static characteristic of a TD pair was plotted by a computer programming. From these static characteristic curves, the triggering behavior of TC pair multi-vibrators was described graphically. Two stable characteristics were analyzed by piecewise linear Method. Theoritical switching Theoritical switching times of a TD pair flip-flop(F-F) circuits were compared with experimental results.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.536-538
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• 2002

Various types of switching inverters such as a full-bridge, a half bridge, a push-pull, and a multi-vibrator, are introduced for multi-lamps backlighting with EEFLs and CCFLs. Synchronizing the phase between voltage and current waves, a high luminance and a high efficiency have been achieved.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.153-159
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• 2002

This paper deals with the measurement of the fluid viscosity by using the torsional vibration of a circular red excited by a torsional vibrator at one end. The effect of an adjacent viscous fluid on the torsional vibration of the rod has been studied theoretically and expressed in terms of the mechanical impedance. The theoretically-obtained trend that the mechanical impedance is proportional to the square root of the viscosity times the density of the fluid has been confirmed by the impedance measurement. The paper demonstrates that a torsionally-vibrating rod can be used as a sensor to measure the viscosity of a fluid.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.506-512
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• 1997

Ultrasonic knives have been successfully used for the surgery of many medical fields. However, the conventional ultrasonic knives for surgical operation cannot be controlled its resonant frequency. So if the material to cut has different characteristic impedance then different ultrasonic knife will be needed. Because the optimum driving frequency of ultrasonic knife is different by characteristic impedance of material. In this work, using a frequency variable ultrasonic transducer made of multi-layered PZT vibrator, a frequency controllable ultrasonic knife will be suggested. The design and computation principles will be also derived. For this work, firstly, the characteristics of this ultrasonic knife will be analyzed by transmission line model equivalent circuit, and the free admittance characteristics and vibrational velocity distributions will be obtained. Secondly, we will design and make the frequency controllable electrical oscillator for driving this ultrasonic knife.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.2
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• pp.214-220
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• 2015

Since resources of fossil fuels are limited, development of alternative energies is emphasized and research on new-regenerative energy is actively in progress worldwide. In present research, physical and chemical characteristics of mixed fuel are analyzed in detail for the different mixture rate of conventional and bio-diesel and ultrasonic irradiation time. Experimental setup consists of ultrasonic generator, vibrator, horn, and reflector. Various physical and chemical characteristics of fuel are investigated for volumetric mixture rate of bio-diesel from 0 to 100%. As results, viscosity and surface tension is increased as mixture rate of bio-diesel is increased. Also, molecular splits and reunions are increased and decreased repeatedly after some period of time as ultrasonic energy irradiation time is increased. As conclusion of experiments, Olefin rate, Branch index, and Aromatic rate are influenced by ultrasonic irradiation time.

• Journal of the korean Society of Automotive Engineers
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• v.9 no.4
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• pp.41-49
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• 1987

It is an experimental study to improve the characteristics of combustion and exhaust emission gas in the gasoline engine. These characteristics are influenced by the fuel droplet size. To improve these characteristics, we make the ultrasonic atomization apparatus, and compare with the commercial carburetor. The results obtained are as follows: 1. Maximum atomization quantity is obtained by the vibrator of resonancy frequency 1.65MHz in the ultrasonic atomization apparatus. 2. With ultrasonic atomization apparatus, more than 99% of atomization rate can be obtained regardless of intake air temperature, velocity, and air-fuel ratio. 3. Atomization rate of the commercial carburetor increases with the air-fuel ratio and intake air temperature. 4. Difference of atomization rate between the ultrasonic atomization apparatus and the commercial carburetor increases with decreasing air-fuel ratio. 5. Droplet size is about 1-5.mu.m at the ultrasonic atomization apparatus, and 80-150.mu.m at the commercial carburetor, which indicates the ultrasonic atomization apparatus is excellent in atomization.