• Journal of the Korean Wood Science and Technology
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• v.26 no.1
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• pp.38-50
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• 1998

Laser cutting tests were conducted to investigate the laser cutting characteristics of solid woods such as 25mm-thick white oak(Quercus acutissima) and maple(Acer mono), and wood-based panels such as 15mm-thick medium density fiberboard and particleboard. Test variables were laser power, cutting speed, grain direction, and moisture content. Specific cutting energy was measured and the qualities of cut surface were estimated in constant laser power. Specific cutting energy of white oak was larger than that of maple, and specific cutting energy of medium density fiberboard was smaller than that of particleboard. For both white oak and maple, specific cutting energy of green wood was smaller than that of air-dried wood because weight loss of moisture evaporation in green wood was larger than that in air-dried wood. In laser-cut surface, wood cells were not deformed and damaged, but in circular saw-cut surface fibers were pushed out and cut, and wood cells were deformed severely. However, mechanical surface roughness of saw-cut surface was smoother than that of laser-cut surface because of the existence of undeformed cell cavity in laser-cut surface.

• Explosives and Blasting
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• v.36 no.4
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• pp.16-25
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• 2018

In order to reduce ground vibration during tunnel excavation, a free surface blasting method has been applied in which a partial free surface is formed on the excavation surface and controlled blasting is performed. In this study, the ground vibration reduction due to artificial joints was evaluated by forming artificial joints on center cut using diamond wire saw and comparing the ground vibration caused by center cut blasting. As a result of comparison, ground vibration was reduced by artificial joints center cut blasting more than normal center cut blasting, and the ground vibration reduction effect of horizontal artificial joints center cut blasting was evaluated more than that of vertical artificial joint center cut blasting.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.10
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• pp.1069-1077
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• 2015

In tunnel excavation using blast, the wire saw rock cutting method generates a discontinuity perimeter around the center cut, and thus prevents blast vibration propagation to reduce vibration and noise. Therefore, the method is expected to be easy to use and economical compared with other methods. In this paper, the cutting mechanism of wire saw in tunnel excavation is investigated. A model describing the changes in cutting depth and wire saw shape inside a rock during cutting is established and validated for this purpose. Through a simulation using the model, the important characteristics of wire saw cut are investigated, and the influences of cutting conditions, such as wire saw tension, wire saw speed, feed speed, depth, and diameter of boring, on cutting performance are also examined. A method to improve the cutting performance is proposed based on the results.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.7
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• pp.94-103
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• 1995

Thin film acoustooptic beam deflector in proton-exchanged Y-cut LiNbO$_{3}$ was fabricated and measured. The planar waveguide was fabricated by using the proton-exchanged and annealing method in Y0cut LiNbO$_{3}$. Interdigital transducer for SAW(surface acoustic wave) was made by the laser lithography. Using above method, the thin film acoustooptic beam deflector was constructed. Its SAW wavelength was 20.mu.m at 174MHz center frequency. The interaction length between guided optical wave and SAW was 2.16mm. The measured 3dB bandwidth was 17MHz using He-Ne laser. And 70% diffraction efficiency was obtained at 970mW RF driving power.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.1053-1060
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• 2003

The temperature variation of the concrete pavement in the early age significantly affects the initiation and propagation of its early age cracks. This implies that the measurement and analysis of early age temperature trend are necessary to examine the causes of early age cracks in the concrete pavement. In this study, it is investigated how the early age temperature trend in the concrete pavement affects the random crack initiation and behaviors of saw-cut joints using the actual construction site which is located at the KHC test road. During 72 hours after placing the concrete pavement, the ambient air temperature and temperatures at the top, middle, and bottom in the concrete pavement were measured and the random crack initiation in concrete slabs and early age behaviors in the joints were surveyed. The investigation results indicate that the first random crack was initiated at one of the slabs placed in the early morning which have higher temperature changes during early 72 hours. In addition, the joints that were saw-cut in the morning were cracked more rapidly than those saw-cut in the afternoon.

• The Journal of the Acoustical Society of Korea
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• v.13 no.1E
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• pp.45-54
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• 1994

Characteristics of a piezoelectric material are evaluated to pick up the optimal crystal cut and propagation direction for a SAW device. For the piezoelectric single crystal $LiTaO_4$, such items are investigated as the Rayleigh wave velocity, the electromechanical coupling factor, the surface permittivity, the frequency-temperature coefficient, the air loading attenuation, the pure mode propagation, the beam steering and the misalignment sensitivity. Theoretical calculations reveal that Y-cut and Z-propagation is the optimal SAW propagation path. The results are confirmed through experiments. The method empolyed in this paper is applicable to other crystals, too, either single or poly crystals.

• Journal of Sensor Science and Technology
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• v.3 no.1
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• pp.40-45
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• 1994

$112^{\circ}$ rot. x-cut $LiTaO_{3}$ wafer was used as the substrate of SAW gas sensor. Dual delay line SAW device with IDTs which consist of the reference delay line and the sensing delay line was fabricated using photolithigraphy. Each IDTs had 10 finger pairs and finger spacing is 10 microns. One delay line channel is the reference, while the second is the sensing channel with Pb-phthalocyanine film in the propagation path. Pb-phthalocyanine film which is p-type organic semiconductor was evaporated in $10^{-5}$ torr vacuum using shadow mask selectively. Dual delay line oscillator was constructed by using the rf amplifier and AGC. Frequency of the IDTs had the range of $87{\sim}$89 MHz oscillation frequency. Oscillation frequency shifts were investigated as a function of the temperature and the concentration of $NO_{2}$ gas.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.31-35
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• 1996

The cross section of the circular rod type workpiece to be cut in the band saw machine is variable at every moment in the sawing process. When the cutting feed rate is fixed to the constant speed, the cutting edges of the band saw teeth are also variabl eat any moment, so this causes the wear of the land saw teeth and the deterioration of the quality in the surface roughness. In this study, to work out this kind of problem basically, the mean cutting force of a tooth in the band saw was estimated by using the workpiece which was smaller than the interval of each tooth, i.e. band saw pitch, in the thickness. Then the static cutting forces were predicted by appling the mean cutting forces referred above to the mechanistic cutting force model which were analyzed through the geometric profile of a band saw tooth.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.6
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• pp.37-42
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• 1983

The TV IF SAW filter if designed using the windowing method. The procedure for fabricating SAW filters is described. The filter is fabricated on the Y-cut, Z-propagation LiNbO3 wafer. The passband ripple and the smaller upper sidelobe attenuation are obseryed. Further improvements and the mass production can be expected.

• Journal of the Korea Safety Management & Science
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• v.18 no.1
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• pp.35-43
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• 2016

The past five years, industrial accidents due to food processing machinery have been occurred 725 cases, injury by the food cutter occurred 390 cases in its. On this study, to prevent food cutter injury, an attempt is made to present the improved documentation of fundamental safety of the food cutter workplace through the injury analysis of food cutter injury and surveys on band saw machine business field. Analyzing the result of 390 cases on food cutter injury, amputation, cut, puncture occupied 75.1 percent (293 cases), compressed occupied 23.3% (91 cases), also it showed constant component without reference to gender, age, scale of work place, service period. In the survey, lack of concentration for workers have been pointed out as the biggest factor in the cause of band saw machine injury. Meanwhile, such as the EU and Japan, whereas presents safety standards about band saw machines that are tailored to each country, on the other hand, South Korea doesn't provide the standards. To prevent the food cutter injury, safety standards need to be established in consideration of amputation, cut, puncture, compressed injury and financial support is required to procure protective equipment at each place of business.