• 한국초지조사료학회지
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• 제10권2호
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• pp.84-88
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• 1990

This experiment was conducted to evaluate the effect of cutting frequency and nitrogen fertilization on $(NO_3$-N leaching losses under 12 years mixture permanent meadow, The results of this study were summarized as follows: 1. There was no difference in the $(NO_3$-N content of soil water within 1 m soil depth during the whole experimental period. It means that the content of $(NO_3$-N leaching losses was not influenced by botanical composition, cutting frequency and nitrogen fertilization in this experiment. 2. The level of $(NO_3$-N content during the whole experimental period was not in excess of 0.5 ppm level.

• 동력기계공학회지
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• 제15권5호
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• pp.22-29
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• 2011

In this study, the damage mechanism of large scale steam turbine due to water induction was analyzed and recovery characteristics were reviewed. A turbine consists of the rotating rotor and the stationary casing, and the clearance between them is very small for the efficiency enhancement. If water induction, while relatively cold steam or water is introduced into turbine, occurs, the considerable humping is caused at the casing near the initial water induction point and that induces the rubbing between rotor and casing. Finally, it leads to the catastrophic failure. Bowed rotor has the different characteristics in the recovery depending on damage degree. The elastic deformation due to light rubbing is recovered by turning the rotor with 3 rpm under normal operation condition, but most plastic deformation due to rubbing deforms the local microstructure and that results in permanent deformation which could not be recovered under normal operation condition. Bowed rotor has diverse characteristics depending on the recovery method, and the method is empirical and needs the cutting edge technology. Careful recovery treatment of the rotor will eliminate the risks and secure the high quality rotor similar to new rotor. If any critical error is made during the recovery, the rotor would not be recovered permanently and it should be scrapped.

• 한국물환경학회지
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• 제20권2호
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• pp.163-169
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• 2004

Feasibility of using PE sheet laminated CSP(Corrugated steel pipe) to sewers were tested via corrosion and abrasion tests for PE sheet laminated CSP; 1) corrosion test for PE film and PE coated plate, 2) corrosion test for joint of PE sheet laminated CSP, 3) corrosion test for outside of PE sheet laminated CSP, and 4) abrasion test for inside of PE sheet laminated CSP. The results for the corrosion and abrasion tests are as follows. 1. Results for corrosion tests on PE films and zinc coated steel plates that were coated with PE films show that the surfaces of both PE were not changed compared to those of original PE samples. Furthermore, PE films maintained strong adhesion on the steel plates even though they were exposed to sewage and seawater provided cutting planes of the steel plates were treated with molding. But, results for corrosion tests on the spots that were previously cut off by a knife and a cutting planes of the steel plates were treated without molding show that steel plates have been corroded if they were exposed to sewage and seawater. 2. Results for corrosion tests on joints of PE sheet laminated corrugated steel using sewage show that gathering rust was observed at cutting plane of PE sheet laminated corrugated steel after 180 days, but PE film was not flaked off. However, PE film at cutting plane was flaked off when PE sheet laminated corrugated steel was exposed to seawater. Furthermore, flaking process was severely progressed at lockseam points of which the surfaces were not smooth. 3. Results for laying PE sheet laminated corrugated steel under the ground show that the surface of untouched PE film was almost identical to that of original PE film. However, the spots that were previously cut off by a knife and a cutting plane of PE sheet laminated corrugated steel have flaked off. 4. As a result of abrasion tests conducted with PE sheet laminated corrugated steel and sand, brilliance and thickness of PE was not greatly changed under the severe abrasion conditions. Therefore, the durability of PE sheet laminated corrugated steel for abrasion was determined to be good.

• 제어로봇시스템학회논문지
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• 제6권6호
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• pp.486-491
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• 2000

The dicing process cuts a semiconductor wafer to lengthwise and crosswise direction by using a rotating circular diamond blade. But inferior goods are made under the influence of several parameters in dicing such as blade, wafer, cutting water and cutting conditions. This paper describes a monitoring algorithm using neural network in order to find out an instant of vibration signal change when bad dicing appears. The algorithm is composed of two steps: feature extraction and decision. In the feature extraction, five features processed from vibration signal which is acquired by accelerometer attached on blade head are proposed. In the decision, back-propagation neural network is adopted to classify the dicing process into normal and abnormal dicing, and normal and damaged blade. Experiments have been performed for GaAs semiconductor wafer in the case of normal/abnormal dicing and normal/damaged blade. Based upon observation of the experimental results, the proposed scheme shown has a good accuracy of classification performance by which the inferior goods decreased from 35.2% to 6.5%.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.729-732
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• 2000

The general dicing process cuts a semiconductor wafer to lengthwise and crosswise direction by using a rotating circular diamond blade. But inferior goods are made under the influence of several parameters in dicing such as blade, wafer, cutting water and cutting condition. Moreover we can not applicable this dicing method to GaN wafer, because the GaN wafer is harder than the other wafer as GaAs. In order to overcome this problem, a new dicing process is necessary. This paper describes a new machine using scriber, breaker, and precision servo mechanism in order to dice an semiconductor wafer.

• 한국정밀공학회지
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• 제17권5호
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• pp.70-75
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• 2000

After the patterning and probe process of wafer have been achieved, the dicing process is necessary to separate chips from a wafer. The dicing process cuts a wafer to lengthwise and crosswise direction to make many chips by using narrow circular rotating diamond blade. But inferior goods are made under the influence of complex dicing environment such as blade, wafer, cutting water and cutting conditions. This paper describes a monitoring algorithm using feature extraction in order to find out an instant of vibration signal change when bad dicing appears. The algorithm is composed of two steps: feature extraction and decision. In the feature extraction, two features processed from vibration signal which is acquired by accelerometer attached on blade head are proposed. In the decision. a threshold method is adopted to classify the dicing process into normal and abnormal dicing. Experiment have been performed for GaAs semiconductor wafer. Based upon observation of the experimental results, the proposed scheme shown a good accuracy of classification performance by which the inferior goods decreased from 35.2% to 12.8%.

• 대한기계학회논문집A
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• 제27권8호
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• pp.1309-1316
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• 2003

The general dicing process cuts a semiconductor wafer to lengthwise and crosswise direction by using a rotating circular diamond blade. But products with inferior quality are produced under the influence of several parameters in dicing process such as blade, wafer, cutting water and cutting conditions. Moreover we can not apply this dicing method to GaN wafer, because the GaN wafer is harder than the other wafer such as SiO2, GaAs, GaAsP, and AlGaAs. In order to overcome this problem, development of a new dicing process and determination of dicing parameters are necessary. This paper describes a new wafer dicing method using fixed diamond scriber and precision servo mechanism and determination of several parameters - scribing depth, scribing force, scriber inclined angle, scribing speed, and factor for scriber replacement - for a new dicing machine using scriber.

• 한국정밀공학회지
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• 제20권2호
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• pp.218-225
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• 2003

The general dicing process cuts a semiconductor wafer to lengthwise and crosswise direction by using a rotating circular diamond blade. However, inferior goods may be made under the influence of several parameters in dicing process such as blade, wafer, cutting water and cutting conditions. Moreover we can not apply this dicing method to a GaN wafer, because the GaN wafer is harder than other wafers such as SiO$_2$, GaAs, GaAsP, and AlGaAs. In order to overcome this problem, development of a new dicing process and determination of dicing parameters are necessary. This paper describes determination of several parameters - scribing depth, scribing force, scriber inclined angle, scribing speed, and factor for scriber replacement - for a new dicing machine using a scriber.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.164-167
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• 2002

The general dicing process cuts a semiconductor wafer to lengthwise and crosswise direction by using a rotating circular diamond blade. But inferior goods are made under the influence of several parameters in dicing process such as blade, wafer, cutting water and cutting conditions. Moreover we can not applicable this dicing method to GaN wafer, because the GaN wafer is harder than the other wafer such as SiO$_2$, GaAs, CaAsP, and AlCaAs. In order to overcome this problem, development of a new dicing process and determination of dicing parameters are necessary. This paper describes determination of several parameters - scribing depth, scribing force, scriber inclined angle, scribing speed, and factor for scriber replacement - for a new dicing machine using scriber.

• 대한소아치과학회지
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• 제28권1호
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• pp.32-44
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• 2001

Er : YAG 레이저의 상아질 삭제효과와 이에 따른 온도변화를 평가하고자 발거된 소구치와 대구치로 상아세관내 조직액과 치수내압을 유지할 수 있는 상아질 시편을 제작하고 $2.94{\mu}m$의 pulsed Er : YAG 레이저(SDL-300EN, 삼성전자, 한국)를 handpiece형의 전달계를 이용한 비접촉식 방법으로 조사세기, pulse repetition rate, 조사시간, 물 분사여부 등의 조사조건을 달리하여 상아질 면에 조사하고 이때의 삭제량과 상아질 두께에 따른 온도변화, 그리고 삭제형태를 조사, 분석하여 다음과 같은 결과를 얻었다. 1. 레이저 조사세기와 pulse repetition rate가 클수록, 그리고 조사시간이 길수록 삭제량이 증가되었다(P<0.05). 그러나 5Hz의 pulse repetition rate에서는 조사시간에 따른 삭제량의 차이가 크지 않았다. 2. 삭제된 와동은 비교적 변연부가 명확하고 깨끗하였으며 와동의 바닥은 원추형이였으며 부드러웠다. 조사세기와 pulse repetition rate가 클수록, 그리고 조사시간이 길수록 와동의 상부 직경이 넓었으며 150mJ, 5Hz, 5sec에서는 와동변연부에 약간의 crack이 관찰되었다. 3. 레이저 조사세기와 pulse repetition rate가 클수록, 그리고 조사시간이 길수록 상아질의 온도가 더 많이 상승하였으며 시편의 두께가 두꺼울수록 온도상승이 적었다(P<0.05). 4. 물을 분사하며 레이저를 조사할 경우 물을 분사하지 않은 경우에 비해 온도상승이 매우 감소되었다(P<0.05). 이상의 결과를 종합해 볼 때 Er : YAG 레이저를 상아질에 조사할 경우 와동의 형태가 명확하고 물을 분사할 경우 온도상승이 많이 유발되지 않으므로써 삭제력이 좋고 치수에 유해작용이 없는 것으로 생각된다. 향후 임상에서 치질을 제거하는데 효율적으로 이용되기 위해서는 더욱 크고 이에 따른 온도상승을 최소로 할 수 있는 조사 시스템 및 방법에 대한 연구가 계속적으로 이루어져야 할 것으로 사료된다.