• 한국농림기상학회지
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• 제2권3호
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• pp.80-86
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• 2000

에디 공분산 방법은 생태계와 대기간의 질량과 에너지 교환을 측정하는데 널리 사용되고 있다. 이 방법은 다른 미기상학적 방법과는 달리 많은 가정을 필요로 하지 않는 직접 측정으로서, 스칼라의 농도 변화를 측정하기 위해 고속 반응의 개회로 또는 폐회로 기기를 필요로 한다. 후자를 사용할 경우, 흡입된 공기가 관을 통과하면서 스칼라의 농도 변동의 감쇠가 일어난다. 이러한 관 감쇠 효과는 측정하고자 하는 난류 플럭스를 과소 평가하게 한다. 난류 흐름의 감쇠 효과를 정량화하기 위해서 개회로 기기와 폐회로 기기로 측정된 수증기 농도를 각각 분석하였다. 통계적 분석에 의하면, 폐회로 기기에서 얻어진 스펙트럼이 0.5 Hz 이상의 영역에서 개회로 기기에서 얻어진 스펙트럼과 서로 다름을 보였다. 낮에는 관 감쇠에 의한 수증기 플럭스의 손실이 5% 이내였으나, 밤에는 풍속이 작고, 난류의 강도가 약하여 플럭스 손실이 상대적으로 크게 나타났다. 이론적으로 계산된 플럭스 손실은 관측 결과와 고주파수 영역에서 약간의 차이를 보였는데, 이것은 수증기가 관의 벽과 상호 작용하면서 플럭스 측정에 영향을 주었기 때문인 것으로 추정된다. 결론적으로, 개회로나 폐회로기기 모두 5% 오차 내에서 수증기 플럭스 관측에 사용할 수 있다. 그러나 대기가 안정할 때는 플럭스 산출시 고주파수에서의 영향을 신중히 고려해 주어야 한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 D
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• pp.641-643
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• 2000

CATV Network Management system of Korea is used for mainly monitor forward broadcasting signal because of the difficulty of tracking, measuring and control reverse path nosie. Thereby Purpose of this Structure is removing return Path noise of CATV Network for maintaining two way Netowrk Service of the Highest quality.

• 한국유체기계학회 논문집
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• 제7권5호
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• pp.7-12
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• 2004

Multi-path ultrasonic flowrate measuring technology is being received much attentions from a variety of industrial fields to exactly measure the flowrate. Multi-path ultrasonic flowmeter has much advantage since it has no moving parts and little pressure loss. It offers good accuracy, repeatability, linearity and turn-down ratio can be over 1:50. The present study investigates flowrate integration errors using weighting factors. A theoretical flow model uses power law to describe a fully developed velocity profiles and wall roughness is changed. Gaussian, Chebyshev, and Tailor methods are used to integrate line-average velocities. The obtained results show that Chebyshev method in 2, 4-path arrangement and Gaussian method in 3, 5-path arrangement are not affected for wall roughness changes.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 금형가공 심포지엄
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• pp.3-10
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• 2002

In this study on machine measuring system based on solid feature was developed. This system was applied with injection mold using 3 dimensional solid modeler for verification. Developed program include pre-processor, main processor, and post processor. In pre-processor there are functions which check intersection, simulate motion of probe and calculate measuring time. Main processor generates measuring path and output NC code in Unigraphics. In post-processor functions that include evaluation of undercut or overcut and display of measuring procedure are offered. In addition analysis module for quality control of measured data on manufactured product was developed with geometric and dimensional tolerance concept. As the result developed program could get stability of system, precision of product, rapidity and cost down of manufacturing process compared with before measuring process.

• 한국정밀공학회지
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• 제20권8호
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• pp.144-152
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• 2003

The purpose of this paper is to establish an effective inspection system by using OMM (On-Machine Measurement) system based PC-NC. This system can reduce manufacturing lead time because part is inspected each process. Inspection process planning is accomplished by determining the number of measuring points, their location, measuring path using fuzzy logic, Hammersley method, traveling salesperson problem. Inspection with contacted sensor improve quality as inspection feature is developed to based machining feature. This method is tested by simulation and experiment, then analyzed measuring data and geometry tolerance.

• 산업공학
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• 제11권1호
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• pp.199-205
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• 1998

This paper describes the development of on-the-machine measuring(OMM) system which can directly measure the two and three dimensional machined accuracy using a scanning probe in milling machine. Two algorithms, NC program based continuous path(CP) measurement and CAD data assisted point to point(PTP) measurement, are developed for three dimensional measurements, with consideration of the characteristics of the scanning probe. The algorithms are used to develop an auto measuring system. The delveloped system is compared with the CMM (Coordinate Measuring Machine) in terms of accuracy and repeatability. The OMM system is expected to realize measurement time reduction and hence result in high productivity.

• 환경생물
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• 제36권4호
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• pp.507-516
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• 2018

벼재배 논에서 온실가스 측정을 위해 사용되는 closed 챔버법은 시 공간적으로 변동 폭이 큰 메탄 플럭스를 측정하는 데는 한계가 있다. 이러한 문제점을 해결하고자 메탄플럭스 측정에 있어 에디공분산을 기반으로 하는 open-path 방법과 closed 챔버법을 비교분석하였다. 벼 재배 기간 중 메탄 플럭스 변동은 두 방법 모두 비슷한 경향을 보였고 closed 챔버를 이용한 메탄 측정 시간대의 값은 open-path 측정에 의한 값과 고도로 유의한 상관을 보였다. 다만 총배출량에 있어서 두 측정 방법 간에 나타난 약 31%의 차이가 발생했는데 이는 closed 챔버법에 따른 과다 측정과 open-path에 의한 과소측정으로 생각해 볼 수 있다. 정확한 원인 분석을 위해서 향후에도 추가적인 연구가 필요할 것으로 판단된다.

• 대한기계학회논문집A
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• 제32권9호
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• pp.761-769
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• 2008

The majority of mechanical parts are manufactured by milling machines. Hence, geometrically efficient algorithms for tool path generation and physical considerations for better machining productivity with guarantee of machining safety are the most important issues in milling tasks. In this paper, an optimized path generation algorithm for direction parallel milling which is commonly used in the roughing stage is presented. First of all, a geometrically efficient tool path generation algorithm using an intersection points-graph is introduced. Although the direction parallel tool path obtained from geometric information have been successful to make desirable shape, it seldom consider physical process concerns like cutting forces and chatters. In order to cope with these problems, an optimized tool path, which maintains constant MRR in order to achieve constant cutting forces and to avoid chatter vibrations at all time, is introduced and the result is verified. Additional tool path segments are appended to the basic tool path by using a pixel based simulation technique. The algorithm has been implemented for two dimensional contiguous end milling operations, and cutting tests are conducted by measuring spindle current, which reflects machining situations, to verify the significance of the proposed method.

• 한국초등과학교육학회지:초등과학교육
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• 제33권1호
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• pp.181-194
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• 2014

The purpose of this study was to analyze the difference between eye movements according to science achievement of elementary school students on measuring tasks. Science achievement was graded by the results of Korea national achievement test conducted in 2012. As an assessment tool to check measuring task, two measuring measure problems from TSPS(Test of Science Process Skill; developed in 1994) which were suitable for eye tracking system were adopted. The subjects of this study were 3 underachievers and 3 overachievers from 6th grade who agreed to participate in the research. SMI was used to collect EMD (eye movement data). Experiment 3.2 and BeGaze 3.2 programs were used to plan experiment and analyze EMD. As a result, eye movements of participants in measuring task did not show the path to the common gaze by groups. To solve the problem of using specific measuring strategies related to the correct answer. Underachiever who failed in measuring tasks don't have enough measurement capabilities and lack eye movement through the area of interest for cognitive thinking. These results show that elementary school science curriculum dealing with measuring have to reflect a lot of step-by-step learning requires.

• 한국정밀공학회지
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• 제21권12호
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• pp.100-108
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• 2004

In reverse engineering, data acquisition methodology can generally be categorized into contacting and non-contacting types. Recently, researches on hybrid or sensor fusion of the two types have been increasing. In addition, efficient construction of a geometric model from the measurement data is required, where considerable amount of user interaction to classify and localize regions of interest is inevitable. Our research focuses on the classification of each bounded region into a pre-defined feature shape fer a hybrid measuring scheme, where the overall procedures are described as fellows. Firstly, the physical model is digitized by a non-contacting laser scanner which rapidly provides cloud-of-points data. Secondly, the overall digitized data are approximated to a z-map model. Each bounding curve of a region of interest (featured area) can be 1.aced out based on our previous research. Then each confined area is systematically classified into one of the pre-defined feature types such as floor, wall, strip or volume, followed by a more accurate measuring step via a contacting probe. Assigned to each feature is a specific digitizing path topology which may reflect its own geometric character. The research can play an important role in minimizing user interaction at the stage of digitizing path planning.