• 한국초등과학교육학회지:초등과학교육
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• 제23권2호
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• pp.152-158
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• 2004

The purpose of this study was to find the difficulties and problems in the carbon dioxide production experiment and to suggest the device for the improvement. Many students have misconception for the smell of carbon dioxide. I found that the smell of carbon dioxide of producting through the experiment didn't concern with the quantity of calcium carbonate. I certificated that the smell of carbon dioxide was related with the concentration of hydrochloric acid. I built two trap applicaing suction in the gas production device to exclude fully the smell of carbon dioxide. So the smell of carbon dioxide was not present by passing the two trap. To find the ideal experimental conditions I perform the experiment step by step. As the result enough carbon dioxide to use for the property experiment was collected under the condition that is 60 mL of 3 molarity hydrochloric acid and 30 g calcium carbonate. I certificated to mesuring flowing quantity of carbon dioxide using the flow meter of carbon dioxide. In the improvement experiment of the property of carbon dioxide, I proposed the experiment device regarding as spreading of the gas and children's interest. To improve the problem of gas production experiment, I proposed the gas certification device using a thread.

• Structural Monitoring and Maintenance
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• 제6권2호
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• pp.85-101
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• 2019

The effects of foundation scour depth and riverbed condition on the natural frequencies of a typical cross-river integral abutment bridge have been studied. The conventional operational modal analysis technique has been employed in order to extract the modal properties of the bridge and the results have been used in the Finite Element (FE) model updating procedure. Two tests have been carried out in two different levels of water and wet condition of the riverbed. In the first test, the riverbed was in dry condition for two subsequent years and the level of water was 10 meter lower than the natural riverbed. In the second test, the river was opened to water flow from the upstream dam and the level of water was 2 meter higher than the natural riverbed. The results of these two tests have also been used in order to find to what extend the presence of water flow in the river and saturation of the surrounding soil affect the bridge natural frequencies. Finally, the updated FE model of the bridge has been applied in a series of parametric analyses incorporating the effect of piles' relative scour depth on the bridge natural frequency of the first four vibration modes.

• 한국수자원학회논문집
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• 제48권7호
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• pp.535-543
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• 2015

기포가 포함된 다상흐름의 측정은 중요함에도 불구하고 많은 제약이 있었다. 특히, 공극률이 높은 다상 흐름은 밀도차의 급격한 변화와 두꺼운 공기-물 경계면으로 인해 측정이 매우 어렵다. 본 연구에서는 공극률에 상관없이 기포흐름을 측정할 수 있는 기포영상유속측정법과 다발 광섬유유동측정계를 소개하고자 한다. 기포영상측정기법의 경우, 화상측정시 발생하는 원근에 의한 오차를 최소화하고 추정할 수 있는 피사계 심도에 대한 계산방법을 제시하여 정도 분석을 위한 방안을 제시하였다. 다발 광섬유유동측정계는 얇은 광섬유의 특성을 이용해 다발로 제작하여 측정률을 증가시키고자 하였다. 제시된 두 기법을 기포플룸에 적용하여 신뢰도를 검토하였으며 잘 일치하는 것을 확인하였다. 소개된 기법으로 대표적인 하천 다상흐름인 도수흐름을 측정하여 그 적용성을 검토하였다.

• 대한기계학회논문집B
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• 제21권7호
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• pp.948-961
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• 1997

The effects of intake port eccentricity and a partition between the two intake ports on the incylinder swirl characteristics in a 4 valve diesel engine having the two intake ports, one is a helical intake port and the other is a tangential intake port, were investigated by using the impulse swirl meter(ISM) in a steady flow test rig. Mean flow coefficient ( $C_{f(mean)}$, swirl ratio ( $R_{s}$) and the mass flowrate through the two intake ports with and without intake port partition were measured. The results showed that the characteristics of in-cylinder swirl ratio formed by a 4-valve cylinder head were largely affected by valve eccentricity ratio ( $N_{y}$) and the existence of an intake port partition between the two intake ports. Mean flow coefficient ( $C_{f(mean)}$) increases and swirl ratio ( $R_{s}$) decreases in case of being the partition between the two intake ports. And also the mass flowrate through the tangential intake port is 19.0% and 7.7% more than that of the helical intake port in case of the two intake ports with and without partition respectively.ively.

• 대한소아치과학회지
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• 제43권3호
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• pp.292-298
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• 2016

본 연구의 목적은 최근 개발된 두 종류의 자이오머(Beautifil Flow Plus F00, Beautifil Flow Plus F03)의 불소유리량과 열순환 후 압축강도를 기존의 자이오머, 레진 강화형 글라스아이오노머, 복합 레진과 비교하여 평가하는 것이다. 불소 유리량 측정을 위해 군별로 15개씩의 시편을 제작하여 31일간 pH/ISE meter를 이용하여 불소 농도를 측정하였고 압축 강도 측정을 위해 군별로 15개씩의 시편을 제작하여 열 순환 후 만능 경성 시험기를 이용하여 시편이 파절된 시점의 최대강도를 측정하였다. 최근 개발되어 출시된 자이오머는 기존의 자이오머에 비해 불소 유리량은 유의하게 증가하였다. 압축 강도도 개선되었으며, 복합 레진과 비교하여 통계적 유의 차가 없는 것으로 나타나 임상적 가치가 높은 것으로 사료되었다.

• 한국습지학회지
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• 제24권1호
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• pp.52-58
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• 2022

최근 낙동강 하구의 통합물관리를 위한 다양한 노력과 연구가 진행되고 있다. 그러한 연구 중 하나로 3차원 고정식 초음파 유속계를 이용한 수문별 개도 방류량의 측정이 수행되고 있으나, 개도별 방류량 산정식 도출을 위한 실측 성과를 활용한 수리학적 및 통계적 처리 절차와 기법에 대한 연구는 기초적인 수준에 머물고 있다. 이에 본 연구에서는 3차원 고정식 초음파 유속계 측정자료를 이용한 자료 처리 기법을 개발하여 측정 데이터 기반의 유량계수 산정하고 이를 이용하여 방류량 산정식 개발 적용성을 검토하였다.

• 한국전기전자재료학회논문지
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• 제23권10호
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• pp.793-797
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• 2010

The basic performance of the ground system is evaluated as the ground resistance by applying low frequency current below 1 kHz. However, characteristics of the ground system should be analyzed by high frequency current up to 1 MHz since transient currents having a few hundred kHz component flow during a line-to-ground fault and/or a lightning strike. This paper deals with the design and fabrication of a wideband ground impedance meter (WGIM) which measures the impedance of ground systems in ranges from 65 Hz to 1.28 MHz. Also, a noise elimination algorithm using a digital bandpass filter is proposed. The maximum error of the WGIM is 4.91% in the measurement frequency range.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1998년도 추계학술대회
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• pp.127-128
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• 1998

It is necessary to maintain constant intravenous (IV) infusion rate. While infusion pump is able to control infusion rate with great accuracy, its rather large size and weight make it difficult for patients to move around. The most commonly used infusion device is gravity IV infusion set with its administration chamber being clamped according to the observed drip rate. In this case it may be easier and more accurate to maintain IV rate to given value if we automate the drip-counting process and tube-clamping work by electronic devices. We calculated volume infusion rate of specific fluid using optical drip rate meter which we had developed. To regulate fluid flow rate, we equipped the rate meter which we had developed with a miniaturized clamping apparatus using DC motor. Also, we Implemented drip detection and clamp control algorithm with PIC16C73 $\mu$-controller (Microchip). This system provides user interface through LCD display and key buttons.

• 한국유체기계학회 논문집
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• 제13권4호
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• pp.18-24
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• 2010

For testing large-capacity pumps, the accurate flow rate measurement is needed in the test loop. As a measuring method of flow rate, venturi tube is recommended due to its low pressure loss. However, upstream disturbance of loop component such as a valve has an effect upon the accuracy of flow rate measurement. For controlling flow rate in case of high flow rate and large-scale piping system, a butterfly-type valve is generally used due to its compactness. However, a butterfly valve disturbs downstream flow by generating turbulence, cavities, or abrupt pressure change. In this study, the effect of downstream disturbance of butterfly valve on the flow rate measurement using a venturi tube is investigated. Test loop consists of circulation pump, reservoir, butterfly valve, venturi tube, and reference flow meter. The test is conducted with regard to a different valve opening angle of butterfly valve. According to the valve opening angle, the uncertainty of flow rate measurement is investigated.

• International Journal of Automotive Technology
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• 제7권4호
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• pp.441-448
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• 2006

In-cylinder flows such as tumble and swirl play an important role on the engine combustion efficiencies and emission formations. The tumble flow, which is dominant in current high performance gasoline engines, is able to effect fuel consumptions and emissions under a partial load condition in addition to the volumetric efficiency under a wide open throttle condition. Therefore, it is important to optimize the tumble ratio of a gasoline engine for better fuel economy, lower emissions, and maximum volumetric efficiency. First step for optimizing a tumble ratio is to measure a tumble ratio accurately. For a tumble ratio measurement, many different methods have been developed and used such as steady flow rig, PIV, PTV, and LDV. However, it is not well known about the relations among the measured tumble ratios using different methods. The purpose of this research is to correlate the tumble ratios measured using three different methods and find out merits and demerits of each measurement method. In this research the tumble flow was measured, compared, and correlated using three different measurement methods at the same engine: steady flow rig; 2-dimensional PIV; and 3-dimensional PTV water flow rig.