건식 3채널 초음파 유량측정 방법에 대한 연구

전세종(Sejong Chun),윤병로(Byung-Ro Yoon),강웅(Woong Kang),권휴상(Hyu-Sang Kwon) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12

Clamp-on ultrasonic flow metering can provide a non-invasive and portable means for flow measurement. However, the clamp-on ultrasonic flow metering indicates flow rates with low measurement accuracy at low flow velocity in pipe flows. Typical accuracy of the clamp-on ultrasonic flow metering amounts as low as ±1 % if the flow velocity in a pipe is greater than 0.5 m/s. The accuracy can be greater than ±2 % if the flow velocity is lowered smaller than 0.5 m/s. These shortcomings of the clamp-on ultrasonic flow metering can be overcome by combining two transit times along a Z-shaped and a V-shaped ultrasonic path. This technique is named as combined V/Z clamp-on ultrasonic flow metering. With the water flow standard system in KRISS, this combined technique exhibited intermediate performance between the two flow metering techniques along the Z-shaped and the V-shaped ultrasonic paths.

Tailored RF 경자사계방향 (TRFGE} 자기공명영상(MRI)에서 유체에 의한 영상신호 변화 : 유체유입효과와 영상면내를 흐르는 유체의 효과에 대하여

문치웅,김상태,노용만,임태환,조장희,Mun, Chi-Ung,Kim, Sang-Tae,No, Yong-Man,Im, Tae-Hwan,Jo, Jang-Hui 대한의용생체공학회 1997 의공학회지 Vol.18 No.3

본 연구에서는 유체보상 경사자장 기법(flow-compensation-gradient of gradient-moment nulling method)을 이용하지 않은 Tailored RF를 이용한 TRFGE(tailored rf gradient echo) 영상에는 유체유입효과(in-flow effect)가 나타나지 않지만 절편(slice)내에서 판독경사자장(reading gradient)과 같은 방향으로 흐르는 유체는 신호가 강조가 됨을 이론과 실험으로 보였다. 절편 내에서 판독경사자장과 같은 방향으로 흐르는 유체의 신호가 TRFGE 영상에서 강조되는 이유를 이론적으로 설명하였으며 이 이론을 뒷받침 할 실험을 위해 유체 모형을 제작하였다. 원통 모양의 물 모형 중앙으로 유체 관을 통해 식염수(saline)가 주자장(B$B_0$)와 평행인 z 축 방향으로 흐를 수 있도록 하였다. 유체가 흐를 때와 흐르지 않을 때 CGE(conventional gradient echo) 영상과 TRFGE 영사을 얻어 각각 비교하였다. 유체 유입효과를 관찰하기 위해서는 횡단면(axial)의 영상을 얻었고 절편 내에서 판독경사자장과 같은 방향으로 흐르는 유체의 영상신호를 관찰하기 위해서 시상면(sagittal) 영상을 얻었다. In this paper, we have reported two interesting flow effects arising in the TRFGE sequence using water flow phantom. First, we have shown that the TRFGE sequence is indeed not affected by "in-flow" effect from the unsaturated spins flowing into the imaging slice. Second, the enhancement of "in-plane flow" signal in the readout gradient direction was observed when the TRFGE sequence was used without flow compensation. These two results have many interesting applications in MR imaging other than fMRI. Results obtained were also compared with the results obtained by the conventional gradient echo(CGE) imaging. Experiments were performed at 4.7T MRI/S animal system (Biospec, BRUKER, Switzerland). A cylindrical phantom was made using acryl and a vinyl tube was inserted at the center(Fig. 1). The whole cylinder was filled with water doped with $MnCl_2$ and the center tube was filled with saline which flows in parallel to the main magnetic field along the tube. Tailored RF pulse was designed to have quadratic ($z^2$) phase distribution in slice direction(z). Imaging parameters were TR/TE = 55~85/10msec, flip angle = $30^{\circ}$, slice thickness = 2mm, matrix size = 256${\times}$256, and FOV= 10cm. In-flow effect : Axial images were obtained with and without flow using the CGE and TRFGE sequences, respectively. The flow direction was perpendicular to the image slice. In-plane flow : Sagittal images were obtained with and without flow using the TRGE sequence. The readout gradient was applied in parallel to the flow direction. We have observed that the "in-flow" effect did not affect the TRFGE image, while "in-plane flow" running along the readout gradient direction enhanced the signal in the TRFGE sequence when flow compensation gradient scheme was not used.

시스템 구성요소의 신뢰도를 기반으로 하는 새로운 GO-FLOW기법 개발

변윤섭(Yoon Sup Byun),이주영(Ju-Yeong Lee),황규석(Kyu Suk Hwang) 한국가스학회 2012 한국가스학회지 Vol.16 No.4

GO-FLOW기법은 시스템이 정상적으로 작동할 가능성을 평가할 수 있는 기법으로써 신호선과 연산자를 사용하여 시스템을 GO-FLOW Chart로 모델화하고, 이 GO-FLOW Chart를 순차적으로 해석하여 시스템의 신뢰도를 평가하는 기법이다. 그러나 GO-FLOW기법은 1개의 시스템 구성요소를 여러 개의 연산자로 모델링하므로 시스템 흐름도와 상이한 GO-FLOW Chart가 작성될 수 있고, 시간점을 지정하여 시간을 모델링하므로 실제 운전시간에 따른 신뢰도 변화를 평가하기 어렵다. 따라서 본 연구에서는 구성요소의 기능(정상/고장)을 기준으로 시스템의 신뢰도를 평가하는 기법을 개발하였다. 본 기법은 구성요소의 운전상태와 상관없이 그 기능을 유지할 가능성을 기준으로 시스템의 신뢰도를 평가하며, 1개의 구성요소는 1개의 연산자로 모델링하므로 시스템 흐름도와 거의 유사한 모델도를 작성할 수 있고, 실제시간을 반영한 연산자를 사용하여 실제시간에 따른 시스템의 신뢰도를 쉽게 평가할 수 있다. The GO-FLOW methodology is capable of assessing system reliability. It models the system into a GO-FLOW chart with signal lines and operators and assesses the reliability of system by assessing the GO-FLOW chart sequential. But, as it models one component of system into several operators, the GO-FLOW chart which is different from the system flow diagram be modeled. Also, as it models the real operation time into time point, it is hard to assess the reliability change according to the real operation time. Therefore, in this paper, the new GO-FLOW methodology which use the function(success/failure) of system components has been developed. It can assess the successful operating probability of system, regardless of the operating status of components. As it models one component of system into one operator, the GO-FLOW chart which is similar the system flow diagram can be modeled. Also, it is able to easily assess the successful probability of system according to the real operation time using the time in the operators.

유량 변동을 고려한 하천유지유량의 적용 방법 및 영향 평가

강성규,최시중,이동률 한국방재학회 2018 한국방재학회논문집 Vol.18 No.7

In this study, we propose a method to apply the flow regime and seasonality for instream flow, which is managed with the minimum flow concept, under present institution. In order to apply the variability of stream flow, monthly low flow series were estimated and set as monthly instream flow. The dams were operated for fulfilling variable instream flow and characteristics of the controlled stream flow were analyzed. Also, the impact on river ecosystems due to flow variation, was estimated qualitatively. The Geumgang river basin was chosen for target watershed and we used results of random climate change scenarios and rainfall runoff, as the future natural stream flow. The result of the water budget analysis was compared to the flow variable, from the concept of minimum flow as instream flow, that is managed in the current system. The concept of flow variability should be applied to the instream flow system, and the method is presented through this study. 본 연구에서는 현재 최소유량 개념으로 관리되고 있는 하천유지유량에 유황 및 계절성을 반영하기 위한 방법을 제시하였다. 유량의 다양성을 반영하기 위해 월별 저유량 계열을 산정하고 이를 월별 하천유지유량으로 설정하여 댐을 운영하였을 때 발생하는 특성에 대해 분석하였다. 유량 변동을 고려할 때 하천 생태계에 미칠 수 있는 영향을 정성적으로 분석하여 함께 제시하였다. 대상유역은 금강유역으로 임의의 기후변화 시나리오와 강우유출 모형을 선택하여 물수지 분석을 수행하고 현행 제도에서 규정하고 있는 최소유량 개념의 하천유지유량을 설정한 경우와 비교하였다. 이 연구를 통해 현행 하천유지유량 제도를 유량 변동성을 고려하도록 개선하고 관리의 방법론을 제시하였다.

Assessment of combined V/Z clamp-on ultrasonic flow metering

전세종,윤병로,강웅,권휴상 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.6

Clamp-on ultrasonic flow metering can provide a non-invasive and portable means for flow measurement. However, it indicates flowrates with low measurement accuracy at low flow velocity in pipe flows. Typical accuracy of the clamp-on ultrasonic flow meteringamounts as low as ±1% if the flow velocity in a pipe is greater than 0.5 m/s. The accuracy can be increased greater than ±2% if the flowvelocity is lowered smaller than 0.5 m/s. Inner pipe diameter can be also an influential factor in flow metering when the exact value ofthe inner diameter is not known. The inner pipe diameter cannot be found if the pipe is too large to measure or if there are erosions oradhesions on the inner pipe surface due to small particles in the flow. These shortcomings of the clamp-on ultrasonic flow metering canbe overcome by combining two transit times along a Z-shaped and a V-shaped ultrasonic path. This technique is termed combined V/Zclamp-on ultrasonic flow metering. With the water flow standard system in KRISS, this combined technique exhibited intermediate performancebetween the two flow metering techniques along the Z-shaped and the V-shaped ultrasonic paths. Notably, the combined techniqueshowed better performance (expanded uncertainty less than 0.76%, k = 2) than the two flow metering techniques (1.61% and1.17%, k = 2) in the flow range of (100 ~ 400) m3/h with pipe diameter of 250 mm.

몰입(flow) 기능의 재구성: 몰입과 행복 관계에 대한 타인맥락의 조절효과를 중심으로

장훈아,한성열 한국사회및성격심리학회 2010 한국심리학회지 사회 및 성격 Vol.24 No.4

The purpose of the present study was to investigate the function of flow in relational context. Previous studies on the function of flow suggested that flow has a positive effect on personal growth and happiness. However, Previous studies were only focused on individual context and aspect of flow. However it was supposed that the function of flow could be changed according to the contexts, the present study focused relational function of flow. In study 1, moderate effects were found that significant other's approval/disapproval, regulation with significant other and self conscious emotion moderated relationship between on flow and happiness. In study 2, the reasons of disapproval on person's flow were that flow activities were not socially valuable and flow pursuing frequently violated relational expectancy. The Results of present studies suggested that the functions of flow could be changed and reconstructed along the contexts. Results of the present research had a valuable implication in that it is not sufficient to conduct a research on individual happiness and positivity only in individual context. Instead, It is necessary that individual positive concepts should be reappraised carefully in relational, interdependent, moral context. 기존 몰입연구는 개인적인 경험측면과 몰입경험이 개인에게 어떠한 긍정적 기능이 있는지 밝히는데 주안점을 두었다. 하지만 본 연구는 몰입경험과 경험의 기능적 측면을 통합적으로 이해하기 위해서 몰입경험에 대한 중요타인의 평가, 중요타인의 평가에 따른 몰입의 심리적 결과물이 어떻게 달라지는지 알아보았다. 이를 위해 연구 1에서는 중요타인의 개인몰입에 대한 동의여부, 몰입으로 인한 자의식 유무, 타인과 의견공유 여부가 몰입과 행복의 관계를 어떻게 조절하는지 알아보았다. 연구 결과, 개인몰입에 대한 중요 타인의 동의여부, 몰입자의식, 의견조율은 몰입수준과 상호작용하여 몰입의 결과물에 영향을 주는 것으로 나타났다. 동의여부, 자의식은 동일한 패턴의 조절효과를 보였고, 의견공유는 반대 패턴의 조절효과를 보였다. 이와 관련해서는 논의부분에 논의 하였다. 연구 2에서는 무엇 때문에 개인의 몰입에 타인이 동의/비동의를 하는지 알아보았다. 연구 결과, 사회적으로 가치 없는 활동, 다른 활동에 지장을 주는 활동에 몰입하는 경우 중요타인은 개인의 몰입에 동의하지 않았고, 사회적 가치가 있는 영역에 몰입하는 것에 동의하는 것으로 나타났다. 이러한 결과를 종합해보면, 타인이 인정할 수 없는 활동에 몰입할 경우, 타인은 개인의 몰입에 대해 부정적인 태도를 취하고, 이는 다시 개인의 몰입의 결과물에 영향을 줄 수 있다고 추론되었다. 이와 관련된 문제를 추가적으로 논의하였다.

광역 토사재해 물리적 취약성 평가를 위한 Flow-R 모델의 매개변수 분석

강효섭(Kang, Hyo-Sub),김윤태(Kim, Yun-Tae) 한국방재학회 2017 한국방재학회논문집 Vol.17 No.4

This study analyzed effects of input parameters (maximum velocity and travel angle) of Flow-R model on debris flow mobility and deposition, which are essential to evaluate physical vulnerability of debris flow disasters in regional scale. The characteristics of debris flow spreading area and the maximum kinetic energy were analyzed through sensitivity analysis according to input parameters. Back analysis was carried out using total 11 cases of debris flow disasters in 2011, and the reasonable values of input parameters were determined through a comparison with investigated debris flow spreading areas. The results of numerical analysis showed that debris flow spreading area and kinetic energy increased with an increase in maximum velocity, but they converged to asymptote values at critical maximum velocity. The debris flow spreading area decreases with an increase in travel angle. Several case studies showed that travel angles of the 11 debris flow disaster regions were ranged from 10° to 22°, with an average of 15°, and the maximum velocities from 11 m/s to 35 m/s, with an average value of 22 m/s. The estimated travel angle and maximum velocity were compared with the results of previous researches. 본 연구는 광역 토사재해 물리적 취약성 평가를 위해 필요한 Flow-R 입력 매개변수(토석류 최대속도, 이동각)가 토석류의 거동특성에 미치는 영향에 대한 분석을 수행하였다. 입력 매개변수에 따른 민감도 분석을 통해 토석류 확산면적과 최대 운동에너지 변화 특성을 분석하였다. 2011년에 발생한 총 11개 토석류 재해 사례에 대해 Flow-R 모델을 이용하여 역해석을 수행하였고, 조사된 토석류 재해영역과의 비교를 통해 합리적인 입력 매개변수를 산정하였다. 최대속도가 증가함에 따라 토석류 확산범위가 증가하는 것으로 나타났으며, 한계 최대속도 이상에서는 토석류 확산범위가 수렴하는 것으로 나타났다. 이동각이 증가함에 따라 토석류 확산면적은 감소하는 것으로 나타났다. 사례 분석을 통해 산정된 총 11개 토석류 재해지역의 이동각은 10°~22°범위를 나타내며, 평균값은 약 15°로 분석되었다. 역해석을 통해 얻어진 한계 최대속도 값은 11 m/s에서 35 m/s범위를 나타내며, 평균 값은 약 22 m/s로 분석되었다. 산정된 이동각과 최대속도를 기존 연구결과와 비교하였다.

Visual observations of flow patterns in downward air-water two-phase flows in a vertical narrow rectangular channel

Kim, Tae Hyeon,Chalgeri, Vikrant Siddharudh,Yoon, Woosung,Yun, Byong Jo,Jeong, Ji Hwan Elsevier 2018 Annals of nuclear energy Vol.114 No.-

<P><B>Abstract</B></P> <P>Flow patterns in downward air–water two-phase flows in a narrow rectangular channel were visually observed. A test section was constructed using transparent acrylic plate with a test channel 2.35 mm thick, 66.6 mm wide, and 780 mm long. The experiments determined that at high liquid velocity the flow patterns for downward flow are similar to those observed in upward flow. However, at low liquid velocity some significant differences were observed between downward and upward flows. The new flow patterns, falling film flow, large-bubbly flow, and intermediate flow, were identified in the low liquid velocity region, where buoyancy force is influential. A flow regime map for downward flow in a narrow rectangular channel was constructed using the experimental data and analyses.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Plate type nuclear fuel has flow passage of narrow rectangular channel. </LI> <LI> The channel is 2.35 mm thick 66.6 mm wide and 780 mm long. </LI> <LI> Flow patterns of downward air-water two-phase flows are visually observed. </LI> <LI> The new flow patterns are identified and a flow regime map is constructed. </LI> </UL> </P>

유량변화에 따른 판형열교환기의 압력강하와 내부유동 가시화에 관한 실험적 연구

황주원(Ju Won Hwang),김덕규(Deok Gyu Kim),박창용(Chang Yong Park) 대한설비공학회 2019 대한설비공학회 학술발표대회논문집 Vol.2019 No.-

This study was carried out to measure the pressure drop and visualize the flow in the flow path between the chevron corrugated two plates in a heat exchanger. A test section was made to visualize the flow characteristics in the flow channels formed by a metal real heat exchanger plate and transparent replica of the counterpart plate. A simple closed loop test facility was made to do the experiment with the change of volume flow rate. The visualization was performed by a high speed camera with 800 fps and air bubbles were injected in the flow to visualize the flow distribution in the channels on the two plates. The measured pressure drop agreed well with the general trend of the pressure drop change with the increase of flow rate. The visualized flow patterns showed that the flow was not evenly distributed in the channels between the two plates, due to the left-sided inlet and outlet location od the flow. The flow visualization with air bubbles showed the limitation to visualize the actual flow velocity distribution on the two plates because Buoyant effect was dominant under upward flow conditions.

Flow-Aware Network에서 QoS제어를 위해 Flow 특성에 따른 대역할당 방법과 특성

김재홍(Jae-Hong Kim),한치문(Chimoon Han) 대한전자공학회 2008 電子工學會論文誌-TC (Telecommunications) Vol.45 No.9

오늘날 인터넷에서는 실시간 및 비실시간 등 다양한 멀티미디어 서비스가 존재하고 있으며, 이러한 개개의 서비스 특성을 만족 시키는 데는 한계가 있다. 따라서 서비스의 QoS를 보장하기 위한 한 방법으로 flow-aware 네트워킹 개념을 갖는 네트워크를 제안하고 있다. 인터넷에서 네트워크 이용율 향상과 통계적으로 서비스 보장을 위해 MBAC(Measurement-Based Admission Control) 방식이 연구되었다. 대부분의 MBAC 방식은 집합 flow에 대해 적용하는 총체적 MBAC 알고리즘이며, 입력 flow에 적용하는 per-flow MBAC 알고리즘이 최근 연구되기 시작하고 있다. 본 논문에서는 per-flow MBAC 알고리즘 기반 시스템에서 flow를 특성에 따라 그룹핑하고, 각 그룹핑된 flow에서 먼저 입력되는 flow에 우선순위를 주는 DPS(Dynamic Priority Scheduling)알고리즘 적용한다. 그리고 각 그룹핑된 그룹에 일정대역을 고정 할당한 다음에 그룹 인접대역간 대역폭차용이 가능한 우선등급 하위대역 차용방식과 각 그룹핑된 flow에 그룹핑된 flow 특성에 따라 대역을 동적으로 할당하는 동적대역할당 방식을 제안한다. 제안한 두 방식을 시뮬레이션을 통해 서비스 지속성, 링크 이용율, 지연 특성을 평가 분석한다. 그 결과 제시한 방식이 기존의 방식보다 우수하고, 다양한 멀티미디어 환경에서 더 효율적 방식이라는 것을 분명히 한다. Recently, many multimedia services have emerged in Internet, such as real-time and non- real time services. However, in this Internet environment, we have some limitations to satisfy each service feature. To guarantee the service features in Measurement-Based Admission Control(MBAC) based system on the flow-aware network, there is the method applying Dynamic Priority Scheduling(DPS) algorithm that gives a higher priority to an earlier incoming flow in all of the link bandwidth. This paper classifies all flows under several groups according to flow characteristics on per-flow MBAC algorithm based system. In each flow group, DPS algorithm is applied. This paper proposes two methods that are a DPS based bandwidth borrowing method and a bandwidth dynamic allocation method. The former is that if low priority class has available bandwidths, the flow of high priority class borrows the bandwidth of low priority class when high priority flow has insufficient bandwidth to connect a flow call. The later is that the each group has a minimum bandwidth and is allocated the bandwidth dynamically according to the excess rate for available bandwidth. We compare and analyze the characteristics of the two proposed methods through the simulation experiments. As the results of the experiment, the proposed methods are more effective than existing DPS based method on the packet loss and delay characteristics. Consequently the proposed two methods are very useful in various multimedia network environments.