정상 한국 남성의 최고 요속 Nomogram

김태헌,양대열,김하영 大韓泌尿器科學會 1998 Korean Journal of Urology Vol.39 No.5

천연가스의 계절별 변동유량을 고려한 이중터보팽창기 감압시스템을 이용한 전기에너지회수에 관한 연구

박철우,유한빛,김효 한국가스학회 2019 한국가스학회지 Vol.23 No.2

천연가스 운송기지에서 전기에너지를 회수하기위하여 팽창 터빈시스템을 사용하는 것은 잘 알려진 기술이다. 터보팽창기의 효율은 천연가스의 유량과 터보팽창기 설계유량의 비에 따라 달라진다. 그러나 감압기지에서 계절적 공급패턴, 즉 여름에는 낮은 유량으로 반면에 겨울에는 높은 유량으로 공급되기 때문에, 단일 터보팽창기로는낮은 유량의 천연가스로부터 감압에너지를 충분히 회수하기가 비효율적이다. 따라서 본 연구에서는 대용량과 소용량의 이중 터보팽창기의 새로운 개념을 제안하게 되었다. 본 연구에서는 저압 정압기지에서 팽창밸브의 평균 입구, 출구 압력조건인 18.5 bar에서 7.5 bar로 감압될 때 입구의 온도, 유량조건에 따라서 생산 가능한 전력을 이론적배경을 통해 계산하였다. 최저 설계 효율 0.72에서 회수 가능한 전력생산량은 단일 터보팽창기로 운전될 때에는12.4 MW이었으나, 여기서 제안한 이중터보팽창기에서는 16.1 MW로 약 30% 증가한 결과를 얻게 되었다. Expansion turbine system to recover the electricity energy from natural gas transmission stations is a well-known technique. The turbo-expander efficiency depends on the ratio of the natural gas flow rates to the design flow rate of the turbo-expander. However, if there is a big difference of the natural gas flow rate through the pressure letdown station because of seasonal supply pattern, that is, high flow rate in winter while low flow rate in summer, single turbo-expander system is not so efficient as to recover the pressurized energy from the low flow-rate natural gas. Therefore, we have proposed a new concept of double turbo-expander system: one is a big capacity and the other a small capacity. Here we have theoretically computed the electric powers at the pressure reduction from 18.5 bar to 7.5 bar depending on the inlet conditions of temperature and flow rate. The calculated electricity generation has been increased by 30% from 12.4 MW in a single turbo expander to 16.1 MW in the proposed double turbo-expander system when a minimal design efficiency of 0.72 is applied.

Evaluation of Roadmap Image Quality by Parameter Change in Angiography

공창기(Chang gi Kong),송종남(Jong Nam Song),한재복(Jae Bok Han) 한국방사선학회 2020 한국방사선학회 논문지 Vol.14 No.1

이 연구의 목적은 Roadmap 영상에서 화질에 영향을 미치는 인자들을 알아보기 위한 것으로, 조영제의 희석률, Collimation Field, Flow Rate를 변화하여 연구를 하였다. 화질의 정량적인 평가를 위해, 아크릴를 이용하여 3mm 혈관모형의 Water Phantom을 자체 제작하였고, 자체 제작한 혈관모형의 Water Phantom으로 Roadmap 영상을 획득하고, SNR(Signal to Noise Ratio)과 CNR(Contrast to Noise Ratio)을 분석하였다. CM : N/S 희석률 변화에 대한 연구에서 CM : N/S 희석률을 (100%~10% : 100%)로 변화를 주었으며, 혈관모형 Water Phantom을 이용하여 촬영한 Roadmap 영상의 SNR과 CNR의 측정 결과 CM에 N/S 희석률이 높아질수록 SNR의 측정값이 점차적으로 낮아짐을 나타났고, CNR의 측정값도 점차적으로 낮아짐을 나타났다. 결론적으로 CM : N/S의 희석률이 높아질수록 SNR과 CNR 낮아짐을 확인하였고, CM : N/S의 희석률(100%~70 : 30%)에서 유의한 이미지를 얻을 수 있음을 확인하였다. Collimation Field 변화에 대한 연구에서 혈관모형 Water Phantom을 이용하여 Colimation Field를 혈관모형 중심으로 좌, 우 2 cm 간격으로 좁히면서 0 cm, 2 cm, 4 cm, 6 cm, 8 cm 10 cm, 12 cm으로 각각 변화를 주었으며, Roadmap을 촬영한 영상의 SNR과 CNR의 측정 결과는 Collimation Field를 혈관모형 중심으로 좁힐수록 SNR과 CNR의 측정값이 증가하는 것을 확인할 수 있었다. Flow rate 변화에 대한 연구에서 Autoinjector의 Volume을 15로 일정하게 하고, Flow Rate를 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 으로 각각 변화를 주었다. 혈관모형 Water Phantom을 이용하여 Roadmap 영상을 촬영한 이미지의 SNR과 CNR의 측정 결과 Flow Rate를 증가했을 때, SNR의 측정값이 점차적으로 감소하다가 Flow Rate 9~10에서 SNR의 측정값이 점차적 증가를 보였고, CNR의 측정값도 점차적으로 감소하다가 Flow Rate 9~10에서 CNR의 측정값이 점차적으로 증가를 보였다. 그러나 ROI Mean 값과 Background Mean 값으로 SNR과 CNR의 상관관계를 확인할 수 없었다. 상관관계를 확인하기 위해 Flow Rate 변화에 따른 Roadmap 연구는 향후 더 많은 연구로 확인해야 할 것으로 사료된다. 결론적으로 Roadmap 영상의 화질에 영향을 미치는 인자들을 알아보기 위해 조영제의 희석률, Collimation Field, Flow Rate 변화에 대한 연구에서 조영제에 N/S의 희석률이 증가할수록 SNR과 CNR이 낮아져 화질과 대조도가 낮아지는 것을 확인하였으며, Collimation Field를 좁힐수록 SNR과 CNR이 증가하여 화질과 대조도가 높아지는 것을 확인하였다. 그러나 Flow Rate 변화에 대한 연구에서는 상관관계를 확인할 수 없었다. 검사 및 시술을 할 때 신장의 영향을 최소화하기 위해 적절한 조영제 농도 선택과 대조도 향상 및 피폭 감소를 위한 적절한 Collimation Field를 사용하는 것이 유용할 것으로 판단된다. The purpose of this study is to identify factors affecting picture quality in Roadmap images, which were studied by varying the dilution rate, collimation field and flow rate of contrast medium. For a quantitative evaluation of the quality of the picture, a 3mm vessel model Water Phantom was self-produced using acrylic, a roadmap image was acquired with a self-produced vascular model Water Phantom, and the SNR(Signal to Noise Ratio) and CNR (Contrast to Noise Ratio) were analyzed. CM:N/S In the study on the change of dilution rate, CM:N/S dilution rate changed to (100%~10%:100%), and the measurement of the roadmap image taken using the vascular model Water Phantom showed that the measurement value of SNR gradually decreased as the N/S dilution rate was increased, and the measurement of CNR was gradually reduced. It was confirmed that the higher the dilution rate of CM:N/S, the lower the SNR and CNR, and also significant image can be obtained at the dilution rate of CM:N/S (100%~70:30%). The study showed the value of SNR and CNR in Roadmap image was increased as the Collimation Field was narrowed to the center of the vascular phantom; the Collimation Field was narrowed to the center of the vessel model by 2cm intervals to 0cm through 12cm. To verify the relationship with Roadmap image and Flow Rate, volume of the autoinjector was kept constant at 15 and the flow rate was gradually increased 1, 2, 3, 4, 5, 6, 7, 8 ,9, 10. The value of SNR and CNR of images taken by using water Phantom gradually decreased as the Flow Rate increased, but at Flow Rate 9 and 10, the SNR and CNR value was increase. It was not possible to confirm the relationship with SNR and CNR by ROI mean value and Background mean value. It is considered that further study is needed to evaluate the correlation about Roadmap image and Flow Rate. In conclusion, as the dilution rate of N/S in contrast medium was increased, the value of SNR and CNR was decreased. The narrower the Collimation Field, the higher image quality by increasing value of SNR and CNR. However, it is not confirmed the relationship Roadmap image and Flow Rate. It is considered that appropriate contrast medium concentration to minimize the effects of kidney and proper Collimation Field to improve contrast of image and reduce exposure X-ray during procedure is needed.

Flow Control Method of Tractor-mounted Boom Sprayer for Precision Spraying

( Ki Duck Kim ),( Hyeon Seung Lee ),( Young Joo Lee ),( Seok Jun Hwang ),( Ju Seok Nam ),( Beom Soo Shin ) 한국농업기계학회 2018 한국농업기계학회 학술발표논문집 Vol.23 No.1

The purpose of this study was to determine the control strategy for precise control by investigating the spray characteristics of nozzle with pressure and flow rate. A test boom sprayer was constructed same scale as actual boom sprayer for grasp spray characteristics of nozzle. The pressure control is done by a regulator of a power sprayer, and the flow control by changing the speed of sprayer pump. It was observed that the 13 nozzles of the boom sprayer discharge the liquid at the flow rate of 0.44 L / min under the pressure condition of 1.0 MPa, respectively. After setting the initial pressure to 1.0 MPa, the pressure decreased and the flow rate decreased to 0.42 L / min when the flow was discharged to the outside through the nozzle. In this case, the results of the single nozzle and the total nozzles were similar, and when the pressure was compensated again by 1.0 MPa, the flow rate was recovered to 0.44 L / min. Thus, a system is implemented that can control the power sprayer regulator to compensate the pressure during operation of the sprayer. In the test of the presence or absence of pressure compensation, each nozzle maintains 0.44 L / min at the time of pressure compensation under the pressure condition of 1 MPa in the case of the single nozzle and the whole nozzle, and when the pressure is not compensated, the flow rate decreased. It was confirmed that a uniform flow rate of 0.44 L / min was maintained only at 8 L/min and 10.6 L/min in the test according to the each supply flow rate. Therefore, the supply flow rate must be larger than the flow rate discharged through 13 nozzles. In this study, we confirmed that constant flow rate can be maintained at all times while maintaining the pressure inside the tube at 1 MPa. The results of this study can be utilized as basic data for site-specific precision chemical application.

Viscosity measurement of non-Newtonian fluids in pressure-driven flows of general geometries based on energy dissipation rate

Jang, Hye Kyeong,Hong, Sun Ok,Lee, Sang Bok,Kim, Ju Min,Hwang, Wook Ryol Elsevier Scientific Pub. Co 2019 Journal of non-Newtonian fluid mechanics Vol.274 No.-

<P><B>Abstract</B></P> <P>A novel viscosity measurement method is presented, which can be applied to the pressure-driven flow of an inelastic non-Newtonian fluid in an arbitrary geometry. The method is established on the balance of the energy dissipation rate such that the external power is dissipated within the system as viscous dissipation in a laminar regime in the absence of a body force. The effective viscosity can be expressed algebraically in terms of the pressure drop and flow rate and the corresponding effective shear rate is readily determined by flow rate; the relationship between effective viscosity and effective shear rate is found identical to the true material viscosity behavior. The two flow numbers, which depend on flow geometry only and are almost independent of fluid rheology, are involved: the coefficient of energy dissipation rate that associates the total energy dissipation rate to the Reynolds number; and the coefficient of effective shear rate, which relates flow rate to effective shear rate. After analytically validating the method for pressure-driven flow of a power-law fluid in a circular pipe, three different flows with complicated geometries were tested: numerical validations for axisymmetric expansion-contraction flows and flows in a Kenics mixer, and experimental validation for flows in a complex microfluidic array with Xanthan gum solutions. Errors in viscosity were less than 2.9% and 16% in simulations and in experiments, respectively. The method is well-suited for on-line monitoring of <I>in-situ</I> viscosity for non-Newtonian fluid flow in industrial processes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An energy dissipation-based viscosity measurement technique is proposed. </LI> <LI> Only two flow numbers are employed for viscosity measurement of inelastic fluids. </LI> <LI> The method is applicable to <I>in-situ</I> viscosity monitoring of non-Newtonian fluids. </LI> </UL> </P>

ATOMIZATION AT ULTRA-LOW LIQUID FLOW RATE USING NOVEL INJECTOR

( Mohammed Asad ),( Hrishikesh Gadgil ),( Sudarshan Kumar ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-

Efficient atomization and evaporation at ultra-low flow rates is an additional challenge for small-scale combustion application since the atomization efficiency deteriorates with decreasing liquid flow rate. Experimental study at ultra-low liquid flow rate (5 - 150 mlph) unveiled the three distinct atomization regimes while air flow rate increases from 0.5 to 5 slpm. For a given ultra-low liquid flow rate, significant shift in injector characteristic was observed with increase in air flow rate; from bubble bursting to weak spray and finally at high air to liquid ratio, recirculation of atomizing air into a liquid tube gives fully developed spray. Injector is designed such that it allows co-flow air to flow back into a liquid tube. Internal flow analysis on Plexiglas injector replica shows that atomization regimes exist due to distinct two phase flow interaction inside the injector. Current study shows that critical air to liquid ratio at which air back flow triggers, decreases as liquid flow rate increases from 5 to 150 mlph. In weak spray regime, atomization occurs through prompt mode of atomization. While two phase slug flow formation inside the liquid tube leads to fine atomization in fully developed spray regime. Shadowgraphy experimental results validate the larger droplet in weak spray regime and fine atomization in fully developed spray regime due to formation of two phase slug flow. A proposed theoretical correlation shows that droplet size (SMD) is only function Reynolds number, Weber number, air to liquid ratio and injector design.

배관내 압력변동 신호를 이용한 유량 추정 방법 연구

이정한,장대식,박진호 한국압력기기공학회 2023 한국압력기기공학회 논문집 Vol.19 No.2

In nuclear power plants, the flow rate information is a major indicator of the performance of rotating equipment such as pumps, and is a very important one required for facility operation and maintenance. To measure a flow rate, various types of methods have been developed and used. Among them, the differential pressure type using orifice and the direct doppler type using ultrasonic waves are the most commonly used. However, these flow rate measurement methods have limitations in installation, conditions and status of the measuring part, etc. To solve this problem, we have studied a new technique for measuring flow rate from scratch. In this paper, we have devised a technique to estimate the flow rate using an average moving velocity of large-scale eddy in turbulence that occurs in the piping flow field. The velocity of the large-scale eddy can be measured using the pressure fluctuation signals on the inner surface of the pipe. To estimate the flow rate, at first a cross-correlation function is applied to the two pressure fluctuation signals located at different positions in the down stream for calculating the time delay between the moving eddies. In order to validate the proposed flow rate estimation method, CFD analyses for the internal turbulence flow in pipe are conducted with a fixed flow condition, where the pressure fluctuation signals on the pipe inner surface are simulated. And then the average flow velocity of the large scale eddy is to be estimated. The estimated flow velocity is turned out to be similar to the fixed (known) flow rate.

정책금리 변화가 캐시플로우 경로를 통해 소비지출에 미치는 영향

채희율 ( Hee-yul Chai ),한상범 ( Sang B. Hahn ) 한국금융연구원 2020 금융연구 Vol.34 No.2

본 연구는 한국에서 통화정책의 캐시플로우 경로를 분석한다. 이를 위해 정책금리 변화에 따른 여신금리와 수신금리의 변화, 이에 따른 이자수지 변화의 방향과 크기, 그리고 지급이자 및 수취이자에 대한 소비지출의 민감도를 ARDL 공적분모형, 자금순환표와 가계금융·복지조사 자료를 활용한 패널 회귀모형을 통해 추정한다. 분석 결과 정책금리의 인상에 대해서는 수신금리보다 여신금리가 더 반응하고 인하에 대해서는 반대로 나타났다. 정책금리의 인상과 인하 양경우 모두 가계의 이자수지를 축소하는 방향으로 작용하였다. 차입가구의 금리민감 캐시플로우에 대한 소비지출 탄력성은 저축가구에 비해 높게 나타났다. 종합적으로 정책금리 인상과 인하 모두 캐시플로우 경로만을 볼 때 소비지출을 줄이는 방향으로 작동하였다. 다만 차입가구 캐시플로우 경로와 저축가구 캐시플로우 경로가 서로 상쇄되면서 종합적으로 그 강도는 약한 것으로 나타났다. Changes in interest rates can affect household consumption expenditures through a variety of channels, including substitution effects, wealth effects, credit channel, cash flow channel, and aggregate demand channel. Most of these channels act to increase consumption expenditures when interest rates fall. But the direction of consumption change via cash flow channel is uncertain. This is because a decrease in interest rates leads to a decrease in interest payments, but also a decrease in interest receipts, and the sensitivities of consumption expenditures to interest payments and interest receipts are not the same. This study analyzes empirically the cash flow channel of monetary policy in Korea. To this end, we estimate first the change in lending rates and deposit rates and interests balance following the change in the policy rate. The ARDL cointegration model is used to analyse the asymmetric movement of bank lending and deposit rates to the change in the policy rate. The sensitivities of consumption expenditure on interest payments and receipts are estimated based on the panel regression model using the data collected from the Household Finance and Welfare Survey. The main results are as follows: the lending rates responded more to the policy rate increase than the deposit rates, and inversely to the policy rate cut. Both policy rate hikes and cuts acted to reduce household interest balances. The elasticity of consumption expenditure to interest-sensitive cash flows for borrowing households was higher compared to saving households. Overall, both policy rate hikes and cuts acted to reduce consumption expenditure when looking only at the cash flow channel. However, as the borrower cash flow channel and the saver cash flow channel canceled each other, its overall strength was weak.

등간격으로 배열된 마이크로폰을 이용한 관내 유량측정 방법

김용범,김양한 한국소음진동공학회 2001 소음 진동 Vol.11 No.1

Proposed in this paper is a method of measurement of the flow rate in a pipe. The sound waves which are propagated within a pipe are characterized by that the wavenumber in the axial direction is changed according to the flow rate, and these characteristics are used in the present method of measurement of the flow rate. The amount of change in wavenumber of sound waves according to the flow rate can be obtained from the relationship among acoustic pressure signals within a pipe, which are measured by using a microphone array. The flow rate can be obtained by using the amount of change in wavenumber of sound waves and the relational equation of the flow rate. With respect to errors that can occur during the measurement of the flow rate, the types of errors and the method of correction of those errors are presented. This method of measurement of the flow rate has application limitation conditions due to the sensor interval, assumption of sound waves as plane waves, etc. The numerical simulation and experiments for measuring the flow rate of air in a pipe are performed in order to verify the applicability of this method of measurement of the flow rate. The experimental results are shown to be similar to those of the numerical simulation. And the flow rate measured is shown to be consistent with the actual value within 5% error bound.

수치해석 기법을 이용한 호흡 유량에 따른 사람의 기도 내 유동 특성 연구

성건혁,유홍선,Sung, Kun Hyuk,Ryou, Hong Sun 대한의용생체공학회 2012 의공학회지 Vol.33 No.4

The inspiratory flow rate of a human is changed with the amount of the workload. The flow characteristic is affected by the inspiratory flow rate. In the flow field of airway, the both of turbulence intensity and secondary flow affect the deposition pattern of particles which is important for the drug-aerosol targeting. Thus the analysis of the flow characteristic in a human airway is important. The purpose of this study is to investigate the effects of the inspiratory flow rate on the flow characteristics in a human airway. The tubular airway is consistent with the oral cavity, pharynx, larynx and trachea. The relatively inspiratory flow rate is used at each case of human states regarding the workload. By the effect of geometric airway changes, transition to turbulent airflow after the larynx can occur with relaminarization further downstream. The low Reynolds number k-${\omega}$ turbulence model is used for analysis with flow regime. As the inspiratory flow rate is larger, the turbulence kinetic energy and secondary flow intensity increase in airway. On the other hand, the area of recirculation zone is smaller.