• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.705-708
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• 1988

Ultrasound Doppler Diagnostic System utilizes the Doppler effect for measurement of blood velocity. The sign of the Doppler frequency shift represents blood flow direction. Pulsed Doppler System uses Phase detector and zerocrossing method to produce simultaneous independent audio and velocity signals for forward and reverse blood flow direction in the time domain, had been fabricated. But time-domain analyzing such as audio evaluation and zerocrossing detection for instantaneous and mean frequency measurement doesn't, provide both an accurate and quantitative result. Therefore, it is necessary to adopt frequency domain technique to improve system performance. In this paper, we describe a unit which is composed of Pulsed Doppler System and real-time spectrum analyzer (installed TMS 32010 DSP Chip). This unit shows time-dependent spectrum variation and mean velocity of blood Signal.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.709-712
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• 1988

Ultrasonic Doppler Diagnostic System utilizes the Doppler effect for measurement of blood velocity. The sign of the Doppler frequency shift represents blood flow direction. CW(Continuous-Wave) Doppler System uses quadrature detection and phase rotation method to produce simultaneous independent audio and velocity signals for forward and reverse blood flow direction in the time-domain, had been fabricated. But time-domain analyzing such as audio evaluation and zero- crossing detection for instantaneous and mean frequnecy measurement do not provide both an accurate and quantitative result. Therefore, it is necessary to adopt frequency-domain technique to improve system performance. In this paper, we describe a unit which is composed of CW Doppler System and real-time spectrum analyzer (installed TMS 32010 DSP Chip). This unit shows time-dependent spectrum variation and mean velocity of Blood signal.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1046-1048
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• 1999

This Paper compares two mathematical decomposition coordination methods to implementing the distributed optimal Power flow(OPF) using the regional decomposition: the Auxiliary Problem Principle(APP) and the Alternating Direction Method(ADM), a variant of the conventional Augmented Lagrangian approach. A case study was performed with IEEE 50-bus system.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1244-1253
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• 1990

Time-Marching methods solving Euler equations are used for calculation of two-dimensional, steady, inviscid flow through a stationary compressor cascade. Calculation method is based on the Denton`s opposed difference scheme. A smoothing in the axial direction is used to increase the stability of solution. The computational grid consists of quadrilateral elements, one of which has four nodes at each corner and the grid points on the upper periodic boundaries are located one pitch away from those on the lower boundaries to satisfy the periodicity condition. Results of calculation show good agreement with other computational and experimental results, proving that the present method of calculation should be applied with confidence for the cascade flow with shock wave.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.11
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• pp.2971-2980
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• 1995

A numerical study of fluid flow in driven cavity was carried out using singular finite element method. The driven cavity problem is known to have infinite velocity gradients as well as dual velocity conditions at the singular points. To overcome such difficulties, a finite element method with singular shape functions was used and a special technique was employed to allow multiple values of velocities at the singular points. Application of singular elements in the driven cavity problem has a significant influence on the stability of solution. It was found the singular elements gave a stable solution, especially, for the pressure distribution of the entire flow field by keeping up a large pressure at the singular points. In the existing solutions of driven cavity problem, most efforts were focused on the study of streamlines and vorticities, and pressure were seldom mentioned. In this study, however, more attention was given to the pressure distribution. Computations showed that pressure decreased very rapidly as the distance from the singular point increased. Also, the pressure distribution along the vertical walls showed a smoother transition with singular elements compared to those of conventional method. At the singular point toward the flow direction showed more pressure increase compared with the other side as Reynolds number increased.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1880-1884
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• 2007

The Natural Resource Conservation Service Curve Number(NRCS-CN) method is one of the widely used methods for computation of runoff from a basin. However, NRCS-CN method has weak point in that the spatial land use distribution characteristics are ignored by using area weighted CN value. This study developed a program which can estimate runoff by considering spatial distribution of CN and flow accumulation at the outlet of the watershed by appling Moglen's method. Comparisons between the results from NRCS-CN method and this study showed good agreement with measured data of experimental watersheds. The developed program predicted lower runoff than the conventional NRCS-CN method. As a conclusion, this study proposes a new design direction which can simulate real runoff phenomena. And the developed program could be applied into runoff minimization design for a basin development.

• Journal of Korean Port Research
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• v.12 no.2
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• pp.303-312
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• 1998

It is necessary to quantitatively asses the influence of tidal currents to analysis the coastal current patterns before or after constructing offshore structures like as breakwaters. This assesment can be made through the use of simulation models designed to reproduce the water movements of the area. And it is very important to predict a phenomenon of pollutant dispersion in the area. In this study, in order to predict the changes of sea water quality for the port development plan, Ilgwang harbour, located at the east coast of Pusan, the numerical computations were carried out. The flow patterns were investigated before and after the development of the harbour bay and coastal area connected on it. The computational models are an extension of earlier work on the flow which used the ADI Method (Alternating Direction Implicit Method) in appling to Osaka Bay by KANEKO et al. The transport of pollutant constituents depends upon the currental characteristics of the water-transporting medium. In the currental flow model, water velocities and water levels are computed throughout the regions of it. These value are then used in the mass-balance equation to obtain the pollutant-constituent transport. As a result of this research, the present water quality of Ilgwang harbour and the coastal areas connected on it was proved out some good condition. The changes of sea water quality due to the port development plan of the Ilgwang habour bay and the coastal area were not large compared with the present condition, but it will be likely able to get worse by increasing the semi-enclosed areas in the harbour bay. In order to improve the water quality of the area after development, the method to activate tidal exchange in the area can be needed, as a mitigation technique.

• Ecology and Resilient Infrastructure
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• v.10 no.4
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• pp.208-216
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• 2023

The purpose of this study is to present the most appropriate hardware and software configurations to produce a practical SIV (surface image velocimeter). To make a practical SIV, we constructed the system with a CCTV, a water stage gauge, and an analysis software installed on an Android board. The camera captures continuously images for 30 seconds with 2 minute intervals. And the 11-parameter projection method was used in the software that analyzes the captured images to reconstruct the exact measurement points according to the changing water stage. In addition, a spatio-temporal image construction method was developed so that the directions of the images could be arranged in the main flow direction at each measurement point. The surface image velocimeter composed of the proposed method was produced and installed at the Insu Stream, Seoul for a test site. And a result of measurement during a heavy rainfall event showed that the proposed system can measure flow discharge in proper, rapid and continuous manner.

• The KSFM Journal of Fluid Machinery
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• v.10 no.6
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• pp.32-37
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• 2007

Aerodynamic forces and moments have been used to control rocket propelled vehicles. If control is required at very low speed, Those systems only provide a limited capability because aerodynamic control force is proportional to the air density and low dynamic pressure. But thrust vector control(TVC) can overcome the disadvantages. TVC is the method which generates the side force and roll moment by controlling exhausted gas directly in a rocket nozzle. TVC is classified by mechanical and fluid dynamic methods. Mechanical methods can change the flow direction by several objects installed in a rocket nozzle exhaust such as tapered ramp tabs and jet vane. Fluid dynamic methods control the flight direction with the injection of secondary gaseous flows into the rocket nozzle. The tapered ramp tabs of mechanical methods are used in this paper. They installed at the rear in the rocket nozzle could be freely moved along axial and radial direction on the mounting ring to provide the mass flow rate which is injected from the rocket nozzle. In this paper, the conceptual design and the study on the tapered ramp tabs of the thurst vector control has been carried out using the supersonic cold flow system and schlieren system. This paper provides the thrust spoilage, three directional forces and moments and distribution of surface pressure on the region enclosed by the tapered ramp tabs.

• The Journal of Korean Medicine
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• v.17 no.1 s.31
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• pp.171-189
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• 1996

Background and Purpose: The greater part of patients to visit Hospital of Oriental Medicine suffer from cerebrovascular accident(CVA). There is transcranial Doppler(TCD) in the diagnostic method to confirm cerebrovascular accident(CVA). Transcranial Doppler(TCD) is an accurate method of monitoring the blood flow velocities of the cerebral vessels and have been generally used to prevent symptomatic vasospasm and confirm cerebral infarction. So we studied, in the crebrovascular accident(CVA), to estimate whether transcranial Doppler(TCD) is useful to. Methods: Using transcranial doppler(Multigon Model 500M Transcranial Doppler System), we measured the mean and peak velocity and the direction of blood flow in 10 cerebrovascular accident(CVA)'s subjects who had been examined by Computed Tomography(CT) or Magnetic Resonance Imaging (MRI). Results : As an anticipation, in cerebrovascular accident(CVA)'s subject with Cb-infarction, the mean and peak velocity of blood flow fell down remarkably and the direction of blood flow was change or irritable. But didn't find out any signal in lacunar infarction. Also, in case with spontaneous hemorrhage, the velocity and direction of blood flow was change but this signal was short of diagnosis for Cb-hemorrhage. Besides, we found signals about embolism, stenosis, thrombosis and occlusion in cerebrovascular accident(CVA)'s subjects. Conclusion: In Cb-infarction, the result of TCD was equal to diagnosis with Computed Tomography(CT) or Magnetic Resonance Imaging (MRI). But about lacunar infarction or spontaneous hemorrhage, signals of TCD couldn't be found out or was insufficient more than Computed Tomography(CT) or Magnetic Resonance Imaging(MRI). In cerebrovascular accident(CVA)'s subject with embolism, stenosis, thrombosis or occlusion, signals of TCD were found out more than Computed Tomography(CT) or Magnetic Resonance Imaging(MRI). Therefore transcranial doppler(TCD) is necessary method which makes a diagnosis of cerebrovascular accident(CVA), with Computed Tomography(CT) or Magnetic Resonance Imaging(MRI).