• Journal of Advanced Marine Engineering and Technology
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• v.27 no.6
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• pp.736-744
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• 2003

This study is conducted to investigate aerodynamic forces and wake structures about the pressure interference of a circular cylinder with slits. An experimental investigation of a circular cylinder with slits is carried out in uniform flow in the range of Reynolds number from 8,000 to 32,000 using X-type hot wire. Flow visualization is executed by smoke-wire method to understand the mechanism of these vortex formation process. Inspection in the wake at X/D=5.5 of the cylinder with the slits suggested that a strong vortex-shedding pattern for these cylinders is revealed compare with a circular cylinder without slits. It is found that the rolling up position of shear layer of the cylinder with slits is shorten compare with a circular cylinder without slits.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.929-933
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• 2003

Internal defects of thin pressure vessel used in the power plants or the chemical plants may be created and grow due to corrosion or creep fatigue to reduce the strength and cause critical failure during operation. Therefore it is very important to detect this defect at the early stage. For this purpose, non-destructive, non-contact and highly sensitive method should be considered for on-line application. In this paper, a laser shearographic interferometer is applied to inspect circular defects and notch defects existed inside of thin pressure vessel under the presence of pressure up to 3 times of atmospheric pressure. The influences of the defect shape and size as well as the internal pressure to the characteristic pattern in the shearography fringe are investigated, and the quantitative evaluation of the defect size is tried. Also the experimental results are compared with the destructive test results to show the applicability of this method to the quantitative evaluation of internal defects in the thin pressure vessel.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.9
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• pp.103-110
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• 2004

Pressure ripples yield noise and vibration in hydraulic pipelines, which are inevitably generated by a fluctuation of flow rate in the pump mechanism, and such noise and vibration deteriorate the stability and accuracy of hydraulic systems. To reduce the pressure ripples, accumulator and hydraulic attenuator are normally used. In this study, parallel pipeline with a bent-axis piston pump is introduced to a hydraulic pipe system as a method for reducing the pressure ripples and using the transfer matrix method, the dynamic characteristics of the pipe system are analysed and compared with experimental results. The results show that the phase interference using parallel pipeline with a bent-axis piston pump is effective to reduce the pressure ripples in the hydraulic pipelines.

• Journal of the Korean Vacuum Society
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• v.14 no.3
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• pp.103-109
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• 2005

A new medium vacuum primary standard using the static expansion method was developed in KRISS. In order to evaluate the performance of the equipment, we compared the medium vacuum standard with an ultrasonic interferometer manometer using two capacitance diaphragm gauges, the measuring ranges of which were 133 Pa and 1,333 Pa respectively. The result, Error normalized values, showed that the two standards are coincident each other within the range of combined uncertainty at calibrated pressure of $3pa\;\sim\;100pa$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.306-309
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• 2006

Passive control of the shock wave/turbulent boundary-layer interaction control utilizing slotted plates over a cavity has been carried out. Effect of various slot configurations on the characteristics of the interactions are tested. Pitot/wall surface pressure distributions and flow visualizations including Schlierens and interference fringe patterns over a thin oil-film have been obtained at the downstream of the shock interactions. It was found that the interaction control by a certain slot-configuration could lead a reduction of the total pressure loss through the shock wave, however, the boundary layer thickness became thicker as compared with the case of no control.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.2
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• pp.18-25
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• 2007

Computational study on the passive control of the oblique shock-wave/turbulent boundary-layer interaction utilizing slotted plates over a cavity has been carried out. The numerical boundary layer profile upstream of the interaction follows the compressible turbulent boundary-layer theory reasonably well, and the other results also show good agreements with the experimental observations, such as the wall surface pressures and Schlieren flow visualizations. Further, the effects of various slot configuration including number, location and angle of the slots on the characteristics of the interactions, such as the variation of the total pressures, the boundary-layer characteristics downstream of the interaction and the recirculating mass flux through the slots, are also tested and compared.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.5
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• pp.663-668
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• 2012

A TPMS(Tire Pressure Monitoring System) is a wireless communication system designed to monitor the pressure and temperature of pneumatic tires of a vehicle. In order to provide the aid in protecting a driver, this system reports tire pressure information to the driver of the vehicle. Since the wireless communication technique should be employed to transmit the TPMS data from each tire to signal processing unit in the vehicle, it suffers from interference signals from external electrical or electronics equipments. In this paper, we propose the TPMS interference cancellation technique based on GSC(Generalized Sidelobe Canceler), which does not have only the excellent performance like MVDR(Minimum-Variance-Distortionless-Response) but also has the low computational complexity comparing with MVDR. The performance of interference suppression is conformed by computer simulation examples.

• Journal of Sensor Science and Technology
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• v.7 no.3
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• pp.147-153
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• 1998

The strain characteristics of a fiber optic Fabry-Perot pressure sensor with high sensitivity using a $Si_{3}N_{4}/SiO_{2}/Si_{3}N_{4}$ (N/O/N) diaphragm is experimentally investigated. A 600 nm thick N/O/N diaphragm was fabricated by silicon anisotropic etching technology in 44 wt% KOH solution. An interferometric fiber optic pressure sensor has been manufactured by using a fiber optic Fabry-Perot intereferometer and a N/O/N diaphragm. The 2 cm length fiber optic Fabry-Perot interferometers in the continuous length of single mode fiber were produced with two pieces of single mode fiber coated with $TiO_{2}$ dielectric film utilizing the fusion splicing technique. The one end of the fiber optic Fabry-Perot interferometer was bonded to a N/O/N diaphragm. and the other end was connected to an optical setup through a 3 dB coupler. For the N/O/N diaphragm sized $2{\times}2\;mm^{2}$ and $8{\times}8\;mm^{2}$, the pressure sensitivity was measured 0.11 rad/kPa and 1.57 rad/kPa, respectively, and both of the nonlinearities were less than 0.2% FS.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.2
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• pp.170-176
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• 2012

In the nuclear industry, wall thinning defect of straight pipe occur the enormous loss in life evaluation and safety evaluation. To use non-destructive technique, we measure deformation, vibration, defect evaluation. But, this techniques are a weak that is the measurement of the wide area is difficult and the time is caught long. In the secondary side of nuclear power plants mostly used steel pipe, artificiality wall thinning defect make in the side and different thickness make to the each other, wall thinning defect part of deformation measure by using shearography. In addition, optical measurement through deformation, vibration, defect evaluation evaluate pipe and thickness defects of pressure vessel is to evaluate quantitatively. By shearography interferometry to measure the pipe's internal wall thinning defect and the variation of pressure use the proposed technique, the quantitative defect is to evaluate the thickness of the surplus. The amount of deformation use thickness of surplus prediction of the actual thickness defect and approximately 7 percent error by ensure reliability. According to pressure the amount of deformation and the thickness of the surplus through DB construction, nuclear power plant pipe use wall thinning part soundness evaluation. In this study, pressure vessel of thickness defect measure proposed nuclear pipe of wall thinning defect prediction and integrity assessment technology development. As a basic research defected theory and experiment, pressure vessel of advanced stability and soundness and maintainability is expected to contribute foundation establishment.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.2
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• pp.177-184
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• 2012

An optical defect detection method using ESPI(electronic speckle pattern interferometry) is proposed. ESPI is widely used as a non-contact measurement system which show deformation and phase map in real time. ESPI can be divided as the in-plane, out-of-plane and shearography by operation principle and target object and also divided with bulk type and optic fiber type by the optic configurations. This paper is focused on optic fiber type out-of-plane ESPI, which has the following advantages: (1) low cost; (2) reduction of the unreliable factors generated by separated optic components; (3) simplification of the optic configuration; (4) great reduction of volume; (5) flexibility, to be easily designed into different structures to adapt to inaccessible environments such as pipeline cavity and so on.