• Journal of the Korean Society for Precision Engineering
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• v.22 no.6 s.171
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• pp.192-198
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• 2005

Recently, Automobile manufacturers regarding stability, economic environmental-friendly problems by the development of automobile. This reason is increasingly strict environmental regulations to lower fuel consumption and reduce emission. Designing more efficient and low emission control exhaust system results in more efficient Performance, reduced back Pressure and higher convert efficiency. Also to reduce the noise and the vibration of the automobile. According to develop variable type muffler, dual muffler and active intelligence exhaust system unit. Improvement in engine performance and fuel consumption rate, higher conversion efficiency demand information of pressure fraction and heat characteristics. To be able to determine these factor fur we experiment on each case of exhaust system unit. In this study, how back pressure is distributed in flow-through in exhaust system and how to design exhaust system flexibleness, efficiency, lower back pressure and optimal performance. This study furnish basic data for engineers, technicians.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.65.1-65.1
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• 2020

We present high-resolution, high-sensitivity continuum data of NGC 4522 observed at 3 cm (X-band) and 10 cm (S-band) in full polarization mode using the JVLA. This observation has 2 - 4 times better spatial resolution and 2 - 5 times better sensitivity compared to previous continuum observations. NGC 4522 is a Virgo spiral galaxy undergoing active ram pressure stripping. This galaxy is particularly well known for the CO emission detected outside its stellar disk, some of which coincides with the extraplanar HI gas and Halpha patches. The major goal of our JVLA observation is to leverage our understanding of the influence of the ram pressure on the general ISM field and multi-phase medium. By combining our new deep radio continuum data and previous observations, we will investigate how the B-field properties can be affected by the ram pressure, and what roles the B-field plays in the stripping process of the multi-phased ISM and in the star formation activity when the ram pressure is present.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.2
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• pp.190-193
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• 2022

In this work, the effect of sputtering working pressure for the tellurium film and its thin-film transistor was investigated. The transfer characteristics of tellurium thin-film transistors were improved by increasing the working pressure during sputtering process. As increasing working pressure, physical and optical properties of Te films such as crystallinity, transmittance, and surface roughness were improved. Therefore, the improved transfer characteristics of Te thin-film transistors may originate from both improved interface properties between the silicon oxide gate dielectric layer and the tellurium active layer with an improved quality of Te film. In conclusion, the control of working pressure during sputtering would be important for obtaining high-performance tellurium-based thin film transistor

• International Journal of Aeronautical and Space Sciences
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• v.7 no.2
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• pp.70-85
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• 2006

The supersonic flutter suppression of a cantilevered plate wing is studied with the finite element method and the quasi-steady aerodynamic theory. We suppress wing flutter by using piezoelectric materials and electric devices. Two approaches to flutter suppression using piezoelectric materials are presented; an energy-recycling semi-active approach and a negative capacitance approach. To assess their flutter suppression performances, we simulate flutter dynamics of the plate wing to which piezoelectric patches are attached. The critical dynamic pressure drastically increases with our flutter control using a negative capacitor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.120-121
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• 2011

• Physical Therapy Korea
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• v.24 no.3
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• pp.40-46
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• 2017

Background: The active knee extension (AKE) test commonly used to assess the flexibility of the hamstring muscles. Many researchers have tested the reliability of the AKE test; however, no published studies have examined the intrarater and interrater reliability of the AKE test using a PBU. Objects: The purpose of this study was to determine the intrarater and interrater reliability of the AKE test performed with a pressure biofeedback unit (PBU) on healthy subjects. Methods: Sixteen healthy male participants volunteered and gave informed consent to participate in this study. Two raters conducted AKE tests independently with a PBU. Each knee was measured twice, and the AKE testing was repeated one week after the first round of testing. Results: The interrater reliability's intraclass correlation coefficients ($ICC_{2,1}$) were .887~.986 for the right knees and .915~.988 for the left knees. In addition, the intrarater (test-retest) reliability ($ICC_{3,1}$) values ranged between .820~.915 and .820~.884 for Raters 1 and 2, respectively. The values for the standard error of mesurement were low for all tests ($.81{\sim}2.97^{\circ}$); the calculated minimum detectable change was $2.24{\sim}8.21^{\circ}$. Conclusion: These findings suggest that the AKE test performed with a PBU had excellent interrater and intrarater reliability for assessing hamstring flexibility in healthy young males.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.518-521
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• 2005

The Structures or buildings nowadays draw more complexity in design due to space limitation and other factor that affect the height and dimensions, that results to instability. So the various methods have been carried out to improve the safety factor from an earthquake or a boom until recently. But, it is very hard to get model precisely because these structures are the non-linear and multi-variable systems. For this reason, we developed the active control system that is applied the adaptive control method on the U type Tuned Liquid Damper(TLD) passive control system. It is proven that the proposed active control strategy of the plate carrying U type TLD system is the more effective control method to suppress the vibration of the structure. The entire hybrid control system is composed of the actuator acted in the opposite direction of the TLD system's motion direction and the active control device with an air pressure adjuster. This paper proposed the adaptive control methods to improve the problem of U type TLD system which is used widely for the passive control of the building. And it is proved by the simulation. In advanced, it is developed the pressure control method that is improved the hybrid controller's performance by using air chamber pressure controller. These methods take the advantage of the decrease of the maximum displacement by using the controller as soon as the impact is loaded. This is a very important element for the safety design and economic design of structures.

• Geotechnical Engineering
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• v.5 no.1
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• pp.47-60
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• 1989

Lateral earth Pressure distributions due to the ,randy soil backfill behind the rigid vertical walls for three different wall movement modes are obtained by the elasto-plastic finite element analys of soil deformation, and these earth pressures are compared with both Rankine's and Dubrova's active earth pressures. Thereby, the effects of the magnitude and the mode of wall displacement on the earth pressure distribution are investigated. Three different modes of wall movement considered in this study are the rotation about bottom, the rotation about top and the translation. For the case of the wall rotation about top, the earth pressure distribution is shown as a reverse S-curve-shaped distribution due to the arching effect. Consequently, the point of application of the lateral thrust is much higher than one-third of the wall height from the base. And, comparing the other modes of wall movement, the magnitude and the point of appliestion of the lateral thrust for the wall rotation about top are larger and higher, respectively. The wedge-shaped plastic zone in the backfill at active failure is developed only for the mode of wall rotation about bottom. The lateral earth pressure distributions on the walls with inclined backfill of several different slopes are shown for the mode of wall rotation about bottom.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.5
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• pp.374-379
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• 2002

A new active muffler system has been developed and its superior performance on both noise reduction and engine torque increase is demonstrated with experiment. Main characteristic of the proposed muffler system is the use of destructive interference by transmission path difference of divided exhaust pipes to reduce major exhaust noise components thereby overcoming problems of other active exhaust noise control methods. The exhaust pipe is divided into two sections and joined again downstream. One divided pipe has a sliding mechanism to vary its length, which is controlled to make half wavelength transmission path difference for the major engine rpm frequency. In this system one divided pipe is used to control major rpm frequency and its Harmonics and another pipe is used to control noise component double the frequency of rpm. An after-market tuning muffler, which has very simple internal structure and minimal back pressure, is also installed to remove remaining wideband noise. To make the system to be small enough to be practical, conventional muffler is also installed and used in low rpm range and active muffler is only employed in high rpm range. Noise reduction of the proposed system is comparable to conventional passive muffler. The engine dynamo test has proved the proposed system can recover almost all the torque lost by conventional muffler.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.2
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• pp.119-125
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• 2001

This paper presents an experimental study on active control of self-excited vibration for a high speed turbomachinery. In order to suppress the self-excited vibration, it is necessary to actively control the air film pressure or the air film thickness. In this study, active pads are used to control the air film thickness. Active pads are supported by pivots containing piezoelectric actuators and their radial position can be actively controlled by applying voltage to the actuators. The transfer characteristics from actuator inputs to shaft vibration outputs are experimentally investigated. In a tilting-pad gas bearing (TPGB), a shaft is supported by the pressurized air film. Four gap sensors were used to measure the vibration of the shaft and PID was used in the feedback control of the shaft vibration. The experimental results show that the self-excited vibration of the rotor can be effectively suppressed if the PID controller gains are properly chosen. As a result we find that the feedback control is effective for suppressing the self-excited vibration of a rotor system using stack-type PZT actuators.