• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.4
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• pp.503-508
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• 1997

The change of the structure of homogeneous turbulence subject to irrotational strains has been studied in an anti-Morel type diffuser (center matched cubic contour) using the hot wire anemometry. It was observed that the profiles of mean velocities and turbulence velocities along the center line were stable at the entrance region but rapidly changed near the matching point. The wall induced turbulence at the entrance region grows fast and was diffused toward the center at downstream. It was also observed that the axial turbulence grows faster than the radial one in the middle region of the diffusing flow and that the diffusing process has the vortex compression mechanism due to the conservation of angular momentum. These phenomena are frequently observed at the initial flow region of the free jet.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.1
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• pp.65-72
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• 1993

An experiment has been carried out to identify flow patterns in a horizontal condensing flow with R-113. Characteristics of flow patterns were determined based upon a statistical analysis of differential pressure fluctuations at an orifice. The probability density function and power spectral density function of instantaneous pressure drop curves for various flow conditions were obtained. In comparison to the results of air-water flows, the flow patterns in a condensing flow such as annular, wavy, slug and plug could be identified. The experimental data determined by this technique were compared with the flow pattern maps suggested by other investigators. The result indicates that the statistical characteristics of differential pressure fluctuations at an orifice may be a useful tool for identifying flow patterns both in condensing flows and in adiabatic two-phase flows.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.3166-3178
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• 1993

The turbulent flow characteristics of impinging jet have been investigated by the hot wire anemometry with a movable impinging wall. Turbulences were generated by the meshed jet as well as the typical round jet and their characteristics were compared, of mean velocity profiles, turbulent intensities. Reynolds stresses, similarities and their centerline flow behaviors. The meshed jet tends to make shear layer wider than the normal one in the initial region and the velocity profiles of the normal jet is rather contractive being compared with those of the meshed one near the wall. The effect of meshed exit appears only within 4D at the begining of jets and the cascading process of the meshed one marches more rapidly than that of the normal jet. The wall effects appear in the downstream of about 0.85 H to the impinging wall for every case of wall positions in both nozzles.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3335-3344
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• 1994

The initial flow characteristics of the turbulent circular jet discharging into the sudden expansion pipes have been investigated by the hot wire anemometry. Evolutions of similarity, centerline behavior, jet boundary and typical turbulent quantities were looked into for the expansion ratios. The results show that the spreading rates of discharging jet seem not to be dependent of the expansion ratio and that the velocity profiles in the radial directions exhibit the similarity in the regions, 2-5d, 2-6d and 3-8d for the corresponding expansion rations of 2, 3 and 5, respectively. With the increase of expansion ratio the centerline velocity decays rather slowly. The anisotropic behaviors of the discharging jets into the sudden expansion pipe look stronger than those of the free jet.

• Proceedings of the KIEE Conference
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• 1998.11b
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• pp.579-581
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• 1998

본 연구에서는 $11.7GHz{\sim}12.2GHz$ 주파수 대역의 무궁화 위성방송 송 수신기 정합표준 2.0과 디지털 위성방송 제한수신 정합 잠정표준을 만족하는 무궁화 위성방송 수신시스템 분야에 대한 연구를 수행하였다. 상위 표준에 의거하여 제한 수신모듈을 탑재한 디지털 위성방송 수신장치 개발에 따른 타당성과 신뢰성을 검증하고자 Subscribed and Per-Per-View 채널 디스크램블링 및 가입자 관리(Subscriber Management)에 필요한 데이터 ECM, EMM, RCM 등의 데이터 축출과 처리과정을 모델링하고 모의 실험 수신기(IRD : Integrated Receiver and Decoder)를 제작하여 한국 전자통신연구원에서 작성한 "제한 수신 시스템 신뢰성 검증시험절차서"에 따라 동작반응을 시험하였다.

• Sijohaknonchong
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• v.23
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• pp.133-159
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• 2005

This thesis is about Sijo(traditional Korean poem) made-up of 35 volumes and 45 poems written by Han Yong-un. The aim of this study is reappraise the Sijo which is not known to Korean people. There are four thesis about Sijo so far. Ko Myeong-su divided Sijo into separate subjects and researched it very deeply. After I read the Chinese Poems of Han Yong-un, I researched the relationships between subject matter and its theme. The relationships are between the moon and religion, spring and aspiration, autumn and grief or lose, and the sword and patriotism. I chose to discuss a Sijo 'Mugunghwa Shimeukwajeo'(무궁화(無窮花)를 심으과저) shich deals with the moon and religion. The main subject matter of this S is the moon. There are three poems in this volume. They are all about the moon. There is a Mugunghwa (無窮花) on the moon. This poem asserts that the moon is good for love, and it is the subject matter of the poet's religion. The moon in the Chinese poem 'Okjungkamwhiy'(獄中感懷) believes there is hope in prison. The moon in 'Wolbang(月方中) is Buddhist thinking. I researched 'Geochon'(早春) tee poems about spring and aspiration. The first poem is about the independent movement against the Japanese. Autumn is about the feeling of lose in the life. Sijo 'Chuyamong' (秋夜夢) is lose the lover. The second poem is about conquering all difficulties of the poet's current circumstance. The third poem is about the feeling of vacuum in his life. The fourth poem is about deploring losing his mind. 'Nam-a'(男兒) and 'Urinim'(우리님) are books about patriotism. These poems have the subject matter of a sword for song patriotism. 'Kiharksaeng'(寄學生), 'Anhaeju'(安海州), and 'Hwangmaecheon'(黃梅泉) are patriotic poems. In this study, I found that the subject matter and the theme in the Chinese poems of Han Yong-un(韓龍雲) are related. Mainly he used the metaphor of the moon for religion, spring for aspiration, autumn for grief or lose, and sword for patriotism.

• Sijohaknonchong
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• v.24
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• pp.259-278
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• 2006

In this study, I've researched the sijo written by Yukdang, Choi, Nam Sun, and Manhae. Han, Yong Woon who were the leading intellectual and the pioneers experiencing the time of flowering and the colonial period. Their lives had the common things in various way. They were involved in Independence movement as the intellectual at that time. They also showed the various activities such as modern poem. sijo, and even Chinese poetry. In this thesis, 1 compared their sijo and considered them. Especially, I've researched the two divided parts focused on the tone shown in the sin one part was focused on the 'lover', and the other was on the 'life'. The summarise which I've researched is as followings. First, I've researched the sijo focused on the 'lover' They have the common things in having the presupposition of farewell to their 'lover'. But there were significant differences as followings. In the case of Yukdang, he expressed the passive tone based upon the despondency and the loss with the absence of his lover. Meanwhile, Manhae tended to reveal the resigned and negative tone based to his lyrical world. The contrasted tone in their poems is considered to have something to do with their realistic matters. There should also be several things to be discussed in the future.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2573-2578
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• 2007

In order to investigate the vortex body frame interaction around the side mirror of a passenger car, velocity vector fields in the wake, pressure distributions and boundary layer flows over both the mirror surface and the mirror housing, have been measured by several experimental tools. It was resulted that only within an half downstream distance of the mirror span there appears the recirculation zone, and also found that vortex trail towards to the driver side window between A and B pillars, making the acoustic noise and vibration. Wake vortex rolls up after this recirculating zone and makes the trail of the vortex center towards the driver side window, which was also confirmed by measurements of wake velocity vectors in the vertical sections of the trail and visualization over the side mirror surfaces as well. It was also observed that total pressure distribution over the mirror surface has the minimum peak near the lower tip region which can be considered as the origin of the vortex center. It can be concluded that the geometrical modification of the lower tip and the upper root area of the mirror housing is the key to control the wake vortex.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.10
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• pp.1343-1350
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• 2000

The evolutionary structure of tip vortices has been investigated with a two-dimensional LDV system for a plain and a slotted blade, respectively. To analyze the effect of slots which bypasses a part of main stream into the tip face, velocity profiles, vortex sizes, their displacements and turbulence intensities during one revolution of the rotor were measured by the phase averaging process. For the comparison of circumferential velocity components of the plain blade and the slotted blade, the peak values of the slotted blade were lower than those of the plain blade, and axial velocity components of the slotted blade were considerably larger than those of the plain blade. The slotted rotor blade enlarged the core size and made the vortex delayed compared with those of the plain blade at the same wake ages. Turbulence profiles had peaks inside the core radii and decayed gradually in the radial direction of vortex coordinate. Also, using a quasi 3-D LDV measurement technique the budget of turbulence kinetic energy was analyzed in radial direction of the vortex core.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.4
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• pp.531-538
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• 2002

Flow characteristics of a round jet with swirl number of 0.17 have been investigated using a hot -wire anemometry in the initial region within 10D(exit diameter). Swirl effects were observed by comparing centerline flow characteristics, similarities and turbulent budgets of a swirl jet and a free jet, respectively. To obtain similarity of the radial profiles mean velocity and higher moments were measured at the vertical pl anes, located at 2.5, 5.0, 7.5D, 10D, respectively. The centerline velocity characteristics were also measured. It is turned out that similarities of mean and Reynolds stress are established. The jet boundary has wider width than that of a free jet and the shear stress also becomes stronger. In addition the centerline decay becomes faster than that of the free jet, indicating that the swirl induces more entrainment in the initial region of the swirl Jet by transferring the axial mean kinetic energy into the swirl energy and, therefore, has wider boundary, compared with that of free jet.