• 설비공학논문집
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• 제29권3호
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• pp.127-133
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• 2017

Performance analysis has been carried out on a high side scroll compressor that had a fixed scroll equipped with a circular oil groove on its thrust surface. Oil was supplied to the oil groove through an intermittent opening from a high pressure oil reservoir formed inside the orbiting scroll hub. Oil in the groove was then delivered to both suction and back pressure chambers by pressure differentials and viscous pumping action of the orbiting scroll base plate. Mathematical modeling of this oil groove system was incorporated into a main compressor performance simulation program for an optimum oil groove design. The study findings were as follows. Pressure in the oil groove can be controlled by changing its configuration and the oil passage area. With an enlarged oil passage, the pressure in the oil groove heightens due to an increased flow rate, but the pressure elevation in the back pressure chamber is small, resulting in reduced friction loss at the thrust surface between the two scrolls. On the other hand, by increasing the oil passage area, the oil content in the refrigerant flow increases. Considering all these factors, the energy efficiency ratio could be improved by about 3.6% under the ARI condition by an optimal oil groove design.

• International Journal of Automotive Technology
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• 제8권3호
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• pp.269-274
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• 2007

A prior fundamental study was executed using a constant volume chamber (CVC) to improve the burning characteristics of lean pre-mixture by the injection of active radicals generated in the sub-chamber of the CVC. The Radical ignition (RI) technique shows remarkable progress in the burning velocity and combustible lean limit compared with the results of the spark ignition (SI) technique. The optimum design value of the sub-chamber geometry is near $0.11cm^{-1}$ for the ratio of the total area of the holes to the sub-chamber volume $(A_h/V_s)$. In this study, based on the former experimental results, the additional works have been performed to examine the effects of the geometry change in the number $(N_h)$, the total section area $(A_h)$, and diameter $(D_h)$ of the passage holes on the combustion characteristics in the CVC. Also ambient conditions such as the initial temperature and the initial pressure of the mixture were selected as experimental parameters and the effects of residual gas at the chamber on the combustion characteristics were investigated. As a result, the correlation between the passage hole number and overall passage hole area was grasped. The effects of the initial temperature were significant, but on the other hand, those of the initial pressure were weak. A more detailed analysis on the residual gas is required in the future.

• 한국주거학회논문집
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• 제13권3호
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• pp.45-53
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• 2002

The purpose of this study is to examine the characteristics of unit plans in the high-rise mixed-use condominium and to provide the data fur architectural planning and design. The tools of statistical analysis are frequency, percentage, mean, cross-tab, and correlation. The results of this study are as fellows; The most frequently found shape of unit is a deformed polygon. The common rooms in housing units are dressing room, powder room, offset-kitchen, family room, passage, hallway, and foyer. The specially prepared spaces are wash room, home bar, independent porch, and garden. As to room size and area ratio in a dwelling unit, those of living room are biggest and highest irrespective of unit size. As the floor area of unit increases, does the size of each room and space but the area ratio of each room decreases. This research is made to develop an Apartment Information System. This integrated information system is to be designed to provide residents of high-rise mixed-use condominiums with convenient, economical, and safe life.

• 한국자동차공학회논문집
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• 제3권5호
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• pp.122-134
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• 1995

The present study was investigated combustion characteristics of methane-air mixtures at stratified charge in a constant volume combustion chamber. The main results obtained from this study can be summarized as follows. In case of ${\phi}_s=1.0$, total burning times greatly affected rather than initial time of pressure increase and maximum combustion pressure. In case of ${\phi}_t=1.0$, initial time of pressure increase and total burning times were affected considerably in comparison with the case of ${\phi}_s=1.0$. Also, even the very lean mixture which total equivalence ratio is ${\phi}_t=0.69$(${\phi}_s=1.0$, ${\phi}_m=0.65$), by changing configuration of the critical passage-hole and using a stratified mixture, it is possible to decrease substantially the initial time of pressure increase. total burning times and NOx concentration without deteriorating combustion characteristics such as maximum combustion pressure, rate of heat release etc. in comparison with the use of single chamber(in case of ${\phi}=1.0$) only. Specifically, our trends were revealed remarkably in the case of Type D which is reduced a flame contact area of sub-chamber side of the passage-hole.

• 한국농촌건축학회논문집
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• 제13권3호
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• pp.29-36
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• 2011

The purpose of this study was analyzing with present conditions and content analysis of the parking area for the handicapped people. The researcher investigate to that establishment ratio, accessibility, the induction and guidance, and safe walking passage security, and proper space of the parking area for the handicapped people was established by lawfully. The results as follows. In spite of the regulation established by law, regulations was not established 40% on region government. The parking area for the handicapped people established Properly consider to the accessibility. But the size and height of the stand-up guide plate of the induction and guidance which corresponds in legal establishment standard of the handicapped people. then this research analyzes problems and suggests alternatives of the facilities.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제29회 추계학술대회논문집
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• pp.297-301
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• 2007

초음속 충동형 터빈과 같이 종횡비가 작은 경우 로터 익형은 반경방향으로 동일한 단면을 갖는 형태로 구현된다. 이 경우 터빈 로터는 터빈 동익의 프로파일 직경에 따라 설계에서 의도하지 않은 유로면적분포와 터빈 성능의 차이를 보인다. 본 연구에서는 터빈 동익 프로파일을 정의하는 직경이 터빈 성능에 미치는 영향을 고찰하기 위하여 3개의 다른 위치에서 정의된 터빈 로터에 대한 유동해석을 수행하고 결과를 고찰하였다. 계산 결과 팁에서 단면이 정의된 경우 설계에서 의도한 유로면적 변화를 보이며 다른 프로파일 직경에서 정의된 터빈에 비해 우수한 성능을 보임을 확인하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3191-3196
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• 2007

The present study addresses a method to operate a fuel-cell system effectively using a recirculation ejector which recycles wasted hydrogen gas. Configuration of a recirculation ejector is changed to investigate the flow behavior through it under varying operating conditions, and how such conditions affect the fuel-cell hydrogen cycle. The numerical simulations are based on a fully implicit finite volume scheme of the axisymmetric, compressible, Reynolds-Averaged, Navier-Stokes equations for hydrogen gas, and are compared with available experimental data for validation. The results show that a hydrogen recirculation ratio is effectively controlled by a configurational alteration within the operational region in which the recirculation passage doesn't plugged by a sonic line.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.447-452
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• 2000

In this study, the design of Free-Fall Simulator was carried out using concept of vertical wind tunnel. Free-Fall Simulator is not an experimental equipment but a training equipment. Therefore Free-Fall Simulator needs a large training section compared with test section of wind tunnel and has critical limit of height. These limits bring about the difficulty of design for a return passage. Due to small area ratio, the downstream flow of training section with high speed is not decelerated adequately to the fan section. High-speed flow leads to great losses in the small area ratio diffuser and corner. So design of diffusers and corners located between training section and fan section has a great effect on the Free-Fall Simulator performance. This study used an estimation method of subsonic wind tunnel performance. It considered each section of Free-Fall Simulator as an independent section. Therefore loss of one section didn't affect loss of other sections. Because losses of corner with vane and $1^{st}$ diffuser are most parts of overall Free-Fall Simulator, this study focused on the design of these sections.

• 대한후두음성언어의학회지
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• 제12권1호
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• pp.34-38
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• 2001

Background and Objectives : With the development of computerized systems, an objective evaluation methods of nasal speech and nasal geometry have become readily available by means of a simple, noninvasive technique. In this study, we assessed the nasality, nasal formant, nasal volume and nasal area in patients with hypertrophic rhinitis before and after turbinate surgery. Material and Method : With the nasometer, we measured nasalance, which reflects the ratio of acoustic energy output of nasal sounds from the nasal and oral cavities. With CSL 4300B, we measured nasal formants. We used acoustic rhinometer to measure nasal area and nasal volume. Postoperative changes of above factors were compared with preoperative values. Paired t-test and Pearson's correlation were used for statistical analysis. Results : The first nasal formant frequency, nasalance scores of three passages(baby, mamma and rabbit passages), minimal cross sectional area(MCA) of narrow side, nasal volume of narrow side and nasal volume of wide side had increased significantly after turbinate surgery (p <0.05). The MCA and nasal volume of narrow side and MCA of wide side showed significant correlation with nasalance score of rabbit passage and baby passage showed significant correlation with nasal volume of narrow side(p<0.05). Conclusion : There were significant increases in nasalance scores, first nasal formant frequency, MCA and nasal volume after turbinate surgery. Thus, we must consider the possibility of voice changes postoperatively in professional voice users.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 추계 학술논문 발표대회
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• pp.44-45
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• 2018

In this study, water vapor pressure of high strength concrete reinforced with amorphous steel fiber(AF) was evaluated. Experimental results show that spalling occurs when the incorporation rate of amorphous steel fiber is 0.5 vol.% or more. This is because the ratio of AF increased per unit area influenced the formation of the water vapor pressure discharge passage by the polypropylene fiber(PPF) melting. Therefore, it is necessary to find the proper mixing ratio of AF and PPF to prevent spalling.