• International Journal of Fluid Machinery and Systems
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• 제9권4호
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• pp.338-353
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• 2016

Information on the surge behaviors and stall stagnation boundaries for a nine-stage axial flow compressor are summarized on the basis of analytical data in comparison with those for a single-stage one, with attention to the pressure ratio effect. The general trends of the surge loop behaviors of the pressure-mass flow are similar for both compressors including the fact that the subharmonic surges tend to appear very near the stall stagnation boundaries. With respect to the nine-stage compressor, however, the mild loops in the subharmonic surges tend to be very small in size relative to the deep loops, and at the same time, insufficient surge recovery phenomenon, which is a kind of subharmonic surge, appears also far from the stagnation boundary for relatively short delivery flow-paths. The latter is found to be a rear-stage surge caused by unstalling and re-stalling of the rear stages with the front-stages kept in stall in the stalled condition of the whole compressor, which situation is caused by stage-wise mismatching in the bottom pressure levels of the in-stall multi-stage compressor. The fundamental information on the stall stagnation boundaries is given by a group of normalized geometrical parameters including relative delivery flow-path length, relative suction flow-path length, and sectional area-pressure ratio, and by another group of normalized frequency parameters including relative surge frequencies, modified reduced resonance frequencies, and modified reduced surge frequencies. Respective groups of the normalized parameters show very similar tendency of behaviors for the nine-stage compressor and the single-stage compressor. The modified reduced resonance frequency could be the more reasonable parameter suggesting the flow-induced oscillation nature of the surge phenomena. It could give the stall stagnation boundary in a more unified manner than the Greitzer's B parameter.

• International Journal of Fluid Machinery and Systems
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• 제9권1호
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• pp.1-16
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• 2016

Behaviors of surges appearing near the stall stagnation boundaries in various fashions in systems of a single-stage compressor and flow-path systems were studied analytically and were tried to put to order. Deep surges, which enclose the stall point in the pressure-mass flow plane, tend to have either near-resonant surge frequencies or subharmonic ones. The subharmonic surge is a multiple-loop one containing, for example, in a (1/2) subharmonic one, a deep surge loop and a mild surge loop, the latter of which does not enclose the stall point, staying only within the stalled zone. Both loops have nearly equal time periods, respectively, resulting in a (1/2) subharmonic surge frequency as a whole. The subharmonic surges are found to appear in a narrow zone neighboring the stall stagnation boundary. In other words, they tend to appear in the final stage of the stall stagnation process. It should be emphasized further that the stall stagnation initiates fundamentally at the situation where a volume-modified reduced resonant-surge frequency becomes coincident with that for the stagnation boundary conditions, where the reduced frequency is defined by the acoustical resonance frequency in the flow-path system, the delivery flow-path length and the compressor tip speed, modified by the sectional area ratio and the effect of the stalling pressure ratio. The real surge frequency turns from the resonant frequency to either near-resonant one or subharmonic one, and finally to stagnation condition, for the large-amplitude conditions, caused by the non-linear self-excitation mechanism of the surge.

• International Journal of Fluid Machinery and Systems
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• 제6권2호
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• pp.56-74
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• 2013

Stall stagnations in the system of axial-flow compressors and ducts occur in transition from deep surge conditions to decayed or converged stall conditions. The present study is concerned with the boundaries between the deep surges and the stagnation stalls on the basis of analytical results by a code on surge transients analysis and simulation. The fundamental acoustical-geometrical stagnation boundaries were made clear from examinations of the results on a variety of duct configurations coupled with a nine-stage compressor and a single stage fan. The boundary was found to be formed by three parts, i.e., B- and A-boundaries, and an intermediate zone. The B-boundary occurs for the suction-duct having a length of about a quarter of the wave-length of the first resonance in the case of very short and fat plenum-type delivery duct. On the other hand, the A-boundary occurs for the long and narrow duct-type delivery flow-path having a length about a fifth of the wavelength and relatively small sectional area in the case of short and narrow suction ducts. In addition to this, the reduced surge-cycle frequencies with respect to the duct lengths are observed to have respective limiting values at the stagnation boundaries. The reduced frequency for the B-boundary is related with a limiting value of the Greitzer's B parameter. The tendency and the characteristic features of the related flow behaviors in the neighborhood of the boundaries were also made clearer.

• 대한기계학회논문집B
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• 제24권6호
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• pp.792-801
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• 2000

The problem of phase change from liquid to solid in the inviscid plane-stagnation flow is theoretically investigated. The solution at the initial stage of freezing is obtained by expanding it in powers of time, and the final equilibrium state is determined from the steady-state governing equations. The transient solution is dependent on the three dimensionless parameters, but the equilibrium state is determined by one parameter of (temperature ratio/conductivity ratio). The effect of the fluid flow on the growth rate of the solid in the pure conduction problem can be clearly seen from the solution of the initial stage and the final equilibrium state. The characteristics of the transient heat transfer at the surface of the solid and the liquid side of the solid-liquid interface for all the dimensionless parameters are elucidated.

• 설비공학논문집
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• 제12권1호
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• pp.1-11
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• 2000

This study investigates the problem of phase change from liquid to solid in the inviscid stagnation flow. The solution of dimensionless governing equations is determined by the three dimensionless parameters of (temperature ratio/conductivity ratio), Stefan number, and diffusi-vity ratio. The solution at the initial stage of freezing is obtained by expanding it in powers of time, and the final equilibrium state is determined from the steady-state governing equations. The equilibrium state is dependent on (temperature ratio/conductivity ratio), but is independent of Stefan number and diffusivity ratio. The effect of fluid flow on the pure conduction problem can be clearly seen from the solution of the initial stage and the final equilibrium state, and the characteristics of the solidification process for all the dimensionless parameters are elucidated.

• 동의생리병리학회지
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• 제31권5호
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• pp.255-263
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• 2017

This article is for understanding relations between the classifications of gastritis and syndrome differentiation types of Korean Medicine through research on syndrome differentiations of clinically applied gastritis and literature of Korean Medicine. Clinical papers were searched in China Academic Journals(CAJ) of China National Knowledge Infrastructure(CNKI) from 1995 to 2015. Conclusions are as follows. First, disease mechanism of chronic gastritis are qi stagnation, damp stagnation, heat obstruction, blood stasis obstruction, yin damage, damage to collaterals with healthy qi deficiency and pathogenic qi. And qi movement stagnation is shown through the status of chronic gastritis. Second, chronic superficial gastritis belongs to qi aspect syndrome and mainly pathogen excess syndrome. And the key mechanisms are congestion and disharmony of stomach qi sometimes combined with liver depression, food accumulation and dampness-heat. Third, chronic atrophic gastritis belongs to qi-blood syndrome and deficiency-excess complex syndrome with the root of spleen qi deficiency and stomach yin deficiency and the tip of blood stasis, qi stagnation. And key mechanism is damage to collaterals with healthy qi deficiency and toxin-blood stasis. Forth, pathogen excess syndromes are shown at the early stage of chronic gastritis and healthy qi deficiency syndromes after the middle stage. Qi deficiency is shown at the beginning of the disease and yin deficiency at the late stage. And qi deficiency is related with superficial gastritis and yin deficiency with atrophic gastritis.

• International Journal of Fluid Machinery and Systems
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• 제7권4호
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• pp.160-173
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• 2014

Surge phenomena in multi-stage axial flow compressors were studied with attention to the frequency behaviors. A new parameter "volume-modified reduced surge frequency" was introduced, which took into consideration the essential surge process, i.e., emptying and filling of the working gas in the delivery plenum. The behaviors of the relative surge frequencies at the stall stagnation boundaries, compared with the corresponding duct resonance frequencies, have demonstrated the existence of two types of surges; i.e., a near-resonant surge and a subharmonic surge. The former, which has fundamentally a near-resonance frequency, occurs predominantly at the stall stagnation boundary for the short -and-fat plenum delivery flow-path and the long-and-narrow delivery duct flow-path, and possibly in the intermediate conditions. The latter, which has a subharmonic frequency of the fundamental near-resonant one and occurs mainly in the intermediate zone, is considered to be caused by the reduced frequency restricted to a limited range. In relation with those dimensionless frequencies at the stall stagnation boundary, the surge frequency behaviors in more general situations away from the boundaries could be estimated, though very roughly.

• 한국조경학회지
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• 제43권6호
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• pp.25-40
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• 2015

우리나라 관광지는 관광진흥법에 따라 지정 관리되고 있으며, 1969년 태종대 관광지가 지정된 이후 현재까지 총 230개소의 관광지가 지정, 조성, 운영되고 있다. 최초 관광지가 지정된 이후 46년이라는 시간이 흘렀으며, 이는 Butler가 주장한 관광지 수명주기 이론에 따라 영고성쇠와 같은 수명주기의 흐름을 보이고 있을 것으로 추정된다. 이에, 본 연구에서는 Butler의 관광지 수명주기 이론을 적용하여 국내 관광지의 수명주기 단계를 분석하고, 향후 관광지가 변화 발전되어야 할 방향성을 제시하는데 기초자료로 활용하고자 연구를 진행하였다. 연구방법은 대상 관광지별 연간방문객수 데이터를 기반으로 변화추이곡선을 도출하였으며, 방문객수 변화율을 기준으로 관광지 수명주기 단계를 구분하였다. 분석 결과, 국내 관광지의 3분의 1 이상이 정체 쇠퇴 단계에 도달하고 있는 것으로 분석되었으며, 특히 온천, 해안/해수욕장 자원유형 관광지가 정체 쇠퇴단계 비율이 높은 것으로 분석되었다. 정체 쇠퇴단계에 도달해 있는 관광지는 쇠퇴의 원인 분석과 해결방안 모색, 새로운 혁신요소 도입의 필요성이 대두되었다. 본 연구의 결과가 국내 관광지의 수명주기 단계를 결정하는 절대적인 기준이 되기에는 부족한 점이 있으나, 우리나라 관광지의 수명주기 단계를 현상학적으로 파악하기에는 적절한 것으로 사료되며, 본 연구를 바탕으로 정체 쇠퇴단계에 도달한 관광지들의 원인을 규명하고, 이를 토대로 새로운 혁신 도입을 통해 관광지의 재활성화 방안 마련의 기초 연구로 활용될 수 있을 것으로 생각된다.

• 대한지리학회지
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• 제38권3호
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• pp.413-425
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• 2003

본 연구의 목적은 우리 나라 온천관광지를 대상으로 개발한 관광지 라이프사이클 모형을 영국의 바스 온천에 검증하는 것이다. 연구의 방법으로는 관광지 라이프사이클 모형의 교통. 관광객의 체류기간. 편의시설. 경쟁 관광지, 광고활동. 관광행정, 환경문제 그리고 지역주민이 태도 등의 각 항목별 지표를 사례지역에 적용하는 비교 분석 방법을 택하였다. 이와 같은 비교분석법에 의한 연구 결과 '경쟁관광지'를 제외한 나머지 7개 항목의 각각의 지표들이 영국 바스 온천에 적용되었다 바스 온천에서 '경쟁관광지'는 관광지 라이프사이클 모형과는 달리 침체단계에 나타나지 않고 성숙단계에 등장하는 것이 특징이다 결론적으로 우리 나라를 사례로 개발된 관광지 라이프사이클 모형은 경쟁관광지의 등장시기만 수정. 보완한다면 규모가 작고 역사가 오래된 서구 온천관광지에 적용이 가능하다.

• 대한한의학회지
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• 제19권1호
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• pp.100-108
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• 1998

We treated 1 case of primary infertility woman. She had three clinical problems. The first was endometrosis stage II, the second was tubar obstruction and the third was chronic persistent hepatitis B. Eometrosis and tubar obstruction are similar to 'blood stagnation'. And another clinical symptoms could be considered with 'asthenia of spleen and stagnation of wetness-evil'. So our prescriptions for this case were Heylbudu.Jcgeu-Tang and Samchulgunbi-Tang. And the prescription of acupuncture therapy was consist with Sp. 6, Ren. 4, Jagung, P. 6, and St. 36. So we got a successful result from above therapies. But we have to take continued follow-up plans for endometriosis and chronic persistent hepatits B.