In previous researches on a jet in cross flow (JICF), which is applied for the liquid jet injection system of air-breathing propulsion systems or rocket engine systems, more than 20 different correlations of jet penetration have been proposed. In these proposed correlations, the relationships between jet penetration and the various flow parameters (momentum flux ratio, Reynolds number, Weber number, viscosity ratio, etc.) were defined. But most of these studies were carried out using the single orifice injector (SOI). In this study, in order to define the interference effects of liquid jet penetration in cross flow, the double orifice injector (DOI) is adopted. First, the jet penetration correlation of the SOI according to the cross-flow temperature controlled by the vitiated air heater is proposed. The jet penetration height for heated cross flow is lower than that for cold cross flow because of the increase of cross-flow velocity despite the lower density. The jet penetration correlation of the DOI is derived for variations of injector orifice spacing. In the case of the DOI, since the front liquid jet acts as a shield of the rear liquid jet, the jet penetration with the DOI is higher than that with the SOI. With the double DOI, the rear jet penetration height is increased as the nozzle spacing is decreased. The penetration height correlation for the rear liquid jet with the DOI was developed. As the nozzle spacing increases, the jet penetration height decreases; therefore, an inverse relationship between nozzle spacing and jet penetration height is expected.
An experimental study was performed to investigate the atomization characteristics of a circular nozzle and elliptical nozzles of small diameter under high injection pressure, which has a hydraulic flip condition for the nozzle internal flow structure. The flow rate and drop size characteristics were measured for various injection pressures. Numerical simulations were attempted to investigate the internal flow structure in the circular and elliptical nozzles because the experimental study was limited in its measurements of flow velocity distributions, pressure distributions, and streamlines in the relatively small orifices. This study showed that the disintegration characteristics of the liquid jet of the elliptical nozzles were very different from those of the circular nozzle. In the case of the elliptical nozzles, the liquid jet became more unstable at the same injection pressure, unlike that of the circular nozzle. Surface breakup was observed at the jet issued from the elliptical nozzles with the increase of injection pressure. Furthermore, the numerical simulations informed that the internal flow structure of the elliptical nozzle was quite different from that of the circular nozzle. In the case of the circular nozzle, as with much of the literature on the internal flow structure of the hydraulic flip, the flow detached from the orifice wall. However, the internal flow structure of the elliptical nozzle in hydraulic flip was reattached to the orifice wall of the minor axis, unlike the flow in the circular nozzle. It has been concluded that the internal flow structure of the elliptical nozzle has influence on the disintegration characteristics of the liquid jet issued from the elliptical nozzle.
Background : Elderly-onset rheumatoid arthritis (EORA) is considered to be different from younger-onset rheumatoid arthritis (YORA) in clinical manifestations, laboratory indices, and in prognosis. However, the differences between these two diseases have not been clearly defined. The aim of this study was to more clearly define the clinical characteristics of EORA. Methods : We retrospectively reviewed 50 EORA and 58 YORA patients who met the classification criteria established by the American College of Rheumatology (ACR). The two groups (EORA and YORA) were compared by three criteria. First, we considered the patterns of the joints involved and the presence of rheumatoid nodules. Second, we compared the disease activity indices and the level of auto-antibodies. Finally, we compared the use of medications. Results : The mean age-of-onset and the women-to-men ratio in the EORA group was 66.2±5.5 years and 2.1:1, respectively. There was more large joint involvement seen in the EORA group. The titer of disease activity indices (ESR, CRP) and positive rate of auto-antibodies (rheumatoid factor, ANA, but not anti-CCP antibody) were also higher in the EORA group. We found no differences in the prescribed medications between the two groups. Conclusions : From these studies, we believe that EORA has higher disease activity indices at onset and greater joint involvement, along with higher titers of auto-antibodies as compared to YORA.(Korean J Med 72:62-67, 2007)
In a liquid-fueled ramjet engine, the insufficient mixing and evaporation result in the low combustion efficiency and combustion instability. Improving its characteristics and devising a means of fuel droplets with air may compensate these disadvantages of liquid fuel ramjet engine. The jet penetrations of various fuel injectors were measured to investigate the spray characteristics of a liquid-fueled ramjet engine under high pressure air-stream conditions. The penetrations in high pressure conditions are smaller than the values calculated from Inamura's or Lee's equations, and the jet penetrations in the high pressure conditions have a similar tendency. In the dual orifice injectors, the jet penetrations of rare orifice is rapidly increased due to the reduction of the drag, which is created by the jet column of front orifice. The jet penetration of rare orifice is increased because of the drag reduction created by the jet column of the front orifice. Because of the drag reduction formed by the column of jet, the jet penetration in the rear orifice of dual orifice injector is much larger than the jet penetrations of single orifice injector. As the distances of the orifice are increased, the jet penetrations of the rear orifice decrease.
Background Prostate cancer incidence and mortality rates in South Korea are relatively low, but rising steadily. Methods We examined age-standardized incidence and mortality trends of prostate cancer in South Korea to gain further insight into prostate cancer etiology. Results Although prostate cancer incidence has been low (7.9 per 100,000 man-years), it has increased up to 28.2% between 1996–1998 and 1999–2001. Prostate cancer mortality increased 12.7-fold over a 20-year period. Despite the increase in prostate cancer incidence and mortality rates, marked differences in rates remain for Koreans, Korean Americans, and Caucasian Americans. Conclusions The rising rates of prostate cancer in South Korea cannot be attributed entirely to PSA screening due to the low PSA screening prevalence; this trend is most likely related to increased westernization among Koreans. Interdisciplinary epidemiological studies incorporating the collection of biological samples are needed to clarify the extent to which lifestyle and genetic factors contribute to the observed racial disparity. Prostate. Published 2006 Wiley-Liss, Inc.
The Gasoline Direct Injection(GDI) system has been highlighted due to the improvement of fuel consumption and the control of exhaust emission from gasoline engines. Main purpose of the present study is to measure spray characteristics of GDSI for real engine application. We have investigated experimentally spray tip penetration, spray angle, tip velocity and spatial spray distribution. Counter-rotating vortex grown on the spray surface plays an important role in the spray characteristics. Accordingly the spray tip penetration and tip velocity do not excess 50mm, 20m/s respectively, under 0.6MPa ambient pressure. the spray cone angle of GDSI have a same tendency to a simplex swirl atomizer.
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