Partial surge is a type of instability inception in transonic compressors and occurs in the form of axisymmetric low-frequency disturbances localized in the hub region.Previous studies illustrate that the frequency of...Partial surge is a type of instability inception in transonic compressors and occurs in the form of axisymmetric low-frequency disturbances localized in the hub region.Previous studies illustrate that the frequency of partial surge is set by the Helmholtz frequency of the entire system,which motivates to propose a hypothesis that the system response performs an important role in the formation of partial surge.For further verification,a series of experiments are conducted to explore the link between the propagating of the partial surge and the system feedback in this study.In the first case,an additional test point is set on the wall of the plenum to detect the system response.Combining the flow behaviors inside the plenum with the disturbances in the rotor tip and stator hub/tip regions,the effects of the system feedback on the occurrence of the continuous disturbances and the rotating stall cells are illustrated.In the second case,a screen is mounted at the compressor outlet to prevent positive feedback from the plenum.The experimental results demonstrate that in the absence of system feedback,it is the occurrence of spike-type stall inception that leads to the flow instability instead of that of partial surge.In addition,three flow phenomena in the second case are discussed,including the occurrence of the single pulse,the unstable process during the stall evolution and the switch of instability inception.展开更多
Severe Acute Respiratory Syndrome (SARS), referred to as 'contagious atypical pneumonia' is the fastest spreading communicable disease known in recent history. This disease is different from other kinds of res...Severe Acute Respiratory Syndrome (SARS), referred to as 'contagious atypical pneumonia' is the fastest spreading communicable disease known in recent history. This disease is different from other kinds of respiratory contagion due to the following aspects: the syndrome happens quickly and the infectivity is high. New problems encountered by the nursing management staff are the precipitate, pestiferous, and large numbers of in-patients and the understanding of appropriate responses, within large complex hospitals, to ensure patient care is actively supported and infectivity is prevented. To deal with these problems, we implemented the following strategies; reinforcement of the management system; optimization of the nursing flow; amendments to related hospital policies; collection of relevant information; adherence to stringent disinfection protocols; isolation of areas; reallocation of hospital resources and more efficient utilization of resources. The above strategies have reinforced the nursing management system's active response, guaranteed daily operation of the hospital's nursing activities, including the quality of care provided by the nurses, and ensured the health of patients, nurses and doctors.展开更多
基金the support of National Natural Science Foundation of China(Nos.51706008,51636001,51976005 and 52006002)National Science and Technology Major Project,China(No.2017-Ⅱ-0005-0018)Aeronautics Power Foundation,China(No.6141B09050375)。
文摘Partial surge is a type of instability inception in transonic compressors and occurs in the form of axisymmetric low-frequency disturbances localized in the hub region.Previous studies illustrate that the frequency of partial surge is set by the Helmholtz frequency of the entire system,which motivates to propose a hypothesis that the system response performs an important role in the formation of partial surge.For further verification,a series of experiments are conducted to explore the link between the propagating of the partial surge and the system feedback in this study.In the first case,an additional test point is set on the wall of the plenum to detect the system response.Combining the flow behaviors inside the plenum with the disturbances in the rotor tip and stator hub/tip regions,the effects of the system feedback on the occurrence of the continuous disturbances and the rotating stall cells are illustrated.In the second case,a screen is mounted at the compressor outlet to prevent positive feedback from the plenum.The experimental results demonstrate that in the absence of system feedback,it is the occurrence of spike-type stall inception that leads to the flow instability instead of that of partial surge.In addition,three flow phenomena in the second case are discussed,including the occurrence of the single pulse,the unstable process during the stall evolution and the switch of instability inception.
文摘Severe Acute Respiratory Syndrome (SARS), referred to as 'contagious atypical pneumonia' is the fastest spreading communicable disease known in recent history. This disease is different from other kinds of respiratory contagion due to the following aspects: the syndrome happens quickly and the infectivity is high. New problems encountered by the nursing management staff are the precipitate, pestiferous, and large numbers of in-patients and the understanding of appropriate responses, within large complex hospitals, to ensure patient care is actively supported and infectivity is prevented. To deal with these problems, we implemented the following strategies; reinforcement of the management system; optimization of the nursing flow; amendments to related hospital policies; collection of relevant information; adherence to stringent disinfection protocols; isolation of areas; reallocation of hospital resources and more efficient utilization of resources. The above strategies have reinforced the nursing management system's active response, guaranteed daily operation of the hospital's nursing activities, including the quality of care provided by the nurses, and ensured the health of patients, nurses and doctors.
