There is a relatively complex flow state inside the high speed on-off valve,which often produces low pressure area and oil reflux in the high-speed opening and closing process of the spool,causing cavitation and vorte...There is a relatively complex flow state inside the high speed on-off valve,which often produces low pressure area and oil reflux in the high-speed opening and closing process of the spool,causing cavitation and vortex and other phenomena.These phenomena will affect the stability of the internal flow field of the plate valve and the flow characteristics of the high speed on-off valve.Aiming at the problems of small flow rate and instability of internal flow field,a new spool structure was designed.The flow field models of two-hole and three-hole plate spools with different openings were established,and software ANSYS Workbench was chosen to mesh the model.The standard k−εturbulence model was selected for numerical simulation using FLUENT software.The pressure distribution and velocity distribution under the same pressure and different opening degree were obtained.The structure and parameters of the optimization model were also obtained.The stability analysis of flow field under different pressure was carried out.The results demonstrate that the three-hole spool has a similar flow field change with the two-hole spool,but it does not create a low pressure zone,and the three-hole spool can work stably at 2 MPa or less.This method improves the appearance of low pressure area and oil backflow in the process of high speed opening and closing of spool.The stability of flow field and the flow rate of high speed switch valve are improved.Finally,the products designed in this paper are compared with existing hydraulic valve products.The results show that the three-hole plate type high speed on-off valve designed in this paper maintains the stability of the internal flow field under the condition of 200 Hz and large opening degree,and realizes the increase of flow rate.展开更多
This paper presents a modeling and control of molten metal＇s pressure in pressing process using an innovative iron casting developed by our group. In this method, molten metal is directly poured into a lower mold, an...This paper presents a modeling and control of molten metal＇s pressure in pressing process using an innovative iron casting developed by our group. In this method, molten metal is directly poured into a lower mold, and then pressed to fill cavity by an upper mold being lowered down. For complex liquid flow during pressing, the liquid＇s pressure changing inside vertical path with various contraction and expansion geometries is newly modeled via the unstationary Bernoulli equation. The mathematical model is derived for a control design of pressing. To conduct the pressing velocity design algorithm, an unknown parameter of proposed model considering viscous flow is identified by using CFD （Computational Fluid Dynamics） with heat flow calculation. Control performance using a multi-switching velocity pattern is confirmed as an effective control design using the pressure model, because the pressure fluctuation has discontinuous variation points. Substituting detailed information for mold shape, poured volume and initial temperature into a developed control input generator, an optimum pressing velocity design and a robust design for defect-free production are proposed by the design algorithm based on the construction of an inverse system comprised of the sequential switching from higher to lower speed. Consequently, the effectiveness of the pressing control with reasonable pressure suppression has been demonstrated through CFD.展开更多
BACKGROUND Sepsis is a severe medical condition that occurs when the body's immune system overreacts to an infection,leading to life-threatening organ dysfunction.The"Third international consensus definitions...BACKGROUND Sepsis is a severe medical condition that occurs when the body's immune system overreacts to an infection,leading to life-threatening organ dysfunction.The"Third international consensus definitions for sepsis and septic shock(Sepsis-3)"defines sepsis as an increase in sequential organ failure assessment score of 2 points or more,with a mortality rate above 10%.Sepsis is a leading cause of intensive care unit(ICU)admissions,and patients with underlying conditions such as cirrhosis have a higher risk of poor outcomes.Therefore,it is critical to recognize and manage sepsis promptly by administering fluids,vasopressors,steroids,and antibiotics,and identifying and treating the source of infection.AIM To conduct a systematic review and meta-analysis of existing literature on the management of sepsis in cirrhotic patients admitted to the ICU and compare the management of sepsis between cirrhotic and non-cirrhotic patients in the ICU.METHODS This study is a systematic literature review that followed the PRISMA statement's standardized search method.The search for relevant studies was conducted across multiple databases,including PubMed,Embase,Base,and Cochrane,using predefined search terms.One reviewer conducted the initial search,and the eligibility criteria were applied to the titles and abstracts of the retrieved articles.The selected articles were then evaluated based on the research objectives to ensure relevance to the study's aims.RESULTS The study findings indicate that cirrhotic patients are more susceptible to infections,resulting in higher mortality rates ranging from 18%to 60%.Early identification of the infection source followed by timely administration of antibiotics,vasopressors,and corticosteroids has been shown to improve patient outcomes.Procalcitonin is a useful biomarker for diagnosing infections in cirrhotic patients.Moreover,presepsin and resistin have been found to be reliable markers of bacterial infection in patients with decompensated liver cirrhosis,with similar diagnostic performance compared to procalcitonin.CONCLUSION This review highlights the importance of early detection and management of infections in cirrhosis patients to reduce mortality.Therefore,early detection of infection using procalcitonin test and other biomarker as presepsin and resistin,associated with early management with antibiotics,fluids,vasopressors and low dose corticosteroids might reduce the mortality associated with sepsis in cirrhotic patients.展开更多
基金Project(51975164)supported by the National Natural Science Foundation of ChinaProject(201908230358)supported by the China Scholarship CouncilProject supported by the Fundamental Research Foundation for Universities of Heilongjiang Province,China。
文摘There is a relatively complex flow state inside the high speed on-off valve,which often produces low pressure area and oil reflux in the high-speed opening and closing process of the spool,causing cavitation and vortex and other phenomena.These phenomena will affect the stability of the internal flow field of the plate valve and the flow characteristics of the high speed on-off valve.Aiming at the problems of small flow rate and instability of internal flow field,a new spool structure was designed.The flow field models of two-hole and three-hole plate spools with different openings were established,and software ANSYS Workbench was chosen to mesh the model.The standard k−εturbulence model was selected for numerical simulation using FLUENT software.The pressure distribution and velocity distribution under the same pressure and different opening degree were obtained.The structure and parameters of the optimization model were also obtained.The stability analysis of flow field under different pressure was carried out.The results demonstrate that the three-hole spool has a similar flow field change with the two-hole spool,but it does not create a low pressure zone,and the three-hole spool can work stably at 2 MPa or less.This method improves the appearance of low pressure area and oil backflow in the process of high speed opening and closing of spool.The stability of flow field and the flow rate of high speed switch valve are improved.Finally,the products designed in this paper are compared with existing hydraulic valve products.The results show that the three-hole plate type high speed on-off valve designed in this paper maintains the stability of the internal flow field under the condition of 200 Hz and large opening degree,and realizes the increase of flow rate.
文摘This paper presents a modeling and control of molten metal＇s pressure in pressing process using an innovative iron casting developed by our group. In this method, molten metal is directly poured into a lower mold, and then pressed to fill cavity by an upper mold being lowered down. For complex liquid flow during pressing, the liquid＇s pressure changing inside vertical path with various contraction and expansion geometries is newly modeled via the unstationary Bernoulli equation. The mathematical model is derived for a control design of pressing. To conduct the pressing velocity design algorithm, an unknown parameter of proposed model considering viscous flow is identified by using CFD （Computational Fluid Dynamics） with heat flow calculation. Control performance using a multi-switching velocity pattern is confirmed as an effective control design using the pressure model, because the pressure fluctuation has discontinuous variation points. Substituting detailed information for mold shape, poured volume and initial temperature into a developed control input generator, an optimum pressing velocity design and a robust design for defect-free production are proposed by the design algorithm based on the construction of an inverse system comprised of the sequential switching from higher to lower speed. Consequently, the effectiveness of the pressing control with reasonable pressure suppression has been demonstrated through CFD.
文摘BACKGROUND Sepsis is a severe medical condition that occurs when the body's immune system overreacts to an infection,leading to life-threatening organ dysfunction.The"Third international consensus definitions for sepsis and septic shock(Sepsis-3)"defines sepsis as an increase in sequential organ failure assessment score of 2 points or more,with a mortality rate above 10%.Sepsis is a leading cause of intensive care unit(ICU)admissions,and patients with underlying conditions such as cirrhosis have a higher risk of poor outcomes.Therefore,it is critical to recognize and manage sepsis promptly by administering fluids,vasopressors,steroids,and antibiotics,and identifying and treating the source of infection.AIM To conduct a systematic review and meta-analysis of existing literature on the management of sepsis in cirrhotic patients admitted to the ICU and compare the management of sepsis between cirrhotic and non-cirrhotic patients in the ICU.METHODS This study is a systematic literature review that followed the PRISMA statement's standardized search method.The search for relevant studies was conducted across multiple databases,including PubMed,Embase,Base,and Cochrane,using predefined search terms.One reviewer conducted the initial search,and the eligibility criteria were applied to the titles and abstracts of the retrieved articles.The selected articles were then evaluated based on the research objectives to ensure relevance to the study's aims.RESULTS The study findings indicate that cirrhotic patients are more susceptible to infections,resulting in higher mortality rates ranging from 18%to 60%.Early identification of the infection source followed by timely administration of antibiotics,vasopressors,and corticosteroids has been shown to improve patient outcomes.Procalcitonin is a useful biomarker for diagnosing infections in cirrhotic patients.Moreover,presepsin and resistin have been found to be reliable markers of bacterial infection in patients with decompensated liver cirrhosis,with similar diagnostic performance compared to procalcitonin.CONCLUSION This review highlights the importance of early detection and management of infections in cirrhosis patients to reduce mortality.Therefore,early detection of infection using procalcitonin test and other biomarker as presepsin and resistin,associated with early management with antibiotics,fluids,vasopressors and low dose corticosteroids might reduce the mortality associated with sepsis in cirrhotic patients.
