Background： Evaluating the hemodynamic status and predicting fluid responsiveness are important in critical ultrasound assessment of shock patients. Transthoracic echocardiography with noninvasive diagnostic paramete...Background： Evaluating the hemodynamic status and predicting fluid responsiveness are important in critical ultrasound assessment of shock patients. Transthoracic echocardiography with noninvasive diagnostic parameters allows the assessment of volume responsiveness. This study aimed to assess tile hemodynamic changes in the liver and systemic hemodynamic changes during fluid challenge and during passive leg raising （PLR） by measuring hepatic venous flow （HVF） velocity. Methods： This is an open-label study in a tertiary teaching hospital. Shock patients with hypoperfusion who required fluid challenge were selected for the study. Patients 〈l 8 years old and those with contraindications to PLR were excluded from the study. Baseline values were measured, PLR tests were performed, and 500 ml of saline was infused over 30 rain. Parameters associated with cardiac output （CO） in the left ventricular outflow tract were measured using the Doppler method. In addition, HVF velocity and right ventricular function parameters were determined. Results： Middle hepatic venous （MHV） S-wave velocity was positively correlated in all patients with CO at baseline （r= 0.706, P〈 0.01 ） and after volume expansion （r= 0.524, P = 0.003）. CO was also significantly correlated with MHV S-wave velocity in responders （r = 0.608, P 〈 0.01）. During PLR, however, hepatic venous S-wave velocity did not correlate with CO. For the parameter AMHV D （increase in change in MHV D-wave velocity after volume expansion）, defined as （MHV D - MHV Dtaseline）/MHV DBaseli.,e x 100%, 〉21% indicated no fluid responsiveness, with a sensitivity of 100%, a specificity of 71.2%, and an area under the receiver operating characteristic curve of 0.918. Conclusions： During fluid expansion, hepatic venous S-wave velocity can be used to monitor CO, whether or not it is increasing. AMHV D 〉21% indicated a lack of fluid responsiveness, thus helping to decide when to stop infusions.展开更多
Background:It is still unclear what the minimal infusion volume is to effectively predict fluid responsiveness.This study was designed to explore the minimal infusion volume to effectively predict fluid responsiveness...Background:It is still unclear what the minimal infusion volume is to effectively predict fluid responsiveness.This study was designed to explore the minimal infusion volume to effectively predict fluid responsiveness in septic shock patients.Hemodynamic effects of fluid administration on arterial load were observed and added values of effective arterial elastance(Ea)in fluid resuscitation were assessed.Methods:Intensive care unit septic shock patients with indwelling pulmonary artery catheter(PAC)received five sequential intravenous boluses of 100 mL 4%gelatin.Cardiac output(CO)was measured with PAC before and after each bolus.Fluid responsiveness was defined as an increase in CO>10%after 500 mL fluid infusion.Results:Forty-seven patients were included and 35(74.5%)patients were fluid responders.CO increasing>5.2%after a 200 mL fluid challenge(FC)provided an improved detection of fluid responsiveness,with a specificity of 80.0%and a sensitivity of 91.7%.The area under the ROC curve(AUC)was 0.93(95%CI:0.84-1.00,P<0.001).Fluid administration induced a decrease in Ea from 2.23(1.46-2.78)mmHg/mL to 1.83(1.34-2.44)mmHg/mL(P=0.002),especially for fluid responders in whom arterial pressure did not increase.Notably,the baseline Ea was able to detect the fluid responsiveness with an AUC of 0.74(95%CI:0.59-0.86,P<0.001),whereas Ea failed to predict the pressure response to FC with an AUC of 0.50(95%CI:0.33-0.67,P=0.086).Conclusion:In septic shock patients,a minimal volume of 200 mL 4%gelatin could reliably detect fluid responders.Fluid administration reduced Ea even when CO increased.The loss of arterial load might be the reason for patients who increased their CO without pressure responsiveness.Moreover,a high level of Ea before FC was able to predict fluid responsiveness rather than to detect the pressure responsiveness.展开更多
Three recent breakthroughs due to AI in arts and science serve as motivation:An award winning digital image,protein folding,fast matrix multiplication.Many recent developments in artificial neural networks,particularl...Three recent breakthroughs due to AI in arts and science serve as motivation:An award winning digital image,protein folding,fast matrix multiplication.Many recent developments in artificial neural networks,particularly deep learning(DL),applied and relevant to computational mechanics(solid,fluids,finite-element technology)are reviewed in detail.Both hybrid and pure machine learning(ML)methods are discussed.Hybrid methods combine traditional PDE discretizations with ML methods either(1)to help model complex nonlinear constitutive relations,(2)to nonlinearly reduce the model order for efficient simulation(turbulence),or(3)to accelerate the simulation by predicting certain components in the traditional integration methods.Here,methods(1)and(2)relied on Long-Short-Term Memory(LSTM)architecture,with method(3)relying on convolutional neural networks.Pure ML methods to solve(nonlinear)PDEs are represented by Physics-Informed Neural network(PINN)methods,which could be combined with attention mechanism to address discontinuous solutions.Both LSTM and attention architectures,together with modern and generalized classic optimizers to include stochasticity for DL networks,are extensively reviewed.Kernel machines,including Gaussian processes,are provided to sufficient depth for more advanced works such as shallow networks with infinite width.Not only addressing experts,readers are assumed familiar with computational mechanics,but not with DL,whose concepts and applications are built up from the basics,aiming at bringing first-time learners quickly to the forefront of research.History and limitations of AI are recounted and discussed,with particular attention at pointing out misstatements or misconceptions of the classics,even in well-known references.Positioning and pointing control of a large-deformable beam is given as an example.展开更多
With the advancement of micro machining technology,the high-heat-flux removal from miniature electronic devices and components has become an attractive topic.Flow boiling in micro-channels is an optimal form of heat t...With the advancement of micro machining technology,the high-heat-flux removal from miniature electronic devices and components has become an attractive topic.Flow boiling in micro-channels is an optimal form of heat transfer and has been widely employed in high-heat-flux cooling applications.This comprehensively-reviewed article focused on the available recent literatures of experimental investigation regarding the flow boiling heat transfer and unstable behaviors of the fluid with lower boiling point in micro-channels.The thermal-fluid characteristics and potential heat transfer mechanisms of low-boiling-point fluids flow boiling in different narrow passages were summarized and discussed.The literatures regarding the pressure drop and occurrence of the unstable phenomena existing in two-phase flow boiling process were also discussed.The emphasis was given to the heat transfer enhancement methods as well as instability elimination,and various methods such as modification of surface and channel flow geometries were considered.Some future researches in the field of micro-scale flow boiling were suggested.展开更多
On November 19, 1999, a seminar on developing mini vehicle market was held in Beijing, with almost all major Chinese mini vehi-cle makers participating in. They are Chana Automobile (Group) Li-ability Corp., Ltd., Cha...On November 19, 1999, a seminar on developing mini vehicle market was held in Beijing, with almost all major Chinese mini vehi-cle makers participating in. They are Chana Automobile (Group) Li-ability Corp., Ltd., Changhe Air-craft Industries (Group), Ltd., Harbin Dong’An Engine Manufac-turing Company, Harbin Aircraft Manufacturing Corp. and Liuzhou Wuling Auto Co., Ltd.. The boss-es of the five enterprises展开更多
文摘Background： Evaluating the hemodynamic status and predicting fluid responsiveness are important in critical ultrasound assessment of shock patients. Transthoracic echocardiography with noninvasive diagnostic parameters allows the assessment of volume responsiveness. This study aimed to assess tile hemodynamic changes in the liver and systemic hemodynamic changes during fluid challenge and during passive leg raising （PLR） by measuring hepatic venous flow （HVF） velocity. Methods： This is an open-label study in a tertiary teaching hospital. Shock patients with hypoperfusion who required fluid challenge were selected for the study. Patients 〈l 8 years old and those with contraindications to PLR were excluded from the study. Baseline values were measured, PLR tests were performed, and 500 ml of saline was infused over 30 rain. Parameters associated with cardiac output （CO） in the left ventricular outflow tract were measured using the Doppler method. In addition, HVF velocity and right ventricular function parameters were determined. Results： Middle hepatic venous （MHV） S-wave velocity was positively correlated in all patients with CO at baseline （r= 0.706, P〈 0.01 ） and after volume expansion （r= 0.524, P = 0.003）. CO was also significantly correlated with MHV S-wave velocity in responders （r = 0.608, P 〈 0.01）. During PLR, however, hepatic venous S-wave velocity did not correlate with CO. For the parameter AMHV D （increase in change in MHV D-wave velocity after volume expansion）, defined as （MHV D - MHV Dtaseline）/MHV DBaseli.,e x 100%, 〉21% indicated no fluid responsiveness, with a sensitivity of 100%, a specificity of 71.2%, and an area under the receiver operating characteristic curve of 0.918. Conclusions： During fluid expansion, hepatic venous S-wave velocity can be used to monitor CO, whether or not it is increasing. AMHV D 〉21% indicated a lack of fluid responsiveness, thus helping to decide when to stop infusions.
基金supported by grants from the Ministry of Science and Technology of People Republic of China(No.2020YFC0841300)Beijing Municipal Science and technology commission(No.Z201100005520037)。
文摘Background:It is still unclear what the minimal infusion volume is to effectively predict fluid responsiveness.This study was designed to explore the minimal infusion volume to effectively predict fluid responsiveness in septic shock patients.Hemodynamic effects of fluid administration on arterial load were observed and added values of effective arterial elastance(Ea)in fluid resuscitation were assessed.Methods:Intensive care unit septic shock patients with indwelling pulmonary artery catheter(PAC)received five sequential intravenous boluses of 100 mL 4%gelatin.Cardiac output(CO)was measured with PAC before and after each bolus.Fluid responsiveness was defined as an increase in CO>10%after 500 mL fluid infusion.Results:Forty-seven patients were included and 35(74.5%)patients were fluid responders.CO increasing>5.2%after a 200 mL fluid challenge(FC)provided an improved detection of fluid responsiveness,with a specificity of 80.0%and a sensitivity of 91.7%.The area under the ROC curve(AUC)was 0.93(95%CI:0.84-1.00,P<0.001).Fluid administration induced a decrease in Ea from 2.23(1.46-2.78)mmHg/mL to 1.83(1.34-2.44)mmHg/mL(P=0.002),especially for fluid responders in whom arterial pressure did not increase.Notably,the baseline Ea was able to detect the fluid responsiveness with an AUC of 0.74(95%CI:0.59-0.86,P<0.001),whereas Ea failed to predict the pressure response to FC with an AUC of 0.50(95%CI:0.33-0.67,P=0.086).Conclusion:In septic shock patients,a minimal volume of 200 mL 4%gelatin could reliably detect fluid responders.Fluid administration reduced Ea even when CO increased.The loss of arterial load might be the reason for patients who increased their CO without pressure responsiveness.Moreover,a high level of Ea before FC was able to predict fluid responsiveness rather than to detect the pressure responsiveness.
文摘Three recent breakthroughs due to AI in arts and science serve as motivation:An award winning digital image,protein folding,fast matrix multiplication.Many recent developments in artificial neural networks,particularly deep learning(DL),applied and relevant to computational mechanics(solid,fluids,finite-element technology)are reviewed in detail.Both hybrid and pure machine learning(ML)methods are discussed.Hybrid methods combine traditional PDE discretizations with ML methods either(1)to help model complex nonlinear constitutive relations,(2)to nonlinearly reduce the model order for efficient simulation(turbulence),or(3)to accelerate the simulation by predicting certain components in the traditional integration methods.Here,methods(1)and(2)relied on Long-Short-Term Memory(LSTM)architecture,with method(3)relying on convolutional neural networks.Pure ML methods to solve(nonlinear)PDEs are represented by Physics-Informed Neural network(PINN)methods,which could be combined with attention mechanism to address discontinuous solutions.Both LSTM and attention architectures,together with modern and generalized classic optimizers to include stochasticity for DL networks,are extensively reviewed.Kernel machines,including Gaussian processes,are provided to sufficient depth for more advanced works such as shallow networks with infinite width.Not only addressing experts,readers are assumed familiar with computational mechanics,but not with DL,whose concepts and applications are built up from the basics,aiming at bringing first-time learners quickly to the forefront of research.History and limitations of AI are recounted and discussed,with particular attention at pointing out misstatements or misconceptions of the classics,even in well-known references.Positioning and pointing control of a large-deformable beam is given as an example.
基金supported by the National Natural Science Foundation of China (No.U2141219)。
文摘With the advancement of micro machining technology,the high-heat-flux removal from miniature electronic devices and components has become an attractive topic.Flow boiling in micro-channels is an optimal form of heat transfer and has been widely employed in high-heat-flux cooling applications.This comprehensively-reviewed article focused on the available recent literatures of experimental investigation regarding the flow boiling heat transfer and unstable behaviors of the fluid with lower boiling point in micro-channels.The thermal-fluid characteristics and potential heat transfer mechanisms of low-boiling-point fluids flow boiling in different narrow passages were summarized and discussed.The literatures regarding the pressure drop and occurrence of the unstable phenomena existing in two-phase flow boiling process were also discussed.The emphasis was given to the heat transfer enhancement methods as well as instability elimination,and various methods such as modification of surface and channel flow geometries were considered.Some future researches in the field of micro-scale flow boiling were suggested.
文摘On November 19, 1999, a seminar on developing mini vehicle market was held in Beijing, with almost all major Chinese mini vehi-cle makers participating in. They are Chana Automobile (Group) Li-ability Corp., Ltd., Changhe Air-craft Industries (Group), Ltd., Harbin Dong’An Engine Manufac-turing Company, Harbin Aircraft Manufacturing Corp. and Liuzhou Wuling Auto Co., Ltd.. The boss-es of the five enterprises
