The mixed venous-to-arterial carbon dioxide(CO_2)tension difference[P(v-a) CO_2]is the difference between carbon dioxide tension(PCO_2) in mixed venous blood(sampled from a pulmonary artery catheter) and the PCO_2 in ...The mixed venous-to-arterial carbon dioxide(CO_2)tension difference[P(v-a) CO_2]is the difference between carbon dioxide tension(PCO_2) in mixed venous blood(sampled from a pulmonary artery catheter) and the PCO_2 in arterial blood.P(v-a) CO_2 depends on the cardiac output and the global CO_2 production,and on the complex relationship between PCO_2 and CO_2 content.Experimental and clinical studies support the evidence that P(v-a) CO_2 cannot serve as an indicator of tissue hypoxia,and should be regarded as an indicator of the adequacy of venous blood to wash out the total CO_2generated by the peripheral tissues.P(v-a) CO_2 can be replaced by the central venous-to-arterial CO_2 difference(△PCO_2),which is calculated from simultaneous sampling of central venous blood from a central vein catheter and arterial blood and,therefore,more easy to obtain at the bedside.Determining the △PCO_2 during the resuscitation of septic shock patients might be useful when deciding when to continue resuscitation despite a central venous oxygen saturation(SCVO_2) > 70%associated with elevated blood lactate levels.Because high blood lactate levels is not a discriminatory factor in determining the source of that stress,an increased △PCO_2(> 6 mmHg)could be used to identify patients who still remain inadequately resuscitated.Monitoring the △PCO_2 from the beginning of the reanimation of septic shock patients might be a valuable means to evaluate the adequacy of cardiac output in tissue perfusion and,thus,guiding the therapy.In this respect,it can aid to titrate inotropes to adjust oxygen delivery to CO_2 production,or to choose between hemoglobin correction or fluid/inotrope infusion in patients with a too low ScvO_2 related to metabolic demand.The combination of P(v-a) CO_2 or △PCO_2 with oxygen-derived parameters through the calculation of the P(v-a) CO_2 or △PCO_2/arteriovenous oxygen content difference ratio can detect the presence of global anaerobic metabolism.展开更多
节能减排已被纳入国家经济社会发展规划之中。冷热电联供CCHP(combined cooling,heating and power)系统因其高效、碳排放量少而被广泛应用。针对多种发电单元的CCHP系统容量配置问题,建立了综合考虑二氧化碳排放量、系统总成本的规划模...节能减排已被纳入国家经济社会发展规划之中。冷热电联供CCHP(combined cooling,heating and power)系统因其高效、碳排放量少而被广泛应用。针对多种发电单元的CCHP系统容量配置问题,建立了综合考虑二氧化碳排放量、系统总成本的规划模型,并采用CPLEX优化软件求解。采用Energy Plus软件模拟计算某宾馆的全年逐时冷、热、电负荷,仿真分析4种不同CCHP系统的容量配置方案,以及不同权重系数对系统容量配置的影响。最后对系统容量配置关于天然气价格和电价的灵敏度进行分析。本研究内容为CCHP系统的规划提供了一定的理论支持。展开更多
The conversion of biomass into hydrogen-rich gas provides a competitive means for producing clean energy and chemicals from renewable resources.Based on the principle of Gibbs free energy minimization, a new method wa...The conversion of biomass into hydrogen-rich gas provides a competitive means for producing clean energy and chemicals from renewable resources.Based on the principle of Gibbs free energy minimization, a new method was presented with better effectiveness and simplicity to be used for the prediction of chemical equilibrium composition of hydrogen production by biomass gasification in supercritical water(SCW).Applying this method to analyzing the process of glucose gasification in SCW, it was found that the product gas consisted primarily of hydrogen and carbon dioxide as well as a small amount of methane and carbon monoxide.The gas yield was strongly affected by reaction temperature and feedstock concentration and less affected by reaction pressure in the following range:temperature 623—1073 K,pressure 22.5—35 MPa,and concentration 0.1—0.8 mol·L -1 .The hydrogen production in product gas increased with the increase of temperature and decreased with the increase of concentration.展开更多
文摘The mixed venous-to-arterial carbon dioxide(CO_2)tension difference[P(v-a) CO_2]is the difference between carbon dioxide tension(PCO_2) in mixed venous blood(sampled from a pulmonary artery catheter) and the PCO_2 in arterial blood.P(v-a) CO_2 depends on the cardiac output and the global CO_2 production,and on the complex relationship between PCO_2 and CO_2 content.Experimental and clinical studies support the evidence that P(v-a) CO_2 cannot serve as an indicator of tissue hypoxia,and should be regarded as an indicator of the adequacy of venous blood to wash out the total CO_2generated by the peripheral tissues.P(v-a) CO_2 can be replaced by the central venous-to-arterial CO_2 difference(△PCO_2),which is calculated from simultaneous sampling of central venous blood from a central vein catheter and arterial blood and,therefore,more easy to obtain at the bedside.Determining the △PCO_2 during the resuscitation of septic shock patients might be useful when deciding when to continue resuscitation despite a central venous oxygen saturation(SCVO_2) > 70%associated with elevated blood lactate levels.Because high blood lactate levels is not a discriminatory factor in determining the source of that stress,an increased △PCO_2(> 6 mmHg)could be used to identify patients who still remain inadequately resuscitated.Monitoring the △PCO_2 from the beginning of the reanimation of septic shock patients might be a valuable means to evaluate the adequacy of cardiac output in tissue perfusion and,thus,guiding the therapy.In this respect,it can aid to titrate inotropes to adjust oxygen delivery to CO_2 production,or to choose between hemoglobin correction or fluid/inotrope infusion in patients with a too low ScvO_2 related to metabolic demand.The combination of P(v-a) CO_2 or △PCO_2 with oxygen-derived parameters through the calculation of the P(v-a) CO_2 or △PCO_2/arteriovenous oxygen content difference ratio can detect the presence of global anaerobic metabolism.
文摘节能减排已被纳入国家经济社会发展规划之中。冷热电联供CCHP(combined cooling,heating and power)系统因其高效、碳排放量少而被广泛应用。针对多种发电单元的CCHP系统容量配置问题,建立了综合考虑二氧化碳排放量、系统总成本的规划模型,并采用CPLEX优化软件求解。采用Energy Plus软件模拟计算某宾馆的全年逐时冷、热、电负荷,仿真分析4种不同CCHP系统的容量配置方案,以及不同权重系数对系统容量配置的影响。最后对系统容量配置关于天然气价格和电价的灵敏度进行分析。本研究内容为CCHP系统的规划提供了一定的理论支持。
文摘The conversion of biomass into hydrogen-rich gas provides a competitive means for producing clean energy and chemicals from renewable resources.Based on the principle of Gibbs free energy minimization, a new method was presented with better effectiveness and simplicity to be used for the prediction of chemical equilibrium composition of hydrogen production by biomass gasification in supercritical water(SCW).Applying this method to analyzing the process of glucose gasification in SCW, it was found that the product gas consisted primarily of hydrogen and carbon dioxide as well as a small amount of methane and carbon monoxide.The gas yield was strongly affected by reaction temperature and feedstock concentration and less affected by reaction pressure in the following range:temperature 623—1073 K,pressure 22.5—35 MPa,and concentration 0.1—0.8 mol·L -1 .The hydrogen production in product gas increased with the increase of temperature and decreased with the increase of concentration.
