AIM To examine whether high-flow nasal oxygen(HFNO) availability influences the use of general anesthesia(GA) in patients undergoing endoscopic retrograde cholangiopancreatography(ERCP) and endoscopic ultrasound(EUS) ...AIM To examine whether high-flow nasal oxygen(HFNO) availability influences the use of general anesthesia(GA) in patients undergoing endoscopic retrograde cholangiopancreatography(ERCP) and endoscopic ultrasound(EUS) and associated outcomes.METHODS In this retrospective study, patients were stratified into 3 eras between October 1, 2013 and June 30, 2014 based on HFNO availability for deep sedation at the time of their endoscopy. During the first and last 3-mo eras(era 1 and 3), no HFNO was available, whereas it was an option during the second 3-mo era(era 2). The primary outcome was the percent utilization of GA vs deep sedation in each period. Secondary outcomes included oxygen saturation nadir during sedation between periods, as well as procedure duration, and anesthesia-only time between periods and for GA vs sedation cases respectively.RESULTS During the study period 238 ERCP or EUS cases were identified for analysis. Statistical testing was employed and a P < 0.050 was significant unless the Bonferroni correction for multiple comparisons was used. General anesthesia use was significantly lower in era 2 compared to era 1 with the same trend between era 2 and 3(P = 0.012 and 0.045 respectively). The oxygen saturation nadir during sedation was significantly higher in era 2 compared to era 3(P < 0.001) but not between eras 1 and 2(P = 0.028) or 1 and 3(P = 0.069). The procedure time within each era was significantly longer under GA compared to deep sedation(P ≤ 0.007) as was the anesthesia-only time(P ≤ 0.001).CONCLUSION High-flow nasal oxygen availability was associated with decreased GA utilization and improved oxygenation for ERCP and EUS during sedation.展开更多
In the Orbal oxidation ditch, denitrification is primarily accomplished in the outer channel. However, the detailed characteristics of the flow field and dissolved oxygen （DO） distribution in the outer channel are n...In the Orbal oxidation ditch, denitrification is primarily accomplished in the outer channel. However, the detailed characteristics of the flow field and dissolved oxygen （DO） distribution in the outer channel are not well understood. Therefore, in this study, the flow velocity and DO concentration in the outer channel of an Orbal oxidation ditch system in a wastewater treatment plant in Beijing （China） were monitored under actual operation conditions. The flow field and DO concentration distributions were analyzed by computed fluid dynamic modeling. In situ monitoring and modeling both showed that the flow velocity was heterogeneous in the outer channel. As a result, the DO was also heterogeneously distributed in the outer channel, with concentration gradients occurring along the flow direction as well as in the cross-section. This heterogeneous DO distribution created many anoxic and aerobic zones, which may have facilitated simultaneous nitrificafion-denitrification in the channel. These findings may provide supporting information for rational optimization of the performance of the Orbal oxidation ditch.展开更多
BACKGROUND Hypoxemia is a common complication in older patients during postoperative recovery and can cause pulmonary complications.Therefore,reducing the incidence of postoperative hypoxemia is a clinical concern.AIM...BACKGROUND Hypoxemia is a common complication in older patients during postoperative recovery and can cause pulmonary complications.Therefore,reducing the incidence of postoperative hypoxemia is a clinical concern.AIM To investigate the clinical efficacy of high-flow nasal cannula oxygen(HFNCO)in the resuscitation period of older orthopedic patients.METHODS In this prospective randomized controlled trial,60 older patients who underwent orthopedic surgery under general anesthesia were randomly divided into two groups:those who used conventional face mask and those who used HFNCO.All patients were treated with 60%oxygen for 1 h after extubation.Patients in the conventional face mask group were treated with a combination of air(2 L)and oxygen(2 L)using a traditional mask,whereas those in the HFNCO group were treated with HFNCO at a constant temperature of 34℃ and flow rate of 40 L/min.We assessed the effectiveness of oxygen therapy by monitoring the patients’arterial blood gas,peripheral oxygen saturation,and postoperative complications.RESULTS The characteristics of the patients were comparable between the groups.One hour after extubation,patients in HFNCO group had a significantly higher arterial partial pressure of oxygen(paO_(2))than that of patients in conventional face mask group(P<0.001).At extubation and 1 h after extubation,patients in both groups showed a significantly higher arterial partial pressure of carbon dioxide(paCO_(2))than the baseline levels(P<0.001).There were no differences in the saturation of peripheral oxygen,paO_(2),and paCO_(2) between the groups before anesthesia and before extubation(P>0.05).There were statistically significant differences in paO_(2) between the two groups before anesthesia and 1 h after extubation and immediately after extubation and 1 h after extubation(P<0.001).However,there were no significant differences in the oxygen tolerance score before leaving the room,airway humidification,and pulmonary complications 3 d after surgery between the two groups(P>0.05).CONCLUSION HFNCO can improve oxygen partial pressure and respiratory function in elderly patients undergoing orthopedic surgery under general endotracheal anesthesia.Thus,HFNCO can be used to prevent postoperative hypoxemia.展开更多
Air flow control is one of the most important control methods for maintaining the stability and reliability of a fuel cell system, which can avoid oxygen starvation or oxygen saturation. The oxygen excess ratio （OER...Air flow control is one of the most important control methods for maintaining the stability and reliability of a fuel cell system, which can avoid oxygen starvation or oxygen saturation. The oxygen excess ratio （OER） is often used to indicate the air flow condition. Based on a fuel cell system model for vehicles, OER performance was analyzed for different stack currents and temperatures in this paper, and the results show that the optimal OER was affected weakly by the stack temperature. In order to ensure the system working in optimal OER, a control scheme that includes an optimal OER regulator and a fuzzy control was proposed. According to the stack current, a reference value of air flow rate was obtained with the optimal OER regulator and then the air compressor motor voltage was controlled with the fuzzy controller to adjust the air flow rate provided by the air compressor. Simulation results show that the control method has good dynamic and static characteristics.展开更多
Based on the operating conditions of oxygen lance utilized for a 50 t converter in Tangsteel,gas jet flow fields of three types of oxygen lances were simulated by FLUENT software.The influence of lance configuration a...Based on the operating conditions of oxygen lance utilized for a 50 t converter in Tangsteel,gas jet flow fields of three types of oxygen lances were simulated by FLUENT software.The influence of lance configuration and lance level on penetrating area was studied through cold model experiment.The results showed that the gas flow velocities of four-hole,variable angle four-hole and five-hole oxygen lances declined rapidly with an increase in gas jet length within 1 m,1 m and 0.8 m,respectively.Besides,the multi gas streams sprayed from these three lances should be syncretized at 1.6 m,1.7 m and 1.4 m,respectively.At the highest lance level,the effective penetrating area of these three lances could be 0.255 m2,0.385 m2 and 0.0907 m2,respectively.It was suggested that the effective penetrating area of variable angle four-hole oxygen lance was the biggest,while that of five-hole oxygen lance was the least.The validity of numerical simulation results was proved through cold model experiment.The lance level was suggested to be controlled in the range of 1-1.6 m,1-1.7 m and 0.8-1.4 m for the four-hole,variable angle four-hole and five-hole oxygen lances,respectively.展开更多
Four different pulverized coals have been used to study the effects of oxygen concentration on combustion characteristics under different enriched-oxygen conditions by entrained flow reactor experiments. The results s...Four different pulverized coals have been used to study the effects of oxygen concentration on combustion characteristics under different enriched-oxygen conditions by entrained flow reactor experiments. The results show that: with the increase of oxygen concentration, the ignition temperature of four coals greatly decreases and the low volatile coals decrease faster; with the increase of oxygen concentration, the ignition mode of pulverized coal has an obviously transformation from homogeneous ignition to heterogeneous ignition, and the corresponding oxygen concentrations are about 40% and 50%-60% respectively for bituminous coal and lignite, and both about 30% for lean coal and anthracite; with the increase of oxygen concentration, the optimal pulverized coal concentrations of bituminous coal and lignite increase firstly and then decrease, but for lean coal and anthracite, the optimal pulverized coal concentrations decrease slowly with the increase of oxygen concentration.展开更多
Aim: The purpose of this case study was to examine the sleep quality of patients receiving noninvasive positive pressure ventilation (NPPV) or nasal high-flow oxygen therapy (NHF) in an intensive care unit and to inve...Aim: The purpose of this case study was to examine the sleep quality of patients receiving noninvasive positive pressure ventilation (NPPV) or nasal high-flow oxygen therapy (NHF) in an intensive care unit and to investigate what types of nursing support are offered to such patients. Methods: We examined one patient each for NPPV and NHF. Polysomnography (PSG), review of the patient charts, and semi-structured interviews were used to collect the data for analysis. Results: Patients treated with NPPV or NHF demonstrated a noticeable reduction in deep sleep, with most of their sleep being shallow. Their sleep patterns varied greatly from those of healthy individuals. These results suggest that, in addition to experiencing extremely fragmented sleep, sleep in these patients was more likely to be interrupted by nursing interventions, such as during auscultation of breath sounds. Furthermore, it was revealed that “anxiety or discomfort that accompanies the mask or air pressure” in patients treated with NPPV and “discomfort that accompanies the nasal cannula or NHF circuit” in patients treated with NHF may be primary causes of disrupted sleep. Our results suggest a need for nursing care aimed at improving sleep quality in patients treated with NPPV or NHF.展开更多
The traditional practice of employing a two-stage coal-fed gasification process is to feed all of the oxygen to provide a vigorous amount of combustion in the first stage but only feed the coal without oxygen in the s...The traditional practice of employing a two-stage coal-fed gasification process is to feed all of the oxygen to provide a vigorous amount of combustion in the first stage but only feed the coal without oxygen in the second stage to allow the endothermic gasification process to occur downstream of the second stage. One of the merits of this 2-stage practice is to keep the gasifier temperature low downstream from the 2nd stage. This helps to extend the life of refractory bricks, decrease gasifier shut-down frequency for scheduled maintenance, and reduce the maintenance costs. In this traditional 2-stage practice, the temperature reduction in the second stage is achieved at the expense of a higher than normal temperature in the first stage. This study investigates a concept totally opposite to the traditional two-stage coal feeding practices in which the injected oxygen is split between the two stages, while all the coal is fed into the first stage. The hypothesis of this two-stage oxygen injection is that a distributed oxygen injection scheme can also distribute the release of heat to a larger gasifier volume and, thus, reduce the peak temperature distribution in the gasifier. The increased life expectancy and reduced maintenance of the refractory bricks can prevail in the entire gasifier and not just downstream from the second stage. In this study, both experiments and computational simulations have been performed to verify the hypothesis. A series of experiments conducted at 2.5 - 3.0 bars shows that the peak temperature and temperature range in the gasifier do decrease from 600?C - 1550?C with one stage oxygen injection to 950?C - 1230?C with a 60 - 40 oxygen split-injection. The CFD results conducted at 2.5 bars show that 1) the carbon conversion ratio for different oxygen injection schemes are all above 95%;2) H2 (about 70% vol.) dominates the syngas composition at the exit;3) the 80% - 20% case yields the lowest peak temperature and the most uniform temperature distribution along the gasifier;and 4) the 40% - 60% case produces the syngas with the highest HHV. Both experimental data and CFD predictions verify the hypothesis that it is feasible to reduce the peak temperature and achieve more uniform temperature in the gasifier by adequately controlling a two-stage oxygen injection with only minor changes of the composition and heating value of the syngas.展开更多
Cuprous oxide(Cu_2O) thin films have been deposited on glass substrate by reactive magnetron sputtering method using Cu target and argon oxygen gas atmosphere.Effect of oxygen flow rate on structural and optical prope...Cuprous oxide(Cu_2O) thin films have been deposited on glass substrate by reactive magnetron sputtering method using Cu target and argon oxygen gas atmosphere.Effect of oxygen flow rate on structural and optical properties of thin films has been discussed.The results of X-ray diffraction,ultraviolet-visible spectrophotometry and atomic force micrograph indicated that the condition window for single Cu_2O phase was about 3.8 to 4.4 cm^3/min,and the optimum oxygen flow rate was 4.2 cm^3/min.The optical band gap E_g of Cu_2O film was determined by using the data of transmittance versus wavelength,and slightly decreased from 2.46 to 2.40 eV with the increase of oxygen flow rate from 3.8 to 4.4 cm^3/min.The Cu_2O film formed at the oxygen flow rate of 4.2 cm^3/min had an optical band gap of 2.43 eV.展开更多
Single-crystalline silicon materials with large dimensions have been widely used as assemblies in plasma silicon etching machines.However,information about large-diameter low-cost preparation technology has not been s...Single-crystalline silicon materials with large dimensions have been widely used as assemblies in plasma silicon etching machines.However,information about large-diameter low-cost preparation technology has not been sufficiently reported.In this paper,it was focused on the preparation of 400-mm silicon（100） crystal lightly doped with boron from 28-in.hot zones.Resistivity uniformity and oxygen concentration of the silicon crystal were investigated by direct-current（DC） four-point probes method and Fourier transform infrared spectroscopy（FTIR）,respectively.The global heat transfer,melt flow and oxygen distribution were calculated by finite element method（FEM）.The results show that 28-in.hot zones can replace conventional 32 in.ones to grow 400-mm-diameter silicon single crystals.The change in crucible diameter can save energy,reduce cost and improve efficiency.The trend of oxygen distribution obtained in calculations is in good agreement with experimental values.The present model can well predict the 400-mm-diameter silicon crystal growth and is essential for the optimization of furnace design and process condition.展开更多
An improved mathematical model to describe the decarburization process in basic oxygen furnaces for steelmaking is presented in this work. This model takes into account those factors or parameters that determine the b...An improved mathematical model to describe the decarburization process in basic oxygen furnaces for steelmaking is presented in this work. This model takes into account those factors or parameters that determine the bath-oxygen impact area, such as the cavity depth, the lance height, the number of nozzles and the nozzles diameter. In the thermal issue, the model includes the targeted carbon content and temperature. The model is numerically solved, and is validated using reported data plant. The oxygen flow rate and the lance height are varied in the numerical simulations to study their effect on the carbon content and decarburization rate.展开更多
Large-scale electrical energy storage with high energy density and round-trip efficiency is important to the resilience of power grids and the effective use of intermittent renewable energy such as solar and wind.Lith...Large-scale electrical energy storage with high energy density and round-trip efficiency is important to the resilience of power grids and the effective use of intermittent renewable energy such as solar and wind.Lithiumoxygen battery,due to its high energy density,is believed to be one of the most promising energy storage systems for the future.However,large overpotentials,poor cycling stability,and degradation of electrolytes and cathodes have been hindering the development of lithium-oxygen batteries.Numerous heterogeneous oxygen electrocatalysts have been investigated to lower the overpotentials and enhance the cycling stability of lithium-oxygen batteries.Unfortunately,the prevailing issues of electrode passivation and clogging remain.Over the past few years,redox mediators were explored as homogenous catalysts to address the issues,while only limited success has been achieved for these soluble catalysts.In conjunction with a flowing electrolyte system,a new redox flow lithium-oxygen battery(RFLOB)has been devised to tackle the aforementioned issues.The working mechanism and schematic processes will be elaborated in this review.In addition,the performance gap of RFLOB with respect to practical requirements will be analysed.With the above,we anticipate RFLOB would be a credible solution for the implementation of lithium-oxygen battery chemistry for the next generation energy storage.展开更多
Comparison of LaFeO3, La0.8Sr0.2FeO3, and La0.8Sr0.2Fe0.9CO0.1O3 perovskite oxides as oxygen carrier for partial oxidation of methane in the absence of gaseous oxygen was investigated by continuous flow reaction and s...Comparison of LaFeO3, La0.8Sr0.2FeO3, and La0.8Sr0.2Fe0.9CO0.1O3 perovskite oxides as oxygen carrier for partial oxidation of methane in the absence of gaseous oxygen was investigated by continuous flow reaction and sequential redox reaction, Methane was oxidized to syngas with high selectivity by oxygen species of perovskite oxides in the absence of gaseous oxygen. The sequential redox reaction revealed that the structural stability and continuous oxygen supply in redox reaction decreased over La0.8Sr0.2Fe0.9Co0. 1O3 oxide, while LaFeO3 and La0.8Sr0.2FeO3 exhibited excellent structural stability and continuous oxygen supply.展开更多
The available studies in the literature on physical and mathematical modeling of the argon oxygen decarburization (AOD) process of stainless steel have briefly been reviewed. The latest advances made by the author wi...The available studies in the literature on physical and mathematical modeling of the argon oxygen decarburization (AOD) process of stainless steel have briefly been reviewed. The latest advances made by the author with his research group have been summarized. Water modeling was used to investigate the fluid flow and mixing characteristics in the bath of an 18 t AOD vessel, as well as the 'back attack' action of gas jets and its effects on the erosion and wear of the refractory lining, with sufficiently full kinematic similarity. The non rotating and rotating gas jets blown through two annular tuyeres, respectively of straight tube and spiral flat tube type, were employed in the experiments. The geometric similarity ratio between the model and its prototype (including the straight tube type tuyeres) was 1:3. The influences of the gas flow rate, the angle included between the two tuyeres and other operating parameters, and the suitability of the spiral tuyere as a practical application, were examined. These latest studies have clearly and successfully brought to light the fluid flow and mixing characteristics in the bath and the overall features of the back attack phenomena of gas jets during the blowing, and have offered a better understanding of the refining process. Besides, mathematical modeling for the refining process of stainless steel was carried out and a new mathematical model of the process was proposed and developed. The model performs the rate calculations of the refining and the mass and heat balances of the system. Also, the effects of the operating factors, including adding the slag materials, crop ends, and scrap, and alloy agents; the non isothermal conditions; the changes in the amounts of metal and slag during the refining; and other factors were all considered. The model was used to deal with and analyze the austenitic stainless steel making (including ultra low carbon steel) and was tested on data of 32 heats obtained in producing 304 grade steel in an 18 t AOD vessel. The changes in the bath composition and temperature during the refining process with time can be accurately predicted using this model. The model can provide some very useful information and a reliable basis for optimizing the process practice of the refining of stainless steel and control of the process in real time and online.展开更多
Background: Oxygen is a commonly used drug in modern medical care. It has biochemical actions, safe dosage ranges, adverse physiologic effects and can be toxic at high doses and prolonged use. As a drug, it needs a fo...Background: Oxygen is a commonly used drug in modern medical care. It has biochemical actions, safe dosage ranges, adverse physiologic effects and can be toxic at high doses and prolonged use. As a drug, it needs a formal prescription prior to administration. The prescription needs to meet certain basic minimums for appropriateness and safety. Objectives: The aim of the study was to assess the standards of prescriptions for oxygen therapy amongst admitted medical patients at the Dr. George Mukhari Academic Hospital. Materials and Methods: It was a cross-sectional study of 159 acutely ill medical admissions who received supplemental oxygen. The medication charts of patients on oxygen were audited;with regards to the availability and/or adequacy of the prescription for oxygen. Results: Of the one hundred and fifty nine patients on oxygen only 43 (27%) had an actual prescription for oxygen written. The target oxygen saturation was specified in 19 (44%) cases. The device for oxygen delivery was specified in 21 (49%) patients and just over half of the patients (56%) had flow rates indicated on their charts. Conclusion: The practice of oxygen administration in our medical wards was sub-optimal. The audit highlights the need for education and training in acute oxygen therapy.展开更多
基金Supported by The Department of Anesthesiology and Perioperative Medicine,Tufts Medical Center,Boston,United States
文摘AIM To examine whether high-flow nasal oxygen(HFNO) availability influences the use of general anesthesia(GA) in patients undergoing endoscopic retrograde cholangiopancreatography(ERCP) and endoscopic ultrasound(EUS) and associated outcomes.METHODS In this retrospective study, patients were stratified into 3 eras between October 1, 2013 and June 30, 2014 based on HFNO availability for deep sedation at the time of their endoscopy. During the first and last 3-mo eras(era 1 and 3), no HFNO was available, whereas it was an option during the second 3-mo era(era 2). The primary outcome was the percent utilization of GA vs deep sedation in each period. Secondary outcomes included oxygen saturation nadir during sedation between periods, as well as procedure duration, and anesthesia-only time between periods and for GA vs sedation cases respectively.RESULTS During the study period 238 ERCP or EUS cases were identified for analysis. Statistical testing was employed and a P < 0.050 was significant unless the Bonferroni correction for multiple comparisons was used. General anesthesia use was significantly lower in era 2 compared to era 1 with the same trend between era 2 and 3(P = 0.012 and 0.045 respectively). The oxygen saturation nadir during sedation was significantly higher in era 2 compared to era 3(P < 0.001) but not between eras 1 and 2(P = 0.028) or 1 and 3(P = 0.069). The procedure time within each era was significantly longer under GA compared to deep sedation(P ≤ 0.007) as was the anesthesia-only time(P ≤ 0.001).CONCLUSION High-flow nasal oxygen availability was associated with decreased GA utilization and improved oxygenation for ERCP and EUS during sedation.
基金supported by the National Natural Science Foundation of China (No. 51138009)the Major Science and Technology Program for Water Pollution Control and Treatment (No. 2012ZX07203-001)
文摘In the Orbal oxidation ditch, denitrification is primarily accomplished in the outer channel. However, the detailed characteristics of the flow field and dissolved oxygen （DO） distribution in the outer channel are not well understood. Therefore, in this study, the flow velocity and DO concentration in the outer channel of an Orbal oxidation ditch system in a wastewater treatment plant in Beijing （China） were monitored under actual operation conditions. The flow field and DO concentration distributions were analyzed by computed fluid dynamic modeling. In situ monitoring and modeling both showed that the flow velocity was heterogeneous in the outer channel. As a result, the DO was also heterogeneously distributed in the outer channel, with concentration gradients occurring along the flow direction as well as in the cross-section. This heterogeneous DO distribution created many anoxic and aerobic zones, which may have facilitated simultaneous nitrificafion-denitrification in the channel. These findings may provide supporting information for rational optimization of the performance of the Orbal oxidation ditch.
文摘BACKGROUND Hypoxemia is a common complication in older patients during postoperative recovery and can cause pulmonary complications.Therefore,reducing the incidence of postoperative hypoxemia is a clinical concern.AIM To investigate the clinical efficacy of high-flow nasal cannula oxygen(HFNCO)in the resuscitation period of older orthopedic patients.METHODS In this prospective randomized controlled trial,60 older patients who underwent orthopedic surgery under general anesthesia were randomly divided into two groups:those who used conventional face mask and those who used HFNCO.All patients were treated with 60%oxygen for 1 h after extubation.Patients in the conventional face mask group were treated with a combination of air(2 L)and oxygen(2 L)using a traditional mask,whereas those in the HFNCO group were treated with HFNCO at a constant temperature of 34℃ and flow rate of 40 L/min.We assessed the effectiveness of oxygen therapy by monitoring the patients’arterial blood gas,peripheral oxygen saturation,and postoperative complications.RESULTS The characteristics of the patients were comparable between the groups.One hour after extubation,patients in HFNCO group had a significantly higher arterial partial pressure of oxygen(paO_(2))than that of patients in conventional face mask group(P<0.001).At extubation and 1 h after extubation,patients in both groups showed a significantly higher arterial partial pressure of carbon dioxide(paCO_(2))than the baseline levels(P<0.001).There were no differences in the saturation of peripheral oxygen,paO_(2),and paCO_(2) between the groups before anesthesia and before extubation(P>0.05).There were statistically significant differences in paO_(2) between the two groups before anesthesia and 1 h after extubation and immediately after extubation and 1 h after extubation(P<0.001).However,there were no significant differences in the oxygen tolerance score before leaving the room,airway humidification,and pulmonary complications 3 d after surgery between the two groups(P>0.05).CONCLUSION HFNCO can improve oxygen partial pressure and respiratory function in elderly patients undergoing orthopedic surgery under general endotracheal anesthesia.Thus,HFNCO can be used to prevent postoperative hypoxemia.
基金supported by the National Natural Science Foundation of China (No. 51177138)the Research Fund for the Doctoral Program of High Education of China (No.20100184110015)Sichuan Province International Technology Cooperation and Exchange Program (No. 2012HH0007)
文摘Air flow control is one of the most important control methods for maintaining the stability and reliability of a fuel cell system, which can avoid oxygen starvation or oxygen saturation. The oxygen excess ratio （OER） is often used to indicate the air flow condition. Based on a fuel cell system model for vehicles, OER performance was analyzed for different stack currents and temperatures in this paper, and the results show that the optimal OER was affected weakly by the stack temperature. In order to ensure the system working in optimal OER, a control scheme that includes an optimal OER regulator and a fuzzy control was proposed. According to the stack current, a reference value of air flow rate was obtained with the optimal OER regulator and then the air compressor motor voltage was controlled with the fuzzy controller to adjust the air flow rate provided by the air compressor. Simulation results show that the control method has good dynamic and static characteristics.
文摘Based on the operating conditions of oxygen lance utilized for a 50 t converter in Tangsteel,gas jet flow fields of three types of oxygen lances were simulated by FLUENT software.The influence of lance configuration and lance level on penetrating area was studied through cold model experiment.The results showed that the gas flow velocities of four-hole,variable angle four-hole and five-hole oxygen lances declined rapidly with an increase in gas jet length within 1 m,1 m and 0.8 m,respectively.Besides,the multi gas streams sprayed from these three lances should be syncretized at 1.6 m,1.7 m and 1.4 m,respectively.At the highest lance level,the effective penetrating area of these three lances could be 0.255 m2,0.385 m2 and 0.0907 m2,respectively.It was suggested that the effective penetrating area of variable angle four-hole oxygen lance was the biggest,while that of five-hole oxygen lance was the least.The validity of numerical simulation results was proved through cold model experiment.The lance level was suggested to be controlled in the range of 1-1.6 m,1-1.7 m and 0.8-1.4 m for the four-hole,variable angle four-hole and five-hole oxygen lances,respectively.
文摘Four different pulverized coals have been used to study the effects of oxygen concentration on combustion characteristics under different enriched-oxygen conditions by entrained flow reactor experiments. The results show that: with the increase of oxygen concentration, the ignition temperature of four coals greatly decreases and the low volatile coals decrease faster; with the increase of oxygen concentration, the ignition mode of pulverized coal has an obviously transformation from homogeneous ignition to heterogeneous ignition, and the corresponding oxygen concentrations are about 40% and 50%-60% respectively for bituminous coal and lignite, and both about 30% for lean coal and anthracite; with the increase of oxygen concentration, the optimal pulverized coal concentrations of bituminous coal and lignite increase firstly and then decrease, but for lean coal and anthracite, the optimal pulverized coal concentrations decrease slowly with the increase of oxygen concentration.
文摘Aim: The purpose of this case study was to examine the sleep quality of patients receiving noninvasive positive pressure ventilation (NPPV) or nasal high-flow oxygen therapy (NHF) in an intensive care unit and to investigate what types of nursing support are offered to such patients. Methods: We examined one patient each for NPPV and NHF. Polysomnography (PSG), review of the patient charts, and semi-structured interviews were used to collect the data for analysis. Results: Patients treated with NPPV or NHF demonstrated a noticeable reduction in deep sleep, with most of their sleep being shallow. Their sleep patterns varied greatly from those of healthy individuals. These results suggest that, in addition to experiencing extremely fragmented sleep, sleep in these patients was more likely to be interrupted by nursing interventions, such as during auscultation of breath sounds. Furthermore, it was revealed that “anxiety or discomfort that accompanies the mask or air pressure” in patients treated with NPPV and “discomfort that accompanies the nasal cannula or NHF circuit” in patients treated with NHF may be primary causes of disrupted sleep. Our results suggest a need for nursing care aimed at improving sleep quality in patients treated with NPPV or NHF.
文摘The traditional practice of employing a two-stage coal-fed gasification process is to feed all of the oxygen to provide a vigorous amount of combustion in the first stage but only feed the coal without oxygen in the second stage to allow the endothermic gasification process to occur downstream of the second stage. One of the merits of this 2-stage practice is to keep the gasifier temperature low downstream from the 2nd stage. This helps to extend the life of refractory bricks, decrease gasifier shut-down frequency for scheduled maintenance, and reduce the maintenance costs. In this traditional 2-stage practice, the temperature reduction in the second stage is achieved at the expense of a higher than normal temperature in the first stage. This study investigates a concept totally opposite to the traditional two-stage coal feeding practices in which the injected oxygen is split between the two stages, while all the coal is fed into the first stage. The hypothesis of this two-stage oxygen injection is that a distributed oxygen injection scheme can also distribute the release of heat to a larger gasifier volume and, thus, reduce the peak temperature distribution in the gasifier. The increased life expectancy and reduced maintenance of the refractory bricks can prevail in the entire gasifier and not just downstream from the second stage. In this study, both experiments and computational simulations have been performed to verify the hypothesis. A series of experiments conducted at 2.5 - 3.0 bars shows that the peak temperature and temperature range in the gasifier do decrease from 600?C - 1550?C with one stage oxygen injection to 950?C - 1230?C with a 60 - 40 oxygen split-injection. The CFD results conducted at 2.5 bars show that 1) the carbon conversion ratio for different oxygen injection schemes are all above 95%;2) H2 (about 70% vol.) dominates the syngas composition at the exit;3) the 80% - 20% case yields the lowest peak temperature and the most uniform temperature distribution along the gasifier;and 4) the 40% - 60% case produces the syngas with the highest HHV. Both experimental data and CFD predictions verify the hypothesis that it is feasible to reduce the peak temperature and achieve more uniform temperature in the gasifier by adequately controlling a two-stage oxygen injection with only minor changes of the composition and heating value of the syngas.
基金the National Natural Science Foundation of China(No.61176062)the Fundamental Research Funds for the Central Universities (No.NZ2012309)
文摘Cuprous oxide(Cu_2O) thin films have been deposited on glass substrate by reactive magnetron sputtering method using Cu target and argon oxygen gas atmosphere.Effect of oxygen flow rate on structural and optical properties of thin films has been discussed.The results of X-ray diffraction,ultraviolet-visible spectrophotometry and atomic force micrograph indicated that the condition window for single Cu_2O phase was about 3.8 to 4.4 cm^3/min,and the optimum oxygen flow rate was 4.2 cm^3/min.The optical band gap E_g of Cu_2O film was determined by using the data of transmittance versus wavelength,and slightly decreased from 2.46 to 2.40 eV with the increase of oxygen flow rate from 3.8 to 4.4 cm^3/min.The Cu_2O film formed at the oxygen flow rate of 4.2 cm^3/min had an optical band gap of 2.43 eV.
基金financially supported by the Major National Science and Technology Projects(No.2008ZX02401)
文摘Single-crystalline silicon materials with large dimensions have been widely used as assemblies in plasma silicon etching machines.However,information about large-diameter low-cost preparation technology has not been sufficiently reported.In this paper,it was focused on the preparation of 400-mm silicon（100） crystal lightly doped with boron from 28-in.hot zones.Resistivity uniformity and oxygen concentration of the silicon crystal were investigated by direct-current（DC） four-point probes method and Fourier transform infrared spectroscopy（FTIR）,respectively.The global heat transfer,melt flow and oxygen distribution were calculated by finite element method（FEM）.The results show that 28-in.hot zones can replace conventional 32 in.ones to grow 400-mm-diameter silicon single crystals.The change in crucible diameter can save energy,reduce cost and improve efficiency.The trend of oxygen distribution obtained in calculations is in good agreement with experimental values.The present model can well predict the 400-mm-diameter silicon crystal growth and is essential for the optimization of furnace design and process condition.
文摘An improved mathematical model to describe the decarburization process in basic oxygen furnaces for steelmaking is presented in this work. This model takes into account those factors or parameters that determine the bath-oxygen impact area, such as the cavity depth, the lance height, the number of nozzles and the nozzles diameter. In the thermal issue, the model includes the targeted carbon content and temperature. The model is numerically solved, and is validated using reported data plant. The oxygen flow rate and the lance height are varied in the numerical simulations to study their effect on the carbon content and decarburization rate.
基金supported by the National Research Foundation, Prime Minister’s Office, Singapore, under its Competitive Research Program (CRP Awards No.NRF-CRP10-2012-06)
文摘Large-scale electrical energy storage with high energy density and round-trip efficiency is important to the resilience of power grids and the effective use of intermittent renewable energy such as solar and wind.Lithiumoxygen battery,due to its high energy density,is believed to be one of the most promising energy storage systems for the future.However,large overpotentials,poor cycling stability,and degradation of electrolytes and cathodes have been hindering the development of lithium-oxygen batteries.Numerous heterogeneous oxygen electrocatalysts have been investigated to lower the overpotentials and enhance the cycling stability of lithium-oxygen batteries.Unfortunately,the prevailing issues of electrode passivation and clogging remain.Over the past few years,redox mediators were explored as homogenous catalysts to address the issues,while only limited success has been achieved for these soluble catalysts.In conjunction with a flowing electrolyte system,a new redox flow lithium-oxygen battery(RFLOB)has been devised to tackle the aforementioned issues.The working mechanism and schematic processes will be elaborated in this review.In addition,the performance gap of RFLOB with respect to practical requirements will be analysed.With the above,we anticipate RFLOB would be a credible solution for the implementation of lithium-oxygen battery chemistry for the next generation energy storage.
基金the Chinese Natural Science Foundation(Project No.20306016)
文摘Comparison of LaFeO3, La0.8Sr0.2FeO3, and La0.8Sr0.2Fe0.9CO0.1O3 perovskite oxides as oxygen carrier for partial oxidation of methane in the absence of gaseous oxygen was investigated by continuous flow reaction and sequential redox reaction, Methane was oxidized to syngas with high selectivity by oxygen species of perovskite oxides in the absence of gaseous oxygen. The sequential redox reaction revealed that the structural stability and continuous oxygen supply in redox reaction decreased over La0.8Sr0.2Fe0.9Co0. 1O3 oxide, while LaFeO3 and La0.8Sr0.2FeO3 exhibited excellent structural stability and continuous oxygen supply.
文摘The available studies in the literature on physical and mathematical modeling of the argon oxygen decarburization (AOD) process of stainless steel have briefly been reviewed. The latest advances made by the author with his research group have been summarized. Water modeling was used to investigate the fluid flow and mixing characteristics in the bath of an 18 t AOD vessel, as well as the 'back attack' action of gas jets and its effects on the erosion and wear of the refractory lining, with sufficiently full kinematic similarity. The non rotating and rotating gas jets blown through two annular tuyeres, respectively of straight tube and spiral flat tube type, were employed in the experiments. The geometric similarity ratio between the model and its prototype (including the straight tube type tuyeres) was 1:3. The influences of the gas flow rate, the angle included between the two tuyeres and other operating parameters, and the suitability of the spiral tuyere as a practical application, were examined. These latest studies have clearly and successfully brought to light the fluid flow and mixing characteristics in the bath and the overall features of the back attack phenomena of gas jets during the blowing, and have offered a better understanding of the refining process. Besides, mathematical modeling for the refining process of stainless steel was carried out and a new mathematical model of the process was proposed and developed. The model performs the rate calculations of the refining and the mass and heat balances of the system. Also, the effects of the operating factors, including adding the slag materials, crop ends, and scrap, and alloy agents; the non isothermal conditions; the changes in the amounts of metal and slag during the refining; and other factors were all considered. The model was used to deal with and analyze the austenitic stainless steel making (including ultra low carbon steel) and was tested on data of 32 heats obtained in producing 304 grade steel in an 18 t AOD vessel. The changes in the bath composition and temperature during the refining process with time can be accurately predicted using this model. The model can provide some very useful information and a reliable basis for optimizing the process practice of the refining of stainless steel and control of the process in real time and online.
文摘Background: Oxygen is a commonly used drug in modern medical care. It has biochemical actions, safe dosage ranges, adverse physiologic effects and can be toxic at high doses and prolonged use. As a drug, it needs a formal prescription prior to administration. The prescription needs to meet certain basic minimums for appropriateness and safety. Objectives: The aim of the study was to assess the standards of prescriptions for oxygen therapy amongst admitted medical patients at the Dr. George Mukhari Academic Hospital. Materials and Methods: It was a cross-sectional study of 159 acutely ill medical admissions who received supplemental oxygen. The medication charts of patients on oxygen were audited;with regards to the availability and/or adequacy of the prescription for oxygen. Results: Of the one hundred and fifty nine patients on oxygen only 43 (27%) had an actual prescription for oxygen written. The target oxygen saturation was specified in 19 (44%) cases. The device for oxygen delivery was specified in 21 (49%) patients and just over half of the patients (56%) had flow rates indicated on their charts. Conclusion: The practice of oxygen administration in our medical wards was sub-optimal. The audit highlights the need for education and training in acute oxygen therapy.
