Hydrogen combustion in a nuclear power plant may threaten the integrity of some important systems and components.In this paper,the effect of hydrogen combustion in the primary pump compartment is analyzed by different...Hydrogen combustion in a nuclear power plant may threaten the integrity of some important systems and components.In this paper,the effect of hydrogen combustion in the primary pump compartment is analyzed by different initial hydrogen concentration and igniter locations using Computational Fluid Dynamics method.The results show that the combustion is confined to a limited area without pump damage at about 6.6%hydrogen volume fraction.Once igniting the hydrogen,the combustion affects the whole compartment at the 12%hydrogen volume fraction.The stress caused by the great temperature gradient or high temperature may damage the primary pump. Igniters at the lower location accelerate the combustion process and cause a threat to the pump integrity.展开更多
Background: Gastroesophageal reflux disease (GERD) is a prevalent disease in Western countries. Despite effective treatment modalities, in some patients total symptom control is not achieved in clinical practice. A cr...Background: Gastroesophageal reflux disease (GERD) is a prevalent disease in Western countries. Despite effective treatment modalities, in some patients total symptom control is not achieved in clinical practice. A cross-sectional study was designed to assess primary care practitioners’ views on the effectiveness of proton pump inhibitors (PPI) as monotherapy in the control of the most common symptoms of GERD (heartburn and regurgitation), as well as to determine the level of implementation of the “combined therapy” (PPI + alginate-antacids). Methods: A questionnaire on different aspects of the management of GERD was completed by 1491 primary care physicians. The questionnaire was composed of 11 close-ended questions with one-choice answer, with a total of 52 items, covering the main data from patients presenting with GERD. Results: Treatment with PPI alone was mostly considered insufficient for the control of GERD symptoms. The combined treatment of PPI + alginate-antacids was used for 37% and 21% of physicians for treating heart-burn and regurgitation, respectively. A better control of symptoms, an increase in the onset of action and to reduce nocturnal acid breakthrough were the most frequently argued reasons for the use of PPI + alginate-antacids. A high percentage of participants believed that treatment with PPI alone was insufficient for the control of symptoms and 39.8% of physicians reported the persistence of heartburn, 38.6% the persistence of regurgitation and 43.2% the persistence of epigastric discomfort in more than 25% of their patients treated with PPI as monotherapy. The most common schedule for the use of the antacid medication was on demand. Conclusions: Spanish primary care physicians consider that a high proportion of GERD patients continue to suffer from symptoms during PPI treatment alone. Ondemand “combined therapy” (PPI + antacid) is considered an efficient option to control reflux symptoms still troublesome in patients with PPI treatment alone.展开更多
The integration of large-scale renewable energy introduces frequency instability challenges due to inherent intermittency.While doubly-fed pumped storage units(DFPSUs)offer frequency regulation potential in pumping mo...The integration of large-scale renewable energy introduces frequency instability challenges due to inherent intermittency.While doubly-fed pumped storage units(DFPSUs)offer frequency regulation potential in pumping mode,conventional strategies fail to address hydraulic-mechanical coupling dynamics and operational constraints,limiting their effectiveness.This paper presents an innovative primary frequency control strategy for double-fed pumped storage units(DFPSUs)operating in pumpingmode,integrating an adaptive parameter calculation method.This method is constrained by operational speed and power limits,addressing key performance factors.A dynamic model that incorporates the reversible pump-turbine characteristics is developed to translate frequency deviations into coordinated adjustments in speed and power during pumping operations.The research thoroughly analyzes the influence of control parameters on the frequency response dynamics.Additionally,the paper introduces a deep reinforcement learning(DRL)-based optimization framework,which enables real-time tuning of control parameters in response to changing rotor speed and frequency states.This method strategicallymanages the utilization of kinetic energy while ensuring compliance with operational safety constraints.The effectiveness of the proposed strategy is validated through simulation studies conducted on a four-machine,two-area DFPSU system.These studies demonstrate the strategy’s potential for improving frequency regulation performance under a variety of operating conditions,highlighting its effectiveness in optimizing energy storage and frequency control in power grids.展开更多
AIM： To determine the diagnostic value of the rabeprazole test in patients seen by general practitioners. METHODS： Eighty-three patients with symptoms suggestive of GERD were enrolled by general practitioners in thi...AIM： To determine the diagnostic value of the rabeprazole test in patients seen by general practitioners. METHODS： Eighty-three patients with symptoms suggestive of GERD were enrolled by general practitioners in this multi-centre, randomized and doubleblind study. All patients received either rabeprazole （20 mg bid） or a placebo for one week. The diagnosis of GERD was established on the presence of mucosal breaks at endoscopy and/or an abnormal esophageal 24-h pH test. The test was considered to be positive if patients reported at least a ＂clear improvement＂ of symptoms on a 7-point Likert scale. RESULTS： The sensitivities of the test for rabeprazole and the placebo were 83% and 40%, respectively. The corresponding specificity, positive and negative predictive values were 45% and 67%, 71% and 71%, and 62% and 35%, respectively. A receiver operating characteristics （ROC） analysis confirmed that the best discriminatory cut-off corresponded to description of ＂clear improvement＂ CONCLUSION： The poor specificity of the proton-pump inhibitor （PPI） test does not support such an approach to establish a diagnosis of GERD in a primary care setting.展开更多
In order to evaluate the heating performance of gas engine heat pump（GEHP） for air-conditioning and hot water supply, a test facility was developed and experiments were performed over a wide range of engine speed（1...In order to evaluate the heating performance of gas engine heat pump（GEHP） for air-conditioning and hot water supply, a test facility was developed and experiments were performed over a wide range of engine speed（1400-2600 r/min）, ambient air temperature（2.4-17.8 ℃） and condenser water inlet temperature（30-50℃）. The results show that as engine speed increases from 1400 r/min to 2600 r/min, the total heating capacity and energy consumption increase by about 30% and 89%, respectively; while the heat pump coefficient of performance（COP） and system primary energy ratio（PER） decrease by 44% and 31%, respectively. With the increase of ambient air temperature from 2.4 ℃ to 17.8 ℃, the heat pump COP and system PER increase by 32% and 19%, respectively. Moreover, the heat pump COP and system PER decrease by 27% and 15%, respectively, when the condenser water inlet temperature changes from 30 ℃ to 50 ℃. So, it is obvious that the effect of engine speed on the performance is more significant than the effects of ambient air temperature and condenser water inlet temperature.展开更多
Most of existing methods for the safety assessment of the primary cooling loop of nuclear reactors in conditions of reactor coolant pump(RCP)failure(rotor seizure accident)essentially rely on the combination of one-di...Most of existing methods for the safety assessment of the primary cooling loop of nuclear reactors in conditions of reactor coolant pump(RCP)failure(rotor seizure accident)essentially rely on the combination of one-dimensional theory and experience.This study introduces a novel three-dimensional model of the‘Hualong-1’(HPR1000)primary loop and uses the method of matching the resistance characteristics of the tube to ensure that the main pump operates at the rated operating condition.In particular,the three-dimensional unsteady numerical calculation of the RCP behavior in the rotor-seizure accident condition is carried out in the framework of the RNG k-εturbulence model.The related transient pressure surge law and hydraulic load response are obtained accordingly.展开更多
海洋生物碳泵(BCP)与古气候的关系是碳循环研究的一个核心科学问题。本文利用罗斯海沉积物总有机碳(TOC)和一些重要的类脂化合物所隐含的生态学特性,即那些可引起海底沉积碳库组成和海洋BCP(包括生物泵BP和微型生物碳泵MCP)效率改变的...海洋生物碳泵(BCP)与古气候的关系是碳循环研究的一个核心科学问题。本文利用罗斯海沉积物总有机碳(TOC)和一些重要的类脂化合物所隐含的生态学特性,即那些可引起海底沉积碳库组成和海洋BCP(包括生物泵BP和微型生物碳泵MCP)效率改变的分子生物标志物,从罗斯海现代海洋出发,追溯到末次冰期以来(27~0.6 ka BP)古海洋生物碳泵演化(重点讨论BP和MCP)及其与一些重大地质事件的联系。研究结果表明:(1)罗斯海表层沉积物中相对高的TOC和较低C/N比值、以及正构烷烃色谱峰型、主峰碳、分子组合特征低碳数和高碳数比值(L/H)和(nC_(21)+nC_(22))/(nC_(28)+nC_(29))比值、低碳烃(nC_(15)+nC_(17)+nC_(19))、中碳烃(nC_(21)+nC_(23)+nC_(25))和高碳烃(nC_(27)+nC_(29)+nC_(31))、细菌(BrGDGT)和较低的陆源土壤指标(BIT)一致性表征海源有机质贡献占主导地位,通过海洋BP和MCP效应将内源有机碳输送到海底进行长期储存;Pr/Ph比值结合Ph/nC_(18)和Pr/C_(17)比值均表明表层沉积物为还原-强还原性的缺氧环境,有利于海底储存有机碳,同时还与海冰消融关系密切。(2)利用低温校正公式TEXL_(86)^(L)-SST[式(2)]反演现代的海洋表层温度(SST),并与WOA-SST(3月)表层水体温度较接近(R^(2)=0.78,p<0.01,n=15);同时利用TEXL_(86)^(L)-SST-2重建罗斯海JB03岩芯末次冰期以来的古海洋温度在-0.74~2.86℃范围(平均为1.03℃),接近现代南极罗斯海夏季温度。(3)JB03岩芯记录年代为27.27~0.6 ka BP,分为末次冰盛期(27.3~21 ka BP)、末次冰消期(21~11.7 ka BP)和全新世(11.7~0.6 ka BP)3个地质历史时期。末次冰期古海洋受冰盖和海冰限制作用的影响,初级生产力低下、沉积速率仅为0.45 cm/ka、Pr/Ph比值、Ph/nC_(18)和Pr/nC_(17)反映沉积环境氧化性较强、不利于MCP和BP储碳,在寒冷气候时段碳储量潜力降低;进入全新世暖期,冰架退缩解体,温暖的气候条件有利于浮游植物生产力和硅藻增加、浮游动物增加及影响粪便物质组成和提高沉降速率,促进有机碳向深海的输送加快,海底沉积为弱还原-弱氧化环境,有利于碳保存;硅藻生物量提高就意味着硅质泵加强,进而微生物活性增强、促进古菌和细菌生长,因而微生物总量-GDGTs、产甲烷古菌或广古菌-GDGT-0、奇古菌-Crenarchaeol生物量大大提高,显示罗斯海全新世以来古海洋BP和MCP作用大大加强,且古海洋BP与现代海洋均以硅藻/硅质泵为绝对主导。研究还发现,罗斯海末次冰期和全新世以来的古海洋BP和MCP储碳效率变化均与古海洋地质事件,即全球性大尺度的气候变化有关,这个碳库的大小与气候冷暖之间存在对应关系,罗斯海古海洋调节大气CO_(2)的能力,尤其在全新世暖期最强,这对于认识全球气候变化的海洋调控机制具有重要的科学意义。展开更多
针对传统阈值报警、人员巡检和人工检查参数来开展核电站状态监测的不足,以CANDU6反应堆主热传输泵(主泵)为例,开展了状态监测技术的研究,提出了主泵智能预警模型。采用分布式策略按照主泵部件功能及测点参数特征分别建立相应的监测模...针对传统阈值报警、人员巡检和人工检查参数来开展核电站状态监测的不足,以CANDU6反应堆主热传输泵(主泵)为例,开展了状态监测技术的研究,提出了主泵智能预警模型。采用分布式策略按照主泵部件功能及测点参数特征分别建立相应的监测模型。采用核主成分分析(Kernel Principal Component Analysis,KPCA)对各部件进行异常检测,在检测出异常后,采用贡献图法对故障进行定位,及时地识别出异常的参数。通过秦山3期CANDU6反应堆主泵的真实异常数据对模型和算法进行测试,测试结果表明该方法可以及时发现异常,并准确定位异常参数。展开更多
基金Supported by National Basic Research Program of China(No.2009CB724301)National Natural Science Foundation of China(No.11075104)
文摘Hydrogen combustion in a nuclear power plant may threaten the integrity of some important systems and components.In this paper,the effect of hydrogen combustion in the primary pump compartment is analyzed by different initial hydrogen concentration and igniter locations using Computational Fluid Dynamics method.The results show that the combustion is confined to a limited area without pump damage at about 6.6%hydrogen volume fraction.Once igniting the hydrogen,the combustion affects the whole compartment at the 12%hydrogen volume fraction.The stress caused by the great temperature gradient or high temperature may damage the primary pump. Igniters at the lower location accelerate the combustion process and cause a threat to the pump integrity.
文摘Background: Gastroesophageal reflux disease (GERD) is a prevalent disease in Western countries. Despite effective treatment modalities, in some patients total symptom control is not achieved in clinical practice. A cross-sectional study was designed to assess primary care practitioners’ views on the effectiveness of proton pump inhibitors (PPI) as monotherapy in the control of the most common symptoms of GERD (heartburn and regurgitation), as well as to determine the level of implementation of the “combined therapy” (PPI + alginate-antacids). Methods: A questionnaire on different aspects of the management of GERD was completed by 1491 primary care physicians. The questionnaire was composed of 11 close-ended questions with one-choice answer, with a total of 52 items, covering the main data from patients presenting with GERD. Results: Treatment with PPI alone was mostly considered insufficient for the control of GERD symptoms. The combined treatment of PPI + alginate-antacids was used for 37% and 21% of physicians for treating heart-burn and regurgitation, respectively. A better control of symptoms, an increase in the onset of action and to reduce nocturnal acid breakthrough were the most frequently argued reasons for the use of PPI + alginate-antacids. A high percentage of participants believed that treatment with PPI alone was insufficient for the control of symptoms and 39.8% of physicians reported the persistence of heartburn, 38.6% the persistence of regurgitation and 43.2% the persistence of epigastric discomfort in more than 25% of their patients treated with PPI as monotherapy. The most common schedule for the use of the antacid medication was on demand. Conclusions: Spanish primary care physicians consider that a high proportion of GERD patients continue to suffer from symptoms during PPI treatment alone. Ondemand “combined therapy” (PPI + antacid) is considered an efficient option to control reflux symptoms still troublesome in patients with PPI treatment alone.
文摘The integration of large-scale renewable energy introduces frequency instability challenges due to inherent intermittency.While doubly-fed pumped storage units(DFPSUs)offer frequency regulation potential in pumping mode,conventional strategies fail to address hydraulic-mechanical coupling dynamics and operational constraints,limiting their effectiveness.This paper presents an innovative primary frequency control strategy for double-fed pumped storage units(DFPSUs)operating in pumpingmode,integrating an adaptive parameter calculation method.This method is constrained by operational speed and power limits,addressing key performance factors.A dynamic model that incorporates the reversible pump-turbine characteristics is developed to translate frequency deviations into coordinated adjustments in speed and power during pumping operations.The research thoroughly analyzes the influence of control parameters on the frequency response dynamics.Additionally,the paper introduces a deep reinforcement learning(DRL)-based optimization framework,which enables real-time tuning of control parameters in response to changing rotor speed and frequency states.This method strategicallymanages the utilization of kinetic energy while ensuring compliance with operational safety constraints.The effectiveness of the proposed strategy is validated through simulation studies conducted on a four-machine,two-area DFPSU system.These studies demonstrate the strategy’s potential for improving frequency regulation performance under a variety of operating conditions,highlighting its effectiveness in optimizing energy storage and frequency control in power grids.
文摘AIM： To determine the diagnostic value of the rabeprazole test in patients seen by general practitioners. METHODS： Eighty-three patients with symptoms suggestive of GERD were enrolled by general practitioners in this multi-centre, randomized and doubleblind study. All patients received either rabeprazole （20 mg bid） or a placebo for one week. The diagnosis of GERD was established on the presence of mucosal breaks at endoscopy and/or an abnormal esophageal 24-h pH test. The test was considered to be positive if patients reported at least a ＂clear improvement＂ of symptoms on a 7-point Likert scale. RESULTS： The sensitivities of the test for rabeprazole and the placebo were 83% and 40%, respectively. The corresponding specificity, positive and negative predictive values were 45% and 67%, 71% and 71%, and 62% and 35%, respectively. A receiver operating characteristics （ROC） analysis confirmed that the best discriminatory cut-off corresponded to description of ＂clear improvement＂ CONCLUSION： The poor specificity of the proton-pump inhibitor （PPI） test does not support such an approach to establish a diagnosis of GERD in a primary care setting.
基金Project(hx2013-87)supported by the Qingdao Economic and Technology Development Zone Haier Water-Heater Co.Ltd.,China
文摘In order to evaluate the heating performance of gas engine heat pump（GEHP） for air-conditioning and hot water supply, a test facility was developed and experiments were performed over a wide range of engine speed（1400-2600 r/min）, ambient air temperature（2.4-17.8 ℃） and condenser water inlet temperature（30-50℃）. The results show that as engine speed increases from 1400 r/min to 2600 r/min, the total heating capacity and energy consumption increase by about 30% and 89%, respectively; while the heat pump coefficient of performance（COP） and system primary energy ratio（PER） decrease by 44% and 31%, respectively. With the increase of ambient air temperature from 2.4 ℃ to 17.8 ℃, the heat pump COP and system PER increase by 32% and 19%, respectively. Moreover, the heat pump COP and system PER decrease by 27% and 15%, respectively, when the condenser water inlet temperature changes from 30 ℃ to 50 ℃. So, it is obvious that the effect of engine speed on the performance is more significant than the effects of ambient air temperature and condenser water inlet temperature.
文摘Most of existing methods for the safety assessment of the primary cooling loop of nuclear reactors in conditions of reactor coolant pump(RCP)failure(rotor seizure accident)essentially rely on the combination of one-dimensional theory and experience.This study introduces a novel three-dimensional model of the‘Hualong-1’(HPR1000)primary loop and uses the method of matching the resistance characteristics of the tube to ensure that the main pump operates at the rated operating condition.In particular,the three-dimensional unsteady numerical calculation of the RCP behavior in the rotor-seizure accident condition is carried out in the framework of the RNG k-εturbulence model.The related transient pressure surge law and hydraulic load response are obtained accordingly.
文摘海洋生物碳泵(BCP)与古气候的关系是碳循环研究的一个核心科学问题。本文利用罗斯海沉积物总有机碳(TOC)和一些重要的类脂化合物所隐含的生态学特性,即那些可引起海底沉积碳库组成和海洋BCP(包括生物泵BP和微型生物碳泵MCP)效率改变的分子生物标志物,从罗斯海现代海洋出发,追溯到末次冰期以来(27~0.6 ka BP)古海洋生物碳泵演化(重点讨论BP和MCP)及其与一些重大地质事件的联系。研究结果表明:(1)罗斯海表层沉积物中相对高的TOC和较低C/N比值、以及正构烷烃色谱峰型、主峰碳、分子组合特征低碳数和高碳数比值(L/H)和(nC_(21)+nC_(22))/(nC_(28)+nC_(29))比值、低碳烃(nC_(15)+nC_(17)+nC_(19))、中碳烃(nC_(21)+nC_(23)+nC_(25))和高碳烃(nC_(27)+nC_(29)+nC_(31))、细菌(BrGDGT)和较低的陆源土壤指标(BIT)一致性表征海源有机质贡献占主导地位,通过海洋BP和MCP效应将内源有机碳输送到海底进行长期储存;Pr/Ph比值结合Ph/nC_(18)和Pr/C_(17)比值均表明表层沉积物为还原-强还原性的缺氧环境,有利于海底储存有机碳,同时还与海冰消融关系密切。(2)利用低温校正公式TEXL_(86)^(L)-SST[式(2)]反演现代的海洋表层温度(SST),并与WOA-SST(3月)表层水体温度较接近(R^(2)=0.78,p<0.01,n=15);同时利用TEXL_(86)^(L)-SST-2重建罗斯海JB03岩芯末次冰期以来的古海洋温度在-0.74~2.86℃范围(平均为1.03℃),接近现代南极罗斯海夏季温度。(3)JB03岩芯记录年代为27.27~0.6 ka BP,分为末次冰盛期(27.3~21 ka BP)、末次冰消期(21~11.7 ka BP)和全新世(11.7~0.6 ka BP)3个地质历史时期。末次冰期古海洋受冰盖和海冰限制作用的影响,初级生产力低下、沉积速率仅为0.45 cm/ka、Pr/Ph比值、Ph/nC_(18)和Pr/nC_(17)反映沉积环境氧化性较强、不利于MCP和BP储碳,在寒冷气候时段碳储量潜力降低;进入全新世暖期,冰架退缩解体,温暖的气候条件有利于浮游植物生产力和硅藻增加、浮游动物增加及影响粪便物质组成和提高沉降速率,促进有机碳向深海的输送加快,海底沉积为弱还原-弱氧化环境,有利于碳保存;硅藻生物量提高就意味着硅质泵加强,进而微生物活性增强、促进古菌和细菌生长,因而微生物总量-GDGTs、产甲烷古菌或广古菌-GDGT-0、奇古菌-Crenarchaeol生物量大大提高,显示罗斯海全新世以来古海洋BP和MCP作用大大加强,且古海洋BP与现代海洋均以硅藻/硅质泵为绝对主导。研究还发现,罗斯海末次冰期和全新世以来的古海洋BP和MCP储碳效率变化均与古海洋地质事件,即全球性大尺度的气候变化有关,这个碳库的大小与气候冷暖之间存在对应关系,罗斯海古海洋调节大气CO_(2)的能力,尤其在全新世暖期最强,这对于认识全球气候变化的海洋调控机制具有重要的科学意义。
文摘针对传统阈值报警、人员巡检和人工检查参数来开展核电站状态监测的不足,以CANDU6反应堆主热传输泵(主泵)为例,开展了状态监测技术的研究,提出了主泵智能预警模型。采用分布式策略按照主泵部件功能及测点参数特征分别建立相应的监测模型。采用核主成分分析(Kernel Principal Component Analysis,KPCA)对各部件进行异常检测,在检测出异常后,采用贡献图法对故障进行定位,及时地识别出异常的参数。通过秦山3期CANDU6反应堆主泵的真实异常数据对模型和算法进行测试,测试结果表明该方法可以及时发现异常,并准确定位异常参数。
