Measuring the internal velocity of debris flows is very important for debris flow dynamics research and designing debris flow control works. However, there is no appropriate method for measuring the internal velocity ...Measuring the internal velocity of debris flows is very important for debris flow dynamics research and designing debris flow control works. However, there is no appropriate method for measuring the internal velocity because of the destructive power of debris flow process. In this paper, we address this problem by using the relationship between velocity and kinetic pressure, as described by surface velocity and surface kinetic pressure data. Kinetic pressure is the difference of impact pressure and static pressure. The former is detected by force sensors installed in the flow direction at the sampling section. Observations show that static pressure can be computed using the formula for static water pressure by simply substituting water density for debris flow density. We describe the relationship between surface velocity and surface kinetic pressure using data from seven laboratory flume experiments. It is consistent with the relationship for single phase flow, which is the measurement principle of the Pitot tube.展开更多
Element parameters including volume filled ratio,surface dimensionless distance,and surface filled ratio for DFDM(direct finite difference method)were proposed to describe shape and location of free surfaces in castin...Element parameters including volume filled ratio,surface dimensionless distance,and surface filled ratio for DFDM(direct finite difference method)were proposed to describe shape and location of free surfaces in casting mold filling processes.A mathematical model of the filling process was proposed specially considering the mass,momentum and heat transfer in the vicinity of free surfaces.Furthermore,a method for gas entrapment was established by tracking flow of entrapped gas.The model and method were applied to practical ADC1 high pressure die castings.The gas entrapment prediction was compared with the fraction and maximum size of porosities in the different casting parts.The comparison shows validity of the proposed model and method.The study indicates that final porosities in high pressure die castings are dependent on both gas entrapment during mold filling process and pressure transfer within solidification period.展开更多
目的探讨维持气管导管套囊压力恒定在预防呼吸机相关性肺炎（VAP）中的作用。方法选择2015年1月-12月入住重症监护病房（ICU）行气管插管并且机械通气时间〉48 h的96例Ⅱ型呼吸衰竭患者为试验组,实施人工气道集束化管理与测压表定时测...目的探讨维持气管导管套囊压力恒定在预防呼吸机相关性肺炎（VAP）中的作用。方法选择2015年1月-12月入住重症监护病房（ICU）行气管插管并且机械通气时间〉48 h的96例Ⅱ型呼吸衰竭患者为试验组,实施人工气道集束化管理与测压表定时测定并维持导管套囊压力恒定的管理模式,记录初始采用指捏法判断所得到的导管套囊压力,校正初始压力为30 cm H2O（1 cm H2O=0.098 k Pa）后,采用不同间隔时间测量导管套囊的压力并记录。回顾该ICU 2014年1月-12月仅采用人工气道集束化管理的88例同种疾病患者为对照组,分别记录两组机械通气时间、VAP发生时间、ICU住院时间、VAP发病率等。结果试验组患者初始指捏法估测导管套囊压力经压力表测量后结果显示仅11.46%的导管套囊压力介于25~30 cm H2O,82.29%的导管套囊压力〉30 cm H2O;采集8、7、6、5、4、3 h不同间隔时间的导管套囊压力值,其压力维持于25~30 cm H2O的比例分别为41.32%、43.75%、64.20%、76.54%、91.13%、91.85%;试验组患者ICU住院时间、机械通气时间短于对照组,组间对比差异有统计学意义（t=4.171,P〈0.001;t=4.061,P〈0.001）;试验组VAP患者的发病时间晚于对照组,差异有统计学意义（t=2.247,P=0.032）。结论指捏法经验性估测气管导管套囊压力存在较大误差,采用测压表监测套囊压力的推荐间隔时间为4 h,采用人工气道集束化管理联合测压表定时测定并维持导管套囊压力恒定的管理模式,可以缩短患者ICU住院时间、机械通气时间,延迟VAP的发生。展开更多
To screen the stable expression genes related to the stress （strong light, dehydration and temperature shock） we applied Absolute real-time PCR technology to determine the transcription numbers of the selected test ...To screen the stable expression genes related to the stress （strong light, dehydration and temperature shock） we applied Absolute real-time PCR technology to determine the transcription numbers of the selected test genes in Porphyra yezoensis, which has been regarded as a potential model species responding the stress conditions in the intertidal. Absolute real-time PCR technology was applied to determine the transcription numbers of the selected test genes in Porphyra yezoensis, which has been regarded as a potential model species in stress responding. According to the results of photosynthesis parameters, we observed that Y（II） and Fv/Fm were significantly affected when stress was imposed on the thalli of Porphyra yezoensis, but underwent almost completely recovered under normal conditions, which were collected for the following experiments. Then three samples, which were treated with different grade stresses combined with salinity, irradiation and temperature, were collected. The transcription numbers of seven constitutive expression genes in above samples were determined after RNA extraction and cDNA synthesis. Finally, a general insight into the selection of internal control genes during stress response was obtained. We found that there were no obvious effects in terms of salinity stress （at salinity 90） on transcription of most genes used in the study. The 18S ribosomal RNA gene had the highest expression level, varying remarkably among different tested groups. RPS8 expression showed a high irregular variance between samples. GAPDH presented comparatively stable expression and could thus be selected as the internal control. EF-la showed stable expression during the series of multiple-stress tests. Our research provided available references for the selection of internal control genes for transcripts determination of P. yezoensis.展开更多
A damage prediction method based on FE simulation was proposed to predict the occurrence of hot shortness crocks and surface cracks in liquid-solid extrusion process. This method integrated the critical temperature cr...A damage prediction method based on FE simulation was proposed to predict the occurrence of hot shortness crocks and surface cracks in liquid-solid extrusion process. This method integrated the critical temperature criterion and Cockcroft ＆ Latham ductile damage model, which were used to predict the initiation of hot shortness cracks and surface cracks of products, respectively. A coupling simulation of deformation with heat transfer as well as ductile damage was carried out to investigate the effect of extrusion temperature and extrusion speed on the damage behavior of Csf/AZ91D composites. It is concluded that the semisolid zone moves gradually toward deformation zone with the punch descending. The amplitude of the temperature rise at the exit of die from the initial billet temperature increases with the increase of extrusion speed during steady-state extrusion at a given punch displacement. In order to prevent the surface temperature of products beyond the incipient melting temperature of composites, the critical extrusion speed is decreased with the increase of extrusion temperature, otherwise the hot shortness cracks will occur. The maximum damage values increase with increasing extrusion speed or extrusion temperature. Theoretical results obtained by the Deform^TM-2D simulation agree well with the experiments.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 40771026)the NSFC-RFBR project (Grant No. 40911120089, 08-05-92206 NSFCa)
文摘Measuring the internal velocity of debris flows is very important for debris flow dynamics research and designing debris flow control works. However, there is no appropriate method for measuring the internal velocity because of the destructive power of debris flow process. In this paper, we address this problem by using the relationship between velocity and kinetic pressure, as described by surface velocity and surface kinetic pressure data. Kinetic pressure is the difference of impact pressure and static pressure. The former is detected by force sensors installed in the flow direction at the sampling section. Observations show that static pressure can be computed using the formula for static water pressure by simply substituting water density for debris flow density. We describe the relationship between surface velocity and surface kinetic pressure using data from seven laboratory flume experiments. It is consistent with the relationship for single phase flow, which is the measurement principle of the Pitot tube.
基金Project(50975093)supported by the National Natural Science Foundation of ChinaProject(08-0209)supported by New Century Excellent Talent in University,Ministry of Education,ChinaProject(2009ZM0283)supported by the Fundamental Research Funds for the Central Universities,China
文摘Element parameters including volume filled ratio,surface dimensionless distance,and surface filled ratio for DFDM(direct finite difference method)were proposed to describe shape and location of free surfaces in casting mold filling processes.A mathematical model of the filling process was proposed specially considering the mass,momentum and heat transfer in the vicinity of free surfaces.Furthermore,a method for gas entrapment was established by tracking flow of entrapped gas.The model and method were applied to practical ADC1 high pressure die castings.The gas entrapment prediction was compared with the fraction and maximum size of porosities in the different casting parts.The comparison shows validity of the proposed model and method.The study indicates that final porosities in high pressure die castings are dependent on both gas entrapment during mold filling process and pressure transfer within solidification period.
文摘目的探讨维持气管导管套囊压力恒定在预防呼吸机相关性肺炎（VAP）中的作用。方法选择2015年1月-12月入住重症监护病房（ICU）行气管插管并且机械通气时间〉48 h的96例Ⅱ型呼吸衰竭患者为试验组,实施人工气道集束化管理与测压表定时测定并维持导管套囊压力恒定的管理模式,记录初始采用指捏法判断所得到的导管套囊压力,校正初始压力为30 cm H2O（1 cm H2O=0.098 k Pa）后,采用不同间隔时间测量导管套囊的压力并记录。回顾该ICU 2014年1月-12月仅采用人工气道集束化管理的88例同种疾病患者为对照组,分别记录两组机械通气时间、VAP发生时间、ICU住院时间、VAP发病率等。结果试验组患者初始指捏法估测导管套囊压力经压力表测量后结果显示仅11.46%的导管套囊压力介于25~30 cm H2O,82.29%的导管套囊压力〉30 cm H2O;采集8、7、6、5、4、3 h不同间隔时间的导管套囊压力值,其压力维持于25~30 cm H2O的比例分别为41.32%、43.75%、64.20%、76.54%、91.13%、91.85%;试验组患者ICU住院时间、机械通气时间短于对照组,组间对比差异有统计学意义（t=4.171,P〈0.001;t=4.061,P〈0.001）;试验组VAP患者的发病时间晚于对照组,差异有统计学意义（t=2.247,P=0.032）。结论指捏法经验性估测气管导管套囊压力存在较大误差,采用测压表监测套囊压力的推荐间隔时间为4 h,采用人工气道集束化管理联合测压表定时测定并维持导管套囊压力恒定的管理模式,可以缩短患者ICU住院时间、机械通气时间,延迟VAP的发生。
基金Supported by the National Natural Science Foundation of China(Nos.41176134,30830015)the Prospective Joint Research Project of Jiangsu Province(No.BY2011188)+1 种基金the National Marine Public Welfare Research Project(Nos.201105008-2,201105023-7)the National Basic Research Program of China(973 Program)(No.2011CB411908)
文摘To screen the stable expression genes related to the stress （strong light, dehydration and temperature shock） we applied Absolute real-time PCR technology to determine the transcription numbers of the selected test genes in Porphyra yezoensis, which has been regarded as a potential model species responding the stress conditions in the intertidal. Absolute real-time PCR technology was applied to determine the transcription numbers of the selected test genes in Porphyra yezoensis, which has been regarded as a potential model species in stress responding. According to the results of photosynthesis parameters, we observed that Y（II） and Fv/Fm were significantly affected when stress was imposed on the thalli of Porphyra yezoensis, but underwent almost completely recovered under normal conditions, which were collected for the following experiments. Then three samples, which were treated with different grade stresses combined with salinity, irradiation and temperature, were collected. The transcription numbers of seven constitutive expression genes in above samples were determined after RNA extraction and cDNA synthesis. Finally, a general insight into the selection of internal control genes during stress response was obtained. We found that there were no obvious effects in terms of salinity stress （at salinity 90） on transcription of most genes used in the study. The 18S ribosomal RNA gene had the highest expression level, varying remarkably among different tested groups. RPS8 expression showed a high irregular variance between samples. GAPDH presented comparatively stable expression and could thus be selected as the internal control. EF-la showed stable expression during the series of multiple-stress tests. Our research provided available references for the selection of internal control genes for transcripts determination of P. yezoensis.
基金Project(50972121) supported by the National Natural Science Foundation of China
文摘A damage prediction method based on FE simulation was proposed to predict the occurrence of hot shortness crocks and surface cracks in liquid-solid extrusion process. This method integrated the critical temperature criterion and Cockcroft ＆ Latham ductile damage model, which were used to predict the initiation of hot shortness cracks and surface cracks of products, respectively. A coupling simulation of deformation with heat transfer as well as ductile damage was carried out to investigate the effect of extrusion temperature and extrusion speed on the damage behavior of Csf/AZ91D composites. It is concluded that the semisolid zone moves gradually toward deformation zone with the punch descending. The amplitude of the temperature rise at the exit of die from the initial billet temperature increases with the increase of extrusion speed during steady-state extrusion at a given punch displacement. In order to prevent the surface temperature of products beyond the incipient melting temperature of composites, the critical extrusion speed is decreased with the increase of extrusion temperature, otherwise the hot shortness cracks will occur. The maximum damage values increase with increasing extrusion speed or extrusion temperature. Theoretical results obtained by the Deform^TM-2D simulation agree well with the experiments.
