The capacity intermittent titration technique (CITT) was developed based on the ratio of potentio-charge capacity to galvano-charge capacity (RPG) method, to continuously determine the solid diffusion coefficient (D) ...The capacity intermittent titration technique (CITT) was developed based on the ratio of potentio-charge capacity to galvano-charge capacity (RPG) method, to continuously determine the solid diffusion coefficient (D) of the intercalary species within insertion-host materials with a small voltage region. The linear equations of D vs the value of ratio of the potentio-charge capacity to the galvano-charge capacity (q) were given. By the CITT technique,the Li+ solid diffusion coefficients within LiMn2 O4 at different voltages were determined. The results show that the values of D varied from 3. 447× 10-9 to 7.60× 10-11 cm2/s in the voltage range of charge from 3.3 to 4.3 V as a function of voltage with "W" shape.展开更多
The solution diffusion coefficient is a great important intrinsical parameter in crystal growth.On earth,it is impossible to accurately determine the diffusion coefficient since there is nature convection.One of the m...The solution diffusion coefficient is a great important intrinsical parameter in crystal growth.On earth,it is impossible to accurately determine the diffusion coefficient since there is nature convection.One of the marked charateristics of space-crystal growth is to eleminate nature convection,so that purely diffusion-controlled condition of crystal growth could be realized and precise measurement of the diffusion coefficient should be approved.展开更多
In arid regions, water vapor diffusion predominates the total water migration in unsaturated soil, which significantly influences agriculture and engineering applications. With the aim of revealing the diffusion mecha...In arid regions, water vapor diffusion predominates the total water migration in unsaturated soil, which significantly influences agriculture and engineering applications. With the aim of revealing the diffusion mechanism of water vapor in unsaturated soil, a water vapor migration test device was developed to conduct the water vapor migration indoor test. The test results demonstrate that the characteristics of water vapor diffusion in unsaturated soil conformed to Fick’s second law. A mathematical model for water vapor diffusion under isothermal conditions in unsaturated soil was established based on Fick’s law. Factors including the initial moisture content gradient, initial moisture content distribution, soil type and temperature that affect the water vapor diffusion coefficient were analyzed. The results show that there was good agreement between the moisture content calculated by the mathematical model and obtained by the indoor experiment. The vapor diffusion coefficient increased with increasing initial moisture content gradient and temperature. When the initial moisture content gradient is constant, the vapor diffusion coefficient increases with the increase of matrix suction ratio in dry and wet soil section. The effect of soil type on the water vapor diffusion coefficient was complex, as both the moisture content and soil particle sizes affected the water vapor diffusion.展开更多
Comparative studies of four common-used anode gas diffusion layers(A-GDLs),namely carbon cloth,carbon paper,carbon paper based on XC-72(in short XC-72)and GDL made of carbon nanotubes(CNT)for direct methanol fuel cell...Comparative studies of four common-used anode gas diffusion layers(A-GDLs),namely carbon cloth,carbon paper,carbon paper based on XC-72(in short XC-72)and GDL made of carbon nanotubes(CNT)for direct methanol fuel cells(DMFCs)were carried out and discussed.The results of scanning electron microscope(SEM),mercury intrusion porosimeter(MIP)and electrochemical test show that CNT has large pore size distribution in pore size of 1000-3000nm and the largest total porosity compared with those of the other three.Carbon paper and XC-72show disadvantageous influences on cell performances at high current density,because carbon paper has many large pores which are unsuited for water transport,while XC-72has many small pores which are unsuited for gas transport.Though cell with carbon cloth has the highest methanol diffusion coefficient,it shows a little lower performance than that with CNT due to its thickness.Anode polarization(AP)results also display that the cell with CNT has the least methanol mass transfer resistance.As a result,the cell with CNT shows the best performance with the highest limiting current density and peak power density of 460 mA·cm^(-2)and 110mW·cm^(-2),respectively.展开更多
目的 探讨表观扩散系数平均值(mean apparent diffusion coefficient,ADCmean)联合前列腺特异性抗原密度(prostate specific antigen density,PSAD)对前列腺影像报告和数据系统(prostate imaging reporting and data system,PI-RADS)≥...目的 探讨表观扩散系数平均值(mean apparent diffusion coefficient,ADCmean)联合前列腺特异性抗原密度(prostate specific antigen density,PSAD)对前列腺影像报告和数据系统(prostate imaging reporting and data system,PI-RADS)≥3分临床显著性前列腺癌(clinical significant prostate cancer,csPCa)的预测价值。材料与方法 回顾性分析2022年2月至2024年8月期间我院行前列腺MRI检查PI-RADS评分≥3分且有病理组织学检查患者的临床资料和影像资料。选择最高PI-RADS评分且最大病灶的最大层面勾画感兴趣区(region of interest,ROI),测量病灶的ADCmean和表观扩散系数最小值(min apparent diffusion coefficient,ADCmin)。单因素和多因素logistic回归分析筛选出预测csPCa的最佳临床和影像指标,采用受试者工作特征(receiver operating characteristics,ROC)曲线比较最佳临床和影像预测模型及两者联合模型的诊断效能,计算曲线下面积(area under the curve,AUC)、敏感度和特异度,并行DeLong检验。结果 本研究共纳入csPCa患者75例(48.39%),非csPCa患者80例(51.61%)。csPCa组的年龄、总前列腺特异性抗原(total prostate specific antigen,tPSA)、游离前列腺特异性抗原(free prostate specific antigen,fPSA)、PSAD大于非csPCa组,csPCa组的前列腺体积(prostate volume,PV)、fPSA和tPSA比值(f/t)、ADCmin、ADCmean均小于非csPCa组,差异具有统计学意义(均P<0.05)。逐步logistic回归筛选和ROC曲线分析,获得预测csPCa的最佳临床指标为PSAD和影像指标ADCmean,AUC分别为0.846、0.898,PSAD诊断阈值为0.307 ng/mL2,敏感度为66.67%,特异度为91.25%,ADCmean诊断阈值为773.5 mm2/s,敏感度为86.67%,特异度为85.00%,两者联合模型的AUC高达0.925。DeLong检验比较联合模型与单一模型的AUC差异有统计学意义(P<0.05),联合模型预测csPCa的敏感性和特异度分别为86.67%和88.75%。结论 ADCmean对PI-RADS≥3分csPCa的预测效能优于ADCmin,与PSAD的联合模型能进一步提高对PI-RADS≥3分csPCa的预测价值,对临床诊疗具有指导意义。展开更多
Many analytical methods have been adopted to estimate the slope stability by providing various stability numbers,e.g.static safety of factor(static FoS)or the critical seismic acceleration coefficient,while little att...Many analytical methods have been adopted to estimate the slope stability by providing various stability numbers,e.g.static safety of factor(static FoS)or the critical seismic acceleration coefficient,while little attention has been given to the relationship between the slope stability numbers and the critical seismic acceleration coefficient.This study aims to investigate the relationship between the static FoS and the critical seismic acceleration coefficient of soil slopes in the framework of the upper-bound limit analysis.Based on the 3D rotational failure mechanism,the critical seismic acceleration coefficient using the pseudo-static method and the static FoS using the strength reduction technique are first determined.Then,the relationship between the static FoS and the critical seismic acceleration coefficient is presented under considering the slope angleβ,the frictional angleφ,and the dimensionless coefficients B/H and c/γH.Finally,a fitting formula between the static FoS and the critical seismic acceleration coefficient is proposed and validated by analytical and numerical results.展开更多
After diffusion couples were annealed at 260-360 ℃, the concentration profiles of Zn element were measured by EPMA. It has been first quantitatively determined by Matano method that the interdiffusion coefficient in ...After diffusion couples were annealed at 260-360 ℃, the concentration profiles of Zn element were measured by EPMA. It has been first quantitatively determined by Matano method that the interdiffusion coefficient in A1-Zn fee solid solution containing high Zn contents is remarkably decreased due to the small addition of Cu. Also, the interdiffusion coefficient in A1-Zn fee solid solution clearly increases with the increasing of Zn concentration. The interdiffusion activity energy remarkably decreases with the increasing of Zn contents. On the other hand, the interdiffusion activity energy markedly increases due to the small addition of Cu in the A1 Zn fcc solid solution containing high Zn contents.展开更多
基金Project (20406024) supported by the National Natural Science Foundation of China project (76600) supported by the Postdoctoral Science Foundation of Central South University
文摘The capacity intermittent titration technique (CITT) was developed based on the ratio of potentio-charge capacity to galvano-charge capacity (RPG) method, to continuously determine the solid diffusion coefficient (D) of the intercalary species within insertion-host materials with a small voltage region. The linear equations of D vs the value of ratio of the potentio-charge capacity to the galvano-charge capacity (q) were given. By the CITT technique,the Li+ solid diffusion coefficients within LiMn2 O4 at different voltages were determined. The results show that the values of D varied from 3. 447× 10-9 to 7.60× 10-11 cm2/s in the voltage range of charge from 3.3 to 4.3 V as a function of voltage with "W" shape.
文摘The solution diffusion coefficient is a great important intrinsical parameter in crystal growth.On earth,it is impossible to accurately determine the diffusion coefficient since there is nature convection.One of the marked charateristics of space-crystal growth is to eleminate nature convection,so that purely diffusion-controlled condition of crystal growth could be realized and precise measurement of the diffusion coefficient should be approved.
基金Projects(51878064, 51378072) supported by the National Natural Science Foundation of ChinaProjects(300102218408, 300102219108) supported by the Fundamental Research Funds for the Central Universities, China。
文摘In arid regions, water vapor diffusion predominates the total water migration in unsaturated soil, which significantly influences agriculture and engineering applications. With the aim of revealing the diffusion mechanism of water vapor in unsaturated soil, a water vapor migration test device was developed to conduct the water vapor migration indoor test. The test results demonstrate that the characteristics of water vapor diffusion in unsaturated soil conformed to Fick’s second law. A mathematical model for water vapor diffusion under isothermal conditions in unsaturated soil was established based on Fick’s law. Factors including the initial moisture content gradient, initial moisture content distribution, soil type and temperature that affect the water vapor diffusion coefficient were analyzed. The results show that there was good agreement between the moisture content calculated by the mathematical model and obtained by the indoor experiment. The vapor diffusion coefficient increased with increasing initial moisture content gradient and temperature. When the initial moisture content gradient is constant, the vapor diffusion coefficient increases with the increase of matrix suction ratio in dry and wet soil section. The effect of soil type on the water vapor diffusion coefficient was complex, as both the moisture content and soil particle sizes affected the water vapor diffusion.
文摘Comparative studies of four common-used anode gas diffusion layers(A-GDLs),namely carbon cloth,carbon paper,carbon paper based on XC-72(in short XC-72)and GDL made of carbon nanotubes(CNT)for direct methanol fuel cells(DMFCs)were carried out and discussed.The results of scanning electron microscope(SEM),mercury intrusion porosimeter(MIP)and electrochemical test show that CNT has large pore size distribution in pore size of 1000-3000nm and the largest total porosity compared with those of the other three.Carbon paper and XC-72show disadvantageous influences on cell performances at high current density,because carbon paper has many large pores which are unsuited for water transport,while XC-72has many small pores which are unsuited for gas transport.Though cell with carbon cloth has the highest methanol diffusion coefficient,it shows a little lower performance than that with CNT due to its thickness.Anode polarization(AP)results also display that the cell with CNT has the least methanol mass transfer resistance.As a result,the cell with CNT shows the best performance with the highest limiting current density and peak power density of 460 mA·cm^(-2)and 110mW·cm^(-2),respectively.
文摘目的探讨动态对比增强磁共振成像(dynamic contrast-enhanced magnetic resonance imaging,DCE-MRI)定量参数直方图特征联合表观弥散系数(apparent diffusion coefficient,ADC)预测局部晚期宫颈癌(locally advanced cervical cancer,LACC)放化疗疗效的价值。材料与方法于甘肃省人民医院回顾性分析2017年1月至2023年12月88例LACC同步放化疗患者的临床及影像资料,前瞻性收集2023年12月至2024年5月15例LACC患者。按照实体瘤临床疗效评价标准(response evaluation criteria in solid tumor,RECIST)v1.1将患者分为显著反应组与非显著反应组。在DCE-MRI图像上选择肿瘤最大层面全肿瘤轮廓作为感兴趣区(region of interest,ROI)获得转运常数(volume transport constant,K^(trans))、血管外细胞外间隙容积分数(extravascular extracellular volume fraction,Ve)、速率常数(rate constant,K^(ep))原始频数表,导入IBM SPSS Statistics 27软件计算直方图特征,103例患者基于时间序列分层分割策略分为训练集88例,验证集15例,利用机器学习筛选最优DCE-MRI定量参数直方图特征并计算灌注参数评分(DCEscore);同时在ADC图测量ADC值。构建DCE直方图特征模型、ADC值及联合模型预测LACC放化疗疗效。采用受试者工作特征(receiver operating characteristic,ROC)曲线、校准曲线和决策曲线评估模型效能。比较临床参数及直方图特征在LACC患者放化疗疗效显著反应组及非显著反应组间差异,单因素及多因素回归分析筛选宫颈癌放化疗疗效独立危险因素。结果基于DCE-MRI定量参数直方图特征模型预测LACC患者放化疗疗效训练集、验证集ROC曲线下面积(area under the curve,AUC)分别为0.922、0.841;ADC值预测LACC患者放化疗疗效训练集、验证集AUC为0.835、0.705;DCEscore联合ADC值预测LACC患者放化疗疗效效能最佳,训练集、验证集AUC为0.943、0.909。临床参数中,身体质量指数(body mass index,BMI)在显著反应组及非显著反应组之间差异具有统计学意义(P=0.032)。单因素逻辑回归分析结果表明BMI、DCEscore、ADC是LACC放化疗疗效的影响因素(OR值分别为1.264、277.9、0.001;P值分别为0.008、<0.001、0.002),多因素逻辑回归筛选DCEscore及ADC值是宫颈癌放化疗疗效的独立危险因素(OR值分别为518.2、0.002;P值分别为<0.001、0.007)。结论基于DCE-MRI定量参数直方图特征联合ADC值构建的联合模型能够治疗前预测宫颈癌放化疗疗效,提示DCE-MRI定量参数直方图特征联合ADC值可能为LACC患者精准医疗提供一种无创评估方法。
文摘目的 探讨表观扩散系数平均值(mean apparent diffusion coefficient,ADCmean)联合前列腺特异性抗原密度(prostate specific antigen density,PSAD)对前列腺影像报告和数据系统(prostate imaging reporting and data system,PI-RADS)≥3分临床显著性前列腺癌(clinical significant prostate cancer,csPCa)的预测价值。材料与方法 回顾性分析2022年2月至2024年8月期间我院行前列腺MRI检查PI-RADS评分≥3分且有病理组织学检查患者的临床资料和影像资料。选择最高PI-RADS评分且最大病灶的最大层面勾画感兴趣区(region of interest,ROI),测量病灶的ADCmean和表观扩散系数最小值(min apparent diffusion coefficient,ADCmin)。单因素和多因素logistic回归分析筛选出预测csPCa的最佳临床和影像指标,采用受试者工作特征(receiver operating characteristics,ROC)曲线比较最佳临床和影像预测模型及两者联合模型的诊断效能,计算曲线下面积(area under the curve,AUC)、敏感度和特异度,并行DeLong检验。结果 本研究共纳入csPCa患者75例(48.39%),非csPCa患者80例(51.61%)。csPCa组的年龄、总前列腺特异性抗原(total prostate specific antigen,tPSA)、游离前列腺特异性抗原(free prostate specific antigen,fPSA)、PSAD大于非csPCa组,csPCa组的前列腺体积(prostate volume,PV)、fPSA和tPSA比值(f/t)、ADCmin、ADCmean均小于非csPCa组,差异具有统计学意义(均P<0.05)。逐步logistic回归筛选和ROC曲线分析,获得预测csPCa的最佳临床指标为PSAD和影像指标ADCmean,AUC分别为0.846、0.898,PSAD诊断阈值为0.307 ng/mL2,敏感度为66.67%,特异度为91.25%,ADCmean诊断阈值为773.5 mm2/s,敏感度为86.67%,特异度为85.00%,两者联合模型的AUC高达0.925。DeLong检验比较联合模型与单一模型的AUC差异有统计学意义(P<0.05),联合模型预测csPCa的敏感性和特异度分别为86.67%和88.75%。结论 ADCmean对PI-RADS≥3分csPCa的预测效能优于ADCmin,与PSAD的联合模型能进一步提高对PI-RADS≥3分csPCa的预测价值,对临床诊疗具有指导意义。
基金Project(2017YFB1201204)supported by the National Key R&D Program of ChinaProject(1053320190957)supported by the Fundamental Research Funds for the Central Universities,China。
文摘Many analytical methods have been adopted to estimate the slope stability by providing various stability numbers,e.g.static safety of factor(static FoS)or the critical seismic acceleration coefficient,while little attention has been given to the relationship between the slope stability numbers and the critical seismic acceleration coefficient.This study aims to investigate the relationship between the static FoS and the critical seismic acceleration coefficient of soil slopes in the framework of the upper-bound limit analysis.Based on the 3D rotational failure mechanism,the critical seismic acceleration coefficient using the pseudo-static method and the static FoS using the strength reduction technique are first determined.Then,the relationship between the static FoS and the critical seismic acceleration coefficient is presented under considering the slope angleβ,the frictional angleφ,and the dimensionless coefficients B/H and c/γH.Finally,a fitting formula between the static FoS and the critical seismic acceleration coefficient is proposed and validated by analytical and numerical results.
文摘After diffusion couples were annealed at 260-360 ℃, the concentration profiles of Zn element were measured by EPMA. It has been first quantitatively determined by Matano method that the interdiffusion coefficient in A1-Zn fee solid solution containing high Zn contents is remarkably decreased due to the small addition of Cu. Also, the interdiffusion coefficient in A1-Zn fee solid solution clearly increases with the increasing of Zn concentration. The interdiffusion activity energy remarkably decreases with the increasing of Zn contents. On the other hand, the interdiffusion activity energy markedly increases due to the small addition of Cu in the A1 Zn fcc solid solution containing high Zn contents.
