基于超阈值峰量法(Peaks Over Threshold,POT)抽样,以武江流域犁市站1956—2010年日径流量观测数据资料为基础,对主观和客观多种阈值确定方法进行对比分析,确定合理阈值,建立了流域超阈值洪水样本,分析了流域超阈值洪峰流量、洪量、洪...基于超阈值峰量法(Peaks Over Threshold,POT)抽样,以武江流域犁市站1956—2010年日径流量观测数据资料为基础,对主观和客观多种阈值确定方法进行对比分析,确定合理阈值,建立了流域超阈值洪水样本,分析了流域超阈值洪峰流量、洪量、洪水历时等不同水文变量的变化趋势。结果表明:武江流域近55 a洪水年均发生次数总体呈下降趋势,1970—1980年洪水发生次数偏少,但20世纪90年代后超阈值洪水发生频率明显增加,年均1.35次;洪峰流量值呈现增长趋势,1991—2010年场次洪峰均比1956—1990年增加了520 m^(3)/s,超阈值洪水历时对应下的洪量呈现增加趋势,洪水集中程度加大;1991—2010年样本序列推求的不同重现期的设计洪峰值明显大于1956—1990年样本序列设计值。由此可见,20世纪90年代以后武江流域洪水发生频率增加,洪峰流量和洪量不断加大,洪水集中程度及洪水风险加剧。展开更多
为探讨含盐量对盐渍土抗剪强度的影响,该研究对采自于青海柴达木盆地大柴旦盐湖地区的盐渍土进行了洗盐试验以获得素土试样;根据该区盐渍土类型及盐渍化程度,在洗盐后土体中分别加入不等量的无水硫酸钠(Na2SO4),以获得不同含盐量的人工...为探讨含盐量对盐渍土抗剪强度的影响,该研究对采自于青海柴达木盆地大柴旦盐湖地区的盐渍土进行了洗盐试验以获得素土试样;根据该区盐渍土类型及盐渍化程度,在洗盐后土体中分别加入不等量的无水硫酸钠(Na2SO4),以获得不同含盐量的人工配制硫酸盐渍土,并对上述不同含盐量的人工配制硫酸盐渍土开展室内直接剪切试验。试验结果表明,洗盐试验后土体中的易溶盐离子含量及p H值均显著低于洗盐前盐渍土;当土体密度和含水量分别为1.41 g/cm3和25.68%时,洗盐后土体粘聚力c值和内摩擦角φ值分别为14.8 k Pa和26.5°,均高于洗盐前盐渍土的粘聚力值(6.7 k Pa)和内摩擦角值(24.6°);不同含盐量梯度条件下的人工配制硫酸盐渍土的粘聚力和内摩擦角,随土体含盐量增加均表现出先减小后增加的变化特征。当含盐量由0.74%增至5.17%时,人工配制硫酸盐渍土粘聚力c值和内摩擦角φ值均呈逐渐减小的变化规律,当土体含盐量由5.17%增至14.17%时,人工配制硫酸盐渍土粘聚力c值和内摩擦角φ值均表现出增加的变化规律,且当含盐量为5.17%时,其粘聚力c值和内摩擦角φ值分别为8.3 k Pa和26.1°,均为最小值,即该值对应的含盐量值即为人工配制硫酸盐渍土的含盐量阈值。本项研究成果对于进一步探讨含盐量变化对盐渍土抗剪强度影响,及含盐量变化与盐渍土粘聚力和内摩擦角之间的关系等方面具有理论研究价值和实际意义。展开更多
目的探讨急性胰腺炎(acute pancreatitis,AP)患者发生急性肾损伤(acute kidney injury,AKI)的尿量阈值,指导早期液体治疗。方法提取美国重症监护医学信息数据库Ⅳ(medical information mart for intensive careⅣ,MIMIC-Ⅳ)中AP患者的...目的探讨急性胰腺炎(acute pancreatitis,AP)患者发生急性肾损伤(acute kidney injury,AKI)的尿量阈值,指导早期液体治疗。方法提取美国重症监护医学信息数据库Ⅳ(medical information mart for intensive careⅣ,MIMIC-Ⅳ)中AP患者的临床资料,计算24 h尿率[24 hour urine output·kg^(-1)·24 hour^(-1),24-UR mL/(kg·h)]和48 h尿率[48 hour urine output·kg^(-1)·48 hour^(-1),48-UR mL/(kg·h)],根据患者7 d内是否发生急性肾损伤(AKI within 7 days,7-AKI)分为7-AKI组和非7-AKI组,绘制受试者工作特征(receiver operating characteristic,ROC)曲线,评估24-UR和48-UR对AP患者7-AKI发生的预测价值,根据ROC曲线得出的最佳截断值分别对24-UR与48-UR分组,采用逻辑回归分析7-AKI的危险因素,绘制Kaplan-Meier(KM)生存曲线分析24-UR和48-UR对AP患者住院病死率的影响。结果共纳入713例AP患者,ROC曲线分析结果显示,24-UR预测AP患者7-AKI的ROC曲线下面积(area under the ROC curve,AUC)为0.76,依据最大约登指数计算出的24-UR截断值为0.795 mL/(kg·h),48-UR的AUC为0.78,48-UR截断值为0.975 mL/(kg·h)。逻辑回归分析结果显示,与24-UR>0.795 mL/(kg·h)相比,24-UR≤0.795 mL/(kg·h)的是7-AKI的独立危险因素(OR:4.22,95%CI:1.5~11.85,P=0.006),同样,与48-UR>0.975 mL/(kg·h)相比,48-UR≤0.975 mL/(kg·h)的是7-AKI的独立危险因素(OR:3.75,95%CI:1.45~9.72,P=0.007);KM生存曲线显示高24-UR组住院生存率高于低24-UR组。结论24-UR可用于指导AP患者早期液体治疗。展开更多
A novel method to characterize CMOS process fluctuations in subthreshold current mirrors （SCM） is reported. The proposed model is succinct in methodology and calculation complexity compared with previous statistical...A novel method to characterize CMOS process fluctuations in subthreshold current mirrors （SCM） is reported. The proposed model is succinct in methodology and calculation complexity compared with previous statistical models. However,it provides favorable estimations of CMOS process fluctuations on the SCM circuit, which makes it promising for engineering applications. The model statistically abstracts physical parameters, which depend on the IC process, into random variables with certain mean values and standard deviations, while aggregating all the random impacts into a discrete martingale. The correctness of the proposed method is experimentally verified on an SCM circuit implemented in an SMIC 0.18μm CMOS 1P6M mixed signal process with a conversion factor of 100 in an input range from 100pA to lμA. The pro- posed theory successfully predicts - 10% of die-to-die fluctuation measured in the experiment, and also suggests the -lmV of threshold voltage standard deviation over a single die,which meets the process parameters suggested by the design kit from the foundry. The deviations between calculated probabilities and measured data are less than 8%. Meanwhile, pertinent suggestions concerning high fluctuation tolerance subthreshold analog circuit design are also made and discussed.展开更多
Studies on first GaN-based blue-violet laser diodes(LDs) in China mainland are reported.High quality GaN materials as well as GaN-based quantum wells laser structures are grown by metal-organic chemical vapor depositi...Studies on first GaN-based blue-violet laser diodes(LDs) in China mainland are reported.High quality GaN materials as well as GaN-based quantum wells laser structures are grown by metal-organic chemical vapor deposition method.The X-ray double-crystal diffraction rocking curve measurements show the full-width half maximum of 180″ and 185″ for (0002) symmetric reflection and (10 12) skew reflection,respectively.A room temperature mobility of 850cm2/(V·s) is obtained for a 3μm thick GaN film.Gain guided and ridge geometry waveguide laser diodes are fabricated with cleaved facet mirrors at room temperature under pulse current injection.The lasing wavelength is 405 9nm.A threshold current density of 5kA/cm2 and an output light power over 100mW are obtained for ridge geometry waveguide laser diodes.展开更多
文摘基于超阈值峰量法(Peaks Over Threshold,POT)抽样,以武江流域犁市站1956—2010年日径流量观测数据资料为基础,对主观和客观多种阈值确定方法进行对比分析,确定合理阈值,建立了流域超阈值洪水样本,分析了流域超阈值洪峰流量、洪量、洪水历时等不同水文变量的变化趋势。结果表明:武江流域近55 a洪水年均发生次数总体呈下降趋势,1970—1980年洪水发生次数偏少,但20世纪90年代后超阈值洪水发生频率明显增加,年均1.35次;洪峰流量值呈现增长趋势,1991—2010年场次洪峰均比1956—1990年增加了520 m^(3)/s,超阈值洪水历时对应下的洪量呈现增加趋势,洪水集中程度加大;1991—2010年样本序列推求的不同重现期的设计洪峰值明显大于1956—1990年样本序列设计值。由此可见,20世纪90年代以后武江流域洪水发生频率增加,洪峰流量和洪量不断加大,洪水集中程度及洪水风险加剧。
文摘为探讨含盐量对盐渍土抗剪强度的影响,该研究对采自于青海柴达木盆地大柴旦盐湖地区的盐渍土进行了洗盐试验以获得素土试样;根据该区盐渍土类型及盐渍化程度,在洗盐后土体中分别加入不等量的无水硫酸钠(Na2SO4),以获得不同含盐量的人工配制硫酸盐渍土,并对上述不同含盐量的人工配制硫酸盐渍土开展室内直接剪切试验。试验结果表明,洗盐试验后土体中的易溶盐离子含量及p H值均显著低于洗盐前盐渍土;当土体密度和含水量分别为1.41 g/cm3和25.68%时,洗盐后土体粘聚力c值和内摩擦角φ值分别为14.8 k Pa和26.5°,均高于洗盐前盐渍土的粘聚力值(6.7 k Pa)和内摩擦角值(24.6°);不同含盐量梯度条件下的人工配制硫酸盐渍土的粘聚力和内摩擦角,随土体含盐量增加均表现出先减小后增加的变化特征。当含盐量由0.74%增至5.17%时,人工配制硫酸盐渍土粘聚力c值和内摩擦角φ值均呈逐渐减小的变化规律,当土体含盐量由5.17%增至14.17%时,人工配制硫酸盐渍土粘聚力c值和内摩擦角φ值均表现出增加的变化规律,且当含盐量为5.17%时,其粘聚力c值和内摩擦角φ值分别为8.3 k Pa和26.1°,均为最小值,即该值对应的含盐量值即为人工配制硫酸盐渍土的含盐量阈值。本项研究成果对于进一步探讨含盐量变化对盐渍土抗剪强度影响,及含盐量变化与盐渍土粘聚力和内摩擦角之间的关系等方面具有理论研究价值和实际意义。
文摘A novel method to characterize CMOS process fluctuations in subthreshold current mirrors （SCM） is reported. The proposed model is succinct in methodology and calculation complexity compared with previous statistical models. However,it provides favorable estimations of CMOS process fluctuations on the SCM circuit, which makes it promising for engineering applications. The model statistically abstracts physical parameters, which depend on the IC process, into random variables with certain mean values and standard deviations, while aggregating all the random impacts into a discrete martingale. The correctness of the proposed method is experimentally verified on an SCM circuit implemented in an SMIC 0.18μm CMOS 1P6M mixed signal process with a conversion factor of 100 in an input range from 100pA to lμA. The pro- posed theory successfully predicts - 10% of die-to-die fluctuation measured in the experiment, and also suggests the -lmV of threshold voltage standard deviation over a single die,which meets the process parameters suggested by the design kit from the foundry. The deviations between calculated probabilities and measured data are less than 8%. Meanwhile, pertinent suggestions concerning high fluctuation tolerance subthreshold analog circuit design are also made and discussed.
文摘Studies on first GaN-based blue-violet laser diodes(LDs) in China mainland are reported.High quality GaN materials as well as GaN-based quantum wells laser structures are grown by metal-organic chemical vapor deposition method.The X-ray double-crystal diffraction rocking curve measurements show the full-width half maximum of 180″ and 185″ for (0002) symmetric reflection and (10 12) skew reflection,respectively.A room temperature mobility of 850cm2/(V·s) is obtained for a 3μm thick GaN film.Gain guided and ridge geometry waveguide laser diodes are fabricated with cleaved facet mirrors at room temperature under pulse current injection.The lasing wavelength is 405 9nm.A threshold current density of 5kA/cm2 and an output light power over 100mW are obtained for ridge geometry waveguide laser diodes.
