目的对急性生理和慢性健康状况Ⅱ(Acute Physiology and Chronic Health EvaluationⅡ,APACHEⅡ)评分预测老年危重症患者住院病死率的效能进行验证。方法 421例老年危重症患者分为生存组281例和死亡组(住院死亡)140例,收集入住ICU 24h...目的对急性生理和慢性健康状况Ⅱ(Acute Physiology and Chronic Health EvaluationⅡ,APACHEⅡ)评分预测老年危重症患者住院病死率的效能进行验证。方法 421例老年危重症患者分为生存组281例和死亡组(住院死亡)140例,收集入住ICU 24h内相关指标,计算APACHEⅡ评分及其预测的住院病死率;应用ROC曲线评估APACHEⅡ评分预测住院病死率的辨别力,采用Hosmer-Lemeshow(HL)goodness-of-fit检验评估APACHEⅡ评分的校准力,采用标准化死亡比值(standardized mortality ratio,SMR)检验APACHEⅡ评分预测住院病死率的准确性,采用Brier评分(Brier score,BS)评估APACHEⅡ评分预测住院病死率的综合能力。结果生存组APACHEⅡ评分[17.0(12.0,24.0)分]低于死亡组[26.5(22.0,31.0)分],APACHEⅡ评分预测住院病死率[7.7(0.5,47.4)%]低于死亡组[71.1(26.1,90.4)%],ICU住院时间[7(4,11)d]较死亡组[11(5,19)d]短,住院时间[27(14,51)d]较死亡组[15(6,34)d]长(P<0.05);生存组患者合并慢性心功能不全(NYHA心功能Ⅲ~Ⅳ级)、痴呆、肿瘤比例(14.9%、14.2%、10.7%)低于死亡组(28.6%、23.6%、19.3%)(P<0.05);APACHEⅡ评分24分确定为最佳截断值,预测住院病死率的AUC为0.77(95%CI:0.72~0.81,P<0.05),HL检验显示校准不良(χ~2=16.690,P=0.034),预测老年重症患者群体住院病死率的准确性良好(SMR=0.90),模型综合能力一般(BS=0.20)。结论 APACHEⅡ评分在预测老年危重症患者住院病死率上有良好的辨别力和总体预测准确性,但校准不良,应专科化模型改善校准。展开更多
In order to address the current aircraft noise problem, the knowledge of impedance of acoustic liners subjected to high-intensity sound and grazing flow is of crucial importance to the design of high-efficiency acoust...In order to address the current aircraft noise problem, the knowledge of impedance of acoustic liners subjected to high-intensity sound and grazing flow is of crucial importance to the design of high-efficiency acoustic nacelles. To this end, the present study is twofold. Firstly, the StraightForward impedance eduction Method(SFM) is evaluated by the strategy that the impedance of a liner specimen is firstly experimentally educed on a flow duct using the SFM, and then its accuracy is checked by comparing the numerical prediction with the measured wall sound pressure of the flow duct. Secondly, the effects of grazing flow and high-intensity sound on the impedance behavior of two single-layer liners are investigated based on comparisons between educed impedance and predictions by three impedance models. The performance of the SFM is validated by showing that the educed impedance leads to excellent agreement between the simulation and the measured wall sound pressure for different grazing flow Mach numbers and Sound Pressure Levels(SPLs) and over a frequency range from 3000 Hz down to 500 Hz. The grazing flow effect generally has the tendency that the acoustic resistance exhibits a slight decrease before it increases linearly with an increase in Mach,predicted successfully by the sound-vortex interaction theoretical model and the Kooi semi-empirical impedance model. However, the Goodrich semi-empirical impedance model gives only a simple linear relation of acoustic resistance starting from Mach zero. Additionally, when the SPL increases from 110 to 140 d B in the present investigation, the acoustic resistance exhibits a significant increase at all frequencies in the absence of flow; however, the resistance decreases slightly under a grazing flow of Mach 0.117. It indicates that the SPL effect can be greatly inhibited when flow is present,and the grazing flow effect can be reduced partly as well at a relatively high SPL.展开更多
基金co-supported by the National Natural Science Foundation of China (No. 51576009)the Projects of International Cooperation and Exchanges National Natural Science Foundation of China (Nos.11661141020 and 51711530036)
文摘In order to address the current aircraft noise problem, the knowledge of impedance of acoustic liners subjected to high-intensity sound and grazing flow is of crucial importance to the design of high-efficiency acoustic nacelles. To this end, the present study is twofold. Firstly, the StraightForward impedance eduction Method(SFM) is evaluated by the strategy that the impedance of a liner specimen is firstly experimentally educed on a flow duct using the SFM, and then its accuracy is checked by comparing the numerical prediction with the measured wall sound pressure of the flow duct. Secondly, the effects of grazing flow and high-intensity sound on the impedance behavior of two single-layer liners are investigated based on comparisons between educed impedance and predictions by three impedance models. The performance of the SFM is validated by showing that the educed impedance leads to excellent agreement between the simulation and the measured wall sound pressure for different grazing flow Mach numbers and Sound Pressure Levels(SPLs) and over a frequency range from 3000 Hz down to 500 Hz. The grazing flow effect generally has the tendency that the acoustic resistance exhibits a slight decrease before it increases linearly with an increase in Mach,predicted successfully by the sound-vortex interaction theoretical model and the Kooi semi-empirical impedance model. However, the Goodrich semi-empirical impedance model gives only a simple linear relation of acoustic resistance starting from Mach zero. Additionally, when the SPL increases from 110 to 140 d B in the present investigation, the acoustic resistance exhibits a significant increase at all frequencies in the absence of flow; however, the resistance decreases slightly under a grazing flow of Mach 0.117. It indicates that the SPL effect can be greatly inhibited when flow is present,and the grazing flow effect can be reduced partly as well at a relatively high SPL.
