The tidal limit is the key interface indicating whether water levels will be affected by tidal waves, which is of great significance to navigation safety and regional flood control. Due to limitations in research meth...The tidal limit is the key interface indicating whether water levels will be affected by tidal waves, which is of great significance to navigation safety and regional flood control. Due to limitations in research methods, recent changes in the Yangtze River tidal limit, caused by sea level rise and large-scale engineering projects, urgently need to be studied. In this study,spectrum analysis was undertaken on measured water level data from downstream Yangtze River hydrological stations from2007 to 2016. The bounds of the tidal limit were identified through comparisons between the spectra and red noise curves, and the fluctuation range and characteristics were summarized. The results showed that:(1) During the extremely dry period, when the flow rate at Jiujiang station was about 8440 m3 s-1, the tidal limit was near Jiujiang; whereas during the flood season, when the flow rate at Jiujiang station was about 66700 m3 s-1, the tidal limit was between Zongyang Sluice and Chikou station.(2)From the upper to lower reach, the effect of the Jiujiang flow rate on the tidal limit weakens, while the effect of the Nanjing tidal range increases. The tidal limit fluctuates under similar flow rates and tidal ranges, and the fluctuation range increases with increasing flow rate and decreasing tidal range.(3) With the continued influence of rising sea levels and construction in river basin estuaries, the tidal limit may move further upstream.展开更多
<b>Background:</span></b><span style="font-family:""><span style="font-family:Verdana;"> Tidal expiratory flow limitation (tEFL) is defined as absence of increase...<b>Background:</span></b><span style="font-family:""><span style="font-family:Verdana;"> Tidal expiratory flow limitation (tEFL) is defined as absence of increase in air flow during forced expiration compared to tidal breathing and is related to dyspnea at rest and minimal exertion in patients with chronic airflow limitation (CAL). Tidal EFL has not been expressed as a continuous variable (0% - 100%) in previous analyses. </span><b><span style="font-family:Verdana;">Objective:</span></b><span style="font-family:Verdana;"> To relate the magnitude of tEFL to spirometric values and Modified Medical Research Council (MMRC) score and Asthma Control Test (ACT). </span><b><span style="font-family:Verdana;">Methods:</span></b><span style="font-family:Verdana;"> Tidal EFL was computed as percent of the tidal volume (0% - 100%) spanned (intersected) by the forced expiratory-volume curve. </span><b><span style="font-family:Verdana;">Results: </span></b><span style="font-family:Verdana;">Of 353 patients screened, 192 (114 M, 78 F) patients (136 with COPD, 56 with asthma) had CAL. Overall characteristics: (mean ± SD) age 59 ± 11 years, BMI 28 ± 7, FVC (% pred) 85 ± 20, FEV1 (% pred) 66 ± 21, FEV1/FVC 55% ± 10%, RV (% pred) 147 ± 42. Tidal EFL in patients with tEFL was 53% ± 39%. Using univariate analysis, strongest correlations were between tEFL and FVC and between tEFL and RV in patients with BMI < 30 kg/m</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;">. In patients with nonreversible CAL, tEFL was positively associated with increasing MMRC, negatively with spirometric measurements, and positively with RV/TLC. In asthmatics, ACT scores were higher in patients with mean BMI ≥ 28 kg/m</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> (p < 0.00014) and RV/TLC values > 40% (p < 0.03). </span><b><span style="font-family:Verdana;">Conclusions:</span></b><span style="font-family:Verdana;"> Dyspnea is strongly associated with tEFL and lung function, particularly in patients with nonreversible CAL. Air trapping and </span><span style="font-family:Verdana;">BMI contribute to tEFL.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 51761135023 & 41476075)the China Geological Survey Nanjing Center Project (Grant No. DD20170246)
文摘The tidal limit is the key interface indicating whether water levels will be affected by tidal waves, which is of great significance to navigation safety and regional flood control. Due to limitations in research methods, recent changes in the Yangtze River tidal limit, caused by sea level rise and large-scale engineering projects, urgently need to be studied. In this study,spectrum analysis was undertaken on measured water level data from downstream Yangtze River hydrological stations from2007 to 2016. The bounds of the tidal limit were identified through comparisons between the spectra and red noise curves, and the fluctuation range and characteristics were summarized. The results showed that:(1) During the extremely dry period, when the flow rate at Jiujiang station was about 8440 m3 s-1, the tidal limit was near Jiujiang; whereas during the flood season, when the flow rate at Jiujiang station was about 66700 m3 s-1, the tidal limit was between Zongyang Sluice and Chikou station.(2)From the upper to lower reach, the effect of the Jiujiang flow rate on the tidal limit weakens, while the effect of the Nanjing tidal range increases. The tidal limit fluctuates under similar flow rates and tidal ranges, and the fluctuation range increases with increasing flow rate and decreasing tidal range.(3) With the continued influence of rising sea levels and construction in river basin estuaries, the tidal limit may move further upstream.
文摘<b>Background:</span></b><span style="font-family:""><span style="font-family:Verdana;"> Tidal expiratory flow limitation (tEFL) is defined as absence of increase in air flow during forced expiration compared to tidal breathing and is related to dyspnea at rest and minimal exertion in patients with chronic airflow limitation (CAL). Tidal EFL has not been expressed as a continuous variable (0% - 100%) in previous analyses. </span><b><span style="font-family:Verdana;">Objective:</span></b><span style="font-family:Verdana;"> To relate the magnitude of tEFL to spirometric values and Modified Medical Research Council (MMRC) score and Asthma Control Test (ACT). </span><b><span style="font-family:Verdana;">Methods:</span></b><span style="font-family:Verdana;"> Tidal EFL was computed as percent of the tidal volume (0% - 100%) spanned (intersected) by the forced expiratory-volume curve. </span><b><span style="font-family:Verdana;">Results: </span></b><span style="font-family:Verdana;">Of 353 patients screened, 192 (114 M, 78 F) patients (136 with COPD, 56 with asthma) had CAL. Overall characteristics: (mean ± SD) age 59 ± 11 years, BMI 28 ± 7, FVC (% pred) 85 ± 20, FEV1 (% pred) 66 ± 21, FEV1/FVC 55% ± 10%, RV (% pred) 147 ± 42. Tidal EFL in patients with tEFL was 53% ± 39%. Using univariate analysis, strongest correlations were between tEFL and FVC and between tEFL and RV in patients with BMI < 30 kg/m</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;">. In patients with nonreversible CAL, tEFL was positively associated with increasing MMRC, negatively with spirometric measurements, and positively with RV/TLC. In asthmatics, ACT scores were higher in patients with mean BMI ≥ 28 kg/m</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> (p < 0.00014) and RV/TLC values > 40% (p < 0.03). </span><b><span style="font-family:Verdana;">Conclusions:</span></b><span style="font-family:Verdana;"> Dyspnea is strongly associated with tEFL and lung function, particularly in patients with nonreversible CAL. Air trapping and </span><span style="font-family:Verdana;">BMI contribute to tEFL.
