A modified piano key weir with a rounded nose and a parapet wall (MPKW) can improve the discharge capacity significantly compared to a standard piano key weir. However, the optimum of the inlet/outlet width ratio (Wi/...A modified piano key weir with a rounded nose and a parapet wall (MPKW) can improve the discharge capacity significantly compared to a standard piano key weir. However, the optimum of the inlet/outlet width ratio (Wi/Wo) on the discharge efficiency of MPKW is still not investigated numerically. The present work utilized the numerical modeling to investigate and analyze the effects of the inlet/outlet key width ratios on the hydraulic characteristics and discharge capacity of the MPKW. To validate the numerical model with the experimental data, the results indicate that the average relative error is 2.96%, which confirms that the numerical model is fairly well to predictthe specifications of flow over on the MPKW. Numerical simulation results indicated that the discharge capacity of the MPKW can be improved up to 8.5% by optimizing the Wi/Wo ratio ranging from 1.53 to 1.67 even if the other parameters of the MPKW keep unchanged. A big Wi/Wo ratio generally leads to an increase in discharge capacity at low heads and a little effect on the discharge efficiency at high heads. The discharge efficiency of the inlet and outlet crests increases up to 9.6% for high heads, while discharge efficiency of the lateral crest decreases up to 23.5% compared with the reference model. The findings of the study revealed that the intrinsic influencing mechanism of the Wi/Wo ratio on the discharge performance of MPKWs.展开更多
目的:评价补充不同维生素对预防早产儿支气管肺发育不良(BPD)的疗效。方法:检索中国知网(CNKI)、万方(Wan fang)、维普网(cqvip)、PubMed、Cochrane Library、Web of Science数据库,纳入关于补充维生素预防早产儿BPD的随机对照试验(RCT...目的:评价补充不同维生素对预防早产儿支气管肺发育不良(BPD)的疗效。方法:检索中国知网(CNKI)、万方(Wan fang)、维普网(cqvip)、PubMed、Cochrane Library、Web of Science数据库,纳入关于补充维生素预防早产儿BPD的随机对照试验(RCTs),筛选符合纳入标准的RCTs,运用Cochrane偏倚风险评估工具进行文献质量评价,通过贝叶斯网状meta分析,分析比较不同维生素预防BPD的疗效。结果:共纳入21篇RCTs,(3188例早产儿)。与安慰剂组相比,中等剂量补充维生素D(400~800IU/d,OR=0.41,95%Cl[0.18,0.90])、小剂量补充维生素A(<1333IU/kg/d,OR=0.50,95%Cl[0.25,0.95])与BPD发生率降低相关。小剂量补充维生素D(<400IU/d,OR=12.36,95%Cl[1.00,600.21])可能与早产儿死亡率增加相关。小剂量补充维生素E(OR=0.59,95%Cl[0.23,1.36]),大剂量补充维生素E(OR=0.74,95%Cl[0.14,3.64])置信区间较宽,2项与预防早产儿BPD关系不大。结论:补充中等剂量维生素D、小剂量维生素A可有效预防早产儿BPD发生。小剂量补充维生素D可能增加早产儿死亡率,提示早产儿补充维生素D时应予足量补充。目前尚未充分证实维生素E在预防BPD方面的有效性。展开更多
文摘A modified piano key weir with a rounded nose and a parapet wall (MPKW) can improve the discharge capacity significantly compared to a standard piano key weir. However, the optimum of the inlet/outlet width ratio (Wi/Wo) on the discharge efficiency of MPKW is still not investigated numerically. The present work utilized the numerical modeling to investigate and analyze the effects of the inlet/outlet key width ratios on the hydraulic characteristics and discharge capacity of the MPKW. To validate the numerical model with the experimental data, the results indicate that the average relative error is 2.96%, which confirms that the numerical model is fairly well to predictthe specifications of flow over on the MPKW. Numerical simulation results indicated that the discharge capacity of the MPKW can be improved up to 8.5% by optimizing the Wi/Wo ratio ranging from 1.53 to 1.67 even if the other parameters of the MPKW keep unchanged. A big Wi/Wo ratio generally leads to an increase in discharge capacity at low heads and a little effect on the discharge efficiency at high heads. The discharge efficiency of the inlet and outlet crests increases up to 9.6% for high heads, while discharge efficiency of the lateral crest decreases up to 23.5% compared with the reference model. The findings of the study revealed that the intrinsic influencing mechanism of the Wi/Wo ratio on the discharge performance of MPKWs.
文摘目的:评价补充不同维生素对预防早产儿支气管肺发育不良(BPD)的疗效。方法:检索中国知网(CNKI)、万方(Wan fang)、维普网(cqvip)、PubMed、Cochrane Library、Web of Science数据库,纳入关于补充维生素预防早产儿BPD的随机对照试验(RCTs),筛选符合纳入标准的RCTs,运用Cochrane偏倚风险评估工具进行文献质量评价,通过贝叶斯网状meta分析,分析比较不同维生素预防BPD的疗效。结果:共纳入21篇RCTs,(3188例早产儿)。与安慰剂组相比,中等剂量补充维生素D(400~800IU/d,OR=0.41,95%Cl[0.18,0.90])、小剂量补充维生素A(<1333IU/kg/d,OR=0.50,95%Cl[0.25,0.95])与BPD发生率降低相关。小剂量补充维生素D(<400IU/d,OR=12.36,95%Cl[1.00,600.21])可能与早产儿死亡率增加相关。小剂量补充维生素E(OR=0.59,95%Cl[0.23,1.36]),大剂量补充维生素E(OR=0.74,95%Cl[0.14,3.64])置信区间较宽,2项与预防早产儿BPD关系不大。结论:补充中等剂量维生素D、小剂量维生素A可有效预防早产儿BPD发生。小剂量补充维生素D可能增加早产儿死亡率,提示早产儿补充维生素D时应予足量补充。目前尚未充分证实维生素E在预防BPD方面的有效性。
