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宾汉体泥浆湍流的统计特征及脉动频谱分布 被引量:4
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作者 王兆印 王兴奎 任裕民 《水利学报》 EI CSCD 北大核心 1993年第4期12-22,共11页
本文根据水槽试验和统计分析,探讨了泥浆湍流的脉动流速概率密度分布和各阶矩,自相关系数及频谱分布。泥浆湍流底部为间歇湍流层,偏态系数为正,而强脉动层上部和扩散层偏态系数为负,说明紊动产生于强脉动层下部(y^+=3—10),由于间歇紊动... 本文根据水槽试验和统计分析,探讨了泥浆湍流的脉动流速概率密度分布和各阶矩,自相关系数及频谱分布。泥浆湍流底部为间歇湍流层,偏态系数为正,而强脉动层上部和扩散层偏态系数为负,说明紊动产生于强脉动层下部(y^+=3—10),由于间歇紊动,分布曲线出现双峰,泥浆湍流自相关系数R显著大于清水,R(t)曲线呈波状,说明流速的脉动部分来自规则的波动。泥浆湍流的频谱分布迥异于清水流。1Hz左右的低频脉动能量在清水湍流中为10—20%,泥浆湍流中则达40—50%,浓度很高(265kg/m^3)时高达70%,同时在2—20Hz的主频范围内,能谱密度G(n)在清水湍流中有关系G(n)-n^(-6-5),而泥浆湍流中则演变成G(n)n-^(-(2-7))。 展开更多
关键词 泥浆湍流 统计 脉动频谱
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管内气固两相流型频谱-层析识别技术 被引量:1
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作者 潘卫国 李杨 +3 位作者 聂雪军 曹绛敏 王启杰 岑可法 《化工学报》 EI CAS CSCD 北大核心 2001年第9期775-781,共7页
基于压力脉动信号的频谱特性和管截面图像重建算法 ,以及提出的流型脉动 -层析模糊判别法则 ,对工程中经常遇到的均匀流、层状流以及有“堵管”危险的流动进行了有效的检测 ,发现本文所提出的用压力脉动信号的频谱特征 ,依据管截面图像... 基于压力脉动信号的频谱特性和管截面图像重建算法 ,以及提出的流型脉动 -层析模糊判别法则 ,对工程中经常遇到的均匀流、层状流以及有“堵管”危险的流动进行了有效的检测 ,发现本文所提出的用压力脉动信号的频谱特征 ,依据管截面图像重建算法 ,在流型脉动 -层析模糊判别法则下 ,对水平管内流型的检测是可行的 。 展开更多
关键词 气固两相流 流型 识别 工程流体力学 脉动频谱 压力信号 管截面 层析成像 图像重建
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变角调节斜流泵振动特性试验测试及数值模拟
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作者 苏晓珍 姚金玲 +1 位作者 张晨 解文辰 《安徽建筑大学学报》 2017年第2期31-35,共5页
大型斜流泵广泛应用于给水排水等重点水利工程中,振动大是影响其稳定运行的关键因素。本文首先对其实际运行过程进行测试,结合数值模拟技术对不同叶片角度下泵内部不稳定流动特性进行分析,结果发现:数值模拟监测点与实测点的脉动频谱变... 大型斜流泵广泛应用于给水排水等重点水利工程中,振动大是影响其稳定运行的关键因素。本文首先对其实际运行过程进行测试,结合数值模拟技术对不同叶片角度下泵内部不稳定流动特性进行分析,结果发现:数值模拟监测点与实测点的脉动频谱变化规律基本相同,脉动主要发生在低频区,转频为主因,通过频率为次因;在小流量区域均有一段不稳定区域,且叶片角度从-80到+20的调度过程中,不稳定区域逐渐增大,在80%以上效率区间,流量范围可以从8 m3/s达到21 m3/s;叶片角为+10时,有效扬程在误差最大,达到6.92%,而其他误差均在5%以内,最大效率误差均小于5%;叶片角为"+"的压力脉动大于叶片角为"-"角时的压力脉动,且最大值均出现在导叶与叶轮耦合交界面处。上述研究成果能够为同类变角调节叶片泵振动特性分析提供参考。 展开更多
关键词 斜流泵 双向FIS 现场测试 脉动频谱
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THE ALTERATION OF THE PULMONARY ARTERY FLOW SPECTRUM WITH PULMONARY HYPERTENSION
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作者 王国干 陈白屏 +1 位作者 刘汉英 蔡如升 《Chinese Medical Sciences Journal》 CAS CSCD 1999年第4期220-223,共4页
Objective and method. To research the alteration of pulmonary flow spectrum of patients with congenital heart disease and the relation between pulmonary flow spectrum and pulmonary artery pr... Objective and method. To research the alteration of pulmonary flow spectrum of patients with congenital heart disease and the relation between pulmonary flow spectrum and pulmonary artery pressure, 33 patients with congenital heart disease were examined by echocardiography and catheterization. Results. The result showed that the spectrum peak early occurring in patients with pulmonary hypertension and the degree of the spectrum peak early occurring was related to pulmonary artery pressure positively. The result suggested that when the pulmonary artery systolic pressure was over 100 mmHg, the flow spectrum showed slender pattern usually. Conclusion. The slender pattern in pulmonary flow spectrum could be a semi quantity parameter to predict that the pulmonary artery systolic pressure more than 100 mmHg. 展开更多
关键词 pulmonary hypertension ECHOCARDIOGRAPHY
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Bispectral index-guided sedation in transfemoral transcatheter aortic valve implantation:a retrospective control study
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作者 Wei HE Rong-rong HUANG +3 位作者 Qing-yu SHI Xian-bao LIU Jian-an WANG Min YAN 《Journal of Zhejiang University-Science B(Biomedicine & Biotechnology)》 SCIE CAS CSCD 2017年第4期353-359,共7页
Objective: Transcatheter aortic valve implantation (TAVI) is a minimally invasive therapy for elderly patients with severe aortic valve stenosis who were refused surgical aortic valve replacement because of the hig... Objective: Transcatheter aortic valve implantation (TAVI) is a minimally invasive therapy for elderly patients with severe aortic valve stenosis who were refused surgical aortic valve replacement because of the high perioperative risk. Traditionally, this procedure has been done under general anesthesia, but more recently local anesthesia and sedation have become popular. This research assessed the effectiveness of transfemoral TAVI under bispectral index (BIS)-guided sedation. Methods: In this single-center retrospective control analysis, clinical data, including demographic characteristics, echocardiography, periprocedural data, and main complications, were collected and assessed in 113 patients undergoing TAVI through the femoral artery under general anesthesia (GA group, n=36) and under BIS-guided sedation (SED group, n=77). Results: The demographic characteristics and echocardi-ographic parameters between the two groups were similar (P〉0.05). Two (2.6%) of patients were moved from BIS-guided sedation to general anesthesia for surgical reasons. Procedures were significantly shorter in the SED group than in the GA group ((127.10±44.43) min vs. (165.90±71.62) min, P=0.004). Patients in the SED group lost less blood and received significantly fewer red blood cells and catecholamines than those in the GA group (5.19% vs. 22.22%, P=0.017 and 67.53% vs. 97.22%, P〈0.001). The length of hospital stay was significantly shorter and there were fewer pulmonary complications in the SED group than in the GA group. Thirty-day mortality was similar between the two groups. Conclusions: BIS-guided sedation is a feasible and safe approach for transfemoral TAVl. The anes- thesiologist should choose the best anesthetic method according to the team's experience. 展开更多
关键词 Transcatheter aortic valve implantation SEDATION Bispectral index
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