期刊文献+
共找到4篇文章
< 1 >
每页显示 20 50 100
基于多参考波的多径超声气体流量计设计 被引量:4
1
作者 高文平 《煤矿机电》 2019年第5期50-56,共7页
超声波气体流量计中使用了多种技术,如多普勒、相关性等,基于实验和基于测量传输时间的方法已经证明了它的优点并变得更加流行。在可用于确定超声波飞行时间(TOF)的技术中,包括阈值检测,互相关算法和其他数字信号处理算法,当接收到的超... 超声波气体流量计中使用了多种技术,如多普勒、相关性等,基于实验和基于测量传输时间的方法已经证明了它的优点并变得更加流行。在可用于确定超声波飞行时间(TOF)的技术中,包括阈值检测,互相关算法和其他数字信号处理算法,当接收到的超声信号受到严重干扰时,互相关算法具有更多优势。然而在多径流量计的应用中,参考波的选择变得困难。对此,在分析引入超声波噪声和波形畸变的影响因素的基础上,提出了一种有助于确定参考波的实用方法。在多路超声波气体流量计的应用中,超声波的每个路径的分析需要其自己的参考波。在案例研究中,设计并测试了6通道超声波气体流量计,其中气流通过管道。结果表明,与使用随机参考波相比,使用平均参考波可以显着提高TOF的流速精度和重复性。 展开更多
关键词 运输时间法 互相关 参考波 平均 多路超声波流量计
下载PDF
Implications of small-bowel transit time in the detection rate of capsule endoscopy: A multivariable multicenter study of patients with obscure gastrointestinal bleeding 被引量:10
2
作者 Carlo Maria Girelli Marco Soncini Emanuele Rondonotti 《World Journal of Gastroenterology》 SCIE CAS 2017年第4期697-702,共6页
AIMTo define the role of small-bowel transit time in the detection rate of significant small-bowel lesions.METHODSSmall-bowel capsule endoscopy records, prospectively collected from 30 participating centers in the Lom... AIMTo define the role of small-bowel transit time in the detection rate of significant small-bowel lesions.METHODSSmall-bowel capsule endoscopy records, prospectively collected from 30 participating centers in the Lombardy Registry from October 2011 to December 2013, were included in the study if the clinical indication was obscure gastrointestinal bleeding and the capsule reached the cecum. Based on capsule findings, we created two groups: P2 (significant findings) and P0-1 (normal/negligible findings). Groups were compared for age, gender, small-bowel transit time, type of instrument, modality of capsule performance (outpatients vs inpatients), bowel cleanliness, and center volume.RESULTSWe retrieved and scrutinized 1,433 out of 2,295 capsule endoscopy records (62.4%) fulfilling the inclusion criteria. Patients were 67 &#x000b1; 15 years old, and 815 (57%) were males. In comparison with patients in the P0-1 group, those in the P2 group (n = 776, 54%) were older (P &#x0003c; 0.0001), had a longer small-bowel transit time (P = 0.0015), and were more frequently examined in low-volume centers (P &#x0003c; 0.001). Age and small-bowel transit time were correlated (P &#x0003c; 0.001), with age as the sole independent predictor on multivariable analysis. Findings of the P2 group were artero-venous malformations (54.5%), inflammatory (23.6%) and protruding (10.4%) lesions, and luminal blood (11.5%).CONCLUSIONIn this selected, prospectively collected cohort of small-bowel capsule endoscopy performed for obscure gastrointestinal bleeding, a longer small-bowel transit time was associated with a higher detection rate of significant lesions, along with age and a low center volume, with age serving as an independent predictor. 展开更多
关键词 Capsule endoscopy Small-bowel transit time Detection rate Diagnostic yield Small bowel Obscure gastrointestinal bleeding PROKINETICS Suspect small-bowel bleeding
下载PDF
The optimized design of duct net disposal for filter-rods based on topology structure
3
作者 Lv wei 《International Journal of Technology Management》 2013年第3期98-100,共3页
The filter-rods were supplied through compressed air conveyed to cigarette-maker by transmitter in my factory. Usually, each maker has two feed-pipes, it adopts fixed and one-to-one fashion, with the flexible manufact... The filter-rods were supplied through compressed air conveyed to cigarette-maker by transmitter in my factory. Usually, each maker has two feed-pipes, it adopts fixed and one-to-one fashion, with the flexible manufacturing system extending, and it's original fashion unable to satisfy the needs of a wide range of cigarette brands already, so it cry for a viable and reliable substitute. This paper creatively bring forward the optimized fashion of duct net about filter-rods based on topology structure, it adopts Freud's algorithm and improved-separated algorithm in order to achieve the optimized route, it has a apparent effect to improve the transport stability and reduce the transport time of filter- rods. 展开更多
关键词 the problem of time control the problem of slow convergence improved-segmentation algorithm
下载PDF
Time-dependent density functional theory for quantum transport 被引量:3
4
作者 Yanho Kwok Yu Zhang GuanHua Chen 《Frontiers of physics》 SCIE CSCD 2014年第6期698-710,共13页
The rapid miniaturization of elect, ronic devices motivates research interests in quantum transport.Recently time-dependent quantum transport has become an important research topic. Here we re- view recent progresses ... The rapid miniaturization of elect, ronic devices motivates research interests in quantum transport.Recently time-dependent quantum transport has become an important research topic. Here we re- view recent progresses in the development of time-dependent density-functional theory for quantum transport including the theoretical foundation and numerical algorithms. In particular, the reducedsingle electron density matrix based hierarchical equation of motion, which can be derived from Liouville---von Neumann equation, is reviewed in details. The numerical implementation is discussed and simulation results of realistic devices will be given. 展开更多
关键词 tim-dependent density functional theory (TDDFT) quantum transports nonequilibrium Green's function
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部