涡轮叶栅叶冠泄漏流动数值研究

以小展弦比涡轮叶栅为研究对象,利用三维数值计算的方法研究了篦齿数、篦齿排列型式、上下游压力以及径向间隙对叶冠泄漏流量的影响,并分析了泄漏流动与主流的相互作用。研究表明,叶片排上下游压比和径向间隙是影响叶冠泄漏流动的主要因素,篦齿数和篦齿排列型式对泄漏流量的大小和出口气流角均有重要影响。考虑了主流的影响之后,叶冠出口流动呈现出高度的三维性和周向不均匀性。在周向压力梯度的作用下,径向速度以正负交替的形式出现,而且周向速度和轴向速度则出现了明显的分层结构。      

Singular perturbation method applied to the closed-loop discrete optimal control problem

An improved singular perturbation method for the singularly perturbed, closed-loop discrete optimal control problem with two terminal boundary layer correction series is presented.     

应用脉冲多普勒对主动脉瓣狭窄下游流场均匀性的研究

目的　通过比较不同程度的主动脉瓣狭窄下游流场均匀性指标以及湍流切应力 (TSS)的差异 ,探讨流场均匀性指标与主动脉瓣狭窄程度的关系 ,及其对手术时机选择的临床应用价值 ;并分析 TSS在病变发展中可能的作用。　方法　对 33例不同程度的主动脉瓣狭窄患者采用脉冲多普勒超声技术 ,于左心室长轴和心尖五腔切面分别测定计算各点的流场均匀性指标以及 TSS。　结果　轻度、中度和重度主动脉瓣狭窄患者间流场均匀性指标最大速度差值 (ΔVmax)和 TSS差别有统计学意义 (P<0 .0 5 ,0 .0 1) ,主动脉瓣越狭窄流场均匀性越差 ,边壁 TSS越小。　结论不同程度的主动脉瓣狭窄之间流场均匀性存在明显的差别 ,其对主动脉瓣狭窄的临床分度及主动脉瓣狭窄患者手术时机的选择具有重要的临床价值。主动脉瓣狭窄程度越重 ,主动脉边壁区的 TSS越小 ,表明低 TSS分布变化在心血管系统狭窄性病变病理过程中可能产生重要作用。     

功能性鼻内镜手术中减少出血的麻醉管理研究进展

功能性鼻内镜手术(FESS)已被广泛应用于鼻窦炎和鼻息肉患者的临床治疗。外科医师必须依赖最佳的手术视野来确认解剖位置,但鼻腔空间狭小,即使是少量出血也会造成解剖结构难以辨别,导致手术时间延长,手术并发症的发生率增加。目前,鼻内镜手术出血原因主要包括3个方面,即手术因素、患者自身因素以及麻醉因素。本文从麻醉方式、机械通气、术中控制性降压、围术期用药等方面对能够减少鼻内镜手术中出血的麻醉技术进行综述,以期为该类手术的麻醉管理提供参考。     

Older women track and field athletes have enhanced calcaneal stiffness

Vigorous weight-bearing exercise is recommended to women as a method of osteoporosis prevention. This study examined older women athletes to see if they indeed were less likely to develop osteoporosis than those in the general population, and to investigate which factors could have contributed to these results. One hundred and thirty-nine women 40–88 years old, all competitors in a USA National Masters Track and Field Championships, volunteered for the study. Masters refers to competitors 40 years old. Their calcaneal stiffness (SI) was measured by a Lunar Achilles+ ultrasonometer. Subjects were also measured for height and weight, and completed a questionnaire on exercise history, diet, lifestyle factors, medical and menopausal issues, and use of hormone replacement therapy (HRT). The women, mean age 57.3 years, had an overall average SI of 99.5 (T-score = 0.04) which is equivalent to that of a 20-year-old woman and 20.8% higher than expected for women of their age. Their median SI remained not different from expected peak bone SI until the age of 70. For analysis, this cohort of women was divided into two groups: premenopausal and postmenopausal athletes. The SI of both groups was correlated with the earliest age at which they had first participated in sports or exercises that impart moderate to high strain rates to the lower limbs and with current participation in high impact track and field events. Variables correlated with SI in the general population, such as weight, HRT, previous fracture, hysterectomy, and current menopausal status, did not predict SI in this cohort. In conclusion, women competing in Masters track and field at the national level had calcaneal stiffness substantially higher than expected for women of their age in the general population, and their participation in vigorous sports and activities, either currently or at a younger age, was predictive of this association.