辐射板强化喷管换热与红外抑制效果试验研究

试验研究了在发动机喷管中加装金属辐射板前后,喷管壁面温度、热喷流温度与喷管红外辐射特征的变化。结果表明,加装金属辐射板后,热喷流与喷管壁面之间的热量传递显著增强,热喷流中心温度降低,壁面温度明显升高,在90°方向上,热喷流3～5μm波段的红外辐射强度降低了38.5%。文中从热喷流、喷管壁面以及金属辐射板等相关部件的温度变化情况对红外辐射强度的变化原因进行了解释。      

ERP沙盘模拟在电子商务专业中的应用分析

某公司设计的ERP沙盘模拟课程在我院电子商务专业应用了几个学期,对激发学生兴趣、提高学生的团队意识和竞争意识起了良好的促进作用。作者在多年实践基础上,提出了课程中出现的常见问题及改进的合理化建议。     

The stress of travel

International travel is an essential part of the life of elite athletes, both for competition and training. It is also becoming increasingly common among recreational sportspersons. Long-distance travel is associated with a group of transient negative effects, collectively referred to as 'travel fatigue', which result from anxiety about the journey, the change to an individual's daily routine, and dehydration due to time spent in the dry air of the aircraft cabin. Travel fatigue lasts for only a day or so, but for those who fly across several time zones, there are also the longer-lasting difficulties associated with 'jet lag'. The problems of jet lag can last for over a week if the flight crosses 10 time zones or more, and they can reduce performance and the motivation to train effectively. Knowledge of the properties of the body clock enables the cause of the difficulties to be understood (an unadjusted body clock), and forms the basis of using light in the new time zone to promote adjustment of the body clock. Sleep loss and its effects are important components of jet lag, and attempts to promote sleep by the use of melatonin and other hypnotics are also relevant. Sleep loss is also found in those who undertake challenges that involve long periods where the normal consolidated sleep of 8 h length is not possible. Advice on sleep regimens in such circumstances is given.     

The longest journeys in Super Rugby: 11 years of travel and performance indicators

ABSTRACT

Regular air travel is common in sport. The aim of this study was to understand the extent to which travel has affected Super Rugby teams’ performance from 2006, the first season with available Key Performance Indicators (KPIs), to 2016. Data were analysed with mixed linear models for the effects of number of time-zones crossed (east or west), travel duration, the away-match disadvantage, difference in ranking, a set of amendments to the laws of Rugby Union in 2008, a change in competition format (introduction of a conference system) in 2011, and a secular trend. In 2006, the predicted combined effects of travelling 24 h across 12 time-zones and playing away were trivial or small and negative but generally unclear for most of the KPIs in both directions of travel. In 2016 more effects were clear, small and negative for westward travel, while most effects for eastward travel were clear, small to moderate and negative. Most KPIs showed small to moderate increases over the 11 years, while difference in ranking, the introduction of new rules and game format led to mostly small changes. Changes in the physical demands of the game, and inadequate recovery time for long-haul travel can explain these effects.     

A computational method for analysis of underwater dolphin kick hydrodynamics in human swimming

We present a new method that combines the use of laser body scans, underwater video footage, software-based animation, and a fully unsteady computational fluid dynamics technique to simulate and examine the hydrodynamics of the dolphin kick. The focus of the current work is to model this particular stroke in all its complexity with minimal ad-hoc assumptions or simplifications. Simulations of one female and one male swimmer (both at about 1.7 m beneath the water surface) at velocities of 0.95 and 1.31 m/s and Strouhal numbers of 1.21 and 1.06 respectively are presented. Vorticity and fluid velocity profiles in the wake are examined in detail for both swimmers. A three-dimensional vortex ring is clearly identified in the wake for one of the cases and a two-dimensional slice through the ring corroborates previous experiments of Miwa et al. (2006). We also find that most of the thrust is produced by the feet and in both cases the down-kick produces much larger thrust than the up-kick.     

明万历间延绥中路边墙的沙壅问题——兼谈生态环境研究中的史料运用

万历二年至三十八年延绥中路边墙外,出现平墙大沙。这不是人为所致。因为明初河套基本是无人地带,正统至成化十二年,前后约四十年,延绥军民确实曾经入套垦殖但总体规模不大。成化十二年以后,明令禁止,且蒙古部落在套内活动日益频繁,入套垦殖结束。所以百年以后,万历间大规模沙壅平墙的现象是自然界突变的结果。又,目前生态环境研究中,对史料不作具体分析,随文按需摘引的做法,是不科学的。     

Critical Heat Flux in Forced Convective Boiling with a Wall Jet

Thecriticalheatflux (CHF)intheforcedconvec tiveboilingwithawalljethasbeenstudied.KattoandIshii[1 ] measuredtheCHFofsaturatedwater,R1 1 3 ,andtrichloroethane (ρl/ ρg =2 0 3— 1 60 3)atatmosphericpressureforadownwardfacingplanewalljet,varyingthevelocityufrom 1 .5to 1 5m/sandtheheaterlengthLfrom 1 0to 2 0mm ,andproposedEq.(1 )topredicttheirCHFdata.　　　 qcoρghfgu=0 .0 1 6 4(ρl/ ρg) 0 .867(σρlu2 L) 1 / 3 (1 )　　KattoandHaramura[2 ] ,further,haveextendedtheirvelocityrangefromu =1 .8t…     

利用锦屏磷矿尾矿砂进行无土栽培的研究

选用适宜的营养液配方 ,用锦屏磷矿尾矿砂作栽培基质对生菜、小白菜、芹菜、马蹄莲等 8种植物进行无土栽培实验 ,取得了良好的效果。对实芹而言 ,营养液配方A最适合其生长 ,其效果比砂培还要理想     

略论水泥地面通病防治

建筑施工的质量是百年大计的关键,而水泥地面的质量是建筑施工诸多环节中的一环。本文指出水泥地面质量的两大通病,一是地面起砂,二是地面空鼓。作者分析这两大通病的表现,产生的原因,同时提出预防措施和治理办法,这些举措无疑会对建筑施工特别是对水泥地面施工起重大的指导作用。