站在更高处——访国家质量竞争力指数课题研究小组负责人蒋家东博士

2011年6月8日,国家质检总局发布2010年全国制造业质量竞争力指数。根据对全国25万家制造企业相关数据的测算,2010年全国质量竞争力指数达到82.57,与2009年相比提高了0.43。这是继2006年首次发布竞争力指数后的第6次发布,发布时间     

航空公司策略对空中交通管制的影响

近年来,我国民用航空的发展呈现出多元化的格局。在国有航空公司快速发展的同时,民营航空也伴随着中国民航发展的契机快速成长起来。与此同时,我国广阔的民航市场前景以及航权的逐步开放,也让国际上越来越多的航空公司涌入中国,共享一片和谐的天空。航空公司的多元化也意味着各     

阿联酋的生活最幸福

最近,世界经济合作与发展组织对全球29个工业化国家进行了一项研究,通过比对各国白领们的具体案例,对他们每天的工作时间和日常安排作出了一项排名。调查结果显示,世界上每天平均工作时间最长的人是墨西哥人,他们每天花在有     

不允许缺货时存储空间存在限制的存储模型研究

针对经济订购批量公式假设中存储空间无限大这一条件不符合实际这一问题,提出了改进方案：租用场地,存储物品。针对这种方案建立了总平均费用存储模型,给出了在总平均费用最小意义下的最优存储决策。并给出实例验证其可行性。     

Numerical investigation of unsteady vortex breakdown past 80°/65° double-delta wing

An improved delayed detached eddy simulation （IDDES） method based on the k-x-SST （shear stress transport） turbulence model was applied to predict the unsteady vortex breakdown past an 80o/65o double-delta wing （DDW）, where the angles of attack （AOAs） range from 30° to 40°. Firstly, the IDDES model and the relative numerical methods were validated by simulating the massively separated flow around an NACA0021 straight wing at the AOA of 60°. The fluctuation properties of the lift and pressure coefficients were analyzed and compared with the available measurements. For the DDW case, the computations were compared with such mea-surements as the mean lift, drag, pitching moment, pressure coefficients and breakdown locations. Furthermore, the unsteady properties were investigated in detail, such as the frequencies of force and moments, pressure fluctuation on the upper surface, typical vortex breakdown patterns at three moments, and the distributions of kinetic turbulence energy at a stream wise section. Two dominated modes are observed, in which their Strouhal numbers are 1.0 at the AOAs of 30°, 32° and 34° and 0.7 at the AOAs of 36o, 38° and 40°. The breakdown vortex always moves upstream and downstream and its types change alternatively. Furthermore, the vortex can be identified as breakdown or not through the mean pressure, root mean square of pressure, or even through correlation analysis.     

Effect of turbulence on NO formation in swirling combustion

Turbulence affects both combustion and NO formation. Fluctuation correlations are ideally used for quantitative analysis. From the instantaneous chemical reaction rate expression,ignoring the third-order correlation terms, the averaged reaction rate will have four terms, including the term of averaged-variable product, a concentration fluctuation correlation term, and temperature-concentration fluctuation correlation term. If the reaction-rate coefficient is denoted as K, the temperature fluctuation would be included in the K fluctuation. In order to quantitatively study the effect of turbulence on NO formation in methane-air swirling combustion, various turbulencechemistry models are tested. The magnitudes of various correlations and their effects on the time-averaged reaction rate are calculated and analyzed, and the simulation results are compared with the experimental measurement data. The results show that among various correlation moments, the correlation between the reaction-rate coefficient K fluctuation with the concentration fluctuation is most important and is a strong nonlinear term.     

恰含d个非零对角元的布尔矩阵的传递指数

利用图论方法，研究了恰含d个非零对角元的布尔矩阵的传递指数的若干性质，并给出了这类布尔矩阵传递指数的上、下界估计。     

汇率升值加速推动股指创出5年新高

代码公司2006111020061210流通股本市盈率(亿股)通市值(亿元)涨跌幅2005年每股收益(元)000089.SZ深圳机场5.286.4221.59.492.450.2515(除权)25.53000099.SZ中信海直3.943.950.25%5.13620.290.177422.27600004.SH白云机场6.837.519.9675.100.2530.04600009.SH上海机场1617     

下体负压的性别差异

在进行达到晕厥前症状（BP和／或者心率骤降，但未丧失意识）的递增性下体负压（LBNP）实验时，女性的耐力比男性低61％。耐力评定的指标是累积压力指数（CSI，在实验方法中有详细说明）。最近，Convertino肯定了女性LBNP耐力低于男性的结论。在他的研究中，女性的CSI比男性低35％。Hogan等在一项达到晕厥前症状的LBNP实验中观察到：用CSI估算女性LBNP耐力比男性弱22％，这些最新的数据有力地证明了女性的LBNP应激耐力低于男性。更早的研究也证明女性LBNP耐力低于男性。