小型亚热带半日潮河口中的湍流

在天然河口,污染物的输送是由湍流动量混合驱动的,而弥散的大小却难以被准确地预测。这是由于对河口的湍流结构缺乏基础的认识而造成的。介绍在一个小型的亚热带半日潮河口进行的高频率及连续50 h的湍流实地测量的情况。在研究的浅水(低潮水深小于0．5 m)小型河口中,使用了最适用于这种水体的声学多普勒流速仪进行测量,并进行了完整的后处理工作。河口水流是一个波动的过程,各种宏观流动参数随潮周期和其它大尺度的过程而波动,但是湍流特性是由即时局部流动特性所决定,它们基本不受流动历程的影响,其结构和瞬时变化受多种机理影响。这导致其只与水流剪切力引起的湍流边界层平衡相关。所有湍流特性在潮周期中均有大波动是本次研究数据的一个显著特征,这一特征在此前少有记载,但本次的测量数据与过往数据的一大差别是,数据连续测量的时间长且频率高。这将为波动特性的动量交换系数及积分时间和长尺度提供新的信息,这些湍流特性不应被视为不变的。     

On Nonlinear Control Systems with Multiple Time Scales

An order reduction procedure for nonlinear control systems with multiple time scales is introduced. A limit system for the slowest motion describing the situation that all singular perturbation parameters vanish is constructed. For this purpose a refined two-scale averaging method is used in a way that allows a re-iteration. For vanishing control range the results reduce to the well-known Tychonoff theorem on order reduction for singularly perturbed ODEs.     

不同规模地质体剩余油的形成与分布研究

针对非均质多层砂岩油田高含水期剩余油分布的复杂性,通过室内物理模拟实验、检查井资料分析、矿场剩余油综合分析,从宏观到微观对油藏规模级、油层规模级、层内规模级和孔隙规模级等4种不同规模地质体剩余油的影响因素进行分析,研究不同规模地质体剩余油的形成、分布特征及成因类型.针对不同规模地质体的剩余油类型,指出相应的挖潜方法.图4表2参39     

Oxidation limited life times of chromia forming ferritic steels

Long term, cyclic oxidation studies of three high – Cr, ferritic steels were carried out at 800°C and 900°C in air. It was found that with decreasing sample thickness the life time of the mentioned alloys decreases due to breakaway phenomena. This effect is caused by faster exhaustion of the chromium reservoir from the bulk alloy in case of thinner components. The observed life time limits can be predicted with reasonable accuracy by a theoretical model, using oxide growth rate parameters, initial alloy Cr content and critical Cr content required for protective chromia scale formation. In the calculation it has, however, to be taken into account that the oxidation rates of the steels increase with decreasing specimen thickness.     

The reading grade level of common measures in child and adolescent clinical psychology.

The purpose of this article is to provide easily accessible readability information for 49 parent- and 35 child- and adolescent-report measures commonly used by clinicians and researchers. There is a great deal of variability in reading ability required across measures. The majority of parent-report measures (65%) required reading ability above the 8th grade level. The average child-/adolescent-report measure required reading ability above the 6th grade level. Given the potential contribution of readability to a measure's reliability, validity, and overall utility, examining and accounting for readability should be a more common practice in test construction and administration (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the consistency of individual classification using short scales.

Short tests containing at most 15 items are used in clinical and health psychology, medicine, and psychiatry for making decisions about patients. Because short tests have large measurement error, the authors ask whether they are reliable enough for classifying patients into a treatment and a nontreatment group. For a given certainty level, proportions of correct classifications were computed for varying test length, cut-scores, item scoring, and choices of item parameters. Short tests were found to classify at most 50% of a group consistently. Results were much better for tests containing 20 or 40 items. Small differences were found between dichotomous and polytomous (5 ordered scores) items. It is recommended that short tests for high-stakes decision making be used in combination with other information so as to increase reliability and classification consistency. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The use of the 18O2‐exposure + SIMS‐based approach to investigate the spallation mechanisms of alumina scales

Spallation of the protective alumina scale accelerates the oxidation‐induced degradation of ?alumina formers’?. Despite of the vast evidence of this process its mechanism has not been elucidated, so far. This paper reports the results of the scale spallation mechanism investigation using a novel ¹⁸O₂‐exposure + SIMS‐based approach. The FeCrAl‐type alumina‐forming alloys, without and with Zr additions, were subjected to high temperature exposure at 1473 K in ¹⁸O₂‐rich atmosphere and, subsequently, cooled down in air. The surfaces exposed after spallation were observed using SEM, while high resolution SIMS was used to determine the elemental distributions. The obtained results indicate that: (i) in all cases the spallation occurs according to the adhesive‐mode; (ii) for reactive‐element‐free alloys the scales spalls away at temperatures high enough to enable the re‐oxidation of the exposed surface already during cooling; (iii) for the Zr‐containing alloys the spallation occurs at fairly low temperatures. Two practical implications of the obtained results should be noted: (i) oxide layers and not ‘bare substrate’ result from the scale spallation process during cooling; (ii) the formation of oxide layers during cooling may affect the behaviour of the system during subsequent heating to the reaction temperature.     

Role of length scales on microwave thawing dynamics in 2D cylinders

Microwave (MW) thawing of 2D frozen cylinders exposed to uniform plane waves from one face, is modeled using the effective heat capacity formulation with the MW power obtained from the electric field equations. Computations are illustrated for tylose (23% methyl cellulose gel) which melts over a range of temperatures giving rise to a mushy zone. Within the mushy region the dielectric properties are functions of the liquid volume fraction. The resulting coupled, time dependent non-linear equations are solved using the Galerkin finite element method with a fixed mesh. Our method efficiently captures the multiple connected thawed domains that arise due to the penetration of MWs in the sample. For a cylinder of diameter D, the two length scales that control the thawing dynamics are D/D_p and D/λ_m, where D_p and λ_m are the penetration depth and wavelength of radiation in the sample respectively. For D/D_p, D/λ_m?1 power absorption is uniform and thawing occurs almost simultaneously across the sample (Regime I). For D/D_p?1 thawing is seen to occur from the incident face, since the power decays exponentially into the sample (Regime III). At intermediate values, 0.2<D/D_p, D/λ_m<2.0 (Regime II) thawing occurs from the unexposed face at smaller diameters, from both faces at intermediate diameters and from the exposed and central regions at larger diameters. Average power absorption during thawing indicates a monotonic rise in Regime I and a monotonic decrease in Regime III. Local maxima in the average power observed for samples in Regime II are due to internal resonances within the sample. Thawing time increases monotonically with sample diameter and temperature gradients in the sample generally increase from Regime I to Regime III.     

考虑源荷储协同优化的增量配售电公司决策模型

增量配售电公司(IDR)具有灵活性资源多元化、经营方式复杂化的特点.合理制定购售电策略、充分利用灵活性资源是IDR提升市场竞争力的关键.为此,考虑源荷储规划和运行的特点,提出了IDR多时间尺度源荷储协同优化综合决策模型.首先,从当前中国电力中长期交易向现货市场过渡的实际需求出发,构建了基于电量合约分解曲线的IDR购电模型.其次,采用用户价格弹性和消费者心理学理论模拟了零售环节中用户的合同类型选择与可中断负荷响应行为.然后,以最大化经营利润为目标,构建了面向IDR合同购电组合、售电定价、用户侧可中断负荷采购与调用、储能配置与运行等决策的综合优化模型.最后,以某区域IDR为例进行仿真分析,结果表明通过综合优化源荷储决策,IDR可以灵活应对合约价格和代理用户结构的变化,最大化自身利润.     

Proposal of a uniform color scale for virgin olive oils

A new color scale was developed from a broad data set of 1700 virgin olive oil samples over four crop seasons, which can be considered highly representative of the whole color range of virgin olive oils available in Spain. This color scale provides a new set of 60 color standards, improving the results achieved by the old 60-color standards proposed by the bromthymol blue method. Seeking the greatest possibility of including a near match between colors of virgin olive oils and proposed standards, we developed our new color scale using a recent uniform color space, with standards placed in a regular rhombohedral lattice like the one employed by the Uniform Color Scales of the Optical Society of America. The average color difference between each of the 1700 virgin olive oils and its nearest standard is reduced from 8.17 CIELAB units, using the bromthymol blue standards, to 3.99 CIELAB units using the new standards. Within a color tolerance of 7.0 CIELAB units, 93.2% of our virgin olive oils can be classified with the new standards, but only 59.1% with the bromthymol blue ones. In the interest of future adoption, the performance of the new color standards should be tested by industry and researchers.