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31.
A Well-Balanced Positivity-Preserving Quasi-Lagrange Moving Mesh DG Method for the Shallow Water Equations 下载免费PDF全文
A high-order, well-balanced, positivity-preserving quasi-Lagrange moving
mesh DG method is presented for the shallow water equations with non-flat bottom
topography. The well-balance property is crucial to the ability of a scheme to simulate perturbation waves over the lake-at-rest steady state such as waves on a lake or
tsunami waves in the deep ocean. The method combines a quasi-Lagrange moving
mesh DG method, a hydrostatic reconstruction technique, and a change of unknown
variables. The strategies in the use of slope limiting, positivity-preservation limiting,
and change of variables to ensure the well-balance and positivity-preserving properties are discussed. Compared to rezoning-type methods, the current method treats
mesh movement continuously in time and has the advantages that it does not need to
interpolate flow variables from the old mesh to the new one and places no constraint
for the choice of a update scheme for the bottom topography on the new mesh. A selection of one- and two-dimensional examples are presented to demonstrate the well-balance property, positivity preservation, and high-order accuracy of the method and
its ability to adapt the mesh according to features in the flow and bottom topography. 相似文献
32.
Ying He & Xiaofei Zhao 《Communications In Computational Physics》2022,31(4):1180-1214
In this paper, we consider the numerics of the dispersion-managed Korteweg-de Vries (DM-KdV) equation for describing wave propagations in inhomogeneous media. The DM-KdV equation contains a variable dispersion map with discontinuity,
which makes the solution non-smooth in time. We formally analyze the convergence
order reduction problems of some popular numerical methods including finite difference and time-splitting for solving the DM-KdV equation, where a necessary constraint on the time step has been identified. Then, two exponential-type dispersion-map integrators up to second order accuracy are derived, which are efficiently incorporated with the Fourier pseudospectral discretization in space, and they can converge
regardless of the discontinuity and the step size. Numerical comparisons show the advantage of the proposed methods with the application to solitary wave dynamics and
extension to the fast & strong dispersion-management regime. 相似文献
33.
目的:探讨二补助育汤对胚胎着床障碍模型小鼠子宫内膜形态及血管生成素-1(Ang-1)mRNA、血管内皮生长因子(VEGF)mRNA的表达和定位的影响。方法:24只ICR雌性小鼠随机分为空白组、模型组、戊酸雌二醇组、二补助育汤组,每组6只,用米非司酮建立胚胎着床障碍动物模型,各组给予相应药物灌胃,妊娠第5天处死小鼠后,检测各组妊娠率、平均着床位点数、子宫内膜Ang-1和VEGF mRNA表达量及其蛋白定位。结果:模型组小鼠平均胚胎着床位点数、Ang-1 mRNA、VEGF mRNA表达量明显低于空白组(均P<0.05);与模型组比较,二补助育汤组平均胚胎着床位点数、Ang-1 mRNA、VEGF mRNA表达量显著提高(均P<0.05)。结论:二补助育汤可提高子宫内膜Ang-1和VEGF蛋白表达量,促进子宫内膜血管生成,从而提高子宫内膜容受性。 相似文献
34.
目的 系统评价德尔菲法在中医临床证候应用中的应用现状,为后续规范与完善证候研究方法提供参考。方法 计算机检索五大数据库关于中医临床证候研究中应用德尔菲法的研究,检索时限自建库至2021年6月1日,由两名研究人员独立进行文献筛选、质量评估和资料提取,对质量A级和B级的研究进行分析。结果 经过质量评价共纳入201篇文献,其中原始研究199篇,方法学研究9篇。研究方向包括候分布特点、证候诊断标准、单一证候研究、证候要素研究、证候变化规律等八类。192篇文献对德尔菲法具体实施进行报道。结论 中医临床证候研究中德尔菲法应用整体较为科学,但在证候研究细节实施尚有不足,有待形成符合中医证候特色的德尔菲法标准规范临床应用。 相似文献
35.
目的:探讨改进Seldinger法经皮穿刺腹膜透析置管术在终末期肾病患者中的应用效果。方法:选取2019年12月~2020年12月于本院进行腹膜透析置管术的终末期肾病患者61例,随机分为观察组(31例)和对照组(30例),对照组患者采用常规开腹手术置管,观察组采用改进Seldinger法置管,比较两组患者完成置管手术的相关指标(手术时间、术后排气时间、切口长度、住院时间),术后3d、1个月患者并发症发生情况。结果:较对照组,观察组手术时间、术后排气时间均更短,腹部切口长度更短(P<0.05),两组患者住院时间比较(P>0.05),观察组穿刺成功率明显高于对照组(100.00%,80.00%,χ2=6.88,P=0.01)。较对照组,观察组患者术后3d并发症发生率明显低于对照组(22.58%,50.00%,χ2=4.97,P=0.03),观察组患者术后1个月并发症发生率明显低于对照组(19.35%,53.33%,χ2=7.05,P=0.01)。结论:对终末期肾病患者运用改进Seldinger法经皮穿刺腹膜透析置管术进行置管可有效缩短手术时间和术后排气时间,创口较小,患者术后早期、远期并发症较少,临床应用效果较好。 相似文献
36.
Kelly H. M. Cooijmans Roseriet Beijers Bonnie E. Brett Carolina de Weerth 《Maternal & child nutrition》2022,18(1):e13241
This randomized controlled trial evaluated the effect of a 5-week daily skin-to-skin contact (SSC) intervention between mothers and their full-term infants, compared with care-as-usual, on exclusive and continued breastfeeding duration during the first post-natal year. Healthy pregnant women (n = 116) from a community sample were enrolled and randomly allocated to the SSC or care-as-usual condition. SSC mothers were requested to provide one daily hour of SSC for the first five post-natal weeks. Twelve months post-partum, mothers indicated the number of exclusive and continued breastfeeding months. Multiple regression analyses were conducted using intention-to-treat, per-protocol and exploratory dose–response frameworks. In intention-to-treat analyses, exclusive and continued breastfeeding duration was not different between groups (exclusive: 3.61 ± 1.99 vs. 3.16 ± 1.77 months; adjusted mean difference 0.28, 95% confidence interval [CI] ?0.33 to 0.89; p = 0.36; continued: 7.98 ± 4.20 vs. 6.75 ± 4.06 months; adjusted mean difference 0.81, 95% CI ?0.46 to 2.08; p = 0.21). In per-protocol analyses, exclusive and continued breastfeeding duration was longer for SSC than care-as-usual dyads (exclusive: 4.89 ± 1.26 vs. 3.25 ± 1.80 months; adjusted mean difference 1.28, 95% CI 0.31–2.24; p = 0.01; continued: 10.81 ± 1.97 vs. 6.98 ± 4.08 months; adjusted mean difference 2.33, 95% CI 0.13–4.54; p = 0.04). Exploratory dose–response effects indicated that more SSC hours predicted longer exclusive and continued breastfeeding duration. This study demonstrates that for the total group, the 5-week daily SSC intervention did not extend exclusive and continued breastfeeding duration. However, for mothers performing a regular daily hour of SSC, this simple and accessible intervention may extend exclusive and continued breastfeeding duration by months. Future studies are required to confirm these promising findings. Trial registration: Netherlands Trial Register (NTR5697). 相似文献
37.
Susan Thurstans Natalie Sessions Carmel Dolan Kate Sadler Bernardette Cichon Sheila Isanaka Dominique Roberfroid Heather Stobaugh Patrick Webb Tanya Khara 《Maternal & child nutrition》2022,18(1):e13246
In 2014, the Emergency Nutrition Network published a report on the relationship between wasting and stunting. We aim to review evidence generated since that review to better understand the implications for improving child nutrition, health and survival. We conducted a systematic review following PRISMA guidelines, registered with PROSPERO. We identified search terms that describe wasting and stunting and the relationship between the two. We included studies related to children under five from low- and middle-income countries that assessed both ponderal growth/wasting and linear growth/stunting and the association between the two. We included 45 studies. The review found the peak incidence of both wasting and stunting is between birth and 3 months. There is a strong association between the two conditions whereby episodes of wasting contribute to stunting and, to a lesser extent, stunting leads to wasting. Children with multiple anthropometric deficits, including concurrent stunting and wasting, have the highest risk of near-term mortality when compared with children with any one deficit alone. Furthermore, evidence suggests that the use of mid-upper-arm circumference combined with weight-for-age Z score might effectively identify children at most risk of near-term mortality. Wasting and stunting, driven by common factors, frequently occur in the same child, either simultaneously or at different moments through their life course. Evidence of a process of accumulation of nutritional deficits and increased risk of mortality over a child's life demonstrates the pressing need for integrated policy, financing and programmatic approaches to the prevention and treatment of child malnutrition. 相似文献
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