Models comparison

  • 文章类型: Journal Article
    石油和天然气处理设施中的储罐含有大量易燃化合物。一旦燃料-空气混合物被点燃,它可能会爆发大火或爆炸。对监测空气质量和评估健康风险的兴趣日益浓厚,这使得评估火灾后果成为一个重要问题。大气扩散模型,可以模拟污染物的空间分布,代表了这种评估越来越广泛的工具。
    本研究讨论了与炼油厂中假设的火灾相关的建模研究的设置和结果。
    选择最合适的色散模型后,即拉格朗日模型SPRAY和抽吸模型CALPUFF,讨论了所需输入数据的估计,专注于源变量,代表最不确定的输入数据。将模拟结果与监管限制进行比较,以有效评估环境后果。最后,我们采用敏感性分析来确定影响最大的变量.
    模拟结果表明,地面浓度值远低于所引用的长期限值。然而,最有趣的结果是,根据色散模型和建模的源类型,可以得到不同的结果。此外,敏感性研究表明,源区是最关键的变量,因为它根据建模的源类型确定了明显不同的行为,生产,在某些情况下,选定受体上污染物地面浓度的变异性高达+/-60%。
    根据所选模型和可用于描述发射物理的算法,结果显示对输入变量的敏感性不同。虽然这可以从数学的角度来解释,问题仍然存在,即逐案选择最接近被调查的附带源的真实行为的选项。
    作者声明没有竞争的金融利益。
    UNASSIGNED: Storage tanks in oil and gas processing facilities contain large volumes of flammable compounds. Once the fuel-air mixture is ignited, it may break out into a large fire or explosion. The growing interest in monitoring air quality and assessing health risks makes the evaluation of the consequences of a fire an important issue. Atmospheric dispersion models, which allow for simulation of the spatial distribution of pollutants, represent an increasingly widespread tool for this type of evaluations.
    UNASSIGNED: The present study discusses the set up and results of a modeling study relevant to a hypothesized fire in an oil refinery.
    UNASSIGNED: After choosing the most suitable dispersion models, i.e. the Lagrangian model SPRAY and the puff model CALPUFF, estimation of the required input data is discussed, focusing on the source variables, which represent the most uncertain input data. The results of the simulations were compared to regulatory limits to effectively evaluate the environmental consequences. Finally, a sensitivity analysis was employed to identify the most influential variables.
    UNASSIGNED: The simulation results revealed that ground concentration values were far below the cited long-term limits. However, the most interesting outcome is that depending on the dispersion model and the source type modeled, different results may be obtained. In addition, the sensitivity study indicates that the source area is the most critical variable, since it determines a significantly different behavior depending on the modeled source types, producing, in some cases, variability in the pollutant ground concentrations on selected receptors up to +/- 60%.
    UNASSIGNED: Depending on the selected model and the algorithms available to describe the physics of emission, the results showed a different sensitivity to the input variables. Although this can be explained from a mathematical point of view, the problem remains of choosing case by case the option that best approximates the real behavior of the incidental source under investigation.
    UNASSIGNED: The authors declare no competing financial interests.
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  • 文章类型: Journal Article
    几种基于图像的计算模型已用于进行动脉粥样硬化斑块进展和易损性调查的机械分析。然而,这些模型的计算预测差异尚未在多患者水平上量化.从7名患者获得体内血管内超声(IVUS)冠状动脉斑块数据。七个具有/不具有圆周收缩的2D/3D模型,7例患者构建了循环弯曲和流体-结构相互作用(FSI),以进行模型比较并量化2D简化的影响,圆周收缩,FSI和循环弯曲斑块壁应力/应变(PWS/PWSn)和流动剪切应力(FSS)计算。使用来自7名患者的PWS/PWSn和FSS平均值(用于2D和3D薄层模型的388个切片)进行比较。与具有收缩过程的2D模型相比,没有收缩过程的2D模型高估了17.26%的PWS。7名患者在具有/不具有循环弯曲的3DFSI模型中曲率变化最大的位置处的PWS变化从15.07%到49.52%(平均=30.13%)。平均最大FSS,最大压力条件下纯流量模型的Min-FSS和Ave-FSS分别为4.02%,比具有循环弯曲的全FSI模型高11.29%和5.45%,分别。FSI和仅结构模型之间的平均PWS和PWSn差异仅为4.38%和1.78%。模型差异具有明显的患者差异。对于最小FSS预测,FSI和纯流量模型差异更大,值得注意的是,已知低FSS与斑块进展有关。仅结构模型可以提供PWS/PWSn计算,作为FSI模型的良好近似,以简化计算并节省时间。
    Several image-based computational models have been used to perform mechanical analysis for atherosclerotic plaque progression and vulnerability investigations. However, differences of computational predictions from those models have not been quantified at multi-patient level. In vivo intravascular ultrasound (IVUS) coronary plaque data were acquired from seven patients. Seven 2D/3D models with/without circumferential shrink, cyclic bending and fluid-structure interactions (FSI) were constructed for the seven patients to perform model comparisons and quantify impact of 2D simplification, circumferential shrink, FSI and cyclic bending plaque wall stress/strain (PWS/PWSn) and flow shear stress (FSS) calculations. PWS/PWSn and FSS averages from seven patients (388 slices for 2D and 3D thin-layer models) were used for comparison. Compared to 2D models with shrink process, 2D models without shrink process overestimated PWS by 17.26%. PWS change at location with greatest curvature change from 3D FSI models with/without cyclic bending varied from 15.07% to 49.52% for the seven patients (average = 30.13%). Mean Max-FSS, Min-FSS and Ave-FSS from the flow-only models under maximum pressure condition were 4.02%, 11.29% and 5.45% higher than those from full FSI models with cycle bending, respectively. Mean PWS and PWSn differences between FSI and structure-only models were only 4.38% and 1.78%. Model differences had noticeable patient variations. FSI and flow-only model differences were greater for minimum FSS predictions, notable since low FSS is known to be related to plaque progression. Structure-only models could provide PWS/PWSn calculations as good approximations to FSI models for simplicity and time savings in calculation.
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  • 文章类型: Comparative Study
    Forensic DNA phenotyping (FDP) has recently provided important advancements in forensic investigations, by predicting the physical appearance of a subject from a biological sample, using SNP markers. The majority of operable prediction models have been developed for iris color; however, replication studies to understand their applicability on a worldwide scale are still limited for many of them. In this work, 4 models for eye color prediction (IrisPlex, Ruiz, Allwood and Hart models) were systematically evaluated in a sample of 296 subjects of Italian origin. Genotypes were determined by a custom NGS-based panel targeting all the predictive SNPs included in the 4 tested models. Overall, 60-69% of the Italian sample could be correctly predicted with the IrisPlex, Ruiz and Allwood models, applying the recommended threshold. The IrisPlex model showed the lowest frequency of errors (17%), but also the highest number of inconclusive results (18%). In the absence of the threshold, the highest proportion of correct predictions was again obtained with the IrisPlex model (76%), followed by the Allwood (73%) and the Ruiz (65%) models. Lastly, the Hart predictive algorithm had the lowest error rate (2%), but the majority of predictions (87%) were restricted to the less informative categories of \"not-blue\" and \"not-brown\", and correct color predictions were obtained only for 11% of the sample. As observed in previous studies, the majority of incorrect and undefined predictions were ascribable to the intermediate category, which represented 25% of the Italian sample. An adjustment of the IrisPlex (multinomial logistic regression) and Ruiz models (Snipper Bayesian classifier) with Italian allele frequencies gave only minor improvements in predicting intermediate eye color and no remarkable overall changes in performance. This suggests an incomplete knowledge underlying the intermediate colors. Considering the impact of this phenotype in the Italian sample as well as in other admixed populations, future improvements of eye color prediction methods should include a better genetic and phenotypic characterization of this category.
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  • 文章类型: Journal Article
    Many watershed model interfaces have been developed in recent years for predicting field-scale sediment loads. They share the goal of providing data for decisions aimed at improving watershed health and the effectiveness of water quality conservation efforts. The objectives of this study were to: 1) compare three watershed-scale models (Soil and Water Assessment Tool (SWAT), Field_SWAT, and the High Impact Targeting (HIT) model) against calibrated field-scale model (RUSLE2) in estimating sediment yield from 41 randomly selected agricultural fields within the River Raisin watershed; 2) evaluate the statistical significance among models; 3) assess the watershed models\' capabilities in identifying areas of concern at the field level; 4) evaluate the reliability of the watershed-scale models for field-scale analysis. The SWAT model produced the most similar estimates to RUSLE2 by providing the closest median and the lowest absolute error in sediment yield predictions, while the HIT model estimates were the worst. Concerning statistically significant differences between models, SWAT was the only model found to be not significantly different from the calibrated RUSLE2 at α = 0.05. Meanwhile, all models were incapable of identifying priorities areas similar to the RUSLE2 model. Overall, SWAT provided the most correct estimates (51%) within the uncertainty bounds of RUSLE2 and is the most reliable among the studied models, while HIT is the least reliable. The results of this study suggest caution should be exercised when using watershed-scale models for field level decision-making, while field specific data is of paramount importance.
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