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关键词： 镍渣   势函数   分子动力学模拟   配位数   均方位移  

摘要： 从非经验参数角度构建基于两原子模型的Fe_(x)O-SiO_(2)-CaO-MgO-"NiO"渣的势函数,利用分子动力学模拟揭示调控镍渣组分与结构及物理化学性能之间的关系。结果表明:BMH(Born-Mayer-Huggins)势函数能够较好表征Fe_(x)O-SiO_(2)-CaO-MgO-"NiO"系镍渣的势能。当镍渣中CaO含量为15 wt.%时,Si4+-Si4+间配位数最小,此时熔渣的聚合度最低,有利于扩散。当Fe元素由Fe^(2+)转换为Fe^(3+)后,和O^(2-)结合能力更强,会导致熔渣更难以扩散,因而镍渣的黏度迅速升高,造成冶炼条件恶化,因此在镍闪速熔炼时要严格控制Fe^(2+)/Fe^(3+)的比例。模拟计算的黏度与实测值吻合较好,表明构建的势函数能够较好地反映镍渣的物化性能。

关键词： Gross-Pitaevskii equation   Scalar auxiliary variable   High-order   Structure-preserving scheme  

摘要： In this paper, we design a novel class of arbitrarily high-order structure-preserving numerical schemes for the time-dependent Gross-Pitaevskii equation with angular momentum rotation. Based on the idea of the scalar auxiliary variable approach which is proposed in the recent papers [J. Comput. Phys., 353 (2018) 407-416 and SIAM Rev., 61(2019) 474-506] for developing energy stable schemes for gradient flow systems, we firstly reformulate the Gross-Pitaevskii equation into an equivalent system with a modified energy conservation law. The reformulated system is then discretized by the Gauss collocation method in time and the standard Fourier pseudo-spectral method in space, respectively. We show that the proposed schemes can preserve the discrete mass and modified energy exactly. Numerical results are addressed to verify the efficiency and high-order accuracy of the proposed schemes. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Tapered fluidized bed (TFB)   Multi-Wall carbon nanotube (MWCNT)   Minimum fluidization velocity   Elevated temperature   Wavelet analysis  

摘要： In this work, the fluidization characteristics of gas-agglomerated carbon nanotube (CNT) particles flow in a tapered fluidized bed (TFB) without a distributor were investigated between 180 and 680 degrees C for the first time. The objective of this work was to investigate the effect of temperature on minimum fluidization velocity (U-mf) and dynamic characteristics of gas-agglomerated CNT particles flow at elevated temperature. To this end, the experimental work was divided into two phases. In the first phase, the influence of temperature on the U mf and the correlations of U-mf for agglomerated CNT particles at different bed temperatures were investigated and obtained. In the second phase, the dynamic characteristics of gas-agglomerated CNT particles flow in the TFB without a distributor at elevated temperature were studied in detail via time-series analysis methods. Experimental results revealed that the U-mf decreased for agglomerated CNT particles with the increase of temperature, and the correlations could be reasonable predicted the U-mf over the range of variables investigated. The inhomogeneous dynamic characteristics were existed in the bed at elevated temperature in the meso-scale due to the stochastic features of small bubbles or cavities movement. Moreover, though the time-series parameters (standard deviation, wavelet energy distribution, and homogeneous index) of the dynamic characteristics were different, the gas-agglomerated CNT particles flow behaviors under different operating conditions showed a high sensitivity to the temperature from the fixed bed to the partial fluidization regime. (C) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

关键词： flow cytometry   immunohistochemistry   Milan system   salivary gland   small tissue block  

摘要： Background: Milan system for reporting salivary gland cytopathology (MSRSGC) was proposed to provide a standardized reporting system for salivary gland fine needle aspiration biopsies. Modified Menghini type semi-automatic aspiration biopsy needles provide small tissue fragments (STFs), as well as cellular smears, and immunohistochemical and molecular studies can be performed using the STFs. Aims: We aimed to evaluate the contribution of STFs and ancillary techniques to pre-operative diagnosis of salivary gland lesions. Materials and Methods: In this study, smears of 287 cases with histopathological correlation were re-reviewed and assigned to one of the MSRSGC categories. In the second step, histopathological and immunohistochemical findings in STFs were evaluated together with cytological findings. Final diagnoses were obtained with the inclusion of flow cytometry (FC) results when available. Risk of malignancy (ROM) was calculated for each diagnostic category. Results: In the evaluation based on smears, a specific diagnosis could be obtained in 64.8% of the cases. ROMs were 0% for nondiagnostic (ND), 5.6% for non-neoplastic (NN), 55% for atypia of undetermined significance (AUS), 0.6% for benign neoplasm (BN), 27.8% for salivary gland neoplasm of uncertain malignant potential (SUMP), and 100% for suspicious for malignancy (SFM) and malignant (M) categories. With the addition of histopathological and immunohistochemical findings and FC results, a specific diagnosis could be obtained in 75.2% of the cases. ROMs were 0% for ND, 4.5% for NN, 53.8% for AUS, 0.6% for BN, 0% for SUMP, and 100% for SFM/M categories. Conclusions: STFs contribute correct categorization of salivary gland lesions. The major contribution of ancillary methods is in the SUMP category.

关键词： Aquatic insect   Current velocity   TITAN2   Flow reduction   Water flow categories  

摘要： The LIFE Index can be useful to determine the effect of changes in river flow on the community of aquatic macroinvertebrates and as a tool for the implementation of environmental flows. This study demonstrates how to classify aquatic macroinvertebrates into a flow category in order to adjust the LIFE Index to Costa Rica. A panel of experts was surveyed to classify the most common genera into a water velocity category, based on their experience. Also, for one-year, aquatic macroinvertebrates were collected in the low and middle basin of the Naranjo River under different velocities, and by using the TITAN2 package, their respective thresholds for current velocity were determined. Variation was observed in the responses of the expert panel;however, several taxa overlapped by more than 60% between the expert classification and the TITAN2 test results. The TITAN2 test assigned a velocity threshold to 32 genera, with the inflection point being 0.1 m/s. The expert panel served as a tool to assign a category to those genera that the TITAN2 test did not contemplate. Organisms without morphological adaptations to survive fast flowing conditions decreased in frequency above 0.1 m/s, while genera related to moderate and high velocities increased in frequency. Through the panel of experts and the TITAN2 test, it was possible to assign the most common genera in the country to a current velocity category and therefore adjust the LIFE index. (C) 2020 European Regional Centre for Ecohydrology of the Polish Academy of Sciences. Published by Elsevier B.V. All rights reserved.

关键词： Protrusion recognition   Feature recognition   Recognition of inner and outer faces   B-rep model   Thin-wall part  

摘要： Thin-wall plastic parts exist in many products and are frequently manufactured by injection molding. The inner surface of a thin-wall part has many functional and structural features, typically divided into depressions and protrusions. While recognition of protrusion features is important in mold flow analysis, this recognition is difficult owing to the complexity and variety of the designed shapes. The purpose of this study was to develop a method for the detection and classification of protrusion features on thin-wall plastic parts. In the proposed algorithm, the inner and outer faces of a part model were detected first. Auxiliary faces, including translational, wall, and bottom faces, were recognized next. With auxiliary faces available, protrusion faces can thus be recognized and grouped in accordance with their neighboring relationship. A feature classification algorithm was finally implemented to classify five types of protrusions, namely tubes, ribs, columns, polygon blocks, and irregular extrusions. A detailed description of the procedures in each step of the proposed algorithm is provided. Twelve CAD models and analysis results are also presented to demonstrate the feasibility of the proposed protrusion recognition algorithm.

关键词： Otolith chemistry   Concentration-discharge   Water chemistry   Random forests  

摘要： Tracemetals found in the calcified structures of fish (i.e. otolith, scales and vertebrae) serve as proxies for the ambient water composition at the time of mineralization, and these trace metals are increasingly used as a tool for assessing population structure and the migratory patterns of fish. However, the appropriate scale (e.g. resolution) for such applications can be uncertain because of a poor understanding of the spatiotemporal variations of metal-to-calcium ratios (Me:Ca) in the studied watersheds. This study aims to assess Me:Ca spatiotemporal variability within the St. Lawrence River and nine major tributaries and evaluate the ability of random-forest models to correctly identify rivers on the basis of their elemental composition. We tested the influence of daily discharge on four measured ratios (Sr:Ca, Ba:Ca, Mg:Ca and Mn:Ca) to document local and regional trace element sources and dynamics. The four element ratios displayed a low spatiotemporal variation, reflecting a marked stability over time. We observed that most element- and tributary-specific concentration-discharge relationships were either not significant or showed a weak influence, thereby confirming a stable point source dynamic. The classification performance based on a four-element model (Sr:Ca, Ba:Ca, Mg:Ca and Mn:Ca) produced a classification accuracy of 92.5%, which correspond to a small decrease of accuracy compared to the full model (25 elements, 96.6% of correct classification). A classification based on two elements (Sr:Ca and Ba:Ca) produced a lower classification accuracy (72.6%). Classification errors related mainly to tributaries in close proximity, a problem tempered by grouping these geochemically similar watersheds. Our results show that surveys of the elemental fingerprint of regional tributaries within a given region can provide critical information to determine the appropriate scale (tributary or watershed) for trace metal analysis of the hard-calcified parts of fish. (C)

标准号: GB/T 39797-2021

摘要： 本标准规定了测量玻璃熔体表面张力的测量原理、仪器设备、试样、试验、结果计算与表示、试验报告。本标准适用于座滴法测量玻璃熔体表面张力。