Modeling intraparticle transports during propylene polymerizations using supported metallocene and dual function metallocene as catalysts: Single particle model

Two improved multigrain models (MGMs) for preparing homopolypropylene and long chain branched polypropylene via propylene polymerization using silica-supported metallocene or dual function metallocene as catalysts are presented in this paper. The presented models are used to predict the intraparticle flow fields involved in the polymerizations. The simulation results show that the flow field distributions involve dare basically identical. The results also show that both the two polymerization processes have an initiation stage and the controlling step for them is reaction-diffusion-reaction with the polymerization proceeding. Furthermore, the simulation results show that the intra particle mass transfer resistance has significant effect on the polymerization but the heat transfer resistance can be ignored

Tree Richness and Climatic Dominance in Different Districts of Beijing City, China

Nonparametric richness estimators, generalized linear models, canonical correspondence analysis and indicator species analysis were applied for revealing the tree diversity and structure in the districts of Beijing City, China. The results indicated that Mentougou has the highest richness of tree species, occupying 75.8% of total species concerned. Based on the non-parametric richness estimators, the tree richness in Beijing area was estimated around 71-79. From the dendrogram of Wards minimum variance algorithm, the studied districts can be grouped into three main groups, the first two of which have representative species as selected by indicator species analysis. Group III (including districts Yanqing and Pinggu) does not have representative species, implying that this areal group is not valid if more species distribution is added in the cluster analysis. Environmental correlation based on generalized linear models found that the current tree richness in Beijing City is significantly associated to the following factors: minimum temperature of coldest month, mean temperature of driest quarter and precipitation of driest quarter, which can take account of 95.8% of the total deviance in species richness. Based on complementary principle, the most valuable districts for tree conservation in Beijing were Mentougou, Miyunxian, Haidianqu and Yanqingxian respectively

Tris(2,2′-bipyridine)­nickel(II) hexa­molybdate

The asymmetric unit of the title compound, [Ni(C10H8N2)3][Mo6O19], consists of one complex [(Ni(C10H8N2)3]2+ cation and one Lindqvist-type [Mo6O19]2− polyanion. The Ni2+ ion is in a distorted octa­hedral coordination by six N atoms from three chelating 2,2′-bipyridine ligands. The Lindqvist-type anion exhibits the characteristic Mo—O bond-length distribution, with the shortest bonds being the Mo—O(terminal) bonds [mean = 1.679 (2) Å] and the longest being those to the central O atom [mean = 2.318 (7) Å]. A number of C—H⋯O inter­actions contribute to the crystal packing

Communicating climate change to young adults in China: examining predictors of user engagement on Chinese social media

Purpose: This study aims to examine how the Chinese climate nongovernmental organization “Chinese Weather Enthusiasts” engaged youth through video strategies. Design/methodology/approach: The research proposed a framework grounded in the 5W model and message sensation value (MSV) to analyze the relationship between video content and user interaction. It categorized Bilibili videos into outer and inner features and introduced rhetorical strategies as content elements. A hybrid video coding framework was used, combining machine learning and deep learning (computer vision) for analyzing formal features, while manual coding was used for content features. Findings: The results revealed that video length, long shots and the number of scenes positively influenced coins and favorites, whereas personification had a negative impact. In addition, tone and language intensity were positively correlated with user engagement. Originality/value: This study offers insights regarding video production for climate communication, broadening the focus from text and images to video content and providing evidence-based guidance for practitioners

Exploring functional and non-functional requirements of social media on knowledge sharing

Social media (SM) are designed for easily online information sharing and communicating among people, and the sites relate to entertainment, educational and business domains. From requirement elicitation and analysis, social media provide effective communication and sharing on the knowledge and information of system development among stakeholders. This paper aims to identify the relevant functional and non-functional requirements for knowledge sharing (KS), and explore the relationships between the requirements and perceived social media to support knowledge sharing. Hence, a survey was conducted that involve software requirements practitioners in order to gather the requirements on KS. Besides that, partial least squares (PLS) method was used to evaluate the hypothesis and research model. The findings of this study represented that there was a positive and strong relationship between functional requirements and Perceived SM to support requirements knowledge sharing (RKS), however, non-functional requirements has a weak relationship with Perceived SM to support RKS

Soil colloidal particles in a subtropical savanna : biogeochemical significance and influence of anthropogenic disturbances

Soil colloids (diameter < 1000 nm) are comprised mainly of clay minerals and organic matter, and play major roles in determining ion exchange capacity and in regulating key biogeochemical processes. Consequently, it is important to understand how soil colloids and their functions are influenced by land cover and anthropogenic disturbances. In grasslands, savannas, and other dryland ecosystems across the globe, woody plants are encroaching due to livestock grazing, fire suppression, elevated CO2 concentrations, and climate change. These major land cover changes could influence soil colloidal properties, with implications for soil C, N, and P cycles. We assessed how woody encroachment, livestock grazing, and fire interact to influence soil colloidal properties in a juniper-oak savanna. Surface soils (0–10 cm) from the southern Great Plains (Texas, USA) were collected from long-term treatments differing in grazing intensity (none, moderate, and heavy) and fire history. Within each treatment, soil samples were taken under grass, juniper, and oak canopies. Water dispersible soil colloids (WDC, d < 500 nm) were isolated and analyzed by asymmetric flow field-flow fractionation and their P species by liquid-state 31P-nuclear magnetic resonance spectroscopy (31P NMR). Soil beneath oak and juniper canopies had smaller WDC and elevated colloidal organic carbon (OC) and P concentrations, especially in nanocolloid (<30 nm) and fine colloid (30–160 nm) size fractions. Woody encroachment enriched Ca, Fe, Al, Si and Mg in WDC in the ungrazed control, but not in any of the other grazed or burned areas. Colloidal soil P mainly occurred as orthophosphate and orthophosphate diesters, and was present as OC-Ca-P complexes in fine and medium colloid fractions (30–500 nm), while P in the nanocolloid fraction (<30 nm) was in direct association with Ca. Moderate grazing did not affect the retention of colloidal P, while heavy grazing potentially increased the loss risk of colloidal P. Fire accelerated soil P loss from colloid fractions only in woody areas. Our findings highlight that woody encroachment strengthens the retention of OC and P by soil colloids, consequently increasing overall C and P pools in savanna soils

Metasurface spectrometers beyond resolution-sensitivity constraints

Optical spectroscopy plays an essential role across scientific research and industry for non-contact materials analysis1-3, increasingly through in-situ or portable platforms4-6. However, when considering low-light-level applications, conventional spectrometer designs necessitate a compromise between their resolution and sensitivity7,8, especially as device and detector dimensions are scaled down. Here, we report on a miniaturizable spectrometer platform where light throughput onto the detector is instead enhanced as the resolution is increased. This planar, CMOS-compatible platform is based around metasurface encoders designed to exhibit photonic bound states in the continuum9, where operational range can be altered or extended simply through adjusting geometric parameters. This system can enhance photon collection efficiency by up to two orders of magnitude versus conventional designs; we demonstrate this sensitivity advantage through ultra-low-intensity fluorescent and astrophotonic spectroscopy. This work represents a step forward for the practical utility of spectrometers, affording a route to integrated, chip-based devices that maintain high resolution and SNR without requiring prohibitively long integration times

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

An analysis of knowledge sharing behaviors in requirement engineering through social media

Requirement engineering activities are very important for software development. However, it is difficult to capture and analyze requirements correctly and completely, and also, how to develop a set of accurate requirements is becoming an important issue. Despite there are many methods developed in order to gain more accurate requirements, there is lacking research highlight capturing more comprehensive requirements through knowledge sharing by using social media. Knowledge sharing is an interactive process which involves exchanging relevant knowledge such as information, idea, experience, knowledge know-how, and procedures from broader scope of resources in requirements engineering. Through knowledge sharing, the quality of communications between analysts and users is improved to make a good understanding of the users requirements. So that, the software developers can produce higher qualitative product. This paper proposes a flow of knowledge sharing activities through social media, and analyzes the knowledge sharing behaviors in process of requirements engineering

CALCULATION OF 3-D SURFACE CRACK STRESS INTENSITY FACTOR BASED ON APDL AND UIDL

In engineering,cracks are usually regarded as semi-elliptical surface cracks. It is not easy to establish a complete finite element model of a semi-elliptical surface crack,thus a quarter of the crack model is generally used to calculate the stress intensity factor by finite element method. This paper adopts APDL and UIDL technologies for secondary development of ANSYS software,establishes a complete model of semi-elliptical surface crack by simple interface operation with the method of model block processing. Using this method,the stress intensity factors of the central semi-elliptical crack and the oblique semielliptical crack were solved respectively. The results are basically consistent with the theoretical solution and the results in the literature,which shows that it is accurate and reliable to use the complete crack model established by this method to calculate the stress intensity factor. The combined development modeling function can be used to solve the stress intensity factors in complex structures under complex loads,and has important value for practical application of engineering