38 research outputs found

    Segregation by Race in Public Schools Retrospect and Prospect

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    Solar energy conversion has been intensively studied in past decades and has been shown to be greatly effective for solving the serious environmental pollution and energy shortage problems. Photoelectrocatalysis and photovoltaics have been considered as the two main approaches for solar energy conversion and utilization, which are generally involved with nanostructured materials and/or catalytic processes, greatly affecting the efficiencies for solar energy conversion. Then, it is necessary to understand the relationship between the physical and chemical properties of nanomaterials and their performances for solar energy conversion. It is also important to explore the fundamentals in catalytic processes for solar energy conversion and make breakthrough in design and synthesis of nanomaterials or nanostructures, characterization of material properties, and performance of novel devices and systems. The aim of this special issue is to present some recent progress in the field of advanced catalysis and nanostructure design for solar energy conversion. A brief summary of all accepted papers is provided below

    Early Abnormal Temperature Structure of X-ray Looptop Source of Solar Flares

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    This Letter is to investigate the physics of a newly discovered phenomenon -- contracting flare loops in the early phase of solar flares. In classical flare models, which were constructed based on the phenomenon of expansion of flare loops, an energy releasing site is put above flare loops. These models can predict that there is a vertical temperature gradient in the top of flare loops due to heat conduction and cooling effects. Therefore, the centroid of an X-ray looptop source at higher energy bands will be higher in altitude, for which we can define as normal temperature distribution. With observations made by {\it RHESSI}, we analyzed 10 M- or X-class flares (9 limb flares). For all these flares, the movement of looptop sources shows an obvious U-shaped trajectory, which we take as the signature of contraction-to-expansion of flare loops. We find that, for all these flares, normal temperature distribution does exist, but only along the path of expansion. The temperature distribution along the path of contraction is abnormal, showing no spatial order at all. The result suggests that magnetic reconnection processes in the contraction and expansion phases of these solar flares are different.Comment: 11 pages, 4 figure

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

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    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

    Synthesis of Branch Fluorinated Cationic Surfactant and Surface Properties

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    A novel fluorinated quaternary ammonium salt cationic surfactant N,N,N-trimethyl-2-[[4-[[3,4,4,4-tetrafluoro-2-[1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl]-1,3-bis(tri-fluoromethyl)-1-buten-1-yl]oxy]-benzoyl]amino]-iodide (FQAS) was synthesized successfully, and its structure was characterized by FTIR, 1H-NMR, 19F-NMR, and MS. The surface activities of FQAS and the effect of temperature, electrolyte, and combination with hydrocarbon surfactant were investigated. The results showed that FQAS exhibited excellent surface activity and combination with hydrocarbon surfactant

    A method of image processing with QR code ablated on rough and highly reflective metal surface by laser

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    For the purpose of solving the tough problem of the recognition of QR code which is marked on rough and highly reflective metal surface by laser, this work proposes a method of image processing based on multi-feature fusion. This method was requested to establish the integrated feature combined by color feature, texture feature and classify pixel points by means of k-means clustering, then optimize the image of QR code by morphology, Finally, this method was applied to the QR code Laser marking on the AL97 casting aluminum ingots to recognize, then compare with the accepted method OTSU algorithm, The experimental results show that the method is effective obviously

    A method of image processing with QR code ablated on rough and highly reflective metal surface by laser

    No full text
    For the purpose of solving the tough problem of the recognition of QR code which is marked on rough and highly reflective metal surface by laser, this work proposes a method of image processing based on multi-feature fusion. This method was requested to establish the integrated feature combined by color feature, texture feature and classify pixel points by means of k-means clustering, then optimize the image of QR code by morphology, Finally, this method was applied to the QR code Laser marking on the AL97 casting aluminum ingots to recognize, then compare with the accepted method OTSU algorithm, The experimental results show that the method is effective obviously
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