1,177 research outputs found
The Effect of substrate geometry and surface orientation on the film structure of DLC deposited using PECVD
No full textPotential applications of diamond-like carbon (DLC) coatings range from precision tools and biomedical implants to micro mechanical devices and engine components. Where uniform coatings are required on substrates with complex geometries, plasma enhanced chemical vapour deposition (PECVD) is often a preferred deposition method. As a non-line of sight process, the geometry of the substrate is often considered negligible. For this reason analysis of PECVD coatings, such as amorphous carbon, has mostly been concerned with reactor deposition variables, such as bias voltage, pressure and gas ratios. Samples are therefore usually prepared and positioned to minimise the influence of other variables. By depositing nominally similar DLC films on silicon samples positioned horizontally and vertically on the reactor cathode plate it was possible to examine the variations in the coating characteristics and mechanical properties that occur due to the geometry of the substrate being coated. Topographic measurements and analysis of bonding structures revealed significant heterogeneity in the coatings. Electron microscopy showed variation in surface structure as well as thickness disparities of up to 50% in the vertical sample. Atomic force microscopy showed roughness, Ra, varied from 0.37 nm to 15.4 nm between samples. Raman spectroscopy highlighted variations in the sp2/sp3 bonding ratios whilst micro wear tests demonstrated how these variations reduce the critical load performance. These effects are explained in terms of the deposition mechanisms involved and are related to variation in deposition species and geometrical field enhancements within the deposition chamber. Improved understanding of these local variations will aid in the optimization of coatings for complex substrate geometries
Relating quantitative soil structure metrics to saturated hydraulic conductivity
No full textSoil structure affects saturated hydraulic conductivity (Ks) by creating highly conductive macropores that preferentially transmit soil water. In this study, we explore the relationship between Ks and macropores in an Oxyaquic Vertic Argiudoll in northeastern Kansas. Macropores were quantified from an excavation wall using multistripe laser triangulation (MLT) scanning. Soil water contents were measured at four depths within a soil lysimeter installed within 2 meters of the MLT-scanned soil profile and adjacent to an Ameriflux tower monitoring precipitation, air temperature, and solar radiation. Selected hydraulic properties of soil horizons within the lysimeter were optimized to water content data using a Markov chain Monte Carlo technique in combination with the mobile-immobile water (MIM) model in HYDRUS-1D. Estimates of Ks varied between 4198 cm d-1 in the A horizon and 0.6 cm d-1 in a 2Btss2 horizon with strongly expressed wedge structure. Approximately 87% of the variation in Ks was explained by the geometric mean of the widths of pores quantified with the MLT technique and modified by the coefficient of extensibility (COLE). The use of COLE allows the widths of the macropores obtained at dry conditions to be approximated at saturation. Two models that predict Ks from either texture or water retention data resulted in Ks estimates that were similar to each other, but significantly lower than Ks values predicted with MIM in horizons where structural pores dominate water flow. This technique shows a great deal of promise in better understanding and predicting the relationship of soil structure to water flow.Peer reviewe
Contour Points based P2P Algorithm for Shape Matching and Image Retrieval
No full textBased on the extracted contours of objects from images, one point to point (P2P) method is proposed for shape matching and image retrieval. Taking contour of one object as reference, contour of another object is transformed to reach their best match, during which the similarity is evaluated by comparison of two corresponding sets of contour points. Translation, scaling and rotation are all considered in transformation, thus the algorithm is robust to objects with different position, size and posture. The experimental results are presented and compared with those from two popular shape based techniques, Hu invariant moments and Zernike moments. Performance of our new approach has proved its efficiency in both matching accuracy and computational expense, and it can be used in related applications together with the other kinds of shape features or even color features, texture features, et
Rates of Return to University Education: The Regression Discontinuity Design
No full textEstimating the rate of return to a university degree has always been difficult due to the problem of omitted variable biases. Benefiting from a special feature of the University Admission system in China, which has clear cutoffs for university entry, combined with a unique data set with information on individual National College Entrance Examination (NCEE) scores, we estimate the Local Average Treatment Effects (LATE) of university education based on a Regression Discontinuity design. To the best of our knowledge, this is the first study to use RD design to estimate the causal effect of a university education on earnings. Our results show that the rates of return to 4-year university education relative to 3-year college education are 40 and 60 per cent for the compliers in the male and female samples, respectively, which are much larger than the simple OLS estimations revealed in previous literature. Since in our sample a large proportion of individuals are compliers (45 per cent for males and 48 per cent for females), the LATEs estimated in this paper have a relatively general implication. In addition, we find that the LATEs are likely to be larger than ATEs, suggesting that the inference drawn from average treatment effects might understate the true effects of the university expansion program introduced in China in 1999 and thereafter.rate of return to education, regression discontinuity design, China
Rates of Return to University Education: the Regression Discontinuity Design
No full textEstimating the rate of return to a university degree has always been difficult due to the problem of omitted variable biases. Benefiting from a special feature of the University Admission system in China, which has clear cutoffs for university entry, combined with a unique data set with information on individual National College Entrance Examination (NCEE) scores, we estimate the Local Average Treatment Effects (LATE) of university education based on a Regression Discontinuity design. To the best of our knowledge, this is the first study to use RD design to estimate the causal effect of a university education on earnings. Our results show that the rates of return to 4-year university education relative to 3-year college education are 40 and 60 per cent for the compliers in the male and female samples, respectively, which are much larger than the simple OLS estimations revealed in previous literature. Since in our sample a large proportion of individuals are compliers (45 per cent for males and 48 per cent for females), the LATEs estimated in this paper have a relatively general implication. In addition, we find that the LATEs are likely to be larger than ATEs, suggesting that the inference drawn from average treatment effects might understate the true effects of the university expansion program introduced in China in 1999 and thereafter.Rate of return to education, Regression Discontinuity Design, China
Bacteriophages assisted bacteria to facilitate soil multifunctionality under organochlorine pesticide contamination
No full textVarieties of alternatives
No full textThis dissertation concerns two focus particles (jiu, dou) and wh-expressions (shenme ‘what’, na geren ‘which person’) in Mandarin Chinese. These items are systematically ‘ambiguous’ and have played important roles in various aspects of Mandarin grammar. An idea based on alternatives and varieties of alternatives in particular – following Chierchia’s 2013 analysis of the polarity system – is pursued to account for the systematic ambiguities. Unambiguous semantics of jiu, dou and wh-expressions is maintained and ‘ambiguity’ explained through varieties of alternatives interacting with other independently motivated aspects of the structure they occur in. A better understanding of a large array of phenomena that involve these items – exhaustivity, distributivity, questions and conditionals – is achieved.Ph.D.Includes bibliographical referencesby Mingming Li
Towards Cultural Resistance in a Postcolonial Context – Translating Culture-loaded Tourist Texts in Shantou
No full textAs tourist texts serve the triple function of providing information, expressing feelings and appealing to the reader, they contain both content-oriented information and culture-bound information. Through an analysis of the English translations of the Eight Sights of Shantou, this paper investigates how content-oriented information and culture-bound information is dealt with differently in the target text. The paper calls for a “thick translation” of culture-loaded tourist texts so as to resist the global hegemony of the Anglophone culture, preserve cultural richness and promote cultural diversity. </jats:p
Visualization studies on evidence-based medicine domain knowledge (series 2): structural diagrams of author networks.
No full textOBJECTIVE: To investigate the output of evidence-based medicine (EBM) researchers in China and elsewhere by examining the EBM domains they work within and the networks that exist among them; using visualization methods to analyze these relationships. This maps the current situation and helps with the identification of areas for future growth. METHODS: We used co-citation matrixes with Pathfinder networks and hierarchical clustering algorithms, and constructed a co-author matrix which were analyzed with a whole network approach. The analyzed matrixes were visualized with the UCINET program. RESULTS: Much of the development of EBM has been centered around three authors, David Sackett, Gordon Guyatt and L Manchikanti, within three different clusters. The main authors of EBM articles in China were divided into nine academic domains. The relations among core authors of articles indexed by the Science Citation Index (SCI) was loose. There was a stronger co-authorship network among core authors in the Chinese literature, with three groups and 21 cliques. Nine distinct academic communities appeared to have formed around Li Youping, Liu Ming and Zhang Mingming. CONCLUSION: The EBM literature contains several key clusters, with universities in high-income countries being the source of the majority of articles. Outside China, McMaster University in Canada, the original home of EBM, is the dominant producer of EBM publications. In China, Sichuan University is the main source of EBM publications. The EBM cooperation network in China is comprised of three major groups, the largest and most productive in this sample is led by Li Youping with Liu Ming, Zhang Mingming, Li Jing, Wang Li, Wu Taixiang, and Liu Guanjian as central members
Weighted spiking neural P systems with structural plasticity working in sequential mode based on maximum spike number
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