1,115 research outputs found
Adapting image processing and clustering methods to productive efficiency analysis and benchmarking: A cross disciplinary approach
No full textThis dissertation explores the interdisciplinary applications of computational methods in quantitative economics. Particularly, this thesis focuses on problems in productive efficiency analysis and benchmarking that are hardly approachable or solvable using conventional methods. In productive efficiency analysis, null or zero values are often produced due to the wrong skewness or low kurtosis of the inefficiency distribution as against the distributional assumption on the inefficiency term. This thesis uses the deconvolution technique, which is traditionally used in image processing for noise removal, to develop a fully non-parametric method for efficiency estimation. Publications 1 and 2 are devoted to this topic, with focus being laid on the cross-sectional case and panel case, respectively. Through Monte-Carlo simulations and empirical applications to Finnish electricity distribution network data and Finnish banking data, the results show that the Richardson-Lucy blind deconvolution method is insensitive to the distributio-nal assumptions, robust to the data noise levels and heteroscedasticity on efficiency estimation. In benchmarking, which could be the next step of productive efficiency analysis, the 'best practice' target may not perform under the same operational environment with the DMU under study. This would render the benchmarks impractical to follow and adversely affects the managers to make the correct decisions on performance improvement of a DMU. This dissertation proposes a clustering-based benchmarking framework in Publication 3. The empirical study on Finnish electricity distribution network reveals that the proposed framework novels not only in its consideration on the differences of the operational environment among DMUs, but also its extreme flexibility. We conducted a comparison analysis on the different combinations of the clustering and efficiency estimation techniques using computational simulations and empirical applications to Finnish electricity distribution network data, based on which Publication 4 specifies an efficient combination for benchmarking in energy regulation. This dissertation endeavors to solve problems in quantitative economics using interdisciplinary approaches. The methods developed benefit this field and the way how we approach the problems open a new perspective
Simulation of sound generated by large-scale vortices in a shear layer by hybrid DVM/APE approach
No full textIn this paper, sound generated by large-scale votices in a two-dimensional low-Mach number turbulent shear layer is investigated. A hybrid DVM/APE (Discrete-Vortex Model and Acoustic Perturbation Equations) approach is proposed to study this vortex sound phenomenon. A discrete-vortex model is used to simulate unsteady fluid motions of the trailing edge shear layer. A conformal mapping is applied to solve the 2D inviscid flow near the half plane, which is originally used for the problem of a slit geometry. At the trailing edge of the plane, the effect of fluid's viscosity is imposed by a vortex shedding model and Kutta condition. The unsteady flow field is obtained after DVM simulation. The background mean flow field is acquired by a time-average algorithm. Then, acoustic perturbation equations are solved to obtain the acoustic field by CAA approaches with both acoustic sources and the background mean flow field determined from the results of DVM. Results demonstrate that this hybrid DVM/APE method is a feasible approach to simulate sound generated by the motions of vortices.</p
Young people’s information practices in library makerspaces as informal learning environments
No full textWithin the past decade, the maker movement and culture have received a lot of interest and support from the government, research institutes, museums, libraries, and schools in the United States. Makerspaces are important because they fit in with broader concerns of science, technology, engineering, and mathematics (STEM) education and provide informal learning opportunities for people to engage in situated and practical intelligence that contributes formal learning. A review of the literature on library makerspaces shows a growing but still limited number of empirical studies in Library and Information Science (LIS) that have explored this phenomenon, especially from the perspective of makerspace users, such as young people. It remains unknown how young people engage with information as they participate in library makerspace activities. This dissertation aims to understand the opportunities and desired outcomes of makerspaces in libraries from the perspective of young people, also to develop a holistic understanding of information practices of young people participating in makerspace activities, and to understand the affordances and constraints of technologies and materials in young people’s information practices. A total of twenty-one young people at two library makerspaces participated in this study. Based on the analysis of qualitative data from field observations, individual interviews, photovoice, and focus groups, this dissertation shows that from the perspective of young people, the opportunities and desired outcomes of makerspace participation are centered on four major themes: make, learn, social, and interest. Young people’s information practices of seeking, using, and sharing at the makerspaces are largely social oriented and embedded in their makerspace activities. One salient practice of becoming informed during makerspace activities is through tinkering and embodiment. Additionally, the makerspaces have a robust culture of asking and information sharing, in which young people can freely generate questions and engage in inquiry. The value of visual information is highlighted in young people’s information-searching practices in the library makerspaces. Situations when young people switch from individual to collaborative information practices are further identified. This dissertation has theoretical, methodological, and practical contributions and implications. Theoretically, it offers an empirical research-based conceptualization of library makerspaces, contributes to the body of scholarly work on young people’s information practices in everyday life and informal learning. Implications for professional practices include a visual guide for makerspace activities and strategies in supporting young people’s information practices in library makerspaces as informal learning environments.Ph.D.Includes bibliographical referencesby Xiaofeng L
Correction: Corrigendum: Protective effects of ginsenoside Rg1 on intestinal ischemia/reperfusion injury-induced oxidative stress and apoptosis via activation of the Wnt/β-catenin pathway
No full textScientific Reports 6: Article number: 38480; published online: 02 December 2016; updated: 31 May 2017 Guangzhi Wang, Anlong Ji and Xiaofeng Tian were omitted from the author list in the original version of this Article. In addition, an additional affiliation for Guo Zu was omitted. The correct affiliation is listed below:</jats:p
Phoebus 10: A Journal of Art History
No full texttableOfContents: Homage to the Past: The Art of Yin Xiaofeng by Ralph Gabbard and Liu Liu.. pages 5-1
The behavior of pesticide during beer brewing and the toxicity of pesticide using state-of-the-art omic tools
No full textBeer is an extremely popular beverage worldwide, representing the third-most popular drink after water and tea. And barley is the major raw material used for beer production. However, various combinations of pesticides are widely used at several stages of barley culti¬vation and during post-harvest storage to control pest and fungal disease. Hence, traces of these pesticides might remain in the beer produced from the treated ingredients. Hence, monitoring trace levels of pesticide residues during beer brewing and investigated the effects of pesticide residue on the quality of beer is essential.
First, the behavior and fate of 3 pesticides (triadimefon, malathion, and dichlorvos) and the main metabolites (triadimenol and malaoxon) during barley storage or beer processing were assessed using a pilot-plant equipment. The residues of all products were determined using liquid chromatography coupled with tandem mass spectrometry. Field investigation of the dissipation rate kinetics for triadimefon and malathion during storage indicated that their half-life was twice as high when 5 times the recommended dosage was used. Milling had little effect on removing dichlorvos and malathion residues, whereas they were substantially removed when the spent grains were mashed. The calculated processing factors after processing were all <1, indicating that the residual ratios of dichlorvos and malathion were reduced during the entire process. In conclusion, storage and processing extensively reduced pesticide residue levels in barley and beer; however, greater focus needs to be paid to the toxicity of their metabolites in commercial by-products.
Then we selected the triadimefon as the target fungicide to further study its behavior, the dissipation kinetics of TF during fermentation mediated by two different yeast strains, Saccharomyces cerevisiae IAPPST 1401 (Y1) and CICC 1202 (Y2), and found that Y2 promoted the degradation of TF. Response surface methodology was used to optimize fermentation process variables, in order to achieve the maximum removal rate of TF and the minimum production of its corresponding metabolite, triadimenol (TN). Triadimefon is also a widely used triazole fungicide with one chiral carbon center, Stereoselective degradation of triadimefon was found during barley storage, the half-life of S-(+)-triadimefon was 36.5d, 31.5d and 30.1d, while R-(-)-traidmefon was 69.3d, 53.3d and 33d under 4°C, 25°C and 40°C, respectively. During brewing process, both enantiomers of triadimefon were easily degraded. After fermentation, little triadimefon detected in the beer, while RS-(+) and SS-(-)-triadimenol were detectable. This research provides accurate information for evaluating the risk of food safety.
Furthermore, we investigated the effect of triadimefon affect the quality and flavor of the fermented beer, The effect of triadimefon on yeast growth and the sensory quality of beer were studied. There were significant differences in sensory quality between beer samples fermented with and without triadimefon based on data obtained with an electronic tongue and nose. Such an effect was most likely underlain by changes in yeast fermentation activity, including decreased utilization of maltotriose and most amino acids, reduced production of isobutyl and isoamyl alcohols, and increased ethyl acetate content in the fungicide treated samples. Furthermore, yeast metabolic profiling by phenotype microarray and UPLC/TOF-MS showed that triadimefon caused significant changes in the metabolism of glutathione, phenylalanine and sphingolipids, and in sterol biosynthesis. Thus, triadimefon negatively affects beer sensory qualities by influencing the metabolic activity of S. cerevisiae during fermentation, emphasizing the necessity of stricter control over fungicide residues in brewing by the food industry
Social Honeypot for Humans: Luring People Through Self-managed Instagram Pages
No full textSocial Honeypots are tools deployed in Online Social Networks (OSN) to attract malevolent activities performed by spammers and bots. To this end, their content is designed to be of maximum interest to malicious users. However, by choosing an appropriate content topic, this attractive mechanism could be extended to any OSN users, rather than only luring malicious actors. As a result, honeypots can be used to attract individuals interested in a wide range of topics, from sports and hobbies to more sensitive subjects like political views and conspiracies. With all these individuals gathered in one place, honeypot owners can conduct many analyses, from social to marketing studies. In this work, we introduce a novel concept of social honeypot for attracting OSN users interested in a generic target topic. We propose a framework based on fully-automated content generation strategies and engagement plans to mimic legit Instagram pages. To validate our framework, we created 21 self-managed social honeypots (i.e., pages) on Instagram, covering three topics, four content generation strategies, and three engaging plans. In nine weeks, our honeypots gathered a total of 753 followers, 5387 comments, and 15739 likes. These results demonstrate the validity of our approach, and through statistical analysis, we examine the characteristics of effective social honeypots.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Cyber Securit
Preliminary Evaluation of Existing Breaching Erosion Models
No full textThe ability to estimate the erosion rate along an underwater breach face is crucial to understand the evolution of breaching failure. To this end, breaching erosion models were developed and applied in numerical models. However, these erosion models have never been validated, owing to the scarcity of direct measurements of turbidity currents that accompany breaching. The aim of this study is to evaluate the existing breaching erosion models using direct measurements of recently performed laboratory experiments on breaching flow slides. We found out that the erosion model put forward by Mastbergen & Van Den Berg (2003) provides good agreement with the data and performs better than the one proposed by Van Rhee (2015). The latter tends to overestimate the erosion rate, particularly at steeper slopes.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Environmental Fluid Mechanic
Representation and Depiction of 2D Shapes using Parts
No full textWe describe a 2D shape abstraction system that aims to clarify the structure without loss of the expressiveness of the original shape. To do this, traditional approaches in computer graph-ics typically use simplification techniques based on local adjustments of vertices, edges and faces. However, this thesis argues that an effective depiction can benefit from a computational representation compatible with a human’s understanding of the shape. To support this argu-ment, we first present a system that parses a 2D planar shape into a part-based structure that approximately respects the structural organization in human perception. Then we show that simplifications of this representation align with the common artistic practices in shape abstrac-tion, in which only prominent parts are preserved and the visual structures are more clarified than using traditional simplification methods based on local adaptation of geometric details. To compute the part structure of a given shape, we first propose that a part connects to the rest of the shape via its transition. Then we use a simple but general model to mathematically locate and describe this transition. We show that our model generalizes previously discovered theories on how the human visual system parses a shape into parts. It also provides a plausible way of explanatory shape analysis that requires clean pruning of parts without leaving attach
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