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关键词： MPEG-DASH   MOOCs videos   Adaptive online streaming   Quality of Experience   Compression  

摘要： The Dynamic Adaptive Streaming over HTTP (MPEG-DASH) ensures online videos display of good quality and without interruption. It provides an adequate streaming for each display device and network transmission. This can be verfield of Massive Open Online Courses (MOOCs). In fact, MPEG-DASH tracks the bandwidth fluctuations so hat the learner profits from continuous streaming, without worrying about frequent interruption of courses videos. Therefore, the learners profit from an exceptional visual experience that improves their commitment level and eases the course assimilation. These MPEG-DASH assets can become more and more advantageous if a good choice of its parameters is made. Being a recent branch, the MPEG-DASH adaptive diffusion presents a research field where the efforts are still limited, even more for MOOCs videos. Most of the work published in this sense focus on the Quality of Service (QoS) and the technical specifications of the network transmission. In this paper, we aim to consider the quality of the streamed content that directly impacts the learners Quality of Experience (QoE). For this, we develop a content-aware dataset that includes several MOOCs videos of different characteristics and types. These videos are firstly encoded using the latest codecs then dashified according to a coding scheme of several combinations of bitrates and display resolutions. Then, and in order to enhance the learners QoE, the so generated MPEG-DASH manifest files and segments are subsequently exploited to study the most appropriate codecs, bitrates and segment durations for each type of MOOCs videos.

关键词： Variability measures   Association measures   Fuzzy sets   Relative frequencies   Categorical random variables  

摘要： The quantification of the variability of the categorical data is an important topic not only in statistics, but also in many other disciplines. We suggest different variability measures to describe the variability of categorical data. In our approach, any set of categorical data for a determinate categorical variable is treated as a fuzzy set. Therefore, measuring the variability of categorical data is the same as measuring its fuzziness. Different measures of association between two categorical variables are also proposed. The measures can be easily applied to categoric random variables. (c) 2020 Elsevier B.V. All rights reserved.

关键词： Bioplastic   Circular economy   Climate tipping points   Sustainability   Waste management  

摘要： The merits of temporary carbon storage are often debated for bio-based and biodegradable plastics. We employed life cycle assessment (LCA) to assess environmental performance of polyhydroxyalkanoate (PHA)-based plastics, considering multiple climate tipping as a new life cycle impact category. It accounts for the contribution of GHG emissions to trigger climate tipping points in the Earth system, considering in total 13 tipping elements that could pass a tipping point with increasing warming. The PHA was either laminated with poly(lactic acid), or metallized with aluminum or aluminum oxides to lower permeability of the resulting plastics toward oxygen, water vapor and aromas. The assessments were made accounting for potential differences in kinetics of evolution of greenhouse gases (CO2, CH4) from bioplastic degradation in the end-of-life. Results show that: (1) PHA films with high biodegradability perform best in relation to the climate tipping, but are not necessarily the best in relation to radiative forcing increase or global temperature change;(2) sugar beet molasses used as feedstock is an environmental hot spot, contributing significantly to a wide range of environmental problems;(3) increasing PHA production scale from pilot to full commercial scale increases environmental impacts, mainly due to decreasing PHA yield;and (4) further process optimization is necessary for the PHA-based plastics to become attractive alternatives to fossil-based plastics. Our study suggests that multiple climate tipping is a relevant impact category for LCA of biodegradable bioplastics. (C) 2021 The Author(s). Published by Elsevier B.V.

关键词： dispersion   incomplete data   nominal time series   ordinal time series   serial dependence  

摘要： In real applications, time series often exhibit missing observations such that standard analytical tools cannot be applied. While there are approaches of how to handle missing data in quantitative time series, the case of categorical time series seems not to have been treated so far. Both for the case of ordinal and nominal time series, solutions are developed that allow to analyze their marginal and serial properties in the presence of missing observations. This is achieved by adapting the concept of amplitude modulation, which allows to obtain closed-form asymptotic expressions for the derived statistics' distribution (assuming that missingness happens independently of the actual process). The proposed methods are investigated with simulations, and they are applied in a project on migraine patients, where the monitored qualitative time series are often incomplete.

关键词： Geometric Langlands   Whittaker   Zastava space  

摘要： This paper begins a series studying D-modules on the FeiginFrenkel semi-infinite flag variety from the perspective of the Beilinson-Drinfeld factorization (or chiral) theory. Here we calculate Whittaker-twisted cohomology groups of Zastava spaces, which are certain finite-dimensional subvarieties of the affine Grassmannian. We show that such cohomology groups realize the nilradical of a Borel subalgebra for the Langlands dual group in a precise sense, following earlier work of Feigin-Finkelberg-Kuznetsov-Mirkovic and BravermanGaitsgory. Moreover, we compare this geometric realization of the Langlands dual group to the standard one provided by (factorizable) geometric Satake. (c) 2021 Published by Elsevier Inc.

关键词： PLS-DA   LDA   SIMCA   Authentication   Food control   Breed purity   Feeding regime  

摘要： The potential of Near Infrared Spectroscopy combining different spectral treatments and classification models was assessed for the classification of individual pre-sliced Iberian dry-cured loin packaged under modified atmosphere packaging (MAP) into three official commercial categories (which involve the breed purity and production system) according to the current Iberian Quality Standard (Black, Red and White) and for the assignment to the shelf-life time (0, 4, 8 and 12 months). External validation results provided acceptable results, with up to 100% of samples correctly assigned to Black and White official commercial category and into all storage times. Actually the 100% assignments were obtained using more than one approach (SIMCA and LDA for commercial categories and PLS-DA, SIMCA and LDA for storage times). These results might contribute to support the on-line control of authenticity of official commercial category and to facilitate the monitoring of the quality of pre-package dry-cured products throughout the shelf-life prediction.

关键词： Categories   Complete residuated lattices   L-fuzzy automata   L-fuzzy languages   L-fuzzy response maps  

摘要： This paper is towards the study of L-fuzzy automata from the categorical point of view, where Lis a complete residuated lattice. We introduce a functor having both the left/right adjoint from the category of L-fuzzy Sigma-semiautomata LFSA(Sigma) to the category-LFTCRL(Sigma), a category of complete residuated lattices corresponding to L-fuzzy Sigma-semiautomata. The L-fuzzy response map of an L-fuzzy automaton leads us to provide a characterization of an L-fuzzy regular language. Interestingly, we show that the category LFSA(Sigma) is a category of T-1-coalgebras/(T-2, T-3)-dialgebras. Moreover, we establish a relationship between the category of T-1-coalgebras and the category of (T-2, T-3)-dialgebras. (C) 2020 Elsevier B.V. All rights reserved.

关键词： 传信   认识情态   视觉传信   听说传信  

摘要： 本文对北京话认识情态副词“光景”和“有信儿”的来源及历时演变进行了系统考察。前者由视觉传信用法发展而来,后者则由听说传信用法发展而来,语义演变路径均可概括为“(证据)可靠性高>(命题)确定度高”。“有信儿”的听说传信用法强调信息来源可靠,具有一定的类型学价值。

关键词： Fine roots   Nitrogen   Phosphorus   Scaling exponents   Scaling theory   Woody species  

摘要： Fine-root nitrogen (N) and phosphorus (P) concentrations play an important role in driving ecological processes such as nutrient cycling in terrestrial ecosystems. Previous studies have demonstrated that the N versus P scaling relationship for fine roots (<2 mm in diameter) on average follows a 0.82-power law across plant functional groups and ecosystems. However, little is known about the N versus P scaling relationships for different fine-root classification groups (classes of diameters, branch orders, and functional categories, e.g., absorptive and transport roots). We used a dataset comprising 1037 N-P paired observations for a total of 227 woody species to explore N versus P scaling relationships in different fine-root groups. The overall means of fine-root N and P concentrations and N:P ratios across all of the woody species were 12.27 mg g-1, 1.01 mg g-1, and 15.14, respectively. N and P concentrations, N:P ratios, and the numerical values of the N versus P scaling exponents differed significantly within and across the different fine-root classes. The numerical values of absorptive roots N versus P scaling exponents varied within plant functional groups (e.g., life-form, phylogenetic and mycorrhizal groups). The numerical values of absorptive roots scaling exponents declined from 0.89 in boreal regions to 0.61 tropical regions. These results indicate that fine roots (<2 mm in diameter) should be carefully classified into different groups/categories when N and P scaling relationships need to be determined to predict plant growth and vegetation productivity. Our results shed important light on attempts to modeling fine-root biogeochemical processes in terrestrial ecosystems.

关键词： 胡塞尔   直观   范畴直观   逻辑  

摘要： 胡塞尔范畴直观的独特之处在于其总是试图通过直观与逻辑相统一的方式思考认识论问题。一方面,范畴直观为直观与逻辑相统一提供了契机,它使二者不再以绝对分裂的状态展现出来;另一方面,范畴直观使以一种新的维度思考认识论问题成为可能,为弥合直观与逻辑之间的裂痕提供了新的视域。胡塞尔提出的范畴直观与现象学的思维方式不仅推进了认识论问题的相关研究,而且对当代西方哲学的发展有重大的意义。