Long Short-Term Memory with Dynamic Skip Connections

In recent years, long short-term memory (LSTM) has been successfully used to model sequential data of variable length. However, LSTM can still experience difficulty in capturing long-term dependencies. In this work, we tried to alleviate this problem by introducing a dynamic skip connection, which can learn to directly connect two dependent words. Since there is no dependency information in the training data, we propose a novel reinforcement learning-based method to model the dependency relationship and connect dependent words. The proposed model computes the recurrent transition functions based on the skip connections, which provides a dynamic skipping advantage over RNNs that always tackle entire sentences sequentially. Our experimental results on three natural language processing tasks demonstrate that the proposed method can achieve better performance than existing methods. In the number prediction experiment, the proposed model outperformed LSTM with respect to accuracy by nearly 20%

Exploring the experiences of instructors teaching massive open online courses in tourism and hospitality: a mixed methods approach

Massive Open Online Courses (MOOCs) have existed as a disruptive educational phenomenon for nine years. Grounded in the roots of distance education, open education, Open Educational Resources, and OpenCourseWare, MOOCs have now survived various critics and have continued growing globally. Reports about MOOCs in both the press and scholarly publications began to grow significantly in 2013 (Sánchez-Vera, Leon Urrutia, & Davis, 2015; Zancanaro & Domingues, 2017) and, since then, more and more researchers have joined the discussions, developing them to explore various new topics. To contribute to the literature of MOOC studies, this doctoral thesis begins with an in-depth analysis of the background, history, growth, and vision, and proposes a tentative definition of MOOCs. Meanwhile, by conducting bibliometric research to review MOOC studies conducted between 2015 and 2017, this thesis fills in the gap that has existed due to a lack of systematic reviews of MOOC literature since 2015. The results of the bibliometric research summarised the relevant MOOC research into nine categories, including learner focused, commentary and concepts, case reports or evaluations, pedagogy, curriculum and design, course object focused, provider focused, technology, systematic review of literature, and learning analytics and big data. They also suggested a limited amount of provider focused research, which became the research interest and focus of this thesis. In the centre of the Europe, Swiss universities have marched forward in the MOOC movement, together with other over 550 universities (Shah, 2016) around the world. Università della Svizzera italiana (USI; Lugano, Switzerland), a Swiss public university, became a MOOC provider in 2015 and offered the first MOOC in the topic of eTourism: eTourism: Communication Perspectives. This doctoral thesis is closely related to this university-level initiative, which was dedicated to producing the first pilot MOOC at USI. Therefore, the cases chosen by this thesis are positioned in the discipline of tourism and hospitality. The first MOOC with a large audience taught artificial intelligence in 2011 (Zancanaro & Domingues, 2017). Nowadays, MOOCs have broken the barrier of space and time to educate the masses in a wide range of subjects. However, the provision of MOOCs in the subject of tourism and hospitality did not appear until 2013, when two MOOCs from two American universities became available. In the past four years since these MOOCs were launched, the number of tourism and hospitality MOOCs available in the market has remained limited (Tracey, Murphy, & Horton-Tognazzini, 2016). This scarcity contradicts the fact that tourism and hospitality is the field that contributes the most to the employment of the global workforce. Pressing problems, such as high turnover, seasonality, and new global challenges have urged for solutions to quickly training people working in this area to become available (Cantoni, Kalbaska, & Inversini, 2009). A call for more studies about tourism and hospitality MOOCs has emerged. The combined reality of the lack of studies regarding MOOC providers, opportunities for first-hand experience of producing a tourism MOOC in a university, and the deficiency in both the research and practises of tourism and hospitality MOOCs has inspired the direction of this thesis in regard to exploring MOOC instructors’ experiences, using cases in the field of tourism and hospitality. It cumulates six studies, using a mixed methods approach, to tackle the two main research objectives: to investigate at large the tourism and hospitality MOOC provisions between 2008 and 2015 and to report the experiences of Università della Svizzera italiana (USI) when producing the eTourism MOOC. In order, the first two studies in Chapter 3 of this thesis focus on tourism and hospitality MOOCs in general and produce a big picture context for the other four studies in Chapter 4. The first study proposes a conceptual framework through which to describe and analyse the course design of a MOOC and applies it to 18 tourism and hospitality MOOCs produced between 2008 and 2015. The second study then continues to interview six tourism and hospitality MOOC instructors, to describe their experiences and perspectives of teaching MOOCs. After exploring a holistic view of the overall development of MOOCs in tourism and hospitality and gaining a deep understanding of the instructors behind these offerings, this thesis introduces the experiences of one single MOOC provider: Università della Svizzera italiana (USI) in Chapter 4. It first introduces its overall implementation process (Study 3), and further elaborates three phases of this process: how it selected a suitable MOOC platform at the beginning (Study 4); how it assessed learner engagement in the MOOC (Study 5); and, eventually, how it evaluated the performance of the MOOC (Study 6). This thesis was written mainly from the perspective of eLearning, with the intention of benefiting its community of scholars and practitioners. It has contributed to the literature by developing a framework with which to review MOOCs (in Study 1), the implementation process of producing MOOCs (in Study 2), practical review schema of MOOC platforms (in Study 4), the MOOC Learner Engagement Online Survey (in Study 5), and how to use the Kirkpatrick model to evaluate MOOCs (in Study 6). These conceptual frameworks and experiential tools can benefit future researchers and practitioners. Meanwhile, due to its intimate connection with the field of tourism and hospitality, by directly using its cases, the research outputs of the six studies can also benefit the tourism and hospitality education and training sector as a reference for further action

Constructing a Non-Negative Low Rank and Sparse Graph with Data-Adaptive Features

This paper aims at constructing a good graph for discovering intrinsic data structures in a semi-supervised learning setting. Firstly, we propose to build a non-negative low-rank and sparse (referred to as NNLRS) graph for the given data representation. Specifically, the weights of edges in the graph are obtained by seeking a nonnegative low-rank and sparse matrix that represents each data sample as a linear combination of others. The so-obtained NNLRS-graph can capture both the global mixture of subspaces structure (by the low rankness) and the locally linear structure (by the sparseness) of the data, hence is both generative and discriminative. Secondly, as good features are extremely important for constructing a good graph, we propose to learn the data embedding matrix and construct the graph jointly within one framework, which is termed as NNLRS with embedded features (referred to as NNLRS-EF). Extensive experiments on three publicly available datasets demonstrate that the proposed method outperforms the state-of-the-art graph construction method by a large margin for both semi-supervised classification and discriminative analysis, which verifies the effectiveness of our proposed method

Exploring the impacts of water resources on economic development in Beijing-Tianjin-Hebei Region

Beijing-Tianjin-Hebei region is one of the most developed areas in China with a most rapid rate of economic growth. It is also a well-known region suffering great water scarcity. The water resources per capita is 118.60m³, 99.46 m³, 240.57 m³ respectively in Beijing, Tianjin and Hebei in 2013, all below 500 m³ that is defined as absolute scarcity by the United Nations. Water resources scarcity restricts the economic growth of the region at large and may account to the economic gaps between the three cities/ provinces. Economic growth in return aggravates its water shortage. The coordinated development of Beijing-Tianjin-Hebei region has been emphasized in recent years by the central government and means of solving regional problems and promoting its coordinated development need to be put forward. This study investigates the impacts of water resources factors on the regional economic growth to explore the direct influential factors of water resources, using panel data collected from 2004 to 2013. The main results show that: (1) the share of water for agricultural use and annual domestic water use per capita are statistically significant to the regional GDP per capita, with coefficients of 0.86 and 0.32 and (2) thus the impact of water resources on regional economic development is attributable to regional water use structure and domestic water use efficiency. Integrated regional governance of water resources, especially regional policies towards efficient water use and enhanced economic structure optimizing would be effective options for governments to propel the sustainable development of the region

Experimental tests of the chiral anomaly magnetoresistance in the Dirac-Weyl semimetals Na3_3Bi and GdPtBi

In the Dirac/Weyl semimetal, the chiral anomaly appears as an "axial" current arising from charge-pumping between the lowest (chiral) Landau levels of the Weyl nodes, when an electric field is applied parallel to a magnetic field $\bf B$. Evidence for the chiral anomaly was obtained from the longitudinal magnetoresistance (LMR) in Na$_3$Bi and GdPtBi. However, current jetting effects (focussing of the current density $\bf J$) have raised general concerns about LMR experiments. Here we implement a litmus test that allows the intrinsic LMR in Na$_3$Bi and GdPtBi to be sharply distinguished from pure current jetting effects (in pure Bi). Current jetting enhances $J$ along the mid-ridge (spine) of the sample while decreasing it at the edge. We measure the distortion by comparing the local voltage drop at the spine (expressed as the resistance $R_{spine}$) with that at the edge ($R_{edge}$). In Bi, $R_{spine}$ sharply increases with $B$ but $R_{edge}$ decreases (jetting effects are dominant). However, in Na$_3$Bi and GdPtBi, both $R_{spine}$ and $R_{edge}$ decrease (jetting effects are subdominant). A numerical simulation allows the jetting distortions to be removed entirely. We find that the intrinsic longitudinal resistivity $\rho_{xx}(B)$ in Na$_3$Bi decreases by a factor of 10.9 between $B$ = 0 and 10 T. A second litmus test is obtained from the parametric plot of the planar angular magnetoresistance. These results strenghthen considerably the evidence for the intrinsic nature of the chiral-anomaly induced LMR. We briefly discuss how the squeeze test may be extended to test ZrTe$_5$.Comment: 17 pages, 8 figures, new co-authors added, new Fig. 6a added. In press, PR

Anomalous Nernst Effect in Dirac Semimetal Cd3As2

Dirac and Weyl semimetals display a host of novel properties. In Cd$_3$As$_2$, the Dirac nodes lead to a protection mechanism that strongly suppresses backscattering in zero magnetic field, resulting in ultrahigh mobility ($\sim$ 10$^7$ cm$^2$ V$^{-1}$ s$^{-1}$). In applied magnetic field, an anomalous Nernst effect is predicted to arise from the Berry curvature associated with the Weyl nodes. We report observation of a large anomalous Nernst effect in Cd$_3$As$_2$. Both the anomalous Nernst signal and transport relaxation time $\tau_{tr}$ begin to increase rapidly at $\sim$ 50 K. This suggests a close relation between the protection mechanism and the anomalous Nernst effect. In a field, the quantum oscillations of bulk states display a beating effect, suggesting that the Dirac nodes split into Weyl states, allowing the Berry curvature to be observed as an anomalous Nernst effect.Comment: 13 pages, 7 figure