Research on visual features based content adaptive strategies for video coding

制度:新 ; 報告番号:甲3744号 ; 学位の種類:博士(工学) ; 授与年月日:2012/9/15 ; 早大学位記番号:新6115Waseda Universit

Hyperthin Organic Membranes for Gas Separations

Gas separation is practically important in many aspects, e.g., clean energy production and global warming prevention. Compared to other separation technologies like cryogenic distillation and pressure swing adsorption, membrane separation is considered to be more energy efficient. For practical purposes, the ultimate goal is to construct membranes producing high flux and high gas permeation selectivity at the same time. Based on the inverse relationship between flux and membrane thickness, it is clear that fabricating highly selective membranes as thin as possible could increase the flux through the membrane without sacrificing selectivity. But it has proven to be challenging to manufacture selective membranes in the hyperthin (\u3c 100nm) region. [Note: 100 nm is the typical dense layer thickness of commercial membranes to separation gases.] In this dissertation, the focus is on the development of hyperthin selective membranes that were supported by poly(1-trimethylsilyl-1-propyne) (PTMSP), using Langmuir-Blodgett (LB) and Layer-by-Layer (LbL) deposition methods. A gluing strategy has been successfully introduced into LB films by our laboratory recently, in which LB monolayers are ionically crosslinked with polyelectrolytes. This success stimulated the pursuance of LB films with improved gas separation properties by: (i) examining calix[n]arene-based surfactants with different sizes (ii) using polymeric surfactants as LB forming materials, and (iii) optimizing the condition of the subphase containing polyelectrolytes. Both a strong polyelectrolyte poly(4-styrene sulfonate) (PSS) and a weak polyelectrolyte poly(acrylic acid) (PAA) were used to create glued LB bilayers. The gas permeation through PSS or PAA-glued LB bilayers made of calix[n]arenes was found to be dominated by solution-diffusion rather than molecular-sieving mechanism. The porous nature of calix[n]arene-based surfactants also turned out to be unnecessary for constructing LB films with high gas selectivities, because a single PAA-glued LB bilayer made of a nonporous polymeric surfactant (ca. 7 nm) was found to exhibit a much higher H2/CO2 selectivity (200), which reached the upper bound . The key factors that are likely to affect the quality of the glued LB bilayers were: (i) the degree of ionic crosslinking between surfactants and polyelectrolytes, (ii) charge repulsion and (iii) hydrogen bonding among the polyelectrolyte chains. In principle, employing a surfactant bearing a large number of ionic sites (e.g., a polymeric surfactant) that can increase the degree of ionic crosslinking and a weak polyelectrolyte (e.g., PAA) that can be optimized to minimize the charge repulsion and maximize the hydrogen bonding should afford glued LB films with high gas selectivities. The current finding also indicated that the PAA layer filled in between two surfactant monolayers served as the main gas barrier. In a related study, polyelectrolyte multilayers (PEMs) (ca. 14 nm in thickness), which were made from structurally matched (i.e., two oppositely charged polyelectrolytes having identical backbones) and unmatched polyelectrolytes pairs, both showed high CO2/N2 selectivities (ca. 100-150). However, the permeabilities of PEMs derived from structurally matched polyelectrolytes were significantly higher than that from an unmatched pair. The larger solubility of CO2 with respect to N2 in these PEMs should be the reason lead to the high CO2/N2 permeation selectivities

Factors Affecting Users\u27 Dynamic Message Deleting Intention on Social Networks: An Empirical Study Based on Impression Management Theory

Social dynamics is a social networking service that allows users to input updates including letters, pictures, videos and share them with their social friends. Previous research mainly focus on the application of dynamic messages in the fields of communication science and economics. Based on impression management theory, this paper studies the influencing factors of users\u27 dynamic message deleting intention on social networks. The results show that impression management performance and social network fatigue significantly affect user\u27s intention to delete the dynamic messages. While message sender factors, such as self-monitoring, interpersonal interaction and image promotion; social platform factors such as information overload and social overload, indirectly influence the deleting intention through intermediary variables. This paper makes up for the lack of relevant empirical research, making users more social flexibility and effectiveness, thereby enhancing social validity, and have some practical implications for social networking services platforms

AutoML from Software Engineering Perspective: Landscapes and Challenges

Machine learning (ML) has been widely adopted in modern software, but the manual configuration of ML (e.g., hyper-parameter configuration) poses a significant challenge to software developers. Therefore, automated ML (AutoML), which seeks the optimal configuration of ML automatically, has received increasing attention from the software engineering community. However, to date, there is no comprehensive understanding of how AutoML is used by developers and what challenges developers encounter in using AutoML for software development. To fill this knowledge gap, we conduct the first study on understanding the use and challenges of AutoML from software developers’ perspective. We collect and analyze 1,554 AutoML downstream repositories, 769 AutoML-related Stack Overflow questions, and 1,437 relevant GitHub issues. The results suggest the increasing popularity of AutoML in a wide range of topics, but also the lack of relevant expertise. We manually identify specific challenges faced by developers for AutoML-enabled software. Based on the results, we derive a series of implications for AutoML framework selection, framework development, and research

Understanding User Acceptance of Micro-Blog Services in China Using the Extended Motivational Model

The growing popularity of micro-blogs has drawn an increasing amount of attention from users keen to expand friendship, facilitate information sharing and information seeking. Given the extensive use of micro-blog services, there is a pressing need to understand users’ behavioral intentions in micro-blog services. Although there are some studies exploring the factors explaining micro-blog users’ acceptance, none of research has been reported from both of the technological characteristics and network effects of micro-blog services. This study extended motivational model with socio-technical approach as a theoretical framework to examine the roles of technological factors and network effect factors in determining micro-blog users’ behavioral intentions. This study suggests that interactivity, convenience, accessibility, network size, existing social contacts, performance expectancy, sense of belonging and hedonic expectancy together provide a strong explanation for micro-blog use intention. The results of this study provide directions for system administrators and service providers to achieve higher levels of micro-blog usage by developing multi-faceted strategies

Energy-aware Graph Job Allocation in Software Defined Air-Ground Integrated Vehicular Networks

The software defined air-ground integrated vehicular (SD-AGV) networks have emerged as a promising paradigm, which realize the flexible on-ground resource sharing to support innovative applications for UAVs with heavy computational overhead. In this paper, we investigate a vehicular cloud-assisted graph job allocation problem in SD-AGV networks, where the computation-intensive jobs carried by UAVs, and the vehicular cloud are modeled as graphs. To map each component of the graph jobs to a feasible vehicle, while achieving the trade-off among minimizing UAVs' job completion time, energy consumption, and the data exchange cost among vehicles, we formulate the problem as a mixed-integer non-linear programming problem, which is Np-hard. Moreover, the constraint associated with preserving job structures poses addressing the subgraph isomorphism problem, that further complicates the algorithm design. Motivated by which, we propose an efficient decoupled approach by separating the template (feasible mappings between components and vehicles) searching from the transmission power allocation. For the former, we present an efficient algorithm of searching for all the subgraph isomorphisms with low computation complexity. For the latter, we introduce a power allocation algorithm by applying convex optimization techniques. Extensive simulations demonstrate that the proposed approach outperforms the benchmark methods considering various problem sizes.Comment: 14 pages, 7 figure

Probabilistic Harmonic Calculation in Distribution Networks with Electric Vehicle Charging Stations

Integrating EV charging station into power grid will bring impacts on power system, among which the most significant one is the harmonic pollution on distribution networks. Due to the uncertainty of the EV charging process, the harmonic currents brought by EV charging stations have a random nature. This paper proposed a mathematical simulation method for studying the working status of charging stations, which considers influencing factors including random leaving factor, electricity price, and waiting time. Based on the proposed simulation method, the probability distribution of the harmonic currents of EV charging stations is obtained and used in the calculation of the probability harmonic power flow. Then the impacts of EVs and EV charging stations on distribution networks can be analyzed. In the case study, the proposed simulation and analysis method is implemented on the IEEE-34 distribution network. The influences of EV arrival rates, the penetration rate, and the accessing location of EV charging station are also investigated. Results show that this research has good potential in guiding the planning and construction of charging station

Exploration of interactive classroom test method in universities based on the module thought

University is an important transit station for students to enter social life, undertaking the important mission of personnel training. Nowadays, a series of challenges exists in university education, such as the popularity of electronic information making students lack the ability to help each other. How to develop the mutual cooperation ability and active learning ability is an important topic in university education. This paper proposes an interactive classroom test method considering the learning characteristics of university students. The module thought is introduced to optimize the teaching system and help teachers to master classroom. In the interactive classroom test method, students can design the test paper based on the learning of course content and understanding. Then the different module group may use and review these test papers. The application and investigation of the proposed method are given by concrete practice. The results show that this method can enhance the spirit of teamwork and competition among students