Browsing by Author "Wang, Yi"

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    Core/shell Cu/FePtCu nanoparticles with face-centered tetragonal texture
    (2018-12-01) Chen, Xu; Wang, Hanbin; Wan, Houzhao; Wu, Tianci; Shu, Dan; Shen, Laifa; Wang, Yi; Ruterana, Pierre; Lund, Peter D.; Wang, Hao; Hubei University; Max Planck Institute for Solid State Research; École nationale supérieure d'ingénieurs de Caen; Department of Applied Physics
    Low-Pt based nanocrystals demonstrate potential as highly active catalysts for the oxygen reduction reaction (ORR), but they suffer from undesirable structural degradation. Therefore, it is highly challenging to optimize their surface and interfacial structures to tune their catalytic properties for both activity and stability. Here core–shell Cu/FePtCu nanoparticles with a face-centered-tetragonal phase are prepared by a facile one–pot polyol method at 320 °C. The optimized core–shell Fe45Pt35Cu20 catalyst with Pt-enriched surface exhibits 0.5 A/mgPt mass activity, which is a factor of 4 better than that of commercial Pt/C (0.13 A/mgPt). In addition, the current density of the catalyst drops only 3.0% after 1000 cycles, which is much better than Pt/C (34.2% decay). Using aberration-corrected scanning transmission electron microscopy and atomically resolved elemental mapping, the morphology and structure evolving between the FePtCu alloy and core–shell Cu/FePtCu could clearly be explained. This work demonstrates that an ordered and core–shell FePtCu catalyst is highly promising for ORR and other electrochemical processes.
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    Describing shopping experience with customer journey maps for digital service design
    (2013) Wang, Yi; Turkki, Laura; Perustieteiden korkeakoulu; Perustieteiden korkeakoulu; School of Science; Nieminen, Marko
    Background: With increasing competition in retail environment, customer retailer loyalty becomes a critical objective for retailers. Results of former study show that a satisfactory shopping experience could enhance customers) cumulative or overall satisfaction and ultimately customer retailer loyalty. As more and more people use smartphone, shopping experience could possibly be improved with different forms of innovative retail mobility solutions that put a wealth of information at customers' fingertips. To support creating innovative mobility solutions for improving shopping experience, this thesis starts from studying customers' current shopping experience with retail services in Finland and China. Methods and Data: The empirical part of this thesis used design probe, mobile probe, semi-structured interviews and photo-elicitation to collect data for answering research questions. 6 Finnish participants and 6 Chinese participants were studied in this research. In total, 12 filled probes were collected and 10 interviews were conducted. Results: As a result, four customer journey maps were created to visually illustrate shopping experience of two personas. There are three types of important shopping related touch-points: physical, digital & intangible, and people-based. Interactions around important touch-points should be well designed to fit customers' needs. Customers' emotional states are relatively active while searching for and comparing products. Currently, customers use mobile more often to assist shopping rather than purchasing directly through mobile. The most common shopping activities with mobile are to compare price and search for product information. Nevertheless, several opportunities to improve current shopping experience with creative mobility solutions were identified, such as mobile inspiration of shopping and decision-making assistant. In future, the work could be continued with the focus on studying more customer groups and, eventually, contributing to create innovative mobility solutions.
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    Design and implement new network architecture for the WAN services of large corporation environment
    (2010) Wang, Yi; Tarkoma, Sasu; Informaatio- ja luonnontieteiden tiedekunta; Perustieteiden korkeakoulu; School of Science; Ylä-Jääski, Antti
    The thesis demonstrates how the new network WAN architecture based on MPLS technology works within the current corporate network in order to meet different requests internally from business units. Firstly, the existing network topology is described in the thesis. It introduces the basic network components, topology and the way that the corporate network is built up. It also shows the weakness of the existing WAN architecture inside the corporate network. Lack of scalability and flexibility, inability to support different service requirements and security risks are the major concerns about the existing rather flat network architecture. Secondly, the thesis shows the new network architecture based on MPLS technology. The entire new topology is built up step by step. The configuration and setup are simulated as is in the real network environment: IP segment, transit network, physical connectivity setup, logical connectivity setup etc. Eventually, the model of the new MPLS based network topology is built up for test and analysis. Lastly, based on the model built up, we design a few scenarios to test the new architecture against the existing network architecture. Demands of different services, scalability and flexibility, and security control are the criteria needed to achieve the target of this thesis.
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    A high-performance self-powered broadband photodetector based on a CH3NH3PbI3 perovskite/ZnO nanorod array heterostructure
    (2016) Yu, Jichao; Chen, Xu; Wang, Yi; Zhou, Hai; Xue, Mengni; Xu, Yang; Li, Zhaosong; Ye, Cong; Zhang, Jun; Van Aken, Peter A.; Lund, Peter D.; Wang, Hao; Department of Applied Physics; New Energy Technologies; Hubei University; Max Planck Institute for Solid State Research
    Here we report a self-powered photodetector based on a ZnO/CH3NH3PbI3 heterojunction and a MoO3 hole-transport layer. The organolead iodide perovskite photodetector is sensitive to broadband wavelengths from the ultraviolet light to the entire visible light region (250-800 nm), showing a high photo-responsivity of 24.3 A W-1 and a high detectivity value of 3.56 × 1014 cm Hz1/2 W-1 at 500 nm without external bias voltage. Meanwhile, we found that the photodetective performances are closely related to the thickness of the MoO3 layer, which acts as a hole-transport layer and an electron-blocking layer and can effectively decrease the recombination of holes and electrons. Additionally, the as-fabricated photodetector exhibits good stability and only 9.3% photoelectric response current decay after a 3-month illumination test. The high detectivity and responsivity of such a ZnO nanorod/perovskite heterojunction are clearly demonstrated and should be widely applicable to other photoelectric detection devices.