Browsing by Author "Xu, Yang"

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Also jewellery — Assemblage as a new way of wearing
(2019) Xu, Yang
School of Arts, Design and Architecture | Master's thesis
The artistic research “Also Jewellery - Assemblage as a New Way of Wearing” is an attempt to untie the knot. A knot that came into formation when the author started to identify herself as a contemporary jewellery artist and noticed a rising query on the definition of wearability in the context of contemporary jewellery. The functionality of jewellery elucidated in the traditional standard as body ornament is suffering from a slow wipeout. The author embarks on an adventure of finding her own answer to the question of what is wearability by invoking the theory of vital materialism by Jane Bennett. Vital materialism acknowledges the agentic forces possessed by the nonhuman which allows manifestation of traces of independence from human subjects. The notion of assemblage is also introduced which points out the heterogeneous groupings of human and nonhuman forces that are constantly being formed in our quotidian life. Considering jewellery as a perfect medium to investigate such concepts, the author creates a body of work during the making of which she examines the dynamic between the maker and the materialities that go into the completion of the work. The study is finalised in the form of a recorded performance. The author therefore is able to propose a new way of looking at the question of wearability, an assemblage where human intentionality is de-centered.
Black phosphorus ink formulation for inkjet printing of optoelectronics and photonics
(2017-12-01) Hu, Guohua; Albrow-Owen, Tom; Jin, Xinxin; Ali, Ayaz; Hu, Yuwei; Howe, Richard C.T.; Shehzad, Khurram; Yang, Zongyin; Zhu, Xuekun; Woodward, Robert I.; Wu, Tien Chun; Jussila, Henri; Wu, Jiang Bin; Peng, Peng; Tan, Ping Heng; Sun, Zhipei; Kelleher, Edmund J.R.; Zhang, Meng; Xu, Yang; Hasan, Tawfique
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Black phosphorus is a two-dimensional material of great interest, in part because of its high carrier mobility and thickness dependent direct bandgap. However, its instability under ambient conditions limits material deposition options for device fabrication. Here we show a black phosphorus ink that can be reliably inkjet printed, enabling scalable development of optoelectronic and photonic devices. Our binder-free ink suppresses coffee ring formation through induced recirculating Marangoni flow, and supports excellent consistency (< 2% variation) and spatial uniformity (< 3.4% variation), without substrate pre-treatment. Due to rapid ink drying (< 10 s at < 60 °C), printing causes minimal oxidation. Following encapsulation, the printed black phosphorus is stable against long-term (> 30 days) oxidation. We demonstrate printed black phosphorus as a passive switch for ultrafast lasers, stable against intense irradiation, and as a visible to near-infrared photodetector with high responsivities. Our work highlights the promise of this material as a functional ink platform for printed devices.
Capture efficiency and thermal comfort in Chinese residential kitchen with push-pull ventilation system in winter-a field study
(2019-02-01) Zhou, Bin; Wei, Peng; Tan, Meilan; Xu, Yang; Ding, Lili; Mao, Xinyue; Zhao, Yongkun; Kosonen, Risto
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The IAQ and thermal comfort in residential kitchen are two major concerns in built environment. The ventilation effectiveness is closely related to the IAQ of the residential kitchen. Therefore, it is necessary to design a cost-effective kitchen ventilation system. In this study, a field experimental study was conducted on a push-pull kitchen ventilation system. The experiment was divided into two parts. The first part was to test the capture efficiency of the push-pull ventilation system under various working conditions. The second part was to investigate the thermal comfort of the human body during cooking process with and without air curtain in winter. The results show that the push-pull ventilation system can effectively improve the capture efficiency of the range hood, and the low-momentum make-up air and the reasonable air distribution around the stove are important to obtain good performance. The optimal working condition of the push-pull ventilation system is a range hood mid gear plus an air curtain velocity of 0.5 m/s when the kitchen window is closed. In winter, when people enter the non-air-conditioned kitchen from the air-conditioned room, the thermal sensation and thermal comfort of people were all decreased significantly. However, they can be improved during cooking processes. The prediction results show that models which used skin temperature as input parameter can predict the thermal sensation of most parts of human body in kitchen. However, the prediction correction model is still needed for the body parts with movement or exposure to severe heat radiation.
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
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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.
Hopping Light Vat Photopolymerization for Multiscale Fabrication
(2023-03-15) Xu, Yang; Mao, Huachao; Liu, Cenyi; Du, Zhengyu; Yan, Weijia; Yang, Zhuoyuan; Partanen, Jouni; Chen, Yong
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
3D objects with features spanning from microscale to macroscale have various applications. However, the fabrication of such objects presents challenges to additive manufacturing (AM) due to the tradeoffs among manufacturable feature resolution, maximum build area, and printing speed. This paper presents a projection-based AM process called hopping light vat photopolymerization (HL-VPP) to address this critical barrier. The key idea of HL-VPP is to synchronize linear scanning projection with a galvo mirror's rotation. The projector moves continuously at a constant speed while periodically rotating a one-axis galvo mirror to compensate for the projector's linear movement so synchronized hopping motion can be achieved. By this means, HL-VPP can simultaneously achieve large-area (over 200 mm), fast-speed (scanning speed of 13.5 mm s-1), and high-resolution (10 µm pixel size) fabrication. The distinguishing characteristic of HL-VPP is that it allows for hundreds of times lower refresh rates without motion blur. Thus, HL-VPP decouples the fabrication efficiency limit imposed by the refresh rate and will enable super-fast curing in the future. This work will significantly advance VPP's use in applications that require macroscale part size with microscale features. The process has been verified by fabricating multiple multiscale objects, including microgrids and biomimetic structures.
Incentive Jamming-Based Secure Routing in Decentralized Internet of Things
(2021-02-15) Xu, Yang; Liu, Jia; Shen, Yulong; Liu, Jun; Jiang, Xiaohong; Taleb, Tarik
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This article focuses on the secure routing problem in the decentralized Internet of Things (IoT). We consider a typical decentralized IoT scenario composed of peer legitimate devices, unauthorized devices (eavesdroppers), and selfish helper jamming devices (jammers), and propose a novel incentive jamming-based secure routing scheme. For a pair of source and destination, we first provide theoretical modeling to reveal how the transmission security performance of a given route is related to the jamming power of jammers in the IoT. Then, we design an incentive mechanism with which the source pays some rewards to stimulate the artificial jamming among selfish jammers, and also develop a two-stage Stackelberg game framework to determine the optimal source rewards and jamming power. Finally, with the help of the theoretical modeling as well as the source rewards and jamming power setting results, we formulate a shortest weighted path-finding problem to identify the optimal route for secure data delivery between the source-destination pair, which can be solved by employing the Dijkstra's or Bellman-Ford algorithm. We prove that the proposed routing scheme is individually rational, stable, distributed, and computationally efficient. Simulation and numerical results are provided to demonstrate the performance of our routing scheme.
Observation of phonon Stark effect
(2024-12) Huang, Zhiheng; Bai, Yunfei; Zhao, Yanchong; Liu, Le; Zhao, Xuan; Wu, Jiangbin; Watanabe, Kenji; Taniguchi, Takashi; Yang, Wei; Shi, Dongxia; Xu, Yang; Zhang, Tiantian; Zhang, Qingming; Tan, Ping Heng; Sun, Zhipei; Meng, Sheng; Wang, Yaxian; Du, Luojun; Zhang, Guangyu
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Stark effect, the electric-field analogue of magnetic Zeeman effect, is one of the celebrated phenomena in modern physics and appealing for emergent applications in electronics, optoelectronics, as well as quantum technologies. While in condensed matter it has prospered only for excitons, whether other collective excitations can display Stark effect remains elusive. Here, we report the observation of phonon Stark effect in a two-dimensional quantum system of bilayer 2H-MoS2. The longitudinal acoustic phonon red-shifts linearly with applied electric fields and can be tuned over ~1 THz, evidencing giant Stark effect of phonons. Together with many-body ab initio calculations, we uncover that the observed phonon Stark effect originates fundamentally from the strong coupling between phonons and interlayer excitons (IXs). In addition, IX-mediated electro-phonon intensity modulation up to ~1200% is discovered for infrared-active phonon A2u. Our results unveil the exotic phonon Stark effect and effective phonon engineering by IX-mediated mechanism, promising for a plethora of exciting many-body physics and potential technological innovations.
Santa Claus is coming to town: A case study of Santa Claus Park in Mohe, China
(2013) Xu, Yang
School of Business | Master's thesis
This study focused on three tasks: 1) identifying the image of Santa Claus and its cultural impact in China, compared to its Western origin; 2) identifying the market segmentation for Mohe Santa Claus Village in China; and 3) providing suggestions for Santa Claus Village marketing activities to best attract potential customers. The study used a single-case approach consisting of qualitative interviews with 16 respondents in three major Chinese cities and a quantitative survey among 100 people from nine provinces in China. Santa Claus Park in Mohe has been chosen as the case company. The present study has provided good insight of how the Chinese perceive Santa Claus as a feature associated with Western culture. It also gave information about current Chinese tourism trends, thus giving guidance for the development of Chinese tourism generally. This study also defined different ways of communication needed to promote Santa Claus Park in China compared to Finland.