| 1. |
- Luo, Yifei, et al.
(författare)
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Technology Roadmap for Flexible Sensors
- 2023
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Ingår i: ACS Nano. - : American Chemical Society. - 1936-0851 .- 1936-086X. ; 17:6, s. 5211-5295
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Forskningsöversikt (refereegranskat)abstract
- Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity.
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| 2. |
- Guo, Zijian, et al.
(författare)
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A Vector Field Approach to Estimating Environmental Exposure Using Human Activity Data
- 2022
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Ingår i: ISPRS International Journal of Geo-Information. - : MDPI AG. - 2220-9964. ; 11:2
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Tidskriftsartikel (refereegranskat)abstract
- Environmental exposure of people plays an important role in assessing the quality of human life. The most existing methods that estimate the environmental exposure either focus on the individual level or do not consider human mobility. This paper adopts a vector field generated from the observed locations of human activities to model the environmental exposure at the population level. An improved vector-field-generation method was developed by considering people’s decision-making factors, and we proposed two indicators, i.e., the total exposure indicator (TEI) and the average exposure indicator (AEI), to assess various social groups’ environmental exposure. A case study about the risky environmental exposure of coronavirus disease 2019 (COVID-19) was conducted in Guangzhou, China. Over 900 participants with various socioeconomic backgrounds were involved in the questionnaire, and the survey-based activity locations were extracted to generate the vector field using the improved method. COVID-19 pandemic exposure (or risk) was estimated for different social groups. The findings show that people in the low-income group have an 8% to 10% higher risk than those in the high-income group. This new method of vector field may benefit geographers and urban researchers, as it provides opportunities to integrate human activities into the metrics of pandemic risk, spatial justice, and other environmental exposures.
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| 3. |
- Guo, Zijian, et al.
(författare)
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Exploring the structural characteristics of intra-urban shared freight network and their associations with socioeconomic status
- 2023
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Ingår i: Travel Behaviour and Society. - : Elsevier BV. - 2214-367X. ; 32
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, shared freight systems have emerged in many cities as a new modality of freight transportation. However, little attention has been paid to the impact of a city's socioeconomic status on the characteristics of a shared freight network. To fill this gap, in this study, the structural characteristics of an intra-urban shared freight network are measured from the perspective of complex networks, and the correlations between network structure and socioeconomic status are examined. A case study is conducted in Hong Kong using large amounts of GPS trajectory data for freight vehicles and socioeconomic data. The results show that socioeconomic variables such as population size, percentage of elderly residents, percentage of residents with a marital status classified as “other” (i.e., separated, widowed, or divorced), and percentage of residents employed in the tertiary sector have distinct correlations with the structural characteristics. These correlations display spatial non-stationarity. This research can potentially assist decision-makers in improving the operating efficiency of shared freight systems and the governance of digital freight transport.
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| 4. |
- Guo, Zijian, et al.
(författare)
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Spatiotemporal heterogeneity of the shared e-scooter–public transport relationships in Stockholm and Helsinki
- 2023
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Ingår i: Transportation Research Part D: Transport and Environment. - 1361-9209. ; 122
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Tidskriftsartikel (refereegranskat)abstract
- Although shared e-scooters have displayed both complementary and competitive relationships with public transport, less attention has been paid to investigating the spatiotemporal variations of such relationships, and how the relationships are associated with the urban built environment. To bridge the gaps, we first explore the spatiotemporal heterogeneity of such relationships by conducting a comparative study of Stockholm and Helsinki based on the empirical data. Then, an explainable AI method is applied to examine the associations between the relationships and built environment. We found that Helsinki presents higher ratios of the competitive dominant areas (DPET) compared with Stockholm showing higher ratios of the complementary dominant areas (DPLE). The correlation analysis results indicate that the distance-to-public-transport is associated with DPET in two cities. Some factors present a non-linear effect, e.g., the density-of-the-population, etc. This study is beneficial for the better integration of shared e-scooters and public transport towards sustainable urban mobility systems.
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| 5. |
- Lin, Zijian, et al.
(författare)
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Low-cost, high-speed multispectral imager via spatiotemporal modulation based on a color camera
- 2023
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Ingår i: Optics Express. - : Optica Publishing Group. - 1094-4087. ; 31:25, s. 42613-42623
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Tidskriftsartikel (refereegranskat)abstract
- Spectral imaging is a powerful tool in industrial processes, medical imaging, and fundamental scientific research. However, for the commonly used spatial/spectral-scanning spectral imager, the slow response time has posed a big challenge for its employment in dynamic scenes. In this paper, we propose a spatiotemporal modulation concept and build a simple, low-cost spectral imager by combining a liquid crystal (LC) cell with a commercial color camera. By the synergic effect of temporal modulation of the LC materials and spatial modulation of the Bayer filter in a color camera, high-quality multispectral imaging is successfully demonstrated with a high rate of 8 Hz, far beyond the counterparts. Experimental results show that even with three tuning states of the LC material, optical signals with a 10-nm band can be resolved in the range between 410 and 700 nm by this method, overcoming the tradeoff between spectral resolution and time resolution. As a proof of demonstration, we present its potential usage for metamerism recognition, showing superiority over traditional color cameras with more spectral details. Considering its low cost, miniaturization and monolithic-integration ability on color sensors, this simple approach may bring the spectral imaging technology closer to the consumer market and even to ubiquitous smartphones for health care, food inspection and other applications.
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| 6. |
- Liu, Tanghong, et al.
(författare)
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Reasonable pressure tap layout to measure the aerodynamic forces of a train at different yaw angles
- 2020
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Ingår i: Measurement: Journal of the International Measurement Confederation. - : Elsevier BV. - 0263-2241. ; 166
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Tidskriftsartikel (refereegranskat)abstract
- The present work studies the aerodynamic loads of a train for different yaw angles from 5.87 degrees to 30 degrees by using the detached-eddy simulation (DES) method. Furthermore, based on the pressure integral method, a reasonable layout of the pressure taps on the train under a crosswind is studied to obtain the aerodynamic forces and moments that are used for a comparison with the results of the wind tunnel test. Considering the lower errors of the pressure integral results and fewer number of pressure taps comprehensively, the pressure integral method in the case of 15-4 (15 represents the tap quantity along the length direction, 4 represents the tap quantity along the height/width direction) on the head car and tail car, the case of 14-4 on the middle car are relatively good among the nine cases discussed in this paper. Compared to the results of the wind tunnel test, for the head car, the maximum error of the side force coefficient (C-y), rolling moment coefficient (M-x), and yawing moment coefficient (M-z) is all less than 10% for yaw angles from 5.87 degrees to 90 degrees, and the maximum errors of lift force coefficient (C-z) is less than 20% for yaw angles from 10.2 degrees to 90'; for the middle car, the maximum error of C-y is less than 20% for yaw angles from 5.87 degrees to 90 degrees, and the maximum error of C-z, M-x and M-z is all less than 15% for yaw angles from 5.87 degrees to 90'; for the tail car, the maximum error of C-y, C-z, M-x and M-z is all less than 15% for yaw angles from 10.2 degrees to 90 degrees. (C) 2020 Elsevier Ltd. All rights reserved.
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| 7. |
- Tian, Jiahan, et al.
(författare)
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Wide-field-of-view auto-coupling optical antenna system for high-speed bidirectional optical wireless communications in C band
- 2023
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Ingår i: Optics Express. - : Optica Publishing Group. - 1094-4087. ; 31:20, s. 33435-33448
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Tidskriftsartikel (refereegranskat)abstract
- Due to a great many superior features of infrared light communication (ILC), like high capacity and strong privacy, ILC is considered a potential candidate for serving the high demands of beyond fifth-generation/sixth-generation (B5G/6 G) communication systems. However, the terminal's limited field-of-view (FOV) induces great difficulty in establishing line-of-sight (LoS) link between the transceiver and the terminal. In this paper, we propose a wide-FOV auto-coupling optical antenna system that utilizes a wide-FOV telecentric lens to collect incident infrared beams and automatically couple them into a specific single-mode-fiber (SMF) channel of fiber array and optical switch. The performance of this optical antenna system is assessed through simulation and manual alignment operation, and validated by automatic alignment results. A coupling loss of less than 10.6 dB within a FOV of 100(degrees )for both downstream and upstream beams in C band is demonstrated by the designed system. Furthermore, we establish a bidirectional optical wireless communications (OWC) system employing this antenna and a fiber-type modulating retro-reflector (MRR) system in the terminal. Both 10-Gbps on-off keying (OOK) downstream and upstream transmissions are successfully realized with the FOV of up to 100(degrees) in C band where the measured bit-error-rate (BER) is lower than 3.8 x 10-3. To the best of our knowledge, this is a brand-new auto-coupling optical antenna system with the largest FOV in ILC automatic alignment works in terminals that have ever been reported.
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| 8. |
- Zhang, Zhi, et al.
(författare)
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Customized Structural Color Filters by Pixel-Level Electrothermal Regulation
- 2023
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Ingår i: Laser & Photonics reviews. - : Wiley. - 1863-8880 .- 1863-8899. ; 17:5
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Tidskriftsartikel (refereegranskat)abstract
- Reflective structural colors have backlight-free supremacy and can provide energy-efficient and environmental-friendly color production for many applications. However, they are hindered by the complex process and incorrect colors after fabrication. Here, a pixelated electrothermal oxidation technique is proposed that can precisely tailor and produce reflective structural colors covering the entire visible range, providing the possibility for customized structural color filter arrays from a titanium canvas. Furthermore, as a demonstration, a photonic-firework-like color filter array is achieved in a single step via thermal engineering. Based on this one-step-forming color array, a computational spectrometer is also realized featuring a resolvability of 10 nm and operating bandwidth covering the whole visible range. Considering its compactness and mass production capability, this method has numerous potential applications in, e.g., imaging, anti-counterfeiting, printing, color display, and spectroscopy.
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| 9. |
- Zhang, Zijian, et al.
(författare)
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Impact of Mountains in Southern China on the Eocene Climates of East Asia
- 2022
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Ingår i: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 127:17
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Tidskriftsartikel (refereegranskat)abstract
- Inconsistencies in the Eocene climates of East Asia have been revealed in both geological studies and simulations. Several earlier reconstructions showed an arid zonal band in mid-latitude China, but others showed a humid climate in the same region. Moreover, previous Eocene modeling studies have demonstrated that climate models can simulate both scenarios in China. Therefore, it is essential to investigate the cause of this model spread. We conducted a series of experiments using Norwegian Earth System Model 1-F and examined the impact of mountains in Southern China on the simulated Eocene climate. These mountains, including the Gangdese and Southeast Mountains, are located along the main path of water vapor transport to East Asia. Our results reveal that the Southeast Mountains play the dominant role in controlling the simulated precipitation in Eastern China during the Eocene. When the heights of the Southeast Mountains exceed similar to 2,000 m, an arid zonal band appears in mid-latitude China, whereas humid climates appear in Eastern China when the elevation of the Southeast Mountains is relatively low.
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