| 1. |
- Hao, Meimei, et al.
(författare)
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Influence of component parameters on propagation characteristics of foaming polyurethane grout in rock fractures
- 2024
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618 .- 1879-0526. ; 428
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Tidskriftsartikel (refereegranskat)abstract
- Polyurethane grouting is an important technical solution used for seepage prevention and mechanical reinforcement of fractured rock. Various components of polyurethane grout significantly affect the grout properties and propagation behavior. The present study focuses on the crucial role of component parameters in controlling the propagation process and designing grouting parameters for foaming polyurethane grout. A coupled modeling approach combining chemical reactions and flow field analysis is developed to investigate the polyurethane foaming process. The proposed modeling approach is validated by comparing simulation results with experimental data from the literature. The influence of key component parameters: isocyanate index, initial water concentration and physical blowing agent, on the propagation characteristics (including propagation distance, maximum pressure, final density, reaction time and maximum temperature) of foaming polyurethane grout in rock fractures are further analyzed. The results reveal two distinct types of effects caused by the components, i.e., a monotonic relationship and a parabolic trend. Critical values are identified for the impact of isocyanate index on maximum propagation distance, final density and characteristic time, as well as for the influence of physical blowing agent on maximum propagation distance, final density and maximum pressure. Other parameters demonstrated a monotonic relationship. Additionally, a quantitative assessment is conducted to evaluate the impact of multiple components on propagation characteristics. The finding indicates that the initial water concentration has a significant effect on all properties, while isocyanate index exerts a more pronounced impact on reaction time and maximum temperature. The effect of the physical blowing agent is relatively minor compared to other factors. This study is helpful for material selection and proportioning of polyurethane grout in practical engineering applications.
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| 2. |
- Hao, Meimei, et al.
(författare)
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Numerical simulation of polymer grouting for rock fracture: Influence of isocyanate index on grout propagation
- 2024
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Ingår i: Tunnelling for a Better Life - Proceedings of the ITA-AITES World Tunnel Congress, WTC 2024. - : CRC Press/Balkema. ; , s. 718-725
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Konferensbidrag (refereegranskat)abstract
- The grout propagation plays a crucial role in the design of polyurethane grouting for reinforcing and sealing fractured rock. Understanding the influence of isocyanate index on the diffusion process is essential for selection and material modification to improve the grouting effectiveness. In this study, a numerical method was developed to simulate the grout propagation of polyurethane, considering the coupled of reaction kinetics and fluid flow. Furthermore, the influence of the isocyanate index on pressure, diffusion distance, component conversion and density were analyzed. These findings contribute to the preparation and selection of polyurethane grout for practical engineering applications.
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| 3. |
- Hao, Zifan, et al.
(författare)
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High-performance eight-channel system with fractal superconducting nanowire single-photon detectors
- 2024
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Ingår i: Chip. - : Elsevier B.V.. - 2709-4723 .- 2772-2724. ; 3:2
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Tidskriftsartikel (refereegranskat)abstract
- Superconducting nanowire single-photon detectors (SNSPDs) have become a mainstream photon-counting technology that has been widely applied in various scenarios. So far, most multi-channel SNSPD systems, either reported in literature or commercially available, are polarization sensitive, that is, the system detection efficiency (SDE) of each channel is dependent on the state of polarization of the to-be-detected photons. Here, we reported an eight-channel system with fractal SNSPDs working in the wavelength range of 930 to 940 nm, which are all featured with low polarization sensitivity. In a close-cycled Gifford-McMahon cryocooler system with the base temperature of 2.2 K, we installed and compared the performance of two types of devices: (1) SNSPD, composed of a single, continuous nanowire and (2) superconducting nanowire avalanche photodetector (SNAP), composed of 16 cascaded units of two nanowires electrically connected in parallel. The highest SDE among the eight channels reaches 96−5+4%, with the polarization sensitivity of 1.02 and a dark-count rate of 13 counts per second. The average SDE for eight channels for all states of polarization is estimated to be 90 ± 5%. It is concluded that both the SNSPDs and the SNAPs can reach saturated, high SDE at the wavelength of interest, and the SNSPDs show lower dark-count (false-count) rates, whereas the SNAPs show better properties in the time domain. With the adoption of this system, we showcased the measurements of the second-order photon-correlation functions of light emission from a single-photon source based on a semiconductor quantum dot and from a pulsed laser. It is believed that this work will provide new choices of systems with single-photon detectors combining the merits of high SDE, low polarization sensitivity, and low noise that can be tailored for different applications.
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| 4. |
- Hao, Zifan, et al.
(författare)
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Multi-channel system with high-performance fractal superconducting nanowire single-photon detectors
- 2024
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Ingår i: 2024 Optical Fiber Communications Conference and Exhibition, OFC 2024 - Proceedings. - : Institute of Electrical and Electronics Engineers Inc..
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Konferensbidrag (refereegranskat)abstract
- We report on an eight-channel fractal SNSPD system in the wavelength range of 940 nm with minimal polarization sensitivity. The best channel exhibits 96% system detection efficiency and 19 cps dark-count rate.
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| 5. |
- Hu, Xiaolong, et al.
(författare)
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Fractal superconducting nanowire single-photon detectors and their applications in polarimetric imaging
- 2024
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Ingår i: Advanced Photon Counting Techniques XVIII. - : SPIE.
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Konferensbidrag (refereegranskat)abstract
- In this paper, we review the research and development of the fractal superconducting nanowire single-photon detectors (SNSPDs), including our demonstrations of high-performance devices and systems with over 80% system detection efficiency, negligibly low residual polarization sensitivity, and low timing jitter. Using the fractal SNSPDs, we demonstrate full-Stokes polarimetric imaging LiDAR.
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| 6. |
- Meng, Yun, et al.
(författare)
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Kilometer-range, full-Stokes polarimetric imaging LiDAR using fractal superconducting nanowire single-photon detectors
- 2024
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 125:4
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Tidskriftsartikel (refereegranskat)abstract
- Full-Stokes polarimetric imaging light detection and ranging (LiDAR) provides rich information about distance, materials, texture, surface orientations, and profiles of objects, and it is an important remote-sensing technology. One major challenge to reach a long distance is to efficiently collect and detect the echo photons, as for long-range LiDAR, echo photons may become sparse. Here, we demonstrate a full-Stokes polarimetric imaging LiDAR, working at the eye-safe, telecommunication wavelength of 1560 nm, that can reach a range of 4 km. The key enabling technology is a four-channel system with multimode-fiber-coupled, large-area fractal superconducting nanowire single-photon detectors. Furthermore, we also explore faster imaging (e.g., pixel-dwell time of 1 ms) of the objects at a shorter distance, approximately 1 km. Our demonstration has significantly extended the working range of full-Stokes polarimetric imaging LiDAR and represents an important step toward practical systems that may enable many applications in remote sensing and the detection and recognition of targets.
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