| 1. |
- Qian, Deping, et al.
(författare)
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Design rules for minimizing voltage losses in high-efficiency organic solar cells
- 2018
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Ingår i: Nature Materials. - : NATURE PUBLISHING GROUP. - 1476-1122 .- 1476-4660. ; 17:8, s. 703-
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Tidskriftsartikel (refereegranskat)abstract
- The open-circuit voltage of organic solar cells is usually lower than the values achieved in inorganic or perovskite photovoltaic devices with comparable bandgaps. Energy losses during charge separation at the donor-acceptor interface and non-radiative recombination are among the main causes of such voltage losses. Here we combine spectroscopic and quantum-chemistry approaches to identify key rules for minimizing voltage losses: (1) a low energy offset between donor and acceptor molecular states and (2) high photoluminescence yield of the low-gap material in the blend. Following these rules, we present a range of existing and new donor-acceptor systems that combine efficient photocurrent generation with electroluminescence yield up to 0.03%, leading to non-radiative voltage losses as small as 0.21 V. This study provides a rationale to explain and further improve the performance of recently demonstrated high-open-circuit-voltage organic solar cells.
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| 2. |
- Chen, Kuan, et al.
(författare)
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Characterization and protein engineering of glycosyltransferases for the biosynthesis of diverse hepatoprotective cycloartane-type saponins in Astragalus membranaceus
- 2023
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Ingår i: Plant Biotechnology Journal. - : John Wiley & Sons. - 1467-7644 .- 1467-7652. ; 21:4, s. 698-710
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Tidskriftsartikel (refereegranskat)abstract
- Although plant secondary metabolites are important source of new drugs, obtaining these compounds is challenging due to their high structural diversity and low abundance. The roots of Astragalus membranaceus are a popular herbal medicine worldwide. It contains a series of cycloartane-type saponins (astragalosides) as hepatoprotective and antivirus components. However, astragalosides exhibit complex sugar substitution patterns which hindered their purification and bioactivity investigation. In this work, glycosyltransferases (GT) from A. membranaceus were studied to synthesize structurally diverse astragalosides. Three new GTs, AmGT1/5 and AmGT9, were characterized as 3-O-glycosyltransferase and 25-O-glycosyltransferase of cycloastragenol respectively. AmGT1(G146V/I) variants were obtained as specific 3-O-xylosyltransferases by sequence alignment, molecular modelling and site-directed mutagenesis. A combinatorial synthesis system was established using AmGT1/5/9, AmGT1(G146V/S) and the reported AmGT8 and AmGT8(A394F). The system allowed the synthesis of 13 astragalosides in Astragalus root with conversion rates from 22.6% to 98.7%, covering most of the sugar-substitution patterns for astragalosides. In addition, AmGT1 exhibited remarkable sugar donor promiscuity to use 10 different donors, and was used to synthesize three novel astragalosides and ginsenosides. Glycosylation remarkably improved the hepatoprotective and SARS-CoV-2 inhibition activities for triterpenoids. This is one of the first attempts to produce a series of herbal constituents via combinatorial synthesis. The results provided new biocatalytic tools for saponin biosynthesis.
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| 3. |
- Huang, Yiqian, et al.
(författare)
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A Novel Maximum Distance Separable Coded OFDM-RIS for 6G Wireless Communications
- 2023
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Ingår i: IEEE Wireless Communications Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 2162-2337 .- 2162-2345. ; 12:5, s. 927-931
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Tidskriftsartikel (refereegranskat)abstract
- The vision of the sixth generation mobile communication (6G) calls for extremely reliable data transmission over complex and diverse wireless channels. By combining the maximum distance separable (MDS) codes with the classic orthogonal frequency division multiplexing (OFDM), we present a new paradigm with the assistance of the reconfigurable intelligent surfaces (RIS). In our design, the RIS with limited phase shifts are adopted and the pairwise error probability (PEP) of the proposed system is first derived. Then, in order to further minimize the bit error rate (BER), we provide a novel method based on phase alignment to obtain the optimal solution for the discrete phase shifts. Our simulation results show that the proposed scheme provides considerable BER performance improvements compared to conventional OFDM systems. Moreover, the proposed discrete phase optimization algorithm is capable of achieving performance similar to that of the system with continuous phase shifts.
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| 4. |
- Huang, Yixuan, et al.
(författare)
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Designing Low-PAPR Waveform for OFDM-Based RadCom Systems
- 2022
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Ingår i: IEEE Transactions on Wireless Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 1536-1276 .- 1558-2248. ; 21:9, s. 6979-6993
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Tidskriftsartikel (refereegranskat)abstract
- This paper is focused on the fusion of radar and wireless communication, called RadCom, which has been extensively studied in recent years for future intelligent transportation systems. We propose a new waveform design algorithm for reducing peak-to-average power ratio (PAPR) in OFDM-based RadCom systems. We consider a flexible and generic RadCom structure in which a number of non-contiguous sub-bands for data transmission are located within a large contiguous spectrum hand for radar detection/sensing. New RadCom waveforms with low PAPR are obtained by carrying out optimization over those subcarriers which are complementary to the communication bands. As an application of the majorization-minimization (MM) optimization method, our major contribution is an l-norm cyclic algorithm which is capable of efficiently reducing the maximum PAPR of RadCom waveforms. We show by numerical simulation results that significant performance enhancements can be achieved compared to OFDM RadCom waveforms from legacy approaches.
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| 5. |
- Li, Xiaojuan, et al.
(författare)
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Climate and soil properties drive soil organic and inorganic carbon patterns across a latitudinal gradient in southwestern China
- 2023
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Ingår i: Journal of Soils and Sediments. - : Springer Science and Business Media LLC. - 1614-7480 .- 1439-0108. ; 23:1, s. 91-102
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Tidskriftsartikel (refereegranskat)abstract
- PurposeDrylands account for 47.2% of land area and contain 15.5% of global carbon (C). However, the variation in organic and inorganic C stocks across latitudinal gradients in arid and semiarid shrubland ecosystems remains understudied, and we lack in-depth understanding of the main drivers of C variation at this spatial scale.MethodsHere, we sampled soils from 95 sites across a latitudinal gradient to explore both the latitudinal patterns and potential drivers of soil organic carbon density (SOCD) and soil inorganic carbon density (SICD). We also assessed variation in SOCD and SICD down the soil profile, by sampling soils at four depths (0 – 10 cm, 10 – 20 cm, 20 – 30 cm, and 30 – 50 cm).ResultBoth SOCD and SICD exhibited a binomial relationship with latitude (P < 0.01). Soil properties accounted for the greatest variation in SOCD, with the most important explanatory factor being exchangeable calcium, followed by mean annual temperature, pH, plant diversity, and silt content. Soil pH and plant diversity were more important in explaining variation in SOCD in the subsoil (> 20 cm depth) than the topsoil. For SICD, soil properties explained the greatest variation at all depths. Soil pH explained the most variance in SICD, followed by exchangeable calcium and mean annual temperature in the topsoil (i.e., 0 – 10 cm and 10 – 20 cm). In the subsoil (i.e., 20 – 30 cm and 30 – 50 cm), exchangeable calcium was the most important predictor, followed by soil organic carbon, mean annual temperature, and pH.ConclusionOur study shows that soil properties are a strong predictor of latitudinal patterns of soil organic and inorganic C in arid and semiarid shrubland ecosystems. We also identified differences in potential drivers of SOCD and SICD with depth, advancing our understanding of large-scale patterns of C storage in arid and semiarid soils.
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| 6. |
- Li, Xiaojuan, et al.
(författare)
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Latitudinal patterns of light and heavy organic matter fractions in arid and semi-arid soils
- 2022
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Ingår i: Catena. - : Elsevier BV. - 0341-8162. ; 215
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Tidskriftsartikel (refereegranskat)abstract
- Semi-arid and arid ecosystems are important for the global C cycle. Despite this, it remains unclear how organic matter fractions vary across latitudinal gradients, and what drives this variation, in dry ecosystems. In this study, we sampled soils from 100 sites across a latitudinal gradient in the dry valleys of southwestern China to explore the latitudinal patterns of light fraction organic matter (LFOM) and heavy fraction organic matter (HFOM) at two soil depths (0–10 cm and 10–20 cm). Across the studied gradient, HFOM accounted for a larger fraction of soil organic matter than LFOM. LFOM increased exponentially with increasing latitude at both 0–10 cm and 10–20 cm depths. Heavy fraction organic C increased linearly with increasing latitude at both depths, while heavy fraction organic N only increased with latitude in soils from 10 to 20 cm depth. Latitudinal patterns of LFOM were mainly explained by climate, with the most important driver being mean annual temperature, followed by mean annual precipitation. Soil physicochemical factors – in particular cation exchange capacity and silt content – explained the most variation in HFOM. Total microbial biomass was also important in explaining variation in HFOM, especially in the 10–20 cm soil layer. Overall, our results shed light on the spatial distribution of organic matter fractions in arid and semi-arid regions. We also identify candidate drivers of the variation in LFOM and HFOM in arid and semi-arid regions, finding that climate primarily explains variation in LFOM while soil physiochemistry primarily explains variation in HFOM.
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| 7. |
- Liu, Baoqing, et al.
(författare)
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Experimental Investigation on Drawdown of Floating Particles in Viscous Systems Driven by Coaxial Mixers
- 2019
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Ingår i: Industrial and Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 58, s. 11060-11071
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Tidskriftsartikel (refereegranskat)abstract
- In view of the current situation of single form and low efficiency, a coaxial mixer with wide adaptability was combined with the drawdown of floating particles in viscous systems, and the effects of operation mode, impeller type, impeller diameter, impeller submergence, system viscosity, solid concentration and particle size were investigated experimentally. It is found that the coaxial mixer under corotation mode can achieve the critical drawdown of floating particles with lower speed and power than the corresponding single-shaft mixer, and the advantage becomes more obvious with increasing system viscosity and solid volume fraction. Under the same conditions, compared with the axial and radial flow impellers, the mixed flow impeller with down-pumping mode can effectively draw the floating particles down with the lowest critical speed and power. Moreover, a larger impeller diameter and smaller impeller submergence are recommended for the drawdown of floating particles, but the impeller diameter should not exceed half of the vessel diameter.
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| 8. |
- Liu, Shungang, et al.
(författare)
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The role of connectivity in significant bandgap narrowing for fused-pyrene based non-fullerene acceptors toward high-efficiency organic solar cells
- 2020
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 8:12, s. 5995-6003
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Tidskriftsartikel (refereegranskat)abstract
- Great attention has been paid to developing low bandgap non-fullerene acceptors (NFAs) for matching wide bandgap donor polymers to increase the photocurrent and therefore the power conversion efficiencies (PCEs) of NFA organic solar cells, while pyrene-core based acceptor-donor-acceptor (A-D-A) NFAs have been mainly reported via the 2,9-position connection due to their bisthieno[3′,2′-b']thienyl[a,h]pyrene fused via a five-membered ring bridge at the ortho-position of pyrene as the representative one named FPIC5, which has prohibited further narrowing their energy gap. Herein, an acceptor FPIC6 was exploited by creating the 1,8-position connection through fusing as bisthieno[3′,2′-b′]thienyl[f-g,m-n]pyrene linked at the bay-position via a six-membered bridge, with enhanced push-pull characteristics within such A-D-A structure. As a structural isomer of FPIC5, FPIC6 exhibited a much lower bandgap of 1.42 eV (1.63 eV for FPIC5). Therefore, the photocurrent and PCE of PTB7-Th:FPIC6 cells were improved to 21.50 mA cm-2 and 11.55%, respectively, due to the balanced mobilities, better photoluminescence quenching efficiency and optimized morphology, which are both ∼40% better than those of PTB7-Th:FPIC5 cells. Our results clearly proved that a pyrene fused core with 1,8-position connection with electron-withdrawing end groups instead of 2,9-position connection is an efficient molecular design strategy to narrow the optical bandgap and improve the photovoltaic performance of NFA based OSCs.
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| 9. |
- Qian, Liangxin, et al.
(författare)
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Multi-Dimensional Polarized Modulation for Land Mobile Satellite Communications
- 2021
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Ingår i: IEEE Transactions on Cognitive Communications and Networking. - : Institute of Electrical and Electronics Engineers (IEEE). - 2332-7731. ; 7:2, s. 383-397
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Tidskriftsartikel (refereegranskat)abstract
- In this article, a novel multiple-input multiple-out (MIMO) transmission scheme, called generalized polarized enhanced spatial modulation (GPESM), is proposed for dual-polarized land mobile satellite (LMS) communications. We first introduce the enhanced spatial modulation (ESM) technique for dual-polarized LMS communications, in which polarization dimension, spatial dimension and multiple signal constellations are used to transmit information and obtain substantial performance gain. Meanwhile, the theoretical upper bound for the average bit error probability (ABEP) of the proposed GPESM scheme is derived. In order to further improve the reliability of the system, we also propose two novel power allocation (PA) algorithms for GPESM system, which are the optimization-driven approximated max-min distance (AMMD)-based PA algorithm and the data-driven deep neural network (DNN)-based PA algorithm. To achieve an enhanced spatial diversity gain, we consider to apply a reconfigurable intelligent surface (RIS) to the GPESM system as a relay to assist in transmitting information. In this way, the user can receive the information transmitted by the satellite on one hand, and the information sent by the satellite via the RIS relay on the other hand. We also extend the above-mentioned two PA algorithms to the RIS-assisted GPESM systems. Our simulation results show that the RIS-assisted GPESM systems are capable of obtaining high bit error rate (BER) performance gain (up to 10 dB) compared to the standard GPESM system and two PA algorithms can further improve the performance to the systems.
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| 10. |
- Qin, Wei, et al.
(författare)
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A two-stage ant colony algorithm for hybrid flow shop scheduling with lot sizing and calendar constraints in printed circuit board assembly
- 2019
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Ingår i: Computers & industrial engineering. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0360-8352 .- 1879-0550. ; 138
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates a multi-stage hybrid flow shop scheduling problem with challenging characteristics including lot sizing, calendar constraints and sequence-dependent setup times in a real-world printed circuit board (PCB) assembly shop. Besides, other characteristics such as unrelated parallel machines and stage skipping also complicate the problem. Such features make the scheduling problem very difficult to find an optimal or near optimal solution. To reduce the complexity of such a PCB scheduling problem, this study develops a hierarchical approach which decomposes the original problem into two highly coupled sub-problems including job sequencing and lot scheduling with lot sizing, and further proposes a two-stage ant colony algorithm with lot sizing to evolve best results in the makespan performance. Extensive computational experiments have been conducted to illustrate the superiority of the algorithm in terms of computational time and stability.
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| 11. |
- Qin, Wei, et al.
(författare)
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An available-to-promise stochastic model for order promising based on dynamic resource reservation policy
- 2023
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Ingår i: International Journal of Production Research. - : Taylor & Francis Ltd. - 0020-7543 .- 1366-588X. ; 61:16, s. 5525-5542
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Tidskriftsartikel (refereegranskat)abstract
- Facing uncertain future customer orders, a pull-based available-to-promise (ATP) mechanism will deteriorate the overall profit since it allocates critical resources only to current customer orders. To prevent current less-profitable customer orders from over-consuming critical resources, this study investigates a push-pull based ATP problem with two time stages and three profit margin levels, and develops a dynamic resource reservation policy to maximise the expected total profit. Then, a corresponding push-pull based stochastic ATP model is established with known independent demand distributions, and the optimal reservation level is derived by the genetic algorithm to maximise the expected total profit. Finally, a series of simulation experiments are conducted to reveal the impact of some key factors, and the experiment results provide theoretical guidance and implementation methods for companies to maximise overall profits.
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| 12. |
- Qin, Wei, et al.
(författare)
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Sustainable service oriented equipment maintenance management of steel enterprises using a two-stage optimization approach
- 2022
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Ingår i: Robotics and Computer-Integrated Manufacturing. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0736-5845 .- 1879-2537. ; 75
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Tidskriftsartikel (refereegranskat)abstract
- Equipment maintenance management is essential for steel enterprises to provide sustainable production services. However, few studies have considered the equipment maintenance scheduling of steel enterprises due to the characteristics of large-scale and complex constraints. This study analyses the characteristics of equipment maintenance scheduling in the steel industry and incorporates multiple complex constraints into a mathematical model. To find an optimal or near optimal solution, a two-stage optimization approach is developed that introduces the rule-based prescheduling method to quickly obtain a reasonable maintenance plan in the first stage and employs a modified genetic algorithm to further optimize the prescheduling maintenance plan in the second stage. The case of Baowu Steel is used for verification and the experimental results demonstrate the superiority and effectiveness of the proposed optimization approach, which improves the comprehensive performance by 40.3% on the basis of prescheduling.
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| 13. |
- Xu, Zilong, et al.
(författare)
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Experimental investigation on solid suspension performance of coaxial mixer in viscous and high solid loading systems
- 2019
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Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509. ; 208
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Tidskriftsartikel (refereegranskat)abstract
- The coaxial mixers consisting of an inner Rushton turbine or propeller and an outer anchor were combined first with the just off-bottom suspension in viscous and high solid loading systems. In this study, a new method based on RGB brightness analysis was proposed to determine the cloud height, and the measures to promote cloud height were also discussed. In addition, the effects of rotation modes, pumping modes and solid loading on the just-suspension power were investigated. The results showed that the co-rotation coaxial mixers with an up-pumping inner impeller could achieve the just suspension at lower power consumption and were recommended. The combination of anchor and up-pumping propeller was the most energy efficient among the investigated mixers, whereas its cloud height was relatively low. The high off-bottom clearance and the combined inner impeller could promote the cloud height with little power variation, but the enlargement of inner impeller had no obvious effect.
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| 14. |
- Yao, Xi, et al.
(författare)
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A Novel Hybrid Code-Domain Index Modulation Scheme
- 2021
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Ingår i: IEEE Communications Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1089-7798 .- 1558-2558. ; 25:10, s. 3403-3407
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, a novel hybrid code-domain index modulation (CDIM) scheme is proposed for future multi-domain communications, where the indices of the interleaving and spreading codes are exploited for information transmission. Specifically, we first provide a general design framework for CDIM, including the bit-to-symbol mapping rule and the detector. Then, we propose a code optimization method to select the utilized interleaver sequence and spreading code, with the objective of significantly improving the bit error ratio (BER) performance. Moreover, an intelligent detector is also proposed for CDIM in complicated wireless communication scenarios, e.g., non-Gaussian wireless channels. Simulation results show that the proposed CDIM is capable of substantially improving the system error performance compared with the conventional coded wireless communication systems.
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| 15. |
- Zhang, Haiwen, et al.
(författare)
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Biologically inspired flexible photonic films for efficient passive radiative cooling
- 2020
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 117:26, s. 14657-14666
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Tidskriftsartikel (refereegranskat)abstract
- Temperature is a fundamental parameter for all forms of lives. Natural evolution has resulted in organisms which have excellent thermoregulation capabilities in extreme climates. Bioinspired materials that mimic biological solution for thermoregulation have proven promising for passive radiative cooling. However, scalable production of artificial photonic radiators with complex structures, outstanding properties, high throughput, and low cost is still challenging. Herein, we design and demonstrate biologically inspired photonic materials for passive radiative cooling, after discovery of longicorn beetles' excellent thermoregulatory function with their dual-scale fluffs. The natural fluffs exhibit a finely structured triangular cross-section with two thermoregulatory effects which effectively reflects sunlight and emits thermal radiation, thereby decreasing the beetles' body temperature. Inspired by the finding, a photonic film consisting of a micropyramid-arrayed polymer matrix with random ceramic particles is fabricated with high throughput. The film reflects similar to 95% of solar irradiance and exhibits an infrared emissivity >0.96. The effective cooling power is found to be similar to 90.8 W center dot m(-2) and a temperature decrease of up to 5.1 degrees C is recorded under direct sunlight. Additionally, the film exhibits hydrophobicity, superior flexibility, and strong mechanical strength, which is promising for thermal management in various electronic devices and wearable products. Our work paves the way for designing and fabrication of high-performance thermal regulation materials.
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