| 1. |
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| 2. |
- He, Yuan, et al.
(författare)
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Acoustic Localization System for Precise Drone Landing
- 2024
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Ingår i: IEEE Transactions on Mobile Computing. ; 23:5, s. 4126-4144
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Tidskriftsartikel (refereegranskat)abstract
- We present MicNest: an acoustic localization system enabling precise drone landing. In MicNest, multiple microphones are deployed on a landing platform in carefully devised configurations. The drone carries a speaker transmitting purposefully-designed acoustic pulses. The drone may be localized as long as the pulses are correctly detected. Doing so is challenging: i) because of limited transmission power, propagation attenuation, background noise, and propeller interference, the Signal-to-Noise Ratio (SNR) of received pulses is intrinsically low; ii) the pulses experience non-linear Doppler distortion due to the physical drone dynamics; iii) as location information is used during landing, the processing latency must be reduced to effectively feed the flight control loop. To tackle these issues, we design a novel pulse detector, Matched Filter Tree (MFT), whose idea is to convert pulse detection to a tree search problem. We further present three practical methods to accelerate tree search jointly. Our experiments show that MicNest can localize a drone 120 m away with 0.53% relative localization error at 20 Hz location update frequency. For navigating drone landing, MicNest can achieve a success rate of 94 %. The average landing error (distance between landing point and target point) is only 4.3 cm.
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| 3. |
- Wang, Weiguo, et al.
(författare)
-
Acoustic localization of drones in precise landing : The research and practice with micnest
- 2023
-
Ingår i: GetMobile. - : Association for Computing Machinery (ACM). - 2375-0529 .- 2375-0537. ; 27:3, s. 27-32
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Delivery drones have the potential to revolutionize transportation and distribution of goods. With their autonomous navigation capabilities, they offer an efficient solution to bypass the challenges posed by complex urban traffic and enable instant package delivery. Many industrial firms are actively exploring the commercial feasibility of instant drone deliveries. Meituan, one of the largest companies in this area, devised a systematic approach to instant delivery using drones. The process begins with loading the package onto the drone, which then takes off, ascends to cruising altitude, and sets a direct course towards the designated destination. Typically, this destination is a Meituan-operated self-collection station located near the customer.
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| 4. |
- Yi, Chuixiang, et al.
(författare)
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Climate control of terrestrial carbon exchange across biomes and continents
- 2010
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 5:3
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate-carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO2 exchange with the atmosphere across biomes and continents are lacking. Here we present data describing the relationships between net ecosystem exchange of carbon (NEE) and climate factors as measured using the eddy covariance method at 125 unique sites in various ecosystems over six continents with a total of 559 site-years. We find that NEE observed at eddy covariance sites is (1) a strong function of mean annual temperature at mid-and high-latitudes, (2) a strong function of dryness at mid-and low-latitudes, and (3) a function of both temperature and dryness around the mid-latitudinal belt (45 degrees N). The sensitivity of NEE to mean annual temperature breaks down at similar to 16 degrees C (a threshold value of mean annual temperature), above which no further increase of CO2 uptake with temperature was observed and dryness influence overrules temperature influence.
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| 5. |
- Su, Changqing, et al.
(författare)
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Gene-Viral Cancer Therapy Using Dual-Regulated Oncolytic Adenovirus with Antiangiogenesis Gene for Increased Efficacy.
- 2008
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Ingår i: Molecular Cancer Research. - 1557-3125. ; 6, s. 568-575
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Tidskriftsartikel (refereegranskat)abstract
- Conditionally replicative adenovirus (CRAD) represents a promising approach for cancer therapy. Several CRADs controlled by the human telomerase reverse transcriptase promoter have been developed. However, because of their replicative capacity, the importance of cancer specificity for CRADs needs to be further emphasized. In this study, we have developed a novel dual-regulated CRAD, CNHK500-mE, which has its E1a and E1b gene controlled by the human telomerase reverse transcriptase promoter and the hypoxia response element, respectively. It also carries a mouse endostatin expression cassette controlled by the cytomegalovirus promoter. These properties allow for increased cancer cell targeting specificity and decreased adverse side effects. We showed that CNHK500-mE preferentially replicated in cancer cells. Compared with a replication-defective vector carrying the same endostatin expression cassette, CNHK500-mE-mediated transgene expression level was markedly increased via viral replication within cancer cells. In the nasopharyngeal tumor xenograft model, CNHK500-mE injection resulted in antitumor efficacy at day 7 after therapy. Three weeks later, it led to significant inhibition of xenograft tumor growth due to the combined effects of viral oncolytic therapy and antiangiogenesis gene therapy. Pathologic examination showed that most cancer cells were positive for adenoviral capsid protein and for apoptotic terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling in the CNHK500-mE-treated tumor tissues, and the microvessels in these tumor tissues were diminished in quantity and abnormal in morphology. These results suggest that, as a potential cancer therapeutic agent, the CNHK500-mE is endowed with higher specificity to cancer cells and low cytotoxicity to normal cells. (Mol Cancer Res 2008;6(4):OF1-8).
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| 6. |
- Su, Wenyan, et al.
(författare)
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Nonconjugated Terpolymer Acceptors with Two Different Fused-Ring Electron-Deficient Building Blocks for Efficient All-Polymer Solar Cells
- 2021
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 13:5, s. 6442-6449
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Tidskriftsartikel (refereegranskat)abstract
- The ternary polymerization strategy of incorporating different donor and acceptor units forming terpolymers as photovoltaic materials has been proven advantageous in improving power conversion efficiencies (PCEs) of polymer solar cells (PSCs). Herein, a series of low band gap nonconjugated terpolymer acceptors based on two different fused-ring electron-deficient building blocks (IDIC16 and ITIC) with adjustable photoelectric properties were developed. As the third component, ITIC building blocks with a larger pi-conjugation structure, shorter solubilizing side chains, and red-shifted absorption spectrum were incorporated into an IDIC16-based nonconjugated copolymer acceptor PF1-TS4, which built up the terpolymers with two conjugated building blocks linked by flexible thioalkyl chain-thiophene segments. With the increasing ITIC content, terpolymers show gradually broadened absorption spectra and slightly down-shifted lowest unoccupied molecular orbital levels. The active layer based on terpolymer PF1-TS4-60 with a 60% ITIC unit presents more balanced hole and electron mobilities, higher photoluminescence quenching efficiency, and improved morphology compared to those based on PF1-TS4. In all-polymer solar cells (all-PSCs), PF1-TS4-60, matched with a wide band gap polymer donor PM6, achieved a similar open-circuit voltage (V-oc) of 0.99 V, a dramatically increased short-circuit current density (J(sc)) of 15.30 mA cm(-2), and fill factor (FF) of 61.4% compared to PF1-TS4 = 0.99 V, J(sc) = 11.21 mA cm(-2), and FF = 55.6%). As a result, the PF1-TS4-60-based all-PSCs achieved a PCE of 9.31%, which is similar to 50% higher than the PF1-TS4-based ones (6.17%). The results demonstrate a promising approach to develop high-performance nonconjugated terpolymer acceptors for efficient all-PSCs by means of ternary polymerization using two different A-D-A-structured fused-ring electron-deficient building blocks.
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| 7. |
- Sun, Yimiao, et al.
(författare)
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AIM : Acoustic Inertial Measurement for Indoor Drone Localization and Tracking
- 2023
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Ingår i: SenSys '22. - New York, NY, USA : Association for Computing Machinery (ACM). - 9781450398862 ; , s. 476-488
-
Konferensbidrag (refereegranskat)abstract
- We present Acoustic Inertial Measurement (AIM), a one-of-a-kind technique for indoor drone localization and tracking. Indoor drone localization and tracking are arguably a crucial, yet unsolved challenge: in GPS-denied environments, existing approaches enjoy limited applicability, especially in Non-Line of Sight (NLoS), require extensive environment instrumentation, or demand considerable hardware/software changes on drones. In contrast, AIM exploits the acoustic characteristics of the drones to estimate their location and derive their motion, even in NLoS settings. We tame location estimation errors using a dedicated Kalman filter and the Interquartile Range rule (IQR). We implement AIM using an off-the-shelf microphone array and evaluate its performance with a commercial drone under varied settings. Results indicate that the mean localization error of AIM is 46% lower than commercial UWB-based systems in complex indoor scenarios, where state-of-the-art infrared systems would not even work because of NLoS settings. We further demonstrate that AIM can be extended to support indoor spaces with arbitrary ranges and layouts without loss of accuracy by deploying distributed microphone arrays.
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| 8. |
- Tang, Wei, et al.
(författare)
-
17.25% high efficiency ternary solar cells with increased open-circuit voltage using a high HOMO level small molecule guest donor in a PM6:Y6 blend
- 2021
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7496 .- 2050-7488. ; 9:36, s. 20493-20501
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Tidskriftsartikel (refereegranskat)abstract
- A small molecule donor TiC12 with an asymmetric thieno[3,2-c]isochromene unit is incorporated into the PM6:Y6 system as the third component for constructing ternary organic solar cells (OSCs). It was found that TiC12 played an outstanding role in improvement of open-circuit voltage (V-oc), short-circuit current (J(sc)) and fill factor (FF) for the OSCs. The effects of TiC12 on the absorption, exciton dissociation, charge extraction, bimolecular recombination and morphology of the active layer are analyzed in detail. The synergetic improvement of J(sc), V-oc and FF parameters is realized to generate an advanced power conversion efficiency (PCE) of 17.25% in the optimized PM6 : TiC12 : Y6 (0.9 : 0.1 : 1.2) ternary device. Furthermore, the V-oc is increased in proportion to the added amount of TiC12 in the ternary devices due to reduced disorder and nonradiative energy loss, although the guest donor TiC12 exhibited a higher HOMO level than PM6. This study provides an effective and innovative approach to elevate V-oc and thus PCE for ternary OSCs by introducing a guest small molecule donor with a higher HOMO level and better miscibility with the acceptor.
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| 9. |
- Wang, Weiguo, et al.
(författare)
-
MicNest : Long-Range Instant Acoustic Localization of Drones in Precise Landing
- 2022
-
Ingår i: SenSys '22. - New York, NY, USA : Association for Computing Machinery (ACM). - 9781450398862 ; , s. 504-517
-
Konferensbidrag (refereegranskat)abstract
- We present MicNest: an acoustic localization system enabling precise landing of aerial drones. Drone landing is a crucial step in a drone's operation, especially as high-bandwidth wireless networks, such as 5G, enable beyond-line-of-sight operation in a shared airspace and applications such as instant asset delivery with drones gain traction. In MicNest, multiple microphones are deployed on a landing platform in carefully devised configurations. The drone carries a speaker transmitting purposefully-designed acoustic pulses. The drone may be localized as long as the pulses are correctly detected. Doing so is challenging: i) because of limited transmission power, propagation attenuation, background noise, and propeller interference, the Signal-to-Noise Ratio (SNR) of received pulses is intrinsically low; ii) the pulses experience non-linear Doppler distortion due to the physical drone dynamics while airborne; iii) as location information is to be used during landing, the processing latency must be reduced to effectively feed the flight control loop. To tackle these issues, we design a novel pulse detector, Matched Filter Tree (MFT), whose idea is to convert pulse detection to a tree search problem. We further present three practical methods to accelerate tree search jointly. Our real-world experiments show that MicNest is able to localize a drone 120 m away with 0.53% relative localization error at 20 Hz location update frequency.
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| 10. |
- Zhuang, Wenliu, 1979, et al.
(författare)
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Synthesis and Electronic Properties of Diketopyrrolopyrrole-Based Polymers with and without Ring-Fusion
- 2021
-
Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 54:2, s. 970-980
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Tidskriftsartikel (refereegranskat)abstract
- Diketopyrrolopyrroles (DPP) have been recognized as a promising acceptor unit for construction of semiconducting donor-acceptor (D-A) polymers, which are typically flanked by spacers such as thiophene rings via a carbon-carbon single bond formation. It may suffer from a decrease in the coplanarity of the molecules especially when bulky side chains are installed. In this work, the two N atoms in the DPP unit are further fused with C-3 of the two flanking thiophene rings, yielding a p-expanded, very planar fused-ring building block (DPPFu). A novel DPPFu-based D-A copolymer (PBDTT-DPPFu) was successfully synthesized, consisting of a benzo[1,2-b:4,5-b]dithiophene (BDTT) unit as a donor and a DPPFu unit as an acceptor. For comparison, the unfused DPP-based counterpart PBDTT-DPP was also synthesized. Two dodecyl alkyl chains were attached to thiophene rings of DPP moieties to ensure good solubility of the DPPFu-based polymer. The influence of the ring-fusion effect on their structure, photophysical properties, electronic properties, molecular packing, and charge transport properties is investigated. Ring-fusion enhances the intermolecular interactions of PBDTT-DPPFu polymer chains as indicated by density functional theory calculation and analysis of electrostatic potential and van der Waals potential and results in significantly improved molecular packing for both the in-plane and out-of-plane directions as suggested by X-ray measurements. Finally, we correlate the molecular packing to the device performance by fabricating field-effect transistors based on these two polymers. The charge carrier mobility of the ring-fused polymer PBDTT-DPPFu is significantly higher as compared to the PBDTT-DPP polymer without ring-fusion, although PBDTT-DPPFu exhibited a much lower number-average molecular weight of 17 kDa as compared to PBDTT-DPP with a molecular weight of 108 kDa. The results from our comparative study provide a robust way to increase the interchain interaction by ring-fusion-promoted coplanarity.
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| 11. |
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| 12. |
- Dang, Dongfeng, 1988, et al.
(författare)
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Enhanced Photovoltaic Performance of Indacenodithiophene-Quinoxaline Copolymers by Side- Chain Modulation
- 2014
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6840 .- 1614-6832. ; 4:15, s. Art. no. 1400680-
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Tidskriftsartikel (refereegranskat)abstract
- Two pairs of indacenodithiophene (IDT) and quinoxaline-based copolymers with meta- or para-hexyl-phenyl side chains on the IDT unit are synthesized. The meta-substituted polymers offer better solubility, higher molecular weight for both fluorinated and non-fluorinated copolymers, and a superior photovoltaic performance with a power conversion efficiency of 7.8%. The side-chain design strategy presented is an efficient way to produce high performance conjugated polymers for organic electronics.
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| 13. |
- Fan, Qunping, 1989, et al.
(författare)
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High-performance all-polymer solar cells enabled by a novel low bandgap non-fully conjugated polymer acceptor
- 2021
-
Ingår i: Science in China Series B. - : Springer Nature. - 1674-7291 .- 1869-1870. ; 64, s. 1380-1388
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Tidskriftsartikel (refereegranskat)abstract
- Anon-fully conjugated polymer as a new class of acceptor materials has shown some advantages over its small molecular counterpart when used in photoactive layers for all-polymer solar cells (all-PSCs), despite a low power conversion efficiency (PCE) caused by its narrow absorption spectra. Herein, a novel non-fully conjugated polymer acceptor PFY-2TS with a low bandgap of similar to 1.40 eV was developed, via polymerizing a large pi-fused small molecule acceptor (SMA) building block (namely YBO) with a non-conjugated thioalkyl linkage. Compared with its precursor YBO, PFY-2TS retains a similar low bandgap but a higher LUMO level. Moreover, compared with the structural analog of YBO-based fully conjugated polymer acceptor PFY-DTC, PFY-2TS shows similar absorption spectrum and electron mobility, but significantly different molecular crystallinity and aggregation properties, which results in optimal blend morphology with a polymer donor PBDB-T and better device physical processes in all-PSCs. As a result, PFY-2TS-based all-PSCs achieved a PCE of 12.31% with a small energy loss of 0.56 eV enabled by the reduced non-radiative energy loss (0.24 eV), which is better than that of 11.08% for the PFY-DTC-based ones. Our work clearly demonstrated that non-fully conjugated polymers as a new class of acceptor materials are very promising for the development of high-performance all-PSCs.
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| 14. |
- Fan, Qunping, 1989, et al.
(författare)
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Over 14% efficiency all-polymer solar cells enabled by a low bandgap polymer acceptor with low energy loss and efficient charge separation
- 2020
-
Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry. - 1754-5692 .- 1754-5706. ; 13:12, s. 5017-5027
-
Tidskriftsartikel (refereegranskat)abstract
- Obtaining both high open-circuit voltage (V-oc) and short-circuit current density (J(sc)) has been a major challenge for efficient all-polymer solar cells (all-PSCs). Herein, we developed a polymer acceptor PF5-Y5 with excellent optical absorption capability (onset extending to similar to 880 nm and maximum absorption coefficient exceeding 105 cm(-1) in a film), high electron mobility (3.18 x 10(3) cm(2) V-1 s(-1)) and high LUMO level (-3.84 eV) to address such a challenge. As a result, the PBDB-T:PF5-Y5-based all-PSCs achieved a high power conversion efficiency of up to 14.45% with both a high Voc (0.946 V) and a high Jsc (20.65 mA cm(-2)), due to the high and broad absorption coverage, small energy loss (0.57 eV) and efficient charge separation and transport in the device, which are among the best values in the all-PSC field. In addition, the all-PSC shows a similar to 15% improvement in PCE compared to its counterpart small molecule acceptor (Y5)-based device. Our results suggest that PF5-Y5 is a very promising polymer acceptor candidate for applications in efficient all-PSCs.
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| 15. |
- Huang, Weiguo, et al.
(författare)
-
InAs quantum wells grown on GaP/Si substrate with Ga(In,As)P metamorphic buffers
- 2022
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Ingår i: Hongwai Yu Haomibo Xuebao/Journal of Infrared and Millimeter Waves. - 1001-9014. ; 41:1, s. 253-261
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Tidskriftsartikel (refereegranskat)abstract
- InAs/In0.83Al0.17As quantum wells have been demonstrated on In0.83Al0.17As metamorphic layers on GaP/Si substrates. The effects of GaxIn1-xP and GaAsyP1-y graded buffer layers on the sample performances are investigated. The sample with GaxIn1-xP metamorphic buffer layer has narrower width in X-ray diffraction reciprocal space maps, indicating less misfit dislocations in the sample. Mid-infrared photoluminescence signals have been observed for both samples at room temperature, while the sample with GaxIn1-xP metamorphic buffer shows stronger photoluminescence intensity at all temperatures. The results indicate the metamorphic buffers with mixed cations show superior effects for the mid-infrared InAs quantum wells on GaP/Si composite substrates.
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| 16. |
- Jiao, Zhejing, et al.
(författare)
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InAs triangular quantum wells grown on InP/SiO 2 /Si heterogeneous substrate for mid-infrared emission
- 2021
-
Ingår i: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001. ; 136
-
Tidskriftsartikel (refereegranskat)abstract
- The properties of InAs/In0.53Ga0.37As triangular quantum wells (QWs) grown on an InP/SiO2/Si integrated substrate by ion-slicing technology are investigated. The material structure and growth quality are characterized by the X-ray diffraction (XRD) and transmission electron microscope measurements. The photoluminescence (PL) spectra at various temperatures are also analyzed. The PL peak wavelengths red-shift from 1.94 to 2.13 μm with the increase of temperature from 12.4 to 300 K. The experimental results of the QWs on InP/SiO2/Si substrate are found to be comparable with the performance of the same QWs grown on an InP substrate. The results are promising for future integration of Si with InP-based optical devices for the applications of light emission in mid-infrared wavelength range.
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| 17. |
- Ma, Zaifei, et al.
(författare)
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A Facile Method to Enhance Photovoltaic Performance of Benzodithiophene-Isoindigo Polymers by Inserting Bithiophene Spacer
- 2014
-
Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6840 .- 1614-6832. ; 4:6, s. Art. no. 1301455-
-
Tidskriftsartikel (refereegranskat)abstract
- This study describes the synthesis and characterization of four polymers based on benzo[1,2-b:4,5-b']dithiophene (BDT) and isoindigo with zero, one, two, and three thiophene spacer groups. Results have demonstrated that the use of bithiophene as a spacer unit improves the geometry of the polymer chain, making it planar, and hence, potentially enhanced π- π stacking occurs. Due to favorable interaction of the polymer chains, enhanced absorption coefficient, and optimal morphology, PBDT-BTI, which possesses bithiophene as a spacer, revealed high current and fill factor leading to a power conversion efficiency of 7.3% in devices, making this polymer the best performing isoindigo-based material in polymer solar cells (PSCs). Also, PBDT-BTI could still maintain efficiency of over 6% with the active layer thickness of 270 nm, making it a potential candidate for a material in printed PSCs. These results demonstrate that the use of thiophene spacers in D-A polymers could be an important design strategy to produce high-performance PSCs.
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| 18. |
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| 19. |
- Wang, Sifan, et al.
(författare)
-
Fire carbon emissions over Equatorial Asia reduced by shortened dry seasons
- 2023
-
Ingår i: npj Climate and Atmospheric Science. - 2397-3722. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- Fire carbon emissions over Equatorial Asia (EQAS) play a critical role in the global carbon cycle. Most regional fire emissions (89.0%) occur in the dry season, but how changes in the dry-season length affect the fire emissions remains poorly understood. Here we show that, the length of the EQAS dry season has decreased significantly during 1979–2021, and the delayed dry season onset (5.4 ± 1.6 (± one standard error) days decade−1) due to increased precipitation (36.4 ± 9.1 mm decade−1) in the early dry season is the main reason. The dry season length is strongly correlated with the length of the fire season. Increased precipitation during the early dry season led to a significant reduction (May: −0.7 ± 0.4 Tg C decade−1; August: −12.9 ± 6.7 Tg C decade−1) in fire carbon emissions during the early and peak fire season. Climate models from the Coupled Model Intercomparison Project Phase 6 project a continued decline in future dry season length in EQAS under medium and high-emission scenarios, implying further reductions in fire carbon emissions.
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| 20. |
- Xiong, Wenjing, 1989, et al.
(författare)
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Combining Benzotriazole and Benzodithiophene Host Units in Host-Guest Polymers for Efficient and Stable Near-Infrared Emission from Light-Emitting Electrochemical Cells
- 2019
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Ingår i: Advanced Optical Materials. - : Wiley. - 2195-1071 .- 2162-7568. ; 7:15
-
Tidskriftsartikel (refereegranskat)abstract
- A set of host-guest copolymers with alternating benzodithiophene and benzotriazole (BTz) derivatives as host units and 4,7-bis(5-bromothiophen-2-yl)-benzo[c][1,2,5]thiadiazole as the minority guest are synthesized, characterized, and evaluated for applications. A light-emitting electrochemical cell (LEC) comprising such a host-guest copolymer delivers fast-response near-infrared (NIR) emission peaked at 723 nm with a high radiance of 169 mu W cm(-2) at a low drive voltage of 3.6 V. The NIR-LEC also features good stability, as the peak NIR output only drops by 8% after 350 h of continuous operation. It is, however, found that the LEC performance is highly sensitive to the detailed chemical structure of the host backbone, and that the addition of electron-donating thiophene bridging units onto the BTz unit is highly positive while the inclusion of fluorine atoms results in a drastically lowered performance, presumably because of the emergence of hydrogen bonding within the active material.
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| 21. |
- Zhang, Zhonggang, et al.
(författare)
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Three-Dimensional CFD Modeling of Transport Phenomena in a Cross-Flow Anode-Supported Planar SOFC
- 2014
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 7:1, s. 80-98
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, a three-dimensional computational fluid dynamics (CFD) model is developed for an anode-supported planar SOFC from the Chinese Academy of Science Ningbo Institute of Material Technology and Engineering (NIMTE). The simulation results of the developed model are in good agreement with the experimental data obtained under the same conditions. With the simulation results, the distribution of temperature, flow velocity and the gas concentrations through the cell components and gas channels is presented and discussed. Potential and current density distributions in the cell and overall fuel utilization are also presented. It is also found that the temperature gradients exist along the length of the cell, and the maximum value of the temperature for the cross-flow is at the outlet region of the cell. The distribution of the current density is uneven, and the maximum current density is located at the interfaces between the channels, ribs and the electrodes, the maximum current density result in a large over-potential and heat source in the electrodes, which is harmful to the overall performance and working lifespan of the fuel cells. A new type of flow structure should be developed to make the current flow be more evenly distributed and promote most of the TPB areas to take part in the electrochemical reactions.
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| 22. |
- Zhang, Zhonggang, et al.
(författare)
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Three-dimensional CFD modeling of transport phenomena in anode-supported planar SOFCs
- 2014
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Ingår i: Heat and Mass Transfer. - : Springer Science and Business Media LLC. - 1432-1181 .- 0947-7411. ; 50:11, s. 1575-1586
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, a three-dimensional computational fluid dynamics model has been developed for an anode-supported planar SOFC. The conservation equations of mass, momentum, species/charges and thermal energy are solved by finite volume method for a complete unit cell consisting of 13 parallel channels in both anode and cathode. The simulation results of the developed model are well in agreement with the experimental data obtained at same conditions. In this study, the co-flow arrangement with hydrogen utilization of 60 % and operating voltage of 0.7 V is used as the base case, and compared with the counter-flow arrangement. The predicted results reveals that the maximum temperature obtained in the counter-flow arrangement is about 10 A degrees C lower than that of co-flow, but the counter-flow arrangement has a higher temperature gradient between the respective anodes and cathodes in a cross-section normal to the main flow direction, especially in the air inlet region of the cell (x = 0.04 m),which is very harmful to the lifetime of materials. The current density is very unevenly distributed along and normal to the flow direction for both the co- and counter-flow arrangements, and the maximum values occur at junctions of the electrodes, channels and ribs, which causes higher over-potentials and ohmic heating.
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| 23. |
- Zhang, Zhonggang, et al.
(författare)
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Three-dimensional CFD modeling of transport phenomena in multi-channel anode-supported planar SOFCs
- 2015
-
Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310. ; 84, s. 942-954
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, a three-dimensional computational fluid dynamics (CFD) model is developed and applied for anode-supported planar SOFC involving multi-channels. The developed model is first validated in agreement with the experimental data obtained at same conditions. Three different flow arrangements (co-, counter- and cross-flow) are simulated and compared in terms of cell overall performance and various transport phenomena occurred inside the SOFC single cell functional components. Local distribution of temperature, mass flow rate, current density, gas concentrations of reactants and products in both fuel and air sides under different flow arrangements is predicted and presented. It is found that the co-flow and counter-flow arrangements have a better performance than that of the cross-flow arrangement at the same operating conditions. It is also found that the temperature for the three flow arrangements is unevenly distributed and the significant temperature gradients exist along the length of the cell. The mass flow rate of fuel at the inlet of each channel is uniform, however its difference between the side channel and the channel at the center is increasing along the fuel flow direction, which reaches a maximum value at the outlet region. It is also predicted that the maximum current density is located at the interfaces between the channels, ribs and the electrodes resulting in a large over-potential and a heat source in the electrodes, which is harmful to the cell overall performance and working life time. (C) 2015 Elsevier Ltd. All rights reserved.
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