45 research outputs found

    Numerical analysis of the solid particle solar receiver with the influence of an air-jet

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    This thesis develops and analyzes a three-dimensional computational model of a solid particle solar receiver (SPSR) for providing the heat source in a hydrogen production process using the sulfur iodine thermochemical water splitting reaction. In this reaction, a heat input of at least 850°C is necessary to keep high hydrogen production efficiency. Previous studies to achieve higher efficiency on a SPSR include changing particle materials, sizes, flow rates, and the geometry designs. The present study is concerned with the use of an air-jet in front of the open aperture and different operation conditions for the SPSR design optimization; The conceptual design of the SPSR is provided by Sandia National Laboratories (SNL). There is an open aperture in front of the receiver cavity, and heat will leak to outside without any protection. Different research topics have suggested that an air-jet consisting of a transparent gas stream injected across the receiver aperture is a good method for isolating the interior from the surroundings. The main purpose of this research is to use numerical analysis to study the SPSR with the influence of an air-jet. A two-way coupled Euler-Lagrange method is applied which includes the continuity, heat, momentum exchanges between the solid and gas two-phase flows. A two-band discrete ordinate solar ray tracing model is used for the radiation interactions and heat transfer within the particle clouds, and between the cloud and the internal surface of the receiver. Different air-jet velocities are compared to evaluate the thermal performance of the receiver. Parametric studies also include varying particle size, mass flow rate, solar flux, and air-jet temperature to determine the optimal operating conditions. The temperature and velocity profiles inside the cavity are also analyzed. In all the parametric studies and thermal analysis, the SPSR with a downward air-jet velocity of 8 m/s, air-jet temperature of 300 K, and particle diameter in the range of 70-80 micron provides the best performance in the presence of a radiant flux of 920 suns. This cavity efficiency is 85%, and average exit particle temperature is 1199 K

    Optimization of terrestrial ecosystem model parameters using atmospheric CO2 concentration data with the Global Carbon Assimilation System (GCAS)

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    Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Biogeosciences 122 (2017): 3218–3237, doi:10.1002/2016JG003716.The Global Carbon Assimilation System that assimilates ground-based atmospheric CO2 data is used to estimate several key parameters in a terrestrial ecosystem model for the purpose of improving carbon cycle simulation. The optimized parameters are the leaf maximum carboxylation rate at 25°C (V25 max), the temperature sensitivity of ecosystem respiration (Q10), and the soil carbon pool size. The optimization is performed at the global scale at 1° resolution for the period from 2002 to 2008. The results indicate that vegetation from tropical zones has lower V25 max values than vegetation in temperate regions. Relatively high values of Q10 are derived over high/midlatitude regions. Both V25 max and Q10 exhibit pronounced seasonal variations at middle-high latitudes. The maxima in V25 max occur during growing seasons, while the minima appear during nongrowing seasons. Q10 values decrease with increasing temperature. The seasonal variabilities of V25 max and Q10 are larger at higher latitudes. Optimized V25 max and Q10 show little seasonal variabilities at tropical regions. The seasonal variabilities of V25 max are consistent with the variabilities of LAI for evergreen conifers and broadleaf evergreen forests. Variations in leaf nitrogen and leaf chlorophyll contents may partly explain the variations in V25 max. The spatial distribution of the total soil carbon pool size after optimization is compared favorably with the gridded Global Soil Data Set for Earth System. The results also suggest that atmospheric CO2 data are a source of information that can be tapped to gain spatially and temporally meaningful information for key ecosystem parameters that are representative at the regional and global scales.National Key R&D Program of China Grant Number: 2016YFA0600204; National Natural Science Foundation of China Grant Number: 415713382018-06-2

    Inter-comparison and evaluation of Arctic sea ice type products

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    oai:publications.copernicus.org:tc102910Arctic sea ice type (SITY) variation is a sensitive indicator of climate change. However, systematic inter-comparison and analysis for SITY products are lacking. This study analysed eight daily SITY products from five retrieval approaches covering the winters of 1999–2019, including purely radiometer-based (C3S-SITY), scatterometer-based (KNMI-SITY and IFREMER-SITY) and combined ones (OSISAF-SITY and Zhang-SITY). These SITY products were inter-compared against a weekly sea ice age product (i.e. NSIDC-SIA – National Snow and Ice Data Center sea ice age) and evaluated with five synthetic aperture radar (SAR) images. The average Arctic multiyear ice (MYI) extent difference between the SITY products and NSIDC-SIA varies from -1.32×106 to 0.49×106 km2. Among them, KNMI-SITY and Zhang-SITY in the QuikSCAT (QSCAT) period (2002–2009) agree best with NSIDC-SIA and perform the best, with the smallest bias of -0.001×106 km2 in first-year ice (FYI) extent and -0.02×106 km2 in MYI extent. In the Advanced Scatterometer (ASCAT) period (2007–2019), KNMI-SITY tends to overestimate MYI (especially in early winter), whereas Zhang-SITY and IFREMER-SITY tend to underestimate MYI. C3S-SITY performs well in some early winter cases but exhibits large temporal variabilities like OSISAF-SITY. Factors that could impact performances of the SITY products are analysed and summarized. (1) The Ku-band scatterometer generally performs better than the C-band scatterometer for SITY discrimination, while the latter sometimes identifies FYI more accurately, especially when surface scattering dominates the backscatter signature. (2) A simple combination of scatterometer and radiometer data is not always beneficial without further rules of priority. (3) The representativeness of training data and efficiency of classification are crucial for SITY classification. Spatial and temporal variation in characteristic training datasets should be well accounted for in the SITY method. (4) Post-processing corrections play important roles and should be considered with caution.</p

    Comprehensive analyses for the coagulation and macrophage-related genes to reveal their joint roles in the prognosis and immunotherapy of lung adenocarcinoma patients

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    PurposeThis study aims to explore novel biomarkers related to the coagulation process and tumor-associated macrophage (TAM) infiltration in lung adenocarcinoma (LUAD).MethodsThe macrophage M2-related genes were obtained by Weighted Gene Co-expression Network Analysis (WGCNA) in bulk RNA-seq data, while the TAM marker genes were identified by analyzing the scRNA-seq data, and the coagulation-associated genes were obtained from MSigDB and KEGG databases. Survival analysis was performed for the intersectional genes. A risk score model was subsequently constructed based on the survival-related genes for prognosis prediction and validated in external datasets.ResultsIn total, 33 coagulation and macrophage-related (COMAR) genes were obtained, 19 of which were selected for the risk score model construction. Finally, 10 survival-associated genes (APOE, ARRB2, C1QB, F13A1, FCGR2A, FYN, ITGB2, MMP9, OLR1, and VSIG4) were involved in the COMAR risk score model. According to the risk score, patients were equally divided into low- and high-risk groups, and the prognosis of patients in the high-risk group was significantly worse than that in the low-risk group. The ROC curve indicated that the risk score model had high sensitivity and specificity, which was validated in multiple external datasets. Moreover, the model also had high efficacy in predicting the clinical outcomes of LUAD patients who received anti-PD-1/PD-L1 immunotherapy.ConclusionThe COMAR risk score model constructed in this study has excellent predictive value for the prognosis and immunotherapeutic clinical outcomes of patients with LUAD, which provides potential biomarkers for the treatment and prognostic prediction

    Resolving Fine-Scale Surface Features on Polar Sea Ice: A First Assessment of UAS Photogrammetry Without Ground Control

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    Mapping landfast sea ice at a fine spatial scale is not only meaningful for geophysical study, but is also of benefit for providing information about human activities upon it. The combination of unmanned aerial systems (UAS) with structure from motion (SfM) methods have already revolutionized the current close-range Earth observation paradigm. To test their feasibility in characterizing the properties and dynamics of fast ice, three flights were carried out in the 2016–2017 austral summer during the 33rd Chinese National Antarctic Expedition (CHINARE), focusing on the area of the Prydz Bay in East Antarctica. Three-dimensional models and orthomosaics from three sorties were constructed from a total of 205 photos using Agisoft PhotoScan software. Logistical challenges presented by the terrain precluded the deployment of a dedicated ground control network; however, it was still possible to indirectly assess the performance of the photogrammetric products through an analysis of the statistics of the matching network, bundle adjustment, and Monte-Carlo simulation. Our results show that the matching networks are quite strong, given a sufficient number of feature points (mostly > 20,000) or valid matches (mostly > 1000). The largest contribution to the total error using our direct georeferencing approach is attributed to inaccuracies in the onboard position and orientation system (POS) records, especially in the vehicle height and yaw angle. On one hand, the 3D precision map reveals that planimetric precision is usually about one-third of the vertical estimate (typically 20 cm in the network centre). On the other hand, shape-only errors account for less than 5% for the X and Y dimensions and 20% for the Z dimension. To further illustrate the UAS’s capability, six representative surface features are selected and interpreted by sea ice experts. Finally, we offer pragmatic suggestions and guidelines for planning future UAS-SfM surveys without the use of ground control. The work represents a pioneering attempt to comprehensively assess UAS-SfM survey capability in fast ice environments, and could serve as a reference for future improvements

    The first comprehensive study of a giant nebula around a radio-quiet quasar in the z<1z < 1 Universe

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    We present the first comprehensive study of a giant,  ⁣ ⁣70\approx \! \! 70 kpc-scale nebula around a radio-quiet quasar at z<1z<1. The analysis is based on deep integral field spectroscopy with MUSE of the field of HE\,0238-1904, a luminous quasar at z=0.6282z=0.6282. The nebula emits strongly in [OII]\mathrm{[O \, II]}, Hβ\rm H \beta, and [OIII]\mathrm{[O \, III]}, and the quasar resides in an unusually overdense environment for a radio-quiet system. The environment likely consists of two groups which may be merging, and in total have an estimated dynamical mass of Mdyn4×1013M_{\rm dyn}\approx 4\times 10^{13} to $10^{14}\ {\rm M_\odot}.Thenebulaexhibitslargelyquiescentkinematicsandirregularmorphology.Thenebulamayariseprimarilythroughinteractionrelatedstrippingofcircumgalacticandinterstellarmedium(CGM/ISM)ofgroupmembers,withsomepotentialcontributionsfromquasaroutflows.Thesimultaneouspresenceofthegiantnebulaandaradioquietquasarinarichenvironmentsuggestsacorrelationbetweensuchcircumquasarnebulaeandenvironmentaleffects.Thispossibilitycanbetestedwithlargersamples.Theupperlimitsontheelectronnumberdensityimpliedbythe. The nebula exhibits largely quiescent kinematics and irregular morphology. The nebula may arise primarily through interaction-related stripping of circumgalactic and interstellar medium (CGM/ISM) of group members, with some potential contributions from quasar outflows. The simultaneous presence of the giant nebula and a radio-quiet quasar in a rich environment suggests a correlation between such circum-quasar nebulae and environmental effects. This possibility can be tested with larger samples. The upper limits on the electron number density implied by the \mathrm{[O \, II]}doubletratiorangefrom doublet ratio range from \log(n_{\rm e, \, [O \, II]} / \mathrm{cm^{-3}}) < 1.2to to 2.8.However,assumingaconstantquasarluminosityandnegligibleprojectioneffects,thedensitiesimpliedfromthemeasuredlineratiosbetweendifferentions(e.g.,. However, assuming a constant quasar luminosity and negligible projection effects, the densities implied from the measured line ratios between different ions (e.g., \mathrm{[O\,II]},, \mathrm{[O\,III]},and, and \mathrm{[Ne\,V]})andphotoionizationsimulationsareoften) and photoionization simulations are often 10{-}400timeslarger.Thislargediscrepancycanbeexplainedbyquasarvariabilityonatimescaleof times larger. This large discrepancy can be explained by quasar variability on a timescale of \approx 10^4{-}10^5$ years.Comment: 19 pages, 9 figures, 3 tables; Submitted to MNRA

    Microbial metabolites indole derivatives sensitize mice to D-GalN/LPS induced-acute liver failure via the Tlr2/NF-κB pathway

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    IntroductionAcute liver failure (ALF) is a clinical condition with many causes, fast progression, and a poor prognosis. Previous research has indicated that microbial factors have a role in ALF, but a clear picture has yet to emerge.MethodsTo investigate the specific involvement of microbial metabolites in ALF development, we pretreated D-GalN/LPS-induced ALF mice with indole derivatives, an influential class of gut microbial metabolites.ResultsContrary to their typical role as anti-inflammatory agents in the host, indole-3-acetic acid (IAA), indole-3-lactic acid (ILA), and indolepropionic acid (IPA) gavage sensitize mice to D-GalN/LPS-induced-ALF with a rapid rise in serum transaminases and histologic lesion. For a clearer picture, we performed comprehensive analysis for the IAA therapy. IAA markedly amplified inflammatory response and cellular damage. The transcriptome analysis indicated the participation of the TNF-α/NF-κB signaling pathway. The structure of gut microbiota in ileum and the expression of Toll-like receptor 2 (Tlr2) in the liver were also significantly changed.DiscussionIn conclusion, IAA pretreatment can exacerbate D-GalN/LPS-induced ALF via probable Tlr2/NF-κB pathway involvement and ileac dysbiosis characterized by enriched gram-positive genus with potential pathogenesis. Microbial metabolites IAA may aggravate individual susceptibility to D-GalN/LPS-induced ALF. Further investigation of the underlying mechanism is needed, and intervention with indole derivatives and related commensal species should be undertaken with caution

    Wind Effect on the Performance of Solid Particle Solar Receivers with and without the Protection of an Aerowindow

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    The wind conditions affect the performance of a solid particle solar receiver (SPSR) by convection heat transfer through the existing open aperture. Aerowindows have the potential of increasing the efficiency of an SPSR. In the present paper, the wind effect on the performance of an SPSR is investigated numerically with and without the protection of an aerowindow. The independence of the calculating domain in a wind field has been studied in order to select a proper domain for the numerical simulation. The cavity thermal efficiencies and the exiting temperature of the solid particles have been calculated and analyzed for different wind conditions. The numerical investigation of the SPSRs’ performance can provide a guide in optimizing the prototype design, finding out the suitable working condition and proposing efficiency enhancing techniques for SPSRs
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