The neutron flux is a crucial factor for neutron scattering measurements, especially for compact sources. Among various neutron optics, grazing‐incidence focusing mirrors have been developed to give ...a significant increase in the neutron flux on a sample owing to their great potential for collecting neutrons in small‐angle neutron scattering (SANS) instruments. Focusing mirrors with a supermirror coating can be nested to collect a neutron beam with large divergence. Nested conical integrated assembly technology is employed to manufacture nested focusing mirrors. This study describes the design of ten‐shell nested fully annular quasi‐ellipsoidal focusing mirrors with an m = 3 Ni/Ti supermirror coating to produce enough neutrons on a sample under the premise of satisfying the specified minimum wavevector transfer Q. For fully annular focusing mirrors, the neutron current received by a sample from the entire annular focusing neutron beam is more relevant. A ray‐tracing method and current gain calculation are used to evaluate the performance of the designed mirrors. The ray‐tracing result shows that the ideal resolution of quasi‐ellipsoidal mirrors with four‐segment conical approximation is 1.354 mm. As the source radius decreases from 20 mm, the neutron current with the designed focusing mirrors can be enhanced by a factor of 13 to over 100 compared with that without focusing mirrors in the same detected area. The effective collecting area is 186 cm2 when the source radius is the optimal 15 mm. An 83‐fold current gain can be obtained for cold neutrons. The proposed mirrors can reach 90.7 and 87.3% of the maximum current of the corresponding optimal mirror structure when the source radii are 10 and 20 mm, respectively. The results demonstrate that the proposed mirrors are adaptable for instruments with changeable sources.
This study describes ten‐shell nested fully annular quasi‐ellipsoidal focusing mirrors with an m = 3 Ni/Ti supermirror coating for small‐angle neutron scattering. The proposed mirrors have been developed to gain enough neutrons on a sample for the specified minimum wavevector transfer Q and the results demonstrate adaptability for instruments with changeable sources.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Developing small-angle neutron scattering techniques at compact accelerator-driven neutron sources (CANS) is of great importance for expanding the user community and advancing CANS capability. At the ...Compact Pulsed Hadron Source (CPHS) at Tsinghua University, neutron-focusing mirrors are under intensive research to address the challenge. A grazing-incidence focusing SANS (gif-SANS) project is initialized. It employs a nested supermirror assembly with a large collecting area to achieve ⩾ 10 5 n/s neutron intensity at Q min ⩽ 0.007 Å − 1 . It will equip two detectors, one being a 3He detector for normal Q-range measurements, and the other being a high-resolution detector for extending the Q min down to 10 − 3 Å − 1 . In this work, we present the conceptual design of the gif-SANS at CPHS. Such a scheme is conducive to enable high-performance SANS measurements at CANS.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Human cytomegalovirus （HCMV） reactivation is a common complication after liver transplantation （LT）. Here, we investigated whether human leukocyte antigen （HLA）-matching was related to HCMV infection ...and subsequent graft failure after LT for hepatitis B virus cirrhosis. This retrospective study reviewed 91 LT recipients. All the patients were grouped according to HLA-A, HLA- B, and HLA-DR locus matching. Clinical data were collected, including complete HLA-typing, HCMV viremia, graft failure, and the time of HCMV viremia. HLA typing was performed using a sequence-specific primer-polymerase chain reaction kit. HCMV was detected by pp65 antigenemia using a commercial kit. The incidence of HCMV infection post-LT was 81.32%. Graft failure was observed in 16 of 91 （17.6%） patients during the 4-year study. The incidence of HCMV viremia was 100% （5/5）, 91.4% （32/35）, and 72.5% （37/51） in HLA-A two locus, one locus, and zero locus compatibility, respectively. Nevertheless, the degree of the HLA-A, HLA-B, or HLA-DR match did not influence the time of HCMV viremia, graft failure, or the time of graft failure after a diagnosis of HCMV viremia （all P 〉 0.05）. An interesting discovery was that the risk of HCMV viremia tended to be higher in patients with better HLA-A compatibility. Graft failure, time of HCMV viremia, and graft failure after a diagnosis of HCMV viremia appear to be independent of HLA allele compatibility.
RGB-T crowd counting aims to utilize the thermal source data to compensate for the insufficient RGB feature representation under low-illumination conditions. However, how to efficiently use ...complementary information from different modalities is still a challenging issue for the target task. Existing CNN-based RGB-T crowd counting methods focus on the cross-modal feature representation via the local fixed-receptive-field convolutional operations and the transformer-based works mainly utilize the mutual attention, failing to realize the global cross-modal feature representation. To this end, this paper designs a multimodal counting network based on the multimodal transformer mixer to realize cross-modal collaborative feature representation. Firstly, we design a Transformer-based multimodal mixer to fully fuse the features from both modalities. And then we utilize the Transformer-based network with the multi-head self-attention layer replaced by the average pooling layer to build the two-stream backbone to extract rich multi-scale feature information of the two modalities. Meanwhile, the features extracted from the mixers are used to enhance the intermediate features to achieve the preservation of crowd detail information and suppression of background information. Finally, we design a pyramid regression head to aggregate the multi-scale feature maps to regress the density maps. Extensive experiments, as well as ablation studies, are conducted on challenging RGB-T crowd counting benchmark datasets (RGBT-CC and DroneRGBT), and the achieved competitive experimental results demonstrate the effectiveness of the proposed method on cross-modal collaborative feature representation for target task.
•Design a Multimodal Transformer Mixer to fuse RGB-T complementary information.•Develop a two-stream cross-modal collaborative feature representation method.•Conduct extensive experiments to validate the effectiveness of the proposed method.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
With the increasing demand for high energy density in portable-device Li-ion batteries (LIBs), efforts are devoted to increase and stabilize the capacity of LiCoO2 at high operation voltages. Herein, ...we report a low-cost and eco-friendly wet-chemical method to coat Al2O3 on LiCoO2, using only aluminium sulphate and water as source materials. A nanoscale oxide layer is coated on the surface of LiCoO2 particles through hydrogen-bonding assisted adsorption of the hydrolysed Al(OH)3 nanoparticles. The as-proposed Al2O3-coating provides excellent physico-chemical protection and kinetically-favourable interfaces for the LiCoO2 electrode, resulting in remarkable improvements of the electrode's cycling stability and rate capability when tested at high cutoff voltages up to 4.7 V (vs. Li/Li+). The synergetic effects of the oxide coating, e.g. alleviated electrolyte decomposition and reduced generation of irreversible solid electrolyte interphase (SEI) constituents (LiF/Li2CO3 and organics), are attributed to the improvements. At the cutoff voltage of 4.5 V, the modified LiCoO2 electrode in this work exhibits excellent cycling stability (147 mA h g−1, 82.6% retention after 500 cycles at 1C) and competitive rate capability (130 mA h g−1 at 10C), which are some of the best results reported so far. The outstanding high-voltage electrode performance and the simple and scalable coating approach show great promise of LiCoO2 cathodes in future high-energy and high-power LIBs.
The Clean Air Plan has been active in China since 2013 to mitigate severe PM2.5 pollution. In this study, we applied the air quality model WRF-Chem to simulate PM2.5 in the Yangtze River Delta (YRD) ...region of China in 2017, with the aim of assessing the air quality improvement and its associated health burden in the final year of the Clean Air Plan. To better describe the fate of various PM2.5 compositions, we updated the chemical mechanisms in the model beforehand, including heterogeneous sulfate reactions, aqueous secondary organic aerosol (SOA) uptake, and volatility basis set (VBS) based SOA production. Both the observation and simulation results agreed that the stringent clear air action effectively reduced the PM2.5 pollution levels by ∼ 30 %. The primary PM2.5 (−6 ∼ − 16 % yr−1) showed a more significant decreasing trend than the secondary PM2.5 (−2 ∼ − 8 % yr−1), which was mainly caused by the directivity of the clear air actions and the worsening ozone pollution in the recent years. The inconsistent decreasing trends of PM2.5 components subsequently led to an increasing proportion of secondary PM2.5. Nitrate particles, higher in the central and western YRD region, have replaced sulfate and have become the largest component of secondary inorganic aerosols year-round, except in summer, when strong ammonium nitrate evaporation occurs. In addition, SOA remains an important component (21 ∼ 22 %) especially in summer, most of which is produced from the oxidation and ageing of semi/intermediate volatile organic compounds (S/IVOC). Furthermore, we quantified the associated health impacts and found that the Clean Air Plan has largely reduced premature mortality due to PM2.5 exposure in the YRD region from 399.1 thousand to 295.7 thousand. Our study highlights the benefits of the Clean Air Plan and suggests that subsequent PM2.5 improvement should be geared more towards controlling secondary pollutants.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We propose a conductively coupled terahertz metallic metamaterial exhibiting analog of electromagnetically induced transparency (EIT), in which the bright and dark mode antennae interact via surface ...currents rather than near-field coupling. Aluminum foil, which is very cheap and often used in food package, is used to fabricate our metamaterials. Thus, our metamaterials are also flexible metamaterials. In our design, aluminum bar resonators and aluminum split ring resonators (SRRs) are connected (rather than separated) in the form of a fork-shaped structure. We conduct a numerical simulation and an experiment to analyze the mechanism of the proposed metamaterial. The surface current due to LSP resonance (bright mode) flows along different paths, and a potential difference is generated at the split gaps of the SRRs. Thus, an LC resonance (dark mode) is induced, and the bright mode is suppressed, resulting in EIT. The EIT-like phenomenon exhibited by the metamaterial is induced by surface conducting currents, which may provide new ideas for the design of EIT metamaterials. Moreover, the process of fabricating microstructures on flexible substrates can provide a reference for producing flexible microstructures in the future.
Decoration of h-BN with a cyclotriphosphazene containing boronate polymer shell can improve the interfacial interaction between h-BN and epoxy resin thus simultaneously achieving high flame ...retardancy and mechanical properties.
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In this report, we develop a simple and controllable coating strategy to decorate h-BN with a cyclotriphosphazene-containing boronate polymer (CPBP), thus forming h-BN-OH@CPBP core-shell nanoplates with different shell thicknesses. By introducing h-BN-OH@CPBPs into epoxy resin (EP), we have found that the thermal stability, flame retardant and mechanical performances of the as formed nanocomposites greatly relies on the CPBP shell thickness. Also, our design effectively improve the compatibility between h-BN nanoplates and polymer matrix and regulate the corresponding interface. The nanocomposites show the highest limiting oxygen index (LOI) of 28.7% and reach V-0 rating in the vertical burning test at loading amount of 2.5 wt%. Also the heat and smoke releases of nanocomposites during burning are significantly reduced. The flexural strengths and modulus of the nanocomposites are at most 42.12% and 27.85% higher than that of pure EP. The glass transition temperature and dynamic mechanical property of the nanocomposites are both improved.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The addition of small molecular plasticizer is an efficient strategy to increase the process ability and macroscopic performance of poly(vinyl alcohol) (PVA). However, how the plasticizer influences ...the chain dynamics and morphology deserves further investigation. In this work, the PVA film with varying glycerol addition levels was used as the model system. The increasing glycerol addition‐level results in the depression of the melting temperature and crystallization temperature, which in line with Flory's theory. The enhanced chain dynamics in the mobile domain was accessed by low‐field NMR, whereas that in the crystalline region remains constant. The domain size as well as the morphology of the mobile phase are accessed by 1H spin‐diffusion NMR. The results indicate the increasing dimensionality of the plasticized PVA film with increasing the addition level of glycerol, where the addition level below 25 wt% leads to the dimensionality of 1D, and higher than 25 wt% results in the dimensionality of 2D. Current results elucidate the critical role of the plasticizer in modulating the dynamics heterogeneity of the plasticized polymer film, which is closely related to the macroscopic performance of the products.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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