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141.
Ruihua Zhang Fan Yang Yan Luo Jianyi Liu Jinbin Li Cong Wang 《Entropy (Basel, Switzerland)》2021,23(6)
Thorax disease classification is a challenging task due to complex pathologies and subtle texture changes, etc. It has been extensively studied for years largely because of its wide application in computer-aided diagnosis. Most existing methods directly learn global feature representations from whole Chest X-ray (CXR) images, without considering in depth the richer visual cues lying around informative local regions. Thus, these methods often produce sub-optimal thorax disease classification performance because they ignore the very informative pathological changes around organs. In this paper, we propose a novel Part-Aware Mask-Guided Attention Network (PMGAN) that learns complementary global and local feature representations from all-organ region and multiple single-organ regions simultaneously for thorax disease classification. Specifically, multiple innovative soft attention modules are designed to progressively guide feature learning toward the global informative regions of whole CXR image. A mask-guided attention module is designed to further search for informative regions and visual cues within the all-organ or single-organ images, where attention is elegantly regularized by automatically generated organ masks and without introducing computation during the inference stage. In addition, a multi-task learning strategy is designed, which effectively maximizes the learning of complementary local and global representations. The proposed PMGAN has been evaluated on the ChestX-ray14 dataset and the experimental results demonstrate its superior thorax disease classification performance against the state-of-the-art methods. 相似文献
142.
Dinglong Cai Mian Wang Jianyi Wang Wengui Duan 《Journal of Physical Organic Chemistry》2012,25(5):400-408
Quantum chemical calculations have been performed to explore the mechanism of intramolecular cyclization of 2‐benzyloxyphenyl trimethylsilyl ketone (acylsilane) to give the benzofuran derivatives stereoselectively. This reaction involves a formation of siloxycarbene intermediate and a C–H bond insertion of siloxycarbene. The comparative studies on three possible insertion of siloxycarbene show that the concerted insertion of siloxycarbene into C–H bond (pathway a), which needs overcoming an energy barrier of 45.1 kcal/mol, is the most unlikely pathway, and the stepwise insertion of siloxycarbene without spin multiplicity change (pathway c) is energetically more favorable than the stepwise insertion of siloxycarbene with spin multiplicity change (pathway b). More importantly, this work can provide an insight into the stereoselectivity in this reaction in atomic molecular level. The formation of siloxycarbene is calculated to be endergonic by 22.9 kcal/mol with an energy barrier of 30.2 kcal/mol, being the rate‐determining step of the whole process. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
143.
使用原位穆斯堡尔谱考察了具有不同担载量的Fe/AC以及Fe-K/AC和Fe-Mn/AC催化剂在300℃合成气(H_2/CO=2)中的碳化行为。发现在活性炭载体上铁的担载量(或分散度)制约着碳化时生成的碳化铁的种类。铁的粒径很小(~30A)时生成ε’-Fe_(2·2)C碳化铁,铁的粒径在70A左右可生成ε-Fe_2C碳化铁,而大粒子铁(>200A)和体相铁则生成x-Fe_5C_2碳化铁,Fe-K/AC和Fe-Mn/AC催化剂在碳化时生成的碳化铁种类仍受铁的粒径制约,助剂K和Mn不影响生成的碳化铁的种类,但Mn可延缓铁的碳化。 相似文献
144.
Polyoxymethylene dimethyl ethers(PODE)were synthesized from the reaction of paraformaldehyde with dimethoxymethane(DMM)over different acid catalysts at different conditions.Products were found to follow the Schulz-Flory distribution law.The chain propagation proceeds through the insertion of an individual segment of CH2O one by one,while the simultaneous insertion of a few CH2O segments or their assembly is unlikely.Due to the restriction of this law,it is difficult to increase the selectivity to the desired products(e.g.,PODE3 4). 相似文献
145.
The mesoporous carbon supported cobalt catalyst (15%Co/MC) was found to be more active and selective to C(5)(+) than the traditionally activated carbon supported one (15%Co/AC) for the Fischer-Tropsch synthesis (FTS). The addition of small amount of K(2)O and ZrO(2) significantly affected the FTS behavior of 15%Co/MC. The addition of 1% K inhibited the FTS activity dramatically, while the addition of 3% Zr increased the FTS activity significantly. The addition of K(2)O decreased the surface acidity while increased the surface basicity of 15%Co/MC, resulting in the increased heat of adsorption of CO and substantially decreased heat of adsorption of H(2) on Co. In contrast, the addition of ZrO(2) increased the surface acidity and heat of adsorption of H(2) on Co. The FTS activity was found to be related to the ratio of heats for the adsorption of CO and H(2) on the catalysts 15%Co/MC, 15%Co-1%K/MC and 15%Co-3%Zr/MC. The highest FTS activity was obtained on the catalyst with the heat ratio of 1.2. 相似文献
146.
Surface structure and reaction performances of highly dispersed and supported bimetallic catalysts 总被引:1,自引:0,他引:1
Surface structures of Pt-Sn and Pt-Fe bimetallic catalysts have been investigated by means of Mssbauer spectroscopy, Pt-L_Ⅲ-edge EXAFS and H_2-adsorption. The results showed that the second component, such as Sn or Fe, remained in the oxidative state and dispersed on the γ-Al_2O_3 surface after reduction, while Pt was completely reduced to the metallic state and dispersed on either the metal oxide surface or the γ-Al_2O_3 surface. By correlating the distribution of Pt species on different surfaces with the reaction and adsorption performances, it is proposed that two kinds of active Pt species existed on the surfaces of both catalysts, named M_1 sites and M_2 sites. M_1 sites are the sites in which Pt directly anchored on the γ-Al_2O_3 surface, while M_2 sites are those in which Pt anchored on the metal oxide surface. M_1 sites are favorable for low temperature H_2 adsorption, and responsible for the hydrogenolysis reaction and carbon deposition, while M_2 sites which adsorb more H_2 at higher tem 相似文献
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Melamine formaldehyde resins were synthesized with encapsulated CaCl(2) as a template. Carbonization at high temperatures led to the formation of carbon materials containing N atoms. Washing with de-ionized water removed encapsulated CaCl(2), resulting in the formation of mesopores (3-30 nm) with the high surface areas (770-1300 m(2)/g). The template can be recycled and the method is simple and cost effective as compared to the hard template techniques. The mesoporous carbons containing nitrogen (NMC) thus prepared exhibited the amphipathic surfaces (both hydrophilic and lipophilic) and adsorbed great amount of water and benzene. In addition, the incorporated N atoms exhibited quite strong basicity for the adsorption of great amount of SO(2). 相似文献