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NOx Emission Reduction Technology for Marine Engine Based on Tier-Ⅲ:A Review

Journal of Thermal Science 2020年第5期29卷 1242-1268页

作者： LU Xiuwei geng peng CHEN Yunyue Merchant Marine College Shanghai Maritime UniversityShanghai 201306China Tianjin Research Institute of Water Transport Engineering Tianjin 300456China

The development of maritime trade has greatly promoted the development of diesel ***,with the increasingly serious environmental problems,more and more attention has been paid to the exhaust emissions of high-power marine diesel *** restrictions on SOx have been implemented globally,and the limitation of the NO,will be the next *** paper illustrates(a)Principle and research progress of NOx emissions-reduction technology of marine diesel engine;(b)Summary of advantages and disadvantages among various reduction technologies and their reduction effects;(c)The application effect of mainstream technology on ***,since exhaust gas recirculation(EGR)can achieve Tier-Ⅲ directly from Tier-Ⅰ without considering the increased fuel *** is deemed as the most promising technology to reduce emissions by controlling combustion ***,EGR has shortcomings of excessive increase in ftiel consumption and generation of waste water,which need to be solved ***,selective catalytic reduction(SCR)is the most effective and straightforward means to achieve Tier-Ⅲ.Despite of the continuous optimization of SCR unit volume,the problem of scrap catalyst seriously limits its wide *** to match the supercharger more efficiently is a key factor in choosing between high and low pressure ***,nature gas(NG)engines are capable of achieving a reduction in NOx,but in order to meet the requirements of Tier-Ⅲ,it still needs to be assisted by other *** emissions of hydrocarbon(HC)and CO in NG engines are huge defects that must be ***,technologies such as the Miller cycle,Two-stage supercharging and mixed-water combustion can also reduce emissions but were rarely used *** technologies can be combined with EGR,SCR and NG engines to optimize the enginesJ economy and emission characteristics.

关键词： marine engine NOx emission Tier-Ill exhaust gas recirculation(EGR) selective catalytic reduction(SCR) dual-fuel

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Calculation of microscopic nuclear level densities based on covariant density functional theory

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Nuclear Science and Techniques 2023年第9期34卷 118-127页

作者： Kun-peng geng peng-Xiang Du Jian Li Dong-Liang Fang College of Physics Jilin UniversityChangchun 130012China Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China

In this study,a microscopic method for calculating the nuclear level density(NLD)based on the covariant density functional theory(CDFT)is *** particle-hole state density is calculated by a combinatorial method using single-particle level schemes obtained from the CDFT,and the level densities are then obtained by considering collective effects such as vibration and *** results are compared with those of other NLD models,including phenomenological,microstatisti-cal and nonrelativistic Hartree–Fock–Bogoliubov combinatorial *** comparison suggests that the general trends among these models are essentially the same,except for some deviations among the different NLD *** addition,the NLDs obtained using the CDFT combinatorial method with normalization are compared with experimental data,including the observed cumulative number of levels at low excitation energies and the measured *** CDFT combinatorial method yields results that are in reasonable agreement with the existing experimental data.

关键词： Nuclear level density Covariant density functional theory Combinatorial method

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Identifiability of intermediate variables on causal paths

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Frontiers of Mathematics in China 2013年第3期8卷 517-539页

作者： Wanlu DENG Zhi geng peng LUO School of Mathematical Sciences Peking University Beijing 100871 China

We discuss the discovery of causal mechanisms and identifiability of intermediate variables on a causal path. Different from variable selection, we try to distinguish intermediate variables on the causal path from other variables. It is also different from ordinary model selection approaches which do not concern the causal relationships and do not contain unobserved variables. We propose an approach for selecting a causal mechanism depicted by a directed acyclic graph （DAG） with an unobserved variable. We consider several causal networks, and discuss their identifiability by observed data. We show that causal mechanisms of linear structural equation models are not identifiable. Furthermore, we present that causal mechanisms of nonlinear models are identifiable, and we demonstrate the identifiability of causal mechanisms of quadratic equation models. Sensitivity analysis is conducted for the identifiability.

关键词： Causal network directed acyclic graph (DAC) identifiability intermediate variable structural equation model

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ANALYSIS OF THE PREDICTION CAPABILITY OF WEB SEARCH DATA BASED ON THE HE-TDC METHOD - PREDICTION OF THE VOLUME OF DAILY TOURISM VISITORS

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Journal of Systems Science and Systems Engineering 2017年第2期26卷 163-182页

作者： geng peng Ying Liu Jiyuan Wang Jifa Gu School of Economic and Management University of Chinese Academy of Sciences Beijing 100190 China Key Laboratory of Big Data Mining and Knowledge Management Chinese Academy of Sciences Beijing 100190 China Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China

Web search query data are obtained to reflect social spots and serve as novel economic indicators. When faced with high-dimensional query data, selecting keywords that have plausible predictive ability and can reduce dimensionality is critical. This paper presents a new integrative method that combines Hurst Exponent （HE） and Time Difference Correlation （TDC） analysis to select keywords with powerful predictive ability. The method is called the HE-TDC screening method and requires keywords with predictive ability to satisfy two characteristics, namely, high correlation and fluctuation memorability similar to the predicting target series. An empirical study is employed to predict the volume of tourism visitors in the Jiuzhai Valley scenic area. The study shows that keywords selected using HE-TDC method produce a model with better robustness and predictive ability.

关键词： Tourism visitor volume prediction web-search data HE-TDC method Jiuzhai Valley,time series Hurst exponent

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DT-Net:Joint Dual-Input Transformer and CNN for Retinal Vessel Segmentation

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Computers, Materials & Continua 2023年第9期76卷 3393-3411页

作者： Wenran Jia Simin Ma peng geng Yan Sun School of Information Science and Technology Shijiazhuang Tiedao UniversityShijiazhuangChina School of Mathematics and Information Science Zhangjiakou UniversityZhangjiakouChina

Retinal vessel segmentation in fundus images plays an essential role in the screening,diagnosis,and treatment of many *** acquired fundus images generally have the following problems:uneven illumination,high noise,and complex *** makes vessel segmentation very *** methods of retinal vascular segmentation mainly use convolutional neural networks on U Network(U-Net)models,and they have many limitations and shortcomings,such as the loss of microvascular details at the end of the *** address the limitations of convolution by introducing the transformer into retinal vessel ***,we propose a hybrid method for retinal vessel segmentation based on modulated deformable convolution and the transformer,named ***,multi-scale image features are extracted by deformable convolution and multi-head selfattention(MHSA).Secondly,image information is recovered,and vessel morphology is refined by the proposed transformer decoder ***,the local prediction results are obtained by the side output *** accuracy of the vessel segmentation is improved by the hybrid loss *** results show that our method obtains good segmentation performance on Specificity(SP),Sensitivity(SE),Accuracy(ACC),Curve(AUC),and F1-score on three publicly available fundus datasets such as DRIVE,STARE,and CHASE_DB1.

关键词： Retinal vessel segmentation deformable convolution multi-scale transformer hybrid loss function

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Apparent Molar Volumes and Solvation Coefficients in Ternary-pseudo-binary Mixtures [(Styrene+Ethyl Acetate or Benzene)+(N-Methyl-2-pyrrolidone+Ethyl Acetate or Benzene)]

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Chemical Research in Chinese Universities 2010年第2期26卷 309-317页

作者： HOU Hai-yun peng San-jun WANG Sheng-ze geng Xing-peng College of Environmental and Chemical Engineering Xi ＇an Polytechnic University Xi＇an 710048 P. R. China College of Chemistry and Biological Engineering Changsha University of Science and Technology Changsha 410004 P. R. China

Over the full range of compositions, in the ternary-pseudo-binary mixtures of x[（1-y）C6H5CH=CH2＋ yCH3COOC2H5（or C6H6）]＋（1-x）[（1-y）NMP＋yCH3COOC2Hs（or C6H6）], the apparent molar volumes of each pseudo-pure component at different y values were calculated from the density data at 298.15 K and atmospheric pressure. The results show that the four parameters cubic polynomial can correlate the apparent molar volume with the molar fraction well over the full molar fraction range. The limiting partial molar volumes and the molar volumes of each pseudo-pure component were evaluated with different methods. Based on the limiting partial molar volume and molar volume at a certain y value, a new universal coefficient termed as solvation coefficient γ was defined to describe quantitatively the solvation degree of pseudo-pure solute and the interactions of solute-solvent molecules from the macroscopical thermodynamics viewpoint. The results demonstrate the solvation coefficients decrease with the amount of the third component increasing for each pseudo-pure solute, irrespective of the pseudo-pure solvent. Then the solvation degrees of each pseudo-pure component, the specific interactions between the solute molecule and the solvent one were discussed in terms of the solvation coefficient.

关键词： Apparent molar volume Ternary-pseudo-binary mixture Solvation coefficient

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Crack Segmentation Based on Fusing Multi-Scale Wavelet and Spatial-Channel Attention

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Structural Durability & Health Monitoring 2023年第1期17卷 1-22页

作者： peng geng Ji Lu Hongtao Ma Guiyi Yang School of Information Sciences and Technology Shijiazhuang Tiedao UniversityShijiazhuang050043China

Accurate and reliable crack segmentation is a challenge and meaningful *** this article,aiming at the characteristics of cracks on the concrete images,the intensity frequency information of source images which is obtained by Discrete Wavelet Transform(DWT)is fed into deep learning-based networks to enhance the ability of network on crack *** well integrate frequency information into network an effective and novel DWTA module based on the DWT and scSE attention mechanism is *** semantic information of cracks is enhanced and the irrelevant information is suppressed by DWTA *** the gap between frequency information and convolution information from network is balanced by DWTA module which can well fuse wavelet information into image segmentation *** Unet-DWTA is proposed to preserved the information of crack boundary and thin crack in intermediate feature maps by adding DWTA module in the encoderdecoder *** decoder,diverse level feature maps are fused to capture the information of crack boundary and the abstract semantic information which is beneficial to crack pixel *** proposed method is verified on three classic datasets including CrackDataset,CrackForest,and DeepCrack *** with the other crack methods,the proposed Unet-DWTA shows better performance based on the evaluation of the subjective analysis and objective metrics about image semantic segmentation.

关键词： Attention mechanism crack segmentation convolutional neural networks discrete wavelet transform

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TC-Fuse: A Transformers Fusing CNNs Network for Medical Image Segmentation

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Computer Modeling in Engineering & Sciences 2023年第11期137卷 2001-2023页

作者： peng geng Ji Lu Ying Zhang Simin Ma Zhanzhong Tang Jianhua Liu School of Information Sciences and Technology Shijiazhuang Tiedao UniversityShijiazhuang050043China College of Resources and Environment Xingtai UniversityXingtai054001China School of Electrical and Electronic Engineering Shijiazhuang Tiedao UniversityShijiazhuang050043China

In medical image segmentation task,convolutional neural networks(CNNs)are difficult to capture long-range dependencies,but transformers can model the long-range dependencies ***,transformers have a flexible structure and seldom assume the structural bias of input data,so it is difficult for transformers to learn positional encoding of the medical images when using fewer images for *** solve these problems,a dual branch structure is *** one branch,Mix-Feed-Forward Network(Mix-FFN)and axial attention are adopted to capture long-range dependencies and keep the translation invariance of the ***-FFN whose depth-wise convolutions can provide position information is better than ordinary positional *** the other branch,traditional convolutional neural networks(CNNs)are used to extract different features of fewer medical *** addition,the attention fusion module BiFusion is used to effectively integrate the information from the CNN branch and Transformer branch,and the fused features can effectively capture the global and local context of the current spatial *** the public standard datasets Gland Segmentation(GlaS),Colorectal adenocarcinoma gland(CRAG)and COVID-19 CT Images Segmentation,the F1-score,Intersection over Union(IoU)and parameters of the proposed TC-Fuse are superior to those by Axial Attention U-Net,U-Net,Medical Transformer and other *** F1-score increased respectively by 2.99%,3.42%and 3.95%compared with Medical Transformer.

关键词： Transformers convolutional neural networks fusion medical image segmentation axial attention

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Topographic controls on the annual runoff coefficient and implications for landscape evolution across semiarid Qilian Mountains, NE Tibetan Plateau

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Journal of Mountain Science 2020年第2期17卷 464-479页

作者： CAI Shun geng Hao-peng PAN Bao-tian HONG Yang CHEN Li-ping Key Laboratory of Western China’s Environmental Systems (Ministry of Education) College of Earth and Environmental Sciences Lanzhou University

The combination of different topographic and climatic conditions results in varied precipitation-runoff relations, which in turn influences hillslope erosion, sediment transport and bedrock incision across mountainous landscapes. The runoff coefficient is a suitable tool to represent precipitation-runoff relations, but the spatial distribution of the runoff coefficient across tectonically active mountains in semi-arid environments has received little attention because of limited data availability. We calculated annual runoff coefficients over 22 years for 26 drainage basins across the semi-arid Qilian Mountains based on:(i) annual discharge records;and(ii) the China Meteorological Forcing Dataset to enhance our understanding of the precipitation-runoff processes. The mean annual runoff coefficients show no obvious spatial trends. When compared to potential controlling factors, mean annual runoff coefficients are highly correlated with mean slope rather than any climatic characteristics(e.g., mean annualprecipitation and Normalized Difference Vegetation Index). The slope-dependent runoff coefficient could theoretically have enhanced the topographic control on erosion rates and dampen the influence of precipitation. The enhanced discharge for drainage basins with less precipitation but steep topography in the western Qilian Mountains will enable fluvial incision to keep pace with ongoing uplift caused by the northward growth of the Qilian Mountains. The geomorphic implications are that tectonic rather than climatic factors are more significant for long-term landscape evolution in arid and semi-arid contexts.

关键词： Landscape evolution Precipitation-runoff process Qilian mountains Semiarid environments

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Experimental and Simulation Studies on Fabricating GCr15/40Cr Bimetallic Compound Rollers Using Electroslag Surfacing with Liquid Metal Method

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Journal of Iron and Steel Research International 2014年第9期21卷 869-877页

作者： Lei RAO Shuang-jun WANG Jian-hua ZHAO Mao-peng geng Gang DING College of Mechanical and Electronic Engineering Hohai University College of Mechanical and Electronic Engineering Nanchang University Xinya Special Steel Forging Co. Ltd.

Electroslag surfacing with liquid metal （ESSLM） is an excellent method for producing high quality bimetallic compound rollers. The quality of each compound roller is primarily determined by the metallurgical quality of the combined interface. A GCrl5/40Cr compound roller is produced using an ESSLM non-consumable electrode electro- slag heating method. The temperature and electric fields produced by the ESSLM system are calculated. As the roller core moves downward in the mold, it passes through five sections., the preheating section, the rapid heating section, the temperature homogenizing section, the bimetal fusing section and the cooling section which listed from the top to bottom of the mold, respectively. The temperature distribution and the degree of the surface temperature fluctuation in the roller core are different for each section. Near the combined interface, four layers are found from the roller core to the cladding layer= the remelting layer, the fusion layer, the interface solidification layer and the chilling layer, re spectively. Among these, the fusion and interface solidification layers are the key transition zones that greatly influ- ence the combination quality. The surface temperature of the roller core prior to cladding is mainly determined by the drawing velocity, and the thickness of the transition layer increases as the drawing velocity decreases. A transition layer that is too thick or too thin will reduce the mechanical properties at the combined interface. Therefore, the drawing velocity should be limited to a moderate range to produce a satisfactory bimetallic Compound roller.

关键词： bimetallic compound roller ESSLM combined interface drawing velocity numerical simulation

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