检索结果-南通市图书馆

Detection of fusarium head blight using a YOLOv5s-based method improved by attention mechanism

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Agricultural and Biological Engineering 2024年第5期17卷 247-254页

作者： Lei Shi Chengkai Yang Xiaoyun sun Jiayue sun Ping Dong Shufeng Xiong Jian Wang College of Information and Management Science Henan Agricultural UniversityZhengzhou 450046China Henan Grain Crop Collaborative Innovation Center Zhengzhou 450046China

Fusarium head blight (FHB) is one of the most destructive diseases in global wheat production. In order to count the FHB-infected wheat ears under field conditions, this study proposed an algorithm for diseased wheat ear detection based on improved YOLOv5s (Tr-YOLOv5s). The Swin Transformer was used to replace the CSPDarknet backbone network to enhance the extraction of characteristic information of the population wheat ears of FHB in the field background. The convolutional block attention module (CBAM) attention mechanism was added to improve the detection effect of target wheat ears, subsequently improving the overall accuracy of the model. The original loss function complete intersection over union (CIoU) was replaced by Scylla intersection over union (SIoU) loss to accelerate the model convergence and decrease the loss value. The results showed that the mean average precision (mAP) of the Tr-YOLOv5s model reached 90.64%, making a 4.63% improvement compared to the original YOLOv5s model. The improved model could quickly detect and count wheat FHB ear in the field environment, which laid a foundation for the subsequent automatic disease identification and grading of wheat FHB under field conditions.

关键词： fusarium head blight YOLOv5s attention mechanism Swin Transformer loss function

Superconvergence of tricubic block finite elements

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Mathematics 2009年第5期52卷 959-972页

作者： LIU JingHong sun HaiNa ZHU QiDing Department of Fundamental Courses Ningbo Institute of TechnologyZhejiang UniversityNingbo 315100China School of Mathematics and Computer Science Hunan Normal UniversityChangsha 410081China

In this paper, we first introduce interpolation operator of projection type in three dimen- sions, from which we derive weak estimates for tricubic block finite elements. Then using the estimate for the W 2, 1-seminorm of the discrete derivative Green's function and the weak estimates, we show that the tricubic block finite element solution uh and the tricubic interpolant of projection type Πh3u have superclose gradient in the pointwise sense of the L∞-norm. Finally, this supercloseness is applied to superconvergence analysis, and the global superconvergence of the finite element approximation is derived.

关键词： block finite element interpolation operator of projection type superconvergence supercloseness weak estimate discrete derivative Green’s function 65N30

The development of silicate matrix phosphors with broad excitation band for phosphor-convered white LED

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2008年第19期53卷 2923-2930页

作者： LUO XiXian CAO WangHe sun Fei Optoelectronic Technology Institute Department of Physics Dalian Maritime University Dalian 116026 China

This paper briefly reviews the recent progress in alkaline earth silicate host luminescent materials with broad excitation band for phosphor-convered white LED. Among them, the Sr-rich binary phases (Sr, Ba, Ca, Mg)2SiO4:Eu2+ and (Sr, Ba, Ca, Mg)3SiO5:Eu2+ are excellent phosphors for blue LED chip white LED. They have very broad excitation bands and exhibit strong absorption of blue radiation in the range of 450―480 nm. And they exhibit green and yellow-orange emission under the InGaN blue LED chip radiation, respectively. The luminous efficiency of InGaN-based (Sr, Ba, Ca, Mg)2SiO4:Eu2+ and (Sr, Ba, Ca, Mg)3SiO5:Eu2+ is about 70-80 lm/W, about 95%―105% that of the InGaN-based YAG:Ce, while the correlated color temperature is between 4600―11000 K. Trinary alkaline earth silicate host luminescent materials MO(M=Sr, Ca, Ba)-Mg(Zn)O-SiO2 show strong absorption of deep blue/near-ultraviolet radia- tion in the range of 370―440 nm. They can convert the deep blue/near-ultraviolet radiation into blue, green, and red emissions to generate white light. The realization of high-performance white-light LEDs by this approach presents excellent chromaticity and high color rendering index, and the application disadvantages caused by the mixture of various matrixes can be avoided. Moreover, the application prospects and the trends of research and development of alkaline earth silicate phosphors are also discussed.

关键词：发光二极管白色宽激励带硅酸盐

Two approaches for calculating female fetal DNA fraction in noninvasive prenatal testing based on size analysis of maternal DNA fragments

在线全文

学校读者我要写书评

暂无评论

BIOCELL 2022年第1期46卷 185-193页

作者： JIANBO LU XIAOHAN sun XU MA Human Genetics Resource Center National Research Institute for Family PlanningBeijing100081China Graduate School Peking Union Medical CollegeBeijing100730China Beijing University of Technology Beijing100124China

The concentration of cell-free fetal DNA fragments should be detected before noninvasive prenatal testing(NIPT).The fetal DNA molecules have significant clinical potential in determining the overall performance of NIPT and clinical *** is important to measure fetal DNA fraction before ***,there is still little research on how to calculate the concentration of female *** estimation approaches were proposed to calculate fetal DNA fraction,including the fragments size-based approach,aneuploid-based approach,which are all approaches based on chromosome *** on high-throughput sequencing data,two approaches to calculate the DNA fraction of male fetuses were tested and obtained the experiment values,which were close to the actual *** correlation coefficient of fragments size-based approach was 0.9243(P<0.0001)and the aneuploid-based approach reached 0.9339(P<0.0001).We calculated the concentration of female fetuses and obtained remarkable experimental *** came up with two approaches for calculating the fetal DNA fraction of female *** provides an important theoretical basis for the detection of female fetal concentration in future clinical diagnosis.

关键词： Fetal DNA fraction Noninvasive prenatal testing Cell-free fetal DNA Female fetus

Review of Denitrogenation of Algae Biocrude Produced by Hydrothermal Liquefaction

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Transactions of Tianjin University 2017年第4期23卷 301-314页

作者： Jinsheng sun Jie Yang Ming Shi School of Chemical Engineering and Technology Tianjin University Wuhan Jinzhong Petrochemical Engineering CO. LTD

Recently, algae biocrude has drawn considerable attention as algae are considered to be one of the major fuel feedstocks of the future. Based on some impressive results achieved under appropriate conditions, the algae hydrothermal liquefaction (HTL) process has proven to be energy efficient. However, the HTL of biocrude is characterized by a high nitrogen content, which prevents its use in the field of transportation due to the associated nitrogen oxide emissions. Despite this toxicity, few research efforts have focused on the denitrogenation of algae biocrude. In this study, we review the effect of different strain-specific operation parameters and process upgrades with respect to the nitrogen content of biocrude. To achieve denitrogenation, chemical engineering may be required, although some improvements in biocrude properties have been achieved in a number of process upgrades. The use of similar successful pathways has the potential to improve the field of HTL biocrude denitrogenation. These methods, including the adsorptive and extractive denitrogenations of fossil fuels and the hydrodenitrogenation of the main nitrogen compounds, are helpful for developing a better understanding of the potential of denitrogenation for algae HTL biocrude. We also recommend the use of some available catalysts and corresponding operation parameters to promote continued research on denitrogenation. © 2017, The Author(s).

关键词： Energy efficiency Fossil fuels Liquefaction Nitrogen compounds Nitrogen oxides

Oligomerization of 1-Decene: Catalyzation by Immobilized AlCl_3/γ-Al_2O_3 Catalyst in Fixed-bed Reactor

在线全文

学校读者我要写书评

暂无评论

China Petroleum Processing & Petrochemical Technology 2014年第3期16卷 50-55页

作者： Li Deng Shen Benxian sun Hui Petroleum Processing Research Center East China University of Science and Technology

1-Decene was oligomerized over the supported AlCl3/γ-Al2O3 catalyst in a fixed-bed reactor. The effects of temperature and LHSV on oligomerization of 1-decene were investigated and the synthetic PAO was characterized with GC technique. Furthermore, the life of immobilized catalyst was tested and the mechanism of catalyst deactivation was discussed. The results showed that with an increasing temperature, the PAO yield increased and the kinematic viscosity of oil decreased. The GC results indicated that the synthesized PAO was a mixture consisting of dimers, trimers, tetramers and pentamers. The results of chloride content measurements and BET tests showed that catalyst deactivation could be mainly attributed to the loss of active components.

关键词： poly-alpha-olefins 1-decene AlCl3/γ-Al2O3 catalyst oligomerization lubricant base stocks

Collocation Methods for Hyperbolic Partial Differential Equations with Singular Sources

在线全文

学校读者我要写书评

暂无评论

Advances in Applied Mathematics and Mechanics 2009年第6期1卷 769-780页

作者： Jae-Hun Jung Wai sun Don Department of Mathematics the State University of New York at BuffaloBuffaloNY 14260-2900USA Department of Mathematics Hong Kong Baptist UniversityHong KongChina

A numerical study is given on the spectral methods and the high order WENO finite difference scheme for the solution of linear and nonlinear hyperbolic partial differential equations with stationary and non-stationary singular *** singular source term is represented by theδ-*** the approximation of theδ-function,the direct projection method is used that was proposed in[6].Theδ-function is constructed in a consistent way to the derivative *** sine-Gordon equation with a stationary singular source was solved with the Chebyshev collocation ***δ-function with the spectral method is highly oscillatory but yields good results with small number of collocation *** results are compared with those computed by the second order finite difference *** modeling general hyperbolic equations with a non-stationary singular source,however,the solution of the linear scalar wave equation with the nonstationary singular source using the direct projection method yields non-physical oscillations for both the spectral method and the WENO *** numerical artifacts arising when the non-stationary singular source term is considered on the discrete grids are explained.

关键词： Singular sources Dirac-δ-function Direct projection method Chebyshev collocation method WENO scheme

Biological control of a predator-prey system through provision of an infected predator

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Biomathematics 2018年第8期11卷 191-215页

作者： Hui Zhang Genjiu Xu Hao sun Department of Applied Mathematics School of Natural and Applied Sciences Northwestern Polytechnical University Xi 'an Shaanxi 710072 P. R. China

Epidemic transmission has a substantial effect on the dynamics and stability of the predator-prey system, in which the transmission rate plays an important role. The probabilistic cellular automaton (PCA) approach is used to investigate the spatiotemporal dynamics of a predator-prey system with the infected predator. Remarkably, it is impossible to achieve a coexistence state of prey, susceptible predators, and infected predators in a spatial population. This is different from the analysis from a non-spatial population with the mean-field approximation, where Hopf bifurcation arises and the interior equilibrium becomes unstable, and a periodic solution appears with the increasing in feet i on rate. The results show that the introduction of the infected predator with a high transmission rate is beneficial for the persistence of the prey population in space. However, a low transmission rate will promote the coexistence state of the prey and the susceptible predator populations. In summary, it is possible to develop management strategies to manipulate the transmission rate of the infected predator for the benefit of biological control.

关键词： Epidemic transmission probabilistic cellular automaton spatiotemporal dynamics management strategies

CFD performance analysis of finned-tube CO_(2)gas coolers with various inlet air flow patterns

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Energy and Built Environment 2020年第3期1卷 233-241页

作者： Xinyu Zhang Yunting Ge Jining sun Sustainable Environment Research Centre Faculty of ComputingEngineering and ScienceUniversity of South WalesPontypridd CF371DLUnited Kingdom RCUK National Centre for sustainable Energy Use in Food Chains(CSEF) Institute of Energy FutureBrunel University LondonUxbridgeMiddlesex UB83PHUnited Kingdom

A detailed model of three-dimensional computational fluid dynamics(CFD)on a finned-tube CO_(2)gas cooler has been developed and *** model is then applied to investigate the effect of uniform and mal-distribution inlet airflow profiles on the coil *** airflow mal-distribution velocity profiles include linear-up,linear-down and parabolic while the effected coil performance parameters contain airside pressure drop,average airside heat transfer coefficient,approach temperature and coil heating *** model also enables to predict the CO_(2)refrigerant temperature profile along the coil pipes from refrigerant inlet to outlet at different operation *** simulation results reveal that different types of inlet airflow velocity profiles have significant effects on the gas cooler *** uniform airflow velocity profile case shows the best thermal performance of gas *** with the cases of linear-up and parabolic air velocity profiles,the linear-down airflow profile can influence more on the coil heat transfer *** to the thermal conduction between neighbour tubes through coil fins,reversed heat transfer phenomenon exists which can be detected and simulated by the CFD *** is predicted that the linear-down airflow profile can increase greatly the reversed heat transfer phenomenon and thus lead to the highest approach temperature and the lowest heating capacity amongst these four types of airflow *** research method and outcomes presented in this paper can have great potentials to optimize the performance of a CO_(2)gas cooler and its associated refrigeration system.

关键词： CO_(2)finned-tube gas cooler Airflow misdistributions Heat transfer coefficient CO_(2)refrigeration system Computational Fluid Dynamics(CFD) modelling