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改进YOLOv5su模型检测桃树缩叶病
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作者 姚凌云 周俊峰 李丽 《农业工程学报》 EI CAS CSCD 北大核心 2024年第14期109-117,共9页
为实现自然环境下桃树缩叶病的检测,该研究提出了一种基于YOLOv5su的桃树缩叶病识别改进模型DLLYOLOv5su。首先,针对桃树缩叶病目标特征变化较大的问题,在骨干网络最后一层C3模块中加入可变形自注意力模块(deformable attention,DA),使... 为实现自然环境下桃树缩叶病的检测,该研究提出了一种基于YOLOv5su的桃树缩叶病识别改进模型DLLYOLOv5su。首先,针对桃树缩叶病目标特征变化较大的问题,在骨干网络最后一层C3模块中加入可变形自注意力模块(deformable attention,DA),使模型更加关注目标区域,降低背景对模型的影响,提高模型在复杂背景下的拟合能力。其次在SPPF(fast spatial pyramid pooling)模块中引入LSKA(large separable kernel attention)结构,大核卷积增大了模型的感受野,使模型能够关注更多信息。最后,提出了LAWD(lightweight adaptive weighted downsampling)模块,使用轻量化的下采样结构替换卷积模块,减少计算开销。在桃树缩叶病数据集上进行试验,结果显示,DLL-YOLOv5su模型权重大小为17.6 MB,检测速度为83帧/s。识别准确率P、召回率R和平均精度均值mAP_(50)分别达到了80.7%、73.1%和80.4%,相较于原始YOLOv5su分别提高了4.2、2.4和4.3个百分点。与YOLOv3-tiny、Faster R-CNN、YOLOv7和YOLOv8相比mAP_(50)分别高出了28.5、11.8、2.1和4.1个百分点。改进模型识别精度高,误检、漏检率低,检测速度满足实时检测的要求,可以为桃树缩叶病的实时监测和预警提供参考。 展开更多
关键词 图像处理 病害 缩叶病 目标检测 YOLOv5su 可变形自注意力 大核卷积 轻量化
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An improved typhoon monitoring model based on precipitable water vapor and pressure
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作者 Junyu Li Haojie Li +7 位作者 Lilong Liu Jiaqing Chen Yibin Yao Mingyun Hu Liangke Huang Fade Chen Tengxu Zhang Lv Zhou 《Geodesy and Geodynamics》 EI CSCD 2024年第3期276-290,共15页
The potential of monitoring the movement of typhoons using the precipitable water vapor(PWV) has been confirmed. However, monitoring the movement of typhoon is focused on PWV, making it difficult to describe the movem... The potential of monitoring the movement of typhoons using the precipitable water vapor(PWV) has been confirmed. However, monitoring the movement of typhoon is focused on PWV, making it difficult to describe the movement of a typhoon in detail minutely and resulting in insufficient accuracy. Hence,based on PWV and meteorological data, we propose an improved typhoon monitoring mode. First, the European Centre for Medium-Range Weather Forecasts Reanalysis 5-derived PWV(ERA5-PWV) and the Global Navigation Satellite System-derived PWV(GNSS-PWV) were compared with the reference radiosonde PWV(RS-PWV). Then, using the PWV and atmospheric parameters derived from ERA5, we discussed the anomalous variations of PWV, pressure(P), precipitation, and wind speed during different typhoons. Finally, we compiled a list of critical factors related to typhoon movement, PWV and P. We developed an improved multi-factor typhoon monitoring mode(IMTM) with different models(i.e.,IMTM-I and IMTM-II) in different cases with a higher density of GNSS observation or only Numerical Weather Prediction(NWP) data. The IMTM was evaluated through the reference movement speeds of HATO and Mangkhut from the China Meteorological Observatory Typhoon Network(CMOTN). The results show that the root mean square(RMS) of the IMTM-I is 1.26 km/h based on ERA5-P and ERA5-PWV,and the absolute bias values are mostly within 2 km/h. Compared with the models considering the single factor ERA5-P/ERA5-PWV, the RMS of the IMTM-I is improved by 26.3% and 38.5%, respectively. The IMTM-II model manifests a residual of only 0.35 km/h. Compared with the single-factor model based on GNSS-PWV/P, the residual of the IMTM-II model is reduced by 90.8% and 84.1%, respectively. These results propose that the typhoon movement monitoring approach combining PWV and P has evident advantages over the single-factor model and is expected to supplement traditional typhoon monitoring. 展开更多
关键词 TYPHOON GNSS/ERA5 PWV PRESsuRE MONITORING Improved model
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Benchmarking YOLOv5 models for improved human detection in search and rescue missions
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作者 Namat Bachir Qurban Ali Memon 《Journal of Electronic Science and Technology》 EI CAS CSCD 2024年第1期70-80,共11页
Drone or unmanned aerial vehicle(UAV)technology has undergone significant changes.The technology allows UAV to carry out a wide range of tasks with an increasing level of sophistication,since drones can cover a large ... Drone or unmanned aerial vehicle(UAV)technology has undergone significant changes.The technology allows UAV to carry out a wide range of tasks with an increasing level of sophistication,since drones can cover a large area with cameras.Meanwhile,the increasing number of computer vision applications utilizing deep learning provides a unique insight into such applications.The primary target in UAV-based detection applications is humans,yet aerial recordings are not included in the massive datasets used to train object detectors,which makes it necessary to gather the model data from such platforms.You only look once(YOLO)version 4,RetinaNet,faster region-based convolutional neural network(R-CNN),and cascade R-CNN are several well-known detectors that have been studied in the past using a variety of datasets to replicate rescue scenes.Here,we used the search and rescue(SAR)dataset to train the you only look once version 5(YOLOv5)algorithm to validate its speed,accuracy,and low false detection rate.In comparison to YOLOv4 and R-CNN,the highest mean average accuracy of 96.9%is obtained by YOLOv5.For comparison,experimental findings utilizing the SAR and the human rescue imaging database on land(HERIDAL)datasets are presented.The results show that the YOLOv5-based approach is the most successful human detection model for SAR missions. 展开更多
关键词 Unmanned aerial vehicle(UAV) Search and rescue(SAR) You look only once(YOLO)model You only look once version 5 (YOLOv5)
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Calculation of the Standard Model Parameters and Particles Based on a SU(4) Preon Model
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作者 Jan Helm 《Journal of Modern Physics》 2024年第1期64-124,共61页
This paper describes an extension and a new foundation of the Standard Model of particle physics based on a SU(4)-force called hyper-color, and on preon subparticles. The hyper-color force is a generalization of the S... This paper describes an extension and a new foundation of the Standard Model of particle physics based on a SU(4)-force called hyper-color, and on preon subparticles. The hyper-color force is a generalization of the SU(2)-based weak interaction and the SU(1)-based right-chiral self-interaction, in which the W-and the Z-bosons are Yukawa residual-field-carriers of the hyper-color force, in the same sense as the pions are the residual-field-carriers of the color SU(3) interaction. Using the method of numerical minimization of the SU(4)-action based on this model, the masses and the inner structure of leptons, quarks and weak bosons are calculated: the mass results are very close to the experimental values. We calculate also precisely the value of the Cabibbo angle, so the mixing matrices of the Standard model, CKM matrix for quarks and PMNS matrix for neutrinos can also be calculated. In total, we reduce the 29 parameters of the Standard Model to a total of 7 parameters. 展开更多
关键词 su(4) Generalization of Weak Interaction Extension of Standard model Numerical Minimization of Action Hyper-Color Preon
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The construction and practice of humanistic care teaching model based on 5C care theory
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作者 Xi-Peng liu Qing-Qing Li +3 位作者 Yu-Zi Zhong Fei-Fei Hong Yan Li Yi-Jing Wang 《Nursing Communications》 2024年第8期1-9,共9页
Objective:To construct a scientific and feasible teaching mode based on 5C caring theory and evaluate it,so as to provide a reference basis for future study about nursing humanistic quality education.Methods:Based on ... Objective:To construct a scientific and feasible teaching mode based on 5C caring theory and evaluate it,so as to provide a reference basis for future study about nursing humanistic quality education.Methods:Based on the 5C caring theory,the teaching design and teaching content were revising and implementing in the intervention group.Before and after the implementation of the course,a questionnaire survey was conducted using the Caring Ability Inventory(CAI).The results of the surveys were collected,and the data were statistically analysis using SPSS.Results:After the implementation of the course,the cognitive dimension,patience dimension,and humanistic caring ability scores of the nursing students in the intervention group improved compared with those before the implementation of the course(P<0.05).There were no significant difference in the control group(P>0.05).Conclusion:The humanistic caring teaching model based on 5C caring theory has a positive effect on improving nursing students'humanistic caring ability.In the future nursing teaching,the modules with the characteristics of humanistic caring ability can be increased,and carry out the educational reform throughout the humanistic caring ability.Actively guiding nursing students to establish the awareness of humanistic caring,so as to lay a solid foundation for high-quality clinical nursing work. 展开更多
关键词 5C caring theory humanistic caring ability undergraduate nursing students teaching model
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SLC6A9对结直肠癌细胞生长和对5-FU药物敏感性的影响 被引量:1
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作者 张岩 田素礼 +1 位作者 周勇旭 刘昶 《现代肿瘤医学》 CAS 2024年第7期1236-1241,共6页
目的:研究溶质载体家族6成员9(solute carrier family 6 member 9,SLC6A9)表达对结直肠癌细胞增殖、迁移和5-氟尿嘧啶(5-fluorouracil,5-FU)药物敏感性的影响。方法:TCGA数据库分析、实时荧光定量PCR和Western blot分析检测SLC6A9在结... 目的:研究溶质载体家族6成员9(solute carrier family 6 member 9,SLC6A9)表达对结直肠癌细胞增殖、迁移和5-氟尿嘧啶(5-fluorouracil,5-FU)药物敏感性的影响。方法:TCGA数据库分析、实时荧光定量PCR和Western blot分析检测SLC6A9在结肠癌组织、正常结肠细胞系(NCM460)和结直肠癌细胞系(SW620、HCT116、HT29、Lovo和SW480)中的表达。将SCL6A9过表达质粒及阴性对照(SLC6A9 OE、Vector)转染HT29细胞,将SCL6A9小干扰RNA及阴性对照(SLC6A9 siRNA1#、siRNA2#和Scramble)转染SW620细胞。划痕愈合实验和Transwell实验检测各组细胞的迁移、侵袭能力。Western blot和细胞免疫荧光检测EMT相关蛋白E-cadherin、Vimentin的表达水平。利用CCK-8法和构建裸鼠移植瘤模型检测SLC6A9过表达对结直肠癌细胞5-FU药物敏感性的影响。结果:与正常结肠组织和NCM460细胞相比,SLC6A9在结肠癌组织和结直肠癌细胞系中低表达(均P<0.05)。SLC6A9过表达引起E-cadherin蛋白表达增加,Vimentin蛋白水平降低,抑制结直肠癌细胞的迁移、侵袭(P<0.05)。SLC6A9低表达引起E-cadherin蛋白表达降低,Vimentin蛋白水平增加,促进结直肠癌细胞的迁移、侵袭能力(P<0.05)。SLC6A9过表达提高了5-FU的药物敏感性,并使肿瘤生长缓慢,质量减轻(P<0.05)。而SLC6A9低表达降低了5-FU的药物敏感性(P<0.05)。结论:SLC6A9过表达能够抑制结直肠癌细胞的迁移、侵袭和EMT进程,并增强5-FU对结直肠癌细胞的药物敏感性。 展开更多
关键词 结肠肿瘤 SLC6A9 细胞迁移和侵袭分析 EMT 5-FU 异种移植模型实验
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Parameters Calibration of the GISSMO Failure Model for SUS301L-MT 被引量:1
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作者 Tao Zhu Haoxu Ding +4 位作者 Chao Wang Yuxin Liu Shoune Xiao Guangwu Yang Bing Yang 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2023年第1期332-343,共12页
With the development of the rail transit industry,more attention has been paid to the passive safety of rail vehicles.Structural damage is one of the main failure behaviors in a rail vehicle collision,but it has been ... With the development of the rail transit industry,more attention has been paid to the passive safety of rail vehicles.Structural damage is one of the main failure behaviors in a rail vehicle collision,but it has been paid little attention to in past research.In this paper,the quasi-static fracture experiments of SUS301L-MT under different stress states were carried out.The mechanical fracture properties of this material were studied,and the corresponding finite element simulation accuracy was improved to guide the design of vehicle crashworthiness.Through the tests,the fracture behavior of materials with wide stress triaxiality was obtained,and each specimen’s fracture locations and fracture strains were determined.Parameters of a generalized incremental stress state dependent damage model(GISSMO)of the material were calibrated,and the model’s accuracy was verified with test results from a 45°shear specimen.The GISSMO failure model accurately reflected the fracture characteristics of the material.The mesh dependency of this model was modified and discussed.The results show that the simulation agrees well with experimental data for the force-displacement curve after correction,but the strain distribution needs to be further studied and improved. 展开更多
关键词 suS301L-MT Fracture failure GISSMO model Finite element simulation Stress state
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Solubility measurement,correlation and thermodynamic properties of 2,3,4-trichloro-1,5-dinitrobenzene in fifteen mono-solvents at temperatures from 278.15 to 323.15 K 被引量:1
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作者 Yun-Zhang Liu Lu-Yao Zhang +3 位作者 Dan He Li-Zhen Chen Zi-Shuai Xu Jian-Long Wang 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2023年第6期224-233,共10页
The solubility of 2,3,4-trichloro-1,5-dinitrobenzene(TCDNB) was measured by a laser dynamic method over the temperature range from 278.15 K to 323.15 K under 0.1 MPa in fifteen mono-solvents(methanol,ethanol,isopropan... The solubility of 2,3,4-trichloro-1,5-dinitrobenzene(TCDNB) was measured by a laser dynamic method over the temperature range from 278.15 K to 323.15 K under 0.1 MPa in fifteen mono-solvents(methanol,ethanol,isopropanol,n-butanol,toluene,dichloromethane,chloroform,tetrachloromethane,1,2-dichloroethane,acetone,ethyl acetate,acetonitrile,N-methylpyrrolidone(NMP),N,Ndimethylformamide dimethyl sulfoxide(DMF),dimethyl sulfoxide(DMSO).The solubility of TCDNB could be increased with increasing temperature in fifteen mono-solvents.TCDNB solubility is in the following order at 298.15 K:NMP>DMF>DMSO>toluene>acetone>ethyl acetate>dichloromethane>1,2-dich loroethane>chloroform>acetonitrile>tetrachloromethane>methanol>ethanol>n-butanol>isopropanol.The KAT-LSER model was used to investigate the solvent effect,which revealed that the hydrogen bond acidity of solvents has a greater effect on TCDNB solubility.The van't Hoff model,the modified Apelblat model,theλh model,and the non-random two liquid(NRTL)model were used to correlate the solubility of TCDNB.The calculated solubility data agreed well with the experimental data,and the modified Apelblat model fit best.Furthermore,the van't Hoff and Gibbs equations were also used to calculate the dissolution thermodynamic properties of TCDNB in various solvents.TCDNB dissolution could be an enthalpy-driven,non-spontaneous,and endothermic process in fifteen mono-solvents.The determination and fitting solubility of TCDNB,as well as the calculation of its thermodynamic properties,would be critical in the purification and crystallization of its preparation process research. 展开更多
关键词 2 3 4-Trichloro-1 5-dinitrobenzene(TCDNB) Solid-liquid equilibrium Laser dynamic method Solubility model Thermodynamics properties
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基于政策工具与5W理论二维视角下中医药文化传播政策量化分析 被引量:1
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作者 袁有树 贾暄 +1 位作者 朱嘉俊 王志伟 《中国卫生事业管理》 北大核心 2024年第3期319-324,共6页
目的:对我国中医药文化传播相关政策文本进行分析,探讨中医药文化传播政策的着重点和存在问题,为后期政策优化提供依据。方法:基于政策工具和5W传播理论的二维视角,对检索出的43份中医药文化传播政策文件进行内容分析。结果:中医药文化... 目的:对我国中医药文化传播相关政策文本进行分析,探讨中医药文化传播政策的着重点和存在问题,为后期政策优化提供依据。方法:基于政策工具和5W传播理论的二维视角,对检索出的43份中医药文化传播政策文件进行内容分析。结果:中医药文化传播政策制定中政策工具整体使用较为丰富,但结构分布不均。对传播媒介(110/200,55.00%)的扩展及传播内容(97/102,95.10%)的丰富均依赖资讯性工具,对传播者(63/64,98.44%)的引导与传播受众(14/14,100%)的调动多依赖组织性工具,对传播效果(11/1291.67%)的评估多依赖市场化工具,经济性工具(2/16,12.50%)在5W维度的激励作用均发挥不足。结论:应借助经济性工具激发中医药文化传播主体的积极性与创造性,运用组织性工具兼顾中医药文化传播受众的需求度与差异化,凭借资讯性工具增强中医药传播内容科学性与表达通俗性,依托管制性工具推动中医药文化传播媒介的多元化与整合化发展,利用市场化工具提高中医药文化传播效果的社会效益与经济效益。 展开更多
关键词 政策工具 中医药文化 5W模式 传播策略
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Precipitation-Surface Temperature Relationship in the IPCC CMIP5 Models 被引量:7
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作者 吴仁广 陈洁鹏 温之平 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2013年第3期766-778,共13页
Precipitation and surface temperature are two important quantities whose variations are closely related through various physical processes. In the present study, we evaluated the precipitation-surface temperature (P-... Precipitation and surface temperature are two important quantities whose variations are closely related through various physical processes. In the present study, we evaluated the precipitation-surface temperature (P-T) relationship in 17 climate models involved in the Coupled Model Intercomparison Project Phase 5 (CMIP5) for the IPCC Assessment Report version 5. Most models performed reasonably well at simulat- ing the large-scale features of the P-T correlation distribution. Based on the pattern correlation of the P-T correlation distribution, the models performed better in November-December-January-February-March (NDJFM) than in May-June-July-August-September (MJJAS) except for the mid-latitudes of the North- ern Hemisphere, and the performance was generally better over the land than over the ocean. Seasonal dependence was more obvious over the land than over the ocean and was more obvious over the mid- and high-latitudes than over the tropics. All of the models appear to have had difficulty capturing the P-T correlation distribution over the mid-latitudes of the Southern Hemisphere in MJJAS. The spatial variabil- ity of the P-T correlation in the models was overestimated compared to observations. This overestimation tended to be larger over the land than over the ocean and larger over the mid- and high-latitudes than over the tropics. Based on analyses of selected model ensemble simulations, the spread of the P-T correlation among the ensemble members appears to have been small. While the performance in the P-T correlation provides a general direction for future improvement of climate models, the specific reasons for the discrep- ancies between models and observations remain to be revealed with detailed and comprehensive evaluations in various aspects. 展开更多
关键词 precipitation-surface temperature relationship CMIP5 models seasonal dependence
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Asymmetry of Surface Climate Change under RCP2.6 Projections from the CMIP5 Models 被引量:3
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作者 辛晓歌 程彦杰 +2 位作者 汪方 吴统文 张洁 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2013年第3期796-805,共10页
The multi-model ensemble (MME) of 20 models from the Coupled Model Intercomparison Project Phase Five (CMIP5) was used to analyze surface climate change in the 21st century under the representative con- centration... The multi-model ensemble (MME) of 20 models from the Coupled Model Intercomparison Project Phase Five (CMIP5) was used to analyze surface climate change in the 21st century under the representative con- centration pathway RCP2.6, to reflect emission mitigation efforts. The maximum increase of surface air temperature (SAT) is 1.86℃ relative to the pre-industrial level, achieving the target to limit the global warming to 2℃. Associated with the "increase-peak-decline" greenhouse gases (GHGs) concentration path- way of RCP2.6, the global mean SAT of MME shows opposite trends during two time periods: warming during 2006-55 and cooling during 2056-2100. Our results indicate that spatial distribution of the linear trend of SAT during the warming period exhibited asymmetrical features compared to that during the cool- ing period. The warming during 2006-55 is distributed globally, while the cooling during 2056-2100 mainly occurred in the NH, the South Indian Ocean, and the tropical South Atlantic Ocean. Different dominant roles of heat flux in the two time periods partly explain the asymmetry. During the warming period, the latent heat flux and shortwave radiation both play major roles in heating the surface air. During the cooling period, the increase of net longwave radiation partly explains the cooling in the tropics and subtropics, which is associated with the decrease of total cloud amount. The decrease of the shortwave radiation accounts for the prominent cooling in the high latitudes of the NH. The surface sensible heat flux, latent heat flux, and shortwave radiation collectively contribute to the especial warming phenomenon in the high-latitude of the SH during the cooling period. 展开更多
关键词 climate models climate change PROJECTION CMIP5 RCP2.6
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Degenerate States in Nonlinear Sigma Model with SU(2) Symmetry
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作者 Tomo Munehisa 《World Journal of Condensed Matter Physics》 CAS 2023年第1期14-39,共26页
Entanglement in quantum theory is a peculiar concept to scientists. With this concept we are forced to re-consider the cluster property which means that one event is irrelevant to another event when they are fully far... Entanglement in quantum theory is a peculiar concept to scientists. With this concept we are forced to re-consider the cluster property which means that one event is irrelevant to another event when they are fully far away. In the recent works we showed that the quasi-degenerate states induce the violation of cluster property in antiferromagnets when the continuous symmetry breaks spontaneously. We expect that the violation of cluster property will be observed in other materials too, because the spontaneous symmetry breaking is found in many systems such as the high temperature superconductors and the superfluidity. In order to examine the cluster property for these materials, we studied a quantum nonlinear sigma model with U(1) symmetry in the previous work. There we showed that the model does have quasi-degenerate states. In this paper we study the quantum nonlinear sigma model with SU(2) symmetry. In our approach we first define the quantum system on the lattice and then adopt the representation where the kinetic term is diagonalized. Since we have no definition on the conjugate variable to the angle variable, we use the angular momentum operators instead for the kinetic term. In this representation we introduce the states with the fixed quantum numbers and carry out numerical calculations using quantum Monte Carlo methods and other methods. Through analytical and numerical studies, we conclude that the energy of the quasi-degenerate state is proportional to the squared total angular momentum as well as to the inverse of the lattice size. 展开更多
关键词 Quantum Nonlinear Sigma model su(2): Special Unitary Group in Two Dimensions Cluster Property Spontaneous Symmetry Breaking Degenerate States Spin-Weighted Harmonics
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Statistical Model of Path Loss for Railway 5G Marshalling Yard Scenario
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作者 DING Jianwen LIU Yao +2 位作者 LIAO Hongjian SUN Bin WANG Wei 《ZTE Communications》 2023年第3期117-122,共6页
The railway mobile communication system is undergoing a smooth transition from the Global System for Mobile Communications-Railway(GSM-R)to the Railway 5G.In this paper,an empirical path loss model based on a large am... The railway mobile communication system is undergoing a smooth transition from the Global System for Mobile Communications-Railway(GSM-R)to the Railway 5G.In this paper,an empirical path loss model based on a large amount of measured data is established to predict the path loss in the Railway 5G marshalling yard scenario.According to the different characteristics of base station directional antennas,the antenna gain is verified.Then we propose the position of the breakpoint in the antenna propagation area,and based on the breakpoint segmentation,a large-scale statistical model for marshalling yards is established. 展开更多
关键词 5G-R marshalling yard path loss prediction statistical modeling
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ZSM-5分子筛结构对苯烷基化反应性能影响的数值模拟研究
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作者 黄静茹 陈佳轩 +4 位作者 张群锋 阮晋 朱来 叶光华 周兴贵 《化工学报》 EI CSCD 北大核心 2024年第7期2544-2555,共12页
以ZSM-5分子筛催化苯和乙烯烷基化为体系,建立并验证了一种三维各向异性扩散-反应数学模型,该模型考虑了分子筛形貌、孔结构和扩散各向异性的影响。模拟发现当分子筛颗粒体积和abc轴尺寸保持不变时,改变分子筛形貌并不会显著影响其表观... 以ZSM-5分子筛催化苯和乙烯烷基化为体系,建立并验证了一种三维各向异性扩散-反应数学模型,该模型考虑了分子筛形貌、孔结构和扩散各向异性的影响。模拟发现当分子筛颗粒体积和abc轴尺寸保持不变时,改变分子筛形貌并不会显著影响其表观活性,因而该情况下无须调控分子筛形貌;而当分子筛颗粒体积不变时,仅缩短b轴尺寸才能显著降低扩散阻力,提高催化剂表观活性,因而合成ZSM-5分子筛时缩短b轴尺寸最有利于扩散和反应。在分子筛颗粒中引入大孔可显著提高分子筛催化剂利用率和表观活性,保持大孔孔隙率不变时,减小大孔孔径更有利。存在最优大孔孔隙率以平衡扩散阻力和活性材料含量,当分子筛粒径4μm、大孔孔径300 nm时,最优大孔孔隙率0.16,对应最高表观反应速率80.5 mol/(m^(3)·s)。另外,由于分子筛内扩散各向异性的影响,当大孔取向平行于c轴时最有利。结果可为苯和乙烯烷基化ZSM-5分子筛催化剂乃至其他分子筛催化剂的设计优化提供一定的理论指导。 展开更多
关键词 苯烷基化 ZSM-5分子筛 扩散-反应模型 孔道 扩散各向异性 颗粒形貌
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Relationship between South China Sea Precipitation Variability and Tropical Indo-Pacific SST Anomalies in IPCC CMIP5 Models during Spring-to-Summer Transition 被引量:1
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作者 HU Wenting WU Renguang 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2015年第9期1303-1318,共16页
The present study evaluates the precipitation variability over the South China Sea(SCS) and its relationship to tropical Indo-Pacific SST anomalies during spring-to-summer transition(April–May–June,AMJ) simulate... The present study evaluates the precipitation variability over the South China Sea(SCS) and its relationship to tropical Indo-Pacific SST anomalies during spring-to-summer transition(April–May–June,AMJ) simulated by 23 Intergovernmental Panel on Climate Change Coupled Model Intercomparison Project Phase 5 coupled models.Most of the models have the capacity to capture the AMJ precipitation variability in the SCS.The precipitation and SST anomaly(SSTA) distribution in the SCS,tropical Pacific Ocean(TPO),and tropical Indian Ocean(TIO) domains is evaluated based on the pattern correlation coefficients between model simulations and observations.The analysis leads to several points of note.First,the performance of the SCS precipitation anomaly pattern in AMJ is model dependent.Second,the SSTA pattern in the TPO and TIO is important for capturing the AMJ SCS precipitation variability.Third,a realistic simulation of the western equatorial Pacific(WEP) and local SST impacts is necessary for reproducing the AMJ SCS precipitation variability in some models.Fourth,the overly strong WEP SST impacts may disrupt the relationship between the SCS precipitation and the TPO–TIO SST.Further work remains to be conducted to unravel the specific reasons for the discrepancies between models and observations in various aspects. 展开更多
关键词 atmosphere–ocean interaction South China Sea CMIP5 models spring-to-summer transition
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β-5型木质素二聚体热解机理模拟计算
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作者 李文涛 高丽娟 +5 位作者 周关正 柴宝华 王美净 胡斌 刘吉 陆强 《能源环境保护》 2024年第2期208-214,共7页
木质素是由苯基丙烷结构通过C—O键和C—C键连接而成的复杂三维网状无定形高聚物,热解是木质素的重要利用方式,探究木质素热解过程中连接键的断裂机理对于开发高效热解技术至关重要。利用密度泛函理论方法,针对典型的β-5连接木质素二... 木质素是由苯基丙烷结构通过C—O键和C—C键连接而成的复杂三维网状无定形高聚物,热解是木质素的重要利用方式,探究木质素热解过程中连接键的断裂机理对于开发高效热解技术至关重要。利用密度泛函理论方法,针对典型的β-5连接木质素二聚体模型化合物,探究其热解过程及取代基的影响。计算结果表明,苯环之间五元环的开环反应是最可能发生的初步反应,其中Cα—O键和Cα—Cβ键的键解离能(BDEs)分别为163.9 kJ/mol和212.9 kJ/mol,是最主要的断键开环反应。通过对比甲基、甲氧基、羟基、正丙基等支链对β-5连接键的断裂的影响,发现当两个苯环和β-5连接五元环上分别连接羟基、丙基、羟甲基取代基时,Cα—O键和Cα—Cβ键的BDEs最低。对于不同取代基类型和位点来说,Cα—O键均裂始终是最容易发生的初始反应,而Cα—O键和Cα—Cβ键连续断裂的路径是β-5连接五元环断裂的主要途径。 展开更多
关键词 木质素 β-5连接 密度泛函理论 模型化合物 热解机理
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基于网格搜索优化CatBoost模型的GF-5卫星影像铬离子含量反演研究
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作者 刘东宜 屈永华 +1 位作者 冯耀伟 屈冉 《生态环境学报》 CSCD 北大核心 2024年第9期1460-1470,共11页
高光谱遥感技术以其低成本、高效率、广泛覆盖范围、宏观性强和动态监测能力等优势而受到关注。利用高光谱遥感技术,对安图县新合乡尾矿库土壤中六价铬离子污染状况进行有效监测;以高分五号(GF-5)卫星的高光谱遥感影像及实测土壤样本为... 高光谱遥感技术以其低成本、高效率、广泛覆盖范围、宏观性强和动态监测能力等优势而受到关注。利用高光谱遥感技术,对安图县新合乡尾矿库土壤中六价铬离子污染状况进行有效监测;以高分五号(GF-5)卫星的高光谱遥感影像及实测土壤样本为数据源,基于皮尔逊相关系数、波段加法和比值指数,提取与土壤重金属含量变化相关的特征,构建反演模型。首先,剔除预处理后的遥感影像中饱和、噪声和水汽吸收波段,同时利用各波段反射率进行代数运算构建加法和比值指数,计算其与实测铬离子含量数据的皮尔逊相关系数;然后,基于皮尔逊相关系数得到的前50最高相关特征变量,采用网格搜索优化的CatBoost回归,建立土壤六价铬离子含量反演模型,并使用SHAP方法评估特征重要性,探究影响GF-5反演土壤重金属重要波段。结果显示,在相同光谱变换条件下,与偏最小二乘回归(PLSR)、随机森林回归(RFR)、支持向量机回归(SVMR)、卷积神经网络(CNN)和多元逐步线性回归模型相比,网格搜索优化的CatBoost模型效果最好,训练集拟合优度为0.92,验证集为0.88。利用网格搜索优化CatBoost回归模型对吉林省安图铬渣填埋场进行了土壤六价铬离子含量反演,结果显示该区域尾矿库开采区域周边六价铬离子污染严重,这与该地矿山开采和尾矿堆放实际情况基本一致。该研究为土壤重金属污染监测和环境管理提供了重要的技术手段和科学依据。 展开更多
关键词 高光谱反演 高光谱遥感 GF-5 六价铬离子 土壤重金属 CatBoost回归模型
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多级孔ZSM-5分子筛催化餐厨废油制备轻质芳烃的研究
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作者 罗文博 郝松源 袁红 《粮食与油脂》 北大核心 2024年第2期53-59,共7页
采用水热法合成不同硅铝摩尔比的多级孔ZSM-5分子筛,并对其结构进行表征,考察不同硅铝摩尔比多级孔ZSM-5分子筛对餐厨废油模型化合物(WCOMC)制备苯、甲苯和二甲苯(3种物质统称BTX)的影响。结果表明:L-赖氨酸的加入提高了多级孔ZSM-5分... 采用水热法合成不同硅铝摩尔比的多级孔ZSM-5分子筛,并对其结构进行表征,考察不同硅铝摩尔比多级孔ZSM-5分子筛对餐厨废油模型化合物(WCOMC)制备苯、甲苯和二甲苯(3种物质统称BTX)的影响。结果表明:L-赖氨酸的加入提高了多级孔ZSM-5分子筛的传质效率,其硅铝摩尔比的变化有效地调节了多级孔ZSM-5分子筛的酸性,且多级孔ZSM-5分子筛的酸性影响目标产物的分布和反应体系的稳定性。随着温度的升高,芳烃的相对含量提高,在600℃条件下多级孔ZSM-5-40分子筛催化WCOMC制备BTX的相对含量最高,为20.3%。 展开更多
关键词 多级孔ZSM-5分子筛 餐厨废油模型化合物 轻质芳烃
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Study on Prediction Model of Number of Rainstorm Days in Summer Based on C5.0 Decision Tree Algorithm
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作者 Shi Yimin Chen Weiwei Zhu Yunfeng 《Meteorological and Environmental Research》 CAS 2019年第2期56-60,共5页
Based on the data of daily precipitation in Lianyungang area from 1951 to 2012 and various climate signal data from the National Climate Center website and the NOAA website,a model for predicting whether the number of... Based on the data of daily precipitation in Lianyungang area from 1951 to 2012 and various climate signal data from the National Climate Center website and the NOAA website,a model for predicting whether the number of rainstorm days in summer in Lianyungang area is large was established by the classical C5. 0 decision tree algorithm. The data samples in 48 years( accounting for about 80% of total number of samples)was as the training set of a model,and the training accuracy rate of the model was 95. 83%. The data samples in the remaining 14 years( accounting for about 20% of total number of samples) were used as the test set of the model to test the model,and the test accuracy of the model was 85. 71%. The results showed that the prediction model of number of rainstorm days in summer constructed by C5. 0 algorithm had high accuracy and was easy to explain. Moreover,it is convenient for meteorological staff to use directly. At the same time,this study provides a new idea for short-term climate prediction of number of rainstorm days in summer. 展开更多
关键词 C5. 0 algorithm NUMBER of RAINSTORM DAYS PREDICTION model
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Aqp5-C末端截断小鼠的构建及其潜在应用
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作者 王晓彤 陈豪 +5 位作者 李德泽 李飞娜 郑惠文 李晶晶 丁谦文 申晨 《标记免疫分析与临床》 CAS 2024年第1期142-150,共9页
目的 Aqp5蛋白的C末端结构对其功能的发挥起着重要作用。本研究旨在通过构建Aqp5-C末端6个氨基酸缺失的突变小鼠,验证Aqp5-C末端6个氨基酸缺失对该蛋白亚细胞定位的影响,并初步比较研究此突变小鼠的肺脏组织结构和转录组的改变,探讨该... 目的 Aqp5蛋白的C末端结构对其功能的发挥起着重要作用。本研究旨在通过构建Aqp5-C末端6个氨基酸缺失的突变小鼠,验证Aqp5-C末端6个氨基酸缺失对该蛋白亚细胞定位的影响,并初步比较研究此突变小鼠的肺脏组织结构和转录组的改变,探讨该突变小鼠用于Aqp5功能研究的潜在应用价值。方法 采用基于gRNA的CRISPER Cas 9技术构建Aqp5末端6个氨基酸缺失的突变小鼠(Aqp5-p.I260*)并进行序列鉴定,采用组织切片、荧光染色和显微镜观察等手段明确突变蛋白在肺泡上皮细胞的亚细胞定位和突变小鼠肺组织结构,采用转录组测序研究突变小鼠肺脏基因差异表达。结果 本研究成功构建了Aqp5蛋白C末端截断小鼠,发现p.I260*改变了亚细胞定位,Aqp5-p.I260*鼠肺泡数目少于野生鼠;Aqp5-p.I260*小鼠肺组织的转录组上调基因主要富集于发育和造血细胞谱系等通路,其Aqp5功能缺陷后诱发炎症相关通路基因(Hspa1a、IL-1β、Col3a1等)的表达水平改变。结论 本研究在体验证了小鼠Aqp5蛋白C末端6个氨基酸缺失突变对该蛋白细胞膜定位的关键作用,表明了以该小鼠作为Aqp5功能缺陷模型探讨Aqp5蛋白在肺发育和骨髓造血、炎症和免疫调节等生物学功能的潜在应用价值。 展开更多
关键词 水通道蛋白5 基因突变 细胞膜 小鼠模型 转录组
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