检索结果-南通市图书馆

Science China Chemistry 2015年第8期58卷 1286-1291页

作者： Xian-Ying Shi Xue-Fen Dong Juan fan Ke-Yan Liu jun-fa wei Chao-jun Li Key Laboratory of Applied Surface and Colloid Chemistry (Ministry of Education) Key Laboratory for Macromolecular Science of Shaanxi Province School of Chemistry and Chemical Engineering Shaanxi Normal University Department of Chemistry McGill University

Carboxylate as a promising and valuable directing group has attracted a great deal of ***,employing it as a traceless direction group has rarely been *** developed the ruthenium-catalyzed amidation of substituted benzoic acids with isocyanates via directed C–H functionalization followed by decarboxylation to afford the corresponding metasubstituted N-aryl benzamides,in which the carboxylate serves as a unique,removable directing ***,this protocol can provide an efficient alternative to access meta-substituted N-aryl benzamides,which are much more difficult to prepare than ortho-substituted analogues.

关键词： amides decarboxylation amidation C-H functionalization homogeneous catalysis

Ruthenium (II)-catalyzed synthesis of phthalides via the cascade addition and cyclization of aromatic acids with aldehydes

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2018年第2期61卷 153-158页

作者： Juan fan Peng-Min Wang Jia-Ni Wang Xue Zhao Zhong-Wen Liu jun-fa wei Xian-Ying Shi Key Laboratory for Macromolecular Science of Shaanxi Province School of Chemistry and Chemical EngineeringShaanxi Normal University

The ruthenium-catalyzed intermolecular cascade cyclization of aromatic acids with aromatic aldehydes, which involves the direct insertion of C–H bond into a polar C=O bond and the successive intramolecular nucleophilic substitution, was developed for the synthesis of 3-substituted phthalides in good to excellent yields. This one-pot procedure characterizes in a short reaction time, the cheaper Ru(II) as a catalyst, readily available acids and aldehydes as starting materials, and water as the only theoretical *** merits make the protocol an efficient and cost-effective route for the synthesis of 3-substituted phthalides.

关键词： nucleophilic addition cascade cyclization ruthenium 3-substituted phthalides C–H activation

A　Methane　Monooxygenase－like　DinuclearIron　（Ⅲ）　Complex　and　its　Catalytic　Ability　for　Asymmetric　Epoxidation　of　Styrene

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 1996年第10期7卷 962-964页

作者： jun fa wei Xian Da YU Dao Sen JIN(Lanzhou Institute of Chemical Physics. Academia Sinica, Lanzhou 730000) Lanzhou Inst. of Chemical Physics Academia Sinica Lanzhou 730000

A methane monooxygenase-like dinuclear complex of iron (Ⅲ) with a chiral heptadentate ligand has been synthesed and tested for catalytic ability for asymmetric epoxidation of styrene with iodosylbenzene. The results show that the complex exhibits many qualitative features, such as electronic spectrum. catalytic behavior. and asymmetric induction similar to those of methane monooxygenase and catalyzes styrene epoxidation to R- (+)-styrene oxide in 9. 3% yield and 72. 9% optical yield.

关键词： Ability Asymmetric DinuclearIron Monooxygenase Catalytic

Effect of droplet characteristics on liquid-phase distribution in spray zone of internal mixing air-mist nozzle

在线全文

学校读者我要写书评

暂无评论

China Foundry 2024年第2期21卷 185-196页

作者： wei-li Wu Chang-gui Cheng Yang Li Shi-fa wei De-li Chen The State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan 430081China Hubei Provincial Key Laboratory for New Processes of Ironmaking and Steelmaking Wuhan University of Science and TechnologyWuhan 430081China Technology Center Fushun Special Steel Co.Ltd.Fushun 113001LiaoningChina

In continuous casting production,droplet characteristics are important parameters for evaluating the nozzle atomization quality,and have a significant impact on the secondary cooling effect and the slab *** order to study the behavior of atomized droplets after reaching the slab surface and to optimize the spray cooling effect,the influence of droplet diameter and droplet velocity on the migration behavior of droplets in the secondary cooling zone was analyzed by FLUENT *** show that the droplets in the spray zone and on the slab surface are mainly concentrated in the center,thus,the liquid volume fraction in the center is higher than that of either *** the droplet diameter increases,the region of high liquid volume fraction on the slab surface becomes wider,and the liquid phase distribution in the slab width direction becomes *** increasing the droplet velocity at the nozzle exit has little effect on droplet diffusion in the spray zone,the distribution becomes more uneven due to more liquid reaches the slab surface per unit time.A prediction formula of the maximum water flow rate on the slab surface for specific droplet characteristics was proposed based on dimensionless analysis and validated by simulated data.A nozzle spacing of 210 mm was recommended under the working conditions in this study,which ensures effective coverage of the spray water over the slab surface and enhances the distribution uniformity of water flow rate in the transverse direction.

关键词： continuous casting secondary cooling zone internal mixing air-mist nozzle droplet characteristics liquid phase distribution water flow rate

An improved deep dilated convolutional neural network for seismic facies interpretation

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2024年第3期21卷 1569-1583页

作者： Na-Xia Yang Guo-fa Li Ting-Hui Li Dong-Feng Zhao wei-wei Gu State Key Laboratory of Petroleum Resources and Engineering CNPC Key Lab of Geophysical ExplorationChina University of Petroleum(Beijing)Beijing 102249China Dagang Branch Research InstituteBGPTianjin300280China

With the successful application and breakthrough of deep learning technology in image segmentation,there has been continuous development in the field of seismic facies interpretation using convolutional neural *** intelligent and automated methods significantly reduce manual labor,particularly in the laborious task of manually labeling seismic ***,the extensive demand for training data imposes limitations on their wider *** overcome this challenge,we adopt the UNet architecture as the foundational network structure for seismic facies classification,which has demonstrated effective segmentation results even with small-sample training ***,we integrate spatial pyramid pooling and dilated convolution modules into the network architecture to enhance the perception of spatial information across a broader *** seismic facies classification test on the public data from the F3 block verifies the superior performance of our proposed improved network structure in delineating seismic facies *** analysis against the traditional UNet model reveals that our method achieves more accurate predictive classification results,as evidenced by various evaluation metrics for image ***,the classification accuracy reaches an impressive 96%.Furthermore,the results of seismic facies classification in the seismic slice dimension provide further confirmation of the superior performance of our proposed method,which accurately defines the range of different seismic *** approach holds significant potential for analyzing geological patterns and extracting valuable depositional information.

关键词： Seismic facies interpretation Dilated convolution Spatial pyramid pooling Internal feature maps Compound loss function

Greedy is Good:Constrained Non-submodular Function Maximization via Weak Submodularity

在线全文

学校读者我要写书评

暂无评论

Journal of the Operations Research Society of China 2024年第3期12卷 627-648页

作者： Ma-jun Shi wei Wang School of Statistics Xi’an University of Finance and EconomicsXi’an710100ShaanxiChina School of Mathematics and Statistics Xi’an Jiaotong UniversityXi’an710049ShaanxiChina

The widely used greedy algorithm has been recently shown to achieve near-optimal theoretical guarantees for the problems of constrained monotone non-submodular function maximization,with competitive performances in *** this paper,we investigate the problems of maximizing monotone non-submodular set functions under three classes of independent system constraints,including p-matroid intersection constraints,p-extendible system constraints and p-system *** prove that the greedy algorithm yields an approximation ratio ofγ/p+γfor the former two problems,andξγ/p+ξγfor the last problem,which further has been improved toγ/p+γ,whereγ,ξdenote the submodularity ratio and the diminishing returns ratio of set function *** addition,we also show that the greedy guarantees have a further refinement of for all the problems mentioned above,whereαis the generalized curvatureξ/p+αγof set ***,we show that our greedy algorithm does yield competitive practical performances using a variety of experiments on synthetic data.

关键词： Non-submodular function p-matroid intersection p-extendible system p-system Greedy algorithm

First Digit Distributions of Gamma-Ray Bursts

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2024年第5期24卷 70-75页

作者： Hou-Yu Lai jun-Jie wei Purple Mountain Observatory Chinese Academy of SciencesNanjing 210023China School of Astronomy and Space Sciences University of Science and Technology of ChinaHefei 230026China

The occurrence of the first significant digits from real world sources is usually not equally distributed,but is consistent with a logarithmic distribution instead,known as Benford’s *** this work,we perform a comprehensive investigation on the first digit distributions of the duration,fluence,and energy flux of gamma-ray bursts (GRBs) for the first *** a complete GRB sample detected by the Fermi satellite,we find that the first digits of the duration and fluence adhere to Benford’s ***,the energy flux shows a significant departure from this law,which may be due to the fact that a considerable part of the energy flux measurements is restricted by lack of spectral *** on the conventional duration classification scheme,we also check if the durations and fluences of long and short GRBs (with duration T_(90)>2 s and T_(90)≤2 s,respectively) obey Benford’s *** find that the fluences of both long and short GRBs still agree with the Benford distribution,but their durations do not follow Benford’s *** results hint that the long–short GRB classification scheme does not directly represent the intrinsic physical classification scheme.

关键词： (stars:)gamma-ray burst general-methods statistical-astronomical databases miscellaneous

Joint Sample Position Based Noise Filtering and Mean Shift Clustering for Imbalanced Classification Learning

在线全文

学校读者我要写书评

暂无评论

Tsinghua Science and Technology 2024年第1期29卷 216-231页

作者： Lilong Duan wei Xue jun Huang Xiao Zheng School of Computer Science and Technology Anhui University of TechnologyMaanshan 243032China Institute of Artificial Intelligence Hefei Comprehensive National Science CenterHefei 230088China

The problem of imbalanced data classification learning has received much *** classification algorithms are susceptible to data skew to favor majority samples and ignore minority *** weighted minority oversampling technique(MWMOTE)is an effective approach to solve this problem,however,it may suffer from the shortcomings of inadequate noise filtering and synthesizing the same samples as the original minority *** this end,we propose an improved MWMOTE method named joint sample position based noise filtering and mean shift clustering(SPMSC)to solve these ***,in order to effectively eliminate the effect of noisy samples,SPMsC uses a new noise filtering mechanism to determine whether a minority sample is noisy or not based on its position and distribution relative to the majority *** that MWMOTE may generate duplicate samples,we then employ the mean shift algorithm to cluster minority samples to reduce synthetic replicate ***,data cleaning is performed on the processed data to further eliminate class *** on extensive benchmark datasets demonstrate the effectiveness of SPMsC compared with other sampling methods.

关键词： imbalanced data classification oversampling noise filtering clustering

Prevalence of prolonged grief disorder and its symptoms among bereaved individuals in China:a systematic review and meta-analysis

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

General Psychiatry 2024年第2期37卷 177-188页

作者： Meng-Di Yuan jun-fa Liu Bao-Liang Zhong Research Center for Psychological and Health Sciences China University of Geosciences(Wuhan)WuhanHubeiChina Department of Psychiatry Wuhan Mental Health CentreWuhanHubeiChina

Background The prevalence of prolonged grief disorder(PGD)and its symptoms among the bereaved population in China vary *** This meta-analysis aims to estimate the prevalence of PGD and its symptoms among bereaved individuals in *** We conducted a literature search in major Chinese and English databases from their inception to 4 October 2023,for cross-sectional studies on the prevalence of PGD or its symptoms in bereaved Chinese *** risk of bias of the included studies and certainty of the evidence were assessed using the Joanna Briggs Institute Critical Appraisal Checklist for Studies Reporting Prevalence Data(‘JBI checklist’)and the Grading of Recommendations,Assessment,Development and Evaluations(GRADE),***‘metaprop’package in R V.4.1.2 was used to synthesise the *** A total of 28 studies involving 10994 bereaved individuals were included in the analysis,with JBI checklist scores between 3 and *** combined prevalence(95%confidence interval)of PGD and its symptoms was 8.9%(4.2%to 17.6%)and 32.4%(18.2%to 50.8%),*** and its symptoms were most prevalent among those who had lost their only child(22.7%)and those bereaved by earthquakes(80.4%),*** GRADE system assigned a very low certainty level to the evidence for the pooled prevalence of PGD and its *** The pooled prevalence of PGD and its symptoms indicate a potential high need for grief counselling services among bereaved individuals in *** need is particularly pronounced in those who have lost their only child and those bereaved due to *** methodologically rigorous studies are needed to provide more accurate prevalence *** registration number CRD42023432553.

关键词： symptoms prevalence analysis

Special Issue: Functional Polymer Materials

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2024年第7期42卷 895-896,I0004页

作者： Gu, jun-wei Wang, Du-Jin Shaanxi Key Laboratory of Macromolecular Science and Technology School of Chemistry and Chemical Engineering Northwestern Polytechnical University Xi’an China Beijing National Laboratory for Molecular Sciences CAS Key Laboratory of Engineering Plastics Institute of Chemistry Chinese Academy of Sciences Beijing China

The rapid development of science has led to a significant role for polymer materials in multitude fields,including industry,medicine,energy,and the environment,*** a leading academic journal in the field of polymer,Chinese Journal of Polymer Science has been dedicated to fostering the advancement and utilization of polymer science.

关键词： polymer Polymer Functional