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Stereochemistry of the coupling step in photo-S_(RN) 1 reaction

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Chinese Journal of Chemistry 1992年第3期10卷 253-261页

作者： WU, Bi-Qi zeng, fan-wen ZHAO, Yong WU, Guo-Sheng Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032 Shanghai Institute of Organic Chemistry Chinese Academy of Sciences Shanghai 200032

The photo-S_(RN) 1 reaction of (+)-camphor and aryl halides was investigated in order to estimate the stereochemistry of the coupling step of aryl radicals with a nucleophile. The ratio of endo to exo products determined by ~1H NMR and CD spectra was found to be 99:1. MNDO calculations of the orbital parameters showed a favorable one-sided overlap of the enolate ion with the SOMO of aryl radical. In addition, fragmentation of (ArX)^- was found to be related to the energy of SOMO of (ArX)^-.

关键词： Ph Stereochemistry of the coupling step in photo-S reaction RN

Artificial neural network-based method for discriminating Compton scattering events in high-purity germaniumγ-ray spectrometer

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Nuclear Science and Techniques 2024年第2期35卷 64-84页

作者： Chun-Di fan Guo-Qiang zeng Hao-wen Deng Lei Yan Jian Yang Chuan-Hao Hu Song Qing Yang Hou College of Nuclear Technology and Automation Engineering Chengdu University of TechnologyChengdu 610059China

To detect radioactive substances with low activity levels,an anticoincidence detector and a high-purity germanium(HPGe)detector are typically used simultaneously to suppress Compton scattering background,thereby resulting in an extremely low detection limit and improving the measurement ***,the complex and expensive hardware required does not facilitate the application or promotion of this ***,a method is proposed in this study to discriminate the digital waveform of pulse signals output using an HPGe detector,whereby Compton scattering background is suppressed and a low minimum detectable activity(MDA)is achieved without using an expensive and complex anticoincidence detector and *** electric-field-strength and energy-deposition distributions of the detector are simulated to determine the relationship between pulse shape and energy-deposition location,as well as the characteristics of energy-deposition distributions for fulland partial-energy deposition *** relationship is used to develop a pulse-shape-discrimination algorithm based on an artificial neural network for pulse-feature *** accurately determine the relationship between the deposited energy of gamma(γ)rays in the detector and the deposition location,we extract four shape parameters from the pulse signals output by the *** learning is used to input the four shape parameters into the ***,the pulse signals are identified and classified to discriminate between partial-and full-energy deposition *** partial-energy deposition events are removed to suppress Compton *** proposed method effectively decreases the MDA of an HPGeγ-energy dispersive *** results show that the Compton suppression factors for energy spectra obtained from measurements on ^(152)Eu,^(137)Cs,and ^(60)Co radioactive sources are 1.13(344 keV),1.11(662 keV),and 1.08(1332 keV),respectively,and that the corresponding MDAs are 1.4%,5.

关键词： High-purity germaniumγ-ray spectrometer Pulse-shape discrimination Compton scattering Artificial neural network Minimum detectable activity

Overwhelming decomposition of 4-bromo-4'-cyanomethylbiphenylyl radical anion without electron transfer to 4,4'-dibromobiphenyl

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Chinese Journal of Chemistry 1994年第2期12卷 148-157页

作者： WU, Guo-Sheng LIU, An HU, Jun zeng, fan-wen WU, Bi-Qi Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China Shanghai Institute of Organic Chemistry Chinese Academy of Sciences Shanghai 200032 China

Dibromobiphenyl reacted with cynomethyl anion in ammonia under irradiation to form nucleophilic bis-substituted product in high yield without substantial monosubstituted product. Quantum yields for the formations of bis- and monosubstituted products were found to be 85.6 and 2.3×10-6 respectively, while the corresponding pseudo-first-order rates were 6.9×10-3 and 5.2×10-10 mol.L-1.S-1. Block up the possible electron transfer of 4-brome-4'-cyanomethylbiphenylyl radical anion to 4-cyanometbyl-biphenylyl radical and bromine ion.

关键词： Photochemistry SRN1 reaction electron transfer dibromobiphenyl.

Photochemical naphthylation at(α-carbon atom of carbonyl and its equivalences

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Chinese Journal of Chemistry 1992年第1期10卷 73-81页

作者： WU,Bi-Qi zeng,fan-wen LI,Wei ZHAO,Yong WU,Guo-Sheng Shanghai Institute of Organic Chemistry,The Chinese Academy of Sciences,Shanghai 200032 Shanghai Institute of Organic Chemistry The Chinese Academy of Sciences Shanghai 200032

The photostimulated reaction of halonaphthalene with a series of carbanions derived from, propionic acid derivatives in liquid ammonia led to the naphthylation at a-carbon of the carbanions in an isolated yield ranging from 25％ to 86％.In all cases,the dehalonaphthalenes were found to, be by-products and the reaction was inhibited by *** electron transfer from the carbanion to the halonaphthalene followed by ejection of halogen led to naphtbyl radical,as predicted by comparing the LUMOs of the carbanions and the halonaphthalenes,was involved in the process. Absence of the alkylnaphthalene and 1,2-dinaphthylalkane in the products indicates the smooth electron transfer between(Naph-Nu)^+ and Naph-X.C-vs.O-naphthylation is fully addressed in terms of MNDO calculations and acid-base principle.

关键词： carbon atom of carbonyl and its equivalences Photochemical naphthylation at

Effects of formal credit on pastoral household expense: Evidence from the Qinghai-Xizang Plateau of China

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Journal of Integrative Agriculture 2024年第5期23卷 1774-1785页

作者： Yan Zhang Yi Huang fan Zhang zeng Tang State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems College of Pastoral Agriculture Science and TechnologyLanzhou UniversityLanzhou 730020China

Formal credit is critical in agricultural production,allowing more expenditure and productive input,thereby improving farmers'*** pastoral China,formal financial institutions are gradually ***,a limited understanding remains of how formal credit affects herders'household *** on a survey of 544 herders from the Qinghai-Xizang Plateau of China,this study adopted the propensity score matching approach to identify the effect of formal credit on herders'total household expenses,daily expenses,and productive *** results found that average age,grassland mortgage,and other variables significantly affected herders'participation in formal *** credit could significantly improve household expenses,especially productive expenses.A heterogeneity analysis showed that formal credit had a greater impact on the household total expense for those at higher levels of wealth;however,it significantly affected the productive expense of herders at lower wealth ***,the mediating effect indicated that formal credit could affect herders'household income,thus influencing their household ***,this study suggests that policies should improve herders'accessibility to formal credit.

关键词： formal credit herders expense Qinghai-Xizang Plateau

Development of a novel Eu^(3+)-doped tantalate red-emitting phosphor for w-LEDs application

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Journal of Rare Earths 2024年第8期42卷 1479-1488,I0003页

作者： fan zeng Jingjing Ru Bing Zhao Feiyun Guo Jianzhong Chen College of Chemistry and Materials Fujian Province University Key Laboratory of Green Energy and Environment CatalysisNingde Normal University.Ningde352100China School of Environment and Resources School of Carbon Neutral and Modern IndustryFujian Normal UniversityFuzhou350007China College of Information and Mechanical&Electrical Engineering Ningde Normal UniversityNingde352100China College of Chemistry Fuzhou UniversityFuzhou350108China

Two novel phosphors LiBa_(4(1-x))Eu_(4x)Ta_(3)O_(12)(H-LBTO:xEu^(3+)) and Li_(0.25)Ba_(1-x)Eu_(x)Ta_(0.75)O_(3)(C-LBTO:xEu^(3+))were prepared successfully by a molten salt *** transformation between these two structures was realized by changing the sintering temperature or changing the Eu^(3+) ions concentration,which was also demonstrated by the X-ray diffraction(XRD),scanning electron microscopy(SEM),diffuse reflectance spectra(DRS),and photoluminescence excitation(PLE) analyses,Both the sintering temperature and the Eu^(3+)ions doping concentration have significant impact on the formation of the crystal *** these phosphors sintered at 1023 K exhibit two major luminescence lines at 594 and 614 nm under nearUV light of 395 nm excitation,corresponding to Eu^(3+)ions typical transitions of ^(5)D_(0)→^(7)F_(1) and ^(5)D_(0)→^(7)F_(2).The optimum concentration of Eu^(3+) ions is 9 mol% for C-LBTO:xEu^(3+) samples and the quenching interaction type is the nearest-neighbor ion *** thermal stability of the C-LBTO:0.09Eu^(3+)sample was investigated in detail and the device application further suggests that C-LBTO:0.09Eu^(3+) can be used as a red phosphor for near-UV excited w-LEDs in lighting.

关键词： Phosphor Tantalate LED device Rare earths

Unsupervised Multi-Expert Learning Model for Underwater Image Enhancement

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IEEE/CAA Journal of Automatica Sinica 2024年第3期11卷 708-722页

作者： Hongmin Liu Qi Zhang Yufan Hu Hui zeng Bin fan the School of Intelligence Science and Technology and the Institute of Artificial Intelligence University of Science and Technology BeijingBeijing 100083China the School of Automation and Electrical Engineering University of Science and Technology BeijingBeijing 100083China IEEE

Underwater image enhancement aims to restore a clean appearance and thus improves the quality of underwater degraded *** methods feed the whole image directly into the model for ***,they ignored that the R,G and B channels of underwater degraded images present varied degrees of degradation,due to the selective absorption for the *** address this issue,we propose an unsupervised multi-expert learning model by considering the enhancement of each color ***,an unsupervised architecture based on generative adversarial network is employed to alleviate the need for paired underwater *** on this,we design a generator,including a multi-expert encoder,a feature fusion module and a feature fusion-guided decoder,to generate the clear underwater ***,a multi-expert discriminator is proposed to verify the authenticity of the R,G and B channels,*** addition,content perceptual loss and edge loss are introduced into the loss function to further improve the content and details of the enhanced *** experiments on public datasets demonstrate that our method achieves more pleasing results in vision *** metrics(PSNR,SSIM,UIQM and UCIQE) evaluated on our enhanced images have been improved obviously.

关键词： Multi-expert learning underwater image enhancement unsupervised learning

Mechanism of selective laser trabeculoplasty:a systemic review

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International Journal of Ophthalmology(English edition) 2024年第5期17卷 963-968页

作者： Yu-Feng Chen wen zeng Department of Ophthalmology Zhongnan Hospital of Wuhan UniversityWuhan 430071Hubei ProvinceChina

Although selective laser trabeculoplasty(SLT)is a recognized method for the treatment of glaucoma,the exact changes in the target tissue and mechanism for its intraocular pressure lowing effect are still *** purpose of this review is to summarize the potential mechanisms of SLT on trabecular meshwork both in vivo and in vitro,so as to reveal the potential mechanism of *** may induce immune or inflammatory response in trabecular meshwork(TM)induced by possible oxidative damage etc,and remodel extracellular *** may also induce monocytes to aggregate in TM tissue,increase Schlemm’s canal(SC)cell conductivity,disintegrate cell junction and promote permeability through autocrine and paracrine *** provides a theoretical basis for SLT treatment in glaucoma.

关键词： mechanisms selective laser trabeculoplasty glaucoma trabecular meshwork

A Study on the Performances of Solar Air Collectors Having a Hemispherical Dimple on the Absorber Plate

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Fluid Dynamics & Materials Processing 2024年第5期20卷 939-955页

作者： Shuilian Li fan zeng Xinli Wei School of Architecture and Environmental Engineering Zhengzhou Technical CollegeZhengzhou450121China School of Mechanical and Power Engineering Zhengzhou UniversityZhengzhou450001China

In order to increase the efficiency of solar air collectors,a new variant with a protrusion is proposed in this study,and its performances are analyzed from two points of view,namely,in terms of optics and thermodynamics *** comparing and analyzing the light paths of the protrusion and the dimple,it can be concluded that when sunlight shines on the dimple,it is reflected and absorbed multiple times,whereas for the sunlight shining on the protrusion,there is no secondary reflection or absorption of *** the lighting area and the properties of the surfaces are the same,the absorption rate of the dimple is 10.3 percentage points higher than that of the *** the range of Reynolds number from 3000 to 11000,numerical simulations about the effects of the relative height(e/Dh=0.033–0.1)and relative spacing(p/e=4.5–8.5)of protrusions on air heat transfer and flow resistance show that,in terms of comprehensive evaluation coefficient(PF),the best relative height is 0.085,when the relative spacing is 5.A correlation of Nu and f with Re,e/Dh and p/e is obtained by linear regression of the results,in order to provide a useful reference for the design and optimization of this kind of solar air collector.

关键词： Heat transfer hemispherical protrusion dimple solar air collector correlation