4,4'-Oxybis(benzoic acid)(Ⅰ)is an important monomer for making synthetic resin,heat resistant film and liquid crystal fiber,etc.It has been synthesized either by the oxidation of 4,4'-dimethyl diphenyl ether,...4,4'-Oxybis(benzoic acid)(Ⅰ)is an important monomer for making synthetic resin,heat resistant film and liquid crystal fiber,etc.It has been synthesized either by the oxidation of 4,4'-dimethyl diphenyl ether,or by the electrophilic substitution of diphenyl ether,these substituents introduced into the benzene ring can be further transformed into carboxylic groups.Diphenyl ethers are usually prepared from phenols and halobenzenes through Ullmann resction.Due to the high reaction temerature(usually above 200℃),long time heating and the formation of isomers,it is difficult to obtain pure products in high yields.展开更多
Dibenzoyl peroxide undergoes oxidative addition on metallic copper with triphenylphosphine in a mixed solvent(acetone,dichloromethane and trichloromethane),and affords the binuclear copper complex (Cu(C_6H_5COO)_2(OPP...Dibenzoyl peroxide undergoes oxidative addition on metallic copper with triphenylphosphine in a mixed solvent(acetone,dichloromethane and trichloromethane),and affords the binuclear copper complex (Cu(C_6H_5COO)_2(OPPh_3))_2.Crystals are monoclinic,space group A_2/a,with cell parameters,a=24.337(3),b=10.566(1),c=21.579(2),β= 93.18(1)°, V=5540(1)~3,Z=4,R=0.042,and Rw=0.044 for 5872 observed reflections. Each copper ion is coordinated by four bridging benzoato ligands and one triphenylphosphine oxide group to form binuclear complexes.展开更多
Metal-organic frameworks(MOFs),which are constructed by metal ions or clusters with organic ligands,have shown great potential in gas storage and separation,luminescence,catalysis,drug delivery,sensing,so on.More than...Metal-organic frameworks(MOFs),which are constructed by metal ions or clusters with organic ligands,have shown great potential in gas storage and separation,luminescence,catalysis,drug delivery,sensing,so on.More than 20,000 MOFs have been reported by adjusting the composition and reaction conditions,most of them were synthesized by hydrothermal or solvothermal methods.The conventional solvothermal methods are favorable for the slow crystallization of MOFs to obtain single crystals or highly crystalline powders,which are suitable for the structure analysis.However,their harsh synthesis conditions,long reaction time,difficulty in continuous synthesis limit their scale-up in industrial production and application.Meanwhile,shaping or processing is also required to bring MOF crystals and powders into the market.Therefore,this review demonstrates the crystallization mechanisms of MOFs to understand how the synthetic parameters affect the final products.Additionally,a variety of promising synthetic routes which can be used for large scale synthesis were reviewed in details.Lastly,the prospects of MOF shaping and processing are provided to promote their industrial application.展开更多
A novel synthetic method for the preparation of aliphatic aldehydes from the corresponding carboxylic acids via 1,3-dimethylbenzimidazolium salts is provided. 1,3-Dimethylbenzimidazolium salts were rapidly reduced wit...A novel synthetic method for the preparation of aliphatic aldehydes from the corresponding carboxylic acids via 1,3-dimethylbenzimidazolium salts is provided. 1,3-Dimethylbenzimidazolium salts were rapidly reduced with sodium/ethanol and then hydrolyzed with hydrochloric acid to obtain aliphatic aldehydes, in which the 1,3-dimethylbenzimidazolium salts can be readily achieved from the corresponding carboxylic acids. The mechanism for the reductive reaction of 1,3-dimethylbenzimidazolium salts with sodium/ethanol was discussed.展开更多
N-Phenylbenzylamine has been converted into a variety of α-substituted derivatives in one-pot sequences,using carbon dioxide both for N-protection and a-carbon activation,and then subsequent lithiation at the a-carbo...N-Phenylbenzylamine has been converted into a variety of α-substituted derivatives in one-pot sequences,using carbon dioxide both for N-protection and a-carbon activation,and then subsequent lithiation at the a-carbon atom by either tert-or n-butyllithium.The resulting lithium carbamate reacts with electrophiles,followed smooth acid-catalyzed decarboxylation under mild condition to give α-substituted N-phenylbenzylamines in good yields.展开更多
On-line measurement for dielectric loss angle can effectively monitor the insulation condition of capacitive equipment in power systems. Synthetic relative measuring methods not only markedly overcome the shortcomings...On-line measurement for dielectric loss angle can effectively monitor the insulation condition of capacitive equipment in power systems. Synthetic relative measuring methods not only markedly overcome the shortcomings of traditional absolute measuring methods but also greatly improve the accuracy of dielectric loss angle measurement. However, synthetic relative measuring methods based on two or three pieces of capacitive equipment do not have the characteristic of generality. In this paper, a principle of synthetic relative measuring method is presented. The example of application for synthetic relative methods based on three and four pieces of capacitive equipment running in the same phase is taken to present the failure judgment matrices for N pieces of equipment. According to these matrices, the fault condition of N pieces of capacitive equipment can be watched, which is more general. Then some problems needing to be concerned along with two diagnostic methods used in diagnostic system are introduced. Finally, two programmable flow charts for the two methods are given and corresponding examples demonstrate their feasibility in practice.展开更多
The synthetic fuzzy assessing method is usually applied to sensory evaluation. The method has simple and reliable virtue, and it is consistent with objective evaluation results. Using this method, system status of pla...The synthetic fuzzy assessing method is usually applied to sensory evaluation. The method has simple and reliable virtue, and it is consistent with objective evaluation results. Using this method, system status of plating solution evaporator is evaluated, and the result is applied to compensate a fuzzy controller. Experimental results have shown the correctness and the validity of the proposed approach.展开更多
The index system, code system, and weights of indexes are established to assess the effects of green construction. The index system consists of index level, factor level and sub-factor level. The analytic hierarchy pr...The index system, code system, and weights of indexes are established to assess the effects of green construction. The index system consists of index level, factor level and sub-factor level. The analytic hierarchy process is used to determine the weights of indexes, and the consistency test indicate that the weight assignment is reasonable. Using fuzzy synthetic judgment method, the assessment model is built, which includes factor set, weight set and conclusion set. An example is given to demonstrate the assessment procedures.展开更多
Based on the extraction and calculation of the short-term seismic precursory information magnitude from the 114 major precursory observations in the North China region, and together with consideration of factors such ...Based on the extraction and calculation of the short-term seismic precursory information magnitude from the 114 major precursory observations in the North China region, and together with consideration of factors such as geological structure, seismicity, crustal thickness, and in particular, the current geodynamics of the region, the authors studied the time-space evolution characteristics of the short-term earthquake precursory information magnitude and its relationship with earthquakes and proposed the index and method for the short-term synthetic prediction of earthquakes with M S≥5.0 in the North China region. The inspection through R-value shows that the method is effective to a certain extent for earthquake prediction.展开更多
α-Trifluoromethyl ketones are a class of useful compounds with versatile applications.Their synthetic application via the transformation of the C—F bonds is of particular interest by allowing the synthesis of organi...α-Trifluoromethyl ketones are a class of useful compounds with versatile applications.Their synthetic application via the transformation of the C—F bonds is of particular interest by allowing the synthesis of organic compounds with diverse structures.Herein,the advances in the research areas ofα-trifluoromethyl ketone synthesis and their defluorination reactions are reviewed.Discussion on the mechanisms of the typical reactions has also been provided,in hope of affording some guides to the chemistry ofα-trifluoromethyl ketones in the synthetic methods toward themselves and their derivatives.展开更多
3-Deoxy-D-manno–oct-2-ulosonic acid(Kdo)is widely distributed in bacteria,and the synthesis of Kdocontaining oligosaccharides is important for the development of novel antibiotics and immunological agents.We have rec...3-Deoxy-D-manno–oct-2-ulosonic acid(Kdo)is widely distributed in bacteria,and the synthesis of Kdocontaining oligosaccharides is important for the development of novel antibiotics and immunological agents.We have recently developed a strategy to achieveα-stereocontrolled glycosylation using a C3-p-tolylthio-substituted Kdo phosphite donor.The wide substrate scope and high reactivity of the donors enabled the efficient synthesis of a series of Kdo-containing glycosides with completeα-stereoselectivity and without the formation of 2,3-ene byproducts.In this study,we improved the method by replacing the leaving group diethyl phosphite with fluoride,which enhanced the stability of the donor and led to cleaner reaction.Furthermore,the substrate range was expanded by synthesizing a series of Kdo O/C/S/Nglycosides,which also opened up a new avenue for the synthesis of CMP-Kdo synthase inhibitors.展开更多
Planar chiral cyclophanes are a type of structurally intriguing organic molecules,which have found increasingly applications in the field of biologically active compounds,asymmetric catalysis,and optically pure materi...Planar chiral cyclophanes are a type of structurally intriguing organic molecules,which have found increasingly applications in the field of biologically active compounds,asymmetric catalysis,and optically pure materials.As such,significant efforts in the development of new methods to build up enantioenriched cyclophanes in a precise manner have attracted increased attention in recent years.Among the plethora of reported synthetic strategies,catalytic enantioselective method has emerged as one of the most straightforward and efficient ways to deliver optically pure planar chiral cyclophanes.In this review,the recent progress in catalytic enantioselective reactions for the synthesis of planar chiral cyclophanes will be discussed,which would stimulate the research interest of chemists for the discovery of novel asymmetric strategies for the preparation of valuable and previously difficult-to-access chiral molecules.展开更多
Polycyclic compounds are widely found in natural products and drug molecules with important biological activities,which attracted the attention of many chemists.Phosphine-catalyzed nucleophilic addition is one of the ...Polycyclic compounds are widely found in natural products and drug molecules with important biological activities,which attracted the attention of many chemists.Phosphine-catalyzed nucleophilic addition is one of the most powerful tools for the construction of various cyclic compounds with the advantages of atom economy,mild reaction conditions and simplicity of operation.Allenolates,Morita−Baylis−Hillman(MBH)alcohols and their derivatives(MBHADs),electron-deficient olefins and alkynes are very efficient substrates in phosphine mediated annulations,which formed many phosphonium species such asβ-phosphonium enolates,β-phosphonium dienolates and vinyl phosphonium ylides as intermediates.This review describes the reactivities of these phosphonium zwitterions and summarizes the synthesis of polycycle compounds through phosphine-mediated intramolecular and intermolecular sequential annulations.Thus,a systematic summary of the research process based on the phosphine-mediated sequential annulations of allenolates,MBH alcohols and MBHADs,electron-deficient olefins and alkynes are presented in Chapters 2-6,respectively.展开更多
In order to suppress the airwave noise in marine controlled-source electromagnetic （CSEM） data, we propose a 3D deconvolution （3DD） interferometry method with a synthetic aperture source and obtain the relative an...In order to suppress the airwave noise in marine controlled-source electromagnetic （CSEM） data, we propose a 3D deconvolution （3DD） interferometry method with a synthetic aperture source and obtain the relative anomaly coefficient （RAC） of the EM field reflection responses to show the degree for suppressing the airwave. We analyze the potential of the proposed method for suppressing the airwave, and compare the proposed method with traditional methods in their effectiveness. A method to select synthetic source length is derived and the effect of the water depth on RAC is examined via numerical simulations. The results suggest that 3DD interferometry method with a synthetic source can effectively suppress the airwave and enhance the potential of marine CSEM to hydrocarbon exploration.展开更多
Plasma synthetic jet actuator（PSJA） has a wide application prospect in the high-speed flow control field for its high jet velocity.In this paper,the influence of the air pressure on the performance of a two-electrod...Plasma synthetic jet actuator（PSJA） has a wide application prospect in the high-speed flow control field for its high jet velocity.In this paper,the influence of the air pressure on the performance of a two-electrode PSJA is investigated by the schlieren method in a large range from 7 k Pa to 100 k Pa.The energy consumed by the PSJA is roughly the same for all the pressure levels.Traces of the precursor shock wave velocity and the jet front velocity vary a lot for different pressures.The precursor shock wave velocity first decreases gradually and then remains at 345 m/s as the air pressure increases.The peak jet front velocity always appears at the first appearance of a jet,and it decreases gradually with the increase of the air pressure.A maximum precursor shock wave velocity of 520 m/s and a maximum jet front velocity of 440 m/s are observed at the pressure of 7 k Pa.The averaged jet velocity in one period ranges from 44 m/s to 54 m/s for all air pressures,and it drops with the rising of the air pressure.High velocities of the precursor shock wave and the jet front indicate that this type of PSJA can still be used to influence the high-speed flow field at 7 k Pa.展开更多
Ceria nanoparticles(CeO_(2) NPs)have become popular materials in biomedical and industrial fields due to their potential applications in anti-oxidation,cancer therapy,photocatalytic degradation of pollutants,sensors,e...Ceria nanoparticles(CeO_(2) NPs)have become popular materials in biomedical and industrial fields due to their potential applications in anti-oxidation,cancer therapy,photocatalytic degradation of pollutants,sensors,etc.Many methods,including gas phase,solid phase,liquid phase,and the newly proposed green synthesis method,have been reported for the synthesis of CeO_(2) NPs.Due to the wide application of CeO_(2) NPs,concerns about their adverse impacts on human health have been raised.This review covers recent studies on the biomedical applications of CeO_(2) NPs,including their use in the treatment of various diseases(e.g.,Alzheimer's disease,ischemic stroke,retinal damage,chronic inflammation,and cancer).CeO_(2) NP toxicity is discussed in terms of the different systems of the human body(e.g.,cytotoxicity,genotoxicity,respiratory toxicity,neurotoxicity,and hepatotoxicity).This comprehensive review covers both fundamental discoveries and exploratory progress in CeO_(2) NP research that may lead to practical developments in the future.展开更多
Whether environmental regulation can increase employment is still controversial in academic circles around the world.An important reason lies in the validity of an empirical method.Using China’s inter-provincial pane...Whether environmental regulation can increase employment is still controversial in academic circles around the world.An important reason lies in the validity of an empirical method.Using China’s inter-provincial panel data from 2003 to 2015 and the synthetic control method(SCM),this paper focuses on a test that was carried out on the basis of a quasi-natural experiment of the 2007 Emission Trading Pilot(ETP)policy.The test results show that the ETP policy has increased the average employment level by 3.25 percentage points and passed a robustness test.The robustness test using the regression control method(RCM)shows that the average employment level has risen by 3.21 percentage points.This means that the ETP policy has significantly increased employment.The paper also puts forward three policy recommendations:optimizing the trading system for emissions rights,encouraging companies to carry out cleaner production and innovation,and incorporating environmental performance assessments.展开更多
Supercapacitors(SCs)have remarkable energy storage capabilities and have garnered considerable interest due to their superior power densities and ultra-long cycling characteristics.However,their comparatively low ener...Supercapacitors(SCs)have remarkable energy storage capabilities and have garnered considerable interest due to their superior power densities and ultra-long cycling characteristics.However,their comparatively low energy density limits their extensive application in large-scale commercial applications.Electrode materials directly affect the performance of SCs.Thus,the development of cutting-edge electrode materials and modification of their morphological and structural properties are vital for advancing the performance of SCs.Transition metal compounds have a high specific capacity and good cycling durability,making them the most promising electrode active materials for high-energy density SCs.Nevertheless,their inadequate conductivity,unfavorable ion diffusion rates,substantial volume expansion and phase transitions during charging and discharging are obstacles to their stable and efficient integration into SCs.To address these challenges,this study provides a comprehensive summary of the current advancements in transition metal nanomaterials as electrode materials for SCs,an overview of the current research status,and the prevailing challenges.Furthermore,this study highlights synthetic techniques and management strategies for electrode materials derived from transition metal compounds,targeting the resolution of the aforementioned challenges.Finally,a concise discussion is provided on the future directions of SC development,with an emphasis on the utilization of transition metal compound electrode materials.展开更多
Estimating cross-range velocity is a challenging task for space-borne synthetic aperture radar（SAR）, which is important for ground moving target indication（GMTI）. Because the velocity of a target is very small com...Estimating cross-range velocity is a challenging task for space-borne synthetic aperture radar（SAR）, which is important for ground moving target indication（GMTI）. Because the velocity of a target is very small compared with that of the satellite, it is difficult to correctly estimate it using a conventional monostatic platform algorithm. To overcome this problem, a novel method employing multistatic SAR is presented in this letter. The proposed hybrid method, which is based on an extended space-time model（ESTIM） of the azimuth signal, has two steps： first, a set of finite impulse response（FIR） filter banks based on a fractional Fourier transform（FrFT） is used to separate multiple targets within a range gate; second, a cross-correlation spectrum weighted subspace fitting（CSWSF） algorithm is applied to each of the separated signals in order to estimate their respective parameters. As verified through computer simulation with the constellations of Cartwheel, Pendulum and Helix, this proposed time-frequency-subspace method effectively improves the estimation precision of the cross-range velocities of multiple targets.展开更多
Generally fuzzy control system (FCS) is worked in washing machine. For the fuzzy set theory, membership functions are the building blocks. In a fuzzy set, fuzziness is determined by its membership functions. The shape...Generally fuzzy control system (FCS) is worked in washing machine. For the fuzzy set theory, membership functions are the building blocks. In a fuzzy set, fuzziness is determined by its membership functions. The shapes of membership functions are important, because it has an effect on fuzzy inference system. The shapes of membership functions can be triangular, trapezoidal and gaussian. The most widely used triangular membership function is used in this paper, because it can capture the short time period. In washing machine, open loop control system is found. This paper applies a fuzzy synthetic evaluation method (FSEM) for washing cloth in washing machine as FSEM can handle the multiple criteria with the help of evaluation matrix generated from membership function and weight matrix generated by Analytical Hierarchy Process (AHP). The purpose of this research is to minimize the wash time. By applying FSEM, we get a wash time which is less than that wash time got from applying the Mamdani approach in FCS. An example is given for illustration. For more reduction of wash time, statistical averaging method is also used. To reduce the wash time, statistical averaging method can be used in Mamdani approach also.展开更多
文摘4,4'-Oxybis(benzoic acid)(Ⅰ)is an important monomer for making synthetic resin,heat resistant film and liquid crystal fiber,etc.It has been synthesized either by the oxidation of 4,4'-dimethyl diphenyl ether,or by the electrophilic substitution of diphenyl ether,these substituents introduced into the benzene ring can be further transformed into carboxylic groups.Diphenyl ethers are usually prepared from phenols and halobenzenes through Ullmann resction.Due to the high reaction temerature(usually above 200℃),long time heating and the formation of isomers,it is difficult to obtain pure products in high yields.
文摘Dibenzoyl peroxide undergoes oxidative addition on metallic copper with triphenylphosphine in a mixed solvent(acetone,dichloromethane and trichloromethane),and affords the binuclear copper complex (Cu(C_6H_5COO)_2(OPPh_3))_2.Crystals are monoclinic,space group A_2/a,with cell parameters,a=24.337(3),b=10.566(1),c=21.579(2),β= 93.18(1)°, V=5540(1)~3,Z=4,R=0.042,and Rw=0.044 for 5872 observed reflections. Each copper ion is coordinated by four bridging benzoato ligands and one triphenylphosphine oxide group to form binuclear complexes.
基金the National Natural Science Foundation of China(Nos.21971017,21901019,and 22205018)the National Key Research and Development Program of China(No.2020YFB1506300),and Beijing Institute of Technology Research Fund Program.
文摘Metal-organic frameworks(MOFs),which are constructed by metal ions or clusters with organic ligands,have shown great potential in gas storage and separation,luminescence,catalysis,drug delivery,sensing,so on.More than 20,000 MOFs have been reported by adjusting the composition and reaction conditions,most of them were synthesized by hydrothermal or solvothermal methods.The conventional solvothermal methods are favorable for the slow crystallization of MOFs to obtain single crystals or highly crystalline powders,which are suitable for the structure analysis.However,their harsh synthesis conditions,long reaction time,difficulty in continuous synthesis limit their scale-up in industrial production and application.Meanwhile,shaping or processing is also required to bring MOF crystals and powders into the market.Therefore,this review demonstrates the crystallization mechanisms of MOFs to understand how the synthetic parameters affect the final products.Additionally,a variety of promising synthetic routes which can be used for large scale synthesis were reviewed in details.Lastly,the prospects of MOF shaping and processing are provided to promote their industrial application.
基金Project supported by the National Natural Science Foundation of China （No. 21072158）, the China Postdoctoral Science Foundation （No. 20070421139）, the Special Foundation of the Education Committee of Shaanxi Province （No. 09JK750）.
文摘A novel synthetic method for the preparation of aliphatic aldehydes from the corresponding carboxylic acids via 1,3-dimethylbenzimidazolium salts is provided. 1,3-Dimethylbenzimidazolium salts were rapidly reduced with sodium/ethanol and then hydrolyzed with hydrochloric acid to obtain aliphatic aldehydes, in which the 1,3-dimethylbenzimidazolium salts can be readily achieved from the corresponding carboxylic acids. The mechanism for the reductive reaction of 1,3-dimethylbenzimidazolium salts with sodium/ethanol was discussed.
文摘N-Phenylbenzylamine has been converted into a variety of α-substituted derivatives in one-pot sequences,using carbon dioxide both for N-protection and a-carbon activation,and then subsequent lithiation at the a-carbon atom by either tert-or n-butyllithium.The resulting lithium carbamate reacts with electrophiles,followed smooth acid-catalyzed decarboxylation under mild condition to give α-substituted N-phenylbenzylamines in good yields.
文摘On-line measurement for dielectric loss angle can effectively monitor the insulation condition of capacitive equipment in power systems. Synthetic relative measuring methods not only markedly overcome the shortcomings of traditional absolute measuring methods but also greatly improve the accuracy of dielectric loss angle measurement. However, synthetic relative measuring methods based on two or three pieces of capacitive equipment do not have the characteristic of generality. In this paper, a principle of synthetic relative measuring method is presented. The example of application for synthetic relative methods based on three and four pieces of capacitive equipment running in the same phase is taken to present the failure judgment matrices for N pieces of equipment. According to these matrices, the fault condition of N pieces of capacitive equipment can be watched, which is more general. Then some problems needing to be concerned along with two diagnostic methods used in diagnostic system are introduced. Finally, two programmable flow charts for the two methods are given and corresponding examples demonstrate their feasibility in practice.
文摘The synthetic fuzzy assessing method is usually applied to sensory evaluation. The method has simple and reliable virtue, and it is consistent with objective evaluation results. Using this method, system status of plating solution evaporator is evaluated, and the result is applied to compensate a fuzzy controller. Experimental results have shown the correctness and the validity of the proposed approach.
基金The Doctoral Program of Higher Educa-tion Institution of China (No.20050487017)
文摘The index system, code system, and weights of indexes are established to assess the effects of green construction. The index system consists of index level, factor level and sub-factor level. The analytic hierarchy process is used to determine the weights of indexes, and the consistency test indicate that the weight assignment is reasonable. Using fuzzy synthetic judgment method, the assessment model is built, which includes factor set, weight set and conclusion set. An example is given to demonstrate the assessment procedures.
文摘Based on the extraction and calculation of the short-term seismic precursory information magnitude from the 114 major precursory observations in the North China region, and together with consideration of factors such as geological structure, seismicity, crustal thickness, and in particular, the current geodynamics of the region, the authors studied the time-space evolution characteristics of the short-term earthquake precursory information magnitude and its relationship with earthquakes and proposed the index and method for the short-term synthetic prediction of earthquakes with M S≥5.0 in the North China region. The inspection through R-value shows that the method is effective to a certain extent for earthquake prediction.
文摘α-Trifluoromethyl ketones are a class of useful compounds with versatile applications.Their synthetic application via the transformation of the C—F bonds is of particular interest by allowing the synthesis of organic compounds with diverse structures.Herein,the advances in the research areas ofα-trifluoromethyl ketone synthesis and their defluorination reactions are reviewed.Discussion on the mechanisms of the typical reactions has also been provided,in hope of affording some guides to the chemistry ofα-trifluoromethyl ketones in the synthetic methods toward themselves and their derivatives.
基金supported by the National Key R&D Program of China(Nos.2022YFF1203005,2022YFC2303700)supported by the National Natural Science Foundation of China(Nos.81930097,82151223).
文摘3-Deoxy-D-manno–oct-2-ulosonic acid(Kdo)is widely distributed in bacteria,and the synthesis of Kdocontaining oligosaccharides is important for the development of novel antibiotics and immunological agents.We have recently developed a strategy to achieveα-stereocontrolled glycosylation using a C3-p-tolylthio-substituted Kdo phosphite donor.The wide substrate scope and high reactivity of the donors enabled the efficient synthesis of a series of Kdo-containing glycosides with completeα-stereoselectivity and without the formation of 2,3-ene byproducts.In this study,we improved the method by replacing the leaving group diethyl phosphite with fluoride,which enhanced the stability of the donor and led to cleaner reaction.Furthermore,the substrate range was expanded by synthesizing a series of Kdo O/C/S/Nglycosides,which also opened up a new avenue for the synthesis of CMP-Kdo synthase inhibitors.
基金financial support provided by Huanghuai University and Hangzhou Medical College.
文摘Planar chiral cyclophanes are a type of structurally intriguing organic molecules,which have found increasingly applications in the field of biologically active compounds,asymmetric catalysis,and optically pure materials.As such,significant efforts in the development of new methods to build up enantioenriched cyclophanes in a precise manner have attracted increased attention in recent years.Among the plethora of reported synthetic strategies,catalytic enantioselective method has emerged as one of the most straightforward and efficient ways to deliver optically pure planar chiral cyclophanes.In this review,the recent progress in catalytic enantioselective reactions for the synthesis of planar chiral cyclophanes will be discussed,which would stimulate the research interest of chemists for the discovery of novel asymmetric strategies for the preparation of valuable and previously difficult-to-access chiral molecules.
基金the National Natural Science Foundation of China(Nos.22171147 and 21871148)for the financial support。
文摘Polycyclic compounds are widely found in natural products and drug molecules with important biological activities,which attracted the attention of many chemists.Phosphine-catalyzed nucleophilic addition is one of the most powerful tools for the construction of various cyclic compounds with the advantages of atom economy,mild reaction conditions and simplicity of operation.Allenolates,Morita−Baylis−Hillman(MBH)alcohols and their derivatives(MBHADs),electron-deficient olefins and alkynes are very efficient substrates in phosphine mediated annulations,which formed many phosphonium species such asβ-phosphonium enolates,β-phosphonium dienolates and vinyl phosphonium ylides as intermediates.This review describes the reactivities of these phosphonium zwitterions and summarizes the synthesis of polycycle compounds through phosphine-mediated intramolecular and intermolecular sequential annulations.Thus,a systematic summary of the research process based on the phosphine-mediated sequential annulations of allenolates,MBH alcohols and MBHADs,electron-deficient olefins and alkynes are presented in Chapters 2-6,respectively.
基金supported by the national project"Deep Exploration Technology and Experimentation"(SinoProbe-09-02)
文摘In order to suppress the airwave noise in marine controlled-source electromagnetic （CSEM） data, we propose a 3D deconvolution （3DD） interferometry method with a synthetic aperture source and obtain the relative anomaly coefficient （RAC） of the EM field reflection responses to show the degree for suppressing the airwave. We analyze the potential of the proposed method for suppressing the airwave, and compare the proposed method with traditional methods in their effectiveness. A method to select synthetic source length is derived and the effect of the water depth on RAC is examined via numerical simulations. The results suggest that 3DD interferometry method with a synthetic source can effectively suppress the airwave and enhance the potential of marine CSEM to hydrocarbon exploration.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51407197,51522606,51336011,91541120,and 11472306)
文摘Plasma synthetic jet actuator（PSJA） has a wide application prospect in the high-speed flow control field for its high jet velocity.In this paper,the influence of the air pressure on the performance of a two-electrode PSJA is investigated by the schlieren method in a large range from 7 k Pa to 100 k Pa.The energy consumed by the PSJA is roughly the same for all the pressure levels.Traces of the precursor shock wave velocity and the jet front velocity vary a lot for different pressures.The precursor shock wave velocity first decreases gradually and then remains at 345 m/s as the air pressure increases.The peak jet front velocity always appears at the first appearance of a jet,and it decreases gradually with the increase of the air pressure.A maximum precursor shock wave velocity of 520 m/s and a maximum jet front velocity of 440 m/s are observed at the pressure of 7 k Pa.The averaged jet velocity in one period ranges from 44 m/s to 54 m/s for all air pressures,and it drops with the rising of the air pressure.High velocities of the precursor shock wave and the jet front indicate that this type of PSJA can still be used to influence the high-speed flow field at 7 k Pa.
基金supported by the National Natural Science Foundation of China(Nos.32161143035 and 81970826)the Yantai Science and Technology Innovation Development Plan(No.2022XDRH033),China。
文摘Ceria nanoparticles(CeO_(2) NPs)have become popular materials in biomedical and industrial fields due to their potential applications in anti-oxidation,cancer therapy,photocatalytic degradation of pollutants,sensors,etc.Many methods,including gas phase,solid phase,liquid phase,and the newly proposed green synthesis method,have been reported for the synthesis of CeO_(2) NPs.Due to the wide application of CeO_(2) NPs,concerns about their adverse impacts on human health have been raised.This review covers recent studies on the biomedical applications of CeO_(2) NPs,including their use in the treatment of various diseases(e.g.,Alzheimer's disease,ischemic stroke,retinal damage,chronic inflammation,and cancer).CeO_(2) NP toxicity is discussed in terms of the different systems of the human body(e.g.,cytotoxicity,genotoxicity,respiratory toxicity,neurotoxicity,and hepatotoxicity).This comprehensive review covers both fundamental discoveries and exploratory progress in CeO_(2) NP research that may lead to practical developments in the future.
文摘Whether environmental regulation can increase employment is still controversial in academic circles around the world.An important reason lies in the validity of an empirical method.Using China’s inter-provincial panel data from 2003 to 2015 and the synthetic control method(SCM),this paper focuses on a test that was carried out on the basis of a quasi-natural experiment of the 2007 Emission Trading Pilot(ETP)policy.The test results show that the ETP policy has increased the average employment level by 3.25 percentage points and passed a robustness test.The robustness test using the regression control method(RCM)shows that the average employment level has risen by 3.21 percentage points.This means that the ETP policy has significantly increased employment.The paper also puts forward three policy recommendations:optimizing the trading system for emissions rights,encouraging companies to carry out cleaner production and innovation,and incorporating environmental performance assessments.
基金supported by the National Natural Science Foundation of China(No.22301151)the Natural Science Foundation of Inner Mongolia Autonomous Region of China(No.2022QN05024)+3 种基金the Fundamental Scientific Research Funds for Universities directly under Inner Mongolia Autonomous Region of China(Nos.JY20230097 and JY20220116)the Program for Innovative Research Team in Universities of Inner Mongolia Autonomous Region(No.NMGIRT2211)Inner Mongolia University of Technology Key Discipline Team Project of Materials Science(No.ZD202012)the Young Leading Talent of“Grassland Talents”Project of Inner Mongolia Autonomous Region(No.QNLJ012010)。
文摘Supercapacitors(SCs)have remarkable energy storage capabilities and have garnered considerable interest due to their superior power densities and ultra-long cycling characteristics.However,their comparatively low energy density limits their extensive application in large-scale commercial applications.Electrode materials directly affect the performance of SCs.Thus,the development of cutting-edge electrode materials and modification of their morphological and structural properties are vital for advancing the performance of SCs.Transition metal compounds have a high specific capacity and good cycling durability,making them the most promising electrode active materials for high-energy density SCs.Nevertheless,their inadequate conductivity,unfavorable ion diffusion rates,substantial volume expansion and phase transitions during charging and discharging are obstacles to their stable and efficient integration into SCs.To address these challenges,this study provides a comprehensive summary of the current advancements in transition metal nanomaterials as electrode materials for SCs,an overview of the current research status,and the prevailing challenges.Furthermore,this study highlights synthetic techniques and management strategies for electrode materials derived from transition metal compounds,targeting the resolution of the aforementioned challenges.Finally,a concise discussion is provided on the future directions of SC development,with an emphasis on the utilization of transition metal compound electrode materials.
基金supported by the National Natural Science Foundation of China (No. 61271343)the Research Fund for the Doctoral Program of Higher Education of China (No. 20122302110012)the 2014 Innovation of Science and Technology Program of China Aerospace Science and Technology Corporation
文摘Estimating cross-range velocity is a challenging task for space-borne synthetic aperture radar（SAR）, which is important for ground moving target indication（GMTI）. Because the velocity of a target is very small compared with that of the satellite, it is difficult to correctly estimate it using a conventional monostatic platform algorithm. To overcome this problem, a novel method employing multistatic SAR is presented in this letter. The proposed hybrid method, which is based on an extended space-time model（ESTIM） of the azimuth signal, has two steps： first, a set of finite impulse response（FIR） filter banks based on a fractional Fourier transform（FrFT） is used to separate multiple targets within a range gate; second, a cross-correlation spectrum weighted subspace fitting（CSWSF） algorithm is applied to each of the separated signals in order to estimate their respective parameters. As verified through computer simulation with the constellations of Cartwheel, Pendulum and Helix, this proposed time-frequency-subspace method effectively improves the estimation precision of the cross-range velocities of multiple targets.
文摘Generally fuzzy control system (FCS) is worked in washing machine. For the fuzzy set theory, membership functions are the building blocks. In a fuzzy set, fuzziness is determined by its membership functions. The shapes of membership functions are important, because it has an effect on fuzzy inference system. The shapes of membership functions can be triangular, trapezoidal and gaussian. The most widely used triangular membership function is used in this paper, because it can capture the short time period. In washing machine, open loop control system is found. This paper applies a fuzzy synthetic evaluation method (FSEM) for washing cloth in washing machine as FSEM can handle the multiple criteria with the help of evaluation matrix generated from membership function and weight matrix generated by Analytical Hierarchy Process (AHP). The purpose of this research is to minimize the wash time. By applying FSEM, we get a wash time which is less than that wash time got from applying the Mamdani approach in FCS. An example is given for illustration. For more reduction of wash time, statistical averaging method is also used. To reduce the wash time, statistical averaging method can be used in Mamdani approach also.
