Electron beam–directed energy deposition(EB–DED)has emerged as a promising wire-based metal additive manufacturing technique.However,the effects of EBs on pendant droplets at wire tips have not yet been determined.T...Electron beam–directed energy deposition(EB–DED)has emerged as a promising wire-based metal additive manufacturing technique.However,the effects of EBs on pendant droplets at wire tips have not yet been determined.The aim of this study is to enhance the understanding of this action by analyzing the mechanism of droplet oscillation.The pendant droplet oscillation phenomenon hinders the stable transfer of droplets to the molten pool and limits the feasibility of manufacturing complex lattice structures by EB–DED.Hence,another aim of this study is to create an oscillation suppression method.An escalating asymmetric amplitude is the main characteristic of droplet oscillation.The primary oscillationinducing force is the recoil force generated from the EB-acted local surface of the droplet.The physical mechanism of this force is the rapid increase and uneven distribution of the local surface temperature caused by the partial action of the EB.The prerequisites for droplet oscillation include vacuum conditions,high power densities,and bypass wire feeding processes.The proposed EB–dynamic surrounding melting(DSM)method can be applied to conveniently and effectively suppress oscillations,enable the accurate transfer of droplets to the molten pool,and achieve stable processes for preparing the strut elements of lattice structures.Lowering the temperature and improving the uniformity of its distribution are the mechanisms of oscillation suppression in EB–DSM.In this study,the physical basis for interpreting the mechanism by which EBs act on droplets and the technical basis for using EB–DED to prepare complex lattice structure parts are provided.展开更多
Let G be a connected graph of order n and m_(RD)^(L)_(G)I denote the number of reciprocal distance Laplacian eigenvaluesof G in an interval I.For a given interval I,we mainly present several bounds on m_(RD)^(L)_(G)I ...Let G be a connected graph of order n and m_(RD)^(L)_(G)I denote the number of reciprocal distance Laplacian eigenvaluesof G in an interval I.For a given interval I,we mainly present several bounds on m_(RD)^(L)_(G)I in terms of various structuralparameters of the graph G,including vertex-connectivity,independence number and pendant vertices.展开更多
The interest in curtailing environmental pollution issues through physical separation processes has inspired an extensive search for novel nanoporous materials with exceptional adsorption capabilities.Covalent triazin...The interest in curtailing environmental pollution issues through physical separation processes has inspired an extensive search for novel nanoporous materials with exceptional adsorption capabilities.Covalent triazine frameworks(CTFs),emerged as a class of crystalline covalent organic frameworks(COFs),have been widely examined for various separation applications,owing to their large porosity,high stability,and rich nitrogen(N)doping.The development of CTFs for efficient adsorption of mercury(Ⅱ)(Hg^(2+))is of great importance for the field,whereas it is rarely attempted,on account of limited synthetic strategies and unknown structural-property relations of conventional CTFs derived from ionothermal approaches.Herein,we report rational synthesis of a crystalline CTF with methylthio pendant arms for efficient removal of Hg^(2+)with an exceptional capacity of 751 mg·g^(-1),ranking at the top among previously-reported adsorbents.This work may open up new possibility in the synthesis of COFs for various separations.展开更多
As part of a better understanding of drying liquids within porous materials, measurements from 293 to 343 K of deionized water surface tension in air as a function of relative humidity are exposed. Experimental work w...As part of a better understanding of drying liquids within porous materials, measurements from 293 to 343 K of deionized water surface tension in air as a function of relative humidity are exposed. Experimental work was carried out using the pendant drop method coupled with image analysis within an adapted instrumented climatic chamber. Results show that surface tension linearly decreases when relative humidity increases. Although the effect of humidity is less compared to that of the temperature and even less compared to a surfactant impact, it must not be neglected and values have to be mentioned when dealing with water evaporation. Modifying surface tension also affects the pendant drop shape. The drying kinetics of the pendant drop volume and its outer shell are connected to this change of shape. Steam in the air can be assimilated to a wetting agent, hence a surfactant, and can be used in an environmental-friendly way to ease the drying stage. Indeed, the challenge is to limit the risk of cracking and damaging pieces during this crucial step in material processing.展开更多
Background:Reviewing historical evidence in the various schools of traditional medicine shows that numerous methods have been used to maintain human good health and treatment of diseases.Persian medicine(PM)scholars h...Background:Reviewing historical evidence in the various schools of traditional medicine shows that numerous methods have been used to maintain human good health and treatment of diseases.Persian medicine(PM)scholars have been employed different methods to prescribe medications,which can be classified into two main groups:internal uses,including oral,parenteral,and anal,and also external uses such as topical,transdermal,and applying pendants.In this study,we aim to introduce some of the therapeutic pendants.Methods:We reviewed the most famous PM textbooks and current evidence in relevant databases such as PubMed,Science Direct,Scopus,Google scholar and SID related to the topic.Results:In this study,about 100 traditional therapeutic substances were found and finally,thirty-two of them were represented.They were often stones,and some of them were other materials such as metals,gums,and herbs.According to the PM,the utilization of pendants,in addition to cosmetic purposes,has been considered to maintain the health and treatment of some diseases.Therapeutic pendants can be considered as a kind of external medication use in which therapeutic materials are hung on the body surface.The external use of pendants could have curative effects with their close contact to the body surface.Conclusion:Pendant therapy may probably be considered as a non-invasive and easy-to-use treatment with unnoticeable side effects that can be utilized along with other therapies.展开更多
Polymeric nanoparticles（NPs）have drawn great interest in the past few years due to their potential applications in the felds of biomedical and optical technologies.However,it is still a challenge to prepare function...Polymeric nanoparticles（NPs）have drawn great interest in the past few years due to their potential applications in the felds of biomedical and optical technologies.However,it is still a challenge to prepare functional polymeric NPs,especially for particle diameters smaller than 50 nm.In this work,we demonstrate a one-pot method to fabricate reactive poly（divinyl benzene-co-maleic anhydride）NPs（PDVBMAH NPs）through a self-stable precipitation polymerization process.The size and morphology of these PDVBMAH NPs were characterized in detail by scanning electronic microscopy,and their chemical structure was determined by IR.The results showed that these NPs were highly cross-linked and their diameter was about 30 nm with narrow distribution.Additionally,the DVB and MAH endow the NPs with reactive surface anhydride and pendant vinyl groups,and these particles could be further functionalized through reaction of these groups.A plausible pathway was proposed for the formation of PDVBMAH NPs.展开更多
The living cationic polymerization of 4-[2-(tert-butyldimethylsiloxy)ethyl]styrene (TBDMES) was studied in methylcyclohexane (MeChx)/methylchloride (MeCl) (50/50 V/V) solvent mixture at -80 degrees C. The initiator 1,...The living cationic polymerization of 4-[2-(tert-butyldimethylsiloxy)ethyl]styrene (TBDMES) was studied in methylcyclohexane (MeChx)/methylchloride (MeCl) (50/50 V/V) solvent mixture at -80 degrees C. The initiator 1,1-diphenylethylene (DPE) capped 2-chloro-2,4,4-trimethylpentane (TMPCl) was formed in situ in conjunction with titanium tetrachloride (TiCl(4)). The Lewis acidity of TiCl(4) was decreased by the addition of titanium(IV) isopropoxide (Ti(OiPr)(4)) to accomplish living polymerization of TBDMES. Hydrolysis of poly(TBDMES) in the presence of tetra-butylammonium fluoride yielded poly[4-(2-hydroxyethyl)styrene] (poly(HOES)). FT-IR, NMR and DSC demonstrated the hydrolysis was complete.展开更多
A series of new macrocyclic dioxo 13 aneN 4 bearing various functional pendants, 2 methylfuran (LF), 2 methylthiophene (LT), 2 methylpyridine (LP), have been synthesized and characterized, where dioxo 13 aneN ...A series of new macrocyclic dioxo 13 aneN 4 bearing various functional pendants, 2 methylfuran (LF), 2 methylthiophene (LT), 2 methylpyridine (LP), have been synthesized and characterized, where dioxo 13 aneN 4 is 1,4,7,10 tetraazacyclotridecane 11,13 dione. The solution behaviours of the nickel(Ⅱ) complexes have been studied by Uv vis, cyclic voltammetric techniques. The red shifts were observed for the absorption band maxima of the electronic spectra from NiLR 1 to NiLR 2 (R=2 methylfuran, 2 methylthiophene, 2 methylpyridine). The value of E 1/2 of the NiLR 2 is less than NiLR 1 and both of them are lower than that of the nickel(Ⅱ) complex of the unsubstituted ligand, and these reasons are discussed.展开更多
A substituted glycolide, 3-benzyloxymethyl-1,4-dioxane-2,5-dione, was synthesized. It is a suitable precursor for the preparation of a new hydrophilic biodegradable poly(a-hydroxy acid). The polymerizations were carri...A substituted glycolide, 3-benzyloxymethyl-1,4-dioxane-2,5-dione, was synthesized. It is a suitable precursor for the preparation of a new hydrophilic biodegradable poly(a-hydroxy acid). The polymerizations were carried out in bulk in the presence of Sn(Oct)(2) at 120-140 degreesC. The resulting polymers were subjected to hydrogenolysis with a Pd/C catalyst in a mixed solvent to remove the protecting benzyl groups. A novel poly(a-hydroxy acid) with pendant hydroxy groups was obtained. The hydrophilicity of the resulting polymer was evaluated preliminarily.展开更多
In this paper, aliphatic polyesters functionalized with pendant carboxylic groups were synthesized via several steps. Firstly, substituted cyclic ketone, 2-（benzyloxycarbonyl methyl）cyclopentanone （BCP） was prepar...In this paper, aliphatic polyesters functionalized with pendant carboxylic groups were synthesized via several steps. Firstly, substituted cyclic ketone, 2-（benzyloxycarbonyl methyl）cyclopentanone （BCP） was prepared through the reaction of enamine with benzyl-2-bromoacetate, and subsequently converted into the relevant functionalized 6-valerolactone derivative, 5-（benzyloxy carbonylmethyl）-δ-valerolaetone （BVL） by the Baeyer-Villiger oxidation. Secondly, the ring-opening polymerization of BVL with ε-caprolactone was carried out in bulk using stannous octoate as the catalyst to produce poly（ε-caprolactone-co-δ-valerolactone） bearing the benzyl-protected carboxyl functional groups [P（CL-co-BVL）]. Finally, the benzyl-protecting groups of P（CL-co-BVL） were effectively removed by H2 using Pd/C as the catalyst to obtain poly（ε-caprolactone-co-δ-valerolactone） bearing pendant carboxylic acids [P（CL-co-CVL）]. The structure and the properties of the polymer have been studied by Nuclear Magnetic Resonance （NMR）, Fourier Infrared Spectroscopy （FT-IR） and Differential Scan Calorimetry （DSC） etc. The NMR and FT-IR results confirmed the polymer structure, and the 13C NMR spectra have clearly interpreted the sequence of ε-caprolactone and 5-（benzyloxycarbonylmethyl）-δ-valerolactone in the copolymer. When the benzyl-protecting groups were removed, the aliphatic polyesters bearing carboxylic groups were obtained. Moreover, the hydrophilicity of the polymer was improved. Thus, poly（ε-caprolactone-co-δ-valerolactone） might have great potential in biomedical fields.展开更多
In order to further improve the serial ports communication mode of the general Flex Pendant for industrial robot,a multiple serial communication mode is put forward. It is used to meet the stability of data transmissi...In order to further improve the serial ports communication mode of the general Flex Pendant for industrial robot,a multiple serial communication mode is put forward. It is used to meet the stability of data transmission,transmission distance,transmission speed,anti-interference and cost-effective. Using ADUM1201 single direction dual channel digital isolator,two pieces of MAX13487 E and a piece of MAX3232 chip to transmit data and files, and to control chip’ s electrical level. Selecting the RS232, RS422 and RS485 communication mode,the serial ports of the general Flex Pendant of industrial robot is optimized.展开更多
Hollow porcelain insulators in substations are frequently confronted with rain flashovers under extreme rainfall.This study aims to investigate the spatial and temporal variation of electric fields between hollow porc...Hollow porcelain insulators in substations are frequently confronted with rain flashovers under extreme rainfall.This study aims to investigate the spatial and temporal variation of electric fields between hollow porcelain insulator sheds affected by dynamic deformation of pendant water drops and effects of the dimensionless number of fluids,the Weber number(We)and the electric Bond number(BoE),on it for influencing factors'analysis.Flow‐electric field coupling simulations were carried out to compute the magnitude and the position of AC electric fields between the sheds.The results show that the maximum electric field at a point in time(Etmax)increases significantly after the breakup of the pendant water drop,and its position alters accordingly.For low We and BoE,the global maximum electric field(Egmax)increases with increasing We and BoE,respectively.It is much closer to the adjacent sheds and occurs later than Etmax at the breakup of the pendant water drop(Ebmax).By contrast,Egmax decreases in different degrees at high We and BoE,respectively.There is little difference between Egmax and Ebmax in the position and the occurring time.The influence mechanism on the maximum electric field and discharges and the relationship between discharges induced by the pendant water drop and rain flashover are discussed.展开更多
This paper presents some bounds on the number of Laplacian eigenvalues contained in various subintervals of [0, n] by using the matching number and edge covering number for G, and asserts that for a connected graph th...This paper presents some bounds on the number of Laplacian eigenvalues contained in various subintervals of [0, n] by using the matching number and edge covering number for G, and asserts that for a connected graph the Laplacian eigenvalue 1 appears with certain multiplicity. Furthermore, as an application of our result （Theorem 13）, Grone and Merris＇ conjecture [The Laplacian spectrum of graph II. SIAM J. Discrete Math., 7, 221-229 （1994）] is partially proved.展开更多
The homopolymerization of 5-methyl-5-hexen-2,4-dione (methacryloylacetone, MAA), a vinyl monomer having beta-diketone group, was carried out in the presence of benzophenone (BP)/N, N-dimenthyl-4-toluidine (DMT) system...The homopolymerization of 5-methyl-5-hexen-2,4-dione (methacryloylacetone, MAA), a vinyl monomer having beta-diketone group, was carried out in the presence of benzophenone (BP)/N, N-dimenthyl-4-toluidine (DMT) system. Graft polymerization of acrylamide initiated by eerie ion onto the homopolymer film was investigated and the mechanism of the grafting reaction was proposed on the basis of ESR study. The grafted copolymer was characterized by means of grafting percentage, water absorption, XPS spectra and scanning electron photomicrographs.展开更多
基金supported by the National Natural Science Foundation of China(52375349)the Beijing Municipal Natural Science Foundation(3222008).
文摘Electron beam–directed energy deposition(EB–DED)has emerged as a promising wire-based metal additive manufacturing technique.However,the effects of EBs on pendant droplets at wire tips have not yet been determined.The aim of this study is to enhance the understanding of this action by analyzing the mechanism of droplet oscillation.The pendant droplet oscillation phenomenon hinders the stable transfer of droplets to the molten pool and limits the feasibility of manufacturing complex lattice structures by EB–DED.Hence,another aim of this study is to create an oscillation suppression method.An escalating asymmetric amplitude is the main characteristic of droplet oscillation.The primary oscillationinducing force is the recoil force generated from the EB-acted local surface of the droplet.The physical mechanism of this force is the rapid increase and uneven distribution of the local surface temperature caused by the partial action of the EB.The prerequisites for droplet oscillation include vacuum conditions,high power densities,and bypass wire feeding processes.The proposed EB–dynamic surrounding melting(DSM)method can be applied to conveniently and effectively suppress oscillations,enable the accurate transfer of droplets to the molten pool,and achieve stable processes for preparing the strut elements of lattice structures.Lowering the temperature and improving the uniformity of its distribution are the mechanisms of oscillation suppression in EB–DSM.In this study,the physical basis for interpreting the mechanism by which EBs act on droplets and the technical basis for using EB–DED to prepare complex lattice structure parts are provided.
基金supported by the Natural Science Foundation of Xinjiang Uygur Autonomous Region of China“Graph problems of topological parameters based on the spectra of graph matrices”(2021D01C069)the National Natural Science Foundation of the People's Republic of China“The investigation of spectral properties of graph operations and their related problems”(12161085)。
文摘Let G be a connected graph of order n and m_(RD)^(L)_(G)I denote the number of reciprocal distance Laplacian eigenvaluesof G in an interval I.For a given interval I,we mainly present several bounds on m_(RD)^(L)_(G)I in terms of various structuralparameters of the graph G,including vertex-connectivity,independence number and pendant vertices.
基金The National Natural Science Foundation of China(22078349,22005319,52170109)Self-deployment Program from Lanzhou Institute of Chemical Physics(E30159SQ).
文摘The interest in curtailing environmental pollution issues through physical separation processes has inspired an extensive search for novel nanoporous materials with exceptional adsorption capabilities.Covalent triazine frameworks(CTFs),emerged as a class of crystalline covalent organic frameworks(COFs),have been widely examined for various separation applications,owing to their large porosity,high stability,and rich nitrogen(N)doping.The development of CTFs for efficient adsorption of mercury(Ⅱ)(Hg^(2+))is of great importance for the field,whereas it is rarely attempted,on account of limited synthetic strategies and unknown structural-property relations of conventional CTFs derived from ionothermal approaches.Herein,we report rational synthesis of a crystalline CTF with methylthio pendant arms for efficient removal of Hg^(2+)with an exceptional capacity of 751 mg·g^(-1),ranking at the top among previously-reported adsorbents.This work may open up new possibility in the synthesis of COFs for various separations.
文摘As part of a better understanding of drying liquids within porous materials, measurements from 293 to 343 K of deionized water surface tension in air as a function of relative humidity are exposed. Experimental work was carried out using the pendant drop method coupled with image analysis within an adapted instrumented climatic chamber. Results show that surface tension linearly decreases when relative humidity increases. Although the effect of humidity is less compared to that of the temperature and even less compared to a surfactant impact, it must not be neglected and values have to be mentioned when dealing with water evaporation. Modifying surface tension also affects the pendant drop shape. The drying kinetics of the pendant drop volume and its outer shell are connected to this change of shape. Steam in the air can be assimilated to a wetting agent, hence a surfactant, and can be used in an environmental-friendly way to ease the drying stage. Indeed, the challenge is to limit the risk of cracking and damaging pieces during this crucial step in material processing.
文摘Background:Reviewing historical evidence in the various schools of traditional medicine shows that numerous methods have been used to maintain human good health and treatment of diseases.Persian medicine(PM)scholars have been employed different methods to prescribe medications,which can be classified into two main groups:internal uses,including oral,parenteral,and anal,and also external uses such as topical,transdermal,and applying pendants.In this study,we aim to introduce some of the therapeutic pendants.Methods:We reviewed the most famous PM textbooks and current evidence in relevant databases such as PubMed,Science Direct,Scopus,Google scholar and SID related to the topic.Results:In this study,about 100 traditional therapeutic substances were found and finally,thirty-two of them were represented.They were often stones,and some of them were other materials such as metals,gums,and herbs.According to the PM,the utilization of pendants,in addition to cosmetic purposes,has been considered to maintain the health and treatment of some diseases.Therapeutic pendants can be considered as a kind of external medication use in which therapeutic materials are hung on the body surface.The external use of pendants could have curative effects with their close contact to the body surface.Conclusion:Pendant therapy may probably be considered as a non-invasive and easy-to-use treatment with unnoticeable side effects that can be utilized along with other therapies.
文摘Polymeric nanoparticles（NPs）have drawn great interest in the past few years due to their potential applications in the felds of biomedical and optical technologies.However,it is still a challenge to prepare functional polymeric NPs,especially for particle diameters smaller than 50 nm.In this work,we demonstrate a one-pot method to fabricate reactive poly（divinyl benzene-co-maleic anhydride）NPs（PDVBMAH NPs）through a self-stable precipitation polymerization process.The size and morphology of these PDVBMAH NPs were characterized in detail by scanning electronic microscopy,and their chemical structure was determined by IR.The results showed that these NPs were highly cross-linked and their diameter was about 30 nm with narrow distribution.Additionally,the DVB and MAH endow the NPs with reactive surface anhydride and pendant vinyl groups,and these particles could be further functionalized through reaction of these groups.A plausible pathway was proposed for the formation of PDVBMAH NPs.
基金supported by the Beijing Municipal Project for Developing Advanced Human Resources for Higher Education(Elastomers and Biomaterials).
文摘The living cationic polymerization of 4-[2-(tert-butyldimethylsiloxy)ethyl]styrene (TBDMES) was studied in methylcyclohexane (MeChx)/methylchloride (MeCl) (50/50 V/V) solvent mixture at -80 degrees C. The initiator 1,1-diphenylethylene (DPE) capped 2-chloro-2,4,4-trimethylpentane (TMPCl) was formed in situ in conjunction with titanium tetrachloride (TiCl(4)). The Lewis acidity of TiCl(4) was decreased by the addition of titanium(IV) isopropoxide (Ti(OiPr)(4)) to accomplish living polymerization of TBDMES. Hydrolysis of poly(TBDMES) in the presence of tetra-butylammonium fluoride yielded poly[4-(2-hydroxyethyl)styrene] (poly(HOES)). FT-IR, NMR and DSC demonstrated the hydrolysis was complete.
文摘A series of new macrocyclic dioxo 13 aneN 4 bearing various functional pendants, 2 methylfuran (LF), 2 methylthiophene (LT), 2 methylpyridine (LP), have been synthesized and characterized, where dioxo 13 aneN 4 is 1,4,7,10 tetraazacyclotridecane 11,13 dione. The solution behaviours of the nickel(Ⅱ) complexes have been studied by Uv vis, cyclic voltammetric techniques. The red shifts were observed for the absorption band maxima of the electronic spectra from NiLR 1 to NiLR 2 (R=2 methylfuran, 2 methylthiophene, 2 methylpyridine). The value of E 1/2 of the NiLR 2 is less than NiLR 1 and both of them are lower than that of the nickel(Ⅱ) complex of the unsubstituted ligand, and these reasons are discussed.
基金This work was supported by the Major State Basic Research Program of China (No. G1999064704).
文摘A substituted glycolide, 3-benzyloxymethyl-1,4-dioxane-2,5-dione, was synthesized. It is a suitable precursor for the preparation of a new hydrophilic biodegradable poly(a-hydroxy acid). The polymerizations were carried out in bulk in the presence of Sn(Oct)(2) at 120-140 degreesC. The resulting polymers were subjected to hydrogenolysis with a Pd/C catalyst in a mixed solvent to remove the protecting benzyl groups. A novel poly(a-hydroxy acid) with pendant hydroxy groups was obtained. The hydrophilicity of the resulting polymer was evaluated preliminarily.
基金Project supported by the National Natural Science Foundation of China （No. 20804015）, the Ftmdamental Research Funds for the Central Universities （Nos. WD0913008, WD1014036）, Specialized Research Fund for the Doctoral Program of Higher Education （No. 20080251102l）, Shanghai Key Laboratory Project （No. 08DZ2230500） and Program for Changjiang Scholars and Innovative Research Team in University （No. IRT0825）.
文摘In this paper, aliphatic polyesters functionalized with pendant carboxylic groups were synthesized via several steps. Firstly, substituted cyclic ketone, 2-（benzyloxycarbonyl methyl）cyclopentanone （BCP） was prepared through the reaction of enamine with benzyl-2-bromoacetate, and subsequently converted into the relevant functionalized 6-valerolactone derivative, 5-（benzyloxy carbonylmethyl）-δ-valerolaetone （BVL） by the Baeyer-Villiger oxidation. Secondly, the ring-opening polymerization of BVL with ε-caprolactone was carried out in bulk using stannous octoate as the catalyst to produce poly（ε-caprolactone-co-δ-valerolactone） bearing the benzyl-protected carboxyl functional groups [P（CL-co-BVL）]. Finally, the benzyl-protecting groups of P（CL-co-BVL） were effectively removed by H2 using Pd/C as the catalyst to obtain poly（ε-caprolactone-co-δ-valerolactone） bearing pendant carboxylic acids [P（CL-co-CVL）]. The structure and the properties of the polymer have been studied by Nuclear Magnetic Resonance （NMR）, Fourier Infrared Spectroscopy （FT-IR） and Differential Scan Calorimetry （DSC） etc. The NMR and FT-IR results confirmed the polymer structure, and the 13C NMR spectra have clearly interpreted the sequence of ε-caprolactone and 5-（benzyloxycarbonylmethyl）-δ-valerolactone in the copolymer. When the benzyl-protecting groups were removed, the aliphatic polyesters bearing carboxylic groups were obtained. Moreover, the hydrophilicity of the polymer was improved. Thus, poly（ε-caprolactone-co-δ-valerolactone） might have great potential in biomedical fields.
基金supported by the National Key Technology R&D Program(2015BAK06B04)the key technologies R&D Program of Tianjin(14ZCZDSF00022)
文摘In order to further improve the serial ports communication mode of the general Flex Pendant for industrial robot,a multiple serial communication mode is put forward. It is used to meet the stability of data transmission,transmission distance,transmission speed,anti-interference and cost-effective. Using ADUM1201 single direction dual channel digital isolator,two pieces of MAX13487 E and a piece of MAX3232 chip to transmit data and files, and to control chip’ s electrical level. Selecting the RS232, RS422 and RS485 communication mode,the serial ports of the general Flex Pendant of industrial robot is optimized.
基金supported by the National Natural Science Foundation of China under Grant No.52077084.
文摘Hollow porcelain insulators in substations are frequently confronted with rain flashovers under extreme rainfall.This study aims to investigate the spatial and temporal variation of electric fields between hollow porcelain insulator sheds affected by dynamic deformation of pendant water drops and effects of the dimensionless number of fluids,the Weber number(We)and the electric Bond number(BoE),on it for influencing factors'analysis.Flow‐electric field coupling simulations were carried out to compute the magnitude and the position of AC electric fields between the sheds.The results show that the maximum electric field at a point in time(Etmax)increases significantly after the breakup of the pendant water drop,and its position alters accordingly.For low We and BoE,the global maximum electric field(Egmax)increases with increasing We and BoE,respectively.It is much closer to the adjacent sheds and occurs later than Etmax at the breakup of the pendant water drop(Ebmax).By contrast,Egmax decreases in different degrees at high We and BoE,respectively.There is little difference between Egmax and Ebmax in the position and the occurring time.The influence mechanism on the maximum electric field and discharges and the relationship between discharges induced by the pendant water drop and rain flashover are discussed.
基金Supported by National Natural Science Foundation of China （Grant No. 10871204） and the Fundamental Research Funds for the Central Universities （Grant No. 09CX04003A）
文摘This paper presents some bounds on the number of Laplacian eigenvalues contained in various subintervals of [0, n] by using the matching number and edge covering number for G, and asserts that for a connected graph the Laplacian eigenvalue 1 appears with certain multiplicity. Furthermore, as an application of our result （Theorem 13）, Grone and Merris＇ conjecture [The Laplacian spectrum of graph II. SIAM J. Discrete Math., 7, 221-229 （1994）] is partially proved.
基金The project was supported by the National Natural Science Foundation of Chna.
文摘The homopolymerization of 5-methyl-5-hexen-2,4-dione (methacryloylacetone, MAA), a vinyl monomer having beta-diketone group, was carried out in the presence of benzophenone (BP)/N, N-dimenthyl-4-toluidine (DMT) system. Graft polymerization of acrylamide initiated by eerie ion onto the homopolymer film was investigated and the mechanism of the grafting reaction was proposed on the basis of ESR study. The grafted copolymer was characterized by means of grafting percentage, water absorption, XPS spectra and scanning electron photomicrographs.
