Polypropylene(PP) accounts for approximately 28.0% of the global polyolefin market,valued at $243.4 billion in 2022.Known for its lightweight,chemical resistance,costeffectiveness,high strength and melting point,PP is...Polypropylene(PP) accounts for approximately 28.0% of the global polyolefin market,valued at $243.4 billion in 2022.Known for its lightweight,chemical resistance,costeffectiveness,high strength and melting point,PP is widely used in various applications.Its properties and applications are closely tied to its tacticity.One-dimensional(1D) conventional 13C NMR has been extensively utilized to analyze PP tacticity,but its low sensitivity and longer relaxation time remain drawbacks.Typically,analyzing a single PP sample requires around 9 h of NMR time.Using of a cryogenically cooled 10 mm NMR probe can significantly reduce this measurement time;however,its high cost makes it inaccessible for most NMR laboratories.While the refocused insensitive nuclei enhanced by polarization transfer(RINEPT) technique is well-known for enhancing NMR sensitivity,there are no published studies using 1D 13C RINEPT to quantify PP tacticity.Relaxation agents like chromium(Ⅲ) acetylacetonate(Cr(acac)_(3)) have also been used to reduce relaxation times in polyolefin NMR analyses.Here we introduce a straightforward and easily implementable 1D 13C NMR method for rapid PP tacticity quantification.This method combines Cr(acac)_(3),Bruker's existing RINEPT pulse sequence(ineptrd),and our recently published ~1H decoupling sequence(bi_waltz65_256 pl) to eliminate ^(1)H decoupling artifacts.It is worth noting that decoupling artifacts are always present.When the signal-to-noise ratio(SNR) is low,these artifacts are obscured by noise.For example,in some two-dimensional(2D) or three-dimensional(3D) NMR spectra,decoupling artifacts are barely visible because of the low SNR.However,when attempting to observe weak signals in ^(1)D spectra,increasing the sample concentration or the number of scans enhances the SNR,revealing the decoupling artifacts.The decoupling artifacts appeared superimpose with some other weak signals,affecting the measurements of signal intensities.Therefore,improved ~1H-decoupling methods are crucial for such data acquisitio n.This synergy results in a 9.4-to 9.7-fold sensitivity enhancement,equating to an 88-to 94-fold reduction(9.4^(2)≈88,9.7^(2)≈94) in NMR acquisition time compared to conventional 1D ^(13)C NMR experiment with Cr(acac)_(3).The time savings are even more substantial compared to experiments without Cr(acac)_(3).The faster and quantitative approach is accessible to researchers with or without cryoprobes.Beyond PP,this method can be applied to tacticity measurements of other polyolefins,such as polybutene,polyhexene and polyoctene.展开更多
Propylene was polymerized with a novel supported Ziegler-Natta catalystcontaining 2,2-di-iso-butyl-1,3-dimethoxy-propane (DIBDMP) as internal donor and in theabsence of external donor. The tacticity distribution of po...Propylene was polymerized with a novel supported Ziegler-Natta catalystcontaining 2,2-di-iso-butyl-1,3-dimethoxy-propane (DIBDMP) as internal donor and in theabsence of external donor. The tacticity distribution of polypropylene was obtained by usingtemperature rising elution fractionation (TREF) technique and microstructure of fractionswas studied with ^(13)C-NMR. Compared with the catalyst without electron donor, this cat-alyst gives a considerably narrower tacticity distribution. Fractionation data demonstratethat DIBDMP shows better performance than aromatic diester DNBP (di-n-butyl phtha-late). Chemically inverted propylene units and less stereoblockiness are found in the firstfraction. Possible reasons for these were presented.展开更多
After tentative ring-opening cross metathesis （ROCM） of endo-bicyclo[3.2.0]hept-6-en-3-yl 4-bromobenzoate with PhCH = CH2 initiated by （Cy3P）2Cl2Ru = CHPh in CH2Cl2, ring-opening metathesis polymerization （ROMP）...After tentative ring-opening cross metathesis （ROCM） of endo-bicyclo[3.2.0]hept-6-en-3-yl 4-bromobenzoate with PhCH = CH2 initiated by （Cy3P）2Cl2Ru = CHPh in CH2Cl2, ring-opening metathesis polymerization （ROMP） of a series of endo-bicyclo[3.2.0]hept-6-en-3-yl benzoates was achieved under the same conditions, furnishing a variety of the corresponding polymers. Then some of them were selected to hydrogenate the C=C double bonds in their backbone with p-tosylhydrazide, affording saturated and thus more flexible polymers. All of these polymers were well characterized by spectroscopic means including GPC, UV-Vis, NMR and IR, based on which the tacticity of these polymers was investigated together with nonlinear optical （electric-field-induced second-harmonic generation, EFISH）） analysis.展开更多
Fourier transform infrared spectroscopy (FTIR) has been used to study the effect of tacticityof PMMA on β phase formation of poly vinylidene fluoride (PVF_2) during quenching process.For pure PVF_2, quenching at lowe...Fourier transform infrared spectroscopy (FTIR) has been used to study the effect of tacticityof PMMA on β phase formation of poly vinylidene fluoride (PVF_2) during quenching process.For pure PVF_2, quenching at lower temperature results in the formation of β phase crystallites.The critical quenching temperature for β phase formation is about 30℃. Adding a given amountof PMMA (30%) results in the increase of the critical quenching temperature. For the blends ofPVF_2 with atactic PMMA (a-PMMA), the critical quenching temperature is about 45℃, whilefor the blends with syndiotactic PMMA (s-PMMA), attains to about 70℃.展开更多
Recent years have witnessed transformative changes brought about by artificial intelligence(AI)techniques with billions of parameters for the realization of high accuracy,proposing high demand for the advanced and AI ...Recent years have witnessed transformative changes brought about by artificial intelligence(AI)techniques with billions of parameters for the realization of high accuracy,proposing high demand for the advanced and AI chip to solve these AI tasks efficiently and powerfully.Rapid progress has been made in the field of advanced chips recently,such as the development of photonic computing,the advancement of the quantum processors,the boost of the biomimetic chips,and so on.Designs tactics of the advanced chips can be conducted with elaborated consideration of materials,algorithms,models,architectures,and so on.Though a few reviews present the development of the chips from their unique aspects,reviews in the view of the latest design for advanced and AI chips are few.Here,the newest development is systematically reviewed in the field of advanced chips.First,background and mechanisms are summarized,and subsequently most important considerations for co-design of the software and hardware are illustrated.Next,strategies are summed up to obtain advanced and AI chips with high excellent performance by taking the important information processing steps into consideration,after which the design thought for the advanced chips in the future is proposed.Finally,some perspectives are put forward.展开更多
With increasingly severe global climate change,a low-carbon economy has become an inevitable trend in the development of the international community.Low-carbon economy is not only related to environmental protection b...With increasingly severe global climate change,a low-carbon economy has become an inevitable trend in the development of the international community.Low-carbon economy is not only related to environmental protection but also has a profound impact on international trade.The purpose of this paper is to explore the impact of a low-carbon economy on the development of international trade and put forward corresponding strategy suggestions.By analyzing the connotation,characteristics,and mechanism of the low-carbon economy on international trade,this paper reveals the important role of the low-carbon economy in promoting the optimization of international trade structure,promoting green technology innovation,and strengthening international cooperation.At the same time,given the challenges brought by a low-carbon economy,this paper puts forward strategies such as strengthening policy guidance,promoting green technology innovation,and improving international trade rules to provide a reference for the sustainable development of international trade[1,2].展开更多
Pretended surrender is a kind of traditional stratagem which was commonly seen in the war history of ancient China.As a matter of fact,it is a kind of special psychological tactic,making full use of the enemy’s carel...Pretended surrender is a kind of traditional stratagem which was commonly seen in the war history of ancient China.As a matter of fact,it is a kind of special psychological tactic,making full use of the enemy’s carelessness.In the war culture of ancient China,strategic deception is one of the most important parts.In history,ancient Chinese military strategists developed many kinds of strategic deceptions in the process of the wars.Pretended surrender is one of the most basic ones.Though it looks simple,this stratagem requires the users to have really excellent psychological analysis ability and acting skill so that they can successfully fool their enemy.This stratagem appeared in ancient China in a very early time.With time going by,it developed some new forms,letting the battlefields become more inscrutable.However,this stratagem has its basic logic.After knowing this logic,we can easily see through most of the stratagems of pretended surrender.This stratagem is still of great use in today’s political struggles and commercial warfare.展开更多
Beauty trap is a kind of traditional stratagem originating from ancient times.This stratagem is a type of strategic deception,making full use of human’s desires and weaknesses.No matter whether you are a genius or a ...Beauty trap is a kind of traditional stratagem originating from ancient times.This stratagem is a type of strategic deception,making full use of human’s desires and weaknesses.No matter whether you are a genius or a fool,you will have the opportunity to fall into a trap,especially if the trap is intended for you.Because of this characteristic,beauty trap was usually seen as a kind of effective non-military method,appearing in the war history of many different countries.With time going by,compared with its original form,this stratagem has greatly changed,developing many new forms.Some of them need to be adopted flexibly,combining with different kinds of psychological tactics.Except the field of military,this stratagem can also be seen in political struggles and commercial warfare.After coming to modern society,the beauty trap does not vanish.It seems that this stratagem will accompany the entire process of humanity,simply because the desires of humans will never disappear.展开更多
Feigning madness without becoming insane is a traditional Chinese stratagem recorded in Thirty-Six Stratagems,one of the most famous military works of ancient China.It can be seen in the military history and the polit...Feigning madness without becoming insane is a traditional Chinese stratagem recorded in Thirty-Six Stratagems,one of the most famous military works of ancient China.It can be seen in the military history and the political history of ancient China.It is a high-level psychological tactic,requiring the users to have extremely strong psychological resilience and great insight.Therefore,adopting the stratagem of feigning madness without becoming insane is the game of smart people.In brief,this stratagem is a kind of psychological defense tactic,helping the users protect themselves and gain enough time to prepare for the counterattack.About this stratagem,in ancient Chinese history,there were many successful examples.At the same time,failed cases are also worth studying.As a matter of fact,this traditional stratagem can be adopted in many different fields such as military,politics,and commerce.Thus,the research about this stratagem will be a good reference for the people of modern times.展开更多
The stratagem of the empty city is a kind of traditional stratagem of ancient China.This stratagem is a type of psychological tactic,making full use of the enemy’s caution.It can be simply seen as a sort of deceptive...The stratagem of the empty city is a kind of traditional stratagem of ancient China.This stratagem is a type of psychological tactic,making full use of the enemy’s caution.It can be simply seen as a sort of deceptive tactic,applying to the situations of standoff and retreat.The stratagem of the empty city appeared many times in the war history of ancient China,offering many examples to the researchers.As a matter of fact,in ancient China,it was proved that the stratagem of the empty city could be adopted in many different fields such as military and politics.This stratagem was recorded in Thirty-Six Stratagems,one of the most famous military works of ancient China.With time goes by,compared with its original form,the stratagem of the empty city has greatly changed,developing some new forms.This stratagem is also of great use in modern politics and warfare.展开更多
The conformational and dynamic properties of polypropylene （PP） for both pure melts and blends with different chain tacticity were investigated by Monte Carlo simulation of isotactic （iPP）, atactic （aPP） and syn...The conformational and dynamic properties of polypropylene （PP） for both pure melts and blends with different chain tacticity were investigated by Monte Carlo simulation of isotactic （iPP）, atactic （aPP） and syndiotactic （sPP） polypropylenes. The simulation of coarse-grained PP models was performed on a high coordination lattice incorporating short- and long-range intramolecular interactions from the rotational isomeric state （RIS） model and Lennard-Jones （LJ） potential function of propane pairs, respectively. The dynamics of chains in binary PP/PP mixture were investigated with the composition of C150H302 with different chain taciticity. The diffusion rates of PP with different stereochemistry are generally in the order as： iPP 〉 aPP 〉〉 sPP. For PP/PP blends with 50：50 wt% binary mixtures, immiscibility was observed when sPP was introduced into the mixtures. The diffusion rate of iPP and aPP became slower after mixing, while sPP diffuses significantly faster in the binary mixtures. The mobility of PP chains depends on both intramolecular （molecular size and chain stiffness） and intermolecular （chain packing） interactions. The effect of intramolecular contribution is greater than that of intermolecular contribution for iPP and aPP chains in binary mixtures. For sPP chain, intermolecular interaction has greater influence on the dynamics than intramolecular contribution.展开更多
The unperturbed dimension and temperature character of poly(dibenzyl itaconate)s (PDBzI) are studied by a revised rotational isomeric state (RIS) method. The improved formulas of the mean-square radius of gyration, de...The unperturbed dimension and temperature character of poly(dibenzyl itaconate)s (PDBzI) are studied by a revised rotational isomeric state (RIS) method. The improved formulas of the mean-square radius of gyration, deduced by the pseudo-stereochemical equilibrium approach, may be used to investigate the configurational-conformational properties of atactic polymers with large side groups [poly(itaconates) for instance]. The calculated results showed that poly(itaconates) have larger dimension of the molecule than other vinyl polymers. Comparison of the dimension between considering and without considering side groups showed that the effect of large side groups on the unperturbed dimension for short-chain polymers is more obvious than that of long-chain polymers and, if the dimension of side groups increases, the effect also increases. The dimension differences of PDBzI between short-chain and long-chain polymers are investigated by the relation of characteristic ratios and temperature coefficients with temperature. Moreover, the dependence between the temperature coefficients and the tacticity of chains shows that the temperature characters of the isotactic, syndiotactic and atactic PDBzI chains have remarkable difference.展开更多
Cognitive models must be able to adapt the students learning behaviors dynamically.In our point of view,the processes of learning and understanding are,in nature,the procedure that gains the meaning of the object to b...Cognitive models must be able to adapt the students learning behaviors dynamically.In our point of view,the processes of learning and understanding are,in nature,the procedure that gains the meaning of the object to be learned.So,ICAI cognitive models should reflect the meaning structure of the domain knowledge in students mind.According to this view,we developed the meaning theory of Ludwig Wittgenstein,and proposed the concept of meaning conjoinism.On the basis of the meaning conjoinism we proposed a meaning oriented ICAI cognitive model and its corresponding teaching tactics.Furthermore,we developed an ICAI system named Thinking and the efficiency of our proposal has been demonstrated.展开更多
The tacticity of vinyl polymers is a key factor affecting the properties of materials.Recently,organic Brønsted acids have been demonstrated as effective catalysts for the development of highly stereoselective ca...The tacticity of vinyl polymers is a key factor affecting the properties of materials.Recently,organic Brønsted acids have been demonstrated as effective catalysts for the development of highly stereoselective cationic reversible addition-fragmentation chain transfer(RAFT)polymerizations of vinyl ethers,in which the use of RAFT agents could allow the control the molecular weight and tacticity of polymer products simultaneously.However,the effect of RAFT agents on the tacticity-regulation remains elusive and lacks of investigation.In this study,we synthesized four types of RAFT agents and evaluated their influence in the stereoselective cationic polymerization of isobutyl vinyl ether in the presence of PADI as a Brønsted acid catalyst,which unveils that the Z group of RAFT agents could not only affect the polydispersity of the products,but also exert a profound effect on the stereoselectivity.After extensive screening of the RAFT agents,high stereoregularity(isotacticity,90%m)was obtained when using dithiocarbonate ester-type RAFT agents with a benzyloxy Z group.展开更多
A series of ethylene-norbornene copolymers were synthesized using VO (Oft) Cl-2/Al2Et3Cl3 catalytic system and their structure was characterized by H-1-NMR, H-1-H-1 COSY NMR and C-13-NMR. Assignments of NMR spectra we...A series of ethylene-norbornene copolymers were synthesized using VO (Oft) Cl-2/Al2Et3Cl3 catalytic system and their structure was characterized by H-1-NMR, H-1-H-1 COSY NMR and C-13-NMR. Assignments of NMR spectra were given and discussed in detail.展开更多
In order to reduce redundant features in air combat information and to meet the requirements of real-time decision in combat, rough set theory is introduced to the tactical decision analysis in cooperative team air co...In order to reduce redundant features in air combat information and to meet the requirements of real-time decision in combat, rough set theory is introduced to the tactical decision analysis in cooperative team air combat. An algorithm of attribute reduction for extracting key combat information and generating tactical rules from given air combat databases is presented. Then, considering the practical requirements of team combat, a method for reduction of attribute-values under single decision attribute is extended to the reduction under multi-decision attributes. Finally, the algorithm is verified with an example for tactical choices in team air combat. The results show that, the redundant attributes in air combat information can be reduced, and that the main combat attributes, i.e., the information about radar command and medium-range guided missile, can be obtained with the algorithm mentioned above, moreover, the minimal reduced strategy for tactical decision can be generated without losing the result of key information classification. The decision rules extracted agree with the real situation of team air combat.展开更多
Salt lakes are a mirror of climatic changes and provide holographic records of environmental changes of lakes. According to a study of geological hazards in typical salt lake areas in China and other regions, the auth...Salt lakes are a mirror of climatic changes and provide holographic records of environmental changes of lakes. According to a study of geological hazards in typical salt lake areas in China and other regions, the authors explain how geological hazards in salt lake areas are caused by natural agents and how humans can seek benefits, avoid hazards and reduce losses on the premise that they have monitored and mastered the trend of salt lake changes in advance and even can store flood and recharge water in lakes and extract saline resources. The climate in western China is probably turning from warm-dry to warm-moist. The authors analyze the change trend of salt lakes sensu lato (with salinity≥0.3 wt% (NaCl)eq) and salt lakes sensu stricto (with salinity ≥3.5 wt% (NaCl)eq) in China in such climatic conditions and distinguish three types of salt lake areas (i.e. lake water rising type, lake water falling type and lake water rising and unstable type) according to the characteristics of lake water rising and shrinking. In order to conform to the climatic and lake changes in China's salt lake areas, the authors propose to add and improve hydrological and meteorological observation stations and integrate observations with remote sensing monitoring in important salt lake areas and set up multidisciplinary and interdepartmental basic projects to monitor and study recent climatic and environmental changes in salt lake areas of western China. Moreover, it is necessary to build additional flood-control and drought-preventing water conservancy facilities in key salt lake areas and work out measures for ecological protection in salt lake areas. Full consideration should be given to the influence of flooding when building saltfields and implementing capital projects.展开更多
The Emei mustache toad, Leptobrachium boringii （Megophryidae）, is terrestrial but breeds in permanent streams. Primarily, it has a polygynous mating system and polyandry also occurs. The species vigorously defends s...The Emei mustache toad, Leptobrachium boringii （Megophryidae）, is terrestrial but breeds in permanent streams. Primarily, it has a polygynous mating system and polyandry also occurs. The species vigorously defends submerged nest sites. We report on a reproductive study at Mt. Emei, western China conducted in 2004, 2006, 2007, 2009, and 2011 during the breeding season. Males produce both advertisement and courtship calls underwater, and the latter differs from the former in having an additional trill-like last note of low intensity. Females might determine the oviposition location and hence the egg mass location. A low, submissive posture can be adopted by the male to avoid being attacked by other males. When fighting, the maxillary nuptial spines are employed as weapons, and males hold their opponents on their spines with the forelimbs that enlarge during the breeding season. Male body size and the quantity of fight wounds on its ventral side are positively correlated. Satellite male mating might exist in L. boringii. Additionally, underwater calls from another population of this species and a population of L. leishanense generally are similar to those of the population from Mt. Emei.展开更多
A silver-based metal-organic framework（Ag-MOFs）, [Ag2（H3 ddcba）（dpp）2]（1）（H5 ddcba = 3,5-（di（2’,5’-dicarboxylphenyl）benozoic acid, dpp = 1,3-di（4-pyridyl）propane）, was successfully constructed via hyd...A silver-based metal-organic framework（Ag-MOFs）, [Ag2（H3 ddcba）（dpp）2]（1）（H5 ddcba = 3,5-（di（2’,5’-dicarboxylphenyl）benozoic acid, dpp = 1,3-di（4-pyridyl）propane）, was successfully constructed via hydrothermal assembly of a pentacaboxylate ligand, a N-donor ligand and Ag（I） ions, which possesses a pcu topology and exhibits excellent catalytic properties in aqueous solution for the degradation of onitrophenol（2-NP）, m-nitrophenol（3-NP） and p-nitrophenol（4-NP）. Related kinetics of such catalytic reactions, photoluminescent and thermal stability of compound 1 were also investigated.展开更多
文摘Polypropylene(PP) accounts for approximately 28.0% of the global polyolefin market,valued at $243.4 billion in 2022.Known for its lightweight,chemical resistance,costeffectiveness,high strength and melting point,PP is widely used in various applications.Its properties and applications are closely tied to its tacticity.One-dimensional(1D) conventional 13C NMR has been extensively utilized to analyze PP tacticity,but its low sensitivity and longer relaxation time remain drawbacks.Typically,analyzing a single PP sample requires around 9 h of NMR time.Using of a cryogenically cooled 10 mm NMR probe can significantly reduce this measurement time;however,its high cost makes it inaccessible for most NMR laboratories.While the refocused insensitive nuclei enhanced by polarization transfer(RINEPT) technique is well-known for enhancing NMR sensitivity,there are no published studies using 1D 13C RINEPT to quantify PP tacticity.Relaxation agents like chromium(Ⅲ) acetylacetonate(Cr(acac)_(3)) have also been used to reduce relaxation times in polyolefin NMR analyses.Here we introduce a straightforward and easily implementable 1D 13C NMR method for rapid PP tacticity quantification.This method combines Cr(acac)_(3),Bruker's existing RINEPT pulse sequence(ineptrd),and our recently published ~1H decoupling sequence(bi_waltz65_256 pl) to eliminate ^(1)H decoupling artifacts.It is worth noting that decoupling artifacts are always present.When the signal-to-noise ratio(SNR) is low,these artifacts are obscured by noise.For example,in some two-dimensional(2D) or three-dimensional(3D) NMR spectra,decoupling artifacts are barely visible because of the low SNR.However,when attempting to observe weak signals in ^(1)D spectra,increasing the sample concentration or the number of scans enhances the SNR,revealing the decoupling artifacts.The decoupling artifacts appeared superimpose with some other weak signals,affecting the measurements of signal intensities.Therefore,improved ~1H-decoupling methods are crucial for such data acquisitio n.This synergy results in a 9.4-to 9.7-fold sensitivity enhancement,equating to an 88-to 94-fold reduction(9.4^(2)≈88,9.7^(2)≈94) in NMR acquisition time compared to conventional 1D ^(13)C NMR experiment with Cr(acac)_(3).The time savings are even more substantial compared to experiments without Cr(acac)_(3).The faster and quantitative approach is accessible to researchers with or without cryoprobes.Beyond PP,this method can be applied to tacticity measurements of other polyolefins,such as polybutene,polyhexene and polyoctene.
基金This work is supported by the National Natural Science Foundation of China
文摘Propylene was polymerized with a novel supported Ziegler-Natta catalystcontaining 2,2-di-iso-butyl-1,3-dimethoxy-propane (DIBDMP) as internal donor and in theabsence of external donor. The tacticity distribution of polypropylene was obtained by usingtemperature rising elution fractionation (TREF) technique and microstructure of fractionswas studied with ^(13)C-NMR. Compared with the catalyst without electron donor, this cat-alyst gives a considerably narrower tacticity distribution. Fractionation data demonstratethat DIBDMP shows better performance than aromatic diester DNBP (di-n-butyl phtha-late). Chemically inverted propylene units and less stereoblockiness are found in the firstfraction. Possible reasons for these were presented.
基金supported by the National Natural Science Foundation of China(No.20902002)the Introduced Talents from Anhui University of Technology and Science(No.2008YQ009)
文摘After tentative ring-opening cross metathesis （ROCM） of endo-bicyclo[3.2.0]hept-6-en-3-yl 4-bromobenzoate with PhCH = CH2 initiated by （Cy3P）2Cl2Ru = CHPh in CH2Cl2, ring-opening metathesis polymerization （ROMP） of a series of endo-bicyclo[3.2.0]hept-6-en-3-yl benzoates was achieved under the same conditions, furnishing a variety of the corresponding polymers. Then some of them were selected to hydrogenate the C=C double bonds in their backbone with p-tosylhydrazide, affording saturated and thus more flexible polymers. All of these polymers were well characterized by spectroscopic means including GPC, UV-Vis, NMR and IR, based on which the tacticity of these polymers was investigated together with nonlinear optical （electric-field-induced second-harmonic generation, EFISH）） analysis.
文摘Fourier transform infrared spectroscopy (FTIR) has been used to study the effect of tacticityof PMMA on β phase formation of poly vinylidene fluoride (PVF_2) during quenching process.For pure PVF_2, quenching at lower temperature results in the formation of β phase crystallites.The critical quenching temperature for β phase formation is about 30℃. Adding a given amountof PMMA (30%) results in the increase of the critical quenching temperature. For the blends ofPVF_2 with atactic PMMA (a-PMMA), the critical quenching temperature is about 45℃, whilefor the blends with syndiotactic PMMA (s-PMMA), attains to about 70℃.
基金supported by the Hong Kong Polytechnic University(1-WZ1Y,1-W34U,4-YWER).
文摘Recent years have witnessed transformative changes brought about by artificial intelligence(AI)techniques with billions of parameters for the realization of high accuracy,proposing high demand for the advanced and AI chip to solve these AI tasks efficiently and powerfully.Rapid progress has been made in the field of advanced chips recently,such as the development of photonic computing,the advancement of the quantum processors,the boost of the biomimetic chips,and so on.Designs tactics of the advanced chips can be conducted with elaborated consideration of materials,algorithms,models,architectures,and so on.Though a few reviews present the development of the chips from their unique aspects,reviews in the view of the latest design for advanced and AI chips are few.Here,the newest development is systematically reviewed in the field of advanced chips.First,background and mechanisms are summarized,and subsequently most important considerations for co-design of the software and hardware are illustrated.Next,strategies are summed up to obtain advanced and AI chips with high excellent performance by taking the important information processing steps into consideration,after which the design thought for the advanced chips in the future is proposed.Finally,some perspectives are put forward.
文摘With increasingly severe global climate change,a low-carbon economy has become an inevitable trend in the development of the international community.Low-carbon economy is not only related to environmental protection but also has a profound impact on international trade.The purpose of this paper is to explore the impact of a low-carbon economy on the development of international trade and put forward corresponding strategy suggestions.By analyzing the connotation,characteristics,and mechanism of the low-carbon economy on international trade,this paper reveals the important role of the low-carbon economy in promoting the optimization of international trade structure,promoting green technology innovation,and strengthening international cooperation.At the same time,given the challenges brought by a low-carbon economy,this paper puts forward strategies such as strengthening policy guidance,promoting green technology innovation,and improving international trade rules to provide a reference for the sustainable development of international trade[1,2].
文摘Pretended surrender is a kind of traditional stratagem which was commonly seen in the war history of ancient China.As a matter of fact,it is a kind of special psychological tactic,making full use of the enemy’s carelessness.In the war culture of ancient China,strategic deception is one of the most important parts.In history,ancient Chinese military strategists developed many kinds of strategic deceptions in the process of the wars.Pretended surrender is one of the most basic ones.Though it looks simple,this stratagem requires the users to have really excellent psychological analysis ability and acting skill so that they can successfully fool their enemy.This stratagem appeared in ancient China in a very early time.With time going by,it developed some new forms,letting the battlefields become more inscrutable.However,this stratagem has its basic logic.After knowing this logic,we can easily see through most of the stratagems of pretended surrender.This stratagem is still of great use in today’s political struggles and commercial warfare.
文摘Beauty trap is a kind of traditional stratagem originating from ancient times.This stratagem is a type of strategic deception,making full use of human’s desires and weaknesses.No matter whether you are a genius or a fool,you will have the opportunity to fall into a trap,especially if the trap is intended for you.Because of this characteristic,beauty trap was usually seen as a kind of effective non-military method,appearing in the war history of many different countries.With time going by,compared with its original form,this stratagem has greatly changed,developing many new forms.Some of them need to be adopted flexibly,combining with different kinds of psychological tactics.Except the field of military,this stratagem can also be seen in political struggles and commercial warfare.After coming to modern society,the beauty trap does not vanish.It seems that this stratagem will accompany the entire process of humanity,simply because the desires of humans will never disappear.
文摘Feigning madness without becoming insane is a traditional Chinese stratagem recorded in Thirty-Six Stratagems,one of the most famous military works of ancient China.It can be seen in the military history and the political history of ancient China.It is a high-level psychological tactic,requiring the users to have extremely strong psychological resilience and great insight.Therefore,adopting the stratagem of feigning madness without becoming insane is the game of smart people.In brief,this stratagem is a kind of psychological defense tactic,helping the users protect themselves and gain enough time to prepare for the counterattack.About this stratagem,in ancient Chinese history,there were many successful examples.At the same time,failed cases are also worth studying.As a matter of fact,this traditional stratagem can be adopted in many different fields such as military,politics,and commerce.Thus,the research about this stratagem will be a good reference for the people of modern times.
文摘The stratagem of the empty city is a kind of traditional stratagem of ancient China.This stratagem is a type of psychological tactic,making full use of the enemy’s caution.It can be simply seen as a sort of deceptive tactic,applying to the situations of standoff and retreat.The stratagem of the empty city appeared many times in the war history of ancient China,offering many examples to the researchers.As a matter of fact,in ancient China,it was proved that the stratagem of the empty city could be adopted in many different fields such as military and politics.This stratagem was recorded in Thirty-Six Stratagems,one of the most famous military works of ancient China.With time goes by,compared with its original form,the stratagem of the empty city has greatly changed,developing some new forms.This stratagem is also of great use in modern politics and warfare.
基金financially supported by the Strategic Scholarships Fellowship Research Network,Commission on Higher Education,Ministry of Education Thailand
文摘The conformational and dynamic properties of polypropylene （PP） for both pure melts and blends with different chain tacticity were investigated by Monte Carlo simulation of isotactic （iPP）, atactic （aPP） and syndiotactic （sPP） polypropylenes. The simulation of coarse-grained PP models was performed on a high coordination lattice incorporating short- and long-range intramolecular interactions from the rotational isomeric state （RIS） model and Lennard-Jones （LJ） potential function of propane pairs, respectively. The dynamics of chains in binary PP/PP mixture were investigated with the composition of C150H302 with different chain taciticity. The diffusion rates of PP with different stereochemistry are generally in the order as： iPP 〉 aPP 〉〉 sPP. For PP/PP blends with 50：50 wt% binary mixtures, immiscibility was observed when sPP was introduced into the mixtures. The diffusion rate of iPP and aPP became slower after mixing, while sPP diffuses significantly faster in the binary mixtures. The mobility of PP chains depends on both intramolecular （molecular size and chain stiffness） and intermolecular （chain packing） interactions. The effect of intramolecular contribution is greater than that of intermolecular contribution for iPP and aPP chains in binary mixtures. For sPP chain, intermolecular interaction has greater influence on the dynamics than intramolecular contribution.
基金Project supported by the National Basic Research Program (973) of China (No. 10574109)the Zhejiang Provincial Science and Technology Department (No. 2005C24008)the Natural Science Foundation of Zhejiang Province (No. Y604064), China
文摘The unperturbed dimension and temperature character of poly(dibenzyl itaconate)s (PDBzI) are studied by a revised rotational isomeric state (RIS) method. The improved formulas of the mean-square radius of gyration, deduced by the pseudo-stereochemical equilibrium approach, may be used to investigate the configurational-conformational properties of atactic polymers with large side groups [poly(itaconates) for instance]. The calculated results showed that poly(itaconates) have larger dimension of the molecule than other vinyl polymers. Comparison of the dimension between considering and without considering side groups showed that the effect of large side groups on the unperturbed dimension for short-chain polymers is more obvious than that of long-chain polymers and, if the dimension of side groups increases, the effect also increases. The dimension differences of PDBzI between short-chain and long-chain polymers are investigated by the relation of characteristic ratios and temperature coefficients with temperature. Moreover, the dependence between the temperature coefficients and the tacticity of chains shows that the temperature characters of the isotactic, syndiotactic and atactic PDBzI chains have remarkable difference.
文摘Cognitive models must be able to adapt the students learning behaviors dynamically.In our point of view,the processes of learning and understanding are,in nature,the procedure that gains the meaning of the object to be learned.So,ICAI cognitive models should reflect the meaning structure of the domain knowledge in students mind.According to this view,we developed the meaning theory of Ludwig Wittgenstein,and proposed the concept of meaning conjoinism.On the basis of the meaning conjoinism we proposed a meaning oriented ICAI cognitive model and its corresponding teaching tactics.Furthermore,we developed an ICAI system named Thinking and the efficiency of our proposal has been demonstrated.
基金supported by the Recruitment Program of Global Experts of China,the National Natural Science Foundation of China(Nos.21602028 and 22371240)Beijing National Laboratory for Molecular Sciences(No.BNLMS201913)100-Talent program of Fujian,Fuzhou University and Xiamen University.
文摘The tacticity of vinyl polymers is a key factor affecting the properties of materials.Recently,organic Brønsted acids have been demonstrated as effective catalysts for the development of highly stereoselective cationic reversible addition-fragmentation chain transfer(RAFT)polymerizations of vinyl ethers,in which the use of RAFT agents could allow the control the molecular weight and tacticity of polymer products simultaneously.However,the effect of RAFT agents on the tacticity-regulation remains elusive and lacks of investigation.In this study,we synthesized four types of RAFT agents and evaluated their influence in the stereoselective cationic polymerization of isobutyl vinyl ether in the presence of PADI as a Brønsted acid catalyst,which unveils that the Z group of RAFT agents could not only affect the polydispersity of the products,but also exert a profound effect on the stereoselectivity.After extensive screening of the RAFT agents,high stereoregularity(isotacticity,90%m)was obtained when using dithiocarbonate ester-type RAFT agents with a benzyloxy Z group.
文摘A series of ethylene-norbornene copolymers were synthesized using VO (Oft) Cl-2/Al2Et3Cl3 catalytic system and their structure was characterized by H-1-NMR, H-1-H-1 COSY NMR and C-13-NMR. Assignments of NMR spectra were given and discussed in detail.
基金Preliminary research foundation of national defense
文摘In order to reduce redundant features in air combat information and to meet the requirements of real-time decision in combat, rough set theory is introduced to the tactical decision analysis in cooperative team air combat. An algorithm of attribute reduction for extracting key combat information and generating tactical rules from given air combat databases is presented. Then, considering the practical requirements of team combat, a method for reduction of attribute-values under single decision attribute is extended to the reduction under multi-decision attributes. Finally, the algorithm is verified with an example for tactical choices in team air combat. The results show that, the redundant attributes in air combat information can be reduced, and that the main combat attributes, i.e., the information about radar command and medium-range guided missile, can be obtained with the algorithm mentioned above, moreover, the minimal reduced strategy for tactical decision can be generated without losing the result of key information classification. The decision rules extracted agree with the real situation of team air combat.
基金This study was supported by the National Natural Science Foundation of China grant 49833010Project of Special Funds for Public Interests Research of the Ministry of Science and Technology grant 2001DIA 10020.
文摘Salt lakes are a mirror of climatic changes and provide holographic records of environmental changes of lakes. According to a study of geological hazards in typical salt lake areas in China and other regions, the authors explain how geological hazards in salt lake areas are caused by natural agents and how humans can seek benefits, avoid hazards and reduce losses on the premise that they have monitored and mastered the trend of salt lake changes in advance and even can store flood and recharge water in lakes and extract saline resources. The climate in western China is probably turning from warm-dry to warm-moist. The authors analyze the change trend of salt lakes sensu lato (with salinity≥0.3 wt% (NaCl)eq) and salt lakes sensu stricto (with salinity ≥3.5 wt% (NaCl)eq) in China in such climatic conditions and distinguish three types of salt lake areas (i.e. lake water rising type, lake water falling type and lake water rising and unstable type) according to the characteristics of lake water rising and shrinking. In order to conform to the climatic and lake changes in China's salt lake areas, the authors propose to add and improve hydrological and meteorological observation stations and integrate observations with remote sensing monitoring in important salt lake areas and set up multidisciplinary and interdepartmental basic projects to monitor and study recent climatic and environmental changes in salt lake areas of western China. Moreover, it is necessary to build additional flood-control and drought-preventing water conservancy facilities in key salt lake areas and work out measures for ecological protection in salt lake areas. Full consideration should be given to the influence of flooding when building saltfields and implementing capital projects.
基金supported by the National Natural Sciences Foundation of China(NSFC-30870278,NSFC-30900134)Chinese Academy of Sciences(08B3031100,09C3011100,KSCX-SW-119,KSCX2-YW-Z-0906,KSCX2-EW-J-22)
文摘The Emei mustache toad, Leptobrachium boringii （Megophryidae）, is terrestrial but breeds in permanent streams. Primarily, it has a polygynous mating system and polyandry also occurs. The species vigorously defends submerged nest sites. We report on a reproductive study at Mt. Emei, western China conducted in 2004, 2006, 2007, 2009, and 2011 during the breeding season. Males produce both advertisement and courtship calls underwater, and the latter differs from the former in having an additional trill-like last note of low intensity. Females might determine the oviposition location and hence the egg mass location. A low, submissive posture can be adopted by the male to avoid being attacked by other males. When fighting, the maxillary nuptial spines are employed as weapons, and males hold their opponents on their spines with the forelimbs that enlarge during the breeding season. Male body size and the quantity of fight wounds on its ventral side are positively correlated. Satellite male mating might exist in L. boringii. Additionally, underwater calls from another population of this species and a population of L. leishanense generally are similar to those of the population from Mt. Emei.
基金financial support from the National Science Foundation of China (Nos. 216731272, 2137312, 21671119, 51572152 and 51502155)
文摘A silver-based metal-organic framework（Ag-MOFs）, [Ag2（H3 ddcba）（dpp）2]（1）（H5 ddcba = 3,5-（di（2’,5’-dicarboxylphenyl）benozoic acid, dpp = 1,3-di（4-pyridyl）propane）, was successfully constructed via hydrothermal assembly of a pentacaboxylate ligand, a N-donor ligand and Ag（I） ions, which possesses a pcu topology and exhibits excellent catalytic properties in aqueous solution for the degradation of onitrophenol（2-NP）, m-nitrophenol（3-NP） and p-nitrophenol（4-NP）. Related kinetics of such catalytic reactions, photoluminescent and thermal stability of compound 1 were also investigated.
