Direct conversion of syngas to aromatics(STA)over oxide-zeolite composite catalysts is promising as an alternative method for aromatics production.However,the structural effect of the oxide component in composite cata...Direct conversion of syngas to aromatics(STA)over oxide-zeolite composite catalysts is promising as an alternative method for aromatics production.However,the structural effect of the oxide component in composite catalysts is still ambiguous.Herein,we investigate the size effect by selecting ZnCr_(2)O_(4)spinel,as a probe oxide,mixing with H-ZSM-5 zeolite as a composite catalyst for STA reaction.The CO conversion,aromatics selectivity and space-time yield(STY)of aromatics are all significantly improved with the crystal size of ZnCr_(2)O_(4)oxide decreases,which can mainly attribute to the higher oxygen vacancy concentration and thus the rapid generation of more C1oxygenated intermediate species.Based on the understanding of the size-performance relationship,ZnCr_(2)O_(4)-400 with a smaller size mixing with H-ZSM-5 can achieve32.6%CO conversion with 76%aromatics selectivity.The STY of aromatics reaches as high as 4.79 mmol g_(cat)^(-1)h^(-1),which outperforms the previously reported some typical catalysts.This study elucidates the importance of regulating the size of oxide to design more efficient oxidezeolite composite catalysts for conversion of syngas to value-added chemicals.展开更多
One of the greatest triumph of condensed matter physics in the past ten years is the classification of materials by the principle of topology.The existence of topological protected dissipationless surface state makes ...One of the greatest triumph of condensed matter physics in the past ten years is the classification of materials by the principle of topology.The existence of topological protected dissipationless surface state makes topological insulators great potential for applications and hotly studied.However,compared with the prosperity of strong topological insulators,theoretical predicted candidate materials and experimental confirmation of weak topological insulators(WTIs) are both extremely rare.By combining systematic first-principles calculation and angle-resolved photoemission spectroscopy measurements,we have studied the electronic structure of the dark surface of the WTI candidate Zintl Ba_(3)Cd_(2)Sb_(4)and another related material Ba_(3)Cd_(2)As_(4).The existence of two Dirac surface states on specific side surfaces predicted by theoretical calculations and the observed two band inversions in the Brillouin zone give strong evidence to prove that the Ba_(3)Cd_(2)Sb_(4)is a WTI.The spectroscopic characterization of this Zintl Ba_(3)Cd_(2)N_(4)(N = As and Sb) family materials will facilitate applications of their novel topological properties.展开更多
Metal-modified H-ZSM-5 has a high selectivity of aromatics in methanol to aromatics(MTA)reaction,which is often attributed to the metal promoting the aromatization of intermediate olefins.However,the effect of methano...Metal-modified H-ZSM-5 has a high selectivity of aromatics in methanol to aromatics(MTA)reaction,which is often attributed to the metal promoting the aromatization of intermediate olefins.However,the effect of methanol dehydrogenation on aromatics formation over these catalysts is rarely studied.Here,we report that HCHO,which is formed by methanol dehydrogenation over Zn/H-ZSM-5 prepared by Zn impregnation,can participate in the synthesis of aromatics.Methanol conversion can produce more aromatics than olefins(propylene or ethylene)conversion over Zn/H-ZSM-5,indicating the conventional MTA pathway including methanol-to-olefins and olefins-to-aromatics is not complete.Moreover,an MTA mechanism including the conventional pathway and the methanol and HCHO coupling pathway is systematically proposed.展开更多
Hydrogenation of methyl acetate is a key step in ethanol synthesis from dimethyl ether carbonylation and Cu-based catalysts are widely studied.We report here that the hydrogenation activity of Cu/ZnO catalysts can be ...Hydrogenation of methyl acetate is a key step in ethanol synthesis from dimethyl ether carbonylation and Cu-based catalysts are widely studied.We report here that the hydrogenation activity of Cu/ZnO catalysts can be enhanced by the addition of MgO promoter.The evolution of crystal phases during coprecipitation and the physicochemical properties of calcined and reduced catalysts by X-ray diffraction(XRD),thermogravimetric(TG)-mass spectrometry(MS),Brunauer-Emmett-Teller(BET),transmission electron microscopy(TEM),N_(2)O titration,in situ CO-Fourier transform infrared spectroscopy(FTIR)and H_(2)-temperature programmed reduction(H_(2)-TPR)reveal that the promoter effect likely lies in the presence of Mg^(2+).A proper amount of Mg^(2+)mediates the precipitation process of Cu and Zn,leading to preferable formation of aurichalcite(Cu_(x)Zn_(1-x))5(CO_(3))_(2)(OH)_(6) crystal phase and a small amount of basic carbonates such as hydrozincite Zn_(5)(CO_(3))_(2)(OH)_(6) and malachite Cu_(2) CO_(3)(OH)_(2).The presence of aurichalcite strengthens the interaction between Cu and Zn species,and thus enhances the dispersity of CuO species and helps generation of Cu^(+)species on reduced catalysts.Furthermore,the performance of Cu/ZnO catalysts exhibits an optimal dependence on the Mg loading,i.e.,17.5%.However,too much Mg^(2+)in the precipitation liquid prohibits formation of aurichalcite but enhances formation of basic nitrates,leading to a dramatically reduced hydrogenation activity.These findings may find applications for optimization of other Cu-based catalysts in a wider range of hydrogenation reactions.展开更多
Realizing high CO conversion and high aromatics selectivity simultaneously in syngas-to-aromatics(STA)reaction is still challenging.Herein,we report a 57.5%CO conversion along with 74%aromatics selectivity over a comp...Realizing high CO conversion and high aromatics selectivity simultaneously in syngas-to-aromatics(STA)reaction is still challenging.Herein,we report a 57.5%CO conversion along with 74%aromatics selectivity over a composite catalyst consisting of Fe/ZnCr_(2)O_(4)(Fe modified ZnCr_(2)O_(4)spinel)oxide and H-ZSM-5 zeolite.Impregnation of only 3 wt%of Fe onto ZnCr_(2)O_(4)can remarkably increase CO conversion without sacrificing the aromatics selectivity.Oxygen vacancy concentration is improved after impregnating Fe.The highly dispersed iron carbide species is formed during the reaction over Fe/ZnCr_(2)O_(4)spinel oxide.The synergistic effect of oxygen vacancy and iron carbide results in a rapid formation of abundant oxygenated intermediate species,which can be continuously transformed to aromatics in H-ZSM-5.This study provides a new insight into the design of highly efficient catalyst for syngas conversion.展开更多
Light olefins (C2–C4olefins) are the most important basic carbon-based building blocks, which are mainly produced from the catalytic cracking of naphtha [1–3]. With the rapid depletion of oil reserves and the growin...Light olefins (C2–C4olefins) are the most important basic carbon-based building blocks, which are mainly produced from the catalytic cracking of naphtha [1–3]. With the rapid depletion of oil reserves and the growing demand for lower olefins, there is an urgent need to develop an alternative technique for producing them from non-petroleum resources such as coal, natural gas, or biomass. Currently, coal has been successfully transformed to olefins in China via the combination of the processes of coal-tosyngas, syngas-to-methanol and methanol-to-olefins [4–6]. In order to further improve efficiency and reduce investment, the direct conversion of syngas to olefins has received extensive attention in recent years [7].展开更多
Direct converting carbon dioxide into hydrocarbon fuels and value-added chemicals would offer a very attractive approach for efficient utilization of CO_(2) as a carbon resource.Although,olefins,aromatics and gasoline...Direct converting carbon dioxide into hydrocarbon fuels and value-added chemicals would offer a very attractive approach for efficient utilization of CO_(2) as a carbon resource.Although,olefins,aromatics and gasoline have been successfully synthesized by CO_(2) hydrogenation,highly selective conversion of CO_(2) and H_(2) into C_(2+)hydrocarbon is still challenging due to a high C-C coupling barrier and inhibiting the production of other long-chain hydrocarbons.Here,we report a composite catalyst made of InZrO_(x) and SSZ-13 molecular sieve(InZrO_(x)+SSZ-13),which exhibits 74.5% propane selectivity at 623 K.The 8-MR micropores and the higher strength of the acid for SSZ-13 benefit the formation of propane.Compared with pure InO_(x) and m-ZrO_(2) the composite oxide InZrO_(x) containing more oxygen vacancies,exhibits to be more readily reduced by H_(2) and easier to adsorb and desorb CO_(2) within the reaction temperature.All those could be beneficial to the activation and conversion of H_(2) and CO_(2).The catalytic performance of InZrO_(x)+SSZ-13 in CO_(2) hydrogenation provides a potential for production of propane.展开更多
We report the magnetoresistance（MR）, de Haas-van Alphen（dHvA） effect and Hall effect measurements on a single crystal of TiSi, which is predicted to be a nodal line semimetal. With application of a magnetic field,...We report the magnetoresistance（MR）, de Haas-van Alphen（dHvA） effect and Hall effect measurements on a single crystal of TiSi, which is predicted to be a nodal line semimetal. With application of a magnetic field, a metal-to-insulator-like transition in ρ（T） and a nonsaturating MR are observed at low temperatures. The dHvA oscillations reveal a small Fermi-surface pocket with a nontrivial Berry phase. The analysis of the nonlinear Hall resistivity shows that TiSi is a multiband system with low carrier densities and high mobilities. All these results unambiguously prove the existence of Dirac fermions in TiSi.展开更多
Ethylene and propylene(C_(2)^(–)3=)are the two most demanded olefin products,which are mainly produced by thermal and catalytic cracking of petroleum-derived hydrocarbons now[1].With the depletion of petroleum resour...Ethylene and propylene(C_(2)^(–)3=)are the two most demanded olefin products,which are mainly produced by thermal and catalytic cracking of petroleum-derived hydrocarbons now[1].With the depletion of petroleum resources,the use of non-petroleum resources such as natural gas,coal,biomass,even CO_(2)etc.展开更多
We investigate the interface between a three-dimensional Dirac semimetal Cd3As2 and a normal metal via softpoint contact spectroscopy measurement.The superconducting gap features were detected below 3.8 K and 7.1 K in...We investigate the interface between a three-dimensional Dirac semimetal Cd3As2 and a normal metal via softpoint contact spectroscopy measurement.The superconducting gap features were detected below 3.8 K and 7.1 K in the case of Cd3As2 single crystals sputter-coated with the Pt and Au films,respectively,in the differential conductance dI/dV-V plots of the point contacts.As the applied magnetic field increased,the drop in the zerobias contact resistance shifted toward lower temperatures.The topologically non-trivial band structure of Cd3As2 is considered to play a crucial role in inducing the superconductivity.Apart from realizing superconductivity in topological materials,our creative approach can be used to investigate possible topological superconductivity and exhibits a high application potential in electronic devices.展开更多
The Seebeck effect encounters a few fundamental constraints hindering its thermoelectric(TE)conversion efficiency.Most notably,there are the charge compensation of electrons and holes that diminishes this effect,and t...The Seebeck effect encounters a few fundamental constraints hindering its thermoelectric(TE)conversion efficiency.Most notably,there are the charge compensation of electrons and holes that diminishes this effect,and the Wiedemann-Franz(WF)law that makes independent optimization of the corresponding electrical and thermal conductivities impossible.Here,we demonstrate that in the topological Dirac semimetal Cd3As2 the Nernst effect,i.e.,the transverse counterpart of the Seebeck effect,can generate a large TE figure of merit zNT.At room temperature,zNT≈0.5 in a small field of 2 T and it significantly surmounts its longitudinal counterpart for any field.A large Nernst effect is generically expected in topological semimetals,benefiting from both the bipolar transport of compensated electrons and holes and their high mobilities.In this case,heat and charge transport are orthogonal,i.e.,not intertwined by the WF law anymore.More importantly,further optimization of zNT by tuning the Fermi level to the Dirac node can be anticipated due to not only the enhanced bipolar transport,but also the anomalous Nernst effect arising from a pronounced Berry curvature.A combination of the topologically trivial and nontrivial advantages promises to open a new avenue towards high-efficient transverse thermoelectricity.展开更多
Dear Editor,Although fusion events involving neurotrophic receptor tyrosine kinase 1,2,and 3 genes(NTRK1,NTRK2,and NTRK3,encoding TRKA/B/C respectively)were found in diverse tumor types,only 0.1%-0.3%of lung cancer pa...Dear Editor,Although fusion events involving neurotrophic receptor tyrosine kinase 1,2,and 3 genes(NTRK1,NTRK2,and NTRK3,encoding TRKA/B/C respectively)were found in diverse tumor types,only 0.1%-0.3%of lung cancer patients harbor an NTRK(and mostly NTRK1)fusion as the primary oncogenic event[1].Such low prevalence may be partially due to the limited availability of first-line assays for detecting rare fusion events[2].Immunohistochemistry is limited by sensitivity and variable tissue background,and fluorescence in-situ hybridization falls short of elucidating functional significance such as the identity of the partner or structure of the transcript.While DNA next-generation sequencing(NGS)is suitable for mutation calling(single nucleotide variation[SNV]and insertion-or-deletion[indel]),and RNA NGS is particularly effective in detecting fusions[3],routinely performing these two assays together is labor-intensive.As a solution,we have developed a single NGS assay(PANO-Seq)for unified RNA/DNA target enrichment library preparation[4],which takes about 12 hours and $10 to prepare.展开更多
Small tracking error correction for electro-optical systems is essential to improve the tracking precision of future mechanical and defense technology.Aerial threats,such as“low,slow,and small(LSS)”moving targets,po...Small tracking error correction for electro-optical systems is essential to improve the tracking precision of future mechanical and defense technology.Aerial threats,such as“low,slow,and small(LSS)”moving targets,pose increasing challenges to society.The core goal of this work is to address the issues,such as small tracking error correction and aiming control,of electro-optical detection systems by using mechatronics drive modeling,composite velocity–image stability control,and improved interpolation filter design.A tracking controller delay prediction method for moving targets is proposed based on the Euler transformation model of a two-axis,two-gimbal cantilever beam coaxial configuration.Small tracking error formation is analyzed in detail to reveal the scientific mechanism of composite control between the tracking controller’s feedback and the motor’s velocity–stability loop.An improved segmental interpolation filtering algorithm is established by combining line of sight(LOS)position correction and multivariable typical tracking fault diagnosis.Then,a platform with 2 degrees of freedom is used to test the system.An LSS moving target shooting object with a tracking distance of S=100 m,target board area of A=1 m^(2),and target linear velocity of v=5 m/s is simulated.Results show that the optimal method’s distribution probability of the tracking error in a circle with a radius of 1 mrad is 66.7%,and that of the traditional method is 41.6%.Compared with the LOS shooting accuracy of the traditional method,the LOS shooting accuracy of the optimized method is improved by 37.6%.展开更多
基金financial support from the National Natural Science Foundation of China(Grant No.21978285,21991093,21991090)the“Transformational Technologies for Clean Energy and Demonstration”,Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21030100)。
文摘Direct conversion of syngas to aromatics(STA)over oxide-zeolite composite catalysts is promising as an alternative method for aromatics production.However,the structural effect of the oxide component in composite catalysts is still ambiguous.Herein,we investigate the size effect by selecting ZnCr_(2)O_(4)spinel,as a probe oxide,mixing with H-ZSM-5 zeolite as a composite catalyst for STA reaction.The CO conversion,aromatics selectivity and space-time yield(STY)of aromatics are all significantly improved with the crystal size of ZnCr_(2)O_(4)oxide decreases,which can mainly attribute to the higher oxygen vacancy concentration and thus the rapid generation of more C1oxygenated intermediate species.Based on the understanding of the size-performance relationship,ZnCr_(2)O_(4)-400 with a smaller size mixing with H-ZSM-5 can achieve32.6%CO conversion with 76%aromatics selectivity.The STY of aromatics reaches as high as 4.79 mmol g_(cat)^(-1)h^(-1),which outperforms the previously reported some typical catalysts.This study elucidates the importance of regulating the size of oxide to design more efficient oxidezeolite composite catalysts for conversion of syngas to value-added chemicals.
基金supported by the National Key R&D Program of China(Grant Nos.2022YFA1403800,2018YFA0305700,and 2019YFA0308602)the Chinese Academy of Sciences(Grant Nos.QYZDB-SSW-SLH043,XDB33000000,and XDB28000000)+2 种基金the National Natural Science Foundation of China (Grant Nos.U22A600018,U1832202,12074425,11874422,11925408,11921004,and 12188101)the Informatization Plan of Chinese Academy of Sciences (Grant No.CAS-WX2021SF-0102)the Synergetic Extreme Condition User Facility (SECUF)。
文摘One of the greatest triumph of condensed matter physics in the past ten years is the classification of materials by the principle of topology.The existence of topological protected dissipationless surface state makes topological insulators great potential for applications and hotly studied.However,compared with the prosperity of strong topological insulators,theoretical predicted candidate materials and experimental confirmation of weak topological insulators(WTIs) are both extremely rare.By combining systematic first-principles calculation and angle-resolved photoemission spectroscopy measurements,we have studied the electronic structure of the dark surface of the WTI candidate Zintl Ba_(3)Cd_(2)Sb_(4)and another related material Ba_(3)Cd_(2)As_(4).The existence of two Dirac surface states on specific side surfaces predicted by theoretical calculations and the observed two band inversions in the Brillouin zone give strong evidence to prove that the Ba_(3)Cd_(2)Sb_(4)is a WTI.The spectroscopic characterization of this Zintl Ba_(3)Cd_(2)N_(4)(N = As and Sb) family materials will facilitate applications of their novel topological properties.
基金the financial support from the National Natural Science Foundation of China(Grant No.21978285,21991093,21991090)the“Transformational Technologies for Clean Energy and Demonstration”,Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21030100)。
文摘Metal-modified H-ZSM-5 has a high selectivity of aromatics in methanol to aromatics(MTA)reaction,which is often attributed to the metal promoting the aromatization of intermediate olefins.However,the effect of methanol dehydrogenation on aromatics formation over these catalysts is rarely studied.Here,we report that HCHO,which is formed by methanol dehydrogenation over Zn/H-ZSM-5 prepared by Zn impregnation,can participate in the synthesis of aromatics.Methanol conversion can produce more aromatics than olefins(propylene or ethylene)conversion over Zn/H-ZSM-5,indicating the conventional MTA pathway including methanol-to-olefins and olefins-to-aromatics is not complete.Moreover,an MTA mechanism including the conventional pathway and the methanol and HCHO coupling pathway is systematically proposed.
基金supported from the National Natural Science Foundation of China(Grant Nos.21972141,21991094,21991090)the“Transformational Technologies for Clean Energy and Demonstration”,Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21030100)。
文摘Hydrogenation of methyl acetate is a key step in ethanol synthesis from dimethyl ether carbonylation and Cu-based catalysts are widely studied.We report here that the hydrogenation activity of Cu/ZnO catalysts can be enhanced by the addition of MgO promoter.The evolution of crystal phases during coprecipitation and the physicochemical properties of calcined and reduced catalysts by X-ray diffraction(XRD),thermogravimetric(TG)-mass spectrometry(MS),Brunauer-Emmett-Teller(BET),transmission electron microscopy(TEM),N_(2)O titration,in situ CO-Fourier transform infrared spectroscopy(FTIR)and H_(2)-temperature programmed reduction(H_(2)-TPR)reveal that the promoter effect likely lies in the presence of Mg^(2+).A proper amount of Mg^(2+)mediates the precipitation process of Cu and Zn,leading to preferable formation of aurichalcite(Cu_(x)Zn_(1-x))5(CO_(3))_(2)(OH)_(6) crystal phase and a small amount of basic carbonates such as hydrozincite Zn_(5)(CO_(3))_(2)(OH)_(6) and malachite Cu_(2) CO_(3)(OH)_(2).The presence of aurichalcite strengthens the interaction between Cu and Zn species,and thus enhances the dispersity of CuO species and helps generation of Cu^(+)species on reduced catalysts.Furthermore,the performance of Cu/ZnO catalysts exhibits an optimal dependence on the Mg loading,i.e.,17.5%.However,too much Mg^(2+)in the precipitation liquid prohibits formation of aurichalcite but enhances formation of basic nitrates,leading to a dramatically reduced hydrogenation activity.These findings may find applications for optimization of other Cu-based catalysts in a wider range of hydrogenation reactions.
基金the financial support from the National Natural Science Foundation of China(Grant No.21978285,21991093,21991090),the‘‘Transformational Technologies for Clean Energy and Demonstration”the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21030100)。
文摘Realizing high CO conversion and high aromatics selectivity simultaneously in syngas-to-aromatics(STA)reaction is still challenging.Herein,we report a 57.5%CO conversion along with 74%aromatics selectivity over a composite catalyst consisting of Fe/ZnCr_(2)O_(4)(Fe modified ZnCr_(2)O_(4)spinel)oxide and H-ZSM-5 zeolite.Impregnation of only 3 wt%of Fe onto ZnCr_(2)O_(4)can remarkably increase CO conversion without sacrificing the aromatics selectivity.Oxygen vacancy concentration is improved after impregnating Fe.The highly dispersed iron carbide species is formed during the reaction over Fe/ZnCr_(2)O_(4)spinel oxide.The synergistic effect of oxygen vacancy and iron carbide results in a rapid formation of abundant oxygenated intermediate species,which can be continuously transformed to aromatics in H-ZSM-5.This study provides a new insight into the design of highly efficient catalyst for syngas conversion.
基金the financial support from the National Natural Science Foundation of China(Grant Nos.21978285,21991093,21991090)the “Transformational Technologies for Clean Energy and Demonstration”,Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21030100)。
文摘Light olefins (C2–C4olefins) are the most important basic carbon-based building blocks, which are mainly produced from the catalytic cracking of naphtha [1–3]. With the rapid depletion of oil reserves and the growing demand for lower olefins, there is an urgent need to develop an alternative technique for producing them from non-petroleum resources such as coal, natural gas, or biomass. Currently, coal has been successfully transformed to olefins in China via the combination of the processes of coal-tosyngas, syngas-to-methanol and methanol-to-olefins [4–6]. In order to further improve efficiency and reduce investment, the direct conversion of syngas to olefins has received extensive attention in recent years [7].
基金the financial support from the National Natural Science Foundation of China(Grant Nos.21978285,21991093,21991090)the“Transformational Technologies for Clean Energy and Demonstration”,Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21030100)。
文摘Direct converting carbon dioxide into hydrocarbon fuels and value-added chemicals would offer a very attractive approach for efficient utilization of CO_(2) as a carbon resource.Although,olefins,aromatics and gasoline have been successfully synthesized by CO_(2) hydrogenation,highly selective conversion of CO_(2) and H_(2) into C_(2+)hydrocarbon is still challenging due to a high C-C coupling barrier and inhibiting the production of other long-chain hydrocarbons.Here,we report a composite catalyst made of InZrO_(x) and SSZ-13 molecular sieve(InZrO_(x)+SSZ-13),which exhibits 74.5% propane selectivity at 623 K.The 8-MR micropores and the higher strength of the acid for SSZ-13 benefit the formation of propane.Compared with pure InO_(x) and m-ZrO_(2) the composite oxide InZrO_(x) containing more oxygen vacancies,exhibits to be more readily reduced by H_(2) and easier to adsorb and desorb CO_(2) within the reaction temperature.All those could be beneficial to the activation and conversion of H_(2) and CO_(2).The catalytic performance of InZrO_(x)+SSZ-13 in CO_(2) hydrogenation provides a potential for production of propane.
基金Supported by the National Key Research Program of China under Grant Nos 2016YFA0401000 and 2016YFA0300604the National Basic Research Program of China under Grant No 2015CB921303+1 种基金the Strategic Priority Research Program(B)of Chinese Academy of Sciences under Grant No XDB07020100the National Natural Science Foundation of China under Grant No11874417
文摘We report the magnetoresistance（MR）, de Haas-van Alphen（dHvA） effect and Hall effect measurements on a single crystal of TiSi, which is predicted to be a nodal line semimetal. With application of a magnetic field, a metal-to-insulator-like transition in ρ（T） and a nonsaturating MR are observed at low temperatures. The dHvA oscillations reveal a small Fermi-surface pocket with a nontrivial Berry phase. The analysis of the nonlinear Hall resistivity shows that TiSi is a multiband system with low carrier densities and high mobilities. All these results unambiguously prove the existence of Dirac fermions in TiSi.
基金the financial support from the National Natural Science Foundation of China(Grant Nos.21978285,21991093,21991090)the"Transformational Technologies for Clean Energy and Demonstration",Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21030100)。
文摘Ethylene and propylene(C_(2)^(–)3=)are the two most demanded olefin products,which are mainly produced by thermal and catalytic cracking of petroleum-derived hydrocarbons now[1].With the depletion of petroleum resources,the use of non-petroleum resources such as natural gas,coal,biomass,even CO_(2)etc.
基金Supported by the National Natural Science Foundation of China(Grant Nos.11704403 and 11874417)the National Key Research Program of China(Grant Nos.2016YFA0401000,2016YFA0300604,and 2018YFA070112)the Strategic Priority Research Program(B)of Chinese Academy of Sciences(Grant No.XDB33010100)。
文摘We investigate the interface between a three-dimensional Dirac semimetal Cd3As2 and a normal metal via softpoint contact spectroscopy measurement.The superconducting gap features were detected below 3.8 K and 7.1 K in the case of Cd3As2 single crystals sputter-coated with the Pt and Au films,respectively,in the differential conductance dI/dV-V plots of the point contacts.As the applied magnetic field increased,the drop in the zerobias contact resistance shifted toward lower temperatures.The topologically non-trivial band structure of Cd3As2 is considered to play a crucial role in inducing the superconductivity.Apart from realizing superconductivity in topological materials,our creative approach can be used to investigate possible topological superconductivity and exhibits a high application potential in electronic devices.
基金supported by the National Natural Science Foundation of China (12141002,52088101,11874417,11974389,and 52172216)the Ministry of Science and Technology of China (2021YFA0718702)+5 种基金the Chinese Academy of Sciences through the Strategic Priority Research Programthe Scientific Instrument Developing Programthe Project for Young Scientists in Basic Research (XDB33000000,YJKYYQ20200017,and YSBR-057)the Chinese Postdoctoral Science Foundation (E0BK181)the funding support of the National Key Research and Development Program of China (2018YFA0702100)the support from the Key Research Project of Zhejiang Laboratory (2021PE0AC02)。
基金the Ministry of Science and Technology of China(Grant Nos.2017YFA0303100,and 2015CB921303)the National Natural Science Foundation of China(Grant Nos.11774404,and11474332)the Chinese Academy of Sciences through the Strategic Priority Research Program(Grant No.XDB07020200)。
文摘The Seebeck effect encounters a few fundamental constraints hindering its thermoelectric(TE)conversion efficiency.Most notably,there are the charge compensation of electrons and holes that diminishes this effect,and the Wiedemann-Franz(WF)law that makes independent optimization of the corresponding electrical and thermal conductivities impossible.Here,we demonstrate that in the topological Dirac semimetal Cd3As2 the Nernst effect,i.e.,the transverse counterpart of the Seebeck effect,can generate a large TE figure of merit zNT.At room temperature,zNT≈0.5 in a small field of 2 T and it significantly surmounts its longitudinal counterpart for any field.A large Nernst effect is generically expected in topological semimetals,benefiting from both the bipolar transport of compensated electrons and holes and their high mobilities.In this case,heat and charge transport are orthogonal,i.e.,not intertwined by the WF law anymore.More importantly,further optimization of zNT by tuning the Fermi level to the Dirac node can be anticipated due to not only the enhanced bipolar transport,but also the anomalous Nernst effect arising from a pronounced Berry curvature.A combination of the topologically trivial and nontrivial advantages promises to open a new avenue towards high-efficient transverse thermoelectricity.
基金This work is supported by the National Natural Science Foundation of China(No.81802276 to Z.S.).
文摘Dear Editor,Although fusion events involving neurotrophic receptor tyrosine kinase 1,2,and 3 genes(NTRK1,NTRK2,and NTRK3,encoding TRKA/B/C respectively)were found in diverse tumor types,only 0.1%-0.3%of lung cancer patients harbor an NTRK(and mostly NTRK1)fusion as the primary oncogenic event[1].Such low prevalence may be partially due to the limited availability of first-line assays for detecting rare fusion events[2].Immunohistochemistry is limited by sensitivity and variable tissue background,and fluorescence in-situ hybridization falls short of elucidating functional significance such as the identity of the partner or structure of the transcript.While DNA next-generation sequencing(NGS)is suitable for mutation calling(single nucleotide variation[SNV]and insertion-or-deletion[indel]),and RNA NGS is particularly effective in detecting fusions[3],routinely performing these two assays together is labor-intensive.As a solution,we have developed a single NGS assay(PANO-Seq)for unified RNA/DNA target enrichment library preparation[4],which takes about 12 hours and $10 to prepare.
基金funded by the National Natural Science Foundation of China(Grant No.U19A2072)the Provincial Department of Education Postgraduate Scientific Research Innovation Project of Hunan Province of China(Grant No.QL20210007)the Ministerial Level Postgraduate Funding Project of China(Grant No.JY2021A007).
文摘Small tracking error correction for electro-optical systems is essential to improve the tracking precision of future mechanical and defense technology.Aerial threats,such as“low,slow,and small(LSS)”moving targets,pose increasing challenges to society.The core goal of this work is to address the issues,such as small tracking error correction and aiming control,of electro-optical detection systems by using mechatronics drive modeling,composite velocity–image stability control,and improved interpolation filter design.A tracking controller delay prediction method for moving targets is proposed based on the Euler transformation model of a two-axis,two-gimbal cantilever beam coaxial configuration.Small tracking error formation is analyzed in detail to reveal the scientific mechanism of composite control between the tracking controller’s feedback and the motor’s velocity–stability loop.An improved segmental interpolation filtering algorithm is established by combining line of sight(LOS)position correction and multivariable typical tracking fault diagnosis.Then,a platform with 2 degrees of freedom is used to test the system.An LSS moving target shooting object with a tracking distance of S=100 m,target board area of A=1 m^(2),and target linear velocity of v=5 m/s is simulated.Results show that the optimal method’s distribution probability of the tracking error in a circle with a radius of 1 mrad is 66.7%,and that of the traditional method is 41.6%.Compared with the LOS shooting accuracy of the traditional method,the LOS shooting accuracy of the optimized method is improved by 37.6%.
