A simple modification converts an electrospray ion source to an ambient-pressure helium plasma ionization source without the need of additional expensive hardware. Peaks for active ingredients were observed in the spe...A simple modification converts an electrospray ion source to an ambient-pressure helium plasma ionization source without the need of additional expensive hardware. Peaks for active ingredients were observed in the spectra recorded from intact pharmaceutical tablets placed in this source. A flow of heated nitrogen was used to thermally desorb analytes to gas phase. The desorption temperatures were sometimes as low as 50 ℃. For example, negative-ion spectra recorded from an aspirin tablet showed peaks at m/z 137 （salicylate anion） and 179 （acetylsalicylate anion） which were absent in the background spectra. The overall ion intensity increased as the desorption gas temperature was elevated. Within the same acquisition experiment, both positive- and negative-ion signals for acetaminophen were recorded from volatiles emanating from Tylenol tablets by switching the polarity of the capillary back and forth. Moreover, different preparations of acetaminophen tablets could be distinguished by their ion-intensity thermograms.展开更多
In the present study, olfactory ensheathing cells were transplanted into the cortices of infarcted （infarct transplantation group）, normal （normal transplantation group）, and bilateral hemispheres （bilateral tran...In the present study, olfactory ensheathing cells were transplanted into the cortices of infarcted （infarct transplantation group）, normal （normal transplantation group）, and bilateral hemispheres （bilateral transplantation group）. Olfactory ensheathing cells migrated to the infarct focus. The number of growth associated protein 43-positive cells and nerve fibers was slightly increased in the infarct area. These changes were more evident in the bilateral cortical transplantation group. Results demonstrated that transplanted olfactory ensheathing cells can migrate in rats with cerebra infarction. The olfactory ensheathing cells on the normal side can also promote neurological function. Bilateral cortical transplantation exhibited superior effects over unilateral transplantation.展开更多
This work focuses on an unmanned aerial vehicle(UAV)-enabled mobile edge computing(MEC) system based on device-to-device(D2D) communication. In this system, the UAV exhibits caching,computing and relaying capabilities...This work focuses on an unmanned aerial vehicle(UAV)-enabled mobile edge computing(MEC) system based on device-to-device(D2D) communication. In this system, the UAV exhibits caching,computing and relaying capabilities to periodically provide specific service to cellular users and D2D receiver nodes in the appointed time slot. Besides, the D2D transmitter can provide additional caching services to D2D receiver to reduce the pressure of the UAV. Note that communication between multi-type nodes is mutually restricted and different links share spectrum resources. To achieve an improved balance between different types of node, we aim to maximize the overall energy efficiency while satisfying the quality-of-service requirements of the cellular nodes.To address this problem, we propose an alternating iteration algorithm to jointly optimize the scheduling strategies of the user, transmitting power of the UAV and D2D-TX nodes, and UAV trajectory. The successive convex approximation, penalty function, and Dinkelbach method are employed to transform the original problem into a group of solvable subproblems and the convergence of the method is proved. Simulation results show that the proposed scheme performs better than other benchmark algorithms, particularly in terms of balancing the tradeoff between minimizing UAV energy consumption and maximizing throughput.展开更多
In the emerging sixth generation(6G)communication network,energy harvesting(EH)is a promising technology to achieve the unlimited energy supply and hence makes the wireless communication systems self-sustainable in te...In the emerging sixth generation(6G)communication network,energy harvesting(EH)is a promising technology to achieve the unlimited energy supply and hence makes the wireless communication systems self-sustainable in terms of energy.However,in practice,the efficiency of energy harvesting is often low due to the limited device capability.In this paper,we formulate three types of different EH architectures,i.e.,the harvest-use architecture,the harvest-store-use architecture,and the harvest-use-store architecture from the perspective of energy storage efficiency.We propose resource allocation schemes to jointly design the sensor power and duty-cycle via an alternating optimization algorithm under the above EH architectures,in both simultaneous and non-simultaneous harvesting and utilization models,aiming at achieving a higher throughput and energy efficiency.Non-ideal circuit power is also considered.Numerical results show that our proposed schemes under EH architectures outperform the existing classic continuous transmission schemes.展开更多
Geopolymers are an important class of materials with potential applications because of their heat resistance,flame resistance,environmental friendliness,and possibilities of being transformed into ceramic matrix compo...Geopolymers are an important class of materials with potential applications because of their heat resistance,flame resistance,environmental friendliness,and possibilities of being transformed into ceramic matrix composites at low cost.However,the low mechanical properties as well as the intrinsic brittleness limit their technological implementations,and it is necessary to enhance the mechanical properties of geopolymers by adopting various kinds of reinforcements.In this work,therefore,two⁃dimensional continuous carbon fiber(Cf)reinforced phosphate⁃based geopolymer composites(Cf/geopolymer)were prepared through ultrasonic⁃assisted impregnation method.Effects of acetone treatment and high⁃temperature treatment on the properties of Cf/geopolymer composites were studied by X⁃ray photoelectron spectroscopy(XPS),X⁃ray diffraction(XRD),and scanning electron microscopy(SEM).Results of the study proved that acetone treatment plays a key role in ameliorating the interfacial interaction between Cf and phosphate matrix,which can thus enhance the mechanical properties of Cf/geopolymer composites.The Cf/geopolymer composites prepared by acetone⁃treated Cf had a flexural strength of 156.1 MPa and an elastic modulus of 39.7 GPa in Y direction.Moreover,an additional Sol⁃SiO2 re⁃impregnation treatment could further enhance the mechanical properties of the acetone⁃treated Cf/geopolymer composites by repairing the cracks and filling the pores.The results in this paper not only provide insights into the surface modification of Cf,but also report a facile and low⁃cost preparation route for Cf/geopolymer composites with potential applications in aerospace and defense technology.展开更多
Background:Moxibustion is a traditional Chinese medicine therapy to cure diseases by fumigating meridians or affected parts via burning of moxa floss.Moxa smoke(MS)is one of the key factors in moxibustion.In this stud...Background:Moxibustion is a traditional Chinese medicine therapy to cure diseases by fumigating meridians or affected parts via burning of moxa floss.Moxa smoke(MS)is one of the key factors in moxibustion.In this study,we adopted digital gene expression profiling,a next-generation gene sequencing technology,to investigate the effect of MS,inhalable particulate matter(PM10),on human lung adenocarcinoma A549 cells.Methods:The effects of MS PM10 on A549 cells,over different treatment durations were investigated in different groups:the 4-h group(4-h MS group and 4-h control group)and the 20-h group(20-h MS group and 20-h control group).Samples collected from the four groups were stored at80C for subsequent digital gene expression analysis.The differentially expressed genes(DEGs),identified after PM10 treatment,were screened,and their expression patterns analyzed by cluster analysis,Gene Ontology term enrichment,and Kyoto Encyclopedia of Genes and Genomes pathway analysis.Results:Compared with two control groups,1109 DEGs were identified after 4 h of MS intervention and 3565 DEGs were found after 20 h of MS intervention,respectively.Compared with that after 4-h intervention,2149 DEGs were identified after 20-h intervention.Cluster analysis demonstrated that PM10 can significantly inhibit cell cycle process with the prolongation of intervention time.Significant pathway enrichment analysis showed that MS PM10 can inhibit A549 cell cycle process at all phases.When MS PM10 exposure time prolongs,the inhibitory effect on cell cycle process becomes more obvious.Conclusion:MS PM10 has many biological activities,and may cause differential expression of genes involved in various biological processes.Nevertheless,further research on MS is warranted for better understanding of the mechanistic details.展开更多
A novel composite ceramics with excellen mechanical and dielectric properties was fabricated by means of low temperature hot-pressing using mechanically alloyed SiBON powders as raw materials.The influences of SiO_2 c...A novel composite ceramics with excellen mechanical and dielectric properties was fabricated by means of low temperature hot-pressing using mechanically alloyed SiBON powders as raw materials.The influences of SiO_2 content on phase microstructure,mechanical and dielectric properties of the SiBON ceramics were investigated.展开更多
Here,we demonstrated a novel synthesis of a polyborosilazane(PBSN)precursor using hydroboration and aminolysis reaction synergies to modify polysilazane(PSN).Specifically,borane tetrahydrofuran and boron trichloride h...Here,we demonstrated a novel synthesis of a polyborosilazane(PBSN)precursor using hydroboration and aminolysis reaction synergies to modify polysilazane(PSN).Specifically,borane tetrahydrofuran and boron trichloride hexane were used as dual boron sources,which not only reacted展开更多
The fully dense amorphous Si-B-C-N monoliths were fabricated at 1000°-1600°C under5 GPa for 30 min where the mechanically alloyed amorphous Si-B-C-N powders were used as raw material.Crystallization and micr...The fully dense amorphous Si-B-C-N monoliths were fabricated at 1000°-1600°C under5 GPa for 30 min where the mechanically alloyed amorphous Si-B-C-N powders were used as raw material.Crystallization and microstructure evolution of the prepared ceramics were展开更多
Because of the excellent mechanical and dielectric properties,Si BN ceramic was regarded as one of the best comprehensive performance thermal-insulation and wave-transparent material.We prepared amorphous Si BN powder...Because of the excellent mechanical and dielectric properties,Si BN ceramic was regarded as one of the best comprehensive performance thermal-insulation and wave-transparent material.We prepared amorphous Si BN powders by mechanical alloying using amorphous nano-Si3N4and h-BN展开更多
The atomic structural features and the mechanical properties of amorphous silicoboron carbonitride ceramics with 13 different compositions in the Si–BN–C phase diagram are investigated employing ab-initio calculatio...The atomic structural features and the mechanical properties of amorphous silicoboron carbonitride ceramics with 13 different compositions in the Si–BN–C phase diagram are investigated employing ab-initio calculations.Both chemical bonds and local structures within the amorphous network relate to the elemental composition.The distribution of nine types of chemical bonds is composition-dependent,where the B–C,Si–N,Si–C,and B–N bonds hold a large proportion for all compositions.Si prefers to be tetrahedrally coordinated,while B and N prefer sp^(2)-like trigonal coordination.In the case of C,the tetrahedral coordination is predominant at relatively low C contents,while the trigonal coordination is found to be the main feature with the increasing C content.Such local structural characteristics greatly influence the mechanical properties of SiBCN ceramics.Among the studied amorphous ceramics,SiB_(2)C_(3)N_(2) and SiB_(3)C_(2)N_(3) with low Si contents and moderate C and/or BN contents have high elastic moduli,high tensile/shear strengths,and good debonding capability.The increment of Si,C,and BN contents on this basis results in the decrease of mechanical properties.The increasing Si content leads to the increment of Si-contained bonds that reduce the bond strength of SiBCN ceramics,while the latter two cases are attributed to the raise of sp^(2)-like trigonal configuration of C and BN.These discoveries are expected to guide the composition-tailored optimization of SiBCN ceramics.展开更多
The atomic structural features and the mechanical properties of the Si_(2)BC_(3)N are investigated employ-ing ab-initio calculations.The chemical bonding types and their proportion are clarified.The tetrahedral and tr...The atomic structural features and the mechanical properties of the Si_(2)BC_(3)N are investigated employ-ing ab-initio calculations.The chemical bonding types and their proportion are clarified.The tetrahedral and trigonal configurations,together with their nesting,are identified,which contribute to the flexibil-ity of structural characteristics.The Si-related coordination aggravates the inhomogeneous distribution of chemical bonding and weakens the tetrahedral units.The accompanying polyhedral distortion is quanti-tatively reflected by the bond length and its deviation of polyhedron units.The elastic moduli and the ideal strengths of Si_(2)BC_(3)N are found to be lower than SiC and Si_(3)N_(4),as a result of the weakening effect of coordination Si on tetrahedral units and the existence of easily distorted trigona.The balance between tetrahedral and trigonal features through composition tailor is believed an effective way for the design of Si-B-C-N ceramics for structural applications.展开更多
Infrared(IR)birefringent materials with large optical anisotropy and wide transparency range are important for efficient light manipulation in various IR optical devices.Herein,two new IR birefringent materials AMgGeS...Infrared(IR)birefringent materials with large optical anisotropy and wide transparency range are important for efficient light manipulation in various IR optical devices.Herein,two new IR birefringent materials AMgGeSe_(3)(A=Li,Na)with large optical anisotropy were rationally designed by a rigid octahedron and flexible dimer combined strategy and fabricated in experiment.The introduction of rigid[LiSe_(6)]/[NaSe_(6)]and[MgSe_(6)]octahedra effectively regulates the geometry and arrangement of the flexible[Ge2Se6]dimers,resulting in the birefringence as large as 0.334@1,064 nm in LiMgGeSe_(3) and 0.445@1,064 nm(the largest one in the reported[Ge_(2)Se_(6)]dimer-contained selenides)in NaMgGeSe_(3).Density functional theory(DFT)calculations and statistical analyses highlight the influence of polarizability anisotropy,density,arrangement of units,as well as layer distance on birefringence.The results indicate that AMgGeSe_(3)(A=Li,Na)crystals are the promising IR birefringent materials and it gives an insight into the exploration of new IR birefringent materials with large birefringence based on the clamping effect from rigid groups.展开更多
Fluorooxoborate has emerged as a promising system for exploring optical materials due to their rich structural chemistry and physicochemical properties,yet so far not fully studied.Herein,we report a new fluorooxobora...Fluorooxoborate has emerged as a promising system for exploring optical materials due to their rich structural chemistry and physicochemical properties,yet so far not fully studied.Herein,we report a new fluorooxoborate,Ba_(2)B_(9)O_(13)F_(4)·BF_(4),which contains the greatest variety of structural basic units,[BO_(3)],[BO_(2)F_(2)],[BO_(3)F],and[BF_(4)],and exhibits unprecedented 1D infinite[B_(18)O_(26)F_(8)]tubes.The unique structure avoids the dangling bonds caused by terminal oxygens,which is beneficial to the large bandgap and deep-ultraviolet cutoff edge.This article expands the crystal structure of fluorooxoborates and contributes to the exploration of deep-ultraviolet optical materials in fluorooxoborate systems.展开更多
Multi-floor buildings for raising pigs have recently attracted widespread attention as an emerging form of intensive livestock production especially in eastern China,due to the fact that they can feed a much larger nu...Multi-floor buildings for raising pigs have recently attracted widespread attention as an emerging form of intensive livestock production especially in eastern China,due to the fact that they can feed a much larger number of animals per unit area of land and thus alleviate the shortage of land available for standard single-floor pig production facilities.However,this more intensive kind of pig building will pose new challenges to the local environment in terms of pollutant dispersion.To compare the dispersion air pollutants(ammonia as a representative)emitted from multi-versus single-floor pig buildings,ammonia dispersion distance and concentration gradients were investigated through three-dimensional simulations based on computational fluid dynamics.The validation of an isolated cubic model was made to ensure the simulation method was effective.The effects of wind direction,wind speed and emission source concentration at 1.5 m(approximate human inhalation height)during summer were investigated.The results showed that the ammonia dispersion distance of the multi-floor pig building was far greater than that of the single-floor building on a plane of Z=1.5 m.When the wind direction was 67.5°,the wind speed was 2 m·s^(−1) and the emission source concentration was 20 ppmv,the dispersion distance of the multi-floor pig building could reach 1380 m.Meanwhile,the ammonia could accumulate in the yard to 7.68 ppmv.Therefore,future site selection,wind speed and source concentration need to be given serious consideration.Based on the simulation used in this study with source concentration is 20 ppmv,the multi-floor pig buildings should be located 1.4 km away from residential areas to avoid affecting residents.The results of this study should guidance for any future development of multi-floor pig buildings.展开更多
The design of new materials with special performances is still a great challenge,especially for the deep-ultraviolet nonlinear optical materials in which it is difficult to balance large bandgaps and strong second har...The design of new materials with special performances is still a great challenge,especially for the deep-ultraviolet nonlinear optical materials in which it is difficult to balance large bandgaps and strong second harmonic generation responses due to their inverse relationship.Cation variation not only influences the whole structure frameworks but also directly participates in the formation of electronic structures,both of which could lead to the uncontrollability of the properties of the designed materials.Here,a novel approach,aiming at purposeful and foreseeable material designs,is proposed to characterize the role of cations.By the verification of several series of borates,the influences of cation variation on property changes are explored systematically.Accordingly,a feasible strategy of designing deep-ultraviolet nonlinear optical materials by substituting barium for lead has been concluded,which could obviously blue-shift the ultraviolet cutoff edge and maintain the relatively strong second harmonic generation response(more than 2 times of KH2PO4),achieving the property optimization,and especially works efficiently in fluorooxoborates.The property optimization design strategy and the cation characterization method are not only helpful in exploring nonlinear optical materials but also enlightening in material design and selection.展开更多
基金supported by the Project SEED Summer Research Program of the American Chemical Society
文摘A simple modification converts an electrospray ion source to an ambient-pressure helium plasma ionization source without the need of additional expensive hardware. Peaks for active ingredients were observed in the spectra recorded from intact pharmaceutical tablets placed in this source. A flow of heated nitrogen was used to thermally desorb analytes to gas phase. The desorption temperatures were sometimes as low as 50 ℃. For example, negative-ion spectra recorded from an aspirin tablet showed peaks at m/z 137 （salicylate anion） and 179 （acetylsalicylate anion） which were absent in the background spectra. The overall ion intensity increased as the desorption gas temperature was elevated. Within the same acquisition experiment, both positive- and negative-ion signals for acetaminophen were recorded from volatiles emanating from Tylenol tablets by switching the polarity of the capillary back and forth. Moreover, different preparations of acetaminophen tablets could be distinguished by their ion-intensity thermograms.
基金the National Natural Science Foundation of China,No.39700048, 30271378a grant from Education Bureau of Guangzhou,No.61092a grant from Science and Technology Department of Guangdong Province,No. 2009B030801354
文摘In the present study, olfactory ensheathing cells were transplanted into the cortices of infarcted （infarct transplantation group）, normal （normal transplantation group）, and bilateral hemispheres （bilateral transplantation group）. Olfactory ensheathing cells migrated to the infarct focus. The number of growth associated protein 43-positive cells and nerve fibers was slightly increased in the infarct area. These changes were more evident in the bilateral cortical transplantation group. Results demonstrated that transplanted olfactory ensheathing cells can migrate in rats with cerebra infarction. The olfactory ensheathing cells on the normal side can also promote neurological function. Bilateral cortical transplantation exhibited superior effects over unilateral transplantation.
基金the supports from the National Natural Science Foundation of China (61571156)Basic Research Project of Shenzhen (JCYJ20170413110004682 and JCYJ20150403161923521)。
文摘This work focuses on an unmanned aerial vehicle(UAV)-enabled mobile edge computing(MEC) system based on device-to-device(D2D) communication. In this system, the UAV exhibits caching,computing and relaying capabilities to periodically provide specific service to cellular users and D2D receiver nodes in the appointed time slot. Besides, the D2D transmitter can provide additional caching services to D2D receiver to reduce the pressure of the UAV. Note that communication between multi-type nodes is mutually restricted and different links share spectrum resources. To achieve an improved balance between different types of node, we aim to maximize the overall energy efficiency while satisfying the quality-of-service requirements of the cellular nodes.To address this problem, we propose an alternating iteration algorithm to jointly optimize the scheduling strategies of the user, transmitting power of the UAV and D2D-TX nodes, and UAV trajectory. The successive convex approximation, penalty function, and Dinkelbach method are employed to transform the original problem into a group of solvable subproblems and the convergence of the method is proved. Simulation results show that the proposed scheme performs better than other benchmark algorithms, particularly in terms of balancing the tradeoff between minimizing UAV energy consumption and maximizing throughput.
基金This work was supported in part by the National Natural Science Foundation of China under Grants 61801145,61972113,61901138,and 61871426in part by the Shenzhen Science and Technology Program under Grants JCYJ20180306171800589,JCYJ20190806112215116,and KQTD 20190929172545139+2 种基金in part by the Natural Science Foundation of Guangdong Province under Grant 2018A030313298in part by the Guangdong Science and Technology Planning Project under Grant 2018B030322004in part by the Natural Scientific Research Innovation Foundation in Harbin Institute of Technology under Grant HIT.NSRIF.2020076.
文摘In the emerging sixth generation(6G)communication network,energy harvesting(EH)is a promising technology to achieve the unlimited energy supply and hence makes the wireless communication systems self-sustainable in terms of energy.However,in practice,the efficiency of energy harvesting is often low due to the limited device capability.In this paper,we formulate three types of different EH architectures,i.e.,the harvest-use architecture,the harvest-store-use architecture,and the harvest-use-store architecture from the perspective of energy storage efficiency.We propose resource allocation schemes to jointly design the sensor power and duty-cycle via an alternating optimization algorithm under the above EH architectures,in both simultaneous and non-simultaneous harvesting and utilization models,aiming at achieving a higher throughput and energy efficiency.Non-ideal circuit power is also considered.Numerical results show that our proposed schemes under EH architectures outperform the existing classic continuous transmission schemes.
基金National Natural Science Foundation of China(Grant Nos.51872063,51832002 and 51621091)the Natural Science Foundation of Heilongjiang Province(Grant No.YQ2019E002)the National Key Research and Development Program of China(Grant No.2017YFB0703200)。
文摘Geopolymers are an important class of materials with potential applications because of their heat resistance,flame resistance,environmental friendliness,and possibilities of being transformed into ceramic matrix composites at low cost.However,the low mechanical properties as well as the intrinsic brittleness limit their technological implementations,and it is necessary to enhance the mechanical properties of geopolymers by adopting various kinds of reinforcements.In this work,therefore,two⁃dimensional continuous carbon fiber(Cf)reinforced phosphate⁃based geopolymer composites(Cf/geopolymer)were prepared through ultrasonic⁃assisted impregnation method.Effects of acetone treatment and high⁃temperature treatment on the properties of Cf/geopolymer composites were studied by X⁃ray photoelectron spectroscopy(XPS),X⁃ray diffraction(XRD),and scanning electron microscopy(SEM).Results of the study proved that acetone treatment plays a key role in ameliorating the interfacial interaction between Cf and phosphate matrix,which can thus enhance the mechanical properties of Cf/geopolymer composites.The Cf/geopolymer composites prepared by acetone⁃treated Cf had a flexural strength of 156.1 MPa and an elastic modulus of 39.7 GPa in Y direction.Moreover,an additional Sol⁃SiO2 re⁃impregnation treatment could further enhance the mechanical properties of the acetone⁃treated Cf/geopolymer composites by repairing the cracks and filling the pores.The results in this paper not only provide insights into the surface modification of Cf,but also report a facile and low⁃cost preparation route for Cf/geopolymer composites with potential applications in aerospace and defense technology.
基金This work was supported by the National Natural Science Foundation of China(81574068).
文摘Background:Moxibustion is a traditional Chinese medicine therapy to cure diseases by fumigating meridians or affected parts via burning of moxa floss.Moxa smoke(MS)is one of the key factors in moxibustion.In this study,we adopted digital gene expression profiling,a next-generation gene sequencing technology,to investigate the effect of MS,inhalable particulate matter(PM10),on human lung adenocarcinoma A549 cells.Methods:The effects of MS PM10 on A549 cells,over different treatment durations were investigated in different groups:the 4-h group(4-h MS group and 4-h control group)and the 20-h group(20-h MS group and 20-h control group).Samples collected from the four groups were stored at80C for subsequent digital gene expression analysis.The differentially expressed genes(DEGs),identified after PM10 treatment,were screened,and their expression patterns analyzed by cluster analysis,Gene Ontology term enrichment,and Kyoto Encyclopedia of Genes and Genomes pathway analysis.Results:Compared with two control groups,1109 DEGs were identified after 4 h of MS intervention and 3565 DEGs were found after 20 h of MS intervention,respectively.Compared with that after 4-h intervention,2149 DEGs were identified after 20-h intervention.Cluster analysis demonstrated that PM10 can significantly inhibit cell cycle process with the prolongation of intervention time.Significant pathway enrichment analysis showed that MS PM10 can inhibit A549 cell cycle process at all phases.When MS PM10 exposure time prolongs,the inhibitory effect on cell cycle process becomes more obvious.Conclusion:MS PM10 has many biological activities,and may cause differential expression of genes involved in various biological processes.Nevertheless,further research on MS is warranted for better understanding of the mechanistic details.
文摘A novel composite ceramics with excellen mechanical and dielectric properties was fabricated by means of low temperature hot-pressing using mechanically alloyed SiBON powders as raw materials.The influences of SiO_2 content on phase microstructure,mechanical and dielectric properties of the SiBON ceramics were investigated.
文摘Here,we demonstrated a novel synthesis of a polyborosilazane(PBSN)precursor using hydroboration and aminolysis reaction synergies to modify polysilazane(PSN).Specifically,borane tetrahydrofuran and boron trichloride hexane were used as dual boron sources,which not only reacted
文摘The fully dense amorphous Si-B-C-N monoliths were fabricated at 1000°-1600°C under5 GPa for 30 min where the mechanically alloyed amorphous Si-B-C-N powders were used as raw material.Crystallization and microstructure evolution of the prepared ceramics were
文摘Because of the excellent mechanical and dielectric properties,Si BN ceramic was regarded as one of the best comprehensive performance thermal-insulation and wave-transparent material.We prepared amorphous Si BN powders by mechanical alloying using amorphous nano-Si3N4and h-BN
基金supported by the Natural Science Foundation of Xinjiang (2023D01E17)the National Natural Science Foundation of China (22335007)+2 种基金Tianshan Talents-Young Science and Technology Top Talents Project (2022TSYCCX0078 and 2022TSYCTD0005)Xinjiang Major Science and Technology Project (2021A01001 and2022A01005-5)the Key Research Program of Frontier Sciences,CAS(ZDBS-LY-SLH035)。
基金supported by the National Natural Science Foundation of China(Nos.52002092,51832002,and 52172071)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning(No.GZ2020012)+1 种基金Heilongjiang Natural Science Fund for Young Scholars(No.YQ2021E017)the Heilongjiang Touyan Innovation Team Program.Ralf Riedel thanks the German Science Foundation(DFG,Bonn,Germany)for financial support within the graduate school GRK 2561.
文摘The atomic structural features and the mechanical properties of amorphous silicoboron carbonitride ceramics with 13 different compositions in the Si–BN–C phase diagram are investigated employing ab-initio calculations.Both chemical bonds and local structures within the amorphous network relate to the elemental composition.The distribution of nine types of chemical bonds is composition-dependent,where the B–C,Si–N,Si–C,and B–N bonds hold a large proportion for all compositions.Si prefers to be tetrahedrally coordinated,while B and N prefer sp^(2)-like trigonal coordination.In the case of C,the tetrahedral coordination is predominant at relatively low C contents,while the trigonal coordination is found to be the main feature with the increasing C content.Such local structural characteristics greatly influence the mechanical properties of SiBCN ceramics.Among the studied amorphous ceramics,SiB_(2)C_(3)N_(2) and SiB_(3)C_(2)N_(3) with low Si contents and moderate C and/or BN contents have high elastic moduli,high tensile/shear strengths,and good debonding capability.The increment of Si,C,and BN contents on this basis results in the decrease of mechanical properties.The increasing Si content leads to the increment of Si-contained bonds that reduce the bond strength of SiBCN ceramics,while the latter two cases are attributed to the raise of sp^(2)-like trigonal configuration of C and BN.These discoveries are expected to guide the composition-tailored optimization of SiBCN ceramics.
基金supported by the Key Laboratory Opening Foundation of Xinjiang Uygur Autonomous Region (2022D04013)the High-level Talent Project of Xinjiang Uygur Autonomous Region (2022D000039)+5 种基金the West Light Foundation of the Chinese Academy of Sciences (2019-YDYLTD-002)the National Natural Science Foundation of China (61835014 and 51972336)Xinjiang Major Science and Technology Project (2021A01001)the International Partnership Program of CAS (1A1365KYSB20200008)the Instrument Developing Project of CAS (GJJSTD20200007)the Science and Technology Service Network Initiative of CAS (KFJ-STS-QYZD-130).
基金This work was financially supported by the National Natu-ral Science Foundation of China(Nos.52002092,51832002,and 52172071)the Program for Professor of Special Appointment(East-ern Scholar)at Shanghai Institutions of Higher Learning(No.GZ2020012)+1 种基金Key Research Project of Zhejiang Laboratory(No.2021PE0AC02)Heilong Jiang Natural Science Fund for Young Scholars(No.YQ2021E017)。
文摘The atomic structural features and the mechanical properties of the Si_(2)BC_(3)N are investigated employ-ing ab-initio calculations.The chemical bonding types and their proportion are clarified.The tetrahedral and trigonal configurations,together with their nesting,are identified,which contribute to the flexibil-ity of structural characteristics.The Si-related coordination aggravates the inhomogeneous distribution of chemical bonding and weakens the tetrahedral units.The accompanying polyhedral distortion is quanti-tatively reflected by the bond length and its deviation of polyhedron units.The elastic moduli and the ideal strengths of Si_(2)BC_(3)N are found to be lower than SiC and Si_(3)N_(4),as a result of the weakening effect of coordination Si on tetrahedral units and the existence of easily distorted trigona.The balance between tetrahedral and trigonal features through composition tailor is believed an effective way for the design of Si-B-C-N ceramics for structural applications.
基金supported by the High-level Talent Project of Xinjiang Uygur Autonomous Region(2020000039)the National Natural Science Foundation of China(52002398,61835014,51972336)the Xinjiang Key Laboratory of Electronic Information Materials and Devices(2017D04029)。
文摘Infrared(IR)birefringent materials with large optical anisotropy and wide transparency range are important for efficient light manipulation in various IR optical devices.Herein,two new IR birefringent materials AMgGeSe_(3)(A=Li,Na)with large optical anisotropy were rationally designed by a rigid octahedron and flexible dimer combined strategy and fabricated in experiment.The introduction of rigid[LiSe_(6)]/[NaSe_(6)]and[MgSe_(6)]octahedra effectively regulates the geometry and arrangement of the flexible[Ge2Se6]dimers,resulting in the birefringence as large as 0.334@1,064 nm in LiMgGeSe_(3) and 0.445@1,064 nm(the largest one in the reported[Ge_(2)Se_(6)]dimer-contained selenides)in NaMgGeSe_(3).Density functional theory(DFT)calculations and statistical analyses highlight the influence of polarizability anisotropy,density,arrangement of units,as well as layer distance on birefringence.The results indicate that AMgGeSe_(3)(A=Li,Na)crystals are the promising IR birefringent materials and it gives an insight into the exploration of new IR birefringent materials with large birefringence based on the clamping effect from rigid groups.
基金financially supported by the National Natural Science Foundation of China(52002092,52172068,52232004)Heilongjiang Natural Science Fund for Young Scholars(YQ2021E017)+1 种基金Heilongjiang Touyan Team Program and Advanced Talents Scientific Research Foundation of Shenzhenthe financial support provided by the Research Training Group GRK 2561“Mat ComCom Mat:Materials Compounds from Composite Materials for Applications in Extreme Conditions”funded by the Deutsche Forschungsgemeinschaft(DFG),Bonn,Germany。
基金supported by the National Key Research Project of China(2022YFE0134500)the National Natural Science Foundation of China(61922084,61835014)+4 种基金the West Light Foundation of Chinese Academy of Sciences(2019-YDYLTD-002)the Instrument Developing Project of Chinese Academy of Sciences(GJJSTD20200007)the Xinjiang Major Science and Technology Project(2021A01001)the International Partnership Program of Chinese Academy of Sciences(1A1365KYSB20200008)the Science and Technology Service Network Initiative of Chinese Academy of Sciences(KFJ-STS-QYZD-130)。
文摘Fluorooxoborate has emerged as a promising system for exploring optical materials due to their rich structural chemistry and physicochemical properties,yet so far not fully studied.Herein,we report a new fluorooxoborate,Ba_(2)B_(9)O_(13)F_(4)·BF_(4),which contains the greatest variety of structural basic units,[BO_(3)],[BO_(2)F_(2)],[BO_(3)F],and[BF_(4)],and exhibits unprecedented 1D infinite[B_(18)O_(26)F_(8)]tubes.The unique structure avoids the dangling bonds caused by terminal oxygens,which is beneficial to the large bandgap and deep-ultraviolet cutoff edge.This article expands the crystal structure of fluorooxoborates and contributes to the exploration of deep-ultraviolet optical materials in fluorooxoborate systems.
基金supported by the National Key R&D Program of China(2022YFE0115600)the Key Research and Development Program of Zhejiang Province(2022C02045).
文摘Multi-floor buildings for raising pigs have recently attracted widespread attention as an emerging form of intensive livestock production especially in eastern China,due to the fact that they can feed a much larger number of animals per unit area of land and thus alleviate the shortage of land available for standard single-floor pig production facilities.However,this more intensive kind of pig building will pose new challenges to the local environment in terms of pollutant dispersion.To compare the dispersion air pollutants(ammonia as a representative)emitted from multi-versus single-floor pig buildings,ammonia dispersion distance and concentration gradients were investigated through three-dimensional simulations based on computational fluid dynamics.The validation of an isolated cubic model was made to ensure the simulation method was effective.The effects of wind direction,wind speed and emission source concentration at 1.5 m(approximate human inhalation height)during summer were investigated.The results showed that the ammonia dispersion distance of the multi-floor pig building was far greater than that of the single-floor building on a plane of Z=1.5 m.When the wind direction was 67.5°,the wind speed was 2 m·s^(−1) and the emission source concentration was 20 ppmv,the dispersion distance of the multi-floor pig building could reach 1380 m.Meanwhile,the ammonia could accumulate in the yard to 7.68 ppmv.Therefore,future site selection,wind speed and source concentration need to be given serious consideration.Based on the simulation used in this study with source concentration is 20 ppmv,the multi-floor pig buildings should be located 1.4 km away from residential areas to avoid affecting residents.The results of this study should guidance for any future development of multi-floor pig buildings.
基金Key Research Program of Frontier Sciences,CAS(ZDBS-LY-SLH035)the National Natural Science Foundation of China(22193044)+4 种基金National Key R&D Program of China(2021YFB3601502)Natural Science Foundation of Xinjiang(2021D01E05)Xinjiang Major Science and Technology Project(2021A01001)the International Partnership Program of CAS(1A1365KYSB20200008)CAS Project for Young Scientists in Basic Research(YSBR-024)。
文摘The design of new materials with special performances is still a great challenge,especially for the deep-ultraviolet nonlinear optical materials in which it is difficult to balance large bandgaps and strong second harmonic generation responses due to their inverse relationship.Cation variation not only influences the whole structure frameworks but also directly participates in the formation of electronic structures,both of which could lead to the uncontrollability of the properties of the designed materials.Here,a novel approach,aiming at purposeful and foreseeable material designs,is proposed to characterize the role of cations.By the verification of several series of borates,the influences of cation variation on property changes are explored systematically.Accordingly,a feasible strategy of designing deep-ultraviolet nonlinear optical materials by substituting barium for lead has been concluded,which could obviously blue-shift the ultraviolet cutoff edge and maintain the relatively strong second harmonic generation response(more than 2 times of KH2PO4),achieving the property optimization,and especially works efficiently in fluorooxoborates.The property optimization design strategy and the cation characterization method are not only helpful in exploring nonlinear optical materials but also enlightening in material design and selection.
