Two new complexes,[Zn_(2)(L1)(HL1)(NO_(3))]·CH_(3)OH(1)and[Zn_(3)(L2)(L3)_(3)Cl]·CH_(3)OH(2),were successfully synthesized by‘one-pot’method based on cinnoline-3-ylhydrazine ligand and zinc with 2-hydroxy-...Two new complexes,[Zn_(2)(L1)(HL1)(NO_(3))]·CH_(3)OH(1)and[Zn_(3)(L2)(L3)_(3)Cl]·CH_(3)OH(2),were successfully synthesized by‘one-pot’method based on cinnoline-3-ylhydrazine ligand and zinc with 2-hydroxy-4-methoxybenzaldehyde and 2-hydroxy-3-methoxybenzaldehyde ligands,respectively,where H_(2)L1=5-methoxy-2-(phthalazin-1-ylhydrazonomethyl)-phenol,H_(2)L2=2-methoxy-6-(phthalazin-1-yl-hydrazonomethyl)-phenol,HL3=2-(1,8-dihydro-[1,2,4]triazolo[3,4-α]phthalazin-3-yl)-6-methoxy-phenol.Complexes 1 and 2 were characterized by infrared spectroscopy,elemental analysis,single-crystal X-ray diffraction,powder X-ray diffraction,etc.It is worth noting that the cinnolin-3-yl-hydrazine ligand and 2-hydroxy-3-methoxybenzaldehyde form two types of Schiff bases(H_(2)L2 and HL3)when in situ reacting and coordinating with Zn(Ⅱ),and HL3 also has two coordination modes.In addition,the fluorescence performance showed that complex 1 can achieve selective and sensitive sensing of Al^(3+)in water with a detection limit of 6.37μmol·L^(-1).CCDC:2413978,1;2413979,2.展开更多
This paper delves into the theoretical mechanisms of the electronic structure and optical properties of aluminum-based semiconductors(AlX,X=N,P,As,Sb)and indium-based semiconductors(InX,X=N,P,As,Sb)as potential materi...This paper delves into the theoretical mechanisms of the electronic structure and optical properties of aluminum-based semiconductors(AlX,X=N,P,As,Sb)and indium-based semiconductors(InX,X=N,P,As,Sb)as potential materials for optical devices.Band structure calculations reveal that,except for InSb,all other compounds are direct bandgap semiconductors,with AlN exhibiting a bandgap of 3.245 eV.The valence band maximum of these eight compounds primarily stems from the p-orbitals of Al/In and X.In contrast,the conduction band minimum is influenced by all orbitals,with a predominant contribution from the p-orbitals.The static dielectric constant increased with the expansion of the unit cell volume.Compared to AlX and InX with larger X atoms,AlN and InN showed broader absorption spectra in the near-ultraviolet region and higher photoelectric conductance.Regarding mechanical properties,AlN and InN displayed greater shear and bulk modulus than the other compounds.Moreover,among these eight crystal types,a higher modulus was associated with a lower light loss function value,indicating that AlN and InN have superior transmission efficiency and a wider spectral range in optoelectronic material applications.展开更多
Because of an unfortunate mistake by authors,the Project(5227010679)of Foundation item was wrong.The corrected Project is shown as follows:Project(52271073).
Two new dinuclear lanthanidecomplexes,namely[Ln_(2)(dbm)_(2)(HL)_(2)(CH_(3)OH)_(2)]·4CH_(3)OH[Ln=Tb(1)and Dy(2),Hdbm=dibenzoylmethane]have been synthesized using prepared multidentate Schiff base ligand H_(3)L(hy...Two new dinuclear lanthanidecomplexes,namely[Ln_(2)(dbm)_(2)(HL)_(2)(CH_(3)OH)_(2)]·4CH_(3)OH[Ln=Tb(1)and Dy(2),Hdbm=dibenzoylmethane]have been synthesized using prepared multidentate Schiff base ligand H_(3)L(hydroxy‑acetic acid(4‑diethylamino‑2‑hydroxy‑benzylidene)‑hydrazide)with good biological activity.Structure characterizations show that the complex comprises two Ln3+ions,two dbm-ions,two HL^(2-)ligands,two CH_(3)OH molecules,and four free methanol molecules.Each Ln^(3+)ion is eight‑coordinated.The two central Lnions are bridged by twoμ_(2)‑O atoms leading to a parallelogram[Ln2O2]core.The interaction between the compounds(H_(3)L,1,and 2)and the calf thymus DNA(CT‑DNA)has been further confirmed by UV‑Vis spectrometry,fluorescence titration,and cyclic voltammetry.The results showed that both 1 and 2 could undergo insertion with CT‑DNA.CCDC:2343005,1;2343006,2.展开更多
The advent of gene editing represents one of the most transformative breakthroughs in life science,making genome manipulation more accessible than ever before.While traditional CRISPR/Cas-based gene editing,which invo...The advent of gene editing represents one of the most transformative breakthroughs in life science,making genome manipulation more accessible than ever before.While traditional CRISPR/Cas-based gene editing,which involves double-strand DNA breaks(DSBs),excels at gene disruption,it is less effective for accurate gene modification.The limitation arises because DSBs are primarily repaired via non-homologous end joining(NHEJ),which tends to introduce indels at the break site.While homology directed repair(HDR)can achieve precise editing when a donor DNA template is provided,the reliance on DSBs often results in unintended genome damage.HDR is restricted to specific cell cycle phases,limiting its application.Currently,gene editing has evolved to unprecedented levels of precision without relying on DSB and HDR.The development of innovative systems,such as base editing,prime editing,and CRISPR-associated transposases(CASTs),now allow for precise editing ranging from single nucleotides to large DNA fragments.Base editors(BEs)enable the direct conversion of one nucleotide to another,and prime editors(PEs)further expand gene editing capabilities by allowing for the insertion,deletion,or alteration of small DNA fragments.The CAST system,a recent innovation,allows for the precise insertion of large DNA fragments at specific genomic locations.In recent years,the optimization of these precise gene editing tools has led to significant improvements in editing efficiency,specificity,and versatility,with advancements such as the creation of base editors for nucleotide transversions,enhanced prime editing systems for more efficient and precise modifications,and refined CAST systems for targeted large DNA insertions,expanding the range of applications for these tools.Concurrently,these advances are complemented by significant improvements in in vivo delivery methods,which have paved the way for therapeutic application of precise gene editing tools.Effective delivery systems are critical for the success of gene therapies,and recent developments in both viral and non-viral vectors have improved the efficiency and safety of gene editing.For instance,adeno-associated viruses(AAVs)are widely used due to their high transfection efficiency and low immunogenicity,though challenges such as limited cargo capacity and potential for immune responses remain.Non-viral delivery systems,including lipid nanoparticles(LNPs),offer an alternative with lower immunogenicity and higher payload capacity,although their transfection efficiency can be lower.The therapeutic potential of these precise gene editing technologies is vast,particularly in treating genetic disorders.Preclinical studies have demonstrated the effectiveness of base editing in correcting genetic mutations responsible for diseases such as cardiomyopathy,liver disease,and hereditary hearing loss.These technologies promise to treat symptoms and potentially cure the underlying genetic causes of these conditions.Meanwhile,challenges remain,such as optimizing the safety and specificity of gene editing tools,improving delivery systems,and overcoming off-target effects,all of which are critical for their successful application in clinical settings.In summary,the continuous evolution of precise gene editing technologies,combined with advancements in delivery systems,is driving the field toward new therapeutic applications that can potentially transform the treatment of genetic disorders by targeting their root causes.展开更多
Flow based Erosion e corrosion problems are very common in fluid handling equipments such as propellers, impellers, pumps in warships, submarine. Though there are many coating materials available to combat erosionecor...Flow based Erosion e corrosion problems are very common in fluid handling equipments such as propellers, impellers, pumps in warships, submarine. Though there are many coating materials available to combat erosionecorrosion damage in the above components, iron based amorphous coatings are considered to be more effective to combat erosionecorrosion problems. High velocity oxy-fuel(HVOF)spray process is considered to be a better process to coat the iron based amorphous powders. In this investigation, iron based amorphous metallic coating was developed on 316 stainless steel substrate using HVOF spray technique. Empirical relationships were developed to predict the porosity and micro hardness of iron based amorphous coating incorporating HVOF spray parameters such as oxygen flow rate, fuel flow rate, powder feed rate, carrier gas flow rate, and spray distance. Response surface methodology(RSM) was used to identify the optimal HVOF spray parameters to attain coating with minimum porosity and maximum hardness.展开更多
Determining the number of components is a crucial issue in a mixture model. A moment-based criterion is considered to estimate the number of components arising from a normal mixture model. This criterion is derived fr...Determining the number of components is a crucial issue in a mixture model. A moment-based criterion is considered to estimate the number of components arising from a normal mixture model. This criterion is derived from an omnibus statistic involving the skewness and kurtosis of each component. The proposed criterion additionally provides a measurement for the model fit in an absolute sense. The performances of our criterion are satisfactory compared with other classical criteria through Monte-Carlo experiments.展开更多
Ongoing research is described that is focused upon modelling the space base information network and simulating its behaviours： simulation of spaced based communications and networking project. Its objective is to dem...Ongoing research is described that is focused upon modelling the space base information network and simulating its behaviours： simulation of spaced based communications and networking project. Its objective is to demonstrate the feasibility of producing a tool that can provide a performance evaluation of various eonstellation access techniques and routing policies. The architecture and design of the simulation system are explored. The algorithm of data routing and instrument scheduling in this project is described. Besides these, the key methodologies of simulating the inter-satellite link features in the data transmissions are also discussed. The performance of both instrument scheduling algorithm and routing schemes is evaluated and analyzed through extensive simulations under a typical scenario.展开更多
The frequent occurrence of safety accidents during the calendering process is caused by the flammable and explosive properties of composite modified double-base(CMDB)propellant.Optimization of process parameters with ...The frequent occurrence of safety accidents during the calendering process is caused by the flammable and explosive properties of composite modified double-base(CMDB)propellant.Optimization of process parameters with the aid of fluid simulation technology could effectively ensure the safety of the calendering process.To improve the accuracy of the simulation results,material parameters and model structure were corrected based on actual conditions,and adaptive grid technology was applied in the local mesh refinement.In addition,the rheological behavior,motion trajectories and heat transfer mechanisms of CMDB propellant slurry were studied with different gaps,rotational rates and temperatures of two rollers.The results indicated that the refined mesh could significantly improve the contour clarity of boundaries and simulate the characteristics of CMDB propellant slurry reflux movement caused by the convergent flow near the outlet.Compared with the gap,the increased rotational rate of roller could promote the reflux movement and intensify the shear flow of slurry inside the flow region by viscous shear dragging.Meanwhile,under the synergistic effect of contact heat transfer as well as convective heat exchange,heat accumulated near the outlet and diffused along the reflux movement,which led to the countercurrent heat dissipation behavior of CMDB propellant slurry.The plasticizing mechanism of slurry and the safety of calendering under different conditions were explored,which provided theoretical guidance and reference data for the optimization of calendering process conditions.Based on the simulation results,the safety of the CMDB propellant calendering process could be significantly improved with a few tests conducted during a short research and development cycle.展开更多
For developing TiO based imitated gold materials, the wettabilities of Fe and Fe Cr Ni Ti on TiO were studied. The results indicated that the wettabilities of Fe and Fe Cr on TiO were poor, and their wetting angles we...For developing TiO based imitated gold materials, the wettabilities of Fe and Fe Cr Ni Ti on TiO were studied. The results indicated that the wettabilities of Fe and Fe Cr on TiO were poor, and their wetting angles were about 90° at melting point. The wetting angles reduced with the increase of wetting temperature, but the influence of temperature was small. Fe and Fe Cr containing Cr 50% or less could react with TiO on the interface to form Fe 2Ti and Ti 2O 3, but this did not improve the wettability effectively. When Ni Ti was added into Fe Cr alloy, Ni 3Ti was formed on the interface, which can reduce the interface energy, improve the wettability, and prevent the formation of Fe 2Ti and Ti 2O 3. The wetting angles could go down to about 40° when 3% Ni Ti was added to Fe Cr alloy.展开更多
Propellants containing micro-aluminium particles have been shown to produce faster burn rates than conventional gun propellants.However,they are also more abrasive than conventional propellants.Nano-material propellan...Propellants containing micro-aluminium particles have been shown to produce faster burn rates than conventional gun propellants.However,they are also more abrasive than conventional propellants.Nano-material propellants have been reported to give similar benefits to micron-material propellants but without the disadvantage of increased abrasion.Tests were conducted to compare the burn rates,ignitability and wear rates of a propellant loaded with 0% aluminium,15% micro-aluminium and 15%nano-aluminium.Closed vessel tests showed a burn rate increase of 39% in the range 30-250 MPa,and 70% at low pressure(50-100MPa)for the nano-aluminium propellant compared with the baseline propellant.The micro-aluminium propellant showed only a 10%increase in the burn rate compared with the standard propellant.The ignition delay for the nano-aluminium propellant was slightly shorter than that of the baseline propellant.Substantially increased wear rates were measured for the micro-aluminium propellant.The nano-aluminium propellant showed reduced wear rates compared with the micro-aluminium propellant but these were still substantially greater than those for the baseline propellant.展开更多
Nowadays, many kinds of software, which have succes sf ully created the integration of CAD, CAPP and CAM, find their disadvantages in p ractical manufacturing. As a result, it is welcomed to develop small CAD/CAPP sy ...Nowadays, many kinds of software, which have succes sf ully created the integration of CAD, CAPP and CAM, find their disadvantages in p ractical manufacturing. As a result, it is welcomed to develop small CAD/CAPP sy stems on a proper CAD platform, which aim at requirements of factories. Based on the one of the most popular three-dimensional design software SolidWorks, we successfully developed a set of gear pump CAD /CAPP software for Huaiyin Gene ral Factory of Mechanics. 1 The architecture and function of the software According to the need of the enterprises, the general structure of the software contain two subsystems, which are detailed as follows: · The gear pump CAD subsystem contains four main modules, including the optiona l design module of gear pump, module of part design, the module of entity modeli ng and the module of drawing which creates 2 D drawings of parts and assembly c orresponding 3 D modals. · The gear pump CAPP subsystem, which is a combination of creative mode and der ivate mode, also includes four modules, they are the module of access to feature s, the module of planning process route, the module of designing process sheets and the module of generating process documents. 2 The developing environment of the system Basing on Windows 98 and SolidWorks2001 platform, this system creates all functi ons by using Visual C++ 6.0 as developing tools. 3 The keys to the CAD/CAPP integration 3.1 The establishment of product information modal The information of parts is the basis of process planning. In this system, we us e feature modeling to describe the information of parts and assembly of gear pum p, and set up a fundamental basis for the whole system. The information module o f gear pump includes the information of both the assembly and the parts; the par t-describing module uses four-layer structure that is subassembly layer, part layer, feature layer and geometric layer. 3.2 The operation of the information on feature modeling After establishment of information mode of gear pump, the next key problem is ho w to transmit information of product to CAPP subsystem. In order to integrate pe rfectly, connecting CAD with CAPP directly can be a good method. In this system, all information of parts is store in the part drawing files, and the CAPP syste m can load these files to get information. The gear pumps, which are produced by Huaiyin General Factory of Mechanics, are usually belong to several similar typ es, and this means that most products possess large number of similar feature. T herefore, we can easily establish a specific feature for gear pump CAD/CAPP syst em. All parts are created by selecting these features and/or adding few special features. In the module of access to feature of CAPP subsystem, the main task is to find the features and the information will be easily got. 4 Conclusion This system successfully creates gear pump CAD/CAPP integration based on SolidWo rks. 3D CAD software provide more convenient platform for integration and will i nevitably become the mainstream of product design. By developing this system, we clearly realize the promising future of SolidWorks.展开更多
By the turn of the 21 st century,the significance of knowledge to be the key factor in urban and regional development is well established. However,it has been recently and in only a few studies that attempts have been...By the turn of the 21 st century,the significance of knowledge to be the key factor in urban and regional development is well established. However,it has been recently and in only a few studies that attempts have been made to identify the specific mechanism and institutional relationships,through which knowledge-based development actually takes place.This paper builds upon the "Triple Helix Model" (Etzkowitz & Klofsten,2005) where university,business and government have been introduced as the key factors behind any knowledge-based development.It refers to a case study of knowledge-based community development in Australia's Smart State Queensland-and examines the role of the "Triple Helix" in the interaction between local and regional level.It shows the central role of the community as an innovation base for the interaction among the key factors and suggests a promotion for a Quadruple Helix Model where community is as important as business,university and government in the new economy.The paper concludes that knowledge-based development will not promote unless all four factors-community,business,university,government-work together.展开更多
The Soil Conservation Monitorins Information System (SCMIS) presented in this paper is oriented to soil erosion control, resources exploitation, utilization, planning and management for a small watershed (about 10 sq....The Soil Conservation Monitorins Information System (SCMIS) presented in this paper is oriented to soil erosion control, resources exploitation, utilization, planning and management for a small watershed (about 10 sq. km.) on the Loess Plateau. It sums up Remote sensing (RS), Geographical Information System (GIS) and Expert System (ES) and consists of a integrated system. As a basic level information system of Loess Plateau, its perfection and psreading will bring about a great advance in resources exploitation and management of Loess Plateau.展开更多
In this paper, 2201 and 2212 phases as the corresponding precursor of forming 2212 and 2223 phases are discussed,and the constructive process of unit cell of 2201 phase is ascertained by XRD and chemical kinetics me...In this paper, 2201 and 2212 phases as the corresponding precursor of forming 2212 and 2223 phases are discussed,and the constructive process of unit cell of 2201 phase is ascertained by XRD and chemical kinetics method. Subsequently, the process of 221展开更多
文摘Two new complexes,[Zn_(2)(L1)(HL1)(NO_(3))]·CH_(3)OH(1)and[Zn_(3)(L2)(L3)_(3)Cl]·CH_(3)OH(2),were successfully synthesized by‘one-pot’method based on cinnoline-3-ylhydrazine ligand and zinc with 2-hydroxy-4-methoxybenzaldehyde and 2-hydroxy-3-methoxybenzaldehyde ligands,respectively,where H_(2)L1=5-methoxy-2-(phthalazin-1-ylhydrazonomethyl)-phenol,H_(2)L2=2-methoxy-6-(phthalazin-1-yl-hydrazonomethyl)-phenol,HL3=2-(1,8-dihydro-[1,2,4]triazolo[3,4-α]phthalazin-3-yl)-6-methoxy-phenol.Complexes 1 and 2 were characterized by infrared spectroscopy,elemental analysis,single-crystal X-ray diffraction,powder X-ray diffraction,etc.It is worth noting that the cinnolin-3-yl-hydrazine ligand and 2-hydroxy-3-methoxybenzaldehyde form two types of Schiff bases(H_(2)L2 and HL3)when in situ reacting and coordinating with Zn(Ⅱ),and HL3 also has two coordination modes.In addition,the fluorescence performance showed that complex 1 can achieve selective and sensitive sensing of Al^(3+)in water with a detection limit of 6.37μmol·L^(-1).CCDC:2413978,1;2413979,2.
文摘This paper delves into the theoretical mechanisms of the electronic structure and optical properties of aluminum-based semiconductors(AlX,X=N,P,As,Sb)and indium-based semiconductors(InX,X=N,P,As,Sb)as potential materials for optical devices.Band structure calculations reveal that,except for InSb,all other compounds are direct bandgap semiconductors,with AlN exhibiting a bandgap of 3.245 eV.The valence band maximum of these eight compounds primarily stems from the p-orbitals of Al/In and X.In contrast,the conduction band minimum is influenced by all orbitals,with a predominant contribution from the p-orbitals.The static dielectric constant increased with the expansion of the unit cell volume.Compared to AlX and InX with larger X atoms,AlN and InN showed broader absorption spectra in the near-ultraviolet region and higher photoelectric conductance.Regarding mechanical properties,AlN and InN displayed greater shear and bulk modulus than the other compounds.Moreover,among these eight crystal types,a higher modulus was associated with a lower light loss function value,indicating that AlN and InN have superior transmission efficiency and a wider spectral range in optoelectronic material applications.
文摘Because of an unfortunate mistake by authors,the Project(5227010679)of Foundation item was wrong.The corrected Project is shown as follows:Project(52271073).
文摘Two new dinuclear lanthanidecomplexes,namely[Ln_(2)(dbm)_(2)(HL)_(2)(CH_(3)OH)_(2)]·4CH_(3)OH[Ln=Tb(1)and Dy(2),Hdbm=dibenzoylmethane]have been synthesized using prepared multidentate Schiff base ligand H_(3)L(hydroxy‑acetic acid(4‑diethylamino‑2‑hydroxy‑benzylidene)‑hydrazide)with good biological activity.Structure characterizations show that the complex comprises two Ln3+ions,two dbm-ions,two HL^(2-)ligands,two CH_(3)OH molecules,and four free methanol molecules.Each Ln^(3+)ion is eight‑coordinated.The two central Lnions are bridged by twoμ_(2)‑O atoms leading to a parallelogram[Ln2O2]core.The interaction between the compounds(H_(3)L,1,and 2)and the calf thymus DNA(CT‑DNA)has been further confirmed by UV‑Vis spectrometry,fluorescence titration,and cyclic voltammetry.The results showed that both 1 and 2 could undergo insertion with CT‑DNA.CCDC:2343005,1;2343006,2.
文摘The advent of gene editing represents one of the most transformative breakthroughs in life science,making genome manipulation more accessible than ever before.While traditional CRISPR/Cas-based gene editing,which involves double-strand DNA breaks(DSBs),excels at gene disruption,it is less effective for accurate gene modification.The limitation arises because DSBs are primarily repaired via non-homologous end joining(NHEJ),which tends to introduce indels at the break site.While homology directed repair(HDR)can achieve precise editing when a donor DNA template is provided,the reliance on DSBs often results in unintended genome damage.HDR is restricted to specific cell cycle phases,limiting its application.Currently,gene editing has evolved to unprecedented levels of precision without relying on DSB and HDR.The development of innovative systems,such as base editing,prime editing,and CRISPR-associated transposases(CASTs),now allow for precise editing ranging from single nucleotides to large DNA fragments.Base editors(BEs)enable the direct conversion of one nucleotide to another,and prime editors(PEs)further expand gene editing capabilities by allowing for the insertion,deletion,or alteration of small DNA fragments.The CAST system,a recent innovation,allows for the precise insertion of large DNA fragments at specific genomic locations.In recent years,the optimization of these precise gene editing tools has led to significant improvements in editing efficiency,specificity,and versatility,with advancements such as the creation of base editors for nucleotide transversions,enhanced prime editing systems for more efficient and precise modifications,and refined CAST systems for targeted large DNA insertions,expanding the range of applications for these tools.Concurrently,these advances are complemented by significant improvements in in vivo delivery methods,which have paved the way for therapeutic application of precise gene editing tools.Effective delivery systems are critical for the success of gene therapies,and recent developments in both viral and non-viral vectors have improved the efficiency and safety of gene editing.For instance,adeno-associated viruses(AAVs)are widely used due to their high transfection efficiency and low immunogenicity,though challenges such as limited cargo capacity and potential for immune responses remain.Non-viral delivery systems,including lipid nanoparticles(LNPs),offer an alternative with lower immunogenicity and higher payload capacity,although their transfection efficiency can be lower.The therapeutic potential of these precise gene editing technologies is vast,particularly in treating genetic disorders.Preclinical studies have demonstrated the effectiveness of base editing in correcting genetic mutations responsible for diseases such as cardiomyopathy,liver disease,and hereditary hearing loss.These technologies promise to treat symptoms and potentially cure the underlying genetic causes of these conditions.Meanwhile,challenges remain,such as optimizing the safety and specificity of gene editing tools,improving delivery systems,and overcoming off-target effects,all of which are critical for their successful application in clinical settings.In summary,the continuous evolution of precise gene editing technologies,combined with advancements in delivery systems,is driving the field toward new therapeutic applications that can potentially transform the treatment of genetic disorders by targeting their root causes.
文摘Flow based Erosion e corrosion problems are very common in fluid handling equipments such as propellers, impellers, pumps in warships, submarine. Though there are many coating materials available to combat erosionecorrosion damage in the above components, iron based amorphous coatings are considered to be more effective to combat erosionecorrosion problems. High velocity oxy-fuel(HVOF)spray process is considered to be a better process to coat the iron based amorphous powders. In this investigation, iron based amorphous metallic coating was developed on 316 stainless steel substrate using HVOF spray technique. Empirical relationships were developed to predict the porosity and micro hardness of iron based amorphous coating incorporating HVOF spray parameters such as oxygen flow rate, fuel flow rate, powder feed rate, carrier gas flow rate, and spray distance. Response surface methodology(RSM) was used to identify the optimal HVOF spray parameters to attain coating with minimum porosity and maximum hardness.
基金supported by the National Natural Sciences Foundation of China(7137102271401193+2 种基金71671193)the Program for Innovation Research in Central University of Finance and Economicsthe Innovation Foundation of BUAA for Ph.D.Graduates
文摘Determining the number of components is a crucial issue in a mixture model. A moment-based criterion is considered to estimate the number of components arising from a normal mixture model. This criterion is derived from an omnibus statistic involving the skewness and kurtosis of each component. The proposed criterion additionally provides a measurement for the model fit in an absolute sense. The performances of our criterion are satisfactory compared with other classical criteria through Monte-Carlo experiments.
基金This project was supported by the National "863" High-Tech Research and Development Program of China(2002AA7170)
文摘Ongoing research is described that is focused upon modelling the space base information network and simulating its behaviours： simulation of spaced based communications and networking project. Its objective is to demonstrate the feasibility of producing a tool that can provide a performance evaluation of various eonstellation access techniques and routing policies. The architecture and design of the simulation system are explored. The algorithm of data routing and instrument scheduling in this project is described. Besides these, the key methodologies of simulating the inter-satellite link features in the data transmissions are also discussed. The performance of both instrument scheduling algorithm and routing schemes is evaluated and analyzed through extensive simulations under a typical scenario.
文摘The frequent occurrence of safety accidents during the calendering process is caused by the flammable and explosive properties of composite modified double-base(CMDB)propellant.Optimization of process parameters with the aid of fluid simulation technology could effectively ensure the safety of the calendering process.To improve the accuracy of the simulation results,material parameters and model structure were corrected based on actual conditions,and adaptive grid technology was applied in the local mesh refinement.In addition,the rheological behavior,motion trajectories and heat transfer mechanisms of CMDB propellant slurry were studied with different gaps,rotational rates and temperatures of two rollers.The results indicated that the refined mesh could significantly improve the contour clarity of boundaries and simulate the characteristics of CMDB propellant slurry reflux movement caused by the convergent flow near the outlet.Compared with the gap,the increased rotational rate of roller could promote the reflux movement and intensify the shear flow of slurry inside the flow region by viscous shear dragging.Meanwhile,under the synergistic effect of contact heat transfer as well as convective heat exchange,heat accumulated near the outlet and diffused along the reflux movement,which led to the countercurrent heat dissipation behavior of CMDB propellant slurry.The plasticizing mechanism of slurry and the safety of calendering under different conditions were explored,which provided theoretical guidance and reference data for the optimization of calendering process conditions.Based on the simulation results,the safety of the CMDB propellant calendering process could be significantly improved with a few tests conducted during a short research and development cycle.
文摘For developing TiO based imitated gold materials, the wettabilities of Fe and Fe Cr Ni Ti on TiO were studied. The results indicated that the wettabilities of Fe and Fe Cr on TiO were poor, and their wetting angles were about 90° at melting point. The wetting angles reduced with the increase of wetting temperature, but the influence of temperature was small. Fe and Fe Cr containing Cr 50% or less could react with TiO on the interface to form Fe 2Ti and Ti 2O 3, but this did not improve the wettability effectively. When Ni Ti was added into Fe Cr alloy, Ni 3Ti was formed on the interface, which can reduce the interface energy, improve the wettability, and prevent the formation of Fe 2Ti and Ti 2O 3. The wetting angles could go down to about 40° when 3% Ni Ti was added to Fe Cr alloy.
基金funded by the Defence Science and Technology Laboratory(Dstl)part of the UK MoD,under the Hazard Modelling and Simulation task of the UK Energetics(UK-E)programme now consumed by the Weapons Science and Technology Centre(WSTC)
文摘Propellants containing micro-aluminium particles have been shown to produce faster burn rates than conventional gun propellants.However,they are also more abrasive than conventional propellants.Nano-material propellants have been reported to give similar benefits to micron-material propellants but without the disadvantage of increased abrasion.Tests were conducted to compare the burn rates,ignitability and wear rates of a propellant loaded with 0% aluminium,15% micro-aluminium and 15%nano-aluminium.Closed vessel tests showed a burn rate increase of 39% in the range 30-250 MPa,and 70% at low pressure(50-100MPa)for the nano-aluminium propellant compared with the baseline propellant.The micro-aluminium propellant showed only a 10%increase in the burn rate compared with the standard propellant.The ignition delay for the nano-aluminium propellant was slightly shorter than that of the baseline propellant.Substantially increased wear rates were measured for the micro-aluminium propellant.The nano-aluminium propellant showed reduced wear rates compared with the micro-aluminium propellant but these were still substantially greater than those for the baseline propellant.
文摘Nowadays, many kinds of software, which have succes sf ully created the integration of CAD, CAPP and CAM, find their disadvantages in p ractical manufacturing. As a result, it is welcomed to develop small CAD/CAPP sy stems on a proper CAD platform, which aim at requirements of factories. Based on the one of the most popular three-dimensional design software SolidWorks, we successfully developed a set of gear pump CAD /CAPP software for Huaiyin Gene ral Factory of Mechanics. 1 The architecture and function of the software According to the need of the enterprises, the general structure of the software contain two subsystems, which are detailed as follows: · The gear pump CAD subsystem contains four main modules, including the optiona l design module of gear pump, module of part design, the module of entity modeli ng and the module of drawing which creates 2 D drawings of parts and assembly c orresponding 3 D modals. · The gear pump CAPP subsystem, which is a combination of creative mode and der ivate mode, also includes four modules, they are the module of access to feature s, the module of planning process route, the module of designing process sheets and the module of generating process documents. 2 The developing environment of the system Basing on Windows 98 and SolidWorks2001 platform, this system creates all functi ons by using Visual C++ 6.0 as developing tools. 3 The keys to the CAD/CAPP integration 3.1 The establishment of product information modal The information of parts is the basis of process planning. In this system, we us e feature modeling to describe the information of parts and assembly of gear pum p, and set up a fundamental basis for the whole system. The information module o f gear pump includes the information of both the assembly and the parts; the par t-describing module uses four-layer structure that is subassembly layer, part layer, feature layer and geometric layer. 3.2 The operation of the information on feature modeling After establishment of information mode of gear pump, the next key problem is ho w to transmit information of product to CAPP subsystem. In order to integrate pe rfectly, connecting CAD with CAPP directly can be a good method. In this system, all information of parts is store in the part drawing files, and the CAPP syste m can load these files to get information. The gear pumps, which are produced by Huaiyin General Factory of Mechanics, are usually belong to several similar typ es, and this means that most products possess large number of similar feature. T herefore, we can easily establish a specific feature for gear pump CAD/CAPP syst em. All parts are created by selecting these features and/or adding few special features. In the module of access to feature of CAPP subsystem, the main task is to find the features and the information will be easily got. 4 Conclusion This system successfully creates gear pump CAD/CAPP integration based on SolidWo rks. 3D CAD software provide more convenient platform for integration and will i nevitably become the mainstream of product design. By developing this system, we clearly realize the promising future of SolidWorks.
文摘By the turn of the 21 st century,the significance of knowledge to be the key factor in urban and regional development is well established. However,it has been recently and in only a few studies that attempts have been made to identify the specific mechanism and institutional relationships,through which knowledge-based development actually takes place.This paper builds upon the "Triple Helix Model" (Etzkowitz & Klofsten,2005) where university,business and government have been introduced as the key factors behind any knowledge-based development.It refers to a case study of knowledge-based community development in Australia's Smart State Queensland-and examines the role of the "Triple Helix" in the interaction between local and regional level.It shows the central role of the community as an innovation base for the interaction among the key factors and suggests a promotion for a Quadruple Helix Model where community is as important as business,university and government in the new economy.The paper concludes that knowledge-based development will not promote unless all four factors-community,business,university,government-work together.
文摘The Soil Conservation Monitorins Information System (SCMIS) presented in this paper is oriented to soil erosion control, resources exploitation, utilization, planning and management for a small watershed (about 10 sq. km.) on the Loess Plateau. It sums up Remote sensing (RS), Geographical Information System (GIS) and Expert System (ES) and consists of a integrated system. As a basic level information system of Loess Plateau, its perfection and psreading will bring about a great advance in resources exploitation and management of Loess Plateau.
文摘In this paper, 2201 and 2212 phases as the corresponding precursor of forming 2212 and 2223 phases are discussed,and the constructive process of unit cell of 2201 phase is ascertained by XRD and chemical kinetics method. Subsequently, the process of 221
