The high pressure die casting (HPDC) process is one of the fastest growing and most efficient methods for the production of complex shape castings of magnesium and aluminum alloys in today's manufacturing industry...The high pressure die casting (HPDC) process is one of the fastest growing and most efficient methods for the production of complex shape castings of magnesium and aluminum alloys in today's manufacturing industry. In this study, a high pressure die casting experiment using AZ91D magnesium alloy was conducted, and the temperature profiles inside the die were measured. By using a computer program based on solving the inverse heat problem, the metal/die interfacial heat transfer coefficient (IHTC) was calculated and studied. The results show that the IHTC between the metal and die increases right after the liquid metal is brought into the cavity by the plunger, and decreases as the solidification process of the liquid metal proceeds until the liquid metal is completely solidified, when the IHTC tends to be stable. The interfacial heat transfer coefficient shows different characteristics under different casting wall thicknesses and varies with the change of solidification behavior.展开更多
A method based on die casting experiments and mathematic modeling is presented for the determination of the heat flow density （HFD） and interfacial heat transfer coefficient （IHTC） during the high pressure die cas...A method based on die casting experiments and mathematic modeling is presented for the determination of the heat flow density （HFD） and interfacial heat transfer coefficient （IHTC） during the high pressure die casting （HPDC） process.Experiments were carried out using step shape casting and a commercial magnesium alloy,AM50.Temperature profiles were measured and recorded using thermocouples embedded inside the die. Based on these temperature readings,the HFD and IHTC were successfully determined and the calculation results show that the HFD and IHTC at the metal-die interface increases sharply right after the fast phase injection process until approaching their maximum values,after which their values decrease to a much lower level until the dies are opened.Different patterns of heat transfer behavior were found between the die and the casting at different thicknesses.The thinner the casting was,the more quickly the HFD and IHTC reached their steady states.Also,the values for both the HFD and IHTC values were different between die and casting at different thicknesses.展开更多
Natural gases containing sour components exhibit different gas compressibility factor （Z） behavior than do sweet gases. Therefore, a new accurate method should be developed to account for these differences. Several ...Natural gases containing sour components exhibit different gas compressibility factor （Z） behavior than do sweet gases. Therefore, a new accurate method should be developed to account for these differences. Several methods are available today for calculating the Z-factor from an equation of state. However, these equations are more complex than the foregoing correlations, involving a large number of parameters, which require more complicated and longer computations. The aim of this study is to develop a simplified calculation method for a rapid estimating Z-factor for sour natural gases containing as much as 90% total acid gas. In this article, two new correlations are first presented for calculating the pseudo- critical pressure and temperature of the gas mixture as a function of the gas specific gravity. Then, a simple correlation on the basis of the standard gas compressibility factor chart is introduced for a quick estimation of sweet gases＇ compressibility factor as a function of reduced pressure and temperature. Finally, a new corrective term related to the mole fractions of carbon dioxide and hydrogen sulfide is developed.展开更多
An inherent problem with natural gas production or transmission is the formation of gas hydrates, which can lead to safety hazards for production/transportation systems, and substantial economic risks. Hydrate inhibit...An inherent problem with natural gas production or transmission is the formation of gas hydrates, which can lead to safety hazards for production/transportation systems, and substantial economic risks. Hydrate inhibition with different inhibitors such as, methanol, ethylene glycol （EG）, triethylene glycol （TEG）, and sodium chloride solution continues to play a critical role in many operations. An understanding of when the hydrates form in the presence of these hydrate inhibitors, is therefore necessary to overcome hydrate problems. Several thermodynamic models have been proposed for predicting the hydrate formation conditions in aqueous solutions containing methanol/glycols and electrolytes. However, available models have limitations that include the types of liquid, compositions of fluids, and inhibitors used. The aim of this study is to develop a simple-to-use correlation for accurate prediction of hydrate-forming pressures of pure alkanes in the presence of different hydrate inhibitors, where the obtained results illustrate good agreement with the reported experimental data.展开更多
Fe-based amorphous alloys with high iron content of 76at%-80at%were synthesized in the Fe-Mo-Si-P-C-B alloy system by the single roller melt-spinning technique.The amorphous ribbons exhibit high Vickers microhardness ...Fe-based amorphous alloys with high iron content of 76at%-80at%were synthesized in the Fe-Mo-Si-P-C-B alloy system by the single roller melt-spinning technique.The amorphous ribbons exhibit high Vickers microhardness and good ductility,which can be indented and bent 180°without breaking.A number of shear bands could be observed around the indents and the bending traces.Studies on the magnetic properties of the amorphous alloys show that they possess high saturation magnetizations of 1.34-1.6 T,which increases with the increase of iron content.The core losses of these Fe-based amorphous alloys at various magnetic inductions were tested and found to be significantly dependent on their components.The Fe-Mo-Si-P-C-B amorphous alloys with excellent mechanical properties and soft magnetic properties have promising potential in functional applications.展开更多
The ultimate goal of current research on carbon nanotubes （CNTs） is to make breakthroughs that advance nanotechnological applications of bulk CNT materials. Especially, there has been growing interest in CNT thin fi...The ultimate goal of current research on carbon nanotubes （CNTs） is to make breakthroughs that advance nanotechnological applications of bulk CNT materials. Especially, there has been growing interest in CNT thin films because of their unique and usually enhanced properties and tremendous potential as components for use in nano-electronic and nano-mechanical device applications or as structural elements in various devices. If a synthetic or a post processing method can produce high yield of nanotube thin films, these structures will provide tremendous potential for fundamental research on these devices. This review will address the synthesis, the post processing and the device applications of self-assembled nanotube thin films.展开更多
Using the molecular electronegativity distance vector descriptors derived directly from the molecular topological structures, the relative retention time （RRT） of polybrominated diphenyl ethers （PBDEs） were predic...Using the molecular electronegativity distance vector descriptors derived directly from the molecular topological structures, the relative retention time （RRT） of polybrominated diphenyl ethers （PBDEs） were predicted. A four-variable regression model （M30） with the correlation coefficient of 0.9816 and the root mean square errors of 0.061 was developed using a training set including 30 PBDEs. The correlation coefficient of 0.9841 and the root mean square errors of 0.054 between the values of RRT predicted by M30 and the RRT observed for 16 external PBDEs show a good predictive potential of M30. The descriptors included in the M30 represent four interactions between four pairs of atom types, i.e., atom -C= and -C=, -C= and 〉C=, 〉C= and 〉C=, -C= and -Br.展开更多
Two new approaches for the accurate prediction of densities of the commonly used glycol solutions in the gasprocessing industry are presented in the article. The first approach is based on developing a simple-to-use p...Two new approaches for the accurate prediction of densities of the commonly used glycol solutions in the gasprocessing industry are presented in the article. The first approach is based on developing a simple-to-use polynomial correlation for an appropriate prediction of density of glycol solutions as a function of temperature and weight percent of glycols in water, where the obtained results show very good agreement with the reported experimental data. The second approach, however, is based on the artificial neural networks （ANN） methodology, wherein the results demonstrate the ability of the introduced method to predict reasonably accurate densities of glycols under operating conditions. Comparisons of the two novel approaches indicated that the simple-to-use correlation appears to be superior owing to its simplicity and clear numerical background, wherein the relevant coefficients can be retuned if new and more accurate data are available in the future. The average deviation of the new proposed polynomial correlation results from reported data is 0.64 kg/m^3 whereas the average deviation of artificial neural networks （ANN） methodology from reported data is 1.1 kg/m^3.展开更多
Two types of electromagnetic edge dams were analyzed by using finite element method in present paper. The magnetic vector potential method and edge element method were used. The distributions of the magnetic field, th...Two types of electromagnetic edge dams were analyzed by using finite element method in present paper. The magnetic vector potential method and edge element method were used. The distributions of the magnetic field, the eddy current intensity and the magnetic force were obtained from the computing. The differences in these fields were explained according to the two types of electromagnetic dam, and characters of their application in twin roll casting were also discussed.展开更多
The copper（II） compound [Cu（Brzhama）（DMF）]2 （C22H24Br4Cu2N4O10S2, Br2hamaH2 = [（3,5-dibromo-2-hydroxybenzylidene）-amino]-methanesulfonic acid, DMF = N,N＇-dimethylformamide） 1 crystallizes in trictinic, spac...The copper（II） compound [Cu（Brzhama）（DMF）]2 （C22H24Br4Cu2N4O10S2, Br2hamaH2 = [（3,5-dibromo-2-hydroxybenzylidene）-amino]-methanesulfonic acid, DMF = N,N＇-dimethylformamide） 1 crystallizes in trictinic, space group P1 with a = 8.477（2）, b = 10.164（2）, c = 10.671（2）A, α= 112.66（3）, β = 104.33（3）, γ = 96.67（3）°, Z = 1, and R = 0.0789 for 1823 observed reflections with I 〉 2σ（I）. The centrosymmetric molecule comprises a pair of copper atoms connected by two anions of [（3,5-dibromo-2-hydroxybenzylidene）-amino]-methanesulfonic acid in a tetradentate coordination mode. The five-coordination of copper（II） is further completed by DME The complex forms a 1-D chain through C-H…π hydrogen bonds. The Cu^II…Cu^II distance is 4.937（1） A.展开更多
A new Mn（Ⅱ） coordination polymer {[Mn（timb）2（H2O）2]·（Cl）2·（H2O）2}n（1,timb = 1,3,5-tris-（imidazol-1-ylmethyl）benzene） has been synthesized and characterized by elemental analysis,IR,TG and sing...A new Mn（Ⅱ） coordination polymer {[Mn（timb）2（H2O）2]·（Cl）2·（H2O）2}n（1,timb = 1,3,5-tris-（imidazol-1-ylmethyl）benzene） has been synthesized and characterized by elemental analysis,IR,TG and single-crystal X-ray diffraction.The title compound crystallizes in the triclinic system,space group P1 with a=9.0774（13）,b=9.8720（15）,c=11.4898（16）A,α=93.378（3）,β= 95.471（3）,γ=101.101（3）°,V=1002.6（3）A^3,Mr=834.67,Dc=1.382 g/cm^3,μ（MoKα）=0.517mm^-1,F（000）=435,GOF=0.986,Z=1,the final R=0.0506 and wR=0.1139 for 3517 observed reflections I〉2σ（I）.It consists of one-dimensional double stranded chains formed through bridging bidentate timb ligands,and these chains are further connected to yield a 3D supramolecular framework by hydrogen bonding interactions and π…π stacking interactions.展开更多
With the rise of cloud computing in recent years, a large number of streaming media has yielded an exponential growth in network traffic. With the now present 5G and future 6G, the development of the Internet of Thing...With the rise of cloud computing in recent years, a large number of streaming media has yielded an exponential growth in network traffic. With the now present 5G and future 6G, the development of the Internet of Things (IoT), social networks, video on demand, and mobile multimedia platforms, the backbone network is bound to bear more traffic. The transmission capacity of Single Core Fiber (SCFs) may be limited in the future and Spatial Division Multiplexing (SDM) leveraging multi-core fibers promises to be one of the solutions for the future. Currently, Elastic optical networks (EONs) with multi-core fibers (MCFs) are a kind of SDM-enabled EONs (SDM-EON) used to enhance the capacity of transmission. The resource assignment in MCFs, however, will be subject to Inter-Core Crosstalk (IC-XT), hence, reducing the effectiveness of transmission. This research highlights the routing, modulation level, and spectrum assignment (RMLSA) problems with anycast traffic mode in SDM-EON. A multipath routing scheme is used to reduce the blocking rate of anycast traffic in SDM-EON with the limit of inter-core crosstalk. Hence, an integer linear programming (ILP) problem is formulated and a heuristic algorithm is proposed. Two core-assignment strategies: First-Fit (FF) and Random-Fit (RF) are used and their performance is evaluated through simulations. The simulation results show that the multipath routing method is better than the single-path routing method in terms of blocking ratio and spectrum utilization ratio. Moreover, the FF is better than the RF in low traffic load in terms of blocking ratio (BR), and the opposite in high traffic load. The FF is better than the RF in terms of a spectrum utilization ratio. In an anycast protection problem, the proposed algorithm has a lower BR than previous works.展开更多
Work hardening is a well-known phenomenon occurring in crystalline metals during deformation,which has been widely used to increase the strength of metals although their ductility is usually reduced simultaneously. He...Work hardening is a well-known phenomenon occurring in crystalline metals during deformation,which has been widely used to increase the strength of metals although their ductility is usually reduced simultaneously. Here we report that the plastic strain of Zr41Ti14Cu12.5Ni10Be22.5 (at.%) bulk metallic glasses has been increased from 0.3% for the as-cast sample to 2.5%-8.0% for samples that have experienced pre-deformation under constrained conditions. The pre-deformed glassy alloys possess more free volume and abundant introduced shear bands,which are believed to promote the activation of shear bands in post-deformation and result in an increase in plasticity. The orientation of the pre-introduced shear bands relative to the loading direction will affect the deformation behavior of pre-deformed samples. The present results show that pre-deformation of this glassy alloy will result in work toughening. This work toughening effect can be removed by isothermal annealing at a sub-Tg (glass transition) temperature,which causes annihilation of free volume and healing of shear bands.展开更多
Pd80+xSi20-x (x=0,1,and 2) binary metallic glasses with the diameter ranging from 7 to 8 mm were prepared by a combination of fluxing and water quenching or air cooling. Thermal analysis results show that with increas...Pd80+xSi20-x (x=0,1,and 2) binary metallic glasses with the diameter ranging from 7 to 8 mm were prepared by a combination of fluxing and water quenching or air cooling. Thermal analysis results show that with increasing Si content,the glass transition temperature Tg,the initial crystallization temperature Tx and the onset crystalliza-tion temperature Tp of Pd-Si binary glassy alloys increase. Moreover,the super-cooled liquid region reaches 61 K. It indicates that Pd-Si binary alloys possess large glass forming ability,which can be greatly improved by fluxing treatment.展开更多
The microwave absorbing properties and magnetic properties of as-grown Fe-filled carbon nanotubes (CNTs), annealed Fe-filled CNTs, and multi-walled CNTs were studied. Vibrating sample magnetometer results showed that ...The microwave absorbing properties and magnetic properties of as-grown Fe-filled carbon nanotubes (CNTs), annealed Fe-filled CNTs, and multi-walled CNTs were studied. Vibrating sample magnetometer results showed that the annealed Fe-filled CNTs have the weakest coercivity and strongest saturation magnetization among the three types CNTs, due to the presence of more ferromagnetic α-Fe nanowires. After annealing, the values increased to 291.0 Oe and 28.0 emu/g and the samples showed excellent microwave absorbing properties. The reflection loss was over 5 dB between 11.6 GHz and 18 GHz with a maximum value of 10.8 dB for annealed Fe-filled CNTs (1.1 wt%)/epoxy composite.展开更多
By using a simple and low-cost arc-discharge method in deionized water, high purity Fe3O4 nanoparti- cles have been synthesized on large scale. The structure of these nanoparticles has been studied by means of transmi...By using a simple and low-cost arc-discharge method in deionized water, high purity Fe3O4 nanoparti- cles have been synthesized on large scale. The structure of these nanoparticles has been studied by means of transmission electron microscope and X-ray diffraction. The synthesized Fe3O4 nanoparticles show well-defined spherical shape, with diameters ranging from 10 to 30 nm and the average diameter about 20 nm. By investigating the effects of the different processing conditions, optimum parameters were obtained. Moreover, the size of the as-grown nanoparticles can also be controlled through ad- justing the processing parameters. These Fe3O4 nanoparticles were magnetic materials, showing saturation magnetization of 64.97 emu/g at room temperature.展开更多
A two-dimensional finite element model was used to analyze the thermal and mechanical behavior during solidification of the strand in a continuous bloom casting mold. The coupled heat transfer and deformation were ana...A two-dimensional finite element model was used to analyze the thermal and mechanical behavior during solidification of the strand in a continuous bloom casting mold. The coupled heat transfer and deformation were analyzed to simulate the formation of the air gap between the mold and the strand. The model was used to investigate the influence of mold taper on the temperature and stress distributions in the strand. The results show that the air gap mainly forms around the strand corner, causing a hotter and thinner solidifying shell in this region. The mold taper partially compensates for the strand shell shrinkage and reduces the influence of the air gap on the heat transfer. The mold taper compresses the shell and changes the stress state around the strand corner region. As the strand moves down into the mold, the mold constraint causes compressive stress beneath the corner surface, which reduces the hot tear that forms on the strand.展开更多
A bulk metal/ceramic composite material with a honeycomb-like micro-cell structure has been prepared by sintering the spherical Al90Mn9Ce1 alloy powders clad by Al2O3 nano-powder with the spark plasma sintering (SPS) ...A bulk metal/ceramic composite material with a honeycomb-like micro-cell structure has been prepared by sintering the spherical Al90Mn9Ce1 alloy powders clad by Al2O3 nano-powder with the spark plasma sintering (SPS) technique. The as-prepared material consists of Al90Mn9Ce1 alloy cell and closed Al2O3 ceramic cell wall. The diameter of the cells is about 20―40 μm, while a thickness of the cell wall is about 1―2 μm. The ultimate compressive strength of the as-sintered materials is about 514 MPa, while its fracture strain is up to about 0.65 %. This composite material might possess good anti-corrosion, thermal endurance and other potential properties due to its unique microstructure. The result shows that the Al90Mn9Ce1/Al2O3 composite powders can be sintered by spark plasma sintering technique despite the large difference in their sintering temperature. This work offers a way of designing and preparing metal/ceramic composite material with functional property.展开更多
As the potential applications of carbon nanotubes in the field of electroluminescence, elements yttrium and europium were introduced to modify the emission properties of double-walled carbon nanotubes (DWNTs) to obtai...As the potential applications of carbon nanotubes in the field of electroluminescence, elements yttrium and europium were introduced to modify the emission properties of double-walled carbon nanotubes (DWNTs) to obtain higher efficacy and other properties. The light emission spectrum of the Y-Eu-doped DWNT filament is suppressed in the near-infrared range, while enhanced in the mid-infrared range. The doped DWNT filament can reach higher efficacy than that of the pure DWNT filament at the same input power and can work stably as long as 5000 h at 12 V. These filaments could be useful for the light sources with special functions, such as infrared light sources operated at low input power.展开更多
文摘The high pressure die casting (HPDC) process is one of the fastest growing and most efficient methods for the production of complex shape castings of magnesium and aluminum alloys in today's manufacturing industry. In this study, a high pressure die casting experiment using AZ91D magnesium alloy was conducted, and the temperature profiles inside the die were measured. By using a computer program based on solving the inverse heat problem, the metal/die interfacial heat transfer coefficient (IHTC) was calculated and studied. The results show that the IHTC between the metal and die increases right after the liquid metal is brought into the cavity by the plunger, and decreases as the solidification process of the liquid metal proceeds until the liquid metal is completely solidified, when the IHTC tends to be stable. The interfacial heat transfer coefficient shows different characteristics under different casting wall thicknesses and varies with the change of solidification behavior.
基金This work was financially supported by the National Natural Science Foundation of China （No. 50675114） the National Basic Research Program of China （2006CB605208-2） The experiments were conducted at the Tsinghua-TOYO R＆D Center of Magnesium and Aluminum Alloys Processing Technology with the help of engineers from the TOYO Machiuery ＆ Metal Co., Ltd.
文摘A method based on die casting experiments and mathematic modeling is presented for the determination of the heat flow density （HFD） and interfacial heat transfer coefficient （IHTC） during the high pressure die casting （HPDC） process.Experiments were carried out using step shape casting and a commercial magnesium alloy,AM50.Temperature profiles were measured and recorded using thermocouples embedded inside the die. Based on these temperature readings,the HFD and IHTC were successfully determined and the calculation results show that the HFD and IHTC at the metal-die interface increases sharply right after the fast phase injection process until approaching their maximum values,after which their values decrease to a much lower level until the dies are opened.Different patterns of heat transfer behavior were found between the die and the casting at different thicknesses.The thinner the casting was,the more quickly the HFD and IHTC reached their steady states.Also,the values for both the HFD and IHTC values were different between die and casting at different thicknesses.
文摘Natural gases containing sour components exhibit different gas compressibility factor （Z） behavior than do sweet gases. Therefore, a new accurate method should be developed to account for these differences. Several methods are available today for calculating the Z-factor from an equation of state. However, these equations are more complex than the foregoing correlations, involving a large number of parameters, which require more complicated and longer computations. The aim of this study is to develop a simplified calculation method for a rapid estimating Z-factor for sour natural gases containing as much as 90% total acid gas. In this article, two new correlations are first presented for calculating the pseudo- critical pressure and temperature of the gas mixture as a function of the gas specific gravity. Then, a simple correlation on the basis of the standard gas compressibility factor chart is introduced for a quick estimation of sweet gases＇ compressibility factor as a function of reduced pressure and temperature. Finally, a new corrective term related to the mole fractions of carbon dioxide and hydrogen sulfide is developed.
文摘An inherent problem with natural gas production or transmission is the formation of gas hydrates, which can lead to safety hazards for production/transportation systems, and substantial economic risks. Hydrate inhibition with different inhibitors such as, methanol, ethylene glycol （EG）, triethylene glycol （TEG）, and sodium chloride solution continues to play a critical role in many operations. An understanding of when the hydrates form in the presence of these hydrate inhibitors, is therefore necessary to overcome hydrate problems. Several thermodynamic models have been proposed for predicting the hydrate formation conditions in aqueous solutions containing methanol/glycols and electrolytes. However, available models have limitations that include the types of liquid, compositions of fluids, and inhibitors used. The aim of this study is to develop a simple-to-use correlation for accurate prediction of hydrate-forming pressures of pure alkanes in the presence of different hydrate inhibitors, where the obtained results illustrate good agreement with the reported experimental data.
基金supported by the National Natural Science Foundation of China(21878062,21878062,and 22111530113)the Natural Science Foundation of Heilongjiang Province for Distinguished Young Scholars(JQ2020B001)+2 种基金Heilongjiang Touyan Team(HITTY20190033)Fundamental Research Funds for the Central UniversitiesState Key Laboratory of Urban Water Resource and Environment(Harbin Institute of Technology)(2020DX02)。
基金supported by the China Postdoctoral Science Foundation(CPSF)(No.2007CB613900)the National Basic Research Priorities Program of China(No.2007CB613905)+1 种基金the Program for New Century Excellent Talents in the University,the Ministry of Education of China(No.50671050)the National Natural Science Foundation of China(Nos.50671050 and 50971073).
文摘Fe-based amorphous alloys with high iron content of 76at%-80at%were synthesized in the Fe-Mo-Si-P-C-B alloy system by the single roller melt-spinning technique.The amorphous ribbons exhibit high Vickers microhardness and good ductility,which can be indented and bent 180°without breaking.A number of shear bands could be observed around the indents and the bending traces.Studies on the magnetic properties of the amorphous alloys show that they possess high saturation magnetizations of 1.34-1.6 T,which increases with the increase of iron content.The core losses of these Fe-based amorphous alloys at various magnetic inductions were tested and found to be significantly dependent on their components.The Fe-Mo-Si-P-C-B amorphous alloys with excellent mechanical properties and soft magnetic properties have promising potential in functional applications.
基金the National Science Foundation(NSF CMMI # 0753462)the University of Delaware Research Foundation are gratefully acknowledged.
文摘The ultimate goal of current research on carbon nanotubes （CNTs） is to make breakthroughs that advance nanotechnological applications of bulk CNT materials. Especially, there has been growing interest in CNT thin films because of their unique and usually enhanced properties and tremendous potential as components for use in nano-electronic and nano-mechanical device applications or as structural elements in various devices. If a synthetic or a post processing method can produce high yield of nanotube thin films, these structures will provide tremendous potential for fundamental research on these devices. This review will address the synthesis, the post processing and the device applications of self-assembled nanotube thin films.
基金the National Basic Research Program of China(2003CB415002)the National Natural Science Foundation of China(No.20377022) the Guangxi Natural Science Fund(No.0236063)for their financial supports.
文摘Using the molecular electronegativity distance vector descriptors derived directly from the molecular topological structures, the relative retention time （RRT） of polybrominated diphenyl ethers （PBDEs） were predicted. A four-variable regression model （M30） with the correlation coefficient of 0.9816 and the root mean square errors of 0.061 was developed using a training set including 30 PBDEs. The correlation coefficient of 0.9841 and the root mean square errors of 0.054 between the values of RRT predicted by M30 and the RRT observed for 16 external PBDEs show a good predictive potential of M30. The descriptors included in the M30 represent four interactions between four pairs of atom types, i.e., atom -C= and -C=, -C= and 〉C=, 〉C= and 〉C=, -C= and -Br.
文摘Two new approaches for the accurate prediction of densities of the commonly used glycol solutions in the gasprocessing industry are presented in the article. The first approach is based on developing a simple-to-use polynomial correlation for an appropriate prediction of density of glycol solutions as a function of temperature and weight percent of glycols in water, where the obtained results show very good agreement with the reported experimental data. The second approach, however, is based on the artificial neural networks （ANN） methodology, wherein the results demonstrate the ability of the introduced method to predict reasonably accurate densities of glycols under operating conditions. Comparisons of the two novel approaches indicated that the simple-to-use correlation appears to be superior owing to its simplicity and clear numerical background, wherein the relevant coefficients can be retuned if new and more accurate data are available in the future. The average deviation of the new proposed polynomial correlation results from reported data is 0.64 kg/m^3 whereas the average deviation of artificial neural networks （ANN） methodology from reported data is 1.1 kg/m^3.
基金This study was fnancially supported by the National Nat-ural Science Foundation of China under grant No.59995440the State Key Development Program on Foundation Research un der the contract No.G2000067208-4.
文摘Two types of electromagnetic edge dams were analyzed by using finite element method in present paper. The magnetic vector potential method and edge element method were used. The distributions of the magnetic field, the eddy current intensity and the magnetic force were obtained from the computing. The differences in these fields were explained according to the two types of electromagnetic dam, and characters of their application in twin roll casting were also discussed.
基金Supported by the Science and Technology Foundation of Jiangxi Provincial Department of Education (No. (2007)348)the Key Laboratory of Non-ferrous Metal Materials and New Processing Technologythe Young Science Foundation of Guangxi Province (No. 0832085)
文摘The copper（II） compound [Cu（Brzhama）（DMF）]2 （C22H24Br4Cu2N4O10S2, Br2hamaH2 = [（3,5-dibromo-2-hydroxybenzylidene）-amino]-methanesulfonic acid, DMF = N,N＇-dimethylformamide） 1 crystallizes in trictinic, space group P1 with a = 8.477（2）, b = 10.164（2）, c = 10.671（2）A, α= 112.66（3）, β = 104.33（3）, γ = 96.67（3）°, Z = 1, and R = 0.0789 for 1823 observed reflections with I 〉 2σ（I）. The centrosymmetric molecule comprises a pair of copper atoms connected by two anions of [（3,5-dibromo-2-hydroxybenzylidene）-amino]-methanesulfonic acid in a tetradentate coordination mode. The five-coordination of copper（II） is further completed by DME The complex forms a 1-D chain through C-H…π hydrogen bonds. The Cu^II…Cu^II distance is 4.937（1） A.
基金Supported by the National Basic Research Program of China (2006CB806104)Science Foundation for Youths of Guangxi Province (No 0991089)Initiation Found of Hechi University (No 2008QS-N022)
文摘A new Mn（Ⅱ） coordination polymer {[Mn（timb）2（H2O）2]·（Cl）2·（H2O）2}n（1,timb = 1,3,5-tris-（imidazol-1-ylmethyl）benzene） has been synthesized and characterized by elemental analysis,IR,TG and single-crystal X-ray diffraction.The title compound crystallizes in the triclinic system,space group P1 with a=9.0774（13）,b=9.8720（15）,c=11.4898（16）A,α=93.378（3）,β= 95.471（3）,γ=101.101（3）°,V=1002.6（3）A^3,Mr=834.67,Dc=1.382 g/cm^3,μ（MoKα）=0.517mm^-1,F（000）=435,GOF=0.986,Z=1,the final R=0.0506 and wR=0.1139 for 3517 observed reflections I〉2σ（I）.It consists of one-dimensional double stranded chains formed through bridging bidentate timb ligands,and these chains are further connected to yield a 3D supramolecular framework by hydrogen bonding interactions and π…π stacking interactions.
文摘With the rise of cloud computing in recent years, a large number of streaming media has yielded an exponential growth in network traffic. With the now present 5G and future 6G, the development of the Internet of Things (IoT), social networks, video on demand, and mobile multimedia platforms, the backbone network is bound to bear more traffic. The transmission capacity of Single Core Fiber (SCFs) may be limited in the future and Spatial Division Multiplexing (SDM) leveraging multi-core fibers promises to be one of the solutions for the future. Currently, Elastic optical networks (EONs) with multi-core fibers (MCFs) are a kind of SDM-enabled EONs (SDM-EON) used to enhance the capacity of transmission. The resource assignment in MCFs, however, will be subject to Inter-Core Crosstalk (IC-XT), hence, reducing the effectiveness of transmission. This research highlights the routing, modulation level, and spectrum assignment (RMLSA) problems with anycast traffic mode in SDM-EON. A multipath routing scheme is used to reduce the blocking rate of anycast traffic in SDM-EON with the limit of inter-core crosstalk. Hence, an integer linear programming (ILP) problem is formulated and a heuristic algorithm is proposed. Two core-assignment strategies: First-Fit (FF) and Random-Fit (RF) are used and their performance is evaluated through simulations. The simulation results show that the multipath routing method is better than the single-path routing method in terms of blocking ratio and spectrum utilization ratio. Moreover, the FF is better than the RF in low traffic load in terms of blocking ratio (BR), and the opposite in high traffic load. The FF is better than the RF in terms of a spectrum utilization ratio. In an anycast protection problem, the proposed algorithm has a lower BR than previous works.
基金supported by the National Basic Research Program of China (2007CB613905)the National Natural Science Foundation of China (50671050 and 50971073)the National Center for Nanoscience and Technology of China
文摘Work hardening is a well-known phenomenon occurring in crystalline metals during deformation,which has been widely used to increase the strength of metals although their ductility is usually reduced simultaneously. Here we report that the plastic strain of Zr41Ti14Cu12.5Ni10Be22.5 (at.%) bulk metallic glasses has been increased from 0.3% for the as-cast sample to 2.5%-8.0% for samples that have experienced pre-deformation under constrained conditions. The pre-deformed glassy alloys possess more free volume and abundant introduced shear bands,which are believed to promote the activation of shear bands in post-deformation and result in an increase in plasticity. The orientation of the pre-introduced shear bands relative to the loading direction will affect the deformation behavior of pre-deformed samples. The present results show that pre-deformation of this glassy alloy will result in work toughening. This work toughening effect can be removed by isothermal annealing at a sub-Tg (glass transition) temperature,which causes annihilation of free volume and healing of shear bands.
基金the National Basic Research Program of China (Grant No. 2007CB613905)the National Natural Science Foundation of China (Grant Nos. 50671050 and 50431030)
文摘Pd80+xSi20-x (x=0,1,and 2) binary metallic glasses with the diameter ranging from 7 to 8 mm were prepared by a combination of fluxing and water quenching or air cooling. Thermal analysis results show that with increasing Si content,the glass transition temperature Tg,the initial crystallization temperature Tx and the onset crystalliza-tion temperature Tp of Pd-Si binary glassy alloys increase. Moreover,the super-cooled liquid region reaches 61 K. It indicates that Pd-Si binary alloys possess large glass forming ability,which can be greatly improved by fluxing treatment.
文摘The microwave absorbing properties and magnetic properties of as-grown Fe-filled carbon nanotubes (CNTs), annealed Fe-filled CNTs, and multi-walled CNTs were studied. Vibrating sample magnetometer results showed that the annealed Fe-filled CNTs have the weakest coercivity and strongest saturation magnetization among the three types CNTs, due to the presence of more ferromagnetic α-Fe nanowires. After annealing, the values increased to 291.0 Oe and 28.0 emu/g and the samples showed excellent microwave absorbing properties. The reflection loss was over 5 dB between 11.6 GHz and 18 GHz with a maximum value of 10.8 dB for annealed Fe-filled CNTs (1.1 wt%)/epoxy composite.
文摘By using a simple and low-cost arc-discharge method in deionized water, high purity Fe3O4 nanoparti- cles have been synthesized on large scale. The structure of these nanoparticles has been studied by means of transmission electron microscope and X-ray diffraction. The synthesized Fe3O4 nanoparticles show well-defined spherical shape, with diameters ranging from 10 to 30 nm and the average diameter about 20 nm. By investigating the effects of the different processing conditions, optimum parameters were obtained. Moreover, the size of the as-grown nanoparticles can also be controlled through ad- justing the processing parameters. These Fe3O4 nanoparticles were magnetic materials, showing saturation magnetization of 64.97 emu/g at room temperature.
基金the Iron and Steel Research Joint Fund of the National Natural Science Foundation of China (No. 50474088)Baoshan Steel Complex of Shanghai in China
文摘A two-dimensional finite element model was used to analyze the thermal and mechanical behavior during solidification of the strand in a continuous bloom casting mold. The coupled heat transfer and deformation were analyzed to simulate the formation of the air gap between the mold and the strand. The model was used to investigate the influence of mold taper on the temperature and stress distributions in the strand. The results show that the air gap mainly forms around the strand corner, causing a hotter and thinner solidifying shell in this region. The mold taper partially compensates for the strand shell shrinkage and reduces the influence of the air gap on the heat transfer. The mold taper compresses the shell and changes the stress state around the strand corner region. As the strand moves down into the mold, the mold constraint causes compressive stress beneath the corner surface, which reduces the hot tear that forms on the strand.
基金This work was supported by the China Postdoctoral Science Foundation(No.2003033133)the Basic Science Research Foundation of Tsinghua University(Grant No.091201107)the National Center for Nanoscience and Technology of China.
文摘A bulk metal/ceramic composite material with a honeycomb-like micro-cell structure has been prepared by sintering the spherical Al90Mn9Ce1 alloy powders clad by Al2O3 nano-powder with the spark plasma sintering (SPS) technique. The as-prepared material consists of Al90Mn9Ce1 alloy cell and closed Al2O3 ceramic cell wall. The diameter of the cells is about 20―40 μm, while a thickness of the cell wall is about 1―2 μm. The ultimate compressive strength of the as-sintered materials is about 514 MPa, while its fracture strain is up to about 0.65 %. This composite material might possess good anti-corrosion, thermal endurance and other potential properties due to its unique microstructure. The result shows that the Al90Mn9Ce1/Al2O3 composite powders can be sintered by spark plasma sintering technique despite the large difference in their sintering temperature. This work offers a way of designing and preparing metal/ceramic composite material with functional property.
基金Supported by the National Natural Science Foundation of China (Grant No. 50672047)
文摘As the potential applications of carbon nanotubes in the field of electroluminescence, elements yttrium and europium were introduced to modify the emission properties of double-walled carbon nanotubes (DWNTs) to obtain higher efficacy and other properties. The light emission spectrum of the Y-Eu-doped DWNT filament is suppressed in the near-infrared range, while enhanced in the mid-infrared range. The doped DWNT filament can reach higher efficacy than that of the pure DWNT filament at the same input power and can work stably as long as 5000 h at 12 V. These filaments could be useful for the light sources with special functions, such as infrared light sources operated at low input power.
